• Journal of the Mineralogical Society of Korea
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• v.26 no.4
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• pp.299-312
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• 2013

Magnetite, a major constituent mineral of the Hongcheon carbonatite-phoscorite complex, was produced over three stages in each rock type and decreased in quantity toward the late stage. Electron microprobe analyses for magnetite revealed that Ti and V were detected in traces, but showed increasing tendency from early to late stage. On the contrary, Mg and Mn decreased distinctly, and it is the general differentiation trend of carbonatitic magma. Al also showed decreasing tendency in carbonatite and phoscorite, and Cr was mostly below detection limit except late phoscorite. In early stage, $Fe^{2+}$ was largely replaced by $Mg{2+}$ and $Mn^{2+}$, and $Fe^{3+}$ by $Al^{3+}$ in magnetite, but it has nearly pure composition in late stage. Tendency of increase in V and decrease in Mn toward late stage represents that magma differentiation progressed under the condition of decreasing oxygen fugacity. Low concentrations of Mg, Al, Cr and Ti, as well as the absence of olivine and phlogopite, suggest that the Hongcheon carbonatite-phoscorite complex was generated from depleted magma. Especially, lower concentrations of Mg in magnetite compared to other typical carbonatite-phoscorite complex, and abundant occurrence of Fe-carbonate minerals and quartz in late stage, suggest that magma differentiation of the Hongcheon carbonatite-phoscorite proceeded to the latest stage.

• Applied Chemistry for Engineering
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• v.8 no.6
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• pp.954-959
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• 1997

The solid solutions of the $Sr_{1-X}M_XFeO_{3-y}$ (x=0.1, 0.2, 0.3, 0.4, 0.5, M=Ca) system having perovskite structures were prepared in air by heat treatment at 1473 K for 18hr. X-ray diffraction assigns cubic system for all the samples and shows that the lattice volume of each system decreases with increasing x value until x=0.3, but increases abruptly from x=0.4. The mole fractions of $Fe^{4+}$ ion($\tau$ value), the amounts of oxygen vacancy (y value) and finally nonstoichiometric chemical formulas for each composition were determined from Mohr salt analysis. TG/DTA thermal analysis (temperature range: 300~1173K) exhibits that 3-y values of the samples having x=0.1 and 0.2, decrease with temperature and increase almost reversibly with decreasing temperature. The samples of $x{\geq}0.3$, however, didn't show the reversible weight change and the 3-y values of them were nearly 2.5 in cooling process. Conductivities of each sample were varied within the semiconductivity range at relatively low temperature. And the conductivity at constant temperature decreases steadily with x value. The conduction mechanism of this ferrite system may be proposed as a hopping model of conducting electrons between the mixed valence states. At high temperature semiconductivity of each sample changed into metallic property.

• Journal of Sensor Science and Technology
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• v.8 no.2
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• pp.115-123
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• 1999

A micro-gas sensor with heater and sensing electrode on the same plane was fabricated on phosphosilicate glass(PSG, 800nm)/$Si_3N_4$ (150nm) dielectric membrane. PSG film was provided by atmospheric pressure chemical vapor deposition(APCVD), and $Si_3N_4$ film by low pressure chemical vapor deposition (LPCVD). Total area of the fabricated device was $3.78{\times}3.78mm^2$. The area of diaphragm was $1.5{\times}1.5mm^2$, and that of the sensing layer was $0.24{\times}0.24mm^2$. Finite-element simulation was employed to estimate temperature distribution for a square-shaped diaphragm. The power consumption of Pt heater was about 85mW at $350^{\circ}C$. Tin thin films were deposited on the silicon substrate by thermal evaporation at room temperature and $232^{\circ}C$, and tin oxide films($SnO_2$) were prepared by thermal oxidation of the metallic tin films at $650^{\circ}C$ for 3 hours in oxygen ambient. The film analyses were carried out by SEM and XRD techniques. Effects of humidity and ambient temperature on the resistance of the sensing layer were found to be negligible. The fabricated micro-gas sensor exhibited high sensitivity to butane gas.

