• Journal of Magnetics
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• v.18 no.2
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• pp.150-154
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• 2013

$La_{1-z}Nd_z(Fe_{0.88}Si_{0.12})_{13}$ and their hydrides were investigated to obtain large magnetocaloric effects (MCEs) in a wide temperature range, including room temperature, for applications in magnetic refrigents. Since the magnetization change due to the itinerant-electron metamagentic (IEM) transition for $La_{1-z}Nd_z(Fe_{0.88}Si_{0.12})_{13}$ becomes larger with increasing z, the isothermal magnetic entropy change ${\Delta}S_m$ and the relative cooling power (RCP) are enhanced. In addition, the Curie temperatrue $T_C$ of $La_{0.8}Nd_{0.2}(Fe_{0.88}Si_{0.12})_{13}$ is increased from 193 to 319 K by hydrogen absorption, with the IEM transition. The maximum value of $-{\Delta}S_m$, $-{\Delta}S{_m}^{max}$, in a magnetic field change of 2 T for $La_{0.8}Nd_{0.2}(Fe_{0.88}Si_{0.12})_{13}H_{1.1}$ is about 23 J/kg K at $T_C$ = 288 K, which is larger than that of 19 J/kg K at $T_C$ = 276 K for $La(Fe_{0.88}Si_{0.12})_{13}H_{1.0}$. The value of RCP = 179 J/kg of the former is also larger than 160 J/kg of the latter. It is concluded that the partial substitution of Nd improves MCEs in a wide temperautre range, including room temperature.

• The Journal of Engineering Geology
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• v.26 no.4
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• pp.515-529
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• 2016

In this study, geochemical composition, CFCs (Chlorofluorocarbons), ${\delta}^{18}O$, ${\delta}D$, ${\delta}^{13}C$ isotopes and noble gases isotopes (He, Ne) were analyzed to determine their recharge age, source of $CO_2$ gas and noble gases of carbonated hot spring water and carbonated-water samples collected in the Seoqwipo of the Jeju. The pH of the carbonated waters ranges from 6.21 to 6.84, and the high electrical conductivity range ($1,928{\sim}4,720{\mu}S/cm$). Their chemical composition is classified as $Mg(Ca,\;Na)-HCO_3$ and $Na(Ca,\;Mg)-HCO_3$ types. As a result of the calculation of groundwater age using CFCs concentrations as an environmental tracer, the carbonated water and groundwater were estimated to be about 47.5~57.2 years and about 30.3~49.5 years, respectively. The ${\delta}^{13}C$ values of carbonated water range from -1.77 to -7.27‰, and are plotted on thr deep-seated field or the mixing field of the deep-seated and inorganic origin. Noble gases isotopic ($^3He/^4He$, $^4He/^{20}Ne$) ratio shows that helium gas of carbonated hot waters comes from deep-seated magma origin.

• Economic and Environmental Geology
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• v.42 no.4
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• pp.315-333
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• 2009

