Firm size and productivity. Evidence from the electricity distribution industry in Brazil
International Nuclear Information System (INIS)
In this paper we apply Stochastic Frontier Analysis through a distance function to investigate the impact of firm size on productivity development in electricity distribution. We use a sample of seventeen Brazilian firms from 1998 to 2005 and decompose productivity into technical efficiency, scale efficiency and technical change. Moreover, a further step is to decompose the technical change measurement into several components. The results indicate that firm size is important for industry's productivity, and therefore a key aspect to consider when making decisions that affect the market structure in the electricity distribution industry. (author)
Firm size and productivity. Evidence from the electricity distribution industry in Brazil
Energy Technology Data Exchange (ETDEWEB)
Tovar, Beatriz [Departmento de Analisis Economico Aplicado y EIT, Universidad de Las Palmas de Gran Canaria (Spain); Javier Ramos-Real, Francisco [Departamento de Analisis Economico, Facultad de Ciencias Economicas y Empresariales, Campus de Guajara, Universidad de La Laguna, La Laguna, S/C de Tenerife, Espana (Spain); De Almeida, Edmar Fagundes [IE-UFRJ (Instituto de Economia-Universidade Federal do Rio de Janeiro) (Brazil)
2011-02-15
In this paper we apply Stochastic Frontier Analysis through a distance function to investigate the impact of firm size on productivity development in electricity distribution. We use a sample of seventeen Brazilian firms from 1998 to 2005 and decompose productivity into technical efficiency, scale efficiency and technical change. Moreover, a further step is to decompose the technical change measurement into several components. The results indicate that firm size is important for industry's productivity, and therefore a key aspect to consider when making decisions that affect the market structure in the electricity distribution industry. (author)
Firm size and productivity. Evidence from the electricity distribution industry in Brazil
International Nuclear Information System (INIS)
In this paper we apply Stochastic Frontier Analysis through a distance function to investigate the impact of firm size on productivity development in electricity distribution. We use a sample of seventeen Brazilian firms from 1998 to 2005 and decompose productivity into technical efficiency, scale efficiency and technical change. Moreover, a further step is to decompose the technical change measurement into several components. The results indicate that firm size is important for industry's productivity, and therefore a key aspect to consider when making decisions that affect the market structure in the electricity distribution industry. - Research Highlights: ?We apply Stochastic Frontier Analysis through a distance function to investigate the impact of firm's size on productivity development in electricity distribution using a sample of eighteen Brazilian firms from 1998 to 2005. ?Productivity is decomposed into technical efficiency, scale-efficiency and technical change. ?Firm size is important for the industry's productivity, and therefore a key aspect to consider when making decisions that affect the market structure in the electricity distribution industry.
Mazzoli, Alida; Moriconi, Giacomo
2014-12-01
The waste management of glass fiber reinforced polymer (GRP) materials, in particular those made with thermosetting resins, is a critical issue for the composites industry because these materials cannot be reprocessed. Therefore, most thermosetting GRP waste is presently sent to landfill, in spite of the significant environmental impact caused by their disposal in this way. The limited GRP waste recycling worldwide is mostly due to its intrinsic thermosetting properties, lack of characterization data and unavailability of viable recycling and recovery routes. One of the possibility for re-using GRP industrial by-product is in form of powder as a partial aggregate replacement or filler addition in cement based composites for applications in sustainable construction materials and technologies. However, the feasibility of this kind of reutilization strongly depends on the morphology and particle size distribution of a powder made up of polymer granules and glass fibers. In the present study, the use of image analysis method, based on scanning electron microscopy (SEM) and ImageJ processing program, is proposed in order to evaluate the morphology of the particles and measure the particle size and size distribution of fine GRP waste powder. The obtained results show a great potential of such a method in order to be considered as a standardized method of measurement and analysis in order to characterize the grain size and size distribution of GRP particles before exploiting any compatibility issue for its recycling management. PMID:25195092
International Nuclear Information System (INIS)
During deactivation and decommissioning activities, thermal cutting tools, such as plasma torch, laser, and gasoline torch, are used to cut metals. These activities generate fumes, smoke and particulates. These airborne species of matter, called aerosols, may be inhaled if suitable respiratory protection is not used. Inhalation of the airborne metallic aerosols has been reported to cause ill health effects, such as acute respiratory syndrome and chromosome damage in lymphocytes. In the nuclear industry, metals may be contaminated with radioactive materials. Cutting these metals, as in size reduction of gloveboxes and tanks, produces high concentrations of airborne transuranic particles. Particles of the respirable size range (size < 10 microm) deposit in various compartments of the respiratory tract, the fraction and the site in the respiratory tract depending on the size of the particles. The dose delivered to the respiratory tract depends on the size distribution of the airborne particulates (aerosols) and their concentration and radioactivity/toxicity. The concentration of airborne particulate matter in an environment is dependent upon the rate of their production and the ventilation rate. Thus, measuring aerosol size distribution and generation rate is important for (1) the assessment of inhalation exposures of workers, (2) the selection of respiratory protection equipment, and (3) the design of appropriate filtration systems. Size distribution of the aerosols generated during cutting of different metals by plasma torch was measured. Cutting rates of different metals, rate of generation of respirable mass, as well as the fraction of the released kerf that become respirable were determined. This report presents results of these studies. Measurements of the particles generated during cutting of metal plates with a plasma arc torch revealed the presence of particles with mass median aerodynamic diameters of particles close to 0.2 micro
Leung, Danny; Meh, Ce?saire; Terajima, Yaz
2008-01-01
This paper examines the relationship between firm size and productivity. In contrast to previous studies, this paper offers evidence of the relationship not only from manufacturing firms, but from non-manufacturing firms as well. Furthermore, the aggregate importance of the firm sizeproductivity relationship is gauged by calculating to what extent shifts in the distribution of employment over firm size categories has affected Canadian aggregate productivity, and whether differences in the emp...
Energy Technology Data Exchange (ETDEWEB)
H.J. Walqui; T.C. Eisele; S.K. Kawatra
2003-10-01
The goal of this project is to improve energy efficiency of industrial crushing and grinding operations (comminution). Mathematical models of the comminution process are being used to study methods for optimizing the product size distribution, so that the amount of excessively fine material produced can be minimized. The goal is to save energy by reducing the amount of material that is ground below the target size, while simultaneously reducing the quantity of materials wasted as ''slimes'' that are too fine to be useful. This will be accomplished by: (1) modeling alternative circuit arrangements to determine methods for minimizing overgrinding and maximizing energy efficiency, and (2) determining whether new technologies, such as high-pressure roll crushing, can be used to alter particle breakage behavior to minimize fines production.
Energy Technology Data Exchange (ETDEWEB)
T.C. Eisele; S.K. Kawatra; H.J. Walqui
2004-10-01
The goal of this project is to improve energy efficiency of industrial crushing and grinding operations (comminution). Mathematical models of the comminution process are being used to study methods for optimizing the product size distribution, so that the amount of excessively fine material produced can be minimized. The goal is to save energy by reducing the amount of material that is ground below the target size, while simultaneously reducing the quantity of materials wasted as ''slimes'' that are too fine to be useful. This is being accomplished by mathematical modeling of the grinding circuits to determine how to correct this problem. The approaches taken included (1) Modeling of the circuit to determine process bottlenecks that restrict flowrates in one area while forcing other parts of the circuit to overgrind the material; (2) Modeling of hydrocyclones to determine the mechanisms responsible for retaining fine, high-density particles in the circuit until they are overground, and improving existing models to accurately account for this behavior; and (3) Evaluation of advanced technologies to improve comminution efficiency and produce sharper product size distributions with less overgrinding.
Energy Technology Data Exchange (ETDEWEB)
S. K. Kawatra; T. C. Eisele; T. Weldum; D. Larsen; R. Mariani; J. Pletka
2005-03-31
The goal of this project is to improve energy efficiency of industrial crushing and grinding operations (comminution). Mathematical models of the comminution process are being used to study methods for optimizing the product size distribution, so that the amount of excessively fine material produced can be minimized. The goal is to save energy by reducing the amount of material that is ground below the target size, while simultaneously reducing the quantity of materials wasted as ''slimes'' that are too fine to be useful. This is being accomplished by mathematical modeling of the grinding circuits to determine how to correct this problem. The approaches taken included (1) Modeling of the circuit to determine process bottlenecks that restrict flow rates in one area while forcing other parts of the circuit to overgrind the material; (2) Modeling of hydrocyclones to determine the mechanisms responsible for retaining fine, high-density particles in the circuit until they are overground, and improving existing models to accurately account for this behavior; and (3) Evaluation of advanced technologies to improve comminution efficiency and produce sharper product size distributions with less overgrinding.
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
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.
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
A technique for production of nanocrystalline cellulose with a narrow size distribution
Energy Technology Data Exchange (ETDEWEB)
Bai, Wen; Holbery, James D.; Li, Kaichang
2009-02-01
Nanocrystalline cellulose (NCC) was prepared by sulfuric acid hydrolysis of microcrystalline cellulose. A differential centrifugation technique was studied to obtain NCC whiskers with a narrow size distribution. It was shown that the volume of NCC in different fractions had an inverse relationship with relative centrifugal force (RCF). The length of NCC whiskers was also fractionized by differential RCF. The aspect ratio of NCC in different fractions had a relatively narrow range. This technique provides an easy way of producing NCC whiskers with a narrow size distribution.
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.
International Nuclear Information System (INIS)
The activity size distributions of indoor and outdoor radioactive aerosol associated with short-lived radon decay products were observed at Nagoya, Japan, for some periods from 2010 to 2012, following the indoor observation by Mostafa et al. [Mostafa, A. M. A., Tamaki, K., Moriizumi, J., Yamazawa, H. and Iida, T. The weather dependence of particle size distribution of indoor radioactive aerosol associated with radon decay products. Radiat. Prot. Dosim. 146(1-3), 19-22 (2011)]. The tendency of smaller indoor activity median aerodynamic diameter (AMAD) after rainfalls showed in the previous study was not consistently obtained, while the consistent tendency of less indoor radioactive particles with diameters in the accumulation mode was observed again after rainfalls. The indoor aerosols showed activity size distributions similar to the outdoor ones. Non-radioactive aerosol particle concentrations measured with a laser particle counter suggested a somewhat liner relationship with AMAD. (authors)
Wachsmann, Philip; Lamprecht, Alf
2014-07-01
Abstract A common technique for the preparation of polymeric nanoparticles (NPs) from preformed polymers is the emulsification solvent evaporation (ESE) method. However, the particle size of such carriers can typically not reduced below 100?nm. A bimodal distribution of particle size when applying ESE to the preparation of ethylcellulose (EC) NPs was intended to obtain very small particles in a size range below 50?nm. The proportion and size of the small particle fraction (SPF) depended on the surfactant as well as on the EC type and concentration. The preparation was conducted with different pharmaceutically relevant surfactants (polyoxyethylene (23) lauryl ether, sodium dodecyl sulfate, cetyltrimethylammonium bromide, polyvinyl alcohol and polysorbate 20) and all permitted obtaining very small NPs. After purification from excess surfactant by diafiltration and separation of the SPF by centrifugation, monodispersed particles with mean sizes between 20.6?±?2.3?nm and 49.7?±?4.8?nm could be isolated. The entrapment of a lipophilic model drug led to encapsulation rates between 34.0?±?2.4% and 78.2?±?12.6%, which were size and surfactant dependent. The preparation of polymeric NPs in a size below 50?nm by a simple centrifugation step holds promise for therapeutic applications where larger particles would be inefficient. PMID:25000483
International Nuclear Information System (INIS)
The pulsed dc magnetron technique was used for generating TiOx nanoparticles by sputtering from a titanium target in a gas aggregation source. It was observed that the deposition rate (DR) of nanoparticles shows a peak followed by a broad tail, even for constant operation conditions. As a key finding of the present investigation, we show that nanoparticle deposition can be stabilized at nonzero DR for the pulsed power regime. Monitoring the oxygen concentration by mass spectrometry provides insight into nanoparticle generation in different processes. Characterization of the nanoparticle film morphology based on transmission electron microscopy reveals a very narrow size distribution. Furthermore, the oxygen admixture has a significant influence on the size distribution and also on the mean size of the formed nanoparticles. In situ analysis of the chemical composition of the deposited films directly after preparation by x-ray photoelectron spectroscopy shows a major contribution by sub-oxide titanium compounds to nanoparticle production. (paper)
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)
Control of the grain size distribution of the raw material mixture in the production of iron sinter
Lwamba, E.; Garbers-craig, Andrie Mariana
2008-01-01
The aim of this study was to examine the effect of grain size distribution control of the raw material mixture on the permeability of the green sinter bed and the properties of the produced sinter. This was achieved by evaluating the granulation characteristics of the sinter mixture (moisture content, granulation time and mean granule diameter) in terms of its green bed permeability, and evaluating the productivity of the sinter bed, the coke rate, tumble index (TI), abrasion index (AI), redu...
International Nuclear Information System (INIS)
In uranium mines the danger of internal irradiation by radon and its active deposit depends on the state of equilibrium between the gas and its daughter products, and of the particle-size of the radioactive aerosols. To carry out continuous determination of radon in the mine air, the authors adapted the equipment developed in Toulouse for measuring atmospheric radon and thoron. This method is valuable because it can be used for observing changes in the radon concentration of the air during the different operations of ore extraction. To study the radioactive equilibrium between radon and its daughter products the authors calculated the changes in alpha activity of the radioactive aerosol filter for different proportions of RaA, RaB and RaC in the air. The shape of the curves of filter activity during and after sampling indicates the quantities of RaA, RaB and RaC contained in the air being analysed. A series of samples were taken in the mine galleries, and for each stage in the work of ore extraction the state of the equilibrium between radon and its daughter products was measured, using the above-mentioned theoretical curves. The authors found that radon is generally in equilibrium with RaA, but there is no equilibrium between radon, RaB and RaC, even when there is only slight ventilation. Radon concentration measurements for protecting the miners therefore offer a margin of safety, since the radon concentration is regarded as being in equilibrium with the first daugh being in equilibrium with the first daughter products in applying the safety regulations. The size of radioactive ions was determined by measuring their mobility for particles of size less than 5 x 10-6 cm (it may be assumed that in this size range an ion has only one charge). This paper gives the ion distribution as a function of ion mobility, size and charge sign; the distribution is similar to that obtained with atmospheric aerosols. (author)
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.
Yamamoto, Yoshihisa; Suzuki, Toyofumi; Matsumoto, Mika; Ohtani, Michiteru; Hayano, Shuichi; Fukami, Toshiro; Tomono, Kazuo
2012-01-01
We used near infrared (NIR) spectroscopy to evaluate the degree of mixing of blended dry syrup (DS) products whose particle sizes are not specified in the Revised 16th Edition of the Japanese Pharmacopoeia, and also evaluated the degree of mixing when powder products or fine granule products were added to DS products. The data obtained were used to investigate the relationship between the particle size distributions of the products studied and the degree of mixing. We found that the particle size distribution characteristics of the 15 DS products studied can be broadly classified into 5 types. Combinations of frequently prescribed products were selected to represent 4 of the 5 particle size distribution types and were blended with a mortar and pestle. The coefficient of variation (CV) decreased as the percent mass of Asverin® Dry Syrup 2% (Asverin-DS) increased in blends of Periactin® Powder 1% (Periactin) and Asverin-DS, indicating an improved degree of mixing (uniformity). In contrast, in blends of Periactin and Mucodyne® DS 33.3%, mixing a combination at a 1:1 mass ratio 40 times resulted in a CV of 20%. Other mixing frequencies and mass ratios resulted in a CV by 50% to 70%, indicating a very poor degree of mixing (poor uniformity). These results suggest that when combining different DSs, or a DS with a powder or fine granule product, the blending obtained with a mortar and pestle improves as the particle size distributions of the components approach each other and as the ranges of the distributions narrow. PMID:22689400
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)
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)
Comparing two mass size distributions
Scientific Electronic Library Online (English)
F., Lombard; G.J., Lyman.
2012-07-01
Full Text Available We consider in this paper the use of a modified version of Hotelling's statistic in the analysis of particle size distributions. The statistic can be adversely affected by the presence of outliers among the data. We propose a competitor to the statistic that is based on ranks, and hence is less sens [...] itive to outlier effects. The results of a Monte Carlo study suggest that the rank test is highly competitive with the Hotelling test in its ability to detect differences between two mass size distributions. The calculation of the rank statistic is explained in detail and its application is illustrated on two sets of data.
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)
Urban aerosol number size distributions
Directory of Open Access Journals (Sweden)
T. Hussein
2004-01-01
Full Text Available Aerosol number size distributions have been measured since 5 May 1997 in Helsinki, Finland. The presented aerosol data represents size distributions within the particle diameter size range 8-400nm during the period from May 1997 to March 2003. The daily, monthly and annual patterns of the aerosol particle number concentrations were investigated. The temporal variation of the particle number concentration showed close correlations with traffic activities. The highest total number concentrations were observed during workdays; especially on Fridays, and the lowest concentrations occurred during weekends; especially Sundays. Seasonally, the highest total number concentrations were observed during winter and spring and lower concentrations were observed during June and July. More than 80% of the number size distributions had three modes: nucleation mode (30nm, Aitken mode (20-100nm and accumulation mode (}$'>90nm. Less than 20% of the number size distributions had either two modes or consisted of more than three modes. Two different measurement sites were used; in the first (Siltavuori, 5.5.1997-5.3.2001, the arithmetic means of the particle number concentrations were 7000cm, 6500cm, and 1000cm respectively for nucleation, Aitken, and accumulation modes. In the second site (Kumpula, 6.3.2001-28.2.2003 they were 5500cm, 4000cm, and 1000cm. The total number concentration in nucleation and Aitken modes were usually significantly higher during workdays than during weekends. The temporal variations in the accumulation mode were less pronounced. The lower concentrations at Kumpula were mainly due to building construction and also the slight overall decreasing trend during these years. During the site changing a period of simultaneous measurements over two weeks were performed showing nice correlation at both sites.
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...
Determination of size distribution function
International Nuclear Information System (INIS)
The theory of a method is outlined which gives the size distribution function (SDF) of a polydispersed system of non-interacting colloidal and microscopic spherical particles, having sizes in the range 0-10-5 cm., from a gedanken experimental scheme. It is assumed that the SDF is differentiable and the result is obtained for rotational frequency in the order of 103 (sec)-1. The method may be used independently, but is particularly useful in conjunction with an alternate method described in a preceding paper. (author). 8 refs, 2 figs
Parameterizing the Raindrop Size Distribution
Haddad, Ziad S.; Durden, Stephen L.; Im, Eastwood
1996-01-01
This paper addresses the problem of finding a parametric form for the raindrop size distribution (DSD) that(1) is an appropriate model for tropical rainfall, and (2) involves statistically independent parameters. Such a parameterization is derived in this paper. One of the resulting three "canonical" parameters turns out to vary relatively little, thus making the parameterization particularly useful for remote sensing applications. In fact, a new set of r drop-size-distribution-based Z-R and k-R relations is obtained. Only slightly more complex than power laws, they are very good approximations to the exact radar relations one would obtain using Mie scattering. The coefficients of the new relations are directly related to the shape parameters of the particular DSD that one starts with. Perhaps most important, since the coefficients are independent of the rain rate itself, the relations are ideally suited for rain retrieval algorithms.
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)
International Nuclear Information System (INIS)
The Materials Chemistry Department 1846 has developed a lab-scale chem-prep process for the synthesis of PNZT 95/5, a ferroelectric material that is used in neutron generator power supplies. This process (Sandia Process, or SP) has been successfully transferred to and scaled by Department 14192 (Ceramics and Glass Department), (Transferred Sandia Process, or TSP), to meet the future supply needs of Sandia for its neutron generator production responsibilities. In going from the development-size SP batch (1.6 kg/batch) to the production-scale TSP powder batch size (10 kg/batch), it was important that it be determined if the scaling process caused any ''performance-critical'' changes in the PNZT 95/5 being produced. One area where a difference was found was in the particle size distributions of the calcined PNZT powders. Documented in this SAND report are the results of an experimental study to determine the origin of the differences in the particle size distribution of the SP and TSP powders
Market Size, Trade, and Productivity
Ottaviano, Gianmarco; Melitz, Marc
2008-01-01
We develop a monopolistically competitive model of trade with firm heterogeneity—in terms of productivity differences—and endogenous differences in the "toughness" of competition across markets—in terms of the number and average productivity of competing firms. We analyse how these features vary across markets of different size that are not perfectly integrated through trade; we then study the effects of different trade liberalization policies. In our model, market size and trade affect...
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.
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)
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)
Size, productivity, and international banking
Buch, Claudia M.; Koch, Cathe?rine; Koetter, Michael
2011-01-01
Heterogeneity in size and productivity is central to models that explain which manufacturing firms export. This study presents descriptive evidence on similar heterogeneity among international banks as financial services providers. A novel and detailed bank-level data set reveals the volume and mode of international activities for all German banks. Only a few, large banks have a commercial presence abroad, consistent with the size pecking order documented for manufacturing firms. However, the...
Gradually Truncated Log-normal distribution - Size distribution of firms
Gupta, Hari M.; Campanha, Jose R.
2001-01-01
Gradually Truncated Log-normal distribution - Size distribution of firms Abstract Many natural and economical phenomena are described through power law or log- normal distributions. In these cases, probability decreases very slowly with step size compared to normal distribution. Thus it is essential to cut-off these distributions for larger step size. Recently we introduce the gradually truncated power law distribution to successfully describe variation of financial, ...
Aggregate size distributions in hydrophobic flocculation
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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
T. A. Rajesh
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...
Scaling in animal group-size distributions
Bonabeau, Eric; Dagorn, Laurent; Fre?on, Pierre
1999-01-01
An elementary model of animal aggregation is presented. The group-size distributions resulting from this model are truncated power laws. The predictions of the model are found to be consistent with data that describe the group-size distributions of tuna fish, sardinellas, and African buffaloes.
Modeling particle size distributions by the Weibull distribution function
International Nuclear Information System (INIS)
A method is proposed for modeling two- and three-dimensional particle size distributions using the Weibull distribution function. Experimental results show that, for tungsten particles in liquid phase sintered W-14Ni-6Fe, the experimental cumulative section size distributions were well fit by the Weibull probability function, which can also be used to compute the corresponding relative frequency distributions. Modeling the two-dimensional section size distributions facilitates the use of the Saltykov or other methods for unfolding three-dimensional (3-D) size distributions with minimal irregularities. Fitting the unfolded cumulative 3-D particle size distribution with the Weibull function enables computation of the statistical distribution parameters from the parameters of the fit Weibull function
Particle Size Distribution in Aluminum Manufacturing Facilities
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Sa Liu
2014-08-01
Full Text Available As part of exposure assessment for an ongoing epidemiologic study of heart disease and fine particle exposures in aluminum industry, area particle samples were collected in production facilities to assess instrument reliability and particle size distribution at different process areas. Personal modular impactors (PMI and Minimicro-orifice uniform deposition impactors (MiniMOUDI were used. The coefficient of variation (CV of co-located samples was used to evaluate the reproducibility of the samplers. PM2.5 measured by PMI was compared to PM2.5 calculated from MiniMOUDI data. Mass median aerodynamic diameter (MMAD and concentrations of sub-micrometer (PM1.0 and quasi-ultrafine (PM0.56 particles were evaluated to characterize particle size distribution. Most of CVs were less than 30%. The slope of the linear regression of PMI_PM2.5 versus MiniMOUDI_PM2.5 was 1.03 mg/m3 per mg/m3 (± 0.05, with correlation coefficient of 0.97 (± 0.01. Particle size distribution varied substantively in smelters, whereas it was less variable in fabrication units with significantly smaller MMADs (arithmetic mean of MMADs: 2.59 µm in smelters vs. 1.31 µm in fabrication units, p = 0.001. Although the total particle concentration was more than two times higher in the smelters than in the fabrication units, the fraction of PM10 which was PM1.0 or PM0.56 was significantly lower in the smelters than in the fabrication units (p < 0.001. Consequently, the concentrations of sub-micrometer and quasi-ultrafine particles were similar in these two types of facilities. It would appear, studies evaluating ultrafine particle exposure in aluminum industry should focus on not only the smelters, but also the fabrication facilities.
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
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.
On the Deepwater Horizon drop size distributions
Ryerson, T. B.; Atlas, E. L.; Blake, D. R.; De Gouw, J. A.; Warneke, C.; Peischl, J.; Brock, C. A.; McKeen, S. A.
2014-12-01
Model simulations of the fate of gas and oil released following the Deepwater Horizon blowout in 2012 depend critically on the assumed drop size distributions. We use direct observations of surfacing time, surfacing location, and atmospheric chemical composition to infer an average drop size distribution for June 10, 2012, providing robust first-order constraints on parameterizations in models. We compare the inferred drop size distribution to published work on Deepwater Horizon and discuss the ability of this approach to determine the efficacy of subsurface dispersant injection.
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.
Evolutionary model of the bank size distribution
Kaldasch, Joachim
2013-01-01
An evolutionary model of the bank size distribution is presented based on the exchange and expansion of deposit money. In agreement with empirical results the derived size distribution is lognormal with a power law tail. The key idea of the theory is to regard the creation of money as a slow process compared to exchange processes of deposit money. The exchange of deposits causes a preferential growth of banks with a fitness determined by the competitive advantage to attract permanent deposits...
Unravelling the size distribution of social groups
Hernando, A; Abad, M; Vesperinas, C
2009-01-01
We present an study of size distributions of social groups based on a recent analogy between scale invariant systems and gases and fluids (arXiv:0902.2738v4). We go beyond the non-interacting system proposing a model for interactions based on complex networks that reproduces the main statistical properties found in city-size distributions and electoral results. We found a scale transformation that shows that these distributions can be classified with only one parameter, what we call the \\emph{competitiveness}. We reproduce well established empirical measures, as the six degrees of separation and the maximum number of stable social relationships that one person can address, known as the Dunbar's number. Finally, we show that the scaled city-size distributions of large countries obeys the same universal distribution, which we use to propose a method to estimate the total population of a country.
The exponential age distribution and the Pareto firm size distribution
Coad, Alex
2008-01-01
Recent work drawing on data for large and small firms has shown a Pareto distribution of firm size. We mix a Gibrat-type growth process among incumbents with an exponential distribution of firm's age, to obtain the empirical Pareto distribution.
Evolution of bivariate particle size distributions
Gokhale, Arun M.
1992-11-01
A simple and general procedure is presented for the calculation of bivariate particle growth paths (and, hence, local particle growth rates) from the experimentally measured series of bi- variate size distributions during an evolutionary process. For modeling of microstructural evo- lution, a mathematical relationship is derived to relate the bivariate particle size distribution function to the nucleation rate and growth rate. A deterministic nucleation and growth process is assumed, and hence, the results are applicable only to the "mean field" models of nucleation and growth. A generalized continuity equation is derived for evolving bivariate and multivariate distributions.
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.
Size Distribution of Sea Spray from Individual Breaking Waves
Lewis, E. R.; Senum, G.; Schwartz, S. E.; Sedlacek, A. J.; Springston, S. R.
2011-12-01
Knowledge of the magnitude and shape (i.e., dependence on particle size) of the production flux of sea spray aerosol is necessary for understanding the budget of cloud condensation nuclei in the marine atmosphere, modeling aerosol optical depth, and similar topics. Magnitudes of production fluxes determined from laboratory experiments with simulated breaking waves using artificial or actual seawater vary by as much as two orders of magnitude, and size distributions vary greatly, but the pertinence of these experiments to particle production in actual oceanic breaking waves is questionable (de Leeuw et al., 2011). In principle these concerns might be overcome by determination of the size distribution of oceanic breaking waves, but this approach is of limited utility because the magnitudes of the production flux from individual waves may differ substantially and because the fraction of production that is sampled depends strongly on the location of the sampler relative to the breaking wave and time after breaking. Consequently simultaneous measurement of the size distribution of primary particles in air directly impacted by individual breaking waves is necessary. The Ultra-High Sensitivity Aerosol Spectrometer (UHSAS) allow simultaneous determination of the particle number concentration over the diameter range 60-1000 nm, allowing examination of the variability of the shape of the sea spray production size distribution for individual waves and the dependence of this size distribution on temperature, biological activity, sea state, and other controlling factors. Results from preliminary experiments demonstrating proof of principle will be presented. de Leeuw, G., E. L Andreas, M. D. Anguelova, C. W. Fairall, E. R. Lewis, C. O'Dowd, M. Schulz, & S. E. Schwartz, "Production flux of sea-spray aerosol," Rev. Geophys., 49, RG2001, 2011. doi:10.1029/2010RG000349
Magnetite Particle Size Distribution and Pellet Oxidation
Cho, Hyeon Jeong; Tang, Ming; Pistorius, Petrus Christiaan
2014-08-01
Oxidation of magnetite pellets is commonly performed to prepare strong pellets for ironmaking. This article presents a contribution to quantitative understanding of fundamental pellet oxidation kinetics, based on measured oxidation kinetics of magnetite particles and pellets. The commonly observed "plateau" oxidation behavior is confirmed to be consistent with the effect of very large differences in magnetite particle sizes in the concentrate from which pellets are produced. The magnetite particles range in size from less than a micron to several tens of a microns; changing the size distribution by inert sintering of pellets decreases both the plateau level of oxidation and the specific surface area, in ways that are compatible with an assumed Rosin-Rammler magnetite particle size distribution.
Understanding Animal Group-Size Distributions
Griesser, Michael; Ma, Qi; Webber, Simone; Bowgen, Katharine; Sumpter, David J. T.
2011-01-01
One of the most striking aspects of animal groups is their remarkable variation in size, both within and between species. While a number of mechanistic models have been proposed to explain this variation, there are few comprehensive datasets against which these models have been tested. In particular, we only vaguely understand how environmental factors and behavioral activities affect group-size distributions. Here we use observations of House sparrows (Passer domesticus) to investigate the f...
Fluctuations and intermittency in fragment size distributions
International Nuclear Information System (INIS)
The intermittency signal on the size frequency of fragments found in various fragmenting systems is reconsidered. This signal extracted from a factorial moment analysis was interpreted as a genuine intermittency. The 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. Any partition of integers exhibiting these two features will provide a similar signal. (author). 38 refs., 9 figs
Size distributions in two porous chondritic micrometeorites
Rietmeijer, Frans J. M.
1993-01-01
Quantitative size measurements of granular units (GUs), and nm-sized minerals in these units, in two porous chondritic micrometeorites are investigated. The matrix of these micrometeorites consist of loosely packed, 0.1 micron-sized, GUs. These objects were a major component of the solar nebula dust that accreted into protoplanets. The matrix in micrometeorite W7010*A2 has a fractal dimension with a small coefficient that supports efficient sticking of carbon-rich GUs during accretion. The fractal nature of the matrix provides a way to calculate the density using the aggregate size. The resulting very low density for porous chondritic micrometeorites is 0.08-0.14 g/cu cm, which supports the view that they are the solid debris from unconsolidated solar system bodies. Chondritic GUs contain ultrafine olivines, pyroxenes, and sulfides, embedded in hydrocarbons and amorphous carbons. Nanocrystals in the micrometeorites W7010*A2 and U2015*B show log normal size distributions. The high incidence of disk-shaped grains, a changeover from disk-shaped to euhedral grains, the unevolved nature of the size distributions, and multiple populations for grains less than 127 nm in size, are consistent with continuous postaccretion nucleation and growth in amorphous GUs, including coarsening via Ostwald ripening.
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...
Crater size distributions on Ganymede and Callisto: fundamental issues
Wagner, Roland; Schmedemann, Nico; Werner, Stefanie; Ivanov, Boris; Stephan, Katrin; Jaumann, Ralf
2015-04-01
Crater size distributions on the two largest Jovian satellites Ganymede and Callisto and the origin of impactors are subject of intense and controversial debates. In this paper, we reinvestigate crater size distributions measured in surface units derived from a recently published global geologic map, based on Voyager and Galileo SSI images at a scale of 1 km/pxl (Collins G. C. et al. (2013), U. S. Geol. Surv., Sci. Inv. Map 3237). These units are used as a context to units mapped in more detail at higher resolution in Galileo SSI images. We focus on the following fundamental issues: (1) Similarity between shapes of crater distributions on the Galilean satellites and on inner solar system bodies; (2) production versus equilibrium distributions; (3) apex/antapex variations in crater distributions. First, our results show a strong similarity in shape between the crater distributions on the most densely cratered regions on Ganymede and Callisto with those in the lunar highlands. We conclude that the shape of the crater distributions on these two Jovian satellites implies the craters were preferentially formed from members of a collisionally evolved projectile family, derived either from Main Belt asteroids as candidates of impactors on the Jovian satellites, or from projectiles stemming from the outer solar system which have undergone collisional evolution, resulting in a size distribution similar to those of Main Belt asteroids. Second, the complex shape of the crater distributions on Ganymede and Callisto indicates they are mostly production distributions and can be used to infer the underlying shape of the projectile size distribution. Locally, equilibrium distributions occur, especially at smaller sub-kilometer diameters. Third, the most densely cratered regions on both satellites do not show apex-antapex variations in crater frequency, as inferred for bodies from heliocentric orbits (e.g., Zahnle K. et al. (2003), Icarus 163, 263-289). This indicates that these craters were predominantly formed by bodies in planetocentric orbits, as maintained by Horedt and Neukum (1984, JGR 89 (B12), 10,405-10,410), or, alternatively, Ganymede and Callisto were rotating non-synchronously at early times (Zahnle et al., 2003). A forth issue is the stability of the shape of crater distributions with time, indicating a stable size distribution of impactors. Our results show that the shape of crater distributions was more or less stable, derived from the record of craters between 2 and 100 km diameters. To examine this topic in more detail, a global coverage of higher resolution imaging data is needed which will be provided by the JANUS camera data aboard ESA's future JUICE mission to Jupiter and Ganymede (Palumbo et al. (2014), LPSC XLV, abstr. No. 2094; Plaut et al. (2014), LPSC XLV, abstr. No. 2717).
Indoor aerosol size distributions in a gymnasium.
Castro, Amaya; Calvo, Ana I; Alves, Célia; Alonso-Blanco, Elisabeth; Coz, Esther; Marques, Liliana; Nunes, Teresa; Fernández-Guisuraga, Jose Manuel; Fraile, Roberto
2015-08-15
In this study, an indoor/outdoor monitoring program was carried out in a gymnasium at the University of Leon, Spain. The main goal was a characterization of aerosol size distributions in a university gymnasium under different conditions and sports activities (with and without magnesia alba) and the study of the mass fraction deposited in each of the parts of the respiratory tract. The aerosol particles were measured in 31 discrete channels (size ranges) using a laser spectrometer probe. Aerosol size distributions were studied under different conditions: i) before sports activities, ii) activities without using magnesia alba, iii) activities using magnesia alba, iv) cleaning procedures, and v) outdoors. The aerosol refractive index and density indoors were estimated from the aerosol composition: 1.577-0.003i and 2.055gcm(-3), respectively. Using the estimated density, the mass concentration was calculated, and the evolution of PM1, PM2.5 and PM10 for different activities was assessed. The quality of the air in the gymnasium was strongly influenced by the use of magnesia alba (MgCO3) and the number of gymnasts who were training. Due to the climbing chalk and the constant process of resuspension, average PM10 concentrations of over 440?gm(-3) were reached. The maximum daily concentrations ranged from 500 to 900?gm(-3). Particle size determines the place in the respiratory tract where the deposition occurs. For this reason, the inhalable, thoracic, tracheobronchial and respirable fractions were assessed for healthy adults and high risk people, according to international standards. The estimations show that, for healthy adults, up to 300?gm(-3) can be retained by the trachea and bronchi, and 130?gm(-3) may reach the alveolar region. The different physical activities and the attendance rates in the sports facility have a significant influence on the concentration and size distributions observed. PMID:25897726
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.
Templated formation of giant polymer vesicles with controlled size distributions
Howse, Jonathan R.; Jones, Richard A. L.; Battaglia, Giuseppe; Ducker, Robert E.; Leggett, Graham J.; Ryan, Anthony J.
2009-06-01
Unilamellar polymer vesicles are formed when a block copolymer self-assembles to form a single bilayer structure, with a hydrophobic core and hydrophilic surfaces, and the resulting membrane folds over and rearranges by connecting its edges to enclose a space. The physics of self-assembly tightly specifies the wall thickness of the resulting vesicle, but, both for polymer vesicles and phospholipids, no mechanism strongly selects for the overall size, so the size distribution of vesicles tends to be very polydisperse. We report a method for the production of controlled size distributions of micrometre-sized (that is, giant) vesicles combining the `top-down' control of micrometre-sized features (vesicle diameter) by photolithography and dewetting with the `bottom-up' control of nanometre-sized features (membrane thickness) by molecular self-assembly. It enables the spontaneous creation of unilamellar vesicles with a narrow size distribution that could find applications in drug and gene delivery, nano- and micro-reactors, substrates for macromolecular crystallography and model systems for studies of membrane function.
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.
Product Distributions for Distributed Optimization. Chapter 1
Bieniawski, Stefan R.; Wolpert, David H.
2004-01-01
With connections to bounded rational game theory, information theory and statistical mechanics, Product Distribution (PD) theory provides a new framework for performing distributed optimization. Furthermore, PD theory extends and formalizes Collective Intelligence, thus connecting distributed optimization to distributed Reinforcement Learning (FU). This paper provides an overview of PD theory and details an algorithm for performing optimization derived from it. The approach is demonstrated on two unconstrained optimization problems, one with discrete variables and one with continuous variables. To highlight the connections between PD theory and distributed FU, the results are compared with those obtained using distributed reinforcement learning inspired optimization approaches. The inter-relationship of the techniques is discussed.
Distribution of domain sizes during overlayer growth
International Nuclear Information System (INIS)
Recently, the kinetics of domain growth in two-dimensional systems has attracted much theoretical and experimental attention. The time evolution of a nonconserved, order-disorder transition has been described by Lifshitz and by Allen and Cahn (LAC). This theory assumes that after the system is quenched from a disordered to an ordered state, domains separated by antiphase boundaries are formed. The degree of ordering of the individual domains is close to the equilibrium value. These domains will grow to reduce the curvature of the boundaries. The theory predicts that the domain size growth is proportional to the square root of time. In this report, the authors construct a microscopic model to describe the distribution of domain or island sizes during the growth of an overlayer. This model is used to describe results from a LEED experiment, the growth of the p(2x1) oxygen antiphase domains on a W(112) surface
Landslide size distribution in seismic areas
Valagussa, Andrea; Frattini, Paolo; Crosta, Giovanni B.
