• 한국자동차공학회논문집
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• 제22권1호
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• pp.103-109
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• 2014

This paper represents the s-cam manufacturing process with the high-carbon steel like S45C using laser welding system. Laser welding of the high-carbon steel is generally difficult because of hardening of the weld zone. Also, existing s-cam manufacturing process, electric resistance welding system, have some problems like increase of production and development cost. To solve those problems, we are introduced the laser welding system with the pre-heating system for precision welding of s-cam with separated shaft and cam part. S-cam manufactured with optimum laser welding conditions is verified the performance like tensile strength, torsional strength and fatigue test. Strength and fatigue test results are described.

• 벤처창업연구
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• 제10권1호
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• pp.95-110
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• 2015

기업가정신이론을 비롯하여 많은 혁신이론들이 경영자의 혁신능력을 혁신의 출발로 보고 있다. 본 연구는 경영자의 혁신DNA라는 역설적 은유를 통해 혁신에 미치는 영향과 환경의 적합성 관계를 규명함으로써 학습과 노력에 의해 후천적으로 혁신역량을 높일 수 있는 구체적인 방향을 모색하는데 목적을 두고 있다. 이를 위해서 대구경북 110개 제조기업을 대상으로 자료를 수집하여 실증분석을 하였다. 실증분석 결과 혁신DNA는 혁신에 전반적으로 긍정적인 영향을 미치는 것을 확인하였다. 특히 발견DNA는 실행DNA보다 제품전략에 더 강하게 작용하는 반면에, 실행DNA는 공정혁신에 더 강하게 작용하는 것으로 나타났다. 혁신DNA와 환경의 적합성에 따른 혁신의 영향의 경우, 발견DNA와 기술격변성은 상호적합성을, 시장격변성은 보완적합성을 통해 제품혁신을 강화하는 것으로 나타났다. 실행DNA와 시장격변성의 상호적합성을 통해 공정혁신을 강화시키는 것으로 나타났다.

• Metals and materials international
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• 제24권6호
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• pp.1202-1212
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• 2018

The effects of Nickle (Ni) addition on bainitic transformation and property of ultrahigh strength bainitic steels are investigated by three austempering processes. The results indicate that Ni addition hinders the isothermal bainite transformation kinetics, and decreases the volume fraction of bainite due to the decrease of chemical driving force for nucleation and growth of bainite transformation. Moreover, the product of tensile strength and total elongation (PSE) of high carbon bainitic steels decreases with Ni addition at higher austempering temperatures (220 and $250^{\circ}C$), while it shows no significant difference at lower austempering temperature ($200^{\circ}C$). For the same steel (Ni-free or Ni-added steel), the amounts of bainite and RA firstly increase and then decrease with the increase of the austempering temperature, resulting in the highest PSE in the sample austempered at temperature of $220^{\circ}C$. In addition, the effects of austempering time on bainite amount and property of high carbon bainitic steels are also analyzed. It indicates that in a given transformation time range of 30 h, more volume of bainite and better mechanical property in high carbon bainitic steels can be obtained by increasing the isothermal transformation time.

• 한국시스템다이내믹스연구
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• 제10권2호
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• pp.103-120
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• 2009

Using various data derived from the regional innovation projects in the IT and BT-sectors within Chungbuk Province, this study tries to observe formation processes of network connecting structure and their spill-over effects. Considering the dynamic nature of key issues, it applies both social network analysis and causal loop methods. After a series of simulation exercises, we find that so-called extroverted regional innovation projects, that is, ones financially supported by the central government, reveal a higher tendency in the centrality, heavily depending on a handful of well reputed organizations. It is quite similar to the reinforcing mechanism, resulting in the rich-get-richer and the poor-get-poorer. Compared with the existing documents, nonetheless, it shows relatively weak in the mechanism strength, implying the fact that regional innovation projects have significantly contributed to ameliorating the unequal distribution of innovation organizations within Chungbuk Province. On the other hand, this study concludes that all the brokerage organizations related to the regional innovation projects have settled in Chungbuk Province. Whereas the Capital Region-based organizations present a higher tendency in the knowledge-network, it seems that the regional innovation projects have significantly contributed to upgrading direct and indirect competitiveness of the local organizations.

