• Proceedings of the Korean Information Science Society Conference
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• 2005.11a
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• pp.1039-1041
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• 2005

가상 풍동 실험은 슈퍼컴퓨터와 같은 고성능의 계산 지원과 실험을 위한 깊은 지식을 요구하여 실험을 수행하는데 많은 어려움이 수반된다. 그리드[1][2]는 산재한 자원을 연계하여 고성능 응용을 위해 효율적으로 활용할 수 있도록 하는 기반구조를 제공한다. 본 논문에서는 그리드 자원을 활용하여 가상 풍동 실험을 빠르고 효과적으로 수행할 수 있는 그리드 웹 포탈 서비스를 제안한다. 통합된 포탈 서비스를 통하여 사용자의 응용 및 실험환경의 요구사항을 반영한 격자생성, 계산 작업, 작업 모니터링, 결과 가시화를 효율적으로 수행한다.

• Geomechanics and Engineering
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• v.15 no.3
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• pp.899-910
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• 2018

Terrace deposits are often encountered in portal areas and tunnels with low overburden. They are challenging to excavate considering their great mechanical and spatial heterogeneity and a very high stiffness contrast within the ground. Terrace deposits are difficult to characterize, considering that samples for laboratory testing are almost unfeasible to obtain, and laboratory tests may not be representative due to scale effects. This paper presents the approach taken for their characterization during the design stage and their posterior validation performed during construction. Lessons learned from several tunnels excavated on terrace deposits on the Bogota-Villavicencio road (central-east Colombia), suggest that based on numerical simulations, laboratory testing and tunnel system behaviour monitoring, an observational approach allows engineers to optimize the excavation and support methods for the encountered ground conditions, resulting in a more economic and safe construction.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.573-576
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• 2008

절토사면 및 천심도 터널의 경우 불연속면을 따른 블록의 미끄러짐 및 회전 등이 안정성에 큰 영향을 미친다. 국도나 지방도 등을 확장 공사함에 따라 산악이 많은 우리나라 지형의 특성상 절토사면이 많이 발생하게 되고, 경우에 따라서는 이러한 절토사면에 터널이 위치하게 된다. 이런 상황의 터널갱구부 및 인접한 절토사면부에서 붕괴 및 균열이 빈번하게 발생되고 있다. 본 연구에서는 대절토사면과 인접한 터널갱구부에 대하여 편토압이 균열의 주원인인지를 결정하기 위하여 변위 및 응력 패턴을 분석한 사례연구를 제시하였다. 조사대상지역은 울진군에 위치한 터널굴진 현장이고, 붕괴는 터널갱구부와 인접한 절토사면부에서 발생하였으며 터널갱구부 상단의 숏크리트 타설지역에서 다수의 균열이 관찰되었다. 언급한 터널갱구부의 변위 및 응력패턴을 모사하기 위하여 유한차분법에 근거한 플랙을 사용하였으며, 세밀한 수치해석을 위해 편재절리모델을 도입하였다. 마지막으로, 터널갱구부의 균열에 영향을 미친 주원인에 대한 고찰을 다루었다.

• Journal of the Korean Geotechnical Society
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• v.26 no.6
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• pp.71-85
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• 2010

Dynamic analyses of tunnels are widely performed in practice in Korea. Accurate performance of a dynamic analysis is very difficult, requiring appropriate application of lower and lateral boundary conditions, deconvolution, constitutive model, and selection of dynamic soil properties etc. Lack of a systematic guideline on how to perform the dynamic analysis makes it even more difficult to perform an analysis. In addition, dynamic analyses are not needed in most cases and pseudo-static analyses are more than adequate. However, they are performed without a clear understanding on the need for the dynamic analysis and differences between the two methods. In this study, firstly, a guideline for correctly performing a 2D dynamic analysis is developed. Secondly, the differences in the tunnel responses using dynamic and pseudo-static analyses are discussed and compared. The results show that the discrepancies between the dynamic and static analyses are not significant for most cases. It is therefore recommended that the dynamic analyses be performed at tunnel portal, very soft ground, or in cases where spatial variation of the ground motion needs to be considered in the seismic analysis of tunnels in transverse direction.

• Journal of the Korean Arthroscopy Society
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• v.14 no.1
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• pp.49-52
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• 2010

Purpose: We introduce arthroscopically assisted mini-open rotator cuff repair using anterolateral approach. Operative Technique: Placing lateral decubitus position on general anesthesia, a standard arthroscopic glenohumeral examination is performed to evaluate lesions of shoulder joint through posterior and anterior portal. And then arthroscope is placed in the subacromial space and we evaluate the size of the torn tendon and perform arthroscopic acromioplasty through lateral portal. A 3 to 4 cm skin incision is performed from anterolateral edge of acromion to distal and dissected along to raphe between anterior and middle deltoid. A deltoid retractor is then placed, allowing direct visualization of the rotator cuff and humeral head. As torn tendon is tagged by traction suture, we try to anatomical reduction on the footprint and then perform single row or double row repair of the rotator cuff using suture anchors. To prevent avulsion of the deltoid from the acromion, additional sutures by bone tunnel with acromion and deltoid is performed. Conclusion: This technique is useful procedure to get direct approach to anterior portion of supraspinatus tendon and to need lesser deltoid retraction than portal extension approach due to dividing along to raphe between anterior and middle deltoid. Also it provide better visualization of the superior portion of subscapularis and infraspinatus.

