WorldWideScience

Sample records for model hi-res size

  1. NASA 3D Models: ISS (Hi-res)

    Data.gov (United States)

    National Aeronautics and Space Administration — A very high resolution model of the International Space Station in many parts. The download includes an image of the final configuration. This model is provided in...

  2. A high resolution coupled hydrologic-hydraulic model (HiResFlood-UCI) for flash flood modeling

    Science.gov (United States)

    Nguyen, Phu; Thorstensen, Andrea; Sorooshian, Soroosh; Hsu, Kuolin; AghaKouchak, Amir; Sanders, Brett; Koren, Victor; Cui, Zhengtao; Smith, Michael

    2016-10-01

    HiResFlood-UCI was developed by coupling the NWS's hydrologic model (HL-RDHM) with the hydraulic model (BreZo) for flash flood modeling at decameter resolutions. The coupled model uses HL-RDHM as a rainfall-runoff generator and replaces the routing scheme of HL-RDHM with the 2D hydraulic model (BreZo) in order to predict localized flood depths and velocities. A semi-automated technique of unstructured mesh generation was developed to cluster an adequate density of computational cells along river channels such that numerical errors are negligible compared with other sources of error, while ensuring that computational costs of the hydraulic model are kept to a bare minimum. HiResFlood-UCI was implemented for a watershed (ELDO2) in the DMIP2 experiment domain in Oklahoma. Using synthetic precipitation input, the model was tested for various components including HL-RDHM parameters (a priori versus calibrated), channel and floodplain Manning n values, DEM resolution (10 m versus 30 m) and computation mesh resolution (10 m+ versus 30 m+). Simulations with calibrated versus a priori parameters of HL-RDHM show that HiResFlood-UCI produces reasonable results with the a priori parameters from NWS. Sensitivities to hydraulic model resistance parameters, mesh resolution and DEM resolution are also identified, pointing to the importance of model calibration and validation for accurate prediction of localized flood intensities. HiResFlood-UCI performance was examined using 6 measured precipitation events as model input for model calibration and validation of the streamflow at the outlet. The Nash-Sutcliffe Efficiency (NSE) obtained ranges from 0.588 to 0.905. The model was also validated for the flooded map using USGS observed water level at an interior point. The predicted flood stage error is 0.82 m or less, based on a comparison to measured stage. Validation of stage and discharge predictions builds confidence in model predictions of flood extent and localized velocities

  3. Hi-Res scan mode in clinical MDCT systems: Experimental assessment of spatial resolution performance.

    Science.gov (United States)

    Cruz-Bastida, Juan P; Gomez-Cardona, Daniel; Li, Ke; Sun, Heyi; Hsieh, Jiang; Szczykutowicz, Timothy P; Chen, Guang-Hong

    2016-05-01

    The introduction of a High-Resolution (Hi-Res) scan mode and another associated option that combines Hi-Res mode with the so-called High Definition (HD) reconstruction kernels (referred to as a Hi-Res/HD mode in this paper) in some multi-detector CT (MDCT) systems offers new opportunities to increase spatial resolution for some clinical applications that demand high spatial resolution. The purpose of this work was to quantify the in-plane spatial resolution along both the radial direction and tangential direction for the Hi-Res and Hi-Res/HD scan modes at different off-center positions. A technique was introduced and validated to address the signal saturation problem encountered in the attempt to quantify spatial resolution for the Hi-Res and Hi-Res/HD scan modes. Using the proposed method, the modulation transfer functions (MTFs) of a 64-slice MDCT system (Discovery CT750 HD, GE Healthcare) equipped with both Hi-Res and Hi-Res/HD modes were measured using a metal bead at nine different off-centered positions (0-16 cm with a step size of 2 cm); at each position, both conventional scans and Hi-Res scans were performed. For each type of scan and position, 80 repeated acquisitions were performed to reduce noise induced uncertainties in the MTF measurements. A total of 15 reconstruction kernels, including eight conventional kernels and seven HD kernels, were used to reconstruct CT images of the bead. An ex vivo animal study consisting of a bone fracture model was performed to corroborate the MTF results, as the detection of this high-contrast and high frequency task is predominantly determined by spatial resolution. Images of this animal model generated by different scan modes and reconstruction kernels were qualitatively compared with the MTF results. At the centered position, the use of Hi-Res mode resulted in a slight improvement in the MTF; each HD kernel generated higher spatial resolution than its counterpart conventional kernel. However, the MTF along the

  4. Simulation of the 2008 Iowa Flood using HiResFlood-UCI Model with Remote Sensing Data

    Science.gov (United States)

    Nguyen, P.; Thorstensen, A. R.; Hsu, K. L.; AghaKouchak, A.; Sanders, B. F.; Sorooshian, S.

    2014-12-01

    Precipitation is a key forcing variable in hydrological modeling of floods and being able to accurately observe precipitation is extremely important in mitigating flood impacts. The Global Precipitation Measurement (GPM) Mission, launched in Feb 2014 also presents an opportunity for high-quality real-time precipitation data and improved flood warnings. The PERSIANN-CCS developed by the scientists at the Center for Hydrometeorology and Remote Sensing (CHRS) at the University of California, Irvine is one algorithm integrated in the IMERG of PMM/GPM. In this research, the high resolution coupled hydrologic/hydraulic model named HiResFlood-UCI was applied to simulate the historical 2008 Iowa flood in the Cedar River basin. HiResFlood-UCI is a coupling of the NWS's distributed hydrologic model HL-RDHM and the hydraulic model BreZo developed by the Computational Hydraulics Group at the University of California, Irvine. The model was forced with the real-time PERSIANN-CCS and NEXRAD Stage 2 precipitation data. Simulations were evaluated based on 2 criteria: hydrographs within the basin and the areal extent of the flooding. Streamflow hydrographs were compared at 7 USGS gages, and simulated inundation maps were evaluated using USDA AWiFS 56m resolution areal flood imagery. The results show reasonable simulated hydrographs compared to USGS streamflow observations when simulating with PERSIANN-CCS and NEXRAD Stage 2 as forcing inputs. The simulation driven by NEXRAD Stage 2 slightly outperforms the PERSIANN-CCS simulation as the latter marginally underestimated the observed hydrographs. The simulation in both cases shows a good agreement (0.672 and 0.727 CSI for Stage 2 and PERSIANN-CCS simulations respectively) with the AWiFS image over the most impacted area in the Cedar Rapids region. Since the PERSIANN-CCS simulation slightly underestimated the discharge, the probability of detection (0.925) is lower than that of the Stage 2 simulation (0.965). As a trade-off, the false

  5. Benefits of the HiRes 120 coding strategy combined with the Harmony processor in an adult European multicentre study.

    Science.gov (United States)

    Büchner, Andreas; Lenarz, Thomas; Boermans, Peter-Paul; Frijns, Johan H M; Mancini, Patrizia; Filipo, Roberto; Fielden, Claire; Cooper, Huw; Eklöf, Martin; Freijd, Anders; Lombaard, Suryn; Meerton, Leah; Pickerill, Margaret; Vanat, Zebunnisa; Wesarg, Thomas; Aschendorff, Antje; Kienast, Barbara; Boyle, Patrick; Arnold, Laure; Meyer, Bernard; Sterkers, Olivier; Müller-Deile, Joachim; Ambrosch, Petra; Helbig, Silke; Frachet, Bruno; Gallego, Stéphane; Truy, Eric; Jeffs, Ellen; Morant, Antonio; Marco, Jaime

    2012-02-01

    The Harmony processor was found to be reliable, comfortable and offered a substantially increased battery life compared with the previous generation processor. No significant improvement in speech understanding with HiRes was demonstrated from objective measures, but the majority of subjects showed a clear subjective preference for the combination HiRes 120/Harmony processor. To evaluate experience with the Harmony™ sound processor, together with the HiRes 120 strategy. Postlingually deafened adults implanted with a CII or HiRes 90K were included and divided into three groups: (1) experienced users using the Platinum body-worn processor; (2) experienced users who had been using other processors; (3) new users with the Harmony processor from first fitting. The latter group entered a randomized crossover protocol where half were initially fitted with HiRes and half with HiRes 120. The initial strategy was used for 3 months and the alternative for a further 3 months. Speech perception tests and questionnaires were performed. The study included 65 subjects. Implementing HiRes 120 was straightforward. The speech test group results did not show significant differences between HiRes and HiRes 120. However, the questionnaires showed significantly higher ratings for HiRes 120 in some instances. Subjects were highly satisfied with the Harmony processor.

  6. Radio-controlled xenon flashers for atmospheric monitoring at the HiRes cosmic ray observatory

    CERN Document Server

    Wiencke, L R; Al-Seady, M; Belov, K; Bird, D J; Boyer, J; Chen, G F; Clay, R W; Dai, H Y; Dawson, B R; Denholm, P; Gloyn, J; He, D; Ho, Y; Huang, M A; Jui, C C H; Kidd, M J; Kieda, D B; Knapp, B; Ko, S; Larson, K; Loh, E C; Mannel, E J; Matthews, J N; Meyer, J R; Salman, A; Simpson, K M; Smith, J D; Sokolsky, P; Steenblik, D; Tang, J K K; Taylor, S; Thomas, S B; Wilkinson, C R

    1999-01-01

    Stable, robust ultraviolet light sources for atmospheric monitoring and calibration pose a challenge for experiments that measure air fluorescence from cosmic ray air showers. One type of light source in use at the High Resolution Fly's Eye (HiRes) cosmic ray observatory features a xenon flashbulb at the focal point of a spherical mirror to produce a 1 mu s pulse of collimated light that includes a strong UV component. A computer-controlled touch tone radio system provides remote operation of bulb triggering and window heating. These devices, dubbed 'flashers', feature stand-alone operation, +-5% shot-to-shot stability, weather proof construction and are well suited for long-term field use. This paper describes the flashers, the radio control system, and a 12-unit array in operation at the HiRes cosmic ray observatory

  7. HiRes camera and LIDAR ranging system for the Clementine mission

    Energy Technology Data Exchange (ETDEWEB)

    Ledebuhr, A.G.; Kordas, J.F.; Lewis, I.T. [and others

    1995-04-01

    Lawrence Livermore National Laboratory developed a space-qualified High Resolution (HiRes) imaging LIDAR (Light Detection And Ranging) system for use on the DoD Clementine mission. The Clementine mission provided more than 1.7 million images of the moon, earth, and stars, including the first ever complete systematic surface mapping of the moon from the ultra-violet to near-infrared spectral regions. This article describes the Clementine HiRes/LIDAR system, discusses design goals and preliminary estimates of on-orbit performance, and summarizes lessons learned in building and using the sensor. The LIDAR receiver system consists of a High Resolution (HiRes) imaging channel which incorporates an intensified multi-spectral visible camera combined with a Laser ranging channel which uses an avalanche photo-diode for laser pulse detection and timing. The receiver was bore sighted to a light-weight McDonnell-Douglas diode-pumped ND:YAG laser transmitter that emmitted 1.06 {micro}m wavelength pulses of 200 mJ/pulse and 10 ns pulse-width, The LIDAR receiver uses a common F/9.5 Cassegrain telescope assembly. The optical path of the telescope is split using a color-separating beamsplitter. The imaging channel incorporates a filter wheel assembly which spectrally selects the light which is imaged onto a custom 12 mm gated image intensifier fiber-optically-coupled into a 384 x 276 pixel frame transfer CCD FPA. The image intensifier was spectrally sensitive over the 0.4 to 0.8 {micro}m wavelength region. The six-position filter wheel contained 4 narrow spectral filters, one broadband and one blocking filter. At periselene (400 km) the HiRes/LIDAR imaged a 2.8 km swath width at 20-meter resolution. The LIDAR function detected differential signal return with a 40-meter range accuracy, with a maximum range capability of 640 km, limited by the bit counter in the range return counting clock.

  8. Percepção da fala de usuários de implante coclear com a estratégia HiRes 120: revisão sistemática Speech perception in cochlear implant users with the HiRes 120 strategy: a systematic review

    Directory of Open Access Journals (Sweden)

    Tatiana Mendes de Melo

    2012-06-01

    Full Text Available Apesar dos avanços tecnológicos empregados nas estratégias de processamento do sinal, um dos obstáculos ainda existentes são as lacunas de detalhes espectrais na informação elétrica transmitida. Considerando a sua importância na percepção da fala, pesquisadores investigaram mecanismos para otimizar o detalhamento espectral, por meio dos canais espectrais virtuais. A aplicação clínica desta técnica resultou em uma nova estratégia de processamento de sinal - a HiRes 120. OBJETIVO: Avaliar o desempenho auditivo de usuários de Implante Coclear com a HiRes 120. METODOLOGIA: Levantamento bibliográfico conduzido em base eletrônica de dados, com busca padronizada até o ano de 2011, utilizando-se palavras-chave específicas. Para a seleção e avaliação dos estudos científicos levantados na busca, foram estabelecidos critérios, contemplando os aspectos: tipo de estudo, participantes, intervenção adotada e avaliação dos resultados. CONCLUSÃO: As evidências científicas apontam uma melhora do desempenho auditivo nas situações de ruído com a estratégia HiRes 120, mas tal fato não ocorre nas situações de silêncio. A otimização da percepção da fala com o uso da estratégia está intimamente relacionada com a idade do usuário de implante coclear, com o tempo de privação sensorial e o tempo de aclimatização necessário para o aproveitamento das informações espectrais da estratégia.Despite technological advances employed in signal processing strategies, one of the remaining obstacles are spectral gap details on the information transmitted. Considering its importance in speech perception, researchers have investigated mechanisms to optimize spectral details through virtual spectral channels. The clinical application of this technique resulted in a new approach to signal processing - the HiRes 120. OBJECTIVE: To assess the auditory performance of cochlear implant users with the HiRes 120 strategy. METHODOLOGY: The

  9. Four equivalent lot-sizing models

    NARCIS (Netherlands)

    W. van den Heuvel (Wilco); A.P.M. Wagelmans (Albert)

    2007-01-01

    textabstractWe study the following lot-sizing models that recently appeared in the literature: a lot-sizing model with a remanufacturing option, a lot-sizing model with production time windows, and a lot-sizing model with cumulative capacities. We show the equivalence of these models with a

  10. A Size-based Ecosystem Model

    DEFF Research Database (Denmark)

    Ravn-Jonsen, Lars

     Ecosystem Management requires models that can link the ecosystem level to the operation level. This link can be created by an ecosystem production model. Because the function of the individual fish in the marine ecosystem, seen in trophic context, is closely related to its size, the model groups...... fish according to size. The model summarises individual predation events into ecosystem level properties, and thereby uses the law of conversation of mass as a framework. This paper provides the background, the conceptual model, basic assumptions, integration of fishing activities, mathematical...... the predator--prey interaction, (ii) mass balance in the predator--prey allocation, and (iii) mortality and somatic growth as a consequence of the predator--prey allocation. By incorporating additional assumptions, the model can be extended to other dimensions of the ecosystem, for example, space or species...

  11. Modeling and optimization of wet sizing process

    International Nuclear Information System (INIS)

    Thai Ba Cau; Vu Thanh Quang and Nguyen Ba Tien

    2004-01-01

    Mathematical simulation on basis of Stock law has been done for wet sizing process on cylinder equipment of laboratory and semi-industrial scale. The model consists of mathematical equations describing relations between variables, such as: - Resident time distribution function of emulsion particles in the separating zone of the equipment depending on flow-rate, height, diameter and structure of the equipment. - Size-distribution function in the fine and coarse parts depending on resident time distribution function of emulsion particles, characteristics of the material being processed, such as specific density, shapes, and characteristics of the environment of classification, such as specific density, viscosity. - Experimental model was developed on data collected from an experimental cylindrical equipment with diameter x height of sedimentation chamber equal to 50 x 40 cm for an emulsion of zirconium silicate in water. - Using this experimental model allows to determine optimal flow-rate in order to obtain product with desired grain size in term of average size or size distribution function. (author)

  12. A Descriptive Evaluation of Software Sizing Models

    Science.gov (United States)

    1987-09-01

    compensate for a lack of understanding of a software job to be done. 1.3 REPORT OUTLINE The guiding principle for model selection for this paper was...MODEL SIZE ESTIMATES FOR THE CAiSS SENSITIVITY MODEL MODEL SLOC ESD 37,600+ SPQR 35,910 BYL 22,402 PRICE SZ 21,410 ASSET-R 11,943 SSM 11,700 ASSET-R...disk. ?. Date LS, De fault current date, Re quire ] - ,, ... perffr: an,- 1 ,’ e e st i ma t e. Quantitative inputs Note- Each of the nine quantitative

  13. A neutral model with fluctuating population size and its effective size.

    OpenAIRE

    Iizuka, Masaru; Tachida, Hidenori; Matsuda, Hirotsugu

    2002-01-01

    We consider a diffusion model with neutral alleles whose population size is fluctuating randomly. For this model, the effects of fluctuation of population size on the effective size are investigated. The effective size defined by the equilibrium average heterozygosity is larger than the harmonic mean of population size but smaller than the arithmetic mean of population size. To see explicitly the effects of fluctuation of population size on the effective size, we investigate a special case wh...

  14. ULY JUP SCE DOPPLER HI-RES DATA

    Data.gov (United States)

    National Aeronautics and Space Administration — The Ulysses spacecraft was occulted by the Io Plasma Torus (IPT) during its Jupiter encounter on 8 February 1992. The Ulysses dual-frequency radio subsystem used by...

  15. A merchant ship size optimization model

    OpenAIRE

    Choi, Ki-Chul

    1983-01-01

    Approved for public release; distribution in unlimited. This paper analyzes how a shipowner or charterer may determine the specification of optimal ship size for a given route with respect to certain market requirements . The theory of optimal ship size, a methodology for estimating scale economics, and the various factors affecting ship size are examined using a typical conventional cargo ship and bulk cargo carriers based on shipowners ' cost data. http://archi...

  16. Size and complexity in model financial systems.

    Science.gov (United States)

    Arinaminpathy, Nimalan; Kapadia, Sujit; May, Robert M

    2012-11-06

    The global financial crisis has precipitated an increasing appreciation of the need for a systemic perspective toward financial stability. For example: What role do large banks play in systemic risk? How should capital adequacy standards recognize this role? How is stability shaped by concentration and diversification in the financial system? We explore these questions using a deliberately simplified, dynamic model of a banking system that combines three different channels for direct transmission of contagion from one bank to another: liquidity hoarding, asset price contagion, and the propagation of defaults via counterparty credit risk. Importantly, we also introduce a mechanism for capturing how swings in "confidence" in the system may contribute to instability. Our results highlight that the importance of relatively large, well-connected banks in system stability scales more than proportionately with their size: the impact of their collapse arises not only from their connectivity, but also from their effect on confidence in the system. Imposing tougher capital requirements on larger banks than smaller ones can thus enhance the resilience of the system. Moreover, these effects are more pronounced in more concentrated systems, and continue to apply, even when allowing for potential diversification benefits that may be realized by larger banks. We discuss some tentative implications for policy, as well as conceptual analogies in ecosystem stability and in the control of infectious diseases.

  17. Simulation of finite size effects of the fiber bundle model

    Science.gov (United States)

    Hao, Da-Peng; Tang, Gang; Xun, Zhi-Peng; Xia, Hui; Han, Kui

    2018-01-01

    In theory, the macroscopic fracture of materials should correspond with the thermodynamic limit of the fiber bundle model. However, the simulation of a fiber bundle model with an infinite size is unrealistic. To study the finite size effects of the fiber bundle model, fiber bundle models of various size are simulated in detail. The effects of system size on the constitutive behavior, critical stress, maximum avalanche size, avalanche size distribution, and increased step number of external load are explored. The simulation results imply that there is no feature size or cut size for macroscopic mechanical and statistical properties of the model. The constitutive curves near the macroscopic failure for various system size can collapse well with a simple scaling relationship. Simultaneously, the introduction of a simple extrapolation method facilitates the acquisition of more accurate simulation results in a large-limit system, which is better for comparison with theoretical results.

  18. Size Evolution and Stochastic Models: Explaining Ostracod Size through Probabilistic Distributions

    Science.gov (United States)

    Krawczyk, M.; Decker, S.; Heim, N. A.; Payne, J.

    2014-12-01

    The biovolume of animals has functioned as an important benchmark for measuring evolution throughout geologic time. In our project, we examined the observed average body size of ostracods over time in order to understand the mechanism of size evolution in these marine organisms. The body size of ostracods has varied since the beginning of the Ordovician, where the first true ostracods appeared. We created a stochastic branching model to create possible evolutionary trees of ostracod size. Using stratigraphic ranges for ostracods compiled from over 750 genera in the Treatise on Invertebrate Paleontology, we calculated overall speciation and extinction rates for our model. At each timestep in our model, new lineages can evolve or existing lineages can become extinct. Newly evolved lineages are assigned sizes based on their parent genera. We parameterized our model to generate neutral and directional changes in ostracod size to compare with the observed data. New sizes were chosen via a normal distribution, and the neutral model selected new sizes differentials centered on zero, allowing for an equal chance of larger or smaller ostracods at each speciation. Conversely, the directional model centered the distribution on a negative value, giving a larger chance of smaller ostracods. Our data strongly suggests that the overall direction of ostracod evolution has been following a model that directionally pushes mean ostracod size down, shying away from a neutral model. Our model was able to match the magnitude of size decrease. Our models had a constant linear decrease while the actual data had a much more rapid initial rate followed by a constant size. The nuance of the observed trends ultimately suggests a more complex method of size evolution. In conclusion, probabilistic methods can provide valuable insight into possible evolutionary mechanisms determining size evolution in ostracods.

  19. Modelling the effect of size-asymmetric competition on size inequality

    DEFF Research Database (Denmark)

    Rasmussen, Camilla Ruø; Weiner, Jacob

    2017-01-01

    Abstract The concept of size asymmetry in resource competition among plants, in which larger individuals obtain a disproportionate share of contested resources, appears to be very straightforward, but the effects of size asymmetry on growth and size variation among individuals have proved...... to be controversial. It has often been assumed that competition among individual plants in a population has to be size-asymmetric to result in higher size inequality than in the absence of competition, but here we question this inference. Using very simple, individual-based models, we investigate how size symmetry...... of competition affects the development in size inequality between two competing plants and show that increased size inequality due to competition is not always strong evidence for size-asymmetric competition. Even absolute symmetric competition, in which all plants receive the same amount of resources...

  20. A size-structured model of bacterial growth and reproduction.

    Science.gov (United States)

    Ellermeyer, S F; Pilyugin, S S

    2012-01-01

    We consider a size-structured bacterial population model in which the rate of cell growth is both size- and time-dependent and the average per capita reproduction rate is specified as a model parameter. It is shown that the model admits classical solutions. The population-level and distribution-level behaviours of these solutions are then determined in terms of the model parameters. The distribution-level behaviour is found to be different from that found in similar models of bacterial population dynamics. Rather than convergence to a stable size distribution, we find that size distributions repeat in cycles. This phenomenon is observed in similar models only under special assumptions on the functional form of the size-dependent growth rate factor. Our main results are illustrated with examples, and we also provide an introductory study of the bacterial growth in a chemostat within the framework of our model.

  1. How to use COSMIC Functional Size in Effort Estimation Models?

    OpenAIRE

    Gencel, Cigdem

    2008-01-01

    Although Functional Size Measurement (FSM) methods have become widely used by the software organizations, the functional size based effort estimation still needs further investigation. Most of the studies on effort estimation consider total functional size of the software as the primary input to estimation models and they mostly focus on identifying the project parameters which might have a significant effect on the size-effort relationship. This study brings suggestions on how to use COSMIC ...

  2. A random energy model for size dependence : recurrence vs. transience

    NARCIS (Netherlands)

    Külske, Christof

    1998-01-01

    We investigate the size dependence of disordered spin models having an infinite number of Gibbs measures in the framework of a simplified 'random energy model for size dependence'. We introduce two versions (involving either independent random walks or branching processes), that can be seen as

  3. Assumptions behind size-based ecosystem models are realistic

    DEFF Research Database (Denmark)

    Andersen, Ken Haste; Blanchard, Julia L.; Fulton, Elizabeth A.

    2016-01-01

    A recent publication about balanced harvesting (Froese et al., ICES Journal of Marine Science; doi:10.1093/icesjms/fsv122) contains several erroneous statements about size-spectrum models. We refute the statements by showing that the assumptions pertaining to size-spectrum models discussed by Fro...... that there is indeed a constructive role for a wide suite of ecosystem models to evaluate fishing strategies in an ecosystem context...

