• Journal of the Korean Chemical Society
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• v.65 no.4
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• pp.260-267
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• 2021

Increasing the needs for eco-friendly natural materials, much attention on natural dyes has been attracted. Curcumin, one of abundant natural dyes available in nature, is an eco-friendly molecule found in turmeric. In this study, the colorimetric sensing behavior characteristics of ammonia and hydrogen chloride gases was analyzed using curcumin ink-printed paper and cotton fabric by inkjet printing method. The fabricated paper and fabric were utilized as a colorimetric sensor that can track food spoilage. The color changes of the samples printed on the paper and cotton upon exposure to the toxic gases, the reversibility of the color changes, and the water resistance were investigated. Both samples showed reversible reactions with NH3 and HCl, and small amount of ammonia produced by food spoilage was successfully sensed with naked eyes, confirming its capability to warn food spoilage in our daily life.

• Journal of Electrochemical Science and Technology
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• v.13 no.4
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• pp.497-503
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• 2022

Spinel ferrites (Ni_xFe_3-xO₄; x = 0.25, 0.5, 0.75 and 1.0) have been prepared at 550℃ by egg white auto-combustion route using egg white at 550℃ and characterized by physicochemical (TGA, IR, XRD, and SEM) and electrochemical (CV and Tafel polarization) techniques. The presence of characteristic vibration peaks in FT-IR and reflection planes in XRD spectra confirmed the formation of spinel ferrites. The prepared oxides were transformed into oxide film on glassy carbon electrodes by coating oxide powder ink using the nafion solution and investigated their electrocatalytic performance for OER in an alkaline solution. The cyclic voltammograms of the oxide electrode did not show any redox peaks in oxygen overpotential regions. The iR-free Tafel polarization curves exhibited two Tafel slopes (b₁ = 59-90 mV decade^-1 and b₂ = 92-124 mV decade^-1) in lower and higher over potential regions, respectively. Ni-substitution in oxide matrix significantly improved the electrocatalytic activity for oxygen evolution reaction. Based on the current density for OER, the 0.75 mol Ni-substituted oxide electrode was found to be the most active electrode among the prepared oxides and showed the highest value of apparent current density (~9 mA cm^-2 at 0.85 V) and lowest Tafel slope (59 mV decade^-1). The OER on oxide electrodes occurred via the formation of chemisorbed intermediate on the active sites of the oxide electrode and follow the second-order mechanism.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.1
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• pp.18-23
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• 2022

Electrohydrodynamic jet (e-jet) printing, a type of direct contactless microfabrication technology, is a versatile fabrication process that enables a wide range of micro/nanopattern arrays by applying a strong electric field between the nozzle and the substrate. In general, the morphology and the thickness of polymers/quantum dot micropatterns show a systematic dependence on the diameter of the nozzle and the ink composition with a fully automated printing machine. The purpose of this report is to provide typical examples of e-jet printed micropatterns of polymers/quantum dots to explain the effect of each process variable on the result of experiments. Here, we demonstrate several operating conditions that allow high-resolution printing of layers of polymers/quantum dots with a precise control over thickness and submicron lateral resolution.

• The Journal of the Convergence on Culture Technology
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• v.9 no.1
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• pp.419-425
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• 2023

The research object of this paper is "Yi" and "Yi" in ancient calligraphy theory, as an aesthetic category with oriental characteristics, from Laozhuang philosophy of pre-Qin Dynasty to literature field of literature.The second chapter describes the emergence and development of the concept of "Yi", which has evolved into two concepts in ancient calligraphy and painting theory, namely, the concept of "Yi".In the third chapter, "Yi" is mainly used as an adjective to describe the speed, power and strength of writing, and in the fourth chapter, "Yi" is used to describe the writer's character.Based on the study of ancient sages' calligraphy, this paper attempts to explore the inner spirit of "Yi" and to systematically analyze and summarize the theory of calligraphy and painting.

• Journal of the Society of Naval Architects of Korea
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• v.60 no.1
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• pp.31-37
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• 2023

In the present study, a method of performing cavitation erosion test directly on the anodized surface of the rudder model is proposed, not applying ink or paint on its surface. An image processing technique is newly developed to quantitatively evaluate the erosion damages on the rudder model surface after erosion test. The preprocessing saturation image, image smoothing, adaptive hysteresis thresholding and eroded area detection algorithms are in the image processing program. The rudder cavitation erosion tests are conducted in the rudder deflection angle range of 0° to -4°, which is used to maintain a straight course at the highest speed of the targeted navy ship. In the case of the conventional flat-type full-spade rudder currently being used in the target ship, surface erosion can occur on the model rudder surface in the above rudder deflection angle range. The bubble type of cavitation occurs on rudder surface, which is estimated to be the main reason of erosion damage on the rudder surface.

