• The Journal of Korean Academy of Prosthodontics
• /
• v.45 no.6
• /
• pp.735-742
• /
• 2007

Statement of problem. Although a number of previous investigations have been carried out on the polymerization shrinkage-strain kinetics of provisional crown and fixed partial denture (FPD) materials, the effect of the changes of liquid monomer to powder ratio on its polymerization shrinkage-strain kinetics has not been reported. Purpose. The purpose of this study was to investigate the influence of liquid monomer to powder ratio of polymer-based provisional crown and FPD materials on the polymerization shrinkage-strain kinetics. Material and methods. Chemically activated acrylic provisional materials (Alike, Jet, Snap) were investigated. Each material was mixed with different liquid monomer to powder ratios by volume (1.0:3.0, 1.0:2.5, 1.0:2.0, 1.0:1.5, 1.0:1.0). Time dependent polymerization shrinkage- strain kinetics of all materials was measured by the bonded-disk method as a function of time at $23^{\circ}C$. Five recordings were taken for each ratio. The results were statistically analyzed using one-way ANOVA and the multiple comparison Scheffe test at the significance level of 0.05. Trends were also examined by linear regression. Results. At 5 minutes after mixing, the polymerization shrinkage-strains of all materials ranged from only 0.01% to 0.49%. At 10 minutes, the shrinkage-strain of Alike was the highest, 3.45% (liquid monomer to powder ratio=1.0:3.0). Jet and Snap were 2.69% (1.0:2.0) and 1.58% (1.0:3.0), respectively (P>0.05). Most shrinkage (94.3%-96.5%) occurred at 30 minutes after mixing for liquid monomer to powder ratio, ranging from 1.0:3.0 to 1.0:1.0. The highest polymerization shrinkage-strain values were observed for the liquid monomer to powder ratio of 1.0:3.0. At 120 minutes after mixing, the shrinkage-strain values were 4.67%, 4.18%, and 3.07% for Jet, Alike, and Snap, respectively. As the liquid monomer to powder ratio increased, the shrinkage-strain values tend to be decreased linearly (r=-0.769 for Alike, -0.717 for Jet, -0.435 for Snap, $r^2=0.592$ for Alike, 0.515 for Jet, 0.189 for Snap; P<0.05). Conclusion. The increase of the liquid monomer to powder ratio from 1.0:3.0 to 1.0:1.0 had a significant effect on the shrinkage-strain kinetics of polymer-based crown and FPD materials investigated. This increased the working time and decreased the shrinkage-strain during polymerization.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.30 no.4
• /
• pp.59-66
• /
• 2022

Lithium-ion batteries have greatly expanded along with the mobile phone market, and as the electric vehicle business is activated in earnest, they will attract many people's attention even afterwards. Until now, many people have attracted attention to the recovery of valuable metals inside lithium-ion batteries, but graphite, which is mainly used as an anode material, is also worth recycling. Therefore, in order to recover graphite with high purity and valuable metals, graphite that can be used as an anode material of a secondary battery may be generated again through a regeneration process of purifying and separating graphite from a waste lithium-ion battery and recovering electrical characteristics of graphite. This paper describes the process of converting waste graphite into regenerated graphite and the environmental and economic effects of regenerated graphite.

• New Physics: Sae Mulli
• /
• v.68 no.12
• /
• pp.1315-1323
• /
• 2018

We studied the carbonization due to the annealing condition of waste coffee powder for application as an active anode material for lithium-ion batteries (LIBs). The coffee powder used as an active anode material for LIBs was obtained from coffee beans, not from a coffee shells. The waste coffee powder was dried in air and heat-treated in an $Ar/H_2$ atmosphere to obtain a pore-forming activated carbon powder. The specific capacity of the sample annealed at $700^{\circ}C$ was still 303 mAh/g after 1000 cycles at a current density of 1000 mA/g and with a coulombic efficiency of over 99.5%. The number of pores and the pore size of the waste coffee powder were increased due to chemical treatment with KOH, which had the some effect as an increased specific surface area. The waste coffee powder is considered to be a very promising active anode material because of both its excellent electrochemical properties due to enhanced carrier conduction and its being a cost effective resource for use in LIBs.

