• 소성∙가공
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• 제19권3호
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• pp.191-196
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• 2010

Tungsten-carbide as typical difficult-to-cut material has excellent mechanical properties such as high thermal resistivity, mechanical strength and chemical durability. However, it is next to impossible for tungsten-carbide to be fabricated the needed parts by cutting process. In this study, for establishing the micro fabrication method of tungsten-carbide for micro injection or compression molding core, the investigation on micro cutting characteristics of tungsten-carbide green part which is made by powder injection molding process and easy to cut relatively was performed. For this, micro endmilling experiments of tungsten-carbide green part were performed according to various cutting conditions. Finally, the wear trend of micro endmill and the appearance of micro rib according to feed-rate and cutting depth per step were analyzed through SEM images of micro cutting feature and microscope images of micro tools.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 춘계학술대회논문집
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• pp.355-358
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• 2003

Recently, micro forming process technology have been developed since the size of machine parts become the crucial factor for minimizing of products in general electronic products. Most small machine parts consist of gear and rotation axis and the wear by mechanical contact is known as the primary factor for life reduction of high precision machine part. Lots of studies for mechanical wear and friction have been reported and many researches of MEMS technology have been studied recently. But just few studies for wear of micro or milli sized machine part have teen implemented. In this research, the wear equation is suggested according to the contact shape of axial part in micro or milli sized machine part. And wear analysis model which can predict the magnitude of wear through this suggested equation with numerical analysis program.

• 대한기계학회논문집B
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• 제20권10호
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• pp.3361-3370
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• 1996

Micro-Macro approach is conducted for the mixture solidification to handle the closely linked phenomena of microscopic solute redistribution and macroscopic solidification behavior. For this purpose, present work combines the efficiency of mixture theory for macro part and the capability of microscopic analysis of two-phase model for micro part. The micro part of present study is verified by comparison with experiment of Al-4.9 mass% Cu alloy. The effect of back diffusion on the macroscopic variables such as temperature and liquid concentration, is appreciable. The effect, however, is considerable on the mixture concentration and eutectic fraction which are indices of macro and micro segregation, respectively. According to the diffusion time, the behavior near the cooling wall where relatively rapid solidification permits short solutal diffusion time, approaches Scheil equation limit and inner part approaches lever rule limit.

• 소성∙가공
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• 제13권3호
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• pp.273-278
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• 2004

This paper subscribes the measurement system that can position the target to measure by moving 2-axis stage, which is controlled by the data from image processing technique. The high resolution camera and lens are used in measurement of micro mechanical part, but the region of measurement is very small. It is necessary the re-positioning to measure several regions in one part. The system described in this paper has the accuracy with about $0.9\mu\textrm{m}$ resolution per one pixel and can be applied to measure micro mechanical part.

• Current Applied Physics
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• 제18권11호
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• pp.1368-1374
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• 2018

In this paper, forced vibration was used to regulate the droplet migration, fully recording the transient migration of droplets on a micro-textured substrate under the resonance frequency by a high-speed camera. The influence of resonance frequency and dynamic migration characteristics of droplets on the solid micro-texture surface under lateral vibration were researched. The experiment demonstrates that the driving force is caused by the difference between the left and right contact angles made the droplet oscillate and migrate, and as time t increases, the left and right contact points are periodically shifted and the amplitude of migration increases. Therefore, based on the droplet migration behavior and its force balance mechanism, a spring vibration model of migration behavior of the vibrating droplet micro unit was set up to predict the complete trajectory of its migration on a solid surface. The calculation results show that the theoretical displacement is less than the experimental displacement, and the longer the time, the larger the difference. Affected by the vibration, part of the droplet permeates through the micro-texture, resulting in the droplet losing height and the contact angle becoming smaller as well. While the other part of droplet overcomes the internal surface tension to migrate.