• Journal of Appropriate Technology
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• v.5 no.1
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• pp.46-53
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• 2019

It should be supported by the ease and economic production in terms of appropriate technology to be widely used in the real applying fields. In particular, the diagnosis of diseases is one of the most difficult areas to apply to the developing countries compared to other fields because of the high costs of professional manpower, equipment, and medial reagents. In recent years, paper, which is one of the most common materials around, has been used to fabricate the disease diagnostic chips, particularly without any special facilities or the equipment. These new technologies lead the possibility of using point-of-care testing devices that can be manufactured quickly in the field by lowering the production cost. These paperbased technologies will contribute to solve many of the deadliest medical problems in developing countries and ultimately improve the quality of human life.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.46 no.3
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• pp.59-68
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• 2023

Currently, yellow phosphor of Y3Al5O12:Ce3+ (YAG:Ce) fluorescent material is applied to a 450~480nm blue LED light source to implement a white LED device and it has a simple structure, can obtain sufficient luminance, and is economical. However, in this method, in terms of spectrum analysis, it is difficult to mass-produce white LEDs having the same color coordinates due to color separation cause by the wide wavelength gap between blue and yellow band. There is a disadvantage that it is difficult to control optical properties such as color stability and color rendering. In addition, this method does not emit purple light in the range of 380 to 420nm, so it is white without purple color that can not implement the spectrum of the entire visible light spectrum as like sunlight. Because of this, it is difficult to implement a color rendering index(CRI) of 90 or higher, and natural light characteristics such as sunlight can not be expected. For this, need for a method of implementing sunlight with one LED by using a method of combining phosphors with one light source, rather than a method of combining red, blue, and yellow LEDs. Using this method, the characteristics of an artificial sunlight LED device with a spectrum similar to that of sunlight were demonstrated by implementing LED devices of various color temperatures with high color rendering by injecting phosphors into a 405nm deep blue LED light source. In order to find the spectrum closest to sunlight, different combinations of phosphors were repeatedly fabricated and tested. In addition, reliability and mass productivity were verified through temperature and humidity tests and ink penetration tests.

• Tribology and Lubricants
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• v.39 no.5
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• pp.197-202
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• 2023

Recently, research on experimental and analytical techniques utilizing microfluidic devices has been pursued. For example, lab-on-a-chip devices that integrate micro-devices onto a single chip for processing small sample quantities have gained significant attention. However, during sample preparation, unnecessary gases can be introduced into the internal channels, thus, impeding device flow and compromising specific function efficiency, including that of analysis and separation. Several methods have been proposed to mitigate this issue, however, many involve cumbersome procedures or suffer from complexities owing to intricate structures. Recently, some approaches have been introduced that utilize hydrophobic device structures to remove gases within channels. In such cases, the permeability of gases passing through the structure becomes a crucial performance factor. In this study, a method involving the deposition and sintering of diluted Ag-ink onto a silicon wafer surface is presented. This is followed by unstructured nano-pattern creation using a Metal Assisted Chemical Etching (MACE) process, which yields a nanostructured surface with unstructured pillar shapes. Subsequently, gas permeability in the spaces formed by these surface structures is investigated. This is achieved by experiments conducted to incorporate a pressure chamber and measure gas permeability. Trends are subsequently analyzed by comparing the results with existing theories. Finally, it can be confirmed that the significance of this study primarily lies in its capability to effectively evaluate gas permeability through unstructured pillar-like nanostructures, thus, providing quantitative values for the appropriate driving pressure and expected gas removal time in practical device operation.

• Journal of the Korea Fashion and Costume Design Association
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• v.25 no.3
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• pp.53-67
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• 2023

Blood circulation is one of the most important life support functions of our body. It is essential to maintain healthy blood circulation as problems with blood circulation can lead to numerous diseases and serious complications. This study developed women's leggings with gradual compression and soft surface heating functions to improve blood circulation, and evaluated their performance and wearability. A silicon print pattern was developed to provide gradual compression, and a flexible heating surface coated with MWCNT (multi-walled carbon nanotube) conductive ink was fabricated for comfort and thermal effect. For the design, incision lines and materials were applied in consideration of aesthetic aspects, and design lines and colors were altered using a 3D program. The developed leggings showed that blood circulation can be improved when gradual compression and heating functions are simultaneously applied. Results were confirmed through measurements of clothing pressure, blood flow, and surface temperature. In the subjective wearability evaluation, it was confirmed that wearers felt gradual pressure, and they showed high satisfaction with wearability and design.

• Journal of Advanced Technology Convergence
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• v.2 no.4
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• pp.1-6
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• 2023

Research on power inductor surface UV printing equipment using cylindrical magnets can prevent damage to quality consumable materials (making plates, Squeegees) during printing and improve printing quality by applying technology to prevent product from flipping or standing up when fixing the product by making the magnetic formation of cylindrical magnets form up and down. The development of cylindrical magnets that changed the direction of magnetic force will stabilize the fixing method for metal products made by powder compression, increasing the production capacity for small products. Finally, by studying the power inductor surface UV printing device using cylindrical magnets, it can be differentiated from the spray and deeping methods that were being worked on, production will be greatly improved, and as a result, cost reduction and competitive production will be possible.