• Journal of Electrochemical Science and Technology
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• v.8 no.4
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• pp.307-313
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• 2017

In this paper we report an electrochemical sensor based on ZnO-functionalized graphene oxide nanocomposite (ZnO-GO) for the sensitive determination of the cabergoline. Cabergoline electrochemical behaviors were investigated by cyclic voltammetry (CV), chronoamperometry (CHA) and differential pulse voltammetry (DPV). The modified electrode shows electrocatalytic activity toward cabergoline oxidation in phosphate buffer solution (PBS) (pH 7.0) with a reduction of the overpotential of about 180 mV and an increase in peak current. The DPV data showed that the obtained anodic peak currents were linearly dependent on the cabergoline concentrations in the range of $1.0-200.0{\mu}M$, with the detection limit of $0.45{\mu}M$. The prepared electrode was successfully applied for the determination of cabergoline in real samples.

• Carbon letters
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• v.14 no.2
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• pp.126-130
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• 2013

In this study, we present a more electrochemically enhanced electrode using activated carbon (AC)-sulfur (S) composite materials, which have high current density. The morphological and micro-structure properties were investigated by transmission electron microscopy. Quantity of sulfur was measured by thermogravimetric analysis analysis. The electrochemical behaviors were investigated by cyclic voltammetry. As a trapping carbon structure, AC could provide a porous structure for containing sulfur. We were able to confirm that the AC-S composite electrode had superior electrochemical activity.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.12
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• pp.2056-2061
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• 2001

Non-proportional loading tests of Nylon 66 at room temperature exhibit path dependent behavior and plasticity-relaxation interactions. The uniaxial formulation of the viscoplasticity theory based on overstress (VBO), which has been used to reproduce the nonlinear strain rate sensitivity, relaxation, significant recovery and cyclic softening behaviors of Nylon 66, is extended to three-dimensions to predict the response in strain-controlled, comer-path tests. VBO consists of a flow law that is easily written for either the stress or the strain as the independent variable. The flow law depends on the overstress, the difference between the stress and the equilibrium stress that is a state variable in VBO. The evolution law of the equilibrium stress in turn contains two additional state variables, the kinematic stress and the isotropic stress. The simulations show that the constitutive model is competent at modeling the deformation behavior of Nylon 66 and other solid polymers.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10c
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• pp.211-216
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• 1998

Recently the shortage of good aggregate has encouraged the use of sea sand in construction field, and the corrosion damage of the reinforced steel in concrete structures has been increased due to chlorides from sea sand and deicing salt. Therefore, a number of researchs are proceeding to prevent the corrosion of the reinforced steel in concrete, especially in marine environments. This study focused on the effect of corrosion inhibitors to evaluate protection characteristics for mortar specimens containing clorides. Corrosion behaviors have been investigated by half-cell potential measurement, linear polarization method, AC impedance method, and cyclic polarization test after immersing in sea water for 7 years. A possitive effect of a corrosion inhibitor has been obtained.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.700-705
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• 2007

In this study, we observe the application of shape memory alloy(SMA) into smart structures for repeatable actuation, because SMA changes its material properties and characteristics progressively under cyclic loading conditions and finally reaches stable path(state) after a certain number of stress/temperature loading-unloading cycles, so called 'training'. In this paper, SMA wires that have been in a stable state through the training are used. Stress-strain curve of the SMA wire at different temperature levels are measured. In addition, we observe other important effects such as the rate effect according to strain rates for rapid actuation response. The current work presents the experimental test using SMA wire after training completion by mechanical cycling. Through these tests, we measure the characteristics of SMA. With the estimated SMA properties and effects, we compare the experimental results with the simulation results based on the SMA constitutive equations.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.214.1-214.1
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• 2011

In this work, the electrochemical properties of the surface treated multi-walled carbon nanotubes (MWNTs) are investigated for supercapacitors. Nitrogen- and oxygen functional groups containing MWNTs are prepared by nitrogen precursors and acidic treatment, respectively. The surface properties of the MWNTs are confirmed by X-ray photoelectron spectroscopy (XPS) and Zeta-potential measurements. The electrochemical properties of the MWNTs are investigated by cyclic voltammetry, impedance spectra, and charge-discharge cycling performance in 1 M $H_2SO_4$ at room temperature. As a result, these functionalized MWNTs lead to an increase in the specific capacitance as compared with the pristine MWNTs. It proposes that the pyridinic and pyridinic-N-oxides nitrogen species influence on the specific capacitance due to their positive charges, and thus an improved electron transfer at high current loads, since they are the most important functional groups affecting capacitive behaviors.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.159.2-159.2
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• 2011

In this study, we prepared the activated graphite nanofibers (A-GNFs) via chemical activation with KOH reagent. The effect of A-GNFs on the surface and textural properties of Ni-loaded graphite nanofibers (Ni/GNFs) was investigated by X-ray diffraction (XRD), transmission electron microscope (TEM), and Brunauer-Emmett-Teller (BET). The textural properties of samples were investigated by $N_2$/77K adsorption isotherms. The electrochemical performances were investigated by cyclic voltammetry. As a results, the electrochemical performances of Ni/GNFs were improved with usage of A-GNFs. This could be interpreted by the high specific surface area and large total pore volume of the A-GNFs.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.6
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• pp.7-13
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• 2010

In this study, we investigated the efficient FE modelling techniques for thermal stress analysis of the exhaust manifold subject to thermo-mechanical cyclic loadings. At first, full engine model was considered to identify the critical locations and their results were compared to failure site shown by the engine bench test. And the equivalent system model was proposed based on the mechanical behavior of the full engine model. The weak areas of both FE models show a good agreement with the experimental crack location. As a result, a simplified modelling methodology was verified to estimate the thermo-mechanical behaviors of the exhaust manifold under thermal shock test condition.

• Journal of Electrochemical Science and Technology
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• v.3 no.2
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• pp.85-89
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• 2012

This study demonstrates the direct anodic electrodeposition of polypyrrole (PPy), poly(3,4-ethyl-enedioxythiophene) (PEDOT), and polythiophene (PTh) on Cu electrodes by employing a corrosion inhibitor, succinonitrile (SN). SN was found to suppress anodic Cu dissolution beyond the oxidation potential of the polymer monomers. It is also revealed that the Cu surface passivated by SN is still adequately conductive to allow the redox reaction of 1,4-difluoro-2,5-dimethoxybenzene (FMB) and the oxidation of the polymer monomers. Through both cyclic voltammetry and galvanostatic techniques, PPy, PEDOT, and PTh films were successfully synthesized on Cu electrodes in the presence of SN, and the redox behaviors of the films were evaluated.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.891-897
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• 2006

The volume control method which utilize a pressure node added into a finite shell element can overcome the drawbacks of conventional load control method and displacement control method. In this study, an improved volume control method is introduced for effective analysis of path-dependant behaviors of RC structures subjected to cyclic loading. RC shell structures including RC hollow columns are anlayized by discretizing the structures with layered shell elements and by applying in-plane two dimensional constitutive equations for concrete layers and reinforcement layers of the shell elements. The so-called path dependant volume control method is verified by comparing analysis results with other data including experimental results.