• Journal of Aerospace System Engineering
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• v.3 no.1
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• pp.42-46
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• 2009

The 1st development of "Human Powered Aircraft(HPA)" in Korea has been conducting by KAFA(Korea Air Force Academy) from Aug. 2008 to now. HPA is an aircraft powered by directly human energy. The thrust provided by the human power may be the only source and that is weak. Therefore, light weight and strong structure is first requirement. In this paper, treating a basic conceptual design of HPA and material property and material choice for HPA. Also analysing the structure and checking the safety of HPA.

• Journal of Power System Engineering
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• v.8 no.1
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• pp.69-74
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• 2004

A structure-control combined optimal design problem is discussed taking a 3-D truss structure as a design object. We use descriptor forms for a controlled object and a generalized plant because the structural parameters appear naturally in these forms. We consider not only minimum weight design problem for structure system, but also suppression problem of the effect of disturbances for control system as the purpose of the design. A numerical example shows the validity of combined optimal design of structure and control systems. We also consider the validity of sensor-actuator collocation for control system design in this paper.

• Journal of Power System Engineering
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• v.12 no.1
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• pp.53-57
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• 2008

The automotive industry faces many competitive challenges including weight and cost reduction to meet need for higher fuel economy. It is a trend that a lot of parts have been currently changed to an aluminum alloy from steel materials. It is required more precise analysis for practical load because of complexities and varieties of vehicle structure. In this study, the shape optimization using a FEA is performed to determine the design of the knuckle. The size optimization is carried out to find thickness while the stiffness constraints are satisfied. A commercial optimization software MSC/NASTRAN is utilized for the structural analysis and the optimization processes.

• Korean Journal of Materials Research
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• v.23 no.2
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• pp.112-115
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• 2013

One of the most important characteristics of Mg alloys is the high ratio of strength to weight. This is why there is a high demand for applications with these alloys in the transportation industries to reduce the fuel consumption and to save energy. In addition, magnesium (and its alloys) is of considerable interest as a structural material, especially in the aerospace and automotive industries thanks to its low density. However, its major drawback is its high sensitivity to corrosion. Therefore, its use requires the application of a surface treatment. This study used a die-casted AZ91D Mg alloyand all the samples were annealed (in $120^{\circ}C$). The surface microstructure and phase distribution in thin-walled AZ91D magnesium components cast on a hot-chamber die-casting machine were investigated by optical microscopy and scanning electron microscopy. The reflectance differences in the bulk state comparison with the annealing state are caused by hydrogenation presence of the Mg layer under an oxidation surface layer.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.128-131
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• 2007

It is very important that there are saving resource and energy in the future as well as in these day. Weight saving of structural parts, which are formed by extrusion, plays a key role in manufacturing field. Especially these aluminum parts used in the car need other processes to vary the cross section in the axial direction. Thus, applications of these parts are limited by high cost. if the cross section of the parts is variable by only extrusion, application of extruded aluminum parts will more increase. Therefore, a new CNC extruder which can control the section area of a car part was invented the nation's first. Using the extrusion machine, the experiment and FE analysis were performed during the varied section extrusion process.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.12
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• pp.3127-3135
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• 1994

An approach to the simultaneous optimal design of structure and control system for large free-free flexible beam is presented. The flexible beam is modeled by the finite element method. And the reduced model of small degree of freedom is constructed by use of modal analysis. The tapered beam is considered so that the number of design variables is not dependent on the increasing number of finite elements. The width of several points of tapered beam and control gain are taken as design variables. The shape of beam and control gain are optimized simultaneously for the minimum weight of total structure including control system subject to the constraints of the magnitude of displacement of beam. It is shown that the simultaneous optimal design of structure and control systems is indeed useful.

• Proceedings of the Membrane Society of Korea Conference
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• 1995.04a
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• pp.1-4
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• 1995

The microstructure of polymer membranes produced via thermally induced phase separation (TIPS) of polymer solutions is a strong function of both the early-stage (by spinodal decomposition or nucleation & growth) and the late-stage phase separation (referred to in general as coarsening). In the case of early stage effects, the membrane morphology resulting from a nucleation & growth mechanism is either a poorly interconnecsed, stringy, beady structure which is mechanically fragile or a well interconnected structure with highly nonuniform pore sizes. In contrast, spinodal decomposition results in a well interconnected, mechanically strong membrane with highly uniform pore sizes. Here I describe recent quantitative studies of the coarsening effects on the microstructure of membranes produced via TIPS process. The dependence of microstructure on coarsening time, quench depth, solution viscosity, and polymer molecular weight was investigated in order to distinguish among three possible coarsening mechanisms, Ostwald ripening, coalescence, and hydrodynamic flow, which may be responsible for structural evolution after the early-stage phase Separation (spinodal decomposition or nucleation & growth).

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1292-1293
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• 2006

A non-equilibrium powder metallurgy processing such as an MA/SPS (Mechanical Alloying / Spark Plasma Sintering) process is examined in a Ti-48moll%Al. TiAl intermetallic compound is a potential light-weight/high-temperature structural material. One of the major problems, however, limiting the practical use of the material is its poor workability. From this point, the powder metallurgy (PM) processing route has been attractive alternative of the conventional processing for such material The MA/SPS process is able to apply to a LIGA process. Optimization of the pseudo-superplasticity enables to fabricate micro-parts made of fine grained ceramics composites of TiAl by the LIGA process.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.714-715
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• 2006

The Application of powder metallurgy (PM) aluminum structural parts is at its early growing stage, despite of some automotive applications. The market potential for PM aluminum, however, is large. Growth is expected from the market expansion of the existing applications and new applications, including the replacements of aluminum and zinc based castings and some ferrous PM automotive parts by PM aluminum. Compared to castings, PM is an efficient mass production technology. The PM aluminum is more competitive than die casting for some automotive applications. Besides weight saving leading to performance improvement, the total cost increase for aluminum PM parts is less than 15% compared to ferrous PM automotive parts. The future is promising for PM aluminum.

• Microbiology and Biotechnology Letters
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• v.19 no.3
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• pp.248-252
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• 1991

- Mutation process and substrate induction of 7i-ichoderma viride cellobiohydrolase were investigated by immunological techniques. Since mutants of Trichodemza uiride such as QM9123, QM9414, TKO41 and MCG77 produced immunologically same cellobiohydrolase, it may be that the mutation be occurred in the reguratory gene rather than in the structural gene of cellobiohydrolase. a-Cellulose and Solka Floc were found to be the best inducer for the production of cellobiohydrolase in Trichodemza viride culture compared to low molecular weight inducer such as carboxylmethyl cellulose and cellobiose.