• The Journal of the Korea Contents Association
• /
• v.22 no.3
• /
• pp.322-330
• /
• 2022

With the development of media, modern times are actively exchanging cultures and information around the world. Therefore, product development using traditional material, which are Korean cultural heritages, can be said to be another medium that can promote our unique culture to the world. Therefore, this study attempted to develop a product suitable for the modern lifestyle that combines tradition and modernity by investigating and analyzing Korean roof tiles and applying the formative elements identified as a result of the study. Among the types of roof tiles, a Sumaksai, which is located on the front of the roof and stands out for decoration, was selected as the subject of the study, and it was developed by combining it with lighting and plates as an item for modern people seeking a life full of personality. In product development, we tried to express the traditional style as it is by making the most of the elements of the Sumaksai, and the lotus pattern, which was most commonly used in each era when roof tiles were made, was simplified and applied to the product. As the products developed in this way are used in our daily lives, we hope that users' interest in ours will increase, and that the development of various products through research on traditional material can be activated as a way to spread our culture around the world.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.44 no.8
• /
• pp.1128-1136
• /
• 2015

This study investigated the anti-inflammatory effects of ethanol extract from Grateloupia elliptica Holmes (GEHEE) on the lipopolysaccharide-induced inflammatory response. Anti-inflammatory effects were detected by enzyme-linked immunosorbent assay, Western blotting, and immunohistochemistry. There were no cytotoxic effects on proliferation of macrophages treated with GEHEE compared to the control. GEHEE remarkably suppressed NO and pro-inflammatory cytokines (interleukin-6, tumor necrosis $factor-{\alpha}$, and $interleukin-1{\beta}$) production and reduced expression of inducible nitric oxide synthase, cyclooxygenase-2, and nuclear $factor-{\kappa}B$ ($NF-{\kappa}B$) proteins in a dose-dependent manner. GEHEE also significantly reduced activation of mitogen-activated protein kinases (MAPKs). The formation of edema in mouse ears was reduced at the highest dose compared to the control. GEHEE also reduced dermal thickness and mast cell numbers based on histological analysis. These results suggest that GEHEE exerts significant anti-inflammatory activity via inhibition of $NF-{\kappa}B$ and MAPKs activation and may be a potential anti-inflammatory therapeutic material.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.45 no.2
• /
• pp.194-201
• /
• 2016

The anti-inflammatory activity of ethanol extract from Chondrus nipponicus Yendo (CNYEE) was investigated by measuring production of a lipopolysaccharide-induced inflammatory response mediator. CNYEE had no cytotoxic effects on proliferation of macrophages compared to the control. CNYEE significantly inhibited (over 50%) NO production at $50{\mu}g/mL$, with inhibitory effects on expression levels of cytokines such as interleukin (IL)-6, tumor necrosis factor-${\alpha}$ (TNF-${\alpha}$), and IL-$1{\beta}$. In particular, IL-6 inhibitory activity of CNYEE was higher than 70% at $100{\mu}g/mL$. CNYEE also reduced protein expression of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), and nuclear factor (NF)-${\kappa}B$ in a dose-dependent manner. CNYEE also significantly reduced phosphorylation of p38, extracellular signal-regulated kinase, and c-Jun N-terminal kinase. Therefore, these results suggest that CNYEE may have anti-inflammatory effects by modulating the NF-${\kappa}B$ and mitogen-activated protein kinases signaling pathways and may be used as an anti-inflammatory therapeutic material.

• Journal of the Korea Concrete Institute
• /
• v.26 no.2
• /
• pp.117-124
• /
• 2014

Globally, there are environmental problems due to greenhouse gas emissions. $CO_2$ emissions rate of the cement industry is very high, but the continued demand of cement is needed in the future. In this study, in order to reduce the environmental impact of $CO_2$ emissions from cement production. The experiments were carried out for the development of non-sintered cement (have not undergone firing burning) by granulated ground blast furnace slag. In order to compare the characteristics by curing, an experiment was conducted by changing the curing conditions such as atmospheric steam curing, observe the mechanical properties for the measurement of flexural compressive strength by mortar, observe the chemical properties such as acid resistance, $Cl^-$ penetrate resistance and analyzed the mechanism of hydration by XRD, SEM experiments. From the experimental results, as compared with portland cement usually confirm the mechanical and chemical properties excellent, it is expected be possible to apply to the undersea, underwater and underground structures that require superior durability. In addition, based on the excellent compressive strength by steam curing, it is expected to be possible to utilize as a cement replacement material in the secondary product of concrete. In the future, to solve the problem through continued research, it will be expected to reduce the effect of environmental load and to be excellent economics.

