• Bulletin of the Korean Chemical Society
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• v.17 no.3
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• pp.262-268
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• 1996

Flow properties of all suspensions are controlled by their flow units. The factors effecting on the flow units are the characteristics of the particle itself (surface properties, particle sizes, particle shapes and etc.), the electrostatic interactions among the particles and the influences of the medium in the suspensions. Here, we studied the transition between the flow units with shear rate which can be added to the above factors. For the concentrated starch-water suspensions, by using the Couette type rotational viscometer, we confirmed that at low shear rate, dilatancy is appeared, but it is transformed to thixotropy with increasing shear rate. In order to explain this fact, we derived the following flow equation, representing the transition from dilatancy to thixotropy with shear rate, by assuming the equilibrium between the flow units. f = X1β1s./α1 + 1/(1+Kexp(c0s.2/RT))((1-X1)/α2)sinh-1{(β2)0 s. exp(c2s.2/RT)} + K exp(c0s.2/RT)/(1+K exp(c0s.2/RT))((1-X1)/α3)sinh-1{(β3)0 s. exp(-c3s.2/RT)} By applying this flow equation to the experimental flow curves for the concentrated starch-water suspensions, the flow parameters were obtained. And, by substituting the obtained flow parameters to the flow equation, the theoretical flow curves were reproduced. Also, Ostwald curve was represented by applying the flow equation, and the applicability for stress relaxation was discussed.

• Journal of Microbiology and Biotechnology
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• v.31 no.1
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• pp.104-114
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• 2021

Petroleum-contaminated soil is considered among the most important potential anthropogenic atmospheric methane sources. Additionally, various rhizoremediation factors can affect methane emissions by altering soil ecosystem carbon cycles. Nonetheless, greenhouse gas emissions from soil have not been given due importance as a potentially relevant parameter in rhizoremediation techniques. Therefore, in this study we sought to investigate the effects of different plant and soil amendments on both remediation efficiencies and methane emission characteristics in diesel-contaminated soil. An indoor pot experiment consisting of three plant treatments (control, maize, tall fescue) and two soil amendments (chemical nutrient, compost) was performed for 95 days. Total petroleum hydrocarbon (TPH) removal efficiency, dehydrogenase activity, and alkB (i.e., an alkane compound-degrading enzyme) gene abundance were the highest in the tall fescue and maize soil system amended with compost. Compost addition enhanced both the overall remediation efficiencies, as well as pmoA (i.e., a methane-oxidizing enzyme) gene abundance in soils. Moreover, the potential methane emission of diesel-contaminated soil was relatively low when maize was introduced to the soil system. After microbial community analysis, various TPH-degrading microorganisms (Nocardioides, Marinobacter, Immitisolibacter, Acinetobacter, Kocuria, Mycobacterium, Pseudomonas, Alcanivorax) and methane-oxidizing microorganisms (Methylocapsa, Methylosarcina) were observed in the rhizosphere soil. The effects of major rhizoremediation factors on soil remediation efficiency and greenhouse gas emissions discussed herein are expected to contribute to the development of sustainable biological remediation technologies in response to global climate change.

• Clean Technology
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• v.30 no.3
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• pp.195-202
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• 2024

Plant polyphenols have attracted attention recently because of their abundance in the human diet, high antioxidant effects, and ability to prevent various diseases associated with oxidative stress, such as cancer and cardiovascular and neurodegenerative diseases. Therefore, this study demonstrated the extraction of bioactive phenolic compounds from Allium hoorkei root (AHR) using subcritical water extraction (scWE) under various temperatures (120 ~ 160 ℃) and times (30 ~ 180 min) at a fixed pressure (10 MPa) and AHR to water ratio (1:20, w/w). Furthermore, this study used severity factors, the combined effect of the temperature and time, in order to optimize the conditions for achieving a high yield and efficient recovery of target bioactive phenolic compounds while minimizing the degradation of the extracted products and maintaining a high selectivity. Subcritical water extraction at 160 ℃ for 30 min (severity of 3.24) produced a relatively high yield (88%) and high number of bioactive compounds including total phenolic contents (31.3 mg GAE/g dry AHR) and rare sugars (D-picose, D-talose, and D-tagatose) compared to Soxhlet extracts obtained from extraction for 8 h with water and 75% ethanol. As a result, the extracts obtained from the green scWE process may have high potential applications in medicines and functional foods because of their high bioactivity and safety.

