• Journal of Sensor Science and Technology
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• v.27 no.5
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• pp.317-327
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• 2018

Terahertz (THz) time-domain spectroscopy(TDS), imaging techniques, and related systems have become mature technologies, widely used in many universities and research laboratories. However, the development of creative technologies still requires improved THz application systems. A few key points are discussed, including the innovative advances of mode-locking energy-emitting semiconductor lasers and better photoconductive semiconductor quantum structures. To realize a compact, low cost, and high performance THz system, it is essential that THz spectroscopy and imaging technologies are better characterized by semiconductor and nano-devices, both static and time-resolved. We introduce the THz spectroscopy and imaging systems, the OSCAT(Optical Sampling by laser CAvity Tuning) system and the ASOPS(ASynchronous Optical Sampling) system, are constructed by our research team. We report on the THz images obtained from their use.

• Journal of the Korean Wood Science and Technology
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• v.41 no.4
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• pp.302-309
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• 2013

The highly porous cellulosic aerogels were prepared by freeze-drying method using sodium hydroxide-urea aqueous solution in the process of dissolution, gelation, regeneration and organic solvent substitution. The structural characteristics of porous aerogel were analyzed using scanning electron microscopy and nitrogen adsorption apparatus. As a result, the dissolving pulp was completely dissolved, but filter papers and holocellulose were divided into two layers (dissolved and undissolved parts) in the process of centrifugation. The structure of aerogel from dissolved pulp showed porous pores in the surface and net-shaped network in the inner part. Aerogels from filter paper and holocellulose had the condensed porous network surface and the open-pore nano-fibril network inner structure. Undissolved form of fibers was observed in the aqueous solution of aerogel from holocellulose. The BET value ($S_{BET}$) of aerogel from dissolved pulp was ranged in 260~326 $m^2/g$, and it was decreased with the increase of concentration. Whereas, the $S_{BET}$ value of aerogel from filter paper (198~418 $m^2/g$) was increased with the increase of concentration. The $S_{BET}$ value of aerogel from holocellulose were 137 $m^2/g$ at 2% (w/w) of cellulose, and it was increased to maximum 401 $m^2/g$ at 4% (w/w) of cellulose. Then, it was decreased at 5% (w/w) of cellulose.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2012.03a
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• pp.63-63
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• 2012

전자제품 패키지에 요구되는 쿠션성과 정전방전 기능을 갖는 폴리우레탄 발포 필름의 제조기술을 확립하게 되면 IT산업용에 적용 가능한 필름제품이 개발되어 ESD(정전방전, Electrostatic Dissipation) 성능을 발휘하게 됨으로서 정전기 쇼크에 의한 각종 전자제품의 오작동이나 파손 방지가 가능하게 되어 포장재, 자동차 전자제품의 하우징 등으로 사용될 수 있게 된다. 전도성 고분자인 Polyaniline (PANI)은 다른 여러 고분자와 비교하여 볼 때 다른 유형의 전도성 고분자보다 합성하기가 쉽고 높은 전기전도도를 보임은 물론 열적 및 대기 안정성이 우수하며 가격이 저렴한 장점을 가지고 있다. 본연구는 CNT 나노기술을 응용한 IT산업용 적층간지용 ESD PU발포필름의 제조 가공기술 및 상품화 개발을 수행하고자 방수, 투습방수성을 가지는 유연재료인 폴리우레탄(PU)의 1액형 PU와 DMF에 PANI의 함량을 5, 10, 15, 20, 25, 30wt%로 변화시켜 제조한 PANI/DMF 분산용액과 IPA/MWNT 3wt% 분산용액의 혼용비에 변화를 주어 $120^{\circ}C$에서 2분 건조시켜 그라운드 필름을 제조하였다. 그리고 2액형 PU와 IPA/MWNT 3wt% 분산용액과 발포제를 사용하여 발포온도 $150^{\circ}C$에서 5분간 건조시켜 발포필름을 제조하였으며 이들의 전기적 특성과 역학적 특성을 조사하였다. 제조된 필름의 전기전도성은 전기저항측정기 KEITHLEY 8009를 사용하여 부피저항과, 표면저항을 각각 측정하여 확인하였으며, 필름의 마찰 대전압은 E.S.T-7 마찰 대전압 시험기를 이용하여 표면 마찰 대전압을 측정하여 확인하고, 필름의 물리적 특성은 인장시험기를 이용하여 breaking stress, breaking strain을 측정하였다. 필름단면의 CNT 발포특성은 주사전자현미경(SEM)을 사용하여 측정하여 발포특성과 물성과의 연관성을 확인하였다. 그 결과 필름의 전기적 특성은 PANI가 30% 함량일 때 전반적으로 낮은 저항값이 측정되었으며, 마찰대전압을 측정한 결과 대부분의 시료가 0에 가까운 낮은 값을 가졌다. 필름의 물리적 인장특성은 PANI가 10wt%의 함량일 때 가장 높은 절단강도를 가졌으며 분산용액의 혼용비에 따른 경향성은 나타나지 않았다. 필름의 단면형상을 확인하여 발포특성을 분석한 결과 PANI의 함량에 따라 발포 cell의 크기는 뚜렷한 경향성을 보이지 않았으나 30wt%의 PANI/DMF 분산용액 20part(gr)와 3wt% IPA/MWNT 분산용액 40part(gr)로 제조한 시료의 cell이 가장 균일하고 고르게 발포되었으며, 3.90E+06ohm으로 가장 낮은 표면저항 값으로 측정되어 가장 좋은 전기전도성을 가짐을 확인하였다.

