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1

Production, depreciation and the size distribution of firms

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.

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

2008-05-01

2

Mars: New Determination of Impact Crater Production Function Size Distribution

Several authors have questioned our knowledge of Martian impact crater production function size-frequency distribution (PFSFD), especially at small diameters D. Plescia (2005) questioned whether any area of Mars shows size distributions used for estimating crater retention ages on Mars. McEwen et al. (2005) and McEwen and Bierhaus (2006) suggested existing PFSFD’s are hopelessly confused by the presence of secondaries, and that my isochrons give primary crater densities off by factors of several thousand at small D. In 2005, I addressed some of these concerns, noting my curves do not estimate primary crater densities per se, but show total numbers of primaries + semi-randomly “distant secondaries” (negating many McEwen et al. critiques). In 2006 I have conducted new crater counts on a PFSFD test area suggested by Ken Tanaka. This area shows young lava flows of similar crater density, west of Olympus Mons (around 30 deg N, 100 deg W). Multiple crater counts were made on several adjacent Odyssey THEMIS images and MGS MOC images, giving the SFD over a range of 11m

Hartmann, William K.

2006-12-01

3

Product differentiation and firm size distribution : an application to carbonated soft drinks

Digital Repository Infrastructure Vision for European Research (DRIVER)

Using brand level retail data, the firm size distribution in Carbonated Soft Drinks is shown to be an outcome of the degree to which firms have placed brands effectively (store coverage) across vertical (flavour, packaging, diet attributes) segments of the market. Regularity in the firm size distribution is not disturbed by the nature of short-run brand competition (turbulence in brand market shares) within segments. Remarkably, product differentiation resulting from firms acquiring variou...

Walsh, Patrick P.; Whelan, Ciara

2001-01-01

4

Product differentiation and firm size distribution : an application to carbonated soft drinks

Digital Repository Infrastructure Vision for European Research (DRIVER)

Using brand level retail data, the firm size distribution in Carbonated Soft Drinks is shown to be an outcome of the degree to which firms have placed brands effectively (store coverage) across vertical (flavour, packaging, diet attributes) segments of the market. Regularity in the firm size distribution is not disturbed by the nature of short-run brand competition (turbulence in brand market shares) within segments. Remarkably, product differentiation resulting from firms acquiring var...

Whelan, Ciara; Walsh, Patrick P.

2002-01-01

5

Firm size and productivity. Evidence from the electricity distribution industry in Brazil

International Nuclear Information System (INIS)

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. - Research Highlights: ?We apply Stochastic Frontier Analysis through a distance function to investigate the impact of firm's size on productivity development in electricity distribution using a sample of eighteen Brazilian firms from 1998 to 2005. ?Productivity is decomposed into technical efficiency, scale-efficiency and technical change. ?Firm size is important for the industry's productivity, and therefore a key aspect to consider when making decisions that affect the market structure in the electricity distribution industry.

2011-02-01

6

The field measurements of the activity-weighted size distributions of radon decay products

International Nuclear Information System (INIS)

Because of the importance of particle size in the calculations of dose deposited in the respiratory tract by radon progeny, the determination of the size distribution of radon decay products in indoor air had increased in interest in recent years. A system for the measurement of the activity-weighted size distribution of radon decay products at environmental levels has been developed. The system (ASC-GSA) utilizes a combination of six multiple wire screens (Graded Screen Array) sampler detector units operated in parallel. The cut off points of the samplers and the data deconvolution procedure allow to obtain the activity fractions of radon progeny in the size range 0.5-500 mn. The computer control of sampling, alpha counting and data storage permits the operation of the system on the semi-continuous basis. The primary application of the ASC-GSA system has been to collect data of activity-weighted size distributions of radon progeny in real house environments. The results of field measurements in several houses with elevated radon levels are presented

1991-05-07

7

Energy Technology Data Exchange (ETDEWEB)

The goal of this project is to improve energy efficiency of industrial crushing and grinding operations (comminution). Mathematical models of the comminution process are being used to study methods for optimizing the product size distribution, so that the amount of excessively fine material produced can be minimized. The goal is to save energy by reducing the amount of material that is ground below the target size, while simultaneously reducing the quantity of materials wasted as ''slimes'' that are too fine to be useful. This will be accomplished by: (1) modeling alternative circuit arrangements to determine methods for minimizing overgrinding, and (2) determining whether new technologies, such as high-pressure roll crushing, can be used to alter particle breakage behavior to minimize fines production.

H.J. Walqui; T.C. Eisele; S.K. Kawatra

2003-07-01

8

Energy Technology Data Exchange (ETDEWEB)

The goal of this project is to improve energy efficiency of industrial crushing and grinding operations (comminution). Mathematical models of the comminution process are being used to study methods for optimizing the product size distribution, so that the amount of excessively fine material produced can be minimized. The goal is to save energy by reducing the amount of material that is ground below the target size, while simultaneously reducing the quantity of materials wasted as ''slimes'' that are too fine to be useful. This will be accomplished by: (1) modeling alternative circuit arrangements to determine methods for minimizing overgrinding and maximizing energy efficiency, and (2) determining whether new technologies, such as high-pressure roll crushing, can be used to alter particle breakage behavior to minimize fines production.

H.J. Walqui; T.C. Eisele; S.K. Kawatra

2003-10-01

9

Digital Repository Infrastructure Vision for European Research (DRIVER)

The main purpose of this study was to optimise the grain size distribution of the raw material mixture for the production of iron sinter. It well known that the constitution of the sinter mix is based on the knowledge of chemical composition and grain size distribution. Although Mittal Vanderbijlpark has fixed specifications on the physical and chemical properties of the sinter for optimal blast furnace performance, the particle size distribution of the sinter mix has not yet been optimized. ...

2008-01-01

10

Energy Technology Data Exchange (ETDEWEB)

The potential risk of lung cancer has evoked interest in the properties of radon decay products. There are two forms of this progeny: either attached to ambient aerosols, or still in the status of ions/molecules/small clusters. This ``unattached`` activity would give a higher dose per unit of airborne activity than the ``attached`` progeny that are rather poorly deposited. In this thesis, a system for determining unattached radon decay products electrical mobility size distribution by measuring their electrical mobilities was developed, based on the fact that about 88% of {sup 218}Po atoms have unit charge at the end of their recoil after decay from {sup 222}Rn, while the remainder are neutral. Essential part of the setup is the radon-aerosol chamber with the Circular Electrical Mobility Spectrometer (CEMS) inside. CEMS is used for sampling and classifying the charged radioactive clusters produced in the chamber. An alpha- sensitive plastic, CR-39 disk, is placed in CEMS as an inlaid disk electrode and the alpha particle detector. CEMS showed good performance in fine inactive particles` classification. If it also works well for radon decay products, it can offer a convenient size distribution measurement for radioactive ultrafine particles. However, the experiments did not obtain an acceptable resolution. Suggestions are made for solving this problem.

Fei, Lin

1996-04-01

11

International Nuclear Information System (INIS)

The potential risk of lung cancer has evoked interest in the properties of radon decay products. There are two forms of this progeny: either attached to ambient aerosols, or still in the status of ions/molecules/small clusters. This ''unattached'' activity would give a higher dose per unit of airborne activity than the ''attached'' progeny that are rather poorly deposited. In this thesis, a system for determining unattached radon decay products electrical mobility size distribution by measuring their electrical mobilities was developed, based on the fact that about 88% of 218Po atoms have unit charge at the end of their recoil after decay from 222Rn, while the remainder are neutral. Essential part of the setup is the radon-aerosol chamber with the Circular Electrical Mobility Spectrometer (CEMS) inside. CEMS is used for sampling and classifying the charged radioactive clusters produced in the chamber. An alpha- sensitive plastic, CR-39 disk, is placed in CEMS as an inlaid disk electrode and the alpha particle detector. CEMS showed good performance in fine inactive particles' classification. If it also works well for radon decay products, it can offer a convenient size distribution measurement for radioactive ultrafine particles. However, the experiments did not obtain an acceptable resolution. Suggestions are made for solving this problem

1996-01-01

12

This study was performed to measure the activity size distribution of aerosol particles associated with short-lived radon decay products in indoor air at Nagoya University, Nagoya, Japan. The measurements were performed using a low pressure Andersen cascade impactor under variable meteorological conditions. The results showed that the greatest activity fraction was associated with aerosol particles in the accumulation size range (100-1000 nm) with a small fraction of nucleation mode (10-100 nm). Regarding the influence of the weather conditions, the decrease in the number of accumulation particles was observed clearly after rainfall without significant change in nucleation particles, which may be due to a washout process for the large particles. PMID:21521771

Mostafa, A M A; Tamaki, K; Moriizumi, J; Yamazawa, H; Iida, T

2011-07-01

13

International Nuclear Information System (INIS)

This study was performed to measure the activity size distribution of aerosol particles associated with short-lived radon decay products in indoor air at Nagoya Univ., Nagoya (Japan). The measurements were performed using a low pressure Andersen cascade impactor under variable meteorological conditions. The results showed that the greatest activity fraction was associated with aerosol particles in the accumulation size range (100-1000 nm) with a small fraction of nucleation mode (10-100 nm). Regarding the influence of the weather conditions, the decrease in the number of accumulation particles was observed clearly after rainfall without significant change in nucleation particles, which may be due to a washout process for the large particles. (authors)

2010-05-24

14

Size distribution of radon decay products in the range 0.1-10 nm.

Information about the size distribution of radioactive aerosols in nanometre range is essential for the purposes of air contamination monitoring, dose assessment to respiratory tract and planning of protective measures. The diffusion battery, which allows capturing particles in the size range of 0.1-10 nm, has developed. Interpreting data obtained from diffusion battery is very complex. The method of expectation maximisation by Maher and Laird was chosen for indirect inversion data. The experiments were performed in the box with equivalent equilibrium concentration of radon in the range of 7000-10 000 Bq m(-3). The three modes of size distribution of radon decay products aerosols were obtained: activity median thermodynamic diameter (AMTD) 0.3, 1.5 and 5 nm. These modes can be identified as: AMTD 0.3 nm-atoms of radon progeny ((218)Po in general); AMTD 1.5 nm-clusters of radon progeny atoms and non-radioactive atoms in the atmosphere; AMTD 5 nm-particles formed by coagulation of previous mode clusters with existing aerosol particles or nucleation of condensation nuclei containing atoms of radon progeny. PMID:24711527

Zhukovsky, Michael; Rogozina, Marina; Suponkina, Anna

2014-07-01

15

Energy Technology Data Exchange (ETDEWEB)

The goal of this project was to improve energy efficiency of industrial crushing and grinding operations (comminution). Mathematical models of the comminution process were used to study methods for optimizing the product size distribution, so that the amount of excessively fine material produced could be minimized. The goal was to save energy by reducing the amount of material that was ground below the target size, while simultaneously reducing the quantity of materials wasted as ''slimes'' that were too fine to be useful. Extensive plant sampling and mathematical modeling of the grinding circuits was carried out to determine how to correct this problem. The approaches taken included (1) Modeling of the circuit to determine process bottlenecks that restrict flowrates in one area while forcing other parts of the circuit to overgrind the material; (2) Modeling of hydrocyclones to determine the mechanisms responsible for retaining fine, high-density particles in the circuit until they are overground, and improving existing models to accurately account for this behavior; and (3) Evaluation of the potential of advanced technologies to improve comminution efficiency and produce sharper product size distributions with less overgrinding. The mathematical models were used to simulate novel circuits for minimizing overgrinding and increasing throughput, and it is estimated that a single plant grinding 15 million tons of ore per year saves up to 82.5 million kWhr/year, or 8.6 x 10{sup 11} BTU/year. Implementation of this technology in the midwestern iron ore industry, which grinds an estimated 150 million tons of ore annually to produce over 50 million tons of iron ore concentrate, would save an estimated 1 x 10{sup 13} BTU/year.

S.K. Kawatra; T.C. Eisele; T. Weldum; D. Larsen; R. Mariani; J. Pletka

2005-07-01

16

International Nuclear Information System (INIS)

The goal of this project is to improve the energy efficiency of industrial crushing and grinding operations (comminution). Mathematical models of the comminution process are being used to study methods for optimizing the product size distribution, so that the amount of excessively fine material produced can be minimized. This will save energy by reducing the amount of material that is ground to below the target size, and will also reduce the quantity of material wasted as slimes that are too fine to be useful. This will be accomplished by: (1) modeling alternative circuit arrangements to determine methods for minimizing overgrinding, and (2) determining whether new technologies, such as high-pressure roll crushing, can be used to alter particle breakage behavior to minimize fines production. In the first quarter of this project, work was completed on a basic comminution model that will be used to carry out the subsequent project tasks. This phase of the work was supported by the Electric Power Research Institute, as their cost-share contribution to the project. The model has been implemented as an Excel spreadsheet, which has the advantage of being a very portable format that can be made widely available to the industry once the project is completed

2001-01-01

17

Energy Technology Data Exchange (ETDEWEB)

The goal of this project is to improve energy efficiency of industrial crushing and grinding operations (comminution). Mathematical models of the comminution process are being used to study methods for optimizing the product size distribution, so that the amount of excessively fine material produced can be minimized. This will save energy by reducing the amount of material that is ground below the target size, and will also reduce the quantity of materials wasted as slimes that are too fine to be useful. This will be accomplished by: (1) modeling alternative circuit arrangements to determine methods for minimizing overgrinding, and (2) determining whether new technologies, such as high-pressure roll crushing, can be used to alter particle breakage behavior to minimize fines production. In the sixth quarter of this project, work was centered on analyzing the considerable plant data gathered during the first year of the project. Modeling is being carried out of the hydrocyclone portion of the grinding circuit, since this has been identified as the primary source of overgrinding and inefficiency.

S.K. Kawatra; T.C. Eisele; H.J. Walqui

2002-07-01

18

A technique for production of nanocrystalline cellulose with a narrow size distribution

Energy Technology Data Exchange (ETDEWEB)

Nanocrystalline cellulose (NCC) was prepared by sulfuric acid hydrolysis of microcrystalline cellulose. A differential centrifugation technique was studied to obtain NCC whiskers with a narrow size distribution. It was shown that the volume of NCC in different fractions had an inverse relationship with relative centrifugal force (RCF). The length of NCC whiskers was also fractionized by differential RCF. The aspect ratio of NCC in different fractions had a relatively narrow range. This technique provides an easy way of producing NCC whiskers with a narrow size distribution.

Bai, Wen; Holbery, James D.; Li, Kaichang

2009-02-01

19

Energy Technology Data Exchange (ETDEWEB)

The goal of this project is to improve energy efficiency of industrial crushing and grinding operations (comminution). Mathematical models of the comminution process are being used to study methods for optimizing the product size distribution, so that the amount of excessively fine material produced can be minimized. The goal is to save energy by reducing the amount of material that is ground below the target size, while simultaneously reducing the quantity of materials wasted as ''slimes'' that are too fine to be useful. This will be accomplished by: (1) modeling alternative circuit arrangements to determine methods for minimizing overgrinding, and (2) determining whether new technologies, such as high-pressure roll crushing, can be used to alter particle breakage behavior to minimize fines production. During this quarter, work was focused on three areas: (1) The mathematical relationship developed for predicting plant throughput was improved, based on ore work index and equipment parameters measured in the plant over an extended period. It was determined that the model would need to fit two distinct regimes of grinding circuit operation, depending on the work index of the feed ore. (2) Plans for a proposed change in the circuit configuration at an iron ore plant are being made, to test predictions based on the work done to date in the project. After determining the desired circuit change, which would require screening a portion of the grinding slurry, samples were sent to an industrial screen manufacturer for pilot plant scale testing. These tests indicated that the screening could be carried out economically, and plans are proceeding to conduct trials of the proposed circuit alteration. (2) The mathematical model used for hydrocyclone simulations was found to be unable to fully predict the ''fish-hook'' behavior that is seen in the plant samples. The model was therefore improved by including empirically-determined terms so that it would be able to account for the observed phenomenon. A more advanced model is currently under development that will take account of measured slurry viscosity, in order to more accurately model the behavior of hydrocyclones with concentrated slurries of very fine particles.

H.J. Walqui; T.C. Eisele; S.K. Kawatra

2003-04-01

20

The activity size distributions of indoor and outdoor radioactive aerosol associated with short-lived radon decay products were observed at Nagoya, Japan, for some periods from 2010 to 2012, following the indoor observation by Mostafa et al. [Mostafa, A. M. A., Tamaki, K., Moriizumi, J., Yamazawa, H. and Iida, T. The weather dependence of particle size distribution of indoor radioactive aerosol associated with radon decay products. Radiat. Prot. Dosim. 146: (1-3), 19-22 (2011)]. The tendency of smaller indoor activity median aerodynamic diameter (AMAD) after rainfalls showed in the previous study was not consistently obtained, while the consistent tendency of less indoor radioactive particles with diameters in the accumulation mode was observed again after rainfalls. The indoor aerosols showed activity size distributions similar to the outdoor ones. Non-radioactive aerosol particle concentrations measured with a laser particle counter suggested a somewhat liner relationship with AMAD. PMID:24723191

Moriizumi, Jun; Yamada, Shinya; Xu, Yang; Matsuki, Satoru; Hirao, Shigekazu; Yamazawa, Hiromi

2014-07-01

21

Production of Palm Shell-Based Activated Carbon with More Homogeniouse Pore Size Distribution

Directory of Open Access Journals (Sweden)

Full Text Available Oil palm shell as a raw material was used for the preparation of activated carbon adsorbents. The precursor was first activated chemically with small proportion of zinc chloride and phosporic acid and then the prepared samples were treated with CO2 flow at 850°C at different activation time. The samples activated chemically with phosphoric acid showed higher surface area and pore volume compared to the samples activated using zinc chloride as chemical agent, at the same duration. In addition, it was shown that extra physical activation will grantees more developed pore structure. In terms of pore size distribution the combined preparation method resulted in a better and more homogenous pore size distribution than the commercial palm shell based activated carbon.

A. Arami-Niya

2010-01-01

22

The unit dose uniformity (UDU) of low-dose drug products can be affected by active pharmaceutical ingredient (API) particle size. UDU relative standard deviation increases as the fraction of large API particles increases and/or as the unit dose decreases. Control of API particle size has traditionally been based on the empirical relationship of d(90) and/or d(50) statistics to drug product uniformity. Several articles have been written that have identified a theoretical relationship between these particle size statistics, dose, and the probability of meeting US Pharmacopeial UDU testing criteria (Huang CY, Ku S. 2010. Int J Pharm 383:70-80; Rohrs B, Amidon G, Meury R, Secreast P, King H, Skoug C. 2006. J Pharm Sci 95(5):1049-1059; Huang CY, Ku S. 2010. J Pharm Sci 99:4351-4362; Yalkowsky SH, Bolton S. 1990. Pharm Res 7(9):962-966). However, these theoretical relationships assume a fixed shape for the API particle size distribution (PSD, i.e., lognormal) and do not account for changes in the distribution shape. A more rigorous method for predicting the effect of a given PSD on UDU is to evaluate the contribution of individual particle size bins on UDU variability. The latter approach is taken in this work, and the derivation reveals that the individual contribution of particles size bins can be expressed completely in terms of a single-particle-size statistic, D[6,3]. D[6,3] is therefore a valid predictor of UDU, regardless of the shape of the PSD (e.g., multimodal) and can form the basis of a particle size control strategy for low-dose drug products. PMID:22504845

Hilden, Jon; Schrad, Mark; Kuehne-Willmore, Jennifer; Sloan, Jessica

2012-07-01

23

Multimodal Raindrop Size Distributions.

The raindrop size distributions (DSDs) observed over a short span usually have an erratic shape, with several relative maxima. This multimodal structure is studied from disdrometer data acquired in tropical and midlatitude areas. It is shown that some modes of DSDs have a persistence larger than several minutes and can be spotted from one DSD to the next one as they migrate through the size classes. It is demonstrated that Nm, the number of modes of DSDs, for diameter larger than 2 mm, is not related to the mean rain rate but depends on the rain-rate fluctuations. Statistical evidence of such a relation is given. The spread of DSDs is found to be dependent on its multimodal structure, that is, on Nm. The large values of Nm are associated with low values of slope and intercept N0 of the fitted exponential distribution.In order to explain the dependence of the DSD shape on Nm, a conceptual model is proposed in which the modes are interpreted as resulting from an overlapping of rain shafts. The associated DSD is termed a synthetic drop size distribution (SDSD). It is shown that the overlapping of rain shafts generated from a sequence of rain cells of increasing intensity, such as observed at the leading edge of a convective system, results in undersloping SDSDs. In the reverse configuration, that is, with a sequence of rain cells with decreasing intensity, such as observed at the ending edge of a convective system, it results in oversloping SDSDs. Observations in agreement with these conclusions are presented. The readability of the modal structure of the DSDs depends on several factors in such a way that an apparent multimodal structure is not necessary for a DSD to be an SDSD. It is suggested that most of the DSDs observed at the ground are synthetic DSDs.

Sauvageot, Henri; Koffi, Manlandon

2000-08-01

24

Control of the grain size distribution of the raw material mixture in the production of iron sinter

Digital Repository Infrastructure Vision for European Research (DRIVER)

The aim of this study was to examine the effect of grain size distribution control of the raw material mixture on the permeability of the green sinter bed and the properties of the produced sinter. This was achieved by evaluating the granulation characteristics of the sinter mixture (moisture content, granulation time and mean granule diameter) in terms of its green bed permeability, and evaluating the productivity of the sinter bed, the coke rate, tumble index (TI), abrasion index (AI), redu...

Lwamba, E.; Garbers-craig, Andrie Mariana

2008-01-01

25

Radon daughter activity size distributions

Energy Technology Data Exchange (ETDEWEB)

The size distributions of radon and thoron daughters have been measured in buildings and in the open air. Because of the low radioactivity concentration a high volume cascade impactor was used. The cascade impactor data were evaluated by using an improved computer programme taking into account the effect of interstage losses on the measured precipitation values of the impactor. The size distributions found for the shortlived radon daughters, /sup 214/Pb, /sup 214/Bi, and thoron daughter, /sup 212/Pb, were unimodal log-normal. There was no significant different between activity size distributions of the short lived radon decay products and the thoron daughter /sup 212/Pb. The activity median aerodynamic diameter (AMAD) measured in different buildings and at different days ranged from 0.07 to 0.29 ..mu..m with a mean value of 0.18 ..mu..m for the radon and thoron daughters in dwellings with low room ventilation. The mean value of the geometric standard deviation was sigmasub(g) = 3.50. The size distributions in the open air are significantly larger with a mean AMAD of 0.39 ..mu..m (range: 0.20 to 0.54 ..mu..m) and a mean standard deviation of sigmasub(g) = 2.31.

Becker, K.H.; Reineking, A.; Scheibel, H.G.; Porstendoerfer, J. (Georg-August-Univ., Goettingen (Germany, F.R.). Isotopenlab.)

1984-01-01

26

Radon daughter activity size distributions

International Nuclear Information System (INIS)

The size distributions of radon and thoron daughters have been measured in buildings and in the open air. Because of the low radioactivity concentration a high volume cascade impactor was used. The cascade impactor data were evaluated by using an improved computer programme taking into account the effect of interstage losses on the measured precipitation values of the impactor. The size distributions found for the shortlived radon daughters, 214Pb, 214Bi, and thoron daughter, 212Pb, were unimodal log-normal. There was no significant different between activity size distributions of the short lived radon decay products and the thoron daughter 212Pb. The activity median aerodynamic diameter (AMAD) measured in different buildings and at different days ranged from 0.07 to 0.29 ?m with a mean value of 0.18 ?m for the radon and thoron daughters in dwellings with low room ventilation. The mean value of the geometric standard deviation was ?sub(g) = 3.50. The size distributions in the open air are significantly larger with a mean AMAD of 0.39 ?m (range: 0.20 to 0.54 ?m) and a mean standard deviation of ?sub(g) = 2.31. (author)

1984-01-01

27

Size distributions in urban aerosols

International Nuclear Information System (INIS)

Data on the size distributions of urban aerosols are reviewed with emphasis on the physical characteristics of the particles. Types of size distributions, the reliability of size distribution data, and factors affecting urban aerosol size distributions are considered. As examples, the grand average number aerosol distribution from the 1969 Los Angeles smog experiment is compared with a Junge power law distribution calculated with the constants of Clark and Whitby. The computer-prepared volume size distribution measured during the General Motors Sulfate Study in Milford, Mich. is presented, the median size distribution by number for the New York Summer Aerosol Study is considered, and volume concentration distributions for Denver-area aerosols are presented

1979-01-12

28

Effect of iron on productivity and size distribution of Antarctic phytoplankton

Energy Technology Data Exchange (ETDEWEB)

In shipboard experiments, addition of Fe to samples from Antarctic shelf waters or from deep waters close to the shelf break did not have any detectable effect on phytoplankton populations. Fe addition to pelagic waters, however, increased Chl a concentrations by a factor of 4-7 times during 1-2 weeks of incubation and also resulted in a shift from a nanoplankton-dominated population to one dominated by microplankton. If these shipboard experimental results are extrapolated to in situ results following enrichment of Antarctic pelagic waters with Fe, there may be some mitigation of the greenhouse effect caused by elevated CO{sub 2} concentrations in the atmosphere. Not only would the rate of primary production increase, but also the percentage of primary production that is exported to deep water might be increased because of Fe favoring the growth of microplankton.

Helbling, E.W.; Villafane, V.; Hoom-Hansen, O. (Scripps Institution of Oceanography, La Jolla (United States))

1991-12-01

29

Effect of iron on productivity and size distribution of Antarctic phytoplankton

International Nuclear Information System (INIS)

In shipboard experiments, addition of Fe to samples from Antarctic shelf waters or from deep waters close to the shelf break did not have any detectable effect on phytoplankton populations. Fe addition to pelagic waters, however, increased Chl a concentrations by a factor of 4-7 times during 1-2 weeks of incubation and also resulted in a shift from a nanoplankton-dominated population to one dominated by microplankton. If these shipboard experimental results are extrapolated to in situ results following enrichment of Antarctic pelagic waters with Fe, there may be some mitigation of the greenhouse effect caused by elevated CO2 concentrations in the atmosphere. Not only would the rate of primary production increase, but also the percentage of primary production that is exported to deep water might be increased because of Fe favoring the growth of microplankton

1991-12-01

30

We used near infrared (NIR) spectroscopy to evaluate the degree of mixing of blended dry syrup (DS) products whose particle sizes are not specified in the Revised 16th Edition of the Japanese Pharmacopoeia, and also evaluated the degree of mixing when powder products or fine granule products were added to DS products. The data obtained were used to investigate the relationship between the particle size distributions of the products studied and the degree of mixing. We found that the particle size distribution characteristics of the 15 DS products studied can be broadly classified into 5 types. Combinations of frequently prescribed products were selected to represent 4 of the 5 particle size distribution types and were blended with a mortar and pestle. The coefficient of variation (CV) decreased as the percent mass of Asverin® Dry Syrup 2% (Asverin-DS) increased in blends of Periactin® Powder 1% (Periactin) and Asverin-DS, indicating an improved degree of mixing (uniformity). In contrast, in blends of Periactin and Mucodyne® DS 33.3%, mixing a combination at a 1:1 mass ratio 40 times resulted in a CV of 20%. Other mixing frequencies and mass ratios resulted in a CV by 50% to 70%, indicating a very poor degree of mixing (poor uniformity). These results suggest that when combining different DSs, or a DS with a powder or fine granule product, the blending obtained with a mortar and pestle improves as the particle size distributions of the components approach each other and as the ranges of the distributions narrow. PMID:22689400

Yamamoto, Yoshihisa; Suzuki, Toyofumi; Matsumoto, Mika; Ohtani, Michiteru; Hayano, Shuichi; Fukami, Toshiro; Tomono, Kazuo

2012-01-01

31

Recurrent frequency-size distribution

Many complex systems, including a sand-pile model, a slider-block model, and actual earthquakes, have been discussed whether they obey the principles of self-organized criticality. Behavior of these systems can be investigated from two different points of view: interoccurrent behavior in a region and recurrent behavior at a given point on a fault or at a given fault. The interoccurrent frequency-size statistics are known to be scale-invariant and obey the power-law Gutenberg-Richter distribution. This paper investigates the recurrent frequency-size behavior at a given point on a fault or at a given fault. For this purpose sequences of creep events at a creeping section of the San Andreas fault are investigated. The applicability of 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 a best-fit distribution. To verify this result the behavior of the numerical slider-block and sand-pile models...

Abaimov, S G

2008-01-01

32

Parameterizing the Raindrop Size Distribution.

This paper addresses the problem of finding a parametric form for the raindrop size distribution (DSD) that 1) is an appropriate model for tropical rainfall, and 2) involves statistically independent parameters. Such a parameterization is derived in this paper. One of the resulting three `canonical' parameters turns out to vary relatively little, thus making the parameterization particularly useful for remote sensing applications. In fact, a new set of drop-size-distribution-based Z-R and k-R relations is obtained. Only slightly more complex than power laws, they are very good approximations to the exact radar relations one would obtain using Mie scattering. The coefficients of the new relations are directly related to the shape parameters of the particular DSD that one starts with. Perhaps most important, since the coefficients are independent of the rain rate itself, the relations are ideally suited for rain retrieval algorithms.

Haddad, Ziad S.; Durden, Stephen L.; Im, Eastwood

1996-01-01

33

Comparing two mass size distributions

Scientific Electronic Library Online (English)

Full Text Available SciELO South Africa | Language: English Abstract in english We consider in this paper the use of a modified version of Hotelling's statistic in the analysis of particle size distributions. The statistic can be adversely affected by the presence of outliers among the data. We propose a competitor to the statistic that is based on ranks, and hence is less sens [...] itive to outlier effects. The results of a Monte Carlo study suggest that the rank test is highly competitive with the Hotelling test in its ability to detect differences between two mass size distributions. The calculation of the rank statistic is explained in detail and its application is illustrated on two sets of data.

F., Lombard; G.J., Lyman.

34

Activity size distribution of some natural radionuclides.

In this study, the results concerning the activity size distribution of the long-lived ((210)Pb) radon decay product aerosols and the thoron decay product aerosols ((212)Pb) and ((7)Be) of the outdoor atmosphere are presented. Also, the mass size distribution of the aerosol particles is determined. The low-pressure Berner cascade impactor Model 20/0.015 was used as a sampling device. The activity size distribution of these radionuclides was determined by one log-normal distribution (accumulation mode) whereas the mass size distribution was by two log-normal distributions (accumulation and coarse mode). The activity median aerodynamic diameter (AMAD) of (212)Pb was found to be 305 nm with a geometric standard deviation (?g) of 2.41. The specific air activity concentration of (212)Pb was found to be 0.14 ± 0.012 Bq m(-3). An AMAD of (210)Pb of 610 nm with ?g of 1.8 was determined, whereas that of 550 nm with ?g of 1.97 was determined for (7)Be. The specific air activity concentration of (210)Pb and (7)Be was found to be 0.0016±2.5×10(-4) and 0.00348 ± 4×10(-4) Bq m(-3), respectively. Using a dosimetric model, the total deposition fraction as well as the total equivalent dose has been evaluated considering the observed parameters of the activity size distribution of (212)Pb. At a total deposition fraction of ?21 %, the total equivalent dose was found to be 0.41 µSv. PMID:24106329

Mohery, M; Abdallah, A M; Al-Amoudi, Z M; Baz, S S

2014-03-01

35

Soil Particle Size Distribution Protocol

The purpose of this resource is to sure the distribution of different sizes of soil particles in each horizon of a soil profile. Using dry, sieved soil from a horizon, students mix the soil with water and a dispersing solution to completely separate the particles from each other. Students shake the mixture to fully suspend the soil in the water. The soil particles are then allowed to settle out of suspension, and the specific gravity and temperature of the suspension are measured using a hydrometer and thermometer. These measurements are taken after 2 minutes and 24 hours.

The GLOBE Program, University Corporation for Atmospheric Research (UCAR)

2003-08-01

36

International Nuclear Information System (INIS)

The Materials Chemistry Department 1846 has developed a lab-scale chem-prep process for the synthesis of PNZT 95/5, a ferroelectric material that is used in neutron generator power supplies. This process (Sandia Process, or SP) has been successfully transferred to and scaled by Department 14192 (Ceramics and Glass Department), (Transferred Sandia Process, or TSP), to meet the future supply needs of Sandia for its neutron generator production responsibilities. In going from the development-size SP batch (1.6 kg/batch) to the production-scale TSP powder batch size (10 kg/batch), it was important that it be determined if the scaling process caused any ''performance-critical'' changes in the PNZT 95/5 being produced. One area where a difference was found was in the particle size distributions of the calcined PNZT powders. Documented in this SAND report are the results of an experimental study to determine the origin of the differences in the particle size distribution of the SP and TSP powders

2002-01-01

37

Energy Technology Data Exchange (ETDEWEB)

Mesocosm experiments were performed in three north temperature lakes to evaluate responses of algal chlorophyll, primary productivity (PPR), and chlorophyll-specific PPR (photosynthetic capacity) to experimental manipulations of zooplankton biomass and size distribution. In all experiments, nutrient enrichment led to increased growth and higher photosynthetic capacity, indicating that the phytoplankton in these lakes were nutrient-limited. In experiments which exposed phytoplankton to a 32-fold range of zooplankton biomass, chlorophyll decreased significantly (p < 0.05), while PPR was unchanged. As a result, specific PPR increased significantly with increasing zooplankton biomass, indicating an improvement in algal physiological status and the occurrence of compensatory growth in response to increased grazing pressure and higher nutrient regeneration. In an experiment which manipulated the zooplankton size distribution at two constant levels of zooplankton biomass (1/4x and 2x ambient zooplankton density), no significant algal responses to zooplankter size occurred at the low biomass level; however, at the high level, chlorophyll decreased and specific PPR increased with increasing average zooplankter size. These results emphasize the close coupling between zooplankton grazing and nutrient regeneration and algal nutrient uptake and growth in such nutrient-deficient systems. (orig.).

Elser, J.J.; MacKay, N.A.

1989-02-01

38

Energy Technology Data Exchange (ETDEWEB)

Isotretinoin is the drug of choice for the management of severe recalcitrant nodular acne. Nevertheless, some of its physical-chemical properties are still poorly known. Hence, the aim of our study consisted to comparatively evaluate the particle size distribution (PSD) and characterize the thermal behavior of the three encapsulated isotretinoin products in oil suspension (one reference and two generics) commercialized in Brazil. Here, we show that the PSD, estimated by laser diffraction and by polarized light microscopy, differed between the generics and the reference product. However, the thermal behavior of the three products, determined by thermogravimetry (TGA), differential thermal (DTA) analyses and differential scanning calorimetry (DSC), displayed no significant changes and were more thermostable than the isotretinoin standard used as internal control. Thus, our study suggests that PSD analyses in isotretinoin lipid-based formulations should be routinely performed in order to improve their quality and bioavailability.

Guimaraes, Carla Aiolfi, E-mail: carlaaiolfi@usp.br [Department of Pharmacy, Faculty of Pharmaceutical Sciences, University of Sao Paulo, Sao Paulo, SP 05508-000 (Brazil); Menaa, Farid [Department of Dermatology, School of Medicine Wuerzburg, Wuerzburg 97080 (Germany); Fluorotronics, Inc., 1425 Russ Bvld, San Diego Technology Incubator, San Diego, CA 92101 (United States); Menaa, Bouzid, E-mail: bouzid.menaa@gmail.com [Fluorotronics, Inc., 1425 Russ Bvld, San Diego Technology Incubator, San Diego, CA 92101 (United States); Quenca-Guillen, Joyce S. [Department of Pharmacy, Faculty of Pharmaceutical Sciences, University of Sao Paulo, Sao Paulo, SP 05508-000 (Brazil); Matos, Jivaldo do Rosario [Department of Fundamental Chemistry, Institute of Chemistry, University of Sao Paulo, Sao Paulo, SP 05508-000 (Brazil); Mercuri, Lucildes Pita [Department of Exact and Earth Sciences, Federal University of Sao Paulo, Diadema, SP 09972-270 (Brazil); Braz, Andre Borges [Department of Engineering of Mines and Oil, Polytechnical School, University of Sao Paulo, SP 05508-900 (Brazil); Rossetti, Fabia Cristina [Department of Pharmaceutical Sciences, Faculty of Pharmaceutical Sciences of Ribeirao Preto, University of Sao Paulo, Ribeirao Preto, SP 14015-120 (Brazil); Kedor-Hackmann, Erika Rosa Maria; Santoro, Maria Ines Rocha Miritello [Department of Pharmacy, Faculty of Pharmaceutical Sciences, University of Sao Paulo, Sao Paulo, SP 05508-000 (Brazil)

2010-06-10

39

International Nuclear Information System (INIS)

A major issue in radiation protection is to protect the population from the harmful effects of exposure to radon and radon progeny. Quantification of the lung cancer risk emanating from exposure to radon decay products in residential and working environments poses problems, as epidemiologic studies yield information deviating from the results obtained by the indirect method of assessment based on dosimetric respiratory tract models. One important task of the publication here was to characterize the various exposure conditions and to quantify uncertainties that may result from application of the ''dose conversion convention''. A special aerosol spectrometer was therefore designed and built in order to measure the size distributions of the short-lived radon decay products in the range between 0.5 nm and 10 000 nm. The aerosol spectrometer consists of a three-step diffusion battery with wire nets, an 11-step BERNER impactor, and a detector system with twelve large-surface proportional detectors. From the measured size distributions, dose conversion coefficients, E/P"e"q, were calculated using the PC software RADEP; the RADEP program was developed by BIRCHALL and JAMES and is based on the respiratory tract model of the ICRP. The E/P"e"q coefficients indicate the effective dose E per unit exposure P"e"q to radon decay products. (orig./CB)

1997-01-01

40

Size, productivity, and international banking

Digital Repository Infrastructure Vision for European Research (DRIVER)

Heterogeneity in size and productivity is central to models that explain which manufacturing firms export. This study presents descriptive evidence on similar heterogeneity among international banks as financial services providers. A novel and detailed bank-level data set reveals the volume and mode of international activities for all German banks. Only a few, large banks have a commercial presence abroad, consistent with the size pecking order documented for manufacturing firms. However, the...

Buch, Claudia M.; Koch, Cathe?rine; Koetter, Michael

2011-01-01

41

Energy Technology Data Exchange (ETDEWEB)

The objective of this workshop was to address the most urgent open science questions for improved quantification of sea spray aerosol-radiation-climate interactions. Sea spray emission and its influence on global climate remains one of the most uncertain components of the aerosol-radiation-climate problem, but has received less attention than other aerosol processes (e.g. production of terrestrial secondary organic aerosols). Thus, the special emphasis was placed on the production flux of sea spray aerosol particles, their number concentration and chemical composition and properties.

Meskhidze, Nicholas [NCSU

2013-10-21

42

Vibro-spring particle size distribution analyser

International Nuclear Information System (INIS)

This thesis describes the design and development of an automated pre-production particle size distribution analyser for particles in the 20 - 2000 ?m 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 feeding of the test powder into the spring, the non-interfering spring extension mechanism and means for measuring the cantilever deflection and hence the sample mass via a non-contact transducer. For an automated operation, a control software is developed which car allow an unattended analysis whilst providing particle size distribution in real-time. Data are reported in conjunction with a variety of powders with different size, density and shape. Typical resolutions in terms of size and mass measurement are better than ±10 ?m and ±0.1 g respectively. (author)

2002-01-01

43

Modeling particle size distributions by the Weibull distribution function

Energy Technology Data Exchange (ETDEWEB)

A method is proposed for modeling two- and three-dimensional particle size distributions using the Weibull distribution function. Experimental results show that, for tungsten particles in liquid phase sintered W-14Ni-6Fe, the experimental cumulative section size distributions were well fit by the Weibull probability function, which can also be used to compute the corresponding relative frequency distributions. Modeling the two-dimensional section size distributions facilitates the use of the Saltykov or other methods for unfolding three-dimensional (3-D) size distributions with minimal irregularities. Fitting the unfolded cumulative 3-D particle size distribution with the Weibull function enables computation of the statistical distribution parameters from the parameters of the fit Weibull function.

