• Transactions of the KSME C: Technology and Education
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• v.5 no.2
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• pp.89-95
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• 2017

LCD robot vertical frame lets a arm assembly with glass substrate move up and down, so it must have high stiffness and strength. We applied new manufacturing process by using design optimization process such as topology and size optimization in order to satisfy the request of high stiffness and light weight. The proposed model should be evaluated for endurance strength. Therefore fatigue assessment for weak point of aluminum welding area of vertical frame studied with hot spot stress approach. And the actual stress measuring from test was compared and evaluated with the dynamic stress calculated from multi-body dynamics considering flexible body.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1A
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• pp.67-74
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• 2006

The use of steel plates has been greatly increased in bridge construction, particularly for long-span bridges. For connections of those steel plates in the field, application of high-tension bold, such as M30, is highly demanded. However, the current steel construction specifications in Korea do not provide information for large-sized bolt connections. In order to evaluate the applicability of the large-sized high-tension bolt, this study experimentally investigates relaxation and slip behavior of M30 bolts with varying bolt size and plate thickness. In addition, internal compressive stress was computed using FEM analysis. The analyzed results were compared with the stress distribution measured from strain gages attached on bolts and bolt holes. From the study presented herein, the M30 high-tension bolts are anticipated to be successfully used with the relaxation less than 10% and the slip coefficient satisfying the specified limit.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.2
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• pp.153-163
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• 2010

In this paper a frequency response analysis using Krylov subspace-based model reduction and its design sensitivity analysis with respect to design variables are presented. Since the frequency response and its design sensitivity information are necessary for a gradient-based optimization, problems of high computational cost and resource may occur in the case that frequency response of a large sized finite element model is involved in the optimization iterations. In the suggested method model order reduction of finite element models are used to calculate both frequency response and frequency response sensitivity, therefore one can maximize the speed of numerical computation for the frequency response and its design sensitivity. As numerical examples, a semi-monocoque shell and an array-type $4{\times}4$ MEMS resonator are adopted to show the accuracy and efficiency of the suggested approach in calculating the FRF and its design sensitivity. The frequency response sensitivity through the model reduction shows a great time reduction in numerical computation and a good agreement with that from the initial full finite element model.

• Journal of Korean Tunnelling and Underground Space Association
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• v.22 no.4
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• pp.383-399
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• 2020

Optimizing the spacing of the disc cutter is a key element in the design of the TBM cutter head, which determines the drilling performance of the TBM. The full-scale linear cutting test is known as the most reliable and accurate test for calculating the spacing of the disc cutter, but it has the disadvantage of costly and time-consuming for the full-scale experiment. In this study, through the numerical analysis study based on the discrete element method, the tendency between Specific Energy-S/P ratio according to uniaxial compression strength and penetration depth of rock was analyzed, and the optimum spacing of 17-inch disc cutter was derived. To examine the appropriateness of the numerical analysis model, the rolling force acting on the disc cutter was compared and reviewed with the CSM model. As a result of numerical analysis for the linear cutting test, the rolling force acting on the disc cutter was analyzed to be similar to the rolling force derived from the theoretical formula of the CSM model. From the numerical analysis on 5 UCS cases (50 MPa, 70 MPa, 100 MPa, 150 MPa, 200 MPa), it is found that the range of the optimum spacing of the disc cutter decreases as the rock strength increases. And it can be concluded that 80~100 mm of disc cutter spacing is the optimum range having minimum specific energy regardless of rock strength. This tends to coincide with the optimal spacing of previously reported disk cutters, which underpins the disk cutter spacing calculated through this study.

• The Journal of Small Business Innovation
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• v.19 no.2
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• pp.37-52
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• 2016

Making efforts to break down the barriers between the intra-company departments as well as cooperating with external partners can become the driving force to create a successful innovation in the new product development (NPD) process. This study deals with how the key factors of collaborative innovation success are working in the process of NPD collaboration. Using case analysis of the NPD process, where a large retailer and small and medium-sized suppliers cooperate, we found that the small and medium-sized suppliers achieved greater 'short-term' performances in the collaboration than the large firm, although the long-term performance is not clear. Among the six antecedents of innovation success, relationship-specific investment played a critical role in motivating the supplier's participation in the NPD process. Adopting a 'closed' network in which the two suppliers interact directly with each other and create new knowledge for the NPD process played an important role in producing a quality product in a reduced development time. Unlike previous studies about the retailer-supplier cooperation for NPD in the food industry suggesting that position differences cause communication problems which is a major obstacle to the NPD success. This study suggests that large retailer's initiative role is a critical success factor in the NPD by the cooperation between small and medium-sized suppliers and large retailers.

