• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.341-346
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• 2001

The gun-type gas burner adopted in this study is generally composed of some slits and swirl vanes. Therefore, this paper is studied to investigate the effect of slits and swirl vanes on the turbulent flow fields in the horizontal plane of gas swirl burner with a cone type baffle plate measured by using X-probe from hot-wire anemometer system. This experiment is carried out at flow rate $450\;{\ell}/min$, which is equivalent to the combustion air flow rate necessary for heat release 15,000 kcal/hr in gas furnace, in the test section of subsonic wind tunnel. When the burner has only swirl vanes, the axial mean velocity component shows the characteristic that spreads more remarkably toward radial direction than axial one, but when it has only slits, that is developed spreading more toward axial direction than radial one. Therefore, because the biggest speed is spurted in slits and it derive main flow toward axial direction encircling rotational flow that comes out from swirl vane that is situated on the inside of slits, both slits and swirl vanes composing of cone type gas burner act role that decreases the speed near slits and increases the flow speed in the central part of a burner. Moreover, because rotational flow by swirl vanes and fast jet flow by slits increase turbulent intensities effectively coexisting, the turbulent kinetic energy is distributed with a bigger size fairly near slits than burner models which have only slit or swirl vanes within X/R<0.6410.

• 한국항공우주학회지
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• 제49권7호
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• pp.529-537
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• 2021

스크램제트 엔진을 갖는 초고속 비행체로 풍동실험을 수행하였다. 스크램제트 엔진은 별도의 압축기가 없기 때문에 간단한 구조를 갖고 있지만 연소실에서 초음속 연소가 일어날 수 있도록 흡입구를 설계하는 것이 중요하다. 본 연구에서는 연소실 직전에 있는 격리부 출구면 압력 측정을 통해 내부 유동 특성 및 흡입구 시동 조건을 판단하였고 흡입구 성능 변수를 계산하여 마하수 별로 결과를 비교하였다. 유동관통형 초고속 비행체의 공력 특성도 분석하였고 정확한 공력 특성 분석을 위해서 내부 항력 보정이 필요하다. 본 연구에서는 내부 항력 보정을 위해 세 가지 프로브를 이용한 실험 기법을 제시하였다. 내부 항력 보정을 적용하여 내부 유동이 비행체 공력에 미치는 영향을 파악할 수 있었다.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2000년도 창립총회 및 춘계학술발표회
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• pp.84-89
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• 2000

Parametric studies based on laboratory pilot tests were performed to investigate the relationships between electrical resistivity and contaminated soil properties. Three kinds of sandy soils sampled and leachates from a industrial waste landfill were mixed to model the contaminated soils. Electrical resistivity of soils were measured by using a simulated resistivity cone penetrometer probe. In the experiments, the electrical resistivity were observed with changing the water content, void ratio, unit weight, degree of saturation, and concentration of the leachate. The test results show that the electrical resistivity of soils depends largely on the water content and the electrical property of pore water rather than unit weight and types of soils.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.318-326
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• 2008

Recently, a new seismic probe, called "MudFork", has been developed and can be utilized for accurate and easy measurements of shear wave velocities of soft soils. To expand its use to estimate undrained shear strength and density, correlations between those and shear wave velocity were being attempted. Cone penetration tests and a seismic test, using MudFork, were performed at a soft ground site near Incheon, Korea. Also, undisturbed samples were obtained and shear wave velocities of the samples were measured as well as undrained shear strength, using triaxial compression test and bender elements. A simple linear relationship between shear strength and shear wave velocity was obtained, and a tentative relationship between density and shear wave velocity was also defined.

• 한국추진공학회지
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• 제21권3호
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• pp.49-55
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• 2017

가스터빈엔진의 성능시험을 위한 엔진 입구덕트를 1D 기법으로 Sizing 하였으며, 압축기 입구유동측정면(AIP, Aerodynamic interface plane)에서 경계층 두께를 최소화하고, 코어부 마하수분포가 균일하도록 설계하였다. 노즈콘 형상은 Haack-series 모델을 적용하고, 덕트 안쪽과 바깥쪽 면적변화율이 동일하도록 입구덕트 채널 바깥반경($r_o$)를 결정하여 설계목적을 구현하고자 하였으며, 이러한 형상이 설계목표에 부합하는지 확인하기 위하여 CFD를 수행하였다. AIP면에서 정압력분포는 최대값과 최소값 차이가 0.16% 이었으며, 마하수분포에서 경계층은 덕트반경 길의 2% 이내로 설계목표를 만족하였다. 이때 균일유동 코어부는 채널높이의 95% 이상이었다. 또한 입구유동의 전온도를 측정하기 위한 키엘 전 온도레이크 위치는 온도 회복계수가 최대화 되도록 마하수가 0.1 이하 지역인 노즈콘 전방 100 mm 이내이어야 함을 확인하였다.

• 대한기계학회논문집B
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• 제28권4호
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• pp.475-485
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• 2004

This paper was studied to investigate and compare the effects of inclined baffle plate on the turbulent flow characteristics of a gun-type gas burner through X-Y plane and Y-Z plane respectively by using X-probe from hot-wire anemometer system. For this purpose, two burner models with a cone-type baffle plate and a flat-type one respectively were used. The fast jet flow spurted from slits plays a role such as an air-curtain because it encircles rotational flow by swirl vanes and drives mixed main flow to axial direction regardless of the inclination of baffle plate. The inclined baffle plate causes axial mean velocity component and turbulent intensities etc. to be greatly concentrated towards the central part of a burner, and its effect especially appears in the range of about X/R=1.0-2.0. Also, it gives much larger size to axial mean velocity component and turbulent intensities etc formed near the slits in the range of X/R=1.4103. Especially the inclined baffle plate shifts more the Reynolds shear stress uw to the central region of a burner(Y/R=${\pm}$0.75) than the flat-type one, moreover it develops more strongly than uv.

