• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2005년도 춘계학술대회 논문집
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• pp.385-390
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• 2005

LMTT(Linear Motor-based Transfer Technology)는 항만 자동화를 위한 수평 이송 시스템이며, 셔틀카(shuttle car)와 격자구조의 레일에 부착된 스테이터 모듈(stator module)로 구성된 PLMSL(Permanent Magnetic Linear Synchronous Motor)에 의해 구동된다. 본 논문에서는 LMTT시스템 부품인 이동체(mover)의 경량화를 위하여 직교배열표 및 크리깅 방법을 이용하여 최적설계를 수행한다. 설계변수로는 가로빔, 세로빔, 휠빔의 두께와 높이 방향의 치수를 결정하는 형상변수를 포함시켰다. 목적함수로는 중량, 제한조건 함수로는 안전율이 고려된 응력으로 설정하였다. 본 연구에서 제시된 방법으로 구한 최적해를 민감도기반 최적설계로 구해진 최적해와 비교, 검토하였다.

• 한국추진공학회지
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• 제15권2호
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• pp.68-73
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• 2011

소형위성발사체 (KSLV-I)의 발사 준비에는 다양한 규격의 질소 가스 및 초저온 액체 질소가 소요된다. 발사대 질소 공급 시스템은 고압의 질소 가스 생성, 추진제 충전 후 발사 대기 중인 발사체의 보호를 위한 공간 퍼지용 질소 가스 생성, 연료 및 산화제의 냉각을 위한 액체 질소 공급 기능을 수행하기 위하여 개발되었다. 대기 환경 조건에 따라 열전달 특성이 민감하게 변화하는 대기식 기화기의 운용 불안정성을 제거하기 위해 기화기의 병렬 설치 및 교대 운용 절차를 도입하였다. 이를 통하여 기후 조건에 상관없이 항시적으로 운용이 가능한 시스템을 개발하였으며, 소형 위성 발사체의 비행 시험을 위한 발사대 운용을 성공적으로 수행하였다.

• 한국정밀공학회지
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• 제29권2호
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• pp.156-160
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• 2012

Recently, the demands of the large scale machine tools gradually increase to machine the large parts, such as large scale crankshaft, yaw and pitch bearings for the wind power generator and the vehicle or aircraft components. But the high technology is necessary in order to develop the huge machine tools. Furthermore, the global market of it has been monopolized by a few companies. So, we need to develop the large scale machine tools and study its core technology to rush into the increasing market. In this study, we carried out the researches for the important core technology of a multi-tasking, machine tool; a large scale 5-axis machine tool of gantry type for multi-task machining. This study is focused on the design of large size gantry type multi-axis machine. In the case of large size of machine the cross rail deflection in the X-axis is significant. To reduce the deflection due to the eccentric spindle head, a special hollow type design in the cross rail with outside ram is adapted in this study. Also, the Zig-Zag motion in the Y-axis is inevitable with the gantry geometry, which is by the un-balancing, different motion at the left and the right columns moving. We tried to reduce the influence of Zig-Zag motion using FEM with different loading conditions at the left and the right side column.

• Structural Monitoring and Maintenance
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• 제1권1호
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• pp.131-157
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• 2014

Special track systems used to divert a train to other directions or other tracks are generally called 'railway turnout'. A traditional turnout system consists of steel rails, switches, crossings, steel plates, fasteners, screw spikes, timber bearers, ballast and formation. The wheel rail contact over the crossing transfer zone has a dip-like shape and can often cause detrimental impact loads on the railway track and its components. The large impact also emits disturbing noises (either impact or ground-borne noise) to railway neighbors. In a brown-field railway track where an existing aged infrastructure requires renewal or maintenance, some physical constraints and construction complexities may dominate the choice of track forms or certain components. With the difficulty to seek for high-quality timbers with dimensional stability, a methodology to replace aged timber bearers in harsh dynamic environments is to adopt an alternative material that could mimic responses and characteristics of timber in both static and dynamic loading conditions. A critical review has suggested an application of an alternative material called fibre-reinforced foamed urethane (FFU). The full-scale capacity design makes use of its comparable engineering characteristics to timber, high-impact attenuation, high damping property, and a longer service life. A field trial to investigate in-situ behaviours of a turnout grillage system using an alternative material, 'fibre-reinforced foamed urethane (FFU)' bearers, has been carried out at a complex turnout junction under heavy mixed traffics at Hornsby, New South Wales, Australia. The turnout junction was renewed using the FFU bearers altogether with new special track components. Influences of the FFU bearers on track geometry (recorded by track inspection vehicle 'AK Car'), track settlement (based on survey data), track dynamics, and acoustic characteristics have been measured. Operational train pass-by measurements have been analysed to evaluate the effectiveness of the replacement methodology. Comparative studies show that the use of FFU bearers generates higher rail and sleeper accelerations but the damping capacity of the FFU help suppress vibration transferring onto other track components. The survey data analysis suggests a small vertical settlement and negligible lateral movement of the turnout system. The static and dynamic behaviours of FFU bearers appear to equate that of natural timber but its service life is superior.

