Effect of SiO₂ Nanoextractor on Far-Field Radiation Pattern of Vertical Light-Emitting Diodes

Son, H.,Lee, J.K.,Kim, S.-M. JAPAN SOCIETY OF APPLIED PHYSICS 2013 Applied physics express Vol.6 No.10

Improvements in the device characteristics of IZO-based transparent thin-film transistors with co-sputtered HfO₂-Al₂O₃ gate dielectrics

Son, H.,Kim, J.,Yang, J.,Cho, D.,Yi, M. Elsevier 2011 Current Applied Physics Vol.11 No.4

Transparent oxide thin-film transistors (TFTs) have been fabricated by RF magnetron sputtering at room temperature using amorphous indium zinc oxide (IZO) as both active channel and source/drain electrodes and co-sputtered HfO<SUB>2</SUB>-Al<SUB>2</SUB>O<SUB>3</SUB> (HfAlO) as gate dielectric. In spite of its high dielectric constant, HfO<SUB>2</SUB> has some drawbacks including a high leakage current and rough surface morphologies due to its small band gap (5.31 eV) and microcrystalline structure. In this work, the incorporation of Al<SUB>2</SUB>O<SUB>3</SUB> into hafnium (Hf) was achieved by co-sputtering of HfO<SUB>2</SUB> and Al<SUB>2</SUB>O<SUB>3</SUB> without any intentional substrate heating, and its structural and electrical properties were investigated by X-ray diffraction (XRD), atomic force microscopy (AFM), and spectroscopic ellipsometry (SE) analyses, depending on the Hf:Al compositional ratio. The XRD studies confirmed that the microcrystalline structures of HfO<SUB>2</SUB> were transformed to amorphous structures of HfAlO at approximately Hf:Al = 3:1 at% ratio. According to the AFM analysis, the HfAlO films (0.54 nm) were considerably smoother than the HfO<SUB>2</SUB> films (4.27 nm) due to their amorphous structure. The band gap (E<SUB>g</SUB>) deduced by spectroscopic ellipsometry was increased from 5.31 eV (HfO<SUB>2</SUB>) to 5.58 eV (HfAlO). The electrical performances of the TFTs, which were made of well-controlled active/electrode IZO materials and co-sputtered HfAlO dielectric material, exhibited a field-effect mobility of more than 10 cm<SUP>2</SUP>/V s, a threshold voltage of about 1.5 V, a sub-threshold swing of about 0.5 V/decade, and an I<SUB>on/off</SUB> ratio of about 10<SUP>5</SUP>5.

Inhibition of Staphylococcus aureus by antimicrobial biofilms formed by competitive exclusion microorganisms on stainless steel

Son, H.,Park, S.,Beuchat, L.R.,Kim, H.,Ryu, J.H. Elsevier Science Publishers 2016 International journal of food microbiology Vol.238 No.-

<P>The goal of this study was to develop a desiccation resistant antimicrobial surface using biofilm of competitive exclusion (CE) microorganism inhibitory to Staphylococcus aureus. We isolated 161 microorganisms from soils, foods, and food-contact surfaces that are inhibitory to S. aureus. Among them, three CE microorganisms (Streptomyces spororaveus strain Gaeunsan-18, Bacillus safensis strain Chamnamu-sup 5-25, and Pseudomonas azotoformans strain Lettuce-9) exhibiting strong antibacterial activity and high growth rates were selected for evaluation. These isolates formed biofilms within 24 h on stainless steel coupons (SSCs) immersed in Bennet's broth and tryptic soy broth at 25 degrees C. Cells in these biofilms showed significantly (P <= 0.05) enhanced resistance to a desiccation (43% relative humidity [RH]) compared to those attached to SSCs but not in biofilms. The antimicrobial activities of biofilms formed by these isolates on SSCs against S. aureus at 25 degrees C and 43% RH were determined. Compared to SSCs lacking biofilms formed by CE microorganisms, populations of S. aureus on SSCs harboring CE biofilms were significantly lower (P 0.05). Results indicate that persistent antimicrobial activity against S. aureus on stainless steel surfaces can be achieved by the presence of biofilms of CE microorganisms. This information will be useful when, developing strategies to improve the microbiological safety of foods during storage, processing, and distribution by facilitating the development of effective antimicrobial food-contact surfaces. (C) 2016 Published by Elsevier B.V.</P>

Structural and optical properties of AlN grown on nanopillar/patterned SiO₂ by hydride vapor phase epitaxy

Son, H.,Lee, Y.,Kim, J.H.,Hwang, J.,Kim, S.H.,Jeon, D.W. Elsevier S.A. 2017 Thin Solid Films Vol.626 No.-

We demonstrate the growth of high-quality AlN layers on an AlN nanopillar structure with a patterned SiO<SUB>2</SUB> layer employing horizontal hydride vapor phase epitaxy (HVPE). The use of the AlN nanopillar structure with the patterned SiO<SUB>2</SUB> resulted in improving the crystalline, and overall material properties of the AlN layer. The full width half maximum (FWHM) of peaks corresponding to (002) and (102) reflections of the AlN layer with the nanopillar structure were significantly decreased from 386 and 576arcsec to 265 and 318arcsec, respectively, as compared with that of the as-grown AlN layer. The laterally overgrown AlN regions consisted of a continuous well-coalesced layer exhibiting a lower dislocation density than that of the templates used owing to the dislocation blocking and dislocation bending effects. Complementary characterization by transmittance, photoluminescence and Raman spectroscope, indicates further the overall good material properties of the AlN layer grown on the nanopillar structure.

