• 한국안전학회지
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• 제35권4호
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• pp.40-47
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• 2020

Although gangform has good workability due to the integration of outer wall forms and working platforms, 22 workers were died from 21 gangform related accidents during 2012 to 2016. Quantitative risk assessment is required for evident based prevention measure selection. In this study, based on 52 accident data from 2004 to the first half of 2019, FTA is conducted for probabilities of direct causes and their contribution to accidents. Three stages are considered; gangform installation, dismantling and lifting, and using. The effectiveness of countermeasures is evaluated through minimum cut set, RAW and RRW. Complete assembly of gangform on the ground level, detailed planning, and fall prevention device are suggested as prevention measures for installation, dismantling and lifting, and using stages, respectively.

• Ocean and Polar Research
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• 제25권2호
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• pp.227-235
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• 2003

In August 1998, during the resumed fourth session of the Authority, the delegation of the Russian Federation reminded the Assembly that, in addition to polymetallic nodules, other mineral resources existed in the Area, including polymetallic sulphides and cobalt crusts, and requested the Authority to adopt rules, regulations and procedures for exploration for such resources. Pursuant to article 162, para. 2(o)(ii), of the 1982 UNCLOS, such rules, regulations and procedures are to be adopted within three years of the date of such a request. This article reviewed the 'Draft Rules and Regulations for the Exploration and Exploitation of Sea-Floor Massive Sulphides and Cobat-rich Ferromanganese Crusts in the Area' by ISA in 2001, and the 'Madang Guideline for Offshore Mineral Policy' written in 1999 in respect of the international trends of polymetallic sulphides and cobalt crusts. Issues for size of mining area and relinquishment, application of the site-banking system, procedure for dealing with overlapping claims and precautionary approach etc. for the establishment of the norm of polymetallic sulphides and cobalt crusts are reviewed as consideration factors.

• 국제학술발표논문집
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• The 6th International Conference on Construction Engineering and Project Management
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• pp.65-69
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• 2015

The aim of this paper is to identify and rank the main causes of fall accidents from scaffolding according to their relative importance as perceived by project managers and site engineers in construction projects in the Gaza Strip. A total of 50 questionnaires were distributed to project managers and site engineers, 35 questionnaires were received yielding 70% response rate. A total of 33 factors that cause fall accidents in scaffolding were identified through a literature review and consolidated by a pilot study. These factors were categorized into six groups: factors related to erection, factors related to the staff (Scaffolders), factors related to loads, factors related to the personal safety, factors related to the workers behavior, factors related to the personal competencies. The results indicated that factors related to the workers behavior are the major factors that caused fall accidents from scaffolds. The results revealed that the top ranked factors which caused falls accidents from scaffolding were: absence of personal protective equipment (PPE), missing ladders, wind loads, disguised the design code, lack of proper assembly or inspection, overhead tools and materials, climbing and neglect using ladders, lack of guardrails, missing bracing and working during fatigue. These findings would help contractors to understand the top factors that caused fall accidents so that they can take them into consideration in safety planning in order to minimize the possibility of their occurrences.

• Design & Manufacturing
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• 제14권1호
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• pp.8-14
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• 2020

In general, auto parts production assembly line is assembled and produced by automatic mounting by an automated robot. In such a production site, quality problems such as misalignment of parts (doors, trunks, roofs, etc.) to be assembled with the vehicle body or collision between assembly robots and components are often caused. In order to solve such a problem, the quality of parts is manually inspected by using mechanical jig devices outside the automated production line. Automotive inspection technology is the most commonly used field of vision, which includes surface inspection such as mounting hole spacing and defect detection, body panel dents and bends. It is used for guiding, providing location information to the robot controller to adjust the robot's path to improve process productivity and manufacturing flexibility. The most difficult weighing and measuring technology is to calibrate the surface analysis and position and characteristics between parts by storing images of the part to be measured that enters the camera's field of view mounted on the side or top of the part. The problem of the machine vision device applied to the automobile production line is that the lighting conditions inside the factory are severely changed due to various weather changes such as morning-evening, rainy days and sunny days through the exterior window of the assembly production plant. In addition, since the material of the vehicle body parts is a steel sheet, the reflection of light is very severe, which causes a problem in that the quality of the captured image is greatly changed even with a small light change. In this study, the distance between the car body and the door part and the door are acquired by the measuring device combining the laser slit light source and the LED pattern light source. The result is transferred to the joint robot for assembling parts at the optimum position between parts, and the assembly is done at the optimal position by changing the angle and step.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.135-136
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• 2012

