• International Journal of Aeronautical and Space Sciences
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• 제13권3호
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• pp.386-397
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• 2012

The stability and structure of bluff-body stabilized hydrogen flames were investigated numerically and experimentally. The velocity of coflowing air was varied from subsonic velocity to a supersonic velocity of Mach 1.8. OH PLIF images and Schlieren images were used for analysis. Flame regimes were used to classify the characteristic flame modes according to the variation of the fuel-air velocity ratio, into jet-like flame, central-jet-dominated flame, and recirculation zone flame. Stability curves were drawn to find the blowout regimes and to show the improvement in flame stability with increasing lip thickness of the fuel tube, which acts as a bluff-body. These curves collapse to a single line when the blowout curves are normalized by the size of the bluff-body. The variation of flame length with the increase in air flow rate was also investigated. In the subsonic coflow condition, the flame length decreased significantly, but in the supersonic coflow condition, the flame length increased slowly and finally reached a near-constant value. This phenomenon is attributed to the air-entrainment of subsonic flow and the compressibility effect of supersonic flow. The closed-tip recirculation zone flames in supersonic coflow had a reacting core in the partially premixed zone, where the fuel jet lost its momentum due to the high-pressure zone and followed the recirculation zone; this behavior resulted in the long characteristic time for the fuel-air mixing.

• 한국광학회지
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• 제21권5호
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• pp.200-205
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• 2010

본 논문에서는 포토닉 밴드갭 광섬유(Photonic Bandgap Fiber: PBGF) 사이에 중공광섬유(Hollow Optical Fiber: HOF)를 융착 접속시켜 만든 광섬유 간섭계와 넓은 모드 면적을 가지는 광자결정 광섬유(Large Mode Area-Photonic Crystal Fiber: LMA-PCF)사이에 HOF를 융착접속시켜 만든 광섬유 간섭계의 온도 및 스트레인에 대한 광학적 특성을 분석하였다. PBGF 또는 LMA-PCF와 HOF의 융착접속시 광섬유내 공기구멍을 최대한 유지하도록 융착조건을 최적화하여 접속 손실을 줄였다. PBGF와 HOF로 구성된 광섬유 간섭계의 온도 및 스트레인에 대한 민감도는 각각 15.4 pm/$^{\circ}C$와 0.24 pm/${\mu}\varepsilon$으로 측정되었으며, LMA-PCF와 HOF로 구성된 광섬유 간섭계의 온도 및 스트레인에 대한 민감도는 각각 17.4 pm/$^{\circ}C$와 0.2 pm/${\mu}\varepsilon$으로 측정되었다.

• Archives of Reconstructive Microsurgery
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• 제15권2호
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• pp.101-106
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• 2006

The purpose of this study was to analyze the mid to long-term clinical and radiological outcome of vascularized pronator quadratus-wrapped radial bone flap arthroplasty for symptomatic advanced $Kienb{\ddot{o}}ck's$ disease. Between 1982 and 2000, 41 cases of advanced $Kienb{\ddot{o}}ck's$ disease were treated with vascularized pronator quadratus wrapped radial bone flap arthroplasty. There were 17 men and 24 women, with a mean age of 39 years at the time of operation. According to Lichtman's classification, there were 13 stage IIIb and 28 stage IV patients. The duration of follow-up averaged 6.1 ($3{\sim}22$) years. We assessed the clinical outcome by subjective pain and active range of motion of the wrist, and evaluated the radiologic outcome by using carpal height ratio and radioscaphoid angle. Postoperatively, all patient reported an improvement in their symptoms. The mean active extension and flexion were improved by $9^{\circ}$ and $6^{\circ}$, respectively (p<0.05). The carpal height ratio was decreased from a mean of 0.52 to 0.48, and the radioscahpoid angle was increased from a mean of $61^{\circ}$ to $66^{\circ}$, but the differences were not significant statistically. Vascularized pronator quadratus-wrapped radial bone flap arthroplasty improves the wrist motion and may prevent serious carpal collapse in advanced $Kienb{\ddot{o}}ck's$ Disease.