• 대한기계학회논문집B
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• 제27권4호
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• pp.466-475
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• 2003

The gun-type gas burner adopted in this study is generally composed of eight slits and swirl vanes. Thus, this paper is studied to investigate the effect of slits and swirl vanes on the turbulent flow fields in the horizontal plane of gas swirl burner with a cone type baffle plate measured by using X-probe from hot-wire anemometer system. This experiment is carried out at flow rate 450 $\ell$/min in the test section of subsonic wind tunnel. The axial mean velocity component in the case of burner model with only swirl vanes shows the characteristic that spreads more remarkably toward the radial direction than axial one, it does, however, directly opposite tendency in the case of burner model with only slits. Consequently. both slits and swirl vanes composing of gun-type gas burner play an important role in decrease of the speed near slits and increase of the flow speed in the central part of a burner because the biggest speed spurted from slits encircles rotational flow by swirl vanes and it drives main flow toward the axial direction. Moreover, the turbulent intensities and turbulent kinetic energy of gun-type gas burner are distributed with a fairly bigger size within X/R<0.6410 than burner models which have only slits or swirl vanes because the rotational flow by swirl vanes and the fast jet flow by slits increase flow mixing, diffusion, and mean velocity gradient effectively.

• 동력기계공학회지
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• 제5권2호
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• pp.22-29
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• 2001

This paper represents axial mean velocity, turbulent kinetic energy and swirl number based on momentum flux measured in the X-Y plane and Y-Z plane respectively of a cone type gas swirl burner by using X-probe from the hot-wire anemometer system. This experiment is carried out at flow rates 350 and $450{\ell}/min$ respectively, which are equivalent to the combustion air flow rate necessary for heat release 15,000 kcal/hr in gas furnace, in the test section of a subsonic wind tunnel. Axial mean velocities and turbulent kinetic energies show that their maximum values exist centering around narrow slits situated radially on the edge of and in the forefront of a burner until $X/R{\fallingdotseq}1.5$, but they have a peculiar shape like a starfish diffusing and developing into inward and outward of a burner by means of the mixing between flows ejected from narrow slits, an inclination baffle plate and swirl vanes respectively according to downstream regions. Moreover, they show a relatively large value in the inner region of 0.5$S_m$ obtained by integration of velocity profiles shows a characteristic that has an inflection point composing of the maximum and minimum value until X/R<3, but shows close agreement with the geometric swirl number after a distance of X/R=3.

• 한국강구조학회 논문집
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• 제15권6호통권67호
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• pp.649-660
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• 2003

본 논문은 비균열 무근콘크리트에 매입된 익스팬션 앵커의 인발내력을 평가하기 위한 실험적 연구이다. 앵커의 인발실험은 익스 팬션 앵커에 해당하는 고하중 앵커와 웨지 앵커를 대상으로 대상으로 삽입깊이, 콘크리트 강도 및 연단거리을 변수로 하여 실험을 수행하였다. 후시공 앵커의 설계식은 EOTA와 ACI 318-02 규준의 근거가 되는 CCD 방법이 제안되어 있다. 본 연구에서는 비균열 무근콘트리트에 매입된 익스팬션 앵커의 콘크리트 콘 파괴강도에 관한 설계식을 분석하였으며, 고하중 앵커와 웨지 앵커의 실험값을 CCD 방법의 예측값과 비교 평가하였다. 실험 결과, 비균열 무근콘크리트에 매입된 웨지 앵커의 콘크리트 콘 파괴 시 공칭강도의 계수는 CCD 방법에 근거하여 9.94임을 알 수 있었다. 고하중 앵커의 콘크리트 콘 파괴 시 공칭강도의 계수는 CCD 방법에 근거하여 11.50임을 알 수 있었다.

• Journal of Periodontal and Implant Science
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• 제51권2호
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• pp.88-99
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• 2021

Purpose: Direct intraoral scanning and superimposing methods have recently been applied to measure the dimensions of periodontal tissues. The aim of this study was to analyze various correlations between labial gingival thickness and underlying alveolar bone thickness, as well as clinical parameters among 3 tooth types (central incisors, lateral incisors, and canines) using a digital method. Methods: In 20 periodontally healthy subjects, cone-beam computed tomography images and intraoral scanned files were obtained. Measurements of labial alveolar bone and gingival thickness at the central incisors, lateral incisors, and canines were performed at points 0-5 mm from the alveolar crest on the superimposed images. Clinical parameters including the crown width/crown length ratio, keratinized gingival width, gingival scallop, and transparency of the periodontal probe through the gingival sulcus were examined. Results: Gingival thickness at the alveolar crest level was positively correlated with the thickness of the alveolar bone plate (P<0.05). The central incisors revealed a strong correlation between labial alveolar bone thickness at 1 and 2 mm, respectively, inferior to the alveolar crest and the thickness of the gingiva at the alveolar crest line (G0), whereas G0 and labial bone thickness at every level were positively correlated in the lateral incisors and canines. No significant correlations were found between clinical parameters and hard or soft tissue thickness. Conclusions: Gingival thickness at the alveolar crest level revealed a positive correlation with labial alveolar bone thickness, although this correlation at identical depth levels was not significant. Gingival thickness, at or under the alveolar crest level, was not associated with the clinical parameters of the gingival features, such as the crown form, gingival scallop, or keratinized gingival width.