• KIEE International Transactions on Electrophysics and Applications
• /
• v.4C no.1
• /
• pp.21-25
• /
• 2004

From the gradual increasing state of charge (GISOC) observations, electrochemical behavior of multi-walled carbon nanotube│(lM LiP $F_{6}$ , EC,DEC,DME 3:5:5 volume ratio)│lithium cells was evaluated using the galvanostatic charge-discharge process. A MWCNT delivers a specific charge capacity of 1,300 mAh/g in a Li cell when cycled up to an end voltage of 0 V (vs. Li/L $i^{＋}$ )at a constant current rate every 10 hours. However, in the present study, the specific discharge capacity obtained is 338 mAh/g, thus amounting to a coulombic efficiency of only 26％. Further, when the MWCNT│Li cells were tested using the GISOC method, two distinguishable linear-fit ranges were observed due to the intercalation/deintercalation of lithium, which were found to have II $E_1$, IIC $s_1$ and II $E_2$of 27.3％, 372 mAh/g, and 25.5％, respectively. Q $c_1$, could be calculated from the data of IIE and IICs of each range by the modified equation "II $C_{sum}$= $\Sigma$( $Q_{C}$- $Q_{D}$)=(II $E_{1}$$^{-1}$ ) $Q_{Dl}$ ＋(II $E_2$$^{-1}$ -1) ( $Q_{D2}$- $Q_{Dl}$ ) ＋ IIC $s_1$= $Q_{Cl}$ - $Q_{Dl}$ ". Results of the GISOC method could be converted to the results of galvanostatic charge-discharge process, irrespective of the state of charge of the cell or battery.ery.y.y.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.19 no.10
• /
• pp.726-734
• /
• 2007

In this study, lower flammability limits (LFLs) of three hydrocarbon refrigerants (R600a, R290, R1270) and two hydrofluorocarbon refrigerants (R152a, R32) and DME (RE170) are measured by the method proposed by ASTM E681-04 Standard. Flammability tests are carried out at three temperatures of $23^{\circ}C,\;60^{\circ}C\;and\;100^{\circ}C$ and relative humidity 50%. Test results show that the present data for isobutane and propane obtained at $23^{\circ}C$ are similar to those found in the literature, confirming indirectly the reliability of the present test method and facility. For propylene, R152a, and R32, LFLs found in the literature differ considerably. Especially, the deviation of LFL of propylene is more than 30% among the literature data. The present data for propylene, R152a, and R32 agree with either of the data sets available. As the temperature increases from $23^{\circ}C\;to\;100^{\circ}C$, LFLs of all refrigerants tested decrease. LFLs of most refrigerants tested in this study at $60^{\circ}C$ decrease by $0.1{\sim}0.3%$ as compared to those at $23^{\circ}C$. Also LFLs of most refrigerants tested in this study at $100^{\circ}C$ decrease by $0.1{\sim}0.3%$ as compared to those at $60^{\circ}C$.

• Journal of Hydrogen and New Energy
• /
• v.29 no.1
• /
• pp.1-10
• /
• 2018

The amount of biogas increases as the amount of organic waste increases. Recently, biogas from organic waste have been made much efforts to utilize as a energy. In particular, the concentration of $CH_4$ and $CO_2$ generated from sewage sludge and livestock manure treatment are 60-70% and 30-35%, and $CH_4$ and $CO_2$ generated from food wastes are 60-80% and 20-40%. In case of landfill gas, $CH_4$ and $CO_2$ have a concentration of 40-60% and 40-60% respectively. Therefore, in order to use the biogas more widely, it is necessary to convert the biogas to methanol, LNG or DME. In this study, experiments were conducted to produce hydrogen and carbon monoxide through various biogas reforming reactions on $Ni/Ce-ZrO_2/Al2O3$ catalysts. The experiment of synthetic gas synthesis was carried out on a wide concentrations of methane and carbon dioxide, which were the major constituents of biogas from various organic wastes. The effect of $(O_2+CO_2)/CH_4$ (=R') on the yields of hydrogen and carbon monoxide, the conversion rate of methane and carbon dioxide was investigated. Also simulation for syngas synthesis on the $CO_2$ reforming of $CH_4$ was computed by employing total Gibbs free energy minimization method using PRO/II simulator, and compared with the experimental results on wet and dry reforming reaction of biogas.

