• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.7
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• pp.20-28
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• 2009

This paper presents the design of zero current switching ZCS pulse frequency modulation type DC-DC converter for magnetron power supply. A magnetron serving as the microwave source in a microwave oven is driven by a switch mode power supply (SMPS). SMPSs have the advantages of improved efficiency, reduced size and weight, regulation and the ability to operate directly from the converter DC bus. The demands of the load system and the design of the power supply required to produce constant power at 4[kV]. A magnetron power supply requires the ability to limit the load current under short circuit conditions. The current source series resonant converter is a circuit configuration which can achieve this. The main features of the proposed converter are an inherent protection against a short circuit at the output, a high voltage gain and zero current switching over a large range of output power. These characteristics make it a viable choice for the implementation of a high voltage magnetron power supply.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.6
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• pp.129-134
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• 2001

One of the most important purposes in the design of machines and structures is to produce the most light products of the lowest price with satisfying function and performance. In this study, a scheme of design optimization for the weight down of vehicle body structure is presented. Design sensitivity of vehicle body structure is investigated and design optimization is performed to get weight down with the allowable stiffness of body in white. Stress, deformation and natural frequencies are the constraint of the optimization.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.2
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• pp.89-96
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• 2015

This paper presents a high efficiency, PSM/DCM/CCM triple mode boost DC-DC converter for mobile application. This device operates at Pulse-Skipping Mode(PSM) when it enters light load, and otherwise operate the operating frequency of 1.4MHz with Pulse-Width Modulation(PWM) mode. Especially in order to improve the efficiency during the Discontinuous-Conduction Mode(DCM) operation period, the reverse current prevention circuit and oscillations caused by the inductor and the parasitic capacitor to prevent the Ringing killer circuit is added. The input voltage of the boost converter ranges from 2.5V ~ 4.2V and it generates the output of 4.8V. The measurement results show that the boost converter provides a peak efficiency of 92% on CCM and 87% on DCM. And an efficiency-improving PWM operation raises the efficiency drop because of transition from PWM to PFM. The converter has been fabricated with a 0.18um Dongbu BCDMOS technology.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.11
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• pp.199-204
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• 2012

The study for developments and economics about the energies from the global warming is very active. For the effective saving and the spanning of the life extension about the 19% rates for the illumination system spending power about the whole electric energies, we proposed the new type of the current control method using a mixing system of the frequency modulation together with the pulse width modulation for the half-bridge power instrument. And we proved the excellence and the stability for our suggested system and analyzed the characteristics.

• Journal of the Semiconductor & Display Technology
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• v.4 no.1 s.10
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• pp.9-16
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• 2005

In this paper, with loosely coupled transformer Relies-parallel resonant type DC/DC converter is analyzed and adopted to the power source of a TFLM(Transverse Flux Linear Motor). To get more efficient operating mode of the series-parallel resonant type DC/DC converter, theoretical analysis using normalized parameters are accepted. The analysis includes a specially made ferrite transformer with two separately wound half cores in order to evaluate analytically and experimentally the changes in magnetizing the leakage fluxes and inductances caused by the distance between the halves. The proposed converter must be operated in switching Pattern III among the three switching patterns for the Zero Voltage Switching operation. According to Pulse Frequency Modulation(PFM) control method, the output voltage of the proposed circuit can be controlled. The results of the theoretical development are compared with practical measurements from a prototype system.

• Journal of the Korean Vacuum Society
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• v.15 no.2
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• pp.173-179
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• 2006

We have investigated structural and electrical properties of $PbZr_{0.3}Ti_{0.7}O_{3}$ (PZT) thin films deposited by pulsed laser deposition methods. PZT thin films have been deposited on $LaMnO_3$ (LMO) bottom electrodes with $LaAlO_3$ (LAO) substrates during different deposition times. High-resolution x-ray diffraction data have shown that all the PZT films and bottom electrodes are highly oriented. The thickness of each film is determined by field-emission scanning electron microscope. We have also observed root mean square roughness by using atomic force microscopy mode, and local polarization distribution and retention behavior of a ferroelectric domain by using piezoelectric force microscopy mode. A PZT/LMO structure has shown good ferroelectric and retention properties as the media for nano-storage devices.

• Journal of dental hygiene science
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• v.9 no.4
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• pp.405-412
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• 2009

The purpose of this study investigated the effect of Au coating on adhesion between porcelain matrix and metal substructure interface. Titanium, Ni-Cr alloy and Co-Cr alloy are well known as proper metal for the dental restorations. The success of a porcelain fused to metal (PFM) restoration depends upon the quality of the porcelain-metal bond. However, adhesion between dental alloys and porcelain is related to diffusion of oxygen during ceramic firing. The excessive oxidized layers make hard adhesion between dental alloy and ceramic. Ni-Cr and Co-Cr specimens were divided into test and a control group and Titanium specimens were divided into three test groups and a control group. Each group had 20 specimens. The adhesion characteristics of porcelain and metal with Au coating layer and without Au coating layer were observed with scanning electron microscopy(SEM). The adhesion was evaluated by a biaxial flexure test and volume fraction of adherent porcelain was determined by SEM/EDS analysis. Result of this study suggest that Au coating layer is effective barrier to diffuse oxide layer completely protect non-precious alloys from oxidation during the porcelain firing. The SEM photomicrographs of cross-section specimens showed a smooth interface between Au coating layer and metals and porcelain which suggested proper chemical bonding, and no gap, porosity were observed. The mode of failure was mainly adhesive for Ti tested specimens, but mixed failures with adhesive and cohesive were observed in Ni-Cr and Co-Cr specimens. The adhesion between non-precious metals and porcelain would not be improved by Au coating agent. However, It is suggested that the continuous study is required further investigation and development.

• Nuclear Engineering and Technology
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• v.55 no.6
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• pp.2139-2146
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• 2023

During reactor operation, the divertor must withstand unprecedented simultaneous high heat fluxes and high-energy neutron irradiation. The extremely severe service environment of the divertor imposes a huge challenge to the bonding quality of divertor joints, i.e., the joints must withstand thermal, mechanical and neutron loads, as well as cyclic mode of operation. In this paper, potassium-doped tungsten (KW) is selected as the plasma facing material (PFM), oxygen-free copper (OFC) as the interlayer, oxide dispersion strengthened copper (ODS-Cu) alloy as the heat sink material, and reduced activation ferritic/martensitic (RAFM) steel as the structural material. In this study, a vacuum brazing technology is proposed and optimized to bond Cu and ODS-Cu alloy with the silver-free brazing material CuSnTi. The most appropriate brazing parameters are a brazing temperature of 940 ℃ and a holding time of 15 min. High-quality bonding interfaces have been successfully obtained by vacuum brazing technology, and the average shear strength of the as-obtained KW/Cu and ODS-Cu alloy joints is ~268 MPa. And a fabrication route for manufacturing the flat-type divertor target based on brazing technology is set. For evaluating the reliability of the fabrication technologies under the reactor relevant condition, the high heat flux test at 20 MW/m² for the as-manufactured flat-type KW/Cu/ODS-Cu/RAFM mockup is carried out by using the Electron-beam Material testing Scenario (EMS-60) with water cooling. This paper reports the improved vacuum brazing technology to connect Cu to ODS-Cu alloy and summarizes the production route, high heat flux (HHF) test, the pre and post non-destructive examination, and the surface results of the flat-type KW/Cu/ODS-Cu/RAFM mockup after the HHF test. The test results demonstrate that the mockup manufactured according to the fabrication route still have structural and interfacial integrity under cyclic high heat loads.