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

Determination of the size distribution of recombination products from atmospheric measurements

The role of ion-ion recombination in new particle formation is still unclear. In this work, we present a new method to estimate the size distribution of recombination products from atmospheric measurements. By applying our method to size distributions of charged and neutral clusters measured in Hyytiälä, Finland, we show that only a minor fraction of all sub-2nm neutral clusters originate from ion-ion recombination in boreal forest conditions.

Kontkanen, Jenni; Nieminen, Tuomo; Manninen, Hanna; Lehtipalo, Katrianne; Kerminen, Veli-Matti; Lehtinen, Kari E. J.; Kulmala, Markku

2013-05-01

3

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

Energy Technology Data Exchange (ETDEWEB)

In this paper we apply Stochastic Frontier Analysis through a distance function to investigate the impact of firm size on productivity development in electricity distribution. We use a sample of seventeen Brazilian firms from 1998 to 2005 and decompose productivity into technical efficiency, scale efficiency and technical change. Moreover, a further step is to decompose the technical change measurement into several components. The results indicate that firm size is important for industry's productivity, and therefore a key aspect to consider when making decisions that affect the market structure in the electricity distribution industry. (author)

Tovar, Beatriz [Departmento de Analisis Economico Aplicado y EIT, Universidad de Las Palmas de Gran Canaria (Spain); Javier Ramos-Real, Francisco [Departamento de Analisis Economico, Facultad de Ciencias Economicas y Empresariales, Campus de Guajara, Universidad de La Laguna, La Laguna, S/C de Tenerife, Espana (Spain); De Almeida, Edmar Fagundes [IE-UFRJ (Instituto de Economia-Universidade Federal do Rio de Janeiro) (Brazil)

2011-02-15

4

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

International Nuclear Information System (INIS)

[en] 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.

2009-08-28

5

International Nuclear Information System (INIS)

Fragments generated by high-velocity collisions between solid planetary bodies are one of the main sources of new interplanetary dust particles. However, only limited ranges of collision velocity, ejecta size, and target materials have been studied in previous laboratory experiments, and the collision condition that enables the production of dust-sized particles remains unclear. We conducted hypervelocity impact experiments on silicate rocks at relative velocities of 9 to 61 km s-1, which is beyond the upper limit of previous laboratory studies. Sub-millimeter-diameter aluminum and gold spheres were accelerated by laser ablation and were shot into dunite and basalt targets. We analyzed the surfaces of aerogel blocks deployed near the targets using an electron probe micro analyzer and counted the number of particles that contained the target material. The size distributions of ejecta ranged from five to tens of microns in diameter. The total cross-sectional area of dust-sized ejecta monotonically increased with the projectile kinetic energy, independent of impact velocity, projectile diameter, and projectile and target material compositions. The slopes of the cumulative ejecta-size distributions ranged from -2 to -5. Most of the slopes were steeper than the -2.5 or -2.7 that is expected for a collisional equilibrium distribution in a collision cascade with mass-independent or mass-dependent catastrophic disruption thresholds, respectively. This suggests that the steep dust size-distribution proposed for the debris disk around HD172555 (an A5V star) could be due to a hypervelocity collision.

2011-06-01

6

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

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

2004-04-01

8

Modelling adipocytes size distribution.

UK PubMed Central (United Kingdom)

Adipocytes are cells whose task is to store excess energy as lipid droplets in their cytoplasm. Adipocytes can adapt their size according to the lipid amount to be stored. Adipocyte size variation can reach one order of magnitude inside the same organism which is unique among cells. A striking feature in adipocytes size distribution is the lack of characteristic size since typical size distributions are bimodal. Since energy can be stored and retrieved and adipocytes are responsible for these lipid fluxes, we propose a simple model of size-dependent lipid fluxes that is able to predict typical adipocytes size distribution.

Soula HA; Julienne H; Soulage CO; Géloën A

2013-09-01

9

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 is being accomplished by mathematical modeling of the grinding circuits 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 advanced technologies to improve comminution efficiency and produce sharper product size distributions with less overgrinding.

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

2005-01-01

10

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 is being accomplished by mathematical modeling of the grinding circuits to determine how to correct this problem. The approaches taken included (1) Modeling of the circuit to determine process bottlenecks that restrict flow rates 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 advanced technologies to improve comminution efficiency and produce sharper product size distributions with less overgrinding.

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

2005-03-31

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

International Nuclear Information System (INIS)

The impact of natural solar ultraviolet radiation (UVR), particularly UVB (297-320 nm), on phytoplankton primary production in Lake Erie was investigated during the spring and summer of 1997. Radiocarbon incorporation and size-selective filtration was used to trace total production and its distribution among particulate and dissolved pools. On average, 1-h exposures produced half the UVB-dependent inhibition of total production realized in 8-h exposures, indicating rapid kinetics of photoinhibition. Cumulative UVB-dependent photoinhibition averaged 36% in 8-h simulated surface exposures. The efficiency of photoinhibition was greater for N-deficient than N-replete communities, but was not related to phytoplankton light history, P limitation, or the dominant genera. The proportion of recently fixed carbon occurring in the dissolved pool after 8-h exposures was significantly greater in higher-UVB treatments, whereas the share in picoplankton (

2002-01-01

13

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

14

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

15

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 he 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 previous quarters, it was determined that the primary grinding mills were operating at less than full capacity, suggesting that a shift of grinding load to the primary mills could liberate more material before it reached the secondary mills, allowing more complete liberation with a coarser grind. In the eighth quarter, further analysis was carried out to determine the full extent of the benefit that could be obtained by this shift in grinding load. A key part of this analysis was the development of a correlation of the circuit capacity with (a) ore work index, (b) the quantity of primary mill ''pebbles'' that were crushed by a cone crusher in the circuit, and (c) the fraction of the crushed pebbles that were also processed by a high-pressure roll mill.

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

2003-01-01

16

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

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. 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

18

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; W.M.A. Wan Daud; F.S. Mjalli

2010-01-01

19

International Nuclear Information System (INIS)

In order to assess the exposure of individuals to the presence of indoor radioactivity arising from the decay of radon, an automated, semicontinuous graded screen array system was developed to permit the measurement of the activity-weighted size distributions of the radon progeny in homes. The system has been modified so that the electronics and sampling heads can be separated from the pump by approximately 15 m. The system was placed in the living room of a one-storey house with basement in Princeton, NJ and operated for 2 weeks while the house was occupied by the home owners in their normal manner. One of the house occupants was a cigarette smoker. Radon and potential alpha energy concentration (PAEC) measurements were also made, but condensation nuclei counts were not performed. PAEC values ranged from 23.4 to 461.6 mWL. In the measured activity size distributions, the amount of activity in the 0.5-1.5 nm size range can be considered to be the unattached fraction. The mean value for the 218Po unattached fraction is 0.217 with a range of 0.054-0.549. The median value for the unattached fraction of PAEC is 0.077 with a range of 0.022-0.178. (author).

1992-01-01

20

International Nuclear Information System (INIS)

More knowledge was gained by this study about the non-adsorbed share of short-lived radon and thoron decay products, about the sources and concentrations of thoron in residential buildings and about the size distribution of the non-adsorbed share of short-lived radon decay products. The results gained were taken to improve the calculation of dose conversion factors important for assessing the general population's radiation exposure to radon and thoron decay products. This also produces a better understanding of the mechanisms governing the physical behaviour of radioactive noble gases and their decay products. (orig./HP).

1994-01-01

21

International Nuclear Information System (INIS)

[en] During deactivation and decommissioning activities, thermal cutting tools, such as plasma torch, laser, and gasoline torch, are used to cut metals. These activities generate fumes, smoke and particulates. These airborne species of matter, called aerosols, may be inhaled if suitable respiratory protection is not used. Inhalation of the airborne metallic aerosols has been reported to cause ill health effects, such as acute respiratory syndrome and chromosome damage in lymphocytes. In the nuclear industry, metals may be contaminated with radioactive materials. Cutting these metals, as in size reduction of gloveboxes and tanks, produces high concentrations of airborne transuranic particles. Particles of the respirable size range (size

2001-01-01

22

Body size distribution of the dinosaurs.

UK PubMed Central (United Kingdom)

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

O'Gorman EJ; Hone DW

2012-01-01

23

Comparing two mass size distributions

Scientific Electronic Library Online (English)

Full Text Available 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 sensitive 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 betwe (more) en two mass size distributions. The calculation of the rank statistic is explained in detail and its application is illustrated on two sets of data.

Lombard, F.; Lyman, G.J.

2012-07-01

24

UK PubMed Central (United Kingdom)

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.

Yamamoto Y; Suzuki T; Matsumoto M; Ohtani M; Hayano S; Fukami T; Tomono K

2012-01-01

25

Urban aerosol number size distributions

Directory of Open Access Journals (Sweden)

Full Text Available Aerosol number size distributions have been measured since 5 May 1997 in Helsinki, Finland. The presented aerosol data represents size distributions within the particle diameter size range 8-400nm during the period from May 1997 to March 2003. The daily, monthly and annual patterns of the aerosol particle number concentrations were investigated. The temporal variation of the particle number concentration showed close correlations with traffic activities. The highest total number concentrations were observed during workdays; especially on Fridays, and the lowest concentrations occurred during weekends; especially Sundays. Seasonally, the highest total number concentrations were observed during winter and spring and lower concentrations were observed during June and July. More than 80% of the number size distributions had three modes: nucleation mode (30nm), Aitken mode (20-100nm) and accumulation mode (}$'>90nm). Less than 20% of the number size distributions had either two modes or consisted of more than three modes. Two different measurement sites were used; in the first (Siltavuori, 5.5.1997-5.3.2001), the arithmetic means of the particle number concentrations were 7000cm, 6500cm, and 1000cm respectively for nucleation, Aitken, and accumulation modes. In the second site (Kumpula, 6.3.2001-28.2.2003) they were 5500cm, 4000cm, and 1000cm. The total number concentration in nucleation and Aitken modes were usually significantly higher during workdays than during weekends. The temporal variations in the accumulation mode were less pronounced. The lower concentrations at Kumpula were mainly due to building construction and also the slight overall decreasing trend during these years. During the site changing a period of simultaneous measurements over two weeks were performed showing nice correlation at both sites.

T. Hussein; A. Puustinen; P. P. Aalto; J. M. Mäkelä; K. Hämeri; M. Kulmala

2004-01-01

26

Urban aerosol number size distributions

Directory of Open Access Journals (Sweden)

Full Text Available Aerosol number size distributions were measured continuously in Helsinki, Finland from 5 May 1997 to 28 February 2003. The daily, monthly and annual patterns were investigated. The temporal variation of the particle number concentration was seen to follow the traffic density. The highest total particle number concentrations were usually observed during workdays; especially on Fridays, and the lower concentrations occurred during weekends; especially Sundays. Seasonally, the highest total number concentrations were usually observed during winter and spring and the lowest during June and July. More than 80\\% of the particle number size distributions were tri-modal: nucleation mode (Dp < 30 nm), Aitken mode (20–100 nm) and accumulation mode (Dp > 90 nm). Less than 20% of the particle number size distributions have either two modes or consisted of more than three modes. Two different measurement sites are used; in the first place (Siltavuori, 5 May 1997–5 March 2001), the overall means of the integrated particle number concentrations were 7100 cm?3, 6320 cm?3, and 960 cm?3, respectively, for nucleation, Aitken, and accumulation modes. In the second site (Kumpula, 6 March 2001–28 February 2003) they were 5670 cm?3, 4050 cm?3, and 900 cm?3. The total number concentration in nucleation and Aitken modes were usually significantly higher during weekdays than during weekends. The variations in accumulation mode were less pronounced. The smaller concentrations in Kumpula were mainly due to building construction and also slight overall decreasing trend during these years. During the site changing a period of simultaneous measurements over two weeks were performed showing nice correlation in both sites.

T. Hussein; A. Puustinen; P. P. Aalto; J. M. Mäkelä; K. Hämeri; M. Kulmala

2003-01-01

27

Lorenz Curves, Size Classification, and Dimensions of Bubble Size Distributions

Directory of Open Access Journals (Sweden)

Full Text Available Lorenz curves of bubble size distributions and their Gini coefficients characterize demixing processes. Through a systematic size classification, bubble size histograms are generated and investigated concerning their statistical entropy. It turns out that the temporal development of the entropy is preserved although characteristics of the histograms like number of size classes and modality are remarkably reduced. Examinations by Rényi dimensions show that the bubble size distributions are multifractal and provide information about the underlying structures like self-similarity.

Sonja Sauerbrei

2009-01-01

28

Lorenz Curves, Size Classification, and Dimensions of Bubble Size Distributions

Digital Repository Infrastructure Vision for European Research (DRIVER)

Lorenz curves of bubble size distributions and their Gini coefficients characterize demixing processes. Through a systematic size classification, bubble size histograms are generated and investigated concerning their statistical entropy. It turns out that the temporal development of the entropy is p...

Sonja Sauerbrei

29

Size distribution of LLNL coarse fill

Energy Technology Data Exchange (ETDEWEB)

The distributions of particle size in the coarse fill used by Lawrence Livermore Laboratory (LLL) were investigated. The relative frequency and cumulative distributions by mass were expressed as truncated lognormal distributions. Nominal particle diameter was found as a linear function of particle size. On the basis of this relation and the distributions by mass, the frequency and cumulative distributions by count were determined. This information may aid in understanding stemming phenomena such as slumps, cable and pipe loading, and cable damage.

Griffiths, S.K.

1981-05-20

30

Patchy Distributions: Optimizing Sample Size.

Discusses a technique for estimating sample size that does not require an a priori definition of desired precision. Presents five modifications that make the method easier to use and reduce the probability of estimating a larger sample size than necessary. The technique can guide the design of environmental sampling programs. (Contains 31…

Hewitt, J. E.; And Others

1993-01-01

31

Grain Size Distributions and Soil Particle Characteristics

Lecture notes focusing on measuring grain size distributions (GSDs) of soils and the two methods used to do this. Provides procedures for Sieve Testing and Hydrometer Testing to find the GSD for particular grain sizes.

2008-06-13

32

Gradually Truncated Log-normal distribution - Size distribution of firms

Gradually Truncated Log-normal distribution - Size distribution of firms Abstract Many natural and economical phenomena are described through power law or log- normal distributions. In these cases, probability decreases very slowly with step size compared to normal distribution. Thus it is essential to cut-off these distributions for larger step size. Recently we introduce the gradually truncated power law distribution to successfully describe variation of financial, educational, physical and citation index. In the present work, we introduce gradually truncated log-normal distribution in which we gradually cut- off larger steps due to physical limitation of the system. We applied this distribution successfully to size distribution of USA.\\'{}s manufactoring firms which is measured through their annual sell. The physical limitation are due to limited market size or shortage of highly competent executives.

Sen-Gupta, H M; Gupta, Hari M.; Campanha, Jose R.

2001-01-01

33

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

34

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

1993-01-01

35

Scaling in animal group-size distributions.

UK PubMed Central (United Kingdom)

An elementary model of animal aggregation is presented. The group-size distributions resulting from this model are truncated power laws. The predictions of the model are found to be consistent with data that describe the group-size distributions of tuna fish, sardinellas, and African buffaloes.

Bonabeau E; Dagorn L; Fréon P

1999-04-01

36

Scaling in Animal Group-Size Distributions

An elementary model of animal aggregation is presented. The group-size distributions resulting from this model are truncated power laws. The predictions of the model are found to be consistent with data that describe the group-size distributions of tuna fish, sardinellas, and African buffaloes.

Bonabeau, Eric; Dagorn, Laurent; Freon, Pierre

1999-04-01

37

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...

Buch, Claudia M; Koch, Cathérine; Koetter, Michael

38

Universality of rain event size distributions

We compare rain event size distributions derived from measurements in climatically different regions, which we find to be well approximated by power laws of similar exponents over broad ranges. Differences can be seen in the large-scale cutoffs of the distributions. Event duration distributions suggest that the scale-free aspects are related to the absence of characteristic scales in the meteorological mesoscale.

Peters, O; Corral, A; Neelin, J D; Holloway, C E

2010-01-01

39

Intelligent Distributed Production Control

This editorial introduces the special issue of the Springer journal, Journal of Intelligent Manufacturing, on intelligent distributed production control. This special issue contains selected papers presented at the 13th IFAC Symposium on Information Control Problems in Manufacturing - INCOM'2009 (Bakhtadze and Dolgui, 2009). The papers in this special issue were selected because of their high quality and their specific way of addressing the variety of issues dealing with intelligent distributed production control. Previous global discussions about the state of the art in intelligent distributed production control are provided, as well as exploratory guidelines for future research in this area.

Thomas, André; Valckenaers, Paul

2011-01-01

40

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

41

KERNEL SIZE DISTRIBUTIONS IN NAKED OATS.

Oat kernel size uniformity is important to the oat milling industry because of the importance of kernel size to impact dehulling settings for optimal dehulling efficiency. Normal hulled oats appear to have bimodal distributions, which appear to be related to the architecture of the oat spikelet. Mos...

42

International Nuclear Information System (INIS)

[en] 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/Peq, 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/Peq coefficients indicate the effective dose E per unit exposure Peq to radon decay products. (orig./CB)[de] 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/Peq mit dem PC-Programm RADEP berechnet; RADEP wurde von BIRCHALL und JAMES entwickelt

1997-01-01

43

Exponential size distribution of von Willebrand factor.

UK PubMed Central (United Kingdom)

Von Willebrand Factor (VWF) is a multimeric protein crucial for hemostasis. Under shear flow, it acts as a mechanosensor responding with a size-dependent globule-stretch transition to increasing shear rates. Here, we quantify for the first time, to our knowledge, the size distribution of recombinant VWF and VWF-eGFP using a multilateral approach that involves quantitative gel analysis, fluorescence correlation spectroscopy, and total internal reflection fluorescence microscopy. We find an exponentially decaying size distribution of multimers for recombinant VWF as well as for VWF derived from blood samples in accordance with the notion of a step-growth polymerization process during VWF biosynthesis. The distribution is solely described by the extent of polymerization, which was found to be reduced in the case of the pathologically relevant mutant VWF-IIC. The VWF-specific protease ADAMTS13 systematically shifts the VWF size distribution toward smaller sizes. This dynamic evolution is monitored using fluorescence correlation spectroscopy and compared to a computer simulation of a random cleavage process relating ADAMTS13 concentration to the degree of VWF breakdown. Quantitative assessment of VWF size distribution in terms of an exponential might prove to be useful both as a valuable biophysical characterization and as a possible disease indicator for clinical applications.

Lippok S; Obser T; Müller JP; Stierle VK; Benoit M; Budde U; Schneppenheim R; Rädler JO

2013-09-01

44

Exponential size distribution of von Willebrand factor.

Von Willebrand Factor (VWF) is a multimeric protein crucial for hemostasis. Under shear flow, it acts as a mechanosensor responding with a size-dependent globule-stretch transition to increasing shear rates. Here, we quantify for the first time, to our knowledge, the size distribution of recombinant VWF and VWF-eGFP using a multilateral approach that involves quantitative gel analysis, fluorescence correlation spectroscopy, and total internal reflection fluorescence microscopy. We find an exponentially decaying size distribution of multimers for recombinant VWF as well as for VWF derived from blood samples in accordance with the notion of a step-growth polymerization process during VWF biosynthesis. The distribution is solely described by the extent of polymerization, which was found to be reduced in the case of the pathologically relevant mutant VWF-IIC. The VWF-specific protease ADAMTS13 systematically shifts the VWF size distribution toward smaller sizes. This dynamic evolution is monitored using fluorescence correlation spectroscopy and compared to a computer simulation of a random cleavage process relating ADAMTS13 concentration to the degree of VWF breakdown. Quantitative assessment of VWF size distribution in terms of an exponential might prove to be useful both as a valuable biophysical characterization and as a possible disease indicator for clinical applications. PMID:24010664

Lippok, Svenja; Obser, Tobias; Müller, Jochen P; Stierle, Valentin K; Benoit, Martin; Budde, Ulrich; Schneppenheim, Reinhard; Rädler, Joachim O

2013-09-01

45

Eroded aggregate size distributions from disturbed lands

Energy Technology Data Exchange (ETDEWEB)

A characterization of eroded soil properties, especially size, is required for proper usage of modern process-based soil erosion models. In a study addressing reclaimed mine land erodibility, over 350 measured eroded aggregate size distributions were collected from erosion plots created on reclaimed and nearby unmined soils at three separate strip mine sites. The experimental design allowed for a comparison of eroded aggregate size distributions as a function of land slope, run sequence, and reclamation treatment. Distributions taken from topsoil and unmined soil treatments were used to develop five regression equations to predict the percentage of total eroded soil mass falling into each of five size classes - clay, silt, and three sand sizes. A stepwise, multivariate regression technique was used to select the best independent variables from 30 soil parameters. Independent variables that proved to be significant in at least one equation include primary particle and water stable aggregate size distributions, bulk density, organic carbon, and soil moisture. The number of significant independent variables ranges from II to 15 and correlation coefficients (R{sub 2}) range from 0.77 to 0.53, which is a general improvement over previously published prediction methods.

Armstrong, S.M.; Stein, O.R. [Montana State University, Bozeman, MT (United States). Dept. of Civil Engineering

1996-01-01

46

Taxonomic Size Frequency Distributions By Dynamical Zone

We investigate the size-frequency distribution of major asteroid taxonomic classes by combining data from the recent Wide-field Infrared Survey Explorer (WISE) and Carvano et al.'s (2010) Sloan Digital Sky Survey (SDSS) based taxonomy. Prior to WISE the limited scope of albedo and diameter studies restricted our understanding of taxonomic size frequency distributions. Our research using the new WISE database extends the number of asteroids analyzed from 4,000 to over 8,000 and expands on previous work by focusing on asteroid classes S, C, X (and its subclasses), and D. We remove asteroids belonging to the major asteroid families as defined by Nesvorny (2010) and control for collisional environment by using dynamical zones as defined by Cellino et al. (1991). Understanding the taxonomic size frequency distributions provides insight into the collisional evolution of asteroids in each class. Our results can be extrapolated to infer the overall volume of each class.

Murphy, Amy; Ziffer, J.; Campins, H.; Kelley, M. S.; Wooden, D. H.

2012-10-01

47

Product Name Placement, Size, and Prominence in ...

Text VersionPage 1. Guidance for Industry Product Name Placement, Size, and ... Advertising Page 2. Guidance for Industry Product Name Placement, Size, and ... More results from www.fda.gov/downloads/drugs/guidancecomplianceregulatoryinformation

48

UK PubMed Central (United Kingdom)

Oil-containing polyterephthalamide microcapsules were prepared by the interfacial polymerization technique. The inner phase of the microcapsules consisted of a mixture of an organic solvent, toluene, and a commercial oil, santosol. Microcapsules with mean Sauter diameters in the range 0.5-20 microns were prepared by varying the rate of agitation (2000-7000 rpm) and the concentration of a poly(vinyl alcohol) stabilizer (0.1-1.0 wt% w/v), in the presence of several ionic and non-ionic cosurfactants. High agitation rates resulted in a significant reduction of the mean size of the oil droplets, although a slight increase in the breadth of the droplet size distribution was observed. High concentrations of PVA also resulted in a decrease of the microcapsule size, although the effect of stabilizer concentration was generally less important than that of the agitation speed. Finally, the effect of various ionic and non-ionic cosurfactants on the microcapsule size distribution was investigated. It was found that the addition of a cosurfactant significantly reduced the mean droplet size of the initial emulsion, leading to the formation of microcapsules in the submicron range.

Alexandridou S; Kiparissides C

1994-11-01

49

Suitable particle size distribution of coke fines for sintering

Energy Technology Data Exchange (ETDEWEB)

Combustion kinetics were analysed to determine the optimum size distribution of coke for sintering ilmenite. A composition of 30% 3-5 mm and 70% {lt}3 mm gave increased productivity and sinter quality as well as a lower fuel consumption.

Xu Li (and others)

1991-01-01

50

Genome sizes and the Benford distribution.

UK PubMed Central (United Kingdom)

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 JL; Goldman T; Pérez-Mercader J

2012-01-01

51

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

52

Radioactive Aerosol Size Distribution Measured in Nuclear Workplaces

International Nuclear Information System (INIS)

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

2002-05-22

53

Particle-size distribution study: PILEDRIVER event

International Nuclear Information System (INIS)

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

1970-01-01

54

Optical method for particle size distribution analysis

International Nuclear Information System (INIS)

Full text: Particle size distribution is one important parameter in powder fabrication developments; it has been decided to use a method complementary to sedimentation method. Thus, the optical method was chosen for that purpose, since it can give additional information, such as identification of geometrical parameters in particles without spherical symmetry and account for those particles, with diameters above 100 microns, that sediment before the run starts. On the other hand, through the use of electronic microscopes it is possible to observe particle sizes lower than 0.1 micron, which is the limit of the sedimentation techniques. It is also possible not to depend on the arbitrary selection of particle density, which is difficult to estimate in the case of compounds with internal porosity. To make this method operative, and to use it normally, it is necessary to have an automatic system of image analysis, which allows to separate the particles for its counting and qualification. Therefore, it is necessary that the particles could be seen in screen separately, individually, without superposing. As in the sedimentation techniques, it is necessary to find the conditions to disperse the particles, in such a way that they can set individually in the slide. In this work, the necessary steps to reach the optical measurement and the method used to perform it, are explained. Distributions of calibrated populations, perfect spheres and particles of varied and irregular morphologies, performed by both methods, are compared, and the correspondence and application range of both is intended to find. Distributions with different number of particles are analyzed, in order to determine the necessary minimum quantity of particles to enable a regular distribution. Also, how dependent is the population considered on the sample diameters dispersion and the number of images at different increases, necessary to cover the selected population

1999-01-01

55

Charge and Size Distributions of Electrospray Drops

The distributions of charge q and diameter d of drops emitted from electrified liquid cones in the cone-jet mode are investigated with two aerosol instruments. A differential mobility analyzer (DMA, Vienna type) first samples the spray drops, selects those with electrical mobilities within a narrow band, and either measures the associated current or passes them to a second instrument. The drops may also be individually counted optically and sized by sampling them into an aerodynamic size spectrometer (API's Aerosizer). For a given cone-jet, the distribution of charge q for the main electrospray drops is some 2.5 times broader than their distribution of diameters d, with qmax/qmin approximately 4. But mobility-selected drops have relative standard deviations of only 5% for both d and q, showing that the support of the (q, d) distribution is a narrow band centered around a curve q(d). The approximate one-dimensionality of this support region is explained through the mechanism of jet breakup, which is a random process with only one degree of freedom: the wavelength of axial modulation of the jet. The observed near constancy of the charge over volume ratio (q approximately d3) shows that the charge is frozen in the liquid surface at the time scale of the breakup process. The charge over volume ratio of the primary drops varies between 98 and 55% of the ratio of spray current I over liquid flow rate Q, and decreases at increasing Q. I/Q is therefore an unreliable measure of the charge density of these drops. PMID:9056353

de Juan L; de la Mora JF

1997-02-15

56

Refinement of size distributions for primary crystallizations

International Nuclear Information System (INIS)

[en] 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

1998-01-01

57

What determines the grain size distribution in galaxies?

We construct a dust evolution model taking into account the grain size distribution, and investigate what kind of dust processes determine the grain size distribution at each stage of galaxy evolution. In addition to the dust production by type II supernovae (SNeII) and asymptotic giant branch (AGB) stars, we consider three processes in the ISM: (i) dust destruction by SN shocks, (ii) metal accretion onto the surface of preexisting grains in the cold neutral medium (CNM) (called grain growth), and (iii) grain-grain collisions (shattering and coagulation) in the warm neutral medium (WNM) and CNM. We found that the grain size distribution in galaxies is controlled by stellar sources in the early stage of galaxy evolution, and that afterwards the main processes that govern the size distribution changes to those in the ISM. Since shattering produces a large abundance of small grains (consequently, the surface-to-volume ratio of grains increases), it enhances the efficiency of grain growth, contributing to the sig...

Asano, Ryosuke S; Hirashita, Hiroyuki; Nozawa, Takaya

2013-01-01

58

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

59

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

60

Aerosol size distribution of the radon progeny in outdoor air

Energy Technology Data Exchange (ETDEWEB)

The activity size distribution of the short-lived radon decay products in ambient air was measured continuously over several weeks. Two different measurement techniques were used: A direct measurement with a low-pressure on-line alpha cascade impactor (OLACI) and an indirect determination based on measurement with a differential mobility analyser (5-200 nm) and a laser aerosol spectrometer (100-5000 nm). In parallel, the meteorological parameters like temperature, rainfall intensity and wind velocity were registered. The measured activity size distribution of the radon progeny can be approximated by a sum of three log-normal distributions. The greatest activity fraction was adsorbed on aerosol particles in the accumulation size range (100-1000 nm) with activity median diameters (AMD{sub a}) and geometric standard deviations ({sigma}{sub ga}) values of 250-450 nm, and 1.5-3.0, respectively. The influence of the weather conditions on the activity of the accumulation particles was not significant. In contrast to the results of measurements in houses, a small but significant fraction of the radon progeny (average value: 2%) was attached to coarse particles (>1000 nm). This fraction varied between 0 and 10%. The direct measurements with the OLACI yielded a higher activity fraction (20-40%) in the nucleation size range (<100 nm) compared to the values evaluated from the number size distribution measurement (indirect measurement). This fraction depends on the number concentration of the atmospheric aerosol in this size range. A diurnal variation of the particle number concentration and of the activity fraction for the nucleation particles was found. In the case of lower particle concentrations (diameters <50 nm) in air during the night no nucleation mode was registered using the indirect measurement technique.

Porstendoerfer, J. E-mail: jporste@gwdg.de; Zock, Ch.; Reineking, A

2000-10-01

61

Aerosol size distribution of the radon progeny in outdoor air

International Nuclear Information System (INIS)

The activity size distribution of the short-lived radon decay products in ambient air was measured continuously over several weeks. Two different measurement techniques were used: A direct measurement with a low-pressure on-line alpha cascade impactor (OLACI) and an indirect determination based on measurement with a differential mobility analyser (5-200 nm) and a laser aerosol spectrometer (100-5000 nm). In parallel, the meteorological parameters like temperature, rainfall intensity and wind velocity were registered. The measured activity size distribution of the radon progeny can be approximated by a sum of three log-normal distributions. The greatest activity fraction was adsorbed on aerosol particles in the accumulation size range (100-1000 nm) with activity median diameters (AMDa) and geometric standard deviations (?ga) values of 250-450 nm, and 1.5-3.0, respectively. The influence of the weather conditions on the activity of the accumulation particles was not significant. In contrast to the results of measurements in houses, a small but significant fraction of the radon progeny (average value: 2%) was attached to coarse particles (>1000 nm). This fraction varied between 0 and 10%. The direct measurements with the OLACI yielded a higher activity fraction (20-40%) in the nucleation size range (

2000-01-01

62

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.

1995-01-01

63

Atmospheric Ion Clusters: Properties and Size Distributions

Ions are continuously generated in the atmosphere by the action of galactic cosmic radiation. Measured charge concentrations are of the order of 103 ~ {cm-3} throughout the troposphere, increasing to about 5 x 103 ~ {cm-3} in the lower stratosphere [Cole and Pierce, 1965; Paltridge, 1965, 1966]. The lifetimes of these ions are sufficient to allow substantial clustering with common trace constituents in air, including water, nitric and sulfuric acids, ammonia, and a variety of organic compounds [e.g., D'Auria and Turco, 2001 and references cited therein]. The populations of the resulting charged molecular clusters represent a pre-nucleation phase of particle formation, and in this regard comprise a key segment of the over-all nucleation size spectrum [e.g., Castleman and Tang, 1972]. It has been suggested that these clusters may catalyze certain heterogeneous reactions, and given their characteristic crystal-like structures may act as freezing nuclei for supercooled droplets. To investigate these possibilities, basic information on cluster thermodynamic properties and chemical kinetics is needed. Here, we present new results for several relevant atmospheric ion cluster families. In particular, predictions based on quantum mechanical simulations of cluster structure, and related thermodynamic parameters, are compared against laboratory data. We also describe a hybrid approach for modeling cluster sequences that combines laboratory measurements and quantum predictions with the classical liquid droplet (Thomson) model to treat a wider range of cluster sizes. Calculations of cluster mass distributions based on this hybrid model are illustrated, and the advantages and limitations of such an analysis are summarized. References: Castelman, A. W., Jr., and I. N. Tang, Role of small clusters in nucleation about ions, J. Chem. Phys., 57, 3629-3638, 1972. Cole, R. K., and E. T. Pierce, Electrification in the Earth's atmosphere for altitudes between 0 and 100 kilometers, J. Geophys. Res. 70, 2735-2749, 1965. D'Auria, R. and R. P. Turco, Ionic clusters in the polar winter stratosphere, Geophys. Res. Lett., 28, 3871-3874, 2001. Paltridge, G. W., Experimental measurements of the small-ion density and electrical conductivity of the stratosphere, J. Geophys. Res. 70, 2751,2761, 1965. Paltridge, G. W., Stratospheric small-ion density measurements from a high-altitude jet aircraft, J. Geophys. Res. 71, 1945-1952, 1966.

D'Auria, R.; Turco, R. P.

2002-12-01

64

Isotope production and distribution

Energy Technology Data Exchange (ETDEWEB)

The DOE intends to ensure a reliable supply of essential isotopes. In deciding which isotope products and services to support, the DOE will give preference to medical applications and research and development.

Lowe, O.W. [Department of Energy, Washington, DC (United States); Schenter, R.E. [Westinghouse Hanford Company, Richland, WA (United States)

1995-12-31

65

Isotope production and distribution

International Nuclear Information System (INIS)

The DOE intends to ensure a reliable supply of essential isotopes. In deciding which isotope products and services to support, the DOE will give preference to medical applications and research and development

1995-01-01

66

Evolution of grain size distribution during deformation of superplastic materials

Energy Technology Data Exchange (ETDEWEB)

Grain size distribution and its evolution during superplastic deformation has been studied for two materials- ultrahigh carbon steel, which has a two phase microstructure, and a copper alloy, which has a quasi-single phase microstructure. For both materials the distribution of initial grain size is very accurately represented by a lognormal throughout the deformation history. The evolution of the parameters characterizing the log normal distribution have also been studied and found to vary in a systematic manner results. Results can be used to specify the grain size distribution as a function of strain during superplastic deformation and thus should prove useful for computational studies in which grain size distribution is evaluated.

