• Structural Engineering and Mechanics
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• v.65 no.3
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• pp.223-231
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• 2018

A numerical investigation of the impact of steel ductility on the strength and ductility of two-way corner and edge-supported concrete slabs containing low ductility welded wire fabric is presented. A finite element model was developed for the investigation and the results of a series of concurrent laboratory experiments were used to validate the numerical solution. A parametric investigation was conducted using the numerical model to investigate the various factors that influence the structural behavior at the strength limit state. Different values of steel uniform elongation and ultimate to yield strength ratios were considered. The results are presented and evaluated, with emphasis on the strength, ductility, and failure mode of the slabs. It was found that the ductility of the flexural reinforcement has a significant impact on the ultimate load behavior of two-way corner-supported slabs, particularly when the reinforcement was in the form of cold drawn welded wire fabric. However, the impact of the low ductility WWF has showed to be less prominent in structural slabs with higher levels of structural indeterminacy. The load-deflection curves of corner-supported slabs containing low ductility WWF are brittle, and the slabs have little ability to undergo plastic deformation at peak load.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2008.05a
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• pp.7-10
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• 2008

As the land price in the downtown area increases, buildings are becoming bigger, deeper and higher. Consequently, the importance of underground construction has increased. Although construction engineers make every effort to complete underground construction without any problem, construction failures like landslides and the collapse of a retaining wall occur because of the uncertainty of the soil conditions as well as the unexpected risks of excavation work. In order to prevent potential excavation accidents, it is essential to understand the causes and impacts of such accidents. However, there are only a few examples of construction failures, which show the economic impact on accidents during excavation because of the sensibility of the information. This paper presents two cases of excavation accidents, which were investigated by construction insurance company. The compensation for the accidents paid by the insurance company was compared with the estimated costs calculated based on the estimation method for excavation accidents proposed by our previous study. The comparison results showed that the estimate calculated by our method was much less than the actual compensation because the estimate solely focused on the construction costs whereas the compensation included other external factors.

• Journal of Information Technology Services
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• v.15 no.1
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• pp.269-287
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• 2016

In general, service failure occurs inevitably and the customers who experienced the greater dissatisfaction have the higher expectations of service recovery. However, most of the previous studies have focused on the evaluation and risk factors of pre-service quality. Thus, this study is contrary to the numerous previous studies and focus on the effectiveness of mobile application advertisement users' perceived perception on service recovery after service fails. A research model presented in this study is based on the Equity Theory and deeply evaluated the effectiveness of Distributive Justice, Interactional Justice, and Authenticity Relevance on Service Recovery. The survey of this study was conducted among 286 users who have experienced a services recovery of mobile application advertising. As a result, among all the factors of users of mobile application advertising, Distributive Justice, Interactive Justice, and Relevance have a positive impact to Satisfaction. In addition, Distributive Justice, Authenticity and Satisfaction also have a positive impact to Trust. Ultimately, Satisfaction and Trust have a positive impact to Service Recovery. The results of this study are expected as a reference for presenting a new business model for mobile application advertising industry, reducing business risk and enriching the related researches.

• Journal of Environmental Impact Assessment
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• v.11 no.2
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• pp.93-107
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• 2002

The choice of big public investment project needs an appropriate feasibility analysis before it is implemented, bemuse a rot wisely chosen one would bring about big and longrun societal costs. But the feasibility analysis for the big public investment project in Korea has been done without linking the economic benefits and environmental damages. Consequently social conflicts arose frequently during and after project implementation, owing to such concerns asincreasing costs and serious ecological damages. The recent social conflict over the Saemangeum Project is a typical case. This reclamation project began in 1991 and finished 60% of the whole process in 1999, when its feasibility was again assessed under the public pressure by the joint assessment team consisting of both citizen's and government's professionals. Even the assessment report by this joint team could not show the convincing results owing to the improper assessment procedure and failure to set proper feasibility criteria. This paper pointed out the limitations of our current procedure of feasibility assessment and identified the concrete problems that atosee during the recent reassessment process of the Saemangeum reclamation project by the joint team. In order to improve the current problem-ridden practices, it is concluded by the policy recommendation for establishing a right feasibility assessment procedure for the public investment projects.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 1993.11a
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• pp.3-3
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• 1993

In mechanical testing of W-Ni-Pe heavy alloys, the cracks nucleate at W/W interface and propagate through W/ Imatrix interface or through matrix phase together with the cleavage of W grains. The mechanical properties can therefore be improved by control of the interfacial strength and area. In this presentation, some experimental result and techniques on this subject will be reviewed and discussed. The hydrogen embrittlement caused by the hydrogen segregation at interfaces during sintering in an hydrogen atmosphere can be removed by an heat-treattnent in vacuum or in an inert atmosphere. The heat-treatment condition can be estimated by using a diffusion equation for a cylindrical shape. The mechanical properties, in particular the impact property, are degraded by the segregation of non-metallic impurities, such as Sand P. The degradation can be prevented by adding a fourth element, such as La or Ca, active with the non-metallic impurities. The cyclic heat-treatment at usual heat-treattnent tempemture causes the penetration of matrix between W/W grain boundaries and results in remarkable increase in impact energy. This is due to an increase in the area of ductile failure during the impact test. The instability of W/matrix interface casued by addition of Mo or Re can be controlled by using W powders of different size. The increase in the interfacial area in found to be related to the presence of non-equilibrium pure W gmins among W(Mo or Re) solid solution gmins.

