• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.130-130
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• 2016

Bioinspired hierarchical nanostructures for self-cleaning s-tnwjurface and SERS substrates are investigated. The multi-level hierarchy is combined with CuO nanowire and additional nanoscale structures. CuO nanowire, which has extremely high aspect ratio, serves as a base structure of multi-level hierarchy and additional flower like structures are placed on the CuO nanowires. Since as-fabricated CuO nanostructures are hydrophilic, the surface is coated with perfluorooctyltrichlorosilane in order to change its wetting property to hydrophobic. While those CuO based nanostructures have a sufficient roughness for superhydrophobic characteristics, hierarchical nanoflowers on nanowire structures lead to a self-cleaning surface. Furthermore, flower like nanostructures provide reentrant curvatures, thus enabling oleophobic property. The surfaces has a repellency even for a tiny droplet (10 nL) of low surface tension liquids (~35 mN/m). On the on hands, nanoflowers provide many number of nanoscale gaps. After a thin layer of silver is deposited on the surface of CuO nanostructures, those nanoscale gaps act as hot-spot for surface enhanced Raman scattering (SERS). To analyze SERS enhancement of the surfaces, Raman shift is measured with varying molar density of 4-Mercaptopyridine from mM to pM. From these results, hierarchical CuO nanostructures are suitable for self-maintenance and cost effective SERS sensing applications.

• Smart Structures and Systems
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• v.15 no.6
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• pp.1625-1642
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• 2015

We propose an electrically self-reliant structural health monitoring (SHM) system that is able to wirelessly transmit sensing data using electrical power generated by vibration without the need for additional external power sources. The provision of reliable electricity to wireless SHM systems is a highly important issue that has often been ignored, and to expand the applicability of various wireless SHM innovations, it will be necessary to develop comprehensive wireless SHM devices including stable electricity sources. In light of this need, we propose a new, highly efficient vibration-powered generator based on a tuned-mass-damper (TMD) mechanism that is quite suitable for vibration-based SHM. The charging time of the TMD generator is shorter than that of conventional generators based on the impedance matching method, and the proposed TMD generator can harvest 16 times the amount of energy that a conventional generator can. The charging time of an SHM wireless transmitter is quantitatively formulated. We conduct wireless monitoring experiments to validate a wireless SHM system composed of a self-reliant SHM and a vibration-powered TMD generator.

• IEMEK Journal of Embedded Systems and Applications
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• v.15 no.2
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• pp.79-85
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• 2020

IIoT stands for Industrial Internet of Things used in manufacturing, healthcare, and transportation in networked smart factories. Recently, IIoT's environment requires an automated control system through intelligent cognition to improve efficiency. In particular, IIoT can be applied to automatic calibration of production equipment for improved management in industrial environments. Such automation systems require a wireless network for transmitting industrial data. Self-calibration systems in laser transmission paths using wireless networks can save resources and improve production quality by real-time monitoring and remote control of laser transmission path. In this paper, we propose a wireless networked system for self-calibration of laser equipment that requires a laser transmission path, and we show the results of the prototype evaluation. The self-calibration system of laser equipment measures the coordinates of the laser points with sensors and sends them to the host using the proposed application protocol. We propose a wireless network service for the wired motor controller to align the laser coordinates. Using this wireless network, the host controls the motor by sending a control command of the motor controller in an HTTP message based on the received coordinate values. Finally, we build a prototype system of the proposed design to verify the detection performance and analyze the network performance.

• Journal of Adhesion and Interface
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• v.10 no.2
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• pp.90-97
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• 2009

Dispersion and self-sensing evaluation for single-carbon fiber reinforced in three different acid-treated CNT-epoxy nanocomposites were investigated by electro-micromechanical techniques and wettability tests. Self-sensing based on contact resistivity exhibited more noise for single carbon fiber/acid-treated CNT-epoxy composites than it did for untreated CNT. However, the apparent modulus was higher the acid treated case than the untreated case which is attributed to better stress transfer. The interfacial shear strength (IFSS) between carbon fibers and the CNT-epoxy was lower than that between carbon fiber and neat epoxy due to the increased viscosity associated with the addition of the CNT. The CNT-epoxy nanocomposite exhibited more hydrophobicity than did neat epoxy. Change in the thermodynamic work of adhesion was consistent with changes in the IFSS but disproportional to that of the apparent modulus. The optimum condition of acid treatment on the need can be obtained instead of the maximum condition.

• Korean Journal of Remote Sensing
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• v.22 no.2
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• pp.111-121
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• 2006

The classification using spectral angle is a new approach based on the fact that the spectra of the same type of surface objects in RS data are approximately linearly scaled variations of one another due to atmospheric and topographic effects. There are many researches on the unsupervised classification using spectral angle recently. Nevertheless, there are only a few which consider the characteristics of Hyperspectral data. On this study, we propose the ISOMUSAC(Iterative Self-Organizing Modified Unsupervised Spectral Angle Classification) which can supplement the defects of previous unsupervised spectral angle classification. ISOMUSAC uses the Angle Division for the selection of seed points and calculates the center of clusters using spectral angle. In addition, ISOMUSAC perform the iterative merging and splitting clusters. As a result, the proposed algorithm can reduce the time of processing and generate better classification result than previous unsupervised classification algorithms by visual and quantitative analysis. For the comparison with previous unsupervised spectral angle classification by quantitative analysis, we propose Validity Index using spectral angle.