• 한국안전학회지
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• 제31권5호
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• pp.95-101
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• 2016

This study proposes a multi-scale dynamic system reliability analysis of control system as a method of quantitative evaluation of its performance in probabilistic terms. In this second paper, we discuss the control effect of the viscous damper on the seismic performance of the structure-level failure. Since the failure of one structural member does not necessarily cause the collapse of the structural system, we need to consider a set of failure scenarios of the structural system and compute the sum of the failure probabilities of the failure scenarios where the statistical dependence between the failure scenarios should be taken into account. Therefore, this computation requires additional system reliability analysis. As a result, the proposed approach takes a hierarchial framework where the failure probability of a structural member is computed using a lower-scale system reliability with the union set of time-sequential member failures and their statistical dependence, and the failure probability of the structural system is again computed using a higher-scale system reliability with the member failure probabilities obtained by the lower-scale system reliability and their statistical dependence. Numerical results demonstrate that the proposed approach can provide an accurate and stable reliability assessment of the control performance of the viscous damper system on the system failure. Also, the parametric study of damper capacity on the seismic performance has been performed to demonstrate the applicability of the proposed approach through the probabilistic assessment of the seismic performance improvement of the damper system.

• 한국강구조학회 논문집
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• 제18권4호
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• pp.491-502
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• 2006

본 논문은 중력하중의 지배를 받는 CFT기둥-RC 무량판 접합부의 실물대 실험결과를 요약한 것이다. CFT구조는 여러 가지 구조및 시공상의 장점으로 인하여 국내 건설 현장에서 상대적으로 짧은 시간에 폭넓게 수용되고 있다. 주차장 용도로 주로 사용되는 지하층은 철근콘크리트 무량판으로 시공하여 경제성을 도모하는 것이 국내에서 일반적으로 요구되는 시공관행이다. 그러나 CFT기둥-R C 무량판 접합부의 효율적인 디테일은 아직 국내 외적으로 제시된 바가 없어서 이 분야의 연구가 매우 필요한 실정이다. 현장 시공시 경제성을 극대화할 수 있는 몇 가지 전략을 기초로 해서, 여러가지 접합 상세를 제안하였고 실험을 통하여 검증하엿다. 실험결과 본 연구에서 제시된 CFT기둥-RC 무량판 접합 상세의 펀칭강도 및 강성이 RC 무량판 접합부와 동등하거나 이를 상회하는 것을 확인할 수 있었다. CFT기둥-RC 무량판 접합부의 초기 탄성거동에서 펀칭파괴이후 휨철근의 국부 현수작용에 이르기까지의 모델링 방안을 제시하고 본 연구의 실험결과를 기초로 5개의 모델링 변수를 캘리브레이션하였다. 또한 무량판구조의 연쇄붕괴방지 설계에 본 연구의 결과를 응용하는 방안을 사례를 통하여 예시하였다.

• 디자인학연구
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• 제14권4호
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• pp.127-136
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• 2001

The decay of the Old Chinese Dynasty, Tang in the 10th century caused the collapse of the political order of Southeast Asia and the neighboring countries began to try to go their own way. Japan abolished the system called "Yudangsa" and nourished the culture of Japanese style. The fang age had a respect of the′Japanese Character Culture", in which when we expressed the sound, they developed the Japanese letters ,that is, reduced Chinese characters, and systematized them as linguistic symbols and developed them into one of letter design styles. The Japanese letters which was mainly the media of the expression of the female literature were delicately shaped ′as natural materials, which finally resulted in Japan′s oldest letter modeling, Asite Letter Design Style. The Japanese letters were blended with ′Reeds around the Lake", "Sea Birds", "Birds′flying", and "Rocks", mixed with the overall shapes of the objects and assimilated into one part, and became a means for the main entertainment of the nobility such as "Singing Festival", "Conference", and "Ceremonial Events" According to the relics, the Japanese feeling of a small cosmos was represented with the fabulous skills of artifacts. In audition, "Play Painting"in the countryside is also a kind of Asite the ordinary people accepted as wit and satire. What we will have to notice is about exchange of the Chinese letter designs, when the thought focused ′on the letter design, Jobcheso was popular. The letter design Jobcheso is -a kind of letter design which represents -natural objects and was popular at the time of Yukjo Dynasty, and there are some documents of that period left both in Japan and Korea. "Hyojedo" in Korea is supposed to have been influenced by the letter design. Asite- is also considered to have been "Japanese Letter Jobcheso." Therefore, the purpose of this study is to look into the origin of the letter designs in the Chinese character culture circle, in terms of the letter design of Jobcheso.

