Time filter

Source Type

Pohang, South Korea

Rahaman H.,Pohang Accelerator Laboratory | Nam J.W.,Pohang Accelerator Laboratory | Nam S.H.,Hankuk Academy of Foreign Studies | Frank K.,Texas Tech University
IEEE Transactions on Plasma Science | Year: 2010

It is our interest to design and develop a high-power pulser system employing an electrical discharge in a spark gap. The type of discharge generates short electric pulses capable of both the characteristics of a fast rise time and a high repetition rate. Such a switch pulser has wide applications in the industry. To generate the electrical discharge in the spark gap in an efficient manner is very important for the switching operation. The regime of the operation utilizes the residual plasma in the interpulse recovery of the spark gap to increase the repetition rate. Therefore, the mechanisms of the discharge in a controlled manner following the electrical breakdown of the spark gap, such as the plasma generation in the spark channel and the dielectric recovery process as well as the residual plasma in the post-spark-discharge period, are of great importance. The understanding of the type of the spark-gap discharge for the switching at a high repetition rate beyond 1 MHz has been the primary goal. The typical voltage and current ratings are below 1 kV and several amperes, respectively. In particular, this paper addresses the optimal set of several parameters, such as the spark-gap geometry, electrode gap distance, gas pressure, and gas type, in conjunction with a unique circuit scheme to drive the discharge in the controlled fashion. © 2010 IEEE.

Lee S.N.,Kookmin University | Shim H.J.,Hankuk Academy of Foreign Studies | Shim I.-B.,Kookmin University
Journal of Magnetics | Year: 2014

CoFe2O4(CFO)/BaTiO3(BTO)/CoFe2O4(CFO) multilayered thin films were deposited on Pt/TiO2/SiO2/Si substrates by the pulsed laser deposition (PLD) system with KrF excimer laser (λ = 248 nm). BTO, CFO, BTO/ CFO and CFO/BTO/CFO structured thin films were prepared and their crystal structures and microstructures, as well as their magnetic and magneto-electrical properties, were studied. The C-V characteristics of these multilayered thin films with different capacitor structures were obtained to confirm the change in their capacitances under a magnetic field. Finally, the capacitance of the CFO/BTO/CFO thin film as a function of bias voltage under an in-plane magnetic field of 1,000 Oe increased to 951.04 pF at 1 MHz, from 831.90 pF measured under no magnetic field, indicating 14.3% increase in magnetocapacitance. © The Korean Magnetics Society. All rights reserved.

Kim J.-H.,LG Corp | Kim J.-W.,Hankuk Academy of Foreign Studies
Quality and Reliability Engineering International | Year: 2016

The lifetime and the reliability of Blu-Ray Recordable media were estimated with an acceleration test varying the temperature and the relative humidity. Some brand of the media showed relatively long lifetime over 80 years, but another brand was immeasurable because the media was broken during the acceleration procedure. A strong dependence of the lifetime of the media on the brand was observed. Effect of the initial recording performance in terms of the random symbol error rate and the jitter on the reliability was analyzed. The random symbol error rate showed a strong correlation with the reliability of the Blu-Ray Recordable media. Copyright © 2014 John Wiley & Sons, Ltd.

Kwon S.Y.,Hankuk Academy of Foreign Studies
33rd Asian Conference on Remote Sensing 2012, ACRS 2012 | Year: 2012

This research was conducted to examine and assess the vulnerability of Korean urban areas to heavy rainfalls and propose a viable solution in preventing floods. The target of this research was Ansan of Gyeonggi Province, an urban area with Ansan and Hwajeong Streams and big river basins. To determine the status of Ansan's flood precaution, a simulation of heavy torrential rain was run on Ansan urban basins using the model CAMEL. The result was that Ansan is inadequately prepared for heavy rainfalls. Simulation showed that most of Ansan's downtown areas will flood during the heavy rain. From the simulation, a list of regions that are most vulnerable to flooding and attention has been compiled. To prevent further flooding in Ansan, this research tested scenarios with different flood preventative measures. After comparing different scenarios, it was discovered that reducing the impervious surfaces and adjusting water content and hydraulic conductivity of the soil show a significant decrease in the level of flooding.

The toxicity of Pinus densiflora (red pine) hydrodistillate, its 19 constituents and 28 structurally related compounds against early third-instar larvae of Aedes albopictus (Ae. albopictus), Aedes aegypti (Ae. aegypti) and Culex pipiens palles (Cx. p. pallens) was examined using direct-contact bioassays. The efficacy of active compounds was further evaluated in semi-field bioassays using field-collected larval Cx. p. pallens. Results were compared with those of two synthetic larvicides, temephos and fenthion. In laboratory bioassays, Pinus densiflora hydrodistillate was found to have 24 h LC50 values of 20.33, 21.01 and 22.36 mg/L against larval Ae. albopictus, Ae. aegypti and Cx. p. pallens respectively. Among the identified compounds, thymol, c5-3-carene and (+)-limonene exhibited the highest toxicity against all three mosquito species. These active compounds were found to be nearly equally effective in field trials as well. In vitro bioassays were conducted to examine the acetylcholinesterase (AChE) inhibitory activity of 10 selected compounds. Results showed that there is a noticeable correlation between larvicidal activity and AChE inhibitory activity. In light of global efforts to find alternatives for currently used insecticides against disease vector mosquitoes, Pinus densiflora hydrodistillate and its constituents merit further research as potential mosquito larvicides. © 2013 by the authors; licensee MDPI, Basel, Switzerland.

Discover hidden collaborations