• Korean Chemical Engineering Research
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• v.62 no.1
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• pp.99-104
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• 2024

In this study, a carbon coated hollow silicon (HSi/C) composite material was prepared for anode material of high-capacity lithiun-ion battery. Hollow silica (HSiO₂) was synthesized by the Stöber method with CTAB (N-Cetyltrimethylammonium bromide). The HSi/C anode composite was manufactured by carbon coating after magnesiothermic reduction of HSiO₂. The physical and electrochemical characteristics of the prepared anode materials were investigated based on CTAB amount. In the FE-SEM analysis, it was found that the HSiO₂ particle size increased as CTAB amount decreased, but shell thickness decreased. The HSi/C composites exhibited high initial discharge capacities of 1866.7, 2164.5 and 2188.6 mAh/g with various CTAB ratios (0.5, 1.0, 1.5), respectively. After 100 cycles of charge-discharge, 0.5-HSi/C demonstrated a high reversible capacity of 1171.3 mAh/g and a capacity retention of 70.9%. Electrochemical impedance spectroscopy (EIS) was employed to analyze the impedance characteristics, and it revealed that 0.5-HSi/C showed more stable resistance characteristics than HSi/C composites with other CTAB amount over 20 cycles.

• Smart Media Journal
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• v.13 no.3
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• pp.18-26
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• 2024

Road surface monitoring is essential for maintaining road environment safety through managing risk factors like rutting and crack detection. Using autonomous driving-based UGVs with high-performance 2D laser sensors enables more precise measurements. However, the increased energy consumption of these sensors is limited by constrained battery capacity. In this paper, we propose a fusion sensor system for efficient surface monitoring with UGVs. The proposed system combines color information from cameras and depth information from line laser sensors to accurately detect surface displacement. Furthermore, a dynamic sampling algorithm is applied to control the scanning frequency of line laser sensors based on the detection status of monitoring targets using camera sensors, reducing unnecessary energy consumption. A power consumption model of the fusion sensor system analyzes its energy efficiency considering various crack distributions and sensor characteristics in different mission environments. Performance analysis demonstrates that setting the power consumption of the line laser sensor to twice that of the saving state when in the active state increases power consumption efficiency by 13.3% compared to fixed sampling under the condition of λ=10, µ=10.

• Applied Chemistry for Engineering
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• v.35 no.2
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• pp.140-147
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• 2024

In order to increase the utilization of biomass, an electrochemical performance was considered after manufacturing a carbon anode material (SV-C) for a Setaria viridis-based lithium ion secondary battery through a heat treatment process. When the heat treatment temperature of the Setaria viridis is as low as 750 ℃, the capacitance (1003.3 mAh/g, at 0.1 C) is high due to the negative (-) charge of oxygen present on the surface attracting lithium, along with the low crystallinity and high specific surface area (126 m²/g), but the capacity retention rate is believed to be as low as 61.0% (at 500 cycles and 1 C). In addition, it was confirmed that when the heat treatment temperature increased to 1150 ℃, the carbon layer was condensed to be excellent in arrangement, and the structural defects were reduced, resulting in a significant reduction in the specific surface area (32 m²/g) of the pores. Furthermore, when the surface defects of the anode material are reduced and the crystallinity is increased, the capacity retention rate is as high as 89.7% (at 500 cycles and 1 C), but the degree of defects is small, the active point is reduced, and the specific capacity is considered to be very low at 471.7 mAh/g. In the scope of this study, it was found that in the case of the Setaria viridis-based carbon anode material manufactured according to the heat treatment temperature, the surface oxygen content and crystallinity have higher reliability on the electrochemical properties of the anode material than the specific surface area.

• Journal of the Microelectronics and Packaging Society
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• v.31 no.2
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• pp.36-44
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• 2024

Copper electrodeposition technology is essential for producing copper films and interconnects in the microelectronics industries including semiconductor packaging, semiconductors and secondary battery, and there are extensive efforts to control the microstructure of these films and interconnects. In this study, we investigated the influence of crystallographic orientation on the local plastic deformation of copper films for secondary batteries deformed by uniaxial tensile load. Crystallographic orientation maps of two electrodeposited copper films with different textures were measured using an electron backscatter diffraction (EBSD) system and then used as initial conditions for crystal plasticity finite element analysis to predict the local plastic deformation behavior within the films during uniaxial tension deformation. Through these processes, the changes of the local plastic deformation behavior and texture of the films were traced according to the tensile strain, and the crystal orientations leading to the inhomogeneous plastic deformation were identified.

