WorldWideScience

Sample records for soot size distribution

  1. Simulation of soot size distribution in an ethylene counterflow flame

    KAUST Repository

    Zhou, Kun

    2014-01-06

    Soot, an aggregate of carbonaceous particles produced during the rich combustion of fossil fuels, is an undesirable pollutant and health hazard. Soot evolution involves various dynamic processes: nucleation soot formation from polycyclic aromatic hydrocarbons (PAHs) condensation PAHs condensing on soot particle surface surface processes hydrogen-abstraction-C2H2-addition, oxidation coagulation two soot particles coagulating to form a bigger particle This simulation work investigates soot size distribution and morphology in an ethylene counterflow flame, using i). Chemkin with a method of moments to deal with the coupling between vapor consumption and soot formation; ii). Monte Carlo simulation of soot dynamics.

  2. Simulation of soot size distribution in an ethylene counterflow flame

    KAUST Repository

    Zhou, Kun; Abdelgadir, Ahmed Gamaleldin; Bisetti, Fabrizio

    2014-01-01

    Soot, an aggregate of carbonaceous particles produced during the rich combustion of fossil fuels, is an undesirable pollutant and health hazard. Soot evolution involves various dynamic processes: nucleation soot formation from polycyclic aromatic

  3. Simulation and analysis of the soot particle size distribution in a turbulent nonpremixed flame

    KAUST Repository

    Lucchesi, Marco; Abdelgadir, Ahmed Gamaleldin; Attili, Antonio; Bisetti, Fabrizio

    2017-01-01

    to the simulation of soot formation and growth in simplified configurations featuring a constant concentration of soot precursors and the evolution of the size distribution in time is found to depend on the intensity of the nucleation rate. Higher nucleation rates

  4. Effect of Dimethyl Ether Mixing on Soot Size Distribution in Premixed Ethylene Flame

    KAUST Repository

    Li, Zepeng

    2016-04-21

    As a byproduct of incomplete combustion, soot attracts increasing attentions as extensive researches exploring serious health and environmental effects from soot particles. Soot emission reduction requires a comprehensive understanding of the mechanism for polycyclic aromatic hydrocarbons and of soot formation and aging processes. Therefore, advanced experimental techniques and numerical simulations have been conducted to investigate this procedure. In order to investigate the effects of dimethyl ether (DME) mixing on soot particle size distribution functions (PSDFs), DME was mixed in premixed ethylene/oxygen/argon at flames at the equivalence ratio of 2.0 with a range of mixing ratio from 0% to 30% of the total carbon fed. Two series of atmospheric pressure flames were tested in which cold gas velocity was varied to obtain different flame temperatures. The evolution of PSDFs along the centerline of the flame was determined by burner stabilized stagnation probe and scanning mobility particle sizer (SMPS) techniques, yielding the PSDFs for various separation distances above the burner surface. Meanwhile, the flame temperature profiles were carefully measured by a thermocouple and the comparison to that of simulated laminar premixed burner-stabilized stagnation flame was satisfactory. Additionally, to understand the chemical role of DME mixing in soot properties, characterization measurements were conducted on soot samples using thermo-gravimetric analysis (TGA) and elemental analysis (EA). Results of the evolution of PSDFs and soot volume fraction showed that adding DME into ethylene flame could reduce soot yield significantly. The addition of DME led to the decrease of both the soot nucleation rate and the particle mass growth rate. To explain the possible mechanism for the observation, numerical simulations were performed. Although DME addition resulted in the slight increase of methyl radicals from pyrolysis, the decrease in acetylene and propargyl radicals

  5. Simulation and analysis of the soot particle size distribution in a turbulent nonpremixed flame

    KAUST Repository

    Lucchesi, Marco

    2017-02-05

    A modeling framework based on Direct Simulation Monte Carlo (DSMC) is employed to simulate the evolution of the soot particle size distribution in turbulent sooting flames. The stochastic reactor describes the evolution of soot in fluid parcels following Lagrangian trajectories in a turbulent flow field. The trajectories are sampled from a Direct Numerical Simulation (DNS) of a n-heptane turbulent nonpremixed flame. The DSMC method is validated against experimentally measured size distributions in laminar premixed flames and found to reproduce quantitatively the experimental results, including the appearance of the second mode at large aggregate sizes and the presence of a trough at mobility diameters in the range 3–8 nm. The model is then applied to the simulation of soot formation and growth in simplified configurations featuring a constant concentration of soot precursors and the evolution of the size distribution in time is found to depend on the intensity of the nucleation rate. Higher nucleation rates lead to a higher peak in number density and to the size distribution attaining its second mode sooner. The ensemble-averaged PSDF in the turbulent flame is computed from individual samples of the PSDF from large sets of Lagrangian trajectories. This statistical measure is equivalent to time-averaged, scanning mobility particle size (SMPS) measurements in turbulent flames. Although individual trajectories display strong bimodality as in laminar flames, the ensemble-average PSDF possesses only one mode and a long, broad tail, which implies significant polydispersity induced by turbulence. Our results agree very well with SMPS measurements available in the literature. Conditioning on key features of the trajectory, such as mixture fraction or radial locations does not reduce the scatter in the size distributions and the ensemble-averaged PSDF remains broad. The results highlight and explain the important role of turbulence in broadening the size distribution of

  6. Soot Particle Size Distribution Functions in a Turbulent Non-Premixed Ethylene-Nitrogen Flame

    KAUST Repository

    Boyette, Wesley

    2017-02-21

    A scanning mobility particle sizer with a nano differential mobility analyzer was used to measure nanoparticle size distribution functions in a turbulent non-premixed flame. The burner utilizes a premixed pilot flame which anchors a C2H4/N2 (35/65) central jet with ReD = 20,000. Nanoparticles in the flame were sampled through a N2-filled tube with a 500- μm orifice. Previous studies have shown that insufficient dilution of the nanoparticles can lead to coagulation in the sampling line and skewed particle size distribution functions. A system of mass flow controllers and valves were used to vary the dilution ratio. Single-stage and two-stage dilution systems were investigated. A parametric study on the effect of the dilution ratio on the observed particle size distribution function indicates that particle coagulation in the sampling line can be eliminated using a two-stage dilution process. Carbonaceous nanoparticle (soot) concentration particle size distribution functions along the flame centerline at multiple heights in the flame are presented. The resulting distributions reveal a pattern of increasing mean particle diameters as the distance from the nozzle along the centerline increases.

  7. Soot Particle Size Distribution Functions in a Turbulent Non-Premixed Ethylene-Nitrogen Flame

    KAUST Repository

    Boyette, Wesley; Chowdhury, Snehaunshu; Roberts, William L.

    2017-01-01

    A scanning mobility particle sizer with a nano differential mobility analyzer was used to measure nanoparticle size distribution functions in a turbulent non-premixed flame. The burner utilizes a premixed pilot flame which anchors a C2H4/N2 (35/65) central jet with ReD = 20,000. Nanoparticles in the flame were sampled through a N2-filled tube with a 500- μm orifice. Previous studies have shown that insufficient dilution of the nanoparticles can lead to coagulation in the sampling line and skewed particle size distribution functions. A system of mass flow controllers and valves were used to vary the dilution ratio. Single-stage and two-stage dilution systems were investigated. A parametric study on the effect of the dilution ratio on the observed particle size distribution function indicates that particle coagulation in the sampling line can be eliminated using a two-stage dilution process. Carbonaceous nanoparticle (soot) concentration particle size distribution functions along the flame centerline at multiple heights in the flame are presented. The resulting distributions reveal a pattern of increasing mean particle diameters as the distance from the nozzle along the centerline increases.

  8. Effect of Dimethyl Ether Mixing on Soot Size Distribution in Premixed Ethylene Flame

    KAUST Repository

    Li, Zepeng

    2016-01-01

    As a byproduct of incomplete combustion, soot attracts increasing attentions as extensive researches exploring serious health and environmental effects from soot particles. Soot emission reduction requires a comprehensive understanding

  9. Evaluation of a Lagrangian Soot Tracking Method for the prediction of primary soot particle size under engine-like conditions

    DEFF Research Database (Denmark)

    Cai Ong, Jiun; Pang, Kar Mun; Walther, Jens Honore

    2018-01-01

    This paper reports the implementation and evaluation of a Lagrangian soot tracking (LST) method for the modeling of soot in diesel engines. The LST model employed here has the tracking capability of a Lagrangian method and the ability to predict primary soot particle sizing. The Moss-Brookes soot...... in predicting temporal soot cloud development, mean soot diameter and primary soot size distribution is evaluated using measurements of n-heptane and n-dodecane spray combustion obtained under diesel engine-like conditions. In addition, sensitivity studies are carried out to investigate the influence of soot....... A higher rate of soot oxidation due to OH causes the soot particles to be fully oxidized downstream of the flame. In general, the LST model performs better than the Eulerian method in terms of predicting soot sizing and accessing information of individual soot particles, both of which are shortcomings...

  10. Size distribution and concentration of soot generated in oil and gas-fired residential boilers under different combustion conditions

    Science.gov (United States)

    Jiménez, Santiago; Barroso, Jorge; Pina, Antonio; Ballester, Javier

    2016-05-01

    In spite of the relevance of residential heating burners in the global emission of soot particles to the atmosphere, relatively little information on their properties (concentration, size distribution) is available in the literature, and even less regarding the dependence of those properties on the operating conditions. Instead, the usual procedure to characterize those emissions is to measure the smoke opacity by several methods, among which the blackening of a paper after filtering a fixed amount of gas (Bacharach test) is predominant. In this work, the size distributions of the particles generated in the combustion of a variety of gaseous and liquid fuels in a laboratory facility equipped with commercial burners have been measured with a size classifier coupled to a particle counter in a broad range of operating conditions (air excesses), with simultaneous determination of the Bacharach index. The shape and evolution of the distribution with progressively smaller oxygen concentrations depends essentially on the state of the fuel: whereas the combustion of the gases results in monomodal distributions that 'shift' towards larger diameters, in the case of the gas-oils an ultrafine mode is always observed, and a secondary mode of coarse particle grows in relevance. In both cases, there is a strong, exponential correlation between the total mass concentration and the Bacharach opacity index, quite similar for both groups of fuels. The empirical expressions proposed may allow other researchers to at least estimate the emissions of numerous combustion facilities routinely characterized by their smoke opacities.

  11. Soot and liquid-phase fuel distributions in a newly designed optically accessible DI diesel engine

    Science.gov (United States)

    Dec, J. E.; Espey, C.

    1993-10-01

    Two-dimensional (2-D) laser-sheet imaging has been used to examine the soot and liquid-phase fuel distributions in a newly designed, optically accessible, direct-injection diesel engine of the heavy-duty size class. The design of this engine preserves the intake port geometry and basic dimensions of a Cummins N-series production engine. It also includes several unique features to provide considerable optical access. Liquid-phase fuel and soot distribution studies were conducted at a medium speed (1,200 rpm) using a Cummins closed-nozzle fuel injector. The scattering was used to obtain planar images of the liquid-phase fuel distribution. These images show that the leading edge of the liquid-phase portion of the fuel jet reaches a maximum length of 24 mm, which is about half the combustion bowl radius for this engine. Beyond this point virtually all the fuel has vaporized. Soot distribution measurements were made at a high load condition using three imaging diagnostics: natural flame luminosity, 2-D laser-induced incandescence, and 2-D elastic scattering. This investigation showed that the soot distribution in the combusting fuel jet develops through three stages. First, just after the onset of luminous combustion, soot particles are small and nearly uniformly distributed throughout the luminous region of the fuel jet. Second, after about 2 crank angle degrees a pattern develops of a higher soot concentration of larger sized particles in the head vortex region of the jet and a lower soot concentration of smaller sized particles upstream toward the injector. Third, after fuel injection ends, both the soot concentration and soot particle size increase rapidly in the upstream portion of the fuel jet.

  12. Mixing state of regionally transported soot particles and the coating effect on their size and shape at a mountain site in Japan

    Science.gov (United States)

    Adachi, Kouji; Zaizen, Yuji; Kajino, Mizuo; Igarashi, Yasuhito

    2014-05-01

    Soot particles influence the global climate through interactions with sunlight. A coating on soot particles increases their light absorption by increasing their absorption cross section and cloud condensation nuclei activity when mixed with other hygroscopic aerosol components. Therefore, it is important to understand how soot internally mixes with other materials to accurately simulate its effects in climate models. In this study, we used a transmission electron microscope (TEM) with an auto particle analysis system, which enables more particles to be analyzed than a conventional TEM. Using the TEM, soot particle size and shape (shape factor) were determined with and without coating from samples collected at a remote mountain site in Japan. The results indicate that ~10% of aerosol particles between 60 and 350 nm in aerodynamic diameters contain or consist of soot particles and ~75% of soot particles were internally mixed with nonvolatile ammonium sulfate or other materials. In contrast to an assumption that coatings change soot shape, both internally and externally mixed soot particles had similar shape and size distributions. Larger aerosol particles had higher soot mixing ratios, i.e., more than 40% of aerosol particles with diameters >1 µm had soot inclusions, whereas <20% of aerosol particles with diameters <1 µm included soot. Our results suggest that climate models may use the same size distributions and shapes for both internally and externally mixed soot; however, changing the soot mixing ratios in the different aerosol size bins is necessary.

  13. Investigation of soot morphology and particle size distrib ution in a turbulent nonpremixed flame via Monte Carlo simulations

    KAUST Repository

    Abdelgadir, Ahmed

    2015-03-30

    Recently, our group performed a set of direct numerical simulations (DNS) of soot formation and growth in a n-heptane three dimensional non-premixed jet flame [Attili et al., Proc. Comb. Inst, 35, 2015], [Attili et al., Comb. Flame, 161, 2014], [Bisetti et al.,Trans of the Royal Soc, 372, 2014]. The evolution of species relevant to soot formation and growth have been sampled along a large number of Lagrangian trajectories in the DNS. In this work, the DNS results are post-processed to compute the soot evolution along selected Lagrangian trajectories using a Monte Carlo method. An operator splitting approach is adopted to split the deterministic processes (nucleation, surface growth and oxidation) from coagulation, which is treated stochastically. The morphological properties of soot and the particlesize distribution are investigated. For trajectories that experience an early strong nucleation event, the particle size distribution is found to be bimodal, as the soot particles have enough time to coagulate and grow while it is unimodal for trajectories characterized by only late nucleation events. As a results, the average size distribution at two different crosswise positions in the flame is unimodal.

  14. Quantitative effects of rapid heating on soot-particle sizing through analysis of two-pulse LII

    KAUST Repository

    Cenker, Emre; Roberts, William L.

    2017-01-01

    particle size, respectively. Overall, effects of these two processes on soot and LII model-based particle sizing are investigated by measuring the two-color time-resolved (2C-TiRe) LII signal decay from in-flame soot after two consecutive laser pulses

  15. Soot particle size measurements in ethylene diffusion flames at elevated pressures

    KAUST Repository

    Steinmetz, Scott

    2016-05-07

    Soot particle size is investigated in laminar nitrogen-diluted ethylene coflow diffusion flames at 4, 8, 12 and 16 atm. Line of sight attenuation and scattering are used to measure two-dimensional soot volume fraction and particle size fields for the first time at elevated pressures. Soot volume fraction dependence on pressure is consistent with the observations of similar studies, scaling approximately with the square of pressure. Scattering intensity is analyzed through Rayleigh and Rayleigh-Debye-Gans polydisperse fractal aggregate theories to provide two estimates of particle size. An increase in overall particle sizes with pressure is found, consistent with similar one-dimensional studies. Particle diameters in the annulus of the flame increase faster with pressure than those on centerline. Contrary to previous studies, the dependence of particle size on pressure was found to taper off between 8 and 12 atm, with little observed growth beyond 12 atm. The measurements provide additional data for one of the International Sooting Flame (ISF) workshop\\'s target pressurized flames.

  16. Diffusion air effects on the soot axial distribution concentration in a premixed acetylene/air flame

    Energy Technology Data Exchange (ETDEWEB)

    Fassani, Fabio Luis; Santos, Alex Alisson Bandeira; Goldstein Junior, Leonardo [Universidade Estadual de Campinas, SP (Brazil). Faculdade de Engenharia Mecanica. Dept. de Engenharia Termica e de Fluidos]. E-mails: fassani@fem.unicamp.br; absantos@fem.unicamp.br; leonardo@fem.unicamp.br; Ferrari, Carlos Alberto [Universidade Estadual de Campinas, SP (Brazil). Inst. de Fisica. Dept. de Eletronica Quantica]. E-mail: ferrari@ifi.unicamp.br

    2000-07-01

    Soot particles are produced during the high temperature pyrolysis or combustion of hydrocarbons. The emission of soot from a combustor, or from a flame, is determined by the competition between soot formation and its oxidation. Several factors affect these processes, including the type of fuel, the air-to-fuel ratio, flame temperature, pressure, and flow pattern. In this paper, the influence of the induced air diffusion on the soot axial distribution concentration in a premixed acetylene/air flame was studied. The flame was generated in a vertical axis burner in which the fuel - oxidant mixture flow was surrounded by a nitrogen discharge coming from the annular region between the burner tube and an external concentric tube. The nitrogen flow provided a shield that protected the flame from the diffusion of external air, enabling its control. The burner was mounted on a step-motor driven, vertical translation table. The use of several air-to-fuel ratios made possible to establish the sooting characteristics of this flame, by measuring soot concentration along the flame height with a non-intrusive laser light absorption technique. (author)

  17. The immersion freezing behavior of size-segregated soot and kaolinite particles

    Science.gov (United States)

    Hartmann, S.; Augustin, S.; Clauss, T.; Niedermeier, D.; Raddatz, M.; Wex, H.; Shaw, R. A.; Stratmann, F.

    2011-12-01

    Heterogeneous ice nucleation plays a crucial role for ice formation in mixed-phase and cirrus clouds and has an important impact on precipitation formation, global radiation balances, and therefore Earth's climate (Cantrell and Heymsfield, 2005). Mineral dust and soot particles are found to be a major component of ice crystal residues (e.g., Pratt et al., 2009) so these substances are potential sources of atmospheric ice nuclei (IN). Experimental studies investigating the immersion freezing behavior of size-segregated soot and kaolinite particles conducted at the Leipzig Aerosol Cloud Interaction Simulator (LACIS) are presented. In our measurements only one aerosol particle is immersed in an air suspended water droplet which can trigger ice nucleation. The method facilitates very precise examinations with respect to temperature, ice nucleation time and ice nucleus size. Considering laboratory studies, the picture of the IN ability of soot particles is quite heterogeneous. Our studies show that submicron flame, spark soot particles and optionally coated with sulfuric acid to simulate chemically aging do not act as IN at temperatures higher than homogeneous freezing taking place. Therefore soot particles might not be an important source of IN for immersion freezing in the atmosphere. In contrast, kaolinite being representative for natural mineral dust with a well known composition and structure is found to be very active in forming ice for all freezing modes (e.g., Mason and Maybank, 1958). Analyzing the immersion freezing behavior of different sized kaolinite particles (300, 500 and 700 nm in diameter) the size effect was clearly observed, i.e. the ice fraction (number of frozen droplets per total number) scales with particle surface, i.e. the larger the ice nucleus surface the higher the ice fraction. The slope of the logarithm of the ice fraction as function of temperature is similar for all particle sizes investigated and fits very well with the results of L

  18. Ultra-small-angle X-ray scattering characterization of diesel/gasoline soot: sizes and particle-packing conditions

    Energy Technology Data Exchange (ETDEWEB)

    Kameya, Yuki, E-mail: ykameya@anl.gov; Lee, Kyeong O. [Argonne National Laboratory, Center for Transportation Research (United States)

    2013-10-15

    Regulations on particulate emissions from internal combustion engines tend to become more stringent, accordingly the importance of particulate filters in the after-treatment system has been increasing. In this work, the applicability of ultra-small-angle X-ray scattering (USAXS) to diesel soot cake and gasoline soot was investigated. Gasoline-direct-injection engine soot was collected at different fuel injection timings. The unified fits method was applied to analyze the resultant scattering curves. The validity of analysis was supported by comparing with carbon black and taking the sample images using a transmission electron microscope, which revealed that the primary particle size ranged from 20 to 55 nm. In addition, the effects of particle-packing conditions on the USAXS measurement were demonstrated by using samples suspended in acetone. Then, the investigation was extended to characterization of diesel soot cake deposited on a diesel particulate filter (DPF). Diesel soot was trapped on a small piece of DPF at different deposition conditions which were specified using the Peclet number. The dependence of scattering curve on soot-deposition conditions was demonstrated. To support the interpretation of the USAXS results, soot cake samples were observed using a scanning electron microscope and the influence of particle-packing conditions on scattering curve was discussed.

  19. Ultra-small-angle X-ray scattering characterization of diesel/gasoline soot: sizes and particle-packing conditions

    Science.gov (United States)

    Kameya, Yuki; Lee, Kyeong O.

    2013-10-01

    Regulations on particulate emissions from internal combustion engines tend to become more stringent, accordingly the importance of particulate filters in the after-treatment system has been increasing. In this work, the applicability of ultra-small-angle X-ray scattering (USAXS) to diesel soot cake and gasoline soot was investigated. Gasoline-direct-injection engine soot was collected at different fuel injection timings. The unified fits method was applied to analyze the resultant scattering curves. The validity of analysis was supported by comparing with carbon black and taking the sample images using a transmission electron microscope, which revealed that the primary particle size ranged from 20 to 55 nm. In addition, the effects of particle-packing conditions on the USAXS measurement were demonstrated by using samples suspended in acetone. Then, the investigation was extended to characterization of diesel soot cake deposited on a diesel particulate filter (DPF). Diesel soot was trapped on a small piece of DPF at different deposition conditions which were specified using the Peclet number. The dependence of scattering curve on soot-deposition conditions was demonstrated. To support the interpretation of the USAXS results, soot cake samples were observed using a scanning electron microscope and the influence of particle-packing conditions on scattering curve was discussed.

  20. Ultra-small-angle X-ray scattering characterization of diesel/gasoline soot: sizes and particle-packing conditions

    International Nuclear Information System (INIS)

    Kameya, Yuki; Lee, Kyeong O.

    2013-01-01

    Regulations on particulate emissions from internal combustion engines tend to become more stringent, accordingly the importance of particulate filters in the after-treatment system has been increasing. In this work, the applicability of ultra-small-angle X-ray scattering (USAXS) to diesel soot cake and gasoline soot was investigated. Gasoline-direct-injection engine soot was collected at different fuel injection timings. The unified fits method was applied to analyze the resultant scattering curves. The validity of analysis was supported by comparing with carbon black and taking the sample images using a transmission electron microscope, which revealed that the primary particle size ranged from 20 to 55 nm. In addition, the effects of particle-packing conditions on the USAXS measurement were demonstrated by using samples suspended in acetone. Then, the investigation was extended to characterization of diesel soot cake deposited on a diesel particulate filter (DPF). Diesel soot was trapped on a small piece of DPF at different deposition conditions which were specified using the Peclet number. The dependence of scattering curve on soot-deposition conditions was demonstrated. To support the interpretation of the USAXS results, soot cake samples were observed using a scanning electron microscope and the influence of particle-packing conditions on scattering curve was discussed

  1. Quantitative effects of rapid heating on soot-particle sizing through analysis of two-pulse LII

    KAUST Repository

    Cenker, Emre

    2017-02-27

    During the rapid laser pulse heating and consecutive cooling in laser-induced incandescence (LII), soot particles may undergo thermal annealing and sublimation processes which lead to a permanent change in its optical properties and its primary particle size, respectively. Overall, effects of these two processes on soot and LII model-based particle sizing are investigated by measuring the two-color time-resolved (2C-TiRe) LII signal decay from in-flame soot after two consecutive laser pulses at 1064-nm wavelength. Experiments are carried out on a non-premixed laminar ethylene/air flame from a Santoro burner with both low and moderate laser fluences suitable for particle sizing. The probe volume is set to a radial position close to the flame axis where the soot particles are known to be immature or less graphitic. With the first pulse, soot is pre-heated, and the LII signal after the consecutive second pulse is used for analysis. The two-color incandescence emission technique is used for the pyrometric determination of the LII-heated peak soot temperature at the second pulse. A new LII simulation tool is developed which accounts for particle heating via absorption and annealing, and cooling via sublimation, conduction, and radiation with various existing sub-models from the literature. The same approach of using two laser pulses is implemented in the simulations. Measurements indicate that thermal annealing and associated absorption enhancement becomes important at laser fluences above 0.17 J/cm2 for the immature in-flame soot. After a heating pulse at 0.33 J/cm2, the increase of the soot absorption function is calculated as 35% using the temperature measured at the second pulse and an absorption model based on the Rayleigh approximation. Present annealing model, on the other hand, predicts graphitization of soot even in the absence of laser heating at typical flame temperatures. Recorded experimental LII signal decays and LII-heated peak soot temperature

  2. Comprehensive Laser-induced Incandescence (LII) modeling for soot particle sizing

    KAUST Repository

    Lisanti, Joel

    2015-03-30

    To evaluate the current state of the art in LII particle sizing, a comprehensive model for predicting the temporal incandescent response of combustion-generated soot to absorption of a pulsed laser is presented. The model incorporates particle heating through laser absorption, thermal annealing, and oxidation at the surface as well as cooling through sublimation and photodesorption, radiation, conduction and thermionic emission. Thermodynamic properties and the thermal accommodation coefficient utilized in the model are temperature dependent. In addition, where appropriate properties are also phase dependent, thereby accounting for annealing effects during laser heating and particle cooling.

  3. Monte carlo simulation for soot dynamics

    KAUST Repository

    Zhou, Kun

    2012-01-01

    A new Monte Carlo method termed Comb-like frame Monte Carlo is developed to simulate the soot dynamics. Detailed stochastic error analysis is provided. Comb-like frame Monte Carlo is coupled with the gas phase solver Chemkin II to simulate soot formation in a 1-D premixed burner stabilized flame. The simulated soot number density, volume fraction, and particle size distribution all agree well with the measurement available in literature. The origin of the bimodal distribution of particle size distribution is revealed with quantitative proof.

  4. Automated determination of size and morphology information from soot transmission electron microscope (TEM)-generated images

    International Nuclear Information System (INIS)

    Wang, Cheng; Chan, Qing N.; Zhang, Renlin; Kook, Sanghoon; Hawkes, Evatt R.; Yeoh, Guan H.; Medwell, Paul R.

    2016-01-01

    The thermophoretic sampling of particulates from hot media, coupled with transmission electron microscope (TEM) imaging, is a combined approach that is widely used to derive morphological information. The identification and the measurement of the particulates, however, can be complex when the TEM images are of low contrast, noisy, and have non-uniform background signal level. The image processing method can also be challenging and time consuming, when the samples collected have large variability in shape and size, or have some degree of overlapping. In this work, a three-stage image processing sequence is presented to facilitate time-efficient automated identification and measurement of particulates from the TEM grids. The proposed processing sequence is first applied to soot samples that were thermophoretically sampled from a laminar non-premixed ethylene-air flame. The parameter values that are required to be set to facilitate the automated process are identified, and sensitivity of the results to these parameters is assessed. The same analysis process is also applied to soot samples that were acquired from an externally irradiated laminar non-premixed ethylene-air flame, which have different geometrical characteristics, to assess the morphological dependence of the proposed image processing sequence. Using the optimized parameter values, statistical assessments of the automated results reveal that the largest discrepancies that are associated with the estimated values of primary particle diameter, fractal dimension, and prefactor values of the aggregates for the tested cases, are approximately 3, 1, and 10 %, respectively, when compared with the manual measurements.

  5. Automated determination of size and morphology information from soot transmission electron microscope (TEM)-generated images

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Cheng; Chan, Qing N., E-mail: qing.chan@unsw.edu.au; Zhang, Renlin; Kook, Sanghoon; Hawkes, Evatt R.; Yeoh, Guan H. [UNSW, School of Mechanical and Manufacturing Engineering (Australia); Medwell, Paul R. [The University of Adelaide, Centre for Energy Technology (Australia)

    2016-05-15

    The thermophoretic sampling of particulates from hot media, coupled with transmission electron microscope (TEM) imaging, is a combined approach that is widely used to derive morphological information. The identification and the measurement of the particulates, however, can be complex when the TEM images are of low contrast, noisy, and have non-uniform background signal level. The image processing method can also be challenging and time consuming, when the samples collected have large variability in shape and size, or have some degree of overlapping. In this work, a three-stage image processing sequence is presented to facilitate time-efficient automated identification and measurement of particulates from the TEM grids. The proposed processing sequence is first applied to soot samples that were thermophoretically sampled from a laminar non-premixed ethylene-air flame. The parameter values that are required to be set to facilitate the automated process are identified, and sensitivity of the results to these parameters is assessed. The same analysis process is also applied to soot samples that were acquired from an externally irradiated laminar non-premixed ethylene-air flame, which have different geometrical characteristics, to assess the morphological dependence of the proposed image processing sequence. Using the optimized parameter values, statistical assessments of the automated results reveal that the largest discrepancies that are associated with the estimated values of primary particle diameter, fractal dimension, and prefactor values of the aggregates for the tested cases, are approximately 3, 1, and 10 %, respectively, when compared with the manual measurements.

  6. Effects of DME mixing on number density and size properties of soot particles in counterflow non-premixed ethylene flames

    KAUST Repository

    Choi, J. H.; Choi, B. C.; Lee, S. M.; Chung, Suk-Ho; Jung, K. S.; Jeong, W. L.; Choi, S. K.; Park, S. K.

    2015-01-01

    In order to investigate the effect of DME mixing on the number density and size of soot particles, DME was mixed in a counter flow non-premixed ethylene flame with mixture ratios of 5%, 14% and 30%. A laser extinction/scattering technique has been adopted to measure the volume fraction, number density, and mean size of soot particles. The experimental results showed that the highest soot concentrations were observed for flames with mixture ratios of 5% and 14%; however, for a mixture ratio of 30% the soot concentration decreased. Numerical results showed that the concentrations of propargyl radicals (C3H3) at the 5% and 14% ratios were higher than those measured in the ethylene-based flame, and the production of benzene (C6H6) in the 5% and 14% DME mixture flames was also increased. This indicates the crucial role of propargyl in benzene ring formation. These reactions generally become stronger with increased DME mixing, except for A1- + H2 → A1 + H (-R554) and n-C4H5 + C2H2 → A1 + H (R542). Therefore, it is indicated that adding DME to ethylene flames promotes benzene ring formation. Note that although the maximum C6H6 concentration is largest in the 30% DME mixing flame, the soot volume fraction is smaller than those for the 5% and 14% mixture ratios. This is because the local C6H6 concentration decreases in the relatively low temperature region in the fuel side where soot growth occurs. © 2015, The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg.

  7. Effects of DME mixing on number density and size properties of soot particles in counterflow non-premixed ethylene flames

    KAUST Repository

    Choi, J. H.

    2015-05-01

    In order to investigate the effect of DME mixing on the number density and size of soot particles, DME was mixed in a counter flow non-premixed ethylene flame with mixture ratios of 5%, 14% and 30%. A laser extinction/scattering technique has been adopted to measure the volume fraction, number density, and mean size of soot particles. The experimental results showed that the highest soot concentrations were observed for flames with mixture ratios of 5% and 14%; however, for a mixture ratio of 30% the soot concentration decreased. Numerical results showed that the concentrations of propargyl radicals (C3H3) at the 5% and 14% ratios were higher than those measured in the ethylene-based flame, and the production of benzene (C6H6) in the 5% and 14% DME mixture flames was also increased. This indicates the crucial role of propargyl in benzene ring formation. These reactions generally become stronger with increased DME mixing, except for A1- + H2 → A1 + H (-R554) and n-C4H5 + C2H2 → A1 + H (R542). Therefore, it is indicated that adding DME to ethylene flames promotes benzene ring formation. Note that although the maximum C6H6 concentration is largest in the 30% DME mixing flame, the soot volume fraction is smaller than those for the 5% and 14% mixture ratios. This is because the local C6H6 concentration decreases in the relatively low temperature region in the fuel side where soot growth occurs. © 2015, The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg.

  8. Size-resolved measurement of the mixing state of soot in the megacity Beijing, China: diurnal cycle, aging and parameterization

    Directory of Open Access Journals (Sweden)

    Y. F. Cheng

    2012-05-01

    Full Text Available Soot particles are the most efficient light absorbing aerosol species in the atmosphere, playing an important role as a driver of global warming. Their climate effects strongly depend on their mixing state, which significantly changes their light absorbing capability and cloud condensation nuclei (CCN activity. Therefore, knowledge about the mixing state of soot and its aging mechanism becomes an important topic in the atmospheric sciences.

    The size-resolved (30–320 nm diameter mixing state of soot particles in polluted megacity air was measured at a suburban site (Yufa during the CAREBeijing 2006 campaign in Beijing, using a volatility tandem differential mobility analyzer (VTDMA. Particles in this size range with non-volatile residuals at 300 °C were considered to be soot particles. On average, the number fraction of internally mixed soot in total soot particles (Fin, decreased from 0.80 to 0.57 when initial Dp increased from 30 to 320 nm. Further analysis reveals that: (1 Fin was well correlated with the aerosol hygroscopic mixing state measured by a CCN counter. More externally mixed soot particles were observed when particles showed more heterogeneous features with regard to hygroscopicity. (2 Fin had pronounced diurnal cycles. For particles in the accumulation mode (Dp at 100–320 nm, largest Fin were observed at noon time, with "apparent" turnover rates (kex → in up to 7.8% h−1. (3 Fin was subject to competing effects of both aging and emissions. While aging increases Fin by converting externally mixed soot particles into internally mixed ones, emissions tend to reduce Fin by emitting more fresh and externally mixed soot particles. Similar competing effects were also found with air mass age indicators. (4 Under the estimated emission

  9. Soot particle size measurements in ethylene diffusion flames at elevated pressures

    KAUST Repository

    Steinmetz, Scott; Fang, Tiegang; Roberts, William L.

    2016-01-01

    for the first time at elevated pressures. Soot volume fraction dependence on pressure is consistent with the observations of similar studies, scaling approximately with the square of pressure. Scattering intensity is analyzed through Rayleigh and Rayleigh

  10. Smog chamber study on aging of combustion soot in isoprene/SO2/NOx system: Changes of mass, size, effective density, morphology and mixing state

    Science.gov (United States)

    Li, Kangwei; Chen, Linghong; Han, Ke; Lv, Biao; Bao, Kaiji; Wu, Xuecheng; Gao, Xiang; Cen, Kefa

    2017-02-01

    Atmospheric soot aging process is always accompanied by secondary particle formation, which is a comprehensive environmental issue that deserves great attention. On one hand, aging of primary soot could change its own physicochemical properties; on the other hand, complex air pollution caused by pollutant emission from various sources (e.g., vehicle exhausts, coal-fired flue gases and biogenic VOCs emission) may contribute to secondary particle formation onto primary particle surface. In this study, aging of combustion soot in isoprene/SO2/NOx system was investigated under controlled laboratory conditions in several smog chamber experiments. During the evolution of soot, several physical properties such as mass, size, effective density, morphology and mixing state were determined simultaneously by an integrated aerosol analytical system of Scanning Mobility Particle Sizer (SMPS), Differential Mobility Analyzer-Aerosol Particle Mass Analyzer-Condensation Particle Counter (DMA-APM-CPC) and Transmission Electron Microscopy coupled with Energy-dispersive X-ray Spectrometry (TEM/EDX) techniques. Here, based on the experimental results of soot aging under different gas-phase composition and relative humidity (RH), we firstly proposed possible aging pathways of soot in isoprene/SO2/NOx system. A synergetic effect was speculated to exist between SO2 and isoprene on soot aging process, which led to more secondary particle formation. At the same time, TEM/EDX analysis showed that a competitive mechanism between H2SO4(g) and isoprene oxidation vapor may exist: H2SO4(g) firstly condensed onto fresh soot, then an acceleration of isoprene oxidation products formed onto H2SO4 pre-coated soot. In isoprene/SO2/NOx system, high RH conditions could contribute to soot aging and new particle formation. The changes of effective density and dynamic shape factor of soot also indicated that high RH conditions could accelerate soot aging process, and led chain-like soot into more spherical

  11. Characterization of Diesel Soot Aggregates by Scattering and Extinction Methods

    Science.gov (United States)

    Kamimoto, Takeyuki

    2006-07-01

    Characteristics of diesel soot particles sampled from diesel exhaust of a common-rail turbo-charged diesel engine are quantified by scattering and extinction diagnostics using newly build two laser-based instruments. The radius of gyration representing the aggregates size is measured by the angular distribution of scattering intensity, while the soot mass concentration is measured by a two-wavelength extinction method. An approach to estimate the refractive index of diesel soot by an analysis of the extinction and scattering data using an aggregates scattering theory is proposed.

  12. Characterization of Diesel Soot Aggregates by Scattering and Extinction Methods

    International Nuclear Information System (INIS)

    Kamimoto, Takeyuki

    2006-01-01

    Characteristics of diesel soot particles sampled from diesel exhaust of a common-rail turbo-charged diesel engine are quantified by scattering and extinction diagnostics using newly build two laser-based instruments. The radius of gyration representing the aggregates size is measured by the angular distribution of scattering intensity, while the soot mass concentration is measured by a two-wavelength extinction method. An approach to estimate the refractive index of diesel soot by an analysis of the extinction and scattering data using an aggregates scattering theory is proposed

  13. Aerosol Size Distributions In Auckland.

    Czech Academy of Sciences Publication Activity Database

    Coulson, G.; Olivares, G.; Talbot, Nicholas

    2016-01-01

    Roč. 50, č. 1 (2016), s. 23-28 E-ISSN 1836-5876 Institutional support: RVO:67985858 Keywords : aerosol size distribution * particle number concentration * roadside Subject RIV: CF - Physical ; Theoretical Chemistry

  14. Effect of Morphology and Composition on the Hygroscopicity of Soot Aerosols

    Science.gov (United States)

    Williams, L.; Slowik, J.; Davidovits, P.; Jayne, J.; Kolb, C.; Worsnop, D.; Rudich, Y.

    2003-12-01

    Freshly generated soot aerosols are initially hydrophobic and unlikely to act as cloud condensation nuclei (CCN). However, during combustion many low vapor pressure gas products are formed that may then condense on existing soot aerosols. Additionally, soot particles may acquire coatings as they age, such as acids, salts, and oxygenated organics. An understanding of this aging process and its effect on soot hygroscopicity is necessary to address the potential of soot to act as a CCN. The transformation of soot from hydrophobic to hydrophilic is the focus of this work. An aim here is to determine the minimum coating required for hygroscopic growth. Soot particles produced by combustion of mixtures of fuel and air are size selected by a Differential Mobility Analyzer (DMA) and entrained in a laminar flow passing through a flow tube. The size selected soot particles are mixed with a controlled amount of the gas phase precursors to produce the coatings to be studied. Initial studies are focused on coatings of H2SO4, NH4NO3, and selected organics. The number of particles per unit volume of air is counted by a Condensation Particle Counter (CPC) and the particles are isokinetically sampled into an Aerosol Mass Spectrometer (AMS). Two distinct types of soot aerosols have been observed depending on the type of fuel and air mixture. With soot produced by the combustion of propane and air, the AMS shows a polydisperse particle size distribution with aerodynamic diameters ranging from 100 nm to 400 nm. The aerodynamic diameter is linearly related to the DMA-determined mobility diameter with the product density x shape factor = 1.2. The organic molecules in this soot are mostly PAH compounds. However, when kerosene is added to the propane flame, the soot particle morphology and composition is strikingly altered. While the DMA shows an essentially unchanged mobility diameter distribution, in the range 100 nm to 400, aerodynamic particle diameter is constant at about 100 nm

  15. Effects of self-absorption on simultaneous estimation of temperature distribution and concentration fields of soot and metal-oxide nanoparticles in nanofluid fuel flames using a spectrometer

    Science.gov (United States)

    Liu, Guannan; Liu, Dong

    2018-06-01

    An improved inverse reconstruction model with consideration of self-absorption effect for the temperature distribution and concentration fields of soot and metal-oxide nanoparticles in nanofluid fuel flames was proposed based on the flame emission spectrometry. The effects of self-absorption on the temperature profile and concentration fields were investigated for various measurement errors, flame optical thicknesses and detecting lines numbers. The model neglecting the self-absorption caused serious reconstruction errors especially in the nanofluid fuel flames with large optical thicknesses, while the improved model was used to successfully recover the temperature distribution and concentration fields of soot and metal-oxide nanoparticles for the flames regardless of the optical thickness. Through increasing detecting lines number, the reconstruction accuracy can be greatly improved due to more flame emission information received by the spectrometer. With the adequate detecting lines number, the estimations for the temperature distribution and concentration fields of soot and metal-oxide nanoparticles in flames with large optical thicknesses were still satisfying even from the noisy radiation intensities with signal to noise ratio (SNR) as low as 46 dB. The results showed that the improved reconstruction model was effective and robust to concurrently retrieve the temperature distribution and volume fraction fields of soot and metal-oxide nanoparticles for the exact and noisy data in nanofluid fuel sooting flames with different optical thicknesses.

  16. Investigation of soot morphology and particle size distrib ution in a turbulent nonpremixed flame via Monte Carlo simulations

    KAUST Repository

    Abdelgadir, Ahmed; Lucchesi, Marco; Attili, Antonio; Bisetti, Fabrizio

    2015-01-01

    the soot evolution along selected Lagrangian trajectories using a Monte Carlo method. An operator splitting approach is adopted to split the deterministic processes (nucleation, surface growth and oxidation) from coagulation, which is treated stochastically

  17. Physical and chemical comparison of soot in hydrocarbon and biodiesel fuel diffusion flames: A study of model and commercial fuels

    Energy Technology Data Exchange (ETDEWEB)

    Matti Maricq, M. [Research and Advanced Engineering, Ford Motor Company, Dearborn, MI (United States)

    2011-01-15

    Data are presented to compare soot formation in both surrogate and practical fatty acid methyl ester biodiesel and petroleum fuel diffusion flames. The approach here uses differential mobility analysis to follow the size distributions and electrical charge of soot particles as they evolve in the flame, and laser ablation particle mass spectrometry to elucidate their composition. Qualitatively, these soot properties exhibit a remarkably similar development along the flames. The size distributions begin as a single mode of precursor nanoparticles, evolve through a bimodal phase marking the onset of aggregate formation, and end in a self preserving mode of fractal-like particles. Both biodiesel and hydrocarbon fuels yield a common soot composition dominated by C{sub x}H{sub y}{sup +} ions, stabilomer PAHs, and fullerenes in the positive ion mass spectrum, and C{sub x}{sup -} and C{sub 2x}H{sup -} in the negative ion spectrum. These ion intensities initially grow with height in the diffusion flames, but then decline during later stages, consistent with soot carbonization. There are important quantitative differences between fuels. The surrogate biodiesel fuel methyl butanoate substantially reduces soot levels, but soot formation and evolution in this flame are delayed relative to both soy and petroleum fuels. In contrast, soots from soy and hexadecane flames exhibit nearly quantitative agreement in their size distribution and composition profiles with height, suggesting similar soot precursor chemistry. (author)

  18. Determination of size distribution function

    International Nuclear Information System (INIS)

    Teshome, A.; Spartakove, A.

    1987-05-01

    The theory of a method is outlined which gives the size distribution function (SDF) of a polydispersed system of non-interacting colloidal and microscopic spherical particles, having sizes in the range 0-10 -5 cm., from a gedanken experimental scheme. It is assumed that the SDF is differentiable and the result is obtained for rotational frequency in the order of 10 3 (sec) -1 . The method may be used independently, but is particularly useful in conjunction with an alternate method described in a preceding paper. (author). 8 refs, 2 figs

  19. Primary and Aggregate Size Distributions of PM in Tail Pipe Emissions form Diesel Engines

    Science.gov (United States)

    Arai, Masataka; Amagai, Kenji; Nakaji, Takayuki; Hayashi, Shinji

    Particulate matter (PM) emission exhausted from diesel engine should be reduced to keep the clean air environment. PM emission was considered that it consisted of coarse and aggregate particles, and nuclei-mode particles of which diameter was less than 50nm. However the detail characteristics about these particles of the PM were still unknown and they were needed for more physically accurate measurement and more effective reduction of exhaust PM emission. In this study, the size distributions of solid particles in PM emission were reported. PMs in the tail-pipe emission were sampled from three type diesel engines. Sampled PM was chemically treated to separate the solid carbon fraction from other fractions such as soluble organic fraction (SOF). The electron microscopic and optical-manual size measurement procedures were used to determine the size distribution of primary particles those were formed through coagulation process from nuclei-mode particles and consisted in aggregate particles. The centrifugal sedimentation method was applied to measure the Stokes diameter of dry-soot. Aerodynamic diameters of nano and aggregate particles were measured with scanning mobility particle sizer (SMPS). The peak aggregate diameters detected by SMPS were fallen in the same size regime as the Stokes diameter of dry-soot. Both of primary and Stokes diameters of dry-soot decreased with increases of engine speed and excess air ratio. Also, the effects of fuel properties and engine types on primary and aggregate particle diameters were discussed.

  20. Soot particulate size characterisation in a heavy-duty diesel engine for different engine loads by laser-induced incandescence

    NARCIS (Netherlands)

    Bougie, B.; Ganippa, L.C.; Vliet, van A.P.; Meerts, W.L.; Dam, N.J.; Meulen, ter J.J.

    2007-01-01

    Time-resolved laser-induced incandescence was used to estimate primary particle size distributions inside the combustion chamber of a heavy-duty diesel engine as a function of the crank angle, for two different engine loads at two different probe locations. Assuming a log-normal particle size

  1. Numerical Investigation of Soot Formation in Non-premixed Flames

    KAUST Repository

    Abdelgadir, Ahmed Gamaleldin

    2017-05-01

    Soot is a carbon particulate formed as a result of the combustion of fossil fuels. Due to the health hazard posed by the carbon particulate, government agencies have applied strict regulations to control soot emissions from road vehicles, airplanes, and industrial plants. Thus, understanding soot formation and evolution is critical. Practical combustion devices operate at high pressure and in the turbulent regime. Elevated pressures and turbulence on soot formation significantly and fundamental understanding of these complex interactions is still poor. In this study, the effects of pressure and turbulence on soot formation and growth are investigated numerically. As the first step, the evolution of the particle size distribution function (PSDF) and soot particles morphology are investigated in turbulent non-premixed flames. A Direct Simulation Monte Carlo (DSMC) code is developed and used. The stochastic reactor describes the evolution of soot in fluid parcels following Lagrangian trajectories in a turbulent flow field. The trajectories are sampled from a Direct Numerical Simulation (DNS) of an n-heptane turbulent non-premixed flame. Although individual trajectories display strong bimodality as in laminar flames, the ensemble-average PSDF possesses only one mode and a broad tail, which implies significant polydispersity induced by turbulence. Secondly, the effect of the flow and mixing fields on soot formation at atmospheric and elevated pressures is investigated in coflow laminar diffusion flames. The experimental observation and the numerical prediction of the spatial distribution are in good agreement. Based on the common scaling methodology of the flames (keeping the Reynolds number constant), the scalar dissipation rate decreases as pressure increases, promoting the formation of PAH species and soot. The decrease of the scalar dissipation rate significantly contributes to soot formation occurring closer to the nozzle and outward on the flames wings as pressure

  2. Soot particles at an elevated site in eastern China during the passage of a strong cyclone

    Energy Technology Data Exchange (ETDEWEB)

    Niu, Hongya [State Key Laboratory of Coal Resources and Safe Mining, School of Geoscience and Surveying Engineering, China University of Mining and Technology, Beijing 100083 (China); Faculty of Environmental and Symbiotic Sciences, Prefectural University of Kumamoto, Kumamoto 862-8502 (Japan); Shao, Longyi [State Key Laboratory of Coal Resources and Safe Mining, School of Geoscience and Surveying Engineering, China University of Mining and Technology, Beijing 100083 (China); Zhang, Daizhou, E-mail: dzzhang@pu-kumamoto.ac.jp [Faculty of Environmental and Symbiotic Sciences, Prefectural University of Kumamoto, Kumamoto 862-8502 (Japan)

    2012-07-15

    Atmospheric particles larger than 0.2 {mu}m were collected at the top of Mt. Tai (36.25 Degree-Sign N, 117.10 Degree-Sign E, 1534 m a.s.l.) in eastern China in May 2008 during the passage of a strong cyclone. The particles were analyzed with electron microscopes and characterized by morphology, equivalent diameter and elemental composition. Soot particles with coating (coated soot particles) and those without apparent coating (naked soot particles) were predominant in the diameter range smaller than 0.6 {mu}m in all samples. The number-size distribution of the relative abundance of naked soot particles in the prefrontal air was similar to that in the postfrontal air and their size modes were around 0.2-0.3 {mu}m. However, the distribution of inclusions of coated soot particles showed a mode in the range of 0.1-0.3 {mu}m. The coating degree of coated soot particles, which was defined by the ratio of the diameter of inclusion to the diameter of particle body, showed a mode around 0.5 with the range of 0.3-0.6. These results indicate that the status of soot particles in the prefrontal and postfrontal air was similar although air pollution levels were dramatically different. In addition, the relative abundance of accumulation mode particles increased with the decrease of soot particles after the front passage. - Highlights: Black-Right-Pointing-Pointer Particles at an elevated site in eastern China in a strong cyclone were studied. Black-Right-Pointing-Pointer Aged status of soot particles in the prefrontal and postfrontal air was similar. Black-Right-Pointing-Pointer Soot particles in elevated layers could be considered as aged ones.

  3. Quantitative characterization of steady and time-varying, sooting, laminar diffusion flames using optical techniques

    Science.gov (United States)

    Connelly, Blair C.

    In order to reduce the emission of pollutants such as soot and NO x from combustion systems, a detailed understanding of pollutant formation is required. In addition to environmental concerns, this is important for a fundamental understanding of flame behavior as significant quantities of soot lower local flame temperatures, increase overall flame length and affect the formation of such temperature-dependent species as NOx. This problem is investigated by carrying out coupled computational and experimental studies of steady and time-varying sooting, coflow diffusion flames. Optical diagnostic techniques are a powerful tool for characterizing combustion systems, as they provide a noninvasive method of probing the environment. Laser diagnostic techniques have added advantages, as systems can be probed with high spectral, temporal and spatial resolution, and with species selectivity. Experimental soot volume fractions were determined by using two-dimensional laser-induced incandescence (LII), calibrated with an on-line extinction measurement, and soot pyrometry. Measurements of soot particle size distributions are made using time-resolved LII (TR-LII). Laser-induced fluorescence measurements are made of NO and formaldehyde. These experimental measurements, and others, are compared with computational results in an effort to understand and model soot formation and to examine the coupled relationship of soot and NO x formation.

  4. Effect of Drive Cycle and Gasoline Particulate Filter on the Size and Morphology of Soot Particles Emitted from a Gasoline-Direct-Injection Vehicle.

    Science.gov (United States)

    Saffaripour, Meghdad; Chan, Tak W; Liu, Fengshan; Thomson, Kevin A; Smallwood, Gregory J; Kubsh, Joseph; Brezny, Rasto

    2015-10-06

    The size and morphology of particulate matter emitted from a light-duty gasoline-direct-injection (GDI) vehicle, over the FTP-75 and US06 transient drive cycles, have been characterized by transmission-electron-microscope (TEM) image analysis. To investigate the impact of gasoline particulate filters on particulate-matter emission, the results for the stock-GDI vehicle, that is, the vehicle in its original configuration, have been compared to the results for the same vehicle equipped with a catalyzed gasoline particulate filter (GPF). The stock-GDI vehicle emits graphitized fractal-like aggregates over all driving conditions. The mean projected area-equivalent diameter of these aggregates is in the 78.4-88.4 nm range and the mean diameter of primary particles varies between 24.6 and 26.6 nm. Post-GPF particles emitted over the US06 cycle appear to have an amorphous structure, and a large number of nucleation-mode particles, depicted as low-contrast ultrafine droplets, are observed in TEM images. This indicates the emission of a substantial amount of semivolatile material during the US06 cycle, most likely generated by the incomplete combustion of accumulated soot in the GPF during regeneration. The size of primary particles and soot aggregates does not vary significantly by implementing the GPF over the FTP-75 cycle; however, particles emitted by the GPF-equipped vehicle over the US06 cycle are about 20% larger than those emitted by the stock-GDI vehicle. This may be attributed to condensation of large amounts of organic material on soot aggregates. High-contrast spots, most likely solid nonvolatile cores, are observed within many of the nucleation-mode particles emitted over the US06 cycle by the GPF-equipped vehicle. These cores are either generated inside the engine or depict incipient soot particles which are partially carbonized in the exhaust line. The effect of drive cycle and the GPF on the fractal parameters of particles, such as fractal dimension and

  5. Soot and radiation in combusting boundary layers

    Energy Technology Data Exchange (ETDEWEB)

    Beier, R.A.

    1981-12-01

    In most fires thermal radiation is the dominant mode of heat transfer. Carbon particles within the fire are responsible for most of this emitted radiation and hence warrant quantification. As a first step toward understanding thermal radiation in full scale fires, an experimental and theoretical study is presented for a laminar combusting boundary layer. Carbon particulate volume fraction profiles and approximate particle size distributions are experimentally determined in both free and forced flow for several hydrocarbon fuels and PMMA (polymethylmethacrylate). A multiwavelength laser transmission technique determines a most probable radius and a total particle concentration which are two unknown parameters in an assumed Gauss size distribution. A sooting region is observed on the fuel rich side of the main reaction zone. For free flow, all the flames are in air, but the free stream ambient oxygen mass fraction is a variable in forced flow. To study the effects of radiation heat transfer, a model is developed for a laminar combusting boundary layer over a pyrolyzing fuel surface. An optically thin approximation simplifies the calculation of the radiant energy flux at the fuel surface. For the free flames in air, the liquid fuel soot volume fractions, f/sub v/, range from f/sub v/ approx. 10/sup -7/ for n-heptane, a paraffin, to f/sub v/ approx. 10/sup -7/ for toluene, an aromatic. The PMMA soot volume fractions, f/sub v/ approx. 5 x 10/sup -7/, are approximately the same as the values previously reported for pool fires. Soot volume fraction increases monotonically with ambient oxygen mass fraction in the forced flow flames. For all fuels tested, a most probable radius between 20 nm and 80 nm is obtained which varies only slightly with oxygen mass fraction, streamwise position, or distance normal to the fuel surface. The theoretical analysis yields nine dimensionless parameters, which control the mass flux rate at the pyrolyzing fuel surface.

  6. Developing a predictive model for the chemical composition of soot nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Violi, Angela [Univ. of Michigan, Ann Arbor, MI (United States); Michelsen, Hope [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Hansen, Nils [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Wilson, Kevin [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2017-04-07

    In order to provide the scientific foundation to enable technology breakthroughs in transportation fuel, it is important to develop a combustion modeling capability to optimize the operation and design of evolving fuels in advanced engines for transportation applications. The goal of this proposal is to develop a validated predictive model to describe the chemical composition of soot nanoparticles in premixed and diffusion flames. Atomistic studies in conjunction with state-of-the-art experiments are the distinguishing characteristics of this unique interdisciplinary effort. The modeling effort has been conducted at the University of Michigan by Prof. A. Violi. The experimental work has entailed a series of studies using different techniques to analyze gas-phase soot precursor chemistry and soot particle production in premixed and diffusion flames. Measurements have provided spatial distributions of polycyclic aromatic hydrocarbons and other gas-phase species and size and composition of incipient soot nanoparticles for comparison with model results. The experimental team includes Dr. N. Hansen and H. Michelsen at Sandia National Labs' Combustion Research Facility, and Dr. K. Wilson as collaborator at Lawrence Berkeley National Lab's Advanced Light Source. Our results show that the chemical and physical properties of nanoparticles affect the coagulation behavior in soot formation, and our results on an experimentally validated, predictive model for the chemical composition of soot nanoparticles will not only enhance our understanding of soot formation since but will also allow the prediction of particle size distributions under combustion conditions. These results provide a novel description of soot formation based on physical and chemical properties of the particles for use in the next generation of soot models and an enhanced capability for facilitating the design of alternative fuels and the engines they will power.

  7. Empirical soot formation and oxidation model

    Directory of Open Access Journals (Sweden)

    Boussouara Karima

    2009-01-01

    Full Text Available Modelling internal combustion engines can be made following different approaches, depending on the type of problem to be simulated. A diesel combustion model has been developed and implemented in a full cycle simulation of a combustion, model accounts for transient fuel spray evolution, fuel-air mixing, ignition, combustion, and soot pollutant formation. The models of turbulent combustion of diffusion flame, apply to diffusion flames, which one meets in industry, typically in the diesel engines particulate emission represents one of the most deleterious pollutants generated during diesel combustion. Stringent standards on particulate emission along with specific emphasis on size of emitted particulates have resulted in increased interest in fundamental understanding of the mechanisms of soot particulate formation and oxidation in internal combustion engines. A phenomenological numerical model which can predict the particle size distribution of the soot emitted will be very useful in explaining the above observed results and will also be of use to develop better particulate control techniques. A diesel engine chosen for simulation is a version of the Caterpillar 3406. We are interested in employing a standard finite-volume computational fluid dynamics code, KIVA3V-RELEASE2.

  8. Experimental determination of soot refractive index in the infrared

    International Nuclear Information System (INIS)

    Ouf, F.X.; Vendel, J.; Ouf, F.X.; Coppalle, A.; Weil, M.E.; Yon, J.

    2007-01-01

    The study of physical properties of soot particles produced during combustion is a complex subject but of a great interest within the framework of the study of the safety of an installation, with respect to the fire hazard. These characteristics are, in this case, particularly useful in order to predict the behaviour of containment barriers in situation of fire, but also in order to estimate the contribution of these particles to radiative transfers. The aim of this study is to determine the radiative properties of soot particles produced during combustion. A specific device, which establishes extinction and vertical-vertical scattering coefficients, has been developed and has allowed to determine the refractive index of soot particles in the infrared. This determination also needed the establishment of size distribution and morphological properties of soot aggregates. We present in this document the experimental device developed, and the validation of this device on latex spheres which optical properties are well known. First results of extinction coefficients will be presented and will underline the similar optical behaviour of different soot aggregates. Values of refractive index will be detailed and discussed, and a direct application of these values will be carried out in order to determine the soot volume fraction. A comparison with reference method will underline the efficiency of our method. We will conclude on the validity of the information brought by this device and on the prospects of this study. A discussion is included, on the utility of mean values of refractive index and on the determination of total emissivity of soot particles. (authors)

  9. Body Size Distribution of the Dinosaurs

    OpenAIRE

    O?Gorman, Eoin J.; Hone, David W. E.

    2012-01-01

    The distribution of species body size is critically important for determining resource use within a group or clade. It is widely known that non-avian dinosaurs were the largest creatures to roam the Earth. There is, however, little understanding of how maximum species body size was distributed among the dinosaurs. Do they share a similar distribution to modern day vertebrate groups in spite of their large size, or did they exhibit fundamentally different distributions due to unique evolutiona...

  10. Morphological study of fluorescent carbon Nanoparticles (F-CNPs) from ground coffee waste soot oxidation by diluted acid

    Science.gov (United States)

    Gea, S.; Tjandra, S.; Joshua, J.; Wirjosentono, B.

    2018-02-01

    Coffee ground waste utilization for fluorescent carbon nanoparticles (F-CNPs) through soot oxidation with diluted HNO3 has been conducted. Soot was obtained through three different treatments to coffee ground waste; which was burned in furnaceat 550°C and 650°C and directly burned in a heat-proofcontainer. Then they were analyzed morphologically with Scanning Electron Microscope (SEM) instrument. Soot from direct burning indicated the optimum result where it has denser pores compared to other two soots. Soot obtained from direct burning was refluxed in diluted HNO3 for 12 hours to perform the oxidation. Yellowish brown supernatant was later observed which lead to green fluorescent under the UV light. F-CNPs characterization was done in Transmission Electron Microscopy, which showed that 7.4-23.4 nm of particle size were distributed.

  11. Numerical investigation on soot particles emission in compression ignition diesel engine by using particulate mimic soot model

    Directory of Open Access Journals (Sweden)

    Ibrahim Fadzli

    2017-01-01

    Full Text Available Research via computational method, specifically by detailed-kinetic soot model offers much more advantages than the simple model as more detailed formation/oxidation process is taken into consideration, thus providing better soot mass concentration, soot size, soot number density as well as information regarding other related species. In the present computational study, investigation of in-cylinder soot concentration as well as other emissions in a single cylinder diesel engine has been conducted, using a commercial multidimensional CFD software, CONVERGE CFD. The simulation was carried out for a close-cycle combustion environment from inlet valve closing (IVC to exhaust valve opening (EVO. In this case, detailed-kinetic Particulate Mimic (PM soot model was implemented as to take benefit of the method of moment, instead of commonly implemented simple soot model. Analyses of the results are successfully plotted to demonstrate that the soot size and soot mass concentration are strongly dependent on the detailed soot formation and oxidation process rates. The calculated of soot mass concentration and average soot size at EVO provide the end value of 29.2 mg/m3 and 2.04 × 10−8 m, respectively. Besides, post-processing using EnSight shows the qualitative results of soot concentration along simulation period in the combustion chamber.

  12. Numerical simulation of combustion and soot under partially premixed combustion of low-octane gasoline

    KAUST Repository

    An, Yanzhao

    2017-09-23

    In-cylinder combustion visualization and engine-out soot particle emissions were investigated in an optical diesel engine fueled with low octane gasoline. Single injection strategy with an early injection timing (−30 CAD aTDC) was employed to achieve partially premixed combustion (PPC) condition. A high-speed color camera was used to record the combustion images for 150 cycles. The regulated emission of carbon dioxide, carbon monoxide, nitrogen oxides and soot mass concentration were measured experimentally. Full cycle engine simulations were performed using CONVERGE™ and the simulation results matched with the experimental results. The in-cylinder soot particle evolution was performed by coupling a reduced toluene reference fuel mechanism including the PAHs formation/oxidation reactions with particulate size mimic model. The results showed that PPC presents typical stratified combustion characteristics, which is significantly different from the conventional diesel spray-driven combustion. The in-cylinder temperature and equivalence ratio overlaid with soot-NO formation regime revealed that PPC operating condition under study mostly avoided the main sooting conditions throughout the entire combustion. The evaluation of temperature distribution showed formaldehyde could be regarded as an indicator for low temperature reactions, while hydroxyl group represents the high temperature reactions. Soot evolution happened during the combustion process, hydroxyl radicals promoted the soot oxidation.

  13. Numerical simulation of combustion and soot under partially premixed combustion of low-octane gasoline

    KAUST Repository

    An, Yanzhao; Jaasim, Mohammed; Vallinayagam, R.; Vedharaj, S.; Im, Hong G.; Johansson, Bengt.

    2017-01-01

    In-cylinder combustion visualization and engine-out soot particle emissions were investigated in an optical diesel engine fueled with low octane gasoline. Single injection strategy with an early injection timing (−30 CAD aTDC) was employed to achieve partially premixed combustion (PPC) condition. A high-speed color camera was used to record the combustion images for 150 cycles. The regulated emission of carbon dioxide, carbon monoxide, nitrogen oxides and soot mass concentration were measured experimentally. Full cycle engine simulations were performed using CONVERGE™ and the simulation results matched with the experimental results. The in-cylinder soot particle evolution was performed by coupling a reduced toluene reference fuel mechanism including the PAHs formation/oxidation reactions with particulate size mimic model. The results showed that PPC presents typical stratified combustion characteristics, which is significantly different from the conventional diesel spray-driven combustion. The in-cylinder temperature and equivalence ratio overlaid with soot-NO formation regime revealed that PPC operating condition under study mostly avoided the main sooting conditions throughout the entire combustion. The evaluation of temperature distribution showed formaldehyde could be regarded as an indicator for low temperature reactions, while hydroxyl group represents the high temperature reactions. Soot evolution happened during the combustion process, hydroxyl radicals promoted the soot oxidation.

  14. Aerosol and NOx emission factors and submicron particle number size distributions in two road tunnels with different traffic regimes

    Directory of Open Access Journals (Sweden)

    D. Imhof

    2006-01-01

    Full Text Available Measurements of aerosol particle number size distributions (18–700 nm, mass concentrations (PM2.5 and PM10 and NOx were performed in the Plabutsch tunnel, Austria, and in the Kingsway tunnel, United Kingdom. These two tunnels show different characteristics regarding the roadway gradient, the composition of the vehicle fleet and the traffic frequency. The submicron particle size distributions contained a soot mode in the diameter range D=80–100 nm and a nucleation mode in the range of D=20–40 nm. In the Kingsway tunnel with a significantly lower particle number and volume concentration level than in the Plabutsch tunnel, a clear diurnal variation of nucleation and soot mode particles correlated to the traffic density was observed. In the Plabutsch tunnel, soot mode particles also revealed a diurnal variation, whereas no substantial variation was found for the nucleation mode particles. During the night a higher number concentration of nucleation mode particles were measured than soot mode particles and vice versa during the day. In this tunnel with very high soot emissions during daytime due to the heavy-duty vehicle (HDV share of 18% and another 40% of diesel driven light-duty vehicles (LDV semivolatile species condense on the pre-existing soot surface area rather than forming new particles by homogeneous nucleation. With the low concentration of soot mode particles in the Kingsway tunnel, also the nucleation mode particles exhibit a diurnal variation. From the measured parameters real-world traffic emission factors were estimated for the whole vehicle fleet as well as differentiated into the two categories LDV and HDV. In the particle size range D=18–700 nm, each vehicle of the mixed fleet emits (1.50±0.08×1014 particles km-1 (Plabutsch and (1.26±0.10×1014 particles km-1 (Kingsway, while particle volume emission factors of 0.209±0.008 cm3 km-1 and 0.036±0.004 cm3 km-1, respectively, were obtained. PM1 emission factors of 104±4 mg

  15. Body size distribution of the dinosaurs.

    Directory of Open Access Journals (Sweden)

    Eoin J O'Gorman

    Full Text Available The distribution of species body size is critically important for determining resource use within a group or clade. It is widely known that non-avian dinosaurs were the largest creatures to roam the Earth. There is, however, little understanding of how maximum species body size was distributed among the dinosaurs. Do they share a similar distribution to modern day vertebrate groups in spite of their large size, or did they exhibit fundamentally different distributions due to unique evolutionary pressures and adaptations? Here, we address this question by comparing the distribution of maximum species body size for dinosaurs to an extensive set of extant and extinct vertebrate groups. We also examine the body size distribution of dinosaurs by various sub-groups, time periods and formations. We find that dinosaurs exhibit a strong skew towards larger species, in direct contrast to modern day vertebrates. This pattern is not solely an artefact of bias in the fossil record, as demonstrated by contrasting distributions in two major extinct groups and supports the hypothesis that dinosaurs exhibited a fundamentally different life history strategy to other terrestrial vertebrates. A disparity in the size distribution of the herbivorous Ornithischia and Sauropodomorpha and the largely carnivorous Theropoda suggests that this pattern may have been a product of a divergence in evolutionary strategies: herbivorous dinosaurs rapidly evolved large size to escape predation by carnivores and maximise digestive efficiency; carnivores had sufficient resources among juvenile dinosaurs and non-dinosaurian prey to achieve optimal success at smaller body size.

  16. EFFECTS OF EFFECTS OF PARTICLE SIZE DISTRIBUTION ...

    African Journals Online (AJOL)

    eobe

    The parameters examined were: moisture content, particle size distribution, total isture content, particle size distribution, total hydrocarbon content, soil pH, available nitrogen, available phosphorus, total heterotrophic bacteria and fungi count. The analysis of the soil characteristics throughout the remediation period showed ...

