WorldWideScience
 
 
1

Focusing nanocrystal size distributions via production control.  

Science.gov (United States)

We present a theoretical description of how continuous monomer production affects the focusing of nanocrystal size distributions in solution. We show that sufficiently high monomer production rates can drive a decrease in the polydispersity even as the average nanocrystal size increases. This is in sharp contrast to Ostwald ripening, where polydispersity increases with mean crystal size. We interpret several experimental nanocrystal studies through our model and show how production-controlled growth promises exquisite control over the size and polydispersity of functional nanocrystals. PMID:21476514

Clark, Michael D; Kumar, Sanat K; Owen, Jonathan S; Chan, Emory M

2011-05-11

2

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Walsh, Patrick P.; Whelan, Ciara

2001-01-01

3

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Whelan, Ciara; Walsh, Patrick P.

2002-01-01

4

Measurement of concentration and size distribution of radon decay products in homes using air cleaners  

International Nuclear Information System (INIS)

By removing particles, air cleaners can also eliminate radon decay products. However, by removing the particles, the open-quotes unattachedclose quotes fraction of the radon progeny is increased leading to a higher dose per unit exposure. Thus, both the concentration and size distributions of the radon decay products are needed to evaluate air cleaners. Three types of room air cleaners, NO-RAD Radon Removal System, Electronic Air Cleaner and PUREFLOW Air Treatment System were tested in a single family home in Arnprior, Ontario (Canada). Semi-continuous measurements of radon gas concentration and radon decay product activity weighted size distribution were performed in the kitchen/dining room under real living conditions. The effects of air cleaners on both the concentration and size distribution of the radon decay products were measured, and their impact on the dose of radiation given to the lung tissue were examined

5

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

International Nuclear Information System (INIS)

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

6

Particle size, size distribution and morphological evaluation of glass fiber reinforced plastic (GRP) industrial by-product.  

Science.gov (United States)

The waste management of glass fiber reinforced polymer (GRP) materials, in particular those made with thermosetting resins, is a critical issue for the composites industry because these materials cannot be reprocessed. Therefore, most thermosetting GRP waste is presently sent to landfill, in spite of the significant environmental impact caused by their disposal in this way. The limited GRP waste recycling worldwide is mostly due to its intrinsic thermosetting properties, lack of characterization data and unavailability of viable recycling and recovery routes. One of the possibility for re-using GRP industrial by-product is in form of powder as a partial aggregate replacement or filler addition in cement based composites for applications in sustainable construction materials and technologies. However, the feasibility of this kind of reutilization strongly depends on the morphology and particle size distribution of a powder made up of polymer granules and glass fibers. In the present study, the use of image analysis method, based on scanning electron microscopy (SEM) and ImageJ processing program, is proposed in order to evaluate the morphology of the particles and measure the particle size and size distribution of fine GRP waste powder. The obtained results show a great potential of such a method in order to be considered as a standardized method of measurement and analysis in order to characterize the grain size and size distribution of GRP particles before exploiting any compatibility issue for its recycling management. PMID:25195092

Mazzoli, Alida; Moriconi, Giacomo

2014-12-01

7

SIZE DISTRIBUTION AND RATE OF PRODUCTION OF AIRBORNE PARTICULATE MATTER GENERATED DURING METAL CUTTING  

International Nuclear Information System (INIS)

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 < 10 microm) deposit in various compartments of the respiratory tract, the fraction and the site in the respiratory tract depending on the size of the particles. The dose delivered to the respiratory tract depends on the size distribution of the airborne particulates (aerosols) and their concentration and radioactivity/toxicity. The concentration of airborne particulate matter in an environment is dependent upon the rate of their production and the ventilation rate. Thus, measuring aerosol size distribution and generation rate is important for (1) the assessment of inhalation exposures of workers, (2) the selection of respiratory protection equipment, and (3) the design of appropriate filtration systems. Size distribution of the aerosols generated during cutting of different metals by plasma torch was measured. Cutting rates of different metals, rate of generation of respirable mass, as well as the fraction of the released kerf that become respirable were determined. This report presents results of these studies. Measurements of the particles generated during cutting of metal plates with a plasma arc torch revealed the presence of particles with mass median aerodynamic diameters of particles close to 0.2 micro

8

The detection and measurement of the electrical mobility size distributions associated with radon decay products  

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

9

The detection and measurement of the electrical mobility size distributions associated with radon decay products  

Energy Technology Data Exchange (ETDEWEB)

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

Fei, Lin

1996-04-01

10

OPTIMIZATION OF COMMINUTION CIRCUIT THROUGHPUT AND PRODUCT SIZE DISTRIBUTION BY SIMULATION AND CONTROL  

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 the seventh quarter of this project, analysis of the plant operation identified sources of overgrinding in the circuit. Overgrinding was primarily caused by two effects: (1) The hydrocyclones used to close the circuit and remove fully-ground particles from the circuit were preferentially returning high-density ore particles to the secondary mills for regrinding even after they were already ground to pass the desired product size, and (2) 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. Circuit modeling is underway to determine how best to modify the circuit to reduce these effects.

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

2002-10-01

11

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

Science.gov (United States)

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

Zhukovsky, Michael; Rogozina, Marina; Suponkina, Anna

2014-07-01

12

Optimization of Comminution Circuit Throughput and Product Size Distribution by Simulation and Control  

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

13

OPTIMIZATION OF COMMINUTION CIRCUIT THROUGHPUT AND PRODUCT SIZE DISTRIBUTION BY SIMULATION AND CONTROL  

Energy Technology Data Exchange (ETDEWEB)

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

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

2002-07-01

14

OPTIMIZATION OF COMMINUTION CIRCUIT THROUGHPUT AND PRODUCT SIZE DISTRIBUTION BY SIMULATION AND CONTROL  

Energy Technology Data Exchange (ETDEWEB)

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.

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

2001-12-01

15

Tracer size distribution measurements  

International Nuclear Information System (INIS)

An experiment has recently been conducted to determine the size distribution and microphysical characteristics of tracers used for in-cloud scavenging experiments. Observations were made of tracer size distribution and changes in cloud condensation nuclei (CCN) during tracer burns. Results show that the design of the Brad Patton aerosol generator currently in use is unsuitable in experiments examining the scavenging of submicron aerosol because the bulk of the aerosol mass generated is in giant particle sizes

16

OPTIMIZATION OF COMMINUTION CIRCUIT THROUGHPUT AND PRODUCT SIZE DISTRIBUTION BY SIMULATION AND CONTROL  

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

17

Assisted spray pyrolysis production and characterisation of ZnO nanoparticles with narrow size distribution  

International Nuclear Information System (INIS)

Nano-sized ZnO particles with a narrow size distribution and high crystallinity were prepared from aqueous solutions with high concentrations of Zn2+ containing salts and citric acid in a conventional spray pyrolysis setup. Structure, morphology and size of the produced material were compared to ZnO material produced by simple spray pyrolysis of zinc nitrates in the same experimental setup. Using transmission electron microscopy and electron tomography it has been shown that citric acid-assisted spray pyrolysed material is made up of micron sized secondary particles comprising a shell of lightly agglomerated, monocrystalline primary ZnO nanoparticles with sizes in the 20-30 nm range, separable by a simple ultrasonic treatment step.

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

2010-01-01

19

Controlling factors on productivity and size abundance distribution of phytoplankton in Patagonian fjords  

Science.gov (United States)

Temperature and resource availability has been suggested to play an important role controlling phytoplankton size structure and productivity. Here we used five independent research cruisers covering the entire Patagonian fjords (41.5-56.0 degress latitude South) to conduct a comparative analysis between zones and to determine the importance of the controlling factors. For the entire Patagonian area phytoplankton size structure seems independent from temperature, but varies with total phytoplankton biomass and productivity. Microphytoplankton contribute with more than 80% in high productivity waters (chlorophyll-a higher than 5 ?g L-1) and picophytoplankton dominates when chlorophyll-a is lower than 1 ?g L-1. In addition, NO3:Si(OH)4 ratio control phytoplankton size structure, where a large decrease in Si(OH)4 from north to south Patagonia (from 20 to 0.1 mM average, respectively) seems to be a major factor of control. Major and prolonged effects expected in fjord areas, such as anthropogenic eutrophication and global warning, may modify the observed relationships leading to important changes in the phytoplankton community and its ecological role.

Cuevas, L. A.; Iriarte, J. L.; Gonzalez, H.; Silva, N.; Vargas, C.

2012-12-01

20

Effect of iron on productivity and size distribution of Antarctic phytoplankton  

International Nuclear Information System (INIS)

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

 
 
 
 
21

Lunar soil grain size distribution  

Science.gov (United States)

A comprehensive review has been made of the currently available data for lunar grain size distributions. It has been concluded that there is little or no statistical difference among the large majority of the soil samples from the Apollo 11, 12, 14, and 15 missions. The grain size distribution for these soils has reached a steady state in which the comminution processes are balanced by the aggregation processes. The median particle size for the steady-state soil is 40 to 130 microns. The predictions of lunar grain size distributions based on the Surveyor television photographs have been found to be quantitatively in error and qualitatively misleading.

Carrier, W. D., III

1973-01-01

22

Centaur size distribution with DECam  

Science.gov (United States)

We present the results of the 2014 centaur search campaign on the Dark Energy Camera (DECam) in Tololo, Chile. This is the largest debiased Centaur survey to date, measuring for the first time the size distribution of small Centaurs (1-10km) and the first time the sizes of planetesimals from which the entire Solar System formed are directly detected.The theoretical model for the coagulation and collisional evolution of the outer solar system proposed in Schlichting et al. 2013 predicts a steep rise in the size distribution of TNOs smaller than 10km. These objects are below the detection limit of current TNO surveys but feasible for the Centaur population. By constraining the number of Centaurs and this feature in their size distribution we can confirm the collisional evolution of the Solar System and estimate the rate at which material is being transferred from the outer to the inner Solar System. If the shallow power law behavior from the TNO size distribution at ~40km can be extrapolated to 1km, the size of the Jupiter Family of Comets (JFC), there would not be enough small TNOs to supply the JFC population (Volk & Malhotra, 2008), debunking the link between TNOs and JFCs.We also obtain the colors of small Centaurs and TNOs, providing a signature of collisional evolution by measuring if there is in fact a relationship between color and size. If objects smaller than the break in the TNO size distribution are being ground down by collisions then their surfaces should be fresh, and then appear bluer in the optical than larger TNOs that are not experiencing collisions.

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

2014-11-01

23

Particle-size distribution of fission products in airborne dust collected at Tsukuba from April to June 1986  

International Nuclear Information System (INIS)

The radioactivity released by the reactor accident at Chernobyl was detected in surface air at Tsukuba, Japan. Gamma-spectrometry of airborne dust collected using aerodynamic separation showed higher concentrations of radionuclides in fine particles. The particle-size distribution of radionuclides changed with time. (author)

24

Evaluation of the degree of mixing of combinations of dry syrup, powder, and fine granule products in consideration of particle size distribution using near infrared spectrometry.  

Science.gov (United States)

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

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

2012-01-01

25

Recurrent frequency-size distribution  

CERN Document Server

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

Abaimov, S G

2008-01-01

26

Determination of size distribution function  

International Nuclear Information System (INIS)

The theory of a method is outlined which gives the size distribution function (SDF) of a polydispersed system of non-interacting colloidal and microscopic spherical particles, having sizes in the range 0-10-5 cm., from a gedanken experimental scheme. It is assumed that the SDF is differentiable and the result is obtained for rotational frequency in the order of 103 (sec)-1. The method may be used independently, but is particularly useful in conjunction with an alternate method described in a preceding paper. (author). 8 refs, 2 figs

27

Diurnal and seasonal variations of concentration and size distribution of nano aerosols (10-1100 nm) enclosing radon decay products in the Postojna Cave, Slovenia.  

Science.gov (United States)

At the lowest point along the tourist route in the Postojna Cave, the activity concentration of radon ((222)Rn) short-lived decay products and number concentration and size distribution of background aerosol particles in the size range of 10-1100 nm were measured. In the warm yearly season, aerosol concentration was low (52 cm(-3)) with 21 % particles smaller than 50 nm, while in the cold season, it was higher (1238 cm(-3)) with 8 % of nm particles. Radon activity concentrations were 4489 and 1108 Bq m(-3), and fractions of unattached radon decay products were 0.62 and 0.13, respectively. PMID:22923245

Bezek, M; Gregoric, A; Kávási, N; Vaupotic, J

2012-11-01

28

Diurnal and seasonal variations of concentration and size distribution of nano aerosols (10-1100 nm) enclosing radon decay products in the Postojna Cave, Slovenia  

International Nuclear Information System (INIS)

At the lowest point along the tourist route in the Postojna Cave, the activity concentration of radon (222Rn) short-lived decay products and number concentration and size distribution of background aerosol particles in the size range of 10-1100 nm were measured. In the warm yearly season, aerosol concentration was low (52 cm-3) with 21 % particles smaller than 50 nm, while in the cold season, it was higher (1238 cm-3) with 8 % of -3, and fractions of unattached radon decay products were 0.62 and 0.13, respectively. (authors)

29

Comparing two mass size distributions  

Scientific Electronic Library Online (English)

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

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

2012-07-01

30

City size distribution and growth  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We discuss theoretical approaches to study the relationship between the size distribution of a nation's cities and macroeconomic growth. The discussion is based on the hypothesis of the New Growth Theory that inter-personal spillovers of education and skills determine the long-run growth of the economy. Growth theory treats such externalities as being uniformly effective over national territories and completely internal to nation-state. This suggests a link to urban economics which has a long...

Kopp, Andreas

2000-01-01

31

Activity size distribution of some natural radionuclides  

International Nuclear Information System (INIS)

In this study, the results concerning the activity size distribution of the long-lived (210Pb) radon decay product aerosols and the thoron decay product aerosols (212Pb) and (7Be) of the outdoor atmosphere are presented. Also, the mass size distribution of the aerosol particles is determined. The low-pressure Berner cascade impactor Model 20/0.015 was used as a sampling device. The activity size distribution of these radionuclides was determined by one log-normal distribution (accumulation mode) whereas the mass size distribution was by two log-normal distributions (accumulation and coarse mode). The activity median aerodynamic diameter (AMAD) of 212Pb was found to be 305 nm with a geometric standard deviation (?g) of 2.41. The specific air activity concentration of 212Pb was found to be 0.14 ± 0.012 Bq m-3. An AMAD of 210Pb of 610 nm with ?g of 1.8 was determined, whereas that of 550 nm with sg of 1.97 was determined for 7Be. The specific air activity concentration of 210Pb and 7Be was found to be 0.0016±2.5x10-4 and 0.00348 ± 4x10-4 Bq m-3, respectively. Using a dosimetric model, the total deposition fraction as well as the total equivalent dose has been evaluated considering the observed parameters of the activity size distribution of 212Pb. At a total deposition fraction of ?21 %, the total equivalent dose was found to be 0.41 ?Sv. (authors)

32

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

2009-12-01

33

Comparative physical-chemical characterization of encapsulated lipid-based isotretinoin products assessed by particle size distribution and thermal behavior analyses  

Energy Technology Data Exchange (ETDEWEB)

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

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

2010-06-10

34

Comparative physical-chemical characterization of encapsulated lipid-based isotretinoin products assessed by particle size distribution and thermal behavior analyses  

International Nuclear Information System (INIS)

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

35

Grain Size Distributions and Soil Particle Characteristics  

Science.gov (United States)

In soil mechanics, it is virtually always useful to quantify the size of the grains in a type of soil. Since a given soil will often be made up of grains of many different sizes, sizes are measured in terms of grain size distributions.Grain size distribution (GSD) information can be of value in providing initial rough estimates of a soilÃÂs engineering properties such as permeability;ability, strength, expansiveness, etc.

Swan, Colby C.

2008-09-22

36

Intelligent Distributed Production Control  

CERN Document Server

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

37

Software Package for Aerosol Size Distribution  

Directory of Open Access Journals (Sweden)

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

T. A. Rajesh

2013-04-01

38

Unravelling the size distribution of social groups  

CERN Document Server

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

39

Evolution of bivariate particle size distributions  

Science.gov (United States)

A simple and general procedure is presented for the calculation of bivariate particle growth paths (and, hence, local particle growth rates) from the experimentally measured series of bi- variate size distributions during an evolutionary process. For modeling of microstructural evo- lution, a mathematical relationship is derived to relate the bivariate particle size distribution function to the nucleation rate and growth rate. A deterministic nucleation and growth process is assumed, and hence, the results are applicable only to the "mean field" models of nucleation and growth. A generalized continuity equation is derived for evolving bivariate and multivariate distributions.

Gokhale, Arun M.

1992-11-01

40

Submicron aerosols at thirteen diversified sites in China: size distribution, new particle formation and corresponding contribution to cloud condensation nuclei production  

Science.gov (United States)

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

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

2014-09-01

 
 
 
 
41

Size Distribution of Sea Spray from Individual Breaking Waves  

Science.gov (United States)

Knowledge of the magnitude and shape (i.e., dependence on particle size) of the production flux of sea spray aerosol is necessary for understanding the budget of cloud condensation nuclei in the marine atmosphere, modeling aerosol optical depth, and similar topics. Magnitudes of production fluxes determined from laboratory experiments with simulated breaking waves using artificial or actual seawater vary by as much as two orders of magnitude, and size distributions vary greatly, but the pertinence of these experiments to particle production in actual oceanic breaking waves is questionable (de Leeuw et al., 2011). In principle these concerns might be overcome by determination of the size distribution of oceanic breaking waves, but this approach is of limited utility because the magnitudes of the production flux from individual waves may differ substantially and because the fraction of production that is sampled depends strongly on the location of the sampler relative to the breaking wave and time after breaking. Consequently simultaneous measurement of the size distribution of primary particles in air directly impacted by individual breaking waves is necessary. The Ultra-High Sensitivity Aerosol Spectrometer (UHSAS) allow simultaneous determination of the particle number concentration over the diameter range 60-1000 nm, allowing examination of the variability of the shape of the sea spray production size distribution for individual waves and the dependence of this size distribution on temperature, biological activity, sea state, and other controlling factors. Results from preliminary experiments demonstrating proof of principle will be presented. de Leeuw, G., E. L Andreas, M. D. Anguelova, C. W. Fairall, E. R. Lewis, C. O'Dowd, M. Schulz, & S. E. Schwartz, "Production flux of sea-spray aerosol," Rev. Geophys., 49, RG2001, 2011. doi:10.1029/2010RG000349

Lewis, E. R.; Senum, G.; Schwartz, S. E.; Sedlacek, A. J.; Springston, S. R.

2011-12-01

42

Distribution of droplet sizes for seed solution  

International Nuclear Information System (INIS)

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

43

Internal particle size distribution of biofuel pellets  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Several methods for disintegration of biofuel pellets were tested and compared for their ability to break up the pellets into the original particles of the raw material. Analyses performed on softwood pellets and straw pellets concluded that wet disintegration in water at ambient temperature is insufficient for a determination of the internal particle size distribution of wood- and straw pellets. When the wet disintegration was performed with water heated to the boiling point and ...

Daugbjerg Jensen, Peter; Temmerman, Michae?l; Westborg, Suzanne

2006-01-01

44

Particle size distribution of plutonium contaminated soil  

International Nuclear Information System (INIS)

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

45

City Size Distributions For India and China  

CERN Document Server

This paper studies the size distributions of urban agglomerations for India and China. We have estimated the scaling exponent for the Zipf's law with the Indian census data for the years of 1981-2001 and the Chinese census data for 1990 and 2000. Along with the biased linear fit estimate, the maximum likelihood estimate for the Pareto and Tsallis q-exponential distribution has been computed. For India, the scaling exponent is in the range of [1.88, 2.06] and for China, it is in the interval [1.82, 2.29]. The goodness-of-fit tests of the estimated distributions are performed using the Kolmogorov-Smirnov statistic.

Gangopadhyay, Kausik

2010-01-01

46

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

47

Estimation of particle size distributions obtained by gas phase processes  

International Nuclear Information System (INIS)

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

48

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)

49

Particle size distribution of indoor aerosol sources  

Energy Technology Data Exchange (ETDEWEB)

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

Shah, K.B.

1990-10-24

50

Measuring the sea ice floe size distribution  

Science.gov (United States)

The sea ice covering the Arctic Ocean is broken into distinct pieces,called floes. In the summer, these floes, which have diameters ranging up to 100 km, are separated from each other by a region of open water. In the winter, floes still exist, but they are less easily identified. An understanding of the geometry of the ice pack is of interest for a number of practical applications associated with transportation in ice-covered seas and with the design of offshore structures intended to survive in the presence of ice. The present investigation has the objective to clarify ideas about floe sizes and to propose techniques for measuring them. Measurements are presented with the primary aim to illustrate points of technique or approach. A preliminary discussion of the floe size distribution of sea ice is devoted to questions of definition and of measurement.

Rothrock, D. A.; Thorndike, A. S.

1984-01-01

51

Distribution of domain sizes during overlayer growth  

International Nuclear Information System (INIS)

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

52

Particle size distribution from a GTL engine.  

Science.gov (United States)

Measurements of exhaust particle number concentration and size distribution from an engine fueled with GTL at different engine loads and speeds were carried out by using a two-stage dilution system. The results for GTL were compared with those from the original engine fueled with diesel. The fuel composition and engine operation condition had significant effects on the exhaust particle size distribution, the total exhaust particle number and volume concentrations. For both fuels, the load had no significant influence on the total exhaust particle number concentration at middle speed, while the total exhaust particle number concentration increased with the increase of the load at high speed. At 1400 rpm and 2200 rpm, the total exhaust particle volume concentration increased as the load increased for both fuels. GTL was found to be a "cleaner" fuel. Compared with diesel, under the same operation conditions, the total exhaust particle number concentrations decreased 18-92%, and the total exhaust particle volume concentrations for GTL decreased 21-59%. PMID:17540433

Li, Xinling; Huang, Zhen; Wang, Jiasong; Zhang, Wugao

2007-09-01

53

New-particle formation, growth and climate-relevant particle production in Egbert, Canada: analysis from 1 year of size-distribution observations  

Science.gov (United States)

Aerosol particle nucleation, or new-particle formation, is the dominant contributor to particle number in the atmosphere. However, these particles must grow through condensation of low-volatility vapors without coagulating with the larger, preexisting particles in order to reach climate-relevant sizes (diameters larger than 50-100 nm), where the particles may affect clouds and radiation. In this paper, we use 1 year of size-distribution measurements from Egbert, Ontario, Canada to calculate the frequency of regional-scale new-particle-formation events, new-particle-formation rates, growth rates and the fraction of new particles that survive to reach climate-relevant sizes. Regional-scale new-particle-formation events occur on 14-31% of the days (depending on the stringency of the classification criteria), with event frequency peaking in the spring and fall. New-particle-formation rates and growth rates are similar to those measured at other midlatitude continental sites. We calculate that roughly half of the climate-relevant particles (with diameters larger than 50-100 nm) at Egbert are formed through new-particle-formation events. With the addition of meteorological and SO2 measurements, we find that new-particle formation at Egbert often occurs under synoptic conditions associated with high surface pressure and large-scale subsidence that cause sunny conditions and clean-air flow from the north and west. However, new-particle formation also occurs when air flows from the polluted regions to the south and southwest of Egbert. The new-particle-formation rates tend to be faster during events under the polluted south/southwest flow conditions.

Pierce, J. R.; Westervelt, D. M.; Atwood, S. A.; Barnes, E. A.; Leaitch, W. R.

2014-08-01

54

New-particle formation, growth and climate-relevant particle production in Egbert, Canada: analysis from one year of size-distribution observations  

Science.gov (United States)

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

Pierce, J. R.; Westervelt, D. M.; Atwood, S. A.; Barnes, E. A.; Leaitch, W. R.

2014-01-01

55

Fisher Information in Flow Size Distribution  

CERN Document Server

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

Tune, Paul

2011-01-01

56

What determines the grain size distribution in galaxies?  

CERN Document Server

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

57

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

58

Aged boreal biomass burning aerosol size distributions from BORTAS 2011  

Science.gov (United States)

Biomass-burning aerosols contribute to aerosol radiative forcing on the climate system. The magnitude of this effect is partially determined by aerosol size distributions, which are functions of source fire characteristics (e.g. fuel type, MCE) and in-plume microphysical processing. The uncertainties in biomass-burning emission number size-distributions in climate model inventories lead to uncertainties in the CCN concentrations and forcing estimates derived from these models. The BORTAS-B measurement campaign was designed to sample boreal biomass-burning outflow over Eastern Canada in the summer of 2011. Using these BORTAS-B data, we implement plume criteria to isolate the characteristic size-distribution of aged biomass-burning emissions (aged ?1-2 days) from boreal wildfires in Northwestern Ontario. The composite median size-distribution yields a single dominant accumulation mode with Dpm = 230 nm (number-median diameter), ? = 1.7, which are comparable to literature values of other aged plumes of a similar type. The organic aerosol enhancement ratios (?OA / ?CO) along the path of Flight b622 show values of 0.05-0.18 ?g m-3 ppbv-1 with no significant trend with distance from the source. This lack of enhancement ratio increase/decrease with distance suggests no detectable net OA production/evaporation within the aged plume over the sampling period. A Lagrangian microphysical model was used to determine an estimate of the freshly emitted size distribution corresponding to the BORTAS-B aged size-distributions. The model was restricted to coagulation and dilution processes based on the insignificant net OA production/evaporation derived from the ?OA / ?CO enhancement ratios. We estimate that the fresh-plume median diameter was in the range of 59-94 nm with modal widths in the range of 1.7-2.8 (the ranges are due to uncertainty in the entrainment rate). Thus, the size of the freshly emitted particles is relatively unconstrained due to the uncertainties in the plume dilution rates.

Sakamoto, K. M.; Allan, J. D.; Coe, H.; Taylor, J. W.; Duck, T. J.; Pierce, J. R.

2014-09-01

59

Aged boreal biomass burning aerosol size distributions from BORTAS 2011  

Directory of Open Access Journals (Sweden)

Full Text Available Biomass-burning aerosols contribute to aerosol radiative forcing on the climate system. The magnitude of this effect is partially determined by aerosol size distributions, which are functions of source fire characteristics (e.g. fuel type, MCE and in-plume microphysical processing. The uncertainties in biomass-burning emission number size-distributions in climate model inventories lead to uncertainties in the CCN concentrations and forcing estimates derived from these models. The BORTAS-B measurement campaign was designed to sample boreal biomass-burning outflow over Eastern Canada in the summer of 2011. Using these BORTAS-B data, we implement plume criteria to isolate the characteristic size-distribution of aged biomass-burning emissions (aged ?1–2 days from boreal wildfires in Northwestern Ontario. The composite median size-distribution yields a single dominant accumulation mode with Dpm = 230 nm (number-median diameter, ? = 1.7, which are comparable to literature values of other aged plumes of a similar type. The organic aerosol enhancement ratios (?OA / ?CO along the path of Flight b622 show values of 0.05–0.18 ?g m?3 ppbv?1 with no significant trend with distance from the source. This lack of enhancement ratio increase/decrease with distance suggests no detectable net OA production/evaporation within the aged plume over the sampling period. A Lagrangian microphysical model was used to determine an estimate of the freshly emitted size distribution corresponding to the BORTAS-B aged size-distributions. The model was restricted to coagulation and dilution processes based on the insignificant net OA production/evaporation derived from the ?OA / ?CO enhancement ratios. We estimate that the fresh-plume median diameter was in the range of 59–94 nm with modal widths in the range of 1.7–2.8 (the ranges are due to uncertainty in the entrainment rate. Thus, the size of the freshly emitted particles is relatively unconstrained due to the uncertainties in the plume dilution rates.