• Journal of the Korean GEO-environmental Society
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• v.15 no.1
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• pp.53-62
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• 2014

In Korea, in general, separation distance between existing parallel tunnels was set at two to five times as distant as the diameter of the tunnels according to ground conditions. Recently, however, actual applicability of closely spaced parallel tunnels whose distance between tunnel centers was shorter than the diameter has increased due to environmental damages resulting from massive cutting, restriction in purchase of required land, and maintenance of linear continuity. In particular, when the pillar width of tunnel decreases, the safety of pillars affects behaviors of the tunnel and therefore the need for diverse relevant studies has emerged. However, research so far has been largely confined to analysis of behavior characteristics of pillars, or parameters affecting design, and actually applicable and quantitative data have not been presented. Accordingly, in order to present a stability evaluation method which may maximally reflect construction conditions of spots, this study reflected topographical and stratigraphic characteristics of the portal part with the highest closeness between the tunnels, simulated multi-layer conditions with rock mass and complete weathering, and assessed the degree of effect the stability of pillars had on the entire tunnels through numerical analysis according to changes in pillar width by ground strength. This study also presented composite analysis result on ground surface settlement rates, interference volume rates, and average strength to stress and a formula, which may be applicable to actual work, to evaluate safety rates of closely spaced parallel tunnel pillars and minimum pillar width by ground strength based on failure criteria by Hoek-Brown (1980).

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.5
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• pp.428-437
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• 2008

e-AIRS, an abbreviation of ‘e-Aerospace Integrated Research System’, is a virtual organization designed to support the aerospace engineering processes in the e-Science environment. As the first step toward a virtual aerospace engineering organization, the e-AIRS intends to give a full support to aerodynamic research processes. Currently, the e-AIRS can handle both the computational and experimental aerodynamic researches on the e-Science infrastructure. In detail, users can conduct the full CFD(Computational Fluid Dynamics) research processes, request wind tunnel experiments, perform the comparative analysis between computational and experimental resultants and finally collaborate with other researchers using the web portal. The current paper will describe those functions and the internal architecture of the e-AIRS system.

• Journal of the Korean Arthroscopy Society
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• v.6 no.1
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• pp.60-63
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• 2002

Purpose : The purpose of this study was to introduce new femoral fixation technique using a cross-pin and a bioabsorbable interference screw in hamstring ACL reconstruction. Method : Semitendinosus and gracilis were harvested for quadrapled graft. After tibial tunnel had been made, femoral tunnel was made 35 mm in depth. Then the graft passed through the tunnels. Cross-pin was fixed through the drill hole which had been made through upper sleeve of the Rigidfix system. While pulling the graft, bioabsorbable interference screw was fixed through the anteromedial portal. Conclusion : We introduced the new femoral fixation technique using a cross-pin and a bioabsorbable interference screw as a good method with high fixation strength and tight graft-bone contact.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.20-27
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• 2011

High-speed railway system is exposed to severe aerodynamic problems and has various requirements both on design and operation; 80% of running resistance is composed of aerodynamic drag, the cross-sectional area and portal shape of tunnel should be designed under aerodynamic consideration, and natural wind velocity should always be monitored to prevent the overturning of train by crosswinds. In addition, most of the aerodynamic problems are proportional to the running speed or square of the running speed. Thus, when the running speed of a high-speed railway system either on operation or under construction is to be increased, the aerodynamic problems should be assessed in advance and the countermeasures should be prepared to alleviate the aerodynamic problems to meet certain requirements. In this study, aerodynamic problems that could occur at speed up of high-speed line have been investigated and aerodynamic requirements to meet the increased operational speed have been studied referring the international and domestic rules, guidance, and recommendations.

• Journal of the Korean Arthroscopy Society
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• v.12 no.2
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• pp.112-117
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• 2008

Purpose: Double-bundle reconstruction of anterior cruciate ligament(ACL) has the advantage of restoring the isometry and original function of ACL. The purpose of this study is to evaluate the clinical results following double-bundle reconstruction of ACL using autogenous hamstring grafts through an accessory anteromedial portal. Materials and Methods: From January 2005 to July 2006, sixty patients(52 males, 8 females) underwent double-bundle ACL reconstruction using autogenous hamstring tendons..The mean age was 31.7 years($20{\sim}51$ years). The mean follow up period was 13.4 months($12{\sim}16$ months). We made a horizontal-oblique skin incision just medial to tibial tuberosity and harvested semitendinosus and gracilis tendon. Tibial tunnel for posterolateral bundle was made near its anatomical position. By modifying an anatomic reconstruction of ACL by Yasuda et al., we made a femoral tunnel for posterolateral bundle through accessory anteromedial portal. Tunnels for anteromedial bundle were made with conventional method. We reconstructed anteromedial bundle with semitendinosus tendon and posterolateral bundle with gracilis tendon. Clinical results at last follow up were evaluated by range of motion, extent of anterior displacement(KT-1000 arthrometer), pivot-shift test. Functional evaluation of clinical outcomes were evaluated by Lysholm score and modified Feagin Scoring System. Results: There was no limitation of motion of knee joint at last follow up. Mean side to side difference of anterior displacement of tibia by KT-1000 arthrometer was improved from 8.4 mm preoperatively to 1.7 mm postoperatively(p<0.05). Average Lysholm score was improved from 64.1 preoperatively to 92.2 postoperatively(p<0.05). In modified Feagin Scoring System, 90% of cases were rated as good or excellent. Conclusion: Double-bundle reconstruction of ACL using autogenous hamstring grafts through accessory anteromedial portal results in good clinical outcomes.