Lesuer, D.R.; Glaser, R.; Syn, C.K.

1997-10-28

67

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. © 2013 Informa Healthcare USA, Inc.

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

2013-01-01

68

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

69

Principles of grain size distribution of crushed coal

Energy Technology Data Exchange (ETDEWEB)

Mathematical and statistical methods are discussed for forecasting grain size distribution of black coal and anthracite after comminution which occurs during coal handling in coal mines. Conventional functions which are used for description of coal grain size distribution are reviewed. Investigations carried out by the IGD im. A.A. Skochinski Institute are evaluated. Equations which characterize effects of coal comminution and coal grain size distribution after comminution are derived. Analyses show that grain size distribution of coal is a function of coal mechanical properties and work of coal comminution. 2 references.

Borisenko, A.A.

1985-04-01

70

The Mars Spherule Size Distribution and the Impact Hypothesis

Opportunity Pancam images are used to determine the spherule size distributions from Endurance to Victoria. The Sequential Fragmentation/Transport model offers a coherent interpretation of these distributions implying formation by accretion.

Royer, D.; Burt, D. M.; Wohletz, K. H.

2008-03-01

71

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.

Juan Carlos Pérez Mesa; Emilio Galdeano-Gómez

2009-01-01

72

Resonance-induced multimodal body-size distributions in ecosystems.

UK PubMed Central (United Kingdom)

The size of an organism reflects its metabolic rate, growth rate, mortality, and other important characteristics; therefore, the distribution of body size is a major determinant of ecosystem structure and function. Body-size distributions often are multimodal, with several peaks of abundant sizes, and previous studies suggest that this is the outcome of niche separation: species from distinct peaks avoid competition by consuming different resources, which results in selection of different sizes in each niche. However, this cannot explain many ecosystems with several peaks competing over the same niche. Here, we suggest an alternative, generic mechanism underlying multimodal size distributions, by showing that the size-dependent tradeoff between reproduction and resource utilization entails an inherent resonance that may induce multiple peaks, all competing over the same niche. Our theory is well fitted to empirical data in various ecosystems, in which both model and measurements show a multimodal, periodically peaked distribution at larger sizes, followed by a smooth tail at smaller sizes. Moreover, we show a universal pattern of size distributions, manifested in the collapse of data from ecosystems of different scales: phytoplankton in a lake, metazoans in a stream, and arthropods in forests. The demonstrated resonance mechanism is generic, suggesting that multimodal distributions of numerous ecological characters emerge from the interplay between local competition and global migration.

Lampert A; Tlusty T

2013-01-01

73

Knife mill operating factors effect on switchgrass particle size distributions

Energy Technology Data Exchange (ETDEWEB)

Biomass particle size impacts handling, storage, conversion, and dust control systems. Switchgrass (Panicum virgatum L.) particle size distributions created by a knife mill were determined for integral classifying screen sizes from 12.7 to 50.8 mm, operating speeds from 250 to 500 rpm, and mass input rates from 2 to 11 kg/min. Particle distributions were classified with standardized sieves for forage analysis that included horizontal sieving motion with machined-aluminum sieves of thickness proportional to sieve opening dimensions. Then, a wide range of analytical descriptors were examined to mathematically represent the range of particle sizes in the distributions. Correlation coefficient of geometric mean length with knife mill screen size, feed rate, and speed were 0.872, 0.349, and 0.037, respectively. Hence, knife mill screen size largely determined particle size of switchgrass chop. Feed rate had an unexpected influence on particle size, though to a lesser degree than screen size. The Rosin Rammler function fit the chopped switchgrass size distribution data with an R2 > 0.982. Mass relative span was greater than 1, which indicated a wide distribution of particle sizes. Uniformity coefficient was more than 4.0, which indicated a large assortment of particles and also represented a well-graded particle size distribution. Knife mill chopping of switchgrass produced strongly fine skewed mesokurtic particles with 12.7 25.4 mm screens and fine skewed mesokurtic particles with 50.8 mm screen. Results of this extensive analysis of particle sizes can be applied to selection of knife mill operating parameters to produce a particular size of switchgrass chop, and will serve as a guide for relations among the various analytic descriptors of biomass particle distributions.

Bitra, V.S.P. [University of Tennessee; Womac, A.R. [University of Tennessee; Yang, Y.T. [University of Tennessee; Igathinathane, C. [Mississippi State University (MSU); Miu, P.I [University of Tennessee; Chevanan, Nehru [University of Tennessee; Sokhansanj, Shahabaddine [ORNL

2009-06-01

74

Production of uniformly sized serum albumin and dextrose microbubbles.

Uniformly-sized preparations with average microbubble (MB) diameters from 1 to 7 ?m 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). PMID:21689961

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

2011-05-27

75

Production of uniformly sized serum albumin and dextrose microbubbles.

UK PubMed Central (United Kingdom)

Uniformly-sized preparations with average microbubble (MB) diameters from 1 to 7 ?m 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 MJ; O'Brien WD Jr; Bernock LJ; Williams HR; Hamilton E; Wu J; Oelze ML; Culp WC

2012-01-01

76

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

77

Directory of Open Access Journals (Sweden)

Full Text Available Step-Up Protein (SUP) rearing regimens can reduce Feed Consumption (FC) and Body Weight (BW), while still resulting in pullets with equal or superior egg production and egg mass to pullets grown on a Step-Down Protein (SDP) program. Egg weight has been reduced due to SUP programs, presumably due to the reduced BW at sexual maturity. Because BW is reduced by SUP regimens and a slight lowering of FC, BW and EW may be economically advantageous. Therefore, the objective of this experiment was to evaluate the impact of SUP regimens on brown-egg layer rearing program on subsequent productivity and the effect of feeder space and density on performance. Two brown-egg strains, Hy-Line Brown (HB) and the H and N Brown Nick (BN) were grown on three different dietary regimens, i.e. a "normal" SDP regimen, a SUP regimen: low energy starter for 9 wk (SUP9) and a SUP regimen: low energy starter for 12 wk (SUP12). The SUP9 and SUP12 feeding regimens resulted in significantly lower BW and feed conversion and shorter sternum length, than the SDP regimen. Egg production was not significantly different among the 3 regimens, but feed conversion was lower while livability was highest in the SUP12 reared hens. Feeder space of 13.6 cm resulted in poorer feed conversion for the SUP12 reared hens. Density per hen of 482 cm2 resulted in significantly improved egg production characteristics, such as 37 more eggs per hen and an 8.1% improvement in flock livability. Only density affected egg income and feed costs and in both egg income and feed costs were higher in hens kept at 482 cm2 were $2.39 and $0.21, respectively. Rearing pullets did not result in a reduced economic return in the laying period, where providing hens a lower density environment increased the per hen income.

K.E. Anderson; P.K. Jenkins

2011-01-01

78

Initial size distributions and hygroscopicity of indoor combustion aerosol particles

Energy Technology Data Exchange (ETDEWEB)

Cigarette smoke, incense smoke, natural gas flames, propane fuel flames, and candle flames are contributors of indoor aerosol particles. To provide a quantitative basis for the modeling of inhaled aerosol deposition pattern, the hygroscopic growth of particles from these five sources as well as the source size distributions were measured. Because the experiments were performed on the bases of particles of single size, it provided not only the averaged particle`s hygroscopic growth of each source, but also the detailed size change for particles of different sizes within the whole size spectrum. The source particle size distribution measurements found that cigarette smoke and incense smoke contained particles in the size range of 100-700 nm, while the natural gas, propane, and candle flames generated particles between 10 and 100 nm. The hygroscopic growth experiments showed that these combustion aerosol particles could grow 10% to 120%, depending on the particle sizes and origins. 18 refs., 15 figs., 3 tabs.

Li, W.; Hopke, P.K. [Clarkson Univ., Potsdam, NY (United States)

1993-10-01

79

Does size matter in platelet production?

UK PubMed Central (United Kingdom)

Platelet (PLT) production represents the final stage of megakaryocyte (MK) development. During differentiation, bone marrow MKs extend and release long, branched proPLTs into sinusoidal blood vessels, which undergo repeated abscissions to yield circulating PLTs. Circular-prePLTs are dynamic intermediate structures in this sequence that have the capacity to reversibly convert into barbell-proPLTs and may be related to "young PLTs" and "large PLTs" of both inherited and acquired macrothrombocytopenias. Conversion is regulated by the diameter and thickness of the peripheral microtubule coil, and PLTs are capable of enlarging in culture to generate barbell-proPLTs that divide to yield 2 smaller PLT products. Because PLT number and size are inversely proportional, this raises the question: do macrothrombocytopenias represent a failure in the intermediate stages of PLT production? This review aims to bring together and contextualize our current understanding of terminal PLT production against the backdrop of human macrothrombocytopenias to establish how "large PLTs" observed in both conditions are similar, how they are different, and what they can teach us about PLT formation. A better understanding of the cytoskeletal mechanisms that regulate PLT formation and determine PLT size offers the promise of improved therapies for clinical disorders of PLT production and an important source of PLTs for infusion.

Thon JN; Italiano JE Jr

2012-08-01

80

Direct characterization of nanocrystal size distribution using Raman spectroscopy

We report a rigorous analytical approach based on one-particle phonon confinement model to realize direct detection of nanocrystal size distribution and volume fraction by using Raman spectroscopy. For the analysis, we first project the analytical confinement model onto a generic distribution function, and then use this as a fitting function to extract the required parameters from the Raman spectra, i.e., mean size and skewness, to plot the nanocrystal size distribution. Size distributions for silicon nanocrystals are determined by using the analytical confinement model agree well with the one-particle phonon confinement model, and with the results obtained from electron microscopy and photoluminescence spectroscopy. The approach we propose is generally applicable to all nanocrystal systems, which exhibit size-dependent shifts in the Raman spectrum as a result of phonon confinement.

Do?an, ?lker; van de Sanden, Mauritius C. M.

2013-10-01

81

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

82

Directory of Open Access Journals (Sweden)

Full Text Available 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 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

2005-01-01

83

Statistical Tools for Drop Size Distributions: Moments and Generalized Gamma.

Several problems associated with drop size distributions are treated. For rainfall rate R or radar reflectivity Z high powers of the drop diameters must be taken into account. This paper suggests methods to deal with the relevant moments and to approximate the distributions by a generalized gamma distribution P(x) = [u,(x/c)r]/(u). Retaining the power r as a parameter is the difference to a gamma distribution. It leads to a large flexibility, enabling one to fit the distribution to the moments of interest. The three parameters r, u, and c can be fitted exactly to three moments of the order , 2, and 3, respectively, where defines the power of the variable. The expressions for the moments and the transformation to another power are simple for generalized gamma distributions. A quickly converging algorithm to calculate the parameters r, u, and c is shown. The solutions can be obtained in a spreadsheet or from the internet. The proposed technique is particularly powerful for describing sampling distributions with R or Z from a known drop size distribution. Whether the sample size is a fixed number or whether it varies according to a Poisson distribution makes a difference, which is treated here. However, the processes associated with precipitation and drop size distributions seem to be more complex, leading to larger variations than expected from simple models of random sampling.

Auf der Maur, A. N.

2001-02-01

84

Distribution of instanton sizes in a simplified instanton gas model

We investigate the distribution of instanton sizes in the framework of a simplified model for ensembles of instantons. This model takes into account the non-diluteness of instantons. The infrared problem for the integration over instanton sizes is dealt with in a self-consistent manner by approximating instanton interactions by a repulsive hard core potential. This leads to a dynamical suppression of large instantons. The characteristic features of the instanton size distribution are studied by means of analytic and Monte Carlo methods. In one dimension exact results can be derived. In any dimension we find a power law behaviour for small sizes, consistent with the semi-classical results. At large instanton sizes the distribution decays exponentially. The results are compared with those from lattice simulations.

Münster, G; Münster, Gernot; Kamp, Christel

2000-01-01

85

Nuclear magnetic resonance characterization of general compartment size distributions

International Nuclear Information System (INIS)

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.

2011-01-01

86

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

87

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

88

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

89

Particle size distributions during diffusion controlled growth and coarsening

International Nuclear Information System (INIS)

[en] 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

2008-01-01

90

UK PubMed Central (United Kingdom)

The size-dependent phase-transfer property of metal nanoparticles is used to develop a simple experimental procedure that can effectively refine the particle size from colloidal solutions prepared by wet-chemistry. The protocol calls for firstly the mixing of the metal hydrosol with an ethanol solution of dodecylamine, and then the extraction of the dodecylamine-stabilized metal nanoparticles into toluene. This method offers an effective approach to prepare metal nanoparticles with narrow size distribution from an arbitrary particle size distribution.

Liu H; Qu J; Ye F; Wang C; Yang J

2013-02-01

91

Particle size distribution in ferrofluid macro-clusters

Under an applied magnetic field, many commercial and concentrated ferrofluids agglomerate and form large micron-sized structures. Although large diameter particles have been implicated in the formation of these macro-clusters, the question of whether the particle size distribution of the macro-clusters are the same as the original fluid remains open. Some studies suggest that these macro-clusters consist of larger particles, while others have shown that there is no difference in the particle size distribution between the macro-clusters and the original fluid. In this study, we use X-ray imaging to aid in a sample (diluted EFH-1 from Ferrotec) separation process and conclusively show that the average particle size in the macro-clusters is significantly larger than those in the original sample. The average particle size in the macro-clusters is 19.6 nm while the average particle size of the original fluid is 11.6 nm.

Lee, Wah-Keat; Ilavsky, Jan

2013-03-01

92

Nanoporous metals with controlled multimodal pore size distribution.

UK PubMed Central (United Kingdom)

A simple two-step dealloying strategy is described to make free-standing metal membranes with hierarchical porous architecture. This structure has a bimodal pore size distribution composed of large porosity channels and small porosity channel walls, where each pore size can be tailored independently of the others. A new gas-phase electroless plating technique was also developed here that could be used to uniformly fill porous structures with pore size as small as 10 nm.

Ding Y; Erlebacher J

2003-07-01

93

Polyester scaffolds with bimodal pore size distribution for tissue engineering.

UK PubMed Central (United Kingdom)

This paper presents a method for the preparation of porous poly(L-lactide)/poly[(L-lactide)-co-glycolide] scaffolds for tissue engineering. Scaffolds were prepared by a mold pressing-salt leaching technique from structured microparticles. The total porosity was in the range 70-85%. The pore size distribution was bimodal. Large pores, susceptible for osteoblasts growth and proliferation had the dimensions 50-400 microm. Small pores, dedicated to the diffusion of nutrients or/and metabolites of bone forming cells, as well as the products of hydrolysis of polyesters from the walls of the scaffold, had sizes in the range 2 nm-5 microm. The scaffolds had good mechanical strength (compressive modulus equal to 41 MPa and a strength of 1.64 MPa for 74% porosity). Scaffolds were tested in vitro with human osteoblast-like cells (MG-63). It was found that the viability of cells seeded within the scaffolds obtained using the mold pressing-salt leaching technique from structured microparticles was better when compared to cells cultured in scaffolds obtained by traditional methods. After 34 d of culture, cells within the tested scaffolds were organized in a tissue-like structure. Photos of section of macro- and mesoporous PLLA/PLGA scaffold containing 50 wt.-% of PLGA microspheres after 34 d of culture. Dark spots mark MG-63 cells, white areas belong to the scaffold. The specimen was stained with haematoxylin/eosin. Bar = 100 microm.

Sosnowski S; Wo?niak P; Lewandowska-Szumie? M

2006-06-01

94

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

95

Gas product distribution from polyethylene pyrolysis

Energy Technology Data Exchange (ETDEWEB)

The disposal of plastic waste is extensively studied nowadays. Of the treatments available, thermal degradation is attracting great interest because it offers the possibility of recovering energy and useful chemicals. PE pyrolysis has already been discussed in a previous paper where the rate of decomposition of a sample was modeled using a detailed kinetic scheme. Its predictions were validated by thermogravimetric experimental results across wide operative pressure and heating rate ranges. The gas product distribution was derived from the random scission hypothesis. Thus, the ratio of alkane, alkene and dialkene species was 1:2:1 and, within the same class of products, the distribution was equimolecular, except for those species which are more favored by allyl resonance. This paper aims to continue the previous work in attempting to model gas products correctly. The principal improvements made here are the introduction of backbiting reactions into the kinetic scheme to predict the larger amounts of selected products and the consideration of the physical aspects of the degradation process. These phenomena are responsible for the production rate and the distribution of volatiles. A simplified model of the in-depth mass transfer through bubble formation is presented which describes the degradation progress for a small-sized polyethylene sample. The model predictions are compared with both the experimental results of polyethylene pyrolysis performed under various temperature conditions and with thermogravimetric analysis

Faravelli, T.; Bozzano, G.; Scassa, C.; Perego, M.; Fabini, S.; Ranzi, E.; Dente, M. [CIIC Dipartimento di Chimica Industriale e Ingegneria Chimica, Politecnico di Milano, Piazza L. da Vinci 32, 20133 Milan (Italy)

1999-09-01

96

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

97

Size distribution of microbubbles as a function of shell composition.

The effect of modifying the shell composition of a population of microbubbles on their size demonstrated through experiment. Specifically, these variations include altering both the mole fraction and molecular weight of functionalized polymer, polyethylene glycol (PEG) in the microbubble phospholipid monolayer shell (1-15 mol% PEG, and 1000-5000 g/mole, respectively). The size distribution is measured with an unbiased image segmentation program written in MATLAB which identifies and sizes bubbles from micrographs. For a population of microbubbles with a shell composition of 5 mol% PEG2000, the mean diameter is 1.42 ?m with a variance of 0.244 ?m. For the remainder of the shell compositions studied herein, we find that the size distributions do not show a statistically significant correlation to either PEG molecular weight or mole fraction. All the measured distributions are nearly Gaussian in shape and have a monomodal peak. PMID:23642496

Dicker, Stephen; Mleczko, Micha?; Schmitz, Georg; Wrenn, Steven P

2013-04-12

98

Size distribution of microbubbles as a function of shell composition.

UK PubMed Central (United Kingdom)

The effect of modifying the shell composition of a population of microbubbles on their size demonstrated through experiment. Specifically, these variations include altering both the mole fraction and molecular weight of functionalized polymer, polyethylene glycol (PEG) in the microbubble phospholipid monolayer shell (1-15 mol% PEG, and 1000-5000 g/mole, respectively). The size distribution is measured with an unbiased image segmentation program written in MATLAB which identifies and sizes bubbles from micrographs. For a population of microbubbles with a shell composition of 5 mol% PEG2000, the mean diameter is 1.42 ?m with a variance of 0.244 ?m. For the remainder of the shell compositions studied herein, we find that the size distributions do not show a statistically significant correlation to either PEG molecular weight or mole fraction. All the measured distributions are nearly Gaussian in shape and have a monomodal peak.

Dicker S; Mleczko M; Schmitz G; Wrenn SP

2013-09-01

99

Particle size distribution from a modern heavy duty diesel engine

Energy Technology Data Exchange (ETDEWEB)

The particle size distribution emitted from a modern heavy duty diesel engine was investigated. It was found that the operation of the engine test bed system, primary and secondary dilution system and instruments were stable and that particle size distributions could be measured repeatedly under specific conditions. The particle size distribution was determined at different engine speed and load. The mode in the number distribution was smaller than 25 nm at engine speed 1600 rev./min and between 40-60 nm at 2600 rev./min. Good agreement of size distributions measured by SMPS and ELPI instruments was found in the region of overlap, and with measurements made with an electron microscope and image analyser. Total particle volume concentrations calculated from SMPS and ELPI data agreed well with those estimated from filter mass data. The measured particle size distribution and total number concentration changes with the dilution conditions and humidity of dilution air. The mechanism is being investigated and preliminary results suggest that sulphuric acid is involved in homogeneous nucleation of new particles during the dilution process.

Shi, J.P.; Harrison, R.M. [Institute of Public and Environmental Health, University of Birmingham, Edgbaston, Birmingham (United Kingdom); Brear, F. [Perkins Engines Company, Peterborough (United Kingdom)

1999-09-01

100

Fast method for computing pore size distributions of model materials.

UK PubMed Central (United Kingdom)

Recently developed atomistic models of highly disordered nanoporous materials offer hope for a much more realistic description of the pore morphology and topology in such materials; however, a factor limiting their application has been the computationally intensive characterization of the models, particularly determination of the pore size distribution. We report a new technique for fast computation of pore size distributions of model materials from knowledge of the molecular coordinates. The pore size distribution (PSD) is defined as the statistical distribution of the radius of the largest sphere that can be fitted inside a pore at a given point. Using constrained nonlinear optimization, we calculate the maximum radii of test particles at random points inside the pore cavity. The final pore size distribution is then obtained by sampling the test particle radii using Monte Carlo integration. The computation time depends on factors such as the number of atoms, the sampling resolution, and the desired accuracy. However, even for large systems, PSDs with very high accuracy (>99.9%) are obtained in less than 24 h on a 3 GHz Pentium IV processor. The technique is validated by applying it to model structures, whose pore size distributions are already known. We then apply this method to investigate the pore structures of several mesoporous silica models such as SBA-15 and mesostructured cellular foams.

Bhattacharya S; Gubbins KE

2006-08-01

101

Fast method for computing pore size distributions of model materials.

Recently developed atomistic models of highly disordered nanoporous materials offer hope for a much more realistic description of the pore morphology and topology in such materials; however, a factor limiting their application has been the computationally intensive characterization of the models, particularly determination of the pore size distribution. We report a new technique for fast computation of pore size distributions of model materials from knowledge of the molecular coordinates. The pore size distribution (PSD) is defined as the statistical distribution of the radius of the largest sphere that can be fitted inside a pore at a given point. Using constrained nonlinear optimization, we calculate the maximum radii of test particles at random points inside the pore cavity. The final pore size distribution is then obtained by sampling the test particle radii using Monte Carlo integration. The computation time depends on factors such as the number of atoms, the sampling resolution, and the desired accuracy. However, even for large systems, PSDs with very high accuracy (>99.9%) are obtained in less than 24 h on a 3 GHz Pentium IV processor. The technique is validated by applying it to model structures, whose pore size distributions are already known. We then apply this method to investigate the pore structures of several mesoporous silica models such as SBA-15 and mesostructured cellular foams. PMID:16922556

Bhattacharya, Supriyo; Gubbins, Keith E

2006-08-29

102

A quantitative description of vehicle exhaust particle size distributions in a highway tunnel.

UK PubMed Central (United Kingdom)

During the period May 18-May 22, 1999, a comprehensive study was conducted in the Tuscarora Mountain Tunnel on the Pennsylvania Turnpike to measure real-world motor-vehicle emissions. As part of this study, size distributions of particle emissions were determined using a scanning mobility particle sizer. Each measured size distribution consisted of two modes: a nucleation mode with midpoint diameter less than 20 nm and an accumulation mode with midpoint diameter less than 100 nm. The nucleation and accumulation components in some distributions also exhibited second maxima, which implies that such particle size distributions are superpositions of two particle size distributions. This hypothesis was utilized in fitting the particle size distributions that exhibited second maxima with four lognormal distributions, two for the nucleation mode and two for the accumulation mode. The fitting assumed that the observed particle size distribution was a combination of two bimodal log-normal distributions, one attributed to the heavy-duty diesel (HDD) vehicles and another attributed either to a different class of HDD vehicles or to the light-duty spark ignition vehicles. Based on this method, estimated particle production rates were 1.8 x 10(13) and 2.8 x 10(14) particles/vehicle-km for light-duty spark ignition and HDD vehicles, respectively, which agreed with independently obtained estimates.

Abu-Allaban M; Rogers CF; Gertler AW

2004-03-01

103

A quantitative description of vehicle exhaust particle size distributions in a highway tunnel.

During the period May 18-May 22, 1999, a comprehensive study was conducted in the Tuscarora Mountain Tunnel on the Pennsylvania Turnpike to measure real-world motor-vehicle emissions. As part of this study, size distributions of particle emissions were determined using a scanning mobility particle sizer. Each measured size distribution consisted of two modes: a nucleation mode with midpoint diameter less than 20 nm and an accumulation mode with midpoint diameter less than 100 nm. The nucleation and accumulation components in some distributions also exhibited second maxima, which implies that such particle size distributions are superpositions of two particle size distributions. This hypothesis was utilized in fitting the particle size distributions that exhibited second maxima with four lognormal distributions, two for the nucleation mode and two for the accumulation mode. The fitting assumed that the observed particle size distribution was a combination of two bimodal log-normal distributions, one attributed to the heavy-duty diesel (HDD) vehicles and another attributed either to a different class of HDD vehicles or to the light-duty spark ignition vehicles. Based on this method, estimated particle production rates were 1.8 x 10(13) and 2.8 x 10(14) particles/vehicle-km for light-duty spark ignition and HDD vehicles, respectively, which agreed with independently obtained estimates. PMID:15061617

Abu-Allaban, Mahmoud; Rogers, C Fred; Gertler, Alan W

2004-03-01

104

Measurement of aggregates' size distribution by angular light scattering

A novel method is introduced for in situ determination of the size distribution of submicronic fractal aggregate particles by unique measurement of angular scattering of light. This method relies on the dependence of a new defined function Rg? on the polydispersity of the aggregates' size distribution. The function Rg? is then interpreted by the use of iso-level charts to determine the parameters of the log-normal soot size distribution. The main advantage of this method is its independence of the particle optical properties and primary sphere diameter. Moreover, except for the knowledge of fractal dimension, this method does not require any additional measurement. It is validated on monodisperse particles selected by a differential mobility analyzer and polydisperse soot from ethylene diffusion flame whose size distribution is independently determined by Transmission Electron Microscopy. Finally, the size distribution of soot generated by a commercial apparatus is measured by the proposed method and the comparison to that given by a commercial granulometer shows a good agreement.

Caumont-Prim, Chloé; Yon, Jérôme; Coppalle, Alexis; Ouf, François-Xavier; Fang Ren, Kuan

2013-09-01

105

Productivity improvements in gas distribution

Energy Technology Data Exchange (ETDEWEB)

In 1993, the Hilmer Report resulted in the introduction of the National Competition Policy which, in the case of the gas industry, aims to promote gas-on-gas competition where to date it has been excluded. In response, and to prepare for wide gas industry reform, Gas and Fuel formed three fundamentally different core businesses on 1 July 1996 - Energy Retail, Network, and Contestable Services. In one productivity improvement initiative which is believed to be unique, Gas and Fuel appointed three companies as strategic alliance partners for distribution system maintenance. Gas and Fuel can now concentrate on its core role as asset manager which owns and operates the distribution system while procuring all services from what will become non-regulated businesses. This Paper details this initiative and the benefits which have resulted from overall changes and improvements, and outlines the challenges facing Gas and Fuel in the future. (au)

Young, M.R. [Gas and Fuel (Australia)

1997-10-01

106

On the challenge of fitting tree size distributions in ecology.

UK PubMed Central (United Kingdom)

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.

Taubert F; Hartig F; Dobner HJ; Huth A

2013-01-01

107

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

2013-02-28

108

Can vesicle size distributions assess eruption intensity during volcanic activity?

We studied three-dimensional (3-D) vesicle size distributions by X-ray microtomography in scoria collected during the relatively quiescent Phase II of the April-May 2010 eruption at Eyjafjallajökull volcano, Iceland. Our goal was to compare cumulative vesicle size distributions (VSDs) measured in these samples with those found in Stromboli volcano, Italy. Stromboli was chosen because its VSDs are well-characterized and show a correlation with eruption intensity: typical Strombolian activity produces VSDs with power-law exponents near 1, whereas larger and more energetic vulcanian-type explosions and Plinian eruptions produce VSDs with power-law exponents near 1.5. The first hypothesis to be tested was whether or not the samples studied in this work would contain VSDs similar to normal Strombolian products, display higher power-law exponents, or be described by exponential functions. Before making this comparison, we tested a second hypothesis, which was that the magma-water interactions in the Eyjafjallajökull eruption might have a significant effect on the VSDs. We performed 1 bar bubble-growth experiments in which the samples were inundated with water and compared them to similar control experiments without water inundation. No significant differences between the VSDs of the two sets of experiments were found, and the second hypothesis is not supported by the experimental evidence. The Phase II Eyjafjallajökull VSDs are described by power-law exponents of ~0.8, typical of normal Strombolian eruptions, and support the first hypothesis. The comparable VSDs and behavior of Phase II of the Eyjafjallajökull 2010 eruption to Stromboli are interpreted to be a reflection of similar conduit systems in both volcanoes that are being constantly fed by the ascent of mingled/mixed magma from depth. Such behavior implies that continued activity during Phase II of the Eyjafjallajökull eruption could be expected and would have been predicted, had our VSDs been measured in real time during the eruption. However, the products studied show no peculiar feature that could herald the renewed eruption intensity observed in the following Phase III of the eruption.

LaRue, A.; Baker, D. R.; Polacci, M.; Allard, P.; Sodini, N.

2013-10-01

109

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

110

Size distributions of member asteroids in seven Hirayama families

Energy Technology Data Exchange (ETDEWEB)

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

Mikami, Takao (Osaka Gakuin Univ., Suita (Japan)); Ishida, Keiichi

1990-01-01

111

Size distributions of member asteroids in seven Hirayama families

International Nuclear Information System (INIS)

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

1990-01-01

112

Estimation of Nanoparticle Size Distributions by Image Analysis

Energy Technology Data Exchange (ETDEWEB)

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, R., E-mail: RF@IMM.DTU.DK; Carstensen, J.M. [Technical University of Denmark, Department of Mathematical Modelling (Denmark); Hansen, M.F.; Bodker, F.; Morup, S. [Technical University of Denmark, Department of Physics (Denmark)

2000-09-15

113

International Nuclear Information System (INIS)

The bubble sizes and their distribution affect directly to other hydrodynamic behavior of two-phase systems such as flow regime, gas-liquid interfacial area, and mass heat transfer between the phases. However, it is difficult to obtained bubble sizes and their distribution directly. By using the probe technique, the vertical length that bubbles insert the probe, or chord length, can be obtained instead of bubble sizes. In order to get the bubble sizes as well as their distribution, some techniques have to be used. This paper discuss the approaches, which are numerical and analytical backward transform, to estimate bubble size distribution from a set of chord length data obtained by a double sensor conductivity probe which installed in the air water vertical loop facility installed in KAERI. The image technique is also used to measure bubble sizes, which used to compare with ones obtained by the probe

2011-01-01

114

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

115

Initial Planetesimal Sizes and the Size Distribution of Small Kuiper Belt Objects

We show, by comparing observations with theoretical models, that the observed Kuiper Belt size distribution is well matched by coagulation models, which start from an initial planetesimal population with radii of about 1km, and subsequent collisional evolution. We find that the observed size distribution for R > 30km has not been modified by collisional evolution over the age of the solar system, and that the size distribution below R ~ 30km 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 0.01km to 30km and find that its slope changes several times as a function of radius before approaching the expected value for an equilibrium collisional cascade of material strength dominated bodies for R < 0.1km. Compared to a single power law size distribution that would span the whole range from 0.01km to 30km, we find a strong deficit of bodies around R ~...

Schlichting, Hilke E; Trilling, David E

2013-01-01

116

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

117

Particle Size Distribution in Saturn’s Ring C

Information about particle sizes in Saturn’s rings is provided by two complementary types of Cassini radio occultation measurements. The first is differential extinction of three coherent sinusoidal signals transmitted by Cassini through the rings back to Earth (wavelength = 0.94, 3.6, and 13 cm, respectively). The differential measurements strongly constraint three parameters of an assumed power-law size distribution n(a) = n0 (a/a0)q, amin ? a ? amax: namely, the power law index q, the minimum radius amin, and reference abundance n0 at reference radius a0. The differential measurements are particularly sensitive to radii in the range 0.1 mm < a < 1 m. Complementing this capability, is a second type of measurements that is particularly sensitive to the larger radii 1 m < a < 20 m and their abundance. Signature of the collective near-forward scattering by these particles is captured in power spectrum measurements as broadened component of width, shape, and strength that depend on ring particle sizes, their spatial distribution, and observation geometry. Contributions of ring features of width as small several hundred kilometers can be identified and isolated in the measured spectra for a small subset of Cassini orbits of favorable geometry. We use three inverse scattering algorithms (Bayes, constrained linear inversion, generalized singular-value-decomposition) to recover the size distribution of particles of resolved ring features over the size range 1 m < a < 20 m without assuming an explicit size distribution model. We also investigate consistency of the results with a single power-law model extending over 0.1 mm < a < 20 m and implications to the spatial distribution of ring particles normal to the ring plane (vertical ring thickness). We present example results for selected features across Saturn’s Ring C where little evidence for gravitational wakes is present, hence the approaches above are applicable.

Marouf, Essam A.; Wong, K.; French, R.; Rappaport, N.

2012-10-01

118

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

119

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

120

Field-size distribution - an exercise in doodling

Energy Technology Data Exchange (ETDEWEB)

The robustness of the suggested log-normal distribution of the size of oil fields when plotted against the cumulative percentage of fields is examined. This was performed by looking at how the distribution varied when certain fields were dropped e.g. some of the smallest and at random. The importance of incomplete sets of values and the mixing of two sets of values is stressed. The possible use of such distributions could improve the accuracy of the original estimates of the oil in place reserves in a group of fields at abandonment. (UK).

Hobson, G.D.

1991-01-01

121

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

122

Size and composition distribution of atmospheric particles in southern California

Energy Technology Data Exchange (ETDEWEB)

Continuous measurements of single particle size and chemical composition in the atmosphere are made using aerosol time-of-flight mass spectrometers (ATOFMS) operated alongside more conventional reference air sampling instruments at a network of three urban air monitoring sites in southern California. Electrical aerosol analyzers and optical particle counters are employed to acquire continuous particle size distribution data, and inertial impactor and bulk filter samples with 4-h resolution are taken for determination of particle size and chemical composition. Filter and impactor samples also are taken upwind of the air basin at Santa Catalina Island in order to characterize background air quality. The airborne particle size and composition distribution as measured by the cascade impactors at inland sites differ from that over the ocean principally due to depletion of sea salt particles accompanied by the addition of fine carbon-containing particles and secondary aerosol nitrate. Data from the ATOFMS systems create a continuous time series of sodium-, ammonium-, nitrate-, and carbon-containing particle counts that provide a high-resolution view of differences in particle composition as a function of location in the air basin. Results show that the characteristic peak in the Los Angeles area aerosol mass distribution in the 0.2--0.3-{micro}m size range observed during the 1987 SCAQS experiments has been reduced, consistent with reductions in diesel soot and elemental carbon emissions since that time.

