• Journal of the Korean Institute of Gas
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• v.12 no.4
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• pp.41-45
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• 2008

This paper presents the numerical study on the strength safety and displacement behaviors of a helmet, which is to protect impact forces and to absorb the impact energy. Four different helmet models including a bead frame and a corrugation damper have been analyzed for the stress and the displacement characteristics by using the finite element method. The computed FEM results show that the bead frame on the summit area of the helmet is very useful to increase the strength safety of the helmet, and the corrugation damper on the lower part of the helmet may increase the energy absorption capacity. Thus, this paper recommends the bead frame and the corrugation damper as new design elements of the helmets.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.10
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• pp.1686-1694
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• 2003

The foam-filled tube beams can be used for the front rail and firewall structures to absorb impact energy during frontal or side collision of vehicles. In the case of side collision where bending is involved in the crushing mechanism, the foam filler would be effective in maintaining progressive crushing of the thin-walled structures so that much impact energy could be absorbed. In this study, bending behaviors of the closed-cell-aluminum-alloy-foam-filled stainless steel tube were investigated. The various foam-filled specimens including piecewise fillers were prepared and tested. The aluminum-alloy-foam filling offered the significant increase of bending resistance. Their suppression of the inward fold formation at the compression flange as well as the multiple propagating folds led to the increase of load carrying capacity of specimens. Moreover, the piecewise foams would provide the easier way to fill the thin-walled shell structures without the drawback of strength.

• Journal of the Korean Society of Safety
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• v.31 no.6
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• pp.6-11
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• 2016

CFRP composite laminates are widely used as structural materials for airplanes, automobile and aerospace vehicles because of their high strength and stiffness. This study aims to examine an effect of curvature on the penetration fracture characteristic of an orthotropic composite laminated shell. For the purpose, we manufactured orthotropic CFRP shell specimen with different curvatures, and conducted a penetration test using an air-gun. Those specimens were prepared to varied curvature radius(${\infty}$, 200mm, 150mm and 100mm)and were stacked to $[O^{\circ}{_3}/90^{\circ}{_3}]_s$. When the specimen is subjected to transverse impact by a steel sphere(${\Phi}10$), the velocity of steel sphere was measured both before and after impact by determining the time for it to pass two ball-screen sensors located a known distance apart. As the curvature increases, the absorption energy and the critical penetration energy increased linearly because the resistance to the bending moment. Patterns of cracks caused by the penetration of CFRP laminated shells included fiber breakage, lamina fracture, matrix crack interlaminar crack and intralaminar crack.

• Fire Science and Engineering
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• v.22 no.5
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• pp.22-28
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• 2008

In this paper, we conducted experiments on damaged patterns of incandescent lamps by external stress, such as external flame or external impact. Glass bulbs were melted and filaments were evaporated by external flame when the bulbs were lit, and finally molten marks were recognized at the filaments. Also, there were some differences in absorption patterns of evaporated filament elements according to set-up directions, and evaporated filament elements were absorbed in lead-in wires, support, inside of glass. In case the bulbs were lit and they were damaged by external impacts, filament burned out. Filaments were not evaporated but melted. We expect that this results could be used to judge whether electric current flew through incandescent lamps or not in fire site.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.2
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• pp.108-113
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• 2005

The damageability and repairability of similar platform type vehicles could be very concerned with design optimization. In all the vehicles crash tested, small size passenger vehicles were weakness in aspect of damageability and repairability. The most critical area appears to be repair cost considering that parts cost is the largest portion of total repair cost segments. Besides repair cost, attaching method of front sidemember and subframe are placed special importance for impact energy absorption and damageability and repairability. So in order to improve damageability and repairability of vehicle structure and body component of the monocoque type passenger vehicles, the end of front side member and front back beam should be designed with optimum level and to supply the end of front side member as a partial condition approx 300mm. The effectiveness of design concept on the 40% offset frontal impact characteristics of the passenger vehicle structure is investigated and summarized.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.8
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• pp.661-668
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• 2016

Oil deflector prevents oil leakage that occurs in thermoelectric power plant at operating lubricant facilities. Vibration of rotating rotor-induced wear of aluminum tooth in existing oil deflector leads to oil leakage as well as life shortening of the tooth. In this study, an advanced oil deflector was developed for shock absorption and prevention of wear by decreasing clearance (from 0.5 mm to 0.2 mm) between rotor and tooth to minimize oil leakage, and by replacing 2 aluminum teeth in outmost of the oil deflector with hi-performance seal made of engineering plastic. The CFD results were compared between advanced vs. existing oil deflector to determine the amount of oil loss. Structural safety was verified through impact analyses according to the three kinds of engineering plastics, considering cost efficiency, and optimal material of hi-performance seal was chosen.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.3
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• pp.1153-1162
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• 2021