Carbon atoms near the surface of W(110) induce reconstructions such as $R(15{\times}12)$ -C/W(110) which consists of two characteristic parts, one square shaped and bright protrusion and two smaller ones. In the atomic resolution STM image, the bigger protrusion shows the periodicities of clean W(110), indicating that it is almost carbon poor region. The smaller protrusion contains hexagonal carbide surface layer of ${\alpha}$-W2C on W(110). Employing this carburized W(110) as templates, we grow Co and Fe clusters of less than ten atoms. Due to the selectivity of bonding sites, growth of larger cluster is highly unfavorable for Co and the size of clusters is very uniform. Since Co atoms prefer to sit on the bigger protrusion rather than smaller one, Co cluster can be arranged one-dimensionally in $R(15{\times}12)$-C/W(110) with quite uniform size distribution. However, Fe clusters sit on both sites without favored site, but still with uniform size distribution. On the other hand, Fe clusters can be grown with quasi one-dimensional order in $R(15{\times}3)$-C/W(110), which consists of only smaller protrusions. We investigate the magnetic properties of the ordered nano-sized clusters. Experiments using XMCD reveals little magnetic moment of Co cluster on $R(15{\times}12)$-C/W(110). This observation is consistent with the predictions of our first principles calculations that small Co clusters can be nonmagnetic or antiferromagnetic with low mean magnetic moment per atom.

• 한국건설관리학회논문집
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• 제22권2호
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• pp.21-30
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• 2021

기존 건설업은 타 산업 분야에 비해 생산성이 낮은 산업에 분류된다. 건설업의 생산성 저하를 해결하고자 전 세계적으로 기존 건설 방식보다 약 40% 생산성이 높은 오프사이트 건설(Off-Site Construction; OSC)에 집중하고 있다. 이러한 높은 생산성이 가능한 이유는 공장에서의 부재를 생산, 현장으로의 운반, 현장 조립 3단계를 연속적인 흐름으로 일관되게 유지하기 때문에 가능하다. 본 연구는 문헌고찰, 1차 사전 현장답사, 2차 온라인 설문, 3차 전문가 심층인터뷰를 통해서 기능조사를 수행하였다. 조사된 기능의 항목들을 편의성, 유연성, 관리 용이성, 의사소통, 안전성 5가지로 분류하였으며, 해당 기능특성에서는 유연성, 관리 용이성, 의사소통이 높은 점수를 나타내었다. 이는 건설현장의 공사 진행에 따른 변화, 공장의 생산일정, 운반 소요시간과 같은 다양성으로 인해 유연성, 관리 용이성, 의사소통이 중요한 기능특성으로 반환된 것으로 판단된다. 마지막으로 설문 조사된 기능 점수 결과에서 평균 점수 4점 이상에 해당된 기능 15개를 바탕으로 Functional Block Diagram을 구성하였다. 본 연구를 통해 OSC 운반 시스템이 구축된다면 성공적인 건설 OSC 프로젝트에 기여하고, 생산성을 높일 수 있을 것으로 판단된다.

• 국제학술발표논문집
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• The 9th International Conference on Construction Engineering and Project Management
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• pp.563-570
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• 2022

Industrialized and modular construction is a growing construction technique that can transfer a large portion of the construction process to off-site fabrication yards. This method of construction often involves the fabrication, pre-assembly, and transportation of massive and long volumetric modules. The module weight keeps increasing as the modules become more complete (with infill) to minimize the work at the site and, as higher productivity can be achieved at the fabrication shop. Thus, a volumetric module delivery gets more challenging and risky. Despite its importance, past research paid relatively insufficient attention to the problem related to the lifting of heavy modules. This can be a complex and time-consuming problem with multiple lifting for transportation-and-installation operations both in fabrication yard and jobsite, and require complex crane operations (sometimes, more than one crane) due to crane load capacity and load balance/stability. This study investigates this problem by focusing on the structural perspective of lifting such long volumetric modules through simulation studies. Various scenarios of lifting a weighty module from the top using four lifting cables attached to crane hooks (either a single crane or double crane) are simulated in SAP software. The simulations account for various factors pertaining to structural indices, e.g., bending stress and deflection, to identify a proper method of module lifting from a structural point of view. The method can identify differences in structural indices allowing identification of structural efficiency and safety levels during lifting, which further allows the selection of the number of cranes and location of lifting points.