Fang, Zhigang (Rogers Tool Works, Rogers, AR (United States)); Patterson, B.R.; Turner, M.E. Jr (Univ. of Alabama, Birmingham, AL (United States))

1993-10-01

44

Modeling particle size distributions by the Weibull distribution function

International Nuclear Information System (INIS)

A method is proposed for modeling two- and three-dimensional particle size distributions using the Weibull distribution function. Experimental results show that, for tungsten particles in liquid phase sintered W-14Ni-6Fe, the experimental cumulative section size distributions were well fit by the Weibull probability function, which can also be used to compute the corresponding relative frequency distributions. Modeling the two-dimensional section size distributions facilitates the use of the Saltykov or other methods for unfolding three-dimensional (3-D) size distributions with minimal irregularities. Fitting the unfolded cumulative 3-D particle size distribution with the Weibull function enables computation of the statistical distribution parameters from the parameters of the fit Weibull function

1993-10-01

45

Particle reagent size distribution measurements for immunoassay

International Nuclear Information System (INIS)

A highly sensitive and rapid method for quantitatively assaying analytes in liquid media by directly measuring changes in particle size distribution of reagent particles having analyte insolubilized thereon in a system undergoing antibody-induced aggregation has been developed. The amount of analyte initially present can be determined by measuring the change in the distribution of particle size with time, the concentration of a particular size particle at a given time, the rate of formation of a particular size particle, or the steady-state maximum concentration for a particular size particle

1985-01-01

46

Aerosol Size Distribution in the marine regions

We would like to present the data obtained during the regular research cruises of the S/Y Oceania over a period of time between 2009 - 2012. The Baltic Sea is a very interesting polygon for aerosol measurements, however, also difficult due to the fact that mostly cases of a mixture of continental and marine aerosols are observed. It is possible to measure clear marine aerosol, but also advections of dust from southern Europe or even Africa. This variability of data allows to compare different conditions. The data is also compared with our measurements from the Arctic Seas, which have been made during the ARctic EXperiment (AREX). The Arctic Seas are very suitable for marine aerosol investigations since continental advections of aerosols are far less frequent than in other European sea regions. The aerosol size distribution was measured using the TSI Laser Aerosol Spectrometer model 3340 (99 channels, measurement range 0.09 ?m to 7 ?m), condensation particle counter (range 0.01 ?m to 3 ?m) and laser particle counter PMS CSASP-100-HV-SP (range 0.5 ?m to 47 ?m in 45 channels). Studies of marine aerosol production and transport are important for many Earth sciences such as cloud physics, atmospheric optics, environmental pollution studies and interaction between ocean and atmosphere. All equipment was placed on one of the masts of S/Y Oceania. Measurements using the laser aerosol spectrometer and condensation particle counter were made on one level (8 meters above sea level). Measurements with the laser particle counter were performed at five different levels above the sea level (8, 11, 14, 17 and 20 m). Based on aerosol size distribution the parameterizations with a Log-Normal and a Power-Law distributions were made. The aerosol source functions, characteristic for the region were also determined. Additionally, poor precision of the sea spray emission determination was confirmed while using only the aerosol concentration data. The emission of sea spray depends on the size of energy lost by the wind waves in the process of a collapse. We present the dependence between aerosol size distribution versus meteorological and micrometeorological parameters, such as wind speed, Monin-Obuchov Length, friction velocity and also turbulent fluxes of heat, momentum and humidity.

Markuszewski, Piotr; Petelski, Tomasz; Zielinski, Tymon; Pakszys, Paulina; Strzalkowska, Agata; Makuch, Przemyslaw; Kowalczyk, Jakub

2014-05-01

47

Intraspecific Body Size Frequency Distributions of Insects

Digital Repository Infrastructure Vision for European Research (DRIVER)

Although interspecific body size frequency distributions are well documented for many taxa, including the insects, intraspecific body size frequency distributions (IaBSFDs) are more poorly known, and their variation among mass-based and linear estimates of size has not been widely explored. Here we provide IaBSFDs for 16 species of insects based on both mass and linear estimates and large sample sizes (n?100). In addition, we review the published IaBSFDs for insects, though doing so is comp...

Gouws, E. Jeanne; Gaston, Kevin J.; Chown, Steven L.

2011-01-01

48

Software Package for Aerosol Size Distribution

Directory of Open Access Journals (Sweden)

Full Text Available The “Software Package for Aerosol Size Distribution” is a novel graphical user interface application software used for the study of atmospheric aerosol size distribution from various aerosol models (Continental clean, Continental average, Continental polluted, Urban, Desert, Maritime clean, Maritime polluted, Maritime tropical, Arctic, Antarctic and/or with different aerosol components (insoluble, water soluble, soot, sea salt (accumulation mode, sea salt (coarse mode, mineral (nucleation mode, mineral (accumulation mode, mineral (coarse mode, mineral (transported, sulfate, as a function of radius. This article discussed about the atmospheric aerosol, aerosol size distribution and the software description. Application case studies to generate the aerosol size distribution for an urban aerosol model and with different components have also been presented in this note.

T. A. Rajesh

2013-04-01

49

Continuous distribution of Mycoplasma genome sizes.

Genome sizes of eleven strains of eight species of Mollicutes Mycoplasmataceae were investigated by pulsed-field gel electrophoresis. Mycoplasma genomic sizes were determined from the sum of the sizes of fragments obtained after digestion of genomic DNA with restriction endonucleases. The sizes of the fragments were determined by comparison of their electrophoretic mobilities with those of lambda DNA concatemers. Specific restriction endonucleases were chosen so that after digestion three to ten fragments were obtained. The values for genome size derived by this method showed a continuous distribution that ranged from approximately 650 kb for Mycoplasma hyorhinis BTS-7 to 1600 kb for Acholeplasma laidlawii FHM. PMID:1841633

Barlev, N A; Borchsenius, S N

1991-01-01

50

Unravelling the size distribution of social groups

We present an study of size distributions of social groups based on a recent analogy between scale invariant systems and gases and fluids (arXiv:0902.2738v4). We go beyond the non-interacting system proposing a model for interactions based on complex networks that reproduces the main statistical properties found in city-size distributions and electoral results. We found a scale transformation that shows that these distributions can be classified with only one parameter, what we call the \\emph{competitiveness}. We reproduce well established empirical measures, as the six degrees of separation and the maximum number of stable social relationships that one person can address, known as the Dunbar's number. Finally, we show that the scaled city-size distributions of large countries obeys the same universal distribution, which we use to propose a method to estimate the total population of a country.

Hernando, A; Abad, M; Vesperinas, C

2009-01-01

51

Particle Size Distributions in Atmospheric Clouds

In this note, we derive a transport equation for a spatially integrated distribution function of particles size that is suitable for sparse particle systems, such as in atmospheric clouds. This is done by integrating a Boltzmann equation for a (local) distribution function over an arbitrary but finite volume. A methodology for evolving the moments of the integrated distribution is presented. These moments can be either tracked for a finite number of discrete populations ('clusters') or treated as continuum variables.

Paoli, Roberto; Shariff, Karim

2003-01-01

52

Understanding the particle number size distributions in diversified atmospheric environments is important in order to design mitigation strategies related to submicron particles and their effect on regional air quality, haze and human health. In this study, we conducted 15 different field measurement campaigns, each one-month long, between 2007 and 2011 at 13 individual sites in China. These were 5 urban sites, 4 regional sites, 3 coastal/background sites and one ship cruise measurement along eastern coastline of China. Size resolved particles were measured in the 15-600 nm size range. The median particle number concentrations (PNC) were found to vary in the range of 1.1-2.2 × 104 cm-3 at urban sites, 0.8-1.5 × 104 cm-3 at regional sites, 0.4-0.6 × 104 cm-3 at coastal/background sites, and 0.5 × 104 cm-3 during cruise measurements. Peak diameters at each of these sites varied greatly from 24 nm to 115 nm. Particles in the 15-25 nm (nucleation mode), 25-100 nm (Aitken mode) and 100-600 nm (accumulation mode) range showed different characteristics at each of the studied sites, indicating the features of primary emissions and secondary formation in these diversified atmospheric environments. Diurnal variations show a build-up of accumulation mode particles belt at regional sites, suggesting the contribution of regional secondary aerosol pollution. Frequencies of new particle formation (NPF) events were much higher at urban and regional sites than at coastal sites and cruise measurement. The average growth rates (GRs) of nucleation mode particles were 8.0-10.9 nm h-1 at urban sites, 7.4-13.6 nm h-1 at regional sites and 2.8-7.5 nm h-1 at both coastal and cruise measurement sites. The high gaseous precursors and strong oxidation at urban and regional sites not only favored the formation of particles, but also accelerated the growth rate of the nucleation mode particles. No significant difference in condensation sink (CS) during NPF days were observed among different site types, suggesting that the NPF events in background area were more influenced by the pollutant transport. In addition, average contributions of NPF events to potential cloud condensation nuclei (CCN) at 0.2% super-saturation in the afternoon of all sampling days were calculated as 11% and 6% at urban sites and regional sites, respectively. On the other hand, NPF events at coastal and cruise measurement sites had little impact on potential production of CCN. This study provides a large dataset of aerosol size distribution in diversified atmosphere of China, improving our general understanding of emission, secondary formation, new particles formation and corresponding CCN activity of submicron aerosols in Chinese environments.

Peng, J. F.; Hu, M.; Wang, Z. B.; Huang, X. F.; Kumar, P.; Wu, Z. J.; Yue, D. L.; Guo, S.; Shang, D. J.; Zheng, Z.; He, L. Y.

2014-06-01

53

Drop size distribution in an electrocontact extractor

Energy Technology Data Exchange (ETDEWEB)

The purpose of the present work was to experimentally find the explicit form of that function of a mathematical model of liquid extraction in an electrocontact apparatus which can serve as a basis for calculation of electrocontact extractors. The dependence was found of the distribution parameters on the voltage of the high-voltage power source. During investigation of the dependence of the drop size distribution on the voltage, the region whose center was situated on the axis of the apparatus near the lower edges of the high-potential electrode plates was photographed. As a result of experimental investigation of the dispersion of water in an electrocontact working in the system kerosene-water and explicit form of the drop size distribution was found, and also the dependence of the parameters of that distribution on the voltage of a high-voltage power source. The results obtained can be used in developing a method of calculating electrocontact extractors.

Afanas' ev, A.A.; Abdullaev, R.K.; Protod' yakov, I.O.; Zhukov, V.V.

1985-06-10

54

Activity Size Distributions of Natural Radioactive Aerosols in Outdoor Air

Energy Technology Data Exchange (ETDEWEB)

Activity size distributions of short lived radon and thoron decay products, long lived radon decay product lead-210 and cosmogenic beryllium-7 in atmospheric aerosol particles were measured using a five-stage high volume cascade impactor. The activity concentrations were measured by gamma spectrometry. The significant difference between the activity median aerodynamic diameters of the short and long-lived radon progeny seems to indicate that, after generation, the primary activity size distribution change to greater particle diameters mainly caused by the coagulation with existing non-active aerosol particles during their residence time in the atmosphere. (author)

Reis, M.J.; Fonseca, H.S. [Instituto Tecnologico e Nuclear, Estrada Nacional 10, 2686-953 Sacavem (Portugal)

2006-05-15

55

Size distributions of submicrometer aerosols from cooking

Energy Technology Data Exchange (ETDEWEB)

Although gas stove usage varies from country to country, it is still one of the major indoor combustion sources. In order to assess the health effects of using gas stoves, the physical characteristics of the particle emissions from cooking were conducted in a first-floor apartment in the Taipei area. The particle size distributions from scrambling eggs, frying chicken, and cooking soup were measured in the kitchen by a high resolution particle sizer, which could measure the particles in the size range of 0.01 [mu]m to 1 [mu]m. The concentrations of the submicrometer particles increased significantly from 15,000 cm[sup [minus]3] to 150,000 cm[sup [minus]3] during cooking. Additionally, the ultrafine particles constituted 60%--70% of the total submicron aerosols. The changes in the size distributions and the concentrations of the submicrometer aerosols before, during, and after the aerosol generations were compared. On the average, the median diameters of scrambling eggs, frying chicken, cooking soup, and of the background conditions were 40 nm, 50 nm, 30 nm, and 70 nm, respectively. Regarding the surface area-weighted size distributions, the surface median diameters of the four situations were 180 nm, 300 nm, 150 nm, and 220 nm, respectively. Furthermore, the volume median diameters in the conditions mentioned above were almost similar, namely 300--350 nm. 10 refs., 6 figs., 2 tabs.

Li, C.S.; Lin, W.H.; Jeng, F.T. (National Taiwan Univ., Taipei (Taiwan, Province of China))

1993-01-01

56

Synthesized grain size distribution in the interstellar medium

We examine a synthetic way of constructing the grain size distribution in the interstellar medium (ISM). First we formulate a synthetic grain size distribution composed of three grain size distributions processed with the following mechanisms that govern the grain size distribution in the Milky Way: (i) grain growth by accretion and coagulation in dense clouds, (ii) supernova shock destruction by sputtering in diffuse ISM, and (iii) shattering driven by turbulence in diffuse ISM. Then, we examine if the observational grain size distribution in the Milky Way (called MRN) is successfully synthesized or not. We find that the three components actually synthesize the MRN grain size distribution in the sense that the deficiency of small grains by (i) and (ii) is compensated by the production of small grains by (iii). The fraction of each {contribution} to the total grain processing of (i), (ii), and (iii) (i.e., the relative importance of the three {contributions} to all grain processing mechanisms) is 30-50%, 20-4...

Hirashita, Hiroyuki

2012-01-01

57

Number size characteristics and PM10 mass concentrations of particles emitted during the packaging of various kinds of carbon blacks were measured continuously in the bag filling areas of three carbon black plants and concurrently at ambient comparison sites. PM10, PM2.5, and PM1 dust fractions were also determined in the bag filling areas. The filter samples were then analyzed for elemental and organic carbon. Comparisons of the measured number size distributions and mass concentrations during bag filling activities with those measured parallel at the ambient site and with those determined during nonworking periods in the work area enabled the characterization of emitted particles. PM10 mass concentrations were consistently elevated (up to a factor of 20 compared to ambient concentrations) during working periods in the bag filling area. Detailed analysis revealed that the carbon black particles released by bag filling activities had a size distribution starting at approximately 400 nm aerodynamic diameter (dae) with modes around 1 microm dae and > 8 microm dae. Ultrafine particles (black sources such as forklift and gas heater emissions. PMID:15631057

Kuhlbusch, T A J; Neumann, S; Fissan, H

2004-10-01

58

Company Size Distributions as Economy Aggregated Indicators

Digital Repository Infrastructure Vision for European Research (DRIVER)

size: 12pt; color: #000000; line-height: 150%;">This paper studies the distribution of company income and provides evidence that income statistics follow a universal law (Zipf-Mandelbrot) and the parameters of this distribution gather relevant information as a proxy of the state's economy. This article contributes to the economic interpretation of these parameters. We find t...

Juan Carlos Pérez Mesa; Emilio Galdeano-Gómez

2009-01-01

59

Barchan dune's size distribution induced by collisions

Large dune fields can overrun for instance infrastructures lying in the way of their motion. Unidirectional wind fields and low sand availability give rise to single barchan dunes moving in the direction of wind. They can interact by directly exchanging their sand through collisions. This kind of interaction play a crucial role in the evolution of barchan dune fields, for instance in the selection of a characteristic dune size. Simulations of dune collisions with lateral offset are studied systematically and described by general phenomenological rules. Moreover, simulations with a simplified model without sand flux considering only collisions show that the sizes of sand dunes in such a scenario follow a Gaussian distribution with a well defined characteristic size.

Dur'an, O; Herrmann, H J

2007-01-01

60

Genome Sizes and the Benford Distribution

Background Data on the number of Open Reading Frames (ORFs) coded by genomes from the 3 domains of Life show the presence of some notable general features. These include essential differences between the Prokaryotes and Eukaryotes, with the number of ORFs growing linearly with total genome size for the former, but only logarithmically for the latter. Results Simply by assuming that the (protein) coding and non-coding fractions of the genome must have different dynamics and that the non-coding fraction must be particularly versatile and therefore be controlled by a variety of (unspecified) probability distribution functions (pdf’s), we are able to predict that the number of ORFs for Eukaryotes follows a Benford distribution and must therefore have a specific logarithmic form. Using the data for the 1000+ genomes available to us in early 2010, we find that the Benford distribution provides excellent fits to the data over several orders of magnitude. Conclusions In its linear regime the Benford distribution produces excellent fits to the Prokaryote data, while the full non-linear form of the distribution similarly provides an excellent fit to the Eukaryote data. Furthermore, in their region of overlap the salient features are statistically congruent. This allows us to interpret the difference between Prokaryotes and Eukaryotes as the manifestation of the increased demand in the biological functions required for the larger Eukaryotes, to estimate some minimal genome sizes, and to predict a maximal Prokaryote genome size on the order of 8–12 megabasepairs.These results naturally allow a mathematical interpretation in terms of maximal entropy and, therefore, most efficient information transmission.

Friar, James L.; Goldman, Terrance; Perez-Mercader, Juan

2012-01-01

61

Remote Laser Diffraction Particle Size Distribution Analyzer

Energy Technology Data Exchange (ETDEWEB)

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.

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

2001-03-01

62

Estimation of particle size distributions obtained by gas phase processes

International Nuclear Information System (INIS)

Nanoparticles intended for high value added applications often require special size distributions. Based on model calculations, this article compares the particle size distributions obtained with conventional and plasma processes. The model is based on an estimation of the probability for collisions; either for neutral or equally charged particles, whereas the growth of the particles is calculated using a model derived from Markov chains. The results of these calculations confirm the empirical knowledge that, under the special conditions of particles carrying electric charges of equal sign, plasma processes deliver products with the narrowest particle size distribution. Synthesis of extremely small particles with conventional processes leads to a significant residue of unreacted precursor. This finding is important in cases of expensive educts. The results of these model calculations are in perfect agreement with experimental findings.

2011-09-01

63

Particle size distribution of indoor aerosol sources

Energy Technology Data Exchange (ETDEWEB)

As concern about Indoor Air Quality (IAQ) has grown in recent years, it has become necessary to determine the nature of particles produced by different indoor aerosol sources and the typical concentration that these sources tend to produce. These data are important in predicting the dose of particles to people exposed to these sources and it will also enable us to take effective mitigation procedures. Further, it will also help in designing appropriate air cleaners. A new state of the art technique, DMPS (Differential Mobility Particle Sizer) System is used to determine the particle size distributions of a number of sources. This system employs the electrical mobility characteristics of these particles and is very effective in the 0.01--1.0 {mu}m size range. A modified system that can measure particle sizes in the lower size range down to 3 nm was also used. Experimental results for various aerosol sources is presented in the ensuing chapters. 37 refs., 20 figs., 2 tabs.

Shah, K.B.

1990-10-24

64

Distribution of domain sizes during overlayer growth

International Nuclear Information System (INIS)

Recently, the kinetics of domain growth in two-dimensional systems has attracted much theoretical and experimental attention. The time evolution of a nonconserved, order-disorder transition has been described by Lifshitz and by Allen and Cahn (LAC). This theory assumes that after the system is quenched from a disordered to an ordered state, domains separated by antiphase boundaries are formed. The degree of ordering of the individual domains is close to the equilibrium value. These domains will grow to reduce the curvature of the boundaries. The theory predicts that the domain size growth is proportional to the square root of time. In this report, the authors construct a microscopic model to describe the distribution of domain or island sizes during the growth of an overlayer. This model is used to describe results from a LEED experiment, the growth of the p(2x1) oxygen antiphase domains on a W(112) surface

1985-03-01

65

Comments on the Instanton Size Distribution

By studying the non-linear effects of overlapping instanton pairs we address difficulties in the identification of instanton distributions when the average instanton size is comparable to the average distance. For the exact charge two solution, we study how its parametrisation relates to a description in terms of individual instantons. There exist two dual sets of parameters describing the same charge two instanton solution. This duality implies the existence of a minimal separation between two instantons. Conventionally used lattice instanton finder algorithms based on the assumption of diluteness tend to underestimate instanton sizes. Finally we numerically confirm this for realistic parameters of the instanton liquid. The effect is enhanced by parallel orientation in group space.

Pérez-Garcia, M; Van Baal, P

2000-01-01

66

Electronic cigarette aerosol particle size distribution measurements.

The particle size distribution of aerosols produced by electronic cigarettes was measured in an undiluted state by a spectral transmission procedure and after high dilution with an electrical mobility analyzer. The undiluted e-cigarette aerosols were found to have particle diameters of average mass in the 250-450 nm range and particle number concentrations in the 10(9) particles/cm(3) range. These measurements are comparable to those observed for tobacco burning cigarette smoke in prior studies and also measured in the current study with the spectral transmission method and with the electrical mobility procedure. Total particulate mass for the e-cigarettes calculated from the size distribution parameters measured by spectral transmission were in good agreement with replicate determinations of total particulate mass by gravimetric filter collection. In contrast, average particle diameters determined for e-cigarettes by the electrical mobility method are in the 50 nm range and total particulate masses calculated based on the suggested diameters are orders of magnitude smaller than those determined gravimetrically. This latter discrepancy, and the very small particle diameters observed, are believed to result from almost complete e-cigarette aerosol particle evaporation at the dilution levels and conditions of the electrical mobility analysis. A much smaller degree, ~20% by mass, of apparent particle evaporation was observed for tobacco burning cigarette smoke. The spectral transmission method is validated in the current study against measurements on tobacco burning cigarette smoke, which has been well characterized in prior studies, and is supported as yielding an accurate characterization of the e-cigarette aerosol particle size distribution. PMID:23216158

Ingebrethsen, Bradley J; Cole, Stephen K; Alderman, Steven L

2012-12-01

67

Investigation of size distribution of silver nanoparticles

In this work, we present a physical methodology of preparing silver nanoparticles suspended in the deionized water. For this purpose, we apply the DC spark method and present the size distribution (by Zetasizer) and optical properties (by UV/VIS) of the nanoparticles in two different voltages. The obtained results using the DC spark method show that the fabrication of silver nanoparticles in deionized water without any surfactants and stabilizers is relatively cheap and pollution free. Using the method, we could prepare the silver nanoparticles smaller than 5 nm.

Khordad, R.; Vakili, M. R.; Bijanzadeh, A. R.

2012-02-01

68

Directory of Open Access Journals (Sweden)

Full Text Available Aerosol particle nucleation, or new-particle formation, is the dominant contributor to particle number in the atmosphere. However, these particles must grow through condensation of low-volatility vapors without coagulating with the larger, pre-existing particles in order to reach climate-relevant sizes (diameters larger than 50–100 nm, where the particles may affect clouds and radiation. In this paper, we use one year of size-distribution measurements from Egbert, Ontario, Canada to calculate the frequency of regional-scale new-particle formation events, new-particle formation rates, growth rates and the fraction of new particles that survive to reach climate-relevant sizes. Regional-scale new-particle formation events occurred on 14–31% of the days (depending on the stringency of the classification criteria, with event frequency peaking in the spring and fall. New-particle formation rates and growth rates were similar to those measured at other mid-latitude continental sites. We calculate that roughly half of the climate-relevant particles (with diameters larger than 50–100 nm at Egbert are formed through new-particle formation events. With the addition of meteorological and SO2 measurements, we find that new-particle formation often occurred under synoptic conditions associated with high surface pressure and large-scale subsidence that cause sunny conditions and clean-air flow from the north and west. However, new-particle formation also occurred when air flow came from the polluted regions to the south and southwest of Egbert. The nucleation rates tend to be faster during events under the polluted south/southwest flow conditions.

J. R. Pierce

2014-01-01

69

PRODUCTION OF UNIFORMLY SIZED SERUM ALBUMIN AND DEXTROSE MICROBUBBLES

Digital Repository Infrastructure Vision for European Research (DRIVER)

Uniformly-sized preparations with average microbubble (MB) diameters from 1 µm to 7 µm were produced reliably by sonicating decafluorobutane-saturated solutions of serum albumin and dextrose. Detailed protocols for producing and size-separating the MBs are presented, along with the effects that changing each production parameter (serum albumin concentration, sonication power, sonication time, etc.) had on MB size distribution and acoustic stability. These protocols can be used to produce MB...

2012-01-01

70

Single-drop fragmentation determines size distribution of raindrops

Like many natural objects, raindrops are distributed in size. By extension of what is known to occur inside the clouds, where small droplets grow by accretion of vapour and coalescence, raindrops in the falling rain at the ground level are believed to result from a complex mutual interaction with their neighbours. We show that the raindrops' polydispersity, generically represented according to Marshall-Palmer's law (1948), is quantitatively understood from the fragmentation products of non-interacting, isolated drops. Both the shape of the drops' size distribution, and its parameters are related from first principles to the dynamics of a single drop deforming as it falls in air, ultimately breaking into a dispersion of smaller fragments containing the whole spectrum of sizes observed in rain. The topological change from a big drop into smaller stable fragments-the raindrops-is accomplished within a timescale much shorter than the typical collision time between the drops.

Villermaux, Emmanuel; Bossa, Benjamin

2009-09-01

71

Single drop fragmentation is the source of raindrops size distribution

Like many natural objects, raindrops are distributed in size. By extension of what is known to occur inside the clouds, where small droplets grow by accretion of vapor and coalescence, raindrops in the falling rain at the ground level are believed to result from a complex mutual interaction with their neighbors. We show that the raindrops polydispersity, generically represented according to Marshall-Palmer's law, is quantitatively understood from the fragmentation products of non interacting, isolated drops. Both the shape of the drops size distribution, and its parameters are related from first principles to the dynamics of a single drop deforming as it falls in air, ultimately breaking into a dispersion of smaller fragments containing the whole spectrum of sizes observed in rain. The transformation is accomplished within a timescale much shorter than the typical collision time between the drops.

Villermaux, Emmanuel; Bossa, Benjamin

2009-11-01

72

Power laws, discontinuities and regional city size distributions

Urban systems are manifestations of human adaptation to the natural environment. City size distributions are the expression of hierarchical processes acting upon urban systems. In this paper, we test the entire city size distributions for the southeastern and southwestern United States (1990), as well as the size classes in these regions for power law behavior. We interpret the differences in the size of the regional city size distributions as the manifestation of variable growth dynamics dependent upon city size. Size classes in the city size distributions are snapshots of stable states within urban systems in flux. ?? 2008.

Garmestani, A. S.; Allen, C. R.; Gallagher, C. M.

2008-01-01

73

Explaining the Size Distribution of Cities: X-treme Economies

Digital Repository Infrastructure Vision for European Research (DRIVER)

The methodology used by theories to explain the size distribution of cities takes an empirical fact and works backward to first obtain a reduced form of a model, then pushes this reduced form back to assumptions on primitives. The induced assumptions on consumer behavior, particularly about their inability to insure against the city-level productivity shocks in the model, are untenable. With either self insurance or insurance markets, and either an arbitrarily small cost of moving or the as...

2008-01-01

74

Explaining the size distribution of cities: x-treme economies

Digital Repository Infrastructure Vision for European Research (DRIVER)

The methodology used by theories to explain the size distribution of cities takes an empirical fact and works backward to first obtain a reduced form of a model, then pushes this reduced form back to assumptions on primitives. The induced assumptions on consumer behavior, particularly about their inability to insure against the city-level productivity shocks in the model, are untenable. With either self insurance or insurance markets, and either an arbitrarily small cost of moving or the as...

2008-01-01

75

Explaining the size distribution of cities: X-treme economies

Digital Repository Infrastructure Vision for European Research (DRIVER)

The methodology used by theories to explain the size distribution of cities is contrived in that it takes an empirical fact and works backward to first obtain a reduced form of a model, then pushes this reduced form back to assumptions on primitives. The induced assumptions on consumer behavior, particularly about their ability to insure against the city-level productivity shocks in the model, are untenable. With either self insurance or insurance markets, and either an arbitrarily small co...

2007-01-01

76

Fisher Information in Flow Size Distribution

The flow size distribution is a useful metric for traffic modeling and management. Its estimation based on sampled data, however, is problematic. Previous work has shown that flow sampling (FS) offers enormous statistical benefits over packet sampling but high resource requirements precludes its use in routers. We present Dual Sampling (DS), a two-parameter family, which, to a large extent, provide FS-like statistical performance by approaching FS continuously, with just packet-sampling-like computational cost. Our work utilizes a Fisher information based approach recently used to evaluate a number of sampling schemes, excluding FS, for TCP flows. We revise and extend the approach to make rigorous and fair comparisons between FS, DS and others. We show how DS significantly outperforms other packet based methods, including Sample and Hold, the closest packet sampling-based competitor to FS. We describe a packet sampling-based implementation of DS and analyze its key computational costs to show that router impl...

Tune, Paul

2011-01-01

77

Refinement of size distributions for primary crystallizations

Energy Technology Data Exchange (ETDEWEB)

The microstructure developed in primary crystallizations is studied under realistic conditions. The primary crystallization of an amorphous alloy is modeled by considering the thermodynamics of a metastable phase transition and the kinetics of nucleation and crystal growth under isothermal annealing. A realistic growth rate, including an interface controlled growth at the beginning of the growth of each single grain and diffusion controlled growth process with soft impingement afterwards is considered. The reduction in the nucleation rate due to the compositional change in the remaining amorphous matrix is also taken into account. The microstructures developed during the transformation are obtained by using the Populational KJMA method, from the above thermodynamic and kinetic factors. Experimental data of transformed fraction, grain density, average grain size, grain size distribution and other related parameters obtained from annealed metallic glasses are modeled. The authors will focus on the nanocrystallization of a FINEMET alloy. In particular, they will analyze the isothermal nanocrystalline precipitation of an {alpha}-Fe(Si) phase, with a DO{sub 3} defective in Si superstructure, in a FINEMET material of composition Fe{sub 73.5}Si{sub 17.5}Cu{sub 1}Nb{sub 3}B{sub 5}.

Pineda, E.; Pradell, T.; Crespo, D. [Univ. Politecnica de Catalunya, Barcelona (Spain); Clavaguera, N. [Univ. de Barcelona (Spain); Zhu, J. [Univ. of Delaware, Newark, DE (United States). Inst of Energy Conversion; Clavaguera-Mora, M.T. [Univ. Autonoma de Barcelona, Bellaterra (Spain)

1998-12-31

78

Refinement of size distributions for primary crystallizations

International Nuclear Information System (INIS)

The microstructure developed in primary crystallizations is studied under realistic conditions. The primary crystallization of an amorphous alloy is modeled by considering the thermodynamics of a metastable phase transition and the kinetics of nucleation and crystal growth under isothermal annealing. A realistic growth rate, including an interface controlled growth at the beginning of the growth of each single grain and diffusion controlled growth process with soft impingement afterwards is considered. The reduction in the nucleation rate due to the compositional change in the remaining amorphous matrix is also taken into account. The microstructures developed during the transformation are obtained by using the Populational KJMA method, from the above thermodynamic and kinetic factors. Experimental data of transformed fraction, grain density, average grain size, grain size distribution and other related parameters obtained from annealed metallic glasses are modeled. The authors will focus on the nanocrystallization of a FINEMET alloy. In particular, they will analyze the isothermal nanocrystalline precipitation of an ?-Fe(Si) phase, with a DO3 defective in Si superstructure, in a FINEMET material of composition Fe73.5Si17.5Cu1Nb3B5

1997-12-01

79

Genome Sizes and the Benford Distribution

Data on the number of Open Reading Frames (ORFs) coded by genomes from the 3 domains of Life show some notable general features including essential differences between the Prokaryotes and Eukaryotes, with the number of ORFs growing linearly with total genome size for the former, but only logarithmically for the latter. Assuming that the (protein) coding and non-coding fractions of the genome must have different dynamics and that the non-coding fraction must be controlled by a variety of (unspecified) probability distribution functions, we are able to predict that the number of ORFs for Eukaryotes follows a Benford distribution and has a specific logarithmic form. Using the data for 1000+ genomes available to us in early 2010, we find excellent fits to the data over several orders of magnitude, in the linear regime for the Prokaryote data, and the full non-linear form for the Eukaryote data. In their region of overlap the salient features are statistically congruent, which allows us to: interpret the differenc...

Friar, James L; Pérez-Mercader, Juan; 10.1371/journal.pone.0036624

2012-01-01

80

Independent production and Poisson distribution

International Nuclear Information System (INIS)

It is shown that statement of factorization of inclusive sections in case of independent production of particles and the conclusion on Poisson distribution over their multiplicity drawn from it do not follow form the probability theory in any way. Using accurately the theorem of the product of independent probabilities, quite different equations are obtained and do consequences relative to multiplicity distributions are obtained

1995-11-01

81

Parameterizing Size Distribution in Ice Clouds

Energy Technology Data Exchange (ETDEWEB)

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 cloud optical properties formulated in terms of PSD parameters in combination with remote measurements of thermal radiances to characterize the small mode. This is possible since the absorption efficiency (Qabs) of small mode crystals is larger at 12 µm wavelength relative to 11 µm wavelength due to the process of wave resonance or photon tunneling more active at 12 µm. This makes the 12/11 µm absorption optical depth ratio (or equivalently the 12/11 µm Qabs ratio) a means for detecting the relative concentration of small ice particles in cirrus. Using this principle, this project tested and developed PSD schemes that can help characterize cirrus clouds at each of the three ARM sites: SGP, NSA and TWP. This was the main effort of this project. These PSD schemes and ice sedimentation velocities predicted from them have been used to test the new cirrus microphysics parameterization in the GCM known as the Community Climate Systems Model (CCSM) as part of an ongoing collaboration with NCAR. Regarding the second problem, we developed and did preliminary testing on a passive thermal method for retrieving the total water path (TWP) of Arctic mixed phase clouds where TWPs are often in the range of 20 to 130 g m-2 (difficult for microwave radiometers to accurately measure). We also developed a new radar method for retrieving the cloud ice water content (IWC), which can be vertically integrated to yield the ice water path (IWP). These techniques were combined to determine the IWP and liquid water path (LWP) in Arctic clouds, and hence the fraction of ice and liquid water. We have tested this approach using a case study from the ARM field campaign called M-PACE (Mixed-Phase Arctic Cloud Experiment). This research led to a new satellite remote sensing method that appears promising for detecting low levels of liquid water in high clouds typically between -20 and -36 oC. We hope to develop this method in future research.

DeSlover, Daniel; Mitchell, David L.

2009-09-25

82

Size measurements of radon decay products by diffusion method

International Nuclear Information System (INIS)

Particle size of radon decay products is very important for dose evaluation. Dose conversion factor (DCF) from concentration to effective dose strongly depends on the particle size. Comparing with attached fraction of radon decay products, the DCF of unattached fraction is very high in a nanometer region. In order to get the size information with adequate resolution, we tried to refine the graded screen array (GSA) method based on diffusion. In the experiments using radon chamber, the mean diameter (MD) for unattached fraction was observed slightly less than 1 nm with small geometric standard deviation (GSD) of 1.1. The size distribution was almost constant in both cases of carrier aerosol free and not. And thus the high size resolution was confirmed. The GSA method was also conducted in the field measurements. Here we show our newly configured GSA and the results of size measurements. (author)

2004-07-02

83

Influence of char fragmentation on ash particle size distributions

Energy Technology Data Exchange (ETDEWEB)

The influence of char fragmentation on the size distribution of combustion-generated ash has been investigated in a detailed laboratory study utilizing both coals and synthetic chars. Combustion of three different coal types resulted in production of ash particles in the 1-10-..mu..m size range at all conditions considered (1500 and 1750 K, 8% O/sub 2/ and above). The amount of ash in the 1-5-..mu..m range was relatively invariant with combustion conditions, and typically represented 10%-20% of the total ash mass, which greatly exceeds the mass predicted from a model assuming that one ash particle is produced per char particle. The macroporosity of the char was found to be the important variable in determining fragmentation behavior, as evidenced by results obtained from combustion of synthetic chars. Macroporous Spherocarb doped with sodium silicate yielded 75 ash particles greater than 1 ..mu..m in diameter per char particle, whereas nonmacroporous sucrose/carbon black chars doped with sodium silicate yielded only 1 ash particle per char particle. A site percolation model was developed to stimulate the process of fly ash formation during pulverized coal combustion. Modeling results, utilizing a monodisperse mineral grain size distribution for the cases of 0% and 10% porosity, qualitatively predicted the features of experimentally observed ash particle size distributions obtained from combustion of synthetic chars.

Helble, J.J.; Sarofim, A.F.

1989-05-01

84

On stratospheric aerosol size distributions from recent optical radar observations

International Nuclear Information System (INIS)

From observational results of ruby laser (lambda=6943 A) radar backscattering and data on small ions, we examined typical stratospheric aerosol size distributions thus far proposed. Power-law size distribution and bimodal size distribution can explain both the lidar backscattering coefficient and density of small ion if we take into account the existence of numerous Aitken particles. Thus we cannot determine aerosol size distribution uniquely at the present stage of the investigations. We examine here bimodal size distribution in some detail by considering the elementary physical processes. The power-law size distribution, we presume, is produced by in situ sulfuric acid particle nucleation. This size distribution is modified by increased outer particle injection such as that from meteors or volcanic eruptions. If meteor particles are undergoing sedimentation, eddy diffusion and growing by attachment of sulfuric acid particles which have mean radius 5 m?, assuming the power-law size distribution, then meteor particle size distribution is log-normal. Bimodal size distribution is produced by both the log-normal size distribution and the pre-existing Aitken-size sulfuric acid particles. (auth.)

1975-01-01

85

Experimental Analysis of Particle Size Distribution using Electromagnetic Sieve

Directory of Open Access Journals (Sweden)

Full Text Available This work is aimed at grading the particle sizes of powders and granular distribution of particle sizes of a local agricultural product, GARRI. To be able to do this, an electromagnetic sieving machine which transforms electromagnetic energy to mechanical energy was designed and constructed. The Choice of Electromagnetic Sieving Machine was to increase the amplitude of oscillation and thereby reducing the time of sieving. With the aid of the machine, sieving was carried out three times at different voltage settings. The tests conducted show that with increase in voltage, the amplitude of oscillation also increased, thereby reducing the sieving time. Optimal output (from 1kg of Garri was obtained in 120 seconds at a voltage setting of 255 volts which generated 5mm amplitude. The different particle sizes were evaluated by the use of an electronic microscope. The efficiency of the machine was evaluated to be 98%.

Ujam, A.J.,

2013-10-01

86

Digital Repository Infrastructure Vision for European Research (DRIVER)

Particle size distributions in the output stream of commercial, fluidized-bed reactors for ethylene polymerization are analyzed using a mathematical model. The impact on the overall reactor performance of the universe of sizes for the particles in the bed, with only a fraction of them being extracted in the product flow, is studied. For the output stream, product size distribution is modeled using both triangular and generalized gamma functions. Extraction system parameters are employed to mo...

2005-01-01

87

Powerlaws for ratios of moments of the fragment size distribution

International Nuclear Information System (INIS)

The method of scaled factorial moments (s.f.m.) is used to study fluctuations of the fragment size distribution in the percolation model and in nuclear multifragmentation following the breakup of the high energy nuclei. It is found that similarly as in several cascade models describing the multiparticle production at ultrarelativistic energies, the site-bond percolation model at around the critical point for large lattice sizes exhibits a power behaviour of the ratio of s.f.m. of different rank which is typical for the self-similar branching mechanism. Both the experimental data and the percolation model events selected according either to the number of intermediate mass fragments or to the total fragment multiplicity can be fitted well by such a power behaviour. Only in small charge/mass bins one observes small but systematic deviations with respect to the power behaviour which may be indicate the possibility of a weak scale-breaking mechanism. Together with an evidence for an intermittent pattern of fluctuations which was found earlier in the fragment charge/mass distributions at E/A?1 GeV/nucl the present results suggest strongly not only the self-similarity in the fragment size distribution and a random character for the scaling law but also the importance of the branching mechanism in the fragment formation process

1990-01-01

88

Evolution of Particle Size Distributions in Fragmentation Over Time

We present a new model of fragmentation based on a probabilistic calculation of the repeated fracture of a particle population. The resulting continuous solution, which is in closed form, gives the evolution of fragmentation products from an initial block, through a scale-invariant power-law relationship to a final comminuted powder. Models for the fragmentation of particles have been developed separately in mainly two different disciplines: the continuous integro-differential equations of batch mineral grinding (Reid, 1965) and the fractal analysis of geophysics (Turcotte, 1986) based on a discrete model with a single probability of fracture. The first gives a time-dependent development of the particle-size distribution, but has resisted a closed-form solution, while the latter leads to the scale-invariant power laws, but with no time dependence. Bird (2009) recently introduced a bridge between these two approaches with a step-wise iterative calculation of the fragmentation products. The development of the particle-size distribution occurs with discrete steps: during each fragmentation event, the particles will repeatedly fracture probabilistically, cascading down the length scales to a final size distribution reached after all particles have failed to further fragment. We have identified this process as the equivalent to a sequence of trials for each particle with a fixed probability of fragmentation. Although the resulting distribution is discrete, it can be reformulated as a continuous distribution in maturity over time and particle size. In our model, Turcotte's power-law distribution emerges at a unique maturation index that defines a regime boundary. Up to this index, the fragmentation is in an erosional regime with the initial particle size setting the scaling. Fragmentation beyond this index is in a regime of comminution with rebreakage of the particles down to the size limit of fracture. The maturation index can increment continuously, for example under grinding conditions, or as discrete steps, such as with impact events. In both cases our model gives the energy associated with the fragmentation in terms of the developing surface area of the population. We show the agreement of our model to the evolution of particle size distributions associated with episodic and continuous fragmentation and how the evolution of some popular fractals may be represented using this approach. C. A. Charalambous and W. T. Pike (2013). Multi-Scale Particle Size Distributions of Mars, Moon and Itokawa based on a time-maturation dependent fragmentation model. Abstract Submitted to the AGU 46th Fall Meeting. Bird, N. R. A., Watts, C. W., Tarquis, A. M., & Whitmore, A. P. (2009). Modeling dynamic fragmentation of soil. Vadose Zone Journal, 8(1), 197-201. Reid, K. J. (1965). A solution to the batch grinding equation. Chemical Engineering Science, 20(11), 953-963. Turcotte, D. L. (1986). Fractals and fragmentation. Journal of Geophysical Research: Solid Earth 91(B2), 1921-1926.