2015-04-01
In seismic areas, the analysis of the landslides size distribution with the distance from the seismic source is very important for hazard zoning and land planning. From numerical modelling (Bourdeau et al., 2004), it has been observed that the area of the sliding mass tends to increase with the ground-motion amplitude up to a certain threshold input acceleration. This has been also observed empirically for the 1989 Loma Prieta earthquake (Keefer and Manson, 1998) and 1999 Chi Chi earthquake (Khazai and Sitar, 2003). Based on this, it possible to assume that the landslide size decreases with the increase of the distance from the seismic source. In this research, we analysed six earthquakes-induced landslides inventories (Papua New Guinea Earthquake, 1993; Northridge Earthquake, 1994; Niigata-Chuetsu Earthquake 2004; Iwate-Miyagi Nairiku Earthquake, 2008; Wenchuan Earthquake, 2008; Tohoku Earthquake, 2011) with a magnitude ranging between 6.6 and 9.0 Mw. For each earthquake, we first analysed the size of landslides as a function of different factors such as the lithology, the PGA, the relief, the distance from the seismic sources (both fault and epicentre). Then, we analysed the magnitude frequency curves for different distances from the source area and for each lithology. We found that a clear relationship between the size distribution and the distance from the seismic source is not evident, probably due to the combined effect of the different influencing factors and to the non-linear relationship between the ground-motion intensity and the distance from the seismic source.
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
Explaining the size distribution of cities: x-treme economies
Berliant, Marcus; Watanabe, Hiroki
2009-01-01
We criticize the theories used to explain the size distribution of cities. They take an empirical fact and work backward to obtain assumptions on primitives. The induced theoretical assumptions on consumer behavior, particularly about their inability to insure against the city-level productivity shocks in the model, are untenable. With either self insurance or insurance markets, and either an arbitrarily small cost of moving or the assumption that consumers do not perfectly observe the sho...
Explaining the size distribution of cities: x-treme economies
Berliant, Marcus; Watanabe, Hiroki
2011-01-01
We criticize the theories used to explain the size distribution of cities. They take an empirical fact and work backward to obtain assumptions on primitives. The induced theoretical assumptions on consumer behavior, particularly about their inability to insure against the city-level productivity shocks in the model, are untenable. With either self insurance or insurance markets, and either an arbitrarily small cost of moving or the assumption that consumers do not perfectly observe the sho...
Explaining the Size Distribution of Cities: X-treme Economies
Berliant, Marcus; Watanabe, Hiroki
2011-01-01
We criticize the theories used to explain the size distribution of cities. They take an empirical fact and work backward to obtain assumptions on primitives. The induced theoretical assumptions on consumer behavior, particularly about their inability to insure against the city-level productivity shocks in the model, are untenable. With either self insurance or insurance markets, and either an arbitrarily small cost of moving or the assumption that consumers do not perfectly observe the sho...
What determines the grain size distribution in galaxies?
Asano, Ryosuke S; 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) (called grain growth), and (iii) grain-grain collisions (shattering and coagulation) in the warm neutral medium (WNM) and CNM. We found that the grain size distribution in galaxies is controlled by stellar sources in the early stage of galaxy evolution, and that afterwards the main processes that govern the size distribution changes to those in the ISM. Since shattering produces a large abundance of small grains (consequently, the surface-to-volume ratio of grains increases), it enhances the efficiency of grain growth, contributing to the sig...
Learning transformed product distributions
Daskalakis, Constantinos; Servedio, Rocco A
2011-01-01
We consider the problem of learning an unknown product distribution $X$ over $\\{0,1\\}^n$ using samples $f(X)$ where $f$ is a \\emph{known} transformation function. Each choice of a transformation function $f$ specifies a learning problem in this framework. Information-theoretic arguments show that for every transformation function $f$ the corresponding learning problem can be solved to accuracy $\\eps$, using $\\tilde{O}(n/\\eps^2)$ examples, by a generic algorithm whose running time may be exponential in $n.$ We show that this learning problem can be computationally intractable even for constant $\\eps$ and rather simple transformation functions. Moreover, the above sample complexity bound is nearly optimal for the general problem, as we give a simple explicit linear transformation function $f(x)=w \\cdot x$ with integer weights $w_i \\leq n$ and prove that the corresponding learning problem requires $\\Omega(n)$ samples. As our main positive result we give a highly efficient algorithm for learning a sum of independ...
Do gravel bed river size distributions record channel network structure?
Sklar, Leonard S.; Dietrich, William E.; Foufoula-Georgiou, Efi; Lashermes, Bruno; Bellugi, Dino
2006-06-01
Bed load sediment particles supplied to channels by hillslopes are reduced in size by abrasion during downstream transport. The branching structure of the channel network creates a distribution of downstream travel distances to a given reach of river and thus may strongly influence the grain size distribution of the long-term bed load flux through that reach. Here we investigate this hypothesis, using mass conservation and the Sternberg exponential decay equation for particle abrasion, to predict bed material variability at multiple scales for both natural and artificial drainage networks. We assume that over a sufficiently long timescale, no net deposition occurs and that grains less than 2 mm are swept away in suspension. We find that abrasion during fluvial transport has a surprisingly small effect on the bed load sediment grain size distribution, for the simple case of spatially uniform supply of poorly sorted hillslope sediments. This occurs because at any point in the channel network, local resupply offsets the size reduction of material transported from upstream. Thus river bed material may essentially mirror the coarse component of the size distribution of hillslope sediment supply. Furthermore, there is a predictable distance downstream at which the bed load grain size distribution reaches a steady state. In the absence of net deposition due to selective transport, large-scale variability in bed material, such as downstream fining, must then be due primarily to spatial gradients in hillslope sediment production and transport characteristics. A second key finding is that average bed load flux will tend to stabilize at a constant value, independent of upstream drainage area, once the rate of silt production by bed load abrasion per unit travel distance is equal to the rate of coarse sediment supply per unit channel length (q). Bed load flux equilibrates over a distance that scales with the inverse of the fining coefficient in the abrasion rate law (?) and can be approximated simply as q/3?. Thus the efficiency of particle abrasion sets a fundamental length scale, shorter for weaker rocks and longer for harder rocks, which controls the expression in the river bed of variability in sediment supply. We explore the role of the abrasion length scale in modulating the influence of sediment supply variability in a number of channel network contexts, including individual tributary junctions, a sequence of tributary inputs along a main stem channel, and variable basin shapes and network architecture as expressed by the width function. These findings highlight the need for both data and theory that can be used to predict the grain size distributions supplied to channels by hillslopes.
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.
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
Evolution of Particle Size Distributions in Fragmentation Over Time
Charalambous, C. A.; Pike, W. T.
2013-12-01
We present a new model of fragmentation based on a probabilistic calculation of the repeated fracture of a particle population. The resulting continuous solution, which is in closed form, gives the evolution of fragmentation products from an initial block, through a scale-invariant power-law relationship to a final comminuted powder. Models for the fragmentation of particles have been developed separately in mainly two different disciplines: the continuous integro-differential equations of batch mineral grinding (Reid, 1965) and the fractal analysis of geophysics (Turcotte, 1986) based on a discrete model with a single probability of fracture. The first gives a time-dependent development of the particle-size distribution, but has resisted a closed-form solution, while the latter leads to the scale-invariant power laws, but with no time dependence. Bird (2009) recently introduced a bridge between these two approaches with a step-wise iterative calculation of the fragmentation products. The development of the particle-size distribution occurs with discrete steps: during each fragmentation event, the particles will repeatedly fracture probabilistically, cascading down the length scales to a final size distribution reached after all particles have failed to further fragment. We have identified this process as the equivalent to a sequence of trials for each particle with a fixed probability of fragmentation. Although the resulting distribution is discrete, it can be reformulated as a continuous distribution in maturity over time and particle size. In our model, Turcotte's power-law distribution emerges at a unique maturation index that defines a regime boundary. Up to this index, the fragmentation is in an erosional regime with the initial particle size setting the scaling. Fragmentation beyond this index is in a regime of comminution with rebreakage of the particles down to the size limit of fracture. The maturation index can increment continuously, for example under grinding conditions, or as discrete steps, such as with impact events. In both cases our model gives the energy associated with the fragmentation in terms of the developing surface area of the population. We show the agreement of our model to the evolution of particle size distributions associated with episodic and continuous fragmentation and how the evolution of some popular fractals may be represented using this approach. C. A. Charalambous and W. T. Pike (2013). Multi-Scale Particle Size Distributions of Mars, Moon and Itokawa based on a time-maturation dependent fragmentation model. Abstract Submitted to the AGU 46th Fall Meeting. Bird, N. R. A., Watts, C. W., Tarquis, A. M., & Whitmore, A. P. (2009). Modeling dynamic fragmentation of soil. Vadose Zone Journal, 8(1), 197-201. Reid, K. J. (1965). A solution to the batch grinding equation. Chemical Engineering Science, 20(11), 953-963. Turcotte, D. L. (1986). Fractals and fragmentation. Journal of Geophysical Research: Solid Earth 91(B2), 1921-1926.
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.
Distribution management by means of cutoff order size: a case study
Nass, R.; Dekker, R.; Sonderen-huisman, W.
1997-01-01
We present a case study on physical distribution management for a production company in Western Europe. The company delivers finished goods both from distribution centers and directly from plants to its customers. The lead time from distribution centres is shorter, but higher costs are involved. The choice for delivery of an individual order is based on the so-called stockmix and cutoff order size. The stockmix is the set of products stocked at the distribution centre, which for efficiency re...
Skewness and kurtosis of measured raindrop size distributions
Yangang, Liu
Skewness and kurtosis are used to investigate particle size distributions. A quantitative method is introduced to distinguish between a gamma distribution and an exponential (e.g. Marshall-Palmer) distribution. For this method, two "deviation coefficients" are introduced, which are the skewness and the square root of the kurtosis of the measured distributions divided by their values for an exponential distribution. The method is illustrated with data for raindrop size distributions from four case studies and demonstrates that the data are inadequately described by the Marshall-Palmer distribution, although it does appear to be an "equilibrium" distribution toward which steady precipitation appears to tend.
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.
Methods of assessing grain-size distribution during grain growth
Tweed, Cherry J.; Hansen, Niels; Ralph, Brian
2011-01-01
This paper considers methods of obtaining grain-size distributions and ways of describing them. In order to collect statistically useful amounts of data, an automatic image analyzer is used, and the resulting data are subjected to a series of tests that evaluate the differences between two related distributions (before and after grain growth). The distributions are measured from two-dimensional sections, and both the data and the corresponding true three-dimensional grain-size distributions (...
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
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).
Scientific Electronic Library Online (English)
W. E., Grosso; M. G., Chiovetta.
2005-01-01
Full Text Available Particle size distributions in the output stream of commercial, fluidized-bed reactors for ethylene polymerization are analyzed using a mathematical model. The impact on the overall reactor performance of the universe of sizes for the particles in the bed, with only a fraction of them being 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.
Distributions of region size and GDP and their relation
Sen, Hu; Chunxia, Yang; Xueshuai, Zhu; Zhilai, Zheng; Ya, Cao
2015-07-01
We first analyze the distribution of metropolitan (city) size, the distribution of metropolitan (city) GDP and the relation of both distributions. It is found that (1) the tails of distributions of size and GDP both obey Pareto Law with the Pareto exponent 1; (2) compared with Pareto exponent in GDP, Pareto exponent in size is bigger. Then an agent model is built to study the underlying formation mechanism of distributions of region size and GDP. Our model presents the mechanism how economic factors flow between regions to reproduce the tail behavior and the difference between the Pareto exponents of size and those of GDP. At last, the simulated results agree with the real empirical well.
Re-examination of the size distribution of firms
Kaizoji, T; Iyetomi, H; Kaizoji, Taisei; Ikeda, Yuichi; Iyetomi, Hiroshi
2006-01-01
In this paper we address the question of the size distribution of firms. To this aim, we use the Bloomberg database comprising firms around the world within the years 1995-2003, and analyze the data of the sales and the total assets of the consolidation base of the Japanese and the US companies, and make a comparison of the size distributions between the Japanese companies and the US companies. We find that (i) the size distribution of the US firms is approximately log-normal, in agreement with Gibrat's observation \\cite{Gibrat}, and in contrast (ii) the size distribution of the Japanese firms is clearly not log-normal, and the upper tail of the size distribution follows the Pareto law. It agree with the predictions of the Simon model \\cite{Simon}.
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.
Distributed size estimation of dynamic anonymous networks
Terelius, Håkan; Varagnolo, Damiano; Johansson, Karl Henrik
2012-01-01
We consider the problem of estimating the size of dynamic anonymous networks, motivated by network maintenance. The proposed algorithm is based on max-consensus information exchange protocols, and extends a previous algorithm for static anonymous networks. A regularization term is accounting for a-priori assumptions on the smoothness of the estimate, and we specifically consider quadratic regularization terms since they lead to closed-form solutions and intuitive design laws. We derive an exp...
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...
Analytic scaling function for island-size distributions
Dubrovskii, V. G.; Sibirev, N. V.
2015-04-01
We obtain an explicit solution for the island-size distribution described by the rate equations for irreversible growth with the simplified capture rates of the form ?s(? ) ??p(a +s -1 ) for all s ?1 , where s is the size and ? is the time-dependent coverage. The intrinsic property of this solution is its scaling form in the continuum limit. The analytic scaling function depends on the two parameters a and p and is capable of describing very dissimilar distribution shapes, both monomodal and monotonically decreasing. The obtained results suggest that the scaling features of the size distributions are closely related to the size linearity of the capture rates. A simple analytic scaling is obtained rigorously here and helps to gain a better theoretical understanding of possible origins of the scaling behavior of the island-size distributions.
Direct characterization of nanocrystal size distribution using Raman spectroscopy
Do?an, ?lker; van de Sanden, Mauritius C. M.
2013-10-01
We report a rigorous analytical approach based on one-particle phonon confinement model to realize direct detection of nanocrystal size distribution and volume fraction by using Raman spectroscopy. For the analysis, we first project the analytical confinement model onto a generic distribution function, and then use this as a fitting function to extract the required parameters from the Raman spectra, i.e., mean size and skewness, to plot the nanocrystal size distribution. Size distributions for silicon nanocrystals are determined by using the analytical confinement model agree well with the one-particle phonon confinement model, and with the results obtained from electron microscopy and photoluminescence spectroscopy. The approach we propose is generally applicable to all nanocrystal systems, which exhibit size-dependent shifts in the Raman spectrum as a result of phonon confinement.
The design of radon progeny radioactive size distribution analysis system
International Nuclear Information System (INIS)
The estimate for the size distribution is determined from indirect observations using computational methods. The paper provides a solution of radon progeny activity size distribution analysis monitoring system which is based on the parallel screen diffusional battery theory and estimate methods such as Twomy algorithm, EM algorithm. In this paper the penetration curve is given by calculation of the wire screen type diffusion battery parameters; Two approximation algorithms including Twomy nonlinear iterative method, Expectation Maximization iterative method, are employed for the determination of size distribution of radon progeny, and these two algorithm is verified by data of standard log-normal Poisson distribution. The experiment results obtained from indoor air and burned kerosene air show a bimodal size distribution, which is similar to other's research. Further intercomparsion studies are needed to further verify the system. (authors)
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...
The research radioactive aerosol size distribution measurement software
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)
Tuning photoresponse through size distribution control of silicon quantum dots
International Nuclear Information System (INIS)
We report a detailed experimental and theoretical investigation on the photocurrent characteristics of nanocrystalline Si thin films, with the emphasis on the effect of Si dot size distribution. Broader photocurrent response has been observed in Si quantum dots with larger size dispersion due to the improvement of light harvest. As a result of tunneling loss in the expanded energy distribution, we have demonstrated that there is a tradeoff between the absorption enhancement and reduced transport for the photocurrent intensity. The present work opens new strategy to maximize the photoresponse through size distribution control for quantum dot solar cell application.
Size distribution of mineral aerosol: using light-scattering models in laser particle sizing
International Nuclear Information System (INIS)
The size distribution of semitransparent irregularly shaped mineral dust aerosol samples is determined using a commonly used laser particle-sizing technique. The size distribution is derived from intensity measurements of singly scattered light at various scattering angles close to the forward-scattering direction at a wavelength of 632.8 nm. We analyze the results based on various light-scattering models including diffraction theory, Mie calculations for spheres with various refractive indices, and T-matrix calculations for spheroidal particles. We identify systematic errors of the retrieved size distribution when the semitransparent and nonspherical properties of the particles are neglected. Synthetic light-scattering data for a variety of parameterized size distributions of spheres and spheroids are used to investigate the effect of simplifying assumptions made when the diffraction model or Mie theory is applied in the retrieval
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 ...
Elemental mass size distribution of the Debrecen urban aerosol
International Nuclear Information System (INIS)
Complete text of publication follows. Size distribution is one of the basic properties of atmospheric aerosol. It is closely related to the origin, chemical composition and age of the aerosol particles, and it influences the optical properties, environmental effects and health impact of aerosol. As part of the ongoing aerosol research in the Group of Ion Beam Applications of the Atomki, elemental mass size distribution of urban aerosol were determined using particle induced X-ray emission (PIXE) analytical technique. Aerosol sampling campaigns were carried out with 9-stage PIXE International cascade impactors, which separates the aerosol into 10 size fractions in the 0.05-30 ?m range. Five 48-hours long samplings were done in the garden of the Atomki, in April and in October, 2007. Both campaigns included weekend and working day samplings. Basically two different kinds of particles could be identified according to the size distribution. In the size distribution of Al, Si, Ca, Fe, Ba, Ti, Mn and Co one dominant peak can be found around the 3 m aerodynamic diameter size range, as it is shown on Figure 1. These are the elements of predominantly natural origin. Elements like S, Cl, K, Zn, Pb and Br appears with high frequency in the 0.25-0.5 mm size range as presented in Figure 2. These elements are originated mainly from anthropogenic sources. However sometimes in the size distribution of these elements a 2nd, smaller peak appears at the 2-4 ?m size ranges, ipeak appears at the 2-4 ?m size ranges, indicating different sources. Differences were found between the size distribution of the spring and autumn samples. In the case of elements of soil origin the size distribution was shifted towards smaller diameters during October, and a 2nd peak appeared around 0.5 ?m. A possible explanation to this phenomenon can be the different meteorological conditions. No differences were found between the weekend and working days in the size distribution, however the concentration values were smaller during the weekend than the other days. The elemental mass size distribution provides information about the origin and sources of aerosol particles, and with emphasis on the PM2.5, serves as an input parameter for the determination of lung deposition probabilities by stochastic lung model calculation. This calculation together with short-term time variation enables us to give a more precise health impact of the urban aerosol
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.)
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.
The accuracy of graphs to describe size distributions
Gonza?lez-val, Rafael; Ramos, Arturo; Sanz-gracia, Fernando
2013-01-01
This paper analyses the performance of the graphs traditionally used to study size distributions: histograms, Zipf plots (double logarithmic graphs of rank compared to size) and plotted cumulative density functions. A lognormal distribution is fitted to urban data from three countries (the US, Spain and Italy) over all of the 20th century. We explain the advantages and disadvantages associated with these graphic methods and derive some statistical properties.
Nonequilibrium grain size distribution with generalized growth and nucleation rates
Lokovic, Kimberly S.; Bergmann, Ralf B.; Bill, Andreas
2013-01-01
We determine the non-equilibrium grain size distribution during the crystallization of a solid in $d$ dimensions at fixed thermodynamic conditions, for the random nucleation and growth model, and in absence of grain coalescence. Two distinct generalizations of the theory established earlier are considered. A closed analytic expression of the grain size distribution useful for experimental studies is derived for anisotropic growth rates. The main difference from the isotropic...
Can vesicle size distributions predict eruption intensity during volcanic activity?
Larue, A; D. R. Baker; Polacci, M.; P Allard; Sodini, N.
2013-01-01
We studied three-dimensional (3-D) vesicle size distributions by X-ray microtomography in scoria collected during the relatively quiescent Phase II of the 2010 eruption at Eyjafjallajökull volcano, Iceland. Our goal was to compare the vesicle size distributions (VSDs) measured in these samples with those found in Stromboli volcano, Italy. Stromboli was chosen because its VSDs are well-characterized and show a correlation with eruption intensity: typical Strombolian activity produces V...
Mobile field sampling system for determining submicron aerosol size distributions
International Nuclear Information System (INIS)
The need to accurately measure size distributions of submicron aerosols in field situations was recognized. A mobile system was assembled consisting of three size distribution measuring instruments, a 1.1 ?m aerodynamic diameter cyclone precutter and a simple dilution method. The new system reduced data collection time, required only one operator (previous systems required two) and was successfully used in several field and laboratory applications
Particle size distribution in ferrofluid macro-clusters
Lee, Wah-Keat; Ilavsky, Jan
2013-03-01
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.
Drop size distribution measurement problems using a laser unit
International Nuclear Information System (INIS)
A laser unit with a probe designed for use in rainfall studies was used to measure the drop size distributions from low pressure agricultural sprinklers. Coincidence error, two or more drops being counted as one large drop, could not be discriminated out of the data. Caution is suggested for those wishing to use this method for sprinkler drop size measurement
Binning effects on in-situ raindrop size distribution measurements
Checa-garcia, R.; Tokay, A.; Tapiador, F. J.
2014-01-01
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...
Competitive intransitivity and size-frequency distributions of interacting populations
Buss, L W
1980-01-01
The competitive ranking of three marine sessile organisms was determined from overgrowth observations and found to be intrasitive. Overgrowth results were dependent upon relative vertical relief which, in turn, was related to colony area. Discriminant function analysis demonstrates that competitive rankings can be largely predicted on the basis of knowledge of the size-frequency distribution of interacting populations. Because size increases with age for these species, size-dependent competit...
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)
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)
Isometric size-scaling of metabolic rate and the size abundance distribution of phytoplankton
Huete-ortega, Mari?a; Cermen?o, Pedro; Calvo-di?az, Alejandra; Maran?o?n, Emilio
2011-01-01
The relationship between phytoplankton cell size and abundance has long been known to follow regular, predictable patterns in near steady-state ecosystems, but its origin has remained elusive. To explore the linkage between the size-scaling of metabolic rate and the size abundance distribution of natural phytoplankton communities, we determined simultaneously phytoplankton carbon fixation rates and cell abundance across a cell volume range of over six orders of magnitude in tropical and subtr...
Influence of particle size distributions on magnetorheological fluid performances
International Nuclear Information System (INIS)
In this paper we investigate the influence that size distributions of the magnetic particles might have on the magnetorheological fluid performances. In our study, several size distributions have been tailored first by sieving a micrometric Fe powder in order to obtain narrow distribution powders and then by recomposing the new size distributions (different from Gaussian). We used spherical Fe particles (mesh -325) commercially available. The powder was sieved by means of a sieve shaker using a series of sieves with the following mesh size: 20, 32, 40, 50, 63, 80 micrometers. All magnetic powders were characterized through Vibrating Sample Magnetometer (VSM) measurements, particle size analysis and also Scanning Electron Microscope (SEM) images were taken. Magnetorheological (MR) fluids based on the resulted magnetic powders were prepared and studied by means of a rheometer with a magnetorheological module. The MR fluids were measured in magnetic field and in zero magnetic field as well. As we noticed in our previous experiments particles size distribution can also influence the MR fluids performances.
The seasonal evolution of sea ice floe size distribution
Perovich, Donald K.; Jones, Kathleen F.
2014-12-01
The Arctic sea ice cover undergoes large changes over an annual cycle. In winter and spring, the ice cover consists of large, snow-covered plate-like ice floes, with very little open water. By the end of summer, the snow cover is gone and the large floes have broken into a complex mosaic of smaller, rounded floes surrounded by a lace of open water. This evolution strongly affects the distribution and fate of the solar radiation deposited in the ice-ocean system and consequently the heat budget of the ice cover. In particular, increased floe perimeter can result in enhanced lateral melting. We attempt to quantify the floe evolution process through the concept of a floe size distribution that is modified by lateral melting and floe breaking. A time series of aerial photographic surveys made during the SHEBA field experiment is analyzed to determine evolution of the floe size distribution from spring through summer. Based on earlier studies, we assume the floe size cumulative distribution could be represented by a power law D-?, where D is the floe diameter. The exponent ? as well as the number density of floes Ntot are estimated from measurements of total ice area and perimeter. As summer progressed, there was an increase in ? as the size distribution shifted toward smaller floes and the number of floes increased. Lateral melting causes the distribution to deviate from a power law for small floe sizes.
Coagulation in processing of ceramic suspensions: Powder size distribution effects
Strauss, M.; Ring, T.; Bleier, A.; Bowen, H. K.
1985-11-01
The origin of agglomerates in slips and slurries of ceramic particles due to particle size distribution effects is considered. Since agglomerates have been related to flaws in sintered ceramic bodies, the parameters which control coagulation of particles into agglomerates need to be defined. Computer calculations, based on Derjaguin, Landau, Verwey, and Overbeek theory, have been used to predict stability curves for particulate suspensions with log normal particle size distributions. Two regimes appear in the calculations: at width parameters (?z) corresponding to the inherent distribution of a powder the coagulation time decreases rapidly with increasing polydispersity; at larger ?zs corresponding to mixing different sizes of powders to get very broad distributions the coagulation time decreases with increasing polydispersity. This change in behavior occurs at aproximately ?z=1.0.
The evolution and distribution of species body size
Clauset, Aaron; 10.1126/science.1157534
2009-01-01
The distribution of species body size within taxonomic groups exhibits a heavy right-tail extending over many orders of magnitude, where most species are significantly larger than the smallest species. We provide a simple model of cladogenetic diffusion over evolutionary time that omits explicit mechanisms for inter-specific competition and other microevolutionary processes yet fully explains the shape of this distribution. We estimate the model's parameters from fossil data and find that it robustly reproduces the distribution of 4002 mammal species from the late Quaternary. The observed fit suggests that the asymmetric distribution arises from a fundamental tradeoff between the short-term selective advantages (Cope's rule) and long-term selective risks of increased species body size, in the presence of a taxon-specific lower limit on body size.
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)
Isometric size-scaling of metabolic rate and the size abundance distribution of phytoplankton
Huete-Ortega, María; Cermeño, Pedro; Calvo-Díaz, Alejandra; Marañón, Emilio
2012-01-01
The relationship between phytoplankton cell size and abundance has long been known to follow regular, predictable patterns in near steady-state ecosystems, but its origin has remained elusive. To explore the linkage between the size-scaling of metabolic rate and the size abundance distribution of natural phytoplankton communities, we determined simultaneously phytoplankton carbon fixation rates and cell abundance across a cell volume range of over six orders of magnitude in tropical and subtropical waters of the Atlantic Ocean. We found an approximately isometric relationship between carbon fixation rate and cell size (mean slope value: 1.16; range: 1.03–1.32), negating the idea that Kleiber's law is applicable to unicellular autotrophic protists. On the basis of the scaling of individual resource use with cell size, we predicted a reciprocal relationship between the size-scalings of phytoplankton metabolic rate and abundance. This prediction was confirmed by the observed slopes of the relationship between phytoplankton abundance and cell size, which have a mean value of ?1.15 (range: ?1.29 to ?0.97), indicating that the size abundance distribution largely results from the size-scaling of metabolic rate. Our results imply that the total energy processed by carbon fixation is constant along the phytoplankton size spectrum in near steady-state marine ecosystems. PMID:22171079
Enzymatic production of specifically distributed hyaluronan oligosaccharides.
Yuan, Panhong; Lv, Mengxian; Jin, Peng; Wang, Miao; Du, Guocheng; Chen, Jian; Kang, Zhen
2015-09-20
High-molecular-mass hyaluronan (HA) was controllably depolymerized in pure aqueous solution with recombinant leech hyaluronidase (HAase). The HAase concentration per unit HA and hydrolysis time played important roles in molecular mass distribution. By modulating the concentrations of HAase and controlling the hydrolysis time, any molar-mass-defined HA oligomers could be efficiently and specifically produced on a large scale (40g/L), such as HA oligosaccharides with weight-average molar mass of 4000, 10,000, and 30,000Da and end hydrolysates containing only HA6 and HA4. High performance liquid chromatography-size exclusion chromatography, polyacrylamide gel electrophoresis, capillary zone electrophoresis, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry confirmed low polydispersity of the produced molar-mass-defined HA oligosaccharides. Therefore, large-scale production of defined HA oligosaccharides with narrow molecular mass distribution will significantly promote progress in related research and its potential applications. PMID:26050905
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.
Can vesicle size distributions predict eruption intensity during volcanic activity?
Directory of Open Access Journals (Sweden)
A. LaRue
2013-06-01
Full Text Available We studied three-dimensional (3-D vesicle size distributions by X-ray microtomography in scoria collected during the relatively quiescent Phase II of the 2010 eruption at Eyjafjallajökull volcano, Iceland. Our goal was to compare the vesicle size distributions (VSDs measured in these samples with those found in Stromboli volcano, Italy. Stromboli was chosen because its VSDs are well-characterized and show a correlation with eruption intensity: typical Strombolian activity produces VSDs with power-law exponents near 1, whereas larger and more energetic Vulcanian-type explosions and Plinian eruptions produce VSDs with power-law exponents near 1.5. The hypothesis to be tested was whether or not the samples studied in this work would contain VSDs similar to normal Strombolian products, display higher power-law exponents, or be described by exponential functions. Before making this comparison we tested the hypothesis that the phreatomagmatic nature of the Eyjafjallajökull eruption might have a significant effect on the VSDs. We performed 1 atm bubble-growth experiments in which the samples were inundated with water and compared them to similar, control, experiments without water inundation. No significant differences between the VSDs of the two sets of experiments were found, and the hypothesis is not supported by the experimental evidence; therefore, VSDs of magmatic and phreatomagmatic eruptions can be directly compared. The Phase II Eyjafjallajökull VSDs are described by power law exponents of ~ 0.8, typical of normal Strombolian eruptions. The comparable VSDs and behavior of Phase II of the Eyjafjallajökull 2010 eruption to Stromboli are interpreted to be a reflection of similar conduit systems in both volcanoes that are being constantly fed by the ascent of deep magma that mixes with resident magma at shallow depths. Such behavior implies that continued activity during Phase II of the Eyjafjallajökull eruption could be expected and would have been predicted, had our VSDs been measured in real time during the eruption. However, the products studied show no peculiar feature that could herald renewed eruption intensity observed in the following Phase III of the eruption.
XRD characterisation of nanoparticle size and shape distributions
International Nuclear Information System (INIS)
Full text: The form of XRD lines and the extent of their broadening provide useful structural information about the shape, size distribution, and modal characteristics of the nanoparticles comprising the specimen. Also, the defect content of the nanoparticles can be determined, including the type, dislocation density, and stacking faults/twinning. This information is convoluted together and can be grouped into 'size' and 'defect' broadening contributions. Modern X-ray diffraction analysis techniques have concentrated on quantifying the broadening arising from the size and defect contributions, while accounting for overlapping of profiles, instrumental broadening, background scattering and noise components. We report on a combined Bayesian/Maximum Entropy (MaxEnt) technique developed for use in the certification of a NIST Standard Reference Material (SRM) for size-broadened line profiles. The approach used was chosen because of its generality in removing instrumental broadening from the observed line profiles, and its ability to determine not only the average crystallite size, but also the distribution of sizes and the average shape of crystallites. Moverover, this Bayesian/MaxEnt technique is fully quantitative, in that it also determines uncertainties in the crystallite-size distribution and other parameters. Both experimental and numerical simulations of size broadened line-profiles modelled on a range of specimens with spherical and non-spherical morphologies are prical and non-spherical morphologies are presented to demonstrate how this information can be retrieved from the line profile data. The sensitivity of the Bayesian/MaxEnt method to determining the size distribution using varying a priori information are emphasised and discussed
Size Evolution and Stochastic Models: Explaining Ostracod Size through Probabilistic Distributions
Krawczyk, M.; Decker, S.; Heim, N. A.; Payne, J.
2014-12-01
The biovolume of animals has functioned as an important benchmark for measuring evolution throughout geologic time. In our project, we examined the observed average body size of ostracods over time in order to understand the mechanism of size evolution in these marine organisms. The body size of ostracods has varied since the beginning of the Ordovician, where the first true ostracods appeared. We created a stochastic branching model to create possible evolutionary trees of ostracod size. Using stratigraphic ranges for ostracods compiled from over 750 genera in the Treatise on Invertebrate Paleontology, we calculated overall speciation and extinction rates for our model. At each timestep in our model, new lineages can evolve or existing lineages can become extinct. Newly evolved lineages are assigned sizes based on their parent genera. We parameterized our model to generate neutral and directional changes in ostracod size to compare with the observed data. New sizes were chosen via a normal distribution, and the neutral model selected new sizes differentials centered on zero, allowing for an equal chance of larger or smaller ostracods at each speciation. Conversely, the directional model centered the distribution on a negative value, giving a larger chance of smaller ostracods. Our data strongly suggests that the overall direction of ostracod evolution has been following a model that directionally pushes mean ostracod size down, shying away from a neutral model. Our model was able to match the magnitude of size decrease. Our models had a constant linear decrease while the actual data had a much more rapid initial rate followed by a constant size. The nuance of the observed trends ultimately suggests a more complex method of size evolution. In conclusion, probabilistic methods can provide valuable insight into possible evolutionary mechanisms determining size evolution in ostracods.
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.
A Model of the Commit Size Distribution of Open Source
Kolassa, Carsten; Riehle, Dirk; Salim, Michel A.
2014-01-01
A fundamental unit of work in programming is the code contribution ("commit") that a developer makes to the code base of the project in work. We use statistical methods to derive a model of the probabilistic distribution of commit sizes in open source projects and we show that the model is applicable to different project sizes. We use both graphical as well as statistical methods to validate the goodness of fit of our model. By measuring and modeling a fundamental dimension ...
On the size distribution of Atlantic tropical cyclones
Emanuel, Kerry Andrew; Chavas, Daniel Robert; Dean, L.
2009-01-01
The size of a tropical cyclone is known to vary considerably across storms, though little is understood about the environmental and internal factors that modulate it. Making use of newly available extended tropical cyclone records that include information about storm structure, we examine the size distribution of Atlantic tropical cyclones, using as a metric the radius of vanishing storm winds normalized by the theoretical upper bound given by the ratio of the potential intensity to the Corio...
Time evolution of cell size distributions in dense cell cultures
Khain, Evgeniy
2015-03-01
Living cells in a dense system are all in contact with each other. The common assumption is that such cells stop dividing due to a lack of space. Recent experimental observations have shown, however, that cells continue dividing for a while, but other cells in the system must shrink, to allow the newborn cells to grow to a normal size. Due to these ``pressure'' effects, the average cell size dramatically decreases with time, and the dispersion in cell sizes decreases, too. The collective cell behavior becomes even more complex when the system is expanding: cells near the edges are larger and migrate faster, while cells deep inside the colony are smaller and move slower. This exciting experimental data still needs to be described theoretically, incorporating the distribution of cell sizes in the system. We propose a mathematical model for time evolution of cell size distribution both in a closed and open system. The model incorporates cell proliferation, cell growth after division, cell shrinking due to ``pressure'' from other cells, and possible cell detachment from the interface of a growing colony. This research sheds light on physical and biological mechanisms of cell response to a dense environment and on the role of mechanical stresses in determining the distribution of cell sizes in the system.
Size Distributions for All Cities: Which One is Best?
González-Val, Rafael; Ramos, Arturo; Sanz, Fernando; Vera-Cabello, María
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...
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...
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
Preparation of leucite powders with controlled particle size distribution.
Czech Academy of Sciences Publication Activity Database
Novotná, Martina; Kloužková, A.; Maixner, J.; Šatava, Vladimír
2005-01-01
Ro?. 49, ?. 4 (2005), s. 252-258. ISSN 0862-5468 R&D Projects: GA ?R GA104/03/0031 Institutional research plan: CEZ:AV0Z40320502 Keywords : leucite * preparation * particle size distribution Subject RIV: CA - Inorganic Chemistry Impact factor: 0.463, year: 2005
Determination of Crystallites Size Distribution in Anatase Nanopowders by XRD.
Czech Academy of Sciences Publication Activity Database
Mat?j, Z.; Mat?jová, Lenka; Kužel, R.
St. Petersburg : -, 2010, 86 /MS10-P14/. ISBN N. [European Powder Diffraction Conference EPDIC 12 /12./. Darmstadt (DE), 27.08.2010-30.08.2010] Institutional research plan: CEZ:AV0Z40720504 Keywords : anatase * size distribution * powder diffraction Subject RIV: CC - Organic Chemistry www.darmstadtium.de
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.
A Merging Algorithm for Aerosol Size Distribution from Multiple Instruments.
Czech Academy of Sciences Publication Activity Database
Ondrá?ek, Jakub; Ždímal, Vladimír; Smolík, Ji?í; Lazaridis, M.
2009-01-01
Ro?. 199, 1-4 (2009), s. 219-233. ISSN 0049-6979 Grant ostatní: MTKD(XE) CT-2004-513849 Institutional research plan: CEZ:AV0Z40720504 Keywords : aerosols * merging particle size distribution * multilognormal model Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.676, year: 2009
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
Size Distribution and Rate of Dust Generated During Grain Elevator Handling
Dust generated during grain handling is an air pollutant that produces safety and health hazards. This study was conducted to characterize the particle size distribution (PSD) of dust generated during handling of wheat and shelled corn in the research elevator of the USDA Grain Marketing and Product...
Thoron progeny size distribution in monazite storage facility
International Nuclear Information System (INIS)
Field experiments in the atmosphere of monazite warehouses with a high content of 220Rn progeny concentration were conducted. Size distribution of aerosol particles was measured with the combined use of diffusion battery with varied capture elements and cascade impactor. Four 212Pb aerosol modes were detected - three in the ultrafine region (aerosol median thermodynamic diameters ?0.3, 1 and 5 nm) and one with an aerosol median aerodynamic diameter of 500 nm. The activity fraction of aerosol particles with the size 220Rn exposure, obtained on the basis of the aerosol size distribution and existing research data on lung absorption types of 212Pb aerosols, is close to 180 nSv per Bq h m-3. (authors)
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.
