• Korean Chemical Engineering Research
• /
• v.60 no.1
• /
• pp.7-11
• /
• 2022

In the membrane forming process of a proton exchange membrane fuel cell (PEMFC), drying and annealing heat treatment processes are required for performance and durability. In this study, the optimal annealing temperature for improving the durability of the polymer membrane was studied. It was annealed in the temperature range of 125~175 ℃, and thermal stability and hydrogen permeability were measured as basic data of durability at each annealing temperature. The electrochemical durability was analyzed by Fenton reaction and open circuit voltage (OCV) holding. The annealing temperature of 165 ℃ was the optimal temperature in terms of thermal stability and hydrogen permeability. In the Fenton reaction, the fluorine emission rate of the membrane annealed at 165 ℃ was the lowest, and the lifespan of the membrane annealed at 165 ℃ was the longest in the OCV holding experiment, confirming that 165 ℃ was the optimal temperature for the durability of the polymer membrane.

• Composites Research
• /
• v.21 no.1
• /
• pp.1-7
• /
• 2008

Composite vessels for high pressure gas storage are commonly used these days because of their competitive weight reduction ability maintaining strong mechanical properties. To supplement permeability of composite under high pressure, it is usually lined by metal, which is called a Type 3 vessel. However, it has many difficulties to design the Type 3 vessel because of its complex geometry, fabrication process variables, etc. In this study, therefore, GUI (graphic user interface) optimal design code for Type 3 vessels was developed based on semi-geodesic algorithm in which various factors of geometry and fabrication variables are considered and genetic algorithm for optimization. In addition, hydrogen vessels for 350/700 bar that can be applied to FCVs(fuel cell vehicles) were designed using this code for verification.

• Restorative Dentistry and Endodontics
• /
• v.21 no.1
• /
• pp.19-34
• /
• 1996

It has been demonstrated that intracoronal bleaching of pulpless teeth may result in cervical root resorption. Several authors postulated that bleaching agents such as hydrogen peroxide penetrated through the dentinal tubules to damage the surrounding tissues that cause cervical root resorption. The purpose of this study was to suggest on in vitro model for direct determination of hydrogen peroxide penetration through CEJ during nonvital bleaching. In addition, this model permit the quantification of the amount of hydrogen peroxide penetrated during the procedure. Freshly extracted intact premolars, removed for orthodontic reasons were used. Root canal treatment was performed in each tooth. And then the outer surface and crown portion of the teeth was sealed with wax leaving the CEJ. The prepared teeth mounted on the wax laminates were placed in plastic assay tubes containing 1.5ml bidistilled water with their entire root, including the CEJ, submerged in the solution. The teeth were dividied into four groups. Thermo group : thermocatalytic bleaching with superoxol Walk group: walking bleaching with sodium perborate & superoxol Combi group : combination of thermocatalytic & walking bleaching Dw group : walking bleaching with sodium perborate & water The bleaching procedure was performed three times. The bleaching intervals were at 3 days. The hydrogen peroxide present in the assay system was added to ferrous ammonium sulfate resulting in ferric ion release. Upon the addition of potassium thiocyanate a ferrithiocyanate complex results, which absorbs light at the wavelength of 467nm. The radicular penetration of hydrogen peroxide in the four groups was assessed directly using spectrophotometer. The amount of hydrogen peroxide in the samples tested is determined by comparing them with a standard curve generated by known amounts of hydrogen peroxide. The results were obtained as follows : 1. In all experimental groups except the Dw group showed lower penetration amount in day 4 than day 1, there was statistical importance in the difference (P<0.05). 2. After 3rd treatment, Thermo group showed slightly increased value and narrow distribution. Walk group showed much more penetration amount and widely dispersed value. Value of Combi group showed wide distribution without regard to treatment time, but value of Dw group evenly distributed. 3. Thermo group, Walk group and Dw group showed a tendency of increasing penetration amount with increasing treatment times(P<0.01), but Combi group revealed no statistically important differences. 4. Combi group showed the highest degree of penetration. Walk group showed lower penetration than Combi group. Thermo group & Dw group showed lower than Walk group. 5. Cervical root permeability to hydrogen peroxide varied from 0 to 35 %.