  4. Improved Mathematical Models for Particle-Size Distribution Data

    African Journals Online (AJOL)

    BirukEdimon

    four existing curve fitting models common to geotechnical applications are reviewed and presented first. Definitions of Important Parameters and. Variables. A given soil will be made up of grains of many different sizes and described by the grain size distribution. The main variables are % Clay, %. Silt, % Sand, % of fine and ...

  5. Influence of horizontal resolution and ensemble size on model performance

    CSIR Research Space (South Africa)

    Dalton, A

    2014-10-01

    Full Text Available Computing costs increase with an increase in global model resolution and ensemble size. This paper strives to determine the extent to which resolution and ensemble size affect seasonal forecast skill when simulating mid-summer rainfall totals over...

  6. Improved mathematical models for particle-size distribution data ...

    African Journals Online (AJOL)

    Prior studies have suggested that particle-size distribution data of soils is central and helpful in this regard. This study proposes two improved mathematical models to describe and represent the varied particle-size distribution (PSD) data for tropically weathered residual (TWR) soils. The theoretical analysis and the ...

  7. A Markov decision model for optimising economic production lot size ...

    African Journals Online (AJOL)

    Abstract. Traditional approaches towards determining the economic production lot (EPL) size in man- ufacturing 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 ...

  8. Optimum workforce-size model using dynamic programming approach

    African Journals Online (AJOL)

    This paper presents an optimum workforce-size model which determines the minimum number of excess workers (overstaffing) as well as the minimum total recruitment cost during a specified planning horizon. The model is an extension of other existing dynamic programming models for manpower planning in the sense ...

  9. optimum workforce-size model using dynamic programming approach

    African Journals Online (AJOL)

    DJFLEX

    This paper presents an optimum workforce-size model which determines the minimum number of excess workers (overstaffing) as well as the minimum total recruitment cost during a specified planning horizon. The model is an extension of other existing dynamic programming models for manpower planning in the sense ...

  10. The theoretical foundations for size spectrum models of fish communities

    DEFF Research Database (Denmark)

    Andersen, Ken Haste; Jacobsen, Nis Sand; Farnsworth, K.D.

    2016-01-01

    assessment of fisheries. We describe the fundamental concepts in size-based models about food encounter and the bioenergetics budget of individuals. Within the general framework three model types have emerged that differs in their degree of complexity: the food-web, the trait-based and the community model...

  11. Multi-Criteria Model for Determining Order Size

    Directory of Open Access Journals (Sweden)

    Katarzyna Jakowska-Suwalska

    2013-01-01

    Full Text Available A multi-criteria model for determining the order size for materials used in production has been presented. It was assumed that the consumption rate of each material is a random variable with a known probability distribution. Using such a model, in which the purchase cost of materials ordered is limited, three criteria were considered: order size, probability of a lack of materials in the production process, and deviations in the order size from the consumption rate in past periods. Based on an example, it has been shown how to use the model to determine the order sizes for polyurethane adhesive and wood in a hard-coal mine. (original abstract

  12. Holonic Business Process Modeling in Small to Medium Sized Enterprises

    Directory of Open Access Journals (Sweden)

    Nur Budi Mulyono

    2012-01-01

    Full Text Available Holonic modeling analysis which is the application of system thinking in design, manage, and improvement, is used in a novel context for business process modeling. An approach and techniques of holon and holarchies is presented specifically for small and medium sized enterprise process modeling development. The fitness of the approach is compared with well known reductionist or task breakdown approach. The strength and weaknesses of the holonic modeling is discussed with illustrating case example in term of its suitability for an Indonesia’s small and medium sized industry. The novel ideas in this paper have great impact on the way analyst should perceive business process. Future research is applying the approach in supply chain context.Key words: Business process, holonic modeling, operations management, small to medium sized enterprise

  13. Holonic Business Process Modeling in Small to Medium Sized Enterprises

    OpenAIRE

    Nur Budi Mulyono; Tezar Yuliansyah Saputra; Nur Arief Rahmatsyah

    2012-01-01

    Holonic modeling analysis which is the application of system thinking in design, manage, and improvement, is used in a novel context for business process modeling. An approach and techniques of holon and holarchies is presented specifically for small and medium sized enterprise process modeling development. The fitness of the approach is compared with well known reductionist or task breakdown approach. The strength and weaknesses of the holonic modeling is discussed with illustrating case exa...

  14. Shrinking microbubbles with microfluidics: mathematical modelling to control microbubble sizes.

    Science.gov (United States)

    Salari, A; Gnyawali, V; Griffiths, I M; Karshafian, R; Kolios, M C; Tsai, S S H

    2017-11-29

    Microbubbles have applications in industry and life-sciences. In medicine, small encapsulated bubbles (methods are distinguished due to their precise control and ease-of-fabrication. Nevertheless, sub-10 μm diameter bubble generation using microfluidics remains challenging, and typically requires expensive equipment and cumbersome setups. Recently, our group reported a microfluidic platform that shrinks microbubbles to sub-10 μm diameters. The microfluidic platform utilizes a simple microbubble-generating flow-focusing geometry, integrated with a vacuum shrinkage system, to achieve microbubble sizes that are desirable in medicine, and pave the way to eventual clinical uptake of microfluidically generated microbubbles. A theoretical framework is now needed to relate the size of the microbubbles produced and the system's input parameters. In this manuscript, we characterize microbubbles made with various lipid concentrations flowing in solutions that have different interfacial tensions, and monitor the changes in bubble size along the microfluidic channel under various vacuum pressures. We use the physics governing the shrinkage mechanism to develop a mathematical model that predicts the resulting bubble sizes and elucidates the dominant parameters controlling bubble sizes. The model shows a good agreement with the experimental data, predicting the resulting microbubble sizes under different experimental input conditions. We anticipate that the model will find utility in enabling users of the microfluidic platform to engineer bubbles of specific sizes.

  15. Modeling the Effect of Tumor Size in Early Breast Cancer

    Science.gov (United States)

    Verschraegen, Claire; Vinh-Hung, Vincent; Cserni, Gábor; Gordon, Richard; Royce, Melanie E.; Vlastos, Georges; Tai, Patricia; Storme, Guy

    2005-01-01

    Summary Background Data: The purpose of this study was to determine the type of relationship between tumor size and mortality in early breast carcinoma. Methods: The data was abstracted from 83,686 cases registered in the Surveillance, Epidemiology, and End Results Program of women diagnosed with primary breast carcinoma between 1988 and 1997 presenting with a T1–T2 lesion and no metastasis in whom axillary node dissection was performed: 58,070 women were node-negative (N0) and 25,616 were node-positive (N+). End point was death from any cause. Tumor size was modeled as a continuous variable by proportional hazards using a generalized additive models procedure. Results: Functionally, a Gompertzian expression exp(-exp(-(size-15)/10)) provided a good fit to the effect of tumor size (in millimeters) on mortality, irrespective of nodal status. Quantitatively, for tumor size between 3 and 50 mm, the increase of crude cumulative death rate (number of observed deaths divided by the number of patients at risk) increased with size from 10% to 25% for N0 and from 20% to 40% for N+. Conclusions: The functional relationship of tumor size with mortality is concordant with current knowledge of tumor growth. However, its qualitative and quantitative independence of nodal status is in contradiction with the prevailing concept of sequential disease progression from primary tumor to regional nodes. This argues against the perception that nodal metastases are caused by the primary tumor. PMID:15650642

  16. On population size estimators in the Poisson mixture model.

    Science.gov (United States)

    Mao, Chang Xuan; Yang, Nan; Zhong, Jinhua

    2013-09-01

    Estimating population sizes via capture-recapture experiments has enormous applications. The Poisson mixture model can be adopted for those applications with a single list in which individuals appear one or more times. We compare several nonparametric estimators, including the Chao estimator, the Zelterman estimator, two jackknife estimators and the bootstrap estimator. The target parameter of the Chao estimator is a lower bound of the population size. Those of the other four estimators are not lower bounds, and they may produce lower confidence limits for the population size with poor coverage probabilities. A simulation study is reported and two examples are investigated. © 2013, The International Biometric Society.

  17. Cloud Computing Adoption Business Model Factors: Does Enterprise Size Matter?

    OpenAIRE

    Bogataj Habjan, Kristina; Pucihar, Andreja

    2017-01-01

    This paper presents the results of research investigating the impact of business model factors on cloud computing adoption. The introduced research model consists of 40 cloud computing business model factors, grouped into eight factor groups. Their impact and importance for cloud computing adoption were investigated among enterpirses in Slovenia. Furthermore, differences in opinion according to enterprise size were investigated. Research results show no statistically significant impacts of in...

  18. Stochastic Modeling of Bacteria Cell Size Control and Homeostasis

    Science.gov (United States)

    Chen, Yanyan; Buceta, Javier

    Besides recent breakthroughs, there is a gap of knowledge about the mechanisms underlying cell size control and homeostasis. In this context, recent studies support the incremental rule in rod-shaped bacteria: cells add a constant length to their size before dividing which is independent of their size at birth. This growing pattern, when coupled with the mid-cell division mechanism, leads to size convergence and homeostasis. However, some aberrantly long mutant strains of E. coli, e.g. ΔFtsW, do not typically divide at the middle. Whether cell size control and homeostasis apply to those mutant backgrounds, or the role played by biomechanical cues, remain open questions. Here we present a combination of theoretical, experimental, and computational approaches to address these questions. First, we introduce a Markov chain model that describes either wild-type (wt) strains or growth-defective strains. Second, we propose a polymer-like model to account for the mechanical inputs. Finally, we test experimentally some of our predictions by using wt and conditional mutant (ΔFtsW) strains. Altogether, our preliminary studies suggest a way to unify the principles of cell size control and homeostasis of wt and growth-defective cell strains.

  19. Model catalysis by size-selected cluster deposition

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, Scott [Univ. of Utah, Salt Lake City, UT (United States)

    2015-11-20

    This report summarizes the accomplishments during the last four years of the subject grant. Results are presented for experiments in which size-selected model catalysts were studied under surface science and aqueous electrochemical conditions. Strong effects of cluster size were found, and by correlating the size effects with size-dependent physical properties of the samples measured by surface science methods, it was possible to deduce mechanistic insights, such as the factors that control the rate-limiting step in the reactions. Results are presented for CO oxidation, CO binding energetics and geometries, and electronic effects under surface science conditions, and for the electrochemical oxygen reduction reaction, ethanol oxidation reaction, and for oxidation of carbon by water.

  20. Linear Model for Optimal Distributed Generation Size Predication

    Directory of Open Access Journals (Sweden)

    Ahmed Al Ameri

    2017-01-01

    Full Text Available This article presents a linear model predicting optimal size of Distributed Generation (DG that addresses the minimum power loss. This method is based fundamentally on strong coupling between active power and voltage angle as well as between reactive power and voltage magnitudes. This paper proposes simplified method to calculate the total power losses in electrical grid for different distributed generation sizes and locations. The method has been implemented and tested on several IEEE bus test systems. The results show that the proposed method is capable of predicting approximate optimal size of DG when compared with precision calculations. The method that linearizes a complex model showed a good result, which can actually reduce processing time required. The acceptable accuracy with less time and memory required can help the grid operator to assess power system integrated within large-scale distribution generation.

  1. 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...

  2. Determining the optimum cell size of digital elevation model for ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Earth System Science; Volume 120; Issue 4. Determining the optimum cell size of digital elevation model for hydrologic ... Technology, Bahal 127 028, Bhiwani, Haryana, India. Agricultural & Food Engineering Department, Indian Institute of Technology, Kharagpur-721302, West Bengal, India.

  3. Finite-Size Effects for Some Bootstrap Percolation Models

    NARCIS (Netherlands)

    Enter, A.C.D. van; Adler, Joan; Duarte, J.A.M.S.

    The consequences of Schonmann's new proof that the critical threshold is unity for certain bootstrap percolation models are explored. It is shown that this proof provides an upper bound for the finite-size scaling in these systems. Comparison with data for one case demonstrates that this scaling

  4. A dynamic lot-sizing model with demand time windows

    NARCIS (Netherlands)

    C.Y. Lee (Chung-Yee); S. Cetinkaya; A.P.M. Wagelmans (Albert)

    1999-01-01

    textabstractOne of the basic assumptions of the classical dynamic lot-sizing model is that the aggregate demand of a given period must be satisfied in that period. Under this assumption, if backlogging is not allowed then the demand of a given period cannot be delivered earlier or later than the

  5. A Dynamic Lot-Sizing Model with Demand Time Windows

    NARCIS (Netherlands)

    C.Y. Lee (Chung-Yee); S. Çetinkaya; A.P.M. Wagelmans (Albert)

    1999-01-01

    textabstractOne of the basic assumptions of the classical dynamic lot-sizing model is that the aggregate demand of a given period must be satisfied in that period. Under this assumption, if backlogging is not allowed then the demand of a given period cannot be delivered earlier or later than the

  6. Determining the optimum cell size of digital elevation model for ...

    Indian Academy of Sciences (India)

    obtained DEMs were explored for their intrinsic quality using four different methods, i.e., sink analy- sis, fractal dimension of derived stream network, entropy measurement and ... ters decrease, and many delicate landscape fea- tures are lost. However, as one can understand, it is not enough to model the cell size effects.

  7. Discriminating Models of Different Sized Color Geometric Figures

    Directory of Open Access Journals (Sweden)

    Y A Chudina

    2013-12-01

    Full Text Available The data obtained by us in two experiments, where the different sized color geometric figures were used as stimuli, are described in the article. We have built configurative and categorical discriminating models differing by formal and intensional characteristics. The models reflect the different ways of visual gestalt generation: additive and non-additive principles of consolidation of neural mechanisms analyzing the visual features of the picture.

  8. Parabolic Free Boundary Price Formation Models Under Market Size Fluctuations

    KAUST Repository

    Markowich, Peter A.

    2016-10-04

    In this paper we propose an extension of the Lasry-Lions price formation model which includes uctuations of the numbers of buyers and vendors. We analyze the model in the case of deterministic and stochastic market size uctuations and present results on the long time asymptotic behavior and numerical evidence and conjectures on periodic, almost periodic, and stochastic uctuations. The numerical simulations extend the theoretical statements and give further insights into price formation dynamics.

  9. The critical domain size of stochastic population models.

    Science.gov (United States)

    Reimer, Jody R; Bonsall, Michael B; Maini, Philip K

    2017-02-01

    Identifying the critical domain size necessary for a population to persist is an important question in ecology. Both demographic and environmental stochasticity impact a population's ability to persist. Here we explore ways of including this variability. We study populations with distinct dispersal and sedentary stages, which have traditionally been modelled using a deterministic integrodifference equation (IDE) framework. Individual-based models (IBMs) are the most intuitive stochastic analogues to IDEs but yield few analytic insights. We explore two alternate approaches; one is a scaling up to the population level using the Central Limit Theorem, and the other a variation on both Galton-Watson branching processes and branching processes in random environments. These branching process models closely approximate the IBM and yield insight into the factors determining the critical domain size for a given population subject to stochasticity.

  10. Size reduction techniques for vital compliant VHDL simulation models

    Science.gov (United States)

    Rich, Marvin J.; Misra, Ashutosh

    2006-08-01

    A method and system select delay values from a VHDL standard delay file that correspond to an instance of a logic gate in a logic model. Then the system collects all the delay values of the selected instance and builds super generics for the rise-time and the fall-time of the selected instance. Then, the system repeats this process for every delay value in the standard delay file (310) that correspond to every instance of every logic gate in the logic model. The system then outputs a reduced size standard delay file (314) containing the super generics for every instance of every logic gate in the logic model.

  11. EMPIRICAL MODEL FOR HYDROCYCLONES CORRECTED CUT SIZE CALCULATION

    Directory of Open Access Journals (Sweden)

    André Carlos Silva

    2012-12-01

    Full Text Available Hydrocyclones are devices worldwide used in mineral processing for desliming, classification, selective classification, thickening and pre-concentration. A hydrocyclone is composed by one cylindrical and one conical section joint together, without any moving parts and it is capable of perform granular material separation in pulp. The mineral particles separation mechanism acting in a hydrocyclone is complex and its mathematical modelling is usually empirical. The most used model for hydrocyclone corrected cut size is proposed by Plitt. Over the years many revisions and corrections to Plitt´s model were proposed. The present paper shows a modification in the Plitt´s model constant, obtained by exponential regression of simulated data for three different hydrocyclones geometry: Rietema, Bradley and Krebs. To validate the proposed model literature data obtained from phosphate ore using fifteen different hydrocyclones geometry are used. The proposed model shows a correlation equals to 88.2% between experimental and calculated corrected cut size, while the correlation obtained using Plitt´s model is 11.5%.

  12. Convergence of surface diffusion parameters with model crystal size

    Science.gov (United States)

    Cohen, Jennifer M.; Voter, Arthur F.

    1994-07-01

    A study of the variation in the calculated quantities for adatom diffusion with respect to the size of the model crystal is presented. The reported quantities include surface diffusion barrier heights, pre-exponential factors, and dynamical correction factors. Embedded atom method (EAM) potentials were used throughout this effort. Both the layer size and the depth of the crystal were found to influence the values of the Arrhenius factors significantly. In particular, exchange type mechanisms required a significantly larger model than standard hopping mechanisms to determine adatom diffusion barriers of equivalent accuracy. The dynamical events that govern the corrections to transition state theory (TST) did not appear to be as sensitive to crystal depth. Suitable criteria for the convergence of the diffusion parameters with regard to the rate properties are illustrated.

  13. SIMPLIFIED MATHEMATICAL MODEL OF SMALL SIZED UNMANNED AIRCRAFT VEHICLE LAYOUT

    OpenAIRE

    2016-01-01

    Strong reduction of new aircraft design period using new technology based on artificial intelligence is the key problem mentioned in forecasts of leading aerospace industry research centers. This article covers the approach to devel- opment of quick aerodynamic design methods based on artificial intelligence neural system. The problem is being solved for the classical scheme of small sized unmanned aircraft vehicle (UAV). The principal parts of the method are the mathe- matical model of layou...

  14. A new model for the body size-metabolism relationship.

    Science.gov (United States)

    Roberts, Michael F; Lightfoot, Edwin N; Porter, Warren P

    2010-01-01

    The allometric 3/4 power relation, initially used for describing the relation between mammalian basal metabolic rate and body size, is often used as a general model for organismal design. The use of allometric regression as a model has important limitations: it is not mechanistic, it combines all physiological variables into one correlate of body size, and it combines data from several physiological states. In reassessing the use of allometric equations, we first describe problems with their use in studies of organismal design and then use a formulation for distributed net heat production and temperature distribution within the body to derive an alternative equation for the relation between basal metabolism and body size. Tests of the heat flow equation against data reported in the literature indicate that it is an accurate estimator of basal metabolism under thermoneutral conditions and suggest that the allometric equation is a special case of this mechanistic and more general model. We propose that our method is more meaningful and widely applicable for thermoneutral conditions than is a purely allometric approach.

  15. Experimental Study Using Functional Size Measurement in Building Estimation Models for Software Project Size

    NARCIS (Netherlands)

    Condori-Fernandez, Nelly; Daneva, Maia; Buglione, Luigi; Ormandjieva, Olga; Ormandjieva, O.; Constantinides, C.; Abran, A.; Lee, R.

    2010-01-01

    This paper reports on an experiment that investigates the predictability of software project size from software product size. The predictability research problem is analyzed at the stage of early requirements by accounting the size of functional requirements as well as the size of non-functional

  16. Building predictive models of soil particle-size distribution

    Directory of Open Access Journals (Sweden)

    Alessandro Samuel-Rosa

    2013-04-01

    Full Text Available Is it possible to build predictive models (PMs of soil particle-size distribution (psd in a region with complex geology and a young and unstable land-surface? The main objective of this study was to answer this question. A set of 339 soil samples from a small slope catchment in Southern Brazil was used to build PMs of psd in the surface soil layer. Multiple linear regression models were constructed using terrain attributes (elevation, slope, catchment area, convergence index, and topographic wetness index. The PMs explained more than half of the data variance. This performance is similar to (or even better than that of the conventional soil mapping approach. For some size fractions, the PM performance can reach 70 %. Largest uncertainties were observed in geologically more complex areas. Therefore, significant improvements in the predictions can only be achieved if accurate geological data is made available. Meanwhile, PMs built on terrain attributes are efficient in predicting the particle-size distribution (psd of soils in regions of complex geology.

  17. Reliable critical sized defect rodent model for cleft palate research.

    Science.gov (United States)

    Mostafa, Nesrine Z; Doschak, Michael R; Major, Paul W; Talwar, Reena

    2014-12-01

    Suitable animal models are necessary to test the efficacy of new bone grafting therapies in cleft palate surgery. Rodent models of cleft palate are available but have limitations. This study compared and modified mid-palate cleft (MPC) and alveolar cleft (AC) models to determine the most reliable and reproducible model for bone grafting studies. Published MPC model (9 × 5 × 3 mm(3)) lacked sufficient information for tested rats. Our initial studies utilizing AC model (7 × 4 × 3 mm(3)) in 8 and 16 weeks old Sprague Dawley (SD) rats revealed injury to adjacent structures. After comparing anteroposterior and transverse maxillary dimensions in 16 weeks old SD and Wistar rats, virtual planning was performed to modify MPC and AC defects dimensions, taking the adjacent structures into consideration. Modified MPC (7 × 2.5 × 1 mm(3)) and AC (5 × 2.5 × 1 mm(3)) defects were employed in 16 weeks old Wistar rats and healing was monitored by micro-computed tomography and histology. Maxillary dimensions in SD and Wistar rats were not significantly different. Preoperative virtual planning enhanced postoperative surgical outcomes. Bone healing occurred at defect margin leaving central bone void confirming the critical size nature of the modified MPC and AC defects. Presented modifications for MPC and AC models created clinically relevant and reproducible defects. Copyright © 2014 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.

  18. Event-based total suspended sediment particle size distribution model

    Science.gov (United States)

    Thompson, Jennifer; Sattar, Ahmed M. A.; Gharabaghi, Bahram; Warner, Richard C.

    2016-05-01

    One of the most challenging modelling tasks in hydrology is prediction of the total suspended sediment particle size distribution (TSS-PSD) in stormwater runoff generated from exposed soil surfaces at active construction sites and surface mining operations. The main objective of this study is to employ gene expression programming (GEP) and artificial neural networks (ANN) to develop a new model with the ability to more accurately predict the TSS-PSD by taking advantage of both event-specific and site-specific factors in the model. To compile the data for this study, laboratory scale experiments using rainfall simulators were conducted on fourteen different soils to obtain TSS-PSD. This data is supplemented with field data from three construction sites in Ontario over a period of two years to capture the effect of transport and deposition within the site. The combined data sets provide a wide range of key overlooked site-specific and storm event-specific factors. Both parent soil and TSS-PSD in runoff are quantified by fitting each to a lognormal distribution. Compared to existing regression models, the developed model more accurately predicted the TSS-PSD using a more comprehensive list of key model input parameters. Employment of the new model will increase the efficiency of deployment of required best management practices, designed based on TSS-PSD, to minimize potential adverse effects of construction site runoff on aquatic life in the receiving watercourses.

  19. Size distribution of mineral aerosol: using light-scattering models in laser particle sizing.

    NARCIS (Netherlands)

    Veihelmann, B.; Konert, M.; van der Zande, W.J.

    2006-01-01

    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

  20. Size distribution of mineral aerosol: using light-scattering models in laser particle sizing

    NARCIS (Netherlands)

    Veihelmann, B.; Konert, M.; Zande, W.J. van der

    2006-01-01

    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

  1. Modeling of aerosol dynamics - Aerosol size and composition

    International Nuclear Information System (INIS)

    Beyak, R.A.; Peterson, T.W.

    1980-01-01

    A mechanism for the evolution of the size and composition of an aerosol particle is investigated by developing a model that includes the transfer of gaseous pollutants to the surface of existing aerosol particles, the transfer of the pollutants across the gas-particle interface, and the reaction of dissolved species within the aerosol particle. The reaction mechanisms considered include homogeneous gas-phase and heterogeneous solution chemistry. Aerosol particles evolving within an urban plume and within power-plant and smelter plumes are studied, along with the evolution of particle size and chemical composition for regions of various relative humidities, with particular emphasis on aqueous chemistry in the low-humidity environments of the southwestern U.S. A simulation of a copper smelting complex in central Arizona indicates that all particles shrink from their original size as plume humidity approaches background relative humidity, that most secondary sulfate formation occurs in the near-plume region, and that the final particle pH is in the range 2.0-2.2 for a wide range of physical conditions

  2. Cosmic structure sizes in generic dark energy models

    Energy Technology Data Exchange (ETDEWEB)

    Bhattacharya, Sourav [Indian Institute of Technology Ropar, Department of Physics, Rupnagar, Punjab (India); Tomaras, Theodore N. [ITCP and Department of Physics, University of Crete, Heraklion (Greece)

    2017-08-15

    The maximum allowable size of a spherical cosmic structure as a function of its mass is determined by the maximum turn around radius R{sub TA,max}, the distance from its center where the attraction on a radial test particle due to the spherical mass is balanced with the repulsion due to the ambient dark energy. In this work, we extend the existing results in several directions. (a) We first show that, for w ≠ -1, the expression for R{sub TA,max} found earlier, using the cosmological perturbation theory, can be derived using a static geometry as well. (b) In the generic dark energy model with arbitrary time dependent state parameter w(t), taking into account the effect of inhomogeneities upon the dark energy as well, it is shown that the data constrain w(t = today) > -2.3. (c) We address the quintessence and the generalized Chaplygin gas models, both of which are shown to predict structure sizes consistent with observations. (orig.)

