• Journal of the Korean Institute of Gas
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• v.16 no.4
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• pp.23-31
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• 2012

The basic understanding of gas diffusion and technology to predict the diffusion phenomena are needed to prepare against a disaster of leakage of natural gas and to design better consistent and reliable gas supply system in enclosure. The experimental results of British Gas Technology Co. are used in present study as a reference of theoretical study using CFD. The present results of 2D CFD analysis for mass flow rate of nozzle release show good agreement with experimental results within 2.6 % error. 3D CFD analysis for the characteristics of natural gas diffusion in enclosure with various ventilation patterns also gives reasonable agreement with experimental results.

• Journal of Korean Society of Rural Planning
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• v.20 no.3
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• pp.67-74
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• 2014

The purpose of this study is to estimate regional economic effects of spatial diffusion of wildfire using Cobb-Douglas production function of agriculture and forestry. The analysis is applied to Gangwon and Gyeongbuk provinces where are the most damaged of wildfire in Korea. The damaged areas are derived from multiplied by the occurrence probability of wildfire and diffusion areas of wildfire for micro-spatial unit level with ArcGIS techniques. The models of wildfire provides that the spatial diffusion of wildfire increases with the rising of highest temperature and average wind speed. Through the production function, value added of Agriculture and Forest sectors get damaged where the Cos-converted slope aspect of mountains are toward the South. The production model provides reductions of regional value added by increasing damaged areas of wildfire. It reveals that the most damaged region is Andong city in Gyeongbuk province, where value added loss is 1.25 billion Won, which is about 0.72% of total value added in agriculture and forestry of the city. As a view of policy makers, it needs to be considered to establish prevention policies against wildfires because regional economic losses from wildfire are depending on geographical conditions and performances of the major industry related to wildfire's diffusion such as agriculture or tourism sector according to the result of analysis.

• Journal of Information Technology Services
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• v.13 no.3
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• pp.25-50
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• 2014

The purpose of this study is to examine factors affecting the diffusion and the intention to use, and how these factors differ among adopter categories. A survey was done to analyze the diffusion of smart-phone, the most popular and innovative product nowdays. We collected 197 survey questionnaires from smart-phone user and analyzed the data using SPSS 18.0 and Smart PLS 2.0. PLS (Partial Least Square) analysis was implemented before multiple group-innovator, early adopter, eraly majority- analysis which is categoriezed by Innovation Diffusion Model of Rogers (1995). The results show that firstly, in innovator group (n=63), the functional and the safety value have significantly positive effect on user satisfaction. In addition, we found that user satisfaction and the brand loyalty are significatly associated with the intention of use. Secondly, in early adopter group (n = 67), the design value has significantly positive effect on user satisfaction and it has significantly positive effect on brand loyalty. Finally, in early majority group (n = 67), the design value has significantly positive effect on the user satisfaction and it has stronger effect on the intention of use and brand loyalty. We conclude this paper with the implication of this study to both academia, business practice, and policy making.

• Journal of the Korean Society of Radiology
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• v.5 no.3
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• pp.149-154
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• 2011

The purpose of this study was to examine the usefulness of diffusion weighted images in breast MRI by performing a quantitative comparative analysis in patients diagnosed with DCIS. On a 3.0T MR scanner, diffusion weighted images and ADC map images were obtained from 20 patients histologically diagnosed with ductal carcinoma in situ (DCIS). The findings from the quantitative image analysis are the following: The diffusion weighted images showed higher SNR and CNR at the lesion area. In addition, the ADC values were lower at the lesion area.

• 한국정보컨버전스학회:학술대회논문집
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• 2008.06a
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• pp.113-116
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• 2008

In this paper we suggest two novel methods for an implementation of the spot detection phase in the 2-DE gel image analysis program. The one is the adaptive thresholding method for eliminating noises and the other is the asymmetric diffusion model for spot matching. Remained noises after the preprocessing phase cause the over-segmentation problem by the next segmentation phase. To identify and exclude the over-segmented background regions, il we use a fixed thresholding method that is choosing an intensity value for the threshold, the spots that are invisible by one's human eyes but mean very small amount proteins which have important role in the biological samples could be eliminated. Accordingly we suggest the adaptive thresholding method which comes from an idea that is got on statistical analysis for the prominences of the peaks. There are the Gaussian model and the diffusion model for the spot shape model. The diffusion model is the closer to the real spot shapes than the Gaussian model, but spots have very various and irregular shapes and especially asymmetric formation in x-coordinate and y-coordinate. The reason for irregularity of spot shape is that spots could not be diffused perfectly across gel medium because of the characteristics of 2-DE process. Accordingly we suggest the asymmetric diffusion model for modeling spot shapes. In this paper we present a brief explanation ol the two methods and experimental results.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.2
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• pp.177-184
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• 2017