Charalambous, C. A.; Pike, W. T.

2013-12-01

89

School Productivity, Class Size, and Choice.

Although the nation is spending more on its public schools than ever before, American students score poorly on standardized tests in comparison to other countries. Rising spending has had little effect on educational results because of a dramatic decline in labor productivity in public schools. Research on class size indicates that efficient class…

Vedder, Richard K.

1988-01-01

90

Particle size distributions from multiple hydrodynamic fragmentation events

International Nuclear Information System (INIS)

A Monte Carlo technique is used to predict particle size distributions resulting from multiple hydrodynamic fragmentation events occurring in gas/liquid systems. Ultimate fragment size distributions are calculated by considering the effects of secondary drop breakup upon the first stage distributions associated with each breakup mechanism. 2 refs

1979-08-23

91

Evaluation of droplet size distributions using univariate and multivariate approaches

DEFF Research Database (Denmark)

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.

GaunÃ¸, Mette HÃ¸g; Larsen, Crilles Casper

2014-01-01

92

How Sample Size Affects a Sampling Distribution

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…

Mulekar, Madhuri S.; Siegel, Murray H.

2009-01-01

93

Using emulsion particle size distribution to optimize emulsion manufacturing processes

Energy Technology Data Exchange (ETDEWEB)

Emulsion particle size distribution can be used in emulsion process optimization studies, when the measurement of emulsion physical properties such as viscosity, are not sensitive enough to changes in process variables such as homogenization pressure. A photomicrographic method for determining emulsion particle size distribution is presented. It is demonstrated how trends in the particle size distribution with changing processing variables can be used to help optimize emulsion manufacturing processes.

Tait, W.S.

1985-01-01

94

How dense can one pack spheres of arbitrary size distribution?

We present the first systematic algorithm to estimate the maximum packing density of spheres when the grain sizes are drawn from an arbitrary size distribution. With an Apollonian filling rule, we implement our technique for disks in 2d and spheres in 3d. As expected, the densest packing is achieved with power-law size distributions. We also test the method on homogeneous and on empirical real distributions, and we propose a scheme to obtain experimentally accessible distributions of grain sizes with low porosity. Our method should be helpful in the development of ultra-strong ceramics and high performance concrete.

Reis, Saulo D S; Andrade, José S; Herrmann, Hans J

2011-01-01

95

Particle size distribution effects on sintering of spherical tungsten

International Nuclear Information System (INIS)

Sintering densification studies have been performed on blends of spherical tungsten powder with controlled variation in particle size distribution width, expressed as 1n. The mean sizes of the distributions by weight frequency and the green densities of the specimens were held relatively constant. The wider distribution blend was found to densify more rapidly than the narrower distribution in spite of having a slightly larger mean size. This enhanced sintering was explained through a statistical model of particle packing which predicted a finer average pore size for the larger 1n powder blend. Microstructures of the sintered materials indicated good qualitative agreement with the model

1985-07-14

96

Company Size Distributions as Economy Aggregated Indicators

Directory of Open Access Journals (Sweden)

Full Text Available This paper studies the distribution of company income and provides evidence that income statistics follow a universal law (Zipf-Mandelbrot and the parameters of this distribution gather relevant information as a proxy of the state's economy. This article contributes to the economic interpretation of these parameters. We find that they are robust indicators of the structure of an economy and should be taken into account when designing policies to promote competition.

Emilio Galdeano-Gómez

2009-08-01

97

Dependence of resid processing selectivity on catalyst pore size distribution

Energy Technology Data Exchange (ETDEWEB)

In the hydroprocessing of resid, catalyst selectivity and the relationship between metals and sulfur distribution in the resid are key factors in achieving required product specifications. Using gradient elution chromatography as a method of analysis, it was found that catalyst pore size distribution can significantly affect selectivity for different metal and sulfur components in residua. A small pore catalyst was observed to be more selective for non-asphaltene sulfur and metals, while a large pore catalyst was found to be very selective for asphaltene metals and sulfur. This variation of catalyst selectivity is a result of the concentration of metals and sulfur in different portions of the resid. For typical Middle Eastern residua, about 70-75% of the sulfur was found to be present in low molecular weight less aromatic GEC fractions, while 95% of the metals were in highly aromatic high molecular weight fractions. Thus the variation of selectivity with pore size was found to result from concentration of the sulfur and metal species in molecules of different size. 25 refs.

Fischer, R.H.; Angevine, P.J.

1986-11-14

98

PRODUCTION OF UNIFORMLY SIZED SERUM ALBUMIN AND DEXTROSE MICROBUBBLES

Uniformly-sized preparations with average microbubble (MB) diameters from 1 µm to 7 µm were produced reliably by sonicating decafluorobutane-saturated solutions of serum albumin and dextrose. Detailed protocols for producing and size-separating the MBs are presented, along with the effects that changing each production parameter (serum albumin concentration, sonication power, sonication time, etc.) had on MB size distribution and acoustic stability. These protocols can be used to produce MBs for experimental applications or serve as templates for developing new protocols that yield MBs with physical and acoustic properties better suited to specific applications. Size stability and ultrasonic performance quality control tests were developed to assure that successive MB preparations perform identically and to distinguish the physical and acoustic properties of identically sized MBs produced with different serum albumin-dextrose formulations and sonication parameters. MBs can be stored at 5°C for protracted periods (2 weeks to one year depending on formulation).

Borrelli, Michael J.; O'Brien, William D.; Bernock, Laura J.; Williams, Heather R.; Hamilton, Eric; Wu, Jonah; Oelze, Michael L.; Culp, William C.

2011-01-01

99

Effect of particle size distribution on sintering of tungsten

International Nuclear Information System (INIS)

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, 1n?, 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 1n? on the microstructural evolution during sintering

1984-01-01

100

Software Sizing and Productivity with Function Points

Directory of Open Access Journals (Sweden)

Full Text Available Software sizing is one of the most challenging, and critical activities in software project management. Effective software sizing help project managers to plan and execute software projects successfully. In software business the technology is changing very quickly. It is impractical to change the measurement rules very often in accordance with the technology. Today’s software applications use different technologies, tools and several programming languages in one go. As a result software systems continue to grow in size and complexity. They are very difficult to understand, asses, and manage. A common method to understand, measure, and communicate size and productivity need to be used and established in the industry for effective project management.Function Point Analysis (FPA is a natural fit into this category. The FPA technique quantifies the user functions contained within software application in terms that are meaningful to the end User. A case study presented in this paper shows how FPA can be used as a common yardstick in software sizing and help establish an effective communication among different stakeholders of the software development project.

H. K. Raju

2013-05-01

101

Ultrasonically controlled particle size distribution of explosives: a safe method.

Size reduction of the high energy materials (HEM's) by conventional methods (mechanical means) is not safe as they are very sensitive to friction and impact. Modified crystallization techniques can be used for the same purpose. The solute is dissolved in the solvent and crystallized via cooling or is precipitated out using an antisolvent. The various crystallization parameters such as temperature, antisolvent addition rate and agitation are adjusted to get the required final crystal size and morphology. The solvent-antisolvent ratio, time of crystallization and yield of the product are the key factors for controlling antisolvent based precipitation process. The advantages of cavitationally induced nucleation can be coupled with the conventional crystallization process. This study includes the effect of the ultrasonically generated acoustic cavitation phenomenon on the solvent antisolvent based precipitation process. CL20, a high-energy explosive compound, is a polyazapolycyclic caged polynitramine. CL-20 has greater energy output than existing (in-use) energetic ingredients while having an acceptable level of insensitivity to shock and other external stimuli. The size control and size distribution manipulation of the high energy material (CL20) has been successfully carried out safely and quickly along with an increase in the final mass yield, compared to the conventional antisolvent based precipitation process. PMID:17532248

Patil, Mohan Narayan; Gore, G M; Pandit, Aniruddha B

2008-03-01

102

Scalar products of elementary distributions

The field of real numbers being extended as a larger commutative field, we investigate the possibility of defining a scalar product for the distributions of finite discrete support. Then we focus on the most simple possible extension (which is an ordered field), we provide explicit formulas for this scalar product, and we exhibit a structure of positive definite inner-product space. In a one-dimensional application to the Schroedinger equation, the distributions supported by the origin are embedded into a bra-ket vector space, where the "singular" potential describing point interaction is defined in a natural way. A contact with the hyperreal numbers that arise in nonstandard analysis is possible but not essential, our extensions of $\\bf R$ and $\\bf C$ being obtained by a quite elementary method.

Droz-Vincent, Philippe

2007-01-01

103

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

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.

Belmonte, Alessandro; Buldyrev, Sergey V

2014-01-01

104

Relationship between particle size distribution and sludge dewaterability

Energy Technology Data Exchange (ETDEWEB)

Sludge dewatering can be presumed to be significantly dependent upon the properties of the particles comprising the suspension, such as particle size, surface charge, and compressibility. Among these, particle size is generally recognized to be the most important factor influencing dewaterability. Many investigators have found that particle size affects dewaterability, but a relationship between the particle size distribution and dewaterability has not been examined. The objective of this research was to measure the particle size distribution and dewaterability of anaerobically digested sludges using an electronic particle counter, to examine the influence of polymer conditioners, pH and filtration on particle size distribution and dewaterability, and to determine if any quantitative relationship between particle size and dewaterability could be developed.

Chang, N.W.

1986-01-01

105

A size distribution of silicate grains in Eta Carinae

International Nuclear Information System (INIS)

Assuming a geometry for Eta Carinae a size distribution for silicate grains has been determined to account for the observed optical linear polarization. From this it is found that grains of size 0.15 ?m contribute most to the scattering at optical wavelengths. Using the same distribution it is found that maximum emission at 10 ?m can be expected from grains of size 0.1 ?m. (author)

1979-01-01

106

Powder Size and Distribution in Ultrasonic Gas Atomization

Ultrasonic gas atomization (USGA) produces powder sizes dependent on the ratio of the nozzle jet diameter to the distance of spread dt/R, Powder size distribution is attributed to the spread of atomizing gas jets during travel from the nozzle exit to the metal stream. The spread diminishes at higher gas atomization pressures. In this paper, calculated powder sizes and distribution are compared with experimentally determined values.

Rai, G.; Lavernia, E.; Grant, N. J.

1985-08-01

107

Particle size distributions in the Eastern Mediterranean troposphere

Digital Repository Infrastructure Vision for European Research (DRIVER)

Atmospheric particle size distributions were measured on Crete island, Greece in the Eastern Mediterranean during an intensive field campaign between 28 August and 20 October 2005. Our instrumentation combined a differential mobility particle sizer (DMPS) and an aerodynamic particle sizer (APS) and measured number size distributions in the size range 0.018 ?m–10 ?m. Four time periods with distinct aerosol characteristics were discriminated, two corresponding to marine and polluted air...

Kalivitis, N.; Birmili, W.; Stock, M.; Wehner, B.; Massling, A.; Wiedensohler, A.; Gerasopoulos, E.; Mihalopoulos, N.

2008-01-01

108

Size and size distribution of CdS nano-particles synthesized by EB irradiation

International Nuclear Information System (INIS)

Cadmium sulfide nano-particles have been successfully prepared by electron beam irradiation in the water system. The products were characterized by X-ray diffraction, transmission electron microscope and fluorescence spectroscopy. The results indicated that the CdS nano-particles were of pure face-centered cubic crystal and in spherical shape of, averaged about 15 nm in size. The UV absorption edge of CdS nano-particles is 487 nm. When the excitation wavelength was 350 nm, the peak of the emission wavelength of CdS nano-particles is at 476 nm, and the fluorescence was attributed to the emission of band edge. The influence of the concentration of PVA on the size of the CdS nano-particles was studied by laser scattering particle size distribution analysis. The results showed that the size of the CdS nano-particles decreased with increasing the concentration of polyvinyl alcohol during a certain extent. (authors)

2006-06-01

109

The Development of Drop Size Distributions in Light Rain.

A model of rain development based on the quasi-stochastic coalescence equation and including the sedimentation of drops has been used to study the formation of drop size distributions in conditions of weak updraft. Comparisons with `box model' results indicate that sedimentation effects are crucial in establishing the shapes of the distribution. Under realistic conditions of cloud droplet distribution with size, the raindrop size distributions as simulated by the model compare well with observations of orographic rain made in Hawaii. On the other hand, Doppler radar measurements of drop size distributions just below a bright band confirm that the Marshall-Palmer distribution results from processes affecting particles in the solid phase rather than from the interaction of raindrops.

Zawadzki, I.; Monteiro, E.; Fabry, F.

1994-04-01

110

Small sample size effects in statistical analyses of eigenvalue distributions

International Nuclear Information System (INIS)

The effects of small sample sizes on the statistical analysis of eigenvalue distributions were analyzed numerically. The behavior of the nearest-neighbor spacing distribution, the ?3 statistic, and the linear correlation coefficient between adjacent spacings was studied, and the effects of missing or spurious levels and of unfolding an energy-dependent level density were explored. For small sample sizes the nearest-neighbor spacing distribution appears to be the most reliable of these three statistics. (orig.)

1992-04-01

111

Fractal Theory and Application in City Size Distribution

Directory of Open Access Journals (Sweden)

Full Text Available City size distribution has become a hot topic in urbanization process and governed by many laws and rules in terms of its evolution and change. This study has discussed relation between fractal theory and city size distribution, Hausdorff index, Pareto distribution and zip’s law as well as index calculation method which ought to be a good method of evaluating urban development.

Liu Zhenling

2013-01-01

112

Size distribution of Amazon River bed sediment

The first recorded observations of bed material of the Amazon River were made in 1843 by Lt William Lewis Herndon of the US Navy, when he travelled the river from its headwaters to its mouth, sounding its depths, and noting the nature of particles caught in a heavy grease smeared to the bottom of his sounding weight1. He reported the bed material of the river to be mostly sand and fine gravel. Oltman and Ames took samples at a few locations in 1963 and 1964, and reported the bed material at O??bidos, Brazil, to be fine sands, with median diameters ranging from 0.15 to 0.25 mm (ref. 2). We present here a summary of particle-size analyses of samples of streambed material collected from the Amazon River and its major tributaries along a reach of the river from Iquitos in Peru, ???3,500 km above Macapa?? Brazil, to a point 220 km above Macapa??3. ?? 1980 Nature Publishing Group.

Nordin, C. F.; Meade, R. H.; Curtis, W. F.; Bosio, N. J.; Landim, P. M. B.

1980-01-01

113

The Collisional Divot in the Kuiper belt Size Distribution

This paper presents the results of collisional evolution calculations for the Kuiper belt starting from an initial size distribution similar to that produced by accretion simulations of that region - a steep power-law large object size distribution that breaks to a shallower slope at r ~1-2 km, with collisional equilibrium achieved for objects r ~0.5 km. We find that the break from the steep large object power-law causes a divot, or depletion of objects at r ~10-20 km, which in-turn greatly reduces the disruption rate of objects with r> 25-50 km, preserving the steep power-law behavior for objects at this size. Our calculations demonstrate that the roll-over observed in the Kuiper belt size distribution is naturally explained as an edge of a divot in the size distribution; the radius at which the size distribution transitions away from the power-law, and the shape of the divot from our simulations are consistent with the size of the observed roll-over, and size distribution for smaller bodies. Both the kink r...

Fraser, Wesley C

2009-01-01

114

Inversion of spheroid particle size distribution in wider size range and aspect ratio range

Directory of Open Access Journals (Sweden)

Full Text Available The non-spherical particle sizing is very important in the aerosol science, and it can be determined by the light extinction measurement. This paper studies the effect of relationship of the size range and aspect ratio range on the inversion of spheroid particle size distribution by the dependent mode algorithm. The T matrix method and the geometric optics approximation method are used to calculate the extinction efficiency of the spheroids with different size range and aspect ratio range, and the inversion of spheroid particle size distribution in these different ranges is conducted. Numerical simulation indicates that a fairly reasonable representation of the spheroid particle size distribution can be obtained when the size range and aspect ratio range are suitably chosen.

Tang Hong

2013-01-01

115

The design of radon progeny radioactive size distribution analysis system

International Nuclear Information System (INIS)

The estimate for the size distribution is determined from indirect observations using computational methods. The paper provides a solution of radon progeny activity size distribution analysis monitoring system which is based on the parallel screen diffusional battery theory and estimate methods such as Twomy algorithm, EM algorithm. In this paper the penetration curve is given by calculation of the wire screen type diffusion battery parameters; Two approximation algorithms including Twomy nonlinear iterative method, Expectation Maximization iterative method, are employed for the determination of size distribution of radon progeny, and these two algorithm is verified by data of standard log-normal Poisson distribution. The experiment results obtained from indoor air and burned kerosene air show a bimodal size distribution, which is similar to other's research. Further intercomparsion studies are needed to further verify the system. (authors)

2005-11-01

116

Scientific Electronic Library Online (English)

Full Text Available SciELO Argentina | Language: English Abstract in english Particle size distributions in the output stream of commercial, fluidized-bed reactors for ethylene polymerization are analyzed using a mathematical model. The impact on the overall reactor performance of the universe of sizes for the particles in the bed, with only a fraction of them being extracte [...] d in the product flow, is studied. For the output stream, product size distribution is modeled using both triangular and generalized gamma functions. Extraction system parameters are employed to model the particle quantity and sizes. The importance of the proper modeling of the extraction system is shown through the analysis of the effects several output schemes have on the particle size distribution inside the fluidized-bed. Some of the main reactor variables, such as yield and temperature, are studied for several distributions. Operating variables, such as catalyst feed rate, are varied according to the reactor capacity in a typical, 12 meter bed, 130,000 ton/year reactor. Predictions indicate higher output rates for higher catalyst loads, as expected. A shift towards smaller particle sizes in the product and in the bed is observed when increasing catalyst load. Bed fluidization and heat exchange conditions are shown as affected by size distributions. Results show that it is appropriate to include both product and bed particle diameter distribution when studying the reactor performance.

W. E., Grosso; M. G., Chiovetta.

117

Experimental study of particle size distribution in suspension polymerization

International Nuclear Information System (INIS)

Particle size distribution is an important characteristic in suspension polymerization. Special condition must satisfy for achievement of an appropriate particle size distribution This condition is studied for some systems. In this work the effect of parameters affecting the suspension polymerization system of styrene was studied and then the approximate optimum range was determined to obtain narrow particle size distribution mainly in the range of 200 to 400 microns. The studied parameters are: position of impeller, impeller type, impeller speed, baffles, stabilizer concentration, initiator concentration and divinylbenzene concentration as cross-linking agent

2001-09-01

118

Energy Technology Data Exchange (ETDEWEB)

A major issue in radiation protection is to protect the population from the harmful effects of exposure to radon and radon progeny. Quantification of the lung cancer risk emanating from exposure to radon decay products in residential and working environments poses problems, as epidemiologic studies yield information deviating from the results obtained by the indirect method of assessment based on dosimetric respiratory tract models. One important task of the publication here was to characterize the various exposure conditions and to quantify uncertainties that may result from application of the ``dose conversion convention``. A special aerosol spectrometer was therefore designed and built in order to measure the size distributions of the short-lived radon decay products in the range between 0.5 nm and 10 000 nm. The aerosol spectrometer consists of a three-step diffusion battery with wire nets, an 11-step BERNER impactor, and a detector system with twelve large-surface proportional detectors. From the measured size distributions, dose conversion coefficients, E/P{sup eq}, were calculated using the PC software RADEP; the RADEP program was developed by BIRCHALL and JAMES and is based on the respiratory tract model of the ICRP. The E/P{sup eq} coefficients indicate the effective dose E per unit exposure P{sup eq} to radon decay products. (orig./CB) [Deutsch] Eines der groessten Probleme des Strahlenschutzes ist der Schutz der Bevoelkerung vor einer Strahlenexposition durch Radon und seine Folgeprodukte. Die Quantifizierung des Lungenkrebsrisikos, das durch Radonexpositionen in Wohnungen und an Arbeitsplaetzen verursacht wird, ist ein grosses Problem, weil epidemiologische Studien ein anderes Ergebnis liefern, als die indirekte Methode der Abschaetzung mit dosimetrischen Atemtrakt-Modellen. Eine wichtige Aufgabe der vorliegenden Arbeit war es, unterschiedliche Expositionsbedingungen zu charakterisieren und die Unsicherheiten zu quantifizieren, die sich aus der Anwendung der `Dosiskonversionskonvention` ergeben koennen. Im Rahmen der vorliegenden Arbeit wurde daher ein spezielles Aerosolspektrometer konzipiert und aufgebaut, mit dem es moeglich ist, die Groessenverteilungen der kurzlebigen Radon-Folgeprodukte im Bereich zwischen 0,5 nm und 10 000 nm zu messen. Das Aerosolspektrometer besteht aus einer dreistufigen Diffusionsbatterie mit Drahtnetzen, einem elfstufigen BERNER-Impaktor und einem Detektorsystem mit zwoelf grossflaechigen Proportionaldetektoren. Aus den gemessenen Groessenverteilungen wurden Dosiskonversionskoeffizienten E/P{sub eq} mit dem PC-Programm RADEP berechnet; RADEP wurde von BIRCHALL und JAMES entwickelt [BIR 94] und beruht auf dem Atemtrakt-Modell der ICRP. Mit E/P{sub eq} wird die effektive Dosis E pro Einheit der Exposition P{sub eq} durch Radon-Folgeprodukte bezeichnet. (orig./MG)

Haninger, T.

1997-12-31

119

SELF-CONSISTENT SIZE AND VELOCITY DISTRIBUTIONS OF COLLISIONAL CASCADES

International Nuclear Information System (INIS)

The standard theoretical treatment of collisional cascades derives a steady-state size distribution assuming a single constant velocity dispersion for all bodies regardless of size. Here we relax this assumption and solve self-consistently for the bodies' steady-state size and size-dependent velocity distributions. Specifically, we account for viscous stirring, dynamical friction, and collisional damping of the bodies' random velocities in addition to the mass conservation requirement typically applied to find the size distribution in a steady-state cascade. The resulting size distributions are significantly steeper than those derived without velocity evolution. For example, accounting self-consistently for the velocities can change the standard q = 3.5 power-law index of the Dohnanyi differential size spectrum to an index as large as q = 4. Similarly, for bodies held together by their own gravity, the corresponding power-law index range 2.88 < q < 3.14 of Pan and Sari can steepen to values as large as q = 3.26. Our velocity results allow quantitative predictions of the bodies' scale heights as a function of size. Together with our predictions, observations of the scale heights for different-sized bodies for the Kuiper belt, the asteroid belt, and extrasolar debris disks may constrain the mass and number of large bodies stirring the cascade as well as the colliding bodies' internal strengths.

2012-03-10

120

SELF-CONSISTENT SIZE AND VELOCITY DISTRIBUTIONS OF COLLISIONAL CASCADES

Energy Technology Data Exchange (ETDEWEB)

The standard theoretical treatment of collisional cascades derives a steady-state size distribution assuming a single constant velocity dispersion for all bodies regardless of size. Here we relax this assumption and solve self-consistently for the bodies' steady-state size and size-dependent velocity distributions. Specifically, we account for viscous stirring, dynamical friction, and collisional damping of the bodies' random velocities in addition to the mass conservation requirement typically applied to find the size distribution in a steady-state cascade. The resulting size distributions are significantly steeper than those derived without velocity evolution. For example, accounting self-consistently for the velocities can change the standard q = 3.5 power-law index of the Dohnanyi differential size spectrum to an index as large as q = 4. Similarly, for bodies held together by their own gravity, the corresponding power-law index range 2.88 < q < 3.14 of Pan and Sari can steepen to values as large as q = 3.26. Our velocity results allow quantitative predictions of the bodies' scale heights as a function of size. Together with our predictions, observations of the scale heights for different-sized bodies for the Kuiper belt, the asteroid belt, and extrasolar debris disks may constrain the mass and number of large bodies stirring the cascade as well as the colliding bodies' internal strengths.

Pan, Margaret [Department of Astronomy, University of California, Berkeley, CA 94720 (United States); Schlichting, Hilke E., E-mail: mpan@astro.berkeley.edu, E-mail: hilke@ucla.edu [Department of Earth and Space Sciences, University of California, Los Angeles, CA 90095 (United States)

2012-03-10

121

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

Energy Technology Data Exchange (ETDEWEB)

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 {approx} 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 {approx} 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 {approx}< 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 {approx} 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 occultation surveys and the observed KBO size distribution can be best matched by an initial planetesimal population that contained about equal mass per logarithmic mass bin in bodies ranging from 0.4 km to 4 km in radius. We further find that we cannot match the observed KBO size distribution if most of the planetesimal mass was contained in bodies that were 10 km in radius or larger simply because their resulting size distribution cannot be sufficiently depleted over 4.5 Gyr to match observations.

Schlichting, Hilke E. [UCLA, Department of Earth and Space Science, 595 Charles E. Young Drive East, Los Angeles, CA 90095 (United States); Fuentes, Cesar I.; Trilling, David E., E-mail: hilke@ucla.edu [Department of Physics and Astronomy, Northern Arizona University, P.O. Box 6010, Flagstaff, AZ 86011 (United States)

2013-08-01

122

Investigations into grain size distribution of coals used for coking

Energy Technology Data Exchange (ETDEWEB)

This paper evaluates 3 methods for forecasting grain size distribution of coal used for coking. Three functions were used for approximating grain size distribution of coal mixtures: the Gaudin-Gates-Andreyev-Schuhmann function, the Rosin-Rammler-Sperling-Benett function and the so-called supplementary Rosin-Rammler-Sperling-Benett function. Accuracy of forecasting methods using the functions was tested in 5 coking plants with standardized coal crushing systems used in Poland. The results of forecasting grain size distribution of coal are given in 2 tables. Comparative evaluations showed that each analyzed function produced accurate results. The Rosin-Rammler-Sperling-Benett function was superior to the other functions. It guaranteed accurate forecasting of grain size distribution of coal in all the analyzed cases. In 37 of 43 cases the function was characterized by the highest correlation coefficient. (6 refs.) (In Polish)

Strugala, A.

1984-01-01

123

Nuclear magnetic resonance characterization of general compartment size distributions

Energy Technology Data Exchange (ETDEWEB)

The influence of molecular diffusion on the nuclear magnetic resonance (NMR) signal can be exploited to estimate compartment size distributions in heterogeneous specimens. Theoretical relationships between the NMR signal intensity at long diffusion times and the moments of a general distribution of isolated pores with characteristic shapes (planar, cylindrical or spherical) are established. A numerical method based on expressing a general diffusion-attenuated NMR signal profile in a series of complete orthogonal basis functions is introduced and subsequently used to estimate the moments of the compartment size distribution. The results on simulated and real data obtained from controlled water-filled microcapillaries demonstrate the power of the approach to create contrast based not only on the mean of the compartment size but also on its variance. The technique can be used to address a variety of problems such as characterizing distributions of droplet sizes in emulsions and of apparent axon diameters in nerve fascicles.

Oezarslan, Evren; Koay, Cheng Guan; Basser, Peter J [Section on Tissue Biophysics and Biomimetics, NICHD, National Institutes of Health, 13 South Drive, Bethesda, MD 20892 (United States); Shemesh, Noam; Cohen, Yoram, E-mail: evren@helix.nih.gov [School of Chemistry, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, 69978 Ramat Aviv (Israel)

2011-01-15

124

A statistical approach to estimate the 3D size distribution of spheres from 2D size distributions

Size distribution of rigidly embedded spheres in a groundmass is usually determined from measurements of the radii of the two-dimensional (2D) circular cross sections of the spheres in random flat planes of a sample, such as in thin sections or polished slabs. Several methods have been devised to find a simple factor to convert the mean of such 2D size distributions to the actual 3D mean size of the spheres without a consensus. We derive an entirely theoretical solution based on well-established probability laws and not constrained by limitations of absolute size, which indicates that the ratio of the means of measured 2D and estimated 3D grain size distribution should be r/4 (=.785). Actual 2D size distribution of the radii of submicron sized, pure Fe0 globules in lunar agglutinitic glass, determined from backscattered electron images, is tested to fit the gamma size distribution model better than the log-normal model. Numerical analysis of 2D size distributions of Fe0 globules in 9 lunar soils shows that the average mean of 2D/3D ratio is 0.84, which is very close to the theoretical value. These results converge with the ratio 0.8 that Hughes (1978) determined for millimeter-sized chondrules from empirical measurements. We recommend that a factor of 1.273 (reciprocal of 0.785) be used to convert the determined 2D mean size (radius or diameter) of a population of spheres to estimate their actual 3D size. ?? 2005 Geological Society of America.

Kong, M.; Bhattacharya, R. N.; James, C.; Basu, A.

2005-01-01

125

Size distribution measurements and chemical analysis of aerosol components

Energy Technology Data Exchange (ETDEWEB)

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 with atmospheric sea salt particles. The chloride loss was found to decrease with increasing particle size suggesting that surface reaction mechanisms were important. Overall, the results obtained in this work describe the present methods used in all steps of accurate size distribution measurements of aerosol components and demonstrate the usefulness and possibilities of size distribution measurements in various scientific studies. (orig.)

Pakkanen, T.A.

1995-12-31

126

Elemental mass size distribution of the Debrecen urban aerosol

International Nuclear Information System (INIS)

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 2nd, smaller peak appears at the 2-4 ?m 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 2nd peak appeared around 0.5 ?m. 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 than the other days. The elemental mass size distribution provides information about the origin and sources of aerosol particles, and with emphasis on the PM2.5, serves as an input parameter for the determination of lung deposition probabilities by stochastic lung model calculation. This calculation together with short-term time variation enables us to give a more precise health impact of the urban aerosol

2007-01-01

127

Size-frequency distributions of EH3 chondrules

Size-frequency distributions of chondrules in three EH3 chondrites, namely Qingzhen, Kota-Kota and ALHA77156, are presently determined. Radial pyroxene chondrules are larger than cryptocrystalline chondrules, while nonporphyritic chondrules have a broader size-frequency distribution than the porphyritic, and porphyritic olivine-pyroxene chondrules are larger than porphyritic pyroxene chondrules. This last result is due to a reaction of fine-grained olivine with free silica to form pyroxene during mild thermal metamorphism of the whole-rocks.

Rubin, Alan E.; Grossman, Jeffrey N.

1987-09-01

128

Mobile field sampling system for determining submicron aerosol size distributions

International Nuclear Information System (INIS)

The need to accurately measure size distributions of submicron aerosols in field situations was recognized. A mobile system was assembled consisting of three size distribution measuring instruments, a 1.1 ?m aerodynamic diameter cyclone precutter and a simple dilution method. The new system reduced data collection time, required only one operator (previous systems required two) and was successfully used in several field and laboratory applications

1981-12-01

129

The size distribution across all "cities": A unifying approach

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper we show that the double Pareto lognormal (DPLN) parameterization provides an excellent fit to the overall US city size distribution, regardless of whether cities are administratively defined Census places or economically defined area clusters. We then consider an economic model that combines scale-independent urban growth (Gibrat's law) with endogenous city creation. City sizes converge to a DPLN distribution in this model, which is much better in line with the data than previou...

2012-01-01

130

Particle size distributions during diffusion controlled growth and coarsening

International Nuclear Information System (INIS)

Theoretical analysis of particle growth and coarsening conducted in the present work, which includes stochastic (random) flux of a solute inside/from the growing particles, predicts normal distribution of the particle sizes, independent of the particle volume fraction. This result agrees well with the numerous experimental data and it solves a long-time problem related with a non-symmetrical size distribution in earlier Lifshitz-Slyozov-Wagner theory

2008-07-01

131

Visualization of bubble size distribution in inclined rectangular channel

International Nuclear Information System (INIS)

Forced convection subcooled water boiling experiments were conducted in inclined rectangular channels. The inclination angle was 45° and the heating surface was downward facing upflow. Bubble diameter distributions in three different axial position of the heating surface had been determined from high-speed digital video camera and image processing. The bubble size had been statistically analyzed under each condition. The result showed that the Probability Distribution Function (PDF) for the bubble diameter often proved to be well represented by a log-normal distribution law. Because of the slipping bubble growth on the heating surface and the bubble coalescence, the bubble size distribution in downstream position was larger than that in upstream position. The results of the bubble size distribution were also presented as cumulative distribution functions, which exhibited in reality a very wide spread of bubble sizes. Compared with vertical upflow in the outlet position, a large number of big slipping bubbles were observed in inclined down facing upflow and the bubble size distribution was larger than that in vertical upflow. (author)

2011-10-24

132

Distribution Of Natural Radioactivity On Soil Size Particles

International Nuclear Information System (INIS)

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 238U, 232Th, 226Ra and 40K 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)

2008-01-01

133

Influence of particle size distributions on magnetorheological fluid performances

International Nuclear Information System (INIS)

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.

2010-01-01

134

Self-consistent size and velocity distributions of collisional cascades

The standard theoretical treatment of collisional cascades derives a steady-state size distribution assuming a single constant velocity dispersion for all bodies regardless of size. Here we relax this assumption and solve self-consistently for the bodies' steady-state size and size-dependent velocity distributions. Specifically, we account for viscous stirring, dynamical friction, and collisional damping of the bodies' random velocities in addition to the mass conservation requirement typically applied to find the size distribution in a steady-state cascade. The resulting size distributions are significantly steeper than those derived without velocity evolution. For example, accounting self-consistently for the velocities can change the standard q=3.5 power-law index of the Dohnanyi (1969) differential size spectrum to an index as large as q=4. Similarly, for bodies held together by their own gravity, the corresponding power-law index range 2.88

Pan, Margaret

2011-01-01

135

Airborne Particle Size Distribution Measurements at USDOE Fernald

Energy Technology Data Exchange (ETDEWEB)

There are no long term measurements of the particle size distribution and concentration of airborne radionuclides at any USDOE facility except Fernald. Yet the determinant of lung dose is the particle size, determining the airway and lower lung deposition. Beginning in 2000, continuous (6 to 8 weeks) measurements of the aerosol particle size distribution have been made with a miniature sampler developed under EMSP. Radon gas decays to a chain of four short lived solid radionuclides that attach immediately to the resident atmospheric aerosol. These in turn decay to long lived polonium 210. Alpha emitting polonium is a tracer for any atmospheric aerosol. Six samplers at Fernald and four at QC sites in New Jersey show a difference in both polonium concentration and size distribution with the winter measurements being higher/larger than summer by almost a factor of two at all locations. EMSP USDOE Contract DE FG07 97ER62522.

Harley, N.H.; Chittaporn, P.; Heikkinen, M.; Medora, R.; Merrill, R.

2003-03-27

136

Seasonal variation of aerosol size distributions in Darwin, Australia

This paper investigates the annual cycle in aerosol size distributions in Darwin, Australia, a coastal site in the Tropical Warm Pool where the major aerosol sources are biomass burning and sea salt. We have used radiometer measurements from the Tropical Western Pacific Atmospheric Radiation Measurement facility for March 2002-June 2003. Constrained linear inversion was used to retrieve aerosol size distributions from the aerosol optical thickness (AOT) measurements. A novel technique combining size distribution shape and aerosol optical properties classified the distributions into three classes: biomass burning, mixed/background and marine/sea salt. The biomass burning aerosol was associated with continental winds and only observed during the dry season. The mixed/background aerosol and marine/sea salt occurred throughout the year. The marine class occurred predominantly in the afternoon and was strongly associated with marine winds; the mixed/background aerosol did not show any strong wind dependence or diurnal cycles.

Bouya, Zahra; Box, Gail P.

2011-08-01

137

Packing fraction of particles with lognormal size distribution

This paper addresses the packing and void fraction of polydisperse particles with a lognormal size distribution. It is demonstrated that a binomial particle size distribution can be transformed into a continuous particle-size distribution of the lognormal type. Furthermore, an original and exact expression is derived that predicts the packing fraction of mixtures of particles with a lognormal distribution, which is governed by the standard deviation, mode of packing, and particle shape only. For a number of particle shapes and their packing modes (close, loose) the applicable values are given. This closed-form analytical expression governing the packing fraction is thoroughly compared with empirical and computational data reported in the literature, and good agreement is found.

Brouwers, H. J. H.

2014-05-01

138

Molecular theory of size exclusion chromatography for wide pore size distributions.

Chromatographic processes can conveniently be modeled at a microscopic level using the molecular theory of chromatography. This molecular or microscopic theory is completely general; therefore it can be used for any chromatographic process such as adsorption, partition, ion-exchange or size exclusion chromatography. The molecular theory of chromatography allows taking into account the kinetics of the pore ingress and egress processes, the heterogeneity of the pore sizes and polymer polydispersion. In this work, we assume that the pore size in the stationary phase of chromatographic columns is governed by a wide lognormal distribution. This property is integrated into the molecular model of size exclusion chromatography and the moments of the elution profiles were calculated for several kinds of pore structure. Our results demonstrate that wide pore size distributions have strong influence on the retention properties (retention time, peak width, and peak shape) of macromolecules. The novel model allows us to estimate the real pore size distribution of commonly used HPLC stationary phases, and the effect of this distribution on the size exclusion process. PMID:24485538

Sepsey, Annamária; Bacskay, Ivett; Felinger, Attila

2014-02-28

139

XRD characterisation of nanoparticle size and shape distributions

International Nuclear Information System (INIS)

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

2004-02-03

140

On the challenge of fitting tree size distributions in ecology.

Patterns that resemble strongly skewed size distributions are frequently observed in ecology. A typical example represents tree size distributions of stem diameters. Empirical tests of ecological theories predicting their parameters have been conducted, but the results are difficult to interpret because the statistical methods that are applied to fit such decaying size distributions vary. In addition, binning of field data as well as measurement errors might potentially bias parameter estimates. Here, we compare three different methods for parameter estimation--the common maximum likelihood estimation (MLE) and two modified types of MLE correcting for binning of observations or random measurement errors. We test whether three typical frequency distributions, namely the power-law, negative exponential and Weibull distribution can be precisely identified, and how parameter estimates are biased when observations are additionally either binned or contain measurement error. We show that uncorrected MLE already loses the ability to discern functional form and parameters at relatively small levels of uncertainties. The modified MLE methods that consider such uncertainties (either binning or measurement error) are comparatively much more robust. We conclude that it is important to reduce binning of observations, if possible, and to quantify observation accuracy in empirical studies for fitting strongly skewed size distributions. In general, modified MLE methods that correct binning or measurement errors can be applied to ensure reliable results. PMID:23469137

Taubert, Franziska; Hartig, Florian; Dobner, Hans-Jürgen; Huth, Andreas

2013-01-01

141

Previous studies indicate that the relationship between empirically derived particle counts, particle mass determinations, and particle size-related silica content are not constant within mines or across mine work tasks. To better understand the variability of particle size distributions and variations in silica content by particle size in a granite quarry, exposure surveys were conducted with side-by-side arrays of four closed face cassettes, four cyclones, four personal environmental monitors, and a real-time particle counter. In general, the proportion of silica increased as collected particulate size increased, but samples varied in an inconstant way. Significant differences in particle size distributions were seen depending on the extent of ventilation and the nature and activity of work performed. Such variability raises concerns about the adequacy of silica exposure assessments based on only limited numbers of samples or short-term samples. PMID:18300081

Sirianni, Greg; Hosgood, Howard Dean; Slade, Martin D; Borak, Jonathan

2008-05-01

142

The Size Frequency Distribution of Small Main-Belt Asteroids

The asteroid size distribution informs us about the formation and composition of the Solar System. We build on our previous work in which we harvest serendipitously observed data of the Taurus region and measure the brightness and size distributions of Main-belt asteroids. This is accomplished with the highly sensitive MIPS 24 micron channel. We expect to catalog 104 asteroids, giving us a statistically significant data set. Results from this investigation will allow us to characterize the total population of small, Main-belt asteroids. Here we will present new results on the completeness of our study; on the presence of size distribution variations with inclination and radial distance in the belt; and early result on other archival fields.