K. M. Sakamoto

2014-09-01

60

Influence of char fragmentation on ash particle size distributions  

Energy Technology Data Exchange (ETDEWEB)

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

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

1989-05-01

 
 
 
 
61

Binary nucleation kinetics. I. Self-consistent size distribution  

International Nuclear Information System (INIS)

Using the principle of detailed balance, we derive a new self-consistency requirement, termed the kinetic product rule, relating the evaporation coefficients and equilibrium cluster distribution for a binary system. We use this result to demonstrate and resolve an inconsistency for an idealized Kelvin model of nucleation in a simple binary mixture. We next examine several common forms for the equilibrium distribution of binary clusters based on the capillarity approximation and ideal vapor behavior. We point out fundamental deficiencies for each expression. We also show that each distribution yields evaporation coefficients that formally satisfy the new kinetic product rule but are physically unsatisfactory because they depend on the monomer vapor concentrations. We then propose a new form of the binary distribution function that is free of the deficiencies of the previous functions except for its reliance on the capillarity approximation. This new self-consistent classical (SCC) size distribution for binary clusters has the following properties: It satisfies the law of mass action; it reduces to an SCC unary distribution for clusters of a single component; and it produces physically acceptable evaporation rate coefficients that also satisfy the new kinetic product rule. Since it is possible to construct other examples of similarly well-behaved distributions, our result is not unique in this respect, but it does give reasonable predictions. As an illustration, we calculate binary nucleation rates and vapor activities for the ethanol--hexanol system at 260 K using the new SCC distribution and compare them to experimental results. The theoretical rates are uniformly higher than the experimental values over the entire vapor composition range. Although the predicted activities are lower, we find good agreement between the measured and theoretical slope of the critical vapor activity curve at a constant nucleation rate of 107 cm-3 s-2

62

Comparison of the Production Size-frequency Distribution (SFD) of Craters on Saturnian Satellites With the Lunar Crater SFD and Asteroid Diameter SFD  

Science.gov (United States)

Introduction: The understanding of the geologic history of the saturnian satellites (and hence of the history of the solar system) is a major goal for us as part of the Cassini imaging experiment (ISS) team. For this reason, the SFDs of craters on Saturn's medium-sized moons have been analyzed and compared with the goal to determine the sources of the primary impactors on the saturnian satellites. Comparison of SFDs: The lunar SFD was derived by Neukum (1983). Multiple measurements of the crater production SFD on the saturnian satellites have shown a high similarity to the lunar curve (Neukum et al., 2006). From measurements on Iapetus, crater counts over 4 orders of magnitude in crater diameter are available now. Those measurements fit nicely to the velocity-corrected lunar curve for crater diameters below 60 km. By analyzing the body-diameter SFD of main-belt asteroids (data source: MPC web site, http://cfa-www.harvard.edu/iau/mpc.html, July 2008), a strong similarity with respect to the lunar curve is found as well. Hence, there are good reasons for the conclusion that asteroidal impactors captured by Saturn are responsible for the cratering record measured on the saturnian satellites. References and notes: Magnitude-to-diameter conversion of asteroids: D2=1/Pv*106.247-0.4*H H: absolute magnitude; Pv: geometric albedo; (Fowler & Chillemi, 1992) Neukum, G. (1983): Meteoritenbombardement und Datierung planetarer Oberflächen. Habilitation Dissertation for Faculty Membership, Ludwig-Maximilians Univ. München, Munich, Germany, 186 pp. Neukum, G.; Wagner, R.; Wolf, U.; Denk, T. (2006): The Cratering Record and Cratering Chronologies of the Saturnian Satellites and the Origin of Impactors: Results from Cassini ISS Data. European Planetary Science Congress (EPSC) 2006, Berlin, Germany, 18-22 September 2006, p.610. Fowler, J.W.; Chillemi, J.R. (1992): IRAS asteroid data processing. In: Tedesco, E.F., Veeder, G.J., Fowler, J.W., Chillemi, J.R. (eds.): The IRAS Minor Planet Survey. Technical Report PL-TR-92-2049, Phillips Laboratory, Hanscom AF Base, MA.

Schmedemann, Nico; Neukum, G.; Denk, T.; Wagner, R.; Hartmann, O.; Michael, G.

2008-09-01

63

Permeability of packed coal beds: The effect of particle size distribution, particle size and coal type  

Energy Technology Data Exchange (ETDEWEB)

Sasol operates 97 Lurgi type gasifiers for the production of syngas using lump coal obtained from 7 captive coal mines. Permeability of packed coal beds of the coal has been identified as one of the major variables affecting stable operation which in turn affects maximum coal throughput and gas production. A tenth scale instrumented cold perspex model simulating a gasifier was constructed in which the pressure drop per unit bed length for a given gas flow could be measured. The effect of particle size distribution, particle size and coal type on the pressure drop (and hence permeability) was measured. The results were augmented by measuring void fractions as well as shape factors for the different coal types. The effect of size segregation during filling of the scale model was also investigated. Results have shown that bed permeability is strongly affected by the 3 variables investigated. The change in void fraction was found to be very small and could not be linked to the change in permeability. Size segregation resulted in a difference in gas flow rate between the center of the coal bed and against the wall of the model. The significance of the observations are discussed in terms of gasifier stability, optimum pressure drop and the effect of thermal size stability of coal upon entering the gasifier.

Greeff, S.C.; Slaghuis, J.H.; Walt, T.J. van der [SASOL Technology, Sasolburg (South Africa). Research and Development Div.

1998-12-31

64

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

65

Company Size Distributions as Economy Aggregated Indicators  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Emilio Galdeano-Gómez; Juan Carlos Pérez Mesa

2009-01-01

66

Particle size distribution effects on sintering of spherical tungsten  

International Nuclear Information System (INIS)

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

67

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

2009-08-01

68

Zooming in on size distribution patterns underlying species coexistence in Baltic Sea phytoplankton.  

Science.gov (United States)

Scale is a key to determining which processes drive community structure. We analyse size distributions of phytoplankton to determine time scales at which we can observe either fixed environmental characteristics underlying communities structure or competition-driven size distributions. Using multiple statistical tests, we characterise size distributions of phytoplankton from 20-year time series in two sites of the Baltic Sea. At large temporal scales (5-20 years), size distributions are unimodal, indicating that fundamental barriers to existence are here subtler than in other systems. Frequency distributions of the average size of the species weighted by biovolume are multimodal over large time scales, although this is the product of often unimodal short-term (structured, high-resolution analysis of phytoplankton size distributions, revealing that short-term analyses are necessary to determine if, and how, competition shapes them. Our results provide a stepping-stone on which to further investigate the intricacies of competition and coexistence. PMID:25040569

Downing, A S; Hajdu, S; Hjerne, O; Otto, S A; Blenckner, T; Larsson, U; Winder, M

2014-10-01

69

Effect of particle size distribution on sintering of tungsten  

International Nuclear Information System (INIS)

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

70

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

Science.gov (United States)

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

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

2008-03-01

71

Hydrogenation of carbon monoxide on CO reducing catalyst and solid acid. III. The effect of the pore size and acid properties of zeolite on the product distribution  

Energy Technology Data Exchange (ETDEWEB)

Synthesis gas reactions over hybrid catalysts composed of Pd/SiO/sub 2/ and zeolites and methanol conversion on the same zeolites were studied. The selectivities to aromatic hydrocarbons were about 30% for the methanol conversions over ZSM-5, de-aluminated mordenite, and de-aluminated Y type zeolite (DAY), which possess strong acid sites. When ZSM-5 or mordenites were combined with Pd/SiO/sub 2/ and subjected to synthesis gas conversion, the selectivities to aromatic hydrocarbons were between 10% and 30%. However, the synthesis gas reaction over the hybrid catalyst composed of pd/SiO/sub 2/ and DAY, gave few aromatic hydrocarbons, but aliphatic paraffins with 2 to 6 carbon atoms. Over large pore zeolites like DAY, the diffusion of olefins is so quick that most of the olefins come out of pores to be hydrogenated to paraffins on the Pd/SiO/sub 2/ catalyst. In contrast, because of the slow diffusion of olefins in the medium size pores of ZSM-5 or mordenite, olefins stay in the pores for long enough to form aromatic hydrocarbons on the strong acid sites before being hydrogenated. 10 references, 10 figures, 4 tables.

Saima, H.; Fujimoto, K.; Tominaga, H.

1985-01-01

72

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

CERN Document Server

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

Belmonte, Alessandro; Buldyrev, Sergey V

2014-01-01

73

Re-examination of the size distribution of firms  

CERN Document Server

In this paper we address the question of the size distribution of firms. To this aim, we use the Bloomberg database comprising firms around the world within the years 1995-2003, and analyze the data of the sales and the total assets of the consolidation base of the Japanese and the US companies, and make a comparison of the size distributions between the Japanese companies and the US companies. We find that (i) the size distribution of the US firms is approximately log-normal, in agreement with Gibrat's observation \\cite{Gibrat}, and in contrast (ii) the size distribution of the Japanese firms is clearly not log-normal, and the upper tail of the size distribution follows the Pareto law. It agree with the predictions of the Simon model \\cite{Simon}.

Kaizoji, T; Iyetomi, H; Kaizoji, Taisei; Ikeda, Yuichi; Iyetomi, Hiroshi

2006-01-01

74

Avalanche size distribution in a random walk model  

CERN Document Server

We introduce a simple model for the size distribution of avalanches based on the idea that the front of an avalanche can be described by a directed random walk. The model captures some of the qualitative features of earthquakes, avalanches and other self-organized critical phenomena in one dimension. We find scaling laws relating the frequency, size and width of avalanches and an exponent $4/3$ in the size distribution law.

Jónsson, T

1996-01-01

75

Fractal Theory and Application in City Size Distribution  

Directory of Open Access Journals (Sweden)

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

Liu Zhenling

2013-01-01

76

Size distribution of atmospheric radioactive aerosols and its measurement  

International Nuclear Information System (INIS)

The variation of the size distribution of radioactive aerosols may cause a large fluctuation of lung dose caused by radon and its daughters. Since the information on the size distribution of radioactive aerosols in China is scanty, authors usually quote the recommended data by UNSCEAR (1988) to estimate the lung dose. In order to check whether the quoted data are reasonable and establish the method of measuring the size distribution of the aerosols, we carried out this study. The penetration curve can be bluffed by measuring the atmospheric radioactivity ratio for the different diffusion using the wire screen (165 meshes) type diffusion battery. The size distribution of atmospheric radioactive aerosols was calculated by ikebe anatical method. The size distribution for outdoors and indoors showed a geometric normal distribution. The arithmetic mean peak diameter for indoor and outdoor size distribution were (0.20 +- 0.09) ?m and (0.27 +- 0.11) ?m, respectively. The correlation between the size distribution and the concentrations of radon and metrological factors was not significant. The measured result for indoors is the same as the recommended data by UNSCEAR (1988), while the result for outdoors is slightly higher than the recommended data, but it is similar to that reported by Jacobi. It is basically feasible for Fujian Province to estimate lung dose using the recommended data by UNSCEAR (1988). Further studies are needed to extend this conclusion nationwide extend this conclusion nationwide

77

Elemental mass size distribution of the Debrecen urban aerosol  

International Nuclear Information System (INIS)

peak appears at the 2-4 ?m size ranges, indicating different sources. Differences were found between the size distribution of the spring and autumn samples. In the case of elements of soil origin the size distribution was shifted towards smaller diameters during October, and a 2nd peak appeared around 0.5 ?m. A possible explanation to this phenomenon can be the different meteorological conditions. No differences were found between the weekend and working days in the size distribution, however the concentration values were smaller during the weekend than the other days. The elemental mass size distribution provides information about the origin and sources of aerosol particles, and with emphasis on the PM2.5, serves as an input parameter for the determination of lung deposition probabilities by stochastic lung model calculation. This calculation together with short-term time variation enables us to give a more precise health impact of the urban aerosol

78

Size distribution of Amazon River bed sediment  

Science.gov (United States)

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

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

1980-01-01

79

Thermokarst Lake Size-Distribution Across Time in Northwestern Siberia  

Science.gov (United States)

Thermokarst lakes are dependent on permafrost, and changes in thermokarst lake size and number have been reported for ice-rich continuous and discontinuous regions. Thermokarst lakes and wetlands dominate the peat-forming lowlands of the Nadym and Pur river basins in Northwestern Siberia, and warming during the last decades has initiated fluctuations in the number and total area of lakes in these basins. Lake size distribution and abundance is important to assess the role of lakes in regional and global biogeochemical processes. In this study we use remote sensing (Landsat images) to help distinguish spatially explicit changes due to permafrost thaw from year 1973, through 1987-1988 to 2007-2009. The results show both increase and decrease in lake area and abundance over time. However, the size-distribution of thermokarst lakes, in the size ranges of our investigation, has not changed as permafrost thaws over the three time periods. The distribution is thus relatively time-invariant with regard to the included lake sizes (mostly ?10ha), which are at the upper size and cutoff end of a possible power law distribution. The latter may extend further over several orders of magnitude of smaller lake sizes that have not been investigated here. However, the distribution time invariance found here persists also when extending the investigated sizes to an order of magnitude smaller lake sizes (down to 1ha lakes) and is important for interpreting the implications of changes in thermokarst lakes in periods of permafrost change.

Mård Karlsson, J.; Lyon, S. W.; Destouni, G.

2013-12-01

80

The design of radon progeny radioactive size distribution analysis system  

International Nuclear Information System (INIS)

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

 
 
 
 
81

Tuning photoresponse through size distribution control of silicon quantum dots  

International Nuclear Information System (INIS)

We report a detailed experimental and theoretical investigation on the photocurrent characteristics of nanocrystalline Si thin films, with the emphasis on the effect of Si dot size distribution. Broader photocurrent response has been observed in Si quantum dots with larger size dispersion due to the improvement of light harvest. As a result of tunneling loss in the expanded energy distribution, we have demonstrated that there is a tradeoff between the absorption enhancement and reduced transport for the photocurrent intensity. The present work opens new strategy to maximize the photoresponse through size distribution control for quantum dot solar cell application.

82

An equation to represent grain-size distribution  

Energy Technology Data Exchange (ETDEWEB)

A simple method by which to classify soils is by grain-size distribution. Grain-size distribution also has the potential as a basis for estimating soil behaviour and estimation of soil-water characteristics. Two mathematical models were presented to describe grain-size distribution curves for both unimodal and bimodal forms. The two equations provide greater flexibility for fitting a wide variety of soils including uniform soils, well-graded soils, and gap-graded soils. The five-parameter unimodal equation provides a closer fit than previous equations. 25 refs., 13 figs.

Fredlund, M.D.; Fredlund, D.G.; Wilson, G.W. [Saskatchewan Univ., Saskatoon, SK (Canada). Dept. of Civil Engineering

2000-08-04

83

Pore-size-distribution of cationic polyacrylamide hydrogels. Progress report  

Energy Technology Data Exchange (ETDEWEB)

The pore size distribution of a AAm/MAPTAC (acrylamide copolymerized with (3-methacrylamidopropyl)trimethylammonium chloride) hydrogel was investigated using Kuga`s mixed-solute-exclusion method, taking into account the wall effect. A Brownian-motion model is also used. Results show the feasibility of determining pore-size distribution of porous materials using the mixed-solute-exclusion method in conjunction with solution of the Fredholm equation; good agreement was obtained with experiment, even for bimodal pore structures. However, different pore size distributions were calculated for the two different probe-solutes (Dextran and poly(ethylene glycol/oxide)). Future work is outlined. 32 figs, 25 refs.

Kremer, M.; Prausnitz, J.M.

1992-06-01

84

Pore-size-distribution of cationic polyacrylamide hydrogels  

Energy Technology Data Exchange (ETDEWEB)

The pore size distribution of a AAm/MAPTAC (acrylamide copolymerized with (3-methacrylamidopropyl)trimethylammonium chloride) hydrogel was investigated using Kuga's mixed-solute-exclusion method, taking into account the wall effect. A Brownian-motion model is also used. Results show the feasibility of determining pore-size distribution of porous materials using the mixed-solute-exclusion method in conjunction with solution of the Fredholm equation; good agreement was obtained with experiment, even for bimodal pore structures. However, different pore size distributions were calculated for the two different probe-solutes (Dextran and poly(ethylene glycol/oxide)). Future work is outlined. 32 figs, 25 refs.

Kremer, M.; Prausnitz, J.M.

1992-06-01

85

Job creation and the intra-distribution dynamics of the firm size distribution  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Based on a three equations model for initial firm size, survival and firm growth we estimate firm-specific transition probabilities between size classes of the firm size distribution. This allows to analyze counterfactual scenarios that assess the impact of changes in exogenous variables on the intra-distribution dynamics of the firm size distribution. We find that a counterfactual decrease in average firm age increases the exit hazard of young firms, and at the same time reduces the probabil...

Huber, Peter; Oberhofer, Harald; Pfaffermayr, Michael

2012-01-01

86

SELF-CONSISTENT SIZE AND VELOCITY DISTRIBUTIONS OF COLLISIONAL CASCADES  

International Nuclear Information System (INIS)

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

87

SELF-CONSISTENT SIZE AND VELOCITY DISTRIBUTIONS OF COLLISIONAL CASCADES  

Energy Technology Data Exchange (ETDEWEB)

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

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

2012-03-10

88

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

Energy Technology Data Exchange (ETDEWEB)

The Kuiper Belt is a remnant from the early solar system and its size distribution contains many important constraints that can be used to test models of planet formation and collisional evolution. We show, by comparing observations with theoretical models, that the observed Kuiper Belt size distribution is well matched by coagulation models, which start with an initial planetesimal population with radii of about 1 km, and subsequent collisional evolution. We find that the observed size distribution above R {approx} 30 km is primordial, i.e., it has not been modified by collisional evolution over the age of the solar system, and that the size distribution below R {approx} 30 km has been modified by collisions and that its slope is well matched by collisional evolution models that use published strength laws. We investigate in detail the resulting size distribution of bodies ranging from 0.01 km to 30 km and find that its slope changes several times as a function of radius before approaching the expected value for an equilibrium collisional cascade of material strength dominated bodies for R {approx}< 0.1 km. Compared to a single power-law size distribution that would span the whole range from 0.01 km to 30 km, we find in general a strong deficit of bodies around R {approx} 10 km and a strong excess of bodies around 2 km in radius. This deficit and excess of bodies are caused by the planetesimal size distribution left over from the runaway growth phase, which left most of the initial mass in small planetesimals while only a small fraction of the total mass is converted into large protoplanets. This excess mass in small planetesimals leaves a permanent signature in the size distribution of small bodies that is not erased after 4.5 Gyr of collisional evolution. Observations of the small Kuiper Belt Object (KBO) size distribution can therefore test if large KBOs grew as a result of runaway growth and constrained the initial planetesimal sizes. We find that results from recent KBO occultation surveys and the observed KBO size distribution can be best matched by an initial planetesimal population that contained about equal mass per logarithmic mass bin in bodies ranging from 0.4 km to 4 km in radius. We further find that we cannot match the observed KBO size distribution if most of the planetesimal mass was contained in bodies that were 10 km in radius or larger simply because their resulting size distribution cannot be sufficiently depleted over 4.5 Gyr to match observations.

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

2013-08-01

89

Methods of assessing grain-size distribution during grain growth  

DEFF Research Database (Denmark)

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

Hansen, Niels

1985-01-01

90

Predictive control of crystal size distribution in protein crystallization.  

Science.gov (United States)

This work focuses on the modelling, simulation and control of a batch protein crystallization process that is used to produce the crystals of tetragonal hen egg-white (HEW) lysozyme. First, a model is presented that describes the formation of protein crystals via nucleation and growth. Existing experimental data are used to develop empirical models of the nucleation and growth mechanisms of the tetragonal HEW lysozyme crystal. The developed growth and nucleation rate expressions are used within a population balance model to simulate the batch crystallization process. Then, model reduction techniques are used to derive a reduced-order moments model for the purpose of controller design. Online measurements of the solute concentration and reactor temperature are assumed to be available, and a Luenberger-type observer is used to estimate the moments of the crystal size distribution based on the available measurements. A predictive controller, which uses the available state estimates, is designed to achieve the objective of maximizing the volume-averaged crystal size while respecting constraints on the manipulated input variables (which reflect physical limitations of control actuators) and on the process state variables (which reflect performance considerations). Simulation results demonstrate that the proposed predictive controller is able to increase the volume-averaged crystal size by 30% and 8.5% compared to constant temperature control (CTC) and constant supersaturation control (CSC) strategies, respectively, while reducing the number of fine crystals produced. Furthermore, a comparison of the crystal size distributions (CSDs) indicates that the product achieved by the proposed predictive control strategy has larger total volume and lower polydispersity compared to the CTC and CSC strategies. Finally, the robustness of the proposed method (achieved due to the presence of feedback) with respect to plant-model mismatch is demonstrated. The proposed method is demonstrated to successfully achieve the task of maximizing the volume-averaged crystal size in the presence of plant-model mismatch, and is found to be robust in comparison to open-loop optimal control strategies. PMID:21727478

Shi, Dan; Mhaskar, Prashant; El-Farra, Nael H; Christofides, Panagiotis D

2005-07-01

91

Measurements of size distributions of radon progeny for improved quantification of the lung cancer risk emanating from exposure to radon decay products; Messungen der Groessenverteilungen von Radon-Folgeprodukten zur Verbesserung der Quantifizierung des durch Radonexposition verursachten Lungenkrebsrisikos  

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

92

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

93

A new procedure modeling the probability distribution of earthquake size  

Science.gov (United States)

The probability distribution of earthquake size is needed as input data for some earthquake analyses. A common procedure is to calibrate the so-called b-value in the Gutenberg-Richter relationship and to use it as the best-estimate model parameter in an algorithm to simulate the observed earthquake-size distribution. This paper introduces a new procedure for such a simulation, on the basis of performing optimization to search for the optimum model parameter. The new option and an existing method are then both utilized to model the earthquake-size distribution around Taiwan since 1978. Owing to the nature and the power of optimization, three case studies presented in this paper all indicate that the new optimization procedure can indeed improve such a simulation over the existing procedure. Moreover, with a proper tool such as Excel Solver, practicing the new method to model the observed earthquake-size distribution is as effortless as using the existing procedure.

Wang, J. P.; Yun, X.; Chang, S. C.

2014-11-01

94

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

Science.gov (United States)

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

95

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

96

Bipartite Producer-Consumer Networks and the Size Distribution of Firms  

CERN Document Server

A bipartite producer-consumer network is constructed to describe the industrial structure. The edges from consumer to producer represent the choices of the consumer for the final products and the degree of producer can represent its market share. So the size distribution of firms can be characterized by producer's degree distribution. The probability for a producer receiving a new consumption is determined by its competency described by initial attractiveness and the self-reinforcing mechanism in the competition described by preferential attachment. The cases with constant total consumption and with growing market are studied. The following results are obtained: 1, Without market growth and a uniform initial attractiveness $a$, the final distribution of firm sizes is Gamma distribution for $a>1$ and is exponential for $a=1$. If $a<1$, the distribution is power in small size and exponential in upper tail; 2, For a growing market, the size distribution of firms obeys the power law. The exponent is affected b...

Dahui, W; Zengru, D; Dahui, Wang; Li, Zhou; Zengru, Di

2005-01-01

97

Mobile field sampling system for determining submicron aerosol size distributions  

International Nuclear Information System (INIS)

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

98

Measurement of aggregates' size distribution by angular light scattering  

International Nuclear Information System (INIS)

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. -- Highlights: ? A novel method is introduced for in situ measurement of aggregates size distribution. ? Only measurements of scattered light at three angles are required. ? Neither the refractive index nor the primary sphere diameter is necessary. ? The method is validated experimentally on monodisperse an

99

Holographic particle size extraction by using Wigner-Ville distribution  

Science.gov (United States)

A new method for measuring object size from in-line holograms by using Wigner-Ville distribution (WVD) is proposed. The proposed method has advantages over conventional numerical reconstruction in that it is free from iterative process and it can extract the object size and position with only single computation of the WVD. Experimental verification of the proposed method is presented.

Chuamchaitrakool, Porntip; Widjaja, Joewono; Yoshimura, Hiroyuki

2014-06-01

100

Visualization of bubble size distribution in inclined rectangular channel  

International Nuclear Information System (INIS)

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

 
 
 
 
101

Zero emission distributed hydrogen production  

International Nuclear Information System (INIS)

The need for distributed production facilities has become a critical issue in developing a hydrogen infrastructure. Hydrogen generation using processes that make effective use of what would normally be considered waste streams or process inefficiencies can have more favorable economics than stand-alone technologies. Currently, natural gas is distributed to industrial and residential customers through a network of pipelines. High pressure main lines move gas to the vicinity of consumers where the pressure is reduced for local, low pressure distribution. Often, the practice is to use an isenthalpic expansion which results in a cooling of the gas stream. Some of the natural gas is burned to preheat the fuel so that the temperature after the expansion is near ambient. This results in the destruction of exergy in the high pressure gas stream and produces CO2 in the process. If, instead, a turbo-expander is used to reduce the stream pressure, work can be recovered using a generator and hydrogen can be produced via electrolysis. This method of hydrogen production is free of green-house gas emissions, makes use of existing gas distribution facilities, and uses exergy that would otherwise be destroyed. Pressure reduction using the work producing process (turbo-expander) is accompanied by a large drop in temperature, on the average of 70 K. The local gas distributor requires the gas temperature to be raised again to near 8oC to prevent damage to valve assep>oC to prevent damage to valve assemblies. The required heating power after expansion can be on the order of megawatts (site dependent.) Supplying the heat can be seen as a cost if energy is taken from the system to reheat the fuel; however, the low temperature stream may also be considered an asset if the cooling power can be used for a local process. This analysis is the second stage of a study to examine the technical and economic feasibility of using pressure let-down sites as hydrogen production facilities. This paper describes a proposed demonstration hydrogen production and fueling station near Victoria, BC. The station would demonstrate the viability of the proposed process to generate hydrogen while increasing the performance of the natural gas distribution system. The station could provide the ability to fuel vehicles as part of the Victoria node of the hydrogen highway project to be implemented for the 2010 Winter Olympic games. (author)

102

Better size estimation for sparse matrix products  

CERN Document Server

We consider the problem of doing fast and reliable estimation of the number of non-zero entries in a sparse boolean matrix product. This problem has applications in databases and computer algebra. Let n denote the total number of non-zero entries in the input matrices. We show how to compute a 1 +- epsilon approximation (with small probability of error) in expected time O(n) for any epsilon > 4/\\sqrt[4]{n}. The previously best estimation algorithm, due to Cohen (JCSS 1997), uses time O(n/epsilon^2). We also present a variant using O(sort(n)) I/Os in expectation in the cache-oblivious model. In contrast to these results, the currently best algorithms for computing a sparse boolean matrix product use time omega(n^{4/3}) (resp. omega(n^{4/3}/B) I/Os), even if the result matrix has only z=O(n) nonzero entries. Our algorithm combines the size estimation technique of Bar-Yossef et al. (RANDOM 2002) with a particular class of pairwise independent hash functions that allows the sketch of a set of the form A x C to be...

Amossen, Rasmus Resen; Pagh, Rasmus

2010-01-01

103

Distribution Of Natural Radioactivity On Soil Size Particles  

International Nuclear Information System (INIS)

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

104

Size Distribution of Superparamagnetic Particles Determined by Magnetic Sedimentation  

CERN Document Server

We report on the use of magnetic sedimentation as a means to determine the size distribution of dispersed magnetic particles. The particles investigated here are i) single anionic and cationic nanoparticles of diameter D = 7 nm and ii) nanoparticle clusters resulting from electrostatic complexation with polyelectrolytes and polyelectrolyte-neutral copolymers. A theoretical expression of the sedimentation concentration profiles at the steady state is proposed and it is found to describe accurately the experimental data. When compared to dynamic light scattering, vibrating sample magnetometry and cryogenic transmission electron microscopy, magnetic sedimentation exhibits a unique property : it provides the core size and core size distribution of nanoparticle aggregates.

Berret, J F; Mauger, A

2006-01-01

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

Self-consistent size and velocity distributions of collisional cascades  

CERN Document Server

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

Pan, Margaret

2011-01-01

107

Methodology of evaluation of size and size-distribution of particles formed during aggregation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The article describes technology of measurement of size and size-distribution of aggregates formed during agitation using the digital camera. This method may be used in laboratory batch reactors, pilot plants as well as in full-scale water treatment plants.

