• International Journal of Aeronautical and Space Sciences
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• v.15 no.3
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• pp.320-334
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• 2014

Over the last two decades, numerous experimental and numerical efforts have examined physical phenomena in plasma discharge devices. The physical mechanisms that govern the anomalous electron diffusion from the cathode to the anode in the Hall Effect Thruster (HET) are not fully understood. This work used 1-D numerical method to improve our understanding and gain insight into the effect of the anomalous electron diffusion in the HET. To this end, numerical solutions are compared with various experimental HET performance measurements and the effects of anomalous electron diffusion are analyzed. The relationships between the anomalous electron diffusion and important parameters of the HET are also studied quantitatively. The work identifies the cathode mass flow rate fraction, radial magnetic field distribution, and discharge voltage as significant factors that affect anomalous electron diffusion. Additionally, the study demonstrates a computational process to determine the radial magnetic field distribution required to achieve specific thruster performance goals.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.2
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• pp.397-404
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• 1994

Smoke is emitted in diesel engines because fuel injected into the high-temperatured and high-pressured combustion chamber burns with its mixture with insufficient oxygeny. In consideration of air pollution, above all, it is necessary to illuminate the cause of smoke emission in diesel engines. The smoke emission, which is characteristic of diffusion combustion in diesel engines, results from pyrolysis of fuel not mixed with air. Therefore the smoke emission is dependent on diffusion combustion quantity, which is in turn controlled by engine parameter. The study aims at making clear and interpreting the interdependence of smoke emission in diesel engines with heat released within combustion chamber, camparing diffusion combustion quantity according to each engine parameter (air fuel ratio, injection timing, and engine speed), and showing the relation between smoke emission and fraction of diffusion combustion through experiment.

• Journal of Biomedical Engineering Research
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• v.17 no.2
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• pp.227-234
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• 1996

This paper is the study of the diffusion constant in order to calculate the percent oxygenation and percent blood volume using reflectance light within biological tissue. The diffusion constant play major role in percent oxygenation and percent blood volume and varies with the biological material such as hemolyzed blood, whole blood, dermis and epidermis in vivo tissue. The diffusion constant can be modeled to consist of a contribution from bloodless tissue and blood present in tissue. The reflectance light for experimental are red light of 660nm, infrared light of 880nm, green light of 569nm. The correlation between the diffusion constant and biological tissue was analyzed by the intensity of reflectance light at different depth within human limb. The reflectance light was changed in response to physiological changes within biological tissue. The data for diffusion constant were obtained at different depth beneath the surface of the skin and will be utilized to amen the percent oxygenation and percent blood volume.

• Corrosion Science and Technology
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• v.4 no.2
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• pp.69-74
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• 2005

The carbonation of concrete is one of the major factors that cause durability problems in concrete structures. The rate of carbonation depends largely upon the diffusivity of carbon dioxide in concrete. The purpose of this study is to identify the diffusion coefficients of carbon dioxide for various concrete mixtures. To this end, several series of tests have been planned and conducted. The test results indicate that the diffusion coefficient increases with the increase of water-cement ratio. The diffusion coefficient decreases with the increase of relative humidity at the same water-cement ratio. The diffusion of carbon dioxide reached the steady state within about five hours after exposure. The content of aggregates also influences the diffusivity of carbon dioxide in concrete. It was found that the diffusion coefficient of cement paste is larger then that of concrete or mortar. The quantitative values of diffusivity of carbon dioxide in this study will allow more realistic assessment of carbonation depth in concrete structures.

• Journal of the Korea Concrete Institute
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• v.12 no.1
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• pp.33-44
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• 2000

Since the mechanism of chloride diffusion and its ratio in concrete depend on structural conditions and concrete as a micro-structure, if these are analyzed quantitatively, the long-term ageing of structures can be predicted. Although, a quantitative analysis of concrete micro-structure, in which the results are affected by various parameters, is very difficult, this can be done indirectly by the durability test of concrete. In this study, the compressive strength, void ratio and air permeability of concrete. In this study, the compressive strength, void ratio and air permeability of concrete are chosen as the parameters in concrete durability test, and these effects on test results are analysed according to changes of mixing properties. The relationships between parameters and chloride diffusion velocity is used for prediction models of chloride diffusion. The developed prediction models for the chloride diffusion according to mixing and physical properties, can be used to estimate the service life and corrosion initiation of reinforcing bars in marine structures.

