• Carbon letters
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• 제26권
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• pp.81-87
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• 2018

Morphological differences in multi-layered graphene flakes or graphene nanoplatelets prepared by oxidative (rGO-NP, reduced graphene oxide-nanoplatelets) and non-oxidative (GIC-NP, graphite intercalation compound-nanoplatelets) routes were investigated with various analytical methods. Both types of NPs have similar specific surface areas but very different structural differences. Therefore, this study proposes an effective and simple method to identify structural differences in graphene-like allotropes. The adsorptive potential peaks of rGO-NP attained by the density functional theory method were found to be more scattered over the basal and non-basal regions than those of GIC-NP. Raman spectra and high resolution TEM images showed more distinctive crystallographic defects in the rGO-NP than in the GIC-NP. Because the R-ratio values of the edge and basal plane of the sample were maintained and relatively similar in the rGO-NP (0.944 for edge & 1.026 for basal), the discrepancy between those values in the GIC-NP were found to be much greater (0.918 for edge & 0.164 for basal). The electrical conductivity results showed a remarkable gap between the rGO-NP and GIC-NP attributed to their inherent morphological and crystallographic properties.

• 한국결정성장학회지
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• 제12권5호
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• pp.229-233
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• 2002

유기화학적 방법인 착체중합법을 이용하여 나노사이즈의 ZnO 분말을 저온에서 합성하였다. 고분자 전구체는 Zn nitrate hexahydrate를 사용하였고, chelating agent로서 citric acid를 reaction medium으로서 ethylene glycol을 혼합하여 제조하였다. 고분자 전구체를 300~$700^{\circ}C$의 온도범위에서 3시간 동안 하소하였으며, 열분해와 결정화 과정을 TG-DTA, FI-IR과 XRD 등을 이용하여 분석하였다. 결정화 온도에 따른 입자의 형상이나 크기를 SEM, TEM의 분석 및 Scherrer's equation을 이용한 계산을 통하여 관찰 및 비교를 하였다. ZnO의 결정화는 $300^{\circ}C$부터 시작되었고, $400^{\circ}C$에서 완전히 합성되었음을 알 수 있었다. 400~$700^{\circ}C$에서 하소된 ZnO 입자들은 대부분 둥근 형태로 균일하게 분포되었으며, $400^{\circ}C$에서 하소된 분말의 평균입도는 약 30~40nm를 보였다. 일반적으로 온도의 상승에 따라 입경이 증가되는 일반적인 경향이 관찰되었다.

• Toxicological Research
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• 제14권3호
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• pp.393-400
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• 1998

As a series of safety studies on DA-3585, a recombinant human erythropoietin, its local irritancy was examined in rabbits after the following treatments; application into the conjunctival sac of the eye(single), subcutaneous injection (single and -day repeated)and intravenous injection (7-day repeated.)In addition, perivascular irritation of DA-3585 was investigated in mice. In the result of ocular irritation test, 10,000IU/ml solution of DA-3585 could be considered as a non-irritating material. The local irritation of DA-3585 by a single and 7-day repeated subcutaneous injection was negligible and not so much different from that of saline. In the vascular irritancy test, macro-and microscopic observations revealed that local irritation of DA-3585 was comparable to that of saline when injected into retroauricular vein of rabbits for 7 consecutive days. Furthermore the perivascular administration of DA-3585 upto the concentration of 10,000 IU/ml did not induce any morphological abnormalities at injection sites. The results obtained from the present study suggest that the local irritancy of DA-3585 is not different from that of saline when injected through intravenous or subcutaneous route for clinical practice.

• 대한임상검사과학회지
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• 제43권4호
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• pp.179-187
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• 2011

Animal models are important tools in thrombosis research and preclinical drug development. In recent studies, ferric chloride ($FeCl_3$) has been widely used to induce arterial thrombosis in a variety of species. The purpose of this study was to find an optimal concentration of $FeCl_3$ and validate this model suited better for thrombosis research. A small piece of filter paper, soaked in $FeCl_3$ solution (10, 20 or 35%, v/v, in distilled water) was topically applied on the carotid artery of SD rats to measure the time to occlusion (TTO) and thrombus weight (TW) to ascertain 35%, as an optimal $FeCl_3$ concentration ($8.63{\pm}0.92min$; p =0.000, $0.79{\pm}0.03mg/mm$; p =0.000, respectively). To validate this experimental model, Ginkgo biloba special extract EGb761 (5, 10 or 30 mg/kg) as a reference agent administered by peritoneal route for 1h prior to the induction of thrombosis, showed significantly delayed TTO in a dose dependent manner ($18.50{\pm}2.17$, $29.17{\pm}1.83$, and $38.00{\pm}1.79min$, respectively) and significantly reduced TW and repaired collagen fibre in the injured vessel compare to vehicle group. Our results provide a simple, reproducible and well controlled in vivo screening system to induce thrombosis in rats by the topical application of 35% $FeCl_3$ to assess the efficacy of the new anti-thrombotic agents.

