Export, Productivity Pattern, and Firm Size Distribution
Sun, Churen; Zhang, Tao
2012-01-01
We show in the Chinese Annual Survey of Industrial Firms that size distributions of non-exporters and exporters have different shapes, which can only be explained by assuming that their productivity distributions have different shapes. Empirical estimations verify this assumption. This paper also analyzes the relationship between firms' size and productivity distributions and shows that: 1) productivity and size distributions change accordingly, and 2) productivity is deterministic for siz...
Product differentiation and firm size distribution : an application to carbonated soft drinks
Whelan, Ciara; Walsh, Patrick P.
2002-01-01
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...
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
Energy Technology Data Exchange (ETDEWEB)
Fei, Lin
1996-04-01
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.
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
Size distribution of radon decay products in the range 0.1-10 nm.
Zhukovsky, Michael; Rogozina, Marina; Suponkina, Anna
2014-07-01
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
Energy Technology Data Exchange (ETDEWEB)
S.K. Kawatra; T.C. Eisele; T. Weldum; D. Larsen; R. Mariani; J. Pletka
2005-07-01
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.
International Nuclear Information System (INIS)
The impact of natural solar ultraviolet radiation (UVR), particularly UVB (297-320 nm), on phytoplankton primary production in Lake Erie was investigated during the spring and summer of 1997. Radiocarbon incorporation and size-selective filtration was used to trace total production and its distribution among particulate and dissolved pools. On average, 1-h exposures produced half the UVB-dependent inhibition of total production realized in 8-h exposures, indicating rapid kinetics of photoinhibition. Cumulative UVB-dependent photoinhibition averaged 36% in 8-h simulated surface exposures. The efficiency of photoinhibition was greater for N-deficient than N-replete communities, but was not related to phytoplankton light history, P limitation, or the dominant genera. The proportion of recently fixed carbon occurring in the dissolved pool after 8-h exposures was significantly greater in higher-UVB treatments, whereas the share in picoplankton (<2 ?m) was significantly lower. Significant UVB-dependent inhibition of total production was limited on average to relatively severe exposures, but the rapid kinetics of inhibition and the apparent effects on the allocation of carbon suggest it may be important to the lake's food web. Differences in optical properties and thermal stratification patterns suggested that the relatively turbid west basin was potentially more susceptible to UVR photoinhibition than the more transparent east or central basins. (author)ntral basins. (author)
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
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.
Verity, Peter G.
1987-05-01
The abundance of tintinnid ciliates in lower Narragansett Bay was measured at weekly intervals over the period 1980-1982. Twenty-nine species representing nine genera ranged in abundance from 10 1 to 10 5 tintinnids l -1. Tintinnopsis was the most numerous genus in terms of numbers of species and individuals. Total abundance increased with water temperature above 6°C, and with nanoplankton chlorophyll a (small to large species coincident with similar shifts in the size of phytoplankton. The production rate of tintinnids was 3·3 mgCl -1 year -1, equivalent to the ingestion of 26% of total annual net primary production and 52% of the estimated production of <10 ?m phytoplankton.
International Nuclear Information System (INIS)
Naturally occurring radioactive material, often referred to as NORM, is found throughout the earth's crust and forms part of the natural radiation background to which all humans are exposed. Normally the radionuclides found in NORM are members of the radioactive decay chains of 238U, 235U and 232Th. The main routes of radionuclide intake are through inhalation of airborne dust and ingestion of food and water. Furthermore, internal irradiation of the bronchial epithelium by alpha particles from the short lived progeny of radon constitutes substantially to the exposure from natural sources. Human activities like mining and mineral processing and extractions of petroleum products may concentrate the radionuclides in the work environment. Such alteration of the natural environment can increase the radiation exposure of workers and the public. An important factor affecting the radiation dose received through inhalation of airborne dust is the size of the particles. The size, to a large extent, determines where the radioactivity deposits in the lung and accordingly the tissue that will be affected. South Africa is a major exporter of mineral products. These minerals may contain natural radionuclides at varying levels depending on the particle size. Most of these mineral products are processed further in local or overseas beneficiation processing plants. The South African Nuclear Energy Corporation (NECSA) developed a protocol to certify the ECSA) developed a protocol to certify the radiological impact on workers from respirable airborne dust potentially generated by handling and/or processing of materials contaminated with NORM. An overview will be provided of the incentive and outcome of the research based on a number of materials known to contain varying amounts of natural radionuclides. (author)
Multimodal Raindrop Size Distributions.
Sauvageot, Henri; Koffi, Manlandon
2000-08-01
The raindrop size distributions (DSDs) observed over a short span usually have an erratic shape, with several relative maxima. This multimodal structure is studied from disdrometer data acquired in tropical and midlatitude areas. It is shown that some modes of DSDs have a persistence larger than several minutes and can be spotted from one DSD to the next one as they migrate through the size classes. It is demonstrated that Nm, the number of modes of DSDs, for diameter larger than 2 mm, is not related to the mean rain rate but depends on the rain-rate fluctuations. Statistical evidence of such a relation is given. The spread of DSDs is found to be dependent on its multimodal structure, that is, on Nm. The large values of Nm are associated with low values of slope and intercept N0 of the fitted exponential distribution.In order to explain the dependence of the DSD shape on Nm, a conceptual model is proposed in which the modes are interpreted as resulting from an overlapping of rain shafts. The associated DSD is termed a synthetic drop size distribution (SDSD). It is shown that the overlapping of rain shafts generated from a sequence of rain cells of increasing intensity, such as observed at the leading edge of a convective system, results in undersloping SDSDs. In the reverse configuration, that is, with a sequence of rain cells with decreasing intensity, such as observed at the ending edge of a convective system, it results in oversloping SDSDs. Observations in agreement with these conclusions are presented. The readability of the modal structure of the DSDs depends on several factors in such a way that an apparent multimodal structure is not necessary for a DSD to be an SDSD. It is suggested that most of the DSDs observed at the ground are synthetic DSDs.
Radon daughter activity size distributions
International Nuclear Information System (INIS)
The size distributions of radon and thoron daughters have been measured in buildings and in the open air. Because of the low radioactivity concentration a high volume cascade impactor was used. The cascade impactor data were evaluated by using an improved computer programme taking into account the effect of interstage losses on the measured precipitation values of the impactor. The size distributions found for the shortlived radon daughters, 214Pb, 214Bi, and thoron daughter, 212Pb, were unimodal log-normal. There was no significant different between activity size distributions of the short lived radon decay products and the thoron daughter 212Pb. The activity median aerodynamic diameter (AMAD) measured in different buildings and at different days ranged from 0.07 to 0.29 ?m with a mean value of 0.18 ?m for the radon and thoron daughters in dwellings with low room ventilation. The mean value of the geometric standard deviation was ?sub(g) = 3.50. The size distributions in the open air are significantly larger with a mean AMAD of 0.39 ?m (range: 0.20 to 0.54 ?m) and a mean standard deviation of ?sub(g) = 2.31. (author)
Energy Technology Data Exchange (ETDEWEB)
A. Faanhof; M. van Staden; I. Kungoane [NECSA, Pretoria (South Africa)
2008-01-15
Naturally occurring radioactive material, often referred to as NORM, is found throughout the earth's crust and forms part of the natural radiation background to which all humans are exposed. Normally the radionuclides found in NORM are members of the radioactive decay chains of {sup 238}U, {sup 235}U and {sup 232}Th. Human activities like mining and mineral processing and extraction of petroleum products may concentrate the radionuclides in the work environment. Such alteration of the natural environment can increase the radiation exposure of workers and the public. Mineral products like zircon, rutile, ilmenite, monazite, baddeleyite, coal and titanium slag obtained from various mineral deposits in South Africa contain noticeable quantities of TENORM. Dust generated during transport, handling and reprocessing of the material could pose a radiological risk on inhalation of the respirable fraction. An analytical procedure has been developed to quantify this potential risk to workers, which may alleviate intensive workplace and personnel monitoring. 30 refs., 1 fig., 1 app.
Lunar soil grain size distribution
Carrier, W. D., III
1973-01-01
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.
Body size distribution of the dinosaurs.
O'Gorman, Eoin J; Hone, David W E
2012-01-01
The distribution of species body size is critically important for determining resource use within a group or clade. It is widely known that non-avian dinosaurs were the largest creatures to roam the Earth. There is, however, little understanding of how maximum species body size was distributed among the dinosaurs. Do they share a similar distribution to modern day vertebrate groups in spite of their large size, or did they exhibit fundamentally different distributions due to unique evolutionary pressures and adaptations? Here, we address this question by comparing the distribution of maximum species body size for dinosaurs to an extensive set of extant and extinct vertebrate groups. We also examine the body size distribution of dinosaurs by various sub-groups, time periods and formations. We find that dinosaurs exhibit a strong skew towards larger species, in direct contrast to modern day vertebrates. This pattern is not solely an artefact of bias in the fossil record, as demonstrated by contrasting distributions in two major extinct groups and supports the hypothesis that dinosaurs exhibited a fundamentally different life history strategy to other terrestrial vertebrates. A disparity in the size distribution of the herbivorous Ornithischia and Sauropodomorpha and the largely carnivorous Theropoda suggests that this pattern may have been a product of a divergence in evolutionary strategies: herbivorous dinosaurs rapidly evolved large size to escape predation by carnivores and maximise digestive efficiency; carnivores had sufficient resources among juvenile dinosaurs and non-dinosaurian prey to achieve optimal success at smaller body size. PMID:23284818
Trudnowska, E.; Basedow, S. L.; Blachowiak-Samolyk, K.
2014-09-01
The estimation of secondary production constitutes an integrating proxy of pelagic ecosystem status, its functions as well as its responses to environmental stressors. The combination of high-resolution automatic measurements with a Laser Optical Plankton Counter (LOPC) and size spectrum analyses was utilized to estimate the secondary production of a high Arctic fjord during a summer post bloom situation in 2012. The dataset comprised 28 vertical and extensive horizontal hauls of a LOPC-CTD-fluorometer platform plus four zooplankton net sampling stations for taxonomic composition designation. A clear gradient in temperature, salinity, chlorophyll a concentrations as well as mesozooplankton abundance, biomass and production was demonstrated along Hornsund fjord axis. The outer fjord part was under the influence of water advection and had the highest chlorophyll a concentrations, numerous opaque mesozooplankton individuals and flat slopes of size spectra, pointing to long food chains in which biomass is recycled several times. The opposite state was found in the glacial bays, where the glacier meltwater discharge led to low chlorophyll a concentrations but high abundance of small and amorphous particles. It resulted in steep size spectra slopes and high intercepts implying higher potential productivity there. The model of mesozooplankton production demonstrated that Hornsund fjord is a highly productive ecosystem, particularly its upper water layer and its central parts. However, we would like to emphasize that a careful approach is needed before going deeper into ecological interpretations based on size spectra analysis, especially in reservoirs, where non-zooplankton particles contribute to the size spectra.
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)
International Nuclear Information System (INIS)
Annealing of zircaloy-4 plate obtained from hot rolling of ingot at varied temperature and time has been carried out. The annealing process has been performed in a furnace in argon atmosphere. Metallographic examination has been done to observe the precipitate formed. The experiments have shown that at the relatively low temperature (7400C);the distribution of precipitate size is not homogeneous. It is considered that the annealing process has still been in the recovery stage. When the temperature increases, the precipitate tends to be in homogeneous distribution. At 8500C, the longer annealing time elapses, the coarser precipitate size will be, while the homogeneity appears after 10 hours annealing time (>3 hours), the homogeneity of precipitate size is formed more frequently. In this paper, the degree of precipitation, W(t), has reached 99.63% in the performed condition that is at temperature of 7400C for 30 minutes annealing time also discussed
Centaur size distribution with DECam
Fuentes, Cesar; Trilling, David E.; Schlichting, Hilke
2014-11-01
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.
International Nuclear Information System (INIS)
Within the framework of radiation protection programmes supported by the CEC, the US-DOE, and the Australian Government, intercomparison measurements were performed in a house with elevated radon concentrations in Northern Bavaria (Germany) in October 1991. Besides the research aspects of aerosol sciences, the purpose of this joint measurement was to compare dose conversion factors calculated from the results obtained by these three laboratories. In low ventilated rooms with moderate aerosol particle concentrations (Z = 4000-8000 cm-3) about 40% of the 218Po activity is associated with clusters, narrow in shape (?g) g) > 1.2, fraction = 10%) of the 'unattached' part of the 218Po distribution with a median diameter of 3-4 nm. The averaged (3 days) derived effective dose conversion factors (HE-DCF) from the 218Po values - measured by the three groups -differ less than 30%. However, the daily averaged values sometimes differ by a factor of 2. In general, it does not appear to make much difference to the derived conversion factors if the ultrafine mode (< 10 nm) is unimodal or bimodal. The median diameters of the aerosol-attached fraction of the short-lived radon decay products ranged between 200 and 350 nm, depending on the different methods used by the three laboratories. However, these fairlthree laboratories. However, these fairly large differences have only little influence on dose conversion factor calculations. This joint exercise clearly showed that accurate particle size measurements in the diameter range 10-100 nm (nucleus mode), which requires combining impactors and diffusion battery techniques, is a difficult task, not fully solved as yet. (author)
Grain size distribution in seeded large grain size UO2
International Nuclear Information System (INIS)
A large grain size fuel is seen as desirable for the reduction of fission gas release. Conventional techniques to obtain a large grained UO2 include the use of dopants, elevated temperatures, oxidising atmospheres (with or without dopants) and greatly increased cycle times. Although each approach may, ultimately, result in a large grain size fuel, manufacturing considerations may outweigh performance benefits. Similarly performance benefits of doped material, in terms of an improved fission gas retention, may also not be realisable. Seeding is a novel technique for obtaining a large grain sized UO2 in which preferential growth of introduced seed crystals results in a large grain microstructure. By selecting the appropriate size and concentration of seeds, a large grain size fuel is obtained using conventional plant and standard processing cycles. Such grain sizes could only be achieved in a similar time in undoped material by sintering at 2000 deg. C. Additionally, as the seed crystals comprise UO2 there can be no implications, for fuel chemistry, of adopting the approach. Grain size distributions are presented on seeded material sintered in production furnaces for one and two conventional cycles. These show that a fully recrystallised microstructure, comprising a large grain size, can be obtained after one process cycle. Where the seed size is larger and the quantity of nuclei is correspondingly reduced, the time to achieve full recrystallisation is longer, necessitating a second pass through the sintering furnace. However the grain size that could potentially be achieved in these circumstances is larger. (author)
Recurrent frequency-size distribution
Abaimov, S G
2008-01-01
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...
City size distribution and growth
Kopp, Andreas
2000-01-01
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...
Technegas and pertechnegas particle size distribution
International Nuclear Information System (INIS)
Technegas and Pertechnegas are radioactive aerosols produced in a commercial generator and used for lung scintigraphy. The aerosols are produced by first evaporating to dryness standard technetium-99m generator eluate (99mTcO4 in normal saline) in a graphite crucible (the simmer stage) and then heating this to 2500 C (the ''burn'' stage). The aim of this work was to measure the particle size distributions of these agents and relate this to regional lung deposition. Factors that may vary during production of the aerosol in routine use were investigated to determine whether they influenced the particle size. Activity size distributions were measured using a serial wire-screen diffusion battery. The Technegas size distribution was approximately log-normal with an activity median diameter of 158 nm and a geometric standard deviation of 1.5. The results for Pertechnegas were similar. The median size increased with the number of simmers and with the time from generation. The increase in size with the number of simmers is thought to be due to the increased salt content in the crucible prior to the ''burn''. The predicted lung deposition is 37% in the alveolar region and 5% in the bronchial region. Significant changes in deposition are not predicted over the range of particle sizes measured. (orig.)
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)
Soil Particle Size Distribution Protocol
The GLOBE Program, University Corporation for Atmospheric Research (UCAR)
2003-08-01
The purpose of this resource is to sure the distribution of different sizes of soil particles in each horizon of a soil profile. Using dry, sieved soil from a horizon, students mix the soil with water and a dispersing solution to completely separate the particles from each other. Students shake the mixture to fully suspend the soil in the water. The soil particles are then allowed to settle out of suspension, and the specific gravity and temperature of the suspension are measured using a hydrometer and thermometer. These measurements are taken after 2 minutes and 24 hours.
Energy Technology Data Exchange (ETDEWEB)
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
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.
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.
International Nuclear Information System (INIS)
A major issue in radiation protection is to protect the population from the harmful effects of exposure to radon and radon progeny. Quantification of the lung cancer risk emanating from exposure to radon decay products in residential and working environments poses problems, as epidemiologic studies yield information deviating from the results obtained by the indirect method of assessment based on dosimetric respiratory tract models. One important task of the publication here was to characterize the various exposure conditions and to quantify uncertainties that may result from application of the ''dose conversion convention''. A special aerosol spectrometer was therefore designed and built in order to measure the size distributions of the short-lived radon decay products in the range between 0.5 nm and 10 000 nm. The aerosol spectrometer consists of a three-step diffusion battery with wire nets, an 11-step BERNER impactor, and a detector system with twelve large-surface proportional detectors. From the measured size distributions, dose conversion coefficients, E/Peq, were calculated using the PC software RADEP; the RADEP program was developed by BIRCHALL and JAMES and is based on the respiratory tract model of the ICRP. The E/Peq coefficients indicate the effective dose E per unit exposure Peq to radon decay products. (orig./CB)
Grain Size Distributions and Soil Particle Characteristics
Swan, Colby C.
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 soilÂ?s engineering properties such as permeability;ability, strength, expansiveness, etc.
Mathematical models of pancreatic islet size distributions
Jo, Junghyo; Hara, Manami; Ahlgren, Ulf; Sorenson, Robert; Periwal, Vipul
2012-01-01
The islets of Langerhans, ranging in size from clusters of a few cells to several thousand cells, are scattered near large blood vessels. While the ?-cell mass in mammals is proportional to body weight, the size ranges of islets are similar between species with different body sizes, possibly reflecting an optimal functional size. The large range of islet sizes suggests a stochastic developmental process. It is not fully understood how islets develop to reach such size distributions, and how ...
Grain Size Distributions and Soil Particle Characteristics
Lecture notes focusing on measuring grain size distributions (GSDs) of soils and the two methods used to do this. Provides procedures for Sieve Testing and Hydrometer Testing to find the GSD for particular grain sizes.
Energy Technology Data Exchange (ETDEWEB)
Meskhidze, Nicholas [NCSU
2013-10-21
The objective of this workshop was to address the most urgent open science questions for improved quantification of sea spray aerosol-radiation-climate interactions. Sea spray emission and its influence on global climate remains one of the most uncertain components of the aerosol-radiation-climate problem, but has received less attention than other aerosol processes (e.g. production of terrestrial secondary organic aerosols). Thus, the special emphasis was placed on the production flux of sea spray aerosol particles, their number concentration and chemical composition and properties.
On a possible cluster size distribution
International Nuclear Information System (INIS)
The problem of the possible cluster size distribution in multiproduction processes at present energies is analyzed. It is shown how the empirically valid distribution can be found, interpreting the free parameter in that equation, as the number of produced clusters and assuming the Boltzmann distribution as distribution of negatives per cluster
Aggregate size distributions in hydrophobic flocculation
Directory of Open Access Journals (Sweden)
Chairoj Rattanakawin
2003-07-01
Full Text Available The evolution of aggregate (floc size distributions resulting from hydrophobic flocculation has been investigated using a laser light scattering technique. By measuring floc size distributions it is possible to distinguish clearly among floc formation, growth and breakage. Hydrophobic flocculation of hematite suspensions with sodium oleate under a variety of agitating conditions produces uni-modal size distributions. The size distribution of the primary particles is shifted to larger floc sizes when the dispersed suspension is coagulated by pH adjustment. By adding sodium oleate to the pre-coagulated suspension, the distribution progresses further to the larger size. However, prolonged agitation degrades the formed flocs, regressing the distribution to the smaller size. Median floc size derived from the distribution is also used as performance criterion. The median floc size increases rapidly at the initial stage of the flocculation, and decreases with the extended agitation time and intensity. Relatively weak flocs are produced which may be due to the low dosage of sodium oleate used in this flocculation study. It is suggested that further investigation should focus on optimum reagent dosage and non-polar oil addition to strengthen these weak flocs.
Software Package for Aerosol Size Distribution
Rajesh, T. A.
2013-01-01
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...
Aerosol Size Distribution in the marine regions
Markuszewski, Piotr; Petelski, Tomasz; Zielinski, Tymon; Pakszys, Paulina; Strzalkowska, Agata; Makuch, Przemyslaw; Kowalczyk, Jakub
2014-05-01
We would like to present the data obtained during the regular research cruises of the S/Y Oceania over a period of time between 2009 - 2012. The Baltic Sea is a very interesting polygon for aerosol measurements, however, also difficult due to the fact that mostly cases of a mixture of continental and marine aerosols are observed. It is possible to measure clear marine aerosol, but also advections of dust from southern Europe or even Africa. This variability of data allows to compare different conditions. The data is also compared with our measurements from the Arctic Seas, which have been made during the ARctic EXperiment (AREX). The Arctic Seas are very suitable for marine aerosol investigations since continental advections of aerosols are far less frequent than in other European sea regions. The aerosol size distribution was measured using the TSI Laser Aerosol Spectrometer model 3340 (99 channels, measurement range 0.09 ?m to 7 ?m), condensation particle counter (range 0.01 ?m to 3 ?m) and laser particle counter PMS CSASP-100-HV-SP (range 0.5 ?m to 47 ?m in 45 channels). Studies of marine aerosol production and transport are important for many Earth sciences such as cloud physics, atmospheric optics, environmental pollution studies and interaction between ocean and atmosphere. All equipment was placed on one of the masts of S/Y Oceania. Measurements using the laser aerosol spectrometer and condensation particle counter were made on one level (8 meters above sea level). Measurements with the laser particle counter were performed at five different levels above the sea level (8, 11, 14, 17 and 20 m). Based on aerosol size distribution the parameterizations with a Log-Normal and a Power-Law distributions were made. The aerosol source functions, characteristic for the region were also determined. Additionally, poor precision of the sea spray emission determination was confirmed while using only the aerosol concentration data. The emission of sea spray depends on the size of energy lost by the wind waves in the process of a collapse. We present the dependence between aerosol size distribution versus meteorological and micrometeorological parameters, such as wind speed, Monin-Obuchov Length, friction velocity and also turbulent fluxes of heat, momentum and humidity.
Universality of rain event size distributions
Peters, Ole
2010-01-01
We compare rain event size distributions derived from measurements in climatically different regions, which we find to be well approximated by power laws of similar exponents over broad ranges. Differences can be seen in the large-scale cutoffs of the distributions. Event duration distributions suggest that the scale-free aspects are related to the absence of characteristic scales in the meteorological mesoscale.
Universality of rain event size distributions
International Nuclear Information System (INIS)
We compare rain event size distributions derived from measurements in climatically different regions, which we find to be well approximated by power laws of similar exponents over broad ranges. Differences can be seen in the large-scale cutoffs of the distributions. Event duration distributions suggest that the scale-free aspects are related to the absence of characteristic scales in the meteorological mesoscale
Aggregate size distributions in sweep flocculation
Directory of Open Access Journals (Sweden)
Chairoj Rattanakawin
2005-09-01
Full Text Available The evolution of aggregate size distributions resulting from sweep flocculation has been investigated using laser light scattering technique. By measuring the (volume distributions of floc size, it is possible to distinguish clearly among floc formation, growth and breakage. Sweep flocculation of stable kaolin suspensions with ferric chloride under conditions of the rapid/slow mixing protocol produces uni-modal size distributions. The size distribution is shifted to larger floc size especially during the rapid mixing step. The variation of the distributions is also shown in the plot of cumulative percent finer against floc size. From this plot, the distributions maintain the same S-shape curves over the range of the mixing intensities/times studied. A parallel shift of the curves indicates that self-preserving size distribution occurred in this flocculation. It is suggested that some parameters from mathematical functions derived from the curves could be used to construct a model and predict the flocculating performance. These parameters will be useful for a water treatment process selection, design criteria, and process control strategies. Thus the use of these parameters should be employed in any further study.
What determines the grain size distribution in galaxies?
Asano, Ryosuke S.; Takeuchi, Tsutomu T.; Hirashita, Hiroyuki; Nozawa, Takaya
2013-01-01
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) (ca...
Software Package for Aerosol Size Distribution
Directory of Open Access Journals (Sweden)
T. A. Rajesh
2013-04-01
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.
Size distributions of chemically synthesized Ag nanocrystals
Thøgersen, Annett; Bonsak, Jack; Fosli, Carl Huseby; Muntingh, Georg
2012-01-01
Silver nanocrystals made by a chemical reduction of silver salts (AgNO$_3$) by sodium borohydride (NaBH$_4$) were studied using Transmission Electron Microscopy (TEM) and light scattering simulations. For various AgNO$_3$/NaBH$_4$ molar ratios, the size distributions of the nanocrystals were found to be approximately log-normal. In addition, a linear relation was found between the mean nanocrystal size and the molar ratio. In order to relate the size distribution of Ag nanoc...
Langevin granulometry of the particle size distribution
International Nuclear Information System (INIS)
The problem of deriving the particle size distribution directly from superparamagnetic magnetization curves is studied by three mathematical methods: (1) least-squares deviation with regularization procedure, (2) simulated annealing and (3) genetic algorithm. Software has been developed for the latest versions of all these methods and its performance compared for various models of underlying particle size distributions (Dirac ?-like, lognormal- and Gaussian-shaped). For single peak distributions all three methods give reasonable and similar results, but for bimodal distributions the genetic algorithm is the only acceptable one. The genetic algorithm is able to recover with the same precision both the lognormal and Gaussian single and double (mixed) model distributions. The sensitivity of the genetic algorithm-the most promising method-to uncertainty of measurements was also tested; correct peak position and its half width were recovered for Gaussian distributions, when the analysed data were contaminated with noise of up to 5% of MS
Fluctuations and intermittency in fragment size distributions
International Nuclear Information System (INIS)
The intermittence signal on the size frequency of fragments found in various fragmenting systems is reconsidered. We believe that this signal, extracted from a factorial moment analysis, was incorrectly interpreted as a genuine intermittency. Indeed, the analysis in factorial moments made at fixed multiplicity, as it should be, reveals a total absence of proper intermittency in the size distribution. Moreover, in percolation theory this intermittency signal, which has often been claimed in the literature to signal a phase transition, vanishes when the size of the system tends to infinity. Our conclusion is that the signal found in earlier works and interpreted as an intermittency behaviour results from both the power law of the mean size fragment distribution and from the finite width of the multiplicity distribution. We conjecture that any partition of integers exhibiting these two features will provide a similar signal. ((orig.))
Avalanche size distribution in the Toom interface
Jeong, H; Kim, D
1993-01-01
We present numerical data of the height-height correlation function and of the avalanche size distribution for the three dimensional Toom interface. The height-height correlation function behaves samely as the interfacial fluctuation width, which diverges logarithmically with space and time for both unbiased and biased cases. The avalanche size defined by the number of changing sites caused by a single noise process, exhibits an exponentially decaying distribution, which is in contrast to power-law distributions appearing in typical self-organized critical phenomena. We also generalize the Toom model into arbitrary dimensions.
Particle Size Distributions in Atmospheric Clouds
Paoli, Roberto; Shariff, Karim
2003-01-01
In this note, we derive a transport equation for a spatially integrated distribution function of particles size that is suitable for sparse particle systems, such as in atmospheric clouds. This is done by integrating a Boltzmann equation for a (local) distribution function over an arbitrary but finite volume. A methodology for evolving the moments of the integrated distribution is presented. These moments can be either tracked for a finite number of discrete populations ('clusters') or treated as continuum variables.
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
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.
Directory of Open Access Journals (Sweden)
J. F. Peng
2014-06-01
Full Text Available Understanding the particle number size distributions in diversified atmospheric environments is important in order to design mitigation strategies related to submicron particles and their effect on regional air quality, haze and human health. In this study, we conducted 15 different field measurement campaigns, each one-month long, between 2007 and 2011 at 13 individual sites in China. These were 5 urban sites, 4 regional sites, 3 coastal/background sites and one ship cruise measurement along eastern coastline of China. Size resolved particles were measured in the 15–600 nm size range. The median particle number concentrations (PNC were found to vary in the range of 1.1–2.2 × 104 cm?3 at urban sites, 0.8–1.5 × 104 cm?3 at regional sites, 0.4–0.6 × 104 cm?3 at coastal/background sites, and 0.5 × 104 cm?3 during cruise measurements. Peak diameters at each of these sites varied greatly from 24 nm to 115 nm. Particles in the 15–25 nm (nucleation mode, 25–100 nm (Aitken mode and 100–600 nm (accumulation mode range showed different characteristics at each of the studied sites, indicating the features of primary emissions and secondary formation in these diversified atmospheric environments. Diurnal variations show a build-up of accumulation mode particles belt at regional sites, suggesting the contribution of regional secondary aerosol pollution. Frequencies of new particle formation (NPF events were much higher at urban and regional sites than at coastal sites and cruise measurement. The average growth rates (GRs of nucleation mode particles were 8.0–10.9 nm h?1 at urban sites, 7.4–13.6 nm h?1 at regional sites and 2.8–7.5 nm h?1 at both coastal and cruise measurement sites. The high gaseous precursors and strong oxidation at urban and regional sites not only favored the formation of particles, but also accelerated the growth rate of the nucleation mode particles. No significant difference in condensation sink (CS during NPF days were observed among different site types, suggesting that the NPF events in background area were more influenced by the pollutant transport. In addition, average contributions of NPF events to potential cloud condensation nuclei (CCN at 0.2% super-saturation in the afternoon of all sampling days were calculated as 11% and 6% at urban sites and regional sites, respectively. On the other hand, NPF events at coastal and cruise measurement sites had little impact on potential production of CCN. This study provides a large dataset of aerosol size distribution in diversified atmosphere of China, improving our general understanding of emission, secondary formation, new particles formation and corresponding CCN activity of submicron aerosols in Chinese environments.
Experimental Analysis of Particle Size Distribution using Electromagnetic Sieve
Ujam, A. J.
2013-01-01
This work is aimed at grading the particle sizes of powders and granular distribution of particle sizes of a local agricultural product, GARRI. To be able to do this, an electromagnetic sieving machine which transforms electromagnetic energy to mechanical energy was designed and constructed. The Choice of Electromagnetic Sieving Machine was to increase the amplitude of oscillation and thereby reducing the time of sieving. With the aid of the machine, sieving was carried out three times at dif...
Raindrop Size Distribution Measurements in Tropical Cyclones
Tokay, Ali; Bashor, Paul G.; Habib, Emad; Kasparis, Takis
2008-01-01
Characteristics of the raindrop size distribution in seven tropical cyclones have been studied through impact-type disdrometer measurements at three different sites during the 2004-06 Atlantic hurricane seasons. One of the cyclones has been observed at two different sites. High concentrations of small and/or midsize drops were observed in the presence or absence of large drops. Even in the presence of large drops, the maximum drop diameter rarely exceeded 4 mm. These characteristics of raindrop size distribution were observed in all stages of tropical cyclones, unless the storm was in the extratropical stage where the tropical cyclone and a midlatitude frontal system had merged. The presence of relatively high concentrations of large drops in extratropical cyclones resembled the size distribution in continental thunderstorms. The integral rain parameters of drop concentration, liquid water content, and rain rate at fixed reflectivity were therefore lower in extratropical cyclones than in tropical cyclones. In tropical cyclones, at a disdrometercalculated reflectivity of 40 dBZ, the number concentration was 700 plus or minus 100 drops m(sup -3), while the liquid water content and rain rate were 0.90 plus or minus 0.05 g m(sup -3) and 18.5 plus or minus 0.5 mm h(sup -1), respectively. The mean mass diameter, on the other hand, was 1.67 plus or minus 0.3 mm. The comparison of raindrop size distributions between Atlantic tropical cyclones and storms that occurred in the central tropical Pacific island of Roi-Namur revealed that the number density is slightly shifted toward smaller drops, resulting in higher-integral rain parameters and lower mean mass and maximum drop diameters at the latter site. Considering parameterization of the raindrop size distribution in tropical cyclones, characteristics of the normalized gamma distribution parameters were examined with respect to reflectivity. The mean mass diameter increased rapidly with reflectivity, while the normalized intercept parameter had an increasing trend with reflectivity. The shape parameter, on the other hand, decreased in a reflectivity range from 10 to 20 dBZ and remained steady at higher reflectivities. Considering the repeatability of the characteristics of the raindrop size distribution, a second impact disdrometer that was located 5.3 km away from the primary site in Wallops Island, Virginia, had similar size spectra in selected tropical cyclones.
Bimodal island size distribution in heteroepitaxial growth.
Chinta, P V; Headrick, R L
2014-02-21
A bimodal size distribution of two-dimensional islands is inferred during interface formation in heteroepitaxial growth of bismuth ferrite on (001) oriented SrTiO3 by sputter deposition. Features observed by in situ x-ray scattering are explained by a model where coalescence of islands determines the growth kinetics with negligible surface diffusion on SrTiO3. Small clusters maintain a compact shape as they coalesce, while clusters beyond a critical size impinge to form large irregular connected islands and a population of smaller clusters forms in the spaces between the larger ones. PMID:24579612
Image Analysis for Particle Size Distribution
Shanthi, C.; Kingsley Porpatham, R.; Pappa, N.
2014-01-01
Particle size distribution (PSD) affects properties of particulate materials and is used for denoting their quality and performance. Among many techniques available to measure PSD, many are quite often offline methods and are time consuming. Also methods like sieving involve, handling of the material physically and electromagnetically, which is healthy, if avoided for certain materials. Thus the need for an online PSD analyzer and the advent of digital image processing has rendered the drift ...
Barchan dune's size distribution induced by collisions
Dur'an, O; Herrmann, H J
2007-01-01
Large dune fields can overrun for instance infrastructures lying in the way of their motion. Unidirectional wind fields and low sand availability give rise to single barchan dunes moving in the direction of wind. They can interact by directly exchanging their sand through collisions. This kind of interaction play a crucial role in the evolution of barchan dune fields, for instance in the selection of a characteristic dune size. Simulations of dune collisions with lateral offset are studied systematically and described by general phenomenological rules. Moreover, simulations with a simplified model without sand flux considering only collisions show that the sizes of sand dunes in such a scenario follow a Gaussian distribution with a well defined characteristic size.
Radioactive Aerosol Size Distribution Measured in Nuclear Workplaces
International Nuclear Information System (INIS)
Inhalation is the main route for internal exposure of workers to radioactive aerosols in the nuclear industry.Aerosol's size distribution and in particular its activity median aerodynamic diameter (AMAD)is important for determining the fractional deposition of inhaled particles in the respiratory tract and the resulting doses. Respiratory tract models have been published by the International Commission on radiological Protection (ICRP).The former model has recommended a default AMAD of 1 micron for the calculation of dose coefficients for workers in the nuclear industry [1].The recent model recommends a 5 microns default diameter for occupational exposure which is considered to be more representative of workplace aerosols [2]. Several researches on radioactive aerosol's size distribution in nuclear workplaces has supported this recommendation [3,4].This paper presents the results of radioactive aerosols size distribution measurements taken at several workplaces of the uranium production process
Size Frequency Distributions for Snow Avalanches
Bair, E. H.; Birkeland, K.; Dozier, J.
2007-12-01
We examine crown size frequencies for two extensive datasets of observations made during operational avalanche control: 10,300 events at Mammoth Mountain, California and 219,000 events from the Westwide Avalanche Network (WAN) which includes ski areas and highway operations. We compare a dozen distributions, and we address observer bias by employing ratio estimates, smoothing functions, and exclusion rules. Knowing that avalanche professionals often do not record small events, we examine both datasets with no exclusions and with a 60 cm exclusion rule. The WAN data are best fit by a power law distribution using the 60 cm exclusion rule. The power law distribution with 60 cm exclusion also fits the Mammoth data, although these data are best fit by a hyperbolic tangent distribution under both the 60 cm exclusion rule and without exclusion. Our findings support past literature showing that power laws provide a good fit for size-frequency relationships across different regions. Power law distributions indicate scale invariance across several orders of magnitude and are consistent with self organized critical systems. Independent of the choice of distribution, we advocate the implementation of probabilistic avalanche forecasts that convey uncertainty to the end-user, unlike deterministic forecasts. We propose the use of cumulative distribution functions (CDFs) as the dependent variables in numerical avalanche forecast models. CDFs allow normalized output for a region or specific path. A user can infer the magnitude of avalanche events for each avalanche path or area of interest from the CDF. We attempt to create a basis for such an implementation in avalanche forecasting.
City Size Distributions For India and China
Gangopadhyay, Kausik
2010-01-01
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.
Bipartite producer consumer networks and the size distribution of firms
Dahui, Wang; Li, Zhou; Zengru, Di
2006-05-01
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 afirms obeys the power-law. The exponent is affected by the market growth and the initial attractiveness of the firms.
Controlling the size and size distribution of magnetite nanoparticles on carbon nanotubes
International Nuclear Information System (INIS)
Nanocomposites composed of carbon nanotubes (CNTs) and magnetite (Fe3O4) nanoparticles were fabricated by using ethylene glycol as reductant at 160 oC. The composites were subsequently annealed under different temperatures in an inert atmosphere. The products were characterized by transmission electron microscopy (TEM), high resolution TEM, X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The results showed that the Fe3O4 transformed from amorphous phase into single crystalline nanoparticles after annealing and that the annealing temperature played a crucial role in controlling the size and the size distribution of Fe3O4 nanoparticles. The average size of Fe3O4 nanoparticles increased with increasing annealing temperature. Meanwhile, the size distribution of nanoparticles became wide with the increase of temperature. It was caused by the gradual decomposition of oleate groups attached on the CNT surface. Magnetic hysteresis loop measurements revealed that crystalline Fe3O4/CNTs displayed superparamagnetic behavior under room temperature.
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)
Directory of Open Access Journals (Sweden)
J. R. Pierce
2014-01-01
Full Text Available Aerosol particle nucleation, or new-particle formation, is the dominant contributor to particle number in the atmosphere. However, these particles must grow through condensation of low-volatility vapors without coagulating with the larger, pre-existing particles in order to reach climate-relevant sizes (diameters larger than 50–100 nm, where the particles may affect clouds and radiation. In this paper, we use one year of size-distribution measurements from Egbert, Ontario, Canada to calculate the frequency of regional-scale new-particle formation events, new-particle formation rates, growth rates and the fraction of new particles that survive to reach climate-relevant sizes. Regional-scale new-particle formation events occurred on 14–31% of the days (depending on the stringency of the classification criteria, with event frequency peaking in the spring and fall. New-particle formation rates and growth rates were similar to those measured at other mid-latitude continental sites. We calculate that roughly half of the climate-relevant particles (with diameters larger than 50–100 nm at Egbert are formed through new-particle formation events. With the addition of meteorological and SO2 measurements, we find that new-particle formation often occurred under synoptic conditions associated with high surface pressure and large-scale subsidence that cause sunny conditions and clean-air flow from the north and west. However, new-particle formation also occurred when air flow came from the polluted regions to the south and southwest of Egbert. The nucleation rates tend to be faster during events under the polluted south/southwest flow conditions.
Pierce, J. R.; Westervelt, D. M.; Atwood, S. A.; Barnes, E. A.; Leaitch, W. R.
2014-01-01
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.
2014-08-01
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.
Electronic cigarette aerosol particle size distribution measurements.
Ingebrethsen, Bradley J; Cole, Stephen K; Alderman, Steven L
2012-12-01
The particle size distribution of aerosols produced by electronic cigarettes was measured in an undiluted state by a spectral transmission procedure and after high dilution with an electrical mobility analyzer. The undiluted e-cigarette aerosols were found to have particle diameters of average mass in the 250-450 nm range and particle number concentrations in the 10(9) particles/cm(3) range. These measurements are comparable to those observed for tobacco burning cigarette smoke in prior studies and also measured in the current study with the spectral transmission method and with the electrical mobility procedure. Total particulate mass for the e-cigarettes calculated from the size distribution parameters measured by spectral transmission were in good agreement with replicate determinations of total particulate mass by gravimetric filter collection. In contrast, average particle diameters determined for e-cigarettes by the electrical mobility method are in the 50 nm range and total particulate masses calculated based on the suggested diameters are orders of magnitude smaller than those determined gravimetrically. This latter discrepancy, and the very small particle diameters observed, are believed to result from almost complete e-cigarette aerosol particle evaporation at the dilution levels and conditions of the electrical mobility analysis. A much smaller degree, ~20% by mass, of apparent particle evaporation was observed for tobacco burning cigarette smoke. The spectral transmission method is validated in the current study against measurements on tobacco burning cigarette smoke, which has been well characterized in prior studies, and is supported as yielding an accurate characterization of the e-cigarette aerosol particle size distribution. PMID:23216158
Optical method for particle size distribution analysis
International Nuclear Information System (INIS)
Full text: Particle size distribution is one important parameter in powder fabrication developments; it has been decided to use a method complementary to sedimentation method. Thus, the optical method was chosen for that purpose, since it can give additional information, such as identification of geometrical parameters in particles without spherical symmetry and account for those particles, with diameters above 100 microns, that sediment before the run starts. On the other hand, through the use of electronic microscopes it is possible to observe particle sizes lower than 0.1 micron, which is the limit of the sedimentation techniques. It is also possible not to depend on the arbitrary selection of particle density, which is difficult to estimate in the case of compounds with internal porosity. To make this method operative, and to use it normally, it is necessary to have an automatic system of image analysis, which allows to separate the particles for its counting and qualification. Therefore, it is necessary that the particles could be seen in screen separately, individually, without superposing. As in the sedimentation techniques, it is necessary to find the conditions to disperse the particles, in such a way that they can set individually in the slide. In this work, the necessary steps to reach the optical measurement and the method used to perform it, are explained. Distributions of calibrated populations, perfect spheres and particles of varied and irregular morphnd particles of varied and irregular morphologies, performed by both methods, are compared, and the correspondence and application range of both is intended to find. Distributions with different number of particles are analyzed, in order to determine the necessary minimum quantity of particles to enable a regular distribution. Also, how dependent is the population considered on the sample diameters dispersion and the number of images at different increases, necessary to cover the selected population
Image Analysis for Particle Size Distribution
Directory of Open Access Journals (Sweden)
C. Shanthi
2014-07-01
Full Text Available Particle size distribution (PSD affects properties of particulate materials and is used for denoting their quality and performance. Among many techniques available to measure PSD, many are quite often offline methods and are time consuming. Also methods like sieving involve, handling of the material physically and electromagnetically, which is healthy, if avoided for certain materials. Thus the need for an online PSD analyzer and the advent of digital image processing has rendered the drift for innovation of image based particle analyzers. Also this method is purely inferential as the particles are not handled physically or electromagnetically as in cases like sieve analysis or tomography. In general, PSD estimation is based on considering a single parameter of the particle profile. Irregularities in analyzed particles increase the error in PSD estimation. Hence, two parameters, equivalent area diameter and Feret's diameter are included for the estimation to reduce the estimation error.
Genome Sizes and the Benford Distribution
Friar, James L; Pérez-Mercader, Juan; 10.1371/journal.pone.0036624
2012-01-01
Data on the number of Open Reading Frames (ORFs) coded by genomes from the 3 domains of Life show some notable general features including essential differences between the Prokaryotes and Eukaryotes, with the number of ORFs growing linearly with total genome size for the former, but only logarithmically for the latter. Assuming that the (protein) coding and non-coding fractions of the genome must have different dynamics and that the non-coding fraction must be controlled by a variety of (unspecified) probability distribution functions, we are able to predict that the number of ORFs for Eukaryotes follows a Benford distribution and has a specific logarithmic form. Using the data for 1000+ genomes available to us in early 2010, we find excellent fits to the data over several orders of magnitude, in the linear regime for the Prokaryote data, and the full non-linear form for the Eukaryote data. In their region of overlap the salient features are statistically congruent, which allows us to: interpret the differenc...
Parameterizing Size Distribution in Ice Clouds
Energy Technology Data Exchange (ETDEWEB)
DeSlover, Daniel; Mitchell, David L.
2009-09-25
PARAMETERIZING SIZE DISTRIBUTIONS IN ICE CLOUDS David L. Mitchell and Daniel H. DeSlover ABSTRACT An outstanding problem that contributes considerable uncertainty to Global Climate Model (GCM) predictions of future climate is the characterization of ice particle sizes in cirrus clouds. Recent parameterizations of ice cloud effective diameter differ by a factor of three, which, for overcast conditions, often translate to changes in outgoing longwave radiation (OLR) of 55 W m-2 or more. Much of this uncertainty in cirrus particle sizes is related to the problem of ice particle shattering during in situ sampling of the ice particle size distribution (PSD). Ice particles often shatter into many smaller ice fragments upon collision with the rim of the probe inlet tube. These small ice artifacts are counted as real ice crystals, resulting in anomalously high concentrations of small ice crystals (D < 100 µm) and underestimates of the mean and effective size of the PSD. Half of the cirrus cloud optical depth calculated from these in situ measurements can be due to this shattering phenomenon. Another challenge is the determination of ice and liquid water amounts in mixed phase clouds. Mixed phase clouds in the Arctic contain mostly liquid water, and the presence of ice is important for determining their lifecycle. Colder high clouds between -20 and -36 oC may also be mixed phase but in this case their condensate is mostly ice with low levels of liquid water. Rather than affecting their lifecycle, the presence of liquid dramatically affects the cloud optical properties, which affects cloud-climate feedback processes in GCMs. This project has made advancements in solving both of these problems. Regarding the first problem, PSD in ice clouds are uncertain due to the inability to reliably measure the concentrations of the smallest crystals (D < 100 µm), known as the “small mode”. Rather than using in situ probe measurements aboard aircraft, we employed a treatment of ice 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.
Experimental Analysis of Particle Size Distribution using Electromagnetic Sieve
Directory of Open Access Journals (Sweden)
Ujam, A.J.,
2013-10-01
Full Text Available This work is aimed at grading the particle sizes of powders and granular distribution of particle sizes of a local agricultural product, GARRI. To be able to do this, an electromagnetic sieving machine which transforms electromagnetic energy to mechanical energy was designed and constructed. The Choice of Electromagnetic Sieving Machine was to increase the amplitude of oscillation and thereby reducing the time of sieving. With the aid of the machine, sieving was carried out three times at different voltage settings. The tests conducted show that with increase in voltage, the amplitude of oscillation also increased, thereby reducing the sieving time. Optimal output (from 1kg of Garri was obtained in 120 seconds at a voltage setting of 255 volts which generated 5mm amplitude. The different particle sizes were evaluated by the use of an electronic microscope. The efficiency of the machine was evaluated to be 98%.
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 calce 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
Pierce, J. R.; Westervelt, D. M.; Atwood, S. A.; Barnes, E. A.; Leaitch, W. R.
2014-01-01
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-distributi...
