• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.31 no.4
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• pp.342-352
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• 2021

Objectives: This study analyzed the local exposure levels of radiation emitted from the equipment with soft X-ray ionizers to investigate the radiation exposure levels in Liquid Crystal Display(LCD) manufacturing processes. Methods: This study measured the local radiation levels for the equipment installed in two LCD manufacturing companies. The equipment were installed at diverse processes and equipped with various number of ionizers. The local radiation levels were measured on the surface of the equipment by using direct reading equipment, and the measurements were converted into annual effective dose by considering the radiation exposure time of workers. Statistical analyses were performed to investigate the radiation exposure characteristics. Results: Annual effective doses for 97.6% of the equipment being measured were less than 1 mSv. However, the range of annual effective doses was 0.004 mSv ~ 2.167 mSv, which indicated a large variation among the equipment. Statistical analyses of the study found that this large variation was raised due to improper shielding of the equipment rather than process and/or equipment characteristics. To pinpoint the cause of this large variation in annual effective dose, this study improved the shielding of the equipment being radiated over 1 mSv and found that their average effective dose was reduced from 1.604 mSv to 0.126 mSv after shielding improvement. Conclusions: Relatively high exposure levels of radiation were observed in some equipment where their shielding were insufficiently thick and/or sealed. This finding implies that the shielding of the equipment is an important engineering countermeasure to control the radiation exposure levels in industries.

• Applied Chemistry for Engineering
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• v.22 no.5
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• pp.486-489
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• 2011

In the present work, diazinon which is known as nondegradable and environmental toxic material was efficiently treated by the cell surface-displayed organophosphorus hydrolase (OPH) biocatalyst. The culture temperature of $25^{\circ}C$ culture temperature and the addition of 0.2 mM ethylenediamine tetraacetate (EDTA) were effective conditions for the production of recombinant OPH in Escherichia coli. 25 and 50 ppm diazinon were treated with removal rate of 4.5 and $7.2mg/g{\cdot}min$, respectively and with all over 90% removal efficiencies using recombinant cell lysates through ultrasonication disruption process. Thus, these experimental results could be utilized in environmental friendly biological treatment system for toxic chemicals such as diazinon.

• Journal of Ceramic Processing Research
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• v.19 no.5
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• pp.361-368
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• 2018

We investigated the interfacial properties of fluorocarbon self-assembled monolayers (FC-SAMs) with different alkyl chain lengths. It was found that the substrate characteristics were changed rapidly with the fabrication time and temperature of the SAM. FC-3SAM, which has the shortest alkyl chain in this study, showed a contact angle of $54.1^{\circ}$ when it was fabricated in an electric oven at $60^{\circ}C$ for the first minute. The FC-3SAM showed a contact angle of up to $76.9^{\circ}$ when it was fabricated in an electric oven at the same temperature condition for 180 minutes. FC-10SAM, which has the longest alkyl chain in this study, showed a contact angle of $64.7^{\circ}$ when it was fabricated at a temperature condition of $60^{\circ}C$ for 1 minute, and a contact angle of $98.7^{\circ}C$ at a temperature condition of $60^{\circ}C$ for 180 minutes. It was found that the FC-10SAM shows an increased contact angle and hydrophobic properties due to a well-aligned molecular structure resulting from a strong van der Waals force. In contrast, the FC-3SAM shows a small contact angle due to the intermolecular disorder resulting from a weak van der Waals force. The average roughness of FC-SAMs was investigated using AFM. The surface roughness of FC-SAMs, which verifies the results of contact angle, was confirmed. At a fabrication time of 120 minutes, the FC-10SAM showed an improvement in average roughness by 62% compared to that of FC-3SAM due to its good alignment.

• Korean Journal of Metals and Materials
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• v.47 no.1
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• pp.44-49
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• 2009

Indium tin oxide(ITO) thin films were deposited on the glass substrates by radio-frequency (RF) magnetron sputtering method. The influence of rapid thermal annealing (RTA) treatment on the optical and electrical properties of the films were investigated for the purpose of fabricating plasma display signboard. Structural properties, surface roughness, sheet resistance and transmittance of the ITO film were analysed by using x-ray diffraction method, atomic force microscopy (AFM), four point prove, and ultraviolet-visible spectrometer, respectively. It was found that the RTA treatment increased the transmittance and decreased the resistivity of the ITO film, respectively. Furthermore, we successfully demonstrated the direct-current plasma signboard by using ITO electrode and phosphors.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.16 no.2
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• pp.109-115
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• 2023

In this paper, we demonstrated the orientation characteristics of liquid crystals using UV-treated FSAM as alignment layer. Moreover we confirmed the FSAM properties before and after UV treatment on indium tin oxide (ITO) glass substrates using physicochemical analysis. The hydrophobic property of the FSAM surface is change to hydrophilic through UV treatment. After UV treatment the LC molecules also were uniformly and horizontally aligned on the FSAM surfaces and the pretilt angle was obviously changed 90° degrees to 0° degrees. EO characteristic of TN cell which was fabricated with UV-treated FSAM was faster response time compare to conventional PI layer. The FSAM before and after UV treatment has a superior application potential as the LC alignment layer for LCD, potentially replacing the conventional polyimide layer.

