• Bulletin of the Korean Chemical Society
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• v.29 no.2
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• pp.417-421
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• 2008

The efficient synthesis of four mesitylene-based receptors 1-4 and their potentiometric response characteristics to alkali metal, alkaline earth metal, and transition metal ions, under various pH conditions are outlined. Receptor 1-based electrode exhibited more sensitive response to Ag+ ion (49 mV/decade of range from 10-6 to 10-2 M) than the 2-based electrode (47 mV/decade of range from 3 ´ 10-5 to 10-2 M), while the 3- and 4-based ones revealed sub-Nernstian below 40 mV/pAg+. All electrodes showed substantial responses to Ag+ ion under acidic condition, but there was almost nil-response to other transition metal ions (Fe2+, Co2+, Zn2+, Ni2+, Pb2+, Cd2+, Cu2+ and Hg2+). The association constant of receptor 1 toward Ag+ ion, measured by 1H NMR titration, showed the largest value (200 M-1) among the tested receptors. The results were interpreted with semi empirically-modeled structures.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.195-196
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• 2008

Doping depth, doping concentration, and resistivity of crystalline silicon solar cell are variables which take important portion in cell's efficiency. To get highly efficient solar cell, PC1D is used to calculate $I_{sc}$, $V_{oc}$, and $P_{max}$. Depth factor, peak doping, and base resistivity was used as variables. As a result, the optimized value of emitter peak doping is $1\times10^{19}cm^{-3}$, depth factor is $1{\mu}m$, and base $\rho$ is $ 0.1\Omega$-cm. Under the optimized condition, the solar cell gets efficiency 19.03(%).

• Journal of the Korean Chemical Society
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• v.32 no.4
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• pp.291-296
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• 1988

Rates of the reaction for p-nitrobenzyl chloride, benzyl chloride and p-methylbenzyl chloride with pyridine in DMF solvent have been measured by an electric conductivity method at $40^{\circ}\;and\;50^{\circ}C$ under various pressures. From those rate constants, the activation parameters ${\Delta}V^{\neq},\;{\Delta}{\beta}^{\neq},\;{\Delta}H^{\neq},\;{\Delta}S^{\neq},\;{\Delta}G^{\neq}$) were evaluated. ${\Delta}V^{\neq}\;and\;{\Delta}{\beta}^{\neq}$ are both negative valued, but ${\Delta}H^{\neq}$ is positive and ${\Delta}S^{\neq}$ is large negative value. From the evaluation of the initial state and transition state which was resulted from substituents and pressure, it was found that this reaction proceeds through bimolecular reaction.

• Korean Journal of Materials Research
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• v.21 no.12
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• pp.639-643
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• 2011

Zinc oxide as an optoelectronic device material was studied to utilize its wide band gap of 3.37 eV and high exciton biding energy of 60 meV. Using anti-site nitrogen to generate p-type zinc oxide has shown a deep acceptor level and low solubility. To increase the nitrogen solubility in zinc oxide, group 13 elements (aluminum, gallium, and indium) was co-added to nitrogen. The effect of aluminum on nitrogen solubility in a $3{\times}3{\times}2$ zinc oxide super cell containing 72 atoms was investigated using density functional theory with hybrid functionals of Heyd, Scuseria, and Ernzerhof (HSE). Aluminum and nitrogen were substituted for zinc and oxygen sites in the super cell, respectively. The band gap of the undoped super cell was calculated to be 3.36 eV from the density of states, and was in good agreement with the experimentally obtained value. Formation energies of a nitrogen molecule and nitric oxide in the zinc oxide super cell in zinc-rich conditions were lower than those in oxygen-rich conditions. When the number of nitrogen molecules near the aluminum increased from one to four in the super cell, their formation energies decreased to approach the valence band maximum to some degree. However, the acceptor level of nitrogen in zinc oxide with the co-incorporation of aluminum was still deep.

