• 한국태양에너지학회:학술대회논문집
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• 2012.03a
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• pp.463-469
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• 2012

Solar thermochemical syngas and hydrogen production process bv redox system of metal oxide was performed under direct irradiation of the metal oxide on the SiC ceramic foam device using solar simulator. $CeO_2/ZrO_2$ nanotube has been synthesized by anodic oxidation method. Syngas and hydrogen production process is one of the promising chemical pathway for storage and transportation of solar heat by converting solar energy to chemical energy. The produced syngas had the $H_2/CO$ ratio of 2, which was suitable for methanol synthesis or Fischer-Tropsch synthesis process. After ten cycles of redox reaction, $CeO_2$ was analyzed using XRD pattern and SEM image in order to characterize the physical and chemical change of metal oxide at the high temperature.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.7
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• pp.97-105
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• 2002

The use of rapid prototyping (RP) has reduced time to market, cut total costs and improved product quality by giving design and manufacturing teams the opportunity to verify and fine tune designs before committing them to expensive tooling and fabrication. In order to improve their unique characteristics according to the working principles, Variable Lamination Manufacturing process (VLM-ST) and corresponding CAD/CAM software (VLM-Slicer) is developed. The objective of this study is to improve the accuracy of VLM-ST process, and it can be done by offset fur cutting error correction, cutting path overrun fur sharp edge and reference shape generation for off-line stacking. It has been shown that, through the verification experiments for given practical shapes, the proposed algorithms are effective for diverse categories of three-dimensional shapes.

• Journal of Korea Foundry Society
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• v.17 no.1
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• pp.93-99
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• 1997

A possibility of production of aluminium matrix composites by using the lost foam process was investigated. Silicon carbide particles, graphite particles, and stainless steel wires were used as reinforcement materials. The reinforcement materials were introduced to the polystyrene to form patterns via injection molding process. The results obtained from this experiment can be summarized as follows. In Al/SiCp system, the particles with the radius of $100{\mu}m$ and over were entrapped in the matrix in the case of upward freezing of which solidification direction was opposite to floating direction of the particles. And few particles were entrapped in the matrix in downward freezing. In Al/graphite system, almost no particles were entrapped in the matrix except the area chill attatched. When the thickness of polystyrene slice was 4mm in Al/stainless steel wire system, the floating tendency of fibers was observed to increase as the distance from the ingate was increased.

• The Korea Journal of Herbology
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• v.38 no.2
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• pp.9-16
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• 2023

Objectives : Many people use natural soap instead of commercially available bar type general soap for skin care. They tend to prefer cp (cold process) type soaps that go through a sufficient maturation process in formulation. The purpose of this study was to investigate the efficacy of PCPS (placenta cp soap). Methods : The researcher selected 36 subjects, 28 as the experimental group and 8 as the control group. I asked participants to wash their face twice a day in the morning and evening, and the period was set for 6 weeks. The researcher had the people who were selected as the control group use a commercially available foam cleanser, meanwhile the experimental group use PCPS. They performed a skin test before the start of the test, and the change status was continuously investigated after 2 weeks, 4 weeks, and 6 weeks after using the soap. Results : In the case of U zone oil and pores, there was a significant decrease and in the case of skin tone, there was a significant increase in the group of using PCPS. In T zone oil change, there was no significant effect in both the experimental group and the control group. Conclusion : In the case of PCPS, it is recommended to use it in the effect of reducing the size of pores and increasing skin tone, but it can reduce u-zone oil content.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.10
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• pp.186-191
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• 2000

We use so many plastic products in everyday. Because polymer materials have a lot of merits including low cost and easiness of forming, they are widely using at many manufacturing industries. Microcellular foaming process appeared at MIT in 1980's to save a quantity of material and increase mechanical properties. The information about the thickness of cavity plays an important role in appling microcellular foaming process to the conventional injection molding process. It is essential to make an effective foam. The goal of this research is to measure the relation between the change of cavity's thickness and foaming magnitude made after inserting a gas. R/t is a conception that indicate proportion between radius and thickness of cavity in mold system. By means of SEM observation of side surface of cavity sample, foaming magnitude of cavity is mold system. By means of SEM observation of side surface of cavity sample, foaming magnitude of polymer in microcellular foaming process is decreasing gradually as the value of R/t is increasing. The proposed foaming magnitude changes data of polymer in relation to mold system can be applied in more extensive injection molding process, such as optimum design of mold for microcellular foaming process.

• Journal of Microbiology and Biotechnology
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• v.27 no.4
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• pp.747-758
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• 2017

Chronic wounds, pressure sores, lesions, and infections of microbial origin in bedridden, paralyzed, or malnutrition patients remain the object of study of many researchers. A variety of factors behind the development of these disorders are related to the patient's immune system, making it unable to respond effectively to the treatment of the wound. These factors can be properly controlled, giving particular importance to the ethiology and stage of the wound, as well as the time periods corresponding to the replacement of the dressings. The present research reports a novel foam/soft material, ${{\small}L}$-Cys-g-PCL, with an application for decubitus/pressure ulcers, especially for wounds with a difficult healing process due to infections and constant oxidation of the soft tissues. During this work, the interactions between S. aureus and ${{\small}L}$-Cys-g-PCL foam were studied under conditions that simulate decubitus ulcers; namely, pH and exudate. The effects of duration of grafting (1 or 8 h) and pH (7.0 and 8.9) on wettability, surface energy, swelling, and porosity were also evaluated. Results showed an effective microbicidal activity exhibiting an inhibition ratio of 99.73% against S. aureus. This new ${{\small}L}$-Cys-g-PCL soft material showed saftey to contact skin, ability to be shaped to fill in sunken holes (craters) - pressure ulcers stage III - and to act as a smart material responsive to pH, which can be tailored to develop better swelling properties at alkaline pH where exudates are normally higher, so as to address exudate self-cleaning and prevention of desiccation.

