• Transactions on Electrical and Electronic Materials
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• v.7 no.5
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• pp.235-239
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• 2006

Charge dynamics in polymeric materials after aged under ac electric field using the pulsed electroacoustic (PEA) technique is reported. The emphasis is placed on charge decay. The charge dynamics of the ac aged additive free low density polyethylene (LDPE) samples under dc bias differ from the sample without ac ageing, indicating changes brought in by ac ageing. It is believed that a slow decay rate of charge in the ac aged sample is related to the formation of deep traps in the material. However, chemical analysis by infrared spectroscope (FTIR) and Raman microscope reveals no significant chemical changes taken place in the bulk of the material after ac ageing. Further experiments on irradiated LDPE have revealed a similar behaviour, i.e. the charge decay is slower in irradiated samples than that of fresh sample. The findings presented clearly indicate that space charge measurement can be used as a diagnostic tool to monitor ageing in polymeric materials.

• Journal of the Korean Society for Precision Engineering
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• v.1 no.2
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• pp.58-68
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• 1984

In this study, the static and dynamic components of cutting resistance were measured with tool dynamometer (Swiss, pieso-electric type) when S45C, A1-alloy and brass were drilled under the some variable conditions. The results obtained are as follows; 1) The dynamic components of these cutting resistance are not related to the depth of drilled hole. 2) The static and dynamic components of cutting resistance are increased in accordance with the increase of feed and drill diameter. 3) The dynamic components of thrust force are increased in accordance with the increase of spindle speed. 4) The rate of the dynamic component to the static component is 0.3 .approx. 0.5 in torque, 0.1 .approx. 0.2 in thrust force. 5) The characteristic of the tool system is affected in dynamic component of cutting resistance, and the creasted frequency and amplitude of the chip are determined by the crilled materials. 6) The maximum amplitude of the dynamic component is increased proportionally in accordance with the feed rate and the spindle speed.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.6
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• pp.104-110
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• 2008

A lot of straight bevel gears have been manufactured by the cold forging process in order to improve the productivity and mechanical property of the product. The die for the cold forging of the gear needs high precision and reproducibility. In the study, cold forging die has been modeled by CAD/CAM and manufactured by machining center using ball end mill coated by (Al, Ti)N for heat-treated alloy steel(STD11, HRC 60). Through the measurement of the machined die, satisfactory dimensional accuracy and surface roughness were obtained. In the future, many 3-d cold forging dies will be directly machined instead of electric discharge machining.

• Proceedings of the KIEE Conference
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• 2008.10c
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• pp.213-214
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• 2008

Since standardization project is composed of complicate system, such as vehicle, signal, electric power and railway, how to build management system of the project has influence on the success of the project for the first stage of the project. The computer system design tool supports to carry out requirement analysis, DB construction, and history and follow-up management efficiently. Therefore, the aim of this study is to investigate the method to optimize schema using computer system design tool.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.10 s.253
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• pp.942-949
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• 2006

A lumped model is proposed to predict liquid ejection characteristics of a thermally driven inkjet print head. The model is based on a two-dimensional heat conduction equation, an empirical pressure-temperature equation and a nonlinear hydraulic flow-pressure equation. It has been simulated through the construction of an equivalent R-C circuit, and subsequently analyzed using SIMULINK and a circuit simulation tool, PLECS. Using the model, heating and cooling characteristics of the head are predicted to be in agreement with the IR temperature measurements. The effects of the head geometry on the drop ejection are also analyzed using the nonlinear hydraulic model. The present model can be used as a design tool for a better design of thermal inkjet print heads.