• Advanced Composite Materials
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• v.17 no.4
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• pp.373-407
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• 2008

This paper will examine the possibilities of the virtual tests of composite structures by simulating mechanical behaviors by using supercomputing technologies, which have now become easily available and powerful but relatively inexpensive. We will describe mainly the applications of large-scale finite element analysis using the direct numerical simulation (DNS), which describes composite material properties considering individual constituent properties. DNS approach is based on the full microscopic concepts, which can provide detailed information about the local interaction between the constituents and micro-failure mechanisms by separate modeling of each constituent. Various composite materials such as metal matrix composites (MMCs), active fiber composites (AFCs), boron/epoxy cross-ply laminates and 3-D orthogonal woven composites are selected as verification examples of DNS. The effective elastic moduli and impact structural characteristics of the composites are determined using the DNS models. These DNS models can also give the global and local information about deformations and influences of high local in-plane and interlaminar stresses induced by transverse impact loading at a microscopic level inside the materials. Furthermore, the multi-scale models based on DNS concepts considering microscopic and macroscopic structures simultaneously are also developed and a numerical low-velocity impact simulation is performed using these multi-scale DNS models. Through these various applications of DNS models, it can be shown that the DNS approach can provide insights of various structural behaviors of composite structures.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.3
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• pp.197-204
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• 2021

If a failure or an abnormal maneuver occurs during the flight test of a missile, the missile is deliberately self-destructed so as not to continue the flight. At this time, debris are produced and it is important to estimate the impact area in real-time whether it is out of the safety area. In this paper, we propose a method to estimate the debris dispersion area and falling time in real-time using a Fully-Connected Neural Network (FCNN). We applied the Unscented Transform (UT) to generate a large amount of training data. UT parameters were selected by comparing with Monte-Carlo (MC) simulation to secure reliability. Also, we analyzed the performance of the proposed method by comparing the estimation result of MC.

• Steel and Composite Structures
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• v.47 no.6
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• pp.781-794
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• 2023

In order to directly apply seawater and sea sand in construction without desalination, a type of square concrete-filled steel tube (CFST) encased with prefabricated seawater sea-sand concrete filled Polyvinyl Chloride (PVC)/Glass Fiber Reinforced Polymer (GFRP) tube column was proposed. Twenty short columns were tested under uniaxial loads, and the test parameters included inner tube types, seawater sea-sand concrete replacement ratios, concrete strength, the wrapping area of Carbon Fiber Reinforced Polymer (CFRP) strips and the thickness of GFRP tube. The effects of the parameters on failure modes, loading capacity, ductility and strain responses were discussed. All the tested specimens failed with serious buckling of the steel tubes and fracture of the inner tubes. The specimens had good residual bearing capacity corresponding to 64% to 88.9% of the peak capacity. The inner GFRP tubes and PVC tubes wrapped by CFRP strips provided stronger confinement to the core concrete, and were good choices for the proposed columns. Moreover, an analytical model for the composite column with different inner tube types was proposed.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.65-66
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• 2023

Recently, the importance of improving air quality has been greatly highlighted due to environmental problems such as indoor air pollution, and efforts are being made to improve indoor air quality not only in Korea but also around the world. In this situation, this study aims to study the physical properties of cement boards using pearlite with excellent physical adsorption performance due to micropores in materials, expanded graphite that is widely used as a flame retardant to prevent heat transfer in the event of a fire. The experimental items are bending fracture load and impact resistance. The bending destruction load at the fiber mixing rates 1, 2, 3, and 4 (%) did not meet the standard 140N, but the bending destruction load at 5% was 168.2N, and the impact resistance of the fiber mixing rates 1 and 2 (%) could not be measured due to cracks and damage, and the impact resistance at 3, 4, and 5 (%).

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.15 no.2
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• pp.33-45
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• 2020

While venture creation is considered to be of high social and economic importance, entrepreneurial outcomes are inherently uncertain and that failure is thus a central feature of entrepreneurship. Although failure in entrepreneurship is pervasive and critical, the impact of prior failure on future entrepreneurship has not received significant attention in the literature. Although failure is a painful and costly experience for entrepreneurs, it can also provide a powerful learning opportunity for those experiencing it. It has been argued that entrepreneurial failure is not just a individual problem but a matter of social concern. As part of the restarting business support system, entrepreneurial re-education program is provided to support failed entrepreneurs. The aim of this study is to examine the effects of failed entrepreneurs' prior entrepreneurial experience and re-education on subsequent venture creation. Moreover, this study also examined the moderating effects of entrepreneurial motivation. For the analyses, we surveyed the entrepreneurs who tried to re-start the subsequent business after the entrepreneurial failure through the "Revitalization Center for Strained Entrepreneur". The result found that failed entrepreneurs who learned a lot from their previous founding experience were more likely to re-start their subsequent business. The failed entrepreneurs who learned a lot from entrepreneurial re-education program were more likely to re-start their subsequent business. Moreover, the positive effect of failed entrepreneurs' previous founding experience and entrepreneurial re-education program on re-starting subsequent business was found to be weaker when entrepreneurial extrinsic motivation was high.