• Korean Journal of Materials Research
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• v.11 no.5
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• pp.427-430
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• 2001

We prepared 10cm-diameter Si(100)/500 $\AA$-Si$_3$N$_4$/Si(100) wafer Pairs adopting 500 $\AA$ -thick Si$_3$N$_4$layer as insulating layer between single crystal Si wafers. Si3N, is superior to conventional SiO$_2$ in insulating. We premated a p-type(100) Si wafer and 500 $\AA$ -thick LPCVD Si$_3$N$_4$∥Si (100) wafer in a class 100 clean room. The cremated wafers are separated in two groups. One group is treated to have hydrophobic surface and the other to have hydrophilic. We employed a FLA(fast linear annealing) bonder to enhance the bond strength of cremated wafers at the scan velocity of 0.1mm/sec with varying the heat input at the range of 400~1125W. We measured bonded area using a infrared camera and bonding strength by the razor blade crack opening method. We used high resolution transmission electron microscopy(HRTEM) to probe cross sectional view of bonded wafers. The bonded area of two groups was about 75%. The bonding strength of samples which have hydrophobic surface increased with heat input up to 1577mJ/$m^2$ However, bonding strength of samples which have hydrophilic surface was above 2000mJ/$m^2$regardless of heat input. The HRTEM results showed that the hydrophilic samples have about 25 $\AA$ -thick SiO layer between Si and Si$_3$N$_4$/Si and that maybe lead to increase of bonding strength.

• Journal of Bio-Environment Control
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• v.27 no.4
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• pp.400-406
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• 2018

In this experiment the effect of supplemental lighting on the growth and yield of cucumber (Cucumis sativus L. 'Fresh') plants during low radiation period of winter season were investigated in glasshouses using common high-pressure sodium (HPS) lamps and newly developed plasma lighting system (PLS) lamps. Plants grown without supplemental lighting were considered as a control. Supplemental lighting was provided from November 20th, 2015 to March 15th, 2016 to ensure 14-hour photoperiod (natural+supplemental light), also lamps were operated automatically when the outside sun radiation levels were less than $100W{\cdot}m^{-2}$. Spectral analysis showed that HPS lamp had a discrete spectrum, lacked of the radiation in the 400-550 nm wave band (blue-green light), but had a high output in the orange-red region (550-650 nm). A higher red light output resulted in an increased red to far-red (R/FR) ratio in HPS lamp. PLS had a continuous spectrum and had a peak radiation in green region (490-550 nm). HPS has 12.6% lower output in photosynthetically active radiation (PAR) but 12.6% higher output in near infra-red (NIR) spectral regions compared to PLS. Both HPS and PLS lamps emitted very low levels of ultra-violet radiation (300-400 nm). Supplemental lighting both from HPS and PLS lamps increased plant height, leaf number, internode number and dry weight of cucumber plants compared to control. Photosynthetic activity of cucumber plants grown under two supplemental lighting systems was comparable. Number of fruits per cucumber plant (fruit weight per plant) in control, PLS, and HPS plots were 21.2 (2.9 kg), 38.7 (5.5 kg), and 40.4 (5.6 kg), respectively, thereby increasing yield by 1.8-1.9 times in comparison with control. An analysis of the economic feasibility of supplemental lighting in cucumber cultivation showed that considering lamp installation and electricity costs the income from supplemental lighting increased by 37% and 62% for PLS and HPS lamps, respectively.

