• Transactions of Materials Processing
• /
• v.13 no.2
• /
• pp.174-179
• /
• 2004

The effect of grain refinement on the plastic deformation behaviour of nanocrystalline metallic materials is investigated. A phase mixture model in which a single phase material is considered as an effectively two-phase one is discussed. A distinctive feature of the model is that grain boundaries are treated as a separate phase deforming by a diffusion mechanism. For the grain interior phase two concurrent mechanisms are considered: dislocation glide and mass transfer by diffusion. The proposed constitutive model was implemented into a finite element code (DEFORM) using a semicoupled approach. The finite element method was applied to simulating room temperature tensile deformation of Cu down to the nanoscale grain size in order to investigate the pre- and post-necking behaviour.

• Journal of the Korean Society of Visualization
• /
• v.5 no.2
• /
• pp.48-55
• /
• 2007

Flow structure inside a refrigerating compartment of a scale-down display cooler model was investigated experimentally by using PIV (particle image velocimetry) method, a reliable velocity field measurement technique, in the present study. In addition, we also carried out flow visualization regarding flow structure and particle movement inside a display cooler by using a tracer method. As a result, the mean velocity field measurement shows a large scale vortical flow structure inside a refrigerating compartment due to strong entrainment flow, going through a base plate open gaps.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2015.11a
• /
• pp.332-332
• /
• 2015

Block Copolymer lithography는 deep nano-scale device 제작을 위한 기존의 top-down방식의 photo-lithography를 대체할만한 기술로 많은 연구가 진행되고 있다. polystyrene(PS)/poly-methyl methacrylate (PMMA)로 구성된 BCP의 nano-scale PS mask는 일반적인 플라즈마 공정에 쉽게 damage를 입는다. 중성빔 식각을 이용하여 식각 공정 중 발생하는 BCP의 degradation을 감소시키고, 비등방성 식각 profile을 얻을 수 있으며 sidewall roughness(SWR)와 sidewall angle(SWA)가 향상되는 것을 알 수 있었다.

• Journal of Information Display
• /
• v.5 no.1
• /
• pp.34-40
• /
• 2004

Time resolved infrared IR absorption spectroscopy is carried out to investigate the dynamics of electric field induced reorientation of the biphenyl molecular core and alkyl tail sub-fragments of the nematic liquid crystal 5CB (4-pentyl-4-cyano-biphenyl). The planar to homeotropic transition for high pre-tilt planar aligned cells, is studied for switching times ranging from 200 ${\mu}sec$ down to 80 ${\mu}sec$, the latter a factor of 1000 times faster than any previous nematic IR study. The reorientation rates of the core and tail are found to be the same to within experimental error and scale inversely with applied field squared, as expected for the balance of field and viscous torques. Thus any molecular conformation change during switching must relax on a shorter time scale. A simple model shows that no substantial differences exist between the reorientational dynamics of the tails and cores on the time scales longer than on the order of 10 ${\mu}s$.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.267-267
• /
• 2013

Band engineering of a nanowire is related to the question what is the minimum size of a nanowire-based device. At the subnanometer scale, there has been a long standing problem whether it is possible to both control an energy band of an isolated nanowire by a dopant and measure it using angle-resolved photoemission spectroscopy (ARPES). This is because an extra atom in the subnanometer wire plays as a defect rather than a dopant and it is challenging to assemble isolated subnanometer wires into an array for an ARPES measurement. We demonstrate that only one of multiple metallic subnanometer wires canbe controlled electronically by a dopant maintaining the whole metallic bands of other wires, which was observed directly by ARPES. Here,the multiple metallic subnanometer wires were produced on a stepped Si(111) surface by a self-assembly method. The selective band engineering proves that the selectively-controlled metallic wire is nearly isolated electronically from other metallic wires and an electronic structure controlcan be realized down to subnanometer scale.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.49 no.11
• /
• pp.616-621
• /
• 2000

This paper deals with the multiresolution analysis of wavelet transform for partial discharge(PD). Test arrangement is based on the needle-plane electrode system and applied AC high voltage. The measured PD signal was decomposed into "approximations" and "details". The approximation are the high scale, low-frequency components of the PD signal. The details are the low-scale, high frequency components. The decomposition process are iterated to 3 level, with successive approximation being decomposed in turn, so that PD signal is broken down into many lower-resolution components. Through the procedure of signal wavelet transform, signal noise extraction and signal reconstruction, the signal is analyzed to determine the magnitude of PD.

