• Progress in Superconductivity
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• v.13 no.2
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• pp.127-132
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• 2011

Many research groups have been manufacturing coated conductor by various processes such as PLD, MOD, and MOCVD, but the methods with production cost suitable for wide and massive application of coated conductor did not develop yet. Spray pyrolysis method adopting ultrasonic atomization was tried as one of the possible option. GdBCO precursor films have been deposited on IBAD substrate by spray pyrolysis method at low temperature and converted to GdBCO by post heat treatment. Ultrasonic atomization was used to generate fine droplets from precursor solution of Gd, Ba, and Cu nitrate dissolved in water. Primary GdBCO films were deposited at $500^{\circ}C$ and oxygen partial pressure of 1 torr. After that, the films were converted at various temperatures and low oxygen partial pressures. C-Axis oriented films were obtained IBAD substrates at conversion temperature of around $870^{\circ}C$ and oxygen partial pressures of 500 mtorr ~ 1 torr in a vacuum. Thick c-axis epitaxial film with the thickness of 0.4 ~ 0.5 ${\mu}m$ was obtained on IBAD substrate. C-axis epitaxial GdBCO films were successfully prepared by ex-situ methods using nitrate precursors on IBAD metal substrate. Converted GdBCO films have very dense microstructures with good grain connectivity. EDS composition analysis of the film showed a number of Cu-rich phase in surface. The precursor solution having high copper concent with the composition of Gd : Ba : Cu = 1 : 2 : 4 showed the better grain connectivity and electrical conductivity.

• Korean Journal of Food Science and Technology
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• v.39 no.1
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• pp.1-6
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• 2007

The effectiveness of cyclodextrin(CD) on binding and/or entrapping hexanal in model solution was investigated. The types and concentration of CDs for entrapping hexanal were studied using electronic nose, which composed of metal oxide sensor or was based on GC with surface acoustic wave sensor. ${\alpha}-CD$ was the most effective for lowering headspace concentration of hexanal in model solution. As concentration of CD increased, hexanal concentration in the headspace decreased significantly. Addition of 5% ${\beta}-CD$ to hexanal in model system resulted in 86% reduction of hexanal in the headspace. There was no difference between control and treatment at the initial stage of binding CD with hexanal while reduction of hexanal in the headspace was found during storage time. This could be estimated by electronic nose.

• Journal of the Korea Organic Resources Recycling Association
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• v.24 no.1
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• pp.3-10
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• 2016

Effects of acid ($HNO_3$ and HCl) modification on the adsorption properties of Pb(II) and Cu(II) onto bamboo-based activated carbon (BAC) were investigated through a series of batch experiments. The carbon content increased and oxygen content decreased with acid treatment. $HNO_3$ induced carboxylic acids and hydroxyl functional groups while HCl added no functional group onto BAC. The pseudo-second order model better described the kinetics of Pb(II) and Cu(II) adsorption onto experimented adsorbents, indicating that the rate-limiting step of the heavy metal sorption is chemical sorption involving valency forces through sharing or exchange of electrons between the adsorbate and the adsorbent. The equilibrium sorption data followed both Langmuir and Freundlich isotherm models. The adsorption capacities of BAC were affected by the surface functional groups added by acid modification. The adsorption capacities were enhanced up to 36.0% and 27.3% for Pb(II) and Cu(II), respectively by the $HNO_3$ modification, however, negligibly affected by HCl.

• JSTS:Journal of Semiconductor Technology and Science
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• v.2 no.2
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• pp.93-101
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• 2002

We have proposed and fabricated two lateral type field emission diodes, poly-Si emitter by utilizing the local oxidation of silicon (LOCOS) and GaN emitter using metal organic chemical vapor deposition (MOCVD) process. The fabricated poly-Si diode exhibited excellent electrical characteristics such as a very low turn-on voltage of 2 V and a high emission current of $300{\;}\bu\textrm{A}/tip$ at the anode-to-cathode voltage of 25 V. These superior field emission characteristics was speculated as a result of strong surface modification inducing a quasi-negative electron affinity and the increase of emitting sites due to local sharp protrusions by an appropriate activation treatment. In respect, two kinds of procedures were proposed for the fabrication of the lateral type GaN emitter: a selective etching method with electron cyclotron resonance-reactive ion etching (ECR-RIE) or a simple selective growth by utilizing $Si_3N_4$ film as a masking layer. The fabricated device using the ECR-RIE exhibited electrical characteristics such as a turn-on voltage of 35 V for $7\bu\textrm{m}$ gap and an emission current of~580 nA/l0tips at anode-to-cathode voltage of 100 V. These new field emission characteristics of GaN tips are believed to be due to a low electron affinity as well as the shorter inter-electrode distance. Compared to lateral type GaN field emission diode using ECR-RIE, re-grown GaN emitters shows sharper shape tips and shorter inter-electrode distance.