  17. Body size distribution of the dinosaurs.

    Science.gov (United States)

    O'Gorman, Eoin J; Hone, David W E

    2012-01-01

    The distribution of species body size is critically important for determining resource use within a group or clade. It is widely known that non-avian dinosaurs were the largest creatures to roam the Earth. There is, however, little understanding of how maximum species body size was distributed among the dinosaurs. Do they share a similar distribution to modern day vertebrate groups in spite of their large size, or did they exhibit fundamentally different distributions due to unique evolutionary pressures and adaptations? Here, we address this question by comparing the distribution of maximum species body size for dinosaurs to an extensive set of extant and extinct vertebrate groups. We also examine the body size distribution of dinosaurs by various sub-groups, time periods and formations. We find that dinosaurs exhibit a strong skew towards larger species, in direct contrast to modern day vertebrates. This pattern is not solely an artefact of bias in the fossil record, as demonstrated by contrasting distributions in two major extinct groups and supports the hypothesis that dinosaurs exhibited a fundamentally different life history strategy to other terrestrial vertebrates. A disparity in the size distribution of the herbivorous Ornithischia and Sauropodomorpha and the largely carnivorous Theropoda suggests that this pattern may have been a product of a divergence in evolutionary strategies: herbivorous dinosaurs rapidly evolved large size to escape predation by carnivores and maximise digestive efficiency; carnivores had sufficient resources among juvenile dinosaurs and non-dinosaurian prey to achieve optimal success at smaller body size.

  18. Body Size Distribution of the Dinosaurs

    Science.gov (United States)

    O’Gorman, Eoin J.; Hone, David W. E.

    2012-01-01

    The distribution of species body size is critically important for determining resource use within a group or clade. It is widely known that non-avian dinosaurs were the largest creatures to roam the Earth. There is, however, little understanding of how maximum species body size was distributed among the dinosaurs. Do they share a similar distribution to modern day vertebrate groups in spite of their large size, or did they exhibit fundamentally different distributions due to unique evolutionary pressures and adaptations? Here, we address this question by comparing the distribution of maximum species body size for dinosaurs to an extensive set of extant and extinct vertebrate groups. We also examine the body size distribution of dinosaurs by various sub-groups, time periods and formations. We find that dinosaurs exhibit a strong skew towards larger species, in direct contrast to modern day vertebrates. This pattern is not solely an artefact of bias in the fossil record, as demonstrated by contrasting distributions in two major extinct groups and supports the hypothesis that dinosaurs exhibited a fundamentally different life history strategy to other terrestrial vertebrates. A disparity in the size distribution of the herbivorous Ornithischia and Sauropodomorpha and the largely carnivorous Theropoda suggests that this pattern may have been a product of a divergence in evolutionary strategies: herbivorous dinosaurs rapidly evolved large size to escape predation by carnivores and maximise digestive efficiency; carnivores had sufficient resources among juvenile dinosaurs and non-dinosaurian prey to achieve optimal success at smaller body size. PMID:23284818

  19. Simulation of temporal and spatial soot evolution in an automotive diesel engine using the Moss–Brookes soot model

    International Nuclear Information System (INIS)

    Pang, Kar Mun; Ng, Hoon Kiat; Gan, Suyin

    2012-01-01

    Highlights: ► Numerical models were validated against experimental data of two diesel engines. ► Soot model constant values were calibrated to predict in-cylinder soot processes. ► Effects of split-main injection parameters on soot distributions were determined. ► Soot cloud was distributed towards cylinder wall when using large dwell period. ► Greater soot deposition expected with large dwell period and retarded injection. - Abstract: In this reported work, computational study on the formation processes of soot particles from diesel combustion is conducted using an approach where Computational Fluid Dynamics (CFD) is coupled with a chemical kinetic model. A multi-step soot model which accounts for inception, surface growth, coagulation and oxidation was applied. Model constant values in the Moss–Brookes soot formation and Fenimore–Jones soot oxidation models were calibrated, and were validated against in-cylinder soot evolution and exhaust soot density of both heavy- and light-duty diesel engines, respectively. Effects of various injection parameters such as start of injection (SOI) timing, split-main ratio and dwell period of the split-main injection strategy on in-cylinder temporal/spatial soot evolution in a light-duty diesel engine were subsequently investigated. The spatial soot distributions at each crank angle degree after start of injection were found to be insensitive to the change of values in SOI and split-main ratio when close-coupled injection was implemented. Soot cloud was also observed to be distributed towards the cylinder wall when a large separation of 20° was used, even with an advanced SOI timing of −6° after top dead centre (ATDC). The use of large separation is hence not desired for this combustion system as it potentially leads to soot deposition on surface oil film and greater tailpipe soot emissions.

  20. Experimental determination of size distributions: analyzing proper sample sizes

    International Nuclear Information System (INIS)

    Buffo, A; Alopaeus, V

    2016-01-01

    The measurement of various particle size distributions is a crucial aspect for many applications in the process industry. Size distribution is often related to the final product quality, as in crystallization or polymerization. In other cases it is related to the correct evaluation of heat and mass transfer, as well as reaction rates, depending on the interfacial area between the different phases or to the assessment of yield stresses of polycrystalline metals/alloys samples. The experimental determination of such distributions often involves laborious sampling procedures and the statistical significance of the outcome is rarely investigated. In this work, we propose a novel rigorous tool, based on inferential statistics, to determine the number of samples needed to obtain reliable measurements of size distribution, according to specific requirements defined a priori. Such methodology can be adopted regardless of the measurement technique used. (paper)

  1. The investigation of soot and temperature distributions in a visualized direct injection diesel engine using laser diagnostics

    Science.gov (United States)

    Han, Yong-taek; Kim, Ki-bum; Lee, Ki-hyung

    2008-11-01

    Based upon the method of temperature calibration using the diffusion flame, the temperature and soot concentrations of the turbulent flame in a visualized diesel engine were qualitatively measured. Two different cylinder heads were used to investigate the effect of swirl ratio within the combustion chamber. From this experiment, we find that the highest flame temperature of the non-swirl head engine is approximately 2400 K and that of the swirl head engine is 2100 K. In addition, as the pressure of fuel injection increases, the in-cylinder temperature increases due to the improved combustion of a diesel engine. This experiment represented the soot quantity in the KL factor and revealed that the KL factor was high when the fuel collided with the cylinder wall. Moreover, the KL factor was also high in the area of the chamber where the temperature dropped rapidly.

  2. Particle size distribution instrument. Topical report 13

    Energy Technology Data Exchange (ETDEWEB)

    Okhuysen, W.; Gassaway, J.D.

    1995-04-01

    The development of an instrument to measure the concentration of particles in gas is described in this report. An in situ instrument was designed and constructed which sizes individual particles and counts the number of occurrences for several size classes. Although this instrument was designed to detect the size distribution of slag and seed particles generated at an experimental coal-fired magnetohydrodynamic power facility, it can be used as a nonintrusive diagnostic tool for other hostile industrial processes involving the formation and growth of particulates. Two of the techniques developed are extensions of the widely used crossed beam velocimeter, providing simultaneous measurement of the size distribution and velocity of articles.

  3. Soot Formation In Turbulent Combusting Flows

    National Research Council Canada - National Science Library

    Santoro, Robert

    1998-01-01

    .... Laser-based techniques were used to measure the soot volume fraction, particle size and number density as well as the temperature and relative concentration of hydroxyl radicals and polycyclic aromatic hydrocarbons...

  4. On the Size Distribution of Sand

    DEFF Research Database (Denmark)

    Sørensen, Michael

    2016-01-01

    A model is presented of the development of the size distribution of sand while it is transported from a source to a deposit. The model provides a possible explanation of the log-hyperbolic shape that is frequently found in unimodal grain size distributions in natural sand deposits, as pointed out......-distribution, by taking into account that individual grains do not have the same travel time from the source to the deposit. The travel time is assumed to be random so that the wear on the individual grains vary randomly. The model provides an interpretation of the parameters of the NIG-distribution, and relates the mean...

  5. Vicarious calibration of the solar reflection channels of radiometers onboard satellites through the field campaigns with measurements of refractive index and size distribution of aerosols

    Science.gov (United States)

    Arai, K.

    A comparative study on vicarious calibration for the solar reflection channels of radiometers onboard satellite through the field campaigns between with and without measurements of refractive index and size distribution of aerosols is made. In particular, it is noticed that the influence due to soot from the cars exhaust has to be care about for the test sites near by a heavy trafficked roads. It is found that the 0.1% inclusion of soot induces around 10% vicarious calibration error so that it is better to measure refractive index properly at the test site. It is found that the vicarious calibration coefficients with the field campaigns at the different test site, Ivanpah (near road) and Railroad (distant from road) shows approximately 10% discrepancy. It seems that one of the possible causes for the difference is the influence due to soot from cars exhaust.

  6. The size distributions of all Indian cities

    Science.gov (United States)

    Luckstead, Jeff; Devadoss, Stephen; Danforth, Diana

    2017-05-01

    We apply five distributions-lognormal, double-Pareto lognormal, lognormal-upper tail Pareto, Pareto tails-lognormal, and Pareto tails-lognormal with differentiability restrictions-to estimate the size distribution of all Indian cities. Since India contains numerous small cities, it is important to explicitly model the lower-tail behavior for studying the distribution of all Indian cities. Our results rigorously confirm, using both graphical and formal statistical tests, that among these five distributions, Pareto tails-lognormal is a better suited parametrization of the Indian city size data, verifying that the Indian city size distribution exhibits a strong reverse Pareto in the lower tail, lognormal in the mid-range body, and Pareto in the upper tail.

  7. The exponential age distribution and the Pareto firm size distribution

    OpenAIRE

    Coad, Alex

    2008-01-01

    Recent work drawing on data for large and small firms has shown a Pareto distribution of firm size. We mix a Gibrat-type growth process among incumbents with an exponential distribution of firm’s age, to obtain the empirical Pareto distribution.

  8. Electrometric aviation soot monitor, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to develop a highly sensitive and portable device to monitor soot particle mass distribution from aircraft engine exhaust. The proposed method is based on...

  9. A multi-probe thermophoretic soot sampling system for high-pressure diffusion flames

    Energy Technology Data Exchange (ETDEWEB)

    Vargas, Alex M.; Gülder, Ömer L. [Institute for Aerospace Studies, University of Toronto, Toronto, Ontario M3H 5T6 (Canada)

    2016-05-15

    Optical diagnostics and physical probing of the soot processes in high pressure combustion pose challenges that are not faced in atmospheric flames. One of the preferred methods of studying soot in atmospheric flames is in situ thermophoretic sampling followed by transmission electron microscopy imaging and analysis for soot sizing and morphology. The application of this method of sampling to high pressures has been held back by various operational and mechanical problems. In this work, we describe a rotating disk multi-probe thermophoretic soot sampling system, driven by a microstepping stepper motor, fitted into a high-pressure chamber capable of producing sooting laminar diffusion flames up to 100 atm. Innovative aspects of the sampling system design include an easy and precise control of the sampling time down to 2.6 ms, avoidance of the drawbacks of the pneumatic drivers used in conventional thermophoretic sampling systems, and the capability to collect ten consecutive samples in a single experimental run. Proof of principle experiments were performed using this system in a laminar diffusion flame of methane, and primary soot diameter distributions at various pressures up to 10 atm were determined. High-speed images of the flame during thermophoretic sampling were recorded to assess the influence of probe intrusion on the flow field of the flame.

  10. Development of high fidelity soot aerosol dynamics models using method of moments with interpolative closure

    KAUST Repository

    Roy, Subrata P.

    2014-01-28

    The method of moments with interpolative closure (MOMIC) for soot formation and growth provides a detailed modeling framework maintaining a good balance in generality, accuracy, robustness, and computational efficiency. This study presents several computational issues in the development and implementation of the MOMIC-based soot modeling for direct numerical simulations (DNS). The issues of concern include a wide dynamic range of numbers, choice of normalization, high effective Schmidt number of soot particles, and realizability of the soot particle size distribution function (PSDF). These problems are not unique to DNS, but they are often exacerbated by the high-order numerical schemes used in DNS. Four specific issues are discussed in this article: the treatment of soot diffusion, choice of interpolation scheme for MOMIC, an approach to deal with strongly oxidizing environments, and realizability of the PSDF. General, robust, and stable approaches are sought to address these issues, minimizing the use of ad hoc treatments such as clipping. The solutions proposed and demonstrated here are being applied to generate new physical insight into complex turbulence-chemistry-soot-radiation interactions in turbulent reacting flows using DNS. © 2014 Copyright Taylor and Francis Group, LLC.

  11. A comparison of chemical structures of soot precursor nanoparticles from liquid fuel combustion in flames and engine

    International Nuclear Information System (INIS)

    Paul, Bireswar; Datta, Amitava; Datta, Aparna; Saha, Abhijit

    2013-01-01

    A comparative study of the chemical structures of soot precursor nanoparticles from the liquid fuel flame and engine exhaust has been performed in this work to establish an association between the particles from both the sources. Different ex-situ measurement techniques have been used to characterize the nanoparticles in samples collected from the laboratory petrol/air and iso-octane/air flames, as well as from a gasoline engine. The TEM images of the sampled material along with the EDS spectra corroborate the existence of carbonaceous nanoparticles. The nature of the UV absorption and fluorescence spectra of the samples from the iso-octane flame environment further confirms the sampled materials to be soot precursor nanoparticles. The DLS size distribution of the particles shows them to be below 10 nm size. FTIR spectrum of the precursor nanoparticles collected form the non-sooting zone of the flame and that of fully grown soot particles show few similarities and dissimilarities among them. The soot particles are found to be much more aromatized as compared to its precursor nanoparticles. The presence of carbonyl functional group (C=O) at around 1,720 cm −1 has been observed in soot precursor nanoparticles, while such oxygenated functional groups are not prominent in soot structure. The absorption (UV and IR) and fluorescence spectra of the carbonaceous material collected from the gasoline engine exhaust show many resemblances with those of soot precursor nanoparticles from flames. These spectroscopic resemblances of the soot precursor nanoparticles from the flame environment and engine exhaust gives the evidence that the in-cylinder combustion is the source of these particles in the engine exhaust.

  12. Fragmentation and bond strength of airborne diesel soot agglomerates

    Directory of Open Access Journals (Sweden)

    Messerer Armin

    2008-06-01

    Full Text Available Abstract Background The potential of diesel soot aerosol particles to break up into smaller units under mechanical stress was investigated by a direct impaction technique which measures the degree of fragmentation of individual agglomerates vs. impact energy. Diesel aerosol was generated by an idling diesel engine used for passenger vehicles. Both the aerosol emitted directly and aerosol that had undergone additional growth by Brownian coagulation ("aging" was investigated. Optionally a thermo-desoption technique at 280°C was used to remove all high-volatility and the majority of low-volatility HC adsorbates from the aerosol before aging. Results It was found that the primary soot agglomerates emitted directly from the engine could not be fragmented at all. Soot agglomerates permitted to grow additionally by Brownian coagulation of the primary emitted particles could be fragmented to a maximum of 75% and 60% respectively, depending on whether adsorbates were removed from their surface prior to aging or not. At most, these aged agglomerates could be broken down to roughly the size of the agglomerates from the primary emission. The energy required for a 50% fragmentation probability of all bonds within an agglomerate was reduced by roughly a factor of 2 when aging "dry" agglomerates. Average bond energies derived from the data were 0.52*10-16 and 1.2*10-16 J, respectively. This is about 2 orders of magnitude higher than estimates for pure van-der-Waals agglomerates, but agrees quite well with other observations. Conclusion Although direct conclusions regarding the behavior of inhaled diesel aerosol in contact with body fluids cannot be drawn from such measurements, the results imply that highly agglomerated soot aerosol particles are unlikely to break up into units smaller than roughly the size distribution emitted as tail pipe soot.

  13. Fragmentation and bond strength of airborne diesel soot agglomerates

    Science.gov (United States)

    Rothenbacher, Sonja; Messerer, Armin; Kasper, Gerhard

    2008-01-01

    Background The potential of diesel soot aerosol particles to break up into smaller units under mechanical stress was investigated by a direct impaction technique which measures the degree of fragmentation of individual agglomerates vs. impact energy. Diesel aerosol was generated by an idling diesel engine used for passenger vehicles. Both the aerosol emitted directly and aerosol that had undergone additional growth by Brownian coagulation ("aging") was investigated. Optionally a thermo-desoption technique at 280°C was used to remove all high-volatility and the majority of low-volatility HC adsorbates from the aerosol before aging. Results It was found that the primary soot agglomerates emitted directly from the engine could not be fragmented at all. Soot agglomerates permitted to grow additionally by Brownian coagulation of the primary emitted particles could be fragmented to a maximum of 75% and 60% respectively, depending on whether adsorbates were removed from their surface prior to aging or not. At most, these aged agglomerates could be broken down to roughly the size of the agglomerates from the primary emission. The energy required for a 50% fragmentation probability of all bonds within an agglomerate was reduced by roughly a factor of 2 when aging "dry" agglomerates. Average bond energies derived from the data were 0.52*10-16 and 1.2*10-16 J, respectively. This is about 2 orders of magnitude higher than estimates for pure van-der-Waals agglomerates, but agrees quite well with other observations. Conclusion Although direct conclusions regarding the behavior of inhaled diesel aerosol in contact with body fluids cannot be drawn from such measurements, the results imply that highly agglomerated soot aerosol particles are unlikely to break up into units smaller than roughly the size distribution emitted as tail pipe soot. PMID:18533015

  14. Thermal fragmentation and deactivation of combustion-generated soot particles

    KAUST Repository

    Raj, Abhijeet

    2014-09-01

    The effect of thermal treatment on diesel soot and on a commercial soot in an inert environment under isothermal conditions at intermediate temperatures (400-900°C) is studied. Two important phenomena are observed in both the soot samples: soot fragmentation leading to its mass loss, and loss of soot reactivity towards O2. Several experimental techniques such as high resolution transmission electron microscopy, electron energy loss spectroscopy, thermo-gravimetric analysis with mass spectrometry, elemental analysis, Fourier transform infrared spectroscopy and X-ray diffraction have been used to identify the changes in structures, functional groups such as oxygenates and aliphatics, σ and π bonding, O/C and H/C ratios, and crystallite parameters of soot particles, introduced by heat. A decrease in the size of primary particles and an increase in the average polycyclic aromatic hydrocarbon (PAH) size was observed in soots after thermal treatment. The activation energies of soot oxidation for thermally treated soot samples were found to be higher than those for the untreated ones at most conversion levels. The cyclic or acyclic aliphatics with sp3 hybridization were present in significant amounts in all the soot samples, but their concentration decreased with thermal treatment. Interestingly, the H/C and the O/C ratios of soot particles increased after thermal treatment, and thus, they do not support the decrease in soot reactivity. The increase in the concentration of oxygenates on soot surface indicate that their desorption from soot surface in the form of CO, CO2 and other oxygenated compounds may not be significant at the temperatures (400-900°C) studied in this work. © 2014 The Combustion Institute.

  15. Emissions of soot particles from heat generators

    Science.gov (United States)

    Lyubov, V. K.; Popov, A. N.; Popova, E. I.

    2017-11-01

    «Soot carbon» or «Soot» - incomplete combustion or thermal decomposition particulate carbon product of hydrocarbons consisting of particles of various shapes and sizes. Soot particles are harmful substances Class 2 and like a dust dispersed by wind for thousands of kilometers. Soot have more powerful negative factor than carbon dioxide. Therefore, more strict requirements on ecological and economical performance for energy facilities at Arctic areas have to be developed to protect fragile Arctic ecosystems and global climate change from degradation and destruction. Quantity of soot particles in the flue gases of energy facilities is a criterion of effectiveness for organization of the burning process. Some of heat generators do not provide the required energy and environmental efficiency which results in irrational use of energy resources and acute pollution of environment. The paper summarizes the results of experimental study of solid particles emission from wide range of capacity boilers burning different organic fuels (natural gas, fuel oil, coal and biofuels). Special attention is paid to environmental and energy performance of the biofuels combustion. Emissions of soot particles PM2.5 are listed. Structure, composition and dimensions of entrained particles with the use of electronic scanning microscope Zeiss SIGMA VP were also studied. The results reveal an impact of several factors on soot particles emission.

  16. Ice Nucleation of Soot Particles in the Cirrus Regime: Is Pore Condensation and Freezing Relevant for Soot?

    Science.gov (United States)

    Kanji, Z. A.; Mahrt, F.; David, R.; Marcolli, C.; Lohmann, U.; Fahrni, J.; Brühwiler, D.

    2017-12-01

    Heterogeneous ice nucleation (HIN) onto soot particles from previous studies have produced inconsistent results of temperature and relative humidity conditions required for freezing depending on the source of soot particle investigated. The ability of soot to act as HIN depended on the type of soot and size of particle. Often homogenous freezing conditions or water saturation conditions were required to freeze soot particles, rendering HIN irrelevant. Using synthesised mesoporous silica particles, we show pore condensation and freezing works with experiments performed in the Zurich Ice Nucleation Chamber (ZINC). By testing a variety of soot particles in parallel in the Horizontal Ice Nucleation Chamber (HINC), we suggest that previously observed HIN on soot particles is not the responsible mechanism for ice formation. Laboratory generated CAST brown and black soot, commercially available soot and acid treated soot were investigated for their ice nucleation abilities in the mixed-phase and cirrus cloud temperature regimes. No heterogeneous ice nucleation activity is inferred at T > -38 °C (mixed-phase cloud regime), however depending on particle size and soot type, HIN was observed for T nucleation of ice in the pores or cavities that are ubiquitous in soot particles between the primary spherules. The ability of some particles to freeze at lower relative humidity compared to others demonstrates why hydrophobicity plays a role in ice nucleation, i.e. controlling the conditions at which these cavities fill with water. Thus for more hydrophobic particles pore filling occurs at higher relative humidity, and therefore freezing of pore water and ice crystal growth. Future work focusses on testing the cloud processing ability of soot particles and water adsorption isotherms of the different soot samples to support the hydrophobicity inferences from the ice nucleation results.

  17. A Nanometer Aerosol Size Analyzer (nASA) for Rapid Measurement of High-concentration Size Distributions

    International Nuclear Information System (INIS)

    Han, H.-S.; Chen, D.-R.; Pui, David Y.H.; Anderson, Bruce E.

    2000-01-01

    We have developed a fast-response nanometer aerosol size analyzer (nASA) that is capable of scanning 30 size channels between 3 and 100 nm in a total time of 3 s. The analyzer includes a bipolar charger (Po 210 ), an extended-length nanometer differential mobility analyzer (Nano-DMA), and an electrometer (TSI 3068). This combination of components provides particle size spectra at a scan rate of 0.1 s per channel free of uncertainties caused by response-time-induced smearing. The nASA thus offers a fast response for aerosol size distribution measurements in high-concentration conditions and also eliminates the need for applying a de-smearing algorithm to resulting data. In addition, because of its thermodynamically stable means of particle detection, the nASA is useful for applications requiring measurements over a broad range of sample pressures and temperatures. Indeed, experimental transfer functions determined for the extended-length Nano-DMA using the tandem differential mobility analyzer (TDMA) technique indicate the nASA provides good size resolution at pressures as low as 200 Torr. Also, as was demonstrated in tests to characterize the soot emissions from the J85-GE engine of a T-38 aircraft, the broad dynamic concentration range of the nASA makes it particularly suitable for studies of combustion or particle formation processes. Further details of the nASA performance as well as results from calibrations, laboratory tests and field applications are presented below

  18. Determination of size distribution using neural networks

    NARCIS (Netherlands)

    Stevens, JH; Nijhuis, JAG; Spaanenburg, L; Mohammadian, M

    1999-01-01

    In this paper we present a novel approach to the estimation of size distributions of grains in water from images. External conditions such as the concentrations of grains in water cannot be controlled. This poses problems for local image analysis which tries to identify and measure single grains.

  19. Cometary dust size distributions from flyby spacecraft

    International Nuclear Information System (INIS)

    Divine, N.

    1988-01-01

    Pior to the Halley flybys in 1986, the distribution of cometary dust grains with particle size were approximated using models which provided reasonable fits to the dynamics of dust tails, anti-tails, and infrared spectra. These distributions have since been improved using fluence data (i.e., particle fluxes integrated over time along the flyby trajectory) from three spacecraft. The fluence derived distributions are appropriate for comparison with simultaneous infrared photometry (from Earth) because they sample the particles in the same way as the IR data do (along the line of sight) and because they are directly proportional to the concentration distribution in that region of the coma which dominates the IR emission

  20. Size distribution, chemical composition and oxidation reactivity of particulate matter from gasoline direct injection (GDI) engine fueled with ethanol-gasoline fuel

    International Nuclear Information System (INIS)

    Luo, Yueqi; Zhu, Lei; Fang, Junhua; Zhuang, Zhuyue; Guan, Chun; Xia, Chen; Xie, Xiaomin; Huang, Zhen

    2015-01-01

    Ethanol-gasoline blended fuels have been widely applied in markets recently, as ethanol reduces life-cycle greenhouse gas emissions and improves anti-knock performance. However, its effects on particulate matter (PM) emissions from gasoline direct injection (GDI) engine still need further investigation. In this study, the effects of ethanol-gasoline blended fuels on particle size distributions, number concentrations, chemical composition and soot oxidation activity of GDI engine were investigated. It was found that ethanol-gasoline blended fuels increased the particle number concentration in low-load operating conditions. In higher load conditions, the ethanol-gasoline was effective for reducing the particle number concentration, indicating that the chemical benefits of ethanol become dominant, which could reduce soot precursors such as large n-alkanes and aromatics in gasoline. The volatile organic mass fraction in ethanol-gasoline particulates matter was higher than that in gasoline particulate matter because ethanol reduced the amount of soot precursors during combustion and thereby reduced the elemental carbon proportions in PM. Ethanol addition also increased the proportion of small particles, which confirmed the effects of ethanol on organic composition. Ethanol-gasoline reduced the concentrations of most PAH species, except those with small aromatic rings, e.g., naphthalene. Soot from ethanol-gasoline has lower activation energy of oxidation than that from gasoline. The results in this study indicate that ethanol-gasoline has positive effects on PM emissions control, as the soot oxidation activity is improved and the particle number concentrations are reduced at moderate and high engine loads. - Highlights: • Ethanol-gasoline reduces elemental carbon in PM. • Ethanol-gasoline increases volatile organic fraction in PM. • Soot generated from ethanol-gasoline has higher oxidation activity.

  1. Velocity Distributions in Inelastic Granular Gases with Continuous Size Distributions

    International Nuclear Information System (INIS)

    Li Rui; Li Zhi-Hao; Zhang Duan-Ming

    2011-01-01

    We study by numerical simulation the property of velocity distributions of granular gases with a power-law size distribution, driven by uniform heating and boundary heating. It is found that the form of velocity distribution is primarily controlled by the restitution coefficient η and q, the ratio between the average number of heatings and the average number of collisions in the system. Furthermore, we show that uniform and boundary heating can be understood as different limits of q, with q ≫ 1 and q ≤ 1, respectively. (general)

  2. Particle size distribution of plutonium contaminated soil

    International Nuclear Information System (INIS)

    Zeng Ke; Wu Wangsuo; Jin Yuren; Shen Maoquan; Han Zhaoyang; Hu Zhiqian; Ma Teqi

    2012-01-01

    Wet classification and γ ray spectroscopy had been applied to study the particle size distribution of Pu in the desert soil of somewhere in Northern China. It was found that nearly 90% of Pu exits in 0.1-10 mm particles. only 10% less in particles under 0.05 mm that still poses notable hazards to biosphere if any resuspension. Providing a decontamination target of 239 Pu <4000 Bq/kg, accident condition. (authors)

  3. Single Particle Soot Photometer intercomparison at the AIDA chamber

    Directory of Open Access Journals (Sweden)

    M. Laborde

    2012-12-01

    Full Text Available Soot particles, consisting of black carbon (BC, organic carbon (OC, inorganic salts, and trace elements, are emitted into the atmosphere during incomplete combustion. Accurate measurements of atmospheric BC are important as BC particles cause adverse health effects and impact the climate.

    Unfortunately, the accurate measurement of the properties and mass concentrations of BC particles remains difficult. The Single Particle Soot Photometer (SP2 can contribute to improving this situation by measuring the mass of refractory BC in individual particles as well as its mixing state.

    Here, the results of the first detailed SP2 intercomparison, involving 6 SP2s from 6 different research groups, are presented, including the most evolved data products that can presently be calculated from SP2 measurements.

    It was shown that a detection efficiency of almost 100% down to 1 fg BC per particle can readily be achieved, and that this limit can be pushed down to ∼0.2 fg BC with optimal SP2 setup. Number and mass size distributions of BC cores agreed within ±5% and ±10%, respectively, in between the SP2s, with larger deviations in the range below 1 fg BC.

    The accuracy of the SP2's mass concentration measurement depends on the calibration material chosen. The SP2 has previously been shown to be equally sensitive to fullerene soot and ambient BC from sources where fossil fuel was dominant and less sensitive to fullerene soot than to Aquadag. Fullerene soot was therefore chosen as the standard calibration material by the SP2 user community; however, many data sets rely solely on Aquadag calibration measurements. The difference in SP2 sensitivity was found to be almost equal (fullerene soot to Aquadag response ratio of ∼0.75 at 8.9 fg BC for all SP2s. This allows the calculation of a fullerene soot equivalent calibration curve from a measured Aquadag calibration, when no fullerene soot calibration is available. It could be

  4. Characterization and reactivity of soot from fast pyrolysis of lignocellulosic compounds and monolignols

    DEFF Research Database (Denmark)

    Trubetskaya, Anna; Brown, Avery; Tompsett, Geoffrey

    2018-01-01

    spectroscopy. The CO2 reactivity of soot was investigated by thermogravimetric analysis. Soot from cellulose was more reactive than soot produced from extractives, lignin and monolignols. Soot reactivity was correlated with the separation distances between adjacent graphene layers, as measured using...... transmission electron microscopy. Particle size, free radical concentration, differences in a degree of curvature and multi-core structures influenced the soot reactivity less than the interlayer separation distances. Soot yield was correlated with the lignin content of the feedstock. The selection...... of the extraction solvent had a strong influence on the soot reactivity. The Soxhlet extraction of softwood and wheat straw lignin soot using methanol decreased the soot reactivity, whereas acetone extraction had only a modest effect....

  5. Comparisons of Particulate Size Distributions from Multiple Combustion Strategies

    Science.gov (United States)

    Zhang, Yizhou

    In this study, a comparison of particle size distribution (PSD) measurements from eight different combustion strategies was conducted at four different load-speed points. The PSDs were measured using a scanning mobility particle sizer (SMPS) together with a condensation particle counter (CPC). To study the influence of volatile particles, PSD measurements were performed with and without a volatile particle remover (thermodenuder, TD) at both low and high dilution ratios. The common engine platform utilized in the experiment helps to eliminate the influence of background particulate and ensures similarity in dilution conditions. The results show a large number of volatile particles were present under LDR sample conditions for most of the operating conditions. The use of a TD, especially when coupled with HDR, was demonstrated to be effective at removing volatile particles and provided consistent measurements across all combustion strategies. The PSD comparison showed that gasoline premixed combustion strategies such as HCCI and GCI generally have low PSD magnitudes for particle sizes greater than the Particle Measurement Programme (PMP) cutoff diameter (23 nm), and the PSDs were highly nuclei-mode particle dominated. The strategies using diesel as the only fuel (DLTC and CDC) generally showed the highest particle number emissions for particles larger than 23 nm and had accumulation-mode particle dominated PSDs. A consistent correlation between the increase of the direct-injection of diesel fuel and a higher fraction of accumulation-mode particles was observed over all combustion strategies. A DI fuel substitution study and injector nozzle geometry study were conducted to better understand the correlation between PSD shape and DI fueling. It was found that DI fuel properties has a clear impact on PSD behavior for CDC and NG DPI. Fuel with lower density and lower sooting tendency led to a nuclei-mode particle dominated PSD shape. For NG RCCI, accumulation

  6. The competition between mineral dust and soot ice nuclei in mixed-phase clouds (Invited)

    Science.gov (United States)

    Murray, B. J.; Atkinson, J.; Umo, N.; Browse, J.; Woodhouse, M. T.; Whale, T.; Baustian, K. J.; Carslaw, K. S.; Dobbie, S.; O'Sullivan, D.; Malkin, T. L.

    2013-12-01

    The amount of ice present in mixed-phase clouds, which contain both supercooled liquid water droplets and ice particles, affects cloud extent, lifetime, particle size and radiative properties. The freezing of cloud droplets can be catalysed by the presence of aerosol particles known as ice nuclei. In this talk our recent laboratory and global aerosol modelling work on mineral dust and soot ice nuclei will be presented. We have performed immersion mode experiments to quantify ice nucleation by the individual minerals which make up desert mineral dusts and have shown that the feldspar component, rather than the clay component, is most important for ice nucleation (Atkinson et al. 2013). Experiments with well-characterised soot generated with eugenol, an intermediate in biomass burning, and n-decane show soot has a significant ice nucleation activity in mixed-phase cloud conditions. Our results for soot are in good agreement with previous results for acetylene soot (DeMott, 1990), but extend the efficiency to much higher temperatures. We then use a global aerosol model (GLOMAP) to map the distribution of soot and feldspar particles on a global basis. We show that below about -15oC that dust and soot together can explain most observed ice nuclei in the Earth's atmosphere, while at warmer temperatures other ice nuclei types are needed. We show that in some regions soot is the most important ice nuclei (below -15oC), while in others feldspar dust dominates. Our results suggest that there is a strong anthropogenic contribution to the ice nuclei population, since a large proportion of soot aerosol in the atmosphere results from human activities. Atkinson, J. D., Murray, B. J., Woodhouse, M. T., Carslaw, K. S., Whale, T. F., Baustian, K. J., Dobbie, S., O'Sullivan, D., and Malkin, T. L.: The importance of feldspar for ice nucleation by mineral dust in mixed-phase clouds, Nature, 10.1038/nature12278, (2013). Demott, P. J. 1990. An Exploratory-Study of Ice Nucleation by Soot

  7. Dynamics of very small soot particles during soot burnout in diesel engines; Dynamik kleinster Russteilchen waehrend der Russausbrandphase im Dieselmotor

    Energy Technology Data Exchange (ETDEWEB)

    Bockhorn, H. [Karlsruhe Univ. (T.H.) (Germany). Inst. fuer Chemische Technik; Peters, N. [RWTH Aachen (DE). Institut fuer Technische Mechanik (ITM); Pittermann, R. [WTZ fuer Motoren- und Maschinenforschung Rosslau gGmbH (Germany); Hentschel, J.; Weber, J.

    2003-07-01

    The investigations used advanced laser-optical methods for measuring soot particle size distributions, temporally and spectrally resolved measurements of engine combustion, measurements of composition and size distribution of particles in exhaust, and further development and validation of reaction-kinetic models. In all, it can be stated that mixing will affect not only soot particle formation but also soot particle emissions. Mixing can be influenced by using a fuel-water emulsion and by CR injection. Experiments and models both showed the advantageous effects of water added to the diesel fuels and of CR injection. The higher OH radical concentrations in the later combustion stages also serve to ensure faster oxidation of soot. (orig.) [German] Ziel des Projektes war es, Informationen ueber die Bildung und Oxidation von Russ sowie die Teilchendynamik der Russteilchen waehrend der Ausbrandphase zu erhalten. Dies wurde erreicht durch die Weiterentwicklung laseroptischer Methoden zur Bestimmung der Groessenverteilung von Russpartikeln, durch zeit- und spektral aufgeloeste Erfassung der motorischen Verbrennung, durch die Bestimmung von Zusammensetzung und Groessenverteilung von Partikeln im Abgas sowie durch die Weiterentwicklung und Validierung von reaktionskinetischen Modellen. Zusammenfassend laesst sich sagen, dass sich die Gemischbildung im Dieselmotor nicht nur auf die Bildung der Russpartikel sondern auch auf die Russpartikelemission auswirkt. Die Verwendung einer Kraftstoff-Wasser-Emulsion und die Common-Rail-Einspritzung stellen zwei Verfahren zur Beeinflussung der Gemischbildung dar. Sowohl die experimentellen Untersuchungen als auch die Modellierung zeigen den die Gemischbildung foerdernden Einfluss des Zusatzes von Wasser zum Dieselbrennstoff. Ein erhoehter Anteil an vorgemischter Verbrennung, wie er auch durch die Verwendung hoher Einspritzdruecke bei der Common-Rail-Einspritzung erreicht werden kann, verringert die waehrend der Verbrennung entstehende

  8. Vibro-spring particle size distribution analyser

    International Nuclear Information System (INIS)

    Patel, Ketan Shantilal

    2002-01-01

    This thesis describes the design and development of an automated pre-production particle size distribution analyser for particles in the 20 - 2000 μm size range. This work is follow up to the vibro-spring particle sizer reported by Shaeri. In its most basic form, the instrument comprises a horizontally held closed coil helical spring that is partly filled with the test powder and sinusoidally vibrated in the transverse direction. Particle size distribution data are obtained by stretching the spring to known lengths and measuring the mass of the powder discharged from the spring's coils. The size of the particles on the other hand is determined from the spring 'intercoil' distance. The instrument developed by Shaeri had limited use due to its inability to measure sample mass directly. For the device reported here, modifications are made to the original configurations to establish means of direct sample mass measurement. The feasibility of techniques for measuring the mass of powder retained within the spring are investigated in detail. Initially, the measurement of mass is executed in-situ from the vibration characteristics based on the spring's first harmonic resonant frequency. This method is often erratic and unreliable due to the particle-particle-spring wall interactions and the spring bending. An much more successful alternative is found from a more complicated arrangement in which the spring forms part of a stiff cantilever system pivoted along its main axis. Here, the sample mass is determined in the 'static mode' by monitoring the cantilever beam's deflection following the wanton termination of vibration. The system performance has been optimised through the variations of the mechanical design of the key components and the operating procedure as well as taking into account the effect of changes in the ambient temperature on the system's response. The thesis also describes the design and development of the ancillary mechanisms. These include the pneumatic

  9. Soot accumulation in diesel particulate filters using ULSD and B20 biodiesel fuel blends

    Energy Technology Data Exchange (ETDEWEB)

    Charbonneau, P.; Wallace, J.S. [Toronto Univ., ON (Canada)

    2009-07-01

    Soot accumulation in a diesel particulate filter was investigated using a newly developed dissection method that loads and dissects diesel particulate filters (DPFs). In particular, this study examined the differences in soot accumulation between ultra-low sulphur diesel (ULSD) and a B20 biodiesel blend. DPFs loaded for exposure times of 1, 2, 5 and 10 hours. Scanning electron microscopy (SEM) was used to analyze the samples of the filter substrate. The differences in particulate size and number distribution between fuels were attributed to performance differences in DPFs. ULSD loaded filters experienced increased loading and a greater pressure drop across the filters. According to SEM images, the soot cake was a relatively shallow feature increasing in density to form discrete coarse agglomerates and cakes. It was concluded that this newly developed methodology has potential for future studies in DPF loading.

  10. Aromatics Oxidation and Soot Formation in Flames

    Energy Technology Data Exchange (ETDEWEB)

    Howard, J. B.; Richter, H.

    2005-03-29

    This project is concerned with the kinetics and mechanisms of aromatics oxidation and the growth process to polycyclic aromatic hydrocarbons (PAH) of increasing size, soot and fullerenes formation in flames. The overall objective of the experimental aromatics oxidation work is to extend the set of available data by measuring concentration profiles for decomposition intermediates such as phenyl, cyclopentadienyl, phenoxy or indenyl radicals which could not be measured with molecular-beam mass spectrometry to permit further refinement and testing of benzene oxidation mechanisms. The focus includes PAH radicals which are thought to play a major role in the soot formation process while their concentrations are in many cases too low to permit measurement with conventional mass spectrometry. The radical species measurements are used in critical testing and improvement of a kinetic model describing benzene oxidation and PAH growth. Thermodynamic property data of selected species are determined computationally, for instance using density functional theory (DFT). Potential energy surfaces are explored in order to identify additional reaction pathways. The ultimate goal is to understand the conversion of high molecular weight compounds to nascent soot particles, to assess the roles of planar and curved PAH and relationships between soot and fullerenes formation. The specific aims are to characterize both the high molecular weight compounds involved in the nucleation of soot particles and the structure of soot including internal nanoscale features indicative of contributions of planar and/or curved PAH to particle inception.

  11. Remote Laser Diffraction Particle Size Distribution Analyzer

    Energy Technology Data Exchange (ETDEWEB)

    Batcheller, Thomas Aquinas; Huestis, Gary Michael; Bolton, Steven Michael

    2001-03-01

    In support of a radioactive slurry sampling and physical characterization task, an “off-the-shelf” laser diffraction (classical light scattering) particle size analyzer was utilized for remote particle size distribution (PSD) analysis. Spent nuclear fuel was previously reprocessed at the Idaho Nuclear Technology and Engineering Center (INTEC—formerly recognized as the Idaho Chemical Processing Plant) which is on DOE’s INEEL site. The acidic, radioactive aqueous raffinate streams from these processes were transferred to 300,000 gallon stainless steel storage vessels located in the INTEC Tank Farm area. Due to the transfer piping configuration in these vessels, complete removal of the liquid can not be achieved. Consequently, a “heel” slurry remains at the bottom of an “emptied” vessel. Particle size distribution characterization of the settled solids in this remaining heel slurry, as well as suspended solids in the tank liquid, is the goal of this remote PSD analyzer task. A Horiba Instruments Inc. Model LA-300 PSD analyzer, which has a 0.1 to 600 micron measurement range, was modified for remote application in a “hot cell” (gamma radiation) environment. This technology provides rapid and simple PSD analysis, especially down in the fine and microscopic particle size regime. Particle size analysis of these radioactive slurries down in this smaller range was not previously achievable—making this technology far superior than the traditional methods used. Successful acquisition of this data, in conjunction with other characterization analyses, provides important information that can be used in the myriad of potential radioactive waste management alternatives.

  12. Particle-size distribution study: PILEDRIVER event

    Energy Technology Data Exchange (ETDEWEB)

    Rabb, David D [Lawrence Radiation Laboratory, University of California, Livermore, CA (United States)

    1970-05-15

    Reentry was made by mining into the chimney of broken rock created by a nuclear detonation in granite at a depth of 1500 feet. The chimney was 160 ft in radius and 890 ft high. An injection of radioactive melt was encountered at 300 ft from shot point. Radiochemical analyses determined that the yield of PILEDRIVER nuclear device was 61 {+-} 10 kt. Two samples of chimney rubble totalling over 5,000 lb were obtained during the postshot exploration. These samples of broken granite underwent screen analysis, a radioactivity-distribution study, and cursory leaching tests. The two samples were separated into 25 different size-fractions. An average of the particle-size data from the two samples showed that 17% of the material is between 20 mesh and I in.; 42% between 1 and 6 in.; and 34% between 6 in. and 3 ft. The distribution of radioactivity varies markedly with the particle size. The minus 100-mesh material comprizes less than 1.5% of the weight but contains almost 20% of the radioactivity. Small-scale batch-leaching tests showed that 25% of the radioactivity could be removed in a few hours by a film-percolation leach with distilled water, and 40% with dilute acid. Brief studies were made of the microfractures in the broken rock and of the radioactivity created by the PILEDRIVER explosion. (author)

  13. Particle-size distribution study: PILEDRIVER event

    International Nuclear Information System (INIS)

    Rabb, David D.

    1970-01-01

    Reentry was made by mining into the chimney of broken rock created by a nuclear detonation in granite at a depth of 1500 feet. The chimney was 160 ft in radius and 890 ft high. An injection of radioactive melt was encountered at 300 ft from shot point. Radiochemical analyses determined that the yield of PILEDRIVER nuclear device was 61 ± 10 kt. Two samples of chimney rubble totalling over 5,000 lb were obtained during the postshot exploration. These samples of broken granite underwent screen analysis, a radioactivity-distribution study, and cursory leaching tests. The two samples were separated into 25 different size-fractions. An average of the particle-size data from the two samples showed that 17% of the material is between 20 mesh and I in.; 42% between 1 and 6 in.; and 34% between 6 in. and 3 ft. The distribution of radioactivity varies markedly with the particle size. The minus 100-mesh material comprizes less than 1.5% of the weight but contains almost 20% of the radioactivity. Small-scale batch-leaching tests showed that 25% of the radioactivity could be removed in a few hours by a film-percolation leach with distilled water, and 40% with dilute acid. Brief studies were made of the microfractures in the broken rock and of the radioactivity created by the PILEDRIVER explosion. (author)

  14. The Sea-Ice Floe Size Distribution

    Science.gov (United States)

    Stern, H. L., III; Schweiger, A. J. B.; Zhang, J.; Steele, M.

    2017-12-01

    The size distribution of ice floes in the polar seas affects the dynamics and thermodynamics of the ice cover and its interaction with the ocean and atmosphere. Ice-ocean models are now beginning to include the floe size distribution (FSD) in their simulations. In order to characterize seasonal changes of the FSD and provide validation data for our ice-ocean model, we calculated the FSD in the Beaufort and Chukchi seas over two spring-summer-fall seasons (2013 and 2014) using more than 250 cloud-free visible-band scenes from the MODIS sensors on NASA's Terra and Aqua satellites, identifying nearly 250,000 ice floes between 2 and 30 km in diameter. We found that the FSD follows a power-law distribution at all locations, with a seasonally varying exponent that reflects floe break-up in spring, loss of smaller floes in summer, and the return of larger floes after fall freeze-up. We extended the results to floe sizes from 10 m to 2 km at selected time/space locations using more than 50 high-resolution radar and visible-band satellite images. Our analysis used more data and applied greater statistical rigor than any previous study of the FSD. The incorporation of the FSD into our ice-ocean model resulted in reduced sea-ice thickness, mainly in the marginal ice zone, which improved the simulation of sea-ice extent and yielded an earlier ice retreat. We also examined results from 17 previous studies of the FSD, most of which report power-law FSDs but with widely varying exponents. It is difficult to reconcile the range of results due to different study areas, seasons, and methods of analysis. We review the power-law representation of the FSD in these studies and discuss some mathematical details that are important to consider in any future analysis.

  15. Sooting Characteristics and Modeling in Counterflow Diffusion Flames

    KAUST Repository

    Wang, Yu

    2013-11-01

    Soot formation is one of the most complex phenomena in combustion science and an understanding of the underlying physico-chemical mechanisms is important. This work adopted both experimental and numerical approaches to study soot formation in laminar counterfl ow diffusion flames. As polycyclic aromatic hydrocarbons (PAHs) are the precursors of soot particles, a detailed gas-phase chemical mechanism describing PAH growth upto coronene for fuels with 1 to 4 carbon atoms was validated against laminar premixed and counter- flow diffusion fl ames. Built upon this gas-phase mechanism, a soot model was then developed to describe soot inception and surface growth. This soot model was sub- sequently used to study fuel mixing effect on soot formation in counterfl ow diffusion flames. Simulation results showed that compared to the baseline case of the ethylene flame, the doping of 5% (by volume) propane or ethane in ethylene tends to increase the soot volume fraction and number density while keeping the average soot size almost unchanged. These results are in agreement with experimental observations. Laser light extinction/scattering as well as laser induced fluorescence techniques were used to study the effect of strain rate on soot and PAH formation in counterfl ow diffusion ames. The results showed that as strain rate increased both soot volume fraction and PAH concentrations decreased. The concentrations of larger PAH were more sensitive to strain rate compared to smaller ones. The effect of CO2 addition on soot formation was also studied using similar experimental techniques. Soot loading was reduced with CO2 dilution. Subsequent numerical modeling studies were able to reproduce the experimental trend. In addition, the chemical effect of CO2 addition was analyzed using numerical data. Critical conditions for the onset of soot were systematically studied in counterfl ow diffusion ames for various gaseous hydrocarbon fuels and at different strain rates. A sooting

  16. Seasonal variations in size distribution, water-soluble ions, and carbon content of size-segregated aerosols over New Delhi.

    Science.gov (United States)

    Kumar, Pawan; Kumar, Sushil; Yadav, Sudesh

    2018-02-01

    Size distribution, water-soluble inorganic ions (WSII), and organic carbon (OC) and elemental carbon (EC) in size-segregated aerosols were investigated during a year-long sampling in 2010 over New Delhi. Among different size fractions of PM 10 , PM 0.95 was the dominant fraction (45%) followed by PM 3-7.2 (20%), PM 7.2-10 (15%), PM 0.95-1.5 (10%), and PM 1.5-3 (10%). All size fractions exceeded the ambient air quality standards of India for PM 2.5 . Annual average mass size distributions of ions were specific to size and ion(s); Ca 2+ , Mg 2+ , K + , NO 3 - , and Cl - followed bimodal distribution while SO 4 2- and NH 4 + ions showed one mode in PM 0.95 . The concentrations of secondary WSII (NO 3 - , SO 4 2- , and NH 4 + ) increased in winters due to closed and moist atmosphere whereas open atmospheric conditions in summers lead to dispersal of pollutants. NH 4 + and Ca 2+ were dominant neutralization ions but in different size fractions. The summer-time dust transport from upwind region by S SW winds resulted in significantly high concentrations of PM 0.95 and PM 3-7.2 and PM 7.2-10 . This indicted influence of dust generation in Thar Desert and its transport is size selective in nature in downwind direction. The mixing of different sources (geogenic, coal combustions, biomass burning, plastic burning, incinerators, and vehicular emissions sources) for soluble ions in different size fractions was noticed in principle component analysis. Total carbon (TC = EC + OC) constituted 8-31% of the total PM 0.95 mass, and OC dominated over EC. Among EC, char (EC1) dominated over soot (EC2 + EC3). High SOC contribution (82%) to OC and OC/EC ratio of 2.7 suggested possible role of mineral dust and high photochemical activity in SOC production. Mass concentrations of aerosols and WSII and their contributions to each size fraction of PM 10 are governed by nature of sources, emission strength of source(s), and seasonality in meteorological parameters.

  17. Time-averaged probability density functions of soot nanoparticles along the centerline of a piloted turbulent diffusion flame using a scanning mobility particle sizer

    KAUST Repository

    Chowdhury, Snehaunshu

    2017-01-23

    In this study, we demonstrate the use of a scanning mobility particle sizer (SMPS) as an effective tool to measure the probability density functions (PDFs) of soot nanoparticles in turbulent flames. Time-averaged soot PDFs necessary for validating existing soot models are reported at intervals of ∆x/D∆x/D = 5 along the centerline of turbulent, non-premixed, C2H4/N2 flames. The jet exit Reynolds numbers of the flames investigated were 10,000 and 20,000. A simplified burner geometry based on a published design was chosen to aid modelers. Soot was sampled directly from the flame using a sampling probe with a 0.5-mm diameter orifice and diluted with N2 by a two-stage dilution process. The overall dilution ratio was not evaluated. An SMPS system was used to analyze soot particle concentrations in the diluted samples. Sampling conditions were optimized over a wide range of dilution ratios to eliminate the effect of agglomeration in the sampling probe. Two differential mobility analyzers (DMAs) with different size ranges were used separately in the SMPS measurements to characterize the entire size range of particles. In both flames, the PDFs were found to be mono-modal in nature near the jet exit. Further downstream, the profiles were flatter with a fall-off at larger particle diameters. The geometric mean of the soot size distributions was less than 10 nm for all cases and increased monotonically with axial distance in both flames.

  18. Parameterizing Size Distribution in Ice Clouds

    Energy Technology Data Exchange (ETDEWEB)

    DeSlover, Daniel; Mitchell, David L.

    2009-09-25

    PARAMETERIZING SIZE DISTRIBUTIONS IN ICE CLOUDS David L. Mitchell and Daniel H. DeSlover ABSTRACT An outstanding problem that contributes considerable uncertainty to Global Climate Model (GCM) predictions of future climate is the characterization of ice particle sizes in cirrus clouds. Recent parameterizations of ice cloud effective diameter differ by a factor of three, which, for overcast conditions, often translate to changes in outgoing longwave radiation (OLR) of 55 W m-2 or more. Much of this uncertainty in cirrus particle sizes is related to the problem of ice particle shattering during in situ sampling of the ice particle size distribution (PSD). Ice particles often shatter into many smaller ice fragments upon collision with the rim of the probe inlet tube. These small ice artifacts are counted as real ice crystals, resulting in anomalously high concentrations of small ice crystals (D < 100 µm) and underestimates of the mean and effective size of the PSD. Half of the cirrus cloud optical depth calculated from these in situ measurements can be due to this shattering phenomenon. Another challenge is the determination of ice and liquid water amounts in mixed phase clouds. Mixed phase clouds in the Arctic contain mostly liquid water, and the presence of ice is important for determining their lifecycle. Colder high clouds between -20 and -36 oC may also be mixed phase but in this case their condensate is mostly ice with low levels of liquid water. Rather than affecting their lifecycle, the presence of liquid dramatically affects the cloud optical properties, which affects cloud-climate feedback processes in GCMs. This project has made advancements in solving both of these problems. Regarding the first problem, PSD in ice clouds are uncertain due to the inability to reliably measure the concentrations of the smallest crystals (D < 100 µm), known as the “small mode”. Rather than using in situ probe measurements aboard aircraft, we employed a treatment of ice

  19. Improved technique for measuring the size distribution of black carbon particles in rainwater and snow samples

    Science.gov (United States)

    Mori, T.; Moteki, N.; Ohata, S.; Koike, M.; Azuma, K. G.; Miyazaki, Y.; Kondo, Y.

    2015-12-01

    Black carbon (BC) is the strongest contributor to sunlight absorption among atmospheric aerosols. Quantitative understanding of wet deposition of BC, which strongly affects the spatial distribution of BC, is important to improve our understandings on climate change. We have devised a technique for measuring the masses of individual BC particles in rainwater and snow samples, as a combination of a nebulizer and a single-particle soot photometer (SP2) (Ohata et al. 2011, 2013; Schwarz et al. 2012; Mori et al. 2014). We show two important improvements in this technique: 1)We have extended the upper limit of detectable BC particle diameter from 0.9 μm to about 4.0 μm by modifying the photodetector for measuring the laser-induced incandescence signal. 2)We introduced a pneumatic nebulizer Marin-5 (Cetac Technologies Inc., Omaha, NE, USA) and experimentally confirmed its high extraction efficiency (~50%) independent of particle diameter up to 2.0 μm. Using our improved system, we simultaneously measured the size distribution of BC particles in air and rainwater in Tokyo. We observed that the size distribution of BC in rainwater was larger than that in air, indicating that large BC particles were effectively removed by precipitation. We also observed BC particles with diameters larger than 1.0 μm, indicating that further studies of wet deposition of BC will require the use of the modified SP2.

  20. Ice nucleation activity of diesel soot particles at cirrus relevant temperature conditions: Effects of hydration, secondary organics coating, soot morphology, and coagulation

    Science.gov (United States)

    Kulkarni, Gourihar; China, Swarup; Liu, Shang; Nandasiri, Manjula; Sharma, Noopur; Wilson, Jacqueline; Aiken, Allison C.; Chand, Duli; Laskin, Alexander; Mazzoleni, Claudio; Pekour, Mikhail; Shilling, John; Shutthanandan, Vaithiyalingam; Zelenyuk, Alla; Zaveri, Rahul A.

    2016-04-01

    Ice formation by diesel soot particles was investigated at temperatures ranging from -40 to -50°C. Size-selected soot particles were physically and chemically aged in an environmental chamber, and their ice nucleating properties were determined using a continuous flow diffusion type ice nucleation chamber. Bare (freshly formed), hydrated, and compacted soot particles, as well as α-pinene secondary organic aerosol (SOA)-coated soot particles at high relative humidity conditions, showed ice formation activity at subsaturation conditions with respect to water but below the homogeneous freezing threshold conditions. However, SOA-coated soot particles at dry conditions were observed to freeze at homogeneous freezing threshold conditions. Overall, our results suggest that heterogeneous ice nucleation activity of freshly emitted diesel soot particles are sensitive to some of the aging processes that soot can undergo in the atmosphere.

  1. Fragment Size Distribution of Blasted Rock Mass

    Science.gov (United States)

    Jug, Jasmin; Strelec, Stjepan; Gazdek, Mario; Kavur, Boris

    2017-12-01

    Rock mass is a heterogeneous material, and the heterogeneity of rock causes sizes distribution of fragmented rocks in blasting. Prediction of blasted rock mass fragmentation has a significant role in the overall economics of opencast mines. Blasting as primary fragmentation can significantly decrease the cost of loading, transport, crushing and milling operations. Blast fragmentation chiefly depends on the specific blast design (geometry of blast holes drilling, the quantity and class of explosive, the blasting form, the timing and partition, etc.) and on the properties of the rock mass (including the uniaxial compressive strength, the rock mass elastic Young modulus, the rock discontinuity characteristics and the rock density). Prediction and processing of blasting results researchers can accomplish by a variety of existing software’s and models, one of them is the Kuz-Ram model, which is possibly the most widely used approach to estimating fragmentation from blasting. This paper shows the estimation of fragmentation using the "SB" program, which was created by the authors. Mentioned program includes the Kuz-Ram model. Models of fragmentation are confirmed and calibrated by comparing the estimated fragmentation with actual post-blast fragmentation from image processing techniques. In this study, the Kuz-Ram fragmentation model has been used for an open-pit limestone quarry in Dalmatia, southern Croatia. The resulting calibrated value of the rock factor enables the quality prognosis of fragmentation in further blasting works, with changed drilling geometry and blast design parameters. It also facilitates simulation in the program to optimize blasting works and get the desired fragmentations of the blasted rock mass.

  2. Evaluation of droplet size distributions using univariate and multivariate approaches

    DEFF Research Database (Denmark)

    Gauno, M.H.; Larsen, C.C.; Vilhelmsen, T.

    2013-01-01

    of the distribution. The current study was aiming to compare univariate and multivariate approach in evaluating droplet size distributions. As a model system, the atomization of a coating solution from a two-fluid nozzle was investigated. The effect of three process parameters (concentration of ethyl cellulose...... in ethanol, atomizing air pressure, and flow rate of coating solution) on the droplet size and droplet size distribution using a full mixed factorial design was used. The droplet size produced by a two-fluid nozzle was measured by laser diffraction and reported as volume based size distribution....... Investigation of loading and score plots from principal component analysis (PCA) revealed additional information on the droplet size distributions and it was possible to identify univariate statistics (volume median droplet size), which were similar, however, originating from varying droplet size distributions...

  3. Two-dimensional quantification of soot and flame-soot interaction in spray combustion at elevated pressures - Final report

    Energy Technology Data Exchange (ETDEWEB)

    Gerber, T.

    2008-07-15

    Single-pulse time-resolved laser-induced incandescence (TiRe-LII) signal transients from soot particulates were acquired during unsteady high pressure Diesel combustion in a constant volume cell near top dead centre conditions typically found in a Diesel engine. Measurements were performed for initial gas pressures between 1 MPa and 3 MPa, injection pressures between 50 MPa and 130 MPa and laser probe timings between 5 ms and 16 ms after start of fuel injection. In separate experiments and for the same cell operating conditions, gas temperatures were deduced from spectrally resolved soot pyrometry measurements. Implementing the LII model of Kock et al. ensemble mean soot particle diameters were evaluated from least-squares fitting of theoretical cooling curves to experimental TiRe-LII signal transients. Since in the experiments the environmental gas temperature and the width of an assumed particle size distribution were not known, the effects of the initial choice of these parameters on retrieved particle diameters were investigated. It is shown that evaluated mean particle diameters are only slightly biased by the choice of typical size distribution widths and gas temperatures. For a fixed combustion phase mean particle diameters are not much affected by gas pressure, however they become smaller at high fuel injection pressure. At a mean chamber pressure of 1.4 MPa evaluated mean particle diameters increased by a factor of two for probe delays between 5 ms and 16 ms after start of injection, irrespective of the choices of first-guess fitting variables, indicating a certain robustness of data analysis procedure. (author)

  4. Sooting turbulent jet flame: characterization and quantitative soot measurements

    Science.gov (United States)

    Köhler, M.; Geigle, K. P.; Meier, W.; Crosland, B. M.; Thomson, K. A.; Smallwood, G. J.

    2011-08-01

    Computational fluid dynamics (CFD) modelers require high-quality experimental data sets for validation of their numerical tools. Preferred features for numerical simulations of a sooting, turbulent test case flame are simplicity (no pilot flame), well-defined boundary conditions, and sufficient soot production. This paper proposes a non-premixed C2H4/air turbulent jet flame to fill this role and presents an extensive database for soot model validation. The sooting turbulent jet flame has a total visible flame length of approximately 400 mm and a fuel-jet Reynolds number of 10,000. The flame has a measured lift-off height of 26 mm which acts as a sensitive marker for CFD model validation, while this novel compiled experimental database of soot properties, temperature and velocity maps are useful for the validation of kinetic soot models and numerical flame simulations. Due to the relatively simple burner design which produces a flame with sufficient soot concentration while meeting modelers' needs with respect to boundary conditions and flame specifications as well as the present lack of a sooting "standard flame", this flame is suggested as a new reference turbulent sooting flame. The flame characterization presented here involved a variety of optical diagnostics including quantitative 2D laser-induced incandescence (2D-LII), shifted-vibrational coherent anti-Stokes Raman spectroscopy (SV-CARS), and particle image velocimetry (PIV). Producing an accurate and comprehensive characterization of a transient sooting flame was challenging and required optimization of these diagnostics. In this respect, we present the first simultaneous, instantaneous PIV, and LII measurements in a heavily sooting flame environment. Simultaneous soot and flow field measurements can provide new insights into the interaction between a turbulent vortex and flame chemistry, especially since soot structures in turbulent flames are known to be small and often treated in a statistical manner.

  5. Investigations of Sooting Laminar Coflow Diffusion Flames at Elevated Pressures

    KAUST Repository

    Steinmetz, Scott A.

    2016-12-01

    Soot is a common byproduct of hydrocarbon based combustion systems. It poses a risk to human and environmental health, and can negatively or positively affect combustor performance. As a result, there is significant interest in understanding soot formation in order to better control it. More recently, the need to study soot formation in engine relevant conditions has become apparent. One engine relevant parameter that has had little focus is the ambient pressure. This body of work focuses on the formation of soot in elevated pressure environments, and a number of investigations are carried out with this purpose. Laminar coflow diffusion flames are used as steady, simple soot producers. First, a commonly studied flame configuration is further characterized. Coflow flames are frequently used for fundamental flame studies, particularly at elevated pressures. However, they are more susceptible to buoyancy induced instabilities at elevated pressures. The velocity of the coflow is known to have an effect on flame stability and soot formation, though these have not been characterized at elevated pressures. A series of flames are investigated covering a range of flowrates, pressures, and nozzle diameters. The stability limits of coflow flames in this range is investigated. Additionally, an alternative strategy for scaling these flames to elevated pressures is proposed. Finally, the effect of coflow rate on soot formation is evaluated. Identification of fundamental flames for coordinated research can facilitate our understanding of soot formation. The next study of this work focuses on adding soot concentration and particle size information to an existing fundamental flame dataset for the purpose of numerical model validation. Soot volume fraction and average particle diameters are successfully measured in nitrogen-diluted ethylene-air laminar coflow flames at pressures of 4, 8, 12, and 16 atm. An increase in particle size with pressure is found up to 12 atm, where particle

  6. Understanding Combustion and Soot Formation in Diesel Engines

    Science.gov (United States)

    2016-09-09

    distributions of PLII signals help understand the soot distributions within diesel/ biodiesel flames. In addition, planar laser-induced Figure 1. Transported ...Prescribed by ANSI Std. Z39.18 Page 1 of 1FORM SF 298 9/14/2016https://livelink.ebs.afrl.af.mil/livelink/llisapi.dll This project investigated biodiesel ...emissions testing. 1 FINAL REPORT Project title: Understanding combustion and soot formation in biodiesel fuelled diesel engines Lead Institute and

  7. How Sample Size Affects a Sampling Distribution

    Science.gov (United States)

    Mulekar, Madhuri S.; Siegel, Murray H.

    2009-01-01

    If students are to understand inferential statistics successfully, they must have a profound understanding of the nature of the sampling distribution. Specifically, they must comprehend the determination of the expected value and standard error of a sampling distribution as well as the meaning of the central limit theorem. Many students in a high…

  8. Distribution of droplet sizes for seed solution

    International Nuclear Information System (INIS)

    Marwah, R.K.; Dixit, N.S.; Venkataramani, N.; Rohatgi, V.K.

    In open cycle MHD power generation, power is generated by passing seeded hot combustion products of a fossil fuel through a magnetic field. Seeding is done with a salt which is readily ionizable, preferably in the form of an aqueous solution, such as potassium carbonate, potassium sulphate, etc. Methods of atomization and the theoretical drop size calculations are presented. Basic parameters necessary for droplet size determination and their measurement are also described. (K.B.)

  9. Evaluation of droplet size distributions using univariate and multivariate approaches.

    Science.gov (United States)

    Gaunø, Mette Høg; Larsen, Crilles Casper; Vilhelmsen, Thomas; Møller-Sonnergaard, Jørn; Wittendorff, Jørgen; Rantanen, Jukka

    2013-01-01

    Pharmaceutically relevant material characteristics are often analyzed based on univariate descriptors instead of utilizing the whole information available in the full distribution. One example is droplet size distribution, which is often described by the median droplet size and the width of the distribution. The current study was aiming to compare univariate and multivariate approach in evaluating droplet size distributions. As a model system, the atomization of a coating solution from a two-fluid nozzle was investigated. The effect of three process parameters (concentration of ethyl cellulose in ethanol, atomizing air pressure, and flow rate of coating solution) on the droplet size and droplet size distribution using a full mixed factorial design was used. The droplet size produced by a two-fluid nozzle was measured by laser diffraction and reported as volume based size distribution. Investigation of loading and score plots from principal component analysis (PCA) revealed additional information on the droplet size distributions and it was possible to identify univariate statistics (volume median droplet size), which were similar, however, originating from varying droplet size distributions. The multivariate data analysis was proven to be an efficient tool for evaluating the full information contained in a distribution.

  10. Firm Size Distribution in Fortune Global 500

    Science.gov (United States)

    Chen, Qinghua; Chen, Liujun; Liu, Kai

    By analyzing the data of Fortune Global 500 firms from 1996 to 2008, we found that their ranks and revenues always obey the same distribution, which implies that worldwide firm structure has been stable for a long time. The fitting results show that simple Zipf distribution is not an ideal model for global firms, while SCL, FSS have better fitting goodness, and lognormal fitting is the best. And then, we proposed a simple explanation.

  11. Unimodal tree size distributions possibly result from relatively strong conservatism in intermediate size classes.

    Directory of Open Access Journals (Sweden)

    Yue Bin

    Full Text Available Tree size distributions have long been of interest to ecologists and foresters because they reflect fundamental demographic processes. Previous studies have assumed that size distributions are often associated with population trends or with the degree of shade tolerance. We tested these associations for 31 tree species in a 20 ha plot in a Dinghushan south subtropical forest in China. These species varied widely in growth form and shade-tolerance. We used 2005 and 2010 census data from that plot. We found that 23 species had reversed J shaped size distributions, and eight species had unimodal size distributions in 2005. On average, modal species had lower recruitment rates than reversed J species, while showing no significant difference in mortality rates, per capita population growth rates or shade-tolerance. We compared the observed size distributions with the equilibrium distributions projected from observed size-dependent growth and mortality. We found that observed distributions generally had the same shape as predicted equilibrium distributions in both unimodal and reversed J species, but there were statistically significant, important quantitative differences between observed and projected equilibrium size distributions in most species, suggesting that these populations are not at equilibrium and that this forest is changing over time. Almost all modal species had U-shaped size-dependent mortality and/or growth functions, with turning points of both mortality and growth at intermediate size classes close to the peak in the size distribution. These results show that modal size distributions do not necessarily indicate either population decline or shade-intolerance. Instead, the modal species in our study were characterized by a life history strategy of relatively strong conservatism in an intermediate size class, leading to very low growth and mortality in that size class, and thus to a peak in the size distribution at intermediate sizes.

  12. A multivariate rank test for comparing mass size distributions

    KAUST Repository

    Lombard, F.; Potgieter, C. J.

    2012-01-01

    Particle size analyses of a raw material are commonplace in the mineral processing industry. Knowledge of particle size distributions is crucial in planning milling operations to enable an optimum degree of liberation of valuable mineral phases

  13. Estimation of particle size distribution of nanoparticles from electrical ...

    Indian Academy of Sciences (India)

    2018-02-02

    Feb 2, 2018 ... An indirect method of estimation of size distribution of nanoparticles in a nanocomposite is ... The present approach exploits DC electrical current–voltage ... the sizes of nanoparticles (NPs) by electrical characterization.

