• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.1
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• pp.56-62
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• 1992

The GaAs bulk crystals are grown by the Synthesis Solute Diffusion(SSD) method and its properties are investigated. The crystal growth rate at optimum condition is 0.28 cm/day and their temperature dependence is R(T) = 2.92 x 10S04T exp(-1.548eV/kS1BTT) [cmS02T/day.K]. Etch pits density distribution along radial direction is order of 10S04TcmS0-2T and 10S03TcmS0-2T at the edge and middle of the wafers, respectively, and it increased exponentially along vertical direction of ingot. Moreover,it is uniformly distributed as order of 10S03TcmS0-2T in radial direction of In doped GaAs. The carrier concentration and mobilities are measured to 0.34-2.1 x 10S016T cmS0-3T and 2.3-3.3x10S03T cmS02T/V.sec, respectively.

• Proceedings of the KSMRM Conference
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• 2003.10a
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• pp.20-20
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• 2003

Purpose： To investigate the difference of fractional anisotropy (FA) values between 6- and 25-direction diffusion tensor images (DTI) in normal adult brain. Materials and Methods： DTI was peformed in 28 normal subjects (15 subjects with 6-direction, 13 subjects with 25-direction) in a 1.5 T MR system. DTI was done with SE-EPI sequence with TR/TE/NEX 10000/84/1, 5mm slice thickness and b=1000 s/mm2. FA values were measured from 8 different anatomical locations which included both cerebral peduncles, both posterior limbs of the internal capsules, both corona radiata, genu and splenium of the corpus callosum. Statistical difference of FA was tested between 6-and 25-direction DTI.

• ETRI Journal
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• v.26 no.4
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• pp.371-374
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• 2004

We propose and demonstrate a fabrication method of chirped fiber gratings by a thermal diffusion process. The method could suggest a direction for a simple and cost-effective implementation of chirped fiber grating-based devices.

• Communications of the Korean Mathematical Society
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• v.26 no.2
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• pp.321-338
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• 2011

In this paper, a class of delayed epidemic model with diffusion is investigated. By analyzing the associated characteristic transcendental equation, its linear stability is investigated and Hopf bifurcation is demonstrated. Some explicit formulae determining the stability and the direction of the Hopf bifurcation periodic solutions bifurcating from Hopf bifurcations are obtained by using the normal form theory and center manifold theory. Some numerical simulation are also carried out to support our analytical findings. Finally, biological explanations and main conclusions are given.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.23 no.2
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• pp.139-155
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• 2019

In this paper, we study the asymptotic behavior and Hopf bifurcation of the modified Holling-Tanner models for the predator-prey interactions in the absence of diffusion. Further the direction of Hopf bifurcation and stability of bifurcating periodic solutions are investigated. Diffusion driven instability of the positive equilibrium solutions and Turing instability region regarding the parameters are established. Finally we illustrate the theoretical results with some numerical examples.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.2
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• pp.146-153
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• 2004

A Promising new approach to achieve low pollutant emissions and improvement of flame stability is tested experimentally using a cyclone jet hybrid combustor employing both premixed and diffusion combustion mode. Three kinds of nozzle are tested for mixing enhancement of fuel and air. The LNG (Liquified Natural Gas) is used as a fuel. The combustor is operated by two methods. One is DC (Diffusion Combustion) mode generated swirl flow by air as general swirl combustor, and the other is HC (Hybrid Combustion) mode. The HC mode consists of diffusion jet flame of axial direction and premixed cyclone flame of tangential direction in order to stabilized the diffusion jet flame. The results showed that the flame stability of HC mode is significantly enhanced than that of DC mode through the change of mixing characteristics by modifications of fuel nozzle. In addition, the reductions of CO and NOx emission in HC mode, as compared with that for the DC mode, is large than about 50% in stable region. Also, even using the low calorific fuel as $CO_2$-blended gas, it is identified that the cyclone jet hybrid combustor has the high performance of flame stability.

