• 전기학회논문지
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• 제66권6호
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• pp.975-980
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• 2017

Overhead catenary system of electric railway has overlap sections which devide and tighten trolley wire supplying electric power to train, where current collection performances may become worse according to railway speed-up. Current collection tests conducted at 400 km/h test-bed section of Honam high-speed railway show that balanced line arrangement at overlap section is needed to secure current collection without arc generation between trolley wire and train current collection device. This paper proposes a design procedure of the overlap section to allow for tension increase and uplift of the trolley wires according to railway speed-up. By applying the proposed procedure to the overhead catenary system of Honam high-speed railway, it is suggested that the minimum span length should be 33.2 m for railway speed-up to 350 km/h and 43.7 m for speed-up to 400 km/h.

• 전기학회논문지
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• 제62권11호
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• pp.1633-1639
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• 2013

In a section of AC electric railway, a phase between the sections is different although voltage levels supplied from substations are the same. Therefore, section insulators have been installed to electrically divide between the sections. Two differenet types of section insulator, namely an overlap type and insulator type, are used. In Korean high-speed lines, overlap type section insulator has been adopted. And, insulator type is used in conventional line. The overlap type has the advantage of having no speed limit, but has the disadvantage of requiring long section length. However, the insulator type has the advantage of section length, but also has the disadvantage of having speed limit. In Korean conventional line, an insulator type one relies on the import and there is some problem with wear. In this study, we developed the insulator type section insulator which adopts Teflon tube insulation material. The Teflon material has advantage of the excellent electrical characteristics and wear-resistance characteristics for a longer expected life than that made of existing FRP. In order to compare wear characteristics between the materials, wear tests with reciprocal wear tester are performed. And dynamic behavior tests between the insulators and pantograph are also performed for showing its better dynamic characteristics.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 춘계학술대회 논문집
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• pp.400-407
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• 1995

The straightness property is one of fundamental geometric tolerances to be strictly controlled for guideways of machine tools and measuring machines. The staightness measurement for long guideways was usually difficult to perform, and it needed additional equipments or special treatment with limited application. In this paper, a new approach is proposed using the profile matching technique for the long guideways, which can be applicable to most of straghtness measurements. An edge of relativelly sthort length is located along a divided section of a long guideway, and the local straightness measurement is performed. The edge is then moved to the next section with several positions overlap. After thelocal straightness profile is measured for every section along the long guideway with overlap, the global straightness profile is constructed using the profile matching technique based on theleast squares method. The proposed techinique is numerically tested for two cases of known global straightness profile arc profile and irregular profile and those profiles with and without random error intervention, respectively. When norandom errors are involved, the constructed golval profile is identical to the original profile. When the random errors are involved, the effect of the number of overlap points are investigated, and it is also found that the difference between the difference between the constructed and original profiles is very close to the limit of random uncertainty with juist few overlap points. The developed technique has been practically applied to a vertical milling machine of moving table type, and showed good performance. Thus the accuracy and efficiency of the proposed method are demonstrated, and shows great potential for variety of application for most of straightness measuirement cases using straight edges, laser optics, and angular measurement equipments.

• 한국지반신소재학회논문집
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• 제17권4호
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• pp.109-118
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• 2018

현재 개발 중에 있는 2열 겹침주열말뚝은 대심도 굴착 시 적용을 위해 2열의 말뚝을 통해 강성을 크게 증대시키고 말뚝 간 엇갈림 겹침부를 통한 연속성 확보로 추가의 그라우팅이 없이 차수벽 역할을 할 수 있도록 고안된 흙막이 벽체이다. 이 벽체는 기존의 주열말뚝벽체에 비해 2열 엇갈림 말뚝 시공으로 단면 형상이 복잡하여 기존의 주열말뚝벽체들에 비해 휨 강성 등 단면 조건에 좌우되는 설계인자의 결정이 용이하지 않다. 본 연구에서는 2열 겹침주열말뚝의 다양한 단면 조건들에 대해서 이론적 방법과 통계적 분석을 통해 간단한 단면 제원, 즉, 말뚝의 직경과 말뚝 간 겹침길이를 이용해 흙막이 벽체의 중요 설계 인자인 휨 강성을 간편하게 산정할 수 있는 계산식을 유도하였다. 개발된 간편 휨강성 산정식은 정밀하게 계산된 휨 강성과 비교해 오차율 3% 이하인 것으로 나타났다.

• 한국자동차공학회논문집
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• 제23권1호
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• pp.105-111
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• 2015

Since 2007, Insurance Institute of Highway Safety(IIHS) has conducted the new bumper test using bumper barrier to estimate the repair cost of impacted vehicle. In this study, for the front body FE model of a medium size passenger car analyzes were carried out to optimize the shape of backbeam center reinforcement bracket. First, overlap effect was examined with changing the overlap magnitude and spot welds were added along the backbeam center line for reducing the section shear deformation. Next, for an overlap model design parameter study was performed for the bracket. Thickness effect was examined and an inner reinforcement was added to the bracket. Also, the lower part of bracket was deleted and additionally the bracket length was extended. The results were discussed in terms of backbeam backward deflection, barrier backstop intrusion and weight. Compared with the current design, the final model showed 44.1% bracket weight reduction with 30.0% decrease of backbeam deflection.