• Journal of the Korean Vacuum Society
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• v.17 no.6
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• pp.538-543
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• 2008

Recently a nano-scale diamond is possible to manufacture forms of powder(below 100 nm) by new processing of explosion or deposition method. Using a sintering of nano-scale diamond is possible to manufacture of grinding tools. We have need of a processing development of coated uniformly inorganic to prevent an abnormal grain growth of nano-crystal and bonding obstacle caused by sintering process. This paper, in order to improve the sintering property of nano-scale diamond, we coated ZnO thin films(thickness: $20{\sim}30\;nm$) in a vacuum by ALD(atomic layer deposition) Economically, in order to deposit ZnO all over the surface of nano-scale diamond powder, we used a new modified fluidized bed processing replaced mechanical vibration effect or fluidized bed reactor which utilized diamond floating owing to pressure of pulse(or purge) processing after inserted diamond powders in quartz tube(L: 20 mm) then closed quartz tube by porosity glass filter. We deposited ZnO thin films by ALD in closed both sides of quartz tube by porosity glass filter by ALD(precursor: DEZn($C_4H_{10}Zn$), reaction gas: $H_2O$) at $10^{\circ}C$(in canister). Processing procedure and injection time of reaction materials set up DEZn pulse-0.1 sec, DEZn purge-20 sec, $H_2O$ pulse-0.1 sec, $H_2O$ purge-40 sec and we put in operation repetitive 100 cycles(1 cycle is 4 steps) We confirmed microstructure of diamond powder and diamond powder doped ZnO thin film by TEM(transmission electron microscope) Through TEM analysis, we confirmed that diamond powder diameter was some $70{\sim}120\;nm$ and shape was tetragonal, hexagonal, etc before ALD. We confirmed that diameter of diamond powders doped ZnO thin film was some $70{\sim}120\;nm$ and uniform ZnO(thickness: $20{\sim}30\;nm$) thin film was successfully deposited on diamond powder surface according to brightness difference between diamond powder and ZnO.

• Journal of the Korean Institute of Gas
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• v.17 no.4
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• pp.58-69
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• 2013

This paper presents production data analysis for two production wells located in the shale gas field, Canada, with the proper analysis method according to each production performance characteristics. In the case A production well, the analysis was performed by applying both time and superposition time because the production history has high variation. Firstly, the flow regimes were classified with a log-log plot, and as a result, only the transient flow was appeared. Then the area of simulated reservoir volume (SRV) analyzed based on flowing material balance plot was calculated to 180 acres of time, and 240 acres of superposition time. And the original gas in place (OGIP) also was estimated to 15, 20 Bscf, respectively. However, as the area of SRV was not analyzed with the boundary dominated flow data, it was regarded as the minimum one. Therefore, the production forecasting was conducted according to variation of b exponent and the area of SRV. As a result, estimated ultimate recovery (EUR) increased 1.2 and 1.4 times respectively depending on b exponent, which was 0.5 and 1. In addition, as the area of SRV increased from 240 to 360 acres, EUR increased 1.3 times. In the case B production well, the formation compressibility and permeability depending on the overburden were applied to the analysis of the overpressured reservoir. In comparison of the case that applied geomechanical factors and the case that did not, the area of SRV was increased 1.4 times, OGIP was increased 1.5 times respectively. As a result of analysis, the prediction of future productivity including OGIP and EUR may be quite different depending on the analysis method. Thus, it was found that proper analysis methods, such as pseudo-time, superposition time, geomechanical factors, need to be applied depending on the production data to gain accurate results.

• Microbiology and Biotechnology Letters
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• v.48 no.2
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• pp.205-214
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• 2020

Cyanobacteria are microorganisms which have important roles in the nitrogen cycle due to their ability to fix nitrogen in water and soil ecosystems. They also produce valuable materials that may be used in various industries. However, some species of cyanobacteria may limit the use of water resources by causing harmful algal blooms in water ecosystems. Many culture collection depositories provide cyanobacterial strains for research, but their systematic preservation is not well-developed in Korea. In this study, we developed a method for the cryopreservation of the cyanobacteria Trichormus variabilis (syn. Anabaena variabilis), using alginate microcapsules. Two approaches were used for the experiments and their outputs were compared. One of the methods involved the cryopreservation of cells using only a cryoprotectant and the other used the cryoprotectant within microcapsules. After cryopreservation for 35 days, cells preserved with both methods were successfully regenerated from the initial 1.0 × 10⁵ cells/ml to a final concentration of 6.7 × 10⁶ cells/ml and 1.1 × 10⁷ cells/ml. Irregular T. variabilis shapes were found after 14 days of regeneration. T. variabilis internal structures were observed by transmission electron microscopy (TEM), revealing that lipid droplets were reduced after cryopreservation. The expression of the mreB gene, known to be related to cell morphology, was downregulated (54.7%) after cryopreservation. Cryopreservation using cryoprotectant alone or with microcapsules is expected to be applicable to other filamentous cyanobacteria in the future.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.6
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• pp.434-441
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• 2014

