• Proceedings of the KIEE Conference
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• 2000.11d
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• pp.754-757
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• 2000

Si PIN diodes are subject to be damaged from the exposure of fast neutron by displacement of Si lattice structure. The defects are effective recombination centers for carriers which migrate through the base region of the PIN diode when forward voltage is applied. It causes an increase in current and a decrease in resistivity of the diode. This paper presents the development of a neutron sensor based on displacement damage effect. PIN diodes having various structures were made by micro-fabrication process, and neutron beam test was performed to identify neutron damage effect to the diode. From a result of the test, it was shown that the forward voltage drop of the diode, at a constant current, has good linearity for neutron dosage. Also it was found that the newton dosage can be measured by the pin diode neutron dosimeter with constant current power.

• Proceedings of the KIEE Conference
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• 2001.07d
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• pp.2522-2525
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• 2001

Si PIN diodes are subject to be damaged from the exposure of fast neutron by displacement of Si lattice structure. The defects are effective recombination centers for carriers which migrate through the base region of the PIN diode when forward voltage is applied. It causes an increase in current and a decrease in resistivity of the diode. This paper presents the development of a neutron sensor based on displacement damage effect. PIN diodes having various structures were made bymicro-fabrication process, and neutron beam test was performed to identify neutron damage effect to the diode. From a result of the test, it was shown that the forward voltage drop of the diode, at a constant current, has good linearity for neutron dosage. Also it was found that the newton dosage can be measured by the pin diode neutron dosimeter with constant current power.

• Progress in Superconductivity and Cryogenics
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• v.23 no.4
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• pp.35-38
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• 2021

Conventional direct current (DC) rotating machines are usually used for crane and press machine using high torque in metal and steel industries, because of a constant output power along variable rotating speed. A general DC motor with permanent field magnets could not increase a magnetic flux density at a gap between armature coils and field magnets. However, a superconducting DC motor has field magnets composed with high temperature superconducting (HTS) coils and it could increase the magnetic flux density at the gap to over 10 times than those of a general DC motor by control the excitation current into HTS coils. The superconducting DC motor could be operated with extremely high torque and constant output power at a low rotational speed. In this paper, a 500 W superconducting DC rotating machine was conceptually designed with a LN₂ (Liquid Nitrogen) cooling method and the operation characteristics results of HTS field magnets were presented. The two no-insulation HTS magnets for a 500 W superconducting DC rotating machine were fabricated. The excitation current for the HTS magnets could be controlled from 0 to 40 A. This test results will be available to design large-sized HTS magnets for a number of hundred kW class superconducting DC rotating machine under LN₂ cooling system.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.7
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• pp.675-682
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• 2009

Instead of direct driving like BLDC, the induction principle is adopted as a driving one for planar stage. The stage composed of four linear induction motors put in square type is activated by two-axial forces; low-frequency attractive force and thrust force of the linear induction motors. Here, the modified vector control whose new inputs are q-axis current and dc current biased to three phase current instead of d-axis current or flux current is applied extensively to overall motion of the stage. For the developed system, the precision step test and the constant velocity test are tried to guarantee its feasibility for TFT-LCD pattern inspection. However, to exclude a discontinuity due to phase shift and minimize a force ripple synchronized with the command frequency, the initial system is revised to the antagonistic structure over the full degree of freedom. Concretely describing, the porous air bearings guide an air-gapping of the stage up and down and a pair of liner induction motors instead of single motor are activated in the opposite direction each other. The performances of the above systems are compared from trapezoid tracking test and sinusoidal test.

• KIEE International Transactions on Electrophysics and Applications
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• v.4C no.3
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• pp.96-100
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• 2004

The Nd： YAG laser is commonly used throughout many fields such as accurate material processing, IC marking, semiconductor annealing, medical operation devices, etc., due to the fact that it has good thermal and mechanical properties and is easy to maintain. In materials processing, it is essential to vary the laser power density for specific materials. The laser power density can be mainly controlled by the current pulse width and pulse repetition rate. It is important to control the laser energy in those fields using a pulsed laser. In this paper we propose the constant-frequency current resonant half-bridge converter and monitoring of capacitor charging voltage. This laser power supply is designed and fabricated to have less switching loss, compact size, isolation with primary and secondary transformers, and detection of capacitor charging voltage. Also, the output stabilization characteristics of this Nd： YAG laser system are investigated. The test results are described as a function of laser output energy and flashlamp arc discharging constant. At the energy storage capacitor charges constant voltage, the laser output power is 2.3％ error range in 600[V].

