• Journal of Korean Society of Environmental Engineers
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• v.31 no.2
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• pp.90-95
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• 2009

Sludge pre-treatment utilizing cavitation is one of the commercialized methods at present. Cavitation can be generated by two different methods, sonotrode and hydrodynamic principle, and there has been no direct comparison between the two methods. In this study, solubilization efficiency, changes in sludge size distribution, and the methane production potential after pre-treatment by the two methods were compared. The maximum solubilization efficiency per unit energy input with the two methods was similar, and was 302 mg ${\Delta}SCOD/g$ TS at the energy input of 0.18 kWh/L. Break-up of sludge flocs were dominant during the early period of pre-treatment, while cell disintegration continued through the pre-treatment with the increase in the number of particles with less than 1 ${\mu}m$. BMP test results indicated that the methane potential increased up to 24.3% without differences between the two pre-treatments, and the increase in methane potential did not proportional to energy input. Although the energy efficiency of the two methods was quite similar, hydrodynamic methods might be a better choice for field application considering the operation and maintenance cost, and its potential improvement in energy efficiency.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2018.04a
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• pp.45-45
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• 2018

We had already reported the successful germination for green pods of purple lady's slipper orchid (Cypripedium macranthos Sw.). The green pod methods is to take immature seeds in green capsules, sterilize the capsule, and take out the sterile seeds. This method, however, needs very critical time of harvest. The critical time of seed harvest changes depending upon the species, condition of the specimen, and climatic influence, and the right time lies between 5 and 12 weeks after fertilization. In this study, the mature seeds were collected after 120-130 days with hand-polination of lady's slipper orchids. Mature seeds are usually dormant and it has to be overcome, either with hormone or storing the seeds near freezing for two or three months to break dormancy. The seeds were first surface sterilized with 70% ethanol and then transferred 1% NaOCl for 10-15 minutes, followed by rinses 3 times with sterilized distilled water. The cypripedium seeds consists of an embryo within a seed coat known as a testa. The testa is water repellent and the seed has a large air space between the embryo and testa so the seed tends to float on water. We had resolved the problems with vacuum pump to soak water into the testa before sterilization. The seeds were placed on liquid or agar solidified germination media. Cultures were incubated at $24{\pm}1^{\circ}C$ in dark. The seeds were germinated in 6-8 weeks in liquid suspension culture (germination percentage over 18%); however, the seeds on agar solidified media took more than 5 months to germinate and the germination percentage less than 5%. The most effective media for liquid culture was 1/4 strength Murashige and Skoog (MS) medium with 50 ml/l coconut water ($4brix^{\circ}$) at pH 5.8.

• Journal of the Korean Society of Food Science and Nutrition
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• v.43 no.1
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• pp.60-66
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• 2014

The aim of this study was to evaluate the antioxidant activity and protective effect of extracts from the stems and leaves of Chrysanthemum boreale (CBSL) on t-BHP induced oxidative stress in human liver cells (Chang cells). Antioxidant activities in the extracts were determined for various radical scavenging activities including ferric reducing antioxidant power, 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging activity, and oxygen radical absorbance capacity (ORAC). CBSL showed a very good scavenging effect of DPPH radical ($IC_{50}$ $0.009{\pm}0.002$ mg/mL), alkyl radical ($IC_{50}$ $0.004{\pm}0.001$ mg/mL), and hydroxyl radical ($IC_{50}$ $6.742{\pm}0.152$ mg/mL). CBSL also showed a strong antioxidant effect in the ORAC assay. In the MTT assay on human liver cells (Chang cells), the extracts showed protective effects by increasing cell viability, decreasing ROS, and restoring mitochondria membrane potential upon t-BHP induced oxidative stress. Our findings suggest that CBSL extracts are a potential therapeutic with protective antioxidant effects upon oxidative stress.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1115-1123
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• 2008