• Earthquakes and Structures
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• 제9권1호
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• pp.127-143
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• 2015

In conventional seismic design, structures are assumed to be fixed at the base. To reduce the impact of earthquake loading, while at the same time providing an economically feasible structure, minor damage is tolerated in the form of controlled plastic hinging at predefined locations in the structure. Uplift is traditionally not permitted because of concerns that it would lead to collapse. However, observations of damage to structures that have been through major earthquakes reveal that partial and temporary uplift of structures can be beneficial in many cases. Allowing a structure to move as a rigid body is in fact one way to limit activated seismic forces that could lead to severe inelastic deformations. To further reduce the induced seismic energy, slip-friction connectors could be installed to act both as hold-downs resisting overturning and as contributors to structural damping. This paper reviews recent research on the concept, with a focus on timber shear walls. A novel approach used to achieve the desired sliding threshold in the slip-friction connectors is described. The wall uplifts when this threshold is reached, thereby imparting ductility to the structure. To resist base shear an innovative shear key was developed. Recent research confirms that the proposed system of timber wall, shear key, and slip-friction connectors, are feasible as a ductile and low-damage structural solution. Additional numerical studies explore the interaction between vertical load and slip-friction connector strength, and how this influences both the energy dissipation and self-centring capabilities of the rocking structure.

• Earthquakes and Structures
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• 제14권4호
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• pp.361-377
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• 2018

In this paper, an alternative reliability-based methodology is developed and implemented on the safety evaluation of structures subjected to seismic loading. To effectively elaborate the approach, structures are represented by finite elements and seismic loading is applied in time domain. The accuracy of the proposed reliability-based methodology is verified using Monte Carlo Simulation. It is confirmed that the presented approach provides adequate accuracy in calculating structural reliability. The efficiency and robustness in problems related to performance-based seismic design are verified. A structure designed by experts satisfying all post-Northridge seismic design requirements is studied. Rigidities related to beam-to-column connections are incorporated. The structure is excited by three suites of ground motions representing three performance levels: immediate occupancy, life safety, and collapse prevention. Using this methodology, it is demonstrated that only hundreds of deterministic finite element analyses are required for extracting reliability information. Several advantages are documented with respect to Monte Carlo Simulation. To showcase an applicability extension of the proposed reliability-based methodology, structural risk is calculated using simulated ground motions generated via the broadband platform developed by the Southern California Earthquake Center. It is validated the accuracy of the broadband platform in terms of structural reliability. Based on the results documented in this paper, a very solid, sound, and precise reliability-based methodology is proved to be acceptable for safety evaluation of structures excited by seismic loading.

• 한국터널지하공간학회 논문집
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• 제18권6호
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• pp.535-544
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• 2016

도심지에서 지하철과 같은 터널의 증가에 따라 특수한 설계, 및 시공 방법이 제안되어 왔다. 터널 붕괴 사고는 막대한 인명, 재산 피해를 가져오기 때문에 터널 굴착 및 주변지반의 거동을 관측하고 분석하는 작업은 매우 중요하다. 하지만 매번 현장시험을 하기에는 경제적인 측면에서 비현실적이다. 따라서 현장시험의 단점을 보완하고, 보다 정밀한 결과를 도출하는 연구가 지속적으로 발표되어 왔다. 본 연구는 군말뚝과 터널 사이 이격거리에 따른 2-arch 정거장 굴착 시 주변 지반의 거동을 측정하였다. 실내모형시험을 위해 trapdoor장치를 고안하였으며, 터널굴착은 2-arch 터널의 체적손실(VL)을 증가시킴으로써 모사하였다. 또한, 근거리 사진계측 및 이미지프로세싱을 통해 지반의 거동을 관측하였으며, 수치해석을 통해 실내모형시험의 결과와 비교하였다.

• 한국인터넷방송통신학회논문지
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• 제20권3호
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• pp.105-111
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• 2020

제주 윈드캐슬을 정의하고 그 주체인 한라산-오름-밭담의 상호관계를 최초로 분석했다. 제주에는 높이 1.5m의 밭담(Black Silk Road), 368개의 오름, 한라산 1950m, 모두 유니크한 풍광이다. 본 논문의 검증은 삼다수 지하수 채취 해수면이 한라산 높이와 같고 중성대 이론에서 이 문제를 수학적으로 완전하게 증명한다. 돈내코(해발700m)-백록담동릉-진달레밭-성판악-교래(453m)-윗세오름(1700m)은 Rain belt로 남동쪽에서 올라오는 북태평양 습도를 먹은 저기압 기단과 한라산 봉우리의 고기압의 찬공기가 부딪치는 -와+가 합해져서 제로가 되는 중성대이기 때문에 비가 많이 온다. 제주역사에서 한라산을 진산(鎭山)이라고 하는데 그 답은 윈드캐슬이다. 제주 오름 수는 한라산 포함 369이며 50m/s이상 불어오는 태풍에도 약 1.5m 높이인 밭담은 무너지지 않는다. 윈드캐슬의 핵(核)은 밭담 1.5m이고 그것은 삼각수이기 때문이다.