A model of size distribution of customer groups and businesses
Zheng, D; Hui, P M; Zheng, Dafang
2001-01-01
We present a generalization of the dynamical model of information transmission and herd behavior proposed by Egu\\'{\\i}luz and Zimmermann. A characteristic size of group of agents $s_{0}$ is introduced. The fragmentation and coagulation rates of groups of agents are assumed to depend on the size of the group. We present results of numerical simulations and mean field analysis. It is found that the size distribution of groups of agents $n_{s}$ exhibits two distinct scaling behavior depending on $s \\leq s_{0}$ or $s > s_{0}$. For $s \\leq s_{0}$, $n_{s} \\sim s^{-(5/2 + \\delta)}$, while for $s > s_{0}$, $n_{s} \\sim s^{-(5/2 -\\delta)}$, where $\\delta$ is a model parameter representing the sensitivity of the fragmentation and coagulation rates to the size of the group. Our model thus gives a tunable exponent for the size distribution together with two scaling regimes separated by a characteristic size $s_{0}$. Suitably interpreted, our model can be used to represent the formation of groups of customers for certain p...
Lot-sizing problem with several production centers
Franklina Maria Bragion de Toledo; André Luís Shiguemoto
2005-01-01
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 as 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 ...
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.
Particle sizes and particle size-fraction distribution in water treatment.
Czech Academy of Sciences Publication Activity Database
Mutl, Silvestr; Polášek, P.
Melbourne : Australian Water Association, 2002, s. -. [ Enviro 2002: International conference of IWA. Melbourne (AU), 07.04.2002-12.04.2002] Institutional research plan: CEZ:AV0Z2060917 Keywords : water treatment * treatability of water * distribution of particle size fractions Subject RIV: BK - Fluid Dynamics
The Distribution of Program Sizes and Its Implications: An Eclipse Case Study
Zhang, Hongyu; Tan, Hee Beng Kuan; 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 J...
Gaedke, Ursula; Straile, Dietmar
1994-01-01
The trophic transfer efficiencies in the planktonic food web of large, deep, and mesoeutrophic Lake Constance were derived independently from biomass size distributions and from mass-balanced carbon flow diagrams based on comprehensive data for biomass, production, and food web structure. The main emphasis was on the transfer of primary production to herbivores since this process dominates the flow of matter within the food web. Biomass size distributions offer an ecosystem approach which rel...
Optimal Location and Sizing of Distributed Storage Systems in Active Distribution Networks
Nick, Mostafa; Hohmann, Marc; Cherkaoui, Rachid; Paolone, Mario
2013-01-01
Energy balance and ancillary services provided by distributed storage systems to active distribution networks represent two aspects of a single problem that needs to be properly treated in view of the typical distribution networks parameters. In this context, the paper focuses on the problem of the optimal siting and sizing of distributed storage systems. In particular, the paper proposes the formulation of a problem that accounts: (i) the voltage support of storage systems to the grid, (ii) ...
Grain size distribution and compaction properties of concrete waste
International Nuclear Information System (INIS)
Low level radioactive concrete waste will be produced in future by breaking up the nuclear facilities, and the waste will be disposed in shallow depth of ground. In order to prepare for those situation, it is needed to clarify the gradation and compaction properties of concrete waste. In this study, full-scale concrete structure specimens were broken up, and a series of grain size analysis and compaction tests on concrete waste were performed. From the test results, close correlations between dry density, void ratio or porosity of the compacted concrete waste and its grain size distribution were found. (author)
Simulating Bandwidth Sharing with Pareto distributed File Sizes
ALTMAN, EITAN; Rojas-Mora, Julio; Jimenez, Tania
2009-01-01
The traffic on the internet has known to be heavy tailed: the size of file transfers through FTP or HTTP applications, as well as those transferred by P2P applications has been observed to have a very heavy tail. Typically modeled as Pareto distributed with parameter between 1.05 to 1.5, the file size has infinite variance. This is the source of many difficulties in simulating data traffic: convergence is very slow, simulations have to be very long, and the standard methods for deriving confi...
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.
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
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.
Droplet Size Distributions in Atomization of Dilute Viscoelastic Solutions
Keshavarz, Bavand; McKinley, Gareth; Houze, Eric; Moore, John; Pottiger, Michael; Cotts, Patricia; M. I. T. Collaboration; DuPont Collaboration
2012-11-01
The droplet size probability distribution functions (PDF) for atomization/fragmentation processes in Newtonian fluids are now generally accepted to be close to Gamma distributions. Despite the great practical importance, little is known about the nature of corresponding distributions for viscoelastic liquids, e.g. polymeric solutions such as pesticide sprays and paints. We present data from air-assisted atomization experiments for model viscoelastic solutions composed of very dilute solutions of polyethylene oxide. Although the addition of small amounts of high molecular weight polymer keeps the fluid shear viscosity and surface tension close to the solvent values, the size distributions are skewed towards higher values of the Sauter mean diameter. We show that the PDF curves for these weakly-elastic fluids are well described by Gamma distributions, but the exponent n is systematically decreased by fluid elasticity. Flow visualization images show that this behavior arises from the non-linear dynamics close to the break-up point which are dominated by an elasto-capillary force balance within the thinning ligaments and the magnitude of the extensional viscosity in the viscoelastic fluid. Mechanical Engineering Department, Cambridge, MA.
Size resolved ultrafine particles emission model--a continues size distribution approach.
Nikolova, Irina; Janssen, Stijn; Vrancken, Karl; Vos, Peter; Mishra, Vinit; Berghmans, Patrick
2011-08-15
A new parameterization for size resolved ultrafine particles (UFP) traffic emissions is proposed based on the results of PARTICULATES project (Samaras et al., 2005). It includes the emission factors from the Emission Inventory Guidebook (2006) (total number of particles, #/km/veh), the shape of the corresponding particle size distribution given in PARTICULATES and data for the traffic activity. The output of the model UFPEM (UltraFine Particle Emission Model) is a sum of continuous distributions of ultrafine particles emissions per vehicle type (passenger cars and heavy duty vehicles), fuel (petrol and diesel) and average speed representative for urban, rural and highway driving. The results from the parameterization are compared with measured total number of ultrafine particles and size distributions in a tunnel in Antwerp (Belgium). The measured UFP concentration over the entire campaign shows a close relation to the traffic activity. The modelled concentration is found to be lower than the measured in the campaign. The average emission factor from the measurement is 4.29E+14 #/km/veh whereas the calculated is around 30% lower. A comparison of emission factors with literature is done as well and in overall a good agreement is found. For the size distributions it is found that the measured distributions consist of three modes--Nucleation, Aitken and accumulation and most of the ultrafine particles belong to the Nucleation and the Aitken modes. The modelled Aitken mode (peak around 0.04-0.05 ?m) is found in a good agreement both as amplitude of the peak and the number of particles whereas the modelled Nucleation mode is shifted to smaller diameters and the peak is much lower that the observed. Time scale analysis shows that at 300 m in the tunnel coagulation and deposition are slow and therefore neglected. The UFPEM emission model can be used as a source term in dispersion models. PMID:21641631
Numerical Study of Crystal Size Distribution in Polynuclear Growth
Sakaguchi, Hidetsugu; Ohishi, Takuma
2015-06-01
The crystal size distribution in polynuclear growth is numerically studied using a coupled map lattice model. The width of the size distribution depends on c/D, where c is the growth rate at interface sites and D is the diffusion constant. When c/D is sufficiently small, the width W increases linearly with c/D and saturates at large c/D. Monodisperse square and cubic crystals are obtained respectively on square and cubic lattices when c/D is sufficiently small for a small kinetic parameter b. The linear dependence of W on c/D in a parameter range of small c/D is explained by the eigenfunction for the first eigenvalue in a two-dimensional model and a mean-field model. For the mean-field model, the slope of the linear dependence is evaluated theoretically.
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)
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.
Pore-Size Distribution from Liquid Expulsion Permporometry.
Czech Academy of Sciences Publication Activity Database
Šolcová, Olga; Schneider, Petr
Praha : Process Engineering Publisher, 2004, s. 573. ISBN 80-86059-40-5. [International Congress of Chemical and Process Engineering CHISA 2004 /16./. Praha (CZ), 22.08.2004-26.08.2004] R&D Projects: GA ?R GA104/04/0963; GA AV ?R IAA4072404 Institutional research plan: CEZ:AV0Z4072921 Keywords : mass transfer * nanostructure * pore size distribution Subject RIV: CF - Physical ; Theoretical Chemistry
Market size, linkages and productivity: A study of Japanese regions
Davis, Donald R.; Weinstein, David E.
2003-01-01
One account of spatial concentration focuses on productivity advantages arising from market size. We investigate this for 40 regions of Japan. Our results identify important effects of a region’s own size, as well as cost linkages between producers and suppliers of inputs. Productivity links to a more general form of ‘market potential’ or Marshall-Arrow- Romer externalities do not appear to be robust in our data. The effects we identify are economically quite important, accounting for a...
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...
An overview of aerosol particle sensors for size distribution measurement
Directory of Open Access Journals (Sweden)
Panich Intra
2007-08-01
Full Text Available Fine aerosols are generally referred to airborne particles of diameter in submicron or nanometer size range. Measurement capabilities are required to gain understanding of these particle dynamics. One of the most important physical and chemical parameters is the particle size distribution. The aim of this article is to give an overview of recent development of already existing sensors for particle size distribution measurement based on electrical mobility determination. Available instruments for particle size measurement include a scanning mobility particle sizer (SMPS, an electrical aerosol spectrometer (EAS, an engine exhaust particle sizer (EEPS, a bipolar charge aerosol classifier (BCAC, a fast aerosol spectrometer (FAS a differential mobility spectrometer (DMS, and a CMU electrical mobility spectrometer (EMS. The operating principles, as well as detailed physical characteristics of these instruments and their main components consisting of a particle charger, a mobility classifier, and a signal detector, are described. Typical measurements of aerosol from various sources by these instruments compared with an electrical low pressure impactor (ELPI are also presented.
Raindrop Size Distribution Observation for GPM/DPR algorithm development
Nakagawa, Katsuhiro; Hanado, Hiroshi; Nishikawa, Masanori; Nakamura, Kenji; Kaneko, Yuki; Kawamura, Seiji; Iwai, Hironori; Minda, Haruya; Oki, Riko
2013-04-01
In order to evaluate and improve the accuracy of rainfall intensity from space-borne radars (TRMM/PR and GPM/DPR), it is important to estimate the rain attenuation, namely the k-Z relationship (k is the specific attenuation, Z is the radar reflectivity) correctly. National Institute of Information and Communications Technology (NICT) developed the mobile precipitation observation system for the dual Ka-band radar field campaign for GPM/DPR algorithm development. The precipitation measurement instruments are installed on the roof of container. The installed instruments for raindrop size distribution (DSD) measurements are 2-dimensional Video disdtrometer (2DVD), Joss-type disdrometer, and Laser Optical disdrometr (Parsival). 2DVD and Persival can measure not only raindrop size distribution but also ice and snow size distribution. Observations using the mobile precipitation observation system were performed in Okinawa Island, in Tsukuba, over the slope of Mt. Fuji, in Nagaoka, and in Sapporo Japan. Using these observed DSD data in the different provinces, the characteristics of DSD itself are analyzed and the k-Z relationship is estimated for evaluation and improvement of the TRMM/PR and GPM/DPR algorithm.
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.
Statistical analysis of bubble and crystal size distributions: Formulations and procedures
Proussevitch, Alexander A.; Sahagian, Dork L.; Tsentalovich, Evgeni P.
2007-07-01
Bubble and crystal size distributions have previously been described only by either exponential or power law functions. Within this limited framework, it has not been possible to characterize size distributions in a fully quantitative manner. We have developed an analytical and computational formulation with which to characterize and study crystal and bubble size distributions (BSD). This formulation demonstrates that all distributions known to date belong to the logarithmic family of statistical distributions. Four functions within the logarithmic family are best suited to natural bubbles and crystals (log normal, logistic, Weibull, and exponential). This characterization is supported by the fact that the power law function widely used for crystal and bubble size analysis is not a statistical distribution function, but rather represents an approximation of the upper regions (larger bubbles/crystals) of the logistic distribution, whose sizes are much larger than the mode. The coefficients for each of the four logarithmic functions can be derived by 1) best fit exceedance function of the logarithmic distribution, and 2) best fit of the linear transformation of the distribution probability density. A close match of the coefficients derived by the above two methods can be used as an indicator of correct function fitting (choice of initial values). Function fitting by exceedance curves leads to the most accurate statistical results, but has certain strict limitations, including 1) a requirement to rescale the base distribution function; 2) a higher failure rate for function fitting than that for distribution density; 3) uncertainty in observational data error estimates; and 4) unsuitability for visual interpretation. The most productive approach to visualization and interpretation of size distributions is through linear transformation of logarithmic distributions on the basis of probability densities. This also makes it possible to 1) clearly discern bimodal distributions; 2) assess the range of observed objects relative to the full range of the indicated distribution; 3) determine number densities for each mode directly; and 4) integrate to obtain total volume fraction for comparison with available observations. The latter could, in some cases, provide more accurate results than many measurement methods. Unambiguous definition of Bubble Number Density (BND) must be based on the number of bubbles per melt volume (not number of bubbles per bulk volume), so that like is done with crystals, it can be directly used as an indicator of basic vesiculation processes such that: a) nucleation leads to increase of BND, b) diffusive or decompressive bubble growth keeps BND constant, and c) coalescence decreases BND.
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.
Grain-size Distributions from Deconvolved Broadband Magnetic Susceptibility
Fukuma, K.
2014-12-01
A magnetic susceptibility meter with several-decade frequency band has recently made it possible to obtain superparamagnetic grain-size distributions only by room-temperature measurement. A rigorous deconvolution scheme of frequency dependence of susceptibility is already available. I have made some corrections on the deconvolution scheme and present its applications to broadband susceptibility data on loess and volcanic rocks. Deconvolution of frequency dependence of susceptibility was originally developed by Shchervakov and Fabian [2005]. Suppose an ensemble of grains distributed for two independent variables of volume (grain-size) and energy barrier. Applying alternating magnetic field with varying frequency results in differentiating grains by energy barrier - not directly by volume. Since the response function for frequency is known, deconvolution of frequency dependence of susceptibility provide a rigorous solution for the second moment of volume on the volume-energy barrier distribution. Based on a common assumption of a linear relation between volume and energy barrier, we can obtain analytical volume or grain-size distributions of superparamagnetic grains. A ZH broadband susceptibility meter comprises of two separated devices for lower (SM-100, 65 - 16kHz) and higher (SM-105, 16k - 512kHz) frequency ranges. At every frequency susceptibility calibration was conducted using three kinds of paramagnetic rare earth oxides [Fukuma and Torii, 2011]. Almost all samples exhibited seemingly linear dependences of in-phase susceptibility on logarithmic frequency. This indicates that the measured data do not suffer serious noise, and that the second moment of volume is relatively constant against energy barrier. Nonetheless, third-order polynomial fittings revealed slight deflections from the quasi-linear susceptibility - logarithmic frequency relations. Deconvolving the polynomials showed that such slight defections come from peaks or troughs in varying second moment of volume against energy barrier. Assuming a linear relation between volume and energy barrier, peaks or troughs around 1 x 10^{-24} m^{3} were found for the derived volume distributions. Long-tailed volume distributions from Chinese loess samples suggest the broad grain-size distribution.
Houghton, J.C.
1988-01-01
The truncated shifted Pareto (TSP) distribution, a variant of the two-parameter Pareto distribution, in which one parameter is added to shift the distribution right and left and the right-hand side is truncated, is used to model size distributions of oil and gas fields for resource assessment. Assumptions about limits to the left-hand and right-hand side reduce the number of parameters to two. The TSP distribution has advantages over the more customary lognormal distribution because it has a simple analytic expression, allowing exact computation of several statistics of interest, has a "J-shape," and has more flexibility in the thickness of the right-hand tail. Oil field sizes from the Minnelusa play in the Powder River Basin, Wyoming and Montana, are used as a case study. Probability plotting procedures allow easy visualization of the fit and help the assessment. ?? 1988 International Association for Mathematical Geology.
Development of a hydrocyclone product size soft-sensor
International Nuclear Information System (INIS)
A technique is presented whereby the particle size of the hydrocyclone overflow product can be predicted by means of a mathematical model. The model uses hydrocyclone feed flowrate and density as well as hydrocyclone overflow density to calculate the required particle size. Various modelling techniques are investigated. Simple linear models are compared to neural network models. Special attention is given to the identification of significant model inputs. Simple linear and more complex neural network models, both utilising an extra model input, cyclone overflow density are identified. Error detection and analysis are explored, resulting in a robust soft-sensor, capable of predicting hydrocyclone product size accurately in the plant environment. (author)
Electron structure: Shape, size, and generalized parton distributions in QED
Miller, Gerald A.
2015-04-01
The shape of the electron is studied. Quantities of interest for 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 this mass depends on experimental conditions, so the size of the electron (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. 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, 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). The shape of the electron is studied. Quantities of interest for 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 this mass depends on experimental conditions, so the size of the electron (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. 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, 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). This material is based upon work supported by the U.S. Department of Energy Office of Science, Office of Basic Energy Sciences program, under Award No. DE-FG02- 97ER-41014.
Estimation of Weibull parameters from parameters of initial distribution of flaw size
International Nuclear Information System (INIS)
The distribution of the largest flaw size is derived from the initial distribution of flaw size based on extreme value statistics, and also the distribution of fracture origin size is given by transforming Weibull distribution by fracture mechanical relation. These two distributions are equivalent under uniaxial loading. By using this relation, their parameters are related each other and Weibull parameters are estimated from the parameters of the initial distribution of flaw size and the number of links.
New limit on the size distribution of ?-ray bursts
International Nuclear Information System (INIS)
It is stated that the flux of detected ?-ray bursts of non-solar origin so far observed has ranged between about 3 x 10-6 erg/cm2 for the smallest burst to 5 x 10-2 erg/cm2 for the largest, and the size distribution of these events above 10-4 erg/cm2 follows an Ssup(-1.5) law, suggesting an isotropic distribution of the sources, although for events with energy less than 10-4 erg/cm2 the observed distribution appears to flatten out. A new upper limit is here presented for the number of bursts that deposit more than about 2 x 10-7 erg/cm2 in the energy range 100 to 1000 keV. Observations were made using a NaI(Tl) detector shielded from photons by a graded shield. The pulses were analysed in four channels between 40 and 1000 keV. The instrument was carried on a transatlantic balloon flight launched from Sicily in August 1975, and the data were transmitted using a high frequency radio link, being recorded in Sicily and Chesapeake Beach, U.S.A. The results seemed to demonstrate that the bursts were not of extragalactic origin. They appeared to be consistent with a size distribution of Ssup(-1.5) above 10-4 erg/cm2 and Ssup(-0.5) below this energy. The true form of the size spectrum is stated to be of great importance in the development of theories to explain ?-ray bursts. (U.K.)
Top pair production distributions at the Tevatron
Directory of Open Access Journals (Sweden)
Takeuchi Yuji
2013-05-01
Full Text Available At the Tevatron, the top quark is mainly produced in pairs through the strong interaction and decays before forming hadrons. Thus the kinematical distributions at top pair production possess rich information on the tt¯$tar t$ production vertex including polarizations of top and anti-top quarks. In this article, recent measurements on top quark pair production distributions at Tevatron (CDF and DO are presented.
Shape, size, and distribution of magnetic particles in Bjurbole chondrules
Nava, David F.
1994-01-01
Chondrules from the Bjurbole chondritic meteorite (L4) exhibit saturation remanence magnetization (SIRM) values which vary over three orders of magnitude. REM values (Natural Remanence Magnetization/SIRM) for Allende (C3V) and Chainpur (LL3) are less than 0.01 but in Bjurbole some chondrules were found to have REM values greater than 0.1 with several greater than 0.2. REM values greater than 0.1 are abnormal and cannot be acquired during weak field cooling. If exposure to a strong field (whatever the source) during the chondrules' history is responsible for the high REM values, was such history associated with a different processing which might have resulted in different shape, size, and distribution of metal particles compared to chondrules having REM values of less than 0.01? Furthermore, magnetic hysteresis results show a broad range of magnetic hardness and other intrinsic magnetic properties. These features must be related to (1) size and amount of metal; and (2) properties of, and amount of, tetrataenite in the chondrules (all chondrules thus far subjected to thermomagnetic analysis show the presence of tetrataenite). A scanning electron microscopy (SEM) study is underway to determine the relationship between the shape, size, and distribution of metal particles within individual chondrules and the magnetic properties of these chondrules. Results from the SEM study in conjunction with magnetic property data may also help to discern effects from possible lightning strikes in the nebula prior to incorporation of the chondrules into the parent body.
Shape, size, and distribution of magnetic particles in Bjurbole chondrules
Nava, David F.
1994-03-01
Chondrules from the Bjurbole chondritic meteorite (L4) exhibit saturation remanence magnetization (SIRM) values which vary over three orders of magnitude. REM values (Natural Remanence Magnetization/SIRM) for Allende (C3V) and Chainpur (LL3) are less than 0.01 but in Bjurbole some chondrules were found to have REM values greater than 0.1 with several greater than 0.2. REM values greater than 0.1 are abnormal and cannot be acquired during weak field cooling. If exposure to a strong field (whatever the source) during the chondrules' history is responsible for the high REM values, was such history associated with a different processing which might have resulted in different shape, size, and distribution of metal particles compared to chondrules having REM values of less than 0.01? Furthermore, magnetic hysteresis results show a broad range of magnetic hardness and other intrinsic magnetic properties. These features must be related to (1) size and amount of metal; and (2) properties of, and amount of, tetrataenite in the chondrules (all chondrules thus far subjected to thermomagnetic analysis show the presence of tetrataenite). A scanning electron microscopy (SEM) study is underway to determine the relationship between the shape, size, and distribution of metal particles within individual chondrules and the magnetic properties of these chondrules. Results from the SEM study in conjunction with magnetic property data may also help to discern effects from possible lightning strikes in the nebula prior to incorporation of the chondrules into the parent body.
Distributed Project Management for New Product Development
Thal, Alfred E.; Jr, Adedeji Badiru; Rupy Sawhney
2007-01-01
This paper presents an integrative distributed project management approach for product development. The core of the integrative model is the Triple C model of project management, which presents a systematic structure for Communication, Cooperation, and Coordination across product development functions. The achievement of lower product development cycles requires strategic implementation of project management techniques. The level of communication, cooperation, and coordination required for ef...
Effect of head size on 10B dose distribution
International Nuclear Information System (INIS)
Boron neutron capture therapy (BNCT) for treatment of brain tumors is based on the utilization of large epithermal-neutron fields. Epithermal neutrons thermalize at depths of ?2.5 cm inside the head and provide a maximum thermal fluence at deep-seated tumor sites with minimum damage to normal tissue. Brain tissue is a highly scattering medium for epithermal and thermal neutrons; therefore, a broad treatment field enables epithermal neutrons to enter the head over a large area. These neutrons slow down as they undergo scattering collisions and contribute to the thermal-neutron fluence at the tumor location. With the use of large neutron fields, the size of the head affects the thermal-neutron distribution and thereby the 10B absorbed dose distribution inside the head. In this paper, the authors describe measurements using a boron trifluoride (BF3)-filled proportional counter to determine the effect of head size on 10B absorbed dose distributions for a broad field accelerator epithermal-neutron source
Size Distributions of Solar Flares and Solar Energetic Particle Events
Cliver, E. W.; Ling, A. G.; Belov, A.; Yashiro, S.
2012-01-01
We suggest that the flatter size distribution of solar energetic proton (SEP) events relative to that of flare soft X-ray (SXR) events is primarily due to the fact that SEP flares are an energetic subset of all flares. Flares associated with gradual SEP events are characteristically accompanied by fast (much > 1000 km/s) coronal mass ejections (CMEs) that drive coronal/interplanetary shock waves. For the 1996-2005 interval, the slopes (alpha values) of power-law size distributions of the peak 1-8 Angs fluxes of SXR flares associated with (a) >10 MeV SEP events (with peak fluxes much > 1 pr/sq cm/s/sr) and (b) fast CMEs were approx 1.3-1.4 compared to approx 1.2 for the peak proton fluxes of >10 MeV SEP events and approx 2 for the peak 1-8 Angs fluxes of all SXR flares. The difference of approx 0.15 between the slopes of the distributions of SEP events and SEP SXR flares is consistent with the observed variation of SEP event peak flux with SXR peak flux.
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.
Size of aerosols-carriers of radon daughter products at the height up to 5 km
International Nuclear Information System (INIS)
The disperse composition of atmospheric aerosols-carriers of daughter radon products was studied with the help of multilayer filters. The method is based on the selectivity of catching differently-sized particles with preliminarily calibrated fibrous filters. The threee-layer composition of fibrous materials used as the size analyzer allows to divide the observed particles according to their size into three groups (with the mean radius from 0.05 to 0.5 ?m, above 0.2 ?m and less than 0.05 ?m). It has been found out that the distribution of radon daughter products in the troposphere according to the size of particles depends on the underlying surface of the observed territory, height of samplings, meteorological conditions, concentration and the spectrum of sizes of inert aerosols
Steele, Sarah E.; Lo?pez-ferna?ndez, Herna?n
2014-01-01
Body size is an important correlate of life history, ecology and distribution of species. Despite this, very little is known about body size evolution in fishes, particularly freshwater fishes of the Neotropics where species and body size diversity are relatively high. Phylogenetic history and body size data were used to explore body size frequency distributions in Neotropical cichlids, a broadly distributed and ecologically diverse group of fishes that is highly representative of body size d...
Saharan Dust Particle Size And Concentration Distribution In Central Ghana
Sunnu, A. K.
2010-12-01
A.K. Sunnu*, G. M. Afeti* and F. Resch+ *Department of Mechanical Engineering, Kwame Nkrumah University of Science and Technology (KNUST) Kumasi, Ghana. E-mail: albertsunnu@yahoo.com +Laboratoire Lepi, ISITV-Université du Sud Toulon-Var, 83162 La Valette cedex, France E-mail: resch@univ-tln.fr Keywords: Atmospheric aerosol; Saharan dust; Particle size distributions; Particle concentrations. Abstract The Saharan dust that is transported and deposited over many countries in the West African atmospheric environment (5°N), every year, during the months of November to March, known locally as the Harmattan season, have been studied over a 13-year period, between 1996 and 2009, using a location at Kumasi in central Ghana (6° 40'N, 1° 34'W) as the reference geographical point. The suspended Saharan dust particles were sampled by an optical particle counter, and the particle size distributions and concentrations were analysed. The counter gives the total dust loads as number of particles per unit volume of air. The optical particle counter used did not discriminate the smoke fractions (due to spontaneous bush fires during the dry season) from the Saharan dust. Within the particle size range measured (0.5 ?m-25 ?m.), the average inter-annual mean particle diameter, number and mass concentrations during the northern winter months of January and February were determined. The average daily number concentrations ranged from 15 particles/cm3 to 63 particles/cm3 with an average of 31 particles/cm3. The average daily mass concentrations ranged from 122 ?g/m3 to 1344 ?g/m3 with an average of 532 ?g/m3. The measured particle concentrations outside the winter period were consistently less than 10 cm-3. The overall dust mean particle diameter, analyzed from the peak representative Harmattan periods over the 13-year period, ranged from 0.89 ?m to 2.43 ?m with an average of 1.5 ?m ± 0.5. The particle size distributions exhibited the typical distribution pattern for atmospheric aerosols with a coarse mode diameter situated at about 3.5 ?m. The experimental results reported in this study will be important in validating satellite based observations and simulation models of the African dust plume towards the Gulf of Guinea during winter.
Outbreak size distributions in epidemics with multiple stages
International Nuclear Information System (INIS)
Multiple-type branching processes that model the spread of infectious diseases are investigated. In these stochastic processes, the disease goes through multiple stages before it eventually disappears. We mostly focus on the critical multistage susceptible–infected–recovered (SIR) infection process. In the infinite-population limit, we compute the outbreak size distributions and show that asymptotic results apply to more general multiple-type critical branching processes. Finally, using heuristic arguments and simulations, we establish scaling laws for a multistage SIR model in a finite population. (paper)
Fluctuating fitness shapes the clone size distribution of immune repertoires
Desponds, Jonathan; Walczak, Aleksandra M
2015-01-01
The adaptive immune system relies on the diversity of receptors expressed on the surface of B and T-cells to protect the organism from a vast amount of pathogenic threats. The proliferation and degradation dynamics of different cell types (B cells, T cells, naive, memory) is governed by a variety of antigenic and environmental signals, yet the observed clone sizes follow a universal power law distribution. Guided by this reproducibility we propose effective models of somatic evolution where cell fate depends on an effective fitness. This fitness is determined by growth factors acting either on clones of cells with the same receptor responding to specific antigens, or directly on single cells with no regards for clones. We identify fluctuations in the fitness acting specifically on clones as the essential ingredient leading to the observed distributions. Combining our models with experiments we characterize the scale of fluctuations in antigenic environments and we provide tools to identify the relevant growth...
Scientific Electronic Library Online (English)
R.A.F., Machado; J.C., Pinto; P.H.H., Araújo; A., Bolzan.
2000-12-01
Full Text Available Particle size distribution (PSD) of polystyrene particles produced by suspension polymerization is of fundamental importance in determining suspension stability and product quality attributes. Within a population balance framework, a model is proposed for suspension polymerization reactors to descri [...] be the evolution of the PSD. The model includes description of breakage and coalescence rates in terms of reaction kinetics and rheology of the dispersed phase. The model is validated with experimental data of styrene suspension polymerization.
Aged boreal biomass-burning aerosol size distributions from BORTAS 2011
Sakamoto, K. M.; Allan, J. D.; Coe, H.; Taylor, J. W.; Duck, T. J.; Pierce, J. R.
2015-02-01
Biomass-burning aerosols contribute to aerosol radiative forcing on the climate system. The magnitude of this effect is partially determined by aerosol size distributions, which are functions of source fire characteristics (e.g. fuel type, MCE) and in-plume microphysical processing. The uncertainties in biomass-burning emission number-size distributions in climate model inventories lead to uncertainties in the CCN (cloud condensation nuclei) concentrations and forcing estimates derived from these models. The BORTAS-B (Quantifying the impact of BOReal forest fires on Tropospheric oxidants over the Atlantic using Aircraft and Satellite) measurement campaign was designed to sample boreal biomass-burning outflow over eastern Canada in the summer of 2011. Using these BORTAS-B data, we implement plume criteria to isolate the characteristic size distribution of aged biomass-burning emissions (aged ~ 1-2 days) from boreal wildfires in northwestern Ontario. The composite median size distribution yields a single dominant accumulation mode with Dpm = 230 nm (number-median diameter) and ? = 1.5, which are comparable to literature values of other aged plumes of a similar type. The organic aerosol enhancement ratios (?OA / ?CO) along the path of Flight b622 show values of 0.09-0.17 ?g m-3 ppbv-1 (parts per billion by volume) with no significant trend with distance from the source. This lack of enhancement ratio increase/decrease with distance suggests no detectable net OA (organic aerosol) production/evaporation within the aged plume over the sampling period (plume age: 1-2 days), though it does not preclude OA production/loss at earlier stages. A Lagrangian microphysical model was used to determine an estimate of the freshly emitted size distribution corresponding to the BORTAS-B aged size distributions. The model was restricted to coagulation and dilution processes based on the insignificant net OA production/evaporation derived from the ?OA / ?CO enhancement ratios. We estimate that the young-plume median diameter was in the range of 59-94 nm with modal widths in the range of 1.7-2.8 (the ranges are due to uncertainty in the entrainment rate). Thus, the size of the freshly emitted particles is relatively unconstrained due to the uncertainties in the plume dilution rates.
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...
Particle size distributions of suspended sediment in the Sacramento-San Joaquin River Delta
Wright, S. A.; Whealdon-Haught, D.
2012-12-01
Particle size distributions of suspended sediment in rivers and estuaries are of interest for a variety of reasons, such as their influence on erosion and deposition processes, their effect on light penetration and primary/secondary aquatic production, and their influence on contaminant adsorption processes. Also, particle size is known to affect the amount of light and sound that is scattered by suspended particles; thus, parameters that are typically used as surrogates for suspended-sediment concentration, such as turbidity and acoustic backscatter, are dependent on particle size distributions. Measurements of in situ particle size distributions were made at seven sites in the Sacramento-San Joaquin River Delta as well as along a longitudinal profile of the Sacramento River from Verona (upstream of tidal influence) to Rio Vista (mostly tidal). Size distributions were measured with a laser diffraction particle sizer. At the seven sites, measurements were made from an instrument package deployed on the channel bed. On the Sacramento River, vertical profiles were collected from a stationary boat. Preliminary data analyses indicate a consistent tri-modal size distribution in the Delta, with a narrow peak in the 3-7 micron range, a broad peak centered at 40-50 microns, and a narrow (smaller) peak in the 200-300 micron range. The relative contribution of the different modes varied by site and by position in the tidal cycle. Physical samples collected alongside the in situ data suggest that flocculation occurs at all sites; further analysis of samples is ongoing that will further quantify the degree of flocculation. The Sacramento River longitudinal profile documents the flocculation process occurring in the vicinity of the fluvial-tidal transition; as this transition is crossed, the measurements indicate transfer of sediment from the 3-7 micron mode primarily to the 40-50 micron mode. Understanding these flocculation processes is critical for robust numerical modeling of Delta sediment transport.
Throughfall Drop Size Distribution in relation to Leaf Canopy State
Hudson, S.; Nanko, K.; Levia, D. F., Jr.
2014-12-01
The partitioning of incident precipitation by a forest canopy into throughfall and stemflow varies as a function of meteorological conditions, tree species, leaf morphology and surface roughness. Little work quantified the throughfall drop size signature of precipitation events relative to changes in leaf canopy state of deciduous forests. This is the first study to compare throughfall drop size distributions in the presence and absence of foliage. To quantify individual throughfall drops, a laser disdrometer gauge was deployed below an observed drip point under a Liriodendron tulipifera L. (yellow poplar) tree, in northeastern Maryland, USA. More than 750,000 individual throughfall droplets have been counted and measured from precipitation events generating more than 5 mm gross rainfall over a period of 12 months. Throughfall during leafless events had significantly larger maximum drop diameters (6.74mm leafless, 5.55mm leafed) and median volume diameter of drops (5.44mm leafless, 3.31mm leafed) than throughfall generated when leaves were present. Statistical techniques have demonstrated the substantial influence of canopy state over the drop size spectra. Principal component analysis and factor analysis both resulted in canopy state loading positively with increases in maximum drop diameter while loading negatively with air temperature. Boosted regression trees analysis corroborated these findings. Our findings correspond with the physical conditions of a leafless canopy, and illustrated the greater extent of surface adhesion of intercepted water films on woody surfaces as opposed to foliar surfaces, thereby underscoring the importance of canopy state on throughfall inputs.
Number size distributions and seasonality of submicron particles in Europe 2008–2009
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A. Asmi
2011-03-01
Full Text Available Two years of harmonized aerosol number size distribution data from 24 European field monitoring sites have been analysed. The results give a comprehensive overview of the European near surface aerosol particle number concentrations and number size distributions between 30 and 500 nm of dry particle diameter. Spatial and temporal distribution of aerosols in the particle sizes most important for climate applications are presented. We also analyse the annual, weekly and diurnal cycles of the aerosol number concentrations, provide log-normal fitting parameters for median number size distributions, and give guidance notes for data users. Emphasis is placed on the usability of results within the aerosol modelling community.
We also show that the aerosol number concentrations of Aitken and accumulation mode particles (with 100 nm dry diameter as a cut-off between modes are related, although there is significant variation in the ratios of the modal number concentrations. Different aerosol and station types are distinguished from this data and this methodology has potential for further categorization of stations aerosol number size distribution types.
The European submicron aerosol was divided into characteristic types: Central European aerosol, characterized by single mode median size distributions, unimodal number concentration histograms and low variability in CCN-sized aerosol number concentrations; Nordic aerosol with low number concentrations, although showing pronounced seasonal variation of especially Aitken mode particles; Mountain sites (altitude over 1000 m a.s.l. with a strong seasonal cycle in aerosol number concentrations, high variability, and very low median number concentrations. Southern and Western European regions had fewer stations, which decreases the regional representativeness of these results. Aerosol number concentrations over the Britain and Ireland had very high variance and there are indications of mixed air masses from several source regions; the Mediterranean aerosol exhibit high seasonality, and a strong accumulation mode in the summer. The highest concentrations were observed at the JRC station in Northern Italy with high accumulation mode number concentrations in the winter. The aerosol number concentrations at the Arctic station Zeppelin in Ny-Ålesund in Svalbard have also a strong seasonal cycle, with higher concentrations of accumulation mode particles in winter, and dominating summer Aitken mode indicating more recently formed particles. Observed particles did not show any statistically significant regional work-week or weekday related variation in number concentrations studied.
Analysis products are made for open-access to the research community, available in a freely accessible internet site. The results give to the modelling community a reliable, easy-to-use and freely available comparison dataset of aerosol size distributions.
Number size distributions and seasonality of submicron particles in Europe 2008–2009
Directory of Open Access Journals (Sweden)
A. Asmi
2011-06-01
Full Text Available Two years of harmonized aerosol number size distribution data from 24 European field monitoring sites have been analysed. The results give a comprehensive overview of the European near surface aerosol particle number concentrations and number size distributions between 30 and 500 nm of dry particle diameter. Spatial and temporal distribution of aerosols in the particle sizes most important for climate applications are presented. We also analyse the annual, weekly and diurnal cycles of the aerosol number concentrations, provide log-normal fitting parameters for median number size distributions, and give guidance notes for data users. Emphasis is placed on the usability of results within the aerosol modelling community.
We also show that the aerosol number concentrations of Aitken and accumulation mode particles (with 100 nm dry diameter as a cut-off between modes are related, although there is significant variation in the ratios of the modal number concentrations. Different aerosol and station types are distinguished from this data and this methodology has potential for further categorization of stations aerosol number size distribution types.
The European submicron aerosol was divided into characteristic types: Central European aerosol, characterized by single mode median size distributions, unimodal number concentration histograms and low variability in CCN-sized aerosol number concentrations; Nordic aerosol with low number concentrations, although showing pronounced seasonal variation of especially Aitken mode particles; Mountain sites (altitude over 1000 m a.s.l. with a strong seasonal cycle in aerosol number concentrations, high variability, and very low median number concentrations. Southern and Western European regions had fewer stations, which decreases the regional coverage of these results. Aerosol number concentrations over the Britain and Ireland had very high variance and there are indications of mixed air masses from several source regions; the Mediterranean aerosol exhibit high seasonality, and a strong accumulation mode in the summer. The greatest concentrations were observed at the Ispra station in Northern Italy with high accumulation mode number concentrations in the winter. The aerosol number concentrations at the Arctic station Zeppelin in Ny-AA lesund in Svalbard have also a strong seasonal cycle, with greater concentrations of accumulation mode particles in winter, and dominating summer Aitken mode indicating more recently formed particles. Observed particles did not show any statistically significant regional work-week or weekday related variation in number concentrations studied.
