• Clean Technology
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• v.25 no.2
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• pp.129-139
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• 2019

Bamboo is an evergreen perennial plant, and it is known as one of the most productive and fastest-growing plants in the world. It grows quickly in moderate climates with only moderate water and fertilizer. Traditionally in Asia, bamboo is used for building materials, as a food source, and as versatile raw materials. Bamboo as a biomass feedstock can be transformed to prepare activated carbon using the thermal treatment of pyrolysis. The effect of process variables such as carbonization temperature, activation temperature, activation time, the amount of steam, and the mixing ratio of phosphoric acid and bamboo were systematically investigated to optimize the preparation conditions. Steam activation was proceeded after carbonization with a vapor flow rate of $0.8{\sim}1.8mL-H_2O\;g-char^{-1}\;h^{-1}$ and activation time of 1 ~ 3 h at $700{\sim}900^{\circ}C$. Carbon yield and surface area reached 2.04 ~ 20.59 wt% and $499.17{\sim}1074.04m^2\;g^{-1}$, respectively, with a steam flow rate of $1.4mL-H_2O\;g-char^{-1}\;h^{-1}$ for 2 h. Also, the carbon yield and surface area were 24.67 wt% and $1389.59m^2\;g^{-1}$, respectively, when the bamboo and phosphoric acid were mixed in a 1:1 weight ratio ($700^{\circ}C$, 2 h, $1.4mL-H_2O\;g-char^{-1}\;h^{-1}$). The adsorption of methylene blue into the bamboo activated carbon was studied based on pseudo first order and second order kinetics models. The adsorption kinetics were found to follow the pseudo second order model, which is governed by chemisorption.

• Journal of Acupuncture Research
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• v.26 no.2
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• pp.159-170
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• 2009

Backgrounds and Objectives: A fracture means a loss of continuity in the substance of bone. Bone differs from other musculoskeletal tissue due to its ability to repair and heal itself without leaving a scar. The cutter head has multinucleated osteoclast cells to resorb the dead bone. The tail, with its conical surface, is lined with osteoblast cells laying down new bone. The conjugation of fracture is a unique biological process regulated by a complex array of signaling molecules and proinflammatory cytokines. Pyritum, one of the important prescriptions in the oriental medicine, has been used for conjugation fracture. The purpose of this study is to evaluate the effects of administration of Pyritum on activation of osteoblast cells in human body & on tibia bone fracture in mice. Materials and Methods : Four weeks aged 30 female DBA mice were used for this study. They were divided three groups, normal group, control group(fracture elicitate mice: FE group) and experimental group(Pyritum administered mice group after fracture elicitation : PA group). Left tibia bones of mice in FE and PA groups were fractured by bone cutters. MG-63 cells in human body th Pyritum in the ratio of 1 mg/m${\ell}$, and the cells were further incubated for 24 hours. Activation of osteoblast was identified using osteopontin, FGF in vitro test. In vivo test, regeneration of fractured tibia through the morphological changes was observed, and also activation of inflammation through NF-${\kappa}$B p65, iNOS, COX-2, osteoblast through osteopontin, FGF and osteoblast's proliferation in each group was measured. Results and Conclusions : 1. In vitro test for activation of osteoblast cells in human body by Pyritum, osteopontin and FGF production were remarkably increased in Pyritum treated MG-63 cells. 2. In regeneration of fractured tibia by Pyritum, fractured area in external tibia morphology was decreased more in the PA group than that of the FE group. Osteogenesis in fractured area was increased more in the PA group than that of the FE group. Also, endochodrial ossification in central area of fracture and osteoid in lateral area of fracture were increased more in the PA group than those of the FE group. 3. In activation of inflammation by Pyritum administered, activation of NF-${\kappa}$B p65, increase of iNOS and COX-2 production were higher in the PA and the FE groups than those of the control group. Especially, the PA group showed higher activation and increase than those of the FE group. 4. In activation of osteoblast by Pyritum, increase of osteopontin, FGF and osteoblast's proliferation were higher in the PA and the FE groups than those of the control group. Especially, the PA group showed higher increase and proliferation than those of the FE group.

