• Environmental engineer
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• s.323
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• pp.86-95
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• 2013

본 발명은 해수의 담수화 장치에 관한 것으로, 해수를 증기와 온수로 변환하도록 태양열을 이용하여 상기 해수를 가열하는 가열기와, 상기 가열기에 의해 변환된 상기 증기와 상기 온수를 분리하는 분리기를 포함하며, 상기 가열기는, 오목한 곡면을 갖는 반원통 형상으로 마련되고, 상기 반원통 형상의 길이방향을 따라 위치하는 다수의 초점을 향하여 내면으로 조사된 태양광을 반사하는 반사렌즈 및 상기 반사렌즈에 의해 반사된 상기 태양광의 열 에너지에 의해 상기 해수를 가열하도록, 상기 반사렌즈의 초점이 위치하는 길이방향의 지점을 따라 상기 해수가 흐를 수 있도록 형성되는 유로관을 포함하는 것을 특징으로 한다.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.5
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• pp.731-736
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• 2017

In this paper, we report the fabrication of concave surface fiber tips for optical resonators. It was confirmed that the radius of curvature on fiber end can be controlled by introducing the hydrofluoric acid solution and the wavelength of $1.55{\mu}m$ laser which is absorbed well in the etchant to induce the photothermal effect. Using the microscope images, we observed the proposed concave fiber tip fabrication method is effective to make the controllable concave tips. We also observed changes in the size of the beam emitted from the tips with the various radius of curvature using the beam profiler. The authors believe that the proposed method will be applied to resonators for optical communications.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.5
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• pp.871-876
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• 2019

We fabricated concave optical fiber tips using hydrofluoric acid solution and photothermal effect induced by $1.55{\mu}m$ wavelength laser applied to an optical fiber. The radius of curvature of the concave optical fiber tips fabricated with different applied laser power, etching time, and concentration of hydrofluoric acid was measured with an optical microscope. Then, we analyzed how the radius of curvature changes for those three variables. In addition, the reliability of the measurement method using a microscope was verified through a free spectral range(FSR) and a scanning electron microscope(SEM). Through this paper, the radius of curvature can be adjusted by the variables of the fabrication process of concave optical fiber tips; thus, it is overcoming the limitations of conventional optical fiber etching methods using hydrofluoric acid solutions.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.6
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• pp.36-44
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• 2021

Numerical analysis was performed on the shock wave-boundary layer interaction generated in the internal flow path of the curved interstage of the scramjet engine flight test vehicle. For numerical analysis, the turbulence model k-ω SST was used in the compressibility Raynolds Averaged Navier Stokes(RANS) equation. Representatively, the separation bubbles on the upper wall of the nozzle, the interaction between the concave shock wave and the boundary layer, and the shock wave-shock wave interaction at the edge were captured. The analysis result visualizes the shock wave-boundary layer interaction of the curved internal flow path to enhance understanding and suggest design considerations.

• Journal of the Korean Society of Visualization
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• v.18 no.2
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• pp.35-38
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• 2020

Airfryer is used to heat a food up by convecting hot air upward around the food. In this study, we investigated the effect of the bottom-shape of the food container in airfryer on the upward convection velocity of hot air to find an optimal bottom-shape by computational fluid dynamics. Numerical experiments were performed by solving the incompressible Navier-Stokes equations with turbulence model. We found that the maximum upward velocity with concave flow-passage on the bottom was bigger than that with the flat bottom and that the maximum upward convection velocity was achieved when the number of concave flow-passage with fan-shape is around six. The pressure drop by the internal flow was found to increase as the number of the concave flow-passage on the bottom increased probably due to increase of the surface area of the bottom. Therefore, it can be said that the optimal number of the concave flow-passage is around six for the flow rate considered in this study.

• Proceedings of KOSOMES biannual meeting
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• 2005.11a
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• pp.153-158
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• 2005

The turbulent shear flaw around a surface-mounted vertical wall was investigated using the two-frame PIV(CACTUS 3.1) system. From this study, it is revealed that at least 500 instantaneous velocity field data are required for ensemble average to get reliable turbulence statistics, but only 200 field data are sufficient for the time-averaged mean velocity information The flow has an unsteady recirculation region post vertical wall with bottom gap, followed by a slow relaxation to the fiat-plate boundary layer flow. The time-averaged reattachment length estimated from the streamline distribution is about x/H=3H. The large eddy structure in the separated shear layer seems to have signification influence on the development of the separated shear layer and the reattachment process.

