• Journal of Surface Science and Engineering
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• v.37 no.6
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• pp.319-325
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• 2004

Fe thin films containing Si particles were prepared on metallic substrates by electrodeposition method in sulfate solutions and the content of codeposited Si particles in the films was investigated as a function of applied current density, the content of Si particels in the solution, solution pH, solution temperature and concentration of $FeSO_4$$7H_2$O in the solution. The amount of Si codeposited in the film was not dependent on the applied current density, solution pH and solution temperature, while it was dependent on the content of Si particles in the solution and the concentration of $FeSO_4$$7H_2$O in the solution. The amount of Si codeposited in the film increased with increasing content of Si particles in the solution but reached a maximum value of about 6 wt% when the content of Si particles in the solution exceeds 100 g/l. On the other hand, the content of Si codeposited in the film increased up to about 17 wt% with decreasing concentration of $FeSO_4$$7H_2$O in the solution. These results would be applied to the fabrication of very thin Fe-6.5 wt% Si sheets for electrical applications.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.395-395
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• 2007

We report on the fabrication of soluble pentacene-based thin-film transistors (TFTs) that consist of $NiO_x$, poly-vinyl phenol (PVP), and Ni for the source-drain (SID) electrodes, gate dielectric, and gate electrode, respectively. The $NiO_x$ SID electrodes of which the work function is well matched to that of soluble pentacene are deposited on a soluble pentacenechannel by sputter deposited of NiO powder and show a moderately low but still effective transmittance of ~65% in the visible range along with a good sheet resistance of ${\sim}40{\Omega}/{\square}$. The maximum saturation current of our soluble pentacene-based TFT is about $15{\mu}A$ at a gate bias of -40showing a high field effect mobility of $0.06cm^2/Vs$ in the dark, and the on/off current ratio of our TFT is about $10^4$. It is concluded that jointly adopting $NiO_x$ for the S/D electrodes and PVP for gate dielectric realizes a high-quality soluble pentacene-based TFT.

• Korean Journal of Metals and Materials
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• v.50 no.7
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• pp.545-548
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• 2012

The optical and electronic properties of Indium Tin Oxide (ITO) thin films deposited on a RF-plasma treated glass substrate were investigated by X-Ray Photoelectron Spectroscopy (XPS), Ultra-violet Photoelectron Spectroscopy (UPS), Reflected Electron Energy Loss Spectroscopy (REELS). The modification of glass substrates was carried out by varying the time of the plasma surface treatment in an oxygen atmosphere. The focus of this research was to examine how the optical and electronic properties of ITO thin films change with the plasma treatment time. The surface energy increased since the carbon bonds were removed from the surface after the glass substrate received the surface treatment. The ITO thin films produced on the glass substrate with surface treatment showed that the high optical transmittance was approximately 85%. The measured band gap energy was as high as 3.23 eV when the plasma treatment time was 60 s and the work function after the treatment was increased by 0.5 eV in comparison to that before the treatment of 60 s. The ITO thin film exhibited an excellent sheet resistance of $2.79{\Omega}/{\Box}$. We found that the optical and electronic properties of ITO thin films can be improved by RF-plasma surface treatment.

• Steel and Composite Structures
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• v.30 no.6
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• pp.517-534
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• 2019

In this paper, the effects of inevitable out-of-plane defects on the postbuckling behavior of single-layered graphene sheets (SLGSs) under in-plane loadings are investigated based on nonlocal first order shear deformation theory (FSDT) and von-Karman nonlinear model. A generic imperfection function, which takes the form of the products of hyperbolic and trigonometric functions, is employed to model out-of-plane defects as initial geometrical imperfections of SLGSs. Nonlinear equilibrium equations are derived from the principle of virtual work and variational formulation. The postbuckling equilibrium paths of imperfect graphene sheets (GSs) are presented by solving the governing equations via isogeometric analysis (IGA) and Newton-Raphson iterative method. Finally, the sensitivity of the postbuckling behavior of GS to shape, amplitude, extension on the surface, and location of initial imperfection is studied. Results showed that the small scale and initial imperfection effects on the postbuckling behavior of defective SLGS are important and cannot be ignored.

