• 한국공간구조학회논문집
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• 제13권3호
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• pp.83-90
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• 2013

A series of wind tunnel tests were conducted on 7 super-tall buildings with various polygon cross-sections, including triangle, square, pentagon, hexagon, octagon, dodecagon, and circular. The primary purpose of the present study is to investigate the effect of increasing number of sides on aerodynamic characteristics for super-tall buildings. Wind tunnel tests were conducted under the turbulent boundary layers whose power-law exponent is 0.27. Fluctuating wind pressures from more than 200 pressure taps were recorded simultaneously, and time series of overturning moments were calculated considering tributary area of each pressure tap. The results show that the overturning moment coefficients and the spectral values decrease with increasing number of sides, and the largest mean and fluctuating overturning moments were found for the triangular super-tall building, and the largest spectral values were found for the square super-tall building. The analysis should be conducted more in detail, but currently it can be roughly said that there seems to be a little differences in the aerodynamic characteristics for the super-tall buildings whose number of sides is larger than 5 or 6.

• JSTS:Journal of Semiconductor Technology and Science
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• 제16권6호
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• pp.800-807
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• 2016

We propose a fast algorithm using Extreme Contour Point (ECP) to detect the angle of rotated images, is implemented by rotation feature of one covered frame image that can be applied to correct the rotated images like in image processing for real time applications, while CORDIC is inefficient to calculate various points like high definition image since it is only possible to detect rotated angle between one point and the other point. The two advantages of this algorithm, namely compatibility to images in preprocessing by using Sobel edge process for pattern recognition. While the other one is its simplicity for rotated angle detection with cyclic shift of two $1{\times}n$ matrix set without complexity in calculation compared with CORDIC algorithm. In ECP, the edge features of the sample image of gray scale were determined using the Sobel Edge Process. Then, it was subjected to binary code conversion of 0 or 1 with circular boundary to constitute the rotation in invariant conditions. The results were extracted to extreme points of the binary image. Its components expressed not just only the features of angle ${\theta}$ but also the square of radius $r^2$ from the origin of the image. The detected angle of this algorithm is limited only to an angle below 10 degrees but it is appropriate for real time application because it can process a 200 degree with an assumption 20 frames per second. ECP algorithm has an O ($n^2$) in Big O notation that improves the execution time about 7 times the performance if CORDIC algorithm is used.

• 대한기계학회논문집A
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• 제36권1호
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• pp.59-71
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• 2012

체적 적분방정식법(Volume Integral Equation Method)이라는 새로운 수치해석 방법을 이용하여, 서로 상호작용을 하는 등방성 또는 이방성 다이아몬드 형 함유체를 포함하는 등방성 무한고체가 정적 인장하중을 받을 때 무한고체 내부에 발생하는 응력분포 해석을 매우 효과적으로 수행하였다. 즉, 등방성 기지에 다수의 등방성 또는 이방성 다이아몬드 형 함유체의 중심이 1) 정사각형 배열 형태 또는 2) 정육각형 배열 형태로 포함되어 있는 경우에, 다양한 다이아몬드 형을 포함하는 원형 실린더 함유체의 체적비에 대하여, 중앙에 위치한 다이아몬드 형 함유체와 등방성 기지의 경계면에서의 인장응력 분포의 변화를 구체적으로 조사하였다. 또한, 체적 적분방정식법을 이용하여 구한 해의 정확도를 검증하기 위하여, 체적 적분방정식법을 이용한 해를 유한요소법을 이용한 해와 비교해 보았다.

• 설비공학논문집
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• 제2권1호
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• pp.37-48
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• 1990

The drag and heat transfer reduction phenomena and degradation effects of drag reducing polymer solutions which are known as the viscoelastic fluids are investigated experimentally for the turbulent circular tube flows. Two stainless steel tubes are used for the experimental flow loops. Aqueous solutions of Polyacrylamide Separan AP-273 with concentrations from 300 to 1000 wppm are used as working fluids. Flow loops are set up to measure the friction factors and heat transfer coefficients of test tubes in the once-through system and the recirculating flow system. Test tubes are heated by power supply directly to apply constant heat flux boundary conditions on the wall. Capillary tube viscometer and falling ball viscometer are used to measure the viscous characteristics of fluids and the characteristic relaxation time of a fluid is determined by the Powell-Eyring model. The order of magnidude of the thermal entrance length of a drag reducing polymer solution is close to the order of magnitude of the laminar entrance length of Newtonian fluids. Dimensionless heat transfer coefficients of the viscoelastic non-Newtonian fluids may be represented as a function of flow behavior index n and newly defined viscoelastic Graetz number. As degradation continues viscosity and the characteristic relaxation time of the testing fluids decrease and heat transfer coefficients increase. The characteristic relaxation time is used to define the Weissenberg number and variations of friction factors and heat transfer coefficients due to degradation are presented in terms of the Weissenberg number.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제34회 춘계학술대회논문집
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• pp.210-213
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• 2010

