• International Journal of Railway
• /
• 제5권2호
• /
• pp.55-64
• /
• 2012

Subject of the paper is a particular configuration of overhead line, in which noise barrier structure is used as supports of the catenary instead of standard poles. This configuration is foreseen in case the noise barrier position is in conflict with the poles location. If the catenary is supported by the noise barrier, the motion that the latter undergo due to wave pressure associated to train transit is transmitted to the overhead line, so that potentially it influences the interaction between the catenary itself and the pantograph of the passing train. The paper focuses on the influence of such peculiar configuration on the quality of the current collection of high speed pantograph, for single and double current collection. The study has been carried out first with an experimental investigation on the pressure distribution on noise barrier, both in wind tunnel and with in-field tests. Subsequently a numerical analysis of the dynamics of the barrier subjected to the wave pressure due to train transit has been carried out, and the output of such analysis has been used as input data for the simulation of the pantograph-dynamic interaction at different speeds and with front or rear pantograph in operation. Consideration of structural modifications was then highlighted, in order to reduce the influence on the contact loss percentage.

• Journal of Power Electronics
• /
• 제5권2호
• /
• pp.83-98
• /
• 2005

As wind turbine technology and control has advanced over the last decade, this has led to a high penetration of wind turbines into the power system. Whether it be for a large wind turbine or an offshore wind farm with hundreds of MW power capacity, the electrical system has become more and more important in controlling the interaction between the mechanical system of the wind turbine and the main power system. The presence of power electronics in wind turbines improves their controllability with respect not only to its mechanical loads but also to its power quality. This paper presents an overview of a developed simulation platform for the modeling, design and optimization of wind turbines. The ability to simulate the dynamic behavior of wind turbines and the wind turbine grid interaction using four simulation tools (Matlab, Saber, DIgSILENT and HAWC) is investigated, improved and extended.

• 대한기계학회논문집
• /
• 제18권3호
• /
• pp.653-661
• /
• 1994

In this paper the CSCM type upwind flux difference splitting Navier-Stokes method has been applied to study the ARL-SL19 supersonic/transonic compressor cascade flow. H-type grid was chosen for its simplicity in applying cyclic tridiagonal matrix algorithm along with conventional slip/no-slip boundary conditions. The thin-layer algebraic model of Baldwin-Lomax was employed for the calculation of turbulent flows. The test case inlet Mach No. was 1.612 and inlet/exit pressure ratio($P_2/P_1$) was 2.15. The results were compared with experimental results from current method were compared well in suction surface with the experiments and other computational results; however, not well in pressure surface. It might be due to the complex flowfields such as shock/boundary layer interaction, turbulence, and flow separation, etc. In the future, a proper turbulence modelling and adaptive grid system will be studied to improve the solution quality.

• 대한기계학회논문집
• /
• 제17권10호
• /
• pp.2509-2517
• /
• 1993

Lapping is a very complicated and random process resulting from the variation of abrasive grains in its sizes and shapes and from the numerous factors having an effect on the process quality. Thus it needs to be analyzed by experimental method rather than by theoretical method to obtain the relative effects of factors quantitatively. In this study, cylindrical lapping experiment designed by Taguchi's L8 orthogonal array was performed and analyzed by Yates' ANOVA table. As a result, effective factors and interaction effects were identified and discussed. Also the optimal factor combination to obtain the largest improvement of surface roughness was selected and confirmatory experiments were peformed.

• 대한기계학회논문집A
• /
• 제26권7호
• /
• pp.1348-1356
• /
• 2002

The present work concerns the optimal design for injection molding processes by using the design of experiments (DOE) and numerical analysis. The DOE approaches is planned to be able to consider two-way interaction, and have been applied progressively for both mold design and process design. Numerical analyses have been carried out as a design of experiments for mold parameters such as runner specifications and cooling channel configurations. In order to determine optimal process parameters, experiments have been performed for various process conditions with the DOE scheduling. As a result, the quality and productivity of the product have been improved, and the proposed approach can be successfully reflected on the industrial injection molding process of precision electronics parts.