• Dementia and Neurocognitive Disorders
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• v.23 no.1
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• pp.30-43
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• 2024

Background and Purpose: The SoUth Korea study to PrEvent cognitive impaiRment and protect BRAIN health through lifestyle intervention (SUPERBRAIN) proved the feasibility of multidomain intervention for elderly people. One-quarter of the Korean population over 65 years of age has mild cognitive impairment (MCI). Digital health interventions may be cost-effective and have fewer spatial constraints. We aim to examine the efficacy of a multidomain intervention through both face-to-face interactions and video communication platforms using a tablet personal computer (PC) application in MCI. Methods: Three hundred participants aged 60-85 years, with MCI and at least one modifiable dementia risk factor, will be recruited from 17 centers and randomly assigned in a 1:1 ratio to the multidomain intervention and the waiting-list control groups. Participants will receive the 24-week intervention through the tablet PC SUPERBRAIN application, which encompasses the following five elements: managing metabolic and vascular risk factors, cognitive training, physical exercise, nutritional guidance, and boosting motivation. Participants will attend the interventions at a facility every 1-2 weeks. They will also engage in one or two self-administered cognitive training sessions utilizing the tablet PC application at home each week. They will participate in twice or thrice weekly online exercise sessions at home via the ZOOM platform. The primary outcome will be the change in the total scale index score of the Repeatable Battery for the Assessment of Neuropsychological Status from baseline to study end. Conclusions: This study will inform the effectiveness of a comprehensive multidomain intervention utilizing digital technologies in MCI.

• Korean Chemical Engineering Research
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• v.62 no.3
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• pp.246-252
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• 2024

In this study, impurities such as Li and F were removed from waste graphite through citric acid treatment, and changes in structural properties, capacity, and cycle stability of regenerated graphite were observed accordingly. Regenerated graphite pretreated in a nitrogen atmosphere was treated with citric acid, and its structure and characteristics were analyzed through SEM (Scanning Electron Microscope), FT-IR (Fourier Transform Infrared spectroscopy), XRD (X-ray Diffraction), and XPS (X-ray Photoelectron Spectroscopy). Waste graphite that was not treated with acid had a rapid decrease in capacity before 70 cycles, but graphite that had been treated with citric acid showed a capacity of 302.9 mAh g^-1 and a capacity retention rate of 93.1% at 100 cycles. In addition, despite changes in current density in rate performance, samples treated with citric acid showed 340.2 mAh g^-1 performance at 1.0C without change in capacity. As a result, it was confirmed that citric acid treatment not only effectively removed impurities and showed a high capacity retention rate, but also showed stability even at high current densities.

• Korean Chemical Engineering Research
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• v.62 no.3
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• pp.262-268
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• 2024

In this study, the MXene/Si composite was prepared by electrostacic assembly with 2-dimensional structured titanium carbide (MXene) and nano silicon for anode material of high-performance lithium-ion battery. Ti₃C₂T_x MXene was synthesized by etching the Ti₃AlC₂ MAX with LiF/HCl, and the surface of nano silicon was charged to positively using CTAB (Cetyltrimethylammonium bromide). The MXene/Si anode composite was successfully manufactured by simple mixing process of synthesized MXene and charged silicon. The physical and electrochemical properties of prepared composite were investigated with MXene-silicon composition ratio, and the surface of electrode after cycles was analyzed to evaluate stability of the electrode. The MXene/Si composites demonstrated high initial discharge capacities of 1962.9, 2395.2 and 2504.3 mAh/g as the silicon composition ratio increased to 2, 3 and 4 compared to MXene, respectively. MXene/Si-4, which is MXene and silicon ratio with 1 : 4, exhibited 1387.5 mAh/g of reversible capacity, 74.5% of capacity retention at 100 cycles and high capacity of 700.5 mAh/g at high rate of 4.0 C. As the results, the MXene/Si composite prepared by electrostatic-assenbly could be applied to anode materials for high-performance LIBs.