• Journal of the Korean Society for Precision Engineering
• /
• v.29 no.3
• /
• pp.346-353
• /
• 2012

The purpose of this study is to verify the energy efficiency of the integrated system combining human and a lower extremity exoskeleton robot when it is applied to the proposed gait pattern. Energy efficient gait pattern of the lower limb was proposed through leg function distribution during stance phase and the dynamic-manipulability ellipsoid (DME). To verify the feasibility and effect of the redefined gait trajectory, simulations and experiments were conducted under the conditions of walking on level ground and ascending and descending from a staircase. Experiments to calculate the metabolic cost of the human body with or without the assistance of the exoskeleton were conducted. The energy consumption of the lower extremity exoskeleton was assessed, with the aim of improving the efficiency of the integrated system.

• Asian-Australasian Journal of Animal Sciences
• /
• v.17 no.12
• /
• pp.1652-1656
• /
• 2004

The aim of this study was to obtain mature ova or embryos at a single cell stage, which can be used in avian transgenesis and nuclear transfer through multiple ovulations, in vitro fertilization and culture. Chicken anterior pituitary extract (CAPE) or acetone-dried chicken anterior pituitary extract (ACAPE) was used to induce multiple ovulations in hens pretreated with pregnant mare' serum gonadotrophin (PMSG). In vitro fertilization of the multiple ovulated ova was performed by inseminating sperm onto the germinal disks in m-Ringer' solution and incubating the ova at 41$^{\circ}C$, 5% $CO_2$ for 10 h in DME-F12 medium containing 20% liquid albumen. The in vitro fertilization process was observed using an environmental scanning electron microscope. When normal laying hens (white Leghorn) were administered daily with PMSG (100 IU), egg laying ceased in most hens within 3 to 8 days. Ovulation began to occur about 7.5 h after injection of CAPE and ACAPE. The number of ovulated ova was 1.00${\pm}$0.00, 2.33${\pm}$0.52 and 2.20${\pm}$0.45, respectively, after receiving 100, 200 and 300 mg CAPE. The number of ovulated ova was 2.00${\pm}$0.00, 2.86${\pm}$0.69 and 3.00${\pm}$1.22, respectively, after receiving 10, 15 and 20 mg ACAPE. The fertilized and cultured ova were able to develop into embryos up to the 32 cell stage. The present experiments demonstrated that multiple ovulations can be induced by CAPE and ACAPE successfully, and the ova resulted from the treatment retained the capability for further fertilization and embryonic development. These data provide new information to support the establishment of an in vitro culture system for future avian transgenesis studies.

• Membrane Journal
• /
• v.25 no.2
• /
• pp.99-106
• /
• 2015

Polysulfone (PSF) hollow fiber membrane was prepared to separate $CO_2$ from the flaring gas. Fabricated PSF membrane system was fulfilled under 1 stage, 2 stage membrane process and simulation in order to confirm the operating condition for 99% of $CH_4$ and 1% of $CO_2$ concentration. Also, $25Nm^3/h$ bench scale $CO_2$ separation membrane system was operated under 1% of $CO_2$ concentration during 100 hr, and $CH_4$ recovery ratio was 98%.

• Journal of Hydrogen and New Energy
• /
• v.22 no.6
• /
• pp.905-912
• /
• 2011

In this study, the novel concept catalytic reactor was designed for water-gas shift reaction (WGS) under high pressure. The novel concept catalytic reactor was composed of an autoclave, the catalyst, and liquid water. Cu-ZnO/$Al_2O_3$ as the low temperature shift catalyst was used for WGS reaction. WGS in the novel concept catalytic reactor was carried out at the ranges of 150~$250^{\circ}C$ and 30~50 atm. The liquid water was filled at the bottom of the autoclave catalytic reactor and the catalyst of pellet type was located at the gas-liquid water interface. It was concluded that WGS reaction occurred over the surface of catalysts partially wetted with liquid water. The conversion of CO for WGS was also controlled with changing content of Cu and ZnO used as the catalytic active components. Meanwhile, the catalyst of honey comb type coated with Cu-ZnO/$Al_2O_3$ was used in order to increase the contact area between wet-surface of catalyst and the reactants of gas phase. It was confirmed from these experiments that $H_2$/CO ratio of the simulated coal gas increased from 0.5 to 0.8 by WGS at gas-liquid water interface over the wet surface of honey comb type catalyst at $250^{\circ}C$ and 50 atm.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.19 no.5
• /
• pp.403-410
• /
• 2007