Pivokonsky?, Martin; Pivokonsky?, Radek; Benes?ova?, Libus?e; Mutl, Silvestr

2003-01-01

108

Size distribution of radon daughters in the atmosphere  

International Nuclear Information System (INIS)

Radon daughter aerosols in the atmosphere are generally classified into two categories attached and unattached. It is however difficult to develop their size distribution model because of the uncertainty about the sticking coefficient. Recently inferred values of this coefficient are in the range of 5 x 10-2 to 8 x 10-2 for radon daughters and even smaller for elemental iodine aerosols. Estimated size of radon daughters in Trombay (Bombay) is in the range of 0.002 ?m to 0.004 ?m which agrees with the median size of aerosols in the nuclei mode. The growth of radon daughter aerosols is thus similar to other nuclei formed through gas-to-particle conversion reactions in the atmosphere. It is suggested that observed size distribution of radon daughters (median size and geometric standard deviation) is a more useful parameter in calculating their health effects than classifying them as attached and unattached

109

Recurrent frequency-size distribution of characteristic events  

Directory of Open Access Journals (Sweden)

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

S. G. Abaimov

2009-04-01

110

Size distributions and failure initiation of submarine landslides (Invited)  

Science.gov (United States)

Landslides are often viewed together with other natural hazards, such as earthquakes and fires, as phenomena whose size distribution obeys an inverse power law. Inverse power law distributions are the result of additive avalanche processes, in which the final size cannot be predicted at the onset of the disturbance. Volume and area distributions of submarine landslides along the U.S. Atlantic continental margin follow a lognormal distribution and not an inverse power law. Using Monte Carlo simulations, we generated source area distributions of submarine landslides that show a characteristic size and with few smaller and larger areas, which can be described well by a lognormal distribution. To generate these distributions we assumed that the area of slope failure depends on earthquake magnitude, i.e., that failure occurs simultaneously over the area affected by horizontal ground shaking, and does not cascade from nucleating points. Furthermore, the downslope movement of displaced sediment does not entrain significant amounts of additional material. Our simulations fit well the area distribution of landslides along the Atlantic continental margin, if we assume that the slope has been subjected to earthquakes of magnitude 6.3 and that less than the maximum predicted area had failed. The hypothesis presented here implies that the maximum area of landslides is generally predictable from the characteristics of the triggering event, however, how much of that area will actually fail depends on local variations in slope angle, material strength, pore pressure, and the presence of pre-existing fractures.

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

2009-12-01

111

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

Science.gov (United States)

We characterize the statistical law according to which Italian primary school-size distributes. We find that the school-size can be approximated by a log-normal distribution, with a fat lower tail that collects a large number of very small schools. The upper tail of the school-size distribution decreases exponentially and the growth rates are distributed with a Laplace PDF. These distributions are similar to those observed for firms and are consistent with a Bose-Einstein preferential attachment process. The body of the distribution features a bimodal shape suggesting some source of heterogeneity in the school organization that we uncover by an in-depth analysis of the relation between schools-size and city-size. We propose a novel cluster methodology and a new spatial interaction approach among schools which outline the variety of policies implemented in Italy. Different regional policies are also discussed shedding lights on the relation between policy and geographical features. PMID:24954714

Belmonte, Alessandro; Di Clemente, Riccardo; Buldyrev, Sergey V

2014-01-01

112

Can vesicle size distributions predict eruption intensity during volcanic activity?  

Directory of Open Access Journals (Sweden)

Full Text Available We studied three-dimensional (3-D vesicle size distributions by X-ray microtomography in scoria collected during the relatively quiescent Phase II of the 2010 eruption at Eyjafjallajökull volcano, Iceland. Our goal was to compare the 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 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 the hypothesis that the phreatomagmatic nature of the Eyjafjallajökull eruption might have a significant effect on the VSDs. We performed 1 atm 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 hypothesis is not supported by the experimental evidence; therefore, VSDs of magmatic and phreatomagmatic eruptions can be directly compared. The Phase II Eyjafjallajökull VSDs are described by power law exponents of ~ 0.8, typical of normal Strombolian eruptions. 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 deep magma that mixes with resident magma at shallow depths. 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 renewed eruption intensity observed in the following Phase III of the eruption.

A. LaRue

2013-06-01

113

Magnetic heating effect of nanoparticles with different sizes and size distributions  

International Nuclear Information System (INIS)

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

114

The Size Frequency Distribution of Small Main-Belt Asteroids  

Science.gov (United States)

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

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

2012-01-01

115

Estimating Clique Composition and Size Distributions from Sampled Network Data  

CERN Document Server

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

116

Rank-Size Distribution of Notes in Harmonic Music: Hierarchic Shuffling of Distributions  

Science.gov (United States)

We trace the rank size distribution of notes in harmonic music, which on previous works we suggested was much better represented by the Two-parameter, first class Beta distribution than the customary power law, to the ranked mixing of distributions dictated by the harmonic and instrumental nature of the piece. The same representation is shown to arise in other fields by the same type of ranked shuffling of distributions. We include the codon content of intergenic DNA sequences and the ranked distribution of sizes of trees in a determined area as examples. We show that the fittings proposed increase their accuracy with the number of distributions that are mixed and ranked.

Del Río, Manuel Beltrán; Cocho, Germinal

117

Recurrent frequency-size distribution of characteristic events  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Statistical frequency-size (frequency-magnitude) properties of earthquake occurrence play an important role in seismic hazard assessments. The behavior of earthquakes is represented by two different statistics: interoccurrent behavior in a region and recurrent behavior at a given point on a fault (or at a given fault). The interoccurrent frequency-size behavior has been investigated by many authors and generally obeys the power-law Gutenberg-Richter distribution to a good approximation. It is...

Abaimov, S. G.; Tiampo, K. F.; Turcotte, D. L.; Rundle, J. B.

2009-01-01

118

Theory of Nanocluster Size Distributions from Ion Beam Synthesis  

Energy Technology Data Exchange (ETDEWEB)

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

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

2008-06-13

119

Liquid Column Deformation and Particle Size Distribution in Gas Atomization  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Antipas, Georgios S. E.

2011-01-01

120

Liquid Column Deformation and Particle Size Distribution in Gas Atomization  

Directory of Open Access Journals (Sweden)

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

Georgios S. E. Antipas

2011-02-01

 
 
 
 
121

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)

122

Estimation of Nanoparticle Size Distributions by Image Analysis  

DEFF Research Database (Denmark)

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

Fisker, Rune; Carstensen, Jens Michael

2000-01-01

123

Correction of bubble size distributions from transmission electron microscopy observations  

International Nuclear Information System (INIS)

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

124

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

125

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

CERN Document Server

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

126

Size-Dependency of Income Distributions and Its Implications  

CERN Document Server

This paper highlights the size-dependency of income distributions, i.e. the income distribution curves change with the population of a country systematically. By using the generalized Lotka-Volterra model to fit the empirical income data in the United States during 1996-2007, we found an important parameter $\\lambda$ can scale with a $\\beta$ power of the size (population) of U.S. in that year. We pointed out that the size-dependency of the income distributions, which is a very important property but seldom addressed by previous studies, has two non-trivial implications: (1) the allometric growth pattern, i.e. the power law relationship between population and GDP in different years, which can be mathematically derived from the size-dependent income distributions and also supported by the empirical data; (2) the connection with the anomalous scaling for the probability density function in critical phenomena since the re-scaled form of the income distributions has the exactly same mathematical expression for the...

Zhang, Jiang

2010-01-01

127

Empirical results on the size distribution of business cycle phases  

Science.gov (United States)

We study the size distribution of business cycles phases, that is expansions and contractions, for a sample of 16 industrialized countries over 120 years. We find that the best-fitting distribution for both expansions and contractions is Weibull, meaning that business cycles possess a characteristic scale. Furthermore, we discuss how parameters’ estimates can be used to make inference on the probability a typical episode ends, that is on what economists call turning points.

Di Guilmi, Corrado; Gaffeo, Edoardo; Gallegati, Mauro

2004-02-01

128

Modeling radon progeny size distributions in an aerosol chamber  

International Nuclear Information System (INIS)

A mathematical model is being developed to simulate the radon progeny behavior in an aerosol chamber. The primary mechanism of particle formation is the transformation of SO2 into a condensable product (H2O and H2SO4) by radon radiolytical reactions. The concentrations of SO2 and water vapor significantly affect the particle number and size distribution. Both homogeneous and heterogeneous nucleation are included in the particle formation and growth mechanisms. The model has been extended to calculate the evolution in time of 218Po, 214Pb, and 214Bi containing particles. The processes in the chamber and considered in this model include: condensation, coagulation, deposition on the chamber surfaces, attachment and recoil to and from aerosol particles, ventilation and radioactive decay. Experiments were performed in the chamber to provide both input data as well as permitting a qualitative comparison of the measured data with predicted results from this model. The model calculation indicates that the heterogeneous formation may contribute significantly to the total particle formation

129

Comet Shoemaker-Levy 9 Dust Size and Velocity Distributions  

Science.gov (United States)

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

Hahn, Joseph M.; Rettig, Terrence W.

2000-01-01

130

Aerosol Size Distribution and Time Evolution in CARES  

Science.gov (United States)

During the 2010 CARES campaign, centered in Sacramento and downwind regions, measurements of aerosol precursors, concentration, and properties were made from the DOE G-1 aircraft Here we focus on size distributions using data from a CPC3025 (Dp > 3 nm), UHSAS (~75 - 1000nm), and a Fast Integrated Particle Spectrometer, FIMS, (30 - 100 nm). Number concentrations of fine particles are highly dependent on relatively small SO2 point sources, with aggregate emissions of order 10 kton/year. Within the Dp> 30 nm size window of observation, varying stages of particle growth (augmented by primary emissions) have been characterized by means of log normal fits of number concentration. Mode sizes range from below 30 nm to ~ 120 nm. In selected cases, the time evolution of the urban plume can be followed as it is intercepted at different downwind distances. More generally, the time evolution of number and volume size distributions have been considered as a function of photochemical age and distance from Sacramento. Changes in size distributions are calculated starting with the simplest scenario of irreversible condensation.

Kleinman, L. I.; Springston, S. R.; Senum, G. I.; Sedlacek, A. J.; Wang, J.; Kuang, C.; Fast, J. D.; Shilling, J. E.; Tomlinson, J. M.; Hubbe, J.; Zaveri, R. A.

2011-12-01

131

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)

132

B AYESAIN ESTIMATION OF SIZE BIASED CLASSICAL GAMMA DISTRIBUTION  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, we present Bayes’ estimator of the parameter of Size biased Gamma distribution (SBGMD, that stems from an extension of Jeffery’s prior (Al - Kutubi (2005 with a new loss function (Al - Bayyati (2002 . We are proposing four different types of estimators. Under squared error loss function, there are two estimators formed by using Jaffrey prior and an extension of Jaffrey’s prior. The two remaining estimators are derived using the same Jeffrey’s prior and extension of Jeffrey’s prior under a new loss function. We are also deriving the survival function of the size biased Gamma distribution. These methods are compared by using mean square error through simulation study with varying sample sizes .

J. A. Reshi

2014-06-01

133

Size distributions and failure initiation of submarine and subaerial landslides  

Science.gov (United States)

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

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

2009-09-01

134

Critical Exponent of Species-Size Distribution in Evolution  

CERN Document Server

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

135

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

International Nuclear Information System (INIS)

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

136

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

Science.gov (United States)

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

137

Photovoltaic production and distribution network  

International Nuclear Information System (INIS)

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

138

Influence of coal texture and rank on breakage energy and resulting size distributions in Australian coals  

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

139

The VSOP Survey: The Angular Size/Brightness Temperature Distribution  

Science.gov (United States)

The VSOP mission is a Japanese-led project to image radio sources with sub-mas resolution using an orbiting 8-m telescope, HALCA, with a global array of telescopes. About 25% of the observing time was devoted to a survey at 5 GHz of the brightest, compact AGN. Using a complete sample of AGN's with ?>-44° which overlapped VLBA observations, we determined the statistical properties of the angular size and brightness temperature distribution by analyzing the observed correlated amplitude versus projected radio spacing. We find that 80% of the radio cores have an angular size in the range 0.031013 K.

Horiuchi, S.; Fomalont, E. B.; Moellenbrock, G. A.; Scott, W. A.; Taylor, A. R.; Lovell, J. E. J.; Dodson, R.; Murata, Y.; Hirabayashi, H.; Edwards, P. G.; Fujisawa, K.

2005-12-01

140

Aerosol size distribution in the Schwartzwalder uranium mine.  

Science.gov (United States)

Few published data are available to describe the size distribution of aerosols within the uranium mining environment. Activity size distribution of the radon progeny attached aerosols was measured at the Schwartzwalder uranium mine (Jefferson County, Colorado, USA) using the diffusion battery method in the summer of 1970. The measurements from five of eight sites in the mine were analyzed. The average activity median diameter was approximately 55.3 nm and ranged from 34.2 to 72.7 nm. The average geometric standard deviation was approximately 2.90. The geometric standard deviation computed from the samples collected during the evening (Sites 3 and 6) was significantly smaller than from samples collected in the daytime (Sites 5, 7, and 8). The results of Site 7 showed the greatest the geometric standard deviation, a significantly higher radon concentration and a low equilibrium condition. PMID:24378559

Liu, Xianan; Doerges, John E; Volckens, John; Johnson, Thomas E

2014-02-01

 
 
 
 
141

Development of sample size allocation program using hypergeometric distribution  

International Nuclear Information System (INIS)

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

142

Onset of Oil Mobilization and Cluster Size Distribution  

Science.gov (United States)

The onset of oil mobilization during imbibition has been imaged under dynamic flow conditions where the visco-capillary balance is maintained by using fast synchrotron-based X-ray computed micro tomography. Oil mobilization under unsteady-state displacement has been studied for sintered glass, sandstone and carbonate rock which show distinctly different behaviour. For sintered glass, in agreement with a previous study under static conditions [Georgiadis et al., Phys.Rev.E 033002, 2013], the cluster size distribution is power-law like only over limited. Also the saturation stays rather constant during the low-rate imbibitions because the visco-capillary balance did not exceed 1, i.e. the macroscopic capillary number remains smaller than 1 which is not sufficient for oil mobilization [Armstrong et al., GeoPhys.Res.Lett. 41, 1-6. 2014]. The carbonate rock shows a power-law like cluster size distribution over the whole range. It is not fully clear whether this behaviour is caused by a more complex pore morphology in carbonates with a broader pore size distribution overlapping with heterogeneity length scales which creates an apparent larger range scale-free behaviour. The sandstone rock shows the most interesting behaviour as during imbibitions a significant amount of oil is mobilized during the imbibitions process. The fast tomography now allows to follow this process step by step providing detailed spatially resolved information on the pore scale and also the statistical relevance. The observations can be summarized that during imbibition oil is mobilized by the biggest (percolating) cluster breaking successively apart into fragments and in particular intermediate size clusters grow in size and increase in frequency.

Ruecker, Maja; Armstrong, Ryan; Georgiadis, Apostolos; Ott, Holger; Berg, Steffen; Leu, Leon; Wolf, Martin; Khan, Faisal; Enzmann, Frieder; Kersten, Michael

2014-05-01

143

Controlling semiconductor nanoparticle size distributions with tailored ultrashort pulses  

International Nuclear Information System (INIS)

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

144

Magnetic heating effect of nanoparticles with different sizes and size distributions  

Energy Technology Data Exchange (ETDEWEB)

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

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

2013-02-15

145

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

Science.gov (United States)

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

Nason, Jeffrey A; Lawler, Desmond F

2009-02-01

146

Time Evolution of the Mutual Fund Size Distribution  

CERN Document Server

We investigate the process of mutual fund growth both empirically and theoretically. The size of large mutual funds has a heavy tailed distribution that has been conjectured to be a power law; we investigate the data more carefully and show that it is better described by a log normal. To explain this we develop a stochastic growth model based on multiplicative growth, creation and annihilation. Under the simplifying assumption that these processes do not depend on fund size we obtain a time-dependent analytic solution of the model. The distribution evolves from a log normal into a power law only over long time scales, suggesting that log-normality comes about because the industry is still young and in a transient state due to its rapid growth in recent years. We make the model more realistic by taking into account size dependent effects, in particular the decay in the rates of diffusion and drift with increasing fund size. The resulting model is in good quantitative agreement with the data. Surprisingly, it a...

Schwarzkopf, Yonathan

2008-01-01

147

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.

Chaiyot Tangsathitkulchai

2010-07-01

148

Controls on phytoplankton cell size distributions in contrasting physical environments  

Science.gov (United States)

A key challenge for marine ecosystem and biogeochemical models is to capture the multiple ecological and evolutionary processes driving the adaptation of diverse communities to changed environmental conditions over different spatial and temporal scales. These range from short-term acclimation in individuals, to population-level selection, immigration and ecological succession on intermediate scales, to shifts in the global biogeochemical cycling of key elements. As part of the "EVE" project, we have been working toward improving the representation of ecological and evolutionary processes in models, with a focus on understanding the role of marine ecosystems in the past, present, and future Earth system. Our approach is to develop a mechanistic understanding of trade-offs between different functional traits through the explicit representation of resource investment in sub-cellular components controlled by a synthetic genome. Trait expression (including size, metabolic strategies on a continuum from autotrophy to heterotrophy, and predation strategies) and adaptation to the environment are then emergent properties of the model, following from natural selection operating in the model environment. Here we show results relating to controls on phytoplankton cell size - a key phytoplankton trait which is inextricably linked to the structuring and functioning of marine ecosystems. Coupled to the MIT OGCM, we use the model to derive dynamic optimal size-class distributions at representative oligotrophic and high-latitude time series sites, which are then compared with in situ data. Particular attention is given to the relative importance of top-down vs bottom-up drivers for phytoplankton cell size, and their influence on global patterns in phytoplankton cell size, as well as changes in the cell size distribution during phytoplankton bloom periods.

Clark, J. R.; Daines, S. J.; Lenton, T. M.

2012-04-01

149

Cluster size distribution of cell aggregates in culture  

Science.gov (United States)

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

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

2001-09-01

150

Radon progeny size distribution in and around closed uranium mine  

International Nuclear Information System (INIS)

table. A screen means a kind of mesh made of stainless steel. Screen-type diffusion battery consists of stack of the screens. The size distribution is calculated from the penetration curve be an iterative calculation based on response matrix of the set of diffusion battery. The measurement of ratio of unattached fraction is based on a screen mesh method. The unattached fraction can be caught by a screen mesh and it is obtained from the radioactivity on the mesh. According to the obtained results, the radon progeny size distribution in a mine site at Katamo in Tottori prefecture is smaller than the results around the site and in control area, while the unattached fraction in the mine site is greater than the results of other place. The measuring place in the mine site is located in front of a temporarily closed mining tunnel where the radon and radon progeny concentration are higher than the concentrations at other places in and around the site (Ito et al. 1998). The place is surrounded by many trees and far from living area where much ambient aerosol is released from many kinds of sources. While other places are surrounded by relatively spacious environment and are close to living area. This difference in condition around the measuring location may affect the results of size distribution. Some models for dose estimation due to radon progeny are recommended in several reports. Although each model has a different dependence on the particle size and unattached fraction, the obtained dose conversion factor for the measurement results in the mine site is evaluated to be twice to four times as long as the factors for other places. However, this influence to radiation monitoring is insignificant because the estimated concentration of radon progeny is low enough to the limit to set up a radiation controlled area by law (Ito et al. 1998). (J.P.N)

151

Educational production and optimal class size  

CERN Document Server

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

152

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

Science.gov (United States)

We have initiated a major new program to determine the grain size distribution of nearly all lunar soils collected in the Apollo program. Following the return of Apollo soil and core samples, a number of investigators including our own group performed grain size distribution studies and published the results [1-11]. Nearly all of these studies were done by sieving the samples, usually with a working fluid such as Freon(TradeMark) or water. We have measured the particle size distribution of lunar soil 10084,2005 in water, using a Microtrac(TradeMark) laser diffraction instrument. Details of our own sieving technique and protocol (also used in [11]). are given in [4]. While sieving usually produces accurate and reproducible results, it has disadvantages. It is very labor intensive and requires hours to days to perform properly. Even using automated sieve shaking devices, four or five days may be needed to sieve each sample, although multiple sieve stacks increases productivity. Second, sieving is subject to loss of grains through handling and weighing operations, and these losses are concentrated in the finest grain sizes. Loss from handling becomes a more acute problem when smaller amounts of material are used. While we were able to quantitatively sieve into 6 or 8 size fractions using starting soil masses as low as 50mg, attrition and handling problems limit the practicality of sieving smaller amounts. Third, sieving below 10 or 20microns is not practical because of the problems of grain loss, and smaller grains sticking to coarser grains. Sieving is completely impractical below about 5- 10microns. Consequently, sieving gives no information on the size distribution below approx.10 microns which includes the important submicrometer and nanoparticle size ranges. Finally, sieving creates a limited number of size bins and may therefore miss fine structure of the distribution which would be revealed by other methods that produce many smaller size bins.

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

2009-01-01

153

Development of laboratory and process sensors to monitor particle size distribution of industrial slurries  

Energy Technology Data Exchange (ETDEWEB)

In this paper we present a novel measurement technique for monitoring particle size distributions of industrial colloidal slurries based on ultrasonic spectroscopy and mathematical deconvolution. An on-line sensor prototype has been developed and tested extensively in laboratory and production settings using mineral pigment slurries. Evaluation to date shows that the sensor is capable of providing particle size distributions, without any assumptions regarding their functional form, over diameters ranging from 0.1 to 100 micrometers in slurries with particle concentrations of 10 to 50 volume percents. The newly developed on-line sensor allows one to obtain particle size distributions of commonly encountered inorganic pigment slurries under industrial processing conditions without dilution.

Pendse, H.P.

1992-10-01

154

Cluster Size Optimization in Gaussian Distributed Wireless Sensor Networks  

Directory of Open Access Journals (Sweden)

Full Text Available To deal with sensor network limitations such as limited energy and short range communication, sensor nodes are grouped into mostly non overlapping subsets called clusters. Choosing optimal number of clusters provides benefits such that limited resources can be utilized more efficiently and network lifetime is improved. Many of the existing researches provided the cluster size optimization in Wireless Sensor Networks (WSNs, in which nodes are uniformly and randomly placed in the sensing field (e.g. controllable WSN. Deployment of sensor nodes affects the energy consumption of WSNs along with individual nodes because the distance between nodes and Base Station (BS is different due to different node position; consequently nodes have different energy loss. The energy efficient way of sensor deployment in sensing field is controlled node deployment with uniform distribution. However this procedure for node deployment may not be practically possible for some applications like, in large WSNs, locations of the sensing field may not be physically accessible because of geographical constraints. In this paper, we provide an analytical framework for the cluster size optimization of WSNs that follow Gaussian node deployment. This type of node deployment reduces energy hole problem, provides enhanced intrusion detection capability and support realistic applications. We have provided expression for optimal number of clusters using circular sensing model of nodes for square sensing field with consideration of boundary effect. We have also compared the cluster size optimization for uniform and Gaussian distributed sensor network.

Vinay Kumar

2014-07-01

155

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

Science.gov (United States)

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

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

2014-05-01

156

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

157

Size Distribution of Fine Particles from Coal Combustion  

Science.gov (United States)

Measurements of the particle size distribution at the outlets of six coalfired utility boilers showed a peak at a particle diameter near 0.1 micrometer. This submicrometer mode appears to be a general feature of coal combustion that results from a volatilization-condensation process in the boiler. At the boilers tested, the submicrometer mode contained 0.2 to 2.2 percent of the total fly ash mass. The importance of this mode is greater than its small quantity suggests because particles in the submicrometer size range are often much more difficult to collect with conventional particulate control devices than larger particles. Thus, the submicrometer mode may significantly influence the design and selection of future power plant emission controls. The particle mass in the submicrometer mode was correlated with the nitric oxide concentration in the flue gas. This correlation suggests that control of nitric oxide by modification of the combustion conditions may reduce the generation and emission of submicrometer particles.

McElroy, M. W.; Carr, R. C.; Ensor, D. S.; Markowski, G. R.

1982-01-01

158

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

159

Size distribution of particulate mercury in marine and coastal atmospheres  

Science.gov (United States)

A study was conducted to determine the size distribution of particulate mercury (HgP) at a marine and coastal site, and to compare the seasonal variability at both sites. Data was collected during summer 2009 and 2010, winter 2010, and spring 2010. Two cascade impactors were used to collect HgP in ten size fractions ranging from > 10 ?m to cycle that matches that of gaseous elemental mercury. Finally, dry deposition rates of HgP were calculated to be 1.7-2.8 ng m-2 day-1 in the summer, 4.6 ng m-2 day-1 in the winter, and 2.5 ng m-2 day-1 in the spring.

Feddersen, D. M.; Talbot, R.; Mao, H.; Sive, B. C.

2012-11-01

160

Study of columnar aerosol size distribution in Hong Kong  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents studies on columnar aerosol optical properties in Hong Kong with focus on aerosol volume size distribution. Long-term ground measurements in the wet season in the years of 2002, 2003, 2004 and 2008 have been performed using a sun-sky radiometer. A bimodal size distribution is found with the fine mode centering at ~0.2 ?m and coarse mode centering at ~6 ?m, respectively. The fine and coarse mode have close volume concentrations of nearly 50% fraction in composing local aerosols. Intercomparison of different years shows similar aerosol properties while a small increase of fine mode aerosol could be observed. A systematic shift of size distribution parameters is observed with different atmospheric conditions, where higher aerosol loadings and Angstrom exponent correspond to more fine aerosols. The fine mode is found to be more closely correlated with this shift than the coarse mode. A higher fine mode volume fraction and smaller median fine radius correspond to a larger Angstrom exponent. The fine aerosol hygroscopic growth is one of the main mechanisms for such systematic shifting. A third mode centering at ~1–2 ?m could be discovered under high aerosol loading and high fine aerosol conditions. It becomes more pronounced with high aerosol optical depth and larger Angstrom exponent. Investigation of its variation with corresponding optical parameters and correlation with atmospheric conditions indicates that it is mainly due to the fine aerosol hygroscopic growth and coagulation rather than the contribution from the coarse mode. While the very humid environment facilitates the aerosol hygroscopic growth, aerosol coagulation might further produce more large aerosols under high fine aerosol conditions. The continental outflow with transported ageing aerosols and biomass burning might have also contributed to this additional mode.

X. Yang

2009-03-01

 
 
 
 
161

Study of columnar aerosol size distribution in Hong Kong  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents studies on columnar aerosol optical properties in Hong Kong with focus on aerosol volume size distribution, which helps understand local aerosol properties, variation, hygroscopic growth and coagulation. Long-term ground measurements in the wet season in the years of 2002, 2003, 2004 and 2008 have been performed using a sun-sky radiometer. Data validation made using MODIS and local AERONET shows agreement. A bimodal size distribution is found with the fine mode centering at ~0.2 ?m and coarse mode centering at ~3 ?m respectively. The fine and coarse mode have close volume concentrations of nearly 50% fraction in composing local aerosols. Intercomparison of different years shows similar aerosol properties while a small increase of fine mode aerosol could be observed. A systematic shift of size distribution parameters is observed with different atmospheric conditions, where higher aerosol loadings and Angstrom exponent correspond to more fine mode aerosols. The fine mode is found to be more closely correlated with this shift than the coarse mode. A higher fine mode volume fraction and smaller median fine radius correspond to a larger Angstrom exponent. The fine mode aerosol hygroscopic growth is one of the main mechanisms for such systematic shifting. A third mode centering at ~1–2 ?m could be discovered under high aerosol loading and high fine mode aerosol conditions. It becomes more pronounced with high aerosol optical depth and larger Angstrom exponent. Investigation of its variation with corresponding optical parameters and correlation with atmospheric conditions appears to support the hypothesis that it is mainly due to the fine mode aerosol hygroscopic growth and coagulation rather than the contribution from the coarse mode. While the very humid environment facilitates the aerosol hygroscopic growth, aerosol coagulation might further produce larger aerosols under high fine aerosol conditions. The continental outflow with transported aging aerosols and biomass burning might have also contributed to this additional mode.