Burt, Brian J.; Trilling, David E.; Hines, Dean C.; Stapelfeldt, Karl R.; Rebull, Luisa M.; Fuentes, Cesar I.; Hulsebus, Alan

2012-01-01

143

Lognormal Size Distribution Theory for Deposition of Polydisperse Aerosol Particles

International Nuclear Information System (INIS)

The moments method of the lognormal size distribution theory was applied to the deposition equation of a radioactive aerosol within a liquid-metal fast breeder reactor for analysis of postulated accidents. The deposition coefficient of Crump and Seinfeld was utilized to represent the Brownian and turbulent diffusions and the gravitational sedimentation. The deposition equation was converted into a set of three ordinary differential equations. This approach takes the view point that the size distribution of an aerosol is represented by a time-dependent lognormal size distribution function during the deposition process. Numerical calculations have been performed, and the results were found to be in good agreement with the exact solution. The derived model for aerosol deposition is convenient to use in a numerical general dynamic equation solution routine based on the moments method, where nucleation, condensation, coagulation, and deposition need to be solved simultaneously

2000-07-01

144

Estimating Clique Composition and Size Distributions from Sampled Network Data

Cliques are defined as complete graphs or subgraphs; they are the strongest form of cohesive subgroup, and are of interest in both social science and engineering contexts. In this paper we show how to efficiently estimate the distribution of clique sizes from a probability sample of nodes obtained from a graph (e.g., by independence or link-trace sampling). We introduce two types of unbiased estimators, one of which exploits labeling of sampled nodes neighbors and one of which does not require this information. We compare the estimators on a variety of real-world graphs and provide suggestions for their use. We generalize our estimators to cases in which cliques are distinguished not only by size but also by node attributes, allowing us to estimate clique composition by size. Finally, we apply our methodology to a sample of Facebook users to estimate the clique size distribution by gender over the social graph.

Gjoka, Minas; Butts, Carter T

2013-01-01

145

Influence of multidroplet size distribution on icing collection efficiency

Calculation of collection efficiencies of two-dimensional airfoils for a monodispersed droplet icing cloud and a multidispersed droplet is carried out. Comparison is made with the experimental results reported in the NACA Technical Note series. The results of the study show considerably improved agreement with experiment when multidroplet size distributions are employed. The study then investigates the effect of collection efficiency on airborne particle droplet size sampling instruments. The biased effect introduced due to sampling from different collection volumes is predicted.

Chang, H.-P.; Kimble, K. R.; Frost, W.; Shaw, R. J.

1983-01-01

146

Liquid Column Deformation and Particle Size Distribution in Gas Atomization

Directory of Open Access Journals (Sweden)

Full Text Available A water-gas flow injected by a close coupled atomizer was studied via High Speed Photography and Phase Doppler Anemometry. The formation of a wave disturbance on the surface of the water column was confirmed. The flow converged within an area approximately 3 mm in diameter, independent of atomization conditions. The particle size distribution across the spray suggested a trend of decreasing particle sizes and particle velocities with increasing distance from the spray axis of symmetry.

Georgios S. E. Antipas

2011-02-01

147

Liquid Column Deformation and Particle Size Distribution in Gas Atomization

Digital Repository Infrastructure Vision for European Research (DRIVER)

A water-gas flow injected by a close coupled atomizer was studied via High Speed Photography and Phase Doppler Anemometry. The formation of a wave disturbance on the surface of the water column was confirmed. The flow converged within an area approximately 3 mm in diameter, independent of atomization conditions. The particle size distribution across the spray suggested a trend of decreasing particle sizes and particle velocities with increasing distance from the spray axis of symmetry.

2011-01-01

148

Estimation of Nanoparticle Size Distributions by Image Analysis

DEFF Research Database (Denmark)

Knowledge of the nanoparticle size distribution is important for the interpretation of experimental results in many studies of nanoparticle properties. An automated method is needed for accurate and robust estimation of particle size distribution from nanoparticle images with thousands of particles. In this paper, we present an automated image analysis technique based on a deformable ellipse model that can perform this task. Results of using this technique are shown for both nearly spherical particles and more irregularly shaped particles. The technique proves to be a very useful tool for nanoparticle research.

Fisker, Rune; Carstensen, Jens Michael

2000-01-01

149

Correction of bubble size distributions from transmission electron microscopy observations

International Nuclear Information System (INIS)

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

1996-01-01

150

Saturn's rings - Particle size distributions for thin layer model

A model incorporating limited interaction between the incident energy and particles in the ring is considered which appears to be consistent with the multiple scattering process in Saturn's rings. The model allows for the small physical thickness of the rings and can be used to relate Voyager 1 observations of 3.6- and 13-cm wavelength microwave scatter from the rings to the ring particle size distribution function for particles with radii ranging from 0.001 to 20 m. This limited-scatter model yields solutions for particle size distribution functions for eight regions in the rings, which exhibit approximately inverse-cubic power-law behavior.

Zebker, H. A.; Marouf, E. A.; Tyler, G. L.

1985-01-01

151

Novel magnetic Fe onion-like fullerene micrometer-sized particles of narrow size distribution

Energy Technology Data Exchange (ETDEWEB)

Magnetic polydivinylbenzene (PDVB)/magnetite micrometer-sized particles of narrow size distribution were prepared by entrapping Fe(CO){sub 5} within the pores of uniform porous PDVB particles, followed by the thermal decomposition of the encapsulated Fe(CO){sub 5} at 300 deg. C in a sealed cell under inert atmosphere. Magnetic Fe onion-like fullerene micrometer-sized particles of narrow size distribution have been prepared by the thermal decomposition of the PDVB/magnetite magnetic microspheres at 1100 deg. C under inert atmosphere. The graphitic coating protects the elemental iron particles from oxidation and thereby preserves their very high magnetic moment for at least a year. Characterization of these unique magnetic carbon graphitic particles was also performed. - Highlights: > Magnetic PDVB/iron-oxide composite particles of narrow size distribution have been synthesized and characterized. > Magnetic C/Fe composite particles of narrow size distribution have been synthesized and characterized. > Magnetic onion-like fullerenes structures have been observed in these different particles.

Snovski, Ron, E-mail: ron.snovski@gmail.com [Institute of Nanotechnology and Advanced Materials, Department of Chemistry, Bar-Ilan University, Ramat Gan 52900 (Israel); Grinblat, Judith, E-mail: grinby@mail.biu.ac.il [Institute of Nanotechnology and Advanced Materials, Department of Chemistry, Bar-Ilan University, Ramat Gan 52900 (Israel); Margel, Shlomo, E-mail: shlomo.margel@mail.biu.ac.il [Institute of Nanotechnology and Advanced Materials, Department of Chemistry, Bar-Ilan University, Ramat Gan 52900 (Israel)

2012-01-15

152

The Particle-Size Toolbox: 3D modelling of particle-size distributions in the subsurface

This paper presents a Matlab toolbox for creating three-dimensional models of complete particle-size distributions in the subsurface. Three modules comprise the toolbox: (i) integration; (ii) optimization, and (iii) interpolation. The integration module accepts a wide variety of input data from boreholes and surface samples. These are converted into a common format. Particle-size data are integrated using a combination of interpolation or Gaussian simulation techniques. Data can be calibrated to minimise the influence of different analytical techniques. Data optimisation relies on subdividing the integrated data into geological units and gridding borehole data to a regular cell size. The optimization step applies principal component analysis to quantify and exclude noise from the data based on individual geological unit volumes. Typically two to three principal components are then used for interpolation. The interpolation module involves standard semi-variogram modelling, cross-validation and interpolation procedures. These can run in Matlab using mGstat, or in Geovariances Isatis via batch processing. Interpolated principal component scores are back-transformed into complete particle-size distributions. Uncertainty in the modelled distributions is quantified by back-transforming the error variance to derive an upper and lower distribution envelope. These data can be used to derive a single measure of uncertainty for each particle-size distribution: the simplicial distance metric.

Roberson, Sam; Weltje, Gert Jan

2014-05-01

153

Comet Shoemaker-Levy 9 Dust Size and Velocity Distributions

Pre-impact observations of Comet Shoemaker-Levy 9 (S-L9) obtained with the Hubble Space Telescope are examined, and a model of an active, dust-producing comet is fitted to images of fragments G, H, K, and L. The model assumes steady isotropic dust emission from each fragment's sunlit hemisphere. Best-fit results indicate that the dominant light-scatterers in these fragments' comae were relatively large dust grains of radii 10 micrometers < R < 3 mm. The fragments' dust size distributions were rather flat in comparison to other comets, dN(R) proportional to R(sup -2.3 +/- 0.1), and the dust ejection speeds were approximately 0.5-1.5 m/s. The S-L9 fragments themselves were not detected directly, and upper limits on their radii are 1.0-1.5 km assuming an albedo a = 0.04. However, these fragments' vigorous production of dust, which ranges from 6 to 22 kg/s, places a lower limit of approximately 100 m on their radii at the moment of tidal breakup. Any fragments smaller than this limit, yet experiencing similar mass loss rates, would have dissipated prior to impact. Such bodies would fail to leave an impact scar at Jupiter's atmosphere, as was realized by fragments F, J, P(sub 1), P(sub 2), T, and U.

Hahn, Joseph M.; Rettig, Terrence W.

2000-01-01

154

The evolution and distribution of species body size

Digital Repository Infrastructure Vision for European Research (DRIVER)

The distribution of species body size within taxonomic groups exhibits a heavy right-tail extending over many orders of magnitude, where most species are significantly larger than the smallest species. We provide a simple model of cladogenetic diffusion over evolutionary time that omits explicit mechanisms for inter-specific competition and other microevolutionary processes yet fully explains the shape of this distribution. We estimate the model's parameters from fossil data...

Clauset, Aaron; Erwin, Douglas H.

2009-01-01

155

The Size-Frequency Distribution of Dormant Jupiter Family Comets

Digital Repository Infrastructure Vision for European Research (DRIVER)

We estimate the total number and the slope of the size frequency distribution (SFD) of dormant Jupiter Family Comets (JFCs) by fitting a one-parameter model to the known population. We first select 61 Near Earth Objects (NEOs) that are likely to be dormant JFCs because their orbits are dynamically coupled to Jupiter (Bottke et al, 2002). Then, from the numerical simulations of Levison & Duncan (1997), we construct an orbit distribution model for JFCs in the NEO orbital eleme...

Whitman, Kathryn; Morbidelli, Alessandro; Jedicke, Robert

2006-01-01

156

On the size-distribution of Poisson Voronoi cells

Digital Repository Infrastructure Vision for European Research (DRIVER)

Poisson Voronoi diagrams are useful for modeling and describing various natural patterns and for generating random lattices. Although this particular space tessellation is intensively studied by mathematicians, in two- and three dimensional spaces there is no exact result known for the size-distribution of Voronoi cells. Motivated by the simple form of the distribution function in the one-dimensional case, a simple and compact analytical formula is proposed for approximating...

Jarai-szabo, F.; Neda, Z.

2004-01-01

157

Size distributions of gold nanoclusters studied by liquid chromatography

Energy Technology Data Exchange (ETDEWEB)

The authors report high pressure liquid chromatography, (HPLC), and transmission electron microscopy, (TEM), studies of the size distributions of nanosize gold clusters dispersed in organic solvents. These metal clusters are synthesized in inverse micelles at room temperature and those investigated range in diameter from 1--10 nm. HPLC is sensitive enough to discern changes in hydrodynamic volume corresponding to only 2 carbon atoms of the passivating agent or metal core size changes of less than 4 {angstrom}. The authors have determined for the first time how the total cluster volume (metal core + passivating organic shell) changes with the size of the passivating agent.

WILCOXON,JESS P.; MARTIN,JAMES E.; PROVENCIO,PAULA P.

2000-05-23

158

Molecular size distribution of Np(V)-humate

Energy Technology Data Exchange (ETDEWEB)

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-0.45{mu}m, 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)

Sakamoto, Yoshiaki; Nagao, Seiya; Tanaka, Tadao [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

1996-10-01

159

THE SIZE-LUMINOSITY DISTRIBUTIONS OF LYMAN-BREAK GALAXIES

Lyman-break galaxies (LBGs) comprise the largest sample of star-forming galaxies at z>3 and are crucial to our understanding of galaxy formation and evolution. Their luminosity functions allow us to calculate the cosmic star formation history, and their sizes also provide valuable information about the angular momentum content of the galaxies and dark matter halos. However, due to surface brightness dimming effects, galaxies at high redshifts are especially susceptible to selection effects; it is important to understand the selection effects before we can draw conclusions from the statistics of LBG properties. In this work we will investigate the size--luminosity distribution of LBGs between 3 and 6 with careful modeling of selection effects and measurement errors of size and magnitude. Our modeling is more careful than previous studies because it is performed in the two-dimensional size--magnitude space. The results of this work show that (1) the effective radii of star-forming galaxies likely evolve as H(z)^{-2/3} at a fixed luminosity, (2) the widths of the LBG size distribution are larger than expected from the spin parameter distribution of dark matter halos, and (3) the size--luminosity relation slopes of LBGs are similar to those for late-type disk galaxies in the local universe. These results favor the disk formation theory put forward by Fall & Efstathiou (1980) if the majority of LBGs are disks, but more observational evidence is needed to confirm the kinematical structure of LBGs as well as to explain the widths of the size distribution.

Huang, Kuang-Han; CANDELS Collaboration

2014-01-01

160

Molecular size distribution of Np(V)-humate

International Nuclear Information System (INIS)

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-0.45?m, 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)

1996-01-01

161

Some studies on the size distribution of crushed coal in Indian coal washeries

Energy Technology Data Exchange (ETDEWEB)

The scope of the size distribution equations for the prediction of crusher performance in Indian Coal Washeries is discussed. The data is taken from the industrial operation of a washery for coking coal. It is found that Gaudin - Meloy distribution is most appropriate for primary single roll crushers and Gates - Gaudin - Schuman distribution for secondary Impactors. For Flow sheet calculations of mineral beneficiation plants and coal washeries it is necessary to predict the size distribution of the products of the crushers. So for the predictions have been made mostly in a qualitative manner depending upon the judgement of the design engineer. The modern tendency is to rely more on Quantitative Simulation Techniques. Using the size distribution equations a fairly large number of which have been published in the literature. The procedures for the prediction of crushing results which is commonly used in India and abroad and is adopted in this paper is illustrated in Appendix I.

Venkateswarlu, C.; Misra, D.D.

1981-01-01

162

Multimodal Size Distributions in Fog: Cloud Microphysics or Measurement Artifact?

In recent years there have been a number of observations during fog events whereby the measured size distributions show more than a single mode, sometimes even three or four. These multiple modes have been explained using various physical models including entrainment and mixing, coalescence, sedimentation, and new particle activation. Whereas all of these mechanisms are physically possible, a simpler explanation may explain how these multiple modes are formed, at least in those cases where optical particle counters (OPC) are used to measure the droplet sizes. The most frequently used OPC is the Droplet Measurement Technology (DMT) FM-100 that measures droplets from 2 - 50 ?m. The technique is single particle light scattering whereby droplets pass through a focused laser beam and the light scattered in a forward, solid angle of 4-12° is collected and converted to a current in a photodetector. The relationship between scattered light and droplet size is determined from Mie theory and for the laser wavelength and collection geometry of the FM-100, this relationship is non-linear and non-monochronic, i.e. the same scattering intensity can be produced by droplets of different sizes in a number of size ranges. This presentation will show how the ambiguities in the scatter versus size relationship in the FM-100 introduces bimodality in the measured size distributions and that the false modes tend to fall where published data has shown modes measured during fog events. These artificial peaks can be removed and size distributions can be extracted that are more representative of the ambient spectra using an inversion algorithm that accounts for the Mie scattering relationship.

Baumgardner, D.; Kok, G.; Chen, P.

2010-07-01

163

Gamma ray burst size-frequency distributions: spectral selection effects

International Nuclear Information System (INIS)

The effects of spectral variation on the detection of gamma ray bursts were investigated. Selection biases resulting from these effects can account for the reported deviation of the observed size-frequency distribution in peak energy flux from that expected for a simple uniform distribution of sources. Thus these observations as yet provide no clear evidence for structure in the burst source distribution. Because of selection biases, the intrinsic average temperature of the bursts is much harder (kT approximately MeV) than the observed average (approximately 200 KeV)

1985-08-01

164

Vesicle sizing: Number distributions by dynamic light scattering.

A procedure is described which optimizes nonnegative least squares and exponential sampling fitting methods for analysis of dynamic light scattering (DLS) data from aqueous suspensions of vesicle/liposome systems. This approach utilizes a Rayleigh-Gans-Debye form factor for a coated sphere and yields number distributions which can be compared directly to distributions obtained by freeze-fracture electron microscopy (EM). Excellent agreement between the DLS and EM results are obtained for vesicle size distributions in the 100-200-nm range. PMID:19431789

Hallett, F R; Watton, J; Krygsman, P

1991-02-01

165

Energy Technology Data Exchange (ETDEWEB)

Researchers are becoming increasingly concerned with airborne particulate matter, not only in the respirable size range, but also in larger size ranges. International Standards Organization (ISO) and the American Conference of Governmental Industrial Hygienist (ACGIH) have developed standards for {open_quotes}inhalable{close_quotes} and {open_quotes}thoracic{close_quotes} particulate matter. These require sampling particles up to approximately 100 {mu}m in diameter. The size distribution and mass concentration of airborne particulate matter have been measured in air quality studies of the working sections of more than 20 underground mines by University of Minnesota and U.S. Bureau of Mines personnel. Measurements have been made in more than 15 coal mines and five metal/nonmetal mines over the past eight years. Although mines using diesel-powered equipment were emphasized, mines using all-electric powered equipment were also included. Particle sampling was conducted at fixed locations, i.e., mine portal, ventilation intake entry, haulageways, ventilation return entry, and near raincars, bolters and load-haul-dump equipment. The primary sampling device used was the MSP Model 100 micro-orifice uniform deposit impactor (MOUDI). The MOUDI samples at a flow rate of 30 LPM and. provides particle size distribution information for particles primarily in the 0.1 to 18 {mu}m size range. Up to five MOUDI samplers were simultaneously deployed at the fixed locations. Sampling times were typically 4 to 6 hrs/shift. Results from these field studies have been summarized to determine the average size distributions and mass concentrations at various locations in the mine section sampled. From these average size distributions, predictions are made regarding the expected levels of respirable and thoracic mass concentrations as defined by various health-based size-selective aerosol-sampling criteria.

Rubow, K.L.; Marple, V.A. [Univ. of Minnesota, Minneapolis, MN (United States); Cantrell, B.K. [Bureau of Mines, Minneapolis, MN (United States)] [and others

1995-12-31

166

Topology by improved cooling: susceptibility and size distributions

International Nuclear Information System (INIS)

We use a cooling algorithm based on an improved action with scale invariant instanton solutions, which needs no monitoring or calibration and has a inherent cut off for dislocations. In an application to the SU(2) theory the method provides good susceptibility data and physical size distributions of instantons. (orig.)

1996-02-01

167

Topology by improved cooling susceptibility and size distributions

We use a cooling algorithm based on an improved action with scale invariant instanton solutions, which needs no monitoring or calibration and has a inherent cut off for dislocations. We present results for SU(2) Yang-Mills theory where the method provides good susceptibility data and physical size distributions of instantons.

De Forcrand, Philippe; Stamatescu, I O; Forcrand, Philippe de; Perez, Margarita Garcia; Stamatescu, Ion-Olimpiu

1996-01-01

168

Topology by improved cooling: susceptibility and size distributions

Energy Technology Data Exchange (ETDEWEB)

We use a cooling algorithm based on an improved action with scale invariant instanton solutions, which needs no monitoring or calibration and has a inherent cut off for dislocations. In an application to the SU(2) theory the method provides good susceptibility data and physical size distributions of instantons. (orig.).

Forcrand, P. de [ETH, Zurich (Switzerland). SCSC; Garcia Perez, M. [Rijksuniversiteit Leiden (Netherlands). Inst. Lorentz voor Theoretische Natuurkunde; Stamatescu, I.-O. [Forschungsstaette der Evangelischen Studiengemeinschaft (FEST), Heidelberg (Germany)]|[Heidelberg Univ. (Germany). Inst. fuer Theoretische Physik

1996-02-01

169

Determination of particle size distribution by FMR measurements

Digital Repository Infrastructure Vision for European Research (DRIVER)

Knowledge of particle size distribution is very important for the study of magnetic fluids, magnetic powders and other magnetic systems. In this work, we describe a simple method for its determination from FMR measurements. The method was applied to the case of MgFe2O4 precipitates in (Mg,Fe)O.

2001-01-01

170

Molecular size distribution of Np(V)-humate.

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...

Y. Sakamoto S. Nagao T. Tanaka

1996-01-01

171

Modeling of Microporosity Size Distribution in Aluminum Alloy A356

Porosity is one of the most common defects to degrade the mechanical properties of aluminum alloys. Prediction of pore size, therefore, is critical to optimize the quality of castings. Moreover, to the design engineer, knowledge of the inherent pore population in a casting is essential to avoid potential fatigue failure of the component. In this work, the size distribution of the porosity was modeled based on the assumptions that the hydrogen pores are nucleated heterogeneously and that the nucleation site distribution is a Gaussian function of hydrogen supersaturation in the melt. The pore growth is simulated as a hydrogen-diffusion-controlled process, which is driven by the hydrogen concentration gradient at the pore liquid interface. Directionally solidified A356 (Al-7Si-0.3Mg) alloy castings were used to evaluate the predictive capability of the proposed model. The cast pore volume fraction and size distributions were measured using X-ray microtomography (XMT). Comparison of the experimental and simulation results showed that good agreement could be obtained in terms of both porosity fraction and size distribution. The model can effectively evaluate the effect of hydrogen content, heterogeneous pore nucleation population, cooling conditions, and degassing time on microporosity formation.

Yao, Lu; Cockcroft, Steve; Zhu, Jindong; Reilly, Carl

2011-12-01

172

Tracing Particle Size Distribution Curves Using an Analogue Circuit.

Proposes an analog circuit for use in sedimentation analysis of finely divided solid materials. Discusses a method of particle size distribution analysis and provides schematics of the circuit with list of components as well as a discussion about the operation of the circuit. (JM)

Bisschop, F. De; Segaert, O.

1986-01-01

173

Size distribution and structure of Barchan dune fields

Directory of Open Access Journals (Sweden)

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.

O. Durán

2011-07-01

174

Size distribution and structure of Barchan dune fields

DEFF Research Database (Denmark)

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 co-operative 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.

Duran, O.; SchwÃ¤mmle, Veit

2011-01-01

175

Lognormal field size distributions as a consequence of economic truncation

The assumption of lognormal (parent) field size distributions has for a long time been applied to resource appraisal and evaluation of exploration strategy by the petroleum industry. However, frequency distributions estimated with observed data and used to justify this hypotheses are conditional. Examination of various observed field size distributions across basins and over time shows that such distributions should be regarded as the end result of an economic filtering process. Commercial discoveries depend on oil and gas prices and field development costs. Some new fields are eliminated due to location, depths, or water depths. This filtering process is called economic truncation. Economic truncation may occur when predictions of a discovery process are passed through an economic appraisal model. We demonstrate that (1) economic resource appraisals, (2) forecasts of levels of petroleum industry activity, and (3) expected benefits of developing and implementing cost reducing technology are sensitive to assumptions made about the nature of that portion of (parent) field size distribution subject to economic truncation. ?? 1985 Plenum Publishing Corporation.

Attanasi, E. D.; Drew, L. J.

1985-01-01

176

Critical Exponent of Species-Size Distribution in Evolution

We analyze the geometry of the species- and genotype-size distribution in evolving and adapting populations of single-stranded self-replicating genomes: here programs in the Avida world. We find that a scale-free distribution (power law) emerges in complex landscapes that achieve a separation of two fundamental time scales: the relaxation time (time for population to return to equilibrium after a perturbation) and the time between mutations that produce fitter genotypes. The latter can be dialed by changing the mutation rate. In the scaling regime, we determine the critical exponent of the distribution of sizes and strengths of avalanches in a system without coevolution, described by first-order phase transitions in single finite niches.

Adami, C; Yirdaw, R; Adami, Christoph; Seki, Ryoichi; Yirdaw, Robel

1998-01-01

177

Particle-Size-Distribution of Nevada Test Site Soils

Energy Technology Data Exchange (ETDEWEB)

The amount of each size particle in a given soil is called the particle-size distribution (PSD), and the way it feels to the touch is called the soil texture. Sand, silt, and clay are the three particle sizes of mineral material found in soils. Sand is the largest sized particle and it feels gritty; silt is medium sized and it feels floury; and clay is the smallest and if feels sticky. Knowing the particle-size distribution of a soil sample helps to understand many soil properties such as how much water, heat, and nutrients the soil will hold, how fast water and heat will move through the soil, and what kind of structure, bulk density and consistence the soil will have. Furthermore, the native particle-size distribution of the soil in the vicinity of ground zero of a nuclear detonation plays a major role in nuclear fallout. For soils that have a high-sand content, the near-range fallout will be relatively high and the far-range fallout will be relatively light. Whereas, for soils that have a high-silt and high-clay content, the near-range fallout will be significantly lower and the far-range fallout will be significantly higher. As part of a program funded by the Defense Threat Reduction Agency (DTRA), the Lawrence Livermore National Laboratory (LLNL) has recently measured the PSDs from the various major areas at the Nevada Test Site where atmospheric detonations and/or nuclear weapon safety tests were performed back in the 50s and 60s. The purpose of this report is to document those results.

Spriggs, G; Ray-Maitra, A

2007-09-17

178

Photovoltaic production and distribution network

International Nuclear Information System (INIS)

The rapid development of photovoltaics boosted by attractive feed-in tariffs caused a sharp increase in requests for connection to public distribution grids, which were originally designed to serve consumers. ERDF, main distribution network operator in France, is facing a challenge in terms of capacity for handling requests for connection and in terms of public distribution network operation and management. (author)

2010-04-01

179

Size distribution of mist generated during metal machining.

Mist generated by machining processes is formed by three mechanisms: impaction, centrifugal force, and evaporation/condensation. This study characterized the size distribution of soluble and mineral oil mists that resulted from these formation mechanisms. Salient parameters influencing the particle size distributions also were identified. Variables investigated included metalworking fluid and machining characteristics. The size distribution of the mist generated on a small lathe by each mechanism was measured using an Aerosizer LD. For impaction, only the mineral oil viscosity influenced the mass median diameter of the mist. No parameter affected the geometric standard deviation. High-viscosity mineral oil mist had a mass median diameter of 6.1 microns and a geometric standard deviation of 2.0. Low-viscosity mineral oil mist had a mass median diameter of 21.9 microns and a geometric standard deviation of 2.2. The mass median diameter of the mist generated by centrifugal force depended on the type of metalworking fluid, fluid flow, and rotational speed of the lathe. Mass median diameters for low-viscosity mineral oil mist ranged from 5 to 110 microns. Mass median diameters for soluble oil mist varied between 40 and 80 microns. The average geometric standard deviation was 2.4, and was not affected by any parameter. The mass median diameter and geometric standard deviation of the mist generated by evaporation/condensation varied with the type of metalworking fluid. The mineral oil mist and soluble oil mist mass median diameters were 2.1 microns and 3.2 microns, respectively. No machining or fluid parameter was important because the mist size distribution depended on the rate of condensation, coagulation processes, and the dynamics of the apparatus. Using the size distribution data from all three mechanisms, the estimated inhalable, thoracic, and respirable fractions of the total mass generated for each metalworking fluid were 60 percent, 12 percent, and 8 percent, respectively. To minimize exposure to the inhalable mass fraction, the amount of mist generated by centrifugal force must be reduced or the size of the drops generated must be increased. Altering the machining or fluid parameters did not change the mist size distribution and reduce exposure to the respirable mass fraction. PMID:10957817

Thornburg, J; Leith, D

2000-08-01

180

Endogenous Product Differentiation, Market Size and Prices

Digital Repository Infrastructure Vision for European Research (DRIVER)

Recent empirical evidence suggests that prices for some goods and services are higher in larger markets. This paper provides a demand-side explanation for this phenomenon when firms can choose how much to differentiate their products in a model of monopolistic competition with horizontal product differentiation. The model proposes that consumers? love of variety makes them more sensitive to product differentiation efforts by firms, which leads to higher prices in larger markets. At the s...

Ferguson, Shon

2011-01-01

181

Siting and sizing of distributed generation using three new indices

Energy Technology Data Exchange (ETDEWEB)

Given the rapid expansion of distributed generation (DG), it is expected to constitute a large part of power generation in future power systems. DGs can improve power supply and reliability, reduce system losses and increase system capacity. However, its impact in a distribution network depends on its size and location. Various indices of the system must be evaluated to ensure that the DGs contribute to improve the performance of the overall system. In this study, the optimal size and location of DG was determined by optimizing an objective function which is a combination of three arbitrary selected indices and limited by economic and DG size and penetration constraints. A technique based on Genetic Algorithm (GA) was proposed for finding the optimal siting and sizing of DGs in a medium voltage (MV) distribution system to improve the system voltage profile. The 3 indices were the average falling time (AFT), average raising time (ART), and average maximum voltage drop (AMVD) which impart the measure of voltage quality under load transfer, load addition and load rejection cases. The performance of the proposed technique was then evaluated on modified IEEE 13 and 37 node test feeders. The study showed that the best location for DG installation is at the furthest branch with a high load level. 7 refs., 3 tabs., 10 figs.

Jahromi, M.J.; Haque, M.H.; Tseng, K.J. [Nanyang Technological Univ. (Singapore). School of Electrical and Electronic Engineering

2009-07-01

182

The changing size distribution of US trade unions and its description by Pareto's distribution

Digital Repository Infrastructure Vision for European Research (DRIVER)

The size distribution of trade unions in the United States and changes in this distribution are documented. Because the most profound changes are taking place among very large unions, these are subject to special analysis by invoking Pareto's distribution. This represents a new application of this distribution. Extensions to trade union wealth and to Britain are broached. The role of the public sector in these changes receives particular attention. A simple model helps account both for the lo...

2013-01-01

183

Optimal Location and Sizing of Distributed Storage Systems in Active Distribution Networks

Digital Repository Infrastructure Vision for European Research (DRIVER)

Energy balance and ancillary services provided by distributed storage systems to active distribution networks represent two aspects of a single problem that needs to be properly treated in view of the typical distribution networks parameters. In this context, the paper focuses on the problem of the optimal siting and sizing of distributed storage systems. In particular, the paper proposes the formulation of a problem that accounts: (i) the voltage support of storage systems to the grid, (ii) ...

2013-01-01

184

Probabilistic Optimal Allocation and Sizing of Distributed Generation

Directory of Open Access Journals (Sweden)

Full Text Available The optimal allocation of Distributed Generation (DG in distribution system is one of the important parts of DG research studies so as to maximize its benefits. For this purpose, a probabilistic approach is proposed in this study to consider time varying load demands as uncertain parameters of distribution system. It is assumed that each load point consists of three categories of voltage dependent loads: residential, industrial and commercial. The proposed algorithm is based on a probabilistic load flow solved by Point Estimate Method (PEM. The objective function is considered as a combination of active power loss, reactive power loss and voltage profiles indices. To solve the optimization problem, an Invasive Weed Optimization (IWO technique is adopted and the optimal location and size of different types of DG are obtained. Examining on a test distribution system, the performance of the proposed approach is assessed and illustrated.

M. Hosseinzadeh

2014-01-01

185

Portfolio effects and firm size distribution: carbonated soft drinks

Digital Repository Infrastructure Vision for European Research (DRIVER)

We use rich brand level retail data to demonstrate that the firm size distribution in Carbonated Soft Drinks is mainly an outcome of the degree to which firms own a portfolio of brands across segments of the market, and not from performance within segments. In addition, while the number of firms in each segment is limited by segment size relative to sunk cost and competition in a segment, idiosyncratic firm effects make some firms more likely to participate in any given segment. This feature ...

Walsh, Patrick Paul; Whelan, Ciara

2002-01-01

186

Portfolio Effects and Firm Size Distribution: Carbonated Soft Drinks

Digital Repository Infrastructure Vision for European Research (DRIVER)

We use rich brand level retail data to demonstrate that the firm size distribution in Carbonated Soft Drinks is mainly an outcome of the degree to which firms own a portfolio of brands across segments of the market, and not from performance within segments. In addition, while the number of firms in each segment is limited by segment size relative to sunk cost and competition in a segment, idiosyncratic firm effects make some firms more likely to participate in any given segment. This feature ...

Walsh, Paul Patrick; Whelan, C.

2002-01-01

187

Portfolio effects and firm size distribution : carbonated soft drinks

Digital Repository Infrastructure Vision for European Research (DRIVER)

We use rich brand level retail data to demonstrate that the firm size distribution in Carbonated Soft Drinks is mainly an outcome of the degree to which firms own a portfolio of brands across segments of the market, and not from performance within segments. In addition, while the number of firms in each segment is limited by segment size relative to sunk cost and competition in a segment, idiosyncratic firm effects make some firms more likely to participate in any given segment. This feature ...

Whelan, Ciara; Walsh, Patrick P.

2002-01-01

188

Rock sampling. [method for controlling particle size distribution

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.

Blum, P. (inventor)

1971-01-01

189

Distributed Project Management for New Product Development

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents an integrative distributed project management approach for product development. The core of the integrative model is the Triple C model of project management, which presents a systematic structure for Communication, Cooperation, and Coordination across product development functions. The achievement of lower product development cycles requires strategic implementation of project management techniques. The level of communication, cooperation, and coordination required for effective product development can be facilitated by using distributed project management.

Alfred E. Thal

2007-06-01

190

Airblast atomization: studies on drop-size distribution

Energy Technology Data Exchange (ETDEWEB)

The influence of air velocity and liquid properties on drop-size distribution is examined using an airblast atomizer in which a flat liquid sheet is exposed to high velocity air on both sides. Both photographic and lightscattering techniques are employed to measure drop sizes. The effect of the physical properties of liquids is studied by preparing special liquid solutions to obtain wide variations in one property while keeping the others sensibly constant. The results obtained show that increases in air velocity and/or reduction in liquid flow rate lead to more uniform sprays and a lower mean drop size. Higher values of viscosity and surface tension result in coarser sprays of larger mean drop size. The effect of liquid density on spray characteristics appears to be quite small. In general, it is found that any change in liquid properties or atomizer operating conditions which tends to lower the mean drop size will also tend to narrow the range of drop sizes produced.

Rizk, N.K.; Lefebvze, A.H.

1982-09-01

191

Development of sample size allocation program using hypergeometric distribution

International Nuclear Information System (INIS)

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)

1996-01-01

192

Pore size distribution in an uncompacted equilibrated ordinary chondrite

Energy Technology Data Exchange (ETDEWEB)

The extraordinarily uncompacted nature of the ordinary L chondrite fall Baszkowka gives a unique opportunity to investigate the potentially pre-compaction pore size distribution in an equilibrated ordinary chondrite. Using X-ray microtomography and helium pycnometry on two samples of Baszkowka, we have found that on average, two-thirds of the 19.0% porosity resides in inter- and intra-granular voids with volumes between {approx}3 x10{sup 05} and 3 mm{sup 3}. We show the cumulative number density of pore volumes observable by X-ray microtomography obeys a power law distribution function in this equilibrated ordinary chondrite. We foresee these data adding to our understanding of the impact processing of chondrites and their parent asteroids, where porosity and pore size play significant roles in the parameterization of impact events.

Friedrich, J.M.; Macke, R.J.; Wignarajah, D.P.; Rivers, M.L.; Britt, D.T.; Ebel, D.S. (Univ of Central FL); (Fordham Univ); (UofC); (Univ of Central FL); (AMNH); (Fordham Univ)

2008-05-30

193

Size distribution of FeNiB nanoparticles

Directory of Open Access Journals (Sweden)

Full Text Available Two samples of amorphous nanoparticles FeNiB, one of them with SiO2 sheath around the core and one without, were investigated by transmission electron microscopy and magnetic measurements. The coating gives mean particle diameters of 4.3 nm compared to 7.2 nm for the uncoated particles. Magnetic measurements prove superparamagnetic behaviour above 160 K (350 K for the coated (uncoated sample. With use of effective anisotropy constant Keff – determined from hysteresis loops – size distributions are determined both from ZFC curves, as well as from relaxation measurements. Both are in good agreement and are very similar for both samples. Comparison with the size distribution determined from TEM pictures shows that magnetic clusters consist of only few physical particles.

Lackner P.

2014-07-01

194

Multifractal Characteristics of Bimodal Mercury Pore Size Distribution Curves

Characterization of Hg pore size distribution (PSDs) curves by monofractal or multifractal analysis has been demonstrated to be an useful tool, which allows a better understanding of the organization of the soil pore space. There are also evidences that multiscale analysis of different segments found in bimodal pore size distributions measured by Hg intrusion can provide further valuable information. In this study we selected bimodal PSDs from samples taken from an experimental area in São Paulo state, Brazil, where a revegetation trial was set up over saprolitic material. The saprolite was left abandoned after decapitation of an Oxisol for building purposes. The field trial consisted of various treatments with different grass species and amendments. Pore size distribution of the sampled aggregates was measured in the equivalent diameter range from 0.005 to about 50 ?m and it was characterized by a bimodal pattern, so that two compartments, i.e. 0.005 to 0.2 ?m and 0.2 to 50 ?m, could be distinguished. The multifractal theory was used to analyse both segments. The scaling properties of these two segments could be fitted reasonably well with multifractal models. Multifractal parameters obtained for equivalent diameters for the segments > 0.2 and < 0.2 ?m showed great differences. For example, entropy dimension, D1, values from the segment 0.005-0.2 ?m were always lower than those for the segment 0.2-50 ?m form NDI , whereas the Hólder exponent of order zero, ?0, were higher for the former segment. These results indicate the probability different degrees of heterogeneity within the Hg pore size distributions studied.

dos Santos Bonini, C.; Alves, M. C.; Paz González, A.

2012-04-01

195

Binning effects on in-situ raindrop size distribution measurements

Directory of Open Access Journals (Sweden)

Full Text Available This paper investigates the binning effects on drop size distribution (DSD measurements obtained by Joss-Waldvogel disdrometer (JWD, Precipitation Occurrence Sensor System (POSS, Thies disdrometer (Thies, Parsivel OTT disdrometer, two-dimensional video disdrometer (2DVD and optical spectro-pluviometer (OSP instruments, therefore the evaluation comprises non-regular bin sizes and the effect of minimum and maximum measured sizes of drops. To achieve this goal, 2DVD measurements and simulated gamma size distributions were considered. The analysis of simulated gamma DSD binned according each instrument was performed to understand the role of discretisation and truncation effects together on the integral rainfall parameters and estimators of the DSD parameters. In addition, the drop-by-drop output of the 2DVD is binned to simulate the raw output of the other disdrometers which allowed us estimate sampling and binning effects on selected events from available dataset. From simulated DSD it has been found that binning effects exist in integral rainfall parameters and in the evaluation of DSD parameters of a gamma distribution. This study indicates that POSS and JWD exhibit underestimation of concentration and mean diameter due to binning. Thies and Parsivel report a positive bias for rainfall and reflectivity (reaching 5% for heavy rainfall intensity events. Regarding to DSD parameters, distributions of estimators for the shape and scale parameters were analyzed by moment, truncated moment and maximum likelihood methods. They reported noticeable differences between instruments for all methodologies of estimation applied. The measurements of 2DVD allow sampling error estimation of instruments with smaller capture areas than 2DVD. The results show that the instrument differences due to sampling were a~relevant uncertainty but that concentration, reflectivity and mass-weighted diameter were sensitive to binning.

R. Checa-Garcia

2014-03-01

196

Drop size distribution in sprays by image processing

Digital Repository Infrastructure Vision for European Research (DRIVER)

An automatic analysis system has been developed and used to analyze photographs obtained by high-speed microphotography, the final aim being to derive the size distributions of drops in sprays. The problem of determining whether photographic images of particles are in focus or not is solved by obtaining a calibration of geometric parameters of particle images as functions both of the particle position in the camera's field of view and of the particle diameter. On the basis of the results of t...

Fantini, E.; Tognotti, L.; Tonazzini, A.

1989-01-01

197

Cotton dust concentrations and particle size distributions associated with genotypes.

Digital Repository Infrastructure Vision for European Research (DRIVER)

The problem of byssinosis has plagued cotton textile mills for hundreds of years, and it is still a problem today. With the regulations on airborne raw cotton dust set by OSHA and the ACGIH, research regarding the measurement of cotton dust in lint fiber is a necessity. A procedure known as the mass concentration particle size distribution (MCPSD) technique, developed at Texas A&M University, was used to measure the characteristics of cotton dust as affected by harvesting method and genotype....

Parnell, C. B.; Niles, G. A.; Rutherford, R. D.

1986-01-01

198

New finite-size correction for local alignment score distributions

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Local alignment programs often calculate the probability that a match occurred by chance. The calculation of this probability may require a “finite-size” correction to the lengths of the sequences, as an alignment that starts near the end of either sequence may run out of sequence before achieving a significant score. Findings We present an improved finite-size correction that considers the distribution of sequence lengths rather than simply the corresponding means. This approach improves sensitivity and avoids substituting an ad hoc length for short sequences that can underestimate the significance of a match. We use a test set derived from ASTRAL to show improved ROC scores, especially for shorter sequences. Conclusions The new finite-size correction improves the calculation of probabilities for a local alignment. It is now used in the BLAST+ package and at the NCBI BLAST web site (http://blast.ncbi.nlm.nih.gov.

