Production, depreciation and the size distribution of firms
Ma, Qi; Chen, Yongwang; Tong, Hui; Di, Zengru
2008-05-01
Many empirical researches indicate that firm size distributions in different industries or countries exhibit some similar characters. Among them the fact that many firm size distributions obey power-law especially for the upper end has been mostly discussed. Here we present an agent-based model to describe the evolution of manufacturing firms. Some basic economic behaviors are taken into account, which are production with decreasing marginal returns, preferential allocation of investments, and stochastic depreciation. The model gives a steady size distribution of firms which obey power-law. The effect of parameters on the power exponent is analyzed. The theoretical results are given based on both the Fokker-Planck equation and the Kesten process. They are well consistent with the numerical results.
The smallest crater production size-frequency distribution on Mars
Werner, Stephanie C.; Popova, Olga P.; Quantin, Cathy; Hartmann, William K.
2015-04-01
We selected areas on Mars that are mapped as very young, where we anticipate minimal surface modification since crater formation. By comparing shapes of the size-frequency distribution (SFD) of craters, measured with HiRISE and other image data in several such areas, we attempt to determine the least altered SFD, and thus identify the shape of the pristine, or "production" distribution (PSFD) at meter- and decameter-scale crater sizes on the surface of Mars. We identify several effects, dependent on factors such as surface materials, layered target materials, surface elevation, and the somewhat stochastic meteorite breakup mechanics, which may cause modest variations in the shape of the observed distributions at meter scales from one place to another on Mars, and suggest that surface modification on Mars, especially aeolian deposition modifies the crater record in very short time-scales. Better understanding of the PSFD shape not only allows more accurate crater chronometry of Mars, but also places limits on losses of weak bolides during passage through the atmosphere of Mars. We estimate the PSFD of Martian craters (including the effects of atmospheric loss of weak meteoroids, for craters down to diameter D ~ 2m) and will propose a new polynomial description for the smallest crater range currently covered by modern imagery.
The size frequency distribution and rate of production of microcraters
Morrison, D. A.; Zinner, E.
1976-01-01
The paper contends that lunar crater size distributions vary to a degree that cannot be explained by variations in lunar surface orientation of the crater detectors or changes in micrometeoroid flux. In an attempt to investigate this size frequency distribution, a flux of micrometeoroid particles producing 0.1 micron diameter craters of approximately 300/sq cm/steradian/yr was obtained. No anisotropy was observed in the 0.1 micron flux between the ecliptic plane and the normal in the direction of lunar north.
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
Takasawa, S.; Nakamura, A. M.; Kadono, T.; Arakawa, M.; Dohi, K.; Ohno, S.; Seto, Y.; Maeda, M.; Shigemori, K.; Hironaka, Y.; Sakaiya, T.; Fujioka, S.; Sano, T.; Otani, K.; Watari, T.; Sangen, K.; Setoh, M.; Machii, N.; Takeuchi, T.
2011-06-01
Fragments generated by high-velocity collisions between solid planetary bodies are one of the main sources of new interplanetary dust particles. However, only limited ranges of collision velocity, ejecta size, and target materials have been studied in previous laboratory experiments, and the collision condition that enables the production of dust-sized particles remains unclear. We conducted hypervelocity impact experiments on silicate rocks at relative velocities of 9 to 61 km s-1, which is beyond the upper limit of previous laboratory studies. Sub-millimeter-diameter aluminum and gold spheres were accelerated by laser ablation and were shot into dunite and basalt targets. We analyzed the surfaces of aerogel blocks deployed near the targets using an electron probe micro analyzer and counted the number of particles that contained the target material. The size distributions of ejecta ranged from five to tens of microns in diameter. The total cross-sectional area of dust-sized ejecta monotonically increased with the projectile kinetic energy, independent of impact velocity, projectile diameter, and projectile and target material compositions. The slopes of the cumulative ejecta-size distributions ranged from -2 to -5. Most of the slopes were steeper than the -2.5 or -2.7 that is expected for a collisional equilibrium distribution in a collision cascade with mass-independent or mass-dependent catastrophic disruption thresholds, respectively. This suggests that the steep dust size-distribution proposed for the debris disk around HD172555 (an A5V star) could be due to a hypervelocity collision.
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
Energy Technology Data Exchange (ETDEWEB)
H.J. Walqui; T.C. Eisele; S.K. Kawatra
2003-07-01
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 (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)
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)
H.J. Walqui, T.C. Eisele, S.K. Kawatra
2004-04-01
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 (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)
H.J. Walqui; T.C. Eisele; S.K. Kawatra
2004-01-01
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 (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)
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.
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
2005-01-01
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.
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)
Fei, Lin
1996-04-01
The potential risk of lung cancer has evoked interest in the properties of radon decay products. There are two forms of this progeny: either attached to ambient aerosols, or still in the status of ions/molecules/small clusters. This ``unattached`` activity would give a higher dose per unit of airborne activity than the ``attached`` progeny that are rather poorly deposited. In this thesis, a system for determining unattached radon decay products electrical mobility size distribution by measuring their electrical mobilities was developed, based on the fact that about 88% of {sup 218}Po atoms have unit charge at the end of their recoil after decay from {sup 222}Rn, while the remainder are neutral. Essential part of the setup is the radon-aerosol chamber with the Circular Electrical Mobility Spectrometer (CEMS) inside. CEMS is used for sampling and classifying the charged radioactive clusters produced in the chamber. An alpha- sensitive plastic, CR-39 disk, is placed in CEMS as an inlaid disk electrode and the alpha particle detector. CEMS showed good performance in fine inactive particles` classification. If it also works well for radon decay products, it can offer a convenient size distribution measurement for radioactive ultrafine particles. However, the experiments did not obtain an acceptable resolution. Suggestions are made for solving this problem.
Energy Technology Data Exchange (ETDEWEB)
S.K. Kawatra; T.C. Eisele; T. Weldum; D. Larsen; R. Mariani; J. Pletka
2005-07-01
The goal of this project was to improve energy efficiency of industrial crushing and grinding operations (comminution). Mathematical models of the comminution process were used to study methods for optimizing the product size distribution, so that the amount of excessively fine material produced could be minimized. The goal was to save energy by reducing the amount of material that was ground below the target size, while simultaneously reducing the quantity of materials wasted as ''slimes'' that were too fine to be useful. Extensive plant sampling and mathematical modeling of the grinding circuits was carried out to determine how to correct this problem. The approaches taken included (1) Modeling of the circuit to determine process bottlenecks that restrict flowrates in one area while forcing other parts of the circuit to overgrind the material; (2) Modeling of hydrocyclones to determine the mechanisms responsible for retaining fine, high-density particles in the circuit until they are overground, and improving existing models to accurately account for this behavior; and (3) Evaluation of the potential of advanced technologies to improve comminution efficiency and produce sharper product size distributions with less overgrinding. The mathematical models were used to simulate novel circuits for minimizing overgrinding and increasing throughput, and it is estimated that a single plant grinding 15 million tons of ore per year saves up to 82.5 million kWhr/year, or 8.6 x 10{sup 11} BTU/year. Implementation of this technology in the midwestern iron ore industry, which grinds an estimated 150 million tons of ore annually to produce over 50 million tons of iron ore concentrate, would save an estimated 1 x 10{sup 13} BTU/year.
International Nuclear Information System (INIS)
The impact of natural solar ultraviolet radiation (UVR), particularly UVB (297-320 nm), on phytoplankton primary production in Lake Erie was investigated during the spring and summer of 1997. Radiocarbon incorporation and size-selective filtration was used to trace total production and its distribution among particulate and dissolved pools. On average, 1-h exposures produced half the UVB-dependent inhibition of total production realized in 8-h exposures, indicating rapid kinetics of photoinhibition. Cumulative UVB-dependent photoinhibition averaged 36% in 8-h simulated surface exposures. The efficiency of photoinhibition was greater for N-deficient than N-replete communities, but was not related to phytoplankton light history, P limitation, or the dominant genera. The proportion of recently fixed carbon occurring in the dissolved pool after 8-h exposures was significantly greater in higher-UVB treatments, whereas the share in picoplankton (<2 ?m) was significantly lower. Significant UVB-dependent inhibition of total production was limited on average to relatively severe exposures, but the rapid kinetics of inhibition and the apparent effects on the allocation of carbon suggest it may be important to the lake's food web. Differences in optical properties and thermal stratification patterns suggested that the relatively turbid west basin was potentially more susceptible to UVR photoinhibition than the more transparent east or central basins. (author)
Energy Technology Data Exchange (ETDEWEB)
S.K. Kawatra; T.C. Eisele; H.J. Walqui
2001-12-01
The goal of this project is to improve the energy efficiency of industrial crushing and grinding operations (comminution). Mathematical models of the comminution process are being used to study methods for optimizing the product size distribution, so that the amount of excessively fine material produced can be minimized. This will save energy by reducing the amount of material that is ground to below the target size, and will also reduce the quantity of material wasted as slimes that are too fine to be useful. This will be accomplished by: (1) modeling alternative circuit arrangements to determine methods for minimizing overgrinding, and (2) determining whether new technologies, such as high-pressure roll crushing, can be used to alter particle breakage behavior to minimize fines production. In the first quarter of this project, work was completed on a basic comminution model that will be used to carry out the subsequent project tasks. This phase of the work was supported by the Electric Power Research Institute, as their cost-share contribution to the project. The model has been implemented as an Excel spreadsheet, which has the advantage of being a very portable format that can be made widely available to the industry once the project is completed.
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.
Energy Technology Data Exchange (ETDEWEB)
H.J. Walqui; T.C. Eisele; S.K. Kawatra
2003-04-01
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 (2) determining whether new technologies, such as high-pressure roll crushing, can be used to alter particle breakage behavior to minimize fines production. During this quarter, work was focused on three areas: (1) The mathematical relationship developed for predicting plant throughput was improved, based on ore work index and equipment parameters measured in the plant over an extended period. It was determined that the model would need to fit two distinct regimes of grinding circuit operation, depending on the work index of the feed ore. (2) Plans for a proposed change in the circuit configuration at an iron ore plant are being made, to test predictions based on the work done to date in the project. After determining the desired circuit change, which would require screening a portion of the grinding slurry, samples were sent to an industrial screen manufacturer for pilot plant scale testing. These tests indicated that the screening could be carried out economically, and plans are proceeding to conduct trials of the proposed circuit alteration. (2) The mathematical model used for hydrocyclone simulations was found to be unable to fully predict the ''fish-hook'' behavior that is seen in the plant samples. The model was therefore improved by including empirically-determined terms so that it would be able to account for the observed phenomenon. A more advanced model is currently under development that will take account of measured slurry viscosity, in order to more accurately model the behavior of hydrocyclones with concentrated slurries of very fine particles.
Control of the grain size distribution of the raw material mixture in the production of iron sinter
Scientific Electronic Library Online (English)
E., Lwamba; A.M., Garbers-Craig.
2008-05-01
Full Text Available 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 conten [...] t, ranulation 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), reduction disintegration index (RDI) and reducibility (RI) of the produced sinter. The raw sinter mixtures contained combinations of Thabazimbi iron ore, Sishen iron ore, coke, lime and return fines. The grain size distributions were controlled by removing the -0.5 mm size fractions of the return fines and coke, and the -1 mm size fraction of lime. Of the examined mixtures, a mixture of 20 mass% Thabazimbi iron ore, 80 mass% Sishen iron ore and fluxes where the coke, lime and return fines were all sized had the highest granulation effectiveness and permeability. The sintering properties of the mixtures in which the grain size distributions were controlled, were very similar for all the mixtures, but superior to the base case mixture in which the grain size distribution was not controlled.
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)
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)
Damgaard, Trine; Lametsch, René; Otte, Jeanette
2015-10-01
The antioxidative capacity of six different tissue hydrolysates (porcine colon, heart and neck and bovine lung, kidney and pancreas) were tested by three different assays monitoring iron chelation, ABTS radical scavenging and inhibition of lipid oxidation in emulsions, respectively. The hydrolysates were also investigated with respect to amino acid composition and peptide size distribution. The hydrolysates contained peptides ranging from 20 kDa to below 100 Da with a predominance of peptides with low molecular weight (53.8 to 89.0 % below 3 kDa). All hydrolysates exhibited antioxidant activity as assessed with all three methods; inhibition of lipid oxidation ranging from 72 to 88 % (at a final protein concentration of 7 mg/mL), iron chelation capacity from 23 to 63 % (at 1.1 mg/mL), and ABTS radical scavenging from 38 to 50 % (at 10 ?g /mL). The antioxidant activity did not correlate with the proportion of low molecular weight peptides in the hydrolysed tissues, but with the content of specific amino acid residues. The ABTS radical scavenging capacity of the tissues was found to correlate with the content of Trp, Tyr, Met and Arg, whereas the ability to inhibit the oxidation of lineoleic acid correlated with the content of Glu and His. The chosen animal by-products thus represent a natural source of antioxidants with potential for food application. PMID:26396396
Centaur size distribution with DECam
Fuentes, Cesar; Trilling, David E.; Schlichting, Hilke
2014-11-01
We present the results of the 2014 centaur search campaign on the Dark Energy Camera (DECam) in Tololo, Chile. This is the largest debiased Centaur survey to date, measuring for the first time the size distribution of small Centaurs (1-10km) and the first time the sizes of planetesimals from which the entire Solar System formed are directly detected.The theoretical model for the coagulation and collisional evolution of the outer solar system proposed in Schlichting et al. 2013 predicts a steep rise in the size distribution of TNOs smaller than 10km. These objects are below the detection limit of current TNO surveys but feasible for the Centaur population. By constraining the number of Centaurs and this feature in their size distribution we can confirm the collisional evolution of the Solar System and estimate the rate at which material is being transferred from the outer to the inner Solar System. If the shallow power law behavior from the TNO size distribution at ~40km can be extrapolated to 1km, the size of the Jupiter Family of Comets (JFC), there would not be enough small TNOs to supply the JFC population (Volk & Malhotra, 2008), debunking the link between TNOs and JFCs.We also obtain the colors of small Centaurs and TNOs, providing a signature of collisional evolution by measuring if there is in fact a relationship between color and size. If objects smaller than the break in the TNO size distribution are being ground down by collisions then their surfaces should be fresh, and then appear bluer in the optical than larger TNOs that are not experiencing collisions.
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)
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.
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)
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
Aggregate size distributions in hydrophobic flocculation
Directory of Open Access Journals (Sweden)
Chairoj Rattanakawin
2003-07-01
Full Text Available The evolution of aggregate (floc size distributions resulting from hydrophobic flocculation has been investigated using a laser light scattering technique. By measuring floc size distributions it is possible to distinguish clearly among floc formation, growth and breakage. Hydrophobic flocculation of hematite suspensions with sodium oleate under a variety of agitating conditions produces uni-modal size distributions. The size distribution of the primary particles is shifted to larger floc sizes when the dispersed suspension is coagulated by pH adjustment. By adding sodium oleate to the pre-coagulated suspension, the distribution progresses further to the larger size. However, prolonged agitation degrades the formed flocs, regressing the distribution to the smaller size. Median floc size derived from the distribution is also used as performance criterion. The median floc size increases rapidly at the initial stage of the flocculation, and decreases with the extended agitation time and intensity. Relatively weak flocs are produced which may be due to the low dosage of sodium oleate used in this flocculation study. It is suggested that further investigation should focus on optimum reagent dosage and non-polar oil addition to strengthen these weak flocs.
Software Package for Aerosol Size Distribution
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 (co...
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.
L'Ecuyer, Tristan S.; Kummerow, Christian; Berg,Wesley
2004-01-01
Variability in the global distribution of precipitation is recognized as a key element in assessing the impact of climate change for life on earth. The response of precipitation to climate forcings is, however, poorly understood because of discrepancies in the magnitude and sign of climatic trends in satellite-based rainfall estimates. Quantifying and ultimately removing these biases is critical for studying the response of the hydrologic cycle to climate change. In addition, estimates of random errors owing to variability in algorithm assumptions on local spatial and temporal scales are critical for establishing how strongly their products should be weighted in data assimilation or model validation applications and for assigning a level of confidence to climate trends diagnosed from the data. This paper explores the potential for refining assumed drop size distributions (DSDs) in global radar rainfall algorithms by establishing a link between satellite observables and information gleaned from regional validation experiments where polarimetric radar, Doppler radar, and disdrometer measurements can be used to infer raindrop size distributions. By virtue of the limited information available in the satellite retrieval framework, the current method deviates from approaches adopted in the ground-based radar community that attempt to relate microphysical processes and resultant DSDs to local meteorological conditions. Instead, the technique exploits the fact that different microphysical pathways for rainfall production are likely to lead to differences in both the DSD of the resulting raindrops and the three-dimensional structure of associated radar reflectivity profiles. Objective rain-type classification based on the complete three-dimensional structure of observed reflectivity profiles is found to partially mitigate random and systematic errors in DSDs implied by differential reflectivity measurements. In particular, it is shown that vertical and horizontal reflectivity structure obtained from spaceborne radar can be used to reproduce significant differences in Z(sub dr) between the easterly and westerly climate regimes observed in the Tropical Rainfall Measuring Mission Large-scale Biosphere-Atmosphere (TRMM-LBA) field experiment as well as the even larger differences between Amazonian rainfall and that observed in eastern Colorado. As such, the technique offers a potential methodology for placing locally observed DSD information into a global framework.
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.
US Fish and Wildlife Service, Department of the Interior Data on population size and productivity of muskoxen Ovibos moschatus Ln the Arctic National Wildlife Refuge were collected during surveys in April and October...
Distribution of sizes of extragalactic radio sources
International Nuclear Information System (INIS)
The relation is dealt with between the distribution of observed (projected) linear sizes and actual linear sizes of extragalactic radio sources. This can give us further information about source sizes in comparison with standard studies on the largest angular scale - redshift relation, which only considers the sources from the upper envelope of the angular scales. The data found in the literature are consistent with the extensive distribution of actual linear sizes of the sources, but larger and statistically more complete samples should be used in the future. (author) 5 figs., 19 refs
Intraspecific Body Size Frequency Distributions of Insects
Gouws, E. Jeanne; Gaston, Kevin J; Chown, Steven L.
2011-01-01
Although interspecific body size frequency distributions are well documented for many taxa, including the insects, intraspecific body size frequency distributions (IaBSFDs) are more poorly known, and their variation among mass-based and linear estimates of size has not been widely explored. Here we provide IaBSFDs for 16 species of insects based on both mass and linear estimates and large sample sizes (n?100). In addition, we review the published IaBSFDs for insects, though doing so is compli...
Software Package for Aerosol Size Distribution
Directory of Open Access Journals (Sweden)
T. A. Rajesh
2013-04-01
Full Text Available The Software Package for Aerosol Size Distribution is a novel graphical user interface application software used for the study of atmospheric aerosol size distribution from various aerosol models (Continental clean, Continental average, Continental polluted, Urban, Desert, Maritime clean, Maritime polluted, Maritime tropical, Arctic, Antarctic and/or with different aerosol components (insoluble, water soluble, soot, sea salt (accumulation mode, sea salt (coarse mode, mineral (nucleation mode, mineral (accumulation mode, mineral (coarse mode, mineral (transported, sulfate, as a function of radius. This article discussed about the atmospheric aerosol, aerosol size distribution and the software description. Application case studies to generate the aerosol size distribution for an urban aerosol model and with different components have also been presented in this note.
Size distribution of planetary nebulae
Asvarov, Abdul; Allahverdiyev, Ahad
2015-08-01
Despite a very long history of investigations, the nature and origin of planetary nebulae (PNe) are not fully understood. It is obvious that the observational properties of PNe are influenced by the properties of the central star and the conditions in the environment. In this presentation in order to understand the effects of these components we have modeled the evolution of radio luminosity and the expansion of PNe in the framework of different hypothesis on the origin of these objects. In this we have used the observational data on the central stars and clustered this data into gourps with the similar parameters of the central stars. For the each of these groups of PNe we have built statistical dependences radio luminosity diameter, number of PNe - diameter which are then compared to the modeled ones. Unfortunately, the comparison of simulations with observations did not allow us to choose between the known models of the evolution of the PN shell. However with the increase of statistics the approach considered in this presentation may become more productive.
International Nuclear Information System (INIS)
In this work, we assessed uranium and some toxic elements distribution according to particle sizes in phosphogypsum cores, in order to improve the knowledge behavior of radioactive (238U and 234U) and toxic elements (Cd, Cr, Cu, Zn, Ag, Zr, Pb, Y, and Sr) Elemental concentration was measured in two phosphogypsum cores, which were separated in three depth intervals. Every sample also was divided in three particle size fractions. Results show that most of elements are not distributed homogeneously in phosphogypsum cores. The differences in distribution of elements suggest that there are fluxes of elements. On the other hand a high fractionation of elements was observed, where most of those were concentrated in fine particles in comparison with coarse and medium particle sizes. The main consequence of that most of these elements are concentrated in the fine fraction (particles <20 ?m), is that make them easily mobilized by leaching and/or erosion. (author)
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 15600 nm size range. The median particle number concentrations (PNC were found to vary in the range of 1.12.2 × 104 cm?3 at urban sites, 0.81.5 × 104 cm?3 at regional sites, 0.40.6 × 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 1525 nm (nucleation mode, 25100 nm (Aitken mode and 100600 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 8.010.9 nm h?1 at urban sites, 7.413.6 nm h?1 at regional sites and 2.87.5 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 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.
Learning transformed product distributions
Daskalakis, Constantinos; Diakonikolas, Ilias; 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 runni...
Raindrop Size Distribution Measurements in Tropical Cyclones
Tokay, Ali; Bashor, Paul G.; Habib, Emad; Kasparis, Takis
2008-01-01
Characteristics of the raindrop size distribution in seven tropical cyclones have been studied through impact-type disdrometer measurements at three different sites during the 2004-06 Atlantic hurricane seasons. One of the cyclones has been observed at two different sites. High concentrations of small and/or midsize drops were observed in the presence or absence of large drops. Even in the presence of large drops, the maximum drop diameter rarely exceeded 4 mm. These characteristics of raindrop size distribution were observed in all stages of tropical cyclones, unless the storm was in the extratropical stage where the tropical cyclone and a midlatitude frontal system had merged. The presence of relatively high concentrations of large drops in extratropical cyclones resembled the size distribution in continental thunderstorms. The integral rain parameters of drop concentration, liquid water content, and rain rate at fixed reflectivity were therefore lower in extratropical cyclones than in tropical cyclones. In tropical cyclones, at a disdrometercalculated reflectivity of 40 dBZ, the number concentration was 700 plus or minus 100 drops m(sup -3), while the liquid water content and rain rate were 0.90 plus or minus 0.05 g m(sup -3) and 18.5 plus or minus 0.5 mm h(sup -1), respectively. The mean mass diameter, on the other hand, was 1.67 plus or minus 0.3 mm. The comparison of raindrop size distributions between Atlantic tropical cyclones and storms that occurred in the central tropical Pacific island of Roi-Namur revealed that the number density is slightly shifted toward smaller drops, resulting in higher-integral rain parameters and lower mean mass and maximum drop diameters at the latter site. Considering parameterization of the raindrop size distribution in tropical cyclones, characteristics of the normalized gamma distribution parameters were examined with respect to reflectivity. The mean mass diameter increased rapidly with reflectivity, while the normalized intercept parameter had an increasing trend with reflectivity. The shape parameter, on the other hand, decreased in a reflectivity range from 10 to 20 dBZ and remained steady at higher reflectivities. Considering the repeatability of the characteristics of the raindrop size distribution, a second impact disdrometer that was located 5.3 km away from the primary site in Wallops Island, Virginia, had similar size spectra in selected tropical cyclones.
Kuhlbusch, T A J; Neumann, S; Fissan, H
2004-10-01
Number size characteristics and PM10 mass concentrations of particles emitted during the packaging of various kinds of carbon blacks were measured continuously in the bag filling areas of three carbon black plants and concurrently at ambient comparison sites. PM10, PM2.5, and PM1 dust fractions were also determined in the bag filling areas. The filter samples were then analyzed for elemental and organic carbon. Comparisons of the measured number size distributions and mass concentrations during bag filling activities with those measured parallel at the ambient site and with those determined during nonworking periods in the work area enabled the characterization of emitted particles. PM10 mass concentrations were consistently elevated (up to a factor of 20 compared to ambient concentrations) during working periods in the bag filling area. Detailed analysis revealed that the carbon black particles released by bag filling activities had a size distribution starting at approximately 400 nm aerodynamic diameter (dae) with modes around 1 microm dae and > 8 microm dae. Ultrafine particles (< 100 nm dae), detected in the bag filling areas, were most likely attributed to noncarbon black sources such as forklift and gas heater emissions. PMID:15631057
City Size Distributions For India and China
Gangopadhyay, Kausik; Basu, B.
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...
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 2.055 g cm(-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 ?g m(-3) were reached. The maximum daily concentrations ranged from 500 to 900 ?g m(-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 ?g m(-3) can be retained by the trachea and bronchi, and 130 ?g m(-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
Fisher Information in Flow Size Distribution
Tune, Paul; Veitch, Darryl
2011-01-01
The flow size distribution is a useful metric for traffic modeling and management. Its estimation based on sampled data, however, is problematic. Previous work has shown that flow sampling (FS) offers enormous statistical benefits over packet sampling but high resource requirements precludes its use in routers. We present Dual Sampling (DS), a two-parameter family, which, to a large extent, provide FS-like statistical performance by approaching FS continuously, with just pac...
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).
Particle size distribution in ground biological samples.
Koglin, D; Backhaus, F; Schladot, J D
1997-05-01
Modern trace and retrospective analysis of Environmental Specimen Bank (ESB) samples require surplus material prepared and characterized as reference materials. Before the biological samples could be analyzed and stored for long periods at cryogenic temperatures, the materials have to be pre-crushed. As a second step, a milling and homogenization procedure has to follow. For this preparation, a grinding device is cooled with liquid nitrogen to a temperature of -190 degrees C. It is a significant condition for homogeneous samples that at least 90% of the particles should be smaller than 200 microns. In the German ESB the particle size distribution of the processed material is determined by means of a laser particle sizer. The decrease of particle sizes of deer liver and bream muscles after different grinding procedures as well as the consequences of ultrasonic treatment of the sample before particle size measurements have been investigated. PMID:9159903
Economies of Size in Production Agriculture
Duffy, Michael
2009-01-01
Economies of size refer to the ability of a farm to lower costs of production by increasing production. Agriculture production displays an L-shaped average cost curve where costs are lower initially but reach a point where no further gains are achieved. Spreading fixed costs, bulk purchases, and marketing power are cited as reasons for economies of size. Labor-reducing technologies may be the primary reason. Most studies do not include the external costs from prophylactic antibiotic use, impa...
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.
Atmospheric particulate mercury: Concentrations and size distributions
Kim, Pyung-Rae; Han, Young-Ji; Holsen, Thomas M.; Yi, Seung-Muk
2012-12-01
In this study, the size distributions of atmospheric particulate mercury (PHg) were measured in both urban and rural areas during the summer, fall, and winter. Both PHg concentrations and the contribution of PHg to total PM aerosol were higher at the urban (PHg = 6.8 ħ 6.5 pg m-3, PHg/total PM = 0.18 pg ?g-1) than at the rural site (PHg = 4.6 ħ 2.7 pg m-3, PHg/total PM = 0.06 pg ?g-1). Based on size-distribution measurements, the fine mode was the dominant size at both sites in winter while the coarse mode became more important during summer. In winter PHg concentrations in the fine mode increased because of the effective adsorption of gaseous Hg onto the fine particles at the low temperature and increased Hg oxidation reactions in the presence of high particles concentrations. During winter elevated concentrations of total PHg were measured when the prevailing winds were northwesterly originating in China.
Particle-size distribution study: PILEDRIVER event
International Nuclear Information System (INIS)
Reentry was made by mining into the chimney of broken rock created by a nuclear detonation in granite at a depth of 1500 feet. The chimney was 160 ft in radius and 890 ft high. An injection of radioactive melt was encountered at 300 ft from shot point. Radiochemical analyses determined that the yield of PILEDRIVER nuclear device was 61 ħ 10 kt. Two samples of chimney rubble totalling over 5,000 lb were obtained during the postshot exploration. These samples of broken granite underwent screen analysis, a radioactivity-distribution study, and cursory leaching tests. The two samples were separated into 25 different size-fractions. An average of the particle-size data from the two samples showed that 17% of the material is between 20 mesh and I in.; 42% between 1 and 6 in.; and 34% between 6 in. and 3 ft. The distribution of radioactivity varies markedly with the particle size. The minus 100-mesh material comprizes less than 1.5% of the weight but contains almost 20% of the radioactivity. Small-scale batch-leaching tests showed that 25% of the radioactivity could be removed in a few hours by a film-percolation leach with distilled water, and 40% with dilute acid. Brief studies were made of the microfractures in the broken rock and of the radioactivity created by the PILEDRIVER explosion. (author)
On the Invariance of Size Distribution of Establishments
Kamanina, Polina
2012-01-01
The thesis examines the establishment size distribution over time and across groups of regions, using data on Swedish establishments during period 1994-2009. The size distribution of establishments is highly skewed and approximates the Pareto distribution. The shape of size distribution is invariant over time and across groups of regions. The distribution of total number of establishments and incumbent distribution are found to rise from the same distribution. Moreover, the invariance of esta...
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
Large-size monodisperse latexes as a commercial space product
Kornfeld, D. M.
1977-01-01
Proposed spacelab production of large-size (2-40 micron diameter) monodispersed latexes is discussed. Explanations are given for the present lack of monodisperse particles in this size range. The four main topics discussed are: (1) the potential uses of these large particle size latexes, (2) why it is necessary for the particles to have a very narrow size distribution, (3) why large amounts of these monodisperse latexes are needed, and (4) why it is necessary to go to microgravity to prepare these latexes.
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.
The economic production lot size model with several production rates
DEFF Research Database (Denmark)
Larsen, Christian
We study an extension of the economic production lot size model, where more than one production rate can be used during a cycle. The production rates and their corresponding runtimes are decision variables. We decompose the problem into two subproblems. First, we show that all production rates should be chosen in the interval between the demand rate and the production rate, which minimize unit production costs, and should be used in an increasing order. Then, given the production rates, we derive closed form solutions for the optimal runtimes as well as the minimum average cost. Finally we derive a near-optimal solution to the general problem.
The Italian primary school-size distribution and the city-size: a complex nexus
Belmonte, Alessandro; Di Clemente, Riccardo; 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 pr...
Batch sizing with controllable production rates
Glock, Christoph H.
2009-01-01
Abstract In this paper, we focus on a production system where a single product is manufactured on a single facility and delivered to the subsequent stage in batch shipments. In contrast to earlier works, we assume that the inventory on the producing stage is depleted at discrete time intervals, and analyse the effect of a variable production rate on the inventory build-up and the total costs of the system. We develop formal models for the case of equal- and unequal-sized batch ship...
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.
Fractal Theory and Application in City Size Distribution
Liu Zhenling
2013-01-01
City size distribution has become a hot topic in urbanization process and governed by many laws and rules in terms of its evolution and change. This study has discussed relation between fractal theory and city size distribution, Hausdorff index, Pareto distribution and zips law as well as index calculation method which ought to be a good method of evaluating urban development.
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. İ 2013 Informa Healthcare USA, Inc.
How Sample Size Affects a Sampling Distribution
Mulekar, Madhuri S.; Siegel, Murray H.
2009-01-01
If students are to understand inferential statistics successfully, they must have a profound understanding of the nature of the sampling distribution. Specifically, they must comprehend the determination of the expected value and standard error of a sampling distribution as well as the meaning of the central limit theorem. Many students in a high
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.
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}.
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.
A study of particle size distribution in zirconia-alumina powders
International Nuclear Information System (INIS)
Powder particles, in general are characterized in terms of particle size, size distributions and composition for reasons associated with manufacturing problem based upon product quality, manufacturing convenience, cost and product handling convenience. Particle size analysis or the measurement of particle size distribution is a common effort in any physical, chemical or mechanical processes. This information and processing methods are intricate factors that relate to material behavior and/or physical properties of the fabricated product. The requirements for the formation of a product of particulate solids and its strength varies as the particle size and the size distribution changes. Also the transport properties and the chemical activity are related to the particle size and the size distribution. The choice of a distribution to represent a physical system is generally motivated by an understanding of the nature of underlying phenomenon and is verified by the available data. After a model has been chosen, its parameter must be determined. The reasonableness of a selected model on the basis of given data is especially important when the model is to be used for prediction. Two different approaches in this problem are probability plotting and statistical tests
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.