X. Yang

2009-08-01

162

Influence of meteorological variability upon aerosol mass size distribution  

Science.gov (United States)

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

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

2009-10-01

163

Cluster size distribution in 1D-CA traffic models  

International Nuclear Information System (INIS)

We propose a useful method to analyze one-dimensional (1D)-cellular automata traffic models based on the distribution of cluster size in the system. By applying this method, we reproduce the exact solution of the totally asymmetric exclusion process and the zero range process (ZRP). Moreover, we confirm that a certain kind of slow-to-start model can be interpreted as the ZRP and also obtain the exact solution of it. Finally, we extend the Fukui–Ishibashi model and obtain promising expressions of the flux. (paper)

164

A Maximum Entropy Modelling of the Rain Drop Size Distribution  

Directory of Open Access Journals (Sweden)

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

Francisco J. Tapiador

2011-01-01

165

Effects of dust size distribution in ultracold quantum dusty plasmas  

International Nuclear Information System (INIS)

The effect of dust size distribution in ultracold quantum dusty plasmas are investigated in this paper. How the dispersion relation and the propagation velocity for the quantum dusty plasma vary with the system parameters and the different dust distribution are studied. It is found that as the Fermi temperature of the dust grains increases the frequency of the wave increases for large wave number dust acoustic wave. The quantum parameter of Hd also increases the frequency of the large wave number dust acoustic wave. It is also found that the frequency ?0 and the propagation velocity ?0 of quantum dust acoustic waves all increase as the total number density increases. They are greater for unusual dusty plasmas than those of the usual dusty plasma. (fluids, plasmas and electric discharges)

166

Distributed Project Management for New Product Development  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 ef...

Thal, Alfred E.; Jr, Adedeji Badiru; Rupy Sawhney

2007-01-01

167

The Superbubble Size Distribution in the Interstellar Medium of Galaxies  

CERN Document Server

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

168

Size distribution of particulate mercury in marine and coastal atmospheres  

Directory of Open Access Journals (Sweden)

Full Text Available A study was conducted to determine the size distribution of particulate mercury (HgP at a marine and coastal site, and to compare the seasonal variability at both sites. Data was collected during summer 2009 and 2010, winter 2010, and spring 2010. Two cascade impactors were used to collect HgP in ten size fractions ranging from > 10 ?m to < 0.4 ?m. During summer 2009, HgP was found mainly (50–60% in coarse fractions, 1.1 to 5.8 ?m, composed of sea salt particles at both our coastal site (Thompson Farm and marine site (Appledore Island. In winter, HgP at Thompson Farm was dominated (65% by fine particles, while in spring and summer 2010, at both sites, HgP was distributed across the coarse and fine fractions (40% each. Using bulk filters to collect total HgP, we show a diurnal cycle that matches that of gaseous elemental mercury. Finally, dry deposition rates of HgP were calculated to be 1.7–2.8 ng m?2 day?1 in the summer, 4.6 ng m?2 day?1 in the winter, and 2.5 ng m?2 day?1 in the spring.

D. M. Feddersen

2012-11-01

169

Newly designed graded screen array for particle size measurements of unattached radon decay products  

International Nuclear Information System (INIS)

A new graded screen array was designed for measuring the particle size distribution of unattached radon decay products. Its validity was verified by experimental approaches using a radon/aerosol chamber. Use of fine wire mesh screens achieved both a high volumetric air flow rate and high alpha count rate. Consequently, this improvement produced both a high sensitivity and good precision in the particle size distribution measurement for unattached radon decay products with an activity median diameter around 1 nm. A special Mylar film cover was used to protect the contamination of detector surface. And shielding effects by wire of a screen were examined in our alpha counting system for precise measurements. As for the results, the particle size distribution of unattached radon decay products was observed at around 1 nm as a narrow peak with the geometrical standard deviation of 1.1. When carrier aerosols were injected into the chamber, typical bimodal distribution was clearly observed. This clear bimodal distribution was observed even in an atmosphere with a relatively low radon concentration of 150 Bq m-3. It indicates that this system is adequate for measurements of the particle size distribution of unattached radon decay products in the natural environment

170

Effect of Pour Size on Concrete Placing Productivity in Nigeria  

Directory of Open Access Journals (Sweden)

Full Text Available Pour size as one of the site factors affecting concreting was examined to determine its effects on concreting productivity. A total of 167 separate concrete pours were observed on 25 building construction sites in Lagos, Nigeria,comprising 35 pours placed by crane and skip; 26 pours placed by dumper; 58 pours placed by wheelbarrow; 37 pours placed by head pan; and 11 pours placed jointly by pump, wheelbarrow and head pan. Data collected from the daily concrete pours were analyzed to determine operational productivity rates. The relationship between concreting productivity and pour size was examined using regression analyses to develop a model relating productivity to pour size. The results showed that irrespective of placing method, productivity generally increased by 1.1 m3/h for every 10 m3 increase in pour size. It was recommended that the obtained index of productivity increase per pour size be standardised for use in improving on-site productivity in the Nigerian construction industry.

Olaoluwa Olatunde

2012-06-01

171

Distribution of costs on agricultural products  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The article deals with the problem of production costs distribution on agricultural products. To solve this problem, the regression model was developed and applied on the data of selected farms of the year 2005. The results of calculated distribution of costs were analysed and compared with the actual data of agricultural companies of the same year. With reference to the calculations, it is assumed that the regression method could serve as an alternative method to estimate costs on agricultur...

Jedik, Andrej

2007-01-01

172

Development of a hydrocyclone product size soft-sensor  

International Nuclear Information System (INIS)

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)

173

Particle size distribution of 82Br aerosols during processing  

International Nuclear Information System (INIS)

Dose estimation from intake of airborne radioactive aerosol is carried out from its particle size in terms of 'Activity Median Aerodynamic Diameter' (AMAD). Hence it is essential to estimate aerosol size/distribution at the facility wherein the radioisotope is handled for accurate estimation of internal dose. 2- Bromo-bi-phenyl, in powder form is irradiated in the reactor to produce 82Br (81Br(n,ã)82Br). At Radiopharmaceutical divisional facility radioactive 82Br powder is chemically processed in shielded processing plant and finally para-di-bromo-bi-phenyl (in kerosene) is produced. 82Br is widely used in Non Destructive Testing Applications (NDTA) as well as radiotracer experiments in various industries. An eight stage Anderson Particle Sizing sampler(Cascade Impactor) is used for the experiment for the first time at our laboratory. During the chemical processing of 82Br, air samples were collected from the plant with all radiological safety measures. The air sampling was carried out using lines drawn from the active side of plant as well as from the lab atmosphere during volume reduction operation for a few batches. The air sampling suction was at 28.8 lit/min for duration of around 1 hr, to trap sizeable activity in the various stages of filters. Spot air samples were collected from the lab at suction rate of 1 m3/min for 5 min to assess the air activity release into the working atmosphectivity release into the working atmosphere. The total activity trapped in the filters of various stages was estimated using calibrated GM based counting device. There was no release of air activity estimated in lab working atmosphere. The cumulative % distribution in various stages of the samples is plotted against the cut-off size. Respective AMAD was calculated and found to be in the ranges of 3? - 5 ?m. The Annual Limit on Intake (ALT) for 82Br was calculated based on experimental results and estimation using LUDEP. This would be useful for correct internal exposure estimation, if any. (author)

174

Informational Divergence Approximations to Product Distributions  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The minimum rate needed to accurately approximate a product distribution based on an unnormalized informational divergence is shown to be a mutual information. This result subsumes results of Wyner on common information and Han-Verd\\'{u} on resolvability. The result also extends to cases where the source distribution is unknown but the entropy is known.

Hou, Jie; Kramer, Gerhard

2013-01-01

175

Mathematical modeling of polystyrene particle size distribution produced by suspension polymerization  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 experime...

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

2000-01-01

176

Mathematical modeling of polystyrene particle size distribution produced by suspension polymerization  

Directory of Open Access Journals (Sweden)

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

R.A.F. Machado

2000-12-01

177

Determination of emulsion size distribution by NMR restricted diffusion measurement  

International Nuclear Information System (INIS)

This paper reports that during the early stage of our study on dispersed-phase texture in porous media, the authors tested the technique proposed by Packer and Rees (1972) that uses NMR (nuclear magnetic resonance) restricted diffusion measurement to determine bulk emulsion-size distribution. It has been known for some time that self-diffusion of molecules having nuclear magnetic moments can be detected by pulsed NMR in the presence of various magnetic field gradients. The method of using pulsed magnetic field gradients was described first by Stejskal and Tanner (1965). A spin echo pulse sequence with two gradient pulses is shown. The final echo intensity reflects the effect of diffusion occurring during the time interval ? between the two

178

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

Science.gov (United States)

In the treatment of surface water for potable use, precipitative coagulation (e.g., lime softening, alum or iron sweep coagulation) is widely utilized prior to particle removal processes. The particle size distribution (PSD) formed during such processes is a prime determinant of the removal efficiency for suspended and dissolved contaminants, but little is known quantitatively about how PSDs change by simultaneous precipitation and flocculation. Using precipitative softening as an example, detailed measurements of the PSD (using electronic particle counting) were made during precipitation of CaCO(3) under conditions of constant solution composition. Examination of the time-varying PSDs revealed dramatic changes resulting from nucleation, crystal growth, and flocculation. The influence of the saturation ratio, seed concentration, and mixing intensity on those processes was quantified. Implications with respect to the design and operation of water treatment facilities are discussed. PMID:18656223

Nason, Jeffrey A; Lawler, Desmond F

2008-08-01

179

Possible universality in the size distribution of fish schools  

Science.gov (United States)

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

180

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

DEFF Research Database (Denmark)

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

Ljungqvist, Martin Georg; Nielsen, Michael Engelbrecht

2011-01-01

 
 
 
 
181

Concentrations and size distributions on Antarctic stratospheric aerosols  

International Nuclear Information System (INIS)

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 ?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 ?m radius, corresponding to type I PSCs, and occasionally, a second mode at 2.0 ?m radius, corresponding to type II PSCs

182

Size distribution control of FePt nanocrystals by superhydride  

Science.gov (United States)

FePt nanoparticle systems with high magnetocrystaline anisotropy in L10 phase are proper candidates for application in magnetic information storage with density more than Gbit/in2. FePt nanoparticles are grown by Pt(acac)2 and FeCl2. 4H2O compounds in phenyl ether solvent using weak reducing agent 1,2Hexadecandiol (C16H34O2) and strong reducing agent superhydride (LiBEt3H) in two steps. Structural and magnetic properties of the nanocrystals are studied by XRD, EDS and VSM analysis. Also, the growth mechanism and the effect of double-stage growth on size distribution and the size of FePt nanoparticles are determined. For this purpose, TEM images and EDS results are used. The results show that such growth as "core-shell" leads to form 5-nm, nearly monosized FePt nanoparticles, in which a relative standard deviation is decreased from 18% to 8%.

Parhizgar, Sara Sadat; Sebt, Seyed Ali

2013-09-01

183

THE EFFECT OF THE DUST SIZE DISTRIBUTION ON ASTEROID POLARIZATION  

International Nuclear Information System (INIS)

We have developed a theoretical description of how of an asteroid's polarization-phase curve will be affected by the removal of the dust from the surface due to a size-dependent phenomenon such as radiation pressure-driven escape of levitated particles. We test our calculations against new observations of four small (D ? 1 km) near-Earth asteroids (NEAs; (85236), (142348), (162900), and 2006 SZ217) obtained with the Dual Beam Imaging Polarimeter on the University of Hawaii's 2.2 m telescope, as well as previous observations of (25143) Itokawa and (433) Eros. We find that the polarization of the light reflected from an asteroid is controlled by the mineralogical and chemical composition of the surface and is independent of dust particle. The relation between the slope of the polarization-phase curve beyond the inversion angle and the albedo of an asteroid is thus independent of the surface regolith size distribution and is valid for both Main Belt and NEAs.

184

Particle size distribution study of 153Sm aerosols during its processing  

International Nuclear Information System (INIS)

ied out to determine particle size distribution of 153Sm aerosols during chemical processing by using eight stages Andersen Cascade sampler. The air activity release inside the production plant during the 153Sm processing was determined in three different operations. Particles size separation was achieved by Anderson eight-stage cascade impactor through the filter media loaded at each stage. The cumulative percent less than the stated size were plotted on log probability paper against Effective Cut off diameter (ECD). From this the AMADs of 153Sm aerosol on three different operations was found to be ? 3 ?m. Dose Conversion Factor (DCF) of 153Sm aerosols for these particle sizes are evaluated using LUDEP 2.0. (author)

185

Size and distribution prediction for nanoparticles produced by microemulsion precipitation: A Monte Carlo simulation study  

Science.gov (United States)

A Monte Carlo simulation approach for BaSO4 nanoparticle precipitation in microemulsions has been applied to a semi-batch reactor experiment. The simulation includes two technical process parameters, the feed rate and the initial volume ratio of the two reactants. A set of experiments with different initial reactant concentrations of BaCl2 and K2SO4 showed a significant change in the particle size. It was compared to the simulated final particle size and with an adaptation of one internal parameter of the Monte Carlo simulation a good agreement between simulated and experimental data was achieved. Using this set of parameters the feed rate and the initial volume ratio is varied. It is shown how these process parameters influence the particle size and the size distribution. The simulation results may help in finding appropriate control parameters in a scale-up approach of the microemulsion technology for nanoparticle production.

Voigt, Andreas; Adityawarman, Dendy; Sundmacher, Kai

2005-07-01

186

Productivity in Swedish electricity retail distribution  

International Nuclear Information System (INIS)

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.)

187

Using radial NMR profiles to characterize pore size distributions  

Science.gov (United States)

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

Deriche, Rachid; Treilhard, John

2012-02-01

188

ANALYTICAL MODEL FOR MARS CRATER-SIZE FREQUENCY DISTRIBUTION  

Directory of Open Access Journals (Sweden)

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

W. Bruckman

2009-01-01

189

The Size-Frequency Distribution of Dormant Jupiter Family Comets  

CERN Document Server

We estimate the total number and the slope of the size frequency distribution (SFD) of dormant Jupiter Family Comets (JFCs) by fitting a one-parameter model to the known population. We first select 61 Near Earth Objects (NEOs) that are likely to be dormant JFCs because their orbits are dynamically coupled to Jupiter (Bottke et al, 2002). Then, from the numerical simulations of Levison & Duncan (1997), we construct an orbit distribution model for JFCs in the NEO orbital element space. We assume an orbit independent SFD for all JFCs, the slope of which is our unique free parameter. Finally, we compute observational biases for dormant JFCs using a calibrated NEO survey simulator (Jedicke et al. 2003). By fitting the biased model to the data, we estimate that there are ~75 dormant JFCs with H<18 in the NEO region and that the slope of their cumulative SFD is -1.5 +/- 0.3. Our slope for the SFD of dormant JFCs is very close to that of active JFCs as determined by Weissman and Lowry (2003). Thus, we argue th...

Whitman, K; Morbidelli, A; Jedicke, Robert; Morbidelli, Alessandro; Whitman, Kathryn

2006-01-01

190

Granular Friction and Interparticle Force Networks; Effects of Particle Size, Size Distribution, and Strain Rate  

Science.gov (United States)

Micromechanical simulations of granular fault gouge, conducted in 2-D, allow us to examine the spatial and orientation distributions of interparticle contact forces, their evolution with time, and influence on fault zone strength and stability. Modeled after laboratory experiments on glass rods and spheres [e.g., Mair et al., 2002, Anthony and Marone, 2005], fault gouge consists of rounded particles with diameters between 53 to 250 ?m, in both well sorted and poorly sorted arrangements, sheared between smooth and rough planar walls. Applied normal stresses of 5 or 10 MPa are in the non-fracturing regime. Simulations are carried out at several different shearing velocities to examine the velocity dependence of friction. The normal and shear stresses acting on the shear zone walls are supported by complex networks of interparticle forces that span the gouge zones. Interparticle forces greater than average define inclined force chains that evolve as the gouge deforms, mapping the internal stress and deformation field. Boundary conditions strongly influence the stability of the force chains. Rough boundaries couple with the gouge zone, causing distributed deformation and continuous reorganization of the force chains. Stress drops occur when major force chains fail and, as in laboratory experiments, their magnitudes correlate directly with the mean size of the particles. In contrast, shear zones with smoother boundaries develop enduring boundary shears that preserve the internal force network; stress drops accompany the onset and cessation of boundary shearing, and are unrelated to particle size. Particle size and boundary conditions also affect the fabric of the shear zone's force network. The mean force orientation within the shear zone shows a dependence on particle size for smooth boundaries, but not for rough boundaries. At the scale of individual particle contacts, the effective radii of two particles in contact appears to dictate the orientation and magnitude of the interparticle force. In general, smaller particles support smaller forces at low angles to horizontal, while larger particles support larger forces closer to the vertical. When time-dependent contact healing is added to the simulations, velocity dependence of certain quantities is also observed, e.g., contact force magnitude, ratio of sliding contacts, and related micromechanical quantities. Velocity stepping experiments result in time-dependent stress drops and gouge strengthening behavior that generally conform to the results of laboratory experiments.

Halpert, A.; Morgan, J. K.

2005-12-01

191

Subglacial bedforms reveal an exponential size-frequency distribution  

Science.gov (United States)

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

192

The Decision to Become an Entrepreneur and the Firm Size Distribution: A Unifying Framework for Policy Analysis  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Developing and emerging economies have high entrepreneurship rates and relatively many small firms. There is enormous heterogeneity among these firms and entrepreneurs. This paper presents a simple occupational choice model that captures motives for entrepreneurship at both edges of the size distribution. The model is then used to analyse the effects of productivity growth, distortions, financial and labor market frictions, and risk. Capturing entrepreneurship across the size distribution all...

Poschke, Markus

2013-01-01

193

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

Directory of Open Access Journals (Sweden)

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

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

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

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

A. Asmi

2011-06-01

194

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

Directory of Open Access Journals (Sweden)

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

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

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

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

A. Asmi

2011-03-01

195

Nano to micro particle size distribution measurement in the fluid by interactive force apparatus for fine particle processing.  

Science.gov (United States)

The direct measurement of fine particles size distribution of dispersions or coagulations in liquid is important for water purification, fine particles separation for recycling and mineral processing, as well as the new material production. The nano to micro particle size is usually measured by light scattering method; however, it is difficult to measure at high concentration of suspension. Here, a novel dynamical method by using the interactive force measurement between particles in liquid under electric field is used for measuring distribution of fine particle. Three types of nano to submicron particles, that is well-dispersed nano particles, coagulated nano particles and settled submicron particles, have been measured by interactive force measurement method. The particle size distributions are compered with the size distributions of dried particles measured by TEM or SEM. The well-dispersed nano particle size distribution by interactive force measurement is influenced by the nano size surfactant micelles. The size distribution of coagulated nano particles in water is larger than the result by TEM. On the other hand, the submicron nickel particle size distribution is similar with the one analyzed by SEM. PMID:24266212

Fujita, Toyohisa; Dodbiba, Gjergj; Okaya, Katsunori; Matsuo, Seiji; Wang, Li Pang; Onda, Kana; Otsuki, Akira

2013-12-01

196

Effects of Fractal Size Distributions on Velocity Distributions and Correlations of a Polydisperse Granular Gas  

International Nuclear Information System (INIS)

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

197

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

Science.gov (United States)

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

198

Electricité, de la production à la distribution  

CERN Document Server

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

199

Distribution of aflatoxins in contaminated corn fractions segregated by size  

Directory of Open Access Journals (Sweden)

Full Text Available The efficiency of segregation, by particle size, in reducing the aflatoxin content of corn lots under the Brazilian conditions was studied. The aflatoxin content, in the corn fractions obtained after sieving thirty contaminated samples, with approximately 3.0 kg each, was determined. The samples were passed through 4.5 mm round-hole sieves and the fractions with particles ³4.5 mm (fraction A and <4.5 mm (fraction B and then analyzed for aflatoxins by TLC. The results showed that the distribution of the aflatoxins among the fractions A and B varied from sample to sample. However, the fraction B presented higher content (6 to 1,422 µg/kg of aflatoxins (P<5%, than samples of fraction A (4 to 389 µg/kg. In spite of that the segregation of this fraction did not reduce significantly the contamination of the samples. This probably occurred because the contribution of the fraction B for the estimated total of the concentration of aflatoxin of the sample was smaller than that of the fraction A, due to the smallest amount of the fraction B in the sample weight total. In spite of being significant for the studied samples the correlation among the percentages of the groups of grains with defects a burning grains, sprouted, burned and moldy and b total injured, with the estimated level of contamination for the samples, more studies will be necessary so that better conclusions can be drawn for this correlation.

Piedade Fabiana S.

2002-01-01

200

Ceramic Membrane Fabrication from Industrial Waste: Effect of Particle Size Distribution on the Porosity  

Directory of Open Access Journals (Sweden)

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

I. Norliza

2009-01-01

 
 
 
 
201

Progresses in the production of large-size THGEM boards  

Science.gov (United States)

The THicK GEM (THGEM) electron multipliers are derived from the GEM design, by scaling the geometrical parameters and changing the production technology. Small-size (a few cm2) detectors exhibit superb performance, while larger ones exhibit gain response and uniformity limitations. We have studied with a systematic approach several aspects concerning the material (type and thickness of the fibreglass plates) and the production procedure, in particular the cleaning and polishing stages. The net result is the production of large THGEM multipliers reproducing the performance of the small ones. We report in detail about the studies and the results.

Alexeev, M.; Birsa, R.; Bradamante, F.; Bressan, A.; Büchele, M.; Chiosso, M.; Ciliberti, P.; Dalla Torre, S.; Dasgupta, S.; Denisov, O.; Duic, V.; Finger, M.; Finger, M., Jr.; Fischer, H.; Giorgi, M.; Gobbo, B.; Gregori, M.; Herrmann, F.; Königsmann, K.; Levorato, S.; Maggiora, A.; Martin, A.; Menon, G.; Novakova, K.; Novy, J.; Panzieri, D.; Pereira, F. A.; Santos, C. A.; Sbrizzai, G.; Schiavon, P.; Schopferer, S.; Slunecka, M.; Sozzi, F.; Steiger, L.; Sulc, M.; Takekawa, S.; Tessarotto, F.; Veloso, J. F. C. A.

2014-03-01

202

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 stereologic...

Yuri Gulbin

2011-01-01

203

Environmental pesticide distribution in horticultural and floricultural periurban production units.  

Science.gov (United States)

The environmental pesticide distribution on non-target systems (soil, drift and agricultural plastics) during the application step at small periurban production units, was studied in open field and greenhouses, for different crops (tomato, lettuce, broccoli, strawberry and flowers) using different pesticides (endosulfan, procymidone, chlorothalonil, chlorpyrifos and deltamethrin). In all cases, soil was the most exposed non-target system. For greenhouses, a general pesticide distribution was found of approximately 2/3 for crop, 1/4 for soil and 1/20 for plastic, of the total amount applied. In horticultural open fields, although the distribution was very dependent on the crop size and type, soil was also the most exposed non-target subsystem. Pesticide drift seems not to be significant in these production units, whilst pesticide accumulation on agricultural plastics reached up to 45% of the total applied, for polyethylene mulching in strawberry fields. PMID:22285036

Querejeta, Giselle A; Ramos, Laura M; Flores, Andrea P; Hughes, Enrique A; Zalts, Anita; Montserrat, Javier M

2012-04-01

204

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

CERN Document Server

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

205

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

206

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

International Nuclear Information System (INIS)

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

207

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

Science.gov (United States)

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

Attanasi, Emil D.; Charpentier, Ronald R.

2007-01-01

208

The grain-size distribution of pyroclasts: Primary fragmentation, conduit sorting or abrasion?  

Science.gov (United States)

Explosive volcanic eruptions expel a mixture of pyroclasts and lithics. Pyroclasts, fragments of the juvenile magma, record the state of the magma at fragmentation in terms of porosity and crystallinity. The grain size distribution of pyroclasts is generally considered to be a direct consequence of the conditions at magma fragmentation that is mainly driven by gas overpressure in bubbles, high shear rates, contact with external water or a combination of these factors. Stress exerted by any of these processes will lead to brittle fragmentation by overcoming the magma's relaxation timescale. As a consequence, most pyroclasts exhibit angular shapes. Upon magma fragmentation, the gas pyroclast mixture is accelerated upwards and eventually ejected from the vent. The total grain size distribution deposited is a function of fragmentation conditions and transport related sorting. Porous pyroclasts are very susceptible to abrasion by particle-particle or particle-conduit wall interaction. Accordingly, pyroclastic fall deposits with angular clasts should proof a low particle abrasion upon contact to other surfaces. In an attempt to constrain the degree of particle interaction during conduit flow, monomodal batches of washed pyroclasts have been accelerated upwards by rapid decompression and subsequently investigated for their grain size distribution. In our set-up, we used a vertical cylindrical tube without surface roughness as conduit. We varied grain size (0.125-0.25; 0.5-1; 1-2 mm), porosity (0; 10; 30 %), gas-particle ratio (10 and 40%), conduit length (10 and 28 cm) and conduit diameter (2.5 and 6 cm). All ejected particles were collected after settling at the base of a 3.3 m high tank and sieved at one sieve size below starting size (half-?). Grain size reduction showed a positive correlation with starting grain size, porosity and overpressure at the vent. Although milling in a volcanic conduit may take place, porous pyroclasts are very likely to be a primary product of magma fragmentation at or close to the fragmentation level. Given the high abrasiveness of pumice, hemispherical clasts should be observed if clast break-up followed efficient clast abrasion. As a consequence, finer grained pyroclastic fall deposits do not necessarily proof efficient secondary fragmentation in the conduit but may rather reveal the influence of conduit length on 'What size of pyroclasts can be erupted'?

Kueppers, U.; Schauroth, J.; Taddeucci, J.

2013-12-01

209

Drop Size Distribution - Based Separation of Stratiform and Convective Rain  

Science.gov (United States)

For applications in hydrology and meteorology, it is often desirable to separate regions of stratiform and convective rain from meteorological radar observations, both from ground-based polarimetric radars and from space-based dual frequency radars. In a previous study by Bringi et al. (2009), dual frequency profiler and dual polarization radar (C-POL) observations in Darwin, Australia, had shown that stratiform and convective rain could be separated in the log10(Nw) versus Do domain, where Do is the mean volume diameter and Nw is the scaling parameter which is proportional to the ratio of water content to the mass weighted mean diameter. Note, Nw and Do are two of the main drop size distribution (DSD) parameters. In a later study, Thurai et al (2010) confirmed that both the dual-frequency profiler based stratiform-convective rain separation and the C-POL radar based separation were consistent with each other. In this paper, we test this separation method using DSD measurements from a ground based 2D video disdrometer (2DVD), along with simultaneous observations from a collocated, vertically-pointing, X-band profiling radar (XPR). The measurements were made in Huntsville, Alabama. One-minute DSDs from 2DVD are used as input to an appropriate gamma fitting procedure to determine Nw and Do. The fitted parameters - after averaging over 3-minutes - are plotted against each other and compared with a predefined separation line. An index is used to determine how far the points lie from the separation line (as described in Thurai et al. 2010). Negative index values indicate stratiform rain and positive index indicate convective rain, and, moreover, points which lie somewhat close to the separation line are considered 'mixed' or 'transition' type precipitation. The XPR observations are used to evaluate/test the 2DVD data-based classification. A 'bright-band' detection algorithm was used to classify each vertical reflectivity profile as either stratiform or convective, depending on whether or not a clearly-defined melting layer is present at an expected height, and if present, maximum reflectivity within the melting layer as well as the corresponding height are determined. We will present results of quantitative comparisons between the XPR observations-based classifications and the simultaneous 2DVD data-based classifications. Time series comparisons will be presented for thirteen events in Huntsville.

Thurai, Merhala; Gatlin, Patrick; Williams, Christopher

2014-01-01

210

Size distributions and dispersions along a 485-year chronosequence for sand dune vegetation.  