• Structural Engineering and Mechanics
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• 제76권1호
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• pp.1-15
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• 2020

The aim of this paper is to simply present live load factor calculation methodology formulation with the addition of a simple new future load projection procedure to previously proposed two methods. For this purpose, Oregon Weigh-in-Motion (WIM) data were used to calculate live load factors by using WIM data. These factors were calculated with two different approaches and by presenting new simple modifications in these methods. A very simple future load projection method is presented in this paper. Using four different WIM sites with different average daily truck traffic (ADTT) volume, and all year data, live load factors were obtained. The live load factors, were proposed as a function of ADTT. ADTT values of these sites correspond to three different levels which are approximately ADTT= 5,000, ADTT = 1,500 and ADTT ≤ 500 cases. WIM data for a full year were used from each site in the calibration procedure. Load effects were projected into the future for the different span lengths considering five-year evaluation period and seventy-five-years design life. The live load factor for ADTT=5,000, AASHTO HS20 loading case and five-year evaluation period was obtained as 1.8. In the second approach, the methodology established in the Manual for Bridge Evaluation (MBE) was used to calibrate the live load factors. It was obtained that the calculated live load factors were smaller than those in the MBE specifications, and smaller than those used in the initial calibration which did not convert to the gross vehicle weight (GVW) into truck type 3S2 defined by AASHTO equivalents.

• 무역상무연구
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• 제13권
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• pp.151-192
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• 2000

This study has been focused on the revisions and characteristics of the 7 non-maritime trade terms(EXW, FCA, CPT, CIP, DAF, DDU and DDP) in Incoterms 2000. Main characteristics are as follows: First, the use of different expressions intended to convey the same meaning has been avoided and the same expressions as appear CISG have been used. Second, the content of preamble in each trade terms has been shortened and definitedly. Third, if the parties are going to use variants of trade terms in Incotrems 2000, the meanings should be made clear by adding explicit wording in the contract of sale. Main revisions of the 7 trade terms are as belows: First, Incoterms 2000 has emphasized that in EXW, the seller delivers when he places the goods at the disposal of the buyer at the seller's premises or another named place(i.e. works, factory, warehouse, etc.) not cleared for export and not loaded on any collecting vehicle. Second, in FCA, delivery is completed; a) If delivery occurs at the seller's premises, the seller is responsible for loading. b) If delivery occurs at any other place, the seller is not responsible for unloading. Third, in CPT and CIP, all costs and charges relating to the goods whilst in transit until their arrival at the agreed place of destination, unloading costs and all duties, taxes and other charges as well as the costs of carrying out customs formalities payable upon import of the goods and for their transit through any country are linked with the content under the contract of carriage. Fourth, Incoterms 2000 has emphasized that in DAF, the seller delivers when the goods are placed at the disposal of the buyer on the arriving means of transport not unloaded, cleared for export, but not cleared for import at the named point and place at the frontier, but before the customs border of the adjoining country. Fifth, Incoterms 2000 has emphasized that in DDU, the seller delivers the goods to the buyer, not cleared for import(in DDP, cleared for import), and not unloaded from any arriving means of transport at the named place of destination. Sixth, if the parties do not intend to deliver the goods across the ship's rail, FCA, CPT and CIP instead of FOB, CFR and CIF should be used.