Park Yonil

2012-06-01

199

Particle size distribution dynamics during precipitative softening: declining solution composition.

Particle removal is a critical step in the treatment of surface water for potable use, and the majority of drinking water treatment plants employ precipitative coagulation processes such as alum and iron "sweep-floc" coagulation or lime softening for particle pre-treatment. Unfortunately, little is quantitatively known about how particle size distributions are shaped by simultaneous precipitation and flocculation. In an earlier paper, we demonstrated the effects of the saturation ratio, the mixing intensity and the seed concentration on the rates of homogeneous nucleation, precipitative growth and flocculation during precipitation of calcium carbonate at constant solution composition using electronic particle counting techniques. In this work, we extend those findings to systems more closely emulating the conditions in actual softening processes (i.e., declining solution composition). Key findings include the strong dependence of the rate of flocculation on the initial saturation ratio and demonstration of the benefits of seeding precipitative softening from the perspective of optimizing the effluent particle size distribution. The mixing intensity during precipitation was also shown to strongly influence the final particle size distribution. Implications of the findings with respect to softening practice are discussed. PMID:18976791

Nason, Jeffrey A; Lawler, Desmond F

2009-02-01

200

Comparative method evaluation for size and size-distribution analysis of gold nanoparticles.

Gold nanoparticles (GNPs) are popular colloidal substrates in various sensor, imaging, and nanomedicine applications. In separation science, they have raised some interest as a support for sample preparation. Reasons for their popularity are their low cost, ability for size-controlled synthesis with well-defined narrow nanoparticle size distributions, as well as straightforward surface functionalization by self-assembling (thiol-containing) molecules on the surface, which allows flexible introduction of functionalities for the selective capture of analytes. Most commonly, the method of first choice for size determination is dynamic light scattering (DLS). However, DLS has some serious shortcomings, and results from DLS may be misleading. For this reason, in this contribution several distinct complementary nanoparticle sizing methodologies were utilized and compared to characterize citrate-capped GNPs of different diameters in the range of 13-26 nm. Weaknesses and strengths of DLS, transmission electron microscopy, asymmetrical-flow field-flow fractionation and nanoelectrospray gas-phase electrophoretic mobility molecular analysis are discussed and the results comparatively assessed. Furthermore, the distinct GNPs were characterized by measuring their zeta-potential and surface plasmon resonance spectra. Overall, the combination of methods for GNP characterization gives a more realistic and comprehensive picture of their real physicochemical properties, (hydrodynamic) diameter, and size distribution. PMID:23857600

Hinterwirth, Helmut; Wiedmer, Susanne K; Moilanen, Maria; Lehner, Angela; Allmaier, Günter; Waitz, Thomas; Lindner, Wolfgang; Lämmerhofer, Michael

2013-09-01

201

Magnetic heating effect of nanoparticles with different sizes and size distributions

Energy Technology Data Exchange (ETDEWEB)

We present a comparative study of dynamic and quasistatic magnetic properties of iron oxide nanoparticles. The samples are prepared by different wet chemical precipitation methods resulting in different sizes and size distributions. The structural characterization was performed by X-ray diffraction and transmission electron microscopy. The heating effect in an ac field in the range 0-30 kA/m at 210 kHz was measured calorimetrically. In addition, a vibrating sample magnetometer was used for hysteresis and remanence curve measurements. - Highlights: Black-Right-Pointing-Pointer Preparation of 4 different types of magnetic nanoparticles with mean sizes from 10-20 nm. Black-Right-Pointing-Pointer Basic characterization by X-ray diffraction and vibrating sample magnetometry. Black-Right-Pointing-Pointer Determination of sizes and size distributions from X-ray and TEM data. Black-Right-Pointing-Pointer Calorimetric measurements of the specific heating power in an ac field of 210 kHz and field amplitudes up to 30 kA/m.

Mueller, R.; Dutz, S. [Department of Nano Biophotonics, Institute of Photonic Technology, Jena (Germany); Neeb, A.; Cato, A.C.B. [Institute of Toxicology and Genetics, Karlsruhe Institute of Technology, Karlsruhe (Germany); Zeisberger, M., E-mail: zeisberger@ipht-jena.de [Department of Spectroscopy and Imaging, Institute of Photonic Technology, Jena (Germany)

2013-02-15

202

Nanometre-size products of uranium bioreduction

International Nuclear Information System (INIS)

One strategy that is being pursued to tackle the international problem of actinide contamination of soils, sediments and water is to use microbial activity to 'fix' these radionuclides into an insoluble form that cannot be readily dispersed. Here we show that uraninite (UO2) particles formed from uranium in sediments by bacterial reduction are typically less than 2 nanometres across and that the small size has important implications for uraninite reactivity and fate. Because these tiny particles may still be transported in an aqueous environment, precipitation of uranium as insoluble uraninite cannot be presumed to immobilize it.

2002-09-12

203

Cluster size distribution of cell aggregates in culture

The growth patterns of established normal and cancer cell lines, cultured in monolayer and collagen gel, have been characterized using the cluster size distribution of cellular aggregates. HN-5 (cancer) cells exhibit, either in gel or in monolayer, power-law distributions at any time in culture, whereas for MDCK (“normal”) and Hep-2 (cancer) cells there is a transition from an exponential behavior to a power-law distribution after a transient time in culture. These results suggest that the transitions in growth regimes observed in MDCK and Hep-2 cell lines might be associated to changes in the control of replication or in the expression patterns of cell adhesion molecules of cell-cell and cell-matrix type related to intracellular signalling. These transitions are irreversible and seems to be an adaptative response to the growth constraints imposed by high cell population density or long permanence in culture.

Mendes, Rosemairy L.; Santos, Anésia A.; Martins, M. L.; Vilela, M. J.

2001-09-01

204

Morphology, size distribution and elemental composition of several dental debris

We investigated morphologies, size distributions and elemental compositions of dental debris formed by cutting/grinding teeth or dental alloys. The average size of debris formed by cutting/grinding dental alloy was around 100 ?m and that of teeth was 20 ?m. The debris formed by grinding with diamond or carborundum point had isotropic irregular shape, while the debris formed by cutting with carbide bar had characteristic lathe-cut shape. The elemental analysis indicated that the debris formed by grinding dental alloy with carborundum point consisted of not only the particles of the alloy but also the particles of Si compounds with the size of around 10 ?m. The particles of Si compounds would be formed by abrasion of the grinding instrument (carborundum, SiC). Similarly, the debris formed by grinding with diamond point also contained submicro-sized particles consisting of C compounds. The results indicate that the morphology and composition of dental debris are varied depending on the combination between the workpiece and the cutting/grinding materials and that the dental debris consist of both the workpiece and the cutting/grinding materials in some combination. In addition, some of the debris of tooth had the size less than 2 ?m, which has a potential to induce inflammation. Though the inflammation can be expected at low level, it is required to investigate the details in future.

Abe, Shigeaki; Iwadera, Nobuki; Esaki, Mitsue; Aoyama, Ken-Ichi; Akasaka, Tsukasa; Uo, Motohiro; Morita, Manabu; Yawaka, Yasutaka; Watari, Fumio

2012-12-01

205

Fog-Influenced Submicron Aerosol Number Size Distributions

The aim of this work is to evaluate the influence of fog on aerosol particle number size distributions (PNSD) in submicron range. Thus, five-year continuous time series of the SMPS (Scanning Mobility Particle Sizer) data giving information on PNSD in five minute time step were compared with detailed meteorological records from the professional meteorological station Kosetice in the Czech Republic. The comparison included total number concentration and PNSD in size ranges between 10 and 800 nm. The meteorological records consist from the exact times of starts and ends of individual meteorological phenomena (with one minute precision). The records longer than 90 minutes were considered, and corresponding SMPS spectra were evaluated. Evaluation of total number distributions showed considerably lower concentration during fog periods compared to the period when no meteorological phenomenon was recorded. It was even lower than average concentration during presence of hydrometeors (not only fog, but rain, drizzle, snow etc. as well). Typical PNSD computed from all the data recorded in the five years is in Figure 1. Not only median and 1st and 3rd quartiles are depicted, but also 5th and 95th percentiles are plotted, to see the variability of the concentrations in individual size bins. The most prevailing feature is the accumulation mode, which seems to be least influenced by the fog presence. On the contrary, the smallest aerosol particles (diameter under 40 nm) are effectively removed, as well as the largest particles (diameter over 500 nm). Acknowledgements: This work was supported by the projects GAUK 62213 and SVV-2013-267308. Figure 1. 5th, 25th, 50th, 75th and 95th percentile of aerosol particle number size distributions recorded during fog events.

Zikova, N.; Zdimal, V.

2013-12-01

206

Coalescent time distributions in trees of arbitrary size.

The relationship between speciation times and the corresponding times of gene divergence is of interest in phylogenetic inference as a means of understanding the past evolutionary dynamics of populations and of estimating the timing of speciation events. It has long been recognized that gene divergence times might substantially pre-date speciation events. Although the distribution of the difference between these has previously been studied for the case of two populations, this distribution has not been explicitly computed for larger species phylogenies. Here we derive a simple method for computing this distribution for trees of arbitrary size. A two-stage procedure is proposed which (i) considers the probability distribution of the time from the speciation event at the root of the species tree to the gene coalescent time conditionally on the number of gene lineages available at the root; and (ii) calculates the probability mass function for the number of gene lineages at the root. This two-stage approach dramatically simplifies numerical analysis, because in the first step the conditional distribution does not depend on an underlying species tree, while in the second step the pattern of gene coalescence prior to the species tree root is irrelevant. In addition, the algorithm provides intuition concerning the properties of the distribution with respect to the various features of the underlying species tree. The methodology is complemented by developing probabilistic formulae and software, written in R. The method and software are tested on five-taxon species trees with varying levels of symmetry. The examples demonstrate that more symmetric species trees tend to have larger mean coalescent times and are more likely to have a unimodal gamma-like distribution with a long right tail, while asymmetric trees tend to have smaller mean coalescent times with an exponential-like distribution. In addition, species trees with longer branches generally have shorter mean coalescent times, with branches closest to the root of the tree being most influential. PMID:18241192

Efromovich, Sam; Kubatko, Laura Salter

2008-01-01

207

Top pair production distributions at the Tevatron

Directory of Open Access Journals (Sweden)

Full Text Available At the Tevatron, the top quark is mainly produced in pairs through the strong interaction and decays before forming hadrons. Thus the kinematical distributions at top pair production possess rich information on the tt¯$tar t$ production vertex including polarizations of top and anti-top quarks. In this article, recent measurements on top quark pair production distributions at Tevatron (CDF and DO are presented.

Takeuchi Yuji

2013-05-01

208

New Measurements of the Particle Size Distribution of Apollo 11 Lunar Soil 10084

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.

McKay, D.S.; Cooper, B.L.; Riofrio, L.M.

2009-01-01

209

Energy Technology Data Exchange (ETDEWEB)

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.

Pendse, H.P.

1992-10-01

210

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

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.

Nava, David F.

1994-01-01

211

Prediction of oil droplet size distribution in agitated aquatic environments

International Nuclear Information System (INIS)

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

2004-06-08

212

Digital Repository Infrastructure Vision for European Research (DRIVER)

The trophic transfer efficiencies in the planktonic food web of large, deep, and mesoeutrophic Lake Constance were derived independently from biomass size distributions and from mass-balanced carbon flow diagrams based on comprehensive data for biomass, production, and food web structure. The main emphasis was on the transfer of primary production to herbivores since this process dominates the flow of matter within the food web. Biomass size distributions offer an ecosystem approach which rel...

Gaedke, Ursula; Straile, Dietmar

1994-01-01

213

Size distributions of nebular solids in chondrites suggest an efficient sorting of these early forming objects within the protoplanetary disk. The effect of this sorting has been documented by investigations of modal abundances of CAIs (e.g., [1-4]) and chondrules (e.g., [5-8]). Evidence for aerodynamic sorting in the disk is largely qualitative, and needs to be carefully assessed. It may be a way of concentrating these materials into planetesimal-mass clumps, perhaps 100 fs of ka after they formed. A key parameter is size/density distributions of particles (i.e., chondrules, CAIs, and metal grains), and in particular, whether the radius-density product (rxp) is a better metric for defining the distribution than r alone [9]. There is no consensus between r versus rxp based models. Here we report our initial tests and preliminary results, which when expanded will be used to test the accuracy of current dynamical disk models.

Christoffersen, P. A.; Simon, Justin I.; Ross, D. K.; Friedrich, J. M.; Cuzzi, J. N.

2012-01-01

214

Size Distributions of Solar Flares and Solar Energetic Particle Events

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 (much > 1000 km/s) coronal mass ejections (CMEs) that drive coronal/interplanetary shock waves. For the 1996-2005 interval, the slopes (alpha values) of power-law size distributions of the peak 1-8 Angs fluxes of SXR flares associated with (a) >10 MeV SEP events (with peak fluxes much > 1 pr/sq cm/s/sr) and (b) fast CMEs were approx 1.3-1.4 compared to approx 1.2 for the peak proton fluxes of >10 MeV SEP events and approx 2 for the peak 1-8 Angs fluxes of all SXR flares. The difference of approx 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.

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

2012-01-01

215

Particle size distributions of radioactive aerosols measured in workplaces

International Nuclear Information System (INIS)

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 ?m to 25 ?m, and most were well fitted by a log-normal distribution with a median value of 4.4 ?m. This supports the choice of a 5 ?m 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 ?m. Uranium mills gave a median value of 6.8 ?m with AMADs frequently greater than 10 ?m. 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 ?m default AMAD will not always be conservative. (author)

1995-01-01

216

SIZE DISTRIBUTIONS OF SOLAR FLARES AND SOLAR ENERGETIC PARTICLE EVENTS

Energy Technology Data Exchange (ETDEWEB)

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{sup -1}) coronal mass ejections (CMEs) that drive coronal/interplanetary shock waves. For the 1996-2005 interval, the slopes ({alpha} values) of power-law size distributions of the peak 1-8 A fluxes of SXR flares associated with (a) >10 MeV SEP events (with peak fluxes {>=}1 pr cm{sup -2} s{sup -1} sr{sup -1}) and (b) fast CMEs were {approx}1.3-1.4 compared to {approx}1.2 for the peak proton fluxes of >10 MeV SEP events and {approx}2 for the peak 1-8 A fluxes of all SXR flares. The difference of {approx}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.

Cliver, E. W. [Space Vehicles Directorate, Air Force Research Laboratory, Sunspot, NM 88349 (United States); Ling, A. G. [Atmospheric Environmental Research, Lexington, MA 02421 (United States); Belov, A. [IZMIRAN, Troitsk, Moscow Region 142190 (Russian Federation); Yashiro, S. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

2012-09-10

217

Finite-size effects on return interval distributions for weakest-link-scaling systems

The Weibull distribution is a commonly used model for the strength of brittle materials and earthquake return intervals. Deviations from Weibull scaling, however, have been observed in earthquake return intervals and the fracture strength of quasibrittle materials. We investigate weakest-link scaling in finite-size systems and deviations of empirical return interval distributions from the Weibull distribution function. Our analysis employs the ansatz that the survival probability function of a system with complex interactions among its units can be expressed as the product of the survival probability functions for an ensemble of representative volume elements (RVEs). We show that if the system comprises a finite number of RVEs, it obeys the ?-Weibull distribution. The upper tail of the ?-Weibull distribution declines as a power law in contrast with Weibull scaling. The hazard rate function of the ?-Weibull distribution decreases linearly after a waiting time ?c?n1/m, where m is the Weibull modulus and n is the system size in terms of representative volume elements. We conduct statistical analysis of experimental data and simulations which show that the ? Weibull provides competitive fits to the return interval distributions of seismic data and of avalanches in a fiber bundle model. In conclusion, using theoretical and statistical analysis of real and simulated data, we demonstrate that the ?-Weibull distribution is a useful model for extreme-event return intervals in finite-size systems.

Hristopulos, Dionissios T.; Petrakis, Manolis P.; Kaniadakis, Giorgio

2014-05-01

218

Melt-clast interaction and power-law size distribution of clasts in pseudotachylytes

Before the onset of melting along frictional interfaces, the wall rocks of seismic faults are crushed to generate a power-law grain-size distribution pattern. Theoretical analysis with the help of numerical models shows that, under conditions of uniform rim melting of the grains, the pre-melting power-law pattern survives in a modified form in the relicts, which occur as clasts in the quenched product, i.e. pseudotachylyte. The size distribution of clasts in experimentally produced as well as natural pseudotachylytes, including those from the Sarwar-Junia fault zone in western India, shows a pattern similar to that predicted by theoretical analysis. A micron-scale mantle of glass±microlites around a large number of clasts, and minute beads of glass set within glassy matrix, are the observed evidence of rim melting. Post-melting clast size distribution in the numerical models follows the relationship N?(1+ z/ z') - D, where N is number of clasts of size ? z. Size z may be represented by mean diameter r, or sectional area a, or volume v, and D(= D r, D a or D v) is the modified power-law exponent. z' (= r', a' or v') is a constant that depends on thickness ( ?) of uniform rim melting, and r'= ?, a' =?2, and v' =?3. The analysis suggests that the modified power-law clast-size distribution pattern is a characteristic feature of all fault-related pseudotachylytes.

Ray, Sumit Kumar

2004-10-01

219

The effect of grain size distribution on river delta morphology

Delta morphology is thought to be controlled by river discharge, tidal range, and wave energy. However, recent research has shown that sediment properties may have a stronger control on the physical processes, size, and shape of a delta than previously recognized. Recent numerical studies have begun to quantify this control, but have been limited to the effect of sediment cohesion and subsurface sediment properties in the basin. This study focuses on how properties of the grain size distribution - the median, standard deviation, and skewness - delivered to the delta head affects delta form. To this end, we conduct numerical experiments using the morphodynamic physics-based model Delft3D. The model setup includes a river carrying constant discharge and sediment load entering a standing body of water devoid of tides, waves, and sea-level change. We conduct 24 runs varying the distribution's median grain size from 0.01 - 1 mm, standard deviation from 0.1 - 3, and skewness from -0.7 - 0.7. Model results are insensitive to user defined model parameters and initial and boundary conditions. Our results show that of the three parameters tested, median grain size and standard deviation have the most substantial effect on morphology while skewness has little. At low median grain size and standard deviation deltas have 3-6 active distributaries that are relatively deep. The planform is elongate and deviates from a semi-circle, and the topset and delta-front have shallow gradients. Interestingly, as median grain size and standard deviation increase, a morphological transition occurs from deltas with elongate channels to ones with braided channels. Whether or not this transition coincides with the onset of braiding for upland alluvial channels remains to be seen. These braided deltas form at high median grain size and standard deviation, and are characterized by many active, shallow distributaries, a semi-circular planform, and steep topset and delta-front gradients. Our results suggest sediment properties exert control on delta morphology, and future analysis will aim to elucidate the underlying processes.

Caldwell, R. L.; Edmonds, D. A.

2011-12-01

220

[Dewaterability and particle size distribution of activated and digestion sludge].

The dewaterability and particle size distribution of activated and digestion sludge were studied. Meanwhile, the related mechanism was explored through analyzing the extracellular polymeric substances (EPS) content and microbe characteristic of activated and digestion sludge. The dewaterability was evaluated using the capillary suction time (CST) and settling property. The CST of activated sludge and digestion sludge are 9.84 s and 607.5 s, respectively. The settling time of the solids of digestion sludge is longer than that of activated sludge. The major reason of poor dewaterability of digestion sludge is the degradation of carbohydrate and protein parts of EPS. In addition, the quantity of protozoan in digestion sludge is less than that of activated sludge, resulting in reducing the excretion of certain matters benefiting the agglomeration between microbes. The EPS content of digestion sludge is 123 mg/g, which was 77% less than that of activated sludge. The degradation of EPS during the digestion process leads to the smaller particle size of digested sludge, and then the poorer dewaterability. The particle size that occupied maximum volume in activated sludge is 133 microm, while it is 44.6 microm in digestion sludge. The mean particle size of activated sludge is 132.6 microm which is larger than that of digestion sludge (70.48 microm). PMID:18268985

Pei, Hai-yan; Hu, Wen-rong; Li, Jing; Chen, Lei

2007-10-01

221

A quantitative method for clustering size distributions of elements

A quantitative method was developed to group similarly shaped size distributions of particle-phase elements in order to ascertain sources of the elements. This method was developed and applied using data from two sites in Houston, TX; one site surrounded by refineries, chemical plants and vehicular and commercial shipping traffic, and the other site, 25 miles inland surrounded by residences, light industrial facilities and vehicular traffic. Twenty-four hour size-segregated (0.056fluid catalytic cracking unit catalysts, fuel oil burning, a coal-fired power plant, and high-temperature metal working. The clustered elements were generally attributed to different sources at the two sites during each sampling day indicating the diversity of local sources that impact heavy metals concentrations in the region.

Dillner, Ann M.; Schauer, James J.; Christensen, William F.; Cass, Glen R.

222

Method for measuring the size distribution of airborne rhinovirus

Energy Technology Data Exchange (ETDEWEB)

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.

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

2002-01-01

223

Influence of meteorological variability upon aerosol mass size distribution

Aerosol mass size distribution has been measured by using an optical particle counter. The measurements were done in an urban background location in the western Mediterranean during winter 2006. The study has been focused in determining the mass size distribution under special meteorological conditions like moderate rain, considerable winds and high atmospheric stability. The results obtained showed a mass predominance of accumulation mode during rain and high stability periods although for different reasons. In the case of rain, it is due to greater atmospheric cleansing effectiveness that rain has upon coarse mode particles. However, during stagnant periods, the meteorological situation favored coagulation processes among nucleation mode particles giving like result a mass increase in the accumulation mode. Finally, strong winds favor the resuspension of the largest particles and the dispersion of particles with sizes inferior to 7.5 ?m. Similar results have been reproduced using principal component analysis (PCA). In this way, three components were identified. The first (PC1) represents particles in the accumulation mode. The second component (PC2) is constituted by coarse particles to 7.5 ?m, and the third (PC3) corresponds to coarser particles. The contribution of each group to the overall average concentration was determined: 27.2% corresponds to particles with sizes belonging within the first component, 35.4% to PC2 and 37.3% to PC3. Important percentage variability for each component under meteorological episodes has been obtained. Results obtained showed an important increase of PC1 during Rainy Days (53.8%) and High Pollution Days (40.2%). Contrary to this on Windy Days this component decreases to 7.4%. However, during this kind of day PC3 increases to 64.6%.

Nicolás, J. F.; Yubero, E.; Pastor, C.; Crespo, J.; Carratalá, A.

2009-10-01

224

A Maximum Entropy Modelling of the Rain Drop Size Distribution

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents a maximum entropy approach to Rain Drop Size Distribution (RDSD modelling. It is shown that this approach allows (1 to use a physically consistent rationale to select a particular probability density function (pdf (2 to provide an alternative method for parameter estimation based on expectations of the population instead of sample moments and (3 to develop a progressive method of modelling by updating the pdf as new empirical information becomes available. The method is illustrated with both synthetic and real RDSD data, the latest coming from a laser disdrometer network specifically designed to measure the spatial variability of the RDSD.

Francisco J. Tapiador

2011-01-01

225

Estimation of Weibull parameters from parameters of initial distribution of flaw size

Energy Technology Data Exchange (ETDEWEB)

The distribution of the largest flaw size is derived from the initial distribution of flaw size based on extreme value statistics, and also the distribution of fracture origin size is given by transforming Weibull distribution by fracture mechanical relation. These two distributions are equivalent under uniaxial loading. By using this relation, their parameters are related each other and Weibull parameters are estimated from the parameters of the initial distribution of flaw size and the number of links.

Wakabayashi, C; Yasuda, K; Shiota, T, E-mail: wakabayashi.c.aa@m.titech.ac.j [Department of Metallurgy and Ceramics Science, Graduate School of Science and Engineering, Tokyo Institute of Technology, 2-12-1-S7-14, Ookayama, Meguro-ku, Tokyo (Japan)

2009-11-15

226

Estimation of Weibull parameters from parameters of initial distribution of flaw size

International Nuclear Information System (INIS)

The distribution of the largest flaw size is derived from the initial distribution of flaw size based on extreme value statistics, and also the distribution of fracture origin size is given by transforming Weibull distribution by fracture mechanical relation. These two distributions are equivalent under uniaxial loading. By using this relation, their parameters are related each other and Weibull parameters are estimated from the parameters of the initial distribution of flaw size and the number of links.

2009-11-01

227

Drop Size Distribution Retrieval with Polarimetric Radar: Model and Application.

Polarimetric radar measurements are used to retrieve properties of raindrop distributions. The procedure assumes that drops are represented by a gamma distribution and retrieves the governing parameters from an empirical relation between the distribution shape and slope parameters and measurements of radar reflectivity and differential reflectivity. Retrieved physical characteristics of the drop size distribution (DSD) were generally well matched with disdrometer observations. The method is applied to select storms to demonstrate utility. Broad DSDs were determined for the core (high reflectivity) regions of thunderstorms. Largest drop median volume diameters were at the leading edge of the storm core and were displaced slightly downwind from updrafts. Rainy downdrafts exhibited what are believed to be equilibrium DSDs in which breakup and accretion are roughly in balance. DSDs for stratiform precipitation were dominated by relatively large drops. Median volume diameters at the ground were closely related to the intensity of an overlying bright band. The radar measurements suggest that, although DSDs in stratiform rain were also broad and nearly constant in the rain layer, they were not at equilibrium but were merely steady. DSD invariance is attributed to small total drop numbers, which result in few collisions.

Brandes, Edward A.; Zhang, Guifu; Vivekanandan, J.

2004-04-01

228

Directory of Open Access Journals (Sweden)

Full Text Available This work provides long-term (2004–2006 size segregated measurements of aerosol mass at a remote coastal station in the southern Europe, with the use of size-selective samplings (SDI impactor. Seven distinct modes were identified in the range 0–10 µm and the dominant were the "Accumulation 1" (0.25–0.55 µm and the "Coarse 2" (3–7 µm modes. The seasonal characteristics of each mode were thoroughly studied and different sources for submicron and supermicron particles were identified, the first being related to local/regional and transported pollution with maximum in summer and the latter to dust from deserted areas in Northern Africa maximizing in spring. On average, PM2.5 and PM1 accounted for 60% and 40% of PM10 mass, respectively.The representativity of the ground-based measurements for the total column was also investigated by comparing the measured aerosol mass distributions with the AERONET volume size distribution data. Similar seasonal patterns were revealed and AERONET was found adequate for the estimation of background levels of both fine and coarse particles near surface, with certain limitations in the case of pollution or dust abrupt episodes due to its low temporal coverage.

N. Mihalopoulos

2007-05-01

229

Directory of Open Access Journals (Sweden)

Full Text Available This work provides long-term (2004–2006 size segregated measurements of aerosol mass at a remote coastal station in the southern Europe, with the use of size-selective samplings (SDI impactor. PM_{2.5} and PM_{1 } account for 60% and 40% of PM_{10} mass in average, respectively. Seven distinct modes were identified in the range 0–10 ?m and the dominant were the "Accumulation 1" (0.25–0.55 ?m and the "Coarse 2" (3–7 ?m modes. Different sources for submicron and supermicron particles were identified, the first being related to local/regional and transported pollution with maximum in summer and the latter to dust from deserted areas in Northern Africa maximizing in spring. The representativity of the ground-based measurements for the total column was also investigated by comparing the measured aerosol mass distributions with the AERONET volume size distribution data and similar seasonal patterns were revealed.

E. Gerasopoulos

2007-01-01

230

Shattering of dust grains in the interstellar medium is a viable mechanism of small grain production in galaxies. We examine the robustness or uncertainty in the theoretical predictions of shattering. We identify $P_1$ (the critical pressure above which the deformation destroys the original lattice structures) as the most important quantity in determining the timescale of small grain production, and confirm that the same $P_1/t$ ($t$ is the duration of shattering) gives the same grain size distribution [$n(a)$, where $a$ is the grain radius] after shattering within a factor of 3. The uncertainty in the fraction of shocked material that is eventually ejected as fragments causes uncertainties in $n(a)$ by a factor of 1.3 and 1.6 for silicate and carbonaceous dust, respectively. The size distribution of shattered fragments have minor effects as long as the power index of the fragment size distribution is less than ~ 3.5, since the slope of grain size distribution $n(a)$ continuously change by shattering and beco...

Hirashita, Hiroyuki

2013-01-01

231

The distribution of granular temperatures in granular gas mixtures is investigated analytically and numerically. We analyze space uniform systems in a homogeneous cooling state (HCS) and under a uniform heating with a mass-dependent heating rate \\Gamma_k\\sim m_k^{\\gamma} . We demonstrate that for steep size distributions of particles the granular temperatures obey a universal power-law distribution, T_k \\sim m_k^{\\alpha} , where the exponent ? does not depend on a particular form of the size distribution, the number of species and inelasticity of the grains. Moreover, ? is a universal constant for a HCS and depends piecewise linearly on ? for heated gases. The predictions of our scaling theory agree well with the numerical results.

Bodrova, Anna; Levchenko, Denis; Brilliantov, Nikolay

2014-04-01

232

Altitude variation of Drop Size Distribution and their parameters

Knowledge of raindrop size distribution DSD is very crucial to understand the microphysics of cloud systems as well as for retrieving the integral rain parameters Vertically pointing wind profilers are excellent tools for retrieving rain drop size distribution Indian MST radar operating at 53 MHz VHF is highly sensitive to Bragg scattering from the radio refractive index fluctuations while Lower Atmospheric Wind Profiler LAWP operating at 1357 5 MHz UHF is sensitive to Rayleigh scattering from hydrometeors during rain At UHF it is possible to resolve echoes from clear air and precipitation during light rain however the precipitation echo masks the clear air echo during moderate to heavy rain This problem is solved by using a dual frequency algorithm i e the information of the ambient air motion and turbulence is retrieved from a VHF profiler and used in UHF spectra to delineate the precipitation part of the spectra A Gamma model is then fitted to the observed precipitation spectra to derive the model parameters From the retrieved DSD integral rain parameters rain rate reflectivity factor liquid water content median volume diameter etc are derived and compared with Disdrometer derived parameters A reasonably good agreement is found between these measurements although radar measurements are volume integrated and Disdrometer is only a point measurement Further variations of DSD as a function of altitude in different rain regimes are studied to understand the microphysics of cloud system During convection the shape

Kirankumar, N. V. P.; Rao, T. N.; Rao, D. N.

233

The Size Distribution of Trans-Neptunian Bodies

[Condensed] We search 0.02 deg^2 for trans-Neptunian objects (TNOs) with m<=29.2 (diameter ~15 km) using the ACS on HST. Three new objects are discovered, roughly 25 times fewer than expected from extrapolation of the differential sky density Sigma(m) of brighter objects. The ACS and other recent TNO surveys show departures from a power law size distribution. Division of the TNO sample into ``classical Kuiper belt'' (CKB) and ``Excited'' samples reveals that Sigma(m) differs for the two populations at 96% confidence. A rolling-index or double power law adequately fits all data. Implications include: The total mass of the CKB is ~0.010 M_Earth, only a few times Pluto's mass, and is predominately in the form of ~100 km bodies. The mass of Excited objects is perhaps a few times larger. The Excited class has a shallower bright-end size distribution; the largest objects, including Pluto, comprise tens of percent of the total mass whereas the largest CKBOs are only ~2% of its mass. The predicted mass of the larg...

Bernstein, G M; Allen, R L; Brown, M E; Holman, M; Malhotra, R

2003-01-01

234

Size Distribution of Main-Belt Asteroids with High Inclination

We investigated the size distribution of high-inclination main-belt asteroids (MBAs) to explore asteroid collisional evolution under hypervelocity collisions of around 10 km/s. We performed a wide-field survey for high-inclination sub-km MBAs using the 8.2-m Subaru Telescope with the Subaru Prime Focus Camera (Suprime-Cam). Suprime-Cam archival data were also used. A total of 616 MBA candidates were detected in an area of 9.0 deg^2 with a limiting magnitude of 24.0 mag in the SDSS r filter. Most of candidate diameters were estimated to be smaller than 1 km. We found a scarcity of sub-km MBAs with high inclination. Cumulative size distributions (CSDs) were constructed using Subaru data and published asteroid catalogs. The power-law indexes of the CSDs were 2.17 +/- 0.02 for low-inclination ( 15 deg) MBAs in the 0.7-50 km diameter range. The high-inclination MBAs had a shallower CSD. We also found that the CSD of S-like MBAs had a small slope with high inclination, whereas the slope did not vary with inclinatio...

Terai, Tsuyoshi

2010-01-01

235

Lotka's Frequency Distribution of Scientific Productivity.

In 1926, Alfred Lotka examined the frequency distribution of scientific productivity of chemists and physicists. After analyzing the number of publications of chemists listed in Chemical Abstracts 1907-1916 and the contributions of physicists listed in Au...

R. C. Coile

1978-01-01

236

Managerial Versus Production Wages: Offshoring, Country Size and Endowments

Digital Repository Infrastructure Vision for European Research (DRIVER)

We look at managerial and production wages in countries that differ in size and relative endowments. Production labor is assumed to be a variable input composed of tradable tasks, while managerial labor is a fixed, non-tradable input. Task performance is subject to increasing returns to scale on the country level, as in Grossman & Rossi-Hansberg (2009). We first analyze country size and relative endowment effects on wages, ruling out task trade altogether, followed by numerical simulations hi...

2010-01-01

237

Raindrop Size Distributions: Characterization and Retrieval from Polarimetric Radar Measurements

Information regarding the raindrop size distribution (DSD) is important for accurate rain estimation with radar, for cloud microphysics studies, and for improving parameterization in numerical weather forecast models. In the paper, time series of ground-based video disdrometer observations of raindrop number concentration and mass distribution as well as values normalized by mass-weighted size and liquid water content for thunderstorms are presented. The observations reveal that the shape of rain DSDs depends on the stage of rain development and that there is no universal shape for rain DSDs even after normalization. An algorithm, based on disdrometer measurements and scattering calculations, for retrieving DSDs from polarimetric radar measurements is then described. Dubbed the constrained-gamma DSD retrieval method, the procedure uses radar reflectivity (Z), differential reflectivity (ZDR), and an empirically determined relation between the shape (? ) and slope (? ) parameters of the gamma DSD model. The constrained-gamma DSD model is similar to a normalized-gamma DSD in that both approaches use two independent parameters to characterize rain DSDs. But the constrained-gamma model allows different shape of DSD even after normalization. While the normalized-gamma model and other (fixed ? ) retrieval algorithms can provide reasonable rain rate estimation from two remote measurements, the constrained-gamma DSD retrieval leads a much better agreement with in-situ measurements for number concentration and characteristic size as well as better microphysical parameters for forecast models. The constrained-gamma retrieval model is applied to a thunderstorm complex to study the spatial and temporal characteristics of the DSD.

Brandes, E.; Zhang, G.

2004-05-01

238

The effect of grain-size distribution on coercivity in nanocrystalline soft magnetic alloys

International Nuclear Information System (INIS)

A simple model considering grain-size distribution has been fabricated based on the random anisotropy model. The model indicates that the effective magnetic anisotropy increases with increasing width of the grain-size distribution even if the mean grain size is constant. The coercivity (Hc) of some nanocrystalline Fe-Nb-B(-P-Cu) alloys with different grain-size distribution has been calculated. Our model explains well the dependence of Hc on the grain-size distribution

2004-05-01

239

Retrieval of spherical particle size distribution with an improved Tikhonov iteration method

Digital Repository Infrastructure Vision for European Research (DRIVER)

The problem of retrieval for spherical particle size distribution in the independent mode is studied, and an improved Tikhonov iteration method is proposed. In this method, the particle size distribution is retrieved from the light extinction data through the Phillips-Twomey method firstly in the independent mode, and then the obtained inversion results of the particle size distribution is used as the initial distribution and the final retrieved particle size distribution is obtained. S...

Tang Hong

2012-01-01

240

Directory of Open Access Journals (Sweden)

Full Text Available Particle size distribution (PSD of polystyrene particles produced by suspension polymerization is of fundamental importance in determining suspension stability and product quality attributes. Within a population balance framework, a model is proposed for suspension polymerization reactors to describe the evolution of the PSD. The model includes description of breakage and coalescence rates in terms of reaction kinetics and rheology of the dispersed phase. The model is validated with experimental data of styrene suspension polymerization.

Machado R.A.F.

2000-01-01

241

Digital Repository Infrastructure Vision for European Research (DRIVER)

The purpose of this study is to measure the size distribution of blasted rock using the digital image processing software “Split-Desktop system” in order to evaluate the efficiency of blasting operation. Site of study is a limestone quarry producing limestone for cement manufacturing. Fragmentation is the ultimate measure of efficiency of any production blasting operations. The degree of fragmentation plays an important role in order to control and minimize the loading, hauling, and crush...

Siddiqui, F.; Shah, S.; Behan, M.

2009-01-01

242

Image Analysis of Pellet Size for a Control System in Industrial Feed Production

DEFF Research Database (Denmark)

When producing aquaculture fish feed pellets, the size of the output product is of immense importance. As the production method cannot produce pellets of constant and uniform size using constant machine settings, there is a demand for size control. Fish fed with feed pellets of improper size are prone to not grow as expected, which is undesirable to the aquaculture industry. In this paper an image analysis method is proposed for automatic size-monitoring of pellets. This is called granulometry and the method used here is based on the mathematical morphological opening operation. In the proposed method, no image object segmentation is needed. The results show that it is possible to extract a general size distribution from an image of piled disordered pellets representing both length and diameter of the pellets in combination as an area.

Ljungqvist, Martin Georg; Nielsen, Michael Engelbrecht

2011-01-01

243

Size-velocity distribution of large ejecta fragments

The characteristics of three primary extraterrestrial craters and the associated craters were examined to generate a size-velocity distribution for large ejecta fragments. The lunar craters Copernicus and Aristillus and the Martian crater Dv on Olympus Mons were used. Attention was focused on the radial distances between the primary and secondary crater centers and the diameters of the secondaries. The primary craters selected are all relatively young, which avoided contamination of the data from secondaries from other primaries. Attempts were made to account for the speed of the hypervelocity impacts and the elemental compositions of the impactors. An apparent velocity cutoff of about 1 km/sec was observed for the secondaries, which implies that no meteoroid impacts can accelerate ejecta to escape velocities from the moon or Mars.

Vickery, A. M.

1986-08-01

244

Retrieval of spherical particle size distribution with an improved Tikhonov iteration method

Directory of Open Access Journals (Sweden)

Full Text Available The problem of retrieval for spherical particle size distribution in the independent mode is studied, and an improved Tikhonov iteration method is proposed. In this method, the particle size distribution is retrieved from the light extinction data through the Phillips-Twomey method firstly in the independent mode, and then the obtained inversion results of the particle size distribution is used as the initial distribution and the final retrieved particle size distribution is obtained. Simulation experiments indicate that the spherical particle size distributions obtained with the proposed method coincide fairly well with the given distributions.

Tang Hong

2012-01-01

245

Size Distribution of Main-Belt Asteroids with High Inclination

We investigated the size distribution of high-inclination main-belt asteroids (MBAs) so as to explore asteroid collisional evolution under hypervelocity collisions of around 10 km s-1. We performed a wide-field survey for high-inclination sub-km MBAs using the 8.2-m Subaru Telescope with the Subaru Prime Focus Camera (Suprime-Cam). Suprime-Cam archival data were also used. A total of 616 MBA candidates were detected in an area of 9.0 deg² with a limiting magnitude of 24.0 mag in the SDSS r filter. Most of the candidate diameters were estimated to be smaller than 1 km. We found a scarcity of sub-km MBAs with high inclination. Cumulative size distributions (CSDs) were constructed using Subaru data and published asteroid catalogs. The power-law indexes of the CSDs were 2.17±0.02 for low-inclination (15°) MBAs in the 0.7-50 km diameter range. The high-inclination MBAs had a shallower CSD. We also found that the CSD of S-like MBAs had a small slope with high inclination, whereas the slope did not vary with the inclination in the C-like group. The most probable cause of the shallow CSD of the high-inclination S-like MBAs is the large power-law index in the diameter-impact strength curve in hypervelocity collisions. The collisional evolution of MBAs may have advanced with oligopolistic survival during the dynamical excitation phase in the final stage of planet formation.

