• Journal of the Korean Ceramic Society
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• v.46 no.3
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• pp.330-335
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• 2009

We investigated the effects of the re-oxidation temperature and time on the positive temperature coefficient (PTC) of resistivity characteristics of Sm-doped $BaTiO_3$ sintered at $1200{\sim}1260^{\circ}C$ for 2 h in a reducing atmosphere (3% $H_2/N_2$), followed by re-oxidization processes in air, in which re-oxidization temperature and time were $600{\sim}1000^{\circ}C$ and $1{\sim}10$h, respectively. The result reveals that Smdoped (Ba,Ca)$TiO_3$ ceramics fired in a reducing atmosphere exhibit low PTC characteristics, whereas the sample re-oxidized at $800^{\circ}C$ for 1 h in air exhibit pronounced PTC characteristics. The room-temperature resistivity and jumping characteristics of resistivity (${\rho}_{max}/{\rho}25^{\circ}C$) decrease with Sm contents. The PTC characteristics with reoxidization time at $800^{\circ}C$ have improved about $2{\sim}3$ orders of magnitude whereas differed according to the sintering temperature. The 0.7 at% Sm-doped (Ba,Ca)$TiO_3$ samples reveal the best PTC characteristics in the present range of formula and processes.

• Bulletin of the Korean Chemical Society
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• v.27 no.9
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• pp.1364-1370
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• 2006

New liquid-crystalline biphenyl carboxylates with an achiral swallow-tail derived from 1,3-dialkoxy-2-propanol $[(ROCH_2)_2CHOH$] where R is methyl, ethyl, propyl, butyl, $CH_2CF_3$, and $CH_2CF_2CF_3$ were prepared. These achiral liquid crystals having 1,3-dialkoxy-2-propyl moieties exhibit diverse phase sequences [I-SmA-(SmC)-(SmCalt)-Cr] depending on the substituent R group of the swallow-tail. The compounds carrying a fluorinated swallow-tail exhibit antiferroelectric-like smectic C phases, and their temperature ranges are broader than the corresponding non-fluorinated swallow-tailed ones.

• Journal of the Korean Institute of Landscape Architecture
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• v.35 no.2 s.121
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• pp.37-48
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• 2007

An exhibit entitled 'Revelatory Landscapes' was held at the San Francisco Museum of Modem Art from May 5 to October 14, 2001. For this Museum's rot off-site outdoor exhibition, five outstanding design teams-Kathryn Gustafson, Hargreaves Associates, Hood Design, Tom Leader Studio, and ADOBE LA-created site-specific installations in Berkeley, Oakland, San Jose, and the San Francisco Bay Area. Each project showcased a hybridization of environmental art and landscape design. The main content revealed through revelatory landscapes were the natural, cultural, and historical palimpsest of the sites-particularly as related to the history of minorities such as Native American, African Americans and Latin Americans-as well as the every day life of ordinary people. To represent these ideas, a juxtaposition of the past and the present was broadly applied. Furthermore, the use of dramatic colors, textures, and forms in consideration of materials coupled with the revelation of natural elements such as wind and sunlight accelerated the effect of this juxtaposition. Every project of the Revelatory Landscapes exhibit requires a phenomenological experience to be appreciated. Via the five senses, these experiences cause a synesthetic experience beyond solely the visual. By examining the projects of 'Revelatory landscapes', the threshold for a new blending between environmental art and landscape design as well as new landscape design strategies that overcome the dichotomy between nature and culture will change and evolve.

• Korean Journal of Child Studies
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• v.31 no.2
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• pp.103-117
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• 2010

The purpose of this study was to investigate the characteristics of internet usage among 5th and 6th grade of elementary school children and to elucidate the path model and the relative effects of various factors on internet addiction in the internet addiction tendency group. According to our results, the normal internet user group exhibit higher educational levels in fathers, secure attachment to mother, and warm friendship when compared to the internet addiction tendency group. At the same time, internet addiction group exhibit longer internet use time, a greater numbers of avatars in use, and higher avatars decoration costs. The research model suggested here was supported by the results. Attachment to mother appears to affect friendship which in turn affects avatars image decoration needs and avatars identification which in turn then has an impact upon internet addiction tendency. These results were then discussed in relation to previous research and theories.