When constructing projects such as road embankments, bridge approaches, dikes or buildings on soft, compressible soils, significant settlements may occur due to the consolidation of these soils under the superimposed loads. The compressibility of the soil skeleton of a soft clay is influenced by such factors as structure and fabric, stress path, temperature and loading rate. Although it is possible to determine appropriate relations and the corresponding material parameters in the laboratory, it is well known that sample disturbance due to stress release, temperature change and moisture content change can have a profound effect on the compressibility of a clay. The early research of Tezaghi and Casagrande has had a lasting influence on our interpretation of consolidation data. The 24 hour, incremental load, oedometer test has become, more or less, the standard procedure for determining the one-dimensional, stress-strain behavior of clays. An important notion relates to the interpretation of the data is the ore-consolidation pressure ${\sigma}_p$, which is located approximately at the break in the slope on the curve. From a practical point of view, this pressure is usually viewed as corresponding to the maximum past effective stress supported by the soil. Researchers have shown, however, that the value of ${\sigma}_p$ depends on the test procedure. furthermore, owing to sampling disturbance, the results of the laboratory consolidation test must be corrected to better capture the in-situ compressibility characteristics. The corrections apply, strictly speaking, to soils where the relation between strain and effective stress is time independent. An important assumption in Terzaghi's one-dimensional theory of consolidation is that the soil skeleton behaves elastically. On the other hand, Buisman recognized that creep deformations in settlement analysis can be important. this has led to extensions to Terzaghi's theory by various investigators, including the applicant and coworkers. The main object of this study is to suggestion the modified compression index value to predict settlements by back calculating the $C_c$ from different numerical models, which are giving best prediction settlements for multi layers including very thick soft clay.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.31 no.2 s.51
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• pp.141-146
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• 2005

Unstable cosmetic active ingredients could rapidly break down in chemical and photochemical process. Therefore, it has become a very important issue to encapsulate active ingredient for the stabilization. 7-Dehydrocholesterol (7-DHC), a precursor of vitamin $D_3$, has been shown to increase levels of protein and mRNA for heat shock protein in normal human epidermal keratinocytes. However, topical dermal application of 7-DHC is restricted due to its poor solubility and chemical unstability. In this study, 7-DHC was incorporated into nano-emulsion (NE), solid lipid nano-particle (SLN), and chitosan coated solid lipid nano-particle (CASLN), respectively. In order to prepare NE and SLN dispersion, high-pressure homogenization at temperature above the melting point of lipid was used Hydrogenated lecithin and polysorbate 60 were used as stabilizer for NE and SLN. CASLN was prepared by high speed homogenizing after adding chitosan solution to the SLN dispersion and showed positively charged particle properties. Decomposition rate of 7-DHC in NE, SLN and CASLN was studied as a function of time at different temperature. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) studies were performed to characterize state of lipid modification. It appeared that CASLN is the most effective to stabilize 7-DHC and may be used for a useful topical dermal delivery system.

• Journal of the Korean Chemical Society
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• v.54 no.2
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• pp.208-214
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• 2010

In the presence of alcohol, phospholipase D (PLD) is known to perform transphosphatidylation activity, during which the overall reaction rate of PLD increased. To elucidate the reaction mechanism of transphosphatidylation further, we investigated rate constants of transphosphatidylation reaction of the purified ${\alpha}$-type PLD from cabbage in the presence of various alcohols. The second-oder rate constants of PLD transphosphatidylation showed a large increase with the primary alcohols examined as expected. In the case of butanol we observed the second-oder rate constant of $33.33{\pm}1.33M^{-1}sec^{-1}$. This second-order rate constant of transphosphatidylation was as 400 times greater as the second-order hydrolysis rate constant of $0.078M^{-1}sec^{-1}$ which was adjusted for the water concentration. A linear free energy relationship between the $pK_a$ of alcohol and transphosphatidylation rate gives a Br${\o}$nsted slope of ${\beta}_{nu}$ = 0.12 ${\pm}$ 0.03. This small ${\beta}_{nu}$ value implicates that the transition state of break down of phosphatidyl-enzyme intermediate (E-P) is likely dissociative. Finally, a reaction mechanism of cabbage PLD is suggested on the basis of our results presented here and the histidine residue known to be located in the active site of cabbage PLD.

