• Current Applied Physics
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• v.18 no.11
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• pp.1388-1392
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• 2018

Metal thin films are used widely to solve the vibration problem. However, damping mechanism is still not clear, which limits the further improvement of the damping properties for film and the development of multi-functional damping coating. In this paper, Damping microscopic mechanism of porous metal films was investigated at both macroscopically and microscopically mixed levels. Molecular dynamics simulation method was used to model and simulate the loading-unloading numerical experiment on the micro-pore and vacancy model to get the stress-strain curve and the microstructure diagram of different defects. And damping factor was calculated by the stress-strain curve. The results show that dislocations and new vacancies appear in the micro-pores when metal film is stretched. The energetic consumption from the motion of dislocation is the main reason for the damping properties of materials. Micro-mechanism of damping properties is discussed with the results of in-situ experiment.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.12
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• pp.8-14
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• 2015

An effective way to ensure that LEDs produce wanted light output is to use a current driving topology, because the brightness of LEDs is directly related to their current. However, this topology may lead to the lifetime shortening of a illumination system because over-currents may flow through non-damaged LEDs in case some LEDs are damaged. This paper presents an adaptive current control circuits for LEDs, which protect LEDs in a good state by limiting the driving currents according to the number of damaged ones. The proposed control circuits consist of a simple constant-current driver and a micro-controller which monitors the voltage of LED array without any auxiliary current sensors for fault diagnosis. And the driving current is automatically controlled into 6-levels according to the number of failures.

• Proceedings of the KWS Conference
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• 2000.10a
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• pp.320-323
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• 2000

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.06a
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• pp.255-256
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• 2007

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.2
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• pp.197-205
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• 2003

A cascade impactor is a multistage impaction device used to separate airborne particles into aerodynamic size classes. A micro-orifice impactor uses micro-orifice nozzles to extend the cut sizes of the lower stages to as small as 0.05 ${\mu}{\textrm}{m}$ in diameter without resorting to low pressures or creating excessive pressure drops across the impactor stages. In this work, the phenomenon of particle clogging in micro-orifice nozzles was experimentally investigated for a commercial micro-orifice uniform deposit impactor (MOUDI). It was observed, using an optical microscope, that the micro-orifice nozzles of the final stages were partially clogged due to particle deposition during the aerosol sampling. Therefore the pressure drops across the nozzles were higher than the nominal values given by the manufacturer. To examine the effect of particle clogging in micro-orifice nozzles, the particle collection efficiency of the MOUDI was evaluated using an electrical method for fine particles with diameters in the range of 0.1-0.6 ${\mu}{\textrm}{m}$. The monodisperse liquid dioctyl sebacate (DOS) particles were used as test aerosols. A faraday cage was employed to measure the low-level current of the charged particles upstream and downstream of each stage. It was found that the collection efficiency curves shifted to correspond to smaller orifice sizes, and the 50-% cutoff sizes were much smaller than those given by the manufacturer for the three stages with nozzles less than 400 ${\mu}{\textrm}{m}$ in diameter.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1627-1628
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• 2006

In this paper, mesoporous only platinum electrode and micro pore platinum electrode with mesoporous Pt are fabricated and characterized on a silicon substrate to check their usability as enzymeless sensing electrodes for developing non-disposable glucose sensors integrated with silicon CMOS read out circuitry. Since most of electrochemical glucose sensors are disposable due to the use of the enzymes that are living creatures, these are limited to use in the in-vivo and continuous monitoring system applications. The proposed mesoporous Pt electrode with approximately 2.5nm in pore diameter and 150nm in height was fabricated by using a nonionic surfactant $C_{16}EO_8$ and an electroplating technique. The micro pore Pt electrode with mesoporous Pt means the mesoporous Pt electrode fabricated on top of micro pore arrayed Pt electrode with approximately $10{\mu}m$ in pore diameter and $80{\mu}m$ in height. The measured current responses at 10mM glucose solution of plane Pt, micro pore Pt, micro pore with mesoporus Pt, and mesoporous Pt electrodes are approximately $9.9nA/mm^2$, $92.4nA/mm^2$, $3320nA/mm^2$ and $44620nA/mm^2$, respectively. These data indicate that the mesoporous Pt electrode is much more sensitive than the other Pt electrodes. Thus, it is promising for non-disposable glucose sensor and electrochemical sensor applications.