  14. Concentration and size distribution of particles in abstracted groundwater.

    Science.gov (United States)

    van Beek, C G E M; de Zwart, A H; Balemans, M; Kooiman, J W; van Rosmalen, C; Timmer, H; Vandersluys, J; Stuyfzand, P J

    2010-02-01

    Particle number concentrations have been counted and particle size distributions calculated in groundwater derived by abstraction wells. Both concentration and size distribution are governed by the discharge rate: the higher this rate the higher the concentration and the higher the proportion of larger particles. However, the particle concentration in groundwater derived from abstraction wells, with high groundwater flow velocities, is much lower than in groundwater from monitor wells, with minimal flow velocities. This inconsistency points to exhaustion of the particle supply in the aquifer around wells due to groundwater abstraction for many years. The particle size distribution can be described with the help of a power law or Pareto distribution. Comparing the measured particle size distribution with the Pareto distribution shows that particles with a diameter >7 microm are under-represented. As the particle size distribution is dependent on the flow velocity, so is the value of the "Pareto" slope beta. (c) 2009 Elsevier Ltd. All rights reserved.

  15. Comprehensive Characterization Of Ultrafine Particulate Emission From 2007 Diesel Engines: PM Size Distribution, Loading And Indidividual Particle Size And Composition.

    Science.gov (United States)

    Zelenyuk, A.; Cuadra-Rodriguez, L. A.; Imre, D.; Shimpi, S.; Warey, A.

    2006-12-01

    The strong absorption of solar radiation by black carbon (BC) impacts the atmospheric radiative balance in a complex and significant manner. One of the most important sources of BC is vehicular emissions, of which diesel represents a significant fraction. To address this issue the EPA has issues new stringent regulations that will be in effect in 2007, limiting the amount of particulate mass that can be emitted by diesel engines. The new engines are equipped with aftertreatments that reduce PM emissions to the point, where filter measurements are subject to significant artifacts and characterization by other techniques presents new challenges. We will present the results of the multidisciplinary study conducted at the Cummins Technical Center in which a suite of instruments was deployed to yield comprehensive, temporally resolved information on the diesel exhaust particle loadings and properties in real-time: Particle size distributions were measured by Engine Exhaust Particle Sizer (EEPS) and Scanning Mobility Particle Sizer (SMPS). Total particle diameter concentration was obtained using Electrical Aerosol Detector (EAD). Laser Induced Incandescence and photoacoustic techniques were used to monitor the PM soot content. Single Particle Laser Ablation Time-of- flight Mass Spectrometer (SPLAT) provided the aerodynamic diameter and chemical composition of individual diesel exhaust particles. Measurements were conducted on a number of heavy duty diesel engines operated under variety of operating conditions, including FTP transient cycles, ramped-modal cycles and steady states runs. We have also characterized PM emissions during diesel particulate filter regeneration cycles. We will present a comparison of PM characteristics observed during identical cycles, but with and without the use of aftertreatment. A total of approximately 100,000 individual particles were sized and their composition characterized by SPLAT. The aerodynamic size distributions of the characterized

  16. TEM and HRTEM of Soot-in-oil particles and agglomerates from internal combustion engines

    International Nuclear Information System (INIS)

    Fay, M W; Rocca, A La; Shayler, P J

    2014-01-01

    Over time, the performance of lubricating oil in a diesel engine is affected by the build-up of carbon soot produced by the combustion process. TEM and HRTEM are commonly used to investigate the characteristics of individual and agglomerated particles from diesel exhaust, to understand the structure and distribution of the carbon sheets in the primary particles and the nanostructure morphology. However, high resolution imaging of soot-in-oil is more challenging, as mineral oil is a contaminant for the electron microscope and leads to instability under the electron beam. In this work we compare solvent extraction and centrifugation techniques for removing the mineral oil contaminant, and the effect on particle size distribution

  17. Soot modeling of counterflow diffusion flames of ethylene-based binary mixture fuels

    KAUST Repository

    Wang, Yu

    2015-03-01

    A soot model was developed based on the recently proposed PAH growth mechanism for C1-C4 gaseous fuels (KAUST PAH Mechanism 2, KM2) that included molecular growth up to coronene (A7) to simulate soot formation in counterflow diffusion flames of ethylene and its binary mixtures with methane, ethane and propane based on the method of moments. The soot model has 36 soot nucleation reactions from 8 PAH molecules including pyrene and larger PAHs. Soot surface growth reactions were based on a modified hydrogen-abstraction-acetylene-addition (HACA) mechanism in which CH3, C3H3 and C2H radicals were included in the hydrogen abstraction reactions in addition to H atoms. PAH condensation on soot particles was also considered. The experimentally measured profiles of soot volume fraction, number density, and particle size were well captured by the model for the baseline case of ethylene along with the cases involving mixtures of fuels. The simulation results, which were in qualitative agreement with the experimental data in the effects of binary fuel mixing on the sooting structures of the measured flames, showed in particular that 5% addition of propane (ethane) led to an increase in the soot volume fraction of the ethylene flame by 32% (6%), despite the fact that propane and ethane are less sooting fuels than is ethylene, which is in reasonable agreement with experiments of 37% (14%). The model revealed that with 5% addition of methane, there was an increase of 6% in the soot volume fraction. The average soot particle sizes were only minimally influenced while the soot number densities were increased by the fuel mixing. Further analysis of the numerical data indicated that the chemical cross-linking effect between ethylene and the dopant fuels resulted in an increase in PAH formation, which led to higher soot nucleation rates and therefore higher soot number densities. On the other hand, the rates of soot surface growth per unit surface area through the HACA mechanism were

  18. Black carbon aerosol properties measured by a single particle soot photometer in emissions from biomass burning in the laboratory and field

    Science.gov (United States)

    G. R. McMeeking; J. W. Taylor; A. P. Sullivan; M. J. Flynn; S. K. Akagi; C. M. Carrico; J. L. Collett; E. Fortner; T. B. Onasch; S. M. Kreidenweis; R. J. Yokelson; C. Hennigan; A. L. Robinson; H. Coe

    2010-01-01

    We present SP2 observations of BC mass, size distributions and mixing state in emissions from laboratory and field biomass fires in California, USA. Biomass burning is the primary global black carbon (BC) source, but understanding of the amount emitted and its physical properties at and following emission are limited. The single particle soot photometer (SP2) uses a...

  19. Changes of firm size distribution: The case of Korea

    Science.gov (United States)

    Kang, Sang Hoon; Jiang, Zhuhua; Cheong, Chongcheul; Yoon, Seong-Min

    2011-01-01

    In this paper, the distribution and inequality of firm sizes is evaluated for the Korean firms listed on the stock markets. Using the amount of sales, total assets, capital, and the number of employees, respectively, as a proxy for firm sizes, we find that the upper tail of the Korean firm size distribution can be described by power-law distributions rather than lognormal distributions. Then, we estimate the Zipf parameters of the firm sizes and assess the changes in the magnitude of the exponents. The results show that the calculated Zipf exponents over time increased prior to the financial crisis, but decreased after the crisis. This pattern implies that the degree of inequality in Korean firm sizes had severely deepened prior to the crisis, but lessened after the crisis. Overall, the distribution of Korean firm sizes changes over time, and Zipf’s law is not universal but does hold as a special case.

  20. Effect of particle size distribution on sintering of tungsten

    International Nuclear Information System (INIS)

    Patterson, B.R.; Griffin, J.A.

    1984-01-01

    To date, very little is known about the effect of the nature of the particle size distribution on sintering. It is reasonable that there should be an effect of size distribution, and theory and prior experimental work examining the effects of variations in bimodal and continuous distributions have shown marked effects on sintering. Most importantly, even with constant mean particle size, variations in distribution width, or standard deviation, have been shown to produce marked variations in microstructure and sintering rate. In the latter work, in which spherical copper powders were blended to produce lognormal distributions of constant geometric mean particle size by weight frequency, blends with larger values of geometric standard deviation, 1nσ, sintered more rapidly. The goals of the present study were to examine in more detail the effects of variations in the width of lognormal particle size distributions of tungsten powder and determine the effects of 1nσ on the microstructural evolution during sintering

  1. Survival Function Analysis of Planet Size Distribution

    OpenAIRE

    Zeng, Li; Jacobsen, Stein B.; Sasselov, Dimitar D.; Vanderburg, Andrew

    2018-01-01

    Applying the survival function analysis to the planet radius distribution of the Kepler exoplanet candidates, we have identified two natural divisions of planet radius at 4 Earth radii and 10 Earth radii. These divisions place constraints on planet formation and interior structure model. The division at 4 Earth radii separates small exoplanets from large exoplanets above. When combined with the recently-discovered radius gap at 2 Earth radii, it supports the treatment of planets 2-4 Earth rad...

  2. Development of a photometric measuring method for soot analysis in flames. Final report; Entwicklung eines photometrischen Messverfahrens zur Russanalyse in Flammen. Abschlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    Weichert, R.; Niemann, J.

    1995-12-31

    The present photometric measuring method for soot analysis in flames meets the following specifications: determination of the volume concentration of soot particles from 2 x 10{sup -7} upwards by means of extinction measurement at three different wavelengths; determination of the particle size distribution of soot particles by means of nephelometry in the range betwenn 20 and 400 nm; contactless measurements on the particle collective in the flame; no need for calibration of the photometric measuring method on the basis of particles of known size and concentration. (orig./SR) [Deutsch] Es ergeben sich fuer das entwickelte photometrische Messverfahren zur Russanalyse in Flammen folgende Spezifikationen: - Bestimmung der Volumenkonzentration der Russpartikel ab 2 x 10{sup -7} mittels Extinktionsmessungen bei drei Lichtwellenlaengen, - Ermittlung der Partikelgroessenverteilung der Russpartikel aus Streulichtmessungen im Bereich von 20 bis 400 nm, - beruehrungsfreie Messung in der Flamme am Partikelkollektiv und, - keine Kalibrierung des photometrischen Messverfahrens mit Partikeln bekannter Groesse bzw. bekannter Konzentration erforderlich. (orig./SR)

  3. Change of particle size distribution during Brownian coagulation

    International Nuclear Information System (INIS)

    Lee, K.W.

    1984-01-01

    Change in particle size distribution due to Brownian coagulation in the continuum regime has been stuied analytically. A simple analytic solution for the size distribution of an initially lognormal distribution is obtained based on the assumption that the size distribution during the coagulation process attains or can, at least, be represented by a time dependent lognormal function. The results are found to be in a form that corrects Smoluchowski's solution for both polydispersity and size-dependent kernel. It is further shown that regardless of whether the initial distribution is narrow or broad, the spread of the distribution is characterized by approaching a fixed value of the geometric standard deviation. This result has been compared with the self-preserving distribution obtained by similarity theory. (Author)

  4. Concentration and size distribution of particles in abstracted groundwater

    NARCIS (Netherlands)

    Van Beek, C.G.E.M.; de Zwart, A.H.; Balemans, M.; Kooiman, J.W.; van Rosmalen, C.; Timmer, H.; Vandersluys, J.; Stuijfzand, P.J.

    2010-01-01

    Particle number concentrations have been counted and particle size distributions calculated in groundwater derived by abstraction wells. Both concentration and size distribution are governed by the discharge rate: the higher this rate the higher the concentration and the higher the proportion of

  5. Distributions of households by size: differences and trends.

    Science.gov (United States)

    Kuznets, S

    1982-01-01

    "This article deals with the distributions of households by size, that is, by number of persons, as they are observed in international comparisons, and for fewer countries, over time." The contribution of differentials in household size to inequality in income distribution among persons and households is discussed. Data are for both developed and developing countries. excerpt

  6. The Italian primary school-size distribution and the city-size: a complex nexus

    Science.gov (United States)

    Belmonte, Alessandro; di Clemente, Riccardo; Buldyrev, Sergey V.

    2014-06-01

    We characterize the statistical law according to which Italian primary school-size distributes. We find that the school-size can be approximated by a log-normal distribution, with a fat lower tail that collects a large number of very small schools. The upper tail of the school-size distribution decreases exponentially and the growth rates are distributed with a Laplace PDF. These distributions are similar to those observed for firms and are consistent with a Bose-Einstein preferential attachment process. The body of the distribution features a bimodal shape suggesting some source of heterogeneity in the school organization that we uncover by an in-depth analysis of the relation between schools-size and city-size. We propose a novel cluster methodology and a new spatial interaction approach among schools which outline the variety of policies implemented in Italy. Different regional policies are also discussed shedding lights on the relation between policy and geographical features.

  7. Prediction of the filtrate particle size distribution from the pore size distribution in membrane filtration: Numerical correlations from computer simulations

    Science.gov (United States)

    Marrufo-Hernández, Norma Alejandra; Hernández-Guerrero, Maribel; Nápoles-Duarte, José Manuel; Palomares-Báez, Juan Pedro; Chávez-Rojo, Marco Antonio

    2018-03-01

    We present a computational model that describes the diffusion of a hard spheres colloidal fluid through a membrane. The membrane matrix is modeled as a series of flat parallel planes with circular pores of different sizes and random spatial distribution. This model was employed to determine how the size distribution of the colloidal filtrate depends on the size distributions of both, the particles in the feed and the pores of the membrane, as well as to describe the filtration kinetics. A Brownian dynamics simulation study considering normal distributions was developed in order to determine empirical correlations between the parameters that characterize these distributions. The model can also be extended to other distributions such as log-normal. This study could, therefore, facilitate the selection of membranes for industrial or scientific filtration processes once the size distribution of the feed is known and the expected characteristics in the filtrate have been defined.

  8. Investigating Soot Morphology in Counterflow Flames at Elevated Pressures

    KAUST Repository

    Amin, Hafiz Muhammad Fahid

    2018-01-01

    Practical combustion devices such as gas turbines and diesel engines operate at high pressures to increase their efficiency. Pressure significantly increases the overall soot yield. Morphology of these ultra-fine particles determines their airborne lifetime and their interaction with the human respiratory system. Therefore, investigating soot morphology at high pressure is of practical relevance. In this work, a novel experimental setup has been designed and built to study the soot morphology at elevated pressures. The experimental setup consists of a pressure vessel, which can provide optical access from 10° to 165° for multi-angle light scattering, and a counterflow burner which produces laminar flames at elevated pressures. In the first part of the study, N2-diluted ethylene/air and ethane air counterflow flames are stabilized from 2 to 5 atm. Two-angle light scattering and extinction technique have been used to study the effects of pressure on soot parameters. Path averaged soot volume fraction is found to be very sensitive to pressure and increased significantly from 2 to 5 atm. Primary particle size and aggregate size also increased with pressure. Multi-angle light scattering is also performed and flames are investigated from 3 to 5 atm. Scattering to absorption ratio is calculated from multi-angle light scattering and extinction data. Scattering to absorption ratio increased with pressure whereas the number of primary particles in an aggregate decreased with increasing pressure. In the next part of the study, Thermophoretic Sampling of soot is performed, in counterflow flames from 3 to 10 atm, followed by transmission electron microscopy. Mean primary particle size increased with pressure and these trends are consistent withour light scattering measurements. Fractal properties of soot aggregates are found to be insensitive to pressure. 2D diffused light line of sight attenuation (LOSA) and Laser Induced Incandescence (LII) are used to measure local soot

  9. Body size distributions signal a regime shift in a lake ...

    Science.gov (United States)

    Communities of organisms, from mammals to microorganisms, have discontinuous distributions of body size. This pattern of size structuring is a conservative trait of community organization and is a product of processes that occur at multiple spatial and temporal scales. In this study, we assessed whether body size patterns serve as an indicator of a threshold between alternative regimes. Over the past 7000 years, the biological communities of Foy Lake (Montana,USA) have undergone a major regime shift owing to climate change. We used a palaeoecological record of diatom communities to estimate diatom sizes, and then analysed the discontinuous distribution of organism sizes over time. We used Bayesian classification and regression tree models to determine that all time intervals exhibited aggregations of sizes separated by gaps in the distribution and found a significant change in diatom body size distributions approximately 150 years before the identified ecosystem regime shift. We suggest that discontinuity analysis is a useful addition to the suite of tools for the detection of early warning signals of regime shifts. Communities of organisms from mammals to microorganisms have discontinuous distributions of body size. This pattern of size structuring is a conservative trait of community organization and is a product of processes that occur at discrete spatial and temporal scales within ecosystems. Here, a paleoecological record of diatom community change is use

  10. Measurement of Soot Deposition in Automotive Components Using Neutron Radiography

    Energy Technology Data Exchange (ETDEWEB)

    Zekveld, David; Liu, Liaohui [AMEC NSS, 700 University Ave, Toronto, Ontario, M5G 1X6 (Canada); UOIT, 2000 Simcoe Street North, Oshawa, Ontario, L1H 7K4 (Canada); Harrison, Andrew; Gill, Spencer; Harvel, Glenn [UOIT, 2000 Simcoe Street North, Oshawa, Ontario, L1H 7K4 (Canada); Chang, Jen-Shih [McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4L8 (Canada)

    2008-07-01

    About 40% of air pollution is generated by vehicles and transportation. The particulate matter (PM) emission significantly impacts human health. Fine particles below 2.5 {mu}m (PM2.5) can enter the lungs and lead to respiratory problems. These particles not only influence human health, but also reduce the capability of many automobile exhaust heat exchanging devices. Neutron radiography is a non-destructive method of analyzing carbonaceous PM. While neutron radiography has been demonstrated for soot measurement in the past, the application has not considered the presence of unburned hydrocarbons, significant amounts of moisture nor examined complex geometrical configurations. The purpose of this work is to study a reliable non-destructive testing methodology using neutron radiography for measurement of soot distribution in automotive components. A soot standard (aluminium target) was designed and manufactured as a calibration tool. The standard is radiographed and used to measure the differences between various soot thickness and compositions. The radiograph images are analyzed to determine a calibration curve based upon the composition of the materials which can then be used for analysis of the automotive components. Experiments are performed using a diesel engine to produce soot deposits on exhaust piping. Soot distribution on exhaust piping is measured using neutron radiography. (authors)

  11. Measurement of Soot Deposition in Automotive Components Using Neutron Radiography

    International Nuclear Information System (INIS)

    Zekveld, David; Liu, Liaohui; Harrison, Andrew; Gill, Spencer; Harvel, Glenn; Chang, Jen-Shih

    2008-01-01

    About 40% of air pollution is generated by vehicles and transportation. The particulate matter (PM) emission significantly impacts human health. Fine particles below 2.5 μm (PM2.5) can enter the lungs and lead to respiratory problems. These particles not only influence human health, but also reduce the capability of many automobile exhaust heat exchanging devices. Neutron radiography is a non-destructive method of analyzing carbonaceous PM. While neutron radiography has been demonstrated for soot measurement in the past, the application has not considered the presence of unburned hydrocarbons, significant amounts of moisture nor examined complex geometrical configurations. The purpose of this work is to study a reliable non-destructive testing methodology using neutron radiography for measurement of soot distribution in automotive components. A soot standard (aluminium target) was designed and manufactured as a calibration tool. The standard is radiographed and used to measure the differences between various soot thickness and compositions. The radiograph images are analyzed to determine a calibration curve based upon the composition of the materials which can then be used for analysis of the automotive components. Experiments are performed using a diesel engine to produce soot deposits on exhaust piping. Soot distribution on exhaust piping is measured using neutron radiography. (authors)

  12. Technical Note: The single particle soot photometer fails to reliably detect PALAS soot nanoparticles

    Directory of Open Access Journals (Sweden)

    M. Gysel

    2012-12-01

    Full Text Available The single particle soot photometer (SP2 uses laser-induced incandescence (LII for the measurement of atmospheric black carbon (BC particles. The BC mass concentration is obtained by combining quantitative detection of BC mass in single particles with a counting efficiency of 100% above its lower detection limit. It is commonly accepted that a particle must contain at least several tenths of a femtogram BC in order to be detected by the SP2.

    Here we show the result that most BC particles from a PALAS spark discharge soot generator remain undetected by the SP2, even if their BC mass, as independently determined with an aerosol particle mass analyser (APM, is clearly above the typical lower detection limit of the SP2. Comparison of counting efficiency and effective density data of PALAS soot with flame generated soot (combustion aerosol standard burner, CAST, fullerene soot and carbon black particles (Cabot Regal 400R reveals that particle morphology can affect the SP2's lower detection limit. PALAS soot particles are fractal-like agglomerates of very small primary particles with a low fractal dimension, resulting in a very low effective density. Such loosely packed particles behave like "the sum of individual primary particles" in the SP2's laser. Accordingly, most PALAS soot particles remain undetected as the SP2's laser intensity is insufficient to heat the primary particles to their vaporisation temperature because of their small size (Dpp ≈ 5–10 nm. Previous knowledge from pulsed laser-induced incandescence indicated that particle morphology might have an effect on the SP2's lower detection limit, however, an increase of the lower detection limit by a factor of ∼5–10, as reported here for PALAS soot, was not expected.

    In conclusion, the SP2's lower detection limit at a certain laser power depends primarily on the total BC mass per particle for compact particles with sufficiently high effective

  13. Role of Fluid-Dynamics in Soot Formation and Microstructure in Acetylene-Air Laminar Diffusion Flames

    Directory of Open Access Journals (Sweden)

    Praveen Pandey

    2015-03-01

    Full Text Available Residence time and thermo-chemical environment are important factors in the soot-formation process in flames. Studies have revealed that flow-dynamics plays a dominant role in soot formation process. For understanding the effect of flow dynamics on soot formation and physical structure of the soot formed in different combustion environments two types of laminar diffusion flames of Acetylene and air, a normal diffusion flame (NDF and an inverse diffusion flame (IDF have been investigated. The fuel and air supply in the reaction zone in two flame types were kept constant but the interchange of relative position of fuel and air altered the burner exit Reynolds and Froude numbers of gases, fuel/air velocity ratio and flame shape. Soot samples were collected using thermophoretic sampling on transmission electron microscope (TEM grids at different flame heights and were analyzed off-line in a Transmission Electron Microscope. Soot primary particle size, soot aggregate size and soot volume fraction were measured using an image analysis software. In NDF the maximum flame temperature was about 1525 K and 1230 K for IDF. The soot primary particles are distinctly smaller in size in IDF (between 19 – 26 nm compared to NDF (between 29–34 nm. Both NDF and IDF show chainlike branched structure of soot agglomerate with soot particles of a nearly spherical shape. The average number of soot primary particles per aggregate in NDF was in the range of 24 to 40 and in IDF it varied between 16 to 24. Soot volume fraction was between 0.6 to 1.5 ppm in NDF where as it was less than 0.2 ppm in IDF. The change in sooting characteristics of the two flame types is attributed to changed fuel/air velocity ratio, entrainment of gas molecules and thermophoresis on soot particles.

  14. Methods of assessing grain-size distribution during grain growth

    DEFF Research Database (Denmark)

    Tweed, Cherry J.; Hansen, Niels; Ralph, Brian

    1985-01-01

    This paper considers methods of obtaining grain-size distributions and ways of describing them. In order to collect statistically useful amounts of data, an automatic image analyzer is used, and the resulting data are subjected to a series of tests that evaluate the differences between two related...... distributions (before and after grain growth). The distributions are measured from two-dimensional sections, and both the data and the corresponding true three-dimensional grain-size distributions (obtained by stereological analysis) are collected. The techniques described here are illustrated by reference...

  15. Modelling soot formation from wall films in a gasoline direct injection engine using a detailed population balance model

    International Nuclear Information System (INIS)

    Wang, Buyu; Mosbach, Sebastian; Schmutzhard, Sebastian; Shuai, Shijin; Huang, Yaqing; Kraft, Markus

    2016-01-01

    Highlights: • Soot formation from a wall film in a GDI engine is simulated. • Spray impingement and wall film evaporation models are added to SRM Engine Suite. • Soot is modelled using a highly detailed population balance model. • Particle size distributions are measured experimentally. • Evolution of wall region is shown in equivalence ratio-temperature diagrams. - Abstract: In this study, soot formation in a Gasoline Direct Injection (GDI) engine is simulated using a Stochastic Reactor Model (SRM Engine Suite) which contains a detailed population balance soot model capable of describing particle morphology and chemical composition. In order to describe the soot formation originating from the wall film, the SRM Engine Suite is extended to include spray impingement and wall film evaporation models. The cylinder is divided into a wall and a bulk zone to resolve the equivalence ratio and temperature distributions of the mixture near the wall. The combustion chamber wall is assumed to exchange heat directly only with the wall zone. The turbulent mixing within each zone and between the two zones are simulated with different mixing models. The effects of key parameters on the temperature and equivalence ratio in the two zones are investigated. The mixing rate between the wall and bulk zone has a significant effect on the wall zone, whilst the mixing rate in the wall zone only has a negligible impact on the temperature and equivalence ratio below a certain threshold. Experimental data are obtained from a four-cylinder, gasoline-fuelled direct injection spark ignition engine operated stoichiometrically. An injection timing sweep, ranging from 120 CAD BTDC to 330 CAD BTDC, is conducted in order to investigate the effect of spray impingement on soot formation. The earliest injection case (330 CAD BTDC), which produces significantly higher levels of particle emissions than any other case, is simulated by the current model. It is found that the in-cylinder pressure

  16. Sediment Size Distribution at Three Rivers with Different Types of ...

    African Journals Online (AJOL)

    ADOWIE PERE

    sediment size distribution based on land use is very crucial in river maintenance. ... a basis for river catchment management study and can be used by river management .... small. In this case, the difference between upstream and downstream ...

  17. application of ant colony optimisation in distribution transformer sizing

    African Journals Online (AJOL)

    HP

    Keywords: ant colony, optimization, transformer sizing, distribution transformer. 1. INTRODUCTION ... more intensive pheromone and higher probability to be chosen [12]. ..... pp.29-41, 1996. [7] EC global market place, “Technical Parameters”,.

  18. Strain rate effect on sooting characteristics in laminar counterflow diffusion flames

    KAUST Repository

    Wang, Yu

    2016-01-20

    The effects of strain rate, oxygen enrichment and fuel type on the sooting characteristics of counterflow diffusion flames were studied. The sooting structures and relative PAH concentrations were measured with laser diagnostics. Detailed soot modeling using recently developed PAH chemistry and surface reaction mechanism was performed and the results were compared with experimental data for ethylene flames, focusing on the effects of strain rates. The results showed that increase in strain rate reduced soot volume fraction, average size and peak number density. Increase in oxygen mole fraction increased soot loading and decreased its sensitivity on strain rate. The soot volume fractions of ethane, propene and propane flames were also measured as a function of global strain rate. The sensitivity of soot volume fraction to strain rate was observed to be fuel dependent at a fixed oxygen mole fraction, with the sensitivity being higher for more sooting fuels. However, when the soot loadings were matched at a reference strain rate for different fuels by adjusting oxygen mole fraction, the dependence of soot loading on strain rate became comparable among the tested fuels. PAH concentrations were shown to decrease with increase in strain rate and the dependence on strain rate is more pronounced for larger PAHs. Soot modeling was performed using detailed PAH growth chemistry with molecular growth up to coronene. A qualitative agreement was obtained between experimental and simulation results, which was then used to explain the experimentally observed strain rate effect on soot growth. However, quantitatively, the simulation result exhibits higher sensitivity to strain rate, especially for large PAHs and soot volume fractions.

  19. Molecular mechanics and quantum mechanical modeling of hexane soot structure and interactions with pyrene

    Directory of Open Access Journals (Sweden)

    Kubicki JD

    2000-09-01

    Full Text Available Molecular simulations (energy minimizations and molecular dynamics of an n-hexane soot model developed by Smith and co-workers (M. S. Akhter, A. R. Chughtai and D. M. Smith, Appl. Spectrosc., 1985, 39, 143; ref. 1 were performed. The MM+ (N. L. Allinger, J. Am. Chem. Soc., 1977, 395, 157; ref. 2 and COMPASS (H. Sun, J. Phys. Chem., 1998, 102, 7338; ref. 3 force fields were tested for their ability to produce realistic soot nanoparticle structure. The interaction of pyrene with the model soot was simulated. Quantum mechanical calculations on smaller soot fragments were carried out. Starting from an initial 2D structure, energy minimizations are not able to produce the observed layering within soot with either force field. Results of molecular dynamics simulations indicate that the COMPASS force field does a reasonably accurate job of reproducing observations of soot structure. Increasing the system size from a 683 to a 2732 atom soot model does not have a significant effect on predicted structures. Neither does the addition of water molecules surrounding the soot model. Pyrene fits within the soot structure without disrupting the interlayer spacing. Polycyclic aromatic hydrocarbons (PAH, such as pyrene, may strongly partition into soot and have slow desorption kinetics because the PAH-soot bonding is similar to soot–soot interactions. Diffusion of PAH into soot micropores may allow the PAH to be irreversibly adsorbed and sequestered so that they partition slowly back into an aqueous phase causing dis-equilibrium between soil organic matter and porewater.

  20. INITIAL PLANETESIMAL SIZES AND THE SIZE DISTRIBUTION OF SMALL KUIPER BELT OBJECTS

    International Nuclear Information System (INIS)

    Schlichting, Hilke E.; Fuentes, Cesar I.; Trilling, David E.

    2013-01-01

    The Kuiper Belt is a remnant from the early solar system and its size distribution contains many important constraints that can be used to test models of planet formation and collisional evolution. We show, by comparing observations with theoretical models, that the observed Kuiper Belt size distribution is well matched by coagulation models, which start with an initial planetesimal population with radii of about 1 km, and subsequent collisional evolution. We find that the observed size distribution above R ∼ 30 km is primordial, i.e., it has not been modified by collisional evolution over the age of the solar system, and that the size distribution below R ∼ 30 km has been modified by collisions and that its slope is well matched by collisional evolution models that use published strength laws. We investigate in detail the resulting size distribution of bodies ranging from 0.01 km to 30 km and find that its slope changes several times as a function of radius before approaching the expected value for an equilibrium collisional cascade of material strength dominated bodies for R ∼< 0.1 km. Compared to a single power-law size distribution that would span the whole range from 0.01 km to 30 km, we find in general a strong deficit of bodies around R ∼ 10 km and a strong excess of bodies around 2 km in radius. This deficit and excess of bodies are caused by the planetesimal size distribution left over from the runaway growth phase, which left most of the initial mass in small planetesimals while only a small fraction of the total mass is converted into large protoplanets. This excess mass in small planetesimals leaves a permanent signature in the size distribution of small bodies that is not erased after 4.5 Gyr of collisional evolution. Observations of the small Kuiper Belt Object (KBO) size distribution can therefore test if large KBOs grew as a result of runaway growth and constrained the initial planetesimal sizes. We find that results from recent KBO

  1. Size distribution measurements and chemical analysis of aerosol components

    Energy Technology Data Exchange (ETDEWEB)

    Pakkanen, T.A.

    1995-12-31

    The principal aims of this work were to improve the existing methods for size distribution measurements and to draw conclusions about atmospheric and in-stack aerosol chemistry and physics by utilizing size distributions of various aerosol components measured. A sample dissolution with dilute nitric acid in an ultrasonic bath and subsequent graphite furnace atomic absorption spectrometric analysis was found to result in low blank values and good recoveries for several elements in atmospheric fine particle size fractions below 2 {mu}m of equivalent aerodynamic particle diameter (EAD). Furthermore, it turned out that a substantial amount of analyses associated with insoluble material could be recovered since suspensions were formed. The size distribution measurements of in-stack combustion aerosols indicated two modal size distributions for most components measured. The existence of the fine particle mode suggests that a substantial fraction of such elements with two modal size distributions may vaporize and nucleate during the combustion process. In southern Norway, size distributions of atmospheric aerosol components usually exhibited one or two fine particle modes and one or two coarse particle modes. Atmospheric relative humidity values higher than 80% resulted in significant increase of the mass median diameters of the droplet mode. Important local and/or regional sources of As, Br, I, K, Mn, Pb, Sb, Si and Zn were found to exist in southern Norway. The existence of these sources was reflected in the corresponding size distributions determined, and was utilized in the development of a source identification method based on size distribution data. On the Finnish south coast, atmospheric coarse particle nitrate was found to be formed mostly through an atmospheric reaction of nitric acid with existing coarse particle sea salt but reactions and/or adsorption of nitric acid with soil derived particles also occurred. Chloride was depleted when acidic species reacted

  2. Elemental mass size distribution of the Debrecen urban aerosol

    International Nuclear Information System (INIS)

    Kertesz, Zs.; Szoboszlai, Z.; Dobos, E.; Borbely-Kiss, I.

    2007-01-01

    Complete text of publication follows. Size distribution is one of the basic properties of atmospheric aerosol. It is closely related to the origin, chemical composition and age of the aerosol particles, and it influences the optical properties, environmental effects and health impact of aerosol. As part of the ongoing aerosol research in the Group of Ion Beam Applications of the Atomki, elemental mass size distribution of urban aerosol were determined using particle induced X-ray emission (PIXE) analytical technique. Aerosol sampling campaigns were carried out with 9-stage PIXE International cascade impactors, which separates the aerosol into 10 size fractions in the 0.05-30 ?m range. Five 48-hours long samplings were done in the garden of the Atomki, in April and in October, 2007. Both campaigns included weekend and working day samplings. Basically two different kinds of particles could be identified according to the size distribution. In the size distribution of Al, Si, Ca, Fe, Ba, Ti, Mn and Co one dominant peak can be found around the 3 m aerodynamic diameter size range, as it is shown on Figure 1. These are the elements of predominantly natural origin. Elements like S, Cl, K, Zn, Pb and Br appears with high frequency in the 0.25-0.5 mm size range as presented in Figure 2. These elements are originated mainly from anthropogenic sources. However sometimes in the size distribution of these elements a 2 nd , smaller peak appears at the 2-4 μm size ranges, indicating different sources. Differences were found between the size distribution of the spring and autumn samples. In the case of elements of soil origin the size distribution was shifted towards smaller diameters during October, and a 2 nd peak appeared around 0.5 μm. A possible explanation to this phenomenon can be the different meteorological conditions. No differences were found between the weekend and working days in the size distribution, however the concentration values were smaller during the weekend

  3. A multivariate rank test for comparing mass size distributions

    KAUST Repository

    Lombard, F.

    2012-04-01

    Particle size analyses of a raw material are commonplace in the mineral processing industry. Knowledge of particle size distributions is crucial in planning milling operations to enable an optimum degree of liberation of valuable mineral phases, to minimize plant losses due to an excess of oversize or undersize material or to attain a size distribution that fits a contractual specification. The problem addressed in the present paper is how to test the equality of two or more underlying size distributions. A distinguishing feature of these size distributions is that they are not based on counts of individual particles. Rather, they are mass size distributions giving the fractions of the total mass of a sampled material lying in each of a number of size intervals. As such, the data are compositional in nature, using the terminology of Aitchison [1] that is, multivariate vectors the components of which add to 100%. In the literature, various versions of Hotelling\\'s T 2 have been used to compare matched pairs of such compositional data. In this paper, we propose a robust test procedure based on ranks as a competitor to Hotelling\\'s T 2. In contrast to the latter statistic, the power of the rank test is not unduly affected by the presence of outliers or of zeros among the data. © 2012 Copyright Taylor and Francis Group, LLC.

  4. Interpretations of family size distributions: The Datura example

    Science.gov (United States)

    Henych, Tomáš; Holsapple, Keith A.

    2018-04-01

    Young asteroid families are unique sources of information about fragmentation physics and the structure of their parent bodies, since their physical properties have not changed much since their birth. Families have different properties such as age, size, taxonomy, collision severity and others, and understanding the effect of those properties on our observations of the size-frequency distribution (SFD) of family fragments can give us important insights into the hypervelocity collision processes at scales we cannot achieve in our laboratories. Here we take as an example the very young Datura family, with a small 8-km parent body, and compare its size distribution to other families, with both large and small parent bodies, and created by both catastrophic and cratering formation events. We conclude that most likely explanation for the shallower size distribution compared to larger families is a more pronounced observational bias because of its small size. Its size distribution is perfectly normal when its parent body size is taken into account. We also discuss some other possibilities. In addition, we study another common feature: an offset or "bump" in the distribution occurring for a few of the larger elements. We hypothesize that it can be explained by a newly described regime of cratering, "spall cratering", which controls the majority of impact craters on the surface of small asteroids like Datura.

  5. Optics of Water Microdroplets with Soot Inclusions: Exact Versus Approximate Results

    Science.gov (United States)

    Liu, Li; Mishchenko, Michael I.

    2016-01-01

    We use the recently generalized version of the multi-sphere superposition T-matrix method (STMM) to compute the scattering and absorption properties of microscopic water droplets contaminated by black carbon. The soot material is assumed to be randomly distributed throughout the droplet interior in the form of numerous small spherical inclusions. Our numerically-exact STMM results are compared with approximate ones obtained using the Maxwell-Garnett effective-medium approximation (MGA) and the Monte Carlo ray-tracing approximation (MCRTA). We show that the popular MGA can be used to calculate the droplet optical cross sections, single-scattering albedo, and asymmetry parameter provided that the soot inclusions are quasi-uniformly distributed throughout the droplet interior, but can fail in computations of the elements of the scattering matrix depending on the volume fraction of soot inclusions. The integral radiative characteristics computed with the MCRTA can deviate more significantly from their exact STMM counterparts, while accurate MCRTA computations of the phase function require droplet size parameters substantially exceeding 60.

  6. Size-biased distributions in the generalized beta distribution family, with applications to forestry

    Science.gov (United States)

    Mark J. Ducey; Jeffrey H. Gove

    2015-01-01

    Size-biased distributions arise in many forestry applications, as well as other environmental, econometric, and biomedical sampling problems. We examine the size-biased versions of the generalized beta of the first kind, generalized beta of the second kind and generalized gamma distributions. These distributions include, as special cases, the Dagum (Burr Type III),...

  7. Recent developments in the Dutch firm-size distribution

    NARCIS (Netherlands)

    M.A. Carree (Martin); A.R. Thurik (Roy)

    1991-01-01

    textabstractThis study investigates the development of the firm-size distribution in the Netherlands using various measures. Data are used for the period 1978 through 1989 covering practically the entire Dutch private sector. The results show a general tendency towards smaller firm sizes in

  8. Juvenile Penaeid Shrimp Density, Spatial Distribution and Size ...

    African Journals Online (AJOL)

    The effects of habitat characteristics (mangrove creek, sandflat, mudflat and seagrass meadow) water salinity, temperature, and depth on the density, spatial distribution and size distribution of juveniles of five commercially important penaied shrimp species (Metapenaus monoceros, M. stebbingi, Fenneropenaeus indicus, ...

  9. The degree distribution of fixed act-size collaboration networks

    Indian Academy of Sciences (India)

    In this paper, we investigate a special evolving model of collaboration net-works, where the act-size is fixed. Based on the first-passage probability of Markov chain theory, this paper provides a rigorous proof for the existence of a limiting degree distribution of this model and proves that the degree distribution obeys the ...

  10. Sample sizes and model comparison metrics for species distribution models

    Science.gov (United States)

    B.B. Hanberry; H.S. He; D.C. Dey

    2012-01-01

    Species distribution models use small samples to produce continuous distribution maps. The question of how small a sample can be to produce an accurate model generally has been answered based on comparisons to maximum sample sizes of 200 observations or fewer. In addition, model comparisons often are made with the kappa statistic, which has become controversial....

  11. Distribution Of Natural Radioactivity On Soil Size Particles

    International Nuclear Information System (INIS)

    Tran Van Luyen; Trinh Hoai Vinh; Thai Khac Dinh

    2008-01-01

    This report presents a distribution of natural radioactivity on different soil size particles, taken from one soil profile. On the results shows a range from 52% to 66% of natural radioisotopes such as 238 U, 232 Th, 226 Ra and 40 K concentrated on the soil particles below 40 micrometers in diameter size. The remained of natural radioisotopes were distributed on a soil particles with higher diameter size. The study is available for soil sample collected to natural radioactive analyze by gamma and alpha spectrometer methods. (author)

  12. Phase size distribution in WC/Co hardmetal

    International Nuclear Information System (INIS)

    Roebuck, B.; Bennett, E.G.

    1986-01-01

    A high-resolution field emission scanning electron microscope was used to perform accurate quantitative metallography on a variety of WC/Co hardmetals. Particular attention was paid to obtaining the mean size and size distribution of the cobalt phase by linear analysis. Cobalt regions are frequently submicron and difficult to resolve adequately by conventional methods. The WC linear intercept distributions, and contiguity were also measured at the same time. The results were used to examine the validity of theoretic derivations of cobalt intercept size

  13. Influence of particle size distributions on magnetorheological fluid performances

    International Nuclear Information System (INIS)

    Chiriac, H; Stoian, G

    2010-01-01

    In this paper we investigate the influence that size distributions of the magnetic particles might have on the magnetorheological fluid performances. In our study, several size distributions have been tailored first by sieving a micrometric Fe powder in order to obtain narrow distribution powders and then by recomposing the new size distributions (different from Gaussian). We used spherical Fe particles (mesh -325) commercially available. The powder was sieved by means of a sieve shaker using a series of sieves with the following mesh size: 20, 32, 40, 50, 63, 80 micrometers. All magnetic powders were characterized through Vibrating Sample Magnetometer (VSM) measurements, particle size analysis and also Scanning Electron Microscope (SEM) images were taken. Magnetorheological (MR) fluids based on the resulted magnetic powders were prepared and studied by means of a rheometer with a magnetorheological module. The MR fluids were measured in magnetic field and in zero magnetic field as well. As we noticed in our previous experiments particles size distribution can also influence the MR fluids performances.

  14. Measurement of size distribution for 220Rn progeny attached aerosols

    International Nuclear Information System (INIS)

    Zhang Lei; Guo Qiuju; Zhuo Weihai

    2008-01-01

    The size distribution of radioactive aerosols is a very important factor for evaluating the inner exposure dose contributed by radon and thoron progeny in environments. In order to measure the size distribution of thoron progeny attached radioactive aerosols, a device was developed using wire screens. The count median diameter (CMD) and the geometric standard deviation (GSD) of attached radioactive aerosols were calculated by collecting ThB and using CR-39 as detector. Field measurement results at Yangjiang City in Guangdong Province show that the CMDs distribute between 30 and 130 nm, and the GSDs are between 1.9 and 3.3. It also shows that the more humid country, the smaller CMDs, and the ventilation has great influence on the size distribution of aerosols. The CMDs of adobe house are smaller than that of the concrete houses. (authors)

  15. Cell-size distribution in epithelial tissue formation and homeostasis.

    Science.gov (United States)

    Puliafito, Alberto; Primo, Luca; Celani, Antonio

    2017-03-01

    How cell growth and proliferation are orchestrated in living tissues to achieve a given biological function is a central problem in biology. During development, tissue regeneration and homeostasis, cell proliferation must be coordinated by spatial cues in order for cells to attain the correct size and shape. Biological tissues also feature a notable homogeneity of cell size, which, in specific cases, represents a physiological need. Here, we study the temporal evolution of the cell-size distribution by applying the theory of kinetic fragmentation to tissue development and homeostasis. Our theory predicts self-similar probability density function (PDF) of cell size and explains how division times and redistribution ensure cell size homogeneity across the tissue. Theoretical predictions and numerical simulations of confluent non-homeostatic tissue cultures show that cell size distribution is self-similar. Our experimental data confirm predictions and reveal that, as assumed in the theory, cell division times scale like a power-law of the cell size. We find that in homeostatic conditions there is a stationary distribution with lognormal tails, consistently with our experimental data. Our theoretical predictions and numerical simulations show that the shape of the PDF depends on how the space inherited by apoptotic cells is redistributed and that apoptotic cell rates might also depend on size. © 2017 The Author(s).

  16. Recurrent frequency-size distribution of characteristic events

    Directory of Open Access Journals (Sweden)

    S. G. Abaimov

    2009-04-01

    Full Text Available Statistical frequency-size (frequency-magnitude properties of earthquake occurrence play an important role in seismic hazard assessments. The behavior of earthquakes is represented by two different statistics: interoccurrent behavior in a region and recurrent behavior at a given point on a fault (or at a given fault. The interoccurrent frequency-size behavior has been investigated by many authors and generally obeys the power-law Gutenberg-Richter distribution to a good approximation. It is expected that the recurrent frequency-size behavior should obey different statistics. However, this problem has received little attention because historic earthquake sequences do not contain enough events to reconstruct the necessary statistics. To overcome this lack of data, this paper investigates the recurrent frequency-size behavior for several problems. First, the sequences of creep events on a creeping section of the San Andreas fault are investigated. The applicability of the Brownian passage-time, lognormal, and Weibull distributions to the recurrent frequency-size statistics of slip events is tested and the Weibull distribution is found to be the best-fit distribution. To verify this result the behaviors of numerical slider-block and sand-pile models are investigated and the Weibull distribution is confirmed as the applicable distribution for these models as well. Exponents β of the best-fit Weibull distributions for the observed creep event sequences and for the slider-block model are found to have similar values ranging from 1.6 to 2.2 with the corresponding aperiodicities CV of the applied distribution ranging from 0.47 to 0.64. We also note similarities between recurrent time-interval statistics and recurrent frequency-size statistics.

  17. In-cylinder Combustion and Soot Evolution in the Transition from Conventional CI mode to PPC

    KAUST Repository

    An, Yanzhao

    2018-01-09

    The present study intends to explore the in-cylinder combustion and evolution of soot emission during the transition from conventional compression ignition (CI) combustion to partially premixed combustion (PPC) at low load conditions. In-cylinder combustion images and engine-out emissions were measured in an optical engine fueled with low octane heavy naphtha fuel (RON = 50). Full cycle engine simulations were performed using a three-dimensional computational fluid dynamics code CONVERGETM, coupled with gas phase chemical kinetics, turbulence, and particulate size mimic soot model. The simulations were performed under low load conditions (IMEP ~ 2 to 3 bar) at an engine speed of 1200 rpm. The start of injection (SOI) was advanced from late (-10 CAD aTDC) to early fuel injection timings (-40 CAD aTDC) to realize the combustion transition from CI combustion to PPC. The simulation results of combustion and emission are compared with the experimental results at both CI and PPC combustion modes. The results of the study show a typical low-temperature stratified lean combustion at PPC mode, while high-temperature spray-driven combustion is evident at CI mode. The in-cylinder small intermediates species such as acetylene (C2H2), propargyl (C3H3), cyclopentadienyl (C5H5) and polycyclic aromatic hydrocarbons (PAHs) were significantly suppressed at PPC mode. Nucleation reaction of PAHs collision contributed to main soot mass production. The distribution of soot mass and particle number density was consistent with the distribution of high-temperature zones at CI and PPC combustion modes.

  18. An investigation of late-combustion soot burnout in a DI diesel engine using simultaneous planar imaging of soot and OH radical

    Energy Technology Data Exchange (ETDEWEB)

    John E. Dec; Peter L. Kelly-Zion

    1999-10-01

    Diesel engine design continues to be driven by the need to improve performance while at the same time achieving further reductions in emissions. The development of new designs to accomplish these goals requires an understanding of how the emissions are produced in the engine. Laser-imaging diagnostics are uniquely capable of providing this information, and the understanding of diesel combustion and emissions formation has been advanced considerably in recent years by their application. However, previous studies have generally focused on the early and middle stages of diesel combustion. These previous laser-imaging studies do provide important insight into the soot formation and oxidation processes during the main combustion event. They indicate that prior to the end of injection, soot formation is initiated by fuel-rich premixed combustion (equivalence ratio > 4) near the upstream limit of the luminous portion of the reacting fuel jet. The soot is then oxidized at the diffusion flame around the periphery of the luminous plume. Under typical diesel engine conditions, the diffusion flame does not burn the remaining fuel and soot as rapidly as it is supplied, resulting in an expanding region of rich combustion products and soot. This is evident in natural emission images by the increasing size of the luminous soot cloud prior to the end of injection. Hence, the amount of soot in the combustion chamber typically increases until shortly after the end of fuel injection, at which time the main soot formation period ends and the burnout phase begins. Sampling valve and two-color pyrometry data indicate that the vast majority (more than 90%) of the soot formed is oxidized before combustion ends; however, it is generally thought that a small fraction of this soot from the main combustion zones is not consumed and is the source of tail pipe soot emissions.

  19. Mass size distribution of particle-bound water

    Science.gov (United States)

    Canepari, S.; Simonetti, G.; Perrino, C.

    2017-09-01

    The thermal-ramp Karl-Fisher method (tr-KF) for the determination of PM-bound water has been applied to size-segregated PM samples collected in areas subjected to different environmental conditions (protracted atmospheric stability, desert dust intrusion, urban atmosphere). This method, based on the use of a thermal ramp for the desorption of water from PM samples and the subsequent analysis by the coulometric KF technique, had been previously shown to differentiate water contributes retained with different strength and associated to different chemical components in the atmospheric aerosol. The application of the method to size-segregated samples has revealed that water showed a typical mass size distribution in each one of the three environmental situations that were taken into consideration. A very similar size distribution was shown by the chemical PM components that prevailed during each event: ammonium nitrate in the case of atmospheric stability, crustal species in the case of desert dust, road-dust components in the case of urban sites. The shape of the tr-KF curve varied according to the size of the collected particles. Considering the size ranges that better characterize the event (fine fraction for atmospheric stability, coarse fraction for dust intrusion, bi-modal distribution for urban dust), this shape is coherent with the typical tr-KF shape shown by water bound to the chemical species that predominate in the same PM size range (ammonium nitrate, crustal species, secondary/combustion species - road dust components).

  20. Lognormal Behavior of the Size Distributions of Animation Characters

    Science.gov (United States)

    Yamamoto, Ken

    This study investigates the statistical property of the character sizes of animation, superhero series, and video game. By using online databases of Pokémon (video game) and Power Rangers (superhero series), the height and weight distributions are constructed, and we find that the weight distributions of Pokémon and Zords (robots in Power Rangers) follow the lognormal distribution in common. For the theoretical mechanism of this lognormal behavior, the combination of the normal distribution and the Weber-Fechner law is proposed.

  1. XRD characterisation of nanoparticle size and shape distributions

    International Nuclear Information System (INIS)

    Armstrong, N.; Kalceff, W.; Cline, J.P.; Bonevich, J.

    2004-01-01

    Full text: The form of XRD lines and the extent of their broadening provide useful structural information about the shape, size distribution, and modal characteristics of the nanoparticles comprising the specimen. Also, the defect content of the nanoparticles can be determined, including the type, dislocation density, and stacking faults/twinning. This information is convoluted together and can be grouped into 'size' and 'defect' broadening contributions. Modern X-ray diffraction analysis techniques have concentrated on quantifying the broadening arising from the size and defect contributions, while accounting for overlapping of profiles, instrumental broadening, background scattering and noise components. We report on a combined Bayesian/Maximum Entropy (MaxEnt) technique developed for use in the certification of a NIST Standard Reference Material (SRM) for size-broadened line profiles. The approach used was chosen because of its generality in removing instrumental broadening from the observed line profiles, and its ability to determine not only the average crystallite size, but also the distribution of sizes and the average shape of crystallites. Moverover, this Bayesian/MaxEnt technique is fully quantitative, in that it also determines uncertainties in the crystallite-size distribution and other parameters. Both experimental and numerical simulations of size broadened line-profiles modelled on a range of specimens with spherical and non-spherical morphologies are presented to demonstrate how this information can be retrieved from the line profile data. The sensitivity of the Bayesian/MaxEnt method to determining the size distribution using varying a priori information are emphasised and discussed

  2. Inversion of particle size distribution by spectral extinction technique using the attractive and repulsive particle swarm optimization algorithm

    Directory of Open Access Journals (Sweden)

    Qi Hong

    2015-01-01

    Full Text Available The particle size distribution (PSD plays an important role in environmental pollution detection and human health protection, such as fog, haze and soot. In this study, the Attractive and Repulsive Particle Swarm Optimization (ARPSO algorithm and the basic PSO were applied to retrieve the PSD. The spectral extinction technique coupled with the Anomalous Diffraction Approximation (ADA and the Lambert-Beer Law were employed to investigate the retrieval of the PSD. Three commonly used monomodal PSDs, i.e. the Rosin-Rammer (R-R distribution, the normal (N-N distribution, the logarithmic normal (L-N distribution were studied in the dependent model. Then, an optimal wavelengths selection algorithm was proposed. To study the accuracy and robustness of the inverse results, some characteristic parameters were employed. The research revealed that the ARPSO showed more accurate and faster convergence rate than the basic PSO, even with random measurement error. Moreover, the investigation also demonstrated that the inverse results of four incident laser wavelengths showed more accurate and robust than those of two wavelengths. The research also found that if increasing the interval of the selected incident laser wavelengths, inverse results would show more accurate, even in the presence of random error.

  3. Linear Model for Optimal Distributed Generation Size Predication

    Directory of Open Access Journals (Sweden)

    Ahmed Al Ameri

    2017-01-01

    Full Text Available This article presents a linear model predicting optimal size of Distributed Generation (DG that addresses the minimum power loss. This method is based fundamentally on strong coupling between active power and voltage angle as well as between reactive power and voltage magnitudes. This paper proposes simplified method to calculate the total power losses in electrical grid for different distributed generation sizes and locations. The method has been implemented and tested on several IEEE bus test systems. The results show that the proposed method is capable of predicting approximate optimal size of DG when compared with precision calculations. The method that linearizes a complex model showed a good result, which can actually reduce processing time required. The acceptable accuracy with less time and memory required can help the grid operator to assess power system integrated within large-scale distribution generation.

  4. Radioactive Aerosol Size Distribution Measured in Nuclear Workplaces

    International Nuclear Information System (INIS)

    Kravchik, T.; Oved, S.; German, U.

    2002-01-01

    Inhalation is the main route for internal exposure of workers to radioactive aerosols in the nuclear industry.Aerosol's size distribution and in particular its activity median aerodynamic diameter (AMAD)is important for determining the fractional deposition of inhaled particles in the respiratory tract and the resulting doses. Respiratory tract models have been published by the International Commission on radiological Protection (ICRP).The former model has recommended a default AMAD of 1 micron for the calculation of dose coefficients for workers in the nuclear industry [1].The recent model recommends a 5 microns default diameter for occupational exposure which is considered to be more representative of workplace aerosols [2]. Several researches on radioactive aerosol's size distribution in nuclear workplaces has supported this recommendation [3,4].This paper presents the results of radioactive aerosols size distribution measurements taken at several workplaces of the uranium production process

  5. Production, depreciation and the size distribution of firms

    Science.gov (United States)

    Ma, Qi; Chen, Yongwang; Tong, Hui; Di, Zengru

    2008-05-01

    Many empirical researches indicate that firm size distributions in different industries or countries exhibit some similar characters. Among them the fact that many firm size distributions obey power-law especially for the upper end has been mostly discussed. Here we present an agent-based model to describe the evolution of manufacturing firms. Some basic economic behaviors are taken into account, which are production with decreasing marginal returns, preferential allocation of investments, and stochastic depreciation. The model gives a steady size distribution of firms which obey power-law. The effect of parameters on the power exponent is analyzed. The theoretical results are given based on both the Fokker-Planck equation and the Kesten process. They are well consistent with the numerical results.

  6. Global patterns of city size distributions and their fundamental drivers.

    Directory of Open Access Journals (Sweden)

    Ethan H Decker

    2007-09-01

    Full Text Available Urban areas and their voracious appetites are increasingly dominating the flows of energy and materials around the globe. Understanding the size distribution and dynamics of urban areas is vital if we are to manage their growth and mitigate their negative impacts on global ecosystems. For over 50 years, city size distributions have been assumed to universally follow a power function, and many theories have been put forth to explain what has become known as Zipf's law (the instance where the exponent of the power function equals unity. Most previous studies, however, only include the largest cities that comprise the tail of the distribution. Here we show that national, regional and continental city size distributions, whether based on census data or inferred from cluster areas of remotely-sensed nighttime lights, are in fact lognormally distributed through the majority of cities and only approach power functions for the largest cities in the distribution tails. To explore generating processes, we use a simple model incorporating only two basic human dynamics, migration and reproduction, that nonetheless generates distributions very similar to those found empirically. Our results suggest that macroscopic patterns of human settlements may be far more constrained by fundamental ecological principles than more fine-scale socioeconomic factors.

  7. Theory of Nanocluster Size Distributions from Ion Beam Synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, C.W.; Yi, D.O.; Sharp, I.D.; Shin, S.J.; Liao, C.Y.; Guzman, J.; Ager III, J.W.; Haller, E.E.; Chrzan, D.C.

    2008-06-13

    Ion beam synthesis of nanoclusters is studied via both kinetic Monte Carlo simulations and the self-consistent mean-field solution to a set of coupled rate equations. Both approaches predict the existence of a steady state shape for the cluster size distribution that depends only on a characteristic length determined by the ratio of the effective diffusion coefficient to the ion flux. The average cluster size in the steady state regime is determined by the implanted species/matrix interface energy.

  8. Size distributions of member asteroids in seven Hirayama families

    International Nuclear Information System (INIS)

    Mikami, Takao; Ishida, Keiichi.

    1990-01-01

    The size distributions of asteroids in the seven Hirayama families are studied for newly assigned member asteroids in the diameter range of about 10 to 100 km. The size distributions for the different families are expressed by the power-law functions with distinctly different power-law indices. The power-law indices for families with small mean orbital inclinations are about 2.5 to 3.0. On the other hand, the power-law indices for families with large mean orbital inclinations are significantly smaller than 2.5. This indicates that the smaller asteroids were removed preferentially from these families after their formation. It is thought that the smaller asteroids left behind the families were dispersed into the main belt. It is consistent with the fact that the power-law index for the size distribution of asteroids with diameters smaller than 25 km in the main belt is larger than the power-law indices for the size distributions of asteroids in the families. This segregation due to the asteroid size can be caused by a drag force caused by the ambient matter deposited on the invariable place of the solar system during the early evolutionary stage. (author)

  9. Reconstructing the size distribution of the primordial Main Belt

    Science.gov (United States)

    Tsirvoulis, G.; Morbidelli, A.; Delbo, M.; Tsiganis, K.

    2018-04-01

    In this work we aim to constrain the slope of the size distribution of main-belt asteroids, at their primordial state. To do so we turn out attention to the part of the main asteroid belt between 2.82 and 2.96 AU, the so-called "pristine zone", which has a low number density of asteroids and few, well separated asteroid families. Exploiting these unique characteristics, and using a modified version of the hierarchical clustering method we are able to remove the majority of asteroid family members from the region. The remaining, background asteroids should be of primordial origin, as the strong 5/2 and 7/3 mean-motion resonances with Jupiter inhibit transfer of asteroids to and from the neighboring regions. The size-frequency distribution of asteroids in the size range 17 size distribution slope q = - 1.43 . In addition, applying the same 'family extraction' method to the neighboring regions, i.e. the middle and outer belts, and comparing the size distributions of the respective background populations, we find statistical evidence that no large asteroid families of primordial origin had formed in the middle or pristine zones.

  10. The size distribution of dissolved uranium in natural waters

    International Nuclear Information System (INIS)

    Mann, D.K.; Wong, G.T.F.

    1987-01-01

    The size distribution of dissolved uranium in natural waters is poorly known. Some fraction of dissolved uranium is known to associate with organic matter which had a wide range of molecular weights. The presence of inorganic colloidal uranium has not been reported. Ultrafiltration has been used to quantify the size distribution of a number of elements, such as dissolved organic carbon, selenium, and some trace metals, in both the organic and/or the inorganic forms. The authors have applied this technique to dissolved uranium and the data are reported here

  11. Correction of bubble size distributions from transmission electron microscopy observations

    International Nuclear Information System (INIS)

    Kirkegaard, P.; Eldrup, M.; Horsewell, A.; Skov Pedersen, J.

    1996-01-01

    Observations by transmission electron microscopy of a high density of gas bubbles in a metal matrix yield a distorted size distribution due to bubble overlap and bubble escape from the surface. A model is described that reconstructs 3-dimensional bubble size distributions from 2-dimensional projections on taking these effects into account. Mathematically, the reconstruction is an ill-posed inverse problem, which is solved by regularization technique. Extensive Monte Carlo simulations support the validity of our model. (au) 1 tab., 32 ills., 32 refs

  12. Size Evolution and Stochastic Models: Explaining Ostracod Size through Probabilistic Distributions

    Science.gov (United States)

    Krawczyk, M.; Decker, S.; Heim, N. A.; Payne, J.

    2014-12-01

    The biovolume of animals has functioned as an important benchmark for measuring evolution throughout geologic time. In our project, we examined the observed average body size of ostracods over time in order to understand the mechanism of size evolution in these marine organisms. The body size of ostracods has varied since the beginning of the Ordovician, where the first true ostracods appeared. We created a stochastic branching model to create possible evolutionary trees of ostracod size. Using stratigraphic ranges for ostracods compiled from over 750 genera in the Treatise on Invertebrate Paleontology, we calculated overall speciation and extinction rates for our model. At each timestep in our model, new lineages can evolve or existing lineages can become extinct. Newly evolved lineages are assigned sizes based on their parent genera. We parameterized our model to generate neutral and directional changes in ostracod size to compare with the observed data. New sizes were chosen via a normal distribution, and the neutral model selected new sizes differentials centered on zero, allowing for an equal chance of larger or smaller ostracods at each speciation. Conversely, the directional model centered the distribution on a negative value, giving a larger chance of smaller ostracods. Our data strongly suggests that the overall direction of ostracod evolution has been following a model that directionally pushes mean ostracod size down, shying away from a neutral model. Our model was able to match the magnitude of size decrease. Our models had a constant linear decrease while the actual data had a much more rapid initial rate followed by a constant size. The nuance of the observed trends ultimately suggests a more complex method of size evolution. In conclusion, probabilistic methods can provide valuable insight into possible evolutionary mechanisms determining size evolution in ostracods.

  13. Fragment size distribution in viscous bag breakup of a drop

    Science.gov (United States)

    Kulkarni, Varun; Bulusu, Kartik V.; Plesniak, Michael W.; Sojka, Paul E.

    2015-11-01

    In this study we examine the drop size distribution resulting from the fragmentation of a single drop in the presence of a continuous air jet. Specifically, we study the effect of Weber number, We, and Ohnesorge number, Oh on the disintegration process. The regime of breakup considered is observed between 12 phase Doppler anemometry. Both the number and volume fragment size probability distributions are plotted. The volume probability distribution revealed a bi-modal behavior with two distinct peaks: one corresponding to the rim fragments and the other to the bag fragments. This behavior was suppressed in the number probability distribution. Additionally, we employ an in-house particle detection code to isolate the rim fragment size distribution from the total probability distributions. Our experiments showed that the bag fragments are smaller in diameter and larger in number, while the rim fragments are larger in diameter and smaller in number. Furthermore, with increasing We for a given Ohwe observe a large number of small-diameter drops and small number of large-diameter drops. On the other hand, with increasing Oh for a fixed We the opposite is seen.

  14. Field size and dose distribution of electron beam

    International Nuclear Information System (INIS)

    Kang, Wee Saing

    1980-01-01

    The author concerns some relations between the field size and dose distribution of electron beams. The doses of electron beams are measured by either an ion chamber with an electrometer or by film for dosimetry. We analyzes qualitatively some relations; the energy of incident electron beams and depths of maximum dose, field sizes of electron beams and depth of maximum dose, field size and scatter factor, electron energy and scatter factor, collimator shape and scatter factor, electron energy and surface dose, field size and surface dose, field size and central axis depth dose, and field size and practical range. He meets with some results. They are that the field size of electron beam has influence on the depth of maximum dose, scatter factor, surface dose and central axis depth dose, scatter factor depends on the field size and energy of electron beam, and the shape of the collimator, and the depth of maximum dose and the surface dose depend on the energy of electron beam, but the practical range of electron beam is independent of field size

  15. Molecular size distribution of Np(V)-humate

    International Nuclear Information System (INIS)

    Sakamoto, Yoshiaki; Nagao, Seiya; Tanaka, Tadao

    1996-10-01

    Molecular size distributions of humic acid and Np(V)-humate were studied as a function of pH and an ionic strength by an ultrafiltration method. Small particle (10,000-30,000 daltons) of humic acid increased slightly with increases in solution pH. The ion strength dependence of the molecular size distribution was clearly observed for humic acid. The abundance ratio of humic acid in the range from 10,000 to 30,000 daltons increased with the ionic strength from 0.015 M to 0.105 M, in place of the decreasing of that in range from 30,000 to 100,000 daltons. Most of neptunium(V) in the 200 mg/l of the humic acid solution was fractionated into 10,000-30,000 daltons. The abundance ratio of neptunium(V) in the 10,000-30,000 daltons was not clearly dependent on pH and the ionic strength of the solution, in spite of the changing in the molecular size distribution of humic acid by the ionic strength. These results imply that the molecular size distribution of Np(V)-humate does not simply obey by that of the humic acid. Stability constant of Np(V)-humate was measured as a function of the molecular size of the humic acid. The stability constant of Np(V)-humate in the range from 10,000 to 30,000 daltons was highest value comparing with the constants in the molecular size ranges of 100,000 daltons-0.45μm, 30,000-100,000, 5,000-10,000 daltons and under 5,000 daltons. These results may indicate that the Np(V) complexation with humic acid is dominated by the interaction of neptunyl ion with the humic acid in the specific molecular size range. (author)

  16. Determination of the void nucleation rate from void size distributions

    International Nuclear Information System (INIS)

    Brailsford, A.D.

    1977-01-01

    A method of estimating the void nucleation rate from one void size distribution and from observation of the maximum void radius at prior times is proposed. Implicit in the method are the assumptions that both variations in the critical radius with dose and vacancy thermal emission processes during post-nucleation quasi-steady-state growth may be neglected. (Auth.)

  17. Preparation of leucite powders with controlled particle size distribution

    Czech Academy of Sciences Publication Activity Database

    Novotná, Martina; Kloužková, A.; Maixner, J.; Šatava, Vladimír

    2005-01-01

    Roč. 49, č. 4 (2005), s. 252-258 ISSN 0862-5468 R&D Projects: GA ČR GA104/03/0031 Institutional research plan: CEZ:AV0Z40320502 Keywords : leucite * preparation * particle size distribution Subject RIV: CA - Inorganic Chemistry Impact factor: 0.463, year: 2005

  18. Polybutadiene latex particle size distribution analysis utilizing a disk centrifuge

    NARCIS (Netherlands)

    Verdurmen, E.M.F.J.; Albers, J.G.; German, A.L.

    1994-01-01

    Polybutadiene (I) latexes prepd. by emulsifier-free emulsion polymn. and having particle diam. 50-300 nm for both unimodal and bimodal particles size distributions were analyzed by the line-start (LIST) method in a Brookhaven disk centrifuge photosedimentometer. A special spin fluid was designed to

  19. Particle size distribution measurements of radionuclides from Chernobyl

    International Nuclear Information System (INIS)

    Georgi, B.; Tschiersch, J.

    1988-01-01

    Characteristics of the size distribution of the Chernobyl aerosol have been measured at four locations along the trajectory of the cloud. Changes in time and differences between 131 I and the other isotopes are explained by aerosol physical processes. The relevance of the measurements for dose calculations are discussed

  20. A Merging Algorithm for Aerosol Size Distribution from Multiple Instruments

    Czech Academy of Sciences Publication Activity Database

    Ondráček, Jakub; Ždímal, Vladimír; Smolík, Jiří; Lazaridis, M.

    2009-01-01

    Roč. 199, 1-4 (2009), s. 219-233 ISSN 0049-6979 Grant - others:MTKD(XE) CT-2004-513849 Institutional research plan: CEZ:AV0Z40720504 Keywords : aerosols * merging particle size distribution * multilognormal model Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.676, year: 2009

  1. Particle size distribution of UO sub 2 aerosols

    Energy Technology Data Exchange (ETDEWEB)

    Raghunath, B. (Radiation Safety Systems Div., BARC, Bombay (India)); Ramachandran, R.; Majumdar, S. (Radiometallurgy Div., BARC, Bombay (India))

    1991-12-01

    The Anderson cascade impactor has been used to determine the activity mean aerodynamic diameter and the particle size distribution of UO{sub 2} powders dispersed in the form of stable aerosols in an air medium. The UO{sub 2} powders obtained by the calcination of ammonium uranyl carbonate (AUC) and ammonium diuranate (ADU) precipitates have been used. (orig./MM).

