• Transactions on Electrical and Electronic Materials
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• v.14 no.2
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• pp.86-89
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• 2013

Dye-sensitized solar cells have a FTO/$TiO_2$/Dye/Electrode/Pt counter electrode structure, yet more than a 10% electron loss occurs at each interface. A passivating layer between the $TiO_2$/FTO glass interface can prevent this loss of electrons. In theory, ZnO has excellent electron collecting capabilities and a 3.4 eV band gap, which suppresses electron mobility. FTO glass was coated with ZnO thin films by RF-magnetron sputtering; each film was deposited under different $O_2$:Ar ratios and RF-gun power. The optical transmittance of the ZnO thin film depends on the thickness and morphology of ZnO. The conversion efficiency was measured with the maximum value of 5.22% at an Ar:$O_2$ ratio of 1:1 and RF-gun power of 80 W, due to effective prevention of the electron recombination into electrolytes.

• Nuclear Engineering and Technology
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• v.36 no.2
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• pp.153-164
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• 2004

A computational fluid dynamics (CFD) analysis has been performed to investigate the turbulent flow and heat transfer in a triangular rod bundle with pitch-to-diameter ratios (P/D) of 1.06 and 1.12. Anisotropic turbulence models predicted the turbulence-driven secondary flow in a triangular subchannel and the distributions of the time mean velocity and temperature, showing a significantly improved agreement with the measurements from the linear standard $k-{\epsilon}$ model. The anisotropic turbulence models predicted the turbulence structure for a rod bundle with a large P/D fairly well, but could not predict the very high turbulent intensity of the azimuthal velocity observed in the narrow flow region (gap) for a rod bundle with a small P/D.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.209-209
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• 2000

Carbon nanotubes have been intensively investigated for its fundamental and technical importances. Structural diversities and the related diverse physical properties with large aspect ratios are fascinating, For instance carbon nanotubes are metal and semiconductors depending on its chirality and furthermore the band gap can be tailored by the diamters. Several issues on its fundamental properties have been discussed. We will review some fundamental problems for band structures, molecular quantum wires, homojunctions, single electron tunneling, and quantum conductance. Several issues related to syntheis of carbon nanotubes including arc discharge, chemical vapor deposition, laser ablation will be extentively discussed. We will further review the applicability of carbon nanotubes on resonator, nanobalance, FET-type transistor, field emission displays electrode for secondary battery and hydrogen storage.

• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.170-173
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• 2006

[ $CuInS_2$ ] filims were appeared from 0.84 to 1.27 of Cu/In composition ratio and sulfur composition ratios of $CuInS_2$ thin films fabricated, Also when Cu/In composition ratio was 1.03, $CuInS_2$ thin film with chalcopyrite structure had the highest XRD peak (112). And lattice constant (a) of and grain size of the film tin s ambient were appeared a little larger than those in only Vacuum The films in S ambient were p-type with resistive of around $10^{-1}{\Omega}cm$ and optical energy band gaps of the films in S ambient were appeared a little larger than those in only Vacuum. Analysis of the optical energy band gap of $CuInS_2$ thin films a value of 1.53eV.

• Journal of Korean Society of Forest Science
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• v.95 no.3
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• pp.342-349
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• 2006

The survey guideline of forest products statistics suggests a certain type of standard to aggregate production amount of each item such as dry bracken, raw dates, cracked nuts, It does not, however, give any information about transition ratios, which would apply to convert weights of fresh bracken into dry one, or cracked nuts into the non-cracked. This has been one of the main factors which would make the statistics unreliable. The purpose of this study is to examine the aggregation realities and to put forward some proposals to improve forest products statistics with transition ratios. Targets of this study are 10 forest products that are strongly related to the mentioned problems. With the calculated transition ratios and some assumptions the changing rate of the official statistics of 2004 production amounts ranged from -41% to 474% for the 10 subjects. The suggested figures for transitions are based only on one-year analysis results. Therefore more periods are required to improve the accuracy and the reliability, and this study would be a good starting point.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.3
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• pp.198-204
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• 2016

The characteristics of the flow field of a circular cylinder having a small vertical plate at the upstream side are investigated by measuring the fluid force on the circular cylinder and by visualizing the flow field using particle image velocimetry. The experimental parameters are the width ratios (H/B = 0.2-0.6) of the vertical plates to the circular cylinder's diameter, and the gap ratios (G/B = 0-3) between the circular cylinder and the vertical plate. The drag reduction rate and Strouhal number of the circular cylinder increased and then decreased with G/B in the case of the same H/B. The drag reduction rate increased with H/B in the case of the same G/B. In the case of a circular cylinder having a small vertical plate, the stagnation regions are represented on the upstream and downstream sides of the circular cylinder, and the size of that region on the upstream side increased with H/B.