• Korean Journal of Radiology
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• v.1 no.3
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• pp.135-141
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• 2000

Objective: To compare the clinical utility of the different imaging techniques used for the evaluation of tracheobronchial diseases. Materials and Methods: Forty-one patients with tracheobronchial diseases [tuberculosis (n = 18), bronchogenic carcinoma (n = 10), congenital abnormality (n = 3), post-operative stenosis (n = 2), and others (n = 8)] underwent chest radiography and spiral CT. Two sets of scan data were obtained: one from routine thick-section axial images and the other from thin-section axial images. Multiplanar reconstruction (MPR) and shaded surface display (SSD) images were obtained from thin-section data. Applying a 5-point scale, two observers compared chest radiography, routine CT, thin-section spiral CT, MPR and SSD imaging with regard to the detection, localization, extent, and characterization of a lesion, information on its relationship with adjacent structures, and overall information. Results: SSD images were the most informative with regard to the detection (3.95±0.31), localization (3.95±0.22) and extent of a lesion (3.85±0.42), and overall information (3.83±0.44), while thin-section spiral CT scans provided most information regarding its relationship with adjacent structures (3.56±0.50) and characterization of the lesion (3.51±0.61). Conclusion: SSD images and thin-section spiral CT scans can provide valuable information for the evaluation of tracheobronchial disease.

• Structural Engineering and Mechanics
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• v.89 no.6
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• pp.557-570
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• 2024

Due to interfacial ageing, chemical action and interfacial damage, the interface debonding may appear in the interfaces of composite laminates. Particularly, the laminates display a side-dependent effect at small scale. In this work, a three-dimensional (3D) and anisotropic thick nanoplate model is proposed to investigate the effects of imperfect interface and nonlocal parameter on the bending deformation, vibrational response and buckling stability of one-dimensional (1D) hexagonal quasicrystal (QC) layered nanoplates. By combining the linear spring model with the transferring matrix method, exact solutions of phonon and phason displacements, phonon and phason stresses of bending deformation, the natural frequencies of vibration and the critical buckling loads of 1D hexagonal QC layered nanoplates are derived with imperfect interfaces and nonlocal effects. Numerical examples are illustrated to demonstrate the effects of the imperfect interface parameter, aspect ratio, thickness, nonlocal parameter, and stacking sequence on the bending deformation, the vibrational response and the critical buckling load of 1D hexagonal QC layered nanoplate. The results indicate that both the interface debonding and nonlocal effect can reduce the stiffness and stability of layered nanoplates. Increasing thickness of QC coatings can enhance the stability of sandwich nanoplates with the perfect interfaces, while it can reduce first and then enhance the stability of sandwich nanoplates with the imperfect interfaces. The biaxial compression easily results in an instability of the QC layered nanoplates compared to uniaxial compression. QC material is suitable for surface layers in layered structures. The mechanical behavior of QC layered nanoplates can be optimized by imposing imperfect interfaces and controlling the stacking sequence artificially. The present solutions are helpful for the various numerical methods, thin nanoplate theories and the optimal design of QC nano-composites in engineering practice with interfacial debonding.

• KSBB Journal
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• v.24 no.1
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• pp.1-8
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• 2009

In the past decade, we have observed rapid advances in the development of biochips in many fields including medical and environmental monitoring. Biochip experiments involve immobilizing a ligand on a solid substrate surface, and monitoring its interaction with an analyte in a sample solution. Metal nanoparticles can display extinction bands on their surfaces. These charge density oscillations are simply known as the localized surface plasmon resonance (LSPR). The high sensitivity of LSPR has been utilized to design biochips for the label-free detection of biomolecular interactions with various ligands. LSPR-based optical biochips and biosensors are easy to fabricate, and the apparatus cost for the evaluation of optical characteristics is lower than that for the conventional surface plasmon resonance apparatus. Furthermore, the operation procedure has become more convenient as it does not require labeling procedure. In this paper, we review the recent advances in LSPR research and also describe the LSPR-based optical biosensor constructed with a core-shell dielectric nanoparticle biochip for its application to label-free biomolecular detections such as antigen-antibody interaction.

• Journal of Mushroom
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• v.10 no.3
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• pp.120-128
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• 2012

