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1

Enhanced Microwave Absorption of CNT Composites Mixing with Fe3O4 and Carbonyl Iron

Park J. H., Choi J., Lee K., Park J., Song J. K., Jeon E.

Archives of Metallurgy and Materials

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2018

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Vol. 63, iss. 3

1513--1516

EN

We fabricated two different kinds of composite materials for absorbing microwave in a frequency range of 2 to 18 GHz using coaxial airline and thru-reflect-line (TRL) method. The composite materials having carbon nanotube (CNT) with carbonyl iron (CI) or iron oxide (Fe3 O4 ) were fabricated by mixing each components. Magnetic properties were measured by SQUID equipment. Complex permittivity and complex permeability were also obtained by measuring S-parameters of the toroidal specimen dispersing CI/CNT and Fe3 O4 /CNT into the 50 weight percent (wt%) epoxy resin. The real permittivity was improved by mixing the CNT however, the real permeability was same as pure magnetic powders. The CI/CNT had a maximum value of real permittivity and real permeability, 11 and 1.4 at 10 GHz, respectively. The CNT composites can be adapted to the radar absorbing materials, band width 8-12 GHz.

2

The Effect Of Grain Size On The Mechanical Properties Of Aluminum

Jeong G., Park J., Nam S., Shin S.-E., Shin J., Bae D., Choi H.

Archives of Metallurgy and Materials

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2015

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Vol. 60, iss. 2B

1287--1291

EN

Although many studies have focused on the unique plastic deformation behavior of nanocrystalline aluminum (e.g., the positive deviation from Hall-Petch relation, the unusual yield-drop phenomenon in tensile mode, etc.), the data reported by different research groups are inconsistent with each other, possibly because of different fabrication processes. In this study, aluminum samples with a wide grain-size spectrum – from a few micrometers down to 100 nanometers – are manufactured by powder metallurgy. The grain size was measured by X-ray diffraction analysis and transmission electron microscope observation. Furthermore, the tensile behavior, which varied according to a grain size, is discussed with a comparison of the theoretical models.

3

Evolution Of Precipitate Morphology During Extrusion In Mg ZK60A Alloy

Park J., Jung K. H., Lee G. A., Kawasaki M., Ahn B.

Archives of Metallurgy and Materials

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2015

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Vol. 60, iss. 2B

1423--1426

EN

In this study, a continuously casted ZK60A magnesium alloy (Mg-Zn-Zr) was extruded in two different extrusion ratios, 6:1 and 10:1. The evolution of precipitates was investigated on the two extruded materials and compared with that of as-casted material. The microstructural analysis was performed by electron backscatter diffraction and transmission electron microscopy, and the compositional information was obtained using energy-dispersive X-ray spectroscopy. Several distinct morphologies of precipitates were observed, such as dot, rod, and disk shaped. The formation mechanisms of those precipitates were discussed with respect to the heat and strain during the extrusion process.

4

Numerical investigation of AAC wall panels based on the damage plasticity constitutive law

Taddei F., Reindl L., Park J., Butenweg C., Karadogan F.

Cement Wapno Beton

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2011

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nr spec.

86-91

EN

This paper gives a short overview on the Ytong Building System and discusses possible seismic verification concepts. Moreover it proposes three-dimensional finite element models for unreinforced and reinforced walls panels in aerated autoclaved concrete on the basis of the concrete damage plasticity constitutive law implemented into the FEM toolkit ABAQUS. The paper focuses on an unreinforced ten panel shear wall and on a reinforced four panel shear wall. For the latter, two different solutions are developed: in the first the reinforcement is directly embedded into the AAC mesh, while in the second grouted cores around the reinforcement bars are taken into account. The quasi-static loading condition was simulated using both static and dynamic implicit analysis, switching from the former to the latter at the occurrence of nonlinearities. The simulation results show that the AAC shear wall models can correctly represent the load-displacement responses as well as the cracking patterns and crack propagations. The concrete damage plasticity constitutive law allows for a proper representation of the cyclic behavior and the damage accumulation of AAC shear walls, which is very important for the performance-based design of structures under seismic loading. Further researches are recommended in order to improve the results and to investigate different combinations of applied axial load, aspect ratios and reinforcement details. The long term goal is the development of a feasible and powerful deformation based seismic verification procedure for the Ytong Building System.

5

"Modified" preferences shaped by the market-driven "housing culture" in South Korea

Park J., Ferrari E.

Architecture Civil Engineering Environment

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2011

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Vol. 4, no. 2

5-20

EN

This paper aims to understand how a "housing culture" is shaped and operates in a market-driven capitalist society, governing our built environment as well as our lifestyles. Specifically, it explores how the market influences consumer preferences through a dominant "housing culture", by conducting in-depth interviews with main housing market actors (including house builders, residents and policymakers). The research looks at the particular case of South Korea, where fundamental changes in the country’s housing market have occurred in tandem with the rise of a so-called "apartment culture". A specific pattern of supply and demand, which may contribute to forming a particular housing culture, depends on the interaction between the market and consumer behaviour under policy constraints. Based on this hypothesis, this research shows that consumer preferences are ‘modified’ by a dominant housing culture structured by the market mechanism. This differs from the rationality implied by "revealed preferences" in mainstream economics. In other words, decision-making in housing choices is not free from cultural structure. Therefore, this paper reveals the importance of housing culture as a complement to existing housing research based on mainstream economics.

PL

Celem tego artykułu jest zrozumienie w jaki sposób kształtuje się metodologia projektowania domów oraz zaspakajania potrzeb, rynkowo napędzanego, kapitalistycznego społeczeństwa, która ma wpływ na nasze środowisko zbudowane jak również na nasz styl życia. Szczegółowym badaniom poddane są rynkowe preferencje konsumenta, mające dominujący wpływ na metodologię projektowania domów, w wyniku prowadzonych dogłębnych wywiadów z głównymi uczestnikami rynku inwestycyjnego domów (wykonawców inwestycji, mieszkańców, decydentów). Badanie dotyczy szczególnego przypadku Korei Południowej, gdzie podstawowe zmiany na rynku inwestycyjnym budowy domów w tym kraju, nastąpiły razem ze wzrostem znaczenia tak zwanej „kultury apartamentu”. Określony wzór podaży i popytu, który może przyczynić się do tworzenia szczególnego standardu i wizerunku domów, zależy od współdziałania między rynkiem i zachowaniem się konsumenta pod presją polityki marketingowej i medialnej. Opierając się na tej hipotezie, badania te dowodzą, że preferencje konsumenta są „zmodyfikowane" przez panujący standard i rozpowszechniony medialnie wizerunek domów zbudowany przez rynkowy mechanizm. To różni się od racjonalnych, nasuwających się wniosków w stosunku do ujawnionych preferencji w ogólnie pojętej ekonomii. Inaczej mówiąc , decyzje podejmowane przy wyborze domu nie są wolne od kulturowego podłoża społeczeństwa i jego preferencji estetycznych. Dlatego, artykuł ten ujawnia znaczenie metodologii projektowania domów jako uzupełnienie do istniejącego badania domów bazującego na ogólnie pojętej ekonomii.