• Ocean and Polar Research
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• v.43 no.3
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• pp.99-111
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• 2021

Occurrence of epiphytic dinoflagellates (EPDs) in coastal waters off Jeju was first reported in 2011 based on 45 substrate samples from 24 macroalgal species. When re-analyzing, the extreme heterogeneous distribution of whole and genus-specific EPDs was reconfirmed across the sampling stations and substrate macroalgal species, as well as even across substrate samples of the same species. Abundance maximum of an EPD genus (cells g-wwt^-1) at a fixed surface-to-volume ratio (SA/V ratio) of the macroalgal species increased as the SA/V ratio increased up to 500 (cm² cm^-3). However, the abundance maximum of Ostreopsis further increased even in the MG2 (morphological group 2) macroalgae with the SA/V ratios over 500. The number of substrate macroalgal species on the plane of the MG and sampling station was more or less evenly scattered than the average EPD abundance, which was primarily driven by Gambierdiscus and Ostreopsis. Of the total EPD abundance of the five stations, 90.6% were represented by the two most common and abundant genera, Gambierdiscus and Ostreopsis, each accounting for 41.6% and 49.0%. Spatially, 95.9% of the total EPD abundance was found in St. 4 and St. 5, of which St. 4 with higher water temperature had more Ostreopsis spp. (31.8%), and St. 5 with higher salinity had more Gambierdiscus spp. (27.3%). Thus, the environmental transition to favorable T-S condition to MG2, the thin filamentous macroalgal group with very high SA/V ratios, is thus likely to support further success in EPD genera led by Ostreopsis in the coastal waters of Jeju.

• Food Science and Preservation
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• v.16 no.6
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• pp.789-796
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• 2009

Benzoic acid (BA) and sorbic acid (SA) are the preservatives most commonly used in food. Although BA and SA are generally safe, some previous studies have shown that consumption of excessive amounts of these food additives can be a health hazard. The aim of this study was to determine the amounts of BA and SA in processed foods in Korea. Different brands of fruit juice, yogurt, cheese, dried fruits, jam, and margarine were purchased at a local market in Daejeon, Korea. Samples were analyzed by high-performance liquid chromatography (HPLC) using a UV detector. Chromatographic separation was achieved with a C18 column. Methanol acetate buffer (pH 4.4) at a 35:65 v/v ratio was used as the initial mobile phase to elute BA and SA. The detector wavelength was set at 254 nm. The average test results observed for BA concentrations in fruit juice, yogurt, cheese, dried fruits, jam, and margarine were $40.26{\pm}0.02$, $2.07{\pm}0.06$, $0.02{\pm}0.09$, $0.36{\pm}08$, $265.30{\pm}0.02$, and $27.34{\pm}0.08\;mg/kg$, respectively. Average concentrations of SA in these samples were $0.92{\pm}0.06$, $1.06{\pm}0.07$, $7.30{\pm}0.01$, $14.14{\pm}0.08$, $25.65{\pm}0.06$, and $4.81{\pm}0.07\;mg/kg$, respectively. Thus, the average levels of BA and SA in the studied food items were lower than the KFDA-permitted limits. Moreover, the estimated daily intake of both BA and SA by a typical consumer were below the maximum recommended daily values.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.11
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• pp.1005-1009
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• 2006

High quality three-dimensional (3D) heterostructures were constructed by selective area (SA) molecular beam epitaxy (MBE) using a specially patterned GaAs (001) substrate to improve the efficiency of tarrier transport. MBE growth parameters such as substrate temperature, V/III ratio, growth ratio, group V sources (As2, As4) were varied to calibrate the selective area growth conditions and the 3D GaAs-AlGaAs heterostructures were fabricated into the ridge type and the V-groove type. Scanning micro-photoluminescence $({\mu}-PL)$ measurements and the following analysis revealed that the gradually (adiabatically) coupled 1D-2DEG (electron gas) field effect transistor (FET) system was successfully realized. These 3D-heterostructures are expected to be useful for the realization of high-performance mesoscopic electronic devices and circuits since it makes it possible to form direct ohmic contact onto the (quasi) 1D electron channel.