Model choice and size distribution: A Bayequentist approach
Engler, John-Oliver; Baumgartner, Stefan
2013-01-01
We propose a new three-step model-selection framework for size distributions in empirical data. It generalizes a recent frequentist plausibility-of-fit analysis (Step 1) and combines it with a relative ranking based on the Bayesian Akaike Information Criterion (Step 2). We enhance these statistical criteria with the additional criterion of microfoundation (Step 3) which is to select the size distribution that comes with a dynamic micro model of size dynamics. A numerical performance test of S...
Distributed size estimation of dynamic anonymous networks
Terelius, Hċkan; 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...
International Nuclear Information System (INIS)
The studies were undertaken in 1998 on phosphorus concentration in river sediment versus sediment grain size distribution as a part of research on water quality and outflow from small agricultural watershed, carried out by the Department of Hydraulic Structures, Agricultural University of Warsaw. Laser particle size analyser was applied to measure suspended sediment size distribution. Sampling procedure, principles of analysis and the results were described
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...
Energy Technology Data Exchange (ETDEWEB)
Haninger, T.
1997-12-31
A major issue in radiation protection is to protect the population from the harmful effects of exposure to radon and radon progeny. Quantification of the lung cancer risk emanating from exposure to radon decay products in residential and working environments poses problems, as epidemiologic studies yield information deviating from the results obtained by the indirect method of assessment based on dosimetric respiratory tract models. One important task of the publication here was to characterize the various exposure conditions and to quantify uncertainties that may result from application of the ``dose conversion convention``. A special aerosol spectrometer was therefore designed and built in order to measure the size distributions of the short-lived radon decay products in the range between 0.5 nm and 10 000 nm. The aerosol spectrometer consists of a three-step diffusion battery with wire nets, an 11-step BERNER impactor, and a detector system with twelve large-surface proportional detectors. From the measured size distributions, dose conversion coefficients, E/P{sup eq}, were calculated using the PC software RADEP; the RADEP program was developed by BIRCHALL and JAMES and is based on the respiratory tract model of the ICRP. The E/P{sup eq} coefficients indicate the effective dose E per unit exposure P{sup eq} to radon decay products. (orig./CB) [Deutsch] Eines der groessten Probleme des Strahlenschutzes ist der Schutz der Bevoelkerung vor einer Strahlenexposition durch Radon und seine Folgeprodukte. Die Quantifizierung des Lungenkrebsrisikos, das durch Radonexpositionen in Wohnungen und an Arbeitsplaetzen verursacht wird, ist ein grosses Problem, weil epidemiologische Studien ein anderes Ergebnis liefern, als die indirekte Methode der Abschaetzung mit dosimetrischen Atemtrakt-Modellen. Eine wichtige Aufgabe der vorliegenden Arbeit war es, unterschiedliche Expositionsbedingungen zu charakterisieren und die Unsicherheiten zu quantifizieren, die sich aus der Anwendung der `Dosiskonversionskonvention` ergeben koennen. Im Rahmen der vorliegenden Arbeit wurde daher ein spezielles Aerosolspektrometer konzipiert und aufgebaut, mit dem es moeglich ist, die Groessenverteilungen der kurzlebigen Radon-Folgeprodukte im Bereich zwischen 0,5 nm und 10 000 nm zu messen. Das Aerosolspektrometer besteht aus einer dreistufigen Diffusionsbatterie mit Drahtnetzen, einem elfstufigen BERNER-Impaktor und einem Detektorsystem mit zwoelf grossflaechigen Proportionaldetektoren. Aus den gemessenen Groessenverteilungen wurden Dosiskonversionskoeffizienten E/P{sub eq} mit dem PC-Programm RADEP berechnet; RADEP wurde von BIRCHALL und JAMES entwickelt [BIR 94] und beruht auf dem Atemtrakt-Modell der ICRP. Mit E/P{sub eq} wird die effektive Dosis E pro Einheit der Exposition P{sub eq} durch Radon-Folgeprodukte bezeichnet. (orig./MG)
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
INITIAL PLANETESIMAL SIZES AND THE SIZE DISTRIBUTION OF SMALL KUIPER BELT OBJECTS
International Nuclear Information System (INIS)
The Kuiper Belt is a remnant from the early solar system and its size distribution contains many important constraints that can be used to test models of planet formation and collisional evolution. We show, by comparing observations with theoretical models, that the observed Kuiper Belt size distribution is well matched by coagulation models, which start with an initial planetesimal population with radii of about 1 km, and subsequent collisional evolution. We find that the observed size distribution above R ? 30 km is primordial, i.e., it has not been modified by collisional evolution over the age of the solar system, and that the size distribution below R ? 30 km has been modified by collisions and that its slope is well matched by collisional evolution models that use published strength laws. We investigate in detail the resulting size distribution of bodies ranging from 0.01 km to 30 km and find that its slope changes several times as a function of radius before approaching the expected value for an equilibrium collisional cascade of material strength dominated bodies for R ?< 0.1 km. Compared to a single power-law size distribution that would span the whole range from 0.01 km to 30 km, we find in general a strong deficit of bodies around R ? 10 km and a strong excess of bodies around 2 km in radius. This deficit and excess of bodies are caused by the planetesimal size distribution left over from the runaway growth phase, which left most of the initial mass in small planetesimals while only a small fraction of the total mass is converted into large protoplanets. This excess mass in small planetesimals leaves a permanent signature in the size distribution of small bodies that is not erased after 4.5 Gyr of collisional evolution. Observations of the small Kuiper Belt Object (KBO) size distribution can therefore test if large KBOs grew as a result of runaway growth and constrained the initial planetesimal sizes. We find that results from recent KBO occultation surveys and the observed KBO size distribution can be best matched by an initial planetesimal population that contained about equal mass per logarithmic mass bin in bodies ranging from 0.4 km to 4 km in radius. We further find that we cannot match the observed KBO size distribution if most of the planetesimal mass was contained in bodies that were 10 km in radius or larger simply because their resulting size distribution cannot be sufficiently depleted over 4.5 Gyr to match observations
Extrema propagation : fast distributed estimation of sums and network sizes
Baquero, Carlos; Almeida, Paulo S??rgio; Menezes, Raquel; Jesus, Paulo
2012-01-01
Aggregation of data values plays an important role on distributed computations, in particular, over peer-to-peer and sensor networks, as it can provide a summary of some global system property and direct the actions of self-adaptive distributed algorithms. Examples include using estimates of the network size to dimension distributed hash tables or estimates of the average system load to direct load balancing. Distributed aggregation using nonidempotent functions, like sums, is not trivial as ...
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 ...
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...
Methods of assessing grain-size distribution during grain growth
DEFF Research Database (Denmark)
Tweed, Cherry J.; Hansen, Niels
1985-01-01
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 (obtained by stereological analysis) are collected. The techniques described here are illustrated by reference to examples.
The best nanoparticle size distribution for minimum thermal conductivity
Zhang, Hang; Minnich, Austin J.
2015-01-01
Which sizes of nanoparticles embedded in a crystalline solid yield the lowest thermal conductivity? Nanoparticles have long been demonstrated to reduce the thermal conductivity of crystals by scattering phonons, but most previous works assumed the nanoparticles to have a single size. Here, we use optimization methods to show that the best nanoparticle size distribution to scatter the broad thermal phonon spectrum is not a similarly broad distribution but rather several discrete peaks at well-chosen nanoparticle radii. For SiGe, the best size distribution yields a thermal conductivity below that of amorphous silicon. Further, we demonstrate that a simplified distribution yields nearly the same low thermal conductivity and can be readily fabricated. Our work provides important insights into how to manipulate the full spectrum of phonons and will guide the design of more efficient thermoelectric materials. PMID:25757414
The best nanoparticle size distribution for minimum thermal conductivity
Zhang, Hang; Minnich, Austin J.
2015-03-01
Which sizes of nanoparticles embedded in a crystalline solid yield the lowest thermal conductivity? Nanoparticles have long been demonstrated to reduce the thermal conductivity of crystals by scattering phonons, but most previous works assumed the nanoparticles to have a single size. Here, we use optimization methods to show that the best nanoparticle size distribution to scatter the broad thermal phonon spectrum is not a similarly broad distribution but rather several discrete peaks at well-chosen nanoparticle radii. For SiGe, the best size distribution yields a thermal conductivity below that of amorphous silicon. Further, we demonstrate that a simplified distribution yields nearly the same low thermal conductivity and can be readily fabricated. Our work provides important insights into how to manipulate the full spectrum of phonons and will guide the design of more efficient thermoelectric materials.
A new procedure modeling the probability distribution of earthquake size
Wang, J. P.; Yun, X.; Chang, S. C.
2014-11-01
The probability distribution of earthquake size is needed as input data for some earthquake analyses. A common procedure is to calibrate the so-called b-value in the Gutenberg-Richter relationship and to use it as the best-estimate model parameter in an algorithm to simulate the observed earthquake-size distribution. This paper introduces a new procedure for such a simulation, on the basis of performing optimization to search for the optimum model parameter. The new option and an existing method are then both utilized to model the earthquake-size distribution around Taiwan since 1978. Owing to the nature and the power of optimization, three case studies presented in this paper all indicate that the new optimization procedure can indeed improve such a simulation over the existing procedure. Moreover, with a proper tool such as Excel Solver, practicing the new method to model the observed earthquake-size distribution is as effortless as using the existing procedure.
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.)
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
The influence of metal nanoparticle size distribution in photoelectron spectroscopy.
Minati, L; Speranza, G; Calliari, L; Micheli, V; Baranov, A; Fanchenko, S
2008-08-28
We present an innovative approach to characterize small metal nanoclusters embedded in an amorphous carbon matrix. A simple mathematical relation linking binding energy shifts to the mean nanoparticle (NP) dimensions allows determination of the distribution of NP sizes by fitting the Au 4f X-ray photoemission spectrum. The NP size distributions obtained using our method are compared with those obtained from X-ray diffraction spectra. PMID:18683914
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...
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, María; Cermeño, Pedro; CALVO-DÍAZ, ALEJANDRA; Marañón, 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.
Linear unbiased estimators for particle size distribution of magnetic nanoparticles
International Nuclear Information System (INIS)
We present two statistical analytical approaches to estimate the particle size distribution of magnetic nanoparticles. They are termed best linear unbiased estimator and linear minimum mean square error estimator. These approaches are implemented and quantified within the formalism of linear unbiased estimation theory. To illustrate the efficiency of the proposed approaches, we give two examples of the application to the particle size distribution analysis in ferrofluids with normal and lognormal samples. In both cases we compare the reconstruction distributions using our methods with those calculated via the electron microscopy images of the ferrofluid particles
UV photolysis of (HBr) n clusters with known size distribution
Baumfalk, R.; Buck, U.; Frischkorn, C.; Gandhi, S. R.; Lauenstein, C.
1997-05-01
The photodissociation of (HBr) n clusters is reported using polarized laser light at 243.1 nm. The cluster size is measured in a deflection experiment with He and Ne atoms. A time-of-flight mass spectrometer with low extraction fields is used to obtain the kinetic energy distributions of the hydrogen atoms. At averaged cluster sizes of overlinen = 8.1 two distributions are observed with fast peaks of uncaged fragments and with a sharp peak at zero velocity which shows an isotropic angular distribution and which is attributed to complete caging.
Fast method for computing pore size distributions of model materials.
Bhattacharya, Supriyo; Gubbins, Keith E
2006-08-29
Recently developed atomistic models of highly disordered nanoporous materials offer hope for a much more realistic description of the pore morphology and topology in such materials; however, a factor limiting their application has been the computationally intensive characterization of the models, particularly determination of the pore size distribution. We report a new technique for fast computation of pore size distributions of model materials from knowledge of the molecular coordinates. The pore size distribution (PSD) is defined as the statistical distribution of the radius of the largest sphere that can be fitted inside a pore at a given point. Using constrained nonlinear optimization, we calculate the maximum radii of test particles at random points inside the pore cavity. The final pore size distribution is then obtained by sampling the test particle radii using Monte Carlo integration. The computation time depends on factors such as the number of atoms, the sampling resolution, and the desired accuracy. However, even for large systems, PSDs with very high accuracy (>99.9%) are obtained in less than 24 h on a 3 GHz Pentium IV processor. The technique is validated by applying it to model structures, whose pore size distributions are already known. We then apply this method to investigate the pore structures of several mesoporous silica models such as SBA-15 and mesostructured cellular foams. PMID:16922556
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 (40 g/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.
Particle size distribution in ferrofluid macro-clusters
International Nuclear Information System (INIS)
Under an applied magnetic field, many commercial and concentrated ferrofluids agglomerate and form large micron-sized structures. Although large diameter particles have been implicated in the formation of these macro-clusters, the question of whether the particle size distribution of the macro-clusters are the same as the original fluid remains open. Some studies suggest that these macro-clusters consist of larger particles, while others have shown that there is no difference in the particle size distribution between the macro-clusters and the original fluid. In this study, we use X-ray imaging to aid in a sample (diluted EFH-1 from Ferrotec) separation process and conclusively show that the average particle size in the macro-clusters is significantly larger than those in the original sample. The average particle size in the macro-clusters is 19.6 nm while the average particle size of the original fluid is 11.6 nm. - Highlights: ? X-ray imaging was used to isolate ferrofluid macro-clusters under an applied field. ? Small angle X-ray scattering was used to determine particle size distributions. ? Results show that macro-clusters consist of particles that are larger than average.
XRD characterisation of nanoparticle size and shape distributions
International Nuclear Information System (INIS)
Full text: The form of XRD lines and the extent of their broadening provide useful structural information about the shape, size distribution, and modal characteristics of the nanoparticles comprising the specimen. Also, the defect content of the nanoparticles can be determined, including the type, dislocation density, and stacking faults/twinning. This information is convoluted together and can be grouped into 'size' and 'defect' broadening contributions. Modern X-ray diffraction analysis techniques have concentrated on quantifying the broadening arising from the size and defect contributions, while accounting for overlapping of profiles, instrumental broadening, background scattering and noise components. We report on a combined Bayesian/Maximum Entropy (MaxEnt) technique developed for use in the certification of a NIST Standard Reference Material (SRM) for size-broadened line profiles. The approach used was chosen because of its generality in removing instrumental broadening from the observed line profiles, and its ability to determine not only the average crystallite size, but also the distribution of sizes and the average shape of crystallites. Moverover, this Bayesian/MaxEnt technique is fully quantitative, in that it also determines uncertainties in the crystallite-size distribution and other parameters. Both experimental and numerical simulations of size broadened line-profiles modelled on a range of specimens with spherical and non-spherical morphologies are presented to demonstrate how this information can be retrieved from the line profile data. The sensitivity of the Bayesian/MaxEnt method to determining the size distribution using varying a priori information are emphasised and discussed
The Size Frequency Distribution of Small Main-Belt Asteroids
Burt, Brian J.; Trilling, David E.; Hines, Dean C.; Stapelfeldt, Karl R.; Rebull, Luisa M.; Fuentes, Cesar I.; Hulsebus, Alan
2012-01-01
The asteroid size distribution informs us about the formation and composition of the Solar System. We build on our previous work in which we harvest serendipitously observed data of the Taurus region and measure the brightness and size distributions of Main-belt asteroids. This is accomplished with the highly sensitive MIPS 24 micron channel. We expect to catalog 104 asteroids, giving us a statistically significant data set. Results from this investigation will allow us to characterize the total population of small, Main-belt asteroids. Here we will present new results on the completeness of our study; on the presence of size distribution variations with inclination and radial distance in the belt; and early result on other archival fields.
Endogenic craters on basaltic lava flows - Size frequency distributions
Greeley, R.; Gault, D. E.
1979-01-01
Circular crater forms, termed collapse depressions, which occur on many basalt flows on the earth have also been detected on the moon and Mars and possibly on Mercury and Io. The admixture of collapse craters with impact craters would affect age determinations of planetary surface units based on impact crater statistics by making them appear anomalously old. In the work described in the present paper, the techniques conventionally used in planetary crater counting were applied to the determination of the size range and size frequency distribution of collapse craters on lava flows in Idaho, California, and New Mexico. Collapse depressions range in size from 3 to 80 m in diameter; their cumulative size distributions are similar to those of small impact craters on the moon.
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.
Novel magnetic Fe onion-like fullerene micrometer-sized particles of narrow size distribution
International Nuclear Information System (INIS)
Magnetic polydivinylbenzene (PDVB)/magnetite micrometer-sized particles of narrow size distribution were prepared by entrapping Fe(CO)5 within the pores of uniform porous PDVB particles, followed by the thermal decomposition of the encapsulated Fe(CO)5 at 300 deg. C in a sealed cell under inert atmosphere. Magnetic Fe onion-like fullerene micrometer-sized particles of narrow size distribution have been prepared by the thermal decomposition of the PDVB/magnetite magnetic microspheres at 1100 deg. C under inert atmosphere. The graphitic coating protects the elemental iron particles from oxidation and thereby preserves their very high magnetic moment for at least a year. Characterization of these unique magnetic carbon graphitic particles was also performed. - Highlights: ? Magnetic PDVB/iron-oxide composite particles of narrow size distribution have been synthesized and characterized. ? Magnetic C/Fe composite particles of narrow size distribution have been synthesized and characterized. ? Magnetic onion-like fullerenes structures have been observed in these different particles.
School Size and the Distribution of Test Scores
Bedard, Kelly; Brown Jr., William O.; Helland, Eric
1999-01-01
After forty years of school consolidation, the preponderance of the evidence, including the results presented in this paper, suggest that the race to reap returns to scale and specialization in education may have come at a high price. This paper uses newly available STAR test score data from California to explore the relationship between school size and the distribution of test scores across elementary, middle, and high schools. We find that school size has a statistically significant and eco...
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...
Particle size distribution studies within a beryllium processing plant
International Nuclear Information System (INIS)
The size distribution of air borne particles of beryllium in the beryllium processing pilot plant at Vashi (India) has been studied. Nearly 50% of the particles in majority of the operational areas are found to be within 5 ?m size. Concentration levels of beryllium aerosols are also found to be well below 2 ?g/M3 which is the limit set for occupational exposure by the OSHA. (M.G.B.). 1 tab
Theory of Nanocluster Size Distributions from Ion Beam Synthesis
Energy Technology Data Exchange (ETDEWEB)
Yuan, C.W.; Yi, D.O.; Sharp, I.D.; Shin, S.J.; Liao, C.Y.; Guzman, J.; Ager III, J.W.; Haller, E.E.; Chrzan, D.C.
2008-06-13
Ion beam synthesis of nanoclusters is studied via both kinetic Monte Carlo simulations and the self-consistent mean-field solution to a set of coupled rate equations. Both approaches predict the existence of a steady state shape for the cluster size distribution that depends only on a characteristic length determined by the ratio of the effective diffusion coefficient to the ion flux. The average cluster size in the steady state regime is determined by the implanted species/matrix interface energy.
Estimation of Nanoparticle Size Distributions by Image Analysis
International Nuclear Information System (INIS)
Knowledge of the nanoparticle size distribution is important for the interpretation of experimental results in many studies of nanoparticle properties. An automated method is needed for accurate and robust estimation of particle size distribution from nanoparticle images with thousands of particles. In this paper, we present an automated image analysis technique based on a deformable ellipse model that can perform this task. Results of using this technique are shown for both nearly spherical particles and more irregularly shaped particles. The technique proves to be a very useful tool for nanoparticle research
Estimation of Nanoparticle Size Distributions by Image Analysis
Energy Technology Data Exchange (ETDEWEB)
Fisker, R., E-mail: RF@IMM.DTU.DK; Carstensen, J.M. [Technical University of Denmark, Department of Mathematical Modelling (Denmark); Hansen, M.F.; Bodker, F.; Morup, S. [Technical University of Denmark, Department of Physics (Denmark)
2000-09-15
Knowledge of the nanoparticle size distribution is important for the interpretation of experimental results in many studies of nanoparticle properties. An automated method is needed for accurate and robust estimation of particle size distribution from nanoparticle images with thousands of particles. In this paper, we present an automated image analysis technique based on a deformable ellipse model that can perform this task. Results of using this technique are shown for both nearly spherical particles and more irregularly shaped particles. The technique proves to be a very useful tool for nanoparticle research.
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.
International Nuclear Information System (INIS)
The bubble sizes and their distribution affect directly to other hydrodynamic behavior of two-phase systems such as flow regime, gas-liquid interfacial area, and mass heat transfer between the phases. However, it is difficult to obtained bubble sizes and their distribution directly. By using the probe technique, the vertical length that bubbles insert the probe, or chord length, can be obtained instead of bubble sizes. In order to get the bubble sizes as well as their distribution, some techniques have to be used. This paper discuss the approaches, which are numerical and analytical backward transform, to estimate bubble size distribution from a set of chord length data obtained by a double sensor conductivity probe which installed in the air water vertical loop facility installed in KAERI. The image technique is also used to measure bubble sizes, which used to compare with ones obtained by the probe
Energy Technology Data Exchange (ETDEWEB)
Hien, Hoang Nhan [University of Science and Technology, Daejeon (Korea, Republic of); Yun, B. J.; Song, C. H. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)
2011-10-15
The bubble sizes and their distribution affect directly to other hydrodynamic behavior of two-phase systems such as flow regime, gas-liquid interfacial area, and mass heat transfer between the phases. However, it is difficult to obtained bubble sizes and their distribution directly. By using the probe technique, the vertical length that bubbles insert the probe, or chord length, can be obtained instead of bubble sizes. In order to get the bubble sizes as well as their distribution, some techniques have to be used. This paper discuss the approaches, which are numerical and analytical backward transform, to estimate bubble size distribution from a set of chord length data obtained by a double sensor conductivity probe which installed in the air water vertical loop facility installed in KAERI. The image technique is also used to measure bubble sizes, which used to compare with ones obtained by the probe
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...
A Merging Algorithm for Aerosol Size Distribution from Multiple Instruments.
Czech Academy of Sciences Publication Activity Database
Ondrá?ek, Jakub; dímal, 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
Nonequilibrium grain size distribution with generalized growth and nucleation rates
Lokovic, Kimberly S.; Bergmann, Ralf B.; Bill, Andreas
2013-06-01
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 growth case is the appearance of a constant prefactor in the distribution. The second generalization considers a Gaussian source term: nuclei are stable when their volume is within a finite range determined by the thermodynamics of the crystallization process. The numerical results show that this generalization does not change the qualitative picture of our previous study. The generalization only affects quantitatively the early stage of crystallization, when nucleation is dominant. The remarkable result of these major generalizations is that the non-equilibrium grain size distribution is robust against anisotropic growth of grains and fluctuations of nuclei sizes.
Preparation of leucite powders with controlled particle size distribution.
Czech Academy of Sciences Publication Activity Database
Novotná, Martina; Klouková, A.; Maixner, J.; atava, 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; Kuel, 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
Application of Gnostic Theory to Analysis of Particle Size Distribution.
Czech Academy of Sciences Publication Activity Database
Wagner, Zden?k; dímal, 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 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.
Determination of atmospheric particle size distribution from forward scattering data.
Fymat, A. L.
1973-01-01
Description of an analytic method of reconstructing the particle size distribution of atmospheric aerosols when no a priori information is available regarding the refractive index of the particles, the analytic form of the distribution, the size range, and the size extremal values. The method applies in principle to angle-dependent scattering data at a fixed wave number, or to wave-number-dependent scattering data at a fixed angle, or to a combination of the two. Some results of an angular scan study of the aureole are presented to illustrate the effectiveness of the method. In conclusion, an analysis is made of the efficiency and accuracy of the method, the uniqueness of the inverse solutions, and the stability of the method relative to experimental noise.
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...
Thresholded Power Law Size Distributions of Instabilities in Astrophysics
Aschwanden, Markus J
2015-01-01
Power law-like size distributions are ubiquitous in astrophysical instabilities. There are at least four natural effects that cause deviations from ideal power law size distributions, which we model here in a generalized way: (1) a physical threshold of an instability; (2) incomplete sampling of the smallest events below a threshold $x_0$; (3) contamination by an event-unrelated background $x_b$; and (4) truncation effects at the largest events due to a finite system size. These effects can be modeled in simplest terms with a "thresholded power law" distribution function (also called generalized Pareto [type II] or Lomax distribution), $N(x) dx \\propto (x+x_0)^{-a} dx$, where $x_0 > 0$ is positive for a threshold effect, while $x_0 < 0$ is negative for background contamination. We analytically derive the functional shape of this thresholded power law distribution function from an exponential-growth evolution model, which produces avalanches only when a disturbance exceeds a critical threshold $x_0$. We app...
Measuring droplet size distributions from overlapping interferometric particle images.
Bocanegra Evans, Humberto; Dam, Nico; van der Voort, Dennis; Bertens, Guus; van de Water, Willem
2015-02-01
Interferometric particle imaging provides a simple way to measure the probability density function (PDF) of droplet sizes from out-focus images. The optical setup is straightforward, but the interpretation of the data is a problem when particle images overlap. We propose a new way to analyze the images. The emphasis is not on a precise identification of droplets, but on obtaining a good estimate of the PDF of droplet sizes in the case of overlapping particle images. The algorithm is tested using synthetic and experimental data. We next use these methods to measure the PDF of droplet sizes produced by spinning disk aerosol generators. The mean primary droplet diameter agrees with predictions from the literature, but we find a broad distribution of satellite droplet sizes. PMID:25725854
Atmospheric Aerosol Size Distribution at Sumas Mountain, Vancouver, BC.
Chan, T. W.; Mozurkewich, M.
2002-12-01
Atmospheric size distributions provide fundamental information for studying atmospheric particle physics. To study and monitor the air quality in the Lower Fraser Valley, Vancouver, BC, Pacific 2001 field study was held in Vancouver during August 13th to September 1st 2001. As part of the Pacific 2001 study, aerosol size distributions were measured at Eagle Ridge, just east of Abbotsford, BC. Atmospheric particles were sampled from a 3/8-inch stainless steel tubing with an inverted U-shape inlet. The sample line located at 2 meters above the top of a trailer that has an elevation of 300 meters above sea level. Particles coming from the sample line were sized using a TSI 3071 Differential Mobility Analysis (DMA) and then counted by a TSI 3010 Condensation Nucleus Counter (CNC). The system measured atmospheric particles with diameters from 9.3 to 604 nm. Each five-minute scan consisted of 30 size bins increasing exponentially in size. All the data was corrected for CNC counting efficiency and multiple charging effects to represent a more realistic description of the size distribution. During the field study, 19 days of data for both sunny and rainy days were obtained. By comparing the measured total concentration from 10 nm and 6 nm onwards, identified local nucleation event was observed in 4 days. Clear observation of particle transport from other remote places to the monitoring site was observed in 13 days during the study. Nucleation mode particles were usually observed between 10 a.m. to noon in all sunny days. These nucleation mode particles are thought to due to nocturnal inversion. As that happen, pollutants that were accumulated overnight in the valley were transported up to the site, with the combination of the sunlight, trigger the formation of new particles. The formation of these nucleation mode particles was usually followed by a short particle growth period, which may last from two to five hours, except for one day, which this growth period extends to midnight. Owing to the high variability of the size distribution, to fit these data using multi-LogNormal distributions may result instability problem. To accomplish this, we have explored a new method to analyse the data. Applying the Principal Component Analysis (PCA) to the data may provide more stable distribution for describing the data. Furthermore, the PCA also provide a mean for reducing a massive data set to a manageable data set.
Particle sizes and particle size-fraction distribution in water treatment.
Czech Academy of Sciences Publication Activity Database
Mutl, Silvestr; Poláek, 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
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 ...
Modelling of Recent Changes In The Urban Particle Size Distribution
Gentry, J.; Heyder, J.; Kreyling, W. G.; Heinrich, J.; Wichmann, H. E.
Measurements of the particle size distribution in the environment of the East German city of Erfurt over the last decade showed a constant or slight increase in the number of particles smaller than 0.1 µm (ultrafine particles) and a decrease in the number of larger particles (fine particles) confirmed by a 3-4 fold decrease in PM2 . This effect .5 may be attributed to a possible increase in ultrafine particle emission, a decrease in fine particle emission and consequently by less scavenging of ultrafine by fine parti- cles. Numerical protocols were developed to examine this conjecture supporting their validity. The measurement protocol, the implications of the increase in ultrafine par- ticles along with a decrease in micron size particles, and the development of a nu- merical code (mathematical model?) to examine this phenomenon are discussed. The codes were developed to simulate coagulation with broad distributions. The simula- tions quantitatively examine the effect of the reduction of micron sized particles on ul- trafine particle persistence. They indicate the necessity of a continual source of micron sized particles, since sedimentation would eliminate such particles without continual renewal. The code is described in detail, with particular attention paid to the effect of the coagulation kernel used in the particle balance equations. These simulations sug- gest that it is important to use coagulation kernels appropriate for the transition regime. Otherwise the collision of similarly sized ultrafine particles are underestimated. Sev- eral protocols accounting for different continual source terms are studied.
Quantitative Grain Size Distributions of Magnetic Organic Thin Films
Gredig, Thomas; Gentry, K. Paul; Schuller, Ivan K.
2009-03-01
Many electronic, optical, and magnetic properties of organic thin films depend on the precise morphology of grains. Quantitative grain size distributions of an asymmetric organic molecule are presented and correlated with the magnetic characteristics. Iron phthalocyanine (FePc) thin films are grown on sapphire substrates at varied deposition temperatures to study the effect of grain growth and to experimentally quantify the grain size distributions in organic thin films based on atomic force microscopy images. The data of over 3000 grains for each sample show a pronounced asymmetric growth of grains from a spherical to an elongated needle-like shape. The size along the major axes increases from 35nm to 200nm and is distributed in a different way than the minor axes, which grow from 25nm to 90nm. The dissimilar distributions are attributed to an asymmetric growth rate. Low-temperature hysteresis loops and temperature-dependent magnetization curves for these FePc thin films illustrate the effect of the length of quasi one-dimensional Fe chains on the magnetic properties.
Rock sampling. [method for controlling particle size distribution
Blum, P. (inventor)
1971-01-01
A method for sampling rock and other brittle materials and for controlling resultant particle sizes is described. The method involves cutting grooves in the rock surface to provide a grouping of parallel ridges and subsequently machining the ridges to provide a powder specimen. The machining step may comprise milling, drilling, lathe cutting or the like; but a planing step is advantageous. Control of the particle size distribution is effected primarily by changing the height and width of these ridges. This control exceeds that obtainable by conventional grinding.
Critical sizes and flux distributions in the shut down pile
International Nuclear Information System (INIS)
An important part of the experiments carried out on the reactor G1 during a period of shut-down has consisted in determinations of critical sizes, and measurements of flux distribution by irradiations of detectors. This report deals with the following points: 1- Critical sizes of the flat pile, the long pile and the uranium-thorium pile. 2- Flux charts of the same piles, and study of an exponential experiment. 3- Determination of the slit effect. 4- Calculation of the anisotropy of the lattice. 5- Description of the experimental apparatus of the irradiation measurements. (author)
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.
Clone size distributions in networks of genetic similarity
Hernández-García, E.; Rozenfeld, A. F.; Eguíluz, V. M.; Arnaud-Haond, S.; Duarte, C. M.
2006-12-01
We build networks of genetic similarity in which the nodes are organisms sampled from biological populations. The procedure is illustrated by constructing networks from genetic data of a marine clonal plant. An important feature in the networks is the presence of clone subgraphs, i.e. sets of organisms with identical genotype forming clones. As a first step to understanding the dynamics that has shaped these networks, we point up a relationship between a particular degree distribution and the clone size distribution in the populations. We construct a dynamical model for the population dynamics, focussing on the dynamics of the clones, and solve it for the required distributions. Scale free and exponentially decaying forms are obtained depending on parameter values, the first type being obtained when clonal growth is the dominant process. Average distributions are dominated by the power law behavior presented by the fastest replicating populations.