Analysis products are made for open-access to the research community, available in a freely accessible internet site. The results give to the modelling community a reliable, easy-to-use and freely available comparison dataset of aerosol size distributions.
On the asteroid belt's orbital and size distribution
Gladman, Brett J.; Davis, Donald R.; Neese, Carol; Jedicke, Robert; Williams, Gareth; Kavelaars, J. J.; Petit, Jean-Marc; Scholl, Hans; Holman, Matthew; Warrington, Ben; Esquerdo, Gil; Tricarico, Pasquale
2009-07-01
For absolute magnitudes greater than the current completeness limit of H-magnitude ˜15 the main asteroid belt's size distribution is imperfectly known. We have acquired good-quality orbital and absolute H-magnitude determinations for a sample of small main-belt asteroids in order to study the orbital and size distribution beyond H=15, down to sub-kilometer sizes ( H>18). Based on six observing nights over a 11-night baseline we have detected, measured photometry for, and linked observations of 1087 asteroids which have one-week time baselines or more. The linkages allow the computation of full heliocentric orbits (as opposed to statistical distances determined by some past surveys). Judged by known asteroids in the field the typical uncertainty in the (a/e/i) orbital elements is less than 0.03 AU/0.03/0.5°. The distances to the objects are sufficiently well known that photometric uncertainties (of 0.3 magnitudes or better) dominate the error budget of their derived H-magnitudes. The detected asteroids range from H=12-22 and provide a set of objects down to sizes below 1 km in diameter. We find an on-sky surface density of 210 asteroids per square degree in the ecliptic with opposition magnitudes brighter than m=23, with the cumulative number of asteroids increasing by a factor of 10 0.27/mag from m=18 down to the m?23.5 limit of our survey. In terms of absolute H magnitudes, we find that beyond H=15 the belt exhibits a constant power-law slope with the number increasing proportional to 100.30H from H?15 to 18, after which incompleteness begins in the survey. Examining only the subset of detections inside 2.5 AU, we find weak evidence for a mildly shallower slope for H=15-19.5. We provide the information necessary such that anyone wishing to model the main asteroid belt can compare a detailed model to our detected sample.
Productivity in Swedish electricity retail distribution
International Nuclear Information System (INIS)
This paper examines productivity growth in electricity retail distribution in Sweden in a multiple output-multiple input framework. The approach used is nonparametric Data Envelopment Analysis (DEA). Productivity is measured by means of the Malmquist index. Productivity comparisons are made between different types of ownership and between different service areas. The study indicates a high rate of productivity growth, due to economics of density, when measured over a period of 17 years. The results show no significant differences in productivity growth between different types of ownership or economic organization. (20 refs., 1 fig., 4 tabs.)
Progresses in the production of large-size THGEM boards
International Nuclear Information System (INIS)
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
Airborne particulate size distribution measurements in nickel smelter plumes
Chan, Walter H.; Vet, Robert J.; Lusis, Maris A.; Skelton, Gregory B.
This paper reports the results of particle sizing measurements in the plume from two smelters at Sudbury, Ontario (INCO and Falconbridge) which were studied in 1979 and 1980. Andersen impactors, mounted on a Hughes 500C helicopter, were used. Due to bounce-off problems, it was found necessary to use sticky substrates for the coarse particles. In both the INCO and Falconbridge smelters, constituents could be classified as coarse particles having mass median diameter equal to or greater than 2.5 ?m (including Fe, Cu, Ni, Al and Mn) and fine particles having mass median diameter less than 2.5 ?m (including SO 4Pb, Zn, Cd and As). Most of these distributions were not log-normal, but displayed bimodal or multi-modal characteristics.
The size distribution of Jupiter Family comet nuclei
Snodgrass, C.; Fitzsimmons, A.; Lowry, S. C.; Weissman, P.
2011-06-01
We present an updated cumulative size distribution (CSD) for Jupiter Family comet (JFC) nuclei, including a rigorous assessment of the uncertainty on the slope of the CSD. The CSD is expressed as a power law, N(>rN) ?r-qN, where rN is the radius of the nuclei and q is the slope. We include a large number of optical observations published by us and others since the comprehensive review in the Comets II book, and make use of an improved fitting method. We assess the uncertainty on the CSD due to all of the unknowns and uncertainties involved (photometric uncertainty, assumed phase function, albedo and shape of the nucleus) by means of Monte Carlo simulations. In order to do this we also briefly review the current measurements of these parameters for JFCs. Our final CSD has a slope q= 1.92 ± 0.20 for nuclei with radius rN? 1.25 km.
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
Modelling of product size from a 90mm ID liquid fed rotary calciner
International Nuclear Information System (INIS)
Particle size reduction in a 90 mm ID indirect fired rotary kiln has been studied using simulated liquid radwaste feeds. The Rosin-Rammler particle size distribution model gave a good fit to the kiln product. A simple model is derived for the energy input for size reduction from a rotary kiln with a rabble bar. It is also demonstrated that the relationship between calculated energy input and particle size can be modelled in terms of Kick's law. The combination of the kiln model and Kick's law, to give an overall model of particle size reduction was tested experimentally for a range of feed types and process conditions. An excellent agreement was found with variation in liquid flowrate. The results obtained with various Magnox feeds showed a concentration dependence which was modelled empirically. (Auth.)
ANALYTICAL MODEL FOR MARS CRATER-SIZE FREQUENCY DISTRIBUTION
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W. Bruckman
2009-01-01
Full Text Available We present a theoretical and analytical curve that reproduces essential features of the frequency distributions vs. diameter of the 42,000 impact craters contained in Barlow's Mars Catalog. The model is derived using reasonable simple assumptions that allow us to relate the present craters population with the craters population at each particular epoch. The model takes into consideration the reduction of the number of craters as a function of time caused by their erosion and obliteration, and this provides a simple and natural explanation for the presence of di erent slopes in the empirical log-log plot of number of craters (N vs. diameter (D. A mean life for martians craters as a function of diameter is deduced, and it is shown that this result is consistent with the corresponding determination of craters mean life based on Earth data. Arguments are given to suggest that this consistency follows from the fact that a crater mean life is proportional to its volumen. It also follows that in the absence of erosions and obliterations, when craters are preserved, we would have N / 1=D4:3, which is a striking conclusion, since the exponent 4:3 is larger than previously thought. Such an exponent implies a similar slope in the extrapolated impactors size-frequency distribution.
Subglacial bedforms reveal an exponential size-frequency distribution
Hillier, J. K.; Smith, M. J.; Clark, C. D.; Stokes, C. R.; Spagnolo, M.
2013-05-01
Subglacial bedforms preserved in deglaciated landscapes record characteristics of past ice-sediment flow regimes, providing insight into subglacial processes and ice sheet dynamics. Individual forms vary considerably, but they can often be grouped into coherent fields, typically called flow-sets, that reflect discrete episodes of ice flow. Within these, bedform size-frequency distributions (predominantly height, width and length) are currently described by several statistics (e.g., mean, median, and standard deviation) that, arguably, do not best capture the defining characteristics of these populations. This paper seeks to create a better description based upon semi-log plots, which reveal that the frequency distributions of bedform dimensions (drumlin, mega-scale glacial lineation, and ribbed moraine) plot as straight lines above the mode (?). This indicates, by definition, an exponential distribution, for which a simple and easily calculated, yet statistically rigorous, description is designed. Three descriptive parameters are proposed: gradient (?; the exponent, characterising bedforms likely least affected by non-glacial factors), area-normalised y-intercept (?0; quantifying spatial density), and the mode (?). Below ?, small features are less prevalent due to i) measurement: data, sampling and mapping fidelity; ii) possible post-glacial degradation; or iii) genesis: not being created sub-glacially. This new description has the benefit of being insensitive to the impact of potentially unmapped or degraded smaller features and better captures properties relating to ice flow. Importantly, using ?, flow sets can now be more usefully compared with each other across all deglaciated regions and with the output of numerical ice sheet models. Applications may also exist for analogous fluvial and aeolian bedforms. Identifying the characteristic exponential and that it is typical of 'emergent' subglacial bedforms is a new and potentially powerful constraint on their genesis, perhaps indicating that ice-sediment interaction is fundamentally stochastic in nature.
Pair production as a probe of colliding beam size
International Nuclear Information System (INIS)
We propose the use of soft e+e- pairs as a non-evasive measurement of the colliding beam size. The angular distribution of the pair particles that have different sign of charge from that of the opposing beam, provides the information about the aspect ratio of the beam. The transverse momentum of the other species in the pair, on the other hand, carries information about the horizontal dimension of the beam. Together, one can in principle measure both ?x and ?y
Kostadinov, T. S.; Milutinovi?, S.; Marinov, I.; Cabré, A.
2015-05-01
Owing to their important roles in biogeochemical cycles, phytoplankton functional types (PFTs) have been the aim of an increasing number of ocean color algorithms. Yet, none of the existing methods are based on phytoplankton carbon (C) biomass, which is a fundamental biogeochemical and ecological variable and the "unit of accounting" in Earth System models. We present a novel bio-optical algorithm to retrieve size-partitioned phytoplankton carbon from ocean color satellite data. The algorithm is based on existing algorithms to estimate particle volume from a power-law particle size distribution (PSD). Volume is converted to carbon concentrations using a compilation of allometric relationships. We quantify absolute and fractional biomass in three PFTs based on size - picophytoplankton (0.5-2 ?m in diameter), nanophytoplankton (2-20 ?m) and microphytoplankton (20-50 ?m). The mean spatial distributions of total phytoplankton C biomass and individual PFTs, derived from global SeaWiFS monthly ocean color data, are consistent with current understanding of oceanic ecosystems, i.e. oligotrophic regions are characterized by low biomass and dominance of picoplankton, whereas eutrophic regions have large biomass to which nanoplankton and microplankton contribute relatively larger fractions. Global spatially integrated phytoplankton carbon biomass standing stock estimates using our PSD-based approach yield on average ~0.2-0.3 Gt of C, consistent with analogous estimates from two other ocean color algorithms, and several state-of-the-art Earth System models. However, the range of phytoplankton C biomass spatial variability globally is larger than estimated by any other models considered here, because the PSD-based algorithm is not a priori empirically constrained and introduces improvement over the assumptions of the other approaches. Satisfactory in situ closure observed between PSD and POC measurements lends support to the theoretical basis of the PSD-based algorithm. Uncertainty budget analyses indicate that absolute carbon concentration uncertainties are driven by the PSD parameter No which determines particle number concentration to first order, while uncertainties in PFTs' fractional contributions to total C biomass are mostly due to the allometric coefficients.
International Nuclear Information System (INIS)
By the Monte Carlo method, the effect of dispersion of disc size distribution on the velocity distributions and correlations of a polydisperse granular gas with fractal size distribution is investigated in the same inelasticity. The dispersion can be described by a fractal dimension D, and the smooth hard discs are engaged in a two-dimensional horizontal rectangular box, colliding inelastically with each other and driven by a homogeneous heat bath. In the steady state, the tails of the velocity distribution functions rise more significantly above a Gaussian as D increases, but the non-Gaussian velocity distribution functions do not demonstrate any apparent universal form for any value of D. The spatial velocity correlations are apparently stronger with the increase of D. The perpendicular correlations are about half the parallel correlations, and the two correlations are a power-law decay function of dimensionless distance and are of a long range. Moreover, the parallel velocity correlations of postcollisional state at contact are more than twice as large as the precollisional correlations, and both of them show almost linear behaviour of the fractal dimension D. (general)
On Distribution of Product of Stable Laws
Karlova, Andrea
2014-01-01
We derive the probability distribution of product of two independent random variables, each distributed according the one-dimensional stable law. We represent the density by its power series and its asymptotic expansions. As Fox's H-functions with a particular choice of parameters well describe the densities of stable laws, we discuss the choice of parameters for Fox's H-function such that it matches the derived densities. As a consequence, we give representations of these p...
Sizes and shapes of subglacial bedforms reveal an exponential size-frequency distribution
Hillier, John K.; Smith, Mike J.; Clark, Chris D.; Stokes, Chris R.; Spagnolo, Matteo
2013-04-01
Subglacial bedforms preserved in deglaciated landscapes record characteristics of past ice-sediment flow regimes, providing insight into subglacial processes and ice sheet dynamics. Individual forms vary considerably, but they can often be grouped into coherent fields, typically called flow-sets, that reflect discrete episodes of ice flow. Within these, bedform size-frequency distributions (predominantly height, width and length) are currently described by several statistics (e.g., mean, median, standard deviation) that, arguably, do not best capture the defining characteristics of these populations. This paper seeks to create a better description based upon semi-log plots, which reveal that the frequency distributions of bedform dimensions (drumlin, MSGL, ribbed moraine) plot as straight lines above the mode (?). This indicates, by definition, an exponential distribution, for which a simple and easily calculated, yet statistically rigorous, description is designed. Three descriptive parameters are proposed: gradient (?; the exponent, characterising bedforms likely least affected by non-glacial factors), area-normalised y-intercept (?0; quantifying spatial density), and the mode (?). Below ?, small features are less prevalent due to i) measurement: data, sampling, mapping fidelity ii) possibly post-glacial degradation or iii) genesis: not being created sub-glacially. This new description has the benefit of being insensitive to the impact of potentially unmapped or degraded smaller features and better captures properties relating to ice flow. Importantly, using ?, flow sets can now be more usefully compared with each other across all deglaciated regions and with the output of numerical ice sheet models. Identifying the characteristic exponential and that it is typical of 'emergent' subglacial bedforms is a new and potentially powerful constraint on their genesis, perhaps indicating that ice-sediment interaction is fundamentally stochastic in nature.
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.
Product angular distributions in dissociative recombination.
Guberman, Steven L
2004-05-22
The dependence of the dissociative recombination cross section upon the angle between the incoming electron beam and the ion internuclear axis is determined for diatomic molecules. Product angular distributions are derived for the component partial waves of the Coulomb wave function. In agreement with earlier results for dissociative attachment, it is shown that in the slow rotation approximation, if electron capture is dominated by a single partial wave, the product angular distribution is given by the square of the absolute value of the partial wave spherical harmonic describing the incoming electron. PMID:15267962
The anomalies of the properties of nanomaterials related to the distribution of the grain sizes
Glinchuk, M. D.; Bykov, P. I.
2004-01-01
We have performed the calculations of the size effect in the temperature dependence of BaTiO3 nanograin ceramics specific heat and dielectric permittivity. We took into account the distribution of the grain sizes, that exists in any real nanomaterial. This distribution lead to the distribution of the temperatures of the size driven transition from ferroelectric to paraelectric phase because of relation between the temperature and the sizes. We calculated the transition tempe...
Rain drop size distribution over the Tibetan Plateau
Porcù, Federico; D'Adderio, Leo Pio; Prodi, Franco; Caracciolo, Clelia
2014-12-01
Over the last decade, interest in measuring and studying rain drop size distribution (DSD) has grown due to applications in cloud physics, in calibration of space-borne and ground-based microwave active precipitation sensors and in soil science and agriculture. Such studies are of particular interest over remote areas, where knowledge of clouds and precipitation processes is lacking while the need for remote sensing based precipitation estimates is growing in global water cycle and climate trend studies. Disdrometric data over the Tibetan Plateau were collected during the 2010 monsoon season using the Pludix disdrometer, a vertically pointing, continuous wave, X-band, low power radar. Three experimental sites were set up at altitudes greater than 3300 m a.s.l., and a total number of 37 rain events were measured at two of the three sites. The analysis focuses on 2-min and 5-min DSD data for selected convective and stratiform events and the results are discussed in comparison with previous studies performed at lower altitudes. The time evolution of DSDs shows a regular behavior with respect to rain intensity: they change concavity and show a breakup signature in cases of the highest rain rates. Collisional breakup takes place for relatively lower rain rates, compared to the low-altitude measurements, and the size of the largest drops is also relatively smaller. An overall rainfall characteristic evaluation is also performed on the whole data set, deriving DSD integral parameters in order to compute a relationship between reflectivity and rain rate, resulting in A = 214 (A = 247) and b = 1.25 (b = 1.15) for convective (stratiform) precipitation.
Vaccine production, distribution, access and uptake
Smith, Jon; Lipsitch, Marc; Almond, Jeffrey W.
2011-01-01
Making human vaccines available on a global scale requires the use of complex production methods, meticulous quality control and reliable distribution channels that ensure the products are potent and effective at their point of use. The technologies involved in manufacturing different types of vaccines may strongly influence vaccine cost, ease of industrial scale-up, stability and ultimately world-wide availability. Manufacturing complexity is compounded by the need for different formulations...
ESTIMATING SOIL PARTICLE-SIZE DISTRIBUTION FOR SICILIAN SOILS
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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.
Controllable microgels from multifunctional molecules: structure control and size distribution
Gu, Zhenyu; Patterson, Gary; Cao, Rong; Armitage, Bruce
2004-03-01
Supramolecular microgels with fractal structures were produced by engineered multifunctional molecules. The combination of static and dynamic light scattering was utilized to characterize the fractal dimension (Df) of the microgels and analyze the aggregation process of the microgels. The microgels are assembled from (1) a tetrafunctional protein (avidin), (2) a trifunctional DNA construct known as a three-way junction, and (3) a biotinylated peptide nucleic acid (PNA) that acts as a crosslinker by binding irreversibly to four equivalent binding sites on the protein and thermoreversibly to three identical binding sites on the DNA. The structure of microgels can be controlled through different aggregation mechanisms. The initial microgels formed by titration have a compact structure with Df ˜2.6; while the reversible microgels formed from melted aggregates have an open structure with Df ˜1.8. The values are consistent with the point-cluster and the cluster-cluster aggregation mechanisms, respectively. A narrow size distribution of microgels was observed and explained in terms of the Flory theory of reversible self-assembly.
Group size versus individual group size frequency distributions: a nontrivial distinction
Jovani, Roger; Mavor, Roddy
2011-01-01
Understanding group size variation is a major challenge in animal ecology. However, we argue that understanding group sizes from an individual point of view (i.e. individual group sizes) and the rela- tionship with population group sizes may be even more important. This may seem redundant, but in the present study we show that it is not. We analysed colony sizes of 20 seabird species breeding in Britain and Ireland from the Seabird 2000 project (19 978 colonies; 3 779 919 ne...
Size distribution dynamics reveal particle-phase chemistry in organic aerosol formation
Shiraiwa, Manabu; Yee, Lindsay D.; Schilling, Katherine A.; Loza, Christine L.; Craven, Jill S.; Zuend, Andreas; Ziemann, Paul J.; Seinfeld, John H.
2013-01-01
Organic aerosols are ubiquitous in the atmosphere and play a central role in climate, air quality, and public health. The aerosol size distribution is key in determining its optical properties and cloud condensation nucleus activity. The dominant portion of organic aerosol is formed through gas-phase oxidation of volatile organic compounds, so-called secondary organic aerosols (SOAs). Typical experimental measurements of SOA formation include total SOA mass and atomic oxygen-to-carbon ratio. These measurements, alone, are generally insufficient to reveal the extent to which condensed-phase reactions occur in conjunction with the multigeneration gas-phase photooxidation. Combining laboratory chamber experiments and kinetic gas-particle modeling for the dodecane SOA system, here we show that the presence of particle-phase chemistry is reflected in the evolution of the SOA size distribution as well as its mass concentration. Particle-phase reactions are predicted to occur mainly at the particle surface, and the reaction products contribute more than half of the SOA mass. Chamber photooxidation with a midexperiment aldehyde injection confirms that heterogeneous reaction of aldehydes with organic hydroperoxides forming peroxyhemiacetals can lead to a large increase in SOA mass. Although experiments need to be conducted with other SOA precursor hydrocarbons, current results demonstrate coupling between particle-phase chemistry and size distribution dynamics in the formation of SOAs, thereby opening up an avenue for analysis of the SOA formation process. PMID:23818634
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...
Thermal Properties, Sizes, and Size Distribution of Jupiter-Family Cometary Nuclei
Fernandez, Y R; Lamy, P L; Toth, I; Groussin, O; Lisse, C M; A'Hearn, M F; Bauer, J M; Campins, H; Fitzsimmons, A; Licandro, J; Lowry, S C; Meech, K J; Pittichova, J; Reach, W T; Snodgrass, C; Weaver, H A
2013-01-01
We present results from SEPPCoN, an on-going Survey of the Ensemble Physical Properties of Cometary Nuclei. In this report we discuss mid-infrared measurements of the thermal emission from 89 nuclei of Jupiter-family comets (JFCs). All data were obtained in 2006 and 2007 with the Spitzer Space Telescope. For all 89 comets, we present new effective radii, and for 57 comets we present beaming parameters. Thus our survey provides the largest compilation of radiometrically-derived physical properties of nuclei to date. We conclude the following. (a) The average beaming parameter of the JFC population is 1.03+/-0.11, consistent with unity, and indicating low thermal inertia. (b) The known JFC population is not complete even at 3 km radius, and even for comets with perihelia near ~2 AU. (c) We find that the JFC nuclear cumulative size distribution (CSD) has a power-law slope of around -1.9. (d) This power-law is close to that derived from visible-wavelength observations, suggesting that there is no strong dependenc...
Batch sizing with controllable production rates in a multi-stage production system
Christoph H. Glock
2011-01-01
Abstract In a recent paper, Glock [2010. Batch sizing with controllable production rates. International Journal of Production Research 20: 5925-5942] studied the impact of a variable production rate on the inventory build-up and the total costs in a two-stage production system. In this paper, we extend Glock’s (2010) model to a multi-stage production system where the production rate at each producing stage may be varied within given limits. We compare our model to the classical c...
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.
Agimelen, Okpeafoh S; McGinty, John; Tachtatzis, Christos; Dziewierz, Jerzy; Haley, Ian; Sefcik, Jan; Mulholland, Anthony J
2015-01-01
Efficient processing of particulate products across various manufacturing steps requires that particles possess desired attributes such as size and shape. Controlling the particle production process to obtain required attributes will be greatly facilitated using robust algorithms providing the size and shape information of the particles from in situ measurements. However, obtaining particle size and shape information in situ during manufacturing has been a big challenge. This is because the problem of estimating particle size and shape (aspect ratio) from signals provided by in-line measuring tools is often ill posed, and therefore it calls for appropriate constraints to be imposed on the problem. One way to constrain uncertainty in estimation of particle size and shape from in-line measurements is to combine data from different measurements such as chord length distribution (CLD) and imaging. This paper presents two different methods for combining imaging and CLD data obtained with in-line tools in order to ...
Estimating AOD using a Quad-Modal Size Distribution
Davies, Will; North, Peter
2013-04-01
A method has been developed to estimate Aerosol Optical Depth (AOD) and Single Scattering Albedo (SSA) over land surfaces using high spatial resolution, hyperspectral, multi-angle CHRIS/PROBA images. The Compact High Resolution Imaging Spectrometer (CHRIS) instrument is mounted aboard the Project for On Board Autonomy 1 (PROBA-1) satellite, and provides up to 62 bands. The PROBA satellite was launched by ESA in October 2001 and allows pointing to obtain imagery from five different view angles within a short time interval. The method uses inversion of a coupled surface/atmosphere radiative transfer model, and includes a general physical model of angular surface reflectance. An iterative process is used to determine the optimum value of the aerosol properties providing the best fit of the corrected reflectance values for a number of view angles and wavelengths with those provided by the physical model. This method of estimating AOD has previously been demonstrated on data from the Advanced Along-Track Scanning Radiometer (AATSR), and is extended here to the spectral and angular sampling of CHRIS/PROBA and the additional aerosol property. The values obtained from these observations are validated using ground based sun-photometer measurements. Results from 23 image sets show an RMS error of 0.09 in AOD at 550nm using standard 6S models. Results from 19 image sets show an RMS error of 0.21 in SSA for the estimates at 868 nm, an RMS error of 0.21 at 672 nm and 0.18 at 442 nm. Estimates of AOD from the extended method using a quad modal size distribution show an RMS error of 0.07.
Stenberg, Johan
1997-01-01
This thesis covers an introduction to the present conditions for newspaper publishing, definitions and analyses of the processes of newspaper production and distribution, expected future developments with respect to products and production processes, and finally, conclusions regarding the need for global coordination of products, production and distribution. Primarily, the conditions in the Nordic countries have been analysed. Particular attention has been drawn to Swedish morning newspapers ...
Some regularity of the grain size distribution in nuclear fuel with controllable structure
International Nuclear Information System (INIS)
It is known, the fission gas release from ceramic nuclear fuel depends from average size of grains. To increase grain size they use additives which activate sintering of pellets. However, grain size distribution influences on fission gas release also. Fuel with different structures, but with the same average size of grains has different fission gas release. Other structure elements, which influence operational behavior of fuel, are pores and inclusions. Earlier, in Kyoto, questions of distribution of grain size for fuel with 'natural' structure were discussed. Some regularity of grain size distribution of fuel with controllable structure and high average size of grains are considered in the report. Influence of inclusions and pores on an error of the automated definition of parameters of structure is shown. The criterion, which describe of behavior of fuel with specific grain size distribution, is offered
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.)
International Nuclear Information System (INIS)
Ambient aerosol size distributions oof 131I, 103Ru, 132Te and 137Cs radionuclides were measured in Helsinki, Finland during May 7 - 14, 1986. Radioactivity size distributions were unimodal. Geometric mean diameter of 131I was in the size range 0.33 - 0.57 ?m a.e.d.. Other isotopes had geometric mean diameters in the size range 0.65 - 0.93 ?m a.e.d.. (author)
Nishiura, Hiroshi; Yan, Ping; Sleeman, Candace K.; Mode, Charles J.
2011-01-01
Use of the final size distribution of minor outbreaks for the estimation of the reproduction numbers of supercritical epidemic processes has yet to be considered. We used a branching process model to derive the final size distribution of minor outbreaks, assuming a reproduction number above unity, and applying the method to final size data for pneumonic plague. Pneumonic plague is a rare disease with only one documented major epidemic in a spatially limited setting. Because the final size dis...
Effects of grain size distribution on the interstellar dust mass growth
Hirashita, Hiroyuki; Kuo, Tzu-ming
2011-01-01
Grain growth by the accretion of metals in interstellar clouds (called `grain growth') could be one of the dominant processes that determine the dust content in galaxies. The importance of grain size distribution for the grain growth is demonstrated in this paper. First, we derive an analytical formula that gives the grain size distribution after the grain growth in individual clouds for any initial grain size distribution. The time-scale of the grain growth is very sensitiv...
The Number and the Size Distribution of Firms in Sweden and Other European Countries
Johansson, Dan
1997-01-01
This study investigates changes in the number and the size distribution of firms in Sweden in the period 1968-1993. The number and the size distribution of Swedish firms are compared to the number and the size distribution of firms in eleven European countries. A decrease in the number of enterprises in the Swedish manufacturing industry is observed in all size classes and intermediate-sized (10-199 employees/firm) firms declined the most. Large differences are found in the number of firms be...
Flow distribution in the accelerator-production-of-tritium target
International Nuclear Information System (INIS)
Achieving nearly uniform flow distributions in the accelerator production of tritium (APT) target structures is an important design objective. Manifold effects tend to cause a nonuniform distribution in flow systems of this type, although nearly even distribution can be achieved. A program of hydraulic experiments is underway to provide a database for validation of calculational methodologies that may be used for analyzing this problem and to evaluate the approach with the most promise for achieving a nearly even flow distribution. Data from the initial three tests are compared to predictions made using four calculational methods. The data show that optimizing the ratio of the supply-to-return-manifold areas can produce an almost even flow distribution in the APT ladder assemblies. The calculations compare well with the data for ratios of the supply-to-return-manifold areas spanning the optimum value. Thus, the results to date show that a nearly uniform flow distribution can be achieved by carefully sizing the supply and return manifolds and that the calculational methods available are adequate for predicting the distributions through a range of conditions
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.
Lot-sizing problem with several production centers
Directory of Open Access Journals (Sweden)
Franklina Maria Bragion de Toledo
2005-12-01
Full Text Available 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 as 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.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.
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
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.
Size, distribution and sediment biodeposition of prolific bivalves in small estuaries
Callaway, Ruth; Grenfell, Suzanne; Bertelli, Chiara; Mendzil, Anouska; Moore, Jon
2014-10-01
The growth and distribution of bivalves in estuaries is generally driven by access to food, hydrodynamic forces and sedimentary conditions that facilitate recruitment and allow persistent settlement. Factors such as site elevation or sediment properties have a significant impact, but there are few studies quantifying the relative importance of different factors in an entire estuary. We carried out an estuary-wide survey of the cockle Cerastoderma edule L. by sampling 343 sites in a small estuary, the Burry Inlet in South Wales, UK. We determined the extent to which site elevation, as an indicator for the duration of feeding, sediment properties and position inside the estuary, explained variation in the size and density of the bivalve. We also analysed the production of faeces and pseudo-faeces per cockle. The population consisted almost entirely of 1-year old cockles, the average size was 14.7 ± 2.7 mm and the average density was 56 ± 189 cockles 0.1 m-2 (mean ± SD). Altogether 37% of the variation in size was explained by two factors: elevation of site (15%) and amount of clay & silt in sediments (22%). Variation in density appeared to play no significant role in determining size. Density was significantly linked to sediment properties (32%) and position inside the estuary (4%). Sediment biodeposition, the amount of material discharged per cockle, was 0.032 ± 0.017 g dry weight, the whole population thereby producing an estimated 387 tonnes of faeces and pseudo-faeces in the entire estuary per day. The study confirmed that access to food is a principal driver of growth, but the relatively small proportion of the variation in size explained by site elevation highlights that other factors play an important role. Sediment characteristics in particular were of importance to variation in size as well as density. It seems plausible that sediment properties were a proxy for factors such as bedload movement and exposure, which are more likely causal factors for distribution patterns. However, the bivalves may also actively favour certain sediment compositions for ease of burrowing and food availability. We suggest that the role of active and passive movement of bivalves within an estuary needs further clarification, which would affect individual growth rates and spatial size distribution patterns. The considerable amount of mucus bound material discharged by cockles suggests that the contribution of prolific bivalves to habitat properties of small estuaries is under-estimated.
Size-fractionated production and bioavailability of dissolved organic matter
DEFF Research Database (Denmark)
Knudsen-Leerbeck, Helle; Bronk, Deborah A.
Production and bioavailability of dissolved organic matter was quantified on a time scale of two days from size fractions ranging from bacteria to zooplankton in the York River, Virginia. The goal was to find the main contributor to DOM. Batch incubation experiments were labeled with N15-ammonium and C13-bicarbonate, and degradation kinetics of dissolved organic matter was measured over 14 days. Chlorophyll a increased to a maximum of 14 ± 0.6 ?g L-1 during the incubation. Inorganic nitrogen was taken up producing a maximum of 10 ± 0.3 ?mol particulate nitrogen L-1. The increase in biomass was mainly in the phytoplankton size fraction, which on average contributed 62 % of total particulate nitrogen and 61 % of total particulate carbon. Up to 5 ± 0.4 ?mol dissolved organic nitrogen L-1 and 33 ± 6.2 ?mol dissolved organic carbon L-1 was produced during the incubation. Bioavailability of phytoplankton produced dissolved organic carbon was 12 ± 1 % and higher than in the presence of bacteria, microzooplankton, orcopepods (7 ± 3 %). The pattern for bioavailability of dissolved organic nitrogen was less clear and ranged from 4 – 7 %. This study revealed that phytoplankton was the main contributor to the production of dissolved organic matter.
Multimodal size distributions of ?' precipitates during continuous cooling of UDIMET 720 Li
International Nuclear Information System (INIS)
The technological properties of many nickel-based superalloys originate in the morphology and distribution of Ni3(Al, Ti) particles (?' precipitates). Starting from the solution-annealed condition, the distribution and the morphology of ?' 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 ?' precipitation kinetics. The theoretical background for occurrence of multimodal size distributions during continuous cooling is discussed.
Simulation of the measure of the microparticle size distribution in two dimensions
International Nuclear Information System (INIS)
Different size distributions of plane figures were generated in a computer as a simply connected network. These size distributions were measured by the Saltykov method for two dimensions. The comparison between the generated and measured distributions showed that the Saltkov method tends to measure larger scattering than the real one and to move the maximum of the real distribution to larger diameters. These erros were determined by means of the ratio of the perimeter of the figures per unit area directly measured and the perimeter calculated from the size distribution obtained by using the SaltyKov method. (Author)
Production of size controlled aluminum and alumina nanoparticles via pulsed laser ablation in water.
Lee, Seulki; Jung, Hyeon Jin; Shin, Jae Ho; Choi, Myong Yong
2012-12-01
An Al metal plate was ablated by a pulsed Nd-YAG laser to produce nano-structured Al and gamma-Al2O3 in deionized water in the absence of any surfactants or catalysts. In this study, the mean diameter and the width of size distribution of the nanoparticles was influenced by the laser power, resulting in the production of smaller and larger sizes of nanoparticles with higher and lower laser power, respectively. The influence of laser power on the mean diameter and the width of size distribution of as-prepared nanoparticles generated by the laser ablation process was explained by the space homogeneity of the plasma plume, where the nucleation of nanoparticles has occurred. Further explanations of the influence of laser power on the size distribution are proposed. Furthermore, structural and morphological characterization of aluminum and gamma-Al2O3 nanoparticles was conducted by X-ray diffraction (XRD) and field emission scanning electron microscope (FE-SEM). PMID:23447935
Determination of Size Distributions in Nanocrystalline Powders by TEM, XRD and SAXS
DEFF Research Database (Denmark)
Jensen, Henrik; Pedersen, JØrgen Houe
2006-01-01
Crystallite size distributions and particle size distributions were determined by TEM, XRD, and SAXS for three commercially available TiO2 samples and one homemade. The theoretical Guinier Model was fitted to the experimental data and compared to analytical expressions. Modeling of the XRD spectra showed a difference between the analytical size dependent expressions and the theoretical Guinier Model. Primay particle size distributions were extracted from SAXS measurements by the hard sphere model including the interparticle interference factor. The size distributions from SAXS were smaller than the size distribution obtained from the XRD experiments; however, a good agreement was obtained between the two techniques. Electron microscopy, SEM and TEM, confirmed the primary particle sizes, the size distributions, and the shapes obtained by XRD and SAXS. The SSEC78 powder and the commercially available powders showed different morphologies. The SSEC78 powder showed the narrowest sizes distribution while UV100 and TiO2_5nm consisted of the smallest primary particles. SSEC78, UV100, and TiO2_5nm consisted of both primary particles as well as a secondary structure comprised of nanosized primary particles agglomeration into larger clusters. P25 showed the largest primary particle size, but didn't show a secondary structure.
[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
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
Borchard, C.; Engel, A.
2015-02-01
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) at present-day and high-CO2 concentrations. 14C incubations were performed to determine primary production (PP), comprised of particulate (PO14C) and dissolved organic carbon (DO14C). Concentration and composition of particulate combined carbohydrates (pCCHO) and high-molecular-weight (>1 kDa, HMW) dissolved combined carbohydrates (dCCHO) were determined by ion chromatography. Information on size distribution of ER products was obtained by investigating distinct size classes (sugars had a significant share on freshly produced pCCHO as well as on HMW-dCCHO. While pCCHO and the smallest size fraction (sugar composition, dominated by high percentage of glucose (74-80 mol%), the composition of HMW-dCCHO size classes >10 kDa was significantly different, with a higher mol% of arabinose. The mol% of acidic sugars increased and that of 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.
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)
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.
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
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
Effect of Flock Size on Fayoumi Layer Production
Directory of Open Access Journals (Sweden)
Muhammad Ismail Rind
2005-01-01
Full Text Available Group size in poultry breeding flock as well as female and male ratio greatly contributes to their production, in this concern from an Egyptian Fayoumi laying flock in 27th week of age,36 layers were weighed (1.60 kg/layer, randomly grouped in A (11, B (12 and C (13 and allocated breeding cock of same age and flock. Layers kept at Poultry Experiment Station, Tandojam, on flour system, each group provided one laying nest, 16 hr florescent light and 2 sq.ft space per layer were provided. Birds fed 100 g/layer/day and water was provided 24 h. Eggs were collected at 10, 14 and 18 h daily, soundness was checked and stored in dark room. 50 candled and fit eggs randomly selected and settled into hatchery for incubation. Candling was practiced on 3rd and 14th day and turning was practiced daily. Hatched chicks of each group were collected, weighed and brooded over two weeks. Layers average feed intake (682, 686 and 685 g/b/w and egg weight (40.36, 40.45 and 40.54 g/egg were almost increased followed by significant increase in egg production (5.03,5.19 and 5.21 egg/b/week with the increase in breeding layer group size for a cock in A,B and groups, respectively. Average fertility and hatchability rates of Fayoumi layer were high for middle (B than small (A and large (C flock size groups during first, second and third hatch of eggs. However, both fertility and hatchability rates were in increasing trend with the progress of age and eggs hatched but hatchability rate was slightly reduced during last hatch and small group reached to its peak of hatching. Overall results of Fayoumi layers kept in middle flock size eggs fertility and hatchability rates were at peak for medium (B than small (A and large (C groups but, chicks from large group to become heavier (29.90 than medium (29.80 and small (29.34 g/b, respectively.
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)
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.
Estimation of pore size distribution using concentric double pulsed-field gradient NMR
Benjamini, Dan; Nevo, Uri
2013-05-01
Estimation of pore size distribution of well calibrated phantoms using NMR is demonstrated here for the first time. Porous materials are a central constituent in fields as diverse as biology, geology, and oil drilling. Noninvasive characterization of monodisperse porous samples using conventional pulsed-field gradient (PFG) NMR is a well-established method. However, estimation of pore size distribution of heterogeneous polydisperse systems, which comprise most of the materials found in nature, remains extremely challenging. Concentric double pulsed-field gradient (CDPFG) is a 2-D technique where both q (the amplitude of the diffusion gradient) and ? (the relative angle between the gradient pairs) are varied. A recent prediction indicates this method should produce a more accurate and robust estimation of pore size distribution than its conventional 1-D versions. Five well defined size distribution phantoms, consisting of 1-5 different pore sizes in the range of 5-25 ?m were used. The estimated pore size distributions were all in good agreement with the known theoretical size distributions, and were obtained without any a priori assumption on the size distribution model. These findings support that in addition to its theoretical benefits, the CDPFG method is experimentally reliable. Furthermore, by adding the angle parameter, sensitivity to small compartment sizes is increased without the use of strong gradients, thus making CDPFG safe for biological applications.
