• Proceedings of the Korea Concrete Institute Conference
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• 1993.04a
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• pp.65-72
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• 1993

Steel fiber reinforced concrete(SFRC) which is made by short, randomly distributed steel fibers in concrete is superior in its tensile mechanical properties to plain concrete in enhancement of tensile strength and tensile ductility. These improvements are attributed to crack arresting mechanism and formation of longer crack paths due to fibers , which as a consequence lead to increase in energy absorption capacity of SFRC. In the post-peak region under tensile stresses, major macrocrack forms at critical section. The opening of this macrocrack is mainly resisted by both of the fiber pull-out bridging the cracked surfaces and the resistance by matrix softening. In this study, micromechaincal approach has been made in order to simulate tensile behavior of SFRC and based on which the theoretical model is presented. This model reflects the features of both the composite material concept and the spacing concept in predicting tensile strength of SFRC. The model also takes into account for the effects of matrix tensile softening and fiber bridging by pull-out on the resistance for the post-peak behavior of SFRC. It has been shown that the developed model satisfactory predicts the experimental results.

• International Journal of Naval Architecture and Ocean Engineering
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• v.8 no.2
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• pp.177-187
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• 2016

To evaluate the tractive performance of tracked trencher on seafloor surface, a new shear stress-displacement empirical model was proposed for saturated soft-plastic soil (SSP model). To validate the SSP model, a test platform, where track segment shear test can be performed in seafloor soil simulacrum (bentonite water mixture), was built. Series shear tests were carried out. Test results indicate that the SSP model can describe the mechanical behavior of track segment with good approximation in seafloor soil simulacrum. Through analyzing the main external forces applied to seafloor tracked trencher during the uniform linear trenching process, a drawbar pull prediction model was deduced with the SSP model. A tracked walking mechanism of the seafloor tracked trencher prototype was built, and verification tests were carried out. Test results indicate that this prediction model was feasible and effective; moreover, from another side, this conclusion also proved that the SSP model was effective.

• Knowledge Management Research
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• v.15 no.1
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• pp.45-63
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• 2014

Due to advance in Internet technology, most tourists tend to search travel information in the Online Travel Communities(OTC). Given this new paradigm in terms of finding travel information, most of relevant studies in this area are still dealt with explaining tourists' behaviors regardless of the types of communications. Therefore, to overcome some limitations in previous studies, we attempt to examine the relationships between both formal and informal communications and tourists' behavioral changes in the OTC context. Specifically, we developed a research model by employing the PPM(push-pull-mooring) framework and tested it to understand why and how tourists' behaviors might be changed. Survey data collected from 323 online tourists were used to test the model the model using SEM(structural equation modeling). The implications of our empirical findings for both research and practice are discussed.

• Journal of the Korean Geotechnical Society
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• v.34 no.10
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• pp.61-74
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• 2018

In this study, the pull-out behavior of tunnel type anchorage of suspension bridges was analyzed based on results from laboratory size model tests and numerical analysis. Tunnel type anchorage has found its applications occasionally in both domestic and oversea projects, therefore design method including failure mode and safety factor is yet to be clearly established. In an attempt to improve the design method, scaled model tests were conducted by employing simplified shapes and structure of the Ulsan grand bridge's anchorage which was the first case history of its like in Korea. In the model tests, the anchorage body and the surrounding rocks were made by using gypsum mixture. The pull-out behavior was investigated under plane strain conditions. The results of the model tests showed that the tunnel type anchorage underwent wedge shape failure. For the verification of the model tests, numerical analysis was carried out using ABAQUS, a finite element analysis program. The failure behavior predicted by numerical analysis was consistent with that by the model tests. The result of numerical analysis also showed that the effect of Poisson's ratio was negligible, and that a plugging type failure mode could occur only when the strength of the surrounding rocks was 10 times larger than that of anchorage body.

