• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2009.01a
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• pp.492-497
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• 2009

Computer-Generated Hologram (CGH) is made for three dimensional image of a virtual object. Error diffusion method is used for the phase quantization of CGH, and it is known to be effective to the image quality improvement of the reconstructed image. However, the image quality of the reconstructed image from the CGH using error diffusion method depends on the selection of error diffusion coefficient. In this paper, we derived the relational expression to obtain the error diffusion coefficient from the position of the input object and size of the input object for CGH. As a result, the method of this thesis was able to obtain an excellent reconstructed image compared with the case to derive the error diffusion coefficient from only the position of the input image.

• Korean Journal of Materials Research
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• v.15 no.12
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• pp.780-785
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• 2005

To investigate the microcrack healing behavior of $Si_3N_4-20wt\%SiC-8wt\%Y_2O_3$ composite ceramics(SNCY8), we observe the crack length evolution a! the time of 20, 40, 60 minutes with in-situ optical microscopy by varying healing temperature of $800\~1200^{\circ}C$. Crack healing obviously occurred as heating temperature and time increased. We proposed a simple model of effective diffusion based on the crack length evolution with healing condition, and determined the effective diffusion coefficient as Our result implies that we may predict the healing ability quantitatively with temperature and time in structural ceramics through the effective diffusion coefficient model.

• Computers and Concrete
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• v.3 no.6
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• pp.401-422
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• 2006

A multi-species model based on the Nernst-Planck equation has been developed by using a finite volume method. The model makes it possible to simulate transport due to an electrical field or by diffusion and to predict chloride penetration through water saturated concrete. The model is used in this paper to assess and analyse chloride diffusion coefficients and chloride binding isotherms. The experimental assessment of the effective chloride diffusion coefficient consists in measuring the chloride penetration depth by using a colorimetric method. The effective diffusion coefficient determined numerically allows to correctly reproduce the chloride penetration depth measured experimentally. Then, a new approach for the determination of chloride binding, based on non-steady state diffusion tests, is proposed. The binding isotherm is identified by a numerical inverse method from a single experimental total chloride concentration profile obtained at a given exposure time and from Freundlich's formula. In order to determine the initial pore solution composition (required as initial conditions for the model), the method of Taylor that describes the release of alkalis from cement and alkali sorption by the hydration products is used here. Finally, with these input data, prediction of total and water-soluble chloride concentration profiles has been performed. The method is validated by comparing the results of numerical simulations to experimental results obtained on various types of concretes and under different exposure conditions.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.555-558
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• 2001

Carbonation of concrete decreases durability of RC structures due to failure of passive film of rebar. Therefore, expecting carbonation depth is a governing parameter of service life prediction for RC structures. This study attempt to estimate carbonation depth quantitatively by using equivalent effective diffusion coefficient of $CO_2$.

• International Journal of Concrete Structures and Materials
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• v.4 no.2
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• pp.105-108
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• 2010

In order to determine the effect of the use of limestone sand on chloride ion ingress in mortar, specimens were cast with two different sands: siliceous sand (used as reference) and limestone crushed sand (used for this study). To compare and assess the resistance of this mortar to chloride penetration, two different diffusions tests were employed: slow migration and rapid migration (AASHTO test). In this study, calculation of the effective diffusion coefficient is proposed using a model based on Nernst. Planck equation. The diffusion coefficients from each sample were compared. The results for all tests show that the diffusion coefficients for siliceous sand mortar are larger than those obtained with limestone sand. It appears also that the diffusion coefficient varies as a function of the W/C ratio.

• Bulletin of the Korean Chemical Society
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• v.32 no.6
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• pp.1970-1974
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• 2011

The effects of convection on the measurement of the diffusion coefficients of liquids by the pulsed gradient spin echo (PGSE) NMR method at low temperature are discussed. To examine the generation of convective flows, we used four different types of sample tubes in the diffusion measurements with temperature variation; a normal 5 mm NMR tube, a Shigemi tube, an ELISE type tube, and a capillary tube. Below room temperature, the calculated diffusion coefficients of chloroform in 5 mm o.d. type tubes increased with decreasing temperature, while those in the capillary tube decreased linearly. The convective flow was found to be significant even at low temperature and it seemed to be mainly induced by the transverse temperature gradient. It was also found that the capillary tube was most appropriate to measure the diffusion coefficients, since its small diameter is effective in suppressing the convective flows at both high and low temperatures.

• ETRI Journal
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• v.34 no.2
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• pp.245-255
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• 2012

Among emerging devices propelling the growth of mobile devices, smartphones and tablet-PCs are among the most recognizable. In this study, a research model is designed for exploring acceptance-diffusion strategies for tablet-PCs from the viewpoint of consumer perception, which is verified through a survey. The results of this study show that tablet-PCs have great potential to be versatile, multifunctional devices, even though they are currently considered mostly as entertainment-oriented rather than fulfilling the essential needs of everyday life. An analysis of the acceptance model for tablet-PCs revealed that playability, cost level, functionality, and complexity significantly affect user acceptance. An analysis of the diffusion model, on the other hand, showed that playability and user interface have a significant influence on satisfaction, trust, and positive behavioral intention. We also found that cost level is not a major hindrance in the market diffusion of tablet-PCs. The results of this study can be used to establish effective acceptance and diffusion strategies for tablet-PCs and other emerging devices.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.9 no.1
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• pp.33-40
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• 2011

In the compacted bentonite containing $Ag_2O$, the transport of iodide ion was investigated by Through-diffusion method. It is confirmed that Iodide ion is transported by diffusion process in the compacted bentonite containing $Ag_2O$ as well as in the compacted bentonite without $Ag_2O$. However, the lag-time of iodide ion in the compacted bentonite containing $Ag_2O$ is larger than that in the compacted bentonite without $Ag_2O$. The increase of the lag-time was observed in pure iodide ion solution and also in 0.1M NaCl-iodide ion solution. The apparent diffusion coefficient of iodide ion in the compacted bentonite containing $Ag_2O$ has lower value than that in the compacted bentonite without $Ag_2O$. The effect of $Ag_2O$ on the effective diffusion coefficient was not clearly investigated in the compacted bentonite containing $Ag_2O$ while the values of effective diffusion coefficient of iodide ion in the compacted bentonite without $Ag_2O$ obtained in this study were similar to those in the compacted bentonite reported in the literature.

• Knowledge Management Research
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• v.9 no.3
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• pp.77-105
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• 2008

This study primarily aims at identifying what factors significantly affect the diffusion of knowledge management systems(KMS) and finding out how these identified factors can be effectively managed, especially for Korean companies. The research model is derived based on previous researches on innovation diffusion, information systems implementation, and KMS. The model is used to examine the role of determinants in influencing the extent to which KMS is diffused within organizations. Independent variables of this research are composed of technical characteristics, organizational characteristics and environmental characteristics. 'Breadth of diffusion' and 'depth of diffusion' concept are used to measure the extent of KMS diffusion which is the dependent variable of this model. The 101 companies of total 1,000 samples responded to the survey. To analyze tile results of this empirical study, we performed the multiple regression analysis. As a result, it was shown that the relative advantage, complexity, information system maturity, size, top management support, champion, competitive pressure have influences on both the breadth and the depth diffusions. On the other hand, the organizational culture, valuation and compensation, and uncertainty of environmental factors were not verified to be significant. This empirical study will provide Korean companies with insights into effective ways to diffuse the KMS and succeed in business competition.

• 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.