In this study, the hydrochemical and the isotopic characteristics of major streams in the Daejeon area were investigated during rainy and dry seasons. The stream water shows the electrical conductivity of the range of $37{\sim}527{\mu}s$/cm, and pH $6.21{\sim}9.83$. The chemical composition of stream waters can be grouped as three types: the upper streams of Ca(Mg)-$HCO_3$ type, Ca(Mg)-$SO_4(Cl)$ type of middle streams flowing through urban area, and Na(Ca)-$HCO_3$(Cl, $SO_4$) type of the down streams. Based on in-situ investigation, the high pH of stream waters flowing through urban area is likely to be caused by the inflow of a synthetic detergent discharging from the apartment complex. The electrical conductivity of stream waters at a dry season is higher than those of at a rainy season. We suggest that the hydro-chemical composition of stream waters in the Daejeon area was affected by the discharging water from the sewage treatment facilities and anthropogenic contaminants as well as the interaction with soil and rocks. ${\delta}D$ and ${\delta}^{18}O$ values of the stream waters show the relationship of ${\delta}D=6.45{\delta}^{18}O-7.4$, which is plotted at a lower area than global meteoric water line(GMWL) of Craig(1961). It is likely that this isotopic range results from the evaporation effect of stram waters and the change of an air mass. The isotope value shows an increasing trend from upper stream to lower stream, that reflects the isotopic altitude effect. The relationship between ${\delta}^{13}C$ and $EpCO_2$ indicates that the carbon as bicarbonate in stream water is mainly originated from $CO_2$ in the air and organic materials. The increasing trend of ${\delta}^{13}C$ value from upper stream waters to lower stream waters can be attributed to the following reasons: (1) an increasing dissolution of $CO_2$ gas from a contaminated air in downtown area of the Daejeon, and (2) the increment of an inorganic carbon of groundwater inflowed into stream by base flow. Based on the relationship between ${\delta}^{34}S$ and $SO_4$ of stream waters, the stream waters can be divided into four groups. $SO_4$ content increases as a following order: upper and middle Gab stream${\delta}^{34}S$ value decreases as above order. ${\delta}^{34}S$ value indicates that sulfur of stream waters is mainly originated from atmosphere, and is additionally supplied by pyrite source according to the increase of sulfate content. The sulfur isotope analysis of a synthetic detergent and sewage water as a potential source of the sulfur in stream waters is furtherly needed.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.48 no.6
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• pp.516-526
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• 2003

Thirty-six barley varieties including Korean modern and local varieties were tested for drought-tolerance in the field of plastic rain shelter, Drought treatment was initiated at initial tillering stage (March 27, 2002) by withholding irrigation and lasted until harvest. Soil water potential maintained at around -0.05㎫ in the control plot and varied from -0.05㎫ (at the initial stage of drought treatment) to -0.29㎫ in the drought treatment plot. At forty days after drought treatment, relative water content (RWC), osmotic potential (OP), osmotic adjustment (OA), and $^{13}\textrm{C}$ discrimination ($\Delta$) were measured and then plants were sampled for leaf area index (LAI) and dry weight (DW). Barley was harvested at maturity for determining DW, grain yield, 1000 grains weight and number of spikelet. The tested varieties revealed wide spectrum of drought tolerance. Dongbori-1, Chalbori, Changyeongjaerae, Samdobori and Weolseong 87-31 showed strong drought-tolerance while Songhagbori and Suwonmaeg360 showed weak drought-tolerance. The drought injury indexes (drought/control ratio) of DW and yield revealed significant positive correlation with leaf RWC in drought treatment plot and $\Delta$ in the control plot, but obvious negative correlation with leaf OP and OA under drought condition. In addition, all the drought indexes of OP, $\Delta$ and RWC showed obvious positive correlation with the drought injury indexes of DW, 1000 grain weight and yield. Thus, OP and RWC under drought condition and $\Delta$ under well-watered condition would be used as the evaluation criteria for drought- tolerance of barley genotypes. However, further investigation is needed for the relationship between $\Delta$ and drought-tolerance as the other reports were not consistent with our result.

• Journal of Ecology and Environment
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• v.43 no.1
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• pp.31-42
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• 2019

