• Nano
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• v.13 no.11
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• pp.1850125.1-1850125.12
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• 2018

To reduce the imbalance of impedance matching between the magnetic metal nanowires and free space, $Fe/TiO_2$ core/shell nanowire arrays with different diameters were fabricated in the templates of anodic aluminum oxide membranes by electrodeposition. The influences of the microstructure on the microwave absorption properties of the $Fe/TiO_2/Al_2O_3$ composites were studied by the transmission/reflection waveguide method. It was demonstrated experimentally that both the interfacial polarization and the diameter of the $Fe/TiO_2$ core/shell nanowires have critical effects on the microwave absorption properties. We also investigated the angle dependence of the microwave absorption properties. Due to the interfacial polarization and associated relaxation, the $Fe/TiO_2/Al_2O_3$ composites exhibited optimal microwave absorption properties when microwave propagation direction was accordant with the axis of the nanowires. Finally, we managed to obtain an optimal reflection loss of below -10 dB (90% absorption) over 10.2-14.8 GHz, with a thickness of 3.0 mm and the minimum value of -39.4 dB at 11.7 GHz.

• Journal of the Korean institute of surface engineering
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• v.53 no.6
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• pp.351-359
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• 2020

Formation behavior and properties of PEO (Plasma Electrolytic Oxidation) film on AA2024 were investigated under application of pulsed current as a function of Na3PO4 concentration in 0.05 M Na2SiO3 solution by analyzing voltage-time behavior, in-situ observation of arc generation, observation of surface morphology and measurements of thickness and surface roughness. Arc generation voltage decreased with increasing Na3PO4 concentration. Color difference of PEO films between edge and inner part disappeared by addition of Na3PO4. It was also observed that size of nodules on PEO film decreased with increasing Na3PO4 concentration. Thickness of PEO films formed on AA2024 increased with increasing Na3PO4 concentration. Whereas, surface roughness of PEO films decreased with increasing Na3PO4 concentration up to 0.05 M of Na3PO4 which is attributed to the deceased size of nodules on the PEO films. However, the surface roughness increased with increasing Na3PO4 concentration more than 0.07 M of Na3PO4 which seems to be due to the formation of non-uniform PEO films with smooth surface and large size pores formed by orange-colored big arcs. The experimental results suggest that added sodium phosphate less than 0.2 M in an alkaline silicate solution can contribute to the formation of relatively thick and uniform thickness of PEO films under arc generation voltage lower than 300 V.

• Journal of Animal Science and Technology
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• v.65 no.1
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• pp.258-270
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• 2023

Climate change has worsened droughts and floods, and created conditions more likely to lead to pathogen contamination of surface water and groundwater. Thus, there is a growing need to disinfect livestock water. Ultraviolet (UV) irradiation is widely accepted as an appropriate method for disinfecting livestock water, as it does not produce hazardous chemical compounds and kills pathogens. However, UV-based disinfection inevitably consumes electricity, so it is necessary to improve UV disinfection effectiveness. Aluminum-based reflective nanolens arrays that enhanced the effectiveness of a continuous-flow UV water disinfection system were developed using electrochemical and chemical processes, including electropolishing and two-step anodization. A continuous UV disinfection system was custom designed and the parts were produced using a three-dimensional printer. Electropolished aluminum was anodized at 40 and 80 V in 0.3 M oxalic acid, at 120 and 160 V in 1.0 M phosphoric acid, and at 200 and 240 V in 1.5 M citric acid. The average nanolens diameters (D) of the aluminum-based reflective nanolens arrays prepared using 40, 80, 120, 160, 200, and 240 V anodization were 95.44, 160.98, 226.64, 309.90, 296.32, and 339.68 nm, respectively. Simple UV reflection behind irradiated water disinfected Escherichia coli O157:H7 in water more than did the non-reflective control. UV reflection and focusing behind irradiated water using an aluminum-based reflective nanolens array disinfected E. coli O157:H7 more than did simple UV reflection. Such enhancement of the UV disinfection effectiveness was significantly effective when a nanolens array with D 226.64 nm, close to the wavelength of the irradiated UV (254 nm), was used.

• Composites Research
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• v.19 no.6
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• pp.23-31
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• 2006

We measured mechanical properties, including Young's modulus, effective bending modulus and nominal fracture strength of nanohoneycomb structures using an Atomic Force Microscope(AFM) and a Nano-Universal Testing Machine(UTM). Anodic aluminum oxide(AAO) films are well suited as nanohoneycomb structures because of the simple fabrication process, high aspect ratio, self-ordered hexagonal pore structure, and simple control of pore dimensions. Bending tests were carried out for cantilever structures by pressing AFM tips, and the results were compared with three-point bending tests and tensile tests using a Nano-UTM. One side of the AAO films is clogged by harrier layers, and looks like a face material of conventional sandwich structures. Analysis of this layer showed that it did not influence the bending rigidity, and was just a crack tip. The present results can act as a design guideline in applications of nanohoneycomb structures.