Analyses of the Particle Size Distributions from TROI FCI Tests
International Nuclear Information System (INIS)
Sometimes fuel coolant interactions are accompanied by destructive shock waves generated from a rapid heat transfer. So, a lot of experimental and analytical researches on steam explosions have been performed. The experimental researches cover small-scale experiments, medium scale experiments, and experiments with a real core material. There exists several steam explosion analysis codes such as ESPROSE.m, IFCI, MC3D, TRACER-II, TEXAS-V, which are different from each other in their dimension, breakup model, and fragmentation model. Thus, their results do not agree with each other, and a difference in their breakup models might be one reason for this disagreement. The TROI experiments were carried out to provide experimental data for a proper estimation of a steam explosion work. The explosion work can be characterized by the explosion pressure wave, and the mixture condition can be characterized by a particle size distribution. Thus, the TROI tests were analyzed in view of a particle size response for various types of fuel coolant explosions. In this study, the final particle size distributions induced by both explosive FCI and non-explosive FCI were discussed. This analysis could indicate a difference between an explosive FCI and a non-explosive quenching. Also, the mixing size of the particles to participate in a steam explosion and the fine particle size produced from a steam explosion could be defined in the TROI test. Considering the several findings in the TROI experiments, the parametric effects on the particle size were analyzed by using the non-explosive TROI tests. This analysis on the particle size response can provide an understanding about the relationship among the initial condition, a mixing, and an explosion
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...
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.
Magnetic heating effect of nanoparticles with different sizes and size distributions
Energy Technology Data Exchange (ETDEWEB)
Mueller, R.; Dutz, S. [Department of Nano Biophotonics, Institute of Photonic Technology, Jena (Germany); Neeb, A.; Cato, A.C.B. [Institute of Toxicology and Genetics, Karlsruhe Institute of Technology, Karlsruhe (Germany); Zeisberger, M., E-mail: zeisberger@ipht-jena.de [Department of Spectroscopy and Imaging, Institute of Photonic Technology, Jena (Germany)
2013-02-15
We present a comparative study of dynamic and quasistatic magnetic properties of iron oxide nanoparticles. The samples are prepared by different wet chemical precipitation methods resulting in different sizes and size distributions. The structural characterization was performed by X-ray diffraction and transmission electron microscopy. The heating effect in an ac field in the range 0-30 kA/m at 210 kHz was measured calorimetrically. In addition, a vibrating sample magnetometer was used for hysteresis and remanence curve measurements. - Highlights: Black-Right-Pointing-Pointer Preparation of 4 different types of magnetic nanoparticles with mean sizes from 10-20 nm. Black-Right-Pointing-Pointer Basic characterization by X-ray diffraction and vibrating sample magnetometry. Black-Right-Pointing-Pointer Determination of sizes and size distributions from X-ray and TEM data. Black-Right-Pointing-Pointer Calorimetric measurements of the specific heating power in an ac field of 210 kHz and field amplitudes up to 30 kA/m.
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.
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
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)
Ultrasound Contrast Agents: Fabrication, size distribution and visualization
Zheng, Miaomiao
2011-01-01
Ultrasound contrast agents composed of micro-bubble filled with gas are introduced to increase the backscattered power from blood. Their intravenously injection results in the improved contrast in the images. The aim of this master thesis project is to manufacture MB suspension at varied temperature and shear forces and to inspect the size distribution and concentration of the PVA-shelled micro-bubble with standard methods according to the developed protocol. A pulser-receiver (Panametrics PR...
Assessment of pore size distribution using image analysis.
Czech Academy of Sciences Publication Activity Database
Doktor, Tomá; Kytŭ?, Daniel; Valach, Jaroslav; Jirouek, Ond?ej
Trieste : Italian Group of Fracture, 2010 - (Iacoviello, F.; Cosmi, F.), s. 155-157 ISBN 978-88-95940-30-4. [Youth Symposium on Experimental Solid Mechanics /9./. Trieste (IT), 07.07.2010-10.07.2010] R&D Projects: GA ?R(CZ) GAP105/10/2305 Institutional research plan: CEZ:AV0Z20710524 Keywords : pore size distribution * image analysis * micro-CT Subject RIV: JJ - Other Materials
Drop size distribution in sprays by image processing
E. Fantini; Tognotti, L.; Tonazzini, A.
1989-01-01
An automatic analysis system has been developed and used to analyze photographs obtained by high-speed microphotography, the final aim being to derive the size distributions of drops in sprays. The problem of determining whether photographic images of particles are in focus or not is solved by obtaining a calibration of geometric parameters of particle images as functions both of the particle position in the camera's field of view and of the particle diameter. On the basis of the results of t...
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.
Nonlinear observer of crystal-size distribution during batch crystallization
Bakir, Toufik; Othman, Sami; Fevotte, Gilles; Hammouri, Hassan
2006-01-01
A high-gain observer was designed to estimate the crystal-size distribution (CSD) in batch crystallization processes. The observer is based on the discretization of population balance equations describing the evolution of the CSD using finite difference method. Due to process impurities and other batch-to-batch variations, the kinetic parameters involved in the dynamic model of the crystallization, relating primary and secondary nucleation in particular, are subject to significant variations....
Size-Distribution Scaling in Clusters of Allelomimetic Agents
Juanico, Dranreb Earl; Saloma, Caesar
2004-01-01
The allelomimesis clustering model is based on only two parameters: a local parameter $\\alpha$ that represents the probability of nearest-neighbor copying and a global parameter $p$ that represents the fraction of unresponsive agents. The model results into the formation of clusters of agents, the sizes of which obey a distribution that is determined by the values of $\\alpha$ and $p$. Several experimental data are fitted by tuning the two parameters. In particular, the signi...
New finite-size correction for local alignment score distributions
Directory of Open Access Journals (Sweden)
Park Yonil
2012-06-01
Full Text Available Abstract Background Local alignment programs often calculate the probability that a match occurred by chance. The calculation of this probability may require a finite-size correction to the lengths of the sequences, as an alignment that starts near the end of either sequence may run out of sequence before achieving a significant score. Findings We present an improved finite-size correction that considers the distribution of sequence lengths rather than simply the corresponding means. This approach improves sensitivity and avoids substituting an ad hoc length for short sequences that can underestimate the significance of a match. We use a test set derived from ASTRAL to show improved ROC scores, especially for shorter sequences. Conclusions The new finite-size correction improves the calculation of probabilities for a local alignment. It is now used in the BLAST+ package and at the NCBI BLAST web site (http://blast.ncbi.nlm.nih.gov.
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.
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.
Finite-size effects on return interval distributions for weakest-link-scaling systems
Hristopulos, Dionissios T.; Petrakis, Manolis P.; Kaniadakis, Giorgio
2014-05-01
The Weibull distribution is a commonly used model for the strength of brittle materials and earthquake return intervals. Deviations from Weibull scaling, however, have been observed in earthquake return intervals and the fracture strength of quasibrittle materials. We investigate weakest-link scaling in finite-size systems and deviations of empirical return interval distributions from the Weibull distribution function. Our analysis employs the ansatz that the survival probability function of a system with complex interactions among its units can be expressed as the product of the survival probability functions for an ensemble of representative volume elements (RVEs). We show that if the system comprises a finite number of RVEs, it obeys the ?-Weibull distribution. The upper tail of the ?-Weibull distribution declines as a power law in contrast with Weibull scaling. The hazard rate function of the ?-Weibull distribution decreases linearly after a waiting time ?c?n1/m, where m is the Weibull modulus and n is the system size in terms of representative volume elements. We conduct statistical analysis of experimental data and simulations which show that the ? Weibull provides competitive fits to the return interval distributions of seismic data and of avalanches in a fiber bundle model. In conclusion, using theoretical and statistical analysis of real and simulated data, we demonstrate that the ?-Weibull distribution is a useful model for extreme-event return intervals in finite-size systems.
Hybrid Organization of Production and Distribution
Claude Menard
2006-01-01
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 ...
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.
Better Size Estimation for Sparse Matrix Products
DEFF Research Database (Denmark)
Amossen, Rasmus Resen; Campagna, Andrea
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. Let n denote the total number of non-zero entries in the input matrices. We show how to compute a 1 ħ ? approximation (with small probability of error) in expected time O(n) for any ? > 4*(n^(-1/4)). The previously best estimation algorithm, due to Cohen (JCSS 1997), uses time O(n/?^2). We also present a variant using O(sort(n)) I/Os in expectation in the cache-oblivious model. We also describe how sampling can be used to maintain (independent) sketches of matrices that allow estimation to be performed in time o(n) if z is sufficiently large. This gives a simpler alternative to the sketching technique of Ganguly et al. (PODS 2005), and matches a space lower bound shown in that paper.
Distribution of cluster sizes from evaporation to total multifragmentation
International Nuclear Information System (INIS)
A model for studying fragmentation phenomena is proposed and developed. The model leads to a single, simple, and exact expression for the cluster size distribution function. Various limits of this distribution function show: (1) evaporation-like behavior, (2) scale-invariant power law behavior, (3) a broad region with a dependence which is linear growth in small clusters and exponential falloff of large clusters and, finally, (4) total multifragmentation with an exponential-like falloff of all clusters except the monomer or unit element. The cluster size distribution function in any region is given by various limits of one expression: YA(k,x)={A exclamation point/[k exclamation point(A-k)exclamation point]}xB(x+A-k,k). Here, the size k is the number of elements in a cluster taken from a fixed total number of A elements, x is an evolutionary tuning parameter which determines the various regions, and B(x+A-k,k) is a beta function. Cellular rules and a particular choice of weight function lead to self-similar behavior on Young's triangular lattice. A scale invariant hyperbolic power law emerges in a row by row evolution of the lattice. A counterclockwise rotation of Ferrer's block diagram of partitions shows a pictorial resemblance of the present model with recent work on self-organized critical states, and a comparison is made. The cumulative mass distribution at a critical point of the model is a staircase function whose continuous limit is analogous to that of a uniform bar. The uniform bar may then be hammered into various shapes which will be discussed. Some observations on the form of x are given by comparing the multifragmentation limit of the model with the law of mass action or Saha equation
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 ttŻ$tar t$ 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.
Image analysis of pellet size for a control system in industrial feed production.
Ljungqvist, Martin Georg; Nielsen, Michael Engelbrecht; Ersbĝll, Bjarne Kjĉr; Frosch, Stina
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. PMID:22031836
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.
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.
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). 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.
Distributed Project Management for New Product Development
Alfred E. Thal; 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...
Particle size distributions of radioactive aerosols measured in workplaces
International Nuclear Information System (INIS)
A survey of published values of Activity Median Aerodynamic Diameter (AMAD) measured in working environments was conducted to assist in the selection of a realistic default AMAD for occupational exposures. Results were compiled from 52 publications covering a wide variety of industries and workplaces. Reported values of AMAD from all studies ranged from 0.12 ?m to 25 ?m, and most were well fitted by a log-normal distribution with a median value of 4.4 ?m. This supports the choice of a 5 ?m default AMAD, as a realistic rounded value for occupational exposures, by the ICRP Task Group on Human Respiratory Tract Models for Radiological Protection and its acceptance by ICRP. Both the nuclear power and nuclear fuel handling industries gave median values of approximately 4 ?m. Uranium mills gave a median value of 6.8 ?m with AMADs frequently greater than 10 ?m. High temperature and arc saw cutting operations generated submicron particles and occasionally, biomodal log-normal particle size distributions. It is concluded that in view of the wide range of AMADs found in the surveyed literature, greater emphasis should be placed on air sampling to characterise aerosol particle size distributions for individual work practices, especially as doses estimated with the new 5 ?m default AMAD will not always be conservative. (author)
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.
International Nuclear Information System (INIS)
The particle size distribution of submicron size, radioactive silver (sup(110m)Ag) aerosols, generated by vapour-condensation method (with Tesla spark-generator) was studied by electron microscopic method and by a centrifugal aerosol-spectrometer (conifuge). These data were compared with the distribution of the elemental spot-diameters of autoradiographs, and evaluated statistically. The autoradiographic particle size distribution analysis is a useful method for replacing the expensive electron microscopic assay. (author)
Evaluation of particle size distributions by means of particle counters
Energy Technology Data Exchange (ETDEWEB)
Fissan, H.J.; Helsper, C.
1979-01-01
The operation and performance of a combination of two instruments used to determine particle size distributions of aerosols emitted by combustion processes in the particle diameter range between 0.01 and 10 microns are discussed. For the particle diameter range below 1.0 micron an electrical aerosol analyzer was used. For large particles an optical particle counter was used. It was found that in the submicron size range the determination of aerosol parameters by particle counting techniques has several advantages compared with gravimetircal methods. As the instruements used were designed for atmospheric aerosol measurements, emission aerosols have to be diluted in most cases to fit the limits of the instruments. Certain systematic errors based on the principle of operation can be corrected to a great extent if necessary by a special correction algorithm. The comparison of the particle counting techniques with a gravimetric method shows a rather good agreement. (LCL)
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-Distribution Scaling in Clusters of Allelomimetic Agents
Juanico, D E; Juanico, Dranreb Earl; Saloma, Caesar
2004-01-01
The allelomimesis clustering model is based on only two parameters: a local parameter $\\alpha$ that represents the probability of nearest-neighbor copying and a global parameter $p$ that represents the fraction of unresponsive agents. The model results into the formation of clusters of agents, the sizes of which obey a distribution that is determined by the values of $\\alpha$ and $p$. Several experimental data are fitted by tuning the two parameters. In particular, the significance of the value of $\\alpha$ that corresponds to an experimental data is discussed and is justified according to behavioral context. Recommendations for possible extensions of the model are also enumerated.
Empirical Reference Distributions for Networks of Different Size
Smith, Anna; Browning, Christopher R
2015-01-01
Network analysis has become an increasingly prevalent research tool across a vast range of scientific fields. Here, we focus on the particular issue of comparing network statistics, i.e. graph-level measures of network structural features, across multiple networks that differ in size. Although "normalized" versions of some network statistics exist, we demonstrate via simulation why direct comparison of raw and normalized statistics is often inappropriate. We examine a recent suggestion to normalize network statistics relative to Erdos-Renyi random graphs and demonstrate via simulation how this is an improvement over direct comparison, but still sometimes problematic. We propose a new adjustment method based on a reference distribution constructed as a mixture model of random graphs which reflect the dependence structure exhibited in the observed networks. We show that using simple Bernoulli models as mixture components in this reference distribution can provide adjusted network statistics that are relatively ...
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...
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...
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.
Modelling the evolution of 210Pb and 210Po size distributions in the atmosphere
International Nuclear Information System (INIS)
The study of radon (222Rn and 220Rn) decay products in the atmosphere is important for estimating air ionization, assessing the inhalation doses to humans and for understanding atmospheric transport processes. The decay products 218Po, 214Pb (T1/2 < 1 hour), 212Pb (T1/2 ? 10.6 hrs) are short lived and 210Po (T1/2 ? 13 days), 210Pb (T1/2 ? 22 years) are long lived. Within a short time after their formation, the decay product atom combine with air constituents to form molecular clusters which then get attached to existing aerosol particles. The activity size distributions of the short-lived components in the atmosphere show two major modes, namely fine and coarse modes. The long-lived components predominantly occur in the coarse mode. Several studies have been carried out on the decay product activity distributions to estimate their atmospheric residence times. An important aspect that has received little attention is the upward size evolution of the decay products due to the persistent coagulation of the coarse mode particles. The present study aims at the development of first principle model for progeny attachment dynamics to a coagulating aerosol, which will provide insight in understanding the evolution of activity size distribution. A theoretical model is formulated by considering the processes such a constant formation of background aerosols, attachment of progeny atoms to the aerosol, coagulation, physical decay, and deposition. A set of integro-differential equations for attached and unattached fractions are formulated and are solved by a comprehensive numerical approach. Comparative studies of the activity size distributions, the degree of mixing of radioactivity within particles are carried out for short-lived and long lived species. The results are in agreement with the observations which show that the mode of the activity size distribution strongly depends on the effective life time of the progeny species in the atmosphere. The size dependence of activity per particle also show interesting behaviour with respect to the life times of the species. (author)
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.
Ramifications of a Divot in the Kuiper Belt's Size Distribution
Gladman, Brett; Shankman, C.; Kaib, N.; Kavelaars, J.; Petit, J.
2012-10-01
Our recent detection (see Shankman et al., this meeting) of a divot in the distribution of numbers of Scattering TNOs as a function of absolute magnitude would, if extended to all Kuiper Belt sub-populations, simultaneously explain several outstanding curiosities in the literature. We examine these puzzles in the context of our proposed divot scenario and provide a cohesive picture of the "hot" Trans-Neptunian populations (the scattering, inner belt, hot main belt, outer/detached, and resonant populations). We explore the observed rollover in the Kuiper Belt's luminosity function, the "missing" Neptune Trojans, the source of the Jupiter Family Comets, and patterns seen in the hot/cold ratio as a function of magnitude. Our interpretation is that a detected divot is a preserved relic of the size distribution made by planetesimal formation, now "frozen in" to portions of the Kuiper Belt which share a "hot" orbital inclination distribution. This research was supported by the Canadian National Sciences and Engineering Research Council.
Development of equilibrium raindrop size distribution in natural rain.
Pio D'Adderio, Leo; Porcu, Federico; Tokay, Ali
2015-04-01
The NASA's Global Precipitation Measurement (GPM) mission dual-frequency precipitation radar retrieval has adopted a three-parameter gamma distribution to retrieve the raindrop size distribution (DSD) from dual-frequency precipitation radar (DPR) measurements. Recent analysis from disdrometric measurements collected during GPM ground validation (GV) field experiments shows that the three-parameter gamma distribution does not well fit the observed spectra in the presence of collisional break-up, i.e. when the DSD reaches the equilibrium stage. An automatic algorithm is used to select equilibrium DSD in six datasets for a total number of more than 12,000 minutes with rain rate higher than 5 mmh-1 collected from 2-DVD disdrometers. The algorithm is based on the analysis of the DSD slope in the interval 1.0-2.5 mm diameter. The 1-minute time series are studied in order to assess the conditions more favorable for equilibrium DSD to take place, showing the transition between the one-peak DSD to the 2-peak DSD, for selected case studies, over a wide range of rainrate values. The results are discussed in terms of precipitation type and intensity, showing a very rapid onset and dissipation of equilibrium DSD conditions. The temporal evolution of some DSD parameters is also analyzed, and, for two of the six datasets (MC3E and Wallops), was also possible to evaluate the small-scale spatial structure of equilibrium DSD.
Sample size calculations for the development of biosimilar products.
Kang, Seung-Ho; Kim, Yongjo
2014-01-01
The most widely used design for a Phase III comparative study for demonstrating the biosimilarity between a biosimilar product and a renovator biological product is the equivalence trial, whose aim is to show that the difference between two population means of a primary endpoint is less than a prespecified equivalence margin. A well-known sample size formula for the equivalence trial is given by [Formula: see text] Since this formula is obtained based on the approximate power rather than the exact power, we investigate in this article the accuracy of the sample size formula. We conclude that the sample size formula is very conservative. Specifically, we show that the exact power based on the sample size calculated from the formula to have power [Formula: see text] is actually [Formula: see text] under some conditions. Therefore, the use of the sample size formula may cause a huge extra cost to biotechnology companies. We propose that the sample size should be calculated based on the exact power precisely and numerically. The R code to calculate the sample size numerically is provided in this article. PMID:25032735
Atmospheric mass and metal size distributions measured around Lake Michigan
Energy Technology Data Exchange (ETDEWEB)
Seung-Muk Yi; Sofuoglu, S.C.; Holsen, T.M. [Illinois Inst. of Technology, Chicago, IL (United States)] [and others
1996-12-31
This study, which was part of a multi-university AEOLOS investigation, involved an assessment of the spatial and temporal variations in the dry deposition fluxes and mass size distributions (MSDs) of total mass, crustal (aluminum and magnesium), and anthropogenic (lead and copper) metals over the southern basin of Lake Michigan. The work included measurement of deposition fluxes and MSDs during winter, summer and fall, concurrently, in Chicago, IL, over Lake Michigan, and in South Haven, MI. A Cascade impactor was used to determine the size distribution in the fine particles (<2.5 {mu}m), while Noll Rotary Impactor (NRI) was used to collect coarse particles (>2.5 {mu}m). The flux of these metals was substantially higher in Chicago than at either South Haven or over Lake Michigan. The measured average aluminum and magnesium fluxes were 2.23 and 5.32 mg/m{sup 2}-day over Chicago, and 0.24 and 0.28 mg/m{sup 2}-day over Lake Michigan, while the average aluminum and magnesium fluxes in South Haven were 0.17 and 0.12 mg/m{sup 2}-day respectively. The measured average lead and copper fluxes were 0.07 and 0.06 mg/m{sup 2}-day in Chicago, 0.003 and 0.01 mg/m{sup 2}-day over Lake Michigan, and 0.004 and 0.003 mg/m{sup 2}-day in South Haven. This research provided evidence of three possible peaks in the MSDs: the first in the 0-1 {mu}m range, the second in the 1-10 {mu}m region, and the third in the > 10-50 {mu}m range, with the MSDs being unimodal, bimodal or trimodal. Temporal variations in flux were not evident in this study. The wind direction (e.g., from over land, or from over lake) had large impact on both fluxes and size distributions. 5 refs., 10 figs., 1 tab.
Mao, Jiandong; Li, Jinxuan
2015-08-01
Particle size distribution is essential for describing direct and indirect radiation of aerosols. Because the relationship between the aerosol size distribution and optical thickness (AOT) is an ill-posed Fredholm integral equation of the first type, the traditional techniques for determining such size distributions, such as the Phillips-Twomey regularization method, are often ambiguous. Here, we use an approach based on an improved particle swarm optimization algorithm (IPSO) to retrieve aerosol size distribution. Using AOT data measured by a CE318 sun photometer in Yinchuan, we compared the aerosol size distributions retrieved using a simple genetic algorithm, a basic particle swarm optimization algorithm and the IPSO. Aerosol size distributions for different weather conditions were analyzed, including sunny, dusty and hazy conditions. Our results show that the IPSO-based inversion method retrieved aerosol size distributions under all weather conditions, showing great potential for similar size distribution inversions.
Number size distributions and seasonality of submicron particles in Europe 20082009
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.
Concentrations and size distributions on Antarctic stratospheric aerosols
International Nuclear Information System (INIS)
Particle Measuring Systems laser particle spectrometer (ASAS-X and FSSP) probes were used to measure aerosol particle concentrations and size distributions during 11 out of 12 ER-2 flights between Punta Arenas (53 degree S) and Antarctica (up to 72 degree S) from August 17 to September 22, 1987. The time resolution was 10 s, corresponding to a spatial resolution of 2 km. The data were divided into two size classes (0.05-0.25 and 0.53-5.5 ?m radius) to separate the small particle from the coarse particle populations. Results show that the small particle concentrations are typical for a background aerosol during volcanic quiescence. This concentration is generally constant along a flight track; in only one instance did the authors measure a depletion of small particles during a polar stratospheric cloud (PSC) encounter, suggesting a nucleation of type I PSC particles on background aerosols. Temporary increases of the coarse particle concentrations indicated the presence of tenuous polar stratospheric clouds that were encountered most frequently at the southernmost portion of a flight track and when the aircraft descended to lower altitudes. During particle events, particle modes were found at 0.6 ?m radius, corresponding to type I PSCs, and occasionally, a second mode at 2.0 ?m radius, corresponding to type II PSCs
Flow distribution in adjacent subchannels of unequal size
International Nuclear Information System (INIS)
This report describes an experimental and analytic investigation of the single phase flow distribution in subchannel geometries. It was intended as an investigation of fundamental transport mechanisms and therefore concentrated on simple geometries with two interconnected subchannels. The experimental phase consisted of detailed measuremnts of the fluid velocity in a geometry representing two communicating subchannels of different sizes. These measurements were made at three axial locations along the test section. The size of one of the subchannels was varied to give subchannel area ratios of 1.0, 0.68, 0.50 and 0.32. Two Reynolds numbers (108000 and 180000) were investigated. Axial pressure gradient data for all of these cases was also taken. The analytic phase concentrated on applying a three dimensional finite difference fluid flow code to subchannel geomtries. The code was applied to the cases studied in the experiment as well as other investigator's results. It used the two equation K-? turbulence model. The performance of this model was assessed. Unique features of the subchannel flows were identified and discussed. Conclusions regarding the transport mechanisms involved and the ability of a multidimensional code to predict the flow fields reliably were presented
Comparison of Raindrop Size Distribution Measurements by Collocated Disdrometers
Tokay, Ali; Petersen, Walter A.; Gatlin, Patrick; Wingo, Matthew
2013-01-01
An impact-type Joss-Waldvogel disdrometer (JWD), a two-dimensional video disdrometer (2DVD), and a laser optical OTT Particle Size and Velocity (PARSIVEL) disdrometer (PD) were used to measure the raindrop size distribution (DSD) over a 6-month period in Huntsville, Alabama. Comparisons indicate event rain totals for all three disdrometers that were in reasonable agreement with a reference rain gauge. In a relative sense, hourly composite DSDs revealed that the JWD was more sensitive to small drops (,1 mm), while the PD appeared to severely underestimate small drops less than 0.76mm in diameter. The JWD and 2DVD measured comparable number concentrations of midsize drops (1-3mm) and large drops (3-5 mm), while the PD tended to measure relatively higher drop concentrations at sizes larger than 2.44mm in diameter. This concentration disparity tended to occur when hourly rain rates and drop counts exceeded 2.5mm/h and 400/min, respectively. Based on interactions with the PD manufacturer, the partially inhomogeneous laser beam is considered the cause of the PD drop count overestimation. PD drop fall speeds followed the expected terminal fall speed relationship quite well, while the 2DVD occasionally measured slower drops for diameters larger than 2.4mm, coinciding with events where wind speeds were greater than 4m/s. The underestimation of small drops by the PD had a pronounced effect on the intercept and shape of parameters of gamma-fitted DSDs, while the overestimation of midsize and larger drops resulted in higher mean values for PD integral rain parameters
Shape and size distribution of chaos areas on Europa
Mikell, T.; Cox, R.
2008-12-01
Chaos terrain is ubiquitous on Europa's surface, but not randomly distributed. The global distribution of chaos areas shows a significant concentration between 30° N and S latitude, decreasing dramatically at higher latitudes. The low-latitude clustering is not an artifact of recognizability, as there is a greater proportion of images with high solar incidence angle (low light) at higher latitudes. Clustering is especially marked in context of the few but vast regional chaos tracts (>15,000 km2) that occupy a substantial proportion of the equatorial region: i.e. the low latitudes have not only greater numbers but much greater areal chaos coverage. Apex-antapex asymmetry is difficult to evaluate because the Galileo longitudinal coverage is so poor; but comparison of the image swaths that follow great circles across the leading and trailing hemispheres respectively shows greater numbers of chaos areas on the leading side. In spite of the equatorial location of a few vast chaos tracts, there is no apparent relationship between chaos area size and latitude. Chaos area outlines vary from smoothly circular to extremely jagged: the irregularity index ranges from 2- 270% (based on the ratio between measured chaos area perimeter and the circumference of a circle of equal area). There is a range of shapes in all size brackets, but smaller chaos areas on average have simpler, more equidimensional shapes, and edge complexity increases for larger chaos areas. Chaos areas of ~10 km equivalent circle diameter (ECD) have outlines that are 4-90% irregular, ones ~50 km ECD are 15-180% and those >100 km ECD are 35-270% irregular. In general, chaos areas with higher irregularity indices also have a higher raft:matrix ratio. These results, while preliminary, are consistent with experimental evidence suggesting an impact origin for some chaos terrain on Europa. In particular, the relationship between shape and size parallels the results of impact experiments into ice over water, in which lower-energy impacts produce small, circular bullet-holes with few or no rafts; and higher-energy impacts generate wide-field fragmentation of the ice, producing large and highly irregular openings with abundant floating crustal blocks.
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.
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
Directory of Open Access Journals (Sweden)
I. Norliza
2009-01-01
Full Text Available Industrial waste from sanitary company is chosen in this study as a precursor to fabricate ceramic membrane. It has been reported that enormous rejects being generated every year by this company. A preliminary characterization of this industrial waste shows the presence of quartz mineral, which is one of the main and suitable elements for the formation of ceramic products. Extrusion method was applied in fabricating tubular type ceramic membrane. In this present study, the effect of three different particle size distribution of the powder waste on the porosity is presented. The characterization of the porosity was performed in order to gain the insights in preparing ceramic membrane with good permeability. Results show that almost 40% porosity is able to be obtained using higher particle size distribution. However, further improvements in working conditions should be optimized in order to have a ceramic membrane with good physical properties.
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.
Directory of Open Access Journals (Sweden)
T. S. Kostadinov
2015-05-01
Full Text Available 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 (0.52 ?m in diameter, nanophytoplankton (220 ?m and microphytoplankton (2050 ?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 ~0.20.3 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.
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.
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.
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.)
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.
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
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
Directory of Open Access Journals (Sweden)
Vincenzo Bagarello
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.
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...
The Bose-Einstein distribution functions and the multiparticle production at high energies
G. A. Kozlov
2001-01-01
The evolution properties of propagating particles produced at high energies in a randomly distributed environment are studied. The finite size of the phase space of the multiparticle production region as well as the chaoticity can be derived.
Distribution of aflatoxins in contaminated corn fractions segregated by size
Directory of Open Access Journals (Sweden)
Piedade Fabiana S.
2002-01-01
Full Text Available The efficiency of segregation, by particle size, in reducing the aflatoxin content of corn lots under the Brazilian conditions was studied. The aflatoxin content, in the corn fractions obtained after sieving thirty contaminated samples, with approximately 3.0 kg each, was determined. The samples were passed through 4.5 mm round-hole sieves and the fractions with particles ³4.5 mm (fraction A and <4.5 mm (fraction B and then analyzed for aflatoxins by TLC. The results showed that the distribution of the aflatoxins among the fractions A and B varied from sample to sample. However, the fraction B presented higher content (6 to 1,422 µg/kg of aflatoxins (P<5%, than samples of fraction A (4 to 389 µg/kg. In spite of that the segregation of this fraction did not reduce significantly the contamination of the samples. This probably occurred because the contribution of the fraction B for the estimated total of the concentration of aflatoxin of the sample was smaller than that of the fraction A, due to the smallest amount of the fraction B in the sample weight total. In spite of being significant for the studied samples the correlation among the percentages of the groups of grains with defects a burning grains, sprouted, burned and moldy and b total injured, with the estimated level of contamination for the samples, more studies will be necessary so that better conclusions can be drawn for this correlation.
Aerosol size distribution seasonal characteristics measured in Tiksi, Russian Arctic
Asmi, E.; Kondratyev, V.; Brus, D.; Laurila, T.; Lihavainen, H.; Backman, J.; Vakkari, V.; Aurela, M.; Hatakka, J.; Viisanen, Y.; Uttal, T.; Ivakhov, V.; Makshtas, A.
2015-07-01
Four years of continuous aerosol number size distribution measurements from an Arctic Climate Observatory in Tiksi Russia are analyzed. Source region effects on particle modal features, and number and mass concentrations are presented for different seasons. The monthly median total aerosol number concentration in Tiksi ranges from 184 cm-3 in November to 724 cm-3 in July with a local maximum in March of 481 cm-3. The total mass concentration has a distinct maximum in February-March of 1.72-2.38 ?g m-3 and two minimums in June of 0.42 ?g m-3 and in September-October of 0.36-0.57 ?g m-3. These seasonal cycles in number and mass concentrations are related to isolated aerosol sources such as Arctic haze in early spring which increases accumulation and coarse mode numbers, and biogenic emissions in summer which affects the smaller, nucleation and Aitken mode particles. The impact of temperature dependent natural emissions on aerosol and cloud condensation nuclei numbers was significant. Therefore, in addition to the precursor emissions of biogenic volatile organic compounds, the frequent Siberian forest fires, although far are suggested to play a role in Arctic aerosol composition during the warmest months. During calm and cold months aerosol concentrations were occasionally increased by nearby aerosol sources in trapping inversions. These results provide valuable information on inter-annual cycles and sources of Arctic aerosols.
The size distribution of Jupiter Family comet nuclei
Snodgrass, C; Lowry, S C; Weissman, P
2011-01-01
We present an updated cumulative size distribution (CSD) for Jupiter Family comet (JFC) nuclei, including a rigourous assessment of the uncertainty on the slope of the CSD. The CSD is expressed as a power law, N(>r_N) \\propto r_N^{-q}, where r_N is the radius of the nuclei and q is the slope. We include a large number of optical observations published by ourselves and others since the comprehensive review in the "Comets II" book (Lamy et al. 2004), and make use of an improved fitting method. We assess the uncertainty on the CSD due to all of the unknowns and uncertainties involved (photometric uncertainty, assumed phase function, albedo and shape of the nucleus) by means of Monte Carlo simulations. In order to do this we also briefly review the current measurements of these parameters for JFCs. Our final CSD has a slope q=1.92\\pm 0.20 for nuclei with radius r_N \\ge 1.25 km.