  2. Effects of Particle Size Distribution on Bioremediation of Crude Oil ...

    African Journals Online (AJOL)

    Bioremediation has been proven to be the most effective method of cleaning up oil contaminated soils through the application of nutrients and microorganism. ... The parameters examined were: moisture content, particle size distribution, total hydrocarbon content, soil pH, available nitrogen, available phosphorus, total ...

  3. Improved Root Normal Size Distributions for Liquid Atomization

    Science.gov (United States)

    2015-11-01

    ANSI Std. Z39.18 j CONVERSION TABLE Conversion Factors for U.S. Customary to metric (SI) units of measurement. MULTIPLY BY TO...Gray (Gy) coulomb /kilogram (C/kg) second (s) kilogram (kg) kilo pascal (kPa) 1 Improved Root Normal Size Distributions for Liquid

  4. Estimation of particle size distribution of nanoparticles from electrical ...

    Indian Academy of Sciences (India)

    ... blockade (CB) phenomena of electrical conduction through atiny nanoparticle. Considering the ZnO nanocomposites to be spherical, Coulomb-blockade model of quantum dot isapplied here. The size distribution of particle is estimated from that model and compared with the results obtainedfrom AFM and XRD analyses.

  5. Assessment of particle size distribution in CO 2 accidental releases

    NARCIS (Netherlands)

    Hulsbosch-Dam, C.E.C.; Spruijt, M.P.N.; Necci, A.; Cozzani, V.

    2012-01-01

    A model was developed to calculate the particle size distribution following the release of pressurised supercritical CO 2. The model combines several sub-models for the different stages of jet break-up and specifically addresses the possible formation of solid particles, which is important for CO 2

  6. Particle size distribution of selected electronic nicotine delivery system products.

    Science.gov (United States)

    Oldham, Michael J; Zhang, Jingjie; Rusyniak, Mark J; Kane, David B; Gardner, William P

    2018-03-01

    Dosimetry models can be used to predict the dose of inhaled material, but they require several parameters including particle size distribution. The reported particle size distributions for aerosols from electronic nicotine delivery system (ENDS) products vary widely and don't always identify a specific product. A low-flow cascade impactor was used to determine the particle size distribution [mass median aerodynamic diameter (MMAD); geometric standard deviation (GSD)] from 20 different cartridge based ENDS products. To assess losses and vapor phase amount, collection efficiency of the system was measured by comparing the collected mass in the impactor to the difference in ENDS product mass. The levels of nicotine, glycerin, propylene glycol, water, and menthol in the formulations of each product were also measured. Regardless of the ENDS product formulation, the MMAD of all tested products was similar and ranged from 0.9 to 1.2 μm with a GSD ranging from 1.7 to 2.2. There was no consistent pattern of change in the MMAD and GSD as a function of number of puffs (cartridge life). The collection efficiency indicated that 9%-26% of the generated mass was deposited in the collection system or was in the vapor phase. The particle size distribution data are suitable for use in aerosol dosimetry programs. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

  7. The Size Distribution of Stardust Injected into the ISM

    Science.gov (United States)

    Krueger, D.; Sedlmayr, E.

    1996-01-01

    A multi-component method for the description of the evolution of the grain size distribution in consideration of a size dependent grain drift and growth rate is applied in order to model dust driven winds around cool C-stars. Grain drift introduces several modifications concerning dust growth: on one hand the residence time in the region of efficient growth is reduced, on the other hand the growth efficiency is higher due to an increased collisional rate. For carbon grains the surface density of radical sites is increased, but on the other hand there is a reduction of the sticking efficiency of the growth species for drift velocities larger than a few km/s. It is found that the consideration of drift results in a considerable distortion of the size distribution as compared to the case of zero drift velocity. Generally, there are less, but larger grains if drift is included.

  8. Growing axons analysis by using Granulometric Size Distribution

    International Nuclear Information System (INIS)

    Gonzalez, Mariela A; Ballarin, Virginia L; Rapacioli, Melina; CelIn, A R; Sanchez, V; Flores, V

    2011-01-01

    Neurite growth (neuritogenesis) in vitro is a common methodology in the field of developmental neurobiology. Morphological analyses of growing neurites are usually difficult because their thinness and low contrast usually prevent to observe clearly their shape, number, length and spatial orientation. This paper presents the use of the granulometric size distribution in order to automatically obtain information about the shape, size and spatial orientation of growing axons in tissue cultures. The results here presented show that the granulometric size distribution results in a very useful morphological tool since it allows the automatic detection of growing axons and the precise characterization of a relevant parameter indicative of the axonal growth spatial orientation such as the quantification of the angle of deviation of the growing direction. The developed algorithms automatically quantify this orientation by facilitating the analysis of these images, which is important given the large number of images that need to be processed for this type of study.

  9. Size distribution and structure of Barchan dune fields

    Directory of Open Access Journals (Sweden)

    O. Durán

    2011-07-01

    Full Text Available Barchans are isolated mobile dunes often organized in large dune fields. Dune fields seem to present a characteristic dune size and spacing, which suggests a cooperative behavior based on dune interaction. In Duran et al. (2009, we propose that the redistribution of sand by collisions between dunes is a key element for the stability and size selection of barchan dune fields. This approach was based on a mean-field model ignoring the spatial distribution of dune fields. Here, we present a simplified dune field model that includes the spatial evolution of individual dunes as well as their interaction through sand exchange and binary collisions. As a result, the dune field evolves towards a steady state that depends on the boundary conditions. Comparing our results with measurements of Moroccan dune fields, we find that the simulated fields have the same dune size distribution as in real fields but fail to reproduce their homogeneity along the wind direction.

  10. Size distributions and failure initiation of submarine and subaerial landslides

    Science.gov (United States)

    ten Brink, Uri S.; Barkan, R.; Andrews, B.D.; Chaytor, J.D.

    2009-01-01

    Landslides are often viewed together with other natural hazards, such as earthquakes and fires, as phenomena whose size distribution obeys an inverse power law. Inverse power law distributions are the result of additive avalanche processes, in which the final size cannot be predicted at the onset of the disturbance. Volume and area distributions of submarine landslides along the U.S. Atlantic continental slope follow a lognormal distribution and not an inverse power law. Using Monte Carlo simulations, we generated area distributions of submarine landslides that show a characteristic size and with few smaller and larger areas, which can be described well by a lognormal distribution. To generate these distributions we assumed that the area of slope failure depends on earthquake magnitude, i.e., that failure occurs simultaneously over the area affected by horizontal ground shaking, and does not cascade from nucleating points. Furthermore, the downslope movement of displaced sediments does not entrain significant amounts of additional material. Our simulations fit well the area distribution of landslide sources along the Atlantic continental margin, if we assume that the slope has been subjected to earthquakes of magnitude ??? 6.3. Regions of submarine landslides, whose area distributions obey inverse power laws, may be controlled by different generation mechanisms, such as the gradual development of fractures in the headwalls of cliffs. The observation of a large number of small subaerial landslides being triggered by a single earthquake is also compatible with the hypothesis that failure occurs simultaneously in many locations within the area affected by ground shaking. Unlike submarine landslides, which are found on large uniformly-dipping slopes, a single large landslide scarp cannot form on land because of the heterogeneous morphology and short slope distances of tectonically-active subaerial regions. However, for a given earthquake magnitude, the total area

  11. Global time-size distribution of volcanic eruptions on Earth.

    Science.gov (United States)

    Papale, Paolo

    2018-05-01

    Volcanic eruptions differ enormously in their size and impacts, ranging from quiet lava flow effusions along the volcano flanks to colossal events with the potential to affect our entire civilization. Knowledge of the time and size distribution of volcanic eruptions is of obvious relevance for understanding the dynamics and behavior of the Earth system, as well as for defining global volcanic risk. From the analysis of recent global databases of volcanic eruptions extending back to more than 2 million years, I show here that the return times of eruptions with similar magnitude follow an exponential distribution. The associated relative frequency of eruptions with different magnitude displays a power law, scale-invariant distribution over at least six orders of magnitude. These results suggest that similar mechanisms subtend to explosive eruptions from small to colossal, raising concerns on the theoretical possibility to predict the magnitude and impact of impending volcanic eruptions.

  12. Effect of relative humidity on soot - secondary organic aerosol mixing: A case study from the Soot Aerosol Aging Study (PNNL-SAAS)

    Science.gov (United States)

    Sharma, N.; China, S.; Zaveri, R. A.; Shilling, J. E.; Pekour, M. S.; Liu, S.; Aiken, A. C.; Dubey, M. K.; Wilson, J. M.; Zelenyuk, A.; OBrien, R. E.; Moffet, R.; Gilles, M. K.; Gourihar, K.; Chand, D.; Sedlacek, A. J., III; Subramanian, R.; Onasch, T. B.; Laskin, A.; Mazzoleni, C.

    2014-12-01

    Atmospheric processing of fresh soot particles emitted by anthropogenic as well as natural sources alters their physical and chemical properties. For example, fresh and aged soot particles interact differently with incident solar radiation, resulting in different overall radiation budgets. Varying atmospheric chemical and meteorological conditions can result in complex soot mixing states. The Soot Aerosol Aging Study (SAAS) was conducted at the Pacific Northwest National Laboratory in November 2013 and January 2014 as a step towards understanding the evolution of mixing state of soot and its impact on climate-relevant properties. Aging experiments on diesel soot were carried out in a controlled laboratory chamber, and the effects of condensation and coagulation processes were systematically explored in separate sets of experiments. In addition to online measurement of aerosol properties, aerosol samples were collected for offline single particle analysis to investigate the evolution of the morphology, elemental composition and fine structure of sample particles from different experiments. Condensation experiments focused on the formation of α-pinene secondary organic aerosol on diesel soot aerosol seeds. Experiments were conducted to study the aging of soot under dry (RH < 2%) and humid conditions (RH ~ 80%). We present an analysis of the morphology of soot, its evolution, and its correlation with optical properties, as the condensation of α-pinene SOA is carried out for the two different RH conditions. The analysis was performed by using scanning electron microscopy, transmission electron microscopy, scanning transmission x-ray microscopy and atomic force microscopy for single particle characterization. In addition, particle size, mass, composition, shape, and density were characterized in-situ, as a function of organics condensed on soot seeds, using single particle mass spectrometer.

  13. A computational study of ethylene–air sooting flames: Effects of large polycyclic aromatic hydrocarbons

    KAUST Repository

    Selvaraj, Prabhu

    2015-11-05

    An updated reduced gas-phase kinetic mechanism was developed and integrated with aerosol models to predict soot formation characteristics in ethylene nonpremixed and premixed flames. A primary objective is to investigate the sensitivity of the soot formation to various chemical pathways for large polycyclic aromatic hydrocarbons (PAH). The gas-phase chemical mechanism adopted the KAUST-Aramco PAH Mech 1.0, which utilized the AramcoMech 1.3 for gas-phase reactions validated for up to C2 fuels. In addition, PAH species up to coronene (C24H12 or A7) were included to describe the detailed formation pathways of soot precursors. In this study, the detailed chemical mechanism was reduced from 397 to 99 species using directed relation graph with expert knowledge (DRG-X) and sensitivity analysis. The method of moments with interpolative closure (MOMIC) was employed for the soot aerosol model. Counterflow nonpremixed flames at low strain rate sooting conditions were considered, for which the sensitivity of soot formation characteristics to different nucleation pathways were investigated. Premixed flame experiment data at different equivalence ratios were also used for validation. The findings show that higher PAH concentrations result in a higher soot nucleation rate, and that the total soot volume and average size of the particles are predicted in good agreement with experimental results. Subsequently, the effects of different pathways, with respect to pyrene- or coronene-based nucleation models, on the net soot formation rate were analyzed. It was found that the nucleation processes (i.e., soot inception) are sensitive to the choice of PAH precursors, and consideration of higher PAH species beyond pyrene is critical for accurate prediction of the overall soot formation.

  14. Laser-induced incandescence: Towards quantitative soot volume fraction measurements

    Energy Technology Data Exchange (ETDEWEB)

    Tzannis, A P; Wienbeucker, F; Beaud, P; Frey, H -M; Gerber, T; Mischler, B; Radi, P P [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1999-08-01

    Laser-Induced Incandescence has recently emerged as a versatile tool for measuring soot volume fraction in a wide range of combustion systems. In this work we investigate the essential features of the method. LII is based on the acquisition of the incandescence of soot when heated through a high power laser pulse. Initial experiments have been performed on a model laboratory flame. The behaviour of the LII signal is studied experimentally. By applying numerical calculations we investigate the possibility to obtain two-dimensional soot volume fraction distributions. For this purpose a combination of LII with other techniques is required. This part is discussed in some extent and the future work is outlined. (author) 4 figs., 3 refs.

  15. Critical sizes and flux distributions in the shut down pile

    International Nuclear Information System (INIS)

    Banchereau, A.; Berthier, P.; Genthon, J.P.; Gourdon, C.; Lattes, R.; Martelly, J.; Mazancourt, R. de; Portes, L.; Sagot, M.; Schmitt, A.P.; Tanguy, P.; Teste du Bailler, A.; Veyssiere, A.

    1957-01-01

    An important part of the experiments carried out on the reactor G1 during a period of shut-down has consisted in determinations of critical sizes, and measurements of flux distribution by irradiations of detectors. This report deals with the following points: 1- Critical sizes of the flat pile, the long pile and the uranium-thorium pile. 2- Flux charts of the same piles, and study of an exponential experiment. 3- Determination of the slit effect. 4- Calculation of the anisotropy of the lattice. 5- Description of the experimental apparatus of the irradiation measurements. (author) [fr

  16. Characterization of Bubble Size Distributions within a Bubble Column

    OpenAIRE

    Shahrouz Mohagheghian; Brian R. Elbing

    2018-01-01

    The current study experimentally examines bubble size distribution (BSD) within a bubble column and the associated characteristic length scales. Air was injected into a column of water via a single injection tube. The column diameter (63–102 mm), injection tube diameter (0.8–1.6 mm) and superficial gas velocity (1.4–55 mm/s) were varied. Large samples (up to 54,000 bubbles) of bubble sizes measured via 2D imaging were used to produce probability density functions (PDFs). The PDFs were used to...

  17. Rock sampling. [method for controlling particle size distribution

    Science.gov (United States)

    Blum, P. (Inventor)

    1971-01-01

    A method for sampling rock and other brittle materials and for controlling resultant particle sizes is described. The method involves cutting grooves in the rock surface to provide a grouping of parallel ridges and subsequently machining the ridges to provide a powder specimen. The machining step may comprise milling, drilling, lathe cutting or the like; but a planing step is advantageous. Control of the particle size distribution is effected primarily by changing the height and width of these ridges. This control exceeds that obtainable by conventional grinding.

  18. A Progress Review on Soot Experiments and Modeling in the Engine Combustion Network (ECN)

    KAUST Repository

    Skeen, Scott A.

    2016-04-05

    The 4th Workshop of the Engine Combustion Network (ECN) was held September 5-6, 2015 in Kyoto, Japan. This manuscript presents a summary of the progress in experiments and modeling among ECN contributors leading to a better understanding of soot formation under the ECN “Spray A” configuration and some parametric variants. Relevant published and unpublished work from prior ECN workshops is reviewed. Experiments measuring soot particle size and morphology, soot volume fraction (fv), and transient soot mass have been conducted at various international institutions providing target data for improvements to computational models. Multiple modeling contributions using both the Reynolds Averaged Navier-Stokes (RANS) Equations approach and the Large-Eddy Simulation (LES) approach have been submitted. Among these, various chemical mechanisms, soot models, and turbulence-chemistry interaction (TCI) methodologies have been considered.

  19. A Progress Review on Soot Experiments and Modeling in the Engine Combustion Network (ECN)

    KAUST Repository

    Skeen, Scott A.; Manin, Julien; Pickett, Lyle M.; Cenker, Emre; Bruneaux, Gilles; Kondo, Katsufumi; Aizawa, Tets; Westlye, Fredrik; Dalen, Kristine; Ivarsson, Anders; Xuan, Tiemin; Garcia-Oliver, Jose M; Pei, Yuanjiang; Som, Sibendu; Hu, Wang; Reitz, Rolf D.; Lucchini, Tommaso; D'Errico, Gianluca; Farrace, Daniele; Pandurangi, Sushant S.; Wright, Yuri M.; Chishty, Muhammad Aqib; Bolla, Michele; Hawkes, Evatt

    2016-01-01

    The 4th Workshop of the Engine Combustion Network (ECN) was held September 5-6, 2015 in Kyoto, Japan. This manuscript presents a summary of the progress in experiments and modeling among ECN contributors leading to a better understanding of soot formation under the ECN “Spray A” configuration and some parametric variants. Relevant published and unpublished work from prior ECN workshops is reviewed. Experiments measuring soot particle size and morphology, soot volume fraction (fv), and transient soot mass have been conducted at various international institutions providing target data for improvements to computational models. Multiple modeling contributions using both the Reynolds Averaged Navier-Stokes (RANS) Equations approach and the Large-Eddy Simulation (LES) approach have been submitted. Among these, various chemical mechanisms, soot models, and turbulence-chemistry interaction (TCI) methodologies have been considered.

  20. Development of sample size allocation program using hypergeometric distribution

    International Nuclear Information System (INIS)

    Kim, Hyun Tae; Kwack, Eun Ho; Park, Wan Soo; Min, Kyung Soo; Park, Chan Sik

    1996-01-01

    The objective of this research is the development of sample allocation program using hypergeometric distribution with objected-oriented method. When IAEA(International Atomic Energy Agency) performs inspection, it simply applies a standard binomial distribution which describes sampling with replacement instead of a hypergeometric distribution which describes sampling without replacement in sample allocation to up to three verification methods. The objective of the IAEA inspection is the timely detection of diversion of significant quantities of nuclear material, therefore game theory is applied to its sampling plan. It is necessary to use hypergeometric distribution directly or approximate distribution to secure statistical accuracy. Improved binomial approximation developed by Mr. J. L. Jaech and correctly applied binomial approximation are more closer to hypergeometric distribution in sample size calculation than the simply applied binomial approximation of the IAEA. Object-oriented programs of 1. sample approximate-allocation with correctly applied standard binomial approximation, 2. sample approximate-allocation with improved binomial approximation, and 3. sample approximate-allocation with hypergeometric distribution were developed with Visual C ++ and corresponding programs were developed with EXCEL(using Visual Basic for Application). 8 tabs., 15 refs. (Author)

  1. Effects of Large Polycyclic Aromatic Hydrocarbons on the Soot Formation in Ethylene-Air Nonpremixed Flames

    KAUST Repository

    Prabhu, S.; Arias, P.G.; Wang, Y.; Gao, Y.; Park, S.; Im, Hong G.; Sarathy, Mani; Chung, Suk-Ho; Lu, T.

    2015-01-01

    This study presents updated comprehensive gas-phase kinetic mechanism and aerosol models to predict soot formation characteristics in ethylene-air nonpremixed flames. A main objective is to investigate the sensitivity of the soot formation rate to various chemical pathways for large polycyclic aromatic hydrocarbons (PAH). In this study, the detailed chemical mechanism was reduced from 397 to 99 species using directed relation graph (DRG) and sensitivity analysis. The method of moments with interpolative closure (MOMIC) was employed for the soot aerosol model. Counterflow nonpremixed flames of pure ethylene at low strain rate sooting conditions are considered, for which the sensitivity of soot formation characteristics with respect to hetrogeneous nucleation is investigated. Results show that higher PAH concentrations result in higher soot nucleation rate, and that the average size of the particles are in good agreement with experimental results. It is found that the nucleation processes (i.e., soot inception) from higher PAH precursors, coronene in particular, is critical for accurate prediction of the overall soot formation.

  2. Effects of Large Polycyclic Aromatic Hydrocarbons on the Soot Formation in Ethylene-Air Nonpremixed Flames

    KAUST Repository

    Prabhu, S.

    2015-03-30

    This study presents updated comprehensive gas-phase kinetic mechanism and aerosol models to predict soot formation characteristics in ethylene-air nonpremixed flames. A main objective is to investigate the sensitivity of the soot formation rate to various chemical pathways for large polycyclic aromatic hydrocarbons (PAH). In this study, the detailed chemical mechanism was reduced from 397 to 99 species using directed relation graph (DRG) and sensitivity analysis. The method of moments with interpolative closure (MOMIC) was employed for the soot aerosol model. Counterflow nonpremixed flames of pure ethylene at low strain rate sooting conditions are considered, for which the sensitivity of soot formation characteristics with respect to hetrogeneous nucleation is investigated. Results show that higher PAH concentrations result in higher soot nucleation rate, and that the average size of the particles are in good agreement with experimental results. It is found that the nucleation processes (i.e., soot inception) from higher PAH precursors, coronene in particular, is critical for accurate prediction of the overall soot formation.

  3. Effects of methyl group on aromatic hydrocarbons on the nanostructures and oxidative reactivity of combustion-generated soot

    KAUST Repository

    Guerrero Peñ a, Gerardo D.J.; Alrefaai, Mhd Maher; Yang, Seung Yeon; Raj, Abhijeet; Brito, Joaquin L.; Stephen, Samuel; Anjana, Tharalekshmy; Pillai, Vinu; Al Shoaibi, Ahmed; Chung, Suk-Ho

    2016-01-01

    The substituted and unsubstituted aromatic hydrocarbons, present in transportation fuels such as gasoline and diesel, are thought to be responsible for most of the soot particles produced during their combustion. However, the effects of the substituted alkyl groups on the aromatic hydrocarbons on their sooting tendencies, and on the physical and chemical properties of soot produced from them are not well understood. In this work, the effect of the presence of methyl groups on aromatic hydrocarbons on their sooting propensity, and on the oxidative reactivity, morphology, and chemical composition of soot generated from them in diffusion flames is studied using benzene, toluene, and m-xylene as fuels. Several experimental techniques including high resolution transmission electron microscopy and X-ray diffraction are used to identify the morphological changes in soot, whereas the elemental and thermo-gravimetric analyses, electron energy loss spectroscopy, and Fourier transform infrared spectroscopy are used to study the changes in its chemical properties and reactivity. The activation energies for soot oxidation are calculated at different conversion levels, and a trend in the reactivity of soots from benzene, toluene and m-xylene is reported. It is observed that the sizes of primary particles and graphene-like sheets, and the concentrations of aliphatics and oxygenated groups in soot particles decreased with the addition of methyl group(s) on the aromatic ring. The physicochemical changes in soot are found to support the oxidative reactivity trends. © 2016 The Combustion Institute

  4. Effects of methyl group on aromatic hydrocarbons on the nanostructures and oxidative reactivity of combustion-generated soot

    KAUST Repository

    Guerrero Peña, Gerardo D.J.

    2016-07-23

    The substituted and unsubstituted aromatic hydrocarbons, present in transportation fuels such as gasoline and diesel, are thought to be responsible for most of the soot particles produced during their combustion. However, the effects of the substituted alkyl groups on the aromatic hydrocarbons on their sooting tendencies, and on the physical and chemical properties of soot produced from them are not well understood. In this work, the effect of the presence of methyl groups on aromatic hydrocarbons on their sooting propensity, and on the oxidative reactivity, morphology, and chemical composition of soot generated from them in diffusion flames is studied using benzene, toluene, and m-xylene as fuels. Several experimental techniques including high resolution transmission electron microscopy and X-ray diffraction are used to identify the morphological changes in soot, whereas the elemental and thermo-gravimetric analyses, electron energy loss spectroscopy, and Fourier transform infrared spectroscopy are used to study the changes in its chemical properties and reactivity. The activation energies for soot oxidation are calculated at different conversion levels, and a trend in the reactivity of soots from benzene, toluene and m-xylene is reported. It is observed that the sizes of primary particles and graphene-like sheets, and the concentrations of aliphatics and oxygenated groups in soot particles decreased with the addition of methyl group(s) on the aromatic ring. The physicochemical changes in soot are found to support the oxidative reactivity trends. © 2016 The Combustion Institute

  5. Coarse and fine root plants affect pore size distributions differently

    OpenAIRE

    Bodner, G.; Leitner, D.; Kaul, H.-P.

    2014-01-01

    Aims Small scale root-pore interactions require validation of their impact on effective hydraulic processes at the field scale. Our objective was to develop an interpretative framework linking root effects on macroscopic pore parameters with knowledge at the rhizosphere scale. Methods A field experiment with twelve species from different families was conducted. Parameters of Kosugi?s pore size distribution (PSD) model were determined inversely from tension infiltrometer data. Measured root tr...

  6. Capital market financing, firm growth, and firm size distribution

    OpenAIRE

    Didier Brandao,Tatiana; Levine,Ross Eric; Schmukler,Sergio L.

    2015-01-01

    How many and which firms issue equity and bonds in domestic and international markets, how do these firms grow relative to non-issuing firms, and how does firm performance vary along the firm size distribution? To evaluate these questions, a new data set is constructed by matching data on firm-level capital raising activity with balance sheet data for 45,527 listed firms in 51 countries. T...

  7. Power law olivine crystal size distributions in lithospheric mantle xenoliths

    Science.gov (United States)

    Armienti, P.; Tarquini, S.

    2002-12-01

    Olivine crystal size distributions (CSDs) have been measured in three suites of spinel- and garnet-bearing harzburgites and lherzolites found as xenoliths in alkaline basalts from Canary Islands, Africa; Victoria Land, Antarctica; and Pali Aike, South America. The xenoliths derive from lithospheric mantle, from depths ranging from 80 to 20 km. Their textures vary from coarse to porphyroclastic and mosaic-porphyroclastic up to cataclastic. Data have been collected by processing digital images acquired optically from standard petrographic thin sections. The acquisition method is based on a high-resolution colour scanner that allows image capturing of a whole thin section. Image processing was performed using the VISILOG 5.2 package, resolving crystals larger than about 150 μm and applying stereological corrections based on the Schwartz-Saltykov algorithm. Taking account of truncation effects due to resolution limits and thin section size, all samples show scale invariance of crystal size distributions over almost three orders of magnitude (0.2-25 mm). Power law relations show fractal dimensions varying between 2.4 and 3.8, a range of values observed for distributions of fragment sizes in a variety of other geological contexts. A fragmentation model can reproduce the fractal dimensions around 2.6, which correspond to well-equilibrated granoblastic textures. Fractal dimensions >3 are typical of porphyroclastic and cataclastic samples. Slight bends in some linear arrays suggest selective tectonic crushing of crystals with size larger than 1 mm. The scale invariance shown by lithospheric mantle xenoliths in a variety of tectonic settings forms distant geographic regions, which indicate that this is a common characteristic of the upper mantle and should be taken into account in rheological models and evaluation of metasomatic models.

  8. Size distribution of radon daughter particles in uranium mine atmospheres

    International Nuclear Information System (INIS)

    George, A.C.; Hinchliffe, L.; Sladowski, R.

    1977-07-01

    An investigation of the particle size distribution and other properties of radon daughters in uranium mines was reported earlier but only summaries of the data were presented. This report consists mainly of tables of detailed measurements that were omitted in the original article. The tabulated data include the size distributions, uncombined fractions and ratios of radon daughters as well as the working levels, radon concentrations, condensation nuclei concentrations, temperature, and relative humidity. The measurements were made in 27 locations in four large underground mines in New Mexico during typical mining operations. The size distributions of the radon daughters were log normal. The activity median diameters ranged from 0.09 μm to 0.3 μm with a mean of 0.17 μm. Geometric standard deviations were from 1.3 to 4 with a mean of 2.7. Uncombined fractions expressed in accordance with the ICRP definition ranged from 0.004 to 0.16 with a mean of 0.04

  9. Controlling semiconductor nanoparticle size distributions with tailored ultrashort pulses

    International Nuclear Information System (INIS)

    Hergenroeder, R; Miclea, M; Hommes, V

    2006-01-01

    The laser generation of size-controlled semiconductor nanoparticle formation under gas phase conditions is investigated. It is shown that the size distribution can be changed if picosecond pulse sequences of tailored ultra short laser pulses (<200 fs) are employed. By delivering the laser energy in small packages, a temporal energy flux control at the target surface is achieved, which results in the control of the thermodynamic pathway the material takes. The concept is tested with silicon and germanium, both materials with a predictable response to double pulse sequences, which allows deduction of the materials' response to complicated pulse sequences. An automatic, adaptive learning algorithm was employed to demonstrate a future strategy that enables the definition of more complex optimization targets such as particle size on materials less predictable than semiconductors

  10. Evaluation and optimisation of phenomenological multi-step soot model for spray combustion under diesel engine-like operating conditions

    DEFF Research Database (Denmark)

    Pang, Kar Mun; Jangi, Mehdi; Bai, Xue-Song

    2015-01-01

    with the spray combustion solver. Prior to the soot modelling, combustion simulations are carried out. Numerical results show that the ignition delay times and lift-off lengths exhibit good agreement with the experimental measurements across a wide range of operating conditions, apart from those in the cases......, variation of spatial soot distribution and soot mass produced at oxygen molar fractions ranging from 10.0 to 21.0% for both low and high density conditions are reproduced....

  11. Coulomb Mechanics And Landscape Geometry Explain Landslide Size Distribution

    Science.gov (United States)

    Jeandet, L.; Steer, P.; Lague, D.; Davy, P.

    2017-12-01

    It is generally observed that the dimensions of large bedrock landslides follow power-law scaling relationships. In particular, the non-cumulative frequency distribution (PDF) of bedrock landslide area is well characterized by a negative power-law above a critical size, with an exponent 2.4. However, the respective role of bedrock mechanical properties, landscape shape and triggering mechanisms on the scaling properties of landslide dimensions are still poorly understood. Yet, unravelling the factors that control this distribution is required to better estimate the total volume of landslides triggered by large earthquakes or storms. To tackle this issue, we develop a simple probabilistic 1D approach to compute the PDF of rupture depths in a given landscape. The model is applied to randomly sampled points along hillslopes of studied digital elevation models. At each point location, the model determines the range of depth and angle leading to unstable rupture planes, by applying a simple Mohr-Coulomb rupture criterion only to the rupture planes that intersect downhill surface topography. This model therefore accounts for both rock mechanical properties, friction and cohesion, and landscape shape. We show that this model leads to realistic landslide depth distribution, with a power-law arising when the number of samples is high enough. The modeled PDF of landslide size obtained for several landscapes match the ones from earthquakes-driven landslides catalogues for the same landscape. In turn, this allows us to invert landslide effective mechanical parameters, friction and cohesion, associated to those specific events, including Chi-Chi, Wenchuan, Niigata and Gorkha earthquakes. The cohesion and friction ranges (25-35 degrees and 5-20 kPa) are in good agreement with previously inverted values. Our results demonstrate that reduced complexity mechanics is efficient to model the distribution of unstable depths, and show the role of landscape variability in landslide size

  12. Size distribution of radon daughter particles in uranium mine atmospheres

    International Nuclear Information System (INIS)

    George, A.C.; Hinchliffe, L.; Sladowski, R.

    1975-01-01

    The size distribution of radon daughters was measured in several uranium mines using four compact diffusion batteries and a round jet cascade impactor. Simultaneously, measurements were made of uncombined fractions of radon daughters, radon concentration, working level, and particle concentration. The size distributions found for radon daughters were log normal. The activity median diameters ranged from 0.09 μm to 0.3 μm with a mean value of 0.17 μm. Geometric standard deviations were in the range from 1.3 to 4 with a mean value of 2.7. Uncombined fractions expressed in accordance with the ICRP definition ranged from 0.004 to 0.16 with a mean value of 0.04. The radon daughter sizes in these mines are greater than the sizes assumed by various authors in calculating respiratory tract dose. The disparity may reflect the widening use of diesel-powered equipment in large uranium mines. (U.S.)

  13. Use of the truncated shifted Pareto distribution in assessing size distribution of oil and gas fields

    Science.gov (United States)

    Houghton, J.C.

    1988-01-01

    The truncated shifted Pareto (TSP) distribution, a variant of the two-parameter Pareto distribution, in which one parameter is added to shift the distribution right and left and the right-hand side is truncated, is used to model size distributions of oil and gas fields for resource assessment. Assumptions about limits to the left-hand and right-hand side reduce the number of parameters to two. The TSP distribution has advantages over the more customary lognormal distribution because it has a simple analytic expression, allowing exact computation of several statistics of interest, has a "J-shape," and has more flexibility in the thickness of the right-hand tail. Oil field sizes from the Minnelusa play in the Powder River Basin, Wyoming and Montana, are used as a case study. Probability plotting procedures allow easy visualization of the fit and help the assessment. ?? 1988 International Association for Mathematical Geology.

  14. Single-size thermometric measurements on a size distribution of neutral fullerenes.

    Science.gov (United States)

    Cauchy, C; Bakker, J M; Huismans, Y; Rouzée, A; Redlich, B; van der Meer, A F G; Bordas, C; Vrakking, M J J; Lépine, F

    2013-05-10

    We present measurements of the velocity distribution of electrons emitted from mass-selected neutral fullerenes, performed at the intracavity free electron laser FELICE. We make use of mass-specific vibrational resonances in the infrared domain to selectively heat up one out of a distribution of several fullerene species. Efficient energy redistribution leads to decay via thermionic emission. Time-resolved electron kinetic energy distributions measured give information on the decay rate of the selected fullerene. This method is generally applicable to all neutral species that exhibit thermionic emission and provides a unique tool to study the stability of mass-selected neutral clusters and molecules that are only available as part of a size distribution.

  15. Morphology and nano-structure analysis of soot particles sampled from high pressure diesel jet flames under diesel-like conditions

    Science.gov (United States)

    Jiang, Hao; Li, Tie; Wang, Yifeng; He, Pengfei

    2018-04-01

    Soot particles emitted from diesel engines have a significant impact on the atmospheric environment. Detailed understanding of soot formation and oxidation processes is helpful for reducing the pollution of soot particles, which requires information such as the size and nano-structure parameters of the soot primary particles sampled in a high-temperature and high-pressure diesel jet flame. Based on the thermophoretic principle, a novel sampling probe minimally disturbing the diesel jet flame in a constant volume combustion vessel is developed for analysing soot particles. The injected quantity of diesel fuel is less than 10 mg, and the soot particles sampled by carriers with a transmission electron microscope (TEM) grid and lacey TEM grid can be used to analyse the morphologies of soot aggregates and the nano-structure of the soot primary particles, respectively. When the quantity of diesel fuel is more than 10 mg, in order to avoid burning-off of the carriers in higher temperature and pressure conditions, single-crystal silicon chips are employed. Ultrasonic oscillations and alcohol extraction are then implemented to obtain high quality soot samples for observation using a high-resolution transmission electron microscope. An in-house Matlab-based code is developed to extract the nano-structure parameters of the soot particles. A complete sampling and analysis procedure of the soot particles is provided to study the formation and oxidation mechanism of soot.

  16. Multimodal Dispersion of Nanoparticles: A Comprehensive Evaluation of Size Distribution with 9 Size Measurement Methods.

    Science.gov (United States)

    Varenne, Fanny; Makky, Ali; Gaucher-Delmas, Mireille; Violleau, Frédéric; Vauthier, Christine

    2016-05-01

    Evaluation of particle size distribution (PSD) of multimodal dispersion of nanoparticles is a difficult task due to inherent limitations of size measurement methods. The present work reports the evaluation of PSD of a dispersion of poly(isobutylcyanoacrylate) nanoparticles decorated with dextran known as multimodal and developed as nanomedecine. The nine methods used were classified as batch particle i.e. Static Light Scattering (SLS) and Dynamic Light Scattering (DLS), single particle i.e. Electron Microscopy (EM), Atomic Force Microscopy (AFM), Tunable Resistive Pulse Sensing (TRPS) and Nanoparticle Tracking Analysis (NTA) and separative particle i.e. Asymmetrical Flow Field-Flow Fractionation coupled with DLS (AsFlFFF) size measurement methods. The multimodal dispersion was identified using AFM, TRPS and NTA and results were consistent with those provided with the method based on a separation step prior to on-line size measurements. None of the light scattering batch methods could reveal the complexity of the PSD of the dispersion. Difference between PSD obtained from all size measurement methods tested suggested that study of the PSD of multimodal dispersion required to analyze samples by at least one of the single size particle measurement method or a method that uses a separation step prior PSD measurement.

  17. Building predictive models of soil particle-size distribution

    Directory of Open Access Journals (Sweden)

    Alessandro Samuel-Rosa

    2013-04-01

    Full Text Available Is it possible to build predictive models (PMs of soil particle-size distribution (psd in a region with complex geology and a young and unstable land-surface? The main objective of this study was to answer this question. A set of 339 soil samples from a small slope catchment in Southern Brazil was used to build PMs of psd in the surface soil layer. Multiple linear regression models were constructed using terrain attributes (elevation, slope, catchment area, convergence index, and topographic wetness index. The PMs explained more than half of the data variance. This performance is similar to (or even better than that of the conventional soil mapping approach. For some size fractions, the PM performance can reach 70 %. Largest uncertainties were observed in geologically more complex areas. Therefore, significant improvements in the predictions can only be achieved if accurate geological data is made available. Meanwhile, PMs built on terrain attributes are efficient in predicting the particle-size distribution (psd of soils in regions of complex geology.

  18. Prediction of oil droplet size distribution in agitated aquatic environments

    International Nuclear Information System (INIS)

    Khelifa, A.; Lee, K.; Hill, P.S.

    2004-01-01

    Oil spilled at sea undergoes many transformations based on physical, biological and chemical processes. Vertical dispersion is the hydrodynamic mechanism controlled by turbulent mixing due to breaking waves, vertical velocity, density gradients and other environmental factors. Spilled oil is dispersed in the water column as small oil droplets. In order to estimate the mass of an oil slick in the water column, it is necessary to know how the droplets formed. Also, the vertical dispersion and fate of oil spilled in aquatic environments can be modelled if the droplet-size distribution of the oil droplets is known. An oil spill remediation strategy can then be implemented. This paper presented a newly developed Monte Carlo model to predict droplet-size distribution due to Brownian motion, turbulence and a differential settling at equilibrium. A kinematic model was integrated into the proposed model to simulate droplet breakage. The key physical input of the model is the maximum droplet size permissible in the simulation. Laboratory studies were found to be in good agreement with field studies. 26 refs., 1 tab., 5 figs

  19. Shape, size, and distribution of magnetic particles in Bjurbole chondrules

    Science.gov (United States)

    Nava, David F.

    1994-01-01

    Chondrules from the Bjurbole chondritic meteorite (L4) exhibit saturation remanence magnetization (SIRM) values which vary over three orders of magnitude. REM values (Natural Remanence Magnetization/SIRM) for Allende (C3V) and Chainpur (LL3) are less than 0.01 but in Bjurbole some chondrules were found to have REM values greater than 0.1 with several greater than 0.2. REM values greater than 0.1 are abnormal and cannot be acquired during weak field cooling. If exposure to a strong field (whatever the source) during the chondrules' history is responsible for the high REM values, was such history associated with a different processing which might have resulted in different shape, size, and distribution of metal particles compared to chondrules having REM values of less than 0.01? Furthermore, magnetic hysteresis results show a broad range of magnetic hardness and other intrinsic magnetic properties. These features must be related to (1) size and amount of metal; and (2) properties of, and amount of, tetrataenite in the chondrules (all chondrules thus far subjected to thermomagnetic analysis show the presence of tetrataenite). A scanning electron microscopy (SEM) study is underway to determine the relationship between the shape, size, and distribution of metal particles within individual chondrules and the magnetic properties of these chondrules. Results from the SEM study in conjunction with magnetic property data may also help to discern effects from possible lightning strikes in the nebula prior to incorporation of the chondrules into the parent body.

  20. Nanoparticle production by UV irradiation of combustion generated soot particles

    International Nuclear Information System (INIS)

    Stipe, Christopher B.; Choi, Jong Hyun; Lucas, Donald; Koshland, Catherine P.; Sawyer, Robert F.

    2004-01-01

    Laser ablation of surfaces normally produce high temperature plasmas that are difficult to control. By irradiating small particles in the gas phase, we can better control the size and concentration of the resulting particles when different materials are photofragmented. Here, we irradiate soot with 193 nm light from an ArF excimer laser. Irradiating the original agglomerated particles at fluences ranging from 0.07 to 0.26 J/cm 2 with repetition rates of 20 and 100 Hz produces a large number of small, unagglomerated particles, and a smaller number of spherical agglomerated particles. Mean particle diameters from 20 to 50 nm are produced from soot originally having a mean electric mobility diameter of 265nm. We use a non-dimensional parameter, called the photon/atom ratio (PAR), to aid in understanding the photofragmentation process. This parameter is the ratio of the number of photons striking the soot particles to the number of the carbon atoms contained in the soot particles, and is a better metric than the laser fluence for analyzing laser-particle interactions. These results suggest that UV photofragmentation can be effective in controlling particle size and morphology, and can be a useful diagnostic for studying elements of the laser ablation process

  1. SIZE DISTRIBUTIONS OF SOLAR FLARES AND SOLAR ENERGETIC PARTICLE EVENTS

    International Nuclear Information System (INIS)

    Cliver, E. W.; Ling, A. G.; Belov, A.; Yashiro, S.

    2012-01-01

    We suggest that the flatter size distribution of solar energetic proton (SEP) events relative to that of flare soft X-ray (SXR) events is primarily due to the fact that SEP flares are an energetic subset of all flares. Flares associated with gradual SEP events are characteristically accompanied by fast (≥1000 km s –1 ) coronal mass ejections (CMEs) that drive coronal/interplanetary shock waves. For the 1996-2005 interval, the slopes (α values) of power-law size distributions of the peak 1-8 Å fluxes of SXR flares associated with (a) >10 MeV SEP events (with peak fluxes ≥1 pr cm –2 s –1 sr –1 ) and (b) fast CMEs were ∼1.3-1.4 compared to ∼1.2 for the peak proton fluxes of >10 MeV SEP events and ∼2 for the peak 1-8 Å fluxes of all SXR flares. The difference of ∼0.15 between the slopes of the distributions of SEP events and SEP SXR flares is consistent with the observed variation of SEP event peak flux with SXR peak flux.

  2. Particle size distributions of radioactive aerosols measured in workplaces

    International Nuclear Information System (INIS)

    Dorrian, M.-D.; Bailey, M.R.

    1995-01-01

    A survey of published values of Activity Median Aerodynamic Diameter (AMAD) measured in working environments was conducted to assist in the selection of a realistic default AMAD for occupational exposures. Results were compiled from 52 publications covering a wide variety of industries and workplaces. Reported values of AMAD from all studies ranged from 0.12 μm to 25 μm, and most were well fitted by a log-normal distribution with a median value of 4.4 μm. This supports the choice of a 5 μm default AMAD, as a realistic rounded value for occupational exposures, by the ICRP Task Group on Human Respiratory Tract Models for Radiological Protection and its acceptance by ICRP. Both the nuclear power and nuclear fuel handling industries gave median values of approximately 4 μm. Uranium mills gave a median value of 6.8 μm with AMADs frequently greater than 10 μm. High temperature and arc saw cutting operations generated submicron particles and occasionally, biomodal log-normal particle size distributions. It is concluded that in view of the wide range of AMADs found in the surveyed literature, greater emphasis should be placed on air sampling to characterise aerosol particle size distributions for individual work practices, especially as doses estimated with the new 5 μm default AMAD will not always be conservative. (author)

  3. Effect of head size on 10B dose distribution

    International Nuclear Information System (INIS)

    Gupta, N.; Blue, T.E.; Gahbauer, R.

    1992-01-01

    Boron neutron capture therapy (BNCT) for treatment of brain tumors is based on the utilization of large epithermal-neutron fields. Epithermal neutrons thermalize at depths of ∼2.5 cm inside the head and provide a maximum thermal fluence at deep-seated tumor sites with minimum damage to normal tissue. Brain tissue is a highly scattering medium for epithermal and thermal neutrons; therefore, a broad treatment field enables epithermal neutrons to enter the head over a large area. These neutrons slow down as they undergo scattering collisions and contribute to the thermal-neutron fluence at the tumor location. With the use of large neutron fields, the size of the head affects the thermal-neutron distribution and thereby the 10 B absorbed dose distribution inside the head. In this paper, the authors describe measurements using a boron trifluoride (BF 3 )-filled proportional counter to determine the effect of head size on 10 B absorbed dose distributions for a broad field accelerator epithermal-neutron source

  4. Effects of biodiesel, engine load and diesel particulate filter on nonvolatile particle number size distributions in heavy-duty diesel engine exhaust

    International Nuclear Information System (INIS)

    Young, Li-Hao; Liou, Yi-Jyun; Cheng, Man-Ting; Lu, Jau-Huai; Yang, Hsi-Hsien; Tsai, Ying I.; Wang, Lin-Chi; Chen, Chung-Bang; Lai, Jim-Shoung

    2012-01-01

    Highlights: ► The effects of waste cooking oil biodiesel, engine load and DOC + DPF on nonvolatile particle size distributions in HDDE exhaust. ► Increasing biodiesel blends cause slight decreases in the total particle number concentrations and negligible changes in size distributions. ► Increasing load results in modest increases in both the total particle number concentrations and sizes. ► The effects of semivolatile materials are strongest at idle, during which nonvolatile cores TOT ) decrease slightly, while the mode diameters show negligible changes with increasing biodiesel blends. For a given biodiesel blend, both the N TOT and mode diameters increase modestly with increasing load of above 25%. The N TOT at idle are highest and their size distributions are strongly affected by condensation and possible nucleation of semivolatile materials. Nonvolatile cores of diameters less than 16 nm are only observed at idle mode. The DOC + DPF shows remarkable filtration efficiency for both the core and soot particles, irrespective of the biodiesel blend and engine load under study. The N TOT post the DOC + DPF are comparable to typical ambient levels of ∼10 4 cm −3 . This implies that, without concurrent reductions of semivolatile materials, the formation of semivolatile nucleation mode particles post the aftertreatment is highly favored.

  5. Aerosol particle mixing state, refractory particle number size distributions and emission factors in a polluted urban environment: Case study of Metro Manila, Philippines

    Science.gov (United States)

    Kecorius, Simonas; Madueño, Leizel; Vallar, Edgar; Alas, Honey; Betito, Grace; Birmili, Wolfram; Cambaliza, Maria Obiminda; Catipay, Grethyl; Gonzaga-Cayetano, Mylene; Galvez, Maria Cecilia; Lorenzo, Genie; Müller, Thomas; Simpas, James B.; Tamayo, Everlyn Gayle; Wiedensohler, Alfred

    2017-12-01

    Ultrafine soot particles (black carbon, BC) in urban environments are related to adverse respiratory and cardiovascular effects, increased cases of asthma and premature deaths. These problems are especially pronounced in developing megacities in South-East Asia, Latin America, and Africa, where unsustainable urbanization ant outdated environmental protection legislation resulted in severe degradation of urban air quality in terms of black carbon emission. Since ultrafine soot particles do often not lead to enhanced PM10 and PM2.5 mass concentration, the risks related to ultrafine particle pollution may therefore be significantly underestimated compared to the contribution of secondary aerosol constituents. To increase the awareness of the potential toxicological relevant problems of ultrafine black carbon particles, we conducted a case study in Metro Manila, the capital of the Philippines. Here, we present a part of the results from a detailed field campaign, called Manila Aerosol Characterization Experiment (MACE, 2015). Measurements took place from May to June 2015 with the focus on the state of mixing of aerosol particles. The results were alarming, showing the abundance of externally mixed refractory particles (soot proxy) at street site with a maximum daily number concentration of approximately 15000 #/cm3. That is up to 10 times higher than in cities of Western countries. We also found that the soot particle mass contributed from 55 to 75% of total street site PM2.5. The retrieved refractory particle number size distribution appeared to be a superposition of 2 ultrafine modes at 20 and 80 nm with a corresponding contribution to the total refractory particle number of 45 and 55%, respectively. The particles in the 20 nm mode were most likely ash from metallic additives in lubricating oil, tiny carbonaceous particles and/or nucleated and oxidized organic polymers, while bigger ones (80 nm) were soot agglomerates. To the best of the authors' knowledge, no other

  6. Floe-size distributions in laboratory ice broken by waves

    Science.gov (United States)

    Herman, Agnieszka; Evers, Karl-Ulrich; Reimer, Nils

    2018-02-01

    This paper presents the analysis of floe-size distribution (FSD) data obtained in laboratory experiments of ice breaking by waves. The experiments, performed at the Large Ice Model Basin (LIMB) of the Hamburg Ship Model Basin (Hamburgische Schiffbau-Versuchsanstalt, HSVA), consisted of a number of tests in which an initially continuous, uniform ice sheet was broken by regular waves with prescribed characteristics. The floes' characteristics (surface area; minor and major axis, and orientation of equivalent ellipse) were obtained from digital images of the ice sheets after five tests. The analysis shows that although the floe sizes cover a wide range of values (up to 5 orders of magnitude in the case of floe surface area), their probability density functions (PDFs) do not have heavy tails, but exhibit a clear cut-off at large floe sizes. Moreover, the PDFs have a maximum that can be attributed to wave-induced flexural strain, producing preferred floe sizes. It is demonstrated that the observed FSD data can be described by theoretical PDFs expressed as a weighted sum of two components, a tapered power law and a Gaussian, reflecting multiple fracture mechanisms contributing to the FSD as it evolves in time. The results are discussed in the context of theoretical and numerical research on fragmentation of sea ice and other brittle materials.

  7. Decadal Variation in Raindrop Size Distributions in Busan, Korea

    Directory of Open Access Journals (Sweden)

    Cheol-Hwan You

    2015-01-01

    Full Text Available This paper investigated the variability of raindrop size distributions (DSDs in Busan, Korea, using data from two different disdrometers: a precipitation occurrence sensor system (POSS and a particle size velocity (Parsivel optical disdrometer. DSDs were simulated using a gamma model to assess the intercomparability of these two techniques. Annual rainfall amount was higher in 2012 than in 2002, as were the annually averaged Dm (which was 0.1 mm greater in 2012 and the frequency of convective rain. Severe rainfall (greater than 20 mm h−1 occurred more frequently and with a larger Dm in 2012. The values of Dm from July, August, and December, 2012, were much greater than from other months when compared with 2002. Larger raindrops contributed to the higher rain rates that were observed in the morning during 2012, whereas relatively smaller raindrops dominated in the afternoon. These results suggest that the increase in raindrop size that has been observed in Busan may continue in the future; however, more research will be required if we are to fully understand this phenomenon. Rainfall variables are highly dependent on drop size and so should be recalculated using the newest DSDs to allow more accurate polarimetric radar rainfall estimation.

  8. Light absorption by coated nano-sized carbonaceous particles

    Science.gov (United States)

    Gangl, Martin; Kocifaj, Miroslav; Videen, Gorden; Horvath, Helmuth

    The optical properties of strongly absorbing soot particles coated by transparent material are investigated experimentally and described by several modeling approaches. Soot is produced by spark discharge and passed through a Sinclair-La Mer generator where non-absorbing carnauba wax is condensed onto it to obtain internal soot-wax mixtures in a controlled way. Measurements of the extinction and volume scattering coefficient show an amplification of absorption by a factor of approximately 1.8. This behavior was described by different approaches of internally mixed materials for the modal diameters of the measured size distributions: concentric-sphere model, effective medium approximations and heterogeneous ellipsoids. The concentric-sphere model describes the absorption increase quantitatively; and hence, it is chosen to be applied to the entire particle population in the size distribution. The growth of the soot particles by condensing wax is described by a simplified growth model to estimate the different contributions of several soot particle diameters to the overall absorption cross-section.

  9. Method for measuring the size distribution of airborne rhinovirus

    International Nuclear Information System (INIS)

    Russell, M.L.; Goth-Goldstein, R.; Apte, M.G.; Fisk, W.J.

    2002-01-01

    About 50% of viral-induced respiratory illnesses are caused by the human rhinovirus (HRV). Measurements of the concentrations and sizes of bioaerosols are critical for research on building characteristics, aerosol transport, and mitigation measures. We developed a quantitative reverse transcription-coupled polymerase chain reaction (RT-PCR) assay for HRV and verified that this assay detects HRV in nasal lavage samples. A quantitation standard was used to determine a detection limit of 5 fg of HRV RNA with a linear range over 1000-fold. To measure the size distribution of HRV aerosols, volunteers with a head cold spent two hours in a ventilated research chamber. Airborne particles from the chamber were collected using an Andersen Six-Stage Cascade Impactor. Each stage of the impactor was analyzed by quantitative RT-PCR for HRV. For the first two volunteers with confirmed HRV infection, but with mild symptoms, we were unable to detect HRV on any stage of the impactor

  10. Dust generation in powders: Effect of particle size distribution

    Directory of Open Access Journals (Sweden)

    Chakravarty Somik

    2017-01-01

    Full Text Available This study explores the relationship between the bulk and grain-scale properties of powders and dust generation. A vortex shaker dustiness tester was used to evaluate 8 calcium carbonate test powders with median particle sizes ranging from 2μm to 136μm. Respirable aerosols released from the powder samples were characterised by their particle number and mass concentrations. All the powder samples were found to release respirable fractions of dust particles which end up decreasing with time. The variation of powder dustiness as a function of the particle size distribution was analysed for the powders, which were classified into three groups based on the fraction of particles within the respirable range. The trends we observe might be due to the interplay of several mechanisms like de-agglomeration and attrition and their relative importance.

  11. Method for measuring the size distribution of airborne rhinovirus

    Energy Technology Data Exchange (ETDEWEB)

    Russell, M.L.; Goth-Goldstein, R.; Apte, M.G.; Fisk, W.J.

    2002-01-01

    About 50% of viral-induced respiratory illnesses are caused by the human rhinovirus (HRV). Measurements of the concentrations and sizes of bioaerosols are critical for research on building characteristics, aerosol transport, and mitigation measures. We developed a quantitative reverse transcription-coupled polymerase chain reaction (RT-PCR) assay for HRV and verified that this assay detects HRV in nasal lavage samples. A quantitation standard was used to determine a detection limit of 5 fg of HRV RNA with a linear range over 1000-fold. To measure the size distribution of HRV aerosols, volunteers with a head cold spent two hours in a ventilated research chamber. Airborne particles from the chamber were collected using an Andersen Six-Stage Cascade Impactor. Each stage of the impactor was analyzed by quantitative RT-PCR for HRV. For the first two volunteers with confirmed HRV infection, but with mild symptoms, we were unable to detect HRV on any stage of the impactor.

  12. Mass size distribution of particles emitted by diesel engines and determination of the contribution of diesel particles to the atmospheric aerosol in Vienna by using a tracer suitable for activation analysis

    International Nuclear Information System (INIS)

    Norek, C.

    1985-01-01

    In Vienna a large fraction of light absorbing aerosols has been found. The traffic could be a source for the high absorption coefficients, since the time dependent absorption coefficients varise similar to the traffic densities. Diesel vehicles have high soot emissions, so they may contribute considerably to light absorption during the summer. The emission factors of the vehicles were estimated by measurements at different motor and driving conditions by the Constant-Volume-Sampling-Method. To determine the size distributions a 10-stage-low pressure impactor with a lower cut size of 0.015 μm aerodynamic particle diameter was used. In order to estimate the contribution of diesel vehicles to the total mass concentrations all diesel fuel sold in Vienna and its vincinity was marked with an organic Dysprosium compound. This rare earth tracer was emitted by vehicles together with the soot particles and collected at eleven stations in Vienna. The filter samples were extracted with diluted HNO 3 and the extraction was analysed for Dy by neutron activation analysis. The mass size distributions of the particles and the soot emitted from diesel engines are only slightly influenced by motor and driving parameters. The total mass emissions showed considerable variations, but the mean emission factor obtained from the tests was 2.43 g per litre fuel; knowing also the concentration of the tracer in the fuel, the contribution of diesel particles to the mass of the suspended particulates could be estimated. During the measuring period the contribution was c. 25% to the total mass and c. 40% to the absorbing matter in the atmosphere. (Author)

  13. Saharan Dust Particle Size And Concentration Distribution In Central Ghana

    Science.gov (United States)

    Sunnu, A. K.

    2010-12-01

    A.K. Sunnu*, G. M. Afeti* and F. Resch+ *Department of Mechanical Engineering, Kwame Nkrumah University of Science and Technology (KNUST) Kumasi, Ghana. E-mail: albertsunnu@yahoo.com +Laboratoire Lepi, ISITV-Université du Sud Toulon-Var, 83162 La Valette cedex, France E-mail: resch@univ-tln.fr Keywords: Atmospheric aerosol; Saharan dust; Particle size distributions; Particle concentrations. Abstract The Saharan dust that is transported and deposited over many countries in the West African atmospheric environment (5°N), every year, during the months of November to March, known locally as the Harmattan season, have been studied over a 13-year period, between 1996 and 2009, using a location at Kumasi in central Ghana (6° 40'N, 1° 34'W) as the reference geographical point. The suspended Saharan dust particles were sampled by an optical particle counter, and the particle size distributions and concentrations were analysed. The counter gives the total dust loads as number of particles per unit volume of air. The optical particle counter used did not discriminate the smoke fractions (due to spontaneous bush fires during the dry season) from the Saharan dust. Within the particle size range measured (0.5 μm-25 μm.), the average inter-annual mean particle diameter, number and mass concentrations during the northern winter months of January and February were determined. The average daily number concentrations ranged from 15 particles/cm3 to 63 particles/cm3 with an average of 31 particles/cm3. The average daily mass concentrations ranged from 122 μg/m3 to 1344 μg/m3 with an average of 532 μg/m3. The measured particle concentrations outside the winter period were consistently less than 10 cm-3. The overall dust mean particle diameter, analyzed from the peak representative Harmattan periods over the 13-year period, ranged from 0.89 μm to 2.43 μm with an average of 1.5 μm ± 0.5. The particle size distributions exhibited the typical distribution pattern for

  14. Size distribution of airbone particulates in monazite dust

    International Nuclear Information System (INIS)

    Cunha, K.M.A.D. da; Carvalho, S.M.M.; Leite, C.V.B.; Baptista, G.B.; Paschoa, A.S.

    1988-01-01

    A six-stage cascade impactor was used to collect airborne dust particulates in the grinding area of a Monazite sepation plant. The samples were analysis using particle-induced X-ray emission (PIXE) to determine the elemental concentrations, with special attention to thorium and uranium concentrations. The particle size distribution of the samples containing thorium and uranium were determined. The mass median aerodynamic diameter (MMAD) obtained was 1.15 μm for both elements. The activity median aerodynamic diameter (AMAD) was estimated based on the MMAD. The results are compared with ICRP recommendations for derived air concentrations (DAC) for thorium and uranium in restricted areas [pt

  15. Higher albedos and size distribution of large transneptunian objects

    Science.gov (United States)

    Lykawka, Patryk Sofia; Mukai, Tadashi

    2005-11-01

    Transneptunian objects (TNOs) orbit beyond Neptune and do offer important clues about the formation of our solar system. Although observations have been increasing the number of discovered TNOs and improving their orbital elements, very little is known about elementary physical properties such as sizes, albedos and compositions. Due to TNOs large distances (>40 AU) and observational limitations, reliable physical information can be obtained only from brighter objects (supposedly larger bodies). According to size and albedo measurements available, it is evident the traditionally assumed albedo p=0.04 cannot hold for all TNOs, especially those with approximately absolute magnitudes H⩽5.5. That is, the largest TNOs possess higher albedos (generally >0.04) that strongly appear to increase as a function of size. Using a compilation of published data, we derived empirical relations which can provide estimations of diameters and albedos as a function of absolute magnitude. Calculations result in more accurate size/albedo estimations for TNOs with H⩽5.5 than just assuming p=0.04. Nevertheless, considering low statistics, the value p=0.04 sounds still convenient for H>5.5 non-binary TNOs as a group. We also discuss about physical processes (e.g., collisions, intrinsic activity and the presence of tenuous atmospheres) responsible for the increase of albedo among large bodies. Currently, all big TNOs (>700 km) would be capable to sustain thin atmospheres or icy frosts composed of CH 4, CO or N 2 even for body bulk densities as low as 0.5 g cm -3. A size-dependent albedo has important consequences for the TNOs size distribution, cumulative luminosity function and total mass estimations. According to our analysis, the latter can be reduced up to 50% if higher albedos are common among large bodies. Lastly, by analyzing orbital properties of classical TNOs ( 42AUbodies. For both populations, distinct absolute magnitude distributions are maximized for an inclination threshold

  16. Pareto Distribution of Firm Size and Knowledge Spillover Process as a Network

    OpenAIRE

    Tomohiko Konno

    2013-01-01

    The firm size distribution is considered as Pareto distribution. In the present paper, we show that the Pareto distribution of firm size results from the spillover network model which was introduced in Konno (2010).

  17. Optimal placement and sizing of multiple distributed generating units in distribution

    Directory of Open Access Journals (Sweden)

    D. Rama Prabha

    2016-06-01

    Full Text Available Distributed generation (DG is becoming more important due to the increase in the demands for electrical energy. DG plays a vital role in reducing real power losses, operating cost and enhancing the voltage stability which is the objective function in this problem. This paper proposes a multi-objective technique for optimally determining the location and sizing of multiple distributed generation (DG units in the distribution network with different load models. The loss sensitivity factor (LSF determines the optimal placement of DGs. Invasive weed optimization (IWO is a population based meta-heuristic algorithm based on the behavior of weeds. This algorithm is used to find optimal sizing of the DGs. The proposed method has been tested for different load models on IEEE-33 bus and 69 bus radial distribution systems. This method has been compared with other nature inspired optimization methods. The simulated results illustrate the good applicability and performance of the proposed method.

  18. A model of litter size distribution in cattle.

    Science.gov (United States)

    Bennett, G L; Echternkamp, S E; Gregory, K E

    1998-07-01

    Genetic increases in twinning of cattle could result in increased frequency of triplet or higher-order births. There are no estimates of the incidence of triplets in populations with genetic levels of twinning over 40% because these populations either have not existed or have not been documented. A model of the distribution of litter size in cattle is proposed. Empirical estimates of ovulation rate distribution in sheep were combined with biological hypotheses about the fate of embryos in cattle. Two phases of embryo loss were hypothesized. The first phase is considered to be preimplantation. Losses in this phase occur independently (i.e., the loss of one embryo does not affect the loss of the remaining embryos). The second phase occurs after implantation. The loss of one embryo in this stage results in the loss of all embryos. Fewer than 5% triplet births are predicted when 50% of births are twins and triplets. Above 60% multiple births, increased triplets accounted for most of the increase in litter size. Predictions were compared with data from 5,142 calvings by 14 groups of heifers and cows with average litter sizes ranging from 1.14 to 1.36 calves. The predicted number of triplets was not significantly different (chi2 = 16.85, df = 14) from the observed number. The model also predicted differences in conception rates. A cow ovulating two ova was predicted to have the highest conception rate in a single breeding cycle. As mean ovulation rate increased, predicted conception to one breeding cycle increased. Conception to two or three breeding cycles decreased as mean ovulation increased because late-pregnancy failures increased. An alternative model of the fate of ova in cattle based on embryo and uterine competency predicts very similar proportions of singles, twins, and triplets but different conception rates. The proposed model of litter size distribution in cattle accurately predicts the proportion of triplets found in cattle with genetically high twinning

  19. Characterization of Bubble Size Distributions within a Bubble Column

    Directory of Open Access Journals (Sweden)

    Shahrouz Mohagheghian

    2018-02-01

    Full Text Available The current study experimentally examines bubble size distribution (BSD within a bubble column and the associated characteristic length scales. Air was injected into a column of water via a single injection tube. The column diameter (63–102 mm, injection tube diameter (0.8–1.6 mm and superficial gas velocity (1.4–55 mm/s were varied. Large samples (up to 54,000 bubbles of bubble sizes measured via 2D imaging were used to produce probability density functions (PDFs. The PDFs were used to identify an alternative length scale termed the most frequent bubble size (dmf and defined as the peak in the PDF. This length scale as well as the traditional Sauter mean diameter were used to assess the sensitivity of the BSD to gas injection rate, injector tube diameter, injection tube angle and column diameter. The dmf was relatively insensitive to most variation, which indicates these bubbles are produced by the turbulent wakes. In addition, the current work examines higher order statistics (standard deviation, skewness and kurtosis and notes that there is evidence in support of using these statistics to quantify the influence of specific parameters on the flow-field as well as a potential indicator of regime transitions.

  20. Subsonic aircraft soot. A tracer documenting barriers to inter-hemispheric mixing

    Energy Technology Data Exchange (ETDEWEB)

    Pueschel, R F [NASA Ames Research Center, Moffett Field, CA (United States)

    1998-12-31

    Meridional observations of soot aerosols and radioactive {sup 14}C, and models of the geographic distribution of nuclear bomb-released {sup 14}C and aircraft-emitted NO{sub x}, all show strong gradients between the hemispheres. Reason for it are decade-long inter-hemispheric mixing times which are much in excess of yearlong stratospheric residence times of tracers. Vertical mixing of soot aerosol is not corroborated by {sup 14}C observations. The reason could be radiometric forces that act on strongly absorbing soot. (author) 10 refs.

  1. Subsonic aircraft soot. A tracer documenting barriers to inter-hemispheric mixing

    Energy Technology Data Exchange (ETDEWEB)

    Pueschel, R.F. [NASA Ames Research Center, Moffett Field, CA (United States)

    1997-12-31

    Meridional observations of soot aerosols and radioactive {sup 14}C, and models of the geographic distribution of nuclear bomb-released {sup 14}C and aircraft-emitted NO{sub x}, all show strong gradients between the hemispheres. Reason for it are decade-long inter-hemispheric mixing times which are much in excess of yearlong stratospheric residence times of tracers. Vertical mixing of soot aerosol is not corroborated by {sup 14}C observations. The reason could be radiometric forces that act on strongly absorbing soot. (author) 10 refs.

  2. Experimental investigation on the morphology of soot aggregates from the burning of typical solid and liquid fuels

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Dongmei, E-mail: 20021567@163.com; Guo, Chenning [China Jiliang University, College of Quality and Safety Engineering (China); Shi, Long [RMIT University, Civil and Infrastructure Engineering Discipline, School of Engineering (Australia)

    2017-03-15

    Soot particles from the burning of typical fuels are one of the critical sources causing environmental problems and human disease. To understand the soot formation of these typical fuels, the size and morphology of soot aggregates produced from the burning of typical solid and liquid fuels, including diesel, kerosene, natural rubber (NR) latex foam, and wood crib, were studied by both extractive sampling and subsequent image analysis. The 2D and 3D fractal dimensions together with the diameter distribution of agglomerate and primary particles were analyzed for these four typical fuels. The average diameters of the primary particles were within 45–85 nm when sampling from different heights above the fire sources. Irregular sheet structures and flake-like masses were observed from the burning of NR latex foam and wood cribs. Superaggregates with a mean maximum length scale of over 100 μm were also found from the burning of all these four tested fuels. The fractal dimension of a single aggregate was 3 for all the tested fuels.

  3. Evaluation and optimisation of phenomenological multi-step soot model for spray combustion under diesel engine-like operating conditions

    Science.gov (United States)

    Pang, Kar Mun; Jangi, Mehdi; Bai, Xue-Song; Schramm, Jesper

    2015-05-01

    In this work, a two-dimensional computational fluid dynamics study is reported of an n-heptane combustion event and the associated soot formation process in a constant volume combustion chamber. The key interest here is to evaluate the sensitivity of the chemical kinetics and submodels of a semi-empirical soot model in predicting the associated events. Numerical computation is performed using an open-source code and a chemistry coordinate mapping approach is used to expedite the calculation. A library consisting of various phenomenological multi-step soot models is constructed and integrated with the spray combustion solver. Prior to the soot modelling, combustion simulations are carried out. Numerical results show that the ignition delay times and lift-off lengths exhibit good agreement with the experimental measurements across a wide range of operating conditions, apart from those in the cases with ambient temperature lower than 850 K. The variation of the soot precursor production with respect to the change of ambient oxygen levels qualitatively agrees with that of the conceptual models when the skeletal n-heptane mechanism is integrated with a reduced pyrene chemistry. Subsequently, a comprehensive sensitivity analysis is carried out to appraise the existing soot formation and oxidation submodels. It is revealed that the soot formation is captured when the surface growth rate is calculated using a square root function of the soot specific surface area and when a pressure-dependent model constant is considered. An optimised soot model is then proposed based on the knowledge gained through this exercise. With the implementation of optimised model, the simulated soot onset and transport phenomena before reaching quasi-steady state agree reasonably well with the experimental observation. Also, variation of spatial soot distribution and soot mass produced at oxygen molar fractions ranging from 10.0 to 21.0% for both low and high density conditions are reproduced.

