• Journal of the Korean Society for Heat Treatment
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• v.22 no.4
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• pp.217-222
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• 2009

The effects of severe plastic deformation by equal channel angular pressing (ECAP) and subsequent heat treatment on the low cycle fatigue behaviors of Al-Mg-Si alloy were investigated. The specimens which were peak aged at $175^{\circ}C$ after solution treatment showed cyclic hardening at all strain amplitudes, while the specimens ECAPed after solution treatment showed cyclic softening at all strain amplitudes during fatigue. The specimens aged at $100^{\circ}C$ after ECAP showed slight cyclic hardening. Various changes of cyclic fatigue behavior after severe plastic deformation and/or heat treatment were discussed in terms of the microstructural changes and precipitation conditions.

• Applied Chemistry for Engineering
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• v.27 no.4
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• pp.444-448
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• 2016

Hollow silicon/carbon (H-Si/C) composites as anode materials for lithium ion batteries were investigated to overcome the large volume expansion. H-Si/C composites were prepared as follows; hollow $SiO_2\;(H-SiO_2)$ was prepared by adding $NaBH_4$ to $SiO_2$ synthesized using $st{\ddot{o}}ber$ method followed by magnesiothermic reduction and carbonization of phenolic resin. The H-Si/C composites were analyzed by XRD, SEM, BET and EDX. To improve the capacity and cycle performance, the electrochemical characteristics of H-Si/C composites synthesized with various $NaBH_4$ contents were investigated by charge/discharge, cycle, cyclic voltammetry and impedance tests. The coin cell using H-Si/C composite ($SiO_2:NaBH_4=1:1$ in weight) in the electrolyte of $LiPF_6$ dissolved in organic solvents (EC : DMC : EMC = 1 : 1 : 1 vol%) has better capacity (1459 mAh/g) than those of other composition coin cells. It is found that the coin cell ($SiO_2:NaBH_4=1:1$ in weight) has an excellent capacity retention from 2nd cycle to 40th cycle.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.3
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• pp.1403-1410
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• 2014

Epigenetic regulators like histone deacetylases (1 and 2), and viral onco-proteins (E6/E7) are known to be overexpressed in cervical cancer cells. The present study was designed to investigate the effect of curcumin on HDACs (1 and 2) and HPV E6/E7 in the cervical cancer cell line SiHa and a drug resistant clone $SiHa^R$ (derived from SiHa). It was further intended to investigate whether curcumin could sensitize the cells towards cisplatin induced cell killing by modulation of multi drug resistant proteins like MRP1 and Pgp1. Curcumin inhibited HDACs, HPV expression and differentially increased acetylation and up-regulation of p53 in SiHa and $SiHa^R$, leading to cell cycle arrest at G1-S phase. Up-regulation of pRb, p21, p27 and corresponding inhibition of cyclin D1 and CDK4 were observed. Cisplatin resistance in $SiHa^R$ due to over-expression of MRP1 and Pgp1 was overcome by curcumin. Curcumin also sensitized both the cervical cancer cells towards cisplatin induced cell killing. Inhibition of HDACs and HPVs led to cell cycle arrest at G1/S phase by alteration of cell cycle regulatory proteins. Suppression of MRP1 and Pgp1 by curcumin resulted in sensitization of cervical cancer cells, lowering the chemotherapeutic dose of the drug cisplatin.

• Korean Chemical Engineering Research
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• v.59 no.1
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• pp.35-41
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• 2021

Silicon is a promising next-generation anode material for lithium-ion battery, and it has been studied for commercialization due to the high theoretical capacity. However, it has problems of the volume change during charge-discharge and the poor electrical conductivity. To solve these problems, formation of SiO2 and carbon coating on the surface of silicon crystal were performed to protect the side reaction and enhance the electrical conductivity of silicon. CNT and CNF were also added to mitigate the volume change and increase the conductivity. Physical properties of asprepared samples were analyzed by XRD, SEM, and EDS. Electrochemical characteristics were investigated by electrical conductivity measurement, EIS, CV and cycle performance test. (Si/SiO2/C)+CNT&CNF showed high electrical conductivity and low charge-transfer resistance, and the capacity was 1528 mAh/g at 1st cycle and 1055 mAh/g at 50th cycle with 83% capacity retention.