• Journal of the Korean Society of Tobacco Science
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• v.26 no.2 s.52
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• pp.93-101
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• 2004

This study was conducted to investigate the relationship between weather factors during the growing season and chemical components of flue-cured tobacco. Chemical components used in this study was from 'Farm Leaf Tobacco Test' conducted at KT&G Central Research Institute from 1986 through 2003. Data of weather factors during growing season(April to July) were collected in 10 districts measured at Korea Meteorological Adminstration(KMA). Nicotine and total sugar contents, and total sugar to nicotine(TS/Nic.) ratio were increased, whereas total nitrogen to nicotine(TN/Nic.) ratio and chloride content were decreased from 1986 through 2003. Year to year variation of rainfall was the largest, followed by that of sunshine hour. Month to month variation of rainfall also was the largest, followed by that of mean daily air temperature(MDAT). Rainfall was correlated positively with relative humidity(RH), but negatively with sunshine hour. Nicotine content was correlated positively with MDAT(in July, June$\~$July, May$\~$July and average), but negatively with rainfall(in May$\~$July) and with RH(in June, July, May $\~$June, June $\~$July, April$\~$June, May $\~$July and average). Total sugar content was correlated positively with MDAT(in May), but negatively with sunshine hour(average) and RH(in June, July, June$\~$July, April$\~$June, May$\~$July and average). The positive correlation was found between total nitrogen content and sunshine hour(in April, May, April$\~$May, May$\~$July, April$\~$June and average). The negative correlation was found between TS/Nic. ratio and sunshine hour(in May$\~$July and average). TN/Nic. ratio was correlated positively with sunshine hour(in May and April$\~$May) and with RH(in July and June$\~$July), but negatively with MDAT(in July, June$\~$July, May$\~$July and average). Ether extraction content was correlated positively with MDAT(in July, June$\~$July, May$\~$July and average) and with sunshine hour(in July and June$\~$July), but negatively with rainfall(in April, July, May­July and average). Chloride content was correlated positively with sunshine hour(in April, July, April$\~$May, June$\~$July, April$\~$June, May$\~$July and average), but negatively with rainfall(in April, April$\~$June and average).

• Applied Chemistry for Engineering
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• v.31 no.2
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• pp.147-152
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• 2020

In this study, we dedicated to optimize the process for a reactive diluent for epoxy resin of improved chemical resistance by using cardanol, a component of natural oil of cashew nut shell liquid (CNSL). The central composite design (CCD) model of response surface methodology (RSM) was used for the optimization. The quantitative factors for CCD-RSM were the cardanol/ECH mole ratio, reaction time, and reaction temperature. The yield, epoxy equivalent, and viscosity were selected as response values. Basic experiments were performed to design the reaction surface analysis. The ranges of quantitative factors were determined as 2~4, 4~8 h, and 100~140 ℃ for the cardanol/ECH reaction mole ratio, reaction time, and reaction temperature, respectively. From the result of CCD-RSM, the optimum conditions were determined as 3.33, 6.18 h, and 120 ℃ for the cardanol/ECH reaction mole ratio, reaction time, and reaction temperature, respectively. At these conditions, the yield, epoxy equivalence, and viscosity were estimated as 100%, 429.89 g/eq., and 41.65 cP, respectively. In addition, the experimental results show that the error rate was less than 0.3%, demonstrating the validity of optimization.

• The Korea Journal of Herbology
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• v.29 no.6
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• pp.1-6
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• 2014

Objectives : This study was aimed to compare Gyejibokryeong-hwan (GBH) decoctions produced using different pressure levels for various extraction times to find the optimal extraction conditions through extraction yield, total soluble solids content (TSSC), hydrogen ion concentration (pH), and the contents of chemical compounds. Methods : Decoctions of GBH were prepared under the pressure levels of 0 or $1kgf/cm^2$ for 30-180 min using water as extraction solvent. The extraction yield, TSSC, and pH were measured, and the amounts of the chemical compounds were determined using high performance liquid chromatography-photodiode array detector. Results : The higher pressure and longer extraction time increased the values of TSSC and extraction yield, while decreased the pH value. The decoctions produced in 180 min by pressurized method and produced in 150 min by non-pressurized method showed maximum values of extraction yield and TSSC with minimum value of pH. The amounts of chemical compounds showed variations in pressurized and non-pressurized decoction during overall extraction times. The influences of pressure and extraction time on extraction yield, TSSC, pH, and the contents of chemical compounds were confirmed by regression analysis, which showed that all extraction values were significantly affected by at least one of two extraction factors, pressure and extraction time. Conclusions : This study suggests that the pressure and extraction time can significantly affect the extraction efficiency of components from GBH decoctions. However, optimal extraction conditions could not be chosen due to the variation of the amounts of chemical compounds.