• Asia pacific journal of information systems
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• v.25 no.2
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• pp.239-264
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• 2015

This study aims to investigate the effect of message content and source user identity on information diffusion in Twitter networks. For the empirical study, we collected 11,346 tweets pertaining to the three major mobile telecom carriers in Korea for three months, from September to December 2011. These tweets generated 59,111 retweets (RTs) and were retweeted at least once. Our analysis indicates that information diffusion in Twitter in terms of RT volume is affected primarily by the type of message content, such as the inclusion of corporate social responsibility activities. However, the effect of message content on information diffusion is heterogeneous to the identity of the information source. We argue that user identity affects recipients' perception of the credibility of focal information. Our study offers insights into the information diffusion mechanism in online social networks and provides managerial implications on the strategic utilization of online social networks for marketing communications with customers.

• 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 the Korea Society of Computer and Information
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• v.15 no.9
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• pp.155-164
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• 2010

Until now, most of studies on Electronic Data Interchange(EDI) have been focused on the introduction of EDI and the performance of EDI. But recently, there have been increasing researches on diffusion of Electronic Data Interchange. The aims of this study are twofold. First, to find the impacts of various factors on EDI diffusion, second, to examine the relationship between EDI diffusion factors and EDI diffusion degree. To accomplish those aims of study, two kinds of methodologies are adopted in the studies, First, model building by wide investigation on previous papers, Second, empirical research for finding the determinants of diffusion of EDI. The results of testing the hypotheses of this research are summarized as follows. First, The important EDI diffusion variables influencing internal diffusion of EDI consist of top management support, scope for EDI, IS sophistication, compatibility, complexity, relative advantages, competition intensity and external pressure. Second, Top management support, scope for EDI, IS sophistication, compatibility, relative advantages, competition intensity and external pressure are associated with external diffusion of EDI. We are aware of the important fact that top management support, scope for EDI, IS sophistication, compatibility, relative advantage, competition intensity and external pressure were simultaneously associated with internal and external diffusion of EDI.

• East Asian mathematical journal
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• v.35 no.1
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• pp.99-108
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• 2019

In this paper, we introduce a numerical approach to solve heat-diffusion equation with discontinuous diffusion coefficients in the three dimensional rectangular domain. First, we study the support operator method and suggest a new method, the continuous velocity method. Further, we apply both methods to a diffusion process for neurotransmitter release in an individual synapse and compare their results.

• Economic and Environmental Geology
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• v.53 no.1
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• pp.99-110
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• 2020

It is a global trend to consider contaminated low-permeability zones as one of the primary management targets for the remediation of DNAPL contaminated sites. In addition, studies on the persistence caused by back diffusion of DNAPLs from low-permeability zones have been actively conducted worldwide. On the other hand, the studies for domestic groundwater contamination with the low-permeability zones are insufficient. Therefore, this study introduces the forward and back diffusions of DNAPL through low-permeability zones and suggests the importance of them by reviewing representative previous studies, especially on back diffusion and plume persistence. We proposed six diffusion scenarios and analytical solutions based on various boundary conditions of low-permeability zones. FI (forward diffusion into infinite domain) and BI (back diffusion form infinite domain) scenarios illustrate forward and back diffusion in which the depths of a low-permeability layer are assumed to be infinite. FFN (forward diffusion into finite domain with no flux boundary) and BFN (back diffusion from finite domain with no flux boundary) scenarios describe forward and back diffusion for a finite domain of a low-permeability layer with no flux boundary at the bottom. When the bottom of a low-permeability layer is considered as flux boundary, forward and back diffusion scenarios correspond to FFF (forward diffusion into finite domain with flux boundary) and BFF (back diffusion from finite domain with flux boundary). The scenarios and analytical solutions in this study may contribute to the determination of an efficient remediation method based on site characteristics such as a thickness of low-permeability zones or duration of contamination exposure.