• 한국기계가공학회지
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• 제17권2호
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• pp.130-136
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• 2018

This study develops a seat with electric motor technology for a one-ton grade commercial vehicle. While applying electric motor technology, the FMVSS 210 seat frame strength test is also conducted to examine the product's weak parts. The seat frame strength test used the FMVSS 210 test standard and the ANSYS program was used to simulate the test and identify weak parts in the deformation and strain values. The test results showed that the cushion frame and slide rail connection bracket were fractured at loads of about 10,000 N. Similarly, the maximum stress and strain values in the bracket were obtained in the simulation results. On this basis, it was evaluated that the connection part bracket was a considerably weak part in the case of the first model, and changing the shape of the bracket and reinforcing the strength were required. In addition, the seat belt anchorage test results and simulation results were compared to assure their validity. In the comparison results, the error for each is about 5-10%. Therefore, the simulation performed in this study is considered to have produced reasonably accurate results.

• 한국기계가공학회지
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• 제17권3호
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• pp.71-77
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• 2018

This paper suggests how to improve the fatigue strength of an axle shaft, which is the vulnerable part of an axle shaft system for a 3.5-ton commercial vehicle. The axle shaft is composed of a universal joint with a spider and yoke, yoke shaft, and so on. Structural analysis of the initial axle shaft was conducted to select the exact area for structural strength fatigue improvement, and as a result, the inner/outer yoke shaft and spider were selected. Four cases considered design variables, such as length and thickness, to verify the enhanced durability of the axle shaft, and fatigue analysis was conducted. Finally, we suggest that the axle shaft system satisfied the working conditions for a 3.5-ton commercial vehicle.

• Asian Journal of Innovation and Policy
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• 제1권1호
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• pp.92-115
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• 2012

The problem Japanese universities face is exactly the same as that of German universities: no international recognition in world rankings of universities despite their high levels of postwar economic and technological developments. This was indeed one reason why world-class Japanese firms, such as Toyota and Sony, have avoided working closely with Japanese universities for R&D partnership and new technology commercialization. To resolve this problem, the Japanese government has continuously implemented aggressive policies of the internationalization, privatization, liberalization, and privatization of universities since the onset of the economic recession in 1989 in order to revitalize the Japanese economy through radical innovation projects between universities and firms. National projects of developing medical robots for Japan's ageing society are some of the ambitious examples that emphasize feed-forward learning in innovation. However, this paper argues that none of these programs of fostering university-firm alliances toward feed-forward learning has been successful in promoting the world ranking of Japanese universities, although they showed potentials of reinforcing their conventional strength of introducing $kaizen$ through feedback learning of tacit knowledge. It is therefore argued in this paper that Japanese universities and firms should focus on feedback learning as a way to motivate firm-university R&D alliances.

• Fibers and Polymers
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• 제7권3호
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• pp.286-294
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• 2006

This study has examined the flexural properties of natural and chemically modified coir fiber reinforced cementitious composites (CFRCC). Coir fibers of two different average lengths were used, and the longer coir fibers were also treated with a 1% NaOH solution for comparison. The fibers were combined with cementitious materials and chemical agents (dispersant, defoamer or wetting agent) to form CFRCC. The flexural properties of the composites, including elastic stress, flexural strength, toughness and toughness index, were measured. The effects of fiber treatments, addition of chemical agents and accelerated ageing of composites on the composites' flexural properties were examined. The results showed that the CFRCC samples were 5-12 % lighter than the conventional mortar, and that the addition of coir fibers improved the flexural strength of the CFRCC materials. Toughness and toughness index, which were associated with the work of fracture, were increased more than ten times. For the alkalized long coir fiber composites, a higher immediate and long-term toughness index was achieved. SEM microstructure images revealed improved physicochemical bonding in the treated CFRCC.

• Earthquakes and Structures
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• 제11권4호
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• pp.563-582
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• 2016

The failure mechanism and maximum collapse load of masonry structures may change significantly under static and dynamic excitations depending on their internal arrangement and material properties. Hence, it is important to understand correctly the nonlinear behavior of masonry structures in order to adequately assess their safety and propose efficient strengthening measures, especially for historical constructions. The discrete element method (DEM) can play an important role in these studies. This paper discusses possible collapse mechanisms and provides a set of parametric analyses by considering the influence of material properties and cross section morphologies on the out of plane strength of masonry walls. Detailed modeling of masonry structures may affect their mechanical strength and displacement capacity. In particular, the structural behavior of stacked and rubble masonry walls, portal frames, simple combinations of masonry piers and arches, and a real structure is discussed using DEM. It is further demonstrated that this structural analysis tool allows obtaining excellent results in the description of the nonlinear behavior of masonry structures.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2023년도 가을학술발표대회논문집
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• pp.83-84
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• 2023

In this study, in order to utilize waste fishing net as a building materail, the possibility of replacing the fiber used in polymer repair mortar with waste fishing net fiber was confirmed. As for basic characteristics, flow, compressive strength, and flexural strength tests were performed to compare and analyze fiber performance, and the test results showed performance equal to or better than existing fibers.