Depth and size effects on cosmogenic nuclide production in meteorites
Englert, P.
1985-01-01
The galactic cosmic particle radiation (GCR) can cause changes in condensed extraterrestrial matter in different ways. It can lose energy via ionization processes of induced nuclear reactions which lead to a wide variety of stable and radioactive cosmogenic nuclides. Heavy particles incur radiation damage in minerals such as olivine and pyroxene. Light particles predominantly tend to induce nuclear reactions, causing the development of a secondary particle cascade of neutrons, protons, pions and gamma-rays and the production of cosmogenic nuclides. Such processes are described by various models, which predict the depth and size dependent production of cosmogenic nuclides.
Sharma, V. K.; Patil, R. S.
In situ measurements of mass concentration of size-distributed aerosols were made using a quartz crystal microbalance cascade impactor. Aerosol samples were also collected by the conventional high-volume sampler for comparison and analysed for size distribution using a centrifugal analyser system and an image analyser system. The number concentrations were calculated for different sizes and these were subjected to factor analysis which gave four factors representing various source types of particulates. A power-function fit was applied to the size-distribution curves for the four size ranges grouped by factor analysis. Generally, size-distribution ranges are either selected according to the change of the slope of the curves or depending upon the measurement size ranges. The use of factor analysis makes the size-distribution groupings source dependent and also avoids the possible errors arising from averaging negative and positive slopes.
Production of Large-Particle-Size Monodisperse Latexes in Microgravity
Vanderhoff, J. W.; Micale, F. J.; El-Aasser, M. S.; Kornfeld, M.
1985-01-01
A latex is a suspension of very tiny (micrometer-size) plastic spheres in water, stabilized by emulsifiers. The growth of billions of these tiny plastic spheres to sizes larger than can be grown on Earth is attempted while keeping all of them exactly the same size and perfectly spherical. Thus far on several of the Monodisperse Latex Reactor (MLR) flights, the latex spheres have been returned to Earth with standard deviations of better than 1.4%. In microgravity the absence of buoyancy effects has allowed growth of the balls up to 30 micrometers in diameter thus far. The MLR has now flown 5 times on the Shuttle. The MLR has now produced the first commercial space product; that is the first commercial material ever manufactured in space and marketed on Earth. Once it is demonstrated that these large-size-monodisperse latexes can be routinely produced in quantity and quality, they can be marketed for many types of scientific applications. They can be used in biomedical research for such things as drug carriers and tracers in the body, human and animal blood flow studies, membrane and pore-sizing in the body, and medical diagnostic tests.
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...
The economic production lot size model extended to include more than one production rate
DEFF Research Database (Denmark)
Larsen, Christian
2005-01-01
We study an extension of the economic production lot size model, where more than one production rate can be used during a cycle. Moreover, the production rates, as well as their corresponding runtimes are decision variables. We decompose the problem into two subproblems. First, we show that all production rates should be chosen in the interval between the demand rate and the production rate which minimizes unit production costs, and should be used in an increasing order. Then, given the production rates, we derive closed-form expressions for all optimal runtimes as well as the minimum average cost. This analysis reveals that it is the size of the setup cost that determines the need for being able to use several production rates. We also show how to derive a near-optimal solution of the general problem.
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 (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.
Quantitative analysis of bimodal grain size distributions in WC-Co hard materials
International Nuclear Information System (INIS)
A special method was implemented to quantify the bimodal character of the 3D grain size distribution in WC-Co sintered materials. The method deals with SEM images of materials sections. Grains are separated on binary images by an automatic algorithm. The intercept length distributions are measured. Data are then fitted with a model population of trigonal prisms with constant shape. Two kinds of grain size distributions are considered for the model: a unimodal (lognormal) distribution or a bimodal (bi-lognormal) size distribution. The method is applied to different WC-Co grades, and the bimodal character of the distribution is discussed. (author)
International Nuclear Information System (INIS)
We analyze the magnetic cluster size (MCS) and magnetic cluster size distribution (MCSD) in a variety of perpendicular magnetic recording (PMR) media designs using resonant small angle x-ray scattering at the Co L3 absorption edge. The different PMR media flavors considered here vary in grain size between 7.5 and 9.5?nm as well as in lateral inter-granular exchange strength, which is controlled via the segregant amount. While for high inter-granular exchange, the MCS increases rapidly for grain sizes below 8.5?nm, we show that for increased amount of segregant with less exchange the MCS remains relatively small, even for grain sizes of 7.5 and 8?nm. However, the MCSD still increases sharply when shrinking grains from 8 to 7.5?nm. We show evidence that recording performance such as signal-to-noise-ratio on the spin stand correlates well with the product of magnetic cluster size and magnetic cluster size distribution
Energy Technology Data Exchange (ETDEWEB)
Igathinathane, C [University of British Columbia, Vancouver; Pordesimo, L.O. [ADM Alliance Nutrition
2009-08-01
Dust management strategies in industrial environment, especially of airborne dust, require quantification and measurement of size and size distribution of the particles. Advanced specialized instruments that measure airborne particle size and size distribution apply indirect methods that involve light scattering, acoustic spectroscopy, and laser diffraction. In this research, we propose a simple and direct method of airborne dust particle dimensional measurement and size distribution analysis using machine vision. The method involves development of a user-coded ImageJ plugin that measures particle length and width and analyzes size distribution of particles based on particle length from high-resolution scan images. Test materials were airborne dust from soft pine wood sawdust pellets and ground pine tree bark pellets. Subsamples prepared by dividing the actual dust using 230 mesh (63 m) sieve were analyzed as well. A flatbed document scanner acquired the digital images of the dust particles. Proper sampling, layout of dust particles in singulated arrangement, good contrast smooth background, high resolution images, and accurate algorithm are essential for reliable analysis. A halo effect around grey-scale images ensured correct threshold limits. The measurement algorithm used Feret s diameter for particle length and pixel-march technique for particle width. Particle size distribution was analyzed in a sieveless manner after grouping particles according to their distinct lengths, and several significant dimensions and parameters of particle size distribution were evaluated. Results of the measurement and analysis were presented in textual and graphical formats. The developed plugin was evaluated to have a dimension measurement accuracy in excess of 98.9% and a computer speed of analysis of <8 s/image. Arithmetic mean length of actual wood and bark pellets airborne dust particles were 0.1138 0.0123 and 0.1181 0.0149 mm, respectively. The airborne dust particles of wood and bark pellets can be described as non uniform, finer particles dominated, very finely skewed with positive skewness, leptokurtic, and very well sorted category. Experimental mechanical sieving and machine vision methods produced comparable particle size distribution. The limitations and merits of using the machine vision technique for the measurement of size and size distribution of fine particles such as airborne dust were discussed.
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.)
Batch sizing with controllable production rates in a multi-stage production system
Glock, Christoph H.
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 Glocks (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 cas...
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 ...
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)
Knouft, Jason H
2004-05-01
Many taxonomic and ecological assemblages of species exhibit a right-skewed body size-frequency distribution when characterized at a regional scale. Although this distribution has been frequently described, factors influencing geographic variation in the distribution are not well understood, nor are mechanisms responsible for distribution shape. In this study, variation in the species body size-frequency distributions of 344 regional communities of North American freshwater fishes is examined in relation to latitude, species richness, and taxonomic composition. Although the distribution of all species of North American fishes is right-skewed, a negative correlation exists between latitude and regional community size distribution skewness, with size distributions becoming left-skewed at high latitudes. This relationship is not an artifact of the confounding relationship between latitude and species richness in North American fishes. The negative correlation between latitude and regional community size distribution skewness is partially due to the geographic distribution of families of fishes and apparently enhanced by a nonrandom geographic distribution of species within families. These results are discussed in the context of previous explanations of factors responsible for the generation of species size-frequency distributions related to the fractal nature of the environment, energetics, and evolutionary patterns of body size in North American fishes. PMID:15069632
Grain-size Distribution of Apollo 11 Soil 10084
Basu, A.; Wentworth, S. J.; McKay, D. S.
2000-01-01
Results of a new grain size analysis of 0.99 g of the submillimeter fraction of the soil 10084, using the JSC methodology, are: 4.28 phi =(51 micrometers) and 2.23 phi (=213 micrometers). A significant fraction (14.2%) of the soil is less than 10 micrometers in size.
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.
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
On the size and velocity distribution of cosmic dust particles entering the atmosphere
Carrillo-Sánchez, J. D.; Plane, J. M. C.; Feng, W.; Nesvornŭ, D.; Janches, D.
2015-08-01
The size and velocity distribution of cosmic dust particles entering the Earth's atmosphere is uncertain. Here we show that the relative concentrations of metal atoms in the upper mesosphere, and the surface accretion rate of cosmic spherules, provide sensitive probes of this distribution. Three cosmic dust models are selected as case studies: two are astronomical models, the first constrained by infrared observations of the Zodiacal Dust Cloud and the second by radar observations of meteor head echoes; the third model is based on measurements made with a spaceborne dust detector. For each model, a Monte Carlo sampling method combined with a chemical ablation model is used to predict the ablation rates of Na, K, Fe, Mg, and Ca above 60 km and cosmic spherule production rate. It appears that a significant fraction of the cosmic dust consists of small (<5 µg) and slow (<15 km s-1) particles.
Distribution, size and sex of bear kills and composition of Kodiak Island bear population
US Fish and Wildlife Service, Department of the Interior Distribution of kill dates, from existing records, by fifteen day periods from April 1 to November 30th and distribution by size, sex, and other variables.
Multi-component Erlang distribution of plant seed masses and sizes
Fan, San-Hong; Wei, Hua-Rong
2012-12-01
The mass and the size distributions of plant seeds are very similar to the multi-component Erlang distribution of final-state particle multiplicities in high-energy collisions. We study the mass, length, width, and thickness distributions of pumpkin and marrow squash seeds in this paper. The corresponding distribution curves are obtained and fitted by using the multi-component Erlang distribution. In the comparison, the method of ?2-testing is used. The mass and the size distributions of the mentioned seeds are shown to obey approximately the multi-component Erlang distribution with the component number being 1.
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 for different countries and age groups. Reliable vaccine production in appropriate quantities and at affordable prices is the cornerstone of developing global vaccination policies. However, ensuring optimal access and uptake also requires strong partnerships between private manufacturers, regulatory authorities and national and international public health services. For vaccines whose supplies are limited, either due to rapidly emerging diseases or longer-term mismatch of supply and demand, prioritizing target groups can increase vaccine impact. Focusing on influenza vaccines as an example that well illustrates many of the relevant points, this article considers current production, distribution, access and other factors that ultimately impact on vaccine uptake and population-level effectiveness. PMID:21664680
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
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)
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.
Determination of grain-size distribution from ultrasonic attenuation: Transformation and inversion
Energy Technology Data Exchange (ETDEWEB)
Nicoletti, D.; Anderson, A. [Electrical and Computer Engineering Department, Worcester Polytechnic Institute, 100 Institute Road, Worcester, Massachusetts 01609 (United States)
1997-02-01
Although researchers often describe a particular medium with only a single grain size or an average grain size, distributions of grain sizes can have significant effects on the physical characteristics of the material. Ultrasonic attenuation due to energy scattered at the grain boundaries depends on the ultrasonic wavelength, the grain size, and certain material properties such as elastic constants. This paper examines the relationship between the wavelength dependency of ultrasonic attenuation and grain-size distributions. A transformation is developed which solves a general class of Fredholm equations of the first kind. The equation relating attenuation to grain-size distributions belongs to this class of equations. The transformation allows attenuation to be calculated by discrete convolution, and provides a method for estimating the grain-size distribution directly from attenuation measurements. {copyright} {ital 1997 Acoustical Society of America.}
Taira, Wataru; Iwasaki, Mayo; Otaki, Joji M.
2015-07-01
The body size of the pale grass blue butterfly, Zizeeria maha, has been used as an environmental indicator of radioactive pollution caused by the Fukushima nuclear accident. However, geographical and temporal size distributions in Japan and temperature effects on size have not been established in this species. Here, we examined the geographical, temporal, and temperature-dependent changes of the forewing size of Z. maha argia in Japan. Butterflies collected in 2012 and 2013 from multiple prefectures throughout Japan demonstrated an inverse relationship of latitude and forewing size, which is the reverse of Bergmanns cline. The Fukushima population was significantly larger than the Aomori and Miyagi populations and exhibited no difference from most of the other prefectural populations. When monitored at a single geographic locality every other month, forewing sizes were the largest in April and the smallest in August. Rearing larvae at a constant temperature demonstrated that forewing size followed the temperature-size rule. Therefore, the converse Bergmanns rule and the temperature-size rule coexist in this multivoltine species. Our study establishes this species as a useful environmental indicator and supports the idea that the size reduction observed only in Fukushima Prefecture in 2011 was caused by the environmental stress of radioactive pollution.
Mikosch, Thomas; 10.3150/10-BEJ255
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 Fr\\'{e}chet distribution. We prove the results in the general framework of point processes and for jump sizes taking values in a separable Banach space.
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
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 produço de um único item em vários centros produtivos que no apresentam restriçġes de capacidade. A demanda pode ser atendida com ou sem atraso. Este problema surge da decomposiço 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 produço limitada. Primeiramente, apresentamos uma implementaço eficiente de um algoritmo de programaço dinâmica progressiva proposto para a soluço do problema com um único centro produtivo. Embora, essa implementaço no 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 so implementados dois algoritmos, o primeiro é uma extenso do algoritmo original e o segundo incorpora as idéias que tornam essa implementaço mais eficiente. O desempenho computacional dos algoritmos é analisado e propostas para futuras pesquisas so 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 produço de um único item em vários centros produtivos que no apresentam restriçġes de capacidade. A demanda pode ser atendida com ou sem atraso. Este problema surge da decomposiço 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 produço limitada. Primeiramente, apresentamos uma implementaço eficiente de um algoritmo de programaço dinâmica progressiva proposto para a soluço do problema com um único centro produtivo. Embora, essa implementaço no 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 so implementados dois algoritmos, o primeiro é uma extenso do algoritmo original e o segundo incorpora as idéias que tornam essa implementaço mais eficiente. O desempenho computacional dos algoritmos é analisado e propostas para futuras pesquisas so apresentadas.
[Particles size distribution and its influence on remote sensing retrieval of turbid Poyang Lake].
Huang, Jue; Chen, Xiao-Ling; Chen, Li-Qiong; Zhang, Li
2014-11-01
The suspended particle size distribution provides crucial information for the study of water environment structure and function. Based on the in-situ data from wet and dry season in 2008-2011, the paper studied suspended particle size distribution of Poyang Lake and its optical features. The suspended particle size distribution showed seasonal variation: the particle size of southern lake was larger than that of northern lake in dry season but showed little variation in wet season. The suspended particle size distribution exerted influence on particulate absorption coefficient, attenuation coefficient and scattering coefficient. The particulate absorption coefficient of northern lake was higher than that of southern lake. The negative correlation between specific absorption coefficient of total suspended particles and median particle size indicated that there was "package effect" of mineral particles in turbid Poyang Lake. The spatial and temporal distribution of particulate attenuation coefficient and scattering coefficient are similar: there were obvious regional differences in dry season but few in wet season. There were good correlations among the remote sensing reflectance, spectra slope of particle size distribution and spectra slope of particulate scattering coefficient. These correlations would provide the foundation for remote sensing retrieval of particle size and quantitative analysis of influence of suspended particle size on the optical properties. The relationship between particle size distribution, particulate back-scattering coefficient and bulk refractive index can provide information of particle composition in Poyang Lake. PMID:25752063
The impact of fuel particle size distribution on neutron transport in stochastic media
International Nuclear Information System (INIS)
This paper presents a study of the particle size distribution impact on neutron transport in three-dimensional stochastic media. An eigenvalue problem is simulated in a cylindrical container consisting of fissile fuel particles with five different size distributions: constant, uniform, power, exponential and Gaussian. We construct 15 cases by altering the fissile particle volume packing fraction and its optical thickness, but keeping the mean chord length of the spherical fuel particle the same at different size distributions. The tallied effective multiplication factor (keff) and flux distribution along axial and radial directions are compared between different size distributions. At low packing fraction and low optical thickness, the size distribution has a significant impact on radiation transport in stochastic media, which can cause as high as ?270 pcm difference in keff value and ?2.6% relative error difference in peak flux. As the packing fraction and optical thickness increase, the impact gradually dissipates. (authors)
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 ħ 0.6 ?g L-1 during the incubation. Inorganic nitrogen was taken up producing a maximum of 10 ħ 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 ħ 0.4 ?mol dissolved organic nitrogen L-1 and 33 ħ 6.2 ?mol dissolved organic carbon L-1 was produced during the incubation. Bioavailability of phytoplankton produced dissolved organic carbon was 12 ħ 1 % and higher than in the presence of bacteria, microzooplankton, orcopepods (7 ħ 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.
A generalized statistical model for the size distribution of wealth
Clementi, F; Kaniadakis, G
2012-01-01
In a recent paper in this journal [J. Stat. Mech. (2009) P02037] we proposed a new, physically motivated, distribution function for modeling individual incomes having its roots in the framework of the k-generalized statistical mechanics. The performance of the k-generalized distribution was checked against real data on personal income for the United States in 2003. In this paper we extend our previous model so as to be able to account for the distribution of wealth. Probabilistic functions and inequality measures of this generalized model for wealth distribution are obtained in closed form. In order to check the validity of the proposed model, we analyze the U.S. household wealth distributions from 1984 to 2009 and conclude an excellent agreement with the data that is superior to any other model already known in the literature.
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)
Distributed Monte Carlo production for D0
Energy Technology Data Exchange (ETDEWEB)
Snow, Joel; /Langston U.
2010-01-01
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.
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.
Czech Academy of Sciences Publication Activity Database
Beddows, D.C.S.; DallOsto, 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.; dímal, Vladimír; Zíková, Nad?da; 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
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.
International Nuclear Information System (INIS)
The influence of initial particle size distribution on coarsening during liquid phase sintering has been experimentally investigated using W-14Ni-6Fe alloy as a model system. It was found that initially wider size distribution particles coarsened more rapidly than those of an initially narrow distribution. The well known linear relationship between the cube of the average particle radius bar r-3, and time was observed for most of the coarsening process, although the early stage coarsening rate constant changed with time, as expected with concomitant early changes in the tungsten particle size distribution. The instantaneous transient rate constant was shown to be related to the geometric standard deviation, 1n?, of the instantaneous size distributions, with higher rate constants corresponding to larger 1n? values. The form of the particle size distributions changed rapidly during early coarsening and reached a quasi-stable state, different from the theoretical asymptotic distribution, after some time. A linear relationship was found between the experimentally observed instantaneous rate constant and that computed from an earlier model incorporating the effect of particle size distribution. The above results compare favorably with those from prior theoretical modeling and computer simulation studies of the effect of particle size distribution on coarsening, based on the DeHoff communicating neighbor model
Indoor radon progeny particle size distribution measurements made with two different methods
International Nuclear Information System (INIS)
Indoor radon progeny particle size measurements using two distinctly different instruments, a diffusion battery and an electrical aerosol size analyser, were carried out in two single-family homes in New Jersey. The activity-weighted size distributions were determined by applying the radon progeny attachment theory to the measured number-weighted particle size spectra and the results are close to those measured by the diffusion battery method. These particle size distributions were found to be more often bimodal than unimodal. The minor modes of the bimodal distributions were located around the 1 nm region, close to the 218Po atom size, except one centred around 10 nm. For both the unimodal and the bimodal distributions, the modal diameter of the major mode ranged from 30 nm to 150 nm, respectively. The results previously reported showed modal diameters around 100 nm. (author)
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
Particles size distribution effect on 3D packing of nanoparticles in to a bounded region
International Nuclear Information System (INIS)
In this paper, the effects of two different Particle Size Distributions on packing behavior of ideal rigid spherical nanoparticles using a novel packing model based on parallel algorithms have been reported. A mersenne twister algorithm was used to generate pseudo random numbers for the particles initial coordinates. Also, for this purpose a nano sized tetragonal confined container with a square floor (300 * 300 nm) were used in this work. The Andreasen and the Lognormal Particle Size Distributions were chosen to investigate the packing behavior in a 3D bounded region. The effects of particle numbers on packing behavior of these two Particle Size Distributions have been investigated. Also the reproducibility and the distribution of packing factor of these Particle Size Distributions were compared
Experimental study on bubble size distributions in a direct-contact evaporator
Directory of Open Access Journals (Sweden)
Ribeiro Jr. C. P.
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.
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.
Bias-corrected population, size distribution, and impact hazard for the near-Earth objects
Stuart, Joseph Scott; Binzel, Richard P.
2004-08-01
Utilizing the largest available data sets for the observed taxonomic (Binzel et al., 2004, Icarus 170, 259-294) and albedo (Delbo et al., 2003, Icarus 166, 116-130) distributions of the near-Earth object population, we model the bias-corrected population. Diameter-limited fractional abundances of the taxonomic complexes are A-0.2%; C-10%, D-17%, O-0.5%, Q-14%, R-0.1%, S-22%, U-0.4%, V-1%, X-34%. In a diameter-limited sample, 30% of the NEO population has jovian Tisserand parameter less than 3, where the D-types and X-types dominate. The large contribution from the X-types is surprising and highlights the need to better understand this group with more albedo measurements. Combining the C, D, and X complexes into a "dark" group and the others into a "bright" group yields a debiased dark-to-bright ratio of 1.6. Overall, the bias-corrected mean albedo for the NEO population is 0.14ħ0.02, for which an H magnitude of 17.8ħ0.1 translates to a diameter of 1 km, in close agreement with Morbidelli et al. (2002, Icarus 158 (2), 329-342). Coupling this bias corrected taxonomic and albedo model with the H magnitude dependent size distribution of (Stuart, 2001, Science 294, 1691-1693) yields a diameter distribution with 1090ħ180 NEOs with diameters larger than 1 km. As of 2004 June, the Spaceguard Survey has discovered 56% of the NEOs larger than 1 km. Using our size distribution model, and orbital distribution of (Stuart, 2001, Science 294, 1691-1693) we calculate the frequency of impacts into the Earth and the Moon. Globally destructive collisions (10 21 J) of asteroids 1 km or larger strike the Earth once every 0.60ħ0.1 Myr on average. Regionally destructive collisions with impact energy greater than 4×10 18 J (200 m diameter) strike the Earth every 56,000ħ6000 yr. Collisions in the range of the Tunguska event (4-8×10 16 J) occur every 2000-3000 yr. These values represent the average time between randomly spaced impacts; actual impacts could occur more or less closely spaced solely by chance. As a verification of these impact rates, the crater production function of Shoemaker et al. (1990, Geological Society of American Special Paper 247) has been updated by combining this new population model with a crater formation model to find that the observed crater production function on both the Earth and Moon agrees with the rate of crater production expected from the current population of NEOs.
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.)
Interpretation of aerosol trace metal particle size distributions
International Nuclear Information System (INIS)
Proton-induced X-ray emission (PIXE) analysis is capable of rapid routine determination of 10--15 elements present in amounts greater than or equal to 1 ng simultaneously in aerosol size fractions as collected by single orifice impactors over short periods of time. This enables detailed study of complex relationships between elements detected. Since absolute elemental concentrations may be strongly influenced by meteorological and topographical conditions, it is useful to normalize to a reference element. Comparison between the ratios of concentrations with aerosol and corresponding values for anticipated sources may lead to the identification of important sources for the elements. Further geochemical insights may be found through linear correlation coefficients, regression analysis, and cluster analysis. By calculating correlations for elemental pairs, an indication of the degree of covariance between the elements is obtained. Preliminary results indicate that correlations may be particle size dependent. A high degree of covariance may be caused either by a common source or may only reflect the conservative nature of the aerosol. In a regression analysis, by plotting elemental pairs and estimating the regression coefficients, we may be able to conclude if there is more than one source operating for a given element in a certain size range. Analysis of clustering of several elements, previously investigated for aerosol filter samples, can be applied to the analysis of aerosol size fractions. Careful statistical treatment of elemental concentrations as a function of aerosol particle size may thus yield significant information on the generation, transport and deposition of trace metals in the atmosphere
Does plot size affect the performance of GIS-based species distribution models?
Pandit, Shubha N.; Hayward, April; de Leeuw, Jan; Kolasa, Jurek
2010-12-01
Species distribution models are used extensively in predicting the distribution of vegetation across a landscape. Accuracy of the species distribution maps produced by these models deserves attention, since low accuracy maps may lead to erroneous conservation decisions. While plot size is known to influence measures of species richness, its effect on our ability to predict species distribution ranges has not been tested. Our aim is to test whether the accuracy of the distribution maps produced depend on the size of the plot (quadrat) used to collect biological data in the field. In this study, the presences of four plant species were recorded in five sizes of circular plots, with radii ranging from 8 to 100 m. Logistic regression-based models were used to predict the distributions of the four plant species based on empirical evidence of their relationship with eight environmental predictors: distance to river, slope, aspect, altitude, and four principle component axes derived using reflectance values from Aster images. We found that plot size affected the probability of recording the four species, with reductions in plot size generally increasing the frequency of recorded absences. Plot size also significantly affected the likelihood of correctly predicting the distribution of species whenever plot size was below the minimum size required to consistently record species presence. Furthermore, the optimal plot size for fitting species distribution models varied among species. Finally, plot size had little impact on overall accuracy, but a strong, positive impact on Kappa accuracy (which provides a stronger measure of model accuracy by accounting for the effects of chance agreements between predictions and observations). Our results suggest that optimal plot size must be considered explicitly in the creation of species distribution models if they are to be successfully adopted into conservation efforts.
Optimizing Batch Size in a Flow-Oriented Synchronized Production
Directory of Open Access Journals (Sweden)
Imran Aslan
2011-06-01
Full Text Available This study was prepared for a leading company, Miele GmbH, the global premium brand of domestic appliancesand commercial machines in the field of laundry care, dishwashing and disinfection in Germany. The productionline of Miele GmbH in Bielefeld, Germany was analyzed to develop a model that can be used for all the firms inthe group.Dynamic programming models are widely used by companies to efficiently meet the demand for a variety ofproducts. In a flow shop, each product has to be processed by a number of machines in synchronized lines. Theproduction smoothing problems under the presence of setup and processing times vary among the products. Themaster production-inventory problem of Miele GmbH was divided into two sub-problems which were concernedwith determining the batch sizes and production sequences of products, respectively. A dynamic programmingprocedure was developed to solve the batching problem for the current problem. A dynamic computational studyfor the first case was conducted so that the solution method is effective in meeting the goals of the firm andefficient in its computational requirements.Scientific problem the firm has a problem of high logistics. Moreover, they want to decrease the cost ofproduction in order to compete with their competitors. Their competitors start to make some of their productionin low labour countries such as China. Miele is a special brand for upper level. However, they now have a morestrict competition with new global players and one way to stay competitive in the market is to decrease the costsand find new market segments.The aim of the research The dynamic programming algorithm is suggested to them to decrease the costs. Thenumbers of products are decreased to explain the algorithm. An example with calculations of this algorithm wasexplained in this study. The number of variables and constraints can be increased. After the logic of algorithm isunderstood, it can be applied many similar problems. The algorithm can be developed by using differentsoftware such as Java. Then, the variables and values of algorithm can be input for the algorithm and the resultscan be gotten in a short time.The object of the research Inventory and Production mix projects.The methods of the research Dynamic Programming.
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...
System Size Dependence of Particle Production at the SPS
Blume, C
2010-01-01
Recent results on the system size dependence of net-baryon and hyperon production as measured at the CERN SPS are discussed. The observed Npart~dependences of yields, but also of dynamical properties, such as average transverse momenta, can be described in the context of the core corona approach. Other observables, such as antiproton yields and net-protons at forward rapidities, do not follow the predictions of this model. Possible implications for a search for a critical point in the QCD phase diagram are discussed. Event-by-event fluctuations of the relative core to corona source contributions might influence fluctuation observables (e.g. multiplicity fluctuations). The magnitude of this effect is investigated.
CHARACTERIZATION OF BIVARIATE SIZE-ORIENTATION DISTRIBUTION OF CIRCULAR PLATE PARTICLES
Karel Bodlák; Arun Balasundarun M Gokhale; Viktor Bene
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...
Fissure formation in coke. 3: Coke size distribution and statistical analysis
Energy Technology Data Exchange (ETDEWEB)
D.R. Jenkins; D.E. Shaw; M.R. Mahoney [CSIRO, North Ryde, NSW (Australia). Mathematical and Information Sciences
2010-07-15
A model of coke stabilization, based on a fundamental model of fissuring during carbonisation is used to demonstrate the applicability of the fissuring model to actual coke size distributions. The results indicate that the degree of stabilization is important in determining the size distribution. A modified form of the Weibull distribution is shown to provide a better representation of the whole coke size distribution compared to the Rosin-Rammler distribution, which is generally only fitted to the lump coke. A statistical analysis of a large number of experiments in a pilot scale coke oven shows reasonably good prediction of the coke mean size, based on parameters related to blend rank, amount of low rank coal, fluidity and ash. However, the prediction of measures of the spread of the size distribution is more problematic. The fissuring model, the size distribution representation and the statistical analysis together provide a comprehensive capability for understanding and predicting the mean size and distribution of coke lumps produced during carbonisation. 12 refs., 16 figs., 4 tabs.
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 rocks 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.
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...
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 dimensġes dos blocos (comprimento e área). Isso fo [...] i implementado de acordo com um protocolo de amostragem específico, que envolve etapas de diviso e de homogeneizaço in situ de uma considerável quantidade de minério (cerca de 259 toneladas). Durante o processo de amostragem, os blocos maiores foram segregados, para mensuraço, 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 caminhġes. Condiçġes operacionais desse tipo de equipamento, tais como configuraçġes das aberturas de posiço aberta (APA) e de posiço fechada (APF), podem ser ajustadas previamente, permitindo, assim, a obtenço de diferentes distribuiçġes 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 diminuiço da produtividade e recuperaço 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.
Verification of CR-39 Technique for Attached Radon Progeny Size Distribution
International Nuclear Information System (INIS)
Full text: A new type cascade impactor has been developed to determine the activity size distribution of radon and thoron progeny in a living environment more efficiently. The modified impactor consists of 4 stages for the collection of aerosol samples. The aerosol cut points in the impactor are set for 10, 2.5, 1 and 0.5 ? m at a flow rate of 4 L.min-1. Five CR-39 chips were used as alpha detectors for each stage. In order to separate ? particles emitted from radon and thoron progeny, CR-39 detectors are covered with aluminum-vaporized Mylar films. Thickness of films is properly adjusted to allow ? particles emitted from radon and thoron progeny to reach the CR-39 detectors. In addition, a 400-mesh metal wire screen was mounted as diffusion collector at the air inlet of the impactor to remove the unattached fraction of radon and thoron decay products. Validation of the technique was performed with the commercial devices. The results confirmed that the developed technique can provide us significant information to estimate the activity size distribution of attached radon and thoron progeny for dose assessment
Kozawa, Kathleen H.; Arthur M Winer; Fruin, Scott A.
2012-01-01
High ambient ultrafine particle (UFP) concentrations may play an important role in the adverse health effects associated with living near busy roadways. However, UFP size distributions change rapidly as vehicle emissions dilute and age. These size changes can influence UFP lung deposition rates and dose because deposition in the respiratory system is a strong function of particle size. Few studies to date have measured and characterized changes in near-road UFP size distribu...
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 13 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.
International Nuclear Information System (INIS)
The Capstone Depleted Uranium (DU) Aerosol Study, which generated and characterized aerosols containing depleted uranium from perforation of armored vehicles with large-caliber DU penetrators, incorporated a sampling protocol to evaluated particle size distributions. Aerosol particle size distribution is an important parameter that influences aerosol transport and deposition processes as well as the dosimetry of the inhaled particles. These aerosols were collected on cascade impactor substrates using a pre-established time sequence following the firing event to analyze the uranium concentration and particle size of the aerosols as a function of time. The impactor substrates were analyzed using beta spectrometry, and the derived uranium content of each served as input to the evaluation of particle size distributions. Activity median aerodynamic diameters (AMADs) of the particle size distributions were evaluated using unimodal and bimodal models. The particle size data from the impactor measurements was quite variable. Most size distributions measured in the test based on activity had bimodal size distributions with a small particle size mode in the range of between 0.2 and 1.2 um and a large size mode between 2 and 15 um. In general, the evolution of particle size over time showed an overall decrease of average particle size from AMADs of 5 to 10 um shortly after perforation to around 1 um at the end of the 2-hr sampling period. The AMADs generally decreased over time because of settling. Additionally, the median diameter of the larger size mode decreased with time. These results were used to estimate the dosimetry of inhaled DU particles
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
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.
