• Korean Chemical Engineering Research
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• v.55 no.6
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• pp.854-860
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• 2017

PSf/D2EHPA/CNTs beads were prepared by immobilizing extractant di-(2-ethylhexyl)- phosphoric acid (D2EHPA) and adsorbent carbon nanotubes (CNTs) on polysulfone (PSf), and the adsorption characteristics of Sr(II) on the beads were studied. The morphological characteristics of the prepared PSf/D2EHPA/CNTs beads were observed by scanning electron microscopy (SEM), thermo gravimetric analysis (TGA), and Fourier transform infrared spectrometer (FTIR). The equilibrium time for the removal of Sr(II) by PSf/D2EHPA/CNTs beads was 60 min. The experimental kinetic data followed pseudo-second-order model more than pseudo-first-order kinetics model. The maximum removal capacity of Sr(II) obtained from Langmuir isotherm was 4.75 mg/g. The removal efficiencies of Sr (II) by PSf/D2EHPA/CNTs beads were improved 2.5 times by adding the adsorbent CNTs more than by using only the extractant D2EHPA.

• Ceramist
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• v.21 no.2
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• pp.4-18
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• 2018

Lastly, neuromorphic computing chip has been extensively studied as the technology that directly mimics efficient calculation algorithm of human brain, enabling a next-generation intelligent hardware system with high speed and low power consumption. Three-terminal based synaptic transistor has relatively low integration density compared to the two-terminal type memristor, while its power consumption can be realized as being so low and its spike plasticity from synapse can be reliably implemented. Also, the strong electrical interaction between two or more synaptic spikes offers the advantage of more precise control of synaptic weights. In this review paper, the results of synaptic transistor mimicking synaptic behavior of the brain are classified according to the channel material, in order of silicon, organic semiconductor, oxide semiconductor, 1D CNT(carbon nanotube) and 2D van der Waals atomic layer present. At the same time, key technologies related to dielectrics and electrolytes introduced to express hysteresis and plasticity are discussed. In addition, we compared the essential electrical characteristics (EPSC, IPSC, PPF, STM, LTM, and STDP) required to implement synaptic transistors in common and the power consumption required for unit synapse operation. Generally, synaptic devices should be integrated with other peripheral circuits such as neurons. Demonstration of this neuromorphic system level needs the linearity of synapse resistance change, the symmetry between potentiation and depression, and multi-level resistance states. Finally, in order to be used as a practical neuromorphic applications, the long-term stability and reliability of the synapse device have to be essentially secured through the retention and the endurance cycling test related to the long-term memory characteristics.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.12
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• pp.672-678
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• 2017

In this study, municipal solid waste (MSW) has collected 3 times and physico-chemical analysis has done. Nitrous oxide emissions from MSW incineration plant were measured continuously by EPA Method 18 and it was compared with the emission by calculation using the emission factor. The $N_2O$ emission of MSW incineration plant was more than twice as large as the emission by calculation. It was found that the installation of abatement facilities in MSW incineration plant is effective in achieving the greenhouse reduction targets and it can be ensure economical efficiency through emission trading system.

• Korean Journal of Materials Research
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• v.20 no.2
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• pp.51-54
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• 2010

Transparent conductive films of single wall carbon nanotube (SWCNT) were prepared by spray coating method. The effect of acid treatment on the SWCNT films was investigated. The field emission scanning electron microscope (FESEM) shows that acid treatment can remove dispersing agent. The electrical and optical properties of acid-treated films were enhanced compared with those of as deposited SWCNT films. Nitric acid ($HNO_3$), sulfuric acid ($H_2SO_4$), nitric acid:sulfuric acid (3:1) were used for post treatment. Although all solutions reduced sheet resistance of CNT films, nitric acid can improve electrical characteristics efficiently. During acid treatment, transmittance was increased continuously with time. But the sheet resistance was decreased for the first 20 minutes and then increased again. Post-treated SWCNT films were transparent (85%) in the visible range with sheet resistance of about $162{\Omega}/sq$. In this paper we discuss simple fabrication, which is suitable for different types of large-scale substrates and simple processes to improve properties of SWCNT films.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.299-299
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• 2013

Indium Tin Oxide (ITO) has widely been used as a transparent conductive oxide (TCE) for photovoltaic devices. Lately, flexibility of ITO becomes an issue as demand of flexible device increases. Several scientists have tried to substitute ITO to different materials such as conductive polymer, graphene, CNT, and metal nanowire because of ITO brittleness. Among the substitute materials, PEDOT:PSS has mostly paid attention because PEDOT:PSS has excellent flexibility and good conductivity. The conductivity of PEDOT:PSS increases up to 1000 S/cm with additives such as DMSO, EG, sorbitol, and so on. In our research group, we introduce a conductive polymer PEDOT:PSS as a buffer layer to improve not only flexibility but also conductivity. As PEDOT:PSS layer forms beneath ITO thin film (20 nm), sheet resistance decreases from $230{\Omega}$/${\Box}$ to $85{\Omega}$/${\Box}$ and crack initiation decreases from 4.5 mm to 3.5 mm as well. We have fabricated organic photovoltaic device and power conversion efficiencies using conventional ITO electrode and ITO/PEDOT:PSS hybrid electrode. The photovoltaic property such as power conversion efficiency for ITO/PEDOT:PSS hybrid electrode is comparable to the value obtained using conventional ITO electrode on glass substrate.