• Transactions of the Korean hydrogen and new energy society
• /
• v.22 no.2
• /
• pp.161-167
• /
• 2011

Proton conductors have attracted considerable attention for solid oxide fuel cell (SOFC), hydrogen pump, gas sensor, and membrane separators. Doped $SrCeO_3$ exhibits appreciable proton conductivity in hydrogen-containing atmosphere at high temperature. However commercial realization has been hampered due to the reactivity of $SrCeO_3$ with $CO_2$. The chemical stability and proton conductivity are dependent on dopant type. The purpose of this work is to investigate chemical stability of $SrCe_{0.95}Gd_{0.05}O_{3-\alpha}-Ce_{0.9}Gd_{0.1}O_{2-\beta}$ composites in $CO_2$ and $H_2$ gases. Thermogravimetric analysis (TGA) was performed in gaseous $CO_2$ and electrical conductivity of the composites were also measured between 500 and $900^{\circ}C$ in air and $H_2$ atmosphere. $SrCe_{0.95}Gd_{0.05}O_{3-\alpha}-Ce_{0.9}Gd_{0.1}O_{2-\beta}$ composite membranes showed good chemical stability of in $CO_2$ atmosphere and high conductivity at hydrogen condition. The hydrogen permeation of $SrCe_{0.95}Gd_{0.05}O_{3-\alpha}-Ce_{0.9}Gd_{0.1}O_{2-\beta}$ composite membranes was investigated as a function of volumetric content of $SrCe_{0.95}Gd_{0.05}O_{3-\alpha}$. The $SrCe_{0.95}Gd_{0.05}O_{3-\alpha}-Ce_{0.9}Gd_{0.1}O_{2-\beta}$(6:4) membrane with a thickness of 1.0 mm showed the highest hydrogen permeability with the flux reaching of 0.12 $ml/min{\cdot}cm^2$ at $800^{\circ}C$ in 100%$H_2/N_2$ as feed gas.

• Journal of the Korean Solar Energy Society
• /
• v.30 no.1
• /
• pp.34-41
• /
• 2010

Gas hydrates are solid solutions when water molecules are linked through hydrogen bonding and create host lattice cavities that can enclose many kinds of guest(gas) molecules. There are plenty of methane(gas) hydrate in the earth and distributed widely at offshore and permafrost. Several schemes, to produce methane hydrates, have been studied. In this study, depressurization method has been utilized for the numerical model due to it's simplicity and effectiveness. IMPES method has been used for numerical analysis to get the saturation and velocity profile of each phase and pressure profile, velocity of dissociation front progress and the quantity of produced gas. The values calculated for the sample length of 10m, show that methane hydrates has been dissolved completely in approximately 223 minutes and the velocity of dissociation front progress is 3.95㎝ per minute. The volume ratio of the produced gas in the porous media is found to be about 50%. Analysing the saturation profile and the velocity profile from the numerical results, the permeability of each phase in porous media is considered to be the most important factor in the two phase flow propagation. Consequently, permeability strongly influences the productivity of gas in porous media for methane hydrates.

• Membrane Journal
• /
• v.12 no.1
• /
• pp.51-53
• /
• 2002

The hydrogen ions in poly (vinyl alcohol) (PVA)/sulfosuccinic acid (SSA) membranes substiuted with $Li^+, Na^+, and K^+/ $of monvoalent metal ions, $Mg^{2+}, Ca^{2+} and Ba^{2+}$ of divalent metal ions, and $Al^{3+}$ of trivalent metal ion. In addition, $Li^+ ions were exchanged with varing reaction time. The effects of metal ions exchanged were investigated in terms of methanol permeability -uling diffusion cell. The methanol permeabilies decreased in the sequence of $Na^+, Li^+ and K^+$ and this might be due to the 'Salting-out' effect while the methanol permeabilities for divalent and trivalent ion-substituted membranes were affected by the combined effects of salting-out, eletrostatic crosslinking and extent of metal ion substiution. As for $Li^+$ ions, methanol permeabilities of PVA/SSA membranes decreased in proportion to the degrees of subsituted $Li^+$ ions.

• Membrane Journal
• /
• v.34 no.2
• /
• pp.146-153
• /
• 2024

In this experiment, a Ti-based flat hydrogen separation membrane was designed and manufactured. In order to find a Ti-based hydrogen separation membrane of a new composition, the correlation between the physical-chemical properties and hydrogen permeability of various alloys was investigated. Based on this, two types of new alloy films (Ti_14.2Zr_66.4Ni_12.6Cu_6.8 (70 ㎛), Ti_17.3Zr_62.7Ni₂₀ (80 ㎛)) was designed and manufactured. The manufactured flat hydrogen separation membrane was tested for hydrogen permeation using mixed gas (H₂, N₂) and sweep gas (Ar) at 300~500℃ and 1~4 bar. The Ti_14.2Zr_66.4Ni_12.6Cu_6.8 alloy film has a maximum flux of 16.35 mL/cm² min at 500℃ and 4 bar, and the Ti_17.3Zr_62.7Ni₂₀ alloy film has a maximum flux of 10.28 mL/cm² min at 450℃ and 4 bar.

