• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1742-1746
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• 2008

An EHD (Electro-Hydro-Dynamic) jet for electrostatic inkjet head shows advantages to print micro-size patterns using various inks because it can generate sub-micron droplets and can use highly viscous inks. Thus, many researchers in industrial fields are concerned about the EHD jet in these days. Since the basic principle of the EHD jet is to form a droplet from an apex of meniscus at the end of the nozzle, the ejection mechanism can be changed by the shape of the meniscus. The stable ejection of the droplet is greatly affected by the shape of the meniscus which is also influenced by surface characteristics of the nozzle, electric potential and ink properties. Experiments have been performed using the nozzles with hydrophilic and hydrophobic coatings in this study. The hydrophobic nozzle forms the stable droplets in wider range of the electric potential than the hydrophilic nozzle does.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.285-286
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• 2006

The essential tasks to operate the welding robot are the acquisition of the position and/or shape of the parent metal. For the seam tracking or the robot automation, many kinds of contact and non-contact sensors are used. Recently, the vision sensor is most popular. In this paper, the development of the system which measures the profile of the welding part is described. The total system will be assembled into a compact module which can be attached to the head of welding robot system. This system uses the line-type structured laser diode and the vision sensor It implemented Direct Linear Transformation (DLT) for the camera calibration as well as radial distortion correction. The three dimensional shape of the parent metal is obtained after simple linear transformation and therefore, the system operates in real time. Some experiments are carried out to evaluate the performance of the developed system.

• International Journal of Naval Architecture and Ocean Engineering
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• 제11권2호
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• pp.723-735
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• 2019

This paper employs computational tools to investigate the cause of resistance reductions in calm water and waves of the sharp bow form compared to the blunt bow in 66,000 DWT bulk carriers. A more slender shape at the fore-shoulder without a bulbous bow is a prominent feature of the sharp bow. The blunt bow incorporates a bulbous shape. A two-phase unsteady Reynolds averaged Navier-Stokes equations have been solved; and a realizable k-ε model has been applied for the turbulent closure. The free-surface is obtained by solving a VOF equation. The computational results have been validated with model tests carried out at a towing tank. The pressure component of resistance in the sharp bow is reduced by 8.9% in calm water, and 6.4-12.7% in regular head waves. The frictional components of resistance in the sharp and blunt bows are largely the same.

• 대한기관식도과학회지
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• 제17권1호
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• pp.40-45
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• 2011

Background and Objectives Detailed information about the impacted esophageal foreign body is essential for safe extraction. Three dimensional reconstruction technique was applied to know shape, size and location of the simulative foreign bodies of stone, hyoid bone and endotracheal tube. Materials and Methods Submandibular gland stone, hyoid bone and endotracheal tube were used to simulate impacted foreign bodies. Axial CT, multi-planar reconstruction, volume of interest and virtual camera of Rapidia software were used to get information about the simulative foreign bodies from CT data. Shape and size were compared with the real materials. Exact locations were measured in appropriate modes of Rapidia. Results Shapes of the simulative foreign bodies matched well with the real materials. Size and location could be measured in various modes with some variable results. Conclusion 3D technique can be applied to get information about the simulative foreign bodies. This technique could be applied to the impacted esophageal foreign body.

• 설비공학논문집
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• 제28권9호
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• pp.350-354
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• 2016

Although fibrous insulations are generally used with resistive insulation type, metallic insulation is proper matter to satisfy low head-loss and equipment life when considering the specific condition, especially for Nuclear power plant. Common insulation is resistance insulation with a low thermal conductivity. but RMI is made of sheet plate with low emissivity and closed air space. Thermal radiation is blocked by stainless steel with low emissivity. Thermal conductivity and thermal convection are blocked by closed air space. This study shows the changes and effects of the heat loss according to shape and method of stacking sheet plates inserted into the insulation and analyzed the most optimized way for thermal insulation performance. The result shows that using sheet plate structure through raised and protruding shape processing was the appropriate model to optimize thermal performance. Additionally, insulating performance of RMI improved by placing the sheet plate in a high temperature region intensively.