• Journal of Korean Institute of Industrial Engineers
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• v.29 no.1
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• pp.65-77
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• 2003

This paper addresses FMS(Flexible Manufacturing System) loading problems with machine, tool and process flexibilities. When designing FMS planning, it is important to take account of these flexibilities for an efficient utilization of the resources. However, almost all the existing researches do not appropriately consider various flexibilities due to the problem complexity. This paper presents a new evolutionary algorithm to solve the FMS loading problems with machine, tool and process flexibilities. The algorithm is named a multi-level symbiotic evolutionary algorithm. The proposed algorithm is compared with the existing ones in terms of solution quality and convergence speed. The experimental results confirm the effectiveness of our approach.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.3
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• pp.200-205
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• 2000

This paper describes the structure modeling and operation characteristics of MFMIS(metal-ferroelectric-metal-insulator-semiconductor) device using the Tsuprem4 which is a semiconductor device tool by Avanti. MFMIS device is being studied for nonvolatile memory application at various semiconductor laboratory but it is difficult to fabricate and analyze MFMIS devices using the semiconductor simulation tool: Tsuprem4, medici and etc. So the new library and new materials parameters for adjusting ferroelectric material and platinum electrodes in the tools are studied. In this paper structural model and operation characteristics of MFMIS devices are measured, which can be easily adopted to analysis of MFMIS device for nonvolatile memory device application.

• Journal of the Semiconductor & Display Technology
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• v.17 no.2
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• pp.61-66
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• 2018

The objective of this research study is to investigate the optimal process parameters of electrical discharge machining (EDM) on SCM440 steel with copper as a tool electrode. The effect of various process parameters on machining performance is investigated in this study. Modern ED machinery is capable of machining geometrically complex or hard material components, that are precise and difficult-to-machine such as heat treated tool steels, composites, super alloys, ceramics, etc. This paper reports the results of an experimental investigation by Taguchi method carried out to study the effects of machining parameters on material surface roughness in electric discharge machining of SCM440 steel. To predict the optimal condition, the experiments are conducted by using Taguchi's L27 orthogonal array. The work material was ED machined with copper electrodes by varying the pulsed current, pulse on-time, voltage, servo speed and spark speed. Investigations indicate that the surface roughness is strongly depend on pulsed current.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.12
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• pp.1185-1191
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• 2011

The kinematic characteristics of cutting device significantly affects cutting performance in 2-dimensional elliptical vibration cutting(EVC) where the cutting tool cuts workpiece, traversing a micro-scale elliptical trajectory in a trochoidal motion. In this study, kinematical characteristics of EVC device constructed with two parallel stacked piezoelectric actuators were analytically modeled and compared with the experimental results. The EVC device was subjected to step and low-frequency(0.1 Hz) sinusoidal inputs to reveal only its kinematical displacement characteristics. Hysteresis in the motion of the device was observed in the thrust direction and distinctive skew of the major axis of the elliptical trajectory of the cutting tool was also noticed. Discrepancy in the voltage-to-displacement characteristics of the piezoelectric actuators was found to largely contribute to the skew of the major axis of the elliptical trajectory of the cutting tool. Analytical kinematical model predicted the cutting direction displacement within 10 % error in magnitude with no phase error, but in estimating the thrust direction displacement, it showed a $27^{\circ}$ of phase-lag compared with the measured displacement with no magnitude error.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.02a
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• pp.245-252
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• 2002

Ultrasonic machining technology has been developed over recent years for the manufacture of cost-effective and quality-assured precision parts for several industrial application such as optics, semiconductors, aerospace, and automobile. Ultrasonic machining process is an efficient and economical means of precision machining of ceramic materials. The process is non-thermal, non-chemical and non-electric md hardly creates changes to the mechanical properties of the brittle materials machined. This paper describes the characteristics of the micro-hole of $Al_2O_3$ by ultrasonic machining with tungsten carbide tool. The effects of various parameters of ultrasonic machining, including abrasives, machining force and pressure, on the material removal rate, hole quality, and tool wear presented and discussed. The ultrasonic Machining of micro-holes in ceramics has been under taken and the machining mechanism in the ultrasonic machining of ceramics based on the fracture-mechanics concept has been analyzed.