• Carbon letters
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• v.15 no.3
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• pp.162-170
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• 2014

Pitch is an attractive raw material for carbon fiber precursors due to its low cost stemming from its availability as a residue of coking and petroleum processes. Ford Motor Company reported a carbon fiber target price of $11.0/kg by using a fast cycle-time manufacturing method with carbon fiber in an inexpensive format, allowing for an average retail price of gasoline of $3.58/gallon. They also recommended the use of carbon fiber with strength of 1700 MPa, modulus of 170 GPa, and 1.5% elongation. This study introduced a ca. $5.5{\mu}m$ carbon fiber with 2000 MPa tensile strength obtained from a precursor through simple distillation of petroleum residue. Petroleum pitch based carbon nanofibers prepared via electrospinning were characterized and potential applications were introduced on the basis of their large specific surface area and relatively high electrical conductivity.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.1001-1004
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• 2002

Accurate prediction of the transmission loss of dissipative silencers has been considered difficult due to the ambiguity and complexity in the physical properties of sound absorbing materials. Additional difficulty lies in the fact that the analytical calculation of the propagation constant is unknown yet. In this paper. as a first step toward obtaining the Propagation constant and thus predicting the transmission loss, an approximation equation stemming from the wave analysis in the lined interior has been derived. Such an analytical solution and numerical solution using the boundary element method are compared for a two-dimensional simple dissipative silencer under the assumption of the locally reacting sound absorbent.

• Journal of the Korean School Mathematics Society
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• v.11 no.4
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• pp.655-676
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• 2008

This paper analyzed contents related to statistics in the 7th elementary mathematics curriculum in conjunction with main changes in the recent revised curriculum. This paper then provided detailed analyses of textbooks and workbooks in terms of main contents, instructional methods of graphs, and comprehension of graphs required to students in order to look closely at how such instructional materials would put the vision of the curriculum into action. It is expected that the issues and suggestions stemming from this analysis are informative in constructing new textbooks and workbooks.

• Journal of the Korean School Mathematics Society
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• v.13 no.1
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• pp.1-21
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• 2010

This paper analyzed the contents and instructional methods of various plane figures presented mainly in a series of elementary mathematics textbooks on the basis of the analysis of related contents in the 2007 revised national mathematics curriculum. As such, this paper provided detailed analyses of how textbooks would implement the vision and intention of the curriculum, how the definition of each plane figure in the textbooks might be different from its mathematical definition, and how textbooks would introduce each plane figure. It is expected that the issues and suggestions stemming from this analysis will be informative in designing new instructional materials.

• Journal of the Korean Society of Clothing and Textiles
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• v.18 no.5
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• pp.739-748
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• 1994

These days the Korean costume becomes the formal dress to be worn on particular occasions. The Westernization of life style, inculding dress, has made the costume of wearing traditional dress disappear from Korean's everyday life. This study is launched to investigate the precious textiles and materials of the past before they vanish; this study deals with the materials of folk costume in the early 20th century, preceding Westernization. The research method adopted in the study was interviews of fifth- five elderly persons living around the Mt. Kumo area in Gyungbuk province. The result was that costume culture in that area was poor because people living in the area were economically less well off due to meager agricultural products. There was no variety in the style of costumes to be worn for various occasions. It was also nothworthy that because of no diversification in naming, only one representative word was used to name several types of costumes. On the other hand, it was discovered that the people in the Mt. Kumo area had religious aspirations stemming from their folk beliefs concerning costumes. They also had an attitude of saving money despite poor economic conditions.

• Journal of the Microelectronics and Packaging Society
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• v.22 no.4
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• pp.99-104
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• 2015

The requirement for success of via filling is its ability to fill via holes completely without producing voids or seams. Defect free via filling was obtained by optimizing plating conditions such as current mode, current density and additives. However, byproducts stemming from the breakdown of these organic additives reduce the lifetime of the devices and plating solutions. In this study, the relationship between JGB and current density on the copper via filling was investigated without the addition of other additives to minimize the contamination of copper via. AR 4 with $15{\mu}m$ diameter via were used for this study. The pulse current was used for the electroplating of copper and the current densities were varied from 10 to $20mA/cm^2$ and the concentrations of JGB were varied from 0 to 25 ppm. The map for the JGB concentration and current density was developed. And the optimum conditions for the AR 4 via filling with $15{\mu}m$ diameter were obtained.