Hughes, L.S.; Allen, J.O.; Kleeman, M.J. [and others

1999-10-15

123

Modeling particle size distribution in emulsion polymerization reactors

Digital Repository Infrastructure Vision for European Research (DRIVER)

A review of the use and limitations of Population Balance Equations (PBE) in the modeling of emulsion polymerisation (EP), and in particular of the particle size distribution of the dispersed system is presented. After looking at the construction of the general form of PBEs for EP, a discussion of t...

Vale, Hugo; Mckenna, Timothy

124

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 ...

Walsh, Patrick Paul; Whelan, Ciara

125

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 ...

Whelan, Ciara; Walsh, Patrick P.

126

Size distribution of airborne aerosol particles with attached ?-active nuclei

International Nuclear Information System (INIS)

A new technique has been employed based on the methods of Soilleux (1971) to measure the size distribution of aerosol particles having attached Rn daughter nuclei. The technique and its limitations are described and a mean radius of approximately 0.1 ?m is reported for such particles suspended in outdoor air. (author)

1981-09-12

127

Technegas: a study of particle structure, size and distribution

International Nuclear Information System (INIS)

Technegas (TcG) was produced using a commercially available TcG generator. The structure and size distribution of TcG particles were examined by means of the following methods: (a) Transmission electron microscopy (TEM), range: 1 nm-100?m; (b) time-of-flight mass spectroscopy (MS), range:

1993-01-01

128

Effect of ball size distribution on milling rate

Energy Technology Data Exchange (ETDEWEB)

This paper focuses on the determination of the selection function parameters {alpha}, a, {mu} and {Lambda} together with the exponent factors {eta} and {xi} describing the effect of ball size on milling rate for a South African coal. A series of batch grinding tests were carried out using three media single sizes, i.e. 30.6, 38.8, and 49.2 mm. Then two ball mixtures were successively considered. The original manufacturer's recommended ball mixture was used to investigate the effect of ball size distribution on the selection function whereas the equilibrium ball mixture was used to validate the model. Results show that with the six parameters abovementioned, the charge mixture is fully characterized with about 5% deviation. Interestingly, the estimated parameters can be used in the simulator model allowing one to find the optimal ball charge distribution for a set of operational constraints.

Katubilwa, F.M.; Moys, M.H. [University of Witwatersrand, Johannesburg (South Africa)

2009-12-15

129

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.; Schwämmle, Veit

2011-01-01

130

A model of size distribution of customer groups and businesses

We present a generalization of the dynamical model of information transmission and herd behavior proposed by Egu\\'{\\i}luz and Zimmermann. A characteristic size of group of agents $s_{0}$ is introduced. The fragmentation and coagulation rates of groups of agents are assumed to depend on the size of the group. We present results of numerical simulations and mean field analysis. It is found that the size distribution of groups of agents $n_{s}$ exhibits two distinct scaling behavior depending on $s \\leq s_{0}$ or $s > s_{0}$. For $s \\leq s_{0}$, $n_{s} \\sim s^{-(5/2 + \\delta)}$, while for $s > s_{0}$, $n_{s} \\sim s^{-(5/2 -\\delta)}$, where $\\delta$ is a model parameter representing the sensitivity of the fragmentation and coagulation rates to the size of the group. Our model thus gives a tunable exponent for the size distribution together with two scaling regimes separated by a characteristic size $s_{0}$. Suitably interpreted, our model can be used to represent the formation of groups of customers for certain p...

Zheng, D; Hui, P M; Zheng, Dafang

2001-01-01

131

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

132

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

133

Evaluation of the Malvern optical particle monitor. [Volumetric size distribution

Energy Technology Data Exchange (ETDEWEB)

The Malvern 2200/3300 Particle Sizer is a laser-based optical particle sizing device which utilizes the principle of Fraunhofer Diffraction as the means of particle size measurement. The instrument is designed to analyze particle sizes in the range of 1 to 1800 microns diameter through a selection of lenses for the receiving optics. It is not a single-particle counter but rather an ensemble averager over the distribution of particles present in the measuring volume. Through appropriate measurement techniques, the instrument can measure the volumetric size distribution of: solids in gas or liquid suspension; liquid droplets in gas or other immiscible liquids; and, gas bubbles in liquid. (Malvern Handbook, Version 1.5). This report details a limited laboratory evaluation of the Malvern system to determine its operational characteristics, limitations, and accuracy. This investigation focused on relatively small particles in the range of 5 to 150 microns. Primarily, well characterized particles of coal in a coal and water mixture were utilized, but a selection of naturally occurring, industrially generated, and standard samples (i.e., glass beads) wer also tested. The characteristic size parameter from the Malvern system for each of these samples was compared with the results of a Coulter particle counter (Model TA II) analysis to determine the size measurement accuracy. Most of the particulate samples were suspended in a liquid media (water or isoton, plus a dispersant) for the size characterization. Specifically, the investigations contained in this report fall into four categories: (a) Sample-to-lense distance and sample concentration studies, (b) studies testing the applicability to aerosols, (c) tests of the manufacturer supplied software, and (d) size measurement comparisons with the results of Coulter analysis. 5 references, 15 figures, 2 tables.

Anderson, R. J.; Johnson, E.

1983-07-01

134

Consideration of grain size distribution in the diffusion of fission gas to grain boundaries

We analyze the accumulation of fission gas on grain boundaries in a polycrystalline microstructure with a distribution of grain sizes. The diffusion equation is solved throughout the microstructure to evolve the gas concentration in space and time. Grain boundaries are treated as infinite sinks for the gas concentration, and we monitor the cumulative gas inventory on each grain boundary throughout time. We consider two important cases: first, a uniform initial distribution of gas concentration without gas production (correlating with post-irradiation annealing), and second, a constant gas production rate with no initial gas concentration (correlating with in-reactor conditions). The results show that a single-grain-size model, such as the Booth model, over predicts the gas accumulation on grain boundaries compared with a polycrystal with a grain size distribution. Also, a considerable degree of scatter, or variability, exists in the grain boundary gas accumulation when comparing all of the grain boundaries in the microstructure.

Millett, Paul C.; Zhang, Yongfeng; Tonks, Michael R.; Biner, S. B.

2013-09-01

135

Energy Technology Data Exchange (ETDEWEB)

A rank and type suite of coals from the Sydney and Bowen Basin was selected for breakage testing using a single particle impact breaker. The objective was to quantitatively link breakage characteristics, either parameters or distributions, to coal rank, type and texture. If relationships exist, then knowledge of the in situ band or lithotype thickness distribution and appropriate breakage energy levels can be used to predict ROM or machine product size distribution. Seams were characterised by their texture (band width distribution and cleat spacing) and the extreme coal types occurring within each sam chosen for breakage testing. Findings corroborate prior knowledge of increased size degradation with increased energies but highlight the differences in required breakage energies which can occur within a single seam as a function of coal type, or across a seam with change in rank or type. Coal seams were shown to reach fatal size distributions at approximately 0.15 kWh/T, which is the equivalent energy used in most coal blasts during open cut operations. By applying these energies and a breakage function to banding size distributions from the face, ROM sizing can be approached. As well, the single particle breakage test also provides a close estimate of ROM sizing at energies above 0.15 kWh/T. 10 refs., 4 figs.

Esterle, J.S.; O`Brien, G.; Kojovic, T. [Centre for Mining Technology and Equipment, Kenmore, Qld. (Australia)

1994-12-31

136

A quantitative method for clustering size distributions of elements

Energy Technology Data Exchange (ETDEWEB)

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 (0.056

Dillner, A.M.; Schauer, J.J.; Christensen, W.F.; Cass, G.R. [Arizona State University, Tempe, AZ (US). Dept. of Civil and Environmental Engineering

2005-03-01

137

Critical sizes and flux distributions in the shut down pile

International Nuclear Information System (INIS)

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

1957-01-01

138

Size distribution of cell pattern observed in gravitational instability.

UK PubMed Central (United Kingdom)

Gravitational instability occurs at the interface of two solutions when a higher-density solution (HDS) is placed on the surface of a lower-density solution (LDS). As the HDS sinks, a cell pattern forms on the surface. We investigate the size distribution of the cells in this pattern. We show that the cumulative size distribution obeys a power law with a power index that is independent of time as long as it is possible to neglect the interactions among the cells. To understand the power law mechanism, a simple model excluding the interactions is proposed, and we demonstrate that this simple model provides the power law measured in experiments. Our results indicate that independent cell generation and growth are key factors to understand the feature of the cell pattern.

Shimokawa M; Kitahata H; Sakurai T

2013-01-01

139

Modelling of the droplet size distribution in LP steam turbine

Energy Technology Data Exchange (ETDEWEB)

Realisation of numerous tests on the droplet size measurement with extinction probe, in 200 MW LP steam turbine, provides necessary experimental data for testing the theoretical models of the droplet nucleation process in steam turbines. The earlier computational model accounting for the unsteady and viscous effects (Bakhtar F., Heaton A.V. - 1988 and Guha A., Young J - 1994), where the steam particles follow randomly chosen different streamlines within the blade rows with prescribed polytropic efficiency distribution in the pitch-wise direction, thus undergoing various nucleation conditions, has been extended in this paper to consider to some extent 2D effects. Due to still existing several uncertainties in the inversion methods, predicting the size distribution of droplets, this contribution is aimed at direct comparison of the computed and measured transmittance data (I/I{sub o}). (author)

Petr, V.; Kolovratnik, M. [Czech Technical University, Prague (Czech Republic). Dept. of Fluid Dynamics and Power Engineering

1999-07-01

140

Tuning Aerosol Particle Size Distribution of Metered Dose Inhalers Using Cosolvents and Surfactants

Objectives. The purpose of these studies was to understand the influence of cosolvent and surfactant contributions to particle size distributions emitted from solution metered dose inhalers (pMDIs) based on the propellant HFA 227. Methods. Two sets of formulations were prepared: (a) pMDIs-HFA 227 containing cosolvent (5–15% w/w ethanol) with constant surfactant (pluronic) concentration and (b) pMDIs-HFA 227 containing surfactant (0–5.45% w/w pluronic) with constant cosolvent concentration. Particle size distributions emitted from these pMDIs were analyzed using aerodynamic characterization (inertial impaction) and laser diffraction methods. Results. Both cosolvent and surfactant concentrations were positively correlated with median particle sizes; that is, drug particle size increased with increasing ethanol and pluronic concentrations. However, evaluation of particle size distributions showed that cosolvent caused reduction in the fine particle mode magnitude while the surfactant caused a shift in the mode position. These findings highlight the different mechanisms by which these components influence droplet formation and demonstrate the ability to utilize the different effects in formulations of pMDI-HFA 227 for independently modulating particle sizes in the respirable region. Conclusion. Potentially, the formulation design window generated using these excipients in combination could be used to match the particle size output of reformulated products to preexisting pMDI products.

Saleem, Imran Y.; Smyth, Hugh D. C.

2013-01-01

141

Size distributions of manure particles released under simulated rainfall.

UK PubMed Central (United Kingdom)

Manure and animal waste deposited on cropland and grazing lands serve as a source of microorganisms, some of which may be pathogenic. These microorganisms are released along with particles of dissolved manure during rainfall events. Relatively little if anything is known about the amounts and sizes of manure particles released during rainfall, that subsequently may serve as carriers, abode, and nutritional source for microorganisms. The objective of this work was to obtain and present the first experimental data on sizes of bovine manure particles released to runoff during simulated rainfall and leached through soil during subsequent infiltration. Experiments were conducted using 200 cm long boxes containing turfgrass soil sod; the boxes were designed so that rates of manure dissolution and subsequent infiltration and runoff could be monitored independently. Dairy manure was applied on the upper portion of boxes. Simulated rainfall (ca. 32.4 mm h(-1)) was applied for 90 min on boxes with stands of either live or dead grass. Electrical conductivity, turbidity, and particle size distributions obtained from laser diffractometry were determined in manure runoff and soil leachate samples. Turbidity of leachates and manure runoff samples decreased exponentially. Turbidity of manure runoff samples was on average 20% less than turbidity of soil leachate samples. Turbidity of leachate samples from boxes with dead grass was on average 30% less than from boxes with live grass. Particle size distributions in manure runoff and leachate suspensions remained remarkably stable after 15 min of runoff initiation, although the turbidity continued to decrease. Particles had the median diameter of 3.8 microm, and 90% of particles were between 0.6 and 17.8 microm. The particle size distributions were not affected by the grass status. Because manure particles are known to affect transport and retention of microbial pathogens in soil, more information needs to be collected about the concurrent release of pathogens and manure particles during rainfall events.

Pachepsky YA; Guber AK; Shelton DR; McCarty GW

2009-03-01

142

Analysis of oil field size distribution in consanguineous basins

Energy Technology Data Exchange (ETDEWEB)

When assessing the amount of ultimately producible petroleum from an unexplored region, two things are important. First, the size distribution of sampled oil fields in the region will indicate the fraction of oil fields which are likely to be found for a given field size. Second, the richness of the region, or ultimately producible oil per unit area, indicates the amount of oil in that region and is directly related to the total number of oil fields in the region. The Klemme basin classification system was used to place each petroleum producing basin of the US into its appropriate tectonic setting. A 1981 excerpt of the Petroleum Data System was used to obtain the distributions of sampled oil field sizes. These distributions were modeled very precisely by the Richards cumulative growth function, whose parameters were then used to compare the oil field size distributions between basins. The parameters of the Richards function were found to be related to the tectonic setting of the basin to some extent. Classical Multidimensional Scaling was used to reduce the dimensionality of the distance matrix between the parameterizations of the basins. The estimated ultimately producible oil in each province was used to create a richness factor for the province. While Craton interior basins are constrained from having a high richness factor and rifted convergent margin basins seem to always have a high richness factor, in general, richness was found to be extremely variable both within and across basin types. The richness is not related to the tectonic setting of the basin and indicates that a province must be at least partially explored before any petroleum resource assessment technique can be of any use.

Bultman, M.W.

1986-01-01

143

Initial Size Distribution of the Galactic Globular Cluster System

Despite the importance of their size evolution in understanding the dynamical evolution of globular clusters (GCs) of the Milky Way, studies are rare that focus specifically on this issue. Based on the advanced, realistic Fokker-Planck (FP) approach, we predict theoretically the initial size distribution (SD) of the Galactic GCs along with their initial mass function and radial distribution. Over one thousand FP calculations in a wide parameter space have pinpointed the best-fit initial conditions for the SD, mass function, and radial distribution. Our best-fit model shows that the initial SD of the Galactic GCs is of larger dispersion than today's SD, and that typical projected half-light radius of the initial GCs is ~4.6 pc, which is 1.8 times larger than that of the present-day GCs (~2.5 pc). Their large size signifies greater susceptibility to the Galactic tides: the total mass of destroyed GCs reaches 3-5x10^8 M_sun$, several times larger than the previous estimates. Our result challenges a recent view t...

Shin, Jihye; Yoon, Suk-Jin; Kim, Juhan

2013-01-01

144

Pore Size Distribution of Carbon with Different Probe Molecules

Directory of Open Access Journals (Sweden)

Full Text Available In this study, a Grand Canonical Monte Carlo simulation (GCMC) method is used to study the adsorption of different probe molecules on activated carbon, while the experimental tests are performed by using a Gravimetric Analyzer. In addition the simulation results together with the measured isotherm data are used for the determination of micropore size distribution. Nitrogen at 77 K and carbon dioxide at 273 and 300 K are proposed as molecular probes. The simulation results obtained for various pore sizes represent the structure of molecular probe packing in the individual pores at different pressures. The reconstructed adsorption isotherm obtained by using these results and a postulated pore size distribution (PSD) function is used to determine the PSD of activated carbon which provides the best match between the simulation isotherm and the experimental isotherm. The PSD obtained using the GCMC agrees very well with the Density Functional Theory (DFT) method. The PSD for carbon dioxide differs from that for nitrogen due to the molecular structure and size. The advantage of GCMC is that it can provide not only adsorption isotherm but also the snapshot that presents the mechanism inside the pore.

Atichat Wongkoblap; Worapot Intomya; Warangkhana Somrup; Sorod Charoensuk; Supunnee Junpirom; Chaiyot Tangsathitkulchai

2010-01-01

145

Photovoltaic production and distribution network

International Nuclear Information System (INIS)

[en] 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)

2010-01-01

146

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

UK PubMed Central (United Kingdom)

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.

Hinterwirth H; Wiedmer SK; Moilanen M; Lehner A; Allmaier G; Waitz T; Lindner W; Lämmerhofer M

2013-09-01

147

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

148

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

UK PubMed Central (United Kingdom)

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

Cauchy C; Bakker JM; Huismans Y; Rouzée A; Redlich B; van der Meer AF; Bordas C; Vrakking MJ; Lépine F

2013-05-01

149

On Learning Monotone DNF under Product Distributions

UK PubMed Central (United Kingdom)

We show that the class of monotone 2O(plog n)-term DNF formulae can be PAC learnedin polynomial time under the uniform distribution. This is an exponential improvement overprevious algorithms in this model, which could learn monotone o(log2n)-term DNF, and is thefirst efficient algorithm for monotone (log n)!(1)-term DNF in any nontrivial model of learningfrom random examples. Our result extends to any constant-bounded product distribution.Supported in part by an NSF Graduate Fellowship, by NSF grant CCR-95-04436 and by ONR grant N00014-961-0550.01 IntroductionA disjunctive normal form formula, or DNF, is a disjunction of conjunctions of Boolean literals.The size of a DNF is the number of conjunctions (also known as terms) which it contains. In aseminal 1984 paper [26] Valiant introduced the distribution-free model of Probably ApproximatelyCorrect (PAC) learning from random examples and posed the question of whether polynomialsizeDNF are PAC learnable ...

Rocco A. Servedio

150

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; Jr, Adedeji Badiru; Rupy Sawhney

2007-01-01

151

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

152

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.

2009-01-01

153

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

154

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.

Ramiro Checa; Francisco J. Tapiador

2011-01-01

155

Simulation study of territory size distributions in subterranean termites.

UK PubMed Central (United Kingdom)

In this study, on the basis of empirical data, we have simulated the foraging tunnel patterns of two subterranean termites, Coptotermes formosanus Shiraki and Reticulitermes flavipes (Kollar), using a two-dimensional model. We have defined a territory as a convex polygon containing a tunnel pattern and explored the effects of competition among termite territory colonies on the territory size distribution in the steady state that was attained after a sufficient simulation time. In the model, territorial competition was characterized by a blocking probability P(block) that quantitatively describes the ease with which a tunnel stops its advancement when it meets another tunnel; higher P(block) values imply easier termination. In the beginning of the simulation run, N=10, 20,…,100 territory seeds, representing the founding pair, were randomly distributed on a square area. When the territory density was less (N=20), the differences in the territory size distributions for different P(block) values were small because the territories had sufficient space to grow without strong competitions. Further, when the territory density was higher (N>20), the territory sizes increased in accordance with the combinational effect of P(block) and N. In order to understand these effects better, we introduced an interference coefficient ?. We mathematically derived ? as a function of P(block) and N: ?(N,P(block))=a(N)P(block)/(P(block)+b(N)). a(N) and b(N) are functions of N/(N+c) and d/(N+c), respectively, and c and d are constants characterizing territorial competition. The ? function is applicable to characterize the territoriality of various species and increases with both the P(block) values and N; higher ? values imply higher limitations of the network growth. We used the ? function, fitted the simulation results, and determined the c and d values. In addition, we have briefly discussed the predictability of the present model by comparing it with our previous lattice model that had been used to explain the territory size distributions of mangrove termites on the Atlantic coast of Panama.

Jeon W; Lee SH

2011-06-01

156

Energy Technology Data Exchange (ETDEWEB)

Particle size is a primary determinant of food resources available to consumers and of the efficiency of energy transfer through planktonic foodwebs. Dual radioisotopic labeling and size fractionation of naturally occurring phytoplankton-bacterioplankton assemblages were employed to examine particle size distributions of planktonic autotrophy and microheterotrophy in five limnologically-dissimilar North American reservoirs. Ultra-nanoplankton (< 8.0 ..mu..m) and free-living bacteria (< 0.8 ..mu..m) were primarily responsible for planktonic autotrophy and microheterotrophy, respectively, in all reservoirs sampled. Grazing experiments indicated that autotrophic particle production is generally more available to filter-feeding macrozooplankton than is microheterotrophic production. The microheterotrophic conversion of allochthonous dissolved organic matter to bacterial biomass appears unlikely to be a major source of particulate organic carbon directly available to macrozooplankton in reservoirs in which significant phytoplankton production occurs.

Kimmel, B.L.

1983-07-01

157

Particle size distribution and chemistry of late winter Arctic aerosols

Energy Technology Data Exchange (ETDEWEB)

Mass size distributions of element concentrations in Arctic aerosols at Barrow, Alaska, were measured from March 16 to May 6, 1986, and their correlations were examined statistically by absolute principal component analysis. In eight particle size fractions from < 0.25 to > 16 {mu}m aerodynamic diameter ({mu}mad), from eight-stage cascade impactor sampling and proton-induced x-ray emission (PIXE) analysis, four types of aerosol components were resolved. One, resembling sea salt in composition, shows a maximum mass at 2-4 {mu}mad and not detected at <0.25 {mu}mad. Sulfur is enriched in fine particles 0.25-1 {mu}mad but not in coarse; chlorine is depleted in 0.5-1 {mu}mad particles, conforms to sea salt composition >8 {mu}mad, but is about 50% enriched in other fine and coarse fractions, suggesting gas-particle chemical interactions during aerosol aging. Dust components are found in all size fractions, with a maximum concentration at 1-2 {mu}mad and a rough symmetry about the maximum when sulfur is not included, suggesting eolian dust particles. Their compositions resemble average crust materials. On these dust particles, sulfur contents show a linear relationship with surface areas, suggesting uptake of gaseous sulfur compounds. Carbonaceous fuel combustion pollutants are indicated by the presence of Si, Cl, and several trace metals and the absence of Al. They are present in all size fractions, usually rich in sulfur with the highest concentration in ultrafine particles <0.25 {mu}mad, strongly suggesting a gas phase origin and consistent with condensation of chloride salt and SiO vapors formed during coal or other fuel combustion. Bromine-sulfur components are in every size fraction and contain most of the measured bromine, greatly in excess of sea salt Br.

Li, Shaomeng; Winchester, J.W. (National Center for Atmospheric Research, Boulder, CO (USA) Florida State Univ., Tallahassee (USA))

1990-08-20

158

Educational production and optimal class size

Lazear (2001) (Quarterly Journal of Economics, v. 116, p. 777-803) provided a model of a private school with a particular profit function. Using an alternative, related profit function I show that an optimal solution has nearly equal class sizes. I also offer a conjecture about the roots of a certain family of polynomials, which if true, allows one to conclude that if students become less disruptive or teacher cost increases, then the optimal solution for a profit maximizing school is generally, but not always, to use fewer classes. I also show that if the school has s>1 types of students, then the optimal solution will have at most s-1 mixed classes and its bipartite graph is a forest.

Foregger, T H

2004-01-01

159

Development of flurbiprofen-loaded nanoparticles with a narrow size distribution using sucrose.

Abstract Objective: A novel flurbiprofen-loaded nanoemulsion which gave uniform emulsion droplets with a narrow size distribution was previously reported to be prepared using membrane emulsification method. The purpose of this study is to develop a novel flurbiprofen-loaded nanoparticle with a narrow size distribution and improved bioavailability. Method: The nanoparticle was prepared by solidifying nanoemulsion using sucrose as a carrier via spray drying method. Its physicochemical properties were investigated using SEM, DSC and PXRD. Furthermore, dissolution and bioavailability in rats were evaluated compared to a flurbiprofen-loaded commercial product. Results: The flurbiprofen-loaded nanoparticles with flurbiprofen/sucrose/surfactant mixture (1/20/2, weight ratio) gave good solidification and no stickiness. They associated with about 70?000-fold improved drug solubility and had a mean size of about 300 nm with a narrow size distribution. Flurbiprofen was present in a changed amorphous state in these nanoparticles. Moreover, the nanoparticles gave significantly shorter Tmax, and higher AUC and Cmax of the drug compared to the commercial product (p?product Conclusion: These flurbiprofen-loaded nanoparticles prepared with sucrose by the membrane emulsification and spray drying method would be a potential candidate for orally delivering poorly water-soluble flurbiprofen with enhanced bioavailability. PMID:23600652

Oh, Dong Hoon; Yan, Yi-Dong; Kim, Dong Wuk; Kim, Jong Oh; Yong, Chul Soon; Choi, Han-Gon

2013-04-19

160

The Superbubble Size Distribution in the Interstellar Medium of Galaxies

We use the standard, adiabatic shell evolution to predict the size distribution N(R) for populations of OB superbubbles in a uniform ISM. We derive N(R) for simple cases of superbubble creation rate and mechanical luminosity function (MLF). For R R_e it is dominated by growing objects. We also briefly investigate N(R) resulting from momentum-conserving shell evolution. We predict a peak in N(R) corresponding to individual SNRs. To estimate the MLF, we also examine evolutionary effects on the HII region luminosity function (HII LF), finding that for nebular luminosity fading as a power law in time, there is a minimum observed slope for the HII LFs. Comparison with the largely complete HI hole catalog for the SMC shows surprising agreement in the predicted and observed slope of N(R), suggesting that no other fundamental process is needed to explain the size distribution of shells in the SMC. Further comparison with largely incomplete HI data for M31, M33, and Holmberg II is also encouraging. We present expressi...

Oey, M S

1997-01-01

161

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

162

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

2013-01-01

163

Better Size Estimation for Sparse Matrix Products

DEFF Research Database (Denmark)

We consider the problem of doing fast and reliable estimation of the number of non-zero entries in a sparse Boolean matrix product. Let n denote the total number of non-zero entries in the input matrices. We show how to compute a 1 ± ? approximation (with small probability of error) in expected time O(n) for any ? > 4*(n^(-1/4)). The previously best estimation algorithm, due to Cohen (JCSS 1997), uses time O(n/?^2). We also present a variant using O(sort(n)) I/Os in expectation in the cache-oblivious model. We also describe how sampling can be used to maintain (independent) sketches of matrices that allow estimation to be performed in time o(n) if z is sufficiently large. This gives a simpler alternative to the sketching technique of Ganguly et al. (PODS 2005), and matches a space lower bound shown in that paper.

Amossen, Rasmus Resen; Campagna, Andrea

2010-01-01

164

Scientific Electronic Library Online (English)

Full Text Available 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 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.; Pinto, J.C.; Araújo, P.H.H.; Bolzan, A.

2000-12-01

165

Possible universality in the size distribution of fish schools

Motivated by the finding that there seems to be some universality in the size distributions of tropical tuna fish schools over several years and in various conditions, we conjecture that a simple model, inspired by a physical model of particle aggregation [H. Takayasu, Phys. Rev. Lett. 63, 2563 (1989)], can be applicable to many instances of schooling in fish, or even of animal grouping in general. This model, which makes no assumption about the specific details of how fish aggregate to form a school but rather assumes that they are able to do so, predicts not only the power-law behavior observed in nature, but also its particular exponent as well as deviations from pure power-law towards exponential decay.

Bonabeau, Eric; Dagorn, Laurent

1995-06-01

166

Stochastic species distributions are driven by organism size.

UK PubMed Central (United Kingdom)

The strengths of environmental drivers and biotic interactions are expected to show large variability across organism groups. We tested two ideas related to the degree of ecological determinism vs. stochasticity using a large data set comprising bacterio-, phyto-, and zooplankton. We expected that (1) there are predictable, size-driven differences in the degree to which planktonic taxa respond to different drivers such as water chemistry, biotic interactions, and climatic variables; and (2) species distribution models show lowest predictive performance for the smallest taxa due to the stochastic distributions of microbes. Generalized linear models (GLMs), generalized additive models (GAMs), and generalized boosted methods (GBMs) were constructed for 84 species to model their occurrence as a function of eight predictors. Predictive performance was measured as the area under the curve (AUC) of the receiver-operating characteristic plot and true skill statistic (TSS) using independent model evaluation data. We found that the model performances were typically remarkably low for all planktonic groups. The proportion of satisfactory models (AUC > 0.7) was lowest for bacteria (11.1% of the models), followed by phyto- (24.2%) and zooplankton (38.1%). The occurrences of taxa within all planktonic groups were related to climatic variables to a certain degree, but bacteria showed the strongest associations with the climatic variables. Moreover, zooplankton occurrences were more related to biotic variables than the occurrences of smaller taxa, while phytoplankton occurrences were more related to water chemistry. We conclude that the occurrences of planktonic taxa are highly unpredictable and that stochasticity in occurrences is negatively related to the organism size perhaps due to efficient dispersal and fast population dynamics among the smallest taxa.

Soininen J; Korhonen JJ; Luoto M

2013-03-01

167

Optimization of bridging agents size distribution for drilling operations

Energy Technology Data Exchange (ETDEWEB)

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

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

2008-07-01

168

Stochastic species distributions are driven by organism size.

The strengths of environmental drivers and biotic interactions are expected to show large variability across organism groups. We tested two ideas related to the degree of ecological determinism vs. stochasticity using a large data set comprising bacterio-, phyto-, and zooplankton. We expected that (1) there are predictable, size-driven differences in the degree to which planktonic taxa respond to different drivers such as water chemistry, biotic interactions, and climatic variables; and (2) species distribution models show lowest predictive performance for the smallest taxa due to the stochastic distributions of microbes. Generalized linear models (GLMs), generalized additive models (GAMs), and generalized boosted methods (GBMs) were constructed for 84 species to model their occurrence as a function of eight predictors. Predictive performance was measured as the area under the curve (AUC) of the receiver-operating characteristic plot and true skill statistic (TSS) using independent model evaluation data. We found that the model performances were typically remarkably low for all planktonic groups. The proportion of satisfactory models (AUC > 0.7) was lowest for bacteria (11.1% of the models), followed by phyto- (24.2%) and zooplankton (38.1%). The occurrences of taxa within all planktonic groups were related to climatic variables to a certain degree, but bacteria showed the strongest associations with the climatic variables. Moreover, zooplankton occurrences were more related to biotic variables than the occurrences of smaller taxa, while phytoplankton occurrences were more related to water chemistry. We conclude that the occurrences of planktonic taxa are highly unpredictable and that stochasticity in occurrences is negatively related to the organism size perhaps due to efficient dispersal and fast population dynamics among the smallest taxa. PMID:23687892

Soininen, Janne; Korhonen, Jenni J; Luoto, Miska

2013-03-01

169

Flow distribution in adjacent subchannels of unequal size

International Nuclear Information System (INIS)

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

1985-01-01

170

Concentrations and size distributions on Antarctic stratospheric aerosols

Energy Technology Data Exchange (ETDEWEB)

Particle Measuring Systems laser particle spectrometer (ASAS-X and FSSP) probes were used to measure aerosol particle concentrations and size distributions during 11 out of 12 ER-2 flights between Punta Arenas (53{degree}S) and Antarctica (up to 72{degree}S) from August 17 to September 22, 1987. The time resolution was 10 s, corresponding to a spatial resolution of 2 km. The data were divided into two size classes (0.05-0.25 and 0.53-5.5 {mu}m radius) to separate the small particle from the coarse particle populations. Results show that the small particle concentrations are typical for a background aerosol during volcanic quiescence. This concentration is generally constant along a flight track; in only one instance did the authors measure a depletion of small particles during a polar stratospheric cloud (PSC) encounter, suggesting a nucleation of type I PSC particles on background aerosols. Temporary increases of the coarse particle concentrations indicated the presence of tenuous polar stratospheric clouds that were encountered most frequently at the southernmost portion of a flight track and when the aircraft descended to lower altitudes. During particle events, particle modes were found at 0.6 {mu}m radius, corresponding to type I PSCs, and occasionally, a second mode at 2.0 {mu}m radius, corresponding to type II PSCs.

Ferry, G.V.; Pueschel, R.F. (NASA Ames Research Center, Moffett Field, CA (United States)); Neish, E. (Neish Automation, Steamboat Springs, CO (United States)); Shultz, M. (Sterling Software, Palo Alto, CA (United States))

1989-11-30

171

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; A. Ruiz; E. Ramos

2009-01-01

172

Subglacial bedforms reveal an exponential size-frequency distribution

Subglacial bedforms preserved in deglaciated landscapes record characteristics of past ice-sediment flow regimes, providing insight into subglacial processes and ice sheet dynamics. Individual forms vary considerably, but they can often be grouped into coherent fields, typically called flow-sets, that reflect discrete episodes of ice flow. Within these, bedform size-frequency distributions (predominantly height, width and length) are currently described by several statistics (e.g., mean, median, and standard deviation) that, arguably, do not best capture the defining characteristics of these populations. This paper seeks to create a better description based upon semi-log plots, which reveal that the frequency distributions of bedform dimensions (drumlin, mega-scale glacial lineation, and ribbed moraine) plot as straight lines above the mode (?). This indicates, by definition, an exponential distribution, for which a simple and easily calculated, yet statistically rigorous, description is designed. Three descriptive parameters are proposed: gradient (?; the exponent, characterising bedforms likely least affected by non-glacial factors), area-normalised y-intercept (?0; quantifying spatial density), and the mode (?). Below ?, small features are less prevalent due to i) measurement: data, sampling and mapping fidelity; ii) possible post-glacial degradation; or iii) genesis: not being created sub-glacially. This new description has the benefit of being insensitive to the impact of potentially unmapped or degraded smaller features and better captures properties relating to ice flow. Importantly, using ?, flow sets can now be more usefully compared with each other across all deglaciated regions and with the output of numerical ice sheet models. Applications may also exist for analogous fluvial and aeolian bedforms. Identifying the characteristic exponential and that it is typical of 'emergent' subglacial bedforms is a new and potentially powerful constraint on their genesis, perhaps indicating that ice-sediment interaction is fundamentally stochastic in nature.