Distributed Monte Carlo production for D0
International Nuclear Information System (INIS)
The D0 collaboration uses a variety of resources on four continents to pursue a strategy of flexibility and automation in the generation of simulation data. This strategy provides a resilient and opportunistic system which ensures an adequate and timely supply of simulation data to support D0's physics analyses. A mixture of facilities, dedicated and opportunistic, specialized and generic, large and small, grid job enabled and not, are used to provide a production system that has adapted to newly developing technologies. This strategy has increased the event production rate by a factor of seven and the data production rate by a factor of ten in the last three years despite diminishing manpower. Common to all production facilities is the SAM (Sequential Access to Metadata) data-grid. Job submission to the grid uses SAMGrid middleware which may forward jobs to the OSG, the WLCG, or native SAMGrid sites. The distributed computing and data handling system used by D0 will be described and the results of MC production since the deployment of grid technologies will be presented.
Distributed Monte Carlo production for DZero
International Nuclear Information System (INIS)
The DZero collaboration uses a variety of resources on four continents to pursue a strategy of flexibility and automation in the generation of simulation data. This strategy provides a resilient and opportunistic system which ensures an adequate and timely supply of simulation data to support DZero's physics analyses. A mixture of facilities, dedicated and opportunistic, specialized and generic, large and small, grid job enabled and not, are used to provide a production system that has adapted to newly developing technologies. This strategy has increased the event production rate by a factor of seven and the data production rate by a factor of ten in the last three years despite diminishing manpower. Common to all production facilities is the SAM (Sequential Access to Metadata) data-grid. Job submission to the grid uses SAMGrid middleware which may forward jobs to the OSG, the WLCG, or native SAMGrid sites. The distributed computing and data handling system used by DZero will be described and the results of MC production since the deployment of grid technologies will be presented.
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
A model study of the size and composition distribution of aerosols in an aircraft exhaust
Energy Technology Data Exchange (ETDEWEB)
Sorokin, A.A. [SRC `ECOLEN`, Moscow (Russian Federation)
1997-12-31
A two-dimensional, axisymmetric flow field model which includes water and sulphate aerosol formation represented by moments of the size and composition distribution function is used to calculate the effect of radial turbulent jet mixing on the aerosol size distribution and mean modal composition. (author) 6 refs.
Dubrovskii, V. G.; Berdnikov, Yu. S.
2015-03-01
We obtain exact solutions of the rate equations for homogeneous and heterogeneous irreversible growth models with linear size dependences of the capture rates. In the limit of high ratios of diffusion constant over deposition rate, both solutions yield simple analytical scaling functions with the correct normalizations. These are given by the cumulative distribution function and the probability density function of the gamma-distribution in homogeneous and heterogeneous cases, respectively. Our size distributions depend on the value of the capture rate a in the reaction of joining two mobile monomers A1 (A1 + A1 ? A2) or the monomer attachment to the reactive defect B (A1 + B ? AB). In homogeneous cases, the size distribution is monotonically decreasing regardless of a. In heterogeneous growth, the distribution is monotonically decreasing when a ? 1 and monomodal when a > 1. The obtained solutions describe fairly well the experimental data on the length distributions of Al, Ga, In, and Mn adatom chains on Si(100)-2 × 1 surfaces.
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.
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...
Experimental study on bubble size distributions in a direct-contact evaporator
Scientific Electronic Library Online (English)
C. P., Ribeiro Jr.; P. L. C., Lage.
2004-01-01
Full Text Available Experimental bubble size distributions and bubble mean diameters were obtained by means of a photographic technique for a direct-contact evaporator operating in the quasi-steady-state regime. Four gas superficial velocities and three different spargers were analysed for the air-water system. In orde [...] r to assure the statistical significance of the determined size distributions, a minimum number of 450 bubbles was analysed for each experimental condition. Some runs were also conducted with an aqueous solution of sucrose to study the solute effect on bubble size distribution. For the lowest gas superficial velocity considered, at which the homogeneous bubbling regime is observed, the size distribution was log-normal and depended on the orifice diameter in the sparger. As the gas superficial velocity was increased, the size distribution progressively acquired a bimodal shape, regardless of the sparger employed. The presence of sucrose in the continuous phase led to coalescence hindrance.
Experimental study on bubble size distributions in a direct-contact evaporator
Directory of Open Access Journals (Sweden)
C. P. Ribeiro Jr.
2004-01-01
Full Text Available Experimental bubble size distributions and bubble mean diameters were obtained by means of a photographic technique for a direct-contact evaporator operating in the quasi-steady-state regime. Four gas superficial velocities and three different spargers were analysed for the air-water system. In order to assure the statistical significance of the determined size distributions, a minimum number of 450 bubbles was analysed for each experimental condition. Some runs were also conducted with an aqueous solution of sucrose to study the solute effect on bubble size distribution. For the lowest gas superficial velocity considered, at which the homogeneous bubbling regime is observed, the size distribution was log-normal and depended on the orifice diameter in the sparger. As the gas superficial velocity was increased, the size distribution progressively acquired a bimodal shape, regardless of the sparger employed. The presence of sucrose in the continuous phase led to coalescence hindrance.
International Nuclear Information System (INIS)
The track-size distribution on electrochemically etched CR-39 foils can be used to obtain some limited information on the incident neutron spectra. Track-size distributions on CR-39 foils can also be used to determine if the tracks were caused by neutrons or if they are merely background tracks (which have a significantly different track-size distribution). Identifying and discarding the high-background foils reduces the number of foils that must be etched. This also lowers the detection limit of the dosimetry system. We have developed an image analyzer program that can more efficiently determine the track density and track-size distribution, as well as read the laser-cut identification numbers on each foil. This new image analyzer makes the routine application of track-size distributions on CR-39 foils feasible. 2 refs., 3 figs
International Nuclear Information System (INIS)
The track-size distribution on electrochemically etched CR-39 foils can be used to obtain some limited information on the incident neutron spectral. Track-size distributions on CR-39 foils can also be used to determine if the tracks were caused by neutrons or if they are merely background tracks (which have a significantly different track-size distribution). Identifying and discarding the high-background foils reduces the number of foils that must be etched. This also lowers the detection limit of the dosimetry system. We have developed an image analyzer program that can more efficiently determine the track density and track-size distribution, as well as read the laser-cut identification numbers on each foil. This new image analyzer makes the routine application of track-size distributions on CR-39 foils feasible
21 CFR 225.202 - Formula, production, and distribution records.
2010-04-01
...Formula, production, and distribution records. 225.202 Section 225.202 Food and Drugs FOOD AND DRUG ADMINISTRATION...production, and distribution records. ...Approved by the Office of Management and Budget under...
Distributed energy production offers many advantages
International Nuclear Information System (INIS)
In this interview with Daniel Dillier, President of the Board of the IWK company, the aims of the Swiss electricity business to build new nuclear power stations and the Swiss Government's proposals for the building of gas-steam combined cycle power plants are discussed. Dillier, in contrast, favours the construction of distributed combined heat and power (CHP) units. Dillier voices his opinions on this subject and stresses the advantages of distributed systems that combine the production of heat and electrical power. These systems can use renewable resources and provide a higher degree of system reliability and availability. A further topic discussed is that of carbon dioxide emissions, which Dillier notes as being 40 percent less than for conventional systems. The potential for the use of decentralised CHP units in Switzerland is examined
The Size Distribution of Desert Dust and Its Impact on the Earth System
Mahowald, N. M.; Albani, S.; Kok, J. F.; Engelstaedter, S.; Scanza, R.; Ward, D. S.; Flanner, M.
2014-12-01
The global cycle of desert dust aerosols responds strongly to climate and human perturbations, and, in turn, impacts climate and biogeochemistry. Here we focus on desert dust size distributions, how these are characterized, emitted from the surface, evolve in the atmosphere, and impact climate and biogeochemistry. Observations, theory and global model results are synthesized to highlight the evolution and impact of dust sizes. Individual particles sizes are, to a large extent, set by the soil properties and the mobilization process. The lifetime of different particle sizes controls the evolution of the size distribution as the particles move downwind, as larger particles fall out more quickly. The dust size distribution strongly controls the radiative impact of the aerosols, as well as their interactions with clouds. The size of particles controls how far downwind they travel, and thus their ability to impact biogeochemistry downwind of the source region.
Finite Size Effect of Nanoparticles to the Atomic Pair Distribution Functions
Kodama, K; Shamoto, S
2005-01-01
The finite size effects of the nanoparticles to the atomic pair distribution functions (PDF) are discussed by calculating the radial distribution functions (RDF) on nanoparticles with various shapes, such as sheet, belt, rod, tube and sphere, assuming continua. Their characteristics are shown depending on the shapes and the sizes of the nanoparticles. Alternately, these PDFs can be used to measure the shapes and the sizes of ordered lattice part inside of any materials such as nanoparticles and bulks.
Birnstiel, T; Dullemond, C P
2010-01-01
Context. Grains in circumstellar disks are believed to grow by mutual collisions and subsequent sticking due to surface forces. Results of many fields of research involving circumstellar disks, such as radiative transfer calculations, disk chemistry, magneto-hydrodynamic simulations largely depend on the unknown grain size distribution. Aims. As detailed calculations of grain growth and fragmentation are both numerically challenging and computationally expensive, we aim to find simple recipes and analytical solutions for the grain size distribution in circumstellar disks for a scenario in which grain growth is limited by fragmentation and radial drift can be neglected. Methods. We generalize previous analytical work on self-similar steady-state grain distributions. Numerical simulations are carried out to identify under which conditions the grain size distributions can be understood in terms of a combination of power-law distributions. A physically motivated fitting formula for grain size distributions is der...
Distribution of quantum states in enclosures of finite size I
International Nuclear Information System (INIS)
The expression for the density of states of a particle in a three-dimensional rectangular box of finite size can be obtained directly by Poissons's Summation formula. The expression for the case of an enclosure in the form of an infinite rectangular slab is derived. (A.C.A.S.)
Plutonium aerosols size distribution in a reprocessing plant
International Nuclear Information System (INIS)
Concern regarding the potential release of radioactive particles in the atmosphere is actually increasing. Because of this interest, a field sampling programm is in progress in the reprocessing plant of LA HAGUE to estimate the atmospheric radioactive contamination by plutonium aerosols. This paper concerns the measurement of size characteristics of plutonium aerosols generated by typical operations of the reprocessing. (orig.)
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.
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.
Western, L.; Watson, M.; Francis, P. N.
2014-12-01
Volcanic ash particle size distributions are critical in determining the fate of airborne ash in drifting clouds. A significant amount of global airspace is managed using dispersion models that rely on a single ash particle size distribution, derived from a single source - Hobbs et al., 1991. This is clearly wholly inadequate given the range of magmatic compositions and eruptive styles that volcanoes present. Available measurements of airborne ash lognormal particle size distributions show geometric standard deviation values that range from 1.0 - 2.5, with others showing mainly polymodal distributions. This paucity of data pertaining to airborne sampling of volcanic ash results in large uncertainties both when using an assumed distribution to retrieve mass loadings from satellite observations and when prescribing particle size distributions of ash in dispersion models. Uncertainty in the particle size distribution can yield order of magnitude differences to mass loading retrievals of an ash cloud from satellite observations, a result that can easily reclassify zones of airspace closure. The uncertainty arises from the assumptions made when defining both the geometric particle size and particle single scattering properties in terms of an effective radius. This has significant implications for airspace management and emphasises the need for an improved quantification of airborne volcanic ash particle size distributions.
CHARACTERIZATION OF BIVARIATE SIZE-ORIENTATION DISTRIBUTION OF CIRCULAR PLATE PARTICLES
Karel Bodlák; Arun Balasundarun M Gokhale; Viktor Beneš
2011-01-01
The paper is devoted to the stereological unfolding problem of bivariate size-orientation distribution of platelike particles in metallography. Gokhale (1996) derived an integral equation which relates this bivariate distribution in three-dimensional (3D) space to the corresponding size-orientation distribution of planar sections of the specimen. The present paper yields a numerical algorithm which enables to transform a bivariate histogram of observed quantities to the histogram of 3D charac...
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 ...
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
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
Lehtipalo, Katrianne; Kontkanen, Jenni; Kangasluoma, Juha; Franchin, Alessandro; Wimmer, Daniela; Schobesberger, Siegfried; Junninen, Heikki; Petäjä, Tuukka; Sipilä, Mikko; Mikkilä, Jyri; Vanhanen, Joonas; Worsnop, Douglas R; Kulmala, Markku
2014-01-01
The most important parameters describing the atmospheric new particle formation process are the particle formation and growth rates. These together determine the amount of cloud condensation nuclei attributed to secondary particle formation. Due to difficulties in detecting small neutral particles, it has previously not been possible to derive these directly from measurements in the size range below about 3 nm. The Airmodus Particle Size Magnifier has been used at the SMEAR II station in Hyytiälä, southern Finland, and during nucleation experiments in the CLOUD chamber at CERN for measuring particles as small as about 1 nm in mobility diameter. We developed several methods to determine the particle size distribution and growth rates in the size range of 1–3 nm from these data sets. Here we introduce the appearance-time method for calculating initial growth rates. The validity of the method was tested by simulations with the Ion-UHMA aerosol dynamic model.
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...
Apollo 14 soils - Size distribution and particle types.
Mckay, D. S.; Heiken, G. H.; Taylor, R. M.; Clanton, U. S.; Morrison, D. A.; Ladle, G. H.
1972-01-01
Particle size characteristics are discussed together with particle types, abundances, variation in the soils, questions of soil maturity, coarse fines, and ropy glasses. It is found that agglutinates are formed primarily by micrometeorite impact into lunar soil. Agglutinates appear to be the major particle type now being formed on the lunar surface. Agglutinate content of a soil increases with particle track densities and with surface exposure time.
Milk lipid globules: control of their size distribution.
Valivullah, H. M.; Bevan, D. R.; Peat, A.; Keenan, T. W.
1988-01-01
Micro lipid droplets fuse with each other in vivo to form larger precursors of milk lipid globules. The extent of fusion dictates the size range of lipid globules in milk. A cell-free system in which micro lipid droplet fusion can be induced has been developed. Fusion was promoted by calcium and a protein complex from cytosol. Exogenously supplied gangliosides were potent fusion-promoting agents. Endogenous gangliosides were detected on micro lipid droplet surfaces by immunocytochemical local...
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.
Scientific Electronic Library Online (English)
F.H. de, Witt; N.P., Kuleile; H.J., van der Merwe; M.D., Fair.
Full Text Available 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.
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.
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.
Wang, Menghua; Gordon, Howard R.
1995-10-01
We report the results of simulations in which an algorithm developed for estimation of aerosol optical properties from the angular distribution of radiance exiting the top of the atmosphere over the oceans [Appl. Opt. 33, 4042 (1994)] is combined with a technique for carrying out radiative transfer computations by synthesis of the radiance produced by individual components of the aerosol-size distribution [Appl. Opt. 33, 7088 (1994)], to estimate the aerosol-size distribution by retrieval of the total aerosol optical thickness and the mixing ratios for a set of candidate component aerosol-size distributions. The simulations suggest that in situations in which the true size-refractive-index distribution can actually be synthesized from a combination of the candidate components, excellent retrievals of the aerosol optical thickness and the component mixing ratios are possible. An exception is the presence of strongly absorbing aerosols. The angular distribution of radiance in a single spectral band does not appear to contain sufficient information to separate weakly from strongly absorbing aerosols. However, when two spectral bands are used in the algorithm, retrievals in the case of strongly absorbing aerosols are improved. When pseudodata were simulated with an aerosol-size distribution that differed in functional form from the candidate components, excellent retrievals were still
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...
International Nuclear Information System (INIS)
The island size distribution, at thermodynamic equilibrium, of interacting particles in a one-dimensional lattice-gas model is revisited. A derivation for the exact island size distribution of nearest neighbor interacting particles using the detailed balance principle is proposed and it is shown that it agrees with the distribution obtained by Gambardella et al who resorted to the minimization of the free energy (2006 Phys. Rev. B 73 245425). We find that the island size distributions change from an exponential shape to one exhibiting a maximum when repulsive interactions with distant neighbors are considered. In this work we present an analytical model that successfully reproduces the island size distribution obtained from Monte Carlo simulations for both interaction schemes and any coverage
Determination of the particle size distribution of aerosols by means of a diffusion battery
International Nuclear Information System (INIS)
The different methods allowing to determine the particle size distribution of aerosols by means of diffusion batteries are described. To that purpose, a new method for the processing of experimental data (percentages of particles trapped by the battery vs flow rate) was developed on the basis of calculation principles which are described and assessed. This method was first tested by numerical simulation from a priori particle size distributions and then verified experimentally using a fine uranine aerosol whose particle size distribution as determined by our method was compared with the distribution previously obtained by electron microscopy. The method can be applied to the determination of particle size distribution spectra of fine aerosols produced by 'radiolysis' of atmospheric gaseous impurities. Two other applications concern the detection threshold of the condensation nuclei counter and the 'critical' radii of 'radiolysis' particles
On the Noncommutative Neutrix Product of Distributions
Directory of Open Access Journals (Sweden)
Biljana Jolevska-Tuneska
2007-11-01
Full Text Available Ã¯Â»Â¿Let f and g be distributions and let gn=(g*ÃŽÂ´n(x, where ÃŽÂ´n(x is a certain sequence converging to the Dirac-delta function ÃŽÂ´(x. The noncommutative neutrix product fÃ¢ÂˆÂ˜g of f and g is defined to be the neutrix limit of the sequence {fgn}, provided the limit h exists in the sense that NÃ¢Â€ÂlimnÃ¢Â†Â’Ã¢ÂˆÂžÃ¢ÂŒÂ©f(xgn(x,ÃÂ†(xÃ¢ÂŒÂª=Ã¢ÂŒÂ©h(x,ÃÂ†(xÃ¢ÂŒÂª, for all test functions in Ã°ÂÂ’ÂŸ. In this paper, using the concept of the neutrix limit due to van der Corput (1960, the noncommutative neutrix products x+rlnx+Ã¢ÂˆÂ˜xÃ¢ÂˆÂ’Ã¢ÂˆÂ’rÃ¢ÂˆÂ’1lnxÃ¢ÂˆÂ’ and xÃ¢ÂˆÂ’Ã¢ÂˆÂ’rÃ¢ÂˆÂ’1lnxÃ¢ÂˆÂ’Ã¢ÂˆÂ˜x+rlnx+ are proved to exist and are evaluated for r=1,2,Ã¢Â€Â¦. It is consequently seen that these two products are in fact equal.
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
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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.
Distribution of quantum states in enclosures of finite size: I
International Nuclear Information System (INIS)
We show that the expression for the density of states of a particle in a three-dimensional rectangular box of finite size can be obtained by using directly the Poisson's summation formula instead of using the Walfisz formula or the generalized Euler formula both of which can be derived from the former. We also derive the expression for the density of states in the case of an enclosure in the form of an infinite rectangular slab and apply it to the problem of the Bose-Einstein condensation of a Bose gas of noninteracting particles confined to a thin-film geometry. (author)
Density, Size and Distribution of Stomata in Different Monocotyledons
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Fatemeh Zarinkamar
2006-01-01
Full Text Available The present study focuses on the stomatal characters of 54 species from 6 families of monocotyledons, the majority of which are grasses. The stomatal density, guard cell lengths on the adaxial and abaxial leaf epidermis and the stomatal type in each family are described and the relationship between stomatal density and guard cell size is reviewed. These plants are collected from one of the Irano-Turany protected area. However, studying of stomata characters, particularly herbaceous plants growing in less contaminated zone such as protected areas, could improve basic knowledge on main characters of monocotyledons.
No new limit on size distribution of ?-ray bursts
International Nuclear Information System (INIS)
Some criticisms are offered on the paper by Carter and others in Nature; 262:370 (1976). These authors derived an upper limit to the intensity of small ?-bursts at approximately 100 below the extrapolated known size spectrum, and concludes that ?-ray bursts are of galactic origin. The present authors give reasons for claiming, however, that Carter's results are entirely consistent with the -1.5 index power law extrapolation, and therefore no conclusions can be drawn regarding the nature or origin of ?-ray bursts from their measurements. A reply by Carter is appended. (U.K.)
ANALYTICAL MODEL FOR MARS CRATER-SIZE FREQUENCY DISTRIBUTION
Bruckman, W.; Ruiz, A.; Ramos, E.
2009-01-01
We present a theoretical and analytical curve that reproduces essential features of the frequency distributions vs. diameter of the 42,000 impact craters contained in Barlow's Mars Catalog. The model is derived using reasonable simple assumptions that allow us to relate the present craters population with the craters population at each particular epoch. The model takes into consideration the reduction of the number of craters as a function of time caused by their erosion and obliteration, and...
Bimodal Nanoparticle Size Distributions Produced by Laser Ablation of Microparticles in Aerosols
International Nuclear Information System (INIS)
Silver nanoparticles were produced by laser ablation of a continuously flowing aerosol of microparticles in nitrogen at varying laser fluences. Transmission electron micrographs were analyzed to determine the effect of laser fluence on the nanoparticle size distribution. These distributions exhibited bimodality with a large number of particles in a mode at small sizes (3-6-nm) and a second, less populated mode at larger sizes (11-16-nm). Both modes shifted to larger sizes with increasing laser fluence, with the small size mode shifting by 35% and the larger size mode by 25% over a fluence range of 0.3-4.2-J/cm2. Size histograms for each mode were found to be well represented by log-normal distributions. The distribution of mass displayed a striking shift from the large to the small size mode with increasing laser fluence. These results are discussed in terms of a model of nanoparticle formation from two distinct laser-solid interactions. Initially, laser vaporization of material from the surface leads to condensation of nanoparticles in the ambient gas. Material evaporation occurs until the plasma breakdown threshold of the microparticles is reached, generating a shock wave that propagates through the remaining material. Rapid condensation of the vapor in the low-pressure region occurs behind the traveling shock wave. Measurement of particle size distributions versus gas pressure in the ablation region, as well as, versus microparticle feedstock size confirversus microparticle feedstock size confirmed the assignment of the larger size mode to surface-vaporization and the smaller size mode to shock-formed nanoparticles
Firm-size distribution and price-cost margins in Dutch manufacturing
Prince, Y. M.; Thurik, A. R.
1993-01-01
Industrial economists surmise a relation between the size distribution of firms and performance. Usually, attention is focused on the high end of the size distribution. The widely used 4-firm seller concentration, C4, ignores what happens at the low end of the size distribution. An investigation is presented of the extent to which the level and the growth of small business presence influence price-cost margins in Dutch manufacturing. A large data set of 66 industries for a 13-year period is u...
Measurement of the size distributions of radon progeny in indoor air
International Nuclear Information System (INIS)
A major problem in evaluating the health risk posed by airborne radon progeny in indoor atmospheres is the lack of available information on the activity-weighted size distributions that occur in the domestic environment. With an automated, semicontinuous, graded screen array system, we made a series of measurements of activity-weighted size distributions in several houses in the northeastern United States. Measurements were made in an unoccupied house, in which human aerosol-generating activities were simulated. The time evolution of the aerosol size distribution was measured in each situation. Results of these measurements are presented
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)
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.
Li Chunfang; Li Dongxiang; Wan Gangqiang; Xu Jie; Hou Wanguo
2011-01-01
Abstract The citrate reduction method for the synthesis of gold nanoparticles (GNPs) has known advantages but usually provides the products with low nanoparticle concentration and limits its application. Herein, we report a facile method to synthesize GNPs from concentrated chloroauric acid (2.5 mM) via adding sodium hydroxide and controlling the temperature. It was found that adding a proper amount of sodium hydroxide can produce uniform concentrated GNPs with low size distribution; otherwis...
Transformation on steel products distribution in Poland and Slovakia
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R. Stefko
2012-01-01
Full Text Available Steel industry is one of the most globalized branch, globalization has had the influence on iron ore supply, steel production and distribution as well. In last years, steel products distribution process has changed significantly, because of rising competitiveness due to common world market influence and main global players actions. The paper presents changes in steel products distribution in Poland and Slovakia focusing on main steel producers activity in distribution as well as distributors response on new market situation.
Transformation on steel products distribution in Poland and Slovakia
R. Stefko; B. Slusarczyk; S. Kot; C. Kolmasiak
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 ...
Kempes, Christopher P; Dooris, William; West, Geoffrey B
2015-01-01
In the face of uncertain biological response to climate change and the many critiques concerning model complexity it is increasingly important to develop predictive mechanistic frameworks that capture the dominant features of ecological communities and their dependencies on environmental factors. This is particularly important for critical global processes such as biomass changes, carbon export, and biogenic climate feedback. Past efforts have successfully understood a broad spectrum of plant and community traits across a range of biological diversity and body size, including tree size distributions and maximum tree height, from mechanical, hydrodynamic, and resource constraints. Recently it was shown that global scaling relationships for net primary productivity are correlated with local meteorology and the overall biomass density within a forest. Along with previous efforts, this highlights the connection between widely observed allometric relationships and predictive ecology. An emerging goal of ecological...
Maaß, S.; Wollny, S.; Voigt, A.; Kraume, M.
2011-02-01
An online measurement technique for drop size distribution in stirred tank reactors is needed but has not yet been developed. Different approaches and different techniques have been published as the new standard during the last decade. Three of them (focus beam reflectance measurement, two-dimensional optical reflectance measurement techniques and a fiber optical FBR sensor) are tested, and their results are compared with trustful image analysis results from an in situ microscope. The measurement of drop sizes in liquid/liquid distribution is a major challenge for all tested measurement probes, and none provides exact results for the tested system of pure toluene/water compared to an endoscope. Not only the size analysis but also the change of the size over time gives unreasonable results. The influence of the power input on the drop size distribution was the only reasonable observation in this study. The FBR sensor was not applicable at all to the used system. While all three probes are based on laser back scattering, the general question of the usability of this principle for measuring evolving drop size distributions in liquid/liquid system is asked. The exterior smooth surface of droplets in such systems is leading to strong errors in the measurement of the size of the drops. That leads to widely divergent results. A different measurement principle should be used for online measurements of drop size distributions than laser back scattering.
Cloud particle size distributions measured with an airborne digital in-line holographic instrument
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R. A. Shaw
2009-06-01
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 image of ice particles and then ice particle size distributions and number densities are calculated using an automated algorithm with minimal user intervention. The holographic method offers the advantages of a well-defined sample volume size that is not dependent on particle size or airspeed, and offers a unique method of detecting shattered particles. The holographic method also allows the volume sample rate to be increased beyond that of the prototype HOLODEC instrument, limited solely by camera technology.
HOLODEC size distributions taken in mixed-phase regions of cloud compare well to size distributions from a PMS FSSP probe also onboard the aircraft during the test flights. A conservative algorithm for detecting shattered particles utilizing their depth-position along the optical axis eliminates the obvious ice particle shattering events from the data set. In this particular case, the size distributions of non-shattered particles are reduced by approximately a factor of two for particles 15 to 70 ?m in equivalent diameter, compared to size distributions of all particles.
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
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.
Turner, Joseph A; Polunin, Nicholas V C; Field, Stuart N; Wilson, Shaun K
2015-05-01
Coral colony size-frequency distribution data offer valuable information about the ecological status of coral reefs. Such data are usually collected by divers in situ, but stereo video is being increasingly used for monitoring benthic marine communities and may be used to collect size information for coral colonies. This study compared the size-frequency distributions of coral colonies obtained by divers measuring colonies 'in situ' with digital video imagery collected using stereo video and later processed using computer software. The size-frequency distributions of the two methods were similar for corymbose colonies, although distributions were different for massive, branching and all colonies combined. The differences are mainly driven by greater abundance of colonies >50 cm and fewer colonies 5 cm and was able to record measurements on 87 % of the colonies detected. However, stereo video only detected 57 % of marked colonies coral recruits. Estimates of colony size made with the stereo video were smaller than the in situ technique for all growth forms, particularly for massive morphologies. Despite differences in size distributions, community assessments, which incorporated genera, growth forms and size, were similar between the two techniques. Stereo video is suitable for monitoring coral community demographics and provided data similar to in situ measure for corymbose corals, but the ability to accurately measure massive and branching coral morphologies appeared to decline with increasing colony size. PMID:25850990
A case study of rain drop size distribution over a tropical indian station
Kunhikrishnan, P. K.; Sivaraman, R.; Alappattu, D. P.
Models for drop size distribution is required for the evaluation of microwave and millimetre wave propagation effects due to rainfall There is a dearth of raindrop size data and models for the tropics especially over Indian continent Under Ka band propagation experiment over Indian tropical region disdrometers microwave rain radars and tipping bucket rain gauge are installed at Ahmedabad Thumba and Shillong This paper describes the raindrop size distribution observed at Thumba a tropical Indian coastal station during southwest monsoon period The disdrometer is operational from June 2005 onwards Microwave rain radar MRR and tipping bucket rain gauge are installed on Sept 2005 Disdrometer data collected during July to September are analysed to study the rain drop spectra During July to October 2005 525 mm rainfall was received over Thumba During this period rain intensity varied from 0 1 mm hr to 130 mm hr Disdrometer measured rain is compared with rain gauge measurements and showed good agreement The disdrometer data collected during the period was analysed to understand the drop size distribution for different rain rates The analysis shows that the drop size follows a lognormal distribution for rain rate varying from 20 to 50 mm hr fairly well For rain rates more than 80 mm hr the drop size spectra doesn t follow well the lognormal distribution This is also the case with drop size distribution for rain rate less than 10 mm hr Details will be presented in the paper
Nano size Aerosols of Radon Decay Products in Various Environments
International Nuclear Information System (INIS)
The radioactive noble gas radon (222Rn, alpha decay, t1/2 = 3.82 days) is always accompanied by its short-lived decay products (RnDP): 218Po (alpha decay, t1/2 = 3.10 min), 214Pb (beta/gamma decay, t1/2 = 26.8 min), 214Bi (beta/gamma decay, t1/2 = 19.9 min), and 214Po (alpha decay, t1/2 = 164 ?s). In indoor and outdoor air, they appear as unattached RnDP in the form of clusters in the size range 0.5-3 nm and as attached RnDP between 200 and 800 nm. Because of plate-out of aerosols on the walls and floor of a room, as well as air movement and entry of fresh air, radioactive equilibrium between RnDP and Rn in indoor air is only partly achieved and is expressed as a fraction between 0 and 1, called the equilibrium factor, F. Birchall and James elaborated a dosimetric approach to calculate the dose conversion factor, DCFD, based on fun. In this paper, the results of our studies on fun in 29 rooms of kindergartens and 26 rooms of elementary and high schools, at the lowest point and the railway station in the Postojna Cave, and in 4 rooms in wineries in Slovenia are reported, and DCFD values based on the Porstendorfer formulae are discussed and compared with the DCFE value recommended by ICRP-65
A Low Sample Size Estimator for K Distributed Noise
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Eduardo X. Alban
2012-08-01
Full Text Available In this paper, we derive a new method for estimating the parameters of the K-distribution when a limited number of samples are available. The method is based on an approximation of the Bessel function of the second kind that reduces the complexity of the estimation formulas in comparison to those used by the maximum likelihood algorithm. The proposed method has better performance in comparison with existing methods of the same complexity giving a lower mean squared error when the number of samples used for the estimation is relatively low.
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.
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.
Occlusion effects and the distribution of interstellar cloud sizes and masses
Scalo, J M
1995-01-01
The frequency distributions of sizes of ``clouds" and ``clumps" within clouds are significantly flatter for extinction surveys than for CO spectral line surveys, even for comparable size ranges. A possible explanation is the blocking of extinction clouds by larger foreground clouds (occlusion), which should not affect spectral line surveys much because clouds are resolved in velocity space along a given line of sight. We present a simple derivation of the relation between the true and occluded size distributions, assuming clouds are uniformly distributed in space or the distance to a cloud comples is much greater than the size of the complex. Because the occlusion is dominated by the largest clouds, we find that occlusion does not affect the measured size distribution except for sizes comparable to the largest size, implying that occlusion is not responsible for the discrepancy if the range in sizes of the samples is large. However, we find that the range in sizes for many of the published observed samples is...
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.
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.
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.
Directory of Open Access Journals (Sweden)
Y. Cai
2013-09-01
Full Text Available This work describes calibration methods for the particle sizing and particle concentration systems of the passive cavity aerosol spectrometer probe (PCASP. Laboratory calibrations conducted over six years, in support of the deployment of a PCASP on a cloud physics research aircraft, are analyzed. Instead of using the many calibration sizes recommended by the PCASP manufacturer, a relationship between particle diameter and scattered light intensity is established using three sizes of mobility-selected polystyrene latex particles, one for each amplifier gain stage. In addition, studies of two factors influencing the PCASP's determination of the particle size distribution – amplifier baseline and particle shape – are conducted. It is shown that the PCASP-derived size distribution is sensitive to adjustments of the sizing system's baseline voltage, and that for aggregates of spheres, a PCASP-derived particle size and a sphere-equivalent particle size agree within uncertainty dictated by the PCASP's sizing resolution. Robust determinations of aerosol concentration, and size distribution, also require calibration of the PCASP's aerosol flowrate sensor. Sensor calibrations, calibration drift, and the sensor's non-linear response are documented.
Comparison of the size distributions of source emission and atmospheric aerosols
Energy Technology Data Exchange (ETDEWEB)
Pilat, M.J. [Univ. of Washington, Seattle, WA (United States); Noll, K.E. [Illinois Institute of Technology, Chicago, IL (United States)
1996-12-31
The atmospheric aerosol size distribution has been shown to be multimodel with peaks in the mass distribution at approximately 0.8 {mu}m and at about the 20 {mu}m aerodynamic diameter. Also the atmospheric aerosol size distribution has been shown to often have a lower mass concentration between the peaks at 0.8 and 20 {mu}m with the bottom of the {open_quotes}valley{close_quotes} at about 2.5 {mu}m diameter. Many emission source aerosols have size distributions which are also multimodel with regards to the particle mass. Particles emitted from pulp mill kraft recovery boilers have mass distribution peaks at about 0.8 and 15 {mu}m aerodynamic diameter. Pulverized coal-fired boilers have aerosol particle emissions with mass distribution peaks at about 0.05, 0.8, and 4 {mu}m aerodynamic diameter. The aerosol particles emitted from chrome plating process operations are generated by gas bubbles bursting at the surface of the chromic acid plating solution and have multimodel mass size distribution peaks at about 0.6 and 20 {mu}m aerodynamic diameter. This paper will present a comparison of the atmospheric and source emission particle size distributions using data measured by the Illinois Institute of Technology and the University of Washington and data from the literature.
Strack, Géraldine; Fortz, Bernard; Riane, Fouad; Van Vyve, Mathieu
2011-01-01
In this paper, we present a mathematical model which integrates tactical-operational production and distribution decisions in a shared resources environment. More precisely, we integrate lot sizing production and distribution decisions with vehicle routing decisions. We obtain a global multi-period multi-item multi-vehicle model where a capacity constraint models the link between production and distribution decisions. Three heuristics are presented in order to solve this global model. The fir...
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...
Estimation of particle size distribution from small-angle scattering profile
International Nuclear Information System (INIS)
Estimation of particle/pore size distribution (PSD) constitutes an important step of analysis in small-angle scattering (SAS) as systems in material science are more commonly polydisperse in nature as far as the inhomogeneities in them are concerned
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...
Kennedy, Grant M; Su, Kate Y L; Stansberry, John A
2011-01-01
We describe a search for dust created in collisions between the Saturnian irregular satellites using archival \\emph{Spitzer} MIPS observations. Although we detected a degree scale Saturn-centric excess that might be attributed to an irregular satellite dust cloud, we attribute it to the far-field wings of the PSF due to nearby Saturn. The Spitzer PSF is poorly characterised at such radial distances, and we expect PSF characterisation to be the main issue for future observations that aim to detect such dust. The observations place an upper limit on the level of dust in the outer reaches of the Saturnian system, and constrain how the size distribution extrapolates from the smallest known (few km) size irregulars down to micron-size dust. Because the size distribution is indicative of the strength properties of irregulars, we show how our derived upper limit implies irregular satellite strengths more akin to comets than asteroids. This conclusion is consistent with their presumed capture from the outer regions o...
Estimating Functions of Distributions Defined over Spaces of Unknown Size
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David H. Wolpert
2013-10-01
Full Text Available We consider Bayesian estimation of information-theoretic quantities from data, using a Dirichlet prior. Acknowledging the uncertainty of the event space size m and the Dirichlet prior’s concentration parameter c, we treat both as random variables set by a hyperprior. We show that the associated hyperprior, P(c, m, obeys a simple “Irrelevance of Unseen Variables” (IUV desideratum iff P(c, m = P(cP(m. Thus, requiring IUV greatly reduces the number of degrees of freedom of the hyperprior. Some information-theoretic quantities can be expressed multiple ways, in terms of different event spaces, e.g., mutual information. With all hyperpriors (implicitly used in earlier work, different choices of this event space lead to different posterior expected values of these information-theoretic quantities. We show that there is no such dependence on the choice of event space for a hyperprior that obeys IUV. We also derive a result that allows us to exploit IUV to greatly simplify calculations, like the posterior expected mutual information or posterior expected multi-information. We also use computer experiments to favorably compare an IUV-based estimator of entropy to three alternative methods in common use. We end by discussing how seemingly innocuous changes to the formalization of an estimation problem can substantially affect the resultant estimates of posterior expectations.
Dust Grain-Size Distributions From MRN to MEM
Clayton, G C; Sofia, U J; Gordon, K D; Misselt, K A; Clayton, Geoffrey C.; Wolff, Michael J.; Sofia, Ulysses J.
2003-01-01
Employing the Maximum Entropy Method algorithm, we fit interstellar extinction measurements which span the wavelength range 0.125-3 micron. We present a uniform set of MEM model fits, all using the same grain materials, optical constants and abundance constraints. In addition, we are taking advantage of improved UV and IR data and better estimates of the gas-to-dust ratio. The model fits cover the entire range of extinction properties that have been seen in the Galaxy and the Magellanic Clouds. The grain models employed for this presentation are the simplistic homogeneous spheres models (i.e., Mathis, Rumpl, & Nordsieck 1977) with two (graphite, silicate) or three (graphite, silicate, amorphous carbon) components. Though such usage is only a first step, the results do provide interesting insight into the use of grain size as a diagnostic of dust environment. We find that the SMC Bar extinction curve cannot be fit using carbon grains alone. This is a challenge to the recent observational result indicating ...
