• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.1085-1088
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• 2001

The process of styrofoam pattern that has been used for material of press die pattern depends chiefly on handwork. Laser manufacturing system developed to increase precision and efficiency of process that is also able to convert the design easily. Applying the RP(rapid prototyping) concept reversely, the unnecessary part of section is vapored away by heat source of laser beam after converting 3-D CAD model into cross-sectional shape information. Laser beam is line-scanned in plane specimens to measure the depth and width of cut, surface roughness, cross-sectional shape as converting laser power, scanning speed, cutting gas pressure. With these basic data, plane surface, inclined surface, hole, outer contour trimming process is experimented and optimum condition are obtained. In plane and inclined surface experiments, 15W laser power and 50mm/s scanning speed make superior processing property and 30W, 10mm/s make processing efficiency increase in trimming process. With these results, simple patterns were manufactured and the possibility of applying laser manufacturing system to styrofoam pattern was convinced.

• Proceedings of the Korean Society of Laser Processing Conference
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• 2001.05a
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• pp.31-34
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• 2001

Laser cladding Processing allows rapid transfer of heat to the material being minimum conduction into base metal. The effects of CO$_2$ laser cladding with high powder were investigated. High viscosity bronze powder consists of bronze powder used at a high temperature. The material has a high viscosity So that it can be substrate. Therefore. Laser cladding can be processed on a curved or slope surface. CO$_2$ laser cladding was designed It consists of the high viscosity bronze powder the shielding gas system and the preheating system The high viscosity powder properly at 0.3g/s and 0.50g/s. Because of the metallic bond between bronze per the hardness of dilution layer was suddenly increased. Experimental as results viscosity mixed powder can be a useful cladding material.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.6
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• pp.185-199
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• 1994

This study has been performed to present a new automatic tool wear measurement by digital image processing. The purpose of this paper is to develop an automatic tool wear measuring system based on the image processing which can be applied to the quasi-real time measurement of the characteristics of insert tip in turning. Tool wear monitoring is one of the key-problems, for the development of control systems of modern unmanned factory which are not completely solved now. In oredr words at present complete qualitative and quantitative information on tool wear morphology is required, at least on the following aspects : flank wear, its dimensions and distribution on the maximum and mean values on VB pqrqmeter in the various zones of the wearland. crater wear, its main dimensions and values of KT parameters. This research has been performed to this technique made possible by designing a proper lighting system to the worn tool with following features : The flank wear is measured by observing the active cutting part from a proper direction and by lighting the wearland by a diffuser optic system. The crater wear is visualized by lighting the tool by a He-Ne gas laser system developed in this study. By means of this system it is research to evaluate classical parameters of tool wear and to have complete information about tool wear morphology.

• JSTS:Journal of Semiconductor Technology and Science
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• v.13 no.4
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• pp.395-401
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• 2013

In-situ optical emission spectroscopy (OES) is employed for leak detection in plasma etching system. A misprocessing is reported for significantly reduced silicon etch rate with chlorine gas, and OES is used as a supplementary sensor to analyze the gas phase species that reside in the process chamber. Potential cause of misprocessing reaches to chamber O-ring wear out, MFC leaks, and/or leak at gas delivery line, and experiments are performed to funnel down the potential of the cause. While monitoring the plasma chemistry of the process chamber using OES, the emission trace for nitrogen species is observed at the chlorine gas supply. No trace of nitrogen species is found in other than chlorine gas supply, and we found that the amount of chlorine gas is slightly fluctuating. We successfully found the root cause of the reported misprocessing which may jeopardize the quality of thin film processing. Based on a quantitative analysis of the amount of nitrogen observed in the chamber, we conclude that the source of the leak is the fitting of the chlorine mass flow controller with the amount of around 2-5 sccm.

