• 한국터널지하공간학회 논문집
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• 제10권3호
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• pp.295-302
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• 2008

콘크리트 현장타설 개착식 터널구조물의 문제점을 해결하기 위하여, 시공성 및 품질관리 등 측면에서 유리한 프리캐스트 세그먼트를 이용한 개착식 터널구조물의 시공이 가장 효과적인 대안이라 할 수 있다. 그러나 프리캐스트 세그먼트를 이용한 개착식 터널구조물의 설계 및 시공은 고성토 또는 광폭터널 조건에서는 시공성 및 구조적 안정성 등과 같은 단점 때문에 그 활용이 제한적이다. 따라서, 본 연구에서는 프리캐스트 세그먼트를 이용한 개착식 터널구조물의 구조적 안정성 및 시공성 향상을 위하여, 리브 보강 프리캐스트 아치를 이용한 개착시 터널구조물을 개발하였으며, 대형 정적하중재하 실험을 통하여 리브보강에 의한 프리캐스트 아치 터널구조물의 역학적 거동 특성을 분석하였다 프리캐스트 세그먼트의 리브 보강 효과로 천단부에 균열이 발생하는 하중은 약 1.7배, 구조물의 극한하중은 약 3.3배 증가하는 등 리브 보강효과를 통하여 프리캐스트 세그먼트를 이용한 개착식 터널구조물의 구조적 안정성을 크게 향상시켰다.

• Journal of Microbiology
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• 제42권3호
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• pp.194-199
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• 2004

Investigation of the expression of the riboflavin (rib) genes, which are found immediately downstream of luxG in the lux operon in Photobacterium phosphoreum, provides more information relevant to the evolution of bioluminescence, as well as to the regulation of supply of flavin substrate for bacterial bioluminescence reactions. In order to answer the question of whether or not the transcriptions of lux and rib genes are integrated, a transcriptional termination assay was performed with P. phoxphoreum DNA, containing the possible stem-loop structures, located in the intergenic region of luxF and luxE ($\Omega$$\_$A/), of luxG and ribE ($\Omega$$\_$B/), and downstream of ribA ($\Omega$$\_$c/). The expression of the CAT (Chloram-phenicol Acetyl Transferase) reporter gene was remarkably decreased upon the insertion of the stem-loop structure ($\Omega$$\_$c/) into the strong lux promoter and the reporter gene. However, the insertion of the structure ($\Omega$$\_$B/) into the intergenic region of the lux and the rib genes caused no significant change in expression from the CAT gene. In addition, the single stranded DNA in the same region was protected by the P. phosphoreum mRNA from the Sl nuclease protection assay. These results suggest that lux genes and rib genes are part of the same operon in P. phosphoreum.

• 한국터널지하공간학회 논문집
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• 제11권3호
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• pp.265-275
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• 2009

프리캐스트 세그먼트를 이용한 개착식 터널구조물의 설계 및 시공은 고성토 또는 광폭터널 조건에서는 시공성 및 구조적 안정성 등과 같은 단점 때문에 그 활용이 제한적이다. 따라서 시공성 및 품질관리 등 측면에서 유리한 프리캐스트 세그먼트를 이용한 개착식 터널구조물의 시공이 가장 효과적인 대안이라 할 수 있다. 따라서, 본 연구에서는 수치해석기법을 이용하여 기존 3분절 리브 보강형 프리캐스트 세그먼트를 이용한 터널구조물 시공기술의 문제점 분석하였으며, 대형 정적하 중재하 실험을 통하여 개선된 리브 보강형 프리캐스트 세그먼트 구조물의 역학적 거동 특성을 분석하였다. 개선된 러브 보강형 프리캐스트 세그먼트 구조물의 극한하중은 기존 리브 보강 프리캐스트 세그먼트 구조물 대비 리브 보강단면은 55% 감소하였으나, 구조적 성능은 약 3% 감소하는 것으로 나타났다. 따라서 리브 보강에 의한 터널구조물 내공단면 축소를 최소화 및 구조물의 하중지지 효과를 크게 향상된 것으로 나타났다.