• Journal of the Korean institute of surface engineering
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• v.53 no.4
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• pp.160-168
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• 2020

A polymer-based carbon nanomaterial composite was fabricated and characterized for the application of a thermal conductive adhesive. Low-dimensional carbon nanomaterials with excellent thermal conductivity such as carbon nanotube (CNT) and graphene were selected as a filler in the composite. Thermal, electrical and adhesive properties of the composite were investigated with respect to the morphology and content of the low-dimensional carbon nanomaterials. As a result, the composite-based adhesive fabricated by the loading of surface-treated MWCNTs of 0.4 wt% showed uniform dispersion, moderate adhesion and effective heat dissipation properties. Finally, it was confirmed through the thermal image analysis of LED module that the temperature reduction of 10℃ was achieved using the fabricated composite adhesive with MWCNT-6A. Expecially, heat dissipation performance of the optimized composite adhesive was evident at the hot spot in the module compared to other samples mixed with graphene or different MWCNT loading ratios.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.152-152
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• 2008

탄소나노튜브(carbon nanotube) 필름은 낮은 전기저항, 높은 투명도, 우수한 기계적 강도 및 유연성, 열적 안정성 등의 뛰어난 특성을 가지고 있다. 본 연구에서는 다양한 계면활성제로 분산시킨 수용액으로부터 제조된 단일벽 탄소나노튜브(single-walled CNT) 필름의 면저항(sheet resistance) 특성을 비교하였다. 먼저 나노튜브의 분산을 위해 널리 사용되는 계면활성제인 sodium dodecyl sulfate(SDS)를 기준으로 탄소나노튜브의 양, 원심분리 시간, 초음파 세기 및 시간 등의 최적 공정조건을 정한 후 각 계면활성제에 대해 분산을 위한 최적 첨가량을 알아내어 계면활성제 별로 탄소나노튜브 수용액을 제조하였다. 다양한 계면활성제로 분산된 단일벽 탄소나노튜브 수용액을 알루미나 재질의 필터에 정량적으로 vacuum-filtration하여 필름을 만들었다. 이 필름들의 면저항을 측정함으로써 계면 활성제에 따른 전기적 특성의 차이를 관찰하였다. 본 연구에서 사용한 여러 가지 계면활성제 중 sodium dodecylbenze nesulfonate (NaDDBS)를 사용하여 만든 필름이 가장 낮은 면저항을 나타내었으며, 이는 NaDDBS가 단일벽 탄소나노 튜브 다발들을 개개의 튜브로 잘 분산시키기 때문인 것으로 생각된다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.3
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• pp.181-185
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• 2016

One of the important issues for fabricating the microelectronic display devices such as FED, PDP, and VFD is to obtain a high vacuum level inside the panel. In addition, sustaining the initial high vacuum level permanently is also very important. In the conventional packing technology using a tabulation method, it is not possible to obtain a satisfiable vacuum level for a proper operation. In case of FED, the poor vacuum level results in the increase of operating voltage for electron emission from field emitter tips and an arcing problem, resultantly shortening a life time. Furthermore, the reduction of a sealing process time in the PDP production is very important in respect of commercial product. The most probable method for obtaining the initial high vacuum level inside the space with such a miniature and complex geometry is a vacuum in-line sealing which seals two glass plates within a high vacuum chamber. The critical solution for the vacuum sealing is to develop a frit glass to avoid the bubbling or crack problems during the sealing process at high temperature of about $400^{\circ}C$ under the vacuum environment. In this study, the suitable frit power was developed using a mixture of vitreous and crystalline type frit powders, and a vacuum sealed CNT FED with 2 inch diagonal size was fabricated and successfully operated.

• Advances in nano research
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• v.8 no.2
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• pp.135-148
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• 2020

The incorporation of carbon nanotubes in a polymer matrix makes it possible to obtain nanocomposite materials with exceptional properties. It's in this scientific background that this work was based. There are several theories that deal with the behavior of plates, in this research based on the Mindlin-Reissner theory that takes into account the transversal shear effect, for analysis of the critical buckling load of a reinforced polymer plate with parabolic distribution of carbon nanotubes. The equations of the model are derived and the critical loads of linear and parabolic distribution of carbon nanotubes are obtained. With different disposition of nanotubes of carbon in the polymer matrix, the effects of different parameters such as the volume fractions, the plate geometric ratios and the number of modes on the critical load buckling are analysed and discussed. The results show that the critical buckling load of parabolic distribution is larger than the linear distribution. This variation is attributed to the concentration of reinforcement (CNTs) at the top and bottom faces for the X-CNT type which make the plate more rigid against buckling.

• Sleep Medicine and Psychophysiology
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• v.6 no.2
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• pp.149-157
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• 1999

A Computerzed Neuropsychological Test(CNT) system using multimedia and object oriented technologies are developed for clinical application in psychiatry. The developed system is composed of 14 neuropsychologial tests which are capable of evaluation of various cognitive functions and functional localization of brain. The system employs Microsoft Window based graphic user interface for easy operation and it has a touch screen and a mouse as input devices from the patient. Speech perception test, color word test, verbal memory test, contingent continuos performance test, and trail making test were translated into korean language, so that usefulness of tests was maximized. Through the results of utilization of this system in the cases of patients with head trauma and psychiatric desorder, this system can be proved to be useful in the evaluation of cognitive function and functional localization of brain.