• Transactions of the Korean Society of Mechanical Engineers
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• v.7 no.1
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• pp.28-35
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• 1983

Quantitative analysis have been carried out on the micro-cracks on the surface and into the depth of unnotched smooth mild steel specimen under cyclic stains by rotating bending fatigue tests. Some of the results are; (1) Cracks initiate at the early stage of fatigue life N$_{I}$/ N$_{f}$=10 to 20%, and propagate during the rest of fatigue life. (2) Coalescence of highly crowded small fatigue cracks of random distribution seems to induce the final fracture at higher stress level. (3) The curves of crack initiation and the equal crack length on the graph of stress versus number of cycles are parallel to the S-N curve. (3) The curves of crack initiation and the equal crack length on the graph of stress versus number of cycles are parallel to the S-N curve. (4) The distributions of micro-surface crack length and depth show the composite Weibull distributions which are approximated to two straight lines separated by the value of transient region between stage I and stage II crack.k.k.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.3
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• pp.158-164
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• 2000

In recent year, desire and request fer micro automation are growing rapidly covering the whole range of the industry. This has been caused mainly by request of more accurate manufacturing process due to a higher density of integrated circuits in semiconductor industry. This paper presents a six d.o.f fine motion stage using magnetic levitation technique, which is one of actuating techniques that have the potential for achieving such a micro motion. There is no limit in motion resolution theoretically that the magnetically levitated part over a fixed stator can realize. In addition, it Is possible to manipulate the position and the force of the moving part at the same time. Then, the magnetic levitation technique is chosen into the actuating method. However, we discuss issues of design, kinematics, dynamics, and control of the proposed system. And a few experimental results fur step input are given.

• Transactions of Materials Processing
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• v.13 no.3
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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.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.04a
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• pp.422-428
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• 2002

In this study, actuator, sensor, guide, power transmission element and control method are considered for ultra-precision positioning apparatus. Through previous process, single plane X-Y stage with ultra-precision positioning is manufactured. Global stage for the purpose of materialization with robust system, is combined by using AC servo motor and ball screw and rolling guide. And ultra-precision positioning system is developed by micro stage with elastic hinge type and piezo element. global servo and micro servo for the purpose of materialization positioning accuracy with nm(nanometer) are controlled simultaneously by using incremental encoder and laser interferometer as displacement measurement sensor. Through previous process, ultra-precision positioning system (100mm stroke and ${\pm}$ 10nm positioning accuracy) with single plane X-Y stage are materialized.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.11 no.5
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• pp.65-72
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• 2002

In this study, actuator, sensor, guide, power transmission element and control method are considered for ultra-precision positioning apparatus. Through previous process, single plane X-Y stage with ultra-precision positioning is manufactured. Global stage for the purpose of materialization with robust system, is combined by using AC servo motor and ball screw and rolling guide. And ultra-precision positioning system is developed by micro stage with elastic hinge type and piezo element. global servo and micro servo for the purpose of materialization positioning accuracy with nm(nanometer) are controlled simultaneously by using incremental encoder and laser interferometer as displacement measurement sensor. Through previous process, ultra-precision positioning system(100mm stroke and $\pm$ l0nm positioning accuracy) with single plane X-Y stage are materialized.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.668-671
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• 2000

An aerostatic stage has frictionless behavior, so it has a advantage of investigation into driven mechanism such as ballscrew. In this paper, fur investigating positioning characteristic of ballscrew and feedback device in aerostatic stage, we compare the positioning characteristic between full-closed(laser scale) and semi-closed(encoder) system. Experimental results show that the aerostatic stage has a 10nm micro step response and repeatability is improved up to 1.00${\mu}{\textrm}{m}$ using laser scale. We confirm the laser scale compensate error motion of ballscrew, so acquire 1.12${\mu}{\textrm}{m}$ positioning accuracy.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.10 no.4
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• pp.39-47
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• 2015

"Series A Crunch"problem has become worse off as funding gap between angel seed investment and traditional VC Series A investment is getting the larger due to big boom over early startup investment both in Korea and US. The strong needs for new concept of fund alternative such as bridge fund is outstanding to fill up the funding gap in the early stage of venture investment. This research is brought to define the concept of 'Series A Crunch' problem and to diagnose its causes, eventually, popping up 'the concept of Micro VC Fund' to come up with this problem in Korea. Also, this paper suggests the policy alternatives to introduce Mivro VC Fund and accommodate its successful performance.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.1 s.190
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• pp.47-56
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• 2007

Recently, demands on mechanical micro machining technology have been increased in manufacturing of micro-scale precision shapes and parts. The main purpose of this research is to verify the accuracy and cost efficiency of the mechanical micro machining. In order to measure the precision and feasibility of mechanical micro machining, various micro features were machined. Aluminum molds were machined by a 3-axis micro stage in order to fabricate microchips with $200{\mu}m$ wide channel for capillary electrophoresis, then the same geometry of microchip was made by injection molding. To evaluate the cost efficiency of various micro manufacturing processes, cost estimation for mechanical micro machining was conducted, and actual costs of microchips fabricated by mechanical micro machining, injection molding, and MEMS (Micro electro mechanical system) were compared.

• Journal of the Economic Geographical Society of Korea
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• v.23 no.1
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• pp.35-55
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• 2020

The support policy of Micro manufacturers clusters should reflect the regional characteristics of Micro manufacturers clusters, but only similar policies are proposed based on the normal collection of information from related companies. Since the regional characteristics of Micro manufacturers clusters are not understood, they are not reflected in the support policy. Therefore, this study analyzed the characteristics of Micro manufacturers clusters as the formation factors of localization, networking/embeddedness, and innovation synergy/collective learning which are the characteristics of clusters, and applied the development stage based on the analyzed formation factors. Since regional characteristics may be different in the same industry, Micro manufacturers clusters in Changsin and Jangwi, which are representative clusters of apparel sewing industry in Seoul, were compared and studied in terms of regional characteristics and developmental stages. As a result of analyzing the characteristics of Apparel Sewing Micro manufacturers clusters, clusters of peers were found to be higher in Changsin than in Jangwi in localization. However, in the synergy and group learning, the Changsin area was mainly centered on designers and the Jangwi area was centered on Micro manufacturers, the Changsin area was active while the Jangwi area was passive in participating in fairs and seminars, and in sample and production. As a result of examining the two formation factors, the development stage of Micro manufacturers clusters in the two regions is progressing beyond the industrial district in the case of Micro manufacturers clusters in Changsin apparel sewing, and the Micro manufacturers clusters in the Jangwi apparel sewing are analyzed to stay in the industrial district. Innovative and long-established garment sewing clusters suggest that the government's support policy needs to reflect the characteristics and development stages of the two regions for sustainable growth.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.10a
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• pp.543-544
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• 2006