1,721,054 research outputs found
Substituent effect in amine-CO2 interaction investigated by NMR and IR spectroscopies
No full textThe donor property changes of amines by methyl or hydroxyl substituents were studied by NMR and FT-IR spectroscopies. This fundamental investigation can contribute for identifying CO2 absorption capacity of amine solution mainly due to electron releasing and withdrawing effects of substituents.This work was performed for the Carbon Dioxide Reduction
&Sequestration Center, and the Greenhouse Gas Research Center
funded by the Ministry of Science and Technology of Korea and
also partially by the Brain Korea 21 Project
An incremental roll forming process for manufacturing doubly curved sheets from general quadrilateral sheet blanks with enhanced process features
No full textIn order to manufacture a doubly curved sheet metal effectively, a flexible incremental roll forming process has been developed by adopting the advantages of the incremental forming process and the roll forming process by combining inherent flexibility of the incremental forming process and continuous deformation of the roll forming process. In the proposed roll forming system, a newly designed gripper system is attached in order to achieve automation and more precision manufacturing of the required sheet intended double curvature. The forming method has been further enhanced to form general quadrilateral blanks (including a square, a rectangle, a symmetrical trapezoid and an asymmetrical trapezoid, etc.) into doubly curved shapes by controlling the forming schedule developed by various experiments
Investigation into a new incremental forming process using an adjustable punch set for the manufacture of a doubly curved sheet metal
No full textFor flexible manufacture of a doubly curved sheet metal, a new sheet metal forming process is proposed that uses a movable punch set composed of two pairs of lower support punches and one upper centre punch. The process is characterized by flexibility compared with the existing conventional processes because it does not require any complex-shaped die and the loss of material is minimized by unconstrained forming. The process involves very little thickness strain by applying the principle of bending deformation instead of stretching. In the preliminary finite element method (FEM) simulation it is found that the curvature of the formed sheet metal is determined by the distance between the supporting punches working in pairs and the forming depth of the centre punch. In the experiments using sheets of aluminium, a method with edge forming is proposed for producing sheet metal in the desired shape. The equation using process variables such as the distance between supporting punches in pairs and the forming depth of the centre punch is proposed for the prediction of curvature of the formed shape. The equation is revised by the experimental results and the FEM simulation results containing springback information. It is then shown that the radius of curvature for the formed sheet metal can be predicted by the revised equation unless a very large amount of springback occurs
New epoxide molten salts: Key intermediates for designing novel ionic liquids
No full textRoom temperature ILs, based pyridinium and imidazolium cations containing glycidyl (2,3-epoxypropyl) chains have been synthesized in an attempt to design new functionalized ILs. The epoxides in glycidyl ILs comprise an extremely versatile group of intermediates and can react with a large range of nucleophiles, electrophiles and others, resulting in the production of novel ILs with different functional groups.This work was performed for Greenhouse Gas Research Center, one of the Critical Technology-21 Programs, funded by the Ministry of Science and Technology of Korea, LG chemical Ltd. and also partially by the Brain Korea 21 Project
Effect of steric hindrance on carbon dioxide absorption into new amine solutions: Thermodynamic and spectroscopic verification through solubility and NMR analysis
No full textAcid gas absorption technology is of great importance in these days for the prevention of global warming and the resulting worldwide climate change. More efficient process design and development for the removal of acid gases has become important, together with the development of new absorbents as one of urgent areas of research in addressing global-warming problems. In the present work, aqueous solutions of 2-amino-2-hydroxymethyl-1,3-propanediol (AHPD), a sterically hindered amine, has been examined as a potential CO2 absorbent and compared with the most commonly used absorbent, monoethanolamine (MEA) solution, through equilibrium solubility measurements and C-13 NMR spectroscopic analyses. The solubilities of CO2 in aqueous 10 mass % AHPD solutions were higher than those in aqueous 10 mass % MEA solutions above 4 kPa at 298.15 K, but below 4 kPa, the solubility behavior appeared to be the opposite. The solubility difference between these two solutions increased with the CO2 partial pressures above the crossover pressure. Equilibrated CO2-MEA-H2O and CO2-AHPD-H2O solutions at various CO2 partial pressures ranging from 0.01 to 3000 kPa were analyzed by C-13 NMR spectroscopy to provide a more microscopic understanding of the reaction mechanisms in the two solutions. In the CO2-amine-H2O solutions, amine reacted with CO2 to form mainly the protonated amine (AMH(+)), bicarbonate ion (HCO3), and carbarnate anion (AMCO(2) where the quantitative ratio of bicarbonate ion to carbamate anion strongly influenced the CO2 loading in the amine solutions. A profusion of bicarbonate ions, but a very small amount of carbarnate anions, was identified in the CO2-AHPD-H2O solution, whereas a considerable amount of carbamate anions was formed in the CO2-MEA-H2O solution. AHPD contains more hydroxyl groups than nonhindered MEA, and hence, the chemical shifts in its C-13 NMR spectra were strongly influenced by the solution pH values. In contrast, MEA appeared to be insensitive to pH. The strong interrelations among CO2 solubility, CO2 partial pressure, bulkiness of the amine structure, and pH identified through the present experimental investigations can provide basic guidelines for finding new potential organic absorbents, including specifically designed amine chemicals.This research was performed for the Carbon Dioxide Reduction&
Sequestration Center, one of the 21st Century Frontier
R&D Programs and the Greenhouse Gas Research Center,
one of the Critical Technology-21 Programs funded by the
Ministry of Science and Technology of Korea, and also
partially supported by the Brain Korea 21 Project
Absorption kinetics and substituent effects in Amine-Co2 interaction investigated by NMR and IR spectroscopy
No full textRecent trends in numerical simulation of three-dimensional sheet forming processes
No full textThe numerical method of analysis plays a key role in simulation of sheet metal forming processes for design innovation through virtual manufacturing. Recently, important advances in research and development of the sheet metal forming processes have been made by many scientists and engineers. This paper covers general issues in sheet metal forming but deals with the most challenging subjects including finite element (FE) techniques, springback, hydroforming and process design. Furthermore, the results of the proposed benchmark problems in NUMISHEET 2002 with both experiments and simulation results will be discussed
INFORMATION CONTENT OF VOLATILITY SPREADS
No full textThis study reexamines the determinants of volatility spreads and suggests a new forecast of future volatilities. Contrary to earlier volatility forecasts, the newly introduced forecast is applicable when investors are not risk-neutral or when underlying returns do not follow a Gaussian probability distribution. This implies that the method is consistent with the presence of risk premia for other risks such as volatility risk. Using S&P 500 index options, we show that the new volatility forecast outperforms other volatility forecasts including risk-neutral implied volatility and historical volatility in two aspects. First, the new forecast is superior to other estimates in terms of forecasting errors for future realized volatilities. Second, it is an unbiased estimator of future realized volatilities. This is shown using an encompassing regression analysis. (C) 2009 Wiley Periodicals, Inc. Jrl Fut Mark 30:533-558, 2010The authors are deeply indebted to Professor Robert Webb (the editor) and an anonymous referee for their
very constructive suggestions. This work was supported by the Korea Research Foundation Grant funded by
the Korean Government (KRF-2008-332-B00141). All remaining errors are the authors’ responsibility
Mobile position location with the constrained bootstrap filter in a cellular communication system
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