• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1995년도 봄 학술발표회 논문집
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• pp.396-401
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• 1995

Epoxy coated reinforcing steels (ECRs) were acquired from ten sources and coatings from each source were initially characterized in terms of defects, thickness, solvent extraction weight loss and hardness. Testing involved exposure in three aqueous solutions at elevated temperature (8$0^{\circ}C$) and in chloride-contaminated concrete slabs under outdoor exposure, It was found that the density and size of coating defects was the promary factor affecting ECR performance. The equivalent circuit analysis using electrochemical impedance spectroscopy (EIS) data indicated that the impedance response for well-performing ECR specimens showed no signs of active degradation at the interface although diffusional processes similar to those noted for poorly performing bars occurred here. Experimental results also indicated a relationship between corrosion behavior and bar source. Weight loss upon solvent extraction correlated with impedance reduction from hot water exposure. Coating defects during most of the tests, especially in high pH solutions containing chloride ions. ECRs with excessive coating defects, either initially present or ones which developed in service, performed poorly in every test category regardless of source. Forms of coating failure were extensive rusting at defects, blistering, wet adhesion loss, cathodic delamination, underfilm corrosion and coating cracks. These occurred sequentially or concurrently, depending on the condition of the ECR and nature of the environment

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.136-141
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• 2007

This paper introduces an artificial neuron which is a nano composite continuous sensor. The continuous nano sensor is fabricated as a thin and narrow polymer film sensor that is made of carbon nanotubes composites with a PMMA or a silicone matrix. The sensor can be embedded onto a structure like a neuron in a human body and it can detect deteriorations of the structure. The electrochemical impedance and dynamic strain response of the neuron change due to deterioration of the structure where the sensor is located. A network of the long nano sensor can form a structural neural system to provide large area coverage and an assurance of the operational health of a structure without the need for actuators and complex wave propagation analyses that are used with other methods. The artificial neuron is expected to effectively detect damage in large complex structures including composite helicopter blades and composite aircraft and vehicles.

• 분석과학
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• 제5권1호
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• pp.79-82
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• 1992

연속적으로 흐르는 시료의 검출을 위한 양극펄스형 전기전도성 검출기를 개발하였다. 개발한 전기전도성 검출기는 동작이 매우 빠를 뿐더러 직렬 혹은 병렬축전 방해효과가 없으므로 사용이 쉽다. 개발한 양극펄스형 전기전도성 검출기의 성능을 $10^1{\sim}10^8$저항을 가진 가상 셀들을 사용하여 시험한 결과 0.01% 상대편차를 보이는 직선성 응답을 얻을 수 있었다. 개발한 전기 전도성 검출기의 장단점과 여러 가능한 응용들에 대해서도 검토하였다.

• Journal of the Optical Society of Korea
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• 제18권4호
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• pp.301-306
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• 2014

A porous silicon microcavity (PSMC) sensor has been made for vapors of solvent solutions, and a method has been developed in order to obtain simultaneous determination of two volatile substances with different concentrations. In our work, the temperature of the solution and the velocity of the air stream flowing through the solution have been used to control the response of the sensor for ethanol and acetone solutions. We study the dependence of the cavity-resonant wavelength shift on solvent concentration, velocity of the airflow and solution temperature. The wavelength shift depends linearly on concentration and increases with solution temperature and velocity of the airflow. The dependence of the wavelength shift on the solution temperature in the measurement contains properties of the temperature dependence of the solvent vapor pressure, which characterizes each solvent. As a result, the dependence of the wavelength shift on the solution temperature discriminates between solutions of ethanol and acetone with different concentrations. This suggests a possibility for the simultaneous determination of the volatile substances and their concentrations.

• 한국재료학회지
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• 제28권7호
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• pp.411-416
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• 2018

Tungsten oxide($WO_3$) films with uniform surface morphology are fabricated using a spin-coating method for applications of electrochromic(EC) devices. To improve the EC performances of the $WO_3$ films, we control the heating rate of the annealing process to 10, 5, and $1^{\circ}C/min$. Compared to the other samples, the $WO_3$ films fabricated at a heating rate of $5^{\circ}C/min$ shows superior EC performances for transmittance modulation(49.5 %), response speeds(8.3 s in a colored state and 11.2 s in a bleached state), and coloration efficiency($37.3cm^2/C$). This performance improvement is mainly related to formation of a uniform surface morphology with increased particle size without any cracks by an optimized annealing heating rate, which improves the electrical conductivity and electrochemical activity of the $WO_3$ films. Thus, the $WO_3$ films with a uniform surface morphology prepared by the optimized annealing heating rate can be used as a potential candidate for performance improvement of the EC devices.