Science.gov (United States)

Using a sand dune chronosequence that spans 485 years of primary succession, we collected nearest-neighbor vegetation data to test two predictions associated with the traditional "size-advantage" hypothesis for plant competitive ability: (1) the relative representation of larger species should increase in later stages of succession; and (2) resident species that are near neighbors should, over successional time, become more similar in plant body size and/or seed size than expected by random assembly. The first prediction was supported over the time period between mid to later succession, but the second prediction was not; that is, there was no temporal pattern across the chronosequence indicating that either larger resident species, or larger seeded resident species, increasingly exclude smaller ones from local neighborhoods over time. Rather, neighboring species were generally more different from each other in seed sizes than expected by random assembly. As larger species accumulate over time, some relatively small species are lost from later stages of succession, but species size distributions nevertheless remain strongly right-skewed-even in late succession-and species of disparate sizes are just as likely as in early succession to coexist as immediate neighbors. This local-scale coexistence of disparate sized neighbors might be accounted for-as in traditional interpretations-in terms of species differences in "physical-space-niches" (e.g., involving different rooting depths), combined with possible facilitation effects. We propose, however, that this coexistence may also occur because competitive ability involves more than just a size advantage, with traits associated with survival (tolerance of intense competition) and fecundity (offspring production despite intense competition) being at least equally important. PMID:22837820

Waugh, Jennifer M; Aarssen, Lonnie W

2012-04-01

211

New image processing software for analyzing object size-frequency distributions, geometry, orientation, and spatial distribution  

Science.gov (United States)

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

Beggan, Ciarán; Hamilton, Christopher W.

2010-04-01

212

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

Science.gov (United States)

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

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

International Nuclear Information System (INIS)

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

214

Radioactivity size distributions of ambient aerosols in Helsinki, Finland during May 1986 after Chernobyl accident  

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)

215

On the size distribution of firms: additional evidence from the G7 countries  

Science.gov (United States)

We analyze the average size distribution of a pool of the G7 group's firms over the period 1987-2000. In particular, firm sizes are measured employing different proxies, and after conditioning on business cycle phases. We find that: (i) the empirical distributions are all consistent with a power law; (ii) point estimates suggest that only in limited cases the exponent is equal to -1, i.e., the resulting size distribution generally is not Zipf; (iii) regardless of the variable employed to measure firm sizes, firms are distributed more equally during recessions than during expansions.

Gaffeo, Edoardo; Gallegati, Mauro; Palestrini, Antonio

2003-06-01

216

Multi-component Erlang distribution of plant seed masses and sizes  

Science.gov (United States)

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

217

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

CERN Document Server

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

Mikosch, Thomas; 10.3150/10-BEJ255

2010-01-01

218

Concentrations and size distributions of fine aerosol particles measured at roof level in urban zone  

Science.gov (United States)

During the experimental Field Experiments to Constrain Models of Atmospheric Pollution and Transport of Emissions (ESCOMPTE) campaign in June-July 2001, concentrations and size distributions of fine particles (14-722 nm) were measured at roof level in downtown Marseille (France). Part of the campaign was dedicated to the study of aerosol behavior in relation to strong photochemical events (which were identified as "IOP" days) and their regional modeling. The analysis of the concentration variations and the evolution of average diurnal size distribution showed that an "IOP day" is not characterized by a specific concentration or its variation, nor by a specific evolution of the average size distribution. The morning traffic rush is detected at roof level by a net increase in particle concentration over the whole size range measured, indicating a production of ultrafine particles by the traffic but also the raising to roof level of particles of the accumulation mode. The increase is observed about 1 hour after the traffic peak at street level, which is characterized by strong increases in NOx and CO concentrations. The corresponding flux of particles at roof level has been estimated around 3 × 104 cm-2 s-1. A specific signature characterized by a strong and rapid burst of concentration (factor 2 to 4 in 15 min) of particles between 25 and 50 nm, independent of the traffic source, has been detected on six occasions during the campaign. These events occur systematically around noon, in cases of strong radiation, low relative humidity, and common wind direction. Despite the high-diameter value of these particles, it is suggested that they could result from a specific "secondary aerosol process" event involving ozone, biogenic, and/or anthropogenic gas precursors like iodine and VOCs.

Despiau, S.; Croci, D.

2007-05-01

219

Flow distribution in the accelerator-production-of-tritium target  

International Nuclear Information System (INIS)

Achieving nearly uniform flow distributions in the accelerator production of tritium (APT) target structures is an important design objective. Manifold effects tend to cause a nonuniform distribution in flow systems of this type, although nearly even distribution can be achieved. A program of hydraulic experiments is underway to provide a database for validation of calculational methodologies that may be used for analyzing this problem and to evaluate the approach with the most promise for achieving a nearly even flow distribution. Data from the initial three tests are compared to predictions made using four calculational methods. The data show that optimizing the ratio of the supply-to-return-manifold areas can produce an almost even flow distribution in the APT ladder assemblies. The calculations compare well with the data for ratios of the supply-to-return-manifold areas spanning the optimum value. Thus, the results to date show that a nearly uniform flow distribution can be achieved by carefully sizing the supply and return manifolds and that the calculational methods available are adequate for predicting the distributions through a range of conditions

220

The pore size distribution of the first and the second generation of silica monolithic stationary phases.  

Science.gov (United States)

The mesopore structure (pore size and its distribution) for the first and second generations of silica-based monolithic columns was determined by inverse size-exclusion chromatography. The effect of pore size distribution was considered via the molecular theory of size-exclusion chromatography. The molecular theory of chromatography allows taking into account the kinetics of the pore ingress and egress processes, the heterogeneity of the pore sizes and polymer polydispersity. Besides, the mesopore structure, the characteristic domain sizes of the macropores present in the first and second generations of silica-based monolithic columns were also characterized. PMID:25085822

Bacskay, Ivett; Sepsey, Annamária; Felinger, Attila

2014-09-12

 
 
 
 
221

Deconvolution of PDA size distributions from sprays of optically inhomogeneous liquids  

Science.gov (United States)

If Phase-Doppler-Anemometry (PDA) is applied to analyze a spray of an optically inhomogeneous liquid a broad particle size distribution is measured. PDA is unsuitable for many applications. To overcome this problem we propose a deconvolution method using the measured size distribution from a droplet generator. The method is described and measurements are conducted on a milk spray and a water spray. The deconvoluted milk distribution compares well with the water distribution.

Wriedt, Thomas; Manasse, Uwe; Bauckhage, K.

1993-08-01

222

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

International Nuclear Information System (INIS)

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

223

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

International Nuclear Information System (INIS)

This paper presents a study of the particle size distribution impact on neutron transport in three-dimensional stochastic media. An eigenvalue problem is simulated in a cylindrical container consisting of fissile fuel particles with five different size distributions: constant, uniform, power, exponential and Gaussian. We construct 15 cases by altering the fissile particle volume packing fraction and its optical thickness, but keeping the mean chord length of the spherical fuel particle the same at different size distributions. The tallied effective multiplication factor (keff) and flux distribution along axial and radial directions are compared between different size distributions. At low packing fraction and low optical thickness, the size distribution has a significant impact on radiation transport in stochastic media, which can cause as high as ?270 pcm difference in keff value and ?2.6% relative error difference in peak flux. As the packing fraction and optical thickness increase, the impact gradually dissipates. (authors)

224

Linking secondary structure of individual size distribution with nonlinear size-trophic level relationship in food webs.  

Science.gov (United States)

Existing individual size distribution (ISD) theories assume that the trophic level (TL) of an organism varies as a linear function of its log-transformed body size. This assumption predicts a power-law distribution of the ISD, i.e., a linear relationship between size and abundance in log space. However, the secondary structure of ISD (nonlinear dome shape structures deviating from a power-law distribution) is often observed. We propose a model that extends the metabolic theory to link the secondary structure of ISD to the nonlinear size-TL relationship. This model is tested with empirical data collected from a subtropical reservoir. The empirical ISD and size-TL relationships were constructed by FlowCAM imaging analysis and stable isotope analyses, respectively. Our results demonstrate that the secondary structure of ISD can be predicted from the nonlinear function of size-TL relationship and vice versa. Moreover, these secondary structures arise due to (1) zooplankton omnivory and (2) the trophic interactions within microbial food webs. PMID:24933809

Chang, Chun-Wei; Miki, Takeshi; Shiah, Fuh-Kwo; Kao, Shuh-Ji; Wu, Jiunn-Tzong; Sastri, Akash R; Hsieh, Chih-Hao

2014-04-01

225

Distributed energy production offers many advantages  

International Nuclear Information System (INIS)

In this interview with Daniel Dillier, President of the Board of the IWK company, the aims of the Swiss electricity business to build new nuclear power stations and the Swiss Government's proposals for the building of gas-steam combined cycle power plants are discussed. Dillier, in contrast, favours the construction of distributed combined heat and power (CHP) units. Dillier voices his opinions on this subject and stresses the advantages of distributed systems that combine the production of heat and electrical power. These systems can use renewable resources and provide a higher degree of system reliability and availability. A further topic discussed is that of carbon dioxide emissions, which Dillier notes as being 40 percent less than for conventional systems. The potential for the use of decentralised CHP units in Switzerland is examined

226

Batch sizing with controllable production rates in a multi-stage production system  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract In a recent paper, Glock [2010. Batch sizing with controllable production rates. International Journal of Production Research 20: 5925-5942] studied the impact of a variable production rate on the inventory build-up and the total costs in a two-stage production system. In this paper, we extend Glock’s (2010) model to a multi-stage production system where the production rate at each producing stage may be varied within given limits. We compare our model to the classical c...

2011-01-01

227

Optimizing the grain size distribution for talc-magnesite ore flotation  

Directory of Open Access Journals (Sweden)

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

?kvarla Jiøí

2001-06-01

228

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

Science.gov (United States)

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

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

2014-01-01

229

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

230

Effect of Flock Size on Fayoumi Layer Production  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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. Bi...

Muhammad Ismail Rind; Nasir Rajput; Rahmatullah Rind

2005-01-01

231

Size Distribution of Genesis Solar Wind Array Collector Fragments Recovered  

Science.gov (United States)

Genesis launched in 2001 with 271 whole and 30 half hexagonally-shaped collectors mounted on 5 arrays, comprised of 9 materials described in [1]. The array collectors were damaged during re-entry impact in Utah in 2004 [2], breaking into many smaller pieces and dust. A compilation of the number and approximate size of the fragments recovered was compiled from notes made during the field packaging performed in the Class 10,000 cleanroom at Utah Test and Training Range [3].

Allton, J. H.; Stansbery, E. K.; McNamara, K. M.

2005-01-01

232

Apollo 14 soils - Size distribution and particle types.  

Science.gov (United States)

Particle size characteristics are discussed together with particle types, abundances, variation in the soils, questions of soil maturity, coarse fines, and ropy glasses. It is found that agglutinates are formed primarily by micrometeorite impact into lunar soil. Agglutinates appear to be the major particle type now being formed on the lunar surface. Agglutinate content of a soil increases with particle track densities and with surface exposure time.

Mckay, D. S.; Heiken, G. H.; Taylor, R. M.; Clanton, U. S.; Morrison, D. A.; Ladle, G. H.

1972-01-01

233

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

Science.gov (United States)

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

Benjamini, Dan; Nevo, Uri

2013-05-01

234

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

235

DOES SIZE MATTER? THE UNDERLYING INTRINSIC SIZE DISTRIBUTION OF RADIO SOURCES AND IMPLICATIONS FOR UNIFICATION BY ORIENTATION  

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

236

DOES SIZE MATTER? THE UNDERLYING INTRINSIC SIZE DISTRIBUTION OF RADIO SOURCES AND IMPLICATIONS FOR UNIFICATION BY ORIENTATION  

International Nuclear Information System (INIS)

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

237

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

238

Evidence of bimodal crystallite size distribution in ?c-Si:H films  

International Nuclear Information System (INIS)

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.

239

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

Science.gov (United States)

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

Köser, Ole; Wriedt, Thomas

1996-05-01

240

Determination of the relative number distribution of particle sizes using photon correlation spectroscopy  

International Nuclear Information System (INIS)

We investigate the determination of relative number distributions of particle sizes using photon correlation spectroscopy (PCS). To distinguish our work from earlier results, we have studied the extraction of the number distribution, relative number as a function of size, from the intensity distribution, relative scattered intensity vs size, and set limits on its usefulness. Expressions relating the scattering intensity distribution to the number distribution are presented. These results are connected to the output of two common PCS analysis techniques, the method of cumulants, and the inverse Laplace transform. These results are tested, and limits are set by generating a synthetic intensity autocorrelation function from a known number distribution and comparing the recovered number distribution to the input. We find good agreement for distributions narrower than a geometric width of 1.40

 
 
 
 
241

On the impact of grain size distribution on the plastic behaviour of polycrystalline metals  

International Nuclear Information System (INIS)

Recent experimental studies have reported improved combinations of strength and uniform elongation in ultrafine-grained polycrystals with bi-modal grain size distributions. Despite these results, the extent to which the grain size distribution affects macroscopic tensile response, particularly at large strains, is unclear. This issue is examined here for polycrystals with varying grain sizes and grain size distributions using a grain size dependent constitutive model within the viscoplastic self-consistent formalism. The evolution of the macroscopic and grain-level stresses and strains has been monitored as a function of the width and mean of the grain size distribution. As an example of highly heterogeneous structures, the stress–strain response of a number of bi-modal microstructures have been examined and compared with their uni-modal counterparts

242

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

2011-05-01

243

The behaviour of water droplet size distributions interacting with radiation  

International Nuclear Information System (INIS)

The interaction with radiation can induce condensation on, or evaporation from, a cloud of water droplets. The effect is important in atomospheric physics, and may also be important for other water aerosols such as one produced in the containment of a PWR (pressurized water reactor) following a possible nuclear accident. Here, we examine the general problem of a water droplet distribution interacting with radiation and give some specific methods for its partial solution. (author)

244

Calculation of pore size distributions of activated carbons from adsorption isotherms  

Energy Technology Data Exchange (ETDEWEB)

The ability to determine whether a pore size distribution can be fitted to a given set of experimental data is relevant to the development of pore network models of the internal structure of activated carbons and other amorphous adsorbents. A closely related problem that arises when pore size distributions can be fitted to a given set of data is to determine suitable methods to calculate reliable, stable, and representative pore size distributions. This paper addresses both of these issues by presenting a procedure to determine whether a pre size distribution based on a specified model pore geometry can be fitted to a set of experimental data and then using this procedure, in conjunction with regularization techniques that stabilize the calculations, to determine statistically significant pore size distributions. This approach has been demonstrated using the adsorption of methane at 308 K onto BPL-activated carbon as a case study.

Davies, G.M.; Seaton, N.A.; Vassiliadis, V.S.

1999-11-09

245

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

International Nuclear Information System (INIS)

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

246

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

Science.gov (United States)

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

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

2014-04-21

247

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

International Nuclear Information System (INIS)

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

248

Techniques for measuring particle size distribution of particulate matter emitted from animal feeding operations  

Science.gov (United States)

While various techniques for measuring particle size distributions (PSD) of particulate matter (PM) exist, there is no a single agreed upon standard or reference method for PM with different characteristics. This study investigated differences in the PSD measurements by four PSD analyzers: LS13 320 multi-wave length laser diffraction particle size analyzer, LS230 laser diffraction particle size analyzer, LA-300 laser scattering particle size analyzer, and Coulter Counter Multisizer3 (CCM3). Simultaneously collected total suspended particulate (TSP) samples in a commercial egg production house were analyzed by the four analyzers for PSDs. In addition, four types of testing powders (limestone, starch, No.3 micro aluminum, and No.5 micro aluminum) were also analyzed by these four PSD analyzers. The results suggest when comparing measured mass median diameters (MMDs) and geometric standard deviations (GSD) of the PSDs, the laser diffraction method (LS13 320, LS230 and LA-300) provided larger MMDs and broader distributions (GSDs) than the electrical sensing zone method (CCM3) for all samples. When comparing mass fractions of PM10 and PM2.5 between the measured values and the lognormal fitting values derived from the measured MMDs and GSDs, lognormal fitting method produced reasonably accurate PM10 mass fraction estimations (within 5%), but it failed to produce accurate PM2.5 mass fraction estimations. The measured PM2.5 mass fractions significantly differed from the lognormal fitting PM2.5 fractions and the mean differences reached as high as 95%. It is strongly recommended that when reporting a PSD of certain PM samples, in addition to MMD and GSD, the mass fractions of PM10 and PM2.5 should also be reported.

Wang-Li, Lingjuan; Cao, Zihan; Buser, Michael; Whitelock, Derek; Parnell, Calvin B.; Zhang, Yuanhui

2013-02-01

249

Crystal size distribution of aluminum potassium sulfate in a batch crystallizer equipped with different types of impeller  

Science.gov (United States)

In order to investigate the effect of impeller type on the crystal size distributions, three different types of impellers, which produce different flow patterns were used in the crystallization of aluminum potassium sulfate in a seeded batch crystallizer. Two maxima in size distributions were obtained when impellers producing radial flow are used at higher impeller speeds, whereas only a single maximum was obtained for the impeller producing axial flow. The mean crystal size was largest for the latter. The flow pattern, particle motion and impact frequency of different impellers were measured in detail prior to the above experiment in order to explain the results obtained. The maxima at the smaller and larger sizes were inferred to secondary nucleation due to the impact of particles on vessel wall and the agglomeration of product crystals, respectively.

Shimizu, Kenji; Nomura, Toshio; Takahashi, Koji

1998-01-01

250

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.

251

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

Science.gov (United States)

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 aerosol (SOA). 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 multi-generation 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 mid-experiment aldehyde injection confirms that heterogeneous reaction of aldehydes with organic hydroperoxides forming peroxyhemiacetals can lead to a large increase in SOA mass. The results of the current work have a number of implications for SOA models. While the dynamics of an aerosol size distribution reflects the mechanism of growth, we demonstrate here that it provides a key constraint in interpreting laboratory and ambient SOA formation. This work, although carried out specifically for the long chain alkane, dodecane, is expected to be widely applicable to other major classes of SOA precursors. SOA consists of a myriad of organic compounds containing various functional groups, which can generally undergo heterogeneous/multiphase reactions forming low-volatility products such as oligomers and other high molecular mass compounds. If particle-phase chemistry is indeed central to SOA growth in general, the size-resolved SOA formation is better described in terms of kinetically limited condensational growth, rather than solely by thermodynamic equilibrium partitioning.

Shiraiwa, M.; Yee, L. D.; Schilling, K.; Loza, C. L.; Craven, J. S.; Zuend, A.; Ziemann, P. J.; Seinfeld, J.

2013-12-01

252

Cluster size distribution in the autocatalytic growth model  

CERN Document Server

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

J?drak, Jakub

2013-01-01

253

Quantitative analysis of crystal/grain sizes and their distributions in 2D and 3D  

DEFF Research Database (Denmark)

We review methods to estimate the average crystal (grain) size and the crystal (grain) size distribution in solid rocks. Average grain sizes often provide the base for stress estimates or rheological calculations requiring the quantification of grain sizes in a rock’s microstructure. The primary data for grain size data are either 1D (i.e. line intercept methods), 2D (area analysis) or 3D (e.g., computed tomography, serial sectioning). These data have been used for different data treatments over the years, whereas several studies assume a certain probability function (e.g., logarithm, square root) to calculate statistical parameters as the mean, median, mode or the skewness of a crystal size distribution. The finally calculated average grain sizes have to be compatible between the different grain size estimation approaches in order to be properly applied, for example, in paleo-piezometers or grain size sensitive flow laws. Such compatibility is tested for different data treatments using one- and two-dimensional measurements. We propose an empirical conversion matrix for different datasets. These conversion factors provide the option to make different datasets compatible with each other, although the primary calculations were obtained in different ways. In order to present an average grain size, we propose to use the area-weighted and volume-weighted mean in the case of unimodal grain size distributions, respectively, for 2D and 3D measurements. The shape of the crystal size distribution is important for studies of nucleation and growth of minerals. The shape of the crystal size distribution of garnet populations is compared between different 2D and 3D measurements, which are serial sectioning and computed tomography. The comparison of different direct measured 3D data; stereological data and direct presented 2D data show the problems of the quality of the smallest grain sizes and the overestimation of small grain sizes in stereological tools, depending on the type of CSD.

Berger, Alfons; Herwegh, Marco

2011-01-01

254

Methods for determining particle size distribution and growth rates between 1 and 3 nm using the Particle Size Magnifier  

CERN Document Server

The most important parameters describing the atmospheric new particle formation process are the particle formation and growth rates. These together determine the amount of cloud condensation nuclei attributed to secondary particle formation. Due to difficulties in detecting small neutral particles, it has previously not been possible to derive these directly from measurements in the size range below about 3 nm. The Airmodus Particle Size Magnifier has been used at the SMEAR II station in Hyytiälä, southern Finland, and during nucleation experiments in the CLOUD chamber at CERN for measuring particles as small as about 1 nm in mobility diameter. We developed several methods to determine the particle size distribution and growth rates in the size range of 1–3 nm from these data sets. Here we introduce the appearance-time method for calculating initial growth rates. The validity of the method was tested by simulations with the Ion-UHMA aerosol dynamic model.

Lehtipalo, Katrianne; Kontkanen, Jenni; Kangasluoma, Juha; Franchin, Alessandro; Wimmer, Daniela; Schobesberger, Siegfried; Junninen, Heikki; Petäjä, Tuukka; Sipilä, Mikko; Mikkilä, Jyri; Vanhanen, Joonas; Worsnop, Douglas R; Kulmala, Markku

2014-01-01

255

Methodology for determining rom size distribution / Metodologia para determinação de curva granulométrica de rom  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese A metodologia para determinar a curva granulométrica de ROM foi desenvolvida em uma mina de ferro localizada no Brasil. O tamanho dos blocos maiores foi determinado a partir de fotografias, por meio das quais foi definida uma escala para analisar as dimensões dos blocos (comprimento e área). Isso fo [...] i implementado de acordo com um protocolo de amostragem específico, que envolve etapas de divisão e de homogeneização in situ de uma considerável quantidade de minério (cerca de 259 toneladas). Durante o processo de amostragem, os blocos maiores foram segregados, para mensuração, por análise de imagens, enquanto que os de menor tamanho foram peneirados. A metodologia foi desenvolvida para avaliar, inicialmente, o desempenho de um britador giratório, alimentado por basculamento direto, a partir de caminhões. Condições operacionais desse tipo de equipamento, tais como configurações das aberturas de posição aberta (APA) e de posição fechada (APF), podem ser ajustadas previamente, permitindo, assim, a obtenção de diferentes distribuições de tamanho de produto. A variabilidade de tamanho dos fragmentos afeta diretamente os estágios seguintes de britagem, podendo causar um aumento significativo na carga circulante do circuito. Isto leva a uma diminuição da produtividade e recuperação nas etapas posteriores. Os resultados de granulometria de ROM mostraram erros de reprodutibilidade e viés desprezíveis para o protocolo de amostragem desenvolvido, aplicado em itabirito friável. Abstract in english A methodology to determine the size distribution curve of the ROM was developed in a Brazilian iron ore mine. The size of the larger fragments was determined taking photographs and setting the scale of the images to analyze their dimensions (length of their edges and areas). This was implemented acc [...] ording to a specific protocol of sampling that involves split and homogenization stages in situ of a considerable quantity of ore (about 259 metric tonnes). During the sampling process, larger fragments were separated and smaller size material was screened. The methodology was developed initially in order to preview the performance of a primary gyratory crusher that is fed directly from trucks. Operational conditions of the equipment such as closed and open-side settings could be adjusted previously, obtaining different product size distributions. Variability of size of the fragments affects subsequent stages of crushing and can increase circulating load in the circuit. This leads to a decrease of productivity or recovery of the ore dressing. The results showed insignificant errors of accuracy and reproducibility of the sampling protocol when applied to friable itabirite rocks.

Christiane Ribeiro da, Silva; Vládia C. G. de, Souza; Jair C., Koppe.

2014-12-01

256

Methodology for determining rom size distribution / Metodologia para determinação de curva granulométrica de rom  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese A metodologia para determinar a curva granulométrica de ROM foi desenvolvida em uma mina de ferro localizada no Brasil. O tamanho dos blocos maiores foi determinado a partir de fotografias, por meio das quais foi definida uma escala para analisar as dimensões dos blocos (comprimento e área). Isso fo [...] i implementado de acordo com um protocolo de amostragem específico, que envolve etapas de divisão e de homogeneização in situ de uma considerável quantidade de minério (cerca de 259 toneladas). Durante o processo de amostragem, os blocos maiores foram segregados, para mensuração, por análise de imagens, enquanto que os de menor tamanho foram peneirados. A metodologia foi desenvolvida para avaliar, inicialmente, o desempenho de um britador giratório, alimentado por basculamento direto, a partir de caminhões. Condições operacionais desse tipo de equipamento, tais como configurações das aberturas de posição aberta (APA) e de posição fechada (APF), podem ser ajustadas previamente, permitindo, assim, a obtenção de diferentes distribuições de tamanho de produto. A variabilidade de tamanho dos fragmentos afeta diretamente os estágios seguintes de britagem, podendo causar um aumento significativo na carga circulante do circuito. Isto leva a uma diminuição da produtividade e recuperação nas etapas posteriores. Os resultados de granulometria de ROM mostraram erros de reprodutibilidade e viés desprezíveis para o protocolo de amostragem desenvolvido, aplicado em itabirito friável. Abstract in english A methodology to determine the size distribution curve of the ROM was developed in a Brazilian iron ore mine. The size of the larger fragments was determined taking photographs and setting the scale of the images to analyze their dimensions (length of their edges and areas). This was implemented acc [...] ording to a specific protocol of sampling that involves split and homogenization stages in situ of a considerable quantity of ore (about 259 metric tonnes). During the sampling process, larger fragments were separated and smaller size material was screened. The methodology was developed initially in order to preview the performance of a primary gyratory crusher that is fed directly from trucks. Operational conditions of the equipment such as closed and open-side settings could be adjusted previously, obtaining different product size distributions. Variability of size of the fragments affects subsequent stages of crushing and can increase circulating load in the circuit. This leads to a decrease of productivity or recovery of the ore dressing. The results showed insignificant errors of accuracy and reproducibility of the sampling protocol when applied to friable itabirite rocks.

Christiane Ribeiro da, Silva; Vládia C. G. de, Souza; Jair C., Koppe.

257

Verification of CR-39 Technique for Attached Radon Progeny Size Distribution  

International Nuclear Information System (INIS)

Full text: A new type cascade impactor has been developed to determine the activity size distribution of radon and thoron progeny in a living environment more efficiently. The modified impactor consists of 4 stages for the collection of aerosol samples. The aerosol cut points in the impactor are set for 10, 2.5, 1 and 0.5 ? m at a flow rate of 4 L.min-1. Five CR-39 chips were used as alpha detectors for each stage. In order to separate ? particles emitted from radon and thoron progeny, CR-39 detectors are covered with aluminum-vaporized Mylar films. Thickness of films is properly adjusted to allow ? particles emitted from radon and thoron progeny to reach the CR-39 detectors. In addition, a 400-mesh metal wire screen was mounted as diffusion collector at the air inlet of the impactor to remove the unattached fraction of radon and thoron decay products. Validation of the technique was performed with the commercial devices. The results confirmed that the developed technique can provide us significant information to estimate the activity size distribution of attached radon and thoron progeny for dose assessment

258

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

Science.gov (United States)

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

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

2014-07-01

259

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 flow field flow fractionation (aF-FFF) measurements, and we calculated particle sizes with the help of X-ray diffraction (XRD) patterns and the shift of the band gap absorption in the UV-vis spectrum. T...

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

2009-01-01

260

Ultrasonically triggered freezing of aqueous solutions: Influence of initial oxygen content on ice crystals' size distribution  

Science.gov (United States)

Samples of mannitol's aqueous solution at various contents of dissolved oxygen were frozen with the help of ultrasound and the ice crystals size distributions were measured by optical microscopy. Increasing the oxygen content led to a fair decreasing of the average crystals size and an increasing of the homogeneity of the size of crystals within the sample. The average size appeared simply as inversely proportional to the oxygen content in the initial liquid solution.

Jabbari-Hichri, Amira; Peczalski, Roman; Laurent, Pierre

2014-09-01

 
 
 
 
261

Photon correlation spectroscopic study of the size distribution of phospholipid vesicles.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The dependence of phospholipid vesicle size on lipid composition is investigated by photon correlation spectroscopy. For each lipid composition prolonged ultracentrifugation was used to isolate a nearly uniform population of minimum-sized vesicles. The residual size variations in the samples were sufficient to cause polydispersity that made comparisons between samples difficult. Analyses of the data by the method of cumulants and by a method for approximating the particle size distributions d...

Goll, J.; Carlson, F. D.; Barenholz, Y.; Litman, B. J.; Thompson, T. E.

