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Jun Wang - One of the best experts on this subject based on the ideXlab platform.
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effect of non solvent additives on the morphology and separation performance of poly m phenylene isophthalamide pmia hollow fiber nanofiltration membrane
Desalination, 2015Co-Authors: Tao Wang, Changwei Zhao, Jun WangAbstract:Newly designed poly(m-phenylene isophthalamide) (PMIA) hollow fiber nanofiltration membranes were fabricated containing non-solvent additives, i.e., lithium chloride (LiCl), acetone and PVP by dry-jet wet spinning technology. The effects of non-solvent additives on the morphology and separation performance were investigated. The addition of non-solvent additives in the dopes enhanced the viscosity significantly. The membrane cross-sections were monitored by scanning electron microscopy (SEM). The results indicated that by increasing the concentration of non-solvent additives, the morphologies changed from finger-like to sponge-like, and the outer skin-layer thickness was slightly increased. The Rejections to various salts and pure water permeability (PWP) of these membranes were determined. The mean pore size and molecular weight cut-off (MWCO) were estimated using the solute Rejection Method. The results showed that the salt Rejection of the membranes decreased in the order of R(Na2SO4) >R(MgSO4) >R(NaCl) >R(MgCl2), and as the concentrations of non-solvent additives increased, the PWPs, mean pore sizes and MWCOs of the PMIA membranes all decreased. The atomic force microscope (AFM) experiments demonstrated that a smooth membrane surface was formed by adding non-solvent additives. Furthermore, the stress values at break, the elongation at break and the elastic modulus of the fibers increased as non-solvent additive contents increased. (C) 2015 Elsevier B.V. All rights reserved.
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fabrication of novel poly m phenylene isophthalamide hollow fiber nanofiltration membrane for effective removal of trace amount perfluorooctane sulfonate from water
Journal of Membrane Science, 2015Co-Authors: Tao Wang, Changwei Zhao, Jun WangAbstract:This study investigated the separation performance of a hollow fiber nanofiltration membrane, which was fabricated from poly(m-phenylene isophthalamide) (PMIA) using a dry-jet wet spinning technology, for sustainable water recovery from water containing trace amount of perfluorooctane sulfonate (PFOS) that was a persistent organic pollutant commonly existed in water. SEM spectra indicated that the cross section of the hollow fiber membrane had an asymmetrical structure that consisted of a dense outer surface acting as a selectively layer, a spongy-like transition layer, and finger-like microvoids close to the inner surface. The average pore size and molecular weight cut-off, which were estimated using the solute Rejection Method, were 0.404 nm and 904 Da, respectively. The PFOS Rejection experiments were carried out at the trans-membrane pressures ranging from 4 x 10(5) Pa to 1.0 x 10(6) Pa and PFOS concentrations from 50 mu g/L to 500 mu g/L. In all cases, the PFOS Rejections were found to be increased as the PFOS concentration increased. The impact of the pH value and Ca2+ concentration of the feed solution on the PFOS Rejections was studied in detail. The PFOS Rejections improved from 91.17% to 97.49% with an increase in pH from 3.2 to 9.5 at 4 x 10(5) Pa. An increase of Ca2+ concentration from 0.1 mM to 2 mM enhanced PFOS Rejection from 97.10% to 99.40% at a trans-membrane pressure of 4 x 10(5) Pa. The sorption/desorption experiments indicated that the amount of PFOS adsorbed on the membrane surface was five times higher in the presence of Ca2+ (2 mM). AFM experiments also demonstrated that the membrane surface was rough with the addition of Ca2+ Hence, the presence of Ca2+ enhanced the PFOS adsorption in the membrane surface and caused more pore blockage of the membrane. As such, the declination in the water flux and augmentation in the PFOS Rejection were observed. (C) 2014 Elsevier B.V. All rights reserved.
S K Solanki - One of the best experts on this subject based on the ideXlab platform.
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sunspot areas and tilt angles for solar cycles 7 10
Astronomy and Astrophysics, 2015Co-Authors: Senthamizh V Pavai, Natalie A Krivova, Rainer Arlt, M Dasiespuig, S K SolankiAbstract:Aims. Extending the knowledge about the properties of solar cycles into the past is essential for understanding the solar dynamo. This paper aims to estimate areas of sunspots observed by Schwabe in 1825−1867 and to calculate the tilt angles of sunspot groups. Methods. The sunspot sizes in Schwabe’s drawings are not to scale and need to be converted into physical sunspot areas. We employed a statistical approach assuming that the area distribution of sunspots was the same in the 19th century as it was in the 20th century. Results. Umbral areas for about 130 000 sunspots observed by Schwabe were obtained, as well as the tilt angles of sunspot groups assuming them to be bipolar. There is, of course, no polarity information in the observations. The annually averaged sunspot areas correlate reasonably with sunspot number. We derived an average tilt angle by attempting to exclude unipolar groups with a minimum separation of the two alleged polarities and an outlier Rejection Method which follows the evolution of each group and detects the moment it turns unipolar at its decay. As a result, the tilt angles, although displaying considerable scatter, average to 5. ◦ 85 ± 0. 25, with the leading polarity located closer to the equator, in good agreement with tilt angles obtained from 20th century data sets. Sources of uncertainties in the tilt angle determination are discussed and need to be addressed whenever different data sets are combined. The sunspot area and tilt angle data are provided at the CDS.