• Advances in nano research
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• 제5권3호
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• pp.215-230
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• 2017

The development of hybrid systems comprising nanoparticles and polymers is an opening pathway for engineering nanocomposites exhibiting outstanding mechanical, optical, electrical, and magnetic properties. Among inorganic counterpart, iron oxide nanoparticles (IONP) exhibit high magnetization, controllable surface chemistry, spintronic properties, and biological compatibility. These characteristics enable them as a platform for biomedical applications and building blocks for bottom-up approaches, such as the layer-by-layer (LbL). In this regard, the present study is addressed to investigate IONP synthesised through co-precipitation route (average diameter around 7 nm), with either positive or negative surface charges, LbL assembled with sodium sulfonated polystyrene (PSS) or polyaniline (PANI). The surface and internal morphologies, and electrochemical properties of these nanocomposites were probed with atomic force microscopy, UV-vis and Raman spectroscopy, scanning electron microscopy, cross-sectional transmission electron microscopy, and electrochemical measurements. The nanocomposites display a globular morphology with IONP densely packed while surface dressed by polyelectrolytes. The investigation of the effect of thermal annealing (300 up to $600^{\circ}C$) on the oxidation process of IONP assembled with PSS was performed using Raman spectroscopy. Our findings showed that PSS protects IONP from oxidation/phase transformation to hematite up to $400^{\circ}C$. The electrochemical performance of nanocomposite comprising IONP and PANI were investigated in $0.5mol{\times}L^{-1}$ $Na_2SO_4$ electrolyte solution by cyclic voltammetry and chronopotentiometry. Our findings indicate this structure as promising candidate for potential application as electrodes for supercapacitors.

• 한국항행학회논문지
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• 제12권1호
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• pp.1-7
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• 2008

전방향표지시설 (VOR : VHF Omni-directional Range)은 1949년 국제민간항공기구(ICAO)에서 국제 항공항법 표준시스템의 하나로 지정한 이후, 각국에서 항공로 구성과 항공기의 이착륙 정보제공에 널리 사용하고 있다. 현재 VOR은 우리나라의 39 대를 포함하여 전 세계적으로 2,000여대가 설치되어 있어 가장 유용하게 활용되고 있는 단거리 항공 항법시스템이나, VHF 반송파를 진폭 및 주파수변조하여 항법정보를 제공하기 때문에 산악지대 등 주변 장애물의 영향을 많이 받아 예상하지 못한 성능 미흡으로 이미 설치한 장비를 다시 옮기는데 따른 비용과 시간이 많이 허비되는 등 사회적인 문제를 야기하기도 한다. 이 논문에서는 원거리 장애물이 VOR의 성능에 어느 정도 영향을 미치는 지를 계측기 등을 장착한 항공기를 이용하여 10개 VOR의 24개 장애물에 대하여 측정 및 분석하고, 이를 VOR의 설치장소 결정에 활용할 수 있도록 하여 성능 미흡으로 설치된 장비를 이전하는 등의 문제점을 해소하는데 도움을 주고자 한다.

• Bulletin of the Korean Chemical Society
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• 제34권12호
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• pp.3835-3839
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• 2013