1982-01-01

262

Effect size measurement in functional milk product marketing  

Directory of Open Access Journals (Sweden)

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

Karmen Pažek

2011-12-01

263

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

Science.gov (United States)

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

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

2010-01-01

264

Size distribution of autotrophy and microheterotrophy in reservoirs: implications for foodweb structure  

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 (< 8.0 ?m) and free-living bacteria (< 3.0 ?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 ?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

265

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

Science.gov (United States)

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

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

2012-12-01

266

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

Directory of Open Access Journals (Sweden)

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

J. F. Kok

2011-10-01

267

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

Directory of Open Access Journals (Sweden)

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

J. F. Kok

2011-07-01

268

Estimating Functions of Distributions Defined over Spaces of Unknown Size  

Directory of Open Access Journals (Sweden)

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

David H. Wolpert

2013-10-01

269

First-principles derivation of static avalanche-size distributions.  

Science.gov (United States)

We study the energy minimization problem for an elastic interface in a random potential plus a quadratic well. As the position of the well is varied, the ground state undergoes jumps, called shocks or static avalanches. We introduce an efficient and systematic method to compute the statistics of avalanche sizes and manifold displacements. The tree-level calculation, i.e., mean-field limit, is obtained by solving a saddle-point equation. Graphically, it can be interpreted as the sum of all tree graphs. The 1-loop corrections are computed using results from the functional renormalization group. At the upper critical dimension the shock statistics is described by the Brownian force model (BFM), the static version of the so-called Alessandro-Beatrice-Bertotti-Montorsi (ABBM) model in the nonequilibrium context of depinning. This model can itself be treated exactly in any dimension and its shock statistics is that of a Lévy process. Contact is made with classical results in probability theory on the Burgers equation with Brownian initial conditions. In particular we obtain a functional extension of an evolution equation introduced by Carraro and Duchon, which recursively constructs the tree diagrams in the field theory. PMID:23005046

Le Doussal, Pierre; Wiese, Kay Jörg

2012-06-01

270

Estimating Functions of Distributions Defined over Spaces of Unknown Size  

CERN Document Server

We consider Bayesian estimation of information-theoretic quantities from data, using a Dirichlet prior. Acknowledging the uncertainty of the event space size $m$ and the Dirichlet prior's concentration parameter $c$, we treat both as random variables set by a hyperprior. We show that the associated hyperprior, $P(c, m)$, obeys a simple "Irrelevance of Unseen Variables" (IUV) desideratum iff $P(c, m) = P(c) P(m)$. Thus, requiring IUV greatly reduces the number of degrees of freedom of the hyperprior. Some information-theoretic quantities can be expressed multiple ways, in terms of different event spaces, e.g., mutual information. With all hyperpriors (implicitly) used in earlier work, different choices of this event space lead to different posterior expected values of these information-theoretic quantities. We show that there is no such dependence on the choice of event space for a hyperprior that obeys IUV. We also derive a result that allows us to exploit IUV to greatly simplify calculations, like the poster...

Wolpert, David H

2013-01-01

271

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

2011-06-01

272

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

International Nuclear Information System (INIS)

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

273

Steady-State Size Distributions for Collisional Populations: Analytical Solution with Size-Dependent Strength  

CERN Document Server

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

O'Brien, David P

2014-01-01

274

Estimated variability of below-cloud aerosol removal by rainfall for observed aerosol size distributions  

Directory of Open Access Journals (Sweden)

Full Text Available Below-cloud scavenging (BCS coefficients of aerosols by rainfall are estimated for reported aerosol size distributions measured during field experiments in various environments. The method employed is based on explicit calculations of the efficiency of collision between a raindrop and aerosol particles. Such BCS coefficients can be used in numerical models that describe: 1 the detailed evolution of aerosol size distribution and, 2 the evolution of total aerosol mass concentration. The effects of raindrop size distribution and aerosol size distribution variability on BCS coefficients are illustrated using observed data. Results show that BCS coefficient increases with rainfall rate and has a significant dependence on aerosol size distribution parameters. Thus, BCS is important for very small particles (with diameters less than 0.01 $mu$m and for coarse particles (with diameters larger than 2 µm. For rainfall rate R ~ 1 mm hr-1, the 0.5-folding time of these particles is of the order of one hour. It is shown that BCS is negligible for aerosol particles in the range [0.1-1] µm if compared with in-cloud scavenging rates for low and moderate rainfall rates ( R ~ 0.1-10 mm hr-1. The results indicate that a boundary layer aerosol size distribution with coarse mode is drastically affected very shortly after rain starts (in a fraction of one hour and consequently, the below-cloud aerosol size distribution becomes dominated by particles in the accumulation mode.

C. Andronache

2003-01-01

275

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

Science.gov (United States)

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

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

2014-08-01

276

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

Directory of Open Access Journals (Sweden)

Full Text Available Particle size distribution from biomass combustion is an important parameter as it affects air quality, climate modelling and health effects. To date particle size distributions reported from prior studies vary not only due to difference in fuels but also difference in experimental conditions. This study aims to report characteristics of particle size distribution in a well controlled repeatable lab scale biomass fires for southwestern US fuels. The combustion facility at the USDA Forest Service's Fire Science Laboratory (FSL, Missoula, MT provided repeatable combustion and dilution environment ideal for particle size distribution study. For a variety of fuels tested the major mode of particle size distribution was in the range of 29 to 52 nm, which was attributable to dilution of the fresh smoke. Comparing volume size distribution from Fast Mobility Particle Sizer (FMPS and Aerodynamic Particle Sizer (APS measurements, ~30% of particle volume was attributable to the particles ranging from 0.5 to 10 ?m for PM10. Geometric mean diameter rapidly increased during flaming and gradually decreased during mixed and smoldering phase combustion. Most of fuels gave unimodal distribution during flaming phase and strong biomodal distribution during smoldering phase. The mode of combustion (flaming, mixed and smoldering could be better distinguished using slopes in Modified Combustion Efficiency (MCE vs. geometric mean diameter from each mode of combustion than only using MCE values.

S. Hosseini

2010-04-01

277

Particle size distribution measurements of manganese-doped ZnS nanoparticles.  

Science.gov (United States)

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 flow field flow fractionation (aF-FFF) measurements, and we calculated particle sizes with the help of X-ray diffraction (XRD) patterns and the shift of the band gap absorption in the UV-vis spectrum. The different methods are explained, and their limitations are discussed, with the conclusion that only a combination of different techniques can yield a realistic and complete picture about the size distribution of the sample. From these methods TEM, AUC, DLS, and aF-FFF measure the actual particle size distribution either in dispersion or after drying of the sample, whereas the particle size obtained from XRD patterns and with the help of the band gap widening corresponds to the average size of the crystal domains within the particles. We obtained particle size distributions with their maximum between 3 and 7 nm and a mean crystallite size of 3.5-4 nm. PMID:19374425

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

2009-05-15

278

Magnetic pattern at supergranulation scale: the void size distribution  

Science.gov (United States)

The large-scale magnetic pattern observed in the photosphere of the quiet Sun is dominated by the magnetic network. This network, created by photospheric magnetic fields swept into convective downflows, delineates the boundaries of large-scale cells of overturning plasma and exhibits "voids" in magnetic organization. These voids include internetwork fields, which are mixed-polarity sparse magnetic fields that populate the inner part of network cells. To single out voids and to quantify their intrinsic pattern we applied a fast circle-packing-based algorithm to 511 SOHO/MDI high-resolution magnetograms acquired during the unusually long solar activity minimum between cycles 23 and 24. The computed void distribution function shows a quasi-exponential decay behavior in the range 10-60 Mm. The lack of distinct flow scales in this range corroborates the hypothesis of multi-scale motion flows at the solar surface. In addition to the quasi-exponential decay, we have found that the voids depart from a simple exponential decay at about 35 Mm.

Berrilli, F.; Scardigli, S.; Del Moro, D.

2014-08-01

279

Magnetic pattern at supergranulation scale: the Void Size Distribution  

CERN Document Server

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

Berrilli, Francesco; Del Moro, Dario

2014-01-01

280

Scale-free Universal Spectrum for Atmospheric Aerosol Size Distribution for Davos, Mauna Loa and Izana  

CERN Document Server

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

Selvam, A M

2011-01-01

 
 
 
 
281

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

CERN Document Server

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

282

Characterization of energy barrier and particle size distribution of lyophilized ferrofluids by magnetic relaxation measurements  

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

283

Characterization of energy barrier and particle size distribution of lyophilized ferrofluids by magnetic relaxation measurements  

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

284

Effect of a polynomial arbitrary dust size distribution on dust acoustic solitons  

Energy Technology Data Exchange (ETDEWEB)

The investigation of dust-acoustic solitons when dust grains are size-distributed and ions adiabatically heated is conducted. The influence of an arbitrary dust size-distribution described by a polynomial function on the properties of dust acoustic waves is investigated. An energy-like integral equation involving Sagdeev potential is derived. The solitary solutions are shown to undergo a transformation into cnoidal ones under some physical conditions. The dust size-distribution can significantly affect both lower and upper critical Mach numbers for both solitons and cnoidal solutions.

Ishak-Boushaki, M.; Djellout, D.; Annou, R. [Faculty of Physics, USTHB, P.B. 32 El Alia, Bab-ezzouar, Algiers (Algeria)

2012-07-15

285

Particle size distributions by transmission electron microscopy: an interlaboratory comparison case study  

Science.gov (United States)

This paper reports an interlaboratory comparison that evaluated a protocol for measuring and analysing the particle size distribution of discrete, metallic, spheroidal nanoparticles using transmission electron microscopy (TEM). The study was focused on automated image capture and automated particle analysis. NIST RM8012 gold nanoparticles (30 nm nominal diameter) were measured for area-equivalent diameter distributions by eight laboratories. Statistical analysis was used to (1) assess the data quality without using size distribution reference models, (2) determine reference model parameters for different size distribution reference models and non-linear regression fitting methods and (3) assess the measurement uncertainty of a size distribution parameter by using its coefficient of variation. The interlaboratory area-equivalent diameter mean, 27.6 nm ± 2.4 nm (computed based on a normal distribution), was quite similar to the area-equivalent diameter, 27.6 nm, assigned to NIST RM8012. The lognormal reference model was the preferred choice for these particle size distributions as, for all laboratories, its parameters had lower relative standard errors (RSEs) than the other size distribution reference models tested (normal, Weibull and Rosin-Rammler-Bennett). The RSEs for the fitted standard deviations were two orders of magnitude higher than those for the fitted means, suggesting that most of the parameter estimate errors were associated with estimating the breadth of the distributions. The coefficients of variation for the interlaboratory statistics also confirmed the lognormal reference model as the preferred choice. From quasi-linear plots, the typical range for good fits between the model and cumulative number-based distributions was 1.9 fitted standard deviations less than the mean to 2.3 fitted standard deviations above the mean. Automated image capture, automated particle analysis and statistical evaluation of the data and fitting coefficients provide a framework for assessing nanoparticle size distributions using TEM for image acquisition.

Rice, Stephen B.; Chan, Christopher; Brown, Scott C.; Eschbach, Peter; Han, Li; Ensor, David S.; Stefaniak, Aleksandr B.; Bonevich, John; Vladár, András E.; Hight Walker, Angela R.; Zheng, Jiwen; Starnes, Catherine; Stromberg, Arnold; Ye, Jia; Grulke, Eric A.

2013-12-01

286

Computer Simulation of Random Packings for Self-Similar Particle Size Distributions in Soil and Granular Materials: Porosity and Pore Size Distribution  

Science.gov (United States)

A 2D computer simulation method of random packings is applied to sets of particles generated by a self-similar uniparametric model for particle size distributions (PSDs) in granular media. The parameter p which controls the model is the proportion of mass of particles corresponding to the left half of the normalized size interval [0,1]. First the influence on the total porosity of the parameter p is analyzed and interpreted. It is shown that such parameter, and the fractal exponent of the associated power scaling, are efficient packing parameters, but this last one is not in the way predicted in a former published work addressing an analogous research in artificial granular materials. The total porosity reaches the minimum value for p = 0.6. Limited information on the pore size distribution is obtained from the packing simulations and by means of morphological analysis methods. Results show that the range of pore sizes increases for decreasing values of p showing also different shape in the volume pore size distribution. Further research including simulations with a greater number of particles and image resolution are required to obtain finer results on the hierarchical structure of pore space.

Martín, Miguel Angel; Muñoz, Francisco J.; Reyes, Miguel; Taguas, F. Javier

2014-09-01

287

A Divot in the Size Distribution of the Kuiper Belt's Scattering Objects  

CERN Document Server

Via joint analysis of a calibrated telescopic survey, which found scattering Kuiper Belt objects, and models of their expected orbital distribution, we measure the form of the scattering object's size distribution. Ruling out a single power-law at greater than 99% confidence, we constrain the form of the size distribution and find that, surprisingly, our analysis favours a very sudden decrease (a divot) in the number distribution as diameters decrease below 100 km, with the number of smaller objects then rising again as expected via collisional equilibrium. Extrapolating at this collisional equilibrium slope produced enough kilometer-scale scattering objects to supply the nearby Jupiter-Family comets. Our interpretation is that this divot feature is a preserved relic of the size distribution made by planetesimal formation, now "frozen in" to portions of the Kuiper Belt sharing a "hot" orbital inclination distribution, explaining several puzzles in Kuiper Belt science. Additionally, we show that to match today...

Shankman, C; Kaib, N; Kavelaars, J J; Petit, J -M

2012-01-01

288

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

International Nuclear Information System (INIS)

Controlling the rheological properties of slurries has been of great interest in various industries such as cosmetics, ceramic processing, and nuclear waste treatment. Many physicochemical parameters, such as particle size, pH, ionic strength, and mass/volume fraction of particles, can influence the rheological properties of slurry. Among such parameters, the particle size distribution of slurry would be especially important for nuclear waste treatment because most nuclear waste slurries show a broad particle size distribution. We studied the rheological properties of several different low activity waste nuclear simulant slurries having different particle size distributions under high salt and high pH conditions. Using rheological and particle size analysis, it was found that the percentage of colloid-sized particles in slurry appears to be a key factor for rheological characteristics and the efficiency of rheological modifiers. This behavior was shown to be coupled with an existing electrostatic interaction between particles under a low salt concentration. Our study suggests that one may need to implement the particle size distribution as a critical factor to understand and control rheological properties in nuclear waste treatment plants, such as the U.S. Department of Energy's Hanford and Savannah River sites, because the particle size distributions significantly vary over different types of nuclear waste slurries.

289

Cloud particle size distributions measured with an airborne digital in-line holographic instrument  

Directory of Open Access Journals (Sweden)

Full Text Available Holographic data from the prototype airborne digital holographic instrument HOLODEC (Holographic Detector for Clouds, taken during test flights are digitally reconstructed to obtain the size (equivalent diameters in the range 23 to 1000 ?m, three-dimensional position, and two-dimensional image of ice particles and then ice particle size distributions and number densities are calculated using an automated algorithm with minimal user intervention. The holographic method offers the advantages of a well-defined sample volume size that is not dependent on particle size or airspeed, and offers a unique method of detecting shattered particles. The holographic method also allows the volume sample rate to be increased beyond that of the prototype HOLODEC instrument, limited solely by camera technology.

HOLODEC size distributions taken in mixed-phase regions of cloud compare well to size distributions from a PMS FSSP probe also onboard the aircraft during the test flights. A conservative algorithm for detecting shattered particles utilizing their depth-position along the optical axis eliminates the obvious ice particle shattering events from the data set. In this particular case, the size distributions of non-shattered particles are reduced by approximately a factor of two for particles 15 to 70 ?m in equivalent diameter, compared to size distributions of all particles.

R. A. Shaw

2009-06-01

290

Cloud particle size distributions measured with an airborne digital in-line holographic instrument  

Directory of Open Access Journals (Sweden)

Full Text Available Holographic data from the prototype airborne digital holographic instrument HOLODEC (Holographic Detector for Clouds, taken during test flights are digitally reconstructed to obtain the size (equivalent diameters in the range 23 to 1000 ?m, three-dimensional position, and two-dimensional profile of ice particles and then ice particle size distributions and number densities are calculated using an automated algorithm with minimal user intervention. The holographic method offers the advantages of a well-defined sample volume size that is not dependent on particle size or airspeed, and offers a unique method of detecting shattered particles. The holographic method also allows the volume sample rate to be increased beyond that of the prototype HOLODEC instrument, limited solely by camera technology.

HOLODEC size distributions taken in mixed-phase regions of cloud compare well to size distributions from a PMS FSSP probe also onboard the aircraft during the test flights. A conservative algorithm for detecting shattered particles utilizing the particles depth-position along the optical axis eliminates the obvious ice particle shattering events from the data set. In this particular case, the size distributions of non-shattered particles are reduced by approximately a factor of two for particles 15 to 70 ?m in equivalent diameter, compared to size distributions of all particles.

J. P. Fugal

2009-03-01

291

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

Energy Technology Data Exchange (ETDEWEB)

Controlling the rheological properties of slurries has been of great interest in various industries such as cosmetics, ceramic processing, and nuclear waste treatment. Many physicochemical parameters, such as particle size, pH, ionic strength, and mass/volume fraction of particles, can influence the rheological properties of slurry. Among such parameters, the particle size distribution of slurry would be especially important for nuclear waste treatment because most nuclear waste slurries show a broad particle size distribution. We studied the rheological properties of several different low activity waste nuclear simulant slurries having different particle size distributions under high salt and high pH conditions. Using rheological and particle size analysis, it was found that the percentage of colloid-sized particles in slurry appears to be a key factor for rheological characteristics and the efficiency of rheological modifiers. This behavior was shown to be coupled with an existing electrostatic interaction between particles under a low salt concentration. Our study suggests that one may need to implement the particle size distribution as a critical factor to understand and control rheological properties in nuclear waste treatment plants, such as the U.S. Department of Energy’s Hanford and Savannah River sites, because the particle size distributions significantly vary over different types of nuclear waste slurries.

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

2011-07-05

292

Rumen Contents and Ruminal Digesta Particle Size Distribution in Buffalo Steers Fed Three Different Size of Alfalfa  

Directory of Open Access Journals (Sweden)

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

A. Teimouri Yansari

2010-02-01

293

Transformation on steel products distribution in Poland and Slovakia  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 ...

Stefko, R.; Slusarczyk, B.; Kot, S.; Kolmasiak, C.

2012-01-01

294

Transformation on steel products distribution in Poland and Slovakia  

Directory of Open Access Journals (Sweden)

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

R. Stefko

2012-01-01

295

Adsorption of dyes and phenol from water on resin adsorbents: effect of adsorbate size and pore size distribution.  

Science.gov (United States)

Batch adsorption runs of two commercial reactive dyes (methylene blue and reactive orange X-GN) and phenol from water onto two resin adsorbents (Amberlite XAD-4, a macroreticular adsorbent and ZCH-101, a hyper-cross-linked adsorbent) were carried out in the present study. Effect of adsorbate size and pore structure of the resin adsorbents on adsorption was discussed and Langmuir and Freundlich models were tested for the relevant adsorption isotherms. In the kinetic section concentration-time profiles were obtained to further elucidate the effect of adsorbate size and porous structure on adsorption mechanism. A pseudo-second-order model was proved to give a satisfactory description of the related kinetic results. Two-stage kinetic curve of methylene blue onto ZCH-101 was observed at a specific experimental condition and modeled schematically according to its specific pore size distribution. Furthermore, other kinetic experiments were performed at different ambient temperature to validate the proposed schematic model. PMID:16704907

Zhang, Xiao; Li, Aimin; Jiang, Zhenmao; Zhang, Quanxing

2006-09-21

296

A theoretical analysis and prediction of pore size and pore size distribution in electrospun multilayer nanofibrous materials.  

Science.gov (United States)

Electrospinning process can fabricate nanomaterials with unique nanostructures for potential biomedical and environmental applications. However, the prediction and, consequently, the control of the porous structure of these materials has been impractical due to the complexity of the electrospinning process. In this research, a theoretical model for characterizing the porous structure of the electrospun nanofibrous network has been developed by combining the stochastic and stereological probability approaches. From consideration of number of fiber-to-fiber contacts in an electrospun nanofibrous assembly, geometrical and statistical theory relating morphological and structural parameters of the network to the characteristic dimensions of interfibers pores is provided. It has been shown that these properties are strongly influenced by the fiber diameter, porosity, and thickness of assembly. It is also demonstrated that at a given network porosity, increasing fiber diameter and thickness of the network reduces the characteristic dimensions of pores. It is also discussed that the role of fiber diameter and number of the layer in the assembly is dominant in controlling the pore size distribution of the networks. The theory has been validated experimentally and results compared with the existing theory to predict the pore size distribution of nanofiber mats. It is believed that the presented theory for estimation of pore size distribution is more realistic and useful for further studies of multilayer random nanofibrous assemblies. PMID:23426993

Bagherzadeh, Roohollah; Najar, Saeed Shaikhzadeh; Latifi, Masoud; Tehran, Mohammad Amani; Kong, Lingxue

2013-07-01

297

Searching for Saturn's Dust Swarm: Limits on the size distribution of Irregular Satellites from km to micron sizes  

CERN Document Server

We describe a search for dust created in collisions between the Saturnian irregular satellites using archival \\emph{Spitzer} MIPS observations. Although we detected a degree scale Saturn-centric excess that might be attributed to an irregular satellite dust cloud, we attribute it to the far-field wings of the PSF due to nearby Saturn. The Spitzer PSF is poorly characterised at such radial distances, and we expect PSF characterisation to be the main issue for future observations that aim to detect such dust. The observations place an upper limit on the level of dust in the outer reaches of the Saturnian system, and constrain how the size distribution extrapolates from the smallest known (few km) size irregulars down to micron-size dust. Because the size distribution is indicative of the strength properties of irregulars, we show how our derived upper limit implies irregular satellite strengths more akin to comets than asteroids. This conclusion is consistent with their presumed capture from the outer regions o...

Kennedy, Grant M; Su, Kate Y L; Stansberry, John A

2011-01-01

298

Self-similar grain size distribution in two dimensions: Analytical solution  

International Nuclear Information System (INIS)

Consideration of the physics and topology of two-dimensional grain growth suggests that a stochastic treatment is required to determine grain size distribution [Pande CS. Acta Metall 1987;35:2671]. In this paper, a size-based continuum stochastic formulation is presented based on topological considerations. As expected, this analysis leads to a Fokker-Planck equation for the size distribution, which should yield a unique self-similar asymptotic state that could be reached from any arbitrary initial state. The approximate solution of the Fokker-Planck equation presented here is limited to two dimensions and is based on the assumption of quasi-stationary distributions reached in the long time limit. The resulting grain size distribution is shown to be in agreement with that obtained from computer simulations, indicating the validity of the stochastic approach

299

EFFECTS ON ELECTROSTATIC PRECIPITATION OF CHANGES IN GRAIN LOADING, SIZE DISTRIBUTION, RESISTIVITY, AND TEMPERATURE  

Science.gov (United States)

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...

300

Droplet Size Distribution in Sprays Based on Maximization of Entropy Generation  

Directory of Open Access Journals (Sweden)

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

Meishen Li

2003-12-01

 
 
 
 
301

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

CERN Document Server

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

302

Estimation of software size and effort distributions using paired ratio comparison matrices  

Science.gov (United States)

This paper describes the approach and algorithms used to generalize the paired ratio comparison matrix technique to use information inherent in multiple estimates, multiple reference projects, and estimator range information to generate estimated effort and size distributions.

Lum, K.; Hihn, J.

2003-01-01

303

Calibration of the passive cavity aerosol spectrometer probe for airborne determination of the size distribution  

Directory of Open Access Journals (Sweden)

Full Text Available This work describes calibration methods for the particle sizing and particle concentration systems of the passive cavity aerosol spectrometer probe (PCASP. Laboratory calibrations conducted over six years, in support of the deployment of a PCASP on a cloud physics research aircraft, are analyzed. Instead of using the many calibration sizes recommended by the PCASP manufacturer, a relationship between particle diameter and scattered light intensity is established using three sizes of mobility-selected polystyrene latex particles, one for each amplifier gain stage. In addition, studies of two factors influencing the PCASP's determination of the particle size distribution – amplifier baseline and particle shape – are conducted. It is shown that the PCASP-derived size distribution is sensitive to adjustments of the sizing system's baseline voltage, and that for aggregate spheres, a PCASP-derived particle size and a sphere-equivalent particle size agree within uncertainty dictated by the PCASP's sizing resolution. Robust determination of aerosol concentration, and size distribution, also require calibration of the PCASP's aerosol flowrate sensor. Sensor calibrations, calibration drift, and the sensor's non-linear response are documented.

Y. Cai

2013-05-01

304

Calibration of the passive cavity aerosol spectrometer probe for airborne determination of the size distribution  

Directory of Open Access Journals (Sweden)

Full Text Available This work describes calibration methods for the particle sizing and particle concentration systems of the passive cavity aerosol spectrometer probe (PCASP. Laboratory calibrations conducted over six years, in support of the deployment of a PCASP on a cloud physics research aircraft, are analyzed. Instead of using the many calibration sizes recommended by the PCASP manufacturer, a relationship between particle diameter and scattered light intensity is established using three sizes of mobility-selected polystyrene latex particles, one for each amplifier gain stage. In addition, studies of two factors influencing the PCASP's determination of the particle size distribution – amplifier baseline and particle shape – are conducted. It is shown that the PCASP-derived size distribution is sensitive to adjustments of the sizing system's baseline voltage, and that for aggregates of spheres, a PCASP-derived particle size and a sphere-equivalent particle size agree within uncertainty dictated by the PCASP's sizing resolution. Robust determinations of aerosol concentration, and size distribution, also require calibration of the PCASP's aerosol flowrate sensor. Sensor calibrations, calibration drift, and the sensor's non-linear response are documented.

Y. Cai

2013-09-01

305

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

Science.gov (United States)

The frequency distributions of sizes and fluxes of supra-arcade downflows (SADs) provide information about the process of their creation. For example, a fractal creation process may be expected to yield a power-law distribution of sizes and/or fluxes. We examine 120 cross-sectional areas and magnetic flux estimates found by Savage & McKenzie for SADs, and find that (1) the areas are consistent with a log-normal distribution and (2) the fluxes are consistent with both a log-normal and an exponential distribution. Neither set of measurements is compatible with a power-law distribution nor a normal distribution. As a demonstration of the applicability of these findings to improved understanding of reconnection, we consider a simple SAD growth scenario with minimal assumptions, capable of producing a log-normal distribution.

McKenzie, D.; Savage, S.

2011-01-01

306

Dust negative ion acoustic shock waves considering dust size distribution effect  

International Nuclear Information System (INIS)

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

307

FRACTAL SCALING OF PARTICLE AND PORE SIZE DISTRIBUTIONS AND ITS RELATION TO SOIL HYDRAULIC CONDUCTIVITY  

Directory of Open Access Journals (Sweden)

Full Text Available Fractal scaling has been applied to soils, both for void and solid phases, as an approach to characterize the porous arrangement, attempting to relate particle-size distribution to soil water retention and soil water dynamic properties. One important point of such an analysis is the assumption that the void space geometry of soils reflects its solid phase geometry, taking into account that soil pores are lined by the full range of particles, and that their fractal dimension, which expresses their tortuosity, could be evaluated by the fractal scaling of particle-size distribution. Other authors already concluded that although fractal scaling plays an important role in soil water retention and porosity, particle-size distribution alone is not sufficient to evaluate the fractal structure of porosity. It is also recommended to examine the relationship between fractal properties of solids and of voids, and in some special cases, look for an equivalence of both fractal dimensions. In the present paper data of 42 soil samples were analyzed in order to compare fractal dimensions of pore-size distribution, evaluated by soil water retention curves (SWRC of soils, with fractal dimensions of soil particle-size distributions (PSD, taking the hydraulic conductivity as a standard variable for the comparison, due to its relation to tortuosity. A new procedure is proposed to evaluate the fractal dimension of pore-size distribution. Results indicate a better correlation between fractal dimensions of pore-size distribution and the hydraulic conductivity for this set of soils, showing that for most of the soils analyzed there is no equivalence of both fractal dimensions. For most of these soils the fractal dimension of particle-size distribution does not indicate properly the pore trace tortuosity. A better equivalence of both fractal dimensions was found for sandy soils.

