• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.6
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• pp.670-676
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• 2004

Most metallic materials and alloys show rate independence or negative rate sensitivity in some temperature region when dynamic strain aging occurs. It is generally recognized that negative rate sensitivity is an essential feature of dynamic strain aging that can depend on strain and/or strain rate. The unified viscoplasticity theory based on overstress is applied to reproduce a change of rate sensitivity type that depends on strain or strain rate. This is accomplished through the introduction of a single new term in the growth law of the equilibrium stress, which is a tensor valued state variable of the model. It is also shown that the new term can be used to reproduce a dramatic increase of rate sensitivity in dynamic plasticity.

• Proceedings of the KWS Conference
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• 1998.10a
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• pp.129-132
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• 1998

The dynamic resistance monitoring in primary circuit or T/C is one of the important issues in that in-process and real time quality assurance of resistance spot weld is needed to increase the product reliability. It is well known that tile dynamic resistance curve gives us very useful information about nugget growth and weldability. In the present paper, a new dynamic resistance detecting method is presented as a practical manner of weld quality assurance using instantaneous current and voltage measured by primary circuit. Primary dynamic resistance patterns are basically similar to those of the secondary, but there is evident advantage such as no extra devices are needed to obtain the quality assurance index and eventually feedback control will be possible caused by T/C based monitoring system.

• Structural Engineering and Mechanics
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• v.10 no.2
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• pp.139-156
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• 2000

This paper concerns the development of a computational model for the damage evolution of engineering materials under dynamic loading. Two models describing the anisotropic damage evolution of a material are presented; the first is based on a power function of the effective equivalent stress and the second on the damage strain energy release rate. The methods for computing the damage accumulated in structural components and their implementation in a finite element programme are presented together with some numerical results. The dynamic response of a damaged structural component and the dynamic behaviour of a damaged material have been studied numerically. This study shows that the frequency spectrum of a damaged structure is down-shifted, while the damping ratio of damaged materials becomes higher, the amplitude of the response significantly increases and the resonance ensuing from the damage growth still occurs in a damaged structure.

• Progress in Superconductivity
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• v.13 no.1
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• pp.58-63
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• 2011

Recently, superconductor flywheel energy storage systems (SFESs) have been developed for application to a regenerative power of train, a power quality improvement, the storage of distributed power sources such as solar and wind power, and a load leveling. As the high temperature superconductor (HTS) bearings offer dynamic stability without the use of active control, accurate analysis of the HTS bearing is very important for application to SFESs. Mechanical property of a HTS bearing is the main index for evaluating the capacity of an HTS bearing and is determined by the interaction between the HTS bulks and the permanent magnet (PM) rotor. HTS bearing rotor consists of PM and iron collector and the proper dimension design of them is very important to determine a supporting characteristics. In this study, we have optimized a rotor magnet array, which depends on the limited bulk size and performed various dimension layouts for thickness of the pole pitch and iron collector. HTS bearing rotor was installed into a single axis universal test machine for a stiffness test. A hydraulic pump was used to control the amplitude and frequency of the rotor vibration. As a result, the stiffness result showed a large difference more than 30 % according to the thickness of permanent magnet and iron collector. This is closely related to the bulk stiffness controlled by flux pining area, which is limited by the total bulk dimension. Finally, the optimized HTS bearing rotor was installed into a flywheel system for a dynamic stability test. We discussed the dynamic properties of the superconductor bearing rotor and these results can be used for the optimal design of HTS bearings of the 10kWh SFESs.

• East Asian Economic Review
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• v.19 no.2
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• pp.143-166
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• 2015

This paper investigates the empirical evidence on the relationship between financial accessibility and economic growth to test the conventional hypothesis that improved financial accessibility leads to financial development and economic growth. First, we built a dynamic panel model on the relationship between financial accessibility and economic growth with a set of controlled variables. We then used several financial access indicators from 165 countries, collected from 2004 to 2011, applying the generalized method of moments (GMM) estimators to estimate their relationship. From these estimations, we found that high financial accessibility leads to high income in general. In addition, we found that an increase in financial access indicators had a greater impact on economic growth in low-income countries than it did on economic growth in high-income countries.