• Horticultural Science & Technology
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• v.28 no.5
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• pp.902-911
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• 2010

Oriental melon ($Cucumis$ $melo$ var. $makuwa$) is a popular and high-value market fruit cultivated in Korea. Consumers are becoming increasingly interested in oriental melon as a healthy diet over the past few years. However, the melons have relatively high quality loss because the fruit are mainly produced for a limited period of time in the summer season. Lack of the proper postharvest treatments and high temperature exposure at harvest or during distribution are the most critical environmental factors limiting postharvest life of fruit. This review focuses on the overview of current research studies for postharvest treatment and functional packaging technology of oriental melon in Korea. Major physiological problems of the harvest fruit include the ripening process in quality changes of the produce such as loss of weight, firmness, flavor, and decay during the storage periods. Low temperature at 7 to $10^{\circ}C$ with high relative humidity of 90 to 95% is the suitable environmental condition used to maintain the quality of fresh oriental melon. Controlled atmosphere (CA) storage or modified atmosphere (MA) packaging can be used as supplemental treatments to extend postharvest-life. For oriental melon, an optimum CA is currently recommended to be 2-3% oxygen and 5-10% carbon dioxide atmosphere. Precooling, pretreatments of ethylene action and functional packaging system can be applied to oriental melon after harvest in order to extend storage life. Major active packaging technologies are concerned with a selectively gas permeable film related to respiration of produce and the packaging applications of ethylene removal, antimicrobial, and antifogging substances to keep the effective freshness of fruit.

• Korean Journal of Clinical Laboratory Science
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• v.50 no.2
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• pp.136-143
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• 2018

The rate pressure product (RPP) is expressed as a product of the heart rate and systolic blood pressure as an index indirectly measuring the myocardial oxygen consumption, and it indicates the burden on the myocardium. The aim of this study was to determine the optimal level of RPP for preventing metabolic syndrome in a treadmill exercise test in Korean adults. Metabolic syndrome was the diagnosis of the third executive summary report on the National Cholesterol Education Program Adult Treatment Panel III (NCEP-ATP III) criteria. According to the criteria, the metabolic syndrome diagnosis group (MetS, N=25), pre-metabolic syndrome group (Pre-MetS, N=106), and non-risk factor group (Non-MetS, N=65) were classified. The exercise stress test was performed based on the Bruce protocol. The RPP was calculated as (heart rate${\times}$systolic blood pressure)${\div}1,000$. The results showed that the maximum systolic blood pressure was high despite the low daily dose reached in the diagnostic group of metabolic syndrome. The optimal threshold of the RPP at the time of the exercise treadmill test for a metabolic syndrome prediction was $12.56mmHg{\times}beats/min{\times}10^{-3}$ in the first stage of the exercise stress test. The second stage of the exercise test was $16.94mmHg{\times}beats/min{\times}10^{-3}$, and at the third stage of the exercise test was $21.11mmHg{\times}beats/min{\times}10^{-3}$.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.4
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• pp.10-18
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• 2018

The primary purposes of this study are to understand a fundamental aspect of current uniformity around a reinforcing bar (rebar) in cement mortar, and to develop an accurate monitoring method in a wet-dry cycling process with the alternative current (AC) impedance method. Three cement mortar specimens with two embedded rebars were prepared in the laboratory. As a main variable, the distance between two rebars was designed to be 10, 20 and 30 mm with the same thickness of 20 mm. To simulate the corrosion of rebars in concrete structures in a marine environment, three cement mortar specimens were exposed to 15 wet-drying cycles (24-hour-immersion in seawater and 48-hour-drying in a room temperature) in the laboratory. It was observed that the potential level shifted to a noble value during corrosion potential monitoring, which is attributed to acceleration of dissolved oxygen diffusion at the drying process. AC impedance was measured in a frequency range from 100 kHz to 1 mHz on a wet-drying process. A theoretical model was proposed to explain the interface condition between the rebars and cement mortar by using the equivalent circuit consisting of a solution resistance, a charge transfer resistance and a CPE (constant phase element). It was observed that the diffusion impedance appeared in a low frequency range as corrosion of rebars progresses. At the drying stage of the wet-drying cycles, the currents line for monitoring tended to be non-uniform at the interface of rebar/mortar, being phase shift, ${\theta}$, close to $-45^{\circ}$.

• Korean Journal of Food Science and Technology
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• v.26 no.2
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• pp.133-137
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• 1994

Functional properties of packaging films prepared with cellulose derivatives were measured. As a presolvation treatments of celluloses, 95% ethanol solution for methylcellulose (MC), hydroxypropyl-methylcellulose (HPMC) and ethylcellulose (EC) and water for hydroxypropyl cellulose (HPC) were used. For film sheeting, the ethanol concentration of final cellulose solution should exceed 50% for MC, HPMC and HPC and 80% for EC. Thickness and functionalities of the prepared films were varied by type, molecular weight and viscosity of the cellulose and kind of plasticizer used. Tensile strength of MC, HPMC and HPC films were $67.7{\sim}275.4\;MPa$, $124.6{\sim}260.0\;MPa$, and $14.8{\sim}29.4\;MPa$, respectively. The strength of MC and HPMC films was higher than that of low density polyethylene (LDPE) films $(13.1{\sim}27.6\;MPa)$. Solubility of the cellulose films varied widely by plasticizer used and the films containing polyethyleneglycol (PEG) as a plasticizer was more soluble than the films by glycerol. Maximum water vapor permeability and oxygen permeability of the cellulose films was more than 1,000 folds and less than one-twelfth of the LDPE film, respectively.

