The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Sheldon K Friedlander - One of the best experts on this subject based on the ideXlab platform.
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on line measurement of ultrafine Aggregate Surface area and volume distributions by electrical mobility analysis i theoretical analysis
Journal of Aerosol Science, 2006Co-Authors: Anshuman A Lall, Sheldon K FriedlanderAbstract:Abstract Electrical mobility analyzers are usually calibrated for spherical particles, and provide number, area and volume distributions for spherical particles. However, these instruments cannot be directly used to obtain the Surface area and volume distributions for Aggregates. Aggregates are important in technological applications, such as the manufacture of fine powdered materials, and in air pollution and atmospheric sciences. Thus, nanoparticle chain Aggregates of low fractal dimension are another important limiting case, in addition to spheres; a method is described which makes it possible to relate Aggregate Surface area and volume distributions to the electrical mobility diameter. This is accomplished by equating the migration velocity of an Aggregate to that of a sphere. Particles of equal migration velocities will trace similar paths in the mobility analyzer and have the same mobility diameter (neglecting the Brownian diffusive spread). By equating the migration velocities of a sphere and Aggregate, the number and size of the primary particles composing the Aggregate can be related to the diameter of a sphere with the same migration velocity. The calculation of Aggregate Surface areas and volumes requires two theoretical “modules”, one for the drag on the Aggregates and the other for Aggregate charging efficiency. Two modules selected from the literature were used. The results indicate that the Surface area distributions of Aggregates with random orientation are somewhat over-predicted when calculated directly from the mobility diameter. However, the volume distributions are greatly over-predicted, up to a factor of ten compared with values based on the mobility diameter. The affect of Aggregate orientation on Surface area estimates was also examined.
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On-line measurement of ultrafine Aggregate Surface area and volume distributions by electrical mobility analysis: II. Comparison of measurements and theory
Journal of Aerosol Science, 2006Co-Authors: Anshuman A Lall, Weizhi Rong, Martin Seipenbusch, Sheldon K FriedlanderAbstract:Abstract Differential mobility analyzers (DMAs) are sometimes used to characterize aerosols that contain Aggregates of low fractal dimension. However, these instruments are normally calibrated for spherical particles and the calibrations are not directly applicable to Aggregates. A method proposed by Lall and Friedlander [(2006). On-line measurement of ultrafine Aggregate Surface area and volume distributions by electrical mobility analysis, I: Theoretical analysis. Journal of Aerosol Science , in press] for characterizing ultrafine Aggregate number, Surface area and volume distributions by electrical mobility measurements was tested experimentally. The method is best applied to idealized Aggregates composed of uniform primary particles smaller than the mean free path of the gas. It relates the number and size of the primary particles that compose the Aggregate to the mobility diameter of a spherical particle. Aggregate number distributions were obtained by calculations based on Aggregate drag and Aggregate charging efficiency; Surface area and volume were obtained by summing over the primary particles that compose the Aggregate. The theory was tested experimentally using silver Aggregates generated by an evaporation–condensation method. Primary particle diameter was 18.5 ± 3.5 nm . To obtain distributions with respect to particle volume, Aggregates were sintered to form spheres. It was assumed that the Aggregate volume does not change upon sintering and coagulation was neglected. Thus the number of Aggregates in a given volume range (number distribution, d N / dlog v vs. v ) should not change after sintering. Agreement between Aggregate number distribution based on idealized Aggregates and the values measured for spheres of sintered Aggregates was good. The agreement also indicates that the Aggregate volumes based on idealized Aggregates were accurate. The Aggregate number distribution and volume based on the conventional calibration for spheres were significantly overpredicted. A separate experimental test of the theory was made using literature data for diesel Aggregates. Primary particle diameter was 31.9 ± 7.2 nm . Aggregate volumes calculated from theory agreed well with Aggregate volumes measured by transmission electron microscope analysis.
Anshuman A Lall - One of the best experts on this subject based on the ideXlab platform.