Recently sawdust cultivation of Shiitake mushroom (Lentinula edodes) is increasing. It is important to make mycelia to be brown on the substrate surface. This browned surface in sawdust cultivation plays an important role like as artificial bark of the oak log, which protects the other pests and suppresses water evaporation in the substrate. In order to isolate genes which related to brown color formation, differential display method was used. Two cDNA fragments obtained by DD-PCR were 1.2 and 1.6kb and these were expressed in white colored mycelia from L. edodes, but not brown colored mycelia. Partial sequencing of these cDNA fragments showed that the 1.6kb cDNA had 100% identity with the microsatellites gene from Dugenia polichroa. However, the other 1.2kb cDNA fragment had poly T tail on 3' region of partial open reading frame on 5' region. The new primer designed based on the sequence of 1.2kb cDNA was constructed. RT-PCR analysis using the newly designed 0.12kb cDNA specific primer showed that the gene was only expressed in white color mycelia, but not in brown color mycelia. Sequence analysis of 5' region of this 1.2kb cDNA revealed that this gene contained partial open reading frame consisted of 110 amino acid. Homology search using DNASIS database showed that this gene had high sequence homology of 66.7% in DNA level and 69.2 % in amino acid level with dTDP-glucose 4,6-dehydratases gene from Arabidopsis thaliata. The dTDP-glucose 4,6-dehydratases gene was known to be function to have tolerance with oxidation stress. These results strongly suggest that this gene isolated from white mycelia of L. edodes might have a function of repressor against mycelia browning. Therefore I designated this gene as BCR (Brown Color Repressor) gene.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.100-101
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• 2012

The plasma damage free and room temperature processedthin film deposition technology is essential for realization of various next generation organic microelectronic devices such as flexible AMOLED display, flexible OLED lighting, and organic photovoltaic cells because characteristics of fragile organic materials in the plasma process and low glass transition temperatures (Tg) of polymer substrate. In case of directly deposition of metal oxide thin films (including transparent conductive oxide (TCO) and amorphous oxide semiconductor (AOS)) on the organic layers, plasma damages against to the organic materials is fatal. This damage is believed to be originated mainly from high energy energetic particles during the sputtering process such as negative oxygen ions, reflected neutrals by reflection of plasma background gas at the target surface, sputtered atoms, bulk plasma ions, and secondary electrons. To solve this problem, we developed the NBAS (Neutral Beam Assisted Sputtering) process as a plasma damage free and room temperature processed sputtering technology. As a result, electro-optical properties of NBAS processed ITO thin film showed resistivity of $4.0{\times}10^{-4}{\Omega}{\cdot}m$ and high transmittance (>90% at 550 nm) with nano- crystalline structure at room temperature process. Furthermore, in the experiment result of directly deposition of TCO top anode on the inverted structure OLED cell, it is verified that NBAS TCO deposition process does not damages to the underlying organic layers. In case of deposition of transparent conductive oxide (TCO) thin film on the plastic polymer substrate, the room temperature processed sputtering coating of high quality TCO thin film is required. During the sputtering process with higher density plasma, the energetic particles contribute self supplying of activation & crystallization energy without any additional heating and post-annealing and forminga high quality TCO thin film. However, negative oxygen ions which generated from sputteringtarget surface by electron attachment are accelerated to high energy by induced cathode self-bias. Thus the high energy negative oxygen ions can lead to critical physical bombardment damages to forming oxide thin film and this effect does not recover in room temperature process without post thermal annealing. To salve the inherent limitation of plasma sputtering, we have been developed the Magnetic Field Shielded Sputtering (MFSS) process as the high quality oxide thin film deposition process at room temperature. The MFSS process is effectively eliminate or suppress the negative oxygen ions bombardment damage by the plasma limiter which composed permanent magnet array. As a result, electro-optical properties of MFSS processed ITO thin film (resistivity $3.9{\times}10^{-4}{\Omega}{\cdot}cm$, transmittance 95% at 550 nm) have approachedthose of a high temperature DC magnetron sputtering (DMS) ITO thin film were. Also, AOS (a-IGZO) TFTs fabricated by MFSS process without higher temperature post annealing showed very comparable electrical performance with those by DMS process with $400^{\circ}C$ post annealing. They are important to note that the bombardment of a negative oxygen ion which is accelerated by dc self-bias during rf sputtering could degrade the electrical performance of ITO electrodes and a-IGZO TFTs. Finally, we found that reduction of damage from the high energy negative oxygen ions bombardment drives improvement of crystalline structure in the ITO thin film and suppression of the sub-gab states in a-IGZO semiconductor thin film. For realization of organic flexible electronic devices based on plastic substrates, gas barrier coatings are required to prevent the permeation of water and oxygen because organic materials are highly susceptible to water and oxygen. In particular, high efficiency flexible AMOLEDs needs an extremely low water vapor transition rate (WVTR) of $1{\times}10^{-6}gm^{-2}day^{-1}$. The key factor in high quality inorganic gas barrier formation for achieving the very low WVTR required (under ${\sim}10^{-6}gm^{-2}day^{-1}$) is the suppression of nano-sized defect sites and gas diffusion pathways among the grain boundaries. For formation of high quality single inorganic gas barrier layer, we developed high density nano-structured Al2O3 single gas barrier layer usinga NBAS process. The NBAS process can continuously change crystalline structures from an amorphous phase to a nano- crystalline phase with various grain sizes in a single inorganic thin film. As a result, the water vapor transmission rates (WVTR) of the NBAS processed $Al_2O_3$ gas barrier film have improved order of magnitude compared with that of conventional $Al_2O_3$ layers made by the RF magnetron sputteringprocess under the same sputtering conditions; the WVTR of the NBAS processed $Al_2O_3$ gas barrier film was about $5{\times}10^{-6}g/m^2/day$ by just single layer.