First-principles derivation of static avalanche-size distributions
Le Doussal, Pierre; Wiese, Kay Jörg
2012-06-01
We study the energy minimization problem for an elastic interface in a random potential plus a quadratic well. As the position of the well is varied, the ground state undergoes jumps, called shocks or static avalanches. We introduce an efficient and systematic method to compute the statistics of avalanche sizes and manifold displacements. The tree-level calculation, i.e., mean-field limit, is obtained by solving a saddle-point equation. Graphically, it can be interpreted as the sum of all tree graphs. The 1-loop corrections are computed using results from the functional renormalization group. At the upper critical dimension the shock statistics is described by the Brownian force model (BFM), the static version of the so-called Alessandro-Beatrice-Bertotti-Montorsi (ABBM) model in the nonequilibrium context of depinning. This model can itself be treated exactly in any dimension and its shock statistics is that of a Lévy process. Contact is made with classical results in probability theory on the Burgers equation with Brownian initial conditions. In particular we obtain a functional extension of an evolution equation introduced by Carraro and Duchon, which recursively constructs the tree diagrams in the field theory.
Clusters of craters on the Saturnian satellite Dione: morphology and size distribution
Wagner, R. J.; Neukum, G.; Schmedemann, N.; Roatsch, T.; Denk, T.; Porco, C. C.
2012-09-01
Crater clusters, mainly double craters as well as chains, occur on the terrestrial planets and on the Galilean satellites of Jupiter and were formed by simultaneous impacts of two or more impactors [1][2][3]. Cassini ISS images show that such features also can be found on the mid-sized satellites of Saturn [4][5]. In this paper we focus on the spatial distribution, morphology and size distribution of double and multiple craters on Dione.
Bed load size distribution and flow conditions in a high mountain catchment of Central Pyrenees
Martínez-Castroviejo, Ricardo
1990-01-01
The bed load size distribution caused by different types of flow are compared in a high mountain catchment located in the upper Gallego river basin (Central Spanish’ Pyrenees). Three kinds of hydrologic events could be defined: those triggered by heavy autumn rainfalls, those originated by isolated summer rainstorms and those promoted by snowmelting. Each one is characterized by a peculiar bed load size distribution. Thus, it could be demonstrated that the coarser fractions, above 30 mm in di...
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
Experimental study on bubble size distributions in a direct-contact evaporator
Ribeiro Jr, C. P.; Lage, P. L. C.
2004-01-01
Experimental bubble size distributions and bubble mean diameters were obtained by means of a photographic technique for a direct-contact evaporator operating in the quasi-steady-state regime. Four gas superficial velocities and three different spargers were analysed for the air-water system. In order to assure the statistical significance of the determined size distributions, a minimum number of 450 bubbles was analysed for each experimental condition. Some runs were also conducted with an aq...
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...
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.
Mohammed Abdullahi MU'AZU
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...
Numerical Model to Predict Wax Crystal Size Distribution in Solvent Dewaxing Unit
Nassir D. Mokhlif; Hussain H. Al-kayiem; 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...
Mass Size Distribution of Water Soluble Ions in Prague and Wiena in Summer
Schwarz, Jaroslav
2012-01-01
Aerosol mass size distribution is a key factor that influences aerosol behavior both on local (health effects, visibility) and global (global warming) level. The content of water soluble ions is the most important factor controlling hygroscopic behavior of aerosol particles. Hygroscopicity is a substantial parameter for particle deposition in lungs, particle – cloud interactions, aerosol optical effects etc. Therefore we studied size distribution of water soluble ions in two Central Europea...
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
Impact of Typhoon Morakot on suspended matter size distributions on the East China Sea inner shelf
Li, Yunhai; Li, Dongyi; Fang, Jianyong; Yin, Xijie; Li, Haidong; Hu, Wenye; Chen, Jian
2015-06-01
Two surveys were conducted on the East China Sea inner shelf before and after the passage of Typhoon Morakot in 2009. The typhoon-induced variations in the size distributions of suspended matters were studied based on the data collected by a Laser In Situ Scattering Transmissometer (LISST). A comparison of the measurements from the two surveys revealed significant changes in seafloor sediment grain size, suspended matter volume concentration and size distribution due to Typhoon Morakot. The mean seafloor sediment grain size increased generally, while the sorting coefficient decreased after the typhoon. Before the typhoon, suspended matter size was generally >100 ?m, which was significantly reduced to between 20-50 ?m after the typhoon. The single-grain fraction with sizes 133 ?m) were largely reduced from >40% before the typhoon to 133 ?m) concentration by strong disturbance of water column and the temporary demise of plankton under heavy cloudy condition.
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
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
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
Effects of grain size distribution on the interstellar dust mass growth
Hirashita, Hiroyuki
2011-01-01
Grain growth by the accretion of metals in interstellar clouds (called `grain growth') could be one of the dominant processes that determine the dust content in galaxies. The importance of grain size distribution for the grain growth is demonstrated in this paper. First, we derive an analytical formula that gives the grain size distribution after the grain growth in individual clouds for any initial grain size distribution. The time-scale of the grain growth is very sensitive to grain size distribution, since the grain growth is mainly regulated by the surface to volume ratio of grains. Next, we implement the results of grain growth into dust enrichment models of entire galactic system along with the grain formation and destruction in the interstellar medium, finding that the grain growth in clouds governs the dust content in nearby galaxies unless the grain size is strongly biased to sizes larger than $\\sim 0.1 \\micron$ or the power index of the grain size distribution is shallower than $\\sim -2.5$. The grai...
Size distribution of BaF2 nanocrystallites in transparent glass ceramics
International Nuclear Information System (INIS)
In glasses with the composition 1.9 Na2O-15 K2O-7.5 Al2O3-69.6 SiO2-6 BaF2 (in mol.%), BaF2 nanocrystalline precipitates are formed upon heat treatment. Using dark-field and bright-field transmission electron micrographs, crystallite size distributions are obtained for samples crystallized at various temperatures. According to the 'tomato-salad problem', the size distributions are corrected and then compared to various theories of grain growth taking into account coarsening of the crystallites during heat treatment. The experimental crystallite size distributions show for smaller mean crystallite sizes a more symmetric shape in comparison to the theories of Lifshitz-Slyozov-Wagner (LSW) or Brailsford and Wynblatt (B and W). With increasing mean crystallite sizes to about 18 nm at higher heat-treatment temperatures, the full width at half maximum of the observed distributions decreases and becomes even narrower than the LSW function. These findings indicate that in the investigated nano glass ceramics no coarsening by Ostwald ripening or coalescence occurs. This is explained by the formation of a diffusion barrier around each nanocrystallite which limits the size of the crystallites and hence results in such a narrow and uniform crystallite size distribution.
Placement and Sizing of DG Using PSO&HBMO Algorithms in Radial Distribution Networks
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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.
The Size Distribution of Chinese Manufacturing Firms: From the Perspective of Industry Life Cycle
Chen, Yanying; Wang, Li; Tian, Gaofeng
2012-01-01
Using panel data of Chinese manufacturing firms between 2003 and 2008, this paper aims to examine the evolution of firm size distribution (FSD) as the industry goes through its life-cycle. The results reveal that during the life-cycle process, China’s manufacturing firms’ average size becomes larger then shrinks, and the degree of firm size heterogeneity and industry concentration increases all the time. Empirical results also indicate that the change rate of FSD is affected by firms’ n...
Korgel, B. A.; Zanten, J. H.; Monbouquette, H. G.
1998-01-01
The separation method, flow field-flow fractionation (flow FFF), is coupled on-line with multiangle laser light scattering (MALLS) for simultaneous measurement of the size and concentration of vesicles eluting continuously from the fractionator. These size and concentration data, gathered as a function of elution time, may be used to construct both number- and mass-weighted vesicle size distributions. Unlike most competing, noninvasive methods, this flow FFF/MALLS technique enables measuremen...
A model for the size distribution of customer groups and businesses
Zheng, Dafang; Rodgers, G. J.; Hui, P. M.
2001-01-01
We present a generalization of the dynamical model of information transmission and herd behavior proposed by Eguiluz and Zimmermann. A characteristic size of group of agents $s_{0}$ is introduced. The fragmentation and coagulation rates of groups of agents are assumed to depend on the size of the group. We present results of numerical simulations and mean field analysis. It is found that the size distribution of groups of agents $n_{s}$ exhibits two distinct scaling behavior...
Empirical evidence for multi-scaled controls on wildfire size distributions in California
Povak, N.; Hessburg, P. F., Sr.; Salter, R. B.
2014-12-01
Ecological theory asserts that regional wildfire size distributions are examples of self-organized critical (SOC) systems. Controls on SOC event-size distributions by virtue are purely endogenous to the system and include the (1) frequency and pattern of ignitions, (2) distribution and size of prior fires, and (3) lagged successional patterns after fires. However, recent work has shown that the largest wildfires often result from extreme climatic events, and that patterns of vegetation and topography may help constrain local fire spread, calling into question the SOC model's simplicity. Using an atlas of >12,000 California wildfires (1950-2012) and maximum likelihood estimation (MLE), we fit four different power-law models and broken-stick regressions to fire-size distributions across 16 Bailey's ecoregions. Comparisons among empirical fire size distributions across ecoregions indicated that most ecoregion's fire-size distributions were significantly different, suggesting that broad-scale top-down controls differed among ecoregions. One-parameter power-law models consistently fit a middle range of fire sizes (~100 to 10000 ha) across most ecoregions, but did not fit to larger and smaller fire sizes. We fit the same four power-law models to patch size distributions of aspect, slope, and curvature topographies and found that the power-law models fit to a similar middle range of topography patch sizes. These results suggested that empirical evidence may exist for topographic controls on fire sizes. To test this, we used neutral landscape modeling techniques to determine if observed fire edges corresponded with aspect breaks more often than expected by random. We found significant differences between the empirical and neutral models for some ecoregions, particularly within the middle range of fire sizes. Our results, combined with other recent work, suggest that controls on ecoregional fire size distributions are multi-scaled and likely are not purely SOC. California wildfire ecosystems appear to be adaptive, governed by stationary and non-stationary controls, which may be either exogenous or endogenous to the system.
Han, Hee-Siew; Chen, Da-Ren; Pui, David Y. H.; Anderson, Bruce E.
2001-01-01
We have developed a fast-response Nanometer Aerosol Size Analyzer (nASA) that is capable of scanning 30 size channels between 3 and 100 nm in a total time of 3 seconds. The analyzer includes a bipolar charger (P0210), 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 second 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 T38 aircraft, the broad dynamic concentration range of the nASA makes it particularly suitable for studies of combustion or particle formation processes. Further details of the nASA performance as well as results from calibrations, laboratory tests and field applications are presented.
ON THE COAGULATION AND SIZE DISTRIBUTION OF PRESSURE CONFINED CORES
International Nuclear Information System (INIS)
Observations of the Pipe Nebula have led to the discovery of dense starless cores. The mass of most cores is too small for their self-gravity to hold them together. Instead, they are thought to be pressure confined. The observed dense cores' mass function (CMF) matches well with the initial mass function of stars in young clusters. Similar CMFs are observed in other star forming regions such as the Aquila Nebula, albeit with some dispersion. The shape of these CMF provides important clues to the competing physical processes which lead to star formation and its feedback on the interstellar media. In this paper, we investigate the dynamical origin of the mass function of starless cores which are confined by a warm, less dense medium. In order to follow the evolution of the CMF, we construct a numerical method to consider the coagulation between the cold cores and their ablation due to Kelvin-Helmholtz instability induced by their relative motion through the warm medium. We are able to reproduce the observed CMF among the starless cores in the Pipe Nebula. Our results indicate that in environment similar to the Pipe Nebula: (1) before the onset of their gravitational collapse, the mass distribution of the progenitor cores is similar to that of the young stars, (2) the observed CMF is a robust consequence of dynamical equilibrium between the coagulation and ablation of cores, and (3) a break in the slope of the CMF is due to the enhancement of collisional cross section annhancement of collisional cross section and suppression of ablation for cores with masses larger than the cores' Bonnor-Ebert mass.
The Size Distribution of the Neptune Trojans and the Missing Intermediate Sized Planetesimals
Sheppard, Scott S
2010-01-01
We present an ultra-deep survey for Neptune Trojans using the Subaru 8.2-m and Magellan 6.5-m telescopes. The survey reached a 50% detection efficiency in the R-band at 25.7 magnitudes and covered 49 square degrees of sky. This depth corresponds to Neptune Trojans that are about 16 km in radius (assuming an albedo of 0.05). A paucity of smaller Neptune Trojans (radii < 45 km) compared to larger ones was found. The brightest Neptune Trojans appear to follow a steep power-law slope (q = 5+-1) similar to the brightest objects in the other known stable reservoirs such as the Kuiper Belt, Jupiter Trojans and main belt asteroids. We find a roll-over for the Neptune Trojans that occurs around a radii of r=45+-10 km (23.5+-0.3 mags), which is also very similar to the other stable reservoirs. All the observed stable regions in the the solar system show evidence for Missing Intermediate Sized Planetesimals (MISPs). This indicates a primordial and not collisional origin, which suggests planetesimal formation proceede...
Oh, Dong Hoon; Balakrishnan, Prabagar; Oh, Yu-Kyoung; Kim, Dae-Duk; Yong, Chul Soon; Choi, Han-Gon
2011-02-14
A Shirasu-porous-glass (SPG) membrane with a mean pore size of 2.5 ?m was used to produce an oil/water (O/W) nanoemulsion of flurbiprofen consisting of methylene chloride as the dispersed phase, polyvinyl alcohol (PVA) as the stabilizer and a mixture of Tween 20 and Tween 80 in demineralized water as the continuous phase. Emulsion droplets with a mean droplet size of 25 times smaller than the mean pore size and a narrow droplet size distribution were produced using 5% emulsifier at a feed pressure of 15 kPa. Under these conditions the z-average diameter and size distribution of the emulsion droplets formed were influenced by the type of surfactant, agitator speed (150-1200 rpm), feed pressure (15-80 kPa), stabilizer concentration (0-4, w/v) and the temperature of the continuous phase. Increasing the agitator speed and stabilizer concentration increased the z-average diameter and decreased the size uniformity. There was a linear relationship between the increased feed pressure and the decreased z-average diameter of the emulsion droplets. However, the uniformity of the size distribution decreased with increasing feed pressure. The continuous phase temperature played an important role in particle size and distribution. The nanoemulsion composed of oil, water, PVA and the surfactant mixture at the weight ratio of 10/100/1/5 was prepared using a SPG membrane at an agitator speed of 300 rpm, a feed pressure of 15 kPa and a continuous phase temperature of 25 °C. Our results indicated that these conditions led to relatively uniform emulsion droplets with a narrow size distribution and high zeta potential. This emulsion was stable for at least 13 h. Furthermore, the droplets in the emulsion containing the drug were not smaller but were more uniform with a narrower distribution compared to those without the drug. PMID:21055456
Size distributions, sources and source areas of water-soluble organic carbon in urban background air
Directory of Open Access Journals (Sweden)
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.
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.
The System Size Distribution for M/G/1 Queueing System under N-Policy with Startup/Closedown
Mingwu Liu; Yongkai Ma; Bin Deng
2010-01-01
This paper develops a new method for calculating the system size distribution on two different M/G/1 queueing system under N-policy with general startup/closedown. Firstly, the stochastic decomposition property is used to derive the p.g.f. of the system size distribution. By the Leibniz formula of derivation, we investigate the additional system size distribution, and then, we get the recursion expression of system sizes distribution. Finally, several examples are given for illustrating the a...
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.
Akbalik, Ayse; Rapine, Christophe
2012-01-01
This paper presents two polynomial time algorithms for the constant capacitated lot sizing problem with a batch production. We give several optimality properties for the general problem. Assuming constant production capacity, constant batch size and Wagner-Whitin cost structure, we derive O(T^4) and O(T^6) time algorithms respectively for the case with production capacity multiple of the batch size and for the case with arbitrary fixed capacities.% the general case.
Energy Technology Data Exchange (ETDEWEB)
Kennedy, M.F.; Erdman, C.A.; Reynolds, A.B.; Waltar, A.E.
1977-11-01
The process of forming aerosols by homogeneous nucleation condensation followed by condensation growth was studied as a potential source of submicrometre aerosols in LMFBR accidents. A model was developed for calculating particle size distributions following nucleation and growth. This model was applied to experiments at ORNL where UO/sub 2/ fuel pellets were partially vaporized in an argon atmosphere and the resulting primary particle size distribution was measured. The low range of particle sizes observed in the ORNL tests could be reproduced by the model by assuming large mixing rates between the fuel vapor and the argon, thus indicating that homogeneous nucleation condensation was likely the source of the small particles observed.
International Nuclear Information System (INIS)
The process of forming aerosols by homogeneous nucleation condensation followed by condensation growth was studied as a potential source of submicrometre aerosols in LMFBR accidents. A model was developed for calculating particle size distributions following nucleation and growth. This model was applied to experiments at ORNL where UO2 fuel pellets were partially vaporized in an argon atmosphere and the resulting primary particle size distribution was measured. The low range of particle sizes observed in the ORNL tests could be reproduced by the model by assuming large mixing rates between the fuel vapor and the argon, thus indicating that homogeneous nucleation condensation was likely the source of the small particles observed
Directory of Open Access Journals (Sweden)
Zi Ye
2012-10-01
Full Text Available 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 model based on Markov chain algorithm is proposed. Results of numerical simulation are added acceptable noise indicate that the algorithm of Markov chain has strong noise immunity and can meet the requirements of on-line measurement.
DEFF Research Database (Denmark)
Berggren, U.; Hansen, B.
1988-01-01
Clearance rates on different sizes of spherically shaped algae were determined in uni-algal experiments for all developmental stages (NII through adult) of the copepodAcartia tonsa, and used to construct food size spectra. Growth and developmental rates were determined at 7 food levels (0 to 1 500 g C l-1 ofRhodomonas baltica). The lower size limit for particle capture was between 2 and 4 m for all developmental stages. Optimum particle size and upper size limit increased during development from 7 m and 10 to 14 m for NII to NIII to 14 to 70 m and 250 m for adults, respectively. When food size spectra were normalized (percent of maximum clearance in a particular stage versus particle diameter/prosome length) they resembled log-normal distributions with near constant width (variance). Optimum, relative particle sizes corresponded to 2 to 5% of prosome length independent of developmental stage. Since the biomass of particulate matter is approximately constant in equal logarithmic size classes in the sea, food availability may be similar for all developmental stages in the average marine environment. Juvenile specific growth rate was exponential and increased hyperbolically with food concentration. It equaled specific female egg-production rate at all food concentrations. The efficiency by which ingested carbon in excess of maintenance requirements was converted into body carbon was 0.44, very similar to the corresponding efficiency of egg-production in females. On the assumptions that food availability is similar for all developmental stages, and that juvenile and female specific growth/egg-production rates are equal, female egg-production rates are representative of turnover rates (production/biomass) of the entireA. tonsa population and probably in other copepod species as well. Therefore, in situ estimates of female fecundity may be used for a rapid time- and site-specific field estimate of copepod production. This approach is shown to be fairly robust to even large deviations from the assumptions.
Birnstiel, T.; Ormel, C. W.; Dullemond, C. P.
2011-01-01
Context. Grains in circumstellar disks are believed to grow by mutual collisions and subsequent sticking due to surface forces. Results of many fields of research involving circumstellar disks, such as radiative transfer calculations, disk chemistry, magneto-hydrodynamic simulations largely depend on the unknown grain size distribution. Aims: As detailed calculations of grain growth and fragmentation are both numerically challenging and computationally expensive, we aim to find simple recipes and analytical solutions for the grain size distribution in circumstellar disks for a scenario in which grain growth is limited by fragmentation and radial drift can be neglected. Methods: We generalize previous analytical work on self-similar steady-state grain distributions. Numerical simulations are carried out to identify under which conditions the grain size distributions can be understood in terms of a combination of power-law distributions. A physically motivated fitting formula for grain size distributions is derived using our analytical predictions and numerical simulations. Results: We find good agreement between analytical results and numerical solutions of the Smoluchowski equation for simple shapes of the kernel function. The results for more complicated and realistic cases can be fitted with a physically motivated “black box” recipe presented in this paper. Our results show that the shape of the dust distribution is mostly dominated by the gas surface density (not the dust-to-gas ratio), the turbulence strength and the temperature and does not obey an MRN type distribution.
Kohei Arai
2014-01-01
Aerosol refractive index and size distribution estimations based on polarized atmospheric irradiance measurements are proposed together with its application to reflectance based vicarious calibration. A method for reflectance based vicarious calibration with aerosol refractive index and size distribution estimation using atmospheric polarization irradiance data is proposed. It is possible to estimate aerosol refractive index and size distribution with atmospheric polarization irradiance measu...
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 D99% confidence; a double power law cannot be rejected outright, but appears to be a uncomfortable match to the available data. A divot, with the parameters found independently for scattering TNOs by Shankman et al. (2013, ApJ vol 764), provides an excellent match; the best match, found from an extensive parameter search, comes with only slightly different parameters; this size-distribution also satisfies the known Neptunian Trojan data.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.
International Nuclear Information System (INIS)
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.
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.
2006-01-01
The ESA space debris population model MASTER (Meteoroid and Space Debris Terrestrial Environment Reference) considers 1032 firings of solid rocket motors (SRM) with the associated generation of SRM slag and dust particles in its current version. The resulting dust population is a major contribution to the sub-millimetre size space debris environment in Earth orbit. For the modelling of each SRM dust release event a detailed knowledge of the particle size distribution is essential. However, the knowledge of the particle sizes after passing the nozzle throat is poor. The current dust implementation in the MASTER model assumes a fixed size distribution which is identically used for both large upper stages and small apogee motors. This assumption can lead to an over-representation of large dust particles in regions, where mainly apogee motors are used (i.e., Geostationary Earth Orbit) and an under-representation in lower altitudes, where large stages predominate. In this paper, a concept for the improvement of SRM dust size modelling is discussed. It will be shown that an introduction of a nozzle throat diameter dependency into the dust size distribution enables a more precise modelling of SRM dust release events. The improved SRM dust size distribution is going to be used by the MASTER-2005 space debris model which is currently under development by the Institute of Aerospace Systems and QinetiQ (UK) under ESA contract.
Planar dust-acoustic waves in electron-positron-ion-dust plasmas with dust size distribution
International Nuclear Information System (INIS)
Nonlinear dust-acoustic solitary waves which are described with a Kortweg-de vries (KdV) equation by using the reductive perturbation method, are investigated in a planar unmagnetized dusty plasma consisting of electrons, positrons, ions and negatively-charged dust particles of different sizes and masses. The effects of the power-law distribution of dust and other plasma parameters on the dust-acoustic solitary waves are studied. Numerical results show that the dust size distribution has a significant influence on the propagation properties of dust-acoustic solitons. The amplitudes of solitary waves in the case of a power-law distribution is observed to be smaller, but the soliton velocity and width are observed to be larger, than those of mono-sized dust grains with an average dust size. Our results indicate that only compressed solitary waves exist in dusty plasma with different dust species. The relevance of the present investigation to interstellar clouds is discussed.
Planar dust-acoustic waves in electron-positron-ion-dust plasmas with dust size distribution
Energy Technology Data Exchange (ETDEWEB)
Wang, Hong-Yan; Zhang, Kai-Biao [Sichuan University of Science and Engineering, Zigong (China)
2014-06-15
Nonlinear dust-acoustic solitary waves which are described with a Kortweg-de vries (KdV) equation by using the reductive perturbation method, are investigated in a planar unmagnetized dusty plasma consisting of electrons, positrons, ions and negatively-charged dust particles of different sizes and masses. The effects of the power-law distribution of dust and other plasma parameters on the dust-acoustic solitary waves are studied. Numerical results show that the dust size distribution has a significant influence on the propagation properties of dust-acoustic solitons. The amplitudes of solitary waves in the case of a power-law distribution is observed to be smaller, but the soliton velocity and width are observed to be larger, than those of mono-sized dust grains with an average dust size. Our results indicate that only compressed solitary waves exist in dusty plasma with different dust species. The relevance of the present investigation to interstellar clouds is discussed.
Analysis of tecniques for measurement of the size distribution of solid particles
Directory of Open Access Journals (Sweden)
F. O. Arouca
2005-03-01
Full Text Available Determination of the size distribution of solid particles is fundamental for analysis of the performance several pieces of equipment used for solid-fluid separation. The main objective of this work is to compare the results obtained with two traditional methods for determination of the size grade distribution of powdery solids: the gamma-ray attenuation technique (GRAT and the LADEQ test tube technique. The effect of draining the suspension in the two techniques used was also analyzed. The GRAT can supply the particle size distribution of solids through the monitoring of solid concentration in experiments on batch settling of diluted suspensions. The results show that use of the peristaltic pump in the GRAT and the LADEQ methods produced a significant difference between the values obtained for the parameters of the particle size model.
The effect of ion beam temperature on ion distribution size into solid surface
International Nuclear Information System (INIS)
Ion implantation has become a versatile and powerful technique for synthesizing nanometer scale cluster and crystal embedded in the near surface region of the materials. One of the major difficulties in order to create nano composite materials by ion implantation are control over the size distribution and spacing of the precipitates. In this paper the relation between ion temperatures and size distribution of implanted ions after collision with a solid surface has been studied and cold ion beam is introduced as a substitute method for focused ion beam methods. SIMION and SRIM software's have been used for transport and interaction of ion distribution to and into the surface, respectively.
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...
An Evolutionary Approach for Optimal Citing and Sizing of Micro-Grid in Radial Distribution Systems
J, Eswari.; Jeyadevi, Dr. S.
2014-01-01
This Paper presents the methodology of penetration of Micro-Grids (MG) in the radial distribution system (RDS). The aim of this paper is to minimize a total real power loss that descends the performance of the radial distribution system by integrating various renewable resources as Distributed Generation (DG). The combination of different types of renewable energy resources contributes a sustainable MG. These resources are optimally sized and located using evolutionary appro...
International Nuclear Information System (INIS)
A dilution source sampling system is augmented to measure the size-distributed chemical composition of fine particle emissions from air pollution sources. Measurements are made using a laser optical particle counter (OPC), a differential mobility analyzer/condensation nucleus counter (DMA/CNC) combination, and a pair of microorifice uniform deposit impactors (MOUDIs). The sources tested with this system include wood smoke (pine, oak, eucalyptus), meat charbroiling, and cigarettes. The particle mass distributions from all wood smoke sources have a single mode that peaks at approximately 0.1--0.2 microm particle diameter. The smoke from meat charbroiling shows a major peak in the particle mass distribution at 0.1--0.2 microm particle diameter, with some material present at larger particle sizes. Particle mass distributions from cigarettes peak between 0.3 and 0.4 microm particle diameter. Chemical composition analysis reveals that particles emitted from the sources tested here are largely composed of organic compounds. Noticeable concentrations of elemental carbon are found in the particles emitted from wood burning. The size distributions of the trace species emissions from these sources also are presented, including data for Na, K, Ti, Fe, Br, Ru, Cl, Al, Zn, Ba, Sr, V, Mn, Sb, La, Ce, as well as sulfate, nitrate, and ammonium ion when present in statistically significant amounts. These data are intended for use with air quality models that seek to predict the size dity models that seek to predict the size distribution of the chemical composition of atmospheric fine particles
Generation and size distribution of droplet in annular two-phase flow
International Nuclear Information System (INIS)
The mean droplet size and size distribution are important for detailed mechanistic modeling of annular two-phase flow. A large number of experimental data indicate that the standard Weber number criterion based on the relative velocity between droplets and gas flow predicts far too large droplet sizes. Therefore, it was postulated that the majority of the droplets were generated at the time of entrainment and the size distribution was the direct reflection of the droplet entrainment mechanism based on roll-wave shearing off. A detailed model of the droplet size in annular flow was then developed based on the above assumption. The correlations for the volume mean diameter as well as the size distribution were obtained in collaboration with a large number of experimental data. A comparison with experimental data indicated that indeed the postulated mechanism has been the dominant factor in determining the drop size. Furthermore, a large number of data can be successfully correlated by the present model. These correlations can supply accurate information on droplet size in annular flow which has not been available previously
Effect of Feedstock Size and its Distribution on the Properties of Detonation Sprayed Coatings
Suresh Babu, P.; Rao, D. S.; Rao, G. V. N.; Sundararajan, G.
2007-06-01
The detonation spraying is one of the most promising thermal spray variants for depositing wear and corrosion resistant coatings. The ceramic (Al2O3), metallic (Ni-20 wt%Cr) , and cermets (WC-12 wt%Co) powders that are commercially available were separated into coarser and finer size ranges with relatively narrow size distribution by employing centrifugal air classifier. The coatings were deposited using detonation spray technique. The effect of particle size and its distribution on the coating properties were examined. The surface roughness and porosity increased with increasing powder particle size for all the coatings consistently. The feedstock size was also found to influence the phase composition of Al2O3 and WC-Co coatings; however does not influence the phase composition of Ni-Cr coatings. The associated phase change and %porosity of the coatings imparted considerable variation in the coating hardness, fracture toughness, and wear properties. The fine and narrow size range WC-Co coating exhibited superior wear resistance. The coarse and narrow size distribution Al2O3 coating exhibited better performance under abrasion and sliding wear modes however under erosion wear mode the as-received Al2O3 coating exhibited better performance. In the case of metallic (Ni-Cr) coatings, the coatings deposited using coarser powder exhibited marginally lower-wear rate under abrasion and sliding wear modes. However, under erosion wear mode, the coating deposited using finer particle size exhibited considerably lower-wear rate.
Wei, Yi; Wang, Yuxia; Wang, Lianyan; Hao, Dongxia; Ma, Guanghui
2011-10-15
Amphiphilic co-polymer, which can maintain the stability of proteins and increase the protein loading efficiency, is considered as an exploring-worthy biodegrade polymer for drug delivery. However, amphiphilic microcapsules prepared by conventional methods, such like mechanical stirring and spray-drying methods, exhibit broad size distributions due to its hydrophilic sequences, leading to poor reproducibility. In this study, we employed poly(monomethoxypoly ethylene glycol-co-D,L-lactide) (mPEG-PLA, PELA), one of common amphiphilic polymers, as model to focus on investigating the process parameters and mechanisms to prepare PELA microcapsules with narrow size distribution and regular sphericity by combining premix membrane emulsification and double emulsion technique. The coarse double emulsion with broad size distribution was repeatedly pressed through Shirasu Porous Glass (SPG) membrane with relatively high pressure to form the fine emulsion with narrow size distribution. Then, the microcapsules with narrow size distribution can be obtained by solvent extraction method. It was found that it was more difficult to obtain PELA microcapsules with narrow size distribution and smooth surface due to its amphiphilic property, compared with the cases of PLA and PLGA. The smooth surface morphology was found to be related to several factors including internal water phase with less volume, slower stirring rate during solidification and using ethyl acetate as oil phase. It was also found that mass ratio of hydrophilic mPEG, stabilizer PVA concentration in external water phase and transmembrane pressure played important role on the distribution of microcapsules size. The suitable preparation conditions were determined as follows: for the membrane with pore size of 2.8 ?m, the mass ratio of PLA/mPEG was 19:1, volume ratio of W(1)/O was 1:10 and O/W(2) was 1:5, PVA concentration (w/v) was 1.0%, magnetic stirring rate during solidification was 60 rpm and 300 kPa was chosen as transmembrane pressure. There was a linear relationship between the diameter of microcapsules and the pore size of the membranes. Finally, by manipulating the process parameters, PELA microcapsules with narrow size distributions (coefficient of variation was less than 15%), smooth morphology and various sizes, were obtained. Most importantly, the key factors affecting fabrication have been revealed and mechanisms were illustrated in detail, which would shed light on the research of amphiphilic polymer formulation. PMID:21683559
Using diffusion measurements to determine pore-size distributions in porous materials
Energy Technology Data Exchange (ETDEWEB)
Brown, L.F.; Travis, B.J.
1980-01-01
The internal structure of the porous solid was modeled as nonintersecting cylindrical pores of random directions. A relationship was derived for the flux as a function of pressure in which the flux is a functional of the pore size distribution. The resulting Fredholm integral equation of the first kind was solved for the diffusion region between Knudsen and bulk diffusion, which can be measured by Wicke-Kallenbach experiments. Calculations of pore size distributions of hypothetical materials with ideal simple or bimodal pore distributions for 0.1-2.0 MPa and 0.1-30.0 MPa showed the validity of the method. The method also predicted the diffusion as a function of pressure in Girdler G-3B porous catalyst, for which Wicke-Kallenbach data were available, but calculated results deviated for the pore size distribution based on available mercury porosimeter data for the same catalyst.
International Nuclear Information System (INIS)
Test aerosols of di(2-ethylhexyl)phthalate (DOP) produced by Laskin nozzle aerosol generators are widely used for in-place filter testing and respirator fit testing. Concern for the health effects of this material has led to a search for substitute materials for test aerosols. Aerosols were generated with a Laskin generator and diluted 6000-fold with clean air. Size distributions were measured for DOP, di(2-ethylhexyl)sebecate, polyethylene glycol, mineral oil, and corn oil aerosols with a PMS ASAS-X optical particle counter. Distributions were slightly bimodal with count median diameters from 0.22 to 0.30 ?m. Size distributions varied little with aerosol material, operating pressure, or liquid level. Mineral oil and corn oil gave the best agreement with the DOP size distribution
Size distribution of matter related to radionuclides released from Fukushima nuclear power plant
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In relation to the Fukushima accident among March 24 to April 13, 2011 were performed consecutive aerosol samples for determination of specific activity depending on its size distribution. The extraction used three five-cascade impactors distributed within SURO Prague. Volume activity deposited on the collection of base liners and filters was determined by semiconductor gamma spectrometry. The obtained spectra were evaluated in terms of size distribution of 131I, 134Cs and 137Cs, compared to control and were also provided for 7Be. The results were compared with data obtained in May and June 1986 after the Chernobyl disaster, when an average AMAD value of volatile radionuclides (which include 131I, 134Cs and 137Cs) 0.5 ?m. The comparison shows that size distribution and the values of AMAD disaster at Chernobyl NPP and Fukushima NPP disaster were very similar.
Accelerating growth and size-dependent distribution of human online activities
Wu, Lingfei; Zhang, Jiang
2011-08-01
Research on human online activities usually assumes that total activity T increases linearly with active population P, that is, T?P?(?=1). However, we find examples of systems where total activity grows faster than active population. Our study shows that the power law relationship T?P?(?>1) is in fact ubiquitous in online activities such as microblogging, news voting, and photo tagging. We call the pattern “accelerating growth” and find it relates to a type of distribution that changes with system size. We show both analytically and empirically how the growth rate ? associates with a scaling parameter b in the size-dependent distribution. As most previous studies explain accelerating growth by power law distribution, the model of size-dependent distribution is worth further exploration.
Accelerating growth and size-dependent distribution of human online activities.
Wu, Lingfei; Zhang, Jiang
2011-08-01
Research on human online activities usually assumes that total activity T increases linearly with active population P, that is, T?P(?) (?=1). However, we find examples of systems where total activity grows faster than active population. Our study shows that the power law relationship T?P(?) (?>1) is in fact ubiquitous in online activities such as microblogging, news voting, and photo tagging. We call the pattern "accelerating growth" and find it relates to a type of distribution that changes with system size. We show both analytically and empirically how the growth rate ? associates with a scaling parameter b in the size-dependent distribution. As most previous studies explain accelerating growth by power law distribution, the model of size-dependent distribution is worth further exploration. PMID:21929070
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
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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)
A joint lot-sizing and marketing model with reworks, scraps and imperfect products
Mohsen Fathollah Bayati; Morteza Rasti Barzoki; Seyed Reza Hejazi
2011-01-01
In this paper, we establish an economic production quantity (EPQ) based inventory model by considering various types of non-perfect products .We classify products in four groups of perfect, imperfect, defective but reworkable and non-reworkable defective items. The demand is a power function of price and marketing expenditure and production unit cost is considered to be a function of lot size. The objective of this paper is to determine lot size, marketing expenditure, selling price, set up c...
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Synthetic washed ITP slurry (200 g) was oven dried for three days at 60--65 degrees C in a pan, to a hard solid that stuck to the pan bottom. Between the cracks that formed were a few small particles of unknown size. The solids that were stuck to the pan bottom were pried free and repetitively ground in a mortar and pestle until they all passed through a 40 mesh sieve. This product was then sieved into 50, 80, 100, 170, 200, 325 sieve fractions and the results plotted. A protion of the fines passing the 325 sieve were further separated by air flotation in a glass tube with fritted bottom. Increasing amounts of air were passed up through the tube that floated out increasing fractions of particles after weighing. ITP washed precipitate, ground and dried, had a particle size distribution versus cumulative weight fraction curve between Powered coal and Filter sand. The minimum particle size was about 20 microns
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.
A possible divot in the Kuiper belt's scattered-object size distribution
Shankman, C.; Kavelaars, J.; Gladman, B.; Petit, J.
2014-07-01
The formation and evolution history of the Solar System, while not directly accessible, has measurable signatures in the present-day size distributions of the Trans-Neptunian Object (TNO) populations. The form of the size distribution is modelled as a power law with number going as size to some characteristic slope. Recent works have shown that a single power law does not match the observations across all sizes; the power law breaks to a different form [1, 2, 3]. The large- size objects record the accretion history, while the small-size objects record the collision history. The changes of size-distribution shape and slope as one moves from 'large' to 'medium' to 'small' KBOs are the signature needed to constrain the formation and collision history of the Solar System. The scattering TNOs are those TNOs undergoing strong (scattering) interactions Neptune. The scattering objects can come to pericentre in the giant planet region. This close-in pericentre passage allows for the observation of smaller objects, and thus for the constraint of the small-size end of the size distribution. Our recent analysis of the Canada France Ecliptic Plane Survey's (CFEPS) scattering objects revealed an exciting potential form for the scattering object size distribution - a divot (see Figure). Our divot (a sharp drop in the number of objects per unit size which then returns at a potentially different slope) matches our observations well and can simultaneously explain observed features in other inclined (so-called "hot") Kuiper Belt populations. In this scenario all of the hot populations would share the same source and have been implanted in the outer solar system through scattering processes. If confirmed, our divot would represent a new exciting paradigm for the formation history of the Kuiper Belt. Here we present the results of an extension of our previous work to include a new, deeper, Kuiper Belt survey. By the addition of two new faint scattering objects from this survey which, in tandem with the full characterizations of the survey's biases (acting like non- detections limits), we better constrain the form of the scattering object size distribution.
