• Polymer(Korea)
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• v.33 no.6
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• pp.555-560
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• 2009

Sulfonic acid of the sulfonated 6FDA-based polyimides were exchanged with the monovalent ($Li^+$, $Na^+$, $K^+$) and divalent ($Mg^{2+}$, $Ca^{2+}$, $Ba^{2+}$) ions. The effect of metal cations exchanged sulfonated polyimides was investigated in terms of gas permeability and selectivity for $CO_2$, $O_2$ and $N_2$ gases. Thermogravimetric analysis showed that thermal stability of sulfonated polyimide was improved by exchanged metal cations. The permeabilities of monovalent cation-exchanged, sulfonated polyimide were reduced as the ion radius reduced [$Li^+$(0.059 nm)>$Na^+$(0.102 nm)>$K^+$(0.138 nm)], and those of divalent cations exchanged were determined by the ionic radii and electrostatic crosslinking between the polymer and metal cations, whereas the selectivities of all the metal cation-exchanged, sulfonated polyimides for $CO_2/N_2$ and $O_2/N_2$, were higher than those of sulfonated polyimide membranes. The sulfonated polyimide exchanged with the potassium cation showed the $O_2$ permeability of 89.98 Barrer [$1\times10^{-10}\;cm^3$(STP) $cm/cm^2{\cdot}s{\cdot}cmHg$] and the sulfonated polyimide exchanged with the lithium cation showed the $O_2/N_2$ selectivity of 12.9.

• Korea journal of population studies
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• v.19 no.2
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• pp.107-137
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• 1996

Under-utilization of Korean women's education in the labor market has been observed and pointed out as a waste of valuable human resources. Although education provides women with positive returns when they work, it has been found that Korean women's education is not much related to the likelihood of women's labor force participation. This tendency cannot be explained by micro-economic theory, which says that educated women are more likely to participate in the labor force. Thus, in this analysis, a macro-level explanation is attempted to understand Korean women's economic behaviors in relation to education. Korea's rapid industrialization since 1960 has provided ample job opportunities mostly for less educated women. On the other hand, increasing demand for educated female labor has been moderate. Various restriction against women, especially married women, have prevailed in the Korean labor market. Restrictions against women and the marriage bar tend to be selectively applied to decent white-collar jobs, mostly affecting educated women. Furthermore, there has been no shortage of educated male labor due to its adequate supply. Since Korean women spend most of their adult lives in marriage, married women's low participation in the labor force is a critical factor for the low economic returns to women's education throughout their lifetime. Restriction against married women in the labor market also existed in the past of the United States and the Great Britain. However, along with the expansion of the service sector, married women in great numbers flowed into non-manual jobs. The post-1940 increase of married women in the labor force in those countries can be understood to be a result of a labor shortage for non-manual jobs. Also in Taiwan, which shares many common cultural and economic backgrounds with Korea, the marriage bar has been in decline since the late 1970s, along with an increasing demand for female labor in the service sector. In sum, the changes in the demand structure and the supply of educated male labor force will contribute to the lift of the marrige bar in Korea.

• The Journal of the Petrological Society of Korea
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• v.22 no.2
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• pp.137-151
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• 2013

This study is focused on element behaviors and mineral compositions of the fault rock developed in Yongdang-ri, Yangbuk-myeon, Gyeongju City, Korea, using XRF, ICP, XRD, and EPMA/BSE in order to better understand the chemical variations in fault rocks during the fault activity, with emphasis on dependence of chemical mobility on mineralogy across the fault zone. As one of the main components of the fault rocks, $SiO_2$ shows the highest content which ranges from 61.6 to 71.0%, and $Al_2O_3$ is also high as having the 10.8~15.8% range. Alkali elements such as $Na_2O$ and $K_2O$ are in the range of 0.22~4.63% and 2.02~4.89%, respectively, and $Fe_2O_3$ is 3.80~12.5%, indicating that there are significant variations within the fault rock. Based on the chemical characteristics in the fault rocks, it is evident that the fault gouge zone is depleted in $Na_2O$, $Al_2O_3$, $K_2O$, $SiO_2$, CaO, Ba and Sr, whereas enriched in $Fe_2O_3$, MgO, MnO, Zr, Hf and Rb relative to the fault breccia zone. Such chemical behaviors are closely related to the difference in the mineral compositions between breccia and gouge zones because the breccia zone consists of the rock-forming minerals including quartz and feldspar, whereas the gouge zone consists of abundant clay minerals such as illite and chlorite. The alteration of the primary minerals leading to the formation of the clay minerals in the fault zone was affected by the hydrothermal fluids involved in fault activity. Taking into account the fact that major, trace and rare earth elements were leached out from the precursor minerals, it is assumed that the element mobility was high during the first stage of the fault activity because the fracture zone is interpreted to have acted as a path of hydrothermal fluids. Moving toward the later stage of fault activity, the center of the fracture zone was transformed into the gouge zone during which the permeability in the fault zone gradually decreased with the formation of clay minerals. Consequently, elements were effectively constrained in the gouge zone mostly filled with authigenic minerals including clay minerals, characterized by the low element mobility.