  4. Small particles big effect? - Investigating ice nucleation abilities of soot particles

    Science.gov (United States)

    Mahrt, Fabian; David, Robert O.; Lohmann, Ulrike; Stopford, Chris; Wu, Zhijun; Kanji, Zamin A.

    2017-04-01

    Atmospheric soot particles are primary particles produced by incomplete combustion of biomass and/or fossil fuels. Thus soot mainly originates from anthropogenic emissions, stemming from combustion related processes in transport vehicles, industrial and residential uses. Such soot particles are generally complex mixtures of black carbon (BC) and organic matter (OM) (Bond et al., 2013; Petzold et al., 2013), depending on the sources and the interaction of the primary particles with other atmospheric matter and/or gases BC absorbs solar radiation having a warming effect on global climate. It can also act as a heterogeneous ice nucleating particle (INP) and thus impact cloud-radiation interactions, potentially cooling the climate (Lohmann, 2002). Previous studies, however, have shown conflicting results concerning the ice nucleation ability of soot, limiting the ability to predict its effects on Earth's radiation budget. Here we present a laboratory study where we systematically investigate the ice nucleation behavior of different soot particles. Commercial soot samples are used, including an amorphous, industrial carbon frequently used in coatings and coloring (FW 200, Orion Engineered Carbons) and a fullerene soot (572497 ALDRICH), e.g. used as catalyst. In addition, we use soot generated from a propane flame Combustion Aerosol Standard Generator (miniCAST, JING AG), as a proxy for atmospheric soot particles. The ice nucleation ability of these soot types is tested on size-selected particles for a wide temperature range from 253 K to 218 K, using the Horizontal Ice Nucleation Chamber (HINC), a Continuous Flow Diffusion Chamber (CFDC) (Kanji and Abbatt, 2009). Ice nucleation results from these soot surrogates will be compared to chemically more complex real world samples, collected on filters. Filters will be collected during the 2016/2017 winter haze periods in Beijing, China and represent atmospheric soot particles with sources from both industrial and residential

  5. Determination of particle size distributions from acoustic wave propagation measurements

    International Nuclear Information System (INIS)

    Spelt, P.D.; Norato, M.A.; Sangani, A.S.; Tavlarides, L.L.

    1999-01-01

    The wave equations for the interior and exterior of the particles are ensemble averaged and combined with an analysis by Allegra and Hawley [J. Acoust. Soc. Am. 51, 1545 (1972)] for the interaction of a single particle with the incident wave to determine the phase speed and attenuation of sound waves propagating through dilute slurries. The theory is shown to compare very well with the measured attenuation. The inverse problem, i.e., the problem of determining the particle size distribution given the attenuation as a function of frequency, is examined using regularization techniques that have been successful for bubbly liquids. It is shown that, unlike the bubbly liquids, the success of solving the inverse problem is limited since it depends strongly on the nature of particles and the frequency range used in inverse calculations. copyright 1999 American Institute of Physics

  6. Dielectric properties of PMMA/Soot nanocomposites.

    Science.gov (United States)

    Clayton, Lanetra M; Cinke, Martin; Meyyappan, M; Harmon, Julie P

    2007-07-01

    Dielectric analysis (DEA) of relaxation behavior in poly(methyl methacrylate) (PMMA) soot nanocomposites is described herein. The soot, an inexpensive material, consists of carbon nanotubes, amorphous and graphitic carbon and metal particles. Results are compared to earlier studies on PMMA/multi-walled nanotube (MWNT) composites and PMMA/single-walled nanotube (SWNT) composites. The beta relaxation process appeared to be unaffected by the presence of the soot, as was noted earlier in nanotube composites. The gamma relaxation region in PMMA, normally dielectrically inactive, was "awakened" in the PMMA/soot composite. This occurrence is consistent with previously published data on nanotube composites. The dielectric permittivity, s', increased with soot content. The sample with 1% soot exhibited a permittivity (at 100 Hz and 25 degrees C) of 7.3 as compared to 5.1 for neat PMMA. Soot increased the dielectric strength, deltaE, of the composites. The 1% soot sample exhibited a dielectric strength of 6.38, while the neat PMMA had a value of 2.95 at 40 degrees C. The symmetric broadening term (alpha) was slightly higher for the 1% composite at temperatures near the secondary relaxation and near the primary relaxation, but all samples deviated from symmetrical semi-circular behavior (alpha = 1). The impact of the soot filler is seen more clearly in dielectric properties than in mechanical properties studies conducted earlier.

  7. Optimization of bridging agents size distribution for drilling operations

    Energy Technology Data Exchange (ETDEWEB)

    Waldmann, Alex; Andrade, Alex Rodrigues de; Pires Junior, Idvard Jose; Martins, Andre Leibsohn [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil)]. E-mails: awaldmann@petrobras.com.br; andradear.gorceix@petrobras.com.br; idvard.gorceix@petrobras.com.br; aleibsohn@petrobras.com.br

    2008-07-01

    The conventional drilling technique is based on positive hydrostatic pressure against well walls to prevent inflows of native fluids into the well. Such inflows can cause security problems for the team well and to probe. As the differential pressure of the well to reservoir is always positive, the filtrate of the fluid tends to invade the reservoir rock. Minimize the invasion of drilling fluid is a relevant theme in the oil wells drilling operations. In the design of drilling fluid, a common practice in the industry is the addition of bridging agents in the composition of the fluid to form a cake of low permeability at well walls and hence restrict the invasive process. The choice of drilling fluid requires the optimization of the concentration, shape and size distribution of particles. The ability of the fluid to prevent the invasion is usually evaluated in laboratory tests through filtration in porous media consolidated. This paper presents a description of the methods available in the literature for optimization of the formulation of bridging agents to drill-in fluids, predicting the pore throat from data psychotherapy, and a sensitivity analysis of the main operational parameters. The analysis is based on experimental results of the impact of the size distribution and concentration of bridging agents in the filtration process of drill-in fluids through porous media submitted to various different differential of pressure. The final objective is to develop a software for use of PETROBRAS, which may relate different types and concentrations of bridging agents with the properties of the reservoir to minimize the invasion. (author)

  8. Flow distribution in adjacent subchannels of unequal size

    International Nuclear Information System (INIS)

    Bugg, J.D.

    1985-11-01

    This report describes an experimental and analytic investigation of the single phase flow distribution in subchannel geometries. It was intended as an investigation of fundamental transport mechanisms and therefore concentrated on simple geometries with two interconnected subchannels. The experimental phase consisted of detailed measuremnts of the fluid velocity in a geometry representing two communicating subchannels of different sizes. These measurements were made at three axial locations along the test section. The size of one of the subchannels was varied to give subchannel area ratios of 1.0, 0.68, 0.50 and 0.32. Two Reynolds numbers (108000 and 180000) were investigated. Axial pressure gradient data for all of these cases was also taken. The analytic phase concentrated on applying a three dimensional finite difference fluid flow code to subchannel geomtries. The code was applied to the cases studied in the experiment as well as other investigator's results. It used the two equation K-ε turbulence model. The performance of this model was assessed. Unique features of the subchannel flows were identified and discussed. Conclusions regarding the transport mechanisms involved and the ability of a multidimensional code to predict the flow fields reliably were presented

  9. Statistical properties of the normalized ice particle size distribution

    Science.gov (United States)

    Delanoë, Julien; Protat, Alain; Testud, Jacques; Bouniol, Dominique; Heymsfield, A. J.; Bansemer, A.; Brown, P. R. A.; Forbes, R. M.

    2005-05-01

    Testud et al. (2001) have recently developed a formalism, known as the "normalized particle size distribution (PSD)", which consists in scaling the diameter and concentration axes in such a way that the normalized PSDs are independent of water content and mean volume-weighted diameter. In this paper we investigate the statistical properties of the normalized PSD for the particular case of ice clouds, which are known to play a crucial role in the Earth's radiation balance. To do so, an extensive database of airborne in situ microphysical measurements has been constructed. A remarkable stability in shape of the normalized PSD is obtained. The impact of using a single analytical shape to represent all PSDs in the database is estimated through an error analysis on the instrumental (radar reflectivity and attenuation) and cloud (ice water content, effective radius, terminal fall velocity of ice crystals, visible extinction) properties. This resulted in a roughly unbiased estimate of the instrumental and cloud parameters, with small standard deviations ranging from 5 to 12%. This error is found to be roughly independent of the temperature range. This stability in shape and its single analytical approximation implies that two parameters are now sufficient to describe any normalized PSD in ice clouds: the intercept parameter N*0 and the mean volume-weighted diameter Dm. Statistical relationships (parameterizations) between N*0 and Dm have then been evaluated in order to reduce again the number of unknowns. It has been shown that a parameterization of N*0 and Dm by temperature could not be envisaged to retrieve the cloud parameters. Nevertheless, Dm-T and mean maximum dimension diameter -T parameterizations have been derived and compared to the parameterization of Kristjánsson et al. (2000) currently used to characterize particle size in climate models. The new parameterization generally produces larger particle sizes at any temperature than the Kristjánsson et al. (2000

  10. Damköhler number effects on soot formation and growth in turbulent nonpremixed flames

    KAUST Repository

    Attili, Antonio

    2015-01-01

    The effect of Damköhler number on turbulent nonpremixed sooting flames is investigated via large scale direct numerical simulation in three-dimensional n-heptane/air jet flames at a jet Reynolds number of 15,000 and at three different Damköhler numbers. A reduced chemical mechanism, which includes the soot precursor naphthalene, and a high-order method of moments are employed. At the highest Damköhler number, local extinction is negligible, while flames holes are observed in the two lowest Damköhler number cases. Compared to temperature and other species controlled by fuel oxidation chemistry, naphthalene is found to be affected more significantly by the Damköhler number. Consequently, the overall soot mass fraction decreases by more than one order of magnitude for a fourfold decrease of the Damköhler number. On the contrary, the overall number density of soot particles is approximately the same, but its distribution in mixture fraction space is different in the three cases. The total soot mass growth rate is found to be proportional to the Damköhler number. In the two lowest Da number cases, soot leakage across the flame is observed. Leveraging Lagrangian statistics, it is concluded that soot leakage is due to patches of soot that cross the stoichiometric surface through flame holes. These results show the leading order effects of turbulent mixing in controlling the dynamics of soot in turbulent flames. © 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

  11. Effects of biodiesel, engine load and diesel particulate filter on nonvolatile particle number size distributions in heavy-duty diesel engine exhaust

    Energy Technology Data Exchange (ETDEWEB)

    Young, Li-Hao, E-mail: lhy@mail.cmu.edu.tw [Department of Occupational Safety and Health, China Medical University, 91, Hsueh-Shih Road, Taichung 40402, Taiwan (China); Liou, Yi-Jyun [Department of Occupational Safety and Health, China Medical University, 91, Hsueh-Shih Road, Taichung 40402, Taiwan (China); Cheng, Man-Ting [Department of Environmental Engineering, National Chung Hsing University, 250, Kuo-Kuang Road, Taichung 40254, Taiwan (China); Lu, Jau-Huai [Department of Mechanical Engineering, National Chung Hsing University, 250, Kuo-Kuang Road, Taichung 40254, Taiwan (China); Yang, Hsi-Hsien [Department of Environmental Engineering and Management, Chaoyang University of Technology, 168, Jifeng E. Road, Taichung 41349, Taiwan (China); Tsai, Ying I. [Department of Environmental Engineering and Science, Chia Nan University of Pharmacy and Science, 60, Sec. 1, Erh-Jen Road, Tainan 71710, Taiwan (China); Wang, Lin-Chi [Department of Chemical and Materials Engineering, Cheng Shiu University, 840, Chengcing Road, Kaohsiung 83347, Taiwan (China); Chen, Chung-Bang [Fuel Quality and Engine Performance Research, Refining and Manufacturing Research Institute, Chinese Petroleum Corporation, 217, Minsheng S. Road, Chiayi 60036, Taiwan (China); Lai, Jim-Shoung [Department of Occupational Safety and Health, China Medical University, 91, Hsueh-Shih Road, Taichung 40402, Taiwan (China)

    2012-01-15

    Highlights: Black-Right-Pointing-Pointer The effects of waste cooking oil biodiesel, engine load and DOC + DPF on nonvolatile particle size distributions in HDDE exhaust. Black-Right-Pointing-Pointer Increasing biodiesel blends cause slight decreases in the total particle number concentrations and negligible changes in size distributions. Black-Right-Pointing-Pointer Increasing load results in modest increases in both the total particle number concentrations and sizes. Black-Right-Pointing-Pointer The effects of semivolatile materials are strongest at idle, during which nonvolatile cores <16 nm were observed. Black-Right-Pointing-Pointer The DOC + DPF shows remarkable filtration efficiency for both the core and soot particles, irrespective of biodiesel blend and load. - Abstract: Diesel engine exhaust contains large numbers of submicrometer particles that degrade air quality and human health. This study examines the number emission characteristics of 10-1000 nm nonvolatile particles from a heavy-duty diesel engine, operating with various waste cooking oil biodiesel blends (B2, B10 and B20), engine loads (0%, 25%, 50% and 75%) and a diesel oxidation catalyst plus diesel particulate filter (DOC + DPF) under steady modes. For a given load, the total particle number concentrations (N{sub TOT}) decrease slightly, while the mode diameters show negligible changes with increasing biodiesel blends. For a given biodiesel blend, both the N{sub TOT} and mode diameters increase modestly with increasing load of above 25%. The N{sub TOT} at idle are highest and their size distributions are strongly affected by condensation and possible nucleation of semivolatile materials. Nonvolatile cores of diameters less than 16 nm are only observed at idle mode. The DOC + DPF shows remarkable filtration efficiency for both the core and soot particles, irrespective of the biodiesel blend and engine load under study. The N{sub TOT} post the DOC + DPF are comparable to typical ambient levels of

  12. Size Dependence of Dust Distribution around the Earth Orbit

    Energy Technology Data Exchange (ETDEWEB)

    Ueda, Takahiro; Takeuchi, Taku [Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Meguro, Tokyo, 152-8551 (Japan); Kobayashi, Hiroshi; Ishihara, Daisuke; Kondo, Toru; Kaneda, Hidehiro, E-mail: t.ueda@geo.titech.ac.jp [Graduate School of Science, Nagoya University, Nagoya, Aichi, 464-8602 (Japan)

    2017-05-01

    In the solar system, interplanetary dust particles (IDPs) originating mainly from asteroid collisions and cometary activities drift to Earth orbit due to Poynting–Robertson drag. We analyzed the thermal emission from IDPs that was observed by the first Japanese infrared astronomical satellite, AKARI . The observed surface brightness in the trailing direction of the Earth orbit is 3.7% greater than that in the leading direction in the 9 μ m band and 3.0% in the 18 μ m band. In order to reveal dust properties causing leading–trailing surface brightness asymmetry, we numerically integrated orbits of the Sun, the Earth, and a dust particle as a restricted three-body problem including radiation from the Sun. The initial orbits of particles are determined according to the orbits of main-belt asteroids or Jupiter-family comets. Orbital trapping in mean motion resonances results in a significant leading–trailing asymmetry so that intermediate sized dust (∼10–100 μ m) produces a greater asymmetry than zodiacal light. The leading–trailing surface brightness difference integrated over the size distribution of the asteroidal dust is obtained to be 27.7% and 25.3% in the 9 μ m and 18 μ m bands, respectively. In contrast, the brightness difference for cometary dust is calculated as 3.6% and 3.1% in the 9 μ m and 18 μ m bands, respectively, if the maximum dust radius is set to be s {sub max} = 3000 μ m. Taking into account these values and their errors, we conclude that the contribution of asteroidal dust to the zodiacal infrared emission is less than ∼10%, while cometary dust of the order of 1 mm mainly accounts for the zodiacal light in infrared.

  13. Size Dependence of Dust Distribution around the Earth Orbit

    International Nuclear Information System (INIS)

    Ueda, Takahiro; Takeuchi, Taku; Kobayashi, Hiroshi; Ishihara, Daisuke; Kondo, Toru; Kaneda, Hidehiro

    2017-01-01

    In the solar system, interplanetary dust particles (IDPs) originating mainly from asteroid collisions and cometary activities drift to Earth orbit due to Poynting–Robertson drag. We analyzed the thermal emission from IDPs that was observed by the first Japanese infrared astronomical satellite, AKARI . The observed surface brightness in the trailing direction of the Earth orbit is 3.7% greater than that in the leading direction in the 9 μ m band and 3.0% in the 18 μ m band. In order to reveal dust properties causing leading–trailing surface brightness asymmetry, we numerically integrated orbits of the Sun, the Earth, and a dust particle as a restricted three-body problem including radiation from the Sun. The initial orbits of particles are determined according to the orbits of main-belt asteroids or Jupiter-family comets. Orbital trapping in mean motion resonances results in a significant leading–trailing asymmetry so that intermediate sized dust (∼10–100 μ m) produces a greater asymmetry than zodiacal light. The leading–trailing surface brightness difference integrated over the size distribution of the asteroidal dust is obtained to be 27.7% and 25.3% in the 9 μ m and 18 μ m bands, respectively. In contrast, the brightness difference for cometary dust is calculated as 3.6% and 3.1% in the 9 μ m and 18 μ m bands, respectively, if the maximum dust radius is set to be s max  = 3000 μ m. Taking into account these values and their errors, we conclude that the contribution of asteroidal dust to the zodiacal infrared emission is less than ∼10%, while cometary dust of the order of 1 mm mainly accounts for the zodiacal light in infrared.

  14. High voltage distribution scheme for large size GEM detector

    International Nuclear Information System (INIS)

    Saini, J.; Kumar, A.; Dubey, A.K.; Negi, V.S.; Chattopadhyay, S.

    2016-01-01

    Gas Electron Multiplier (GEM) detectors will be used for Muon tracking in the Compressed Baryonic Matter (CBM) experiment at the Facility for Anti-proton Ion Research (FAIR) at Darmstadt, Germany. The sizes of the detector modules in the Muon chambers are of the order of 1 metre x 0.5 metre. For construction of these chambers, three GEM foils are used per chamber. These foils are made by two layered 50μm thin kapton foil. Each GEM foil has millions of holes on it. In such a large scale manufacturing of the foils, even after stringent quality controls, some of the holes may still have defects or defects might develop over the time with operating conditions. These defects may result in short-circuit of the entire GEM foil. A short even in a single hole will make entire foil un-usable. To reduce such occurrences, high voltage (HV) segmentation within the foils has been introduced. These segments are powered either by individual HV supply per segment or through an active HV distribution to manage such a large number of segments across the foil. Individual supplies apart from being costly, are highly complex to implement. Additionally, CBM will have high intensity of particles bombarding on the detector causing the change of resistive chain current feeding the GEM detector with the variation in the intensity. This leads to voltage fluctuations across the foil resulting in the gain variation with the particle intensity. Hence, a low cost active HV distribution is designed to take care of the above discussed issues

  15. Analytical Approach for Loss Minimization in Distribution Systems by Optimum Placement and Sizing of Distributed Generation

    Directory of Open Access Journals (Sweden)

    Bakshi Surbhi

    2016-01-01

    Full Text Available Distributed Generation has drawn the attention of industrialists and researchers for quite a time now due to the advantages it brings loads. In addition to cost-effective and environmentally friendly, but also brings higher reliability coefficient power system. The DG unit is placed close to the load, rather than increasing the capacity of main generator. This methodology brings many benefits, but has to address some of the challenges. The main is to find the optimal location and size of DG units between them. The purpose of this paper is distributed generation by adding an additional means to reduce losses on the line. This paper attempts to optimize the technology to solve the problem of optimal location and size through the development of multi-objective particle swarm. The problem has been reduced to a mathematical optimization problem by developing a fitness function considering losses and voltage distribution line. Fitness function by using the optimal value of the size and location of this algorithm was found to be minimized. IEEE-14 bus system is being considered, in order to test the proposed algorithm and the results show improved performance in terms of accuracy and convergence rate.

  16. NASA: Black soot fuels global warming

    CERN Multimedia

    2003-01-01

    New research from NASA's Goddard Space Center scientists suggests emissions of black soot have been altering the way sunlight reflects off Earth's snow. The research indicates the soot could be responsible for as much as 25 percent of global warming over the past century (assorted news items, 1 paragraph each).

  17. Dispersant Effectiveness, In-Situ Droplet Size Distribution and ...

    Science.gov (United States)

    This report summarizes two projects covered under an Interagency Agreement between the Bureau of Safety and Environmental Enforcement (BSEE) and the U.S. Environmental Protection Agency (EPA) in collaboration with the Bedford Institute of Oceanography, Department of Fisheries and Oceans Canada (BIO DFO), New Jersey Institute of Technology (NJIT) and Dalhousie University. Both projects dovetail together in addressing the ability to differentiate physical from chemical dispersion effectiveness using dispersed oil simulations within a flume tank for improving forensic response monitoring tools. This report is split into separateTasks based upon the two projects funded by BSEE: 1) Dispersant Effectiveness, In-Situ Droplet Size Distribution and Numerical Modeling to Assess Subsurface Dispersant Injection as a Deepwater Blowout Oil Spill Response Option. 2) Evaluation of Oil Fluorescence Characteristics to Improve Forensic Response Tools. This report summarizes 2 collaborative projects funded through an Interagency Agreement with DOI BSEE and a Cooperative Agreement with DFO Canada. BSEE required that the projects be combined into one report as they are both covered under the one Interagency Agreement. Task B (Fluorescence of oils) is an SHC 3.62 FY16 product.

  18. Evolution of drop size distribution in natural rain

    Science.gov (United States)

    D'Adderio, Leo Pio; Porcù, Federico; Tokay, Ali

    2018-02-01

    Both numerical modeling and laboratory experiments document the possibility of a raindrop size distribution (DSD) to evolve to an equilibrium stage (EDSD), where all the principal processes occur at steady rates. The aim of this work is to observe the temporal behavior of the DSD and to directly investigate the conditions favorable to the onset of the EDSD in natural rain. We exploited a large disdrometer dataset collected in the framework of the Ground Validation activities related to the NASA Global Precipitation Measurement mission. More than 200,000 one-minute data of two-dimensional video disdrometer (2DVD) are collected over USA to represent a wide range of precipitation types. The original data are averaged over 2 min and an automatic algorithm is used on a selected subset to identify samples with EDSD. Results show that the EDSD occurs mainly in convective events and lasts for very short time intervals (2 to 4 min). It is more frequent for rain rate between 20 and 40 mm h- 1 and it mostly occurs during sharp increase of precipitation rates.

  19. Variability of the raindrop size distribution at small spatial scales

    Science.gov (United States)

    Berne, A.; Jaffrain, J.

    2010-12-01

    Because of the interactions between atmospheric turbulence and cloud microphysics, the raindrop size distribution (DSD) is strongly variable in space and time. The spatial variability of the DSD at small spatial scales (below a few km) is not well documented and not well understood, mainly because of a lack of adequate measurements at the appropriate resolutions. A network of 16 disdrometers (Parsivels) has been designed and set up over EPFL campus in Lausanne, Switzerland. This network covers a typical operational weather radar pixel of 1x1 km2. The question of the significance of the variability of the DSD at such small scales is relevant for radar remote sensing of rainfall because the DSD is often assumed to be uniform within a radar sample volume and because the Z-R relationships used to convert the measured radar reflectivity Z into rain rate R are usually derived from point measurements. Thanks to the number of disdrometers, it was possible to quantify the spatial variability of the DSD at the radar pixel scale and to show that it can be significant. In this contribution, we show that the variability of the total drop concentration, of the median volume diameter and of the rain rate are significant, taking into account the sampling uncertainty associated with disdrometer measurements. The influence of this variability on the Z-R relationship can be non-negligible. Finally, the spatial structure of the DSD is quantified using a geostatistical tool, the variogram, and indicates high spatial correlation within a radar pixel.

  20. Bubble Size Distribution in a Vibrating Bubble Column

    Science.gov (United States)

    Mohagheghian, Shahrouz; Wilson, Trevor; Valenzuela, Bret; Hinds, Tyler; Moseni, Kevin; Elbing, Brian

    2016-11-01

    While vibrating bubble columns have increased the mass transfer between phases, a universal scaling law remains elusive. Attempts to predict mass transfer rates in large industrial scale applications by extrapolating laboratory scale models have failed. In a stationary bubble column, mass transfer is a function of phase interfacial area (PIA), while PIA is determined based on the bubble size distribution (BSD). On the other hand, BSD is influenced by the injection characteristics and liquid phase dynamics and properties. Vibration modifies the BSD by impacting the gas and gas-liquid dynamics. This work uses a vibrating cylindrical bubble column to investigate the effect of gas injection and vibration characteristics on the BSD. The bubble column has a 10 cm diameter and was filled with water to a depth of 90 cm above the tip of the orifice tube injector. BSD was measured using high-speed imaging to determine the projected area of individual bubbles, which the nominal bubble diameter was then calculated assuming spherical bubbles. The BSD dependence on the distance from the injector, injector design (1.6 and 0.8 mm ID), air flow rates (0.5 to 5 lit/min), and vibration conditions (stationary and vibration conditions varying amplitude and frequency) will be presented. In addition to mean data, higher order statistics will also be provided.

  1. Optimal Placement and Sizing of Renewable Distributed Generations and Capacitor Banks into Radial Distribution Systems

    Directory of Open Access Journals (Sweden)

    Mahesh Kumar

    2017-06-01

    Full Text Available In recent years, renewable types of distributed generation in the distribution system have been much appreciated due to their enormous technical and environmental advantages. This paper proposes a methodology for optimal placement and sizing of renewable distributed generation(s (i.e., wind, solar and biomass and capacitor banks into a radial distribution system. The intermittency of wind speed and solar irradiance are handled with multi-state modeling using suitable probability distribution functions. The three objective functions, i.e., power loss reduction, voltage stability improvement, and voltage deviation minimization are optimized using advanced Pareto-front non-dominated sorting multi-objective particle swarm optimization method. First a set of non-dominated Pareto-front data are called from the algorithm. Later, a fuzzy decision technique is applied to extract the trade-off solution set. The effectiveness of the proposed methodology is tested on the standard IEEE 33 test system. The overall results reveal that combination of renewable distributed generations and capacitor banks are dominant in power loss reduction, voltage stability and voltage profile improvement.

  2. Firm-size distribution and price-cost margins in Dutch manufacturing

    NARCIS (Netherlands)

    Y.M. Prince (Yvonne); A.R. Thurik (Roy)

    1993-01-01

    textabstractIndustrial economists surmise a relation between the size distribution of firms and performance. Usually, attention is focused on the high end of the size distribution. The widely used 4-firm seller concentration, C4, ignores what happens at the low end of the size distribution. An

  3. An alternative method for determining particle-size distribution of forest road aggregate and soil with large-sized particles

    Science.gov (United States)

    Hakjun Rhee; Randy B. Foltz; James L. Fridley; Finn Krogstad; Deborah S. Page-Dumroese

    2014-01-01

    Measurement of particle-size distribution (PSD) of soil with large-sized particles (e.g., 25.4 mm diameter) requires a large sample and numerous particle-size analyses (PSAs). A new method is needed that would reduce time, effort, and cost for PSAs of the soil and aggregate material with large-sized particles. We evaluated a nested method for sampling and PSA by...

  4. Energetic tradeoffs control the size distribution of aquatic mammals

    Science.gov (United States)

    Gearty, William; McClain, Craig R.; Payne, Jonathan L.

    2018-04-01

    Four extant lineages of mammals have invaded and diversified in the water: Sirenia, Cetacea, Pinnipedia, and Lutrinae. Most of these aquatic clades are larger bodied, on average, than their closest land-dwelling relatives, but the extent to which potential ecological, biomechanical, and physiological controls contributed to this pattern remains untested quantitatively. Here, we use previously published data on the body masses of 3,859 living and 2,999 fossil mammal species to examine the evolutionary trajectories of body size in aquatic mammals through both comparative phylogenetic analysis and examination of the fossil record. Both methods indicate that the evolution of an aquatic lifestyle is driving three of the four extant aquatic mammal clades toward a size attractor at ˜500 kg. The existence of this body size attractor and the relatively rapid selection toward, and limited deviation from, this attractor rule out most hypothesized drivers of size increase. These three independent body size increases and a shared aquatic optimum size are consistent with control by differences in the scaling of energetic intake and cost functions with body size between the terrestrial and aquatic realms. Under this energetic model, thermoregulatory costs constrain minimum size, whereas limitations on feeding efficiency constrain maximum size. The optimum size occurs at an intermediate value where thermoregulatory costs are low but feeding efficiency remains high. Rather than being released from size pressures, water-dwelling mammals are driven and confined to larger body sizes by the strict energetic demands of the aquatic medium.

  5. An investigation on the particulate number and size distributions over the whole engine map from an optimized combustion strategy combining RCCI and dual-fuel diesel-gasoline

    International Nuclear Information System (INIS)

    Benajes, Jesús; García, Antonio; Monsalve-Serrano, Javier; Boronat, Vicente

    2017-01-01

    Highlights: • Optimized dual-mode dual-fuel strategy to cover the whole engine map. • High coherence between smoke and total particles number for diffusive dual-fuel mode. • Fully premixed RCCI regime dominated by small particles of 30 nm diameter peak. • Highly premixed RCCI mode has a transitional behavior with two particle diameter peaks. - Abstract: Literature demonstrates that, for premixed low temperature combustion concepts, particulate matter cannot be directly extrapolated from soot emissions measurements, as typically done for conventional diesel combustion. This is because the particulate matter from low temperature combustion has low fraction of carbonaceous compounds and great amount of soluble organic fraction, which is not captured by the smoke measurement techniques such as the optical reflectometry. By this reason, the study of the particulate matter characteristics from this combustion techniques requires using specific equipment. The aim of the current work is to gain understanding on the particulate matter characteristics from the dual-mode dual-fuel combustion, which is an optimized combustion strategy that combines fully and highly premixed RCCI regimes at low and medium loads, and switches to dual-fuel diffusion combustion at full load. The study was performed over the whole engine map, using a 15.3:1 compression ratio medium-duty EURO VI diesel engine. In particular, the particulate number and size distributions were sampled using a scanning mobility particle sizer and a condensation particle counter, which allow measuring the size distribution and total number of particles from 5 to 250 nm. Results demonstrate that the fully premixed RCCI combustion is dominated by small particles (less than 30 nm in mobility diameter), the dual-fuel diffusion mode is dominated by larger particles (around 100 nm in mobility diameter) showing more diesel-like particle size distributions, and the highly premixed reactivity controlled compression

  6. Investigation of black soot staining in houses

    Energy Technology Data Exchange (ETDEWEB)

    Fugler, D. [Canada Mortgage and Housing Corp., Ottawa, ON (Canada)

    2000-07-01

    Air quality investigators are frequently called upon to determine the origin of streaking, staining or soot marks in both new and old homes. Those marks display common characteristics: black marks along baseboards at interior or exterior walls, behind furniture and at doorways; black smudges on window frames and plastic cabinets; and even shadowing of studs on exterior wall drywall in a few cases. In most instances, carbon soot from a combustion source is the culprit. The combustion sources include furnaces, water heaters, fireplaces, gas dryers, gas ranges, smoking, vehicle exhaust and candle burning. Scepticism about candle soot is prevalent among callers. As a result, a study was initiated in homes where occupants burn candles regularly to investigate soot problems. Samples were collected from five homes, and included stained carpets, filters, and swab samples of black dust or soot. All the houses selected for the study had been built within a three-year period. Some samples of candles commonly burned in those homes were burnt in a laboratory. Air quality audits had been performed in the homes and had revealed other potential pollutant sources. Best practices for cost-effective clean up and control of soot were researched in industry information. The tests conducted in the laboratory found materials consistent with candle soot or residue during microscopic investigations, but no link was established with the stained material obtained from the homes. A few tips for homeowners were included concerning candle burning, and tips for builders were also offered. 1 tab.

  7. Effect of strain rate on sooting limits in counterflow diffusion flames of gaseous hydrocarbon fuels: Sooting temperature index and sooting sensitivity index

    KAUST Repository

    Wang, Yu

    2014-05-01

    The effect of the strain rate on the sooting limits in counterflow diffusion flames was investigated in various gaseous hydrocarbon fuels by varying the nitrogen dilution in the fuel and oxidizer streams. The sooting limit was defined as the critical fuel and oxygen mole fraction at which soot started to appear in the elastic light scattering signal. The sooting region for normal alkane fuels at a specified strain rate, in terms of the fuel and oxygen mole fraction, expanded as the number of carbon atoms increased. The alkene fuels (ethylene, propene) tested had a higher propensity for sooting as compared with alkane fuels with the same carbon numbers (ethane, propane). Branched iso-butane had a higher propensity for sooting than did n-butane. An increase in the strain rate reduced the tendency for sooting in all the fuels tested. The sensitivity of the sooting limit to the strain rate was more pronounced for less sooting fuels. When plotted in terms of calculated flame temperature, the critical oxygen mole fraction exhibited an Arrhenius form under sooting limit conditions, which can be utilized to significantly reduce the effort required to determine sooting limits at different strain rates. We found that the limiting temperatures of soot formation flames are viable sooting metrics for quantitatively rating the sooting tendency of various fuels, based on comparisons with threshold soot index and normalized smoke point data. We also introduce a sooting temperature index and a sooting sensitivity index, two quantitative measures to describe sooting propensity and its dependence on strain rate. © 2013 The Combustion Institute.

  8. Effects of grain size distribution on the interstellar dust mass growth

    OpenAIRE

    Hirashita, Hiroyuki; Kuo, Tzu-Ming

    2011-01-01

    Grain growth by the accretion of metals in interstellar clouds (called `grain growth') could be one of the dominant processes that determine the dust content in galaxies. The importance of grain size distribution for the grain growth is demonstrated in this paper. First, we derive an analytical formula that gives the grain size distribution after the grain growth in individual clouds for any initial grain size distribution. The time-scale of the grain growth is very sensitive to grain size di...

  9. Planar measurements of soot volume fraction and OH in a JP-8 pool fire

    Energy Technology Data Exchange (ETDEWEB)

    Henriksen, Tara L.; Ring, Terry A.; Eddings, Eric G. [Department of Chemical Engineering, University of Utah, Salt Lake City, UT 84112 (United States); Nathan, Graham J. [School of Mechanical Engineering, University of Adelaide, SA 5005 (Australia); Alwahabi, Zeyad T.; Qamar, Nader [School of Chemical Engineering, University of Adelaide, SA 5005 (Australia)

    2009-07-15

    The simultaneous measurement of soot volume fraction by laser induced incandescence (LII) and qualitative imaging of OH by laser induced fluorescence (LIF) was performed in a JP-8 pool fire contained in a 152 mm diameter pan. Line of sight extinction was used to calibrate the LII system in a laminar flame, and to provide an independent method of measuring average soot volume fraction in the turbulent flame. The presence of soot in the turbulent flame was found to be approximately 50% probable, resulting in high levels of optical extinction, which increased slightly through the flame from approximately 30% near the base, to approximately 50% at the tip. This high soot loading pushes both techniques toward their detection limit. Nevertheless, useful accuracy was obtained, with the LII measurement of apparent extinction in the turbulent flame being approximately 21% lower than a direct measurement, consistent with the influence of signal trapping. The axial and radial distributions of soot volume fraction are presented, along with PDFs of volume fraction, and new insight into the behavior of soot sheets in pool fires are sought from the simultaneous measurements of OH and LII. (author)

  10. Drop Size Distribution - Based Separation of Stratiform and Convective Rain

    Science.gov (United States)

    Thurai, Merhala; Gatlin, Patrick; Williams, Christopher

    2014-01-01

    For applications in hydrology and meteorology, it is often desirable to separate regions of stratiform and convective rain from meteorological radar observations, both from ground-based polarimetric radars and from space-based dual frequency radars. In a previous study by Bringi et al. (2009), dual frequency profiler and dual polarization radar (C-POL) observations in Darwin, Australia, had shown that stratiform and convective rain could be separated in the log10(Nw) versus Do domain, where Do is the mean volume diameter and Nw is the scaling parameter which is proportional to the ratio of water content to the mass weighted mean diameter. Note, Nw and Do are two of the main drop size distribution (DSD) parameters. In a later study, Thurai et al (2010) confirmed that both the dual-frequency profiler based stratiform-convective rain separation and the C-POL radar based separation were consistent with each other. In this paper, we test this separation method using DSD measurements from a ground based 2D video disdrometer (2DVD), along with simultaneous observations from a collocated, vertically-pointing, X-band profiling radar (XPR). The measurements were made in Huntsville, Alabama. One-minute DSDs from 2DVD are used as input to an appropriate gamma fitting procedure to determine Nw and Do. The fitted parameters - after averaging over 3-minutes - are plotted against each other and compared with a predefined separation line. An index is used to determine how far the points lie from the separation line (as described in Thurai et al. 2010). Negative index values indicate stratiform rain and positive index indicate convective rain, and, moreover, points which lie somewhat close to the separation line are considered 'mixed' or 'transition' type precipitation. The XPR observations are used to evaluate/test the 2DVD data-based classification. A 'bright-band' detection algorithm was used to classify each vertical reflectivity profile as either stratiform or convective

  11. Application of ant colony optimisation in distribution transformer sizing

    African Journals Online (AJOL)

    This study proposes an optimisation method for transformer sizing in power system using ant colony optimisation and a verification of the process by MATLAB software. The aim is to address the issue of transformer sizing which is a major challenge affecting its effective performance, longevity, huge capital cost and power ...

  12. Oxidation kinetics and soot formation

    Science.gov (United States)

    Glassman, I.; Brezinsky, K.

    1983-01-01

    The research objective is to clarify the role of aromaticity in the soot nucleation process by determining the relative importance of phenyl radical/molecular oxygen and benzene/atomic oxygen reactions in the complex combustion of aromatic compounds. Three sets of chemical flow reactor experiments have been designed to determine the relative importance of the phenyl radical/molecular oxygen and benzene/atomic oxygen reactions. The essential elements of these experiments are 1) the use of cresols and anisole formed during the high temperature oxidation of toluene as chemical reaction indicators; 2) the in situ photolysis of molecular oxygen to provide an oxygen atom perturbation in the reacting aromatic system; and 3) the high temperature pyrolysis of phenol, the cresols and possibly anisole.

  13. Measuring agglomerate size distribution and dependence of localized surface plasmon resonance absorbance on gold nanoparticle agglomerate size using analytical ultracentrifugation.

    Science.gov (United States)

    Zook, Justin M; Rastogi, Vinayak; Maccuspie, Robert I; Keene, Athena M; Fagan, Jeffrey

    2011-10-25

    Agglomeration of nanoparticles during measurements in relevant biological and environmental media is a frequent problem in nanomaterial property characterization. The primary problem is typically that any changes to the size distribution can dramatically affect the potential nanotoxicity or other size-determined properties, such as the absorbance signal in a biosensor measurement. Herein we demonstrate analytical ultracentrifugation (AUC) as a powerful method for measuring two critical characteristics of nanoparticle (NP) agglomerates in situ in biological media: the NP agglomerate size distribution, and the localized surface plasmon resonance (LSPR) absorbance spectrum of precise sizes of gold NP agglomerates. To characterize the size distribution, we present a theoretical framework for calculating the hydrodynamic diameter distribution of NP agglomerates from their sedimentation coefficient distribution. We measure sedimentation rates for monomers, dimers, and trimers, as well as for larger agglomerates with up to 600 NPs. The AUC size distributions were found generally to be broader than the size distributions estimated from dynamic light scattering and diffusion-limited colloidal aggregation theory, an alternative bulk measurement method that relies on several assumptions. In addition, the measured sedimentation coefficients can be used in nanotoxicity studies to predict how quickly the agglomerates sediment out of solution under normal gravitational forces, such as in the environment. We also calculate the absorbance spectra for monomer, dimer, trimer, and larger gold NP agglomerates up to 600 NPs, to enable a better understanding of LSPR biosensors. Finally, we validate a new method that uses these spectra to deconvolute the net absorbance spectrum of an unknown bulk sample and approximate the proportions of monomers, dimers, and trimers in a polydisperse sample of small agglomerates, so that every sample does not need to be measured by AUC. These results

  14. Determination of Size Distributions in Nanocrystalline Powders by TEM, XRD and SAXS

    DEFF Research Database (Denmark)

    Jensen, Henrik; Pedersen, Jørgen Houe; Jørgensen, Jens Erik

    2006-01-01

    Crystallite size distributions and particle size distributions were determined by TEM, XRD, and SAXS for three commercially available TiO2 samples and one homemade. The theoretical Guinier Model was fitted to the experimental data and compared to analytical expressions. Modeling of the XRD spectra...... the size distribution obtained from the XRD experiments; however, a good agreement was obtained between the two techniques. Electron microscopy, SEM and TEM, confirmed the primary particle sizes, the size distributions, and the shapes obtained by XRD and SAXS. The SSEC78 powder and the commercially...

  15. Simulation of the measure of the microparticle size distribution in two dimensions

    International Nuclear Information System (INIS)

    Lameiras, F.S.; Silva Neto, P.P. da

    1987-01-01

    For the nuclear ceramic industry, the determination of the porous size distribution is very important to predict the dimensional thermal stability of uranium dioxide sintered pellets. The determination of the grain size distribution is still very important to predict the operation behavior of these pellets, as well as to control the fabrication process. The Saltykov method is commonly used to determine the microparticles size distribution. A simulation for two-dimensions, using this method and the size distribution of cords to calculate the area distribution [pt

  16. Test of methods for retrospective activity size distribution determination from filter samples

    International Nuclear Information System (INIS)

    Meisenberg, Oliver; Tschiersch, Jochen

    2015-01-01

    Determining the activity size distribution of radioactive aerosol particles requires sophisticated and heavy equipment, which makes measurements at large number of sites difficult and expensive. Therefore three methods for a retrospective determination of size distributions from aerosol filter samples in the laboratory were tested for their applicability. Extraction into a carrier liquid with subsequent nebulisation showed size distributions with a slight but correctable bias towards larger diameters compared with the original size distribution. Yields in the order of magnitude of 1% could be achieved. Sonication-assisted extraction into a carrier liquid caused a coagulation mode to appear in the size distribution. Sonication-assisted extraction into the air did not show acceptable results due to small yields. The method of extraction into a carrier liquid without sonication was applied to aerosol samples from Chernobyl in order to calculate inhalation dose coefficients for 137 Cs based on the individual size distribution. The effective dose coefficient is about half of that calculated with a default reference size distribution. - Highlights: • Activity size distributions can be recovered after aerosol sampling on filters. • Extraction into a carrier liquid and subsequent nebulisation is appropriate. • This facilitates the determination of activity size distributions for individuals. • Size distributions from this method can be used for individual dose coefficients. • Dose coefficients were calculated for the workers at the new Chernobyl shelter

  17. Stochastic Simulation of Soot Formation Evolution in Counterflow Diffusion Flames

    Directory of Open Access Journals (Sweden)

    Xiao Jiang

    2018-01-01

    Full Text Available Soot generally refers to carbonaceous particles formed during incomplete combustion of hydrocarbon fuels. A typical simulation of soot formation and evolution contains two parts: gas chemical kinetics, which models the chemical reaction from hydrocarbon fuels to soot precursors, that is, polycyclic aromatic hydrocarbons or PAHs, and soot dynamics, which models the soot formation from PAHs and evolution due to gas-soot and soot-soot interactions. In this study, two detailed gas kinetic mechanisms (ABF and KM2 have been compared during the simulation (using the solver Chemkin II of ethylene combustion in counterflow diffusion flames. Subsequently, the operator splitting Monte Carlo method is used to simulate the soot dynamics. Both the simulated data from the two mechanisms for gas and soot particles are compared with experimental data available in the literature. It is found that both mechanisms predict similar profiles for the gas temperature and velocity, agreeing well with measurements. However, KM2 mechanism provides much closer prediction compared to measurements for soot gas precursors. Furthermore, KM2 also shows much better predictions for soot number density and volume fraction than ABF. The effect of nozzle exit velocity on soot dynamics has also been investigated. Higher nozzle exit velocity renders shorter residence time for soot particles, which reduces the soot number density and volume fraction accordingly.

  18. A generalized statistical model for the size distribution of wealth

    International Nuclear Information System (INIS)

    Clementi, F; Gallegati, M; Kaniadakis, G

    2012-01-01

    In a recent paper in this journal (Clementi et al 2009 J. Stat. Mech. P02037), we proposed a new, physically motivated, distribution function for modeling individual incomes, having its roots in the framework of the κ-generalized statistical mechanics. The performance of the κ-generalized distribution was checked against real data on personal income for the United States in 2003. In this paper we extend our previous model so as to be able to account for the distribution of wealth. Probabilistic functions and inequality measures of this generalized model for wealth distribution are obtained in closed form. In order to check the validity of the proposed model, we analyze the US household wealth distributions from 1984 to 2009 and conclude an excellent agreement with the data that is superior to any other model already known in the literature. (paper)

  19. A generalized statistical model for the size distribution of wealth

    Science.gov (United States)

    Clementi, F.; Gallegati, M.; Kaniadakis, G.

    2012-12-01

    In a recent paper in this journal (Clementi et al 2009 J. Stat. Mech. P02037), we proposed a new, physically motivated, distribution function for modeling individual incomes, having its roots in the framework of the κ-generalized statistical mechanics. The performance of the κ-generalized distribution was checked against real data on personal income for the United States in 2003. In this paper we extend our previous model so as to be able to account for the distribution of wealth. Probabilistic functions and inequality measures of this generalized model for wealth distribution are obtained in closed form. In order to check the validity of the proposed model, we analyze the US household wealth distributions from 1984 to 2009 and conclude an excellent agreement with the data that is superior to any other model already known in the literature.

  20. Self-similar drop-size distributions produced by breakup in chaotic flows

    International Nuclear Information System (INIS)

    Muzzio, F.J.; Tjahjadi, M.; Ottino, J.M.; Department of Chemical Engineering, University of Massachusetts, Amherst, Massachusetts 01003; Department of Chemical Engineering, Northwestern University, Evanston, Illinois 60208)

    1991-01-01

    Deformation and breakup of immiscible fluids in deterministic chaotic flows is governed by self-similar distributions of stretching histories and stretching rates and produces populations of droplets of widely distributed sizes. Scaling reveals that distributions of drop sizes collapse into two self-similar families; each family exhibits a different shape, presumably due to changes in the breakup mechanism

  1. Method for removing soot from exhaust gases

    Science.gov (United States)

    Suib, Steven L.; Dharmarathna, D. A. Saminda; Pahalagedara, Lakshitha R.

    2018-01-16

    A method for oxidizing soot from diesel exhaust gas from a diesel engine. The method involves providing a diesel particulate filter for receiving the diesel exhaust gas; coating a catalyst composition on the diesel particulate filter; and contacting the soot from the diesel exhaust gas with the catalyst coated diesel particulate filter at a temperature sufficient to oxidize the soot to carbon dioxide. The catalyst composition is a doped or undoped manganese oxide octahedral molecular sieve (OMS-2) material. A diesel exhaust gas treatment system that includes a diesel particulate filter for receiving diesel exhaust gas from a diesel engine and collecting soot; and a catalyst composition coated on the diesel particulate filter. The catalyst composition is a doped or undoped manganese oxide octahedral molecular sieve (OMS-2).

  2. Diesel soot oxidation under controlled conditions

    OpenAIRE

    Song, Haiwen

    2003-01-01

    This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University, 11/12/2003. In order to improve understanding of diesel soot oxidation, an experimental rig was designed and set up, in which the soot oxidation conditions, such as temperature, oxygen partial pressure, and CO2 partial pressure, could be varied independently of each other. The oxidizing gas flow in the oxidizer was under laminar condition. This test rig comprised a naturally-aspirated single ...

  3. Size distribution of rare earth elements in coal ash

    Science.gov (United States)

    Scott, Clinton T.; Deonarine, Amrika; Kolker, Allan; Adams, Monique; Holland, James F.

    2015-01-01

    Rare earth elements (REEs) are utilized in various applications that are vital to the automotive, petrochemical, medical, and information technology industries. As world demand for REEs increases, critical shortages are expected. Due to the retention of REEs during coal combustion, coal fly ash is increasingly considered a potential resource. Previous studies have demonstrated that coal fly ash is variably enriched in REEs relative to feed coal (e.g, Seredin and Dai, 2012) and that enrichment increases with decreasing size fractions (Blissett et al., 2014). In order to further explore the REE resource potential of coal ash, and determine the partitioning behavior of REE as a function of grain size, we studied whole coal and fly ash size-fractions collected from three U.S commercial-scale coal-fired generating stations burning Appalachian or Powder River Basin coal. Whole fly ash was separated into , 5 um, to 5 to 10 um and 10 to 100 um particle size fractions by mechanical shaking using trace-metal clean procedures. In these samples REE enrichments in whole fly ash ranges 5.6 to 18.5 times that of feedcoals. Partitioning results for size separates relative to whole coal and whole fly ash will also be reported. 

  4. Sooting limit in counterflow diffusion flames of ethylene/propane fuels and implication to threshold soot index

    KAUST Repository

    Joo, Peter H.

    2013-01-01

    Sooting limits in counterflow diffusion flames of propane/ethylene fuels have been studied experimentally using a light scattering technique, including the effects of dilution, fuel mixing, and strain rate. The results are discussed in view of the threshold soot index (TSI). In soot-formation (SF) flames, where the flame is located on the oxidizer side of the stagnation plane, the sooting limit depends critically on fuel type and subsequently on flame temperature. The sooting limit has a non-linear dependence on the fuel-mixing ratio, which is similar to the non-linear mixing rule for TSI observed experimentally in rich premixed flames, where soot oxidation is absent for both SF and rich premixed flames. In soot-formation-oxidation (SFO) flames, where the flame is located on the fuel side, the sooting limit depends critically on flame temperature, while it is relatively independent on fuel type. This result suggests a linear mixing rule for sooting limits in SFO flames, which is similar to the TSI behavior for coflow diffusion flames. Soot oxidation takes place for both types of flames. The aerodynamic strain effect on the sooting limits has also been studied and an appreciable influence has been observed. Under sooting conditions, soot volume fraction was measured using a light extinction technique. The soot loadings in SF flames of the mixture fuels demonstrated a synergistic effect, i.e., soot production increased for certain mixture fuels as compared to the respective singlecomponent fuels. © 2012 The Combustion Institute.

  5. Estimating soot emissions from an elevated flare

    Science.gov (United States)

    Almanza, Victor; Sosa, Gustavo

    2009-11-01

    Combustion aerosols are one of the major concerns in flaring operations, due to both health and environmental hazards. Preliminary results are presented for a 2D transient simulation of soot formation in a reacting jet with exit velocity of 130 m/s under a 5 m/s crossflow released from a 50 m high elevated flare and a 50 cm nozzle. Combustion dynamics was simulated with OpenFOAM. Gas-phase non-premixed combustion was modeled with the Chalmers PaSR approach and a κ-ɛ turbulence model. For soot formation, Moss model was used and the ISAT algorithm for solving the chemistry. Sulfur chemistry was considered to account for the sourness of the fuel. Gas composition is 10 % H2S and 90 % C2H4. A simplified Glassman reaction mechanism was used for this purpose. Results show that soot levels are sensitive to the sulfur present in the fuel, since it was observed a slight decrease in the soot volume fraction. NSC is the current oxidation model for soot formation. Predicted temperature is high (about 2390 K), perhaps due to soot-radiation interaction is not considered yet, but a radiation model implementation is on progress, as well as an oxidation mechanism that accounts for OH radical. Flame length is about 50 m.

  6. NATO Workshop on Soot in Combustion Systems

    CERN Document Server

    Prado, G

    1983-01-01

    Our interest in Mulhouse for carbon black and soot began some 30 years ago when J.B. Donnet developed the concept of surface chemistry of carbon and its involvement in interactions with gas, liquid and solid phases. In the late sixties, we began to study soot formation in pyrolytic systems and later on in flames. The idea of organ1z1ng a meeting on soot formation originated some four or five years ago, through discussions among Professor J.B. Howard, Dr. A. D'Alessio and ourselves. At that time the scientific community was becoming aware of the necessity to strictly control soot formation and emission. Being involved in the study of surface properties of carbon black as well as of formation of soot, we realized that the combustion community was not always fully aware of the progress made by the physical-chemists on carbon black. Reciprocally, the carbon specialists were often ignoring the research carried out on soot in flames. One objective of this workshop was to stimulate discussions between these two scie...

  7. Size distributions of non-volatile particle residuals (Dp<800 nm at a rural site in Germany and relation to air mass origin

    Directory of Open Access Journals (Sweden)

    T. Tuch

    2007-11-01

    Full Text Available Atmospheric aerosol particle size distributions at a continental background site in Eastern Germany were examined for a one-year period. Particles were classified using a twin differential mobility particle sizer in a size range between 3 and 800 nm. As a novelty, every second measurement of this experiment involved the removal of volatile chemical compounds in a thermodenuder at 300°C. This concept allowed to quantify the number size distribution of non-volatile particle cores – primarily associated with elemental carbon, and to compare this to the original non-conditioned size distribution. As a byproduct of the volatility analysis, new particles originating from nucleation inside the thermodenuder can be observed, however, overwhelmingly at diameters below 6 nm. Within the measurement uncertainty, every particle down to particle sizes of 15 nm is concluded to contain a non-volatile core. The volume fraction of non-volatile particulate matter (non-conditioned diameter < 800 nm varied between 10 and 30% and was largely consistent with the experimentally determined mass fraction of elemental carbon. The average size of the non-volatile particle cores was estimated as a function of original non-conditioned size using a summation method, which showed that larger particles (>200 nm contained more non-volatile compounds than smaller particles (<50 nm, thus indicating a significantly different chemical composition. Two alternative air mass classification schemes based on either, synoptic chart analysis (Berliner Wetterkarte or back trajectories showed that the volume and number fraction of non-volatile cores depended less on air mass than the total particle number concentration. In all air masses, the non-volatile size distributions showed a more and a less volatile ("soot" mode, the latter being located at about 50 nm. During unstable conditions and in maritime air masses, smaller values were observed compared to stable or continental conditions

  8. Some regularity of the grain size distribution in nuclear fuel with controllable structure

    International Nuclear Information System (INIS)

    Loktev, Igor

    2008-01-01

    It is known, the fission gas release from ceramic nuclear fuel depends from average size of grains. To increase grain size they use additives which activate sintering of pellets. However, grain size distribution influences on fission gas release also. Fuel with different structures, but with the same average size of grains has different fission gas release. Other structure elements, which influence operational behavior of fuel, are pores and inclusions. Earlier, in Kyoto, questions of distribution of grain size for fuel with 'natural' structure were discussed. Some regularity of grain size distribution of fuel with controllable structure and high average size of grains are considered in the report. Influence of inclusions and pores on an error of the automated definition of parameters of structure is shown. The criterion, which describe of behavior of fuel with specific grain size distribution, is offered

  9. Surface properties, more than size, limiting convective distribution of virus-sized particles and viruses in the central nervous system.

    Science.gov (United States)

    Chen, Michael Y; Hoffer, Alan; Morrison, Paul F; Hamilton, John F; Hughes, Jeffrey; Schlageter, Kurt S; Lee, Jeongwu; Kelly, Brandon R; Oldfield, Edward H

    2005-08-01

    Achieving distribution of gene-carrying vectors is a major barrier to the clinical application of gene therapy. Because of the blood-brain barrier, the distribution of genetic vectors to the central nervous system (CNS) is even more challenging than delivery to other tissues. Direct intraparenchymal microinfusion, a minimally invasive technique, uses bulk flow (convection) to distribute suspensions of macromolecules widely through the extracellular space (convection-enhanced delivery [CED]). Although acute injection into solid tissue is often used for delivery of oligonucleotides, viruses, and liposomes, and there is preliminary evidence that certain of these large particles can spread through the interstitial space of the brain by the use of convection, the use of CED for distribution of viruses in the brain has not been systematically examined. That is the goal of this study. Investigators used a rodent model to examine the influence of size, osmolarity of buffering solutions, and surface coating on the volumetric distribution of virus-sized nanoparticles and viruses (adeno-associated viruses and adenoviruses) in the gray matter of the brain. The results demonstrate that channels in the extracellular space of gray matter in the brain are large enough to accommodate virus-sized particles and that the surface characteristics are critical determinants for distribution of viruses in the brain by convection. These results indicate that convective distribution can be used to distribute therapeutic viral vectors in the CNS.

  10. The limit distribution of the maximum increment of a random walk with regularly varying jump size distribution

    DEFF Research Database (Denmark)

    Mikosch, Thomas Valentin; Rackauskas, Alfredas

    2010-01-01

    In this paper, we deal with the asymptotic distribution of the maximum increment of a random walk with a regularly varying jump size distribution. This problem is motivated by a long-standing problem on change point detection for epidemic alternatives. It turns out that the limit distribution...... of the maximum increment of the random walk is one of the classical extreme value distributions, the Fréchet distribution. We prove the results in the general framework of point processes and for jump sizes taking values in a separable Banach space...

  11. Investigating the formation mechanism of soot-like materials present in blast furnace coke samples

    Energy Technology Data Exchange (ETDEWEB)

    S. Dong; P. A' lvarez; N. Paterson; D.R. Dugwell; R. Kandiyoti [Imperial College London, London (United Kingdom). Department of Chemical Engineering

    2008-09-15

    An attempt to gain an understanding of the formation mechanism of these 'soot-like' materials has been made by means of tracing the changes in the molecular-mass distribution and molecular structure of the NMP-extractable materials from an injectant coal as well as its partially gasified chars and its pyrolytic tars. Variations in the SEC chromatograms provide clues about changes in the apparent molecular-mass distributions of these NMP extracts. Results suggest that the build-up of 'soot-like' materials follows from the secondary reactions of tars evolved from the injectant coal. The likely secondary-reaction pathways have been probed by collating structural information on these NMP extracts. The time-resolved 13-16 and 22-25 min elution fractions from the SEC column have been characterized using UV fluorescence (UV F) spectroscopy. Greater concentrations of larger aromatic ring systems are found present in samples formed under conditions appearing more prone for soot formation. The 11-16 min (large apparent molecular mass) effluent from SEC has been examined by Fourier transform infrared (FTIR) spectroscopy and transmission electron microscopy (TEM). Results from FTIR spectroscopy are consistent with the UV F data, showing more significant extents of dehydrogenation under conditions more prone to form soot. Similarly, TEM results show that larger amount of graphene layers exist in samples exposed to more soot-prone conditions. The emerging picture for the formation of 'soot-like' materials involves a well-defined sequence. Tars evolved from the injectant coal undergo secondary dehydrogenation, condensation, and repolymerization reactions, which eventually lead to the formation of the NMP-extractable 'soot-like' materials of large apparent molecular mass. 44 refs., 7 figs., 3 tabs.

  12. Evolution of the sedimentation technique for particle size distribution analysis

    International Nuclear Information System (INIS)

    Maley, R.

    1998-01-01

    After an introduction on the significance of particle size measurements, sedimentation methods are described, with emphasis on the evolution of the gravitational approach. The gravitational technique based on mass determination by X-ray adsorption allows fast analysis by automation and easy data handling, in addition to providing the accuracy required by quality control and research applications [it

  13. Distribution of quantum states in enclosures of finite size I

    International Nuclear Information System (INIS)

    Souto, J.H.; Chaba, A.N.

    1989-01-01

    The expression for the density of states of a particle in a three-dimensional rectangular box of finite size can be obtained directly by Poissons's Summation formula. The expression for the case of an enclosure in the form of an infinite rectangular slab is derived. (A.C.A.S.) [pt

  14. The effect of surface albedo and grain size distribution on ...

    African Journals Online (AJOL)

    Sand dams are very useful in arid and semi arid lands (ASALs) as facilities for water storage and conservation. Soils in ASALs are mainly sandy and major water loss is by evaporation and infiltration. This study investigated the effect of sand media characteristics, specifically surface albedo, grain size and stratification on ...

  15. Dependence of size and size distribution on reactivity of aluminum nanoparticles in reactions with oxygen and MoO3

    International Nuclear Information System (INIS)

    Sun, Juan; Pantoya, Michelle L.; Simon, Sindee L.

    2006-01-01

    The oxidation reaction of aluminum nanoparticles with oxygen gas and the thermal behavior of a metastable intermolecular composite (MIC) composed of the aluminum nanoparticles and molybdenum trioxide are studied with differential scanning calorimetry (DSC) as a function of the size and size distribution of the aluminum particles. Both broad and narrow size distributions have been investigated with aluminum particle sizes ranging from 30 to 160 nm; comparisons are also made to the behavior of micrometer-size particles. Several parameters have been used to characterize the reactivity of aluminum nanoparticles, including the fraction of aluminum that reacts prior to aluminum melting, heat of reaction, onset and peak temperatures, and maximum reaction rates. The results indicate that the reactivity of aluminum nanoparticles is significantly higher than that of the micrometer-size samples, but depending on the measure of reactivity, it may also depend strongly on the size distribution. The isoconversional method was used to calculate the apparent activation energy, and the values obtained for both the Al/O 2 and Al/MoO 3 reaction are in the range of 200-300 kJ/mol

  16. Interpretation of aerosol trace metal particle size distributions

    International Nuclear Information System (INIS)

    Johansson, T.B.; Van Grieken, R.E.; Winchester, J.W.

    1974-01-01

    Proton-induced X-ray emission (PIXE) analysis is capable of rapid routine determination of 10--15 elements present in amounts greater than or equal to 1 ng simultaneously in aerosol size fractions as collected by single orifice impactors over short periods of time. This enables detailed study of complex relationships between elements detected. Since absolute elemental concentrations may be strongly influenced by meteorological and topographical conditions, it is useful to normalize to a reference element. Comparison between the ratios of concentrations with aerosol and corresponding values for anticipated sources may lead to the identification of important sources for the elements. Further geochemical insights may be found through linear correlation coefficients, regression analysis, and cluster analysis. By calculating correlations for elemental pairs, an indication of the degree of covariance between the elements is obtained. Preliminary results indicate that correlations may be particle size dependent. A high degree of covariance may be caused either by a common source or may only reflect the conservative nature of the aerosol. In a regression analysis, by plotting elemental pairs and estimating the regression coefficients, we may be able to conclude if there is more than one source operating for a given element in a certain size range. Analysis of clustering of several elements, previously investigated for aerosol filter samples, can be applied to the analysis of aerosol size fractions. Careful statistical treatment of elemental concentrations as a function of aerosol particle size may thus yield significant information on the generation, transport and deposition of trace metals in the atmosphere

  17. Single-Size Thermometric Measurements on a Size Distribution of Neutral Fullerenes

    NARCIS (Netherlands)

    Cauchy, C.; Bakker, J. M.; Huismans, Y.; Rouzee, A.; Redlich, B.; van der Meer, A. F. G.; Bordas, C.; Vrakking, M. J. J.; Lepine, F.

    2013-01-01

    We present measurements of the velocity distribution of electrons emitted from mass-selected neutral fullerenes, performed at the intracavity free electron laser FELICE. We make use of mass-specific vibrational resonances in the infrared domain to selectively heat up one out of a distribution of

  18. The modelled raindrop size distribution of Skudai, Peninsular Malaysia, using exponential and lognormal distributions.

    Science.gov (United States)

    Yakubu, Mahadi Lawan; Yusop, Zulkifli; Yusof, Fadhilah

    2014-01-01

    This paper presents the modelled raindrop size parameters in Skudai region of the Johor Bahru, western Malaysia. Presently, there is no model to forecast the characteristics of DSD in Malaysia, and this has an underpinning implication on wet weather pollution predictions. The climate of Skudai exhibits local variability in regional scale. This study established five different parametric expressions describing the rain rate of Skudai; these models are idiosyncratic to the climate of the region. Sophisticated equipment that converts sound to a relevant raindrop diameter is often too expensive and its cost sometimes overrides its attractiveness. In this study, a physical low-cost method was used to record the DSD of the study area. The Kaplan-Meier method was used to test the aptness of the data to exponential and lognormal distributions, which were subsequently used to formulate the parameterisation of the distributions. This research abrogates the concept of exclusive occurrence of convective storm in tropical regions and presented a new insight into their concurrence appearance.

  19. The Modelled Raindrop Size Distribution of Skudai, Peninsular Malaysia, Using Exponential and Lognormal Distributions

    Science.gov (United States)

    Yakubu, Mahadi Lawan; Yusop, Zulkifli; Yusof, Fadhilah

    2014-01-01

    This paper presents the modelled raindrop size parameters in Skudai region of the Johor Bahru, western Malaysia. Presently, there is no model to forecast the characteristics of DSD in Malaysia, and this has an underpinning implication on wet weather pollution predictions. The climate of Skudai exhibits local variability in regional scale. This study established five different parametric expressions describing the rain rate of Skudai; these models are idiosyncratic to the climate of the region. Sophisticated equipment that converts sound to a relevant raindrop diameter is often too expensive and its cost sometimes overrides its attractiveness. In this study, a physical low-cost method was used to record the DSD of the study area. The Kaplan-Meier method was used to test the aptness of the data to exponential and lognormal distributions, which were subsequently used to formulate the parameterisation of the distributions. This research abrogates the concept of exclusive occurrence of convective storm in tropical regions and presented a new insight into their concurrence appearance. PMID:25126597

  20. Size distributions of micro-bubbles generated by a pressurized dissolution method

    Science.gov (United States)

    Taya, C.; Maeda, Y.; Hosokawa, S.; Tomiyama, A.; Ito, Y.

    2012-03-01

    Size of micro-bubbles is widely distributed in the range of one to several hundreds micrometers and depends on generation methods, flow conditions and elapsed times after the bubble generation. Although a size distribution of micro-bubbles should be taken into account to improve accuracy in numerical simulations of flows with micro-bubbles, a variety of the size distribution makes it difficult to introduce the size distribution in the simulations. On the other hand, several models such as the Rosin-Rammler equation and the Nukiyama-Tanazawa equation have been proposed to represent the size distribution of particles or droplets. Applicability of these models to the size distribution of micro-bubbles has not been examined yet. In this study, we therefore measure size distribution of micro-bubbles generated by a pressurized dissolution method by using a phase Doppler anemometry (PDA), and investigate the applicability of the available models to the size distributions of micro-bubbles. Experimental apparatus consists of a pressurized tank in which air is dissolved in liquid under high pressure condition, a decompression nozzle in which micro-bubbles are generated due to pressure reduction, a rectangular duct and an upper tank. Experiments are conducted for several liquid volumetric fluxes in the decompression nozzle. Measurements are carried out at the downstream region of the decompression nozzle and in the upper tank. The experimental results indicate that (1) the Nukiyama-Tanasawa equation well represents the size distribution of micro-bubbles generated by the pressurized dissolution method, whereas the Rosin-Rammler equation fails in the representation, (2) the bubble size distribution of micro-bubbles can be evaluated by using the Nukiyama-Tanasawa equation without individual bubble diameters, when mean bubble diameter and skewness of the bubble distribution are given, and (3) an evaluation method of visibility based on the bubble size distribution and bubble

  1. Simulation of the measure of the microparticle size distribution in two dimensions

    International Nuclear Information System (INIS)

    Lameiras, F.S.; Pinheiro, P.

    1987-01-01

    Different size distributions of plane figures were generated in a computer as a simply connected network. These size distributions were measured by the Saltykov method for two dimensions. The comparison between the generated and measured distributions showed that the Saltkov method tends to measure larger scattering than the real one and to move the maximum of the real distribution to larger diameters. These erros were determined by means of the ratio of the perimeter of the figures per unit area directly measured and the perimeter calculated from the size distribution obtained by using the SaltyKov method. (Author) [pt

  2. Effects of Mixtures on Liquid and Solid Fragment Size Distributions

    Science.gov (United States)

    2016-05-01

    bins, too few size bins, fixed bin widths, or inadequately- varying bin widths. Overpopulated bins – which typically occur for smaller fragments...2010 C. V. B. Cunningham, The Kuz-Ram Fragmentation Model – 20 Years On, In R. Holmberg et. al., Editors, Proceedings of the 3 rd World ...1992 P. K. Sahoo and T. Riedel, Mean Value Theorems and Functional Equations, World Scientific, 1998 K. A. Sallam, C. Aalburg, G.M. Faeth

  3. Body size distributions of the pale grass blue butterfly in Japan: Size rules and the status of the Fukushima population

    Science.gov (United States)

    Taira, Wataru; Iwasaki, Mayo; Otaki, Joji M.