• Nuclear Engineering and Technology
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• v.37 no.5
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• pp.503-510
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• 2005

An instrumental neutron activation analysis was used to measure the concentrations of about 24 elements associated with airborne particulates (PM10) that were collected in the most polluted urban region of Daejeon city, Korea from 2000 to 2002. Using the measurement data for various elements, both the extent of elemental pollution in the study area and the seasonality in their distribution characteristics were examined. Examinations of their distribution patterns indicated that most elements with crustal origin tend to exhibit seasonal peaks during spring, while most elements with anthropogenic origin tend to exhibit seasonal peaks during fall or winter. In order to explain the factors regulating their mobilization properties, the data were processed by a factor analysis. Results of the factor analysis suggested competing roles of both industrial and natural source processes, despite that the study site is located at a downwind position of the industrial complex. Based on the overall results of this study, it is concluded that the site may be strongly impacted by man-made sources but the general patterns of elemental distributions in the study area inspected over a seasonal scale are quite consistent with those typically observed from natural environment.

• 한국지구과학회:학술대회논문집
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• 2005.09a
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• pp.292-302
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• 2005

Science museum are the typical channels for students to experience science as outside school science lessons. Hereupon, in this study, middle school earth science contents system and achievement standards by the 7th Curriculum analyzed exhibit of science museum for basis. As a result, relevance between accomplishment level and Exhibition was insufficient in curriculum, and the area of geology in the exhibition overemphasized. Therefore, exhibit that consider curriculum is required. hereafter, Result of this study presents display of science museum and direction of education.

• East Asian Economic Review
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• v.21 no.4
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• pp.385-432
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• 2017

This paper investigates how firm age, size and ownership are related with job creation and destruction, and how these patterns differ across transition and non-transition economies. The analysis finds that age is inversely related with gross job creation and net job creation in the two samples. This finding is consistent with the theory of the learning effect. The relationship between age and job destruction is indifferent in non-transition economies. On the contrary, old firms in transition economies destroy more jobs than young ones. The paper further establishes an inverse relationship between size and gross job creation in the two groups. However, there is divergence between the two samples; small firms in non-transition economies also exhibit a higher gross job destruction rate. Consequently large firms have a higher net job creation rate. In transition economies, small and large firms exhibit similar rates of job destruction. But small firms retain a higher net job creation rate. A more intriguing finding is that state owned firms do not underperform domestic private ones. This means these countries may be using soft budget constraint which allows state owned firms to overstaff. Finally, crowding out of SMEs by foreign owned firms is not evident in transition economies.

• Journal of Mechanical Science and Technology
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• v.16 no.9
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• pp.1093-1101
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• 2002

Continuous fiber ceramic composites (CFCCs) have advantages over monolithic ceramics : Silicon Nitride composites are not well used for application because of their low fracture toughness and fracture strength, but CFCCs exhibit increased toughness for damage tolerance, and relatively high stiffness in spite of low specific weight. Thus it is important to characterize the fracture resistance and properties of new CFCCs materials. Tensile and flexural tests were carried out for mechanical properties and the fracture resistance behavior of a SCS6 fiber reinforced Si$_3$N$_4$ matrix CFCC was evaluated. The results indicated that CFCC composite exhibit a rising R curve behavior in flexural test. The fracture toughness was about 4.8 MPa$.$m$\^$1/2 , which resulted in a higher value of the fracture toughness because of fiber bridging. Mechanical properties as like the elastic modulus, proportional limit and the ultimate strength in a flexural test are greater than those in a tensile test. Also a numerical modeling of failure process was accomplished for a flexural test. This numerical results provided a good simulation of the cumulative fracture process of the fiber and matrix in CFCCs.

• Journal of KIISE:Computing Practices and Letters
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• v.15 no.3
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• pp.167-177
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• 2009

This paper is about our experience of developing a context-aware exhibit guide system called MyGuide by applying Simtext development methodology. In particular, we introduce some issues to be considered in development process, the way that we solved them, and other things related to context. In requirements elicitation phase, we reduced the complexity of requirements by separating business logic requirements and context-awareness related requirements. After that, we modeled context, and designed software architecture, classes, and database in sequence during design phase. We considered system requirements and context modeling issues for context modeling because it influences class and database design.

• Nuclear Engineering and Technology
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• v.13 no.4
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• pp.245-253
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• 1981

The properties of polyethylene materials exhibit good insulation and radiation resistance, but exhibit poor flame resistance. Flame retardant properties of the polyethylene were improved by the radiation induced grafting or crosslinking. When the various flame retardants were fixed onto polyethylene, the amount of fixation in grafting was increased with the increase of radiation dosages. In the case of grafting, it is necessary for high grafting yield that the polyethylene films were swelled before irradiation with ${\gamma}$-rays or electron beams. It is the suitable method for the fixation of flame retardant that polyethylene samples were blended with various flame retardants at 1$25^{\circ}C$ and then blended polymers were crosslinked by the electron beams at room temperature.