• Korean Journal of Ecology and Environment
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• v.33 no.1 s.89
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• pp.38-50
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• 2000

Seasonal changes of the phytoplankton and the periphyton community were investigated from August 1998 to April 1999 at five stations at the Suer stream in Kwangyang. A total of 112 species of phytoplankton were identified. Of those, the diatoms were present at all stations but the green algae, the bluegreen algae, and the dioflagellates were present at Station 4 and Station 5 more frequently than the other stations. The phytoplankton standing crops varied from 10,100 cells/1 at Station 4 in April 1999 to 1,489,100 cells/1 at Station 4 in October 1998. The seasonal variation patterns of phytoplankton standing crops were different among stations as well as the pattern of presence. The dominant species were as follows: Achnanthes minutissima, Aulacoseira distans v. alpigena, Cocconeis placentula v. lineata, Cymbella minuta, C. silesiaca, Fragilaria arcus v. recta, Peridinium cinctum, Rhizosofenia longiseta, Synedra rumpens and filamentous algae. Of those, Achnanthes minutissima, Rhizosolenia longiseta, Synedra rumpens and filamentous algae showed the highest rate of occupation in the phytoplankton standing crops during the investigated periods. A total of 99 species of periphyton were identified. Among those, the diatoms of the periphyton community were observed frequently rather than those of the phytoplankton community. The ecological indicator values showed ${\bate}$-mesosaprobous in saprobity and was close to eutraphentic in trophic state. There were no considerable differences between the ecological indicator values by planktonic diatoms and periphytic diatoms.

• Journal of Navigation and Port Research
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• v.28 no.3
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• pp.213-219
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• 2004

In this paper, a LNA(Low Noise Amplifier) has been developed, which is operating at L-band i.e., 1452∼1492 MHz for satellite DAB(Digital Audio Brcadcasting) receiver. The LNA is designed to improve input and output reflection coefficient and VSWR(Voltage Standing Wave Ratio) by balanced amplifier. The LNA consists of low noise amplification stage and gain amplification stage, which make a using of GaAs FET ATF-10136 and VNA-25 respectively, and is fabricated by hybrid method. To supply most suitable voltage and current, active bias circuit is designed Active biasing offers the advantage that variations in $V_P$ and $I_{DSS}$ will not necessitate a change in either the source or drain resistor value for a given bias condition. The active bias network automatically sets $V_{gs}$ for the desired drain voltage and drain current. The LNA is fabricated on FR-4 substrate with RF circuit and bias circuit, and integrated in aluminum housing. As a reults, the characteristics of the LNA implemented more than 32 dB in gain. 0.2 dB in gain flatness. lower than 0.95 dB in noise figure, 1.28 and 1.43 each input and output VSWR, and -13 dBm in $P_{1dB}$.

• Journal of Korean Society of Forest Science
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• v.99 no.1
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• pp.131-135
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• 2010

This study was carried out to establish a proper cultivation condition and diagnose the drought-tolerance of three wild edible greens belonging to genus of Ligularia by using pressure-volume curves methods. The result of the original bulk osmotic pressure at maximum turgor ${\Psi}_{\circ}{^{sat}}$ was -0.8 MPa in Ligularia fischeri and L. stenocephala, which was somewhat lower than the value, -0.7 MPa, in L. fischeri var. spiciformis. In addition, the values of the osmotic pressure at incipient plasmolysis ${\Psi}_{\circ}{^{tlp}}$ in L. fischeri and L. stenocephala, both of which were -0.9 MPa, These were slightly lower than that of -0.8 MPa in L. fischeri var. spiciformis. On the other hand, it appeared that the values of maximum bulk modulus of elasticity $E_{max}$ of L. fischeri and L. stenocephala were approximately two times higher than that of L. fischeri var. spiciformis. However, There was a distinct difference between the values of the relative water contents in these three species. Therefore, Ligularia spp, occurring incipient plasmolysis in the high water contents, have a relatively low property of drought-tolerance, suggesting that growth of those Ligularia spp. are appropriate for relative moisture forest.