• Journal of Biosystems Engineering
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• v.36 no.5
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• pp.342-347
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• 2011

The effect of SNC(silver nano colloid) on the emission reduction of odors such as ammonia ($NH_3$), hydrogen sulfide ($H_2S$), and methane ($CH_4$) from swine excreta was studied. Silver has been used as an universal antibiotic substance and can reduce the emission of some gases by sterilizing action. Therefore, an apparatus which produces SNC was developed and was conducted its performance test. Also, the SNC made by the apparatus was applied to swine excreta sampled from a piggery in oder to find the effect on the reduction of odor emission. An electrolysis apparatus was developed to produce SNC and its capacity was 0.024 ppm/$hr{\cdot}L$. The effects of SNC on the reduction of odor emission from swine excreta were tested for bad smell gases of ammonia ($NH_3$), hydrogen sulfide ($H_2S$) and methane ($CH_4$). For ammonia gas, factorial experiments were conducted to find the effects of concentration and application rate of SNC. The test results for the different concentrations of 20 ppm, 50 ppm, and 100 ppm showed that the more concentration of SNC was increased, the more emission reduction of ammonia gas increased. From the test results about the effect of application rate, the more SNC was applied, the more emission reduction of $NH_3$ increased. In order to reduce the concentration of $NH_3$ below 5 ppm, SNC of 50 ppm is recommended to be applied at an interval of 6 hours, and is mixed with swine excreta in the volumetric ratio of 4:1. For hydrogen sulfide gas, the concentration was decreased as time went by and was reduced rapidly in the first stage of the tests for all applied concentrations of SNC (20 ppm, 50 ppm, and 100 ppm). Especially, when 100 ml of SNC with 100 ppm was applied, emission of hydrogen sulfide gas was reduced rapidly during early 4 hours after the application of SNC. And, concentration of hydrogen sulfide gas was maintained below 20 ppm after 12 hours. For methane gas, t-test showed that there was no significance on the effect of its application for all applied concentrations of SNC. Therefore, it was concluded that the application of SNC on swine excreta had no effect on the emission reduction of $CH_4$.

• Journal of the Korean Electrochemical Society
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• v.9 no.1
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• pp.1-5
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• 2006

Lithium titanium oxide $(Li_4Ti_5O_{12})$ with spinel-framework structures as anode material for lithium-ion battery was prepared by sol-gel and high energy ball milling (HEBH) method. According to the X-ray diffraction (XRD), Particle Size Analyses(PSA) and scanning electron microscopy (SEM) analysis, uniformly distributed $Li_4Ti_5O_{12}$ particles with grain sizes of 100 nm were observed. Half cells, consisting of $Li_4Ti_5O_{12}$ as working electrode and lithium foil as both counter and reference electrodes showed the high performance of high rate discharge capacity and 173 mAh/g at 0.2C in the range of $1.0\sim2.5 V$. Furthermore, the crystalline structure of $Li_4Ti_5O_{12}$ didn't transform during the lithium intercalation and deintercalation process.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.20 no.3
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• pp.77-84
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• 2014

Biodegradable nanocomposites were fabricated with poly (lactic acid) (PLA) and Nanomer$^{(R)}$ I.44P using ultrasonication (US). Processing conditions were optimized to obtain the maximum tensile properties of the nanocomposites. Poly (ethylene glycol) (PEG) was used as a plasticizer to avoid the brittleness of nanocompsoties. In order to disperse nanoclay into the PLA matrix, PEG and Nanomer$^{(R)}$ I.44P were firstly mixed and dispersed in the chloroform and followed by ultrasonication for 1 min With 10% PEG 400, tensile stress and Young's modulus of the nanocomposites decreased from 53.5 MPa and 2225 MPa to 37.0 MPa and 1757 MPa, respectively, while the elongation was increased from 4% to 21%. Tensile stress, Young's modulus, and elongation of nanocomposites were also increased with nanoclay concentration up to 2% (w/w) and were decreased with further increase in the nanoclay concentration. Transmittance of nanocomposites were significantly decreased from 62.5% for pure PLA film to 7.8% for 5% nanoclay containing nanocomposites. Water vapor permeability of the nanocomposites was also significantly decreased with nanoclay concentration and the minimum WVP of $3.5{\times}10^{-11}g{\cdot}m/m^2{\cdot}s{\cdot}Pa$ was obtained with 5% (w/w) nanoclay concentration. The PLA/Nanomer$^{(R)}$ I.44P nanocomposites showed a great potential as a environmental friendly food packaging material.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.11
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• pp.935-941
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• 2016