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.
On the Noncommutative Neutrix Product of Distributions
Directory of Open Access Journals (Sweden)
Biljana Jolevska-Tuneska
2007-11-01
Full Text Available ŻÂğÂżLet f and g be distributions and let gn=(g*Â´n(x, where Â´n(x is a certain sequence converging to the Dirac-delta function Â´(x. The noncommutative neutrix product f˘ÂÂg of f and g is defined to be the neutrix limit of the sequence {fgn}, provided the limit h exists in the sense that N˘ÂÂlimn˘ÂÂ˘ÂÂ˘ÂÂİf(xgn(x,Â(x˘ÂÂŞ=˘ÂÂİh(x,Â(x˘ÂÂŞ, for all test functions in °ÂÂÂ. In this paper, using the concept of the neutrix limit due to van der Corput (1960, the noncommutative neutrix products x+rlnx+˘ÂÂx˘ÂÂ˘ÂÂr˘ÂÂ1lnx˘ÂÂ and x˘ÂÂ˘ÂÂr˘ÂÂ1lnx˘ÂÂ˘ÂÂx+rlnx+ are proved to exist and are evaluated for r=1,2,˘ÂÂĤ. It is consequently seen that these two products are in fact equal.
Does the size distribution of mineral dust aerosols depend on the wind speed at emission?
Directory of Open Access Journals (Sweden)
J. F. Kok
2011-07-01
Full Text Available The size distribution of mineral dust aerosols greatly affects their interactions with clouds, radiation, ecosystems, and other components of the Earth system. Several theoretical dust emission models predict that the dust size distribution depends on the wind speed at emission, with larger wind speeds predicted to produce smaller aerosols. The present study investigates this prediction using a compilation of published measurements of the size-resolved vertical dust flux emitted by eroding soils. Surprisingly, these measurements indicate that the size distribution of naturally emitted dust aerosols is independent of the wind speed. This finding is consistent with the recently formulated brittle fragmentation theory of dust emission, but inconsistent with other theoretical dust emission models. The independence of the emitted dust size distribution with wind speed simplifies both the parameterization of dust emission in atmospheric circulation models as well as the interpretation of geological records of dust deposition.
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.
International Nuclear Information System (INIS)
The moment method can be used to determine the time evolution of particle size distribution due to Brownian coagulation based on the general dynamic equation (GDE). But the function form of the initial particle size distribution must be determined beforehand for the moment method. If the assumed function type of the initial particle size distribution has an obvious deviation from the true particle population, the evolution of particle size distribution may be different from the real evolution tendency. Thus, a simple and general method is proposed based on the moment method. In this method, the Johnson's SB function is chosen as a general distribution function to fit the initial distributions including the log normal (L-N), RosinRammler (R-R), normal (N-N) and gamma distribution functions, respectively. Meanwhile, using the modified beta function to fit the L-N, R-R, N-N and gamma functions is also conducted as a comparison in order to present the advantage of the Johnson's SB function as the general distribution function. And then, the time evolution of particle size distributions using the Johnson's SB function as the initial distribution can be obtained by several lower order moment equations of the Johnson's SB function in conjunction with the GDE during the Brownian coagulation process. Simulation experiments indicate that fairly reasonable results of the time evolution of particle size distribution can be obtained with this proposed method in the free molecule regime, transition regime and continuum plus near continuum regime, respectively, at the early time stage of evolution. The Johnson's SB function has the ability of describing the early time evolution of different initial particle size distributions. (paper)
Hirashita, Hiroyuki
2015-03-01
Full calculations of the evolution of grain size distribution in galaxies are in general computationally heavy. In this paper, we propose a simple model of dust enrichment in a galaxy with a simplified treatment of grain size distribution by imposing a two-size approximation; that is, the whole grain population is represented by small grains (radius a 0.03 ?m). We include in the model dust supply from stellar ejecta, destruction in supernova shocks, dust growth by accretion, grain growth by coagulation and grain disruption by shattering, and consider how these processes work on the small and large grains. We show that this simple framework reproduces the main features of full calculations of grain size distributions as follows. Dust enrichment starts with a supply of large grains from stars. At a metallicity level, referred to as the critical metallicity of accretion, the abundance of small grains formed by shattering becomes large enough to increase grain abundance rapidly by accretion. Associated with this epoch, the mass ratio of small grains to large grains reaches a maximum. Afterwards, this ratio converges to the value determined by the balance between shattering and coagulation, and the dust-to-metal ratio is determined by the balance between accretion and shock destruction. Using a Monte Carlo simulation, we demonstrate that the simplicity of our model has an advantage in predicting statistical properties. We also show some applications for predicting observational dust properties such as extinction curves.
Hirashita, Hiroyuki
2014-01-01
Full calculations of the evolution of grain size distribution in galaxies are in general computationally heavy. In this paper, we propose a simple model of dust enrichment in a galaxy with a simplified treatment of grain size distribution by imposing a `two-size approximation'; that is, all the grain population is represented by small (grain radius a 0.03 micron) grains. We include in the model dust supply from stellar ejecta, destruction in supernova shocks, dust growth by accretion, grain growth by coagulation and grain disruption by shattering, considering how these processes work on the small and large grains. We show that this simple framework reproduces the main features found in full calculations of grain size distributions as follows. The dust enrichment starts with the supply of large grains from stars. At a metallicity level referred to as the critical metallicity of accretion, the abundance of the small grains formed by shattering becomes large enough to rapidly increase the grain abundance by acc...
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
Engler, Christa; Heinold, Bernd; Tegen, Ina
2014-05-01
The atmospheric Chemistry Transport Model system COSMO-MUSCAT was used to determine the particle mass concentrations of dust and anthropogenically emitted aerosol particles over Europe. The model system consists of the online coupled code of the operational forecast model COSMO (Schättler et al., 2009) and the chemistry-transport model MUSCAT (Wolke et al., 2012). For a four-months-period in 2008 (May to August), the dust and anthropogenic aerosol mass concentrations for six different species (sulfate, nitrate, ammonium, organic and elemental carbon and sea salt) were simulated. For the dust, five different size bins were used and a representative particle size and density were assumed for each size bin. Afterwards, the number concentration was calculated. For the anthropogenic aerosol, lognormal modes were assumed with a representative mode diameter, sigma and density for each component. These parameters were then used to convert the simulated mass concentrations to number concentrations and number size distributions for each component. Those individual size distributions can then be summed up to a total particle number size distribution. A first comparison with measurement data from the Cape Verde Islands showed a good agreement between observed and simulated dust particle size distributions. Both, the shape of the number size distributions and the order of magnitude of the particle number concentrations compared well. Only for the smallest size bin, observed numbers were occasionally higher, which can be explained by anthropogenic or biomass burning aerosol, which is included in the measurements of the total particle size distributions but was not included in the model runs. Comparisons of measured and simulated size distributions of the anthropogenic aerosol will be available soon. In case the data are available, we will also present an estimation of the particle number concentrations with the aerosol microphysical aerosol module ext-M7 for the duration of a measurement campaign in spring 2013 (HOPE).
Size Distribution Imaging by Non-Uniform Oscillating-Gradient Spin Echo (NOGSE) MRI
Shemesh, Noam; Álvarez, Gonzalo A.; Frydman, Lucio
2015-01-01
Objects making up complex porous systems in Nature usually span a range of sizes. These size distributions play fundamental roles in defining the physicochemical, biophysical and physiological properties of a wide variety of systems ranging from advanced catalytic materials to Central Nervous System diseases. Accurate and noninvasive measurements of size distributions in opaque, three-dimensional objects, have thus remained long-standing and important challenges. Herein we describe how a recently introduced diffusion-based magnetic resonance methodology, Non-Uniform-Oscillating-Gradient-Spin-Echo (NOGSE), can determine such distributions noninvasively. The method relies on its ability to probe confining lengths with a (length)6 parametric sensitivity, in a constant-time, constant-number-of-gradients fashion; combined, these attributes provide sufficient sensitivity for characterizing the underlying distributions in ?m-scaled cellular systems. Theoretical derivations and simulations are presented to verify NOGSEs ability to faithfully reconstruct size distributions through suitable modeling of their distribution parameters. Experiments in yeast cell suspensions where the ground truth can be determined from ancillary microscopy corroborate these trends experimentally. Finally, by appending to the NOGSE protocol an imaging acquisition, novel MRI maps of cellular size distributions were collected from a mouse brain. The ensuing micro-architectural contrasts successfully delineated distinctive hallmark anatomical sub-structures, in both white matter and gray matter tissues, in a non-invasive manner. Such findings highlight NOGSEs potential for characterizing aberrations in cellular size distributions upon disease, or during normal processes such as development. PMID:26197220
Energy Technology Data Exchange (ETDEWEB)
Schmidl, Frank [Institut of Solid State Physics, Friedrich-Schiller-University Jena, D-07743 Jena (Germany)]. E-mail: Frank.Schmidl@uni-jena.de; Weber, Peter [Institut of Solid State Physics, Friedrich-Schiller-University Jena, D-07743 Jena (Germany); Koettig, Torsten [Institut of Solid State Physics, Friedrich-Schiller-University Jena, D-07743 Jena (Germany); Buettner, Markus [Institut of Solid State Physics, Friedrich-Schiller-University Jena, D-07743 Jena (Germany); Prass, Stefan [Institut of Solid State Physics, Friedrich-Schiller-University Jena, D-07743 Jena (Germany); Becker, Christoph [Institut of Solid State Physics, Friedrich-Schiller-University Jena, D-07743 Jena (Germany); Mans, Michael [Institut of Solid State Physics, Friedrich-Schiller-University Jena, D-07743 Jena (Germany); Heinrich, Jochen [Innovent Technologieentwicklung, Pruessingstrasse 27B, D-07743 Jena (Germany); Roeder, Michael [Innovent Technologieentwicklung, Pruessingstrasse 27B, D-07743 Jena (Germany); Wagner, Kerstin [Innovent Technologieentwicklung, Pruessingstrasse 27B, D-07743 Jena (Germany); Berkov, Dimitr V. [Innovent Technologieentwicklung, Pruessingstrasse 27B, D-07743 Jena (Germany); Goernert, Peter [Innovent Technologieentwicklung, Pruessingstrasse 27B, D-07743 Jena (Germany); Gloeckl, Gunnar [Institute of Pharmacy, Ernst-Moritz-Arndt-University, D-17487 Greifswald (Germany); Weitschies, Werner [Institute of Pharmacy, Ernst-Moritz-Arndt-University, D-17487 Greifswald (Germany); Seidel, Paul [Institut of Solid State Physics, Friedrich-Schiller-University Jena, D-07743 Jena (Germany)
2007-04-15
The magnetic properties of a ferrofluid are strongly influenced by its particle size distribution. We analyzed a ferrofluid with an unknown particle size distribution as well as fractionated samples of the original material. The ferrofluid in our investigations consists of a mixture of maghemite and magnetite. We investigated these different samples using temperature-dependent magnetorelaxometry method. The evaluation of the Neel relaxation signal allows us a direct determination of the energy barrier distribution, which is one of the most important parameters of such systems of magnetic nanoparticles. The calculated particle volumes were compared with particle sizes determined by transmission electron microscopy.
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)
The magnetic properties of a ferrofluid are strongly influenced by its particle size distribution. We analyzed a ferrofluid with an unknown particle size distribution as well as fractionated samples of the original material. The ferrofluid in our investigations consists of a mixture of maghemite and magnetite. We investigated these different samples using temperature-dependent magnetorelaxometry method. The evaluation of the Neel relaxation signal allows us a direct determination of the energy barrier distribution, which is one of the most important parameters of such systems of magnetic nanoparticles. The calculated particle volumes were compared with particle sizes determined by transmission electron microscopy
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
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.
A Divot in the Size Distribution of the Kuiper Belt's Scattering Objects
Shankman, C; Kaib, N; Kavelaars, J J; Petit, J -M
2012-01-01
Via joint analysis of a calibrated telescopic survey, which found scattering Kuiper Belt objects, and models of their expected orbital distribution, we measure the form of the scattering object's size distribution. Ruling out a single power-law at greater than 99% confidence, we constrain the form of the size distribution and find that, surprisingly, our analysis favours a very sudden decrease (a divot) in the number distribution as diameters decrease below 100 km, with the number of smaller objects then rising again as expected via collisional equilibrium. Extrapolating at this collisional equilibrium slope produced enough kilometer-scale scattering objects to supply the nearby Jupiter-Family comets. Our interpretation is that this divot feature is a preserved relic of the size distribution made by planetesimal formation, now "frozen in" to portions of the Kuiper Belt sharing a "hot" orbital inclination distribution, explaining several puzzles in Kuiper Belt science. Additionally, we show that to match today...
Transformation on steel products distribution in Poland and Slovakia
Directory of Open Access Journals (Sweden)
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 ...
Agimelen, Okpeafoh S.; Hamilton, Peter; Haley, Ian; Nordon, Alison; Vasile, Massimiliano; Sefcik, Jan; 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 di...
Undersampling power-law size distributions: effect on the assessment of extreme natural hazards
Geist, Eric L.; Parsons, Thomas E.
2014-01-01
The effect of undersampling on estimating the size of extreme natural hazards from historical data is examined. Tests using synthetic catalogs indicate that the tail of an empirical size distribution sampled from a pure Pareto probability distribution can range from having one-to-several unusually large events to appearing depleted, relative to the parent distribution. Both of these effects are artifacts caused by limited catalog length. It is more difficult to diagnose the artificially depleted empirical distributions, since one expects that a pure Pareto distribution is physically limited in some way. Using maximum likelihood methods and the method of moments, we estimate the power-law exponent and the corner size parameter of tapered Pareto distributions for several natural hazard examples: tsunamis, floods, and earthquakes. Each of these examples has varying catalog lengths and measurement thresholds, relative to the largest event sizes. In many cases where there are only several orders of magnitude between the measurement threshold and the largest events, joint two-parameter estimation techniques are necessary to account for estimation dependence between the power-law scaling exponent and the corner size parameter. Results indicate that whereas the corner size parameter of a tapered Pareto distribution can be estimated, its upper confidence bound cannot be determined and the estimate itself is often unstable with time. Correspondingly, one cannot statistically reject a pure Pareto null hypothesis using natural hazard catalog data. Although physical limits to the hazard source size and by attenuation mechanisms from source to site constrain the maximum hazard size, historical data alone often cannot reliably determine the corner size parameter. Probabilistic assessments incorporating theoretical constraints on source size and propagation effects are preferred over deterministic assessments of extreme natural hazards based on historic data.
Energy Technology Data Exchange (ETDEWEB)
Kauppinen, E.; Heiskanen, M.; Hahkala, M.
1989-05-01
A real time method to measure combustion aerosol size distributions with high particle size resolution has been developed. Flue gas is first diluted and cooled with the dilution system, followed by the differential mobility particle size analyzer (DMPS) and the aerodynamic particle sizer (APS) used to measure aerosol number size distributions in the size ranges 0.01-1 /mu/m, respectively. The dilution system includes two dilution units, which have the dilution ratio in the range 4.3-71. The total dilution ratio can be adjusted within the range 19-5041. The dilution units were calibrated in laboratory conditions. When the sample and the dilution ai flow rates were 1.0-2.7 l/min and 10-70 l/min, respectively, and the particle diameter 0.014-0.191 /mu/m, calculated and measured dilution ratios agreed within the accuracy of the measured results. The size distributions of the oil combustion aerosols were measured with the developed method. Light fuel oil was burned in 19 kW boiler using two different burners. The number size distributions were unimodal with most of the particles in the size range 0.02-0.2 /mu/m. The mass distributions were clearly bimodal, having a fine mode at about 0.2 /mu/m and a coarse mode above 10 /mu/m. Fine particle concentrations and mean particle diameter increased with increased furnace efficiency and flue gas CO concentration, i.e., when decreasing the air/fuel ratio. They also increased when the air/fuel ratio was very large. The shape of the size distribution measured for buners 1 and 2 under similar conditions was similar, but boiler 1 produced flue gases with higher particle concentrations. The differences in the size distributions measured for the burner 2 when burning summe and winter grades of light fuel oil, respectively, were found to be negligible.
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
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 Energys 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
Image Analysis of Pellet Size for a Control System in Industrial Feed Production
Ljungqvist, Martin Georg; Nielsen, Michael Engelbrecht; Ersbĝll, Bjarne Kjĉr; Frosch, Stina
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 granulometr...
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...
The effects of particle size distribution and induced unpinning during grain growth
International Nuclear Information System (INIS)
The effect of a second-phase particle size distribution on grain boundary pinning was studied using a Monte Carlo simulation technique. Simulations were run using a constant number density of both whisker and rhombohedral particles, and the effect of size distribution was studied by varying the standard deviation of the distribution around a constant mean particle size. The results of present simulations indicate that, in accordance with the stereological assumption of the topological pinning model, changes in distribution width had no effect on the pinned grain size. The effect of induced unpinning of particles on microstructure was also studied. In contrast to predictions of the topological pinning model, a power law dependence of pinned grain size on particle size was observed at T=0.0. Based on this, a systematic deviation to the stereological predictions of the topological pinning model is observed. The results of simulations at higher temperatures indicate an increasing power law dependence of pinned grain size on particle size, with the slopes of the power law dependencies fitting an Arrhenius relation. The effect of induced unpinning of particles was also studied in order to obtain a correlation between particle/boundary concentration and equilibrium grain size. The results of simulations containing a constant number density of monosized rhombohedral particles suggest a strong power law correlation between the two parameters. copyright 1996 Materials Research Society
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...
Rosin's law and size distribution of particles in regolith like samplesan 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.
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.
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 ...
Estimating Functions of Distributions Defined over Spaces of Unknown Size
Directory of Open Access Journals (Sweden)
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 priors 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.
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
Sample size determination for health psychology interventions with binomially distributed outcomes.
Hittner, James B; May, Kim; Silver, N Clayton
2010-09-01
Health intervention outcomes are often assessed as binomially distributed variables. In designing such interventions it is important to model the pre-intervention rate of the target behavior when performing sample size calculations. Unfortunately, the majority of sample size programs model post-intervention outcomes only, which results in exaggerated sample size estimates. An exception is Yoo and Spoth's (1993) conditional binomial method of sample size determination. This approach explicitly models pre-intervention behavior by focusing on baserate-adjusted post-intervention outcomes, and always results in smaller sample size estimates than conventional approaches. Advantages of the conditional binomial method are discussed and user-friendly software is presented. PMID:20453047
A theory of banks, bonds, and the distribution of firm size
Russ, Katheryn N.; Valderrama, Diego
2009-01-01
We draw on stylized facts from the finance literature to build a model where altering the relative costs of bank and bond financing changes the entire distribution of firm size, with implications for the aggregate capital stock, output, and welfare.
Surface modification and particles size distribution control in nano-CdS/polystyrene composite film
International Nuclear Information System (INIS)
Preparation of nano-CdS particles with surface thiol modification by microemulsion method and their influences on the particle size distribution in highly filled polystyrene-based composites were studied. The modified nano-CdS was characterized by X-ray photoelectron spectroscopy (XPS), light absorption and emission measurements to reveal the morphologies of the surface modifier, which are consistent with the surface molecules packing calculation. The morphologies of the surface modifier exerted a great influence not only on the optical performance of the particles themselves, but also on the size distribution of the particle in polystyrene matrix. A monolayer coverage with tightly packed thiol molecules was believed to be most effective in promoting a uniform particle size distribution and eliminating the surface defects that cause radiationless recombination. Control of the particles size distribution in polystyrene can be attained by adjusting surface coverage status of the thiol molecules based on the strong interaction between the surface modifier and the matrix
The paper discusses the simulation of the effects of changes to particle loading, particle size distribution, and electrostatic precipitator (ESP) operating temperatures using ESP models. It also illustrates the usefulness of modern ESP models for this type of analysis. Increasin...
Droplet Size Distribution in Sprays Based on Maximization of Entropy Generation
Directory of Open Access Journals (Sweden)
Meishen Li
2003-12-01
Full Text Available Abstract: The maximum entropy principle (MEP, which has been popular in the modeling of droplet size and velocity distribution in sprays, is, strictly speaking, only applicable for isolated systems in thermodynamic equilibrium; whereas the spray formation processes are irreversible and non-isolated with interaction between the atomizing liquid and its surrounding gas medium. In this study, a new model for the droplet size distribution has been developed based on the thermodynamically consistent concept - the maximization of entropy generation during the liquid atomization process. The model prediction compares favorably with the experimentally measured size distribution for droplets, near the liquid bulk breakup region, produced by an air-blast annular nozzle and a practical gas turbine nozzle. Therefore, the present model can be used to predict the initial droplet size distribution in sprays.
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...
Snowflake Size Distribution Measurements in South Central Ontario, Canada
Tokay, A.; Bringi, V. N.; Huang, G.; Schoenhuber, M.; Bashor, P. G.; Hudak, D.; Jackson, G. S.; Petersen, W. A.
2007-05-01
In support of NASA's Global Precipitation Measurement (GPM) mission ground validation program, NASA's two laser optical disdrometers (Parsivel) and Colodaro State University (CSU) two-dimensional video disdrometer (2dvd) were deployed to a well-equipped precipitation observation site in South Central Ontario, Canada. The instruments were collocated and have been operating since late November 2006. So far, there has been numerous lake effect and synoptic winter storms over the site. In one event, parsivel disdrometers recorded 50 cm of snowfall. In addition, there have been at least 10 storms where the snow accumulation exceeded 4 cm. The leading objective of this study was to compare the parsivel and 2dvd size and fall velocity measurements for selected cases and relate the findings to the physical processes within and below the cloud. Unlike 2dvd, parsivel measures the maximum dimension of the snowflake in a single plane, while the fall velocity is calculated from the duration of the flake within the laser beam. The 2dvd samples the same flake in two planes from which fall velocity is obtained. The 2dvd also measures the maximum width and height in both planes. At the time of this abstract, two parsivels and 2dvd were operated nearly continuously for almost three months and preliminary data analysis is encouraging. The field site, which is known as Centre for Atmospheric Research Experiments (CARE), is an atmospheric research facility operated by the Air Quality Research Branch of the Meteorological Service of Canada and is located 80 km north of Toronto, Ontario, Canada in a rural agricultural and forested region. During the past three winters, a field campaign was conduced in support of Canadian CloudSat/CALIPSO validation project (c3vp). However, 2006-07 winter was the first since the satellites were in orbit. The coordinated efforts of aircraft missions over the CARE facility during the Intensive Operation Periods will enhance our understanding of cold cloud microphysics.
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
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...
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...
Finite size effects of nanoparticles on the atomic pair distribution functions.
Kodama, Katsuaki; Iikubo, Satoshi; Taguchi, Tomitsugu; Shamoto, Shin Ichi
2006-11-01
The finite size effects of nanoparticles on 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. The formulas of a PDF analysis which take account of such effects are presented and are found to reproduce the experimental data. PMID:17057353
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...
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...
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...
David, C.; S. Bekki; Jumelet, J.; Keckhut, P.
2008-01-01
A method for estimating the stratospheric particle size distribution from multiwavelength lidar measurements is presented. It is based on matching measured and model-simulated backscatter coefficients. The lidar backscatter coefficients measured at the three commonly used wavelengths 355, 532 and 1064 nm are compared to a precomputed look-up table of model-calculated values. The optical model assumes that particles are spherical and that their size distribution is unimodal. This inverse probl...
Droplet Size Distribution in Sprays Based on Maximization of Entropy Generation
Meishen Li; Xianguo Li
2003-01-01
Abstract: The maximum entropy principle (MEP), which has been popular in the modeling of droplet size and velocity distribution in sprays, is, strictly speaking, only applicable for isolated systems in thermodynamic equilibrium; whereas the spray formation processes are irreversible and non-isolated with interaction between the atomizing liquid and its surrounding gas medium. In this study, a new model for the droplet size distribution has been developed based on the thermodynamically consist...
Grain Size Distributions and Photo-Electric Heating in Ionized Regions
van Hoof, P. A. M.; Weingartner, J.C.; Martin, P. G.; Volk, K; Ferland, G. J.
2003-01-01
In this paper we present results obtained with the new grain code in Cloudy which underline the strong effect of photo-electric heating by grains in photo-ionized regions. We study the effect that the distribution of grain sizes has on the magnitude of the effect, and show that this effect is nothing short of dramatic. This makes the grain size distribution an important parameter in modeling of photo-ionized regions such as H II regions and planetary nebulae.
Models for the size distribution of businesses in a price driven market
D'Hulst, R.; G. J. Rodgers
2000-01-01
A microscopic model of aggregation and fragmentation is introduced to investigate the size distribution of businesses. In the model, businesses are constrained to comply with the market price, as expected by the customers, while customers can only buy at the prices offered by the businesses. We show numerically and analytically that the size distribution scales like a power-law. A mean-field version of our model is also introduced and we determine for which value of the para...
The encapsulation of an amphiphile into polystyrene microspheres of narrow size distribution
Pellach Michal; Margel Shlomo
2011-01-01
Abstract Encapsulation of compounds into nano- or microsized organic particles of narrow size distribution is of increasing importance in fields of advanced imaging and diagnostic techniques and drug delivery systems. The main technology currently used for encapsulation of molecules within uniform template particles while retaining their size distribution is based on particle swelling methodology, involving penetration of emulsion droplets into the particles. The swelling method, however, is ...
A facile synthesis of Tenanoparticles 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 Tenanocrystals with binary uniform size distributions at room temperature. The binary-sized Tenanocrystals 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 Tenanocrystals with binary uniform size distributions at room temperature. The binary-sized Tenanocrystals were well separated into two size regimes and assembled into films by electrophoretic deposition. The research provides a new platform for nanomaterials to be efficiently synthesized and manipulated. Electronic supplementary information (ESI) available: Synthetic procedures, FTIR analysis, ED pattern, AFM image, and EPD current curve. See DOI: 10.1039/c1nr10025d
Demographic properties shape tree size distribution in a Malaysian rain forest.
Kohyama, Takashi S; Potts, Matthew D; Kohyama, Tetsuo I; Kassim, Abd Rahman; Ashton, Peter S
2015-03-01
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
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...
ON THE COAGULATION AND SIZE DISTRIBUTION OF PRESSURE CONFINED CORES
Energy Technology Data Exchange (ETDEWEB)
Huang Xu; Zhou Tingtao; Lin, D. N. C., E-mail: xuhuang@princeton.edu [Kavli Institute for Astronomy and Astrophysics and School of Physics, Peking University, Beijing (China)
2013-05-20
Observations of the Pipe Nebula have led to the discovery of dense starless cores. The mass of most cores is too small for their self-gravity to hold them together. Instead, they are thought to be pressure confined. The observed dense cores' mass function (CMF) matches well with the initial mass function of stars in young clusters. Similar CMFs are observed in other star forming regions such as the Aquila Nebula, albeit with some dispersion. The shape of these CMF provides important clues to the competing physical processes which lead to star formation and its feedback on the interstellar media. In this paper, we investigate the dynamical origin of the mass function of starless cores which are confined by a warm, less dense medium. In order to follow the evolution of the CMF, we construct a numerical method to consider the coagulation between the cold cores and their ablation due to Kelvin-Helmholtz instability induced by their relative motion through the warm medium. We are able to reproduce the observed CMF among the starless cores in the Pipe Nebula. Our results indicate that in environment similar to the Pipe Nebula: (1) before the onset of their gravitational collapse, the mass distribution of the progenitor cores is similar to that of the young stars, (2) the observed CMF is a robust consequence of dynamical equilibrium between the coagulation and ablation of cores, and (3) a break in the slope of the CMF is due to the enhancement of collisional cross section and suppression of ablation for cores with masses larger than the cores' Bonnor-Ebert mass.
Digital Repository Service at National Institute of Oceanography (India)
Valsangkar, A.B.; Rebello, J.M.S.
2015-01-01
variation and inverse relationship of nodule size with the occurrence, distribution, grade, abundance, and Mn/Fe ratios. The study indicates that only 34 cm sized nodules in the first generation mine (FGM) site area are resources and have highest economical...
Effects of Grain Size on the Spectral Energy Distribution of Dusty Circumstellar Envelopes
Carciofi, A. C.; Bjorkman, J. E.; Magalhaes, A. M.
2003-01-01
We study the effects of dust grain size on the spectral energy distribution (SED) of spherical circumstellar envelopes. Based on the self-similarity relations of dusty SEDs derived by Ivezic & Elitzur (1997), we expect an approximate invariance of the IR SED for models with different grain sizes. Approximate invariance follows from the fact that differently sized grains have similar optical properties at long wavelengths where the dust reprocesses the starlight. In this pape...
Unraveling the size distributions of surface properties for purple soil and yellow soil.
Tang, Ying; Li, Hang; Liu, Xinmin; Zhu, Hualing; Tian, Rui
2015-06-01
Soils contain diverse colloidal particles whose properties are pertinent to ecological and human health, whereas few investigations systematically analyze the surface properties of these particles. The objective of this study was to elucidate the surface properties of particles within targeted size ranges (i.e. >10, 1-10, 0.5-1, 0.2-0.5 and minerals within the diverse particle-size fractions could fully explain the size distributions of surface properties. PMID:26040734
Grain-size distribution of volcaniclastic rocks 1: A new technique based on functional stereology
M. Jutzeler; Proussevitch, A.A.; Allen, S.R.
2012-01-01
The power of explosive volcanic eruptions is reflected in the grain size distribution and dispersal of their pyroclastic deposits. Grain size also forms part of lithofacies characteristics that are necessary to determine transport and depositional mechanisms responsible for producing pyroclastic deposits. However, the common process of welding and rock lithification prevents quantification of grain size by traditional sieving methods for deposits in the rock record. Here we show that function...
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.
Bonesronning, Hans
2004-01-01
The present paper supplements the traditional class size literature by exploring the causal relationship between class size and parental effort in education production. Class size variation that is exogenous to parental effort comes from interaction between enrollment and a maximum class size rule of 30 students in the lower secondary school in
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 25ħ7.7% and 7.5ħ3.4% of aerosol PM_{1} mass and the PM_{1?10} mass, respectively. Inorganic ions contributed 33ħ12% and 28ħ19% 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.
Effects of pore-size and shape distributions on diffusion pore imaging by nuclear magnetic resonance
Kuder, Tristan Anselm; Laun, Frederik Bernd
2015-08-01
In medical imaging and porous media research, NMR diffusion measurements are extensively used to investigate the structure of diffusion restrictions such as cell membranes. Recently, several methods have been proposed to unambiguously determine the shape of arbitrary closed pores or cells filled with an NMR-visible medium by diffusion experiments. The first approach uses a combination of a long and a short diffusion-weighting gradient pulse, while the other techniques employ short gradient pulses only. While the eventual aim of these methods is to determine pore-size and shape distributions, the focus has been so far on identical pores. Thus, the aim of this work is to investigate the ability of these different methods to resolve pore-size and orientation distributions. Simulations were performed comparing the various pore imaging techniques employing different distributions of pore size and orientation and varying timing parameters. The long-narrow gradient profile is most advantageous to investigate pore distributions, because average pore images can be directly obtained. The short-gradient methods suppress larger pores or induce a considerable blurring. Moreover, pore-shape-specific artifacts occur; for example, the central part of a distribution of cylinders may be largely underestimated. Depending on the actual pore distribution, short-gradient methods may nonetheless yield good approximations of the average pore shape. Furthermore, the application of short-gradient methods can be advantageous to differentiate whether pore-size distributions or intensity distributions, e.g., due to surface relaxation, are predominant.
A POSSIBLE DIVOT IN THE SIZE DISTRIBUTION OF THE KUIPER BELT'S SCATTERING OBJECTS
International Nuclear Information System (INIS)
Via joint analysis of a calibrated telescopic survey, which found scattering Kuiper Belt objects, and models of their expected orbital distribution, we explore the scattering-object (SO) size distribution. Although for D > 100 km the number of objects quickly rise as diameters decrease, we find a relative lack of smaller objects, ruling out a single power law at greater than 99% confidence. After studying traditional ''knees'' in the size distribution, we explore other formulations and find that, surprisingly, our analysis is consistent with a very sudden decrease (a divot) in the number distribution as diameters decrease below 100 km, which then rises again as a power law. Motivated by other dynamically hot populations and the Centaurs, we argue for a divot size distribution where the number of smaller objects rises again as expected via collisional equilibrium. Extrapolation yields enough kilometer-scale SOs to supply the nearby Jupiter-family comets. Our interpretation is that this divot feature is a preserved relic of the size distribution made by planetesimal formation, now ''frozen in'' to portions of the Kuiper Belt sharing a ''hot'' orbital inclination distribution, explaining several puzzles in Kuiper Belt science. Additionally, we show that to match today's SO inclination distribution, the supply source that was scattered outward must have already been vertically heated to the of order 10°.