• Journal of Korea Multimedia Society
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• v.11 no.9
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• pp.1302-1309
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• 2008

Traditional clustering methods, like k-means or fuzzy clustering, are prototype-based methods which are applicable only to convex clusters. On the other hand, spectral clustering tries to find clusters only using local similarity information. Its ability to handle concave clusters has gained the popularity recent years together with support vector machine (SVM) which is a kernel-based classification method. However, as is in SVM, the kernel width plays an important role and has a great impact on the result. Several methods are proposed to decide it automatically, it is still determined based on heuristics. In this paper, we proposed an adaptive method deciding the kernel width based on distance histogram. The proposed method is motivated by the fact that the affinity matrix should be formed into a block diagonal matrix to generate the best result. We use the tradition Euclidean distance together with the random walk distance, which make it possible to form a more apparent block diagonal affinity matrix. Experimental results show that the proposed method generates more clear block structured affinity matrix than the existing one does.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2020.08a
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• pp.42-42
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• 2020

오이(Cucumis sativa L.)는 1년생 초본의 덩굴성 박과 작물로 미숙한 과실을 다양한 식품 용도로 이용하고 있다. 오이는 시설재배기술 확립으로 연중 생산과 공급이 가능하나 내병성 품종개발이 필요한 실정이다. 또한 오이의 다양한 생리활성 물질에 대한 관심이 높아지고 있어 이를 위한 다양한 오이 자원이 필요한 실정이다. 본 연구에서는 국내외에서 수집한 오이 180자원의 형태적 특성을 분석하여 육종 소재로 활용하는데 있어 기초 정보를 제공하고자 하였다. 본 연구에서 사용된 오이 자원의 원산지는 조지아 98자원, 한국 37자원, 중국 28자원, 우즈베키스탄 17자원이었다. 오이 180자원은 모두 덩굴손을 가졌으며 자웅동주로 조사되었다. 착과습성은 주지형 83자원, 주지 및 측지형 97자원으로 조사되었고 절화당 자화수는 175자원이 2개로 조사되었으며 5자원은 1개로 조사되었다. 과형은 장원형 87자원, 단원형 92자원으로 대부분을 차지하였으며 과선단좁은형이 1자원 조사되었다. 과기부형태는 평평한 형태 83자원, 휘어진 형태 94자원으로 대부분이었으며 오목한 형태 1자원, 뽀족한 형태 2자원이 조사되었다. 과선단의 형태는 평평한 형태 148자원, 휘어지 형태 32자원으로 조사되었다. 오이 유전자원의 개화기는 60~80일로 평균 66.1일 이었으며 과실 성숙기는 33~68일로 평균 49.6일이었다. 국가별로 개화기는 62.4일(중국)~68.5일(한국), 과실성숙기는 48.3일(중국,조지아)~54.1일(우즈베키스탄)로 조사되었다. 본 실험에서 조사된 오이 유전자원의 형태적 특성은 오이 선발에 있어 기초 정보로 활용 가능할 것이며 추가적으로 농업형질, 내병성, 기능성 분석등의 오이 육종 프로그램을 위한 다양한 자원 평가 및 선발이 필요할 것이다.

• Parasites, Hosts and Diseases
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• v.22 no.2
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• pp.171-180
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• 1984

In order to provide some clues for differential diagnosis of trematode infections in fecal examination, the comparative morphology of eggs of 5 kinds of heterophyid flukes (Metagonimus yokogawai, Heterophyes heterophyes nocens, Heterophyopsis continua, Stellantchasmus falcatus and Pygidiopsis summa) and Clonorchis sinensis was studied. The eggs were obtained from distal portion of uteri of worms which were recovered from men after treatment. The characteristic shape and appearance of each kind of eggs were observed in detail under light microscope, and their length and width measured and compared one another. The results are as follows: 1. Eggs of C. sinensis are elongated ovoidal in shape with attenuated anterior end, 25.3~33. 2 (28. 3 in average) ${\mu}m$ long and 14.2~17.4(5.9) ${\mu}m$ wide with length/width ratio of 1.60~2.00 (1.78). They differ from all heterophyid eggs in that they have prominent wrinkling (muskmelon pattern) at their shell surface. 2. P. summa eggs are ovoid to pyriform in shape and characterized by the smallest size of all kinds examined, 19.8~22.9 (21.6) ${\mu}m$ long and 11.1~13.4 (12.1) ${\mu}m$ wide and the ratio 1.63~1.99 (1.78). 3. Eggs of S. falcatus are elongated ovoidal and most slender form, 25.3~29.2 (27.2) ${\mu}m$ long and 11.1~13.4 (12.5) ${\mu}m$ wide with the ratio of 2.00~2.57 (2.17). 4. Eggs of M. yokogawai are ellipsoid to elliptical in shape with round both ends, 26.9~31.6 (28.5) ${\mu}m$ long and 14.2~18.2 (16.8)${\mu}m$ wide with the ratio of 1.48~2.11 (1.70). 5. H. continua eggs are oval in shape, sometimes similar to M. yokogawai or H. h. nocen$ eggs, however, the relative breadth is broadest among all kinds, with maximum width at posterior half portion. They are 23.7~27.7 (25.0) ${\mu}m$ long, 15.8~18.9 (16.4) ${\mu}m$ wide with the ratio of 1. 33~1.75 (1.53). 6. Eggs of H. h. nocens are ellipsoid to ovoid in shape but sometimes more slender than M. yokogawai and have slightly pointed both ends. They are 23.7~29.2 (25.7) p.m long, 14.2~15.8 (15.4) ${\mu}m$ wide, and the ratio 1.50~2.06 (1.67). From the results, it is concluded that eggs, of 5 kinds of heterophyids and C. sinensis can be morphologically differentiated one another, however, careful observation and measurement on sufficient number of eggs are needed.