Fooling functions of halfspaces under product distributions
Gopalan, P; Wu, Y; Zuckerman, D
2010-01-01
We construct pseudorandom generators that fool functions of halfspaces (threshold functions) under a very broad class of product distributions. This class includes not only familiar cases such as the uniform distribution on the discrete cube, the uniform distribution on the solid cube, and the multivariate Gaussian distribution, but also includes any product of discrete distributions with probabilities bounded away from 0. Our first main result shows that a recent pseudorandom generator construction of Meka and Zuckerman [MZ09], when suitably modifed, can fool arbitrary functions of d halfspaces under product distributions where each coordinate has bounded fourth moment. To eps-fool any size-s, depth-d decision tree of halfspaces, our pseudorandom generator uses seed length O((d log(ds/eps)+log n) log(ds/eps)). For monotone functions of d halfspaces, the seed length can be improved to O((d log(d/eps)+log n) log(d/eps)). We get better bounds for larger eps; for example, to 1/polylog(n)-fool all monotone functi...
Powerlaws for ratios of moments of the fragment size distribution
International Nuclear Information System (INIS)
The method of scaled factorial moments (s.f.m.) is used to study fluctuations of the fragment size distribution in the percolation model and in nuclear multifragmentation following the breakup of the high energy nuclei. It is found that similarly as in several cascade models describing the multiparticle production at ultrarelativistic energies, the site-bond percolation model at around the critical point for large lattice sizes exhibits a power behaviour of the ratio of s.f.m. of different rank which is typical for the self-similar branching mechanism. Both the experimental data and the percolation model events selected according either to the number of intermediate mass fragments or to the total fragment multiplicity can be fitted well by such a power behaviour. Only in small charge/mass bins one observes small but systematic deviations with respect to the power behaviour which may be indicate the possibility of a weak scale-breaking mechanism. Together with an evidence for an intermittent pattern of fluctuations which was found earlier in the fragment charge/mass distributions at E/A?1 GeV/nucl the present results suggest strongly not only the self-similarity in the fragment size distribution and a random character for the scaling law but also the importance of the branching mechanism in the fragment formation process
Greve, Michelle; Gaston, Kevin J.; Rensburg, Berndt J.; Chown, Steven Loudon
2008-01-01
AIM: To determine how well variation in median body size of avian assemblages is predicted by (1) the environmental models usually employed in analyses of Bergmann's rule and (2) random sampling from the regional body size frequency distribution. If body size frequency distributions of local assemblages represent a random sample of a regional frequency distribution, then geographical variation in body sizes of assemblages might be a consequence of the determinants of spatial variation in spe...
Atmospheric Ion Clusters: Properties and Size Distributions
D'Auria, R.; Turco, R. P.
2002-12-01
Ions are continuously generated in the atmosphere by the action of galactic cosmic radiation. Measured charge concentrations are of the order of 103 ~ {cm-3} throughout the troposphere, increasing to about 5 x 103 ~ {cm-3} in the lower stratosphere [Cole and Pierce, 1965; Paltridge, 1965, 1966]. The lifetimes of these ions are sufficient to allow substantial clustering with common trace constituents in air, including water, nitric and sulfuric acids, ammonia, and a variety of organic compounds [e.g., D'Auria and Turco, 2001 and references cited therein]. The populations of the resulting charged molecular clusters represent a pre-nucleation phase of particle formation, and in this regard comprise a key segment of the over-all nucleation size spectrum [e.g., Castleman and Tang, 1972]. It has been suggested that these clusters may catalyze certain heterogeneous reactions, and given their characteristic crystal-like structures may act as freezing nuclei for supercooled droplets. To investigate these possibilities, basic information on cluster thermodynamic properties and chemical kinetics is needed. Here, we present new results for several relevant atmospheric ion cluster families. In particular, predictions based on quantum mechanical simulations of cluster structure, and related thermodynamic parameters, are compared against laboratory data. We also describe a hybrid approach for modeling cluster sequences that combines laboratory measurements and quantum predictions with the classical liquid droplet (Thomson) model to treat a wider range of cluster sizes. Calculations of cluster mass distributions based on this hybrid model are illustrated, and the advantages and limitations of such an analysis are summarized. References: Castelman, A. W., Jr., and I. N. Tang, Role of small clusters in nucleation about ions, J. Chem. Phys., 57, 3629-3638, 1972. Cole, R. K., and E. T. Pierce, Electrification in the Earth's atmosphere for altitudes between 0 and 100 kilometers, J. Geophys. Res. 70, 2735-2749, 1965. D'Auria, R. and R. P. Turco, Ionic clusters in the polar winter stratosphere, Geophys. Res. Lett., 28, 3871-3874, 2001. Paltridge, G. W., Experimental measurements of the small-ion density and electrical conductivity of the stratosphere, J. Geophys. Res. 70, 2751,2761, 1965. Paltridge, G. W., Stratospheric small-ion density measurements from a high-altitude jet aircraft, J. Geophys. Res. 71, 1945-1952, 1966.
Evaluation of droplet size distributions using univariate and multivariate approaches
DEFF Research Database (Denmark)
Gauno, M.H.; Larsen, C.C.
2013-01-01
Pharmaceutically relevant material characteristics are often analyzed based on univariate descriptors instead of utilizing the whole information available in the full distribution. One example is droplet size distribution, which is often described by the median droplet size and the width of the distribution. The current study was aiming to compare univariate and multivariate approach in evaluating droplet size distributions. As a model system, the atomization of a coating solution from a two-fluid nozzle was investigated. The effect of three process parameters (concentration of ethyl cellulose in ethanol, atomizing air pressure, and flow rate of coating solution) on the droplet size and droplet size distribution using a full mixed factorial design was used. The droplet size produced by a two-fluid nozzle was measured by laser diffraction and reported as volume based size distribution. Investigation of loading and score plots from principal component analysis (PCA) revealed additional information on the droplet size distributions and it was possible to identify univariate statistics (volume median droplet size), which were similar, however, originating from varying droplet size distributions. The multivariate data analysis was proven to be an efficient tool for evaluating the full information contained in a distribution. © 2013 Informa Healthcare USA, Inc.
Location and size distribution of entertainment and arts establishments
Ru?tt, Benjamin
2001-01-01
This thesis analyzes the location and size distribution of arts and entertainment industries in Sweden as well as the size distribution of Swedish labor market regions. Several sectors of the arts and entertainment industry are investigated empirically by comparing their location and overall capacity to the size of their respective markets and testing their conformity with the rank-size rule. The analyzed establishments are opera houses, football stadiums, concert performances and movie theat...
Ultrasonically controlled particle size distribution of explosives: a safe method.
Patil, Mohan Narayan; Gore, G M; Pandit, Aniruddha B
2008-03-01
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
Methods of computing vocabulary size for the two-parameter rank distribution
Edmundson, H. P.; Fostel, G.; Tung, I.; Underwood, W.
1972-01-01
A summation method is described for computing the vocabulary size for given parameter values in the 1- and 2-parameter rank distributions. Two methods of determining the asymptotes for the family of 2-parameter rank-distribution curves are also described. Tables are computed and graphs are drawn relating paris of parameter values to the vocabulary size. The partial product formula for the Riemann zeta function is investigated as an approximation to the partial sum formula for the Riemann zeta function. An error bound is established that indicates that the partial product should not be used to approximate the partial sum in calculating the vocabulary size for the 2-parameter rank distribution.
Company Size Distributions as Economy Aggregated Indicators
Juan Carlos Pérez Mesa; Emilio Galdeano-Gómez
2009-01-01
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.
Knife mill operating factors effect on switchgrass particle size distributions
Energy Technology Data Exchange (ETDEWEB)
Bitra, V.S.P. [University of Tennessee; Womac, A.R. [University of Tennessee; Yang, Y.T. [University of Tennessee; Igathinathane, C. [Mississippi State University (MSU); Miu, P.I [University of Tennessee; Chevanan, Nehru [University of Tennessee; Sokhansanj, Shahabaddine [ORNL
2009-06-01
Biomass particle size impacts handling, storage, conversion, and dust control systems. Switchgrass (Panicum virgatum L.) particle size distributions created by a knife mill were determined for integral classifying screen sizes from 12.7 to 50.8 mm, operating speeds from 250 to 500 rpm, and mass input rates from 2 to 11 kg/min. Particle distributions were classified with standardized sieves for forage analysis that included horizontal sieving motion with machined-aluminum sieves of thickness proportional to sieve opening dimensions. Then, a wide range of analytical descriptors were examined to mathematically represent the range of particle sizes in the distributions. Correlation coefficient of geometric mean length with knife mill screen size, feed rate, and speed were 0.872, 0.349, and 0.037, respectively. Hence, knife mill screen size largely determined particle size of switchgrass chop. Feed rate had an unexpected influence on particle size, though to a lesser degree than screen size. The Rosin Rammler function fit the chopped switchgrass size distribution data with an R2 > 0.982. Mass relative span was greater than 1, which indicated a wide distribution of particle sizes. Uniformity coefficient was more than 4.0, which indicated a large assortment of particles and also represented a well-graded particle size distribution. Knife mill chopping of switchgrass produced strongly fine skewed mesokurtic particles with 12.7 25.4 mm screens and fine skewed mesokurtic particles with 50.8 mm screen. Results of this extensive analysis of particle sizes can be applied to selection of knife mill operating parameters to produce a particular size of switchgrass chop, and will serve as a guide for relations among the various analytic descriptors of biomass particle distributions.
Distributions of households by size: differences and trends.
Kuznets, S
1982-01-01
"This article deals with the distributions of households by size, that is, by number of persons, as they are observed in international comparisons, and for fewer countries, over time." The contribution of differentials in household size to inequality in income distribution among persons and households is discussed. Data are for both developed and developing countries. PMID:12264898
The Italian primary school-size distribution and the city-size: a complex nexus
Belmonte, Alessandro; di Clemente, Riccardo; Buldyrev, Sergey V.
2014-06-01
We characterize the statistical law according to which Italian primary school-size distributes. We find that the school-size can be approximated by a log-normal distribution, with a fat lower tail that collects a large number of very small schools. The upper tail of the school-size distribution decreases exponentially and the growth rates are distributed with a Laplace PDF. These distributions are similar to those observed for firms and are consistent with a Bose-Einstein preferential attachment process. The body of the distribution features a bimodal shape suggesting some source of heterogeneity in the school organization that we uncover by an in-depth analysis of the relation between schools-size and city-size. We propose a novel cluster methodology and a new spatial interaction approach among schools which outline the variety of policies implemented in Italy. Different regional policies are also discussed shedding lights on the relation between policy and geographical features.
The Italian primary school-size distribution and the city-size: a complex nexus
Belmonte, Alessandro; Buldyrev, Sergey V
2014-01-01
We characterize the statistical law according to which Italian primary school-size distributes. We find that the school-size can be approximated by a log-normal distribution, with a fat lower tail that collects a large number of very small schools. The upper tail of the school-size distribution decreases exponentially and the growth rates are distributed with a Laplace PDF. These distributions are similar to those observed for firms and are consistent with a Bose-Einstein preferential attachment process. The body of the distribution features a bimodal shape suggesting some source of heterogeneity in the school organization that we uncover by an in-depth analysis of the relation between schools-size and city-size. We propose a novel cluster methodology and a new spatial interaction approach among schools which outline the variety of policies implemented in Italy. Different regional policies are also discussed shedding lights on the relation between policy and geographical features.
Coleman, Victoria A.; Jämting, Åsa K.; Catchpoole, Heather J.; Roy, Maitreyee; Herrmann, Jan
2011-10-01
Nanoparticles and products incorporating nanoparticles are a growing branch of nanotechnology industry. They have found a broad market, including the cosmetic, health care and energy sectors. Accurate and representative determination of particle size distributions in such products is critical at all stages of the product lifecycle, extending from quality control at point of manufacture to environmental fate at the point of disposal. Determination of particle size distributions is non-trivial, and is complicated by the fact that different techniques measure different quantities, leading to differences in the measured size distributions. In this study we use both mono- and multi-modal dispersions of nanoparticle reference materials to compare and contrast traditional and novel methods for particle size distribution determination. The methods investigated include ensemble techniques such as dynamic light scattering (DLS) and differential centrifugal sedimentation (DCS), as well as single particle techniques such as transmission electron microscopy (TEM) and microchannel resonator (ultra high-resolution mass sensor).
Optical heterodyne measurement of cloud droplet size distributions.
Gollub, J P; Chabay, L; Flygare, W H
1973-12-01
Optical heterodyne spectra of laser light quasi-elastically scattered by falling water droplets (1-10-micro radius) in a diffusion cloud chamber were used to determine the droplet size distribution. The rate of fall depends on radius in a known way, thus yielding a heterodyne spectrum manifesting a distribution of Doppler shifts. This spectrum, in conjunction with the calculated Mie scattering intensity as a function of droplet radius, provides a direct measure of the droplet size distribution for droplets large enough that Brownian motion is negligible. The experiments described in this paper demonstrate the technique and establish the potential for further more quantitative studies of size distributions. PMID:20125881
On the size distribution of private microsatellite alleles
Szpiech, Zachary A.; Rosenberg, Noah A.
2011-01-01
Private microsatellite alleles tend to be found in the tails rather than in the interior of the allele size distribution. To explain this phenomenon, we have investigated the size distribution of private alleles in a coalescent model of two populations, assuming the symmetric stepwise mutation model as the mode of microsatellite mutation. For the case in which four alleles are sampled, two from each population, we condition on the configuration in which three distinct allele sizes are present...
Model choice and size distribution: A Bayequentist approach
Engler, John-oliver; Baumgartner, Stefan
2013-01-01
We propose a new three-step model-selection framework for size distributions in empirical data. It generalizes a recent frequentist plausibility-of-fit analysis (Step 1) and combines it with a relative ranking based on the Bayesian Akaike Information Criterion (Step 2). We enhance these statistical criteria with the additional criterion of microfoundation (Step 3) which is to select the size distribution that comes with a dynamic micro model of size dynamics. A numerical performance test of S...
Scientific Electronic Library Online (English)
W. E., Grosso; M. G., Chiovetta.
2005-01-01
Full Text Available SciELO Argentina | Language: English Abstract in english Particle size distributions in the output stream of commercial, fluidized-bed reactors for ethylene polymerization are analyzed using a mathematical model. The impact on the overall reactor performance of the universe of sizes for the particles in the bed, with only a fraction of them being extracte [...] d in the product flow, is studied. For the output stream, product size distribution is modeled using both triangular and generalized gamma functions. Extraction system parameters are employed to model the particle quantity and sizes. The importance of the proper modeling of the extraction system is shown through the analysis of the effects several output schemes have on the particle size distribution inside the fluidized-bed. Some of the main reactor variables, such as yield and temperature, are studied for several distributions. Operating variables, such as catalyst feed rate, are varied according to the reactor capacity in a typical, 12 meter bed, 130,000 ton/year reactor. Predictions indicate higher output rates for higher catalyst loads, as expected. A shift towards smaller particle sizes in the product and in the bed is observed when increasing catalyst load. Bed fluidization and heat exchange conditions are shown as affected by size distributions. Results show that it is appropriate to include both product and bed particle diameter distribution when studying the reactor performance.
Slant visual range from drop-size distribution
Arrance, E. S.
1980-08-01
This research investigated the feasibility of obtaining visual range and slant visual range by use of drop-size distribution. The results of Davies' equation for computing visibility from drop-size distribution were compared to known values and those obtained from Mie scattering theory based on a program developed by Kattawar and Plass. Next, Davies' equation was applied to a Marshall-Palmer drop-size distribution and a vertically varying distribution obtained from a program developed by Borchers. The Marshall-Palmer distribution and visibility agree with those from Borchers' work. Davies' method of obtaining visibility then was used successfully to compute slant visual range along a glideslope. The drop-size distribution at various levels along the glideslope was produced by Borchers' program.
Effect of size distribution on metastability in magnetic nanoparticles
Yamamoto, Yoh; Park, Kyungwha
2011-03-01
Magnetic nanoparticles that have been synthesized using various methods have size distributions. This results in distributions in the magnetic anisotropy of magnetic nanoparticles. Considering the particle size distributions, we investigate metastability in magnetic nanoparticles at low temperatures. To model this system, we use a spin S=1 ferromagnetic Blume-Capel model on a square lattice with periodic boundary conditions. The particle size distribution is incorporated in the model such that the uniaxial magnetic anisotropy parameter has a Gaussian distribution. We perform kinetic Monte Carlo simulations of the Blume-Capel model with the Glauber dynamic to explore magnetization relaxation in the regime where a single droplet of flipped spins forms a critical droplet. We present the lifetime of the metastable state as a function of temperature and standard deviation of the magnetic anisotropy distribution as well as a finite-size effect on the lifetime.
Genome Sizes and the Benford Distribution
Friar, James L.; Goldman, Terrance; Pe?rez–mercader, Juan
2012-01-01
Data on the number of Open Reading Frames (ORFs) coded by genomes from the 3 domains of Life show some notable general features including essential differences between the Prokaryotes and Eukaryotes, with the number of ORFs growing linearly with total genome size for the former, but only logarithmically for the latter. Assuming that the (protein) coding and non-coding fractions of the genome must have different dynamics and that the non-coding fraction must be controlled by ...
Particle size distribution in the tilapia Recirculating Aquaculture System
Stokic, Jelena
2012-01-01
This study was to evaluate methods for measuring and describing particle size distribution from three different spots in Tilapia recirculating system at University of Life Ccience in Ås, Norway. For this purpose serial filtration over different mesh size and parallel filtration over different mesh size methods were compared. Water samples were taken from before drum filter, after drum filter and after bio-filter (MBBR) and filtrated through eight different mesh size classes and calculated in...
Inversion of spheroid particle size distribution in wider size range and aspect ratio range
Directory of Open Access Journals (Sweden)
Tang Hong
2013-01-01
Full Text Available The non-spherical particle sizing is very important in the aerosol science, and it can be determined by the light extinction measurement. This paper studies the effect of relationship of the size range and aspect ratio range on the inversion of spheroid particle size distribution by the dependent mode algorithm. The T matrix method and the geometric optics approximation method are used to calculate the extinction efficiency of the spheroids with different size range and aspect ratio range, and the inversion of spheroid particle size distribution in these different ranges is conducted. Numerical simulation indicates that a fairly reasonable representation of the spheroid particle size distribution can be obtained when the size range and aspect ratio range are suitably chosen.
Power-law versus exponential distributions of animal group sizes
Niwa, H S
2003-01-01
There has been some confusion concerning the animal group-size: an exponential distribution was deduced by maximizing the entropy; lognormal distributions were practically used; a power-law decay with exponent {3/2} was proposed in physical analogy to aerosol condensation. Here I show that the animal group-size distribution follows a power-law decay with exponent 1, and is truncated at a cut-off size which is the expected size of the groups an arbitrary individual engages in. An elementary model of animal aggregation based on binary splitting and coalescing on contingent encounter is presented. The model predicted size distribution holds for various data from pelagic fishes and mammalian herbivores in the wild.
Energy Technology Data Exchange (ETDEWEB)
Haninger, T.
1997-12-31
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)
Bipartite Producer-Consumer Networks and the Size Distribution of Firms
Dahui, W; Zengru, D; Dahui, Wang; Li, Zhou; Zengru, Di
2005-01-01
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...
Generic grain size distribution for liquid phase sintering
German, R. M.; Yang, Sung-Chul
1992-01-01
In order to develop an empirical model to represent a generic grain size distribution for liquid phase sintering, experimental data and theoretical models are analyzed using the plot of standard normal vs normalized size. From the experimental 3D grain size plot, the most representative line is deduced. The line best fits the Lifshitz-Slyozov encounter modified model except for the small size ranges of the lower 15 percent of the distribution. It is shown that grain coalescence might be a cause for this departure from theory.
Better size estimation for sparse matrix products
Amossen, Rasmus Resen; Pagh, Rasmus
2010-01-01
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...
INITIAL PLANETESIMAL SIZES AND THE SIZE DISTRIBUTION OF SMALL KUIPER BELT OBJECTS
Energy Technology Data Exchange (ETDEWEB)
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
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.
Size distribution of Amazon River bed sediment
Nordin, C.F.; Meade, R.H.; Curtis, W.F.; Bosio, N.J.; Landim, P.M.B.
1980-01-01
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.
Agimelen, Okpeafoh S; Vasile, Massimiliano; Nordon, Alison; Haley, Ian; Mulholland, Anthony J
2014-01-01
Information about size and shape of particles produced in various manufacturing processes is very important for process and product development because design of downstream processes as well as final product properties strongly depend on these geometrical particle attributes. However, recovery of particle size and shape information in situ during crystallisation processes has been a major challenge. The focused beam reflectance measurement (FBRM) provides the chord length distribution (CLD) of a population of particles in a suspension flowing close to the sensor window. Recovery of size and shape information from the CLD requires a model relating particle size and shape to its CLD as well as solving the corresponding inverse problem. This paper presents a comprehensive algorithm which produces estimates of particle size distribution and particle aspect ratio from measured CLD data. While the algorithm searches for a global best solution to the inverse problem without requiring further a priori information on ...
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)
The best nanoparticle size distribution for minimum thermal conductivity.
Zhang, Hang; Minnich, Austin J
2015-01-01
Which sizes of nanoparticles embedded in a crystalline solid yield the lowest thermal conductivity? Nanoparticles have long been demonstrated to reduce the thermal conductivity of crystals by scattering phonons, but most previous works assumed the nanoparticles to have a single size. Here, we use optimization methods to show that the best nanoparticle size distribution to scatter the broad thermal phonon spectrum is not a similarly broad distribution but rather several discrete peaks at well-chosen nanoparticle radii. For SiGe, the best size distribution yields a thermal conductivity below that of amorphous silicon. Further, we demonstrate that a simplified distribution yields nearly the same low thermal conductivity and can be readily fabricated. Our work provides important insights into how to manipulate the full spectrum of phonons and will guide the design of more efficient thermoelectric materials. PMID:25757414
The best nanoparticle size distribution for minimum thermal conductivity
Zhang, Hang; Minnich, Austin J.
2015-03-01
Which sizes of nanoparticles embedded in a crystalline solid yield the lowest thermal conductivity? Nanoparticles have long been demonstrated to reduce the thermal conductivity of crystals by scattering phonons, but most previous works assumed the nanoparticles to have a single size. Here, we use optimization methods to show that the best nanoparticle size distribution to scatter the broad thermal phonon spectrum is not a similarly broad distribution but rather several discrete peaks at well-chosen nanoparticle radii. For SiGe, the best size distribution yields a thermal conductivity below that of amorphous silicon. Further, we demonstrate that a simplified distribution yields nearly the same low thermal conductivity and can be readily fabricated. Our work provides important insights into how to manipulate the full spectrum of phonons and will guide the design of more efficient thermoelectric materials.
Size distribution measurements and chemical analysis of aerosol components
Energy Technology Data Exchange (ETDEWEB)
Pakkanen, T.A.
1995-12-31
The principal aims of this work were to improve the existing methods for size distribution measurements and to draw conclusions about atmospheric and in-stack aerosol chemistry and physics by utilizing size distributions of various aerosol components measured. A sample dissolution with dilute nitric acid in an ultrasonic bath and subsequent graphite furnace atomic absorption spectrometric analysis was found to result in low blank values and good recoveries for several elements in atmospheric fine particle size fractions below 2 {mu}m of equivalent aerodynamic particle diameter (EAD). Furthermore, it turned out that a substantial amount of analyses associated with insoluble material could be recovered since suspensions were formed. The size distribution measurements of in-stack combustion aerosols indicated two modal size distributions for most components measured. The existence of the fine particle mode suggests that a substantial fraction of such elements with two modal size distributions may vaporize and nucleate during the combustion process. In southern Norway, size distributions of atmospheric aerosol components usually exhibited one or two fine particle modes and one or two coarse particle modes. Atmospheric relative humidity values higher than 80% resulted in significant increase of the mass median diameters of the droplet mode. Important local and/or regional sources of As, Br, I, K, Mn, Pb, Sb, Si and Zn were found to exist in southern Norway. The existence of these sources was reflected in the corresponding size distributions determined, and was utilized in the development of a source identification method based on size distribution data. On the Finnish south coast, atmospheric coarse particle nitrate was found to be formed mostly through an atmospheric reaction of nitric acid with existing coarse particle sea salt but reactions and/or adsorption of nitric acid with soil derived particles also occurred. Chloride was depleted when acidic species reacted 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.)
Modelling complete particle-size distributions from operator estimates of particle-size
Roberson, Sam; Weltje, Gert Jan
2014-05-01
Estimates of particle-size made by operators in the field and laboratory represent a vast and relatively untapped data archive. The wide spatial distribution of particle-size estimates makes them ideal for constructing geological models and soil maps. This study uses a large data set from the Netherlands (n = 4837) containing both operator estimates of particle size and complete particle-size distributions measured by laser granulometry. This study introduces a logit-based constrained-cubic-spline (CCS) algorithm to interpolate complete particle-size distributions from operator estimates. The CCS model is compared to four other models: (i) a linear interpolation; (ii) a log-hyperbolic interpolation; (iii) an empirical logistic function; and (iv) an empirical arctan function. Operator estimates were found to be both inaccurate and imprecise; only 14% of samples were successfully classified using the Dutch classification scheme for fine sediment. Operator estimates of sediment particle-size encompass the same range of values as particle-size distributions measured by laser analysis. However, the distributions measured by laser analysis show that most of the sand percentage values lie between zero and one, so the majority of the variability in the data is lost because operator estimates are made to the nearest 1% at best, and more frequently to the nearest 5%. A method for constructing complete particle-size distributions from operator estimates of sediment texture using a logit constrained cubit spline (CCS) interpolation algorithm is presented. This model and four other previously published methods are compared to establish the best approach to modelling particle-size distributions. The logit-CCS model is the most accurate method, although both logit-linear and log-linear interpolation models provide reasonable alternatives. Models based on empirical distribution functions are less accurate than interpolation algorithms for modelling particle-size distributions in sandy sediments. Interpolation-based models represent a more practical approach to modelling distributions, because they can be adaptable to use as much data as available. Complete particle-size distributions modelled from operator estimates using the CCS algorithm are approximately six times less accurate than their equivalent distributions measured by laser analysis. Modelled distributions are limited by input data accuracy, rather than the specific interpolation algorithm used, which in comparison has very little influence.
Productivity improvements in gas distribution
International Nuclear Information System (INIS)
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)
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)
Market size, competition, and the product mix of exporters
Mayer, Thierry; Melitz, Marc J.; Ottaviano, Gianmarco I. P.
2011-01-01
We build a theoretical model of multi-product firms that highlights how market size and ge- ography (the market sizes of and bilateral economic distances to trading partners) affect both a firm's exported product range and its exported product mix across market destinations (the dis- tribution of sales across products for a given product range). We show how tougher competition in an export market induces a firm to skew its export sales towards its best performing products. We f...
Size Distribution of Superparamagnetic Particles Determined by Magnetic Sedimentation
Berret, J F; Mauger, A
2006-01-01
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.
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)
Distribution of particle sizes in food comminuted by human mastication.
Olthoff, L W; van der Bilt, A; Bosman, F; Kleizen, H H
1984-01-01
The masticatory performance of an individual may be quantified by describing the size distribution of particles of a comminuted test food as a function of the number of chewing strokes. A standardized sieving method and a standardized artificial test food (Optosil) were used to obtain reproducible results. Some measurements were performed using peanuts. The distribution of particle sizes of the comminuted food was adequately described by a Rosin-Rammler distribution function for the seven participating individuals which characterizes the size distribution by the median particle size (x50) and the broadness of the distribution (b). The broadness variable b hardly depends on the number of chewing strokes, and the differences in b between the individuals are small. Considerable differences in the median particle sizes at a given number of chewing strokes were observed between the subjects, reflecting differences in efficiency of comminution of a test food. For all subjects, the median particle size decreased as a function of the number of chewing strokes N according to the relation, x50 = c X N-d. Variables c and d characterized the efficiency of comminution by the subjects. PMID:6596036
Self-consistent size and velocity distributions of collisional cascades
Pan, Margaret
2011-01-01
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
Effect of Bimodal Grain Size Distribution on Scatter in Toughness
Chakrabarti, Debalay; Strangwood, Martin; Davis, Claire
2009-04-01
Blunt-notch tests were performed at -160 °C to investigate the effect of a bimodal ferrite grain size distribution in steel on cleavage fracture toughness, by comparing local fracture stress values for heat-treated microstructures with uniformly fine, uniformly coarse, and bimodal grain structures. An analysis of fracture stress values indicates that bimodality can have a significant effect on toughness by generating high scatter in the fracture test results. Local cleavage fracture values were related to grain size distributions and it was shown that the largest grains in the microstructure, with an area percent greater than approximately 4 pct, gave rise to cleavage initiation. In the case of the bimodal grain size distribution, the large grains from both the “fine grain” and “coarse grain” population initiate cleavage; this spread in grain size values resulted in higher scatter in the fracture stress than in the unimodal distributions. The notch-bend test results have been used to explain the difference in scatter in the Charpy energies for the unimodal and bimodal ferrite grain size distributions of thermomechanically controlled rolled (TMCR) steel, in which the bimodal distribution showed higher scatter in the Charpy impact transition (IT) region.
Recurrent frequency-size distribution of characteristic events
Directory of Open Access Journals (Sweden)
S. G. Abaimov
2009-04-01
Full Text Available Statistical frequency-size (frequency-magnitude properties of earthquake occurrence play an important role in seismic hazard assessments. The behavior of earthquakes is represented by two different statistics: interoccurrent behavior in a region and recurrent behavior at a given point on a fault (or at a given fault. The interoccurrent frequency-size behavior has been investigated by many authors and generally obeys the power-law Gutenberg-Richter distribution to a good approximation. It is expected that the recurrent frequency-size behavior should obey different statistics. However, this problem has received little attention because historic earthquake sequences do not contain enough events to reconstruct the necessary statistics. To overcome this lack of data, this paper investigates the recurrent frequency-size behavior for several problems. First, the sequences of creep events on a creeping section of the San Andreas fault are investigated. The applicability of the Brownian passage-time, lognormal, and Weibull distributions to the recurrent frequency-size statistics of slip events is tested and the Weibull distribution is found to be the best-fit distribution. To verify this result the behaviors of numerical slider-block and sand-pile models are investigated and the Weibull distribution is confirmed as the applicable distribution for these models as well. Exponents ? 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 C_{V} 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.
Ionization cluster size distribution for alpha particles: Experiment, modelling
International Nuclear Information System (INIS)
The paper presents data for measured ionization cluster size distributions by alpha particles in tissue equivalent media and comparison with the simulated data for liquid water. The experiments were carried out with a beam of 4.6 MeV alpha particles performed in a setup called the JET Counter. The theoretically derived cluster size distributions for alphas particles were obtained using the K-means algorithm. The simulation was carried out by Monte Carlo track structure calculations using cross sections for liquid water. The first moments of cluster size distributions, derived from K-means algorithm as a function of diameter of cluster centroid, were compared with the corresponding moments derived from the experiments for nitrogen and propane targets. It was found that the ratio of the first moments for water to gas targets correlates well with the corresponding ratio of the mean free paths for primary ionization by alpha particles in the two media. It is shown that the cluster size distributions for alpha particles in water, obtained from K-means algorithm, are in agreement with the corresponding distributions measured experimentally in nitrogen or propane gas targets of nano-meter sizes. (authors)
Particle size distribution in ferrofluid macro-clusters
Energy Technology Data Exchange (ETDEWEB)
Lee, Wah-Keat, E-mail: wklee@bnl.gov [X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, 9700S. Cass Avenue, Argonne, IL 60439 (United States); Ilavsky, Jan [X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, 9700S. Cass Avenue, Argonne, IL 60439 (United States)
2013-03-15
Under an applied magnetic field, many commercial and concentrated ferrofluids agglomerate and form large micron-sized structures. Although large diameter particles have been implicated in the formation of these macro-clusters, the question of whether the particle size distribution of the macro-clusters are the same as the original fluid remains open. Some studies suggest that these macro-clusters consist of larger particles, while others have shown that there is no difference in the particle size distribution between the macro-clusters and the original fluid. In this study, we use X-ray imaging to aid in a sample (diluted EFH-1 from Ferrotec) separation process and conclusively show that the average particle size in the macro-clusters is significantly larger than those in the original sample. The average particle size in the macro-clusters is 19.6 nm while the average particle size of the original fluid is 11.6 nm. - Highlights: Black-Right-Pointing-Pointer X-ray imaging was used to isolate ferrofluid macro-clusters under an applied field. Black-Right-Pointing-Pointer Small angle X-ray scattering was used to determine particle size distributions. Black-Right-Pointing-Pointer Results show that macro-clusters consist of particles that are larger than average.
Particle size distribution in ferrofluid macro-clusters
International Nuclear Information System (INIS)
Under an applied magnetic field, many commercial and concentrated ferrofluids agglomerate and form large micron-sized structures. Although large diameter particles have been implicated in the formation of these macro-clusters, the question of whether the particle size distribution of the macro-clusters are the same as the original fluid remains open. Some studies suggest that these macro-clusters consist of larger particles, while others have shown that there is no difference in the particle size distribution between the macro-clusters and the original fluid. In this study, we use X-ray imaging to aid in a sample (diluted EFH-1 from Ferrotec) separation process and conclusively show that the average particle size in the macro-clusters is significantly larger than those in the original sample. The average particle size in the macro-clusters is 19.6 nm while the average particle size of the original fluid is 11.6 nm. - Highlights: ? X-ray imaging was used to isolate ferrofluid macro-clusters under an applied field. ? Small angle X-ray scattering was used to determine particle size distributions. ? Results show that macro-clusters consist of particles that are larger than average.
Aerosol size distribution at Nansen Ice Sheet Antarctica
Belosi, F.; Contini, D.; Donateo, A.; Santachiara, G.; Prodi, F.
2012-04-01
During austral summer 2006, in the framework of the XXII Italian Antarctic expedition of PNRA (Italian National Program for Research in Antarctica), aerosol particle number size distribution measurements were performed in the 10-500 range nm over the Nansen Ice Sheet glacier (NIS, 74°30' S, 163°27' E; 85 m a.s.l), a permanently iced branch of the Ross Sea. Observed total particle number concentrations varied between 169 and 1385 cm- 3. A monomodal number size distribution, peaking at about 70 nm with no variation during the day, was observed for continental air mass, high wind speed and low relative humidity. Trimodal number size distributions were also observed, in agreement with measurements performed at Aboa station, which is located on the opposite side of the Antarctic continent to the NIS. In this case new particle formation, with subsequent particle growth up to about 30 nm, was observed even if not associated with maritime air masses.
Lognormal Size Distribution Theory for Deposition of Polydisperse Aerosol Particles
International Nuclear Information System (INIS)
The moments method of the lognormal size distribution theory was applied to the deposition equation of a radioactive aerosol within a liquid-metal fast breeder reactor for analysis of postulated accidents. The deposition coefficient of Crump and Seinfeld was utilized to represent the Brownian and turbulent diffusions and the gravitational sedimentation. The deposition equation was converted into a set of three ordinary differential equations. This approach takes the view point that the size distribution of an aerosol is represented by a time-dependent lognormal size distribution function during the deposition process. Numerical calculations have been performed, and the results were found to be in good agreement with the exact solution. The derived model for aerosol deposition is convenient to use in a numerical general dynamic equation solution routine based on the moments method, where nucleation, condensation, coagulation, and deposition need to be solved simultaneously
Estimating Clique Composition and Size Distributions from Sampled Network Data
Gjoka, Minas; Butts, Carter T
2013-01-01
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.
Liquid Column Deformation and Particle Size Distribution in Gas Atomization
Antipas, Georgios S. E.
2011-01-01
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.
Liquid Column Deformation and Particle Size Distribution in Gas Atomization
Directory of Open Access Journals (Sweden)
Georgios S. E. Antipas
2011-02-01
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.
Particle size distribution studies within a beryllium processing plant
International Nuclear Information System (INIS)
The size distribution of air borne particles of beryllium in the beryllium processing pilot plant at Vashi (India) has been studied. Nearly 50% of the particles in majority of the operational areas are found to be within 5 ?m size. Concentration levels of beryllium aerosols are also found to be well below 2 ?g/M3 which is the limit set for occupational exposure by the OSHA. (M.G.B.). 1 tab
Recurrent frequency-size distribution of characteristic events
Abaimov, S. G.; Tiampo, K. F.; Turcotte, D. L.; Rundle, J. B.
2008-01-01
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...
Fooling functions of halfspaces under product distributions
Gopalan, P.; O Donnell, R.; Wu, Y.; Zuckerman, D.
2010-01-01
We construct pseudorandom generators that fool functions of halfspaces (threshold functions) under a very broad class of product distributions. This class includes not only familiar cases such as the uniform distribution on the discrete cube, the uniform distribution on the solid cube, and the multivariate Gaussian distribution, but also includes any product of discrete distributions with probabilities bounded away from 0. Our first main result shows that a recent pseudora...
Size Distributions for All Cities: Which One is Best?
Gonza?lez-val, Rafael; Ramos, Arturo; Sanz, Fernando; Vera-cabello, Mari?a
2013-01-01
This paper analyses in detail the features offered by three distributions used in urban economics to describe city size distributions: lognormal, q-exponential and double Pareto lognormal, and another one of use in other areas of economics: the log-logistic. We use a large database which covers all cities with no size restriction in the US, Spain and Italy from 1900 until 2010, and, in addition, the last available year for the rest of the countries of the OECD. We estimate the previous four d...
On the upper tail of Italian firms’ size distribution
Cirillo, Pasquale; Hüsler, Jürg
2009-04-01
In this paper we analyze the upper tail of the size distribution of Italian companies with limited liability belonging to the CEBI database. Size is defined in terms of net worth. In particular, we show that the largest firms follow a power law distribution, according to the well-known Pareto law, for which we give estimates of the shape parameter. Such a behavior seems to be quite persistent over time, view that for almost 20 years of observations, the shape parameter is always in the vicinity of 1.8. The power law hypothesis is also positively tested using graphical and analytical methods.
Space Shuttle exhausted aluminum oxide - A measured particle size distribution
Cofer, W. R., III; Purgold, G. C.; Edahl, R. A.; Winstead, E. L.
1991-01-01
Aluminum oxide (A2O3) particles were collected from the Space Shuttle exhaust plume immediately following the launch of STS-34 on October 18, 1989. A2O3 samples were obtained at 2.4, 3.0, 3.2, and 7.4 km in altitude. The samples were analyzed using SEM to develope particle size distributions. There were no indications that the particle size distribution changed as a function of altitude. The particle number concentrations per cubic meter of air sampled for the four collections was found to fit an exponential expression.
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
Size-Dependency of Income Distributions and Its Implications
Zhang, Jiang
2010-01-01
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...
Endogenous Product Differentiation, Market Size and Prices
Ferguson, Shon
2011-01-01
Recent empirical evidence suggests that prices for some goods and services are higher in larger markets. This paper provides a demand-side explanation for this phenomenon when firms can choose how much to differentiate their products in a model of monopolistic competition with horizontal product differentiation. The model proposes that consumers? love of variety makes them more sensitive to product differentiation efforts by firms, which leads to higher prices in larger markets. At the same ...
Size distributions of metal nanoparticles in polyelectrolyte gels
Svergun, D. I.; Shtykova, E. V.; Dembo, A. T.; Bronstein, L. M.; Platonova, O. A.; Yakunin, A. N.; Valetsky, P. M.; Khokhlov, A. R.
1998-12-01
Small-angle x-ray scattering is used to study size distributions of noble metal nanoparticles embedded in polyelectrolyte hydrogels with oppositely charged surfactants. A procedure is proposed to subtract matrix scattering and to extract pure scattering due to the nanoparticles allowing to evaluate their size distribution functions by means of a regularization technique. Two kinds of collapsed gel-surfactant complexes were studied: a complex of a cationic gel of poly(diallyldimethylammonium chloride) with an anionic surfactant sodium dodecyl sulfate (PDADMACl/SDS), and that of an anionic gel of poly(methacrylic acid) with a cationic surfactant cetylpyridinium chloride (PMA/CPC). Addition of a gold compound (HAuCl4?3H2O) to the PDADMACl/SDS system forms the metal compound clusters and leads to a partial distortion of the gel structure. After subsequent reduction of the gold compound with sodium borohydride (NaBH4) ordering in the gel disappears and gold nanoparticles are formed. Their size distribution includes a fraction of small particles with approximately the same size as the compound clusters before reduction and a fraction of larger particles with the radii up to 40 nm. For the collapsed PDADMACl/SDS gels, aging does not change the size distribution profile; for the noncollapsed PDADMACl gels without surfactant, metal particles are found to grow with time. This suggests that the aggregation of metal colloids is prevented by the ordering in the collapsed gel-surfactant complex. The addition of HAuCl4?3H2O and the subsequent reduction of the metal ions in the PMA/CPC system does not distort the gel structure as the degree of incorporation of AuCl4- ions is very low. Particle sizes in the PMA/CPC system are found to be somewhat larger than those in the PDADMACl/SDS system. The PDADMACl/SDS gels loaded with the PtCl4 compound were also studied to analyze the influence of the reducing agent type on the particle size distribution distributions. Fast reduction with NaBH4 yielded mostly small particles with the radii around 2 nm grown from the compound clusters similar to those observed for the gold-loaded gels. In contrast, slow reduction with N2H4?H2O was found to produce larger nanoparticles and the size distribution function shows a major fraction of the particles with the radii up to 30 nm.
Molecular size distribution of Np(V)-humate
International Nuclear Information System (INIS)
Molecular size distributions of humic acid and Np(V)-humate were studied as a function of pH and an ionic strength by an ultrafiltration method. Small particle (10,000-30,000 daltons) of humic acid increased slightly with increases in solution pH. The ion strength dependence of the molecular size distribution was clearly observed for humic acid. The abundance ratio of humic acid in the range from 10,000 to 30,000 daltons increased with the ionic strength from 0.015 M to 0.105 M, in place of the decreasing of that in range from 30,000 to 100,000 daltons. Most of neptunium(V) in the 200 mg/l of the humic acid solution was fractionated into 10,000-30,000 daltons. The abundance ratio of neptunium(V) in the 10,000-30,000 daltons was not clearly dependent on pH and the ionic strength of the solution, in spite of the changing in the molecular size distribution of humic acid by the ionic strength. These results imply that the molecular size distribution of Np(V)-humate does not simply obey by that of the humic acid. Stability constant of Np(V)-humate was measured as a function of the molecular size of the humic acid. The stability constant of Np(V)-humate in the range from 10,000 to 30,000 daltons was highest value comparing with the constants in the molecular size ranges of 100,000 daltons-0.45?m, 30,000-100,000, 5,000-10,000 daltons and under 5,000 daltons. These results may indicate that the Np(V) complexation with humic acid is dominated by the interaction of neptunyl ion with the humic acid in the specific molecular size range. (author)
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
Zooming in on size distribution patterns underlying species coexistence in Baltic Sea phytoplankton.
Downing, A S; Hajdu, S; Hjerne, O; Otto, S A; Blenckner, T; Larsson, U; Winder, M
2014-10-01
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 (<1 year) patterns. Our study represents a much-needed 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
Application of Gnostic Theory to Analysis of Particle Size Distribution.
Czech Academy of Sciences Publication Activity Database
Wagner, Zden?k; Ždímal, Vladimír; Smolík, Ji?í
Vol. 56. Helsinki : University of Helsinki, 2002 - (Korhonen, H.), s. 164-168 ISBN 952-5027-34-1. [Czech-Finnish Aerosol Symposium. Prague (CZ), 23.05.2002-26.05.2002] Grant ostatní: EVK2(XE) CT/1999/00052 Institutional research plan: CEZ:AV0Z4072921 Keywords : SMPS * particle size distribution * modal analysis Subject RIV: CF - Physical ; Theoretical Chemistry
Tracing Particle Size Distribution Curves Using an Analogue Circuit.
Bisschop, F. De; Segaert, O.
1986-01-01
Proposes an analog circuit for use in sedimentation analysis of finely divided solid materials. Discusses a method of particle size distribution analysis and provides schematics of the circuit with list of components as well as a discussion about the operation of the circuit. (JM)
Modeling of Microporosity Size Distribution in Aluminum Alloy A356
Yao, Lu; Cockcroft, Steve; Zhu, Jindong; Reilly, Carl
2011-12-01
Porosity is one of the most common defects to degrade the mechanical properties of aluminum alloys. Prediction of pore size, therefore, is critical to optimize the quality of castings. Moreover, to the design engineer, knowledge of the inherent pore population in a casting is essential to avoid potential fatigue failure of the component. In this work, the size distribution of the porosity was modeled based on the assumptions that the hydrogen pores are nucleated heterogeneously and that the nucleation site distribution is a Gaussian function of hydrogen supersaturation in the melt. The pore growth is simulated as a hydrogen-diffusion-controlled process, which is driven by the hydrogen concentration gradient at the pore liquid interface. Directionally solidified A356 (Al-7Si-0.3Mg) alloy castings were used to evaluate the predictive capability of the proposed model. The cast pore volume fraction and size distributions were measured using X-ray microtomography (XMT). Comparison of the experimental and simulation results showed that good agreement could be obtained in terms of both porosity fraction and size distribution. The model can effectively evaluate the effect of hydrogen content, heterogeneous pore nucleation population, cooling conditions, and degassing time on microporosity formation.
Pore-size distributions of N-isopropylacrylamide (NIPA) hydrogels
Energy Technology Data Exchange (ETDEWEB)
Walther, D.H.; Blanch, H.W.; Prausnitz, J.M. [Univ. of California, Berkeley, CA (United States). Dept. of Chemical Engineering]|[Lawrence Berkeley Lab., CA (United States)
1993-11-01
Pore-size distributions have been measured for N-isopropylacrylamide (NIPA) hydrogels at 25 and 32{degrees}C with swelling capacities 11.3 and 6.0 g swollen gel per g dry gel. The mixed-solute-exclusion method (introduced by Kuga) was used to obtain the experimental solute-exclusion curve which represents the amount of imbibed liquid inside the gel inaccessible for a solute of radius r. The pore-size distributions were obtained by using Casassa`s Brownian-motion model and numerically solving the Fredholm integral equation. The pore-size distributions of temperature-sensitive NIPA hydrogels are strongly dependent on temperature which determines swelling capacity. With increasing swelling capacity (from 6.0 to 11.3), the pore-size distribution shifts to higher mode values (27.3 to 50.6 {angstrom}) and to higher variance (1.07{center_dot}10{sup 3} to 3.58{center_dot}10{sup 3} {angstrom}{sup 2}).
International Nuclear Information System (INIS)
Simulated crack size distributions are taken as an example to study the goodness of the fit of a distribution function to incomplete data. Special topics are whether the original parameters and distribution functions may be recovered, which are the appropriate methods of curve fitting and how the results are influenced by a lower bound. (orig.)
Size distribution and structure of Barchan dune fields
DEFF Research Database (Denmark)
Duran, O.; Schwämmle, Veit
2011-01-01
Barchans are isolated mobile dunes often organized in large dune fields. Dune fields seem to present a characteristic dune size and spacing, which suggests a co-operative behavior based on dune interaction. In Duran et al. (2009), we propose that the redistribution of sand by collisions between dunes is a key element for the stability and size selection of barchan dune fields. This approach was based on a mean-field model ignoring the spatial distribution of dune fields. Here, we present a simplified dune field model that includes the spatial evolution of individual dunes as well as their interaction through sand exchange and binary collisions. As a result, the dune field evolves towards a steady state that depends on the boundary conditions. Comparing our results with measurements of Moroccan dune fields, we find that the simulated fields have the same dune size distribution as in real fields but fail to reproduce their homogeneity along the wind direction.