Phase behavior analysis of heavy oil containing asphaltene

Son, H.,Lee, Y.,Seo, J.,Kim, S.,Lee, W.,Sung, W. KOREAN INSTITUTE OF CHEMICAL ENGINEER 2011 Korean Journal of Chemical Engineering Vol.28 No.11

Neuritin produces antidepressant actions and blocks the neuronal and behavioral deficits caused by chronic stress

Son, H.,Banasr, M.,Choi, M.,Chae, S.Y.,Licznerski, P.,Lee, B.,Voleti, B.,Li, N.,Lepack, A.,Fournier, N.M. National Academy of Sciences 2012 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.109 No.28

Data analytic approach for bankruptcy prediction

Son, H.,Hyun, C.,Phan, D.,Hwang, H.J. Pergamon 2019 Expert Systems with Applications Vol. No.

<P><B>Abstract</B></P> <P>Bankruptcy prediction problem has been intensively studied over the past decades. From traditional statistical models to state of the art machine learning models, various predictive models are developed and applied to various datasets. However, models that use machine learning are not used in the field of business, for two main reasons. First, the prediction accuracy does not far exceed the statistical models and second, the results are not interpretable. In this study, we focused on solving the skewness which is a characteristic of financial data. By solving this problem, we obtained 17% average improvement in AUC over existing models. To address the second shortcoming, we analyze the importance of features identified by the XGBoost model. The interpretation of the model differs among categories of data. Our bankruptcy prediction model has high predictive accuracy with clear explanations and is therefore directly applicable to the industry.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Features to predict a company’s bankruptcy have highly skewed distributions. </LI> <LI> A Box–Cox transformation is a powerful technique to remove skewness of data. </LI> <LI> Machine learning algorithms are more suitable for bankruptcy prediction than statistical models. </LI> <LI> By combining feature’s importance, we can understand the model. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Dielectric relaxation of hydration water in the Dickerson-Drew duplex solution probed by THz spectroscopy

Son, H.,Choi, D.H.,Jung, S.,Park, J.,Park, G.S. North Holland ; Elsevier Science Ltd 2015 Chemical physics letters Vol.627 No.-

The contribution of water to DNA conformational change, DNA-protein interactions, and DNA-ligand recognition has been underlined. Here, we investigate the relaxation process of water around the Dickerson-Drew B-DNA duplex using terahertz spectroscopy. By controlling the DNA concentration, the relaxation time for water reorientation and the width of the DNA hydration layer are determined. We found that a layer of weakly bound hydration water, with a relaxation time of 11.6ps, extends 7.6A from the tight-binding water layer. This result demonstrates that a shell of hydration water, with reorientation time on the order of tens of picoseconds, exists beyond the structurally integrated water usually observed around DNA.

Effect of turning direction on timed up and go test results in stroke patients

Son, H.,Park, C. Elsevier 2018 Annals of Physical and Rehabilitation Medicine Vol.61 No.suppl

<P><B>Background</B></P> <P>The Timed Up and Go (TUG) test is an assessment tool for measuring mobility for stroke patients. In the stroke patients, turning direction of the affected and unaffected side may influence turning time.</P> <P><B>Aim</B></P> <P>To investigate the effects of the turning direction according to the affected and non-affected sides of stroke patients during their Timed Up and Go (TUG) test and to define clinically salient outcomes during TUG tests performed in the clinic</P> <P><B>Design</B></P> <P>Observational design.</P> <P><B>Setting</B></P> <P>Department of physical therapy in rehabilitation center.</P> <P><B>Population</B></P> <P>One hundred thirteen hemiparetic stroke patients.</P> <P><B>Methods</B></P> <P>Stroke patients were asked to perform the TUG tests by turning toward their affected and unaffected sides. Patients were divided according to gait speed, and their gait speed from the 10mWT was used. Those with a gait speed<48m/min were assigned to the severe ambulatory dysfunction (SAD) group, whereas those with a gait speed ≥ 48m/min were assigned to the moderate ambulatory dysfunction (MAD) group.</P> <P><B>Results</B></P> <P>The TUG test results showed a longer turning time when turning with the non-affected side as the turning axis (17.10±5.69 s) than with the affected side was the turning axis (17.52±5.90 s). When the patients were divided into the MAD and SAD groups based on the 10mWT results, patients in the SAD group exhibited slightly longer times (0.55±1.11 s) than did those patients in the MAD group (0.29±1.03 s); however, this difference was not significant.</P> <P><B>Conclusions</B></P> <P>The present study found that stroke patients showed differences in the TUG test results based on their turning direction, and less time was required when turning in the direction of the affected side compared to the non-affected side.</P> <P><B>Clinical rehabilitation impact</B></P> <P>Turning direction can affect the results of TUG test, it should be controlled in the execution of the TUG test in clinical settings.</P>

Mannitol induces the conversion of conidia to chlamydospore-like structures that confer enhanced tolerance to heat, drought, and UV in Gibberella zeae

Son, H.,Lee, J.,Lee, Y.W. G. Fischer 2012 MICROBIOLOGICAL RESEARCH Vol.167 No.10

Fungi use mannitol to store carbon, balance redox, and mannitol serves as an antioxidant. Several fungi also increase stress tolerance by accumulating mannitol. The results of this study showed that conidia of the cereal head blight fungus Gibberella zeae were readily changed to chlamydospore-like structures (CLS) in cultures supplemented with high amounts of mannitol. CLS cellular features were atypical of chlamydospores, but accumulated high levels of glycogen, lipids, and chitin in the cytoplasm. In addition, CLS exhibited increased tolerance to environmental stresses, including UV, heat, and drought compared to normal conidia. Molecular approaches revealed that several genes associated with lipid metabolism, signal transduction, acetyl-CoA production, and chitin synthesis were involved in CLS formation. This is the first report to characterize conidia modifications similar to chlamydospores in G. zeae applying histological and molecular approaches. The results suggest CLS serve a role in G. zeae survival strategies under hot and dry field conditions.