• Food Science and Preservation
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• v.20 no.5
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• pp.650-658
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• 2013

Apple juices were sterilized by continuous pulsed electric field (PEF) treatments of pulse width of 25 ${\mu}s$ at electric field intensity of 20.0 kV/cm, and with the varied pulse frequencies of 35 Hz (40 kJ/L), 55 Hz (70 kJ/L), 72 Hz (100 kJ/L) and 85 Hz (130 kJ/L). The PEF treatments of apple juice reduced the microbial counts from 5.3 log CFU/mL of initial state to 3.0 log CFU/mL after PEF treatment at energy density of 130 kJ/L. Also yeast and fungi after PEF treatments were reduced from 5.3 log CFU/mL to 3.0 log CFU/mL and Escherichia coli were from 5.3 log CFU/mL of initial state to 4.7 log CFU/mL to < $10^1$ CFU/mL. The soluble solids and free sugars did not significantly differ (p<0.05) depending on conditions of PEF treatment. The total phenolic contents and antioxidant activity such as the DPPH and ferric reducing antioxidant power (FRAP) by PEF treatments were significantly partly reduced, but the PEF-reduced value came in smaller quantities than the heat treatment at $65^{\circ}C$. The iterative PEF treatments with pulse width of 25 ${\mu}s$ and pulse frequency of 85 Hz at electric field intensity of 20.0 kV/cm showed limited in microbial reduction. Also, total phenolic contents and antioxidant activity such as DPPH and FRAP, significantly decreased depending on treatment numbers of PEF (p<0.05).

• Korean Journal of Plant Resources
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• v.23 no.4
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• pp.374-378
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• 2010

Determining plant moisture characteristics is an essential study not only for cultivation, but also for ex-situ conservation. In this study, employing pressure-volume curve we examined moisture characteristics of Rhododendron micranthum, known as rare plant, with the aim of its ex-situ conservation. Several individuals growing in Mt. Worak, Youngwol-gun Yeonha-ri and Bongwa-gun Seokpo-ri were selected for this study, from which we collected leaves. The original bulk osmotic pressure at maximum turgor(${{\Psi}_o}^{sat}$)was -1.5 MPa in those of Mt. Worak and Seokpo-ri, which is somewhat lower than that of Yeonha-ri(-1.2 MPa). It appeared that the osmotic pressure at incipient plasmolysis(${{\Psi}_o}^{tlp}$) of leaves collected in both Mt. Worak and Seokpo-ri were -1.29 MPa, and -1.26 MPa, respectively, which are lower than that of Yeonha-ri(-1.02MPa). Maximum bulk modulus of elasticity($E_{max}$) was 14.0 MPa, 8.67 MPa in leaves collected from both Seokpo-ri and Mt. Worak, respectively, those value of which were approximately 3 times higher than that of Yeonha-ri(4.00 MPa). The values of $RWC_{tlp}$(Relative water content at incipient plasmolysis) of leaves collected in three areas, were roughly 83%, suggesting that Rhododendron micranthum has relatively high capability of containing water. Our finding on moisture characteristics of Rhododendron micranthum is similar to those of other Rhododendron spp. We suggest that individuals growing in both Worak and Seokpo-ri, are preferable to those in Yeonha-ri for ex-situ transplantation since those individuals are found to have better drought resistance.

• Korean Journal of Food Science and Technology
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• v.37 no.2
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• pp.189-193
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• 2005

Effect of enzyme treatment on physicochemical characteristics of small tea bean percolate were estimated. Three types of small red bean percolate were prepared by heat treatment for 30 min at $95^{\circ}C$ (1st), 30 min at $95^{\circ}C$ (2nd), and 40 min at $120^{\circ}C$ (3rd). They were then treated with 0.5% ${\alpha}-amylase$ (v/v) for 4 hr at $108^{\circ}C$ (${\alpha}-amylase$ treatment), then with 0.5% ${\beta}-amylase$ (v/v) for 4 hr at $60^{\circ}C$ (${\alpha}-$ and ${\beta}-amylase$ treatment). Crude saponin contents of 1st-3rd percolates were 0.82, 1.44, and 1.52 mg/g, respectively. ${\circ}Brix$ of small red bean percolates treated with enzymes increased to $0.8-1.2\;{\circ}Brix$ with 2nd and 3rd percolates showing no significant difference between ${\alpha}-amylase$ and ${\alpha}-$ and ${\beta}-amylase$ treatments. pH of 3rd percolate treated with ${\alpha}-$ and ${\beta}-amylase$ decreased from initial 6.2 to 4.7. Hunter L value of small red bean percolate treated with ${\alpha}-$ and ${\beta}-$ decreased, whereas a and b values increased. Small red bean beverage made with 3rd percolate showed high score in flavor, taste, and overall acceptability. Results suggest small red bean percolate treated with enzymes could be used for preparation of small red bean beverage.