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.
International Nuclear Information System (INIS)
Two different dispersion methods were studied in order to obtain rhenium [188Re] sulfide suspension with different particle size distributions. The manufactured swirling device offers Suspension I with larger particles (55% > 5 ?m, 19% > 10 ?m). However, ultrasonication can only produce Suspension II with smaller particles (93% 10 ?m). Stability tests indicated that deposition appears after 6 and 15 minutes for Suspensions I and II, respectively. Radiochemical purity and particle size distribution did not change distinctively within 24 hours. So, both suspensions can be used in animal tests to find out the optimal particle size ranges for intra-articular injection. (author)
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.
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.
Charalambous, C. A.; Pike, W. T.
2013-12-01
We present the development of a soil evolution framework and multiscale modelling of the surface of Mars, Moon and Itokawa thus providing an atlas of extra-terrestrial Particle Size Distributions (PSD). These PSDs are profoundly based on a tailoring method which interconnects several datasets from different sites captured by the various missions. The final integrated product is then fully justified through a soil evolution analysis model mathematically constructed via fundamental physical principles (Charalambous, 2013). The construction of the PSD takes into account the macroscale fresh primary impacts and their products, the mesoscale distributions obtained by the in-situ data of surface missions (Golombek et al., 1997, 2012) and finally the microscopic scale distributions provided by Curiosity and Phoenix Lander (Pike, 2011). The distribution naturally extends at the magnitudinal scales at which current data does not exist due to the lack of scientific instruments capturing the populations at these data absent scales. The extension is based on the model distribution (Charalambous, 2013) which takes as parameters known values of material specific probabilities of fragmentation and grinding limits. Additionally, the establishment of a closed-form statistical distribution provides a quantitative description of the soil's structure. Consequently, reverse engineering of the model distribution allows the synthesis of soil that faithfully represents the particle population at the studied sites (Charalambous, 2011). Such representation essentially delivers a virtual soil environment to work with for numerous applications. A specific application demonstrated here will be the information that can directly be extracted for the successful drilling probability as a function of distance in an effort to aid the HP3 instrument of the 2016 Insight Mission to Mars. Pike, W. T., et al. "Quantification of the dry history of the Martian soil inferred from in situ microscopy." Geophysical Research Letters 38.24 (2011). C. A. Charalambous and W. T. Pike (2013). 'Evolution of Particle Size Distributions in Fragmentation Over Time' Abstract Submitted to the AGU 46th Fall Meeting. Charalambous, C., Pike, W. T., Goetz, W., Hecht, M. H., & Staufer, U. (2011, December). 'A Digital Martian Soil based on In-Situ Data.' In AGU Fall Meeting Abstracts (Vol. 1, p. 1669). Golombek, M., & Rapp, D. (1997). 'Size-frequency distributions of rocks on Mars and Earth analog sites: Implications for future landed missions.' Journal of Geophysical Research, 102(E2), 4117-4129. Golombek, M., Huertas, A., Kipp, D., & Calef, F. (2012). 'Detection and characterization of rocks and rock size-frequency distributions at the final four Mars Science Laboratory landing sites.' Mars, 7, 1-22.
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.
Schuck, Peter; Matthew A. Perugini; Gonzales, Noreen R.; Howlett, Geoffrey J.; Schubert, Dieter
2002-01-01
Strategies for the deconvolution of diffusion in the determination of size-distributions from sedimentation velocity experiments were examined and developed. On the basis of four different model systems, we studied the differential apparent sedimentation coefficient distributions by the time-derivative method, g(s*), and by least-squares direct boundary modeling, ls-g*(s), the integral sedimentation coefficient distribution by the van Holde-Weischet method, G(s), and the previously introduced...
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
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.
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.
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.
Are range-size distributions consistent with species-level heritability?
DEFF Research Database (Denmark)
Borregaard, Michael Krabbe; Gotelli, Nicholas
2012-01-01
The concept of species-level heritability is widely contested. Because it is most likely to apply to emergent, species-level traits, one of the central discussions has focused on the potential heritability of geographic range size. However, a central argument against range-size heritability has been that it is not compatible with the observed shape of present-day species range-size distributions (SRDs), a claim that has never been tested. To assess this claim, we used forward simulation of range-size evolution in clades with varying degrees of range-size heritability, and compared the output of three different models to the range-size distribution of the South American avifauna. Although there were differences among the models, a moderate-to-high degree of range-size heritability consistently leads to SRDs that were similar to empirical data. These results suggest that range-size heritability can generate realistic SRDs, and may play an important role in shaping observed patterns of range sizes.
The ?-generalized distribution: A new descriptive model for the size distribution of incomes
Clementi, F.; Di Matteo, T.; Gallegati, M.; Kaniadakis, G.
2008-05-01
This paper proposes the ?-generalized distribution as a model for describing the distribution and dispersion of income within a population. Formulas for the shape, moments and standard tools for inequality measurement-such as the Lorenz curve and the Gini coefficient-are given. A method for parameter estimation is also discussed. The model is shown to fit extremely well the data on personal income distribution in Australia and in the United States.
The k-generalized distribution: A new descriptive model for the size distribution of incomes
Clementi, F; Gallegati, M; Kaniadakis, G
2007-01-01
This paper proposes the k-generalized distribution as a model for describing the distribution and dispersion of income within a population. Formulas for the shape, moments and standard tools for inequality measurement - such as the Lorenz curve and the Gini coefficient - are given. A method for parameter estimation is also discussed. The model is shown to fit extremely well the data on personal income distribution in Australia and the United States.
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
Directory of Open Access Journals (Sweden)
WANG Weidong
2010-11-01
Full Text Available the key to reduce coal pollution is the development of clean coal technology and the improvement of the backward coal-burning technology. The coal water slurry (CWS is the first substitute of the oil. The particle size distribution of CWS plays an important role in the quality control of CWS. Now there are three methods that are used to analysis the particle size distribution of CWS, screening method, settlement method, laser method. These methods produce some disadvantages when be used to forecast the distribution of CWS. Thus, this article proposes an ultrasonic method with effective medium theory model which can be accurately reflected in the acoustic attenuation characteristics of coal-water slurry based on structural average. Experimental simulation proved that effective medium model is fully capable of achieving on-line detection of coal-water slurry particle size, for detection of fine-and coarse-sized particle size distribution. Non-linear relationship between attenuation and particle size, the three-frequency method can be used to inverse calculation of its. Which we can achieve CWS granularity on-line, and continuously control the quality of CWS.
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...
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 1015% is required to explain observed growth rates. Coagulation is acknowledged to be highly important in modelled cases.
Aerosol Size Distribution Determined From Multiple Field-Of-View Lidar
Liu, Y.; Yabuki, M.; Tsuda, T.; Uesugi, T.
2014-12-01
Knowledge of aerosol size distribution is essential for its influence on atmosphere and human health, especially for small particles because they are able to penetrate lung tissues, thus increasing the risk of bronchitis or lung diseases. Lidar as an active optical remote sensing technique is effective for monitoring aerosols with high temporal and spatial variations. Particles with diameters comparable to the detecting light wavelength have been effectively detected by using UV, VIS, and near-IR wavelengths. However, to quantitatively estimate the shape of the particle size distribution, more information is required with respect to sub-micrometer and smaller particles. Conventional lidar employs tiny field-of-view (FOV) to detect single scatter reflected from aerosols in the direction opposite to incident light. However, the complicated reflection on the path of laser causes multiple scatter which contains also the size distribution information of aerosols. In this study, a UV Lidar with multiple FOV receiver was used for detecting such multiple scattering effects in order to obtain more quantitative information related to particle size distribution. The FOV of Lidar receiver was program controlled in a range from 0.1 mrad to 12.4 mrad. The pacific retrieval method for aerosol size distribution using this feature and field measurement results will be introduced in the presentation.
Remote sensing of water cloud droplet size distributions using the backscatter glory: a case study
Directory of Open Access Journals (Sweden)
B. Mayer
2004-05-01
Full Text Available Cloud single scattering properties are mainly determined by the effective radius of the droplet size distribution. There are only few exceptions where the shape of the size distribution affects the optical properties, in particular the rainbow and the glory directions of the scattering phase function. Using observations by the Compact Airborne Spectrographic Imager (CASI in 180° backscatter geometry, we found that high angular resolution aircraft observations of the glory provide unique new information which is not available from traditional remote sensing techniques: Using only one single wavelength, 753 nm, we were able to determine not only optical thickness and effective radius, but also the width of the size distribution at cloud top. Applying this novel technique to the ACE-2 CLOUDYCOLUMN experiment, we found that the size distributions were much narrower than usually assumed in radiation calculations which is in agreement with in-situ observations during this campaign. While the shape of the size distribution has only little relevance for the radiative properties of clouds, it is extremely important for understanding their formation and evolution.
Ultrasonic Production of Nano-Size Dispersions and Emulsions
Hielscher, Thomas
2007-01-01
Ultrasound is a well-established method for particle size reduction in dispersions and emulsions. Ultrasonic processors are used in the generation of nano-size material slurries, dispersions and emulsions because of the potential in the deagglomeration and the reduction of primaries. These are the mechanical effects of ultrasonic cavitation. Ultrasound can also be used to influence chemical reactions by the cavitation energy. This is sonochemistry. As the market for nano-siz...
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.
ASSESSMENT OF THE MAIN PETROLEUM PRODUCT DISTRIBUTION STRATEGY
Florea Vlad
2013-01-01
This paper investigates the main petroleum product distribution strategy. Three main criteria are identified in this respect: the economic criterion, the control criterion and adjustment criterion. In addition, aspects pertaining to the administration of petroleum product distribution network are also revealed.
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...
Managerial Versus Production Wages: Offshoring, Country Size and Endowments
Benz, Sebastian; Kohler, Wilhelm
2010-01-01
We explore the role of trade in differentiated final goods as well ollshoring of tasks for inequality both within and between countries. We emphasize the distinction between managerial and production labor. Managerial labor is a fixed input while production labor is a variable input. Following Grossman & Rossi-Hansberg (2010b) we assume that production labor is composed of tradable tasks, with "Marshallian" economies of scale on the task level. We first identify the key determinants of income...
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
Size Distribution of Inorganic Species and Their Inhaled Dose in a Detergent Industrial Workplace
International Nuclear Information System (INIS)
Aerosol particles in the workplace of a detergent industry were sampled during July 2005 by a Berner low-pressure impactor. The samples were analyzed by atomic absorption spectrometry and ion chromatography in order to determine the size distribution of metallic elements and water-soluble inorganic ions. The size distributions of some characteristic metallic elements (Cu, Fe, Al) were unimodal with their maximum found in coarse particles. Among the water-soluble aerosol components SO4+, NO3-, Cl-, NH4+ and Ca++ were the major contributors to total particle mass. The lung deposition resulting from the partially hygroscopic aerosol is estimated. The calculated lung deposition reveals the impact of separate chemical aerosol compounds on the levels of the inhaled dose. The differences observed between the total and regional deposition of the different compounds appear mainly due to their different size distributions
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.
Numerical Model to Predict Wax Crystal Size Distribution in Solvent Dewaxing Unit
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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
Prediction of size distribution of Ag nanoparticles synthesized via gamma-ray radiolysis
Liang, Jia-liang; Shen, Sheng-wen; Ye, Sheng-ying; Ye, Lü-meng
2015-09-01
The spherical shape Ag nanoparticles synthesized via gamma-ray radiolysis were observed with the transmission electron microscope (TEM). Diameters of Ag nanoparticles were measured from the TEM photographs. Statistical analysis showed that the particle diameter complied with a linear-converted Poisson distribution. The distribution parameter, which was the average of diameters, was related to the ultraviolet-visible spectrum peak position of the nanosilver collosol. An empirical equation was established to predicting size distribution of Ag nanoparticles with the peak position. Nanosilver of different sizes could be synthesized by adjusting the intensity of ?-irradiation, the kind and the addition amount of the stabilizing agent. Because particle size affects the physiochemical properties of nanosilver material, results of this paper would be of practical significance for the application of nanosilver.
Energy Technology Data Exchange (ETDEWEB)
Montazeri, G.H. [Islamic Azad University, Mahshahr (Iran, Islamic Republic of). Dept. of Chemical and Petroleum Engineering], E-mail: montazeri_gh@yahoo.com; Tahami, S.A. [Mad Daneshgostar Tabnak Co. (MDT),Tehran (Iran, Islamic Republic of); Moradi, B.; Safari, E. [Iranian Central Oil Fields Co, Tehran (Iran, Islamic Republic of)], E-mail: morady.babak@gmail.com
2011-07-15
This paper presents a model for pressure transient and derivative analysis for naturally fractured reservoirs by a formulation of inter porosity flow incorporating variations in matrix block size, which is inversely related to fracture intensity. Geologically realistic Probability Density Functions (PDFs) of matrix block size, such as uniform, bimodal, linear and exponential distributions, are examined and pseudo-steady-state and transient models for inter porosity flow are assumed. The results have been physically interpreted, and, despite results obtained by other authors, it was found that the shape of pressure derivative curves for different PDFs are basically identical within some ranges of block size variability, inter porosity skin, PDFs parameters and matrix storage capacity. This tool can give an insight on the distribution of block sizes and shapes, together with other sources of information such as Logs and geological observations. (author)
Size and DNA distributions of electrophoretically separated cultured human kidney cells
Kunze, M. E.; Plank, L. D.; Todd, P. W.
1985-01-01
Electrophoretic purification of purifying cultured cells according to function presumes that the size of cycle phase of a cell is not an overriding determinant of its electrophoretic velocity in an electrophoretic separator. The size distributions and DNA distributions of fractions of cells purified by density gradient electrophoresis were determined. No systematic dependence of electrophoretic migration upward in a density gradient column upon either size or DNA content were found. It was found that human leukemia cell populations, which are more uniform function and found in all phases of the cell cycle during exponential growth, separated on a vertical sensity gradient electrophoresis column according to their size, which is shown to be strictly cell cycle dependent.
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.
A study of the drop size distributions and hold-up in short Kühni columns
N. S. Oliveira; D. Moraes Silva; M. P. C. Gondim; M. Borges Mansur
2008-01-01
The hydrodynamic behaviour of a short Kühni column was investigated under no mass transfer conditions using the binary system water (continuous phase) and Exxsol D-80 (dispersed phase). The counter-current flow pattern of the liquid phases was characterised regarding the Sauter mean drop diameter, drop size distribution and hold-up; a photographic method was used to assess drop sizes. The following operating variables were studied: rotor speed, flow rate of both liquid phases and column stage...
Location and rank-size distribution of Arts and Entertainment : A study of US Metropolitan Regions
Ruett, Benjamin
2010-01-01
This thesis describes and analyzes the location and size distribution of artand entertainment establishments and metropolitan regions in the UnitedStates. The included sectors are sound recording, motion picture and video,book and newspaper publishing as well as the live performing arts. Their sizeis analyzed by total employment and brought in context to their respectivemarkets and the rank-size rule. The results are interpreted within the economictraits specific to the art and entertainment ...
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; Novotnŭ, F.; Drahokoupil, Jan; Kuel, 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
Fymat, A. L.; Mease, K. D.
1981-01-01
The approximation of Penndorf (1962) and Shifrin-Punina (1968) to the Mie solution at forward scattering angles are extended to small size parameters. The proposed semiempirical approximation accurately represents the Mie results down to x = 0.5-1 for refractive index m = 1.33, and to x = 2.0 for larger index values. The implications of the result for the inversion of particle size distribution from single scattering data in the forward direction are discussed.
A Random Structure for Optimum Cache Size Distributed hash table (DHT) Peer-to-Peer design
Sarshar, Nima; Roychowdhury, Vwani
2002-01-01
We propose a new and easily-realizable distributed hash table (DHT) peer-to-peer structure, incorporating a random caching strategy that allows for {\\em polylogarithmic search time} while having only a {\\em constant cache} size. We also show that a very large class of deterministic caching strategies, which covers almost all previously proposed DHT systems, can not achieve polylog search time with constant cache size. In general, the new scheme is the first known DHT structu...
Explaining National Differences in the Size and Industrial Distribution of Employment
Davis, Steven J.; Henrekson, Magnus
1997-01-01
What factors determine national differences in the size and industry distribution of employment? This study stresses the role of business taxation, employment security laws, credit market policies, wage-setting institutions and the size of the public sector. We characterize these aspects of the economic policy environment in Sweden prior to 1990-91 and compare them to the situation in other European countries and the United States. Our characterization and international comparisons show that ...
Does size matter? The impact of changes in household structure on income distribution in Germany
Peichl, Andreas; Pestel, Nico; Schneider, Hilmar
2010-01-01
In Germany, two observations can be made over the past 20 years: First, income inequality has been constantly increasing while, second, the average household size has been declining dramatically. The analysis of income distribution relies on equivalence-weighted incomes which take into account household size. Therefore, there is an obvious link between these two developments. The aim of the paper is to quantify how the trend towards smaller households has influenced the change in income distr...
Farlow, N. H.; Oberbeck, V. R.; Snetsinger, K. G.; Ferry, G. V.; Polkowski, G.; Hayes, D. M.
1981-01-01
Samples from the stratosphere obtained by U-2 aircraft after the first three major eruptions of Mount St. Helens contained large globules of liquid acid and ash. Because of their large size, these globules had disappeared from the lower stratosphere by late June 1980, leaving behind only smaller acid droplets. Particle size distributions and mineralogy of the stratospheric ash grains demonstrate inhomogeneity in the eruption clouds.
Performance of DMPS/C System in Determining Aerosol Particle Size Distribution
International Nuclear Information System (INIS)
An evaluation of performance of DMPS/C system TSI-3932 in determining aerosol particle size has been carried out. The evaluation consist of validity of experimentally transfer function, instrument resolution, and test of measurement accuracy and precision for monodisperse and polydisperse aerosol size distribution. Evaluation of measurement accuracy gave a deviation of 0.74 %, and evaluation of measurement precision gave variation coefficient of 0,50 % and 1.63 % for monodisperse aerosol and polydisperse aerosol respectively
The uniqueness of company size distribution function from tent-shaped growth rate distribution
Ishikawa, Atushi
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 Jap...
International Nuclear Information System (INIS)
Domestic wood combustion was shown to contribute significantly to the PM levels in a residential area in Lycksele, a small city in northern Sweden. This study further extends these results to include an analysis of the source contribution to the aerosol number size distribution. A campaign was performed between January and March, 2002 in Forsdala, a residential area in Lycksele, northern Sweden. Here, wood stoves and boilers are widely used to heat homes during winter-time. A differential mobility particle sizer (DMPS) was used to measure the aerosol number size distribution (3-850 nm) in this study, and a soot photometer measured the particulate soot content
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%.
Application of digital image analysis for size distribution measurements of microbubbles
Energy Technology Data Exchange (ETDEWEB)
Burns, S.E.; Yiacoumi, S.; Frost, D. [Georgia Inst. of Tech., Atlanta, GA (United States). School of Civil and Environmental Engineering; Tsouris, C. [Oak Ridge National Lab., TN (United States). Chemical Technology Div.
1997-03-01
This work employs digital image analysis to measure the size distribution of microbubbles generated by the process of electroflotation for use in solid/liquid separation processes. Microbubbles are used for separations in the mineral processing industry and also in the treatment of potable water and wastewater.As the bubbles move upward in a solid/liquid column due to buoyancy, particles collide with and attach to the bubbles and are carried to the surface of the column where they are removed by skimming. The removal efficiency of solids is strongly affected by the size of the bubbles. In general, higher separation is achieved by a smaller bubble size. The primary focus of this study was to characterize the size and size distribution of bubbles generated in electroflotation using image analysis. The study found that bubble diameter increased slightly as the current density applied to the system was increased. Additionally, electroflotation produces a uniform bubble size with narrow distribution which optimizes the removal of fine particles from solution.
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
Size distribution of possible dust carriers for the extended red emission
International Nuclear Information System (INIS)
Power-law size distributions expected to be applicable to possible carriers of extended red emission (ERE) have been examined using Monte Carlo (MC) simulations. Si nanoparticles and some polycyclic aromatic hydrocarbon complexes such as oligoacene and oligorylenes with energy gaps close to 2 eV have been considered. In the simplest case of unit quantum efficiency, the MC-generated size distributions are used to obtain photoluminescence (PL) spectra that are then corrected for dust extinction and reddening effects for comparison with observed ERE spectra. It is shown that a power-law size distribution with a decay exponent of ? = 7/2, which closely agrees with starlight extinction data, fails to produce an ERE-like spectrum. However, size distributions with decay exponents of ? = 19/12 and 3/2 are found to lead to acceptable spectra. Results indicate that energetic photon-induced breakup and competing aggregation effects dominate collisional effects in producing the observed steady-state mass distribution. It is shown that the peak wavelength of emission critically depends on the band gap, rather than cluster mass, which for oligoacenes and oligorylenes is widely different. The peak wavelength is also shown to be insensitive to dust attenuation.
Pore size distribution in porous glass: fractal dimension obtained by calorimetry
Neffati, R.; Rault, J.
2001-05-01
By differential Scanning Calorimetry (DSC), at low heating rate and using a technique of fractionation, we have measured the equilibrium DSC signal (heat flow) J q 0 of two families of porous glass saturated with water. The shape of the DSC peak obtained by these techniques is dependent on the sizes distribution of the pores. For porous glass with large pore size distribution, obtained by sol-gel technology, we show that in the domain of ice melting, the heat flow Jq is related to the melting temperature depression of the solvent, ? T m , by the scaling law: J q 0? T m - (1 + D). We suggest that the exponent D is of the order of the fractal dimension of the backbone of the pore network and we discuss the influence of the variation of the melting enthalpy with the temperature on the value of this exponent. Similar D values were obtained from small angle neutron scattering and electronic energy transfer measurements on similar porous glass. The proposed scaling law is explained if one assumes that the pore size distribution is self similar. In porous glass obtained from mesomorphic copolymers, the pore size distribution is very sharp and therefore this law is not observed. One concludes that DSC, at low heating rate ( q? 2°C/min) is the most rapid and less expensive method for determining the pore distribution and the fractal exponent of a porous material.
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.
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.)
THE SENSITIVITY OF THE CATALYST EFFECTIVENESS FACTOR TO PORE SIZE DISTRIBUTION
Scientific Electronic Library Online (English)
Z., Bensetiti; D., Schweich; C.A.M., Abreu.
1997-09-01
Full Text Available A model is proposed for the average effective diffusivity for an arbitrary pore size distribution. It is shown that the average diffusivity must also depend on the distribution of the catalyst sites. The reaction diffusivity is compared with the average diffusivities defined by Wakao and Smith (1962 [...] ) and Johnson and Stewart (1965). For the methanol dehydration and n-butene isomerization, the reaction diffusivity gives a better estimation of the effectiveness factor than the other models
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...
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 ...
PSO Based Multi Objective Approach for Optimal Sizing and Placement of Distributed Generation
Ali Aref; Mohsen Davoudi; Mohammad Dosaranian Moghadam; Iraj Ganjkhany Majid Davoodi; Robabe Jahanbakhshi
2012-01-01
This study presents a multi-objective formulation using Particle Swarm Optimization (PSO) approach, for optimal placement and sizing of Distributed Generation (DG) resources in the power distribution systems in order to minimize the cost of power losses and improve the voltage profile and energy not supplied. The proposed method considers the options of the DGs installation and takes more number of significant parameters into account compare to the previous studies which consider only a few p...
The firm size distribution in a small open economy : theory and evidence
Walsh, Patrick P.; Li, Qi
2009-01-01
We construct a theoretical model of the dynamic processes (firm entry, growth, decline, and exit) that underpin the determination of a limiting firm size distribution (FSD). In particular, we model such dynamic processes using key structural parameters; sunk cost, exogenous entry constraints, and opportunity values of finite duration. The limiting FSD we derive, in steady state, turns out to be a combination of a Logarithmic and Zipf distribution. We estimate these structural p...
Production versus Distribution-oriented FDI
Kleinert, Jörn; Toubal, Farid
2010-01-01
The business literature has long recognized the importance of multinationals' distribution networks. The empirical analysis of distribution-oriented FDI has, however, received little attention which is at least partly due to the lack of appropriate data. We present a slightly modified version of Helpman, Melitz, and Yeaple (2004) that explicitly models the possibility for a multinational firm to export through its wholesale trade affiliate. We analyze the multinational firms' choice between f...
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 19962000. 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
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
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.
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 rainfall accompanying the typhoon. The typhoon process also decreased the suspended matter size and macrofloc (>133 ?m) concentration by strong disturbance of water column and the temporary demise of plankton under heavy cloudy condition.
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.
Determining Economic Production Quantity in the Presence of Varying Item Size and Stochastic Demand
Kizito Paul Mubiru
2014-01-01
The classical Economic Production Quantity (EPQ) model as applied in production-inventory management assumes constant demand of a single item, often of a specific size. In this paper, an optimization method is developed for determining the EPQ of an item with varying size and stochastic demand. Adopting a Markov decision process approach, the states of a Markov chain represent possible states of demand for a given size of item. The decision of whether or not to...
Zelenyuk, A.; Cuadra-Rodriguez, L. A.; Imre, D.; Shimpi, S.; Warey, A.
2006-12-01
The strong absorption of solar radiation by black carbon (BC) impacts the atmospheric radiative balance in a complex and significant manner. One of the most important sources of BC is vehicular emissions, of which diesel represents a significant fraction. To address this issue the EPA has issues new stringent regulations that will be in effect in 2007, limiting the amount of particulate mass that can be emitted by diesel engines. The new engines are equipped with aftertreatments that reduce PM emissions to the point, where filter measurements are subject to significant artifacts and characterization by other techniques presents new challenges. We will present the results of the multidisciplinary study conducted at the Cummins Technical Center in which a suite of instruments was deployed to yield comprehensive, temporally resolved information on the diesel exhaust particle loadings and properties in real-time: Particle size distributions were measured by Engine Exhaust Particle Sizer (EEPS) and Scanning Mobility Particle Sizer (SMPS). Total particle diameter concentration was obtained using Electrical Aerosol Detector (EAD). Laser Induced Incandescence and photoacoustic techniques were used to monitor the PM soot content. Single Particle Laser Ablation Time-of- flight Mass Spectrometer (SPLAT) provided the aerodynamic diameter and chemical composition of individual diesel exhaust particles. Measurements were conducted on a number of heavy duty diesel engines operated under variety of operating conditions, including FTP transient cycles, ramped-modal cycles and steady states runs. We have also characterized PM emissions during diesel particulate filter regeneration cycles. We will present a comparison of PM characteristics observed during identical cycles, but with and without the use of aftertreatment. A total of approximately 100,000 individual particles were sized and their composition characterized by SPLAT. The aerodynamic size distributions of the characterized particles were between 50 and 300 nm, depending on engine operating conditions and particle composition. We will show that while the drastically reduced diesel PM emissions often render the PM filter measurements inadequate due to organic vapor artifacts SPLAT demonstrated its capability to provide real-time information on size and composition of individual diesel exhaust particles as function of engine operating conditions with better than 1 minute resolution.
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.
Pair production in laser fields: finite size effects
T. Heinzl; Ilderton, A.; M. Marklund
2010-01-01
We discuss pair creation in a strong laser background. Using lightfront field theory, we show that all the physics is contained in the lightfront momentum transfer from the laser, and probe, to the produced pair. The dependence of this momentum transfer on the geometry of the laser leads to resonance and diffraction effects in pair production spectra. The lightfront approach naturally explains the interpretation of laser-stimulated pair production as a multi-photon process c...
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.
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.
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...
International Nuclear Information System (INIS)
Highlights: Pour point depressant (PPD) has great impact on particulate matters. The number of nanoparticles increases sharply after PPD is added. Ambiguous boundaries can be found when the PPD additive was added. PPD changes the size distribution into bimodal logarithmic. Three nanostructure parameters are changed greatly by PPD. - Abstract: Effects of lubricant oil additive on the characterization of particles from a four-cylinder turbocharged diesel engine were investigated. Neat diesel and blended fuel containing oil pour point depressant (PPD) additive were chosen as the test fuels. Effects of different fuels on size distribution, morphology, and nanostructure of the diesel particles were studied. Transmission electron microscopy (TEM) and high resolution TEM (HRTEM) were employed to study the morphology and nanostructure parameters. Particle size distribution was measured by fast particulate spectrometer (DMS 500). According to the experimental results, distribution of the primary particles size of the two fuels conforms to Gaussian distribution, whereas the mean diameter of blended fuel is larger than that of neat diesel at 1200 rpm, which is contrarily smaller at 2400 rpm. Besides, fractal dimension (Df) of aggregates increases close to 2 (Df = 1.991), indicating that the structure became compacter with adding PPD. As to the nanostructure parameters of the blended fuel particles, the layer fringe length decreases from 1.191 nm to 1.064 nm, while both the separation distance and tortuosity increase. The changes in the nanostructure parameters indicate that the particles are more ordered and compressed with burning pure diesel. Results of blended fuel from DMS show that more particles, particularly nucleation mode particles, were discharged. In addition, its size distribution become bimodal logarithmic at 2400 rpm. All these results can provide new information of the effects of oil PPD additive on the formation and characterization of diesel particles
Production of large-particle-size monodisperse latexes
Vanderhoff, J. W.; El-Aasser, M. L.; Micale, F. J.; Sudol, E. D.; Tseng, C. M.; Silwanowicz, A.
1984-01-01
The research program achieved two objectives: (1) it has refined and extended the experimental techniques for preparing monodisperse latexes in quantity on the ground up to a particle diameter of 10 microns; and (2) it has demonstrated that a microgravity environment can be used to grow monodisperse latexes to larger sizes, where the limitations in size have yet to be defined. The experimental development of the monodisperse latex reactor (MLR) and the seeded emulsion polymerizations carried out in the laboratory prototype of the flight hardware, as a function of the operational parameters is discussed. The emphasis is directed towards the measurement, interpretation, and modeling of the kinetics of seeded emulsion polymerization and successive seeded emulsion polymerization. The recipe development of seeded emulsion polymerization as a function of particle size is discussed. The equilibrium swelling of latex particles with monomers was investigated both theoretically and experimentally. Extensive studies are reported on both the type and concentration of initiators, surfactants, and inhibitors, which eventually led to the development of the flight recipes. The experimental results of the flight experiments are discussed, as well as the experimental development of inhibition of seeded emulsion polymerization in terms of time of inhibition and the effect of inhibitors on the kinetics of polymerization.
Santana, Steven Michael; Antonyak, Marc A.; Cerione, Richard A.; Kirby, Brian J.
2014-12-01
Extracellular shed vesicles (ESVs) facilitate a unique mode of cellcell communication wherein vesicle uptake can induce a change in the recipient cell?s state. Despite the intensity of ESV research, currently reported data represent the bulk characterization of concentrated vesicle samples with little attention paid to heterogeneity. ESV populations likely represent diversity in mechanisms of formation, cargo and size. To better understand ESV subpopulations and the signaling cascades implicated in their formation, we characterize ESV size distributions to identify subpopulations in normal and cancerous epithelial cells. We have discovered that cancer cells exhibit bimodal ESV distributions, one small-diameter and another large-diameter population, suggesting that two mechanisms may govern ESV formation, an exosome population and a cancer-specific microvesicle population. Altered glutamine metabolism in cancer is thought to fuel cancer growth but may also support metastatic niche formation through microvesicle production. We describe the role of a glutaminase inhibitor, compound 968, in ESV production. We have discovered that inhibiting glutamine metabolism significantly impairs large-diameter microvesicle production in cancer cells.
A study of the drop size distributions and hold-up in short Kühni columns
Scientific Electronic Library Online (English)
N. S., Oliveira; D. Moraes, Silva; M. P. C., Gondim; M. Borges, Mansur.
2008-12-01
Full Text Available The hydrodynamic behaviour of a short Kühni column was investigated under no mass transfer conditions using the binary system water (continuous phase) and Exxsol D-80 (dispersed phase). The counter-current flow pattern of the liquid phases was characterised regarding the Sauter mean drop diameter, d [...] rop size distribution and hold-up; a photographic method was used to assess drop sizes. The following operating variables were studied: rotor speed, flow rate of both liquid phases and column stage. The log-normal probability density function was found to be adequate to fit the experimental drop size distributions along the column. As expected, smaller drops and more uniform drop size distributions were obtained with the increase of rotor speed and column stage number, thus indicating the predominance of drop breakage phenomena in short columns. The total hold-up was influenced mainly by rotor speed and flow rate of the dispersed phase. Recommended correlations available in the literature were found to be inadequate for predicting experimental drop sizes and hold-up, so alternative expressions, valid only for short Kühni columns, were proposed.