• Korean Management Science Review
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• v.13 no.1
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• pp.71-95
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• 1996

Many researchers have studied the theme on CASE technology. However, there are no many researches which lightened the diffusion of CASE technology and organizational change. The purpose of this study is to investigate the factors that influence on the diffusion of CASE technology and the way how IS organization changes as a result of the diffusion. We exploited a case study research as a methodology. We selected five software development firms which possessed the leading IS technology abilities as the case companies. We realized that the diffusion of CASE technology proceeded under the three context variables - managerial context of information systems, the intent and behavior of key players and implementation strategy of organization - to enhance the performance of information systems. The contribution of this study is to clarify the change of IS organization as a result of CASE technology diffusion. This study has the limitation that tried to analyze the organizational change only in a direction.

• Investigative Magnetic Resonance Imaging
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• v.11 no.2
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• pp.110-118
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• 2007

Purpose: The objective of this work to construct eigenvalue maps that have information of magnitude of three primary diffusion directions using diffusion tensor images. Materials and Methods: To construct eigenvalue maps, we used a 3.0T MRI scanner. We also compared the Moore-Penrose pseudo-inverse matrix method and the SVD (single value decomposition) method to calculate magnitude of three primary diffusion directions. Eigenvalue maps were constructed by calculating of magnitude of three primary diffusion directions. We did investigate the relationship between eigenvalue maps and fractional anisotropy map. Results: Using Diffusion Tensor Images by diffusion tensor imaging sequence, we did construct eigenvalue maps of three primary diffusion directions. Comparison between eigenvalue maps and Fractional Anisotropy map shows what is difference of Fractional Anisotropy value in brain anatomy. Furthermore, through the simulation of variable eigenvalues, we confirmed changes of Fractional Anisotropy values by variable eigenvalues. And Fractional anisotropy was not determined by magnitude of each primary diffusion direction, but it was determined by combination of each primary diffusion direction. Conclusion: By construction of eigenvalue maps, we can confirm what is the reason of fractional anisotropy variation by measurement the magnitude of three primary diffusion directions on lesion of brain white matter, using eigenvalue maps and fractional anisotropy map.

• IE interfaces
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• v.25 no.2
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• pp.255-263
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• 2012

In order to ensure the reliability and specialty of weapon system test results, a policy of extending certified testing service institutions has been driven by applying accreditation system of the ones in defense industry. Bass and Logistic models are used to apply the policy effectively and forecast the diffusion pattern of certified testing service institutions. The parameters for diffusion forecast are estimated using the diffusion pattern of certified testing service institutions in non-defense industry, and these are applied to forecast the diffusion of certified ones in defense industry. Coefficients of innovation and imitation of Bass model are analyzed to derive the factors influencing the early adoption and diffusion patterns. The more increasing the coefficients, the earlier adoption occurred. Diffusion pattern due to coefficient of imitation, internal factor, has larger effect on sensitivity of diffusion pattern. This means that the self recognition of necessity is more effectively worked than the policy or regulations driven by government.

• Journal of Environmental Science International
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• v.33 no.8
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• pp.583-589
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• 2024

Seawater movement analyses and dye diffusion experiments were conducted to understand the characteristics of eddy diffusion in the southwest coastal zone of Korea. The findings indicate that pollutants entering the study area were most influenced by tidal currents and showed temporal and spatial variations according to the turbulent characteristics of the tidal current. Pollutants entering the study area are likely to travel a distance of approximately 2 km (within 1 h) following the direction of the tidal currents and show a spreading distance (diameter of the diffusion area) of within 10% of the travel distance (within 200 m). The dispersion of the diffusion area is expected to increase in proportion to the elapsed time raised to a power of 1.19 to 1.23. The results are expected to provide a basis for using the eddy diffusion coefficient as a temporally variable value (previously assumed to be a constant based on empirical data), thereby contributing to improving the predictive accuracy of ocean diffusion models.