• ETRI Journal
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• v.30 no.4
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• pp.516-525
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• 2008

This paper proposes a compact, energy-efficient, and smart gas sensor platform technology for ubiquitous sensor network (USN) applications. The compact design of the platform is realized by employing silicon-on-insulator (SOI) technology. The sensing element is fully integrated with SOI CMOS circuits for signal processing and communication. Also, the micro-hotplate operates at high temperatures with extremely low power consumption, which is important for USN applications. ZnO nanowires are synthesized onto the micro-hotplate by a simple hydrothermal process and are patterned by a lift-off to form the gas sensor. The sensor was operated at $200^{\circ}C$ and showed a good response to 100 ppb $NO_2$ gas.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.201-210
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• 2018

This paper proposes a new start-up method for a load commutated inverter (LCI) in a large synchronous gas-turbine generator. The initial rotor position for start-up torque is detected by the proposed initial angle detector, which consists of an integrator and a phase-locked loop. The initial rotor position is accurately detected within 150ms, and the angle difference between the real position and the detected position is less than 1%. The LCI system operates in two modes (forced commutation mode and natural commutation mode) according to operating speed range. The proposed controllers include a forced commutation controller for the low-speed range, a PI speed controller and a PI current controller, where the forced commutation controller is connected to the current controller in parallel. The current controller is modeled by Matlab/Simulink, where a six-pulse delay of the thyristor and a processing delay are considered by using a zero-order hold. The performance of the proposed start-up method is evaluated in Matlab/Psim at standstill and at low speed. To verify the feasibility of the method, a 5kVA LCI system prototype is implemented, and the proposed initial angle detector and the system performance are confirmed by experimental results from standstill to 900rpm.

• Journal of Fashion Business
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• v.22 no.6
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• pp.94-104
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• 2018

The objective of this study was to develop a wearable systems that protect users, based on sensors that are easy to use, from accidents caused by harmful gases in the operator's poor working environment or the risk of ultraviolet rays during outdoor activities. By developing smart wappen with Light Emitting Diode (LED) light alarm function including UV sensor and gas sensor and central processing unit, systems that are applied to daily wear and work clothes to explore the possibility of user-centered, harmful environment monitoring products in real time were proposed. Each sensor was applied to sportswear and work clothes and the wappen system consisted of lightweight and thin form as a whole. Wappen to cover the device had one sheet cover on the front and another cover from the inside to form a sandwich like formation. Wappen was made in the same form as regular clothes that doesn't damage the exterior then a removable wappen system was developed using Velcro and snap methods to enable the separation of device or the exchange of batteries. De-adhesion method can occur in two ways, from the outside and from the inside, so the design is selected depending on the application. This study shows the significance of the development of sensor-based smart clothing, in that it presented a universal model for users.

• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.1963-1966
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• 2004

An ultra wide band ultra-high frequency (UHF) signal processing module was designed for on-line UHF partial discharge (PD) monitoring systems for gas-insulated switchgears (GIS). Major advantage of the unit is an improved PD detection sensitivity through minimizing the effect of surrounding interference signals. The detection sensitivity of the unit was <-60 dBm that is sufficient to detect UHF PD signals as low as 1 pC. Precise detection of PD occurred in the GIS, due to internal defects, is possible by using the signal processing unit.

• Journal of the Korean Ceramic Society
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• v.51 no.2
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• pp.107-114
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• 2014

In the present work, we report a novel microstructure of scalenohedral calcite synthesized without any additives by a simple and ecofriendly carbonation process carried out in a liquid-gas system as well as the effects of experimental conditions on the crystal growth of the scalenohedral calcite phase. Various process parameters, pH, temperature, $Ca(OH)_2$ concentration, $CO_2$ flow rates, and the total volume concentration, were investigated to enhance the sensitivity of the process. The highest average length of the scalenohedral calcite was obtained at pH 6.0, temperature of $45^{\circ}C$, $Ca(OH)_2$ concentration of 0.2M, $CO_2$ flow rate of 80mL/min, and total volume of 1L. The synthesized calcite was characterized by XRD, SEM, and FTIR to identify the phases and surface morphology.

• Proceedings of the KIEE Conference
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• 2004.05b
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• pp.128-131
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• 2004

An ultra wide band ultra-high frequency (UHF) signal processing module was designed for on-line UHF partial discharge (PD) monitoring systems for gas-insulated switchgears (GIS). Major advantage of the unit is an improved PD detection sensitivity through minimizing the effect of surrounding interference signals. The detection sensitivity of the unit was <-60 dBm that is sufficient to detect UHF PD signals as low as 1 pC. Precise detection of PD occurred in the GIS, due to internal defects, is possible by using the signal processing unit.