• Journal of Powder Materials
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• v.10 no.6
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• pp.374-382
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• 2003

During the sintering of powder materials, many these are microstructural phenomena are caused by atomic diffusion. (1) neck formation and compact densification, (2) grain growth, i.e., growth of matrix grains and dispersed grains, (3) alloying or generation of compound, (4) generations of peculiar and hard layers near sintered compact surface, etc. The studies of the present author and co-workers on these phenomena which were carried out during 40 years are briefly introduced.

• Journal of the Korean Electrochemical Society
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• v.8 no.1
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• pp.47-54
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• 2005

This article covers the fundamentals of stress-induced diffusion, focusing on the theoretical model for hydrogen transport through self-stressed electrode. First, the relationship between hydrogen diffusion and macroscopic deformation of the electrode specimen was briefly introduced, and then it was classified into the diffusion-elastic and elasto-diffusive phenomena. Next, the transport equation for the flux of hydrogen caused simultaneously by both the concentration gradient and the stress gradient was theoretically derived. Finally, stress-induced diffusion was discussed on the basis of the numerical solutions to the derived transport equation under the permeable and impermeable boundary conditions.

• Journal of The Korean Association For Science Education
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• v.31 no.6
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• pp.1009-1024
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• 2011

Previous studies showed that many secondary school students and teachers have difficulties in distinguishing the phenomena of dissolution and diffusion, as well as the phenomena of diffusion and effusion. In this study, currently accepted term definitions of dissolution, diffusion and effusion were searched from the IUPAC Gold Book and the physical chemistry textbooks, and the points to differentiate the definitions were sought. Also, the term definitions of these three phenomena in the secondary school text books and the college general chemistry textbooks were surveyed and compared to the currently accepted definitions. It was found that dissolution is formation of one new phase from mixing two phases, while diffusion is the migration of matter down from the concentration gradient. The "concentration gradient" is considered to be a key point to distinguish diffusion from the dissolution. However, the concentration gradient was not mentioned in the definitions of diffusion in most of the secondary school textbooks and the college general chemistry textbooks. Effusion is differentiated from diffusion by the gas molecules escaping from the container through a tiny hole without collision. The definition of effusion was not found in most of the secondary school textbooks.

• The Southeast Asian review
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• v.21 no.2
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• pp.77-123
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• 2011

Recently, Southeast Asian people, its food, natural sceneries and so on have been increasingly exposed to Korean people through mass media and multi-cultural events. At the same time, Koreans can frequently encounter Southeast Asians in their everyday lives. Thus, specific images and discourses of Southeast Asia has been established in our society, which creates a new social trend called 'Southeast Asia phenomena'. In short, 'Southeast Asia phenomena' means a totality of Korean people's experience of Southeast Asian and their perception on the region. On the one hand, 'Southeast Asia phenomena' is a result of inflow of Southeast Asians and their culture into Korea. On the other hand, it is also a consequence of Korean people's understanding of Southeast Asia from their trip to Southeast Asia or from their interactions with Southeast Asian people. This article aims to analyze the origin and diffusion of 'Southeast Asian Phenomena' in Korea in the context of Southeast Asia focusing on 4 topics, that is, migrant workers, overseas investments, retirement migration, study-abroad categorized as human movement. This article is also about a country-by-country comparative analysis both at the macro level and the micro level. At the macro level, overseas investments and trade, human exchanges, positive perception to Koreans which considered to be the structural causes become a strong mechanism playing a important bridge role between Korea and Southeast Asia. So these create the high probability of the emergence of 'Southeast Asian Phenomena' At the micro level which is more direct causes of 'Southeast Asian Phenomena', the economic cause is the most important common cause for 4 Southeast Asian Phenomena. Additionally, Korean wave is also remarkable common cause creating 'Southeast Asian Phenomena' even it is not the origin in the context of Southeast Asia. The diffusion of 'Southeast Asian Phenomena' is different by the topics and the elements contributing to create the favorable situation for the diffusion are not only overseas investments and trade, human exchanges at the macro level but also policy elements at the micro level. The relative differences of the causes of 'Southeast Asian Phenomena' in the country-by-country analysis are found. Regarding overseas investments in Vietnam and Cambodia, the economic degree of freedom in Cambodia is higher than in Vietnam. Even Korean Wave has had the longer history in Vietnam, but the favorable perspectives on Korean Wave are stronger in Cambodia. For migrant workers from Vietnam and Indonesia, the economic causes in Vietnam are more significant than in Indonesia. The impact of Korean Wave is stronger in Vietnam than in Indonesia. In case of study-abroad, the social-cultural elements and policy elements are more diverse in Malaysia than in Korea. For the Korean retirees who immigrate to the Philippines and Malaysia, the economic causes in the Philippines is more significant in Malaysia.