• 한국항공우주학회지
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• 제41권5호
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• pp.366-372
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• 2013

한국형 달탐사선은 국가 우주개발계획에 따라 한국형 발사체인 KSLV-2(Korea Space Launch Vehicle 2)에 탑재하여 2020년 이후 발사될 예정이다. 한국형 달탐사선은 무인 탐사선으로 궤도선과 착륙선 2종으로 구성되며 발사체의 탑재능력에 따라 발사중량 550kg 이내의 소형 경량으로 개발되어야 한다. 달탐사선 구조체는 임무 탑재장비의 수용 뿐 아니라 발사 및 운용환경에서 견딜 수 있도록 충분한 강성과 강도가 요구된다. 본 논문에서는 한국형 달탐사선 구조모델의 설계에 대한 선행 연구결과를 기술한다.

• 한국구조물진단유지관리공학회 논문집
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• 제22권1호
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• pp.23-31
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• 2018

최근 사용 중인 중앙분리대의 성능 등급을 뛰어넘는 사고가 발생하고 있다. 그러므로 피해를 줄이기 위해 중앙분리대의 성능 등급을 현재의 SB5-B등급보다 상향된 기준에 맞춰 개선하는 것이 필요하다. 이에 본 연구에서는 중앙분리대 충돌시험결과를 활용하여 적절한 모델을 개발 및 검증하고 강도성능이 향상된 콘크리트 중앙분리대 개발을 목표로 하였다. 중앙분리대 성능은 SB6등급으로 목표성능등급을 설정하였고, 중앙분리대의 강도성능 개선 요소로 강성보강과 연성보강의 두 가지 형태를 고려하였다. 강성보강으로는 와이어 메쉬 직경 증가, 중앙분리대 상단 부위 철판보강을 고려하였고, 연성보강을 위해서는 중앙분리대 하단에 고무패드를 설치하여 성능향상을 컴퓨터 시뮬레이션을 통해서 확인하였다. 시뮬레이션 결과, 와이어 메쉬 직경이 증가할 수록 중앙분리대의 부피 손실은 감소하였으며, 고무패드 사용시 트럭의 충격에너지를 중앙분리대의 변형에너지로 전환하여 충격흡수에 효과적인 것으로 나타났다.

• 한국안전학회지
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• 제21권2호
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• pp.15-21
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• 2006

The railroad bogie's components experience repeated loading during service. Especially, oil damper bush has been fatigue fractured on the plane between rubber and steel stem during service, and which results in inferior of performance of the bogie. In this study, in order to offer a proper maintenance method of the bush, bubber bush used for the oil damper was fatigue tested and its damage fraction during service was estimated. Also, FEM analysis on the bush was conducted. When 1400, 1200, and 1000kgf of repeated loads were applied to the oil damper bush, final damage fraction exhibited 63.7%, 50% and 40%. From the results of FEM analysis, deformation energy density was found to be $0.5452kgf/mm^{2}$ at an applied load of 1400kgf and the location with maximum value coincided with the fractured location of the bush. Finally, it will be desirable to adopt the normalized damage fraction rather than absolute damage fraction in estimating remaining service lifetime of the bush.

• 유기물자원화
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• 제9권3호
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• pp.111-118
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• 2001

본 연구의 목적은 음식폐기물의 수거에 소요되는 인력과 장비를 파악할 수 있도록 수거요소를 분석하는데 두었다. 이를 위해 수거단계를 기능단위로 분류하고, 수거요소들은 현장조사를 통하여 분석하였다. 실측결과로부터 단계별 요소들을 산정한 결과, 단독주택 인력시간소요량의 경우 3.3인${\cdot}$시, 단독주택 운반속도의 경우 22.4km/시, 2.5톤 차량의 하차시간 5분 등의 산정이 가능하였다. 인력과 장비에 관한 여건을 동일하게 설정하고 2.5톤의 음식폐기물을 수거하는데 소요되는 지역유형별 수거시간을 산정한 결과, 아파트지역의 경우 1회의 수거에 3.03시간이 소요되었으며, 단독주택지역은 아파트지역보다 3배의 수거시간이 요구되었다. 본 연구에서는 1개 지역만을 대상으로 극히 작은 수거회수에 대해 조사한 결과이므로, 대표성 있는 수거요소들을 산정하려면 많은 후속 연구가 필요하다고 본다.