Size distribution and structure of Barchan dune fields
Directory of Open Access Journals (Sweden)
O. Durán
2011-07-01
Full Text Available Barchans are isolated mobile dunes often organized in large dune fields. Dune fields seem to present a characteristic dune size and spacing, which suggests a cooperative behavior based on dune interaction. In Duran et al. (2009, we propose that the redistribution of sand by collisions between dunes is a key element for the stability and size selection of barchan dune fields. This approach was based on a mean-field model ignoring the spatial distribution of dune fields. Here, we present a simplified dune field model that includes the spatial evolution of individual dunes as well as their interaction through sand exchange and binary collisions. As a result, the dune field evolves towards a steady state that depends on the boundary conditions. Comparing our results with measurements of Moroccan dune fields, we find that the simulated fields have the same dune size distribution as in real fields but fail to reproduce their homogeneity along the wind direction.
[Characterization of bubble size distribution in ES-DAF unit].
Chen, Fu-tai; Zuo, Hua; Li, Jiu-yi; Fan, Zheng-hong; Luan, Zhao-kun
2004-01-01
ES-DAF unit was introduced and studied in this paper. Without a costly air saturator, ES-DAF consists of an ejector and a static mixer between the pressure side and suction side of the recycle rotary pump. The bubble size distribution in this novel unit was studied by using a CCD imagination through a microscope. The bubble size decreased with the increase of cycle ratio or the decrease of superficial air-water ratio. These results suggest that smaller bubbles would be formed when the initial number of nucleation sites increase by enhancing the turbulence intensity in the saturation system. The bubble size distribution became lower and wider with the increase of saturation pressure because of more frequent bubble collision and coalescence. PMID:15330434
Kitchen, J. C.
1977-01-01
Various methods of presenting and mathematically describing particle size distribution are explained and evaluated. The hyperbolic distribution is found to be the most practical but the more complex characteristic vector analysis is the most sensitive to changes in the shape of the particle size distributions. A method for determining onshore-offshore flow patterns from the distribution of particulates was presented. A numerical model of the vertical structure of two size classes of particles was developed. The results show a close similarity to the observed distributions but overestimate the particle concentration by forty percent. This was attributed to ignoring grazing by zooplankton. Sensivity analyses showed the size preference was most responsive to the maximum specific growth rates and nutrient half saturation constants. The verical structure was highly dependent on the eddy diffusivity followed closely by the growth terms.
Critical Exponent of Species-Size Distribution in Evolution
Adami, C; Yirdaw, R; Adami, Christoph; Seki, Ryoichi; Yirdaw, Robel
1998-01-01
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.
Measuring droplet size distributions from overlapping interferometric particle images.
Bocanegra Evans, Humberto; Dam, Nico; van der Voort, Dennis; Bertens, Guus; van de Water, Willem
2015-02-01
Interferometric particle imaging provides a simple way to measure the probability density function (PDF) of droplet sizes from out-focus images. The optical setup is straightforward, but the interpretation of the data is a problem when particle images overlap. We propose a new way to analyze the images. The emphasis is not on a precise identification of droplets, but on obtaining a good estimate of the PDF of droplet sizes in the case of overlapping particle images. The algorithm is tested using synthetic and experimental data. We next use these methods to measure the PDF of droplet sizes produced by spinning disk aerosol generators. The mean primary droplet diameter agrees with predictions from the literature, but we find a broad distribution of satellite droplet sizes. PMID:25725854
Measuring droplet size distributions from overlapping interferometric particle images
Bocanegra Evans, Humberto; Dam, Nico; van der Voort, Dennis; Bertens, Guus; van de Water, Willem
2015-02-01
Interferometric particle imaging provides a simple way to measure the probability density function (PDF) of droplet sizes from out-focus images. The optical setup is straightforward, but the interpretation of the data is a problem when particle images overlap. We propose a new way to analyze the images. The emphasis is not on a precise identification of droplets, but on obtaining a good estimate of the PDF of droplet sizes in the case of overlapping particle images. The algorithm is tested using synthetic and experimental data. We next use these methods to measure the PDF of droplet sizes produced by spinning disk aerosol generators. The mean primary droplet diameter agrees with predictions from the literature, but we find a broad distribution of satellite droplet sizes.
Grain size effects on He bubbles distribution and evolution
Wang, J.; Gao, X.; Gao, N.; Wang, Z. G.; Cui, M. H.; Wei, K. F.; Yao, C. F.; Sun, J. R.; Li, B. S.; Zhu, Y. B.; Pang, L. L.; Li, Y. F.; Wang, D.; Xie, E. Q.
2015-02-01
Grain boundary and grain size effects on He bubble distribution and evolution were investigated by He implantation into nanometer-size-grained T91 obtained by Surface Mechanical Attrition Treatment (SMAT) and the conventional coarse-grained T91. It was found that bubbles in the nanometer-size-grained T91 were smaller than those in the conventional coarse-grained T91 in as-implanted case, and bubbles in the matrix of nanograins were undetectable while those at nanograin boundaries (GBs) coalesced and filled in GBs after heat treatment. These results suggested that the grain size of structural material should be larger than the mean free path of bubble's Brownian motion and/or denuded zone around GBs in order to prevent bubbles accumulation at GBs, and multiple instead of one type of defects should be introduced into structural materials to effectively reduce the susceptibility of materials to He embrittlement and improve the irradiation tolerance of structural materials.
Size distribution of mist generated during metal machining.
Thornburg, J; Leith, D
2000-08-01
Mist generated by machining processes is formed by three mechanisms: impaction, centrifugal force, and evaporation/condensation. This study characterized the size distribution of soluble and mineral oil mists that resulted from these formation mechanisms. Salient parameters influencing the particle size distributions also were identified. Variables investigated included metalworking fluid and machining characteristics. The size distribution of the mist generated on a small lathe by each mechanism was measured using an Aerosizer LD. For impaction, only the mineral oil viscosity influenced the mass median diameter of the mist. No parameter affected the geometric standard deviation. High-viscosity mineral oil mist had a mass median diameter of 6.1 microns and a geometric standard deviation of 2.0. Low-viscosity mineral oil mist had a mass median diameter of 21.9 microns and a geometric standard deviation of 2.2. The mass median diameter of the mist generated by centrifugal force depended on the type of metalworking fluid, fluid flow, and rotational speed of the lathe. Mass median diameters for low-viscosity mineral oil mist ranged from 5 to 110 microns. Mass median diameters for soluble oil mist varied between 40 and 80 microns. The average geometric standard deviation was 2.4, and was not affected by any parameter. The mass median diameter and geometric standard deviation of the mist generated by evaporation/condensation varied with the type of metalworking fluid. The mineral oil mist and soluble oil mist mass median diameters were 2.1 microns and 3.2 microns, respectively. No machining or fluid parameter was important because the mist size distribution depended on the rate of condensation, coagulation processes, and the dynamics of the apparatus. Using the size distribution data from all three mechanisms, the estimated inhalable, thoracic, and respirable fractions of the total mass generated for each metalworking fluid were 60 percent, 12 percent, and 8 percent, respectively. To minimize exposure to the inhalable mass fraction, the amount of mist generated by centrifugal force must be reduced or the size of the drops generated must be increased. Altering the machining or fluid parameters did not change the mist size distribution and reduce exposure to the respirable mass fraction. PMID:10957817
Distributed Project Management for New Product Development
Directory of Open Access Journals (Sweden)
Alfred E. Thal
2007-06-01
Full Text Available This paper presents an integrative distributed project management approach for product development. The core of the integrative model is the Triple C model of project management, which presents a systematic structure for Communication, Cooperation, and Coordination across product development functions. The achievement of lower product development cycles requires strategic implementation of project management techniques. The level of communication, cooperation, and coordination required for effective product development can be facilitated by using distributed project management.
Fractal bird nest distribution produces scale-free colony sizes.
Jovani, Roger; Tella, José L
2007-10-01
The spatial distribution of organisms often differs across scales. For instance, colonial bird populations could be described, from large to small scale, as scattered clumps of otherwise regularly distributed breeding pairs. We analysed the distribution of nests of a large colonial population of white storks (Ciconia ciconia) and found a fractal pattern in each of the 4 study years. Moreover, we found that the often-observed, long-tailed frequency distribution of colony sizes was well described by a power law, regardless of the cut-off used to define colonies (from 16 to 1024 m). Thus, although storks were locally highly clumped even with tens of nests in a single tree, the population was not structured in colonies (a simple clustered distribution) as previously thought. Rather, they were distributed in a continuous hierarchical set of clusters within clusters across scales, clusters lacking the commonly assumed characteristic mean size. These quantitative solutions to previously perceived scaling problems will potentially improve our understanding of the ecology and evolution of bird coloniality and animal spacing patterns and group living in general. PMID:17666378
Portfolio effects and firm size distribution : carbonated soft drinks
Whelan, Ciara; Walsh, Patrick P.
2002-01-01
We use rich brand level retail data to demonstrate that the firm size distribution in Carbonated Soft Drinks is mainly an outcome of the degree to which firms own a portfolio of brands across segments of the market, and not from performance within segments. In addition, while the number of firms in each segment is limited by segment size relative to sunk cost and competition in a segment, idiosyncratic firm effects make some firms more likely to participate in any given segment. This feature ...
Probabilistic Optimal Allocation and Sizing of Distributed Generation
Directory of Open Access Journals (Sweden)
M. Hosseinzadeh
2014-01-01
Full Text Available The optimal allocation of Distributed Generation (DG in distribution system is one of the important parts of DG research studies so as to maximize its benefits. For this purpose, a probabilistic approach is proposed in this study to consider time varying load demands as uncertain parameters of distribution system. It is assumed that each load point consists of three categories of voltage dependent loads: residential, industrial and commercial. The proposed algorithm is based on a probabilistic load flow solved by Point Estimate Method (PEM. The objective function is considered as a combination of active power loss, reactive power loss and voltage profiles indices. To solve the optimization problem, an Invasive Weed Optimization (IWO technique is adopted and the optimal location and size of different types of DG are obtained. Examining on a test distribution system, the performance of the proposed approach is assessed and illustrated.
Educational production and optimal class size
Foregger, T H
2004-01-01
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.
Gründel, M.; Porstendörfer, J.
The results of the activity size distribution of the short-lived ( 218Po, 214Bi/ 214Po) and long-lived ( 210Pb, 210Po) radon decay product aerosols, the thoron decay product aerosols ( 212Pb, 212Po) and 7Be of the outdoor atmosphere are presented. The results were obtained from measurements averaged over an extended period (4 weeks) and were carried out with a low-pressure On-Line Alpha Cascade Impactor (OLACI). The size distributions of the radionuclides were obtained from the same measurement run with the OLACI, so that the size classification technique and the atmospheric and weather conditions for all radionuclides were identical. This measurement technique made it possible to measure the correct differences between the size distributions of the different natural radionuclides in the environmental air. The differences between the activity size distributions of the long- and short-lived radionuclides could be explained by coagulation with aerosol particles of the atmosphere as for instance 210Pb was shown.
Size distribution of FeNiB nanoparticles
Directory of Open Access Journals (Sweden)
Lackner P.
2014-07-01
Full Text Available Two samples of amorphous nanoparticles FeNiB, one of them with SiO2 sheath around the core and one without, were investigated by transmission electron microscopy and magnetic measurements. The coating gives mean particle diameters of 4.3 nm compared to 7.2 nm for the uncoated particles. Magnetic measurements prove superparamagnetic behaviour above 160 K (350 K for the coated (uncoated sample. With use of effective anisotropy constant Keff – determined from hysteresis loops – size distributions are determined both from ZFC curves, as well as from relaxation measurements. Both are in good agreement and are very similar for both samples. Comparison with the size distribution determined from TEM pictures shows that magnetic clusters consist of only few physical particles.
Magnetic heating effect of nanoparticles with different sizes and size distributions
Energy Technology Data Exchange (ETDEWEB)
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
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.
Comparative method evaluation for size and size-distribution analysis of gold nanoparticles.
Hinterwirth, Helmut; Wiedmer, Susanne K; Moilanen, Maria; Lehner, Angela; Allmaier, Günter; Waitz, Thomas; Lindner, Wolfgang; Lämmerhofer, Michael
2013-09-01
Gold nanoparticles (GNPs) are popular colloidal substrates in various sensor, imaging, and nanomedicine applications. In separation science, they have raised some interest as a support for sample preparation. Reasons for their popularity are their low cost, ability for size-controlled synthesis with well-defined narrow nanoparticle size distributions, as well as straightforward surface functionalization by self-assembling (thiol-containing) molecules on the surface, which allows flexible introduction of functionalities for the selective capture of analytes. Most commonly, the method of first choice for size determination is dynamic light scattering (DLS). However, DLS has some serious shortcomings, and results from DLS may be misleading. For this reason, in this contribution several distinct complementary nanoparticle sizing methodologies were utilized and compared to characterize citrate-capped GNPs of different diameters in the range of 13-26 nm. Weaknesses and strengths of DLS, transmission electron microscopy, asymmetrical-flow field-flow fractionation and nanoelectrospray gas-phase electrophoretic mobility molecular analysis are discussed and the results comparatively assessed. Furthermore, the distinct GNPs were characterized by measuring their zeta-potential and surface plasmon resonance spectra. Overall, the combination of methods for GNP characterization gives a more realistic and comprehensive picture of their real physicochemical properties, (hydrodynamic) diameter, and size distribution. PMID:23857600
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)
Onset of Oil Mobilization and Cluster Size Distribution
Ruecker, Maja; Armstrong, Ryan; Georgiadis, Apostolos; Ott, Holger; Berg, Steffen; Leu, Leon; Wolf, Martin; Khan, Faisal; Enzmann, Frieder; Kersten, Michael
2014-05-01
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.
Analysis of Time Evolution of Particle Size Distribution.
Czech Academy of Sciences Publication Activity Database
Wagner, Zden?k; Schwarz, Jaroslav; Ždímal, Vladimír; Eleftheriadis, K.; Lazaridis, M.; Smolík, Ji?í
Prague : Orgit, 2009 - (Smolík, J.; O'Dowd, C.), S.116-119 ISBN 978-80-02-12161-2. [International Conference Nucleation and Atmospheric Aerosols /18./. Prague (CZ), 10.08.2009-14.08.2009] Grant ostatní: MF CZ(NO) 0049 Institutional research plan: CEZ:AV0Z40720504 Keywords : tropospheric aerosol * particle size distribution * time series filtration and interpolation Subject RIV: CF - Physical ; Theoretical Chemistry http://www.icnaa.cz/
Determination of particle size distribution by FMR measurements
Scientific Electronic Library Online (English)
Walter S. D., Folly; Ronaldo S. de, Biasi.
2001-09-01
Full Text Available SciELO Brazil | Language: English Abstract in english Knowledge of particle size distribution is very important for the study of magnetic fluids, magnetic powders and other magnetic systems. In this work, we describe a simple method for its determination from FMR measurements. The method was applied to the case of MgFe2O4 precipitates in (Mg,Fe)O. [...
Binning effects on in-situ raindrop size distribution measurements
Directory of Open Access Journals (Sweden)
R. Checa-Garcia
2014-03-01
Full Text Available This paper investigates the binning effects on drop size distribution (DSD measurements obtained by Joss-Waldvogel disdrometer (JWD, Precipitation Occurrence Sensor System (POSS, Thies disdrometer (Thies, Parsivel OTT disdrometer, two-dimensional video disdrometer (2DVD and optical spectro-pluviometer (OSP instruments, therefore the evaluation comprises non-regular bin sizes and the effect of minimum and maximum measured sizes of drops. To achieve this goal, 2DVD measurements and simulated gamma size distributions were considered. The analysis of simulated gamma DSD binned according each instrument was performed to understand the role of discretisation and truncation effects together on the integral rainfall parameters and estimators of the DSD parameters. In addition, the drop-by-drop output of the 2DVD is binned to simulate the raw output of the other disdrometers which allowed us estimate sampling and binning effects on selected events from available dataset. From simulated DSD it has been found that binning effects exist in integral rainfall parameters and in the evaluation of DSD parameters of a gamma distribution. This study indicates that POSS and JWD exhibit underestimation of concentration and mean diameter due to binning. Thies and Parsivel report a positive bias for rainfall and reflectivity (reaching 5% for heavy rainfall intensity events. Regarding to DSD parameters, distributions of estimators for the shape and scale parameters were analyzed by moment, truncated moment and maximum likelihood methods. They reported noticeable differences between instruments for all methodologies of estimation applied. The measurements of 2DVD allow sampling error estimation of instruments with smaller capture areas than 2DVD. The results show that the instrument differences due to sampling were a~relevant uncertainty but that concentration, reflectivity and mass-weighted diameter were sensitive to binning.
Size distribution of drops from containment spray nozzles
International Nuclear Information System (INIS)
Typically PWR nuclear reactor containment vessels are equipped with an array of spray nozzles that would be used to decontaminate the vessel atmosphere in the unlikely event of a loss-of-coolant accident (LOCA). Since the decontamination rate is highly dependent upon the spray drop size, knowledge of the size distribution of the drops from a specified nozzle is required for mathematical prediction of washout rates for the radionuclides present in the vessle atmosphere. Spray washout rates for 1713A and 7G3 nozzles were empirically determined in the Containment System Experiments (CSE). The values obtained compared reasonably well with those calculated using the mathematical model. The mass median diameter (MMD) drop sizes of the sprays used for the mathematical prediction were those supplied by the manufacturers which were based on an early photographic method
Size distribution of drops from containment spray nozzles. [PWR
Energy Technology Data Exchange (ETDEWEB)
Powers, T.B.; Reid, D.L.
1979-01-01
Typically PWR nuclear reactor containment vessels are equipped with an array of spray nozzles that would be used to decontaminate the vessel atmosphere in the unlikely event of a loss-of-coolant accident (LOCA). Since the decontamination rate is highly dependent upon the spray drop size, knowledge of the size distribution of the drops from a specified nozzle is required for mathematical prediction of washout rates for the radionuclides present in the vessle atmosphere. Spray washout rates for 1713A and 7G3 nozzles were empirically determined in the Containment System Experiments (CSE). The values obtained compared reasonably well with those calculated using the mathematical model. The mass median diameter (MMD) drop sizes of the sprays used for the mathematical prediction were those supplied by the manufacturers which were based on an early photographic method.
New Measurements of the Particle Size Distribution of Apollo 11 Lunar Soil 10084
McKay, D.S.; Cooper, B.L.; Riofrio, L.M.
2009-01-01
We have initiated a major new program to determine the grain size distribution of nearly all lunar soils collected in the Apollo program. Following the return of Apollo soil and core samples, a number of investigators including our own group performed grain size distribution studies and published the results [1-11]. Nearly all of these studies were done by sieving the samples, usually with a working fluid such as Freon(TradeMark) or water. We have measured the particle size distribution of lunar soil 10084,2005 in water, using a Microtrac(TradeMark) laser diffraction instrument. Details of our own sieving technique and protocol (also used in [11]). are given in [4]. While sieving usually produces accurate and reproducible results, it has disadvantages. It is very labor intensive and requires hours to days to perform properly. Even using automated sieve shaking devices, four or five days may be needed to sieve each sample, although multiple sieve stacks increases productivity. Second, sieving is subject to loss of grains through handling and weighing operations, and these losses are concentrated in the finest grain sizes. Loss from handling becomes a more acute problem when smaller amounts of material are used. While we were able to quantitatively sieve into 6 or 8 size fractions using starting soil masses as low as 50mg, attrition and handling problems limit the practicality of sieving smaller amounts. Third, sieving below 10 or 20microns is not practical because of the problems of grain loss, and smaller grains sticking to coarser grains. Sieving is completely impractical below about 5- 10microns. Consequently, sieving gives no information on the size distribution below approx.10 microns which includes the important submicrometer and nanoparticle size ranges. Finally, sieving creates a limited number of size bins and may therefore miss fine structure of the distribution which would be revealed by other methods that produce many smaller size bins.
Initial Size Distribution of the Galactic Globular Cluster System
Shin, Jihye; Yoon, Suk-Jin; Kim, Juhan
2013-01-01
Despite the importance of their size evolution in understanding the dynamical evolution of globular clusters (GCs) of the Milky Way, studies are rare that focus specifically on this issue. Based on the advanced, realistic Fokker-Planck (FP) approach, we predict theoretically the initial size distribution (SD) of the Galactic GCs along with their initial mass function and radial distribution. Over one thousand FP calculations in a wide parameter space have pinpointed the best-fit initial conditions for the SD, mass function, and radial distribution. Our best-fit model shows that the initial SD of the Galactic GCs is of larger dispersion than today's SD, and that typical projected half-light radius of the initial GCs is ~4.6 pc, which is 1.8 times larger than that of the present-day GCs (~2.5 pc). Their large size signifies greater susceptibility to the Galactic tides: the total mass of destroyed GCs reaches 3-5x10^8 M_sun$, several times larger than the previous estimates. Our result challenges a recent view t...
Size distribution measurement of vesicles by atomic force microscopy.
Kanno, Takashi; Yamada, Tadanori; Iwabuki, Hidehiko; Tanaka, Hiroyuki; Kuroda, Shun'ichi; Tanizawa, Katsuyuki; Kawai, Tomoji
2002-10-15
Vesicles have been utilized as nanoscale vehicles for reagents including potential drug delivery systems. When used to deliver drugs, vesicle size and the size distribution are important factors in the determination of the dosage, cell specificity, and rate of clearance from the body. Current size measurement techniques for vesicles are electron microscopy and dynamic light scattering, but their results are not equal. Therefore atomic force microscopy was attempted as another size measurement technique. After adsorption of the vesicles from a low-concentration solution of vesicles on mica substrate, each vesicle is generally found as a flattened structure. The diameters of vesicles in these solutions and their distribution have been successfully estimated from the surface area of the flattened structure of each vesicle. At higher concentrations, we have found a monolayer crammed with dome-shaped vesicles on the substrate. The diameters of vesicles in these solutions have also been successfully estimated from the surface area of the dome-shaped structure of each vesicle. Diameters of vesicles in solution estimated from two different vesicle concentrations are not close to those reported by electron microscope studies but are close to those reported by dynamic light scattering studies. PMID:12413451
Time Evolution of the Mutual Fund Size Distribution
Schwarzkopf, Yonathan
2008-01-01
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...
Controls on phytoplankton cell size distributions in contrasting physical environments
Clark, J. R.; Daines, S. J.; Lenton, T. M.
2012-04-01
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.
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
Finite-size effects on return interval distributions for weakest-link-scaling systems
Hristopulos, Dionissios T.; Petrakis, Manolis P.; Kaniadakis, Giorgio
2014-05-01
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.
Finite-size effects on return interval distributions for weakest-link-scaling systems.
Hristopulos, Dionissios T; Petrakis, Manolis P; Kaniadakis, Giorgio
2014-05-01
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) ? n(1/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. PMID:25353774
Christoffersen, P. A.; Simon, Justin I.; Ross, D. K.; Friedrich, J. M.; Cuzzi, J. N.
2012-01-01
Size distributions of nebular solids in chondrites suggest an efficient sorting of these early forming objects within the protoplanetary disk. The effect of this sorting has been documented by investigations of modal abundances of CAIs (e.g., [1-4]) and chondrules (e.g., [5-8]). Evidence for aerodynamic sorting in the disk is largely qualitative, and needs to be carefully assessed. It may be a way of concentrating these materials into planetesimal-mass clumps, perhaps 100 fs of ka after they formed. A key parameter is size/density distributions of particles (i.e., chondrules, CAIs, and metal grains), and in particular, whether the radius-density product (rxp) is a better metric for defining the distribution than r alone [9]. There is no consensus between r versus rxp based models. Here we report our initial tests and preliminary results, which when expanded will be used to test the accuracy of current dynamical disk models.
Bodrova, Anna; Levchenko, Denis; Brilliantov, Nikolay
2014-01-01
Distribution of granular temperatures in granular gas mixtures is investigated analytically and numerically. We analyze space uniform systems in a homogeneous cooling state (HCS) and under a uniform heating with a mass-dependent heating rate $\\Gamma_k\\sim m_k^{\\gamma}$. We demonstrate that for steep size distributions of particles the granular temperatures obey a universal power-law distribution, $T_k \\sim m_k^{\\alpha}$, where the exponent $\\alpha$ does not depend on a parti...
Fog-Influenced Submicron Aerosol Number Size Distributions
Zikova, N.; Zdimal, V.
2013-12-01
The aim of this work is to evaluate the influence of fog on aerosol particle number size distributions (PNSD) in submicron range. Thus, five-year continuous time series of the SMPS (Scanning Mobility Particle Sizer) data giving information on PNSD in five minute time step were compared with detailed meteorological records from the professional meteorological station Kosetice in the Czech Republic. The comparison included total number concentration and PNSD in size ranges between 10 and 800 nm. The meteorological records consist from the exact times of starts and ends of individual meteorological phenomena (with one minute precision). The records longer than 90 minutes were considered, and corresponding SMPS spectra were evaluated. Evaluation of total number distributions showed considerably lower concentration during fog periods compared to the period when no meteorological phenomenon was recorded. It was even lower than average concentration during presence of hydrometeors (not only fog, but rain, drizzle, snow etc. as well). Typical PNSD computed from all the data recorded in the five years is in Figure 1. Not only median and 1st and 3rd quartiles are depicted, but also 5th and 95th percentiles are plotted, to see the variability of the concentrations in individual size bins. The most prevailing feature is the accumulation mode, which seems to be least influenced by the fog presence. On the contrary, the smallest aerosol particles (diameter under 40 nm) are effectively removed, as well as the largest particles (diameter over 500 nm). Acknowledgements: This work was supported by the projects GAUK 62213 and SVV-2013-267308. Figure 1. 5th, 25th, 50th, 75th and 95th percentile of aerosol particle number size distributions recorded during fog events.
Image Analysis of Pellet Size for a Control System in Industrial Feed Production
DEFF Research Database (Denmark)
Ljungqvist, Martin Georg; Nielsen, Michael Engelbrecht
2011-01-01
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.
Size of RJVs and Degree of Cooperation in Product Development
Bourreau, Marc; Dogan, Pinar; Manant, Matthieu
2010-01-01
In this paper we provide a model of Research Joint Venture (RJV), and study the incentives of competing firms to cooperate in product development. Firms that participate in the RJV decide on the product components for joint development, i.e., they decide on how much to cooperate. We consider three cases: (i) an RJV with an exogenous size and an endogenous scope, (ii) an RJV with an endogenous size and an exogenous scope, and (iii) an RJV with an endogenous size and scope. Using numerical simu...
Cluster analysis of roadside ultrafine particle size distributions
Sabaliauskas, Kelly; Jeong, Cheol-Heon; Yao, Xiaohong; Jun, Yun-Seok; Evans, Greg
2013-05-01
This study reports the diurnal, seasonal, and annual variation of ultrafine particle size distributions in downtown Toronto. The k-means clustering algorithm was applied to five years of size-resolved data for particles with diameters less than 100 nm. Continuous particle number concentrations were measured 16 m from a major arterial roadway between March 2006 and May 2011 using a Fast Mobility Particle Sizer. Eight particle size distribution (PSD) types were identified. The PSD types exhibited distinct weekday-weekend and diurnal patterns. The relative frequency that each PSD occurred varied with season and wind direction and was correlated with other pollutants. These temporal patterns and correlation helped in elucidating the sources and processes that each of the eight PSD represent. Finally, similar PSD types were observed in residential areas located 6 and 15 km away from the central monitoring site suggesting that these PSD types may be generalizable to other sites. Identification of PSD types was found to be a valuable tool to support the interpretation of PSD data so as to elucidate the sources and processes contributing to ultrafine particle concentrations.
Hirashita, Hiroyuki
2013-01-01
Shattering of dust grains in the interstellar medium is a viable mechanism of small grain production in galaxies. We examine the robustness or uncertainty in the theoretical predictions of shattering. We identify $P_1$ (the critical pressure above which the deformation destroys the original lattice structures) as the most important quantity in determining the timescale of small grain production, and confirm that the same $P_1/t$ ($t$ is the duration of shattering) gives the same grain size distribution [$n(a)$, where $a$ is the grain radius] after shattering within a factor of 3. The uncertainty in the fraction of shocked material that is eventually ejected as fragments causes uncertainties in $n(a)$ by a factor of 1.3 and 1.6 for silicate and carbonaceous dust, respectively. The size distribution of shattered fragments have minor effects as long as the power index of the fragment size distribution is less than ~ 3.5, since the slope of grain size distribution $n(a)$ continuously change by shattering and beco...
SIZE DISTRIBUTIONS OF SOLAR FLARES AND SOLAR ENERGETIC PARTICLE EVENTS
Energy Technology Data Exchange (ETDEWEB)
Cliver, E. W. [Space Vehicles Directorate, Air Force Research Laboratory, Sunspot, NM 88349 (United States); Ling, A. G. [Atmospheric Environmental Research, Lexington, MA 02421 (United States); Belov, A. [IZMIRAN, Troitsk, Moscow Region 142190 (Russian Federation); Yashiro, S. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
2012-09-10
We suggest that the flatter size distribution of solar energetic proton (SEP) events relative to that of flare soft X-ray (SXR) events is primarily due to the fact that SEP flares are an energetic subset of all flares. Flares associated with gradual SEP events are characteristically accompanied by fast ({>=}1000 km s{sup -1}) coronal mass ejections (CMEs) that drive coronal/interplanetary shock waves. For the 1996-2005 interval, the slopes ({alpha} values) of power-law size distributions of the peak 1-8 A fluxes of SXR flares associated with (a) >10 MeV SEP events (with peak fluxes {>=}1 pr cm{sup -2} s{sup -1} sr{sup -1}) and (b) fast CMEs were {approx}1.3-1.4 compared to {approx}1.2 for the peak proton fluxes of >10 MeV SEP events and {approx}2 for the peak 1-8 A fluxes of all SXR flares. The difference of {approx}0.15 between the slopes of the distributions of SEP events and SEP SXR flares is consistent with the observed variation of SEP event peak flux with SXR peak flux.
Effects of YORP-Induced Rotational Fission on the Asteroid Size Distribution at the Small Size End
Rossi, A.; Marzari, F.; Scheeres, D. J.; Jacobson, S.
2012-03-01
The asteroid belt size distribution was shaped by collisions grinding the population into smaller bodies via cratering or fragmentation. At the small size end YORP may contribute by accelerating the spin of the bodies beyond the disruption limit.
Grain-size distribution and rheology of the upper mantle
Karato, Shun-Ichiro
1984-04-01
The physical processes that govern the grain size of rocks in the upper mantle are examined. The analysis is based on the experimental data on creep, recrystallization, and grain growth in dunites and on a theoretical model for the thermomechanical structure of the cooling moving lithosphere. The grain size of rocks is shown to be determined by the in situ stress only at the deeper part where the temperature is high enough to allow significant strain rate. Above this depth, the microstructures record the thermomechanical history of rocks rather than the in situ stress. In the case of the oceanic lithosphere where the thermomechanical history is best known, the following features of grain-size distribution are found. At the uppermost mantle, where the amount of grain growth is limited, the grain size is determined by the initial value and the growth rate, and, where the effect of grain growth dominates, it increases with depth. When the amount of grain growth becomes large and the grain size reaches the steady state size corresponding to the ambient stress while the rock is hot enough to deform, the grain size is then determined by the applied stress. This grain size is, however, frozen, when the rock gets cool and the strain rate becomes too small to induce any further dynamic recrystallization. Thus, at the intermediate depth region, the grain size records the fossil (frozen) stress at which the microstructures of rock have been frozen. Since the frozen stress increases with age, the grain size in this depth interval decreases with depth. Finally, the grain size below this level reflects the in situ stress, and increases with depth, its extent being dependent on the nature of return flow in the deep mantle. Thus the grain size versus depth relation may show a sigmoid curve. The qualitative features of this curve may be similar also in the case of the continental lithosphere, if a similar thermal event (i.e., the intrusion of hot material and subsequent cooling) occurs. The results are quite consistent with the observed depth variation of olivine grain size in peridotite nodules (Avé Lallemant et al., 1980). The present model suggests that the depth of minimum grain size (65 and 150 km at the continental rift zone and the shield region respectively) corresponds to that where the mechanical properties of the upper mantle change from elastic to ductile at tectonic stress levels (~ 1 MPa) and in the geological time scale. This result leads to a new definition of the thickness of lithosphere in terms of its rheological properties. This thickness is about twice as large as that inferred from the flexure of lithosphere but approximately equal to seismic thickness. The model suggests the importance of grain growth as well as dynamic recrystallization and plastic flow in determining the texture of upper mantle rocks and therefore seismic anisotropy.
A new microencapsulation device for controlled membrane and capsule size distributions.
Ceausoglu, I; Hunkeler, D
2002-01-01
Microbeads and microcapsules, employed for the microencapsulation of bioactive material, should provide sufficient mechanical protection to the encapsulated material, insure an optimal diffusion of desired molecules and, for transplantation-related applications, block the ingress of the imunoagents. Microcapsules are also often required to be smooth, spherical, within narrow size and membrane thickness distributions. In addition, the bioactive material has to be centred within the capsule, whose size should be minimized in relation to the bioactive material in order to optimise the diffusion of active molecules. The production process of such microcapsules should respect the aforementioned constraints and, in addition, be sterile, repeatable, robust, and harmless to the bioactive material while showing a high output. Two prototypes, dedicated to the microencapsulation of bioactive materials are presented. A semi-manual device permits the control of microcapsule properties for small scale (< 10 000 microcapsules), sterile production. An 'automated reaction control' system has also been developed. The features of the former are demonstrated for the repeatable production of 400 microm-microcapsules using the alginate/cellulose sulphate/poly(methylene-co-guanidine) system. The production rate is 500 000 microcapsules/h, with a size distribution within +/-10% and membrane thickness distribution within +/-5 microm. The latter in particular is, to the authors' knowledge, better than can be achieved with currently disclosed technologies, and is due to the precise control of the reaction conditions and time. PMID:12569021
Method for measuring the size distribution of airborne rhinovirus
Energy Technology Data Exchange (ETDEWEB)
Russell, M.L.; Goth-Goldstein, R.; Apte, M.G.; Fisk, W.J.
2002-01-01
About 50% of viral-induced respiratory illnesses are caused by the human rhinovirus (HRV). Measurements of the concentrations and sizes of bioaerosols are critical for research on building characteristics, aerosol transport, and mitigation measures. We developed a quantitative reverse transcription-coupled polymerase chain reaction (RT-PCR) assay for HRV and verified that this assay detects HRV in nasal lavage samples. A quantitation standard was used to determine a detection limit of 5 fg of HRV RNA with a linear range over 1000-fold. To measure the size distribution of HRV aerosols, volunteers with a head cold spent two hours in a ventilated research chamber. Airborne particles from the chamber were collected using an Andersen Six-Stage Cascade Impactor. Each stage of the impactor was analyzed by quantitative RT-PCR for HRV. For the first two volunteers with confirmed HRV infection, but with mild symptoms, we were unable to detect HRV on any stage of the impactor.
COD fractionation of tannery wastewaters--particle size distribution, biodegradability and modeling.
Karahan, O; Dogruel, S; Dulekgurgen, E; Orhon, D
2008-02-01
This study aims to establish the scientific link between particle size distribution (PSD) and biodegradability of different COD fractions of tannery wastewater, by means of sequential filtration/ultrafiltration, respirometric analysis and model evaluation. PSD profiles were determined in physical segregation experiments, using eight membrane discs, each with different pore sizes between 2 and 1600 nm. Biodegradability-related COD fractionation was determined at each size interval by model simulation and calibration of the corresponding oxygen uptake rate (OUR) profiles. Activated Sludge Model No. 3 (ASM3), modified for direct growth on hydrolysis products, was adopted for evaluation. PSD analyses defined a COD fingerprint with two significant portions at the two ends of size distribution, with 60% of the total COD at the particulate range, 25% at the soluble range and the remaining 15% well distributed among the colloidal range. Comparative evaluation of the sequence of OUR profiles yielded values of applicable model coefficients. It also enabled the assessment of size distribution for each major COD fraction, as an original tool for better interpretation of specific biodegradation characteristics of the selected tannery wastewater. Results also revealed a very slowly biodegradable/residual particulate COD component with a significant inhibitory effect. Model-based evaluation of the OUR profiles enabled quantifying the impact of inhibition in terms of changes in rate coefficients for growth, hydrolysis of soluble COD and endogenous decay. PMID:17991509
Lot-sizing for inventory systems with product recovery
Teunter, R. H.
2003-01-01
We study inventory systems with product recovery. Recovered items are as-good-as-new and satisfy the same demands as new items. The demand rate and return fraction are deterministic. The relevant costs are those for ordering recovery lots, for ordering production lots, for holding recoverable items in stock, and for holding new/recovered items in stock. We derive simple formulae that determine the optimal lot-sizes for the production/procurement of new items and for the r...
Simulation study of territory size distributions in subterranean termites.
Jeon, Wonju; Lee, Sang-Hee
2011-06-21
In this study, on the basis of empirical data, we have simulated the foraging tunnel patterns of two subterranean termites, Coptotermes formosanus Shiraki and Reticulitermes flavipes (Kollar), using a two-dimensional model. We have defined a territory as a convex polygon containing a tunnel pattern and explored the effects of competition among termite territory colonies on the territory size distribution in the steady state that was attained after a sufficient simulation time. In the model, territorial competition was characterized by a blocking probability P(block) that quantitatively describes the ease with which a tunnel stops its advancement when it meets another tunnel; higher P(block) values imply easier termination. In the beginning of the simulation run, N=10, 20,…,100 territory seeds, representing the founding pair, were randomly distributed on a square area. When the territory density was less (N=20), the differences in the territory size distributions for different P(block) values were small because the territories had sufficient space to grow without strong competitions. Further, when the territory density was higher (N>20), the territory sizes increased in accordance with the combinational effect of P(block) and N. In order to understand these effects better, we introduced an interference coefficient ?. We mathematically derived ? as a function of P(block) and N: ?(N,P(block))=a(N)P(block)/(P(block)+b(N)). a(N) and b(N) are functions of N/(N+c) and d/(N+c), respectively, and c and d are constants characterizing territorial competition. The ? function is applicable to characterize the territoriality of various species and increases with both the P(block) values and N; higher ? values imply higher limitations of the network growth. We used the ? function, fitted the simulation results, and determined the c and d values. In addition, we have briefly discussed the predictability of the present model by comparing it with our previous lattice model that had been used to explain the territory size distributions of mangrove termites on the Atlantic coast of Panama. PMID:21426908
The size distribution of Jupiter Family comet nuclei
Snodgrass, C.; Fitzsimmons, A.; Lowry, S. C.; Weissman, P.
2011-01-01
We present an updated cumulative size distribution (CSD) for Jupiter Family comet (JFC) nuclei, including a rigourous assessment of the uncertainty on the slope of the CSD. The CSD is expressed as a power law, N(>r_N) \\propto r_N^{-q}, where r_N is the radius of the nuclei and q is the slope. We include a large number of optical observations published by ourselves and others since the comprehensive review in the "Comets II" book (Lamy et al. 2004), and make use of an improve...
Retrieval of spherical particle size distribution with an improved Tikhonov iteration method
Tang Hong
2012-01-01
The problem of retrieval for spherical particle size distribution in the independent mode is studied, and an improved Tikhonov iteration method is proposed. In this method, the particle size distribution is retrieved from the light extinction data through the Phillips-Twomey method firstly in the independent mode, and then the obtained inversion results of the particle size distribution is used as the initial distribution and the final retrieved particle size distribution is obtained. S...
Light scattering by lunar-like particle size distributions
Goguen, Jay D.
1991-01-01
A fundamental input to models of light scattering from planetary regoliths is the mean phase function of the regolith particles. Using the known size distribution for typical lunar soils, the mean phase function and mean linear polarization for a regolith volume element of spherical particles of any composition were calculated from Mie theory. The two contour plots given here summarize the changes in the mean phase function and linear polarization with changes in the real part of the complex index of refraction, n - ik, for k equals 0.01, the visible wavelength 0.55 micrometers, and the particle size distribution of the typical mature lunar soil 72141. A second figure is a similar index-phase surface, except with k equals 0.1. The index-phase surfaces from this survey are a first order description of scattering by lunar-like regoliths of spherical particles of arbitrary composition. They form the basis of functions that span a large range of parameter-space.
Modelling the gap size distribution of parked cars
Rawal, S.; Rodgers, G. J.
2005-02-01
We have measured the distribution of distances between parked cars in a number of roads in central London. We compare the results with models of random sequential adsorption, or random car parking models, as they are often called. Our empirical results do not agree with these models, and hence we introduce alternative models for the parking process. The first model we propose is one where cars can only park if the space is greater than or equal to a chosen minimum size; where the extra space can be used for manoeuvering. The results of this model suggest that in addition to a deposition process, a re-positioning process is required to explain our empirical results. Hence, we introduce a further model where at each time step, with probability p, a car is randomly placed on a line if the space is empty and with probabilty 1-p, is placed in a space but then rolls to the nearest parked car so that it is y distance from the nearest car with probability f(y). We concentrate on two specific probabilities f(y) and find that for one case, the gap size distribution agrees with the empirical results.
Size Distribution of Main-Belt Asteroids with High Inclination
Terai, Tsuyoshi
2010-01-01
We investigated the size distribution of high-inclination main-belt asteroids (MBAs) to explore asteroid collisional evolution under hypervelocity collisions of around 10 km/s. We performed a wide-field survey for high-inclination sub-km MBAs using the 8.2-m Subaru Telescope with the Subaru Prime Focus Camera (Suprime-Cam). Suprime-Cam archival data were also used. A total of 616 MBA candidates were detected in an area of 9.0 deg^2 with a limiting magnitude of 24.0 mag in the SDSS r filter. Most of candidate diameters were estimated to be smaller than 1 km. We found a scarcity of sub-km MBAs with high inclination. Cumulative size distributions (CSDs) were constructed using Subaru data and published asteroid catalogs. The power-law indexes of the CSDs were 2.17 +/- 0.02 for low-inclination ( 15 deg) MBAs in the 0.7-50 km diameter range. The high-inclination MBAs had a shallower CSD. We also found that the CSD of S-like MBAs had a small slope with high inclination, whereas the slope did not vary with inclinatio...
Drew, L.J.; Attanasi, E.D.; Schuenemeyer, J.H.
1988-01-01
If observed oil and gas field size distributions are obtained by random samplings, the fitted distributions should approximate that of the parent population of oil and gas fields. However, empirical evidence strongly suggests that larger fields tend to be discovered earlier in the discovery process than they would be by random sampling. Economic factors also can limit the number of small fields that are developed and reported. This paper examines observed size distributions in state and federal waters of offshore Texas. Results of the analysis demonstrate how the shape of the observable size distributions change with significant hydrocarbon price changes. Comparison of state and federal observed size distributions in the offshore area shows how production cost differences also affect the shape of the observed size distribution. Methods for modifying the discovery rate estimation procedures when economic factors significantly affect the discovery sequence are presented. A primary conclusion of the analysis is that, because hydrocarbon price changes can significantly affect the observed discovery size distribution, one should not be confident about inferring the form and specific parameters of the parent field size distribution from the observed distributions. ?? 1988 International Association for Mathematical Geology.
Voigt, Andreas; Adityawarman, Dendy; Sundmacher, Kai
2005-07-01
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.
Electron structure: Shape, size, and generalized parton distributions in QED
Miller, Gerald A.
2014-12-01
The shape of the electron is studied using lowest-order perturbation theory. Quantities used to probe the structure of the proton—form factors, generalized parton distributions, transverse densities, Wigner distributions and the angular momentum content—are computed for the electron-photon component of the electron wave function. The influence of longitudinally polarized photons, demanded by the need for infrared regularization via a nonzero photon mass, is included. The appropriate value of the photon mass depends on experimental conditions, and consequently the size of the electron (as defined by the slope of its Dirac form factor) bound in a hydrogen atom is found to be about four times larger than when the electron is in a continuum scattering state. The shape of the electron, as determined from the transverse density and generalized parton distributions, is shown not to be round, and the continuum electron is shown to be far less round than the bound electron. An electron distribution function (analogous to the quark distribution function) is defined, and that of the bound electron is shown to be suppressed compared to that of the continuum electron. If the relative transverse momentum of the virtual electron and photon is large compared with the electron mass, the virtual electron and photon each carry nearly the total angular momentum of the physical electron (1 /2 ), with the orbital angular momentum being nearly (-1 /2 ). Including the nonzero photon mass leads to the suppression of end-point contributions to form factors. Implications for proton structure and color transparency are discussed.
Finite-size scaling in the multiparticle production
International Nuclear Information System (INIS)
The finite-size scaling analysis of the scaled factorial moment data is proposed. This analysis allows to extract the scaling indices of the underlying higher-dimensional scale-invariant multiparticle distributions. Moreover, it exhibits the change of the effective scale involved in the dimensional projection with transverse momentum cuts applied to the data. (author) 15 refs., 2 figs
Financial openness, volatility, and the size of productive government
Erauskin, In?aki
2011-01-01
This paper analyzes the impact of financial openness on the size of the government in a stochastically growing small open economy when public spending is productive and volatility-reducing using a portfolio approach. The main result of the model is that economies that are more open are associated with a smaller productive public sector. The lower risk associated with more open economies due to risk diversification implies that the government is less inclined to increase the scale of its activ...
Optimization of bridging agents size distribution for drilling operations
Energy Technology Data Exchange (ETDEWEB)
Waldmann, Alex; Andrade, Alex Rodrigues de; Pires Junior, Idvard Jose; Martins, Andre Leibsohn [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil)]. E-mails: awaldmann@petrobras.com.br; andradear.gorceix@petrobras.com.br; idvard.gorceix@petrobras.com.br; aleibsohn@petrobras.com.br
2008-07-01
The conventional drilling technique is based on positive hydrostatic pressure against well walls to prevent inflows of native fluids into the well. Such inflows can cause security problems for the team well and to probe. As the differential pressure of the well to reservoir is always positive, the filtrate of the fluid tends to invade the reservoir rock. Minimize the invasion of drilling fluid is a relevant theme in the oil wells drilling operations. In the design of drilling fluid, a common practice in the industry is the addition of bridging agents in the composition of the fluid to form a cake of low permeability at well walls and hence restrict the invasive process. The choice of drilling fluid requires the optimization of the concentration, shape and size distribution of particles. The ability of the fluid to prevent the invasion is usually evaluated in laboratory tests through filtration in porous media consolidated. This paper presents a description of the methods available in the literature for optimization of the formulation of bridging agents to drill-in fluids, predicting the pore throat from data psychotherapy, and a sensitivity analysis of the main operational parameters. The analysis is based on experimental results of the impact of the size distribution and concentration of bridging agents in the filtration process of drill-in fluids through porous media submitted to various different differential of pressure. The final objective is to develop a software for use of PETROBRAS, which may relate different types and concentrations of bridging agents with the properties of the reservoir to minimize the invasion. (author)
Hagendorfer, Harald; Lorenz, Christiane; Kaegi, Ralf; Sinnet, Brian; Gehrig, Robert; Goetz, Natalie V.; Scheringer, Martin; Ludwig, Christian; Ulrich, Andrea
2010-01-01
This study describes methods developed for reliable quantification of size- and element-specific release of engineered nanoparticles (ENP) from consumer spray products. A modified glove box setup was designed to allow controlled spray experiments in a particle-minimized environment. Time dependence of the particle size distribution in a size range of 10-500 nm and ENP release rates were studied using a scanning mobility particle sizer (SMPS). In parallel, the aerosol was transferred to a size...
