• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.430-430
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• 2011

Graphene, one single atomic layer of graphite, has attracted extensive attention in various research fields since its first isolation from graphite. Application in the future electronics requires better understanding and manipulation of electronic properties of graphene supported on various solid substrates. Here, we present a study on charge doping and morphology of graphene prepared on atomically flat and highly polar mica substrates. Ultra-flat single-layer graphene was prepared by micro-exfoliation of graphite followed by deposition on cleaved mica substrates. Atomic force microscopy (AFM) revealed presence of ultra-thin water films formed in a layer-by-layer manner between graphene and mica substrates. Raman spectroscopy showed that a few angstrom-thick water films efficiently block electron transfer from graphene to mica. Hole doping in graphene caused by underlying mica substrates was also visualized by scanning Kelvin probe microscopy (SKPM).

• Clean Technology
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• v.14 no.4
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• pp.242-247
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• 2008

Poly(N-vinyl-2-pyrrolidone) (PVP) has been used as biocompatible and biodegradable polymer in cosmetics, pharmaceuticals and electronics. Micro-particles of PVP were produced using an aerosol solvent extraction system (ASES). Dichloromethane (DCM) and supercritical carbon dioxide were used as solvent and antisolvent, respectively. The mean diameter of the obtained polymer particles ranged from 0.184 to $0.249\;{\mu}m$. The relationship between particle size and initial drop size was also considered.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.108-111
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• 2007

It's important to measure quantitative properties about thermal-nano variation conduct of polymer for producing high quality components using NIL process. NanoScale indents can be used ad cells for molecular electronics and drug deliver, slots for integration into nanodevices, and defects for tailoring the structure and properties. In this study, it's to evaluate mechanical characteristic of polymer such as PMMA and PC at high temperature for manufacture of nano/micro size of polymer using indenter at high temperature. At high temperature mechanical properties of polymer have extreme variation. Because heating the polymer, it becomes softer than room temperature. In this case it is especially important to study for mechanical properties of polymer at high temperature.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.10 s.253
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• pp.1298-1304
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• 2006

The present paper is aiming at the evaluation for failure mechanisms and static strength of brazed joints used in household electronics. For these purposes, the failure analysis was performed on the various brazed joints, through the bursting, the micro-Victors hardness tests and 3-dimensional X-ray technique. The failure modes of brazed joints were classified into two different types, based on the results of bursting pressure test by means of self-designed internal-pressure testing machine. Their failure mechanism was dependent on the relationship between heat effect occurred in manufacturing process and internal flaws such as incomplete penetration and pin hole. Also, a finite element analysis was performed to evaluate the stress distribution with respect to the heat and the internal flaws.

• ETRI Journal
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• v.38 no.6
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• pp.1104-1113
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• 2016

Non-linear document navigation refers to the process of repeatedly reading a document at different levels to provide an overview, including selective reading to search for useful information within a document under time constraints. Currently, this function is not supported well by small-screen tablets. In this study, we propose the concept of structure-aware touch-based scrolling (SATS), which allows structural document navigation using region-dependent touch gestures for non-sequential navigation within tablets or tablet-sized e-book readers. In SATS, the screen is divided into four vertical sections representing the different structural levels of a document, where dragging into the different sections allows navigating from the macro to micro levels. The implementation of a prototype is presented, as well as details of a comparative evaluation using typical non-sequential navigation tasks performed under time constraints. The results showed that SATS obtained better performance, higher user satisfaction, and a lower usability workload compared with a conventional structural overview interface.

• JSTS:Journal of Semiconductor Technology and Science
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• v.4 no.2
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• pp.128-132
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• 2004

This paper presents the design, fabrication sequence and measurement results of a highly sensitive capacitive-type humidity sensor using a polyimide film without hydrophobic elements. The structure of the humidity sensor is MIM (metalinsulator-metal). For a high sensitivity, a modified aromatic polyimides as a moisture absorbing layer has been synthesized instead of using general polyimides containing hydrophobic elements. The polyimide film was obtained by synthesizing and thermally polymerizing polyamic acid composed of m-pyromellitic dianhydride, phenelenediamine and dimethylacetamide. Characteristics of fabricated sensors which include sensitivity, hysteresis and stability have been measured. The measurement result shows the percent normalized capacitance change of 0.37/%RH over a range from 10 to 90%RH, hysteresis of 0.77% over the same %RH range and maximum drift of 0.25% at 50%RH. The result shows that the developed humidity sensor can be applied to evaluate a hermeticity of various sensors and actuator systems as well as micro packages.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.541-542
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• 2006

In this paper, I propose the field emission tip for the E-beam array system that is made by carbon nanotubes(CNT). CNT is one of the most expected future materials, because of its great mechanical, chemical and electrical characteristics. So CNT can be used for many applications such as electron emitter, sensor, single electron transistor and AFM tip. And CNT will be applied to our E-beam array system as field emission tip so we will improve the system's electrical characteristics.

• Proceedings of the IEEK Conference
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• 2002.07c
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• pp.1867-1870
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• 2002

In the present paper, we will focus on the characterization of the biological network behaviour, in terms of synchronization and desynchronization of the measured signals by Micro Electrode array. We evaluate a easy calculable estimator that implies de/synchronization property of the biological neural network.

• 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 KIPE Conference
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• 2005.07a
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• pp.162-165
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• 2005

전력연구원은 고속의 DSP TMS320C33를 이용하여 실시간 정지형 계통연계 발전기 시뮬레이터를 개발하였다. 특히 소프트웨어로는 MicroC-OS를 이용하였으며 제어주기는 2500Hz이상으로 설계되었다. 실제 발전소에서 상업 운전되고 있는 여자시스템을 대상으로 하여 시뮬레이터 시험을 완료하였다.