• Journal of Fashion Business
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• v.22 no.6
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• pp.94-104
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• 2018

The objective of this study was to develop a wearable systems that protect users, based on sensors that are easy to use, from accidents caused by harmful gases in the operator's poor working environment or the risk of ultraviolet rays during outdoor activities. By developing smart wappen with Light Emitting Diode (LED) light alarm function including UV sensor and gas sensor and central processing unit, systems that are applied to daily wear and work clothes to explore the possibility of user-centered, harmful environment monitoring products in real time were proposed. Each sensor was applied to sportswear and work clothes and the wappen system consisted of lightweight and thin form as a whole. Wappen to cover the device had one sheet cover on the front and another cover from the inside to form a sandwich like formation. Wappen was made in the same form as regular clothes that doesn't damage the exterior then a removable wappen system was developed using Velcro and snap methods to enable the separation of device or the exchange of batteries. De-adhesion method can occur in two ways, from the outside and from the inside, so the design is selected depending on the application. This study shows the significance of the development of sensor-based smart clothing, in that it presented a universal model for users.

• Current Photovoltaic Research
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• v.11 no.1
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• pp.13-17
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• 2023

Functional transparent electrode was achieved by metal oxide-metal-Metal oxide (OMO) structure. Tailoring of metal oxide and metal layers, optically transparent and electrically excellent OMO films were investigated. Silver (Ag) is adopted for the metal layer and Ag oxide (AgO) is reactively formed by flowing O₂ gas during the sputtering process. This spontaneous AgO formation from Ag simultaneously provides the good electrical interface with high transparency. Due to the feature of transparent electrode of OMO, it endows the shielding effect (SE) function of electromagnetic interference. Optically transparent and electrically conductive OMO electrode shows the high transmittance (83.7%) and low sheet resistance (6.5 Ω/☐) with SE of 29.54 dB.

• Advances in nano research
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• v.17 no.1
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• pp.19-32
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• 2024

Functionally graded-carbon nanotube (FG-CNT) is expected to be a new generation of materials with a wide range of potential applications in technological fields such as aerospace, defense, energy, and structural industries. In this paper, an exact finite strip method for functionally graded-carbon nanotube sandwich plates is developed using first-order shear deformation theory to get the exact natural frequencies of the plates. The face sheets of the plates are made of FG-CNT with continuous and smooth grading based on the power law index. The equations of motion have been generated based on the Hamilton principle. By extracting the exact stiffness matrix for any strip of the sandwich plate as a non-algebraic function of natural frequencies, it is possible to calculate the exact free vibration frequencies. The accuracy and efficiency of the current method is established by comparing its findings to the results of the literature works. Examples are presented to prove the efficiency of the generated method to deal with various problems, such as the influence of the length-to-height ratio, the power law index, and a core-to-face sheet thickness of the single and multi-span sandwich plates with various boundary conditions on the natural frequencies. The exact results obtained from this analysis can check the validity and accuracy of other numerical methods.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.32 no.4
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• pp.295-307
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• 2006