Terai, Tsuyoshi; Itoh, Yoichi

2011-04-01

246

Particle size distributions of suspended sediment in the Sacramento-San Joaquin River Delta

Particle size distributions of suspended sediment in rivers and estuaries are of interest for a variety of reasons, such as their influence on erosion and deposition processes, their effect on light penetration and primary/secondary aquatic production, and their influence on contaminant adsorption processes. Also, particle size is known to affect the amount of light and sound that is scattered by suspended particles; thus, parameters that are typically used as surrogates for suspended-sediment concentration, such as turbidity and acoustic backscatter, are dependent on particle size distributions. Measurements of in situ particle size distributions were made at seven sites in the Sacramento-San Joaquin River Delta as well as along a longitudinal profile of the Sacramento River from Verona (upstream of tidal influence) to Rio Vista (mostly tidal). Size distributions were measured with a laser diffraction particle sizer. At the seven sites, measurements were made from an instrument package deployed on the channel bed. On the Sacramento River, vertical profiles were collected from a stationary boat. Preliminary data analyses indicate a consistent tri-modal size distribution in the Delta, with a narrow peak in the 3-7 micron range, a broad peak centered at 40-50 microns, and a narrow (smaller) peak in the 200-300 micron range. The relative contribution of the different modes varied by site and by position in the tidal cycle. Physical samples collected alongside the in situ data suggest that flocculation occurs at all sites; further analysis of samples is ongoing that will further quantify the degree of flocculation. The Sacramento River longitudinal profile documents the flocculation process occurring in the vicinity of the fluvial-tidal transition; as this transition is crossed, the measurements indicate transfer of sediment from the 3-7 micron mode primarily to the 40-50 micron mode. Understanding these flocculation processes is critical for robust numerical modeling of Delta sediment transport.

Wright, S. A.; Whealdon-Haught, D.

2012-12-01

247

ANALYTICAL MODEL FOR MARS CRATER-SIZE FREQUENCY DISTRIBUTION

Directory of Open Access Journals (Sweden)

Full Text Available We present a theoretical and analytical curve that reproduces essential features of the frequency distributions vs. diameter of the 42,000 impact craters contained in Barlow's Mars Catalog. The model is derived using reasonable simple assumptions that allow us to relate the present craters population with the craters population at each particular epoch. The model takes into consideration the reduction of the number of craters as a function of time caused by their erosion and obliteration, and this provides a simple and natural explanation for the presence of di erent slopes in the empirical log-log plot of number of craters (N vs. diameter (D. A mean life for martians craters as a function of diameter is deduced, and it is shown that this result is consistent with the corresponding determination of craters mean life based on Earth data. Arguments are given to suggest that this consistency follows from the fact that a crater mean life is proportional to its volumen. It also follows that in the absence of erosions and obliterations, when craters are preserved, we would have N / 1=D4:3, which is a striking conclusion, since the exponent 4:3 is larger than previously thought. Such an exponent implies a similar slope in the extrapolated impactors size-frequency distribution.

W. Bruckman

2009-01-01

248

Size distribution of circumstellar disks in the Trapezium cluster

In this paper we present results on the size distribution of circumstellar disks in the Trapezium cluster as measured from HST/WFPC2 data. Direct diameter measurements of a sample of 135 bright proplyds and 14 silhouettes disks suggest that there is a single population of disks well characterized by a power-law distribution with an exponent of -1.9 +- 0.3 between disk diameters 100-400 AU. For the stellar mass sampled (from late G to late M stars) we find no obvious correlation between disk diameter and stellar mass. We also find that there is no obvious correlation between disk diameter and the projected distance to the ionizing Trapezium OB stars. We estimate that about 40% of the disks in the Trapezium have radius larger than 50 AU. We suggest that the origin of the Solar system's (Kuiper belt) outer edge is likely to be due to the star formation environment and disk destruction processes (photoevaporation, collisions) present in the stellar cluster on which the Sun was probably formed. Finally, we identif...

Vicente, S

2005-01-01

249

Using radial NMR profiles to characterize pore size distributions

Extracting information about axon diameter distributions in the brain is a challenging task which provides useful information for medical purposes; for example, the ability to characterize and monitor axon diameters would be useful in diagnosing and investigating diseases like amyotrophic lateral sclerosis (ALS)1 or autism.2 Three families of operators are defined by Ozarslan,3 whose action upon an NMR attenuation signal extracts the moments of the pore size distribution of the ensemble under consideration; also a numerical method is proposed to continuously reconstruct a discretely sampled attenuation profile using the eigenfunctions of the simple harmonic oscillator Hamiltonian: the SHORE basis. The work presented here extends Ozarlan's method to other bases that can offer a better description of attenuation signal behaviour; in particular, we propose the use of the radial Spherical Polar Fourier (SPF) basis. Testing is performed to contrast the efficacy of the radial SPF basis and SHORE basis in practical attenuation signal reconstruction. The robustness of the method to additive noise is tested and analysed. We demonstrate that a low-order attenuation signal reconstruction outperforms a higher-order reconstruction in subsequent moment estimation under noisy conditions. We propose the simulated annealing algorithm for basis function scale parameter estimation. Finally, analytic expressions are derived and presented for the action of the operators on the radial SPF basis (obviating the need for numerical integration, thus avoiding a spectrum of possible sources of error).

Deriche, Rachid; Treilhard, John

2012-02-01

250

Size distribution of PM at Cape Verde - Santiago Island

The archipelago of Cape Verde is located on the eastern North Atlantic, about 500 km west of the African coast. Its geographical location, inside the main area of dust transport over tropical Atlantic and near the coast of Africa, is strongly affected by mineral dust from the Sahara and the Sahel regions. In the scope of the CVDust project a surface field station was implemented in the surroundings of Praia City, Santiago Island (14° 55' N e 23° 29' W, 98 m at sea level), where aerosol sampling throughout different samplers was performed during one year. To study the size distribution of aerosol, an optical dust monitor (Grimm 180), from 0.250 to 32 ?m in 31 size channels, was running almost continuously from January 2011 to December 2011. The performance of Grimm 180 to quantify PM mass concentration in an area affected by the transport of Saharan dust particles was evaluated throughout the sampling period by comparison with PM10 mass concentrations obtained with the gravimetric reference method (PM10 TSI High-Volume, PM10 Partisol and PM10 TCR-Tecora). PM10 mass concentration estimated with the Grimm 180 dust monitor, an optical counter, showed a good correlation with the reference gravimetric method, with R2= 0.94 and a linear regression equation of PM10Grimm = 0.81PM10TCR- 5.34. The number and mass size distribution of PM at ground level together with meteorological and back trajectories were analyzed and compared for different conditions aiming at identifying different signatures related to sources and dust transport. January and February, the months when most Saharan dust events occurred, showed the highest concentrations, with PM10 daily average of 66.6±60.2 ?g m-3 and 91.6±97.4 ?g m-3, respectively. During these months PM1 and PM2.5 accounted for less than 11% and 47% of PM10 respectively, and the contribution of fine fractions (PM1 and PM2.5) to PM mass concentrations tended to increase for the other months. During Saharan dust events, the PM2.5 hourly average could reach mass concentrations higher than 200 ?g m-3 whereas PM10 overpass 600 ?g m-3. Acknowledgement: This work was funded by the Portuguese Science Foundation (FCT) through the project PTDD/AAC-CLI/100331/2008 and FCOMP-01-0124-FEDER-008646 (CV-Dust). J. Cardoso acknowledges the PhD grant SFRH-BD-6105-2009 from FCT.

Pio, C.; Nunes, T.; Cardoso, J.; Caseiro, A.; Cerqueira, M.; Custodio, D.; Freitas, M. C.; Almeida, S. M.

2012-04-01

251

Crystal Size Distributions in Igneous rocks: Where are we now?

Modern Crystal Size Distributions (CSD) studies started in 1988 and have expanded since then, albeit somewhat slowly. We have now measured CSDs in a variety of different compositions and for both plutonic and volcanic rocks. However, the subject still lags far behind chemical petrology and we need many more studies. CSD methodology has advanced considerably, both for 3D and 2D methods, but it is unfortunate that some 2D studies still do not use appropriate stereological conversions or publish their raw data. The nature of the lower size limit is very important, real or measurement artefact, but is not commonly stated. All this is especially important for comparing data with earlier studies. Individual CSDs of minerals are not always very informative. A much better approach is to look at suites of related CSDs. For instance, different minerals within a single sample, ensembles of related whole rock samples, comparison of late and early textures as preserved in oikocrysts, dykes or volcanic rocks. As more data become available it will be possible to compare usefully unrelated suites of rocks. Straight or nearly straight CSDs in volcanic rocks can be produced by steady-state crystallisation. If the growth rate is known then the residence time can be determined. In some rocks there is a good agreement with other chronometric techniques, but others show no such concordance. In the latter case another model may be more appropriate, such as textural coarsening. This model has been applied in some cases in inappropriate situations, which has cast doubt on the whole subject of CSDs. For plutonic rocks exponentially increasing undercooling can also produce straight CSDs. However, many CSDs are slightly curved and other models are possible, especially if no small crystals are present. Within ensembles of straight CSDs the slope and intercept are commonly correlated. This is mostly accounted for by closure and hence this correlation is not significant, although the variation in either slope of intercept is significant and can be related to other parameters. Concave down CSDs, with no small crystals, are commonly encountered in porphyritic, oikocrystic and plutonic rocks. This texture may be produced by textural coarsening (Ostwald ripening, annealing): this occurs when the magma is maintained close to the mineral liquidus. In this situation the nucleation rate is zero, but growth rates are significant. The classic LSW model is not the only solution possible: more modern solutions, such as Communicating Neighbours may be more appropriate. Variable degrees of textural coarsening will produce CSDs that appear to rotate about a single point. This again reflects closure. Concave up CSDs with no lower size limit are very common. They do not generally have a lognormal or fractal size distribution. They can be produced by mixing of two or more magmas, or crystallisation under several different conditions of undercooling. They can also result from alternations of nucleation and growth followed by textural coarsening. Crystal accumulation and fraction should modify existing CSDs in a predictable manner. An exact solution to this problem has not yet been developed, but simplistic models suggest that CSDs should rotate upwards about the size origin for accumulation and downwards for fractionation. However, clear evidence for such effects has not yet been observed, even in well-layered rocks. There are many igneous systems still to be explored using CSDs. An exiting new domain may be the application of CSDs in experimental petrology.

Higgins, M.

2003-12-01

252

Number size distributions and seasonality of submicron particles in Europe 2008–2009

Directory of Open Access Journals (Sweden)

Full Text Available Two years of harmonized aerosol number size distribution data from 24 European field monitoring sites have been analysed. The results give a comprehensive overview of the European near surface aerosol particle number concentrations and number size distributions between 30 and 500 nm of dry particle diameter. Spatial and temporal distribution of aerosols in the particle sizes most important for climate applications are presented. We also analyse the annual, weekly and diurnal cycles of the aerosol number concentrations, provide log-normal fitting parameters for median number size distributions, and give guidance notes for data users. Emphasis is placed on the usability of results within the aerosol modelling community.

We also show that the aerosol number concentrations of Aitken and accumulation mode particles (with 100 nm dry diameter as a cut-off between modes are related, although there is significant variation in the ratios of the modal number concentrations. Different aerosol and station types are distinguished from this data and this methodology has potential for further categorization of stations aerosol number size distribution types.

The European submicron aerosol was divided into characteristic types: Central European aerosol, characterized by single mode median size distributions, unimodal number concentration histograms and low variability in CCN-sized aerosol number concentrations; Nordic aerosol with low number concentrations, although showing pronounced seasonal variation of especially Aitken mode particles; Mountain sites (altitude over 1000 m a.s.l. with a strong seasonal cycle in aerosol number concentrations, high variability, and very low median number concentrations. Southern and Western European regions had fewer stations, which decreases the regional representativeness of these results. Aerosol number concentrations over the Britain and Ireland had very high variance and there are indications of mixed air masses from several source regions; the Mediterranean aerosol exhibit high seasonality, and a strong accumulation mode in the summer. The highest concentrations were observed at the JRC station in Northern Italy with high accumulation mode number concentrations in the winter. The aerosol number concentrations at the Arctic station Zeppelin in Ny-Ålesund in Svalbard have also a strong seasonal cycle, with higher concentrations of accumulation mode particles in winter, and dominating summer Aitken mode indicating more recently formed particles. Observed particles did not show any statistically significant regional work-week or weekday related variation in number concentrations studied.

Analysis products are made for open-access to the research community, available in a freely accessible internet site. The results give to the modelling community a reliable, easy-to-use and freely available comparison dataset of aerosol size distributions.

A. Asmi

2011-03-01

253

Number size distributions and seasonality of submicron particles in Europe 2008–2009

Directory of Open Access Journals (Sweden)

Full Text Available Two years of harmonized aerosol number size distribution data from 24 European field monitoring sites have been analysed. The results give a comprehensive overview of the European near surface aerosol particle number concentrations and number size distributions between 30 and 500 nm of dry particle diameter. Spatial and temporal distribution of aerosols in the particle sizes most important for climate applications are presented. We also analyse the annual, weekly and diurnal cycles of the aerosol number concentrations, provide log-normal fitting parameters for median number size distributions, and give guidance notes for data users. Emphasis is placed on the usability of results within the aerosol modelling community.

We also show that the aerosol number concentrations of Aitken and accumulation mode particles (with 100 nm dry diameter as a cut-off between modes are related, although there is significant variation in the ratios of the modal number concentrations. Different aerosol and station types are distinguished from this data and this methodology has potential for further categorization of stations aerosol number size distribution types.

The European submicron aerosol was divided into characteristic types: Central European aerosol, characterized by single mode median size distributions, unimodal number concentration histograms and low variability in CCN-sized aerosol number concentrations; Nordic aerosol with low number concentrations, although showing pronounced seasonal variation of especially Aitken mode particles; Mountain sites (altitude over 1000 m a.s.l. with a strong seasonal cycle in aerosol number concentrations, high variability, and very low median number concentrations. Southern and Western European regions had fewer stations, which decreases the regional coverage of these results. Aerosol number concentrations over the Britain and Ireland had very high variance and there are indications of mixed air masses from several source regions; the Mediterranean aerosol exhibit high seasonality, and a strong accumulation mode in the summer. The greatest concentrations were observed at the Ispra station in Northern Italy with high accumulation mode number concentrations in the winter. The aerosol number concentrations at the Arctic station Zeppelin in Ny-AA lesund in Svalbard have also a strong seasonal cycle, with greater concentrations of accumulation mode particles in winter, and dominating summer Aitken mode indicating more recently formed particles. Observed particles did not show any statistically significant regional work-week or weekday related variation in number concentrations studied.

Analysis products are made for open-access to the research community, available in a freely accessible internet site. The results give to the modelling community a reliable, easy-to-use and freely available comparison dataset of aerosol size distributions.

A. Asmi

2011-06-01

254

Number size distributions and seasonality of submicron particles in Europe 2008-2009

Two years of harmonized aerosol number size distribution data from 24 European field monitoring sites have been analysed. The results give a comprehensive overview of the European near surface aerosol particle number concentrations and number size distributions between 30 and 500 nm of dry particle diameter. Spatial and temporal distribution of aerosols in the particle sizes most important for climate applications are presented. We also analyse the annual, weekly and diurnal cycles of the aerosol number concentrations, provide log-normal fitting parameters for median number size distributions, and give guidance notes for data users. Emphasis is placed on the usability of results within the aerosol modelling community. We also show that the aerosol number concentrations of Aitken and accumulation mode particles (with 100 nm dry diameter as a cut-off between modes) are related, although there is significant variation in the ratios of the modal number concentrations. Different aerosol and station types are distinguished from this data and this methodology has potential for further categorization of stations aerosol number size distribution types. The European submicron aerosol was divided into characteristic types: Central European aerosol, characterized by single mode median size distributions, unimodal number concentration histograms and low variability in CCN-sized aerosol number concentrations; Nordic aerosol with low number concentrations, although showing pronounced seasonal variation of especially Aitken mode particles; Mountain sites (altitude over 1000 m a.s.l.) with a strong seasonal cycle in aerosol number concentrations, high variability, and very low median number concentrations. Southern and Western European regions had fewer stations, which decreases the regional representativeness of these results. Aerosol number concentrations over the Britain and Ireland had very high variance and there are indications of mixed air masses from several source regions; the Mediterranean aerosol exhibit high seasonality, and a strong accumulation mode in the summer. The highest concentrations were observed at the JRC station in Northern Italy with high accumulation mode number concentrations in the winter. The aerosol number concentrations at the Arctic station Zeppelin in Ny-Ålesund in Svalbard have also a strong seasonal cycle, with higher concentrations of accumulation mode particles in winter, and dominating summer Aitken mode indicating more recently formed particles. Observed particles did not show any statistically significant regional work-week or weekday related variation in number concentrations studied. Analysis products are made for open-access to the research community, available in a freely accessible internet site. The results give to the modelling community a reliable, easy-to-use and freely available comparison dataset of aerosol size distributions.

Asmi, A.; Wiedensohler, A.; Laj, P.; Fjaeraa, A.-M.; Sellegri, K.; Birmili, W.; Weingartner, E.; Baltensperger, U.; Zdimal, V.; Zikova, N.; Putaud, J.-P.; Marinoni, A.; Tunved, P.; Hansson, H.-C.; Fiebig, M.; Kivekäs, N.; Lihavainen, H.; Asmi, E.; Ulevicius, V.; Aalto, P. P.; Swietlicki, E.; Kristensson, A.; Mihalopoulos, N.; Kalivitis, N.; Kalapov, I.; Kiss, G.; de Leeuw, G.; Henzing, B.; Harrison, R. M.; Beddows, D.; O'Dowd, C.; Jennings, S. G.; Flentje, H.; Weinhold, K.; Meinhardt, F.; Ries, L.; Kulmala, M.

2011-03-01

255

Evolution of particle size distribution in air in the rainfall process via the moment method

Digital Repository Infrastructure Vision for European Research (DRIVER)

Population balance equation is converted to three moment equations to describe the dynamical behavior of particle size distribution in air in the rainfall. The scavenging coefficient is expressed as a polynomial function of the particle diameter, the raindrop diameter and the raindrop velocity. The evolutions of particle size distribution are simulated numerically and the effects of the raindrop size distribution on particle size distribution are studied. The results show that the raind...

Gan Fu-Jun; Lin Jian-Zhong

2012-01-01

256

International Nuclear Information System (INIS)

By the Monte Carlo method, the effect of dispersion of disc size distribution on the velocity distributions and correlations of a polydisperse granular gas with fractal size distribution is investigated in the same inelasticity. The dispersion can be described by a fractal dimension D, and the smooth hard discs are engaged in a two-dimensional horizontal rectangular box, colliding inelastically with each other and driven by a homogeneous heat bath. In the steady state, the tails of the velocity distribution functions rise more significantly above a Gaussian as D increases, but the non-Gaussian velocity distribution functions do not demonstrate any apparent universal form for any value of D. The spatial velocity correlations are apparently stronger with the increase of D. The perpendicular correlations are about half the parallel correlations, and the two correlations are a power-law decay function of dimensionless distance and are of a long range. Moreover, the parallel velocity correlations of postcollisional state at contact are more than twice as large as the precollisional correlations, and both of them show almost linear behaviour of the fractal dimension D. (general)

2008-05-01

257

Molecular size and molecular size distribution affecting traditional balsamic vinegar aging.

A first attempt at a semiquantitative study of molecular weight (MW) and molecular weight distribution (MWD) in cooked grape must and traditional balsamic vinegar (TBV) with increasing well-defined age was performed by high-performance liquid size exclusion chromatography (SEC) using dual detection, that is, differential refractive index (DRI) and absorbance (UV-vis) based detectors. With this aim, MW and MWD, including number- and weight-average MW and polydispersity, were determined with respect to a secondary standard and then analyzed. All investigated vinegar samples were recognized as compositionally and structurally heterogeneous blends of copolymers (melanoidins) spreading over a wide range of molecular sizes: the relative MW ranged from 2 to >2000 kDa. The extent of the polymerization reactions was in agreement with the TBV browning kinetics. MWD parameters varied asymptotically toward either upper or lower limits during aging, reflecting a nonequilibrium status of the balance between polymerization and depolymerization reactions in TBV. MWD parameters were proposed as potential aging markers of TBV. PMID:18656930

Falcone, Pasquale Massimiliano; Giudici, Paolo

2008-08-27

258

Electricité, de la production à la distribution

La production, le transport et la distribution de l'énergie électrique étant devenus très abstraits et réservés aux initiés, cet article est destiné à donner une approche simpliste et une vision générale des réseaux, compréhensible de tous. Depuis la centrale de production d'électricité, au travers des lignes de transfert haute-tension, l'abaissement par transformateur et la distribution, une explication simple et schématisée permettra de comprendre de manière générale le fonctionnement de ces installations trop souvent considérées comme occultes.

Pierlot, J

2002-01-01

259

Particle size distribution of molybdenum aerosols during 99Mo processing

International Nuclear Information System (INIS)

Dose estimation from internal exposure of airborne particulate is done from the measurement of the particle size in terms of 'Activity Median Aerodynamic Diameter' (AMAD). Particle size spectrum during the molybdenum-99 process was continuously taken by Anderson 1 ACFM non-viable ambient particle sizing sampler from the laboratory. The respective ALIs were obtained for different particle size. (author)

2008-11-19

260

Invariant size–frequency distributions along a latitudinal gradient in marine bivalves

Digital Repository Infrastructure Vision for European Research (DRIVER)

In the most extensive analysis of body size in marine invertebrates to date, we show that the size–frequency distributions of northeastern Pacific bivalves at the provincial level are surprisingly invariant in modal and median size as well as size range, despite a 4-fold change in species richness from the tropics to the Arctic. The modal sizes and shapes of these size–frequency distributions are consistent with the predictions of an energetic model previously appl...

Roy, Kaustuv; Jablonski, David; Martien, Karen K.

2000-01-01

261

Financial openness, volatility, and the size of productive government

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper analyzes the impact of financial openness on the size of the government in a stochastically growing small open economy when public spending is productive and volatility-reducing using a portfolio approach. The main result of the model is that economies that are more open are associated with a smaller productive public sector. The lower risk associated with more open economies due to risk diversification implies that the government is less inclined to increase the scale of its activ...

2011-01-01

262

Niger delta oil production, reserves, field sizes assessed

Energy Technology Data Exchange (ETDEWEB)

The article presents tables and figures showing the reserve estimates and production histories of the 252 fields in the Niger delta, then makes forecasts of the likelihood of discoveries above a given size. The paper discusses oil reserves, development programs, drilling and 3D seismic surveying, secondary and tertiary EOR, reserve incentives, production facilities, capital spending required, Nigerian export blends, and the trend in these blends.

Thomas, D. [Thomas and Associates, Hastings (United Kingdom)

1995-11-13

263

Directory of Open Access Journals (Sweden)

Full Text Available Industrial waste from sanitary company is chosen in this study as a precursor to fabricate ceramic membrane. It has been reported that enormous rejects being generated every year by this company. A preliminary characterization of this industrial waste shows the presence of quartz mineral, which is one of the main and suitable elements for the formation of ceramic products. Extrusion method was applied in fabricating tubular type ceramic membrane. In this present study, the effect of three different particle size distribution of the powder waste on the porosity is presented. The characterization of the porosity was performed in order to gain the insights in preparing ceramic membrane with good permeability. Results show that almost 40% porosity is able to be obtained using higher particle size distribution. However, further improvements in working conditions should be optimized in order to have a ceramic membrane with good physical properties.

I. Norliza

2009-01-01

264

Kellogg Company Optimizes Production, Inventory, and Distribution.

For over a decade, the Kellogg Company has used its planning system (KPS), a large-scale, multiperiod linear program, to guide production and distribution decisions for its cereal and convenience foods business. An operational version of KPS, at a weekly ...

B. Vigus G. Brown J. Keegan K. Wood

2001-01-01

265

Photooxidation of isoprene leads to the formation of secondary organic aerosol (SOA). In this study, the chemical composition of SOA formed from OH-initiated photooxidation of isoprene has been investigated with gas chromatography/mass spectrometry (GC/MS) and a home-made aerosol time-of-flight mass spectrometer. Sampling particles generated in a home-made smog chamber. The size distribution of SOA particles was detected by a TSI 3321 aerodynamic particle size spectrometer in real time. Results showed that SOA created by isoprene photooxidation was predominantly in the form of fine particles, which have diameters less than 2.5 microm. The obtained mass spectra of individual particles show that products of the OH-initiated oxidation of isoprene contain methyl vinyl ketone, methacrolein, formaldehyde, and some other hydroxycarbonyls. The possible reaction mechanisms leading to these products were also discussed. PMID:20108685

Liu, Xianyun; Zhang, Weijun; Wang, Zhenya; Zhao, Weixiong; Tao, Ling; Yang, Xibin

2009-01-01

266

Test Charge Response of a Dusty Plasma with Grain Size Distribution and Charging Dynamics

Digital Repository Infrastructure Vision for European Research (DRIVER)

This doctoral thesis reports analytical and numerical results for the electrostatic response of a dusty plasma to a moving test charge. Two important physical aspects of dusty plasmas, namely grain size distribution and grain charging dynamics were taken into account. In the first case, a dusty plasma in thermal equilibrium and with a distribution of grain sizes is considered. A size distribution is assumed which decreases exponentially with the grain mass for large sizes and gives a simple s...

2006-01-01

267

Piecewise log-normal approximation of size distributions for aerosol modelling

Digital Repository Infrastructure Vision for European Research (DRIVER)

An efficient and accurate method for the representation of particle size distributions in atmospheric models is proposed. The method can be applied, but is not necessarily restricted, to aerosol mass and number size distributions. A piecewise log-normal approximation of the number size distribution within sections of the particle size spectrum is used. Two of the free parameters of the log-normal approximation are obtained from the integrated number and mass concentration in each section. A t...

Von Salzen, K.

2005-01-01

268

Piecewise log-normal approximation of size distributions for aerosol modelling

Digital Repository Infrastructure Vision for European Research (DRIVER)

An efficient and accurate method for the representation of particle size distributions in atmospheric models is proposed. The method can be applied, but is not necessarily restricted, to aerosol mass and number size distributions. A piecewise log-normal approximation of the number size distribution within sections of the particle size spectrum is used. Two of the free parameters of the log-normal approximation are obtained from the integrated number and mass concentration in each section. The...

Von Salzen, K.

2006-01-01

269

Production and Distribution of NASA MODIS Remote Sensing Products

The two Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on-board NASA's Earth Observing System (EOS) Terra and Aqua satellites make key measurements for understanding the Earth's terrestrial ecosystems. Global time-series of terrestrial geophysical parameters have been produced from MODIS/Terra for over 7 years and for MODIS/Aqua for more than 4 1/2 years. These well calibrated instruments, a team of scientists and a large data production, archive and distribution systems have allowed for the development of a new suite of high quality product variables at spatial resolutions as fine as 250m in support of global change research and natural resource applications. This talk describes the MODIS Science team's products, with a focus on the terrestrial (land) products, the data processing approach and the process for monitoring and improving the product quality. The original MODIS science team was formed in 1989. The team's primary role is the development and implementation of the geophysical algorithms. In addition, the team provided feedback on the design and pre-launch testing of the instrument and helped guide the development of the data processing system. The key challenges the science team dealt with before launch were the development of algorithms for a new instrument and provide guidance of the large and complex multi-discipline processing system. Land, Ocean and Atmosphere discipline teams drove the processing system requirements, particularly in the area of the processing loads and volumes needed to daily produce geophysical maps of the Earth at resolutions as fine as 250 m. The processing system had to handle a large number of data products, large data volumes and processing loads, and complex processing requirements. Prior to MODIS, daily global maps from heritage instruments, such as Advanced Very High Resolution Radiometer (AVHRR), were not produced at resolutions finer than 5 km. The processing solution evolved into a combination of processing the lower level (Level 1) products and the higher level discipline specific Land and Atmosphere products in the MODIS Science Investigator Lead Processing System (SIPS), the MODIS Adaptive Processing System (MODAPS), and archive and distribution of the Land products to the user community by two of NASA s EOS Distributed Active Archive Centers (DAACs). Recently, a part of MODAPS, the Level 1 and Atmosphere Archive and Distribution System (LAADS), took over the role of archiving and distributing the Level 1 and Atmosphere products to the user community.

Wolfe, Robert

2007-01-01

270

Digital Repository Infrastructure Vision for European Research (DRIVER)

This study describes methods developed for reliable quantification of size- and element-specific release of engineered nanoparticles (ENP) from consumer spray products. A modified glove box setup was designed to allow controlled spray experiments in a particle-minimized environment. Time dependence of the particle size distribution in a size range of 10-500 nm and ENP release rates were studied using a scanning mobility particle sizer (SMPS). In parallel, the aerosol was transferred to a size...

Hagendorfer, Harald; Lorenz, Christiane; Kaegi, Ralf; Sinnet, Brian; Gehrig, Robert; Goetz, Natalie V.; Scheringer, Martin; Ludwig, Christian; Ulrich, Andrea

2010-01-01

271

The anomalies of the properties of nanomaterials related to the distribution of the grain sizes

We have performed the calculations of the size effect in the temperature dependence of BaTiO3 nanograin ceramics specific heat and dielectric permittivity. We took into account the distribution of the grain sizes, that exists in any real nanomaterial. This distribution lead to the distribution of the temperatures of the size driven transition from ferroelectric to paraelectric phase because of relation between the temperature and the sizes. We calculated the transition temperature distribution function on the basis of the sizes distribution function. This function allowed to calculate the temperature dependence of any physical quantity in a nanomaterial. As an examples we calculated specific heat and dielectric permittivity in nanograin ferroelectric ceramics. The results demonstrate the strong influence of the size distribution on the observed properties and especially on extracted from experiment values of critical size and temperature. We carried out the comparison of the theory with the measured specific ...

Glinchuk, M D

2004-01-01

272

Evolution of particle size distribution in air in the rainfall process via the moment method

Directory of Open Access Journals (Sweden)

Full Text Available Population balance equation is converted to three moment equations to describe the dynamical behavior of particle size distribution in air in the rainfall. The scavenging coefficient is expressed as a polynomial function of the particle diameter, the raindrop diameter and the raindrop velocity. The evolutions of particle size distribution are simulated numerically and the effects of the raindrop size distribution on particle size distribution are studied. The results show that the raindrops with smaller geometric mean diameter and geometric standard deviation of size remove particles much more efficiently. The particles which fall in the “greenfield gap” are the most difficult to be scavenged from the air.

Gan Fu-Jun

2012-01-01

273

A Program for Partitioning Shifted Truncated Lognormal Distributions into Size-Class Bins

In recent years, oil and gas accumulation-size frequency distributions have become a standard way to characterize undiscovered conventional oil and gas resources that have been postulated by geologic assessments. The preparation of such distributions requires the assessment geologists to explicitly choose parameters for the probability distribution for the sizes of undiscovered accumulations. The purpose of this report is to present a computational scheme for obtaining a binned size frequency distribution of undiscovered accumulations when the undiscovered accumulation size distribution is shifted truncated lognormal.

Attanasi, Emil D.; Charpentier, Ronald R.

2007-01-01

274

Adaptive Metropolis Sampling with Product Distributions

The Metropolis-Hastings (MH) algorithm is a way to sample a provided target distribution pi(z). It works by repeatedly sampling a separate proposal distribution T(x,x') to generate a random walk {x(t)}. We consider a modification of the MH algorithm in which T is dynamically updated during the walk. The update at time t uses the {x(t' less than t)} to estimate the product distribution that has the least Kullback-Leibler distance to pi. That estimate is the information-theoretically optimal mean-field approximation to pi. We demonstrate through computer experiments that our algorithm produces samples that are superior to those of the conventional MH algorithm.

Wolpert, David H.; Lee, Chiu Fan

2005-01-01

275

Drop Size Distribution - Based Separation of Stratiform and Convective Rain

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, depending on whether or not a clearly-defined melting layer is present at an expected height, and if present, maximum reflectivity within the melting layer as well as the corresponding height are determined. We will present results of quantitative comparisons between the XPR observations-based classifications and the simultaneous 2DVD data-based classifications. Time series comparisons will be presented for thirteen events in Huntsville.

Thurai, Merhala; Gatlin, Patrick; Williams, Christopher

2014-01-01

276

Porous TiO2 with a controllable bimodal pore size distribution from natural ilmenite

Digital Repository Infrastructure Vision for European Research (DRIVER)

Ilmenite (FeTiO3) is an inexpensive abundant natural mineral and it would be a perfect precursor for the production of porous TiO2 if a suitable synthesis method was developed. A new method combining a series of processing steps of ball milling, high-temperature annealing, selective chemical leaching and final calcining in air is proposed in this paper. The resulting TiO2 is a porous material with a bimodal pore structure. The pore size distribution has two clear maxima corresponding to small...

Zhang, Hongzhou

2011-01-01

277

The corrosion induced change of pore size distribution and surface area of a fuel element graphite

International Nuclear Information System (INIS)

The transport behaviour of fission products in HTGR-fuel element graphite may be altered by changes of the pore structure of the graphite due to corrosion. The corrosion rate was measured at temperatures between 850 and 9000C in a CO2 atmosphere by a thermogravimetric method. Surface area and pore size distribution were determined before and after corrosion by measuring nitrogen adsorption isotherms at 77 K. The corrosion rate remained constant regardless of the pronounced increase in the specific surface area. (Auth.)

1979-01-01

278

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english Particle size distribution (PSD) of polystyrene particles produced by suspension polymerization is of fundamental importance in determining suspension stability and product quality attributes. Within a population balance framework, a model is proposed for suspension polymerization reactors to descri [...] be the evolution of the PSD. The model includes description of breakage and coalescence rates in terms of reaction kinetics and rheology of the dispersed phase. The model is validated with experimental data of styrene suspension polymerization.

Machado, R.A.F.; Pinto, J.C.; Araújo, P.H.H.; Bolzan, A..

279

Modelling of product size from a 90mm ID liquid fed rotary calciner

International Nuclear Information System (INIS)

Particle size reduction in a 90 mm ID indirect fired rotary kiln has been studied using simulated liquid radwaste feeds. The Rosin-Rammler particle size distribution model gave a good fit to the kiln product. A simple model is derived for the energy input for size reduction from a rotary kiln with a rabble bar. It is also demonstrated that the relationship between calculated energy input and particle size can be modelled in terms of Kick's law. The combination of the kiln model and Kick's law, to give an overall model of particle size reduction was tested experimentally for a range of feed types and process conditions. An excellent agreement was found with variation in liquid flowrate. The results obtained with various Magnox feeds showed a concentration dependence which was modelled empirically. (Auth.)

1986-01-01

280

Geological Image Analysis Software (GIAS) combines basic tools for calculating object area, abundance, radius, perimeter, eccentricity, orientation, and centroid location, with the first automated method for characterizing the aerial distribution of objects using sample-size-dependent nearest neighbor (NN) statistics. The NN analyses include tests for (1) Poisson, (2) Normalized Poisson, (3) Scavenged k=1, and (4) Scavenged k=2 NN distributions. GIAS is implemented in MATLAB with a Graphical User Interface (GUI) that is available as pre-parsed pseudocode for use with MATLAB, or as a stand-alone application that runs on Windows and Unix systems. GIAS can process raster data (e.g., satellite imagery, photomicrographs, etc.) and tables of object coordinates to characterize the size, geometry, orientation, and spatial organization of a wide range of geological features. This information expedites quantitative measurements of 2D object properties, provides criteria for validating the use of stereology to transform 2D object sections into 3D models, and establishes a standardized NN methodology that can be used to compare the results of different geospatial studies and identify objects using non-morphological parameters.

Beggan, Ciarán; Hamilton, Christopher W.

2010-04-01

281

The distribution of sun glints sizes on the sea surface

The problem is studied both theoretically and experimentally. Statistical distributions of the total curvature and the reciprocal to the total curvature at the specular points (SP) of a random Gaussian uniform sea surface are discussed. The theoretical distribution and its asymptotes are completely investigated. The validity of the theoretical distribution is verified by numerical simulations and natural experiments. In the experimental study of this distribution, Sun glint images taken with a high time and spatial resolution digital camera are used. Those images are developed by using a specially-designed Fortran program which calculates the statistical characteristics of the glints. The experimentally derived distribution of the glint areas is compared with the theoretical distribution. The main causes (origins) of small divergence between the theoretical and experimental results are discussed.

Gardashov, Rauf

2011-06-01

282

Energy Technology Data Exchange (ETDEWEB)

Dust management strategies in industrial environment, especially of airborne dust, require quantification and measurement of size and size distribution of the particles. Advanced specialized instruments that measure airborne particle size and size distribution apply indirect methods that involve light scattering, acoustic spectroscopy, and laser diffraction. In this research, we propose a simple and direct method of airborne dust particle dimensional measurement and size distribution analysis using machine vision. The method involves development of a user-coded ImageJ plugin that measures particle length and width and analyzes size distribution of particles based on particle length from high-resolution scan images. Test materials were airborne dust from soft pine wood sawdust pellets and ground pine tree bark pellets. Subsamples prepared by dividing the actual dust using 230 mesh (63 m) sieve were analyzed as well. A flatbed document scanner acquired the digital images of the dust particles. Proper sampling, layout of dust particles in singulated arrangement, good contrast smooth background, high resolution images, and accurate algorithm are essential for reliable analysis. A halo effect around grey-scale images ensured correct threshold limits. The measurement algorithm used Feret s diameter for particle length and pixel-march technique for particle width. Particle size distribution was analyzed in a sieveless manner after grouping particles according to their distinct lengths, and several significant dimensions and parameters of particle size distribution were evaluated. Results of the measurement and analysis were presented in textual and graphical formats. The developed plugin was evaluated to have a dimension measurement accuracy in excess of 98.9% and a computer speed of analysis of <8 s/image. Arithmetic mean length of actual wood and bark pellets airborne dust particles were 0.1138 0.0123 and 0.1181 0.0149 mm, respectively. The airborne dust particles of wood and bark pellets can be described as non uniform, finer particles dominated, very finely skewed with positive skewness, leptokurtic, and very well sorted category. Experimental mechanical sieving and machine vision methods produced comparable particle size distribution. The limitations and merits of using the machine vision technique for the measurement of size and size distribution of fine particles such as airborne dust were discussed.

Igathinathane, C [University of British Columbia, Vancouver; Pordesimo, L.O. [ADM Alliance Nutrition

2009-08-01

283

Magsoft to distribute research centre product

Energy Technology Data Exchange (ETDEWEB)

Distribution in the United States by Magsoft Corporation of Winnipeg-based Manitoba HVDC Research Centre's power system computer-aided design (PSCAD) product is announced. The system, a product of 25 years of power system simulation research, development and innovation, is a fast, accurate, and easy-to-use simulator for all types of power systems. The product enables users to construct a circuit, run a simulation, interact dynamically with the simulation to change the state of components or subcircuits, view the transient results, and manage the data in a completely integrated graphical environment. The PSCAD is reputed to have a wide variety of industrial applications, and is expected to be widely used by engineers and technologists from energy utilities, electrical equipment manufacturers, and research and academic institutions.

Anon

2002-10-01

284

MORTALITY ESTIMATES FROM SIZE DISTRIBUTIONS: A CRITIQUE OF SMITH'S MODEL

Smith (1972) described a method of computing mortality rates from growth and size-frequency data for a population which meets several assumptions. (Copyright (c) 1977 by The American Society of Limnology and Oceanography, Inc.)...

285

Study of particle size distribution during 177Lu processing

International Nuclear Information System (INIS)

Lutetium Chloride (177LuCl3) produced in Radiopharmaceuticals Division of BARC is regularly being used for the preparation of 177Lu-DOTA-TATE and used for the treatment of cancer patients suffering from neuro endocrine tumors at various hospitals in India. An effort has been made to establish the particle size of 177Lu aerosols and hence estimation of ALI (Annual Limit on Intake) was carried out for various particle sizes. Particle size spectrum during processing was continuously taken by Anderson 1 ACFM Non-viable Ambient Particle Sizing sampler from the processing plant i.e. a shielded enclosure. The AMAD values of lutetium aerosol and corresponding Dose Conversion Factor (Sv/Bq) has been estimated. (author)

2011-02-22

286

Size distribution measurements of natural alpha active aerosols

International Nuclear Information System (INIS)

Internal contamination by alpha emitting aerosols is particularly important both for workers and the general public. The main route of incorporation is through the respiratory tract: the first step of this process is deposition, which in total or in the detail of regions is always strongly size dependent. Natural alpha contamination stretches in size over many orders of magnitude. Efforts have been made to characterize the radioactive particles in the whole size range. This work describes a combination of diffusive and aerodynamic technique in the range from a few nanometers to several micrometers. The potential alpha energy per each size interval can be measured, a regional deposition probability can be assigned to it and constitutes the input for a more realistic dosimetry of the respiratory tract. (author)

1983-01-01

287

Optimization of grain size distribution aimed at increasing bulk density of the coal charge

Energy Technology Data Exchange (ETDEWEB)

Development of a mathematical model is discussed which describes dependence of bulk density on grain size distribution of a coal charge for coking. The following stages of model development are evaluated: determining functions which describe grain size distribution of coal and range of changes of its characteristic parameters (3 functions are compared: the Gaudin-Gates function, the Rosin-Rammler function and the complementary Rosin-Rammler function), determining mathematical models which describe dependence of bulk density on content of selected grain fractions for various levels of moisture content in coal, calculating grain size distribution which guarantees the highest bulk density under operational conditions. Coal mixtures with grain size distribution described by the Rosin-Rammler function are analyzed. Bulk density dependence on grain size distribution is characterized by means of 2 parameters according to the Rosin-Rammler function. Recommendations for the optimum grain size distribution of coal mixtures for coking are made. 13 references.

