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31 results on '"Yoo, Youngmin"'

9. Argon and Oxygen Gas Flow Rate Dependency of Sputtering-Based Indium-Gallium-Zinc Oxide Thin-Film Transistors

Author

Yoo, Youngmin Han, Dong Hyun Lee, Eou-Sik Cho, Sang Jik Kwon, and Hocheon

Subjects
a-IGZO, magnetron sputtering, thin-film transistors, oxygen vacancy, oxygen flow rate
Abstract

Oxygen vacancies are a major factor that controls the electrical characteristics of the amorphous indium-gallium-zinc oxide transistor (a-IGZO TFT). Oxygen vacancies are affected by the composition ratio of the a-IGZO target and the injected oxygen flow rate. In this study, we fabricated three types of a-IGZO TFTs with different oxygen flow rates and then investigated changes in electrical characteristics. Atomic force microscopy (AFM) was performed to analyze the surface morphology of the a-IGZO films according to the oxygen gas rate. Furthermore, X-ray photoelectron spectroscopy (XPS) analysis was performed to confirm changes in oxygen vacancies of a-IGZO films. The optimized a-IGZO TFT has enhanced electrical characteristics such as carrier mobility (μ) of 12.3 cm2/V·s, on/off ratio of 1.25 × 1010 A/A, subthreshold swing (S.S.) of 3.7 V/dec, and turn-on voltage (Vto) of −3 V. As a result, the optimized a-IGZO TFT has improved electrical characteristics with oxygen vacancies having the highest conductivity.

Published
2023
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11. Surface modification of a PVDF membrane by co‐grafting hydroxyl and zwitterionic polymers to enhance wettability and antifouling property.

Author

Lee, Jin Yeon, Cho, Young Hoon, Nam, Seung‐Eun, Kim, In‐Chul, Park, Ho Bum, Park, You‐In, Bae, Sun Ho, and Yoo, Youngmin

Subjects
POLYZWITTERIONS, WETTING, POLYVINYLIDENE fluoride, SERUM albumin, HYDROXYL group, ANTIFOULING paint, GRAFT copolymers
Abstract

Polyvinylidene fluoride (PVDF) membranes have been widely applied in the separation of various organic matters owing to their excellent properties. However, they possess low wettability and undergo fouling because of the hydrophobic nature of PVDF. In this study, poly (2‐hydroxyethyl methacrylate) (PHEMA) and poly (sulfobetaine methacrylate) (PSBMA) were co‐introduced to modify the highly hydrophobic PVDF membrane surface via UV photo‐irradiation. Facile UV photo‐grafting was performed by irradiating the pristine PVDF membrane immersed in a PHEMA/PSBMA mixture solution with UV light for 5 min. The performance of the as‐prepared PHEMA/PSBMA‐grafted membrane was compared with that of membranes modified with solely PHEMA or PSBMA. The hydroxyl and zwitterionic groups of the grafted membranes enhanced wettability and increased flux. A tightly bound water layer was formed because of the enhanced wettability, significantly suppressing protein adsorption. The initial flux of bovine serum albumin (BSA) solution through the PHEMA/PSBMA‐grafted membrane was 2861 LMH, which was 3.1 times higher than that obtained by the pristine PVDF membrane. Furthermore, the flux decline of the modified membrane caused by BSA fouling was 49% lower than that of the pristine PVDF membrane. Finally, the PHEMA/PSBMA‐grafted PVDF membrane showed antifouling properties after three BSA filtration cycles. [ABSTRACT FROM AUTHOR]

Published
2023
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17. Testing the Spatial Accuracy of Address Based Geocoding for Gun Shot Locations

Author

Wheeler, Andrew, Gerell, Manne, and Yoo, Youngmin

Subjects
bepress|Social and Behavioral Sciences|Sociology, SocArXiv|Social and Behavioral Sciences|Sociology, SocArXiv|Social and Behavioral Sciences|Urban Studies and Planning, bepress|Social and Behavioral Sciences|Sociology|Criminology, bepress|Social and Behavioral Sciences, bepress|Social and Behavioral Sciences|Urban Studies and Planning, SocArXiv|Social and Behavioral Sciences, SocArXiv|Social and Behavioral Sciences|Geography, bepress|Social and Behavioral Sciences|Geography, SocArXiv|Social and Behavioral Sciences|Sociology|Crime, Law, and Deviance
Abstract

We assess the positional accuracy of address based geocoding of shooting incidents relative to the location recorded via acoustic gun-shot detection technology. This provides a test of the accuracy of typical address based geocoding methods used in crime analysis, as well as provides evidence for how much accuracy one gains when using sensors. Examining over 1,000 shooting incidents in Wilmington, North Carolina, we find that the majority of address-based incidents are quite accurate, on average within 60 feet of the actual location (using a street centerline geocoder), or within 90 feet (using Google rooftop geocoding). However, based on the incident narrative we identify a subset of transcription errors in over 10% of the cases that increases the distance between the true shooting location and that geocoded using address data. This suggests mechanisms to prevent human errors may be more frugal than those relying on sensors in geocoding shooting incidents. Data to replicate the analysis can be downloaded from https://www.dropbox.com/sh/bceyldwgj84ztlw/AABdQBnjKGdO3GUxWM0ZMd3Ya?dl=0.

Published
2019
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20. Testing the Spatial Accuracy of Address-Based Geocoding for Gunshot Locations.

Author

Wheeler, Andrew P., Gerell, Manne, and Yoo, Youngmin

Subjects
CRIME analysis, HUMAN error, STREETS, DETECTORS, TECHNOLOGY, FOOT
Abstract

Copyright of Professional Geographer is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Published
2020
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31. A Simple, Cost-Efficient Method to Separate Microalgal Lipids from Wet Biomass Using Surface Energy-Modified Membranes

Author

Kwak, Moo Jin, Yoo, Youngmin, Lee, Han Sol, Kim, Jiyeon, Yang, Ji-Won, Han, Jong-In, Im, Sung Gap, and Kwon, Jong-Hee

Abstract

For the efficient separation of lipid extracted from microalgae cells, a novel membrane was devised by introducing a functional polymer coating onto a membrane surface by means of an initiated chemical vapor deposition (iCVD) process. To this end, a steel-use-stainless (SUS) membrane was modified in a way that its surface energy was systemically modified. The surface modification by conformal coating of functional polymer film allowed for selective separation of oil–water mixture, by harnessing the tuned interfacial energy between each liquid phase and the membrane surface. The surface-modified membrane, when used with chloroform-based solvent, exhibited superb permeate flux, breakthrough pressure, and also separation yield: it allowed separation of 95.5 ± 1.2% of converted lipid (FAME) in the chloroform phase from the water/MeOH phase with microalgal debris. This result clearly supported that the membrane-based lipid separation is indeed facilitated by way of membrane being functionalized, enabling us to simplify the whole downstream process of microalgae-derived biodiesel production.

Published
2016
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