• Bulletin of the Korean Chemical Society
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• v.35 no.3
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• pp.811-814
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• 2014

Bio-oil instability, or aging, is a significant problem for the long-term storage of fast pyrolysis oils. We investigated bio-oil aging at the molecular level using Fourier-transform ion cyclotron resonance mass spectrometry. Petroleomic analysis suggests that bio-oil aging is resulted from the oligomerization of phenolic lignin products whereas 'sugaric' cellulose/hemicellulose products have negligible effect.

• Journal of Practical Engineering Education
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• v.14 no.1
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• pp.165-177
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• 2022

The purpose of this study is to present the direction of employment guidance for long-term service through the analysis of the cause of employment of employed students who graduated from specialized high school. In particular, the purpose is to present student guidance plans for long-term service by analyzing personal reasons for students graduating from commercial high schools and policy factors for individual, school, company, and government service after employment. To this end, a survey was conducted for graduates of commercial high schools nationwide, and the validity, reliability, and causality of the survey data were analyzed by applying Exploratory Factor Analysis, Cronbach's Alpha, and decision tree analysis techniques. We found that personal goal setting for employment is an important factor for working for more than 1 year, personal relationships at work and personal characteristics are important factors for working for more than 3 years. In addition, we found that the reason for getting a job is that personal reasons and school recommendations are great, special lectures on employment, camps, and 'advice from seniors and teachers' programs are helpful in finding a job, and accounting and computer related subjects are helpful for long-term employment. Accordingly, in specialized high schools, it is required to prepare specific instructional measures for education such as setting personal goals and the formation of human relationships that are the basis of social life, and to actively operate the above subjects and programs to help with employment and longevity.

• Proceedings of the IEEK Conference
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• 2000.11a
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• pp.217-220
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• 2000

This paper studies a real-time VBR traffic characterization. There are two big approaches to determine traffic. One is a statistic approach and the other is a deterministic approach. This paper proposes a new constraint function, what we called “Sub-Sum Constraint Function”(SSCF). This function is mainly based on a deterministic approach and uses a statistic approach. It predicts and calculates the next rate with a present information about the stream. SSCF captures the intuitive bounded by a rate lower than its peak rate and closer to its long-term average rate. This model makes a order of the constraint function much less than any other works (O(n)). It can also be mapped on a token bucket algorithm which consists of r (token rate) and b (token depth). We use a concept, EB(effective bandwidth) for a utility of our function and comparing with other techniques such as CBR, average VBR. We simulated 21 multimedia sources for verifying the utility of our function.

• Journal of Animal Reproduction and Biotechnology
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• v.38 no.1
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• pp.26-31
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• 2023

Chicken embryonic stem (ES) cells have great potential and provide a powerful tool to investigate embryonic development and to manipulate genetic modification in a genome. However, very limited studies are available on the functional characterization and robust expansion of chicken ES cells compared to other species. Here, we have developed a method to generate chicken embryonic stem cell-like cells under pluripotent culture conditions. The chicken embryonic stem cell-like cells were cultivated long-term over several passages of culture without loss of pluripotency in vitro and had the specific expression of key stem cell markers. Furthermore, they showed severe changes in morphology and a significant reduction in pluripotent genes after siRNA-mediated NANOG knockdown. Collectively, these results demonstrate the efficient generation of chicken embryonic stem cell-like cells from EGK stage X blastoderm-derived singularized cells and will facilitate their potential use for various purposes, such as biobanking genetic materials and understanding stemness in the fields of animal biotechnology.

• Transactions of the Korean hydrogen and new energy society
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• v.22 no.4
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• pp.488-494
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• 2011

Gasket plays an important role on sealing of the polymer electrolyte membrane fuel cell (PEMFC) stack. Stack requires gaskets in each cell to keep the hydrogen and air/oxygen within their respective regions. The failure of the gasket creates the problems of fuel leakage, mixing, damage on parts and can be a direct reason for the degrading the efficiency of fuel cell. The purpose of this paper researches on how mechanical properties of EPDM gasket in PEMFC are changed after long-term operations. The EPDM (ethylenepropylene-diene monomer) gaskets are obtained from the stack after long-term operations. DMA (dynamic mechanical analysis) is conducted to access the change of mechanical properties of the EPDM gasket. SEM/EDS (scanning electron microscope/energy dispersive spectroscopy) was used to show the surface topography and chemical characterization on the sample surface.

