• Journal of Conservation Science
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• v.30 no.1
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• pp.95-101
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• 2014

Silver objects tarnish with black from reaction with sulfurous acid or hydrogen sulfide of atmospheric. Blackening of silver objects results from formation of silver sulfide($Ag_2O$) on the surface. Silver sulfide usually is usually removed by conservation treatment. There are several cleaning methods such as chemical, electrochemical and micro-abrasion cleaning, but all of them consume silver. This study investigated the safe and effective parameter of laser cleaning by test on silver coupons. Laser cleaning is a selective process for the removal of specific substances. At first, laser cleaning applied to plain silver coupons, which were not corroded, to find out the safe range of laser energy density. From results, plain silver coupons were not changed at 1064nm below $4.00J/cm^2$ and at 532nm below $2.39J/cm^2$. The corrosion layer(silver sulfide) of artifical corroded silver coupons was removed at 1064nm with $2.39J/cm^2$ by 5~10 pulses and at 532nm with $1.19J/cm^2$ by 5~10 pulses. The removal thickness of corrosion layer was about 13-25nm per a laser pulse using AES analysis. In addition, laser cleaning tested the tarnish silver rings based on the results of silver coupons. As a result of test, the black surface were clean successfully and gave luster of silver, which showed the application possibility of laser cleaning for silver objects.

• Journal of the Korea Computer Industry Society
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• v.8 no.2
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• pp.97-102
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• 2007

[ $CO_2$ ] laser sees that is most suitable to get this effect through minimum formation damage and advantage that is root enemy of effect that happen in minimum cellular tissue depth of 0.1mm is stable living body organization or internal organs institution. Formation damage by ten can be related in formation's kind or energy density, length of evaporation time. If shorten evaporation time, surroundings cellular thermal damage 200 - because happen within 400um laser beam in rain focus sacred ground surroundings cellular tissue without vitiation me by evaporation Poe of very small floor as is clean steam can . Application is possible to vulva cuticle cousins by a paternal aunt quantity, uterine cancer, cuticle tumor by laser system that $CO_2$ laser gets into standard in obstetrics and gynecology application. Because effect that super pulse output is ten enemies of laser if uniformity one pulse durations are short almost is decreased, most of all pulse module special quality of Pulse style $CO_2$ laser for obstetrics and gynecology mode stabilization by weight very, in this research to get into short pulse duration and higher frequency density, do switching by high frequency in DC-DC Converter output DC's ripple high frequency to be changed, high frequency done current ripple amount of condenser for output filter greatly reduce can . Ripple of output approximately to Zero realization applying possible inductor realization through a special quality experiment do.

• Membrane Journal
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• v.27 no.2
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• pp.199-204
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• 2017

In this study, a study was carried out for the separation of metal ions in lignin extract discharged from the pulp process. alumina powders were mixed with DMAc (N, N-dimethylacetamide) solvent and PESf (Polyethersulfone) polymer, PVP (polyvinylpyrrolidone) dispersant was added and slip casting method was used to prepare the membrane. The membrane was measured for pore size through a CFP (Capillary Flow Porometer) device and the surface and cross-section of the membrane were observed through a FE-SEM (Field Emission Scanning Electron Microscope). The flux was calculated by measuring the filtered weight per hour using a separation experiment device. Pore size measurements were performed under increasing pressure from 0 psi to 30 psi. The pore size of the membrane was $0.4{\mu}m$ and the flux decreased from the initial flux value of $6.36kg{\cdot}m^{-2}{\cdot}h^{-1}$ to $1.98kg{\cdot}m^{-2}{\cdot}h^{-1}$ due to the fouling of the membrane. After the permeation experiment, membrane contaminants were removed by simple washing. Separation experiments showed that Na contained in the initial lignin extract was reduced by 69%, Fe was removed by 87%, K by 95%, Ca by 93% and Mg by 96%.