• Journal of The Korean Association For Science Education
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• v.28 no.5
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• pp.383-394
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• 2008

We analyzed the description of diffusion phenomena in a 7th-grade textbook, and investigated teachers' understanding and teaching methods on diffusion concepts. The data were collected from textbook analysis and questionnaires from 46 science teachers and interviews with 5 teachers. Based on texts' analysis by definition, example, and representation of the diffusion, we found that most of the representations were macroscopically explained by observing the movement of ink in water and smelling the fragrance of perfume in the air. The analysis of questionnaire and interviews also revealed that the definition and the explanation of the diffusion were too abstract for teachers to understand and teach the concept without further information about the microscopic concept of collision of the matter with the medium. Such examples and models lead science teachers to form indistinctive concepts such as dissolution, effusion, and evaporation. Furthermore, the analytical data showed that teachers' understanding of the diffusion concept has been heavily dependent upon the textbook and the level of the understanding was very similar with that of textual description.

• Journal of the Korean Chemical Society
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• v.53 no.5
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• pp.585-608
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• 2009

The aim of this study was to research the characteristics of science teachers' thinking related to dissolution and diffusion. For this study, five science teachers who majored in chemistry or chemistry education were selected and interviewed. These teachers have been teaching on average for 2$\sim$6 years. From the study, it was discovered that the science teachers didn't recognize the necessity of sorting out diffusion from dissolution. The teachers divided in various mixing phenomena with diverse criteria. The science teachers had difficulty in sorting out diffusion from dissolution based on solubility and Gibbs' energy. The teachers didn't see the linkage between the contents that were divided into chapters, and didn't find omitted contents themselves in the chapters that introduced applicable principles. During the interviews, the teachers felt the need to understand the principles for understanding phenomena. But they did not have the ability to teach these principles after learning about the principles themselves. Therefore, it is necessary to develop teacher education programs, as well as a science curriculum, that helps in linking the knowledge between natural phenomena and principles.

• Journal of the Korean Chemical Society
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• v.52 no.1
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• pp.73-83
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• 2008

The purpose of this study was to investigate the types of conceptions of mixing phenomena related to dissolution and diffusion in high school students. The subjects of the investigation consisted of 108 students who took chemistry I course at 11th grade and 29 students who took chemistry II course at 12th grade. For this study, it was found that the many students had the alternative conception that chalk didn't dissolve in water because chalk was a nonpolar material. Most of the students understood the phenomena which carbon tetrachloride and water will not mix as the attraction conception. But many of the other students understood the phenomenon as characteristic of the materials such as difference of density. Many of the students understood the phenomenon of mixing ethanol and water constantly as ‘Attraction conception'. The phenomenon which is mixed ink and water was just accepted by the most students as the spreading of ink in water without understanding the reason of mixing. The phenomena of mixing iodine and carbon tetrachloride was understood as ‘Space conception' or ‘Attraction conception'. It could be inferred that the diverse alternative conceptions related to dissolution and diffusion phenomena were generated by the absence of entropy concept. Therefore, the explanations of science textbooks related to dissolution and diffusion phenomena need to change for students to understand them correctly.

• Journal of the Korean Ceramic Society
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• v.28 no.5
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• pp.383-389
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• 1991

The analysis of degradation phenomena of poled PZT ceramics was investigated relate to piezoelectric equivalent circuit elements. As a result, in the case of impressed mechanical shock on poled specimen of degradation phenomena was explained by domain rearrangement, and in the case of left in air, degradation phenomena was explained by space charge diffusion.

• Fire Science and Engineering
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• v.8 no.1
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• pp.9-20
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• 1994

To understand the phenomena of laminar diffusion flame along vortical walt, the numerical analysis has been performed. Keller-box method was used to solve the problem in the boundary layer. The governing equation is simplified by thin-flame approxiamtion. And energy and chemical species equations are normalized with Schvab-Zeldovich variables. A physical domain is divided the boundary layer along streamwise coordinate as the combustion region and the propagation region. And Radiation model is concerned in these region. As a result, typical phenomena have been observed. Comparison of the numerical results with experimental data shows that the present method can successfully predict phenomena of laminar diffusion flame along upright surface.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.35 no.5
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• pp.199-204
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• 1986

The breakdown phenomena of N2 gas by 13.56MHz electric field are very different from those under steady field. In this paper we analyzed the breakdown phenomena by using electron distribution function and diffusion equation. The second-order differential equation derived from the Boltzmann equation is solved for the electron distribution function. The ionization rate and diffusion coefficient are calculated using kinetic theory formulas. The breakdown condition is that the number of electrons produced by ionization equal the number diffusing to the walls of the discharge chamber. Theses theoretical breakdown electric fields are calculated by the computer and compared with the experimental values.