• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.1455-1456
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• 2011

• Applied Chemistry for Engineering
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• v.34 no.5
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• pp.556-565
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• 2023

Fast industrial and agricultural expansion result in the production of heavy metal ions (HMIs). These are exceedingly hazardous to both humans and the environment, and the necessity to eliminate them from aqueous systems prompts the development of novel materials. In the present study, a UIO-66 (COOH)₂ metal-organic framework (MOF) containing free carboxylic acid groups was post-synthetically modified with L-glutamic acid via the solid-solid reaction route. Pristine and glutamic acid-treated MOF materials were characterized in detail using several physicochemical techniques. Single-ion batch adsorption studies of Pb(II) and Hg(II) ions were carried out using pristine as well as amino acid-modified MOFs. We further examined parameters that influence removal efficiency, such as the initial concentration and contact time. The bare MOF had a higher ion adsorption capacity for Pb(II) (261.87 mg/g) than for Hg(II) ions (10.54 mg/g) at an initial concentration of 150 ppm. In contrast, an increased Hg(II) ion adsorption capacity was observed for the glutamic acid-modified MOF (80.6 mg/g) as compared to the bare MOF. The Hg(II) ion adsorption capacity increased by almost 87% after modification with glutamic acid. Fitting results of isotherm and kinetic data models indicated that the adsorption of Pb(II) on both pristine and glutamic acid-modified MOFs was due to surface complexation of Pb(II) ions with available -COOH groups (pyromellitic acid). Adsorption of Hg(II) on the glutamic acid-modified MOF was attributed to chelation, in which glutamic acid grafted onto the surface of the MOF formed chelates with Hg(II) ions.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.124-124
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• 2003

To improve the electrochemical properties of thin-film LiCoO$_2$ cathodes, metal oxides were coated on the LiCoO$_2$ thin films using f sputtering. Galvanostatic charge-discharge experiments showed the enhanced cycling behaviors in the metal-oxide coated LiCoO$_2$ thin films than the uncoated ones. These results are because the metal-oxide coating layer suppresses the degradation of Li-diffusion kinetics during cycling, which is related to the protection of cathode surface from the electrolytes [l-3]. The variation in the metal-oxide coating thickness ranging from 10 to 300 nm did not affect the electrochemical properties. Changes of lattice constants in the coated and bare LiCoO$_2$ thin films at different charged states will also be discussed.

• Journal of Soil and Groundwater Environment
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• v.15 no.5
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• pp.16-22
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• 2010

Heavy metals in soils exist in various forms dependent upon surrounding conditions. As the Janghang smelter area is of concern for its high elevated heavy metal concentrations, Korean government decided to remediate the area. Main objectives of this research were; to analyze heavy metal concentrations and their existing forms in the vicinity of the smelter; and to understand differences made by analysis techniques of heavy metals. Top soils of rice field, crop field, bare field, and forestry in the area were sampled and analyzed for their physicochemical characteristics. Concentrations of Cu, Cd, Pb, and As were analyzed with two pretreatment techniques adopted using 0.1 N HCl and aqua regia. To analyze existing forms of heavy metals, Tessier's schemes for sequential extraction technique were adopted. Exchangeable fraction and carbonate bound fraction of heavy metals may pose potential threat to environment and were in the order of Pb > As > Cu > Cd. If assessing mobile fraction of heavy metals by land uses, the order was forestry > bare land > crop field > rice field. When analyzed using Tessier's scheme, high ratio of residual fractions to total arsenic concentration should be considered for remediation design of the area.

• Applied Chemistry for Engineering
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• v.30 no.5
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• pp.586-590
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• 2019

The aim of this study was to fabricate a dextran polyelectrolyte multi-layer on a bare metal stent (BMS) and to evaluate bio-physical properties of the layer. Diethylaminoethyl-dextran (DEAE-D) as a polycation and dextran sulfate (DS) as a polyanion were successively coated on the bare metal stent by a well-known layer-by-layer procedure. The morphology of the stent surface and its cell adhesion were studied after each coating step by scanning electron microscopy. The stent showed more blotched and slightly rougher morphology after dextran-DS coating. The contact angle of the DEAE-DS group ($39.5{\pm}0.15^{\circ}$) was significantly higher than that of the BMS group ($45.16{\pm}0.08^{\circ}$), indicating the improvement of hydrophilic. The SMC proliferation inhibition in the DEAE-DS-coated stent group ($20.9{\pm}0.04%$) was stronger than that in the control group ($21.7{\pm}0.10%$ in DS-coated group only). The DEAE-DS coating is desired for stent coating materials with biocompatibility and anti-restenosis effect.