BACCHI O.O.S.

1996-01-01

308

Evaluation of Plasticity and Particle Size Distribution Characteristics of Bagasse Ash on Cement Treated Lateritic Soil  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 Siev...

Mu Azu, Mohammed Abdullahi

2007-01-01

309

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

310

Droplet Size Distribution in Sprays Based on Maximization of Entropy Generation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Meishen Li; Xianguo Li

2003-01-01

311

Application of absolute principal component analysis to size distribution data: identification of particle origins  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Absolute principal component analysis can be applied, with suitable modifications, to atmospheric aerosol size distribution measurements. This method quickly and conveniently reduces the dimensionality of a data set. The resulting representation of the data is much simpler, but preserves virtually all the information present in the original measurements. Here we demonstrate how to combine the simplified size distribution data with trace gas measurements and meteorological data to determine th...

Chan, T. W.; Mozurkewich, M.

2006-01-01

312

Application of absolute principal component analysis to size distribution data: identification of particle origins  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Absolute principal component analysis can be applied, with suitable modifications, to atmospheric aerosol size distribution measurements. This method quickly and conveniently reduces the dimensionality of a data set. The resulting representation of the data is much simpler, but preserves virtually all the information present in the original measurements. Here we demonstrate how to combine the simplified size distribution data with trace gas measurements and meteorological data to determine th...

Chan, T. W.; Mozurkewich, M.

2007-01-01

313

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

the key to reduce coal pollution is the development of clean coal technology and the improvement of the backward coal-burning technology. The coal water slurry (CWS) is the first substitute of the oil. The particle size distribution of CWS plays an important role in the quality control of CWS. Now there are three methods that are used to analysis the particle size distribution of CWS, screening method, settlement method, laser method. These methods produce some disadvantages when be used to f...

Wang, Weidong; Zhang, Chenglian; Chu, Fengge

2010-01-01

314

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

Science.gov (United States)

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

315

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

Science.gov (United States)

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. PMID:23283537

Li, He; Zuo, Xiao Jun

2013-04-01

316

Aerosol optical properties during coagulation and condensation in multimodal aerosol size distribution  

Science.gov (United States)

The aerosols in the atmosphere continuously change their size and composition through the dynamic processes such as coagulation or condensation. For example, the Brownian motion of particles, turbulence, presence of a shear field, aerosol particle growth with the accretion of monomers on existing particle, and external forces such as gravity and electrical forces could cause coagulation. This means that the change of the size distribution due to coagulation and condensation process affect Ångstrom exponent. For this reasons, the aerosol dynamics play an important role in estimating optical properties such as Ångstrom exponent. Usually, the atmospheric aerosol shows the multimodal distribution (such as bimodal or three modal distribution). In this study, the change of the Ångstrom exponent for polydispersed aerosol size distribution during the aerosol dynamic processes was investigated. Multimodal Log-normal aerosol size distribution was assumed and the sensitive analysis of the Ångstrom exponent during the coagulation and condensation process was performed. The sensitivities of coarse mode particles are analyzed in order to find the effect of dust particles on optical properties with large particle size such as Asian dust. This study also investigated the sensitivity of aerosol refractive index to analyze the Angstrom exponent due to aerosol composition change during the aerosol dynamic process. The results showed that the Ångstrom exponent changes sensitively as a function of multimodal size distribution and refractive index.

Jung, C.; Park, R.; Kim, Y.

2012-12-01

317

Recognizing overlapped particles during a crystallization process from in situ video images for measuring their size distributions  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Quantification of the overlapping particles in crystallization processes is very important for the quality control of chemical products or drugs. We present a method of segmentation of polygonal-shaped (i.e., rectangles, regular/irregular prisms) and overlapping particles from in situ images during a crystallization process for measuring their size distributions. The method is first based on detecting the geometric features of the particles identified by their salient corners. A clustering te...

Ahmad, Ola; Debayle, Johan; Gherras, Nesrine; Presles, Benoi?t; Fe?votte, Gilles; Pinoli, Jean-charles

2012-01-01

318

Supply of FDG : production and distribution  

International Nuclear Information System (INIS)

Full text: Aim: To review the means of production of PET tracers and the logistIcs of their distribution, with special emphasis on 18 FDG - from an end-user point of view. Material and method: The experience of a satellite center (i.e. without in-house cyclotron) over one year. Results: The following topics are presented: Basic introduction to FDG and its radio-synthesis; properties of cyclotrons and linear accelerators; the economics of buying and running a cyclotron to produce FDG; satellite facilities (availability from radiopharmacies; fraction of FDG in the cost of running a PET center; recent developments in PET cameras, and their implications of FDG supply; diversification in the offer of commercial PET tracers; regulatory issues, and their influence on FDG supply; possible developments in onco-PET, neuro-PET, cardio-PET; generators and full PET Nuclear Medicine. Conclusion: The European experience is not necessarily completely applicable to a large country like South Africa; the question can be raised whether it is advisable to move the patients, the FDG or the camera around the country or its provinces. (author)

319

222Rn decay products as tracers of indoor and outdoor aerosol particle size  

International Nuclear Information System (INIS)

Measurements of the air concentration of 210Pb indoors and outdoors were made at a single-family suburban home in northern New Jersey over a 1.5 year period. A sampler with 5 fine mesh screens and a backup Millipore filter was used to determine the indoor and outdoor ultrafine particle size distribution. A sample of the total airborne particulates was collected simultaneously. The long-lived 222Rn decay product 210Pb presents a unique and highly sensitive tracer to study atmospheric aerosol particles. The aerosol particle size sampler integrates ultrafine particulates deposited over 3-4 weeks. The measurement of 210Pb (210Po) on the screens and filter was performed using very low background alpha scintillation counters (3-5 counts/day), and long count times (5000 min). Deconvolution of the alpha counting data was performed using an extreme value estimation program (EVE) that provides an accurate evaluation of the particle size distribution. The particle size data show that a significant fraction (20-60%) of the atmospheric aerosol particles in this suburban location are in the ultrafine region. The indoor to outdoor 210Pb ratio revealed that 65% of the outdoor aerosol particles in this suburban location comprise the indoor particle concentration

320

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.

M. Thiele

2010-02-01

 
 
 
 
321

Size distribution of trace organic species emitted from heavy-duty diesel vehicles.  

Science.gov (United States)

Size distributions of particulate hopanes, steranes, and polycyclic aromatic hydrocarbons (PAHs) were measured in the exhaust from four heavy-duty diesel vehicles (HDDVs) operated under idle, creep, transient, and two high-speed driving modes. Particulate matter was collected using a chassis dynamometer and a dilution sampling system equipped with cascade impactors and filter samplers. Samples were extracted using organic solvents and analyzed using gas chromatography-mass spectrometry. Size distributions of hopanes and steranes were functions of engine load conditions and vehicle technology. Hopanes and steranes peaked in size ranges larger than 0.18 microm aerodynamic particle diameter under light load conditions and less than 0.10 microm aerodynamic particle diameter under heavier load conditions. The eight hopane size distributions emitted from newertechnology (> 1998) vehicles were unimodal while the four hopane size distributions emitted from older technology vehicles (hopanes and steranes to total organic carbon were functions of vehicle load condition. Increasing load reduced the relative abundance of motor oil tracers in the PM1.8 size fraction and increased the abundance of these tracers in the PM0.1 size fraction. The relative abundances of PAHs in the PM0.1 and PM1.8 size fractions emitted from the oldest vehicle tested (1985 HDDV) were significantly higher than for any other vehicle tested. PMID:17410791

Riddle, Sarah G; Robert, Michael A; Jakober, Chris A; Hannigan, Michael P; Kleeman, Michael J

2007-03-15

322

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

323

Negative binomial multiplicity distribution from binomial cluster production  

International Nuclear Information System (INIS)

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

324

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

Calving activity at the termini of tidewater glaciers produces a wide range of iceberg sizes at irregular intervals. We present calving-event data obtained from continuous observations of the termini 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 terminus. The event-size distributi...

Chapuis, Anne; Tetzlaff, Tom

2012-01-01

325

Quantitative ultrasound estimates from populations of scatterers with continuous size distributions: effects of the size estimator algorithm.  

Science.gov (United States)

Quantitative ultrasonic techniques using backscatter coefficients (BSCs) may fail to produce physically meaningful estimates of effective scatterer diameter (ESD) when the analysis media contains scatterers of different sizes. In this work, three different estimator algorithms were used to produce estimates of ESD. The performance of the three estimators was compared over different frequency bands using simulations and experiments with physical phantoms. All estimators produced ESD estimates by comparing the estimated BSCs with a scattering model based on the backscattering cross section of a single spherical fluid scatterer. The first estimator consisted of minimizing the average square deviation of the logarithmically compressed ratio between the estimated BSCs and the scattering model. The second and third estimators consisted of minimizing the mean square error between the estimated BSCs and a linear transformation of the scattering model with and without considering an intercept, respectively. Simulations were conducted over several analysis bandwidths between 1 and 40 MHz from populations of scatterers with either a uniform size distribution or a distribution based on the inverse cubic of the size. Diameters of the distributions ranged between [25, 100], [25, 50], [50, 100], and [50, 75] ?m. Experimental results were obtained from two gelatin phantoms containing cross-linked dextran gel spheres ranging in diameter from 28 to 130 ?m and 70 to 130 ?m, respectively, and 5-, 7.5-, 10-, and 13-MHz focused transducers. Significant differences in the performances of the ESD estimator algorithms as a function of the analysis frequency were observed. Specifically, the third estimator exhibited potential to produce physically meaningful ESD estimates even for large ka values when using a single-size scattering model if sufficient analysis bandwidth was available. PMID:23007782

Lavarello, Roberto; Oelze, Michael

2012-09-01

326

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

Directory of Open Access Journals (Sweden)

Full Text Available Particle size distribution from biomass combustion is an important parameter as it affects air quality, climate modelling and health effects. To date, particle size distributions reported from prior studies vary not only due to difference in fuels but also difference in experimental conditions. This study aims to report characteristics of particle size distributions in well controlled repeatable lab scale biomass fires for southwestern United States fuels with focus on chaparral. The combustion laboratory at the United States Department of Agriculture-Forest Service's Fire Science Laboratory (USDA-FSL, Missoula, MT provided a repeatable combustion and dilution environment ideal for measurements. For a variety of fuels tested the major mode of particle size distribution was in the range of 29 to 52 nm, which is attributable to dilution of the fresh smoke. Comparing mass size distribution from FMPS and APS measurement 51–68% of particle mass was attributable to the particles ranging from 0.5 to 10 ?m for PM10. Geometric mean diameter rapidly increased during flaming and gradually decreased during mixed and smoldering phase combustion. Most fuels produced a unimodal distribution during flaming phase and strong biomodal distribution during smoldering phase. The mode of combustion (flaming, mixed and smoldering could be better distinguished using the slopes in MCE (Modified Combustion Efficiency vs. geometric mean diameter than only using MCE values.

S. Hosseini

2010-08-01

327

De novo synthesis of a narrow size distribution low-molecular-weight heparin.  

Science.gov (United States)

Heparin, a commonly used anticoagulant drug, is a mixture of highly sulfated polysaccharides with various molecular weights (MWs). The unique sulfation pattern dictates the anticoagulant activity of heparin. Commercial heparins are categorized into three forms according to their average MW: unfractionated heparin (UFH, MWavg 14,000), low-MW heparin (LMWH, MWavg 3500-6500) and the synthetic pentasaccharide (fondaparinux, MW 1508.3). UFH is isolated from porcine intestine while LMWH is derived from UFH by various methods of depolymerization, which generate a wide range of oligosaccharide chain lengths. Different degradation methods result in structurally distinct LMWH products, displaying different pharmacological and pharmacokinetic properties. In this report, we utilized a chemoenzymatic method to synthesize LMWH with the emphasis on controlling the size distribution of the oligosaccharides. A tetrasaccharide primer and a controlled enzyme-based polymerization were employed to build a narrow size oligosaccharide backbone. The oligosaccharide backbones were further modified by a series of sulfation and epimerization steps in order to obtain a full anticoagulation activity. Determination of the anticoagulation activity in vitro and ex vivo indicated that the synthetic LMWH has higher potency than enoxaparin, a commercial LMWH drug in clinical usage. PMID:24626379

Chandarajoti, Kasemsiri; Xu, Yongmei; Sparkenbaugh, Erica; Key, Nigel S; Pawlinski, Rafal; Liu, Jian

2014-05-01

328

Preparation of ThO2 sols having colloid-size distributions suitable for gelation into microspheres  

International Nuclear Information System (INIS)

Production conditions of ThO2 sols suitable for gelling into crackfree microspheres in an external gelation process were studied. The sols were prepared under pH control and colloid size distributions of the resulting sols were determined. The gelation was carried out by using hexone as a drop formation medium and ammonia as a gelling agent. The crackfree gelation was achieved by the use of ThO2 sols produced under favorable pH, which were large in colloid size and high in colloid fraction. ''Preneutralization'' preceding the pH control is also important for the good sols. Analyzing the colloid fraction, colloid size and crystallite size of sol, it was found that, under the favorable pH, colloid nuclei generating at early stages grow in the form of single-crystals with their number kept constant and, after cooling, they exist as polycrystalline colloids. The mechanism of cracking is also discussed. (author)

329

Statistical product distributions for ultracold reactions in external fields  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The main limitation of most ultracold chemistry studies to date is the lack of an analysis of reaction products. Here, we discuss the first generally tractable, rigorous theoretical framework for computing statistical product-state distributions for ultracold reactions in external fields. We show that fields have two main effects on the products of a statistical reaction, by: (1) modifying the product energy levels thus potentially reshaping the product distributions; and/or...

Gonza?lez-marti?nez, Maykel L.; Dulieu, Olivier; Larre?garay, Pascal; Bonnet, Laurent

2014-01-01

330

Optimal Location and Size of Distributed Generation inDistribution System by Artificial Bees Colony Algorithm  

Directory of Open Access Journals (Sweden)

Full Text Available Distributed generation (DG application hasreceived increasing attention during recent years. The impactof DG on various aspects of distribution system operation,such as reliability and energy loss, depend highly on DGlocation in distribution feeder. Optimal DG placement is animportant. This paper presents a new methodology usingartificial bee’s conoly algorithm (ABC for the placement andsize of Distributed Generators (DG in the radial distributionsystems. The proposed method is tested in standard IEEE 33bus test system and the results are presented.

Nguyen Tung Linh

2013-01-01

331

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

2008-04-01

332

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

2008-09-01

333

Detection of the Concentration and Size Distribution of Indoor Inhalable Particle Based on Mathematical Morphology  

Directory of Open Access Journals (Sweden)

Full Text Available Adopting the microscopic observation imaging and digital image processing technologies, this paper researches a new measuring method of indoor inhalable particulate matter concentration and size distribution .It realizes denoising, binarization, filtering and edge detection to based on mathematical morphology, regional filled and calibration detection to particulate matter image, designs the parameters recognition algorithm for particulate matter size, fractal dimension ,shape factors and so on, then calculates the concentration and size distribution of particulate matter using data fusion method. The experimental results show that the method has advantages with intuitive, high precision, fast processing speed ,easily data statistics, clearly data analysis and stable measuring results.

Hongli Liu

2012-11-01

334

Size distribution of aerosol particles: comparison between agricultural and industrial areas in Egypt  

International Nuclear Information System (INIS)

Mie theory has been used in this work to obtain a theoretical calculation of the size distribution of aerosol particles by using tabulated mean of the Angstrom wavelength exponent ?o. Comparison was done between an industrial polluted area (Helwan, which is a neighbor to Cairo city), and an agricultural relatively unpolluted area (Mansoura, about 140 km from Cairo). The results show that the size distribution obeys the Junge power law. The size of particles in the polluted area is larger than that in the unpolluted area. (Author)

335

Effect of pore size distribution and flow segregation on dispersion in porous media  

International Nuclear Information System (INIS)

In order to study the effect of the pore size distribution and flow segregation on dispersion in a porous media, the dispersion of solute in an array of parallel pores is considered. Equations are obtained for the dispersion coefficient in laminar and turbulent flow, as a function of the particle Peclet number. The theory fits quite well cumulative experimental data from various researchers in the Peclet number range from 10-3 to 106. The model also predicts some trends, backed by experimental data, regarding the effect of particle size, particle size distribution and fluid velocity on dispersion

336

The measurement of aerosol size distributions (AMAD) in buildings on BNFL's Sellafield site  

International Nuclear Information System (INIS)

Cascade centripeters were used to make measurements of aerosol activity size distributions in several buildings involved in the reprocessing of Magnox Nuclear Reactor Fuel on BNFL's Sellafield site. Whilst the 50 measurements made demonstrate significant variations in size distribution between buildings (2.8 ?m-4.2 ?m) and even between sampling locations within particular buildings (1.9 ?m-9.0 ?m), they demonstrate consistently larger particle sizes than the 1 ?m AMAD default value recommended in ICRP Publication 30 and provide further empirical support for the adoption of a 5 ?m AMAD default value as most recently proposed in ICRP Publication 66 for workplaces. (Author)

337

Effect of pore size distribution and flow segregation on dispersion in porous media  

Energy Technology Data Exchange (ETDEWEB)

In order to study the effect of the pore size distribution and flow segregation on dispersion in a porous media, the dispersion of solute in an array of parallel pores is considered. Equations are obtained for the dispersion coefficient in laminar and turbulent flow, as a function of the particle Peclet number. The theory fits quite well cumulative experimental data from various researchers in the Peclet number range from 10/sup -3/ to 10/sup 6/. The model also predicts some trends, backed by experimental data, regarding the effect of particle size, particle size distribution and fluid velocity on dispersion.

Carbonell, R.G.

1978-11-01

338

Mass and angular distribution formation of heavy ion reaction products  

International Nuclear Information System (INIS)

An equation for angular and mass distributions of products of heavy ion reactions has been obtained with a series of approximations of the density matrix equation. At small values of time of realization of definite internal excitation energy, angular distribution corresponds to masses of nuclei slightly differing from those of cooliding heavy ions, but at t ? infinity angular distribution corresponds to equilibrium mass distribution

339

Narrowly size-distributed cobalt salt containing poly(2-hydroxyethyl methacrylate) particles by inverse miniemulsion.  

Science.gov (United States)

Cobalt-containing hybrid particles have been prepared through the encapsulation of cobalt tetrafluoroborate hexahydrate (CoTFB) via inverse miniemulsion polymerization of 2-hydroxyethyl methacrylate (HEMA). We systematically varied the amount and type of cosolvent (water, methanol, ethanol, ethylene glycol), apolar continuous phase (cyclohexane, isooctane, isopar M, hexadecane), amount of cobalt salt, and molecular weight of the polymeric surfactant. The influence of those parameters on the particle size, size distribution, and particle morphology were investigated. Narrowly size-distributed hybrid particles with good colloidal stability could be obtained in a wide range of cobalt content between 5.7 and 22.6 wt % salt relative to the monomer. The addition of a cosolvent such as water not only promotes the loading of metal salt but also has a positive influence on narrowing the particle size distribution. We assume that generally narrowly size-distributed particles can be obtained for a large variety of combinations of polar/apolar phase by adjusting the balance between osmotic and Laplace pressure via the solubility of the metal salt in the continuous phase and lowering the interfacial tension by adjusting the hydrophilic-lipophilic balance (HLB) value of the surfactant. The results show a significant advantage of the inverse miniemulsion over the direct system with respect to the variability and total amount of metal salt without losing the narrow particle size distribution and colloidal stability. PMID:20112941

Cao, Zhihai; Wang, Zhuo; Herrmann, Christine; Ziener, Ulrich; Landfester, Katharina

2010-05-18

340

Measurements of Aerosol Charge and Size Distribution for Graphite, Gold, Palladium, and Silver Nanoparticles  

Energy Technology Data Exchange (ETDEWEB)

The role of charge on aerosol evolution and hence the nuclear source term has been an issue of interest, and there is a need for both experimental techniques and modeling for quantifying this role. Our focus here is on further exploration of a tandem differential mobility analyzer (TDMA) technique to simultaneously measure both the size and charge (positive, negative and neutral) dependent aerosol distributions. We have generated graphite, gold, silver, and palladium nanoparticles (aerosol) using a spark generator. We measure the electrical mobility-size distributions for these aerosols using a TDMA, and from these data we deduce the full charge-size distributions. We observe asymmetry in the particle size distributions for negative and positive charges. This asymmetry could have a bearing on the dynamics of charged aerosols, indicating that the assumption of symmetry for size distributions of negatively and positively charged particles in source term simulations may not be always appropriate. Also, the experimental technique should find applications in measurements of aerosol rate processes that are affected by both particle charge and size (e.g. coagulation, deposition, resuspension), and hence in modeling and simulation of the nuclear source term.

Simones, Matthew P.; Gutti, Veera R.; Meyer, Ryan M.; Loyalka, Sudarshan K.

2011-11-01

 
 
 
 
341

TNOs as probes of planet building: the Plutino size- & colour-distributions  

Science.gov (United States)

Planetesimals are the building blocks of giant planet cores; some are preserved as large transneptunian objects (TNOs). Previous work concluded steep power-law size-distributions for TNOs of diameters > 100 km. Recent results claim a dramatic roll-over or divot (sudden drop in number of objects at a transition size) in the size-distribution of Neptunian Trojans and scattering TNOs, with a significant lack of intermediate-size D99% confidence; a double power law cannot be rejected outright, but appears to be a uncomfortable match to the available data. A divot, with the parameters found independently for scattering TNOs by Shankman et al. (2013, ApJ vol 764), provides an excellent match; the best match, found from an extensive parameter search, comes with only slightly different parameters; this size-distribution also satisfies the known Neptunian Trojan data. Both large TNOs and small nearby Centaurs are known to feature a bimodal colour-distribution; however, recent work (Peixinho et al. 2012, A&A vol 546) has suggested that intermediate-size TNOs may not show bimodality. We present g-r photometric colours for our Plutino sample, obtained with the Gemini North telescope in 2013-2014. This telescopically-expensive endeavour has provided us with unique insight into the colour-distribution of the physically smallest Plutinos.

Alexandersen, Mike; Gladman, Brett; Kavelaars, Jj; Petit, Jean-Marc; Gwyn, Stephen; Shankman, Cory; Pike, Rosemary

2014-11-01

342

Measurements of Aerosol Charge and Size Distribution for Graphite, Gold, Palladium, and Silver Nanoparticles  

International Nuclear Information System (INIS)

The role of charge on aerosol evolution and hence the nuclear source term has been an issue of interest, and there is a need for both experimental techniques and modeling for quantifying this role. Our focus here is on further exploration of a tandem differential mobility analyzer (TDMA) technique to simultaneously measure both the size and charge (positive, negative and neutral) dependent aerosol distributions. We have generated graphite, gold, silver, and palladium nanoparticles (aerosol) using a spark generator. We measure the electrical mobility-size distributions for these aerosols using a TDMA, and from these data we deduce the full charge-size distributions. We observe asymmetry in the particle size distributions for negative and positive charges. This asymmetry could have a bearing on the dynamics of charged aerosols, indicating that the assumption of symmetry for size distributions of negatively and positively charged particles in source term simulations may not be always appropriate. Also, the experimental technique should find applications in measurements of aerosol rate processes that are affected by both particle charge and size (e.g. coagulation, deposition, resuspension), and hence in modeling and simulation of the nuclear source term.

343

Size Distribution of Radar Echoes as an Indicator of Growth Mechanisms in Monsoon Clouds around Madras.  

Science.gov (United States)

A study of the size distribution of radar echoes from precipitating clouds around Madras during the southwest and northeast monsoon seasons shows a preponderance of echo sizes in the D scale (up to 100 km2) with relatively small percentages in the C scale (101 to 1000 km2) and in the B/C scale (>1000 km2). The largest echo size observed was 21 000 km2. If the cumulative percentage frequencies of areas of cells are plotted on logarithmic probability paper, the smaller cells constituting 85-95% of the total population are seen to follow a lognormal distribution. In the larger size ranges, however, systematic deviations on either side of the lognormal graph occur.The lognormal distribution points to a growth mechanism of convective cells by a process whereby growth at every step is a random proportion of the initial size. The deviations from the lognormal distribution in the land area in the northeast monsoon season indicate limitation of growth after the cells which develop over the sea drift over the land. In the southwest monsoon season and in the sea area during the northeast monsoon, growth is found to occur to very large sizes more often than a lognormal distribution would predict. The deviation from lognormality appears to be due to development of a stratiform mesoscale anvil cloud similar to the model of Leary and Houze in the Global Atmospheric Research Program's (GARP) Atlantic Tropical Experiment (GATE).

Raghavan, S.; Sivarmakrishnan, T. R.; Ramakrishnan, B.

1983-02-01

344

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

2012-10-01

345

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

Science.gov (United States)

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.

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

2012-10-01

346

An Evolutionary Approach for Optimal Citing and Sizing of Micro-Grid in Radial Distribution Systems  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This Paper presents the methodology of penetration of Micro-Grids (MG) in the radial distribution system (RDS). The aim of this paper is to minimize a total real power loss that descends the performance of the radial distribution system by integrating various renewable resources as Distributed Generation (DG). The combination of different types of renewable energy resources contributes a sustainable MG. These resources are optimally sized and located using evolutionary appro...

J, Eswari; Jeyadevi, Dr S.

2014-01-01

347

Planar dust-acoustic waves in electron-positron-ion-dust plasmas with dust size distribution  

Science.gov (United States)

Nonlinear dust-acoustic solitary waves which are described with a Kortweg-de vries (KdV) equation by using the reductive perturbation method, are investigated in a planar unmagnetized dusty plasma consisting of electrons, positrons, ions and negatively-charged dust particles of different sizes and masses. The effects of the power-law distribution of dust and other plasma parameters on the dust-acoustic solitary waves are studied. Numerical results show that the dust size distribution has a significant influence on the propagation properties of dust-acoustic solitons. The amplitudes of solitary waves in the case of a power-law distribution is observed to be smaller, but the soliton velocity and width are observed to be larger, than those of mono-sized dust grains with an average dust size. Our results indicate that only compressed solitary waves exist in dusty plasma with different dust species. The relevance of the present investigation to interstellar clouds is discussed.

Wang, Hong-Yan; Zhang, Kai-Biao

2014-06-01

348

Time integrated measurements of the activity-weighted size distribution of radon progeny  

International Nuclear Information System (INIS)

The dose to the lung is dependent on the size distribution as well as the concentration of radon progeny. The principal indicator of particle size is the diffusion coefficient. The diffusion coefficient of radon progeny is the most important parameter in determining whether the particle will deposit its alpha energy in the tracheobronchial region of the respiratory tract. Due to the importance of the size distribution of progeny when characterizing health effects, a detector was developed that exploits the difference in diffusion coefficients to provide integrated measurements of the activity-weighted size distribution. This paper reports on several radon chamber tests that were performed in which the diffusion coefficient and unattached fraction of radon progeny were varied by the use of trace gasses and aerosol particles. The technical feasibility of this new detector design was demonstrated in all cases

349

Neutron spectra evaluation obtained from the track-size distribution on electrochemically etched CR-39 foils  

Energy Technology Data Exchange (ETDEWEB)

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.

Hankins, D.E.; Westermark, J.

1987-05-01

350

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

Science.gov (United States)

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. PMID:22962740

Jiang, Jing; Wang, Bing; Jin, Shengming; Feng, Weiyue

2012-08-01

351

Characterization of the Size Distribution of Mountains Extracted from Multiscale Digital Elevation Models  

Directory of Open Access Journals (Sweden)

Full Text Available In general, analysis of mountains is performed at singular scales of measurement. However, analysis of a location at multiple scales allows for a greater amount of information to be extracted from a DEM about the spatial characteristics of a feature. In this study, the variation in the spatial extent over which mountains are defined is used as the basis to characterize the size distribution of mountains. First, the lifting scheme is used to generate multiscale DEMs. Mountains extraction is then performed on the generated multiscale DEMs. The size distribution of the extracted mountains is characterized by implementing opening by reconstruction iteratively on the extracted mountains using square kernels of increasing size. A power law relationship is observed between the number and total area of mountain objects remaining. This power law arises as a consequence of the fractal properties of the size distribution of mountains extracted from multiscale DEMs.