• Korean Journal of Ecology and Environment
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• v.35 no.1 s.97
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• pp.28-35
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• 2002

The effect of physical parameters on water quality was analyzed using monitoring data of 193 agricultural reservoirs. The retention time of reservoirs ($t_d$) ranged between 10 and 140 days, and the ratio of drainage area (DA) to reservoir surface area (SA) was between 10 and 120. Both ratios of DA/SA and total area (TA)/ reservoir storage (ST) in Korean agricultural reservoirs were relatively greater than those in natural lakes in other countries. As retention time was plotted against DA/SA ratio, it was shorter in Korean reservoirs than natural lakes. The semi-logarithmic relationship between TA/SA and t>$t_d$ was $t_d\;=\;42.21(TA/ST)^{-1}$ (n = 50, $R^2\;=\;0.89$). While areal loading of total phosphorus (TP) was below $4\;gTP{\cdot}m^{-2}{\cdot}yr^{-1}$ in general, it exceeded $10\;gTP{\cdot}m^{-2}{\cdot}yr^{-1}$ in reservoirs where DA/SA ratio was greater than 100, which implies that areal loading of TP increases as DA/SA ratio increases. Chl-a concentration was positively related with the mean depth of reservoir, implying the higher Chl-a concentration with deeper the mean depth. Therefore, the deeper reservoir might be advantageous in water quality management perspective if other morphological conditions are similar. The empirical regression equation using physical parameters was also suggested in the estimation of TP concentration in the reservoirs. Combined information presented in this paper might be applicable to the water quality management in agricultural reservoirs.

• Proceedings of the KIEE Conference
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• 1997.07d
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• pp.1326-1329
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• 1997

In this paper, PNN-PZN-PZT ceramics were fabricated with various mole ratio of the PZT[$Pb(Zr_{1/2}Tid_{1/2})O_3$]. PNN [$Pb(Ni_{1/3}Nb_{2/3})O_3$] and PZN[$Pb(Ni_{1/3}Nb_{2/3})O_3$ powders prepared by double calcination and PZT powders prepared by molten-salt synthesis method. The formation rate of perovskite phase in PNN-PZN-PZT ceramics could be obtained about 92% at PZT 0.3 mole ratio. The relative permittivity of specimen with PZT 0.3 mole ratio was shown 5,320 and appeared the relaxor ferroelectric feature. The maximum piezoelectric coefficient $d_{31}$ to be used for evaluation the displacement of piezoceramics in PNN-PZN-PZT ceramics was $324{\times}10^{-12}$(C/V) at the vicinity of morphotropic phase boundary and was larger than that of solid PZT ceramics($120{\times}10^{-12}C/V$).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.167-168
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• 2006

High quality 3D-heterostructures were constructed by selective area (SA) molecular beam epitaxy (MBE) using a specially patterned GaAs (001) substrate. MBE growth parameters such as substrate temperature, V/III ratio, growth ratio, group V sources ($As_2$, $As_4$) were varied to calibrate the selective area growth conditions. Scanning micro-photoluminescence ($\mu$-PL) measurements and following analysis revealed that the gradually (adiabatically) coupled 2DEG-1D-1DEG field effect transistor (FET) system was realized. This 3D-heterostructure is very promising for the realization of the meso-scopic electronic devices and circuits since it makes it possible to form direct ohmic contact to the (quasi) 1DEG.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.4
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• pp.300-305
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• 2000

We have investigated the dielectric and electrical characteristics of palmitic acid(PA) stearic acid(SA) and arachidic acid(AA) Langmuir-Blodgett(LB) films because these fatty acid systems have a same hydrophilic group and a different hydrophobic one(methylene group or alkyl chain length). The fatty acid systems were used as LB films and the status of the deposited films was confirmed by evaluating the transfer ratio the UV absorption and the capacitance. The dielectric characteristics such as the frequency-capacitance characteristics and the dielectric dispersion and absorption characteristics of PA SA and AA through-plane were measured. The relative dielectric constants of PA, SA and AA LB films were about 3.0~4.6, 2.7~3.0 and 2.4~3.0 respectively. That is the relative dielectric constants were decreased in proportion to the chain length of methylene group. Also the dielectric dispersion and absorption of each fatty acid LB films have arisen from spontaneous polarization of dipole polarization in the range of 10$^4$~10$^{5}$ ［Hz］. The conductivity of PA, SA and AA LB films obtained from I-V characteristics were about 9$\times$10$^{-14}$ , 3$\times$10$^{-14}$ and 5$\times$10$^{-15}$ ［S/cm］. respectively. These results have shown the insulating materials and could control the conductivity y changing the length of methylene group. Also we have confirmed that the barrier height of fatty acid systems were almost the same ones obtained from dielectric characteristics.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.34 no.3
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• pp.157-165
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• 2008

