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모바일 AR에서 효율적인 연속 공간 질의를 위한 프리패칭 기법
정용희 ( Yong Hee Jung ),조현구 ( Hyun Gu Jo ),양평우 ( Pyoung Woo Yang ),송충원 ( Chung Won Song ),이연식 ( Yon Sik Lee ),남광우 ( Kwang Woo Nam ) 한국정보처리학회 2012 한국정보처리학회 학술대회논문집 Vol.19 No.1
최근에 스마트폰 기반의 다양한 증강현실 서비스들이 제공되고 있다. 이러한 증강현실 서비스들은 공간질의를 하고 검색되어진 데이터를 실제 영상화면에 표현해주는 것을 말한다. 본 논문은 증강현실 서비스에서 많이 이용되는 공간 검색 성능을 향상 시키기 위하여 기존의 속도기반 프리패칭 기법에 사용자의 시점을 이용한 영역 검색 방법을 혼합하여 효율적이고 의미 있는 검색을 가능하게 하였다.
Nitrided Pressureless Sintering 공정을 이용한 질화규소 세라믹스의 제조 및 특성
천승호,한인섭,정용희,서두원,이시우,홍기석,우상국,Cheon, Sung-Ho,Han, In-Sub,Chung, Yong-Hee,Seo, Doo-Won,Lee, Shi-Woo,Hong, Kee-Soeg,Woo, Sang-Kuk 한국세라믹학회 2004 한국세라믹학회지 Vol.41 No.12
Nitrided Pressureless Sintering(NPS) 공정에 의한 질화규소 세라믹스의 기계적 특성, 미세구조 및 열적 특성을 세 가지조성을 갖는 $Al_{2}O_3,\;Y_{2}O_3$ 소결조제의 변화에 따라 조사하였다. 또한 각 조성에서 금속 실리콘의 첨가량을 0, 5, 10, 15, 그리고 $20wt\%$로 변화를 주어 실리콘의 첨가효과를 조사하였다. $5wt\%\;Al_{2}O_3,\;5wt\%\;Y_{2}O_3$, 그리고 $5wt\%$ Si 조성에서 질화규소 소결체의 치밀화가 진행되었으며, 4점 꺽임강도와 상대밀도는 각각 500 MPa과 $98\%$를 나타내었다. 또한 상온에서 열팽창계수와 열전도도는 각각 $2.89{\times}10^{-6}/^{\circ}C$와 $28W/m^{\circ}C$를 나타내었으며, 20,000회의 열충격 싸이클을 반복한 후, 꺽임강도를 측정한 결과, 초기 500MPa의 강도를 유지하고 있었다. The mechanical properties and microstructure and thermal properties of Nitrided Pressureless Sintering(NPS) silicon nitride ceramics, containing three type of $Al_{2}O_3,\;Y_{2}O_3$ sintering additives, were investigated. Also, we have investigated the effect of silicon metal content changing with 0, 5, 10, 15, and $20wt\%$ Si in each composition. In $5wt\%\;Al_{2}O_3,\;5wt\%\;Y_{2}O_3,\;and\;5wt\%$ Si composition, silicon nitride sintered body was successfully densified to a high density. The average 4-point flexural strength and relative density of these specimens were 500 MPa and 98% respectively. Also, Thermal expansion coefficient and thermal conductivity of specimens at room temperature were $2.89{\times}10^{-6}/^{\circ}C\;and\;28W/m^{\circ}C$, respectively. The flexural strength of sintered specimens after thermal shock test of 20,000 cycles was maintained as-received value of 500 MPa.
金泰勳,鄭容熙 영남대학교 자원문제연구소 1990 資源問題硏究 Vol.9 No.-
In this paper, the normal noise attenuations for material chracteristics of curtain fabrics were measured by using sound intensity analyzer system in the anechoic chamber. Eight Kinds of curtain fabrics having different material characteristics were used to investigate the noise attenuation effect. Noise attenuation rate was calculated by difference of incidence SPL(without curtain fabrics ) and transmission SPL(through curtain fabrics). The relations between these values and factors relating to the material characteristics of curtain fabrics were investigated. The results of experiment were shown as follows ; 1. Noise attenuation mechanism of curtain fabrics was explained by the frequency chracteristics curve. The attenuation rate of noise in curtain fabrics was increased according to the frequency. It was lower in 315Hz, 630Hz and 1,000Hz frequency, on the other hand higher in 400Hz, 800Hz and above 1,250Hz frequency. 2. The cover factor and thickness of materials were increased as the attenuation rate of noise were greater. 3. Air permeability of materials was decreased as the attenuation rate of noise was greater. The results were shown that the nise attenuation rate of curtain fabrics depended not only on the frequency used for the measurement but also its air permeability, thickness and cover factor