• International Journal of Vascular Biomedical Engineering
• /
• 제1권1호
• /
• pp.13-23
• /
• 2003

Backgrounds: The present study in angulated coronary stenosis was to evaluate the influence of velocity and wall shear stress (WSS) on coronary atherosclerosis, the changes of hemodynamic indices following coronary stenting, as well as their effect of evolving in-stent restenosis using human in vivo hemodynamic parameters and computed simulation quantitatively and qualitatively. Methods: Initial and follow-up coronary angiographies in the patients with angulated coronary stenosis were performed (n=80). Optimal coronary stenting in angulated coronary stenosis had two models: < 50 % angle changed(model 1, n=43), > 50% angle changed group (model 2, n=37) according to percent change of vascular angle between pre- and post-intracoronary stenting. Flow-velocity wave obtained from in vivo intracoronary Doppler study data was used for in vitro numerical simulation. Spatial and temporal patterns of velocity vector and recirculation area were drawn throughout the selected segment of coronary models. WSS of pre/post-intracoronary stenting were calculated from three-dimensional computer simulation. Results: Follow-up coronary angiogram demonstrated significant difference in the percent of diameter stenosis between two groups (group 1: $40.3{\pm}30.2$ vs. group 2: $25.5{\pm}22.5%$, p<0.05). Negative WSS area on 3D simulation, which is consistent with re-circulation area of velocity vector, was noted on the inner wall of post-stenotic area before stenting. The negative WSS was disappeared after stenting. High spatial and temporal WSS before stenting fell into within physiologic WSS after stenting. This finding was prominent in Model 2 (p<0.01) Conclusions: The present study suggests that hemodynamic forces exerted by pulsatile coronary circulation termed as WSS might affect on the evolution of atherosclerosis within the angulated vascular curvature. Moreover, geometric change, such as angular difference between pre / post-intracoronary stenting might give proper information of optimal hemodynamic charateristics for vascular repair after stenting.

• Wind and Structures
• /
• 제26권5호
• /
• pp.331-341
• /
• 2018

A numerical study on the flow over a square cylinder in the vicinity of a wall is conducted for different Couette-Poiseuille-based non-uniform flow with the non-dimensional pressure gradient P varying from 0 to 5. The non-dimensional gap ratio L (=$H^{\ast}/a^{\ast}$) is changed from 0.1 to 2, where $H^{\ast}$ is gap height between the cylinder and wall, and $a^{\ast}$ is the cylinder width. The governing equations are solved numerically through finite volume method based on SIMPLE algorithm on a staggered grid system. Both P and L have a substantial influence on the flow structure, time-mean drag coefficient ${\bar{C}}_D$, fluctuating (rms) lift coefficient ($C_L{^{\prime}}$), and Strouhal number St. The changes in P and L leads to four distinct flow regimes (I, II, III and IV). Following the flow structure change, the ${\bar{C}}_D$, $C_L{^{\prime}}$, and St all vary greatly with the change in L and/or P. The ${\bar{C}}_D$ and $C_L{^{\prime}}$ both grow with increasing P and/or L. The St increases with P for a given L, being less sensitive to L for a smaller P (< 2) and more sensitive to L for a larger P (> 2). A strong relationship is observed between the flow regimes and the values of ${\bar{C}}_D$, $C_L{^{\prime}}$ and St. An increase in P affects the pressure distribution more on the top surface than on bottom surface while an increase in L does the opposite.

• 한국지반공학회지:지반
• /
• 제13권2호
• /
• pp.155-168
• /
• 1997

격자지보는 NATM에서 터널굴착 후 곧바로 설치되는 강지보재의 한 종류로서 기존의 H형강 지보재를 대체하고자 유럽에서 개발된 새로운 종류의 지보재이다. 격자지보는 강봉을 삼각형태로 엮어 만들었기 때문에 숏크리트 타설이 용이하고 지보재 배면에 생기는 공동을 최소화 할 수 있는 장점이 있다. 또한 격자지보와 숏크리트 복합구조체는 결합력이 우수하여 일체화된 구조체로서 거동하기 때문에 지압을 효과적으로 지지할 수 있다. 본 연구에서는 격자지보와 숏크리트 복합구조체의 특성파악을 위해 실시한 모형벽체 시험, 모형벽체에 타설된 숏크리트의 강도특성시험, 격자지보와 숏크리트의 부착강도시험 결과를 제시하였다. 실험결과 숏크리트가 타설된 격자지보는 숏크리트가 타설된 H형강 지보재에 비해 숏크리 트 리바운드, 타설된 숏크리트의 강도, 부착특성 등이 우수한 것으로 판명되었고, 이로써 격자지로는 적절한 터널지보재로서의 역할을 할 것으로 판단되었다.