• International Journal of Automotive Technology
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• v.6 no.4
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• pp.323-332
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• 2005

A cylindrical constant volume combustion chamber was used to investigate the flow characteristics at the spark electrode gap and the combustion characteristics of a homogeneous charged methane-air mixture under various overall charge pressures, excess air ratios and ignition times. The flow characteristics, including the mean velocity and turbulence intensity, were analyzed with a hot wire anemometer. Combustion pressure development measured by piezoelectric pressure transducer, a flame propagation image acquired by ICCD camera and exhaust emissions measured by 2-valve gas chromatography were used to investigate effects of initial pressures, excess air ratios and ignition times on the combustion characteristics. It was found that the mean velocity and turbulence intensity had the maximum value around 200-300 ms and then decreased gradually to a near-zero value after 3000 ms and that the combustion duration was shorten and the flame speed and laminar burning velocity had the highest value under the condition of an excess air ratio of 1.1, an overall charge pressure of 0.15 MPa and an ignition time of 300 ms in the present study. The $CO_2$ concentration was proportional to the ignition time and overall charge pressure, the $CO_2$ concentration was proportional to the excess air ratio, and the UHC concentration was inversely proportional to the ignition time and overall charge pressure.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.6
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• pp.808-813
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• 2012

The Characteristics of the drag reduction of a square prism having a detached splitter plate at the wake side were investigated by measuring of lift and drag on the square prism. The experimental parameters were the width ratios(H/B=0.5~1.5) of splitters to the prism width and the gap ratios (G/B=0~2) between the prism and the splitter plate. As the results the amplitude of the lift on the square prism having a detached splitter plate was remarkably decreased by comparison with the prototypical square prism. The drag reduction rate of the square prism was increased with H/B in case of the same G/B, and was increased and decreased with G/B in case of the same H/B. The maximum drag reduction rate was represented by 24.2% at H/B=1.5 and G/B=0.5.

• Coupled systems mechanics
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• v.6 no.3
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• pp.229-249
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• 2017

A new technique to mitigate irregular buildings with soil structure interaction (SSI) effect subjected to critical seismic waves is presented. The L-shape in plan irregular building for various reasons was selected, subjected to seismic a load which is a big problem for structural design especially without separation gap. The L-shape in plan building with different dimensions was chosen to study, with different rectangularity ratios and various soil kinds, to show the effect of the irregular building on the seismic response. A 3D building subjected to critical earthquake was analyzed by structural analysis program (SAP2000) fixed and with SSI (three types of soils were analyzed, soft, medium and hard soils) to find their effect on top displacement, base shear, and base torsion. The straining actions were appointed and the treatment of the effect of irregular shape under critical earthquake was made by using tuned mass damper (TMD) with different configurations with SSI and without. The study improve the success of using TMDs to mitigate the effect of critical earthquake on irregular building for both cases of study as fixed base and raft foundation (SSI) with different TMDs parameters and configurations. Torsion occurs when the L-shape in plan building subjected to earthquake which may be caused harmful damage. TMDs parameters which give the most effective efficiency in the earthquake duration must be defined, that will mitigate these effects. The parameters of TMDs were studied with structure for different rectangularity ratios and soil types, with different TMD configurations. Nonlinear time history analysis is carried out by SAP2000 with El Centro earthquake wave. The numerical results of the parametric study help in understanding the seismic behavior of L-shape in plan building with TMDs mitigation system.

• Earthquakes and Structures
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• v.8 no.6
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• pp.1325-1348
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• 2015

Real-time hybrid testing (RTHT) involves virtual splitting of the structure into two parts: physical substructure that contains the key region of interest which is tested in a laboratory and numerical substructure that contains the remaining part of the structure in the form of a numerical model. This paper numerically assesses four step-by-step integration methods (Central difference method (CDM), Operator splitting method (OSM), Rosenbrock based method (RBM) and CR-integration method (CR)) which are widely used in RTHT. The methods have been assessed in terms of stability and accuracy for various realistic damping ratios of the physical substructure. The stability is assessed in terms of the spectral radii of the amplification matrix while the accuracy in terms of numerical damping and period distortion. In order to evaluate the performance of the methods, five carefully chosen examples have been studied - undamped SDOF, damped SDOF, instantaneous softening, instantaneous hardening and hysteretic system. The performance of the methods is measured in terms of a non-dimensional error index for displacement and velocity. Based on the error indices, it is observed that OSM and RBM are robust and performs fairly well in all the cases. CDM performed well for undamped SDOF system. CR method can be used for the system showing softening behaviour. The error indices indicate that accuracy of OSM is more than other method in case of hysteretic system. The accuracy of the results obtained through time integration methods for different damping ratios of the physical substructure is addressed in the present study. In the presence of a number of integration methods, it is preferable to have criteria for the selection of the time integration scheme. As such criteria are not available presently, this paper attempts to fill this gap by numerically assessing the four commonly used step-by-step methods.