• Bulletin of the Korean Chemical Society
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• v.35 no.8
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• pp.2519-2522
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• 2014

Recently, the observation of the electrocatalytic behavior of individual nanoparticles (NPs) by electrochemical amplification method has been reported. For example, the Iridium oxide ($IrO_x$) NP collision on the Pt UME was observed via electrocatalytic water oxidation. However, the bare Pt UME had poor reproducibility for the observation of NP collision signal and required an inconvenient surface pre-treatment for the usage. In this manuscript, we has been investigated other metal electrode such as Cu UME for the reproducible data analysis and convenient use. The $IrO_x$ NP collision was successively observed on the bare Cu UME and the reproducibility in collision frequency was improved comparing with previous case using the $NaBH_4$ pre-treated Pt UME. Also, the adhesion coefficient between NP and the Cu UME was studied for better understanding of the single NP collision system.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.3 no.4
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• pp.329-333
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• 2005

To identify the effect of engineered barriers on the leach rate of cesium from spent PWR fuel under a synthetic granitic groundwater, the related leach tests with and without bentonite or metals have been performed up to about 6 years. The leach rates were decreased as a function of leaching time and then became a constant after a certain period. The period in a bare spent fuel was much longer than that with bentonite or metal sheets. The cumulative fraction of cesium released from the spent fuel with bentonite or with copper and stainless steel sheets was steadily increased, but the fraction from bare fuel was rapidly and then sluggishly increased. However, the values deducted its gap inventory from the cumulative fraction of cesium released from the bare fuel was almost very close to the others. These suggest that the initial release of cesium from bare fuel might be dependant on its gap inventory and the effect of engineered barriers on the long-term leach rate of cesium would be insignificant but the rate with engineered barriers could be reduced in the initial transient period due to their retardation effect. And the long-term leach rate of cesium from spent fuel in a repository would be approached to a constant rate of $2\times10^{-2}g/m^2-day$.

• The Journal of the Korea Contents Association
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• v.12 no.7
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• pp.273-283
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• 2012

Drug-eluting stents (DES) have significantly reduced in-stent restenosis, compared to bare-metal stents (BMS). However, there remains concern for the increased risk of stent thrombosis (ST) associated with DES. The present study sought to evaluate the incidence, clinical characteristics and outcome of ST in patients with acute myocardial infarction (MI) during a 1-year follow-up. 80 patients who developed ST were divided into 2 groups according to stent type: group I (DES-ST, n = 57 ) and group II (BMS-ST, n = 23 ). There were no differences between group I and II in the overall incidence of ST (2.7% vs. 4.3%, p=0.064) and in the incidence of each type of ST: acute ST (8.8% vs. 2.3%), subacute ST (50.9% vs. 60.9%), late ST (19.3% vs. 8.7%), and very late ST (21.1% vs. 17.4%) (p=0.605). Predictors of 1-year mortality were the occurrence of ST (OR 8.12, 95% CI 2.83-23.61, p<0.001), left ventricular ejection fraction<40% (OR 6.41, 95% CI 2.42-16.96, p<0.001), and age${\geq}$75 years (OR 4.98, 95% CI 1.95-12.74, p=0.001).

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.4
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• pp.747-754
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• 1988

High strength steels (HS) of dual phase and monogalvanized steel sheets (GA ; plated plane, GAB ; bare plane0 were used to investigate the fatigue strengths of four kinds of single-spot-welded joint specimen under tensile-shear repeated load. The specimen is classified as the same mating metal specimen (HS*HS, GA*GAB) and different mating metal specimen (HS*GA, HS*GAB). Some of the results are ; (1) Static tensile load of single-spot-welded joint specimens is proportional to tensile strength of metal and rigidity of mating metal sheet. (2) Fatigue life of HS*HS specimens increased about 20% longer than that of GA*GAB specimens in low cycle range. (3) In different mating metal specimens, the fatigue life of HS*GA specimens increased about 84% more that of HS*HS specimens in high cycle range.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.05a
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• pp.57-60
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• 2001

The characterization of organic Metal/Insulator/Metal(MIM) devices were investigated from LB films. The physicochemical properties of the LB films were by UV absorption spectrum and AFM. We give pressure stimulation into organic thin films and then manufacture a device under the accumulation condition that the state surface pressure is 2, 10, 30[mN/ml The stable images are probably due to a strong interaction between the monolayer film and glass substrate. We are unable to obtain molecule resolution in images of the films but did see a marked contrast between images of the bare substrate and those with the network structure film deposited onto it.