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A high speed electrohydrodynamic (EHD) jet printing method for line printing
Phung, Thanh Huy,Kim, Seora,Kwon, Kye-Si IOP 2017 JOURNAL OF MICROMECHANICS AND MICROENGINEERING - Vol.27 No.9
<P>Electrohydrodynamic (EHD) jet printing has drawn attention due to its capability to produce smaller dots and patterns with finer lines when compared to those obtained from using conventional inkjet printing. Previous studies have suggested that drop-on-demand EHD-patterning applications should be limited to very slow printing cases with speeds far less than 10 mm s<SUP>−1</SUP> due to the small dot size and limited jetting frequency. In this study, a new EHD printing method is proposed to significantly increase the line-patterning printing speed by modifying the ink and thereby changing the relic shape. The proposed method has the additional advantage of reducing the line-pattern width. The results of the experiment show that the pattern width could be reduced from 20 <I>?</I>m to 4 <I>?</I>m by increasing the printing speed from 10 mm s<SUP>−1</SUP> to 50 mm s<SUP>−1</SUP>, respectively.</P>
Anton Nailevich Gafurov,Thanh Huy Phung,Beyong-Hwan Ryu,Inyoung Kim,Taik-Min Lee 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.10 No.2
Screen printing has been adopted for fabricating a wide variety of electronic devices. However, the printing defects and reliability have been an obstacle for industrialization of printed electronics. In this research, the artificial intelligence (AI) model was developed and integrated with the in-house roll-to-roll screen printing system to detect smearing defect, which is one of the main defects of screen printing. The U-Net architecture was adopted, and a total of 19 models were designed with model sizes ranging from 8E + 3 to 3E + 7 number of parameters. Their performances as validation mean Intersection over Union (IoU) were analyzed, and the optimal model was chosen with a validation mean IoU of 95.1% and a number of parameters of 8E + 6. The printed line images were evaluated by the AI model for various printing conditions, such as printed line widths, printing paste premixing, printing speeds, and printed line directions, which showed that the model could effectively detect the smearing defects. Also, the AI model capabilities were investigated for repeated printing, which demonstrated that it can be used for the reliability assessment of the screen printing process.
지하수 함양시설 또는 LID시설에서의 질산성질소 오염방지를 위한 농업부산물의 탈질효율 실험연구
이진원,이병선,김강주,이규상,Lee, Jinwon,Phung, Thanh Huy,Lee, Byungsun,Kim, Kangjoo,Lee, Gyusang 한국지하수토양환경학회 2021 지하수토양환경 Vol.26 No.6
Facilities for low impact development (LID) or groundwater recharge have the high potential spreading groundwater nitrate contamination because of the rapid infiltration. This study was initiated to remove nitrate from the waters using agricultural byproducts as organic sources for denitrification during infiltration. As the first step of this purpose, we experimentally tested the denitrifying efficiency of 4 organic materials (pine tree woodchips, cherry leaves, rice straws, and rice hulls) and tried to identify the key factors controlling the efficiency. For this study, we precisely investigated the change of chemical reactions during the experiment by analyzing various geochemical parameters. The result shows that the denitrification efficiency is not simply linked to the availability of the easily decomposable contents in the organic matter. It is found that avoiding the severe pH decrease due to the CO<sub>2</sub> generation is the essence to derive the efficient denitrifying conditions when organic matters were used.
A hydrogeological and geochemical review of groundwater issues in southern Vietnam
Quang Khai Ha,김강주,Nam Long Phan,Thanh Huy Phung,이진원,Viet Ky Nguyen,Chu Nam Phan 한국지질과학협의회 2019 Geosciences Journal Vol.23 No.6
Southern Vietnam is known as one of the most vulnerable areas to climate change in the world due to its low elevation and flat topography, heavy groundwater use, and dense population. This paper introduces hydrogeological conditions and critically reviews groundwater issues that southern Vietnam faces by summarizing previous literatures. Issues that this paper covers include groundwater use and associated phenomenon, acid sulfate soils, the occurrence of saline groundwaters, seawater intrusion, land subsidence, groundwater acidification, and groundwater contamination by nitrate, ammonium, and trace metals such as As, Fe, Mn, Al, Cd, and Pb. This paper shows that most of these issues are inter-related and essentially linked with the unique hydrogeological setting of the study area. However, many of these problems have also been triggered or aggravated by human activities that use water resources and land. Issues such as those of As contamination and groundwater acidification are connected with the aquifer characteristics that are generally confined and rich in organics and pyrite. However, groundwater salinization, acidification, groundwater level declining, land subsidence, and high heavy metal concentrations are in large part caused by human activities such as well installation and heavy groundwater abstraction. While previous studies have proposed artificial recharge as a promising means of mitigating groundwater issues in the study area, the development of techniques that help minimizing aquifer disturbances is also likely required.