• Electrical & Electronic Materials
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• v.11 no.11
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• pp.46-52
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• 1998

Barium titanate owes its great importance to the fact that its dielectric constant is about 100 times higher than that of conventional dielectric materials provided its compositional and structural purity is extremely high. The value of crystalline BaTiO3 bodies as used, for instance, in computer elements, magnetic amplifiers, memory device, ets., depend on boththe compositional and the structural purity of the BaTiO3 crystals. This purity will, in turn, depend on the purity of the raw materials used in manufacturing the BaTiO3 compound and on the particularmethods of manufacture which determine the size, homogeneity, and the structural purity of the crystals. This paper reviews the important theoretical considerations, processing techniques and applications related to sol-gel derived thin films.

• Advanced Composite Materials
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• v.17 no.3
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• pp.215-224
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• 2008

The present study aims to design a multilayer microstrip antenna with composite sandwich construction and investigate fatigue behavior of this multilayer SAS (surface antenna structure) that was asymmetric sandwich structure for the next generation of structural surface technology. This term, SAS, indicates that the structural surface becomes an antenna. Constituent materials were selected considering electrical properties, dielectric constant and tangent loss as well as mechanical properties. For the antenna performance, antenna elements inserted into structural layers were designed for satellite communication at a resonant frequency of 12.2 GHz. From electrical measurements, it was shown that antenna performances were in good agreement with design requirements. In cyclic 4-point bending, flexure behavior was investigated by static and fatigue test. Fatigue life curve of the SAS was obtained. The experimental results of bending fatigue were compared with single load level fatigue life prediction equations and in good agreement. The SAS concept is can be extended to give a useful guide for manufacturers of structural body panels as well as antenna designers.

• Corrosion Science and Technology
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• v.22 no.3
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• pp.201-213
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• 2023

Corrosion management of an aircraft and its engine relies on rinsing and cleaning using tap water. Few studies have reported effects of tap water species on corrosion behaviors of structural materials. In this study, a series of experiments were conducted based on the design of experiment. Solutions with different levels of chloride and sulfate ions were prepared using a full factorial design. Two structural materials (aluminum alloy and steel) were used for an alternate immersion test. Weight loss was then measured. In addition, a silver specimen was utilized as a sensor for chloride deposition measurement. The silver specimen was examined using the electrochemical reduction method, XPS, and SEM-EDS. Surface analysis revealed that levels of chloride and sulfate ions were sufficient for the formation of silver chloride and silver surface. Statistical analysis of weight loss and chloride deposition rate showed significant differences in measured values. Concentration of chloride ions greatly affected corrosion behaviors of structural materials. Sulfate ion hindered the adsorption reaction. These results emphasize the importance of controlling ion concentration of tap water used for cleaning and rinsing an aircraft.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.10a
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• pp.119-122
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• 2003

This report describes the procedure of detailed design and structural test for the composite flexure which is a part of the hingeless hub system. First, stacking sequence design for composite flexure was done, and structural analysis by using NASTRAN was made to verify structural stability and safety. Using FPS installed at KIMM, composite flexure was laid up and cured using a autoclave. Before rotor ground test, the basic structural tests such as a bench test, tensile strength test and shear strength test, for flexure, were accomplished. Through replacing existing metal hub part with new fabricated composite flexure, improvement of aeroelastic stability and weight reduction were achieved. This result will be applied to composite rotor system design fur helicopter.

• Structural Engineering and Mechanics
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• v.41 no.1
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• pp.139-155
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• 2012

Structural health monitoring systems are often installed on bridges to provide assessments of the need for structural maintenance and repair. Damage or deterioration may be detected by observation of changes in bridge characteristics evaluated from measured structural responses. However, construction materials such as concrete and steel cables exhibit certain time-dependent behaviour, which also results in changes in structural characteristics. If these are not accounted for properly, false alarms may arise. This paper proposes a systematic and efficient method to study the time-dependent effects on the dynamic properties of cable-stayed bridges. After establishing the finite element model of a cable-stayed bridge taking into account geometric nonlinearities and time-dependent behaviour, long-term time-dependent analysis is carried out by time integration. Then the dynamic properties of the bridge after a certain period can be obtained. The effects of time-dependent behaviour of construction materials on the dynamic properties of typical cable-stayed bridges are investigated in detail.

• International Journal of High-Rise Buildings
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• v.12 no.4
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• pp.307-320
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• 2023

Tall buildings are built with an abundant amount of materials, including structural materials, coming from our limited natural resources. Tall buildings that began from about 10-story tall office towers have evolved to over 150-story tall mixed-use megastructures. As a building becomes taller, structural material requirement to resist lateral wind loads becomes exponentially larger. Therefore, it is crucial to employ efficient structural systems and optimize their design, which will contribute to sustainable vertical built environments through preservation of resources. Tube type structures with large perimeter diagonals are among the most efficient structural systems for tall buildings. Developments of braced tube, braced megatube, diagrid structures, and their optimal design strategies are reviewed. Superframed conjoined towers, produced by interconnecting multiple clustered braced tubes, are presented as a new design direction to achieve not only structural but also architectural and social sustainable design goals.

• Journal of the Korean Ceramic Society
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• v.56 no.2
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• pp.130-145
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• 2019

Widespread commercialization of solid oxide fuel cells (SOFCs) is expected to be realized in various application fields with the advent of cost-effective fabrication of cells and stacks in high volumes. Cost-reduction efforts have focused on production yield, power density, operation temperature, and continuous manufacturing. In this article, we examine several issues associated with processing for SOFCs from the standpoint of the bimodal packing model, considering the external constraints imposed by rigid substrates. Optimum compositions of composite cathode materials with high volume fractions of the second phase (particles dispersed in matrix) have been analyzed using the bimodal packing model. Constrained sintering of thin electrolyte layers is also discussed in terms of bimodal packing, with emphasis on the clustering of dispersed particles during anisotropic shrinkage. Finally, the structural transition of dispersed particle clusters during constrained sintering has been correlated with the structural stability of thin-film electrolyte layers deposited on porous solid substrates.

• Proceedings of the Materials Research Society of Korea Conference
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• 1998.08a
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• pp.43.2-43
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• 1998

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.04b
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• pp.3-20
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• 1995

Advanced ceramics have excellent thermal resistance, wear resistance, corrosion resistance, and other properties, and are promising materials as structural materials. Over the past decade, they have been applied to some machine parts, for example, glow plugs and turbochargers of automotive engines. In the case where the advanced ceramics are used as these structural parts, te low-dimensional accuracy of sintered bodies requires secondary machining.

• Korean Journal of Construction Engineering and Management
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• v.4 no.4 s.16
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• pp.137-144
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• 2003

Recently, the interest in a complex building increases rapidly in Korea. High-rise complex is not simply the combination of a residential apartment and a business office as previous but a building with the object of the convenience of the residents familiar with city-life style through adapting the high class life style and new residential culture to the business space, and the efficiency in using the limited building site in the town. This study presents an exploratory analysis focusing the structural system with the help of the extensive survey of the construction site in Korea, and aims a guideline for the structural design and construction of high rise complex. Through the survey, change and development in the design and the construction can be seen as the height and size of the complex grow. It is almost indispensable to design a structural system against lateral forces like earthquake or wind, which is usually measured by story drift ratio or story displacement. Improvement of the structural materials and their usages is also included for the efficiency of the structural system. Useful slab-beam system contributing to the decrease of the story height is still a concern.