Research of CWS’ Particle Size Distribution based on Ultrasonic Attenuation Theory
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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.
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...
An estimate of field size distributions for selected sites in the major grain producing countries
Podwysocki, M. H.
1977-01-01
The field size distributions for the major grain producing countries of the World were estimated. LANDSAT-1 and 2 images were evaluated for two areas each in the United States, People's Republic of China, and the USSR. One scene each was evaluated for France, Canada, and India. Grid sampling was done for representative sub-samples of each image, measuring the long and short axes of each field; area was then calculated. Each of the resulting data sets was computer analyzed for their frequency distributions. Nearly all frequency distributions were highly peaked and skewed (shifted) towards small values, approaching that of either a Poisson or log-normal distribution. The data were normalized by a log transformation, creating a Gaussian distribution which has moments readily interpretable and useful for estimating the total population of fields. Resultant predictors of the field size estimates are discussed.
Two-phase dynamics of volcanic eruptions: Particle size distribution and the conditions for choking
Yarushina, Viktoriya M.; Bercovici, David; Michaut, Chloé
2015-03-01
Explosive volcanic eruptions are studied using a two-phase model of polydisperse suspensions of solid particles in gas. Eruption velocities depend on choking conditions in the volcanic conduit, which depend on acoustic wave propagation that is, in turn, influenced by the particle size distribution in the two-phase mixture. The acoustic wave spectrum is divided into three regions of superfast short waves moving at the pure gas sound speed, purely attenuated domain at intermediate wavelengths, and slower long waves for a dusty pseudogas. The addition of solid phases with differing particle sizes qualitatively preserves the features of two-phase acoustic wave dispersion, although it narrows the regions of short-fast and intermediate-blocked waves. Choking conditions, however, strongly depend on the number and size distribution of solid phases. Changes in particle sizes lead to variations in the choking conditions, which determine the eruption velocities and the resulting height of the erupting column. Smaller particles always exit the choking point faster than big particles, as expected. Even though particle-particle interaction is neglected, the particle distributions influence each other by momentum exchange through the gas. Therefore, the structure of the dispersion relation as well as the eruption or choking velocities and subsequent column height and particle deposition bear information on how eruption dynamics are controlled by size distribution and relative volume fractions of small and big particles. We suggest that unimodal distributions, with one dominant small particle size, favor development of vertical plinian eruptions, while bimodal distributions, with a comparable mean size, lead to pyroclastic lateral flows.
Moessbauer and magnetic studies in nickel ferrite nanoparticles: Effect of size distribution
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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.
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.
Kourtchev, Ivan
Terrestrial vegetation releases substantial amounts of reactive volatile organic compounds (VOCs; e.g., isoprene, monoterpenes) into the atmosphere. The VOCs can be rapidly photooxidized under conditions of high solar radiation, yielding products that can participate in new particle formation and growth processes above forests. This thesis focuses on the characterization, identification and quantification of oxidation products of biogenic VOC (BVOCs) as well as other species (tracer compounds) that provide information on aerosol sources and source processes. Atmospheric aerosols from various forested sites (i.e., Hyytiala, southern Finland; Rondonia, Brazil; K-Puszta, Hungary and Julich, Germany) were analyzed with Gas Chromotography/Mass Spectrometry (GC/MS) using analytical procedure that targets polar organic compounds. The study demonstrated that isoprene (i.e., 2-methyerythritol, 2-methylthreitol, 2-methylglyceric acid and C5-alkene triols (2-methyl-1,3,4-trihydroxy-l-butene (cis and trans) and 3 methyl-2,3,4-trihydroxy-1-butene)) and monoterpene (pinic acid, norpinic acid, 3-hydroxyglutaric acid and 3-methyl-1,2,3-butanetricarboxylic acid) oxidation products were present in substantial concentrations in atmospheric aerosols suggesting that oxidation of BVOC from the vegetation is an important process in all studied sites. On the other hand, presence of levoglucosan, biomass burning marker, especially in Amazonian rain forest site at Rondonia, Brazil, pointed that all sites were affected by anthropogenic activities, namely biomass burning. Other identified compounds included plyols, arabitol, mannitol and erythritol, which are marker compounds for fungal spores and monosacharides, glucose and fructose, markers for plant polens. Temporal variations as well as mass size distributions of the detected species confirmed the possible formation mechanisms of marker compounds.
Measurements of the size distribution of unattached radon progeny by using the imaging plate
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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
Kova?evi?, Nemanja; ?uri?, Mladjen
2015-05-01
A cloud-resolving mesoscale model with a two-moment bulk microphysical scheme is used to perform cloud simulations for two different modes of the liquid water spectrum: a unified Khrgian-Mazin size distribution for the entire spectrum of drops and the monodisperse size distribution for cloud droplets with the exponential Marshall-Palmer distribution for raindrops. The cloud model calculates the mixing ratios and number concentrations of the six microphysical categories: raindrops, cloud ice, snow, graupel, frozen raindrops and hail. The cloud droplet number concentration was prescribed. The main purpose of this sensitivity study was to analyse the differences in simulated surface precipitation (rain and hail) for the two assumed approaches with different values of cloud droplet number concentration. The study showed that there are significant differences in the occurrence, amount and spatial distribution of accumulated precipitation at the surface. It can be noted that the unified Khrgian-Mazin size distribution is generally more sensitive to changes in the cloud droplet number concentration than an alternative approach. The rain showers and cloud splitting are well simulated with the unified Khrgian-Mazin size distribution, especially for smaller values of cloud droplet number concentration.
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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.
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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.
Aerial observations of floe size distribution in the marginal ice zone of summer Prydz Bay
Lu, P.; Li, Z. J.; Zhang, Z. H.; Dong, X. L.
2008-02-01
On the basis of aerial photographs of sea ice floes in the marginal ice zone (MIZ) of Prydz Bay acquired from December 2004 to February 2005 during the 21st Chinese National Antarctic Research Expedition, image processing techniques are employed to extract some geometric parameters of floes from two merged transects covering the whole MIZ. Variations of these parameters with the distance into the MIZ are then obtained. Different parameters of floe size, namely area, perimeter, and mean caliper diameter (MCD), follow three similar stages of increasing, flat and increasing again, with distance from the open ocean. Floe shape parameters (roundness and the ratio of perimeter to MCD), however, have less significant variations than that of floe size. Then, to modify the deviation of the cumulative floe size distribution from the ideal power law, an upper truncated power-law function and a Weibull function are used, and four calculated parameters of the above functions are found to be important descriptors of the evolution of floe size distribution in the MIZ. Among them, Lr of the upper truncated power-law function indicates the upper limit of floe size and roughly equals the maximum floe size in each square sample area. L0 in the Weibull distribution shows an increasing proportion of larger floes in squares farther from the open ocean and roughly equals the mean floe size. D in the upper truncated power-law function is closely associated with the degree of confinement during ice breakup. Its decrease with the distance into MIZ indicates the weakening of confinement conditions on floes owing to wave attenuation. The ? of the Weibull distribution characterizes the degree of homogeneity in a data set. It also decreases with distance into MIZ, implying that floe size distributes increase in range. Finally, a statistical test on floe size is performed to divide the whole MIZ into three distinct zones made up of floes of quite different characteristics. This zonal structure of floe size also agrees well with the trends of floe shape and floe size distribution, and is believed to be a straightforward result of wave-ice interaction in the MIZ.
Production and characterization of deposited mono-sized clusters
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Using high energy rare gas ion sputtering of metal targets, the authors are able to produce nanoamps of mass selected transition metal clusters. Mono-sized cluster ions are deposited at low kinetic energy upon substrates, e.g. silica or carbon, and are then characterized using UV and x-ray photoemission. In this paper the authors discuss photoemission measurements of the 4f7/2 core level energies of Au (1-5,7 atom samples) clusters deposited on silica. From such studies the authors are beginning to understand how electronic structure, cluster stability and mobility depend on (deposited) cluster size, surface coverage, and substrate temperature
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
Decision trees are PAC-learnable from most product distributions: a smoothed analysis
Kalai, Adam Tauman
2008-01-01
We consider the problem of PAC-learning decision trees, i.e., learning a decision tree over the n-dimensional hypercube from independent random labeled examples. Despite significant effort, no polynomial-time algorithm is known for learning polynomial-sized decision trees (even trees of any super-constant size), even when examples are assumed to be drawn from the uniform distribution on {0,1}^n. We give an algorithm that learns arbitrary polynomial-sized decision trees for {\\em most product distributions}. In particular, consider a random product distribution where the bias of each bit is chosen independently and uniformly from, say, [.49,.51]. Then with high probability over the parameters of the product distribution and the random examples drawn from it, the algorithm will learn any tree. More generally, in the spirit of smoothed analysis, we consider an arbitrary product distribution whose parameters are specified only up to a [-c,c] accuracy (perturbation), for an arbitrarily small positive constant c.
Energy Technology Data Exchange (ETDEWEB)
Mastandrea, J. P.; Sherburne, M. P.; Boswell-Koller, C. N.; Sawyer, C. A.; Guzman, J.; Bustillo, K. C.; Haller, E. E.; Chrzan, D. C. [Department of Materials Science and Engineering, University of California, Berkeley, California 94720 (United States); Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Ager, J. W. [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)
2013-12-21
A simple mathematical argument explains a recently identified route for the ion beam synthesis of nanoclusters with a narrowed size distribution. The key idea is that growth conditions for which the average nanocluster size is increasing rapidly can lead to narrowed size distributions. Modeling candidate processes using a self-consistent, mean-field theory shows that normalized nanocluster size distributions with full-width at half-maximum of 17% of the average can be attained.
International Nuclear Information System (INIS)
A simple mathematical argument explains a recently identified route for the ion beam synthesis of nanoclusters with a narrowed size distribution. The key idea is that growth conditions for which the average nanocluster size is increasing rapidly can lead to narrowed size distributions. Modeling candidate processes using a self-consistent, mean-field theory shows that normalized nanocluster size distributions with full-width at half-maximum of 17% of the average can be attained
Multi-product allocation and distribution
Currin, D. C.; Ittmann, H. W.
2003-01-01
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 ...
Evolution of fission-gas-bubble-size distribution in recrystallized U-10Mo nuclear fuel
Rest, J.
2010-12-01
An analytical model for the nucleation and growth of intra and intergranular fission-gas bubbles, used to characterize fission-gas bubble development in U-Mo alloy fuel with burnup limited to less than 10 at.% U in order to capture the fuel swelling stage prior to irradiation-induced recrystallization, is extended to recrystallized fuel at a burnup of ˜16 at.% U. During recrystallization the grain size is transformed from micron to sub-micron sizes. The intergranular bubble-size distribution post-recrystallization is found to evolve with similar kinetics and morphology to that pre-recrystallization with any differences primarily due to gas content and initial and/or boundary conditions (e.g., fuel microstructure). The predictions of the theory are compared with measured bubble-size distributions in pre and post recrystallized U-10Mo alloy fuel.
Analysis of tecniques for measurement of the size distribution of solid particles
Scientific Electronic Library Online (English)
F. O., Arouca; M. A. S., Barrozo; J. J. R., Damasceno.
2005-03-01
Full Text Available Determination of the size distribution of solid particles is fundamental for analysis of the performance several pieces of equipment used for solid-fluid separation. The main objective of this work is to compare the results obtained with two traditional methods for determination of the size grade di [...] stribution of powdery solids: the gamma-ray attenuation technique (GRAT) and the LADEQ test tube technique. The effect of draining the suspension in the two techniques used was also analyzed. The GRAT can supply the particle size distribution of solids through the monitoring of solid concentration in experiments on batch settling of diluted suspensions. The results show that use of the peristaltic pump in the GRAT and the LADEQ methods produced a significant difference between the values obtained for the parameters of the particle size model.
International Nuclear Information System (INIS)
An experiment designed to measure aerosol size distributions and turbidity simultaneously over a metropolitan area is described. The particle volume size distributions measured in the city plume are found to be bimodal, with the total particle volume in the fine or submicron mode decreasing dramatically above the inversion. Aerosol extinction coefficients derived from sunphotometer optical depth measurements at four wavelengths are compared to those calculated from the measured size distributions using Mie theory with several different particle refractive indices. The accuracy of the experimental method for determining the aerosol extinction coefficient prevented any meaningful choice of the real part of particle refractive index between 1.5--1.6 and an imaginary part between 0 and -0.1i. Improvements to this type of experiment are discussed
International Nuclear Information System (INIS)
A study on the sources of variability in the measurement of particle size distribution using a two-stage dilution system and an engine exhaust particle sizer was conducted to obtain a comprehensive and repeatable methodology that can be used to measure the particle size distribution of aerosols emitted by a light-duty diesel engine under transient operating conditions. The paper includes three experimental phases: an experimental validation of the measurement method; an evaluation of the influence of sampling factors, such as dilution system pre-conditioning; and a study of the effects of the dilution conditions, such as the dilution ratio and the dilution air temperature. An examination of the type and degree of influence of each studied factor is presented, recommendations for reducing variability are given and critical parameter values are identified to develop a highly reliable measurement methodology that could be applied to further studies on the effect of engine operating parameters on exhaust particle size distributions
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
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
Sol-gel synthesis of forsterite nanopowders with narrow particle size distribution
International Nuclear Information System (INIS)
Forsterite (FS) nanopowders (?27 nm) were synthesized using a sol-gel route with magnesium nitrate hexahydrate and tetra ethyl ortho-silicate as magnesium and silicon precursors, respectively. Nitric acid was used as a catalyst. After aging, the FS gel was calcined at 800 oC for 30 min. The calcined powders were characterized for phase composition using X-ray diffractrometry and fourier transform-infrared spectroscopy. The particle size and morphology was studied using transmission electron microscopy. The particle size distribution analysis of FS powders showed skewed distribution plot with particle size ranging from 5-90 nm. This study showed that high phase purity and narrowly distributed FS nanoparticles could be obtained using this simple sol-gel technique.
Moustakas, Aristides; Chorti, Arsenia; Hristopulos, Dionissios T.
2007-10-01
We propose using geostatistical methods for the spatial analysis of data pertaining to the size of trees (in terms of canopy surface area) obtained by means of remote sensing methods. Geostatistical methods are suitable because the locations of the trees are at the nodes of an unstructured grid. More specifically, we present a semivariogram analysis to detect correlations in the tree size spatial distribution, and we apply a novel method of anisotropy analysis to search for possible anisotropy in the size distribution. We use a combination of aerial photographs and satellite images in four snapshots covering 37 years to investigate the temporal behavior in addition to the spatial distribution at a single time. The aerial photographs were taken in 1964, 1984, 1993, and the IKONOS satellite image in 2001. We follow a study area covering over 139 ha and over 2,000 tree individuals. Our plots are located in the Southern Kalahari savanna near the city of Kimberley, South Africa.
Roselli, Leonilde; Basset, Alberto
2015-01-01
Understanding the mechanisms of phytoplankton community assembly is a fundamental issue of aquatic ecology. Here, we use field data from transitional (e.g. coastal lagoons) and coastal water environments to decode patterns of phytoplankton size distribution into organization and adaptive mechanisms. Transitional waters are characterized by higher resource availability and shallower well-mixed water column than coastal marine environments. Differences in physico-chemical regime between the two environments have been hypothesized to exert contrasting selective pressures on phytoplankton cell morphology (size and shape). We tested the hypothesis focusing on resource availability (nutrients and light) and mixed layer depth as ecological axes that define ecological niches of phytoplankton. We report fundamental differences in size distributions of marine and freshwater diatoms, with transitional water phytoplankton significantly smaller and with higher surface to volume ratio than marine species. Here, we hypothesize that mixing condition affecting size-dependent sinking may drive phytoplankton size and shape distributions. The interplay between shallow mixed layer depth and frequent and complete mixing of transitional waters may likely increase the competitive advantage of small phytoplankton limiting large cell fitness. The nutrient regime appears to explain the size distribution within both marine and transitional water environments, while it seem does not explain the pattern observed across the two environments. In addition, difference in light availability across the two environments appear do not explain the occurrence of asymmetric size distribution at each hierarchical level. We hypothesize that such competitive equilibria and adaptive strategies in resource exploitation may drive by organism's behavior which exploring patch resources in transitional and marine phytoplankton communities. PMID:25974052
The Effect of Product Size on the Pulling Force in Pultrusion
DEFF Research Database (Denmark)
Baran, Ismet; Carlone, Pierpaolo
2014-01-01
In the present work, pultrusion of a composite rod is simulated for various part thicknesses using the finite element method. The pultrusion process set-up is taken from literature in which the temperature and the degree of cure evolutions inside the rod were measured. The predicted temperature and degree of cure profiles in the three dimensional (3D) thermo-chemical analysis are found to agree well with the measured data. The contact pressure between the part and the heating die is calculated using a mechanical contact formulation in the 2D mechanical process model for 9 different part thickness values. Using the contact pressure distribution along the die, the process induced pulling force is predicted. For the simulated cases, a non-linear relation is found between the total force and the product size.
On the parametric description of the French, German, Italian and Spanish city size distributions
Puente-Ajovin, Miguel; Ramos, Arturo
2014-01-01
We study the parametric description of the city size distribution of four European countries: France, Germany, Italy and Spain. The parametric models used are the lognormal, the double Pareto lognormal, the normal-Box-Cox (defined in this paper) and the threshold double Pareto Singh--Maddala (introduced in a cited recent paper when studying US city size). The results are quite regular. The preferred model is always the threshold double Pareto Singh--Maddala in the four countries....
Air Mass Back Trajectories and Dry Atmospheric Aerosol Mass Size Distributions in Prague
Schwarz, Jaroslav
2013-01-01
Ambient aerosol size distribution is an important factor influencing aerosol behavior and properties including particle deposition in lungs and aerosol influence on clouds. Both influences are also driven by aerosol hygroscopicity. Cascade impactors used for size resolved determination of chemical composition suffer from changes of ambient RH during sampling. Due to this factor the same particle might be deposited at different impactor stage when it is sampled at noon at 40% RH or in the earl...
Shekhar, Himanshu; Rychak, Joshua J.; Doyley, Marvin M.
2013-01-01
Purpose: Subharmonic imaging is of interest for high frequency (>10 MHz) nonlinear imaging, because it can specifically detect the response of ultrasound contrast agents (UCA). However, conventional UCA produce a weak subharmonic response at high frequencies, which limits the sensitivity of subharmonic imaging. We hypothesized that modifying the size distribution of the agent can enhance its high-frequency subharmonic response. The overall goal of this study was to investigate size-manipulate...
Engineering metal precipitate size distributions to enhance gettering in multicrystalline silicon
Hofstetter, Jasmin; Fenning, David P.; Lelievre, Jean Francoise; Can?izo Nadal, Carlos Del; Buonassisi, Tonio
2012-01-01
The extraction of metal impurities during phosphorus diffusion gettering (PDG) is one of the crucial process steps when fabricating high-efficiency solar cells using low-cost, lower-purity silicon wafers. In this work, we show that for a given metal concentration, the size and density of metal silicide precipitates strongly influences the gettering efficacy. Different precipitate size distributions can be already found in silicon wafers grown by different techniques. In our experiment, howeve...
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
Log-Cubic Method for Generation of Soil Particle Size Distribution Curve
Songhao Shang
2013-01-01
Particle size distribution (PSD) is a fundamental physical property of soils. Traditionally, the PSD curve was generated by hand from limited data of particle size analysis, which is subjective and may lead to significant uncertainty in the freehand PSD curve and graphically estimated cumulative particle percentages. To overcome these problems, a log-cubic method was proposed for the generation of PSD curve based on a monotone piecewise cubic interpolation method. The log-cubic method and com...
Beddows, D. C. S.; Harrison, R. M.; Green, D. C.; Fuller, G. W.
2015-04-01
Positive Matrix Factorisation (PMF) analysis was applied to PM10 chemical composition and particle Number Size Distribution (NSD) data measured at an urban background site (North Kensington) in London, UK for the whole of 2011 and 2012. The PMF analyses revealed six and four factors respectively which described seven sources or aerosol types. These included Nucleation, Traffic, Diffuse Urban, Secondary, Fuel Oil, Marine and Non-Exhaust/Crustal sources. Diffuse Urban, Secondary and Traffic sources were identified by both the chemical composition and particle number size distribution analysis, but a Nucleation source was identified only from the particle Number Size Distribution dataset. Analysis of the PM10 chemical composition dataset revealed Fuel Oil, Marine, Non-Exhaust Traffic/Crustal sources which were not identified from the number size distribution data. The two methods appear to be complementary, as the analysis of the PM10 chemical composition data is able to distinguish components contributing largely to particle mass whereas the number particle size distribution dataset is more effective for identifying components making an appreciable contribution to particle number. Analysis was also conducted on the combined chemical composition and number size distribution dataset revealing five factors representing Diffuse Urban, Nucleation, Secondary, Aged Marine and Traffic sources. However, the combined analysis appears not to offer any additional power to discriminate sources above that of the aggregate of the two separate PMF analyses. Day-of-the-week and month-of-the-year associations of the factors proved consistent with their assignment to source categories, and bivariate polar plots which examined the wind directional and wind speed association of the different factors also proved highly consistent with their inferred sources.
The influence of fractal size distribution of covers on radon exhalation from uranium mill tailings
International Nuclear Information System (INIS)
Tailings produced during mining and milling of uranium ores represent potentially large volumes of low level radioactive materials. A typical environmental problem associated with mill tailings is radon emanation. Covering tailings is widely applied to reduce radon exhalation rate. In this paper, the fractal theories and field covering tests are used to study the fractal characters of size distribution of six types of covering materials, including waste rock, sand, laterite, kaolin, mixture of sand and laterite, and mixture of waste rock and laterite, and their influences on radon exhalation. The size distributions of uranium tailings and the six aforementioned covering materials all exhibit a good fractal structure. The contents of fine grain increase with the increasing value of fractal dimension. The results of field radon measurement show that the radon emanation rate of tailings without covers is 14.7–18.6 Bq/m2 s. Covering tests were carried out of the six abovementioned covering materials with thickness of 0.4 m, 0.8 m, 1.2 m, 1.6 m and 2.0 m. The results indicate that the application of these materials for cover layers can decrease the radon exhalation rate markedly. The effectiveness of a cover layer in reducing radon exhalation is related to its fractal texture of size distribution. Under the same thickness conditions, the attenuation coefficient of radon exhalation rate increases with the increasing fractal dimension of size distribution of coval dimension of size distribution of covers. The empirical expressions of the attenuation coefficients in relation to fractal dimension D of size distribution and thickness x of covers is obtained for evaluating the effectiveness of final covers for uranium tailings impoundments.
DEFF Research Database (Denmark)
Mikosch, Thomas Valentin; Moser, Martin
2013-01-01
We investigate the maximum increment of a random walk with heavy-tailed jump size distribution. Here heavy-tailedness is understood as regular variation of the finite-dimensional distributions. The jump sizes constitute a strictly stationary sequence. Using a continuous mapping argument acting on the point processes of the normalized jump sizes, we prove that the maximum increment of the random walk converges in distribution to a Fréchet distributed random variable.
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
Bimodal size distributions of ?' precipitates in Ni-Al-Mo. 1: Small-angle neutron scattering
International Nuclear Information System (INIS)
The evolution of the microstructure during the decomposition of two Ni-Al-Mo alloys with a bimodal size distribution of precipitates was studied using small-angle neutron scattering. Precipitate size distributions and space correlations of the bimodal precipitate ensemble were determined by model fitting of the scattering curves. The correlation effects between the precipitates were taken into account by the locally-monodisperse (LMD) hard-sphere model. This model assumes that the ensemble of precipitates have their positions correlated with their sizes, being locally monodisperse. The form factors were used according to the shape of the precipitates, spherical in the case of alloy I, Ni-8.8Al-9.6Mo (at.%) (isotropic system), and cuboidal for alloy II, Ni-9,5Al-5.4Mo (anisotropic system). To characterize the microstructure of the two alloys a set of characteristic parameters (e.g. volume fraction, average radii, precipitate number density, etc.) were obtained using relations between the moments rn of the size distribution N(r). The model proved particularly suited to characterize the isotropic system. In the case of the anisotropic system it was insensitive to changes of the size distribution N(r) during aging
Modeling of fission-gas bubble size distribution in U-Mo metal alloys
International Nuclear Information System (INIS)
A mechanistic model developed and validated against fission-gas bubble size distribution and fission gas release and fuel swelling data for oxide nuclear fuel has been modified in order to describe the fission gas behaviors in metallic fuel - in this particular study, U-Mo type alloys. Traditional validations of such models are accomplished by adjusting materials properties and parameters to obtain good agreement with experimentally measured fission-gas release, swelling, and mean values of bubble size and density. However, the uncertainty in these properties and parameters generate an inherent uncertainty in the validity of underlying physics. Validations using measured fission-gas bubble size distributions have been shown to be more promising in terms of interpreting the physics behind the fission-gas behavioral mechanisms. Measured intergranular fission-gas bubble size distribution data were used in this study for the purpose of model validation, and to explore the underlying physics of fission-gas bubble nucleation and coalescence. Plausible interpretation of the observed fission-gas bubble size distribution in irradiated U-10Mo alloys is provided. (author)
International Nuclear Information System (INIS)
Nanoparticles (NPs) were generated by ArF excimer laser ablation of graphite and tungsten targets in N2 ambient at atmospheric pressure. The size distribution of the particles was monitored in situ by a scanning mobility particle sizer (SMPS) system, based on differential mobility analyser. The experimental conditions made possible to record the size distributions in the 7-133-nm diameter range and results are presented for different laser fluences, repetition rates and ablated areas, respectively. Material analysis was performed by photoelectron spectroscopy (XPS), Raman spectroscopy, X ray diffraction and SEM
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%.
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...
18th ICPR paper: NEGOTIATION IN DISTRIBUTED PRODUCTION PLANNING ENVIRONMENTS
Lo Nigro, G.; Bruccoleri, Manfredi; Perrone, Giovanni
2006-01-01
Abstract Mass customization and global competition push enterprises to adopt proper business models able to capture all the opportunities arising from emerging competition rules. An increasing number of industrial enterprise distributes its production capacity world wide to achieve lower production costs, lower distribution costs (due to the higher closeness to customers), and deeper knowledge of customer needs. As drawback, coordination of the different production plants and the b...
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.
The effect of magnetic particles on pore size distribution in soft polyurethane foams
Schümann, M.; Günther, S.; Odenbach, S.
2014-07-01
The combination of elastomeric matrices with magnetic particles to obtain magnetically controllable hybrid materials is an actual field of intense research. An important aspect in this context is the stiffness of the matrix, which determines the effectiveness of the magnetically driven changes in the material properties. In this paper an approach has been undertaken to use soft polyurethane foams as matrix material. By means of x-ray computed microtomography and digital image processing the pore size distribution has been determined to get information on how this distribution is affected by the introduction of magnetic microparticles. To do so, 20 000 to 40 000 pores per foam sample were evaluated. As a result, it could be proven that the pore sizes of the analysed foams clearly obey the Weibull distribution. Increasing the carbonyl iron particle concentrations leads to a decrement of the shape parameter of the distribution. Based on known particle stabilization mechanisms, an approach to explain the experimental results is proposed.
A model of the spatial and size distribution of Enceladus' dust plume
Meier, Patrick; Kriegel, Hendrik; Motschmann, Uwe; Schmidt, Jürgen; Spahn, Frank; Hill, Thomas W.; Dong, Yaxue; Jones, Geraint H.
2014-12-01
The structure of Enceladus' south polar plume of charged dust is studied by simulations of the dust grain dynamics. The model considers the Lorentz force and charging of the grains by the plasma environment within the plume. Simulated dust plumes are investigated by applying 10 selected sets of dust parameters that include variations of the grain production rate, the slope of the grain size distribution and the start conditions (velocity, direction) of the grains. The modeled dust plume profiles are in good agreement with nanograin data of Cassini Plasma Spectrometer (CAPS). Major results are (1) due to the local plasma environment the nanograins are accelerated by the Lorentz force and form a structured tail; (2) due to the finite charging time the peak dust charge density is located about 0.3 - 0.6rE below Enceladus' south pole; (3) nanograins smaller than 10 nm are more than 99% of the produced dust; (4) CAPS data are best matched if the nanograins are launched with high, collimated start velocities; (5) the grain charging time is crucially affected by inhomogeneities in the local plasma environment.
Aouaini, F.; Knani, S.; Ben Yahia, M.; Ben Lamine, A.
2015-08-01
Water sorption isotherms of foodstuffs are very important in different areas of food science engineering such as for design, modeling and optimization of many processes. The equilibrium moisture content is an important parameter in models used to predict changes in the moisture content of a product during storage. A formulation of multilayer model with two energy levels was based on statistical physics and theoretical considerations. Thanks to the grand canonical ensemble in statistical physics. Some physicochemical parameters related to the adsorption process were introduced in the analytical model expression. The data tabulated in literature of water adsorption at different temperatures on: chickpea seeds, lentil seeds, potato and on green peppers were described applying the most popular models applied in food science. We also extend the study to the newest proposed model. It is concluded that among studied models the proposed model seems to be the best for description of data in the whole range of relative humidity. By using our model, we were able to determine the thermodynamic functions. The measurement of desorption isotherms, in particular a gas over a solid porous, allows access to the distribution of pore size PSD.
Stable Size Distribution of Amyloid Plaques Over the Course of Alzheimer Disease
Serrano-pozo, Alberto; Mielke, Matthew L.; Muzitansky, Alona; Go?mez-isla, Teresa; Growdon, John H.; Bacskai, Brian J.; Betensky, Rebecca A.; Frosch, Matthew P.; Hyman, Bradley T.
2012-01-01
Amyloid-? plaques are a key pathological feature of Alzheimer disease (AD), but whether plaque sizes increase or stabilize over the course of AD is unknown. We measured the size distribution of total immunoreactive (10D5-positive) and dense-core (Thioflavine-S-positive) plaques in the temporal neocortex of a large group of AD and plaque-bearing age-matched non-demented subjects to test the hypothesis that amyloid plaques continue to grow along with the progression of the disease. The size of...
Scale economies and optimal size in the Swiss gas distribution sector
International Nuclear Information System (INIS)
This paper studies the cost structure of Swiss gas distribution utilities. Several econometric models are applied to a panel of 26 companies over 1996–2000. Our main objective is to estimate the optimal size and scale economies of the industry and to study their possible variation with respect to network characteristics. The results indicate the presence of unexploited scale economies. However, very large companies in the sample and companies with a disproportionate mixture of output and density present an exception. Furthermore, the estimated optimal size for majority of companies in the sample has shown a value far greater than the actual size, suggesting remarkable efficiency gains by reorganization of the industry. The results also highlight the effect of customer density on optimal size. Networks with higher density or greater complexity have a lower optimal size. - highlights: • Presence of unexploited scale economies for small and medium sized companies. • Scale economies vary considerably with customer density. • Higher density or greater complexity is associated with lower optimal size. • Optimal size varies across the companies through unobserved heterogeneity. • Firms with low density can gain more from expanding firm size
Energy Technology Data Exchange (ETDEWEB)
Tu, Keng-Wu
1997-07-01
Because there is no standard method for {sup 222}Rn progeny size measurements, verifying the performance of various measurement techniques is important. This report describes results of an international intercomparison and calibration of {sup 222}Rn progeny size measurements involving low pressure impactors (MOUDI and Berner) and diffusion battery systems, as well as both alpha- and gamma- counting methods. The intercomparison was at EML on June 12-15, 1995. 5 different particle sizes (80, 90, 165, 395, 1200 nm) of near monodisperse condensation Carbauba wax aerosol and 2 bimodal size spectra (160 and 365 nm, and 70 and 400 nm) were used. 20 tests were completed, covering both low and high concentrations of {sup 222}Rn and test aerosols. For the single-mode test aerosol, the measurements agreed within the size range. Best agreement was found between the two low pressure impactors. Some differences between the impactor and diffusion battery methods were observed in the specific peak locations and the resultant geometric mean diameters. For the two bimodal size distribution aerosols, the MOUDI measurements showed two modes, while the other 3 devices showed a single mode size distribution.
Kashyap, Dheerendra; Giller, Cole A.; Liu, Hanli
2005-04-01
The ability to retrieve particle size information from back scattering reflectance with a small source-detector separation would significantly enhance the potential for development of non-invasive and minimally invasive diagnostic techniques. We present a technique for inverse determination of particle size distribution and volume fractions and validate it with polystyrene microspheres. Two of monotonic, third-degree polynomial equations were fitted from Mie theory to relate wavelength exponent 'n' and particle radii. These two equations allow us to inversely estimate the particle size from the measured 'n' value. A genetic algorithm was applied to optimize the particle size distribution and volume fraction. The experimental setup consisted of a tungsten light, CCD spectrometer with a bifurcated optical fiber for light delivery and detection. The measurement system was calibrated with a reflectance standard; different sizes and volume fractions of the suspensions were chosen for measurements. The wavelength dependence of reduced scattering coefficient was derived from the measured reflectance. Polystyrene microsphere suspensions with diameters 0.43 - 2.00 ?m were characterized using the developed algorithm. The results show a good agreement between the particle size retrieved by our algorithm and manufacturer"s data, demonstrating a robust method for particle size determination using near infrared reflectance and small source-detector separation.
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
International Nuclear Information System (INIS)
Because there is no standard method for 222Rn progeny size measurements, verifying the performance of various measurement techniques is important. This report describes results of an international intercomparison and calibration of 222Rn progeny size measurements involving low pressure impactors (MOUDI and Berner) and diffusion battery systems, as well as both alpha- and gamma- counting methods. The intercomparison was at EML on June 12-15, 1995. 5 different particle sizes (80, 90, 165, 395, 1200 nm) of near monodisperse condensation Carbauba wax aerosol and 2 bimodal size spectra (160 and 365 nm, and 70 and 400 nm) were used. 20 tests were completed, covering both low and high concentrations of 222Rn and test aerosols. For the single-mode test aerosol, the measurements agreed within the size range. Best agreement was found between the two low pressure impactors. Some differences between the impactor and diffusion battery methods were observed in the specific peak locations and the resultant geometric mean diameters. For the two bimodal size distribution aerosols, the MOUDI measurements showed two modes, while the other 3 devices showed a single mode size distribution
Dowty, James G; Byrnes, Graham B.; Gertig, Dorota M.
2013-01-01
Ductal carcinoma {\\em in situ} (DCIS) lesions are non-invasive tumours of the breast which are thought to precede most invasive breast cancers (IBC). As individual DCIS lesions are initiated, grow and invade (i.e. become IBC) the size distribution of the DCIS lesions present in a given human population will evolve. We derive a differential equation governing this evolution and show, for given assumptions about growth and invasion, that there is a unique distribution which do...
Using HBMO Algorithm to Optimal Sizing & Sitting of Distributed Generation in Power System
Noradin Ghadimi
2014-01-01
This paper analyzes of HBMO placement method efficiency in comparison with PSO and GA in order to sizing and sitting of distributed generation in distribution power system. These algorithms for optimization in this paper is tested on IEEE 33 bus reconfigured test system. The proposed objective function considers active power losses and the voltage profile in nominal load of system. In order to use of optimization algorithms, at first, placement problem is written as an optimization problem wh...
Baryonic impact on the dark matter distribution in Milky Way-size galaxies and their satellites
Zhu, Qirong; Marinacci, Federico; Maji, Moupiya; Li, Yuexing; Springel, Volker; Hernquist, Lars
2015-01-01
We study the impact of baryons on the distribution of dark matter in a Milky Way-size halo by comparing a high-resolution, moving-mesh cosmological simulation with its dark matter-only counterpart. We identify three main processes related to baryons -- adiabatic contraction, tidal disruption and reionization -- which jointly shape the dark matter distribution in both the main halo and its subhalos. The relative effect of each baryonic process depends strongly on the subhalo ...
Precipitation classification at mid-latitudes in terms of drop size distribution parameters
Caracciolo, C.; Porcù, F.; Prodi, F.
2008-01-01
The drop size distribution (DSD) is a fundamental property of rainfall because the shape of the distribution reflects the physics of rain formation processes. Given the lack of studies on the DSD at mid-latitudes, the present work focuses on the microphysical characterization of precipitation events occurring in Italy, using two different types of disdrometer. A large number of different rain events was collected: they underwent microphysical analysis by computing the Z-R relationships, obser...
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.)
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
Starch was isolated from 98 hard red winter (HRW) wheat and 99 hard red spring (HRS) wheat. Granule size/volume distributions of the isolated starches were analyzed using a laser diffraction particle size analyzer. There were significant differences in the size distribution between HRW and HRS whe...
Factors determining the most efficient spray size distribution for marine cloud brightening
Wood, R.; Connolly, P.; McFiggans, G.
2014-12-01
We investigate the sensitivity of marine cloud brightening geoengineering to the properties of the added salt particle distribution using a cloud parcel model, with an aim to address the question: what is the most efficient particle size distribution to produce a desired cooling effect?. We investigate this by using a parcel model with different configurations of salt spray size distribution to assess the approximate power required to generate an albedo increase sufficient to approximately offset a doubling of carbon dioxide. Our findings show that this question depends on the spray generation method employed. We find that for all three methods of spray generation investigated (supercritical fluid, Taylor cone, and Rayleigh jet), distributions of salt particles with median dry diameters in the range Dm = 30 to 100 nm are the are the most effective in terms of brightening per power consumed in generating the particles. Size distributions that resemble the present day emitted sea-spray distribution are not particularly efficient for brightening clouds. The Rayleigh jet method is found to be the most energy efficient method when compared to the supercritical fluid and Taylor cone-jet method. We also find that care needs to be taken when using droplet activation parameterizations: for the concentrations considered Aitken particles do not result in a decrease in the total albedo, as was found in a recent study, and such findings are likely a result of the parameterization's inability to simulate the effect of swollen aerosol.
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.
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.
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.
Chun-Yang Yin; Muhammad Afiq Aizuddin Musa; Robert Mikhail Savory
2011-01-01
Analysis of the textural characteristics and pore size distribution of a commercial zeolite (Sigma Aldrich, product No. 96096) have been conducted experimentally using a surface analyzer by measuring the N2 adsorption isotherm at 77 K. The resulting data were fitted to several well-known adsorption models, i.e., the Brunauer-Emmett-Teller (BET) model, the de Boer model, the Dubinin-Redushkevich (DR) model, the Barret, -Joyner-Halenda (BJH) model, the Horvath-Kawazoe (HK) model and the Density...
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).