  3. Modeling photoacoustic spectral features of micron-sized particles.

    Science.gov (United States)

    Strohm, Eric M; Gorelikov, Ivan; Matsuura, Naomi; Kolios, Michael C

    2014-10-07

    The photoacoustic signal generated from particles when irradiated by light is determined by attributes of the particle such as the size, speed of sound, morphology and the optical absorption coefficient. Unique features such as periodically varying minima and maxima are observed throughout the photoacoustic signal power spectrum, where the periodicity depends on these physical attributes. The frequency content of the photoacoustic signals can be used to obtain the physical attributes of unknown particles by comparison to analytical solutions of homogeneous symmetric geometric structures, such as spheres. However, analytical solutions do not exist for irregularly shaped particles, inhomogeneous particles or particles near structures. A finite element model (FEM) was used to simulate photoacoustic wave propagation from four different particle configurations: a homogeneous particle suspended in water, a homogeneous particle on a reflecting boundary, an inhomogeneous particle with an absorbing shell and non-absorbing core, and an irregularly shaped particle such as a red blood cell. Biocompatible perfluorocarbon droplets, 3-5 μm in diameter containing optically absorbing nanoparticles were used as the representative ideal particles, as they are spherical, homogeneous, optically translucent, and have known physical properties. The photoacoustic spectrum of micron-sized single droplets in suspension and on a reflecting boundary were measured over the frequency range of 100-500 MHz and compared directly to analytical models and the FEM. Good agreement between the analytical model, FEM and measured values were observed for a droplet in suspension, where the spectral minima agreed to within a 3.3 MHz standard deviation. For a droplet on a reflecting boundary, spectral features were correctly reproduced using the FEM but not the analytical model. The photoacoustic spectra from other common particle configurations such as particle with an absorbing shell and a

  4. A mathematical model to predict the size of the pellets formed in freeze pelletization techniques: parameters affecting pellet size.

    Science.gov (United States)

    Cheboyina, Sreekhar; O'Haver, John; Wyandt, Christy M

    2006-01-01

    A mathematical model was developed based on the theory of drop formation to predict the size of the pellets formed in the freeze pelletization process. Further the model was validated by studying the effect of various parameters on the pellet size such as viscosity of the pellet forming and column liquids, surface/interfacial tension, density difference between pellet forming and column liquids; size, shape, and material of construction of the needle tips and temperatures maintained in the columns. In this study, pellets were prepared from different matrices including polyethylene glycols and waxes. The column liquids studied were silicone oils and aqueous glycerol solutions. The surface/interfacial tension, density difference between pellet forming and column liquids and needle tip size were found to be the most important factors affecting pellet size. The viscosity of the column liquid was not found to significantly affect the size of the pellets. The size of the pellets was also not affected by the pellet forming liquids of low viscosities. An increase in the initial column temperature slightly decreased the pellet size. The mathematical model developed was found to successfully predict the size of the pellets with an average error of 3.32% for different matrices that were studied.

  5. Queuing theory models used for port equipment sizing

    Science.gov (United States)

    Dragu, V.; Dinu, O.; Ruscă, A.; Burciu, Ş.; Roman, E. A.

    2017-08-01

    The significant growth of volumes and distances on road transportation led to the necessity of finding solutions to increase water transportation market share together with the handling and transfer technologies within its terminals. It is widely known that the biggest times are consumed within the transport terminals (loading/unloading/transfer) and so the necessity of constantly developing handling techniques and technologies in concordance with the goods flows size so that the total waiting time of ships within ports is reduced. Port development should be achieved by harmonizing the contradictory interests of port administration and users. Port administrators aim profit increase opposite to users that want savings by increasing consumers’ surplus. The difficulty consists in the fact that the transport demand - supply equilibrium must be realised at costs and goods quantities transiting the port in order to satisfy the interests of both parties involved. This paper presents a port equipment sizing model by using queueing theory so that the sum of costs for ships waiting operations and equipment usage would be minimum. Ship operation within the port is assimilated to a mass service waiting system in which parameters are later used to determine the main costs for ships and port equipment.

  6. Particle size - An important factor in environmental consequence modeling

    International Nuclear Information System (INIS)

    Yuan, Y.C.; MacFarlane, D.

    1991-01-01

    Most available environmental transport and dosimetry codes for radiological consequence analysis are designed primarily for estimating dose and health consequences to specific off-site individuals as well as the population as a whole from nuclear facilities operating under either normal or accident conditions. Models developed for these types of analyses are generally based on assumptions that the receptors are at great distances (several kilometers), and the releases are prolonged and filtered. This allows the use of simplified approaches such as averaged meteorological conditions and the use of a single (small) particle size for atmospheric transport and dosimetry analysis. Source depletion from particle settling, settle-out, and deposition is often ignored. This paper estimates the effects of large particles on the resulting dose consequences from an atmospheric release. The computer program AI-RISK has been developed to perform multiparticle-sized atmospheric transport, dose, and pathway analyses for estimating potential human health consequences from the accidental release of radioactive materials. The program was originally developed to facilitate comprehensive analyses of health consequences, ground contamination, and cleanup associated with possible energetic chemical reactions in high-level radioactive waste (HLW) tanks at a US Department of Energy site

  7. Wind erosion model of a multiple sized particles bed

    Energy Technology Data Exchange (ETDEWEB)

    Descamps, I.; Pons, A.; Harion, J.-L. [IMP-CNRS UPR 8521, Perpignan (France)

    2006-07-01

    A model has been developed in order to predict more accurately fugitive dust emissions by aeolian erosion on industrial sites. This model takes into account the time evolution of the bed surface features during erosion by a turbulent flow. It consists of four parts corresponding to aerodynamic entrainment and is based on the interaction between particle take-off and wall turbulence. A take-off criterion compares the lift force exerted by the flow on the particle with the sum of the weight and adhesive force. Bed pavement and saltation are also taken into account. Bed pavement is induced by the non-erodible particles. On steel plants stockpiles, ores and coals have granulometric spectra going a few microns to a few centimetres in diameter. In fact, the non-erodible particles, that cannot take-off because of their inertia, form obstacles in the finer particle take-off and lead to a time decrease in emitted mass flux. The new model has been tested for the case of a bimodal size distribution by comparison with relevant experimental data. The results demonstrate that the mode allows predicting the mass flux time decrease due to non-erodible particles. 17 refs., 6 figs.

  8. Glottal aerodynamics in compliant, life-sized vocal fold models

    Science.gov (United States)

    McPhail, Michael; Dowell, Grant; Krane, Michael

    2013-11-01

    This talk presents high-speed PIV measurements in compliant, life-sized models of the vocal folds. A clearer understanding of the fluid-structure interaction of voiced speech, how it produces sound, and how it varies with pathology is required to improve clinical diagnosis and treatment of vocal disorders. Physical models of the vocal folds can answer questions regarding the fundamental physics of speech, as well as the ability of clinical measures to detect the presence and extent of disorder. Flow fields were recorded in the supraglottal region of the models to estimate terms in the equations of fluid motion, and their relative importance. Experiments were conducted over a range of driving pressures with flow rates, given by a ball flowmeter, and subglottal pressures, given by a micro-manometer, reported for each case. Imaging of vocal fold motion, vector fields showing glottal jet behavior, and terms estimated by control volume analysis will be presented. The use of these results for a comparison with clinical measures, and for the estimation of aeroacoustic source strengths will be discussed. Acknowledge support from NIH R01 DC005642.

  9. SIMPLIFIED MATHEMATICAL MODEL OF SMALL SIZED UNMANNED AIRCRAFT VEHICLE LAYOUT

    Directory of Open Access Journals (Sweden)

    2016-01-01

    Full Text Available Strong reduction of new aircraft design period using new technology based on artificial intelligence is the key problem mentioned in forecasts of leading aerospace industry research centers. This article covers the approach to devel- opment of quick aerodynamic design methods based on artificial intelligence neural system. The problem is being solved for the classical scheme of small sized unmanned aircraft vehicle (UAV. The principal parts of the method are the mathe- matical model of layout, layout generator of this type of aircraft is built on aircraft neural networks, automatic selection module for cleaning variety of layouts generated in automatic mode, robust direct computational fluid dynamics method, aerodynamic characteristics approximators on artificial neural networks.Methods based on artificial neural networks have intermediate position between computational fluid dynamics methods or experiments and simplified engineering approaches. The use of ANN for estimating aerodynamic characteris-tics put limitations on input data. For this task the layout must be presented as a vector with dimension not exceeding sev-eral hundred. Vector components must include all main parameters conventionally used for layouts description and com- pletely replicate the most important aerodynamics and structural properties.The first stage of the work is presented in the paper. Simplified mathematical model of small sized UAV was developed. To estimate the range of geometrical parameters of layouts the review of existing vehicle was done. The result of the work is the algorithm and computer software for generating the layouts based on ANN technolo-gy. 10000 samples were generated and the dataset containig geometrical and aerodynamic characteristics of layoutwas created.

  10. Effects of Sample Size, Estimation Methods, and Model Specification on Structural Equation Modeling Fit Indexes.

    Science.gov (United States)

    Fan, Xitao; Wang, Lin; Thompson, Bruce

    1999-01-01

    A Monte Carlo simulation study investigated the effects on 10 structural equation modeling fit indexes of sample size, estimation method, and model specification. Some fit indexes did not appear to be comparable, and it was apparent that estimation method strongly influenced almost all fit indexes examined, especially for misspecified models. (SLD)

  11. Modeling the Effects of Beam Size and Flaw Morphology on Ultrasonic Pulse/Echo Sizing of Delaminations in Carbon Composites

    Science.gov (United States)

    Margetan, Frank J.; Leckey, Cara A.; Barnard, Dan

    2012-01-01

    The size and shape of a delamination in a multi-layered structure can be estimated in various ways from an ultrasonic pulse/echo image. For example the -6dB contours of measured response provide one simple estimate of the boundary. More sophisticated approaches can be imagined where one adjusts the proposed boundary to bring measured and predicted UT images into optimal agreement. Such approaches require suitable models of the inspection process. In this paper we explore issues pertaining to model-based size estimation for delaminations in carbon fiber reinforced laminates. In particular we consider the influence on sizing when the delamination is non-planar or partially transmitting in certain regions. Two models for predicting broadband sonic time-domain responses are considered: (1) a fast "simple" model using paraxial beam expansions and Kirchhoff and phase-screen approximations; and (2) the more exact (but computationally intensive) 3D elastodynamic finite integration technique (EFIT). Model-to-model and model-to experiment comparisons are made for delaminations in uniaxial composite plates, and the simple model is then used to critique the -6dB rule for delamination sizing.

  12. Modeling the effects of beam size and flaw morphology on ultrasonic pulse/echo sizing of delaminations in carbon composites

    Science.gov (United States)

    Margetan, Frank J.; Leckey, Cara A.; Barnard, Dan

    2013-01-01

    The size and shape of a delamination in a multi-layered structure can be estimated in various ways from an ultrasonic pulse/echo image. For example the -6dB contours of measured response provide one simple estimate of the boundary. More sophisticated approaches can be imagined where one adjusts the proposed boundary to bring measured and predicted UT images into optimal agreement. Such approaches require suitable models of the inspection process. In this paper we explore issues pertaining to model-based size estimation for delaminations in carbon fiber reinforced laminates. In particular we consider the influence on sizing when the delamination is non-planar or partially transmitting in certain regions. Two models for predicting broadband sonic time-domain responses are considered: (1) a fast "simple" model using paraxial beam expansions and Kirchhoff and phase-screen approximations; and (2) the more exact (but computationally intensive) 3D elastodynamic finite integration technique (EFIT). Model-to-model and model-to experiment comparisons are made for delaminations in uniaxial composite plates, and the simple model is then used to critique the -6dB rule for delamination sizing.

  13. Portfolio size as funktion of the premium: modeling and optimization

    DEFF Research Database (Denmark)

    Asmussen, Søren; Christensen, Bent Jesper; Taksar, Michael I

    , where r is the risk-free interest rate. Based on calculations of the customers' present values of the alternative strategies of insuring and not insuring, the portfolio size n(p) is derived, and also the rate of claims from the insured customers is given. Further, the value of p which is optimal......An insurance company has a large number N of potential customers characterized by i.i.d. r.v.'s A1,…,AN giving the arrival rates of claims. Customers are risk averse, and a customer accepts an offered premium p according to his A-value. The modeling further involves a discount rate d>r of customers...... for minimizing the ruin probability is derived in a diffusion approximation to the Cramér-Lundberg risk process with an added liability rate L of the company. The solution involves the Lambert W function. Similar discussion is given for extensions involving customers having only partial information...

  14. Sensitivity of Mantel Haenszel Model and Rasch Model as Viewed From Sample Size

    OpenAIRE

    ALWI, IDRUS

    2011-01-01

    The aims of this research is to study the sensitivity comparison of Mantel Haenszel and Rasch Model for detection differential item functioning, observed from the sample size. These two differential item functioning (DIF) methods were compared using simulate binary item respon data sets of varying sample size,  200 and 400 examinees were used in the analyses, a detection method of differential item functioning (DIF) based on gender difference. These test conditions were replication 4 tim...

  15. The Hierarchy Model of the Size Distribution of Centres

    NARCIS (Netherlands)

    J. Tinbergen (Jan)

    1968-01-01

    textabstractWe know that human beings live in centres, that is, cities, towns and villages of different size. Both large and small centres have a number of advantages and disadvantages, different for different people and this is why we have a whole range of sizes. Statistically, we even find that

  16. A grain size distribution model for non-catalytic gas-solid reactions

    NARCIS (Netherlands)

    Heesink, Albertus B.M.; Prins, W.; van Swaaij, Willibrordus Petrus Maria

    1993-01-01

    A new model to describe the non-catalytic conversion of a solid by a reactant gas is proposed. This so-called grain size distribution (GSD) model presumes the porous particle to be a collection of grains of various sizes. The size distribution of the grains is derived from mercury porosimetry

  17. A multidimensional stability model for predicting shallow landslide size and shape across landscapes

    Science.gov (United States)

    David G. Milledge; Dino Bellugi; Jim A. McKean; Alexander L. Densmore; William E. Dietrich

    2014-01-01

    The size of a shallow landslide is a fundamental control on both its hazard and geomorphic importance. Existing models are either unable to predict landslide size or are computationally intensive such that they cannot practically be applied across landscapes. We derive a model appropriate for natural slopes that is capable of predicting shallow landslide size but...

  18. Characteristic length scale of input data in distributed models: implications for modeling grid size

    Science.gov (United States)

    Artan, G. A.; Neale, C. M. U.; Tarboton, D. G.

    2000-01-01

    The appropriate spatial scale for a distributed energy balance model was investigated by: (a) determining the scale of variability associated with the remotely sensed and GIS-generated model input data; and (b) examining the effects of input data spatial aggregation on model response. The semi-variogram and the characteristic length calculated from the spatial autocorrelation were used to determine the scale of variability of the remotely sensed and GIS-generated model input data. The data were collected from two hillsides at Upper Sheep Creek, a sub-basin of the Reynolds Creek Experimental Watershed, in southwest Idaho. The data were analyzed in terms of the semivariance and the integral of the autocorrelation. The minimum characteristic length associated with the variability of the data used in the analysis was 15 m. Simulated and observed radiometric surface temperature fields at different spatial resolutions were compared. The correlation between agreement simulated and observed fields sharply declined after a 10×10 m2 modeling grid size. A modeling grid size of about 10×10 m2 was deemed to be the best compromise to achieve: (a) reduction of computation time and the size of the support data; and (b) a reproduction of the observed radiometric surface temperature.

  19. Characteristic length scale of input data in distributed models: implications for modeling grain size

    Science.gov (United States)

    Artan, Guleid A.; Neale, C. M. U.; Tarboton, D. G.

    2000-01-01

    The appropriate spatial scale for a distributed energy balance model was investigated by: (a) determining the scale of variability associated with the remotely sensed and GIS-generated model input data; and (b) examining the effects of input data spatial aggregation on model response. The semi-variogram and the characteristic length calculated from the spatial autocorrelation were used to determine the scale of variability of the remotely sensed and GIS-generated model input data. The data were collected from two hillsides at Upper Sheep Creek, a sub-basin of the Reynolds Creek Experimental Watershed, in southwest Idaho. The data were analyzed in terms of the semivariance and the integral of the autocorrelation. The minimum characteristic length associated with the variability of the data used in the analysis was 15 m. Simulated and observed radiometric surface temperature fields at different spatial resolutions were compared. The correlation between agreement simulated and observed fields sharply declined after a 10×10 m2 modeling grid size. A modeling grid size of about 10×10 m2 was deemed to be the best compromise to achieve: (a) reduction of computation time and the size of the support data; and (b) a reproduction of the observed radiometric surface temperature.

  20. Recurrent violations of invariant rules for offspring size: evidence from turtles and the implications for small clutch size models.

    Science.gov (United States)

    Rollinson, Njal; Edge, Christopher B; Brooks, Ronald J

    2013-08-01

    Smith and Fretwell's classic model predicts that parents can maximize fitness by dividing the energy available for reproduction into offspring of an optimal size. However, this model breaks down when clutch size is small (~1-10 offspring). Invariant rules are an extension of the Smith-Fretwell model, and these rules predict how offspring size will vary among and within individuals that produce small clutch sizes. Here, we provide a narrow test of invariant rules using three turtle species, then we synthesize and re-analyze existing data from 18 different species (comprising five Orders) to evaluate whether invariant rules are followed across broad taxa. We do not find support for most invariant rules in turtles, and our re-analysis demonstrates a general mismatch between observed and expected values across all taxa evaluated, suggesting that invariant rules fail to predict reproductive patterns in nature. Morphological constraints on offspring size and reproductive effort may be important reasons for disparities between theory and observation both in turtles and other taxa. Paradoxically, morphological constraints are most common in small-bodied species and individuals, but these same candidates are also those which produce the small clutch sizes that are necessary to test invariant rules, such that a fair test of invariant rules will often be challenging. Mismatches between theory and observation might also occur because theory assumes that mothers exert control over resource allocation to offspring. In fact, there is evidence of widespread genetic correlations among investment per offspring and reproductive effort, such that these traits are not independent.

  1. Number-average size model for geological systems and its application in economic geology

    Directory of Open Access Journals (Sweden)

    Q. F. Wang

    2011-07-01

    Full Text Available Various natural objects follow a number-size relationship in the fractal domain. In such relationship, the accumulative number of the objects beyond a given size shows a power-law relationship with the size. Yet in most cases, we also need to know the relationship between the accumulative number of the objects and their average size. A generalized number-size model and a number-average size model are constructed in this paper. In the number-average size model, the accumulative number shows a power-law relationship with the average size when the given size is much less than the maximum size of the objects. When the fractal dimension Ds of the number-size model is smaller than 1, the fractal dimension Ds of the number-average size model is almost equal to 1; and when Ds > 1, the Dm is approximately equal to Ds. In mineral deposits, according to the number-average size model, the ore tonnage may show a fractal relationship with the grade, as the cutoff changes for a single ore deposit. This is demonstrated by a study of the relationship between tonnage and grade in the Reshuitang epithermal hot-spring gold deposit, China.

  2. Sample size for collecting germplasms – a polyploid model with ...

    Indian Academy of Sciences (India)

    Unknown

    Conservation; diploid; exploration; germplasm; inbreeding; polyploid; seeds ... A seed factor which influences the plant sample size has also been isolated to aid the collectors in selecting the appropriate combination of number of plants and seeds per plant. ..... able saving of resources during collection and storage of.

  3. A Markov decision model for optimising economic production lot size ...

    African Journals Online (AJOL)

    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 ...

  4. Size Matters: Observed and Modeled Camouflage Response of European Cuttlefish (Sepia officinalis) to Different Substrate Patch Sizes during Movement.

    Science.gov (United States)

    Josef, Noam; Berenshtein, Igal; Rousseau, Meghan; Scata, Gabriella; Fiorito, Graziano; Shashar, Nadav

    2016-01-01

    Camouflage is common throughout the phylogenetic tree and is largely used to minimize detection by predator or prey. Cephalopods, and in particular Sepia officinalis cuttlefish, are common models for camouflage studies. Predator avoidance behavior is particularly important in this group of soft-bodied animals that lack significant physical defenses. While previous studies have suggested that immobile cephalopods selectively camouflage to objects in their immediate surroundings, the camouflage characteristics of cuttlefish during movement are largely unknown. In a heterogenic environment, the visual background and substrate feature changes quickly as the animal swim across it, wherein substrate patch is a distinctive and high contrast patch of substrate in the animal's trajectory. In the current study, we examine the effect of substrate patch size on cuttlefish camouflage, and specifically the minimal size of an object for eliciting intensity matching response while moving. Our results indicated that substrate patch size has a positive effect on animal's reflectance change, and that the threshold patch size resulting in camouflage response falls between 10 and 19 cm (width). These observations suggest that the animal's length (7.2-12.3 cm mantle length in our case) serves as a possible threshold filter below which objects are considered irrelevant for camouflage, reducing the frequency of reflectance changes-which may lead to detection. Accordingly, we have constructed a computational model capturing the main features of the observed camouflaging behavior, provided for cephalopod camouflage during movement.

  5. mizer: an R package for multispecies, trait-based and community size spectrum ecological modelling

    DEFF Research Database (Denmark)

    Scott, Finlay; Blanchard, Julia L.; Andersen, Ken Haste

    2014-01-01

    1. Size spectrum ecological models are representations of a community of individuals which grow and change trophic level. A key emergent feature of these models is the size spectrum; the total abundance of all individuals that scales negatively with size. The models we focus on are designed...... to capture fish community dynamics useful for assessing the community impacts of fishing. 2. We present mizer, anRpackage for implementing dynamic size spectrum ecological models of an entire aquatic community subject to fishing.Multiple fishing gears can be defined and fishing mortality can change through...... time making it possible to simulate a range of exploitation strategies and management options. 3. mizer implements three versions of the size spectrum modelling framework: the communitymodel,where individuals are only characterized by their size; the trait-based model, where individuals are further...

  6. Applying Model Checking to Industrial-Sized PLC Programs

    CERN Document Server

    AUTHOR|(CDS)2079190; Darvas, Daniel; Blanco Vinuela, Enrique; Tournier, Jean-Charles; Bliudze, Simon; Blech, Jan Olaf; Gonzalez Suarez, Victor M

    2015-01-01

    Programmable logic controllers (PLCs) are embedded computers widely used in industrial control systems. Ensuring that a PLC software complies with its specification is a challenging task. Formal verification has become a recommended practice to ensure the correctness of safety-critical software but is still underused in industry due to the complexity of building and managing formal models of real applications. In this paper, we propose a general methodology to perform automated model checking of complex properties expressed in temporal logics (\\eg CTL, LTL) on PLC programs. This methodology is based on an intermediate model (IM), meant to transform PLC programs written in various standard languages (ST, SFC, etc.) to different modeling languages of verification tools. We present the syntax and semantics of the IM and the transformation rules of the ST and SFC languages to the nuXmv model checker passing through the intermediate model. Finally, two real cases studies of \\CERN PLC programs, written mainly in th...

  7. Modeling postnatal exposures and their interactions with birth size.

    Science.gov (United States)

    Cole, Tim J

    2004-01-01

    The fetal origins of adult disease hypothesis postulates that the inverse association between birth weight and later adverse outcome reflects fetal programming that increases the risk of later disease. However, low birth weight is associated with catch-up after birth, and weight gain is itself a risk factor for later disease. It is difficult to disentangle the effects on outcome of the size and growth components of weight change through time. This paper presents the life course plot, a device to display both size and growth effects simultaneously. It is based on the multiple-regression analysis of the outcome on the various weights, expressed as z-scores, and the plot displays the coefficients plotted against the corresponding ages of measurement. Examples from Brazil (Pelotas) and the Phillippines (Cebu) relate blood pressure in adolescence to weight through childhood. They show small inverse weight effects in infancy, but early weight is less important than weight and weight gain during adolescence. In addition, birth length in the Cebu study affects the strength of the relationship between weight and blood pressure in adolescence. This suggests a fetal programming effect, with children who were relatively long at birth having a more sensitive relationship between blood pressure and weight at age 15. Whether this is a good or a bad thing is not immediately clear.