최근의 실험 결과를 통해 하이브리드 로켓 연료의 표면에 연소가 진행되지 않은 채 남아있는 고립된 부분들이 존재함을 확인하였다. 이러한 불규칙적인 spot은 연료의 기화로 인한 분출유동(wall blowing)과 산화제의 유동 사이에서 발생하는 경계층 교란에 의한 현상인 것으로 여겨진다. 본 연구에서는 23,000의 높은 Reynolds수와 벽면분출 현상을 효과적으로 처리할 수 있도록 LES 기법을 이용하여, 연료 표면 근처의 난류 유동 특성을 해석하였다. 원형 단면을 갖는 하이브리드 로켓 모터의 그레인 형상을 사실적으로 모사하기 위하여 곡률효과를 포함한 3차원 실린더 형태의 지오메트리를 고려하였다. 연료 표면에서 발생하는 불규칙한 spot의 발생은 경계층과 분출되는 유동이 상호 간섭함으로써 난류구조들의 기구학적 특성을 변경시키기 때문인 것으로 추측되는 결과들을 얻을 수 있었다.

• Steel and Composite Structures
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• 제22권6호
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• pp.1417-1443
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• 2016

Cellular and castellated steel beams are used to obtain higher stiffness and bending capacity using the same weight of steel. In addition, the beam openings may be used as a pass for different mechanical fixtures such as ducts and pipes. The aim of this study is to investigate the effect of different parameters on both elastic and inelastic critical buckling stresses of steel web plates with openings. These parameters are plate aspect ratio; opening shape (circular or rectangular); end distance to the first opening; opening spacing; opening size; plate slenderness ratio; steel grade; and initial web imperfection. The web/flange interaction has been simplified by web edge restraints representing simply supported boundary conditions. A numerical parametric study has been performed through linear and nonlinear finite element (FE) models, where the FE results have been verified against both experimental and numerical results in the literature. The web plates are subject to in-plane linearly varying compression with different loading patterns, ranging from uniform compression to pure bending. A buckling stress modification factor (${\beta}$-factor) has been introduced as a ratio of buckling stress of web plate with openings to buckling stress of the corresponding solid web plate. The variation of ${\beta}$-factor against the aforementioned parameters has been reported. Furthermore, the critical plate slenderness ratio separating elastic buckling and yielding has been identified and discussed for two steel grades of DIN-17100, namely: ST-37/2 and ST-52/3. The FE results revealed that the minimum ${\beta}$-factor is 0.9 for web plates under uniform compression and 0.7 for those under both compression and tension.

• 한국조경학회지
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• 제29권6호
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• pp.1-10
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• 2002

The purpose of this study is to establish a model of cultural sustainability in the traditional village. Cultural sustainability is being advanced by promoting the viability of traditional arts and the unique regional features of traditional culture, such as folklore, traditional landscapes, buildings and other environments of outstanding historical value. These cultural resources were also created or occurred at specific geographic locations at certain points in time by different individuals. The content of this study was to develop a model using indicators for cultural sustainability, and to apply and evaluate the model. In older to evaluate the model, Sonwon-ri village in Yongchon, located in Kyungsangbuk-do, was selected as the case study area. The major findings are as follows: 1) Sonwon-ri village has maintained the vernacular landscape except at the entrance of village. Also, the village people have pride and have adapted to the natural environment. 2) Sonwon-ri village has a self-sustaining system and circular network within its environmental capacity. Sonwon-ri village has many historical sites and buildings such as important folk resources, cultural assets, traditional houses and pavilions. 3) The people how the theory of fens-shui which interprets the location of village in relationship to a crane mountain with the village situated as a crane head. These symbolic and cultural elements have an important role in establishing the boundary of the village. From the research it can be seen that Sonwon-ri village kept many cultural sustainability indicators in terms of active factors, physical factors and psychological factors. By analysing the participation of different scientific disciplines and identifying disciplinary categories, this study provides a basis for understanding how cultural sustainability is subjected to research in the field of landscape planning and design.