• Journal of the Korean Society of Marine Environment & Safety
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• v.18 no.6
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• pp.569-576
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• 2012

In general, aluminum alloys forms the passive film($Al_2O_3$, $Al_2O_3{\cdot}3H_2O$) in neutral solution. However, the passive film created on the surface will be destroyed by chloride ions contained in sea water so the corrosion will occur. In this study, in order to solve the problem of corrosion under a seawater environment, potentiostatic protection techniques were applied to Al-4.5%Mg-0.6%Mn aluminum alloy in seawater. At polarization experiments, active state were observed at anodic polarization and concentration polarization by reduction of dissolves oxygen and activation polarization were found at anodic polarization. As a results of potentiostatic experiment, calcareous deposit were created much more as applying time increase from the turning point of the concentration polarization and activation polarization and crevice corrosion was partially observed between calcareous deposit and surface of base metal. Overall potentiostatic anodic polarization experiment was difficult to apply potentiostatic corrosion protection technology by occurrence of active state, whereas potentiostatic cathodic polarization experiment examined optimum corrosion protection condition of -1.1 V~-0.75 V within the range of concentration polarization considered various applying time.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.9 no.2
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• pp.73-80
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• 2011

The radiation shielding analysis for a Burnup-credit (BUC) cask designed under the management of Korea Radioactive Waste Management Corporation (KRMC) was performed to examine the contribution of each radiation source affecting dose rate distribution around the cask. Various radiation sources, which contain neutron and gamma-ray sources placed in active fuel region and the activation source, and imaginary nuclear fuel were all considered in the MCNP calculation model to realistically simulate the actual situations. It was found that the maximum external and surface dose rates of the spent fuel cask were satisfied with the domestic standards both in normal and accident conditions. In normal condition, the radiation dose rate distribution around the cask was mainly influenced by activation source ($^{60}Co$ radioisotope); in another case, the neutron emitted in active fuel region contributed about 90% to external dose rate at 1m distance from side surface of the cask. Besides, the contribution level of activation source was dramatically increased to the dose rates in top and bottom regions of the cask. From this study, it was recognized that the detailed investigation on the radiation sources should be performed conservatively and accurately in the process of radiation shielding analysis for a BUC cask.

• Korean Journal of Materials Research
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• v.7 no.3
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• pp.188-195
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• 1997

Copper ions were adsorbed on amorphous Si films by spincoating of Cu solutions and were employed as surface nucleation sites for low-temperature crystallization. The crystallization temperature can bc lo~vered down to $500^{\circ}C$ and rhe crystallization time can be shortened by Cu adsorption. The Cu-adsorbed amorphous films were crystallized by fractal growth with the shape of tree branches. The fractal size ranged from $30 to 300{\mu}m$, depending on the Cu solution concentration. The fractals consisted of f e a t h e r like elliptical grains with the size of $0.3~0.4{\mu}m$. which was comparable to that of the intrinsic films crystallized at $600^{\circ}C$. Both the nucleation activation energy and grotvth activation energy decreased as the Cu concentration in the solution increased. The results suggest thcit the adsorbed Cu increases preferred nucleation sites at the surface and enhmces crystallization by reducing thc activation energies of nucleation and growth.

• Applied Chemistry for Engineering
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• v.34 no.4
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• pp.426-433
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• 2023

Capacitor performance was considered using coffee grounds-based activated carbon produced through oil extraction and KOH activation to increase the utilization of boiwaste. Oil extraction from coffee grounds was performed by solvent extraction using n-Hexane and isopropyl alcohol solvents. The AC_CG-Hexane/IPA produced by KOH activation after oil extraction increased the specific surface area by up to 16% and the average pore size by up to 2.54 nm compared to AC_CG produced only by KOH activation without oil extraction. In addition, the pyrrolic/pyridinic N functional group of the prepared activated carbon increased with the extraction of oil from coffee grounds. In the cyclic voltage-current method measurement experiment, the specific capacitance of AC_CG-Hexane/IPA at a voltage scanning speed of 10 mV/s is 133 F/g, which is 33% improved compared to the amorphous capacity of AC_CG (100 F/g). The results show improved electrochemical properties by improving the size and specific surface area of the mesopores of activated carbon by removing components from coffee grounds oil and synergistic effects by increasing electrical conductivity with pyrrolic/pyridinic N functional groups. In this study, the recycling method and application of coffee grounds, a bio-waste, is presented, and it is considered to be one of the efficient methods that can be utilized as an electrode material for high-performance supercapacitors.