Evolution of particle size distribution in air in the rainfall process via the moment method
Gan Fu-Jun; Lin Jian-Zhong
2012-01-01
Population balance equation is converted to three moment equations to describe the dynamical behavior of particle size distribution in air in the rainfall. The scavenging coefficient is expressed as a polynomial function of the particle diameter, the raindrop diameter and the raindrop velocity. The evolutions of particle size distribution are simulated numerically and the effects of the raindrop size distribution on particle size distribution are studied. The results show that the raind...
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
Flow distribution in adjacent subchannels of unequal size
International Nuclear Information System (INIS)
This report describes an experimental and analytic investigation of the single phase flow distribution in subchannel geometries. It was intended as an investigation of fundamental transport mechanisms and therefore concentrated on simple geometries with two interconnected subchannels. The experimental phase consisted of detailed measuremnts of the fluid velocity in a geometry representing two communicating subchannels of different sizes. These measurements were made at three axial locations along the test section. The size of one of the subchannels was varied to give subchannel area ratios of 1.0, 0.68, 0.50 and 0.32. Two Reynolds numbers (108000 and 180000) were investigated. Axial pressure gradient data for all of these cases was also taken. The analytic phase concentrated on applying a three dimensional finite difference fluid flow code to subchannel geomtries. The code was applied to the cases studied in the experiment as well as other investigator's results. It used the two equation K-? turbulence model. The performance of this model was assessed. Unique features of the subchannel flows were identified and discussed. Conclusions regarding the transport mechanisms involved and the ability of a multidimensional code to predict the flow fields reliably were presented
Aerosol size distributions measured at the South Pole during ISCAT
Park, Jongsup; Sakurai, Hiromu; Vollmers, Karl; McMurry, Peter H.
Aerosol physical size distributions were measured at the South Pole during December 1998 and December 2000 as part of the ISCAT program. The size ranges covered by these measurements were 3 to 250 nm in 1998 and 3 nm-2 ?m in 2000. "Typical background aerosols" measured during both periods were similar. Total aerosol number concentrations ranged from 100 to 300 cm -3 with occasional spikes as high as 10,000 cm -3. We believe the spikes were due to local emissions. The number mean size of background aerosols ranged from 50 to 70 nm, and total aerosol surface area concentrations were 2.8±0.4 ?m 2 cm -3. Aerosols measured in December 2000 were cleanly separated into "low volume" and "high volume" periods. During the low-volume periods, volume concentrations were 0.07±0.01 ?m 3cm -3 with a volume mean diameter of 0.27±0.05 ?m, and these volume concentrations were mostly within a factor two of values that would be expected based on reconstructed mass from particulate chemical composition. Volume concentrations during the "high volume" periods exceed levels that can be explained from aerosol chemistry and calculated light-scattering coefficients exceed values that have been recorded historically. We have been unable to identify why this might have occurred. We observed one 4-h event on December 15, 2000 during which nanoparticles grew slowly from ˜3.0 to 3.6 nm.We believe these particles had recently been formed by nucleation. Because this occurred during a period of stagnation, it is possible that this event was associated with local emissions.
Normalized particle size distribution for remote sensing application
Delanoë, J. M. E.; Heymsfield, A. J.; Protat, A.; Bansemer, A.; Hogan, R. J.
2014-04-01
The ice particle size distribution (PSD) is fundamental to the quantitative description of a cloud. It is also crucial in the development of remote sensing retrieval techniques using radar and/or lidar measurements. The PSD allows one to link characteristics of individual particles (area, mass, and scattering properties) to characteristics of an ensemble of particles in a sampling volume (e.g., visible extinction (?), ice water content (IWC), and radar reflectivity (Z)). The aim of this study is to describe a normalization technique to represent the PSD. We update an earlier study by including recent in situ measurements covering a large variety of ice clouds spanning temperatures ranging between -80°C and 0°C. This new data set also includes direct measurements of IWC. We demonstrate that it is possible to scale the PSD in size space by the volume-weighted diameter Dm and in the concentration space by the intercept parameter N0? and obtain the intrinsic shape of the PSD. Therefore, by combining N0?, Dm, and a modified gamma function representing the normalized PSD shape, we are able to approximate key cloud variables (such as IWC) as well as cloud properties which can be remotely observed (such as Z) with an absolute mean relative error smaller than 20%. The underlying idea is to be able to retrieve the PSD using two independent measurements. We also propose parameterizations for ice cloud key parameters derived from the normalized PSD. We also investigate the effects of uncertainty present in the ice crystal mass-size relationships on the parameterizations and the normalized PSD approach.
Progresses in the production of large-size THGEM boards
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
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.
Hybrid Organization of Production and Distribution
Directory of Open Access Journals (Sweden)
Claude Menard
2006-03-01
Full Text Available This paper emphasizes the central role of arrangements called “hybrids” in the organization of production and distribution in market economies. Several forms are taken into account, such as subcontracting, supply-chain systems, distribution networks, franchising, partnerships, alliances, or cooperatives. It is argued that under the apparent heterogeneity of these forms are shared characteristics qualifying them as specific “institutional structures of production”. The paper stresses that beyond their relevance for economists wishing to understand the coexistence of alternative modes of governance in market economies, hybrid arrangements provide unique opportunities for theoretical investigation on the nature of inter-firm coordination.
The Distribution of Program Sizes and Its Implications: An Eclipse Case Study
Zhang, Hongyu; Marchesi, Michele
2009-01-01
A large software system is often composed of many inter-related programs of different sizes. Using the public Eclipse dataset, we replicate our previous study on the distribution of program sizes. Our results confirm that the program sizes follow the lognormal distribution. We also investigate the implications of the program size distribution on size estimation and quality predication. We find that the nature of size distribution can be used to estimate the size of a large Java system. We also find that a small percentage of largest programs account for a large percentage of defects, and the number of defects across programs follows the Weibull distribution when the programs are ranked by their sizes. Our results show that the distribution of program sizes is an important property for understanding large and complex software systems.
Influence of particle size distribution on liquid phase sintering of W-Ni-Fe alloy
International Nuclear Information System (INIS)
This paper reports on the influence of initial particle size distribution on the coarsening of tungsten particles during liquid phase sintering of W-14Ni-6Fe alloy. Powder blends with relatively narrow and wide initial tungsten particle size distributions but with identical mean particle size were liquid phase sintered at 1490 degrees C for times up to 8 hours. The 2-D section size distributions of the tungsten particles were measured on an image analysis system and the 3-D means particle size and size distributions were calculated using stereological techniques. It was found that the wider initial particle size distribution tungsten particles coarsened more rapidly than those of the initially narrow distribution. The well known linear relationship between the cube of average radius of particles, F3, and time was observed for most of the coarsening process, although the early stage coarsening rate constant changed with time, as expected with concomitant early changes in the tungsten particle size distribution
Air activity concentrations and particle size distributions of the Chernobyl aerosol
International Nuclear Information System (INIS)
The concentrations of radioactive isotopes attached to aerosol particles resulting from the accident in the nuclear power plant at Chernobyl were determined in the ambient air of Goettingen (FRG) during May 1986 by means of gamma spectroscopy. Measurements of the activity concentration of the long lived fission product 137Cs were continued up to December 1986. During May some measurements were performed with charcoal filters to determine the gaseous fraction of 131I. Size distributions of the radioactive aerosol particles were determined by a low pressure Berner impactor and a high volume Sierra impactor. Most of the measurements yield unimodal distributions with activity median aerodynamic diameters (AMAD) in the range 500-1000 nm. Some distributions were bimodal with an additional AMAD in the size range greater than 5000 nm. The AMADs of the 131I distributions were shifted to slightly smaller values than those of the other isotopes. In some air samples 'hot particles', containing the isotopes 95Zr, 95Nb, 141Ce and 144Ce were determined with diameters in the size range 2000-5000 nm and activities of about 0.3-3.1 Bq. (author)
Particle size distribution of molybdenum aerosols during 99Mo processing
International Nuclear Information System (INIS)
Dose estimation from internal exposure of airborne particulate is done from the measurement of the particle size in terms of 'Activity Median Aerodynamic Diameter' (AMAD). Particle size spectrum during the molybdenum-99 process was continuously taken by Anderson 1 ACFM non-viable ambient particle sizing sampler from the laboratory. The respective ALIs were obtained for different particle size. (author)
ESTIMATING SOIL PARTICLE-SIZE DISTRIBUTION FOR SICILIAN SOILS
Directory of Open Access Journals (Sweden)
Giuseppe Giordano
2009-09-01
Full Text Available The soil particle-size distribution (PSD is commonly used for soil classification and for estimating soil behavior. An accurate mathematical representation of the PSD is required to estimate soil hydraulic properties and to compare texture measurements from different classification systems. The objective of this study was to evaluate the ability of the Haverkamp and Parlange (HP and Fredlund et al. (F PSD models to fit 243 measured PSDs from a wide range of 38 005_Bagarello(547_33 18-11-2009 11:55 Pagina 38 soil textures in Sicily and to test the effect of the number of measured particle diameters on the fitting of the theoretical PSD. For each soil textural class, the best fitting performance, established using three statistical indices (MXE, ME, RMSE, was obtained for the F model with three fitting parameters. In particular, this model performed better in the fine-textured soils than the coarse-textured ones but a good performance (i.e., RMSE < 0.03 was detected for the majority of the investigated soil textural classes, i.e. clay, silty-clay, silty-clay-loam, silt-loam, clay-loam, loamy-sand, and loam classes. Decreasing the number of measured data pairs from 14 to eight determined a worse fitting of the theoretical distribution to the measured one. It was concluded that the F model with three fitting parameters has a wide applicability for Sicilian soils and that the comparison of different PSD investigations can be affected by the number of measured data pairs.
Activity size distribution of the short-lived and long-lived radionuclides in outdoor air
International Nuclear Information System (INIS)
There are a number of radioactive isotopes of different elements in the atmosphere near ground level. Most of them are decay products from the 238U- and 232Th-chains with the highest activity concentration of the short-lived 222Rn-(radon)(1-100 Bq/m3) and 220Rn-(thoron) (0.01-1 Bq/m3) decay products. The long-lived radon decay products (210Pb/210Po) have concentrations between 1-5x10-4 Bq/m3. In contrast to these nuclides the amount of the activity concentration of 7Be (1-7x10-3 Bq/m3)is produced by interaction of the cosmic rays with atmospheric gases. Most of these airborne radionuclides are adsorbed on the surface of aerosol particles and form radioactive aerosol. Therefore the behaviour of the airborne radionuclides is determined by the behaviour of the aerosol particles in the atmosphere. Besides the generation rate the activity concentration of the radionuclides in air is influenced by their transport in the atmosphere and by the radioactive decay. In addition, for the longer-lived radionuclides (half-live >1 d) the removal processes (dry deposition, wet deposition) from the atmosphere have an influence on the activity concentration and the coagulation process will significantly change the activity size distribution of the original radioactive aerosol. The activity size distribution of the radioactive aerosol is the dominant parameter for the behaviour of the radionuclides in the environment. The removal processes from the atmosphere, the deposition rate on ground and vegetation and the deposition probability in the lung during inhalation depend on the particle size. In this paper the measurement results of the activity size distribution of the short-lived (218Po, 214Po) and the long-lived (210Pb, 210Po) radon and thoron (212Pb, 212Po) decay products and 7Be are summarised, obtained from measurements over a longer period in outdoor air during the last years. Especially, the aim was to find out the differences between the size distributions of these radionuclides. Therefore it was important to use measurement techniques, which made it possible, to register simultaneously almost all of these radionuclides during one measurement run over a longer time period
Regional variability of raindrop size distribution over Indonesia
Marzuki, M.; Hashiguchi, H.; Yamamoto, M. K.; Mori, S.; Yamanaka, M. D.
2013-11-01
Regional variability of raindrop size distribution (DSD) along the Equator was investigated through a network of Parsivel disdrometers in Indonesia. The disdrometers were installed at Kototabang (KT; 100.32° E, 0.20° S), Pontianak (PT; 109.37° E, 0.00° S), Manado (MN; 124.92° E, 1.55° N) and Biak (BK; 136.10° E, 1.18° S). It was found that the DSD at PT has more large drops than at the other three sites. The DSDs at the four sites are influenced by both oceanic and continental systems, and majority of the data matched the maritime-like DSD that was reported in a previous study. Continental-like DSDs were somewhat dominant at PT and KT. Regional variability of DSD is closely related to the variability of topography, mesoscale convective system propagation and horizontal scale of landmass. Different DSDs at different sites led to different Z-R relationships in which the radar reflectivity at PT was much larger than at other sites, at the same rainfall rate.
Production and Distribution of NASA MODIS Remote Sensing Products
Wolfe, Robert
2007-01-01
The two Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on-board NASA's Earth Observing System (EOS) Terra and Aqua satellites make key measurements for understanding the Earth's terrestrial ecosystems. Global time-series of terrestrial geophysical parameters have been produced from MODIS/Terra for over 7 years and for MODIS/Aqua for more than 4 1/2 years. These well calibrated instruments, a team of scientists and a large data production, archive and distribution systems have allowed for the development of a new suite of high quality product variables at spatial resolutions as fine as 250m in support of global change research and natural resource applications. This talk describes the MODIS Science team's products, with a focus on the terrestrial (land) products, the data processing approach and the process for monitoring and improving the product quality. The original MODIS science team was formed in 1989. The team's primary role is the development and implementation of the geophysical algorithms. In addition, the team provided feedback on the design and pre-launch testing of the instrument and helped guide the development of the data processing system. The key challenges the science team dealt with before launch were the development of algorithms for a new instrument and provide guidance of the large and complex multi-discipline processing system. Land, Ocean and Atmosphere discipline teams drove the processing system requirements, particularly in the area of the processing loads and volumes needed to daily produce geophysical maps of the Earth at resolutions as fine as 250 m. The processing system had to handle a large number of data products, large data volumes and processing loads, and complex processing requirements. Prior to MODIS, daily global maps from heritage instruments, such as Advanced Very High Resolution Radiometer (AVHRR), were not produced at resolutions finer than 5 km. The processing solution evolved into a combination of processing the lower level (Level 1) products and the higher level discipline specific Land and Atmosphere products in the MODIS Science Investigator Lead Processing System (SIPS), the MODIS Adaptive Processing System (MODAPS), and archive and distribution of the Land products to the user community by two of NASA s EOS Distributed Active Archive Centers (DAACs). Recently, a part of MODAPS, the Level 1 and Atmosphere Archive and Distribution System (LAADS), took over the role of archiving and distributing the Level 1 and Atmosphere products to the user community.
Impact of grain size distributions on the dust enrichment in high-redshift quasars
Kuo, Tzu-Ming; Hirashita, Hiroyuki
2012-07-01
In high-redshift (z > 5) quasars, a large amount of dust (˜108 M?) has been observed. In order to explain the large dust content, we focus on a possibility that grain growth by the accretion of heavy elements is the dominant dust source. We adopt a chemical evolution model applicable to nearby galaxies, but utilize parameters adequate to high-z quasars. It is assumed that metals and dust are predominantly ejected by Type II supernovae (SNe). We have found that grain growth strongly depends on the grain size distribution. If we simply use the size distribution of grains ejected from SNe, grain growth is inefficient because of the lack of small grains (i.e. small surface-to-volume ratio of the dust grains). However, if we take small grain production by interstellar shattering into consideration, grain growth is efficient enough to account for the rich dust abundance in high-z quasars. Our results not only confirm that grain growth is necessary to explain the large amount of dust in high-z quasars, but also demonstrate that grain size distributions have a critical impact on grain growth.
Radioisotope production and distribution in Australia
International Nuclear Information System (INIS)
The high quality of radioactive products and services, provided by the Commercial Products Unit of Australian Atomic Energy Agency for industrial and medical applications are discussed. The production program has changed from research driven to being market driven. The Commission in fact not only manufactures radioisotopes and radiopharmaceuticals but also acts as a Centralized Dispensing Service for over sea products. The advantages associated with centralize distribution are discussed. The delivery arrangements and the existed problems are explained. With the unique experience, assistance and advice are provided for many years now to Nuclear Energy Unit at PUSPATI via staff training programs and many visits by the Commission staff to assist in the commissioning of the facilities in which enables PUSPATI to provide Malaysia and surrounding neighbour countries (on a smaller scale) with the similar type of service that the Commission does within Australia. (A.J.)
The effects of mergers and acquisitions on the firm size distribution
Cefis, E.; Marsili, O.; Schenk, H.
2009-01-01
This paper provides new empirical evidence on the effects of mergers and acquisitions (M&As) on the shape of the firm size distribution, by using data of the population of manufacturing firms in the Netherlands. Our analysis shows that M&As do not affect the size distribution when we consider the entire population of firms. When we focus on the firms involved in an M&A event, we observe a shift of the firm size distribution towards larger sizes. Firm size distribution becomes more concentrate...
Size distributions of different orders of kernels within the oat spikelet
Oat kernel size uniformity is of interest to the oat milling industry because of the importance of kernel size in the dehulling process. Previous studies have indicated that oat kernel size distributions fit a bimodal better than a normal distribution. Here we have demonstrated by spikelet dissectio...
Zook, Justin M; Rastogi, Vinayak; Maccuspie, Robert I; Keene, Athena M; Fagan, Jeffrey
2011-10-25
Agglomeration of nanoparticles during measurements in relevant biological and environmental media is a frequent problem in nanomaterial property characterization. The primary problem is typically that any changes to the size distribution can dramatically affect the potential nanotoxicity or other size-determined properties, such as the absorbance signal in a biosensor measurement. Herein we demonstrate analytical ultracentrifugation (AUC) as a powerful method for measuring two critical characteristics of nanoparticle (NP) agglomerates in situ in biological media: the NP agglomerate size distribution, and the localized surface plasmon resonance (LSPR) absorbance spectrum of precise sizes of gold NP agglomerates. To characterize the size distribution, we present a theoretical framework for calculating the hydrodynamic diameter distribution of NP agglomerates from their sedimentation coefficient distribution. We measure sedimentation rates for monomers, dimers, and trimers, as well as for larger agglomerates with up to 600 NPs. The AUC size distributions were found generally to be broader than the size distributions estimated from dynamic light scattering and diffusion-limited colloidal aggregation theory, an alternative bulk measurement method that relies on several assumptions. In addition, the measured sedimentation coefficients can be used in nanotoxicity studies to predict how quickly the agglomerates sediment out of solution under normal gravitational forces, such as in the environment. We also calculate the absorbance spectra for monomer, dimer, trimer, and larger gold NP agglomerates up to 600 NPs, to enable a better understanding of LSPR biosensors. Finally, we validate a new method that uses these spectra to deconvolute the net absorbance spectrum of an unknown bulk sample and approximate the proportions of monomers, dimers, and trimers in a polydisperse sample of small agglomerates, so that every sample does not need to be measured by AUC. These results demonstrate the potential utility of AUC to characterize NP agglomeration and sedimentation for nanotoxicity and biosensor studies, as well as to characterize NP agglomerate size and absorbance to improve LSPR and surface-enhanced Raman spectroscopy based biosensors. PMID:21888410
Clark, Catherine D; De Bruyn, Warren J; Jones, Joshua G
2009-06-01
Hydrogen peroxide (H(2)O(2)) photochemical production was measured in bulk and size-fractionated surf zone and source waters (Orange County, California, USA). Post-irradiation (60 min; 300 W ozone-free xenon lamp), maximum H(2)O(2) concentrations were approximately 10000 nM (source) and approximately 1500 nM (surf zone). Average initial hydrogen peroxide production rates (HPPR) were higher in bulk source waters (11+/-7.0 nM s(-1)) than the surf zone (2.5+/-1 nM s(-1)). A linear relationship was observed between non-purgeable dissolved organic carbon and absorbance coefficient (m(-1) (300 nm)). HPPR increased with increasing absorbance coefficient for bulk and size-fractionated source waters, consistent with photochemical production from CDOM. However, HPPR varied significantly (5x) for surf zone samples with the same absorbance coefficients, even though optical properties suggested CDOM from salt marsh source waters dominates the surf zone. To compare samples with varying CDOM levels, apparent quantum yields (Phi) for H(2)O(2) photochemical production were calculated. Source waters showed no significant difference in Phi between bulk, large (>1000 Da (>1 kDa)) and small (production efficiency is homogeneously distributed across CDOM size. However, surf zone waters had significantly higher Phi than source (bulk 0.086+/-0.04 vs. 0.034+/-0.013; 1 kDa 0.151+/-0.090 vs. 0.016+/-0.009), suggesting additional production from non-CDOM sources. H(2)O(2) photochemical production was significant for intertidal beach sand and senescent kelp (sunlight; approximately 42 nM h(-1) vs. approximately 5 nM h(-1)), on the order of CDOM production rates previously measured in coastal and oceanic waters. This is the first study of H(2)O(2) photochemical production in size-fractionated coastal waters showing significant production from non-CDOM sources in the surf zone. PMID:19269002
Size distribution and islet concentration of condensed phase of excitons in quantum well
International Nuclear Information System (INIS)
The theory of condensed phase formation ranges at high concentration of excitons in quantum well is presented. The condensed phase may be exciton or electron-hole liquid. In the range of the condensed phase and exciton gas existence islets of the condensed phase are considered to be disk-shaped. Joint solution to kinetic equation, determining the islets size, and diffusion equation for the excitons beyond the islets during steady-state excitation has been found. The function of the islets distribution over the radius and the islets density, depending on excitons production rate and the system parameters, has been obtained
Cost and performance of woody biomass size reduction for energy production
Energy Technology Data Exchange (ETDEWEB)
Naimi, L.J.; Sokhansanj, S.; Mani, S.; Hoque, M.; Bi, T. [British Columbia Univ., Vancouver, BC (Canada). Dept. of Chemical and Biological Engineering; Womac, A.R. [Tennessee Univ., Knoxville, T (United States). Dept. of Biosystems Engineering and Soil Science; Narayan, S. [First American Scientific Corp., Delta, BC (Canada)
2006-07-01
One of the major pre-processing operations in using biomass as a source of energy or using it for producing pulp for paper industries involves size reduction or grinding. Grinders are the dominant machines in an energy wood harvesting system and possess the highest productivity and cost. Depending on the material and grinding mechanisms (shear, impact, attrition), grinders use a wide range of energy. The design and choice of the grinder is important for reducing the energy input in preparing biomass. This paper reviewed the performance of various commercial wood grinders with respect to ground quality and their cost estimation. The paper presented a review of commercial equipment used for size reduction of woody biomass. The review also included the capital cost, operating costs and performance of equipment. The performance of equipment was evaluated based on its power consumption and the quality of chip production, which included average particle size and particle size distribution. The paper discussed size reduction machinery classification; quality specification of wood particles after size reduction for energy conversion; and cost estimation of size reduction machines. It was concluded that hammer hogs are relatively less expensive than chippers. Future research should be directed to analyzing the performance of hammer mills for woody biomass and its energy requirement during grinding. 14 refs., 5 tabs., 7 figs.
Scaling of angular distributions in multiparticle production
International Nuclear Information System (INIS)
We find that a simple scaling relation, -/sub x/ = deltaeta/R, is consistent with data on multiparticle production from 30 -- 400 GeV, where eta = -ln tan(theta/2) is the pseudorapidity of produced fast particles, /sub x/ is the average pseudorapidity of particles in excess of the hydrogen-target pseudorapidity distribution, and R = //sub H/ is the ratio of average multiplicity on a nuclear target to the average proton-proton multiplicity at equal energy. We find that the distance between the centroids of the hydrogen-target eta distribution and the excess-particle distribution deltaeta = /sub H/-/sub x/ = 1.74 +- 0.06 is independent of energy, target mass, and possibly projectile. This result implies that R increases with energy, and asymptotically is approximately proportional to ?, the number of collisions of the projectile
Vertical distribution of grain size for wind blown sand
Farrell, E. J.; Sherman, D. J.; Ellis, J. T.; Li, B.
2012-12-01
Grain size-sorting characteristics from twenty-five vertical, mass-flux profiles for a mixed grain population are presented from a field study conducted in Jericoacoara, Brazil. The vertical mass flux profile is best described using an exponential decay function. An analysis of the grain-size statistics shows that a reverse in grain-size trends occurs at an inflection zone located 0.05-0.15 m above the bed. Below this inflection, mean grain-size decreases steeply with elevation in the near bed region dominated by reptation and saltation modes of transport. Above the inflection there is a coarsening of grain size with elevation. Sorting improves with elevation above the surface. There is not a strong relationship between skewness and kurtosis with elevation. The grain-size inflection above the surface is a characteristic of saltation in some natural environments, with important implications for numerical modeling of grain trajectories.
Quantitative analysis of bimodal grain size distributions in WC-Co hard materials
International Nuclear Information System (INIS)
A special method was implemented to quantify the bimodal character of the 3D grain size distribution in WC-Co sintered materials. The method deals with SEM images of materials sections. Grains are separated on binary images by an automatic algorithm. The intercept length distributions are measured. Data are then fitted with a model population of trigonal prisms with constant shape. Two kinds of grain size distributions are considered for the model: a unimodal (lognormal) distribution or a bimodal (bi-lognormal) size distribution. The method is applied to different WC-Co grades, and the bimodal character of the distribution is discussed. (author)
Minimum sample size determination for generalized extreme value distribution
Cai, Yuzhi; Hames, Dominic
2010-01-01
Abstract Sample size determination is an important issue in statistical analysis. Obviously, the larger the sample size is, the better the statistical results we have. However, in many areas such as coastal engineering and environmental sciences, it can be very expensive or even impossible to collect large samples. In this paper, we propose a general method for determining the minimum sample size required by estimating the return levels from a generalized...
Energy Technology Data Exchange (ETDEWEB)
Igathinathane, C [University of British Columbia, Vancouver; Pordesimo, L.O. [ADM Alliance Nutrition
2009-08-01
Dust management strategies in industrial environment, especially of airborne dust, require quantification and measurement of size and size distribution of the particles. Advanced specialized instruments that measure airborne particle size and size distribution apply indirect methods that involve light scattering, acoustic spectroscopy, and laser diffraction. In this research, we propose a simple and direct method of airborne dust particle dimensional measurement and size distribution analysis using machine vision. The method involves development of a user-coded ImageJ plugin that measures particle length and width and analyzes size distribution of particles based on particle length from high-resolution scan images. Test materials were airborne dust from soft pine wood sawdust pellets and ground pine tree bark pellets. Subsamples prepared by dividing the actual dust using 230 mesh (63 m) sieve were analyzed as well. A flatbed document scanner acquired the digital images of the dust particles. Proper sampling, layout of dust particles in singulated arrangement, good contrast smooth background, high resolution images, and accurate algorithm are essential for reliable analysis. A halo effect around grey-scale images ensured correct threshold limits. The measurement algorithm used Feret s diameter for particle length and pixel-march technique for particle width. Particle size distribution was analyzed in a sieveless manner after grouping particles according to their distinct lengths, and several significant dimensions and parameters of particle size distribution were evaluated. Results of the measurement and analysis were presented in textual and graphical formats. The developed plugin was evaluated to have a dimension measurement accuracy in excess of 98.9% and a computer speed of analysis of <8 s/image. Arithmetic mean length of actual wood and bark pellets airborne dust particles were 0.1138 0.0123 and 0.1181 0.0149 mm, respectively. The airborne dust particles of wood and bark pellets can be described as non uniform, finer particles dominated, very finely skewed with positive skewness, leptokurtic, and very well sorted category. Experimental mechanical sieving and machine vision methods produced comparable particle size distribution. The limitations and merits of using the machine vision technique for the measurement of size and size distribution of fine particles such as airborne dust were discussed.
Note on a Strongly Unimodal Bibliometric Size Frequency Distribution.
Sichel, H. S.
1992-01-01
This study demonstrates that the number of references at the end of scientific research papers forms a strongly unimodal frequency distribution and that the generalized Gaussian-Poisson distribution fits such unimodal data extremely well. (three references) (Author/MES)
Fractal bird nest distribution produces scale-free colony sizes
Jovani, Roger; Tella, Jose? Luis
2007-01-01
The spatial distribution of organisms often differs across scales. For instance, colonial bird populations could be described, from large to small scale, as scattered clumps of otherwise regularly distributed breeding pairs. We analysed the distribution of nests of a large colonial population of white storks (Ciconia ciconia) and found a fractal pattern in each of the 4 study years. Moreover, we found that the often- observed, long-tailed frequency distribution of ...
Weber, Benjamin; Lee, Sau L.; Lionberger, Robert; Li, Bing V.; Tsong, Yi; Hochhaus, Guenther
2013-01-01
Demonstration of equivalence in aerodynamic particle size distribution (APSD) is one key component for establishing bioequivalence of orally inhaled drug products. We previously proposed a modified version of the Chi-square ratio statistic (mCSRS) for APSD equivalence testing and demonstrated that the median of the distribution of the mCSRS (MmCSRS) is a robust metric when test (T) and reference (R) cascade impactor (CI) profiles are identical. Here, we systematically evaluate the behavior of...
Particle size distributions from laboratory-scale biomass fires using fast response instruments
Hosseini, S.; Li, Q.; Cocker, D.; Weise, D.; Miller, A.; Shrivastava, M.; Miller, J. W.; Mahalingam, S.; Princevac, M.; Jung, H.
2010-01-01
Particle size distribution from biomass combustion is an important parameter as it affects air quality, climate modelling and health effects. To date particle size distributions reported from prior studies vary not only due to difference in fuels but also difference in experimental conditions. This study aims to report characteristics of particle size distribution in a well controlled repeatable lab scale biomass fires for southwestern US fuels. The combustion facility at the USDA Forest Serv...
Drop Size Distribution - Based Separation of Stratiform and Convective Rain
Thurai, Merhala; Gatlin, Patrick; Williams, Christopher
2014-01-01
For applications in hydrology and meteorology, it is often desirable to separate regions of stratiform and convective rain from meteorological radar observations, both from ground-based polarimetric radars and from space-based dual frequency radars. In a previous study by Bringi et al. (2009), dual frequency profiler and dual polarization radar (C-POL) observations in Darwin, Australia, had shown that stratiform and convective rain could be separated in the log10(Nw) versus Do domain, where Do is the mean volume diameter and Nw is the scaling parameter which is proportional to the ratio of water content to the mass weighted mean diameter. Note, Nw and Do are two of the main drop size distribution (DSD) parameters. In a later study, Thurai et al (2010) confirmed that both the dual-frequency profiler based stratiform-convective rain separation and the C-POL radar based separation were consistent with each other. In this paper, we test this separation method using DSD measurements from a ground based 2D video disdrometer (2DVD), along with simultaneous observations from a collocated, vertically-pointing, X-band profiling radar (XPR). The measurements were made in Huntsville, Alabama. One-minute DSDs from 2DVD are used as input to an appropriate gamma fitting procedure to determine Nw and Do. The fitted parameters - after averaging over 3-minutes - are plotted against each other and compared with a predefined separation line. An index is used to determine how far the points lie from the separation line (as described in Thurai et al. 2010). Negative index values indicate stratiform rain and positive index indicate convective rain, and, moreover, points which lie somewhat close to the separation line are considered 'mixed' or 'transition' type precipitation. The XPR observations are used to evaluate/test the 2DVD data-based classification. A 'bright-band' detection algorithm was used to classify each vertical reflectivity profile as either stratiform or convective, 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.
Particle size distributions of currently used pesticides in a rural atmosphere of France
Coscollà, Clara; Yahyaoui, Abderrazak; Colin, Patrice; Robin, Corine; Martinon, Laurent; Val, Stéphanie; Baeza-Squiban, Armelle; Mellouki, Abdelwahid; Yusà, Vicent
2013-12-01
This work presents first data on the particle size distributions of current-used pesticides in the atmosphere. Ambient air samples were collected using a cascade impactor distributed into four size fractions in a rural site of Centre Region (France). Most pesticides were accumulated in the fine (0.1-1 ?m) particle size fraction such as cyprodinil, pendimethalin, fenpropidin, fenpropimorph and spiroxamine. Other pesticides such as acetochlor and metolachlor presented a bimodal distribution with maximum concentrations in the ultrafine (0.03-0.1 ?m)-coarse (1-10 ?m) and in the ultrafine-fine size ranges, respectively. No pesticides were detected in the size fraction >10 ?m.
Evolution of 2D Potts Model Grain Microstructures from an Initial Hillert Size Distribution
Energy Technology Data Exchange (ETDEWEB)
Battaile, C.C.; Holm E.A.
1998-10-19
Grain growth experiments and simulations exhibit self-similar grain size distributions quite different from that derived via a mean field approach by Hillert [ 1]. To test whether this discrepancy is due to insufficient anneal times, two different two-dimensional grain structures with realistic topologies and Hillert grain size distributions are generated and subjected to grain growth via the Monte Carlo Potts Model (MCPM). In both cases, the observed self-similar grain size distributions deviate from the initial Hillert form and conform instead to that observed in MCPM grain growth simulations that start from a random microstructure. This suggests that the Hillert grain size distribution is not an attractor.
Cai, Li; Hayes, Nancy L.; Takahashi, Takao; Caviness, Verne S Jr; Nowakowski, Richard S.
2002-01-01
Mechanisms that regulate neuron production in the developing mouse neocortex were examined by using a retroviral lineage marking method to determine the sizes of the lineages remaining in the proliferating population of the ventricular zone during the period of neuron production. The distribution of clade sizes obtained experimentally in four different injection-survival paradigms (E11-E13, E11-E14, E11-E15, and E12-E15) from a total of over 500 labeled lineages was compared with that obtained from three models in which the average behavior of the proliferating population [i.e., the proportion of cells remaining in the proliferative population (P) vs. that exiting the proliferative population (Q)] was quantitatively related to lineage size distribution. In model 1, different proportions of asymmetric, symmetric terminal, and symmetric nonterminal cell divisions coexisted during the entire developmental period. In model 2, the developmental period was divided into two epochs: During the first, asymmetric and symmetric nonterminal cell divisions occurred, but, during the second, asymmetric and symmetric terminal cell divisions occurred. In model 3, the shifts in P and Q are accounted for by changes in the proportions of the two types of symmetric cell divisions without the inclusion of any asymmetric cell divisions. The results obtained from the retroviral experiments were well accounted for by model 1 but not by model 2 or 3. These findings demonstrate that: 1) asymmetric and both types of symmetric cell divisions coexist during the entire period of neurogenesis in the mouse, 2) neuron production is regulated in the proliferative population by the independent decisions of the two daughter cells to reenter S phase, and 3) neurons are produced by both asymmetric and symmetric terminal cell divisions. In addition, the findings mean that cell death and/or tangential movements of cells in the proliferative population occur at only a low rate and that there are no proliferating lineages "reserved" to make particular laminae or cell types. Copyright 2002 Wiley-Liss, Inc.
International Nuclear Information System (INIS)
The oxidation reaction of aluminum nanoparticles with oxygen gas and the thermal behavior of a metastable intermolecular composite (MIC) composed of the aluminum nanoparticles and molybdenum trioxide are studied with differential scanning calorimetry (DSC) as a function of the size and size distribution of the aluminum particles. Both broad and narrow size distributions have been investigated with aluminum particle sizes ranging from 30 to 160 nm; comparisons are also made to the behavior of micrometer-size particles. Several parameters have been used to characterize the reactivity of aluminum nanoparticles, including the fraction of aluminum that reacts prior to aluminum melting, heat of reaction, onset and peak temperatures, and maximum reaction rates. The results indicate that the reactivity of aluminum nanoparticles is significantly higher than that of the micrometer-size samples, but depending on the measure of reactivity, it may also depend strongly on the size distribution. The isoconversional method was used to calculate the apparent activation energy, and the values obtained for both the Al/O2 and Al/MoO3 reaction are in the range of 200-300 kJ/mol
Source size scaling of fragment production in projectile breakup
Beaulieu, L; Fox, D; Das-Gupta, S; Pan, J; Ball, G C; Djerroud, B; Doré, D; Galindo-Uribarri, A; Guinet, D; Hagberg, E; Horn, D; Laforest, R; Larochelle, Y; Lautesse, P; Samri, M; Roy, R; Saint-Pierre, C
1996-01-01
Fragment production has been studied as a function of the source mass and excitation energy in peripheral collisions of $^{35}$Cl+$^{197}$Au at 43 MeV/nucleon and $^{70}$Ge+$^{nat}$Ti at 35 MeV/nucleon. The results are compared to the Au+Au data at 600 MeV/nucleon obtained by the ALADIN collaboration. A mass scaling, by $A_{source} \\sim$ 35 to 190, strongly correlated to excitation energy per nucleon, is presented, suggesting a thermal fragment production mechanism. Comparisons to a standard sequential decay model and the lattice-gas model are made. Fragment emission from a hot, rotating source is unable to reproduce the experimental source size scaling.
Borchard, C.; Engel, A.
2014-11-01
Extracellular release (ER) by phytoplankton is the major source of fresh dissolved organic carbon (DOC) in marine ecosystems and accompanies primary production during all growth phases. Little is known, so far, on size and composition of released molecules, and to which extent ER occurs passively, by leakage, or actively, by exudation. Here, we report on ER by the widespread and bloom-forming coccolithophore Emiliania huxleyi grown under steady state conditions in phosphorus controlled chemostats (N : P = 29, growth rate of ? = 0.2 d-1). 14C incubations were accomplished to determine primary production (PP), comprised by particulate (PO14C) and dissolved organic carbon (DO14C), and the concentration and composition of particulate combined carbohydrates (pCCHO), and of high molecular weight (>1 kDa, HMW) dissolved combined carbohydrates (dCCHO) as major components of ER. Information on size distribution of ER products was obtained by investigating distinct size classes (10 kDa was significantly different with higher Mol% of arabinose. Mol% of acidic sugars increased and Mol% glucose decreased with increasing size of HMW-dCCHO. We conclude that larger polysaccharides follow different production and release pathways than smaller molecules, potentially serving distinct ecological and biogeochemical functions.
Lot-sizing problem with several production centers
Scientific Electronic Library Online (English)
Franklina Maria Bragion de, Toledo; André Luís, Shiguemoto.
2005-12-01
Full Text Available Neste trabalho, estudamos um caso particular do problema de dimensionamento de lotes, envolvendo o planejamento da produção de um único item em vários centros produtivos que não apresentam restrições de capacidade. A demanda pode ser atendida com ou sem atraso. Este problema surge da decomposição de [...] problemas práticos, como o sistema de requerimento de materiais (MRP), e também de problemas de dimensionamento de lotes com múltiplos itens e capacidade de produção limitada. Primeiramente, apresentamos uma implementação eficiente de um algoritmo de programação dinâmica progressiva proposto para a solução do problema com um único centro produtivo. Embora, essa implementação não reduza a complexidade do algoritmo, experimentos computacionais mostraram que ela é significativamente mais rápida. Em seguida, estudamos o problema com vários centros, para o qual são implementados dois algoritmos, o primeiro é uma extensão do algoritmo original e o segundo incorpora as idéias que tornam essa implementação mais eficiente. O desempenho computacional dos algoritmos é analisado e propostas para futuras pesquisas são apresentadas. Abstract in english In this paper, a case study is carried out concerning the lot-sizing problem involving a single item production planning in several production centers that do not present capacity constraints. Demand can be met with backlogging or not. This problem results from simplifying practical problems, such a [...] s the material requirement planning (MRP) system and also lot-sizing problems with multiple items and limited production capacity. First we propose an efficient implementation of a forward dynamic programming algorithm for problems with one single production center. Although this does not reduce its complexity, it has shown to be rather effective, according to computational tests. Next, we studied the problem with a production environment composed of several production centers. For this problem two algorithms are implemented, the first one is an extension of the dynamic programming algorithm for one production center and the second one is an efficient implementation of the first algorithm. Their efficiency are shown by computational testing of the algorithms and proposals for future research are presented.
Errors in the measurement of bubble size distribution in foam
International Nuclear Information System (INIS)
The determination of foam bubble size by planimetric measurement of the area of the contact face a the glass wall of a column containing essentially homogeneous new foam yielded excellent agreement with the bubble size as known a priori. Furthermore, the said determination proved to be more reliable than measurement based on either the longest chord or the commonly employed longest median of the contact face. However, for highly heterogeneous new foam, all three measures of foam bubble size underestimated the true mean. Apparently, small bubbles wedge large bubbles away from the wall. The effects are presented quantitatively, along with correlations for their approximate prediction
Energy Technology Data Exchange (ETDEWEB)
Yoo, Dong Suk; Lee, Kwang Rae [Kangwon National University, Chuncheon (Korea, Republic of); Lee, Sang Deuk; Ahn, Byoung Sung [Korea Advanced Institute of Science and Technology, Taejon (Korea, Republic of)
1997-06-30
For the quantitative analysis of crystallization of calcium carbonate formed by carbonation of lime milk, PSD(particle size distribution) of the calcium carbonate, which is the carbonation product of lime milk, was numerically simulated by the method of discretization of population balance and compared with the experimental data of semi-batch precipitative crystallizer. The simulated PSD was well correlated with the experimental data. And the simulated results of PSD for size-dependent agglomeration were well-matched to the experimental data than for the size-independent agglomeration. As the agglomeration kernel increases, the particle size distribution (PSD) becomes broader and the average particle size(APS) is getting larger. In the range of agglomeration kernel from 0 {mu}l/hr to 0.2 {mu}l/hr, the PSD and APS are strongly affected by the agglomeration kernel. Above 0.2 {mu}l/hr, however, the effect is not so strong on PSD and APS. In contrast to the effect of agglomeration kernel, the PSD becomes narrower and APS is getting smaller with increasing rupture kernel. In the range of rupture kernel from 0 {mu}m{sup -1.5} {center_dot}hr{sup -1} to 100 {mu}m{sup -1.5}{center_dot}hr{sup -1}, the rupture kernel appreciably affects the PSD and APS. An increase in rupture kernel above 100 {mu}m{sup -1.5} centre dothr{sup -1}, however, has only a minor effect on PSD and APS. Moreover, it is shown that agglomeration kernel has greater effect on PSD than rupture kernel. (author). 24 refs., 1 tab., 10 figs.
Probabilistic Optimal Allocation and Sizing of Distributed Generation
Hosseinzadeh, M.; Afrakhte, H.
2014-01-01
The optimal allocation of Distributed Generation (DG) in distribution system is one of the important parts of DG research studies so as to maximize its benefits. For this purpose, a probabilistic approach is proposed in this study to consider time varying load demands as uncertain parameters of distribution system. It is assumed that each load point consists of three categories of voltage dependent loads: residential, industrial and commercial. The proposed algorithm is based on a probabilist...
A generalized statistical model for the size distribution of wealth
Clementi, F.; Gallegati, M.; Kaniadakis, G.
2012-01-01
In a recent paper in this journal [J. Stat. Mech. (2009) P02037] we proposed a new, physically motivated, distribution function for modeling individual incomes having its roots in the framework of the k-generalized statistical mechanics. The performance of the k-generalized distribution was checked against real data on personal income for the United States in 2003. In this paper we extend our previous model so as to be able to account for the distribution of wealth. Probabil...
Ultrasonic energy in liposome production: process modelling and size calculation.
Barba, A A; Bochicchio, S; Lamberti, G; Dalmoro, A
2014-04-21
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
DEFF Research Database (Denmark)
Mikosch, Thomas Valentin; Rackauskas, Alfredas
2010-01-01
In this paper, we deal with the asymptotic distribution of the maximum increment of a random walk with a regularly varying jump size distribution. This problem is motivated by a long-standing problem on change point detection for epidemic alternatives. It turns out that the limit distribution of the maximum increment of the random walk is one of the classical extreme value distributions, the Fréchet distribution. We prove the results in the general framework of point processes and for jump sizes taking values in a separable Banach space
[Particles size distribution and its influence on remote sensing retrieval of turbid Poyang Lake].
Huang, Jue; Chen, Xiao-Ling; Chen, Li-Qiong; Zhang, Li
2014-11-01
The suspended particle size distribution provides crucial information for the study of water environment structure and function. Based on the in-situ data from wet and dry season in 2008-2011, the paper studied suspended particle size distribution of Poyang Lake and its optical features. The suspended particle size distribution showed seasonal variation: the particle size of southern lake was larger than that of northern lake in dry season but showed little variation in wet season. The suspended particle size distribution exerted influence on particulate absorption coefficient, attenuation coefficient and scattering coefficient. The particulate absorption coefficient of northern lake was higher than that of southern lake. The negative correlation between specific absorption coefficient of total suspended particles and median particle size indicated that there was "package effect" of mineral particles in turbid Poyang Lake. The spatial and temporal distribution of particulate attenuation coefficient and scattering coefficient are similar: there were obvious regional differences in dry season but few in wet season. There were good correlations among the remote sensing reflectance, spectra slope of particle size distribution and spectra slope of particulate scattering coefficient. These correlations would provide the foundation for remote sensing retrieval of particle size and quantitative analysis of influence of suspended particle size on the optical properties. The relationship between particle size distribution, particulate back-scattering coefficient and bulk refractive index can provide information of particle composition in Poyang Lake. PMID:25752063
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)
On the size distribution of sunspot groups in the Greenwich sunspot record 1874-1976
Baumann, I.; Solanki, S. K.
2005-01-01
We investigate the size distribution of the maximum areas and the instantaneous distribution of areas of sunspot groups using the Greenwich sunspot group record spanning the interval 1874-1976. Both distributions are found to be well described by log-normal functions. Using a simple model we can transform the maximum area distribution into the instantaneous area distribution if the sunspot area decay rates are also distributed log-normally. For single-valued decay rates the ...
Optimizing the grain size distribution for talc-magnesite ore flotation
Directory of Open Access Journals (Sweden)
?kvarla Jiøí
2001-06-01
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.
A generalized statistical model for the size distribution of wealth
International Nuclear Information System (INIS)
In a recent paper in this journal (Clementi et al 2009 J. Stat. Mech. P02037), we proposed a new, physically motivated, distribution function for modeling individual incomes, having its roots in the framework of the ?-generalized statistical mechanics. The performance of the ?-generalized distribution was checked against real data on personal income for the United States in 2003. In this paper we extend our previous model so as to be able to account for the distribution of wealth. Probabilistic functions and inequality measures of this generalized model for wealth distribution are obtained in closed form. In order to check the validity of the proposed model, we analyze the US household wealth distributions from 1984 to 2009 and conclude an excellent agreement with the data that is superior to any other model already known in the literature. (paper)
A generalized statistical model for the size distribution of wealth
Clementi, F; Kaniadakis, G
2012-01-01
In a recent paper in this journal [J. Stat. Mech. (2009) P02037] we proposed a new, physically motivated, distribution function for modeling individual incomes having its roots in the framework of the k-generalized statistical mechanics. The performance of the k-generalized distribution was checked against real data on personal income for the United States in 2003. In this paper we extend our previous model so as to be able to account for the distribution of wealth. Probabilistic functions and inequality measures of this generalized model for wealth distribution are obtained in closed form. In order to check the validity of the proposed model, we analyze the U.S. household wealth distributions from 1984 to 2009 and conclude an excellent agreement with the data that is superior to any other model already known in the literature.