• Transactions of the Korean hydrogen and new energy society
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• v.25 no.5
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• pp.516-524
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• 2014

Proper discharge of nitrogen gas and water condensate is required in a conventional fuel cell system for performance, stability and durability of fuel cell stacks. Present study covers the development of integrated unit and its functioning logic for simultaneous nitrogen gas purge and water condensate drainage in a fuel cell vehicle system. Configuration of condensate drainage pipe, purge valve and level sensor is considered and optimized in physical integration. As a key factor, discharge time is considered and optimized based on the test result of constant-current operation with various operating temperature in logic development. Consequently, derived optimal values are applied and verified in actual vehicle drive mode test. Increase of system design flexibility, weight reduction and cost reduction are anticipated with this study. Additional study for physical and logical improvement is currently being implemented.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1963-1965
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• 2000

This paper deals with a problem of detecting the inner corrosion of the ACSR(Aluminum Conductor Steel Reinforced) power lines using a detector which consists of an ECT(Eddy Current Test) sensor, a constant current service, a signal processing unit, and a RF transmitter/receiver unit. The detector runs on the ACSR transmission line and inspects the corrosion of the conductor using the technic of the nondestructive eddy current test. The experimental result shows this detector can efficiently find the zinc loss in ACSR power lines.

• International Journal of Automotive Technology
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• v.8 no.6
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• pp.723-730
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• 2007

The typical design of automotive driveshafts generally utilizes Constant Velocity(CV) joints as a solution to NVH. CV joints are an integral part of vehicles and significantly affect steering, suspension, and vehicle vibration comfort levels. Thus, CV joints have been favored over universal joints due to the constant velocity torque transfer and plunging capability. Although CV joints are common in vehicle applications, current research works on modeling CV joint friction and assumes constant empirical friction coefficient values. However, such models are long known to be inaccurate, especially under dynamic conditions, which is the case for CV joints. In this paper, an instrumented advanced CV joint friction apparatus was developed to measure the internal friction behavior of CV joints using actual tripod-type joint assemblies. The setup is capable of measuring key performance of friction under different realistic operating conditions of oscillatory speeds, torque and joint installation angles. The apparatus incorporates a custom-installed triaxial force sensor inside of the joint to measure the internal CV joint forces(including friction). Using the designed test setup, the intrinsic interfacial parameters of CV joints were investigated in order to understand their contact and friction mechanisms. The results provide a better understanding of CV joint friction characteristics in developing improved automotive driveshafts.

• Journal of the Korean institute of surface engineering
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• v.49 no.5
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• pp.423-430
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• 2016

In this study, we investigated the corrosion damage characteristics of steel for offshore wind turbine tower substructure using an accelerated electrochemical test. The galvanostatic corrosion test method was employed with a conventional 3 electrode cell in natural sea water, and the steel specimen was served as a working electrode to induce corrosion in an accelerated manner. Surface and cross-sectional image of the damaged area were obtained by optical microscope and scanning electron microscope. The weight of the specimens was measured to determine the gravimetric change before and after corrosion test. The result revealed that the steel tended to suffer uniform corrosion rather than localized corrosion due to active dissolution reaction under the constant current regime. With increasing galvanostatic current density, the damage depth and surface roughness of surface was increased, showing approximately 25 times difference in damage depth between the lowest current density ($1mA/cm^2$) and the highest current density ($200mA/cm^2$). The gravimetric observation showed that the weight loss was proportionally increased with increment of current density that has 75 times different according by experimental conditions. Consequently, uniform corrosion of the steel specimen was conveniently induced by the electrochemically accelerated corrosion technique, and it was possible to control the extent of the corrosion damage by varying the current density.

• 한국항공운항학회:학술대회논문집
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• 2015.11a
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• pp.175-178
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• 2015

A-SMGCS(Advanced Surface Movement Guidance and Control system)의 ILCMS(Individual Light Control&Monitoring System) 고도화의 목표를 달성하기 위한 일체형 CCR(CONSTANT CURRENT REGULATOR)을 제작하고, 개발되어진 LCU(LOCAL CONTROL UNIT)모듈 및 LK CCR FILTER가 일체형 CCR의 실제 동작에 끼치는 영향과 일체형 CCR의 동작 상태를 실험을 통해 결과를 표현 하였다.