This study is purposed to measure airborne asbestos concentrations at demolition sites and surrounding areas of asbestos containing buildings in Seoul and examine whether the measurement results correspond with allowable exhaust standard for asbestos of the Asbestos Safety Control Act. The airborne asbestos concentrations for 37 sites were below the detection limit ($7fiber/mm^2$) in 101 (35%) out of 288 samples. The whole average airborne asbestos concentration in 37 sites was $0.003{\pm}0.002f/cc$(max 0.0013 f/cc) and almost the whole airborne asbestos concentrations were satisfied with allowable exhaust standard for asbestos, 0.01 f/cc, of the Asbestos Safety Control Act. So possibility of asbestos exposure is not yet a major concern at current levels for sites demolished of asbestos containing buildings in Seoul. Looking at each sampling point, the average airborne asbestos concentrations in boundary line of site, entrance of sanitation, around the workplace (in), around the workplace (out), negative pressure units, storage area for waste, outlet for waste and residential area of residents were respectively $0.002{\pm}0.002f/cc$, $0.004{\pm}0.002f/cc$, $0.004{\pm}0.002f/cc$, $0.004{\pm}0.002f/cc$, $0.004{\pm}0.002f/cc$, $0.005{\pm}0.004f/cc$, $0.005{\pm}0.003f/cc$ and $0.003{\pm}0.002f/cc$. As a result, all sampling points of study were satisfied with allowable exhaust standard for asbestos, 0.01 f/cc, of the Asbestos Safety Control Act.

• The Korean Journal of Pesticide Science
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• v.5 no.2
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• pp.45-50
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• 2001

In recent, non virus-induced mosaic symptoms(NVMS) on potato leaves were observed in the seed potato fields, and its incidence rate was $5{\sim}20%$ nationwide. It made difficult to rogue out virus-infected plants, and caused much arguments between seed potato production farmers and seed potato inspectors. The objectives of these experiments were to find out the causes of NVMS, and also to induce mosaic symptom(phytotoxicity) on potato plants by treatment of several herbicides. No significant correlations were found between incidence rates of NVMS and values from soil analyses; soil pH, soil EC, organic matter content, and contents of inorganic constituents($P_2O_5,\;NO_3$, Ca, Mg, K) in the soil around the potato planted. The examinations by ELISA, virus indicator plants, and TEM showed that NVMS on potato leaves was not caused by the viruses infection. But, the use of herbicides could induced the NVMS on potato leaves. The incidence rates of potato treated with pendimethalin linuron of 400 mL/10 a, pendimethalin of 200 mL/10 a, pendimethalin.oxadiazon of 300 mL/10 a, and control were 61.1%, 47.2%, 19.4%, and 1.4%, respectively. Based on these results, we confirmed that the treatment of pendimethalin alone and in mixture with other herbicides were the reason of NVMS on potato leaves. The yields among test plots were similar except dicamba treated plot, which decreased by about 23% compared to control plot. When their progenies harvested in 1999 were planted in the following season, no symptoms of mosaic were observed.