Background: Han River estuary is a national wetland reserve near the Demilitarized Zone (DMZ) between South Korea and North Korea. This trans-boundary estuary area has been well preserved and shows distinctive plant communities along the salinity gradient. To elucidate energy flows and nutrient cycling in this area, we studied trophic relations between the dominant sesarmid crab, Sesarma dehaani, and food sources in three wetlands with different environments along the estuarine gradients. Results: Stable isotope signatures (${\delta}^{13}C$ and ${\delta}^{15}N$) of the crabs were significantly different among the sites and body size classes. Seasonal changes in ${\delta}^{13}C$ of small crabs were distinct from those of large individuals at all the sites. The isotopic values and fatty acid profiles of the crabs were more different among the sites in September than in May. In May, large-sized crabs utilized more plant materials compared to other dietary sources in contrast to small-sized crabs as revealed by a stable isotope mixing modeling, whereas contributions to diets of crabs were not dominated by a specific diet for different body size in September except at site 1. Based on PCA loadings, fatty acid content of $18:3{\omega}3$, known as a biomarker of plant materials, was the main factor to separate size groups of crabs in May and September. The ${\delta}^{13}C$ value of sediment had high correlation with those of small-sized crabs at site 1 and 2 when 1-month time lag was applied to the value for crabs during the surveyed period. Conclusions: Based on the stable isotope and fatty acid results, the consumption habits of S. dehaani appear to be distinguished by sites and their size. In particular, smaller size of S. dehaani appears to be more dependent on fewer food sources and is influenced more by the diet sources from the sediments in Han River estuary.

• Analytical Science and Technology
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• v.25 no.5
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• pp.300-306
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• 2012

This study reports the stable carbon and nitrogen isotope of mummy, the preserved human time capsule from Joseon Dynasty. The stable isotopic composition of biological tissue is expected to be a direct and constant function of diet because the stable isotope ratios do not decay or change in abundance through time. Over the past three decades, stable carbon and nitrogen isotope analysis has been extensively applied for archaeological topics. However, this is the first case in Korean mummy to extract palaeodietary information using stable isotope analysis. We extracted isotopic information from bone collagen and hair keratin, which reflects the lifetime average diet and short-term diet, respectively. The average values of ${\delta}^{13}C$ and ${\delta}^{15}N$ values are -19.0‰ and 11.4‰ (bone collagen), and -21.3‰ and 14.3‰ (hair keratin). Stable carbon isotope shows a mainly $C_3$-based diet from cradle to grave. On the other hand, there is significant difference in stable nitrogen isotope which implies a relatively enriched diet before death. We expect this study opens up a potential to understand the palaeodietary lifestyle in Joseon Dynasty.

• Economic and Environmental Geology
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• v.35 no.2
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• pp.121-136
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• 2002

The $CO_2$-rich springs in the Kyungpook Province has been found at 16 locations. Most of the $CO_2$-rich springs outflow along either fault zones or the geologic boundary between Mesozoic granites and their adjacent rocks. The $CO_2$-rich water samples show a high $CO_2$ concentration ( $P_{CO2}0.46 to 5.21 atm), weak acidic pHs, wide electrical conductivity values ranging from 422 to 2,280 $\mu\textrm{S}$/cm, and high re content. They are classified into the ca-HC $O_3$ type in chemical composition.$\delta$$^{18}$ O and $\delta$$^2$H data indicate that $CO_2$-rich water is meteoric origin. The $\delta$$^{13}$ C values (-1.5$\textperthousand$ to -6.1$\textperthousand$ PDB) suggest that dissolved $H_2$C $O_3$$^{0}$ C $O_3$- are mainly derived from a deep-seated $CO_2$ and carbonate minerals. The thermodynamic equilibrium state between $CO_2$-rich water and major minerals, and hydrochemical characteristics indicate that major source minerals determining the chemical composition of $CO_2$-rich water are carbonate minerals, plagioclase, K-feldspar and Fe-oxides. Under high $CO_2$ pressure and the weak acidic condition, most of the $CO_2$-rich water samples are thermodynamically in the dissolution state with respect to albite and carbonate minerals.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.3
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• pp.421-424
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• 2016

In order to evaluate the insulation deterioration in the stator windings of air-cooled gas turbine generators(119.2 MVA, 13.8 kV) which has been operating for more than 15 years, diagnostic test and AC dielectric breakdown test were performed on phases A, B and C. Diagnostic test included measurements of AC current, dissipation factor, partial discharge (PD) magnitude and capacitance. ${\Delta}I$ and ${\Delta}tan{\delta}$ in all three phases (A, B, and C) of generator stator windings showed that they were in good condition but PD magnitude indicated marginally serviceable condition. After the diagnostic test, an AC overvoltage test was performed by gradually increasing the voltage applied to the generator stator windings until electrical insulation failure occurred, in order to determine the breakdown voltage. Although phase A of generator stator windings failed at breakdown voltage of 29.0 kV, phases B and C endured the 29.0 kV. The breakdown voltage in all three phases was higher than that expected for good-quality windings (28.6 kV) in a 13.8 kV class generator.