• 한국건설관리학회논문집
• /
• 제6권4호
• /
• pp.71-79
• /
• 2005

건설 프로젝트가 점차 대형화, 전문화, 복잡화되어감에 따라 건설공사에서의 리스크 요인과 불확실성 요인이 증가하고 있다. 따라서 이와 같은 건설 사업 과정에서 발생하는 불확실한 요인을 미리 파악하고, 이에 대처하는 것은 프로젝트 성공을 위해 매우 중요한 요소이다. 따라서 본 연구에서는 전체 공종 중 공기, 공사비, 민원발생 등으로 인해 공사에 크게 영향을 미치며, 후속공정에 미치는 영향이 큰 커튼월 공사를 시공 프로세스 검토를 통한 리스크 인자의 적출을 통해 구체적인 리스크 인자의 구체적인 대응방안을 제시하여 실무에 직접적으로 접근할수 있도록 하였다. 이러한 리스크 인자의 적출은 정량적인 리스크의 분석을 가능하게 하고, 이에 따라 각각의 공종에서 발생하는 리스크 인자들의 우선순위를 결정할 수 있으며 이를 바탕으로 제시한 공정 리스크 관리 도구를 통하여 현장마다 경험과 지식의 정도가 다른 실무자로 하여금 업무를 수행함에 있어서 사전에 리스크를 인지할 수 있으며 리스크가 발생했을 때 신속하게 대응할 수 있고 그러한 리스크를 최소화할 수 있는 업무 지침을 제공하는 역할을 하게 될 것이다.

• 비파괴검사학회지
• /
• 제21권5호
• /
• pp.501-509
• /
• 2001

증기발생기 전열관에서 1차측 응력부식균열의 발생빈도가 증가하고 있으므로 이의 정확한 탐지와 평가를 위해서는 균열 형상에 따른 와전류 신호특성을 규명하고 적합한 탐촉자를 선정하는 것이 매우 중요하다. 본 연구에서는 증기발생기 전열관의 내면 축방향 균열에 대한 와전류 검사의 검출능과 크기예측에 대한 신뢰도를 정량적으로 평가하고 pancake coil과 plus coil과의 신호특성 차이를 비교하였다. 이를 위하여 전열관 내면에 EDM으로 노치를 가공한 시편과 실제 증기발생기에서 1차측 응력부식균열이 발생하여 인출한 전열관을 시험편으로 사용하였다. 본 연구에서 얻어진 결과를 토대로 내면 축방향 균열에 대한 와전류 검사 신뢰도 향상을 위한 방안을 제시하였다.

• Journal of the Korean Wood Science and Technology
• /
• 제16권1호
• /
• pp.9-20
• /
• 1988

Lespedeza species have been widely used not only as plant resources for bark, leaves and honey, but also as erosion control materials. This study was carried out to investigate the structural and wood tiber characteristics in order to obtain basic information for the utilization of the wood. The wood structure was investigated for 10 selected species and the wood fiber, for the 5 selected species among Lespedeza species distributed all over the country. The following results were obtained. In the cross section, campylotropis showed ray diffuse porous wood, L. bicolor, L. cyrtobotrya, L. thunbergii var. intermedia, diffuse porous wood, and L. tomentella, L. angustifolioides. L. maritima, L. robusta, L. patentibicolor, ring porous wood. The maximum diameter of a single vessel ranged 66-123 ${\mu}$ in all species. Campylotropis showed the most number of vessels, L. angustifolioides, the least. The number of ray per mm ranged 7-22, Campylotropis showed the most number of rays, L. angustifolioides, the least. In the radial section the average length of vessel ranged 121-250 ${\mu}$ in all species. L. thunbergii var. intermedia showed the longest vessel, L. tomentella, the shortest. In tangential section the average width of the uniseriate ray ranged 9.2-14.7${\mu}$, that of the multiseriate ray, 19.2-42.1 ${\mu}$. The average height of the uniseriate ray ranged 143.0-1162.0 ${\mu}$. The width of fiber ranged 10.12-13.61 ${\mu}$, L. maximowiezii showed the narrowest tiber, L. thunbergii var. intermedia. the widest, the thickness of fiber wall ranged 2.93-3.71 ${\mu}$ in the five species. L. maximowiezii showed the most thin fiber wall, L. thunbergii var. intermedia, the thickest, L. cyrtobotrya showed the difference in the size of fiber between the shade and the sunny sites but L. maximowiezii showed no difference. There was significant difference in fiber length, fiber width and wall thickness between L. eyrtobotrya and L. maximowiezii.

• Journal of Periodontal and Implant Science
• /
• 제40권4호
• /
• pp.172-179
• /
• 2010

Purpose: Accurate and exact measurement is an important factor for generating meaningful results in any properly designed study. If all the participating examiners are able to yield similar results, it will be possible to evaluate the objective results of the study more easily and quickly. The purpose of this study was to evaluate the intra- and inter-examiner reproducibility of histometric measurements in the intrabony periodontal defect model. Methods: One wall intrabony defects were surgically created at the distal aspect of the second and the medial aspect of the fourth mandibular premolars in the right and left jaw quadrants in twenty beagle dogs and the defect sites received the following ${\beta}$-tri calcium phosphate, growth differentiation factor-0, growth differentiation factor-100 and sham surgery. Histometric analysis was performed after 8 weeks. Histometric parameters were recorded and repeated at three months interval by three examiners. Intra- and inter-examiner reproducibility was assessed. Results: Most parameters of all the groups showed high intra- and inter-examiner reproducibility. Parameters including defect height, bone regeneration height, cementum regeneration height, and formation of junctional epithelium yielded interexaminer correlation ${\geq}0.9$. The intra-examiner reproducibility showed a high result, over 0.9. Conclusions: Histometric evaluation of the one-wall intra-alveolar periodontal defect model showed high reproducibility not only for a single given examiner but also among the three examiners.