Directory of Open Access Journals (Sweden)
T. S. Kostadinov
2010-10-01
Full Text Available 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 global scales assumes that the open ocean particulate assemblage is biogenic. The retrieved PSD's can be integrated to define three size-based PFT's by the percent volume concentration contribution of three phytoplankton size classes – picoplankton (0.5–2 ?m in equivalent spherical diameter, nanoplankton (2–20 ?m and microplankton (20–50 ?m. Validation with in-situ HPLC diagnostic pigments resulted in better match-ups for the pico- and micro-phytoplankton size classes as compared to nanoplankton. Global decadal averages derived from SeaWiFS monthly data reveal PFT and particle abundance spatial patterns that are consistent with current understanding. Oligotrophic gyres are characterized by lower particle abundance and higher contribution by picoplankton-sized particles than transitional or eutrophic regions. Seasonal succession patterns for size-based PFT's reveal good correspondence between increasing chlorophyll concentration and percent contribution by microplankton, as well as increasing particle abundance. Long-term trends in particle abundances are generally well correlated with the MEI index indicating increased oligotrophy (i.e. lower particle abundance and increased contribution of picoplankton-sized particles during the warm phase of an El Niño event. This work demonstrates the utility and future potential of assessing phytoplankton functional types using remote characterization of the particle size distribution.
Directory of Open Access Journals (Sweden)
T. S. Kostadinov
2010-06-01
Full Text Available 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 global scales assumes that the open ocean particulate assemblage is biogenic. The retrieved PSD's can be integrated to define three size-based PFT's by the percent volume concentration contribution of three phytoplankton size classes – picoplankton (0.5–2 ?m in equivalent spherical diameter, nanoplankton (2–20 ?m and microplankton (20–50 ?m. Validation with in-situ HPLC diagnostic pigments results in satisfactory match-ups for the pico- and micro-phytoplankton size classes. Global climatologies derived from SeaWiFS monthly data reveal PFT and particle abundance spatial patterns that are consistent with current understanding. Oligotrophic gyres are characterized by lower particle abundance and higher contribution by picoplankton-sized particles than transitional or eutrophic regions. Seasonal succession patterns for size-based PFT's reveal good correspondence between increasing chl and percent contribution by microplankton, as well as increasing particle abundance. Long-term trends in particle abundances are generally inconclusive yet are well correlated with the MEI index indicating increased oligotrophy (i.e. lower particle abundance and increased contribution of picoplankton-sized particles during the warm phase of an El Niño event. This work demonstrates the utility and future potential of assessing phytoplankton functional types using remote characterization of the particle size distribution.
The uniqueness of company size distribution function from tent-shaped growth rate distribution
Ishikawa, A
2007-01-01
We report the proof that the extension of Gibrat's law in the middle scale region is unique and the probability distribution function (pdf) is also uniquely derived from the extended Gibrat's law and the law of detailed balance. In the proof, two approximations are employed. The pdf of growth rate is described as tent-shaped exponential functions and the value of the origin of the growth rate distribution is constant. These approximations are confirmed in profits data of Japanese companies 2003 and 2004. The resultant profits pdf fits with the empirical data with high accuracy. This guarantees the validity of the approximations.
Particle Sampling and Real Time Size Distribution Measurement in H2/O2/TEOS Diffusion Flame
International Nuclear Information System (INIS)
Growth characteristics of silica particles have been studied experimentally using in situ particle sampling technique from H2/O2/Tetraethylorthosilicate (TEOS) diffusion flame with carefully devised sampling probe. The particle morphology and the size comparisons are made between the particles sampled by the local thermophoretic method from the inside of the flame and by the electrostatic collector sampling method after the dilution sampling probe. The Transmission Electron Microscope (TEM) image processed data of these two sampling techniques are compared with Scanning Mobility Particle Sizer (SMPS) measurement. TEM image analysis of two sampling methods showed a good agreement with SMPS measurement. The effects of flame conditions and TEOS flow rates on silica particle size distributions are also investigated using the new particle dilution sampling probe. It is found that the particle size distribution characteristics and morphology are mostly governed by the coagulation process and sintering process in the flame. As the flame temperature increases, the effect of coalescence or sintering becomes an important particle growth mechanism which reduces the coagulation process. However, if the flame temperature is not high enough to sinter the aggregated particles then the coagulation process is a dominant particle growth mechanism. In a certain flame condition a secondary particle formation is observed which results in a bimodal particle size distrh results in a bimodal particle size distribution
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.
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.
Finite-size scaling analysis of the distributions of pseudo-critical temperatures in spin glasses
International Nuclear Information System (INIS)
Using the results of large scale numerical simulations we study the probability distribution of the pseudo-critical temperature for the three-dimensional Edwards–Anderson Ising spin glass and for the fully connected Sherrington–Kirkpatrick model. We find that the behaviour of our data is nicely described by straightforward finite-size scaling relations
Topological susceptibility and Instanton size distribution from over-improved cooling
Forcrand, Philippe de; Kim, Seyong
1995-01-01
We measure the topological susceptibility by cooling with an over-improved action. In contrast with usual cooling, large instantons survive over-improved cooling {\\em indefinitely}. By varying the parameter of the over-improved cooling action, we measure the instanton size distribution.
Atmospheric Aerosols in Suburb of Prague: The Dynamics of Particle Size Distributions.
Czech Academy of Sciences Publication Activity Database
?imná?ová, Daniela; Ždímal, Vladimír; Schwarz, Jaroslav; Smolík, Ji?í; ?imná?, Martin
2011-01-01
Ro?. 101, ?. 3 (2011), s. 539-552. ISSN 0169-8095 Grant ostatní: MF NF(CZ) CZ0049 Institutional research plan: CEZ:AV0Z40720504; CEZ:AV0Z10300504 Keywords : atmospheric aerosols * atmospheric nucleation * part size distribution Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 1.911, year: 2011
Effect of a RF Wave on Ion Cyclotron Instability in Size Distributed Impurities Containing Plasmas
International Nuclear Information System (INIS)
The effect of a large amplitude lower hybrid wave on current driven ion cyclotron waves in a dusty plasma where dust grains are size distributed is examined. The influence of the lower hybrid wave on the stabilization of the instability is studied. The efficacy of rf is dust density dependent.
Air Mass Back Trajectories and Dry Atmospheric Aerosol Mass Size Distributions in Prague.
Czech Academy of Sciences Publication Activity Database
Schwarz, Jaroslav; Štefancová, Lucia; Maenhaut, W.; Smolík, Ji?í; Ždímal, Vladimír
Prague : Czech Aerosol Society, 2013, A228. ISBN N. [European Aerosol Conference (EAC 2013). Prague (CZ), 01.09.2013-06.09.2013] R&D Projects: GA ?R GAP209/11/1342 Institutional support: RVO:67985858 Keywords : mass size distribution * air mass back trajectories * water soluble ions Subject RIV: CF - Physical ; Theoretical Chemistry http://eac2013.cz/index.php
Czech Academy of Sciences Publication Activity Database
Zíková, Nad?žda; Wagner, Zden?k; Schwarz, Jaroslav; Smolík, Ji?í; Ždímal, Vladimír
Helsinky : -, 2010, s. 1-3. ISBN N. [EUCAARI Annual Meeting. Helsinki (FI), 22.11.2010-26.11.2010] Grant ostatní: EUCAARI(XE) 036833-2; UECAARI(XE) SVV-2010-261308 Institutional research plan: CEZ:AV0Z40720504 Keywords : atmospheric aerosol * particle size distributions * gaseous pollutants Subject RIV: CF - Physical ; Theoretical Chemistry
Size-distribution of airborne radioactive particles from the Fukushima accident
International Nuclear Information System (INIS)
The particle size distribution of radioactive aerosols has been observed using the Andersen-type classifier combined with a high volume air sampler. Estimated AMADs of 131I-, 134Cs- and 137Cs-aerosols were ranging from 0.56 to 0.60 ?m, which were larger than that of 7Be-aerosols, about 0.2 ?m. (author)
Retrieval of multimodal aerosol size distribution by inversion of multiwavelength data
Bo?ckmann, Christine; Biele, Jens; Neuber, Roland; Niebsch, Jenny
1997-01-01
The ill-posed problem of aerosol size distribution determination from a small number of backscatter and extinction measurements was solved successfully with a mollifier method which is advantageous since the ill-posed part is performed on exactly given quantities, the points r where n(r) is evaluated may be freely selected. A new twodimensional model for the troposphere is proposed.
Fabrication of silver nanoparticles with limited size distribution on TiO2 containing zeolites.
Mazzocut, Andrea; Coutino-Gonzalez, Eduardo; Baekelant, Wouter; Sels, Bert; Hofkens, Johan; Vosch, Tom
2014-09-21
Here we present a simple route to produce well-defined photo-reduced silver nanoparticles on TiO2 containing zeolites. We used natural and artificial irradiation sources to study their effect on the particle size distribution. The samples were investigated by electron microscopy, X-ray diffraction, fluorescence microscopy and UV-Vis diffuse reflectance spectroscopy. PMID:25083739
Seif, Dariush; Ghoniem, Nasr M.
2014-12-01
A rate theory model based on the theory of nonlinear stochastic differential equations (SDEs) is developed to estimate the time-dependent size distribution of helium bubbles in metals under irradiation. Using approaches derived from Itô's calculus, rate equations for the first five moments of the size distribution in helium-vacancy space are derived, accounting for the stochastic nature of the atomic processes involved. In the first iteration of the model, the distribution is represented as a bivariate Gaussian distribution. The spread of the distribution about the mean is obtained by white-noise terms in the second-order moments, driven by fluctuations in the general absorption and emission of point defects by bubbles, and fluctuations stemming from collision cascades. This statistical model for the reconstruction of the distribution by its moments is coupled to a previously developed reduced-set, mean-field, rate theory model. As an illustrative case study, the model is applied to a tungsten plasma facing component under irradiation. Our findings highlight the important role of stochastic atomic fluctuations on the evolution of helium-vacancy cluster size distributions. It is found that when the average bubble size is small (at low dpa levels), the relative spread of the distribution is large and average bubble pressures may be very large. As bubbles begin to grow in size, average bubble pressures decrease, and stochastic fluctuations have a lessened effect. The distribution becomes tighter as it evolves in time, corresponding to a more uniform bubble population. The model is formulated in a general way, capable of including point defect drift due to internal temperature and/or stress gradients. These arise during pulsed irradiation, and also during steady irradiation as a result of externally applied or internally generated non-homogeneous stress fields. Discussion is given into how the model can be extended to include full spatial resolution and how the implementation of a path-integral approach may proceed if the distribution is known experimentally to significantly stray from a Gaussian description.
Martin, A. P.; Srokosz, M. A.
2002-12-01
Transects of a region of the North Atlantic, conducted in spring 1997, provide simultaneous measurements of a number of biophysical variables. These data are used to quantify the degree of spatial heterogeneity in the horizontal distributions of zooplankton, phytoplankton and potential temperature. More specifically, the spectral slope is calculated for the distribution of chlorophyll a, potential temperature and individual size-classes of zooplankton. A comparison of the estimated slopes provides the first evidence, from continuous measurements, that the gradient of zooplankton spectra may vary according to the size of the organism and, furthermore, that it may be steeper than that for phytoplankton both as an individual size class (500-1000 ?m) and as an ensemble (250-2000 ?m). The latter result is the exact opposite of conventional wisdom founded on previous observations. Our results highlight significant deficiencies in current models for plankton patchiness.
A new method for measurement of droplet size distribution in superheated emulsions
International Nuclear Information System (INIS)
Superheated emulsion contains micron-sized superheated liquid droplets suspended in a host liquid medium. The superheated droplets nucleate to vapor bubbles when energetic radiation deposits a sufficient amount of energy within a very small localized region of the active liquid. Droplet nucleation is associated with a change in volume and also emission of an acoustic pulse, both of which can be detected electronically. When exposed to energetic radiation, the metastable superheated droplets nucleate independently of each other, and the number of drops nucleated and volume of vapor formed due to nucleation of these droplets are both acquired simultaneously as a function of time. These two data are then fitted simultaneously to obtain the droplet size distribution of the emulsion. The size distributions of R-114 (C2Cl2F4)- and R-12 (CCl2F2)-based emulsions are obtained by this method and compared with direct optical measurements
Size effects on void growth in single crystals with distributed voids
DEFF Research Database (Denmark)
Borg, Ulrik; Niordson, Christian Frithiof
2008-01-01
The effect of void size on void growth in single crystals with uniformly distributed cylindrical voids is studied numerically using a finite deformation strain gradient crystal plasticity theory with an intrinsic length parameter. A plane strain cell model is analyzed for a single crystal with three in-plane slip systems. It is observed that small voids allow much larger overall stress levels than larger voids for all the stress triaxialities considered. The amount of void growth is found to be suppressed for smaller voids at low stress triaxialities. Significant differences are observed in the distribution of slips and on the shape of the deformed voids for different void sizes. Furthermore, the orientation of the crystalline lattice is found to have a pronounced effect on the results, especially for the smaller void sizes.
Kashani, Alireza; Provis, John L.; van Deventer, Jannie S. J.
2013-06-01
Ground granulated blast furnace slag is widely combined with Portland cement as a supplementary material, and is also used in alkali-activated binders (geopolymers) and in supersulfated cements, which are potential replacements for Portland cement with significantly reduced carbon dioxide emissions. The rheology of a cementitious material is important in terms of its influence on workability, especially in self leveling concretes. The current research investigates the effects of different particle size distributions of slag particles on paste rheology. Rheological measurements results show a direct relationship between the modal particle size and the yield stress of the paste. An empirical model is introduced to calculate the yield stress value of each paste based on the particle size distribution, and applied to a range of systems at single water to solids ratio. The model gives a very good match with the experimental data.
DEFF Research Database (Denmark)
Liu, Hong-Sheng; Mishnaevsky, Leon
2013-01-01
A computational model of martensitic phase transformation in nanostructured nitinol is developed which takes into account the grain size effect. On the basis of the theoretical analysis of the thermodynamic transformation criterion and the energy barrier for phase transformation, it was demonstrated that the energy barrier for martensitic phase transformation in nanocrystalline nitinol increase drastically with decreasing the grain size. Finite element simulations of phase transformations and structure evolution in nanocrystalline nitinol under mechanical (tensile) loading are carried out for different structures of the materials. It was observed that the volume content of martensitic phase decreases drastically with reducing the grain size. When the grain size is smaller than some critical value (around 50–80nm, both in our simulations and in experimental data), the martensitic phase transformation are totally suppressed. Graded and localized distributions of grain sizes of nitinol were compared with nitinolsamples with homogeneous grain size distribution. In the materials with localized region of small grains, it was observed that the martensite rich regions form first on the border between the coarse and fine grained regions, and expand inside the region with small grains along the shear band direction.
Energy Technology Data Exchange (ETDEWEB)
Felix, V.; Jannot, Y.; Degiovanni, A. [LEMTA, Nancy-Universite, CNRS, 2, avenue de la Foret de Haye, BP160, 54504 Vandoeuvre Cedex (France)
2012-05-15
Standard pore size determination methods such as mercury porosimetry, nitrogen sorption, microscopy, or x-ray tomography are not always applicable to highly porous, low density, and thus very fragile materials. For this kind of materials, a method based on thermal characterization is proposed. Indeed, the thermal conductivity of a highly porous and insulating medium is significantly dependent on the thermal conductivity of the interstitial gas that depends on both gas pressure and size of the considered pore (Knudsen effect). It is also possible to link the pore size with the thermal conductivity of the medium. Thermal conductivity measurements are realized on specimens placed in an enclosure where the air pressure is successively set to different values varying from 10{sup -1} to 10{sup 5} Pa. Knowing the global porosity ratio, an effective thermal conductivity model for a two-phase air-solid material based on a combined serial-parallel model is established. Pore size distribution can be identified by minimizing the sum of the quadratic differences between measured values and modeled ones. The results of the estimation process are the volume fractions of the chosen ranges of pore size. In order to validate the method, measurements done on insulating materials are presented. The results are discussed and show that pore size distribution estimated by the proposed method is coherent.
Directory of Open Access Journals (Sweden)
M. Krudysz
2008-05-01
Full Text Available Ultrafine particle (UFP number concentrations vary significantly on small spatial and temporal scales due to their short atmospheric lifetimes and multiplicity of sources. To determine UFP exposure gradients within a community, simultaneous particle number concentration measurements at a network of sites are necessary. Concurrent particle size distribution measurements aid in identifying UFP sources, while providing data to investigate local scale effects of both photochemical and physical processes on UFP. From April to December 2007, we monitored particle size distributions at 13 sites within 350 m to 11 km of each other in the vicinity of the Ports of Los Angeles and Long Beach using Scanning Mobility Particle Sizers (SMPS. Typically, three SMPS units were simultaneously deployed and rotated among sites at 1–2 week intervals. Total particle number concentration measurements were conducted continuously at all sites. Seasonal and diurnal size distribution patterns are complex, highly dependent on local meteorology, nearby PM sources, and times of day, and cannot be generalized over the study area nor inferred from one or two sampling locations. Spatial variation in particle number size distributions was assessed by calculating the coefficient of divergence (COD and correlation coefficients (r between site pairs. Results show an overall inverse relationship between particle size and CODs, implying that number concentrations of smaller particles (<40 nm differ from site to site, whereas larger particles tend to have similar concentrations at various sampling locations. In addition, variations in r values as a function of particle size are not necessarily consistent with corresponding COD values, indicating that using results from correlation analysis alone may not accurately assess spatial variability.
Seasonal cycle and modal structure of particle number size distribution at Dome C, Antarctica
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E. Järvinen
2013-08-01
Full Text Available We studied new particle formation and modal behavior of ultrafine aerosol particles on the high East Antarctic plateau at the Concordia station, Dome C (75°06' S, 123°23' E. Aerosol particle number size distributions were measured in the size range 10–600 nm from 14 December 2007 to 7 November 2009. We used an automatic algorithm for fitting up to three modes to the size distribution data. The total particle number concentration was low with the median of 109 cm?3. There was a clear seasonal cycle in the total particle number and the volume concentrations. The concentrations were at their highest during the austral summer with the median values of 260 cm?3 and 0.086 ?m3 cm?3, and at their lowest during the austral winter with corresponding values of 15 cm?3 and 0.009 ?m3 cm?3. New particle formation events were determined from the size distribution data. During the measurement period, natural new particle formation was observed on 60 days and for 15 of these days the particle growth rates from 10 to 25 nm in size could be determined. The median particle growth rate during all these events was 2.5 nm h?1 and the median formation rate of 10 nm particles was 0.023 cm?3 s?1. Most of the events were similar to those observed at other continental locations, yet also some variability in event types was observed. Exceptional features in Dome C were the winter events that occurred during dark periods, as well as the events for which the growth could be followed during several consecutive days. We called these latter events slowly growing events. This paper is the first one to analyze long-term size distribution data from Dome C, and also the first paper to show that new particle formation events occur in central Antarctica.
Seasonal cycle and modal structure of particle number size distribution at Dome C, Antarctica
Directory of Open Access Journals (Sweden)
E. Järvinen
2013-03-01
Full Text Available We studied new particle formation and modal behavior of ultrafine aerosol particles on the high Antarctic East-Plateau at the Concordia station, Dome C (75°06' S, 123°23' E. Aerosol particle number size distributions were measured in the size range 10–600 nm from 14 December 2007 to 7 November 2009. We used an automatic algorithm for fitting up to three modes to the size distribution data. The total particle number concentration was low with the median of 109 cm?3. There was a clear seasonal cycle in the total particle number and the volume concentrations. The concentrations were at their highest during the austral summer with the median values of 260 cm?3 and 0.086 ?m3 cm?3, and at their lowest during the austral winter with corresponding values of 15 cm?3 and 0.009 ?m3 cm?3. New particle formation events were determined from the size distribution data. During the measurement period, new particle formation was seen on 80 days and for 15 of these days the particle growth rates from 10 to 25 nm size could be determined. The median particle growth rate during all these events was 2.5 nm h?1 and the median formation rate of 10 nm particles was 0.023 cm?3 s?1. Most of the events were similar to those observed in other continental locations, yet also some variability in event types was observed. Exceptional features in Dome C were the winter events that occurred during dark periods, as well as the events for which the growth could be followed during several consecutive days. We called these latter events as slowly-growing events. This paper is the first one to analyze long-term size distribution data from Dome C, and also the first paper to show that new particle formation events occur in the central Antarctica.
Using diffusion measurements to determine pore-size distributions in porous materials
Energy Technology Data Exchange (ETDEWEB)
Brown, L.F.; Travis, B.J.
1980-01-01
A method for determining pore-size distrbutions from diffusion measurements is presented. A Wicke-Kallenbach experiment, for measuring diffusion fluxes within porous materials, was carried out over a significant portion of the transition range between Knudsen flow and bulk diffusion. If the internal porous structure of the material is modeled as myriad nonintersecting cylindrical pores, an equation may be derived for the flux as a function of pressure, in which the flux is a functional of the pore-size distribution. The equation is a Fredholm integral equation of the first kind. This is an application of the general inversion problem, and solution of the equation for the pore-size distribution is possible. It is demonstrated from calculated fluxes using postulated ideal distributions that the method works very well for both unimodal and bimodal distributions. The method is no extraordinarily sensitivire to experimental error. An example of a distribution obtained from a commercial porous catalyst is presented and compared with that obtained by mercury porosimetry.
Distributed production planning and control agent based system
Rui M Lima; Rui M Sousa; Martins, Paulo Jorge de Figueiredo
2005-01-01
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...
Determination of pore size distribution at the cell-hydrogel interface
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Nowicki Marcin
2011-05-01
Full Text Available Abstract Background Analyses of the pore size distribution in 3D matrices such as the cell-hydrogel interface are very useful when studying changes and modifications produced as a result of cellular growth and proliferation within the matrix, as pore size distribution plays an important role in the signaling and microenvironment stimuli imparted to the cells. However, the majority of the methods for the assessment of the porosity in biomaterials are not suitable to give quantitative information about the textural properties of these nano-interfaces. Findings Here, we report a methodology for determining pore size distribution at the cell-hydrogel interface, and the depth of the matrix modified by cell growth by entrapped HepG2 cells in microcapsules made of 0.8% and 1.4% w/v alginate. The method is based on the estimation of the shortest distance between two points of the fibril-like network hydrogel structures using image analysis of TEM pictures. Values of pore size distribution determined using the presented method and those obtained by nitrogen physisorption measurements were compared, showing good agreement. A combination of these methodologies and a study of the cell-hydrogel interface at various cell culture times showed that after three days of culture, HepG2 cells growing in hydrogels composed of 0.8% w/v alginate had more coarse of pores at depths up to 40 nm inwards (a phenomenon most notable in the first 20 nm from the interface. This coarsening phenomenon was weakly observed in the case of cells cultured in hydrogels composed of 1.4% w/v alginate. Conclusions The method purposed in this paper allows us to obtain information about the radial deformation of the hydrogel matrix due to cell growth, and the consequent modification of the pore size distribution pattern surrounding the cells, which are extremely important for a wide spectrum of biotechnological, pharmaceutical and biomedical applications.
Size distribution of submarine landslides and its implication to tsunami hazard in Puerto Rico
ten Brink, Uri S.; Geist, Eric L.; Andrews, Brian D.
2006-06-01
We have established for the first time a size frequency distribution for carbonate submarine slope failures. Using detailed bathymetry along the northern edge of the carbonate platform north of Puerto Rico, we show that the cumulative distribution of slope failure volumes follows a power-law distribution. The power-law exponent of this distribution is similar to those for rock falls on land, commensurate with their interpreted failure mode. The carbonate volume distribution and its associated volume-area relationship are significantly different from those for clay-rich debris lobes in the Storegga slide, Norway. Coupling this relationship with tsunami simulations allows an estimate of the maximum tsunami runup and the maximum number of potentially damaging tsunamis from landslides to the north shore of Puerto Rico.
On the size distribution functions and their application in regolith studies
Deb, Dwaipayan
2015-01-01
The knowledge of particle size distribution (PSD) of regolith surfaces on terrestrial planets, their satellites and minor bodies, has an important role in the field of remote sensing and the study of regolith evolution. Various mathematical distribution functions (dfs) which are currently in use to describe regolith PSD, have been compared on the basis of their best fitting with terrestrial and lunar samples. The correspondences of parameters of the dfs with known physical characteristics of the samples have also been analyzed so that a distribution function suitable for practical applications can be obtained. Rosin's distribution comes out to be one which can be fitted to both terrestrial and lunar samples with confidence (LSSE/data < 0.003), and also numerically obtained physical parameters from the distribution are close to the sample values (errors < 10% on average).
Directory of Open Access Journals (Sweden)
S. Pfeifer
2013-05-01
Full Text Available Multiple charge inversion is an essential procedure to convert the raw mobility distributions recorded by mobility particle size spectrometers, such as the DMPS or SMPS (Differential or Scanning Mobility Particle Sizers into true particle number size distributions. In this work, we present a new multiple charge inversion algorithm with extended functionality. The algorithm can incorporate size distribution information from sensors that measure beyond the upper sizing limit of the mobility spectrometer, such as an aerodynamic particle sizer (APS, or an optical particle counter (OPC. This feature can considerably improve the multiple charge inversion result in the upper size range of the mobility spectrometer, for example, when substantial numbers of coarse particles are present. The program also yields a continuous size distribution from both sensors as an output. The algorithm is able to calculate the propagation of measurement errors, such as those based on counting statistics, into on the final particle number size distribution. As an additional aspect, the algorithm can perform all inversion steps under the assumption of non-spherical particle shape, including constant or size-dependent shape factor profiles.
A collaborative ant colony metaheuristic for distributed multi-level lot-sizing
Buer, Tobias; Gehring, Hermann
2012-01-01
The paper presents an ant colony optimization metaheuristic for collaborative planning. Collaborative planning is used to coordinate individual plans of self-interested decision makers with private information in order to increase the overall benefit of the coalition. The method consists of a new search graph based on encoded solutions. Distributed and private information is integrated via voting mechanisms and via a simple but effective collaborative local search procedure. The approach is applied to a distributed variant of the multi-level lot-sizing problem and evaluated by means of 352 benchmark instances from the literature. The proposed approach clearly outperforms existing approaches on the sets of medium and large sized instances. While the best method in the literature so far achieves an average deviation from the best known non-distributed solutions of 46 percent for the set of the largest instances, for example, the presented approach reduces the average deviation to only 5 percent.
Sample size for estimating the quantiles of endothelial cell-area distribution.
Garsd, A; Ford, G E; Waring, G O; Rosenblatt, L S
1983-06-01
The estimation of corneal endothelium mean cell area (and, hence, mean cell density) is an important problem in clinical ophthalmology. Mitotic division of these cells is not known to occur, and cell deaths are followed by the enlargement of adjacent cells. As a consequence, cell-area distributions change drastically as functions of age and disease. Changes in cell-area distributions, in particular multimodality and skewness due to aging, are observed, and give rise to some difficult sampling problems. In this paper, sample quantiles are investigated as an alternative to the use of the sample mean. Asymptotic approximations are provided for the sample sizes required to estimate population quantiles with a desired precision. Asymptotic sample sizes are then compared with those obtained from tolerance limits. Empirical sample quantiles that can be used as benchmarks to compare corneas of normal individuals against corneas with unknown cell-area distributions are also presented. Aspects that merit further investigation are noted. PMID:6354288
Theoretical size distribution of fossil taxa: analysis of a null model
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Hughes Barry D
2007-03-01
Full Text Available Abstract Background This article deals with the theoretical size distribution (of number of sub-taxa of a fossil taxon arising from a simple null model of macroevolution. Model New species arise through speciations occurring independently and at random at a fixed probability rate, while extinctions either occur independently and at random (background extinctions or cataclysmically. In addition new genera are assumed to arise through speciations of a very radical nature, again assumed to occur independently and at random at a fixed probability rate. Conclusion The size distributions of the pioneering genus (following a cataclysm and of derived genera are determined. Also the distribution of the number of genera is considered along with a comparison of the probability of a monospecific genus with that of a monogeneric family.
Carney, Randy P.
2011-06-07
Nanoparticles are finding many research and industrial applications, yet their characterization remains a challenge. Their cores are often polydisperse and coated by a stabilizing shell that varies in size and composition. No single technique can characterize both the size distribution and the nature of the shell. Advances in analytical ultracentrifugation allow for the extraction of the sedimentation (s) and diffusion coefficients (D). Here we report an approach to transform the s and D distributions of nanoparticles in solution into precise molecular weight (M), density (?P) and particle diameter (dp) distributions. M for mixtures of discrete nanocrystals is found within 4% of the known quantities. The accuracy and the density information we achieve on nanoparticles are unparalleled. A single experimental run is sufficient for full nanoparticle characterization, without the need for standards or other auxiliary measurements. We believe that our method is of general applicability and we discuss its limitations. 2011 Macmillan Publishers Limited. All rights reserved.
DEFF Research Database (Denmark)
Grunow, Martin; Rong, Aiying
2008-01-01
After a number of food safety crises, the design and implementation of traceability systems became an important focus of the food industry. As a result, food product traceability ranks high on senior management agendas for supply chain activities. In the literature, numerous studies deal with traceability from the viewpoint of information system development and technology development such as radio frequency identification (RFID) and DNA-based techniques. However, traceability and its implications for food safety are thus far not incorporated in the standard operations management literature on production and distribution planning. Here, we develop a methodology for production and distribution planning in food supply chains which minimizes production and logistics costs and at the same time reduces food safety concerns, limits the size of potential recalls, and satisfies product quality requirements throughout the supply chain. We also demonstrate the effectiveness of the methodology using a small case study.
MinSORTING: an Excel macro for modelling sediment composition and grain-size distribution
Resentini, Alberto; Malusà, Marco G.; Garzanti, Eduardo
2013-04-01
Detrital mineral analyses are gaining increasing attention in the geosciences as new single-grain analytical techniques are constantly improving their resolution, and consequently widening their range of application, including sedimentary petrology, tectonic geomorphology and archaeology (Mange and Wright, 2007; von Eynatten and Dunkl, 2012). We present here MinSORTING, a new tool to quickly predict the size distribution of various minerals and rock fragments in detrital sediments, based on the physical laws that control sedimentation by tractive wind or water currents (Garzanti et al., 2008). The input values requested by the software are the sediment mean size, sorting, fluid type (seawater, freshwater, air) and standard sediment composition chosen from a given array including nine diverse tectonic settings. MinSORTING calculates the bulk sediment density and the settling velocity. The mean size of each single detrital component, assumed as lognormally-distributed, is calculated from its characteristic size-shift with respect to bulk sediment mean size, dependent in turn on its density and shape. The final output of MinSORTING is the distribution of each single detrital mineral in each size classes (at the chosen 0.25, 0.5 or 1 phi intervals). This allows geochronolgists to select the most suitable grain size of sediment to be sampled in the field, as well as the most representative size-window for analysis. Also, MinSORTING provides an estimate of the volume/weight of the fractions not considered in both sizes finer and coarser than the selected size-window. A beta version of the software is available upon request from: alberto.resentini@unimib.it Mange, M., and Wright, D. (eds), 2007. Heavy minerals in use. Developments in Sedimentology Series, 58. Elsevier, Amsterdam. Garzanti, E., Andò, S., Vezzoli, G., 2008. Settling-equivalence of detrital minerals and grain-size dependence of sediment composition. Earth and Planetary Science Letters 273, 138-151. von Eynatten, H., and Dunkl, I., 2012. Assessing the sediment factory: The role of single grain analysis. Earth Sciences Reviews, 115, 97-120.
Directory of Open Access Journals (Sweden)
Hisham S. Alshiyab
2009-01-01
Full Text Available Problem statement: One of the main factors influenced the bacterial productivity and total yield of hydrogen is the partial pressure of produced gas. A novel solution to enhance the bacterial productivity was through reduction of gas pressure. Approach: Increasing the reactor size showed to enhance the bacterial production of hydrogen. Results: The technique of increasing reactor size resulted to enhance the hydrogen yield (YP/S from 269 mL g-1 glucose utilized to maximum yield of 448 mL g-1 glucose utilized by using 125 mL and 2 L reactor size respectively. The hydrogen productivity was also enhanced from 71 mL-1 h-1 to maximum of 91 mL L-1 h-1 was obtained by using 125 mL and 1 L reactor size respectively. Biomass concentration was enhanced from 1.03 g L-1 to maximum of 1.68 g L-1 by using 125 mL and 2 L reactor size were used respectively, hydrogen yield per biomass (YP/X of 267 mL g-1 L-1, biomass per substrate utilized (YX/S of 0.336 and produced hydrogen in gram per gram of glucose utilized (YH2/s of 0.04 when 2 L reactor size was employed. Conclusion: By using bigger reactor size, the effect of gaseous products in fermentation medium was reduced and enhanced both bacterial productivity and biomass concentration.
Energy Technology Data Exchange (ETDEWEB)
Majid, Z.A.; Mahmud, H.; Shaaban, M.G.
1996-12-31
Stabilization/solidification of hazardous wastes is used to convert hazardous metal hydroxide waste sludge into a solid mass with better handling properties. This study investigated the pore size development of ordinary portland cement pastes containing metal hydroxide waste sludge and rice husk ash using mercury intrusion porosimetry. The effects of acre and the addition of rice husk ash on pore size development and strength were studied. It was found that the pore structures of mixes changed significantly with curing acre. The pore size shifted from 1,204 to 324 {angstrom} for 3-day old cement paste, and from 956 to 263 {angstrom} for a 7-day old sample. A reduction in pore size distribution for different curing ages was also observed in the other mixtures. From this limited study, no conclusion could be made as to any correlation between strength development and porosity. 10 refs., 6 figs., 3 tabs.
Size distribution of planktonic autotrophy and microheterotrophy in DeGray Reservoir, Arkansas
International Nuclear Information System (INIS)
Naturally occurring assemblages of phytoplankton and bacterioplankton were radiolabelled with sodium 14C-bicarbonate and sodium 3H-acetate and size fractionated to determine the size structure of planktonic autotrophy and microheterotrophy in DeGray Reservoir, an oligotrophic impoundment of the Caddo River in south-central Arkansas. Size distributions of autotrophy and microheterotrophy were remarkably uniform seasonally, vertically within the water column, and along the longitudinal axis of the reservoir despite significant changes in environmental conditions. Planktonic autotrophy was dominated by small algal cells with usually >50% of the photosynthetic carbon uptake accounted for by organisms 75% of the planktonic microheterotrophy. Longitudinal patterns in autotrophic and microheterotrophic activities associated with >3-?m and >1-?m size fractions, respectively, suggest an uplake to downlake shift from riverine to lacustrine environmental influences within the reservoir. 83 references, 7 figures
Tailoring the size and distribution of Ag nanoparticles in silica glass by defects
Energy Technology Data Exchange (ETDEWEB)
Yang, Yitao, E-mail: yangyt@impcas.ac.cn [Materials Research Center, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Zhang, Chonghong; Song, Yin; Gou, Jie; Zhang, Liqing [Materials Research Center, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Zhang, Hengqing; Liu, Juan; Xian, Yongqiang [Materials Research Center, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Ma, Yizhun [Materials Research Center, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China)
2014-02-15
The composites embedded with metallic nanoparticles show large nonlinear optical susceptibility and strong surface plasmon resonance absorption, which enable potential application in opto-electronics. Ion implantation has been proven to be a powerful technique of synthesis of metallic nanoparticles due to its versatility and compatibility. However, the synthesis of nanoparticles by ion implantation inevitably leads to a broad size distribution due to Ostwald ripening process. The broad size distribution has a negative effect on improving the figure of merits for nonlinear optics. In this paper, we tried to introduce defects in silica glass to act as pre-nucleation centers to mediate the size and distribution of Ag nanoparticles. In experiment, the silica glass samples were pre-irradiated by 200 keV Ar ions to fluences of 0.8, 2.0 and 5.0 × 10{sup 16} ions/cm{sup 2}, and then 200 keV Ag ions were implanted into the pre-irradiated samples to fluence of 2.0 × 10{sup 16} ions/cm{sup 2}. UV–VIS results show that the absorbance intensity of Ag SPR peak initially increases and then decreases with pre-irradiation fluence, which implies the change in size and density of Ag nanoparticles in samples. TEM results verify that Ag nanoparticles in the sample pre-irradiated to the fluence of 0.8 × 10{sup 16} ions/cm{sup 2} grow bigger and distribute in a relatively narrow region comparing with that without pre-irradiation. With further increase of pre-irradiation fluence, the size of Ag nanoparticles shows a depth dependent distribution. A boundary can be clear seen at the depth of 110 nm, larger Ag nanoparticles disperse in region shallower than 110 nm, and smaller Ag nanoparticles disperse in the region deeper than 110 nm. The average size of Ag nanoparticles initially increases and then decreases with pre-irradiation fluence. Therefore, the introduction of defects by pre-irradiation could be an effective way to tailor the size and distribution of metallic nanoparticles in matrix.
Tailoring the size and distribution of Ag nanoparticles in silica glass by defects
International Nuclear Information System (INIS)
The composites embedded with metallic nanoparticles show large nonlinear optical susceptibility and strong surface plasmon resonance absorption, which enable potential application in opto-electronics. Ion implantation has been proven to be a powerful technique of synthesis of metallic nanoparticles due to its versatility and compatibility. However, the synthesis of nanoparticles by ion implantation inevitably leads to a broad size distribution due to Ostwald ripening process. The broad size distribution has a negative effect on improving the figure of merits for nonlinear optics. In this paper, we tried to introduce defects in silica glass to act as pre-nucleation centers to mediate the size and distribution of Ag nanoparticles. In experiment, the silica glass samples were pre-irradiated by 200 keV Ar ions to fluences of 0.8, 2.0 and 5.0 × 1016 ions/cm2, and then 200 keV Ag ions were implanted into the pre-irradiated samples to fluence of 2.0 × 1016 ions/cm2. UV–VIS results show that the absorbance intensity of Ag SPR peak initially increases and then decreases with pre-irradiation fluence, which implies the change in size and density of Ag nanoparticles in samples. TEM results verify that Ag nanoparticles in the sample pre-irradiated to the fluence of 0.8 × 1016 ions/cm2 grow bigger and distribute in a relatively narrow region comparing with that without pre-irradiation. With further increase of pre-irradiation fluence, the size of Ag nanoparticles shows a depth dependent distribution. A boundary can be clear seen at the depth of 110 nm, larger Ag nanoparticles disperse in region shallower than 110 nm, and smaller Ag nanoparticles disperse in the region deeper than 110 nm. The average size of Ag nanoparticles initially increases and then decreases with pre-irradiation fluence. Therefore, the introduction of defects by pre-irradiation could be an effective way to tailor the size and distribution of metallic nanoparticles in matrix