• Knowledge Management Research
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• v.16 no.2
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• pp.113-137
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• 2015

Many scholars have addressed the technological convergence of small-medium sized firms in Korea and their impact on the economic growth of nation. Nevertheless, most studies have been investigated the relationship between entrepreneurship and venture creation, and a few studies have analyzed the innovation and technological convergence of SMEs. The purpose of this research is to gain industrial insight into the technological convergence and to suggest a dynamic growth policy for entrepreneurs of SMEs to improve their convergence performance based on IT and BT. Therefore, we intend to propose solutions to these key questions in convergence such as; what are the key patterns in the process of technological convergence of SMEs on IT and BT, and what kinds of strategy do their need? In order to answer these research questions, we adopt network analysis using patent citation information. Results of network analysis revealed that building ecosystem based on government and universities is one of the most important factors for the future growth of SMEs in Korea. Also, the fit between technological convergence direction of SMEs and division of convergence structure of government and universities will be positively associated with dynamic growth of SMEs in Korea. In conclusion, this research extends the current studies on important aspects of SMEs in the technological convergence process by proposing their growth in convergence process to a newly converging context, IT and BT, and shed light on the integrative perspectives of crucial roles of SMEs on innovation performance in the IT and BT technological convergence.

• Journal of Technology Innovation
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• v.8 no.1
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• pp.125-153
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• 2000

This study empirically examined the relationships between the growth stage of ventures and their business characteristics such as KSFs, environmental attributes, CEO roles, and utilization of external resources, based on data from 2,515 Korean ventures. ANOVA results of this study revealed that 1) Key success factors appeared different across the different growth stage of Korean ventures. Financial resources were most critical in the early stage of growth, while the foreign technology licensing appeared to be most important for the success of ventures at later growth stage; 2) As the Korean ventures grew, their environments became more dynamic and hostile; 3) Strategic and external activity roles of top management were critical in younger ventures, while roles for marketing and production were important in older ventures; and 4) Utilization of external resources were more frequent at the later stage of ventures than at the early stage of growth. Based on the research, this study offered several managerial, theoretical, and policy implications.

• Proceedings of the Korea Technology Innovation Society Conference
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• 2006.11b
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• pp.371-396
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• 2006

To see the implication of trade policy in endogeneous growth model, we introduce trade protection that takes the form of an import tariff and represents one plus the rate of protection provided to industry sector. We showed that considering goodness of fit of regression model, we can see that the empirical evidence is strongly in favor of the character of trade policies as the instrument spurring economic growth. As for import tariff, we see that 1% increase in the rate of tariff that protect domestic market causes the rate of growth to increase by 0.87%. An import tariff to final product significantly spurs product development and faster growth come as a result. But, we should note that the effects of trade policy are muted by the induced changes in the output of intermediates in an economy that is relatively unproductive in the research lab.

• Journal of Forest and Environmental Science
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• v.24 no.3
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• pp.143-149
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• 2008

We conduct economic analysis of the snow damage on sugi (Cryptomeria japonica) forest stands in Toyama Prefecture, Japan. We utilize a single tree and distant independent growth simulator called "Silv-Forest." With this growth simulator, we developed an optimization model by dynamic programming, called DP-Silv (Dynamic Programming Silv-Forest). The MS-PATH (multiple stage projection alternative technique) algorithm was embedded as a searching algorithm of dynamic programming. The height / DBH ratio was used to constrain the thinning regime for snow damage protection. The optimal rotation age turned out to be 65 years for the non-restricted case, while it was 50 years for the restricted case. The difference in NPV of these two cases as the induced costs ranged from 179,867 to 1,910,713yen/ha over the rotation age of 20 to 75 years. Under the optimal rotation of 65 years, the cost became 914,226 yen/ha. The estimated annual payment based on the difference in NPV, was from 9,869 yen/ha/yr to 85,900 yen/ha/yr. All in all, 10,000 yen/ha/yr to 20,000 yen/ha/yr seems to cover the payment from the rotation age of 35 to 75 years.

• The Journal of the Korea Contents Association
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• v.15 no.3
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• pp.396-405
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• 2015

Based on the number of employees and sales of tourism establishments in Chungnam ares for the period from 2009 to 2013, this study analyzes the regional growth characteristic of tourism industry using dynamic shift-share analysis. The data used for this analysis are obtained from "The Census on Basic Characteristic of Tourism Establishments". This study decomposes characteristics of Chungnam Area tourism industrial structure into three components: national growth effect, industrial mix effect and regional share effect. The results help to well understand the development and the competitive situation of Chungnam area tourism industry.