  8. A hybrid mathematical model for controlling particle size, particle size distribution, and color properties of toner particles

    Science.gov (United States)

    Ataeefard, Maryam; Shadman, Alireza; Saeb, Mohammad Reza; Mohammadi, Yousef

    2016-08-01

    A mathematical modeling approach was proposed combining the capabilities of response surface methodology (RSM) and desirability function (DF) and implemented successfully in production of printing toner particles. Toner powders were systematically synthesized through suspension copolymerization process. Applying RSM, a series of experiments were designed and toner particles were prepared and the effects of monomer ratio, colorant and surfactant content on the particle size (PS), particle size distribution (PSD), thermal and colorimetric properties (∆ E) of the resulting toner were monitored and discussed. The second-order models corresponding to each target characteristic, i.e., PS, PSD, and ∆ E of different types of toner powders, were obtained by individual optimization to express variation of each property in terms of polymerization parameters. Applying statistical calculations, the best reduced models were identified to be fed in the second step of optimization. Since toners with appropriate PS, PSD, and CP were needed, we applied multi-objective optimization based on DF approach. The results show that exact tuning of toner properties is closely possible with the aid of hybrid mathematical model developed in this work. Noticeably, desirabilities are very close to 100 %.

  9. NOAA ESRI Grid - sediment size predictions model in New York offshore planning area from Biogeography Branch

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This dataset represents sediment size predictions from a sediment spatial model developed for the New York offshore spatial planning area. The model also includes...

  10. Determining the optimum cell size of digital elevation model for ...

    Indian Academy of Sciences (India)

    obtained DEMs were explored for their intrinsic quality using four different methods, i.e., sink analy- sis, fractal dimension of derived stream network, entropy measurement and semivariogram modelling. These methods were applied to determine the level artifacts (interpolation error) in DEM surface as well as derived stream ...

  11. Waif goodbye! Average-size female models promote positive body image and appeal to consumers.

    Science.gov (United States)

    Diedrichs, Phillippa C; Lee, Christina

    2011-10-01

    Despite consensus that exposure to media images of thin fashion models is associated with poor body image and disordered eating behaviours, few attempts have been made to enact change in the media. This study sought to investigate an effective alternative to current media imagery, by exploring the advertising effectiveness of average-size female fashion models, and their impact on the body image of both women and men. A sample of 171 women and 120 men were assigned to one of three advertisement conditions: no models, thin models and average-size models. Women and men rated average-size models as equally effective in advertisements as thin and no models. For women with average and high levels of internalisation of cultural beauty ideals, exposure to average-size female models was associated with a significantly more positive body image state in comparison to exposure to thin models and no models. For men reporting high levels of internalisation, exposure to average-size models was also associated with a more positive body image state in comparison to viewing thin models. These findings suggest that average-size female models can promote positive body image and appeal to consumers.

  12. Analysis of litter size and average litter weight in pigs using a recursive model

    DEFF Research Database (Denmark)

    Varona, Luis; Sorensen, Daniel; Thompson, Robin

    2007-01-01

    An analysis of litter size and average piglet weight at birth in Landrace and Yorkshire using a standard two-trait mixed model (SMM) and a recursive mixed model (RMM) is presented. The RMM establishes a one-way link from litter size to average piglet weight. It is shown that there is a one-to-one...

  13. The Impact of Sample Size and Other Factors When Estimating Multilevel Logistic Models

    Science.gov (United States)

    Schoeneberger, Jason A.

    2016-01-01

    The design of research studies utilizing binary multilevel models must necessarily incorporate knowledge of multiple factors, including estimation method, variance component size, or number of predictors, in addition to sample sizes. This Monte Carlo study examined the performance of random effect binary outcome multilevel models under varying…

  14. Medical Modeling of Particle Size Effects for CB Inhalation Hazards

    Science.gov (United States)

    2015-09-01

    warfare) may create adverse health effects when inhaled. Once the materials enter the respiratory tract, they may deposit on the airway surfaces...mppd.htm). New features in this version include a deposition model specifically for nanoparticles, nonuniform lung ventilation to include the effect ... mechanisms cause local lesions, but the more virulent strains may then spread throughout the body via blood or lymph (Celli 2008). The effects of

  15. Size exclusion chromatography models and its comparison with experiment

    Czech Academy of Sciences Publication Activity Database

    Netopilík, Miloš

    2017-01-01

    Roč. 8, 4 (Suppl) (2017), s. 29 E-ISSN 2157-7064. [International Conference and Exhibition on Advances in Chromatography & HPLC Techniques /3./. 13.07.2017-14.07.2017, Berlin] R&D Projects: GA ČR(CZ) GC17-04258J Institutional support: RVO:61389013 Keywords : model of separation * flow-rate influence Subject RIV: CD - Macromolecular Chemistry

  16. A Size and Boundary Effects Model for Quasi-Brittle Fracture

    Directory of Open Access Journals (Sweden)

    Xiaofeng Gao

    2016-12-01

    Full Text Available The fracture behaviors of quasi-brittle materials are commonly specimen size (size effect and crack size (boundary effect dependent. In this study, a new failure model is developed for characterizing the size and boundary effects. The derivative of the energy release rate is firstly introduced to predict the nominal strength dominated by the strength mechanism. Combined with the energy criterion for the energy mechanism, an asymptotic model is developed to capture the effect of any crack size on the nominal strength, and its expression for geometrically similar specimens is also established, which is able to characterize the size effect. Detailed comparisons of the proposed model with the size effect law and the boundary effect model are performed, respectively. The nominal strength predictions based on the proposed model are validated with the experimental results of cracked three-point bending beam specimens made of concrete, of limestone and of hardened cement paste and compared with the model predictions given by the size effect law and the boundary effect model.

  17. Noise-Induced Transitions in a Population Growth Model Based on Size-Dependent Carrying Capacity

    Directory of Open Access Journals (Sweden)

    Neeme Lumi

    2014-01-01

    Full Text Available The stochastic dynamics of a population growth model with size-dependent carrying capacity is considered. The effect of a fluctuating environment on population growth is modeled as a multiplicative dichotomous noise. At intermediate values of population size the deterministic counterpart of the model behaves similarly to the Von Foerster model for human population, but at small and very large values of population size substantial differences occur. In the stochastic case, an exact analytical solution for the stationary probability distribution is found. It is established that variation of noise correlation time can cause noise-induced transitions between three different states of the system characterized by qualitatively different behaviors of the probability distributions of the population size. Also, it is shown that, in some regions of the system parameters, variation of the amplitude of environmental fluctuations can induce single unidirectional abrupt transitions of the mean population size.

  18. Modelling size-dependent cannibalism in barramundi Lates calcarifer: cannibalistic polyphenism and its implication to aquaculture.

    Directory of Open Access Journals (Sweden)

    Flavio F Ribeiro

    Full Text Available This study quantified size-dependent cannibalism in barramundi Lates calcarifer through coupling a range of prey-predator pairs in a different range of fish sizes. Predictive models were developed using morphological traits with the alterative assumption of cannibalistic polyphenism. Predictive models were validated with the data from trials where cannibals were challenged with progressing increments of prey sizes. The experimental observations showed that cannibals of 25-131 mm total length could ingest the conspecific prey of 78-72% cannibal length. In the validation test, all predictive models underestimate the maximum ingestible prey size for cannibals of a similar size range. However, the model based on the maximal mouth width at opening closely matched the empirical observations, suggesting a certain degree of phenotypic plasticity of mouth size among cannibalistic individuals. Mouth size showed allometric growth comparing with body depth, resulting in a decreasing trend on the maximum size of ingestible prey as cannibals grow larger, which in parts explains why cannibalism in barramundi is frequently observed in the early developmental stage. Any barramundi has the potential to become a cannibal when the initial prey size was 58% of their size, suggesting that 50% of size difference can be the threshold to initiate intracohort cannibalism in a barramundi population. Cannibalistic polyphenism was likely to occur in barramundi that had a cannibalistic history. An experienced cannibal would have a greater ability to stretch its mouth size to capture a much larger prey than the models predict. The awareness of cannibalistic polyphenism has important application in fish farming management to reduce cannibalism.

  19. Modeling the effects of size on patch dynamics of an inert tracer

    Directory of Open Access Journals (Sweden)

    P. Xiu

    2010-03-01

    Full Text Available Mesoscale iron enrichment experiments have revealed that additional iron affects the phytoplankton productivity and carbon cycle. However, the role of initial size of fertilized patch in determining the patch evolution is poorly quantified due to the limited observational capability and complex of physical processes. Using a three-dimensional ocean circulation model, we simulated different sizes of inert tracer patches that were only regulated by physical circulation and diffusion. Model results showed that during the first few days since release of inert tracer, the calculated dilution rate was found to be a linear function with time, which was sensitive to the initial patch size with steeper slope for smaller size patch. After the initial phase of rapid decay, the relationship between dilution rate and time became an exponential function, which was also size dependent. Therefore, larger initial size patches can usually last longer and ultimately affect biogeochemical processes much stronger than smaller patches.

  20. Estimating required information size by quantifying diversity in random-effects model meta-analyses

    DEFF Research Database (Denmark)

    Wetterslev, Jørn; Thorlund, Kristian; Brok, Jesper

    2009-01-01

    BACKGROUND: There is increasing awareness that meta-analyses require a sufficiently large information size to detect or reject an anticipated intervention effect. The required information size in a meta-analysis may be calculated from an anticipated a priori intervention effect or from...... an intervention effect suggested by trials with low-risk of bias. METHODS: Information size calculations need to consider the total model variance in a meta-analysis to control type I and type II errors. Here, we derive an adjusting factor for the required information size under any random-effects model meta......-trial variability and a sampling error estimate considering the required information size. D2 is different from the intuitively obvious adjusting factor based on the common quantification of heterogeneity, the inconsistency (I2), which may underestimate the required information size. Thus, D2 and I2 are compared...

  1. Sample size and power calculations based on generalized linear mixed models with correlated binary outcomes.

    Science.gov (United States)

    Dang, Qianyu; Mazumdar, Sati; Houck, Patricia R

    2008-08-01

    The generalized linear mixed model (GLIMMIX) provides a powerful technique to model correlated outcomes with different types of distributions. The model can now be easily implemented with SAS PROC GLIMMIX in version 9.1. For binary outcomes, linearization methods of penalized quasi-likelihood (PQL) or marginal quasi-likelihood (MQL) provide relatively accurate variance estimates for fixed effects. Using GLIMMIX based on these linearization methods, we derived formulas for power and sample size calculations for longitudinal designs with attrition over time. We found that the power and sample size estimates depend on the within-subject correlation and the size of random effects. In this article, we present tables of minimum sample sizes commonly used to test hypotheses for longitudinal studies. A simulation study was used to compare the results. We also provide a Web link to the SAS macro that we developed to compute power and sample sizes for correlated binary outcomes.

  2. Positive global solutions for a general model of size-dependent population dynamics

    OpenAIRE

    Kato, Nobuyuki

    2000-01-01

    We study size-structured population models of general type which have the growth rate depending on the size and time. The local existence and uniqueness of the solution have been shown by Kato and Torikata (1997). Here, we discuss the positivity of the solution and global existence as well as $L^\\infty$ solutions.

  3. Effect Size Measures for Differential Item Functioning in a Multidimensional IRT Model

    Science.gov (United States)

    Suh, Youngsuk

    2016-01-01

    This study adapted an effect size measure used for studying differential item functioning (DIF) in unidimensional tests and extended the measure to multidimensional tests. Two effect size measures were considered in a multidimensional item response theory model: signed weighted P-difference and unsigned weighted P-difference. The performance of…

  4. A final size relation for epidemic models of vector-transmitted diseases

    Directory of Open Access Journals (Sweden)

    Fred Brauer

    2017-02-01

    Full Text Available We formulate and analyze an age of infection model for epidemics of diseases transmitted by a vector, including the possibility of direct transmission as well. We show how to determine a basic reproduction number. While there is no explicit final size relation as for diseases transmitted directly, we are able to obtain estimates for the final size of the epidemic.

  5. Impact of Sample Size on the Performance of Multiple-Model Pharmacokinetic Simulations▿

    OpenAIRE

    Tam, Vincent H.; Kabbara, Samer; Yeh, Rosa F.; Leary, Robert H.

    2006-01-01

    Monte Carlo simulations are increasingly used to predict pharmacokinetic variability of antimicrobials in a population. We investigated the sample size necessary to provide robust pharmacokinetic predictions. To obtain reasonably robust predictions, a nonparametric model derived from a sample population size of ≥50 appears to be necessary as the input information.

  6. 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.

  7. Firm Size and Monetary Policy Transmission: A Theoretical Model on the Role of Capital Investment Expenditures

    NARCIS (Netherlands)

    Raabe, K.; Arnold, I.; Kool, C.J.M.

    This paper presents a dynamic investment model that explains differences in the sensitivity of small- and large-sized firms to changes in the money market interest rate. In contrast to existing studies on the firm size effects of monetary policy, the importance of firms as monetary transmission

  8. Sample Size and Item Parameter Estimation Precision When Utilizing the One-Parameter "Rasch" Model

    Science.gov (United States)

    Custer, Michael

    2015-01-01

    This study examines the relationship between sample size and item parameter estimation precision when utilizing the one-parameter model. Item parameter estimates are examined relative to "true" values by evaluating the decline in root mean squared deviation (RMSD) and the number of outliers as sample size increases. This occurs across…

  9. Gap-size distribution functions of a random sequential adsorption model of segments on a line

    Science.gov (United States)

    Araújo, N. A. M.; Cadilhe, A.

    2006-05-01

    We performed extensive simulations accompanied by a detailed study of a two-segment size random sequential model on the line. We followed the kinetics towards the jamming state, but we paid particular attention to the characterization of the jamming state structure. In particular, we studied the effect of the size ratio on the mean-gap size, the gap-size dispersion, gap-size skewness, and gap-size kurtosis at the jamming state. We also analyzed the above quantities for the four possible segment-to-segment gap types. We ranged the values of the size ratio from one to twenty. In the limit of a size ratio of one, one recovers the classical car-parking problem. We observed that at low size ratios the jamming state is constituted by short streaks of small and large segments, while at high values of the size ratio the jamming state structure is formed by long streaks of small segments separated by a single large segment. This view of the jamming state structure as a function of the size ratio is supported by the various measured quantities. The present work can help provide insight, for example, on how to minimize the interparticle distance or minimize fluctuations around the mean particle-to-particle distance.

  10. An Empirical Bayes Mixture Model for Effect Size Distributions in Genome-Wide Association Studies

    DEFF Research Database (Denmark)

    Thompson, Wesley K.; Wang, Yunpeng; Schork, Andrew J.

    2015-01-01

    minimizing discrepancies between the parametric mixture model and resampling-based nonparametric estimates of replication effect sizes and variances. We describe in detail the implications of this model for estimation of the non-null proportion, the probability of replication in de novo samples, the local...... for discovery, and polygenic risk prediction. To this end, previous work has used effect-size models based on various distributions, including the normal and normal mixture distributions, among others. In this paper we propose a scale mixture of two normals model for effect size distributions of genome...... analytically and in simulations. We apply this approach to meta-analysis test statistics from two large GWAS, one for Crohn’s disease (CD) and the other for schizophrenia (SZ). A scale mixture of two normals distribution provides an excellent fit to the SZ nonparametric replication effect size estimates. While...

  11. A Comparison of Uniform DIF Effect Size Estimators under the MIMIC and Rasch Models

    Science.gov (United States)

    Jin, Ying; Myers, Nicholas D.; Ahn, Soyeon; Penfield, Randall D.

    2013-01-01

    The Rasch model, a member of a larger group of models within item response theory, is widely used in empirical studies. Detection of uniform differential item functioning (DIF) within the Rasch model typically employs null hypothesis testing with a concomitant consideration of effect size (e.g., signed area [SA]). Parametric equivalence between…

  12. Finite-size effects in the three-state quantum asymmetric clock model

    International Nuclear Information System (INIS)

    Gehlen, G. v.; Rittenberg, V.

    1983-04-01

    The one-dimensional quantum Hamiltonian of the asymmetric three-state clock model is studied using finite-size scaling. Various boundary conditions are considered on chains containing up to eight sites. We calculate the boundary of the commensurate phase and the mass gap index. The model shows an interesting finite-size dependence in connexion with the presence of the incommensurate phase indicating that for the infinite system there is no Lifshitz point. (orig.)

  13. Evaluating a flash size and energy dissipation relationship through various modeling techniques

    Science.gov (United States)

    Salinas, V.; Brothers, M.; Bruning, E. C.; Mansell, E.

    2017-12-01

    Many studies have investigated the influence of the electrostatic and kinematic environments of thunderstorms on lightning flash size. Recent work has demonstrated a coupling of turbulent kinematic properties to flash size distribution in different regions of a storm. Additional work has also theorized a relationship of flash size and energy to the TKE spectrum. However, the physical basis for using flash size alone in these estimates remains absent. This study used the National Severe Storms Laboratory's Collaborative Model for Multiscale Atmospheric Simulation model (N-COMMAS) to simulate an observed multicellular thunderstorm to investigate the relationship between flash size and energy. Model output included the total energy dissipated for each flash, and the charge, electric potential, electric field where it propagated. These flashes were then modeled in two simplified ways. First, each flash was assumed to be convex hull volumes of charge. A 3D Poisson solver was then used on each charge volume for charge density retrieval and computation of the electric potential, using a theoretical electric field breakeven threshold and charge conservation. Second, a capacitor model was used to estimate the energy dissipated using flash area, charge, and plate spacing obtained from the COMMAS model. These two calculations of flash energy were compared to the COMMAS energy. The results suggested that flash size alone was insufficient in characterizing the energetic properties.

  14. Influence of Li-ion Battery Models in the Sizing of Hybrid Storage Systems with Supercapacitors

    DEFF Research Database (Denmark)

    Pinto, Claudio; Barreras, Jorge Varela; de Castro, Ricardo

    2014-01-01

    This paper presents a comparative study of the influence of different aggregated electrical circuit battery models in the sizing process of a hybrid energy storage system (ESS), composed by Li-ion batteries and supercapacitors (SCs). The aim is to find the number of cells required to propel......-order dynamics of the battery. Simulation results demonstrate that the adoption of a more accurate battery model in the sizing of hybrid ESSs prevents over-sizing, leading to a reduction in the number of cells of up to 29%, and a cost decrease of up to 10%....

  15. Modelling size-fractionated primary production in the Atlantic Ocean from remote sensing

    Science.gov (United States)

    Brewin, Robert J. W.; Tilstone, Gavin H.; Jackson, Thomas; Cain, Terry; Miller, Peter I.; Lange, Priscila K.; Misra, Ankita; Airs, Ruth L.

    2017-11-01

    Marine primary production influences the transfer of carbon dioxide between the ocean and atmosphere, and the availability of energy for the pelagic food web. Both the rate and the fate of organic carbon from primary production are dependent on phytoplankton size. A key aim of the Atlantic Meridional Transect (AMT) programme has been to quantify biological carbon cycling in the Atlantic Ocean and measurements of total primary production have been routinely made on AMT cruises, as well as additional measurements of size-fractionated primary production on some cruises. Measurements of total primary production collected on the AMT have been used to evaluate remote-sensing techniques capable of producing basin-scale estimates of primary production. Though models exist to estimate size-fractionated primary production from satellite data, these have not been well validated in the Atlantic Ocean, and have been parameterised using measurements of phytoplankton pigments rather than direct measurements of phytoplankton size structure. Here, we re-tune a remote-sensing primary production model to estimate production in three size fractions of phytoplankton (10 μm) in the Atlantic Ocean, using measurements of size-fractionated chlorophyll and size-fractionated photosynthesis-irradiance experiments conducted on AMT 22 and 23 using sequential filtration-based methods. The performance of the remote-sensing technique was evaluated using: (i) independent estimates of size-fractionated primary production collected on a number of AMT cruises using 14C on-deck incubation experiments and (ii) Monte Carlo simulations. Considering uncertainty in the satellite inputs and model parameters, we estimate an average model error of between 0.27 and 0.63 for log10-transformed size-fractionated production, with lower errors for the small size class (10 μm), and errors generally higher in oligotrophic waters. Application to satellite data in 2007 suggests the contribution of cells 2 μm to total

  16. Details Matter: Noise and Model Structure Set the Relationship between Cell Size and Cell Cycle Timing

    Directory of Open Access Journals (Sweden)

    Felix Barber

    2017-11-01

    Full Text Available Organisms across all domains of life regulate the size of their cells. However, the means by which this is done is poorly understood. We study two abstracted “molecular” models for size regulation: inhibitor dilution and initiator accumulation. We apply the models to two settings: bacteria like Escherichia coli, that grow fully before they set a division plane and divide into two equally sized cells, and cells that form a bud early in the cell division cycle, confine new growth to that bud, and divide at the connection between that bud and the mother cell, like the budding yeast Saccharomyces cerevisiae. In budding cells, delaying cell division until buds reach the same size as their mother leads to very weak size control, with average cell size and standard deviation of cell size increasing over time and saturating up to 100-fold higher than those values for cells that divide when the bud is still substantially smaller than its mother. In budding yeast, both inhibitor dilution or initiator accumulation models are consistent with the observation that the daughters of diploid cells add a constant volume before they divide. This “adder” behavior has also been observed in bacteria. We find that in bacteria an inhibitor dilution model produces adder correlations that are not robust to noise in the timing of DNA replication initiation or in the timing from initiation of DNA replication to cell division (the C+D period. In contrast, in bacteria an initiator accumulation model yields robust adder correlations in the regime where noise in the timing of DNA replication initiation is much greater than noise in the C + D period, as reported previously (Ho and Amir, 2015. In bacteria, division into two equally sized cells does not broaden the size distribution.

  17. Modelling an exploited marine fish community with 15 parameters - results from a simple size-based model

    NARCIS (Netherlands)

    Pope, J.G.; Rice, J.C.; Daan, N.; Jennings, S.; Gislason, H.

    2006-01-01

    To measure and predict the response of fish communities to exploitation, it is necessary to understand how the direct and indirect effects of fishing interact. Because fishing and predation are size-selective processes, the potential response can be explored with size-based models. We use a

  18. Influences of model structure and calibration data size on predicting chlorine residuals in water storage tanks.

    Science.gov (United States)

    Hua, Pei; de Oliveira, Keila Roberta Ferreira; Cheung, Peter; Gonçalves, Fábio Veríssimo; Zhang, Jin

    2018-04-09

    This study evaluated the influences of model structure and calibration data size on the modelling performance for the prediction of chlorine residuals in household drinking water storage tanks. The tank models, which consisted of two modules, i.e., hydraulic mixing and water quality modelling processes, were evaluated under identical calibration conditions. The hydraulic mixing modelling processes investigated included the continuously stirred tank reactor (CSTR) and multi-compartment (MC) methods, and the water quality modelling processes included first order (FO), single-reactant second order (SRSO), and variable reaction rate coefficients (VRRC) second order chlorine decay kinetics. Different combinations of these hydraulic mixing and water quality methods formed six tank models. Results show that by applying the same calibration datasets, the tank models that included the MC method for modelling the hydraulic mixing provided better predictions compared to the CSTR method. In terms of water quality modelling, VRRC kinetics showed better predictive abilities compared to FO and SRSO kinetics. It was also found that the overall tank model performance could be substantially improved when a proper method was chosen for the simulation of hydraulic mixing, i.e., the accuracy of the hydraulic mixing modelling plays a critical role in the accuracy of the tank model. Advances in water quality modelling improve the calibration process, i.e., the size of the datasets used for calibration could be reduced when a suitable kinetics method was applied. Although the accuracies of all six models increased with increasing calibration dataset size, the tank model that consisted of the MC and VRRC methods was the most suitable of the tank models as it could satisfactorily predict chlorine residuals in household tanks by using invariant parameters calibrated against the minimum dataset size. Copyright © 2018 Elsevier B.V. All rights reserved.