A new synthesis route for Pt nanoparticles by direct electrochemical reduction of a solid-state Pt ion precursor ($K_2PtCl_6$) is demonstrated. Solid $K_2PtCl_6$-supported polyethyleneimine (PEI) coatings on the surface of glassy carbon electrode were prepared by simple mixing of solid $K_2PtCl_6$ into a 1.0% PEI solution. The potential cycling or a constant potential in a PBS (pH 7.4) medium were applied to reduce the solid $K_2PtCl_6$ precursor. The reduction of Pt(IV) began at around -0.2 V and the reduction potential was ca. -0.4 V. A steady state current was achieved after 10 potential cycling scans, indicating that continuous formation of Pt nanoparticles by electrochemical reduction occurred for up to 10 cycles. After applying the reduction potential of -0.6 V for 300 s, Pt nanoparticles with diameters ranging from $0.02-0.5{\mu}m$ were observed, with an even distribution over the entire glassy carbon electrode surface. Characteristics of the Pt nanoparticles, including their performance in electrochemical reduction of $H_2O_2$ are examined. A distinct reduction peak observed at about -0.20 V was due to the electrocatalytic reduction of $H_2O_2$ by Pt nanoparticles. From the calibration plot, the linear range for $H_2O_2$ detection was 0.1-2.0 mM and the detection limit for $H_2O_2$ was found to be 0.05 mM.

• Corrosion Science and Technology
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• 제17권3호
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• pp.101-108
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• 2018

AA7010 is an Al-Zn-Mg-Cu alloy containing Zr, developed as an alternate to traditional AA7075 alloy owing to their high strength combined with better fracture toughness. It is necessary to improve the corrosion resistance and surface properties of the alloy by incorporating plasma electrolytic oxidation (PEO) method. AA7010-T7452 aluminum alloy has been processed through the forging route with multi-stage working operations, and was coated with $10{\mu}m$ thick $Al_2O_3$ ceramic aluminina coating using the plasma electrolytic oxidation (PEO) method. The corrosion, stress corrosion cracking (SCC) and nano-mechanical behaviours were examined by means of potentiodynamic polarization, slow strain rate test (SSRT) and nano-indentation tests. The results indicated that the additional thermomechanical treatment during the forging process caused a fully recrystallized microstructure, which lead to the poor environmental cracking resistance of the alloy in 3.5% NaCl solution, despite the overaging treatment. Although the fabricated PEO coating improved general corrosion resistance, the brittle nature of the coating did not provide any improvement in SCC resistance of the alloy. However, the hardness and elastic modulus of the coating were significantly higher than the base alloy.

• 한국세라믹학회지
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• 제41권4호
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• pp.289-296
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• 2004

양론조성에 근접하는 (Ca/P=1.62-1.67, molar ratio) 휘스커 및 짧은 막대형상의 수산화아파타이트 (Ca$_{10}$(PO$_4$)$_{6}$(OH)$_2$를 $\alpha$-Ca$_3$(PO$_4$)$_2$($\alpha$-TCP) 수용액 (pH 11)의 가수분해와 수열반응으로 각각 합성하였다. 생성된 HAp의 입자형상은 합성방법에, 미세구조의 발달은 반응조건에 주로 의존하였다 가수분해의 경우 반응시간의 경과와 더불어 휘스커 입자들의 상호 교차와 장축방향에서의 응집이 일어났다 반면에, 수열처리에 있어서는 반응과정 중 임계크기(길이 0.75$mu extrm{m}$, 지름 0.3$\mu\textrm{m}$) 이상으로의 입성장은 일어나지 않았으며 과다한 반응시간(20$0^{\circ}C$, $\geq$3시간)은 입자들의 심한 응집을 유발하였다.

• 한국ITS학회 논문지
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• 제18권6호
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• pp.76-95
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• 2019

자중계는 화물차 운전자들이 자신의 화물무게를 인지하지 못해서 생기는 부득이한 과적을 방지하기 위해서 반드시 필요한 기술이다. 본 연구에서는 자중계의 일본의 의무장착 사례와 국내 활용현황에 대하여 조사하고 자중계와 GPS, 모뎀을 연동한 IoT 관제시스템을 시험차량에 설치한 후 원격 모니터링을 통해 과적운행패턴을 규명하고, 자중계 설치 시 과적 예방효과와 운송 효율성에 대하여 분석하고자 하였다. 장기 모니터링 데이터를 분석한 결과, 자중계 설치 후 운전자가 화물중량을 인지함으로써 과적율과 과적 중량이 감소되는 효과를 확인하였으며, 건설기계 차량의 경우 운송거리 단축에 의한 운송효율이 높아지는 결과를 확인하였다. 또한 단속지점의 GPS 좌표와 화물차량의 이동경로를 매칭하여 과적상태인 경우 회피 운행경로를 분석하였으며, 적재물의 종류에 따른 운행거리와 적재중량을 분석하였다.