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on line measurement of ultrafine Aggregate Surface area and volume distributions by electrical mobility analysis i theoretical analysis
Journal of Aerosol Science, 2006Co-Authors: Anshuman A Lall, Sheldon K FriedlanderAbstract:Abstract Electrical mobility analyzers are usually calibrated for spherical particles, and provide number, area and volume distributions for spherical particles. However, these instruments cannot be directly used to obtain the Surface area and volume distributions for Aggregates. Aggregates are important in technological applications, such as the manufacture of fine powdered materials, and in air pollution and atmospheric sciences. Thus, nanoparticle chain Aggregates of low fractal dimension are another important limiting case, in addition to spheres; a method is described which makes it possible to relate Aggregate Surface area and volume distributions to the electrical mobility diameter. This is accomplished by equating the migration velocity of an Aggregate to that of a sphere. Particles of equal migration velocities will trace similar paths in the mobility analyzer and have the same mobility diameter (neglecting the Brownian diffusive spread). By equating the migration velocities of a sphere and Aggregate, the number and size of the primary particles composing the Aggregate can be related to the diameter of a sphere with the same migration velocity. The calculation of Aggregate Surface areas and volumes requires two theoretical “modules”, one for the drag on the Aggregates and the other for Aggregate charging efficiency. Two modules selected from the literature were used. The results indicate that the Surface area distributions of Aggregates with random orientation are somewhat over-predicted when calculated directly from the mobility diameter. However, the volume distributions are greatly over-predicted, up to a factor of ten compared with values based on the mobility diameter. The affect of Aggregate orientation on Surface area estimates was also examined.
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On-line measurement of ultrafine Aggregate Surface area and volume distributions by electrical mobility analysis: II. Comparison of measurements and theory
Journal of Aerosol Science, 2006Co-Authors: Anshuman A Lall, Weizhi Rong, Martin Seipenbusch, Sheldon K FriedlanderAbstract:Abstract Differential mobility analyzers (DMAs) are sometimes used to characterize aerosols that contain Aggregates of low fractal dimension. However, these instruments are normally calibrated for spherical particles and the calibrations are not directly applicable to Aggregates. A method proposed by Lall and Friedlander [(2006). On-line measurement of ultrafine Aggregate Surface area and volume distributions by electrical mobility analysis, I: Theoretical analysis. Journal of Aerosol Science , in press] for characterizing ultrafine Aggregate number, Surface area and volume distributions by electrical mobility measurements was tested experimentally. The method is best applied to idealized Aggregates composed of uniform primary particles smaller than the mean free path of the gas. It relates the number and size of the primary particles that compose the Aggregate to the mobility diameter of a spherical particle. Aggregate number distributions were obtained by calculations based on Aggregate drag and Aggregate charging efficiency; Surface area and volume were obtained by summing over the primary particles that compose the Aggregate. The theory was tested experimentally using silver Aggregates generated by an evaporation–condensation method. Primary particle diameter was 18.5 ± 3.5 nm . To obtain distributions with respect to particle volume, Aggregates were sintered to form spheres. It was assumed that the Aggregate volume does not change upon sintering and coagulation was neglected. Thus the number of Aggregates in a given volume range (number distribution, d N / dlog v vs. v ) should not change after sintering. Agreement between Aggregate number distribution based on idealized Aggregates and the values measured for spheres of sintered Aggregates was good. The agreement also indicates that the Aggregate volumes based on idealized Aggregates were accurate. The Aggregate number distribution and volume based on the conventional calibration for spheres were significantly overpredicted. A separate experimental test of the theory was made using literature data for diesel Aggregates. Primary particle diameter was 31.9 ± 7.2 nm . Aggregate volumes calculated from theory agreed well with Aggregate volumes measured by transmission electron microscope analysis.
Jae-suk Ryou - One of the best experts on this subject based on the ideXlab platform.