  19. Modeling size effects on the transformation behavior of shape memory alloy micropillars

    International Nuclear Information System (INIS)

    Hernandez, Edwin A Peraza; Lagoudas, Dimitris C

    2015-01-01

    The size dependence of the thermomechanical response of shape memory alloys (SMAs) at the micro and nano-scales has gained increasing attention in the engineering community due to existing and potential uses of SMAs as solid-state actuators and components for energy dissipation in small scale devices. Particularly, their recent uses in microelectromechanical systems (MEMS) have made SMAs attractive options as active materials in small scale devices. One factor limiting further application, however, is the inability to effectively and efficiently model the observed size dependence of the SMA behavior for engineering applications. Therefore, in this work, a constitutive model for the size-dependent behavior of SMAs is proposed. Experimental observations are used to motivate the extension of an existing thermomechanical constitutive model for SMAs to account for the scale effects. It is proposed that such effects can be captured via characteristic length dependent material parameters in a power-law manner. The size dependence of the transformation behavior of NiFeGa micropillars is investigated in detail and used as model prediction cases. The constitutive model is implemented in a finite element framework and used to simulate and predict the response of SMA micropillars with different sizes. The results show a good agreement with experimental data. A parametric study performed using the calibrated model shows that the influence of micropillar aspect ratio and taper angle on the compression response is significantly smaller than that of the micropillar average diameter. It is concluded that the model is able to capture the size dependent transformation response of the SMA micropillars. In addition, the simplicity of the calibration and implementation of the proposed model make it practical for the design and numerical analysis of small scale SMA components that exhibit size dependent responses. (paper)

  20. Modeling size effects on the transformation behavior of shape memory alloy micropillars

    Science.gov (United States)

    Peraza Hernandez, Edwin A.; Lagoudas, Dimitris C.

    2015-07-01

    The size dependence of the thermomechanical response of shape memory alloys (SMAs) at the micro and nano-scales has gained increasing attention in the engineering community due to existing and potential uses of SMAs as solid-state actuators and components for energy dissipation in small scale devices. Particularly, their recent uses in microelectromechanical systems (MEMS) have made SMAs attractive options as active materials in small scale devices. One factor limiting further application, however, is the inability to effectively and efficiently model the observed size dependence of the SMA behavior for engineering applications. Therefore, in this work, a constitutive model for the size-dependent behavior of SMAs is proposed. Experimental observations are used to motivate the extension of an existing thermomechanical constitutive model for SMAs to account for the scale effects. It is proposed that such effects can be captured via characteristic length dependent material parameters in a power-law manner. The size dependence of the transformation behavior of NiFeGa micropillars is investigated in detail and used as model prediction cases. The constitutive model is implemented in a finite element framework and used to simulate and predict the response of SMA micropillars with different sizes. The results show a good agreement with experimental data. A parametric study performed using the calibrated model shows that the influence of micropillar aspect ratio and taper angle on the compression response is significantly smaller than that of the micropillar average diameter. It is concluded that the model is able to capture the size dependent transformation response of the SMA micropillars. In addition, the simplicity of the calibration and implementation of the proposed model make it practical for the design and numerical analysis of small scale SMA components that exhibit size dependent responses.

  1. MODEL JOINT ECONOMIC LOT SIZE PADA KASUS PEMASOK-PEMBELI DENGAN PERMINTAAN PROBABILISTIK

    Directory of Open Access Journals (Sweden)

    Wakhid Ahmad Jauhari

    2009-01-01

    Full Text Available In this paper we consider single vendor single buyer integrated inventory model with probabilistic demand and equal delivery lot size. The model contributes to the current literature by relaxing the deterministic demand assumption which has been used for almost all integrated inventory models. The objective is to minimize expected total costs incurred by the vendor and the buyer. We develop effective iterative procedures for finding the optimal solution. Numerical examples are used to illustrate the benefit of integration. A sensitivity analysis is performed to explore the effect of key parameters on delivery lot size, safety factor, production lot size factor and the expected total cost. The results of the numerical examples indicate that our models can achieve a significant amount of savings. Finally, we compare the results of our proposed model with a simulation model. Abstract in Bahasa Indonesia: Pada penelitian ini akan dikembangkan model gabungan pemasok-pembeli dengan permintaan probabilistik dan ukuran pengiriman sama. Pada model setiap lot pemesanan akan dikirim dalam beberapa lot pengiriman dan pemasok akan memproduksi barang dalam ukuran batch produksi yang merupakan kelipatan integer dari lot pengiriman. Dikembangkan pula suatu algoritma untuk menyelesaikan model matematis yang telah dibuat. Selain itu, pengaruh perubahan parameter terhadap perilaku model diteliti dengan analisis sensitivitas terhadap beberapa parameter kunci, seperti ukuran lot, stok pengaman dan total biaya persediaan. Pada penelitian ini juga dibuat model simulasi untuk melihat performansi model matematis pada kondisi nyata. Kata kunci: model gabungan, permintaan probabilistik, lot pengiriman, supply chain

  2. Women's Preferences for Penis Size: A New Research Method Using Selection among 3D Models.

    Science.gov (United States)

    Prause, Nicole; Park, Jaymie; Leung, Shannon; Miller, Geoffrey

    2015-01-01

    Women's preferences for penis size may affect men's comfort with their own bodies and may have implications for sexual health. Studies of women's penis size preferences typically have relied on their abstract ratings or selecting amongst 2D, flaccid images. This study used haptic stimuli to allow assessment of women's size recall accuracy for the first time, as well as examine their preferences for erect penis sizes in different relationship contexts. Women (N = 75) selected amongst 33, 3D models. Women recalled model size accurately using this method, although they made more errors with respect to penis length than circumference. Women preferred a penis of slightly larger circumference and length for one-time (length = 6.4 inches/16.3 cm, circumference = 5.0 inches/12.7 cm) versus long-term (length = 6.3 inches/16.0 cm, circumference = 4.8 inches/12.2 cm) sexual partners. These first estimates of erect penis size preferences using 3D models suggest women accurately recall size and prefer penises only slightly larger than average.

  3. Women's Preferences for Penis Size: A New Research Method Using Selection among 3D Models.

    Directory of Open Access Journals (Sweden)

    Nicole Prause

    Full Text Available Women's preferences for penis size may affect men's comfort with their own bodies and may have implications for sexual health. Studies of women's penis size preferences typically have relied on their abstract ratings or selecting amongst 2D, flaccid images. This study used haptic stimuli to allow assessment of women's size recall accuracy for the first time, as well as examine their preferences for erect penis sizes in different relationship contexts. Women (N = 75 selected amongst 33, 3D models. Women recalled model size accurately using this method, although they made more errors with respect to penis length than circumference. Women preferred a penis of slightly larger circumference and length for one-time (length = 6.4 inches/16.3 cm, circumference = 5.0 inches/12.7 cm versus long-term (length = 6.3 inches/16.0 cm, circumference = 4.8 inches/12.2 cm sexual partners. These first estimates of erect penis size preferences using 3D models suggest women accurately recall size and prefer penises only slightly larger than average.

  4. Battery Sizing for Plug-in Hybrid Electric Vehicles in Beijing: A TCO Model Based Analysis

    Directory of Open Access Journals (Sweden)

    Cong Hou

    2014-08-01

    Full Text Available This paper proposes a total cost of ownership (TCO model for battery sizing of plug-in hybrid electric vehicles (PHEVs. The proposed systematic TCO model innovatively integrates the Beijing driving database and optimal PHEV energy management strategies developed earlier. The TCO, including battery, fuel, electricity, and salvage costs, is calculated in yearly cash flows. The salvage cost, based on battery degradation model, is proposed for the first time. The results show that the optimal battery size for PHEVs in Beijing is 6–8 kWh. Several additional scenarios are also analyzed: (1 10% increase in battery price or discount rate leads to an optimal battery size of 6 kWh, and 10% increase in fuel price shifts the optimal battery size to 8 kWh; (2 the longer and more dispersive daily range distribution in the U.S. increases the optimal battery size to 14 kWh; (3 the subsidy in China results in an optimal battery size of 13 kWh, while that in the U.S. results in 17 kWh, and a fuel savings rate based subsidy policy is innovatively proposed; (4 the optimal battery size with Li4Ti5O12 batteries is 2 kWh, but the TCO of Li4Ti5O12 batteries is higher than that of LiFePO4 batteries.

  5. Surface tension of different sized single-component droplets, according to macroscopic data obtained using the lattice gas model and the critical droplet size during phase formation

    Science.gov (United States)

    Tovbin, Yu. K.; Zaitseva, E. S.; Rabinovich, A. B.

    2017-10-01

    Size dependences of the surface tension of spherical single-component droplets are calculated using equations of the lattice gas model for 19 compounds. Parameters of the model are found from experimental data on the surface tension of these compounds for a macroscopic planar surface. The chosen low-molecular compounds satisfy the law of corresponding states. To improve agreement with the experimental data, Lennard-Jones potential parameters are varied within 10% deviations. The surface tensions of different sized equilibrium droplets are calculated at elevated and lowered temperatures. It is found that the surface tension of droplets grows monotonically as the droplet size increases from zero to its bulk value. The droplet size R 0 corresponding to zero surface tension corresponds to the critical size of the emergence of a new phase. The critical droplet sizes in the new phase of the considered compounds are estimated for the first time.

  6. Modeling of LEO Orbital Debris Populations in Centimeter and Millimeter Size Regimes

    Science.gov (United States)

    Xu, Y.-L.; Hill, . M.; Horstman, M.; Krisko, P. H.; Liou, J.-C.; Matney, M.; Stansbery, E. G.

    2010-01-01

    The building of the NASA Orbital Debris Engineering Model, whether ORDEM2000 or its recently updated version ORDEM2010, uses as its foundation a number of model debris populations, each truncated at a minimum object-size ranging from 10 micron to 1 m. This paper discusses the development of the ORDEM2010 model debris populations in LEO (low Earth orbit), focusing on centimeter (smaller than 10 cm) and millimeter size regimes. Primary data sets used in the statistical derivation of the cm- and mm-size model populations are from the Haystack radar operated in a staring mode. Unlike cataloged objects of sizes greater than approximately 10 cm, ground-based radars monitor smaller-size debris only in a statistical manner instead of tracking every piece. The mono-static Haystack radar can detect debris as small as approximately 5 mm at moderate LEO altitudes. Estimation of millimeter debris populations (for objects smaller than approximately 6 mm) rests largely on Goldstone radar measurements. The bi-static Goldstone radar can detect 2- to 3-mm objects. The modeling of the cm- and mm-debris populations follows the general approach to developing other ORDEM2010-required model populations for various components and types of debris. It relies on appropriate reference populations to provide necessary prior information on the orbital structures and other important characteristics of the debris objects. NASA's LEO-to-GEO Environment Debris (LEGEND) model is capable of furnishing such reference populations in the desired size range. A Bayesian statistical inference process, commonly adopted in ORDEM2010 model-population derivations, changes a priori distribution into a posteriori distribution and thus refines the reference populations in terms of data. This paper describes key elements and major steps in the statistical derivations of the cm- and mm-size debris populations and presents results. Due to lack of data for near 1-mm sizes, the model populations of 1- to 3.16-mm

  7. Stability patterns for a size-structured population model and its stage-structured counterpart

    DEFF Research Database (Denmark)

    Zhang, Lai; Pedersen, Michael; Lin, Zhigui

    2015-01-01

    delayed system consisting of a renewal equation for the consumer population birth rate and a delayed differential equation for the resource. Results show that the size- and stage-structured models differ considerably with respect to equilibrium stability, although the two models have completely identical...

  8. On periodic cohort solurions of a size-structured population model

    NARCIS (Netherlands)

    W. Huyer

    1995-01-01

    textabstractWe consider a size-structured population model with discontinuous reproduction and feedback through the environmental variable ``substrate''. The model admits solutions with finitely many cohorts and in that case the problem is described by a system of ODEs involving a bifurcation

  9. Resolving Microzooplankton Functional Groups In A Size-Structured Planktonic Model

    Science.gov (United States)

    Taniguchi, D.; Dutkiewicz, S.; Follows, M. J.; Jahn, O.; Menden-Deuer, S.

    2016-02-01

    Microzooplankton are important marine grazers, often consuming a large fraction of primary productivity. They consist of a great diversity of organisms with different behaviors, characteristics, and rates. This functional diversity, and its consequences, are not currently reflected in large-scale ocean ecological simulations. How should these organisms be represented, and what are the implications for their biogeography? We develop a size-structured, trait-based model to characterize a diversity of microzooplankton functional groups. We compile and examine size-based laboratory data on the traits, revealing some patterns with size and functional group that we interpret with mechanistic theory. Fitting the model to the data provides parameterizations of key rates and properties, which we employ in a numerical ocean model. The diversity of grazing preference, rates, and trophic strategies enables the coexistence of different functional groups of micro-grazers under various environmental conditions, and the model produces testable predictions of the biogeography.

  10. A new model to describe the relationship between species richness and sample size

    Directory of Open Access Journals (Sweden)

    WenJun Zhang

    2017-03-01

    Full Text Available In the sampling of species richness, the number of newly found species declines as increase of sample size, and the number of distinct species tends to an upper asymptote as sample size tends to the infinity. This leads to a curve of species richness vs. sample size. In present study, I follow my principle proposed earlier (Zhang, 2016, and re-develop the model, y=K(1-e^(-rx/K, for describing the relationship between species richness (y and sample size (x, where K is the expected total number of distinct species, and r is the maximum variation of species richness per sample size (i.e., max dy/dx. Computer software and codes were given.

  11. Model choice and sample size in item response theory analysis of aphasia tests.

    Science.gov (United States)

    Hula, William D; Fergadiotis, Gerasimos; Martin, Nadine

    2012-05-01

    The purpose of this study was to identify the most appropriate item response theory (IRT) measurement model for aphasia tests requiring 2-choice responses and to determine whether small samples are adequate for estimating such models. Pyramids and Palm Trees (Howard & Patterson, 1992) test data that had been collected from individuals with aphasia were analyzed, and the resulting item and person estimates were used to develop simulated test data for 3 sample size conditions. The simulated data were analyzed using a standard 1-parameter logistic (1-PL) model and 3 models that accounted for the influence of guessing: augmented 1-PL and 2-PL models and a 3-PL model. The model estimates obtained from the simulated data were compared to their known true values. With small and medium sample sizes, an augmented 1-PL model was the most accurate at recovering the known item and person parameters; however, no model performed well at any sample size. Follow-up simulations confirmed that the large influence of guessing and the extreme easiness of the items contributed substantially to the poor estimation of item difficulty and person ability. Incorporating the assumption of guessing into IRT models improves parameter estimation accuracy, even for small samples. However, caution should be exercised in interpreting scores obtained from easy 2-choice tests, regardless of whether IRT modeling or percentage correct scoring is used.

  12. Modeling group size and scalar stress by logistic regression from an archaeological perspective.

    Directory of Open Access Journals (Sweden)

    Gianmarco Alberti

    Full Text Available Johnson's scalar stress theory, describing the mechanics of (and the remedies to the increase in in-group conflictuality that parallels the increase in groups' size, provides scholars with a useful theoretical framework for the understanding of different aspects of the material culture of past communities (i.e., social organization, communal food consumption, ceramic style, architecture and settlement layout. Due to its relevance in archaeology and anthropology, the article aims at proposing a predictive model of critical level of scalar stress on the basis of community size. Drawing upon Johnson's theory and on Dunbar's findings on the cognitive constrains to human group size, a model is built by means of Logistic Regression on the basis of the data on colony fissioning among the Hutterites of North America. On the grounds of the theoretical framework sketched in the first part of the article, the absence or presence of colony fissioning is considered expression of not critical vs. critical level of scalar stress for the sake of the model building. The model, which is also tested against a sample of archaeological and ethnographic cases: a confirms the existence of a significant relationship between critical scalar stress and group size, setting the issue on firmer statistical grounds; b allows calculating the intercept and slope of the logistic regression model, which can be used in any time to estimate the probability that a community experienced a critical level of scalar stress; c allows locating a critical scalar stress threshold at community size 127 (95% CI: 122-132, while the maximum probability of critical scale stress is predicted at size 158 (95% CI: 147-170. The model ultimately provides grounds to assess, for the sake of any further archaeological/anthropological interpretation, the probability that a group reached a hot spot of size development critical for its internal cohesion.

  13. Martensitic transformations in nanostructured nitinol: Finite element modeling of grain size and distribution effects

    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 demonstra......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...... transformation are totally suppressed. Graded and localized distributions of grain sizes of nitinol were compared with nitinol samples 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...

  14. Modeling of an once through helical coil steam generator of a superheated cycle for sizing analysis

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Yeon Sik; Sim, Yoon Sub; Kim, Eui Kwang [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    1997-12-31

    A thermal sizing code, named as HSGSA (Helical coil Steam Generator Sizing Analyzer), for a sodium heated helical coil steam generator is developed for KALIMER (Korea Advanced LIquid MEtal Reactor) design. The theoretical modeling of the shell and tube sides is described and relevant correlations are presented. For assessment of HSGSA, a reference plant design case is compared to the calculational outputs from HSGSA simulation. 9 refs., 6 figs. (Author)

  15. Investigation of the charging characteristics of micrometer sized droplets based on parallel plate capacitor model.

    Science.gov (United States)

    Zhang, Yanzhen; Liu, Yonghong; Wang, Xiaolong; Shen, Yang; Ji, Renjie; Cai, Baoping

    2013-02-05

    The charging characteristics of micrometer sized aqueous droplets have attracted more and more attentions due to the development of the microfluidics technology since the electrophoretic motion of a charged droplet can be used as the droplet actuation method. This work proposed a novel method of investigating the charging characteristics of micrometer sized aqueous droplets based on parallel plate capacitor model. With this method, the effects of the electric field strength, electrolyte concentration, and ion species on the charging characteristics of the aqueous droplets was investigated. Experimental results showed that the charging characteristics of micrometer sized droplets can be investigated by this method.

  16. Does litter size variation affect models of terrestrial carnivore extinction risk and management?

    Directory of Open Access Journals (Sweden)

    Eleanor S Devenish-Nelson

    Full Text Available Individual variation in both survival and reproduction has the potential to influence extinction risk. Especially for rare or threatened species, reliable population models should adequately incorporate demographic uncertainty. Here, we focus on an important form of demographic stochasticity: variation in litter sizes. We use terrestrial carnivores as an example taxon, as they are frequently threatened or of economic importance. Since data on intraspecific litter size variation are often sparse, it is unclear what probability distribution should be used to describe the pattern of litter size variation for multiparous carnivores.We used litter size data on 32 terrestrial carnivore species to test the fit of 12 probability distributions. The influence of these distributions on quasi-extinction probabilities and the probability of successful disease control was then examined for three canid species - the island fox Urocyon littoralis, the red fox Vulpes vulpes, and the African wild dog Lycaon pictus. Best fitting probability distributions differed among the carnivores examined. However, the discretised normal distribution provided the best fit for the majority of species, because variation among litter-sizes was often small. Importantly, however, the outcomes of demographic models were generally robust to the distribution used.These results provide reassurance for those using demographic modelling for the management of less studied carnivores in which litter size variation is estimated using data from species with similar reproductive attributes.

  17. Modelling the response of size and diversity spectra of fish assemblages to changes in exploitation

    DEFF Research Database (Denmark)

    Gislason, Henrik; Rice, J.

    1998-01-01

    In this paper we investigate whether single and multispecies fisheries models call be used to predict the response of sire and diversity spectra of fish assemblages to changes in exploitation. Both types of models estimate that the slope of the size spectrum will steepen and the intercept...... will increase when fishing intensity increases, while the response of the slope and intercept of the diversity spectrum depend on the model used. The changes in the slope and intercept of the size spectrum are found to be proportional to the change in fishing intensity. The proportionality is insensitive...... to changes in natural mortality, but sensitive to changes in growth and to the relationship between stock and recruitment. The results agree will with results obtained from previous analysis of survey data from the North Sea and suggest that the slope of the size spectrum is a useful measure of fishing...

  18. Mathematical modeling of pigment dispersion taking into account the full agglomerate particle size distribution

    DEFF Research Database (Denmark)

    Kiil, Søren

    2017-01-01

    . The only adjustable parameter used was an apparent rate constant for the linear agglomerate erosion rate. Model simulations, at selected values of time, for the full agglomerate particle size distribution were in good qualitative agreement with the measured values. A quantitative match of the experimental...... particle size distribution was simulated. Data from two previous experimental investigations were used for model validation. The first concerns two different yellow organic pigments dispersed in nitrocellulose/ethanol vehicles in a ball mill and the second a red organic pigment dispersed in a solvent...... particle size distributions could be obtained using time-dependent fragment distributions, but this resulted in a very slight improvement in the simulated transient mean diameter only. The model provides a mechanistic understanding of the agglomerate breakage process that can be used, e...

  19. Contact behavior modelling and its size effect on proton exchange membrane fuel cell

    Science.gov (United States)

    Qiu, Diankai; Peng, Linfa; Yi, Peiyun; Lai, Xinmin; Janßen, Holger; Lehnert, Werner

    2017-10-01

    Contact behavior between the gas diffusion layer (GDL) and bipolar plate (BPP) is of significant importance for proton exchange membrane fuel cells. Most current studies on contact behavior utilize experiments and finite element modelling and focus on fuel cells with graphite BPPs, which lead to high costs and huge computational requirements. The objective of this work is to build a more effective analytical method for contact behavior in fuel cells and investigate the size effect resulting from configuration alteration of channel and rib (channel/rib). Firstly, a mathematical description of channel/rib geometry is outlined in accordance with the fabrication of metallic BPP. Based on the interface deformation characteristic and Winkler surface model, contact pressure between BPP and GDL is then calculated to predict contact resistance and GDL porosity as evaluative parameters of contact behavior. Then, experiments on BPP fabrication and contact resistance measurement are conducted to validate the model. The measured results demonstrate an obvious dependence on channel/rib size. Feasibility of the model used in graphite fuel cells is also discussed. Finally, size factor is proposed for evaluating the rule of size effect. Significant increase occurs in contact resistance and porosity for higher size factor, in which channel/rib width decrease.

  20. Interaction of rate- and size-effect using a dislocation density based strain gradient viscoplasticity model

    Science.gov (United States)

    Nguyen, Trung N.; Siegmund, Thomas; Tomar, Vikas; Kruzic, Jamie J.

    2017-12-01

    Size effects occur in non-uniform plastically deformed metals confined in a volume on the scale of micrometer or sub-micrometer. Such problems have been well studied using strain gradient rate-independent plasticity theories. Yet, plasticity theories describing the time-dependent behavior of metals in the presence of size effects are presently limited, and there is no consensus about how the size effects vary with strain rates or whether there is an interaction between them. This paper introduces a constitutive model which enables the analysis of complex load scenarios, including loading rate sensitivity, creep, relaxation and interactions thereof under the consideration of plastic strain gradient effects. A strain gradient viscoplasticity constitutive model based on the Kocks-Mecking theory of dislocation evolution, namely the strain gradient Kocks-Mecking (SG-KM) model, is established and allows one to capture both rate and size effects, and their interaction. A formulation of the model in the finite element analysis framework is derived. Numerical examples are presented. In a special virtual creep test with the presence of plastic strain gradients, creep rates are found to diminish with the specimen size, and are also found to depend on the loading rate in an initial ramp loading step. Stress relaxation in a solid medium containing cylindrical microvoids is predicted to increase with decreasing void radius and strain rate in a prior ramp loading step.

  1. Modified Continuum Mechanics Modeling on Size-Dependent Properties of Piezoelectric Nanomaterials: A Review

    Directory of Open Access Journals (Sweden)

    Zhi Yan

    2017-01-01

    Full Text Available Piezoelectric nanomaterials (PNs are attractive for applications including sensing, actuating, energy harvesting, among others in nano-electro-mechanical-systems (NEMS because of their excellent electromechanical coupling, mechanical and physical properties. However, the properties of PNs do not coincide with their bulk counterparts and depend on the particular size. A large amount of efforts have been devoted to studying the size-dependent properties of PNs by using experimental characterization, atomistic simulation and continuum mechanics modeling with the consideration of the scale features of the nanomaterials. This paper reviews the recent progresses and achievements in the research on the continuum mechanics modeling of the size-dependent mechanical and physical properties of PNs. We start from the fundamentals of the modified continuum mechanics models for PNs, including the theories of surface piezoelectricity, flexoelectricity and non-local piezoelectricity, with the introduction of the modified piezoelectric beam and plate models particularly for nanostructured piezoelectric materials with certain configurations. Then, we give a review on the investigation of the size-dependent properties of PNs by using the modified continuum mechanics models, such as the electromechanical coupling, bending, vibration, buckling, wave propagation and dynamic characteristics. Finally, analytical modeling and analysis of nanoscale actuators and energy harvesters based on piezoelectric nanostructures are presented.