• Journal of Environmental Health Sciences
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• v.42 no.2
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• pp.102-111
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• 2016

Objectives: This study was conducted to evaluate the use of polyurethane foam disk passive air samplers (PUF PAS) for better measurement of atmospheric polychlorinared dibenzo-p-dioxins/furans (PCDD/Fs) concentrations compared to PUF PAS combined with high volume air samplers (HVS). Methods: Air samples were collected by a low volume air sampler (LVS) and PUF PAS. A total of two pairs were continuously collected for six months, but the PUF was replaced every two months. Results: A good correlation was shown ($R^2=0.8595$, p<0.0001) between atmospheric PCDD/Fs concentration measured by the LVS and PUF PAS. The average air sampling rate ($1.5m^3/day-sampler$) of all PCDD/Fs congeners showed a middle of the means which were measured using a HVS by other researchers in different cities. In addition, the air sampling rates of the LVS for each congener made less difference than did those of the HVS. Conclusion: It was found that measurements using the LVS were less influenced by atmospheric peak PCDD/Fs concentrations. However, trace POPs such as PCDD/Fs may involve relatively large analytical errors in measurement, and as a result the air sampling rate of the respective PCDD/Fs isomer is also likely to involve errors. The method of using a regression straight line between the concentrations obtained from the LVS and those from the PUF PAS was judged higher than the method using the air sampling rate, since the former compensated for the experimental errors in the process of evaluation of atmospheric PCDD/F concentrations using the PUF PAS.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.692-697
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• 2005

A canard type aircraft, which has good wing stall and stall/spin proof characteristics, is being developed. The previous first and second prototypes, having full depth core sandwich type wing and fixed landing gear, was built for test flights. Newly developing Firefly will be equipped with retractable landing gear and conventional foam core sandwich laminate for wing and fuselage. For manufacturing, composite material process has been studied including coupon tests. Wet lay-up onto foam core with glass fabric using lay-up mold has been chosen, and composite material parts are cured under room temperature and atmospheric pressure condition. In general, molded parts show so good surface smoothness and standardized quality that are best in mass production. In this study, we present the mold technology and development status for small aircraft firefly.

• Polymer(Korea)
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• v.24 no.4
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• pp.529-537
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• 2000

The effects of the gel content on the cell structures of PP sheets by using an electron-curing system were investigated. Three extruded PP sheets crosslinked by three different doses were used for the batch foaming process with the supercritical state $CO_2$. Experiments were also performed in order to study the effects of the gel content, saturation pressure and temperature on cell structures. Then foaming conditions, such as temperature and duration of time, were changed. The amount of gas absorbed into PP samples was not affected by gel contents and the operating condition of saturation pressure, which was higher than 2000 psi. The foam cells of PP with a low gel content grew irregularly at a higher foaming temperature and for a longer duration of foaming time. However, PP samples with high gel content showed even cell structures and narrow tell size distributions under the severe conditions of high foaming temperatures and long duration of foaming time.

• Journal of the Korean Applied Science and Technology
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• v.13 no.3
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• pp.61-71
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• 1996

In acid-catalyzed acetal cyclization of long aliphatic aldehydes($R=n-C_7H_{15}$ ; $n-C_9H_{19}$ ; $n-C_{11}H_{23}$) with 1,1,1-tris(hydroxymethyl)propane, 2-alkyl-5-hydroxymethyl-5-ethyl-1,3-dioxanes were obtained. The final products, sodium 2-alkyl-5-(sulfonatedpropylethermethyl)-5-ethyl-1,3-propanesultion in the presence of sodium hydride. These compounds were a new group of destructible surfactants which were readily hydrolyzed and oxidized in natural water reservoirs. Physical properties of these new compounds involved some surface properties such as Krafft point(Kp), critical micelle concentration(cmc), surface tension of aqueous solutions near cmc(${\gamma}_{min}$), foaming power, emulsion power and hydrolysis properties were determined. The destructible surfactants containing 1,3-dioxane ring were synthesized to about $85{\pm}5.5%$ yield. The cmc values of the compounds by ring method were assumed to $0.5{\sim}5.0{\times}10^{-3}mol/L$ range and surface tensions at cmc were $29.5{\sim}33.0dyne/cm$ respectively at $25^{\circ}C$. The foaming power and foam stability were $170{\sim}230mm$ and $52{\sim}135mm$ respectively at $1{\times}10^{-2}mol/L$, foam was occurred rarely below $1{\times}10^{-3}mol/L$. The emulsion property of liquid paraffin was better than that of soybean oil. For hydrolysis property with ph and time, these compounds were decomposed within about 200minutes at $ph1{\sim}2$. Hopefully these compounds are expected to be a good O/W emulsifier that have decomposability in acid and may be used in the process which do not need foaming.