• Journal of the Korean Electrochemical Society
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• v.17 no.2
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• pp.111-118
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• 2014

The electrochemical properties using the cells assembled with the synthesized $LiCoO_2$(LCO) were evaluated in this study. The LCO was synthesized from high-purity cobalt sulfate($CoSO_4$) which is recovered from the cathode scrap in the wastes lithium ion secondary battery(LIB). The leaching process for dissolving the metallic elements from the LCO scrap was controlled by the quantities of the sulfuric acid and hydrogen peroxide. The metal precipitation to remove the impurities was controlled by the pH value using the caustic soda. And also, D2EHPA and $CYANEX^{(R)}272$ were used in the solvent extraction process in order to remove the impurities again. The high-purity $CoSO_4$ solution was recovered by the processes mentioned above. We made the 6 wt.% $CoSO_4$ solution mixed with distilled water. And the 6 wt.% $CoSO_4$ solution was mixed with oxalic acid by the stirring method and dried in oven. $LiCoO_2$ as a cathode material for LIB was formed by the calcination after the drying and synthesis with the $Li_2CO_3$ powder. We assembled the cells using the $LiCoO_2$ powders and evaluated the electrochemical properties. And then, we confirmed possibility of the recyclability about the cathode materials for LIBs.

• The Korean Journal of Pesticide Science
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• v.17 no.4
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• pp.335-342
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• 2013

Sophorae radix extract (SRE) has been registered as an environment-friendly organic material that is widely used in the cultivation of crops in Korea. Matrine, the active ingredient in SRE, was reported as a toxic substance in the nervous system in mice. However, no information is available on its toxic effects in other organisms. Therefore, antimutagenicity and two kinds of genotoxicity tests (bacterial reverse mutation and chromosome aberration test) of two samples of SRE were investigated in this study. Antimutagenicity test was experimented by using bacterial reverse mutation test. In the reverse mutation test, Salmonella Typhimurim TA98, TA1535 and TA1537 were used to evaluate the mutagenic potential of SRE. Bacterial reverse mutation test was also performed on positive and negative control groups in the presence of the metabolic activation system (with S-9 mix) and metabolic non-activation system (without S-9 mix). In the chromosome aberration test, Chinese hamster lung cells were exposed to SRE for 6 or 24 hours without S-9 mix, or for 6 hours with S-9 mix. Negative and positive control groups were experimented for chromosome aberration test. As a result, the number of mutated colonies induced by 4-NQO were reduced by SRE treatment in all strains, indicating that SRE may have antimutagenic effects. Reverse mutation was not shown at all concentrations of SRE, regardless of application of the metabolic activation system. In the chromosomal aberration test, one of the SRE sample gave a suspicious positive result at 250 ${\mu}g/ml$ in the presence of S-9 mix. For the more adequate evaluation of the genotoxic potential of SRE samples, other in vivo genotoxicity study is needed.

• Tuberculosis and Respiratory Diseases
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• v.62 no.5
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• pp.382-388
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• 2007

Background: The cognitive function is impaired in patients with hypoxemic chronic obstructive pulmonary disease (COPD). However, there are conflicting results regarding the cognitive function in patients with non-hypoxemic COPD. COPD patients also have sleep disorders. This study examined the cognitive function in non-hypoxemic COPD patients, and nocturnal sleep was assessed in COPD patients with a cognitive dysfunction. Methods: Twenty-eight COPD patients (mean age, 70.7 years) with an oxygen saturation > 90%, and 33 healthy control subjects (mean age, 69.5 years) who had visited for a routine check-up were selected. The neurocognitive tests were performed using the Korean version of the Consortium to Establish a Registry for Alzheimer's Disease (CERAD-K) Neuropsychological Battery. Results: The scores of the word list recall test (p=0.03) and the word list recognition test (p=0.006) in the COPD group were significantly lower than those in the control group. Nine patients showed a significantly impaired cognitive function. Seven of these underwent polysomnography, which revealed apnea-hypopnea indices ${\geq}$ five per hour in five patients. The median oxygen desaturation index and median limb movement index were 3.6/h and 38.6/h, respectively. Conclusion: These results suggest that the verbal memory function is impaired in non-hypoxemic COPD patients. Six out of seven COPD patients with an impaired cognitive function had sleep disorders of sleep apnea and/or periodic limb movements during sleep.