• Journal of Korea Technology Innovation Society
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• v.21 no.2
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• pp.491-521
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• 2018

This paper aims to uncover success factors in technology transfer of Korean government sponsored research institutes. It presents an analytical framework of technology transfer integrating factors concerning actors, object and process. Qualitative analysis mainly based on In-depth interviews is designed and conducted to examine characteristics, similarities and differences of three types technology transfer including a supply-push model, a demand-pull model, and an interactive model. Empirical results show that capabilities and experiences of researchers, capabilities and willingness of the company and active communications in the technology transfer appear to be important factors. In particular, it was found that technology transfer was led by TLO in the demand-pull model. In addition, the demand-pull and interactive approaches tends to be more effective in the technology development and transfer process compared to the supply-push model. In other words, market-oriented R&D is needed instead of technology-driven R&D. This paper also pointed out that one of the major factors in successful technology transfer is the enhancement of TLO capacity, and the improvement of recognition about TLO.

• Korea Trade Review
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• v.47 no.6
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• pp.71-96
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• 2022

This research will study the conversion intention of the users in China from fuel vehicle to new energy vehicles through the empirical methods. To this end, a questionnaire survey was conducted with car users as the object, combined with the theory of user migration and the PPM model to analyze the impact of fuel vehicle users' conversion intention to new-energy vehicles factor. The results showed that purchase experience contains the moderating effect, in which perceived risk and switching costs had a greater impact on the groups without purchase experience, whereas social identity, perceived value, personal attitude, and willingness to switch had a greater impact on groups with the purchase experience. Among all five factors, perceived risk had no discernible impact on the switching intention, but social identity, perceived value, attitude toward switching, and switching costs all had discernible impact on the switching intention. This study expects to come out with sustainable advises for the future growth of new energy vehicles from the study of car users' switching intention and the collective difference test of purchasing experience.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.1184-1186
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• 2002

Recently, according to the industrial development relative to multimedia, demand of display system is radically increase, thus development for power supply of back-lighting is advanced lively. Fluorescent lamp operated at high frequency by the electronic ballast provide benefits like unnoticeable flicker effect and higher luminous efficiency. This paper presents analysis of Push-Pull type resonant inverter for CCFL drive for stable characteristic and life improvement of fluorescent lamp operated at high frequency. Also it has proposed design procedure of Current-Fed type resonant inverter. On the basis of equivalent circuit, component characteristic and suitable region of operation frequency from simulation using Matlab and Pspice is predicted. Suitability of applied equivalent model and validity of design process from the experimental results with CCFL inverter.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.10a
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• pp.467-471
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• 2009

In this study a cantilevered carbon nanotube(CNT) switch was investigated with the linear and the nonlinear structural models incorporating the electrostatic force and van der Waals interactions between the CNT and ground surface. Due to the applied voltage and van der Waals interactions the CNT deforms statically and dynamically and finally pull into the surface. When the nonlinear model is considered in case of the relatively large gap between the CNT and the surface, the static pull-in voltage was increased due to the nonlinear hardening effect. Also the dynamic response was investigated with the different external dc and ac voltages. The CNT shows various dynamic behaviors and instabilities including dynamic pull-in. Based on this study, further research on the dynamic and nonlinear stability of CNT nanodevices should be requested to develop the new type of nano switches or nano-memory.

• Journal of electromagnetic engineering and science
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• v.7 no.4
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• pp.175-182
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• 2007

In this paper, a study on the reflector type frequency doubler, to suppress the undesired harmonics, is presented. A 12 to 24 GHz reflective frequency doubler is simulated and experimented. Design procedure of the frequency doubler with reflector is provided and the frequency doubler with good spectral purity is fabricated successfully. It has harmonic suppression of the $40{\sim}50\;dBc$ in the $1^{st}$ harmonic and the $50{\sim}60\;dB$ in the $3^{rd}$ harmonic with no additional filter. And, it has conversion gain with the input power of 0 dBm over bandwidth of 500 MHz. A NEC's ne71300(N) GaAs FET is used and the nonlinear model(EEFET3) using IC-CAP program is extracted for harmonic load pull simulation. Good agreement between simulated and measured results has been achieved.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09b
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• pp.88-95
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• 2010

Screw piles(Helical piles and anchors) are increasingly used to support and rehabilitate reinforced structures subjected to both tensile and compressive axial loads. This study presents a variety of detailed investigation on especially pull-out characteristics of screw piles performed to both reduced scale and numerical analysis to identify fundamental failure mechanisms and empirical optimized geometry of screw piles. It was found that the pull-out characteristics of screw piles are influenced with mainly different frequencies of compaction around soil and screw pile's pitch and followings are practical data based on empirical analysis.