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sunspot areas and tilt angles for solar cycles 7 10
arXiv: Solar and Stellar Astrophysics, 2015Co-Authors: Senthamizh V Pavai, Natalie A Krivova, Rainer Arlt, M Dasiespuig, S K SolankiAbstract:Extending the knowledge about the properties of solar cycles into the past is essential for understanding the solar dynamo. This paper aims at estimating areas of sunspots observed by Schwabe in 1825-1867 and at calculating the tilt angles of sunspot groups. The sunspot sizes in Schwabe's drawings are not to scale and need to be converted into physical sunspot areas. We employed a statistical approach assuming that the area distribution of sunspots was the same in the 19th century as it was in the 20th century. Umbral areas for about 130,000 sunspots observed by Schwabe were obtained, as well as the tilt angles of sunspot groups assuming them to be bipolar. There is, of course, no polarity information in the observations. The annually averaged sunspot areas correlate reasonably with sunspot number. We derived an average tilt angle by attempting to exclude unipolar groups with a minimum separation of the two alleged polarities and an outlier Rejection Method which follows the evolution of each group and detects the moment it turns unipolar at its decay. As a result, the tilt angles, although displaying considerable scatter, place the leading polarity on average 5.85+-0.25 closer to the equator, in good agreement with tilt angles obtained from 20th-century data sets. Sources of uncertainties in the tilt angle determination are discussed and need to be addressed whenever different data sets are combined. The sunspot area and tilt angle data are provided online.
Yoram Koren - One of the best experts on this subject based on the ideXlab platform.
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noise Rejection for ultrasonic sensors in mobile robot applications
International Conference on Robotics and Automation, 1992Co-Authors: Johann Borenstein, Yoram KorenAbstract:The authors categorize different types of noise and discuss Methods for rejecting each type of noise. They introduce a Method called error eliminating rapid ultrasonic firing (EERUF). EERUF combines different noise Rejection techniques and optimizes them for rapid firing. EERUF almost completely rejects crosstalk. Its unique noise Rejection capability allows multiple mobile robots to collaborate in the same environment, even if their ultrasonic sensors operate at the same frequencies. For each noise category Methods are described to identify and reject the resulting errors. These individual Rejection measures were combined into one error Rejection Method which was then combined with a fast firing algorithm. The resulting combination was EERUF. The EERUF Method was implemented on a mobile robot and experimental results are presented. With EERUF, a mobile robot was able to traverse an obstacle course of densely spaced, pencil-thin poles at up to 1 m/s. >
Tao Wang - One of the best experts on this subject based on the ideXlab platform.
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effect of non solvent additives on the morphology and separation performance of poly m phenylene isophthalamide pmia hollow fiber nanofiltration membrane
Desalination, 2015Co-Authors: Tao Wang, Changwei Zhao, Jun WangAbstract:Newly designed poly(m-phenylene isophthalamide) (PMIA) hollow fiber nanofiltration membranes were fabricated containing non-solvent additives, i.e., lithium chloride (LiCl), acetone and PVP by dry-jet wet spinning technology. The effects of non-solvent additives on the morphology and separation performance were investigated. The addition of non-solvent additives in the dopes enhanced the viscosity significantly. The membrane cross-sections were monitored by scanning electron microscopy (SEM). The results indicated that by increasing the concentration of non-solvent additives, the morphologies changed from finger-like to sponge-like, and the outer skin-layer thickness was slightly increased. The Rejections to various salts and pure water permeability (PWP) of these membranes were determined. The mean pore size and molecular weight cut-off (MWCO) were estimated using the solute Rejection Method. The results showed that the salt Rejection of the membranes decreased in the order of R(Na2SO4) >R(MgSO4) >R(NaCl) >R(MgCl2), and as the concentrations of non-solvent additives increased, the PWPs, mean pore sizes and MWCOs of the PMIA membranes all decreased. The atomic force microscope (AFM) experiments demonstrated that a smooth membrane surface was formed by adding non-solvent additives. Furthermore, the stress values at break, the elongation at break and the elastic modulus of the fibers increased as non-solvent additive contents increased. (C) 2015 Elsevier B.V. All rights reserved.