• The International Journal of Costume Culture
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• 제7권2호
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• pp.77-86
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• 2004

The purpose of this study is to characterize physical and tensile properties according to a knitting method as basic materials for solving the difficulties that occur due to the fact that the crosswise elongation is most different among knit stitch at the time of measuring elongation of knitwear. The sample used for this study was wool $100\%$ and was knitted into two, that is, controlled loop length controlled to properties of structure and fixed loop length by using Shimaseiki SES-124S 12G computer automatic flat knitting machine with DSCS device. Also, the density of rib fabric was 12gauge and its quantity was a total of seven of $0{\times}0,\;1{\times}1,\;2{\times}1,\;2{\times}2,\;3{\times}3,\;4{\times}4$ and including plain fabric, and knitted 2 pieces of sample of 300 wale${\times}400$ course. In conclusion, rib stitch has the much higher stretch rate in the direction of the course than other stitches.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1996년도 추계학술대회논문집
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• pp.105-112
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• 1996

Aluminium alloy have been used extensively as forging materials for aircraft components due to their high specific strength and corrosion resistance. A large portions of these materials are used as airframe components consisted of various combination of such Rib-Web structure. But the problem of high forging pressure and defect which were caused by narrow Rib thickness prevented from the favorable developments and laboratory scaled trials. In this study, optimization of forging variables such as corner radius and temperature in Rib-Wed structure were established. The 2 mm of corner radius minimized the forging pressure to get the fixed Rib height, which well coincided with theoretical result according to Upper-Bound analysis. And optimum workpiece temperature was below 450$^{\circ}C$ in consideration of grain growth and forging defects by local melting.

• 한국산학기술학회논문지
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• 제18권11호
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• pp.747-754
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• 2017

본 논문은 강관과 콘크리트가 함께 축력에 저항하는 합리적인 콘크리트 강관구조형식에 대해 무피복상태에서 내화성능을 높이는 연구이다. 콘크리트 강관구조는 내부 콘크리트로 인한 열저항 성능이 매우 우수하지만, 국내에서는 일정시간 동안 내화성능을 확보하도록 규정하고 있는 내화구조시스템으로 피복처리가 되지 않는 상태에서는 활발하게 적용되지 못하고 있다. 따라서 콘크리트충전 강관구조 기둥의 구조성능을 향상시키기 위하여 강관 내측면에 부착하는 리브요소를 개발하고 그것의 효과적인 형상을 개발하는 연구로서 콘크리트 강관기둥 내측면에 Corrugated Rib를 부착하여 구조적압축 및 좌굴 저항능력을 향상시키는 CFT 시스템을 개발하고자 한다. 이에 대한 연구 결과, 강관 내면 부착 리브의 적용으로 내화시 CFT 기둥의 내력상승에 의한 좌굴방지를 확인하였고, 내화성능기준 또한 만족하였다. 따라서 본 연구를 통해 개발된 강재리브(Corrugate rib)구조 보강재를 활용한 CFT의 공법은 내화피복 없이 구조 및 내화성능을 만족시키는 것으로 판단된다. 향후 rib의 다양한 형태를 변수로 하는 연구와 공장생산에서 공정을 효율화 시키고, 경제성 있는 시스템으로 활용할 수 있도록 추가 연구가 필요할 것으로 판단된다.

• 대한기계학회논문집B
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• 제25권11호
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• pp.1640-1649
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• 2001

The present study investigates the effects of various rib arrangements on heat/mass transfer in the cooling passage of gas turbine blades. A complex flow structure occurs in the cooling passage with rib turbulators which promote heat transfer on the wall. It is important to increase not only the heat transfer rates but also the uniformity of heat transfer in the cooling passage. A numerical computation is performed using a commercial code to calculate the flow structures and experiments are conducted to measure heat/mass transfer coefficients using a naphthalene sublimation technique. A square channel (50 mm $\times$ 50 mm) with rectangular ribs (4 mm $\times$ 5 mm) is used fur the stationary duct test. The experiments focus on the effects of rib arrangements and gap positions in the discrete ribs on the heat/mass transfer on the duct wall. The rib angle of attack is 60°and the rib-to-rib pitch is 32 mm, that is 8 times of the rib height. With the inclined rib angle of attack (60°), the parallel rib arrangements make a pair of counter rotating secondary flows in the cross section, but the cross rib arrangements make a single large secondary flow including a small secondary vortex. These secondary flow patterns affect significantly the heat/mass transfer on the ribbed wall. The heat/mass transfer in the parallel arrangements is 1.5 ∼2 times higher than that in the cross arrangements. However, the shifted rib arrangements change little the heat/mass transfer from the inline rib arrangements. The gap position in the discrete rib affects significantly the heat/mass transfer because a strong flow acceleration occurs locally through the gap.