Hillier, J. K.; Smith, M. J.; Clark, C. D.; Stokes, C. R.; Spagnolo, M.

2013-05-01

173

UK PubMed Central (United Kingdom)

The present study was conducted in 47 different riparian areas distributed throughout Denmark to investigate diversity and distributional patterns of plant communities along a lowland stream size gradient (first to fifth order). The investigated areas were representative for Danish riparian areas not in use for agricultural production. We investigated plant community richness along a stream size gradient and the influence of eutrophication on the abundance of different plant communities. Vegetation analyses were performed in transects placed perpendicular to the stream channel, with a total of 1798 plots analyzed. Overall, we found a positive relationship between stream mean depth as a measure of stream size and the number of plant community types identified in the riparian areas. We also found that the abundance of the identified communities was positively correlated with their nutrient preference and negatively correlated with their moisture preference. The abundance of alkaline fens and Molinia meadows (protected community types) in riparian areas decreased with increasing size of the stream, whereas the abundance of humid meadows and wet herb fringes increased with increasing size of the stream. Based on our findings, we recommend that wide buffer zones be established along streams with protected habitat types in the associated riparian areas to reduce the direct impact from agriculture. Furthermore, we recommend that wide buffer zones be established along middle-sized and large streams because several community types may develop.

Dybkjær JB; Baattrup-Pedersen A; Kronvang B; Thodsen H

2012-03-01

174

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

2011-01-01

175

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

2011-01-01

176

Development of a hydrocyclone product size soft-sensor

International Nuclear Information System (INIS)

[en] A technique is presented whereby the particle size of the hydrocyclone overflow product can be predicted by means of a mathematical model. The model uses hydrocyclone feed flowrate and density as well as hydrocyclone overflow density to calculate the required particle size. Various modelling techniques are investigated. Simple linear models are compared to neural network models. Special attention is given to the identification of significant model inputs. Simple linear and more complex neural network models, both utilising an extra model input, cyclone overflow density are identified. Error detection and analysis are explored, resulting in a robust soft-sensor, capable of predicting hydrocyclone product size accurately in the plant environment. (author)

1999-01-01

177

Directory of Open Access Journals (Sweden)

Full Text Available Several samples of potato flour ex-trudates were obtained by simple and screw extruder. The effects of process variables (moisture, temperature) were related to the following extrudates features: expansion, density, and shearing stress. The microstructure of the extruded products was examined by mercury porosimeter. Total porosity and changes of the average pore radius were stated in relation to physical properties of the extrudates. Total porosity decreased when the expansion of the products increased. Feed moisture was the principal determinante of physical strength, and affected changes in the number, size and distribution of the pores.

J. Jamroz; M. Hajnos; Z. SokoÃ…Â‚owska

1996-01-01

178

The Distribution of Program Sizes and Its Implications: An Eclipse Case Study

A large software system is often composed of many inter-related programs of different sizes. Using the public Eclipse dataset, we replicate our previous study on the distribution of program sizes. Our results confirm that the program sizes follow the lognormal distribution. We also investigate the implications of the program size distribution on size estimation and quality predication. We find that the nature of size distribution can be used to estimate the size of a large Java system. We also find that a small percentage of largest programs account for a large percentage of defects, and the number of defects across programs follows the Weibull distribution when the programs are ranked by their sizes. Our results show that the distribution of program sizes is an important property for understanding large and complex software systems.

Zhang, Hongyu; Marchesi, Michele

2009-01-01

179

Productivity in Swedish electricity retail distribution

International Nuclear Information System (INIS)

[en] This paper examines productivity growth in electricity retail distribution in Sweden in a multiple output-multiple input framework. The approach used is nonparametric Data Envelopment Analysis (DEA). Productivity is measured by means of the Malmquist index. Productivity comparisons are made between different types of ownership and between different service areas. The study indicates a high rate of productivity growth, due to economics of density, when measured over a period of 17 years. The results show no significant differences in productivity growth between different types of ownership or economic organization. (20 refs., 1 fig., 4 tabs.)

1992-01-01

180

Productivity in Swedish electricity retail distribution

Energy Technology Data Exchange (ETDEWEB)

This paper examines productivity growth in electricity retail distribution in Sweden in a multiple output-multiple input framework. The approach used is nonparametric Data Envelopment Analysis (DEA). Productivity is measured by means of the Malmquist index. Productivity comparisons are made between different types of ownership and between different service areas. The study indicates a high rate of productivity growth, due to economics of density, when measured over a period of 17 years. The results show no significant differences in productivity growth between different types of ownership or economic organization. (20 refs., 1 fig., 4 tabs.).

Hjalmarsson, L.; Veiderpass, A. (Gothenburg Univ. (Sweden))

1992-01-01

181

Sizes and shapes of subglacial bedforms reveal an exponential size-frequency distribution

Subglacial bedforms preserved in deglaciated landscapes record characteristics of past ice-sediment flow regimes, providing insight into subglacial processes and ice sheet dynamics. Individual forms vary considerably, but they can often be grouped into coherent fields, typically called flow-sets, that reflect discrete episodes of ice flow. Within these, bedform size-frequency distributions (predominantly height, width and length) are currently described by several statistics (e.g., mean, median, standard deviation) that, arguably, do not best capture the defining characteristics of these populations. This paper seeks to create a better description based upon semi-log plots, which reveal that the frequency distributions of bedform dimensions (drumlin, MSGL, ribbed moraine) plot as straight lines above the mode (?). This indicates, by definition, an exponential distribution, for which a simple and easily calculated, yet statistically rigorous, description is designed. Three descriptive parameters are proposed: gradient (?; the exponent, characterising bedforms likely least affected by non-glacial factors), area-normalised y-intercept (?0; quantifying spatial density), and the mode (?). Below ?, small features are less prevalent due to i) measurement: data, sampling, mapping fidelity ii) possibly post-glacial degradation or iii) genesis: not being created sub-glacially. This new description has the benefit of being insensitive to the impact of potentially unmapped or degraded smaller features and better captures properties relating to ice flow. Importantly, using ?, flow sets can now be more usefully compared with each other across all deglaciated regions and with the output of numerical ice sheet models. Identifying the characteristic exponential and that it is typical of 'emergent' subglacial bedforms is a new and potentially powerful constraint on their genesis, perhaps indicating that ice-sediment interaction is fundamentally stochastic in nature.

Hillier, John K.; Smith, Mike J.; Clark, Chris D.; Stokes, Chris R.; Spagnolo, Matteo

2013-04-01

182

ESTIMATING SOIL PARTICLE-SIZE DISTRIBUTION FOR SICILIAN SOILS

Directory of Open Access Journals (Sweden)

Full Text Available The soil particle-size distribution (PSD) is commonly used for soil classification and for estimating soil behavior. An accurate mathematical representation of the PSD is required to estimate soil hydraulic properties and to compare texture measurements from different classification systems. The objective of this study was to evaluate the ability of the Haverkamp and Parlange (HP) and Fredlund et al. (F) PSD models to fit 243 measured PSDs from a wide range of 38 005_Bagarello(547)_33 18-11-2009 11:55 Pagina 38 soil textures in Sicily and to test the effect of the number of measured particle diameters on the fitting of the theoretical PSD. For each soil textural class, the best fitting performance, established using three statistical indices (MXE, ME, RMSE), was obtained for the F model with three fitting parameters. In particular, this model performed better in the fine-textured soils than the coarse-textured ones but a good performance (i.e., RMSE < 0.03) was detected for the majority of the investigated soil textural classes, i.e. clay, silty-clay, silty-clay-loam, silt-loam, clay-loam, loamy-sand, and loam classes. Decreasing the number of measured data pairs from 14 to eight determined a worse fitting of the theoretical distribution to the measured one. It was concluded that the F model with three fitting parameters has a wide applicability for Sicilian soils and that the comparison of different PSD investigations can be affected by the number of measured data pairs.

Vincenzo Bagarello; Vito Ferro; Giuseppe Giordano

2009-01-01

183

Body size and sexual size dimorphism in primates: influence of climate and net primary productivity.

UK PubMed Central (United Kingdom)

Understanding the evolution of body size and sexual size dimorphism has been a longstanding goal in evolutionary biology. Previous work has shown that environmental stress can constrain male-biased sexual size dimorphism at the population level, but we know little about how this might translate to geographical patterns of body size and sexual size dimorphism at the species level. Environmental constraints due to a highly seasonal, resource-poor and/or variable environment have often been cited to explain the unusual lack of sexual size dimorphism among Madagascar's diverse and numerous primate taxa; however, empirical tests of this hypothesis are lacking. Using a phylogenetic approach and a geographical information system platform, we explored the role of seasonality, interannual variability and annual measures of temperature and rainfall, and net primary productivity on patterns of body size and sexual size dimorphism across 130 species of primates. Phylogenetically controlled comparisons showed no support for a role of environmental constraints in moderating sexual size dimorphism at the interspecific level, despite significant associations of environmental variables with body mass. Results suggest that the focus of discussions that have dominated in the last two decades regarding the role of environmental constraints in driving patterns of monomorphism of Madagascar's lemurs should be reconsidered; however, the conundrum remains.

Dunham AE; Maitner BS; Razafindratsima OH; Simmons MC; Roy CL

2013-11-01

184

Body size and sexual size dimorphism in primates: influence of climate and net primary productivity.

Understanding the evolution of body size and sexual size dimorphism has been a longstanding goal in evolutionary biology. Previous work has shown that environmental stress can constrain male-biased sexual size dimorphism at the population level, but we know little about how this might translate to geographical patterns of body size and sexual size dimorphism at the species level. Environmental constraints due to a highly seasonal, resource-poor and/or variable environment have often been cited to explain the unusual lack of sexual size dimorphism among Madagascar's diverse and numerous primate taxa; however, empirical tests of this hypothesis are lacking. Using a phylogenetic approach and a geographical information system platform, we explored the role of seasonality, interannual variability and annual measures of temperature and rainfall, and net primary productivity on patterns of body size and sexual size dimorphism across 130 species of primates. Phylogenetically controlled comparisons showed no support for a role of environmental constraints in moderating sexual size dimorphism at the interspecific level, despite significant associations of environmental variables with body mass. Results suggest that the focus of discussions that have dominated in the last two decades regarding the role of environmental constraints in driving patterns of monomorphism of Madagascar's lemurs should be reconsidered; however, the conundrum remains. PMID:24016213

Dunham, A E; Maitner, B S; Razafindratsima, O H; Simmons, M C; Roy, C L

2013-09-10

185

Droplet size distributions in chemical dispersion of oil spills

Energy Technology Data Exchange (ETDEWEB)

The results are presented of a series of chemical dispersion tests in which three crude oils (Gullfaks, Statfjord, and Arabian Heavy) each at 4 states of weathering have been dispersed at 13 {sup o}C with two dispersants (Finasol OSR-5 and OSR-12) using three laboratory tests (Warren Spring Rotating Flask - WSL-test, Institute Francais du P-trole flow test - IFP-test and Mackay Nadeau Steeleman - MNS-test). Effectiveness and dispersed oil droplet size distribution in the different test methods have been studied and an attempt has been made to develop correlation or mathematical models of the chemical dispersion phenomena. This mathematical treatment helps to explain the reasons that the tests give different results. It is concluded that at present our understanding of the basic dispersion phenomena is not sufficient to form a basis for a reliable model. Several modeling approaches are discussed in the hope that when further data and insights become available, reliable models may be developed to describe this complex process. 14 refs., 5 figs., 4 tabs.

Daling, P.S.; Mackay, D.; Mackay, N.; Brandvik, P.J.

1990-09-01

186

The size distribution of Jupiter Family comet nuclei

We present an updated cumulative size distribution (CSD) for Jupiter Family comet (JFC) nuclei, including a rigourous assessment of the uncertainty on the slope of the CSD. The CSD is expressed as a power law, N(>r_N) \\propto r_N^{-q}, where r_N is the radius of the nuclei and q is the slope. We include a large number of optical observations published by ourselves and others since the comprehensive review in the "Comets II" book (Lamy et al. 2004), and make use of an improved fitting method. We assess the uncertainty on the CSD due to all of the unknowns and uncertainties involved (photometric uncertainty, assumed phase function, albedo and shape of the nucleus) by means of Monte Carlo simulations. In order to do this we also briefly review the current measurements of these parameters for JFCs. Our final CSD has a slope q=1.92\\pm 0.20 for nuclei with radius r_N \\ge 1.25 km.

Snodgrass, C; Lowry, S C; Weissman, P

2011-01-01

187

Thermal properties, sizes, and size distribution of Jupiter-family cometary nuclei

We present results from SEPPCoN, an on-going Survey of the Ensemble Physical Properties of Cometary Nuclei. In this report we discuss mid-infrared measurements of the thermal emission from 89 nuclei of Jupiter-family comets (JFCs). All data were obtained in 2006 and 2007 using imaging capabilities of the Spitzer Space Telescope. The comets were typically 4-5 AU from the Sun when observed and most showed only a point-source with little or no extended emission from dust. For those comets showing dust, we used image processing to photometrically extract the nuclei. For all 89 comets, we present new effective radii, and for 57 comets we present beaming parameters. Thus our survey provides the largest compilation of radiometrically-derived physical properties of nuclei to date. We have six main conclusions: (a) The average beaming parameter of the JFC population is 1.03 ± 0.11, consistent with unity; coupled with the large distance of the nuclei from the Sun, this indicates that most nuclei have Tempel 1-like thermal inertia. Only two of the 57 nuclei had outlying values (in a statistical sense) of infrared beaming. (b) The known JFC population is not complete even at 3 km radius, and even for comets that approach to ˜2 AU from the Sun and so ought to be more discoverable. Several recently-discovered comets in our survey have small perihelia and large (above ˜2 km) radii. (c) With our radii, we derive an independent estimate of the JFC nuclear cumulative size distribution (CSD), and we find that it has a power-law slope of around -1.9, with the exact value depending on the bounds in radius. (d) This power-law is close to that derived by others from visible-wavelength observations that assume a fixed geometric albedo, suggesting that there is no strong dependence of geometric albedo with radius. (e) The observed CSD shows a hint of structure with an excess of comets with radii 3-6 km. (f) Our CSD is consistent with the idea that the intrinsic size distribution of the JFC population is not a simple power-law and lacks many sub-kilometer objects.

Fernández, Y. R.; Kelley, M. S.; Lamy, P. L.; Toth, I.; Groussin, O.; Lisse, C. M.; A’Hearn, M. F.; Bauer, J. M.; Campins, H.; Fitzsimmons, A.; Licandro, J.; Lowry, S. C.; Meech, K. J.; Pittichová, J.; Reach, W. T.; Snodgrass, C.; Weaver, H. A.

2013-09-01

188

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

189

Activity size distribution of the short-lived and long-lived radionuclides in outdoor air

International Nuclear Information System (INIS)

[en] There are a number of radioactive isotopes of different elements in the atmosphere near ground level. Most of them are decay products from the 238U- and 232Th-chains with the highest activity concentration of the short-lived 222Rn-(radon)(1-100 Bq/m3) and 220Rn-(thoron) (0.01-1 Bq/m3) decay products. The long-lived radon decay products (210Pb/210Po) have concentrations between 1-5x10-4 Bq/m3. In contrast to these nuclides the amount of the activity concentration of 7Be (1-7x10-3 Bq/m3)is produced by interaction of the cosmic rays with atmospheric gases. Most of these airborne radionuclides are adsorbed on the surface of aerosol particles and form radioactive aerosol. Therefore the behaviour of the airborne radionuclides is determined by the behaviour of the aerosol particles in the atmosphere. Besides the generation rate the activity concentration of the radionuclides in air is influenced by their transport in the atmosphere and by the radioactive decay. In addition, for the longer-lived radionuclides (half-live >1 d) the removal processes (dry deposition, wet deposition) from the atmosphere have an influence on the activity concentration and the coagulation process will significantly change the activity size distribution of the original radioactive aerosol. The activity size distribution of the radioactive aerosol is the dominant parameter for the behaviour of the radionuclides in the environment. The removal processes from the atmosphere, the deposition rate on ground and vegetation and the deposition probability in the lung during inhalation depend on the particle size. In this paper the measurement results of the activity size distribution of the short-lived (218Po, 214Po) and the long-lived (210Pb, 210Po) radon and thoron (212Pb, 212Po) decay products and 7Be are summarised, obtained from measurements over a longer period in outdoor air during the last years. Especially, the aim was to find out the differences between the size distributions of these radionuclides. Therefore it was important to use measurement techniques, which made it possible, to register simultaneously almost all of these radionuclides during one measurement run over a longer time period

2002-01-01

190

Thermal Properties, Sizes, and Size Distribution of Jupiter-Family Cometary Nuclei

We present results from SEPPCoN, an on-going Survey of the Ensemble Physical Properties of Cometary Nuclei. In this report we discuss mid-infrared measurements of the thermal emission from 89 nuclei of Jupiter-family comets (JFCs). All data were obtained in 2006 and 2007 with the Spitzer Space Telescope. For all 89 comets, we present new effective radii, and for 57 comets we present beaming parameters. Thus our survey provides the largest compilation of radiometrically-derived physical properties of nuclei to date. We conclude the following. (a) The average beaming parameter of the JFC population is 1.03+/-0.11, consistent with unity, and indicating low thermal inertia. (b) The known JFC population is not complete even at 3 km radius, and even for comets with perihelia near ~2 AU. (c) We find that the JFC nuclear cumulative size distribution (CSD) has a power-law slope of around -1.9. (d) This power-law is close to that derived from visible-wavelength observations, suggesting that there is no strong dependenc...

Fernandez, Y R; Lamy, P L; Toth, I; Groussin, O; Lisse, C M; A'Hearn, M F; Bauer, J M; Campins, H; Fitzsimmons, A; Licandro, J; Lowry, S C; Meech, K J; Pittichova, J; Reach, W T; Snodgrass, C; Weaver, H A

2013-01-01

191

It is demonstrated that a fine control over the size and size distribution of nanoparticles could be achieved using digestive ripening at different temperatures. Such variations in size and size distributions hugely influence the self-assembled processes in nanoparticles, and result in superlattice structures that are controlled by subtle interplay between ligand orientational entropy and their interdigitation and the van der Waals attraction between the metal cores.It is demonstrated that a fine control over the size and size distribution of nanoparticles could be achieved using digestive ripening at different temperatures. Such variations in size and size distributions hugely influence the self-assembled processes in nanoparticles, and result in superlattice structures that are controlled by subtle interplay between ligand orientational entropy and their interdigitation and the van der Waals attraction between the metal cores. Electronic supplementary information (ESI) available: Experimental details of nanoparticle synthesis and digestive ripening. Details of instruments used and more TEM images are provided as ESI. See DOI: 10.1039/c2nr32855k

Sahu, Puspanjali; Prasad, B. L. V.

2013-02-01

192

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

193

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; Lin Jian-Zhong

2012-01-01

194

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

195

Vertical distribution of grain size for wind blown sand

Grain size-sorting characteristics from twenty-five vertical, mass-flux profiles for a mixed grain population are presented from a field study conducted in Jericoacoara, Brazil. The vertical mass flux profile is best described using an exponential decay function. An analysis of the grain-size statistics shows that a reverse in grain-size trends occurs at an inflection zone located 0.05-0.15 m above the bed. Below this inflection, mean grain-size decreases steeply with elevation in the near bed region dominated by reptation and saltation modes of transport. Above the inflection there is a coarsening of grain size with elevation. Sorting improves with elevation above the surface. There is not a strong relationship between skewness and kurtosis with elevation. The grain-size inflection above the surface is a characteristic of saltation in some natural environments, with important implications for numerical modeling of grain trajectories.

Farrell, E. J.; Sherman, D. J.; Ellis, J. T.; Li, B.

2012-12-01

196

The aerosol of Jinamar valley during 1993-94. 2. Particulates size distribution

Energy Technology Data Exchange (ETDEWEB)

The size distribution of the aerosol plays a key role in determining air pollution effects. Health hazards associated with airborne particles depend upon the site of deposition in the lungs, which is related to particle size, shape and density. Aerosol size distribution in the atmosphere of Jinamar Valley (Gran Canaria isle, Canary Islands) from November 1993 to October 1994 was determined

Ling Ling, F.; Castellano, A.V.; Cancio, J.A.L. [Industriales Univ. Las Plamas GC. (Spain). Depto. de Ingenieria de Procesos

1995-12-31

197

Method determining particle size distribution in material flow and device for its realization

International Nuclear Information System (INIS)

Method fo determinin particle size distribution in material flow moving wth constant velocity is described. The method eies in transmission o narro ray of X-quanta through the flow of moving particles an detection of quanta which passed through the flow. Distribution of time intervals between quanta before and after passage through material is detected in order to improve the accuracy of measuring small size particles. The difference of time interval distributions is used to determine particle size distribution. A device for determinin particle size distribution in material flow is described

1977-01-01

198

Dependence of size distribution for liquid cluster ions on retarding voltage.

UK PubMed Central (United Kingdom)

We have succeeded in producing liquid clusters such as ethanol and water clusters by an adiabatic expansion phenomenon, and the cluster size distribution was analyzed by using the time-of-flight method. For ethanol cluster ions, the size was distributed between a few hundreds and a few thousands, and the peak size was approximately 1200 molecules per cluster. For water cluster ions, the size distribution shifted to higher values, and the peak size was approximately 2500 molecules per cluster. Furthermore, the cluster size distribution was measured by changing the retarding voltage, and it was found that the minimum size increased with increase of the retarding voltage. In addition, the minimum size was larger than the critical size estimated by the theoretical calculation.

Takaoka GH; Okada T; Sugiyama K; Kawashita M

2008-02-01

199

Dependence of size distribution for liquid cluster ions on retarding voltage

We have succeeded in producing liquid clusters such as ethanol and water clusters by an adiabatic expansion phenomenon, and the cluster size distribution was analyzed by using the time-of-flight method. For ethanol cluster ions, the size was distributed between a few hundreds and a few thousands, and the peak size was approximately 1200 molecules per cluster. For water cluster ions, the size distribution shifted to higher values, and the peak size was approximately 2500 molecules per cluster. Furthermore, the cluster size distribution was measured by changing the retarding voltage, and it was found that the minimum size increased with increase of the retarding voltage. In addition, the minimum size was larger than the critical size estimated by the theoretical calculation.

Takaoka, Gikan H.; Okada, Takeshi; Sugiyama, Kazumichi; Kawashita, Masakazu

2008-02-01

200

Size distribution dynamics reveal particle-phase chemistry in organic aerosol formation.

UK PubMed Central (United Kingdom)

Organic aerosols are ubiquitous in the atmosphere and play a central role in climate, air quality, and public health. The aerosol size distribution is key in determining its optical properties and cloud condensation nucleus activity. The dominant portion of organic aerosol is formed through gas-phase oxidation of volatile organic compounds, so-called secondary organic aerosols (SOAs). Typical experimental measurements of SOA formation include total SOA mass and atomic oxygen-to-carbon ratio. These measurements, alone, are generally insufficient to reveal the extent to which condensed-phase reactions occur in conjunction with the multigeneration gas-phase photooxidation. Combining laboratory chamber experiments and kinetic gas-particle modeling for the dodecane SOA system, here we show that the presence of particle-phase chemistry is reflected in the evolution of the SOA size distribution as well as its mass concentration. Particle-phase reactions are predicted to occur mainly at the particle surface, and the reaction products contribute more than half of the SOA mass. Chamber photooxidation with a midexperiment aldehyde injection confirms that heterogeneous reaction of aldehydes with organic hydroperoxides forming peroxyhemiacetals can lead to a large increase in SOA mass. Although experiments need to be conducted with other SOA precursor hydrocarbons, current results demonstrate coupling between particle-phase chemistry and size distribution dynamics in the formation of SOAs, thereby opening up an avenue for analysis of the SOA formation process.

Shiraiwa M; Yee LD; Schilling KA; Loza CL; Craven JS; Zuend A; Ziemann PJ; Seinfeld JH

2013-07-01

201

International Nuclear Information System (INIS)

[en] This report describes the experiences from the use of QUANTIMET image analyzing instrument (QTM) together with some results from the densification experiments. It was demonstrated that the grain size measurement by QTM for standard specimen was very accurate, and the method was applied for the grain size determination of the UO2 from the densification experiment. The technical problems in the determinations of pore size and pore distribution were discussed and the methods to treat the problems were proposed. The pore distribution obtained by this method are demonstrated. (auth.)

1977-01-01

202

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

203

Size and Scar Distributions of the Yeast Saccharomyces Cerevisiae.

A model for the growth of populations of Saccharomyces cerevisiae is formulated and analyzed. The probability of bud emergence is assumed to depend on the size of the cell. Under certain conditions on birth size the model can be reduced to a single renewa...

M. Gyllenberg

1985-01-01

204

The size distributions for the linear step-growth polymerization containing a relatively small number of molecules (in the range of 20-10000) have been calculated using computer simulations. Contrary to the most probable distribution of Flory, which predicts a continuous linear increase of the polydispersity index (PDI) from the value of 1 to 2, it has been found that the PDI increases up to a certain maximum value followed by a decrease to unity as the extent of conversion (p) approaches unity. The maxima of the PDI versus p curves as well as the sharpness of the decrease of these curves to unity have been found to strongly depend on the number of reacting species. In addition, on the basis of a rigorous statistical treatment, the number and the weight-average size distributions have been derived, which are in perfect agreement with those obtained by computer simulation. Furthermore, the derived distributions can also be applied for the description of reaction products of depolymerization reactions. PMID:23517507

Kéki, Sándor; Zsuga, Miklós; Kuki, Ákos

2013-04-04

205

UK PubMed Central (United Kingdom)

The size distributions for the linear step-growth polymerization containing a relatively small number of molecules (in the range of 20-10000) have been calculated using computer simulations. Contrary to the most probable distribution of Flory, which predicts a continuous linear increase of the polydispersity index (PDI) from the value of 1 to 2, it has been found that the PDI increases up to a certain maximum value followed by a decrease to unity as the extent of conversion (p) approaches unity. The maxima of the PDI versus p curves as well as the sharpness of the decrease of these curves to unity have been found to strongly depend on the number of reacting species. In addition, on the basis of a rigorous statistical treatment, the number and the weight-average size distributions have been derived, which are in perfect agreement with those obtained by computer simulation. Furthermore, the derived distributions can also be applied for the description of reaction products of depolymerization reactions.

Kéki S; Zsuga M; Kuki Á

2013-04-01

206

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

207

Large and mono-sized product crystals from natural cooling mode batch crystallizer

Energy Technology Data Exchange (ETDEWEB)

The performance of a 12.2L batch crystallizer operated under natural cooling mode was remarkably improved with seeding. The product crystal size distribution (CSD) was bi-modal at low seed concentrations, reflecting the contribution of crystals newly generated by a secondary nucleation mechanism. With increasing seed concentration, the fraction of the newly generated particles decreased. At high seed concentrations, a large and mono-dispersed product was obtained. A comprehensive seed chart for potassium alum crystallization incorporating the effects of seed concentration, seed size and seed quality on the product weight mean size was developed. With the aid of this chart, an appropriate seed size and seed concentration can be chosen either to maximize growth or to minimize nucleation in a given batch crystallizer configuration. In addition to the natural cooling mode, the other two cooling policies, either of which requires a respective temperature control, were examined. The bi-modal crystal size distribution characteristics remained the same at low seed concentrations. At high seed concentrations, no effect of cooling mode on the CSD was observed. Hence, natural cooling, a simple and easily operable mode with no temperature control, can be beneficially applied to obtain large and mono-dispersed product crystals with adequate seed concentration. 12 refs., 8 figs., 1 tab.

Jagadesh, D.; Kubota, N.; Yokota, M.; Sato, A.; Tavare, N. [Iwate University, Iwate (Japan)

1996-10-20

208

Pair production as a probe of colliding beam size

International Nuclear Information System (INIS)

We propose the use of soft e+e- pairs as a non-evasive measurement of the colliding beam size. The angular distribution of the pair particles that have different sign of charge from that of the opposing beam, provides the information about the aspect ratio of the beam. The transverse momentum of the other species in the pair, on the other hand, carries information about the horizontal dimension of the beam. Together, one can in principle measure both ?x and ?y

1994-07-01

209

UK PubMed Central (United Kingdom)

Follicle sections vary in size according to their inclination mainly in hypertrophied thyroids. Sagittal sections elicit a shift to small classes, while transversal sections, to large classes. There is no mathematical transformation able to convert data obtained by sections into "true" sizes of follicles, as may be achieved by isolation. All papers emphasizing only section diameters and inferring about follicle size must be cautiously interpreted, and even discarded, if they tend to establish differences in follicle size solely on that basis. Follicle isolation is necessary if we need to establish follicle size and shape. Although proportions are almost stable for rats of the same age and weight, the proportions of follicle size may vary, as dependent on age and other internal and external conditions. The situation is most complicated by colloid accumulation; but despite these impedimenta, TSH secretion enlarges the follicles, a situation hitherto not well established. Cell enlargement is consequently followed by follicle enlargement, despite colloid resorption.

Barbier A; Radu M; Repciuc E

1976-01-01

210

Energy Technology Data Exchange (ETDEWEB)

Coal particle size and mineral matter content have important effects on coal combustion. The mineral content of five Chinese coals was determined by a method combining densitometry and particle-size analysis. The finer particles of pulverized samples were found to contain more mineral content. Rank also had a significant influence on the particle-size ash-content distribution of pulverized coal particles. The sharpest size-ash distribution was found in pulverized anthracite samples; a broader distribution was found with bituminous coal samples, while a uniform distribution was observed in pulverized lignite samples. Ash in higher ash anthracite or lower ash bituminous coal is more evenly distributed. It is a combined effect of size distribution, yield, and proximate analysis of their density separation fractions. Mineral matter tends to distribute more evenly in finer pulverized coals. This results from a relative increase of the low-density fraction in the finer particles. 13 refs., 10 figs., 10 tabs.

Hong Zhang; Yan-xue Mo; Ming Sun; Xian-yong Wei [China University of Mining and Technology, Jiangsu (China). School of Chemical Engineering

2005-12-01

211

Energy Technology Data Exchange (ETDEWEB)

Charged product multiplicities and Z distributions were measured for single multi-fragmenting sources (A = 200 - 400) produced in collisions between heavy nuclei at the same available energy per nucleon. Z distributions are found independent of the source size while fragment multiplicities scale as the charge of the total systems. A complete dynamical simulation, in which multifragmentation originates in the spinodal decomposition of a finite piece of nuclear matter, well accounts for this experimental observation. (authors) 3 refs., 1 fig.

Rivet, M.F.; Bacri, C.O.; Borderie, B.; Dore, D.; Frankland, J.D.; Plagnol, E.; Squalli, M.; Tassan-Got, L. [Experimental Research Division, Inst. de Physique Nucleaire, Paris-11 Univ., 91 - Orsay (France); INDRA collaboration

1999-11-01

212

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.)...

213

International Nuclear Information System (INIS)

Ambient aerosol size distributions oof 131I, 103Ru, 132Te and 137Cs radionuclides were measured in Helsinki, Finland during May 7 - 14, 1986. Radioactivity size distributions were unimodal. Geometric mean diameter of 131I was in the size range 0.33 - 0.57 ?m a.e.d.. Other isotopes had geometric mean diameters in the size range 0.65 - 0.93 ?m a.e.d.. (author).

1986-01-01

214

Testing study on the law of anthracite's impacting dust particle-size distribution

Energy Technology Data Exchange (ETDEWEB)

Using fractal theory to analyse the impacting dust particle size distribution characteristics of Bofang Mine No. 3 coal seam's coal sample, the paper concludes that fractal characteristics exist between the particle size of impacting coal dust and its weight. With the increase of impact height and impact times, the total amount of small size dust is also increased. This offers a new method to describe coal dust particle size distribution characteristics quantifiably. 8 refs., 1 fig., 2 tabs.

Zheng, G.; Kang, T.; Zhai, D. (and others) [Coal Co. Ltd., Dongsheng (China)

2007-06-15

215

A generalized statistical model for the size distribution of wealth

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

Clementi, F; Kaniadakis, G

2012-01-01

216

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

217

The Bose-Einstein distribution functions and the multiparticle production at high energies

Energy Technology Data Exchange (ETDEWEB)

The evolution properties of propagating particles produced at high energies in a randomly distributed environment are studied. The finite size of the phase space of the multiparticle production region as well as the chaoticity can be derived. (author)

Kozlov, G.A. [Bogoliubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, Dubna (Russian Federation)]. E-mail: kozlov@thsun1.jinr.ru

2002-04-01

218

The Bose-Einstein distribution functions and the multiparticle production at high energies

International Nuclear Information System (INIS)

The evolution properties of propagating particles produced at high energies in a randomly distributed environment are studied. The finite size of the phase space of the multiparticle production region as well as the chaoticity can be derived. (author)

2002-01-01

219

The Bose-Einstein distribution functions and the multiparticle production at high energies

The evolution properties of propagating particles produced at high energies in a randomly distributed environment are studied. The finite size of the phase space of the multiparticle production region as well as the chaoticity can be derived.

Kozlov, G. A.

2002-04-01

220

Multi-component Erlang distribution of plant seed masses and sizes

The mass and the size distributions of plant seeds are very similar to the multi-component Erlang distribution of final-state particle multiplicities in high-energy collisions. We study the mass, length, width, and thickness distributions of pumpkin and marrow squash seeds in this paper. The corresponding distribution curves are obtained and fitted by using the multi-component Erlang distribution. In the comparison, the method of ?2-testing is used. The mass and the size distributions of the mentioned seeds are shown to obey approximately the multi-component Erlang distribution with the component number being 1.

Fan, San-Hong; Wei, Hua-Rong

2012-12-01

221

City-size distributions and the world urban system in the twentieth century.

UK PubMed Central (United Kingdom)

"In this paper we trace and interpret changes in the geographical pattern and city-size distribution of the world's largest cities in the twentieth century. Since 1900 the geographical distribution of these cities has become increasingly dispersed; their city-size distribution by rank was nearly linear in 1900 and 1940, and convex in 1980. We interpret the convex distribution which emerged following World War 2 as reflecting an economically integrated but politically and demographically partitioned global urban system. Our interpretation of changes in size distribution of cities emphasizes demographic considerations, largely neglected in previous investigations, including migration and relative rates of population change."

