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곽종호(Jong-Ho GWAK),권용훈(Yong-Hun KWEON),木俊之(Toshiyuki AOKI),김희동(Heuy-Dong KIM) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.11
The effects of absorbing materials on the characteristics of supersonic jet noise were experimentally investigated using a convergent-divergent nozzle with a design Mach number of 2.0. Overall sound pressure levels (OASPL) and noise spectra were obtained at far-field locations. Schlieren optical system was used to visualize the flow-fields of supersonic jets. In order to investigate the effect of absorbing materials, baffle plates of different materials (metal, grass wool and polyurethane foam) were installed at the exit of the nozzle. Experiment was carried out over a wide range of nozzle pressure ratios from 2.0 and 18.0, which corresponds to over- and under-expanded conditions. The results obtained show that the screech tone amplitude and the overall sound pressure level reduce by using the baffle plates of absorbing materials, compared with the metal baffle plate. It is also found that the characteristics of supersonic jet noise are strongly dependent on the size of baffle plate.
적외선 카메라를 이용한 초음속 충돌 동축제트의 벽면 온도 측정
곽종호(Jong-Ho Gwak),V. R. Sanal Kumar,김희동(Heuy-Dong Kim) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.4
The supersonic impinging jet has been extensively applied to rocket launching system, gas jet cutting control, gas turbine blade cooling, etc. In such applications, wall temperature of an object on which supersonic jet impinges is a very important factor to determine the performance and life of the device. However, wall temperature data of supersonic impinging jets are not enough to data. The present study describes an experimental work to measure the wall temperatures of a vertical flat plate on which supersonic, dual, coaxial jet impinges. An Infrared camera is employed to measure the wall temperature distribution on the impinging plate. The pressure ratio of the jet is varied to obtain the supersonic jets in the range of over-expanded to moderately under-expanded conditions at the exit of coaxial nozzle. The distance between the coaxial nozzle and the flat plate was also varied. The coaxial jet flows are visualized using a Shadow optical method. The results show that the wall temperature distribution of the impinging plate is strongly dependent on the jet pressure ratio and the distance between the nozzle and plate.
곽종호(Jong-Ho Gwak),김희동(Heuy-Dong Kim) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.11
Perforated wall has long been employed to control a variety of flow phenomena. It has been, in<br/> general, characterized by a porosity of the perforated wall. However, this porosity value does not take<br/> account of the number and detailed shape of porous holes, but is defined by only the ratio of the<br/> perforated area to total wall surface area. In order to quantify the porous wall effects on the flow<br/> control performance, an effective porosity should be known with the detailed flow properties inside the<br/> porous holes. In the present study, a theoretical analysis using a small disturbance method is performed<br/> to investigate detailed flow information through porous hole and a computational work is also carried<br/> out using the two-dimensional, compressible Navier-Stokes equations. Both the results are compared<br/> with existing experimental data. The gasdynamical porosity is defined to elucidate the effect of<br/> perforated wall.
Photoluminescence of YVO4:Eu3+ Prepared by Li2CO3 Addition
문성준,정현곤,곽종호,손기선 한국세라믹학회 2008 한국세라믹학회지 Vol.45 No.11
Deep red color emitting YVO4:Eu3+ phosphors were investigated in an attempt to achieve promising performances in cold cathode fluorescent lamp (CCFL) applications. For this purpose, several additives such as LiF, LiCO3 and HBO3 were introduced in the processing. While two of the additives were ineffective, the inclusion of LiCO3 during the solid state synthesis of YVO4:Eu3+ phosphors was proven to enhance photoluminescent intensity and the color chromaticity. Unlike the commercially available Y(V,P)O4:Eu3+ red phosphor for use in PDP applications, pure YVO4:Eu3+ excluding phosphorous was shown to be favorable for CCFL applications, improving color chromaticity at 254 nm excitations. Deep red color emitting YVO4:Eu3+ phosphors were investigated in an attempt to achieve promising performances in cold cathode fluorescent lamp (CCFL) applications. For this purpose, several additives such as LiF, LiCO3 and HBO3 were introduced in the processing. While two of the additives were ineffective, the inclusion of LiCO3 during the solid state synthesis of YVO4:Eu3+ phosphors was proven to enhance photoluminescent intensity and the color chromaticity. Unlike the commercially available Y(V,P)O4:Eu3+ red phosphor for use in PDP applications, pure YVO4:Eu3+ excluding phosphorous was shown to be favorable for CCFL applications, improving color chromaticity at 254 nm excitations.
장거리 도보여행길과 연계한 강변 그린로드 모형 및 노선 개발
임창수,홍광우,김은자,곽종호,최진아 한국농촌계획학회 2012 농촌계획 Vol.18 No.4
In recent years, the central ministries and regional self are competitively developing program for creating a trail and theme path by the increase of the number of trekkers. Even though these projects are developed in rural areas, it has been pointed out that most of projects do not directly linked to the revitalization of rural villages and improvement of non-farm income because of the main road itself as a resource in rural area. Therefore, in this study, we try to connect the citizen and the agriculture and rural area through the development of the green road which is the experience road with rural resource. To achieve this, we investigated the status and characteristics of the 36 villages where are the village was promoted various major project of first step. In second step, we considered the distinct characteristics of the area with conference of expert and site investigation for the final selection of 15 villages. Through two rounds' expert group consulting with checking, related literatures review and similar case-projects benchmarking, a riverside green road which is linked long distance trail and adjacent to the riverside was developed 15 courses by 2-development types proposed.