• 한국의류학회지
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• 제21권1호
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• pp.170-181
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• 1997

The purpose of this study was to determine the effect of knit structure and knit density (machine tightness factor) on the dimensional properties and K1-4 values of weft-knitted fabrics followed over eleven cycles of mechanical relaxation to provide the basic data for constructing weft-knitted fabrics for outwear with excellent dimensional stability The eighteenth weft-knitted fabrics were produced with different knit structure (1$\times$1 rib, half-cardigan rib, half-milano rib, interlock, single pique, crossmiss interlock) and machine tightness factor (loose, medium, tight) for this study. Dimensional properties such as width, lengh, area shrinkage and dimensional parameter (K) of eighteenth knitted fabrics including thickness and bulk property were measured. The results were as follows; 1. The dimensional behavior of the Ix1 rib and interlock in relaxation cycles was anisotropic, i.e., length shrinkage was usually associated with a width expansion, whereas the other weft-kntted fabrics which have tuck or miss loops in the knit structure behaved isotropically, i.e., length and width shrinkages were usually found. It was proposed that the difference in dimensional behavior between these structures was due to the dissimilar nonrelaxed geometrical shapes of the individual structural units forming these weft-knitted structures. The mechanical relaxation shrinkage of weft-knitted cotton fabrics was dependent on the tightness of construction. For a range of fabrics knitted on this study, an increase in fabric tightness caused a decrease in the length shrinkage of the fabric accompanied by an increase in its width shrinkage.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.782-789
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• 2001

Local heat/mass transfer and friction loss in a square duct roughened with various types of continuous and discrete rib turbulators are investigated. The combined effects of the gap flows of the discrete ribs and the secondary flows are examined for the purpose of the reduction of thermally weak regions and the promotion of the uniformity of heat/mass transfer distributions as well as the augmentation of average heat/mass transfer. The rib-to-rib pitch to the rib height ratio (p/e) of 8 and the rib angles of 90 and 60 deg are selected with $e/D_{h}=0.08$. The vortical structure of the secondary flows induced by the parallel angled arrays are quite distinct from that induced by the cross angled arrays. This distinction influences on heat/mass transfer and friction loss in all the tested cases. The gap flows of the discrete ribs reduce the strength of the secondary flows but promote local turbulence and flow mixing. As a result, the fairly uniform heat/mass transfer distributions are obtained with two row gaps.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.22-29
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• 2001

The present study investigates the effects of various rib arrangements and rotating on heat/mass transfer in the cooling passage of gas turbine blades. The cooling passage has very complex flow structure, because of the rib turbulator and rotating effect. Experiments and numerical calculation are conducted to investigate the complex flow structures and heat transfer characteristics; the numerical computation is performed using a commercial code, FLUENT ver.5, to calculate the flow structures and the experiments are conducted to measure heat/mass transfer coefficients using a naphthalene sublimation technique. For the rotating duct tests, the test duct, which is the cross section of is $20mm\times40mm$ (the hydraulic diameter, $D_h$, of 26.7 mm, has two-pass with $180^{\circ}$ turning and the rectangular ribs on the wall. The rib angle of attack is $70^{\circ}$ and the maximum radius of rotation is $21.63D_h$. The partition wall has 10 mm thickness, which is 0.5 times to the channel width, and the distance between the tip of the partition wall and the outer wall of the turning region is 26.7 mm $(1D_h)$. The turning effect of duct flow makes the very complex flow structure including Dean type vortex and high turbulence, so that the heat/mass transfer increases in the turning region and at the entrance of the second pass. The Coriolis effect deflects the flow to the trailing surface, resulting in enhancement of the heat/mass transfer on the trailing surface and reduction on the leading surface in the first pass. However, the opposite phenomena are observed in the second pass. The each rib arrangement makes different secondary flow patterns. The complex heat/mass transfer characteristics are observed by the combined effects of the rib arrangements, duct rotation and flow turning.