Understanding trends and drivers of technology diffusion is imperative to forecast new technology adoption and understand the process of technological innovation. Our research utilizes a quantitative trend analysis considering both technological and economic indicators for trends and drivers of technology diffusion for 32nm, 22nm, and 14nm logic semiconductor technology. In terms of technological performance, the technology diffusion curve showed an S-curve pattern during the stages of maturity and decline, and the diffusion curve showed evidence supporting the learning curve. The diffusion curve showed the life cycle duration of 2 years, and the rate of technological performance and obsolescence are observed quantitatively between generations. Architectural innovation is affected by technological drivers more significantly than economic drivers. This research has implications as empirical research on the trends and drivers of technology diffusion in the high-tech semiconductor industry, and is meaningful in forecasting new technology adoption or build technology strategy.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.14 no.1
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• pp.15-23
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• 2018

A compact heat exchanger is one of critical components in a very high temperature gas-cooled reactor (VHTR). Alloy 617 (Ni-Cr-Co-Mo) is considered as one of leading candidates for this application due to its excellent thermal stability and strengths in anticipated operating conditions. On the basis of current ASME code requirements, sixty sheets of this alloy are prepared for diffusion welding, which is the key technology to have a reliable compact heat exchanger. Optical microscopic analysis show that there are no cracks, incomplete bond, and porosity at/near the interface of diffusion weldment, but Cr-rich carbides and Al-rich oxides are identified through high resolution electron microscopic analysis. In high-temperature tensile testing, superior yield strengths of the diffusion weldment compared to the code requirement are obtained up to 1223 K ($950^{\circ}C$). However, both tensile strength and ductility drop rapidly at higher temperature due to the insufficient grain boundary migration across the interface of diffusion weldment. Best fit curves for minimum yield strength and average tensile strength are drawn from the experimental tensile results of this study.

• Corrosion Science and Technology
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• v.16 no.4
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• pp.201-208
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• 2017

A finite element analysis is proposed to study the effect of specimen dimensions on lateral diffusion of hydrogen during hydrogen permeation flux measurements. The error of measurement on thick specimens because of 1D diffusion approximation may be as much as 70%. A critical condition for accurate measurements is to designate the area of hydrogen monitoring/exit surface smaller than the area of hydrogen charging/entry surface. For thin to medium thickness specimens (ratio of thickness to specimen radius of 5:10 and below), the charging surface should be maximized and the monitoring surface should be minimized. In case of relatively thick specimens (ratio of thickness to specimen radius above of 5:10), use of a hydrogen-diffusion barrier on the specimen boundaries is recommended. It would completely eliminate lateral losses of hydrogen, but cannot eliminate the deviation towards 2D diffusion near the side edges. In such a case, the charging surface should be maximized and the monitoring surface should be as closer in dimension as the charging surface. A regression analysis was carried out and an analytical relationship between the maximum measurement error and the specimen dimensions is proposed.

• 한국방재학회:학술대회논문집
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• 2007.02a
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• pp.177-180
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• 2007

Numerical simulations on the suspended load in the Do jang fish port are carried out. Suspended load is analysed by using the two-dimensional advection-diffusion equation. To describe behaviors of a pollutant in costal zone, a split-operator method is applied to the numerical model. The advection part is first solved by SOWMAC and then the diffusion part is solved by a three-level locally implicit scheme.

• Journal of the Korean Mathematical Society
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• v.57 no.1
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• pp.249-281
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• 2020

A reaction-diffusion model with spatiotemporal delay modeling the dynamical behavior of a single species is investigated. The parameter regions for the local stability, global stability and instability of the unique positive constant steady state solution are derived. The conditions of the occurrence of Turing (diffusion-driven) instability are obtained. The existence of time-periodic solutions, the existence and nonexistence of nonconstant positive steady state solutions are proved by bifurcation method and energy method. Numerical simulations are presented to verify and illustrate the theoretical results.