• Journal of Sensor Science and Technology
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• v.26 no.3
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• pp.149-154
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• 2017

Detection of rain is one of the essential weather factors that are monitored by automatic weather stations in Korea. In this work, we studied the operation standards required for impedance-based rain detectors in terms of surface temperature and sensitivity, in an effort to establish a qualification procedure for rain detectors. The surface temperature of rain detectors was measured at varying air temperatures from $-30^{\circ}C$ to $20^{\circ}C$, considering the hypothetical presence and absence of rain/snow. In addition, the sensitivity of rain detectors was studied generating artificial raindrops of regular size. The sensitivity was evaluated in terms of the critical number of droplets that triggers the activation of the rain detector. We found that the sensitivity is affected by stationary, horizontal, and vertical droplet deposition methods. The critical number of droplets for the stationary deposition is higher than that for both horizontal and vertical depositions, which provides the maximum limit of droplets required to activate the detector. Based on our experiments considering surface temperature measurements and sensitivity tests, we suggest a revised version of surface temperature and sensitivity requirements for the qualification of impedance-based rain detectors.

• Fire Science and Engineering
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• v.22 no.2
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• pp.44-48
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• 2008

In this paper, we measured a contact angle, surface resistivity and XPS to study the thermal aging characteristics of the epoxy resin for cast resin transformer. As a result of this experiment, we found that the contact angle increases up to $200^{\circ}C$ as it causes a re-crosslinking on the surface, but starts decreasing at $250^{\circ}C$ as it causes heat condensation. As a result of examining the oxygen/carbon peaks through the XPS analysis, we obtained a higher oxygen peak vs. carbon in the first untreated sample, but it showed the opposite trend after heat treatment. That rise in the carbon peak continued up to $200^{\circ}C$, but decreased again at the temperatures above. That's because it kept forming a stable surface structure up to $200^{\circ}C$ but its carbon combination got destroyed due to a rapid oxidization at $250^{\circ}C$. And a conduction path was formed easily with the hydrophile property caused by rapid surface activation.

• Bulletin of the Korean Chemical Society
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• v.35 no.7
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• pp.2013-2018
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• 2014

The adsorption and decomposition of trimethylene oxide ($C_3H_6O$) molecule on the Al(111) surface were investigated by the generalized gradient approximation (GGA) of density functional theory (DFT). The calculations employed a supercell ($6{\times}6{\times}3$) slab model and three-dimensional periodic boundary conditions. The strong attractive forces between $C_3H_6O$ molecule and Al atoms induce the C-O bond breaking of the ring $C_3H_6O$ molecule. Subsequently, the dissociated radical fragments of $C_3H_6O$ molecule oxidize the Al surface. The largest adsorption energy is about -260.0 kJ/mol in V3, V4 and P2, resulting a ring break at the C-O bond. We also investigated the decomposition mechanism of $C_3H_6O$ molecules on the Al(111) surface. The activation energies ($E_a$) for the dissociations V3, V4 and P2 are 133.3, 166.8 and 174.0 kJ/mol, respectively. The hcp site is the most reactive position for $C_3H_6O$ decomposing.

• Korean Journal of Materials Research
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• v.24 no.3
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• pp.166-173
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• 2014

The effects of printed circuit board electroless nickel immersion gold (ENIG) and organic solderability preservative (OSP) surface finishes on the electromigration reliability and shear strength of Sn-3.5Ag Pb-free solder bump were systematically investigated. In-situ annealing tests were performed in a scanning electron microscope chamber at 130, 150, and $170^{\circ}C$ in order to investigate the growth kinetics of intermetallic compound (IMC). Electromigration lifetime and failure modes were investigated at $150^{\circ}C$ and $1.5{\times}10^5A/cm^2$, while ball shear tests and failure mode analysis were conducted under the high-speed conditions from 10 mm/s to 3000 mm/s. The activation energy of ENIG and OSP surface finishes during annealing were evaluated as 0.84 eV and 0.94 eV, respectively. The solder bumps with ENIG surface finish showed longer electromigration lifetime than OSP surface finish. Shear strengths between ENIG and OSP were similar, and the shear energies decreased with increasing shear speed. Failure analysis showed that electrical and mechanical reliabilities were very closely related to the interfacial IMC stabilities.