• Nuclear Engineering and Technology
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• 제53권8호
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• pp.2682-2695
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• 2021

This paper aims to evaluate the structural dynamic responses and damage/failure of the nuclear fuel reprocessing plant under the free drop impact of spent fuel cask (SFC) and fuel assembly (FA) during the on-site transportation. At the present Part I of this paper, the large-scale SFC model free drop test and the corresponding numerical simulations are performed. Firstly, a composite target which is composed of the protective structure, i.e., a thin RC plate (representing the inverted U-shaped slab in the loading shaft) and/or an autoclaved aerated concrete (AAC) blocks sacrificial layer, as well as a thick RC plate (representing the bottom slab in the loading shaft) is designed and fabricated. Then, based on the large dropping tower, the free drop test of large-scale SFC model with the mass of 3 t is carried out from the height of 7 m-11 m. It indicates that the bottom slab in the loading shaft could not resist the free drop impact of SFC. The composite protective structure can effectively reduce the damage and vibrations of the bottom slab, and the inverted U-shaped slab could relieve the damage of the AAC blocks layer dramatically. Furthermore, based on the finite element (FE) program LS-DYNA, the corresponding refined numerical simulations are performed. By comparing the experimental and numerical damage and vibration accelerations of the composite structures, the present adopted numerical algorithms, constitutive models and parameters are validated, which will be applied in the further assessment of drop impact effects of full-scale SFC and FA on prototype nuclear fuel reprocessing plant in the next Part II of this paper.

• 한국건설관리학회논문집
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• 제24권2호
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• pp.24-36
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• 2023

기존 현장 노무 중심의 건설생산방식의 생산성 문제 및 현장 안전·품질 문제 등의 한계를 보완하기 위하여 OSC가 주목받고 있다. 국내 건설 시장에 OSC의 도입 및 활용이 활성화되기 위해서는 OSC 프로세스(설계 및 엔지니어링, 공장제조, 현장조립, 유지보수) 각 단계별로 적용되는 기술의 혁신도 중요하지만, OSC 방식에 적합한 프로젝트 관리 방식의 개발도 필요하다. 하지만, 현재 국내에서 진행되고 있는 OSC 관련 연구는 관련 기술 개발 측면의 연구가 주를 이루며, OSC 프로젝트의 성공을 위한 프로젝트 관리 방안 도출과 관련한 연구는 미진한 실정이다. 이에 OSC 프로젝트의 핵심성공요인에 기반한 프로젝트 관리 방안 도출에 대한 연구가 필요한 시점이다. 따라서, 본 연구에서는 이전 연구에서 도출한 69개의 OSC 핵심성공요인을 대상으로 중요도-성취도 분석(Importance-Performance Analysis)을 실시함으로써, OSC 도입 및 활용성 향상을 위한 중점 개선요인을 도출하고, 이와 관련한 시사점을 제시하는 것을 목적으로 연구를 진행하였다. 본 연구의 결과는 향후 OSC 활성화를 위한 R&D 계획 및 정책 수립하는 과정에 유용한 시사점을 줄 수 있을 것으로 기대된다.

• 대한안전경영과학회지
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• 제18권4호
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• pp.131-137
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• 2016

In unlimited competition era changed rapidly, productivity improvement and raw cost reduction by working improvement are very important for the survival of middle and small-sized companies. At this moment, middle and small-sized companies are cleary important in domestic industry. Therefore, this researcher applied TPS(Toyota production system) 7 wastes by experiment planning method for wastes of lots of working processes at the manufacturing site of automobile assembly manufacturing company, D company, analyzed current system of D company applied so as to verify if value creation works and factors were minimized during the production and drew results by analyzing experimental planning for analyzing waste elimination.