Effects of fuel particle size distributions on neutron transport in stochastic media
International Nuclear Information System (INIS)
Highlights: • Effects of fuel particle size distributions on neutron transport are evaluated. • Neutron channeling is identified as the fundamental reason for the effects. • The effects are noticeable at low packing and low optical thickness systems. • Unit cells of realistic reactor designs are studied for different size particles. • Fuel particle size distribution effects are not negligible in realistic designs. - Abstract: This paper presents a study of the fuel particle size distribution effects on neutron transport in three-dimensional stochastic media. Particle fuel is used in gas-cooled nuclear reactor designs and innovative light water reactor designs loaded with accident tolerant fuel. Due to the design requirements and fuel fabrication limits, the size of fuel particles may not be perfectly constant but instead follows a certain distribution. This brings a fundamental question to the radiation transport computation community: how does the fuel particle size distribution affect the neutron transport in particle fuel systems? To answer this question, size distribution effects and their physical interpretations are investigated by performing a series of neutron transport simulations at different fuel particle size distributions. An eigenvalue problem is simulated in a cylindrical container consisting of fissile fuel particles with five different size distributions: constant, uniform, power, exponential and Gaussian. A total of 15 parametric cases are constructed by altering the fissile particle volume packing fraction and its optical thickness, but keeping the mean chord length of the spherical fuel particle the same at different size distributions. The tallied effective multiplication factor (keff) and the spatial distribution of fission power density along axial and radial directions are compared between different size distributions. At low packing fraction and low optical thickness, the size distribution shows a noticeable effect on neutron transport. As high as 1.00% relative difference in keff and ?1.50% relative difference in peak fission power density are observed. As the packing fraction and optical thickness increase, the effect gradually dissipates. Neutron channeling between fuel particles is identified as the effect most responsible for the different neutronic results. Different size distributions result in the difference in the average number of fuel particles and their average size. As a result, different degrees of neutron channeling are produced. The size effect in realistic reactor unit cells is also studied and, from the predicted values of infinite multiplication factors, it is concluded that the fuel particle size distribution effects are not negligible
Eigenvalue distributions from a star product approach
International Nuclear Information System (INIS)
We use the well-known isomorphism between operator algebras and function spaces equipped with a star product to study the asymptotic properties of certain matrix sequences in which the matrix dimension D tends to infinity. Our approach is based on the su(2) coherent states which allow for a systematic 1/D expansion of the star product. This produces a trace formula for functions of the matrix sequence elements in the large-D limit which includes higher order (finite-D) corrections. From this a variety of analytic results pertaining to the asymptotic properties of the density of states, eigenstates and expectation values associated with the matrix sequence follows. It is shown how new and existing results in the settings of collective spin systems and orthogonal polynomial sequences can be readily obtained as special cases. In particular, this approach allows for the calculation of higher order corrections to the zero distributions of a large class of orthogonal polynomials. (paper)
Chang, Chun-Wei; Miki, Takeshi; Shiah, Fuh-Kwo; Kao, Shuh-Ji; Wu, Jiunn-Tzong; Sastri, Akash R; Hsieh, Chih-Hao
2014-04-01
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
Effect size measurement in functional milk product marketing
Directory of Open Access Journals (Sweden)
Karmen Pažek
2011-12-01
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.
Particle size distribution from small angle x-ray scattering
International Nuclear Information System (INIS)
Using X-ray-scattering data at small angles, a study is developed to investigate the distribution of the particle diameters in DuPont Ludox type HS, dilute colloidal dispersions of noninteracting silica spheres in water. The data furnish the average diameter and the diameter distribution to each sample. The results suggest that this method may often be a useful procedure for the analysis of small angle X-ray-scattering data. (auth.)
Spatial distribution of the arctic haze aerosol size distribution in western and eastern Arctic
Dreiling, Volker; Friederich, Berthold
Since June 1993, four flight campaigns to the Arctic have been carried out by a group of scientists from Russia and Germany. Optical remote-sensing methods and in-situ chemical and aerosol measurements have been combined on board a Russian IL-18 research aircraft. From arctic air bases in Siberia, Alaska, Canada, and Spitsbergen, respectively, flights have been undertaken to determine spatial structure of arctic haze events. This paper reports on aerosol data obtained during the expedition of Spring 1994. Haze events have been found in the east and west Arctic, containing about the same concentration of particles. Horizontal and vertical layer extensions are given and the size distribution of number and surface is estimated from integral parameters.
International Nuclear Information System (INIS)
A method of and equipment for the determination of the particle size distribution in suspensions are described. The size distribution curve of the particles is presented. The Moessbauer spectra at 20 degC were computer-calculated for particle radii of 0.2, 0.4, 0.6, 1.0, 1.2 and 1.5 ?. (Z.S.)
Varma, Vijaykumar B.; Tank, Chiti M.; Nandi, Amiya; Pant, Arti; Prashant, Hima; Pandey, R. K.; Das, A. K.; Bhoraskar, S. V.; Mathe, V. L.
2013-02-01
Synthesizing nano-particles with narrow size distribution in the gas phase process, via thermal plasma reactor is a challenge. The paper addresses this problem by introducing a crucial modification in thermal plasma reactor, used to produce nano-aluminum particles for propellant applications. The size distribution is assessed by transmission electron microscopy.
An analysis of the size distribution of Italian firms by age
Cirillo, Pasquale
2010-02-01
In this paper we analyze the size distribution of Italian firms by age. In other words, we want to establish whether the way that the size of firms is distributed varies as firms become old. As a proxy of size we use capital. In [L.M.B. Cabral, J. Mata, On the evolution of the firm size distribution: Facts and theory, American Economic Review 93 (2003) 1075-1090], the authors study the distribution of Portuguese firms and they find out that, while the size distribution of all firms is fairly stable over time, the distributions of firms by age groups are appreciably different. In particular, as the age of the firms increases, their size distribution on the log scale shifts to the right, the left tails becomes thinner and the right tail thicker, with a clear decrease of the skewness. In this paper, we perform a similar analysis with Italian firms using the CEBI database, also considering firms’ growth rates. Although there are several papers dealing with Italian firms and their size distribution, to our knowledge a similar study concerning size and age has not been performed yet for Italy, especially with such a big panel.
Czech Academy of Sciences Publication Activity Database
Beddows, D.C.S.; Dall’Osto, M.; Harrison, R.M.; Kulmala, M.; Asmi, A.; Wiedensohler, A.; Laj, P.; Fjaeraa, A.M.; Sellegri, K.; Birmili, W.; Bukowiecki, N.; Weingartner, E.; Baltensperger, U.; Ždímal, Vladimír; Zíková, Nad?žda; Putaud, J.-P.; Marinoni, A.; Tunved, P.; Hansson, H.-C.; Feibig, M.; Kivekäs, N.; Swietlicki, E.; Lihavainen, H.; Asmi, E.; Ulevicius, V.; Aalto, P.P.; Mihalopoulos, N.; Kalivitis, N.; Kalapov, I.; Kiss, G.; de Leeuw, G.; Henzing, B.; O'Dowd, C.; Jennings, S.G.; Flentje, H.; Meinhardt, F.; Ries, L.; Denier van der Gon19, H.A.C.; Visschedijk, A.J.H.; Swietlicki, E.
2014-01-01
Ro?. 14, ?. 8 (2014), s. 4327-4348. ISSN 1680-7316 Grant ostatní: EUCAARI(XE) 036833; EUSAAR(XE) 026140 Institutional support: RVO:67985858 Keywords : particle size distribution * clusters * aerosol size distribution Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 5.298, year: 2013
Influence of microsphere size upon their intrarenal distribution in the rat
International Nuclear Information System (INIS)
Applying radioactive microspheres, their intrarenal distribution in dependence on their size is investigated (with mean diameters of 12.7 +- 1.2 SD and 8.5 +- 0.8 SD micrometers). The discussion on the influence of the microsphere size on the intraglomerular, cortical distribution takes place with reference to the hemodynamic parameters and the microscopic examination. (APR)
Pfeifer, S.; Birmili, W.; Schladitz, A.; Mu?ller, T.; Nowak, A.; Wiedensohler, A.
2013-01-01
Multiple charge inversion is an essential procedure to convert the raw mobility distributions recorded by mobility particle size spectrometers, such as the DMPS or SMPS (Differential or Scanning Mobility Particle Sizers) into true particle number size distributions. In this work, we present a new multiple charge inversion algorithm with extended functionality. The algorithm can incorporate size distribution information from sensors that me...
Evidence of bimodal crystallite size distribution in {mu}c-Si:H films
Energy Technology Data Exchange (ETDEWEB)
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
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.
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.
Optimizing Batch Size in a Flow-Oriented Synchronized Production
Directory of Open Access Journals (Sweden)
Imran Aslan
2011-06-01
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.
Evolution of the sedimentation technique for particle size distribution analysis
International Nuclear Information System (INIS)
After an introduction on the significance of particle size measurements, sedimentation methods are described, with emphasis on the evolution of the gravitational approach. The gravitational technique based on mass determination by X-ray adsorption allows fast analysis by automation and easy data handling, in addition to providing the accuracy required by quality control and research applications
Measuring the Kuiper Belt Size Distribution Using Stellar Occultations
Schlichting, H. E.; Ofek, E. O.; Sari, R.; Wenz, M.; Gal-Yam, A.; Livio, M.; Nelan, E.; Zucker, S.
2012-05-01
A sub-km-sized KBO has been reported recently by Schlichting et al. (2009), who analyzed archival data taken by HST FGS. I will present the final results of our analysis of the remaining FGS data, which will more than triple the number of star hours.
Indoor radon progeny particle size distribution measurements made with two different methods
International Nuclear Information System (INIS)
Indoor radon progeny particle size measurements using two distinctly different instruments, a diffusion battery and an electrical aerosol size analyser, were carried out in two single-family homes in New Jersey. The activity-weighted size distributions were determined by applying the radon progeny attachment theory to the measured number-weighted particle size spectra and the results are close to those measured by the diffusion battery method. These particle size distributions were found to be more often bimodal than unimodal. The minor modes of the bimodal distributions were located around the 1 nm region, close to the 218Po atom size, except one centred around 10 nm. For both the unimodal and the bimodal distributions, the modal diameter of the major mode ranged from 30 nm to 150 nm, respectively. The results previously reported showed modal diameters around 100 nm. (author)
ON ESTIMATION AND HYPOTHESIS TESTING OF THE GRAIN SIZE DISTRIBUTION BY THE SALTYKOV METHOD
Directory of Open Access Journals (Sweden)
Yuri Gulbin
2011-05-01
Full Text Available The paper considers the problem of validity of unfolding the grain size distribution with the back-substitution method. Due to the ill-conditioned nature of unfolding matrices, it is necessary to evaluate the accuracy and precision of parameter estimation and to verify the possibility of expected grain size distribution testing on the basis of intersection size histogram data. In order to review these questions, the computer modeling was used to compare size distributions obtained stereologically with those possessed by three-dimensional model aggregates of grains with a specified shape and random size. Results of simulations are reported and ways of improving the conventional stereological techniques are suggested. It is shown that new improvements in estimating and testing procedures enable grain size distributions to be unfolded more efficiently.
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
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
Cheng, Yu-Hsiang; Liao, Chung-Wen; Liu, Zhen-Shu; Tsai, Chuen-Jinn; Hsi, Hsing-Cheng
2014-06-01
Understanding the characteristics of the size distribution of ambient black carbon (BC) in distinct environments is critical because the influence of BC aerosols on climate, visibility, and human health depends strongly on the distribution of BC aerosols over the particle size spectrum. In this study, a novel method for determining the mass size distribution of BC in atmospheric aerosols was developed. This size-segregation method relies on measuring BC in parallel using two aethalometers, one of which is used to measure the total BC (BCT) mass concentration as a reference level and the other is used to measure the BC (BCi) mass concentration for BC sizes below specific particle sizes that are selected using a size cut-off inlet. In this study, this method was applied to measure BC in atmospheric samples at an urban traffic site. The aethalometers were operated continually from December 15, 2012 to January 31, 2013, and from February 15, 2013 to March 31, 2013. The measurement results presented in this paper are for the diurnal variation patterns, average concentrations, mass fractions, and size distributions of BC aerosols. The results indicate that BCT mass concentration is approximately 2.8 ?g m-3 in the Taipei urban area. The levels of BC at this sampling site were affected markedly by traffic emission levels and local wind speed. At the sampling site, the average BC2.5/BCT, BC1.0/BCT, BC0.5/BCT, BC0.25/BCT, and BC0.1/BCT were 0.96 ± 0.04, 0.92 ± 0.07, 0.89 ± 0.04, 0.73 ± 0.10, and 0.18 ± 0.08, respectively. The results indicate that approximately 90% of the BC aerosols were smaller than 0.5 ?m, that most of the BC aerosols (55%) were in the size range of 0.1-0.25 ?m, and that approximately 18% of the BC aerosols were ultrafine. Moreover, the daily average mass size distribution of BC exhibited a single accumulation mode at 0.16 ?m at this sampling site. The mode of the BC mass size distribution at rush hour (9 AM) was only 0.14 ?m, which is smaller than the daily average. Moreover, the mode of the BC mass size distribution at an early morning hour (3 AM) was 0.18 ?m, and a minor coarse mode was also observed during this period. The results further revealed that the geometric diameter (Dpg) of the BC aerosols varied between 0.14 and 0.22 ?m and the geometric standard deviation (?g) of these BC aerosols ranged between 1.4 and 2.3 during the sampling period. Because BC exhibits extremely low chemical reactivity; the size distribution of BC in the atmosphere does not change substantially except through coagulation.
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
Particles size distribution effect on 3D packing of nanoparticles in to a bounded region
International Nuclear Information System (INIS)
In this paper, the effects of two different Particle Size Distributions on packing behavior of ideal rigid spherical nanoparticles using a novel packing model based on parallel algorithms have been reported. A mersenne twister algorithm was used to generate pseudo random numbers for the particles initial coordinates. Also, for this purpose a nano sized tetragonal confined container with a square floor (300 * 300 nm) were used in this work. The Andreasen and the Lognormal Particle Size Distributions were chosen to investigate the packing behavior in a 3D bounded region. The effects of particle numbers on packing behavior of these two Particle Size Distributions have been investigated. Also the reproducibility and the distribution of packing factor of these Particle Size Distributions were compared
Dust Grain Size Distributions and Extinction in the Milky Way, LMC, and SMC
Weingartner, J C; Weingartner, Joseph C.
2001-01-01
We construct size distributions for carbonaceous and silicate grain populations in different regions of the Milky Way, LMC, and SMC. The size distributions include sufficient very small carbonaceous grains (including polycyclic aromatic hydrocarbon molecules) to account for the observed infrared and microwave emission from the diffuse interstellar medium. Our distributions reproduce the observed extinction of starlight, which varies depending upon the interstellar environment through which the light travels. As shown by Cardelli, Clayton & Mathis in 1989, these variations can be roughly parameterized by the ratio of visual extinction to reddening, R_V. We adopt a fairly simple functional form for the size distribution, characterized by several parameters. We tabulate these parameters for various combinations of values for R_V and b_C, the C abundance in very small grains. We also find size distributions for the line of sight to HD 210121, and for sightlines in the LMC and SMC. For several size distributio...
The Influence of Ball Charge and Media Size Distribution in Grinding Plant
Costea, Claudiu Raul; Silaghi, Helga; Kovendi, Zoltan
2011-01-01
This paper presents an analysis of theperformances of an mill grinding circuits. This studyrelieve fineness of cement for certain condition, suchare: ball size distribution, charge of grinding media,weight for all balls from the same category. Becausethe size of media has to match the size of materialbeing ground, it is necessary an analysis of these.Finally, some simulation results are shown.
Lock, James A.; Hovenac, Edward A.
1989-01-01
A correction algorithm for evaluating the particle size distribution measurements of atmospheric aerosols obtained with a forward-scattering spectrometer probe (FSSP) is examined. A model based on Poisson statistics is employed to calculate the average diameter and rms width of the particle size distribution. The dead time and coincidence errors in the measured number density are estimated. The model generated data are compared with a Monte Carlo simulation of the FSSP operation. It is observed that the correlation between the actual and measured size distribution is nonlinear. It is noted that the algorithm permits more accurate calculation of the average diameter and rms width of the distribution compared to uncorrected measured quantities.
Yakubu, Mahadi Lawan; Yusop, Zulkifli; Yusof, Fadhilah
2014-01-01
This paper presents the modelled raindrop size parameters in Skudai region of the Johor Bahru, western Malaysia. Presently, there is no model to forecast the characteristics of DSD in Malaysia, and this has an underpinning implication on wet weather pollution predictions. The climate of Skudai exhibits local variability in regional scale. This study established five different parametric expressions describing the rain rate of Skudai; these models are idiosyncratic to the climate of the region. Sophisticated equipment that converts sound to a relevant raindrop diameter is often too expensive and its cost sometimes overrides its attractiveness. In this study, a physical low-cost method was used to record the DSD of the study area. The Kaplan-Meier method was used to test the aptness of the data to exponential and lognormal distributions, which were subsequently used to formulate the parameterisation of the distributions. This research abrogates the concept of exclusive occurrence of convective storm in tropical regions and presented a new insight into their concurrence appearance. PMID:25126597
Poorter, L.; Hawthorne, W.; Bongers, F.; Sheil, D.
2008-01-01
1. The diversity and structure of communities are partly determined by how species partition resource gradients. Plant size is an important indicator of species position along the vertical light gradient in the vegetation. 2. Here, we compared the size distribution of tree species in 44 Ghanaian tropical forest communities, using data from 880 one-hectare plots and over 118 000 trees belonging to more than 210 species. 3. The size distribution of forest species showed a continuous normal or l...
Modeling size-number distributions of seeds for use in soil bank studies
Casco, H.; Dias, A. S.; Dias, L. S.
2008-01-01
Knowledge of soil seed banks is essential to understand the dynamics of plant populations and communities and would greatly benefit from the integration of existing knowledge on ecological correlates of seed size and shape. This paper aims to establish a feasible and meaningful method to describe size-number distributions of seeds in multi-species situations. For that purpose, size-number distributions of seeds with known length, width and thickness were determined by sequential sieving. The ...
Zi Ye; Xiaoping Jiang; Zhenchong Wang
2012-01-01
Measuring particle size distribution through calculating light scattering intensity is a typical inverse problem. This paper builds an inverse mathematical model based on Mie scattering, deduces the inversion formulas for particle size, and calculates the relative coefficients through programming with built-in functions in MATLAB. In order to improve the accuracy and noise immunity of particle size distribution measurement, the development of stochastic inversion algorithm: an inverse problem...
Does plot size affect the performance of GIS-based species distribution models?
Pandit, Shubha N.; Hayward, April; de Leeuw, Jan; Kolasa, Jurek
2010-12-01
Species distribution models are used extensively in predicting the distribution of vegetation across a landscape. Accuracy of the species distribution maps produced by these models deserves attention, since low accuracy maps may lead to erroneous conservation decisions. While plot size is known to influence measures of species richness, its effect on our ability to predict species distribution ranges has not been tested. Our aim is to test whether the accuracy of the distribution maps produced depend on the size of the plot (quadrat) used to collect biological data in the field. In this study, the presences of four plant species were recorded in five sizes of circular plots, with radii ranging from 8 to 100 m. Logistic regression-based models were used to predict the distributions of the four plant species based on empirical evidence of their relationship with eight environmental predictors: distance to river, slope, aspect, altitude, and four principle component axes derived using reflectance values from Aster images. We found that plot size affected the probability of recording the four species, with reductions in plot size generally increasing the frequency of recorded absences. Plot size also significantly affected the likelihood of correctly predicting the distribution of species whenever plot size was below the minimum size required to consistently record species’ presence. Furthermore, the optimal plot size for fitting species distribution models varied among species. Finally, plot size had little impact on overall accuracy, but a strong, positive impact on Kappa accuracy (which provides a stronger measure of model accuracy by accounting for the effects of chance agreements between predictions and observations). Our results suggest that optimal plot size must be considered explicitly in the creation of species distribution models if they are to be successfully adopted into conservation efforts.
Human Capital and the Size Distribution of Firms
Gomes, Pedro Maia; Kuehn, Zoe?
2014-01-01
Countries that have relatively fewer workers with a secondary education have smaller firms. The shortage of skilled workers limits the growth of more productive firms. Two factors influence the availability of skilled workers: i) the education level of the workforce and ii) large public sectors that predominantly hire individuals with a better education. We set up a model economy with a government and private firm formation where production requires unskilled and skilled jobs. Workers with a ...
Granier, John J.; Pantoya, Michelle L.
2004-09-01
Burn rates of thermites are typically calculated in terms of an average particle size that characterizes the bulk mixture. As the particle diameter approaches the nano-scale the burn rate calculation becomes increasingly sensitive to changes in the particle diameter. In this study, burn rate estimates for nano-scale particle composite thermites are statistically evaluated in terms of an integral that employs a probability density function (pdf) for particle size distribution and a diameter dependent burn rate equation. It is shown that the burn rates depend sensitively on the mean particle diameter and the particle size distribution. Both single mode and bimodal particle size distributions were studied. The analysis shows that as the particle size is reduced to the nano-scale, the size distribution, rather than the average particle size alone, becomes increasingly important. Large variability in burn rate is associated with large standard deviations in particle size. Combining nano-scale with bulk-scale particles in a bimodal distribution does not significantly increase the burn rate as compared to a composite consisting of strictly nanoparticles. The results presented here suggest that better reproducibility of the burn rate may be achieved experimentally by selecting a material with a narrow particle size distribution.
Size distribution of particle systems analyzed with organic photodetectors
Sentis, Matthias
2015-01-01
As part of a consortium between academic and industry, this PhD work investigates the interest and capabilities of organic photo-sensors (OPS) for the optical characterization of suspensions and two-phase flows. The principle of new optical particle sizing instruments is proposed to characterize particle systems confined in a cylinder glass (standard configuration for Process Analytical Technologies). To evaluate and optimize the performance of these systems, a Monte-Carlo model has been specifically developed. This model accounts for the numerous parameters of the system: laser beam profile, mirrors, lenses, sample cell, particle medium properties (concentration, mean & standard deviation, refractive indices), OPS shape and positions, etc. Light scattering by particles is treated either by using Lorenz-Mie theory, Debye, or a hybrid model (that takes into account the geometrical and physical contributions). For diluted media (single scattering), particle size analysis is based on the inversion of scatter...
Exact Sample Size Methods for Estimating Parameters of Discrete Distributions
Chen, Xinjia; Chen, Zhengjia
2012-01-01
In this paper, we develop an approach for the exact determination of the minimum sample size for estimating the parameter of an integer-valued random variable, which is parameterized by its expectation. Under some continuity and unimodal property assumptions, the exact computation is accomplished by reducing infinite many evaluations of coverage probability to finite many evaluations. Such a reduction is based on our discovery that the minimum of coverage probability with re...
Acoustic estimation of size distribution and abundance of zooplankton
Kristensen, A?ge; Dalen, John
1986-01-01
A series of investigations were undertaken to observe and describe the sound backscattering process from larger zooplankton (euphausiids). The target strength versus frequency, size, and aspect angle of the organism was measured. The target strength is highly dependent on the density and sound speed contrasts between the target and the medium, and both these parameters were measured. From the target strength observations it was concluded that the fluid sphere model was insufficient as a scatt...
Scientific Electronic Library Online (English)
Christiane Ribeiro da, Silva; Vládia C. G. de, Souza; Jair C., Koppe.
2014-12-01
Full Text Available 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.
Mu, Guo-hua; Chen, Wei; Kerte?sz, Ja?nos; Zhou, Wei-xing
2008-01-01
The distribution of trade sizes and trading volumes are investigated based on the limit order book data of 22 liquid Chinese stocks listed on the Shenzhen Stock Exchange in the whole year 2003. We observe that the size distribution of trades for individual stocks exhibits jumps, which is caused by the number preference of traders when placing orders. We analyze the applicability of the "$q$-Gamma" function for fitting the distribution by the Cram\\'{e}r-von Mises criterion. T...
Quantitative analysis of crystal/grain sizes and their distributions in 2D and 3D
DEFF Research Database (Denmark)
Berger, Alfons; Herwegh, Marco
2011-01-01
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.
Diel size distributions reveal seasonal growth dynamics of a coastal phytoplankter.
Hunter-Cevera, Kristen R; Neubert, Michael G; Solow, Andrew R; Olson, Robert J; Shalapyonok, Alexi; Sosik, Heidi M
2014-07-01
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
Impact of grain size distributions on the dust enrichment in high-redshift quasars
Kuo, Tzu-Ming
2012-01-01
In high-redshift ($z>5$) quasars, a large amount of dust ($\\textstyle\\sim 10^{8} \\mathrm{M}_{\\sun}$) has been observed. In order to explain the large dust content, we focus on a possibility that grain growth by the accretion of heavy elements is the dominant dust source. We adopt a chemical evolution model applicable to nearby galaxies but utilize parameters adequate to high-$z$ quasars. It is assumed that metals and dust are predominantly ejected by Type II supernovae (SNe). We have found that grain growth strongly depends on the grain size distribution. If we simply use the size distribution of grains ejected from SNe, grain growth is inefficient because of the lack of small grains (i.e.\\ small surface-to-volume ratio of the dust grains). However, if we take small grain production by interstellar shattering into consideration, grain growth is efficient enough to account for the rich dust abundance in high-$z$ quasars. Our results not only confirm that grain growth is necessary to explain the large amount of...
Energy Technology Data Exchange (ETDEWEB)
Kimmel, B.L.
1981-01-01
Particle size is a primary determinant of resources available to consumers and of the efficiency of energy transfer through planktonic food chains. Dual radioisotopic labeling (with /sup 14/C-bicarbonate and /sup 3/H-acetate) and size fractionation of naturally-occurring phytoplankton-bacterioplankton assemblages were employed to examine the particle size distributions of planktonic autotrophy and microheterotrophy in four limnologically-dissimilar US reservoirs (Lake Mead, Arizona-Nevada, oligo-mesotrophic; Broken Bow Lake, Oklahoma, mesotrophic; Lake Texoma, Oklahoma-Texas, eutrophic; and Normandy Lake, Tennessee, eutrophic). Small nano- and ultraphytoplankton (< 8.0 ..mu..m) and free-living bacteria (< 3.0 ..mu..m) were primarly responsible for planktonic autotrophy and microheterotrophy, respecitvely, even in eutrophic conditions. Zooplankton grazing experiments indicated that (1) most grazing pressure occurs on 3.0 to 8.0 ..mu..m particles, (2) grazer limitation of the occurrence of attached bacteria amd microbial-detrital aggregates is unlikely, and (3) free-living bacteria are inefficiently harvested, relative to algae, by most reservoir zooplankton. Relative to autorophy, the microheterotrophic conversion of allochthonous dissolved organic matter and algal excretion products to bacterial biomass appears unlikely to be a significant source of organic carbon for planktonic grazers in most reservoirs.
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
Particle Size Distribution Measurements of Manganese-Doped ZnS Nanoparticles
Dieckmann, Yvonne; Co?lfen, Helmut; Hofmann, Heinrich; Petri-fink, Alke
2009-01-01
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...
On wildfire complexity, simple models and environmental templates for fire size distributions
Boer, M. M.; Bradstock, R.; Gill, M.; Sadler, R.
2012-12-01
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.
Endotoxins in cotton: washing effects and size distribution
Energy Technology Data Exchange (ETDEWEB)
Olenchock, S.A.; Mull, J.C.; Jones, W.G.
1983-01-01
Endotoxin contamination was measured in washed and unwashed cottons from three distinct growing areas, California, Mississippi, and Texas. The data show differences in endotoxin contamination based upon the geographic source of the cotton. It is also shown that washing bulk cotton before the carding process results in lower endotoxin in the cotton dust. Washing conditions can affect the endotoxin levels, and all size fractions of the airborne dust contain quantifiable endotoxin contamination. Endotoxin analyses provide a simple and reliable method for monitoring the cleanliness of cotton or airborne cotton dusts.
International Nuclear Information System (INIS)
Natural radioactivity level in the Mumbai Harbour bay sediment was estimated and their association with particle size was investigated. Seven different particle size fractions from 300 ?m were separated by wet sewing using electromagnetic sieve shaker and particle size distribution was studied in the marine sediment. The particle size fractions were analysed for 226Ra, 228Ra and 40K content using 50% relative efficiency p-type Co-axial HPGe detector. It was observed that, 71.8 % of the total sediment contained 40K was observed to be associated in the size fraction of <60 to 90 ?m size particles. (author)
Size Distributions and Characterization of Native and Ground Samples for Toxicology Studies
McKay, David S.; Cooper, Bonnie L.; Taylor, Larry A.
2010-01-01
This slide presentation shows charts and graphs that review the particle size distribution and characterization of natural and ground samples for toxicology studies. There are graphs which show the volume distribution versus the number distribution for natural occurring dust, jet mill ground dust, and ball mill ground dust.
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
Scientific Electronic Library Online (English)
F.H. de, Witt; N.P., Kuleile; H.J., van der Merwe; M.D., Fair.
Full Text Available SciELO South Africa | Language: English Abstract in english A study was conducted to determine the influence of different particle size limestone in layer diets on egg production and eggshell quality during the later stages of egg production (>54 weeks of age). Calcitic limestone (360 g Ca/kg), consisting of small ([...] 2.0 - 3.8 mm) particles were obtained from a specific South African source that is extensively used in poultry diets Isoenergetic (14.32 MJ AME/kg DM) and isonitrogenous (172.01 g CP/kg DM) diets with a dietary Ca content of 39.95 g Ca/kg DM were used. Sixty nine, individual caged Lohmann-Silver pullets, 17 weeks of age, were randomly allocated to the three treatments (n = 23) for the determination of various egg production and eggshell quality characteristics. Egg production and eggshell quality data recorded on individual basis at 54, 58, 64 and 70 weeks of age were pooled to calculate and statistical analysed parameter means for the late production period. Different limestone particle sizes had no effect on any of the tested egg production and eggshell quality parameters. These results suggested that larger particles limestone are not necessarily essential to provide sufficient Ca2+ to laying hens for egg production and eggshell quality at end-of-lay, provided that the dietary Ca content satisfies the requirements of the laying hen.
Transformation on steel products distribution in Poland and Slovakia
Stefko, R.; Slusarczyk, B.; Kot, S.; Kolmasiak, C.
2012-01-01
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 ...
Okuzumi, Satoshi; Takeuchi, Taku; Sakagami, Masa-aki
2010-01-01
Collisional growth of submicron-sized dust grains into macroscopic aggregates is the first step of planet formation in protoplanetary disks. These aggregates are considered to carry nonzero negative charges in the weakly ionized gas disks, but its effect on their collisional growth has not been fully understood so far. In this paper, we investigate how the charging of dust aggregates affects the evolution of their size distribution properly taking into account the charging mechanism in a weakly ionized gas. To clarify the role of the size distribution, we divide our analysis into two steps. First, we analyze the collisional growth of charged aggregates assuming a monodisperse (i.e., narrow) size distribution. We show that the monodisperse growth stalls due to the electrostatic repulsion when a certain condition is met, as is already expected in the previous work. Second, we numerically simulate dust coagulation using Smoluchowski's method to see how the outcome changes when the size distribution is allowed to...
Air activity concentrations and aerosol activity size distributions after the accident at Chernobyl
International Nuclear Information System (INIS)
The activity concentration of the Chernobyl aerosol was measured from April 29, 1986 till December 1986. In addition measurements were carried out with charcoal filters which showed that only 15-23% of the total 131I was adsorbed on aerosol particles. The activity size distributions of the aerosol were measured by means of a low pressure cascade impactor (Type BERNER) and a high volume cascade impactor (Type SIERRA). Most of the measurements yielded unimodal distributions with activity median aerodynamic diameters (AMAD) in the size range 700-1000 nm. Sometimes the size distributions were bimodal with a significant activity amount on a coarse mode with sizes greater 2000 nm. The iodine distributions were shifted to smaller particle diameters with an average median value near 600 nm. In some air samples single ''hot'' particles of the isotopes 95Zr/95Nb, 141Ce and 144Ce were measured only in the coarse size mode
Does the size distribution of mineral dust aerosols depend on the wind speed at emission?
Kok, Jasper F
2011-01-01
The size distribution of mineral dust aerosols partially determines their interactions with clouds, radiation, ecosystems, and other components of the Earth system. Several theoretical models predict that the dust size distribution depends on the wind speed at emission, with larger wind speeds predicted to produce smaller aerosols. The present study investigates this prediction using a compilation of published measurements of the size-resolved vertical dust flux emitted by eroding soils. Surprisingly, these measurements indicate that the size distribution of naturally emitted dust aerosols is independent of the wind speed. The recently formulated brittle fragmentation theory of dust emission is consistent with this finding, whereas other theoretical dust emission models are not. The independence of the emitted dust size distribution with wind speed simplifies both the interpretation of geological records of dust deposition and the parameterization of dust emission in atmospheric circulation models.
Optimizing the grain size distribution of allografts in bone impaction grafting.
Putzer, David; Coraça-Huber, Debora; Wurm, Alexander; Schmoelz, Werner; Nogler, Michael
2014-08-01
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
Hirashita, Hiroyuki
2015-03-01
Full calculations of the evolution of grain size distribution in galaxies are in general computationally heavy. In this paper, we propose a simple model of dust enrichment in a galaxy with a simplified treatment of grain size distribution by imposing a two-size approximation; that is, the whole grain population is represented by small grains (radius a 0.03 ?m). We include in the model dust supply from stellar ejecta, destruction in supernova shocks, dust growth by accretion, grain growth by coagulation and grain disruption by shattering, and consider how these processes work on the small and large grains. We show that this simple framework reproduces the main features of full calculations of grain size distributions as follows. Dust enrichment starts with a supply of large grains from stars. At a metallicity level, referred to as the critical metallicity of accretion, the abundance of small grains formed by shattering becomes large enough to increase grain abundance rapidly by accretion. Associated with this epoch, the mass ratio of small grains to large grains reaches a maximum. Afterwards, this ratio converges to the value determined by the balance between shattering and coagulation, and the dust-to-metal ratio is determined by the balance between accretion and shock destruction. Using a Monte Carlo simulation, we demonstrate that the simplicity of our model has an advantage in predicting statistical properties. We also show some applications for predicting observational dust properties such as extinction curves.
Hirashita, Hiroyuki
2014-01-01
Full calculations of the evolution of grain size distribution in galaxies are in general computationally heavy. In this paper, we propose a simple model of dust enrichment in a galaxy with a simplified treatment of grain size distribution by imposing a `two-size approximation'; that is, all the grain population is represented by small (grain radius a 0.03 micron) grains. We include in the model dust supply from stellar ejecta, destruction in supernova shocks, dust growth by accretion, grain growth by coagulation and grain disruption by shattering, considering how these processes work on the small and large grains. We show that this simple framework reproduces the main features found in full calculations of grain size distributions as follows. The dust enrichment starts with the supply of large grains from stars. At a metallicity level referred to as the critical metallicity of accretion, the abundance of the small grains formed by shattering becomes large enough to rapidly increase the grain abundance by acc...
Selvam, A M
2011-01-01
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...
Particle size distributions from laboratory-scale biomass fires using fast response instruments
Directory of Open Access Journals (Sweden)
S. Hosseini
2010-04-01
Full Text Available Particle size distribution from biomass combustion is an important parameter as it affects air quality, climate modelling and health effects. To date particle size distributions reported from prior studies vary not only due to difference in fuels but also difference in experimental conditions. This study aims to report characteristics of particle size distribution in a well controlled repeatable lab scale biomass fires for southwestern US fuels. The combustion facility at the USDA Forest Service's Fire Science Laboratory (FSL, Missoula, MT provided repeatable combustion and dilution environment ideal for particle size distribution study. For a variety of fuels tested the major mode of particle size distribution was in the range of 29 to 52 nm, which was attributable to dilution of the fresh smoke. Comparing volume size distribution from Fast Mobility Particle Sizer (FMPS and Aerodynamic Particle Sizer (APS measurements, ~30% of particle volume was attributable to the particles ranging from 0.5 to 10 ?m for PM_{10}. Geometric mean diameter rapidly increased during flaming and gradually decreased during mixed and smoldering phase combustion. Most of fuels gave unimodal distribution during flaming phase and strong biomodal distribution during smoldering phase. The mode of combustion (flaming, mixed and smoldering could be better distinguished using slopes in Modified Combustion Efficiency (MCE vs. geometric mean diameter from each mode of combustion than only using MCE values.
3D Hail Size Distribution Interpolation/Extrapolation Algorithm
Lane, John
2013-01-01
Radar data can usually detect hail; however, it is difficult for present day radar to accurately discriminate between hail and rain. Local ground-based hail sensors are much better at detecting hail against a rain background, and when incorporated with radar data, provide a much better local picture of a severe rain or hail event. The previous disdrometer interpolation/ extrapolation algorithm described a method to interpolate horizontally between multiple ground sensors (a minimum of three) and extrapolate vertically. This work is a modification to that approach that generates a purely extrapolated 3D spatial distribution when using a single sensor.
DEFF Research Database (Denmark)
Köster, Fritz; Trippel, E.A.
2013-01-01
Sexual maturation patterns of 22 North Atlantic stocks of cod (Gadus morhua) were examined and related to geographical distribution area, ambient water temperature, growth and surplus production. Four patterns were identified, i.e. sexual maturation early in life at small size, early in life at large size, late in life at small size and lastly, late in life at large size. These maturation patterns were geographically clustered and associated with differences in growth and surplus production. Stocks maturing late in life at small size were characterised by slow growth and low surplus production (e.g. stocks in the Gulf of St. Lawrence, Labrador/Newfoundland). Stocks maturing early in life at large size exhibited high to intermediate growth and surplus production (e.g. Celtic Sea, North Sea). Stocks maturing late in life at large size had low to intermediate growth rates and surplus production (e.g. Iceland, North East Arctic), while stocks maturing early in life at small size generally showed intermediate growth and surplus production (e.g. Baltic stocks). Production of recruits per unit biomass showed a latitudinal trend, but appeared largely independent of maturation pattern, growth rate and surplus production. Recruit production of northernmost stocks was lowest and variability highest, mid-latitude stocks exhibited highest productivity and least variability, while stocks at the southern distribution range also showed low productivity. Thus, southern Gulf of St. Lawrence and eastern Scotian Shelf cod maturing late in life at small size with slow growth and low surplus production showed highest recruit production in the Western Atlantic, while the early maturing, fast growing and productive Icelandic and Faroese stocks showed the lowest recruitment production of all Eastern Atlantic stocks. This comparative analysis suggests that maturation patterns relate to growth potential and surplus production whereas annual production of recruits per unit biomass appears unrelated to average size at sexual maturation
Wolf, David B.; Tokay, Ali; Petersen, Walt; Williams, Christopher; Gatlin, Patrick; Wingo, Mathew
2010-01-01
Proper characterization of the precipitation drop size distribution (DSD) is integral to providing realistic and accurate space- and ground-based precipitation retrievals. Current technology allows for the development of DSD products from a variety of platforms, including disdrometers, vertical profilers and dual-polarization radars. Up to now, however, the dissemination or availability of such products has been limited to individual sites and/or field campaigns, in a variety of formats, often using inconsistent algorithms for computing the integral DSD parameters, such as the median- and mass-weighted drop diameter, total number concentration, liquid water content, rain rate, etc. We propose to develop a framework for the generation and dissemination of DSD characteristic products using a unified structure, capable of handling the myriad collection of disdrometers, profilers, and dual-polarization radar data currently available and to be collected during several upcoming GPM Ground Validation field campaigns. This DSD super-structure paradigm is an adaptation of the radar super-structure developed for NASA s Radar Software Library (RSL) and RSL_in_IDL. The goal is to provide the DSD products in a well-documented format, most likely NetCDF, along with tools to ingest and analyze the products. In so doing, we can develop a robust archive of DSD products from multiple sites and platforms, which should greatly benefit the development and validation of precipitation retrieval algorithms for GPM and other precipitation missions. An outline of this proposed framework will be provided as well as a discussion of the algorithms used to calculate the DSD parameters.
Cluster size distribution in the autocatalytic growth model
J?drak, Jakub
2013-01-01
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.
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
International Nuclear Information System (INIS)
Based on screen diffusion battery of particle size distribution of the radioactive aerosol measuring system developed a measurement and analysis software, the software operating environment was the embedded ARM-based hardware system and embedded linux operating system. The software is developed by the open source package QT. System functions included the measurement process control, screen diffusion battery transmittance calculations, particle size distribution measurement, measurement data analysed by the EM algorithm and Twomey algorithms, particle size distribution showed, system communication and other functions. (authors)
Size distribution of interplanetary iron and stony particles related with deep-sea spherules
Matsuzaki, H.; Yamakoshi, K.
1993-01-01
To study origin and evolution of the interplanetary dust, it is very important to investigate the size distribution. Here the changes of the size distributions of meteoroid particles due to the ablative effects during atmospheric entry were investigated by numerical computer simulation. Using the results, the pre-atmospheric size distributions of the interplanetary dust particles could be estimated from that of ablated spherules taken from deep-sea sediments. We are now analyzing deep-sea spherules from some aspects and examining if we could get any information about the interplanetary dust.
A Model for Scaling in Firms' Size and Growth Rate Distribution
Metzig, Cornelia
2013-01-01
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.
Moniruzzaman, Chowdhury G.
Combustion emission of soot and pollutant gas species contributes to poor regional air quality near emission sources and to climate change. It is important to understand the formation mechanism and time evolution of these pollutants inside the combustion engine, through detailed modeling of combustion chemistry and microphysics as well as comparison with observation. In this thesis, two multi-zone gas parcel combustion engine models, one for aircraft engines and another for diesel engines, have been developed to study soot size distribution evolution and pollutant formation inside the engines as well as emissions. The models take into account size-resolved (sectional) soot aerosol dynamics (nucleation, growth, and coagulation) and detailed combustion chemistry of jet and diesel fuel. For the aircraft engine, the model considers 362 chemical species, 2657 reversible reactions and 75 aerosol size bins. The model was applied to a CFM56-2-C1 aircraft engine for idle operating conditions. This is the first model to simulate soot size distribution evolution inside an aircraft engine (to our knowledge). The simulated values for major species are generally consistent with measurements. Model simulation shows that, for idle operating conditions, concentrations of most key combustion products don't change significantly in the post-combustor, however, HONO, H2SO4, and HO 2 concentrations change by more than a factor of 10. The sulfur oxidation efficiency (SOE), ([SO3]+[H2SO4])/([SO 2]+[SO3] +[H2SO4]), was found to be 2.1% at the engine exit. For the diesel engine, the multi-zone gas parcel model has been further enhanced by including fuel injection, droplet break-up, fuel evaporation and air entrainment rate. The model considers 283 chemical species, 2137 reversible reactions, and 75 aerosol size bins. The developed model calculates the time evolution of concentrations of these chemical species and soot size distributions inside a diesel engine. This is the first model to simulate soot size distribution evolution inside a diesel engine (to our knowledge). Model calculations are generally consistent with measurements. SOE was found to be 2% at end of the expansion stroke. The diesel engine emission model was used to study the effects of fuel sulfur content (FSC), relative humidity (RH) of intake air and fuel injection angle (FIA) on pollutant formation and emission as well as engine performances. The model simulation shows that FSC does not affect non-sulfur species, however, SO2 and SO3 increase linearly with increase in FSC. Simulation also shows that both higher RH and late injection (higher FIA) increase soot but decrease NOx. The model enables us to test the predictive capability of any existing or newly developed chemical kinetic mechanism of surrogate fuel and soot microphysics inside diesel engines.
Kornilov, Oleg; Toennies, J. Peter
2008-05-01
Clusters consisting of normal H2 molecules, produced in a free jet expansion, are size selected by diffraction from a transmission nanograting prior to electron impact ionization. For each neutral cluster (H2)N (N=2-40), the relative intensities of the ion fragments Hn+ are measured with a mass spectrometer. H3+ is found to be the most abundant fragment up to N =17. With a further increase in N, the abundances of H3+, H5+, H7+, and H9+ first increase and, after passing through a maximum, approach each other. At N =40, they are about the same and more than a factor of 2 and 3 larger than for H11+ and H13+, respectively. For a given neutral cluster size, the intensities of the ion fragments follow a Poisson distribution. The fragmentation probabilities are used to determine the neutral cluster size distribution produced in the expansion at a source temperature of 30.1K and a source pressure of 1.50bar. The distribution shows no clear evidence of a magic number N=13 as predicted by theory and found in experiments with pure para-H2 clusters. The ion fragment distributions are also used to extract information on the internal energy distribution of the H3+ ions produced in the reaction H2++H2?H3++H, which is initiated upon ionization of the cluster. The internal energy is assumed to be rapidly equilibrated and to determine the number of molecules subsequently evaporated. The internal energy distribution found in this way is in good agreement with data obtained in an earlier independent merged beam scattering experiment.
Effect of Particle Size Distribution on Slurry Rheology: Nuclear Waste Simulant Slurries
Energy Technology Data Exchange (ETDEWEB)
Chun, Jaehun; Oh, Takkeun; Luna, Maria L.; Schweiger, Michael J.
2011-07-05
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.
Cloud particle size distributions measured with an airborne digital in-line holographic instrument
Directory of Open Access Journals (Sweden)
J. P. Fugal
2009-03-01
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.
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.
O'Brien, David P
2014-01-01
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.
Vertical profile and aerosol size distribution measurements in Iceland (LOAC)
Dagsson Waldhauserova, Pavla; Olafsson, Haraldur; Arnalds, Olafur; Renard, Jean-Baptiste; Vignelles, Damien; Verdier, Nicolas
2014-05-01
Cold climate and high latitudes regions contain important dust sources where dust is frequently emitted, foremost from glacially-derived sediments of riverbeds or ice-proximal areas (Arnalds, 2010; Bullard, 2013). Iceland is probably the most active dust source in the arctic/sub-arctic region (Dagsson-Waldhauserova, 2013). The frequency of days with suspended dust exceeds 34 dust days annually. Icelandic dust is of volcanic origin; it is very dark in colour and contains sharp-tipped shards with bubbles. Such properties allow even large particles to be easily transported long distances. Thus, there is a need to better understand the spatial and temporal variability of these dusts. Two launch campaigns of the Light Optical Aerosols Counter (LOAC) were conducted in Iceland with meteorological balloons. LOAC use a new optical design that allows to retrieve the size concentrations in 19 size classes between 0.2 and 100 microm, and to provide an estimate of the main nature of aerosols. Vertical stratification and aerosol composition of the subarctic atmosphere was studied in detail. The July 2011 launch represented clean non-dusty season with low winds while the November 2013 launch was conducted during the high winds after dusty period. For the winter flight (performed from Reykjavik), the nature of aerosols strongly changed with altitude. In particular, a thin layer of volcanic dust was observed at an altitude of 1 km. Further LOAC measurements are needed to understand the implication of Icelandic dust to the Arctic warming and climate change. A new campaign of LAOC launches is planned for May 2014. Reference: Arnalds, O., 2010. Dust sources and deposition of aeolian materials in Iceland. Icelandic Agricultural Sciences 23, 3-21. Bullard, J.E., 2013. Contemporary glacigenic inputs to the dust cycle. Earth Surface Processes and Landforms 38, 71-89. Dagsson-Waldhauserova, P., Arnalds O., Olafsson H. 2013. Long-term frequency and characteristics of dust storm events in Northeast Iceland (1949-2011). Atmospheric Environment 77:117-127.