• Journal of the Korean Chemical Society
• /
• v.54 no.3
• /
• pp.323-328
• /
• 2010

In this work, an intention to synthesize the carbon molecular sieve (CMS) with ideal sieving properties from palm shell has been attempted. The process includes three main stages: carbonization, carbon dioxide activation and polymer deposition using polyfurfuryl alcohols. Palm shell based activated carbon (AC) produced by carbon dioxide activation was used as raw material in synthesis of CMS. After preparing palm shell based AC, optimum concentration ratio of furfuryl alcohols and formaldehyde to AC for CMS synthesis was obtained in this study. Deposition of polyfurfuryl alcohols on the palm shell based AC was then carried out prior to carbonization. These polymer deposited AC was subjected to carbonization at $700-900^{\circ}C$ under inert condition. All the microporous materials were analyzed using micromeritics ASAP/2020. The results show that optimum concentration ratio of furfuryl alcohol and formaldehyde to AC is 1:2.5. The micropore with pore width less than 7 ${\AA}$ was formed on the polymer deposited AC at $700^{\circ}C$, $800^{\circ}C$ and $900^{\circ}C$ for 1.5 hours. Carbonization temperature at $900^{\circ}C$ for 1.5 hours was found to be optimum for CMS synthesis. The CMS produced under this condition has pore width of 5.884 ${\AA}$.

• Journal of the Korea Concrete Institute
• /
• v.18 no.4 s.94
• /
• pp.449-458
• /
• 2006

The discharge of fly ash that is produced by coal-fired electric power plants is rapidly increasing in Korea. The utilization of fly ash in the raw materials would contribute to the elimination of an environmental problem and to the development of new high-performance materials. So it is needed to study the binder obtained by chemically activation of pozzolanic materials by means of a substitute for the cement. Fly ash consists of a glass phase. As it is produced from high temperature, it is a chemically stable material. Fly ash mostly consists of $SiO_2\;and\;Al_2O_3$, and it assumes the form of an oxide in the inside of fly ash. Because this reaction has not broken out by itself, it is need to supply it with additional $OH^-$ through alkali activators. Alkali activators were used for supplying it with additional $OH^-$. This paper concentrated on the strength development according to the kind of chemical activators, the curing temperature, the heat curing time. Also, according to scanning electron microscopy and X-Ray diffraction, the main reaction product in the alkali activated fly ash mortar is Zeolite of $Na_6-(AlO_2)_6-(SiO_2)_{10}-12H_2O$ type.

• Journal of Korean Society of Environmental Engineers
• /
• v.30 no.12
• /
• pp.1218-1224
• /
• 2008

A liquid culture of yeast "Candida tropicalis" was used in a fluidized bioreactor to achieve high removal efficiencies of volatile organic compounds (VOCs). In this study, granular activated carbon (GAC) was used as a fluidized material to improve adsorptive capacity as well as mass transfer of gaseous toluene, the model VOC. The GAC fluidized bioreactor demonstrated toluene removal efficiencies ranging from 50 to 80%, when inlet toluene loading varied in a range between 13.1 and 37.4 g/m$^3$-hr. The maximum elimination capacity determined in the GAC fluidized bioreactor was 172 g/m$^3$-hr at a toluene loading of 291 g/m$^3$-hr. Transient loading experiments revealed that the removal efficiency was remained unchanged during an increased loading period, and toluene introduced to the bioreactor was first absorbed to GAC and then slowly desorbed and became available to the yeast culture. Hence the fluidized GAC helped to achieve an improved mass transfer between the gas and liquid phases, resulting in high toluene removal capacity. Consequently, the GAC fluidized bioreactor using C. tropicalis can be successfully applied for the removal of VOCs, and is a feasible alternative over conventional processes such as packed-bed biofilters.