• Biomolecules & Therapeutics
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• v.9 no.4
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• pp.285-290
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• 2001

Bioequivalence of two acetyl-1-carnitine tablets, test product (Carnitile tablet: Hanmi Pharm. Co., Ltd.) and reference product (Nicetil $e^{R}$ tablet: Dong-A Pharm. Co., Ltd.), was evaluated according to the guide- lines of Korea Food and Drug Administration (KFDA). Twenty-six healthy volunteers were divided randomly into two groups and administered the drug orally at the dose of 500 mg as acetyl-1-carnitine in a 2$\times$2 crossover study. Blood samples were taken at predetermined time intervals for 12 hours and the plasma concentration of acetyl-1-carnitine was determined using HPLC by derivatization with p-bromophenacyl bromide. The pearmacokinetic parameters (AU $C_{0-}$12h/ $C_{max}$ and $T_{max}$) were calculated and ANOVA was utilized for the statistical analysis of parameters. The apparent differences of these parameters between two drugs were less than 20% (i.e., 1.26,-5.08 and 8.59% for AU $C_{0-}$12h/ $C_{max}$ and $T_{max}$, respectively). The powers (1-$\beta$) for AU $C_{0-}$12h/ $C_{max}$ and $T_{max}$, and Tmax were over 0.9. Minimal detectable difference ($\Delta$) at $\alpha$=0.05, 1-$\beta$=0.8 were less than 20% (i.e.,7.31, 14.88 and 11.77% for AU $C_{0-}$12h/ $C_{max}$ and $T_{max}$, respectively). The confidence intervals ($\delta$) for these parameters were also within $\pm$ 20% (i.e.,-3.03$\leq$$\delta$$\leq$5.54, -13.80$\leq$$\delta$$\leq$3.64 and 1.69$\leq$$\delta$$\leq$15.48 for AU $C_{0-}$12h/ $C_{max}$ and $T_{max}$, respectively). These results satisfied the criteria of KFDA guideline for bioequivalence, indicating Carnitile bioequivalent to Nicetil $e^{R}$ .TEX>$^{R}$ .> R/ . R/ .

• Korean Journal of Materials Research
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• v.13 no.3
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• pp.200-204
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• 2003

A statistical experiment method was employed to investigate the window of the thermal stability of $TiSi_2$films which are popular for Ti-salicide and ohmic layers. The statistical experimental results showed that the first order term of $TiSi_2$thickness and annealing temperature was acceptable as a function of $\Delta$resistivity by 95% reliability criteria, and R-sq value implying a fit accuracy of the model also showed a high value of 93.80%. We found that $\Delta$resistivity of the $TiSi_2$film annealed at $700^{\circ}C$ for 1 hr changed from 3.35 to $0.379\mu$$\Omega$$\cdot$cm with increasing thickness from 185 to $703\AA$, and TEX>$\Delta$resistivity of the $TiSi_2$film with a fixed thickness of 444 $\AA$ changed from 0.074 to 17.12 $\mu$$\Omega$$\cdot$cm with increasing temperature increase from 600 to $800^{\circ}C$. From these results, we report that the process conditions of$ 692^{\circ}C$-1 hr, $715^{\circ}C$-1 hr, and 73$0^{\circ}C$-1 hr for $TiSi_2$($400 \AA$) are stable by the criteria of 1, 2, and 3 $\mu$$\Omega$$\cdot$cm of $\Delta$resistivity, respectively.