• Bulletin of the Korean Chemical Society
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• 제31권1호
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• pp.140-145
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• 2010

The simultaneous detection of Cd (II), Pb (II), Cu (II), and Hg (II) ions in aqueous medium using a BDD electrode with DPASV is described. XPS was used to characterize the chemical states of trace metal ions deposited on the BDD electrode surface. Experimental parameters that affect response, such as pH, deposition time, deposition potential, and pulse amplitude were carefully optimized. The detection limits for Cd (II), Pb (II), Cu (II), and Hg (II) ions were 3.5 ppb, 2.0 ppb, 0.1 ppb and 0.7 ppb, respectively. The application of the BDD electrode on the electrochemical pretreatment for the simultaneous metal detection in the dye waste water was also investigated.

• Bulletin of the Korean Chemical Society
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• 제35권1호
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• pp.204-210
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• 2014

The nitrogen doped porous carbon nanopolyhedrons (N-PCNPs)-multi-walled carbon nanotubes (MWCNTs) hybrid materials were prepared for the first time. Combining the excellent catalytic activities, good electrical conductivities and high surface areas of N-PCNPs and MWCNTs, the simultaneous determination of hydroquinone (HQ), catechol (CC) and resorcinol (RE) with good analytical performance was achieved at the N-PCNPs-MWCNTs modified electrode. The linear response ranges for HQ, CC and RE are 0.2-455 ${\mu}M$, 0.7-440 ${\mu}M$ and 3.0-365 ${\mu}M$, respectively, and the detection limits (S/N = 3) are $0.03{\mu}M$, $0.11{\mu}M$ and $0.38{\mu}M$, respectively. These results are much better than that obtained on some graphene or CNTs-based materials modified electrodes. Furthermore, the developed sensor was successfully applied to simultaneously detect HQ, CC and RE in the local river water samples.

• 한국태양에너지학회 논문집
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• 제34권1호
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• pp.91-97
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• 2014

This paper proposes a modeling of fuel cell which replaces dc source during simulation. Fuel cells are electrochemical devices that convert chemical energy in fuels into electrical energy. This system has high efficiency and heat, no environmental chemical pollutions and noise. Proton exchange membrane fuel cells (PEMFC) are commonly used as a residential generator. These fuel cells have different electrical characteristics such as a low voltage and high current compared with solar cells. And there are different behaviors in the V-I curve in the temperature and pressure. Therefore, the modeling of fuel cell should consider wide voltage range and slow current response and the resulting electrical model is applied to boost converter with fuel cell as an input source.

• Bulletin of the Korean Chemical Society
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• 제24권1호
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• pp.37-44
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• 2003

We examined the effect of polyether-type nonionic surfactants (Brij 35, Triton X-100, Tween 20 and Tween 80) on the potentiometric properties of sodium-, potassium- and calcium-selective membranes which are prepared with widely used ionophores and four kinds of polymer matrices [poly(vinyl chloride) (PVC), polyurethane (PU), PVC/PU blend, and silicone rubber (SR)]. It was found that the PVC-based membranes, which provide the best performance among all other matrix-based membranes in the absence of nonionic surfactants, exhibited larger change in their potentiometric properties when nonionic surfactants are added to the sample solution. On the other hand, the sodium-selective SR-based membrane with calix[4]arene, potassium-selective PVC/PU- or SR-based membrane with valinomycin, and the calcium-selective SR-based membrane with ETH 1001 provide almost identical analytical performance in the presence and absence of Tween 20 or Tween 80 surfactants. The origin of nonionic surfactants effect was also investigated by interpreting the experimental results obtained with various matrices and ionophores. The results suggest that the nonionic surfactant extracted into the membrane phase unselectively form complexes with the primary and interfering ions, resulting in increased background potential and lower binding ability for the ionophore. Such effects should result in deteriorated detection limits, reduced response slopes and lower selectivity for the primary ions.

• 한국환경과학회지
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• 제16권10호
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• pp.1111-1118
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• 2007

A bismuth-coated carbon fiber microelectrode was prepared using cyclic voltammetry (CV). An analytical application was performed for the copper analysis with Square Wave Stripping Voltammetry (SWSV). Gallic acid n-propyl ester (PG) was used for the complex formation with a copper ion, and electrochemical measurements were performed with a pre-amplifier of a low-current module for nano am per detection. The effects of various parameters on the response were optimized. Analytical working ranges of $0.03-25.9\;{\mu}gl^{-1}$ and $0-25\'mgl^{-1}$ Cu(II) were obtained. The relative standard deviation at $13\;mgl^{-1}$ Cu was 0.9% (n = 12) in optimum conditions. The detection limit was found to have been $0.019\;{\mu}gl^{-1}$, with a 30-sec accumulation time. The developed methods were applied to a copper assay in water samples.