• Korean Journal of Materials Research
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• v.27 no.2
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• pp.107-112
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• 2017

The BCBJ (Back Contact and Back Junction) or back-lit solar cell design eliminates shading loss by placing the pn junction and metal electrode contacts all on one side that faces away from the sun. However, as the electron-hole generation sites now are located very far from the pn junction, loss by minority-carrier recombination can be a significant issue. Utilizing Medici, a 2-dimensional semiconductor device simulation tool, the interdependency between the substrate thickness and the minority-carrier recombination lifetime was studied in terms of how these factors affect the solar cell power output. Qualitatively speaking, the results indicate that a very high quality substrate with a long recombination lifetime is needed to maintain the maximum power generation. The quantitative value of the recombination lifetime of minority-carriers, i.e., electrons in p-type substrates, required in the BCBJ cell is about one order of magnitude longer than that in the front-lit cell, i.e., $5{\times}10^{-4}sec$ vs. $5{\times}10^{-5}sec$. Regardless of substrate thickness up to $150{\mu}m$, the power output in the BCBJ cell stays at nearly the maximum value of about $1.8{\times}10^{-2}W{\cdot}cm^{-2}$, or $18mW{\cdot}cm^{-2}$, as long as the recombination lifetime is $5{\times}10^{-4}s$ or longer. The output power, however, declines steeply to as low as $10mW{\cdot}cm^{-2}$ when the recombination lifetime becomes significantly shorter than $5{\times}10^{-4}sec$. Substrate thinning is found to be not as effective as in the front-lit case in stemming the decline in the output power. In view of these results, for BCBJ applications, the substrate needs to be only mono-crystalline Si of very high quality. This bars the use of poly-crystalline Si, which is gaining wider acceptance in standard front-lit solar cells.

• Explosives and Blasting
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• v.35 no.4
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• pp.19-26
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• 2017

The most widely used method for determining the blast effects of explosives is the Trauzl lead block test. This test is used to measure the explosive power (strength) of a substance by determining volume increase, which is produced by the detonation of a test explosive charged in the cavity of a lead block with defined quantity and size. In this paper, Trazul lead block test and AUTODYN numerical analysis were conducted to evaluate the coupling medium effect of blast hole. The effects of coupling materials can be expressed as the expansion of the cavity in a standard lead block through explosion of the explosives. The tests were conducted with emulsion explosives. The coupling mediums used as the filling material around a explosive charge were air, sand, water and gelatine. Results of test and numerical analysis showed that expansion of lead block were much more affected by water&gel than by sand and air. The water and gel showed similar results. As expected, the transmitted pressure and dynamic strain was higher in water and gelatine coupled blast hole than in air and sand.

• Journal of the Microelectronics and Packaging Society
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• v.19 no.2
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• pp.55-59
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• 2012

Defects such as voids or seams are frequently found in TSV via filling process. To achieve defect-free copper via filling, organic additives such as suppressor, accelerator and leveler were necessary in a copper plating bath. However, by-products stemming from the breakdown of these organic additives reduce the lifetime of the devices and plating solutions. In this research, the effects of levelers on copper electrodeposition were investigated without suppressor and accelerator to lower the concentration of additives. Threelevelers(janus green B, methylene violet, diazine black) were investigated to study the effects of levelers on copper deposition. Electrochemical behaviors of these levelers were different in terms of deposition rate. Filling performances were analyzed by cross sectional images and its characteristics were different with variations of levelers.

• Journal of Distribution Science
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• v.3 no.2
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• pp.121-142
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• 2005

We're living in a world of one global village. The globalization of business is acceleration as more companies cross national borders to find customers, materials and money. Many foreign companies and organizations are doing their business aggressively in Korea and many Korean companies and rushing into foreign market. When people communicate for business with someone from another culture, there could be difficult communication barriers to overcome resulting from differences in their values, beliefs, norms for behavior, expectations, attitudes and so on. To do successfully business, we need to understand culture background and communication style that is different from nation, race, language. Communication barriers stemming from cultural differences may vary. Largely, they can be divided into value system, non-verbal communication, and perception process. Value system can be divided into individualism versus group orientation, avoidance of uncertainty degree, power distance, and high- context culture versus low-context culture. Also non-verbal communication method and perception process may play decisive roles in communication effectiveness. Especially nonverbal communication barriers which sometimes play more important roles than the verbal parts are composed of eye contact, gesture, kinesics, proxemics, chronemics, paralanguage and language of color Cross-cultural communication affect business situation. I expect that if we understand cultural background, and then we overcome cross-cultural communication barriers. To overcome and to adapt inter-cultural business, we need to develope curriculum on the cross-cultural education which I will study in the next paper.