• Applied Biological Chemistry
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• v.43 no.3
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• pp.218-224
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• 2000

The efforts were made to optimite ethanol extraction from persimmon leaf with the time of extraction$(1.5{\sim}2.5\;hrs)$, the temperature of extraction$(70{\sim}90^{\circ}C)$, and the concentration of ethanol$(0{\sim}40%)$ as three primary variables together with several functional characteristics of persimmon leaf as reaction variables. The conditions of extraction was best fitted by using response surface methodology through the center synthesis plan, and the optimal conditions of extraction were established. The contents of soluble solid and soluble tannin went up as the concentration of ethanol went up and the temperature of extraction went down, and the turbidity went down as the concentration of ethanol went down. Electron donation ability was hardly affected by the extraction temperature and had the tendency to go up as the concentration of ethanol went up. The inhibitory activity of xanthine oxidase(XOase) had the tendency to go up as both the concentration of ethanol and the temperature of extraction went up. The inhibitory activity of angiotensin converting enzyme(ACE), the significance of which still was not recognized, showed the maximum when the concentration of ethanol was 27%. In result, the optimal conditions of extraction was the extraction time of two hours, the extraction temperature of $75{\sim}81^{\circ}C$, and the ethanol concentration of $33{\sim}35%$.

• Korean Journal of Dental Materials
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• v.44 no.2
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• pp.151-161
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• 2017

The purpose of this study was to examine the effect of shade and thickness of resin-nanoceramic CAD-CAM block (RNB) on the microhardness of dual-cured resin cement, as well as to measure the number of photons transmitted through RNBs of different thicknesses and colors. One dual-cured resin cement was used to prepare resin cement specimens. Resin cement specimens were light-cured for 40 seconds through 3 shades (A1, A2, A3 in HT (high translucency) and LT (low translucency) respectively) and four thicknesses (1, 2, 3, 4 mm) of RNB specimens. Vickers microhardness measurements of resin cement specimens were performed using a Vickers hardness tester. The light transmission of RNB specimens was measured using a spectrometer (SpectroPro-500, Acton Research, Acton, MA, U.S.A.), and the translucency parameter was calculated using the CIEL*a*b* system. Data were statistically analyzed by ANOVA and Tukey's test. There was a significant decrease of microhardness of resin cement specimen with an overlay of 4 mm of RNB thickness and A3 shade in comparison to A1 and 1 mm, respectively (p<0.05). The translucency parameter values and light transmission of RNBs tested differed significantly, according to the thicknesses of the specimen (p<0.05). Light transmission is decreased with increase in the thicknesses of RNBs. Shade A1 transmitted more light than darker blocks. A decrease in microhardness of resin cement specimens was observed with increasing thickness and shade (A1 to A3) of RNBs.

• Journal of the Korean Magnetics Society
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• v.17 no.3
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• pp.120-123
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• 2007

The typical double-barrier magnetic tunnel junction (DMTJ) structure examined in this paper consists of a Ta 45/Ru 9.5/IrMn 10/CoFe7/$AlO_x$/free layer/AlO/CoFe 7/IrMn 10/Ru 60 (nm). The free layer consists of an $Ni_{16}Fe_{62}Si_8B_{14}$ 7 nm, $Co_{90}Fe_{10}$ (fcc) 7 nm, or CoFe $t_1$/NiFeSiB $t_2$/CoFe $t_1$ layer in which the thicknesses $t_1$ and $t_2$ are varied. The DMTJ with an NiFeSiB-free layer had a tunneling magnetoresistance (TMR) of 28%, an area-resistance product (RA) of $86\;k{\Omega}{\mu}m^2$, a coercivity ($H_c$) of 11 Oe, and an interlayer coupling field ($H_i$) of 20 Oe. To improve the TMR ratio and RA, a DMTJ comprising an amorphous NiFeSiB layer that could partially substitute for the CoFe free layer was investigated. This hybrid DMTJ had a TMR of 30%, an RA of $68\;k{\Omega}{\mu}m^2$, and a of 11 Oe, but an increased of 37 Oe. We confirmed by atomic force microscopy and transmission electron microscopy that increased as the thickness of NiFeSiB decreased. When the amorphous NiFeSiB layer was thick, it was effective in retarding the columnar growth which usually induces a wavy interface. However, if the NiFeSiB layer was thin, the roughness was increased and became large because of the magnetostatic $N{\acute{e}}el$ coupling.