    2015-01-01

    The body size of the pale grass blue butterfly, Zizeeria maha, has been used as an environmental indicator of radioactive pollution caused by the Fukushima nuclear accident. However, geographical and temporal size distributions in Japan and temperature effects on size have not been established in this species. Here, we examined the geographical, temporal, and temperature-dependent changes of the forewing size of Z. maha argia in Japan. Butterflies collected in 2012 and 2013 from multiple prefectures throughout Japan demonstrated an inverse relationship of latitude and forewing size, which is the reverse of Bergmann’s cline. The Fukushima population was significantly larger than the Aomori and Miyagi populations and exhibited no difference from most of the other prefectural populations. When monitored at a single geographic locality every other month, forewing sizes were the largest in April and the smallest in August. Rearing larvae at a constant temperature demonstrated that forewing size followed the temperature-size rule. Therefore, the converse Bergmann’s rule and the temperature-size rule coexist in this multivoltine species. Our study establishes this species as a useful environmental indicator and supports the idea that the size reduction observed only in Fukushima Prefecture in 2011 was caused by the environmental stress of radioactive pollution. PMID:26197998

  4. Body size diversity and frequency distributions of Neotropical cichlid fishes (Cichliformes: Cichlidae: Cichlinae.

    Directory of Open Access Journals (Sweden)

    Sarah E Steele

    Full Text Available Body size is an important correlate of life history, ecology and distribution of species. Despite this, very little is known about body size evolution in fishes, particularly freshwater fishes of the Neotropics where species and body size diversity are relatively high. Phylogenetic history and body size data were used to explore body size frequency distributions in Neotropical cichlids, a broadly distributed and ecologically diverse group of fishes that is highly representative of body size diversity in Neotropical freshwater fishes. We test for divergence, phylogenetic autocorrelation and among-clade partitioning of body size space. Neotropical cichlids show low phylogenetic autocorrelation and divergence within and among taxonomic levels. Three distinct regions of body size space were identified from body size frequency distributions at various taxonomic levels corresponding to subclades of the most diverse tribe, Geophagini. These regions suggest that lineages may be evolving towards particular size optima that may be tied to specific ecological roles. The diversification of Geophagini appears to constrain the evolution of body size among other Neotropical cichlid lineages; non-Geophagini clades show lower species-richness in body size regions shared with Geophagini. Neotropical cichlid genera show less divergence and extreme body size than expected within and among tribes. Body size divergence among species may instead be present or linked to ecology at the community assembly scale.

  5. Soot and Spectral Radiation Modeling for a High-Pressure Turbulent Spray Flame

    Energy Technology Data Exchange (ETDEWEB)

    Ferreryo-Fernandez, Sebastian [Pennsylvania State Univ., University Park, PA (United States); Paul, Chandan [Pennsylvania State Univ., University Park, PA (United States); Sircar, Arpan [Pennsylvania State Univ., University Park, PA (United States); Imren, Abdurrahman [Pennsylvania State Univ., University Park, PA (United States); Haworth, Daniel C [Pennsylvania State Univ., University Park, PA (United States); Roy, Somesh P [Marquette University (United States); Modest, Michael F [University of California Merced (United States)

    2017-04-26

    Simulations are performed of a transient high-pressure turbulent n-dodecane spray flame under engine-relevant conditions. An unsteady RANS formulation is used, with detailed chemistry, a semi-empirical two-equation soot model, and a particle-based transported composition probability density function (PDF) method to account for unresolved turbulent fluctuations in composition and temperature. Results from the PDF model are compared with those from a locally well-stirred reactor (WSR) model to quantify the effects of turbulence-chemistry-soot interactions. Computed liquid and vapor penetration versus time, ignition delay, and flame lift-off height are in good agreement with experiment, and relatively small differences are seen between the WSR and PDF models for these global quantities. Computed soot levels and spatial soot distributions from the WSR and PDF models show large differences, with PDF results being in better agreement with experimental measurements. An uncoupled photon Monte Carlo method with line-by-line spectral resolution is used to compute the spectral intensity distribution of the radiation leaving the flame. This provides new insight into the relative importance of molecular gas radiation versus soot radiation, and the importance of turbulent fluctuations on radiative heat transfer.

  6. Effects of fuel particle size distributions on neutron transport in stochastic media

    International Nuclear Information System (INIS)

    Liang, Chao; Pavlou, Andrew T.; Ji, Wei

    2014-01-01

    Highlights: • Effects of fuel particle size distributions on neutron transport are evaluated. • Neutron channeling is identified as the fundamental reason for the effects. • The effects are noticeable at low packing and low optical thickness systems. • Unit cells of realistic reactor designs are studied for different size particles. • Fuel particle size distribution effects are not negligible in realistic designs. - Abstract: This paper presents a study of the fuel particle size distribution effects on neutron transport in three-dimensional stochastic media. Particle fuel is used in gas-cooled nuclear reactor designs and innovative light water reactor designs loaded with accident tolerant fuel. Due to the design requirements and fuel fabrication limits, the size of fuel particles may not be perfectly constant but instead follows a certain distribution. This brings a fundamental question to the radiation transport computation community: how does the fuel particle size distribution affect the neutron transport in particle fuel systems? To answer this question, size distribution effects and their physical interpretations are investigated by performing a series of neutron transport simulations at different fuel particle size distributions. An eigenvalue problem is simulated in a cylindrical container consisting of fissile fuel particles with five different size distributions: constant, uniform, power, exponential and Gaussian. A total of 15 parametric cases are constructed by altering the fissile particle volume packing fraction and its optical thickness, but keeping the mean chord length of the spherical fuel particle the same at different size distributions. The tallied effective multiplication factor (k eff ) and the spatial distribution of fission power density along axial and radial directions are compared between different size distributions. At low packing fraction and low optical thickness, the size distribution shows a noticeable effect on neutron

  7. [Size distributions of aerosol during the Spring Festival in Nanjing].

    Science.gov (United States)

    Wang, Hong-Lei; Zhu, Bin; Shen, Li-Juan; Liu, Xiao-Hui; Zhang, Ze-Feng; Yang, Yang

    2014-02-01

    In order to investigate the firework burning impacts on spectrum distribution of atmospheric aerosol during the Spring Festival in Nanjing, number concentration and mass concentration of aerosol as well as mass concentration of gas pollutants were measured during January 19-31, 2012. The results indicated that the concentration of aerosol between 10-20 nm decreased, aerosol concentration in the range of 50-100 nm, 100-200 nm and 200-500 nm increased during the firework burning period comparing to those during the non-burning period. However, there was no obvious variation for aerosol between 20-50 nm and 0.5-10 microm. The spectrum distribution of number concentration was bimodal during the non-burning period and unimodal during the burning period, with the peak value shifting to large diameter section. The mass concentration presented a bimodal distribution, the value of PM2.5/PM10 and PM10/PM10 increased by 10% during the burning period. The firework burning events had big influence on the density of aerosol between 1.0-2.1 microm.

  8. Compositional effects on PAH and soot formation in counterflow diffusion flames of gasoline surrogate fuels

    KAUST Repository

    Park, Sungwoo

    2017-02-05

    Gasoline surrogate fuels are widely used to understand the fundamental combustion properties of complex refinery gasoline fuels. In this study, the compositional effects on polycyclic aromatic hydrocarbons (PAHs) and soot formation were investigated experimentally for gasoline surrogate mixtures comprising n-heptane, iso-octane, and toluene in counterflow diffusion flames. A comprehensive kinetic model for the gasoline surrogate mixtures was developed to accurately predict the fuel oxidation along with the formation of PAHs and soot in flames. This combined model was first tested against ignition delay times and laminar burning velocities data. The proposed model for the formation and growth of PAHs up to coronene (C24H12) was based on previous studies and was tested against existing and present new experimental data. Additionally, in the accompanied soot model, PAHs with sizes larger than (including) pyrene were used for the inception of soot particles, followed by particle coagulations and PAH condensation/chemical reactions on soot surfaces. The major pathways for the formation of PAHs were also identified for the surrogate mixtures. The model accurately captures the synergistic PAH formation characteristics observed experimentally for n-heptane/toluene and iso-octane/toluene binary mixtures. Furthermore, the present experimental and modeling results also elucidated different trends in the formation of larger PAHs and soot between binary n-heptane/iso-octane and ternary n-heptane/iso-octane/toluene mixtures. Propargyl radicals (C3H3) were shown to be important in the formation and growth of PAHs for n-heptane/iso-octane mixtures when the iso-octane concentration increased; however, reactions involving benzyl radicals (C6H5CH2) played a significant role in the formation of PAHs for n-heptane/iso-octane/toluene mixtures. These results indicated that the formation of PAHs and subsequently soot was strongly affected by the composition of gasoline surrogate mixtures.

  9. Compositional effects on PAH and soot formation in counterflow diffusion flames of gasoline surrogate fuels

    KAUST Repository

    Park, Sungwoo; Wang, Yu; Chung, Suk-Ho; Sarathy, Mani

    2017-01-01

    Gasoline surrogate fuels are widely used to understand the fundamental combustion properties of complex refinery gasoline fuels. In this study, the compositional effects on polycyclic aromatic hydrocarbons (PAHs) and soot formation were investigated experimentally for gasoline surrogate mixtures comprising n-heptane, iso-octane, and toluene in counterflow diffusion flames. A comprehensive kinetic model for the gasoline surrogate mixtures was developed to accurately predict the fuel oxidation along with the formation of PAHs and soot in flames. This combined model was first tested against ignition delay times and laminar burning velocities data. The proposed model for the formation and growth of PAHs up to coronene (C24H12) was based on previous studies and was tested against existing and present new experimental data. Additionally, in the accompanied soot model, PAHs with sizes larger than (including) pyrene were used for the inception of soot particles, followed by particle coagulations and PAH condensation/chemical reactions on soot surfaces. The major pathways for the formation of PAHs were also identified for the surrogate mixtures. The model accurately captures the synergistic PAH formation characteristics observed experimentally for n-heptane/toluene and iso-octane/toluene binary mixtures. Furthermore, the present experimental and modeling results also elucidated different trends in the formation of larger PAHs and soot between binary n-heptane/iso-octane and ternary n-heptane/iso-octane/toluene mixtures. Propargyl radicals (C3H3) were shown to be important in the formation and growth of PAHs for n-heptane/iso-octane mixtures when the iso-octane concentration increased; however, reactions involving benzyl radicals (C6H5CH2) played a significant role in the formation of PAHs for n-heptane/iso-octane/toluene mixtures. These results indicated that the formation of PAHs and subsequently soot was strongly affected by the composition of gasoline surrogate mixtures.

  10. Intercomparison of 15 Aerodynamic Particle Size Spectrometers (APS 3321): Uncertainties in Particle Sizing and Number Size Distribution.

    Czech Academy of Sciences Publication Activity Database

    Pfeifer, S.; Müller, T.; Weinhold, K.; Zíková, Naděžda; dos Santos, S.M.; Marinoni, A.; Bischof, O.F.; Kykal, C.; Ries, L.; Meinhardt, F.; Aalto, P.; Mihalopoulos, N.; Wiedensohler, A.

    2016-01-01

    Roč. 9, č. 4 (2016), s. 1545-1551 ISSN 1867-1381 EU Projects: European Commission(XE) 262254 - ACTRIS Institutional support: RVO:67985858 Keywords : counting efficiency * aerodynamic particle size spectrometers * laboratory study Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.089, year: 2016

  11. Simultaneous measurements of acetylene and soot during the pyrolysis of ethylene and benzene in a shock tube

    KAUST Repository

    KC, Utsav

    2016-10-12

    Acetylene is one of the most important precursors of soot and contributes to soot growth by the hydrogen-abstraction acetylene-addition (HACA) mechanism. In this work, we undertake time-resolved simultaneous measurements of acetylene and soot behind reflected shock waves at temperatures of 1600-2200. K and pressures of 3-5. bar. Acetylene mole fraction time-histories are measured from the absorption of a quantum-cascade laser operating around 13.6. μm. The soot volume fraction, particle size and number densities are calculated from the extinction and scattering of a cw Nd:Yag laser at 532. nm. Acetylene and soot are generated from the pyrolysis of 1% benzene in argon, 2.35% ethylene in argon, and binary mixtures of ethylene with propane/methane in argon. We note that acetylene time-histories exhibit a two-stage growth during the pyrolysis of benzene, which can be correlated to the initial rapid increase of soot volume fraction and a later plateauing. In comparison to ethylene pyrolysis, the pyrolysis of benzene results in larger values of the soot volume fraction, particle diameter and number density. We compare the measured data against the values simulated using the method-of-moments routine in Chemkin-Pro and a detailed PAH mechanism based on KM2 [1] and AramcoMech 1.3 [2]. Large discrepancies are observed between the measured and predicted values of the soot parameters. The data obtained from our experiments may assist future validation and development of soot mechanisms.

  12. Particle Size Distributions in Chondritic Meteorites: Evidence for Pre-Planetesimal Histories

    Science.gov (United States)

    Simon, J. I.; Cuzzi, J. N.; McCain, K. A.; Cato, M. J.; Christoffersen, P. A.; Fisher, K. R.; Srinivasan, P.; Tait, A. W.; Olson, D. M.; Scargle, J. D.

    2018-01-01

    Magnesium-rich silicate chondrules and calcium-, aluminum-rich refractory inclusions (CAIs) are fundamental components of primitive chondritic meteorites. It has been suggested that concentration of these early-formed particles by nebular sorting processes may lead to accretion of planetesimals, the planetary bodies that represent the building blocks of the terrestrial planets. In this case, the size distributions of the particles may constrain the accretion process. Here we present new particle size distribution data for Northwest Africa 5717, a primitive ordinary chondrite (ungrouped 3.05) and the well-known carbonaceous chondrite Allende (CV3). Instead of the relatively narrow size distributions obtained in previous studies (Ebel et al., 2016; Friedrich et al., 2015; Paque and Cuzzi, 1997, and references therein), we observed broad size distributions for all particle types in both meteorites. Detailed microscopic image analysis of Allende shows differences in the size distributions of chondrule subtypes, but collectively these subpopulations comprise a composite "chondrule" size distribution that is similar to the broad size distribution found for CAIs. Also, we find accretionary 'dust' rims on only a subset (approximately 15-20 percent) of the chondrules contained in Allende, which indicates that subpopulations of chondrules experienced distinct histories prior to planetary accretion. For the rimmed subset, we find positive correlation between rim thickness and chondrule size. The remarkable similarity between the size distributions of various subgroups of particles, both with and without fine grained rims, implies a common size sorting process. Chondrite classification schemes, astrophysical disk models that predict a narrow chondrule size population and/or a common localized formation event, and conventional particle analysis methods must all be critically reevaluated. We support the idea that distinct "lithologies" in NWA 5717 are nebular aggregates of

  13. A model study of the size and composition distribution of aerosols in an aircraft exhaust

    Energy Technology Data Exchange (ETDEWEB)

    Sorokin, A.A. [SRC `ECOLEN`, Moscow (Russian Federation)

    1997-12-31

    A two-dimensional, axisymmetric flow field model which includes water and sulphate aerosol formation represented by moments of the size and composition distribution function is used to calculate the effect of radial turbulent jet mixing on the aerosol size distribution and mean modal composition. (author) 6 refs.

  14. A model study of the size and composition distribution of aerosols in an aircraft exhaust

    Energy Technology Data Exchange (ETDEWEB)

    Sorokin, A A [SRC ` ECOLEN` , Moscow (Russian Federation)

    1998-12-31

    A two-dimensional, axisymmetric flow field model which includes water and sulphate aerosol formation represented by moments of the size and composition distribution function is used to calculate the effect of radial turbulent jet mixing on the aerosol size distribution and mean modal composition. (author) 6 refs.

  15. Variations in Tropospheric Submicron Particle Size Distributions Across the European Continent 2008–2009

    Czech Academy of Sciences Publication Activity Database

    Beddows, D.C.S.; Dall’Osto, M.; Harrison, R. M.; Kulmala, M.; Asmi, A.; Wiedensohler, A.; Laj, P.; Fjaeraa, A.M.; Sellegri, K.; Birmili, W.; Bukowiecki, N.; Weingartner, E.; Baltensperger, U.; Ždímal, Vladimír; Zíková, Naděžda; Putaud, J.-P.; Marinoni, A.; Tunved, P.; Hansson, H.-C.; Feibig, M.; Kivekäs, N.; Swietlicki, E.; Lihavainen, H.; Asmi, E.; Ulevicius, V.; Aalto, P.P.; Mihalopoulos, N.; Kalivitis, N.; Kalapov, I.; Kiss, G.; de Leeuw, G.; Henzing, B.; O'Dowd, C.; Jennings, S.G.; Flentje, H.; Meinhardt, F.; Ries, L.; Denier van der Gon19, H.A.C.; Visschedijk, A.J.H.; Swietlicki, E.

    2014-01-01

    Roč. 14, č. 8 (2014), s. 4327-4348 ISSN 1680-7316 EU Projects: European Commission(XE) 36833 - EUCAARI; European Commission(XE) 26140 - EUSAAR Institutional support: RVO:67985858 Keywords : particle size distribution * clusters * aerosol size distribution Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 5.053, year: 2014

  16. Statistical thermodynamics and the size distributions of tropical convective clouds.

    Science.gov (United States)

    Garrett, T. J.; Glenn, I. B.; Krueger, S. K.; Ferlay, N.

    2017-12-01

    Parameterizations for sub-grid cloud dynamics are commonly developed by using fine scale modeling or measurements to explicitly resolve the mechanistic details of clouds to the best extent possible, and then to formulating these behaviors cloud state for use within a coarser grid. A second is to invoke physical intuition and some very general theoretical principles from equilibrium statistical thermodynamics. This second approach is quite widely used elsewhere in the atmospheric sciences: for example to explain the heat capacity of air, blackbody radiation, or even the density profile or air in the atmosphere. Here we describe how entrainment and detrainment across cloud perimeters is limited by the amount of available air and the range of moist static energy in the atmosphere, and that constrains cloud perimeter distributions to a power law with a -1 exponent along isentropes and to a Boltzmann distribution across isentropes. Further, the total cloud perimeter density in a cloud field is directly tied to the buoyancy frequency of the column. These simple results are shown to be reproduced within a complex dynamic simulation of a tropical convective cloud field and in passive satellite observations of cloud 3D structures. The implication is that equilibrium tropical cloud structures can be inferred from the bulk thermodynamic structure of the atmosphere without having to analyze computationally expensive dynamic simulations.

  17. The size distribution of the earth-approaching asteroids

    Science.gov (United States)

    Rabinowitz, D. L.

    1993-01-01

    The discovery circumstances of the first asteroids ever observed outside the earth's atmosphere but within the neighborhood of the earth-moon system are described. Four natural objects with diameters in the range 5-50 m were detected during a search for earth-approaching asteroids conducted each month at the 0.91-m Spacewatch Telescope at Kitt Peak. An additional 19 earth approachers with sizes in the range 50 m to 5 km were discovered. These obervations determine the cumulative flux of asteroids near earth as a function of absolute magnitude. For asteroids larger than about 100 m, a power-law dependence with exponent of about 0.9 is observed, consistent with their evolution from the main-belt population. At about 10 m, the flux is more than two orders of magnitude greater than this power-law extrapolation.

  18. Experimental investigation of particle size distribution influence on diffusion controlled coarsening

    International Nuclear Information System (INIS)

    Fang, Zhigang; Patterson, B.R.

    1993-01-01

    The influence of initial particle size distribution on coarsening during liquid phase sintering has been experimentally investigated using W-14Ni-6Fe alloy as a model system. It was found that initially wider size distribution particles coarsened more rapidly than those of an initially narrow distribution. The well known linear relationship between the cube of the average particle radius bar r -3 , and time was observed for most of the coarsening process, although the early stage coarsening rate constant changed with time, as expected with concomitant early changes in the tungsten particle size distribution. The instantaneous transient rate constant was shown to be related to the geometric standard deviation, 1nσ, of the instantaneous size distributions, with higher rate constants corresponding to larger 1nσ values. The form of the particle size distributions changed rapidly during early coarsening and reached a quasi-stable state, different from the theoretical asymptotic distribution, after some time. A linear relationship was found between the experimentally observed instantaneous rate constant and that computed from an earlier model incorporating the effect of particle size distribution. The above results compare favorably with those from prior theoretical modeling and computer simulation studies of the effect of particle size distribution on coarsening, based on the DeHoff communicating neighbor model

  19. Polydisperse-particle-size-distribution function determined from intensity profile of angularly scattered light

    International Nuclear Information System (INIS)

    Alger, T.W.

    1979-01-01

    A new method for determining the particle-size-distribution function of a polydispersion of spherical particles is presented. The inversion technique for the particle-size-distribution function is based upon matching the measured intensity profile of angularly scattered light with a summation of the intensity contributions of a series of appropriately spaced, narrowband, size-distribution functions. A numerical optimization technique is used to determine the strengths of the individual bands that yield the best agreement with the measured scattered-light-intensity profile. Because Mie theory is used, the method is applicable to spherical particles of all sizes. Several numerical examples demonstrate the application of this inversion method

  20. Iterative inversion of phase-Doppler-anemometry size distributions from sprays of optically inhomogeneous liquids.

    Science.gov (United States)

    Köser, O; Wriedt, T

    1996-05-20

    Using phase Doppler anemometry (PDA) to investigate sprays of optically inhomogeneous liquids leads to blurred measured size distributions. The blurring function is formed by performance of PDA measurements on single-size droplets generated by a piezoelectric droplet generator. To obtain the undistorted droplet-size distributions, a constrained iterative inversion algorithm is applied. The number of iteration steps to achieve the best possible restoration is determined by the use of synthetically generated data that has noise properties similar to the measured histograms. The obtained size distributions are checked by comparison with undistorted measurement results of an atomized optical homogeneous liquid.

  1. Thermal and particle size distribution effects on the ferromagnetic resonance in magnetic fluids

    International Nuclear Information System (INIS)

    Marin, C.N.

    2006-01-01

    Thermal and particle size distribution effects on the ferromagnetic resonance of magnetic fluids were theoretically investigated, assuming negligible interparticle interactions and neglecting the viscosity of the carrier liquid. The model is based on the usual approach for the ferromagnetic resonance description of single-domain magnetic particle systems, which was amended in order to take into account the finite particle size effect, the particle size distribution and the orientation mobility of the particles within the magnetic fluid. Under these circumstances the shape of the resonance line, the resonance field and the line width are found to be strongly affected by the temperature and by the particle size distribution of magnetic fluids

  2. ON ESTIMATION AND HYPOTHESIS TESTING OF THE GRAIN SIZE DISTRIBUTION BY THE SALTYKOV METHOD

    Directory of Open Access Journals (Sweden)

    Yuri Gulbin

    2011-05-01

    Full Text Available The paper considers the problem of validity of unfolding the grain size distribution with the back-substitution method. Due to the ill-conditioned nature of unfolding matrices, it is necessary to evaluate the accuracy and precision of parameter estimation and to verify the possibility of expected grain size distribution testing on the basis of intersection size histogram data. In order to review these questions, the computer modeling was used to compare size distributions obtained stereologically with those possessed by three-dimensional model aggregates of grains with a specified shape and random size. Results of simulations are reported and ways of improving the conventional stereological techniques are suggested. It is shown that new improvements in estimating and testing procedures enable grain size distributions to be unfolded more efficiently.

  3. Personnel neutron dosimetry applications of track-size distributions on electrochemically etched CR-39 foils

    International Nuclear Information System (INIS)

    Hankins, D.E.; Homann, S.G.; Westermark, J.

    1988-01-01

    The track-size distribution on electrochemically etched CR-39 foils can be used to obtain some limited information on the incident neutron spectra. Track-size distributions on CR-39 foils can also be used to determine if the tracks were caused by neutrons or if they are merely background tracks (which have a significantly different track-size distribution). Identifying and discarding the high-background foils reduces the number of foils that must be etched. This also lowers the detection limit of the dosimetry system. We have developed an image analyzer program that can more efficiently determine the track density and track-size distribution, as well as read the laser-cut identification numbers on each foil. This new image analyzer makes the routine application of track-size distributions on CR-39 foils feasible. 2 refs., 3 figs

  4. Particles size distribution effect on 3D packing of nanoparticles in to a bounded region

    International Nuclear Information System (INIS)

    Farzalipour Tabriz, M.; Salehpoor, P.; Esmaielzadeh Kandjani, A.; Vaezi, M. R.; Sadrnezhaad, S. K.

    2007-01-01

    In this paper, the effects of two different Particle Size Distributions on packing behavior of ideal rigid spherical nanoparticles using a novel packing model based on parallel algorithms have been reported. A mersenne twister algorithm was used to generate pseudo random numbers for the particles initial coordinates. Also, for this purpose a nano sized tetragonal confined container with a square floor (300 * 300 nm) were used in this work. The Andreasen and the Lognormal Particle Size Distributions were chosen to investigate the packing behavior in a 3D bounded region. The effects of particle numbers on packing behavior of these two Particle Size Distributions have been investigated. Also the reproducibility and the distribution of packing factor of these Particle Size Distributions were compared

  5. A GENERALIZED CLASS OF TRANSFORMATION MATRICES FOR THE RECONSTRUCTION OF SPHERE SIZE DISTRIBUTIONS FROM SECTION CIRCLE SIZE DISTRIBUTIONS

    Directory of Open Access Journals (Sweden)

    Willi Pabst

    2017-03-01

    Full Text Available A generalized formulation of transformation matrices is given for the reconstruction of sphere diameter distributions from their section circle diameter distributions. This generalized formulation is based on a weight shift parameter that can be adjusted from 0 to 1. It includes the well-known Saltykov and Cruz-Orive transformations as special cases (for parameter values of 0 and 0.5, respectively. The physical meaning of this generalization is explained (showing, among others, that the Woodhead transformation should be bounded by the Saltykov transformation on the one side and by our transformation from the other and its numerical performance is investigated. In particular, it is shown that our generalized transformation is numerically highly unstable, i.e. introduces numerical artefacts (oscillations or even unphysical negative sphere frequencies into the reconstruction, and can lead to completely wrong results when a critical value of the parameter (usually in the range 0.7-0.9, depending on the type of distribution is exceeded. It is shown that this numerical instability is an intrinsic feature of these transformations that depends not only on the weight shift parameter value and is affected both by the type and the position of the distribution. It occurs in a natural way also for the Cruz-Orive and other transformations with finite weight shift parameter values and is not just caused by inadequate input data (e.g. as a consequence of an insufficient number of objects counted, as commonly assumed. Finally it is shown that an even more general class of transformation matrices can be defined that includes, in addition to the aformentioned transformations, also the Wicksell transformation.

  6. Why liquid displacement methods are sometimes wrong in estimating the pore-size distribution

    NARCIS (Netherlands)

    Gijsbertsen-Abrahamse, A.J.; Boom, R.M.; Padt, van der A.

    2004-01-01

    The liquid displacement method is a commonly used method to determine the pore size distribution of micro- and ultrafiltration membranes. One of the assumptions for the calculation of the pore sizes is that the pores are parallel and thus are not interconnected. To show that the estimated pore size

  7. TEM study of soot, organic aerosol, and sea-salt particles collected during CalNex

    Science.gov (United States)

    Adachi, K.; Buseck, P. R.

    2010-12-01

    Anthropogenic aerosol particles are emitted in abundance from megacities. Those particles can have important effects on both human health and climate. In this study, aerosol particles having aerodynamic diameters between 50 and 300 nm were collected during the CalNex campaign at the Pasadena ground site from May 15 to June 15, 2010, ~15 km northeast of downtown Los Angeles. The samples were analyzed using transmission electron microscopes (TEMs) to characterize particle shapes and compositions. Most samples are dominated by soot, organic aerosol (OA), sulfate, sea salt, or combinations thereof. Sizes and amounts of OA particles increased during the afternoons, and most soot particles were internally mixed with OA and sulfate in the afternoons. The proportion of soot to other material in individual particles increased and soot particles were more compact during the nights and early mornings. Sea-salt particles were commonly internally mixed with other materials. They have high Na contents with lesser N, Mg, S, K, and Ca and almost no Cl, suggesting that the Cl was replaced by sulfate or nitrate in the atmosphere. There is less OA and more sea salt and sulfate in the CalNex samples than in the samples from Mexico City that were collected during the MILAGRO campaign. Our study indicates that compositions of internally mixed aerosol particles and shapes of soot particles change significantly within a day. These changes probably influence the estimates of their effects on human health and climate.

  8. A study of radiative properties of fractal soot aggregates using the superposition T-matrix method

    International Nuclear Information System (INIS)

    Li Liu; Mishchenko, Michael I.; Patrick Arnott, W.

    2008-01-01

    We employ the numerically exact superposition T-matrix method to perform extensive computations of scattering and absorption properties of soot aggregates with varying state of compactness and size. The fractal dimension, D f , is used to quantify the geometrical mass dispersion of the clusters. The optical properties of soot aggregates for a given fractal dimension are complex functions of the refractive index of the material m, the number of monomers N S , and the monomer radius a. It is shown that for smaller values of a, the absorption cross section tends to be relatively constant when D f f >2. However, a systematic reduction in light absorption with D f is observed for clusters with sufficiently large N S , m, and a. The scattering cross section and single-scattering albedo increase monotonically as fractals evolve from chain-like to more densely packed morphologies, which is a strong manifestation of the increasing importance of scattering interaction among spherules. Overall, the results for soot fractals differ profoundly from those calculated for the respective volume-equivalent soot spheres as well as for the respective external mixtures of soot monomers under the assumption that there are no electromagnetic interactions between the monomers. The climate-research implications of our results are discussed

  9. Bimodal distribution of the magnetic dipole moment in nanoparticles with a monomodal distribution of the physical size

    NARCIS (Netherlands)

    van Rijssel, Jozef; Kuipers, Bonny W M; Erne, Ben

    2015-01-01

    High-frequency applications of magnetic nanoparticles, such as therapeutic hyperthermia and magnetic particle imaging, are sensitive to nanoparticle size and dipole moment. Usually, it is assumed that magnetic nanoparticles with a log-normal distribution of the physical size also have a log-normal

  10. Bimodal distribution of the magnetic dipole moment in nanoparticles with a monomodal distribution of the physical size

    International Nuclear Information System (INIS)

    Rijssel, Jos van; Kuipers, Bonny W.M.; Erné, Ben H.

    2015-01-01

    High-frequency applications of magnetic nanoparticles, such as therapeutic hyperthermia and magnetic particle imaging, are sensitive to nanoparticle size and dipole moment. Usually, it is assumed that magnetic nanoparticles with a log-normal distribution of the physical size also have a log-normal distribution of the magnetic dipole moment. Here, we test this assumption for different types of superparamagnetic iron oxide nanoparticles in the 5–20 nm range, by multimodal fitting of magnetization curves using the MINORIM inversion method. The particles are studied while in dilute colloidal dispersion in a liquid, thereby preventing hysteresis and diminishing the effects of magnetic anisotropy on the interpretation of the magnetization curves. For two different types of well crystallized particles, the magnetic distribution is indeed log-normal, as expected from the physical size distribution. However, two other types of particles, with twinning defects or inhomogeneous oxide phases, are found to have a bimodal magnetic distribution. Our qualitative explanation is that relatively low fields are sufficient to begin aligning the particles in the liquid on the basis of their net dipole moment, whereas higher fields are required to align the smaller domains or less magnetic phases inside the particles. - Highlights: • Multimodal fits of dilute ferrofluids reveal when the particles are multidomain. • No a priori shape of the distribution is assumed by the MINORIM inversion method. • Well crystallized particles have log-normal TEM and magnetic size distributions. • Defective particles can combine a monomodal size and a bimodal dipole moment

  11. Estimating Functions of Distributions Defined over Spaces of Unknown Size

    Directory of Open Access Journals (Sweden)

    David H. Wolpert

    2013-10-01

    Full Text Available We consider Bayesian estimation of information-theoretic quantities from data, using a Dirichlet prior. Acknowledging the uncertainty of the event space size m and the Dirichlet prior’s concentration parameter c, we treat both as random variables set by a hyperprior. We show that the associated hyperprior, P(c, m, obeys a simple “Irrelevance of Unseen Variables” (IUV desideratum iff P(c, m = P(cP(m. Thus, requiring IUV greatly reduces the number of degrees of freedom of the hyperprior. Some information-theoretic quantities can be expressed multiple ways, in terms of different event spaces, e.g., mutual information. With all hyperpriors (implicitly used in earlier work, different choices of this event space lead to different posterior expected values of these information-theoretic quantities. We show that there is no such dependence on the choice of event space for a hyperprior that obeys IUV. We also derive a result that allows us to exploit IUV to greatly simplify calculations, like the posterior expected mutual information or posterior expected multi-information. We also use computer experiments to favorably compare an IUV-based estimator of entropy to three alternative methods in common use. We end by discussing how seemingly innocuous changes to the formalization of an estimation problem can substantially affect the resultant estimates of posterior expectations.

  12. Transient Properties of Probability Distribution for a Markov Process with Size-dependent Additive Noise

    Science.gov (United States)

    Yamada, Yuhei; Yamazaki, Yoshihiro

    2018-04-01

    This study considered a stochastic model for cluster growth in a Markov process with a cluster size dependent additive noise. According to this model, the probability distribution of the cluster size transiently becomes an exponential or a log-normal distribution depending on the initial condition of the growth. In this letter, a master equation is obtained for this model, and derivation of the distributions is discussed.

  13. Effects of biodiesel, engine load and diesel particulate filter on nonvolatile particle number size distributions in heavy-duty diesel engine exhaust.

    Science.gov (United States)

    Young, Li-Hao; Liou, Yi-Jyun; Cheng, Man-Ting; Lu, Jau-Huai; Yang, Hsi-Hsien; Tsai, Ying I; Wang, Lin-Chi; Chen, Chung-Bang; Lai, Jim-Shoung

    2012-01-15

    Diesel engine exhaust contains large numbers of submicrometer particles that degrade air quality and human health. This study examines the number emission characteristics of 10-1000 nm nonvolatile particles from a heavy-duty diesel engine, operating with various waste cooking oil biodiesel blends (B2, B10 and B20), engine loads (0%, 25%, 50% and 75%) and a diesel oxidation catalyst plus diesel particulate filter (DOC+DPF) under steady modes. For a given load, the total particle number concentrations (N(TOT)) decrease slightly, while the mode diameters show negligible changes with increasing biodiesel blends. For a given biodiesel blend, both the N(TOT) and mode diameters increase modestly with increasing load of above 25%. The N(TOT) at idle are highest and their size distributions are strongly affected by condensation and possible nucleation of semivolatile materials. Nonvolatile cores of diameters less than 16 nm are only observed at idle mode. The DOC+DPF shows remarkable filtration efficiency for both the core and soot particles, irrespective of the biodiesel blend and engine load under study. The N(TOT) post the DOC+DPF are comparable to typical ambient levels of ≈ 10(4)cm(-3). This implies that, without concurrent reductions of semivolatile materials, the formation of semivolatile nucleation mode particles post the after treatment is highly favored. Copyright © 2011 Elsevier B.V. All rights reserved.

  14. Numerical Investigation of Soot Formation in Non-premixed Flames

    KAUST Repository

    Abdelgadir, Ahmed Gamaleldin

    2017-01-01

    Soot is a carbon particulate formed as a result of the combustion of fossil fuels. Due to the health hazard posed by the carbon particulate, government agencies have applied strict regulations to control soot emissions from road vehicles, airplanes

  15. Differentiating gold nanorod samples using particle size and shape distributions from transmission electron microscope images

    Science.gov (United States)

    Grulke, Eric A.; Wu, Xiaochun; Ji, Yinglu; Buhr, Egbert; Yamamoto, Kazuhiro; Song, Nam Woong; Stefaniak, Aleksandr B.; Schwegler-Berry, Diane; Burchett, Woodrow W.; Lambert, Joshua; Stromberg, Arnold J.

    2018-04-01

    Size and shape distributions of gold nanorod samples are critical to their physico-chemical properties, especially their longitudinal surface plasmon resonance. This interlaboratory comparison study developed methods for measuring and evaluating size and shape distributions for gold nanorod samples using transmission electron microscopy (TEM) images. The objective was to determine whether two different samples, which had different performance attributes in their application, were different with respect to their size and/or shape descriptor distributions. Touching particles in the captured images were identified using a ruggedness shape descriptor. Nanorods could be distinguished from nanocubes using an elongational shape descriptor. A non-parametric statistical test showed that cumulative distributions of an elongational shape descriptor, that is, the aspect ratio, were statistically different between the two samples for all laboratories. While the scale parameters of size and shape distributions were similar for both samples, the width parameters of size and shape distributions were statistically different. This protocol fulfills an important need for a standardized approach to measure gold nanorod size and shape distributions for applications in which quantitative measurements and comparisons are important. Furthermore, the validated protocol workflow can be automated, thus providing consistent and rapid measurements of nanorod size and shape distributions for researchers, regulatory agencies, and industry.

  16. Fissure formation in coke. 3: Coke size distribution and statistical analysis

    Energy Technology Data Exchange (ETDEWEB)

    D.R. Jenkins; D.E. Shaw; M.R. Mahoney [CSIRO, North Ryde, NSW (Australia). Mathematical and Information Sciences

    2010-07-15

    A model of coke stabilization, based on a fundamental model of fissuring during carbonisation is used to demonstrate the applicability of the fissuring model to actual coke size distributions. The results indicate that the degree of stabilization is important in determining the size distribution. A modified form of the Weibull distribution is shown to provide a better representation of the whole coke size distribution compared to the Rosin-Rammler distribution, which is generally only fitted to the lump coke. A statistical analysis of a large number of experiments in a pilot scale coke oven shows reasonably good prediction of the coke mean size, based on parameters related to blend rank, amount of low rank coal, fluidity and ash. However, the prediction of measures of the spread of the size distribution is more problematic. The fissuring model, the size distribution representation and the statistical analysis together provide a comprehensive capability for understanding and predicting the mean size and distribution of coke lumps produced during carbonisation. 12 refs., 16 figs., 4 tabs.

  17. Do detailed simulations with size-resolved microphysics reproduce basic features of observed cirrus ice size distributions?

    Science.gov (United States)

    Fridlind, A. M.; Atlas, R.; van Diedenhoven, B.; Ackerman, A. S.; Rind, D. H.; Harrington, J. Y.; McFarquhar, G. M.; Um, J.; Jackson, R.; Lawson, P.

    2017-12-01

    It has recently been suggested that seeding synoptic cirrus could have desirable characteristics as a geoengineering approach, but surprisingly large uncertainties remain in the fundamental parameters that govern cirrus properties, such as mass accommodation coefficient, ice crystal physical properties, aggregation efficiency, and ice nucleation rate from typical upper tropospheric aerosol. Only one synoptic cirrus model intercomparison study has been published to date, and studies that compare the shapes of observed and simulated ice size distributions remain sparse. Here we amend a recent model intercomparison setup using observations during two 2010 SPARTICUS campaign flights. We take a quasi-Lagrangian column approach and introduce an ensemble of gravity wave scenarios derived from collocated Doppler cloud radar retrievals of vertical wind speed. We use ice crystal properties derived from in situ cloud particle images, for the first time allowing smoothly varying and internally consistent treatments of nonspherical ice capacitance, fall speed, gravitational collection, and optical properties over all particle sizes in our model. We test two new parameterizations for mass accommodation coefficient as a function of size, temperature and water vapor supersaturation, and several ice nucleation scenarios. Comparison of results with in situ ice particle size distribution data, corrected using state-of-the-art algorithms to remove shattering artifacts, indicate that poorly constrained uncertainties in the number concentration of crystals smaller than 100 µm in maximum dimension still prohibit distinguishing which parameter combinations are more realistic. When projected area is concentrated at such sizes, the only parameter combination that reproduces observed size distribution properties uses a fixed mass accommodation coefficient of 0.01, on the low end of recently reported values. No simulations reproduce the observed abundance of such small crystals when the

  18. A review of the literature on soot production during in-situ burning of oil

    International Nuclear Information System (INIS)

    Fraser, J.; Buist, I.

    1997-01-01

    Available literature on soot production during in-situ burning of oil was reviewed to determine the range of smoke yields generated by in-situ burning of petroleum oils in water, and to determine the effects of the size of fire and the type of oil burned. For crude oil, data sets statistical analysis showed that, with a fairly high degree of confidence, smoke yield increases with fire diameter. Based on a limited number of available data sets for identifiable oil types, it appears that most oils (Arabian crude the only exception) show roughly the same correlation of smoke yield with fire diameter. Pool fires from aromatic hydrocarbons such as toluene appear to produce more soot than similar fires with crude oil. Fires of lower molecular weight non-aromatics produce an order of magnitude less soot than crude oil fires. Predictive equations with correlation coefficients are provided for specific crude oils. 50 refs., 5 tabs., 13 figs

  19. Investigation of Chemical Kinetics on Soot Formation Event of n-Heptane Spray Combustion

    DEFF Research Database (Denmark)

    Pang, Kar Mun; Jangi, Mehdi; Bai, Xue-Song

    2014-01-01

    . Numerical computation is performed using OpenFOAM and chemistry coordinate mapping (CCM) approach is used to expedite the calculation. Three n-heptane kinetic mechanisms with different chemistry sizes and comprehensiveness in oxidation pathways and soot precursor formation are adopted. The three examined...

  20. In-cylinder Combustion and Soot Evolution in the Transition from Conventional CI mode to PPC

    KAUST Repository

    An, Yanzhao; Jaasim, Mohammed; Raman, Vallinayagam; Im, Hong G.; Johansson, Bengt

    2018-01-01

    with gas phase chemical kinetics, turbulence, and particulate size mimic soot model. The simulations were performed under low load conditions (IMEP ~ 2 to 3 bar) at an engine speed of 1200 rpm. The start of injection (SOI) was advanced from late (-10 CAD a

  1. Estimating particle number size distributions from multi-instrument observations with Kalman Filtering

    Energy Technology Data Exchange (ETDEWEB)

    Viskari, T.

    2012-07-01

    Atmospheric aerosol particles have several important effects on the environment and human society. The exact impact of aerosol particles is largely determined by their particle size distributions. However, no single instrument is able to measure the whole range of the particle size distribution. Estimating a particle size distribution from multiple simultaneous measurements remains a challenge in aerosol physical research. Current methods to combine different measurements require assumptions concerning the overlapping measurement ranges and have difficulties in accounting for measurement uncertainties. In this thesis, Extended Kalman Filter (EKF) is presented as a promising method to estimate particle number size distributions from multiple simultaneous measurements. The particle number size distribution estimated by EKF includes information from prior particle number size distributions as propagated by a dynamical model and is based on the reliabilities of the applied information sources. Known physical processes and dynamically evolving error covariances constrain the estimate both over time and particle size. The method was tested with measurements from Differential Mobility Particle Sizer (DMPS), Aerodynamic Particle Sizer (APS) and nephelometer. The particle number concentration was chosen as the state of interest. The initial EKF implementation presented here includes simplifications, yet the results are positive and the estimate successfully incorporated information from the chosen instruments. For particle sizes smaller than 4 micrometers, the estimate fits the available measurements and smooths the particle number size distribution over both time and particle diameter. The estimate has difficulties with particles larger than 4 micrometers due to issues with both measurements and the dynamical model in that particle size range. The EKF implementation appears to reduce the impact of measurement noise on the estimate, but has a delayed reaction to sudden

  2. ON THE COAGULATION AND SIZE DISTRIBUTION OF PRESSURE CONFINED CORES

    International Nuclear Information System (INIS)

    Huang Xu; Zhou Tingtao; Lin, D. N. C.

    2013-01-01

    Observations of the Pipe Nebula have led to the discovery of dense starless cores. The mass of most cores is too small for their self-gravity to hold them together. Instead, they are thought to be pressure confined. The observed dense cores' mass function (CMF) matches well with the initial mass function of stars in young clusters. Similar CMFs are observed in other star forming regions such as the Aquila Nebula, albeit with some dispersion. The shape of these CMF provides important clues to the competing physical processes which lead to star formation and its feedback on the interstellar media. In this paper, we investigate the dynamical origin of the mass function of starless cores which are confined by a warm, less dense medium. In order to follow the evolution of the CMF, we construct a numerical method to consider the coagulation between the cold cores and their ablation due to Kelvin-Helmholtz instability induced by their relative motion through the warm medium. We are able to reproduce the observed CMF among the starless cores in the Pipe Nebula. Our results indicate that in environment similar to the Pipe Nebula: (1) before the onset of their gravitational collapse, the mass distribution of the progenitor cores is similar to that of the young stars, (2) the observed CMF is a robust consequence of dynamical equilibrium between the coagulation and ablation of cores, and (3) a break in the slope of the CMF is due to the enhancement of collisional cross section and suppression of ablation for cores with masses larger than the cores' Bonnor-Ebert mass.

  3. Size Distributions and Characterization of Native and Ground Samples for Toxicology Studies

    Science.gov (United States)

    McKay, David S.; Cooper, Bonnie L.; Taylor, Larry A.

    2010-01-01

    This slide presentation shows charts and graphs that review the particle size distribution and characterization of natural and ground samples for toxicology studies. There are graphs which show the volume distribution versus the number distribution for natural occurring dust, jet mill ground dust, and ball mill ground dust.

  4. The evolution of body size in extant groups of North American freshwater fishes: speciation, size distributions, and Cope's rule.

    Science.gov (United States)

    Knouft, Jason H; Page, Lawrence M

    2003-03-01

    Change in body size within an evolutionary lineage over time has been under investigation since the synthesis of Cope's rule, which suggested that there is a tendency for mammals to evolve larger body size. Data from the fossil record have subsequently been examined for several other taxonomic groups to determine whether they also displayed an evolutionary increase in body size. However, we are not aware of any species-level study that has investigated the evolution of body size within an extant continental group. Data acquired from the fossil record and data derived from the evolutionary relationships of extant species are not similar, with each set exhibiting both strengths and weaknesses related to inferring evolutionary patterns. Consequently, expectation that general trends exhibited in the fossil record will correspond to patterns in extant groups is not necessarily warranted. Using phylogenetic relationships of extant species, we show that five of nine families of North American freshwater fishes exhibit an evolutionary trend of decreasing body size. These trends result from the basal position of large species and the more derived position of small species within families. Such trends may be caused by the invasion of small streams and subsequent isolation and speciation. This pattern, potentially influenced by size-biased dispersal rates and the high percentage of small streams in North America, suggests a scenario that could result in the generation of the size-frequency distribution of North American freshwater fishes.

  5. Early-stage evolution of particle size distribution with Johnson's SB function due to Brownian coagulation

    International Nuclear Information System (INIS)

    Tang Hong; Lin Jianzhong

    2013-01-01

    The moment method can be used to determine the time evolution of particle size distribution due to Brownian coagulation based on the general dynamic equation (GDE). But the function form of the initial particle size distribution must be determined beforehand for the moment method. If the assumed function type of the initial particle size distribution has an obvious deviation from the true particle population, the evolution of particle size distribution may be different from the real evolution tendency. Thus, a simple and general method is proposed based on the moment method. In this method, the Johnson's S B function is chosen as a general distribution function to fit the initial distributions including the log normal (L-N), Rosin–Rammler (R-R), normal (N-N) and gamma distribution functions, respectively. Meanwhile, using the modified beta function to fit the L-N, R-R, N-N and gamma functions is also conducted as a comparison in order to present the advantage of the Johnson's S B function as the general distribution function. And then, the time evolution of particle size distributions using the Johnson's S B function as the initial distribution can be obtained by several lower order moment equations of the Johnson's S B function in conjunction with the GDE during the Brownian coagulation process. Simulation experiments indicate that fairly reasonable results of the time evolution of particle size distribution can be obtained with this proposed method in the free molecule regime, transition regime and continuum plus near continuum regime, respectively, at the early time stage of evolution. The Johnson's S B function has the ability of describing the early time evolution of different initial particle size distributions. (paper)

  6. The measurement of activity-weighted size distributions of radon progeny: methods and laboratory intercomparison studies

    International Nuclear Information System (INIS)

    Hopke, P.K.; Strydom, R.; Ramamurthi, M.; Knutson, E.O.; Tu, K.W.; Scofield, P.; Holub, R.F.; Cheng, Y.S.; Su, Y.F.; Winklmayr, W.

    1992-01-01

    Over the past 5 y, there have been significant improvements in measurement of activity-weighted size distributions of airborne radon decay products. The modification of screen diffusion batteries to incorporate multiple screens of differing mesh number, called graded screen arrays, have permitted improved size resolution below 10 nm such that the size distributions can now be determined down to molecular sized activities (0.5 nm). In order to ascertain the utility and reliability of such systems, several intercomparison tests have been performed in a 2.4 m3 radon chamber in which particles of varying size have been produced by introducing SO2 and H2O along with the radon to the chamber. In April 1988, intercomparison studies were performed between direct measurements of the activity-weighted size distributions as measured by graded screen arrays and an indirect measurement of the distribution obtained by measuring the number size distribution with a differential mobility analyzer and multiplying by the theoretical attachment rate. Good agreement was obtained in these measurements. A second set of intercomparison studies among a number of groups with graded screen array systems was made in April 1989 with the objective of resolving spectral structure below 10 nm. Again, generally good agreement among the various groups was obtained although some differences were noted. It is thus concluded that such systems can be constructed and can be useful in making routine measurements of activity-weighted size distributions with reasonable confidence in the results obtained

  7. Species distribution model transferability and model grain size - finer may not always be better.

    Science.gov (United States)

    Manzoor, Syed Amir; Griffiths, Geoffrey; Lukac, Martin

    2018-05-08

    Species distribution models have been used to predict the distribution of invasive species for conservation planning. Understanding spatial transferability of niche predictions is critical to promote species-habitat conservation and forecasting areas vulnerable to invasion. Grain size of predictor variables is an important factor affecting the accuracy and transferability of species distribution models. Choice of grain size is often dependent on the type of predictor variables used and the selection of predictors sometimes rely on data availability. This study employed the MAXENT species distribution model to investigate the effect of the grain size on model transferability for an invasive plant species. We modelled the distribution of Rhododendron ponticum in Wales, U.K. and tested model performance and transferability by varying grain size (50 m, 300 m, and 1 km). MAXENT-based models are sensitive to grain size and selection of variables. We found that over-reliance on the commonly used bioclimatic variables may lead to less accurate models as it often compromises the finer grain size of biophysical variables which may be more important determinants of species distribution at small spatial scales. Model accuracy is likely to increase with decreasing grain size. However, successful model transferability may require optimization of model grain size.

  8. Laboratory and modeling studies on the effects of water and soot emissions and ambient conditions on the properties of contrail ice particles in the jet regime

    Directory of Open Access Journals (Sweden)

    H.-W. Wong

    2013-10-01

    Full Text Available Contrails and contrail-induced cirrus clouds are identified as the most uncertain components in determining aviation impacts on global climate change. Parameters affecting contrail ice particle formation immediately after the engine exit plane (< 5 s in plume age may be critical to ice particle properties used in large-scale models predicting contrail radiative forcing. Despite this, detailed understanding of these parametric effects is still limited. In this paper, we present results from recent laboratory and modeling studies conducted to investigate the effects of water and soot emissions and ambient conditions on near-field formation of contrail ice particles and ice particle properties. The Particle Aerosol Laboratory (PAL at the NASA Glenn Research Center and the Aerodyne microphysical parcel model for contrail ice particle formation were employed. Our studies show that exhaust water concentration has a significant impact on contrail ice particle formation and properties. When soot particles were introduced, ice particle formation was observed only when exhaust water concentration was above a critical level. When no soot or sulfuric acid was introduced, no ice particle formation was observed, suggesting that ice particle formation from homogeneous nucleation followed by homogeneous freezing of liquid water was unfavorable. Soot particles were found to compete for water vapor condensation, and higher soot concentrations emitted into the chamber resulted in smaller ice particles being formed. Chamber conditions corresponding to higher cruising altitudes were found to favor ice particle formation. The microphysical model captures trends of particle extinction measurements well, but discrepancies between the model and the optical particle counter measurements exist as the model predicts narrower ice particle size distributions and ice particle sizes nearly a factor of two larger than measured. These discrepancies are likely due to particle

  9. Determination of the particle size distribution of aerosols by means of a diffusion battery

    International Nuclear Information System (INIS)

    Maigne, J.P.

    1978-09-01

    The different methods allowing to determine the particle size distribution of aerosols by means of diffusion batteries are described. To that purpose, a new method for the processing of experimental data (percentages of particles trapped by the battery vs flow rate) was developed on the basis of calculation principles which are described and assessed. This method was first tested by numerical simulation from a priori particle size distributions and then verified experimentally using a fine uranine aerosol whose particle size distribution as determined by our method was compared with the distribution previously obtained by electron microscopy. The method can be applied to the determination of particle size distribution spectra of fine aerosols produced by 'radiolysis' of atmospheric gaseous impurities. Two other applications concern the detection threshold of the condensation nuclei counter and the 'critical' radii of 'radiolysis' particles [fr

  10. Size Distribution Imaging by Non-Uniform Oscillating-Gradient Spin Echo (NOGSE MRI.

    Directory of Open Access Journals (Sweden)

    Noam Shemesh

    Full Text Available Objects making up complex porous systems in Nature usually span a range of sizes. These size distributions play fundamental roles in defining the physicochemical, biophysical and physiological properties of a wide variety of systems - ranging from advanced catalytic materials to Central Nervous System diseases. Accurate and noninvasive measurements of size distributions in opaque, three-dimensional objects, have thus remained long-standing and important challenges. Herein we describe how a recently introduced diffusion-based magnetic resonance methodology, Non-Uniform-Oscillating-Gradient-Spin-Echo (NOGSE, can determine such distributions noninvasively. The method relies on its ability to probe confining lengths with a (length6 parametric sensitivity, in a constant-time, constant-number-of-gradients fashion; combined, these attributes provide sufficient sensitivity for characterizing the underlying distributions in μm-scaled cellular systems. Theoretical derivations and simulations are presented to verify NOGSE's ability to faithfully reconstruct size distributions through suitable modeling of their distribution parameters. Experiments in yeast cell suspensions - where the ground truth can be determined from ancillary microscopy - corroborate these trends experimentally. Finally, by appending to the NOGSE protocol an imaging acquisition, novel MRI maps of cellular size distributions were collected from a mouse brain. The ensuing micro-architectural contrasts successfully delineated distinctive hallmark anatomical sub-structures, in both white matter and gray matter tissues, in a non-invasive manner. Such findings highlight NOGSE's potential for characterizing aberrations in cellular size distributions upon disease, or during normal processes such as development.

  11. Electron impact ionization of size selected hydrogen clusters (H2)N: ion fragment and neutral size distributions.

    Science.gov (United States)

    Kornilov, Oleg; Toennies, J Peter

    2008-05-21

    Clusters consisting of normal H2 molecules, produced in a free jet expansion, are size selected by diffraction from a transmission nanograting prior to electron impact ionization. For each neutral cluster (H2)(N) (N=2-40), the relative intensities of the ion fragments Hn+ are measured with a mass spectrometer. H3+ is found to be the most abundant fragment up to N=17. With a further increase in N, the abundances of H3+, H5+, H7+, and H9+ first increase and, after passing through a maximum, approach each other. At N=40, they are about the same and more than a factor of 2 and 3 larger than for H11+ and H13+, respectively. For a given neutral cluster size, the intensities of the ion fragments follow a Poisson distribution. The fragmentation probabilities are used to determine the neutral cluster size distribution produced in the expansion at a source temperature of 30.1 K and a source pressure of 1.50 bar. The distribution shows no clear evidence of a magic number N=13 as predicted by theory and found in experiments with pure para-H2 clusters. The ion fragment distributions are also used to extract information on the internal energy distribution of the H3+ ions produced in the reaction H2+ + H2-->H3+ +H, which is initiated upon ionization of the cluster. The internal energy is assumed to be rapidly equilibrated and to determine the number of molecules subsequently evaporated. The internal energy distribution found in this way is in good agreement with data obtained in an earlier independent merged beam scattering experiment.

  12. Measurement of the size distributions of radon progeny in indoor air

    International Nuclear Information System (INIS)

    Hopke, P.K.; Ramamurthi, M.; Li, C.S.

    1990-01-01

    A major problem in evaluating the health risk posed by airborne radon progeny in indoor atmospheres is the lack of available information on the activity-weighted size distributions that occur in the domestic environment. With an automated, semicontinuous, graded screen array system, we made a series of measurements of activity-weighted size distributions in several houses in the northeastern United States. Measurements were made in an unoccupied house, in which human aerosol-generating activities were simulated. The time evolution of the aerosol size distribution was measured in each situation. Results of these measurements are presented

  13. Connection between the growth rate distribution and the size dependent crystal growth

    Science.gov (United States)

    Mitrović, M. M.; Žekić, A. A.; IIić, Z. Z.

    2002-07-01

    The results of investigations of the connection between the growth rate dispersions and the size dependent crystal growth of potassium dihydrogen phosphate (KDP), Rochelle salt (RS) and sodium chlorate (SC) are presented. A possible way out of the existing confusion in the size dependent crystal growth investigations is suggested. It is shown that the size independent growth exists if the crystals belonging to one growth rate distribution maximum are considered separately. The investigations suggest possible reason for the observed distribution maxima widths, and the high data scattering on the growth rate versus the crystal size dependence.

  14. A simple algorithm for measuring particle size distributions on an uneven background from TEM images

    DEFF Research Database (Denmark)

    Gontard, Lionel Cervera; Ozkaya, Dogan; Dunin-Borkowski, Rafal E.

    2011-01-01

    Nanoparticles have a wide range of applications in science and technology. Their sizes are often measured using transmission electron microscopy (TEM) or X-ray diffraction. Here, we describe a simple computer algorithm for measuring particle size distributions from TEM images in the presence of a...... application to images of heterogeneous catalysts is presented.......Nanoparticles have a wide range of applications in science and technology. Their sizes are often measured using transmission electron microscopy (TEM) or X-ray diffraction. Here, we describe a simple computer algorithm for measuring particle size distributions from TEM images in the presence...

  15. Location and Size Planning of Distributed Photovoltaic Generation in Distribution network System Based on K-means Clustering Analysis

    Science.gov (United States)

    Lu, Siqi; Wang, Xiaorong; Wu, Junyong

    2018-01-01

    The paper presents a method to generate the planning scenarios, which is based on K-means clustering analysis algorithm driven by data, for the location and size planning of distributed photovoltaic (PV) units in the network. Taken the power losses of the network, the installation and maintenance costs of distributed PV, the profit of distributed PV and the voltage offset as objectives and the locations and sizes of distributed PV as decision variables, Pareto optimal front is obtained through the self-adaptive genetic algorithm (GA) and solutions are ranked by a method called technique for order preference by similarity to an ideal solution (TOPSIS). Finally, select the planning schemes at the top of the ranking list based on different planning emphasis after the analysis in detail. The proposed method is applied to a 10-kV distribution network in Gansu Province, China and the results are discussed.

  16. Experimental equivalent cluster-size distributions in nano-metric volumes of liquid water

    International Nuclear Information System (INIS)

    Grosswendt, B.; De Nardo, L.; Colautti, P.; Pszona, S.; Conte, V.; Tornielli, G.

    2004-01-01

    Ionisation cluster-size distributions in nano-metric volumes of liquid water were determined for alpha particles at 4.6 and 5.4 MeV by measuring cluster-size frequencies in small gaseous volumes of nitrogen or propane at low gas pressure as well as by applying a suitable scaling procedure. This scaling procedure was based on the mean free ionisation lengths of alpha particles in water and in the gases measured. For validation, the measurements of cluster sizes in gaseous volumes and the cluster-size formation in volumes of liquid water of equivalent size were simulated by Monte Carlo methods. The experimental water-equivalent cluster-size distributions in nitrogen and propane are compared with those in liquid water and show that cluster-size formation by alpha particles in nitrogen or propane can directly be related to those in liquid water. (authors)

  17. Undersampling power-law size distributions: effect on the assessment of extreme natural hazards

    Science.gov (United States)

    Geist, Eric L.; Parsons, Thomas E.

    2014-01-01

    The effect of undersampling on estimating the size of extreme natural hazards from historical data is examined. Tests using synthetic catalogs indicate that the tail of an empirical size distribution sampled from a pure Pareto probability distribution can range from having one-to-several unusually large events to appearing depleted, relative to the parent distribution. Both of these effects are artifacts caused by limited catalog length. It is more difficult to diagnose the artificially depleted empirical distributions, since one expects that a pure Pareto distribution is physically limited in some way. Using maximum likelihood methods and the method of moments, we estimate the power-law exponent and the corner size parameter of tapered Pareto distributions for several natural hazard examples: tsunamis, floods, and earthquakes. Each of these examples has varying catalog lengths and measurement thresholds, relative to the largest event sizes. In many cases where there are only several orders of magnitude between the measurement threshold and the largest events, joint two-parameter estimation techniques are necessary to account for estimation dependence between the power-law scaling exponent and the corner size parameter. Results indicate that whereas the corner size parameter of a tapered Pareto distribution can be estimated, its upper confidence bound cannot be determined and the estimate itself is often unstable with time. Correspondingly, one cannot statistically reject a pure Pareto null hypothesis using natural hazard catalog data. Although physical limits to the hazard source size and by attenuation mechanisms from source to site constrain the maximum hazard size, historical data alone often cannot reliably determine the corner size parameter. Probabilistic assessments incorporating theoretical constraints on source size and propagation effects are preferred over deterministic assessments of extreme natural hazards based on historic data.

  18. Particle size distribution properties in mixed-phase monsoon clouds from in situ measurements during CAIPEEX

    Science.gov (United States)

    Patade, Sachin; Prabha, T. V.; Axisa, D.; Gayatri, K.; Heymsfield, A.

    2015-10-01

    A comprehensive analysis of particle size distributions measured in situ with airborne instrumentation during the Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX) is presented. In situ airborne observations in the developing stage of continental convective clouds during premonsoon (PRE), transition, and monsoon (MON) period at temperatures from 25 to -22°C are used in the study. The PRE clouds have narrow drop size and particle size distributions compared to monsoon clouds and showed less development of size spectra with decrease in temperature. Overall, the PRE cases had much lower values of particle number concentrations and ice water content compared to MON cases, indicating large differences in the ice initiation and growth processes between these cloud regimes. This study provided compelling evidence that in addition to dynamics, aerosol and moisture are important for modulating ice microphysical processes in PRE and MON clouds through impacts on cloud drop size distribution. Significant differences are observed in the relationship of the slope and intercept parameters of the fitted particle size distributions (PSDs) with temperature in PRE and MON clouds. The intercept values are higher in MON clouds than PRE for exponential distribution which can be attributed to higher cloud particle number concentrations and ice water content in MON clouds. The PRE clouds tend to have larger values of dispersion of gamma size distributions than MON clouds, signifying narrower spectra. The relationships between PSDs parameters are presented and compared with previous observations.

  19. Effect of Particle Size Distribution on Slurry Rheology: Nuclear Waste Simulant Slurries

    International Nuclear Information System (INIS)

    Chun, Jaehun; Oh, Takkeun; Luna, Maria L.; Schweiger, Michael J.

    2011-01-01

    Controlling the rheological properties of slurries has been of great interest in various industries such as cosmetics, ceramic processing, and nuclear waste treatment. Many physicochemical parameters, such as particle size, pH, ionic strength, and mass/volume fraction of particles, can influence the rheological properties of slurry. Among such parameters, the particle size distribution of slurry would be especially important for nuclear waste treatment because most nuclear waste slurries show a broad particle size distribution. We studied the rheological properties of several different low activity waste nuclear simulant slurries having different particle size distributions under high salt and high pH conditions. Using rheological and particle size analysis, it was found that the percentage of colloid-sized particles in slurry appears to be a key factor for rheological characteristics and the efficiency of rheological modifiers. This behavior was shown to be coupled with an existing electrostatic interaction between particles under a low salt concentration. Our study suggests that one may need to implement the particle size distribution as a critical factor to understand and control rheological properties in nuclear waste treatment plants, such as the U.S. Department of Energy's Hanford and Savannah River sites, because the particle size distributions significantly vary over different types of nuclear waste slurries.

  20. A study of particle size distribution in zirconia-alumina powders

    International Nuclear Information System (INIS)

    Ramakrishnan, K.N.; Venkadesan, S.; Nagarajan, R.

    1996-01-01

    Powder particles, in general are characterized in terms of particle size, size distributions and composition for reasons associated with manufacturing problem based upon product quality, manufacturing convenience, cost and product handling convenience. Particle size analysis or the measurement of particle size distribution is a common effort in any physical, chemical or mechanical processes. This information and processing methods are intricate factors that relate to material behavior and/or physical properties of the fabricated product. The requirements for the formation of a product of particulate solids and its strength varies as the particle size and the size distribution changes. Also the transport properties and the chemical activity are related to the particle size and the size distribution. The choice of a distribution to represent a physical system is generally motivated by an understanding of the nature of underlying phenomenon and is verified by the available data. After a model has been chosen, its parameter must be determined. The reasonableness of a selected model on the basis of given data is especially important when the model is to be used for prediction. Two different approaches in this problem are probability plotting and statistical tests

  1. The problem of predicting the size distribution of sediment supplied by hillslopes to rivers

    Science.gov (United States)

    Sklar, Leonard S.; Riebe, Clifford S.; Marshall, Jill A.; Genetti, Jennifer; Leclere, Shirin; Lukens, Claire L.; Merces, Viviane

    2017-01-01

    Sediments link hillslopes to river channels. The size of sediments entering channels is a key control on river morphodynamics across a range of scales, from channel response to human land use to landscape response to changes in tectonic and climatic forcing. However, very little is known about what controls the size distribution of particles eroded from bedrock on hillslopes, and how particle sizes evolve before sediments are delivered to channels. Here we take the first steps toward building a geomorphic transport law to predict the size distribution of particles produced on hillslopes and supplied to channels. We begin by identifying independent variables that can be used to quantify the influence of five key boundary conditions: lithology, climate, life, erosion rate, and topography, which together determine the suite of geomorphic processes that produce and transport sediments on hillslopes. We then consider the physical and chemical mechanisms that determine the initial size distribution of rock fragments supplied to the hillslope weathering system, and the duration and intensity of weathering experienced by particles on their journey from bedrock to the channel. We propose a simple modeling framework with two components. First, the initial rock fragment sizes are set by the distribution of spacing between fractures in unweathered rock, which is influenced by stresses encountered by rock during exhumation and by rock resistance to fracture propagation. That initial size distribution is then transformed by a weathering function that captures the influence of climate and mineralogy on chemical weathering potential, and the influence of erosion rate and soil depth on residence time and the extent of particle size reduction. Model applications illustrate how spatial variation in weathering regime can lead to bimodal size distributions and downstream fining of channel sediment by down-valley fining of hillslope sediment supply, two examples of hillslope control on

  2. Finding the magnetic size distribution of magnetic nanoparticles from magnetization measurements via the iterative Kaczmarz algorithm

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, Daniel, E-mail: frank.wiekhorst@ptb.de; Eberbeck, Dietmar; Steinhoff, Uwe; Wiekhorst, Frank

    2017-06-01

    The characterization of the size distribution of magnetic nanoparticles is an important step for the evaluation of their suitability for many different applications like magnetic hyperthermia, drug targeting or Magnetic Particle Imaging. We present a new method based on the iterative Kaczmarz algorithm that enables the reconstruction of the size distribution from magnetization measurements without a priori knowledge of the distribution form. We show in simulations that the method is capable of very exact reconstructions of a given size distribution and, in that, is highly robust to noise contamination. Moreover, we applied the method on the well characterized FeraSpin™ series and obtained results that were in accordance with literature and boundary conditions based on their synthesis via separation of the original suspension FeraSpin R. It is therefore concluded that this method is a powerful and intuitive tool for reconstructing particle size distributions from magnetization measurements. - Highlights: • A new method for the size distribution fit of magnetic nanoparticles is proposed. • Employed Kaczmarz algorithm does not need a priori input or eigenwert regularization. • The method is highly robust to noise contamination. • Size distributions are reconstructed from simulated and measured magnetization curves.