• Journal of the Korean institute of surface engineering
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• v.56 no.1
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• pp.62-68
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• 2023

Silicon (Si) is considered as a promising substitute for the conventional graphite due to its high theoretical specific capacity (3579 mAh/g, Li₁₅Si₄) and proper working voltage (~0.3V vs Li⁺/Li). However, the large volume change of Si during (de)lithiation brings about severe degradation of battery performances, rendering it difficult to be applied in the practical battery directly. As a one feasible candidate of industrial Si anode, silicon monoxide (SiO_x) demonstrates great electrochemical stability with its specialized strategy, downsized Si nanocrystallites surrounded by Li⁺ inactive buffer phase (Li₂O and Li₄SiO₄). Nevertheless, SiO_x inherently has the initial irreversible capacity and poor electrical conductivity. To overcome those issues, conformal carbon coating has been performed on SiO_x utilizing ethylbenzene as the carbon precursor of chemical vapor deposition (CVD). Through various characterizations, it is confirmed that the carbon is homogeneously coated on the surface of SiO_x. Accordingly, the carbon-coated SiOx from CVD using ethylbenzene demonstrates 73% of the first cycle efficiency and great cycle life (88.1% capacity retention at 50th cycle). This work provides a promising synthetic route of the uniform and scalable carbon coating on Si anode for high-energy density.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.2
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• pp.133-140
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• 2009

A fast-response $CO_2$ analyzer has been developed for measuring the $CO_2$ concentration during transient condition of a SI engine. The analyzer consists of the non-dispersive infrared absorption method, electrical chopping system and water cooling system. The analyzer has good repeatability, linearity and permissible drift characteristic. Besides, it showed 18ms of a response to measure the $CO_2$ concentration. The fast-response $CO_2$ analyzer was applied to a single cylinder SI engine and the $CO_2$ emission was examined during engine start. Simultaneously, the standard exhaust gas analyzer, which has slow response time, was used for confirming the accuracy of the exhaust gas analysis using the fast-response $CO_2$ analyzer. The developed analyzer showed much faster responsive characteristic than that of a standard analyzer and made cycle by cycle exhaust gas analysis possible. The transient engine operating characteristics will be estimated from the $CO_2$ concentration of engine-out emissions and engine operating variables.

• Journal of Environmental Impact Assessment
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• v.22 no.5
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• pp.397-408
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• 2013

The purpose of this study is to analyze water cycle area ratio and spatial evaluation of water cycle in urban area of Changwon-si, Gyeongsangnam-do. Water cycle area ratio are analyzed by using spatial data of land-cover and land-use, and Hot spot analysis of GIS program was used for spatial evaluation of water cycle. The results are as below. Firstly, the high water cycle area ratio areas were forests, parks, and rivers, but urban areas covered asphalt and concrete were low under 40%. Public institutions and co-residential of urban areas were higher than others because of high area ratio of pervious land-cover. Spatial evaluation of water cycle was analyzed to vulnerable areas there are dense residential and commercial area. These areas are really occurring frequently flooding and immersion, therefore, is required water management facilities and improvement of land-cover from impervious to pervious. In the future, it will require additionally analysis of water cycle area ratio supplemented data of water management facility and ground water.

• 한국기계연구소 소보
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• s.13
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• pp.53-63
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• 1984

• Journal of the Microelectronics and Packaging Society
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• v.21 no.1
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• pp.45-50
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• 2014

Effects of wet chemical treatment and thermal cycle conditions on the quantitative interfacial adhesion energy of $Cu/SiN_x$ thin film interfaces were evaluated by 4-point bending test method. The test samples were cleaned by chemical treatment after Cu chemical-mechanical polishing (CMP). The thermal cycle test between Cu and $SiN_x$ capping layer was experimented at the temperature, -45 to $175^{\circ}C$ for 250 cycles. The measured interfacial adhesion energy increased from 10.57 to $14.87J/m^2$ after surface chemical treatment. After 250 thermal cycles, the interfacial adhesion energy decreased to $5.64J/m^2$ and $7.34J/m^2$ for without chemical treatment and with chemical treatment, respectively. The delaminated interfaces were confirmed as $Cu/SiN_x$ interface by using the scanning electron microscope and energy dispersive spectroscopy. From X-ray photoelectron spectroscopy analysis results, the relative Cu oxide amounts between $SiN_x$ and Cu decreased by chemical treatment and increased after thermal cycle. The thermal stress due to the mismatch of thermal expansion coefficient during thermal cycle seemed to weaken the $Cu/SiN_x$ interface adhesion, which led to increased CuO amounts at Cu film surface.

• Journal of Powder Materials
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• v.16 no.6
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• pp.389-395
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• 2009

A Si-CuO-graphite composite was prepared by a mechanical alloying (MA) method. The Si-CuO composite has a mixture structure, where CuO is homogeneously dispersed in Si. Also, $Cu_2O$ and $Cu_3Si$ phases were formed during MA and heat treatment. Graphite with the Si-CuO composite was mixed in the same mill for 30 minutes with weight ratio of Si-CuO composite and graphite as 1:1. The Si-CuO composite was homogeneously covered with graphite. SiC phase was not formed. Electrochemical tests of the composite have been investigated, and the first charge and discharge capacities of the material were about 870mAh/g and 660mAh/g, respectively. Those values are about 76% of the first cycle efficiency. The cycle life of the composite showed that the initial discharge capacity of 660 mAh/g could be maintained up to 92% after 20 cycles.