This study investigated the influence of high temperature and UNSM on the fatigue behavior of Inconel 718 alloy at RT, 300, 500, and $600^{\circ}C$. Fatigue properties of Inconel 718 were reduced at high temperatures compared to those at room temperature. However, the endurance limit was similar to that of the room temperature sample at the design stress level. High-temperature fatigue characteristics of the UNSM-treated specimen were significantly improved at the design stress level as compared to the untreated specimens. Specifically, the influence of temperature on the S-N curves at the design stress level of the UNSM-treated specimen showed the tendency of longer fatigue lives than those of untreated ones. Researchers can obtain rotary fatigue test results simply by heating specimens with a halogen lamp to precise temperatures during specific operations.

• Membrane Journal
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• v.28 no.4
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• pp.265-270
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• 2018

In previous studies, a poly(ethylene oxide)(PEO)/Ag nanoparicles (AgNPs)(precursor $AgBF_4$)/p-benzoquinone (p-BQ) composite membrane was prepared for olefin/paraffin separation and the performance of this composite membrane was maintained at a selectivity of 10 and a permeability of 15 GPU. However, since the price of $AgBF_4$ precursor is high, this study used $AgNO_3$ as a precursor of Ag nanoparticles which is competitive in terms of price. As a result, it was observed that the separation performance was not obtained because the existing $NO_3{^-}$ could surround AgNPs. In this study, we fabricated PEO, poly(vinyl alcohol)(PVA), and polyether block amide-1657 (PEBAX-1657) polymer composite membrane using electron acceptor 7,7,8,8-tetracyanoquinodimethane (TCNQ) for separation performance even when $AgNO_3$ was used as a precursor of Ag nanoparticles. As a result, it was analyzed that the performance was not observed regardless of the influence of the polymer and the electron acceptor, indicating that the anion of the precursor plays a crucial role in the separation performance.

• Journal of the Korean Vacuum Society
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• v.21 no.6
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• pp.328-332
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• 2012

The work function of Ag (silver) is too low (~4.3 eV) to be used as an electrode of T-OLED (Top Emission Organic Light Emitting Diode). To solve this weakness, researches used plasma-, UV-, or thermal treatment on Ag films in order to increase the work function (~5.0 eV). So, most of studies have focused only on the work function of various treated Ag films, but studies focusing on nanomechanical properties were very important to investigate the efficiency and life time of T-OLED etc. In this paper, we focused on the mechanical properties of the Ag and $AgO_x$ film. The Ag was deposited on a glass substrate with the thickness of 150 nm by using rf-magnetron sputter with the power was fixed at 100 W and working pressure was 3 mTorr. The deposited Ag film was UV treated by UV lamp for several minutes (0~9 min). We measured the sheet resistance and mechanical property of the deposited film. From the experimental result, there were some differences of the sheet resistance and surface hardness of Ag thin film between short time (0~3 min) and long time UV treatment. These result presumed that the induced stress was taken place by the surface oxidation after UV treatment.

• Research in Plant Disease
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• v.15 no.2
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• pp.130-133
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• 2009

We have conducted in vitro experiments with nano-silver liquid for their effect against various plant pathogenic bacteria. Different types of nano-silver liquid WA-CV-WA13B, WA-AT-WB13R and WA-PR-WB13R were used. These are classified based on different manufacturing processes. The tested bacteria were provided by KACC. We experimented ten bacterial isolates in Clavibacter, Erwinia, Pseudomonas, Ralstonia, and Xanthomonas genera. In order to determine the level of concentrations of control effects, different concentrations (10, 25, 50, and 100 ppm) of each different nano-silver liquid were added in the culture media. As a result, WA-CV-WA13B showed high inhibition effect against C-1 at 10 ppm, and showed minor inhibition effects against P-6, X-1, and X-2. WA-AT-WB13R showed bactericidal effect against P-6 at 10 ppm. At 10 ppm, WA-AT-WB13R showed relatively high inhibition effects against C-1, X-1, and X-2. WA-PR-WB13R showed bactericidal effects against P-5, P-6 and X-2 at 10 ppm or higher concentrations. All the tested three nano-silver liquid showed bactericidal effects against all the tested plant pathogenic bacteria at concentrations of 25 ppm or higher. These results indicated the possible use of nano-silver liquid for the control of plant pathogenic bacteria.