Martín, Miguel Angel; Muñoz, Francisco J.; Reyes, Miguel; Taguas, F. Javier
2014-09-01
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.
Abdul Samad, Noor Asma Fazli; Singh, Ravendra; Sin, Gu?rkan; Gernaey, Krist; Gani, Rafiqul
2011-01-01
Batch cooling crystallization is one of the important unit operations involving separation of solid-liquid phases. Usually the most common crystal product qualities are directly related to the crystal size distribution (CSD). However the main difficulty in batch crystallization is to obtain a uniform and reproducible CSD. Therefore supersaturation control can be applied to drive the process within the metastable zone and thereby enhance the control of the CSD. Although this approach has been ...
Estimating Functions of Distributions Defined over Spaces of Unknown Size
Wolpert, David H
2013-01-01
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...
Directory of Open Access Journals (Sweden)
A. Teimouri Yansari
2010-02-01
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.
Rosin's law and size distribution of particles in regolith like samples—an analysis
Deb, D.; Sen, A. K.
2013-07-01
Rosin's law describes the cumulative distribution of particle size obtained by crushing the solid materials into dusts. Although, this distribution has been found to agree with lunar regolith samples, it should be tested with sufficient amount of experimental data for regolith like samples of known particle size distribution, so that it can be used for various remote sensing applications. In this work, we have tested the applicability of Rosin's distribution by comparing with experimental data for 28 different regolith like samples reported by other authors. Finally we draw a simple interpretation of the Rosin numbers (k and n) in relation to the physical parameters of the samples.
Xianwu, Tang; Haishu, Ding; Guangzhi, Wang; Zhongqi, Liu
2004-01-01
ln this paper, the relationship between surface temperature distribution and internal heat source size of the in-vitro tissue was discussed. The method of obtaining internal heat source information from surface temperature distribution will promote the application of thermography. Through approximation, the relationship between surface temperature distribution and internal beat source size of the in-vitro tissue was induced. The reasonability of the approximation was validated by the high match degree between the template generated by the approximation solution and the practical surface temperature distribution. PMID:17271816
PBO Strainmeters: Distribution, Design and Data Products
Hodgkinson, K.; Anderson, G.; Hasting, M.; Mueller, B.
2004-12-01
PBO will install and operate up to 143 three-component borehole strainmeters and five long-baseline laser strainmeters along the Pacific-North American plate boundary over the next four years. Drilling for the first borehole strainmeter, located in the Cascadia region of Washington, will start in October/November 2004 with instrumentation being installed in early 2005. Installing the first borehole station in Cascadia at that time should allow us to capture the next anticipated silent earthquake on the Cascadia subduction zone. In the second year of PBO, four new borehole strainmeters will be installed at Parkfield, 11 more in the Cascadia region, and up to four on Vancouver Island. The remaining strainmeters will be distributed so as to improve our understanding of tectonic and volcanic processes along the entire plate boundary. Three-component borehole strainmeters (BSM) measure change in diameter of the borehole in 3 directions oriented 120 degrees apart. The 3 measurements are then combined to determine the change in areal and shear strains. The BSMs will be installed at depths of between 150 m and 240 m. Long-baseline laser strainmeters (LSM) measure change in the relative position of end monuments hundreds of meters apart using an unequal-arm Michelson interferometer. The LSMs will be installed on the surface. Each BSM station will have a 2 Hz, 3 component, passive borehole seismometer installed above the strainmeter making the PBO BSM network the second largest borehole seismic network in the world. Each BSM station will monitor pore and atmospheric pressures, and some will monitor rainfall, temperature, wind speed, and relative humidity. Some BSM stations will also be colocated with PBO GPS stations. The BSM data, collected at 20 samples per second (sps), will be buffered on-site and downloaded in near real time to PBO via direct Internet connections, along with environmental data. BSM data will be transferred to a central quality-checking system and then passed to the Strainmeter Analysis and Archive Centers. LSM data, collected at 1 sps, will be buffered on-site and downloaded at least daily to PBO. It will then be sent to Scripps Institution of Oceanography for analysis and to the archives for storage. Strainmeter data analysis will include: instrument calibration, removal of spikes and offsets, identification of strain induced by changes in atmospheric and pore pressure, removal of borehole relaxation trends in BSM data, and production of an earth tide model. Borehole seismic data will likely be sent to the Array Network Facility (ANF) located at Scripps for analysis, quality-checking, distribution and arching. The ANF also process and analyses data for the USArray arm of EarthScope. PBO strain data products will be divided into 3 levels. The raw data will be considered the Level 0 product. Level 1 data will consist of clean, scaled, gauge data. The Level 2 data set will contain derived products: areal and shear strains, tidal and pressure corrections. Level 2 data will be further divided into 3 sub-levels ranging from a rapid solution produced every 24 hours to a final verified data set updated every 3 months. The data will be available in XML and SEED format from the EarthScope Data Access System. Metadata such as site information and scale factors will be retrievable from the PBO Operational Database.
Voss, Benjamin; Haase, Markus
2013-12-23
We have studied the Ostwald ripening of colloids containing nanocrystals of two different crystal phases of the same material. Ostwald ripening in such polymorphic systems is shown to result in an intrinsic focusing of the particle size distribution of the thermodynamically preferred phase while the particles of the less stable phase completely dissolve. Experimentally, a colloidal system of this kind was realized by mixing small NaEuF4 nanocrystals of the cubic ?-phase with particles of the hexagonal ?-phase having the same mean size and size distribution. The temporal evolution of the particle sizes of both phases can be understood and numerically simulated within the framework of LSW theory. The simulations show that small differences in the bulk solubility or the surface energy of the two phases are sufficient to explain the experimentally observed narrowing of the particle size distribution. PMID:24206197
Evolutionary implications of a power-law distribution of protein family sizes
Bader, J S
1999-01-01
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.
Demystifying Crystal Size Distribution (CSD): A Comparison of Methodologies Using Eucrite Meteorites
Jaret, S. J.; Mayne, R. G.; McSween, H. Y.
2008-03-01
Crystal size distribution (CSD) of eucrite meteorites was performed using three methods of converting 2D thin section measurements into 3D estimates. Methods were compared to determine the effect of 3D correction on interpretation of growth history.
Dong, Lili; Su, Mingxu; Xue, Minghua; Cai, Xiaoshu; Shang, Zhitao
2007-06-01
The determination of particle size distribution in concentrated polydisperse fat emulsions measured by ultrasonic attenuation spectrum is studied in this paper. Based on theoretical analysis, ultrasonic attenuation spectrum of fat emulsion samples containing different droplet concentrations (1˜20%) is measured over the range of 2˜13MHz. Then the droplet size and distribution are determined by processing the experiment data with inversion arithmetic. The particle size distribution of original sample determined by ultrasonic spectrum gives excellent agreement with that of diluted sample measured by an optical instrument TSM(Totally Scattering Measurement). This indicates that ultrasonic spectrum is capable of determining the particle size distribution and dispersed-phase volume fraction of concentrated fat emulsions in a non-destructive approach.
Mazumder, M. K.; Biris, A. S.; Trigwell, S.; Calle, C. I.; Buhler, C. R.
2003-03-01
Measurements of triboelectrically charged Martian simulant were taken using the E-SPART Analyzer providing both the size and charge distributions of the particles after contact with stainless steel beads.
Berman, D. C.; Crown, D. A.; Joseph, E. C. S.
2011-03-01
Categorized crater size-frequency distributions (SFD) of small craters (~25 m-1 km diameter) in Deuteronilus Mensae, Mars provide new insights into the erosional and depositional histories of geologic units as well as refinements of formation ages.
Fienen, Michael N.; Selbig, William R.
2012-01-01
A new sample collection system was developed to improve the representation of sediment entrained in urban storm water by integrating water quality samples from the entire water column. The depth-integrated sampler arm (DISA) was able to mitigate sediment stratification bias in storm water, thereby improving the characterization of suspended-sediment concentration and particle size distribution at three independent study locations. Use of the DISA decreased variability, which improved statistical regression to predict particle size distribution using surrogate environmental parameters, such as precipitation depth and intensity. The performance of this statistical modeling technique was compared to results using traditional fixed-point sampling methods and was found to perform better. When environmental parameters can be used to predict particle size distributions, environmental managers have more options when characterizing concentrations, loads, and particle size distributions in urban runoff.
Enhanced resolution particle size distributions by multiple angle photon correlation spectroscopy
Bott, Steven E.
1989-01-01
Photon correlation spectroscopy (PCS) has become a method of choice for measuring submicrometer particles. It is capable of rapid, accurate measurements of mean particle size. Since the measurements are nonperturbing, it is ideal for monitoring systems undergoing dynamic changes. Despite its widespread acceptance, the information content of PCS measurements for particle size distributions is low and provides limited resolution. A method is presented whereby PCS measurements made at several scattering angles plus the angular distribution of light scattered from the particles are combined in a single simultaneous analysis to effect an enhanced resolution particle size distribution. The efficacy of the method is assessed by recovering size distributions from computer simulated data and by comparisons of conventional PCS measurements of polystyrene spheres with those made by the new method.
Surface modification and particles size distribution control in nano-CdS/polystyrene composite film
International Nuclear Information System (INIS)
Preparation of nano-CdS particles with surface thiol modification by microemulsion method and their influences on the particle size distribution in highly filled polystyrene-based composites were studied. The modified nano-CdS was characterized by X-ray photoelectron spectroscopy (XPS), light absorption and emission measurements to reveal the morphologies of the surface modifier, which are consistent with the surface molecules packing calculation. The morphologies of the surface modifier exerted a great influence not only on the optical performance of the particles themselves, but also on the size distribution of the particle in polystyrene matrix. A monolayer coverage with tightly packed thiol molecules was believed to be most effective in promoting a uniform particle size distribution and eliminating the surface defects that cause radiationless recombination. Control of the particles size distribution in polystyrene can be attained by adjusting surface coverage status of the thiol molecules based on the strong interaction between the surface modifier and the matrix
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...
Ripening and Focusing of Aggregate Size Distributions with Overall Volume Growth
Vollmer, J; Rohloff, M
2014-01-01
We explore the evolution of the aggregate size distribution in systems where aggregates grow by diffusive accretion of mass. Supersaturation is controlled in such a way that the overall aggregate volume grows linearly in time. Classical Ostwald ripening, which is recovered in the limit of vanishing overall growth, constitutes an unstable solution of the dynamics. In the presence of overall growth evaporation of aggregates always drives the dynamics into a new, qualitatively different growth regime where ripening ceases, and growth proceeds at a constant number density of aggregates. We provide a comprehensive description of the evolution of the aggregate size distribution in the constant density regime: the size distribution does not approach a universal shape, and even for moderate overall growth rates the standard deviation of the aggregate radius decays monotonically. The implications of this theory for the focusing of aggregate size distributions are discussed for a range of different settings including t...
Magnetic pattern at supergranulation scale: the Void Size Distribution
Berrilli, Francesco; Del Moro, Dario
2014-01-01
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.
International Nuclear Information System (INIS)
This study describes methods developed for reliable quantification of size- and element-specific release of engineered nanoparticles (ENP) from consumer spray products. A modified glove box setup was designed to allow controlled spray experiments in a particle-minimized environment. Time dependence of the particle size distribution in a size range of 10-500 nm and ENP release rates were studied using a scanning mobility particle sizer (SMPS). In parallel, the aerosol was transferred to a size-calibrated electrostatic TEM sampler. The deposited particles were investigated using electron microscopy techniques in combination with image processing software. This approach enables the chemical and morphological characterization as well as quantification of released nanoparticles from a spray product. The differentiation of solid ENP from the released nano-sized droplets was achieved by applying a thermo-desorbing unit. After optimization, the setup was applied to investigate different spray situations using both pump and gas propellant spray dispensers for a commercially available water-based nano-silver spray. The pump spray situation showed no measurable nanoparticle release, whereas in the case of the gas spray, a significant release was observed. From the results it can be assumed that the homogeneously distributed ENP from the original dispersion grow in size and change morphology during and after the spray process but still exist as nanometer particles of size <100 nmist as nanometer particles of size <100 nm. Furthermore, it seems that the release of ENP correlates with the generated aerosol droplet size distribution produced by the spray vessel type used. This is the first study presenting results concerning the release of ENP from spray products.
Mächtle, W
1999-02-01
Sedimentation velocity is a powerful tool for the analysis of complex solutions of macromolecules. However, sample turbidity imposes an upper limit to the size of molecular complexes currently amenable to such analysis. Furthermore, the breadth of the particle size distribution, combined with possible variations in the density of different particles, makes it difficult to analyze extremely complex mixtures. These same problems are faced in the polymer industry, where dispersions of latices, pigments, lacquers, and emulsions must be characterized. There is a rich history of methods developed for the polymer industry finding use in the biochemical sciences. Two such methods are presented. These use analytical ultracentrifugation to determine the density and size distributions for submicron-sized particles. Both methods rely on Stokes' equations to estimate particle size and density, whereas turbidity, corrected using Mie's theory, provides the concentration measurement. The first method uses the sedimentation time in dispersion media of different densities to evaluate the particle density and size distribution. This method works provided the sample is chemically homogeneous. The second method splices together data gathered at different sample concentrations, thus permitting the high-resolution determination of the size distribution of particle diameters ranging from 10 to 3000 nm. By increasing the rotor speed exponentially from 0 to 40,000 rpm over a 1-h period, size distributions may be measured for extremely broadly distributed dispersions. Presented here is a short history of particle size distribution analysis using the ultracentrifuge, along with a description of the newest experimental methods. Several applications of the methods are provided that demonstrate the breadth of its utility, including extensions to samples containing nonspherical and chromophoric particles. PMID:9916040
Mächtle, W
1999-01-01
Sedimentation velocity is a powerful tool for the analysis of complex solutions of macromolecules. However, sample turbidity imposes an upper limit to the size of molecular complexes currently amenable to such analysis. Furthermore, the breadth of the particle size distribution, combined with possible variations in the density of different particles, makes it difficult to analyze extremely complex mixtures. These same problems are faced in the polymer industry, where dispersions of latices, pigments, lacquers, and emulsions must be characterized. There is a rich history of methods developed for the polymer industry finding use in the biochemical sciences. Two such methods are presented. These use analytical ultracentrifugation to determine the density and size distributions for submicron-sized particles. Both methods rely on Stokes' equations to estimate particle size and density, whereas turbidity, corrected using Mie's theory, provides the concentration measurement. The first method uses the sedimentation time in dispersion media of different densities to evaluate the particle density and size distribution. This method works provided the sample is chemically homogeneous. The second method splices together data gathered at different sample concentrations, thus permitting the high-resolution determination of the size distribution of particle diameters ranging from 10 to 3000 nm. By increasing the rotor speed exponentially from 0 to 40,000 rpm over a 1-h period, size distributions may be measured for extremely broadly distributed dispersions. Presented here is a short history of particle size distribution analysis using the ultracentrifuge, along with a description of the newest experimental methods. Several applications of the methods are provided that demonstrate the breadth of its utility, including extensions to samples containing nonspherical and chromophoric particles. PMID:9916040
Distribution Functions of Sizes and Fluxes Determined from Supra-Arcade Downflows
McKenzie, David E; 10.1088/2041-8205/735/1/L6
2011-01-01
The frequency distributions of sizes and fluxes of supra-arcade downflows (SADs) provide information about the process of their creation. For example, a fractal creation process may be expected to yield a power-law distribution of sizes and/or fluxes. We examine 120 cross-sectional areas and magnetic flux estimates found by Savage & McKenzie for SADs, and find that (1) the areas are consistent with a log-normal distribution and (2) the fluxes are consistent with both a log-normal and an exponential distribution. Neither set of measurements is compatible with a power-law distribution nor a normal distribution. As a demonstration of the applicability of these findings to improved understanding of reconnection, we consider a simple SAD growth scenario with minimal assumptions, capable of producing a log-normal distribution.
Notes on representing grain size distributions obtained by electron backscatter diffraction
International Nuclear Information System (INIS)
Grain size distributions measured by electron backscatter diffraction are commonly represented by histograms using either number or area fraction definitions. It is shown here that they should be presented in forms of density distribution functions for direct quantitative comparisons between different measurements. Here we make an interpretation of the frequently seen parabolic tales of the area distributions of bimodal grain structures and a transformation formula between the two distributions are given in this paper. - Highlights: • Grain size distributions are represented by density functions. • The parabolic tales corresponds to equal number of grains in a bin of the histogram. • A simple transformation formula is given to number and area weighed distributions. • The particularities of uniform and lognormal distributions are examined
Notes on representing grain size distributions obtained by electron backscatter diffraction
Energy Technology Data Exchange (ETDEWEB)
Toth, Laszlo S., E-mail: laszlo.metz@univ-lorraine.fr [Laboratoire d' Etude des Microstructures et de Mécanique des Matériaux (LEM3), UMR 7239, CNRS/Université de Lorraine, F-57045 Metz (France); Laboratory of Excellence on Design of Alloy Metals for low-mAss Structures (DAMAS), Université de Lorraine (France); Biswas, Somjeet, E-mail: somjeetbiswas@gmail.com [Laboratory of Excellence on Design of Alloy Metals for low-mAss Structures (DAMAS), Université de Lorraine (France); Gu, Chengfan, E-mail: chengfan.gu@unsw.edu.au [School of Materials Science and Engineering, The University of New South Wales, Sydney, NSW 2052 (Australia); Beausir, Benoit, E-mail: benoit.beausir@univ-lorraine.fr [Laboratoire d' Etude des Microstructures et de Mécanique des Matériaux (LEM3), UMR 7239, CNRS/Université de Lorraine, F-57045 Metz (France); Laboratory of Excellence on Design of Alloy Metals for low-mAss Structures (DAMAS), Université de Lorraine (France)
2013-10-15
Grain size distributions measured by electron backscatter diffraction are commonly represented by histograms using either number or area fraction definitions. It is shown here that they should be presented in forms of density distribution functions for direct quantitative comparisons between different measurements. Here we make an interpretation of the frequently seen parabolic tales of the area distributions of bimodal grain structures and a transformation formula between the two distributions are given in this paper. - Highlights: • Grain size distributions are represented by density functions. • The parabolic tales corresponds to equal number of grains in a bin of the histogram. • A simple transformation formula is given to number and area weighed distributions. • The particularities of uniform and lognormal distributions are examined.
DISTRIBUTION FUNCTIONS OF SIZES AND FLUXES DETERMINED FROM SUPRA-ARCADE DOWNFLOWS
International Nuclear Information System (INIS)
The frequency distributions of sizes and fluxes of supra-arcade downflows (SADs) provide information about the process of their creation. For example, a fractal creation process may be expected to yield a power-law distribution of sizes and/or fluxes. We examine 120 cross-sectional areas and magnetic flux estimates found by Savage and McKenzie for SADs, and find that (1) the areas are consistent with a log-normal distribution and (2) the fluxes are consistent with both a log-normal and an exponential distribution. Neither set of measurements is compatible with a power-law distribution nor a normal distribution. As a demonstration of the applicability of these findings to improved understanding of reconnection, we consider a simple SAD growth scenario with minimal assumptions, capable of producing a log-normal distribution.
Chan, T. W.; Mozurkewich, M.
2007-01-01
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...
Size distributions, sources and source areas of water-soluble organic carbon in urban background air
Timonen, H.; Saarikoski, S.; Tolonen-kivima?ki, O.; Aurela, M.; Saarnio, K.; Peta?ja?, T.; Aalto, P. P.; Kulmala, M.; Pakkanen, T.; Hillamo, R.
2008-01-01
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,...
Directory of Open Access Journals (Sweden)
BACCHI O.O.S.
1996-01-01
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.
The size distribution of galaxies in the Sloan Digital Sky Survey
Shen, Shiyin; Mo, H. J.; White, Simon D. M.; Blanton, Michael R.; Kauffmann, Guinevere; Voges, Wolfgang; Brinkmann, J.; Csabai, Istvan
2003-01-01
abridged: We use a complete sample of about 140,000 galaxies from the Sloan Digital Sky Survey (SDSS) to study the size distribution of galaxies and its dependence on their luminosity, stellar mass, and morphological type. The large SDSS database provides statistics of unprecedented accuracy. For each type of galaxy, the size distribution at given luminosity (or stellar mass) is well described by a log-normal function, characterized by its median $\\bar{R}$ and dispersion $\\s...
Research of CWS’ Particle Size Distribution based on Ultrasonic Attenuation Theory
Wang, Weidong; Zhang, Chenglian; Chu, Fengge
2010-01-01
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...
Remote sensing of water cloud droplet size distributions using the backscatter glory: a case study
Mayer, B.; Schro?der, M.; Preusker, R.; Schu?ller, L.
2004-01-01
Cloud single scattering properties are mainly determined by the effective radius of the droplet size distribution. There are only few exceptions where the shape of the size distribution affects the optical properties, in particular the rainbow and the glory directions of the scattering phase function. Using observations by the Compact Airborne Spectrographic Imager (CASI) in 180° backscatter geometry, we found that high angular resolution aircraft observations of the glory provide uni...
Smyth, Hugh D. C.
2003-01-01
The purpose of this research was to investigate the measurement and in vitro delivery implications of multimodal distributions, occurring near or in the respirable range, emitted from pressurized metered-dose inhalers (pMDIs). Particle size distributions of solution pMDIs containing hydrofluoroalkane-134a (HFA-134a) and ethanol were evaluated using 2 complementary particle-sizing methods: laser diffraction (LD) and cascade impaction (CI). Solution pMDIs were formulated from mixtures of HFA-13...
Ormel, C. W.; Min, M.; Tielens, A. G. G. M.; Dominik, C.; Paszun, D.
2011-01-01
The dust size distribution in molecular clouds can be strongly affected by ice-mantle formation and (subsequent) grain coagulation. Following previous work where the dust size distribution has been calculated from a state-of-the art collision model for dust aggregates that involves both coagulation and fragmentation (Paper I), the corresponding opacities are presented in this study. The opacities are calculated by applying the effective medium theory assuming that the dust aggregates...
A simple technique to determine the size distribution of nuclear crater fallback and ejecta
International Nuclear Information System (INIS)
This report describes the results of an investigation to find an economic method for determining the block size distribution of nuclear crater fallback and ejecta. It is shown that the modal analysis method of determining relative proportions can be applied with the use of a special sampling technique, to provide a size distribution curve for clastic materials similar to one obtainable by sieving and weighing the same materials
Mu Azu, Mohammed Abdullahi
2007-01-01
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...
David, C.; Bekki, S.; Jumelet, J.; Keckhut, P.
2008-01-01
A method for estimating the stratospheric particle size distribution from multiwavelength lidar measurements is presented. It is based on matching measured and model-simulated backscatter coefficients. The lidar backscatter coefficients measured at the three commonly used wavelengths 355, 532 and 1064 nm are compared to a precomputed look-up table of model-calculated values. The optical model assumes that particles are spherical and that their size distribution is unimodal. This inverse probl...
Horoshenkov, K. V.; Attenborough, Keith; Chandler-wilde, S. N.
1998-01-01
Expressions for the viscosity correction function, and hence bulk complex impedance, density, compressibility, and propagation constant, are obtained for a rigid frame porous medium whose pores are prismatic with ?xed cross-sectional shape, but of variable pore size distribution. The lowand high-frequency behavior of the viscosity correction function is derived for the particular case of a log-normal pore size distribution, in terms of coef?cients which can, in general, be computed num...
Numerical Model to Predict Wax Crystal Size Distribution in Solvent Dewaxing Unit
Mokhlif, Nassir D.; Al-kayiem, Hussain H.; Masri Bin Baharom
2014-01-01
A mathematical model was implemented to predict the wax crystal size distribution of distillate lube oil SN500. The model solved the coupled equations for the heat transfer and moments of the population balance numerically. The predicted temperatures and wax crystal size distributions were validated with actual unit database and experimental measurements. The kinetics of the wax crystallization considered only the nucleation and crystal growth. N-alkanes from n-C22 to n-C36 were tested to sel...
On the Coagulation and Size Distribution of Pressure Confined Cores
Huang, Xu; Zhou, Tingtao; Lin, D. N. C.
2013-05-01
Observations of the Pipe Nebula have led to the discovery of dense starless cores. The mass of most cores is too small for their self-gravity to hold them together. Instead, they are thought to be pressure confined. The observed dense cores' mass function (CMF) matches well with the initial mass function of stars in young clusters. Similar CMFs are observed in other star forming regions such as the Aquila Nebula, albeit with some dispersion. The shape of these CMF provides important clues to the competing physical processes which lead to star formation and its feedback on the interstellar media. In this paper, we investigate the dynamical origin of the mass function of starless cores which are confined by a warm, less dense medium. In order to follow the evolution of the CMF, we construct a numerical method to consider the coagulation between the cold cores and their ablation due to Kelvin-Helmholtz instability induced by their relative motion through the warm medium. We are able to reproduce the observed CMF among the starless cores in the Pipe Nebula. Our results indicate that in environment similar to the Pipe Nebula: (1) before the onset of their gravitational collapse, the mass distribution of the progenitor cores is similar to that of the young stars, (2) the observed CMF is a robust consequence of dynamical equilibrium between the coagulation and ablation of cores, and (3) a break in the slope of the CMF is due to the enhancement of collisional cross section and suppression of ablation for cores with masses larger than the cores' Bonnor-Ebert mass.
A facile synthesis of Te nanoparticles with binary size distribution by green chemistry
He, Weidong; Krejci, Alex; Lin, Junhao; Osmulski, Max E.; Dickerson, James H.
2011-04-01
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
Demographic properties shape tree size distribution in a malaysian rain forest.
Kohyama, Takashi S; Potts, Matthew D; Kohyama, Tetsuo I; Kassim, Abd Rahman; Ashton, Peter S
2015-03-01
Abstract Different mechanisms have been proposed to explain how vertical and horizontal heterogeneity in light conditions enhances tree species coexistence in forest ecosystems. The foliage partitioning theory proposes that differentiation in vertical foliage distribution, caused by an interspecific variation in mortality-to-growth ratio, promotes stable coexistence. In contrast, successional niche theory posits that horizontal light heterogeneity, caused by gap dynamics, enhances species coexistence through an interspecific trade-off between growth rate and survival. To distinguish between these theories of species coexistence, we analyzed tree inventory data for 370 species from the 50-ha plot in Pasoh Forest Reserve, Malaysia. We used community-wide Bayesian models to quantify size-dependent growth rate and mortality of every species. We compared the observed size distributions and the projected distributions from size-dependent demographic rates. We found that the observed size distributions were not simply correlated with the rate of population increase but were related to demographic properties such as size growth rate and mortality. Species with low relative abundance of juveniles in size distribution showed high growth rate and low mortality at small tree sizes and low per-capita recruitment rate. Overall, our findings were in accordance with those predicted by foliage partitioning theory. PMID:25674691
Multimodal size distributions of {gamma}' precipitates during continuous cooling of UDIMET 720 Li
Energy Technology Data Exchange (ETDEWEB)
Radis, R., E-mail: rene.radis@tugraz.at [Christian Doppler Laboratory for ' Early Stages of Precipitation' , Vienna University of Technology, Favoritenstrasse 9-11, A-1040 Vienna (Austria)] [Institute for Materials Science and Welding, Graz University of Technology, Kopernikusgasse 24, A-8010 Graz (Austria); Schaffer, M.; Albu, M.; Kothleitner, G.; Poelt, P. [Research Institute for Electron Microscopy, Graz University of Technology, Steyrergasse 17, A-8010 Graz (Austria); Kozeschnik, E. [Christian Doppler Laboratory for ' Early Stages of Precipitation' , Vienna University of Technology, Favoritenstrasse 9-11, A-1040 Vienna (Austria)] [Materials Center Leoben Forschung GmbH, Roseggerstrasse 12, A-8700 Leoben (Austria)] [Institute of Materials Science and Technology, Vienna University of Technology, Favoritenstrasse 9-11, A-1040 Vienna (Austria)
2009-11-15
The technological properties of many nickel-based superalloys originate in the morphology and distribution of Ni{sub 3}(Al, Ti) particles ({gamma}' precipitates). Starting from the solution-annealed condition, the distribution and the morphology of {gamma}' precipitates are investigated experimentally during continuous cooling of the nickel-base superalloy UDIMET 720 Li. Characterization of the precipitates is carried out by scanning electron microscopy and energy-filtered transmission electron microscopy investigations. Depending on cooling rate, monomodal, bimodal and even trimodal size distributions are observed. The experimental observations of the size distributions are confirmed by numerical simulations of the {gamma}' precipitation kinetics. The theoretical background for occurrence of multimodal size distributions during continuous cooling is discussed.
Placement and Sizing of DG Using PSO&HBMO Algorithms in Radial Distribution Networks
Directory of Open Access Journals (Sweden)
M. A.Taghikhani
2012-09-01
Full Text Available Optimal placement and sizing of DG in distribution network is an optimization problem with continuous and discrete variables. Many researchers have used evolutionary methods for finding the optimal DG placement and sizing. This paper proposes a hybrid algorithm PSO&HBMO for optimal placement and sizing of distributed generation (DG in radial distri-bution system to minimize the total power loss and improve the voltage profile. The proposed method is tested on a standard 13 bus radial distribution system and simulation results carried out using MATLAB software. The simulation results indicate that PSO&HBMO method can obtain better results than the simple heuristic search method and PSO algorithm. The method has a potential to be a tool for identifying the best location and rating of a DG to be installed for improving voltage profile and line losses reduction in an electrical power system. Moreover, current reduction is obtained in distribution system.
Size distribution of spray droplets from simple two-fluid nozzle
Energy Technology Data Exchange (ETDEWEB)
Stakic, M.B. [Inst. of Nuclear Sciences VINCA, Belgrade (Yugoslavia). Lab. for Thermal Engineering and Energy
1995-12-31
The results of the investigation of the performance characteristics of two-fluid nozzle (a type of simple pneumatic nozzle) are shown in this paper. A comparison of the drop-size distribution for the conditions studied. Studies were carried out of the effect of nozzle internal diameter, exit orifices` diameters, feed rate and gas pressure on droplet size distribution. In all experiments performed, air has been used as a gas phase, and 3% solution of nigrosine in water as a liquid phase. After detailed analysis of existing droplet sampling techniques, immersion sampling technique was accepted. Solution was sprayed into small cells, with glass bottom, filled with kerosene, positioned at the several distances from the nozzle. Results obtained were processed using different size distribution functions (experimental: Nukiyama-Tanasawa, Rosin-Rammler, Mugele-Evans, and theoretical: Gaussian, logarithmic, Gamma, etc.), by calculating adequate parameters for each distribution function. The most appropriate agreement of experimental results was obtained by Nukiyama-Tanasawa and Gamma size distribution functions. The Sauter mean diameter was also calculated and compared with the same diameter obtained from different size distribution functions. An equation is recommended for estimation of droplet size (Sauter mean diameter) under different nozzle working conditions. Preliminary experimental investigations, have shown that direct incineration of liquid fuels can be performed in a fluidized bed by means of a simple pneumatic two-fluid nozzle. That was the main reason for carrying out this investigation.
Fat globule size distribution in milk of a German buffalo herd
Thiele, M.; Swalve, H. H.; Schmidt, R.; Schafberg, R.
2010-01-01
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.
Fat globule size distribution in milk of a German buffalo herd
Directory of Open Access Journals (Sweden)
M. Thiele
2010-02-01
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.
The Effect of Mineralization on Pore-size Distribution Patterns in Sandstone
Emmanuel, S.; Ague, J. J.
2008-12-01
In geological media, pore-size distributions can strongly influence important physical parameters such as permeability and specific surface area. Mineralization in rock and soil often reduces the overall porosity and can also induce changes in the distribution of pore sizes. However, the way in which mineralization affects pore size is poorly understood, with relatively little data available from field-based studies. Here, we present a high-resolution profile of pore-size distributions from a variably mineralized sandstone section. The samples were obtained from a Barents Sea core in which quartz cement had preferentially precipitated around stylolite (pressure solution) interfaces; pore-size distributions were measured in 15 samples using mercury injection porosimetry. The results demonstrate that mineralization led to a reduction in porosity of around 40% in samples closest to the stylolite. However, this reduction was not uniform over the range of pore-sizes: the greatest level of porosity reduction occurred in the 10-5-10-4 m size range, while there was no discernible change in the porosity associated with smaller pores. A reactive transport model - simulating the dissolution of quartz at the stylolite interface and subsequent reprecipitation in the rock matrix - was used to predict the evolution of the porosity associated with multiple pore-sizes; the model was successfully able to reproduce the observed porosity patterns, indicating that such an approach could be integrated into efforts to model the evolution of porosity in geological formations, including during CO2 sequestration.
Effects of Particle Size Distribution on the Burn Ability of Limestone
Suleiman, Ismaila E.; Abubakar, Abdulkareem; Otuoze, Hassan S.; Suleiman, Mejidi A.; Momoh, Raheem O.; Aliyu, Sadiq N.
2013-01-01
The effect of particle size reduction on the burn ability of Limestone was investigated using the limestone obtained from Obajana Cement Mines. Limestone samples were grinded and were classified into following particles size distribution: 90µm, 200µm, 250µm and 500µm graduated in different sieve sizes. The decomposition rates of these samples were monitored under the same temperature condition in a pre-heated furnace of 1000°C and at constant time interval of 0-35 minutes. From the resul...
La Hera, Esther; Go?mez, Manuel; Rosell, Cristina M.
2013-01-01
Rice flour is becoming very attractive as raw material, but there is lack of information about the influence of particle size on its functional properties and starch digestibility. This study evaluates the degree of dependence of the rice flour functional properties, mainly derived from starch behavior, with the particle size distribution. Hydration properties of flours and gels and starch enzymatic hydrolysis of individual fractions were assessed. Particle size heterogeneity on rice flour si...
Guzmán, G.; Gómez, J. A.; Giráldez, J. V.
2010-05-01
Soil particle size distribution has been traditionally determined by the hydrometer or the sieve-pipette methods, both of them time consuming and requiring a relatively large soil sample. This might be a limitation in situations, such as for instance analysis of suspended sediment, when the sample is small. A possible alternative to these methods are the optical techniques such as laser diffractometry. However the literature indicates that the use of this technique as an alternative to traditional methods is still limited, because the difficulty in replicating the results obtained with the standard methods. In this study we present the percentages of soil grain size determined using laser diffractometry within ranges set between 0.04 - 2000 ?m. A Beckman-Coulter ® LS-230 with a 750 nm laser beam and software version 3.2 in five soils, representative of southern Spain: Alameda, Benacazón, Conchuela, Lanjarón and Pedrera. In three of the studied soils (Alameda, Benacazón and Conchuela) the particle size distribution of each aggregate size class was also determined. Aggregate size classes were obtained by dry sieve analysis using a Retsch AS 200 basic ®. Two hundred grams of air dried soil were sieved during 150 s, at amplitude 2 mm, getting nine different sizes between 2000 ?m and 10 ?m. Analyses were performed by triplicate. The soil sample preparation was also adapted to our conditions. A small amount each soil sample (less than 1 g) was transferred to the fluid module full of running water and disaggregated by ultrasonication at energy level 4 and 80 ml of sodium hexametaphosphate solution during 580 seconds. Two replicates of each sample were performed. Each measurement was made for a 90 second reading at a pump speed of 62. After the laser diffractometry analysis, each soil and its aggregate classes were processed calibrating its own optical model fitting the optical parameters that mainly depends on the color and the shape of the analyzed particle. As a second alternative a unique optical model valid for a broad range of soils developed by the Department of Soil, Water, and Environmental Science of the University of Arizona (personal communication, already submitted) was tested. The results were compared with the particle size distribution measured in the same soils and aggregate classes using the hydrometer method. Preliminary results indicate a better calibration of the technique using the optical model of the Department of Soil, Water, and Environmental Science of the University of Arizona, which obtained a good correlations (r2>0.85). This result suggests that with an appropriate calibration of the optical model laser diffractometry might provide a reliable soil particle characterization.
Particle size distributions from laboratory-scale biomass fires using fast response instruments
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S. Hosseini
2010-08-01
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 PM_{10}. 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.
Lavarello, Roberto; Oelze, Michael
2012-09-01
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
Sahagian, D. L.; Proussevitch, A. A.; Mulukutla, G. K.; Genareau, K.
2010-12-01
We have conducted an analysis of bubble (BSD) and ash particle (PSD) size distributions for ashes from two contrasting eruptions. The first is the May, 1980 eruption of Mt. St. Helens (MSH), a dacitic plinian eruption that spread ash over a large area of the Western U.S. The second is the basaltic sub-plinian 1974 eruption of Fuego (Guatemala), which was confined to local deposition with less variation of ash PSDs. Four successive small explosive eruptions of Fuego produced less than 0.02 km3 of dense rock equivalent (DRE) in a dispersal area of 80 km from the volcano. In contrast, the May 1980 plinian eruption of Mount St. Helens resulted in a distal fallout leading to a large subaerial ash deposit as far away as 325 km from the volcano. Pyroclastic flows added extensive fine material to the eruption column resulting in extensive ash dispersal. MSH samples were collected from a range of distances away from the vent, while collection of samples from Fuego was limited to nearer regions due to the lesser dispersal of the ash. Technique- Stereo SEM analysis of BSD of eruptions products (ash) to determine the pre-fragmentation properties of ash-producing magma bodies. This information is normally considered lost due to fragmentation of bubbles in late stages of eruptions. However, using SSEM, we have devised a technique to determine the pre-fragmentation BSDs that reflect the conduit processes of bubble nucleation and growth, and magma rise history. Using standard off-the-shelf software (Alicona MeX) to create Digital Elevation Models (DEMs) of individual ash particles, we built a database of ash surface characteristics. These surfaces include imprints of bubbles that exploded during fragmentation. We use the curvature of these imprints to reconstruct the complete bubbles, using newly developed software we call “Bubblemaker” that extrapolates the measured DEMs using best-fit ellipsoids of revolution (not necessarily spherical). We have now reconstructed the bubble volumes. These data are used in turn to characterize the statistical parameters of the bubble population, including size distribution, distribution function type (log-normal), its moments, and bubble number density. Our results show that the silicic energetic MSH eruption ashes contain smaller bubbles and higher number densities than do the ashes collected from the more basaltic Fuego eruption. From these results, it is possible to speculate regarding eruption processes. It appears that within a single eruption, there is relatively little variability of bubble sizes as a function of depositional distance from the vent, although other ash characteristics such as PSD vary more strongly with distance.
Size distributions, sources and source areas of water-soluble organic carbon in urban background air
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H. Timonen
2008-04-01
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 PM_{1} mass and the PM_{1?10} mass, respectively. Inorganic ions contributed 33±12% and 28±19% of the analyzed PM_{1} and PM_{1?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.
Munchak, Stephen Joseph; Kummerow, Christian; Elsaesser, Gregory
2013-01-01
Variability in the raindrop sized distribution (DSD) has long been recognized as a source of uncertainty in relationships between radar reflectivity Z and rain rate R. In this study, we analyze DSD retrievals from two years of data gathered by the Tropical Rainfall Measuring Mission (TRMM) satellite and processed with a combined radar-radiometer retrieval algorithm over the global oceans equatorward of 35?. Numerous variables describing properties of each reflectivity profile, large-scale organization, and the background environment are examined for relationships to the reflectivity-normalized median drop diameter, epsilonDSD. In general, we find that higher freezing levels and relative humidities are associated with smaller epsilonDSD. Within a given environment, the mesoscale organization of precipitation and the vertical profile of reflectivity are associated with DSD characteristics. In the tropics, the smallest epsilonDSD values are found in large but shallow convective systems, where warm rain formation processes are thought to be predominant, whereas larger sizes are found in the stratiform regions of organized deep convection. In the extratropics, the largest epsilonDSD values are found in the scattered convection that occurs when cold, dry continental air moves over the much warmer ocean after the passage of a cold front. The geographical distribution of the retrieved DSDs is consistent with many of the observed regional Z-R relationships found in the literature as well as discrepancies between the TRMM radar-only and radiometer-only precipitation products. In particular, mid-latitude and tropical regions near land tend to have larger drops for a given reflectivity, whereas the smallest drops are found in the eastern Pacific Intertropical Convergence Zone.
A POSSIBLE DIVOT IN THE SIZE DISTRIBUTION OF THE KUIPER BELT'S SCATTERING OBJECTS
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Shankman, C.; Gladman, B. J. [Department of Physics and Astronomy, University of British Columbia, 6224 Agriculture Road, Vancouver, BC V6T 1Z1 (Canada); Kaib, N. [Department of Physics and Astronomy, Queens University (Canada); Kavelaars, J. J. [National Research Council of Canada, Victoria, BC V9E 2E7 (Canada); Petit, J. M. [Institut UTINAM, CNRS-Universite de Franche-Comte, Besancon (France)
2013-02-10
Via joint analysis of a calibrated telescopic survey, which found scattering Kuiper Belt objects, and models of their expected orbital distribution, we explore the scattering-object (SO) size distribution. Although for D > 100 km the number of objects quickly rise as diameters decrease, we find a relative lack of smaller objects, ruling out a single power law at greater than 99% confidence. After studying traditional ''knees'' in the size distribution, we explore other formulations and find that, surprisingly, our analysis is consistent with a very sudden decrease (a divot) in the number distribution as diameters decrease below 100 km, which then rises again as a power law. Motivated by other dynamically hot populations and the Centaurs, we argue for a divot size distribution where the number of smaller objects rises again as expected via collisional equilibrium. Extrapolation yields enough kilometer-scale SOs to supply the nearby Jupiter-family comets. Our interpretation is that this divot feature is a preserved relic of the size distribution made by planetesimal formation, now ''frozen in'' to portions of the Kuiper Belt sharing a ''hot'' orbital inclination distribution, explaining several puzzles in Kuiper Belt science. Additionally, we show that to match today's SO inclination distribution, the supply source that was scattered outward must have already been vertically heated to the of order 10 Degree-Sign .
Analysis of particle size distribution effects on the pipeline transportation of coal slurry fuels
Energy Technology Data Exchange (ETDEWEB)
Dabak, T.; Yucel, O.
1988-10-01
A methodology is proposed for determining the optimum particle size distribution of a highly concentrated suspension that will yield the lowest combined energy consumption for comminution and pumping of a specified annual throughput in pipe of specified size and length. A summary is presented on the physically based approach used in the development of a basic rheologic formulation and the computational procedures that facilitate the optimization methodology described. Finally, some of the results obtained from the calculations made for a highly concentrated coal slurry are presented to demonstrate the significance of the particle size distribution in these rheologic analyses and the viability of the concept of optimization. 11 figs., 18 refs., 3 tabs.
The Influence of Wildfires on Aerosol Size Distributions in Rural Areas
Alonso-blanco, E.; Calvo, A. I.; Fraile, R.; Castro, A.
2012-01-01
The number of particles and their size distributions were measured in a rural area, during the summer, using a PCASP-X. The aim was to study the influence of wildfires on particle size distributions. The comparative studies carried out reveal an average increase of around ten times in the number of particles in the fine mode, especially in sizes between 0.10 and 0.14??m, where the increase is of nearly 20 times. An analysis carried out at three different points in time—before, during, an...
Effects of transverse electron beam size on transition radiation angular distribution
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Chiadroni, E., E-mail: enrica.chiadroni@lnf.infn.it [Laboratori Nazionali di Frascati-INFN, via E. Fermi, 40, 00044 Frascati (Italy); Castellano, M. [Laboratori Nazionali di Frascati-INFN, via E. Fermi, 40, 00044 Frascati (Italy); Cianchi, A. [University of Rome ' Tor Vergata' and INFN-Tor Vergata, Via della Ricerca Scientifica 1, 00133 Rome (Italy); Honkavaara, K.; Kube, G. [Deutsches Elektronen-Synchrotron, Notkestrasse 85, 22607 Hamburg (Germany)
2012-05-01
In this paper we consider the effect of the transverse electron beam size on the Optical Transition Radiation (OTR) angular distribution in case of both incoherent and coherent emission. Our results confute the theoretical argumentations presented first in Optics Communications 211, 109 (2002), which predicts a dependence of the incoherent OTR angular distribution on the beam size and emission wavelength. We present here theoretical and experimental data not only to validate the well-established Ginzburg-Frank theory, but also to show the impact of the transverse beam size in case of coherent emission.
Charalambous, C. A.; Pike, W. T.
2013-12-01
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.
Yanamandra-Fisher, Padmavati Anantha
A bimodal size distribution for particles in Saturn's rings was determined via an analysis of PPS, UVS and RSS occultation data. The variation of the size distribution in featureless regions indicates that the dust variation is nearly constant in the Saturn's rings and exhibits a slight anti-correlation with 1 cm sized particles. Subcentimeter sized particles increase outward in the rings, with a maximum in the B ring, similar to the variation of 1 cm sized particles. However, the ratio of subcentimeter sized particles to 1 cm sized particles does not vary significantly in the rings. Janus 5:4 density wave differs significantly from the featureless regions. The amount of dust is greater by a factor of about 2. Both dust and subcentimeter sized particles are strongly anti-correlated with 1 cm sized particles. Partial formation of gaps is evident for both sub- and supra-centimeter sized particles, consistent with the predictions of Goldreich and Tremaine (1978). Dust is insensitive to the gravitational torque associated with the resonance. Results are also consistent with Dones (1987). In wave regions, large particles collide and produce dust and do not break up into smaller particles. The Uranian rings were searched via time series analysis methods to identify periodic phenomena in the rings. Comparison of density waves in the two ring systems are similar, indicating the similarity of the local ring environments.
Size Distribution of Tropical Cirrus Cloud Particles from ACE-FTS and MAESTRO Measurements
Sloan, James; McElroy, C. Thomas; Sioris, Chris; Ayache, Tarek
2012-07-01
Cirrus clouds are a major component of the climate system because of their effect on radiative transfer in the atmosphere. Of all their properties, their crystal size distributions are the most important for quantification of these effects. The observations of the Atmospheric Chemistry Experiment Fourier transform spectrometer (ACE-FTS) and theMeasurement of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation (MAESTRO) instruments on the Canadian SciSat satellite mission are ideal for the retrieval of cirrus particle size distributions because they are obtained in solar occultation and therefore are vertically resolved. Previous condensed phase retrievals from the SciSat mission have focussed on the IR data from ACE-FTS. The measurements of MAESTRO at visible wavelengths, however, give valuable information on the size distributions of the smaller crystals, which are important for the poorly understood radiative properties of sub-visible cirrus clouds. Accordingly, we have combined the ACE-FTS and MAESTRO observations and retrieved cloud particle size distributions from the concatenated observations, using constrained least squares fitting techniques developed previously . We analysed the combined measurements from occultations measured between February 2004 and February 2011 having tangent points within 25 degrees of the equator. We will report the resulting vertically-resolved particle size distributions of tropical cirrus clouds and discuss the advantages of retrieving particle sizes from both visible and infrared measurements, as opposed to infrared alone.