  2. Modified Continuum Mechanics Modeling on Size-Dependent Properties of Piezoelectric Nanomaterials: A Review.

    Science.gov (United States)

    Yan, Zhi; Jiang, Liying

    2017-01-26

    Piezoelectric nanomaterials (PNs) are attractive for applications including sensing, actuating, energy harvesting, among others in nano-electro-mechanical-systems (NEMS) because of their excellent electromechanical coupling, mechanical and physical properties. However, the properties of PNs do not coincide with their bulk counterparts and depend on the particular size. A large amount of efforts have been devoted to studying the size-dependent properties of PNs by using experimental characterization, atomistic simulation and continuum mechanics modeling with the consideration of the scale features of the nanomaterials. This paper reviews the recent progresses and achievements in the research on the continuum mechanics modeling of the size-dependent mechanical and physical properties of PNs. We start from the fundamentals of the modified continuum mechanics models for PNs, including the theories of surface piezoelectricity, flexoelectricity and non-local piezoelectricity, with the introduction of the modified piezoelectric beam and plate models particularly for nanostructured piezoelectric materials with certain configurations. Then, we give a review on the investigation of the size-dependent properties of PNs by using the modified continuum mechanics models, such as the electromechanical coupling, bending, vibration, buckling, wave propagation and dynamic characteristics. Finally, analytical modeling and analysis of nanoscale actuators and energy harvesters based on piezoelectric nanostructures are presented.

  3. Modified Continuum Mechanics Modeling on Size-Dependent Properties of Piezoelectric Nanomaterials: A Review

    Science.gov (United States)

    Yan, Zhi; Jiang, Liying

    2017-01-01

    Piezoelectric nanomaterials (PNs) are attractive for applications including sensing, actuating, energy harvesting, among others in nano-electro-mechanical-systems (NEMS) because of their excellent electromechanical coupling, mechanical and physical properties. However, the properties of PNs do not coincide with their bulk counterparts and depend on the particular size. A large amount of efforts have been devoted to studying the size-dependent properties of PNs by using experimental characterization, atomistic simulation and continuum mechanics modeling with the consideration of the scale features of the nanomaterials. This paper reviews the recent progresses and achievements in the research on the continuum mechanics modeling of the size-dependent mechanical and physical properties of PNs. We start from the fundamentals of the modified continuum mechanics models for PNs, including the theories of surface piezoelectricity, flexoelectricity and non-local piezoelectricity, with the introduction of the modified piezoelectric beam and plate models particularly for nanostructured piezoelectric materials with certain configurations. Then, we give a review on the investigation of the size-dependent properties of PNs by using the modified continuum mechanics models, such as the electromechanical coupling, bending, vibration, buckling, wave propagation and dynamic characteristics. Finally, analytical modeling and analysis of nanoscale actuators and energy harvesters based on piezoelectric nanostructures are presented. PMID:28336861

  4. Use of the LQ model with large fraction sizes results in underestimation of isoeffect doses

    International Nuclear Information System (INIS)

    Sheu, Tommy; Molkentine, Jessica; Transtrum, Mark K.; Buchholz, Thomas A.; Withers, Hubert Rodney; Thames, Howard D.; Mason, Kathy A.

    2013-01-01

    Purpose: To test the appropriateness of the linear-quadratic (LQ) model to describe survival of jejunal crypt clonogens after split doses with variable (small 1–6 Gy, large 8–13 Gy) first dose, as a model of its appropriateness for both small and large fraction sizes. Methods: C3Hf/KamLaw mice were exposed to whole body irradiation using 300 kVp X-rays at a dose rate of 1.84 Gy/min, and the number of viable jejunal crypts was determined using the microcolony assay. 14 Gy total dose was split into unequal first and second fractions separated by 4 h. Data were analyzed using the LQ model, the lethal potentially lethal (LPL) model, and a repair-saturation (RS) model. Results: Cell kill was greater in the group receiving the larger fraction first, creating an asymmetry in the plot of survival vs size of first dose, as opposed to the prediction of the LQ model of a symmetric response. There was a significant difference in the estimated βs (higher β after larger first doses), but no significant difference in the αs, when large doses were given first vs small doses first. This difference results in underestimation (based on present data by approximately 8%) of isoeffect doses using LQ model parameters based on small fraction sizes. While the LPL model also predicted a symmetric response inconsistent with the data, the RS model results were consistent with the observed asymmetry. Conclusion: The LQ model underestimates doses for isoeffective crypt-cell survival with large fraction sizes (in the present setting, >9 Gy)

  5. Glassy dynamics of model colloidal polymers: The effect of "monomer" size

    Science.gov (United States)

    Li, Jian; Zhang, Bo-kai; Li, Hui-shu; Chen, Kang; Tian, Wen-de; Tong, Pei-qing

    2016-05-01

    In recent years, attempts have been made to assemble colloidal particles into chains, which are termed "colloidal polymers." An apparent difference between molecular and colloidal polymers is the "monomer" size. Here, we propose a model to represent the variation from molecular polymer to colloidal polymer and study the quantitative differences in their glassy dynamics. For chains, two incompatible local length scales, i.e., monomer size and bond length, are manifested in the radial distribution function and intramolecular correlation function. The mean square displacement of monomers exhibits Rouse-like sub-diffusion at intermediate time/length scale and the corresponding exponent depends on the volume fraction and the monomer size. We find that the threshold volume fraction at which the caging regime emerges can be used as a rescaling unit so that the data of localization length versus volume fraction for different monomer sizes can gather close to an exponential curve. The increase of monomer size effectively increases the hardness of monomers and thus makes the colloidal polymers vitrify at lower volume fraction. Static and dynamic equivalences between colloidal polymers of different monomer sizes have been discussed. In the case of having the same peak time of the non-Gaussian parameter, the motion of monomers of larger size is much less non-Gaussian. The mode-coupling critical exponents for colloidal polymers are in agreement with that of flexible bead-spring chains.

  6. Does size matter? : An empirical study modifying Fama & French's three factor model to detect size-effect based on turnover in the Swedish markets

    OpenAIRE

    Boros, Daniel; Eriksson, Claes

    2014-01-01

    This thesis investigates whether the estimation of the cost of equity (or the expected return) in the Swedish market should incorporate an adjustment for a company’s size. This is what is commonly known as the size-effect, first presented by Banz (1980) and has later been a part of models for estimating cost of equity, such as Fama & French’s three factor model (1992). The Fama & French model was developed based on empirical research. Since the model was developed, the research on the...

  7. Modeling grain size variations of aeolian gypsum deposits at White Sands, New Mexico, using AVIRIS imagery

    Science.gov (United States)

    Ghrefat, H.A.; Goodell, P.C.; Hubbard, B.E.; Langford, R.P.; Aldouri, R.E.

    2007-01-01

    also show that there are no significant differences between modeled and laboratory-measured grain size values. Hyperspectral grain size modeling can help to determine dynamic processes shaping the formation of the dunes such as wind directions, and the relative strengths of winds through time. This has implications for studying such processes on other planetary landforms that have mineralogy with unique absorption bands in VNIR-SWIR hyperspectral data. ?? 2006 Elsevier B.V. All rights reserved.

  8. How does language model size effects speech recognition accuracy for the Turkish language?

    Directory of Open Access Journals (Sweden)

    Behnam ASEFİSARAY

    2016-05-01

    Full Text Available In this paper we aimed at investigating the effect of Language Model (LM size on Speech Recognition (SR accuracy. We also provided details of our approach for obtaining the LM for Turkish. Since LM is obtained by statistical processing of raw text, we expect that by increasing the size of available data for training the LM, SR accuracy will improve. Since this study is based on recognition of Turkish, which is a highly agglutinative language, it is important to find out the appropriate size for the training data. The minimum required data size is expected to be much higher than the data needed to train a language model for a language with low level of agglutination such as English. In the experiments we also tried to adjust the Language Model Weight (LMW and Active Token Count (ATC parameters of LM as these are expected to be different for a highly agglutinative language. We showed that by increasing the training data size to an appropriate level, the recognition accuracy improved on the other hand changes on LMW and ATC did not have a positive effect on Turkish speech recognition accuracy.

  9. A simulation study of sample size for multilevel logistic regression models

    Directory of Open Access Journals (Sweden)

    Moineddin Rahim

    2007-07-01

    Full Text Available Abstract Background Many studies conducted in health and social sciences collect individual level data as outcome measures. Usually, such data have a hierarchical structure, with patients clustered within physicians, and physicians clustered within practices. Large survey data, including national surveys, have a hierarchical or clustered structure; respondents are naturally clustered in geographical units (e.g., health regions and may be grouped into smaller units. Outcomes of interest in many fields not only reflect continuous measures, but also binary outcomes such as depression, presence or absence of a disease, and self-reported general health. In the framework of multilevel studies an important problem is calculating an adequate sample size that generates unbiased and accurate estimates. Methods In this paper simulation studies are used to assess the effect of varying sample size at both the individual and group level on the accuracy of the estimates of the parameters and variance components of multilevel logistic regression models. In addition, the influence of prevalence of the outcome and the intra-class correlation coefficient (ICC is examined. Results The results show that the estimates of the fixed effect parameters are unbiased for 100 groups with group size of 50 or higher. The estimates of the variance covariance components are slightly biased even with 100 groups and group size of 50. The biases for both fixed and random effects are severe for group size of 5. The standard errors for fixed effect parameters are unbiased while for variance covariance components are underestimated. Results suggest that low prevalent events require larger sample sizes with at least a minimum of 100 groups and 50 individuals per group. Conclusion We recommend using a minimum group size of 50 with at least 50 groups to produce valid estimates for multi-level logistic regression models. Group size should be adjusted under conditions where the prevalence

  10. The effect of food portion sizes on the obesity prevention using system dynamics modelling

    Science.gov (United States)

    Abidin, Norhaslinda Zainal; Zulkepli, Jafri Hj; Zaibidi, Nerda Zura

    2014-09-01

    The rise in income and population growth have increased the demand for food and induced changes in food habits, food purchasing and consumption patterns in Malaysia. With this transition, one of the plausible causes of weight gain and obesity is the frequent consumption of outside food which is synonymous with bigger portion size. Therefore, the aim of this paper is to develop a system dynamics model to analyse the effect of reducing food portion size on weight and obesity prevention. This study combines the different strands of knowledge comprise of nutrition, physical activity and body metabolism. These elements are synthesized into a system dynamics model called SIMULObese. Findings from this study suggested that changes in eating behavior should not emphasize only on limiting the food portion size consumption. The efforts should also consider other eating events such as controlling the meal frequency and limiting intake of high-calorie food in developing guidelines to prevent obesity.

  11. An Empirical Bayes Mixture Model for Effect Size Distributions in Genome-Wide Association Studies.

    Directory of Open Access Journals (Sweden)

    Wesley K Thompson

    2015-12-01

    Full Text Available Characterizing the distribution of effects from genome-wide genotyping data is crucial for understanding important aspects of the genetic architecture of complex traits, such as number or proportion of non-null loci, average proportion of phenotypic variance explained per non-null effect, power for discovery, and polygenic risk prediction. To this end, previous work has used effect-size models based on various distributions, including the normal and normal mixture distributions, among others. In this paper we propose a scale mixture of two normals model for effect size distributions of genome-wide association study (GWAS test statistics. Test statistics corresponding to null associations are modeled as random draws from a normal distribution with zero mean; test statistics corresponding to non-null associations are also modeled as normal with zero mean, but with larger variance. The model is fit via minimizing discrepancies between the parametric mixture model and resampling-based nonparametric estimates of replication effect sizes and variances. We describe in detail the implications of this model for estimation of the non-null proportion, the probability of replication in de novo samples, the local false discovery rate, and power for discovery of a specified proportion of phenotypic variance explained from additive effects of loci surpassing a given significance threshold. We also examine the crucial issue of the impact of linkage disequilibrium (LD on effect sizes and parameter estimates, both analytically and in simulations. We apply this approach to meta-analysis test statistics from two large GWAS, one for Crohn's disease (CD and the other for schizophrenia (SZ. A scale mixture of two normals distribution provides an excellent fit to the SZ nonparametric replication effect size estimates. While capturing the general behavior of the data, this mixture model underestimates the tails of the CD effect size distribution. We discuss the

  12. An Empirical Bayes Mixture Model for Effect Size Distributions in Genome-Wide Association Studies.

    Science.gov (United States)

    Thompson, Wesley K; Wang, Yunpeng; Schork, Andrew J; Witoelar, Aree; Zuber, Verena; Xu, Shujing; Werge, Thomas; Holland, Dominic; Andreassen, Ole A; Dale, Anders M

    2015-12-01

    Characterizing the distribution of effects from genome-wide genotyping data is crucial for understanding important aspects of the genetic architecture of complex traits, such as number or proportion of non-null loci, average proportion of phenotypic variance explained per non-null effect, power for discovery, and polygenic risk prediction. To this end, previous work has used effect-size models based on various distributions, including the normal and normal mixture distributions, among others. In this paper we propose a scale mixture of two normals model for effect size distributions of genome-wide association study (GWAS) test statistics. Test statistics corresponding to null associations are modeled as random draws from a normal distribution with zero mean; test statistics corresponding to non-null associations are also modeled as normal with zero mean, but with larger variance. The model is fit via minimizing discrepancies between the parametric mixture model and resampling-based nonparametric estimates of replication effect sizes and variances. We describe in detail the implications of this model for estimation of the non-null proportion, the probability of replication in de novo samples, the local false discovery rate, and power for discovery of a specified proportion of phenotypic variance explained from additive effects of loci surpassing a given significance threshold. We also examine the crucial issue of the impact of linkage disequilibrium (LD) on effect sizes and parameter estimates, both analytically and in simulations. We apply this approach to meta-analysis test statistics from two large GWAS, one for Crohn's disease (CD) and the other for schizophrenia (SZ). A scale mixture of two normals distribution provides an excellent fit to the SZ nonparametric replication effect size estimates. While capturing the general behavior of the data, this mixture model underestimates the tails of the CD effect size distribution. We discuss the implications of

  13. Finite difference approximations for measure-valued solutions of a hierarchically size-structured population model.

    Science.gov (United States)

    Ackleh, Azmy S; Chellamuthu, Vinodh K; Ito, Kazufumi

    2015-04-01

    We study a quasilinear hierarchically size-structured population model presented in [4]. In this model the growth, mortality and reproduction rates are assumed to depend on a function of the population density. In [4] we showed that solutions to this model can become singular (measure-valued) in finite time even if all the individual parameters are smooth. Therefore, in this paper we develop a first order finite difference scheme to compute these measure-valued solutions. Convergence analysis for this method is provided. We also develop a high resolution second order scheme to compute the measure-valued solution of the model and perform a comparative study between the two schemes.

  14. 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...

  15. The economic production lot size model extended to include more than one production rate

    DEFF Research Database (Denmark)

    Larsen, Christian

    2001-01-01

    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. First, we show that all production rates should be choosen in the interval...

  16. Mathematical model for sizing combined nitrification and pre-denitrification activated sludge systems

    NARCIS (Netherlands)

    Esposito, G.; Fabbricino, M.; Lens, P.N.L.; Pirozzi, F.

    2007-01-01

    Two mathematical steady-state models for sizing single activated sludge systems aimed at nitrogen and organics removal from wastewater are proposed. The attention is focused on the combined nitrification system and the pre-denitrification system, considering three (soluble and particulate

  17. Sufficient Sample Sizes for Discrete-Time Survival Analysis Mixture Models

    NARCIS (Netherlands)

    Moerbeek, Mirjam

    2014-01-01

    Long-term survivors in trials with survival endpoints are subjects who will not experience the event of interest. Membership in the class of long-term survivors is unobserved and should be inferred from the data by means of a mixture model. An important question is how large the sample size should

  18. Multiscale computational modeling of size effects in carbon nanotube-polymer composites

    NARCIS (Netherlands)

    Malagu, M.

    2017-01-01

    The development of carbon nanotube(CNT)-polymer composites advocates for a better understanding of their physical and mechanical properties that depend on the diameter of the embedded CNTs. Given that the experimental assessment of size effects is extremely difficult, the use of numerical models can

  19. Modelling Visual Quality of Kalanchoe Blossfeldiana: Influence of Cultivar and Pot Size

    NARCIS (Netherlands)

    Carvalho, S.M.P.; Almeida, J.; Eveleens-Clark, B.A.; Bakker, M.J.; Heuvelink, E.

    2008-01-01

    An explanatory model for predicting kalanchoe plant height and cropping duration has been developed for one cultivar and one pot size, as described in earlier papers. In two experiments (winter and summer) seven contrasting cultivars (`Anatole¿, `Debbie¿, `Delia¿, `Mie¿, `Pandora¿, `Tenorio¿ and

  20. Virus-sized colloid transport in a single pore: Model development and sensitivity analysis

    NARCIS (Netherlands)

    Seetha, N.; Mohan Kumar, M.S.; Hassanizadeh, S.M.; Raoof, A.

    2014-01-01

    A mathematical model is developed to simulate the transport and deposition of virus-sized colloids in a cylindrical pore throat considering various processes such as advection, diffusion, colloid–collector surface interactions and hydrodynamic wall effects. The pore space is divided into three

  1. Multivariate Effect Size Estimation: Confidence Interval Construction via Latent Variable Modeling

    Science.gov (United States)

    Raykov, Tenko; Marcoulides, George A.

    2010-01-01

    A latent variable modeling method is outlined for constructing a confidence interval (CI) of a popular multivariate effect size measure. The procedure uses the conventional multivariate analysis of variance (MANOVA) setup and is applicable with large samples. The approach provides a population range of plausible values for the proportion of…

  2. Floc size distributions of suspended kaolinite in an advection transport dominated tank: measurements and modeling

    Science.gov (United States)

    Shen, Xiaoteng; Maa, Jerome P.-Y.

    2017-11-01

    In estuaries and coastal waters, floc size and its statistical distributions of cohesive sediments are of primary importance, due to their effects on the settling velocity and thus deposition rates of cohesive aggregates. The development of a robust flocculation model that includes the predictions of floc size distributions (FSDs), however, is still in a research stage. In this study, a one-dimensional longitudinal (1-DL) flocculation model along a streamtube is developed. This model is based on solving the population balance equation to find the FSDs by using the quadrature method of moments. To validate this model, a laboratory experiment is carried out to produce an advection transport-dominant environment in a cylindrical tank. The flow field is generated by a marine pump mounted at the bottom center, with its outlet facing upward. This setup generates an axially symmetric flow which is measured by an acoustic Doppler velocimeter (ADV). The measurement results provide the hydrodynamic input data required for this 1-DL model. The other measurement results, the FSDs, are acquired by using an automatic underwater camera system and the resulting images are analyzed to validate the predicted FSDs. This study shows that the FSDs as well as their representative sizes can be efficiently and reasonably simulated by this 1-DL model.

  3. A socio-hydrologic model of coupled water-agriculture dynamics with emphasis on farm size.

    Science.gov (United States)

    Brugger, D. R.; Maneta, M. P.

    2015-12-01

    Agricultural land cover dynamics in the U.S. are dominated by two trends: 1) total agricultural land is decreasing and 2) average farm size is increasing. These trends have important implications for the future of water resources because 1) growing more food on less land is due in large part to increased groundwater withdrawal and 2) larger farms can better afford both more efficient irrigation and more groundwater access. However, these large-scale trends are due to individual farm operators responding to many factors including climate, economics, and policy. It is therefore difficult to incorporate the trends into watershed-scale hydrologic models. Traditional scenario-based approaches are valuable for many applications, but there is typically no feedback between the hydrologic model and the agricultural dynamics and so limited insight is gained into the how agriculture co-evolves with water resources. We present a socio-hydrologic model that couples simplified hydrologic and agricultural economic dynamics, accounting for many factors that depend on farm size such as irrigation efficiency and returns to scale. We introduce an "economic memory" (EM) state variable that is driven by agricultural revenue and affects whether farms are sold when land market values exceed expected returns from agriculture. The model uses a Generalized Mixture Model of Gaussians to approximate the distribution of farm sizes in a study area, effectively lumping farms into "small," "medium," and "large" groups that have independent parameterizations. We apply the model in a semi-arid watershed in the upper Columbia River Basin, calibrating to data on streamflow, total agricultural land cover, and farm size distribution. The model is used to investigate the sensitivity of the coupled system to various hydrologic and economic scenarios such as increasing market value of land, reduced surface water availability, and increased irrigation efficiency in small farms.

  4. Nature of size effects in compact models of field effect transistors

    Energy Technology Data Exchange (ETDEWEB)

    Torkhov, N. A., E-mail: trkf@mail.ru [Tomsk State University, Tomsk 634050 (Russian Federation); Scientific-Research Institute of Semiconductor Devices, Tomsk 634050 (Russian Federation); Tomsk State University of Control Systems and Radioelectronics, Tomsk 634050 (Russian Federation); Babak, L. I.; Kokolov, A. A.; Salnikov, A. S.; Dobush, I. M. [Tomsk State University of Control Systems and Radioelectronics, Tomsk 634050 (Russian Federation); Novikov, V. A., E-mail: novikovvadim@mail.ru; Ivonin, I. V. [Tomsk State University, Tomsk 634050 (Russian Federation)

    2016-03-07

    Investigations have shown that in the local approximation (for sizes L < 100 μm), AlGaN/GaN high electron mobility transistor (HEMT) structures satisfy to all properties of chaotic systems and can be described in the language of fractal geometry of fractional dimensions. For such objects, values of their electrophysical characteristics depend on the linear sizes of the examined regions, which explain the presence of the so-called size effects—dependences of the electrophysical and instrumental characteristics on the linear sizes of the active elements of semiconductor devices. In the present work, a relationship has been established for the linear model parameters of the equivalent circuit elements of internal transistors with fractal geometry of the heteroepitaxial structure manifested through a dependence of its relative electrophysical characteristics on the linear sizes of the examined surface areas. For the HEMTs, this implies dependences of their relative static (A/mm, mA/V/mm, Ω/mm, etc.) and microwave characteristics (W/mm) on the width d of the sink-source channel and on the number of sections n that leads to a nonlinear dependence of the retrieved parameter values of equivalent circuit elements of linear internal transistor models on n and d. Thus, it has been demonstrated that the size effects in semiconductors determined by the fractal geometry must be taken into account when investigating the properties of semiconductor objects on the levels less than the local approximation limit and designing and manufacturing field effect transistors. In general, the suggested approach allows a complex of problems to be solved on designing, optimizing, and retrieving the parameters of equivalent circuits of linear and nonlinear models of not only field effect transistors but also any arbitrary semiconductor devices with nonlinear instrumental characteristics.

  5. A thermo dynamical model for the shape and size effect on melting of boron carbide nanoparticles.

    Science.gov (United States)

    Antoniammal, Paneerselvam; Arivuoli, Dakshanamoorthy

    2012-02-01

    The size and shape dependence of the melting temperature of Boron Carbide (B4C) nanoparticles has been investigated with a numerical thermo dynamical approach. The problem considered in this paper is the inward melting of nanoparticles with spherical and cylindrical geometry. The cylindrical Boron Carbide (B4C) nanoparticles, whose melting point has been reported to decrease with decreasing particle radius, become larger than spherical shaped nanoparticle. Comparative investigation of the size dependence of the melting temperature with respect to the two shapes is also been done. The melting temperature obtained in the present study is approximately a dealing function of radius, in a good agreement with prediction of thermo dynamical model.

  6. Sensitivity in reflectance attributed to phytoplankton cell size: forward and inverse modelling approaches

    CSIR Research Space (South Africa)

    Evers-King, H

    2014-05-01

    Full Text Available ocean colour products To put these results in to the context of current ocean colour products, Fig. 5 shows an approx- imation of the maximum band ratio (MBR) approach used in the OC4 algorithm [37] using forward model output (ES) analogous to the data...], suggesting that variability in a∗φ (in our case, coincident with changes in size) may be obscured by agd , particularly at lower biomass, where the majority of the size related signal occurs in the blue and MBR approaches are typically applied (Fig. 1). Sauer...

  7. Chemical modelling of Alkali Silica reaction: Influence of the reactive aggregate size distribution

    International Nuclear Information System (INIS)

    Poyet, S.; Sellier, A.; Capra, B.; Foray, G.; Torrenti, J.M.; Cognon, H.; Bourdarot, E.