• Journal of the Korean Geographical Society
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• v.44 no.4
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• pp.447-462
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• 2009

Kohyun River basin is located at southern parts of Taebaek Mountains and most of river basins consists of sedimentary rock. The aims of this study are to investigate the distribution characteristics and processes of fluvial terraces at Kohyun River, using scientific methods such as classification of fluvial landforms, analysis of geomorphological deposits, XRD and OSL age dating. In Kohyun River basin are three levels terraces from T1 to T3. Fluvial terraces are assumed to be erosional terraces according to deposited situation of alurium and existences of bedrock riverbed. From the result of OSL age dating, formation age of fluvial terrace 1(T1) is calculated about 37,000 yr.B.P.(MIS 3), and fluvial terrace 2(T2) is calculated about 113,000 yr.B.P.(MIS 5). Therefore, fluvial terraces at Kohyun River are assumed to be formed at warmer period in the glacial stages or cooler period in the interglacial stages. The incision rate of fluvial terrace 1 at Kohyun River is calculated to be 0.054m/ka, and the incision rate of fluvial terrace 2 is calculated to be 0.115m/ka. This results suggest to lower incision rate than other rivers in Korea because of low uplift rates and little discharge.

• Journal of Korean Society on Water Environment
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• v.31 no.2
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• pp.181-195
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• 2015

Algal blooms in lakes are one of major environmental issues in Korea. A three-dimensional, hydrodynamic and water quality model was developed and tested in Lake Euiam to assess the performance and limitations of numerical modeling with multiple algal groups using field data commonly collected for algal management. In this study, EFDC was adopted as the basic model framework. Simulated vertical profiles of water temperature, dissolved oxygen and nutrients monitored at five water quality monitoring stations from March to October 2013, which are closely related to algal dynamics simulation, showed good agreement with those of observed data. The overall spatio-temporal variations of three algal groups were reasonably simulated against the chlorophyll-a levels of those estimated from the limited monitoring data (chlorophyll-a level and cell numbers of algal species) with the RMSEs ranging from 2.6 to $17.5mg/m^3$. Also, note that $PO_4-P$ level in the water column was a key limiting factor controlling the growth of three algal groups during most of simulation period. However, the algal modeling results were not fully attainable to the levels of observation during short periods of time showing abrupt increase in algae throughout the lake. In particular, the green algae/cyanobacteria and diatom simulations were underestimated in late June to early July and early October, respectively. The results shows that better understanding of internal algal processes, neglected in most algal modeling studies, is necessary to predict the sudden algal blooms more accurately because the concentrations of external $PO_4-P$ and specific algal groups originated from the tributaries (mainly, dam water releases) during the periods were too low to fully capture the sharp rise of internal algal levels. In this respect, this study suggests that future modeling efforts should be focused on the quantification of internal cycling processes including vertical movement of algal species with respect to changes in environmental conditions to enhance the modeling performance on complex algal dynamics.

• Journal of Life Science
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• v.25 no.7
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• pp.819-825
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• 2015

The use of fructose-containing sports beverage drinks has increased in recent years, especially at sport events, because of their reported ergogenic effects. However, the ingestion of low to moderate doses of caffeinated energy drinks has been associated with adverse side effects such as insomnia or increased nervousness. The purpose of this study was to investigate the effects of fructose beverage supplementation on cardiopulmonary function, blood lactate levels, and inflammatory reactions. We recruited 8 young adult subjects from D university and measured their cardiopulmonary functions before and after supplementation with sports beverage drinks. We also measured blood lactate and inflammatory reactions after a 20 min recovery period. Exercise time, maximal oxygen uptake (V0₂max), and AT HRmax were significantly increased (p<0.05) in the period of before and after sports beverage supplementation. However, no significant differences were observed in RPE, AT RER, V0₂max RER, AT V0₂max, and maximum heart rate (HRmax). Lactate levels also significantly decreased after 20 min recovery with sports beverage supplementation. Sports beverage supplementation therefore may enhance maximal V0₂max and increase the exercise duration time. These drinks may also be helpful in promoting rapid recovery of fatigue variables and increasing exercise performance time.