• Korean Chemical Engineering Research
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• v.53 no.2
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• pp.211-215
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• 2015

The hydrolysis of defatted rice bran using near-critical water was performed, and the feasibility of consequent hydrolyzate as a growth medium was investigated by the cultivation of Saccharomyces cerevisiae. The near-critical water hydrolysis was carried out through a series of batch experiments, and the contents of total carbohydrates, disaccharides, and monosaccharides, total organic carbon (TOC), total nitrogen (TN), pH of products were measured. The growth rate of Saccharomyces cerevisiae was measured with optical density. The yield of total carbohydrates, TOC, and TN increased with temperature below $240^{\circ}C$, however, decreased above $240^{\circ}C$. The decrease of yields above $240^{\circ}C$ was caused by the formation of organic acids, and it agreed with the change of pH of products. The yield of glucose was a maximum at $200^{\circ}C$ and it decreased dramatically at higher temperature. The growth rate of Saccharomyces cerevisiae cultivated in the hydrolyzate was similar with that in the commercial medium under certain conditions. The growth rate was correlated with the content of glucose in hydrolyzate.

• Korea journal of population studies
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• v.29 no.1
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• pp.269-292
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• 2006

The current environmental problem is global, and threatens the very existence of human beings. Many factors have been argued as the causes of environmental problem. The examples include anthroponcentric human perspective on nature, increase in the knowledge on nature, development of technology, economic growth and unequal distribution, and population increase, etc. The scholars who argues population increase have focused on over-population. However, the estimation of optimum population size has not been attempted in terms of environmental carrying capacity. In such a context, this paper aims at estimating optimum population size in South Korea in terms of environmental carrying capacity. The estimation was done from two approaches. One was based on the state of environment, the other was based on 'the desirable state of environment' Koreans expect. The former is termed an objective approach, while the latter is termed an approach based on social consensus. About 47.5 millions were estimated from the former approach, and 48.5 millions from the latter approach. However, optimum population size increase by 50.5 millions if government increase environmental budget to 2.00% among total budget. As such, different optimum population size is estimated according to the values of variables. The most significant variable determining optimum population size is environmental budget, and followed by supply of clean energy. The estimated optimum population size was based on the time-series data from 1993 to 2002. Therefore, time-series data collected from other years will result in different estimation model, and then different optimum population size will be estimated.

• Journal of the Mineralogical Society of Korea
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• v.23 no.3
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• pp.199-209
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• 2010

Coal gasification technology in the sector of domestic clean coal technologies is being into the limelight since recent dramatic rise of international oil price. In this study, we used a low rank coal from Inner Mongolia, China as a starting material for gasification. Various properties including optical, mineralogical, X-ray spectroscopic, X-ray diffraction, and drying property were measured and tested in order to estimate the suitability of the coal to gasification. The coal was identified as a brown coal of lignite group from the measurement of vitrinite reflectance. The coal has very low slagging and fouling potentials, and the ignition temperature is about $250^{\circ}C$. The major impurities consist of quartz, siderite, and clay minerals. Additionally, the coal had moisture content above 28%. Tests for finding effective drying method showed that the microwave drying is more effective than thermal drying.

• Korean Chemical Engineering Research
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• v.49 no.6
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• pp.816-822
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• 2011

Pervaporation is known to be a low energy consumption process since it needs only an electric power to maintain the permeate side in vacuum. Also, the pervaporation is an environmentally clean technology because it does not use the third material such as an entrainer for either an azeotropic distillation or an extractive distillation. In this study, Silicalite-1 particles are hydrothermally synthesized and polydimethylsiloxane(PDMS)-zeolite composite membranes are prepared with a mixture of synthesized Silicalite-1 particles and PDMS-polymer. They are used to separate n-butanol from its aqueous solution. Pervaporation characteristics such as a permeation flux and a separation factor are investigated as a function of the feed concentration and the weight % of Silicalite-1 particles in the membrane. A 1,000 $cm^3$ aqueous solution containing butanol of low mole fraction such as order of 0.001 was used as a feed to the membrane cell while the pressure of the permeation side was kept about 0.2~0.3 torr. When the butanol concentration in the feed solution was 0.015 mole fraction, the flux of n-butanol significantly increased from 14.5 g/ $m^2$/hr to 186.3 g/$m^2$/hr as the Silicalite-1 content increased from 0 wt% to 10 wt%, indicating that the Silicalite-1 molecular sieve improved the membrane permselectivity from 4.8 to 11.8 due to its unique crystalline microporous structure and its strong hydrophobicity. Consequently, the concentration of n-butanol in the permeate substantially increased from 0.07 to 0.15 mole fraction. This composite membrane could be potentially appliable for separation of n-butanol from insitu fermentation broth where n-butanol is produced at a fairly low concentration of 0.015 mole fraction.