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.
Directory of Open Access Journals (Sweden)
I.M. Bolesta
2012-12-01
Full Text Available Substantiated method determining the distribution of metal particle size on the optical absorption data for composites consisting of dielectric medium and metallic inclusions and tested this method on hydrosols of gold nanoparticles compared to the data obtained by microscopic examination.
Self-consistent rate equation theory of cluster size distribution in aggregation phenomena
Family, Fereydoon; Popescu, Mihail N.; Amar, Jacques G.
2002-04-01
Cluster nucleation and growth by aggregation is the central feature of many physical processes, from polymerization and gelation in polymer science, flocculation and coagulation in aerosol and colloidal chemistry, percolation and coarsening in phase transitions and critical phenomena, agglutination and cell adhesion in biology, to island nucleation and thin-film growth in materials science. Detailed information about the kinetics of aggregation is provided by the time dependent cluster size-distribution, a quantity which can be measured experimentally. While the standard Smoluchowski rate-equation approach has been in general successful in predicting average quantities like the total cluster density, it fails to account for spatial fluctuations and correlations and thus predicts size distributions that are in significant disagreement with both experiments and kinetic Monte Carlo simulations. In this work we outline a new method which takes into account such correlations. We show that by coupling a set of evolution equations for the capture-zone distributions with a set of rate-equations for the island densities one may obtain accurate predictions for the time- and size-dependent rates of monomer capture. In particular, by using this method we obtain excellent results for the capture numbers and island-size distributions in irreversible growth on both one- and two-dimensional substrates.
Kochkina, N. E.; Padokhin, V. A.; Skobeleva, O. A.
2013-05-01
The unimodal distribution of hydrodynamic radii is determined by DLS measurements of starch molecule sizes. The starch was hydrolyzed in 0.3 M hydrochloric acid for 3-9 h. The ratio of amylose to amylopectin is shown to remain constant.
Czech Academy of Sciences Publication Activity Database
Zíková, Nad?da; Wagner, Zden?k; Schwarz, Jaroslav; Smolík, Ji?í; dímal, 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
Air Mass Back Trajectories and Dry Atmospheric Aerosol Mass Size Distributions in Prague.
Czech Academy of Sciences Publication Activity Database
Schwarz, Jaroslav; tefancová, Lucia; Maenhaut, W.; Smolík, Ji?í; dímal, 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
Size distribution of aerosols. Some ideas about the techniques used to obtain it
International Nuclear Information System (INIS)
This paper makes a classification of the techniques permitting to estimate the size distribution of aerosols in three categories: dynamical methods (cascade impactors, diffusion batteries, SDI 2000, APS - Aerodynamic Particle Sizer), electrical methods (DMA - Differential Electrical Mobility Analysers, DMPS, SMEC) and optical ones (CNC - Continuous Flow Condensation Nucleus Counter). Performance and limits of different devices/instruments are indicated. (author)
Size distribution of atomic clusters formed by energetic-heavy-ion sputtering
Energy Technology Data Exchange (ETDEWEB)
Yadav, R.T.; Ramamurthy, V.S.; Mahapatra, D.P.; Raviprasad, G.V. [Institute of Physics, Bhubaneswar 751005 (India)
1994-03-01
A cesium sputter ion source is used to produce cluster beams of various materials. The size distributions of these clusters have been studied. The dependence of the cluster yields on the structure of the substrate used has also been studied for carbon.
Atmospheric Aerosols in Suburb of Prague: The Dynamics of Particle Size Distributions.
Czech Academy of Sciences Publication Activity Database
?imná?ová, Daniela; dímal, 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
Product market integration, tax distortions and public sector size
DEFF Research Database (Denmark)
Andersen, Torben M.; SĜrensen, 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).
A Markov decision model for optimising economic production lot size under stochastic demand
PK Mubiru
2010-01-01
Traditional approaches towards determining the economic production lot (EPL) size in manufacturing applications assume deterministic demand, often at a constant rate. In this paper, an optimisation model is developed for determining the EPL size that minimises production and inventory costs of a periodic review production-inventory system under stochastic demand. Adopting such a Markov decision process approach, the states of a Markov chain represent possible states of demand. The decision of...
International Nuclear Information System (INIS)
The calculation of dose rates for humans by the inhalation of Rn fission products is done using close rate calculating models providing conversion equations including also the aerosol size of the oriented and non-oriented portion of Rn fission products as a variable value. These value which are required for the evaluation of Rn inquiry measurements were determined by measurements in appartments. The experimental investigations show that in rooms lacking additional aerosol sources the non-oriented portion of the potential ? energy of the Rn fission products is about 0.08 (fluctuation range 0.05 to 0.15) and that, in the final report of the Rn inquiry measurements, the suppposed non-oriented portion (fsub(p)=0.02) was too small for the dose rate calculation. The measured medians (diameter) of the size distributions of the radioactive aerosol fluctuate in the range of 100 to 200 nm. (orig.)
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.
History of water-column anoxia in the Black Sea indicated by pyrite framboid size distributions
Wilkin, R.T.; Arthur, M.A.; Dean, W.E.
1997-01-01
A detailed study of size distributions of framboidal pyrite in Holocene Black Sea sediments establishes the timing of a change from deposition under an oxic water column to deposition under an anoxic and sulfidic water column. In the most recent carbonate-rich sediments (Unit I) and in the organic carbon-rich sapropel (Unit II), framboid size distributions are remarkably uniform (mean diameter= 5 ??m); over 95% of the framboids in Unit I and Unit II are water column, followed by transport to the sediment-water interface, cessation of pyrite growth due to the exhaustion of reactive iron, and subsequent burial. In contrast, the organic carbon-poor sediments of lacustrine Unit III contain pyrite framboids that are generally much larger in size (mean diameter = 10 ??m). In Unit III, over 95% of the framboids are water-column anoxia in the Black Sea coincided with the initiation of deposition of laminated Unit II sapropels.
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 5080nm, 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.
Mena, Rodrigo; Li, Yan-Fu; Hennebel, Martin; Ruiz, Carlos; Zio, Enrico
2013-01-01
This paper presents a computational framework for the integration of renewable generators DG into an electrical power distribution network. Reliability of power supply is targeted, taking into account the uncertainty of loads and renewable energy sources and, in addition to the failure behavior of the system components. The computational framework developed integrates Monte Carlo simulation for the generation of the uncertain scenarios of operation and Optimal Power Flow (MCS-OPF) into a mult...
COLOR DEPENDENCE IN THE SIZE DISTRIBUTION OF MAIN BELT ASTEROIDS REVISITED
International Nuclear Information System (INIS)
The size distribution of the asteroid belt is examined with 16956 main belt asteroids detected in data taken from the Canada-France-Hawaii Telescope Legacy Survey in two filters (g' and r'). The cumulative H (absolute magnitude) distribution is examined in both filters, and both match well to simple power laws down to H = 17, with slopes in rough agreement with those reported the literature. This implies that disruptive collisions between asteroids are gravitationally dominated down to at least this size, and probably sub-kilometer scales. The slopes of these distributions appear shallower in the outer belt than the inner belt, and the g' distributions appear slightly steeper than the r'. The slope shallowing in the outer belt may reflect a real compositional difference: the inner asteroid belt has been suggested to consist mostly of stony and/or metallic S-type asteroids, whereas carbonaceous C-types are thought to be more prevalent further from the Sun. No waves are seen in the size distribution above H = 15. Since waves are expected to be produced at the transition from gravitationally-dominated to internal strength-dominated collisions, their absence here may imply that the transition occurs at sub-kilometer scales, much smaller than the H = 17 (diameter ? 1.6 km) cutoff of this study.
Seasonal cycle and modal structure of particle number size distribution at Dome C, Antarctica
Directory of Open Access Journals (Sweden)
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 10600 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.
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 12 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.
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).
Sarabia, José María; Jordá, Vanesa
2014-12-01
The importance of the Pietra index in socioeconomic systems and econophysics has been highlighted by Eliazar and Sokolov (2010). In this paper, we obtain closed expressions for the Pietra index for the generalized function for the size of income proposed by McDonald (1984). This family is composed of three classes of distributions: the generalized gamma distribution (GG), the generalized beta of the first kind (GB1) and the generalized beta of the second kind (GB2). For the different distributions, we obtain closed and simple expressions of the Pietra index, which can be easily computed. We also obtain the Pietra index for other relevant income models including finite mixtures of distributions and the ?-generalized distribution (Clementi et al., 2008). Finally, two empirical applications with real income data are given.
Determination of pore size distribution at the cell-hydrogel interface
Directory of Open Access Journals (Sweden)
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.
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 14.718.6 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 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.
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.
Grain-size distributions and grain boundaries of chalcopyrite-type thin films
International Nuclear Information System (INIS)
CuInSe2, CuGaSe2, Cu(In,Ga)Se2 and CuInS2 thin-film solar absorbers in completed solar cells were studied in cross section by means of electronbackscatter diffraction. From the data acquired, grain-size distributions were extracted, and also the most frequent grain boundaries were determined. The grain-size distributions of all chalcopyrite-type thin films studied can be described well by lognormal distribution functions. The most frequent grainboundary types in these thin films are 60 - left angle 221 right angle tet and 71 - left angle 110 right angle tet (near) ?3 twin boundaries. These results can be related directly to the importance of {112}tet planes during the topotactical growth of chalcopyrite-type thin films. Based on energetic considerations, it is assumed that the most frequent twin boundaries exhibit a 180 - left angle 221 right angle tet constellation. (orig.)
Location and Size of Distributed Generation Using a Modified Water Cycle Algorithm
Directory of Open Access Journals (Sweden)
John Edwin Candelo Becerra
2015-06-01
Full Text Available This paper presents a modified water cycle algorithm (WCA adapted to the problem of finding the location and size of distributed generation (DG. Power losses minimization was used as an objective function to compare the proposed algorithm with particle swarm optimization (PSO, the batinspired Algorithm (BA, and harmony search (HS. The test scenarios consisted of locating five to seven generators with a maximum real and reactive power in the 33-node and 69-node radial distribution networks. The experiment was designed to start iterations from the same initial population to identify the algorithms performance when searching for the best solutions. The results demonstrate that the modified WCA found the minimum power losses after locating and sizing distributed generators for most of the test scenarios. The algorithm converged quickly to the best solution and the solutions for all repetitions tested were close to the best for each case simulated.
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
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.
DISTRIBUTION OF BANKING PRODUCTS AND SERVICES
Directory of Open Access Journals (Sweden)
BULGAREA CATALIN NICOLAE
2010-12-01
Full Text Available Starting with the 90s, retails banks have faced several challenges. One of them is how to efficiently deliver their products and services to the customers. In fact, the most important challenge of a bank is how to efficiently reach the customer, with the right product or service, at the right time. Today, they can choose between branches, contact centers, ATMs, online channels, portals and web banks. Multichannel banking is, therefore, more relevant than ever. Multichannel banking is more than just offering multiple channels, but offering integrated channels, with the optimal balance of services, prices and offer across channels. Banks should have the ability to deliver the right service at the right time in the right channel. The bank should define exactly how they are going to use each channels, which services and products in which channels, how to mix and integrate the channels and how to support the channels
Bubble size distributions across some basaltic lava flows with simple vesiculation
Proussevitch, A.; Sahagian, D. L.; Carlson, W. D.
2006-12-01
Cross-sections of Cenozoic basaltic lava flows from the Colorado Plateau were analyzed using high resolution X-ray tomographic imagery and newly developed software for object recognition. Each cross-section is represented by a series of about 10 samples drilled from a lava flow at intervals of 2 to 50 cm depending on visible vesicularity variability in the exposed profile. The choice of flows being analyzed bears on our previous study in which we were able to identify flows with "simple" log normal monomodal vesiculation histograms in their quenched top and bottom crusts. A simple vesicle size distribution in the quenched crusts reflects a single pre-eruptive nucleation and bubble growth event. Identification of simple pre-eruptive vesiculation history enabled us to track the post-eruptive evolution of vesicularity and bubble size distributions in the flow interior caused by bubble flotation and coalescence during progressive solidification of the flow from top and bottom. The results show that the studied lavas are stratified into vesicular zones. These zones include (1) bottom quenched crust, (2) lower low vesicular, (3) bubble free, (4) upper low vesicular, (5) upper highly vesicular, and (6) top quenched crust. Transformations of initial log normal monomodal distributions caused by flotation and coalescence can be traced across lava flow profiles. These are reflected in changes not only of bulk vesicularity, but also in the parameters of bubble size distribution functions as well as in the nature of the distribution functions themselves. Consequently, quantitative analysis of basalt vesicle size distributions can provide insights into pre-eruptive as well as post-eruptive behavior of the gas/melt systems.
International Nuclear Information System (INIS)
In the present study, it is predicted that the band gap energy of a three-dimensional quantum dot assembly exhibits a red shift when the dispersion of the crystal size distribution is enlarged, even at a fixed average value thereof. The effect is manifested when the size quantization regime in individual quantum dots constituting the assembly has been entered. Under the same conditions, the sub-band gap absorption tails are characterized with large Urbach energies, which could be one or two orders of magnitude larger than the value characteristic for the non-quantized case. - Graphical abstract: Band gap shifts due to size-distribution of nanoparticles in 3D assemblies built up by quantum dots in size-quantization regime. Display Omitted - Highlights: Optical absorption of 3D QD assemblies in size-quantization regime is modeled. Band gap energy of the QD solid depends on the size-distribution of the nanoparticles. QD solid samples with same ?R? exhibit band gap shift depending on size distribution. QD size distribution leads to large Urbach energies
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
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.
Discover logistik mit SAP procurement, production and distribution logistics
Kappauf, Jens; Koch, Matthias
2011-01-01
This book shows how SAP's business suite supports logistic end-to-end processes, exploring relevant functionality, system and application integration to outline closed-loop supply chain processes in procurement, production, distribution logistics and compliance.
Determination of the particle size distribution in a powder using radiotracers
International Nuclear Information System (INIS)
To determine experimentally the particle size distribution in a powder the meshed method is generally used. This method has the disadvantage that in the obtained distribution is not observed at detail the fine structure of such distribution. In this work, a method for obtaining the distribution of particle size using radiotracers is presented. In the obtained distribution by this method it is observed with more detail the fine structure of the distribution, comparing with the obtained results by the classical method of meshed. The radiotracer method has major resolution for the experimental determination mentioned. In the chapter 1, it is done a brief analysis about theoretical aspects related with the method. In the first part it is analysed the particle behavior (sedimenting) in a fluid. The second part treats the relating with the radioactivity of an activated material as well as its detection. In the chapter 2, a description of the method is done also the experimental problems to applying to the alumina crystals sample are discussed. In the chapter 3 the obtained results and the mistake calculations in such results are showed. Finally, in the chapter 4 the conclusions and recommendations are given which is possible to obtain better results and improve to those in this work were obtained. (Author)
International Nuclear Information System (INIS)
The intersublevel absorption peak energy and absorption coefficient of non-uniform quantum dot (QD) ensembles are calculated analytically. The effect of size variations and size distribution of QDs on their energy states is analyzed. The dots are considered as a quantum box with finite potential at the barriers and the size distribution described by a Gaussian function. The influence of the aspect ratio (base to height ratio) of the QDs on the optical transitions is studied. Our model predicts the dot size (height and base) accurately to determine the absorption peaks and corresponding absorption coefficient. We also compute the absorption coefficient of the QD with different size distributions to verify the results calculated using this model with the reported experimental and other theoretical results
International Nuclear Information System (INIS)
We demonstrate a method for synthesizing free standing silicon nanocrystals in an argon/silane gas mixture by using a remote expanding thermal plasma. Transmission electron microscopy and Raman spectroscopy measurements reveal that the distribution has a bimodal shape consisting of two distinct groups of small and large silicon nanocrystals with sizes in the range 210 nm and 50120 nm, respectively. We also observe that both size distributions are lognormal which is linked with the growth time and transport of nanocrystals in the plasma. Average size control is achieved by tuning the silane flow injected into the vessel. Analyses on morphological features show that nanocrystals are monocrystalline and spherically shaped. These results imply that formation of silicon nanocrystals is based on nucleation, i.e., these large nanocrystals are not the result of coalescence of small nanocrystals. Photoluminescence measurements show that silicon nanocrystals exhibit a broad emission in the visible region peaked at 725 nm. Nanocrystals are produced with ultrahigh throughput of about 100 mg/min and have state of the art properties, such as controlled size distribution, easy handling, and room temperature visible photoluminescence.
Evidence for a colour dependence in the size distribution of main belt asteroids
Wiegert, P A; Moss, A; Veillet, C; Connors, M; Shelton, I; Wiegert, Paul; Balam, David; Moss, Andrea; Veillet, Christian; Connors, Martin; Shelton, Ian
2006-01-01
We present the results of a project to detect small (~1 km) main-belt asteroids with the 3.6 meter Canada-France-Hawaii Telescope (CFHT). We observed in 2 filters (MegaPrime g' and r') in order to compare the results in each band. Owing to the observational cadence we did not observe the same asteroids through each filter and thus do not have true colour information. However strong differences in the size distributions as seen in the two filters point to a colour-dependence at these sizes, perhaps to be expected in this regime where asteroid cohesiveness begins to be dominated by physical strength and composition rather than by gravity. The best fit slopes of the cumulative size distributions (CSDs) in both filters tend towards lower values for smaller asteroids, consistent with the results of previous studies. In addition to this trend, the size distributions seen in the two filters are distinctly different, with steeper slopes in r' than in g'. Breaking our sample up according to semimajor axis, the differe...
International Nuclear Information System (INIS)
As a part of resolving optical properties in atmosphere radiative transfer calculations, this paper focuses on obtaining aerosol optical thicknesses (AOTs) in the visible and near infrared wave band through indirect method by gleaning the values of aerosol particle size distribution parameters. Although various inverse techniques have been applied to obtain values for these parameters, we choose a stochastic particle swarm optimization (SPSO) algorithm to perform an inverse calculation. Computational performances of different inverse methods are investigated and the influence of swarm size on the inverse problem of computation particles is examined. Next, computational efficiencies of various particle size distributions and the influences of the measured errors on computational accuracy are compared. Finally, we recover particle size distributions for atmospheric aerosols over Beijing using the measured AOT data (at wavelengths ?=0.400, 0.690, 0.870, and 1.020 ?m) obtained from AERONET at different times and then calculate other AOT values for this band based on the inverse results. With calculations agreeing with measured data, the SPSO algorithm shows good practicability.
Ackleh, Azmy S; Farkas, József Z; Li, Xinyu; Ma, Baoling
2015-07-01
We consider a size-structured population model where individuals may be recruited into the population at different sizes. First- and second-order finite difference schemes are developed to approximate the solution of the model. The convergence of the approximations to a unique weak solution is proved. We then show that as the distribution of the new recruits become concentrated at the smallest size, the weak solution of the distributed states-at-birth model converges to the weak solution of the classical Gurtin-McCamy-type size-structured model in the weak* topology. Numerical simulations are provided to demonstrate the achievement of the desired accuracy of the two methods for smooth solutions as well as the superior performance of the second-order method in resolving solution-discontinuities. Finally, we provide an example where supercritical Hopf-bifurcation occurs in the limiting single state-at-birth model and we apply the second-order numerical scheme to show that such bifurcation also occurs in the distributed model. PMID:24890735
Energy Technology Data Exchange (ETDEWEB)
Dogan, Ilker; Kramer, Nicolaas J.; Westermann, Rene H. J.; Verheijen, Marcel A. [Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands); Dohnalova, Katerina; Gregorkiewicz, Tom [Van der Waals-Zeeman Institute, University of Amsterdam, Science Park 904, 1098 XH Amsterdam (Netherlands); Smets, Arno H. M. [Photovoltaic Materials and Devices Laboratory, Delft University of Technology, P.O. Box 5031, 2600 GA Delft (Netherlands); Sanden, Mauritius C. M. van de [Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands); Dutch Institute for Fundamental Energy Research (DIFFER), P.O. Box 1207, 3430 BE Nieuwegein (Netherlands)
2013-04-07
We demonstrate a method for synthesizing free standing silicon nanocrystals in an argon/silane gas mixture by using a remote expanding thermal plasma. Transmission electron microscopy and Raman spectroscopy measurements reveal that the distribution has a bimodal shape consisting of two distinct groups of small and large silicon nanocrystals with sizes in the range 2-10 nm and 50-120 nm, respectively. We also observe that both size distributions are lognormal which is linked with the growth time and transport of nanocrystals in the plasma. Average size control is achieved by tuning the silane flow injected into the vessel. Analyses on morphological features show that nanocrystals are monocrystalline and spherically shaped. These results imply that formation of silicon nanocrystals is based on nucleation, i.e., these large nanocrystals are not the result of coalescence of small nanocrystals. Photoluminescence measurements show that silicon nanocrystals exhibit a broad emission in the visible region peaked at 725 nm. Nanocrystals are produced with ultrahigh throughput of about 100 mg/min and have state of the art properties, such as controlled size distribution, easy handling, and room temperature visible photoluminescence.
A Stochastic Theory for Deep Bed Filtration Accounting for Dispersion and Size Distributions
DEFF Research Database (Denmark)
Shapiro, Alexander; Bedrikovetsky, P. G.
2010-01-01
We develop a stochastic theory for filtration of suspensions in porous media. The theory takes into account particle and pore size distributions, as well as the random character of the particle motion, which is described in the framework of the theory of continuous-time random walks (CTRW). In the limit of the infinitely many small walk steps we derive a system of governing equations for the evolution of the particle and pore size distributions. We consider the case of concentrated suspensions, where plugging the pores by particles may change porosity and other parameters of the porous medium. A procedure for averaging of the derived system of equations is developed for polydisperse suspensions with several distinctive particle sizes. A numerical method for solution of the flow equations is proposed. Sample calculations are applied to compare the roles of the particle size distribution and of the particle flight dispersion on the deposition profiles. It is demonstrated that the temporal flight dispersion is the most likely mechanism forming the experimentally observed hyperexponential character of the deposition profiles.
Effects of the confining solvent on the size distribution of silver NPs by laser ablation
Energy Technology Data Exchange (ETDEWEB)
Oseguera-Galindo, D. O., E-mail: david.omar0927@hotmail.com; Martinez-Benitez, A.; Chavez-Chavez, A.; Gomez-Rosas, G.; Perez-Centeno, A.; Santana-Aranda, M. A., E-mail: miguelangelsantana@gmail.com [CUCEI, Universidad de Guadalajara, Departamento de Fisica (Mexico)
2012-09-15
Laser ablation of a silver target confined in acetone, ethanol, methanol, propanol, and distilled water allowed us to obtain silver nanoparticles with different size distributions. We employed a pulsed Nd:YAG laser ({lambda} = 532 nm, 0.5 J/pulse) with a high fluence of 64 J/cm{sup 2} with a scanning density of 2,500 pulses/cm{sup 2}, having overlapping of consecutive pulses. The analysis of transmission electron micrographs showed that the smaller particle sizes were obtained confining the target in propanol, while the larger ones were obtained employing ethanol. Nanoparticle size distributions were fitted with two Gaussian peaks in all five cases, being the smaller sizes the most frequent. Predominant peaks were centered at 4.8 and 13.9 nm in propanol and ethanol, respectively, having a broader distribution for the nanoparticles obtained in ethanol. Furthermore, comparison of electron micrographs taken the day of synthesis and 4 and 9 months later in the case of water and propanol, respectively, shows that nanoparticle suspension is more stable in propanol.
Effects of the confining solvent on the size distribution of silver NPs by laser ablation
International Nuclear Information System (INIS)
Laser ablation of a silver target confined in acetone, ethanol, methanol, propanol, and distilled water allowed us to obtain silver nanoparticles with different size distributions. We employed a pulsed Nd:YAG laser (? = 532 nm, 0.5 J/pulse) with a high fluence of 64 J/cm2 with a scanning density of 2,500 pulses/cm2, having overlapping of consecutive pulses. The analysis of transmission electron micrographs showed that the smaller particle sizes were obtained confining the target in propanol, while the larger ones were obtained employing ethanol. Nanoparticle size distributions were fitted with two Gaussian peaks in all five cases, being the smaller sizes the most frequent. Predominant peaks were centered at 4.8 and 13.9 nm in propanol and ethanol, respectively, having a broader distribution for the nanoparticles obtained in ethanol. Furthermore, comparison of electron micrographs taken the day of synthesis and 4 and 9 months later in the case of water and propanol, respectively, shows that nanoparticle suspension is more stable in propanol.
A Divot in the Size Distribution of the Kuiper Belt's Scattering Objects?
Shankman, Cory; Gladman, B.; Kaib, N.; Kavelaars, J. J.; Petit, J.
2013-10-01
The scattering objects are a small-body population of the Kuiper Belt undergoing strong (scattering) interactions with the giant planets. 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 scattering objects revealed an exciting potential form for the scattering object size distribution - a divot. Our divot (a sharp drop in the number of objects that then recovers) 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 early results of an extension of our previous work to include two new Kuiper Belt surveys. We expect an additional few scattering objects from these surveys which, in tandem with the full characterizations of their biases (which can act like non-detections limits), will allow us to better constrain the form of the scattering object size distribution.
Stark, Scott C; Enquist, Brian J; Saleska, Scott R; Leitold, Veronika; Schietti, Juliana; Longo, Marcos; Alves, Luciana F; Camargo, Plinio B; Oliveira, Raimundo C
2015-07-01
Forest biophysical structure - the arrangement and frequency of leaves and stems - emerges from growth, mortality and space filling dynamics, and may also influence those dynamics by structuring light environments. To investigate this interaction, we developed models that could use LiDAR remote sensing to link leaf area profiles with tree size distributions, comparing models which did not (metabolic scaling theory) and did allow light to influence this link. We found that a light environment-to-structure link was necessary to accurately simulate tree size distributions and canopy structure in two contrasting Amazon forests. Partitioning leaf area profiles into size-class components, we found that demographic rates were related to variation in light absorption, with mortality increasing relative to growth in higher light, consistent with a light environment feedback to size distributions. Combining LiDAR with models linking forest structure and demography offers a high-throughput approach to advance theory and investigate climate-relevant tropical forest change. PMID:25963522
Normality distribution testing for leveling data obtained from production measurements
Directory of Open Access Journals (Sweden)
Milan Trifkovi?
2015-04-01
Full Text Available Normal distribution of data is of crucial importance in data processing and hypothesis testing in geodesy. Models of geodetic measurements adjustment assume that data are normally distributed. However, results of measurements could be affected by different influences because geodetic data are obtained under external conditions and under different limitations such as the deadlines or other processes on the construction site. These possibilities implicate certain risks that deviations from normal distribution in geodetic data could appear. Those deviations from normal distribution could spread through the mathematical and stochastic models and violate conclusions based on geodetic data. To avoid mentioned risks it is of considerable importance to devote attention to testing normality distribution of geodetic data obtained from production measurements. In this paper one set of leveling data obtained from production measurements was considered from aspect of its normal distribution curve.
Size and The City: Productivity, Match Quality and Wage Inequality
Yip, Chi Man
2011-01-01
This paper elucidates the impact of city growth on wage and wage inequality using a search-theoretical approach. Firms differ in capital intensity and land intensity of the jobs created. When a worker meets a job via a matching technology, a match-specific productivity level is realized and they sign a job contract when they agree with the bargaining wage. A rise in population density leads to rental increment. As a consequence, a higher expected flow profit is required for the creation of a ...
Sizing up the nuclear glue in J/?-production
International Nuclear Information System (INIS)
Nuclear gluon densities are of great importance to the physics of relativistic heavy ion collisions, in particular, in assessing the origin of J/?-suppression. We describe our attempts to distinguish various models of the gluonic EMC-effect, using the existing J/?-production data in proton-nucleus collisions. We find that no model is capable of explaining all the features of the high precision E772 data although the overall trend suggests this to be more a matter of fine-tuning the models than the presence of new physical effects. (orig.)
Optimizing Batch Size in a Flow-Oriented Synchronized Production
Imran Aslan; Dilsad Guzel
2011-01-01
This study was prepared for a leading company, Miele GmbH, the global premium brand of domestic appliancesand commercial machines in the field of laundry care, dishwashing and disinfection in Germany. The productionline of Miele GmbH in Bielefeld, Germany was analyzed to develop a model that can be used for all the firms inthe group.Dynamic programming models are widely used by companies to efficiently meet the demand for a variety ofproducts. In a flow shop, each product has to be processed ...
Dudkiewicz, Agnieszka; Wagner, Stephan; Lehner, Angela; Chaudhry, Qasim; Pietravalle, Stéphane; Tiede, Karen; Boxall, Alistair B A; Allmaier, Guenter; Tiede, Dirk; Grombe, Ringo; von der Kammer, Frank; Hofmann, Thilo; Mĝlhave, Kristian
2015-08-01
Available measurement methods for nanomaterials are based on very different measurement principles and hence produce different values when used on aggregated nanoparticle dispersions. This paper provides a solution for relating measurements of nanomaterials comprised of nanoparticle aggregates determined by different techniques using a uniform expression of a mass equivalent diameter (MED). The obtained solution is used to transform into MED the size distributions of the same sample of synthetic amorphous silica (nanomaterial comprising aggregated nanoparticles) measured by six different techniques: scanning electron microscopy in both high vacuum (SEM) and liquid cell setup (Wet-SEM); gas-phase electrophoretic mobility molecular analyzer (GEMMA); centrifugal liquid sedimentation (CLS); nanoparticle tracking analysis (NTA); and asymmetric flow field flow fractionation with inductively coupled plasma mass spectrometry detection (AF4-ICP-MS). Transformed size distributions are then compared between the methods and conclusions drawn on methods' measurement accuracy, limits of detection and quantification related to the synthetic amorphous silca's size. Two out of the six tested methods (GEMMA and AF4-ICP-MS) cross validate the MED distributions between each other, providing a true measurement. The measurement accuracy of other four techniques is shown to be compromised either by the high limit of detection and quantification (CLS, NTA, Wet-SEM) or the sample preparation that is biased by increased retention of smaller nanomaterials (SEM). This study thereby presents a successful and conclusive cross-method comparison of size distribution measurements of aggregated nanomaterials. The authors recommend the uniform MED size expression for application in nanomaterial risk assessment studies and clarifications in current regulations and definitions concerning nanomaterials. PMID:26081166
Energy Technology Data Exchange (ETDEWEB)
El-Atwani, Osman, E-mail: oelatwan@purdue.edu [School of Materials Engineering, Purdue University, West Lafayette, IN 47907 (United States); Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907 (United States); Quach, Dat V. [Department of Chemical Engineering and Materials Science, University of California, Davis, CA 95616 (United States); Efe, Mert [School of Materials Engineering, Purdue University, West Lafayette, IN 47907 (United States); Cantwell, Patrick R. [School of Materials Engineering, Purdue University, West Lafayette, IN 47907 (United States); Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907 (United States); Heim, Bryan [Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907 (United States); School of Nuclear Engineering, Purdue University, West Lafayette, IN 47907 (United States); Schultz, Bradley [School of Materials Engineering, Purdue University, West Lafayette, IN 47907 (United States); Stach, Eric A. [School of Materials Engineering, Purdue University, West Lafayette, IN 47907 (United States); Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907 (United States); Groza, Joanna R. [Department of Chemical Engineering and Materials Science, University of California, Davis, CA 95616 (United States); Allain, Jean Paul [School of Materials Engineering, Purdue University, West Lafayette, IN 47907 (United States); Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907 (United States); School of Nuclear Engineering, Purdue University, West Lafayette, IN 47907 (United States)
2011-07-15
Graphical abstract: Cross-sectional micrograph of spark plasma sintered tungsten with multimodal grain size distribution: (a) using focused ion beam (b) Bright field TEM image. Highlights: {yields} High applied external pressure during SPS led to high density of the samples. {yields} The consolidated samples by SPS had a multimodal size distribution. {yields} Ultrafine grains were present within the samples sintered at low temperatures. {yields} High Vickers hardness was obtained compared to commercial tungsten. {yields} The consolidated samples were proved to be pure by chemical analysis. - Abstract: Preparation of fine grained, hard and ductile pure tungsten for future fusion reactor applications was tested using the bottom-up approach via powder consolidation by spark plasma sintering (SPS) at different temperature (1300-1800 deg. C) and pressure (90-266 MPa) conditions. Pure tungsten powders with an average particle size of about 1 {mu}m were sintered to high density (about 94%) with almost no grain growth at a temperature below 1400 deg. C and an applied pressure up to 266 MPa. These samples had a multi-modal grain size distribution (resembling the size distribution of the initial powder) and a very high Vickers hardness (up to 530 kg/mm{sup 2}). Above 1500 deg. C fast grain growth occurred and resulted in a drop in hardness. XRD on the surface of bulk samples showed a small amount of tungsten oxides; however, XPS and EDS indicated that these oxides were only surface contaminants and suggested a high purity for the bulk samples. The results demonstrate that SPS can lead to ultrafine and nanocrystalline tungsten if used to consolidate pure nano tungsten powders.