• Journal of Mechanical Science and Technology
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• 제20권9호
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• pp.1502-1513
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• 2006

This study analyzes the design and part load performance of a power generation system combining a micro gas turbine (MGT) and an organic Rankine cycle (ORC). Design performances of cycles adopting several different organic fluids are analyzed and compared with performance of the steam based cycle. All of the organic fluids recover greater MGT exhaust heat than the steam cycle (much lower stack temperature), but their bottoming cycle efficiencies are lower. R123 provides higher combined cycle efficiency than steam does. The efficiencies of the combined cycle with organic fluids are maximized when the turbine exhaust heat of the MGT is fully recovered at the MGT recuperator, whereas the efficiency of the combined cycle with steam shows an almost reverse trend. Since organic fluids have much higher density than steam, they allow more compact systems. The efficiency of the combined cycle, based on a MGT with 30 percent efficiency, can reach almost 40 percent. hlso, the part load operation of the combined system is analyzed. Two representative power control methods are considered and their performances are compared. The variable speed control of the MGT exhibits far better combined cycle part load efficiency than the fuel only control despite slightly lower bottoming cycle performance.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 심포지엄 논문집 정보 및 제어부문
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• pp.137-140
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• 2005

The electronic dispenser is composed of electronic part and mechanical part. Electronic part is consisted of input keypad, micro-controller, display module, and pump module. In this paper we designed micro-controller for electronic part. The micro-controller controls display module and pump module. The display module is composed by LCD device, and the pump module is composed by motor device. The micro-controller for an electronic dispenser is designed by VHDL. We used WX12864APl for the LCD device and SPS20 for the stepping motor. Also, the micro-controller is designed by Altera Quartus tool and verified with Agent 2000 Design-kit using APEX20K Device. In this paper, we present possibility to adopt of biotechnology field through designing of one-chip controller for an electronic dispenser.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.591-596
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• 2001

Micron-size mechanical devices are becoming more prevalent, both in commercial applications and in scientific inquiry. Within the last decade, a dramatic increase in research activities has taken place, mostly due to the rapidly expanding growth of applications in areas of MEMS(Micro-Electro-Mechanical Systems), bioengineering, chemical systems, and advanced energy systems. In this study, we have described the effects of vortex viscosity variation on the flowfields in a micro-slot between rotating surfaces of revolution using a micropolar fluid theory. In order to solve this problem, we have used boundary layer equations and applied non-zero values of the microrotation vector on the wall. The results are compared with the corresponding flow problems for Newtonian fluid. Results show that the coefficient $\delta$ controls the main part of velocity ${\upsilon}_x$ and the coefficient M controls the main part of microrotation component ${\Omega}_{\theta}$.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.907-910
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• 1997

With increasing the needs for micro and precision parts, micro machining technology has been studied to fabricate a small part with high density such as electronics, optics, communications, and medicine industry more than before. But there are many problems to be solved requiring a high-level technology. So this research presents the new method to fabricate a small part through applying chemical mechanical micro machining (C3M) for the Al wafer. Al(thickness I ,u m) was sputtered on the Si substrate. Al is widely used as a lightweight material. However form defect such as burr has a bad effect on products. To improve machinability of ductile material, oxide layer was formed on the surface of AI wafcr before grooving by chemical reaction with HN03(10wt%). And then workpieces were machined to compare conventional micro-machining process with newly suggested method at different machining condition such as load and feed rate. To evaluate whether or not the machinability was improved by the effect of chemical condition, such as the size, the width of grooves 'and burr generation were measured. Finally, it is confirmed that C3M is one of the feasible tools for micro machining with the aid of effect of the chemical reaction.

• 소성∙가공
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• 제15권8호
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• pp.621-627
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• 2006

Recently, micro-alloyed steels which could eliminate heat treatments after forging has been developed. These non heat-treated micro-alloyed steels have several advantages over the conventional quenched and tempered steel for cold forging. First of all, long components can be fabricated with a better dimensional accuracy since bending of long forged part after quenching treatment could be avoided. And it is possible to eliminate two energy consuming heat treatment steps, which are a spherodizing before forging and quenching/tempering after forging. Therefore, more cost effective and environment friendly process could be designed. However, there is non-uniform distribution of strain occurred across the forged part, since these non heat-treated micro-alloyed steel use strain hardening mechanism. In the present study, it was investigated how to lessen non-uniformity and increase strength together for cold forging when a baking heat treatment is applied in micro-alloyed steels. For this purpose, micro-alloyed steels developed by Se-A Besteel recently was used for the experiment.