  3. The effects of particle size distribution and induced unpinning during grain growth

    International Nuclear Information System (INIS)

    Thompson, G.S.; Rickman, J.M.; Harmer, M.P.; Holm, E.A.

    1996-01-01

    The effect of a second-phase particle size distribution on grain boundary pinning was studied using a Monte Carlo simulation technique. Simulations were run using a constant number density of both whisker and rhombohedral particles, and the effect of size distribution was studied by varying the standard deviation of the distribution around a constant mean particle size. The results of present simulations indicate that, in accordance with the stereological assumption of the topological pinning model, changes in distribution width had no effect on the pinned grain size. The effect of induced unpinning of particles on microstructure was also studied. In contrast to predictions of the topological pinning model, a power law dependence of pinned grain size on particle size was observed at T=0.0. Based on this, a systematic deviation to the stereological predictions of the topological pinning model is observed. The results of simulations at higher temperatures indicate an increasing power law dependence of pinned grain size on particle size, with the slopes of the power law dependencies fitting an Arrhenius relation. The effect of induced unpinning of particles was also studied in order to obtain a correlation between particle/boundary concentration and equilibrium grain size. The results of simulations containing a constant number density of monosized rhombohedral particles suggest a strong power law correlation between the two parameters. copyright 1996 Materials Research Society

  4. Optimal Sizing and Placement of Battery Energy Storage in Distribution System Based on Solar Size for Voltage Regulation

    Energy Technology Data Exchange (ETDEWEB)

    Nazaripouya, Hamidreza [Univ. of California, Los Angeles, CA (United States); Wang, Yubo [Univ. of California, Los Angeles, CA (United States); Chu, Peter [Univ. of California, Los Angeles, CA (United States); Pota, Hemanshu R. [Univ. of California, Los Angeles, CA (United States); Gadh, Rajit [Univ. of California, Los Angeles, CA (United States)

    2016-07-26

    This paper proposes a new strategy to achieve voltage regulation in distributed power systems in the presence of solar energy sources and battery storage systems. The goal is to find the minimum size of battery storage and its corresponding location in the network based on the size and place of the integrated solar generation. The proposed method formulates the problem by employing the network impedance matrix to obtain an analytical solution instead of using a recursive algorithm such as power flow. The required modifications for modeling the slack and PV buses (generator buses) are utilized to increase the accuracy of the approach. The use of reactive power control to regulate the voltage regulation is not always an optimal solution as in distribution systems R/X is large. In this paper the minimum size and the best place of battery storage is achieved by optimizing the amount of both active and reactive power exchanged by battery storage and its gridtie inverter (GTI) based on the network topology and R/X ratios in the distribution system. Simulation results for the IEEE 14-bus system verify the effectiveness of the proposed approach.

  5. Bimodal Nanoparticle Size Distributions Produced by Laser Ablation of Microparticles in Aerosols

    International Nuclear Information System (INIS)

    Nichols, William T.; Malyavanatham, Gokul; Henneke, Dale E.; O'Brien, Daniel T.; Becker, Michael F.; Keto, John W.

    2002-01-01

    Silver nanoparticles were produced by laser ablation of a continuously flowing aerosol of microparticles in nitrogen at varying laser fluences. Transmission electron micrographs were analyzed to determine the effect of laser fluence on the nanoparticle size distribution. These distributions exhibited bimodality with a large number of particles in a mode at small sizes (3-6-nm) and a second, less populated mode at larger sizes (11-16-nm). Both modes shifted to larger sizes with increasing laser fluence, with the small size mode shifting by 35% and the larger size mode by 25% over a fluence range of 0.3-4.2-J/cm 2 . Size histograms for each mode were found to be well represented by log-normal distributions. The distribution of mass displayed a striking shift from the large to the small size mode with increasing laser fluence. These results are discussed in terms of a model of nanoparticle formation from two distinct laser-solid interactions. Initially, laser vaporization of material from the surface leads to condensation of nanoparticles in the ambient gas. Material evaporation occurs until the plasma breakdown threshold of the microparticles is reached, generating a shock wave that propagates through the remaining material. Rapid condensation of the vapor in the low-pressure region occurs behind the traveling shock wave. Measurement of particle size distributions versus gas pressure in the ablation region, as well as, versus microparticle feedstock size confirmed the assignment of the larger size mode to surface-vaporization and the smaller size mode to shock-formed nanoparticles

  6. A new stochastic algorithm for inversion of dust aerosol size distribution

    Science.gov (United States)

    Wang, Li; Li, Feng; Yang, Ma-ying

    2015-08-01

    Dust aerosol size distribution is an important source of information about atmospheric aerosols, and it can be determined from multiwavelength extinction measurements. This paper describes a stochastic inverse technique based on artificial bee colony (ABC) algorithm to invert the dust aerosol size distribution by light extinction method. The direct problems for the size distribution of water drop and dust particle, which are the main elements of atmospheric aerosols, are solved by the Mie theory and the Lambert-Beer Law in multispectral region. And then, the parameters of three widely used functions, i.e. the log normal distribution (L-N), the Junge distribution (J-J), and the normal distribution (N-N), which can provide the most useful representation of aerosol size distributions, are inversed by the ABC algorithm in the dependent model. Numerical results show that the ABC algorithm can be successfully applied to recover the aerosol size distribution with high feasibility and reliability even in the presence of random noise.

  7. The κ-generalized distribution: A new descriptive model for the size distribution of incomes

    Science.gov (United States)

    Clementi, F.; Di Matteo, T.; Gallegati, M.; Kaniadakis, G.

    2008-05-01

    This paper proposes the κ-generalized distribution as a model for describing the distribution and dispersion of income within a population. Formulas for the shape, moments and standard tools for inequality measurement-such as the Lorenz curve and the Gini coefficient-are given. A method for parameter estimation is also discussed. The model is shown to fit extremely well the data on personal income distribution in Australia and in the United States.

  8. The effect of particle size distributions on the microstructural evolution during sintering

    DEFF Research Database (Denmark)

    Bjørk, Rasmus; Tikare, V.; Frandsen, Henrik Lund

    2013-01-01

    Microstructural evolution and sintering behavior of powder compacts composed of spherical particles with different particle size distributions (PSDs) were simulated using a kinetic Monte Carlo model of solid state sintering. Compacts of monosized particles, normal PSDs with fixed mean particle...

  9. NON-COHESIVE SOILS’ COMPRESSIBILITY AND UNEVEN GRAIN-SIZE DISTRIBUTION RELATION

    Directory of Open Access Journals (Sweden)

    Anatoliy Mirnyy

    2016-03-01

    Full Text Available This paper presents the results of laboratory investigation of soil compression phases with consideration of various granulometric composition. Materials and Methods Experimental soil box with microscale video recording for compression phases studies is described. Photo and video materials showing the differences of microscale particle movements were obtained for non-cohesive soils with different grain-size distribution. Results The analysis of the compression tests results and elastic and plastic deformations separation allows identifying each compression phase. It is shown, that soil density is correlating with deformability parameters only for the same grain-size distribution. Basing on the test results the authors suggest that compaction ratio is not sufficient for deformability estimating without grain-size distribution taken into account. Discussion and Conclusions Considering grain-size distribution allows refining technological requirements for artificial soil structures, backfills, and sand beds. Further studies could be used for developing standard documents, SP45.13330.2012 in particular.

  10. Surface modification and particles size distribution control in nano-CdS/polystyrene composite film

    International Nuclear Information System (INIS)

    Min Zhirong; Ming Qiuzhang; Hai Chunliang; Han Minzeng

    2003-01-01

    Preparation of nano-CdS particles with surface thiol modification by microemulsion method and their influences on the particle size distribution in highly filled polystyrene-based composites were studied. The modified nano-CdS was characterized by X-ray photoelectron spectroscopy (XPS), light absorption and emission measurements to reveal the morphologies of the surface modifier, which are consistent with the surface molecules packing calculation. The morphologies of the surface modifier exerted a great influence not only on the optical performance of the particles themselves, but also on the size distribution of the particle in polystyrene matrix. A monolayer coverage with tightly packed thiol molecules was believed to be most effective in promoting a uniform particle size distribution and eliminating the surface defects that cause radiationless recombination. Control of the particles size distribution in polystyrene can be attained by adjusting surface coverage status of the thiol molecules based on the strong interaction between the surface modifier and the matrix

  11. Data Descriptor : Collocated observations of cloud condensation nuclei, particle size distributions, and chemical composition

    NARCIS (Netherlands)

    Schmale, Julia; Henning, Silvia; Henzing, Bas; Keskinen, Helmi; Sellegri, Karine; Ovadnevaite, Jurgita; Bougiatioti, Aikaterini; Kalivitis, Nikos; Stavroulas, Iasonas; Jefferson, Anne; Park, Minsu; Schlag, Patrick; Kristensson, Adam; Iwamoto, Yoko; Pringle, Kirsty; Reddington, Carly; Aalto, Pasi; Äijälä, Mikko; Baltensperger, Urs; Bialek, Jakub; Birmili, Wolfram; Bukowiecki, Nicolas; Ehn, Mikael; Fjæraa, Ann Mari; Fiebig, Markus; Frank, Göran; Fröhlich, Roman; Frumau, Arnoud; Furuya, Masaki; Hammer, Emanuel; Heikkinen, Liine; Herrmann, Erik; Holzinger, Rupert; Hyono, Hiroyuki; Kanakidou, Maria; Kiendler-Scharr, Astrid; Kinouchi, Kento; Kos, Gerard P A; Kulmala, Markku; Mihalopoulos, Nikolaos; Motos, Ghislain; Nenes, Athanasios; O'Dowd, Colin; Paramonov, Mikhail; Petäjä, Tuukka; Picard, David; Poulain, Laurent; Prévôt, André Stephan Henry; Slowik, Jay; Sonntag, Andre; Swietlicki, Erik; Svenningsson, Birgitta; Tsurumaru, Hiroshi; Wiedensohler, Alfred; Wittbom, Cerina; Ogren, John A.; Matsuki, Atsushi; Yum, Seong Soo; Myhre, Cathrine Lund; Carslaw, Ken; Stratmann, Frank; Gysel, Martin

    2017-01-01

    Cloud condensation nuclei (CCN) number concentrations alongside with submicrometer particle number size distributions and particle chemical composition have been measured at atmospheric observatories of the Aerosols, Clouds, and Trace gases Research InfraStructure (ACTRIS) as well as other

  12. FIELD COMPARISONS OF DUAL SMPS-APS SYSTEMS TO MEASURE INDOOR-OUTDOOR PARTICLE SIZE DISTRIBUTIONS

    Science.gov (United States)

    Simultaneous measurements of particle size distributions across multiple locations can provide critical information to accurately assess human exposure to particles. These data are very useful to describe indoor-outdoor particle relationships, outdoor particle penetration thro...

  13. Simulating SAL formation and aerosol size distribution during SAMUM-I

    KAUST Repository

    Khan, Basit Ali; Stenchikov, Georgiy L.; Weinzierl,  Bernadett; Kalenderski, Stoitchko; Osipov, Sergey

    2015-01-01

    -Chem) to reproduce the meteorological environment and spatial and size distributions of dust. The experimental domain covers northwest Africa including the southern Sahara, Morocco and part of the Atlantic Ocean with 5 km horizontal grid spacing and 51 vertical

  14. Notes on representing grain size distributions obtained by electron backscatter diffraction

    International Nuclear Information System (INIS)

    Toth, Laszlo S.; Biswas, Somjeet; Gu, Chengfan; Beausir, Benoit

    2013-01-01

    Grain size distributions measured by electron backscatter diffraction are commonly represented by histograms using either number or area fraction definitions. It is shown here that they should be presented in forms of density distribution functions for direct quantitative comparisons between different measurements. Here we make an interpretation of the frequently seen parabolic tales of the area distributions of bimodal grain structures and a transformation formula between the two distributions are given in this paper. - Highlights: • Grain size distributions are represented by density functions. • The parabolic tales corresponds to equal number of grains in a bin of the histogram. • A simple transformation formula is given to number and area weighed distributions. • The particularities of uniform and lognormal distributions are examined

  15. Distribution Functions of Sizes and Fluxes Determined from Supra-Arcade Downflows

    Science.gov (United States)

    McKenzie, D.; Savage, S.

    2011-01-01

    The frequency distributions of sizes and fluxes of supra-arcade downflows (SADs) provide information about the process of their creation. For example, a fractal creation process may be expected to yield a power-law distribution of sizes and/or fluxes. We examine 120 cross-sectional areas and magnetic flux estimates found by Savage & McKenzie for SADs, and find that (1) the areas are consistent with a log-normal distribution and (2) the fluxes are consistent with both a log-normal and an exponential distribution. Neither set of measurements is compatible with a power-law distribution nor a normal distribution. As a demonstration of the applicability of these findings to improved understanding of reconnection, we consider a simple SAD growth scenario with minimal assumptions, capable of producing a log-normal distribution.

  16. Are range-size distributions consistent with species-level heritability?

    DEFF Research Database (Denmark)

    Borregaard, Michael Krabbe; Gotelli, Nicholas; Rahbek, Carsten

    2012-01-01

    The concept of species-level heritability is widely contested. Because it is most likely to apply to emergent, species-level traits, one of the central discussions has focused on the potential heritability of geographic range size. However, a central argument against range-size heritability has...... been that it is not compatible with the observed shape of present-day species range-size distributions (SRDs), a claim that has never been tested. To assess this claim, we used forward simulation of range-size evolution in clades with varying degrees of range-size heritability, and compared the output...

  17. Soot volume fraction in a piloted turbulent jet non-premixed flame of natural gas

    Energy Technology Data Exchange (ETDEWEB)

    Qamar, N.H.; Alwahabi, Z.T.; King, K.D. [Fluid Mechanics, Energy and Combustion Group, University of Adelaide, Adelaide, SA 5005 (Australia); School of Chemical Engineering, University of Adelaide, Adelaide, SA 5005 (Australia); Chan, Q.N. [Fluid Mechanics, Energy and Combustion Group, University of Adelaide, Adelaide, SA 5005 (Australia); School of Chemical Engineering, University of Adelaide, Adelaide, SA 5005 (Australia); School of Mechanical Engineering, University of Adelaide, Adelaide, SA 5005 (Australia); Nathan, G.J. [Fluid Mechanics, Energy and Combustion Group, University of Adelaide, Adelaide, SA 5005 (Australia); School of Mechanical Engineering, University of Adelaide, Adelaide, SA 5005 (Australia); Roekaerts, D. [Department of Multi-Scale Physics, Faculty of Applied Sciences, Delft University of Technology, Lorentzweg, 1, NL-2628 CJ Delft (Netherlands)

    2009-07-15

    Planar laser-induced incandescence (LII) has been used to measure soot volume fraction in a well-characterised, piloted, turbulent non-premixed flame known as the ''Delft Flame III''. Simulated Dutch natural gas was used as the fuel to produce a flame closely matching those in which a wide range of previous investigations, both experimental and modelling, have been performed. The LII method was calibrated using a Santoro-style burner with ethylene as the fuel. Instantaneous and time-averaged data of the axial and radial soot volume fraction distributions of the flame are presented here along with the Probability Density Functions (PDFs) and intermittency. The PDFs were found to be well-characterised by a single exponential distribution function. The distribution of soot was found to be highly intermittent, with intermittency typically exceeding 97%, which increases measurement uncertainty. The instantaneous values of volume fraction are everywhere less than the values in strained laminar flames. This is consistent with the soot being found locally in strained flame sheets that are convected and distorted by the flow. (author)

  18. A simple technique to determine the size distribution of nuclear crater fallback and ejecta

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, II, Brooks D [U.S. Army Engineer Nuclear Cratering Group, Lawrence Radiation Laboratory, Livermore, CA (United States)

    1970-05-15

    This report describes the results of an investigation to find an economic method for determining the block size distribution of nuclear crater fallback and ejecta. It is shown that the modal analysis method of determining relative proportions can be applied with the use of a special sampling technique, to provide a size distribution curve for clastic materials similar to one obtainable by sieving and weighing the same materials.

  19. A simple technique to determine the size distribution of nuclear crater fallback and ejecta

    International Nuclear Information System (INIS)

    Anderson, Brooks D. II

    1970-01-01

    This report describes the results of an investigation to find an economic method for determining the block size distribution of nuclear crater fallback and ejecta. It is shown that the modal analysis method of determining relative proportions can be applied with the use of a special sampling technique, to provide a size distribution curve for clastic materials similar to one obtainable by sieving and weighing the same materials

  20. Characterizing germania concentration and structure in fiber soot using multiphoton microscopy and spectroscopy technology

    Science.gov (United States)

    Chen, Minghan; Li, Ming-Jun; Liu, Anping

    2015-02-01

    Germania doping is commonly used in the core of optical fiber due to its advantages compared to other materials such as superior transparency in near-infrared telecommunication wavelength region. During fiber preform manufacturing using the outside vapor deposition (OVD) process, Ge is doped into a silica soot preform by chemical vapor deposition. Since the Ge doping concentration profile is directly correlated with the fiber refractive index profile, its characterization is critical for the fiber industry. Electron probe micro-analyzer (EPMA) is a conventional analysis method for characterizing the Ge concentration profile. However, it requires extensive sample preparation and lengthy measurement. In this paper, a multiphoton microscopy technique is utilized to measure the Ge doping profile based on the multiphoton fluorescence intensity of the soot layers. Two samples, one with ramped and another with stepped Ge doping profiles were prepared for measurements. Measured results show that the technique is capable of distinguishing ramped and stepped Ge doping profiles with good accuracy. In the ramped soot sample, a sharp increment of doping level was observed in about 2 mm range from soot edge followed by a relative slow gradient doping accretion. As for the stepped doping sample, step sizes ranging from around 1 mm (at soot edge) to 3 mm (at soot center) were observed. All the measured profiles are in close agreement with that of the EPMA measurements. In addition, both multiphoton fluorescence (around 420 nm) and sharp second harmonic generations (at 532 nm) were observed, which indicates the co-existence of crystal and amorphous GeO2.

  1. Experimental and computational investigation of temperature effects on soot mechanisms

    Directory of Open Access Journals (Sweden)

    Bi Xiaojie

    2014-01-01

    Full Text Available Effects of initial ambient temperatures on combustion and soot emission characteristics of diesel fuel were investigated through experiment conducted in optical constant volume chamber and simulation using phenomenological soot model. There are four difference initial ambient temperatures adopted in our research: 1000 K, 900 K, 800 K and 700 K. In order to obtain a better prediction of soot behavior, phenomenological soot model was revised to take into account the soot oxidation feedback on soot number density and good agreement was observed in the comparison of soot measurement and prediction. Results indicated that ignition delay prolonged with the decrease of initial ambient temperature. The heat release rate demonstrated the transition from mixing controlled combustion at high ambient temperature to premixed combustion mode at low ambient temperature. At lower ambient temperature, soot formation and oxidation mechanism were both suppressed. But finally soot mass concentration reduced with decreasing initial ambient temperature. Although the drop in ambient temperature did not cool the mean in-cylinder temperature during the combustion, it did shrink the total area of local high equivalence ratio, in which soot usually generated fast. At 700 K initial ambient temperature, soot emissions were almost negligible, which indicates that sootless combustion might be achieved at super low initial temperature operation conditions.

  2. The magnetized sheath of a dusty plasma with grains size distribution

    International Nuclear Information System (INIS)

    Ou, Jing; Gan, Chunyun; Lin, Binbin; Yang, Jinhong

    2015-01-01

    The structure of a plasma sheath in the presence of dust grains size distribution (DGSD) is investigated in the multi-fluid framework. It is shown that effect of the dust grains with different sizes on the sheath structure is a collective behavior. The spatial distributions of electric potential, the electron and ion densities and velocities, and the dust grains surface potential are strongly affected by DGSD. The dynamics of dust grains with different sizes in the sheath depend on not only DGSD but also their radius. By comparison of the sheath structure, it is found that under the same expected value of DGSD condition, the sheath length is longer in the case of lognormal distribution than that in the case of uniform distribution. In two cases of normal and lognormal distributions, the sheath length is almost equal for the small variance of DGSD, and then the difference of sheath length increases gradually with increase in the variance

  3. Size distribution of BaF2 nanocrystallites in transparent glass ceramics

    International Nuclear Information System (INIS)

    Bocker, Christian; Bhattacharyya, Somnath; Hoeche, Thomas; Ruessel, Christian

    2009-01-01

    In glasses with the composition 1.9 Na 2 O-15 K 2 O-7.5 Al 2 O 3 -69.6 SiO 2 -6 BaF 2 (in mol.%), BaF 2 nanocrystalline precipitates are formed upon heat treatment. Using dark-field and bright-field transmission electron micrographs, crystallite size distributions are obtained for samples crystallized at various temperatures. According to the 'tomato-salad problem', the size distributions are corrected and then compared to various theories of grain growth taking into account coarsening of the crystallites during heat treatment. The experimental crystallite size distributions show for smaller mean crystallite sizes a more symmetric shape in comparison to the theories of Lifshitz-Slyozov-Wagner (LSW) or Brailsford and Wynblatt (B and W). With increasing mean crystallite sizes to about 18 nm at higher heat-treatment temperatures, the full width at half maximum of the observed distributions decreases and becomes even narrower than the LSW function. These findings indicate that in the investigated nano glass ceramics no coarsening by Ostwald ripening or coalescence occurs. This is explained by the formation of a diffusion barrier around each nanocrystallite which limits the size of the crystallites and hence results in such a narrow and uniform crystallite size distribution.

  4. Measurement of particle size distribution of soil and selected aggregate sizes using the hydrometer method and laser diffractometry

    Science.gov (United States)

    Guzmán, G.; Gómez, J. A.; Giráldez, J. V.

    2010-05-01

    Soil particle size distribution has been traditionally determined by the hydrometer or the sieve-pipette methods, both of them time consuming and requiring a relatively large soil sample. This might be a limitation in situations, such as for instance analysis of suspended sediment, when the sample is small. A possible alternative to these methods are the optical techniques such as laser diffractometry. However the literature indicates that the use of this technique as an alternative to traditional methods is still limited, because the difficulty in replicating the results obtained with the standard methods. In this study we present the percentages of soil grain size determined using laser diffractometry within ranges set between 0.04 - 2000 μm. A Beckman-Coulter ® LS-230 with a 750 nm laser beam and software version 3.2 in five soils, representative of southern Spain: Alameda, Benacazón, Conchuela, Lanjarón and Pedrera. In three of the studied soils (Alameda, Benacazón and Conchuela) the particle size distribution of each aggregate size class was also determined. Aggregate size classes were obtained by dry sieve analysis using a Retsch AS 200 basic ®. Two hundred grams of air dried soil were sieved during 150 s, at amplitude 2 mm, getting nine different sizes between 2000 μm and 10 μm. Analyses were performed by triplicate. The soil sample preparation was also adapted to our conditions. A small amount each soil sample (less than 1 g) was transferred to the fluid module full of running water and disaggregated by ultrasonication at energy level 4 and 80 ml of sodium hexametaphosphate solution during 580 seconds. Two replicates of each sample were performed. Each measurement was made for a 90 second reading at a pump speed of 62. After the laser diffractometry analysis, each soil and its aggregate classes were processed calibrating its own optical model fitting the optical parameters that mainly depends on the color and the shape of the analyzed particle. As a

  5. Determination of size and shape distributions of metal and ceramic powders

    International Nuclear Information System (INIS)

    Jovanovic, DI.

    1961-01-01

    For testing the size and shape distributions of metal and ceramic uranium oxide powders the following method for analysing the grain size of powders were developed and implemented: microscopic analysis and sedimentation method. A gravimetry absorption device was constructed for determining the specific surfaces of powders

  6. Measurement and analysis of the concentration and size distribution of aerosols in a copper mine

    International Nuclear Information System (INIS)

    Li Dehong; Zhuo Weihai; Huang Gang; Su Xu; Sun Quanfu

    2008-01-01

    Objective: To explore the general characteristics of the concentration and size distribution of aerosols in a mine. Methods: In different areas of a non-uranium mine, the particle number and mass concentration of aerosols were surveyed with a condensation particle counter and a personal aerosol monitor, respectively, and the size distribution of aerosols larger than 1 μm in size was estimated according to the size- selective measurements of mass concentrations. The size distribution of submicron aerosols was evaluated based on the method of screen diffusion battery (SOB), and the measurements were performed in both inside and outside of a control room. Results: The mass concentration of inhaled particles (PM10) was averaged to be 0.42 mg/m 3 in the whole mine, and it varied with different working areas and significantly affected with human activities. In the mine, particles lager than 1 μm in size widely distributed, while the particles less than 5 nm in size were seldom observed. Conclusions: The characteristics of aerosol significantly change with different working areas, human activities and Antilation condition in mine. The dose contribution from inhaled radioactive particles larger than 1 μm in size should be considered in mine. (authors)

  7. Evaluation of 1H NMR relaxometry for the assessment of pore size distribution in soil samples

    NARCIS (Netherlands)

    Jaeger, F.; Bowe, S.; As, van H.; Schaumann, G.E.

    2009-01-01

    1H NMR relaxometry is used in earth science as a non-destructive and time-saving method to determine pore size distributions (PSD) in porous media with pore sizes ranging from nm to mm. This is a broader range than generally reported for results from X-ray computed tomography (X-ray CT) scanning,

  8. Empirical evidence for multi-scaled controls on wildfire size distributions in California

    Science.gov (United States)

    Povak, N.; Hessburg, P. F., Sr.; Salter, R. B.

    2014-12-01

    Ecological theory asserts that regional wildfire size distributions are examples of self-organized critical (SOC) systems. Controls on SOC event-size distributions by virtue are purely endogenous to the system and include the (1) frequency and pattern of ignitions, (2) distribution and size of prior fires, and (3) lagged successional patterns after fires. However, recent work has shown that the largest wildfires often result from extreme climatic events, and that patterns of vegetation and topography may help constrain local fire spread, calling into question the SOC model's simplicity. Using an atlas of >12,000 California wildfires (1950-2012) and maximum likelihood estimation (MLE), we fit four different power-law models and broken-stick regressions to fire-size distributions across 16 Bailey's ecoregions. Comparisons among empirical fire size distributions across ecoregions indicated that most ecoregion's fire-size distributions were significantly different, suggesting that broad-scale top-down controls differed among ecoregions. One-parameter power-law models consistently fit a middle range of fire sizes (~100 to 10000 ha) across most ecoregions, but did not fit to larger and smaller fire sizes. We fit the same four power-law models to patch size distributions of aspect, slope, and curvature topographies and found that the power-law models fit to a similar middle range of topography patch sizes. These results suggested that empirical evidence may exist for topographic controls on fire sizes. To test this, we used neutral landscape modeling techniques to determine if observed fire edges corresponded with aspect breaks more often than expected by random. We found significant differences between the empirical and neutral models for some ecoregions, particularly within the middle range of fire sizes. Our results, combined with other recent work, suggest that controls on ecoregional fire size distributions are multi-scaled and likely are not purely SOC. California

  9. Development and test of a soot-specific method for immission measurement. Pt. 3. Content determination of tire abrasion in atmospherical elementary carbon; Weiterentwicklung und Erprobung eines Immissionsmessverfahrens zur spezifischen Erfassung von Russpartikeln. T. 3. Ermittlung des Anteils von Reifenabrieb am atmosphaerischen elementaren Kohlenstoff

    Energy Technology Data Exchange (ETDEWEB)

    Pfaender, N.; Weinberg, G.; Wild, U.

    1996-12-01

    The purpose of this study was to find out methods of discrimination between diesel soot and tire abrasion in carbons of aerosol filter samples. A method of determination between diesel soot and tire abrasion should be found because of the offered standard methods (combustion methods) do not distinguish between the carbon forms. A considerable content of tire abrasion traffic control samples of ``carbon`` would require a correction of the integral ascertained carbon concentration. Three sets of samples have been investigated with the help of TEM, SEM, EDX and ESCA. One basis for discrimination is the chemical activity of the surfaces. While the tire abrasion shows a chemically saturated polymer surface, the diesel soot has a chemically very active soot surface. A second basis for discrimination is the very different particle-size distribution of the diesel soot and the tire abrasion particles. This has been ascertained with the help of TEM and SEM. The results of 3 sets of samples show that a corresponding semi-quantitative discrimination with morphological, element analytical and surface analytical methods between diesel soot and tire abrasion is possible. The main result is a low to very low abundance of the tire abrasion in the total carbon contents. An absolute determination fails mainly because of the interference of the tire abrasion analysis with molecular hydrocarbons. The samples succumb to chemical ageing, where especially diesel soot partially oxidizes. A Thermal treatment also changes the chemical nature of the soot components. (orig.) [Deutsch] Die Aufgabe dieser Arbeit war es, Methoden zu finden, die in einer Aerosolfilterprobe Kohlenstoffe nach Dieselruss und Reifenabrieb zu unterscheiden vermoegen. Es sollte eine grobe Quantitifizerung des Reifenabrieb am Dieselruss ermittelt werden, da in den vorgeschlagenen Standardverfahren (Oxidationsverfahren) nicht zwischen den Kohlenstoff-Formen unterschieden werden kann, was bei erheblichen Anteilen von

  10. A POSSIBLE DIVOT IN THE SIZE DISTRIBUTION OF THE KUIPER BELT'S SCATTERING OBJECTS

    Energy Technology Data Exchange (ETDEWEB)

    Shankman, C.; Gladman, B. J. [Department of Physics and Astronomy, University of British Columbia, 6224 Agriculture Road, Vancouver, BC V6T 1Z1 (Canada); Kaib, N. [Department of Physics and Astronomy, Queens University (Canada); Kavelaars, J. J. [National Research Council of Canada, Victoria, BC V9E 2E7 (Canada); Petit, J. M. [Institut UTINAM, CNRS-Universite de Franche-Comte, Besancon (France)

    2013-02-10

    Via joint analysis of a calibrated telescopic survey, which found scattering Kuiper Belt objects, and models of their expected orbital distribution, we explore the scattering-object (SO) size distribution. Although for D > 100 km the number of objects quickly rise as diameters decrease, we find a relative lack of smaller objects, ruling out a single power law at greater than 99% confidence. After studying traditional ''knees'' in the size distribution, we explore other formulations and find that, surprisingly, our analysis is consistent with a very sudden decrease (a divot) in the number distribution as diameters decrease below 100 km, which then rises again as a power law. Motivated by other dynamically hot populations and the Centaurs, we argue for a divot size distribution where the number of smaller objects rises again as expected via collisional equilibrium. Extrapolation yields enough kilometer-scale SOs to supply the nearby Jupiter-family comets. Our interpretation is that this divot feature is a preserved relic of the size distribution made by planetesimal formation, now ''frozen in'' to portions of the Kuiper Belt sharing a ''hot'' orbital inclination distribution, explaining several puzzles in Kuiper Belt science. Additionally, we show that to match today's SO inclination distribution, the supply source that was scattered outward must have already been vertically heated to the of order 10 Degree-Sign .

  11. On the size distribution of one-, two- and three-dimensional Voronoi cells

    International Nuclear Information System (INIS)

    Marthinsen, K.

    1994-03-01

    The present report gives a presentation of the different cell size distribution obtained by computer simulations of random Voronoi cell structures in one-, two- and three-dimensional space. The random Voronoi cells are constructed from cell centroids randomly distributed along a string, in the plane and in three-dimensional space, respectively. The size distributions are based on 2-3 · 10 4 cells. For the spacial polyhedra both the distribution of volumes, areas and radii are presented, and the two latter quantities are compared to the distributions of areas and radii from a planar section through the three-dimensional structure as well as to the corresponding distributions obtained from a pure two-dimensional cell structure. 11 refs., 11 figs

  12. Thermodynamic limits on the size and size distribution of nucleic acids synthesized in vitro: the role of pyrophosphate hydrolysis.

    Science.gov (United States)

    Peller, L

    1977-02-08

    The free-energy change of phosphodiester bond formation from nucleoside triphosphates is more favorable than with nucleoside diphosphates as substrates. Base-stacking interactions can make significant contributions to both delta G degrees ' values. Pyrophosphate hydrolysis when it accompanies the former reaction dominates all thermodynamic considerations. Three experimental situations are discussed in which high-molecular-weight polynucleotides are synthesized without a strong driving force for covalent bond formation. For one of these, a kinetic scheme is presented which encompasses an early narrow Poisson distribution of chain lengths with ultimate passage to a disperse equilibrium population of chain sizes. Hydrolytic removal of pyrophosphate expands the time scale for this undesirable process by a factor of 10(9), while it enormously elevates the thermodynamic ceiling for the average degrees of polymerization in the other two examples. The electron micrographically revealed broad size population from an early study of partial replication of a T7 DNA template is found to adhere (fortuitously) to a disperse most probable representation. Some possible origins are examined for the branched structures in this product, as well as in a later investigation of replication of this nucleic acid. The achievement of both very high molecular weights and sharply peaked size distributions in polynucleotides synthesized in vitro will require coupling to inorganic pyrophosphatase action as in vivo.

  13. Effect of pore size distribution and flow segregation on dispersion in porous media

    International Nuclear Information System (INIS)

    Carbonell, R.G.

    1978-11-01

    In order to study the effect of the pore size distribution and flow segregation on dispersion in a porous media, the dispersion of solute in an array of parallel pores is considered. Equations are obtained for the dispersion coefficient in laminar and turbulent flow, as a function of the particle Peclet number. The theory fits quite well cumulative experimental data from various researchers in the Peclet number range from 10 -3 to 10 6 . The model also predicts some trends, backed by experimental data, regarding the effect of particle size, particle size distribution and fluid velocity on dispersion

  14. Quantification of the evolution of firm size distributions due to mergers and acquisitions.

    Science.gov (United States)

    Lera, Sandro Claudio; Sornette, Didier

    2017-01-01

    The distribution of firm sizes is known to be heavy tailed. In order to account for this stylized fact, previous economic models have focused mainly on growth through investments in a company's own operations (internal growth). Thereby, the impact of mergers and acquisitions (M&A) on the firm size (external growth) is often not taken into consideration, notwithstanding its potential large impact. In this article, we make a first step into accounting for M&A. Specifically, we describe the effect of mergers and acquisitions on the firm size distribution in terms of an integro-differential equation. This equation is subsequently solved both analytically and numerically for various initial conditions, which allows us to account for different observations of previous empirical studies. In particular, it rationalises shortcomings of past work by quantifying that mergers and acquisitions develop a significant influence on the firm size distribution only over time scales much longer than a few decades. This explains why M&A has apparently little impact on the firm size distributions in existing data sets. Our approach is very flexible and can be extended to account for other sources of external growth, thus contributing towards a holistic understanding of the distribution of firm sizes.

  15. Quantification of the evolution of firm size distributions due to mergers and acquisitions

    Science.gov (United States)

    Sornette, Didier

    2017-01-01

    The distribution of firm sizes is known to be heavy tailed. In order to account for this stylized fact, previous economic models have focused mainly on growth through investments in a company’s own operations (internal growth). Thereby, the impact of mergers and acquisitions (M&A) on the firm size (external growth) is often not taken into consideration, notwithstanding its potential large impact. In this article, we make a first step into accounting for M&A. Specifically, we describe the effect of mergers and acquisitions on the firm size distribution in terms of an integro-differential equation. This equation is subsequently solved both analytically and numerically for various initial conditions, which allows us to account for different observations of previous empirical studies. In particular, it rationalises shortcomings of past work by quantifying that mergers and acquisitions develop a significant influence on the firm size distribution only over time scales much longer than a few decades. This explains why M&A has apparently little impact on the firm size distributions in existing data sets. Our approach is very flexible and can be extended to account for other sources of external growth, thus contributing towards a holistic understanding of the distribution of firm sizes. PMID:28841683

  16. Quantification of the evolution of firm size distributions due to mergers and acquisitions.

    Directory of Open Access Journals (Sweden)

    Sandro Claudio Lera

    Full Text Available The distribution of firm sizes is known to be heavy tailed. In order to account for this stylized fact, previous economic models have focused mainly on growth through investments in a company's own operations (internal growth. Thereby, the impact of mergers and acquisitions (M&A on the firm size (external growth is often not taken into consideration, notwithstanding its potential large impact. In this article, we make a first step into accounting for M&A. Specifically, we describe the effect of mergers and acquisitions on the firm size distribution in terms of an integro-differential equation. This equation is subsequently solved both analytically and numerically for various initial conditions, which allows us to account for different observations of previous empirical studies. In particular, it rationalises shortcomings of past work by quantifying that mergers and acquisitions develop a significant influence on the firm size distribution only over time scales much longer than a few decades. This explains why M&A has apparently little impact on the firm size distributions in existing data sets. Our approach is very flexible and can be extended to account for other sources of external growth, thus contributing towards a holistic understanding of the distribution of firm sizes.

  17. Why Does Zipf's Law Break Down in Rank-Size Distribution of Cities?

    OpenAIRE

    Kuninaka, Hiroto; Matsushita, Mitsugu

    2008-01-01

    We study rank-size distribution of cities in Japan on the basis of data analysis. From the census data after World War II, we find that the rank-size distribution of cities is composed of two parts, each of which has independent power exponent. In addition, the power exponent of the head part of the distribution changes in time and Zipf's law holds only in a restricted period. We show that Zipf's law broke down due to both of Showa and Heisei great mergers and recovered due to population grow...

  18. Particle size distribution of iron nanomaterials in biological medium by SR-SAXS method

    International Nuclear Information System (INIS)

    Jing Long; Feng Weiyue; Wang Bing; Wang Meng; Ouyang Hong; Zhao Yuliang; Chai Zhifang; Wang Yun; Wang Huajiang; Zhu Motao; Wu Zhonghua

    2009-01-01

    A better understanding of biological effects of nanomaterials in organisms requests knowledge of the physicochemical properties of nanomaterials in biological systems. Affected by high concentration salts and proteins in biological medium, nanoparticles are much easy to agglomerate,hence the difficulties in characterizing size distribution of the nanomaterials in biological medium.In this work, synchrotron radiation small angle X-ray scattering(SR-SAXS) was used to determine size distributions of Fe, Fe 2 O 3 and Fe 3 O 4 nanoparticles of various concentrations in PBS and DMEM culture medium. The results show that size distributions of the nanomaterials could perfectly analyzed by SR-SAXS. The SR-SAXS data were not affected by the particle content and types of the dispersion medium.It is concluded that SR-SAXS can be used for size measurement of nanomaterials in unstable dispersion systems. (authors)

  19. Analysis of tecniques for measurement of the size distribution of solid particles

    Directory of Open Access Journals (Sweden)

    F. O. Arouca

    2005-03-01

    Full Text Available Determination of the size distribution of solid particles is fundamental for analysis of the performance several pieces of equipment used for solid-fluid separation. The main objective of this work is to compare the results obtained with two traditional methods for determination of the size grade distribution of powdery solids: the gamma-ray attenuation technique (GRAT and the LADEQ test tube technique. The effect of draining the suspension in the two techniques used was also analyzed. The GRAT can supply the particle size distribution of solids through the monitoring of solid concentration in experiments on batch settling of diluted suspensions. The results show that use of the peristaltic pump in the GRAT and the LADEQ methods produced a significant difference between the values obtained for the parameters of the particle size model.

  20. Zipf's law and city size distribution: A survey of the literature and future research agenda

    Science.gov (United States)

    Arshad, Sidra; Hu, Shougeng; Ashraf, Badar Nadeem

    2018-02-01

    This study provides a systematic review of the existing literature on Zipf's law for city size distribution. Existing empirical evidence suggests that Zipf's law is not always observable even for the upper-tail cities of a territory. However, the controversy with empirical findings arises due to sample selection biases, methodological weaknesses and data limitations. The hypothesis of Zipf's law is more likely to be rejected for the entire city size distribution and, in such case, alternative distributions have been suggested. On the contrary, the hypothesis is more likely to be accepted if better empirical methods are employed and cities are properly defined. The debate is still far from to be conclusive. In addition, we identify four emerging areas in Zipf's law and city size distribution research including the size distribution of lower-tail cities, the size distribution of cities in sub-national regions, the alternative forms of Zipf's law, and the relationship between Zipf's law and the coherence property of the urban system.

  1. Size distributions of aerosols produced from substitute materials by the Laskin cold DOP aerosol generator

    International Nuclear Information System (INIS)

    Hinds, W.; Macher, J.; First, M.W.

    1981-01-01

    Test aerosols of di(2-ethylhexyl)phthalate (DOP) produced by Laskin nozzle aerosol generators are widely used for in-place filter testing and respirator fit testing. Concern for the health effects of this material has led to a search for substitute materials for test aerosols. Aerosols were generated with a Laskin generator and diluted 6000-fold with clean air. Size distributions were measured for DOP, di(2-ethylhexyl)sebecate, polyethylene glycol, mineral oil, and corn oil aerosols with a PMS ASAS-X optical particle counter. Distributions were slightly bimodal with count median diameters from 0.22 to 0.30 μm. Size distributions varied little with aerosol material, operating pressure, or liquid level. Mineral oil and corn oil gave the best agreement with the DOP size distribution

  2. Austenite Grain Size Estimtion from Chord Lengths of Logarithmic-Normal Distribution

    Directory of Open Access Journals (Sweden)

    Adrian H.

    2017-12-01

    Full Text Available Linear section of grains in polyhedral material microstructure is a system of chords. The mean length of chords is the linear grain size of the microstructure. For the prior austenite grains of low alloy structural steels, the chord length is a random variable of gamma- or logarithmic-normal distribution. The statistical grain size estimation belongs to the quantitative metallographic problems. The so-called point estimation is a well known procedure. The interval estimation (grain size confidence interval for the gamma distribution was given elsewhere, but for the logarithmic-normal distribution is the subject of the present contribution. The statistical analysis is analogous to the one for the gamma distribution.

  3. Comparing particle-size distributions in modern and ancient sand-bed rivers

    Science.gov (United States)

    Hajek, E. A.; Lynds, R. M.; Huzurbazar, S. V.

    2011-12-01

    Particle-size distributions yield valuable insight into processes controlling sediment supply, transport, and deposition in sedimentary systems. This is especially true in ancient deposits, where effects of changing boundary conditions and autogenic processes may be detected from deposited sediment. In order to improve interpretations in ancient deposits and constrain uncertainty associated with new methods for paleomorphodynamic reconstructions in ancient fluvial systems, we compare particle-size distributions in three active sand-bed rivers in central Nebraska (USA) to grain-size distributions from ancient sandy fluvial deposits. Within the modern rivers studied, particle-size distributions of active-layer, suspended-load, and slackwater deposits show consistent relationships despite some morphological and sediment-supply differences between the rivers. In particular, there is substantial and consistent overlap between bed-material and suspended-load distributions, and the coarsest material found in slackwater deposits is comparable to the coarse fraction of suspended-sediment samples. Proxy bed-load and slackwater-deposit samples from the Kayenta Formation (Lower Jurassic, Utah/Colorado, USA) show overlap similar to that seen in the modern rivers, suggesting that these deposits may be sampled for paleomorphodynamic reconstructions, including paleoslope estimation. We also compare grain-size distributions of channel, floodplain, and proximal-overbank deposits in the Willwood (Paleocene/Eocene, Bighorn Basin, Wyoming, USA), Wasatch (Paleocene/Eocene, Piceance Creek Basin, Colorado, USA), and Ferris (Cretaceous/Paleocene, Hanna Basin, Wyoming, USA) formations. Grain-size characteristics in these deposits reflect how suspended- and bed-load sediment is distributed across the floodplain during channel avulsion events. In order to constrain uncertainty inherent in such estimates, we evaluate uncertainty associated with sample collection, preparation, analytical

  4. Fullerene Soot in Eastern China Air: Results from Soot Particle-Aerosol Mass Spectrometer

    Science.gov (United States)

    Wang, J.; Ge, X.; Chen, M.; Zhang, Q.; Yu, H.; Sun, Y.; Worsnop, D. R.; Collier, S.

    2015-12-01

    In this work, we present for the first time, the observation and quantification of fullerenes in ambient airborne particulate using an Aerodyne Soot Particle - Aerosol Mass Spectrometer (SP-AMS) deployed during 2015 winter in suburban Nanjing, a megacity in eastern China. The laser desorption and electron impact ionization techniques employed by the SP-AMS allow us to differentiate various fullerenes from other aerosol components. Mass spectrum of the identified fullerene soot is consisted by a series of high molecular weight carbon clusters (up to m/z of 2000 in this study), almost identical to the spectral features of commercially available fullerene soot, both with C70 and C60 clusters as the first and second most abundant species. This type of soot was observed throughout the entire study period, with an average mass loading of 0.18 μg/m3, accounting for 6.4% of the black carbon mass, 1.2% of the total organic mass. Temporal variation and diurnal pattern of fullerene soot are overall similar to those of black carbon, but are clearly different in some periods. Combining the positive matrix factorization, back-trajectory and analyses of the meteorological parameters, we identified the petrochemical industrial plants situating upwind from the sampling site, as the major source of fullerene soot. In this regard, our findings imply the ubiquitous presence of fullerene soot in ambient air of industry-influenced area, especially the oil and gas production regions. This study also offers new insights into the characterization of fullerenes from other environmental samples via the advanced SP-AMS technique.

  5. New Measurements of the Particle Size Distribution of Apollo 11 Lunar Soil 10084

    Science.gov (United States)

    McKay, D.S.; Cooper, B.L.; Riofrio, L.M.

    2009-01-01

    We have initiated a major new program to determine the grain size distribution of nearly all lunar soils collected in the Apollo program. Following the return of Apollo soil and core samples, a number of investigators including our own group performed grain size distribution studies and published the results [1-11]. Nearly all of these studies were done by sieving the samples, usually with a working fluid such as Freon(TradeMark) or water. We have measured the particle size distribution of lunar soil 10084,2005 in water, using a Microtrac(TradeMark) laser diffraction instrument. Details of our own sieving technique and protocol (also used in [11]). are given in [4]. While sieving usually produces accurate and reproducible results, it has disadvantages. It is very labor intensive and requires hours to days to perform properly. Even using automated sieve shaking devices, four or five days may be needed to sieve each sample, although multiple sieve stacks increases productivity. Second, sieving is subject to loss of grains through handling and weighing operations, and these losses are concentrated in the finest grain sizes. Loss from handling becomes a more acute problem when smaller amounts of material are used. While we were able to quantitatively sieve into 6 or 8 size fractions using starting soil masses as low as 50mg, attrition and handling problems limit the practicality of sieving smaller amounts. Third, sieving below 10 or 20microns is not practical because of the problems of grain loss, and smaller grains sticking to coarser grains. Sieving is completely impractical below about 5- 10microns. Consequently, sieving gives no information on the size distribution below approx.10 microns which includes the important submicrometer and nanoparticle size ranges. Finally, sieving creates a limited number of size bins and may therefore miss fine structure of the distribution which would be revealed by other methods that produce many smaller size bins.

  6. Spatial distribution and size of small canopy gaps created by Japanese black bears: estimating gap size using dropped branch measurements.

    Science.gov (United States)

    Takahashi, Kazuaki; Takahashi, Kaori

    2013-06-10

    Japanese black bears, a large-bodied omnivore, frequently create small gaps in the tree crown during fruit foraging. However, there are no previous reports of black bear-created canopy gaps. To characterize physical canopy disturbance by black bears, we examined a number of parameters, including the species of trees in which canopy gaps were created, gap size, the horizontal and vertical distribution of gaps, and the size of branches broken to create gaps. The size of black bear-created canopy gaps was estimated using data from branches that had been broken and dropped on the ground. The disturbance regime was characterized by a highly biased distribution of small canopy gaps on ridges, a large total overall gap area, a wide range in gap height relative to canopy height, and diversity in gap size. Surprisingly, the annual rate of bear-created canopy gap formation reached 141.3 m2 ha-1 yr-1 on ridges, which were hot spots in terms of black bear activity. This rate was approximately 6.6 times that of tree-fall gap formation on ridges at this study site. Furthermore, this rate was approximately two to three times that of common tree-fall gap formation in Japanese forests, as reported in other studies. Our findings suggest that the ecological interaction between black bears and fruit-bearing trees may create a unique light regime, distinct from that created by tree falls, which increases the availability of light resources to plants below the canopy.

  7. Catalytic oxidation of soot over alkaline niobates

    International Nuclear Information System (INIS)

    Pecchi, G.; Cabrera, B.; Buljan, A.; Delgado, E.J.; Gordon, A.L.; Jimenez, R.

    2013-01-01

    Highlights: ► No previous reported studies about alkaline niobates as catalysts for soot oxidation. ► NaNbO 3 and KNbO 3 perovskite-type oxides show lower activation energy than other lanthanoid perovskite-type oxides. ► The alkaline niobate does not show deactivation by metal loss. - Abstract: The lack of studies in the current literature about the assessment of alkaline niobates as catalysts for soot oxidation has motivated this research. In this study, the synthesis, characterization and assessment of alkaline metal niobates as catalysts for soot combustion are reported. The solids MNbO 3 (M = Li, Na, K, Rb) are synthesized by a citrate method, calcined at 450 °C, 550 °C, 650 °C, 750 °C, and characterized by AAS, N 2 adsorption, XRD, O 2 -TPD, FTIR and SEM. All the alkaline niobates show catalytic activity for soot combustion, and the activity depends basically on the nature of the alkaline metal and the calcination temperature. The highest catalytic activity, expressed as the temperature at which combustion of carbon black occurs at the maximum rate, is shown by KNbO 3 calcined at 650 °C. At this calcination temperature, the catalytic activity follows an order dependent on the atomic number, namely: KNbO 3 > NaNbO 3 > LiNbO 3 . The RbNbO 3 solid do not follow this trend presumably due to the perovskite structure was not reached. The highest catalytic activity shown by of KNbO 3 , despite the lower apparent activation energy of NaNbO 3 , stress the importance of the metal nature and suggests the hypothesis that K + ions are the active sites for soot combustion. It must be pointed out that alkaline niobate subjected to consecutive soot combustion cycles does not show deactivation by metal loss, due to the stabilization of the alkaline metal inside the perovskite structure.

  8. On the Response of Nascent Soot Nanostructure and Oxidative Reactivity to Photoflash Exposure

    Directory of Open Access Journals (Sweden)

    Wei Wang

    2017-07-01

    Full Text Available Soot particles are a kind of major pollutant from fuel combustion. To enrich the understanding of soot, this work focuses on investigating detailed influences of instantaneous external irradiation (conventional photoflash exposure on nanostructure as well as oxidation reactivity of nascent soot particles. By detailed soot characterizations flash can reduce the mass of soot and soot nanostructure can be reconstructed substantially without burning. After flash, the degree of soot crystallization increases while the soot reactive rate decreases and the activation energy increases. In addition, nanostructure and oxidative reactivity of soot in air and Ar after flash are different due to their different thermal conductivities.

  9. Soot oxidation over NOx storage catalysts. Activity and deactivation

    International Nuclear Information System (INIS)

    Krishna, K.; Makkee, M.

    2006-01-01

    Soot oxidation activity and deactivation of NO x storage and reduction (NSR) catalysts containing Pt, K, and Ba supported on Al 2 O 3 , are studied under a variety of reaction conditions. K-containing catalysts decrease soot oxidation temperature with O 2 alone and the presence of Pt further enhance the activity due to synergetic effect. The active species responsible for synergism on Pt/K-Al 2 O 3 are unstable and cannot be regenerated. Soot oxidation temperature decreases by about 150 o C with NO+O 2 exhaust feed gas and under lean conditions NSR system acts as catalysed soot filter (CSF). The reactions that are mainly responsible for decreasing soot oxidation temperature are: (1) soot oxidation with NO 2 followed by NO recycles to NO 2 , and (2) soot oxidation with O 2 assisted by NO 2 . Only a part of the stored NO x that is decomposed at high temperatures under lean conditions is found to be useful for soot oxidation. NO x storage capacity of NSR catalysts decreases upon ageing under soot oxidising conditions. This will lead to a decreased soot oxidation activity on stored nitrate decomposition. Pt/K-Al 2 O 3 catalyst is more active, but least stable compared with Pt/Ba-Al 2 O 3 . (author)

  10. Optimal placement and sizing of wind / solar based DG sources in distribution system

    Science.gov (United States)

    Guan, Wanlin; Guo, Niao; Yu, Chunlai; Chen, Xiaoguang; Yu, Haiyang; Liu, Zhipeng; Cui, Jiapeng

    2017-06-01

    Proper placement and sizing of Distributed Generation (DG) in distribution system can obtain maximum potential benefits. This paper proposes quantum particle swarm algorithm (QPSO) based wind turbine generation unit (WTGU) and photovoltaic (PV) array placement and sizing approach for real power loss reduction and voltage stability improvement of distribution system. Performance modeling of wind and solar generation system are described and classified into PQ\\PQ (V)\\PI type models in power flow. Considering the WTGU and PV based DGs in distribution system is geographical restrictive, the optimal area and DG capacity limits of each bus in the setting area need to be set before optimization, the area optimization method is proposed . The method has been tested on IEEE 33-bus radial distribution systems to demonstrate the performance and effectiveness of the proposed method.

  11. Stable Size Distribution of Amyloid Plaques Over the Course of Alzheimer Disease

    Science.gov (United States)

    Serrano-Pozo, Alberto; Mielke, Matthew L.; Muzitansky, Alona; Gómez-Isla, Teresa; Growdon, John H.; Bacskai, Brian J.; Betensky, Rebecca A.; Frosch, Matthew P.; Hyman, Bradley T.

    2012-01-01

    Amyloid-β plaques are a key pathological feature of Alzheimer disease (AD), but whether plaque sizes increase or stabilize over the course of AD is unknown. We measured the size distribution of total immunoreactive (10D5-positive) and dense-core (Thioflavine-S-positive) plaques in the temporal neocortex of a large group of AD and plaque-bearing age-matched non-demented subjects to test the hypothesis that amyloid plaques continue to grow along with the progression of the disease. The size of amyloid-β (10D5)-positive plaques did not differ between groups whereas dense-core plaques from the AD group were slightly larger than those in the non-demented group (~25%–30%, p = 0.01). Within the AD group, dense-core plaque size did not independently correlate with duration of clinical disease (from 4 to 21 years, p = 0.68), whereas 10D5-positive plaque size correlated negatively with disease duration (p = 0.01). By contrast, an earlier age of symptom onset strongly predicted a larger postmortem plaque size; this effect was independent of disease duration and the presence of the APOEε4 allele (p = 0.0001). We conclude that plaques vary in size among patients, with larger size distributions correlating with an earlier age of onset, but plaques do not substantially increase in size over the clinical course of the disease. PMID:22805771

  12. Size distribution of magnetic iron oxide nanoparticles using Warren-Averbach XRD analysis

    Science.gov (United States)

    Mahadevan, S.; Behera, S. P.; Gnanaprakash, G.; Jayakumar, T.; Philip, J.; Rao, B. P. C.

    2012-07-01

    We use the Fourier transform based Warren-Averbach (WA) analysis to separate the contributions of X-ray diffraction (XRD) profile broadening due to crystallite size and microstrain for magnetic iron oxide nanoparticles. The profile shape of the column length distribution, obtained from WA analysis, is used to analyze the shape of the magnetic iron oxide nanoparticles. From the column length distribution, the crystallite size and its distribution are estimated for these nanoparticles which are compared with size distribution obtained from dynamic light scattering measurements. The crystallite size and size distribution of crystallites obtained from WA analysis are explained based on the experimental parameters employed in preparation of these magnetic iron oxide nanoparticles. The variation of volume weighted diameter (Dv, from WA analysis) with saturation magnetization (Ms) fits well to a core shell model wherein it is known that Ms=Mbulk(1-6g/Dv) with Mbulk as bulk magnetization of iron oxide and g as magnetic shell disorder thickness.

  13. X-ray diffraction microstructural analysis of bimodal size distribution MgO nano powder

    International Nuclear Information System (INIS)

    Suminar Pratapa; Budi Hartono

    2009-01-01

    Investigation on the characteristics of x-ray diffraction data for MgO powdered mixture of nano and sub-nano particles has been carried out to reveal the crystallite-size-related microstructural information. The MgO powders were prepared by co-precipitation method followed by heat treatment at 500 degree Celsius and 1200 degree Celsius for 1 hour, being the difference in the temperature was to obtain two powders with distinct crystallite size and size-distribution. The powders were then blended in air to give the presumably bimodal-size- distribution MgO nano powder. High-quality laboratory X-ray diffraction data for the powders were collected and then analysed using Rietveld-based MAUD software using the lognormal size distribution. Results show that the single-mode powders exhibit spherical crystallite size (R) of 20(1) nm and 160(1) nm for the 500 degree Celsius and 1200 degree Celsius data respectively with the nano metric powder displays narrower crystallite size distribution character, indicated by lognormal dispersion parameter of 0.21 as compared to 0.01 for the sub-nano metric powder. The mixture exhibits relatively more asymmetric peak broadening. Analysing the x-ray diffraction data for the latter specimen using single phase approach give unrealistic results. Introducing two phase models for the double-phase mixture to accommodate the bimodal-size-distribution characteristics give R = 100(6) and σ = 0.62 for the nano metric phase and R = 170(5) and σ= 0.12 for the σ sub-nano metric phase. (author)

  14. Size Distribution and Dispersion of Droplets Generated by Impingement of Breaking Waves on Oil Slicks

    Science.gov (United States)

    Li, C.; Miller, J.; Wang, J.; Koley, S. S.; Katz, J.

    2017-10-01

    This laboratory experimental study investigates the temporal evolution of the size distribution of subsurface oil droplets generated as breaking waves entrain oil slicks. The measurements are performed for varying wave energy, as well as large variations in oil viscosity and oil-water interfacial tension, the latter achieved by premixing the oil with dispersant. In situ measurements using digital inline holography at two magnifications are applied for measuring the droplet sizes and Particle Image Velocimetry (PIV) for determining the temporal evolution of turbulence after wave breaking. All early (2-10 s) size distributions have two distinct size ranges with different slopes. For low dispersant to oil ratios (DOR), the transition between them could be predicted based on a turbulent Weber (We) number in the 2-4 range, suggesting that turbulence plays an important role. For smaller droplets, all the number size distributions have power of about -2.1, and for larger droplets, the power decreases well below -3. The measured steepening of the size distribution over time is predicted by a simple model involving buoyant rise and turbulence dispersion. Conversely, for DOR 1:100 and 1:25 oils, the diameter of slope transition decreases from ˜1 mm to 46 and 14 µm, respectively, much faster than the We-based prediction, and the size distribution steepens with increasing DOR. Furthermore, the concentration of micron-sized droplets of DOR 1:25 oil increases for the first 10 min after entrainment. These phenomena are presumably caused by the observed formation and breakup oil microthreads associated with tip streaming.

  15. Methods for obtaining true particle size distributions from cross section measurements

    Energy Technology Data Exchange (ETDEWEB)

    Lord, Kristina Alyse [Iowa State Univ., Ames, IA (United States)

    2013-01-01

    Sectioning methods are frequently used to measure grain sizes in materials. These methods do not provide accurate grain sizes for two reasons. First, the sizes of features observed on random sections are always smaller than the true sizes of solid spherical shaped objects, as noted by Wicksell [1]. This is the case because the section very rarely passes through the center of solid spherical shaped objects randomly dispersed throughout a material. The sizes of features observed on random sections are inversely related to the distance of the center of the solid object from the section [1]. Second, on a plane section through the solid material, larger sized features are more frequently observed than smaller ones due to the larger probability for a section to come into contact with the larger sized portion of the spheres than the smaller sized portion. As a result, it is necessary to find a method that takes into account these reasons for inaccurate particle size measurements, while providing a correction factor for accurately determining true particle size measurements. I present a method for deducing true grain size distributions from those determined from specimen cross sections, either by measurement of equivalent grain diameters or linear intercepts.

  16. Effect of particle size distribution on permeability in the randomly packed porous media

    Science.gov (United States)

    Markicevic, Bojan

    2017-11-01

    An answer of how porous medium heterogeneity influences the medium permeability is still inconclusive, where both increase and decrease in the permeability value are reported. A numerical procedure is used to generate a randomly packed porous material consisting of spherical particles. Six different particle size distributions are used including mono-, bi- and three-disperse particles, as well as uniform, normal and log-normal particle size distribution with the maximum to minimum particle size ratio ranging from three to eight for different distributions. In all six cases, the average particle size is kept the same. For all media generated, the stochastic homogeneity is checked from distribution of three coordinates of particle centers, where uniform distribution of x-, y- and z- positions is found. The medium surface area remains essentially constant except for bi-modal distribution in which medium area decreases, while no changes in the porosity are observed (around 0.36). The fluid flow is solved in such domain, and after checking for the pressure axial linearity, the permeability is calculated from the Darcy law. The permeability comparison reveals that the permeability of the mono-disperse medium is smallest, and the permeability of all poly-disperse samples is less than ten percent higher. For bi-modal particles, the permeability is for a quarter higher compared to the other media which can be explained by volumetric contribution of larger particles and larger passages for fluid flow to take place.

  17. The size distributions of fragments ejected at a given velocity from impact craters

    Science.gov (United States)

    O'Keefe, John D.; Ahrens, Thomas J.

    1987-01-01

    The mass distribution of fragments that are ejected at a given velocity for impact craters is modeled to allow extrapolation of laboratory, field, and numerical results to large scale planetary events. The model is semi-empirical in nature and is derived from: (1) numerical calculations of cratering and the resultant mass versus ejection velocity, (2) observed ejecta blanket particle size distributions, (3) an empirical relationship between maximum ejecta fragment size and crater diameter, (4) measurements and theory of maximum ejecta size versus ejecta velocity, and (5) an assumption on the functional form for the distribution of fragments ejected at a given velocity. This model implies that for planetary impacts into competent rock, the distribution of fragments ejected at a given velocity is broad, e.g., 68 percent of the mass of the ejecta at a given velocity contains fragments having a mass less than 0.1 times a mass of the largest fragment moving at that velocity. The broad distribution suggests that in impact processes, additional comminution of ejecta occurs after the upward initial shock has passed in the process of the ejecta velocity vector rotating from an initially downward orientation. This additional comminution produces the broader size distribution in impact ejecta as compared to that obtained in simple brittle failure experiments.

  18. THE EFFECTS OF GRAIN SIZE AND TEMPERATURE DISTRIBUTIONS ON THE FORMATION OF INTERSTELLAR ICE MANTLES

    Energy Technology Data Exchange (ETDEWEB)

    Pauly, Tyler; Garrod, Robin T., E-mail: tap74@cornell.edu [Cornell Center for Astrophysics and Planetary Science, Cornell University, Ithaca, NY 14853-6801 (United States)

    2016-02-01

    Computational models of interstellar gas-grain chemistry have historically adopted a single dust-grain size of 0.1 micron, assumed to be representative of the size distribution present in the interstellar medium. Here, we investigate the effects of a broad grain-size distribution on the chemistry of dust-grain surfaces and the subsequent build-up of molecular ices on the grains, using a three-phase gas-grain chemical model of a quiescent dark cloud. We include an explicit treatment of the grain temperatures, governed both by the visual extinction of the cloud and the size of each individual grain-size population. We find that the temperature difference plays a significant role in determining the total bulk ice composition across the grain-size distribution, while the effects of geometrical differences between size populations appear marginal. We also consider collapse from a diffuse to a dark cloud, allowing dust temperatures to fall. Under the initial diffuse conditions, small grains are too warm to promote grain-mantle build-up, with most ices forming on the mid-sized grains. As collapse proceeds, the more abundant, smallest grains cool and become the dominant ice carriers; the large population of small grains means that this ice is distributed across many grains, with perhaps no more than 40 monolayers of ice each (versus several hundred assuming a single grain size). This effect may be important for the subsequent processing and desorption of the ice during the hot-core phase of star formation, exposing a significant proportion of the ice to the gas phase, increasing the importance of ice-surface chemistry and surface–gas interactions.

  19. The Effects of Grain Size and Temperature Distributions on the Formation of Interstellar Ice Mantles

    Science.gov (United States)

    Pauly, Tyler; Garrod, Robin T.

    2016-02-01

    Computational models of interstellar gas-grain chemistry have historically adopted a single dust-grain size of 0.1 micron, assumed to be representative of the size distribution present in the interstellar medium. Here, we investigate the effects of a broad grain-size distribution on the chemistry of dust-grain surfaces and the subsequent build-up of molecular ices on the grains, using a three-phase gas-grain chemical model of a quiescent dark cloud. We include an explicit treatment of the grain temperatures, governed both by the visual extinction of the cloud and the size of each individual grain-size population. We find that the temperature difference plays a significant role in determining the total bulk ice composition across the grain-size distribution, while the effects of geometrical differences between size populations appear marginal. We also consider collapse from a diffuse to a dark cloud, allowing dust temperatures to fall. Under the initial diffuse conditions, small grains are too warm to promote grain-mantle build-up, with most ices forming on the mid-sized grains. As collapse proceeds, the more abundant, smallest grains cool and become the dominant ice carriers; the large population of small grains means that this ice is distributed across many grains, with perhaps no more than 40 monolayers of ice each (versus several hundred assuming a single grain size). This effect may be important for the subsequent processing and desorption of the ice during the hot-core phase of star formation, exposing a significant proportion of the ice to the gas phase, increasing the importance of ice-surface chemistry and surface-gas interactions.

  20. Efficient low-temperature soot combustion by bimetallic Ag-Cu/SBA-15 catalysts.

    Science.gov (United States)

    Wen, Zhaojun; Duan, Xinping; Hu, Menglin; Cao, Yanning; Ye, Linmin; Jiang, Lilong; Yuan, Youzhu

    2018-02-01

    In this study, the effects of copper (Cu) additive on the catalytic performance of Ag/SBA-15 in complete soot combustion were investigated. The soot combustion performance of bimetallic Ag-Cu/SBA-15 catalysts was higher than that of monometallic Ag and Cu catalysts. The optimum catalytic performance was acquired with the 5Ag 1 -Cu 0.1 /SBA-15 catalyst, on which the soot combustion starts at T ig =225°C with a T 50 =285°C. The temperature for 50% of soot combustion was lower than that of conventional Ag-based catalysts to more than 50°C (Aneggi et al., 2009). Physicochemical characterizations of the catalysts indicated that addition of Cu into Ag could form smaller bimetallic Ag-Cu nanolloy particles, downsizing the mean particle size from 3.7nm in monometallic catalyst to 2.6nm in bimetallic Ag-Cu catalyst. Further experiments revealed that Ag and Cu species elicited synergistic effects, subsequently increasing the content of surface active oxygen species. As a result, the structure modifications of Ag by the addition of Cu strongly intensified the catalytic performance. Copyright © 2017. Published by Elsevier B.V.

  1. Polycyclic aromatic hydrocarbons in urban atmosphere of Guangzhou, China: Size distribution characteristics and size-resolved gas-particle partitioning

    Science.gov (United States)

    Yu, Huan; Yu, Jian Zhen

    2012-07-01

    Size distributions of thirteen polycyclic aromatic hydrocarbons (PAHs), elemental carbon (EC), and organic carbon (OC) in the range of 0.01-18 μm were measured using a nano Micro-Orifice Uniform Deposit Impactor (nano-MOUDI) in an urban location in Guangzhou, China in July 2006. PAH size distributions were fit with five modes and the respective mass median aerodynamic diameters (MMAD) are: Aitken mode (MMAD: ˜0.05 μm), three accumulation modes AMI, AMII, AMIII (MMAD: 0.13-0.17 μm, 0.4-0.45 μm, and 0.9-1.2 μm, respectively), and coarse mode (MMAD: 4-6 μm). Seven-ring PAH was mainly in AMII and AMIII. Five- and six-ring PAHs were found to be abundant in all the three AM. Three- and four-ring PAHs had a significant presence in the coarse mode in addition to the three AM. Size-resolved gas-particle partition coefficients of PAHs (Kp) were estimated using measured EC and OC data. The Kp values of a given PAH could differ by a factor of up to ˜7 on particles in different size modes, with the highest Kp associated with the AMI particles and the lowest Kp associated with the coarse mode particles. Comparison of calculated overall Kp with measured Kp values in Guangzhou by Yang et al. (2010) shows that adsorption on EC appeared to be the dominant mechanism driving the gas-particle partitioning of three- and four-ring PAHs while absorption in OM played a dominant role for five- and six-ring PAHs. The calculated equilibrium timescales of repartitioning indicate that five- to seven-ring PAHs could not achieve equilibrium partitioning within their typical residence time in urban atmospheres, while three- and four-ring PAHs could readily reach new equilibrium states in particles of all sizes. A partitioning flux is therefore proposed to replace the equilibrium assumption in modeling PAH transport and fate.

