• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.67-68
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• 2002

The properties and mechanism of silicon protuberance and groove processing by diamond tip sliding using atomic force microscope (AFM) in atmosphere were studied. To control the height of protuberance and the depth of groove, the processed height and depth depended on load and diamond tip radius were evaluated. Nanoprotuberances and grooves were fabricated on a silicon surface by approximately 100-nm-radius diamond tip sliding using an atomic force microscope in atmosphere. To clarify the mechanical and chemical properties of these parts processed, changes in the protuberance and groove profiles due to additional diamond tip sliding and potassium hydroxide (KOH) solution etching were evaluated. Processed protuberances were negligibly removed, and processed grooves were easily removed by additional diamond tip sliding. The KOH solution selectively etched the unprocessed silicon area. while the protuberances, grooves and flat surfaces processed by diamond tip sliding were negligibly etched. Three-dimensional nanofabrication is performed in this study by utilizing these mechanic-chemically processed parts as protective etching mask for KOH solution etching.

• Structural Engineering and Mechanics
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• v.50 no.3
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• pp.403-417
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• 2014

The present paper addresses a general formulation for the thermo elastic analysis of a functionally graded cylindrical shell subjected to external loads. The shear deformation theory and energy method is employed for this purpose. This method presents the final relations by using a set of second order differential equations in terms of integral of material properties along the thickness direction. The proposed formulation can be considered for every distribution of material properties, whether functional or non functional. The obtained formulation can be used for manufactured materials or structures with numerical distribution of material properties which are obtained by using the experiments. The governing differential equation is applied for two well-known functionalities and some previous results are corrected with present true results.

• Proceedings of the Korean Geotechical Society Conference
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• 1991.10a
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• pp.195-215
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• 1991

This report deals with the process of the finite element computation and the design of the particular example tunnel (the double track section tunnel for Line 5, 7, 8 of Seoul Subway). The finite element calculations are performed with the program MISES 3 was developed from Austria which have been used in Eroupe. The principles of mechanic and mathematic analysis for the program MISES 3 are based on "The Finite Element Method -3rd Edition" by O.C zienkiewicz. The calculations are approximate analysis method divide continuum into quadrilateral element and calculate deformation and stress, according to the force equations at the node of the element. On the calculation of under excavation, this is a very convenient method and able to calculate compounded structure with tunnel lining and surrounding materials. Although calculated under the same factor and conditions, the result is not same solution, according to the shape of mesh. Therefore , it is important that we collect the construction results of NATM on the spot and by comparing the results of the finite element method with the surveying results review the validity of analysis model.sis model.

• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.547-549
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• 2004

This system is monitors the degree of aging happened at the electric machine. It detects electromagnetic wave generated from the insulator when the voltage is applied to the machine. By analyzing the internal and external factors make the electric, mechanic, or thermal characteristics of the electric machinery deteriorate the electric insulation and eventually cause the partial electric discharge. The continuous partial electric charge accelerates the insulation aging and the insulation breakdown happens at last. This system consists of the relays connected with 10 sensors (40 total) detecting the partial electric discharge ans the temperature, the server, ans the program analyzing and storing the data.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.1
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• pp.47-53
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• 2011

From recent research, it has revealed that Electroacitve polymer(EAP) has a physical limitation. Carbon nanotube(CNT) is known as the promising material which has excellent electro-mechanical characteristics and is mostly defect-free. It is expected that a successful synthesis of CNT and Nafion known as a primary material for IPMC would make a great improvement on its electro-mechanic feature. In this paper, we suggest the method of synthesis of CNT with Nafion which improves electro-mechanical characteristic. Using mechanical dispersion with Nafion and Isopropyl Alcohol(IPA), we disperse Single-walled carbon nanotubes(SWCNT). For a uniformly layer of CNT, we used a spray gun on a hot plate by a simplified method. In the result, we fabricated a disperse SWCNT/Nafion composite uniformly.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.6
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• pp.62-72
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• 2007

Fracture analysis of human bone is necessary to predict the failure of musculoskeletal structures and to heal them by several possible mechanisms under different loading conditions. But human bone is a complex material, with a multiphase, heterogeneous and anisotropic microstructure. Due to the difficulty of obtaining experimental and clinical results, the importance of numerical analysis and computational simulations in biomechanics are increasing gradually. In this study, stress analysis for human femur model is performed by using the 2-dimensional finite element method(FEM) and its stress distribution is determined. From these results, the fracture mechanic parameters are calculated and the fracture criteria on human femur are investigated and discussed.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.28 no.3
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• pp.12-17
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• 2020

Avionics is a compound word of aviation and electronics that began to be used in the late 1930s. In the components or sub-systems installed to the aircraft, avionics is something that works by electronic technology. In the past, the aircraft mate, the flight engineer, and the radar operators performed the work on board the aircraft but the modern aircraft have replaced these tasks with avionics. the aircraft mechanics who maintain and manage such complex aircraft must have expertise and technics with the development of avionics to maintain aircraft airworthiness. This paper is about the introduction of domestic avionics qualification system and the development of avionics maintenance technology. For this, the SWOT analysis is performed by identifying the internal and external environment. And recommend the strategy and direction of domestic avionics qualification and education system.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.988-992
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• 2002

Ultrasonic machining technology has been developed over recent years for the manufacture of and quality-assured precision parts for several industrial application such as optics, semiconductors, aerospace, and automobile application. The past decade has seen a tremendous in the use of ceramics in structural application. The excellent thermal, chemical and wear resistance of these material can be realized because of recent improvements in the overall strength and uniformity of advanced ceramics. Ultrasonic machining, in which abrasive particles in slurry with water are presented to the work surface in the presence of an ultrasonic-vibrating tool, is process which should be of considerable interest, as its potential is not limited by the electrical or chemical characteristics of the work material, making it suitable for application to ceramics. This paper intends to further the understanding of the basic mechanism of ultrasonic machining for brittle material and ultrasonic machining of ceramics based in the fracture-mechanic concept has been analyzed.

• Proceedings of the Korea Concrete Institute Conference
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• 1994.10a
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• pp.217-222
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• 1994

Generally speaking, grouting on the base stabilizes the ground as the aspects of mechanic and engineering properties, with drilling hole at any depth of the earth, and pressuring the cement milk or special chemical grouting material in it. The purpose of grouting on the base is waterproofness and solidification of the ground by earth concreting that the cement milk pass through paticles of soil or crack of rock. This report shows the fundamental properties of microcement compared with those of ordinary portland cement in a point of grouting. It also describes that experimental applications on the treatment of the weathered rock at the constructior of Taegu subway and Boryong earth filled dam site, south of chungchung province, resulted in success.

• Journal of the Korean Ceramic Society
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• v.31 no.9
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• pp.941-948
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• 1994

An underwater grout on material resistance against segregation in water were studied by water soluble polymer (methyl cellulose and acrylic acid ester and styrene). The mechanical properties of the grout agents were investigated through the observation of the microstructure and application of fracture mechanic. When the soluble polymer MC+AAES added with 0.6 wt% to the underwater grout agents the compressive strength, flexural strength and Young's modulus were about 58 MPa, 10 MPa and 3.2 GPa respectively, and critical stress intensity was about 0.8 MNm-1.5. It can be considered that the strength improvement and fracture toughness increase may be due to the pore decrease and bonding force by material resistance against segregation in water.