• 디지털융복합연구
• /
• 제13권1호
• /
• pp.163-176
• /
• 2015

공적불평행동에서 회사에 대한 직접 불평을 하고, 배상을 요구하는 경우가 빈번하게 나타나고 있는 현 상황에서 콜센터의 대응은 매우 중요한 시점이다. 본 연구의 목적은 콜센터의 서비스품질차원과 세부요인을 찾아내고, 서비스품질차원이 서비스회복, 고객충성도와 어떠한 관련성이 있는지를 연구하는 것이다. 불만족을 경험한 조사대상자 139명을 대상으로 콜센타 서비스품질과 고객충성도 관계성을 검증하기 위해서 가설과 연구모형을 설정하였다. 가설 검증 결과 3개의 콜센타 상담원 서비스 품질과 서비스 회복에 정에 영향을 미치는 것으로 나타났다. 서비스회복은 고객충성도에 정에 영향을 미치는 것으로 나타났다. 결과품질은 상담후의 고객한테 남는 결과물로서 고객의 입장에서 보면 콜센터 이용의 궁극적인 목적이라고 할 수 있으며, 조사 결과 콜센터 서비스품질 세 가지 차원 중 서비스회복에 미치는 영향력이 가장 큰 것으로 드러났다. 서비스회복과 고객충성도 간의 관계에서 서비스회복은 고객충성도에 유의한 영향을 미치는 것으로 나타났다. 콜센터에서는 서비스회복을 도모하고 고객의 고객만족도 및 충성도를 높이기 위하여 콜센터 서비스품질의 관리가 필요하다.

• 한국생산제조학회지
• /
• 제23권2호
• /
• pp.103-108
• /
• 2014

Growing concerns about environmental pollution have led to an increase in the demand for compressed natural gas (CNG) vehicles in recent years. CNG vehicles are equipped with a cylinder valve installed in a high-pressure vessel to control the CNG flow. The cylinder valve must meet high quality safety standards because the pressure vessel stores high-pressure CNG. Therefore, safety evaluation of the cylinder valve is necessary to ensure the safety of CNG vehicles. In this study, fluid-structure interaction analysis for the structural integrity of the cylinder valve were conducted using a commercial finite element analysis code(ANSYS WORKBENCH V14). The CFD analysis was performed using a steady-state technique according to the inlet and outlet pressures in order to predict the pressure distribution. Structural analysis was performed by a static structure technique at the maximum working pressure to evaluate the structural integrity of the cylinder valve. From the results, the safety factor of the valve component is between 1.57 and 21.5.

• Tribology and Lubricants
• /
• 제18권5호
• /
• pp.351-356
• /
• 2002

The surfaces of machine components in sliding contact such as bearing, gears and pistons etc. frequently operate under the condition of mixed lubrication due to high load, high speed and slip. These machine components often undergo the inception of scuffing in practical application. The scuffing failure is a critical problem in modern machine components, especially for the requirement of high efficiency and small size. However, it is difficult to find a universal mechanism to explain all scuffing phenomena because there are so many factors affecting the onset of scuffing. In this study, scuffing experiments are conducted using Acoustic Emission(AE) measurement by an indirect sensing approach to detect scuffing failure. Acoustic Emission(AE) signal has been widely utilized to monitor the interaction at the friction interface. Using AE signals we can get an indication about the state of the friction processes, about the quality of solid and liquid layers on the contacting surfaces in real time. The FFT(Fast Fourier Transform) analyses of the AE signal are sued to understand the interfacial interaction and the relationship between the AE signal and the state of contact is presented.

• Journal of Welding and Joining
• /
• 제32권2호
• /
• pp.22-28
• /
• 2014

To enhance productivity and provide high quality production material in a GMA welding process, weld quality, productivity and cost reduction affects the number of process variables. In addition, a reliable welding process and conditions must be implemented to reduce weld structure failure. In various industries the welding process mathematical model is not fully formulated for the process parameter and on the welding conditions, therefore only partial variables can be predicted. The research investigates the interaction between the welding parameters (welding speed, distance between electrodes, and flow rate of shielding gas) and bead geometry for predicting the weld bead geometry (bead width, bead height). Taguchi techniques are applied to bead shape to develope curve equation for predicting the optimized process parameters and quality characteristics by analyzing the S/N ratio. The experimental results and measured error is within the range of 10% presenting satisfactory accuracy. The curve equation was developed in such a way that you can predict the bead geometry of constructed machinery that can be used for making tandem welding process.

• 대한기계학회논문집A
• /
• 제36권2호
• /
• pp.173-178
• /
• 2012

최근 RFID, 유연디스플레이, 태양전지, 전자 종이 등의 소자를 프린팅 방식을 이용하여 생산하려는 연구가 활발하게 진행 되고 있다. 이런 방식이 기존의 노광기술과 식각기술에 의존하는 반도체 공정에 비해 가격 경쟁력에서 우수하기 때문이다. 특히 RFID, 유연디스플레이, 태양전지, 전자 종이 등은 유연성과 대량생산을 필요로 하기 때문에 롤투롤(roll to roll)공정과 같은 저가격화, 대형생산화에 관심이 집중되고 있다. 이 롤투롤 기술을 사용하기 위해서는 인쇄 패턴의 빠른 구현, 표면 균일도, 두께 등의 높은 인쇄 품질이 보장 되어야 한다. 본 연구는 실험계획법(Design of Experiment)을 적용하여 인자들의 주효과와 교호작용 효과를 분석하고, 롤투롤 전자인쇄 시스템에서 닙 롤의 특성에 따른 인쇄 품질의 영향과 인쇄 품질의 향상 방안을 찾기 위한 매칭기술을 제안 하였다.