• Resources Recycling
• /
• v.28 no.1
• /
• pp.40-46
• /
• 2019

The solvent extraction of Tb(III) from hydrochloric acid solution was investigated by employing single organophosphorus (D2EHPA, PC88A and Cyanex 272), its mixture with Alamine 336 and ionic liquids with Aliquat 336. The equilibrium pH after the extraction with extractant mixtures and ionic liquids was higher than that by single extractants. Among the mixtures and ionic liquids, only the ionic liquid with Cyanex 272 and Aliquat 336 showed synergism to the extraction of Tb(III). The extraction percentage of Tb(III) by the extractant mixtures was lower than that by single extractant and the extraction order was in the following order : D2EHPA + Alamine 336 > PC88A + Alamine 336 > Cyanex 272 + Alamine 336. The extraction order of Tb(III) by the ionic liquids was Cyanex 272 + Aliqaut 336 > PC88A + Aliquat 336 > D2EHPA + Aliquat 336.

• Journal of the Society of Disaster Information
• /
• v.16 no.4
• /
• pp.832-841
• /
• 2020

Purpose: This study attempts at analyzing mechanical response of functionally graded material (FGM) plates in bending. An accurate and effective numerical approach based on isogeometric analysis (IGA) combined with higher-order shear deformation plate theory to predict the nonlinear flexural behavior is developed. Method: A higher-order shear deformation theory(HSDT) which accounts for the geometric nonlinearity in the von Karman sense is presented and used to derive the equilibrium and governing equations for FGM plate in bending. The nonlinear equations are solved by the modified Newton-Raphson iterative technique. Result: The volume fraction, plate length-to-thickness ratio and boundary condition have signifiant effects on the nonlinear flexural behavior of FGM plates. Conclusion: The proposed IGA method can be used as an accurate and effective numerical tool for analyzing the mechanical responses of FGM plates in flexure.

• Applied Chemistry for Engineering
• /
• v.22 no.6
• /
• pp.697-702
• /
• 2011

Ion exchange resins have been synthesized from chloromethylated styrene-1,4-divinylbenzene (DVB) with 1%, 2%, 5% and 15%-crosslinkage and macrocyclic ligand of $OenNdien-H_4$ by copolymerization. The adsorption characteristics of uranium (${UO_2}^{2+}$), potassium ($K^+$) and neodymium ($Nd^{3+}$) metallic ions have been investigated. The synthesis of these resins was confirmed by content of chlorine, element analysis, and IR-spectrum. The effects of pH, time, and crosslinkage on adsorption of metallic ions were also studied. The uranium ion showed the fast adsorption on the resins above pH 3. The optimum equilibrium time for the adsorption of metallic ions was about two hours. The adsorption selectivity determined in methanol solution was in increasing order uranium (${UO_2}^{2+}$) > potassium ($K^+$) > neodymium ($Nd^{3+}$) ion. Moreover, the adsorption was increased with the crosslinkage concentration in order of 1%, 2%, 5% and 15%-crosslinkage resin.

• Journal of the Korean Electrochemical Society
• /
• v.24 no.1
• /
• pp.7-12
• /
• 2021

In this study, we investigated the formation of the metal oxide nanostructure by anodization of aluminum 3104H18 alloy. The anodization was performed in pyrophosphoric acid (H4P2O7) electrolyte. By the control of anodization condition such as concentration of electrolyte, anodization temperature and applied voltage, nanoporous or nanofiber structures were obtained. The optimal anodization condition to form nanofiber structures are 75 wt% of H4P2O7 at 30 V and 20℃. When anodization was performed at over 40 V, nanoporous structures were formed due to accelerated dissolution reaction rate of nanofiber structures or increasing thickness of channel wall.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.20 no.1
• /
• pp.30-36
• /
• 1984

It is well known that the application of linear elastic fracture mechanics is inadequate to solve the large deformation fracture failures which occurr in ductile manner because of the large scale yielding due to the severe stress concentration in the region adjacent to the crack tip. The authors have been evolved a fracture model, the crack plane equilibrium model, for this kinds of elastic-plastic fracture problems in the previous report. In this report, the crack plane equilibrium model was compared with the Irwin's plastic zone corrected linear elastic fracture mechanics through theoretical comparisons and experimental results to examine the validity of the crack plane equilibrium model as an available tool for nonlinear fracture analysis. Through this study, the main results were reached as follows; Irwin's plastic zone corrected linear elastic fracture mechanics could be applicable only for small scale yielding problems as expected while the crack plane equilibrium model valid as a fracture model for large deformation fracture failure. However, the followings should be considered for the more precise evaluations of CPE model; 1) It is necessary to test more specimens which contain small cracks in the range of 2a/W<0.1. 2) It is important to detect the crack initiation point during the fracture test for determining an accurate fracture load. 3) Effects of specimen thickness in the fracture process zone should be examined.