• Korean Journal of Optics and Photonics
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• v.20 no.5
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• pp.266-271
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• 2009

We designed a thermo-optic switch based on a directional coupler with not only a high extinction ratio but also significantly low power consumption. The switch operates by using the thermo-optic effect of the polymer which the refractive index changes by heating the electrode. If the electrode is not powered (OFF), the input light will be coupled completely to the other waveguide. When the electrode is powered at a certain level (ON), input light launched into the input waveguide will remain in that waveguide due to the lower index adjusted in the other waveguide. The switch based on the directional coupler was designed using the generalized extinction ratio curve and the lateral shift of the input waveguide. The coupling length is 1,610 ${\mu}m$ and the extinction ratios are -28 and -30 dB for ON and OFF states, respectively. The electrode structures were optimized by thermal analysis. The transported heat into the waveguide is increased, as the electrode width (w) is increased and the center distance between the electrode and the waveguide (d) is decreased. Also, because the heat generated in the electrode affects the other waveguide, the temperature difference between two waveguides is varied as the given w and d. There are specific conditions which have the maximum of the temperature difference. That of the temperature difference is increased as the width and the temperature of the electrode are increased. Especially, when the switch is designed using the condition with the maximum of the temperature difference for switching, the temperature of the electrode can be decreased. We expect this condition will be the novel method for the reduction of the power consumption in a thermo-optic switch.

• Journal of the Korean Vacuum Society
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• v.19 no.3
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• pp.211-216
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• 2010

The luminescence properties of $In_{0.5}Ga_{0.5}As/In_{0.5}Al_{0.5}As$ multiple quantum wells (MQWs) grown on $In_{0.5}Al_{0.5}As$ buffer layers have been studied by using photoluminescence (PL) and time-resolved PL measurements. A$1-{\mu}m$ thick $In_{0.5}Al_{0.5}As$ buffer layers were deposited on a 500 nm thick GaAs layer, followed by the deposition of the InGaAs/InAlAs MQWs. In order to investigate the effects of InAlAs buffer layer on the optical properties of the MQWs, four different temperature sequences are used for the growth of InAlAs buffer layer. The growth temperature for InAlAs buffer layer was varied from 320^{\circ}C to $580^{\circ}C$. The MQWs consist of three $In_{0.5}Ga_{0.5}$As wells with different well thicknesses (2.5 nm, 4.0 nm, and 6.0 nm thick) and 10 nm thick $In_{0.5}Al_{0.5}$As barriers. The PL spectra from the MQWs with InAlAs layer grown at lower temperature range ($320-580^{\circ}C$) showed strong peaks from 4 nm QW and 6 nm QW. However, for the MQWs with InAlAs buffer grown at higher temperature range ($320-480^{\circ}C$), the PL spectra only showed a strong peak from 6 nm QW. The strongest PL intensity was obtained from the MQWs with InAlAs layer grown at the fixed temperature of $480^{\circ}C$, while the MQWs with buffer layer grown at higher temperature from $530^{\circ}C$ to $580^{\circ}C$ showed the weakest PL intensity. From the emission wavelength dependence of PL decay times, the fast and slow decay times may be related to the recombination of carriers in the 4 nm QW and 6 nm QW, respectively. These results indicated that the growth temperatures of InAlAs layer affect the structural and optical properties of the MQWs.