Ettlinger N; Archer JC

1987-09-01

222

City-size distributions and the world urban system in the twentieth century.

"In this paper we trace and interpret changes in the geographical pattern and city-size distribution of the world's largest cities in the twentieth century. Since 1900 the geographical distribution of these cities has become increasingly dispersed; their city-size distribution by rank was nearly linear in 1900 and 1940, and convex in 1980. We interpret the convex distribution which emerged following World War 2 as reflecting an economically integrated but politically and demographically partitioned global urban system. Our interpretation of changes in size distribution of cities emphasizes demographic considerations, largely neglected in previous investigations, including migration and relative rates of population change." PMID:12268629

Ettlinger, N; Archer, J C

1987-09-01

223

Digital Repository Infrastructure Vision for European Research (DRIVER)

Batch cooling crystallization is one of the important unit operations involving separation of solid-liquid phases. Usually the most common crystal product qualities are directly related to the crystal size distribution (CSD). However the main difficulty in batch crystallization is to obtain a unifor...

Abdul Samad, Noor Asma Fazli; Singh, Ravendra; Sin, Gürkan; Gernaey, Krist; Gani, Rafiqul

224

Energy Technology Data Exchange (ETDEWEB)

For the quantitative analysis of crystallization of calcium carbonate formed by carbonation of lime milk, PSD(particle size distribution) of the calcium carbonate, which is the carbonation product of lime milk, was numerically simulated by the method of discretization of population balance and compared with the experimental data of semi-batch precipitative crystallizer. The simulated PSD was well correlated with the experimental data. And the simulated results of PSD for size-dependent agglomeration were well-matched to the experimental data than for the size-independent agglomeration. As the agglomeration kernel increases, the particle size distribution (PSD) becomes broader and the average particle size(APS) is getting larger. In the range of agglomeration kernel from 0 {mu}l/hr to 0.2 {mu}l/hr, the PSD and APS are strongly affected by the agglomeration kernel. Above 0.2 {mu}l/hr, however, the effect is not so strong on PSD and APS. In contrast to the effect of agglomeration kernel, the PSD becomes narrower and APS is getting smaller with increasing rupture kernel. In the range of rupture kernel from 0 {mu}m{sup -1.5} {center_dot}hr{sup -1} to 100 {mu}m{sup -1.5}{center_dot}hr{sup -1}, the rupture kernel appreciably affects the PSD and APS. An increase in rupture kernel above 100 {mu}m{sup -1.5} centre dothr{sup -1}, however, has only a minor effect on PSD and APS. Moreover, it is shown that agglomeration kernel has greater effect on PSD than rupture kernel. (author). 24 refs., 1 tab., 10 figs.

Yoo, Dong Suk; Lee, Kwang Rae [Kangwon National University, Chuncheon (Korea, Republic of); Lee, Sang Deuk; Ahn, Byoung Sung [Korea Advanced Institute of Science and Technology, Taejon (Korea, Republic of)

1997-06-30

225

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

DEFF Research Database (Denmark)

Crystallite size distributions and particle size distributions were determined by TEM, XRD, and SAXS for three commercially available TiO2 samples and one homemade. The theoretical Guinier Model was fitted to the experimental data and compared to analytical expressions. Modeling of the XRD spectra showed a difference between the analytical size dependent expressions and the theoretical Guinier Model. Primay particle size distributions were extracted from SAXS measurements by the hard sphere model including the interparticle interference factor. The size distributions from SAXS were smaller than the size distribution obtained from the XRD experiments; however, a good agreement was obtained between the two techniques. Electron microscopy, SEM and TEM, confirmed the primary particle sizes, the size distributions, and the shapes obtained by XRD and SAXS. The SSEC78 powder and the commercially available powders showed different morphologies. The SSEC78 powder showed the narrowest sizes distribution while UV100 and TiO2_5nm consisted of the smallest primary particles. SSEC78, UV100, and TiO2_5nm consisted of both primary particles as well as a secondary structure comprised of nanosized primary particles agglomeration into larger clusters. P25 showed the largest primary particle size, but didn't show a secondary structure.

Jensen, Henrik; Pedersen, JØrgen Houe

2006-01-01

226

Cluster size distributions in particle systems with asymmetric dynamics.

We present exact and asymptotic results for clusters in the one-dimensional totally asymmetric exclusion process (TASEP) with two different dynamics. The expected length of the largest cluster is shown to diverge logarithmically with an increasing system size for ordinary TASEP dynamics and as a logarithm divided by a double logarithm for generalized dynamics, where the hopping probability of a particle depends on the size of the cluster it belongs to. The connection with the asymptotic theory of extreme order statistics is discussed in detail. We also consider a related model of interface growth, where the deposited particles are allowed to relax to the local gravitational minimum. PMID:11736021

Pulkkinen, O; Merikoski, J

2001-10-23

227

Cluster size distributions in particle systems with asymmetric dynamics.

UK PubMed Central (United Kingdom)

We present exact and asymptotic results for clusters in the one-dimensional totally asymmetric exclusion process (TASEP) with two different dynamics. The expected length of the largest cluster is shown to diverge logarithmically with an increasing system size for ordinary TASEP dynamics and as a logarithm divided by a double logarithm for generalized dynamics, where the hopping probability of a particle depends on the size of the cluster it belongs to. The connection with the asymptotic theory of extreme order statistics is discussed in detail. We also consider a related model of interface growth, where the deposited particles are allowed to relax to the local gravitational minimum.

Pulkkinen O; Merikoski J

2001-11-01

228

Distribution of quantum states in enclosures of finite size I

International Nuclear Information System (INIS)

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

1989-01-01

229

Density gradient separation and size distribution of beagle lymphocytes

International Nuclear Information System (INIS)

[en] 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

230

Gradually truncated log-normal in USA publicly traded firm size distribution

We study the statistical distribution of firm size for USA and Brazilian publicly traded firms through the Zipf plot technique. Sale size is used to measure firm size. The Brazilian firm size distribution is given by a log-normal distribution without any adjustable parameter. However, we also need to consider different parameters of log-normal distribution for the largest firms in the distribution, which are mostly foreign firms. The log-normal distribution has to be gradually truncated after a certain critical value for USA firms. Therefore, the original hypothesis of proportional effect proposed by Gibrat is valid with some modification for very large firms. We also consider the possible mechanisms behind this distribution.

Gupta, Hari M.; Campanha, José R.; de Aguiar, Daniela R.; Queiroz, Gabriel A.; Raheja, Charu G.

2007-03-01

231

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

232

The effects of mergers and acquisitions on the firm size distribution

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper provides new empirical evidence on the effects of mergers and acquisitions (M&As) on the shape of the firm size distribution, by using data of the population of manufacturing firms in the Netherlands. Our analysis shows that M&As do not affect the size distribution when we consider the en...

Cefis, E.; Marsili, O.; Schenk, H.

233

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

234

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

235

Evidence of bimodal crystallite size distribution in {mu}c-Si:H films

Energy Technology Data Exchange (ETDEWEB)

We report on the microstructural characterization studies carried out on plasma deposited highly crystalline undoped microcrystalline silicon films to explore the crystallite size distribution present in this material. The modeling of results of spectroscopic ellipsometry using two different sized crystallites is corroborated by the deconvolution of experimental Raman profiles using a modeling method that incorporates a bimodal size distribution of crystallites. The presence of a bimodal size distribution of crystallites is demonstrated as well by the results of atomic force microscopy and X-ray diffraction studies. The qualitative agreement between the results of different studies is discussed.

Ram, Sanjay K. [Laboratoire de Physique des Interfaces et des Couches Minces (UMR 7647 du CNRS), Ecole Polytechnique, 91128 Palaiseau Cedex (France); Department of Physics, Indian Institute of Technology Kanpur, Kanpur 208016 (India)], E-mail: sanjayk.ram@gmail.com; Islam, Md. Nazrul [QAED-SRG, Space Application Centre (ISRO), Ahmedabad 380015 (India); Kumar, Satyendra [Department of Physics, Indian Institute of Technology Kanpur, Kanpur 208016 (India); Roca i Cabarrocas, P. [Laboratoire de Physique des Interfaces et des Couches Minces (UMR 7647 du CNRS), Ecole Polytechnique, 91128 Palaiseau Cedex (France)

2009-03-15

236

Tritium production distribution in the accelerator production of tritium device

Energy Technology Data Exchange (ETDEWEB)

Helium-3 ({sup 3}He) gas is circulated throughout the accelerator production of tritium target/blanket (T/B) assembly to capture neutrons and convert {sup 3}He to tritium. Because {sup 3}He is very expensive, it is important to know the tritium producing effectiveness of {sup 3}He at all points throughout the T/B. The purpose of this paper is to present estimates of the spatial distributions of tritium production, {sup 3}He inventory, and the {sup 3}He FOM.

Kidman, R.B.

1997-11-01

237

A series of experiments designed to study the production of new particulate matter by photolysis of dimethyl sulfide (DMS) and the effect that nonprecipitating clouds, have on the aerosol size distributions were carried out in Calspan Corporation's 600 cu...

W. A. Hoppel J. W. Fitzgerald G. M. Frick R. E. Larson B. J. Wattle

1987-01-01

238

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

Directory of Open Access Journals (Sweden)

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

Yuri Gulbin

2008-01-01

239

Energy Technology Data Exchange (ETDEWEB)

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.

DiPompeo, M. A.; Runnoe, J. C.; Myers, A. D. [Department of Physics and Astronomy 3905, University of Wyoming, 1000 E. University, Laramie, WY 82071 (United States); Boroson, T. A. [National Optical Astronomy Observatory, P.O. Box 26732, Tucson, AZ 85726 (United States)

2013-09-01

240

International Nuclear Information System (INIS)

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

1988-11-03

241

International Nuclear Information System (INIS)

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

1988-11-03

242

Experimental study on bubble size distributions in a direct-contact evaporator

Directory of Open Access Journals (Sweden)

Full Text Available Experimental bubble size distributions and bubble mean diameters were obtained by means of a photographic technique for a direct-contact evaporator operating in the quasi-steady-state regime. Four gas superficial velocities and three different spargers were analysed for the air-water system. In order to assure the statistical significance of the determined size distributions, a minimum number of 450 bubbles was analysed for each experimental condition. Some runs were also conducted with an aqueous solution of sucrose to study the solute effect on bubble size distribution. For the lowest gas superficial velocity considered, at which the homogeneous bubbling regime is observed, the size distribution was log-normal and depended on the orifice diameter in the sparger. As the gas superficial velocity was increased, the size distribution progressively acquired a bimodal shape, regardless of the sparger employed. The presence of sucrose in the continuous phase led to coalescence hindrance.

C. P. Ribeiro Jr.; P. L. C. Lage

2004-01-01

243

Experimental study on bubble size distributions in a direct-contact evaporator

Scientific Electronic Library Online (English)

Full Text Available Abstract in english Experimental bubble size distributions and bubble mean diameters were obtained by means of a photographic technique for a direct-contact evaporator operating in the quasi-steady-state regime. Four gas superficial velocities and three different spargers were analysed for the air-water system. In order to assure the statistical significance of the determined size distributions, a minimum number of 450 bubbles was analysed for each experimental condition. Some runs were also (more) conducted with an aqueous solution of sucrose to study the solute effect on bubble size distribution. For the lowest gas superficial velocity considered, at which the homogeneous bubbling regime is observed, the size distribution was log-normal and depended on the orifice diameter in the sparger. As the gas superficial velocity was increased, the size distribution progressively acquired a bimodal shape, regardless of the sparger employed. The presence of sucrose in the continuous phase led to coalescence hindrance.

Ribeiro Jr., C. P.; Lage, P. L. C.

2004-01-01

244

A facile synthesis of Te nanoparticles with binary size distribution by green chemistry.

UK PubMed Central (United Kingdom)

Our work reports a facile route to colloidal Te nanocrystals with binary uniform size distributions at room temperature. The binary-sized Te nanocrystals were well separated into two size regimes and assembled into films by electrophoretic deposition. The research provides a new platform for nanomaterials to be efficiently synthesized and manipulated.

He W; Krejci A; Lin J; Osmulski ME; Dickerson JH

2011-04-01

245

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 ?...

Dieckmann, Yvonne; Cölfen, Helmut; Hofmann, Heinrich; Petri-Fink, Alke

246

Cost and performance of woody biomass size reduction for energy production

Energy Technology Data Exchange (ETDEWEB)

One of the major pre-processing operations in using biomass as a source of energy or using it for producing pulp for paper industries involves size reduction or grinding. Grinders are the dominant machines in an energy wood harvesting system and possess the highest productivity and cost. Depending on the material and grinding mechanisms (shear, impact, attrition), grinders use a wide range of energy. The design and choice of the grinder is important for reducing the energy input in preparing biomass. This paper reviewed the performance of various commercial wood grinders with respect to ground quality and their cost estimation. The paper presented a review of commercial equipment used for size reduction of woody biomass. The review also included the capital cost, operating costs and performance of equipment. The performance of equipment was evaluated based on its power consumption and the quality of chip production, which included average particle size and particle size distribution. The paper discussed size reduction machinery classification; quality specification of wood particles after size reduction for energy conversion; and cost estimation of size reduction machines. It was concluded that hammer hogs are relatively less expensive than chippers. Future research should be directed to analyzing the performance of hammer mills for woody biomass and its energy requirement during grinding. 14 refs., 5 tabs., 7 figs.

Naimi, L.J.; Sokhansanj, S.; Mani, S.; Hoque, M.; Bi, T. [British Columbia Univ., Vancouver, BC (Canada). Dept. of Chemical and Biological Engineering; Womac, A.R. [Tennessee Univ., Knoxville, T (United States). Dept. of Biosystems Engineering and Soil Science; Narayan, S. [First American Scientific Corp., Delta, BC (Canada)

2006-07-01

247

From the results of a comprehensive asteroid population evolution model, we conclude that the YORP-induced rotational fission hypothesis has strong repercussions for the small size end of the Main Belt asteroid size frequency distribution. These results are consistent with observed asteroid population statistics. The foundation of this model is the asteroid rotation model of Marzari et al. (2011), which incorporates both the YORP effect and collisional evolution. This work adds to that model the rotational fission hypothesis (i.e. when the rotation rate exceeds a critical value, erosion and binary formation occur). The YORP effect timescale for large asteroids with diameters D > ~6 km is longer than the collision timescale in the Main Belt, thus the frequency of large asteroids is determined by a collisional equilibrium (e.g. Bottke 2005), but for small asteroids with diameters D distribution. Using the outputs of the asteroid population evolution model and a 1-D collision evolution model, we can generate this new size frequency distribution and it matches the change in slope observed by the SKADS survey (Gladman 2009). This agreement is achieved with both an accretional power-law or a truncated “Asteroids were Born Big” size frequency distribution (Weidenschilling 2010, Morbidelli 2009).

Rossi, Alessandro; Jacobson, S.; Marzari, F.; Scheeres, D.; Davis, D. R.

2013-10-01

248

Finite Size Effect of Nanoparticles to the Atomic Pair Distribution Functions

The finite size effects of the nanoparticles to the atomic pair distribution functions (PDF) are discussed by calculating the radial distribution functions (RDF) on nanoparticles with various shapes, such as sheet, belt, rod, tube and sphere, assuming continua. Their characteristics are shown depending on the shapes and the sizes of the nanoparticles. Alternately, these PDFs can be used to measure the shapes and the sizes of ordered lattice part inside of any materials such as nanoparticles and bulks.

Kodama, K; Shamoto, S

2005-01-01

249

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

Directory of Open Access Journals (Sweden)

Full Text Available 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, organic carbon (OC) and monosaccharide anhydrides from the filter samples. During the measurements gravimetric mass in the MOUDI collections varied between 3.4 and 55.0 ?g m?3 and the WSOC concentration was between 0.3 and 7.4 ?g m?3. On average, water-soluble particulate organic matter (WSPOM, WSOC multiplied by 1.6) comprised 25±7.7% and 7.5±3.4% of aerosol PM1 mass and the PM1?10 mass, respectively. Inorganic ions contributed 33±12% and 28±19% of the analyzed PM1 and PM1?10 aerosol mass. Five different aerosol categories corresponding to different sources or source areas were identified (long-range transport aerosols, biomass burning aerosols from wild land fires and from small-scale wood combustion, aerosols originating from marine areas and from the clean arctic areas). Clear differences in WSOC concentrations and size distributions originating from different sources or source areas were observed, although there are also many other factors which might affect the results. E.g. the local conditions and sources of volatile organic compounds (VOCs) and aerosols as well as various transformation processes are likely to have an impact on the measured aerosol composition. Using the source categories, it was identified that especially the oxidation products of biogenic VOCs in summer had a clear effect on WSOC concentrations.

H. Timonen; S. Saarikoski; O. Tolonen-Kivimäki; M. Aurela; K. Saarnio; T. Petäjä; P. P. Aalto; M. Kulmala; T. Pakkanen; R. Hillamo

2008-01-01

250

Endotoxins in cotton: washing effects and size distribution

Energy Technology Data Exchange (ETDEWEB)

Endotoxin contamination was measured in washed and unwashed cottons from three distinct growing areas, California, Mississippi, and Texas. The data show differences in endotoxin contamination based upon the geographic source of the cotton. It is also shown that washing bulk cotton before the carding process results in lower endotoxin in the cotton dust. Washing conditions can affect the endotoxin levels, and all size fractions of the airborne dust contain quantifiable endotoxin contamination. Endotoxin analyses provide a simple and reliable method for monitoring the cleanliness of cotton or airborne cotton dusts.

Olenchock, S.A.; Mull, J.C.; Jones, W.G.

1983-01-01

251

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

252

Energy Technology Data Exchange (ETDEWEB)

Particle size distributions determined by small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) are investigated for samples of interacting hard spheres. Polydispersity in the samples is determined from the SAXS data by fitting the Porod region to the form factor of a sphere of uniform electron density smeared by a Gaussian distribution of sphere diameters. The authors find good agreement between SAXS-determined particle size distributions and those calculated from TEM image analysis.

Rieker, T.; Hanprasopwattana, A.; Datye, A.; Hubbard, P. [Univ. of New Mexico, Albuquerque, NM (United States)

1999-01-19

253

Energy Technology Data Exchange (ETDEWEB)

Grain size measurements by X-ray diffraction (XRD) analysis and transmission electron microscopy (TEM) observations were carried out on nanocrystalline copper processed by inert gas condensation. Grain size distributions obtained by XRD and TEM follow a log normal relationship. The distributions of both number and volume fractions of grain sizes were evaluated. The mode of the latter was found to be much larger than that of the former. The results of XRD and TEM matched closely in cases of finer mean grain size with a relatively narrow distribution. It was observed that extensive twinning could lead to underestimation of grain size through XRD methods. Grain sizes increased significantly on use of higher compaction temperature during processing or on extended room temperature exposure. Finally, a micromechanical model was used to understand the effect of grain size (volume) distribution on the yielding of nanocrystalline metals. An increase in the mean grain size of standard deviation, which means an increase in the volume fraction of relatively coarse grains, reduces the yield stress significantly. This implies it is not just the average grain size, but the character of the grain size distribution, that controls the mechanical behavior of nanocrystalline metals.

Mitra, R.; Ungar, T.; Morita, T.; Sanders, P.G.; Weertman, J.R.

1999-07-01

254

A Theoretical Model for Mars Crater-Size Frequency Distribution

We present a theoretical and analytical curve with reproduce essential features of the frequency distributions vs. diameter, of the 42,000 crater contained in the Barlow 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 different slopes in the empirical log-log plot of number of craters (N) vs. diameter (D).

Bruckman, W A; Ramos, E

2004-01-01

255

The Pareto-positive stable distribution: A new descriptive model for city size data

The Pareto-positive stable (PPS) distribution is introduced as a new model for describing city size data in a country. The PPS distribution provides a flexible model for fitting the entire range of a set of city size data, where zero and unimodality are possible, and the classical Pareto and Zipf distributions are included as a particular case. Expressions for the shape, moments and other descriptive probabilistic measures are given. Estimation methods are discussed and a simple graphical method for studying the adequacy of the data to model is given. Finally, we consider city size data for Spain for several different years. The new distribution is compared with three classical models: Pareto, lognormal and Tsallis distributions. In all the data sets considered, the PPS distribution outperforms the fits of these three previous distributions.

Sarabia, José María; Prieto, Faustino

2009-10-01

256

THE SIZE DISTRIBUTION OF THE NEPTUNE TROJANS AND THE MISSING INTERMEDIATE-SIZED PLANETESIMALS

International Nuclear Information System (INIS)

We present an ultra-deep survey for Neptune Trojans using the Subaru 8.2 m and Magellan 6.5 m telescopes. The survey reached a 50% detection efficiency in the R band at mR = 25.7 mag and covered 49 deg2 of sky. mR = 25.7 mag corresponds to Neptune Trojans that are about 16 km in radius (assuming an albedo of 0.05). A paucity of smaller Neptune Trojans (radii R = 23.5 ± 0.3), which is also very similar to the other stable reservoirs. All the observed stable regions in the solar system show evidence for Missing Intermediate-Sized Planetesimals (MISPs). This indicates a primordial and not collisional origin, which suggests that planetesimal formation proceeded directly from small to large objects. The scarcity of intermediate- and smaller-sized Neptune Trojans may limit them as being a strong source for the short period comets.

2010-11-10

257

A solvable model of fracture with power-law distribution of fragment sizes

The present paper describes a stochastic model of fracture, whose fragment size distribution can be calculated analytically as a power-law-like distribution. The model is basically cascade fracture, but incorporates the effect that each fragment in each stage of cascade ceases fracture with a certain probability. When the probability is constant, the exponent of the power-law cumulative distribution lies between -1 and 0, depending not only on the probability but the distribution of fracture points. Whereas, when the probability depends on the size of a fragment, the exponent is less than -1, irrespective of the distribution of fracture points.

Yamamoto, Ken

2011-01-01

258

Measurements of rain drop size distributions and estimation of radio-wave attenuation coefficients

Results of photoelectron-detector measurements of rain drop size distributions carried out near Dubna, USSR during May-September, 1987 are presented. It is shown that, for large and small drop diameters, these distributions differ from the Marshall-Palmer ones. Radio-wave attenuation coefficients are evaluated for such distributions.

Zakharian, M. V.; Kornilov, L. N.; Pozhidaev, V. N.

1989-10-01

259

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

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 dust emission 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.

Kok, Jasper F

2011-01-01

260

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

261

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

2011-01-01

262

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

2011-01-01

263

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; Li WANG; Gaofeng TIAN

2012-01-01

264

Catalytic reforming catalyst with modified pore size distribution

Energy Technology Data Exchange (ETDEWEB)

In a naphtha reforming catalyst having at least one catalytic metal deposited on a porous solid catalyst support, an improvement is described which comprises the catalyst having the following in combination: (A) a surface area above about 250M/sup 2//gram of catalyst; (B) A pore volume above about 0.4 cc/gram of catalyst in pores having diameters of from about 30 angstroms to about 38,000 angstroms; and (C) A pore volume distribution wherein about 70 percent or less of the pore volume is in pores having diameters of from about 30 angstroms to about 400 angstroms, and 30 percent or more of the pore volume is in pores having diameters of from about 400 angstroms to about 38,000 angstroms.

Unmuth, E.E.; Fleming, B.A.

1987-10-27

265

Energy Technology Data Exchange (ETDEWEB)

Particle size is a primary determinant of resources available to consumers and of the efficiency of energy transfer through planktonic food chains. Dual radioisotopic labeling (with /sup 14/C-bicarbonate and /sup 3/H-acetate) and size fractionation of naturally-occurring phytoplankton-bacterioplankton assemblages were employed to examine the particle size distributions of planktonic autotrophy and microheterotrophy in four limnologically-dissimilar US reservoirs (Lake Mead, Arizona-Nevada, oligo-mesotrophic; Broken Bow Lake, Oklahoma, mesotrophic; Lake Texoma, Oklahoma-Texas, eutrophic; and Normandy Lake, Tennessee, eutrophic). Small nano- and ultraphytoplankton (< 8.0 ..mu..m) and free-living bacteria (< 3.0 ..mu..m) were primarly responsible for planktonic autotrophy and microheterotrophy, respecitvely, even in eutrophic conditions. Zooplankton grazing experiments indicated that (1) most grazing pressure occurs on 3.0 to 8.0 ..mu..m particles, (2) grazer limitation of the occurrence of attached bacteria amd microbial-detrital aggregates is unlikely, and (3) free-living bacteria are inefficiently harvested, relative to algae, by most reservoir zooplankton. Relative to autorophy, the microheterotrophic conversion of allochthonous dissolved organic matter and algal excretion products to bacterial biomass appears unlikely to be a significant source of organic carbon for planktonic grazers in most reservoirs.

Kimmel, B.L.

1981-01-01

266

Characterization and modeling of bubbles size distribution in mechanical flotation cells

International Nuclear Information System (INIS)

In this work, bubble size distribution is determined for tests in a batch flotation cells, for different impeller speed and air flowrate. Bubbles are sampled and their sizes are measured using image analysis. Size distributions by surface are expressed as cumulative percent passing as well as percent retained. The distributions show a common shape for all tests and are represented with a unique model, selected due to its goodness of fit. This model corresponds to an equation used in heavy media separation and considers two parameters: x50, the 50% passing size, and 1, an adjustable parameter. The correlation coefficient for all tests averages 0.999 for the cumulative distributions and 0.912 for the retained distributions. (Author) 15 refs

2005-01-01

267

Raindrop size distributions and radar reflectivity–rain rate relationships for radar hydrology

Directory of Open Access Journals (Sweden)

Full Text Available The conversion of the radar reflectivity factor Z(mm6m-3) to rain rate R(mm h-1 ) is a crucial step in the hydrological application of weather radar measurements. It has been common practice for over 50 years now to take for this conversion a simple power law relationship between Z and R. It is the purpose of this paper to explain that the fundamental reason for the existence of such power law relationships is the fact that Z and R are related to each other via the raindrop size distribution. To this end, the concept of the raindrop size distribution is first explained. Then, it is demonstrated that there exist two fundamentally different forms of the raindrop size distribution, one corresponding to raindrops present in a volume of air and another corresponding to those arriving at a surface. It is explained how Z and R are defined in terms of both these forms. Using the classical exponential raindrop size distribution as an example, it is demonstrated (1) that the definitions of Z and R naturally lead to power law Z–R relationships, and (2) how the coefficients of such relationships are related to the parameters of the raindrop size distribution. Numerous empirical Z–R relationships are analysed to demonstrate that there exist systematic differences in the coefficients of these relationships and the corresponding parameters of the (exponential) raindrop size distribution between different types of rainfall. Finally, six consistent Z–R relationships are derived, based upon different assumptions regarding the rain rate dependence of the parameters of the (exponential) raindrop size distribution. An appendix shows that these relationships are in fact special cases of a general Z–R relationship that follows from a recently proposed scaling framework for describing raindrop size distributions and their properties. Keywords: radar hydrology, raindrop size distribution, radar reflectivity–rain rate relationship

R. Uijlenhoet; J. H. Pomeroy

2001-01-01

268

Dust Grain-Size Distributions From MRN to MEM

Employing the Maximum Entropy Method algorithm, we fit interstellar extinction measurements which span the wavelength range 0.125-3 micron. We present a uniform set of MEM model fits, all using the same grain materials, optical constants and abundance constraints. In addition, we are taking advantage of improved UV and IR data and better estimates of the gas-to-dust ratio. The model fits cover the entire range of extinction properties that have been seen in the Galaxy and the Magellanic Clouds. The grain models employed for this presentation are the simplistic homogeneous spheres models (i.e., Mathis, Rumpl, & Nordsieck 1977) with two (graphite, silicate) or three (graphite, silicate, amorphous carbon) components. Though such usage is only a first step, the results do provide interesting insight into the use of grain size as a diagnostic of dust environment. We find that the SMC Bar extinction curve cannot be fit using carbon grains alone. This is a challenge to the recent observational result indicating ...

Clayton, G C; Sofia, U J; Gordon, K D; Misselt, K A; Clayton, Geoffrey C.; Wolff, Michael J.; Sofia, Ulysses J.

2003-01-01

269

Dust Grain Size Distributions from MRN to MEM

Employing the maximum entropy method (MEM) algorithm, we fit interstellar extinction measurements that span the wavelength range 0.125-3 ?m. We present a uniform set of MEM model fits, all using the same grain materials, optical constants, and abundance constraints. In addition, we are taking advantage of improved UV and IR data and better estimates of the gas-to-dust ratio. The model fits cover the entire range of extinction properties that have been seen in the Galaxy and the Magellanic Clouds. The grain models employed for this presentation are the simplistic homogeneous sphere models (i.e., those of Mathis, Rumpl, & Nordsieck in 1977) with two (graphite, silicate) or three (graphite, silicate, amorphous carbon) components. Although such usage is only a first step, the results do provide interesting insight into the use of grain size as a diagnostic of dust environment. We find that the SMC bar extinction curve cannot be fitted using carbon grains alone. This is a challenge to the recent observational result indicating little silicon depletion in the SMC.

Clayton, Geoffrey C.; Wolff, Michael J.; Sofia, Ulysses J.; Gordon, K. D.; Misselt, K. A.

2003-05-01

270

International Nuclear Information System (INIS)

Infrared observations of the broken comet 73P/Schwassmann-Wachmann 3 were performed at 24 ?m with the Spitzer Space Telescope in 2006 May. The image reveals the fragments and the meteoroid stream associated with the comet. Heavy numerical simulation of the production and evolution of the meteoroids ejected by the comet during the last century, coupled with a model of thermal emission of cometary grains, allows us to determine the dust size distribution. As found by in situ measurements performed during spacecraft encounters with 1P/Halley and 81P/Wild 2, the size distribution for 73P shows a plateau for the mass range 10-10 to 10-7 kg. Except for this mass bin, the cumulative mass index is in the range 0.85-1, so the size distribution has the same slope for dust and meteoroids separately, but with a significantly different normalization such that there are more large particles than would be expected from an extrapolation of the small-particle size distribution. The abundance of meteoroids with masses larger than 10-5 kg is poorly determined by in situ measurements due to the small number of detections; infrared observations provide a unique way to constrain it. The stream is mainly composed of particles ejected during the 1995 and 2001 passages. We show that the dust production rate increased by a factor of 11 during the 1995 outburst.

271

The Pareto-positive stable distribution: a descriptive model for city size data

Energy Technology Data Exchange (ETDEWEB)

The Pareto-positive stable (PPS) distribution is introduced as a new model for describing city size data in several countries. The PPS distribution provides a flexible model for fitting all the range of a set of city size data, where zero and unimodality are possible, and the classical Pareto and Zipf distributions are included as a particular case. The new model has a twofold origin. Initially, it can be obtained by mixing the shape parameter of a classical Pareto distribution with a positive stable distribution. In this way we can model the possible heterogeneity in the set of city sizes. The distribution obtained is also genuine by extending the range of the characteristic exponent in the stable law. PPS distribution can be also obtained from a monotonic transformation of the classical Weibull distribution. Probabilistic properties are studied and several descriptive measures are obtained. Maximum likelihood estimators are proposed. Initial estimators of the parameters can be obtained using regression methods. A simple graphical method for studying the adequacy of the data to model is given. Finally, we consider city size data for USA and Spain for several years, because they are the countries with highest migration shocks in recent years. Some classical distributions as well as PPS distribution are fitted, and we conclude that PPS distribution outperforms previous models.

Sarabia, Jose Maria; Prieto, Faustino [University of Cantabria, Santander (Spain)

2009-07-01

272

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

2007-01-01

273

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

274

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

275

ON THE COAGULATION AND SIZE DISTRIBUTION OF PRESSURE CONFINED CORES

International Nuclear Information System (INIS)

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

2013-05-20

276

On the Coagulation and Size Distribution of Pressure Confined Cores

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

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

2013-05-01

277

Combustion emission of soot and pollutant gas species contributes to poor regional air quality near emission sources and to climate change. It is important to understand the formation mechanism and time evolution of these pollutants inside the combustion engine, through detailed modeling of combustion chemistry and microphysics as well as comparison with observation. In this thesis, two multi-zone gas parcel combustion engine models, one for aircraft engines and another for diesel engines, have been developed to study soot size distribution evolution and pollutant formation inside the engines as well as emissions. The models take into account size-resolved (sectional) soot aerosol dynamics (nucleation, growth, and coagulation) and detailed combustion chemistry of jet and diesel fuel. For the aircraft engine, the model considers 362 chemical species, 2657 reversible reactions and 75 aerosol size bins. The model was applied to a CFM56-2-C1 aircraft engine for idle operating conditions. This is the first model to simulate soot size distribution evolution inside an aircraft engine (to our knowledge). The simulated values for major species are generally consistent with measurements. Model simulation shows that, for idle operating conditions, concentrations of most key combustion products don't change significantly in the post-combustor, however, HONO, H2SO4, and HO 2 concentrations change by more than a factor of 10. The sulfur oxidation efficiency (SOE), ([SO3]+[H2SO4])/([SO 2]+[SO3] +[H2SO4]), was found to be 2.1% at the engine exit. For the diesel engine, the multi-zone gas parcel model has been further enhanced by including fuel injection, droplet break-up, fuel evaporation and air entrainment rate. The model considers 283 chemical species, 2137 reversible reactions, and 75 aerosol size bins. The developed model calculates the time evolution of concentrations of these chemical species and soot size distributions inside a diesel engine. This is the first model to simulate soot size distribution evolution inside a diesel engine (to our knowledge). Model calculations are generally consistent with measurements. SOE was found to be 2% at end of the expansion stroke. The diesel engine emission model was used to study the effects of fuel sulfur content (FSC), relative humidity (RH) of intake air and fuel injection angle (FIA) on pollutant formation and emission as well as engine performances. The model simulation shows that FSC does not affect non-sulfur species, however, SO2 and SO3 increase linearly with increase in FSC. Simulation also shows that both higher RH and late injection (higher FIA) increase soot but decrease NOx. The model enables us to test the predictive capability of any existing or newly developed chemical kinetic mechanism of surrogate fuel and soot microphysics inside diesel engines.

Moniruzzaman, Chowdhury G.