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Scanning Mobility Particle Sizer (SMPS) is a high resolution nanoparticle sizing system that has long been hailed as the researcher's choice for airborne nanoparticle size characterization for nano applications including nanotechnology research and development. SMPS is widely used as the standard method to measure airborne particle size distributions below 1 ?m. It is composed of two devices: a Differential Mobility Analyzer (DMA) selects particle sizes thanks to their electrical mobility and a Condensation Particle Counter (CPC) enlarges particles to make them detectable by common optical counters. System raw data represent the number of particles counted over several classes of mobility diameters. Then, common inversion procedures lead to the estimation of the aerosol size distribution. In this paper, we develop a methodology to compute the uncertainties associated with the estimation of the size distribution when several experiences have been carried out. The requirement to repeat the measure ensures a realistic variability on the simulated data to be generated. The work we present consists in considering both the uncertainties coming from the experimental dispersion and the uncertainties induced by the lack of knowledge on physical phenomena. Experimental dispersion is quantified with the experimental data while the lack of knowledge is modelled via the existing physical theories and the judgements of experts in the field of aerosol science. Thus, running Monte-Cof aerosol science. Thus, running Monte-Carlo simulations give an estimation of the size distribution and its corresponding confidence region.
Voronoï cell-size distribution and Edwards' compactivity of the parking lot model.
Hernández, K; Reyes, L I
2008-06-01
We find by Monte Carlo simulations that the distribution of Voronoï cell sizes for the parking lot model follows a gamma distribution with shape parameter k approximately 2 for high enough packing fractions varphi . A gamma distribution of Voronoï cells sizes was found recently by Aste [Europhys. Lett. 79, 24003 (2007)] in experiments of static packings of monodisperse spheres. This statistic implies that, for high varphi , Edwards' compactivity of the parking lot model depends linearly on the average volume per cell, as predicted by the statistical mechanics calculation of Tarjus and Viot, which explicitly counted the blocked configurations of this model [Phys. Rev. E 69, 011307 (2004)]. PMID:18643320
Effect of particle size distribution on the separation efficiency in liquid chromatography.
Horváth, Krisztián; Lukács, Diána; Sepsey, Annamária; Felinger, Attila
2014-09-26
In this work, the influence of the width of particle size distribution (PSD) on chromatographic efficiency is studied. The PSD is described by lognormal distribution. A theoretical framework is developed in order to calculate heights equivalent to a theoretical plate in case of different PSDs. Our calculations demonstrate and verify that wide particle size distributions have significant effect on the separation efficiency of molecules. The differences of fully porous and core-shell phases regarding the influence of width of PSD are presented and discussed. The efficiencies of bimodal phases were also calculated. The results showed that these packings do not have any advantage over unimodal phases. PMID:25160957
Effect of interaction between chains on their size distribution: Strong magnetic field
Iskakova, L. Yu.; Zubarev, A. Yu
2002-10-01
We consider ferrofluid consisting of identical spherical particles with permanent magnetic moment. Under the assumption that linear chains can appear in the ferrofluid, we estimate the distribution function of a number of the particles inside the chains. The main new moment of our consideration is that we estimate the influence of interaction between the chains on the size distribution as well as on the mean number of the particles in the chain. The analysis is done and simple expressions for an the size distribution function are obtained for infinitely strong magnetic field in asymptotics of strong magnetic interaction between the particles inside one chain.
Chen, Hua; Chen, Kun
2013-01-01
The distributions of coalescence times and ancestral lineage numbers play an essential role in coalescent modeling and ancestral inference. Both exact distributions of coalescence times and ancestral lineage numbers are expressed as the sum of alternating series, and the terms in the series become numerically intractable for large samples. More computationally attractive are their asymptotic distributions, which were derived in Griffiths (1984) for populations with constant size. In this arti...
Finite-Size Effects on Return Interval Distributions for Weakest-Link-Scaling Systems
Hristopulos, Dionissios T.; Petrakis, Manolis P.; Kaniadakis, Giorgio
2013-01-01
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 in the fracture strength of quasi-brittle materials. We investigate weakest-link scaling in finite-size systems and deviations of empirical return interval distributions from the Weibull distribution function. We use the ansatz that the survival probability func...
Effects of Particle Size Distribution on the Burn Ability of Limestone
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Ismaila E. SULEIMAN
2013-11-01
Full Text Available The effect of particle size reduction on the burn ability of Limestone was investigated using the limestone obtained from Obajana Cement Mines. Limestone samples were grinded and were classified into following particles size distribution: 90µm, 200µm, 250µm and 500µm graduated in different sieve sizes. The decomposition rates of these samples were monitored under the same temperature condition in a pre-heated furnace of 1000°C and at constant time interval of 0-35 minutes. From the results of the investigation, the material with particle size distribution of 90µm has the fastest reaction rate of 0.1369g/min and highest lime conversion of 52.0 weight percent; loss on ignition being 48 weight percent. This reaction rate increases as the particle size decreases from 500µm to 90µm.
Mu, G.-H.; Chen, W.; Kertész, J.; Zhou, W.-X.
2009-03-01
The distributions of trade sizes and trading volumes are investigated based on the limit order book data of 22 liquid Chinese stocks listed on the Shenzhen Stock Exchange in the whole year 2003. We observe that the size distribution of trades for individualstocks exhibits jumps, which is caused by the number preference of traders when placing orders. We analyze the applicability of the “q-Gamma” function for fitting the distribution by the Cramér-von Mises criterion. The empirical PDFs of tradingvolumes at different timescales ?t ranging from 1 min to 240 min can be well modeled. The applicability of the q-Gamma functions for multiple trades is restricted to the transaction numbers ?n? 8. We find that all the PDFs have power-law tails for large volumes. Using careful estimation of the average tail exponents ? of the distributions of trade sizes and trading volumes, we get ?> 2, well outside the Lévy regime.
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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
Comparing particle-size distributions in modern and ancient sand-bed rivers
Hajek, E. A.; Lynds, R. M.; Huzurbazar, S. V.
2011-12-01
Particle-size distributions yield valuable insight into processes controlling sediment supply, transport, and deposition in sedimentary systems. This is especially true in ancient deposits, where effects of changing boundary conditions and autogenic processes may be detected from deposited sediment. In order to improve interpretations in ancient deposits and constrain uncertainty associated with new methods for paleomorphodynamic reconstructions in ancient fluvial systems, we compare particle-size distributions in three active sand-bed rivers in central Nebraska (USA) to grain-size distributions from ancient sandy fluvial deposits. Within the modern rivers studied, particle-size distributions of active-layer, suspended-load, and slackwater deposits show consistent relationships despite some morphological and sediment-supply differences between the rivers. In particular, there is substantial and consistent overlap between bed-material and suspended-load distributions, and the coarsest material found in slackwater deposits is comparable to the coarse fraction of suspended-sediment samples. Proxy bed-load and slackwater-deposit samples from the Kayenta Formation (Lower Jurassic, Utah/Colorado, USA) show overlap similar to that seen in the modern rivers, suggesting that these deposits may be sampled for paleomorphodynamic reconstructions, including paleoslope estimation. We also compare grain-size distributions of channel, floodplain, and proximal-overbank deposits in the Willwood (Paleocene/Eocene, Bighorn Basin, Wyoming, USA), Wasatch (Paleocene/Eocene, Piceance Creek Basin, Colorado, USA), and Ferris (Cretaceous/Paleocene, Hanna Basin, Wyoming, USA) formations. Grain-size characteristics in these deposits reflect how suspended- and bed-load sediment is distributed across the floodplain during channel avulsion events. In order to constrain uncertainty inherent in such estimates, we evaluate uncertainty associated with sample collection, preparation, analytical 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.
A numerical study of the particle size distribution of an aerosol undergoing turbulent coagulation
Reade, Walter C.; Collins, Lance R.
2000-07-01
Coagulation and growth of aerosol particles subject to isotropic turbulence has been explored using direct numerical simulations. The computations follow the trajectories of 262 144 initial particles as they are convected by the turbulent flow field. Collision between two parent particles leads to the formation of a new daughter particle with the mass and momentum (but not necessarily the energy) of the parent particles. The initially monodisperse population of particles will develop a size distribution over time that is controlled by the collision dynamics. In an earlier study, Sundaram & Collins (1997) showed that collision rates in isotropic turbulence are controlled by two statistics: (i) the radial distribution of the particles and (ii) the relative velocity probability density function. Their study considered particles that rebound elastically; however, we find that the formula that they derived is equally valid in a coagulating system. However, coagulation alters the numerical values of these statistics from the values they attain for the elastic rebound case. This difference is substantial and must be taken into consideration to properly predict the evolution of the size distribution of a population of particles. The DNS results also show surprising trends in the relative breadth of the particle size distribution. First, in all cases, the standard deviation of the particle size distribution of particles with finite Stokes numbers is much larger than the standard deviation for either the zero-Stokes-number or infinite-Stokes-number limits. Secondly, for particles with small initial Stokes numbers, the standard deviation of the final particle size distribution decreases with increasing initial particle size; however, the opposite trend is observed for particles with slightly larger initial Stokes numbers. An explanation for these phenomena can be found by carefully examining the functional dependence of the radial distribution function on the particle size and Stokes number.
On the behavior of mud floc size distribution: model calibration and model behavior
Mietta, F.; Chassagne, C.; Verney, R.; Winterwerp, J. C.
2011-01-01
In this paper, we study a population balance equation (PBE) where flocs are distributed into classes according to their mass. Each class i contains i primary particles with mass m p and size L p. All differently sized flocs can aggregate, binary breakup into two equally sized flocs is used, and the floc’s fractal dimension is d 0?=?2, independently of their size. The collision efficiency is kept constant, and the collision frequency derived by Saffman and Turner (J Fluid Mech 1:16–30,...
DOMAIN SIZE DISTRIBUTION OF Y-TZP NANO-PARTICLES USING XRD AND HRTEM
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Florence Boulc'h
2011-05-01
Full Text Available Yttria doped nanocrystalline zirconia powder was prepared by spray-pyrolysis technique. Powder crystallized into tetragonal form, as dense and compositionally homogeneous polycrystalline spheres. X-Ray diffraction (XRD and high resolution transmission electron microscopy (HRTEM have been used in order to characterize the mean size and the size distribution of crystalline domains. An average size of 6 nm was calculated by Scherrer formula from X-Ray diffraction pattern. The domain size, determined by analysis method developed by Hytch from HRTEM observations, ranges from 5 to 22 nm with a main population around the value 12 nm. Limits and complementary nature of XRD and HRTEM methods are discussed.
Collection strategy, inner morphology, and size distribution of dust particles in ASDEX Upgrade
International Nuclear Information System (INIS)
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. (paper)
Collection strategy, inner morphology, and size distribution of dust particles in ASDEX Upgrade
Balden, M.; Endstrasser, N.; Humrickhouse, P. W.; Rohde, V.; Rasinski, M.; von Toussaint, U.; Elgeti, S.; Neu, R.; the ASDEX Upgrade Team
2014-07-01
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.
Collection strategy, inner morphology, and size distribution of dust particles in ASDEX Upgrade
Energy Technology Data Exchange (ETDEWEB)
M. Balden; N. Endstrasser; P. W. Humrickhouse; V. Rohde; M. Rasinski; U. von Toussaint; S. Elgeti; R. Neu
2014-04-01
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.
The k-generalized distribution: A new descriptive model for the size distribution of incomes
Clementi, F; Gallegati, M; Kaniadakis, G
2007-01-01
This paper proposes the k-generalized distribution as a model for describing the distribution and dispersion of income within a population. Formulas for the shape, moments and standard tools for inequality measurement - such as the Lorenz curve and the Gini coefficient - are given. A method for parameter estimation is also discussed. The model is shown to fit extremely well the data on personal income distribution in Australia and the United States.
ASSESSMENT OF THE MAIN PETROLEUM PRODUCT DISTRIBUTION STRATEGY
Florea Vlad
2013-01-01
This paper investigates the main petroleum product distribution strategy. Three main criteria are identified in this respect: the economic criterion, the control criterion and adjustment criterion. In addition, aspects pertaining to the administration of petroleum product distribution network are also revealed.
Are range-size distributions consistent with species-level heritability?
DEFF Research Database (Denmark)
Borregaard, Michael Krabbe; Gotelli, Nicholas
2012-01-01
The concept of species-level heritability is widely contested. Because it is most likely to apply to emergent, species-level traits, one of the central discussions has focused on the potential heritability of geographic range size. However, a central argument against range-size heritability has been that it is not compatible with the observed shape of present-day species range-size distributions (SRDs), a claim that has never been tested. To assess this claim, we used forward simulation of range-size evolution in clades with varying degrees of range-size heritability, and compared the output 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.
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.
An Aggregate Model for the Particle Size Distribution in Saturn's Rings
Brilliantov, Nikolai; Hayakawa, Hisao; Bodrova, Anna; Spahn, Frank; Schmidt, Juergen
2013-01-01
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...
Research of CWS’ Particle Size Distribution based on Ultrasonic Attenuation Theory
Directory of Open Access Journals (Sweden)
WANG Weidong
2010-11-01
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.
Particle size distributions in Saturn's rings from Voyager 1 radio occultation
Marouf, E. A.; Tyler, G. L.; Zebker, H. A.; Simpson, R. A.; Eshleman, V. R.
1983-01-01
Information on Saturn ring particle sizes obtained with the Voyager 1 ring occultation experiment is discussed. The theory underlying the determination of the particle size distribution is presented, including differential extinction and inversion of the scattered signal. Experimental observations and results for the observed spectra, differential cross sections, suprameter and sub- to suprameter size distributions are presented. The size and mass distributions both cut off sharply at about 4-5 m; the mass distribution peaks over the 3-4 m size range for four ring system features at 1.35, 1.51, 2.01, and 2.12 Saturn radii. A power-law type model is consistent with the data over a limited size range of 0.01 to 1 m. The fractional contribution of the suprameter particles to the microwave opacity for the four features appears to be about 1/3, 1/3, 2/3, and 1, respectively, and their cumulative surface mass per unit area are about 11, 16, 41, and 132 g/sq cm if the particles are solid water ice.
Directory of Open Access Journals (Sweden)
P. Tunved
2004-11-01
Full Text Available The evolution of the aerosol size distribution during transport between Aspvreten (58.8° N, 17.4° E and Värriö (67.46° N, 29.35° E was studied using a pseudo-Lagrangian approach. Aerosol dynamic processes were studied and interpreted utilizing a state-of-the-art aerosol dynamic box model UHMA (University of Helsinki Multicomponent Aerosol model complemented with OH, NO_{3}, O_{3} and terpene chemistry. In the model simulations, the growth and formation of aerosol particles was controlled by sulphuric acid, ammonia, water and an unidentified low volatile organic compound. This organic compound was assumed to be a product of terpene oxidation with a yield of 13% in the base case conditions.
Changes of aerosol size distribution properties during transport between the stations were examined in twelve clear sky cases. On average, the modelled number agreed fairly well with observations. Mass concentration was overestimated by 10%.
Apart from dilution, the only removal mechanism for aerosol mass is dry deposition. A series of sensitivity tests performed revealed that the absolute magnitude of dry deposition effects on the aerosol size distribution is slow overall. Furthermore, nucleation does not leave a significant contribution to aerosol number in the selected cases. The sensitivity of the modelled size distribution to concentration of precursor gases and oxidants is, however, obvious. In order to explain observed mass increase during transport we conclude that a yield of low volatile products from oxidation of terpenes of 10–15% is required to explain observed growth rates. Coagulation is acknowledged to be highly important in modelled cases.
Introduction of a Nozzle Throat Diameter Dependency into the SRM Dust Size Distribution
Stabroth, S.; Wegener, P.; Oswald, M.; Wiedemann, C.; Klinkrad, H.; Vörsmann, P.
In the exhaust gas of SRM (Solid Rocket Motor) firings, a considerable amount of very small aluminium oxide (Al2O3) particles is generally included. In order to increase motor performance and to dampen burn instabilities, aluminium is used as an additive in the propellant. During the burn process this aluminium is transformed into Al2O3. A large number of small dust particles (databases. Thus, a fixed distribution is identically used for large upper stages as well as small apogee motors. This assumption can lead to an over-representation of large dust in regions, where mainly apogee motors are used (i.e. GEO) and an under-representation in lower altitudes, where large stages predominate. In this paper, a concept for the improvement of SRM dust size modelling is discussed. It will be shown that an introduction of a nozzle throat diameter dependency into the dust size distribution could lead to a more precise modelling of SRM dust release events. Investigations showed that there is a good correlation between the propellant mass flow and the nozzle's throat diameter, which is in turn the determining term for the actual diameter distribution. Based on this correlation, the paper will outline a size distribution taking into account the actual motor size. The improved SRM dust size distribution is going to be used by the MASTER-2005 space debris model which is currently under development by the Institute of Aerospace Systems and QinetiQ under ESA contract.
Remote sensing of water cloud droplet size distributions using the backscatter glory: a case study
Directory of Open Access Journals (Sweden)
B. Mayer
2004-05-01
Full Text Available Cloud single scattering properties are mainly determined by the effective radius of the droplet size distribution. There are only few exceptions where the shape of the size distribution affects the optical properties, in particular the rainbow and the glory directions of the scattering phase function. Using observations by the Compact Airborne Spectrographic Imager (CASI in 180° backscatter geometry, we found that high angular resolution aircraft observations of the glory provide unique new information which is not available from traditional remote sensing techniques: Using only one single wavelength, 753 nm, we were able to determine not only optical thickness and effective radius, but also the width of the size distribution at cloud top. Applying this novel technique to the ACE-2 CLOUDYCOLUMN experiment, we found that the size distributions were much narrower than usually assumed in radiation calculations which is in agreement with in-situ observations during this campaign. While the shape of the size distribution has only little relevance for the radiative properties of clouds, it is extremely important for understanding their formation and evolution.
Size distribution of magnetic iron oxide nanoparticles using Warren-Averbach XRD analysis
Mahadevan, S.; Behera, S. P.; Gnanaprakash, G.; Jayakumar, T.; Philip, J.; Rao, B. P. C.
2012-07-01
We use the Fourier transform based Warren-Averbach (WA) analysis to separate the contributions of X-ray diffraction (XRD) profile broadening due to crystallite size and microstrain for magnetic iron oxide nanoparticles. The profile shape of the column length distribution, obtained from WA analysis, is used to analyze the shape of the magnetic iron oxide nanoparticles. From the column length distribution, the crystallite size and its distribution are estimated for these nanoparticles which are compared with size distribution obtained from dynamic light scattering measurements. The crystallite size and size distribution of crystallites obtained from WA analysis are explained based on the experimental parameters employed in preparation of these magnetic iron oxide nanoparticles. The variation of volume weighted diameter (Dv, from WA analysis) with saturation magnetization (Ms) fits well to a core shell model wherein it is known that Ms=Mbulk(1-6g/Dv) with Mbulk as bulk magnetization of iron oxide and g as magnetic shell disorder thickness.
International Nuclear Information System (INIS)
We have developed a fast-response nanometer aerosol size analyzer (nASA) that is capable of scanning 30 size channels between 3 and 100 nm in a total time of 3 s. The analyzer includes a bipolar charger (Po210), an extended-length nanometer differential mobility analyzer (Nano-DMA), and an electrometer (TSI 3068). This combination of components provides particle size spectra at a scan rate of 0.1 s per channel free of uncertainties caused by response-time-induced smearing. The nASA thus offers a fast response for aerosol size distribution measurements in high-concentration conditions and also eliminates the need for applying a de-smearing algorithm to resulting data. In addition, because of its thermodynamically stable means of particle detection, the nASA is useful for applications requiring measurements over a broad range of sample pressures and temperatures. Indeed, experimental transfer functions determined for the extended-length Nano-DMA using the tandem differential mobility analyzer (TDMA) technique indicate the nASA provides good size resolution at pressures as low as 200 Torr. Also, as was demonstrated in tests to characterize the soot emissions from the J85-GE engine of a T-38 aircraft, the broad dynamic concentration range of the nASA makes it particularly suitable for studies of combustion or particle formation processes. Further details of the nASA performance as well as results from calibrations, laboratory tests and field applications are prratory tests and field applications are presented below
Modeling Diffraction Spikes to Characterize the Particle Size Distribution in Saturn’s A Ring
Becker, Tracy M.; Colwell, Joshua E.; Esposito, Larry W.
2014-11-01
Stellar occultation data from Cassini’s Ultraviolet Imaging Spectrograph (UVIS) have revealed diffraction spikes near sharp edges in Saturn’s rings. The UVIS High Speed Photometer (HSP) observes these signals as photon counts surpassing measurements of the unocculted stellar signal in the ring gaps and in regions beyond the rings. In Saturn’s A ring, forward-scattered light can augment the direct stellar signal by up to 5%, and the signals typically extend tens of kilometers radially from the ring edge. The extent of the diffraction signals at the HSP wavelength of 150 nanometers indicates the presence of centimeter- and sub-centimeter-sized particles throughout the A ring. We reproduce the diffraction signals detected at the outer edge of the A ring and the edges of the Encke Gap and the Keeler Gap by modeling the particle populations at those edges with a power-law size distribution. We find centimeter-sized particles at the edges of the Encke Gap and millimeter-sized particles at the outer edge of the A ring. In addition to a decrease in particle size, we also find a steepening of the slope of the power-law size distribution with distance from Saturn. These constraints on the particle size distribution suggest that interparticle collisions caused by satellite perturbations in the region result in more shedding or fragmentation of particles in the outermost parts of the A ring.
Moessbauer and magnetic studies in nickel ferrite nanoparticles: Effect of size distribution
International Nuclear Information System (INIS)
The magnetic properties of nickel ferrite nanoparticles in the form of powders, prepared by the sol-gel process and subjected to different annealing temperatures, were investigated using both static and dynamic measurements namely hysteresis, zero field cooled-field cooled magnetization (ZFC-FC) measurements and Moessbauer spectroscopy. The Transmission Electron Microscopy (TEM) studies reveal particle sizes ?2-8nm for the as-prepared particles which increases upto 52 nm with annealing. A bimodal distribution, upto an annealing temperature of 300oC was observed. ZFC-FC measurements for the as-prepared samples reveal twin peaks, indicative of the bimodal size distribution. ZFC-FC measurements performed for fields varying from 100 Oe to 3 kOe show a superparamagnetic phase with blocking temperatures between 320 and 85K. Numerical simulations for the ZFC-FC studies indicate that the signature of the bimodal size distribution can be seen only at very low fields. The variation of coercivity with particle size, as determined from the hysteresis measurements, shows a transition from a single domain to a multi domain state for particle sizes larger than 35 nm. Moessbauer measurements performed at room temperature for the as-prepared sample shows a six finger pattern for the samples with higher particle size and a doublet pattern for the samples with smaller particle size, which is indicative of their superparamagnetic nature.netic nature.
Moessbauer and magnetic studies in nickel ferrite nanoparticles: Effect of size distribution
Energy Technology Data Exchange (ETDEWEB)
Malik, Rakesh [Department of Physics and Astrophysics, University of Delhi, Delhi 110 007 (India); Annapoorni, S., E-mail: annapoorni@physics.du.ac.i [Department of Physics and Astrophysics, University of Delhi, Delhi 110 007 (India); Lamba, Subhalakshmi [Indira Gandhi National Open University, Maidangarhi, Delhi 110 068 (India); Raghavendra Reddy, V.; Gupta, Ajay [UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452017 (India); Sharma, Parmanand; Inoue, Akihisa [Institute of Materials Research, Tohoku University, Sendai 980-8577 (Japan)
2010-12-15
The magnetic properties of nickel ferrite nanoparticles in the form of powders, prepared by the sol-gel process and subjected to different annealing temperatures, were investigated using both static and dynamic measurements namely hysteresis, zero field cooled-field cooled magnetization (ZFC-FC) measurements and Moessbauer spectroscopy. The Transmission Electron Microscopy (TEM) studies reveal particle sizes {approx}2-8nm for the as-prepared particles which increases upto 52 nm with annealing. A bimodal distribution, upto an annealing temperature of 300{sup o}C was observed. ZFC-FC measurements for the as-prepared samples reveal twin peaks, indicative of the bimodal size distribution. ZFC-FC measurements performed for fields varying from 100 Oe to 3 kOe show a superparamagnetic phase with blocking temperatures between 320 and 85K. Numerical simulations for the ZFC-FC studies indicate that the signature of the bimodal size distribution can be seen only at very low fields. The variation of coercivity with particle size, as determined from the hysteresis measurements, shows a transition from a single domain to a multi domain state for particle sizes larger than 35 nm. Moessbauer measurements performed at room temperature for the as-prepared sample shows a six finger pattern for the samples with higher particle size and a doublet pattern for the samples with smaller particle size, which is indicative of their superparamagnetic nature.
Measurements of the size distribution of unattached radon progeny by using the imaging plate
International Nuclear Information System (INIS)
The size distribution of unattached radon progeny is an important parameter for an accurate estimation of the internal dose of radon exposure. In this study, a new measuring system was developed to evaluate the size distribution of unattached radon progeny in air. In the system, airborne radon progeny were collected with a newly designed graded screen array (GSA), the activity concentrations were measured by using the imaging plate technique, and the size distribution of unattached fraction was retrieved by using an iterative nonlinear algorithm. The simulation results indicated that the collection characteristics of the new GSA system were well agreed with other systems. Test experiments showed that the activity-weighted median diameters (AMD) for unattached 218Po, 214Pb and 214Bi were 0.89 ± 0.11 nm, 0.96 ± 0.13 nm and 1.01 ± 0.25 nm in a particle-free radon chamber, and the distribution changed with different concentrations of particles. As multiple measurements can be simultaneously carried out with a single IP, the new technique is considered as an optional and useful way to measure the size distribution measurement of unattached radon progeny. - Highlights: • A new graded screen array system based on imaging plate technique is developed. • The front to total activity ratio of wire screens measured by the imaging plate technique is considered in the system. • The system is capable to evaluate the size distribution of unattached radon progeny in air. • The size distribution of 218Pb, 214Po, 214Bi is measured by the system under different particle concentrations
Multi-product allocation and distribution
Directory of Open Access Journals (Sweden)
D.C. Currin
2003-12-01
Full Text Available This paper describes techniques used by a beer company to optimise the allocation and distribution of their beer. These techniques are also applicable to other manufacturing and distribution environments. Of particular interest is a two-phase model that allows a "look-ahead" to future sales, the decomposition of the problem into a large number of sub-problems (to reduce solution time, and the equitable distribution of material when stocks are over- or undersupplied. The optimisation is part of an interactive planning system, and the relationship between the optimisation module and the rest of the system is briefly described.
Effect of Particle Size Distribution on Ammonium Sulphate Dried in a Rotary Dryer
Directory of Open Access Journals (Sweden)
Susianto Susianto
2010-08-01
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.
Investigation of size and intensity distribution of the focal spot of microfocus X-Ray tubes
International Nuclear Information System (INIS)
The spatial resolution of x-ray setups with high magnification factors is limited by the size of the focal spot. Therefore, the size and the intensity distribution of the focal spot at a given energy are very important characteristic parameters of x-ray tubes. Difficulties will arise if the small focal spot of a ?-CT setup is to be measured using a pinhole. In order to overcome these limitations, a novel method for measuring the intensity distribution of the focal spot of microfocus x-ray tubes with transmission targets was developed. Hereby, the focus intensity distribution is determined under standard industrial working conditions using a spatially coded mask. With this method, the intensity distribution of focal spots with a size of a few micrometers was measured: The dependence of the focus size and shape on tube voltage and current was investigated. Furthermore, changes of the focus intensity distribution while the target gradually deteriorates were determined, as outlined in the figure below. Finally, a measurement of the focus intensity distribution of an x-ray tube with a structured target, of which only certain areas emit x-rays, is presented. (authors)
Investigation of size and intensity distribution of the focal spot of microfocus X-Ray tubes
Energy Technology Data Exchange (ETDEWEB)
Engelhardt, M.; Baumann, J. [Siemens AG, Munchen (Germany)]|[TU-Munchen, Garching (Germany); Jefimovs, K. [Paul Scherrer Institut, Villigen (Switzerland)
2007-07-01
The spatial resolution of x-ray setups with high magnification factors is limited by the size of the focal spot. Therefore, the size and the intensity distribution of the focal spot at a given energy are very important characteristic parameters of x-ray tubes. Difficulties will arise if the small focal spot of a {mu}-CT setup is to be measured using a pinhole. In order to overcome these limitations, a novel method for measuring the intensity distribution of the focal spot of microfocus x-ray tubes with transmission targets was developed. Hereby, the focus intensity distribution is determined under standard industrial working conditions using a spatially coded mask. With this method, the intensity distribution of focal spots with a size of a few micrometers was measured: The dependence of the focus size and shape on tube voltage and current was investigated. Furthermore, changes of the focus intensity distribution while the target gradually deteriorates were determined, as outlined in the figure below. Finally, a measurement of the focus intensity distribution of an x-ray tube with a structured target, of which only certain areas emit x-rays, is presented. (authors)
Particle size distributions in a DC-cast and rolled AA3104 alloy
Energy Technology Data Exchange (ETDEWEB)
Ekstroem, H.-E.; Oestensson, L. [Graenges Technol., Finspang (Sweden); Hagstroem, J.
2000-07-01
Particle size distributions in an AA3104 alloy homogenised at different temperatures have been determined using both scanning electron microscope with a field emission electron gun (FEG-SEM) and transmission electron microscope (TEM). Constituent particles and dispersoids were measured at different depths for two hot rolled gauges. The measured area size distributions are transformed to 3D distributions using a modified Johnson-Saltykov method assuming different shapes of the particles and considering the information depth in the SEM and the TEM foil thickness. The analysis shows that the assumptions made regarding information depths have a large influence on the 3D size distributions and consequently also on calculated Zener drag. The very inhomogeneous particle distribution in the ingots makes it important to spread out the selected image fields to achieve reliable statistics also during the measurements on the hot bands. The TEM and FEG-SEM measurements give results in excellent agreement. Calculation of the Zener drag from the mean particle diameter and volume fraction gives values 4-5 times larger than those obtained using a more rigorous method considering the particle size distribution. (orig.)
The size distributions of fragments ejected at a given velocity from impact craters
Okeefe, J. D.; Ahrens, T. J.
1986-01-01
The mass distribution of fragments that are ejected at a given velocity for impact craters is modeled to allow extrapolation of laboratory, field, and numerical results to large scale planetary events. The model is semi-empirical in nature and is derived from: (1) numerical calculations of cratering and the resultant mass versus ejection velocity, (2) observed ejecta blanket particle size distributions, (3) an empirical relationship between maximum ejecta fragment size and crater diameter, (4) measurements and theory of maximum ejecta size versus ejecta velocity, and (5) an assumption on the functional form for the distribution of fragments ejected at a given velocity. This model implies that or planetary impacts into competent rock, the distribution of fragments ejected at a given velocity is broad, e.g., 68% 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.
International Nuclear Information System (INIS)
Particle size distribution in a fluidized-bed dryer (where a solution is converted to a solid granular particle) depends on several different rate processes taking place. These include particle growth, particle attrition, product rate, feed deposition rate, elutriation rate, and seed attrition rate. While these rate processes are basic, depending on the material being dried, some become more important than others. Few new seed particles are generated within the bed when the physical properties of many materials being dried are such that little particle attrition takes place. Under these conditions, the particle size distribution in the bed continually increases unless some measure is taken to introduce into, or generate within the bed, new seed particles. This paper briefly describes the mathematical model which predicts the particle size distribution expected when drying solutions in a fluidized bed. The important role that seed particles play in determining the steady-state particle size distribution of the bed is stressed. An experiment is described in which information was obtained that helped determine what seed particles are, and what size particles became seeds
Determination of size distribution of small DNA fragments by polyacrylamide gel electrophoresis
International Nuclear Information System (INIS)
Size distribution determination of DNA fragments can be normally determined by the agarose gel electrophoresis, including the normal DNA banding pattern analysis. However this method is only good for large DNA, such as the DNA of the size of kilo base pairs to mega base pairs range. DNA of size less than kilo base pairs is difficult to be quantified by the agarose gel method. Polyacrylamide gel electrophoresis however can be used to measure the quantity of DNA fragments of size less than kilo base pairs in length, down to less than ten base pairs. This method is good for determining the quantity of the smaller size DNA, single stranded polymers or even some proteins, if the known standards are available. In this report detail description of the method of preparing the polyacrylamide gel, and the experimental set up is discussed. Possible uses of this method, and the comparison with the standard sizes of DNA is also shown. This method is used to determine the distribution of the amount of the fragmented DNA after the Calf-thymus DNA has been exposed to various types of radiation and of different doses. The standards were used to determine the sizes of the fragmented Calf-thymus DNA. The higher the dose the higher is the amount of the smaller size DNA measured
Sensitivity analysis of the Ångstrom exponent for multimodal aerosol size distributions
Jung, Chang H.; Um, Junshik; Lee, Ji Yi; Kim, Yong P.
2013-11-01
This study characterizes the Ångstrom exponent for polydispersed aerosol size distributions. Under the assumption of a lognormal size distribution, the dependence of Ångstrom exponent on the size distribution and the refractive index with varying real and imaginary parts are determined. Further, the influence of coarse mode particles on the Ångstrom exponent is investigated quantitatively. The results show that the nuclei mode has less influence under the simulation conditions considered in this study. It is also shown that the refractive index is an important factor influencing the Ångstrom exponent. The effect of the coarse mode on the Ångstrom exponent computed with different aerosol number concentrations and as a function of a geometric standard deviation and a geometric mean diameter is tested. It is shown that the coarse mode is crucial for determining the Ångstrom exponent.
Jacobson, Seth A; Rossi, Alessandro; Scheeres, Daniel J; Davis, Donald R
2014-01-01
The size distribution of small asteroids in the Main Belt is assumed to be determined by an equilibrium between the creation of new bodies out of the impact debris of larger asteroids and the destruction of small asteroids by collisions with smaller projectiles. However, for a diameter less than 6 km we find that YORP-induced rotational disruption significantly contributes to the erosion even exceeding the effects of collisional fragmentation. Including this additional grinding mechanism in a collision evolution model for the asteroid belt, we generate size-frequency distributions from either an accretional (Weidenschilling, 2011) or an "Asteroids were born big" (Morbidelli, 2009) initial size-frequency distribution that are consistent with observations reported in Gladman et al. (2009). Rotational disruption is a new mechanism that must be included in all future collisional evolution models of asteroids.
Increasing Returns to Scale, Dynamics of Industrial Structure and Size Distribution of Firms
Fan, Y; Di, Z; Fan, Ying; Li, Menghui; Di, Zengru
2004-01-01
A model is presented of the market dynamics to emphasis the effects of increasing returns to scale, including the description of the born and death of the adaptive producers. The evolution of market structure and its behavior with the technological shocks are discussed. Its dynamics is in good agreement with some empirical stylized facts of industrial evolution. Together with the diversities of demand and adaptive growth strategies of firms, the generalized model has reproduced the power-law distribution of firm size. Three factors mainly determine the competitive dynamics and the skewed size distributions of firms: 1. Self-reinforcing mechanism; 2. Adaptive firm grows strategies; 3. Demand diversities or widespread heterogeneity in the technological capabilities of different firms. Key words: Econophysics, Increasing returns, Industry dynamics, Size distribution of firms
Accelerating Growth and Size-dependent Distribution of Collective Human Activities Online
Wu, Lingfei
2011-01-01
Research on human activities online usually assumes the linear relationship between active population $P$ and total activity $T$, that is, $T\\sim P^{\\gamma}(\\gamma=1)$. However, in our research, we find that the power law relationship $T\\sim P^{\\gamma}(\\gamma>1)$, also called accelerating growth, turns out to be ubiquitous in online activities such as micro-blogging, voting and tagging. Moreover, in the online activities under study, a unique type of distribution that changes with system size emerges. We name it size-dependent distribution and find it may give rise to accelerating growth. Interestingly, the power law exponent of accelerating growth $\\gamma$ is determined by the size-dependent exponent but not the Zipf or power law exponent of distributions. This is contradict to our intuition and previous studies.
Zhao, Jian-Qi; Zhang, Feng; Li, Jiangnan
2014-12-01
For a variety of non-spherical particles (oriented spheroids, cuboids, triangular prisms, and hexagonal prisms), analytical transform techniques are proposed to retrieve the particle size distribution (PSD) from measured absorption spectra. The absorption efficiency of particles is calculated using the anomalous diffraction theory (ADT). We find that for each type of non-spherical particles, there exists an ADT transform pair between the size distribution and the complex absorption spectrum, which provides the physical basis for solving the inverse problem. Furthermore, the relation between the size distribution and real absorption spectrum is established by using Gaver-Stehfest?s method. The numerical calculations show that the use of extended precision instead of double precision arithmetic can produce more reliable results at the expense of computational efficiency. Also it is shown that a small Stehfest number (standing for truncation number) tends to enhance the anti-noise level of inversion.
Porosity and pore size distribution of black cherry carbonized in an inert atmosphere
Energy Technology Data Exchange (ETDEWEB)
Blankenhorn, P.R.; Barnes, D.P.; Kline, D.E.; Murphey, W.K.
1978-07-01
Changes in total porosity, pore size distribution, apparent density, and real density as a function of carbonization temperature (up to 900/sup 0/C) were investigated using a mercury porosimeter. Total measured intrusion, total porosity, pore size distribution, and apparent density change as a function of carbonization temperature. Total porosity (up to 600/sup 0/C), apparent density (up to 600/sup 0/C), and pore size distribution above 1.75 ..mu..m are linear functions of carbonization temperature. Total measured intrusion and total porosity increase with increasing carbonization temperatures up to 600/sup 0/C and then decrease with carbonization temperatures up to 900/sup 0/C. Apparent density decreases with carbonization temperatures up to 600/sup 0/C and then increases with increasing carbonization temperatures.
Porosity and pore size distribution of black cherry carbonized in an inert atmosphere
Energy Technology Data Exchange (ETDEWEB)
Blankenhorn, P.R. (Pennsylvanic State Univ., University Park); Barnes, D.P.; Kline, D.E.; Murphey, W.K.
1978-07-01
Changes in total porosity, pore size distribution, apparent density, and real density as a function of carbonization temperature (up to 900/sup 0/C) were investigated using a mercury porosimeter. Total measured intrusion, total porosity, pore size distribution, and apparent density change as a function of carbonization temperature. Total porosity (up to 600/sup 0/C), apparent density (up to 600/sup 0/C), and pore size distribution above 1.75 ..mu..m are linear functions of carbonization temperature. Total measured intrusion and total porosity increase with increasing carbonization temperatures up to 600/sup 0/C and then decrease with carbonization temperatures up to 900/sup 0/C. Apparent density decreases with carbonization temperatures up to 600/sup 0/C and then increases with increasing carbonization temperatures. 3 figures, 2 tables.
Numerical Model to Predict Wax Crystal Size Distribution in Solvent Dewaxing Unit
Directory of Open Access Journals (Sweden)
Nassir D. Mokhlif
2014-02-01
Full Text Available A mathematical model was implemented to predict the wax crystal size distribution of distillate lube oil SN500. The model solved the coupled equations for the heat transfer and moments of the population balance numerically. The predicted temperatures and wax crystal size distributions were validated with actual unit database and experimental measurements. The kinetics of the wax crystallization considered only the nucleation and crystal growth. N-alkanes from n-C22 to n-C36 were tested to select compound for representation of the wax fraction. The nucleation process order constant was fitted from wax recovery experimental measurements. The developed numerical model was proved to be capable to predict wax crystal size distribution in real solvent dewaxing plant. The model results were found to be in good agreement with the process data
Energy Technology Data Exchange (ETDEWEB)
Zhang, R.L. [Open Project of State Key Laboratory Breeding Base for Mining Disaster Prevention and Control, Shandong University of Science and Technology (China); School of Materials Science and Engineering, Shandong University of Science and Technology, 266590 Qingdao (China); Liu, Y. [School of Materials Science and Engineering, Shandong University of Science and Technology, 266590 Qingdao (China); Huang, Y.D., E-mail: rlzhit@126.com [School of Chemical Engineering and Technology, State Key laboratory of Urban Water Resource and Environment Department of Applied Chemistry, Harbin Institute of Technology, 150001 Harbin (China); Liu, L. [School of Chemical Engineering and Technology, State Key laboratory of Urban Water Resource and Environment Department of Applied Chemistry, Harbin Institute of Technology, 150001 Harbin (China)
2013-12-15
Effect of particle size and distribution of the sizing agent on the performance of carbon fiber and carbon fiber composites has been investigated. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to characterize carbon fiber surface topographies. At the same time, the single fiber strength and Weibull distribution were also studied in order to investigate the effect of coatings on the fibers. The interfacial shear strength and hygrothermal aging of the carbon fiber/epoxy resin composites were also measured. The results indicated that the particle size and distribution is important for improving the surface of carbon fibers and its composites performance. Different particle size and distribution of sizing agent has different contribution to the wetting performance of carbon fibers. The fibers sized with P-2 had higher value of IFSS and better hygrothermal aging resistant properties.
The flux density-angular size distribution for extragalactic radio sources
International Nuclear Information System (INIS)
The median values of angular sizes of weak extragalactic radio sources, the flux densities of which lie in the range of about 0.3 to 5 Jy at 327 MHz, have been determined for a new sample of 119 sources observed during 1973-74, and agree well with the value of about 10 arc sec determined earlier by Swarup (1975). For 8 different flux density ranges, the angular size distribution for the A11-sky, 3CR and Ooty radio sources have been compared with theoretical predictions based on the evolutionary model by Kapahi (1975) and show a remarkable agreement with his model except that the best fit is found for a linear size evolution proportional to (1+z)-1. In this paper are presented some new data on the flux density angular size distribution, N(S, theta), for extragalactic radio sources and these data are used for cosmological investigations. (Auth.)
Directory of Open Access Journals (Sweden)
Ghaith Mustafa Al-Abdallah
2014-02-01
Full Text Available Internet importance and effect is increasing in every part of daily life, especially in business where internet canprovide some serious solutions for many issues, it can alter many traditional methods and procedures that wouldinclude distribution. Distribution channels are traditionally the organization, or set of organizations, responsiblefor delivering a product from the manufacturer to the end-users, Internet has affected traditional distributionchannels in developed countries and markets, as a matter of fact; internet itself can be viewed as a newdistribution channel. Accordingly, this study aims at identifying the effect of internet usage on the traditionaldistribution channels in Jordanian private commercial firms in terms of creating new direct online sales channeland reducing the numbers of intermediaries. The study also examines the moderating effect of firm’s size on theoriginal relation between internet usage and traditional distribution channels. In order to achieve theseobjectives, two main hypotheses were formed based on the literature review. A regulated research methodologywas applied to test the hypotheses over a proportional systematic random sample from large, medium, and smallprivate commercial firms in Jordan. A questionnaire was constructed and distributed to top and middlemanagement of private commercial firms in Jordan. 904 screened and filtered questionnaires were processesusing SPSS. The results of the statistical analysis were demonstrated. The study had shown that internet partlyeffect traditional distribution channels, the effect is limited to creating new direct online channel, and even thiseffect is weak, and got even weaker as the firms size got smaller.
Species size and distribution jointly and differentially determine diatom densities in U.S. streams.
Passy, Sophia I
2008-02-01
Among the most studied relationships in ecology are those of population density with (1) body size and (2) species distribution. The first relationship, in conjunction with metabolic rate, determines the energy flows through species communities, whereas the second relationship shows how local communities are influenced by the species history of dispersal and establishment. Traditionally, these two relationships have been examined separately. Here, I explored how diatom density was affected by cell size (biovolume) and species distribution in benthic and planktonic stream habitats all the way from individual localities and hydrologic systems (regions) to the entire United States. At all scales, density was predominantly a negative function of biovolume and a positive function of distribution. Biovolume was more strongly related to density in the benthos than in the phytoplankton. Partial regressions revealed that biovolume, by itself, explained a substantially higher percentage of the variance in density at local than at regional and continental scales. Conversely, species distribution was a much more important descriptor of density at larger scales and a slightly better predictor than biovolume at local scales. At large scales density was explained primarily by distribution and, to a lesser extent and only in the benthos, by the covariance of distribution and biovolume, whereas biovolume was a marginal predictor in all habitats. This discovery suggests that the strong relationships between density and body size, reported for populations ranging from unicellular algae to mammals, may be less direct than previously thought but mediated by large-scale species distributions. PMID:18409436
International Nuclear Information System (INIS)
Collisional growth of submicron-sized dust grains into macroscopic aggregates is the first step of planet formation in protoplanetary disks. These grains are expected to carry nonzero negative charges in the weakly ionized disks, but its effect on their collisional growth has not been fully understood so far. In this paper, we investigate how the charging affects the evolution of the dust size distribution properly taking into account the charging mechanism in a weakly ionized gas as well as porosity evolution through low-energy collisions. To clarify the role of the size distribution, we divide our analysis into two steps. First, we analyze the collisional growth of charged aggregates assuming a monodisperse (i.e., narrow) size distribution. We show that the monodisperse growth stalls due to the electrostatic repulsion when a certain condition is met, as was already expected in our previous work. Second, we numerically simulate dust coagulation using Smoluchowski's method to see how the outcome changes when the size distribution is allowed to freely evolve. We find that, under certain conditions, the dust undergoes bimodal growth where only a limited number of aggregates continue to grow, carrying a major part of the dust mass in the system. This occurs because remaining small aggregates efficiently sweep up free electrons to prevent the larger aggregates from being strongly charged. We obtain a set of simple criteria that allows us to predict how the size distributilows us to predict how the size distribution evolves for a given condition. In Paper II, we apply these criteria to dust growth in protoplanetary disks.
Liu, Cenwei; Lobb, David; Li, Sheng; Owens, Philip; Kuzyk, ZouZou
2014-05-01
Lake Winnipeg has recently brought attention to the deteriorated water quality due to in part to nutrient and sediment input from agricultural land. Improving water quality in Lake Winnipeg requires the knowledge of the sediment sources within this ecosystem. There are a variety of environmental fingerprinting techniques have been successfully used in the assessment of sediment sources. In this study, we used particle size distribution to evaluate spatial and temporal variations of suspended sediment and potential sediment sources collected in the Tobacco Creek Watershed in Manitoba, Canada. The particle size distribution of suspended sediment can reflect the origin of sediment and processes during sediment transport, deposition and remobilization within the watershed. The objectives of this study were to quantify visually observed spatial and temporal changes in sediment particles, and to assess the sediment source using a rapid and cost-effective fingerprinting technique based on particle size distribution. The suspended sediment was collected by sediment traps twice a year during rainfall and snowmelt periods from 2009 to 2012. The potential sediment sources included the top soil of cultivated field, riparian area and entire profile from stream banks. Suspended sediment and soil samples were pre-wet with RO water and sieved through 600 ?m sieve before analyzing. Particle size distribution of all samples was determined using a Malvern Mastersizer 2000S laser diffraction with the measurement range up to 600?m. Comparison of the results for different fractions of sediment showed significant difference in particle size distribution of suspended sediment between snowmelt and rainfall events. An important difference of particle size distribution also found between the cultivated soil and forest soil. This difference can be explained by different land uses which provided a distinct fingerprint of sediment. An overall improvement in water quality can be achieved by managing sediment according to the identified sediment sources in the watershed.
Moreno de Las Heras, M.; Saco, P. M.; Willgoose, G. R.