• 대한조선학회논문집
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• 제56권4호
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• pp.361-372
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• 2019

The flow pattern of air layers and skin-friction drag reduction by air injection are investigated to find the suitable multiphase flow model using unstructured finite-volume CFD solver for the Reynolds-averaged Navier-Stokes equations. In the present computations, two different multiphase flow modeling approaches, such as the Volume of Fluid (VOF) and the Eulerian Multi-Phase (EMP), are adopted to investigate their performances in resolving the two-phase flow pattern and in estimating the frictional drag reduction. First of all, the formation pattern of air layers generated by air injection through a circular opening on the bottom of a flat plate are investigated. These results are then compared with those of MMkiharju's experimental results. Subsequently, the quantitative ratios of skin-friction drag reduction including the behavior of air layers, within turbulent boundary layers in large scale and at high Reynolds number conditions, are investigated under the same conditions as the model test that has been conducted in the US Navy's William B. Morgan Large Cavitation Channel (LCC). From these results, it is found that both VOF and EMP models have similar capability and accuracy in capturing the topology of ventilated air cavities so called'air pockets and branches'. However, EMP model is more favorable in predicting quantitatively the percentage of frictional drag reduction by air injection.

• 한국미생물·생명공학회지
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• 제47권1호
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• pp.25-33
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• 2019

Lactobacillus rhamnosus BFE5264, isolated from a Maasai fermented milk product ("kule naoto"), was previously shown to exhibit bile acid resistance, cholesterol assimilation, and adhesion to HT29-MTX cells in vitro. In this study, we re-annotated and analyzed the previously reported complete genome sequence of strain BFE5264. The genome consists of a circular chromosome of 3,086,152 bp and a putative plasmid, which is the largest one identified among L. rhamnosus strains. Among the 2,883 predicted protein-coding genes, those with carbohydrate-related functions were the most abundant. Genome analysis of strain BFE5264 revealed two consecutive CRISPR regions and no known virulence factors or antimicrobial resistance genes. In addition, previously known highly variable regions in the genomes of L. rhamnosus strains were also evident in strain BFE5264. Pairwise comparison with the most studied probiotic strain L. rhamnosus GG revealed strain BFE5264-specific deletions, probably due to insertion sequence-mediated recombination. The latter was associated with loss of the spaCBA pilin gene cluster and exopolysaccharide biosynthetic genes. Comparative genomic analysis of the sequences from all available L. rhamnosus strains revealed that they were clustered into two groups, being within the same species boundary based on the average nucleotide identities. Strain BFE5264 had a sister group relationship with the group that contained strain GG, but neither ANI-based hierarchical clustering nor core-gene-based phylogenetic tree construction showed a clear distinctive pattern associated with the isolation source, implying that the genotype alone cannot account for their ecological niches. These results provide insights into the probiotic mechanisms of strain BFE5264 at the genomic level.

• 한국소프트웨어감정평가학회 논문지
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• 제16권2호
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• pp.135-142
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• 2020

본 논문에서는 RGB 영상에서 홍채 검출 방법에 관하여 기술하였다. 기존의 홍채 검출 방법은 대부분 적외선 영상을 대상으로 하고 있어, 다양한 응용을 위해서는 RGB 영상의 홍채 검출 기술이 요구된다. 제안된 홍채 검출 방법은 i) 입력 영상에서 원형 허프 변환을 사용한 홍채 후보 영역 검출, ii) 딥러닝 기반의 동공 중심점 검출, iii) 동공 중심점을 이용한 홍채 영역 선택, iv) 선택된 홍채 영역 보정 과정으로 구성된다. 홍채 후보 영역은 허프 공간을 생성한 후 중심점 후보의 교차 개수가 많은 순으로 검출하며, 후보 영역 중 홍채는 검출된 동공의 중심점을 기준으로 선택한다. 그리고, 홍채의 모양이 왜곡되어 오차가 발생하는 것을 보완하기 위해 검출된 홍채 중심을 기준으로 새로운 경계점을 찾아 보정하는 방법을 사용하였다. 또한, 실험을 통하여 제안된 방법이 기존 원형 허프 변환 방법 대비 약 27.4% 향상된 정확도를 갖는 것을 확인하였다.