    2007-01-01

    This article presents a new model which aims at predicting the expansion induced by Alkali Silica Reaction (ASR) and describing the chemical evolution of affected concretes. It is based on the description of the transport and reaction of alkalis and calcium ions within a Relative Elementary Volume (REV). It takes into account the influence of the reactive aggregate size grading on ASR, i.e. the effect of the simultaneous presence of different sized reactive aggregates within concrete. The constitutive equations are detailed and fitted using experimental results. Results from numerical simulations are presented and compared with experiments. (authors)

  8. Model for evolution of grain size in the rim region of high burnup UO2 fuel

    Science.gov (United States)

    Xiao, Hongxing; Long, Chongsheng; Chen, Hongsheng

    2016-04-01

    The restructuring process of the high burnup structure (HBS) formation in UO2 fuel results in sub-micron size grains that accelerate the fission gas swelling, which will raise some concern over the safety of extended the nuclear fuel operation life in the reactor. A mechanistic and engineering model for evolution of grain size in the rim region of high burnup UO2 fuel based on the experimental observations of the HBS in the literature is presented. The model takes into account dislocations evolution under irradiation and the grain subdivision occur successively at increasing local burnup. It is assumed that the original driving force for subdivision of grain in the HBS of UO2 fuel is the production and accumulation of dislocation loops during irradiation. The dislocation loops can also be annealed through thermal diffusion when the temperature is high enough. The capability of this model is validated by the comparison with the experimental data of temperature threshold of subdivision, dislocation density and sub-grain size as a function of local burnup. It is shown that the calculated results of the dislocation density and subdivided grain size as a function of local burnup are in good agreement with the experimental results.

  9. Sensitivity of Population Size Estimation for Violating Parametric Assumptions in Log-linear Models

    Directory of Open Access Journals (Sweden)

    Gerritse Susanna C.

    2015-09-01

    Full Text Available An important quality aspect of censuses is the degree of coverage of the population. When administrative registers are available undercoverage can be estimated via capture-recapture methodology. The standard approach uses the log-linear model that relies on the assumption that being in the first register is independent of being in the second register. In models using covariates, this assumption of independence is relaxed into independence conditional on covariates. In this article we describe, in a general setting, how sensitivity analyses can be carried out to assess the robustness of the population size estimate. We make use of log-linear Poisson regression using an offset, to simulate departure from the model. This approach can be extended to the case where we have covariates observed in both registers, and to a model with covariates observed in only one register. The robustness of the population size estimate is a function of implied coverage: as implied coverage is low the robustness is low. We conclude that it is important for researchers to investigate and report the estimated robustness of their population size estimate for quality reasons. Extensions are made to log-linear modeling in case of more than two registers and the multiplier method

  10. Adsorption of diclofenac and nimesulide on activated carbon: Statistical physics modeling and effect of adsorbate size

    Science.gov (United States)

    Sellaoui, Lotfi; Mechi, Nesrine; Lima, Éder Cláudio; Dotto, Guilherme Luiz; Ben Lamine, Abdelmottaleb

    2017-10-01

    Based on statistical physics elements, the equilibrium adsorption of diclofenac (DFC) and nimesulide (NM) on activated carbon was analyzed by a multilayer model with saturation. The paper aimed to describe experimentally and theoretically the adsorption process and study the effect of adsorbate size using the model parameters. From numerical simulation, the number of molecules per site showed that the adsorbate molecules (DFC and NM) were mostly anchored in both sides of the pore walls. The receptor sites density increase suggested that additional sites appeared during the process, to participate in DFC and NM adsorption. The description of the adsorption energy behavior indicated that the process was physisorption. Finally, by a model parameters correlation, the size effect of the adsorbate was deduced indicating that the molecule dimension has a negligible effect on the DFC and NM adsorption.

  11. Fourth-Order Method for Numerical Integration of Age- and Size-Structured Population Models

    Energy Technology Data Exchange (ETDEWEB)

    Iannelli, M; Kostova, T; Milner, F A

    2008-01-08

    In many applications of age- and size-structured population models, there is an interest in obtaining good approximations of total population numbers rather than of their densities. Therefore, it is reasonable in such cases to solve numerically not the PDE model equations themselves, but rather their integral equivalents. For this purpose quadrature formulae are used in place of the integrals. Because quadratures can be designed with any order of accuracy, one can obtain numerical approximations of the solutions with very fast convergence. In this article, we present a general framework and a specific example of a fourth-order method based on composite Newton-Cotes quadratures for a size-structured population model.

  12. Finite size scaling study of a two parameter percolation model: Constant and correlated growth

    Science.gov (United States)

    Roy, Bappaditya; Santra, S. B.

    2018-02-01

    A new percolation model of enhanced parameter space with nucleation and growth is developed taking the initial seed concentration ρ and a growth parameter g as two tunable parameters. Percolation transition is determined by the final static configurations of spanning clusters once taking uniform growth probability for all the clusters and then taking a cluster size dependent dynamic growth probability. The uniform growth probability remains constant over time and leads to a constant growth model whereas the dynamically varying growth probability leads to a correlated growth model. In the first case, the growth of a cluster will encounter partial hindrance due to the presence of other clusters whereas in the second case the growth of a larger cluster will be further suppressed in comparison to the growth of smaller clusters. A finite size scaling theory for percolation transition is developed and numerically verified for both the models. The scaling functions are found to depend on both g and ρ. At the critical growth parameter gc, the values of the critical exponents are found to be same as that of the original percolation at all values of ρ for the constant growth model whereas in the case of correlated growth model the scaling behavior deviates from ordinary percolation in the dilute limit of ρ. The constant growth model then belongs to the same universality class of percolation for a wide range of ρ whereas the correlated growth model displays a continuously varying universality class as ρ decreases towards zero.

  13. Multi-objective analytical model for optimal sizing of stand-alone photovoltaic water pumping systems

    International Nuclear Information System (INIS)

    Olcan, Ceyda

    2015-01-01

    Highlights: • An analytical optimal sizing model is proposed for PV water pumping systems. • The objectives are chosen as deficiency of power supply and life-cycle costs. • The crop water requirements are estimated for a citrus tree yard in Antalya. • The optimal tilt angles are calculated for fixed, seasonal and monthly changes. • The sizing results showed the validity of the proposed analytical model. - Abstract: Stand-alone photovoltaic (PV) water pumping systems effectively use solar energy for irrigation purposes in remote areas. However the random variability and unpredictability of solar energy makes difficult the penetration of PV implementations and complicate the system design. An optimal sizing of these systems proves to be essential. This paper recommends a techno-economic optimization model to determine optimally the capacity of the components of PV water pumping system using a water storage tank. The proposed model is developed regarding the reliability and cost indicators, which are the deficiency of power supply probability and life-cycle costs, respectively. The novelty is that the proposed optimization model is analytically defined for two-objectives and it is able to find a compromise solution. The sizing of a stand-alone PV water pumping system comprises a detailed analysis of crop water requirements and optimal tilt angles. Besides the necessity of long solar radiation and temperature time series, the accurate forecasts of water supply needs have to be determined. The calculation of the optimal tilt angle for yearly, seasonally and monthly frequencies results in higher system efficiency. It is, therefore, suggested to change regularly the tilt angle in order to maximize solar energy output. The proposed optimal sizing model incorporates all these improvements and can accomplish a comprehensive optimization of PV water pumping systems. A case study is conducted considering the irrigation of citrus trees yard located in Antalya, Turkey

  14. Model of tooth morphogenesis predicts carabelli cusp expression, size, and symmetry in humans.

    Directory of Open Access Journals (Sweden)

    John P Hunter

    Full Text Available BACKGROUND: The patterning cascade model of tooth morphogenesis accounts for shape development through the interaction of a small number of genes. In the model, gene expression both directs development and is controlled by the shape of developing teeth. Enamel knots (zones of nonproliferating epithelium mark the future sites of cusps. In order to form, a new enamel knot must escape the inhibitory fields surrounding other enamel knots before crown components become spatially fixed as morphogenesis ceases. Because cusp location on a fully formed tooth reflects enamel knot placement and tooth size is limited by the cessation of morphogenesis, the model predicts that cusp expression varies with intercusp spacing relative to tooth size. Although previous studies in humans have supported the model's implications, here we directly test the model's predictions for the expression, size, and symmetry of Carabelli cusp, a variation present in many human populations. METHODOLOGY/PRINCIPAL FINDINGS: In a dental cast sample of upper first molars (M1s (187 rights, 189 lefts, and 185 antimeric pairs, we measured tooth area and intercusp distances with a Hirox digital microscope. We assessed Carabelli expression quantitatively as an area in a subsample and qualitatively using two typological schemes in the full sample. As predicted, low relative intercusp distance is associated with Carabelli expression in both right and left samples using either qualitative or quantitative measures. Furthermore, asymmetry in Carabelli area is associated with asymmetry in relative intercusp spacing. CONCLUSIONS/SIGNIFICANCE: These findings support the model's predictions for Carabelli cusp expression both across and within individuals. By comparing right-left pairs of the same individual, our data show that small variations in developmental timing or spacing of enamel knots can influence cusp pattern independently of genotype. Our findings suggest that during evolution new cusps

  15. Model of Tooth Morphogenesis Predicts Carabelli Cusp Expression, Size, and Symmetry in Humans

    Science.gov (United States)

    Hunter, John P.; Guatelli-Steinberg, Debbie; Weston, Theresia C.; Durner, Ryan; Betsinger, Tracy K.

    2010-01-01

    Background The patterning cascade model of tooth morphogenesis accounts for shape development through the interaction of a small number of genes. In the model, gene expression both directs development and is controlled by the shape of developing teeth. Enamel knots (zones of nonproliferating epithelium) mark the future sites of cusps. In order to form, a new enamel knot must escape the inhibitory fields surrounding other enamel knots before crown components become spatially fixed as morphogenesis ceases. Because cusp location on a fully formed tooth reflects enamel knot placement and tooth size is limited by the cessation of morphogenesis, the model predicts that cusp expression varies with intercusp spacing relative to tooth size. Although previous studies in humans have supported the model's implications, here we directly test the model's predictions for the expression, size, and symmetry of Carabelli cusp, a variation present in many human populations. Methodology/Principal Findings In a dental cast sample of upper first molars (M1s) (187 rights, 189 lefts, and 185 antimeric pairs), we measured tooth area and intercusp distances with a Hirox digital microscope. We assessed Carabelli expression quantitatively as an area in a subsample and qualitatively using two typological schemes in the full sample. As predicted, low relative intercusp distance is associated with Carabelli expression in both right and left samples using either qualitative or quantitative measures. Furthermore, asymmetry in Carabelli area is associated with asymmetry in relative intercusp spacing. Conclusions/Significance These findings support the model's predictions for Carabelli cusp expression both across and within individuals. By comparing right-left pairs of the same individual, our data show that small variations in developmental timing or spacing of enamel knots can influence cusp pattern independently of genotype. Our findings suggest that during evolution new cusps may first appear as

  16. Comprehensive Laser-induced Incandescence (LII) modeling for soot particle sizing

    KAUST Repository

    Lisanti, Joel

    2015-03-30

    To evaluate the current state of the art in LII particle sizing, a comprehensive model for predicting the temporal incandescent response of combustion-generated soot to absorption of a pulsed laser is presented. The model incorporates particle heating through laser absorption, thermal annealing, and oxidation at the surface as well as cooling through sublimation and photodesorption, radiation, conduction and thermionic emission. Thermodynamic properties and the thermal accommodation coefficient utilized in the model are temperature dependent. In addition, where appropriate properties are also phase dependent, thereby accounting for annealing effects during laser heating and particle cooling.

  17. Large Time Asymptotics for a Continuous Coagulation-Fragmentation Model with Degenerate Size-Dependent Diffusion

    KAUST Repository

    Desvillettes, Laurent

    2010-01-01

    We study a continuous coagulation-fragmentation model with constant kernels for reacting polymers (see [M. Aizenman and T. Bak, Comm. Math. Phys., 65 (1979), pp. 203-230]). The polymers are set to diffuse within a smooth bounded one-dimensional domain with no-flux boundary conditions. In particular, we consider size-dependent diffusion coefficients, which may degenerate for small and large cluster-sizes. We prove that the entropy-entropy dissipation method applies directly in this inhomogeneous setting. We first show the necessary basic a priori estimates in dimension one, and second we show faster-than-polynomial convergence toward global equilibria for diffusion coefficients which vanish not faster than linearly for large sizes. This extends the previous results of [J.A. Carrillo, L. Desvillettes, and K. Fellner, Comm. Math. Phys., 278 (2008), pp. 433-451], which assumes that the diffusion coefficients are bounded below. © 2009 Society for Industrial and Applied Mathematics.

  18. Modelling size structured food webs using a modified niche model with two predator traits

    Czech Academy of Sciences Publication Activity Database

    Klečka, Jan

    2014-01-01

    Roč. 9, č. 8 (2014), e99355 E-ISSN 1932-6203 Grant - others:GA JU(CZ) 145/2010/P Institutional support: RVO:60077344 Keywords : body-size * ecological networks * stability Subject RIV: EH - Ecology, Behaviour Impact factor: 3.234, year: 2014 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4137999/pdf/pone.0099355.pdf

  19. Development and application of an aerosol screening model for size-resolved urban aerosols.

    Science.gov (United States)

    Stanier, Charles O; Lee, Sang-Rin

    2014-06-01

    Predictive models of vehicular ultrafine particles less than 0.1 microm in diameter (UFPs*) and other urban pollutants with high spatial and temporal variation are useful and important in applications such as (1) decision support for infrastructure projects, emissions controls, and transportation-mode shifts; (2) the interpretation and enhancement of observations (e.g., source apportionment, extrapolation, interpolation, and gap-filling in space and time); and (3) the generation of spatially and temporally resolved exposure estimates where monitoring is unfeasible. The objective of the current study was to develop, test, and apply the Aerosol Screening Model (ASM), a new physically based vehicular UFP model for use in near-road environments. The ASM simulates hourly average outdoor concentrations of roadway-derived aerosols and gases. Its distinguishing features include user-specified spatial resolution; use of the Weather Research and Forecasting (WRF) meteorologic model for winds estimates; use of a database of more than 100,000 road segments in the Los Angeles, California, region, including freeway ramps and local streets; and extensive testing against more than 9000 hours of observed particle concentrations at 11 sites. After initialization of air parcels at an upwind boundary, the model solves for vehicle emissions, dispersion, coagulation, and deposition using a Lagrangian modeling framework. The Lagrangian parcel of air is subdivided vertically (into 11 levels) and in the crosswind direction (into 3 parcels). It has overall dimensions of 10 m (downwind), 300 m (vertically), and 2.1 km (crosswind). The simulation is typically started 4 km upwind from the receptor, that is, the location at which the exposure is to be estimated. As parcels approach the receptor, depending on the user-specified resolution, step size is decreased, and crosswind resolution is enhanced through subdivision of parcels in the crosswind direction. Hourly concentrations and size

  20. Investigating the Minimum Size of Study Area for an Activity-Based Travel Demand Forecasting Model

    Directory of Open Access Journals (Sweden)

    Qiong Bao

    2015-01-01

    Full Text Available Nowadays, considerable attention has been paid to the activity-based approach for transportation planning and forecasting by both researchers and practitioners. However, one of the practical limitations of applying most of the currently available activity-based models is their computation time, especially when large amount of population and detailed geographical unit level are taken into account. In this research, we investigated the possibility of restraining the size of the study area in order to reduce the computation time when applying an activity-based model, as it is often the case that only a small territory rather than the whole region is the focus of a specific study. By introducing an accuracy level of the model, we proposed in this research an iteration approach to determine the minimum size of the study area required for a target territory. In the application, we investigated the required minimum size of the study area surrounding each of the 327 municipalities in Flanders, Belgium, with regard to two different transport modes, that is, car as driver and public transport. Afterwards, a validation analysis and a case study were conducted. All the experiments were carried out by using the FEATHERS, an activity-based microsimulation modeling framework currently implemented for the Flanders region of Belgium.

  1. Effects of Prepolymerized Particle Size and Polymerization Kinetics on Volumetric Shrinkage of Dental Modeling Resins

    Directory of Open Access Journals (Sweden)

    Tae-Yub Kwon

    2014-01-01

    Full Text Available Dental modeling resins have been developed for use in areas where highly precise resin structures are needed. The manufacturers claim that these polymethyl methacrylate/methyl methacrylate (PMMA/MMA resins show little or no shrinkage after polymerization. This study examined the polymerization shrinkage of five dental modeling resins as well as one temporary PMMA/MMA resin (control. The morphology and the particle size of the prepolymerized PMMA powders were investigated by scanning electron microscopy and laser diffraction particle size analysis, respectively. Linear polymerization shrinkage strains of the resins were monitored for 20 minutes using a custom-made linometer, and the final values (at 20 minutes were converted into volumetric shrinkages. The final volumetric shrinkage values for the modeling resins were statistically similar (P>0.05 or significantly larger (P<0.05 than that of the control resin and were related to the polymerization kinetics (P<0.05 rather than the PMMA bead size (P=0.335. Therefore, the optimal control of the polymerization kinetics seems to be more important for producing high-precision resin structures rather than the use of dental modeling resins.

  2. A Simple Size Effect Model for Tension Perpendicular to the Grain

    DEFF Research Database (Denmark)

    Pedersen, M. U.; Clorius, Christian Odin; Damkilde, Lars

    2003-01-01

    The strength in tension perpendicular to the grain is known to decrease with an increase in the stressed volume. Usually this size effect is explained on a stochastic basis, that is, an explanation relying on the increased probability of encountering a strength reducing flaw when the volume of th...... on a deterministic basis. Arguments for such a simple deterministic explanation of size effect is found in finite element modelling, using the orthotropic stiffness characteristics in the transverse plane of wood.......The strength in tension perpendicular to the grain is known to decrease with an increase in the stressed volume. Usually this size effect is explained on a stochastic basis, that is, an explanation relying on the increased probability of encountering a strength reducing flaw when the volume...... of the material under stress is increased. This paper presents an experimental investigation on specimens with a well-defined structural orientation of the material. The experiments exhibit a large size effect and the nature of the failures encountered suggests that the size effect can be explained...

  3. Heap Leaching of Caliche Ore. Modeling of a Multicomponent System with Particle Size Distribution

    Directory of Open Access Journals (Sweden)

    Javier I. Ordóñez

    2017-09-01

    Full Text Available Caliche is a mineral exploited in northern Chile, from which iodine and Nitrate salts (saltpeter are obtained. This ore is the most important source of iodine in the world and is processed mainly by heap leaching using water as a leaching agent. Heap leaching of caliche ore is carried out by the stacking of ROM (Run-Of-Mine material, where the particle size distribution covers a wide range, from a few millimeters up to several decimeters, even diameters about 1 m. During the leaching, the multiple soluble species of caliche, which can reach total fractions larger than 40%, are dissolved at different rates, mainly controlled by their solubilities. When it occurs and unlike most other leachable ores, the particle size diminishes. The leaching modeling of several soluble species of caliche has been recently addressed; however, one of the main assumptions is the idealization that the heap is composed of particles of the same size. The present work aims to complement the previously formulated phenomenological models for caliche ore leaching, through a model that considers the simultaneous dissolution of two species from caliche with three different particle sizes. These two water-soluble species have different solubilities and dissolution rates and the conceptual model considers that both species are dissolved at the particle surface. When the most soluble species is being depleted, the particle collapses, leaving a remaining fraction of the less soluble species together with insoluble material. The less soluble species is now being dissolved from the collapsed material. This article also includes the experimental verification of the conceptual model using data obtained from column leaching tests conducted for this purpose, focusing on the dissolution of two soluble species: Nitrate and Magnesium.

  4. Modeling of correlated data with informative cluster sizes: An evaluation of joint modeling and within-cluster resampling approaches.

    Science.gov (United States)

    Zhang, Bo; Liu, Wei; Zhang, Zhiwei; Qu, Yanping; Chen, Zhen; Albert, Paul S

    2017-08-01

    Joint modeling and within-cluster resampling are two approaches that are used for analyzing correlated data with informative cluster sizes. Motivated by a developmental toxicity study, we examined the performances and validity of these two approaches in testing covariate effects in generalized linear mixed-effects models. We show that the joint modeling approach is robust to the misspecification of cluster size models in terms of Type I and Type II errors when the corresponding covariates are not included in the random effects structure; otherwise, statistical tests may be affected. We also evaluate the performance of the within-cluster resampling procedure and thoroughly investigate the validity of it in modeling correlated data with informative cluster sizes. We show that within-cluster resampling is a valid alternative to joint modeling for cluster-specific covariates, but it is invalid for time-dependent covariates. The two methods are applied to a developmental toxicity study that investigated the effect of exposure to diethylene glycol dimethyl ether.

  5. Modeling the light-travel-time effect on the far-infrared size of IRC +10216

    Science.gov (United States)

    Wright, Edward L.; Baganoff, Frederick K.

    1995-01-01

    Models of the far-infrared emission from the large circumstellar dust envelope surrounding the carbon star IRC +10216 are used to assess the importance of the light-travel-time effect (LTTE) on the observed size of the source. The central star is a long-period variable with an average period of 644 +/- 17 days and a peak-to-peak amplitude of two magnituds, so a large light-travel-time effect is seen at 1 min radius. An attempt is made to use the LTTE to reconcile the discrepancy between the observations of Fazio et al. and Lester et al. regarding the far-infrared source size. This discrepancy is reviewed in light of recent, high-spatial-resolution observations at 11 microns by Danchi et al. We conclude that IRC +10216 has been resolved on the arcminute scale by Fazio et al. Convolution of the model intensity profile at 61 microns with the 60 sec x 90 sec Gaussian beam of Fazio et al. yields an observed source size full width at half maximum (FWHM) that ranges from approximately 67 sec to 75 sec depending on the phase of the star and the assumed distance to the source. Using a simple r(exp -2) dust distribution and the 106 deg phase of the Fazio et al. observations, the LTTE model reaches a peak size of 74.3 sec at a distance of 300 pc. This agrees favorably with the 78 sec x 6 sec size measured by Fazio et al. Finally, a method is outlined for using the LTTE as a distance indicator to IRC +10216 and other stars with extended mass outflows.

  6. Characteristic size and mass of galaxies in the Bose–Einstein condensate dark matter model

    Directory of Open Access Journals (Sweden)

    Jae-Weon Lee

    2016-05-01

    Full Text Available We study the characteristic length scale of galactic halos in the Bose–Einstein condensate (or scalar field dark matter model. Considering the evolution of the density perturbation we show that the average background matter density determines the quantum Jeans mass and hence the spatial size of galaxies at a given epoch. In this model the minimum size of galaxies increases while the minimum mass of the galaxies decreases as the universe expands. The observed values of the mass and the size of the dwarf galaxies are successfully reproduced with the dark matter particle mass m≃5×10−22 eV. The minimum size is about 6×10−3m/Hλc and the typical rotation velocity of the dwarf galaxies is O(H/m c, where H is the Hubble parameter and λc is the Compton wave length of the particle. We also suggest that ultra compact dwarf galaxies are the remnants of the dwarf galaxies formed in the early universe.

  7. Modelling size and structure of nanoparticles formed from drying of submicron solution aerosols

    Energy Technology Data Exchange (ETDEWEB)

    Bandyopadhyay, Arpan A.; Pawar, Amol A.; Venkataraman, Chandra; Mehra, Anurag, E-mail: mehra@iitb.ac.in [Indian Institute of Technology Bombay, Department of Chemical Engineering (India)

    2015-01-15

    Drying of submicron solution aerosols, under controlled conditions, has been explored to prepare nanoparticles for drug delivery applications. A computational model of solution drop evaporation is developed to study the evolution of solute gradients inside the drop and predict the size and shell thickness of precipitating nanoparticles. The model considers evaporation as a two-stage process involving droplet shrinkage and shell growth. It was corroborated that droplet evaporation rate controls the solute distribution within a droplet and the resulting particle structure (solid or shell type). At higher gas temperatures, rapid build-up of solute near drop surface from high evaporation rates results in early attainment of critical supersaturation solubility and a steeper solute gradient, which favours formation of larger, shell-type particles. At lower gas temperatures, formation of smaller, solid nanoparticles is indicated. The computed size and shell thickness are in good agreement with experimentally prepared lipid nanoparticles. This study indicates that solid or shell structure of precipitated nanoparticles is strongly affected by evaporation rate, while initial solute concentration in the precursor solution and atomized droplet size affect shell thickness. For the gas temperatures considered, evaporative cooling leads to droplet temperature below the melting point of the lipid solute. Thus, we conclude that control over nanoparticle size and structure, of thermolabile precursor materials suitable for drug delivery, can be achieved by controlling evaporation rates, through selection of aerosol processing conditions.