In the previous study, the anti-oxidant activity of oxtract/fraction of Sueada aspparagoides(SA) and the stability test for the cream containing SA extract were investigated respectively[1,2]. In this study, the components of SA extract were analyzed by TLC, HPLC, and LC/ESI-MS/MS, $^1H$-NMR. TLC chromatogram of ethyl acetate fraction of SA extract revealed 5 bands $(SA1{\sim}SA5)$. HPLC chromatogram of aglycone fractions obtained from deglycoylation reaction of ethyl acetate fraction showed 2 bands (SAA 2 and SAA 1), which were identified as quercetin (composition ratio, 16.88%) and kaempferol (83.12%) in the order of elution time. Among 5 bands of TLC chromatogram, 4 bands $(SA2{\sim}SA5)$ also were Identified as kaempferol-3-O-glucoside (SA 2), quercetin-3-O-glucoside (SA3), kaempferol-3-O-rutinoside (SA 4), quercetin-3-O-rutinoside (SA 5) by LC/ESI-MS/MSMS/MS. respectively. The spectrum generated for SAA 1 by LC/ESI-MS/MS in the negative ion mode also gave the ion corresponding to the deprotonated aglycone $[M-H]^-$ (285m/z), the $^1H$-NMR spectrum contained signals [${\delta}$ 6.19 (1H, d, J=1.8Hz, H-6), ${\delta}$ 6.44 (1H, d, J=1.8Hz, H-8), ${\delta}$ 6.92 (2H, d, J=9.0Hz, H-3', 5'), ${\delta}$ 8.04 (2H, d, J=9.0Hz, H-2', 6', thus SAA 1 was identified as kaempferol. SAA 2 yielded the deprotonated agycone ion $[M-H]^-$ (301m/z), $^1H$-NMR spectrum showed signals [${\delta}$ 6.20 (1H, d, J=2.0Hz, H-6), ${\delta}$ 6.42 (1H, d, J=2.0Hz, H-8), ${\delta}$ 6.90 (1H, d, J=8.6Hz, H-5'), ${\delta}$ 7.55 (1H, dd, J=8.6, 2.2Hz, H-6'), ${\delta}$ 7.69 (1H, d, J=2.2Hz, H-2', thus SAA 2 was Identified as quercetin. In conclusion, with the anti-oxidant activity and the stability test reported previously, component analysis of SA extracts could be applicable to new cosmeceuticals.

• Journal of the Korean Solar Energy Society
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• v.31 no.2
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• pp.82-88
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• 2011

The artificial increase in the solar intensity incident on solar cells using lenses or mirrors can allow solar cells to generate equivalent power with a lower cost. There are two types of concentration optics for solar energy conversion. One is to use mirrors, and the other is to use Fresnel lenses. The gains that can be achieved with a Fresnel lens or a parabolic mirror are compared. The result showed the gains are comparable and the two configurations were developed competitively. In application areas of Fresnel lenses as solar concentrators, several variations of design were devised and tested. Some PV systems still use commercially available flat Fresnel lenses as concentrators. A convex linear Fresnel lens to improve the concentration ratio and the efficiency is devised and flat linear Fresnel lens in thermal energy collection is utilized. In this study, we designed and optimized flat Fresnel lens and the 'light pipe' to develop 500X concentrated solar PV system. In the process, we compare the transmission efficiencies according to groove types. We performed rigorous ray tracing simulation of the flat Fresnel lenses. The computer aided simulation showed the 'grooves in case' has the better efficiency than that of 'grooves out case'. Based on the ray-trace results we designed and manufactured sample Fresnel lenses. The optical performance were measured and compared with ray-trace results. Finally, the optical efficiency was measured to be above 75%. All the design and manufacturing were performed based on that InGaP/InGaAs/Ge triple junction solar cell is used to convert the photon energy to electrical power. Field test will be made and analyzed in the near future.

• Journal of Sensor Science and Technology
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• v.21 no.6
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• pp.408-412
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• 2012

An in-line dispersive delay line (DDL) demands low and controllable reflectivity of the reflectors, especially if the surface acoustic wave (SAW) propagates all the way along the reflecting structure. The metal reflectors are usually too strong and introduce too much attenuation in such a device. The proposed solution of this problem is to spatially separate the acoustic channels for different frequencies with the help of Fan-shaped Transducers (FIDT) and to use narrow open metal reflectors to reduce reflectivity. Special arrangement of FIDT is performed to use 180-deg. reflection of the SAW. Narrow open metal strips with a metallisation ratio of the order of 20% are used as reflectors with small and controllable reflectivity. Reflectivity of such strips is estimated both theoretically and experimentally. Experimental performance of the proposed DDL is presented.