• 한국추진공학회지
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• 제15권1호
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• pp.19-28
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• 2011

본 연구에서는 속도 복합형 초음속 충동형 터빈의 최적 동익 오버랩을 선정하기에 앞서, 사전연구차원에서 동익 오버랩에 따른 터빈 성능특성을 분석하였다. 축대칭 노즐과 환형 노즐 대신에 사각단면 초음속 노즐이 적용된 속도 복합형 터빈에 대해 연구를 수행하였다. 상용 유동해석 프로그램을 이용한 터빈의 3차원 전산해석을 통해 익근보다는 익단에 오버랩을 적용한 경우가 터빈의 성능을 향상시키는데 더 효과적이며, 익근과 익단 모두 오버랩을 적용한 경우가 터빈의 성능 향상 가장 큰 것으로 나타났다. 2단 동익 오버랩의 경우, 전체 터빈에서 2단이 발생시키는 출력이 약 22~23%에 지나지 않으므로 2단 동익 오버랩에 의한 터빈 성능 향상은 크지 않은 것으로 파악되었다.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제43권6호
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• pp.363-367
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• 2017

Headaches are one of the most common conditions associated with temporomandibular disorder (TMD). In the present paper, we evaluated the relationship between headache and TMD, determined whether headache influences the symptoms of TMD, and reported two cases of TMD accompanied by headache. Our practical experience and a review of the literature suggested that headache increases the frequency and intensity of pain parameters, thus complicating dysfunctional diseases in both diagnostic and treatment phases. Therefore, early and multidisciplinary treatment of TMD is necessary to avoid the overlap of painful events that could result in pain chronicity.

• 한국도로학회논문집
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• 제14권1호
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• pp.95-102
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• 2012

본 연구는 평면선형과 종단선형이 겹친 복합선형 구간에서 복합선형요소와 교통사고와의 특성을 파악하기 위한 목적으로 진행되었다. 이를 위해 설계속도 및 제한속도가 100km/h인 4차로 고속도로 중 평면곡선부를 대상으로 연구를 진행하였다. 기하구조자료는 한국도로공사 "지리도형정보시스템" 자료를 이용하였고 교통사고자료는 "고속도로 교통사고 통계' 자료를 활용하였다. 분석결과, 종단곡선이 없는 경우가 종단곡선이 있는 경우보다 사고율이 높게 나타났으며, 종단곡선이 1개인 경우가 종단곡선이 2개 이상인 경우보다 사고율이 높게 나타났다. 종단곡선이 1개인 경우, 오목종단곡선(SAG) 구간이 볼록종단곡선(CREST) 구간보다 사고율이 높게 나타났으며, 평면곡선부 이전 선형이 직선부인 경우가 곡선부인 경우보다 사고율이 높게 나타났다. 특히 노면상태가 습기(강우)일 때에는 평면곡선내 오목종단곡선인 경우이거나 평면곡선방향이 좌향구간의 경우 교통사고와 관련성이 높음을 확인하였다. 본 연구에서는 도로의 안전성을 높이기 위해 3차원적인 복합선형 조건을 고려한 도로 선형 설계의 중요성을 제시하였다는 점에서 의미가 있을 것이다.

• Journal of information and communication convergence engineering
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• 제11권2호
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• pp.82-94
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• 2013

In this paper, we propose a novel tunnel-free scheme in a proxy mobile IPv6 (PMIPv6)-based nested network mobility environment; several mobile nodes (MNs) and mobile routers (MRs) compose a hierarchical wireless network topology. Because tunnels created by several MRs overlap and data packets travel along several local mobility anchors (LMAs), the utilization of the wireless section is reduced and the packet forwarding path of the wire-line section is not optimal. In our tunnel-free scheme, the mobile access gateway (MAG) plays an important role in both the wireless and wire-line sections. Using a local binding update, this tunnel-free scheme forwards data packets with a host-based routing table without any tunnel. Establishing a direct tunnel between the MAG and the last LMA, this scheme removes nested tunnels between intermediate LMAs and MRs, and optimizes the forwarding path to the MN in the wire-line section.

• Journal of Welding and Joining
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• 제19권3호
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• pp.317-324
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• 2001

This study deals with high power Nd:YAG laser welding of thin steels for small pressure vessels. Full penetration welding at the overlap joint was performed so as to assure sufficient weld strength. Results showed that mid-depth weld size reduced drastically with increasing the travel speed. Position of focus had little effect on the bead formation even though short focal system was used. However, the shape factor and the bead width had closely related with the position of focus. Based on the microstructural inspection, acceptable weld was obtained when the overlap clearance was controlled up to 20% of the base metal thickness. In the case that the joint contained more clearance than the critical value, both the tensile shear strength and the tear strength were reduced. Results also demonstrated that shielding gases were proved to play a key role as far as the bead formation characteristics was taken into consideration. Blowing dry air through 5mm in diameter nozzle produced narrower bead cross-section than that of argon or nitrogen shielding.