• Journal of the Korean Institute of Navigation
• /
• v.15 no.3
• /
• pp.73-97
• /
• 1991

The analysis and investigation are described for White's[2] equations compared to the equations of Runeburg[3] and Milano[5] for continuous icebreaking mode, Tunik[8-1] and Ghoneim[8-2] for ramming icebreaking mode. Calculation results compare reasonably well with published model-scale and full-scale icebreaker data by Baker[1] and Dick[11]. During continuous and ramming mode operation, using characteristics of an incebreaker, down ward force on ice and standard ice thickness broken are predicted. Additionally draft, trim and extraction difficulty are also predicted. The bow part line of an icebreakin $g^{ply}$ vessel is designed aiming to maximize the ice breaking capabiltiy as following conditions-low bow angle[20 degrees] at designed waterline, small spread angle complement [6 degrees] at designed waterline, small spread angle complement [6 degrees] and high propeller thrust [220tons]. with plow, two reamers and wave type bumper.

• Convergence Security Journal
• /
• v.3 no.2
• /
• pp.85-97
• /
• 2003

At the end of last January, 2003, a domestic top-level domain name server (DNS) shut down the server and it caused the wired and wireless internet services to be completely paralyzed in the aftermath of a virus attack incurring a various range of losses nationwide. The main reason of this event is the lack of our awareness of cyber security. In particular, in the small-scale network, there are few security administrators and no operating devices to protect information as well. Under this circumstance, using ESM center to service real-time security supervision and correspondence for network, it can be one option. However, due to the economic efficiency, most of security systems have been being developed focusing on the large-scale network first. Therefore, ESM centers which inspect security state of network concentrate on IDC or large-scale network services. This dissertation studies economical ESM service by designing exclusive SnSA for small-scale network for widespread use. Firstly, network invasion feeler function N_SnSA and host invasion feeler function H_SnSA are embodied to collect more informations in the small-scale network. Secondarily, the existing vulnerability is studied to find the solutions linked with a low cost to a Public center such as Kyonggi Univ ESM center.

• The Bulletin of The Korean Astronomical Society
• /
• v.40 no.1
• /
• pp.42.2-42.2
• /
• 2015

High frequency peakers (HFPs) are promising candidates for young active galactic nuclei (AGNs). Their small physical scale (< 1 kpc) and radio spectrum peaked at high frequency (> 5 GHz) are suggestive that it has been only about $10^2-10^3$ years since a central massive black hole in their host galaxies was launched. Until recently however, long-term monitoring radio observations at frequencies which are high enough to cover the true peak of HFP candidates were rare. Therefore, previous HFP samples are often contaminated by blazars, which are highly variable, hence may show a similar radio spectrum as HFPs depending on the observational epoch. In this work, we challenge to identify genuine young AGNs by monitoring HFP candidates at high radio frequencies. We performed single-dish monitoring of 19 candidates in 18 epochs over 2.5 years at 22 and 43 GHz using the Korean VLBI Network (KVN). Also, using KaVA, a combined array of the KVN and the VERA in Japan, we carried out 22 GHz VLBI observations of two HFPs and one blazar selected from our sample in order to compare their parsec scale (milli-arcsecond scale) morphology. HFPs are expected to have double/triple features, so called compact symmetric objects, which are scaled-down versions of extended radio galaxies, while blazars typically show core-jet morphology. We discuss the properties of AGNs at their very early evolutionary stage based on the results of the KVN and KaVA observations.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.9 no.4
• /
• pp.240-248
• /
• 2009

Moore's law has driven silicon technology scale down aggressively, and it results in significant increase of leakage current on nano-meter scale CMOS. Especially, in mobile devices, leakage current has been one of designers' main concerns, and thus many studies have introduced low power methodologies. However, there are few studies to minimize implementation cost in the mixed use of the methodologies to the best of our knowledge. In this paper, we introduce industrial applications of low power design methodologies for the decrease of leakage current. We focus on the design cost reduction of power gating and reverse body bias when used together. Also, we present voltage scale as an alternative to reverse body bias. To sustain gate leakage current, we discuss the adoption of high-$\kappa$ metal gate, which cuts gate leakage current by a factor of 10 in 32 nm CMOS technology. A 45 nm mobile SoC is shown as the case study of the mixed use of low power methodologies.