• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 춘계학술대회 논문집
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• pp.1092-1096
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• 2011

The "standard regulation" of the vehicles from "urban transit law" are being adopted to electric multiple unit in domestic. In the standard regulation, there are two types for EMU. One is heavy EMU for Seoul. The other is large EMU for Pusan, Daegu, Gwangju, Daejeon, Incheon. Korea Railroad Research Institute, with the assistance of the Ministry of Land, Transport and Maritime Affairs, "advanced EMU development project" are progressed, and 6th year started at September, one unit to six cars is completed. Now "urban transit vehicle performance tests are on the current progress. The main characteristics of AUTS(Advanced Urban Transit System) are as follows. One inverter control one motor, DDM(Dircet Drive Motor), no driving gear, plug door and steps, mounting and maintenance costs down, passenger convenience improvement. This paper describes the key features the next generation EMU, and performance test results, and the commercial success method of national R&D business.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.2276-2279
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• 2011

The AUTS(Advanced Urban Transit System) are developed by government R&D business. This units are under main line performance test in Daebul test line. Both AC and DC could apply to the AUTS for pantagraph voltage. So main transformer and some high voltage filters are added to the under-frame. As a result the total weight of each car(Mc1-Tp1-M-T-Tp2-Mc2) is different. And axle load is different each other. The main characteristics of AUTS(Advanced Urban Transit System) are as follows. One inverter control one motor, DDM(Dircet Drive Motor), no driving gear, plug no end door, self-steering bogie etc. These matters could be appeared to strange vibration. So vibration test is important. The vibration test performed to Mc1 and Tp1. The results were checked to the up-down direction and left-right direction for acceleration.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2005년도 춘계 학술발표회 논문집
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• pp.335-342
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• 2005

Using higher order Mindlin plates and piezoelectric materials, eigenvalue problems are considered. Since piezoelectric crystal resonators produce a proper amount of electric signal for a thickness-shear frequency, the objective is to decouple the thickness-shear mode from the others. Design variables are the bulk material densities corresponding to the mass of masking plates for electrodes. The design sensitivity expressions for the thickness-shear frequency and mode shape vector are derived using direct differentiation method(DDM). Using the developed design sensitivity analysis (DSA) method, we formulate a topology optimization problem whose objective function is to maximize the thickness-shear component of strain energy density at the thickness-shear mode. Constraints are the allowable volume and area of masking plate. Numerical examples show that the optimal design yields an improved mode shape and thickness-shear energy.

• Geomechanics and Engineering
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• 제11권2호
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• pp.269-288
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• 2016

The jointed rock mass behavior often plays a major role in the design of underground excavation, and their failures during excavation and in operation, are usually closely related to joints. This research attempts to evaluate the effects of two basic geometric factors influencing tunnel behavior in a jointed rock mass; joints spacing and joints orientation. A hybridized indirect boundary element code known as TFSDDM (Two-dimensional Fictitious Stress Displacement Discontinuity Method) is used to study the stress distribution around the tunnels excavated in jointed rock masses. This numerical analysis revealed that both the dip angle and spacing of joints have important influences on stress distribution on tunnel walls. For example the tensile and compressive tangential stresses at the boundary of the circular tunnel increase by reduction in the joint spacing, and by increase the dip joint angle the tensile stress in the tunnel roof decreases.

• Macromolecular Research
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• 제15권1호
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• pp.10-16
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• 2007

In this work, we prepared epoxy/BMI composites by using N,N'-bismaleimide-4,4'-diphenylmethane (BMI), epoxy resin (diglycidyl ether of bisphenol-A (DGEBA)), and 4,4'-diamino diphenyl methane (DDM). The thermal properties and water sorption behaviors of the epoxy and BMI composites were investigated. For the epoxy/BMI composites, the glass transition and decomposition temperatures both increased with increasing BMI addition, which indicates the effect of BMI addition on improved thermal stability. The water sorption behaviors were gravi-metrically measured as a function of humidity, temperature, and composition. The diffusion coefficient and water uptake decreased and the activation energy for water diffusion increased with increasing BMI content, indicating that the water sorption in epoxy resin, which causes reliability problems in electronic devices, can be diminished by BMI addition. The water sorption behaviors in the epoxy/BMI composites were interpreted in terms of their chemical and morphological structures.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 추계학술대회 논문집 전력기술부문
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• pp.141-143
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• 2008

Due to the demand for high-output motors in the limited space between the wheels in an electric train, self-ventilating traction motors have been used for many years. periodical disassembly maintenance is necessary to remove the small quantities of dust that enter the motor from the open-air ventilation. Reducing this burden, as well as increasing efficiency and reducing noise, would benefit the next generation of moters To address these needs, KRRI is developing a fully enclosed type traction motor, a fully enclosed type traction motor with outer fans, a high-efficiency permanent-magnet synchronous motor and a direct-drive motor(DDM) as traction motors for the next generation of trains.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 추계학술발표대회 논문집
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• pp.273-275
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• 2002

In this studies, curing behavior and mechanical properties of tetrafunctional epoxy resin (4EP)/ fluorine-containing epoxy resin (FEP) blend systems was investigated with 4, 4'-diaminodiphenol methane (DDM) as a curing agent. The cure activation energies $(E_a)$) were studied by Flynn-Wall-Ozawa's equation with dynamic DSC method. For the fracture toughness of the casting specimens, the critical stress intensity factor ($K_{IC}$) and the specific fracture energy ($G_{IC}$) were determined by fracture toughness test.

• Journal of Mechanical Science and Technology
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• 제19권spc1호
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• pp.350-356
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• 2005

A method of dynamic analysis of mechanical systems considering probabilistic properties is proposed in this paper. Probabilistic properties that result from manufacturing tolerances can be represented by means and standard deviations (or variances). The probabilistic characteristics of dynamic responses of constrained multi-body systems are obtained by two ways : the proposed analytical approach and the Monte Carlo simulation. The formerpaper, necessitates sensitivity information to calculate the standard deviations. In this a direct differentiation method is employed to find the sensitivities of constrained multi-body systems. To verify the accuracy of the proposed method, numerical examples are solved and the results obtained by using the proposed method are compared to those obtained by Monte Carlo simulation.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1988년도 춘계학술대회 논문집
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• pp.67-69
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• 1988

In this study, after changing the curing condition of hardner(DDM) and filler($SiO_2$) contents dielectric and dynamic mechanical properties were studied according to the variation of temperature. As the result we obtained a correlative $\alpha$-peak at 125-150[$^{\circ}C$] from dielectric and mechanical properties. With increasing curing condition and filler contents both dielectric and internal friction loss were, decreased, peak temperature shifted to high temperature, but there was no variation on peak temperature with filler contents. As the above result we knew the correspondence between dielectric and mechanical characteristics.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2002년도 제25회 KOSCI SYMPOSIUM 논문집
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• pp.193-207
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• 2002

The present study is mainly motivated to investigate the vaporization, autoignition, and combustion of liquid fuel spray injected into high pressure environment. In order to represent these phenomena realistically, discrete droplet model (DDM) which simulates the spray using finite number of representative droplets was adopted for detailed consideration of the finite rate of uansport between liquid and gas phases. The Eulerian-Lagrangian formulation was used to analyze the two-phase interactions. The high pressure vaporization model was applied using the thermodynamic and phase equilibrium at droplet surface. The high pressure effect as well as high temperature effect was considered in the calculation of liquid and gas properties. The characteristics of spray in high pressure environment were explained by comparison with normal pressure case.