• Corrosion Science and Technology
• /
• v.22 no.4
• /
• pp.242-251
• /
• 2023

The electrochemical corrosion behaviors of 304 stainless steels (STSs) with various coatings (organic coating and dry coating) were examined, and their applicability as bipolar plates in polymer electrolyte membrane fuel cells (PEMFCs) was validated. The results showed that the organic-coated samples had a significant decrease in anodic and cathodic current density compared to the uncoated sample. However, an increase in carbon black content in the organic coating or additional heat treatment at 700 ℃ resulted in a decrease in corrosion resistance. In addition, improvements in corrosion resistance achieved by adding TiO₂ powder to the organic coating were found to be limited. In contrast, dry coating with TiC and CrC exhibited higher corrosion potential, significantly lower current density, and reduced contact resistance compared to the organic coatings. Notably, the TiC-coated sample showed a comparatively lower current density and more stable behavior than the CrC-coated sample. Based on a series of experimental results, a thin TiC coating without defects is proposed as a promising surface treatment strategy for STS bipolar plates in PEMFC.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.67 no.3
• /
• pp.374-382
• /
• 2018

This paper has done a hardware-based approach to increase the modulation index in 3-phase inverters, unlike the conventional software algorithm-based approaches. The minimum required time to measure the currents in a three-phase inverters with shunt resistors has also been analyzed. By the analysis, the longest time in minimum required time is AD conversion time. To shorten the minimum required time, this paper proposed a sample-and-hold(S/H) circuit implemented at the inverter current signal output to retain the current signal. When the linear operation region of an inverter with S/H was compared with that without it, the modulation index was increased by 7.8 %. Inverters with S/H circuits can employ the traditional software algorithms, such as the voltage injection method or current restoration method, and it will yield further increase the modulation index.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.13 no.12
• /
• pp.983-988
• /
• 2000

The leadframe of thin plate fabricated by stamping method generates a lot of burr and stress in the processing surface because of the mold. The electropolishing equipment was produced in order to increase accuracy and surface roughness for 42%Ni-Fe leadframe. An electrolyte consisted of phosphoric acid, ethylene glycol and deionized water. Experiments were accomplished as polishing conditions were changed such as current density, polishing time, electrode gap and sample shape. The burr from the cutting was eliminated and surface characteristics of high flatness and high luster wre obtained after electropolishing. In addition, the electroplishing had good characteristic in 1.0 A current density and 4㎜ of electrode spaces, and it was affected by the composition of electrolyte and the sample shape.

• Progress in Superconductivity and Cryogenics
• /
• v.15 no.2
• /
• pp.44-47
• /
• 2013

Large AC loss from the second generation (2G) high temperature superconducting (HTS) wires has been one of the major bottlenecks in power applications with HTS materials. Moreover, the large power applications also require the large current capacity from the HTS wires, which makes them produce larger AC losses. In order to reduce the AC loss from the HTS conductors with large current capacity, an HTS compact cable with some striations on the superconducting layers has been proposed. In this paper, we prepared some sample HTS compact conductors with striations, and measured their magnetization loss from the external magnetic field. We also made some slits on the superconducting layer of the HTS wire by laser cutting to reduce the aspect ratio of the superconducting layers. It would make the low eddy current loss and magnetic decoupling. Finally, the magnetization losses of the sample HTS compact conductors were measured and analyzed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1992.11a
• /
• pp.63-66
• /
• 1992

Using an aromatic system, we made a ultra thin insulator through LB-method. We measured and wrote down afternating currant characteristics of ultraviolet rays extincting-spectrum and I.R extincting-spectrum. We surveyed the thickness of a film through X-ray diffracting method and certified about $4{\AA}$ by the layer. Measuring the characteristics of direct current voltage and electric current with this sample, we produced its conductivity and discovered that this sample had a god insulating performance. Addition to this, we measured the characteristics of voltage and electric current, and the temperature dependency of conductivity in a high voltage system and with these results tried to interpret a mechanism of conduction.

• Journal of Distribution Science
• /
• v.12 no.3
• /
• pp.33-41
• /
• 2014

Purpose - The purpose of this study was to predict the selection of independent auditors in the companies listed on the Tehran Stock Exchange (TSE) using a combination of PSO algorithm and CART. This study involves applied research. Design, approach and methodology - The population consisted of all the companies listed on TSE during the period 2005-2010, and the sample included 576 data specimens from 95 companies during six consecutive years. The independent variables in the study were the financial ratios of the sample companies, which were analyzed using two data mining techniques, namely, PSO algorithm and CART. Results - The results of this study showed that among the analyzed variables, total assets, current assets, audit fee, working capital, current ratio, debt ratio, solvency ratio, turnover, and capital were predictors of independent auditor selection. Conclusion - The current study is practically the first to focus on this topic in the specific context of Iran. In this regard, the study may be valuable for application in developing countries.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2006.06a
• /
• pp.501-502
• /
• 2006

In this paper, new and aging sample of MCCB and ELCB are investigated the main performance test such as short circuit test, mechanical and electrical endurance test, dielectric test and surge current test. The surface conditions of new and aging sample are analyzed by SEM, TGA and DSC. The ELCB occurred badness mainly in short circuit test and surge current test. The badness cause of short circuit test was confirmed due to imperfect contact of contact part.

• Progress in Superconductivity and Cryogenics
• /
• v.25 no.4
• /
• pp.40-44
• /
• 2023

For high-temperature superconducting power applications that need large current capacity, a large current conductor manufactured using multiple superconducting tape is required. Conductors being studied for large currents capacity such as CORC, TSTC, and RACC have advantages and disadvantages, and in order to use these conductors in coil form and apply them to AC power devices, research on magnetization loss occurring in superconductors due to external magnetic fields is essential. To accurately measure magnetization loss in a conductor that is twisted by stacking straight conductors like TSTC, the correlation between the measuring system and the shape of the sample must be clearly known to accurately measure the loss. In this paper, we will confirm the difference in magnetization loss measurement values according to the correlation between the length of the pickup coil and the twist pitch of the sample in CORC and TSTC shapes, and review considerations for accurate magnetization loss measurement from the results.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.24 no.4
• /
• pp.400-406
• /
• 2015

This study researched the structure of the source of an ion milling machine used to fabricate a scanning electron microscope (SEM) sample. An ion source is used to mill out samples of over 1 mm dimension using a broad ion beam to generate plasma between the anode and cathode using a permanent magnet. To mill the sample in the vacuum chamber, the ion source should be greater than 6 kV for a positive ion current over $200{\mu}A$. To discover the optimum operating conditions for the ion miller, the diameter of the extractor, anode shape, and strength of the permanent magnet were varied in the experiments. A silicon wafer was used as the sample. The sputter yield was measured on the milled surface, which was analyzed using the SEM. The wafer was milled by injecting 1 sccm of argon gas into the 0.5 mTorr vacuum chamber.

• Survey Research
• /
• v.10 no.1
• /
• pp.141-154
• /
• 2009

With the current sampling scheme, the sampling variance is getting larger in producing smaller regional statistics than the designed area, The larger sample size can make the variance reduced but the efficiency of sample survey lower. The desired confidence level of sampling survey can be obtained using the current sample scheme with the same sample size and administrative data. In this paper, the number of the unemployed of 5 regions in Daejon are estimated using small area estimation methods and the CV values in each estimation method is calculated and compared for their estimation efficiency as empirical study. Jackknife method is proposed to estimate the MSE of synthetic estimator and composite estimator more accurately.