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Influence of the Surface roughness of crushed natural Aggregates on the microhardness of the interfacial transition zone of concrete with mineral admixtures and polymer latex
Construction and Building Materials, 2018Co-Authors: Abdul Qudoos, Atta-ur-rehman, Jae-suk RyouAbstract:Abstract Aggregate Surface roughness has a significant effect on the interfacial transition zone of concrete. For this study, concrete specimens were prepared from five crushed natural coarse Aggregates with varying Surface roughnesses obtained from five different sources. The influence of polymer latex and mineral admixtures such as metakaolin, silica fume, slag, and fly ash were also studied. The effect of Surface roughness on the interfacial transition zone was characterized by microhardness testing. The microhardness test results were validated via energy-dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM) analysis. The results showed that Surface roughness has a prominent effect on microhardness of the transition zone and the effect significantly increases with the addition of cementitious materials. Polymer latex showed a slight influence on the microhardness while the effect of cementitious materials was found to be profoundly increased.
Evamaria Schoetz - One of the best experts on this subject based on the ideXlab platform.
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coaction of intercellular adhesion and cortical tension specifies tissue Surface tension
Proceedings of the National Academy of Sciences of the United States of America, 2010Co-Authors: Lisa M Manning, Ramsey A Foty, Malcolm S Steinberg, Evamaria SchoetzAbstract:In the course of animal morphogenesis, large-scale cell movements occur, which involve the rearrangement, mutual spreading, and compartmentalization of cell populations in specific configurations. Morphogenetic cell rearrangements such as cell sorting and mutual tissue spreading have been compared with the behaviors of immiscible liquids, which they closely resemble. Based on this similarity, it has been proposed that tissues behave as liquids and possess a characteristic Surface tension, which arises as a collective, macroscopic property of groups of mobile, cohering cells. But how are tissue Surface tensions generated? Different theories have been proposed to explain how mesoscopic cell properties such as cell–cell adhesion and contractility of cell interfaces may underlie tissue Surface tensions. Although recent work suggests that both may be contributors, an explicit model for the dependence of tissue Surface tension on these mesoscopic parameters has been missing. Here we show explicitly that the ratio of adhesion to cortical tension determines tissue Surface tension. Our minimal model successfully explains the available experimental data and makes predictions, based on the feedback between mechanical energy and geometry, about the shapes of Aggregate Surface cells, which we verify experimentally. This model indicates that there is a crossover from adhesion dominated to cortical-tension dominated behavior as a function of the ratio between these two quantities.
Kai Lyu - One of the best experts on this subject based on the ideXlab platform.
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the effect of rough vs smooth Aggregate Surfaces on the characteristics of the interfacial transition zone
Cement & Concrete Composites, 2019Co-Authors: Kai Lyu, Edward J Garboczi, Wei She, Changwen MiaoAbstract:Abstract Due to its higher porosity, the interfacial transition zone (ITZ) between cement paste and Aggregates in cementitious composites is often viewed as a weak link in the microstructure. Sectional plane analysis based on back-scattered electron scanning electron microscope (SEM-BSE) images is used to quantify the ITZ porosity gradient, yet not much research has focused on the effect of Aggregate Surface morphology on the ITZ composition. In this paper, a model concrete specimen with a single spherical ceramic particle acting as an Aggregate is used to study the properties of the ITZ and its uneven distribution around the Aggregate based on quantitative analysis of SEM-BSE images. A careful treatment of the statistics of the ITZ was employed. The average porosity of the ITZ at a smooth part of the Aggregate Surface was smaller than that found at a rough part of the Aggregate Surface. A method is proposed to describe the local Surface roughness (SR) at the pixel level and relate this quantity to other ITZ properties. The relationship between the Surface roughness and the ITZ porosity gradient within 30 μm of the Aggregate Surface was analyzed with the “K-means” clustering method. The role of gravity was seen, since more porous ITZ regions tended to form underneath the Aggregate than above the Aggregate, with intermediate results at the Aggregate sides.