In this study, natural refrigerants and their mixtures that can supplement and replace R12 and R134a in automobile air-conditioners are studied. R134a is currently used as the refrigerant in new motor vehicle air conditioners, replacing the ozone depleting refrigerant R12. Although R134a has no ozone depletion potential, it has a relatively large global warming potential, approximately 1300 times that of $CO_2$ over a 100 year time horizon. For this reason, performance of natural refrigerants and their mixtures containing R152a, RE170 (Dimethylether, DME) and R600a (Isobutane) are measured under 2 different temperature conditions. They were tested in a refrigerating bench tester with an open type compressor. The test bench provided about 4 kW capacity and water and water/glycol mixture were employed as the secondary heat transfer fluids. Test results show that the coefficient of performance (COP) of these refrigerants is up to 21.55% higher than that of R12 in all temperature conditions. Overall, these fluids provide good performance with reasonable energy savings without any environmental problem and thus can be used as long term alternatives for automobile air-conditioners.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.18 no.4
• /
• pp.312-319
• /
• 2006

In this study, performance of 2 pure hydrocarbons and 7 mixtures was measured in an attempt to substitute HCFC22 used in air-conditioners and heat pumps. The mixtures were composed of R1270 (propylene), R290 (propane), HFC152a, and RE170 (Dimethyl ether, DME). The pure and mixed refrigerants tested have GWPs of $3{\sim}58$ as compared to that of $CO_2$ and the mixtures are all near-azeotropic showing the gliding temperature difference (GTD) of less than $0.6^{\circ}C$. Thermodynamic cycle analysis was carried out to determine the optimum compositions and actual tests were performed in a laboratory heat pump test bench at the evaporation and condensation temperatures of 7.5 and $45.1^{\circ}C$ respectively. Test results show that the coefficient of performance (COP) of these mixtures is up to 5.7% higher than that of HCFC22. While propane showed 11.5% reduction in capacity, most of the fluids tested had the similar capacity to that of HCFC22. Compressor discharge temperatures were reduced by $11{\sim}17^{\circ}C$ with these fluids. There was no problem with mineral oil since the mixtures were mainly composed of hydrocarbons. The amount of charge was reduced up to 55% as compared to HCFC22. Overall, these fluids provide good performance with reasonable energy savings without any environmental problem and thus can be used as long term alternatives for. residential air-conditioning and heat pumping application.

• Advances in concrete construction
• /
• v.13 no.2
• /
• pp.123-132
• /
• 2022

This paper aims to adapt Multilinear regression (MLR) to predict the strength and toughness of SIFCON containing various pozzolanic materials. Slurry Infiltrated Fibrous Concrete (SIFCON) is one of the most common terms used in concrete manufacturing, known for its benefits such as high ductility, toughness and high ultimate strength. Assessment of compressive strength (CS.), flexural strength (F.S.), splitting tensile strength (STS), dynamic elasticity modulus (DME) and impact energy (I.E.) using the experimental approach is too costly. It is time-consuming, and a slight error can lead to a repeat of the test and, to solve this, alternative methods are used to predict the strength and toughness properties of SIFCON. In the present study, the experimentally investigated SIFCON data about various mix proportions are used to predict the strength and toughness properties using regression analysis-multilinear regression (MLR) models. The input parameters used in regression models are cement, fibre, fly ash, Metakaolin, fine aggregate, blast furnace slag, bottom ash, water-cement ratio, and the strength and toughness properties of SIFCON at 28 days is the output parameter. The models are developed and validated using data obtained from the experimental investigation. The investigations were done on 36 SIFCON mixes, and specimens were cast and tested after 28 days of curing. The MLR model yields correlation between predicted and actual values of the compressive strength (C.S.), flexural strength, splitting tensile strength, dynamic modulus of elasticity and impact energy. R-squared values for the relationship between observed and predicted compressive strength are 0.9548, flexural strength 0.9058, split tensile strength 0.9047, dynamic modulus of elasticity 0.8611 for impact energy 0.8366. This examination shows that the MLR model can predict the strength and toughness properties of SIFCON.