• Korean Journal of Plant Resources
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• v.16 no.3
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• pp.264-274
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• 2003

Many potato genetic resources have been collected and improved for their diverse traits over the years using breeding program in KPGR. To select potential varieties for table and processing in Korea, 58 elite potato breeding lines and several 'Valley' varieties were cultivated and harvested at Korea Alpine area in 2001. The cultivated lines and varieties were evaluated using their cultural adaptability in the environment and tuber characteristics, such as the depth of tuber eye, tuber shape, skin color, flesh color, scab resistance, yield, and the resistance of hollow heart and internal brown spot disease. Additionally, in the selection of potential processing varieties, reducing sugar content (sum of glucose and fructose concentration) of tubers is critically considered, because it mainly influence on the chip color of processing potato tuber. For table stock varieties with white skin color, 'Early Valley', 'Summer Valley', 'Winter Valley', and 'Taebok Valley' were selected. In the aspect of diverse potato tuber color, several varieties were selected such as 'Golden Valley' for its yellow fresh and skin color, 'Gogu Valley', 'Juice Valley', and 'Rose Valley' for their red skin color, and 'Purple Valley' for its purple skin. Compared with world wide known processing cultivar 'Atlantic', 24 lines (or varieties) were selected for the potential potato processing industry due to their low reducing sugar contents (below 0.3％), high yield (above 4.0 ton/ha), and unique chip colors. Selected white chipping varieties were 'Taedong Valley', 'Kangshim Valley', and 'Kangwon Valley', which have 0.23％, 0.27％, and 0.29％ of reducing sugar contents, respectively. 'Bora Valley', having deep purple color in both skin and fresh, was selected for purple chip variety and has 0.26％ of reducing sugar content. Light yellow chip varieties (lines) were 'Rose Valley' and Valley 54, having 0.19％ and 0.269％ of reducing sugar content, respectively. For French frying potatoes, 'Stick Valley' of 0.22％ and Valley 72 of 0.151％ in reducing sugars were selected. All of these selected lines and 'Valley' varieties can be used as parents to improve potato genetic resources and to develop better varieties with unique traits and colors.

• Korean Journal of Food Science and Technology
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• v.37 no.4
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• pp.636-641
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• 2005

Mulberry leaves, high in dietary fiber and some nutritional materials, are thought to have hypocholesterolemic effect. Therefore, effect of mulberry leaf powder on serum lipid profiles were studied using rats with diet-induced hypercholesterolemia. Male Sprague-Dawley rats were fed AIN-93 diet (control group), and diets containing high-cholesterol and 0% mulberry leaves powder, high-cholesterol and 5% mulberry leaves powder, and high-cholesterol and 10% mulberry leaves powder for 4 weeks. Hypercholesterolemia was induced by adding 1% cholesterol and 0.5% cholic acid to all diets except in control group. Although no differences were observed in food intake and initial body weight among groups, mulberry leaf treatment resulted in significant decreases in food efficiency ratio and body weight gain. Mulberry leaf treatment decreased serum lipid profiles, atherogenic index, cardiac risk factor, low density lipoprotein cholesterol ratio, serum aspartate transaminase, and liver lipid levels. High density lipoprotein cholesterol, total cholesterol, serum HDL-cholesterol, and fecal lipid levels increased, suggesting mulberry leaves could improve hyperlipidemia and liver action, thereby proventing cardiovascular disease.

• Korean Journal of Food Science and Technology
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• v.35 no.4
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• pp.604-609
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• 2003

In order to investigate the transfer rate of calcium into rice and the effect of soaking conditions-temperature (20, 30, 40, 50 and $60^{\circ}C$, $X_1$), calcium concentration of soaking solution (0, 250, 500, 750 and 1000 mg/L, $X_2$) and soaking time (5, 10, 15, 20 and 25 min, $X_3$), moisture absorption rate, hardness and calcium content of rice after soaking were analyzed. When the soaking temperature and time were increased the moisture absorption rate also increased (p<0.01). Quadratic and interaction effects on the moisture absorption rate among variables were highly significant, within 5%. The predictive model for moisture absorption rate $(Y_1)$ was as follows: $Y=16.14+0.78X_1+1.24X_3-0.23X_1{^2}+0.14X_2{^2}-0.42X_3X_1-0.38X_3{^2}\;(R^2=0.9123)$. Hardness was decreased as soaking time and temperature increased. Calcium contents of soaked rice increased as temperature, the calcium concentration of soaking solution and soaking time were increased (p<0.01). Also the interactive effect between soaking time and calcium concentration of soaking solution was high. The predictive model for calcium content $(Y_3)$ was as follows: $Y_3=470.80+110.87X_1+123.47X_2+52.29X_3-7.42X_1{^2}-14.87X_2{^2}-9.49X_3X_2-20.57X_3{^2}\;(R^2=0.9840)$. From the results in this study, if adults and children take 400 g of calcium enriched rice with 600 mg/kg and $700{\sim}900\;mg/kg$, respectively, they can expect to take more calcium than the recommended intake without other calcium reinforcing agents.

