• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
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• pp.220-221
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• 2007

Recently, imprint lithography have received significant attention due to an alternative technology for photolithography on high performance microelectronic devices. In this work, we investigated thermal stabilities and dynamic mechanical properties of dielectric materials for thermal imprint lithography. Curing behaviours, thermal stabilities, and dynamic mechanical properties of the dielectric materials cured with various curing agent and spherical filler were studied using dynamic differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), rheometer and universal test machine(UTM).

• 한국철도학회논문집
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• 제5권1호
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• pp.18-25
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• 2002

This paper is to study a comparison of ride stabilities for the guideway vehicle between its three primary steering types; the front-rear wheel steering type, tile independent wheel steering and the front wheel steering. A numerical model were built to investigate various factors to have an influence on the vehicular stability. It was shown that dynamic stabilities of the three types were dependent on the steering gain ratio of front wheel steering to rear. The front-rear wheel steering type was more stable for the value of positive steering gains and the shorter distance between front axle and guide link showed better stabilities. On the contrary, the independent wheel steering was more stable for the value of negative gains and the longer distance between front axle and guide link showed better stabilities. Ride characteristics of he front wheel steering seemed to be found midway. Ride behaviors due to time delay from front steering to rear were very different from steering type to type.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
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• pp.207-208
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• 2007

Recently, high performance microelectronic devices are designed in multi-layer structure in order to make dense wiring of metal conductors in compact size. Imprint lithography have received significant attention due to an alternative technology for photolithography on such devices. In this work, we synthesized dielectric composite materials based on epoxy resin, and investigated their thermal stabilities and dynamic mechanical properties for thermal imprint lithography. In order to enhance the mechanical properties and toughness of dielectric material, various modified polyetherimide(PEI) was applied in the resin system. Curing behaviours, thermal stabilities, and dynamic mechanical properties of the dielectric materials cured with various conditions were studied using dynamic differential scanning calorimetry (DSC), thermo gravimetric analysis (TGA), and Universal Test Method (INSTRON).

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2003년도 춘계학술발표대회 논문집
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• pp.180-183
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• 2003

In this work. a potential inexpensive epoxy resin. epoxidized soybean oil (ESO) was synthesized and applied as a toughening agent for 4.4'-tetradiglycidyl diaminodiphenyl methane (TGDDM). The chemical structure of ESO was characterized by FT-IR, $^1H NMR, and ^{13}C NMR$ spectroscopy. The curing behaviors. thermal stabilities. fracture toughness. and flexural strength of TGDDM/ESO blend systems were investigated by using the dynamic DSC. thermogravimetric analysis (TGA). and flexural tests. The thermal stabilities of TGDDM/ESO blend systems were decreased with increasing ESO contents. whereas the critical stress intensity factor ($K_{IC}$) and flexural strength ($\sigma_f$) were increased with ESO contents up to 10 wt% ESO.

• 한국항해학회지
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• 제16권3호
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• pp.33-41
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• 1992

Handling performance of a vessel is greatly related with her steering characteristics which consist of two kinds of motion characteristics ; namely course stability and turning ability. The correct prediction of the qualities, especially the steering characteristics is as much important in ship handling as in ship design. It is the purpose of this paper to provide ships handlers better understanding of steering characteristics and then to help them in safe controlling and maneuvering of vessels presenting distinct inherent steering characteristic difference that lies between a fine-form vessel and full-form vessel. The authors calculated dynamic course stabilities of two kinds of ideal models, one of which represents a fine-form ship and the other a full-form ship, based on hydrodynamic data of forces and moments obtained by model tests in maneuvering tanks. The result of calculations indicated that a ship of full-form configuration has inhernet course instability. Though significant nonlinearties affect ship montions in maneuvers, application of linear theory is sufficient for prediction of the maneuvering characteristics of vessels on calm waters for handling reference.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2003년도 춘계학술대회 논문집
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• pp.494-499
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• 2003

This paper concerns the static, dynamic and thermal characteristics analysis of a high-speed spindle system for horizontal machining centers with 45mm x50,000rpm. The spindle system is designed based on the angular contact ceramic ball bearings, built-in motor, oil-air lubrication method and oil jacket cooling method. The structural and thermal analysis models of spindle system are constructed by the finite element method. The static and dynamic characteristics are estimated based on the static deformation, modal parameter, mode shape and frequency response function, and the thermal characteristics are estimated based on the temperature rise, temperature distribution and thermal deformation. The analysis results illustrate that the designed spindle system has excellent structural and thermal stabilities

• Structural Engineering and Mechanics
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• 제73권6호
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• pp.685-698
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• 2020

The dynamic stability of a functionally graded polymer microbeam reinforced by graphene oxides subjected to a periodic axial force is investigated. The microbeam is assumed to rest on an elastic substrate and is subjected to various immovable boundary restraints. The weight fraction of graphene oxides nanofillers is graded across the beam thickness. The effective Young's modulus of the functionally graded graphene oxides reinforced composite (FG-GORC) was determined using modified Halpin-Tsai model, with the mixture rule used to evaluate the effective Poisson's ratio and the mass density. An improved third order shear deformation theory (TSDT) is used in conjunction with the Chebyshev polynomial-based Ritz method to derive the Mathieu-Hill equations for dynamic stability of the FG-GORC microbeam, in which the scale effect is taken into account based on modified couple stress theory. Then, the Mathieu-Hill equation was solved using Bolotin's method to predict the principle unstable regions of the FG-GORC microbeams. The numerical results show the effects of the small scale, the graphene oxides nanofillers as well as the elastic substrate on the dynamic stability behaviors of the FG-GORC microbeams.

• 한국군사과학기술학회지
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• 제7권3호
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• pp.84-92
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• 2004

The metal forming behavior of Ti-6Al-4V tube during hot backward extrusion was investigated with various forming stabilities or instabilities criteria. that is, Ziegler's instability criterion, dynamic materials model(DMM) stability criteria and Rao's instability criterion. These approaches also were coupled to the internal variables generated from FE simulation. In order to validate the reliabilities of three criteria, hot backward extrusions for Ti-6Al-4V tube making were carried out with different backward extrusion designs. The useful model for predicting the forming defects was suggested through the comparison between experimental observations and simulation results.

• 대한기계학회논문집A
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• 제31권8호
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• pp.889-895
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• 2007

Quantifying dynamic stability is important to assessment of falling risk or functional recovery for leg injured people. Human locomotion is complex and known to exhibit nonlinear dynamical behaviors. The purpose of this study is to quantify major joints of the body using chaos analysis during walking. Time series of the chaotic signals show how gait patterns change over time. The gait experiments were carried out for ten young males walking on a motorized treadmill. Joint motions were captured using eight video cameras, and then three dimensional kinematics of the neck and the upper and lower extremities were computed by KWON 3D motion analysis software. The correlation dimension and the largest Lyapunov exponent were calculated from the time series to quantify stabilities of the joints. This study presents a data set of nonlinear dynamic characteristics for eleven joints engaged in normal level walking.

• Journal of Mechanical Science and Technology
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• 제18권3호
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• pp.395-406
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• 2004

The spectral element model is known to provide very accurate structural dynamic characteristics, while reducing the number of degree-of-freedom to resolve the computational and cost problems. Thus, the spectral element model for an axially moving Bernoulli-Euler beam subjected to axial tension is developed in the present paper. The high accuracy of the spectral element model is then verified by comparing its solutions with the conventional finite element solutions and exact analytical solutions. The effects of the moving speed and axial tension on the vibration characteristics, wave characteristics, and the static and dynamic stabilities of a moving beam are investigated.