• The Journal of Pediatrics of Korean Medicine
• /
• v.12 no.1
• /
• pp.183-210
• /
• 1998

Cheonggisan(CGS) is well known for its effect on such allergic disease as urticaria and atopic dermatitis. Gagamcheonggisan(GCGS) was formulated by subtracting several herbs from CGS and adding several herbs to CGS. Even though it is being used frequently in the clinicai medicine for the treatment of above hypersensitivity diseases, basic study to make sure the mechanism of its action is rare. In this study the author tried to know the effect of CGS and GCGS on the vascular permeability, contact dermatitis, granular secretion from mast cells and function of macrophages. The results obtained in this study are as follows : 1. Administration of CGS and GCGS decreased the vascular permeability induced by serotonin and histamine. The decrease by serotonin is more typical and dose-dependent. 2. Administration of CGS and GCGS inhibited foot-pad and ear swelling responses induced by sheep red blood cells and picryl chloride respectively, the inhibition of foot-pad swelling responses is bigger than that of ear swelling responses and both of them are not dependent on the dose3. Treatment of peritoneal mast cells with CGS and GCGS water extract decreased the histamine release triggered by compound 48／80 in a dose dependent fashion 4. Administration of CGS and GCGS increased the phagocvtic activity of peritoneal macrophages and treatment of peritoneal macrophages with CGS activated phagocytic function in a dose dependent fashion. 5. Administration of CGS and GCGS enhanced such reactive oxygen intermediates(ROIs) as superoxide and hydrogen peroxide production from peritoneal macrophages. 6. Treatment of CGS and GCGS activated peritoneal macrophages for the production of ROIs. The above results show that CGS and GCGS decreased the hypersensitivity reactions by inhibiting non-specific inflammatory mediator release and vascular permeability without affecting general immune responsiveness.

• Membrane Journal
• /
• v.25 no.2
• /
• pp.107-114
• /
• 2015

PTMSP-NaA zeolite composite membranes were prepared by adding 0~50 wt% NaA zeolite to PTMSP. The membranes were characterized by FT-IR, $^1H$-NMR, GPC, DSC, TGA, SEM. The permeabilities of $H_2$ and $N_2$ gases through PTMSP-NaA zeolite composite membranes was studied as a function of NaA zeolite contents. According to TGA measurements, when zeolite was inserted into the polymer, weight loss temperature and weight loss wt% of PTMSP-NaA zeolite composite membranes were decreased. Based on SEM observation, NaA zeolite was dispersed in the PTMSP-NaA zeolite composite membrane with the size $2{\sim}5{\mu}m$. The permeability of PTMSP-NaA zeolite composite membranes increased added as NaA zeolite content increased. On the contrary, the selectivity ($H_2/N_2$) of the composite membranes decreased as NaA zeolite content increased. PTMSP-NaA zeolite composite membrane showed better permeability and selectivity ($H_2/N_2$) of $H_2$ and $N_2$ than PTMSP-NaY zeolite composite membrane.

• Journal of Microbiology and Biotechnology
• /
• v.32 no.12
• /
• pp.1583-1588
• /
• 2022

In this study, we investigated the effect of lactic acid bacteria (LAB) strains used as starters for kimchi fermentation, namely Lactococcus lactis WiKim0124, Companilactobacillus allii WiKim39, Leuconostoc mesenteroides WiKim0121Leuconostoc mesenteroides WiKim33, and Leuconostoc mesenteroides WiKim32, on the intestinal epithelial tight junctions (TJs). These LAB strains were not cytotoxic to Caco-2 cells at 500 ㎍/ml concentration. In addition, hydrogen peroxide (H₂O₂) decreased Caco-2 viability, but the LAB strains protected the cells against H₂O₂-induced cytotoxicity. We also found that lipopolysaccharide (LPS) promoted Caco-2 proliferation; however, no specific changes were observed upon treatment with LAB strains and LPS. Our evaluation of the permeability in the Caco-2 monolayer model confirmed its increase by both LPS and H₂O₂. The LAB strains inhibited the increase in permeability by protecting TJs, which we evaluated by measuring TJ proteins such as zonula occludens-1 and occludin, and analyzing them by western blotting and immunofluorescence staining. Our findings show that LAB strains used for kimchi fermentation can suppress the increase in intestinal permeability due to LPS and H₂O₂ by protecting TJs. Therefore, these results suggest the possibility of enhancing the functionality of kimchi through its fermentation using functional LAB strains.