278

Aerosol size information is very important for the risk estimation of radon exposure. Recently, a cascade impactor called the electrical low pressure impactor (ELPI) was developed and commercialized. The impactor, which covers a wide diameter range from 0.03 to10 ?m, gives number-weighted size distribution in real time by an electrical detection method. Prior to size measurements of the radon decay products being available, the effects of impaction substrates on size classification were studied. Tested substrate materials were stainless steel plate and aluminum foil, and those surfaces were as follows: (1) untreated, (2) covered with double sided adhesive tape, and (3) silicon grease coated. A large difference was observed among the measured size distributions. Compared with other sizing methods, it was found that the use of grease coated substrates did not interfere with the electrical measurements in the ELPI and also prevented particle rebound or redispersion. It was also confirmed that the coatings caused no damage to energy spectrum analysis in spite of the weak penetration power of radon's alpha ray. Using the ELPI allows size distribution data on aerosol number and activity to be independently determined for the same impactor sample. The ELPI will be useful for the size determination of radon decay products, and thus information on the attachment of radon decay products will be forthcoming.

Yamada, Yuji; Tokonami, Shinji; Yamasaki, Keizo

2005-06-01

279

The problem of determining the size distribution and population density of a population of spherical particles randomly distributed throughout a transparent matrix from data obtained by transmission microscopy on parallel plane-faced sections of known field area and thickness may be readily solved by the use of matrix algebra. The solution presented in this paper may be used to construct conversion matrices whereby the particle size distribution and the numerical density can be calculated directly from the frequency distribution of the observed diameters; the only mathematical processes necessary being mulitplication and addition. Specimen conversion matrices valid for a wide range of conditions are presented in the appended tables. PMID:7359580

Rose, P E

1980-02-01

280

UK PubMed Central (United Kingdom)

The problem of determining the size distribution and population density of a population of spherical particles randomly distributed throughout a transparent matrix from data obtained by transmission microscopy on parallel plane-faced sections of known field area and thickness may be readily solved by the use of matrix algebra. The solution presented in this paper may be used to construct conversion matrices whereby the particle size distribution and the numerical density can be calculated directly from the frequency distribution of the observed diameters; the only mathematical processes necessary being mulitplication and addition. Specimen conversion matrices valid for a wide range of conditions are presented in the appended tables.

Rose PE

1980-02-01

281

Occlusion effects and the distribution of interstellar cloud sizes and masses

The frequency distributions of sizes of ``clouds" and ``clumps" within clouds are significantly flatter for extinction surveys than for CO spectral line surveys, even for comparable size ranges. A possible explanation is the blocking of extinction clouds by larger foreground clouds (occlusion), which should not affect spectral line surveys much because clouds are resolved in velocity space along a given line of sight. We present a simple derivation of the relation between the true and occluded size distributions, assuming clouds are uniformly distributed in space or the distance to a cloud comples is much greater than the size of the complex. Because the occlusion is dominated by the largest clouds, we find that occlusion does not affect the measured size distribution except for sizes comparable to the largest size, implying that occlusion is not responsible for the discrepancy if the range in sizes of the samples is large. However, we find that the range in sizes for many of the published observed samples is...

Scalo, J M

1995-01-01

282

Effect of Flock Size on Fayoumi Layer Production

Directory of Open Access Journals (Sweden)

Full Text Available Group size in poultry breeding flock as well as female and male ratio greatly contributes to their production, in this concern from an Egyptian Fayoumi laying flock in 27th week of age,36 layers were weighed (1.60 kg/layer), randomly grouped in A (11), B (12) and C (13) and allocated breeding cock of same age and flock. Layers kept at Poultry Experiment Station, Tandojam, on flour system, each group provided one laying nest, 16 hr florescent light and 2 sq.ft space per layer were provided. Birds fed 100 g/layer/day and water was provided 24 h. Eggs were collected at 10, 14 and 18 h daily, soundness was checked and stored in dark room. 50 candled and fit eggs randomly selected and settled into hatchery for incubation. Candling was practiced on 3rd and 14th day and turning was practiced daily. Hatched chicks of each group were collected, weighed and brooded over two weeks. Layers average feed intake (682, 686 and 685 g/b/w) and egg weight (40.36, 40.45 and 40.54 g/egg) were almost increased followed by significant increase in egg production (5.03,5.19 and 5.21 egg/b/week) with the increase in breeding layer group size for a cock in A,B and groups, respectively. Average fertility and hatchability rates of Fayoumi layer were high for middle (B) than small (A) and large (C) flock size groups during first, second and third hatch of eggs. However, both fertility and hatchability rates were in increasing trend with the progress of age and eggs hatched but hatchability rate was slightly reduced during last hatch and small group reached to its peak of hatching. Overall results of Fayoumi layers kept in middle flock size eggs fertility and hatchability rates were at peak for medium (B) than small (A) and large (C) groups but, chicks from large group to become heavier (29.90) than medium (29.80) and small (29.34) g/b, respectively.

Nasir Rajput; Muhammad Ismail Rind; Rahmatullah Rind

2005-01-01

283

Energy Technology Data Exchange (ETDEWEB)

A major objective of the extrusion process is to precisely control green and fired densities and associated shrinkages. In this study, the properties of extruded alumina rods were examined as functions of particle size distribution and extrusion rate.

Woodard, K.J.; Dinger, D.R. [Clemson Univ., SC (United States)

1996-06-01

284

MICROFIBROUS CELLULOSE HAVING A PARTICLE SIZE DISTRIBUTION FOR STRUCTURED SURFACTANT COMPOSITIONS

UK PubMed Central (United Kingdom)

An aqueous composition comprising surfactant, water, and a suspending agent comprising microfibrous cellulose that is characterized by a particle size distribution of the microfibrous cellulose that provides for increased structuring of the composition to suspend material.

D AMBROGIO ROBERT; PERU DEBORAH ANN; GAMBOGI JOAN ETHEL; KINSCHERF KEVIN MARK; PATEL DIPAK; TAVARES ROBERT

285

The paper discusses the simulation of the effects of changes to particle loading, particle size distribution, and electrostatic precipitator (ESP) operating temperatures using ESP models. It also illustrates the usefulness of modern ESP models for this type of analysis. Increasin...

286

Evolutionary implications of a power-law distribution of protein family sizes

Current-day genomes bear the mark of the evolutionary processes. One of the strongest indications is the sequence homology among families of proteins that perform similar biological functions in different species. The number of proteins in a family can grow over time as genetic information is duplicated through evolution. We explore how evolution directs the size distribution of these families. Theoretical predictions for family sizes are obtained from two models, one in which individual genes duplicate and a second in which the entire genome duplicates. Predictions from these models are compared with the family size distributions for several organisms whose complete genome sequence is known. We find that protein family size distributions in nature follow a power-law distribution. Comparing these results to the model systems, we conclude that genome duplication is the dominant mechanism leading to increased genetic material in the species considered.

Bader, J S

1999-01-01

287

FIELD COMPARISONS OF DUAL SMPS-APS SYSTEMS TO MEASURE INDOOR-OUTDOOR PARTICLE SIZE DISTRIBUTIONS

Simultaneous measurements of particle size distributions across multiple locations can provide critical information to accurately assess human exposure to particles. These data are very useful to describe indoor-outdoor particle relationships, outdoor particle penetration thro...

288

International Nuclear Information System (INIS)

A mechanism of Ostwald ripening of islands under conditions of dislocation-surface diffusion is suggested for semiconductor heterostructures with quantum dots. The island size distribution is calculated for the suggested growth mechanism. Experimental histograms are compared with calculated curves

2006-01-01

289

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.

Xianguo Li; Meishen Li

2003-01-01

290

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; ?rtomir Rozman; Jernej Turk; Darja Majkovi?; Sebjan Hari; Matej Kolenko; Sašo Pami?; Jernej Prišenk

2011-01-01

291

The role of material properties and landscape morphology on landslide size distributions

It has been observed that landslide size distribution shows power-law scaling for large landslide areas, with a roll-over for landslides below a certain threshold which frequently coincides with the modal peak of the distribution. The physical reasons leading to this distribution are not yet fully understood. The analysis of non-cumulative size distribution of two landslide inventories in the Italian Alps confirms the existence of a power-law scaling with exponent of 2.56±0.02, and demonstrates that the roll-over is not due to under-sampling since it occurs at landslide sizes significantly larger than mapping resolution. The control of topography on landslide size distribution is investigated by a topographic analysis using the virtual tiling method. We observe a power-law scaling of topography with a roll-over for finer scales, which is comparable with that of landslide size distribution. The control of material properties on landslide size and geometry is examined through deterministic and probabilistic 2D limit-equilibrium slope stability analyses. Incoherent materials favour shallow landslides with no limitation in size; cohesive materials favour deep landslides and show a limitation for small sizes. Multilayered materials with depth-dependent strength show a limitation for both small and large landslides. The joint probability of (1) the probability that a slope with a given size and slope gradient is unstable (i.e., failure probability from probabilistic stability analysis) and (2) the probability that a slope with a given size and slope gradient exists (topographic analysis) allows to build synthetic size distributions which show both power-law scaling and roll-over. For multilayered materials, we obtain a scaling exponent of the power law of 2.58±0.02. We suggest that the power-law scaling in landslide size distribution results, in the study area, from the constraint of topography and the presence of multilayered materials or depth-dependent strength. The roll-over is an intrinsic characteristic of the size distribution, due to the contribution of cohesion to slope stability.

Frattini, Paolo; Crosta, Giovanni B.

2013-01-01

292

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, David E; 10.1088/2041-8205/735/1/L6

2011-01-01

293

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

International Nuclear Information System (INIS)

[en] 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

294

The effect of particle-size distribution on thixotropy of coal-water slurry fuels

Energy Technology Data Exchange (ETDEWEB)

The effects of particle size distribution (PSD) on the thixotropic behaviour of coal-water slurries has been investigated. Slurries with bimodal particle size distributions gave PSD characterised by weight-average particle diameter, blend ratio, and weight percent of fine fraction blended. Rheology models are discussed. Results of an experimental procedure to follow the effects of characteristic parameters involved with the original PSD of bimodal coal-water slurry fuels on the possible thixotropic behaviour are presented. 5 refs., 4 figs.

Pulido, J.E.; Ortiz, N. [Universidad Industrial de Santander, Bucaramanga (Colombia). School of Chemical Engineering

1999-07-01

295

UK PubMed Central (United Kingdom)

Secondary organic aerosol (SOA) formed from C1-initiated oxidation of toluene was investigated in a home-made smog chamber. The size distribution and chemical composition of SOA particles were measured using aerodynamic particle sizer spectrometer and the aerosol laser time-of-flight mass spectrometer (ALTOFMS), respectively. According to a large number of single aerosol diameter and mass spectra, the size distribution and chemical composition of SOA were obtained statistically. Experimental results showed that SOA particles created by C1-initiated oxidation of toluene is predominantly in the form of fine particles, which have diameters less than 2.5 microm (i.e., PM2.5), and glyoxal, benzaldehyde, benzyl alcohol, benzoquinone, benzoic acid, benzyl hydroperoxide and benzyl methyl nitrate are the major products components in the SOA. The possible reaction mechanisms leading to these products are also proposed.

Huang M; Zhang W; Gu X; Hu C; Zhao W; Wang Z; Fang L

2012-01-01

296

Characterizations of particle size distribution of the droplets exhaled by sneeze.

UK PubMed Central (United Kingdom)

This work focuses on the size distribution of sneeze droplets exhaled immediately at mouth. Twenty healthy subjects participated in the experiment and 44 sneezes were measured by using a laser particle size analyser. Two types of distributions are observed: unimodal and bimodal. For each sneeze, the droplets exhaled at different time in the sneeze duration have the same distribution characteristics with good time stability. The volume-based size distributions of sneeze droplets can be represented by a lognormal distribution function, and the relationship between the distribution parameters and the physiological characteristics of the subjects are studied by using linear regression analysis. The geometric mean of the droplet size of all the subjects is 360.1 µm for unimodal distribution and 74.4 µm for bimodal distribution with geometric standard deviations of 1.5 and 1.7, respectively. For the two peaks of the bimodal distribution, the geometric mean (the geometric standard deviation) is 386.2 µm (1.8) for peak 1 and 72.0 µm (1.5) for peak 2. The influences of the measurement method, the limitations of the instrument, the evaporation effects of the droplets, the differences of biological dynamic mechanism and characteristics between sneeze and other respiratory activities are also discussed.

Han ZY; Weng WG; Huang QY

2013-01-01

297

Optimizing Batch Size in a Flow-Oriented Synchronized Production

Directory of Open Access Journals (Sweden)

Full Text Available This study was prepared for a leading company, Miele GmbH, the global premium brand of domestic appliancesand commercial machines in the field of laundry care, dishwashing and disinfection in Germany. The productionline of Miele GmbH in Bielefeld, Germany was analyzed to develop a model that can be used for all the firms inthe group.Dynamic programming models are widely used by companies to efficiently meet the demand for a variety ofproducts. In a flow shop, each product has to be processed by a number of machines in synchronized lines. Theproduction smoothing problems under the presence of setup and processing times vary among the products. Themaster production-inventory problem of Miele GmbH was divided into two sub-problems which were concernedwith determining the batch sizes and production sequences of products, respectively. A dynamic programmingprocedure was developed to solve the batching problem for the current problem. A dynamic computational studyfor the first case was conducted so that the solution method is effective in meeting the goals of the firm andefficient in its computational requirements.Scientific problem –the firm has a problem of high logistics. Moreover, they want to decrease the cost ofproduction in order to compete with their competitors. Their competitors start to make some of their productionin low labour countries such as China. Miele is a special brand for upper level. However, they now have a morestrict competition with new global players and one way to stay competitive in the market is to decrease the costsand find new market segments.The aim of the research –The dynamic programming algorithm is suggested to them to decrease the costs. Thenumbers of products are decreased to explain the algorithm. An example with calculations of this algorithm wasexplained in this study. The number of variables and constraints can be increased. After the logic of algorithm isunderstood, it can be applied many similar problems. The algorithm can be developed by using differentsoftware such as Java. Then, the variables and values of algorithm can be input for the algorithm and the resultscan be gotten in a short time.The object of the research – Inventory and Production mix projects.The methods of the research –Dynamic Programming.

Imran Aslan; Dilsad Guzel

2011-01-01

298

Placement and Sizing of DG Using PSO&HBMO Algorithms in Radial Distribution Networks

Directory of Open Access Journals (Sweden)

Full Text Available Optimal placement and sizing of DG in distribution network is an optimization problem with continuous and discrete variables. Many researchers have used evolutionary methods for finding the optimal DG placement and sizing. This paper proposes a hybrid algorithm PSO&HBMO for optimal placement and sizing of distributed generation (DG) in radial distri-bution system to minimize the total power loss and improve the voltage profile. The proposed method is tested on a standard 13 bus radial distribution system and simulation results carried out using MATLAB software. The simulation results indicate that PSO&HBMO method can obtain better results than the simple heuristic search method and PSO algorithm. The method has a potential to be a tool for identifying the best location and rating of a DG to be installed for improving voltage profile and line losses reduction in an electrical power system. Moreover, current reduction is obtained in distribution system.

M.Afzalan; M. A.Taghikhani

2012-01-01

299

Speciation and size distribution of copper and zinc in urban road runoff.

UK PubMed Central (United Kingdom)

The impact of pollutants from road runoff on receiving water bodies becomes increasingly serious. However, less is known about the study on the distribution of metal speciation in particles with different sizes, and the interaction among metal speciation. Our research is aimed at investigating speciation distribution of copper (Cu) and zinc (Zn) in particles and the interaction among metal speciation. Stainless steel sieves in different sizes were used to accomplish filtration scheme. Sequential extraction procedures contained five steps for the chemical fractionation of metals. Flame atomic absorption spectrometry (Shimadzu, AA-6800) was used to determine the concentration of metal speciation. Speciation distribution of Cu was similar to that of Zn. Size distribution implied that small particles (<75 ?m) determined the distribution for both Cu and Zn, as well as their migration. Correlation analysis indicated that the interaction among speciation of Cu was different from that of Zn.

Li H; Zuo XJ

2013-04-01

300

A facile synthesis of Te nanoparticles with binary size distribution by green chemistry

Our work reports a facile route to colloidal Te nanocrystals with binary uniform size distributions at room temperature. The binary-sized Te nanocrystals were well separated into two size regimes and assembled into films by electrophoretic deposition. The research provides a new platform for nanomaterials to be efficiently synthesized and manipulated.Our work reports a facile route to colloidal Te nanocrystals with binary uniform size distributions at room temperature. The binary-sized Te nanocrystals were well separated into two size regimes and assembled into films by electrophoretic deposition. The research provides a new platform for nanomaterials to be efficiently synthesized and manipulated. Electronic supplementary information (ESI) available: Synthetic procedures, FTIR analysis, ED pattern, AFM image, and EPD current curve. See DOI: 10.1039/c1nr10025d

He, Weidong; Krejci, Alex; Lin, Junhao; Osmulski, Max E.; Dickerson, James H.

2011-04-01

301

Effects of grain size distribution on the interstellar dust mass growth

Grain growth by the accretion of metals in interstellar clouds (called `grain growth') could be one of the dominant processes that determine the dust content in galaxies. The importance of grain size distribution for the grain growth is demonstrated in this paper. First, we derive an analytical formula that gives the grain size distribution after the grain growth in individual clouds for any initial grain size distribution. The time-scale of the grain growth is very sensitive to grain size distribution, since the grain growth is mainly regulated by the surface to volume ratio of grains. Next, we implement the results of grain growth into dust enrichment models of entire galactic system along with the grain formation and destruction in the interstellar medium, finding that the grain growth in clouds governs the dust content in nearby galaxies unless the grain size is strongly biased to sizes larger than $\\sim 0.1 \\micron$ or the power index of the grain size distribution is shallower than $\\sim -2.5$. The grai...

Hirashita, Hiroyuki

2011-01-01

302

Droplet-based microreactors are used for the continuous production of Pd nanocrystals. Specifically, commercially available polytetrafluoroethylene (PTFE) tube and silica capillaries are utilized to fabricate a fluidic device capable of generating water-in-oil droplets. In addition to the feasibility of using such droplets as microreactors for conducting a synthesis, the ability to control the composition and concentration of reagents by adjusting the flow rates is demonstrated; reagents are mixed by periodically pinching the PTFE tube, and nanocrystals are produced with uniform size distribution in a continuous fashion. The capability to tailor the size and shape of the resultant nanocrystals is further demonstrated by introducing the reducing agent and capping agent at different flow rates to control the nucleation and growth processes. The ability to transform a bulk synthesis into a droplet-based system holds great potential for the development of a new route to the high-volume production of nanocrystals. PMID:23606671

Kim, Yun Ho; Zhang, Lei; Yu, Taekyung; Jin, Minshang; Qin, Dong; Xia, Younan

2013-04-18

303

UK PubMed Central (United Kingdom)

Droplet-based microreactors are used for the continuous production of Pd nanocrystals. Specifically, commercially available polytetrafluoroethylene (PTFE) tube and silica capillaries are utilized to fabricate a fluidic device capable of generating water-in-oil droplets. In addition to the feasibility of using such droplets as microreactors for conducting a synthesis, the ability to control the composition and concentration of reagents by adjusting the flow rates is demonstrated; reagents are mixed by periodically pinching the PTFE tube, and nanocrystals are produced with uniform size distribution in a continuous fashion. The capability to tailor the size and shape of the resultant nanocrystals is further demonstrated by introducing the reducing agent and capping agent at different flow rates to control the nucleation and growth processes. The ability to transform a bulk synthesis into a droplet-based system holds great potential for the development of a new route to the high-volume production of nanocrystals.

Kim YH; Zhang L; Yu T; Jin M; Qin D; Xia Y

2013-04-01

304

Nano-sized crystalline drug production by milling technology.

UK PubMed Central (United Kingdom)

Nano-formulation of poorly water-soluble drugs has been developed to enhance drug dissolution. In this review, we introduce nano-milling technology described in recently published papers. Factors affecting the size of drug crystals are compared based on the preparation methods and drug and excipient types. A top-down approach using the comminution process is a method conventionally used to prepare crystalline drug nanoparticles. Wet milling using media is well studied and several wet-milled drug formulations are now on the market. Several trials on drug nanosuspension preparation using different apparatuses, materials, and conditions have been reported. Wet milling using a high-pressure homogenizer is another alternative to preparing production-scale drug nanosuspensions. Dry milling is a simple method of preparing a solid-state drug nano-formulation. The effect of size on the dissolution of a drug from nanoparticles is an area of fundamental research, but it is sometimes incorrectly evaluated. Here, we discuss evaluation procedures and the associated problems. Lastly, the importance of quality control, process optimization, and physicochemical characterization are briefly discussed.

Moribe K; Ueda K; Limwikrant W; Higashi K; Yamamoto K

2013-01-01

305

For a bimodal size distribution of ambient aerosol, an upper limit in particle size can be chosen for the fine aerosol fraction so that the extinction coefficient for light scattering and absorption is directly proportional to the fine mass concentration, with no dependence on th...

306

Energy Technology Data Exchange (ETDEWEB)

In response to concern over the number of fine particles emitted by diesel engines, a programme of work was undertaken to measure particle size distribution in diesel exhaust. Different diesel engine technologies were tested on a non-additised base fuel and fuel treated with smoke reducing organo metallic additive. Two different particle size measuring techniques were used, namely SMPS and ELPI. (author)

Richards, P.; Terry, B.; Trivett, A.S. [Associated Octel Co. Ltd., Milton Keynes (United Kingdom)

1998-07-01

307

Fat globule size distribution in milk of a German buffalo herd

Directory of Open Access Journals (Sweden)

Full Text Available The volume-surface average diameter of fat globules are larger in buffalo milk than in cow milk and the volume frequency distribution in buffalo milk is more balanced. The globule size was affected by animal, stage of lactation, and test day. An interesting contrast compared to cow milk is the negative correlation between diurnal fat yield and globule size.

R. Schafberg; R. Schmidt; M. Thiele; H.H. Swalve

2010-01-01

308

The size distribution of open access publishers: A problem for open access?

Digital Repository Infrastructure Vision for European Research (DRIVER)

I stumbled across the question of publisher size while preparing for an earlier article. From the viewpoint of an economist, the size distribution of Open Access publishers looked inefficient. In this article I first explore reasons to be sceptical to a situation with a large number of small publish...

Jan Erik Frantsvåg; University of Tromsø

309

Determination of size and shape distributions of metal and ceramic powders

International Nuclear Information System (INIS)

For testing the size and shape distributions of metal and ceramic uranium oxide powders the following method for analysing the grain size of powders were developed and implemented: microscopic analysis and sedimentation method. A gravimetry absorption device was constructed for determining the specific surfaces of powders

1961-01-01

310

International Nuclear Information System (INIS)

The effect of the magnetic anisotropy at temperatures above the blocking temperature of a uniaxial, randomly oriented, nanoparticulate magnetic system has been studied. If anisotropy is disregarded in fitting the magnetization curves, apparent particle-size distributions emerge from the calculations, even for monodisperse systems. Apparent mean grain size increases with temperature, with a saturation value corresponding to the actual particle size. This evolution collapses to a master curve for anisotropy energy terms up to the fourth order

2004-01-01

311

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; B. Slusarczyk; S. Kot; C. Kolmasiak

2012-01-01

312

How stand productivity results from size- and competition-dependent growth and mortality.

UK PubMed Central (United Kingdom)

BACKGROUND: A better understanding of the relationship between stand structure and productivity is required for the development of: a) scalable models that can accurately predict growth and yield dynamics for the world's forests; and b) stand management regimes that maximize wood and/or timber yield, while maintaining structural and species diversity. METHODS: We develop a cohort-based canopy competition model ("CAIN"), parameterized with inventory data from Ontario, Canada, to examine the relationship between stand structure and productivity. Tree growth, mortality and recruitment are quantified as functions of diameter and asymmetric competition, using a competition index (CAI(h)) defined as the total projected area of tree crowns at a given tree's mid-crown height. Stand growth, mortality, and yield are simulated for inventoried stands, and also for hypothetical stands differing in total volume and tree size distribution. RESULTS: For a given diameter, tree growth decreases as CAI(h) increases, whereas the probability of mortality increases. For a given CAI(h), diameter growth exhibits a humped pattern with respect to diameter, whereas mortality exhibits a U-shaped pattern reflecting senescence of large trees. For a fixed size distribution, stand growth increases asymptotically with total density, whereas mortality increases monotonically. Thus, net productivity peaks at an intermediate volume of 100-150 m(3)/ha, and approaches zero at 250 m(3)/ha. However, for a fixed stand volume, mortality due to senescence decreases if the proportion of large trees decreases as overall density increases. This size-related reduction in mortality offsets the density-related increase in mortality, resulting in a 40% increase in yield. CONCLUSIONS: Size-related variation in growth and mortality exerts a profound influence on the relationship between stand structure and productivity. Dense stands dominated by small trees yield more wood than stands dominated by fewer large trees, because the relative growth rate of small trees is higher, and because they are less likely to die.

Caspersen JP; Vanderwel MC; Cole WG; Purves DW

2011-01-01

313

UK PubMed Central (United Kingdom)

Knowledge of the particle size distributions for workplace aerosols is invaluable in the assessment of aerosol-related health effects. Cascade impactors have been widely used for obtaining such information, including a small number that have been developed as personal samplers of the type that can be used for the assessment of the exposures of individual workers. Common limitations for most samplers of this type have been that (a) the aspiration efficiency has not been well defined (leading to biases in particle size distribution measurement), and (b) the range of particle size has been constrained by particle bounce in impactors for particle sizes beyond about 20 micro m. This article describes a modification of the Marple personal cascade impactor that addresses these limitations. The sampler has a new entry whose aspiration efficiency is known and a new top stage that employs porous plastic foam filtration media and significantly extends the particle size range of the instrument. The new instrument is referred to as the modified-Marple sampler. A numerical simulation was performed to investigate the ability of the new instrument to accurately retrieve particle size distributions over the range typical of aerosols found in workplaces. The retrieval process was carried out using a simple inversion algorithm of the "zeroth-order" type. The results are presented in terms of the ability of the new sampler to retrieve the masses contained in the inhalable, thoracic, and respirable fractions. They suggest that the more narrowly distributed the particle size distribution, the more restricted the ability to accurately retrieve the particle size distribution. However, for most aerosols of the type encountered in the real world of industrial hygiene, the modified-Marple sampler provides particle size information of sufficient quality for most practical purposes.

Wu YH; Vincent JH

2007-10-01

314

Size distributions of thirteen polycyclic aromatic hydrocarbons (PAHs), elemental carbon (EC), and organic carbon (OC) in the range of 0.01-18 ?m were measured using a nano Micro-Orifice Uniform Deposit Impactor (nano-MOUDI) in an urban location in Guangzhou, China in July 2006. PAH size distributions were fit with five modes and the respective mass median aerodynamic diameters (MMAD) are: Aitken mode (MMAD: ˜0.05 ?m), three accumulation modes AMI, AMII, AMIII (MMAD: 0.13-0.17 ?m, 0.4-0.45 ?m, and 0.9-1.2 ?m, respectively), and coarse mode (MMAD: 4-6 ?m). Seven-ring PAH was mainly in AMII and AMIII. Five- and six-ring PAHs were found to be abundant in all the three AM. Three- and four-ring PAHs had a significant presence in the coarse mode in addition to the three AM. Size-resolved gas-particle partition coefficients of PAHs (Kp) were estimated using measured EC and OC data. The Kp values of a given PAH could differ by a factor of up to ˜7 on particles in different size modes, with the highest Kp associated with the AMI particles and the lowest Kp associated with the coarse mode particles. Comparison of calculated overall Kp with measured Kp values in Guangzhou by Yang et al. (2010) shows that adsorption on EC appeared to be the dominant mechanism driving the gas-particle partitioning of three- and four-ring PAHs while absorption in OM played a dominant role for five- and six-ring PAHs. The calculated equilibrium timescales of repartitioning indicate that five- to seven-ring PAHs could not achieve equilibrium partitioning within their typical residence time in urban atmospheres, while three- and four-ring PAHs could readily reach new equilibrium states in particles of all sizes. A partitioning flux is therefore proposed to replace the equilibrium assumption in modeling PAH transport and fate.

Yu, Huan; Yu, Jian Zhen

2012-07-01

315

Energy Technology Data Exchange (ETDEWEB)

Activity size distributions of the short-lived radon decay products /sup 218/Po, /sup 214/Pb and /sup 214/Bi//sup 214/Po were measured in dwellings with a low pressure cascade impactor (type Berner) and a device using high volume screen diffusion batteries under various conditions. In low ventilated rooms without additional aerosol sources, the activity size distributions can be described by one log normal distribution (accumulation mode) with average activity median aerodynamic diameters (AMAD) of 188-234 nm (range 115-370 nm) and average geometric standard deviations /sigma//sub g/ of 2.0-2.5 (range 1.4-4.3). The mean diffusion equivalent diameter of the unattached activity of /sup 218/Po was determined to be 1.2 nm (range 0.5-2.0 nm). Additional aerosol sources (electric motor, candle light) sometimes yield a second maximum of the attached fraction in the diameter size range of 10-100 nm (nuclei mode) or the accumulation mode can be shifted to greater sizes (cigarette smoke: AMAD = 300 nm). Activity size distributions in the open air were only measured with the impactor. Most of the activities are also associated with the accumulation mode with an average AMAD of 369 nm (range 173-645 nm) and an average /sigma//sub g/ of 2.5 (range 1.6-4.4). Depending on outdoor aerosol sources and meteorological parameters, a small fraction of the nuclei mode in the diameter size range 10-100 nm and a small fraction in the size range of some microns (coarse mode) were sometimes found. (author).

Reineking, A.; Becker, K.H.; Porstendoerfer, J.

1988-01-01

316

International Nuclear Information System (INIS)

Activity size distributions of the short-lived radon decay products 218Po, 214Pb and 214Bi/214Po were measured in dwellings with a low pressure cascade impactor (type Berner) and a device using high volume screen diffusion batteries under various conditions. In low ventilated rooms without additional aerosol sources, the activity size distributions can be described by one log normal distribution (accumulation mode) with average activity median aerodynamic diameters (AMAD) of 188-234 nm (range 115-370 nm) and average geometric standard deviations ?g of 2.0-2.5 (range 1.4-4.3). The mean diffusion equivalent diameter of the unattached activity of 218Po was determined to be 1.2 nm (range 0.5-2.0 nm). Additional aerosol sources (electric motor, candle light) sometimes yield a second maximum of the attached fraction in the diameter size range of 10-100 nm (nuclei mode) or the accumulation mode can be shifted to greater sizes (cigarette smoke: AMAD = 300 nm). Activity size distributions in the open air were only measured with the impactor. Most of the activities are also associated with the accumulation mode with an average AMAD of 369 nm (range 173-645 nm) and an average ?g of 2.5 (range 1.6-4.4). Depending on outdoor aerosol sources and meteorological parameters, a small fraction of the nuclei mode in the diameter size range 10-100 nm and a small fraction in the size range of some microns (coarse mode) were sometimes found. (author).

1988-01-01

317

Energy Technology Data Exchange (ETDEWEB)

Starting from simulated histograms of typical crack size distributions the difficulties in attributing a unique distribution function to a specific histogram are investigated. A curve-fitting procedure, which can be employed for the calculation of failure probabilities in probabilistic fracture mechanics, is established.

Brueckner, A. (Kernforschungszentrum Karlsruhe G.m.b.H. (Germany, F.R.). Inst. fuer Reaktorbauelemente); Haeberer, R.; Munz, D. (Karlsruhe Univ. (T.H.) (Germany, F.R.). Inst. fuer Zuverlaessigkeit und Schadenskunde im Maschinenbau)

1985-01-01

318

The ?-generalized distribution: A new descriptive model for the size distribution of incomes

This paper proposes the ?-generalized distribution as a model for describing the distribution and dispersion of income within a population. Formulas for the shape, moments and standard tools for inequality measurement such as the Lorenz curve and the Gini coefficient are given. A method for parameter estimation is also discussed. The model is shown to fit extremely well the data on personal income distribution in Australia and in the United States.

Clementi, F.; di Matteo, T.; Gallegati, M.; Kaniadakis, G.

2008-05-01

319

Characterization of ceramic tubular membranes by active pore-size distribution

Energy Technology Data Exchange (ETDEWEB)

A description of the use of a liquid displacement (modified bubble-point) method to characterize tubular membrane microfilters in terms of pore sizes and pore-size distributions is given. Following a theoretical analysis the method, some comments about pore-size distribution of tubular filters and experimental results for different ceramic microfilters are presented. The characterization studies reported in this paper are applicable to other ceramic membranes, and they represent a significant step in an understanding of ceramic membranes in various applications. 3 refs., 6 figs.

Mikulasek, P.; Dolecek, P. (Univ. of Chemical Technology, Pardubice (Czechoslovakia))

1994-06-01

320

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

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, organic carbon (OC) and monosaccharide anhydrides from the filter samples (particle aerodynamic diameter smaller than 1 ?m, PM1). Gravimetric mass concentration varied during the MOUDI samplings between 3.4 and 55.0 ?g m-3 and the WSOC concentrations were between 0.3 and 7.4 ?g m-3. On average, water-soluble particulate organic matter (WSPOM, WSOC multiplied by 1.6 to convert the analyzed carbon mass to organic matter mass) comprised 25±7.7% and 7.5±3.4% of aerosol PM1 mass and the PM1-10 mass, respectively. Inorganic ions contributed 33±12% and 28±19% of the analyzed PM1 and PM1-10 aerosol mass. Five different aerosol categories corresponding to different sources or source areas were identified (long-range transport aerosols, biomass burning aerosols from wild land fires and from small-scale wood combustion, aerosols originating from marine areas and from the clean arctic areas). Categories were identified mainly using levoglucosan concentration level for wood combustion and air mass backward trajectories for other groups. Clear differences in WSOC concentrations and size distributions originating from different sources or source areas were observed, although there are also many other factors which might affect the results. E.g. the local conditions and sources of volatile organic compounds (VOCs) and aerosols as well as various transformation processes are likely to have an impact on the measured aerosol composition. Using the source categories, it was identified that especially the oxidation products of biogenic VOCs in summer had a clear effect on WSOC concentrations.

Timonen, H.; Saarikoski, S.; Tolonen-Kivimäki, O.; Aurela, M.; Saarnio, K.; Petäjä, T.; Aalto, P. P.; Kulmala, M.; Pakkanen, T.; Hillamo, R.