• The Journal of Advanced Prosthodontics
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• v.1 no.3
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• pp.118-123
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• 2009

STATEMENT OF PROBLEM. Proper proximal contact is important for maintaining and stabilizing the dental arch. However, the proximal contact strength (PCS) is not a constant value and can be affected by a variety of factors. PURPOSE. This study examined the influences of postural changes on the posterior PCS. MATERIAL AND METHODS. Twelve adults with a normal occlusion and had not undergone prosthetic treatment or proximal restoration were participated in this study. A metal strip was inserted into the proximal surface and removed at a constant velocity. The contact strength was measured in every contact point between canine to second molar in both arches. The PCSs were obtained initially in the upright position, secondly in the supine position and finally in the upright position again. All measurements were repeated after a 2 hour period. Statistical analysis was carried out using the Friedman test (P < .05). RESULTS. Generally, a decrease in PCS occurred when the posture was changed from the initial upright to supine position, while it increased when the posture was changed from the supine to upright position. A significant change was observed in all areas except for between the canine-first premolar in the maxilla and between the first molar-second molar in the mandible areas. CONCLUSION. The posterior PCS, which dentists generally believe to be a static feature of occlusion, is affected significantly by posture.

• Journal of the Korean Institute of Telematics and Electronics
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• v.21 no.4
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• pp.52-57
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• 1984

The electrical properties and their instability of InP tunnel MIS diodes fabricated by inserting the chemically grown oxide between metal and n-lnP (100) surface have been in-vestigated. The structure of the gown oxide was the mixture of In2O3 and P2O5, as was other low-temperature grown oxide, and its thickness was estimated to be the order of 200 $A^{\circ}$. The forward and reverse currents increased even with slight heat treatment of diodes in vacuum, and they were reduced when the diodes were exposed to humid ambient. It was discussed that the observed instability in I-V characteristics is due to a change of the physicochemical properties of the oxide film and of the interface states between oxide and InP according to the absorption of H2O.

• Applied Chemistry for Engineering
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• v.29 no.5
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• pp.571-580
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• 2018

In this study, hybrid adsorbents (SS) were prepared by mixing spent coffee grounds (SCG) and sericite, a kind of clay minerals, to adsorb Pb(II) from an aqueous solution. In FT-IR analyses, the main functional groups of SS adsorbents were O-H, C=O and C-N groups. The specific surface area, cation exchange capacity and the pore diameter of SS were larger than those of using SCG and sericite. Formation conditions of the SS adsorbent were the optimum pyrolysis temperature of $300^{\circ}C$, SCG : sericite ratio of 8 : 2, and particle size of 0.3 mm. Langmuir adsorption isotherm was more suitable than Freundlich one, and the maximum adsorption capacity was reached 44.42 mg/g. As a result of the adsorption thermodynamic analysis, the adsorption of Pb(II) onto SS was the physical adsorption and exothermic process in nature. The regeneration of SS adsorbent using distilled water showed 88~92% recovery and the active site of SS adsorbent decreased with increasing the reuse cycle time. As a result, SS adsorbent showed that it can be used to remove Pb(II) easily, inexpensively and efficiently without any pre-treatment from aqueous solutions.