  2. Comparison of outdoor activity size distributions of 220 Rn and 222 Rn progeny and their Influences on lung dosimetry distributions

    International Nuclear Information System (INIS)

    Mohamed, A.; El-Hussein, A.; Ahmed, A.

    2005-01-01

    In the case of internally deposited radionuclides, direct measurement of the energy absorbed from ionizing radiation emitted by the decaying radionuclides is rarely, if ever, possible. Therefore, one must rely on dosimetric models to obtain estimates of the spatial and temporal patterns of energy deposition in human lung. T These models always need some information about the parameters of activity size distributions of thoron and radon progeny. In the present work, the attached and unattached activity size distributions of thoron and radon progeny were measured in outdoor air of El-Minia, Egypt. The attached samples were collected using a low pressure Berner cascade impactor technique, while a constructed screen diffusion b attery was used for collecting the unattached samples. Most of the attached activities for 222 Rn and 220 Rn progeny were associated with the aerosol particles of the accumulation mode. The activity size distribution of thoron progeny was found to be shifted to slightly smaller particle size, compared to radon progeny. An analytical method has been developed to compute the local energy deposition of 2l2 Bi alpha particles in a target volume of 1 jam spheres located at different depths in bronchial epithelium. In order to reach the target, alpha particles travel either through tissue alone (near-wall dose) or through air and tissue (far-wall dose). It was found that the contribution of near-wall dose is higher than that of the far wall dose. While the depth-dose distributions for nuclides uniformly distributed within the epithelium are practically constant with

  3. Experiments and Model Development for the Investigation of Sooting and Radiation Effects in Microgravity Droplet Combustion

    Science.gov (United States)

    Choi, Mun Young; Yozgatligil, Ahmet; Dryer, Frederick L.; Kazakov, Andrei; Dobashi, Ritsu

    2001-01-01

    Today, despite efforts to develop and utilize natural gas and renewable energy sources, nearly 97% of the energy used for transportation is derived from combustion of liquid fuels, principally derived from petroleum. While society continues to rely on liquid petroleum-based fuels as a major energy source in spite of their finite supply, it is of paramount importance to maximize the efficiency and minimize the environmental impact of the devices that burn these fuels. The development of improved energy conversion systems, having higher efficiencies and lower emissions, is central to meeting both local and regional air quality standards. This development requires improvements in computational design tools for applied energy conversion systems, which in turn requires more robust sub-model components for combustion chemistry, transport, energy transport (including radiation), and pollutant emissions (soot formation and burnout). The study of isolated droplet burning as a unidimensional, time dependent model diffusion flame system facilitates extensions of these mechanisms to include fuel molecular sizes and pollutants typical of conventional and alternative liquid fuels used in the transportation sector. Because of the simplified geometry, sub-model components from the most detailed to those reduced to sizes compatible for use in multi-dimensional, time dependent applied models can be developed, compared and validated against experimental diffusion flame processes, and tested against one another. Based on observations in microgravity experiments on droplet combustion, it appears that the formation and lingering presence of soot within the fuel-rich region of isolated droplets can modify the burning rate, flame structure and extinction, soot aerosol properties, and the effective thermophysical properties. These observations led to the belief that perhaps one of the most important outstanding contributions of microgravity droplet combustion is the observation that in the

  4. Detailed modeling of size distribution functions and hydrogen content in combustion-formed particles

    Energy Technology Data Exchange (ETDEWEB)

    Sirignano, Mariano; D' Anna, Andrea [Dipartimento di Ingegneria Chimica, Universita di Napoli ' ' Federico II' ' , Napoli (Italy); Kent, John [School of Aerospace, Mechanical and Mechatronic Engineering, University of Sydney, Sydney (Australia)

    2010-06-15

    A kinetic modeling approach is proposed to delve into the nature and chemistry of combustion-produced particles. A sectional method is used for the first time on this purpose. It is based on modeling of gas-to-particle transitions by sections containing 125 lumped species with C numbers ranging from 24 to 4 x 10{sup 8} and H/C ratio ranging from 0 to 1. This allows not only the mass evolution of particles, but also their hydrogen content to be followed. The model is tested in an atmospheric pressure premixed flat flame of ethylene/oxygen with C/O = 0.8 and cold gas flow velocity of 4 cm/s. Comparison of modeled results with experimental data is satisfying in terms of species concentrations and H/C ratio of the particles. Analysis of model results in comparison with the experimental data has shown that it is possible to distinguish different precursors of particles moving from the exit of the burner into the post-oxidation region of the flame. At particle inception, i.e. just downstream from the flame front, gas-phase PAHs are responsible for particle nucleation and oligomers of aromatic hydrocarbons and small pericondensed hydrocarbons are predominantly present. Then the dehydrogenation process takes place and soot formation starts; in this zone large pericondensed and stacked structures are produced. Further up soot maturation generally linked with dehydrogenation is present, but still a few particles with higher H/C and with low coagulation efficiency are produced and remain present along the flame. The model, in accordance with experimental structural soot analysis, shows that in soot particles condensed structures typical of clusters of large pericondensed hydrocarbons are present whereas high-molecular mass condensed species mainly comprise oligomers of small aromatic compounds of clusters of small pericondensed hydrocarbons. (author)

  5. Simultaneous aerosol size distribution and turbidity measurements over St. Louis during METROMEX 1975

    International Nuclear Information System (INIS)

    Laulainen, N.S.; Alkezweeny, A.J.; Thorp, J.M.

    1978-01-01

    An experiment designed to measure aerosol size distributions and turbidity simultaneously over a metropolitan area is described. The particle volume size distributions measured in the city plume are found to be bimodal, with the total particle volume in the fine or submicron mode decreasing dramatically above the inversion. Aerosol extinction coefficients derived from sunphotometer optical depth measurements at four wavelengths are compared to those calculated from the measured size distributions using Mie theory with several different particle refractive indices. The accuracy of the experimental method for determining the aerosol extinction coefficient prevented any meaningful choice of the real part of particle refractive index between 1.5--1.6 and an imaginary part between 0 and -0.1i. Improvements to this type of experiment are discussed

  6. INCREASING RETURNS TO SCALE, DYNAMICS OF INDUSTRIAL STRUCTURE AND SIZE DISTRIBUTION OF FIRMS

    Institute of Scientific and Technical Information of China (English)

    Ying FAN; Menghui LI; Zengru DI

    2006-01-01

    A multi-agent model is presented to discuss the market dynamics and the size distribution of firms.The model emphasizes the effects of increasing returns to scale and gives the description of the born and death of adaptive producers. The evolution of market structure and its behavior under the technological shocks are investigated. Its dynamical results are in good agreement with some empirical "stylized facts" of industrial evolution. With the diversity of demand and adaptive growth strategies of firms, the firm size in the generalized model obeys the power-law distribution. Three factors mainly determine the competitive dynamics and the skewed size distributions of firms: 1. Self-reinforcing mechanism; 2. Adaptive firm growing strategies; 3. Demand diversity or widespread heterogeneity in the technological capabilities of firms.

  7. Development of laboratory and process sensors to monitor particle size distribution of industrial slurries

    Energy Technology Data Exchange (ETDEWEB)

    Pendse, H.P.

    1992-10-01

    In this paper we present a novel measurement technique for monitoring particle size distributions of industrial colloidal slurries based on ultrasonic spectroscopy and mathematical deconvolution. An on-line sensor prototype has been developed and tested extensively in laboratory and production settings using mineral pigment slurries. Evaluation to date shows that the sensor is capable of providing particle size distributions, without any assumptions regarding their functional form, over diameters ranging from 0.1 to 100 micrometers in slurries with particle concentrations of 10 to 50 volume percents. The newly developed on-line sensor allows one to obtain particle size distributions of commonly encountered inorganic pigment slurries under industrial processing conditions without dilution.

  8. Measurement of concentration and size distribution of radon decay products in homes using air cleaners

    International Nuclear Information System (INIS)

    Montassier, N.; Hopke, P.K.; Shi, Y.; McCallum, B.

    1992-01-01

    By removing particles, air cleaners can also eliminate radon decay products. However, by removing the particles, the open-quotes unattachedclose quotes fraction of the radon progeny is increased leading to a higher dose per unit exposure. Thus, both the concentration and size distributions of the radon decay products are needed to evaluate air cleaners. Three types of room air cleaners, NO-RAD Radon Removal System, Electronic Air Cleaner and PUREFLOW Air Treatment System were tested in a single family home in Arnprior, Ontario (Canada). Semi-continuous measurements of radon gas concentration and radon decay product activity weighted size distribution were performed in the kitchen/dining room under real living conditions. The effects of air cleaners on both the concentration and size distribution of the radon decay products were measured, and their impact on the dose of radiation given to the lung tissue were examined

  9. Effects of cement particle size distribution on performance properties of Portland cement-based materials

    Energy Technology Data Exchange (ETDEWEB)

    Bentz, D.P.; Garboczi, E.J.; Haecker, C.J.; Jensen, O.M.

    1999-10-01

    The original size, spatial distribution, and composition of Portland cement particles have a large influence on hydration kinetics, microstructure development, and ultimate properties of cement-based materials. In this paper, the effects of cement particle size distribution on a variety of performance properties are explored via computer simulation and a few experimental studies. Properties examined include setting time, heat release, capillary porosity percolation, diffusivity, chemical shrinkage, autogenous shrinkage, internal relative humidity evolution, and interfacial transition zone microstructure. The effects of flocculation and dispersion of the cement particles in the starting microstructures on resultant properties are also briefly evaluated. The computer simulations are conducted using two cement particle size distributions that bound those commonly in use today and three different water-to-cement ratios: 0.5, 0.3, and 0.246. For lower water-to-cement ratio systems, the use of coarser cements may offer equivalent or superior performance, as well as reducing production costs for the manufacturer.

  10. Characterizing property distributions of polymeric nanogels by size-exclusion chromatography.

    Science.gov (United States)

    Mourey, Thomas H; Leon, Jeffrey W; Bennett, James R; Bryan, Trevor G; Slater, Lisa A; Balke, Stephen T

    2007-03-30

    Nanogels are highly branched, swellable polymer structures with average diameters between 1 and 100nm. Size-exclusion chromatography (SEC) fractionates materials in this size range, and it is commonly used to measure nanogel molar mass distributions. For many nanogel applications, it may be more important to calculate the particle size distribution from the SEC data than it is to calculate the molar mass distribution. Other useful nanogel property distributions include particle shape, area, and volume, as well as polymer volume fraction per particle. All can be obtained from multi-detector SEC data with proper calibration and data analysis methods. This work develops the basic equations for calculating several of these differential and cumulative property distributions and applies them to SEC data from the analysis of polymeric nanogels. The methods are analogous to those used to calculate the more familiar SEC molar mass distributions. Calibration methods and characteristics of the distributions are discussed, and the effects of detector noise and mismatched concentration and molar mass sensitive detector signals are examined.

  11. Asymptotic distributions of coalescence times and ancestral lineage numbers for populations with temporally varying size.

    Science.gov (United States)

    Chen, Hua; Chen, Kun

    2013-07-01

    The distributions of coalescence times and ancestral lineage numbers play an essential role in coalescent modeling and ancestral inference. Both exact distributions of coalescence times and ancestral lineage numbers are expressed as the sum of alternating series, and the terms in the series become numerically intractable for large samples. More computationally attractive are their asymptotic distributions, which were derived in Griffiths (1984) for populations with constant size. In this article, we derive the asymptotic distributions of coalescence times and ancestral lineage numbers for populations with temporally varying size. For a sample of size n, denote by Tm the mth coalescent time, when m + 1 lineages coalesce into m lineages, and An(t) the number of ancestral lineages at time t back from the current generation. Similar to the results in Griffiths (1984), the number of ancestral lineages, An(t), and the coalescence times, Tm, are asymptotically normal, with the mean and variance of these distributions depending on the population size function, N(t). At the very early stage of the coalescent, when t → 0, the number of coalesced lineages n - An(t) follows a Poisson distribution, and as m → n, $$n\\left(n-1\\right){T}_{m}/2N\\left(0\\right)$$ follows a gamma distribution. We demonstrate the accuracy of the asymptotic approximations by comparing to both exact distributions and coalescent simulations. Several applications of the theoretical results are also shown: deriving statistics related to the properties of gene genealogies, such as the time to the most recent common ancestor (TMRCA) and the total branch length (TBL) of the genealogy, and deriving the allele frequency spectrum for large genealogies. With the advent of genomic-level sequencing data for large samples, the asymptotic distributions are expected to have wide applications in theoretical and methodological development for population genetic inference.

  12. Determination of size distribution of small DNA fragments by polyacrylamide gel electrophoresis

    International Nuclear Information System (INIS)

    Lau How Mooi

    1998-01-01

    Size distribution determination of DNA fragments can be normally determined by the agarose gel electrophoresis, including the normal DNA banding pattern analysis. However this method is only good for large DNA, such as the DNA of the size of kilo base pairs to mega base pairs range. DNA of size less than kilo base pairs is difficult to be quantified by the agarose gel method. Polyacrylamide gel electrophoresis however can be used to measure the quantity of DNA fragments of size less than kilo base pairs in length, down to less than ten base pairs. This method is good for determining the quantity of the smaller size DNA, single stranded polymers or even some proteins, if the known standards are available. In this report detail description of the method of preparing the polyacrylamide gel, and the experimental set up is discussed. Possible uses of this method, and the comparison with the standard sizes of DNA is also shown. This method is used to determine the distribution of the amount of the fragmented DNA after the Calf-thymus DNA has been exposed to various types of radiation and of different doses. The standards were used to determine the sizes of the fragmented Calf-thymus DNA. The higher the dose the higher is the amount of the smaller size DNA measured

  13. Effects of different block size distributions in pressure transient response of naturally fractured reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Montazeri, G.H. [Islamic Azad University, Mahshahr (Iran, Islamic Republic of). Dept. of Chemical and Petroleum Engineering], E-mail: montazeri_gh@yahoo.com; Tahami, S.A. [Mad Daneshgostar Tabnak Co. (MDT),Tehran (Iran, Islamic Republic of); Moradi, B.; Safari, E. [Iranian Central Oil Fields Co, Tehran (Iran, Islamic Republic of)], E-mail: morady.babak@gmail.com

    2011-07-15

    This paper presents a model for pressure transient and derivative analysis for naturally fractured reservoirs by a formulation of inter porosity flow incorporating variations in matrix block size, which is inversely related to fracture intensity. Geologically realistic Probability Density Functions (PDFs) of matrix block size, such as uniform, bimodal, linear and exponential distributions, are examined and pseudo-steady-state and transient models for inter porosity flow are assumed. The results have been physically interpreted, and, despite results obtained by other authors, it was found that the shape of pressure derivative curves for different PDFs are basically identical within some ranges of block size variability, inter porosity skin, PDFs parameters and matrix storage capacity. This tool can give an insight on the distribution of block sizes and shapes, together with other sources of information such as Logs and geological observations. (author)

  14. Sample size determination for logistic regression on a logit-normal distribution.

    Science.gov (United States)

    Kim, Seongho; Heath, Elisabeth; Heilbrun, Lance

    2017-06-01

    Although the sample size for simple logistic regression can be readily determined using currently available methods, the sample size calculation for multiple logistic regression requires some additional information, such as the coefficient of determination ([Formula: see text]) of a covariate of interest with other covariates, which is often unavailable in practice. The response variable of logistic regression follows a logit-normal distribution which can be generated from a logistic transformation of a normal distribution. Using this property of logistic regression, we propose new methods of determining the sample size for simple and multiple logistic regressions using a normal transformation of outcome measures. Simulation studies and a motivating example show several advantages of the proposed methods over the existing methods: (i) no need for [Formula: see text] for multiple logistic regression, (ii) available interim or group-sequential designs, and (iii) much smaller required sample size.

  15. Candle Soot-Driven Performance Enhancement in Pyroelectric Energy Conversion

    Science.gov (United States)

    Azad, Puneet; Singh, V. P.; Vaish, Rahul

    2018-05-01

    We observed substantial enhancement in pyroelectric output with the help of candle soot coating on the surface of lead zirconate titanate (PZT). Candle soot of varying thicknesses was coated by directly exposing pyroelectric material to the candle flame. The open-circuit pyroelectric voltage and closed-circuit pyroelectric current were recorded while applying infrared heating across the uncoated and candle soot-coated samples for different heating and cooling cycles. In comparison to the uncoated sample, the maximum open-circuit voltage improves seven times for the candle soot-coated sample and electric current increases by eight times across a resistance of 10Å. Moreover, the harvested energy is enhanced by 50 times for candle soot-coated sample. Results indicate that candle soot coating is an effective and economic method to improve infrared sensing performance of pyroelectric materials.

  16. Decoding size distribution patterns in marine and transitional water phytoplankton: from community to species level.

    Directory of Open Access Journals (Sweden)

    Leonilde Roselli

    Full Text Available Understanding the mechanisms of phytoplankton community assembly is a fundamental issue of aquatic ecology. Here, we use field data from transitional (e.g. coastal lagoons and coastal water environments to decode patterns of phytoplankton size distribution into organization and adaptive mechanisms. Transitional waters are characterized by higher resource availability and shallower well-mixed water column than coastal marine environments. Differences in physico-chemical regime between the two environments have been hypothesized to exert contrasting selective pressures on phytoplankton cell morphology (size and shape. We tested the hypothesis focusing on resource availability (nutrients and light and mixed layer depth as ecological axes that define ecological niches of phytoplankton. We report fundamental differences in size distributions of marine and freshwater diatoms, with transitional water phytoplankton significantly smaller and with higher surface to volume ratio than marine species. Here, we hypothesize that mixing condition affecting size-dependent sinking may drive phytoplankton size and shape distributions. The interplay between shallow mixed layer depth and frequent and complete mixing of transitional waters may likely increase the competitive advantage of small phytoplankton limiting large cell fitness. The nutrient regime appears to explain the size distribution within both marine and transitional water environments, while it seem does not explain the pattern observed across the two environments. In addition, difference in light availability across the two environments appear do not explain the occurrence of asymmetric size distribution at each hierarchical level. We hypothesize that such competitive equilibria and adaptive strategies in resource exploitation may drive by organism's behavior which exploring patch resources in transitional and marine phytoplankton communities.

  17. Particle size distribution of main-channel-bed sediments along the upper Mississippi River, USA

    Science.gov (United States)

    Remo, Jonathan; Heine, Ruben A.; Ickes, Brian

    2016-01-01

    In this study, we compared pre-lock-and-dam (ca. 1925) with a modern longitudinal survey of main-channel-bed sediments along a 740-km segment of the upper Mississippi River (UMR) between Davenport, IA, and Cairo, IL. This comparison was undertaken to gain a better understanding of how bed sediments are distributed longitudinally and to assess change since the completion of the UMR lock and dam navigation system and Missouri River dams (i.e., mid-twentieth century). The comparison of the historic and modern longitudinal bed sediment surveys showed similar bed sediment sizes and distributions along the study segment with the majority (> 90%) of bed sediment samples having a median diameter (D50) of fine to coarse sand. The fine tail (≤ D10) of the sediment size distributions was very fine to medium sand, and the coarse tail (≥ D90) of sediment-size distribution was coarse sand to gravel. Coarsest sediments in both surveys were found within or immediately downstream of bedrock-floored reaches. Statistical analysis revealed that the particle-size distributions between the survey samples were statistically identical, suggesting no overall difference in main-channel-bed sediment-size distribution between 1925 and present. This was a surprising result given the magnitude of river engineering undertaken along the study segment over the past ~ 90 years. The absence of substantial differences in main-channel-bed-sediment size suggests that flow competencies within the highly engineered navigation channel today are similar to conditions within the less-engineered historic channel.

  18. Effect of exhaust gas recirculation (EGR) and multiple injections on diesel soot nano-structure and reactivity

    International Nuclear Information System (INIS)

    Rohani, Behzad; Bae, Choongsik

    2017-01-01

    Highlights: • EGR reduced the nano-structural order, regardless of injection strategy. • EGR reduces both VOF and reactivity, regardless of injection strategy. • Longer dwell time between pilot and main injection increases VOF and reactivity. • With EGR, VOF and reactivity are both reduced and un-affected by injection strategy. • VOF-reactivity correlation (without causality) suggests role of surface roughness. - Abstract: The physio-chemical characteristics of soot particles are of importance with regard to performance of diesel after-treatment systems. In this study, the soot particles generated in a single-cylinder heavy-duty diesel engine are examined in terms of nanostructure, oxidative reactivity and volatile organic fraction (VOF), using thermogravimetric analysis (TGA), X-ray diffraction (XRD), Raman micro-spectroscopy, and high resolution transmission electron microscopy (HRTEM). Five different injection strategies including single injection and multiple injections with various pilot injection amounts and dwell times were tested with and without exhaust gas recirculation (EGR), while combustion phasing, engine speed, and fuel injection quantity was matched for all cases. Results indicate that for the soot produced under EGR condition, nano-structural order (indicated by crystallite size obtained from XRD and AD1/AG resulted from the Raman Analysis) can explain the soot reactivity. However, in the absence of EGR, the reactivity trend cannot be explained by the structural order. It is discussed that a possible reason can be a higher level of in-cylinder oxidation in non-EGR cases (indicated by higher level of surface functional groups) which roughens the soot surface, and enhances the oxidation by increasing the specific soot surface area. It is also found that in the absence of EGR, different injection strategies impact the soot reactivity and VOF content, which can be explained mainly through the level of charge premixed-ness and the in

  19. Determination of Crystallite Size Distribution Histogram in Nanocrystalline Anatase Powders by XRD

    Czech Academy of Sciences Publication Activity Database

    Matěj, Z.; Matějová, Lenka; Novotný, F.; Drahokoupil, Jan; Kužel, R.

    2011-01-01

    Roč. 1, - (2011), s. 87-92 [European Powder Diffraction Conference EPDIC 12 /12./. Darmstadt, 27.08.2010-30.08.2010] R&D Projects: GA AV ČR KAN400720701 Institutional research plan: CEZ:AV0Z40720504; CEZ:AV0Z10100520 Keywords : titanium dioxide * crystallite size * crystallite size distribution Subject RIV: CA - Inorganic Chemistry http://www.oldenbourg-link.com/ toc /zkpr/current

  20. Significant Climate Changes Caused by Soot Emitted From Rockets in the Stratosphere

    Science.gov (United States)

    Mills, M. J.; Ross, M.; Toohey, D. W.

    2010-12-01

    A new type of hydrocarbon rocket engine with a larger soot emission index than current kerosene rockets is expected to power a fleet of suborbital rockets for commercial and scientific purposes in coming decades. At projected launch rates, emissions from these rockets will create a persistent soot layer in the northern middle stratosphere that would disproportionally affect the Earth’s atmosphere and cryosphere. A global climate model predicts that thermal forcing in the rocket soot layer will cause significant changes in the global atmospheric circulation and distributions of ozone and temperature. Tropical ozone columns decline as much as 1%, while polar ozone columns increase by up to 6%. Polar surface temperatures rise one Kelvin regionally and polar summer sea ice fractions shrink between 5 - 15%. After 20 years of suborbital rocket fleet operation, globally averaged radiative forcing (RF) from rocket soot exceeds the RF from rocket CO_{2} by six orders of magnitude, but remains small, comparable to the global RF from aviation. The response of the climate system is surprising given the small forcing, and should be investigated further with different climate models.

  1. One size does not fit all: The impact of primary vaccine container size on vaccine distribution and delivery.

    Science.gov (United States)

    Haidari, Leila A; Wahl, Brian; Brown, Shawn T; Privor-Dumm, Lois; Wallman-Stokes, Cecily; Gorham, Katie; Connor, Diana L; Wateska, Angela R; Schreiber, Benjamin; Dicko, Hamadou; Jaillard, Philippe; Avella, Melanie; Lee, Bruce Y

    2015-06-22

    While the size and type of a vaccine container (i.e., primary container) can have many implications on the safety and convenience of a vaccination session, another important but potentially overlooked consideration is how the design of the primary container may affect the distribution of the vaccine, its resulting cost, and whether the vial is ultimately opened. Using our HERMES software platform, we developed a simulation model of the World Health Organization Expanded Program on Immunization supply chain for the Republic of Benin and used the model to explore the effects of different primary containers for various vaccine antigens. Replacing vaccines with presentations containing fewer doses per vial reduced vaccine availability (proportion of people arriving for vaccines who are successfully immunized) by as much as 13% (from 73% at baseline) and raised logistics costs by up to $0.06 per dose administered (from $0.25 at baseline) due to increased bottlenecks, while reducing total costs by as much as $0.15 per dose administered (from $2.52 at baseline) due to lower open vial wastage. Primary containers with a greater number of doses per vial each improved vaccine availability by 19% and reduced logistics costs by $0.05 per dose administered, while reducing the total costs by up to $0.25 per dose administered. Changes in supply chain performance were more extreme in departments with greater constraints. Implementing a vial opening threshold reversed the direction of many of these effects. Our results show that one size may not fit all when choosing a primary vaccine container. Rather, the choice depends on characteristics of the vaccine, the vaccine supply chain, immunization session size, and goals of decision makers. In fact, the optimal vial size may vary among locations within a country. Simulation modeling can help identify tailored approaches to improve availability and efficiency. Copyright © 2015 Elsevier Ltd. All rights reserved.

  2. Forecasting grain size distribution of coal cut by a shearer loader

    Energy Technology Data Exchange (ETDEWEB)

    Sikora, W; Chodura, J; Siwiec, J

    1983-02-01

    Analyzed are effects of shearer loader design on grain size distribution of coal, particularly on proportion of the finest size group and proportion of largest coal grains. The method developed by the IGD im. A.A. Skochinski Institute in Moscow is used. Effects of cutting tool design and mechanical coal properties are analyzed. Of the evaluated factors, two are of decisive importance: thickness of the coal chip cut by a cutting tool and coefficient of coal disintegration which characterizes coal behavior during cutting. Grain size distribution is also influenced by cutting tool geometry. Two elements of cutting tool design are of major importance: dimensions of the cutting edge and angle of attack. Effects of cutting tool design and coal mechanical properties on grain size distribution are shown in 12 diagrams. Using the forecasting method developed by the IGD im. A.A. Skochinski Institute in Moscow grain size distribution of coal cut by three shearer loaders is calculated: the KWB-3RDU with a drum 1600 mm in diameter, the KWB-6W with a drum 2500 mm in diameter, and a shearer loader being developed with a 1550 mm drum. The results of comparative evaluations are shown in two tables. 5 references.

  3. Inversion of multiwavelength Raman lidar data for retrieval of bimodal aerosol size distribution

    Science.gov (United States)

    Veselovskii, Igor; Kolgotin, Alexei; Griaznov, Vadim; Müller, Detlef; Franke, Kathleen; Whiteman, David N.

    2004-02-01

    We report on the feasibility of deriving microphysical parameters of bimodal particle size distributions from Mie-Raman lidar based on a triple Nd:YAG laser. Such an instrument provides backscatter coefficients at 355, 532, and 1064 nm and extinction coefficients at 355 and 532 nm. The inversion method employed is Tikhonov's inversion with regularization. Special attention has been paid to extend the particle size range for which this inversion scheme works to ~10 μm, which makes this algorithm applicable to large particles, e.g., investigations concerning the hygroscopic growth of aerosols. Simulations showed that surface area, volume concentration, and effective radius are derived to an accuracy of ~50% for a variety of bimodal particle size distributions. For particle size distributions with an effective radius of rims along which anthropogenic pollution mixes with marine aerosols. Measurement cases obtained from the Institute for Tropospheric Research six-wavelength aerosol lidar observations during the Indian Ocean Experiment were used to test the capabilities of the algorithm for experimental data sets. A benchmark test was attempted for the case representing anthropogenic aerosols between a broken cloud deck. A strong contribution of particle volume in the coarse mode of the particle size distribution was found.

  4. A comparative study of size distribution of nanoparticles generated by laser ablation of graphite and tungsten

    International Nuclear Information System (INIS)

    Marton, Zs.; Landstroem, L.; Boman, M.; Heszler, P.

    2003-01-01

    Nanoparticles (NPs) were generated by ArF excimer laser ablation of graphite and tungsten targets in N 2 ambient at atmospheric pressure. The size distribution of the particles was monitored in situ by a scanning mobility particle sizer (SMPS) system, based on differential mobility analyser. The experimental conditions made possible to record the size distributions in the 7-133-nm diameter range and results are presented for different laser fluences, repetition rates and ablated areas, respectively. Material analysis was performed by photoelectron spectroscopy (XPS), Raman spectroscopy, X ray diffraction and SEM

  5. On the size distribution of cities: an economic interpretation of the Pareto coefficient.

    Science.gov (United States)

    Suh, S H

    1987-01-01

    "Both the hierarchy and the stochastic models of size distribution of cities are analyzed in order to explain the Pareto coefficient by economic variables. In hierarchy models, it is found that the rate of variation in the productivity of cities and that in the probability of emergence of cities can explain the Pareto coefficient. In stochastic models, the productivity of cities is found to explain the Pareto coefficient. New city-size distribution functions, in which the Pareto coefficient is decomposed by economic variables, are estimated." excerpt

  6. Firm size and productivity. Evidence from the electricity distribution industry in Brazil

    International Nuclear Information System (INIS)

    Tovar, Beatriz; Javier Ramos-Real, Francisco; De Almeida, Edmar Fagundes

    2011-01-01

    In this paper we apply Stochastic Frontier Analysis through a distance function to investigate the impact of firm size on productivity development in electricity distribution. We use a sample of seventeen Brazilian firms from 1998 to 2005 and decompose productivity into technical efficiency, scale efficiency and technical change. Moreover, a further step is to decompose the technical change measurement into several components. The results indicate that firm size is important for industry's productivity, and therefore a key aspect to consider when making decisions that affect the market structure in the electricity distribution industry. (author)

  7. Retrieval of size distribution for urban aerosols using multispectral optical data

    International Nuclear Information System (INIS)

    Kocifaj, M; Horvath, H

    2005-01-01

    We are dealing with retrieval of aerosol size distribution using multispectral extinction data collected in highly industrialized urban region. Especially, a role of the particle morphology is in the focus of this work. As well known, at present, still many retrieval algorithms are based on simple Lorenz-Mie's theory applicable for perfectly spherical and homogeneous particles, because that approach is fast and can handle the whole size distribution of particles. However, the solid-phase aerosols never render simple geometries, and rather than being spherical or spheroidal they are quite irregular. It is shown, that identification of the modal radius a M of both, the size distribution f(a) and the distribution of geometrical cross section s(a) of aerosol particles is not significantly influenced by the particle's morphology in case the aspect ratio is smaller than 2 and the particles are randomly oriented in the atmospheric environment. On the other hand, the amount of medium-sized particles (radius of which is larger than the modal radius) can be underestimated if distribution of non-spherical grains is substituted by system of volume equivalent spheres. Retrieved volume content of fine aerosols (as characterized by PM 2.5 and PM 1.0 ) can be potentially affected by inappropriate assumption on the particle shape

  8. Estimating the transmission potential of supercritical processes based on the final size distribution of minor outbreaks.

    Science.gov (United States)

    Nishiura, Hiroshi; Yan, Ping; Sleeman, Candace K; Mode, Charles J

    2012-02-07

    Use of the final size distribution of minor outbreaks for the estimation of the reproduction numbers of supercritical epidemic processes has yet to be considered. We used a branching process model to derive the final size distribution of minor outbreaks, assuming a reproduction number above unity, and applying the method to final size data for pneumonic plague. Pneumonic plague is a rare disease with only one documented major epidemic in a spatially limited setting. Because the final size distribution of a minor outbreak needs to be normalized by the probability of extinction, we assume that the dispersion parameter (k) of the negative-binomial offspring distribution is known, and examine the sensitivity of the reproduction number to variation in dispersion. Assuming a geometric offspring distribution with k=1, the reproduction number was estimated at 1.16 (95% confidence interval: 0.97-1.38). When less dispersed with k=2, the maximum likelihood estimate of the reproduction number was 1.14. These estimates agreed with those published from transmission network analysis, indicating that the human-to-human transmission potential of the pneumonic plague is not very high. Given only minor outbreaks, transmission potential is not sufficiently assessed by directly counting the number of offspring. Since the absence of a major epidemic does not guarantee a subcritical process, the proposed method allows us to conservatively regard epidemic data from minor outbreaks as supercritical, and yield estimates of threshold values above unity. Crown Copyright © 2011. Published by Elsevier Ltd. All rights reserved.

  9. The particle size distribution of fragmented melt debris from molten fuel coolant interactions

    International Nuclear Information System (INIS)

    Fletcher, D.F.

    1984-04-01

    Results are presented of a study of the types of statistical distributions which arise when examining debris from Molten Fuel Coolant Interactions. The lognormal probability distribution and the modifications of this distribution which result from the mixing of two distributions or the removal of some debris are described. Methods of fitting these distributions to real data are detailed. A two stage fragmentation model has been developed in an attempt to distinguish between the debris produced by coarse mixing and fine scale fragmentation. However, attempts to fit this model to real data have proved unsuccessful. It was found that the debris particle size distributions from experiments at Winfrith with thermite generated uranium dioxide/molybdenum melts were Upper Limit Lognormal. (U.K.)

  10. Morphological transformation of soot: investigation of microphysical processes during the condensation of sulphuric acid and limonene ozonolysis products vapours

    Science.gov (United States)

    Pathak, R. K. P.; Pei, X.; Hallquist, M.; Pagels, J. H.

    2017-12-01

    Morphological transformation of soot particle by condensation of low volatility materials on it is a dominant atmospheric process with serious implications for its optical and hygroscopic properties, and atmospheric lifetime. In this study, the morphological transformation of soot agglomerate under the influence of condensation of vapours of sulphuric acid, and/or limonene ozonolysis products were investigated systematically using a Differential Mobility Analyser-Aerosol Particle Mass Analyser (DMA-APM) and the Tandem DMA techniques integrated with a laminar flow-tube system. We discovered that the morphology transformation of soot in general was a sequence of two-step process, i.e. (i) filling of void space within soot agglomerate; (ii) growth of particle diameter. These two steps followed and complimented each other. In the very beginning the filling was the dominant process followed by growth until it led to the accumulation of enough material that in turn exerted surface forces that eventually facilitated the further filling. The filling of void space was constrained by the initial morphology of fresh soot and the nature and amount of the material condensed. This process continued in several sequential steps until all void space within the soot agglomerate was filled completely and then growth of a spherical particle continued as long as mass was condensed on it. In this study, we developed a framework to quantify the microphysical transformation of soot upon the condensation of various materials. The framework utilized experimental data and hypothesis of ideal sphere growth and filling of voids to quantify the distribution of condensed materials in these two processes complimenting each other. Using this framework, we have quantified the percentage of material that went into processes of particle growth and void filling at each step. Using the same framework, we further estimated the fraction of internal voids and open voids and used this information to derive

  11. [Characteristics and its forming mechanism on grain size distribution of suspended matter at Changjiang Estuary].

    Science.gov (United States)

    Pang, Chong-guang; Yu, Wei; Yang, Yang

    2010-03-01

    In July of 2008, under the natural condition of sea water, the Laser in-situ scattering and transmissometry (LISST-100X Type C) was used to measure grain size distribution spectrum and volume concentration of total suspended matter in the sea water, including flocs at different layers of 24 sampling stations at Changjiang Estuary and its adjacent sea. The characteristics and its forming mechanism on grain size distribution of total suspended matter were analyzed based on the observation data of LISST-100X Type C, and combining with the temperature, salinity and turbidity of sea water, simultaneously observed by Alec AAQ1183. The observation data showed that the average median grain size of total suspended matter was about 4.69 phi in the whole measured sea area, and the characteristics of grain size distribution was relatively poor sorted, wide kurtosis, and basically symmetrical. The conclusion could be drawn that vertically average volume concentration decreased with the distance from the coastline, while median grain size had an increase trend with the distance, for example, at 31.0 degrees N section, the depth-average median grain size had been increased from 11 microm up to 60 microm. With the increasing of distance from the coast, the concentration of fine suspended sediment reduced distinctly, nevertheless some relatively big organic matter or big flocs appeared in quantity, so its grain size would rise. The observation data indicated that the effective density was ranged from 246 kg/m3 to 1334 kg/m, with average was 613 kg/m3. When the concentration of total suspended matter was relatively high, median grain size of total suspended matter increased with the water depth, while effective density decreased with the depth, because of the faster settling velocity and less effective density of large flocs that of small flocs. As for station 37 and 44, their correlation coefficients between effective density and median grain size were larger than 0.9.

  12. The in-situ cometary particulate size distribution measured for one comet: P/Halley

    International Nuclear Information System (INIS)

    McDonnell, J.A.M.; Pankiewicz, G.S.

    1989-01-01

    The close approach of Giotto to comet Halley during its 1986 apparition offered an opportunity to study the particulate mass distribution to masses of up to one gram. Data acquired by the front end channels of the highly sensitive mass spectrometer PIA and the dust shield detector system, DIDSY, provide definition to the detected distribution as close as 1000 km to the nucleus. Dynamic motion of the particulates after emission leads to a spatial differentiation affecting the size distribution in several forms: (1) ejecta velocity dispersion; (2) radiation pressure; (3) varying heliocentric distance; and (4) anisotropic nucleus emission. Transformation of the in-situ distribution from PIA and DIDSY weighted heavily by the near-nucleus fluxes leads to a presumed nucleus distribution. The data lead to a puzzling distribution at large masses, not readily explained in an otherwise monotonous power law distribution. Although temporal changes in nucleus activity could and do modify the in-situ size distribution, such an explanation is not wholly possible, because the same form is observed at differing locations in the coma where the time of flight from the nucleus greatly varies. Thus neither a general change in comet activity nor spatial variations lead to a satisfactory explanation

  13. Thermal induced carrier's transfer in bimodal size distribution InAs/GaAs quantum dots

    Science.gov (United States)

    Ilahi, B.; Alshehri, K.; Madhar, N. A.; Sfaxi, L.; Maaref, H.

    2018-06-01

    This work reports on the investigation of the thermal induced carriers' transfer mechanism in vertically stacked bimodal size distribution InAs/GaAs quantum dots (QD). A model treating the QD as a localized states ensemble (LSE) has been employed to fit the atypical temperature dependence of the photoluminescence (PL) emission energies and linewidth. The results suggest that thermally activated carriers transfer within the large size QD family occurs through the neighboring smaller size QD as an intermediate channel before direct carriers redistribution. The obtained activation energy suggests also the possible contribution of the wetting layer (WL) continuum states as a second mediator channel for carriers transfer.

  14. Asteroid size distributions for the main belt and for asteroid families

    Science.gov (United States)

    Kazantzev, A.; Kazantzeva, L.

    2017-12-01

    The asteroid-size distribution for he Eos family was constructed. The WISE database containing the albedo p and the size D of over 80,000 asteroids was used. The b parameter of the power-law dependence has a minimum at some average values of the asteroid size of the family. A similar dependence b(D) exists for the whole asteroid belt. An assumption on the possible similarity of the formation mechanisms of the asteroid belt as a whole and separate families is made.

  15. Family size, the physical environment, and socioeconomic effects across the stature distribution.

    Science.gov (United States)

    Carson, Scott Alan

    2012-04-01

    A neglected area in historical stature studies is the relationship between stature and family size. Using robust statistics and a large 19th century data set, this study documents a positive relationship between stature and family size across the stature distribution. The relationship between material inequality and health is the subject of considerable debate, and there was a positive relationship between stature and wealth and an inverse relationship between stature and material inequality. After controlling for family size and wealth variables, the paper reports a positive relationship between the physical environment and stature. Copyright © 2012 Elsevier GmbH. All rights reserved.

  16. Kinetics of cesium lead halide perovskite nanoparticle growth; focusing and de-focusing of size distribution

    Science.gov (United States)

    Koolyk, Miriam; Amgar, Daniel; Aharon, Sigalit; Etgar, Lioz

    2016-03-01

    In this work we study the kinetics of cesium lead halide perovskite nanoparticle (NP) growth; the focusing and de-focusing of the NP size distribution. Cesium lead halide perovskite NPs are considered to be attractive materials for optoelectronic applications. Understanding the kinetics of the formation of these all-inorganic perovskite NPs is critical for reproducibly and reliably generating large amounts of uniformly sized NPs. Here we investigate different growth durations for CsPbI3 and CsPbBr3 NPs, tracking their growth by high-resolution transmission electron microscopy and size distribution analysis. As a result, we are able to provide a detailed model for the kinetics of their growth. It was observed that the CsPbI3 NPs exhibit focusing of the size distribution in the first 20 seconds of growth, followed by de-focusing over longer growth durations, while the CsPbBr3 NPs show de-focusing of the size distribution starting from the beginning of the growth. The monomer concentration is depleted faster in the case of CsPbBr3 than in the case of CsPbI3, due to faster diffusion of the monomers, which increases the critical radius and results in de-focusing of the population. Accordingly, focusing is not observed within 40 seconds of growth in the case of CsPbBr3. This study provides important knowledge on how to achieve a narrow size distribution of cesium lead halide perovskite NPs when generating large amounts of these promising, highly luminescent NPs.In this work we study the kinetics of cesium lead halide perovskite nanoparticle (NP) growth; the focusing and de-focusing of the NP size distribution. Cesium lead halide perovskite NPs are considered to be attractive materials for optoelectronic applications. Understanding the kinetics of the formation of these all-inorganic perovskite NPs is critical for reproducibly and reliably generating large amounts of uniformly sized NPs. Here we investigate different growth durations for CsPbI3 and CsPbBr3 NPs, tracking

  17. Soot Formation in Freely-Propagating Laminar Premixed Flames

    Science.gov (United States)

    Lin, K.-C.; Hassan, M. I.; Faeth, G. M.

    1997-01-01

    Soot formation within hydrocarbon-fueled flames is an important unresolved problem of combustion science. Thus, the present study is considering soot formation in freely-propagating laminar premixed flames, exploiting the microgravity environment to simplify measurements at the high-pressure conditions of interest for many practical applications. The findings of the investigation are relevant to reducing emissions of soot and continuum radiation from combustion processes, to improving terrestrial and spacecraft fire safety, and to developing methods of computational combustion, among others. Laminar premixed flames are attractive for studying soot formation because they are simple one-dimensional flows that are computationally tractable for detailed numerical simulations. Nevertheless, studying soot-containing burner-stabilized laminar premixed flames is problematical: spatial resolution and residence times are limited at the pressures of interest for practical applications, flame structure is sensitive to minor burner construction details so that experimental reproducibility is not very good, consistent burner behavior over the lengthy test programs needed to measure soot formation properties is hard to achieve, and burners have poor durability. Fortunately, many of these problems are mitigated for soot-containing, freely-propagating laminar premixed flames. The present investigation seeks to extend work in this laboratory for various soot processes in flames by observing soot formation in freely-propagating laminar premixed flames. Measurements are being made at both Normal Gravity (NG) and MicroGravity (MG), using a short-drop free-fall facility to provide MG conditions.

  18. Comparison of photon correlation spectroscopy with photosedimentation analysis for the determination of aqueous colloid size distributions

    Science.gov (United States)

    Rees, Terry F.

    1990-01-01

    Colloidal materials, dispersed phases with dimensions between 0.001 and 1 μm, are potential transport media for a variety of contaminants in surface and ground water. Characterization of these colloids, and identification of the parameters that control their movement, are necessary before transport simulations can be attempted. Two techniques that can be used to determine the particle-size distribution of colloidal materials suspended in natural waters are compared. Photon correlation Spectroscopy (PCS) utilizes the Doppler frequency shift of photons scattered off particles undergoing Brownian motion to determine the size of colloids suspended in water. Photosedimentation analysis (PSA) measures the time-dependent change in optical density of a suspension of colloidal particles undergoing centrifugation. A description of both techniques, important underlying assumptions, and limitations are given. Results for a series of river water samples show that the colloid-size distribution means are statistically identical as determined by both techniques. This also is true of the mass median diameter (MMD), even though MMD values determined by PSA are consistently smaller than those determined by PCS. Because of this small negative bias, the skew parameters for the distributions are generally smaller for the PCS-determined distributions than for the PSA-determined distributions. Smaller polydispersity indices for the distributions are also determined by PCS.

  19. Strain rate effect on sooting characteristics in laminar counterflow diffusion flames

    KAUST Repository

    Wang, Yu; Chung, Suk-Ho

    2016-01-01

    The effects of strain rate, oxygen enrichment and fuel type on the sooting characteristics of counterflow diffusion flames were studied. The sooting structures and relative PAH concentrations were measured with laser diagnostics. Detailed soot

  20. Soot blowing methods and soot steam consumption in Swedish recovery boilers; Sotningsmetoder och sotaangfoerbrukning i svenska sodapannor

    Energy Technology Data Exchange (ETDEWEB)

    Svedin, Kristoffer; Wallin, Erik; Ahlroth, Mikael

    2008-09-15

    high availability. Furthermore the conditions vary in between and no general conclusions can be drawn. There is a correlation between recovery boilers with availability problems and the amount of sootblowing. However, it is clear that in these cases a larger amount of sootblowing won't be enough to reach good availability. The general conclusion that can be made is that the recovery boiler design, size and load influence the accessibility more than the differences in soot blowing. The authors' ambition to elucidate differences between intelligent and conventional sootblowing systems has been hard to realize. The reason is explained above. A more effective method would be to choose a less number of recovery boilers and study the operational conditions before and after the installation of new sootblowing equipment. The selection could be made among the participating mills, where the sootblowing sequences and the intelligent systems were investigated in detail. In the cases were the sequences are not effective they could be rewritten and followed up within the scope of the project

  1. Finite-size analysis of continuous-variable measurement-device-independent quantum key distribution

    Science.gov (United States)

    Zhang, Xueying; Zhang, Yichen; Zhao, Yijia; Wang, Xiangyu; Yu, Song; Guo, Hong

    2017-10-01

    We study the impact of the finite-size effect on the continuous-variable measurement-device-independent quantum key distribution (CV-MDI QKD) protocol, mainly considering the finite-size effect on the parameter estimation procedure. The central-limit theorem and maximum likelihood estimation theorem are used to estimate the parameters. We also analyze the relationship between the number of exchanged signals and the optimal modulation variance in the protocol. It is proved that when Charlie's position is close to Bob, the CV-MDI QKD protocol has the farthest transmission distance in the finite-size scenario. Finally, we discuss the impact of finite-size effects related to the practical detection in the CV-MDI QKD protocol. The overall results indicate that the finite-size effect has a great influence on the secret-key rate of the CV-MDI QKD protocol and should not be ignored.

  2. A statistical analysis of North East Atlantic (submicron aerosol size distributions

    Directory of Open Access Journals (Sweden)

    M. Dall'Osto

    2011-12-01

    Full Text Available The Global Atmospheric Watch research station at Mace Head (Ireland offers the possibility to sample some of the cleanest air masses being imported into Europe as well as some of the most polluted being exported out of Europe. We present a statistical cluster analysis of the physical characteristics of aerosol size distributions in air ranging from the cleanest to the most polluted for the year 2008. Data coverage achieved was 75% throughout the year. By applying the Hartigan-Wong k-Means method, 12 clusters were identified as systematically occurring. These 12 clusters could be further combined into 4 categories with similar characteristics, namely: coastal nucleation category (occurring 21.3 % of the time, open ocean nucleation category (occurring 32.6% of the time, background clean marine category (occurring 26.1% of the time and anthropogenic category (occurring 20% of the time aerosol size distributions. The coastal nucleation category is characterised by a clear and dominant nucleation mode at sizes less than 10 nm while the open ocean nucleation category is characterised by a dominant Aitken mode between 15 nm and 50 nm. The background clean marine aerosol exhibited a clear bimodality in the sub-micron size distribution, with although it should be noted that either the Aitken mode or the accumulation mode may dominate the number concentration. However, peculiar background clean marine size distributions with coarser accumulation modes are also observed during winter months. By contrast, the continentally-influenced size distributions are generally more monomodal (accumulation, albeit with traces of bimodality. The open ocean category occurs more often during May, June and July, corresponding with the North East (NE Atlantic high biological period. Combined with the relatively high percentage frequency of occurrence (32.6%, this suggests that the marine biota is an important source of new nano aerosol particles in NE Atlantic Air.

  3. Passive acoustic measurement of bedload grain size distribution using self-generated noise

    Directory of Open Access Journals (Sweden)

    T. Petrut

    2018-01-01

    Full Text Available Monitoring sediment transport processes in rivers is of particular interest to engineers and scientists to assess the stability of rivers and hydraulic structures. Various methods for sediment transport process description were proposed using conventional or surrogate measurement techniques. This paper addresses the topic of the passive acoustic monitoring of bedload transport in rivers and especially the estimation of the bedload grain size distribution from self-generated noise. It discusses the feasibility of linking the acoustic signal spectrum shape to bedload grain sizes involved in elastic impacts with the river bed treated as a massive slab. Bedload grain size distribution is estimated by a regularized algebraic inversion scheme fed with the power spectrum density of river noise estimated from one hydrophone. The inversion methodology relies upon a physical model that predicts the acoustic field generated by the collision between rigid bodies. Here we proposed an analytic model of the acoustic energy spectrum generated by the impacts between a sphere and a slab. The proposed model computes the power spectral density of bedload noise using a linear system of analytic energy spectra weighted by the grain size distribution. The algebraic system of equations is then solved by least square optimization and solution regularization methods. The result of inversion leads directly to the estimation of the bedload grain size distribution. The inversion method was applied to real acoustic data from passive acoustics experiments realized on the Isère River, in France. The inversion of in situ measured spectra reveals good estimations of grain size distribution, fairly close to what was estimated by physical sampling instruments. These results illustrate the potential of the hydrophone technique to be used as a standalone method that could ensure high spatial and temporal resolution measurements for sediment transport in rivers.

  4. Passive acoustic measurement of bedload grain size distribution using self-generated noise

    Science.gov (United States)

    Petrut, Teodor; Geay, Thomas; Gervaise, Cédric; Belleudy, Philippe; Zanker, Sebastien

    2018-01-01

    Monitoring sediment transport processes in rivers is of particular interest to engineers and scientists to assess the stability of rivers and hydraulic structures. Various methods for sediment transport process description were proposed using conventional or surrogate measurement techniques. This paper addresses the topic of the passive acoustic monitoring of bedload transport in rivers and especially the estimation of the bedload grain size distribution from self-generated noise. It discusses the feasibility of linking the acoustic signal spectrum shape to bedload grain sizes involved in elastic impacts with the river bed treated as a massive slab. Bedload grain size distribution is estimated by a regularized algebraic inversion scheme fed with the power spectrum density of river noise estimated from one hydrophone. The inversion methodology relies upon a physical model that predicts the acoustic field generated by the collision between rigid bodies. Here we proposed an analytic model of the acoustic energy spectrum generated by the impacts between a sphere and a slab. The proposed model computes the power spectral density of bedload noise using a linear system of analytic energy spectra weighted by the grain size distribution. The algebraic system of equations is then solved by least square optimization and solution regularization methods. The result of inversion leads directly to the estimation of the bedload grain size distribution. The inversion method was applied to real acoustic data from passive acoustics experiments realized on the Isère River, in France. The inversion of in situ measured spectra reveals good estimations of grain size distribution, fairly close to what was estimated by physical sampling instruments. These results illustrate the potential of the hydrophone technique to be used as a standalone method that could ensure high spatial and temporal resolution measurements for sediment transport in rivers.

  5. Effect of particle size and distribution of the sizing agent on the carbon fibers surface and interfacial shear strength (IFSS) of its composites

    International Nuclear Information System (INIS)

    Zhang, R.L.; Liu, Y.; Huang, Y.D.; Liu, L.

    2013-01-01

    Effect of particle size and distribution of the sizing agent on the performance of carbon fiber and carbon fiber composites has been investigated. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to characterize carbon fiber surface topographies. At the same time, the single fiber strength and Weibull distribution were also studied in order to investigate the effect of coatings on the fibers. The interfacial shear strength and hygrothermal aging of the carbon fiber/epoxy resin composites were also measured. The results indicated that the particle size and distribution is important for improving the surface of carbon fibers and its composites performance. Different particle size and distribution of sizing agent has different contribution to the wetting performance of carbon fibers. The fibers sized with P-2 had higher value of IFSS and better hygrothermal aging resistant properties.

  6. Scale economies and optimal size in the Swiss gas distribution sector

    International Nuclear Information System (INIS)

    Alaeifar, Mozhgan; Farsi, Mehdi; Filippini, Massimo

    2014-01-01

    This paper studies the cost structure of Swiss gas distribution utilities. Several econometric models are applied to a panel of 26 companies over 1996–2000. Our main objective is to estimate the optimal size and scale economies of the industry and to study their possible variation with respect to network characteristics. The results indicate the presence of unexploited scale economies. However, very large companies in the sample and companies with a disproportionate mixture of output and density present an exception. Furthermore, the estimated optimal size for majority of companies in the sample has shown a value far greater than the actual size, suggesting remarkable efficiency gains by reorganization of the industry. The results also highlight the effect of customer density on optimal size. Networks with higher density or greater complexity have a lower optimal size. - highlights: • Presence of unexploited scale economies for small and medium sized companies. • Scale economies vary considerably with customer density. • Higher density or greater complexity is associated with lower optimal size. • Optimal size varies across the companies through unobserved heterogeneity. • Firms with low density can gain more from expanding firm size

  7. Particle size distribution of mainstream tobacco and marijuana smoke. Analysis using the electrical aerosol analyzer.

    Science.gov (United States)

    Anderson, P J; Wilson, J D; Hiller, F C

    1989-07-01

    Accurate measurement of cigarette smoke particle size distribution is important for estimation of lung deposition. Most prior investigators have reported a mass median diameter (MMD) in the size range of 0.3 to 0.5 micron, with a small geometric standard deviation (GSD), indicating few ultrafine (less than 0.1 micron) particles. A few studies, however, have suggested the presence of ultrafine particles by reporting a smaller count median diameter (CMD). Part of this disparity may be due tot he inefficiency to previous sizing methods in measuring ultrafine size range, to evaluate size distribution of smoke from standard research cigarettes, commercial filter cigarettes, and from marijuana cigarettes with different delta 9-tetrahydrocannabinol contents. Four 35-cm3, 2-s puffs were generated at 60-s intervals, rapidly diluted, and passed through a charge neutralizer and into a 240-L chamber. Size distribution for six cigarettes of each type was measured, CMD and GSD were determined from a computer-generated log probability plot, and MMD was calculated. The size distribution parameters obtained were similar for all cigarettes tested, with an average CMD of 0.1 micron, a MMD of 0.38 micron, and a GSD of 2.0. The MMD found using the EAA is similar to that previously reported, but the CMD is distinctly smaller and the GSD larger, indicating the presence of many more ultrafine particles. These results may explain the disparity of CMD values found in existing data. Ultrafine particles are of toxicologic importance because their respiratory tract deposition is significantly higher than for particles 0.3 to 0.5 micron and because their large surface area facilitates adsorption and delivery of potentially toxic gases to the lung.

  8. Spatial arrangement and size distribution of normal faults, Buckskin detachment upper plate, Western Arizona

    Science.gov (United States)

    Laubach, S. E.; Hundley, T. H.; Hooker, J. N.; Marrett, R. A.

    2018-03-01

    Fault arrays typically include a wide range of fault sizes and those faults may be randomly located, clustered together, or regularly or periodically located in a rock volume. Here, we investigate size distribution and spatial arrangement of normal faults using rigorous size-scaling methods and normalized correlation count (NCC). Outcrop data from Miocene sedimentary rocks in the immediate upper plate of the regional Buckskin detachment-low angle normal-fault, have differing patterns of spatial arrangement as a function of displacement (offset). Using lower size-thresholds of 1, 0.1, 0.01, and 0.001 m, displacements range over 5 orders of magnitude and have power-law frequency distributions spanning ∼ four orders of magnitude from less than 0.001 m to more than 100 m, with exponents of -0.6 and -0.9. The largest faults with >1 m displacement have a shallower size-distribution slope and regular spacing of about 20 m. In contrast, smaller faults have steep size-distribution slopes and irregular spacing, with NCC plateau patterns indicating imposed clustering. Cluster widths are 15 m for the 0.1-m threshold, 14 m for 0.01-m, and 1 m for 0.001-m displacement threshold faults. Results demonstrate normalized correlation count effectively characterizes the spatial arrangement patterns of these faults. Our example from a high-strain fault pattern above a detachment is compatible with size and spatial organization that was influenced primarily by boundary conditions such as fault shape, mechanical unit thickness and internal stratigraphy on a range of scales rather than purely by interaction among faults during their propagation.

  9. Effect of lubricant oil additive on size distribution, morphology, and nanostructure of diesel particulate matter

    International Nuclear Information System (INIS)

    Wang, Yuesen; Liang, Xingyu; Shu, Gequn; Wang, Xiangxiang; Sun, Xiuxiu; Liu, Changwen

    2014-01-01

    Highlights: • Pour point depressant (PPD) has great impact on particulate matters. • The number of nanoparticles increases sharply after PPD is added. • Ambiguous boundaries can be found when the PPD additive was added. • PPD changes the size distribution into bimodal logarithmic. • Three nanostructure parameters are changed greatly by PPD. - Abstract: Effects of lubricant oil additive on the characterization of particles from a four-cylinder turbocharged diesel engine were investigated. Neat diesel and blended fuel containing oil pour point depressant (PPD) additive were chosen as the test fuels. Effects of different fuels on size distribution, morphology, and nanostructure of the diesel particles were studied. Transmission electron microscopy (TEM) and high resolution TEM (HRTEM) were employed to study the morphology and nanostructure parameters. Particle size distribution was measured by fast particulate spectrometer (DMS 500). According to the experimental results, distribution of the primary particles size of the two fuels conforms to Gaussian distribution, whereas the mean diameter of blended fuel is larger than that of neat diesel at 1200 rpm, which is contrarily smaller at 2400 rpm. Besides, fractal dimension (D f ) of aggregates increases close to 2 (D f = 1.991), indicating that the structure became compacter with adding PPD. As to the nanostructure parameters of the blended fuel particles, the layer fringe length decreases from 1.191 nm to 1.064 nm, while both the separation distance and tortuosity increase. The changes in the nanostructure parameters indicate that the particles are more ordered and compressed with burning pure diesel. Results of blended fuel from DMS show that more particles, particularly nucleation mode particles, were discharged. In addition, its size distribution become bimodal logarithmic at 2400 rpm. All these results can provide new information of the effects of oil PPD additive on the formation and characterization of

  10. Aerosol number size distributions over a coastal semi urban location: Seasonal changes and ultrafine particle bursts

    International Nuclear Information System (INIS)

    Babu, S. Suresh; Kompalli, Sobhan Kumar; Moorthy, K. Krishna

    2016-01-01

    Number-size distribution is one of the important microphysical properties of atmospheric aerosols that influence aerosol life cycle, aerosol-radiation interaction as well as aerosol-cloud interactions. Making use of one-yearlong measurements of aerosol particle number-size distributions (PNSD) over a broad size spectrum (~ 15–15,000 nm) from a tropical coastal semi-urban location-Trivandrum (Thiruvananthapuram), the size characteristics, their seasonality and response to mesoscale and synoptic scale meteorology are examined. While the accumulation mode contributed mostly to the annual mean concentration, ultrafine particles (having diameter < 100 nm) contributed as much as 45% to the total concentration, and thus constitute a strong reservoir, that would add to the larger particles through size transformation. The size distributions were, in general, bimodal with well-defined modes in the accumulation and coarse regimes, with mode diameters lying in the range 141 to 167 nm and 1150 to 1760 nm respectively, in different seasons. Despite the contribution of the coarse sized particles to the total number concentration being meager, they contributed significantly to the surface area and volume, especially during transport of marine air mass highlighting the role of synoptic air mass changes. Significant diurnal variation occurred in the number concentrations, geometric mean diameters, which is mostly attributed to the dynamics of the local coastal atmospheric boundary layer and the effect of mesoscale land/sea breeze circulation. Bursts of ultrafine particles (UFP) occurred quite frequently, apparently during periods of land-sea breeze transitions, caused by the strong mixing of precursor-rich urban air mass with the cleaner marine air mass; the resulting turbulence along with boundary layer dynamics aiding the nucleation. These ex-situ particles were observed at the surface due to the transport associated with boundary layer dynamics. The particle growth rates from

  11. Aerosol number size distributions over a coastal semi urban location: Seasonal changes and ultrafine particle bursts

    Energy Technology Data Exchange (ETDEWEB)

    Babu, S. Suresh, E-mail: s_sureshbabu@vssc.gov.in [Space Physics Laboratory, Vikram Sarabhai Space Centre, Thiruvananthapuram 695022 (India); Kompalli, Sobhan Kumar [Space Physics Laboratory, Vikram Sarabhai Space Centre, Thiruvananthapuram 695022 (India); Moorthy, K. Krishna [Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bangalore 560 012 (India)

    2016-09-01

    Number-size distribution is one of the important microphysical properties of atmospheric aerosols that influence aerosol life cycle, aerosol-radiation interaction as well as aerosol-cloud interactions. Making use of one-yearlong measurements of aerosol particle number-size distributions (PNSD) over a broad size spectrum (~ 15–15,000 nm) from a tropical coastal semi-urban location-Trivandrum (Thiruvananthapuram), the size characteristics, their seasonality and response to mesoscale and synoptic scale meteorology are examined. While the accumulation mode contributed mostly to the annual mean concentration, ultrafine particles (having diameter < 100 nm) contributed as much as 45% to the total concentration, and thus constitute a strong reservoir, that would add to the larger particles through size transformation. The size distributions were, in general, bimodal with well-defined modes in the accumulation and coarse regimes, with mode diameters lying in the range 141 to 167 nm and 1150 to 1760 nm respectively, in different seasons. Despite the contribution of the coarse sized particles to the total number concentration being meager, they contributed significantly to the surface area and volume, especially during transport of marine air mass highlighting the role of synoptic air mass changes. Significant diurnal variation occurred in the number concentrations, geometric mean diameters, which is mostly attributed to the dynamics of the local coastal atmospheric boundary layer and the effect of mesoscale land/sea breeze circulation. Bursts of ultrafine particles (UFP) occurred quite frequently, apparently during periods of land-sea breeze transitions, caused by the strong mixing of precursor-rich urban air mass with the cleaner marine air mass; the resulting turbulence along with boundary layer dynamics aiding the nucleation. These ex-situ particles were observed at the surface due to the transport associated with boundary layer dynamics. The particle growth rates from

  12. Effect of dust size distribution on ion-acoustic solitons in dusty plasmas with different dust grains

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Dong-Ning; Yang, Yang; Yan, Qiang [Northwest Normal University, College of Physics and Electronic Engineering (China); Wang, Xiao-Yun [Lanzhou Jiao Tong University, Department of Mathematics and Physics (China); Duan, Wen-Shan, E-mail: duanws@126.com [Northwest Normal University, College of Physics and Electronic Engineering (China)

    2017-02-15

    Theoretical studies are carried out for ion acoustic solitons in multicomponent nonuniform plasma considering the dust size distribution. The Korteweg−de Vries equation for ion acoustic solitons is given by using the reductive perturbation technique. Two special dust size distributions are considered. The dependences of the width and amplitude of solitons on dust size parameters are shown. It is found that the properties of a solitary wave depend on the shape of the size distribution function of dust grains.

  13. Zipf's law and influential factors of the Pareto exponent of the city size distribution: Evidence from China

    OpenAIRE

    GAO Hongying; WU Kangping

    2007-01-01

    This paper estimates the Pareto exponent of the city size (population size and economy size) distribution, all provinces, and three regions in China in 1997, 2000 and 2003 by OLS, comparatively analyzes the Pareto exponent cross section and times, and empirically analyzes the factors which impacts on the Pareto exponents of provinces. Our analyses show that the size distributions of cities in China follow the Pareto distribution and are of structural features. Variations in the value of the P...

  14. Use of commercial vessels in survey augmentation: the size-frequency distribution

    Directory of Open Access Journals (Sweden)

    Eric N. Powell

    2006-09-01

    Full Text Available The trend towards use of commercial vessels to enhance survey data requires assessment of the advantages and limitations of various options for their use. One application is to augment information on size-frequency distributions obtained in multispecies trawl surveys where stratum boundaries and sampling density are not optimal for all species. Analysis focused on ten recreationally and commercially important species: bluefish, butterfish, Loligo squid, weakfish, summer flounder, winter flounder, silver hake (whiting, black sea bass, striped bass, and scup (porgy. The commercial vessel took 59 tows in the sampled domain south of Long Island, New York and the survey vessel 18. Black sea bass, Loligo squid, and summer flounder demonstrated an onshore-offshore gradient such that smaller fish were caught disproportionately inshore and larger fish offshore. Butterfish, silver hake, and weakfish were characterized by a southwest-northeast gradient such that larger fish were caught disproportionately northeast of the southwestern-most sector. All sizes of scup, striped bass, and bluefish were caught predominately inshore. Winter flounder were caught predominately offshore. The commercial vessel was characterized by an increased frequency of large catches for most species. Consequently, patchiness was assayed to be higher by the commercial vessel in nearly all cases. The size-frequency distribution obtained by the survey vessel for six of the ten species, bluefish, butterfish, Loligo squid, summer flounder, weakfish, and silver hake, could not be obtained by chance from the size-frequency distribution obtained by the commercial vessel. The difference in sample density did not significantly influence the size-frequency distribution. Of the six species characterized by significant differences in size-frequency distribution between boats, all but one was patchy at the population level and all had one or more size classes so characterized. Although the

  15. Sodium leakage and combustion tests. Measurement and distribution of droplet size using various spray nozzles

    International Nuclear Information System (INIS)

    Nagai, Keiichi; Hirabayashi, Masaru; Onojima, T.; Gunji, Minoru; Ara, Kuniaki; Oki, Yoshihisa

    1999-04-01

    In order to develop a numerical code simulating sodium fires initiated frame dispersion of droplets, measured data of droplet diameter as well as its distribution are needed. In the present experiment the distribution of droplet diameter was measured using water, oil and sodium. The tests elucidated the influential factors with respect to the droplet diameter. In addition, we sought to develop a similarity law between water and sodium. The droplet size distribution of sodium using the large diameter droplet (Elnozzle) was predicted. (J.P.N.)

  16. Determination of the particle size distribution of an aerosol using a diffusion battery

    International Nuclear Information System (INIS)

    Maigne, Jean-Pierre

    1974-02-01

    The principal methods for the treatment of concentration measurements both upstream and downstream of a diffusion battery are reviewed and discussed, the purpose of the measurements being the determination of the aerosol particle size distribution. It is then demonstrated that the resolution of the equations arising from the problem leads to the imposing of physical constraints on the distribution sought, these constraints being more and more restrictive with increasing experimental inaccuracies. An algorithm is proposed which provides an approximate solution to the system of equations, certain predetermined criteria, and the constraints imposed on the distribution being taken into account. (author)

  17. The limit distribution of the maximum increment of a random walk with dependent regularly varying jump sizes

    DEFF Research Database (Denmark)

    Mikosch, Thomas Valentin; Moser, Martin

    2013-01-01

    We investigate the maximum increment of a random walk with heavy-tailed jump size distribution. Here heavy-tailedness is understood as regular variation of the finite-dimensional distributions. The jump sizes constitute a strictly stationary sequence. Using a continuous mapping argument acting...... on the point processes of the normalized jump sizes, we prove that the maximum increment of the random walk converges in distribution to a Fréchet distributed random variable....

  18. Soot, organics, and ultrafine ash from air- and oxy-fired coal combustion

    KAUST Repository

    Andersen, Myrrha E.

    2016-10-19

    Pulverized bituminous coal was burned in a 10. W externally heated entrained flow furnace under air-combustion and three oxy-combustion inlet oxygen conditions (28, 32, and 36%). Experiments were designed to produce flames with practically relevant stoichiometric ratios (SR. =1.2-1.4) and constant residence times (2.3. s). Size-classified fly ash samples were collected, and measurements focused on the