• Elastomers and Composites
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• v.42 no.1
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• pp.20-31
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• 2007

Material characteristics and lifetime evaluation are very important in design procedure to assure the safety and reliability of the rubber components. In this paper, the NBR compound was prepared by sulfur-cure system, and was used in predicting the lifetime of rubber gasket made by the compound. The accelerated material aging was investigated at different temperatures at 120, 140 and $160^{\circ}C$ and aging time from 3 hours to 600 hours at 5, 6, 7 vol %. of $H_2SO_4$ concentrations The rubber strips were placed in acid solution using pyrex g1ass tube. Both ends of pyrex g1ass tube were sealed to avoid evaporation of solution during heating at given time. The material test and accelerated acid-heat aging test were carried out to predict the useful life of NBR rubber gasket for a fuel cell stack. In order to investigate the effects of acid-heat aging on the properties of the NBR, tensile strength, elongation at break, hardness and crosslink-density were measured. The tensile strength decreases as the $H_2SO_4$ concentrations and temperature increase. Results were evaluated using Arrhenius equation.

• Korean Journal of Food Science and Technology
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• v.35 no.2
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• pp.217-221
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• 2003

Effect of direct addition of $CaCl_2$ into sodium alginate film-making solution and immersion of alginate films into $CaCl_2$ solutions on tensile strength (TS), percentage elongation at break (E), water vapor permeability (WVP), and water solubility (WS) of the films were investigated. TS of alginate films prepared by both methods increased. E of $CaCl_2-added$ films did not change significantly (P>0.05), whereas that of $CaCl_2-immersion$ films decreased significantly (p<0.05). WVP of films prepared by both methods decreased significantly, but the effect was more significant in the $CaCl_2-immersion$ films. Water resistance was not changed in the $CaCl_2-added$ films, whreras increased significantly in $CaCl_2-immersion$ films (p<0.05). Properties of alginate films depend on the concentration of $CaCl_2$ treatments in both methods, and they also depend on treatment time in the immersion method.

• KIPS Transactions on Computer and Communication Systems
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• v.1 no.2
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• pp.71-78
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• 2012

The digital tachograph is a device that automatically records speed and distance of a vehicle, together with the driver's activity and vehicle status at an accident. It records vehicle speed, break status, acceleration, engine RPM, longitude and latitude of GPS, accumulated distance, and so on. European Commission regulation made digital tachographs mandatory for all trucks from 2005. Republic of Korea made digital tachographs mandatory for all new business vehicles from 2011 and is widening the range of vehicles that must install digital tachographs year by year. This device is used to analyze driver's daily driving information and car accidents. Under a car accident that makes the device reliability unpredictable, it is very important to store driving information with maximum reliability for its original mission. We designed and implemented a practical digital tachograph. This paper presents a storage scheme that consists of a first storage device with small capacity at a high reliability and a second storage device with large capacity at a low cost in order to reliably records data with a hardware at a low cost. The first storage device records data in a SLC NAND flash memory in a log-structured style. We present a reverse partial scan that overcomes the slow scan time of log-structured storages at the boot stage. The scheme reduced the scan time of the first storage device by 1/50. In addition, our design includes a scheme that fast stores data at a moment of accident by 1/20 of data transfer time of a normal method.

• Journal of Energy Engineering
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• v.17 no.2
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• pp.67-76
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• 2008

A thermal-hydraulic integral effect test facility, ATLAS (Advanced Thermal-hydraulic Test Loop for Accident Simulation), has been constructed at KAERI (Korea Atomic Energy Research Institute). Recently several integral effect tests for the reflood period of a LBLOCA (Large Break LOss of Coolant Accident) of the APR1400 have been performed with the ATLAS. In the APR1400 a high flow condition is changed to a low flow condition due to an fluidic device during an operation of the SIT. As the self-controlled fluidic device was not installed in the ATLAS, a set of characterization tests was performed to simulate its injection capability from the SIT for the APR1400 simulation. In the ATLAS the required SIT flow rate in the high flow condition was acquired by installing orifices with an optimized flow area to throttle the SIT discharge line and the low flow condition was achieved by changing the opening of the flow control valve in the SIT injection line. The test results showed that the safety injection systems of the ATLAS could simulate the required high and low flow rates of the SIT for the APR1400 simulation efficiently.