• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2006.09b
• /
• pp.975-976
• /
• 2006

The present paper is a parameter study of zinc flake production using a Simoloyer CM01 horizontal high energy rotary ball mill. The manufactured flakes have a dimension in thickness (t) < $1{\mu}m$ and diameters (d) 5-100 ${\mu}m$, consequently a ratio d/t up to 200. The flake geometry is mainly controlled by the variation of process parameters such as rotary speed of the rotor, ratio of powder/ball charge, load ratio of the system, process temperature, operating model and the quantity of process control agent (PCA). The Zn flakes were characterized by SEM, tap densitometry, laser diffraction and water coverage measurement.

• Progress in Superconductivity and Cryogenics
• /
• v.11 no.4
• /
• pp.29-32
• /
• 2009

This paper proposes the bus-tie application scheme of 154 kV SFCL (superconducting fault current limiter) in Korean power system. The reduced amount of fault current by SFCL is different by where the SFCL is installed. Therefore the inflow ratio of fault current (IRFC) is suggested to consider the effect of an SFCL's location. The proposed scheme was applied to the Korean Power System of 2010, and fault currents were calculated and analyzed with this coefficient. Simulations show that the location with high IRFC is adequate to install SFCL but more consideration of other things is required to determine the location and capacity of SFCL.

• Proceedings of the KWS Conference
• /
• 2002.10a
• /
• pp.38-42
• /
• 2002

HAZ(Heat Affected Zone of weldm ents) properties were investigated for a high nitrogen austenitic stainless steel with a chemical composition of Fe-0.02C-0.15Si-6.00Mn-10.0Ni-23.0Cr-2.00Mo-0.48N-0.14V. Thermal cycle of HAZ was simulated by the thermal cycle simulator (Gleeble 1500). The heat treatment was applied to the Charpy test size sample without notch under various peak temperatures and/or the holding times condition. V-notch Charpy test was performed at the temperature range of 273~77 K. Metallographic examination also was carried out by using optical microscopy, scanning electron microscopy and transmission electron microscopy. The simulated specimens revealed a slight embrittlement compared with the base materials. The impact toughness of the specimens deteriorated with the decreasing test temperature. The results from Charpy V-notch test, however, showed that significant degradation of absorbed energy caused by brittle fracture was not observed for the specimen tested in the test temperature range.

• Korean Journal of Radiology
• /
• v.23 no.7
• /
• pp.775-776
• /
• 2022

• Transactions of the Korean hydrogen and new energy society
• /
• v.12 no.2
• /
• pp.129-136
• /
• 2001

An investigation on the A/V(ampere/volt) gradient according to the concentration and the kind of solution in a electrolyzer is carried out to obtain the basic data on the ultrasonic application for the efficiency elevation of the hydrogen fuel production. KOH is selected as an electrolyte and concentrations are 0%, 10%, 20% and 30%. The solutions are city water, city water with nitrogen. distilled water and distilled water with nitrogen. The Electrochemical analyzer(BAS Co.) is used as a measuring device to observe the A/V gradient. And the limit of volt is from -3000mV to +3000mV. The 28kHz magnetic transducer is selected to give them ultrasonic forcing. In results, it is clarified that ultrasonic influences the A/V gradient in the electrolytic solution.

• Journal of the Korean Society of Safety
• /
• v.34 no.1
• /
• pp.1-7
• /
• 2019

Electromagnetic measurements of the power cable tunnel were conducted from August 10 to 20, 2018, in the ${\bigcirc}{\bigcirc}$ city underground utility tunnel. During this period, the average temperature was $31.89^{\circ}C$ and the humidity was 67.56% in power cable tunnel. As a result of the electromagnetic measurement, the highest electric field was 25.3 V/m and the magnetic flux density was $42.6{\mu}T$. The average electric field was 18.56 V/m and the magnetic flux density was $29.32{\mu}T$ in the power cable tunnel. As a result of comparison with the electric equipment technical standard, the electric field in the power cable tunnel was 0.5% of the electric equipment standard and 35.2% of the magnetic flux density. It's similar value that electric field is about robotic vacuum(15.53 V/m), and magnetic flux density is similar value about capsule- type coffee machine ($23.07{\mu}T$). The number of cable lines and the size of the electromagnetic waves were not proportional to each other through comparison of cable lines in the power cable tunnel. It was confirmed that 154 kV, rather than 22.9 kV, could have a greater influence on occupational.