• Journal of Convergence Korean Medicine
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• v.2 no.1
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• pp.5-12
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• 2021

Objectives: The purpose of this study is to fabricate an ultra-fine ginsenoside particle atomizer that can provide a new treatment method by delivering ginsenoside components that have a therapeutic effect on respiratory diseases directly to the lungs. Methods: We fabricated the AAO vibrating mesh by using the micromachining process. The starting substrate of an AAO wafer has a 350nm pore diameter with 50㎛ thickness. A photomask having several 5㎛ opening holes with a 100㎛ pitch was used to separate each nanopore nozzle. The photoresist structure was optimized to pattern the nozzle area during the lift-off process precisely. The commercial vibrating mesh was removed from OMRON's NE-U100 product, and the fabricated AAO vibrating mesh was installed. A diluted sample of 20mL with 30% red ginseng concentrate was prepared to atomize from the device. Results: As a result of liquid chromatography analysis before spraying the ginsenoside solution, ginsenoside components such as 20S-Rg3, 20R-Rg3, and Rg5 were detected. After spraying through the AAO vibrating mesh, ginsenosides of the same component could be detected. Conclusion: A nutrient solution containing ginsenosides was successfully sprayed through the AAO vibrating mesh with 350 nm selective pores. In particular, during the atomizing experiment of ginsenoside drug solution having excellent efficacy in respiratory diseases, it was confirmed that atomizing through the AAO vibrating mesh while maintaining most of the active ingredients was carried out.

• The Journal of the Korea Contents Association
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• v.14 no.2
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• pp.181-191
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• 2014

In the past, making IR photography needed somewhat complicated process, so its application fields were limited. However, it has become easy to make IR photography with advanced digital technology, so it is expected that the fields of IR photography and existing limit due to difficult making process will be expanded. Therefore, in this study, it is decided that the need of IR standard chart which allows us to manage exposure and tone of IR photography for scientific purpose will increase. Two methods were used to make IR standard chart. First method is to use aluminum. When aluminum has oxide coating through anodic oxidation, it has high durability, corrosion resistance and heat resistance. Also, IR reflectance of aluminum can be controlled in some degree depending on the thickness of oxide coating. Second method is to use pigments. Yellow 10P150 pigment is used for the brightest patch. This pigment is appropriate in this study due to high heat resistance and IR reflectance. Carbon black is used for the darkest patch. Carbon black absorbs much IR, and its color is not faded by any source of light. IR reflectance is adjusted elaborately by mixing two pigments. Finally, 6 patches are selected with consideration for actual IR reflectance of patches. As a result, IR reflectance of random subjects can be known approximately and IR photographs can have appropriate contrast with the IR standard chart.

• Journal of the Korean Electrochemical Society
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• v.19 no.1
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• pp.1-8
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• 2016

Capacity of layered lithium nickel-cobalt-manganese oxide ($LiNi_{1-x-y}Co_xMn_yO_2$) cathode material can increase by raising the charge cut-off voltage above 4.3 V vs. $Li/Li^+$, but it is limited due to anodic instability of conventional electrolyte. We have been screening and evaluating various sulfone-based compounds of dimethyl sulfone (DMS), diethyl sulfone (DES), ethyl methyl sulfone (EMS) as electrolyte additives for high-voltage applications. Here we report improved cycling performance of $LiNi_{0.5}Co_{0.2}Mn_{0.3}O_2$ cathode by the use of dimethyl sulfone (DMS) additive under an aggressive charge condition of 4.6 V, compared to that in conventional electrolyte, and cathode-electrolyte interfacial reaction behavior. The cathode with DMS delivered discharge capacities of $198-173mAhg^{-1}$ over 50 cycles and capacity retention of 84%. Surface analysis results indicate that DMS induces to form a surface protective film at the cathode and inhibit metal-dissolution, which is correlated to improved high-voltage cycling performance.

• Journal of Sensor Science and Technology
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• v.11 no.3
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• pp.163-170
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• 2002

This paper proposes a $10\;{\mu}m$ thick oxide air-bridge structure which can be used as a substrate for RF circuits. The structure was fabricated by anodic reaction, complex oxidation and micromachining technology using TMAH etching. High quality films were obtained by combining low temperature thermal oxidation ($500^{\circ}C$, 1 hr at $H_2O/O_2$) and rapid thermal oxidation (RTO) process ($1050^{\circ}C$, 2 min). This structure is mechanically stable because of thick oxide layer up to $10\;{\mu}m$ and is expected to solve the problem of high dielectric loss of silicon substrate in RF region. The properties of the transmission line formed on the oxidized porous silicon (OPS) air-bridge were investigated and compared with those of the transmission line formed on the OPS layers. The insertion loss of coplanar waveguide (CPW) on OPS air-bridge was (about 2dB) lower than that of CPW on OPS layers. Also, the return loss of CPW on OPS air-bridge was less than about -20 dB at measured frequency region for 2.2 mm. Therefore, this technology is very promising for extending the use of CMOS circuitry to higher RF frequencies.

• Journal of the Korean Ceramic Society
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• v.40 no.9
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• pp.909-915
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• 2003

Anodic oxide films on aluminum play an important role as a dielectrics in aluminum electrolytic capacitor. In order to obtain the high capacitance, ZrO$_2$ films were coated on aluminum foils by sol-gel method and then, the properties of anodized films were studied. The coating and drying of the films were repeated 4-10 times and annealed at 300～$600^{\circ}C$ and the triple layer of ZrO$_2$/Al-ZrO$_{x}$ /Al$_2$O$_3$ was formed onto aluminum substrates after anodizing of ZrO$_2$/Al film. The thickness of $Al_2$O$_3$ layer was decreased with increasing the annealing temperature due to the densification of ZrO$_2$ film. The ZrO$_2$ films were crystallized even at 30$0^{\circ}C$ and showed nanocrystalline structure. The. capacitance of aluminum foil annealed at low temperature was higher than that at high temperature. The increase of capacitance was due to the high capacitance of ZrO$_2$ film annealed at low temperature. The capacitance of ZrO$_2$ coated aluminum increased about 3 times compared to that without a ZrO$_2$ layer after anodizing to 400 V. From these results, the aluminum foils with composite oxide layers are found to be applicable to the aluminum electrolytic capacitor.