• Journal of Welding and Joining
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• v.32 no.3
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• pp.95-101
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• 2014

Joining of grey cast iron by fusion welding has much difficulties for its extremely low ductility and low toughness because of the flake form of the graphite. And the brittle microstructure, i.e. ledeburite may be formed during fusion welding by its rapid cooling rates. By these kinds of welding problem, preheat and post heat treatment temperature must be increased to avoid weld crack or welding problems. In order to avoid these fusion welding problem, friction welding of cast iron was carried out for improving joint soundness, establishing friction welding variables. There is no factor for evaluating friction weldability in continuous drive type friction welding. In this point of view, this study proposed the parameters for calculating friction weld heat input. The results obtained are as follows ; 1. There was a close relationship between tensile strength and flash appearance of friction welded joint. 2. Tensile strength was decreased and flash was severely oxidized as increasing frictional heating time. 3. As increased forging pressure $P_2$, flash had a large crack and tensile strength was decreased. 4. As powdered graphite by rotational frictional force induced flat surface and hindered plastic flow of metal, tensile strength of welded joint was decreased. 5. Heat input for continuous drive type friction welding could be calculated by the factors of $P_1$, $P_2$ and upset distance(${\delta}$).

• Membrane and Water Treatment
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• v.11 no.1
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• pp.41-48
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• 2020

Lead is a highly toxic heavy metal that causes serious health problems. Nonetheless, it is increasingly being used for industrial applications and is often discharged into the environment without adequate purification. In this study, Pb(II) was removed by powdered waste sludge (PWS) based on the biosorption mechanism. Different PWSs were collected from a submerged moving media intermittent aeration reactor (SMMIAR) and modified Ludzack-Ettinger (MLE) processes. The contents of extracellular polymeric substances were similar, but the surface area of MLE-PWS (2.07 ㎡/g) was higher than that of SMMIAR-PWS (0.82 ㎡/g); this is expected to be the main parameter determining Pb(II) biosorption capacity. The Bacillaceae family was dominant in both PWSs and may serve as the major responsible bacterial group for Pb(II) biosorption. Pb(II) biosorption using PWS was evaluated for reaction time, salinity effect, and isotherm equilibrium. For all experiments, MLE-PWS showed higher removal efficiency. At a fixed initial Pb(II) concentration of 20 mg/L and a reaction time of 180 minutes, the biosorption capacities (q_e) for SMMIAR- and MLE-PWSs were 2.86 and 3.07 mg/g, respectively. Pb(II) biosorption using PWS was rapid; over 80% of the maximum biosorption capacity was achieved within 10 minutes. Interestingly, MLE-PWS showed enhanced Pb(II) biosorption with salinity values of up to 30 g NaCl/L. Linear regression of the Freundlich isotherm revealed high regression coefficients (R² > 0.968). The fundamental Pb(II) biosorption capacity, represented by the K_F value, was consistently higher for MLE-PWS than SMMIAR-PWS.

• Restorative Dentistry and Endodontics
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• v.43 no.1
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• pp.7.1-7.7
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• 2018

Objectives: The aim of this study is to compare the shear bond strengths of ceramic brackets bonded to zirconia surfaces using different zirconia primers and universal adhesive. Materials and Methods: Fifty zirconia blocks ($15{\times}15{\times}10mm$, Zpex, Tosoh Corporation) were polished with 1,000 grit sand paper and air-abraded with $50{\mu}m$ $Al_2O_3$ for 10 seconds (40 psi). They were divided into 5 groups: control (CO), Metal/Zirconia primer (MZ, Ivoclar Vivadent), Z-PRIME Plus (ZP, Bisco), Zirconia Liner (ZL, Sun Medical), and Scotchbond Universal adhesive (SU, 3M ESPE). Transbond XT Primer (used for CO, MZ, ZP, and ZL) and Transbond XT Paste was used for bracket bonding (Gemini clear ceramic brackets, 3M Unitek). After 24 hours at $37^{\circ}C$ storage, specimens underwent 2,000 thermocycles, and then, shear bond strengths were measured (1 mm/min). An adhesive remnant index (ARI) score was calculated. The data were analyzed using one-way analysis of variance and the Bonferroni test (p = 0.05). Results: Surface treatment with primers resulted in increased shear bond strength. The SU group showed the highest shear bond strength followed by the ZP, ZL, MZ, and CO groups, in that order. The median ARI scores were as follows: CO = 0, MZ = 0, ZP = 0, ZL = 0, and SU = 3 (p < 0.05). Conclusions: Within this experiment, zirconia primer can increase the shear bond strength of bracket bonding. The highest shear bond strength is observed in SU group, even when no primer is used.