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Park, Minwoo,Im, Jungkyun,Shin, Minkwan,Min, Yuho,Park, Jaeyoon,Cho, Heesook,Park, Soojin,Shim, Mun-Bo,Jeon, Sanghun,Chung, Dae-Young,Bae, Jihyun,Park, Jongjin,Jeong, Unyong,Kim, Kinam Nature Pub. Group 2012 Nature nanotechnology Vol.7 No.12
<P>Conductive electrodes and electric circuits that can remain active and electrically stable under large mechanical deformations are highly desirable for applications such as flexible displays, field-effect transistors, energy-related devices, smart clothing and actuators. However, high conductivity and stretchability seem to be mutually exclusive parameters. The most promising solution to this problem has been to use one-dimensional nanostructures such as carbon nanotubes and metal nanowires coated on a stretchable fabric, metal stripes with a wavy geometry, composite elastomers embedding conductive fillers and interpenetrating networks of a liquid metal and rubber. At present, the conductivity values at large strains remain too low to satisfy requirements for practical applications. Moreover, the ability to make arbitrary patterns over large areas is also desirable. Here, we introduce a conductive composite mat of silver nanoparticles and rubber fibres that allows the formation of highly stretchable circuits through a fabrication process that is compatible with any substrate and scalable for large-area applications. A silver nanoparticle precursor is absorbed in electrospun poly (styrene-block-butadiene-block-styrene) (SBS) rubber fibres and then converted into silver nanoparticles directly in the fibre mat. Percolation of the silver nanoparticles inside the fibres leads to a high bulk conductivity, which is preserved at large deformations (σ???2,200?S?cm(-1) at 100% strain for a 150-?m-thick mat). We design electric circuits directly on the electrospun fibre mat by nozzle printing, inkjet printing and spray printing of the precursor solution and fabricate a highly stretchable antenna, a strain sensor and a highly stretchable light-emitting diode as examples of applications.</P>
Development of a Learner Profiling System Using Multidimensional Characteristics Analysis
Park, Kinam,Ji, Hyesung,Lim, Heuiseok Hindawi Limited 2015 Mathematical problems in engineering Vol.2015 No.-
<P>We propose a learner profiling system that uses the multidimensional characteristic analysis of learners. For this purpose, a real-time monitoring system for learners was developed and then used to extract information of the characteristics of learners that appear in learning environments. The extracted information on the characteristics of learners is automatically constructed into personalized learner profiles through the learner profiling system. The contents of learner profiles consist of the cognitive ability of learners, the learning condition, and teacher assessment. To verify the effectiveness of the proposed study method, profiles of actual learners were constructed, with 210 elementary school students as subjects. As a result, the group that learned using the learner profiling showed a significant level of satisfaction in comparison to the group that did not use learner profiling. From this, it was demonstrated that the learner profiling system proposed in this paper could enhance learning effectiveness.</P>
Evaluation of Time-Based Arc Flash Detection with Non-contact UV Sensor
Park Chulmin,Lee Kiwon,Kim Kinam,Lim Hunyoung,Park Young 대한전기학회 2024 Journal of Electrical Engineering & Technology Vol.19 No.3
An arc fash is caused by electrical faults or mechanical non-contact such as insulation failure, short circuit, partial disconnection, and poor contact, emits high energy and strong light, so it can be detected by optical methods with relatively simple structures. The optical detection methods using the wavelength of light may malfunction depending on the surrounding environment, the sunlight and lighting. In addition, with such methods, it is difcult to measure the detection distance to the point where the arc fash occurs, measure the detection range of the detection sensor, and monitor how amounts of harmful from the arc fash. This paper aims to examine the techniques for quantitatively detecting arc fash caused by electrical faults. To this end, a system for detecting the time when an arc fash occurs and the techniques for calibrating this system were analyzed, respectively. A feld test was also conducted to detect the arc fash caused by mechanical non-contact between the pantograph of electric railway vehicles and the catenary. In the feld test, 9 number of arc fashes were detected using the percentage (%) technique for quantitative detection. The technique of detecting the time when an arc fash occurs is a new quantitative evaluation method, which is expected to be widely used to prevent negligent accidents in the electrical feld as well as being able to determine in real time whether there is a harmful arc.
Park, Hyojin,Park, Kinam,Kim, Dukjoon Wiley Subscription Services, Inc., A Wiley Company 2006 Journal of biomedical materials research. Part A Vol.a76 No.1
<P>Chitosan and glycol chitosan hydrogels were prepared, and their swelling behaviors in acidic solution were studied to investigate their application for gastric retention device. The optimum preparation condition of superporous hydrogels was obtained from the gelation and blowing kinetics measured at varying acidic conditions. Both the swelling rate and swelling ratio of glycol chitosan hydrogels were higher than those of chitosan hydrogels. Swelling behaviors were significantly affected by not only foaming/drying methods but also crosslinking density, as the sizes and structures of pores generated were highly dependent on those preparation conditions. The prepared superporous hydrogels were highly sensitive to pH of swelling media, and showed reversible swelling and de-swelling behaviors maintaining their mechanical stability. The degradation kinetics in simulated gastric fluid was also studied. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res, 2006</P>