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fabrication of novel poly m phenylene isophthalamide hollow fiber nanofiltration membrane for effective removal of trace amount perfluorooctane sulfonate from water
Journal of Membrane Science, 2015Co-Authors: Tao Wang, Changwei Zhao, Jun WangAbstract:This study investigated the separation performance of a hollow fiber nanofiltration membrane, which was fabricated from poly(m-phenylene isophthalamide) (PMIA) using a dry-jet wet spinning technology, for sustainable water recovery from water containing trace amount of perfluorooctane sulfonate (PFOS) that was a persistent organic pollutant commonly existed in water. SEM spectra indicated that the cross section of the hollow fiber membrane had an asymmetrical structure that consisted of a dense outer surface acting as a selectively layer, a spongy-like transition layer, and finger-like microvoids close to the inner surface. The average pore size and molecular weight cut-off, which were estimated using the solute Rejection Method, were 0.404 nm and 904 Da, respectively. The PFOS Rejection experiments were carried out at the trans-membrane pressures ranging from 4 x 10(5) Pa to 1.0 x 10(6) Pa and PFOS concentrations from 50 mu g/L to 500 mu g/L. In all cases, the PFOS Rejections were found to be increased as the PFOS concentration increased. The impact of the pH value and Ca2+ concentration of the feed solution on the PFOS Rejections was studied in detail. The PFOS Rejections improved from 91.17% to 97.49% with an increase in pH from 3.2 to 9.5 at 4 x 10(5) Pa. An increase of Ca2+ concentration from 0.1 mM to 2 mM enhanced PFOS Rejection from 97.10% to 99.40% at a trans-membrane pressure of 4 x 10(5) Pa. The sorption/desorption experiments indicated that the amount of PFOS adsorbed on the membrane surface was five times higher in the presence of Ca2+ (2 mM). AFM experiments also demonstrated that the membrane surface was rough with the addition of Ca2+ Hence, the presence of Ca2+ enhanced the PFOS adsorption in the membrane surface and caused more pore blockage of the membrane. As such, the declination in the water flux and augmentation in the PFOS Rejection were observed. (C) 2014 Elsevier B.V. All rights reserved.
Senthamizh V Pavai - One of the best experts on this subject based on the ideXlab platform.
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sunspot areas and tilt angles for solar cycles 7 10
Astronomy and Astrophysics, 2015Co-Authors: Senthamizh V Pavai, Natalie A Krivova, Rainer Arlt, M Dasiespuig, S K SolankiAbstract:Aims. Extending the knowledge about the properties of solar cycles into the past is essential for understanding the solar dynamo. This paper aims to estimate areas of sunspots observed by Schwabe in 1825−1867 and to calculate the tilt angles of sunspot groups. Methods. The sunspot sizes in Schwabe’s drawings are not to scale and need to be converted into physical sunspot areas. We employed a statistical approach assuming that the area distribution of sunspots was the same in the 19th century as it was in the 20th century. Results. Umbral areas for about 130 000 sunspots observed by Schwabe were obtained, as well as the tilt angles of sunspot groups assuming them to be bipolar. There is, of course, no polarity information in the observations. The annually averaged sunspot areas correlate reasonably with sunspot number. We derived an average tilt angle by attempting to exclude unipolar groups with a minimum separation of the two alleged polarities and an outlier Rejection Method which follows the evolution of each group and detects the moment it turns unipolar at its decay. As a result, the tilt angles, although displaying considerable scatter, average to 5. ◦ 85 ± 0. 25, with the leading polarity located closer to the equator, in good agreement with tilt angles obtained from 20th century data sets. Sources of uncertainties in the tilt angle determination are discussed and need to be addressed whenever different data sets are combined. The sunspot area and tilt angle data are provided at the CDS.
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sunspot areas and tilt angles for solar cycles 7 10
arXiv: Solar and Stellar Astrophysics, 2015Co-Authors: Senthamizh V Pavai, Natalie A Krivova, Rainer Arlt, M Dasiespuig, S K SolankiAbstract:Extending the knowledge about the properties of solar cycles into the past is essential for understanding the solar dynamo. This paper aims at estimating areas of sunspots observed by Schwabe in 1825-1867 and at calculating the tilt angles of sunspot groups. The sunspot sizes in Schwabe's drawings are not to scale and need to be converted into physical sunspot areas. We employed a statistical approach assuming that the area distribution of sunspots was the same in the 19th century as it was in the 20th century. Umbral areas for about 130,000 sunspots observed by Schwabe were obtained, as well as the tilt angles of sunspot groups assuming them to be bipolar. There is, of course, no polarity information in the observations. The annually averaged sunspot areas correlate reasonably with sunspot number. We derived an average tilt angle by attempting to exclude unipolar groups with a minimum separation of the two alleged polarities and an outlier Rejection Method which follows the evolution of each group and detects the moment it turns unipolar at its decay. As a result, the tilt angles, although displaying considerable scatter, place the leading polarity on average 5.85+-0.25 closer to the equator, in good agreement with tilt angles obtained from 20th-century data sets. Sources of uncertainties in the tilt angle determination are discussed and need to be addressed whenever different data sets are combined. The sunspot area and tilt angle data are provided online.