• Korean Journal of Agricultural Science
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• v.47 no.3
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• pp.605-614
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• 2020

This study was conducted to compare the growth performances of three groups of commercial Korean native chickens (KNCs) including two strains of crossbreeds and H3 (Hanhyeop 3) from hatch to twelve weeks of age. (1A, 2A, and H3). A total of 468 one-day-old chicks were allocated in a completely randomized design with 15 replicates per treatment for the crossbreeds and 9 replicates per treatment for H3 (12 birds per cage). Commercial broiler diets (i.e., Week 0 - 5 crude protein [CP] 22.0%, metabolizable energy [ME] 3,025 kcal·kg^-1; week 5 - 8 CP 20.0%, ME 3,100 kcal·kg^-1; week 8 - 12 CP 19.0%, ME 3,150 kcal·kg^-1) were provided according to the Korean Feeding Standard for Poultry on an ad-libitum basis with fresh clean water during the twelve-week period. Body weight gain and shank length (SL) were measured weekly until week 6 and bi-weekly during week 6 to 12. Compared to H3, the two crossbreed groups had a higher body weight (BW) on weeks 3 to 8; however, the bodyweight of H3 on week 10 was significantly higher than the other groups (p < 0.05). Moreover, the average daily feed intake (ADFI) of H3 was higher than that of the two crossbreed groups from hatching to 84 days except for week 3, and H3 showed a lower average daily gain (ADG) on weeks 3 and 10 (p < 0.05). Furthermore, H3 had a higher feed conversion ratio compared to another crossbreed chicken on weeks 1 to 8 and the last week after hatching. Among all the groups, there was no significant difference for shank length during the experimental period.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.5
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• pp.26-35
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• 2016

As a potential clean energy resource, the production and consumption of hydrogen gas are expected to gradually increase, so that hydrogen related studies are also increasing. The thermal and chemical properties of hydrogen result in its high flammability; in particular, there is a high risk if leaks occur within an enclosed space. In this study, we applied the computational fluid dynamics method to conduct a numerical study on the leakage behavior of hydrogen gas and compared these numerical study results with an experimental study. The leakage hole diameter was selected as an important parameter and the hydrogen gas dispersion behavior in an enclosed space was investigated through various analytical methods. Moreover, the flammable regions were investigated as a function of the leakage time and leakage hole size. We found that the growth rate of the flammable region increases rapidly with increasing leakage hole size. We also investigated the relation between the mass flow rate and the critical time when the hydrogen gas reaches the ceiling. The analysis of the monitoring points showed that the hydrogen gas dispersion behavior is isotropic and independent of the geometry. We found that the concentration of gas in an enclosed space is affected by both the leakage flow rate and amount of gas accumulated in the enclosure.

• Membrane Journal
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• v.31 no.2
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• pp.101-119
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• 2021

The demand for clean water is virtually present in all modern human societies even as our society has developed increasingly more advanced and sophisticated technologies to improve human life. However, as global climate change begins to show more dramatic effects in many regions in the world, the demand for a cheap, effective way to treat wastewater or to remove harmful bacteria, microbes, viruses, and other solvents detrimental to human health has continued to remain present and remains as important as ever. Well-established synthetic membranes composed of polyaniline (PANI), polyvinylidene fluoride (PVDF), and others have been extensively studied to gather information regarding the characteristics and performance of the membrane, but recent studies have shown that making these synthetic membranes conductive to electrical current by doping the membrane with another material or incorporating conductive materials onto the surface of the membrane, such as allotropes of carbon, have shown to increase the performance of these membranes by allowing the adjustability of pore size, improving antifouling and making the antibacterial property better. In this review, modern electrically conductive membranes are compared to conventional membranes and their performance improvements under electric fields are discussed, as well as their potential in water filtration and wastewater treatment applications.