• Journal of Korea Port Economic Association
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• v.24 no.2
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• pp.289-315
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• 2008

In Korea-China shipping route, the level of freight rate has been maintained very low for last two decades not only because supply of shipping capacity is higher than its demand but also because the route was regulated by the two governments. An examination is made of the effects of openness of Korea-China Liner Shipping Route on competitiveness of Korean-flag Liner Shipping companies. This task is undertaken by detailing the development of the cargo sharing respectively by shipping companies of each country. Then it is suggested the ways to cope with the new environmental changes in Korea-China liner shipping route for the future by examining the future strategies for Korean-flag companies by in-depth interviews with major shipping companies.

• Journal of the Society of Naval Architects of Korea
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• v.30 no.3
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• pp.116-126
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• 1993

The finite element method(FEM) has been commonly used for structural dynamic analysis. However, the direct global application of FEM to large complex structures such as ships and offshore structures requires considerable computational efforts, and remarkably more in structural dynamic optimization problems. Adoption of the component-mode synthesis method is an efficient means to overcome the above difficulty. Among three classes of the component-mode synthesis method, the free-interface mode method is recognized to have the advantages of better computational efficiency and easier implementation of substructures' experimental results, but the disadvantage of lower accuracy in analytical results. In this paper, an advanced method to improve the accuracy in the application of the free-interface mode method for the vibration analysis of large complex structures is presented. In order to compensate the truncation effect of the higher modes of substructures in the synthesis process, both residual inertia and stiffness effects are taken into account and a frequency shifting technique is introduced in the formulation of the residual compliance of substructures. The introduction of the frequency shrift ins not only excludes cumbersome manipulation of singular matrices for semi-definite substructural systems but gives more accurate results around the specified shifting frequency. Numerical examples of typical structural models including a ship-like two dimensional finite element model show that the analysis results based on the presented method are well competitive in accuracy with those obtained by the direst global FEM analysis for the frequencies which are lower than the highest one employed in the synthesis with remarkably higher computational efficiency and that the presented method is more efficient and accurate than the fixed-interface mode method.

• Journal of the Korea Institute of Building Construction
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• v.10 no.4
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• pp.83-93
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• 2010

With construction projects continuously becoming more massive and complex, risk factors have been consistently increasing. To achieve a successful project, it is very important to identify and cope with such risk factors. Therefore, the purpose of this study is to suggest plans of reducing risk, not only for describing the drafting process for construction planning but also for systematically organizing constraints and risk factors in earth work, foundation work and reinforced concrete construction. To achieve these objectives, this study 1) analyzes previous theories about risk classification structure, 2) performs a case study of an actual project to embody the problems of safety management by analyzing the results of an interview with a construction engineer. In conclusion, the following factors were systematically organized: 1) characteristics of construction site (purpose, structure, floor, etc.); 2) the actual application conditions of the main construction methods; 3) the relationship between constraints and risk factors.

• Journal of Digital Convergence
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• v.15 no.1
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• pp.117-127
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• 2017

Even well trained personnel may fall victim to panic, and a wrong assessment of the situation can turn a small accident into a huge disaster. At the disaster site, the event is commonly broadcasted in real time and is unfiltered. Thus, the commander of the site must be able to accurately assess the scene while not missing out on key considerations. Despite the necessity of good situational assessment, there is barely any research on this topic. This study utilizes METT-TC(Mission, Enemy, Troops, Terrain and weather, Time available, and Civil considerations) which is used by militaries to assess combat situations, and proposes MORT-TAC(Mission, Object, Resources available, Terrain and weather, Time available, Ability, and Civil considerations) as factors to consider in effectively controlling the disaster site. The standard model is used for assessing disaster scenes by applying the Delphi analytical method on each sub-factor of MORT-TAC.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.2
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• pp.952-962
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• 2015

In this study, multilayered rings with a large outer diameter have been developed using a hot ring rolling process. The ring rolling process has been analyzed by rigid plastic finite element analyses (FEA) using the AFDEX2D and AFDEX3D/HEXA/RING simulators, where the finite element meshes received severe plastic deformation are remeshed into a fine mesh-size using a dual-mesh system. According to the simulated results, the design variables of the multilayered rings were determined and real tests were conducted to check the validity of the simulation results. By adopting the hot ring rolling process, the input weight of raw materials was reduced by 40% against the conventional hot forging process and that the recovery rate was increased by 24%. The measurement of the averaged roundness was satisfied within 0.5 mm for both the inner and outer diameters. Moreover, the hot ring rolling processes yielded 1.49 Cpk for the outer-diameter and 0.84 Cpk 0.84 for the inner-diameter.