• The Journal of the Korea Contents Association
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• v.21 no.12
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• pp.517-535
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• 2021

The development of digital technology has not only brought many changes to our lives, but also many changes to the online education environment. The emergence of micro-learning is to meet the needs of individual learners who hopes to receive personalized learning content immediately when they need it. Therefore, Micro-learning can be said to be 'adaptive' education. This research attempts to explore the development principles of adaptive micro-learning through literature research and case analysis. The results of the research draw four aspects of the development principles, including adaptive learning environment, adaptive learning content, adaptive learning sequence and adaptive learning evaluation, as well as detailed elements of each aspect. Micro-learning is a new form of e-learning that reflects the needs of the current society. As exploratory research, this research attempts to point out the direction for future follow-up research.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2000.10a
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• pp.581-584
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• 2000

This paper describes the effect of lightning impulse current on ZnO varistors(390 V, 6.5 kA) used in low-voltage AC mains as a protective device against transient overvoltages. A lightning impulse current standardized in IEC 61000-4-5 is applied to the varistors, and the energy applied to the varistor at each time is about 12 J. In the experiment, various Parameters such as leakage current, reference voltage are measured with the number of applied impulse current. Also, micro-structure changes of the varistors after applying the lightning impulse current of 200 times are compared. The electrical characteristics of the varistors are degraded by overtime impulse current, showing increase in leakage current and decrease in reference voltage.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.5
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• pp.58-68
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• 2000

When SS400 steel was welded with low hydrogen type and ilmennite type welding, the effect of post-weld heat treatment(PWHT) was investigated with parameters such as micro vickers hardness, corrosion potential, polarization behaviors, galvanic current, Al anode generating current and Al anode weight loss etc. Hardness of each parts(HAZ, BM, WM) by PWHT in case of low hydrogen type and ilmennite type welding was lower than that of each parts by As-welded However hardness of WM area in case of low hydrogen type and ilmennite type welding was the highest among those three parts regardless of PWHT, Whereas in case of ilmennite type welding, WM area was the highest potential among these three parts on galvanic potential series with As-welded while BM area was the highest potential among these three parts by PWHT on the contrary. And in case of low hydrogen type welding, galvanic corrosion and micro cell corrosion of welding parts was decreased with PWHT. However, It was increased with PWHT in case of ilmennite type welding. Moreover Al anode generating current and anode weight loss in case of low hydrogen type was decreased by PWHT compared to As-wedled but, which was increased than that of As-welded in case of ilmennite type welding. Therefore, it is suggested that Corrosion resistance property in case of low hydrogen type welding is increased by PWHT. However its property was devreased with PWHT in case of ilmennite type welding.

• IMMUNE NETWORK
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• v.11 no.1
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• pp.11-41
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• 2011

The discovery of microRNA (miRNA) is one of the major scientific breakthroughs in recent years and has revolutionized current cell biology and medical science. miRNAs are small (19~25nt) noncoding RNA molecules that post-transcriptionally regulate gene expression by targeting the 3' untranslated region (3'UTR) of specific messenger RNAs (mRNAs) for degradation of translation repression. Genetic ablation of the miRNA machinery, as well as loss or degradation of certain individual miRNAs, severely compromises immune development and response, and can lead to immune disorders. Several sophisticated regulatory mechanisms are used to maintain immune homeostasis. Regulatory T (Treg) cells are essential for maintaining peripheral tolerance, preventing autoimmune diseases and limiting chronic inflammatory diseases. Recent publications have provided compelling evidence that miRNAs are highly expressed in Treg cells, that the expression of Foxp3 is controlled by miRNAs and that a range of miRNAs are involved in the regulation of immunity. A large number of studies have reported links between alterations of miRNA homeostasis and pathological conditions such as cancer, cardiovascular disease and diabetes, as well as psychiatric and neurological diseases. Although it is still unclear how miRNA controls Treg cell development and function, recent studies certainly indicate that this topic will be the subject of further research. The specific circulating miRNA species may also be useful for the diagnosis, classification, prognosis of diseases and prediction of the therapeutic response. An explosive literature has focussed on the role of miRNA. In this review, I briefly summarize the current studies about the role of miRNAs in Treg cells and in the regulation of the innate and adaptive immune response. I also review the explosive current studies about clinical application of miRNA.