Strugala, A.

1985-04-01

288

International Nuclear Information System (INIS)

Complex initial permeability spectra are modeled by taking into account the microstructure of polycrystalline ferrite. The modeling demonstrates an acceptable mathematical presentation of the spectra and confirms the important role of average grain size as well as grain size distribution

2004-05-01

289

Digital Repository Infrastructure Vision for European Research (DRIVER)

Principal component analysis provides a fast and robust method to reduce the data dimensionality of an aerosol size distribution data set. Here we describe a methodology for applying principal component analysis to aerosol size distribution measurements. We illustrate the method by applying it to data obtained during five field studies. Most variations in the sub-micrometer aerosol size distribution over periods of weeks can be described using 5 components. Using 6 to 8 components preserves v...

Chan, T. W.; Mozurkewich, M.

2007-01-01

290

Digital Repository Infrastructure Vision for European Research (DRIVER)

Principal component analysis provides a fast and robust method to reduce the data dimensionality of an aerosol size distribution data set. Here we describe a methodology for applying principal component analysis to aerosol size distribution measurements. We illustrate the method by applying it to data obtained during five field studies. Most variations in the sub-micrometer aerosol size distribution over periods of weeks can be described using 5 components. Using 6 to 8 components preserves v...

Chan, T. W.; Mozurkewich, M.

2006-01-01

291

Models of the water retention curve for soils with a fractal pore size distribution

Digital Repository Infrastructure Vision for European Research (DRIVER)

The relationship between water content and water potential for a soil is termed its water retention curve. This basic hydraulic property is closely related to the soil pore size distribution, for which it serves as a conventional method of measurement. In this paper a general model of the water retention curve is derived for soil whose pore size distribution is fractal in the sense of the Mandelbrot number-size distribution. This model, which contains two adjustable parameters (the fractal di...

Perrier, Edith; Rieu, Michel; Sposito, G.; Marsily, G.

1996-01-01

292

Measurement of aggregate size distribution by inversion of angular light scattering

Directory of Open Access Journals (Sweden)

Full Text Available The aim of this work is to propose a new method for determining the size distribution of submicronic particles by inversion of the measured angular scattering of light. This method relies on the determination of a function Rg*. by angular scattering. The variation of this function informs us about the polydispersity of the aggregates size. We show that, by supposing the nature of the size distributions (lognormal, it is possible to determine the governing parameters of these distributions.

K. F. Ren

2011-09-01

293

Particle size distributions from laboratory-scale biomass fires using fast response instruments

Digital Repository Infrastructure Vision for European Research (DRIVER)

Particle size distribution from biomass combustion is an important parameter as it affects air quality, climate modelling and health effects. To date particle size distributions reported from prior studies vary not only due to difference in fuels but also difference in experimental conditions. This study aims to report characteristics of particle size distribution in a well controlled repeatable lab scale biomass fires for southwestern US fuels. The combustion facility at the USDA Forest Serv...

Hosseini, S.; Qi, L.; Cocker, D.; Weise, D.; Miller, A.; Shrivastava, M.; Miller, W.; Mahalingam, S.; Princevac, M.; Jung, H.

2010-01-01

294

Evolution of 2D Potts Model Grain Microstructures from an Initial Hillert Size Distribution

Energy Technology Data Exchange (ETDEWEB)

Grain growth experiments and simulations exhibit self-similar grain size distributions quite different from that derived via a mean field approach by Hillert [ 1]. To test whether this discrepancy is due to insufficient anneal times, two different two-dimensional grain structures with realistic topologies and Hillert grain size distributions are generated and subjected to grain growth via the Monte Carlo Potts Model (MCPM). In both cases, the observed self-similar grain size distributions deviate from the initial Hillert form and conform instead to that observed in MCPM grain growth simulations that start from a random microstructure. This suggests that the Hillert grain size distribution is not an attractor.

Battaile, C.C.; Holm E.A.

1998-10-19

295

DEFF Research Database (Denmark)

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 FrÃ©chet distribution. We prove the results in the general framework of point processes and for jump sizes taking values in a separable Banach space

Mikosch, Thomas Valentin; Rackauskas, Alfredas

2010-01-01

296

Vesicle sizing: Number distributions by dynamic light scattering

Digital Repository Infrastructure Vision for European Research (DRIVER)

A procedure is described which optimizes nonnegative least squares and exponential sampling fitting methods for analysis of dynamic light scattering (DLS) data from aqueous suspensions of vesicle/liposome systems. This approach utilizes a Rayleigh-Gans-Debye form factor for a coated sphere and yields number distributions which can be compared directly to distributions obtained by freeze-fracture electron microscopy (EM). Excellent agreement between the DLS and EM results are obtained for vesi...

Hallett, F. R.; Watton, J.; Krygsman, P.

1991-01-01

297

Density gradient separation and size distribution of beagle lymphocytes

International Nuclear Information System (INIS)

Density gradient techniques for obtaining pure, single-cell suspensions of peripheral blood mononuclear cells were applied to beagle dogs that had inhaled plutonium. There was a tendency toward a loss of intermediate-size lymphocytes in dogs with 239Pu lung burdens, and a shift to larger cells when compared with control dogs

1976-01-01

298

Evolution of the sedimentation technique for particle size distribution analysis

International Nuclear Information System (INIS)

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

1998-01-01

299

The impact of fuel particle size distribution on neutron transport in stochastic media

Energy Technology Data Exchange (ETDEWEB)

This paper presents a study of the particle size distribution impact on neutron transport in three-dimensional stochastic media. 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. We construct 15 cases 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{sub eff}) and flux distribution along axial and radial directions are compared between different size distributions. At low packing fraction and low optical thickness, the size distribution has a significant impact on radiation transport in stochastic media, which can cause as high as {approx}270 pcm difference in k{sub eff} value and {approx}2.6% relative error difference in peak flux. As the packing fraction and optical thickness increase, the impact gradually dissipates. (authors)

Liang, C.; Pavlou, A. T.; Ji, W. [Department of Mechanical, Aerospace, and Nuclear Engineering, Rensselaer Polytechnic Institute, 110 8th Street, Troy, NY 12180 (United States)

2013-07-01

300

The impact of fuel particle size distribution on neutron transport in stochastic media

International Nuclear Information System (INIS)

This paper presents a study of the particle size distribution impact on neutron transport in three-dimensional stochastic media. 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. We construct 15 cases 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 (keff) and flux distribution along axial and radial directions are compared between different size distributions. At low packing fraction and low optical thickness, the size distribution has a significant impact on radiation transport in stochastic media, which can cause as high as ?270 pcm difference in keff value and ?2.6% relative error difference in peak flux. As the packing fraction and optical thickness increase, the impact gradually dissipates. (authors)

2013-05-05

301

Labor Productivity Distribution with Negative Temperature

Exhaustive financial data of firms in Japan enables us to shed light on how the labor productivity, defined here as value added produced by one worker in a year, is diverse across firms and workers. Statistical equilibrium theory reinforced with the concept of negative temperature turns out to be useful to explain the empirical facts on a major part of the distribution of workers over labor productivity states, where particle and single-particle energy are replaced by worker and labor productivity, respectively. The zero-temperature state in the negative temperature regime corresponds to the optimized state for the current mainstream economics, where all workers are allocated to a state of the highest productivity. Significant difference in temperature is observed between the manufacturing and nonmanufacturing sectors. The negative temperature in the nonmanufacturing sector is three times lower than that in the manufacturing sector, indicating that the former may suffer from a much wider demand gap. In contrast, the two sectors are almost in equilibrium with respect to exchange of workers.

Iyetomi, H.

302

Optimizing the grain size distribution for talc-magnesite ore flotation

Directory of Open Access Journals (Sweden)

Full Text Available Flotation is the only separation method with an universal utilization. Along with the separation of particulate valuable or hazardous components from primary and seconadry mineral raw materials, it is of usage in biotechnologies and water cleaning. The success of the flotation separation crucially depends on the particle size distribution or composition of the ore charge entering the process. The paper deals with the problem of flotation treatment of talc-magnesite ore. The main components of the ore, i.e. talc and magnesite are appreciably different in their grindability and floatability. For such a type of raw material, grinding of the charge plays a very important role in the process. The (unwanted influence of ultrafine particles on the course of the flotation process is well known. On the other hand, in order to liberate and subsequently to selectively separate both the components, a maximum particle size has to be respected.An influence of artificial samples of selected particle size fractions on the flotation efficiency has been studied experimentally by the quantitative evaluation of flotation products. The flotation experiments on the samples provided an information not obtainable from traditional flotation tests. An adverse effect of the size fraction 0 ? 0.04 mm was revealed, decreasing the flotation selectivity appreciably. These results are of theoretical and practical importance.

?kvarla Jiøí

2001-06-01

303

Maximal Queue Size with Standard Normal Distribution for Arrival Times

Directory of Open Access Journals (Sweden)

Full Text Available There is always a problem in estimation of the appropriate time, for the system to make it stable and if the study time of the queue system Outside the appropriate time period that will lead the system to instability and the occurrence of losses by the maximum this time .The queue system has contains the maximum length of a queue and in this study were obtained within the time appropriate some of the data input and system-specific, where the distribution of inter-arrival time follows the standard normal distribution.

Mohammed Mohammed El Genidy

2011-01-01

304

Particle size distribution study of 153Sm aerosols during its processing

International Nuclear Information System (INIS)

153Sm is one of the most important therapeutic nuclides (? : 806.822 ± 0.736 keV, T1/2 : 46.3 hours) used for targeted therapy applications especially in solid tumors and for the relief of pain in bone cancer. The isotope is being regularly produced at Radiopharmaceuticals Division of Bhabha Atomic Research Centre. Study to establish the particle size of 153Sm aerosols and hence estimation of ALI was carried out. Particle size spectrum during processing was continuously taken by Anderson ACFM Non-viable Ambient particle sizing sampler from the processing plant, i.e. a shielded enclosure. The AMAD values of 153Sm aerosol and corresponding Dose Conversion Factor (Sv/Bq) has been estimated. Based on the particle size arrived at from the experiment a more realistic estimate of the dose for occupational workers can be calculated. The human respiratory tract is an aerodynamic classifying system for airborne particles. The sampling device is used as a substitute for the respiratory tract as a dust collector. This instrument reproduces the dust collecting characteristic of the human respiratory systems with a reasonable degree of accuracy so that the lung penetration by air borne particles can be predicted from the sampling data. The stage-wise distribution of the collected material indicates the extent to which the sample would have penetrated the respiratory system. Hence, a study was carried out to determine particle size distribution of 153Sm aerosols during chemical processing by using eight stages Andersen Cascade sampler. The air activity release inside the production plant during the 153Sm processing was determined in three different operations. Particles size separation was achieved by Anderson eight-stage cascade impactor through the filter media loaded at each stage. The cumulative percent less than the stated size were plotted on log probability paper against Effective Cut off diameter (ECD). From this the AMADs of 153Sm aerosol on three different operations was found to be ? 3 ?m. Dose Conversion Factor (DCF) of 153Sm aerosols for these particle sizes are evaluated using LUDEP 2.0. (author)

2012-01-01

305

Density, Size and Distribution of Stomata in Different Monocotyledons

Digital Repository Infrastructure Vision for European Research (DRIVER)

The present study focuses on the stomatal characters of 54 species from 6 families of monocotyledons, the majority of which are grasses. The stomatal density, guard cell lengths on the adaxial and abaxial leaf epidermis and the stomatal type in each family are described and the relationship between stomatal density and guard cell size is reviewed. These plants are collected from one of the Irano-Turany protected area. However, studying of stomata characters, particularly herbaceous plants gro...

Fatemeh Zarinkamar

2006-01-01

306

Exact Sample Size Methods for Estimating Parameters of Discrete Distributions

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper, we develop an approach for the exact determination of the minimum sample size for estimating the parameter of an integer-valued random variable, which is parameterized by its expectation. Under some continuity and unimodal property assumptions, the exact computation is accomplished by reducing infinite many evaluations of coverage probability to finite many evaluations. Such a reduction is based on our discovery that the minimum of coverage probability with re...

Chen, Xinjia; Chen, Zhengjia

2012-01-01

307

Source size scaling of fragment production in projectile breakup

Fragment production has been studied as a function of the source mass and excitation energy in peripheral collisions of $^{35}$Cl+$^{197}$Au at 43 MeV/nucleon and $^{70}$Ge+$^{nat}$Ti at 35 MeV/nucleon. The results are compared to the Au+Au data at 600 MeV/nucleon obtained by the ALADIN collaboration. A mass scaling, by $A_{source} \\sim$ 35 to 190, strongly correlated to excitation energy per nucleon, is presented, suggesting a thermal fragment production mechanism. Comparisons to a standard sequential decay model and the lattice-gas model are made. Fragment emission from a hot, rotating source is unable to reproduce the experimental source size scaling.

Beaulieu, L; Fox, D; Das-Gupta, S; Pan, J; Ball, G C; Djerroud, B; Doré, D; Galindo-Uribarri, A; Guinet, D; Hagberg, E; Horn, D; Laforest, R; Larochelle, Y; Lautesse, P; Samri, M; Roy, R; Saint-Pierre, C

1996-01-01

308

Estimation of pore size distribution using concentric double pulsed-field gradient NMR.

Estimation of pore size distribution of well calibrated phantoms using NMR is demonstrated here for the first time. Porous materials are a central constituent in fields as diverse as biology, geology, and oil drilling. Noninvasive characterization of monodisperse porous samples using conventional pulsed-field gradient (PFG) NMR is a well-established method. However, estimation of pore size distribution of heterogeneous polydisperse systems, which comprise most of the materials found in nature, remains extremely challenging. Concentric double pulsed-field gradient (CDPFG) is a 2-D technique where both q (the amplitude of the diffusion gradient) and ? (the relative angle between the gradient pairs) are varied. A recent prediction indicates this method should produce a more accurate and robust estimation of pore size distribution than its conventional 1-D versions. Five well defined size distribution phantoms, consisting of 1-5 different pore sizes in the range of 5-25 ?m were used. The estimated pore size distributions were all in good agreement with the known theoretical size distributions, and were obtained without any a priori assumption on the size distribution model. These findings support that in addition to its theoretical benefits, the CDPFG method is experimentally reliable. Furthermore, by adding the angle parameter, sensitivity to small compartment sizes is increased without the use of strong gradients, thus making CDPFG safe for biological applications. PMID:23548563

Benjamini, Dan; Nevo, Uri

2013-05-01

309

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

Energy Technology Data Exchange (ETDEWEB)

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.

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

1997-12-31

310

International Nuclear Information System (INIS)

Size distribution of radioactive aerosols inside the object 'Ukryttya' and in his industrial site are seen. Methodical and technical means for measuring of concentrations and size distributions of radionuclide carriers ar. They were used at investigations during 1986-2004. General attention paid to aerosols with aerodynamics diameter up to 10 ?m. 109 refs., 18 tab., 29 figs

311

X-ray determination of the lognormal distribution of the particles in size in nanocrystal materials

International Nuclear Information System (INIS)

Analytical expressions are derived which put into correspondence parameters of the lognormal distribution of the particles in size and the components of spreading of the x-ray diffraction profile. Easy to use procedures of the x-ray analysis are developed for determination of the particle distribution in size. Comparative analysis of the data obtained match the data of electron microscopy

2000-11-01

312

A model for predicting size distributions delivered from pMDIs with suspended drug.

A new model has been developed for predicting size distributions delivered from pressurized metered dose inhalers (pMDIs) that contain suspended drug particles. This model enables the residual particle size distribution to be predicted for a broad range of formulations. It expands on previous models by allowing for polydisperse micronized input drug, multiple suspended drugs, dissolved drug, and dissolved or suspended excipient to be included in the formulation. The model indicates that for most pMDI configurations, the majority of droplets contain no drug or a single drug particle and the residual particle size distribution delivered from the pMDI is essentially equivalent to the size distribution of the micronized drug used in the formulation. However, for pMDIs with a high drug concentration or that use small micronized drug particles, there can be a substantial fraction of the droplets that contain multiple drug particles. The residual particle size distribution obtained from these pMDIs can be substantially larger than the size distribution of the micronized drug. Excellent agreement was observed between size distributions predicted using this model and those obtained from experimental cascade impactor measurements (r(2)=0.97), thus demonstrating the ability of the model to accurately predict the size distributions obtained from suspension pMDIs. PMID:22044537

Stein, Stephen W; Sheth, Poonam; Myrdal, Paul B

2012-01-17

313

Energy Technology Data Exchange (ETDEWEB)

Fly ash particles, which are predominantly spherical and glassy, are produced by melting of the mineral inclusions in the coal during combustion. Particle diameters can range from sub-micrometer (micron or {mu}m) to greater than 100 {mu}m. The size distribution of fly ash is needed to determine its role in the radiation transfer process in pulverized coal combustors. The Coulter Multisizer is an useful instrument for sizing powders with a broad size distribution. A single Multisizer orifice can size particles only within a specific size range limited at the lower end to a few percent of orifice diameter by sensitivity and at the upper end by increasing non-linearity of the signal-volume relation. A scheme for combining data obtained using orifices of different diameters is described. The manufacturers state that the smallest particle which can be sized accurately is nominally 2% of the diameter of the orifice. However, it was found that the data for particles less than 4% of the orifice diameter were not reliable. In order to use the smaller orifices, the larger particles have to be removed from the sample. A wet-sieving apparatus, designed for accurate separation of the particles by size, is described. A log-normal distribution function, truncated outside the measurement limits, fits the size distribution data well. Size parameters for fly ashes of six representative US coals are presented.

Ghosal, S.; Ebert, J.L.; Self, S.A.

1991-11-01

314

International Nuclear Information System (INIS)

Unification by orientation is a ubiquitous concept in the study of active galactic nuclei. A gold standard of the orientation paradigm is the hypothesis that radio galaxies and radio-loud quasars are intrinsically the same, but are observed over different ranges of viewing angles. Historically, strong support for this model was provided by the projected sizes of radio structure in luminous radio galaxies, which were found to be significantly larger than those of quasars, as predicted due to simple geometric projection. Recently, this test of the simplest prediction of orientation-based models has been revisited with larger samples that cover wider ranges of fundamental properties—and no clear difference in projected sizes of radio structure is found. Cast solely in terms of viewing angle effects, these results provide convincing evidence that unification of these objects solely through orientation fails. However, it is possible that conflicting results regarding the role orientation plays in our view of radio sources simply result from insufficient sampling of their intrinsic size distribution. We test this possibility using Monte Carlo simulations constrained by real sample sizes and properties. We develop models for the real intrinsic size distribution of radio sources, simulate observations by randomly sampling intrinsic sizes and viewing angles, and analyze how likely each sample is to support or dispute unification by orientation. We find that, while it is possible to reconcile conflicting results purely within a simple, orientation-based framework, it is very unlikely. We analyze the effects that sample size, relative numbers of radio galaxies and quasars, the critical angle that separates the two subclasses, and the shape of the intrinsic size distribution have on this type of test

2013-09-01

315

Understanding the characteristics of the size distribution of ambient black carbon (BC) in distinct environments is critical because the influence of BC aerosols on climate, visibility, and human health depends strongly on the distribution of BC aerosols over the particle size spectrum. In this study, a novel method for determining the mass size distribution of BC in atmospheric aerosols was developed. This size-segregation method relies on measuring BC in parallel using two aethalometers, one of which is used to measure the total BC (BCT) mass concentration as a reference level and the other is used to measure the BC (BCi) mass concentration for BC sizes below specific particle sizes that are selected using a size cut-off inlet. In this study, this method was applied to measure BC in atmospheric samples at an urban traffic site. The aethalometers were operated continually from December 15, 2012 to January 31, 2013, and from February 15, 2013 to March 31, 2013. The measurement results presented in this paper are for the diurnal variation patterns, average concentrations, mass fractions, and size distributions of BC aerosols. The results indicate that BCT mass concentration is approximately 2.8 ?g m?3 in the Taipei urban area. The levels of BC at this sampling site were affected markedly by traffic emission levels and local wind speed. At the sampling site, the average BC2.5/BCT, BC1.0/BCT, BC0.5/BCT, BC0.25/BCT, and BC0.1/BCT were 0.96 ± 0.04, 0.92 ± 0.07, 0.89 ± 0.04, 0.73 ± 0.10, and 0.18 ± 0.08, respectively. The results indicate that approximately 90% of the BC aerosols were smaller than 0.5 ?m, that most of the BC aerosols (55%) were in the size range of 0.1–0.25 ?m, and that approximately 18% of the BC aerosols were ultrafine. Moreover, the daily average mass size distribution of BC exhibited a single accumulation mode at 0.16 ?m at this sampling site. The mode of the BC mass size distribution at rush hour (9 AM) was only 0.14 ?m, which is smaller than the daily average. Moreover, the mode of the BC mass size distribution at an early morning hour (3 AM) was 0.18 ?m, and a minor coarse mode was also observed during this period. The results further revealed that the geometric diameter (Dpg) of the BC aerosols varied between 0.14 and 0.22 ?m and the geometric standard deviation (?g) of these BC aerosols ranged between 1.4 and 2.3 during the sampling period. Because BC exhibits extremely low chemical reactivity; the size distribution of BC in the atmosphere does not change substantially except through coagulation.

Cheng, Yu-Hsiang; Liao, Chung-Wen; Liu, Zhen-Shu; Tsai, Chuen-Jinn; Hsi, Hsing-Cheng

2014-06-01

316

Ultrasonic energy in liposome production: process modelling and size calculation.

The use of liposomes in several fields of biotechnology, as well as in pharmaceutical and food sciences is continuously increasing. Liposomes can be used as carriers for drugs and other active molecules. Among other characteristics, one of the main features relevant to their target applications is the liposome size. The size of liposomes, which is determined during the production process, decreases due to the addition of energy. The energy is used to break the lipid bilayer into smaller pieces, then these pieces close themselves in spherical structures. In this work, the mechanisms of rupture of the lipid bilayer and the formation of spheres were modelled, accounting for how the energy, supplied by ultrasonic radiation, is stored within the layers, as the elastic energy due to the curvature and as the tension energy due to the edge, and to account for the kinetics of the bending phenomenon. An algorithm to solve the model equations was designed and the relative calculation code was written. A dedicated preparation protocol, which involves active periods during which the energy is supplied and passive periods during which the energy supply is set to zero, was defined and applied. The model predictions compare well with the experimental results, by using the energy supply rate and the time constant as fitting parameters. Working with liposomes of different sizes as the starting point of the experiments, the key parameter is the ratio between the energy supply rate and the initial surface area. PMID:24647821

Barba, A A; Bochicchio, S; Lamberti, G; Dalmoro, A

2014-04-21

317

Indoor radon progeny particle size distribution measurements made with two different methods

International Nuclear Information System (INIS)

Indoor radon progeny particle size measurements using two distinctly different instruments, a diffusion battery and an electrical aerosol size analyser, were carried out in two single-family homes in New Jersey. The activity-weighted size distributions were determined by applying the radon progeny attachment theory to the measured number-weighted particle size spectra and the results are close to those measured by the diffusion battery method. These particle size distributions were found to be more often bimodal than unimodal. The minor modes of the bimodal distributions were located around the 1 nm region, close to the 218Po atom size, except one centred around 10 nm. For both the unimodal and the bimodal distributions, the modal diameter of the major mode ranged from 30 nm to 150 nm, respectively. The results previously reported showed modal diameters around 100 nm. (author)

1987-12-07

318

Size distribution of trace metals in Ponce, Puerto Rico air particulate matter

The atmospheric particulate size distribution of nine heavy metals was measured in Ponce, a moderately industrial city in the south of Puerto Rico. Samples were collected in the city center and outlying suburban and rural locations during 1986. The size measurements were done with a cascade impactor. The elemental content of the size fractionated aerosol samples was determined by inductively coupled plasma atomic emission spectroscopy. The particle size distributions observed for Cu, Cd, Pb, Mn and Fe were bimodal with a gradual progression from mainly coarse mode to mainly fine mode. Al, Ni and Zn were mostly associated with coarse particles and V size distribution was unimodal with maxima associated with fine particles. The particle size distribution did not vary significantly with the sites sampled in the urban area although some regional characteristics are observed. The data obtained strongly suggest motor vehicle traffic and fuel combustion as the principal pollution pources in Ponce aerosol.

Infante, Rafael; Acosta, Iris L.

319

Density, Size and Distribution of Stomata in Different Monocotyledons

Directory of Open Access Journals (Sweden)

Full Text Available The present study focuses on the stomatal characters of 54 species from 6 families of monocotyledons, the majority of which are grasses. The stomatal density, guard cell lengths on the adaxial and abaxial leaf epidermis and the stomatal type in each family are described and the relationship between stomatal density and guard cell size is reviewed. These plants are collected from one of the Irano-Turany protected area. However, studying of stomata characters, particularly herbaceous plants growing in less contaminated zone such as protected areas, could improve basic knowledge on main characters of monocotyledons.

Fatemeh Zarinkamar

2006-01-01

320

Dryout heat fluxes in debris beds containing particles of different size distributions

International Nuclear Information System (INIS)

Results of dryout heat fluxes observed in volumetrically heated particulate beds cooled with acetone and containing particles of different size distributions are presented. Semi-theoretical model developed earlier and based on dryout heat fluxes in deep beds of single size particles has been extended to a mixture of different size particles. 7 refs

1979-08-23

321

Effects of grain size distribution on the creep damage evolution of polycrystalline materials

International Nuclear Information System (INIS)

It is evident that realistic microstructures of polycrystalline materials demonstrate a certain distribution of grain size, which has not been widely studied in most analyses of mechanical properties of materials at high temperatures. In this work, the effects of grain size distribution on the creep damage evolution induced by void growth of polycrystalline materials were investigated by the Voronoi tessellation approach, taking into account the void evolution on the grain boundaries in a grain aggregate cell. The results indicate that with the decrease in mean grain size, the damage variable increases faster. When the mean grain sizes are the same, the more uniform the grain size is, the faster the damage variable increases.

2010-04-28

322

Does plot size affect the performance of GIS-based species distribution models?

Species distribution models are used extensively in predicting the distribution of vegetation across a landscape. Accuracy of the species distribution maps produced by these models deserves attention, since low accuracy maps may lead to erroneous conservation decisions. While plot size is known to influence measures of species richness, its effect on our ability to predict species distribution ranges has not been tested. Our aim is to test whether the accuracy of the distribution maps produced depend on the size of the plot (quadrat) used to collect biological data in the field. In this study, the presences of four plant species were recorded in five sizes of circular plots, with radii ranging from 8 to 100 m. Logistic regression-based models were used to predict the distributions of the four plant species based on empirical evidence of their relationship with eight environmental predictors: distance to river, slope, aspect, altitude, and four principle component axes derived using reflectance values from Aster images. We found that plot size affected the probability of recording the four species, with reductions in plot size generally increasing the frequency of recorded absences. Plot size also significantly affected the likelihood of correctly predicting the distribution of species whenever plot size was below the minimum size required to consistently record species’ presence. Furthermore, the optimal plot size for fitting species distribution models varied among species. Finally, plot size had little impact on overall accuracy, but a strong, positive impact on Kappa accuracy (which provides a stronger measure of model accuracy by accounting for the effects of chance agreements between predictions and observations). Our results suggest that optimal plot size must be considered explicitly in the creation of species distribution models if they are to be successfully adopted into conservation efforts.

Pandit, Shubha N.; Hayward, April; de Leeuw, Jan; Kolasa, Jurek

2010-12-01

323

Digital Repository Infrastructure Vision for European Research (DRIVER)

The diversity and structure of communities are partly determined by how species partition resource gradients. Plant size is an important indicator of species position along the vertical light gradient in the vegetation. 2. Here, we compared the size distribution of tree species in 44 Ghanaian tropical forest communities, using data from 880 one-hectare plots and over 118 000 trees belonging to more than 210 species. 3. The size distribution of forest species showed a continuous normal or lo...

Poorter, L.; Hawthorne, W. D.; Sheil, D.; Bongers, F. J. J. M.

2008-01-01

324

Digital Repository Infrastructure Vision for European Research (DRIVER)

The size distribution of domains in phase-separated lung surfactant monolayers influences monolayer viscoelasticity and compressibility which, in turn, influence monolayer collapse and set the compression at which the minimum surface tension is reached. The surfactant-specific protein SP-B decreases the mean domain size and polydispersity as shown by fluorescence microscopy. From the images, the line tension and dipole density difference are determined by comparing the measured size distribut...

2012-01-01

325

Digital Repository Infrastructure Vision for European Research (DRIVER)

Measuring particle size distribution through calculating light scattering intensity is a typical inverse problem. This paper builds an inverse mathematical model based on Mie scattering, deduces the inversion formulas for particle size, and calculates the relative coefficients through programming with built-in functions in MATLAB. In order to improve the accuracy and noise immunity of particle size distribution measurement, the development of stochastic inversion algorithm: an inverse problem...

2012-01-01

326

Effect of the size distribution of nanoscale dispersed particles on the Zener drag pressure:

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this article, a new relationship for the calculation of the Zener drag pressure is described in which the effect of the size distribution of nanoscale dispersed particles is taken into account, in addition to particle radius and volume fraction, which have been incorporated in the existing relationships. Microstructural observations indicated a clear correlation between the size distribution of dispersed particles and recrystallized grain sizes in the AA7020 aluminum alloy. However, the ex...

2010-01-01

327

Context. Grains in circumstellar disks are believed to grow by mutual collisions and subsequent sticking due to surface forces. Results of many fields of research involving circumstellar disks, such as radiative transfer calculations, disk chemistry, magneto-hydrodynamic simulations largely depend on the unknown grain size distribution. Aims. As detailed calculations of grain growth and fragmentation are both numerically challenging and computationally expensive, we aim to find simple recipes and analytical solutions for the grain size distribution in circumstellar disks for a scenario in which grain growth is limited by fragmentation and radial drift can be neglected. Methods. We generalize previous analytical work on self-similar steady-state grain distributions. Numerical simulations are carried out to identify under which conditions the grain size distributions can be understood in terms of a combination of power-law distributions. A physically motivated fitting formula for grain size distributions is der...

Birnstiel, T; Dullemond, C P

2010-01-01

328

Bubble size and velocity distribution in bubbly two-phase flows

International Nuclear Information System (INIS)

The bubble size and velocity distributions in bubbly air/water two-phase flow have been inferred from the measured bubble passage time distribution for bubbles penetrating a single-sensor hot film anemometer probe. The results indicate that the bubble sizes follow a Poisson distribution, and that the bubble velocity is well described by a hydrodynamic model that accounts for the wake effect

1987-01-01

329

Graphene layer number dependent size distribution of silver nanoparticles

We observe that silver atoms deposited by thermal evaporation deposition onto n-layer graphene films condense upon annealing to form nanoparticles with an average diameter and density that is determined by the layer numbers of graphene films. The optical microscopy and Raman spectroscopy were utilized to identify the number of the graphene layers and the SEM (scanning electron microscopy) was used to observe the morphologies of the particles. Systematic analysis revealed that the average sizes of the nanoparticles increased with the number of graphene layers. The density of nanoparticles decreased as the number of graphene layers increased, revealing a large variation in the surface diffusion strength of nanoparticles on the different substrates. The mechanisms of formation of these layer-dependent morphologies of silver nanoparticles are related to the surface free energy and surface diffusion of the n-layer graphenes.

Lin, Hsing-Ying; Hung, Meei-Ling; Huang, Chen-Han; Chui, Hsiang-Chen; Lin, Jui-Sheng

2014-05-01

330

Cluster size distribution in the autocatalytic growth model

We generalize the model of transition-metal nanocluster growth in aqueous solution, proposed recently [Phys. Rev. E \\textbf{87}, 022132 (2013)]. In order to model time evolution of the system, kinetic equations describing time dependence of the rate of chemical reactions are combined with Smoluchowski coagulation equation. In the absence of coagulation and fragmentation processes, the model equations are solved in two steps. First, for any injective functional dependence of the autocatalytic reaction rate constant on the cluster size, we obtain explicit analytical form of the $i$-mer concentration, $\\xi_{i}$, as a function of $\\xi_{1}$. This result allows us to reduce considerably the number of time-evolution equations. In the simplest situation, the remaining single kinetic equation for $\\xi_{1}(t)$ is solved in quadratures. In a general case, we obtain small system of time-evolution equations, which, although rarely analytically tractable, can be relatively easily solved by using numerical methods.

J?drak, Jakub

2013-01-01

331

Diel size distributions reveal seasonal growth dynamics of a coastal phytoplankter.

Phytoplankton account for roughly half of global primary production; it is vital that we understand the processes that control their abundance. A key process is cell division. We have, however, been unable to estimate division rate in natural populations at the appropriate timescale (hours to days) for extended periods of time (months to years). For phytoplankton, the diel change in cell size distribution is related to division rate, which offers an avenue to obtain estimates from in situ observations. We show that a matrix population model, fit to hourly cell size distributions, accurately estimates division rates of both cultured and natural populations of Synechococcus. Application of the model to Synechococcus at the Martha's Vineyard Coastal Observatory provides an unprecedented view that reveals a distinct seasonality in division rates. This information allows us to separate the effects of growth and loss quantitatively over an entire seasonal cycle. We find that division and loss processes are tightly coupled throughout the year. The large seasonal changes in cell abundance are the result of periods of time (weeks to months) when there are small systematic differences that favor either net growth or loss. We also find that temperature plays a critical role in limiting division rate during the annual spring bloom. This approach opens a path to quantify the role of Synechococcus in ecological and biogeochemical processes in natural systems. PMID:24958866

Hunter-Cevera, Kristen R; Neubert, Michael G; Solow, Andrew R; Olson, Robert J; Shalapyonok, Alexi; Sosik, Heidi M

2014-07-01

332

...2010-07-01 false Critical Parameters of Idealized Ambient Particle Size Distributions F Table F-3 to Subpart F of Part...Part 53âCritical Parameters of Idealized Ambient Particle Size Distributions Idealized Distribution Fine...

2010-07-01

333

Effect size measurement in functional milk product marketing

Directory of Open Access Journals (Sweden)

Full Text Available The paper presents the application possibility of “Effect size” and Cohen’s-d index in the case of introduction of new milk products on the market. The field and online survey were used to establish the potential interest of final consumers for new functional food product of dairy company in Slovenia - milk with phytosterols additives. Two techniques possibilities of Cohen-d index were calculated; manual and using the Cohen’s-d calculator. Further, the application is focused on two main questions in survey regarding observed problem: 1 Would you buy milk with phytosterols additives, which scientifically proven lowers concentration of cholesterol in blood? 2 Would you pay for it at a higher price? The sample includes 419 surveys, 150 surveys were conducted on field (control group and 269 surveys were provided online (experimental group. The Cohen’s-d index (d results show by using manual and Cohen’s-d calculator for both groups “small” effect (d=0.35, i.e. d=0.34 , and “zero or near zero” effect (d=0.15, i.e.= 0.15 when deciding to buy new milk product.

Karmen Pažek

2011-12-01

334

Pore characteristics of sandstones analyzed by pore-size distribution curves

Energy Technology Data Exchange (ETDEWEB)

Numerous mechanically-packed sands were prepared to elucidate characteristics of segmentations from nonporous sphere-glass beads and porous mudrock fragments which represent constituent mineral grains and rock fragments of sandstones, respectively. These assemblages are clarified into five groups; (1) equal-size glass beads of 1, 1.5, 3, 5 phi, (2) variably-sorted glass beads, of which sorting index are 0.42, 0.64, 0.89, (3) bimodal mixtures of sand-size and matrix-size glass beads, (4) mixtures of equal-size glass beads and angular quartz grains, and (5) mixtures of equal-size glass beads and porous mudrock fragments. According to these packed models, each segment of normal distribution may be explicitly explained by (1) a framework distribution of intergranular pores built up by sand-size grain packing followed by a subordinate toroidal void distribution around grain contacts, (2) a framework distribution of intergranular pores built up by matrix-size grain packing followed by a toroidal void distribution, and (3) intragrain pore-size distributions contained in mudrock fragments. The gradients and positions of segments are influenced by grain size sorting, roundness, and presence of matrix and porous fragments as well as by porosity types. The same conclusions are obtained in various arenites and wackes, whose shapes of cumulative pore-size distribution curves well correspond to rock types of sandstones. Thus, porosity properties such as intergranular porosities, matrix porosities and intragrain porosities of mudrock fragments can be quantitatively evaluated individually from analyses of pore-size distribution curves of sandstones. These values are in conformity with those estimated by point-counter analyses executed in thin sections and SEM images. Consequently, these porosity properties may indicate the degree of compaction undergone on sandstones during diagenesis.

Uchida, Takashi (JAPEX Research Center, Chiba (Japan)); Tada, Ryuji (Tokyo Univ. (Japan). Geological Inst.)

1992-01-01

335

Prediction of the droplet size and velocity joint distribution for sprays

Energy Technology Data Exchange (ETDEWEB)

This work addresses the development of a mathematical model to predict the joint distribution for both size and velocity of the droplets in sprays, based on the maximum entropy formalism. Using this joint distribution, models to obtain separated distributions for size and velocity of sprays are also presented. Correlations for the average velocity for both pressure jet and airblast atomiser, based on assumed profiles in the atomiser gun, are obtained as a function of easily measurable parameters. Several distributions for different types of atomisers are then predicted. Agreement between available data for the velocity distribution and the corresponding predictions is satisfactory. 26 refs., 8 figs.

Ayres, D.; Caldas, M.; Semio, V.; Da Graca Carvalho, M. [Instituto Superior Tecnico, Lisbon (Portugal). Departamento de Engenharia Mecanica

2001-02-01

336

Size distribution and speciation of chromium in paint spray aerosol at an aerospace facility.

Spray painters are potentially exposed to aerosol containing Cr(VI) via inhalation of chromate-based paint spray. Two field studies were conducted at an aerospace facility to determine the size distribution and speciation of Cr(VI) in paint spray aerosol. Sampled paint products consisted of sparingly soluble strontium chromate in an epoxy resin matrix, a matrix generally known for its durability and toughness. Personal aerosol samples were collected using Sierra Marple personal cascade impactors and analyzed for Cr(VI) and total Cr. The size distribution of total Cr particles in the paint aerosol had a Mass Median Aerodynamic Diameter (MMAD) of 7.5 mum [Geometric Standard Deviation (GSD = 2.7 mum)] in both field studies. The MMAD of Cr(VI) particles was 8.5 mum (GSD = 2.2 mum). Particles >2 mum constituted 90% or more of the total Cr and the Cr(VI) mass, in all sampled paint aerosols and were lognormally distributed. The target site for respiratory deposition of Cr in the aerosol was estimated based on the mass distribution of Cr according to particle size. On an average, 62% of the Cr and Cr(VI) mass in the paint aerosol consisted of particles >10 mum. This study showed that 71.8% of Cr(VI) mass in paint spray aerosol potentially inhaled by a spray painter may deposit in the head airways region. Only 2.0 and 1.4% of Cr(VI) mass in the paint aerosol may potentially deposit in the alveolar and tracheobronchial region, respectively. The ratio of Cr(VI) mass to total Cr mass was determined in bulk paint and the data indicate that Cr was predominantly in the Cr(VI) valence state, before spraying. The ratio of Cr(VI) mass to total Cr mass was also determined in paint aerosol samples. The data indicated that there was a reduction of Cr(VI) regardless of Cr aerosol particle size. Cr(VI) reduction occurred most likely during the 8 h sample collection time period. These findings are in agreement with the findings that observed Cr(VI) reduction during collection of airborne Cr(VI) in samples of chromic acid mist. The use of Cr(VI) stabilizing sampling media and the storage of samples at lower temperatures (4 degrees C ) during and after sampling may avoid the underestimation of Cr(VI). PMID:15591325

Sabty-Daily, Rania A; Harris, Patricia A; Hinds, William C; Froines, John R

2005-01-01

337

Particle Size Distribution Measurements of Manganese-Doped ZnS Nanoparticles

Digital Repository Infrastructure Vision for European Research (DRIVER)

We performed particle size and particle size distribution measurements for L-cysteine-stabilized ZnS/Mn nanoparticles in the size region below 10 nm. For this we applied transmission electron microscopy (TEM), analytical ultracentrifugation (AUC), dynamic light scattering (DLS), and asymmetric ?ow ?eld ?ow fractionation (aF-FFF) measurements, and we calculated particle sizes with the help of X-ray diffraction (XRD) patterns and the shift of the band gap absorption in the UV-vis spectrum...

Dieckmann, Yvonne; Co?lfen, Helmut; Hofmann, Heinrich; Petri-fink, Alke

2009-01-01

338

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

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.

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

2010-01-01

339

Production of size controlled aluminum and alumina nanoparticles via pulsed laser ablation in water.