International Nuclear Information System (INIS)
Graphical abstract: Cross-sectional micrograph of spark plasma sintered tungsten with multimodal grain size distribution: (a) using focused ion beam (b) Bright field TEM image. Highlights: ? High applied external pressure during SPS led to high density of the samples. ? The consolidated samples by SPS had a multimodal size distribution. ? Ultrafine grains were present within the samples sintered at low temperatures. ? High Vickers hardness was obtained compared to commercial tungsten. ? The consolidated samples were proved to be pure by chemical analysis. - Abstract: Preparation of fine grained, hard and ductile pure tungsten for future fusion reactor applications was tested using the bottom-up approach via powder consolidation by spark plasma sintering (SPS) at different temperature (1300-1800 deg. C) and pressure (90-266 MPa) conditions. Pure tungsten powders with an average particle size of about 1 ?m were sintered to high density (about 94%) with almost no grain growth at a temperature below 1400 deg. C and an applied pressure up to 266 MPa. These samples had a multi-modal grain size distribution (resembling the size distribution of the initial powder) and a very high Vickers hardness (up to 530 kg/mm2). Above 1500 deg. C fast grain growth occurred and resulted in a drop in hardness. XRD on the surface of bulk samples showed a small amount of tungsten oxides; however, XPS and EDS indicated that these oxides were only surface contaminants and suggested a high purity for the bulk samples. The results demonstrate that SPS can lead to ultrafine and nanocrystalline tungsten if used to consolidate pure nano tungsten powders.
Tillmann, Ralf; Zhao, Defeng; Ehn, Mikael; Hofzumahaus, Andreas; Holland, Frank; Rohrer, Franz; Kiendler-Scharr, Astrid; Wahner, Andreas
2014-05-01
Atmospheric particles play a key role for regional and global climate due to their direct and indirect radiative forcing effects. The concentration and size of the particles are important variables to these effects. Within the continental planetary boundary layer (PBL) the particle number size distribution is influenced by meteorological parameters, local sinks and sources resulting in variable spatial distributions. However, measurements of particle number size distributions over a broad vertical range of the PBL are rare. The airship ZEPPELIN NT is an ideal platform to measure atmospheric aerosols on a regional scale within an altitude range up to 1000 m. For campaigns in the Netherlands, Northern Italy and South Finland in 2012 and 2013 the airship was deployed with a wide range of instruments, including measurements of different trace gases, short lived radicals, solar radiation, aerosols and meteorological parameters. Flights were carried out at different times of the day to investigate the influence of the diurnal evolution of the PBL on atmospheric trace gases and aerosols. During night and early morning hours the concentration and size distribution of atmospheric particles were found to be strongly influenced by the layered structure of the PBL, i.e. the nocturnal boundary layer and the residual layer. Within the residual layer particle concentrations stay relatively constant as this layer is decoupled from ground sources. The particles persist in the accumulation mode as expected for an aged aerosol. In the nocturnal boundary layer particle concentrations and size are more dynamic with higher concentrations than in the residual layer. A few hours after sunrise, the layered structure of the PBL intermixes. During daytime the PBL is well mixed and a negative concentration gradient with increasing height is observed. Several height profiles at different times of the day and at different locations in Europe were measured. The aerosol measurements will be discussed together with meteorological parameters and trace gas measurements. Acknowledgement: PEGASOS project funded by the European Commission and the Framework Program 7 (FP7-ENV-2010-265148).
Production, distribution and applications of californium-252 neutron sources.
Martin, R C; Knauer, J B; Balo, P A
2000-01-01
The radioisotope 252Cf is routinely encapsulated into compact, portable, intense neutron sources with a 2.6-yr half-life. A source the size of a person's little finger can emit up to 10(11) neutrons s(-1). Californium-252 is used commercially as a reliable, cost-effective neutron source for prompt gamma neutron activation analysis (PGNAA) of coal, cement and minerals, as well as for detection and identification of explosives, land mines and unexploded military ordinance. Other uses are neutron radiography, nuclear waste assays, reactor start-up sources, calibration standards and cancer therapy. The inherent safety of source encapsulations is demonstrated by 30 yr of experience and by US Bureau of Mines tests of source survivability during explosions. The production and distribution center for the US Department of Energy (DOE) Californium Program is the Radiochemical Engineering Development Center (REDC) at Oak Ridge National Laboratory (ORNL). DOE sells 252Cf to commercial reencapsulators domestically and internationally. Sealed 252Cf sources are also available for loan to agencies and subcontractors of the US government and to universities for educational, research and medical applications. The REDC has established the Californium User Facility (CUF) for Neutron Science to make its large inventory of 252Cf sources available to researchers for irradiations inside uncontaminated hot cells. Experiments at the CUF include a land mine detection system, neutron damage testing of solid-state detectors, irradiation of human cancer cells for boron neutron capture therapy experiments and irradiation of rice to induce genetic mutations. PMID:11003521
Production, distribution and applications of californium-252 neutron sources
International Nuclear Information System (INIS)
The radioisotope 252Cf is routinely encapsulated into compact, portable, intense neutron sources with a 2.6-yr half-life. A source the size of a person's little finger can emit up to 1011 neutrons s-1. Californium-252 is used commercially as a reliable, cost-effective neutron source for prompt gamma neutron activation analysis (PGNAA) of coal, cement and minerals, as well as for detection and identification of explosives, land mines and unexploded military ordnance. Other uses are neutron radiography, nuclear waste assays, reactor start-up sources, calibration standards and cancer therapy. The inherent safety of source encapsulations is demonstrated by 30 yr of experience and by US Bureau of Mines tests of source survivability during explosions. The production and distribution center for the US Department of Energy (DOE) Californium Program is the Radiochemical Engineering Development Center (REDC) at Oak Ridge National Laboratory (ORNL). DOE sells 252Cf to commercial reencapsulators domestically and internationally. Sealed 252Cf sources are also available for loan to agencies and subcontractors of the US government and to universities for educational, research and medical applications. The REDC has established the Californium User Facility (CUF) for Neutron Science to make its large inventory of 252Cf sources available to researchers for irradiations inside uncontaminated hot cells. Experiments at the CUF include a land mine detection system, neutron damage testing of solid-state detectors, irradiation of human cancer cells for boron neutron capture therapy experiments and irradiation of rice to induce genetic mutations
Kurek, Wojciech; Ostfeld, Avi
2013-01-30
A multi-objective methodology utilizing the Strength Pareto Evolutionary Algorithm (SPEA2) linked to EPANET for trading-off pumping costs, water quality, and tanks sizing of water distribution systems is developed and demonstrated. The model integrates variable speed pumps for modeling the pumps operation, two water quality objectives (one based on chlorine disinfectant concentrations and one on water age), and tanks sizing cost which are assumed to vary with location and diameter. The water distribution system is subject to extended period simulations, variable energy tariffs, Kirchhoff's laws 1 and 2 for continuity of flow and pressure, tanks water level closure constraints, and storage-reliability requirements. EPANET Example 3 is employed for demonstrating the methodology on two multi-objective models, which differ in the imposed water quality objective (i.e., either with disinfectant or water age considerations). Three-fold Pareto optimal fronts are presented. Sensitivity analysis on the storage-reliability constraint, its influence on pumping cost, water quality, and tank sizing are explored. The contribution of this study is in tailoring design (tank sizing), pumps operational costs, water quality of two types, and reliability through residual storage requirements, in a single multi-objective framework. The model was found to be stable in generating multi-objective three-fold Pareto fronts, while producing explainable engineering outcomes. The model can be used as a decision tool for both pumps operation, water quality, required storage for reliability considerations, and tank sizing decision-making. PMID:23262407
On geological interpretations of crystal size distributions: Constant vs. proportionate growth
Eberl, D.D.; Kile, D.E.; Drits, V.A.
2002-01-01
Geological interpretations of crystal size distributions (CSDs) depend on understanding the crystal growth laws that generated the distributions. Most descriptions of crystal growth, including a population-balance modeling equation that is widely used in petrology, assume that crystal growth rates at any particular time are identical for all crystals, and, therefore, independent of crystal size. This type of growth under constant conditions can be modeled by adding a constant length to the diameter of each crystal for each time step. This growth equation is unlikely to be correct for most mineral systems because it neither generates nor maintains the shapes of lognormal CSDs, which are among the most common types of CSDs observed in rocks. In an alternative approach, size-dependent (proportionate) growth is modeled approximately by multiplying the size of each crystal by a factor, an operation that maintains CSD shape and variance, and which is in accord with calcite growth experiments. The latter growth law can be obtained during supply controlled growth using a modified version of the Law of Proportionate Effect (LPE), an equation that simulates the reaction path followed by a CSD shape as mean size increases.
International Nuclear Information System (INIS)
Size distribution of maritime background aerosol was measured by use of an eight-staged Andersen impactor with a back-up filter. Sampling was made for 11 days on a cliff, 150 m above sea level, at one of Ogasawara Is. located ca. 1000 km to the south of Tokyo. The weighed samples were analyzed by nondestructive neutron activation analysis for 25 elements. Neutron irradiation and cooling were conducted so as to reduce interfering activities by radionuclides, especially Cl-38 and Na-24, for the measurement of short-lived nuclides. The continuous size distribution curves of the elements were drawn with reliable analytical data by numerical differentiation of the cumulative distribution curves. Aerosol concentration was very low, and its size distribution was unimodal with a peak at about 5 ?m. These feature is quite different from those in urban aerosols whose size distribution is generally bimodal. Among the elements determined, the major components of sea salt, sodium and chlorine, showed a typical unimodal pattern with 5 ?m peak, and this fact enables us to conclude that sodium and chlorine could be generated from one common source and/or behave together. A number of cubic crystals of NaCl were observed by scanning electron microscope in samples collected by a two-staged Lundgren impactor. A peak of ''coarse'' sea salt particles is thought to depend on gravitational settling of larger particles while the particles are transported from sea surface to the cliff. Iron, scandium, cobalt and chromium that generated from terrestrial origins are unimodal characteristics with one peak of coarse particles. On the other hand, zinc, selenium and antimony that were more enriched than those in sea water and crustal materials, were mostly found in the ''fine'' particle range below 2 ?m in aerodynamic diameter. This suggests that these elements might be transported from remote sources of industries or other anthropological activities. (auth.)
Szabó, Judit Alexandra; Jakab, Gergely; Szabó, Boglárka
2015-04-01
Soil structure degradation has effect through the soil water balance and nutrient supply on the agricultural potential of an area. The soil erosion process comprises two phases: detachment and transport by water. To study the transport phase nozzle type laboratory-scale rainfall simulator was used with constant 80 mmhr-1 intensity on an arable haplic Cambisol. Measuring the aggregate and particle size distribution of the soil loss gives a good approach the erosion process. The primary objective of this study was to examine the sediment concentration, and detect the quality and quantity change of the soil loss during a single precipitation under six treatment combinations (recently tilled and crusty soil surface on two different slope steepness, inland inundation and drought soil conditions). Soil loss were collected continually, and separated per aggregate size fractions with sieves in three rounds during a rain to measure the weights. The particle size distribution was measured with Horiba LA-950 particle size analyzer. In general the ratio of the macro aggregates decreases and the ratio of the micro aggregates and clay fraction increases in the sediment with time during the precipitation due to the raindrop impact. Sediment concentration depends on the slope steepness, as from steeper slopes the runoff can transport bigger amount of sediment, but from the tilled surface bigger aggregates were washing down. Micro aggregate fraction is one of the indicators of good soil structure. The degradation of micro aggregates occurs in steeper slopes and the most erosive time period depends on the micromorphology of the surface. And while the aggregate size distribution of the soil loss of the treatments shows high variety of distribution and differs from the original soil, the particle size distribution of each aggregate size fraction shows similar trends except the 50-250 µm fraction where the fine sand fraction is dominating instead of the loam. This anomaly may be connected with the TC content of this fraction, but more research is needed. In agricultural areas micro aggregate fraction plays important role in nutrient supply thus understanding the erosion process is necessary because of the better protection in the future.
Stone Tool Production-Distribution Systems at Huizui, China
Directory of Open Access Journals (Sweden)
Anne Ford
2009-09-01
Full Text Available Different ground stone tool production-distribution systems have been proposed as present at the site of Huizui in the Yiluo River Basin, central China, during the Erlitou period (1900-1500 BC. The current study used an economic approach to identify if differences could be observed between the systems. Using efficiency as the main parameter for comparison; raw material procurement and on-site production were investigated. Raw material procurement was shown to be efficient for all of the tool types studied, with particular focus on distance to source and the functional and extractive properties of the raw materials. Efficiency in production was less clear, with scale of production instead being the distinguishing factor. In total, two different production-distribution systems were identified; the mass produced oolitic dolomite spades which appear to be distributed regionally, and the locally produced and consumed adzes, axes, chisels, knifes and grinding slabs. Both of these systems appeared to be retained within the household context and may have operated independently of elite control, which is a contrast to the heavily circumscribed production and distribution of elite items. This study also showed that whilst efficiency is a useful tool to elicit detailed information from the stone tool production-distribution systems, further parameters need to be included to provide a more accurate contrast between systems.
Directory of Open Access Journals (Sweden)
A. R. Sepaskhah
2004-10-01
Full Text Available To obtain soil-moisture characteristic curve experimentally is time-consuming and usually subject to considerable errors. So, many investigators have tried to predict soil-moisture characteristic curve by different models. One of these models predicts soil moisture characteristic curve based on soil particle size distribution and bulk density. In this model, soil particle size distribution curve is divided into a number of segments, each with a specific particle radius and cumulative particle mass greater than that of the radius. Using these data, soil-moisture characteristic curve was estimated. In this model, a scale factor, ?, is used which may be considered as a constant, or obtained by logistic or linear procedures. The average values of ? for clay, silty clay, sandy loam, two loam soils, and two silty clay loam soils were 1.159, 1.229, 1.494, 1.391, 1.393, 1.253 and 1.254, respectively. For most conditions, soil particle size distribution curve is not available, but only the percentages of clay, silt, and sand could be obtained using soil textural data, which is not enough to draw a precise soil particle size distribution curve. In this situation, a precise soil particle size distribution curve must be initially developed on the basis of which the soil moisture characteristic curve can be predicted. In this study, using soil textural data of seven different soils, soil moisture characteristic curve of each was estimated. In these estimations, logistic and linear methods were used to obtain the ? value. Then, the results were compared with those of measured soil moisture characteristic curve. For estimation of soil particle size distribution curve, two extreme values for soil particle radius, 125 and 999 m, were used. The results indicated that using particle radius of 999 µm is more appropriate. On the other hand, it was found that for clay, silty clay, and sitly clay loam texture, it is more appropriate to employ a linear equation to determine for estimating soil-moisture characteristic curve while the logistic equation can be more appropriately used for loam and sand loam textures.
Grain Size Distribution in Mudstones: A Question of Nature vs. Nurture
Schieber, J.
2011-12-01
Grain size distribution in mudstones is affected by the composition of the source material, the processes of transport and deposition, and post-depositional diagenetic modification. With regard to source, it does make a difference whether for example a slate belt is eroded vs a stable craton. The former setting tends to provide a broad range of detrital quartz in the sub 62 micron size range in addition to clays and greenschist grade rock fragments, whereas the latter may be biased towards coarser quartz silt (30-60 microns), in addition to clays and mica flakes. In flume experiments, when fine grained materials are transported in turbulent flows at velocities that allow floccules to transfer to bedload, a systematic shift of grain size distribution towards an increasingly finer grained suspended load is observed as velocity is lowered. This implies that the bedload floccules are initially constructed of only the coarsest clay particles at high velocities, and that finer clay particles become incorporated into floccules as velocity is lowered. Implications for the rock record are that clay beds deposited from decelerating flows should show subtle internal grading of coarser clay particles; and that clay beds deposited from continuous fast flows should show a uniform distribution of coarse clays. Still water settled clays should show a well developed lower (coarser) and upper (finer) subdivision. A final complication arises when diagenetic processes, such as the dissolution of biogenic silica, give rise to diagenetic quartz grains in the silt to sand size range. This diagenetic silica precipitates in fossil cavities and pore spaces of uncompacted muds, and on casual inspection can be mistaken for detrital quartz. In distal mudstone successions close to 100 % of "apparent" quartz silt can be of that origin, and reworking by bottom currents can further enhance a detrital perception by producing rippled and laminated silt beds. Although understanding how size distributions in mudstones evolve is considered central to problems in hillslope, fluvial, aeolian, coastal, and submarine systems, one can not simply measure distributions and hope to arrive at an answer. The complex origins of mudstones are reflected in their very broad compositional range, and multiple overprinted processes have to be considered in order to make sense out of observed grain size distributions.
DEFF Research Database (Denmark)
Jensen, Kaare Hartvig; Valente, Andre X. C. N.
2014-01-01
We examine the fluid mechanics of viscous flow through filters consisting of perforated thin plates. We classify the effects that contribute to the hydraulic resistance of the filter. Classical analyses assume a single pore size and account only for filter thickness. We extend these results to obtain an analytical formula for the pressure drop across the microfilter versus the flow rate that accounts for the non-uniform distribution of pore sizes, the hydrodynamic interactions between the pores given their layout pattern, and wall slip. Further, we discuss inertial effects and their order of scaling. (C) 2014 AIP Publishing LLC.
Investigation of methods for measuring the particle size distribution of submicron flue dusts (II)
Energy Technology Data Exchange (ETDEWEB)
Makino, H.; Nagayama, T.; Matsuda, H.; Maruta, J.; Ayabe, S.; Misaka, T.; Nakamura, T.
1984-01-01
The performance of various methods for measuring the particle size distributions of submicron flue dusts at thermal power stations was compared and a study made of dust generation characteristics. The following equipment was used for the measurements: 1) an electrostatic particle size analyzer, 2) a laser dust monitor, 3) a differential mobility analyzer, 4) a low-pressure cascade impactor, and 5) an Anderson sampler. Various findings are reported, including the fact that accuracy of measurement using 1), 2) and 3) can be improved by carrying out preliminary classification with a cascade impactor. 8 references.
Fymat, A L; Mease, K D
1981-01-15
The approximations of Penndorf and Shifrin-Punina to the Mie solution at forward scattering angles are extended to smaller size parameter values. The present approximation, Eq. (7), is found to represent accurately the Mie result down to x ~ 0.5-1.0 for refractive index m = 1.33, and to x ~ 2.0 for much larger index values. The implications of this result are discussed relative to the reconstruction of particle size distributions utilizing the Shifrin-Fymat analytical inversion formula of forward scattered intensities. PMID:20309090
Pore Size Distribution in Chicken Eggs as Determined by Mercury Porosimetry
Directory of Open Access Journals (Sweden)
La Scala Jr N
2000-01-01
Full Text Available In this study we investigated the application of mercury porosimetry technique into the determination of porosity features in 28 week old hen eggshells. Our results have shown that the majority of the pores have sizes between 1 to 10 mu m in the eggshells studied. By applying mercury porosimetry technique we were able to describe the porosity features better, by determining a pore size distribution in the eggshells. Here, we introduce mercury porosimetry technique as a new routine technique applied into the study of eggshells.
International Nuclear Information System (INIS)
Based on the results of this study and literature review, the following conclusions can be made: Sediment grain size and TOC (total organic carbon) influence contaminant fate and transport (in general, sediments with higher TOC content and finer grain-size distribution can have higher contaminant burdens than sediments from a given river section that have less TOC and greater amounts of coarse-grained sediments). Physiochemical sediment characteristics are highly variable among monitoring sites along the Columbia River. Sediment grain characterization and TOC analysis should be included in interpretations of sediment-monitoring data
Determining Economic Production Quantity in the Presence of Varying Item Size and Stochastic Demand
Directory of Open Access Journals (Sweden)
Kizito Paul Mubiru
2014-01-01
Full Text Available The classical Economic Production Quantity (EPQ model as applied in production-inventory management assumes constant demand of a single item, often of a specific size. In this paper, an optimization method is developed for determining the EPQ of an item with varying size and stochastic demand. Adopting a Markov decision process approach, the states of a Markov chain represent possible states of demand for a given size of item. The decision of whether or not to produce additional units of a specific size of item is made using dynamic programming over a finite period planning horizon. Empirical results show the existence of an optimal state dependent economic production quantity for a specific size of it
Li, Chunfang; Li, Dongxiang; Wan, Gangqiang; Xu, Jie; Hou, Wanguo
2011-07-01
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; otherwise, the largely distributed nanoparticles or instable colloids were obtained. The low reaction temperature is helpful to control the nanoparticle formation rate, and uniform GNPs can be obtained in presence of optimized NaOH concentrations. The pH values of the obtained uniform GNPs were found to be very near to neutral, and the pH influence on the particle size distribution may reveal the different formation mechanism of GNPs at high or low pH condition. Moreover, this modified synthesis method can save more than 90% energy in the heating step. Such environmental-friendly synthesis method for gold nanoparticles may have a great potential in large-scale manufacturing for commercial and industrial demand.
A Markov decision model for optimising economic production lot size under stochastic demand
Directory of Open Access Journals (Sweden)
PK Mubiru
2010-06-01
Full Text Available Traditional approaches towards determining the economic production lot (EPL size in manufacturing applications assume deterministic demand, often at a constant rate. In this paper, an optimisation model is developed for determining the EPL size that minimises production and inventory costs of a periodic review production-inventory system under stochastic demand. Adopting such a Markov decision process approach, the states of a Markov chain represent possible states of demand. The decision of whether or not to produce additional inventory units is made using dynamic programming. This approach demonstrates the existence of an optimal state-dependent EPL size, and produces an optimal lot sizing policy, as well as the corresponding total production and inventory costs.
Biomass transportation model and optimum plant size for the production of ethanol.
Leboreiro, Jose; Hilaly, Ahmad K
2011-02-01
A detailed model based on a non-dimensional transportation factor is developed to assess the economics of biomass collection, transportation, and storage. The optimum plant size for bio-refineries is investigated; ethanol production from corn stover via dilute acid hydrolysis is presented as a case study. The conversion of straight-line, farm-to-plant distances to road distances via a winding factor leads to a shift in the distribution of transportation distances towards shorter hauls. The capital investment scaling exponent was calculated using the model developed at the National Renewable Energy Laboratory (Aden et al., NREL/TP-510-32438, 2002) and found to be 0.7. The cost of the delivered corn stover is proportional to the square root of the inverse of the farmer participation; as a consequence, bio-fuel producers intending to use agricultural residues as feedstock should work towards a farmer participation of fifty percent. Costs associated with storage represent a significant portion of the production cost. PMID:21109426
On the size distribution of supernova remnants in the Magellanic Clouds
Badenes, Carles; Draine, Bruce
2010-01-01
The physical sizes of supernova remnants (SNRs) in a number of nearby galaxies follow an approximately linear cumulative distribution, contrary to what is expected for decelerating shock fronts. This has been attributed to selection effects, or to a majority of SNRs propagating in "free expansion", at constant velocity, into a tenuous ambient medium. We compile a list of 77 known SNRs in the Magellanic Clouds (MCs), and argue that they are a largely complete record of the SNe that have exploded over the last ~20kyr, with most now in the adiabatic, Sedov phase of their expansions. The roughly linear cumulative size distribution (uniform in a differential distribution) can result from the combination of a deceleration during this phase, a transition to a radiation-loss-dominated phase at a radius that depends on the local gas density, and a distribution of ambient densities varying roughly as rho^{-1}. This explanation is supported by the observed -1 power-law distributions of three independent tracers of densi...
Near-coastal Antarctic Iceberg Size Distributions Determined From SAR Images
Wesche, Christine; Dierking, Wolfgang
2015-04-01
Over the past decades, the iceberg size distribution in Antarctic waters is a recurrent topic. Icebergs are moving sources of freshwater. Their drift and decay have an impact on the hydrology, circulation and biology of the ocean regions and are needed for a realistic simulation of the ocean dynamics. During the Radarsat-1 Antarctic Mapping Project (RAMP) Antarctic Mapping Mission-1 (AMM-1) a mosaic of Antarctica and the adjacent ocean zone was compiled from more than 3000 high-resolution Synthetic Aperture Radar (SAR) images. The mosaic offered the unique opportunity to determine spatial distributions of icebergs sizes along the entire coastline of Antarctica. A combination of automated iceberg detection and visual control as well as a correction of false detections resulted in identifying nearly 7000 icebergs with areas between 0.3 and 4717.7 qkm. Their spatial distribution showed correlations with coastline classes. These classes are based on the spatial distribution of surface features on ice shelves close to the calving front. From the detections and assumed mean iceberg thicknesses, we can calculate the distribution of floating freshwater ice mass within the coastal zone of Antarctica at the time of image acquisitions. For models of ocean dynamics, this dataset offers the opportunity to simulate the freshwater input into the Southern Ocean on a more realistic basis.
Energy efficiency and cost analysis of canola production in different farm sizes
S. H. Mousavi-Avval, S. Rafiee, A. Jafari, A. Mohammadi
2011-01-01
Efficient use of energy in agriculture is one of the conditions for sustainable agricultural production. The aims of this study were to determine the amount of inputoutput energy used in canola production, to investigate the efficiency of energy consumption and to make an economic analysis of canola production in different farm sizes. Data used in this study were obtained from 130 randomly selected farms in Golestan province, the most important centre of oilseed production in Iran. The surve...
Productivity and size of the export market: evidence for west and east German plants, 2004
Wagner, Joachim
2007-01-01
Using unique recently released nationally representative high-quality data at the plant level, this paper presents the first comprehensive evidence on the relationship bet-ween productivity and size of the export market for Germany, a leading actor on the world market for manufactured goods. It documents that firms that export to countries inside the euro-zone are more productive than firms that sell their products in Ger-many only, but less productive than firms that export to countries outs...
Quodbach, Julian; Kleinebudde, Peter
2014-11-01
The aim of this study is the introduction of a novel apparatus that is capable of continuously measuring the particle size reduction of disintegrating tablets and analysis of the obtained results. The apparatus is constructed such that no particles pass directly through the pumping system. Thereby, the overall energy input into the particle suspension is reduced, and continuous measurement is possible without rapid destruction of the generated particles. The detected particle sizes at the beginning and at the end of the measurement differ greatly, depending on the applied disintegrant. The median particle sizes at the end of the measurement vary between 621.5 and 178.0 ?m for different disintegrants. It is demonstrated that the particle size reduction follows an exponential function and that the fit parameters can be used to describe the disintegration behavior. A strong correlation between the median particle size of crospovidone disintegrants and generated particle size of the tablets is observed. This could be due to a more homogeneous distribution of the disintegrant particles in the tablets. Similar trends are observed for sodium starch glycolate and croscarmellose sodium. The new apparatus provides an innovative method to describe disintegrant effectiveness and efficiency. PMID:25223505
Business results change under effects of farm size and degree of production specialization
Bastaji? Ljubomir
2003-01-01
The study was conducted with the objective of analyzing the economic effects provoked by the change in farm size, depending on the degree of production specialization (questionnaires encompassing 30 farms of different size were used) using comparative analysis, regression analysis, correlation analysis and production function analysis. Research comprised essential parameters of business conditions on the farms and results of their business. The farms analyzed were classified according to the ...
International Nuclear Information System (INIS)
This study concerns essentially solid aerosols produced by combustion and more particulary the aerosol liberated by a sodium fire taken into account in safety studies related to sodium cooled nuclear reactors. The accurate determination of the aerosol size distribution depends on the selection device use. An experimental study of the parameters affecting the solid aerosol collection efficiency was made with the Andersen Mark II cascade impactor (blow off and bounce, electrical charge of particles, wall-loss). A sedimentation chamber was built and calibrated for the range between 4 and 10 ?m. The second part describes a comparative study of different data reduction methods for the impactor and a new method for setting up the aerosol size distribution with data obtained by the sedimentation chamber
Ultrafine particle size distribution during high velocity impact of high density metals
Buonanno, Giorgio; Stabile, Luca; Ruggiero, Andrew; Iannitti, Gianluca; Bonora, Nicola
2011-06-01
In the event of kinetic energy penetrator impact, survival personnel is exposed to the additional hazard stemming from ultrafine metallic particles, i.e. exposure, inhalation, and respiration of aerolized metals. Aerosol particle size distribution is an important parameter that influences aerosol transport and deposition processes. In order to have reliable quantitative measure of the aerosol particles generated under controlled impact conditions, an experimental set-up has been developed. Both non penetrating and penetrating impacts tests have been designed and performed with light gas-gun in chamber. During the impact, size distribution, total concentration and chemical composition of ultrafine particles have been measured and correlated with impact parameters (such as energy and velocity). In order to avoid measurement contamination, as a result of undesired participating materials, target and projectile have been made of the same metal and tests have been performed in clean environmental chamber. In this study the results relative to high purity copper are presented.
Neural networks to estimate bubble diameter and bubble size distribution of flotation froth surfaces
Scientific Electronic Library Online (English)
R.H., Estrada-Ruiz; R., Pérez-Garibay.
2009-07-01
Full Text Available This work analyses a new approach to estimates bubble size distribution of froth surfaces using artificial neural networks (ANN). Also, the robustness of ANN to interpret images with illumination perturbations, produced by light problems or dirt attached to the window of the video camera is evaluate [...] d. The experimental work was carried out in a laboratory flotation column, instrumented with an image acquisition system. The images were processed making use of a perceptron model with a hidden layer, sigmoidal transfer function and unitary bias, and the ANN trained with a back propagation algorithm. The results of validation show that ANN are reliable for learning and producing generalized predictions of the froth mean bubble diameter and bubble size distribution, when the model is trained using a database that contains information on the illumination intensity.
Particle size distribution measurements at Hada Al Sham, western Saudi Arabia
Hyvärinen, A.-P.; Al-Jeelani, H.; Alghamdi, M.; Hussein, T.; Khodeir, M.; Lihavainen, H.; Kulmala, M.; Laaksonen, A.
2013-05-01
Particle size distribution measurements from 7 nm to 850 nm are being conducted in Western Saudi Arabia utilizing a Differential Mobility Particle Sizer (DMPS). The early results show that the particle size distribution is highly variable, with signatures from the nucleation, Aitken, and accumulation mode. The accumulation mode dominates from midnight to early morning, after which an elevated Aitken mode appears, denoting to local morning activities. New particle formation begins regularly around 10 am, elevating first the nucleation mode concentrations and then the Aitken mode. During evening hours, the nucleation-and Aitken mode concentrations decrease, and the accumulation mode becomes dominant again. The average particle number concentration from December 2012 was 1640 ?/cm3. The maximum particle concentration in the region is originated from new particle formation, with a maximum 1h-average of 11400 ?/cm3.
Simultaneous retrieval of the complex refractive index and particle size distribution.
Ren, Yatao; Qi, Hong; Chen, Qin; Ruan, Liming; Tan, Heping
2015-07-27
A secondary optimization technique is proposed that allows the complex refractive index and particle size distribution (PSD) to be retrieved simultaneously by using the diffuse transmittance (T), diffuse reflectance (R), and collimated transmittance (Tc) of a 1-D spherical particle systems as measured values. In the proposed method, two 1-D experimental samples of different thicknesses were exposed to continuous wave lasers of two different wavelengths. First, T, R, and Tc were calculated by solving the radiative transfer equation. Then, the complex refractive index and PSDs were retrieved simultaneously by applying the inversion technique, quantum particle swarm optimization. However, the estimated results of the PSDs proved to be inaccurate. Hence, a secondary optimization was performed to improve the accuracy of the PSDs on the basis of the first optimization process. The results showed that the proposed technique can estimate the complex refractive index and particle size distribution accurately. PMID:26367593