• Proceedings of the National Institute of Ecology of the Republic of Korea
• /
• v.2 no.2
• /
• pp.101-107
• /
• 2021

The objective of this study was to analyze social wasps' urban distribution tendency based on 10 species found in two metropolitan cities (Busan and Daegu) of South Korea. There 10 species included six species (Vespa mandarinia, V. ducalis, V. crabro flavofasciata, Vespula koreensis koreensis, Parapolybia indica, and Polistes snelleni) of forest dwellers that inhabited urban main forests and satellite forests, two species (V. simillima simillima and V. analis parallela) of facultative dwellers that nested at diverse sites of urban areas with greater preference for urban forest, and two species (V. velutina nigrithorax and P. rothneyi koreanus) of urban dwellers that nested at almost all sites, including urban and forest areas. These urban dwellers were found to adapt well to an urban environment based on their far higher rate of urban nesting compared to facultative dwellers. When distribution tendencies of facultative dwellers and urban dwellers in Busan and Daegu were compared, a regular distribution was mostly observed in Busan with a dense forest network. For Daegu that lacked forest connectivity, the greatest distribution of species was found in the nearby urban forest. For Daegu, a city further away from forests, urban dwellers occurred far beyond forest sites compared to Busan with a dense forest network.

• Proceedings of the KIEE Conference
• /
• 2005.10a
• /
• pp.75-78
• /
• 2005

Fuel cell is remarkable for one of the clean energy recently. But in the fuel cell case, it has characteristics with low voltage and high current. Therefore, for using domestic power, it should be changed to the power source with commercial voltage and frequency. In this paper fuel cell simulator having electrical characteristics is designed and constructed instead of fuel cell stack. Voltage generated from fuel cell is from 39V to 72V dc and should be boosted to 400V dc for home appliances. A stand alone system including the inverter and DC/DC converter for the fuel cell is then proposed. Simulation result is used to support the analysis.

• Journal of Life Science
• /
• v.21 no.6
• /
• pp.845-850
• /
• 2011

Norovirus (NoV) causes major acute non-bacterial gastroenteritis in humans. NoV genus is a member of the family Caliciviridae, which is transmitted by contaminated food and water or from human to human. Many genotypes of genogroups I and II have been reported because of their high genetic diversity. To obtain molecular epidemiological information on gastroenteritis sporadic cases in Busan, Korea, we analyzed the nucleotide sequences of NoV strains detected during 2008~2010. We performed one step RT-PCR amplifying the open reading frame (ORF) 2 (capsid region) followed by semi-nested PCR. Fecal samples were collected from 4,071 acute gastroenteritis, and genotypes of the 421 positive samples were determined by sequence analysis. Based on partial sequence of capsid region, 7 NoV were categorized into genogroup I and 13 into genogroup II. Prevalent genotypes among gastroenteritis patients within Busan were GII.4, GI.6, GII.5 in 2008~2010. The results of this study will contribute to the currently available epidemiological data and improve public health and hygiene via development of diagnostic methods and sustainable surveillance.

• Journal of Sensor Science and Technology
• /
• v.3 no.1
• /
• pp.12-18
• /
• 1994

In this study, we fabricated and characterized a calorimetric-type flow sensing element using a micromachined silicon substrate. The cooling and heating effects resulted from the gas flow were measured by two temperature sensors located at both sides of the heating resistor, and the insulator diaphragm was employed as a substrate in order to improve thermal isolation. The sensor generated $0{\sim}378.4mV$ output signal under 10V bridge-applied voltage when the nitrogen gas was passed on the sensor surface having a mass flow rate of $0{\sim}0.25grs/min$, and reached to the stable operating condition within 10 seconds.