• KIEAE Journal
• /
• 제1권2호
• /
• pp.47-54
• /
• 2001

Single sound absorbers such as porous materials, panels, and Helmholts resonators have limited performance with some extents of frequency region. For example, porous materials do not attenuate low frequency sounds, while panels do not absorb high frequency sounds. Composite absorption structure with coverings, porous materials, and air gaps are an alternative for wide band sound absorption. Slits, panels, perforated panels are those materials for coverings, glass wool, mineral wool, polyester, and polyurethane are frequently used porous materials. Air gap between the porous material and background surface is one of major factors which governs the absorption characteristics of composite absorption structures, especially in the low frequency area. Calculations and measurements show that the absorption coefficients of composite absorption structure, in mid and low frequency bands, are getting higher with increased air gaps. Perforated panels rather than slits and panels are good coverings with higher number as far as absorption coefficient is concerned. Perforated panels with porous materials and 37 cm of air gaps in background have high absorption coefficients for all frequency bands, above 0.7 to 1.0. All measurements are performed in reverberation chamber, Mokpo National University, according to ISO 354 and ISO 3382.

• 대한수학회지
• /
• 제28권1호
• /
• pp.157-166
• /
• 1991

• 대한수학회논문집
• /
• 제6권2호
• /
• pp.299-310
• /
• 1991

• 대한수학회지
• /
• 제47권3호
• /
• pp.585-598
• /
• 2010

We deal with Matveev complexity of compact orientable 3-manifolds represented via Heegaard diagrams. This lead us to the definition of modified Heegaard complexity of Heegaard diagrams and of manifolds. We define a class of manifolds which are generalizations of Dunwoody manifolds, including cyclic branched coverings of two-bridge knots and links, torus knots, some pretzel knots, and some theta-graphs. Using modified Heegaard complexity, we obtain upper bounds for their Matveev complexity, which linearly depend on the order of the covering. Moreover, using homology arguments due to Matveev and Pervova we obtain lower bounds.

• 복식문화연구
• /
• 제3권2호
• /
• pp.201-214
• /
• 1995

The purpose of this study was to identify the key features of Sokol(蘇骨) and Kolso(骨蘇) and to determined the relation between sokol and kolso. A Comparative linguistical method was used for the analysis of this resarch. Also, sokol(蘇骨) and julpoong(折風) were examined to determine the relationship between the sokol and the julpoong. Results of this study indicated that the sokol and the kolso were identical head covering used by the nobility of Koguryo. The characteristics features of the sokol and kolso were that these tow head coverings wee made of purple ra(羅) and were decorated with gold and silver. The investigation found that the sokol and the kolso were not of Koguryo's native words. These words were derived from this neighboring words. The sokol and kolso were transliterations of neighboring words. The sokol and julpoong were different head coverings: The sokol was for the nobility while the julpoong was for a man of lowly position.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2002년도 추계학술대회논문집
• /
• pp.682-686
• /
• 2002

It is increasing the interest on the comfortable dwelling environment, while sound Insulation performance of materials and elements used in building is falling down as they become thicker and lighter. Therefore, sound insulation performance in building has become the most important factor determining the level of housing, especially for apartment that has common wall and floor with next neighbors. This paper aims to experiment the sound insulation characteristics of floor coverings as their types and to analyse their noise reduction effect.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2003년도 추계학술대회논문집
• /
• pp.756-759
• /
• 2003

It is increasing the interest on the comfortable dwelling environment and the efforts to solve the problem of the floor impact noise in apartment houses have been realized, as a result numerous products have been made. The purpose of this study is to investigate the sound insulation performances according to foaming rate of floor impact noise insulators and flooring coverings in Mock-up Test Room. The test results of impact insulation performance for each floor impact noise insulators is that double structure of insulator is excel than one in low-middle frequency band and as foaming rate go up, the sound insulation performance is improved.

• 한국화재소방학회:학술대회논문집
• /
• 한국화재소방학회 2008년도 춘계학술논문발표회 논문집
• /
• pp.61-64
• /
• 2008

Applying fire resistive coating to steel members is one of the general methods to secure fire resistance performance of steel members. And intumescent coating system is currently one of methods giving fire resistance to steel members. Intumescent coating system for fire resistance, however, has undesirable weaknesses that fire resistance performance of steel members is being deteriorated due to cracks and falling-offs of the coverings as time goes after completion of the coverings to the members. This study is designed to understand changes in fire resistance performance of intumescent coating system through follow-up tests on temperature of unexposed surface for the domestic intumescent coating system.

• 한국화재소방학회:학술대회논문집
• /
• 한국화재소방학회 2008년도 춘계학술논문발표회 논문집
• /
• pp.65-68
• /
• 2008

Intumescent coating system for fire resistance has undesirable weaknesses that fire resistance performance of steel members is being deteriorated due to cracks and falling-offs of the coverings as time goes after completion of the coverings to the members. This study is designed to understand changes in durability of intumescent coating system through follow-up tests on bond strength and thickness for the domestic intumescent coating system.

• 한국지능시스템학회논문지
• /
• 제8권4호
• /
• pp.78-81
• /
• 1998

We introduce the concepts of coverings, direct products, cascade products and wreath products of fuzzy finite state machines and investigate their algebraic structures.