• Journal of IKEEE
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• v.18 no.1
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• pp.57-63
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• 2014

This paper is to technically implement the sensing platform for Home-Wellness Robot. The self-Localization of indoor mobile robot is very important for the sophisticated trajectory control. In this paper, the robot's self-localization algorithm is designed by RF sensor network and fuzzy inference. The robot realizes its self-localization, using RFID sensors, through the collaboration algorithm which uses fuzzy inference for combining the strengths of triangulation and triangulation. For the triangulation self-Localization, RSSI is implemented. TOA method is used for realizing the triangulation self-localization. The final improved position is, through fuzzy inference, made by the fusion algorithm of the resultant coordinates from trilateration and triangulation in real time. In this paper, good performance of the proposed self-localization algorithm is confirmed through the results of a variety of experiments in the base of RFID sensor network and reader system.

• Korean Journal of Childcare and Education
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• v.12 no.1
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• pp.171-185
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• 2016

The purpose of this study is to investigate the pervasive MBTI psychological preferences of childcare teachers and to examine the effects of MBTI psychological preferences and teachers' educational beliefs on childcare teachers'self-efficacy. The participants of this study were 141 childcare teachers. An independent samples t-test, Pearson's productive correlation, and step-wise multiple regression were employed to analyze the data. The results are as follows: First, Depending on the MBTI psychological preferences trends in childcare teachers, there were differences in self-efficacy. Second, personality type Sensing(S) was positively correlated with preference for easy tasks. Personality type Thinking(T) was negatively correlated with behavioral education belief, and was positively correlated with interactional education belief, self-regulated efficacy and total score of self-efficacy. Personality type Judging(J) was positively correlated with interactional/maturational education belief and self-regulated efficacy. Third, interactional education belief and MBTI psychological preferences of childcare teachers had asignificant influence on self-efficacy.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.431-431
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• 2011

Graphene, two dimensional sheet of sp2-hybridized carbon, has attracted an enormous amount of interest due to excellent electrical, chemical and mechanical properties for the application of transparent conducting films, clean energy devices, field-effect transistors, optoelectronic devices and chemical sensors. Especially, graphene is promising candidate to detect the gas molecules and biomolecules due to the large specific surface area and signal-to-noise ratios. Despite of importance to the disease diagnosis, there are a few reports to demonstrate the graphene- and rGO-FET for biological sensors and the sensing mechanism are not fully understood. Here we describe scalable and facile fabrication of rGO-FET with the capability of label-free, ultrasensitive electrical detection of a cancer biomarker, prostate specific antigen/${\alpha}1$-antichymotrypsin (PSA-ACT) complex, in which the ultrathin rGO sensing channel was simply formed by a uniform self-assembly of two-dimensional rGO nanosheets on aminated pattern generated by inkjet printing. Sensing characteristics of rGO-FET immunosensor showed the highly precise, reliable, and linear shift in the Dirac point with the analyte concentration of PSA-ACT complex and extremely low detection limit as low as 1 fg/ml. We further analyzed the charge doping mechanism, which is the change in the charge carrier in the rGO channel varying by the concentration of biomolecules. Amenability of solution-based scalable fabrication and extremely high performance may enable rGO-FET device as a versatile multiplexed diagnostic biosensor for disease biomarkers.

• Korean Journal of Materials Research
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• v.24 no.3
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• pp.152-158
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• 2014

We report the effect of the fabric of the surface microstructure on the CO gas sensing properties of $SnO_2$ thin films deposited on self-assembled Au nanodots ($SnO_2$/Au) that were formed on $SiO_2/Si$ substrates. We characterized structural and morphological properties, comparing them to those of $SnO_2$ thin films deposited directly onto $SiO_2/Si$ substrates. We observed a significant enhancement of CO gas sensing properties in the $SnO_2$/Au gas sensors, specifically exhibiting a high maximum response at $200^{\circ}C$ and quite a low detection limit of 1 ppm level in dry air. In particular, the response of the $SnO_2/Au$ gas sensor was found to reach the maximum value of 32.5 at $200^{\circ}C$, which is roughly 27 times higher than the response (~1.2) of the $SnO_2$ gas sensor obtained at the same operating temperature of $200^{\circ}C$. Furthermore, the $SnO_2/Au$ gas sensors displayed very fast response and recovery behaviors. The observed enhancement in the CO gas sensing properties of the $SnO_2/Au$ sensors is mainly ascribed to the formation of a nanostructured morphology in the active $SnO_2$ layer having a high specific surface-reaction area by the insertion of a nanodot form of Au nucleation layer.

• Journal of Sensor Science and Technology
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• v.33 no.1
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• pp.34-39
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• 2024

Energy harvesting technology that converts the wasted energy resources into electrical energy is emerging as a semipermanent power source for self-powered electronics and wireless low-power sensor systems. Among the various energy conversion techniques, flexible piezoelectric energy harvesters (f-PEHs), using materials with piezoelectric effects, have attracted significant interest because they can harvest a small mechanical energy into electrical signals without constraints of time and space in various environments. In this study, we used a flexible piezoelectric composite film fabricated by dispersing BaHf_xTi_(1-x)O₃ (x = 0, 0.01, 0.05, 0.1) piezoelectric powders inside a polymeric matrix to facilitate f-PEHs. The fabricated f-PEH with optimal Hf contents (x = 0.05) generated a maximum output voltage of 0.95 V and current signal of 130 nA with stable electrical/mechanical disabilities under periodically bending deformations. In addition, we demonstrated a cantilever-type f-PEH and investigated its potential as a sensor by characterizing the output performance under mechanical vibrations at various frequencies. This study provides the breakthrough for realizing self-powered energy harvesting and sensing systems by adopting the lead-free piezoelectric composites under vibrational environments.