• Journal of the Korean Geotechnical Society
• /
• v.25 no.1
• /
• pp.21-29
• /
• 2009

On plane strain condition, many researchers have investigated the earth pressure according to the shape of wall, and standardized method has been applied to the design of the retaining wall. But on cylindrical diaphragm wall, at-rest earth pressure has been generally used. Even though this method is on conservative side, it may lead to over-design. In this paper, the application of convergence confinement method to the calculation of the earth pressure acting on the cylindrical diaphragm wall of a shaft was suggested. In addition, a model test was carried out to investigate the distributions of earth pressure. Model test results show that the earth pressures of diaphragm wall are about 1.4 times larger than active earth pressure and about 0.8 times less than at-rest earth pressure.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.30 no.6A
• /
• pp.581-590
• /
• 2010

This study introduces a layered sectional analysis for a PSC girder with a vaiable cross section and curved tendons. To consider the shear equilibrium at a concrete layer with curved tendons, the shear stress distribution has been computed at each section. In addition, to improve the convergence to the solution, a system identification technique is newly adopted in the solution process for strain computation. To examine the feasibility of the proposed approach, a static load test has been conducted for a full scale PSC girder with variable cross section. The prediction shows a good agreement with experiment. It is seen that a uniform cross section has the same moment capacity with a variable cross section while the variable cross section has more shear capacity than the uniform cross section. It is also noted that the maximum displacement of a variable cross section is a little smaller than a uniform cross section.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.30 no.4A
• /
• pp.383-389
• /
• 2010

The concrete structural design provisions in Korea are based on ultimate strength design. Up to service load stage, it is assumed a linear stress-strain relation, but there is no stress-strain relationship for a concrete material from service load stage to limat state. According to the current provisions, an independent method is provided for the each calculation of deflection and crack width. In EC2 provisions based on limit state design, however, a stress-strain relationship of concrete is provided. Thereby, it is able to calculate a strength as well as a deflection directly from concrete stress-strain relationship. In this paper the moment-curvature relationship is directly calculated from a material law using equilibrium and compatibility conditions. Then strength and deflection are formulated. These results are compared with the values from the current provisions in Korea. From the results, the deflection based on a moment-curvature relationship is well agreed with experimental results and it is appeared that the deflection after the yielding of steel is also possible.

• The Korean Journal of Quaternary Research
• /
• v.33 no.1_2
• /
• pp.49-58
• /
• 2021

In the Paleoclimate Modeling Intercomparison Project phase 4 (PMIP4), various experiments for quaternary climatic change are being carried out along with the Coupled Model Intercomparison Project phase 6 (CMIP6). With the CMIP6 preindustrial climate experiment (piControl), the equilibrium climate simulations of 6 ka Holocene experiment (midHolocene), 21 ka Last Glacial Maximum experiment (lgm), and 127 ka Last Interglacial experiment (lig127k) experiment, and transient climate simulations of 850-1849 Common Era Last Millennium experiment (past1000), 21-9 ka last deglaciation, and 140-127 ka penultimate deglaciation experiment have been carried out under PMIP4 protocols by several modeling groups. In this technical note, important physical parameters and boundary conditions of these Tier 1 experiments and a list of additional Tier 2 and 3 experiments are summarized.

• Korean Chemical Engineering Research
• /
• v.50 no.4
• /
• pp.666-671
• /
• 2012

Gas hydrates are inclusion compounds formed when small-sized guest molecules are incorporated into the well defined cages made up of hydrogen bonded water molecules. Since large masses of natural gas hydrates exist in permafrost regions or beneath deep oceans, these naturally occurring gas hydrates in the earth containing mostly $CH_4$ are regarded as future energy resources. The heat of dissociation is one of the most important thermal properties in exploiting natural gas hydrates. The accurate and direct method to measure the dissociation enthalpies of gas hydrates is to use a calorimeter. In this study, the high pressure micro DSC (Differential Scanning Calorimeter) was used to measure the dissociation enthalpies of methane, ethane, and propane hydrates. The accuracy and repeatability of the data obtained from the DSC was confirmed by measuring the dissociation enthalpy of ice. The dissociation enthalpies of methane, ethane, and propane hydrates were found to be 54.2, 73.8, and 127.7 kJ/mol-gas, respectively. For each gas hydrate, at given pressures the dissociation temperatures which were obtained in the process of enthalpy measurement were compared with three-phase (hydrate (H) - liquid water (Lw) - vapor (V)) equilibrium data in the literature and found to be in good agreement with literature values.