• Applied Chemistry for Engineering
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• v.20 no.2
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• pp.140-144
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• 2009

Triethanolamine-type cationic surfactants were synthesized and their applications were established. The production of mono-, di-, and tri-TEA-EQ (triethanol-amine-esterquater) were dependent on the molar ratio of fatty acid and triethanolamine under the controlled reaction temperature. The structures were elucidated by $H^{1}$ NMR. Long-term stability was dependent on the amount of mono- and tri-TEA-EQ. When the amount of mono-TEA-EQ was increased, long-term stability was increased. However, the more tri-TEA-EQ made long-term stability decreased. Softening was dependent on the amount of saturated fatty acid, and re-wettability was counted on the amount of unsaturated fatty acid. Softening was measured by the method of sense estimation e.g. touching to home-towel. Absorption was determined to calculate the height of water on a towel after treatment.

• Journal of the Korean Solar Energy Society
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• v.37 no.4
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• pp.35-47
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• 2017

Energy efficiency solutions are being pursued as a sustainable approach to reducing energy consumption and related gas emissions across various sectors of the economy. Vacuum Insulation Panel (VIP) is an energy efficient advanced insulation system that facilitates slim but high-performance insulation, based on a porous core material evacuated and encapsulated in a barrier envelope. Although VIP has been applied in buildings for over a decade, it wasn't until recently that efforts have been initiated to propose and adopt a global standard on characterization and testing of VIP. One of the issues regarding VIP is its durability and aging due to pressure and moisture dependent increase of the initial low thermal conductivity with time; more so in building applications. In this paper, the aging of commercially available VIP was investigated experimentally; thermal conductivity was tested in accordance with ISO 8302 standard (guarded hot box method) and long-term durability was estimated based on a non-linear pressure-humidity dependent equation based on study of IEA/ECBCS Annex 39, with the aim of assessing durability of VIP for use in buildings. The center-of-panel thermal conductivity after 25 years based on initial 90% fractile with a confidence level of 90 % for the thermal conductivity (${\lambda}90/90$) ranged from 0.00726-0.00814 (W/m K) for silica core VIP. Significant differences between manufacturer-provided data and measurements of thermal conductivity and internal pressure were observed.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.10 no.1
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• pp.82-89
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• 2014

In this study, the metallurgical analysis and mechanical property measurement have been performed to investigate the effect of long-term thermal aging on the microstructural evolution in the fusion boundary region between weld metal and low alloy steel in dissimilar metal welds. A representative dissimilar weld mock-up made of Alloy 690-Alloy 152-A533 Gr. B was fabricated and aged at $450^{\circ}C$ for 2,750 hours. The microstructural characterization was conducted mainly near in a weld root region by using optical microscopy, scanning electron microscopy, transmission electron microscopy. And the mechanical properties were measured with Vickers microhardness test and nanoindentation method. A steep gradient was shown in the chemical composition profile across the interface between A533 Gr. B and Alloy 152. Type-II boundaries were found in weld side of DMW and the hardness was the highest at the narrow zone between Type-II boundary and fusion boundary.

• Journal of Korean Society on Water Environment
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• v.25 no.3
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• pp.411-418
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• 2009

The analysis of characteristics of water use evaluation and nighttime domestic flow evaluation was performed by using result from flow monitoring and surveying water supply records and nighttime domestic flow for a year. The analysis of correlations showed that, for both sites, the infiltration ratio and wastewater flow have shown a good relationship with high correlation factor and that the calculation of wastewater flow was highly affected by monthly rainfall depth as well as number of rain days. From this result, it was concluded that the measurement of infiltration should be performed when the rainfall does not significantly affect the sewer flow. Also, it is notable that each value of calculated using method for infiltration evaluation are not comparable to each other, but independent methods. In selecting of evaluation method for infiltration, therefore, a great emphasis should be imposed to the character of area and the seasonal factor in order to select optimal one. It is desirable way for evaluating infiltration and reduction ratio using result from an optimal method.

• Korean Membrane Journal
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• v.6 no.1
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• pp.55-60
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• 2004

In recent years, an increasing interest in membrane technology has been observed in chemical and environmental industry. Membrane technology has advantages of low cost, energy saving and environmental clean technology comparing to conventional separation processes. Pervaporation is one of new advanced membrane technology applied for separation of azeotropic mixtures, aqueous organic mixtures, organic solvent and petrochemical mixtures. Sodium alginate composite membranes were prepared for the enhancement of long-term stability of pervaporation performance of water-ethanol mixture using pervaporation. Sodium alginate membranes were crosslinked with CaCl$_2$ and coated with polyelectrolyte chitosan to protect washing out of calcium ions from the polymer. The surface structures of PAN and hydrolysed PAN membrane were confirmed by ATR Fourier transform infrared (FT-IR). A field emission scanning electron microscopy (FE-SEM; Jeol 6340F) operated at 15 kV. Concentration profiles for Ca in the membrane surface and membrane cross-section were taken by an energy dispersive X-ray (EDX) analyser (Jeol) attached to the field emission scanning electron microscopy (Jeol 6340F). Pervaporation experiments were done with several operation run times to investigate long-term stability of the membranes.