• Journal of Life Science
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• v.17 no.11
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• pp.1562-1570
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• 2007

This experiment was conducted to develop fertilizer which promotes plant growth as well as suppressing pathogenic fungi. The fertilizer was made from the mixture of Ju-Back (Korean rice wine cake) and indigenous rhizosphere-bacterium. The main ingredients of Ju-Back were investigated as 6.04% total nitrogen, 42.59% total carbohydrate, 1.01% available phosphate, 73.42% organic matter, 7.72% potassium oxide, 1.35% calcium oxide, 0.53% magnesium oxide. The enzyme activities of Ju-Back were estimated to be 980 units/g for ${\alpha}-amylase$, 300 units/g for glucoamylase, and 1800 units/g for acid pretense. Indigenous rhizosphere bacteria which produced antifungal agent were isolated from soil, and was selected KMU-13 strain which can antagonize against various plant pathogenic fungi (Botrytis cinerea KACC 40573, Sclerotinia sclerotiorum KACC 41065, Fusairum oxysporum KACC 40052, Pythium aphanidermatum KACC 40156, Phytophthora capsici KACC 40476 and Glomerella cingulata KACC 40299). KMU-13 strain was identified as Bacillus subtilis KMU-13 by biochemical and 16s rDNA analysis. The organic fertilizer was made as prototype which was composed 20% Ju-Back, 70% carrier, 9.7% microorganism cultivated solution, 0.3% trace-element. We also investigated an application of fertilizer using Ju-Back for cultivating lettuce (Lactuca sativar) which were grown in three soil conditions that had chemical fertilizer, barnyard manure, lime power, urea, potassium chloride and superphosphate as a control, the whole quantity (80 kg/10a) of posted fertilizer with the control and the half quantity (40 kg/10a) with the control. The growth characteristics were examined and analysed with several weeks interval from 3 weeks to 8 weeks on head length (cm), head width (cm/head), number of leaf and fresh weight (g/plant). The results are summarized as follows. The head width and fresh weight of lettuce were the highest at posted fertilizer 1 (whole quantity) was applied chemical, organic matter (Ju-Back) and carrier. The head length was the highest at posted fertilizer 2 (whole quantity) was applied Ju-Back only.

• Journal of Life Science
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• v.21 no.9
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• pp.1234-1243
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• 2011

Liriope platyphylla has been used in oriental medicine as an effective medical plant to improve symptoms of cough, sputum production, neurodegenerative disorders, obesity and diabetes for long time. In order to investigate the effects of novel extracts on nerve growth factors (NGF)-stimulated neuritic outgrowth, the alteration of NGF expression and NGF receptor signaling pathway were detected in neuroblastoma cells and C57BL/6 mice. Of a total of 13 novel extracts, 4 extracts (LP-E, LP-M, LP-M50, LP2E17PJ) showed high viability on MTT assay. Also, all of these extracts induced NGF secretion and NGF mRNA expression in neuroblastoma cells. However, the NGF-induced neuritic outgrowth from PC12 cells was only stimulated by LP-E, LP-M and LP-M50. Furthermore, we selected LP-M as a best candidate, based on method and amounts of extraction, in order to verify its effect in mice. C57BL/6 mice were treated with 50 mg/kg of LP-M for 2 weeks and the effects on NGF regulation were analyzed with various methods. The expression of NGF mRNA was significantly increased in LP-M treated mice compared to vehicle treated mice. Also, the signaling pathway of p75NTR was inhibited in the cortex by LP-M treatment, with no change in the hippocampus of brain. However, the signaling pathway of TrkA was dramatically activated in only hippocampus via LP-M treatment. Therefore, these results suggest that the novel four extracts of L. platyphylla may contribute to the regulation of NGF expression and secretion in neuronal cells. LP-M was especially considered to be an excellent candidate for a neurodegenerative disease-therapeutic drug.