Styela clava, called non-native tunicate or sea squirt, is habitat which include bays and harbors in Korea and several sites in the sea faced world. We fabricate cellulose membrane nerve conduit (CMNC) from this native sea squirt skin, and evaluate the capacity of promoting peripheral nerve regeneration in the rat sciatic nerve defect model. After processing the pure cellulose membrane from the sea squirt skin as we already published before, CMNC was designed as a non-tubular sheet with 14 mm length and 4 mm width. Total eleven male Spraque-Dawley rats (12 weeks, weighing 250 to 300g) were divided into sham group (n=2), silicone tube grafted control group (n=3) and experimental group (n=6). Each CMNC grafted nerve was evaluated after 4, 8 and 12 weeks in the experimental group, and after 12 weeks, sciatic function was evaluated with sciatic function index (SFI) and gait analysis, and histomorphology of nerve conduit and the innervated tissues of sciatic nerve were all examined using image analyzer and electromicroscopic methods in the all groups. The regenerated axon and nerve sheath were found only in the inner surface of the CMNC after 4 weeks and became more thicker after 8 and 12 weeks. In the TEM study, CMNC grafted group showed more abundant organized myelinated nerve fibers with thickened extracellular matrix than silicone conduit grafted group after 12 weeks. The sciatic function index (SFI) and ankle stance angle (ASA) in the functional evaluation were $-47.2{\pm}3.9$, $35.5^{\circ}{\pm}4.9^{\circ}$ in CMNC grafted group (n=2) and $-80.4{\pm}7.4$, $29.2^{\circ}{\pm}5.3^{\circ}$ in silicone conduit grafted group (n=3), respectively. And the myelinated axon was 41.59% in CMNC group and 9.51% in silicone conduit group to the sham group. The development of a bioactive CMNC to replace autogenous nerve grafts offers a potential and available approach to improved peripheral nerve regeneration. As we already published before, small peptide fragment derived from the basement membrane matrix proteins of squirt skin, which is a kind of anchoring protein composed of glycocalyx, induced the effective axonal regeneration with rapid growth of Schwann cells beneath the inner surface of CMNC. So the possibilities of clinical application as a peripheral nerve regeneration will be able to be suggested.

• Journal of Korea Port Economic Association
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• v.37 no.2
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• pp.73-89
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• 2021

The handysize bulk carriers are capable of transporting a variety of cargo that cannot be transported by mid-large size ship, and the spot chartering market is active, and it is a market that is independent of mid-large size market, and is more risky due to market conditions and charterage variability. In this study, Granger causality test, the Impulse Response Function(IRF) and Forecast Error Variance Decomposition(FEVD) were performed using monthly time series data. As a result of Granger causality test, coal price for coke making, Japan steel plate commodity price, hot rolled steel sheet price, fleet volume and bunker price have causality to Baltic Handysize Index(BHSI) and charterage. After confirming the appropriate lag and stability of the Vector Autoregressive model(VAR), IRF and FEVD were analyzed. As a result of IRF, the three variables of coal price for coke making, hot rolled steel sheet price and bunker price were found to have significant at both upper and lower limit of the confidence interval. Among them, the impulse of hot rolled steel sheet price was found to have the most significant effect. As a result of FEVD, the explanatory power that affects BHSI and charterage is the same in the order of hot rolled steel sheet price, coal price for coke making, bunker price, Japan steel plate price, and fleet volume. It was found that it gradually increased, affecting BHSI by 30% and charterage by 26%. In order to differentiate from previous studies and to find out the effect of short term lag, analysis was performed using monthly price data of major cargoes for Handysize bulk carriers, and meaningful results were derived that can predict monthly market conditions. This study can be helpful in predicting the short term market conditions for shipping companies that operate Handysize bulk carriers and concerned parties in the handysize chartering market.

• Journal of Sericultural and Entomological Science
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• v.41 no.1
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• pp.41-47
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• 1999

Silk fibroin dissolved in highly concentrated calcium chloride and ethanol mixture aqueous solution turned into gel under suitable conditions. Preparation conditions and properties of gel were investigated as a function of parameters such as pH of solution, fibroin concentration, glycerol concentration and molecular weight. When pH of silk fibroin aqueous solution was near the isoelectronic point(pH 3.9~4.0), gelation occurred rapidly and strength of gel was stonger than that of pH-unadjusted due to electrostatic repulsion decrease between silk fibroin macromolecules. As concentration of silk fibroin and glycerol was higher, gelation occurred more rapid. FT Infra-red spectra of freeze-dried fibroin gel showed that gelation was derived by intermolecular anti-parallel ${\beta}$-sheet structure formation. In addition to, it was found that white-precipitate occurred instead of gelation when aqueous silk fibroin was treated by enzyme(flavouzyme), however, after flavouzyme-treated silk fibroin aqueous solution was centrifugated gelation occurred instantly. The results of differential scanning thermal analysis and infra-red spectroscopy showed that thermal stability and crystallinity of enzyme-hydrolyzed fibroin are superior to those of unhydrolyzed fibroin.