• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.2
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• pp.94-97
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• 2018

Lead zirconate titanate/poly-vinylidene fluoride (PZT/PVDF) piezoelectric devices were fabricated by incorporating carbon nanotubes (CNTs), for use as flexible energy harvesting devices. CNTs were added to maximize the formation of the ${\beta}$ phase of PVDF to enhance the piezoelectricity of the devices. The phase transition of PVDF induced by the addition of CNTs was confirmed by analyzing the X-ray diffraction patterns, scanning electron microscopy images, and atomic force microscopy images. The enhanced output efficiency of the PZT/PVDF piezoelectric devices was confirmed by measuring the output current and voltage of the fabricated devices. The maximum output current and voltage of the PZT/PVDF piezoelectric devices was 200 nA and 350 mV, respectively, upon incorporation of 0.06 wt% CNTs.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.3
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• pp.212-215
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• 2005

Modified illumination techniques have been used to enhance the resolution of the sub-wavelength lithography. But, since they shield the central part of incident light, the light efficiency is seriously degraded, which in turn reduces the throughput of a lithography process. In this research, we introduced an annular illumination structure that enhances the light efficiency with a concentric circular grating at the backside of a photomask. The efficiency of the structure was theoretically analyzed.

• Journal of the Korean Ceramic Society
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• v.54 no.4
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• pp.308-313
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• 2017

In this study we examined the photo-degradation efficiency of $CoS_2-G-TiO_2$ nanocomposites under visible light irritation using Reactive Black B (RBB) as standard dye, $CoS_2-G-TiO_2$ nanocomposites synthesized by facial microwave assist technique, and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopic analysis. Our results show the efficiency of the $CoS_2-G-TiO_2$ ternary nanocomposite is better than $CoS_2-G$ and $TiO_2-G$ nanocomposite. The degradation efficiency of $CoS_2-G-TiO_2$ nanocomposite was found approximately 89% of Reactive Black B (RBB) degraded after 180 min. Our results will open new way for the development of a new ternary nanocomposite photocatalytic application.

• Carbon letters
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• v.5 no.4
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• pp.186-190
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• 2004

In this work, a nickel metal (Ni) electroplating on the activated carbon fiber (Ni/ACFs) surfaces was carried out to remove the toxic hydrogen chloride (HCl) gas. The surface properties of the treated ACFs were determined by using nitrogen adsorption isotherms at 77 K, SEM, and X-ray diffraction (XRD) measurements. HCl removal efficiency was confirmed by a gas-detecting tube technique. As a result, the nickel metal contents on the ACF surfaces were increased with increasing the plating time. And, it was found that the specific surface area or the micropore volume of the ACFs studied was slightly decreased as increasing the plating time. Whereas, it was revealed that the HCl removal efficiency containing nickel metal showed higher efficiency values than that of untreated ACFs. These results indicated that the presence of nickel metal on the ACF surfaces played an important role in improving the HCl removal over the Ni/ACFs, due to the catalytic reactions between nickel and chlorine.

• Transactions on Electrical and Electronic Materials
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• v.12 no.3
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• pp.123-126
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• 2011

Titanium dioxide ($TiO_2$) thin films were deposited by the sol-gel method with a surfactant-assisted mechanism. Its application for dye-sensitized solar cells (DSSCs) was investigated. Brunauer-Emmett-Teller, X-ray diffraction and field emission scanning electron microscopy techniques were used to characterize the surface characteristics of thin films. Photovoltaic-current density measurements were performed to determine the photoelectrochemical properties of the thin films and the performance of DSSCs. Energy conversion efficiency of about 6.1% was achieved for cells with conductive glass under illumination with AM 1.5 (100 $mWcm^{-2}$) simulated sunlight. Investigation showed higher photo-energy conversion efficiency for mesoporous $TiO_2$ nanocrystalline films used in DSSCs relative to commercially available Degussa P25 films.

• International Journal of Fluid Machinery and Systems
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• v.10 no.2
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• pp.146-153
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• 2017

Sediment flow through hydropower components causes hydro-abrasive erosion resulting in loss of efficiency, interruptions in power production and downtime for repair/maintenance. Online instruments are required to measure/capture the variations in sediment parameters along with collecting samples manually to analyse in laboratory for verification. In this paper, various sediment parameters viz. size, concentration (TSS), shape and mineral composition relevant to hydro-abrasive erosion were measured and discussed with respect to a hydropower plant in Himalayan region, India. A multi-frequency acoustic instrument was installed at a desilting chamber to continuously monitor particle size distribution (PSD) and TSS entering the turbine during 27 May to 6 August 2015. The sediment parameters viz. TSS, size distribution, mineral composition and shape entering the turbine were also measured and analysed, using manual samples collected twice daily from hydropower plant, in laboratory with instruments based on laser diffraction, dynamic digital image processing, gravimetric method, conductivity, scanning electron microscope, X-ray diffraction and turbidity. The acoustic instrument was able to capture the variation in TSS; however, significant deviations were found between measured mean sediment sizes compared to values found in the laboratory. A good relation was found for turbidity ($R^2=0.86$) and laser diffraction ($R^2=0.93$) with TSS, which indicated that turbidimeter and laser diffraction instrument can be used for continuous monitoring of TSS at the plant. Total sediment load passed through penstock during study period was estimated to be 15,500 ton. This study shall be useful for researchers and hydropower managers in measuring/monitoring sediment for hydro-abrasive erosion study in hydropower plants.

• Korean Journal of Mineralogy and Petrology
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• v.34 no.4
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• pp.227-239
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• 2021

A practical and effective method of X-ray powder diffraction analysis was investigated for quantitative analysis of the mineral content of natural samples. Sample mounting experiments were conducted to select the best randomly oriented powder sample mount. A comparative experiment was also made between a reference intensity ratio (RIR) method, which compares a single peak intensity with standard material, and the Rietveld method, which calculates a full X-ray diffraction pattern, to search for the effective method of mineral quantification. In addition, samples containing amorphous minerals were quantitatively analyzed by the Rietveld method and the efficiency was reviewed. As a result of the study, the optimal random orientation could be reached by the side mounting method. The Rietveld method using the full pattern of X-ray diffraction was more suitable for mineral quantitative analysis, rather than the RIR method using a specific peak. However, either method could depend on the analyst's experience in addition to analytical technique. Moreover, amorphous minerals can be quantitatively analyzed by the Rietveld method, and the analysis results make the geological analysis possible.

• Journal of the Optical Society of Korea
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• v.7 no.4
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• pp.264-268
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• 2003

A new approach to design binary phase holograms, with less computation time and equal effi-ciency compared with the genetic algorithm method, is proposed. Synthesized holograms having diffraction efficiency of 75.8% and uniformity of 5.8% are tested in computer simulation and experimentally demonstrated.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.1216-1219
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• 2004

LC and polymer miscibility in HPDLC has been studied in terms of solubility parameter. It was found that better grating formation and diffraction efficiency were obtained when the difference in solubility parameters between polymer and LC is greater.

• Proceedings of the Optical Society of Korea Conference
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• 1990.02a
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• pp.126-130
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• 1990

A single-layer Perceptron with 4x4 input neurons and one output neuron is optically implemented. Holo-graphic lenslet arrays are usee for the programmable optical interconnection topology. The hologram is bleached in order to increase the diffraction efficiency. It is shown that the performance of Perceptron depends on the learning rate, the inertia rate, and the correlation of input patterns.