An Al metal plate was ablated by a pulsed Nd-YAG laser to produce nano-structured Al and gamma-Al2O3 in deionized water in the absence of any surfactants or catalysts. In this study, the mean diameter and the width of size distribution of the nanoparticles was influenced by the laser power, resulting in the production of smaller and larger sizes of nanoparticles with higher and lower laser power, respectively. The influence of laser power on the mean diameter and the width of size distribution of as-prepared nanoparticles generated by the laser ablation process was explained by the space homogeneity of the plasma plume, where the nucleation of nanoparticles has occurred. Further explanations of the influence of laser power on the size distribution are proposed. Furthermore, structural and morphological characterization of aluminum and gamma-Al2O3 nanoparticles was conducted by X-ray diffraction (XRD) and field emission scanning electron microscope (FE-SEM). PMID:23447935

Lee, Seulki; Jung, Hyeon Jin; Shin, Jae Ho; Choi, Myong Yong

2012-12-01

340

Vertical profile and aerosol size distribution measurements in Iceland (LOAC)

Cold climate and high latitudes regions contain important dust sources where dust is frequently emitted, foremost from glacially-derived sediments of riverbeds or ice-proximal areas (Arnalds, 2010; Bullard, 2013). Iceland is probably the most active dust source in the arctic/sub-arctic region (Dagsson-Waldhauserova, 2013). The frequency of days with suspended dust exceeds 34 dust days annually. Icelandic dust is of volcanic origin; it is very dark in colour and contains sharp-tipped shards with bubbles. Such properties allow even large particles to be easily transported long distances. Thus, there is a need to better understand the spatial and temporal variability of these dusts. Two launch campaigns of the Light Optical Aerosols Counter (LOAC) were conducted in Iceland with meteorological balloons. LOAC use a new optical design that allows to retrieve the size concentrations in 19 size classes between 0.2 and 100 microm, and to provide an estimate of the main nature of aerosols. Vertical stratification and aerosol composition of the subarctic atmosphere was studied in detail. The July 2011 launch represented clean non-dusty season with low winds while the November 2013 launch was conducted during the high winds after dusty period. For the winter flight (performed from Reykjavik), the nature of aerosols strongly changed with altitude. In particular, a thin layer of volcanic dust was observed at an altitude of 1 km. Further LOAC measurements are needed to understand the implication of Icelandic dust to the Arctic warming and climate change. A new campaign of LAOC launches is planned for May 2014. Reference: Arnalds, O., 2010. Dust sources and deposition of aeolian materials in Iceland. Icelandic Agricultural Sciences 23, 3-21. Bullard, J.E., 2013. Contemporary glacigenic inputs to the dust cycle. Earth Surface Processes and Landforms 38, 71-89. Dagsson-Waldhauserova, P., Arnalds O., Olafsson H. 2013. Long-term frequency and characteristics of dust storm events in Northeast Iceland (1949-2011). Atmospheric Environment 77:117-127.

Dagsson Waldhauserova, Pavla; Olafsson, Haraldur; Arnalds, Olafur; Renard, Jean-Baptiste; Vignelles, Damien; Verdier, Nicolas

2014-05-01

341

On wildfire complexity, simple models and environmental templates for fire size distributions

Vegetation fires affect some 370 Mha annually. At global and continental scales, fire activity follows predictable spatiotemporal patterns driven by gradients and seasonal fluctuations of primary productivity and evaporative demand that set constraints for fuel accumulation rates and fuel dryness, two key ingredients of fire. At regional scales, fires are also known to affect some landscapes more than others and within landscapes to occur preferentially in some sectors (e.g. wind-swept ridges) and rarely in others (e.g. wet gullies). Another common observation is that small fires occur relatively frequent yet collectively burn far less country than relatively infrequent large fires. These patterns of fire activity are well known to management agencies and consistent with their (informal) models of how the basic drivers and constraints of fire (i.e. fuels, ignitions, weather) vary in time and space across the landscape. The statistical behaviour of these landscape fire patterns has excited the (academic) research community by showing some consistency with that of complex dynamical systems poised at a phase transition. The common finding that the frequency-size distributions of actual fires follow power laws that resemble those produced by simple cellular models from statistical mechanics has been interpreted as evidence that flammable landscapes operate as self-organising systems with scale invariant fire size distributions emerging 'spontaneously' from simple rules of contagious fire spread and a strong feedback between fires and fuel patterns. In this paper we argue that the resemblance of simulated and actual fire size distributions is an example of equifinality, that is fires in model landscapes and actual landscapes may show similar statistical behaviour but this is reached by qualitatively different pathways or controlling mechanisms. We support this claim with two key findings regarding simulated fire spread mechanisms and fire-fuel feedbacks. Firstly, we demonstrate that the power law behaviour of fire size distributions in the widely used Drossel and Schwabl (1992) Forest Fire Model (FFM) is strictly conditional on simulating fire spread as a cell-to-cell contagion over a fixed distance; the invariant scaling of fire sizes breaks down under the slightest variation in that distance, suggesting that pattern formation in the FFM is irreconcilable with the reality of disparate rates and modes of fire spread observed in the field. Secondly, we review field evidence showing that fuel age effects on the probability of fire spread, a key assumption in simulation models like the FFM, do not generally apply across flammable environments. Finally, we explore alternative explanations for the formation of scale invariant fire sizes in real landscapes. Using observations from southern Australian forest regions we demonstrate that the spatiotemporal patterns of fuel dryness and magnitudes of fire driving weather events set strong environmental templates for regional fire size distributions.

Boer, M. M.; Bradstock, R.; Gill, M.; Sadler, R.

2012-12-01

342

International Nuclear Information System (INIS)

Natural radioactivity level in the Mumbai Harbour bay sediment was estimated and their association with particle size was investigated. Seven different particle size fractions from 300 ?m were separated by wet sewing using electromagnetic sieve shaker and particle size distribution was studied in the marine sediment. The particle size fractions were analysed for 226Ra, 228Ra and 40K content using 50% relative efficiency p-type Co-axial HPGe detector. It was observed that, 71.8 % of the total sediment contained 40K was observed to be associated in the size fraction of <60 to 90 ?m size particles. (author)

2014-01-20

343

The Size Distribution of Chinese Manufacturing Firms: From the Perspective of Industry Life Cycle

Directory of Open Access Journals (Sweden)

Full Text Available Using panel data of Chinese manufacturing firms between 2003 and 2008, this paper aims to examine the evolution of firm size distribution (FSD as the industry goes through its life-cycle. The results reveal that during the life-cycle process, China’s manufacturing firms’ average size becomes larger then shrinks, and the degree of firm size heterogeneity and industry concentration increases all the time. Empirical results also indicate that the change rate of FSD is affected by firms’ net entry rate into industry. When net entry rate is higher, average firm size’s growth rate is smaller, while size heterogeneity and industry concentration rises more dramatically.

Yanying CHEN

2012-06-01

344

Does the size distribution of mineral dust aerosols depend on the wind speed at emission?

Directory of Open Access Journals (Sweden)

Full Text Available The size distribution of mineral dust aerosols partially determines their interactions with clouds, radiation, ecosystems, and other components of the Earth system. Several theoretical models predict that the dust size distribution depends on the wind speed at emission, with larger wind speeds predicted to produce smaller aerosols. The present study investigates this prediction using a compilation of published measurements of the size-resolved vertical dust flux emitted by eroding soils. Surprisingly, these measurements indicate that the size distribution of naturally emitted dust aerosols is independent of the wind speed. The recently formulated brittle fragmentation theory of dust emission is consistent with this finding, whereas other theoretical models are not. The independence of the emitted dust size distribution with wind speed simplifies both the interpretation of geological records of dust deposition and the parameterization of dust emission in atmospheric circulation models.

J. F. Kok

2011-10-01

345

Does the size distribution of mineral dust aerosols depend on the wind speed at emission?

Directory of Open Access Journals (Sweden)

Full Text Available The size distribution of mineral dust aerosols greatly affects their interactions with clouds, radiation, ecosystems, and other components of the Earth system. Several theoretical dust emission models predict that the dust size distribution depends on the wind speed at emission, with larger wind speeds predicted to produce smaller aerosols. The present study investigates this prediction using a compilation of published measurements of the size-resolved vertical dust flux emitted by eroding soils. Surprisingly, these measurements indicate that the size distribution of naturally emitted dust aerosols is independent of the wind speed. This finding is consistent with the recently formulated brittle fragmentation theory of dust emission, but inconsistent with other theoretical dust emission models. The independence of the emitted dust size distribution with wind speed simplifies both the parameterization of dust emission in atmospheric circulation models as well as the interpretation of geological records of dust deposition.

J. F. Kok

2011-07-01

346

Earthquake Size Distribution: Power-Law with Exponent Beta = 1/2 ?

We propose that the widely observed and universal Gutenberg-Richter relation is a mathematical consequence of the critical branching nature of earthquake process in a brittle fracture environment. These arguments, though preliminary, are confirmed by recent investigations of the seismic moment distribution in global earthquake catalogs and by the results on the distribution in crystals of dislocation avalanche sizes. We consider possible systematic and random errors in determining earthquake size, especially its seismic moment. These effects increase the estimate of the parameter beta of the power-law distribution of earthquake sizes. In particular we find that the decrease in relative moment uncertainties with earthquake size causes inflation in the beta-value by about 1-3%. Moreover, earthquake clustering greatly influences the beta-parameter. If clusters (aftershock sequences) are taken as the entity to be studied, then the exponent value for their size distribution would decrease by 5-10%. The complexity ...

Kagan, Yan Y

2009-01-01

347

Energy Technology Data Exchange (ETDEWEB)

The effect of particle-size and coal kinds on the sedimentation stability of highly loaded coal-water slurry (CWS) was studied. Optimal concentrations of additives to make the stability best were found. The optimal concentrations of the dispersant (sodium betanaphtalene sulfonate formaline condensate) and pH controller (NaOH) were 0.25 to 0.66 and 0.15 to 0.25% to CWS respectively. The particle size distribution which gave the maximum packing fraction to the multi components random particle packing zone was indicated at distribution modulus q=0.43 of the Gaudin-Schuhmann size distribution from particle size measurements. The maximum stability of CWS was achieved at q=0.28, which was considerably smaller than q value giving the maximum packing fraction. Therefore the particle size distribution should be finer than that giving the minimum viscosity to maintain the CWS stability. (8 figs, 1 tab, 17 refs)

Osasa, Kunihisa; Sanbuichi, Masao; Nakakura, Hideo; Tabata, Kazuki

1987-11-10

348

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 SB 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 SB function as the general distribution function. And then, the time evolution of particle size distributions using the Johnson's SB function as the initial distribution can be obtained by several lower order moment equations of the Johnson's SB 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 SB function has the ability of describing the early time evolution of different initial particle size distributions.

Tang, Hong; Lin, Jianzhong

2013-05-01

349

Optimizing the grain size distribution of allografts in bone impaction grafting.

In bone impaction grafting, allografts in the form of bone chips are used for reconstruction of defects and to induce bone remodeling. Optimizing grain size distribution of this allograft material should help prevent implant subsidence by achieving higher primary stability of the graft. We evaluated the influence of grain size distribution on the mechanical stability of allograft material. Bone tissue was rinsed, and the grain size distribution of the allograft material was determined by performing a sieve analysis. Uniaxial compression tests were carried out before and after a standardized compaction procedure for samples with controlled grain size distribution and a control group. Allografts with controlled grain size distribution showed a yield limit almost twice as high as in the control group after a standardized compaction procedure. A better interlocking between bone particles was observed compared to the control group. Thus, grain size distribution has a major impact on the mechanical stability of bone grafts. By controlling the grain size distribution of allograft material, a tighter packing can be achieved and subsequently implant subsidence of implants could be avoided. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:1024-1029, 2014. PMID:24797323

Putzer, David; Coraça-Huber, Debora; Wurm, Alexander; Schmoelz, Werner; Nogler, Michael

2014-08-01

350

The steady-state population of bodies resulting from a collisional cascade depends on how material strength varies with size. We find a simple expression for the power-law index of the population, given a power law that describes how material strength varies with size. This result is extended to the case relevant for the asteroid belt and Kuiper belt, in which the material strength is described by 2 separate power laws--one for small bodies and one for larger bodies. We find that the power-law index of the small body population is unaffected by the strength law for the large bodies, and vice versa. Simple analytical expressions describe a wave that is superimposed on the large body population because of the transition between the two power laws describing the strength. These analytical results yield excellent agreement with a numerical simulation of collisional evolution. These results will help to interpret observations of the asteroids and KBOs, and constrain the strength properties of those objects.

O'Brien, David P

2014-01-01

351

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

International Nuclear Information System (INIS)

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

1978-01-01

352

Magnetic pattern at supergranulation scale: the Void Size Distribution

The large-scale magnetic pattern of the quiet sun is dominated by the magnetic network. This network, created by photospheric magnetic fields swept into convective downflows, delineates the boundaries of large scale cells of overturning plasma and exhibits voids in magnetic organization. Such voids include internetwork fields, a mixed-polarity sparse field that populate the inner part of network cells. To single out voids and to quantify their intrinsic pattern a fast circle packing based algorithm is applied to 511 SOHO/MDI high resolution magnetograms acquired during the outstanding solar activity minimum between 23 and 24 cycles. The computed Void Distribution Function shows a quasi-exponential decay behavior in the range 10-60 Mm. The lack of distinct flow scales in such a range corroborates the hypothesis of multi-scale motion flows at the solar surface. In addition to the quasi-exponential decay we have found that the voids reveal departure from a simple exponential decay around 35 Mm.

Berrilli, Francesco; Del Moro, Dario

2014-01-01

353

The atmospheric Chemistry Transport Model system COSMO-MUSCAT was used to determine the particle mass concentrations of dust and anthropogenically emitted aerosol particles over Europe. The model system consists of the online coupled code of the operational forecast model COSMO (Schättler et al., 2009) and the chemistry-transport model MUSCAT (Wolke et al., 2012). For a four-months-period in 2008 (May to August), the dust and anthropogenic aerosol mass concentrations for six different species (sulfate, nitrate, ammonium, organic and elemental carbon and sea salt) were simulated. For the dust, five different size bins were used and a representative particle size and density were assumed for each size bin. Afterwards, the number concentration was calculated. For the anthropogenic aerosol, lognormal modes were assumed with a representative mode diameter, sigma and density for each component. These parameters were then used to convert the simulated mass concentrations to number concentrations and number size distributions for each component. Those individual size distributions can then be summed up to a total particle number size distribution. A first comparison with measurement data from the Cape Verde Islands showed a good agreement between observed and simulated dust particle size distributions. Both, the shape of the number size distributions and the order of magnitude of the particle number concentrations compared well. Only for the smallest size bin, observed numbers were occasionally higher, which can be explained by anthropogenic or biomass burning aerosol, which is included in the measurements of the total particle size distributions but was not included in the model runs. Comparisons of measured and simulated size distributions of the anthropogenic aerosol will be available soon. In case the data are available, we will also present an estimation of the particle number concentrations with the aerosol microphysical aerosol module ext-M7 for the duration of a measurement campaign in spring 2013 (HOPE).

Engler, Christa; Heinold, Bernd; Tegen, Ina

2014-05-01

354

Particle size distributions from laboratory-scale biomass fires using fast response instruments

Directory of Open Access Journals (Sweden)

Full Text Available Particle size distribution from biomass combustion is an important parameter as it affects air quality, climate modelling and health effects. To date particle size distributions reported from prior studies vary not only due to difference in fuels but also difference in experimental conditions. This study aims to report characteristics of particle size distribution in a well controlled repeatable lab scale biomass fires for southwestern US fuels. The combustion facility at the USDA Forest Service's Fire Science Laboratory (FSL, Missoula, MT provided repeatable combustion and dilution environment ideal for particle size distribution study. For a variety of fuels tested the major mode of particle size distribution was in the range of 29 to 52 nm, which was attributable to dilution of the fresh smoke. Comparing volume size distribution from Fast Mobility Particle Sizer (FMPS and Aerodynamic Particle Sizer (APS measurements, ~30% of particle volume was attributable to the particles ranging from 0.5 to 10 ?m for PM_{10}. Geometric mean diameter rapidly increased during flaming and gradually decreased during mixed and smoldering phase combustion. Most of fuels gave unimodal distribution during flaming phase and strong biomodal distribution during smoldering phase. The mode of combustion (flaming, mixed and smoldering could be better distinguished using slopes in Modified Combustion Efficiency (MCE vs. geometric mean diameter from each mode of combustion than only using MCE values.

S. Hosseini

2010-04-01

355

Atmospheric flows exhibit fractal fluctuations and inverse power law form for power spectra indicating an eddy continuum structure for the selfsimilar fluctuations. A general systems theory for fractal fluctuations developed by the author is based on the simple visualisation that large eddies form by space-time integration of enclosed turbulent eddies, a concept analogous to Kinetic Theory of Gases in Classical Statistical Physics. The ordered growth of atmospheric eddy continuum is in dynamical equilibrium and is associated with Maximum Entropy Production. The model predicts universal (scale-free) inverse power law form for fractal fluctuations expressed in terms of the golden mean. Atmospheric particulates are held in suspension in the fractal fluctuations of vertical wind velocity. The mass or radius (size) distribution for homogeneous suspended atmospheric particulates is expressed as a universal scale-independent function of the golden mean, the total number concentration and the mean volume radius. Mode...

Selvam, A M

2011-01-01

356

Transformation on steel products distribution in Poland and Slovakia

Directory of Open Access Journals (Sweden)

Full Text Available Steel industry is one of the most globalized branch, globalization has had the influence on iron ore supply, steel production and distribution as well. In last years, steel products distribution process has changed significantly, because of rising competitiveness due to common world market influence and main global players actions. The paper presents changes in steel products distribution in Poland and Slovakia focusing on main steel producers activity in distribution as well as distributors response on new market situation.

R. Stefko

2012-01-01

357

International Nuclear Information System (INIS)

The magnetic properties of a ferrofluid are strongly influenced by its particle size distribution. We analyzed a ferrofluid with an unknown particle size distribution as well as fractionated samples of the original material. The ferrofluid in our investigations consists of a mixture of maghemite and magnetite. We investigated these different samples using temperature-dependent magnetorelaxometry method. The evaluation of the Neel relaxation signal allows us a direct determination of the energy barrier distribution, which is one of the most important parameters of such systems of magnetic nanoparticles. The calculated particle volumes were compared with particle sizes determined by transmission electron microscopy

2007-04-01

358

Energy Technology Data Exchange (ETDEWEB)

The magnetic properties of a ferrofluid are strongly influenced by its particle size distribution. We analyzed a ferrofluid with an unknown particle size distribution as well as fractionated samples of the original material. The ferrofluid in our investigations consists of a mixture of maghemite and magnetite. We investigated these different samples using temperature-dependent magnetorelaxometry method. The evaluation of the Neel relaxation signal allows us a direct determination of the energy barrier distribution, which is one of the most important parameters of such systems of magnetic nanoparticles. The calculated particle volumes were compared with particle sizes determined by transmission electron microscopy.

Schmidl, Frank [Institut of Solid State Physics, Friedrich-Schiller-University Jena, D-07743 Jena (Germany)]. E-mail: Frank.Schmidl@uni-jena.de; Weber, Peter [Institut of Solid State Physics, Friedrich-Schiller-University Jena, D-07743 Jena (Germany); Koettig, Torsten [Institut of Solid State Physics, Friedrich-Schiller-University Jena, D-07743 Jena (Germany); Buettner, Markus [Institut of Solid State Physics, Friedrich-Schiller-University Jena, D-07743 Jena (Germany); Prass, Stefan [Institut of Solid State Physics, Friedrich-Schiller-University Jena, D-07743 Jena (Germany); Becker, Christoph [Institut of Solid State Physics, Friedrich-Schiller-University Jena, D-07743 Jena (Germany); Mans, Michael [Institut of Solid State Physics, Friedrich-Schiller-University Jena, D-07743 Jena (Germany); Heinrich, Jochen [Innovent Technologieentwicklung, Pruessingstrasse 27B, D-07743 Jena (Germany); Roeder, Michael [Innovent Technologieentwicklung, Pruessingstrasse 27B, D-07743 Jena (Germany); Wagner, Kerstin [Innovent Technologieentwicklung, Pruessingstrasse 27B, D-07743 Jena (Germany); Berkov, Dimitr V. [Innovent Technologieentwicklung, Pruessingstrasse 27B, D-07743 Jena (Germany); Goernert, Peter [Innovent Technologieentwicklung, Pruessingstrasse 27B, D-07743 Jena (Germany); Gloeckl, Gunnar [Institute of Pharmacy, Ernst-Moritz-Arndt-University, D-17487 Greifswald (Germany); Weitschies, Werner [Institute of Pharmacy, Ernst-Moritz-Arndt-University, D-17487 Greifswald (Germany); Seidel, Paul [Institut of Solid State Physics, Friedrich-Schiller-University Jena, D-07743 Jena (Germany)

2007-04-15

359

Effects of size distribution on the combustion efficiency of a liquid propellant rocket motor

Energy Technology Data Exchange (ETDEWEB)

This paper studies the effects of size distribution of sprays on the combustion efficiency of a one-dimensional, steady state liquid propellant rocket motor in terms of (1) mean radius, (2) degree of dispersity, (3) range of droplet size, and (4) the shape of the distribution. The combustion process of the droplet groups is analysed by a step-by-step numerical scheme. Results indicate that better combustion efficiency can be achieved by reducing the droplet size and improving the monodispersity ofthe sprays. The effects of the range of droplet sizeand the shape of the distribution on the combustion efficiency are relatively small, and may be ignored in most cases 9 references.

Chan, K.K.; Chyn, L.

1985-10-01

360

Measurement of the size distributions of radon progeny in indoor air

International Nuclear Information System (INIS)

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

1990-10-16

361

A Model for Scaling in Firms' Size and Growth Rate Distribution

We introduce a simple agent-based model which allows us to analyze three stylized facts: a fat-tailed size distribution of companies, a `tent-shaped' growth rate distribution, the scaling relation of the growth rate variance with firm size, and the causality between them. This is achieved under the simple hypothesis that firms compete for a scarce quantity (either aggregate demand or workforce) which is allocated probabilistically. The model allows us to relate size and growth rate distributions. We compare the results of our model to simulations with other scaling relationships, and to similar models and relate it to existing theory.

Metzig, Cornelia

2013-01-01

362

A model for scaling in firms’ size and growth rate distribution

We introduce a simple agent-based model which allows us to analyze three stylized facts: a fat-tailed size distribution of companies, a ‘tent-shaped’ growth rate distribution, the scaling relation of the growth rate variance with firm size, and the causality between them. This is achieved under the simple hypothesis that firms compete for a scarce quantity (either aggregate demand or workforce) which is allocated probabilistically. The model allows us to relate size and growth rate distributions. We compare the results of our model to simulations with other scaling relationships, and to similar models and relate it to existing theory. Effects arising from binning data are discussed.

Metzig, Cornelia; Gordon, Mirta B.

2014-03-01

363

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

Industrial 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 investigation is presented of the extent to which the level and the growth of small business presence influence price-cost margins in Dutch manufacturing. A large data set of 66 industries for a 13-year period is u...

Prince, Y. M.; Thurik, A. R.

1993-01-01

364

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.

Kornilov, Oleg; Toennies, J. Peter

2008-05-01

365

Digital Repository Infrastructure Vision for European Research (DRIVER)

Multiple charge inversion is an essential procedure to convert the raw mobility distributions recorded by mobility particle size spectrometers, such as the DMPS or SMPS (Differential or Scanning Mobility Particle Sizers) into true particle number size distributions. In this work, we present a new multiple charge inversion algorithm with extended functionality. The algorithm can incorporate size distribution information from sensors that measure beyond the upper sizing limit of the mobi...

Pfeifer, S.; Birmili, W.; Schladitz, A.; Mu?ller, T.; Nowak, A.; Wiedensohler, A.

2013-01-01

366

An online measurement technique for drop size distribution in stirred tank reactors is needed but has not yet been developed. Different approaches and different techniques have been published as the new standard during the last decade. Three of them (focus beam reflectance measurement, two-dimensional optical reflectance measurement techniques and a fiber optical FBR sensor) are tested, and their results are compared with trustful image analysis results from an in situ microscope. The measurement of drop sizes in liquid/liquid distribution is a major challenge for all tested measurement probes, and none provides exact results for the tested system of pure toluene/water compared to an endoscope. Not only the size analysis but also the change of the size over time gives unreasonable results. The influence of the power input on the drop size distribution was the only reasonable observation in this study. The FBR sensor was not applicable at all to the used system. While all three probes are based on laser back scattering, the general question of the usability of this principle for measuring evolving drop size distributions in liquid/liquid system is asked. The exterior smooth surface of droplets in such systems is leading to strong errors in the measurement of the size of the drops. That leads to widely divergent results. A different measurement principle should be used for online measurements of drop size distributions than laser back scattering.

Maaß, S.; Wollny, S.; Voigt, A.; Kraume, M.

2011-02-01

367

Effect of Particle Size Distribution on Slurry Rheology: Nuclear Waste Simulant Slurries

Energy Technology Data Exchange (ETDEWEB)

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.

Chun, Jaehun; Oh, Takkeun; Luna, Maria L.; Schweiger, Michael J.

2011-07-05

368

Directory of Open Access Journals (Sweden)

Full Text Available This study was conducted to investigate the effects of three sizes of alfalfa and time post-feeding on rumen contents and on particle size distribution of ruminal digesta. Three ruminally fistulated buffalo steers received a diet consisting just alfalfa that was harvested at 15% of flowering and chopped in three sizes. Individual small rectangular bales were chopped with a forage field harvester for theoretical cut length 19 and 10 mm for preparation of long and medium particle size, also the fine particles were prepared by milling. The geometric means and its standard deviation were 8.5, 5.5 and 2.5 mm; and 1.24, 1.16 and 1.06 mm, in coarse, medium and fine, respectively. The experimental design was a repeated 3×3 Latin squares with 21 day periods. The diets were offered twice daily at 09:00 and 21:00 h at ad libitum level. The rumens were evacuated manually at 3, 7.5 and 12h post-feeding and total ruminal contents separated into mat and bailable liquids. Dry matter weight distribution of total recovered particles was determined by a wet-sieving procedure and used to partition ruminal mat and bailable liquids among percentages of large (?4.0 mm, medium (<4.0mm and ?1.18 mm, and fine (<1.18 mm and ?0.05 mm particles. Intake did not influence markedly the distribution of different particle fractions, whereas particle size and time post-feeding had a pronounced effect. With increasing time after feeding, percentage of large and medium particles significantly decreased, whereas the percentage of fine particles significantly increased. The ruminal digesta particle distributions illustrated intensive particle breakdown in the reticulo-rumen for coarse particle more than others. Dry matter contents and the proportion of particulate dry matter in the rumen increased as intake increased, i.e. ruminal mat increased at the expense of bailable liquids. It can be concluded that reduction of forage particle size for buffaloes at maintenance level, influences the structure of rumen contents, ruminal mat formation and consistency, ruminal pH, the mass of ruminal escapable and non escapable dry matter pool size.

A. Teimouri Yansari

2010-02-01

369

Characterization of the mass distribution of Slovak brown coal after size reduction processes

Directory of Open Access Journals (Sweden)

Full Text Available Distribution of pulverised particles is in general affected by the fragmentation process, initial size distribution, energy input, number of fracturing events, etc. and have been studied for several decades. Empirical studies of crushing and grinding by the mineral processing industry provide a major source of information on the distributions. There are many statistical relations describing the distributions of particles: between the number of particles and their size, or the particle mass and size.The aim of this paper is to reveal the fractal relation in the mass distribution of coal samples from locality Cíge¾ after size reduction processes-crushing and grinding. The acquired data can be obtained from sieve analyse, where the particles are distributed to various fractions. The fractal distribution is characterized by the fractal dimension D, that can be determined from the gradient of the graph of ln M against ln r, where M denotes the cumulative mass of all particles with the size less then r. It is useful to specify the range over which the fractal relation is a good fit to the experimental data. The range is bounded by the upper and lower limit on the particle size. From the obtained values it can be concluded that the value of fractal dimension for the ground sample is higher, due to higher number of reducing events.

Tur?ániová ?udmila

2000-09-01

370

THE TEMPORAL DYNAMICS OF REGIONAL CITY SIZE DISTRIBUTION: ANDHRA PRADESH (1951-2001

Directory of Open Access Journals (Sweden)

Full Text Available Systems with measurable entities are characterized by certain properties of their size distribution. City Size Distribution (CSD and the underlying city size dynamics have received attention in the urban economic literature in recent years. In this approach we aim at evaluating the temporal dynamics of city size distribution in Andhra Pradesh, an Indian state for the period 1951-2001. The research framework-which is based on a function relating population size to rank-is used to test for the trends of deconcentration cities of population over the study period. The expansion methodology is used to investigate the dynamics of rank size function in temporal dimension. We have studied the threshold size and its influence on temporal trends. The size distribution of cities/towns from one period to another is modeled by way of a Markov Chain. Our findings reveal that all places in the urban system are growing with small towns growing at a faster rate during study period. The largest cities and the smallest towns display higher persistence than the medium sized cities.

G. Kumar

2014-01-01

371

Negative binomial multiplicity distribution from binomial cluster production

Energy Technology Data Exchange (ETDEWEB)

Two-step interpretation of negative binomial multiplicity distribution as a compound of binomial cluster production and negative binomial like cluster decay distribution is proposed. In this model we can expect the average multiplicity for the cluster production increases with increasing energy, different from a compound Poisson-Logarithmic distribution. (orig.).

Iso, C. (Tokyo Inst. of Tech. (Japan). Dept. of Physics); Mori, K. (Saitama Univ., Urawa (Japan). Dept. of Physics)

1990-03-01

372

Description of sprays using joint hyperbolic distribution in particle size and velocity

The joint probability density functions of droplet size and velocity have been represented in sprays by the two-dimensional hyperbolic distribution. A brief description of the hyperbolic distribution is provided, and a procedure to compute its eight parameters outlined. Analytical expressions for certain statistical quantities, such as mean diameters, momentum, and kinetic energy, applicable under certain restrictions, are obtained. The computations for a water spray issuing from a Danfoss 60-deg solid cone oil-burner nozzle demonstrate not only that the hyperbolic distribution provides an excellent approximation for the joint size and velocity distributions for the measurements taken along the entire length of the spray axis, but also that such representation presents a clear insight into the physics of the motion and the related size formation. The computations reveal a developing region, with areas dominated by breakup or coalescence of droplets, followed by a developed state with little change in droplet size but continuously decreasing velocity.

Bhatia, J. C.; Durst, F.

1990-09-01

373

Size Frequency Distributions of Blocks on Lunar Volcanic Landforms: Results from LROC

We present the results from a comprehensive effort to obtain detailed size-frequency distributions for blocks associated with volcanic landforms by digitizing blocks from LROC NAC images and discuss implications for understanding the geology of the Marius Hills region.

Lawrence, S. J.; Denevi, B. W.; Hawke, B. R.; Giguere, T. A.; Robinson, M. S.; Stopar, J. D.; Tran, T.; Jolliff, B. L.; Bussey, D. B. J.; Stelling, R.

2011-03-01

374

Variability in Rainfall Drop-Size Distributions observed at the Darwin ARM site

The variability of rainfall drop-size distributions as a function of large-scale atmospheric conditions and cloud/storm characteristics is investigated using observations from the Atmospheric Radiation Measurement (ARM) program's research facility at Darwin, Australia. Drop-size distribution observations are obtained from an impact disdrometer over four years (2006-2010) including the YOTC. The suite of complementary long-term observations from the ARM suite of instruments, including a millimeter cloud radar, micropulse lidar, ceilometers, microwave radiometer, radiosondes, solar and infrared radiometers, etc.provide a means to describe the cloud and storm characteristics and the local atmospheric state and partition the statistics of drop-size distribution observations. Larger-scale precipitation radar and satellite observations will also provide a context for partitioning the drop-size distribution variability at different scales.

Jensen, M. P.; Giangrande, S.; Bartholomew, M. J.

2010-12-01

375

Existing techniques were surveyed, an experimental procedure was developed, a laboratory test model was fabricated, limited data were recovered for proof of principle, and the relationship between particle size distribution and amplitude measurements was illustrated in an effort to develop a low cost, simplified optical technique for measuring particle size distributions and velocities in fluidized bed combustors and gasifiers. A He-Ne laser illuminated Rochi Rulings (range 10 to 500 lines per inch). Various samples of known particle size distributions were passed through the fringe pattern produced by the rulings. A photomultiplier tube converted light from the fringe volume to an electrical signal which was recorded using an oscilloscope and camera. The signal amplitudes were correlated against the known particle size distributions. The correlation holds true for various samples.

Smith, J. L.

1983-01-01

376

Ripening and Focusing of Aggregate Size Distributions with Overall Volume Growth

We explore the evolution of the aggregate size distribution in systems where aggregates grow by diffusive accretion of mass. Supersaturation is controlled in such a way that the overall aggregate volume grows linearly in time. Classical Ostwald ripening, which is recovered in the limit of vanishing overall growth, constitutes an unstable solution of the dynamics. In the presence of overall growth evaporation of aggregates always drives the dynamics into a new, qualitatively different growth regime where ripening ceases, and growth proceeds at a constant number density of aggregates. We provide a comprehensive description of the evolution of the aggregate size distribution in the constant density regime: the size distribution does not approach a universal shape, and even for moderate overall growth rates the standard deviation of the aggregate radius decays monotonically. The implications of this theory for the focusing of aggregate size distributions are discussed for a range of different settings including t...

Vollmer, J; Rohloff, M

2014-01-01

377

Droplet Size Distribution in Sprays Based on Maximization of Entropy Generation

Directory of Open Access Journals (Sweden)

Full Text Available Abstract: The maximum entropy principle (MEP, which has been popular in the modeling of droplet size and velocity distribution in sprays, is, strictly speaking, only applicable for isolated systems in thermodynamic equilibrium; whereas the spray formation processes are irreversible and non-isolated with interaction between the atomizing liquid and its surrounding gas medium. In this study, a new model for the droplet size distribution has been developed based on the thermodynamically consistent concept - the maximization of entropy generation during the liquid atomization process. The model prediction compares favorably with the experimentally measured size distribution for droplets, near the liquid bulk breakup region, produced by an air-blast annular nozzle and a practical gas turbine nozzle. Therefore, the present model can be used to predict the initial droplet size distribution in sprays.

Meishen Li

2003-12-01

378

Application of digital image analysis for size distribution measurements of microbubbles.

This work employs digital image analysis to measure the size distribution of microbubbles generated by the process of electroflotation for use in solid/liquid separation processes. Microbubbles are used for separations in the mineral processing industry a...

S. E. Burns S. Yiacoumi D. Frost C. Tsouris

1997-01-01

379

Distribution Functions of Sizes and Fluxes Determined from Supra-Arcade Downflows

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.

McKenzie, D.; Savage, S.

2011-01-01

380

DISTRIBUTION FUNCTIONS OF SIZES AND FLUXES DETERMINED FROM SUPRA-ARCADE DOWNFLOWS

International Nuclear Information System (INIS)

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 and 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.

2011-07-01

381

Air mass origin and its influence over the aerosol size distribution: a study in SE Spain

Digital Repository Infrastructure Vision for European Research (DRIVER)

A k-means cluster analysis of 96 hour trajectories arriving in Southeast (SE) Spain at 3000, 1500 and 500 m for the 7-year period 2000–2006 has been performed to identify and describe the main flows arriving at the study area. The dependence of the aerosol size distribution on the air mass origin has been studied by using non-parametric statistics. There are statistically significant differences on aerosol size distribution and meteorological variables at surface level according to the ...

Cabello, M.; Orza, J. A. G.; Galiano, V.

2008-01-01

382

Dust negative ion acoustic shock waves considering dust size distribution effect

Energy Technology Data Exchange (ETDEWEB)

A multi-ion dusty plasma containing hot isothermal electrons, ions (light positive ions and heavy negative ions), and extremely and negatively charged dust grains is studied in the present paper. The dust negative ion acoustic shock waves have been investigated by employing the reductive perturbation method. How the dust size distribution affects the height and the thickness of the nonlinear shock wave is studied. It is noted that the different dust size distribution has different shock wave form and different moving speed.

Ma Yirong; Wang Canglong; Zhang Jianrong; Sun Jianan; Duan Wenshan [College of Physics and Electronic Engineering and Joint Laboratory of Atomic and Molecular Physics of NWNU and IMP CAS, Northwest Normal University, Lanzhou 730070, China and Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Yang Lei [College of Physics and Electronic Engineering and Joint Laboratory of Atomic and Molecular Physics of NWNU and IMP CAS, Northwest Normal University, Lanzhou 730070 (China) and Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Department of Physics, Lanzhou University, Lanzhou 730000 (China)

2012-11-15

383

Pore size distribution of porous solid by gas-liquid chromatography

Energy Technology Data Exchange (ETDEWEB)

Based on the facts that the lowering of freezing point in capillaries is a function of their radii and the retention value bears an exponential relation to the reciprocal of absolute temperature above the melting point, a new method for the determination of pore size distribution is presented. The retention values determined below the freezing point of the partition liquid reflect the pore size distribution of solids with macropores. The results are in agreement with those obtained by mercury porosimetry. 2 references.

Wang Xinkui; Hu Lizhi; Peng Shaoyi

1985-09-01

384

Droplet Size Distribution in Sprays Based on Maximization of Entropy Generation

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract: The maximum entropy principle (MEP), which has been popular in the modeling of droplet size and velocity distribution in sprays, is, strictly speaking, only applicable for isolated systems in thermodynamic equilibrium; whereas the spray formation processes are irreversible and non-isolated with interaction between the atomizing liquid and its surrounding gas medium. In this study, a new model for the droplet size distribution has been developed based on the thermodynamically consist...

Xianguo Li; Meishen Li

2003-01-01

385

Zipf law and the firm size distribution: A critical discussion of popular estimators

Digital Repository Infrastructure Vision for European Research (DRIVER)

The upper tail of the firm size distribution is often assumed to follows a Power Law behavior. Recently, using different estimators and on different data sets, several papers conclude that this distribution follows the Zipf Law, that is that the fraction of firms whose size is above a given value is inversely proportional to the value itself. We compare the different methods through which this conclusion has been reached. We find that the family of estimators most widely adopted, based on an ...

Bottazzi, Giulio; Pirino, Davide; Tamagni, Federico

2013-01-01

386

Analysis of tecniques for measurement of the size distribution of solid particles

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 G...

Arouca, F. O.; Barrozo, M. A. S.; Damasceno, J. J. R.

2005-01-01

387

Size distributions, sources and source areas of water-soluble organic carbon in urban background air

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper represents the results of one year long measurement period of the size distributions of water-soluble organic carbon (WSOC), inorganic ions and gravimetric mass of particulate matter. Measurements were done at an urban background station (SMEAR III) by using a micro-orifice uniform deposit impactor (MOUDI). The site is located in northern European boreal region in Helsinki, Finland. The WSOC size distribution measurements were completed with the chemical analysis of inorganic ions,...

2008-01-01

388

Digital Repository Infrastructure Vision for European Research (DRIVER)

The plasmalemma of mature and growing olfactory axons of the bullfrog has been studied by freeze-fracture. Intramembrane particles (IMPs) of mature olfactory axons are found to be uniformly distributed along the shaft. However, during growth, a decreasing gradient of IMP density is evident along the somatofugal axis. The size histograms of axolemmal IMPs from different segments of growing nerve reveal regional differences in the particle composition. The distribution of each individual size c...

1984-01-01

389

Digital Repository Infrastructure Vision for European Research (DRIVER)

Below-cloud scavenging (BCS) coefficients of aerosols by rainfall are estimated for reported aerosol size distributions measured during field experiments in various environments. The method employed is based on explicit calculations of the efficiency of collision between a raindrop and aerosol particles. Such BCS coefficients can be used in numerical models that describe: 1) the detailed evolution of aerosol size distribution and, 2) the evolution of total aerosol mass concentration. The effe...

2003-01-01

390

The encapsulation of an amphiphile into polystyrene microspheres of narrow size distribution

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract Encapsulation of compounds into nano- or microsized organic particles of narrow size distribution is of increasing importance in fields of advanced imaging and diagnostic techniques and drug delivery systems. The main technology currently used for encapsulation of molecules within uniform template particles while retaining their size distribution is based on particle swelling methodology, involving penetration of emulsion droplets into the particles. The swelling method, ho...

Pellach Michal; Margel Shlomo

2011-01-01

391

Research of CWS’ Particle Size Distribution based on Ultrasonic Attenuation Theory

Digital Repository Infrastructure Vision for European Research (DRIVER)

the key to reduce coal pollution is the development of clean coal technology and the improvement of the backward coal-burning technology. The coal water slurry (CWS) is the first substitute of the oil. The particle size distribution of CWS plays an important role in the quality control of CWS. Now there are three