• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1517-1521
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• 2007

On this study, technical aspects were reviewed to drill a series of micro holes (${\phi}$0.10) over 200 within a few micron tolerance in diameter and position on the stainless steel material. Dedicated tools & jigs were designed and manufactured and optimum cutting conditions were found. On this micro hole drilling process, guide drill and step feeding were applied to help chip discharge, prevent drill breakage and finally improve the accuracy of positioning and roundness. The processing results indicated that most holes are distributed within a few micron tolerance in diameter and position intervals.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.932-936
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• 1997

In order to increase the productivity of electrical parts, manufacturing processes using progressive die have been widely used in the industry. If closed-die forging process may be included in the series of the forming process, however, there arise many problems in the die design, such as determination of blank size, feeding method and formability, etc. For the proper design of a process, a prediction of the process is requred to obtain many design parameters. In this work, three-dimensional rigid-plastic finite element analysis is carried out to simulate precision forging process. The forging process of STEM, a part of photo pick-up hologram device, is simulated with the two types of processes, open die forging and semi-closed die forging, respectively. Form the results of analyses, the forging processes can be predicted successfully, which enables to design appropriately the die and the process.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.3
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• pp.134-140
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• 2008

Micro electrochemical machining (ECM) is conducted on stainless steel 304 using non-toxic electrolyte of citric acid. Electrochemical dissolution region is minimized by applying a few hundred second duration pulses between the tungsten SPM tip and the work material. ECM characteristics according to citric acid concentration, feeding velocity and electric conditions such as pulse amplitude, pulse frequency, and offset voltage are investigated through a series of experiments. Micro holes of $60{\mu}m$ in diameter with the depth of $50{\mu}m$ and $90{\mu}m$ in diameter with the depth of $100{\mu}m$ are perforated. Square and circular micro cavities are also manufactured by electrochemical milling. This research can contribute to the development of safe and environmentally friendly micro ECM process.

• 제어로봇시스템학회:학술대회논문집
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• 1990.10a
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• pp.275-280
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• 1990

A neural network method is applied for recognizing the orientation o f individual parts being fed from a bowl feeder. The system is designed in such a way that a part can be discriminated and sorting according to every possible stable orientation without implementing any a mechanical tooling. The operation of the bowl feeder is based on a 2D image obtained from an array of fiber optic sensor located on the feeder track. The acquired binary image of a moving and vibrating part is used as input to a neural network which, in turn, determines t he orientation of the part. The main task of the neural network, here is to synthesize the appropriate internal discriminant functions for the part orientation using the part features. A series of the experiments reveals several promising points on performance. Since the operation of the feeder is highly programmable, it is well suited for feeding and sorting small parts prior to small batch assembly work.

• Journal of the Korean Institute of Telematics and Electronics
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• v.20 no.3
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• pp.40-44
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• 1983

A wide band quasi-log periodic microstrip antenna is designed using circular-disc microstrip patches as a basic radiator. The radiating elements are series-fed by a coplanar feeding network which consists of an open circuited feed line with a branch line connected to each radiating element. Experiment results show that the values of VSWR are less than 2.3 over the range of 2.72-3.43 GHz.

• Journal of Power Electronics
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• v.12 no.2
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• pp.357-362
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• 2012

In this paper, a power electronic converter which is composed of two converters - bidirectional AC/DC converter and Series Active Power Filter (SAPF), is discussed. Structural schemas and ways of operation of control systems of converters, which are used to eliminate non sinusoidal parts of the network source voltage, are presented. At the same time, the control used stabilizes the value of the voltage feeding the load. Taking in consideration the combined functions which the device executes, it may be called Unified Voltage Conditioner - UVC.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.3
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• pp.99-106
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• 2002

This study presents an approach to model the Electric Railway System with the common grounding based on the 8-port network model and to analyse traction power feeding system focused on the amplification of harmonic current. The entire system can be easily modeled by the combination of 8-port representation of each component in parallel and/or series. Through the research, 8-port network model which can be effectively applied to harmonic analysis is derived.

• Proceedings of the KIEE Conference
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• 1988.07a
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• pp.144-147
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• 1988

The current-fed DC-DC converter, which is known as the most stable DC-DC converter, has a two-winding reactor in series with the input. In this paper the new multi-output DC-DC converter circuit, in which the 2nd winding of the reactor is creating the 2nd output, while the 2nd winding is feeding the energy to input in the current-fed converter, is proposed. The steady state characteristics of the new circuit are clarified. And it is found that the maximum value exists in the 2nd output.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.05a
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• pp.295-300
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• 2001

The progressive die performs a series of fundamental sheet metal working, particularly this study regards to develop the center carrier feeding type die for thick sheet metal(SS41, 2.5mm) production that is a specific division. In order to prevent defect on the production, the analysis of production part, optimum design of strip process layout, die design and die making and tryout etc. are necessary. In this study, we designed and predicted a progressive die of multi stages by wide collected data base and computer aided method.

• Journal of the Korean Institute of Telematics and Electronics
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• v.20 no.4
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• pp.41-46
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• 1983

The current-fed DC-DC converter has only one energy storage reactor in series with the input for any number of outputs and is insensitive to transformer volt-second unbalance. It is considered that these properties of the converter are considerable advantages over other maltiple-output circuits. The steady-state and dynamic characteristic and stability for the current-fed DC-DC con-verter are analyzed in detail. The analysis is carried out by the state-space averaging method for the operation with the duty ratio less than 50% and is confirmed by the experiment. From the evaluation of stability it is identified that the stability of this converter is excellent as compared with that of the conventional buck type converter.