2008-09-01

321

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

Directory of Open Access Journals (Sweden)

Full Text Available 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, organic carbon (OC) and monosaccharide anhydrides from the filter samples (particle aerodynamic diameter smaller than 1 ?m, PM1). Gravimetric mass concentration varied during the MOUDI samplings between 3.4 and 55.0 ?g m?3 and the WSOC concentrations were between 0.3 and 7.4 ?g m?3. On average, water-soluble particulate organic matter (WSPOM, WSOC multiplied by 1.6 to convert the analyzed carbon mass to organic matter mass) comprised 25±7.7% and 7.5±3.4% of aerosol PM1 mass and the PM1–10 mass, respectively. Inorganic ions contributed 33±12% and 28±19% of the analyzed PM1 and PM1–10 aerosol mass. Five different aerosol categories corresponding to different sources or source areas were identified (long-range transport aerosols, biomass burning aerosols from wild land fires and from small-scale wood combustion, aerosols originating from marine areas and from the clean arctic areas). Categories were identified mainly using levoglucosan concentration level for wood combustion and air mass backward trajectories for other groups. Clear differences in WSOC concentrations and size distributions originating from different sources or source areas were observed, although there are also many other factors which might affect the results. E.g. the local conditions and sources of volatile organic compounds (VOCs) and aerosols as well as various transformation processes are likely to have an impact on the measured aerosol composition. Using the source categories, it was identified that especially the oxidation products of biogenic VOCs in summer had a clear effect on WSOC concentrations.

H. Timonen; S. Saarikoski; O. Tolonen-Kivimäki; M. Aurela; K. Saarnio; T. Petäjä; P. P. Aalto; M. Kulmala; T. Pakkanen; R. Hillamo

2008-01-01

322

UK PubMed Central (United Kingdom)

Hydrogen peroxide (H(2)O(2)) photochemical production was measured in bulk and size-fractionated surf zone and source waters (Orange County, California, USA). Post-irradiation (60 min; 300 W ozone-free xenon lamp), maximum H(2)O(2) concentrations were approximately 10000 nM (source) and approximately 1500 nM (surf zone). Average initial hydrogen peroxide production rates (HPPR) were higher in bulk source waters (11+/-7.0 nM s(-1)) than the surf zone (2.5+/-1 nM s(-1)). A linear relationship was observed between non-purgeable dissolved organic carbon and absorbance coefficient (m(-1) (300 nm)). HPPR increased with increasing absorbance coefficient for bulk and size-fractionated source waters, consistent with photochemical production from CDOM. However, HPPR varied significantly (5x) for surf zone samples with the same absorbance coefficients, even though optical properties suggested CDOM from salt marsh source waters dominates the surf zone. To compare samples with varying CDOM levels, apparent quantum yields (Phi) for H(2)O(2) photochemical production were calculated. Source waters showed no significant difference in Phi between bulk, large (>1000 Da (>1 kDa)) and small (<1 kDa) size fractions, suggesting H(2)O(2) production efficiency is homogeneously distributed across CDOM size. However, surf zone waters had significantly higher Phi than source (bulk 0.086+/-0.04 vs. 0.034+/-0.013; <1 kDa 0.183+/-0.012 vs. 0.027+/-0.018; >1 kDa 0.151+/-0.090 vs. 0.016+/-0.009), suggesting additional production from non-CDOM sources. H(2)O(2) photochemical production was significant for intertidal beach sand and senescent kelp (sunlight; approximately 42 nM h(-1) vs. approximately 5 nM h(-1)), on the order of CDOM production rates previously measured in coastal and oceanic waters. This is the first study of H(2)O(2) photochemical production in size-fractionated coastal waters showing significant production from non-CDOM sources in the surf zone.

Clark CD; De Bruyn WJ; Jones JG

2009-06-01

323

The effect of ion beam temperature on ion distribution size into solid surface

International Nuclear Information System (INIS)

[en] Ion implantation has become a versatile and powerful technique for synthesizing nanometer scale cluster and crystal embedded in the near surface region of the materials. One of the major difficulties in order to create nano composite materials by ion implantation are control over the size distribution and spacing of the precipitates. In this paper the relation between ion temperatures and size distribution of implanted ions after collision with a solid surface has been studied and cold ion beam is introduced as a substitute method for focused ion beam methods. SIMION and SRIM software's have been used for transport and interaction of ion distribution to and into the surface, respectively.

2006-01-01

324

Introduction of a nozzle throat diameter dependency into the SRM dust size distribution

The ESA space debris population model MASTER (Meteoroid and Space Debris Terrestrial Environment Reference) considers 1032 firings of solid rocket motors (SRM) with the associated generation of SRM slag and dust particles in its current version. The resulting dust population is a major contribution to the sub-millimetre size space debris environment in Earth orbit. For the modelling of each SRM dust release event a detailed knowledge of the particle size distribution is essential. However, the knowledge of the particle sizes after passing the nozzle throat is poor. The current dust implementation in the MASTER model assumes a fixed size distribution which is identically used for both large upper stages and small apogee motors. This assumption can lead to an over-representation of large dust particles in regions, where mainly apogee motors are used (i.e., Geostationary Earth Orbit) and an under-representation in lower altitudes, where large stages predominate. In this paper, a concept for the improvement of SRM dust size modelling is discussed. It will be shown that an introduction of a nozzle throat diameter dependency into the dust size distribution enables a more precise modelling of SRM dust release events. The improved SRM dust size distribution is going to be used by the MASTER-2005 space debris model which is currently under development by the Institute of Aerospace Systems and QinetiQ (UK) under ESA contract.

Stabroth, S.; Wegener, P.; Oswald, M.; Wiedemann, C.; Klinkrad, H.; Vörsmann, P.

2006-01-01

325

The size distribution and mixing state of black carbon aerosol over Europe

Directory of Open Access Journals (Sweden)

Full Text Available Black carbon-containing aerosol particles play an important role in the direct and indirect radiative forcing of climate. However, the magnitude and sign of the net radiative effect is strongly dependent on the physical properties of the black carbon (BC) component of the particles, such as mass, number concentration and size distribution. Here we use a global aerosol model combined with aircraft measurements of BC particle number and size from the Single Particle Soot Photometer (SP2) to assess the realism with which these physical properties are predicted by global models. The comparison reveals a substantial mismatch between the measured and modelled BC size distribution over the size range of the SP2 instrument (90–400 nm BC diameter). The model predicts BC particle number concentrations a factor ~3.5–5.7 higher than measured and a mode diameter that is 40–65 nm smaller than observed. More than 90% of the model particles in the SP2 size range contain BC, while the observations suggest only 21%. These model-observation biases in the BC properties are considerably greater than for the overall particle distribution, suggesting that the discrepancy is associated with model assumptions about the size and mixing state of the emitted carbonaceous particles. We expect the discrepancy in BC size distribution to be common among most global aerosol models, with implications for model estimates of absorption optical depth and direct radiative forcing.

C. L. Reddington; G. McMeeking; G. W. Mann; H. Coe; M. G. Frontoso; D. Liu; M. Flynn; D. V. Spracklen; K. S. Carslaw

2012-01-01

326

International Nuclear Information System (INIS)

[en] We are studying the relationship between neutron energy and track-size distribution on electrochemically etched CR-39 foils using a two-stage etching procedure. Although the electrochemical etching process alters the track size, we now find that the track diameter is related to the neutron energy even after the second stage (blowup) is completed. This relationship is complex, being effected by the etching parameters, including oven temperature, etching high voltage, and etching time. Current studies are directed at establishing the effect of each of these parameters on the track-size distribution and at determining an optimal etching procedure for neutron spectra evaluation. If neutron spectral information can be determined from the track-size distribution, dose can be calculated directly from the neutron fluence and spectrum

1987-01-01

327

Temperature-controlled synthesis of CdSe nanocrystals with narrow size distribution.

UK PubMed Central (United Kingdom)

CdSe quantum dots (QDs) with narrow size distribution and fine crystallinity were synthesized in paraffin liquid through temperature-control method. TEM, HRTEM, SEAD, XRD, PL and UV-VIS spectra were used to characterize the size, crystal structure and photoluminescence (PL) properties of CdSe nanocrystals. The PL spectra and TEM results revealed that the monodispersed and uniformed CdSe QDs with narrow size distribution were synthesized at a certain reaction temperature. HRTEM images combined with selected area electron diffraction (SAED) and XRD patterns illustrated that CdSe QDs showed near-perfect zinc-blende and wurtzite crystallinity at different temperatures. The Gibbs-Thomson calculation provided a thermodynamic explanation for obtaining the CdSe nanocrystals with narrow size distribution by temperature-control method.

Jiang J; Wang B; Jin S; Feng W

2012-08-01

328

Nowadaysthe formula to calculate the sample size for estimate a proportion (as prevalence) is based on the Normal distribution, however it would be based on a Binomial distribution which confidence interval was possible to be calculated using the Wilson Score method. By comparing the two formulae (Normal and Binomial distributions), the variation of the amplitude of the confidence intervals is relevant in the tails and the center of the curves. In order to calculate the needed sample size we have simulated an iterative sampling procedure, which shows an underestimation of the sample size for values of prevalence closed to 0 or 1, and also an overestimation for values closed to 0.5. Attending to these results we proposed an algorithm based on Wilson Score method that provides similar values for the sample size than empirically obtained by simulation. PMID:23623739

Vallejo, Adriana; Muniesa, Ana; Ferreira, Chelo; Blas, Ignacio de

2013-04-25

329

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

Directory of Open Access Journals (Sweden)

Full Text Available Determination of the size distribution of solid particles is fundamental for analysis of the performance several pieces of equipment used for solid-fluid separation. The main objective of this work is to compare the results obtained with two traditional methods for determination of the size grade distribution of powdery solids: the gamma-ray attenuation technique (GRAT) and the LADEQ test tube technique. The effect of draining the suspension in the two techniques used was also analyzed. The GRAT can supply the particle size distribution of solids through the monitoring of solid concentration in experiments on batch settling of diluted suspensions. The results show that use of the peristaltic pump in the GRAT and the LADEQ methods produced a significant difference between the values obtained for the parameters of the particle size model.

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

2005-01-01

330

Energy Technology Data Exchange (ETDEWEB)

Field size distributions in three Petroleum Systems have been analyzed using different approaches. The parabolic fractal model shows the Niger delta and the Gulf of Mexico (GOM) Outer Continental Shelf (OCS) have similar dispersed habitats, in contrast to the Saharan Triassic, which has a concentrated habitat. On a lognormal model, the Niger delta and the Saharan Triassic field size distributions are similar, being almost linear and coinciding. However, field sizes in the GOM OCS lie on a curved and very different plot. Using a stretched exponential model, all are different but close to linear. Evidently a single model does not adequately represent the complexity of field size distribution, and several should be used. (Author)

Laherrere, Jean

2000-04-01

331

Particle size distribution of iron nanomaterials in biological medium by SR-SAXS method

International Nuclear Information System (INIS)

A better understanding of biological effects of nanomaterials in organisms requests knowledge of the physicochemical properties of nanomaterials in biological systems. Affected by high concentration salts and proteins in biological medium, nanoparticles are much easy to agglomerate,hence the difficulties in characterizing size distribution of the nanomaterials in biological medium.In this work, synchrotron radiation small angle X-ray scattering(SR-SAXS) was used to determine size distributions of Fe, Fe2O3 and Fe3O4 nanoparticles of various concentrations in PBS and DMEM culture medium. The results show that size distributions of the nanomaterials could perfectly analyzed by SR-SAXS. The SR-SAXS data were not affected by the particle content and types of the dispersion medium.It is concluded that SR-SAXS can be used for size measurement of nanomaterials in unstable dispersion systems. (authors)

2009-01-01

332

Energy Technology Data Exchange (ETDEWEB)

Cloud reflectance models currently used in cloud property retrievals from satellites have been developed using size distributions defined by a set of fixed effective radii with a fixed effective variance. The satellite retrievals used for the Atmospheric Radiation Measurement (ARM) program assume droplet size distributions with an effective variance value of 0.10 (Minnis et al. 1998); the International Satellite Cloud Climatology Project uses 0.15 (Rossow and Schiffer 1999); and the Moderate Resolution Imaging Spectroradiometer (MODIS) team uses 0.13 (Nakajima and King 1990). These distributions are not necessarily representative of the actual sizes present in the clouds being observed. Because the assumed distributions can affect the reflectance patterns and near-infrared absorption, even for the same droplet effective radius reff, it is desirable to use the optimal size distributions in satellite retrievals of cloud properties. Collocated observations of the same clouds from different geostationary satellites, at different viewing angles, indicate that the current models may not be optimal (Ayers et al. 2005). Similarly, hour-to-hour variations in effective radius and optical depth reveal an unexplained dependence on scattering angle. To explore this issue, this paper examines the sensitivity of the cloud reflectance at 0.65 and 3.90-{micro}m to changes in the effective variance, or the spectral dispersion, of the modeled size distributions. The effects on the scattering phase functions and on the cloud reflectances are presented, as well as some resultant effects on the retrieved cloud properties.

Arduini, R.F.; Minnis, P.; Smith, W.L.Jr.; Ayers, J.K.; Khaiyer, M.M.; Heck, P.

2005-03-18

333

Monte Carlo Method for Predicting a Physically Based Drop Size Distribution Evolution of a Spray

We report in this paper a method for predicting the evolution of a physically based drop size distribution of a spray, by coupling the Maximum Entropy Formalism and the Monte Carlo scheme. Using the discrete or continuous population balance equation, a Mass Flow Algorithm is formulated taking into account interactions between droplets via coalescence. After deriving a kernel for coalescence, we solve the time dependent drop size distribution equation using a Monte Carlo method. We apply the method to the spray of a new print-head known as a Spray On Demand (SOD) device; the process exploits ultrasonic spray generation via a Faraday instability where the fluid/structure interaction causing the instability is described by a modified Hamilton's principle. This has led to a physically-based approach for predicting the initial drop size distribution within the framework of the Maximum Entropy Formalism (MEF): a three-parameter generalized Gamma distribution is chosen by using conservation of mass and energy. The calculation of the drop size distribution evolution by Monte Carlo method shows the effect of spray droplets coalescence both on the number-based or volume-based drop size distributions.

Tembely, Moussa; Lécot, Christian; Soucemarianadin, Arthur

2010-03-01

334

Improved statistical characterization of particle-size distributions in sand-bedded rivers

Measured particle-size distributions are commonly reduced to one characteristic value (e.g., median grain diameter) that is used in sediment transport modeling. While convenient, this approach cannot be used to explore the potential influence grain-size distributions may have on sediment transport and deposition. We statistically characterize grain-size distributions in samples of bed-material load, suspended load, and slackwater deposits from the sand-bedded Calamus, North Loup, and Niobrara rivers (Nebraska, USA). Transported sediment samples are best modeled with log-hyperbolic distributions, and slackwater deposits are bi- or multi-modal mixtures. Despite large overlaps in the grain sizes of bed-material-load and suspended-load samples, estimated parameters of fitted log-hyperbolic distributions show consistent differences between these samples across all rivers. Bed-material load samples have higher modes and positive (coarse-grained) asymmetry, whereas suspended load samples have lower modes and weaker asymmetry. In all three rivers, slackwater deposits contain the entire range of grain sizes present in suspended load, but with a significant component of very fine-grained (< 0.02 mm) material that is undetectable in suspended sediment samples. This suggests some degree of fractionated deposition of suspended sediment in areas of near-zero flow velocities. Ultimately, in order to explore the effect of grain-size distributions on sediment transport and river processes, these modeled distributions can be incorporated into a Bayesian hierarchical framework where standard sediment transport equations can be modeled in relation to probability-density particle curves for grain size.

Huzurbazar, S.; Hajek, E.; Lynds, R.; Heller, P.; Mohrig, D.

2007-12-01

335

UK PubMed Central (United Kingdom)

We address several questions on the behavior of a numerical model recently introduced to study seismic phenomena, which includes relaxation in the plates as a key ingredient. First, we make an analysis of the scaling of the largest events with system size and show that, when parameters are appropriately interpreted, the typical size of the largest events scale as the system size, without the necessity to tune any parameter. Second, we show that the temporal activity in the model is inherently nonstationary and obtain from here justification and support for the concept of a "seismic cycle" in the temporal evolution of seismic activity. Finally, we ask for the reasons that make the model display a realistic value of the decaying exponent b in the Gutenberg-Richter law for the avalanche size distribution. We explain why relaxation induces a systematic increase in b from its value b?0.4 observed in the absence of relaxation. However, we have not been able to justify the actual robustness of the model in displaying a consistent b value around the experimentally observed value b?1.

Aragón LE; Jagla EA; Rosso A

2012-04-01

336

Prediction and evolution of drop-size distribution for a new ultrasonic atomizer

International Nuclear Information System (INIS)

Complete modeling of a new ultrasonic atomizer, the Spray On Demand (SOD) printhead, was carried out to enable its optimization. The modeling was focused on various factors, including nozzle vibrations and a theoretical prediction of the SOD drop-size distribution. Assuming that the spray is generated based on Faraday instability, a prediction of the drop-size distribution within the framework of a specific and general Maximum Entropy Formalism (MEF) was developed. This prediction was formulated using the conservation laws of energy and mass, as well as the three-parameter generalized Gamma distribution. After establishing an analytical expression to estimate the Sauter Mean Diameter, a qualitative validation of the model was performed by comparing predictions with experimental measurements of the drop-size distribution. The dynamic model is shown to be sensitive to operating conditions and physical properties of the fluid. The prediction capabilities of the model were found to be adequate, paving the way for optimization of the atomizer. The evolution of the drop-size distribution, under the coalescence effect, was also assessed using a convergent Monte Carlo method to solve the distribution equation. This was formulated in a mass flow algorithm, leading to a more physically relevant distribution. - Research highlights: ? A theoretical study of the drop-size distribution evolution applied to a new atomizer device is proposed. ? From two approaches of the Maximum Entropy Formalism( MEF),a specific and a general formulations, a new physically based formulation for spray modeling is derived. ? To solve the problem, a Monte-Carlo Method, which was shown to be convergent, was developed to highlight the formation of new drops due to coalescence, leading to a physically based bi-modal distribution. ? The new approach avoids the traditional adjustment for each operating condition and has better predictive capabilities.

2011-01-01

337

UK PubMed Central (United Kingdom)

Boric acid, sulphanilamide and citric acid have been mixed separately with lactose and then granulated by massing and screening. The granules have been fractionated by sieving and each fraction has been analysed for lactose content. The effect of premixing time, massing time, binder volume and ratio of components on the distribution of lactose between size fractions of granules prepared from lactose: boric acid mixtures has been investigated. Uneven distribution of lactose has been found for all blends examined. There is a premixing time and massing time that gives the optimum distribution of lactose for any given blend and binder volume. Increased binder volume in some cases improves granule uniformity. The proportion of lactose in the blend has a major effect on the distribution of this component in the granules, as does the particle size of the lactose. Granules prepared from blends of lactose with sulphanilamide and with citric acid were also examined for lactose distribution.

Opakunle WO; Spring MS

1977-05-01

338

Boric acid, sulphanilamide and citric acid have been mixed separately with lactose and then granulated by massing and screening. The granules have been fractionated by sieving and each fraction has been analysed for lactose content. The effect of premixing time, massing time, binder volume and ratio of components on the distribution of lactose between size fractions of granules prepared from lactose: boric acid mixtures has been investigated. Uneven distribution of lactose has been found for all blends examined. There is a premixing time and massing time that gives the optimum distribution of lactose for any given blend and binder volume. Increased binder volume in some cases improves granule uniformity. The proportion of lactose in the blend has a major effect on the distribution of this component in the granules, as does the particle size of the lactose. Granules prepared from blends of lactose with sulphanilamide and with citric acid were also examined for lactose distribution. PMID:17695

Opakunle, W O; Spring, M S

1977-05-01

339

Cost implications of feedstock combinations for community sized biodiesel production

Energy Technology Data Exchange (ETDEWEB)

Biodiesel can be processed from oilseeds or animal fats and used in unmodified diesel engines. This fuel has been produced commercially in Europe for three years. Research indicates that biodiesel can replace diesel fuel without causing harmful effects to an unmodified engine and can reduce harmful emissions . Some European biodiesel plants operate at the community level effectively supplying both fuel and animal feeds. This study examines multiple feedstocks that could be utilized by a community sized biodiesel plant. The model plant used is a 500,000 gallon processing facility. The model plant is assumed to be installed in an existing grain handling facility or feed mill. Animal fats would be purchased from outside sources and oilseeds would be provided by area producers. Producers would retain ownership of the oilseeds and pay a processing fee to the cooperative. Oilseeds would be extruded before being separated into meal and crude oil. The crude oil would be esterified into biodiesel using continuous flow esterification technology. This study concludes under specific conditions, biodiesel can be processed economically at the community level. The results indicate that without farm program benefits to minor oilseeds, soybeans are the most economic feedstock to use in a community based operation. Realistic price information suggests that biodiesel (from soybeans) could be produced for $1.26 per gallon. If producers participate in government programs and are capable of growing minor oilseeds, canola may represent a better feedstock than soybeans. Achieving the lowest costs of production depends on the value assigned to co-product credits such as oilseed meal. The more producers pay for high protein meal for their livestock and poultry, the lower the residual price of biodiesel.

Weber, J.A.; Van Dyne, D.L. [Univ. of Missouri, Columbia, MO (United States)

1993-12-31

340

The mass and number size distributions of black carbon aerosol over Europe

Directory of Open Access Journals (Sweden)

Full Text Available Black carbon-containing aerosol particles play an important role in the direct and indirect radiative forcing of climate. However, the magnitude and sign of the net radiative effect is strongly dependent on the physical properties of the black carbon (BC) component of the particles, such as mass concentration, number size distribution and mixing state. Here we use a global aerosol model combined with aircraft measurements of BC particle number and size from the Single Particle Soot Photometer (SP2) to assess the realism with which these physical properties are predicted by global models. The comparison reveals a substantial mismatch between the measured and modelled BC size distribution over the size range of the SP2 instrument (90–400 nm BC diameter). The model predicts BC particle number concentrations a factor ~3.5–5.7 higher than measured and a mode diameter that is ~40–65 nm smaller than observed. More than ~90% of the model particles with dry diameters ≳260 nm contain BC, while the observations suggest only 14% on average. These model–observation biases in the BC properties are considerably greater than for the overall particle distribution, suggesting that the discrepancy is associated with model assumptions about the size and mixing state of the emitted carbonaceous particles. We expect the discrepancy in BC size distribution to be common among most global aerosol models, with implications for model estimates of absorption optical depth and direct radiative forcing.

C. L. Reddington; G. McMeeking; G. W. Mann; H. Coe; M. G. Frontoso; D. Liu; M. Flynn; D. V. Spracklen; K. S. Carslaw

2013-01-01

341

UK PubMed Central (United Kingdom)

BACKGROUND: Iron oxide nanoparticles hold great promise for future biomedical applications. To this end numerous studies on iron oxide nanoparticles have been conducted. One aspect these studies reveal is that nanoparticle size and shape can trigger different cellular responses through endocytic pathways, cell viability and early apoptosis. However, systematic studies investigating the size dependence of iron oxide nanoparticles with highly defined diameters across multiple cells lines are not available yet. METHODS: Iron oxide nanoparticles with well-defined size distributions were prepared. All samples were thoroughly characterized and the cytotoxicity for four standard cell lines (HeLa Kyoto, human osteosarcoma (U2OS), mouse fibroblasts (NIH 3T3) and mouse macrophages (J7442)). RESULTS: Our findings show that small differences in size distribution (ca. 10nm) of iron oxide nanoparticles do not influence cytotoxicity, while uptake is size dependent. Cytotoxicity is dose-dependent. Broad distributions of nanoparticles are more easily internalized as compared to the narrow distributions for two of the cell lines tested (HeLa Kyoto and mouse macrophages (J7442)). CONCLUSION: The data indicate that it is not feasible to probe changes in cytotoxicity within a small size range (10nm). However, TEM investigations of the nanoparticles indicate that cellular uptake is size dependent. GENERAL SIGNIFICANCE: The present work compares narrow and broad distributions for various samples of carbon-coated iron oxide nanoparticles. The data highlights that cells differentiate between nanoparticle sizes as indicated by differences in cellular uptake. This information provides valuable knowledge to better understand the interaction of nanoparticles and cells.

Mendes RG; Koch B; Bachmatiuk A; El-Gendy AA; Krupskaya Y; Springer A; Klingeler R; Schmidt O; Büchner B; Sanchez S; Rümmeli MH

2013-09-01

342

Nano size Aerosols of Radon Decay Products in Various Environments

International Nuclear Information System (INIS)

The radioactive noble gas radon (222Rn, alpha decay, t1/2 = 3.82 days) is always accompanied by its short-lived decay products (RnDP): 218Po (alpha decay, t1/2 = 3.10 min), 214Pb (beta/gamma decay, t1/2 = 26.8 min), 214Bi (beta/gamma decay, t1/2 = 19.9 min), and 214Po (alpha decay, t1/2 = 164 ?s). In indoor and outdoor air, they appear as unattached RnDP in the form of clusters in the size range 0.5-3 nm and as attached RnDP between 200 and 800 nm. Because of plate-out of aerosols on the walls and floor of a room, as well as air movement and entry of fresh air, radioactive equilibrium between RnDP and Rn in indoor air is only partly achieved and is expressed as a fraction between 0 and 1, called the equilibrium factor, F. Birchall and James elaborated a dosimetric approach to calculate the dose conversion factor, DCFD, based on fun. In this paper, the results of our studies on fun in 29 rooms of kindergartens and 26 rooms of elementary and high schools, at the lowest point and the railway station in the Postojna Cave, and in 4 rooms in wineries in Slovenia are reported, and DCFD values based on the Porstendorfer formulae are discussed and compared with the DCFE value recommended by ICRP-65.

2008-01-01

343

On the size distribution of sunspot groups in the Greenwich sunspot record 1874-1976

We investigate the size distribution of the maximum areas and the instantaneous distribution of areas of sunspot groups using the Greenwich sunspot group record spanning the interval 1874-1976. Both distributions are found to be well described by log-normal functions. Using a simple model we can transform the maximum area distribution into the instantaneous area distribution if the sunspot area decay rates are also distributed log-normally. For single-valued decay rates the resulting snapshot distribution is incompatible with the observations. The current analysis therefore supports the results of Howard (1992) and MartinezPillet (1993). It is not possible to distinguish between a linear and a quadratic decay law, however, with the employed data set.

Baumann, I

2005-01-01

344

Size distributions of trace metals in atmospheric aerosols in the United Kingdom

Energy Technology Data Exchange (ETDEWEB)

The size distributions of Ba, Cd, Co, Cu, Hg, Mn, Ni, Pb, Sn, Se, Sr, Zn and Fe in atmospheric aerosols were measured using impactors at three background sites in central England and southern Scotland. Coarse aerosols (>10.0{mu}m) were found to be undercollected by a micro-orifice uniform deposit impactor (MOUDI) when compared to an isokinetic technique, to a degree dependent on the size distribution of individual metals. The size distributions obtained in Scotland, which were typically trimodal, differed from those in central England, where modes were more variable. Characteristics size distributions allowed identification of three main behavioural types: (i) metals whose mass resided mainly within the accumulation mode (Cd, Sn, Pb, Se), (ii) those which were distributed between fine, intermediate and coarse modes (Ni, Zn, Cu, Co, Mn, Hg), and (iii) those which were mainly found within coarse particles (Fe, Sr, Ba). The measured distributions are believed to result from a combination of processes including local anthropogenic and natural sources, long-range transport and resuspension. (Author)

Allen, A.G.; Shi, J.P.; Harrison, R.M. [Birmingham Univ., Div. of Environmental Health and Risk Management, Birmingham (United Kingdom); Nemitz, E. [Centre for Ecology and Hydrology (CEH), Edinburgh Research Station, Penicuik (United Kingdom); Greenwood, J.C. [Kingston Univ., School of Earth Sciences and Geography, Kingston upon Thames (United Kingdom)

2001-07-01

345

Effect of Particle Size Distribution on Ammonium Sulphate Dried in a Rotary Dryer

Directory of Open Access Journals (Sweden)

Full Text Available The aim of this work is to study theoretically, by mathematical model development, the effect of particle size distribution on the performance of rotary dryer to dry ammonium sulphate fertilizer assuming plug flow with axial dispersion pattern (PFDA model) for solid particle flow. The mathematical model development was carried out by combining the drying processes model with particle size distribution model. Particle size distribution models used are Rosin-Rommler model and Gamma distribution model. For simplicity, the model of drying processes of solid particles in the rotary dryer was developed by assuming of uniform air conditions (temperature and humidity) along the rotary dryer as in the entry conditions. The resulting differential equations were solved analytically under Matlab 6.1 facility.Since this model, solid hold up, and axial dispersion number were obtained from empirical correlations in the literatures. The drying rate of ammonium sulphate fertilizer in rotary dryer was estimated using isothermal diffusion model with effective diffusivity of moisture in the particle obtained from previous study [2]. Using Gamma function distribution, this research showed that for the value of the coefficient of variance (CV) less than 0.5, particle size distribution does not have significant effect on dryer performance. For the value of CV greater than 0.5, the dryer performance increase (or outlet solid moisture content decrease) with increasing the value of CV. The application of Rosin-Rammler model gives lower prediction of outlet solid moisture content compared to the application of Gamma function model.

Susianto Susianto; Ali Altway; Kuswandi Kuswandi; Margono Margono

2010-01-01

346

Interpretations and implications of negative binomial distributions of multiparticle productions

International Nuclear Information System (INIS)

The number of particles produced in high energy experiments is approximated by a negative binomial distribution. Deriving a representation of the distribution from a stochastic equation, conditions for the process to satisfy the distribution are clarified. Based on them, it is proposed that multiparticle production consists of spontaneous and induced production. The rate of the induced production is proportional to the number of existing particles. The ratio of the two production rates remains constant during the process. The ''NBD space'' is also defined where the number of particles produced in its subspaces follows negative binomial distributions with different parameters.

2006-11-01

347

EVOLUTION OF SIZE DISTRIBUTION OF ICY GRAINS BY SUBLIMATION AND CONDENSATION

International Nuclear Information System (INIS)

In the outer part of a protoplanetary disk, dust grains consist of silicate core covered by an ice mantle. A temporal heating event in the disk results in sublimation of the ice mantle. After the end of the heating event, as the temperature decreases, H2O molecules recondense on the surface of the dust grain. Ultimately, the dust grain is covered by an ice mantle. Because the equilibrium vapor pressure on the grain surface decreases with the grain size, a large grain grows faster than a small grain. As a result, the size of an icy dust grain changes as a result of the heating event. The change in size also affects the mechanical properties of the dust aggregates formed by the icy grains. In this paper, we investigated the evolution of the size distribution of icy dust grains during sublimation and condensation. We found that the size evolution of icy grains can be divided into two stages. In the first stage, the icy grains grow through condensation of H2O molecules. In the second stage, the size of grains changes further as H2O molecules are transferred between icy grains while the surrounding gas condenses. The size distribution of the icy dust grains becomes bimodal, with a small number of relatively large grains and many small grains without an icy mantle. Possible effects of the size change on the evolution of icy dust aggregates are discussed.

2011-09-20

348

Terrestrial vegetation releases substantial amounts of reactive volatile organic compounds (VOCs; e.g., isoprene, monoterpenes) into the atmosphere. The VOCs can be rapidly photooxidized under conditions of high solar radiation, yielding products that can participate in new particle formation and growth processes above forests. This thesis focuses on the characterization, identification and quantification of oxidation products of biogenic VOC (BVOCs) as well as other species (tracer compounds) that provide information on aerosol sources and source processes. Atmospheric aerosols from various forested sites (i.e., Hyytiala, southern Finland; Rondonia, Brazil; K-Puszta, Hungary and Julich, Germany) were analyzed with Gas Chromotography/Mass Spectrometry (GC/MS) using analytical procedure that targets polar organic compounds. The study demonstrated that isoprene (i.e., 2-methyerythritol, 2-methylthreitol, 2-methylglyceric acid and C5-alkene triols (2-methyl-1,3,4-trihydroxy-l-butene (cis and trans) and 3 methyl-2,3,4-trihydroxy-1-butene)) and monoterpene (pinic acid, norpinic acid, 3-hydroxyglutaric acid and 3-methyl-1,2,3-butanetricarboxylic acid) oxidation products were present in substantial concentrations in atmospheric aerosols suggesting that oxidation of BVOC from the vegetation is an important process in all studied sites. On the other hand, presence of levoglucosan, biomass burning marker, especially in Amazonian rain forest site at Rondonia, Brazil, pointed that all sites were affected by anthropogenic activities, namely biomass burning. Other identified compounds included plyols, arabitol, mannitol and erythritol, which are marker compounds for fungal spores and monosacharides, glucose and fructose, markers for plant polens. Temporal variations as well as mass size distributions of the detected species confirmed the possible formation mechanisms of marker compounds.

Kourtchev, Ivan

349

Shunt Capacitor Position and Size Selection for Radial Distribution System using GA

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents a new approach for shunt Capacitor position and size for radial distribution network based on genetic approach. Distribution networks experience distinct changes from low load level to high load level every day. In certain industrial areas, it has been observed that under certain critical loading conditions, the distribution system experience voltage collapse. Due to this phenomenon, system voltage collapses periodically and urgent reactive compensation needs to be supplied to avoid repeated voltage collapse. In this Paper a new approach for finding Capacitor size and Position presented .The node having the voltage stability index minimum is more prone to voltage collapse. That node is identified as candidate node. Further capacitors are installed at the candidate nodes for improvement of Voltage stability index. Genetic Algorithm is more suitable for such problems. So Genetic Algorithm is used for sizing of capacitors at selected locations.