• Korean Journal of Poultry Science
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• v.39 no.4
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• pp.279-282
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• 2012

Clinical-chemical traits are commonly used biomarkers to examine the health status of individuals. There is an appreciable range of normal variation in most clinical-chemical traits and the determining factors of this variation have been relatively uninvestigated in chickens. The aim of this study was to estimate the genetic parameters (i.e., heritability, genetic correlation) for 8 clinical-chemical traits (glucose, total protein, creatinine, high-density lipoprotein cholesterol, total cholesterol, glutamic oxaloacetic transaminase, glutamic pyruvic transaminase and amylase) in an $F_1$ intercross established by purebred breeding among the 5 lines of Korean native chickens. Phenotypic data were collected from approximately 600 $F_1$ animals. The genetic parameters for the clinical-chemical traits estimated by a mixed animal model using the restricted maximum likelihood method were presented. Estimated heritabilities ranged from 8.9% (glucose) to 39.6% (high-density lipoprotein cholesterol). Interestingly, both the sign and the size of the genetic and phenotypic correlations were largely different between the same several pair of clinical-chemical traits. The findings in this study will provide useful information to address issues in both quantitative trait locus study and genetic management in Korean native chickens.

• Bulletin of the Korean Chemical Society
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• v.35 no.12
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• pp.3521-3526
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• 2014

A magnetic sonophotocatalyst $Fe_3O_4@SiO_2@TiO_2$ is synthesized for the enhanced biodegradability of organophosphate pesticide. The as-prepared catalysts were characterized using different techniques, such as X-ray diffraction (XRD) and transmission electron microscopy (TEM). The radial sonophotocatalytic activity of $Fe_3O_4@SiO_2@TiO_2$ nanocomposite was investigated, in which commercial dichlorvos (DDVP) was chosen as an object. The degradation efficiency was evaluated in terms of chemical oxygen demand (COD) and enhancement of biodegradability. The effect of different factors, such as reaction time, pH, the added amount of catalyst on $COD_{Cr}$ removal efficiency were investigated. The average $COD_{Cr}$ removal efficiency reached 63.13% after 240 min in 12 L sonophotocatalytic reactor (catalyst $0.2gL^{-1}$, pH 7.3). The synergistic effect occurs in the combined sonolysis and photocatalysis which is proved by the significant improvement in $COD_{Cr}$ removal efficiency compared with that of solo photocatalysis. Under this experimental condition, the $BOD_5/COD_{Cr}$ ratio rose from 0.131 to 0.411, showing a remarkable improvement in biodegradability. These results showed that sonophotocatalysis may be applied as pre-treatment of pesticide wastewater, and then for biological treatment. The synthesized magnetic nanocomposite had good photocatalytic performance and stability, as when it was used for the fifth time, the $COD_{Cr}$ removal efficiency was still about 62.38%.

• Journal of Korean Society for Quality Management
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• v.43 no.3
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• pp.359-372
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• 2015

Purpose: Through studying the expert's and non-experts panel responses to the questions regarding the attributes of chemical-biological protection cloth quality in terms of the levels of customer demand and technical factors has been studied. We are applied to a QFD matrix with find out the relationship between the selective removal efficiency of chemical-biological cloth and the guidelines of technical approach. Methods: We fabricated several composite of ion-exchange resins with selectively permeable performance designed to facilities water vapor transport and selective adsorption of the harmful gases. With these materials, we characterized on the selectively permeable performance to identify ion-exchange resin with chemical-biological protective cloth. Results: Results showed that ion exchange materials possessed performance with selectively efficiencies as NH3, SOx, NOx and HCl gas. The selective adsorption amount of ammonia and hydrogen gases were $90-80{\mu}g/g$ with TRILITE SCR-BH sulfonated ion exchange resin. The PP non-woven/ion exchange resin adsorbent materials possessed performance with water vapor permeability were 1,100-1,350 g/m2/day, it's was two times high value compare with activated carbon. With these materials, we characterized selectively removal efficiency to identify new ion-exchange material with chemical-biological protective capability. Conclusion: This study shows that a QFD aids in deciding with of the adsorption parameters to optimized with chemical-biological protection cloth manufacturing.

• Journal of the Korea Institute of Military Science and Technology
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• v.18 no.4
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• pp.387-394
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• 2015

We have recently developed a cost-effective and pouch-type chemical vapor sampler which consists of a selectively permeable high density polyethylene(HDPE) membrane, aluminum/nylon barrier film, and adsorbents. Since the sampler mimics the actual adsorption process that occurs when the skin is exposed to chemical vapors, it can be applied to man-in-simulant test(MIST) to determine the protective capability of individual protective ensembles for chemical warfare agents. In this study, we describe the manufacturing process of samplers and results for performance testing on MIST. Methyl salicylate(MeS) is used to simulate chemical agent vapor and the vapor sampler was used to monitor chemical concentration of MeS inside the protective suit system while worn. Values of protection factors(PF) were also analyzed to provide an indication of the protection level of the suit system evaluate by MIST. The results obtained by home-made samplers(ADD samplers) and commercially avaliable ones(Natick samplers) showed no significant differences.