S. Dinesh

2007-01-01

352

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

International Nuclear Information System (INIS)

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.

353

Finite-size scaling behavior of the magnetization distribution for 5d Ising model  

Science.gov (United States)

We have previously established that the magnetization distribution of the 5-dimensional Ising model can be fitted by a p,q-binomial distribution. Our extensive sampled Monte Carlo data can be used to determine the parameters' finite-size behavior. Now we use a long series expansion of the p,q-binomial coefficients to obtain finite-size scaling formulas not only for the Binder ratio and the susceptibility near Tc, but also for the entire magnetization distribution, including corrections-to-scaling terms.

Lundow, P. H.; Rosengren, A.

2013-03-01

354

Sensitivity of Satellite-Retrieved Cloud Properties to the Effective Variance of Cloud Droplet Size Distribution  

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

355

Seismic cycles, size of the largest events, and the avalanche size distribution in a model of seismicity  

CERN Document Server

We address several questions on the behavior of a numerical model recently introduced to study seismic phenomena, that includes relaxation in the plates as a key ingredient. 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. Secondly, we show that the temporal activity in the model is inherently non-stationary, 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 of $b$ from its value $b\\simeq 0.4$ observed in the absence of relaxation. However, we have not been able to justify the actual robustness of the model in d...

Aragón, L E; Rosso, A

2012-01-01

356

Briquetting of coal fines and sawdust - effect of particle-size distribution  

Energy Technology Data Exchange (ETDEWEB)

The coal industry usually discards fine-size (-150 microns) coal because of its high-moisture content and handling problems. One avenue for utilization is to either pelletize or briquette this material. However, industry has not adopted this route due in large part to significant drying and binder costs. In an effort to reduce these costs, compacting and briquetting studies were conducted to determine the effect of combining a coarse (1.18x0.15mm) spiral separator product with a fine coal flotation product (-150microns), with and without adding sawdust. Maximizing the packing density of the coal and wood waste mixture could potentially reduce the binder requirement by minimizing the void space as well as reducing shipping costs. Accordingly, work reported here focused on evaluating the impact of the particle-size distribution of different blends of fine and coarse coal, with and without sawdust and/or binder. The modified Proctor density of compacted blends along with the porosity and compressive strengths of briquettes made from each blend were determined. For the coal-only blends, the packing density was maximized by a relatively high (70% to 80%) coarse coal content. However, the packing density did not correlate with the compressive strength of the briquette that instead maximized with 100% fine flotation coal and continuously decreased as higher proportions of coarse coal were added. Similar compaction and compressive-strength results were obtained with mixtures of sawdust and varying proportions of coarse and fine coal. With the addition of a binder, the highest strengths were no longer obtained with 100% fine coal but instead maximized between 20% and 50% coarse coal addition depending on how long the briquettes were cured.

Patil, D.P.; Taulbee, D.; Parekh, B.K.; Honaker, R. [University of Kentucky, Lexington, KY (United States). Center for Applied Energy Research

2009-07-01

357

Analytical results for the cluster size distribution in controlled deposition processes  

International Nuclear Information System (INIS)

This paper proposes a controlled particle deposition model for cluster growth on the substrate surface and then presents exact results for the cluster (island) size distribution. In the system, at every time step a fixed number of particles are injected into the system and immediately deposited onto the substrate surface. It investigates the cluster size distribution by employing the generalized rate equation approach. The results exhibit that the evolution behaviour of the system depends crucially on the details of the adsorption rate kernel. The cluster size distribution can take the Poisson distribution or the conventional scaling form in some cases, while it is of a quite complex form in other cases. (condensed matter: structure, thermal and mechanical properties)

358

Size distributions of aerosols produced from substitute materials by the Laskin cold DOP aerosol generator  

International Nuclear Information System (INIS)

Test aerosols of di(2-ethylhexyl)phthalate (DOP) produced by Laskin nozzle aerosol generators are widely used for in-place filter testing and respirator fit testing. Concern for the health effects of this material has led to a search for substitute materials for test aerosols. Aerosols were generated with a Laskin generator and diluted 6000-fold with clean air. Size distributions were measured for DOP, di(2-ethylhexyl)sebecate, polyethylene glycol, mineral oil, and corn oil aerosols with a PMS ASAS-X optical particle counter. Distributions were slightly bimodal with count median diameters from 0.22 to 0.30 ?m. Size distributions varied little with aerosol material, operating pressure, or liquid level. Mineral oil and corn oil gave the best agreement with the DOP size distribution

359

Estimates of zooplankton abundance and size distribution with the Optical Plankton Counter (OPC)  

DEFF Research Database (Denmark)

The capability of the Optical Plankton Count er (OPC) to examine the abundance and size distribution of zooplankton was tested in Storfjorden, Norway, in June 1993. Selected material obtained from net sampling was measured with a laboratory version of the OPC and compared with microscope analysis in order to identify main species in the in situ size frequency distributions obtained by the submersible version of the OPC. Differences in the particle concentration between shallow and deep water layers were clearly resolved by the submersible OPC, but the high diversity of the zooplankton community and widely overlapping size ranges prevented a detailed analysis of the fine scale vertical distribution and the horizontal variability of abundance for distinct species. These results are used to discuss the limitations of the OPC for rapid and continuous surveying of spatial distribution and abundance of zooplankton

Wieland, Kai

1997-01-01

360

Size distribution of matter related to radionuclides released from Fukushima nuclear power plant  

International Nuclear Information System (INIS)

In relation to the Fukushima accident among March 24 to April 13, 2011 were performed consecutive aerosol samples for determination of specific activity depending on its size distribution. The extraction used three five-cascade impactors distributed within SURO Prague. Volume activity deposited on the collection of base liners and filters was determined by semiconductor gamma spectrometry. The obtained spectra were evaluated in terms of size distribution of 131I, 134Cs and 137Cs, compared to control and were also provided for 7Be. The results were compared with data obtained in May and June 1986 after the Chernobyl disaster, when an average AMAD value of volatile radionuclides (which include 131I, 134Cs and 137Cs) 0.5 ?m. The comparison shows that size distribution and the values of AMAD disaster at Chernobyl NPP and Fukushima NPP disaster were very similar.

 
 
 
 
361

Effect of Feedstock Size and its Distribution on the Properties of Detonation Sprayed Coatings  

Science.gov (United States)

The detonation spraying is one of the most promising thermal spray variants for depositing wear and corrosion resistant coatings. The ceramic (Al2O3), metallic (Ni-20 wt%Cr) , and cermets (WC-12 wt%Co) powders that are commercially available were separated into coarser and finer size ranges with relatively narrow size distribution by employing centrifugal air classifier. The coatings were deposited using detonation spray technique. The effect of particle size and its distribution on the coating properties were examined. The surface roughness and porosity increased with increasing powder particle size for all the coatings consistently. The feedstock size was also found to influence the phase composition of Al2O3 and WC-Co coatings; however does not influence the phase composition of Ni-Cr coatings. The associated phase change and %porosity of the coatings imparted considerable variation in the coating hardness, fracture toughness, and wear properties. The fine and narrow size range WC-Co coating exhibited superior wear resistance. The coarse and narrow size distribution Al2O3 coating exhibited better performance under abrasion and sliding wear modes however under erosion wear mode the as-received Al2O3 coating exhibited better performance. In the case of metallic (Ni-Cr) coatings, the coatings deposited using coarser powder exhibited marginally lower-wear rate under abrasion and sliding wear modes. However, under erosion wear mode, the coating deposited using finer particle size exhibited considerably lower-wear rate.

Suresh Babu, P.; Rao, D. S.; Rao, G. V. N.; Sundararajan, G.

2007-06-01

362

Comparing particle-size distributions in modern and ancient sand-bed rivers  

Science.gov (United States)

Particle-size distributions yield valuable insight into processes controlling sediment supply, transport, and deposition in sedimentary systems. This is especially true in ancient deposits, where effects of changing boundary conditions and autogenic processes may be detected from deposited sediment. In order to improve interpretations in ancient deposits and constrain uncertainty associated with new methods for paleomorphodynamic reconstructions in ancient fluvial systems, we compare particle-size distributions in three active sand-bed rivers in central Nebraska (USA) to grain-size distributions from ancient sandy fluvial deposits. Within the modern rivers studied, particle-size distributions of active-layer, suspended-load, and slackwater deposits show consistent relationships despite some morphological and sediment-supply differences between the rivers. In particular, there is substantial and consistent overlap between bed-material and suspended-load distributions, and the coarsest material found in slackwater deposits is comparable to the coarse fraction of suspended-sediment samples. Proxy bed-load and slackwater-deposit samples from the Kayenta Formation (Lower Jurassic, Utah/Colorado, USA) show overlap similar to that seen in the modern rivers, suggesting that these deposits may be sampled for paleomorphodynamic reconstructions, including paleoslope estimation. We also compare grain-size distributions of channel, floodplain, and proximal-overbank deposits in the Willwood (Paleocene/Eocene, Bighorn Basin, Wyoming, USA), Wasatch (Paleocene/Eocene, Piceance Creek Basin, Colorado, USA), and Ferris (Cretaceous/Paleocene, Hanna Basin, Wyoming, USA) formations. Grain-size characteristics in these deposits reflect how suspended- and bed-load sediment is distributed across the floodplain during channel avulsion events. In order to constrain uncertainty inherent in such estimates, we evaluate uncertainty associated with sample collection, preparation, analytical particle-size analysis, and statistical characterization in both modern and ancient settings. We consider potential error contributions and evaluate the degree to which this uncertainty might be significant in modern sediment-transport studies and ancient paleomorphodynamic reconstructions.

Hajek, E. A.; Lynds, R. M.; Huzurbazar, S. V.

2011-12-01

363

Multi-Scale Particle Size Distributions of Mars, Moon and Itokawa based on a time-maturation dependent fragmentation model  

Science.gov (United States)

We present the development of a soil evolution framework and multiscale modelling of the surface of Mars, Moon and Itokawa thus providing an atlas of extra-terrestrial Particle Size Distributions (PSD). These PSDs are profoundly based on a tailoring method which interconnects several datasets from different sites captured by the various missions. The final integrated product is then fully justified through a soil evolution analysis model mathematically constructed via fundamental physical principles (Charalambous, 2013). The construction of the PSD takes into account the macroscale fresh primary impacts and their products, the mesoscale distributions obtained by the in-situ data of surface missions (Golombek et al., 1997, 2012) and finally the microscopic scale distributions provided by Curiosity and Phoenix Lander (Pike, 2011). The distribution naturally extends at the magnitudinal scales at which current data does not exist due to the lack of scientific instruments capturing the populations at these data absent scales. The extension is based on the model distribution (Charalambous, 2013) which takes as parameters known values of material specific probabilities of fragmentation and grinding limits. Additionally, the establishment of a closed-form statistical distribution provides a quantitative description of the soil's structure. Consequently, reverse engineering of the model distribution allows the synthesis of soil that faithfully represents the particle population at the studied sites (Charalambous, 2011). Such representation essentially delivers a virtual soil environment to work with for numerous applications. A specific application demonstrated here will be the information that can directly be extracted for the successful drilling probability as a function of distance in an effort to aid the HP3 instrument of the 2016 Insight Mission to Mars. Pike, W. T., et al. "Quantification of the dry history of the Martian soil inferred from in situ microscopy." Geophysical Research Letters 38.24 (2011). C. A. Charalambous and W. T. Pike (2013). 'Evolution of Particle Size Distributions in Fragmentation Over Time' Abstract Submitted to the AGU 46th Fall Meeting. Charalambous, C., Pike, W. T., Goetz, W., Hecht, M. H., & Staufer, U. (2011, December). 'A Digital Martian Soil based on In-Situ Data.' In AGU Fall Meeting Abstracts (Vol. 1, p. 1669). Golombek, M., & Rapp, D. (1997). 'Size-frequency distributions of rocks on Mars and Earth analog sites: Implications for future landed missions.' Journal of Geophysical Research, 102(E2), 4117-4129. Golombek, M., Huertas, A., Kipp, D., & Calef, F. (2012). 'Detection and characterization of rocks and rock size-frequency distributions at the final four Mars Science Laboratory landing sites.' Mars, 7, 1-22.

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

2013-12-01

364

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 ? 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.

365

Collection strategy, inner morphology, and size distribution of dust particles in ASDEX Upgrade  

Energy Technology Data Exchange (ETDEWEB)

The dust collection and analysis strategy in ASDEX Upgrade (AUG) is described. During five consecutive operation campaigns (2007–2011), Si collectors were installed, which were supported by filtered vacuum sampling and collection with adhesive tapes in 2009. The outer and inner morphology (e.g. shape) and elemental composition of the collected particles were analysed by scanning electron microscopy. The majority of the ~50?000 analysed particles on the Si collectors of campaign 2009 contain tungsten—the plasma-facing material in AUG—and show basically two different types of outer appearance: spheroids and irregularly shaped particles. By far most of the W-dominated spheroids consist of a solid W core, i.e. solidified W droplets. A part of these particles is coated with a low-Z material; a process that seems to happen presumably in the far scrape-off layer plasma. In addition, some conglomerates of B, C and W appear as spherical particles after their contact with plasma. By far most of the particles classified as B-, C- and W-dominated irregularly shaped particles consist of the same conglomerate with varying fraction of embedded W in the B–C matrix and some porosity, which can exceed 50%. The fragile structures of many conglomerates confirm the absence of intensive plasma contact. Both the ablation and mobilization of conglomerate material and the production of W droplets are proposed to be triggered by arcing. The size distribution of each dust particle class is best described by a log-normal distribution allowing an extrapolation of the dust volume and surface area. The maximum in this distribution is observed above the resolution limit of 0.28 µm only for the W-dominated spheroids, at around 1 µm. The amount of W-containing dust is extrapolated to be less than 300 mg on the horizontal areas of AUG.

M. Balden; N. Endstrasser; P. W. Humrickhouse; V. Rohde; M. Rasinski; U. von Toussaint; S. Elgeti; R. Neu

2014-04-01

366

Are range-size distributions consistent with species-level heritability?  

DEFF Research Database (Denmark)

The concept of species-level heritability is widely contested. Because it is most likely to apply to emergent, species-level traits, one of the central discussions has focused on the potential heritability of geographic range size. However, a central argument against range-size heritability has been that it is not compatible with the observed shape of present-day species range-size distributions (SRDs), a claim that has never been tested. To assess this claim, we used forward simulation of range-size evolution in clades with varying degrees of range-size heritability, and compared the output of three different models to the range-size distribution of the South American avifauna. Although there were differences among the models, a moderate-to-high degree of range-size heritability consistently leads to SRDs that were similar to empirical data. These results suggest that range-size heritability can generate realistic SRDs, and may play an important role in shaping observed patterns of range sizes.

Borregaard, Michael Krabbe; Gotelli, Nicholas

2012-01-01

367

Comparison of photon correlation spectroscopy with photosedimentation analysis for the determination of aqueous colloid size distributions  

Science.gov (United States)

Photon correlation spectroscopy (PCS) utilizes the Doppler frequency shift of photons scattered off particles undergoing Brownian motion to determine the size of colloids suspended in water. Photosedimentation analysis (PSA) measures the time-dependent change in optical density of a suspension of colloidal particles undergoing centrifugation. A description of both techniques, important underlying assumptions, and limitations are given. Results for a series of river water samples show that the colloid-size distribution means are statistically identical as determined by both techniques. This also is true of the mass median diameter (MMD), even though MMD values determined by PSA are consistently smaller than those determined by PCS. Because of this small negative bias, the skew parameters for the distributions are generally smaller for the PCS-determined distributions than for the PSA-determined distributions. Smaller polydispersity indices for the distributions are also determined by PCS. -from Author

Rees, T.F.

1990-01-01

368

On the accuracy of fragment size measurement by image analysis in combination with some distribution functions  

Science.gov (United States)

Size distributions of fragments of crushed rock in conveyor belts and of blasted rock in a muckpile obtained by sieving are compared with the size distributions obtained by digital image analysis of photographs of the same materials taken on-site. Several calculation methods are tested, based on the raw distribution of fragment areas and on the volume-transformed ones. The influence of the calibration of the system on the results and the performance of the system in a non-calibrated mode are evaluated. The capacity of some distributions (Rosin-Rammler, Swebrec and lognormal) to fit the data in the coarse region (where particles can be delineated, i.e. discriminated individually) and to extrapolate to the non-delineated fines (where particles cannot be outlined and their contour delineated) is assessed. The error between the sizes measured and the sizes of the reference distributions (determined by sieving) increases from the coarse to the fines region. The maximum error at a given size depends primarily on its value relative to the fines cut-off (FCO) of the image analysis. In general, at sizes greater than the FCO, where the system is able to delineate fragments reliably, both volume and surface-based, calibrated, calculations can determine the sizes with maximum error expectancy of about 30%. Below the FCO, only the calibrated, volume calculation maintains a maximum error of 30%, down to sizes of about one fourth the FCO, rapidly increasing for smaller sizes. Where the calibration is done based on data above the FCO, errors can be large below this point, in excess of 80% at sizes half the FCO. In the fines range (sizes smaller than 0.2 times the FCO) the maximum errors can be close to or greater than 100% for most of the calculations and function fittings. Of the distributions tested, all of them are acceptable at sizes above the FCO; below that, the Swebrec function seems to adapt better towards the fines than the Rosin-Rammler and lognormal.

Sanchidrián, J. A.; Segarra, P.; Ouchterlony, F.; López, L. M.

2009-02-01

369

Bubble size distribution in acoustic droplet vaporization via dissolution using an ultrasound wide-beam method.  

Science.gov (United States)

Performance and efficiency of numerous cavitation enhanced applications in a wide range of areas depend on the cavitation bubble size distribution. Therefore, cavitation bubble size estimation would be beneficial for biological and industrial applications that rely on cavitation. In this study, an acoustic method using a wide beam with low pressure is proposed to acquire the time intensity curve of the dissolution process for the cavitation bubble population and then determine the bubble size distribution. Dissolution of the cavitation bubbles in saline and in phase-shift nanodroplet emulsion diluted with undegassed or degassed saline was obtained to quantify the effects of pulse duration (PD) and acoustic power (AP) or peak negative pressure (PNP) of focused ultrasound on the size distribution of induced cavitation bubbles. It was found that an increase of PD will induce large bubbles while AP had only a little effect on the mean bubble size in saline. It was also recognized that longer PD and higher PNP increases the proportions of large and small bubbles, respectively, in suspensions of phase-shift nanodroplet emulsions. Moreover, degassing of the suspension tended to bring about smaller mean bubble size than the undegassed suspension. In addition, condensation of cavitation bubble produced in diluted suspension of phase-shift nanodroplet emulsion was involved in the calculation to discuss the effect of bubble condensation in the bubble size estimation in acoustic droplet vaporization. It was shown that calculation without considering the condensation might underestimate the mean bubble size and the calculation with considering the condensation might have more influence over the size distribution of small bubbles, but less effect on that of large bubbles. Without or with considering bubble condensation, the accessible minimum bubble radius was 0.4 or 1.7 ?m and the step size was 0.3 ?m. This acoustic technique provides an approach to estimate the size distribution of cavitation bubble population in opaque media and might be a promising tool for applications where it is desirable to tune the ultrasound parameters to control the size distribution of cavitation bubbles. PMID:24360840

Xu, Shanshan; Zong, Yujin; Li, Wusong; Zhang, Siyuan; Wan, Mingxi

2014-05-01

370

An Aggregate Model for the Particle Size Distribution in Saturn's Rings  

CERN Document Server

Saturn's rings are known to consist of a large number of water ice particles. They form a flat disk, as the result of an interplay of angular momentum conservation and the steady loss of energy in dissipative particle collisions. For particles in the size range from a few centimeters to about a few meters a power law distribution of radii r^(-q), with q = 3, is implied by the light scattering properties of the rings. In contrast, for larger sizes the distribution drops steeply with increasing r. It has been suggested that this size distribution may arise from a balance between aggregation and fragmentation of ring particles, but to date neither the power-law dependence, nor the upper size-cutoff have been explained or quantified within a unique theory. Here we present a new kinetic model for the collisional evolution of the size distribution and show that the exponent q is expected to be constrained to the interval 2.75 < q < 3.5. An exponential cutoff towards larger particle sizes establishes naturally...

Brilliantov, Nikolai; Hayakawa, Hisao; Bodrova, Anna; Spahn, Frank; Schmidt, Juergen

2013-01-01

371

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

Directory of Open Access Journals (Sweden)

Full Text Available the key to reduce coal pollution is the development of clean coal technology and the improvement of the backward coal-burning technology. The coal water slurry (CWS is the first substitute of the oil. The particle size distribution of CWS plays an important role in the quality control of CWS. Now there are three methods that are used to analysis the particle size distribution of CWS, screening method, settlement method, laser method. These methods produce some disadvantages when be used to forecast the distribution of CWS. Thus, this article proposes an ultrasonic method with effective medium theory model which can be accurately reflected in the acoustic attenuation characteristics of coal-water slurry based on structural average. Experimental simulation proved that effective medium model is fully capable of achieving on-line detection of coal-water slurry particle size, for detection of fine-and coarse-sized particle size distribution. Non-linear relationship between attenuation and particle size, the three-frequency method can be used to inverse calculation of its. Which we can achieve CWS granularity on-line, and continuously control the quality of CWS.

WANG Weidong

2010-11-01

372

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

Science.gov (United States)

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.

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

2013-05-01

373

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

2013-05-01

374

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

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English 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 orde [...] r 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.

375

Determination of the pore size distribution and hydraulic properties from Nuclear Magnetic Resonance relaxometry  

Science.gov (United States)

Known pore size distributions can be directly linked to the water retention characteristic which is essential for the prognosis of water and solute movement through the material. In our study, we evaluated the feasibility to use Nuclear Magnetic Resonance (NMR) relaxometry measurements for the characterization of pore size distribution in four porous samples with different texture and composition. Therefore, NMR T2 and T1 relaxation measurements at 6.47 MHz were carried out for three model samples (medium sand; fine sand; and a homogenous sand / kaolin clay mixture) and a natural soil. To quantify the goodness of the approach, the NMR measurements were compared in terms of cumulated pore size distribution functions and mean pore diameter with the two classical techniques based on water retention and mercury porosimetry measurements. The results showed that T1 and T2 derived mean pore size diameters are in good agreement with each other but deviate from retention curve derived ones. This is especially the case for well sorted sands with n values > 2.7. For finer materials differences are less pronounced. A short study was performed to evaluate the influence of the variations observed in the pore diameter distributions on the hydraulic properties of the samples: ?S, ?, and n. In conclusion, NMR T1 and T2 relaxation measurements can be used to estimate pore size distribution, mean pore diameter, as well as the retention function and corresponding hydraulic properties.

Stingaciu, Laura R.; Weihermüller, Lutz; Haber-Pohlmeier, Sabina; Stapf, Siegfried; Vereecken, Harry; Pohlmeier, Andreas

2010-05-01

376

X-ray diffraction microstructural analysis of bimodal size distribution MgO nano powder  

International Nuclear Information System (INIS)

Investigation on the characteristics of x-ray diffraction data for MgO powdered mixture of nano and sub-nano particles has been carried out to reveal the crystallite-size-related microstructural information. The MgO powders were prepared by co-precipitation method followed by heat treatment at 500 degree Celsius and 1200 degree Celsius for 1 hour, being the difference in the temperature was to obtain two powders with distinct crystallite size and size-distribution. The powders were then blended in air to give the presumably bimodal-size- distribution MgO nano powder. High-quality laboratory X-ray diffraction data for the powders were collected and then analysed using Rietveld-based MAUD software using the lognormal size distribution. Results show that the single-mode powders exhibit spherical crystallite size (R) of 20(1) nm and 160(1) nm for the 500 degree Celsius and 1200 degree Celsius data respectively with the nano metric powder displays narrower crystallite size distribution character, indicated by lognormal dispersion parameter of 0.21 as compared to 0.01 for the sub-nano metric powder. The mixture exhibits relatively more asymmetric peak broadening. Analysing the x-ray diffraction data for the latter specimen using single phase approach give unrealistic results. Introducing two phase models for the double-phase mixture to accommodate the bimodal-size-distribution characteristics give R = 100(6) and ? = 0.62 for the nano metric phase and R = 170(5) and ?= 0.1o metric phase and R = 170(5) and ?= 0.12 for the ? sub-nano metric phase. (author)

377

Size and composition distribution of fine particulate matter emitted from wood burning, meat charbroiling, and cigarettes  

International Nuclear Information System (INIS)

A dilution source sampling system is augmented to measure the size-distributed chemical composition of fine particle emissions from air pollution sources. Measurements are made using a laser optical particle counter (OPC), a differential mobility analyzer/condensation nucleus counter (DMA/CNC) combination, and a pair of microorifice uniform deposit impactors (MOUDIs). The sources tested with this system include wood smoke (pine, oak, eucalyptus), meat charbroiling, and cigarettes. The particle mass distributions from all wood smoke sources have a single mode that peaks at approximately 0.1--0.2 microm particle diameter. The smoke from meat charbroiling shows a major peak in the particle mass distribution at 0.1--0.2 microm particle diameter, with some material present at larger particle sizes. Particle mass distributions from cigarettes peak between 0.3 and 0.4 microm particle diameter. Chemical composition analysis reveals that particles emitted from the sources tested here are largely composed of organic compounds. Noticeable concentrations of elemental carbon are found in the particles emitted from wood burning. The size distributions of the trace species emissions from these sources also are presented, including data for Na, K, Ti, Fe, Br, Ru, Cl, Al, Zn, Ba, Sr, V, Mn, Sb, La, Ce, as well as sulfate, nitrate, and ammonium ion when present in statistically significant amounts. These data are intended for use with air quality models that seek to predict the size distribution of the chemical composition of atmospheric fine particles

378

The size distributions of fragments ejected at a given velocity from impact craters  

Science.gov (United States)

The mass distribution of fragments that are ejected at a given velocity for impact craters is modeled to allow extrapolation of laboratory, field, and numerical results to large scale planetary events. The model is semi-empirical in nature and is derived from: (1) numerical calculations of cratering and the resultant mass versus ejection velocity, (2) observed ejecta blanket particle size distributions, (3) an empirical relationship between maximum ejecta fragment size and crater diameter, (4) measurements and theory of maximum ejecta size versus ejecta velocity, and (5) an assumption on the functional form for the distribution of fragments ejected at a given velocity. This model implies that for planetary impacts into competent rock, the distribution of fragments ejected at a given velocity is broad, e.g., 68 percent of the mass of the ejecta at a given velocity contains fragments having a mass less than 0.1 times a mass of the largest fragment moving at that velocity. The broad distribution suggests that in impact processes, additional comminution of ejecta occurs after the upward initial shock has passed in the process of the ejecta velocity vector rotating from an initially downward orientation. This additional comminution produces the broader size distribution in impact ejecta as compared to that obtained in simple brittle failure experiments.

O'Keefe, John D.; Ahrens, Thomas J.

1987-01-01

379

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

2010-08-01

380

Rock size distributions on lava flow surfaces: New results from a range of compositions  

Science.gov (United States)

We measured block sizes along 15-25m orthogonal transects on 12 lava flows of compositions ranging from basalt to rhyolite. At each site, we stretched a line across the flow surface then measured the length of each block cut by this line that were greater than 3-12cm (depending on composition). The measurements from each site were reduced to cumulative size frequency distribution plots, with block size (D) plotted against the fraction of the line f(D) composed of blocks greater than or equal to that size, and fitted with an exponential curve of the form f(D) = k exp(-qD) where k is the intercept and q is the decay parameter. Average block size and geometric mean were also determined for each site. Our data show no clear trends linking average or mean block size to composition, although there does seem to be relationship between block size and the decay parameter. Block size corresponds with the decay parameter at each site except for the basaltic andesite flow at Paint Pot Crater (CA). Many sites at this flow were covered with secondary spatter deposits. Largest blocks and smallest decay parameters were found for the andesite flows at Sabancaya (Peru), while the basalt flows at Cima (CA) exhibited the smallest blocks and largest decay parameters. The second largest block sizes occurred at the four Inyo domes composed of both crystal-rich and glassy rhyolite, and these domes also s