2010-12-01
Semiarid ecosystems are especially sensitive to the effects of both climate change and human disturbance, frequently showing critical degradation thresholds which make rehabilitation considerably more difficult. Recent studies suggested that the patch-size distribution of vegetation in drylands can be described using power law metrics, and that these scale-free distributions deviate from power law linearity with characteristic scale lengths under the effects of increasing aridity or human disturbance. These findings have been questioned by several modeling approaches, which have identified the presence of characteristic scale lengths on the patch-size distribution of semiarid periodic landscapes. We analyze this issue by exploring diagnostic metrics of periodicity and degradation on the patch-size distribution of semiarid vegetation. Our assessment is based on the study of vegetation patterns derived from high resolution remote sensing in a series of semiarid Australian shrublands with different degree of periodicity (i.e. banding) and subjected to different disturbance levels. Our results suggest that a variety of forms can characterized the patch-size distribution of vegetation, depending on the methodology of analysis applied and specific landscape traits. A common signal of land degradation is observed: the largest vegetation patches become increasingly less abundant under the effects of disturbance leading to a deviation from power law behavior (which is consistent with previous results). However, we also find that characteristic scale lengths are detected in nearly periodic banded ecosystems when critical landscape anisotropies are recognised by the methodology of the patch-size analysis (using transects in the direction of flow paths), breaking the general applicability of the power law metrics. These results emphasize the complexity of structure assessment in dryland ecosystems, while recognise the usefulness of the patch-size distribution of vegetation for monitoring landscape organization and health.
Karnieli, E.; Barzilai, A.; Rafaeloff, R.; Armoni, M.
1986-01-01
We examined insulin's effects on glucose transport and on subcellular transporter distribution in isolated human omental adipocytes of various sizes. Insulin stimulated 3-O-methylglucose transport by twofold in small cells, while a smaller and insignificant effect was measured in large cells. In the small cells, basal concentrations of glucose transporters were 2.9 and 17.2 pmol/mg membrane protein in the plasma and the low density microsomal membranes, respectively. Increasing cell size was ...
Likar, Z?iga
2012-01-01
The effect of the stress path and the initial grain size distribution on grain crushing was investigated on artificial material of a sand grain size. The thesis consists of two parts. In the first part isotropic compression test, oedometer test, conventional triaxial test (at constant cell pressure) and triaxial compresion test with constant mean effective stress are analysed. For the purpose of the research described in this part of thesis crushed artificial material known under ...
SIZE DISTRIBUTION OF NANOPARTICLES GENERATED BY A HEATING STOVE BURNING WOOD PELLETS
Mario Commodo; Lee Anne Sgro; Andrea D’Anna; Patrizia Minutolo
2012-01-01
In this work we investigate the size distribution of particulate matter emitted from a heating stove burning pellet. The effect of fuel contamination by metal nanoparticle is also investigated by seeding the pellet with Cu nanoparticles. Pellet stove emit mainly nanometric particles. The initial transient regime is characterized by stronger oscillations over time and a larger amount of emitted particles respect to the stationary regime. The larger number of emitted particles are in the size r...
Ma?chtle, W.
1999-01-01
Sedimentation velocity is a powerful tool for the analysis of complex solutions of macromolecules. However, sample turbidity imposes an upper limit to the size of molecular complexes currently amenable to such analysis. Furthermore, the breadth of the particle size distribution, combined with possible variations in the density of different particles, makes it difficult to analyze extremely complex mixtures. These same problems are faced in the polymer industry, where dispersions of latices, p...
A differentiation method for separating a mixture of suspended particle size distributions
Wang, H. Q.; Dupont, J. P.; Lafite, R.; Meyer, R.
1999-01-01
A simple method is proposed to partition a mixture of two populations in suspended particle size data. The method, termed here 'the differentiation method' is based on the function of the lognormal distribution. Suspended material in marine or estuarine situations often consists of difficult-to-interpret complex populations. The treatment of particle size data by the method described enables the confirmation of the lognormal law and also the demonstration of the occurrence of a combination of...
Determination of Crystallite Size Distribution Histogram in Nanocrystalline Anatase Powders by XRD.
Czech Academy of Sciences Publication Activity Database
Mat?j, Z.; Mat?jová, Lenka; Novotný, F.; Drahokoupil, Jan; Kužel, R.
2011-01-01
Ro?. 1, - (2011), s. 87-92. [European Powder Diffraction Conference EPDIC 12 /12./. Darmstadt, 27.08.2010-30.08.2010] R&D Projects: GA AV ?R KAN400720701 Institutional research plan: CEZ:AV0Z40720504; CEZ:AV0Z10100520 Keywords : titanium dioxide * crystallite size * crystallite size distribution Subject RIV: CA - Inorganic Chemistry http://www.oldenbourg-link.com/toc/zkpr/current
Grain size distribution of different minerals in a sediment as a function of their specific density
International Nuclear Information System (INIS)
A beach sediment from Ameland, the Netherlands was divided into 9 grain size fractions. For each fraction the heavy minerals were separated subsequently and split in a number of magnetic fractions, roughly coinciding with particular minerals. All these fractions were weighed, and their mineral composition determined. The resulting grain size distribution for each different mineral turns out to be determined mainly by its specific density, and only to a minor degree by differences in the shape of grains. (Auth.)
Performance of DMPS/C System in Determining Aerosol Particle Size Distribution
International Nuclear Information System (INIS)
An evaluation of performance of DMPS/C system TSI-3932 in determining aerosol particle size has been carried out. The evaluation consist of validity of experimentally transfer function, instrument resolution, and test of measurement accuracy and precision for monodisperse and polydisperse aerosol size distribution. Evaluation of measurement accuracy gave a deviation of 0.74 %, and evaluation of measurement precision gave variation coefficient of 0,50 % and 1.63 % for monodisperse aerosol and polydisperse aerosol respectively
Size dependency in the migrations and distribution of Norwegian spring spawning herring
Slotte, Aril
2003-01-01
The size at first spawning is comparatively larger in Norwegian spring spawning herring (Clupea harengus L.) than in other herring stocks in the Atlantic and Pacific oceans. This is probably an adaptation to a life with long seasonal migrations between wintering-, spawning- and feeding grounds. The present paper presents empirical data and model results suggesting that also historic long-term shifts and annual variations in migrations and distribution pattern may be attributed to size depende...
TNOs as probes of planet building: the Plutino size- & colour-distributions
Alexandersen, Mike; Gladman, Brett; Kavelaars, JJ; Petit, Jean-Marc; Gwyn, Stephen; Pike, Rosemary E.; Shankman, Cory
2015-01-01
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 Dbig, skipping the intermediate sizes, contrary to the expectation of bottom-up planetesimal formation.Using the Canada-France-Hawaii Telescope, our 32 sq.deg. survey, near RA=2 hr with limiting magnitude m_r=24.6, detected and tracked 77 TNOs and Centaurs for up to 28 months, providing both the high-quality orbits and the quantitative detection efficiency needed for precise modelling. We used the 18 Plutinos (3:2 Neptunian mean motion resonance) from our survey to constrain the size- and orbital-distribution model of this population. We show that the Plutino size-distribution cannot continue as a rising power-law past H_r ? 8.3 (D? 100 km); a sharp dramatic change must occur near this point. A single power-law is rejectable at >99% 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.We also present g-r photometric colours for our Plutino sample, obtained with the Gemini North telescope in 2013-2014.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. Our telescopically-expensive endeavour has provided us with unique insight into the colour-distribution of the physically smallest Plutinos.
Particle size distribution analysis for the rapid detection of microbial infection of urine.
Dow, C S; France, A D; Khan, M S; Johnson, T
1979-01-01
The accuracy and practicality of particle size distribution analysis for rapid screening of urine specimens are assessed. Six hundred urines were subjected simultaneously to routine bacteriological examinations and particle size distribution analysis using a Coulter Counter (ZBI) linked to a C1000 Channelyzer. There was complete agreement in the results of 593 (98.8%) specimens. Characteristic profiles of various bacterial species in infected specimens were consistently obtained. This system can easily be linked to any existing computer reporting in a district hospital laboratory, and the results of negative specimens (70--80%) can be obtained within 5--10 minutes. PMID:376561
A study of the pore-size distributions of some virgin Oldbury test-well graphites
International Nuclear Information System (INIS)
The pore-size distributions of some virgin Oldbury test-well graphite specimens have been determined using both image analysis and mercury porosimetry. Image analysis has revealed that the pore-size distribution (PSD) is not a function of distance from the channel wall (fuel and interstitial). Differences found between the PSDs of individual specimens have led to predicted weight losses which exhibit a variability similar to that found in installed-specimen data. The results, therefore, confirm that the channel wall densification is unlikely to be pore related, but rather to be due to short-range inhibition in the gas phase. (author)
International Nuclear Information System (INIS)
Tensile tests were conducted on several cast aluminum specimens with different degrees of porosity. The effects of non uniform void size and shape distributions, including spherical and non spherical types, on stress-strain behavior resulting from different initiation mechanisms were investigated. A micro mechanics based statistical approach was employed, and the heterogeneous microstructures could therefore be modeled during the deformation process. The predicted changes of the distributions of void size and void shape generally agreed with experimental results. Void spatial variation was also quantified, and its effects on the level of failure were analyzed. The void spatial variation facilitated development of inhomogeneous deformation, which results in failure
Energy Technology Data Exchange (ETDEWEB)
Song, Jun Su; Kang, Dong Hwan; Kim, Tae Won; Bae, Dae Sung [Hanyang Univ., Seoul (Korea, Republic of); Yoon, Hyung Sop [Hyundai Kia Motors R and D Division, Hwaseong (Korea, Republic of)
2012-07-15
Tensile tests were conducted on several cast aluminum specimens with different degrees of porosity. The effects of non uniform void size and shape distributions, including spherical and non spherical types, on stress-strain behavior resulting from different initiation mechanisms were investigated. A micro mechanics based statistical approach was employed, and the heterogeneous microstructures could therefore be modeled during the deformation process. The predicted changes of the distributions of void size and void shape generally agreed with experimental results. Void spatial variation was also quantified, and its effects on the level of failure were analyzed. The void spatial variation facilitated development of inhomogeneous deformation, which results in failure.
Effect of void-size distribution on the Hugoniot state at low shock pressures
Griffiths, David J.; Buettner, Douglas J.; Tsou, Peter
1991-01-01
In most theoretical and experimental investigations into the shock response of underdense solid media, the influence of the medium's mesostructure on the resulting pressure and degree of compaction has not been taken into account. In typical cases examined, shock pressures are well in excess of 1 GPa and this approach is clearly justified. However, at low pressures, calculations show that the distribution of void sizes can affect the final state achieved upon shocking the medium from a given initial porosity. This paper analyzes the response of porous aluminum to low pressure shocking and demonstrates a dependence of the final shocked state on the distribution of void sizes.
History of water-column anoxia in the Black Sea indicated by pyrite framboid size distributions
Wilkin, Richard T.; Arthur, Michael A.; Dean, Walter E.
1997-05-01
A detailed study of size distributions of framboidal pyrite in Holocene Black Sea sediments establishes the timing of a change from deposition under an oxic water column to deposition under an anoxic and sulfidic water column. In the most recent carbonate-rich sediments (Unit I) and in the organic carbon-rich sapropel (Unit II), framboid size distributions are remarkably uniform (mean diameter = 5 ?m); over 95% of the framboids in Unit I and Unit II are Black Sea coincided with the initiation of deposition of laminated Unit II sapropels.
Particle size distribution and its relation to sintering --- A case study for UO2 powders
International Nuclear Information System (INIS)
It is generally recognized that the particle size distribution (PSD) of powders plays a very significant role in powder compaction and sintering. However, particle size distribution data are generally presented in the form of one number (mean diameter). In the case of PSD data obtained by sedimentation, analysis of the whole curve reveals some interesting information. The type of information obtained by such an analysis and its application to an analysis of compaction and sintering is discussed using the case of uranium dioxide powders as an example
Directory of Open Access Journals (Sweden)
Mohammed Abdullahi MU'AZU
2007-01-01
Full Text Available Lateritic soil was treated with 1-4% cement contents and was admixtured with 2-8% bagasse ash content. The paper evaluated the plasticity and particle size distribution characteristic of bagasse ash on cement treated laterite. It was observed that liquid limit and plasticity index reduced while plastic limit increased. As regards the particle size distribution, the was reduction in the percentage of fines as a result of formation of heavier pseudo- and particle with percentage passing BS Sieve No. 200 reduced from 63% to almost zero. However the recommended percentage of bagasse ash should be between 4%-6%.
Directory of Open Access Journals (Sweden)
Guoquan Liu
2011-05-01
Full Text Available The conventional serial sectioning analysis and a set of modern stereological methods, including disector, selector, point-sampled intercepts, point-sampled area, and their combinations, have been used in this paper to measure the grain size, grain size distribution, topological parameters and their distributions in a spacefilling single-phase grain structure of steel. The results from different methods are compared and used to evaluate the methods quantitatively, based on which some suggestions will be given for selection of experimental methods in materials stereology research.
Application of digital image analysis for size distribution measurements of microbubbles
Energy Technology Data Exchange (ETDEWEB)
Burns, S.E.; Yiacoumi, S.; Frost, D. [Georgia Inst. of Tech., Atlanta, GA (United States). School of Civil and Environmental Engineering; Tsouris, C. [Oak Ridge National Lab., TN (United States). Chemical Technology Div.
1997-03-01
This work employs digital image analysis to measure the size distribution of microbubbles generated by the process of electroflotation for use in solid/liquid separation processes. Microbubbles are used for separations in the mineral processing industry and also in the treatment of potable water and wastewater.As the bubbles move upward in a solid/liquid column due to buoyancy, particles collide with and attach to the bubbles and are carried to the surface of the column where they are removed by skimming. The removal efficiency of solids is strongly affected by the size of the bubbles. In general, higher separation is achieved by a smaller bubble size. The primary focus of this study was to characterize the size and size distribution of bubbles generated in electroflotation using image analysis. The study found that bubble diameter increased slightly as the current density applied to the system was increased. Additionally, electroflotation produces a uniform bubble size with narrow distribution which optimizes the removal of fine particles from solution.
Eigenvalue distributions from a star product approach
Kriel, J. N.; Scholtz, F. G.
2012-01-01
We use the well-known isomorphism between operator algebras and function spaces equipped with a star product to study the asymptotic properties of certain matrix sequences in which the matrix dimension $D$ tends to infinity. Our approach is based on the $su(2)$ coherent states which allow for a systematic 1/D expansion of the star product. This produces a trace formula for functions of the matrix sequence elements in the large-$D$ limit which includes higher order (finite-$D...
Okonski, Krzysztof; Degrendele, Céline; Melymuk, Lisa; Landlová, Linda; Kuku?ka, Petr; Vojta, Šimon; Kohoutek, Ji?í; ?upr, Pavel; Klánová, Jana
2014-12-16
This study investigates the distribution of polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCD) and a group of novel flame retardants (NFRs) on atmospheric aerosols. Two high volume cascade impactors were used to collect particulate fractions of ambient air over a one year period at urban and rural sites. The majority of FRs were found on the finest aerosols (particulate matter (PM) itself. When normalized by PM, the size distributions of the FRs exhibited much greater heterogeneity. Differences existed between the FR distributions by molecular weight, with the higher molecular weight FRs (e.g., BDE-209, Dechlorane Plus) distributed more uniformly across all particulate size fractions. The seasonal, spatial, and compound-specific differences are of crucial importance when estimating dry and wet deposition of FRs as smaller aerosols have longer atmospheric residence times. Estimated wet and dry deposition of four representative FRs (BDE-47, BDE-209, HBCD, and Dechlorane Plus) using size-segregated aerosol data resulted in lower deposition estimates than when bulk aerosol data were used. This has implications for estimates of long-range atmospheric transport and atmospheric residence times, as it suggests that without size-specific distributions, these parameters could be underestimated for FRs. PMID:25380095
Size Distribution of Possible Dust Carriers for the Extended Red Emission
Mahapatra, D. P.; Chutjian, A.; Machacek, J. R.; Mangina, R. S.
2014-08-01
Power-law size distributions expected to be applicable to possible carriers of extended red emission (ERE) have been examined using Monte Carlo (MC) simulations. Si nanoparticles and some polycyclic aromatic hydrocarbon complexes such as oligoacene and oligorylenes with energy gaps close to 2 eV have been considered. In the simplest case of unit quantum efficiency, the MC-generated size distributions are used to obtain photoluminescence (PL) spectra that are then corrected for dust extinction and reddening effects for comparison with observed ERE spectra. It is shown that a power-law size distribution with a decay exponent of ? = 7/2, which closely agrees with starlight extinction data, fails to produce an ERE-like spectrum. However, size distributions with decay exponents of ? = 19/12 and 3/2 are found to lead to acceptable spectra. Results indicate that energetic photon-induced breakup and competing aggregation effects dominate collisional effects in producing the observed steady-state mass distribution. It is shown that the peak wavelength of emission critically depends on the band gap, rather than cluster mass, which for oligoacenes and oligorylenes is widely different. The peak wavelength is also shown to be insensitive to dust attenuation.
The variability of tidewater-glacier calving: origin of event-size and interval distributions
Chapuis, Anne
2012-01-01
Calving activity at the front of tidewater glaciers is characterized by a large variability in iceberg sizes and inter-event intervals. We present calving-event data obtained from continuous observations of the fronts of two tidewater glaciers on Svalbard, and show that the distributions of event sizes and inter-event intervals can be reproduced by a simple calving model focusing on the mutual interplay between calving and the destabilization of the glacier front. The event-size distributions of both the field and the model data extend over several orders of magnitude and resemble power laws. The distributions of inter-event intervals are broad, but have a less pronounced tail. In the model, the width of the size distribution increases with the calving susceptibility of the glacier front, a parameter measuring the effect of calving on the stress in the local neighborhood of the calving region. Inter-event interval distributions, in contrast, are insensitive to the calving susceptibility. Above a critical susc...
Size distribution and waiting times for the avalanches of the Cell Network Model of Fracture
Villalobos, Gabriel; Linero, Dorian L; Muñoz, Jose D
2010-01-01
The Cell Network Model is a fracture model recently introduced that resembles the microscopical structure and drying process of the parenchymatous tissue of the Bamboo Guadua angustifolia. The model exhibits a power-law distribution of avalanche sizes, with exponent -3.0 when the breaking thresholds are randomly distributed with uniform probability density. Hereby we show that the same exponent also holds when the breaking thresholds obey a broad set of Weibull distributions, and that the humidity decrements between successive avalanches (the equivalent to waiting times for this model) follow in all cases an exponential distribution. Moreover, the fraction of remaining junctures shows an exponential decay in time. In addition, introducing partial breakings and cumulative damages induces a crossover behavior between two power-laws in the avalanche size histograms. This results support the idea that the Cell Network Model may be in the same universality class as the Random Fuse Model.
International Nuclear Information System (INIS)
In the case of internally deposited radionuclides, direct measurement of the energy absorbed from ionizing radiation emitted by the decaying radionuclides is rarely, if ever, possible. Therefore, one must rely on dosimetric models to obtain estimates of the spatial and temporal patterns of energy deposition in human lung. T These models always need some information about the parameters of activity size distributions of thoron and radon progeny. In the present work, the attached and unattached activity size distributions of thoron and radon progeny were measured in outdoor air of El-Minia, Egypt. The attached samples were collected using a low pressure Berner cascade impactor technique, while a constructed screen diffusion battery was used for collecting the unattached samples. Most of the attached activities for 222Rn and 220Rn progeny were associated with the aerosol particles of the accumulation mode. The activity size distribution of thoron progeny was found to be shifted to slightly smaller particle size, compared to radon progeny. An analytical method has been developed to compute the local energy deposition of 2l2Bi alpha particles in a target volume of 1 jam spheres located at different depths in bronchial epithelium. In order to reach the target, alpha particles travel either through tissue alone (near-wall dose) or through air and tissue (far-wall dose). It was found that the contribution of near-wall dose is higher than that of the far wall dose. While the depth-dose distributions for nuclides uniformly distributed within the epithelium are practically constant with
Directory of Open Access Journals (Sweden)
Xiaolan Song
2009-01-01
Full Text Available Two kinds of RDX samples, with broad and narrow particle size distribution, have been fabricated by wet riddling and solvent/non-solvent methods, respectively. By controlling the technical condition, the RDX powders with different particle sizes were obtained for each sample. All samples were characterised by laser granularity measurement and scanning electron microscope (SEM. Using mechanical sensitivity tests, slow cook-off test and differential scanning calorimetry (DSC, the mechanical safety and thermal stability of RDX samples, depending on the particle sizes and size distribution, were studied. Results indicated that, for each kind of RDX particles, the mechanical sensitivity and thermal stability of samples changed according to the particle size. However, although two samples had almost the same average particle size, their safety changed when two particle size distributions differed. Concretely, the mechanical sensitivity of RDX reduced and their thermal stability increased gradually along with the decreasing of particle size. Meanwhile, RDX with broad size distribution had higher mechanical sensitivity and thermal stability than samples with narrow size distribution.Defence Science Journal, 2009, 59(1, pp.37-42, DOI:http://dx.doi.org/10.14429/dsj.59.1482
The particle size distribution of fragmented melt debris from molten fuel coolant interactions
International Nuclear Information System (INIS)
Results are presented of a study of the types of statistical distributions which arise when examining debris from Molten Fuel Coolant Interactions. The lognormal probability distribution and the modifications of this distribution which result from the mixing of two distributions or the removal of some debris are described. Methods of fitting these distributions to real data are detailed. A two stage fragmentation model has been developed in an attempt to distinguish between the debris produced by coarse mixing and fine scale fragmentation. However, attempts to fit this model to real data have proved unsuccessful. It was found that the debris particle size distributions from experiments at Winfrith with thermite generated uranium dioxide/molybdenum melts were Upper Limit Lognormal. (U.K.)
Kostadinov, T. S.; Siegel, D. A.; Maritorena, S.
2010-01-01
A new method of retrieving the parameters of a power-law particle size distribution (PSD) from ocean color remote sensing data was used to assess the global distribution and dynamics of phytoplankton functional types (PFT's). The method retrieves the power-law slope, ?, and the abundance at a reference diameter, N_{0}, based upon the shape and magnitude of the particulate backscattering coefficient spectrum. Relating the PSD to PFT's on glob...
Distribution of domain sizes in the zero temperature Glauber dynamics of the 1 D Potts model
Derrida, Bernard; Zeitak, Reuven
1996-01-01
For the zero temperature Glauber dynamics of the $q$-state Potts model, we calculate the exact distribution of domain sizes by mapping the problem on an exactly soluble one-species coagulation model ($A+A\\rightarrow A$). In the long time limit, this distribution is universal and from its (complicated) exact expression, we extract its behavior in various regimes. Our results are tested in a simulation and compared to the predictions of a simple approximation proposed recently...
Comparison of methods for developing contaminant-particle size distributions for suspended sediment
International Nuclear Information System (INIS)
Relationships between contaminant concentration and particle size distribution are required for modeling the transport of contaminated sediment. Standard methods, including the pipette and bottom withdrawal techniques, are unsatisfactory because of the lack of homogeneous separations of each size fraction, which results in uncertainty in the contaminant-particle size relation. In addition, the size fractions produced with these techniques do not contain enough mass for accurate contaminant analyses. To avoid these problems, an alternative method using a settling column and withdrawal times based on Stokes Law has been developed. Tests have been conducted using sediment samples contaminated with Cs-137 from a waste area at Oak Ridge National Laboratory. The samples were separated into sand, coarse and fine silt, and clay-sized particles. The results for particle size distribution and associated contaminant concentrations were evaluated for the settling column, pipette, and bottom withdrawal methods. The settling column method provides homogeneous size fractions, larger aliquots of sediment for contaminant analysis, and is quicker in some cases and less complicated to perform than the other two methods
Optimum waveguide-core size for reducing device property distribution of Si-wire waveguide devices
Soma, Munetoshi; Kita, Tomohiro; Tanushi, Yuichiro; Toyama, Munehiro; Seki, Miyoshi; Yokoyama, Nobuyuki; Ohtsuka, Minoru; Yamada, Hirohito
2015-04-01
We investigated the waveguide-core size distribution of ring resonators fabricated on a 300 mm silicon-on-insulator (SOI) wafer using a CMOS-compatible process featuring ArF immersion lithography. These ring resonators were constructed in a Si-wire waveguide with a standard core size of 400 nm width and 220 nm height. The group refractive indices of the waveguide were derived from the transmission spectra of the ring resonators. From the deviation of these group refractive indices, the waveguide-core width distribution was estimated to be 5 nm, and the waveguide-core height distribution was estimated to be 1 nm. Moreover, the device property distribution of various Si-wire waveguide depended on the estimated fabrication error was calculated. The waveguide core with the smallest device property distribution had a 540 nm width and a 160 nm height, and this waveguide has a device property distribution of 2/3 value compared with the standard core size.
Mahadi Lawan Yakubu; Zulkifli Yusop; Fadhilah Yusof
2014-01-01
This paper presents the modelled raindrop size parameters in Skudai region of the Johor Bahru, western Malaysia. Presently, there is no model to forecast the characteristics of DSD in Malaysia, and this has an underpinning implication on wet weather pollution predictions. The climate of Skudai exhibits local variability in regional scale. This study established five different parametric expressions describing the rain rate of Skudai; these models are idiosyncratic to the climate of the region...
A statistical analysis of North East Atlantic (submicron aerosol size distributions
Directory of Open Access Journals (Sweden)
M. Dall'Osto
2011-12-01
Full Text Available The Global Atmospheric Watch research station at Mace Head (Ireland offers the possibility to sample some of the cleanest air masses being imported into Europe as well as some of the most polluted being exported out of Europe. We present a statistical cluster analysis of the physical characteristics of aerosol size distributions in air ranging from the cleanest to the most polluted for the year 2008. Data coverage achieved was 75% throughout the year. By applying the Hartigan-Wong k-Means method, 12 clusters were identified as systematically occurring. These 12 clusters could be further combined into 4 categories with similar characteristics, namely: coastal nucleation category (occurring 21.3 % of the time, open ocean nucleation category (occurring 32.6% of the time, background clean marine category (occurring 26.1% of the time and anthropogenic category (occurring 20% of the time aerosol size distributions. The coastal nucleation category is characterised by a clear and dominant nucleation mode at sizes less than 10 nm while the open ocean nucleation category is characterised by a dominant Aitken mode between 15 nm and 50 nm. The background clean marine aerosol exhibited a clear bimodality in the sub-micron size distribution, with although it should be noted that either the Aitken mode or the accumulation mode may dominate the number concentration. However, peculiar background clean marine size distributions with coarser accumulation modes are also observed during winter months. By contrast, the continentally-influenced size distributions are generally more monomodal (accumulation, albeit with traces of bimodality. The open ocean category occurs more often during May, June and July, corresponding with the North East (NE Atlantic high biological period. Combined with the relatively high percentage frequency of occurrence (32.6%, this suggests that the marine biota is an important source of new nano aerosol particles in NE Atlantic Air.
Abrahamson, Warren G; Layne, James N
2002-01-01
This study examined variation in two components of acorn production. Percentage of bearing ramets (stems) and number of acorns per bearing ramet were examined in five clonal oaks in three xeric habitats of south-central peninsular Florida in relation to ramet size within and between species and vegetative associations. Counts of acorns on two white oaks (Quercus chapmanii and Q. geminata) and three red oaks (Q. inopina, Q. laevis, and Q. myrtifolia) were conducted annually from 1969 to 1996 (except in 1991) on permanent grids in southern ridge sandhill, sand pine scrub, and scrubby flatwoods associations at the Archbold Biological Station, Florida, USA. Percentage of bearing individuals and mean number of acorns per bearing individual increased with increasing ramet size for all species across all vegetation associations. However, in Q. geminata and Q. myrtifolia, acorn production declined in the largest size class (>3.2 m), implying that larger individuals of these clonal species may become senescent. All oak species in sand pine scrub, which had a nearly closed overstory, had lower frequencies of bearing oaks and mean numbers of acorns compared with similar-sized individuals of the same species in the more open-canopied southern ridge sandhill and scrubby flatwoods associations, suggesting light limitation. The annual production of acorns by a given oak species was correlated across vegetative associations and annual acorn production of oak species was correlated for species within the same section. Intermediate-size class oaks contributed the most acorns per unit area, suggesting that stands managed with short fire-return times will provide fewer acorns to wildlife than stands managed to produce more variable distributions of oak size classes. However, our study suggests that long-unburned stands, such as those studied here, will maintain relatively constant levels of acorn production as a consequence of ramet replacement within the clones of these shrubby oaks to create a variable distribution of size classes. Of the oak species studied, Q. myrtifolia had the highest acorn production and the smallest acorns, while Q. laevis had the lowest acorn production and the largest acorns, suggesting an allocation trade-off between acorn numbers and size. PMID:21669720
Five-years of atmospheric aerosol number size distribution measurements in Eastern Mediterranean
Kalivitis, Nikolaos; Kouvarakis, Giorgos; Bougiatioti, Aikaterini; Stavroulas, Iasonas; Wiedensohler, Alfred; Mihalopoulos, Nikolaos
2014-05-01
The first long term measurements of atmospheric particle size distributions from the Eastern Mediterranean region are reported. Atmospheric aerosol number size distributions have been measured at the environmental research station of University of Crete at Finokalia, Crete, Greece (35° 20' N, 25° 40' E, 250m a.s.l) on a continuous base since 2008. A custom built (TROPOS type) scanning mobility particle sizer (SMPS) is used covering size ranges from 8 to 900 nm. The system is humidity controlled so that relative humidity is kept below 40% most of the time. Throughout the measuring period the average number concentration of the particles in the studied size range was found to be 2354 ± 1332 cm-3 (median of 2098 cm-3). Maximum concentrations are observed during summer while minimum during winter, reflecting the effectiveness of the removal processes in the region. Clear annual circles are found for the number concentrations of nucleation, Aitken and accumulation mode particles. Nucleation mode is presenting different pattern from the other two modes, with the highest concentrations during winter (and March) and the lowest during summer. New particle formation events are more frequently observed during March and October. The number size distributions present different seasonal patterns. During summer, unimodal distributions centering on the lower end of the accumulation mode size range are dominant in our observations. The prevailing meteorology characterized by the Etesian winds (Meltemi) and the lack of precipitation along the trajectory results to the arrival of well mixed air masses at Finokalia, carrying aged aerosol mainly from central and Eastern Europe. Regarding the other seasons, the shape of the distributions is more variable and strongly dependent on the air mass history: When the air masses are of marine origin or precipitation has affected them, the size distributions are mainly bimodal (peaking both in Aitken and in Accumulation mode). These distributions are representative of the background marine conditions at Finokalia. Unimodal distributions can be observed as well during the rest of the seasons depending on whether aged anthropogenic aerosol reach Crete before being removed from the atmosphere or not. The nucleation mode is observed mainly when new particle formation occurs and rarely can it be attributed to combustion processes or other sources.
Distributed production planning and control agent based system
Lima, Rui M.; Sousa, Rui M.; Martins, Paulo Jorge Figueiredo
2006-01-01
A model of an Agent-based Production Planning and Control (PPC) system that can be dynamically adaptable to local and distributed utilization of production resources and materials is presented. The PPC system is based on the selection of resources to deal with one order of different quantities of one product each time. In this way, one scheduling solution is provided for that particular order. The production resources are selected and scheduled using a multi-agent system supported by an imple...
Product market integration, tax distortions and public sector size
DEFF Research Database (Denmark)
Andersen, Torben M.; SØrensen, Allan
2013-01-01
The implications of product market integration for public sector activities (transfers and public consumption) are considered in a standard setting. The analysis supports that a larger public sector (higher tax rate) tends to increase wages and worsen wage competitiveness. However, the implications of product market integration for the public sector are far from straightforward. The reason is gains-from-trade effects which tend to increase the tax base and decrease the opportunity costs of public consumption (marginal utility of private consumption falls). It follows that the retrenchment view that product market integration inevitable leads to a downward pressure on public sector activities does not get support in a standard setting. A particularly noteworthy finding is that a country with a large public sector (strong preferences for public consumption) may benefit more by integrating with a country with a smaller public sector (weak preferences for public consumption).
Santana, Steven Michael; Antonyak, Marc A.; Cerione, Richard A.; Kirby, Brian J.
2014-12-01
Extracellular shed vesicles (ESVs) facilitate a unique mode of cell–cell communication wherein vesicle uptake can induce a change in the recipient cell?s state. Despite the intensity of ESV research, currently reported data represent the bulk characterization of concentrated vesicle samples with little attention paid to heterogeneity. ESV populations likely represent diversity in mechanisms of formation, cargo and size. To better understand ESV subpopulations and the signaling cascades implicated in their formation, we characterize ESV size distributions to identify subpopulations in normal and cancerous epithelial cells. We have discovered that cancer cells exhibit bimodal ESV distributions, one small-diameter and another large-diameter population, suggesting that two mechanisms may govern ESV formation, an exosome population and a cancer-specific microvesicle population. Altered glutamine metabolism in cancer is thought to fuel cancer growth but may also support metastatic niche formation through microvesicle production. We describe the role of a glutaminase inhibitor, compound 968, in ESV production. We have discovered that inhibiting glutamine metabolism significantly impairs large-diameter microvesicle production in cancer cells.
A kinetic-empirical model for particle size distribution evolution during pulverised fuel combustion
Energy Technology Data Exchange (ETDEWEB)
Kalpit V. Shah; Mariusz K. Cieplik; Christine I. Betrand; Willem L. van de Kamp; Hari B. Vuthaluru [Curtin University of Technology, Perth, WA (Australia). Department of Chemical Engineering
2010-09-15
Particle size is an essential parameter in pulverised fuel (PF) combustion as many of the problems or further areas of development in these systems are strongly influenced by the fuel and ash size distribution. This is particularly true for dynamic processes like pollutant formation, corrosion, erosion, slagging and fouling and the related decrease of the combustion and boiler efficiency. The evolution of particle size distribution (PSD) is a complex interaction of various competing chemical and physical transformations. Char oxidation, devolatilization and fragmentation, etc. represent first line physical and chemical transformations which can amend the particle size in the radiation zone. The evolution of the PSD represents the convolution of all of these physical and chemical transformations, operating over the entire size distribution. As a consequence, it is difficult to extract the relative importance of all competing size altering processes from the experiments. Various models such as break-up, thermal stress, shrinking core, percolation and particle-population model have been developed by incorporating numerous ash transformation mechanisms to predict the particle size evolution during the pulverised fuel combustion. The present work describes an adaptation of the numerical kinetic-based particle-population balance for predicting particle size evolution during PF combustion developed by Dunn-Rankin and Mitchell. The model is further simplified analytically and validated against experimental results. Several empirical parameters derived from the experiments are incorporated into the model. The resulting simplified PSD evolution model shows good agreement with literature and experimental results, with maximum 10% absolute standard deviation. 29 refs., 10 figs., 2 tabs.
Çakal, G. Ö.; Ero?lu, ?.; Özkar, S.
2006-04-01
Colemanite, one of the important boron minerals, is dissolved in aqueous sulfuric acid to produce boric acid. In this reaction, gypsum is obtained as a by-product. Gypsum crystals are in the shape of thin needles. These crystals should be grown to an easily filterable size in order to increase the production yield and purity of boric acid. In this paper, the particle size distributions and the volume-weighted mean diameters of the gypsum crystals obtained in batch and continuous flow systems were compared. Experiments in both batch and continuous reactors were performed at a temperature of 85 °C, a stirring rate of 400 rpm, and the inlet CaO to SO42- molar ratio of 1.0 using colemanite mineral in particle size smaller than 150 ?m. The average diameter of the gypsum crystals obtained at 3.5 h from the batch reactor was found to be 37-41 ?m. This value for the continuous system at steady state was observed to change between 44-163 ?m. The particle size of the gypsum crystals was found to increase with the residence time of the solid in the continuous system.
Sediment production and distribution across the margins
Elana Leithold
This activity is an exploration of the relationship among tectonics, sediment production, and sediment dispersal from watersheds to the continental margins. Students will examine data on a suite of watersheds and make measurements and observations in Google Earth or GeoMapApp.
Particle size distribution from small-angle X-ray scattering data
International Nuclear Information System (INIS)
An improved transform technique has been developed for calculating the particle size distribution N(R) for spherical particles with radii R from small-angle X-ray scattering data. This method permits N(R) to be calculated from analytical expressions that were derived for point collimation and for infinitely long slit collimation. A special procedure has been introduced in order to reduce termination errors. The technique described and those developed by Schmidt were used for calculating particle size distributions from theoretical scattering curves and from an experimental scattering curve of suspended SiO2 particles (Ludox). The results obtained by the different techniques were compared, and reasonable results are given by all methods employed. The accuracy of the size distributions calculated by the improved method is somewhat higher than that obtained by Schmidt's transform technique. With Glatter's procedure, the deviations from the exact distributions are comparable to those from this improved transform technique, but the use of Glatter's program requires a large computer, whereas the new method has the advantage of being suitable for a small computer. Vonk's program also requires a large computer, and the deviations obtained are larger than those produced by other methods. The experimental scattering curve of the Ludox sample was also evaluated by assuming a log-normal distribution for the particles. The parameters ? and sigma of this function were deters ? and sigma of this function were determined from a set of small-angle X-ray scattering structural parameters. The resulting log-normal distribution is significantly different from the size distribution calculated by our method. (orig./BHO)
Bubble size distribution in a steady-state column of aqueous foam.
Feitosa, Klebert; Durian, Douglas J.
2006-03-01
We report on measurements of the distribution of bubble sizes in a vertical column of aqueous foam. The sample is generated and maintained in steady-state by continuous bubbling of gas (CO2) in a surfactant solution (H2O + AOS + NaCl) at the bottom of a tall Lucite cylinder. The constant flow of gas produces nearly identical bubbles that accumulate at the liquid/foam interface and subsequently move up with constant velocity. The distribution of bubble sizes depends on height, being monodisperse near the bottom, turning bidisperse at some intermediate height, and then becoming polydisperse further up in the column. This behavior is exclusively due to coarsening and drainage, since film-rupture and convection are not observed. The development of a bidisperse distribution cannot be explained by mean-field theories of coarsening, in which bubbles of a given size grow or shrink at a rate that depends only on their size in comparison with a mean size.
Xu, Shanshan; Zong, Yujin; Feng, Yi; Liu, Runna; Liu, Xiaodong; Hu, Yaxin; Han, Shimin; Wan, Mingxi
2015-01-01
In this study, we investigated the relationship between the efficiency of pulsed, focused ultrasound (FUS)-induced thrombolysis, the duty cycle (2.3%, 9%, and 18%) and the size distribution of cavitation bubbles. The efficiency of thrombolysis was evaluated through the degree of mechanical fragmentation, namely the number, mass, and size of clot debris particles. First, we found that the total number and mass of clot debris particles were highest when a duty cycle of 9% was used and that the mean diameter of clot debris particles was smallest. Second, we found that the size distribution of cavitation bubbles was mainly centered around the linear resonance radius (2.5?m) of the emission frequency (1.2MHz) of the FUS transducer when a 9% duty cycle was used, while the majority of cavitation bubbles became smaller or larger than the linear resonance radius when a 2.3% or 18% duty cycle was used. In addition, the inertial cavitation dose from the treatment performed at 9% duty cycle was much higher than the dose obtained with the other two duty cycles. The data presented here suggest that there is an optimal duty cycle at which the thrombolysis efficiency and cavitation activity are strongest. They further indicate that using a pulsed FUS may help control the size distribution of cavitation nuclei within an active size range, which we found to be near the linear resonance radius of the emission frequency of the FUS transducer. PMID:25043556
Energy Technology Data Exchange (ETDEWEB)
Tsakiris, N.; Gill-Comeau, M.; Lewis, L. J. [Département de Physique et Regroupement Québécois sur les Matériaux de Pointe (RQMP), Université de Montréal, C.P. 6128, Succursale Centre-Ville, Montréal, Québec H3C 3J7 (Canada); Anoop, K. K.; Ausanio, G.; Bruzzese, R.; Amoruso, S., E-mail: amoruso@na.infn.it [Dipartimento di Fisica, Università degli Studi di Napoli Federico II and CNR-SPIN, Complesso Universitario di Monte S. Angelo, Via Cintia, I-80126 Napoli (Italy)
2014-06-28
We address the role of laser pulse fluence on expansion dynamics and size distribution of the nanoparticles produced by irradiating a metallic target with an ultrashort laser pulse in a vacuum, an issue for which contrasting indications are present in the literature. To this end, we have carried out a combined theoretical and experimental analysis of laser ablation of a bulk copper target with ?50 fs, 800?nm pulses, in an interval of laser fluencies going from few to several times the ablation threshold. On one side, molecular dynamics simulations, with two-temperature model, describe the decomposition of the material through the analysis of the evolution of thermodynamic trajectories in the material phase diagram, and allow estimating the size distribution of the generated nano-aggregates. On the other side, atomic force microscopy of less than one layer nanoparticles deposits on witness plates, and fast imaging of the nanoparticles broadband optical emission provide the corresponding experimental characterization. Both experimental and numerical findings agree on a size distribution characterized by a significant fraction (?90%) of small nanoparticles, and a residual part (?10%) spanning over a rather large size interval, evidencing a weak dependence of the nanoparticles sizes on the laser pulse fluence. Numerical and experimental findings show a good degree of consistency, thus suggesting that modeling can realistically support the search for experimental methods leading to an improved control over the generation of nanoparticles by ultrashort laser ablation.
Measurements of the lateral distribution of air shower and its size spectrum in Kobe
International Nuclear Information System (INIS)
The results of measurements of the lateral distribution of charged particles in air shower and its size spectrum are described. Ten plastic scintillators (N-detectors) with 1 m2 of effective area and 5 cm thickness and 54 plastic scintilators (S-detectors) with 0.25 m2 of effective area were used for the detection of the particle density of air shower (EAS). These scintillators were arranged inside and outside of the laboratory. Some scintillators were placed in two-layer arrangement with a 3 mm thick iron plate between the detectors. The energy flow of EAS was measured with 9 lead glass Cherenkov detectors. The system was operated for the period from January to October in 1977, with three trigger conditions which were four-fold-coincidence, two-fold-coincidence and anyone of five designated S-detectors. The following results were obtained from the measurements. The lateral distribution in the range around 50 m was able to be expressed by a single age NKG function. The average value of the age parameter decreased gradually with the increase of size, and approached to a constant value. The ratio of the standard deviation of age to the average value of the age parameter decreased simply with the increase of size. The zenith angle distribution was almost constant. In the size from 8 x 104 to 5 x 106, the observed size spectrum was able to be expressed with a single power function. (Kato, T.), T.)
Vervoort, R. W.; Cattle, S. R.
2003-03-01
To enable a link between the pore size distribution of the soil measured in two dimensions and the hydraulic conductivity, a factor, which includes the connectivity and tortuosity of the pore network in three dimensions, is needed. In order to increase confidence in the models which predict hydraulic conductivity, this paper aims to gain insight into relationship between tortuosity and connectivity parameters used in statistical models of hydraulic conductivity and soil structural form measurements derived with image analysis. The analysis was based on a dataset of the hydraulic and soil structural properties of 19 Vertisol samples from Eastern Australia. The soil structural data were measured on large (200 mm height and 150 mm diameter) cores at 5-7 depth slices. Several soil structural form parameters, including a pore size distribution, were calculated using an image analysis program ( Solicon v2.1). The hydraulic conductivity model developed by Kosugi [Soil Sci. Soc. Am. J. 63 (1999) 270] based on the lognormal pore size distribution was fitted to measured hydraulic conductivities. Hydraulic conductivity was strongly related to porosity and a measure of connectivity in the horizontal direction (pore genus). The tortuosity parameters ? and ? from the Kosugi [Soil Sci. Soc. Am. J. 63 (1999) 270] model were related to the mean pore size, with increasing mean pore size indicating decreasing tortuosity of the sample.
International Nuclear Information System (INIS)
We address the role of laser pulse fluence on expansion dynamics and size distribution of the nanoparticles produced by irradiating a metallic target with an ultrashort laser pulse in a vacuum, an issue for which contrasting indications are present in the literature. To this end, we have carried out a combined theoretical and experimental analysis of laser ablation of a bulk copper target with ?50 fs, 800?nm pulses, in an interval of laser fluencies going from few to several times the ablation threshold. On one side, molecular dynamics simulations, with two-temperature model, describe the decomposition of the material through the analysis of the evolution of thermodynamic trajectories in the material phase diagram, and allow estimating the size distribution of the generated nano-aggregates. On the other side, atomic force microscopy of less than one layer nanoparticles deposits on witness plates, and fast imaging of the nanoparticles broadband optical emission provide the corresponding experimental characterization. Both experimental and numerical findings agree on a size distribution characterized by a significant fraction (?90%) of small nanoparticles, and a residual part (?10%) spanning over a rather large size interval, evidencing a weak dependence of the nanoparticles sizes on the laser pulse fluence. Numerical and experimental findings show a good degree of consistency, thus suggesting that modeling can realistically support the search for experimental methods leading to an improved control over the generation of nanoparticles by ultrashort laser ablation.
Coscollà, Clara; Muñoz, Amalia; Borrás, Esther; Vera, Teresa; Ródenas, Milagros; Yusà, Vicent
2014-10-01
This work presents first data on the particle size distribution of 16 pesticides currently used in Mediterranean agriculture in the atmosphere. Particulate matter air samples were collected using a cascade impactor distributed into four size fractions in a rural site of Valencia Region, during July to September in 2012 and from May to July in 2013. A total of 16 pesticides were detected, including six fungicides, seven insecticides and three herbicides. The total concentrations in the particulate phase (TSP: Total Suspended Particulate) ranged from 3.5 to 383.1 pg m-3. Most of the pesticides (such as carbendazim, tebuconazole, chlorpyrifos-ethyl and chlorpyrifos-methyl) were accumulated in the ultrafine-fine (<1 ?m) and coarse (2.5-10 ?m) particle size fractions. Others like omethoate, dimethoate and malathion were presented only in the ultrafine-fine size fraction (<1 ?m). Finally, diuron, diphenylamine and terbuthylazine-desethyl-2-OH also show a bimodal distribution but mainly in the coarse size fractions.
Forms of density regulation and (quasi-) stationary distributions of population sizes in birds
DEFF Research Database (Denmark)
Sæther, Bernt-Erik; Engen, Steinar
2008-01-01
The theta-logistic model of density regulation is an especially flexible class of density regulation models where different forms of non-linear density regulation can be expressed by only one parameter, u. Estimating the parameters of the thetalogistic model is, however, challenging. This is mainly due to the need for information concerning population growth at low densities as well as data on fluctuations around the carrying capacity K in order to estimate the strength of density regulation. Here we estimate parameters of the theta-logistic model for 28 populations of three species of birds that have grown from very small population sizes followed by a period of fluctuations around K. We then use these parameters to estimate the quasi-stationary distribution of population size. There were often large uncertainties in these parameters specifying the form of density regulation that were generally independent of the duration of the study period. In contrast, precision in the estimates of environmental variance increased with the length of the time series. In most of the populations, a large proportion of the probability density of the (quasi-) stationary distribution of population sizes was located at intermediate population sizes relative to K. Thus, we suggest that the (quasi-) stationary distribution of population sizes represents a useful summary statistic that in many cases provides a more robust characterisation of basic population dynamics (e.g. range of variation in population fluctuations or proportion of time spent close to K) than can be obtained from analyses of single model parameters