• Journal of Microbiology and Biotechnology
• /
• 제27권2호
• /
• pp.395-404
• /
• 2017

Fungal cell walls and cell membranes are the main targets of antifungals. In this study, we report on the antifungal activity of an ethanol extract from Paeonia lactiflora against Candida albicans, showing that the antifungal activity is associated with the synergistic actions of preventing cell wall synthesis, enabling membrane depolarization, and compromising permeability. First, it was shown that the ethanol extract from P. lactiflora was involved in damaging the integrity of cell walls in C. albicans. In isotonic media, cell bursts of C. albicans by the P. lactiflora ethanol extract could be restored, and the minimum inhibitory concentration (MIC) of the P. lactiflora ethanol extract against C. albicans cells increased 4-fold. In addition, synthesis of $(1,3)-{\beta}-{\small{D}}-glucan$ polymer was inhibited by 87% and 83% following treatment of C. albicans microsomes with the P. lactiflora ethanol extract at their $1{\times}MIC$ and $2{\times}MIC$, respectively. Second, the ethanol extract from P. lactiflora influenced the function of C. albicans cell membranes. C. albicans cells treated with the P. lactiflora ethanol extract formed red aggregates by staining with a membrane-impermeable dye, propidium iodide. Membrane depolarization manifested as increased fluorescence intensity by staining P. lactiflora-treated C. albicans cells with a membrane-potential marker, $DiBAC_4(3)$ ((bis-1,3-dibutylbarbituric acid) trimethine oxonol). Membrane permeability was assessed by crystal violet assay, and C. albicans cells treated with the P. lactiflora ethanol extract exhibited significant uptake of crystal violet in a concentration-dependent manner. The findings suggest that P. lactiflora ethanol extract is a viable and effective candidate for the development of new antifungal agents to treat Candida-associated diseases.

• 한국실내디자인학회논문집
• /
• 제15권2호
• /
• pp.150-157
• /
• 2006

Founded on a close relationship between exhibition scenarios and media, this study was conducted 1) to establish exhibition arrangement types by using three analytical indicators, such as arrangement types of exhibition, groupings of similar exhibition media, and exhibition density; and 2) to demonstrate the importance of considering the characteristics of exhibition arrangement types by using viewing behavior codes as a major analytical indicator. The following three types were investigated in this research: First, the Independent type (Type C) was found to be strongly influenced by architectural and spatial forms, especially by low exhibition density and high visual information. Also, compared with the Wall Dominant type, low number of viewing behavior codes and distribution was found even though there were high correlations among viewing behavior codes. This is assumed to be due to low exhibition density. Second, the Wall Dominant type (Type A) was found to be not influenced by architectural and spatial forms. This is because space is planned and restructured centering on the wall type showcases. At the planning stage of exhibition, it is easy to divide or combine space according to the contents and structure of exhibition scenarios. Compared with the Independent type, low correlations were found among viewing behavior codes. This is due to low participation or manipulation exhibitions. However, this implies that more active viewing behaviors can be induced if appropriate exhibition techniques and arrangement methods are used for each exhibition content. Third, the Independent Dominant type (Type B) was found to confuse visitors in selecting routes by displaying too many exhibits at a limited space in a disorderly fashion. It failed to attract visitors to the main exhibition area, where a big space is formed in the center. Visitors were found to view exhibits that are arranged near the major traffic line.

• 한국실내디자인학회논문집
• /
• 제26권6호
• /
• pp.97-105
• /
• 2017

Korea is promoted STEAM education since 2011. Furthermore, in high school education, based on the in-depth elective course's teaching and learning contents of science. The STEAM program can improve students' competence because it encourages to self-directed learning through the vocational project performance. Therefore, in this study, we researched a design education program for the experience of fusion and complex design based on STEAM education concept. We developed an education program to design insulation wall systems using up-cycling concepts to increase energy efficiency. As a result, the characteristics of the fusion education and the theoretical study about the learner-centered education curriculum, the analysis of the high school curriculum, the STEAM elements, The program was revised and supplemented through consultation with STEAM experts. In addition, the developed program was applied to high school students, and each step were analyzed based on the educational method theory. The following results were obtained. First, this study presented a program to cope with the needs of high school intensive education. Second, it provided learning motivation by combining flipped-learning as a way to train STEAM education contents. Third, it is required to develop differentiated and continuous program development and data sharing Fourth, in order to operate and promote the future environment design STEAM school, it is necessary to expand educational programs for high school students in the region through linkage with various universities.