U.Ramesh Babu; V.Vijay Kumar Reddy; S.Tarakalyani

2012-01-01

350

Increasing Returns to Scale, Dynamics of Industrial Structure and Size Distribution of Firms

A model is presented of the market dynamics to emphasis the effects of increasing returns to scale, including the description of the born and death of the adaptive producers. The evolution of market structure and its behavior with the technological shocks are discussed. Its dynamics is in good agreement with some empirical stylized facts of industrial evolution. Together with the diversities of demand and adaptive growth strategies of firms, the generalized model has reproduced the power-law distribution of firm size. Three factors mainly determine the competitive dynamics and the skewed size distributions of firms: 1. Self-reinforcing mechanism; 2. Adaptive firm grows strategies; 3. Demand diversities or widespread heterogeneity in the technological capabilities of different firms. Key words: Econophysics, Increasing returns, Industry dynamics, Size distribution of firms

Fan, Y; Di, Z; Fan, Ying; Li, Menghui; Di, Zengru

2004-01-01

351

Activity and size distributions of aerosols in the Laboratory for experimental fuels AEE Winfrith

International Nuclear Information System (INIS)

Measurements have been made of the particle activity and particle size distributions of aerosols encountered in a building in which uranium and plutonium oxides are fabricated into experimental fuel elements in freestanding glove boxes. The particle size distribution has been determined by examination of the filter papers of personal air samplers and installed air samplers operating on occasions on which such aerosols were accidentally released into the building due to damaged gloves or posting ports. When large numbers of particles are released, the aerosol is characterised by a log-normal particle-size distribution; the respirable fraction is rather variable, but it would appear that the amount retained in the lung is unlikely to differ from the amount deduced on the basis of the ICRP lung model by more than a factor of four. In many of the less severe incidents, the activity collected on the filter paper was almost entirely due to a very small number of particles. (author)

1979-01-01

352

Energy Technology Data Exchange (ETDEWEB)

In evaluating fuel nozzle performance, the droplets size distribution - frequently characterized by the Sauter mean diameter - is found to be one of the dominant parameters. Using examples from ongoing experimental studies with pressurized and airblast atomizers, attention is directed towards the importance of flow parameters and size distribution in applying non-intrusive optical techniques. In particular, an optical diffraction-type particle sizer has been used in analyzing fuel sprays from airblast and pressure atomizers. It is shown that the Sauter mean diameter alone is generally not suited for describing the nozzle performance. Emphasis is directed towards the influence of the flow field on the apparent droplet size distribution explaining a variety of observations reported in other studies.

Wittig, S.; Aigner, M.; Sakbani, K.; Sattelmayer, T.

1984-01-01

353

UK PubMed Central (United Kingdom)

The distributions of coalescence times and ancestral lineage numbers play an essential role in coalescent modeling and ancestral inference. Both exact distributions of coalescence times and ancestral lineage numbers are expressed as the sum of alternating series, and the terms in the series become numerically intractable for large samples. More computationally attractive are their asymptotic distributions, which were derived in Griffiths (1984) for populations with constant size. In this article, we derive the asymptotic distributions of coalescence times and ancestral lineage numbers for populations with temporally varying size. For a sample of size n, denote by Tm the mth coalescent time, when m + 1 lineages coalesce into m lineages, and An(t) the number of ancestral lineages at time t back from the current generation. Similar to the results in Griffiths (1984), the number of ancestral lineages, An(t), and the coalescence times, Tm, are asymptotically normal, with the mean and variance of these distributions depending on the population size function, N(t). At the very early stage of the coalescent, when t ? 0, the number of coalesced lineages n - An(t) follows a Poisson distribution, and as m ? n, $$n\\left(n-1\\right){T}_{m}/2N\\left(0\\right)$$ follows a gamma distribution. We demonstrate the accuracy of the asymptotic approximations by comparing to both exact distributions and coalescent simulations. Several applications of the theoretical results are also shown: deriving statistics related to the properties of gene genealogies, such as the time to the most recent common ancestor (TMRCA) and the total branch length (TBL) of the genealogy, and deriving the allele frequency spectrum for large genealogies. With the advent of genomic-level sequencing data for large samples, the asymptotic distributions are expected to have wide applications in theoretical and methodological development for population genetic inference.

Chen H; Chen K

2013-07-01

354

The distributions of coalescence times and ancestral lineage numbers play an essential role in coalescent modeling and ancestral inference. Both exact distributions of coalescence times and ancestral lineage numbers are expressed as the sum of alternating series, and the terms in the series become numerically intractable for large samples. More computationally attractive are their asymptotic distributions, which were derived in Griffiths (1984) for populations with constant size. In this article, we derive the asymptotic distributions of coalescence times and ancestral lineage numbers for populations with temporally varying size. For a sample of size n, denote by Tm the mth coalescent time, when m + 1 lineages coalesce into m lineages, and An(t) the number of ancestral lineages at time t back from the current generation. Similar to the results in Griffiths (1984), the number of ancestral lineages, An(t), and the coalescence times, Tm, are asymptotically normal, with the mean and variance of these distributions depending on the population size function, N(t). At the very early stage of the coalescent, when t ? 0, the number of coalesced lineages n - An(t) follows a Poisson distribution, and as m ? n, $$n\\left(n-1\\right){T}_{m}/2N\\left(0\\right)$$ follows a gamma distribution. We demonstrate the accuracy of the asymptotic approximations by comparing to both exact distributions and coalescent simulations. Several applications of the theoretical results are also shown: deriving statistics related to the properties of gene genealogies, such as the time to the most recent common ancestor (TMRCA) and the total branch length (TBL) of the genealogy, and deriving the allele frequency spectrum for large genealogies. With the advent of genomic-level sequencing data for large samples, the asymptotic distributions are expected to have wide applications in theoretical and methodological development for population genetic inference. PMID:23666939

Chen, Hua; Chen, Kun

2013-05-11

355

A model for the size distribution of shops in a price driven market

A microscopic model is introduced to investigate the size distribution of shops. In the model, shops are constrained to comply with the market price, as expected by the customers, while customers can only buy at the prices offered by the shops. We show numerically and analytically that the size distribution scales like a power-law, with an exponent in agreement with empirical data on company sizes in the U.S. and debt sizes in Japan. A mean-field version of our model is also introduced and we determine for which value of the parameters the mean-field model agrees with both the microscopic model and the empirical data. Finally, possible extensions of the mean-field model are discussed, to cope with other empirical data.

D'Hulst, R

2000-01-01

356

Energy Technology Data Exchange (ETDEWEB)

This paper presents a model for pressure transient and derivative analysis for naturally fractured reservoirs by a formulation of inter porosity flow incorporating variations in matrix block size, which is inversely related to fracture intensity. Geologically realistic Probability Density Functions (PDFs) of matrix block size, such as uniform, bimodal, linear and exponential distributions, are examined and pseudo-steady-state and transient models for inter porosity flow are assumed. The results have been physically interpreted, and, despite results obtained by other authors, it was found that the shape of pressure derivative curves for different PDFs are basically identical within some ranges of block size variability, inter porosity skin, PDFs parameters and matrix storage capacity. This tool can give an insight on the distribution of block sizes and shapes, together with other sources of information such as Logs and geological observations. (author)

Montazeri, G.H. [Islamic Azad University, Mahshahr (Iran, Islamic Republic of). Dept. of Chemical and Petroleum Engineering], E-mail: montazeri_gh@yahoo.com; Tahami, S.A. [Mad Daneshgostar Tabnak Co. (MDT),Tehran (Iran, Islamic Republic of); Moradi, B.; Safari, E. [Iranian Central Oil Fields Co, Tehran (Iran, Islamic Republic of)], E-mail: morady.babak@gmail.com

2011-07-15

357

International Nuclear Information System (INIS)

[en] The literature on plutonium aerosols was surveyed for information (1) particle size distributions of plutonium aerosols from nuclear facilities, (2) collection efficiencies for plutonium aerosol particles of multi-stage HEPA filter systems used as exhaust air cleaning systems in these facilities, and (3) particle size distributions of plutonium aerosols discharged through the air cleaning systems. Following are the results. 1. Mean particle sizes of plutonium aerosols from chemical plants are about 0.5 ?m AMAD and from fuel fabrication plants about 3 ?m AMAD. 2. Average collection efficiencies for plutonium aerosols of the first and second stage HEPA filters in the multi-stage HEPA filter systems exceed 99.99%. 3. Mean particle sizes of plutonium aerosols discharged through the air cleaning systems are 0.2 ?m-0.4 ?m AMAD for chemical plants and 0.5 ?m-1.2 ?m AMAD for fuel fabrication plants. (author)

1984-01-01

358

Energy Technology Data Exchange (ETDEWEB)

Samples from the stratosphere obtained by U-2 aircraft after the first three major eruptions of Mount St. Helens contained large globules of liquid acid and ash. Because of their large size, these globules had disappeared from the lower stratosphere by late June 1980, leaving behind only smaller acid droplets. Particle-size distributions and mineralogy of the stratospheric ash grains demonstrate inhomogeneity in the eruption clouds.

Farlow, N.H.; Oberbeck, V.R.; Snetsinger, K.G.; Ferry, G.V.; Polkowski, G.; Hayes, D.M.

1981-01-01

359

Energy Technology Data Exchange (ETDEWEB)

Synthetic washed ITP slurry (200 g) was oven dried for three days at 60--65{degrees}C in a pan, to a hard solid that stuck to the pan bottom. Between the cracks that formed were a few small particles of unknown size. The solids that were stuck to the pan bottom were pried free and repetitively ground in a mortar and pestle until they all passed through a 40 mesh sieve. This product was then sieved into 50, 80, 100, 170, 200, 325 sieve fractions and the results plotted. A protion of the fines passing the 325 sieve were further separated by air flotation in a glass tube with fritted bottom. Increasing amounts of air were passed up through the tube that floated out increasing fractions of particles after weighing. ITP washed precipitate, ground and dried, had a particle size distribution versus cumulative weight fraction curve between Powered coal and Filter sand. The minimum particle size was about 20 microns.

Kilpatrick, L.L.

1993-10-13

360

Measurements of ultrafine particle concentration and size distribution in the urban atmosphere

Energy Technology Data Exchange (ETDEWEB)

Particle size distributions were measured at three adjacent sites in Birmingham: a busy roadside (A38); 30 m away from the road and a nearby urban background site. Two scanning mobility particle sizers (SMPS), an electrical low pressure impactor (ELPI), a condensation particle counter and a thermophoretic precipitator were employed to measure and collect particles. Excellent agreement on the number weighted size distribution was found between the SMPS and ELPI, as well as with sizes measured by transmission electron microscopy. The average number concentration at roadside measured on four separate days was between 1.6 and 1.9x10{sup 5} cm{sup -3} with similar size distributions and more than half of measured particles smaller than 30 nm. Traffic was the main source of ultrafine particles at the roadside. A 24-h average of 2.68x10{sup 4}{+-}1.29x10{sup 4} cm{sup -3} was measured, which is close to that in Hughes et al. (Physical and chemical characterization of atmospheric ultrafine particles in the Los Angeles area, Environ Sci Technol 1998; 32:1153-1161) in Pasadena, CA, USA. Total particle number concentration declined downwind of the traffic, faster than the mass concentration. Model calculations show that dilution with background air is the main mechanism for the rapid drop in particle number concentration and change in particle size distribution when moving away from traffic.

Shi, J.P.; Khan, A.A.; Harrison, R.M. [Environmental Health, Institute of Public and Environmental Health, The University of Birmingham, Edgbaston, Birmingham (United Kingdom)

1999-09-01

361

Forecasting grain size distribution of coal cut by a shearer loader

Energy Technology Data Exchange (ETDEWEB)

Analyzed are effects of shearer loader design on grain size distribution of coal, particularly on proportion of the finest size group and proportion of largest coal grains. The method developed by the IGD im. A.A. Skochinski Institute in Moscow is used. Effects of cutting tool design and mechanical coal properties are analyzed. Of the evaluated factors, two are of decisive importance: thickness of the coal chip cut by a cutting tool and coefficient of coal disintegration which characterizes coal behavior during cutting. Grain size distribution is also influenced by cutting tool geometry. Two elements of cutting tool design are of major importance: dimensions of the cutting edge and angle of attack. Effects of cutting tool design and coal mechanical properties on grain size distribution are shown in 12 diagrams. Using the forecasting method developed by the IGD im. A.A. Skochinski Institute in Moscow grain size distribution of coal cut by three shearer loaders is calculated: the KWB-3RDU with a drum 1600 mm in diameter, the KWB-6W with a drum 2500 mm in diameter, and a shearer loader being developed with a 1550 mm drum. The results of comparative evaluations are shown in two tables. 5 references.

Sikora, W.; Chodura, J.; Siwiec, J.

1983-02-01

362

Aerosol size distributions of polycyclic aromatic hydrocarbons in urban and over-water atmospheres

Energy Technology Data Exchange (ETDEWEB)

Aerosol mass size distributions of 41 polycyclic aromatic hydrocarbons (PAHs) were measured during 20 different 12-h periods in urban Chicago and over Lake Michigan during July 1994 and January 1995. Geometric mean aerodynamic equivalent diameters (GMDs) range from 0.72 to 2.39 {mu}m for particulate matter and from 0.33 to 9.85 {mu}m for individual PAHs. GMDs of the less volatile PAHs are larger in the urban atmosphere than over the water during the summer. Geometric standard deviations of the particle size distributions, however, are larger at the urban location for many PAHs, indicating a broader mass size distributions. GMDs of unsubstituted PAHs (except perylene) are well correlated with their log subcooled liquid vapor pressures (p{sub l} Pa). Higher molecular weight PAHs are sorbed to the finest sized aerosols, but more volatile PAHs are associated with larger particles. PAH size distributions change downwind of urban emission sources due to selective deposition of larger aerosols during atmospheric transport. 80 refs., 5 figs., 1 tab.

Offenberg, J.H.; Baker, J.E. [Chesapeake Biological Laboratory, Maryland, MD (US)

1999-10-01

363

Modeling of fission-gas bubble size distribution in U-Mo metal alloys

International Nuclear Information System (INIS)

A mechanistic model developed and validated against fission-gas bubble size distribution and fission gas release and fuel swelling data for oxide nuclear fuel has been modified in order to describe the fission gas behaviors in metallic fuel - in this particular study, U-Mo type alloys. Traditional validations of such models are accomplished by adjusting materials properties and parameters to obtain good agreement with experimentally measured fission-gas release, swelling, and mean values of bubble size and density. However, the uncertainty in these properties and parameters generate an inherent uncertainty in the validity of underlying physics. Validations using measured fission-gas bubble size distributions have been shown to be more promising in terms of interpreting the physics behind the fission-gas behavioral mechanisms. Measured intergranular fission-gas bubble size distribution data were used in this study for the purpose of model validation, and to explore the underlying physics of fission-gas bubble nucleation and coalescence. Plausible interpretation of the observed fission-gas bubble size distribution in irradiated U-10Mo alloys is provided. (author)

2011-01-01

364

Temporal change in the size distribution of airborne Radiocesium derived from the Fukushima accident

The accident of Fukushima Dai-ichi nuclear power plant discharged a large amount of radioactive materials into the environment. After 40 days of the accident, we started to collect the size-segregated aerosol at Tsukuba City, Japan, located 170 km south of the plant, by use of a low-pressure cascade impactor. The sampling continued from April 28, through October 26, 2011. The number of sample sets collected in total was 8. The radioactivity of 134Cs and 137Cs in aerosols collected at each stage were determined by gamma-ray with a high sensitivity Germanic detector. After the gamma-ray spectrometry analysis, the chemical species in the aerosols were analyzed. The analyses of first (April 28-May 12) and second (May 12-26) samples showed that the activity size distributions of 134Cs and 137Cs in aerosols reside mostly in the accumulation mode size range. These activity size distributions almost overlapped with the mass size distribution of non-sea-salt sulfate aerosol. From the results, we regarded that sulfate is the main transport medium of these radionuclides, and re-suspended soil particles that attached radionuclides were not the major airborne radioactive substances by the end of May, 2011 (Kaneyasu et al., 2012). We further conducted the successive extraction experiment of radiocesium from the aerosol deposits on the aluminum sheet substrate (8th stage of the first aerosol sample, 0.5-0.7 ?m in aerodynamic diameter) with water and 0.1M HCl. In contrast to the relatively insoluble property of Chernobyl radionuclides, those in aerosols collected at Tsukuba in fine mode are completely water-soluble (100%). From the third aerosol sample, the activity size distributions started to change, i.e., the major peak in the accumulation mode size range seen in the first and second aerosol samples became smaller and an additional peak appeared in the coarse mode size range. The comparison of the activity size distributions of radiocesium and the mass size distributions of major aerosol components collected by the end of August, 2011, (i.e., sample No.5) and its implication will be discussed in the presentation. Reference Kaneyasu et al., Environ. Sci. Technol. 46, 5720-5726 (2012).

Kaneyasu, Naoki; Ohashi, Hideo; Suzuki, Fumie; Okuda, Tomoaki; Ikemori, Fumikazu; Akata, Naofumi

2013-04-01

365

Directory of Open Access Journals (Sweden)

Full Text Available Lateritic soil was treated with 1-4% cement contents and was admixtured with 2-8% bagasse ash content. The paper evaluated the plasticity and particle size distribution characteristic of bagasse ash on cement treated laterite. It was observed that liquid limit and plasticity index reduced while plastic limit increased. As regards the particle size distribution, the was reduction in the percentage of fines as a result of formation of heavier pseudo- and particle with percentage passing BS Sieve No. 200 reduced from 63% to almost zero. However the recommended percentage of bagasse ash should be between 4%-6%.

Mohammed Abdullahi MU'AZU

2007-01-01

366

International Nuclear Information System (INIS)

Tensile tests were conducted on several cast aluminum specimens with different degrees of porosity. The effects of non uniform void size and shape distributions, including spherical and non spherical types, on stress-strain behavior resulting from different initiation mechanisms were investigated. A micro mechanics based statistical approach was employed, and the heterogeneous microstructures could therefore be modeled during the deformation process. The predicted changes of the distributions of void size and void shape generally agreed with experimental results. Void spatial variation was also quantified, and its effects on the level of failure were analyzed. The void spatial variation facilitated development of inhomogeneous deformation, which results in failure

2012-01-01

367

Size and excitation energy distributions of projectile spectators in ALADIN multifragmentation data

International Nuclear Information System (INIS)

The size and energy distributions of spectators in ALADIN fragmentation experiments with gold projectiles are inferred from experimental data. For the most violent collisions of Au on Cu, the mean projectile spectator has the size of an iron nucleus, with an excitation energy of about 23 MeV/nucleon. A correct interpretation of these data should take into account the large range covered by the extracted distributions, which are in good agreement with the prediction of BUU calculations and with those of a new diabatic abrasion model. (author). 12 refs., 4 figs

1994-01-01

368

Potts model simulation of grain size distributions during final stage sintering

Energy Technology Data Exchange (ETDEWEB)

The Potts Monte Carlo model was used to simulate microstructural evolution and characterize grain size distribution during the final stages of sintering. Simultaneous grain growth, pore migration and pore shrinkage were simulated in a system with an initial porosity of 10% with varying ratios of grain boundary mobility to pore shrinkage rates. This investigation shows that the presence of pores changes the grain size distribution and the topological characteristics due to pinning of grains by pores. As pores shrink away, their pinning effect decreases. Once pore shrinkage is complete, normal grain growth is achieved.

Zeng, P. [Univ. of Connecticut, Storrs, CT (United States). Center for Materials Simulations; Tikare, V. [Sandia National Labs., Albuquerque, NM (United States)

1998-09-01

369

Directory of Open Access Journals (Sweden)

Full Text Available The conventional serial sectioning analysis and a set of modern stereological methods, including disector, selector, point-sampled intercepts, point-sampled area, and their combinations, have been used in this paper to measure the grain size, grain size distribution, topological parameters and their distributions in a spacefilling single-phase grain structure of steel. The results from different methods are compared and used to evaluate the methods quantitatively, based on which some suggestions will be given for selection of experimental methods in materials stereology research.

Guoquan Liu; Haibo Yu

2000-01-01

370

UK PubMed Central (United Kingdom)

Aerosol size distributions of varying types selected from those measured in clear air, smog, and fog in the Los Angeles Basin have been used with Lorenz-Mie scattering theory to predict radiation scattering by aerosols. Eleven different indices of refraction were assumed for wavelengths from 0.488 microm to 8.4 microm for aerosol materials with varying humidity, and for water and quartz. The effect on the scattering by the type of size distribution and the complex index of refraction is shown as a function of the polarization parameters of polarization, polarization ratio, ellipticity, and the inclination angle of the polarization ellipse.

Harris FS Jr

1972-11-01

371

Particle size distribution of aerosols and associated heavy metals in kitchen environments.

UK PubMed Central (United Kingdom)

Mass size distributions of total suspended particulate matter (TSPM) was measured from Sep 2002 to April 2003 in indoor kitchen environments of five locations in Jawaharlal Nehru University (JNU), New Delhi, with the help of a high volume cascade impactor. Particulate matters were separated in five different size ranges, i.e. >10.9 microm, 10.9-5.4 microm, 5.4-1.6 microm, 1.6-0.7 microm and <0.7 microm. The particle size distribution at various sites appears to follow uni-modal trend corresponding to fine particles i.e. size range <0.7 microm. The contributions of fine particles are estimated to be approximately 50% of TSPM and PM10.9, while PM10.9 comprises 80% of TSPM. Good correlations were observed between various size fractions. Regression results reveal that TSPM can adequately act as a surrogate for PM10.9 and fine particles, while PM10.9 can also act as surrogate for fine particles. The concentrations of heavy metals are found to be dominantly associated with fine particles. However, the concentration of some metals and their size distribution, to some extent is also site specific (fuel type used).

Gupta S; Srivastava A; Jain VK

2008-07-01

372

The particle size distribution (PSD) of a polydisperse or multimodal system can often be difficult to obtain due to the inherent limitations in established measurement techniques. For this reason, the resolution, accuracy and precision of three new and one established, commercially available and fundamentally different particle size analysis platforms were compared by measuring both individual and a mixed sample of monodisperse, sub-micron (220, 330, and 410 nm - nominal modal size) polystyrene particles. The platforms compared were the qNano Tunable Resistive Pulse Sensor, Nanosight LM10 Particle Tracking Analysis System, the CPS Instruments's UHR24000 Disc Centrifuge, and the routinely used Malvern Zetasizer Nano ZS Dynamic Light Scattering system. All measurements were subjected to a peak detection algorithm so that the detected particle populations could be compared to 'reference' Transmission Electron Microscope measurements of the individual particle samples. Only the Tunable Resistive Pulse Sensor and Disc Centrifuge platforms provided the resolution required to resolve all three particle populations present in the mixed 'multimodal' particle sample. In contrast, the light scattering based Particle Tracking Analysis and Dynamic Light Scattering platforms were only able to detect a single population of particles corresponding to either the largest (410 nm) or smallest (220 nm) particles in the multimodal sample, respectively. When the particle sets were measured separately (monomodal) each platform was able to resolve and accurately obtain a mean particle size within 10% of the Transmission Electron Microscope reference values. However, the broadness of the PSD measured in the monomodal samples deviated greatly, with coefficients of variation being ~2-6-fold larger than the TEM measurements across all four platforms. The large variation in the PSDs obtained from these four, fundamentally different platforms, indicates that great care must still be taken in the analysis of samples known to have complex PSDs. All of the platforms were found to have high precision, i.e. they gave rise to less than 5% variance in PSD shape descriptors over the replicate measurements. PMID:23759321

Anderson, Will; Kozak, Darby; Coleman, Victoria A; Jämting, Åsa K; Trau, Matt

2013-03-01

373

UK PubMed Central (United Kingdom)

The particle size distribution (PSD) of a polydisperse or multimodal system can often be difficult to obtain due to the inherent limitations in established measurement techniques. For this reason, the resolution, accuracy and precision of three new and one established, commercially available and fundamentally different particle size analysis platforms were compared by measuring both individual and a mixed sample of monodisperse, sub-micron (220, 330, and 410 nm - nominal modal size) polystyrene particles. The platforms compared were the qNano Tunable Resistive Pulse Sensor, Nanosight LM10 Particle Tracking Analysis System, the CPS Instruments's UHR24000 Disc Centrifuge, and the routinely used Malvern Zetasizer Nano ZS Dynamic Light Scattering system. All measurements were subjected to a peak detection algorithm so that the detected particle populations could be compared to 'reference' Transmission Electron Microscope measurements of the individual particle samples. Only the Tunable Resistive Pulse Sensor and Disc Centrifuge platforms provided the resolution required to resolve all three particle populations present in the mixed 'multimodal' particle sample. In contrast, the light scattering based Particle Tracking Analysis and Dynamic Light Scattering platforms were only able to detect a single population of particles corresponding to either the largest (410 nm) or smallest (220 nm) particles in the multimodal sample, respectively. When the particle sets were measured separately (monomodal) each platform was able to resolve and accurately obtain a mean particle size within 10% of the Transmission Electron Microscope reference values. However, the broadness of the PSD measured in the monomodal samples deviated greatly, with coefficients of variation being ~2-6-fold larger than the TEM measurements across all four platforms. The large variation in the PSDs obtained from these four, fundamentally different platforms, indicates that great care must still be taken in the analysis of samples known to have complex PSDs. All of the platforms were found to have high precision, i.e. they gave rise to less than 5% variance in PSD shape descriptors over the replicate measurements.

Anderson W; Kozak D; Coleman VA; Jämting ÅK; Trau M

2013-09-01

374

The variability of tidewater-glacier calving: origin of event-size and interval distributions

Calving activity at the front of tidewater glaciers is characterized by a large variability in iceberg sizes and inter-event intervals. We present calving-event data obtained from continuous observations of the fronts of two tidewater glaciers on Svalbard, and show that the distributions of event sizes and inter-event intervals can be reproduced by a simple calving model focusing on the mutual interplay between calving and the destabilization of the glacier front. The event-size distributions of both the field and the model data extend over several orders of magnitude and resemble power laws. The distributions of inter-event intervals are broad, but have a less pronounced tail. In the model, the width of the size distribution increases with the calving susceptibility of the glacier front, a parameter measuring the effect of calving on the stress in the local neighborhood of the calving region. Inter-event interval distributions, in contrast, are insensitive to the calving susceptibility. Above a critical susc...

Chapuis, Anne

2012-01-01

375

UK PubMed Central (United Kingdom)

Ductal carcinoma in situ (DCIS) lesions are non-invasive tumours of the breast that are thought to precede most invasive breast cancers (IBCs). As individual DCIS lesions are initiated, grow and invade (i.e. become IBC), the size distribution of the DCIS lesions present in a given human population will evolve. We derive a differential equation governing this evolution and show, for given assumptions about growth and invasion, that there is a unique distribution which does not vary with time. Further, we show that any initial distribution converges to this stationary distribution exponentially quickly. Therefore, it is reasonable to assume that the stationary distribution governs the size of DCIS lesions in human populations which are relatively stable with respect to the determinants of breast cancer. Based on this assumption and the size data of 110 DCIS lesions detected in a mammographic screening programme between 1993 and 2000, we produce maximum likelihood estimates for certain growth and invasion parameters. Assuming that DCIS size is proportional to a positive power p of the time since tumour initiation, we estimate p to be 0.50 with a 95% confidence interval of (0.35, 0.71). Therefore, we estimate that DCIS lesions follow a square-root growth law and hence that they grow rapidly when small and relatively slowly when large. Our approach and results should be useful for other mathematical studies of cancer, especially those investigating biological mechanisms of invasion.

Dowty JG; Byrnes GB; Gertig DM

2013-07-01

376

Effect of particle size distribution on particle based composite anode models

Particle based models of composite anodes are useful tools for exploring the behavior of SOFC systems. As part of our efforts to develop models for understanding fuel cells, we have been building models of Ni-YSZ composite anodes using experimentally measured particle size distributions. The objectives of this study were to characterize the percolation threshold and conductivity of these models in comparison to simpler mono dispersed and biphasic particle size distributions from the literature. We found that the average values for the onset of percolation and the measured conductivity of the models with experimentally measured particle size distributions are similar to those for the simple distributions and the experimentally measured distributions. For all of the configurations evaluated, the onset of percolation in the Nickel phase occurred at a solid fraction of Nickel between 20% and 25%. This corresponded almost exactly to the point at which the coordination number between Nickel phase particles reached 2.2. The significant finding was that the variation in the value for the conductivity, as measured by the standard deviation of the results, was several orders of magnitude higher than for the simpler systems. We explored the validity of our assumptions, specifically the assumption of random particle placement, by building a particle model directly from FIB-SEM data. In this reconstruction, it was clear that the location of particles was not random. Particles of the same type and size had much likelihood of contact higher than would indicated by random location.

Thomas, Vaughan L.

2013-06-01

377

UK PubMed Central (United Kingdom)

Use of the final size distribution of minor outbreaks for the estimation of the reproduction numbers of supercritical epidemic processes has yet to be considered. We used a branching process model to derive the final size distribution of minor outbreaks, assuming a reproduction number above unity, and applying the method to final size data for pneumonic plague. Pneumonic plague is a rare disease with only one documented major epidemic in a spatially limited setting. Because the final size distribution of a minor outbreak needs to be normalized by the probability of extinction, we assume that the dispersion parameter (k) of the negative-binomial offspring distribution is known, and examine the sensitivity of the reproduction number to variation in dispersion. Assuming a geometric offspring distribution with k=1, the reproduction number was estimated at 1.16 (95% confidence interval: 0.97-1.38). When less dispersed with k=2, the maximum likelihood estimate of the reproduction number was 1.14. These estimates agreed with those published from transmission network analysis, indicating that the human-to-human transmission potential of the pneumonic plague is not very high. Given only minor outbreaks, transmission potential is not sufficiently assessed by directly counting the number of offspring. Since the absence of a major epidemic does not guarantee a subcritical process, the proposed method allows us to conservatively regard epidemic data from minor outbreaks as supercritical, and yield estimates of threshold values above unity.

Nishiura H; Yan P; Sleeman CK; Mode CJ

2012-02-01

378

A sign of superspreading in tuberculosis: highly skewed distribution of genotypic cluster sizes.

UK PubMed Central (United Kingdom)

BACKGROUND: Molecular typing is a valuable tool for gaining insight into spread of Mycobacterium tuberculosis. Typing allows for clustering of cases whose isolates share an identical genotype, revealing epidemiologic relatedness. Observed distributions of genotypic cluster sizes of tuberculosis (TB) are highly skewed. A possible explanation for this skewness is the concept of "superspreading": a high heterogeneity in the number of secondary cases caused per infectious individual. Superspreading has been previously found for diseases such as severe acute respiratory syndrome and smallpox, where the entire transmission tree is known. So far, no method exists to relate superspreading to the distribution of genotypic cluster sizes. METHODS: We quantified heterogeneity in secondary infections per infectious individual by describing this number as a negative binomial distribution. The dispersion parameter k is a measure of superspreading; standard (homogeneous) models use values of k ? 1, whereas small values of k imply superspreading. We estimated this negative binomial dispersion parameter for TB in the Netherlands, using the genotypic cluster size distribution for all 8330 cases of culture confirmed, pulmonary TB diagnosed between 1993 and 2007 in the Netherlands. RESULTS: The dispersion parameter k was estimated at 0.10 (95% confidence interval = 0.09-0.12), well in the range of values consistent with superspreading. Simulation studies showed the method reliably estimates the dispersion parameter across a range of scenarios and parameter values. CONCLUSION: Heterogeneity in the number of secondary cases caused per infectious individual is a plausible explanation for the observed skewness in genotypic cluster size distribution of TB.

Ypma RJ; Altes HK; van Soolingen D; Wallinga J; van Ballegooijen WM

2013-05-01

379

THE SENSITIVITY OF THE CATALYST EFFECTIVENESS FACTOR TO PORE SIZE DISTRIBUTION

Directory of Open Access Journals (Sweden)

Full Text Available A model is proposed for the average effective diffusivity for an arbitrary pore size distribution. It is shown that the average diffusivity must also depend on the distribution of the catalyst sites. The reaction diffusivity is compared with the average diffusivities defined by Wakao and Smith (1962) and Johnson and Stewart (1965). For the methanol dehydration and n-butene isomerization, the reaction diffusivity gives a better estimation of the effectiveness factor than the other models

Bensetiti Z.; Schweich D.; Abreu C.A.M.

1997-01-01

380

Finite Size Effects on the Real-Space Pair Distribution Function of Nanoparticles

Energy Technology Data Exchange (ETDEWEB)

The pair distribution function (PDF) method is a powerful approach for the analysis of the structure of nanoparticles. An important approximation used in nanoparticle PDF simulations is the incorporation of a form factor describing nanoparticle size and shape. The precise effect of the form factor on the PDF is determined by both particle shape and structure if these characteristics are both anisotropic and correlated. The correct incorporation of finite size effects is important for distinguishing and quantifying the structural consequences of small particle size in nanomaterials.

Gilbert, Benjamin

2008-10-01

381

International Nuclear Information System (INIS)

Particle size is a primary determinant of resources available to consumers and of the efficiency of energy transfer through planktonic food chains. Dual radioisotopic labeling (with 14C-bicarbonate and 3H-acetate) and size fractionation of naturally-occurring phytoplankton-bacterioplankton assemblages were employed to examine the particle size distributions of planktonic autotrophy and microheterotrophy in four limnologically-dissimilar US reservoirs (Lake Mead, Arizona-Nevada, oligo-mesotrophic; Broken Bow Lake, Oklahoma, mesotrophic; Lake Texoma, Oklahoma-Texas, eutrophic; and Normandy Lake, Tennessee, eutrophic). Small nano- and ultraphytoplankton (

1981-06-03

382

Comparison of methods for developing contaminant-particle size distributions for suspended sediment

International Nuclear Information System (INIS)

Relationships between contaminant concentration and particle size distribution are required for modeling the transport of contaminated sediment. Standard methods, including the pipette and bottom withdrawal techniques, are unsatisfactory because of the lack of homogeneous separations of each size fraction, which results in uncertainty in the contaminant-particle size relation. In addition, the size fractions produced with these techniques do not contain enough mass for accurate contaminant analyses. To avoid these problems, an alternative method using a settling column and withdrawal times based on Stokes Law has been developed. Tests have been conducted using sediment samples contaminated with Cs-137 from a waste area at Oak Ridge National Laboratory. The samples were separated into sand, coarse and fine silt, and clay-sized particles. The results for particle size distribution and associated contaminant concentrations were evaluated for the settling column, pipette, and bottom withdrawal methods. The settling column method provides homogeneous size fractions, larger aliquots of sediment for contaminant analysis, and is quicker in some cases and less complicated to perform than the other two methods.

1994-01-01

383