The innovation of enterprises allowed firms to promote technological innovation as an important choice to improve sustainable competitiveness. This study aims to investigate the relationship between absorptive capacity and innovation performance of Chinese high-tech enterprises and focuses on the mediating role of innovation culture in high-tech enterprises. Data came from surveying high-tech enterprises in China, and the reliability analysis, factor analysis, and correlation analysis, path analysis (SEM) were analyzed using SPSS23, AMOS. The results show that intellectual capital composed of human capital, structural capital, and relational has a significant impact on acquisition performance; intellectual capital is composed of human capital; structural capital has a significant influence on innovation performance; and absorptive capital has a significant impact on innovation performance. In addition, innovative culture plays a partial mediating role between absorptive capacity and innovation performance. The findings of this study suggest that, to ensure the better absorption and operation of knowledge, high-tech enterprises can accumulate more knowledge, promote the transformation of knowledge into technology, and strengthen the capability of knowledge absorptive capacity, and at the same time, create an innovation culture atmosphere and encourage employees to develop new products to achieve enterprise goals in order to promote the improvement of innovation performance.

• The Journal of Asian Finance, Economics and Business
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• v.9 no.6
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• pp.139-149
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• 2022

The article investigates the impact mechanism of absorption capacity (potential absorptive capacity - PAC and realized absorptive capacity - RAC) on the innovation efficiency of enterprises through the intermediate variable of dual innovation (exploratory innovation- INOR and exploitative innovation- INOI), based on the actual situation of Vietnam's small and medium enterprises (SMEs). A survey of Vietnam's SMEs was conducted from August 2020 to April 2021. The data was collected through interviews and questionnaires, and 146 valid questionnaires were received. The following results were acquired using SPSS 20.0 software to do correlation and regression analysis of data results.: The results show that the absorptive capacity of enterprises has a positive impact on innovation performance and dual innovation acts as a mediator in how absorptive capacity affects innovation performance. This study deepens the understanding of how absorptive capacity affects innovation performance and provides important new evidence for developing absorptive capacity and dual innovation in both theories and practice in Vietnam's SMEs. The study also proposes several solutions and recommendations to help Vietnam's small and medium enterprises improve their innovation capacity, competitiveness, and performance.

• Structural Engineering and Mechanics
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• v.92 no.2
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• pp.173-187
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• 2024

In this study, the cyclic behavior of Bar Damper (BD) and its effect on the seismic performance of the steel frame was investigated using numerical and analytical methods. Initially, the calibrated model was used to conduct parametric studies on the cyclic behavior of the damper. The purpose of parametric studies was to provide equations for calculating effective and elastic stiffness, ultimate strength, and energy dissipation using its diameter and height. The impact of BD on the steel frame was examined in the second section of the research. In this section, studies were conducted using pushover analysis to investigate the impact of BD on the elastic stiffness, energy absorption, ductility, and strength of the frame. The results demonstrated that increasing the height of the BDs resulted in higher energy dissipation. However, reducing the height and increasing the diameter increased effective stiffness, yield strength, and elastic stiffness. The EVDR results showed that the diameter of the damper has a negligible effect on it, and its value increases with the decrease in height. In the best case, the addition of BD causes a 23% increase in energy dissipation and a 60% increase in frame ductility.

• Journal of the Korean Institute of Gas
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• v.13 no.4
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• pp.27-32
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• 2009

This paper presents the stress and deformation behaviors using the finite element method as a function of the thickness of the helmets without the bead frames on the top of the shell structure. The helmet that would provide head and neck protections without causing discomfort to the user when it was worn for long periods of time should be manufactured for increasing the safety and impact energy absorption. The FEM computed results show that when the impulsive force is applied on the top surface of a helmet, the maximum stress and strain have been occurred around the position of an applied impact force, which may lead to the initial failure on the top surface of the helmet shell. As the helmet thickness is decreased from 4mm to 2mm, the impact energy absorbing rate is radically increased, and the maximum stress of the helmet is increased over the tensile strength, 54.3MPa of the thermoplastic material. Thus, the top surface of the helmet should be supported by a bead frame and increased thickness of the shell structure.