• 식물분류학회지
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• 제48권3호
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• pp.172-184
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• 2018

We examined the floral morphology of 15 taxa of five genera (Cynanchum, Marsdenia, Metaplexis, Tylophora, and Vincetoxicum) in Korean Asclepiadoideae using a stereoscopic and scanning electronic microscope to clarify and describe the floral characteristics. In this study, the corolla and corona types, the types of corona lobes, appendages on the corona lobes, and the apex shape of the style head are considered as diagnostic characteristics at the generic level. The genus Vincetoxicum, which is treated as a synonym of the genus Cynanchum in Korea, is distinguished from Cynanchum by the interstaminal part on the corona, fleshy and mainly triangular or ellipsoid corona lobes, and various corolla colors. In Cynanchum, various corona types have been observed, while Vincetoxicum have similar corona types among the taxa. In addition, the main floral characteristics at the species level were as follows: flowering time, inflorescence, corolla color, trichomes on the corolla surfaces, apex shape of the corona lobe, and trichomes on the ovary. This study presents the taxonomic importance of floral morphology by providing descriptions and diagnostic characteristics among the genera and species investigated.

• 대한기계학회논문집B
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• 제41권8호
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• pp.545-552
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• 2017

본 연구에서는 1 kW급 가정용 열병합 시스템의 원동기로 설계된 스털링 엔진의 고온 열교환기에 대하여 Fin 길이, 간격, 각도 등을 조정한 새로운 형상 및 기존 형상에 대하여 수치해석을 수행하여 형상 개선에 따른 성능 향상을 확인하였다. 형상을 개선하는 과정에서 고려하지 않았던 공기예열기를 포함하여 수치해석을 수행한 결과 실린더 헤드 부분에서 음의 열유속이 발생하는 현상이 관찰되었다. 배가스 온도 및 연소실 벽면 온도를 분석하여 이 현상을 규명하였다. 다음으로 이상적인 사이클을 가정하여 형상 개선에 의한 열전달량 증가가 열역학적 사이클 및 시스템 성능에 미치는 영향을 예측하였다.

• 한국산학기술학회논문지
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• 제8권6호
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• pp.1319-1324
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• 2007

입출력 헤드 구조의 형상을 정확하게 조절할 수 있는 기술은 하드디스크 드라이브의 성능에 결정적인 요소이다. 본 논문에서 연구한 슬라이더는 알루미나 티타늄 카아바이드로 구성되었으며 디스크를 통과할 때 공기 베어링 역할을 한다. 그러므로 슬라이더의 곡률을 조절하는 것은 매우 중요하다. 본 연구에서 곡률을 조절하기 위해 헤드 슬라이더에 잔류응력을 발생시켜 곡률을 생성하는 레이저 화선 시스템이 사용된다. 슬라이더 형상의 조절을 강화하기 위해 화선(scribe)의 형상에 따른 곡률을 예측할 수 있는 방법이 중요하다. 레이저 화선과 유사한 효과를 얻을 수 있는 응력을 발생하는 하중계를 유한요소 모델에 적용한다. 하중계에 의해 형성된 곡률은 측정값을 통해 보정된다.

• 한국수소및신에너지학회논문집
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• 제32권4호
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• pp.277-284
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• 2021

This paper deals with multi-objective optimization using response surface method to improve the hydraulic performances of a 2 vane pump for wastewater treatment. For analyzing the internal flow field in the pump, steady Reynolds-averaged Navier-Stokes equations were solved with the shear stress transport turbulence model as a turbulence closure model. The impeller and volute variables were defined in the shape of the 2 vane pump. The objective functions were set to satisfy the total head at the design flow rate as well as to improve the efficiency. The hydraulic performance of the optimally designed shape was verified by numerical analysis results.

• Journal of the Korean Wood Science and Technology
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• 제52권3호
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• pp.276-288
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• 2024

This study was conducted to reproduce the woodworking process of Baekje wooden storage facilities. Green timber of Quercus spp. was processed using ancient woodworking tools, and the tool-trace formed in this process were compared with the tool-trace of actual excavated artifacts. In the tool-trace analysis, the length and shape of the tool-trace were objectively recorded using a 3D Scan, and that were difficult to confirm with photograph were confirmed through stereoscopic microscope. As a result, there were two types of adze's tool-trace. One of them is minute straight Blade-top trace line when trimming the wood surface and the other is Plucked trace that appear when strongly chop at the wood. When a chisel bat was not used, a long and wide continuous shape blade trace was produced. And when the chisel head was struck with the chisel bat, a straight blade-top trace was regularly observed. Saw-trace was identified in several layers with fine straight stripes. Through this, it was found that the tool-trace of the woodworking tools, which is estimated to have been used in each process, and the tool-trace remaining in the Baekje wooden storage facility coincide.