  8. A variational constitutive model for the distribution and interactions of multi-sized voids

    KAUST Repository

    Liu, Jinxing

    2013-07-29

    The evolution of defects or voids, generally recognized as the basic failure mechanism in most metals and alloys, has been intensively studied. Most investigations have been limited to spatially periodic cases with non-random distributions of the radii of the voids. In this study, we use a new form of the incompressibility of the matrix to propose the formula for the volumetric plastic energy of a void inside a porous medium. As a consequence, we are able to account for the weakening effect of the surrounding voids and to propose a general model for the distribution and interactions of multi-sized voids. We found that the single parameter in classical Gurson-type models, namely void volume fraction is not sufficient for the model. The relative growth rates of voids of different sizes, which can in principle be obtained through physical or numerical experiments, are required. To demonstrate the feasibility of the model, we analyze two cases. The first case represents exactly the same assumption hidden in the classical Gurson\\'s model, while the second embodies the competitive mechanism due to void size differences despite in a much simpler manner than the general case. Coalescence is implemented by allowing an accelerated void growth after an empirical critical porosity in a way that is the same as the Gurson-Tvergaard-Needleman model. The constitutive model presented here is validated through good agreements with experimental data. Its capacity for reproducing realistic failure patterns is shown by simulating a tensile test on a notched round bar. © 2013 The Author(s).

  9. A simple approach to power and sample size calculations in logistic regression and Cox regression models.

    Science.gov (United States)

    Vaeth, Michael; Skovlund, Eva

    2004-06-15

    For a given regression problem it is possible to identify a suitably defined equivalent two-sample problem such that the power or sample size obtained for the two-sample problem also applies to the regression problem. For a standard linear regression model the equivalent two-sample problem is easily identified, but for generalized linear models and for Cox regression models the situation is more complicated. An approximately equivalent two-sample problem may, however, also be identified here. In particular, we show that for logistic regression and Cox regression models the equivalent two-sample problem is obtained by selecting two equally sized samples for which the parameters differ by a value equal to the slope times twice the standard deviation of the independent variable and further requiring that the overall expected number of events is unchanged. In a simulation study we examine the validity of this approach to power calculations in logistic regression and Cox regression models. Several different covariate distributions are considered for selected values of the overall response probability and a range of alternatives. For the Cox regression model we consider both constant and non-constant hazard rates. The results show that in general the approach is remarkably accurate even in relatively small samples. Some discrepancies are, however, found in small samples with few events and a highly skewed covariate distribution. Comparison with results based on alternative methods for logistic regression models with a single continuous covariate indicates that the proposed method is at least as good as its competitors. The method is easy to implement and therefore provides a simple way to extend the range of problems that can be covered by the usual formulas for power and sample size determination. Copyright 2004 John Wiley & Sons, Ltd.

  10. A Markov model for the temporal dynamics of balanced random networks of finite size

    Science.gov (United States)

    Lagzi, Fereshteh; Rotter, Stefan

    2014-01-01

    The balanced state of recurrent networks of excitatory and inhibitory spiking neurons is characterized by fluctuations of population activity about an attractive fixed point. Numerical simulations show that these dynamics are essentially nonlinear, and the intrinsic noise (self-generated fluctuations) in networks of finite size is state-dependent. Therefore, stochastic differential equations with additive noise of fixed amplitude cannot provide an adequate description of the stochastic dynamics. The noise model should, rather, result from a self-consistent description of the network dynamics. Here, we consider a two-state Markovian neuron model, where spikes correspond to transitions from the active state to the refractory state. Excitatory and inhibitory input to this neuron affects the transition rates between the two states. The corresponding nonlinear dependencies can be identified directly from numerical simulations of networks of leaky integrate-and-fire neurons, discretized at a time resolution in the sub-millisecond range. Deterministic mean-field equations, and a noise component that depends on the dynamic state of the network, are obtained from this model. The resulting stochastic model reflects the behavior observed in numerical simulations quite well, irrespective of the size of the network. In particular, a strong temporal correlation between the two populations, a hallmark of the balanced state in random recurrent networks, are well represented by our model. Numerical simulations of such networks show that a log-normal distribution of short-term spike counts is a property of balanced random networks with fixed in-degree that has not been considered before, and our model shares this statistical property. Furthermore, the reconstruction of the flow from simulated time series suggests that the mean-field dynamics of finite-size networks are essentially of Wilson-Cowan type. We expect that this novel nonlinear stochastic model of the interaction between

  11. Explicit all-atom modeling of realistically sized ligand-capped nanocrystals

    KAUST Repository

    Kaushik, Ananth P.

    2012-01-01

    We present a study of an explicit all-atom representation of nanocrystals of experimentally relevant sizes (up to 6 nm), capped with alkyl chain ligands, in vacuum. We employ all-atom molecular dynamics simulation methods in concert with a well-tested intermolecular potential model, MM3 (molecular mechanics 3), for the studies presented here. These studies include determining the preferred conformation of an isolated single nanocrystal (NC), pairs of isolated NCs, and (presaging studies of superlattice arrays) unit cells of NC superlattices. We observe that very small NCs (3 nm) behave differently in a superlattice as compared to larger NCs (6 nm and above) due to the conformations adopted by the capping ligands on the NC surface. Short ligands adopt a uniform distribution of orientational preferences, including some that lie against the face of the nanocrystal. In contrast, longer ligands prefer to interdigitate. We also study the effect of changing ligand length and ligand coverage on the NCs on the preferred ligand configurations. Since explicit all-atom modeling constrains the maximum system size that can be studied, we discuss issues related to coarse-graining the representation of the ligands, including a comparison of two commonly used coarse-grained models. We find that care has to be exercised in the choice of coarse-grained model. The data provided by these realistically sized ligand-capped NCs, determined using explicit all-atom models, should serve as a reference standard for future models of coarse-graining ligands using united atom models, especially for self-assembly processes. © 2012 American Institute of Physics.

  12. MAID : An effect size based model for microarray data integration across laboratories and platforms

    Directory of Open Access Journals (Sweden)

    Edwards Aled M

    2008-07-01

    Full Text Available Abstract Background Gene expression profiling has the potential to unravel molecular mechanisms behind gene regulation and identify gene targets for therapeutic interventions. As microarray technology matures, the number of microarray studies has increased, resulting in many different datasets available for any given disease. The increase in sensitivity and reliability of measurements of gene expression changes can be improved through a systematic integration of different microarray datasets that address the same or similar biological questions. Results Traditional effect size models can not be used to integrate array data that directly compare treatment to control samples expressed as log ratios of gene expressions. Here we extend the traditional effect size model to integrate as many array datasets as possible. The extended effect size model (MAID can integrate any array datatype generated with either single or two channel arrays using either direct or indirect designs across different laboratories and platforms. The model uses two standardized indices, the standard effect size score for experiments with two groups of data, and a new standardized index that measures the difference in gene expression between treatment and control groups for one sample data with replicate arrays. The statistical significance of treatment effect across studies for each gene is determined by appropriate permutation methods depending on the type of data integrated. We apply our method to three different expression datasets from two different laboratories generated using three different array platforms and two different experimental designs. Our results indicate that the proposed integration model produces an increase in statistical power for identifying differentially expressed genes when integrating data across experiments and when compared to other integration models. We also show that genes found to be significant using our data integration method are of direct

  13. SEIR Model of Rumor Spreading in Online Social Network with Varying Total Population Size

    Science.gov (United States)

    Dong, Suyalatu; Deng, Yan-Bin; Huang, Yong-Chang

    2017-10-01

    Based on the infectious disease model with disease latency, this paper proposes a new model for the rumor spreading process in online social network. In this paper what we establish an SEIR rumor spreading model to describe the online social network with varying total number of users and user deactivation rate. We calculate the exact equilibrium points and reproduction number for this model. Furthermore, we perform the rumor spreading process in the online social network with increasing population size based on the original real world Facebook network. The simulation results indicate that the SEIR model of rumor spreading in online social network with changing total number of users can accurately reveal the inherent characteristics of rumor spreading process in online social network. Supported by National Natural Science Foundation of China under Grant Nos. 11275017 and 11173028

  14. SEIR Model of Rumor Spreading in Online Social Network with Varying Total Population Size

    International Nuclear Information System (INIS)

    Dong Suyalatu; Deng Yan-Bin; Huang Yong-Chang

    2017-01-01

    Based on the infectious disease model with disease latency, this paper proposes a new model for the rumor spreading process in online social network. In this paper what we establish an SEIR rumor spreading model to describe the online social network with varying total number of users and user deactivation rate. We calculate the exact equilibrium points and reproduction number for this model. Furthermore, we perform the rumor spreading process in the online social network with increasing population size based on the original real world Facebook network. The simulation results indicate that the SEIR model of rumor spreading in online social network with changing total number of users can accurately reveal the inherent characteristics of rumor spreading process in online social network . (paper)

  15. Theoretical size distribution of fossil taxa: analysis of a null model

    Directory of Open Access Journals (Sweden)

    Hughes Barry D

    2007-03-01

    Full Text Available Abstract Background This article deals with the theoretical size distribution (of number of sub-taxa of a fossil taxon arising from a simple null model of macroevolution. Model New species arise through speciations occurring independently and at random at a fixed probability rate, while extinctions either occur independently and at random (background extinctions or cataclysmically. In addition new genera are assumed to arise through speciations of a very radical nature, again assumed to occur independently and at random at a fixed probability rate. Conclusion The size distributions of the pioneering genus (following a cataclysm and of derived genera are determined. Also the distribution of the number of genera is considered along with a comparison of the probability of a monospecific genus with that of a monogeneric family.

  16. Finite size effects in a model for platicity of amorphous composites

    DEFF Research Database (Denmark)

    Tyukodi, Botond; Lemarchand, Claire A.; Hansen, Jesper Schmidt

    2016-01-01

    We discuss the plastic behavior of an amorphous matrix reinforced by hard particles. A mesoscopic depinning-like model accounting for Eshelby elastic interactions is implemented. Only the effect of a plastic disorder is considered. Numerical results show a complex size dependence of the effective...... numerically. Predictions of the effective flow stress accounting for further logarithmic corrections show a very good agreement with numerical results.......We discuss the plastic behavior of an amorphous matrix reinforced by hard particles. A mesoscopic depinning-like model accounting for Eshelby elastic interactions is implemented. Only the effect of a plastic disorder is considered. Numerical results show a complex size dependence of the effective...... flow stress of the amorphous composite. In particular, the departure from the mixing law shows opposite trends associated to the competing effects of the matrix and the reinforcing particles, respectively. The reinforcing mechanisms and their effects on localization are discussed. Plastic strain...

  17. Finite element model of size, shape and blood pressure on rupture of intracranial saccular aneurysms

    Science.gov (United States)

    Rica Nabong, Jennica; David, Guido

    2017-10-01

    Rupture of intracranial saccular aneurysms is a primary concern for neurologists and patients because it leads to stroke and permanent disability. This paper examines the role of blood pressure, in connection with size of and wall thickness, in the rupture of saccular aneurysms. A bulb-shaped geometry of a saccular aneurysm is obtained from angiographic images of a patient and modeled using Finite Elements based on the principle of virtual work under the Fung stress-strain relationship. The numerical model is subjected to varying levels of systolic blood pressure. Rupture is assumed to occur when the wall stress exceeded its mechanical strength. The results show which sizes of this class of aneurysms are at high risk of rupture for varying levels of blood pressure.

  18. A mass-density model can account for the size-weight illusion

    Science.gov (United States)

    Bergmann Tiest, Wouter M.; Drewing, Knut

    2018-01-01

    When judging the heaviness of two objects with equal mass, people perceive the smaller and denser of the two as being heavier. Despite the large number of theories, covering bottom-up and top-down approaches, none of them can fully account for all aspects of this size-weight illusion and thus for human heaviness perception. Here we propose a new maximum-likelihood estimation model which describes the illusion as the weighted average of two heaviness estimates with correlated noise: One estimate derived from the object’s mass, and the other from the object’s density, with estimates’ weights based on their relative reliabilities. While information about mass can directly be perceived, information about density will in some cases first have to be derived from mass and volume. However, according to our model at the crucial perceptual level, heaviness judgments will be biased by the objects’ density, not by its size. In two magnitude estimation experiments, we tested model predictions for the visual and the haptic size-weight illusion. Participants lifted objects which varied in mass and density. We additionally varied the reliability of the density estimate by varying the quality of either visual (Experiment 1) or haptic (Experiment 2) volume information. As predicted, with increasing quality of volume information, heaviness judgments were increasingly biased towards the object’s density: Objects of the same density were perceived as more similar and big objects were perceived as increasingly lighter than small (denser) objects of the same mass. This perceived difference increased with an increasing difference in density. In an additional two-alternative forced choice heaviness experiment, we replicated that the illusion strength increased with the quality of volume information (Experiment 3). Overall, the results highly corroborate our model, which seems promising as a starting point for a unifying framework for the size-weight illusion and human heaviness

  19. CFD modeling of a commercial‐size circle‐draft biomass gasifier

    OpenAIRE

    Liu, Hui; Cattolica, Robert J.; Seiser, Reinhard; Liao, Chang-hsien; Summers, Matthew

    2017-01-01

    This work was focused on a commercial-size (2MWth.) circle-draft biomass gasifier. In this work a threedimensional transient CFD (computational fluid dynamics) model was established to simulate the circledraft biomass gasifier. The MP-PIC (multiphase particlein- cell) method was applied to simulate multiphase reactive flows in the gasifier. In the MP-PIC method, the Navier-Stokes equation coupled with the large-eddy simulation (LES) was applied to describe the gas phase. The particulate phase...

  20. Modelling of the costs of decision support for small and medium-sized enterprises

    Directory of Open Access Journals (Sweden)

    Viera Tomišová

    2017-01-01

    Full Text Available The support of decision-making activities in small and medium-sized enterprises (SME has its specific features. When suggesting steps for the implementation of decision-support tools in the enterprise, we identified two main ways of decision-making support based on the data analysis: ERP (Enterprise Resource Planning without BI (Business Intelligence and ERP with BI. In our contribution, we present costs models of both mentioned decision support systems and their practical interpretation.

  1. Unified dataflow model for the analysis of data and pipeline parallelism, and buffer sizing

    OpenAIRE

    Hausmans, J.P.H.M.; Geuns, S.J.; Wiggers, M.H.; Bekooij, Marco Jan Gerrit

    2014-01-01

    Real-time stream processing applications such as software defined radios are usually executed concurrently on multiprocessor systems. Exploiting coarse-grained data parallelism by duplicating tasks is often required, besides pipeline parallelism, to meet the temporal constraints of the applications. However, no unified model and analysis method exists that can be used to determine the required amount of data and pipeline parallelism, and buffer sizes simultaneously. This paper presents an ana...

  2. Genomic selection models for directional dominance: an example for litter size in pigs.

    Science.gov (United States)

    Varona, Luis; Legarra, Andrés; Herring, William; Vitezica, Zulma G

    2018-01-26

    The quantitative genetics theory argues that inbreeding depression and heterosis are founded on the existence of directional dominance. However, most procedures for genomic selection that have included dominance effects assumed prior symmetrical distributions. To address this, two alternatives can be considered: (1) assume the mean of dominance effects different from zero, and (2) use skewed distributions for the regularization of dominance effects. The aim of this study was to compare these approaches using two pig datasets and to confirm the presence of directional dominance. Four alternative models were implemented in two datasets of pig litter size that consisted of 13,449 and 11,581 records from 3631 and 2612 sows genotyped with the Illumina PorcineSNP60 BeadChip. The models evaluated included (1) a model that does not consider directional dominance (Model SN), (2) a model with a covariate b for the average individual homozygosity (Model SC), (3) a model with a parameter λ that reflects asymmetry in the context of skewed Gaussian distributions (Model AN), and (4) a model that includes both b and λ (Model Full). The results of the analysis showed that posterior probabilities of a negative b or a positive λ under Models SC and AN were higher than 0.99, which indicate positive directional dominance. This was confirmed with the predictions of inbreeding depression under Models Full, SC and AN, that were higher than in the SN Model. In spite of differences in posterior estimates of variance components between models, comparison of models based on LogCPO and DIC indicated that Model SC provided the best fit for the two datasets analyzed. Our results confirmed the presence of positive directional dominance for pig litter size and suggested that it should be taken into account when dominance effects are included in genomic evaluation procedures. The consequences of ignoring directional dominance may affect predictions of breeding values and can lead to biased

  3. Modeling the influence of body size on weightlifting and powerlifting performance.

    Science.gov (United States)

    Marković, Goran; Sekulić, Damir

    2006-09-01

    The purpose of this study was to examine 1) if lifting performance in both the weightlifting (WL) and powerlifting (PL) scale with body mass (M) in line with theory of geometric similarity, and 2) whether there are any gender differences in the allometric relationship between lifting performance and body size. This was performed by analyzing ten best WL and PL total results for each weight class, except for super heavyweight, achieved during 2000-2003. Data were analysed with the allometric and second-order polynomial model, and detailed regression diagnostics was applied in order to examine appropriateness of the models used. Results of the data analyses indicate that 1) women's WL and men's PL scale for M in line with theory of geometric similarity, 2) both WL and PL mass exponents are gender-specific, probably due to gender differences in body composition, 3) WL and PL results scale differently for M possibly due to their structural and functional differences. However, the obtained mass exponents does not provide size-independent indices of lifting performances since the allometric model exhibit a favourable bias toward middleweight lifters in most lifting data analyzed. Due to possible deviations from presumption of geometric similarity among lifters, future studies on scaling lifting performance should use fat-free mass and height as indices of body size.

  4. Group size, grooming and fission in primates: a modeling approach based on group structure.

    Science.gov (United States)

    Sueur, Cédric; Deneubourg, Jean-Louis; Petit, Odile; Couzin, Iain D

    2011-03-21

    In social animals, fission is a common mode of group proliferation and dispersion and may be affected by genetic or other social factors. Sociality implies preserving relationships between group members. An increase in group size and/or in competition for food within the group can result in decrease certain social interactions between members, and the group may split irreversibly as a consequence. One individual may try to maintain bonds with a maximum of group members in order to keep group cohesion, i.e. proximity and stable relationships. However, this strategy needs time and time is often limited. In addition, previous studies have shown that whatever the group size, an individual interacts only with certain grooming partners. There, we develop a computational model to assess how dynamics of group cohesion are related to group size and to the structure of grooming relationships. Groups' sizes after simulated fission are compared to observed sizes of 40 groups of primates. Results showed that the relationship between grooming time and group size is dependent on how each individual attributes grooming time to its social partners, i.e. grooming a few number of preferred partners or grooming equally or not all partners. The number of partners seemed to be more important for the group cohesion than the grooming time itself. This structural constraint has important consequences on group sociality, as it gives the possibility of competition for grooming partners, attraction for high-ranking individuals as found in primates' groups. It could, however, also have implications when considering the cognitive capacities of primates. Copyright © 2010 Elsevier Ltd. All rights reserved.

  5. Size graded sediment dynamics: from the processes characterization to the transport modelling in the English Channel

    International Nuclear Information System (INIS)

    Blanpain, O.

    2009-10-01

    The purpose of this work is the implementation of a sediment transport model in the English Channel. The design of such a model requires the identification of the physical processes, their modelling and their in-situ validation. Because of the sedimentary particularities of the study area, modelling of the mechanical behaviour of a non uniform mixture of sediments and particularly of the fine grains within a coarse matrix is required. This study focused on the characterization of the relevant processes by acquisition of experimental and in-situ data. Data acquired in hydro-sedimentary conditions comparable to those found in the English Channel are scarce. A new instrument and image processing technique were specifically conceived and implemented in-situ to observe and measure, with a high temporal resolution, the dynamics of a strongly heterogeneous mixture of particles in a grain-size scale. The data collected compared well with several existing formulations. One of these formulations was chosen to be adapted. The transfer dynamics of fine grains in coarse sediments and their depth of penetration were acquired from stratigraphic samples. The sediment transport model deals with multi-size grains and multi sedimentary layers, it is forced by swell and currents, and accounts for bead load and suspended load transports. It was applied to realistic scenarios for the English Channel. (author)

  6. A stochastic simulation model for reliable PV system sizing providing for solar radiation fluctuations

    International Nuclear Information System (INIS)

    Kaplani, E.; Kaplanis, S.

    2012-01-01

    Highlights: ► Solar radiation data for European cities follow the Extreme Value or Weibull distribution. ► Simulation model for the sizing of SAPV systems based on energy balance and stochastic analysis. ► Simulation of PV Generator-Loads-Battery Storage System performance for all months. ► Minimum peak power and battery capacity required for reliable SAPV sizing for various European cities. ► Peak power and battery capacity reduced by more than 30% for operation 95% success rate. -- Abstract: The large fluctuations observed in the daily solar radiation profiles affect highly the reliability of the PV system sizing. Increasing the reliability of the PV system requires higher installed peak power (P m ) and larger battery storage capacity (C L ). This leads to increased costs, and makes PV technology less competitive. This research paper presents a new stochastic simulation model for stand-alone PV systems, developed to determine the minimum installed P m and C L for the PV system to be energy independent. The stochastic simulation model developed, makes use of knowledge acquired from an in-depth statistical analysis of the solar radiation data for the site, and simulates the energy delivered, the excess energy burnt, the load profiles and the state of charge of the battery system for the month the sizing is applied, and the PV system performance for the entire year. The simulation model provides the user with values for the autonomy factor d, simulating PV performance in order to determine the minimum P m and C L depending on the requirements of the application, i.e. operation with critical or non-critical loads. The model makes use of NASA’s Surface meteorology and Solar Energy database for the years 1990–2004 for various cities in Europe with a different climate. The results obtained with this new methodology indicate a substantial reduction in installed peak power and battery capacity, both for critical and non-critical operation, when compared to

  7. Particle size-shape distributions: the general spheroid problem. I. Mathematical model.

    Science.gov (United States)

    Orive, L M

    1976-08-01

    The development of stereological methods for the study of dilute phases of particles, voids or organelles embedded in a matrix, from measurements made on plane or linear intercepts through the aggregate, has deserved a great deal of effort. With almost no exception, the problem of describing the particulate phase is reduced to that of identifying the statistical distribution--histogram in practice--of a relevant size parameter, with the previous assumption that the particles are modelled by geometrical objects of a constant shape (e.g. spheres). Therefore, particles exhibiting a random variation about a given type of shape as well as a random variation in size, escape previous analyses. Such is the case of unequiaxed particles modelled by triaxial ellipsoids of variable size and eccentricity parameters. It has been conjectured (Moran, 1972) that this problem is indetermined in its generally (i.e. the elliptical sections do not furnish a sufficient information which permits a complete description of the ellipsoids). A proof of this conjecture is given in the Appendix. When the ellipsoids are biaxial (spheroids) and of the same type (prolate or oblate), the problem is identifiable. Previous attempts to solve it assume statistical independence between size and shape. A complete, theoretical solution of the spheroids problem--with the independence condition relaxed--is presented. A number of exact relationships--some of them of a striking simplicity--linking particle properties (e.g. mean-mean caliper length, mean axial ratio, correlation coefficient between principal diameters, etc.) on the one hand, with the major and minor dimensions of the ellipses of section on the other, emerge, and natural, consistent estimators of the mentioned properties are made easily accessible for practical computation. Finally, the scope and limitations of the mathematical model are discussed.

  8. Effect of the Initial Vortex Size on Intensity Change in the WRF-ROMS Coupled Model

    Science.gov (United States)

    Zhao, Xiaohui; Chan, Johnny C. L.

    2017-12-01

    Numerous studies have demonstrated that the tropical cyclone (TC) induced sea surface temperature (SST) cooling strongly depends on the preexisting oceanic condition and TC characteristics. However, very few focused on the correlation of SST cooling and the subsequent intensity with TC size. Therefore, a series of idealized numerical experiments are conducted using the Weather Research Forecasting (WRF) model coupled with the Regional Ocean Model System (ROMS) model to understand how the vortex size is related to SST cooling and subsequent intensity changes of a stationary TC-like vortex. In the uncoupled experiments, the radius of maximum wind (RMW) and size (radius of gale-force wind (R17)) both depend on the initial size within the 72 h simulation. The initially small vortex is smaller than the medium and large vortices throughout its life cycle and is the weakest. In other words, thermodynamic processes do not contribute as much to the R17 change as the dynamic processes proposed (e.g., angular momentum transport) in previous studies. In the coupled experiments, the area-averaged SST cooling induced by medium and large TCs within the inner-core region is comparable due to the similar surface winds and thus mixing in the ocean. Although a stronger SST cooling averaged within a larger region outside the inner-core is induced by the larger TC, the intensity of the larger TC is more intense. This is because that the enthalpy flux in the inner-core region is higher in the larger TC than that in the medium and small TCs.

  9. Modelling the relationship between soil color and particle size for soil survey in Ferralsol environments

    Directory of Open Access Journals (Sweden)

    B. Kone

    2009-05-01

    Full Text Available Soil texture is an important property for evaluating its inherent fertility especially by using pedo-transfers functions requiring particle size data. However, there is no existing quantitative method for in situ estimation of soil particle size, delaying judgement of soil chemical properties in the field. For this purpose, laboratory particle size analyses of 1028 samples from 281 Ferralsol profiles, located between latitudes 7º N and 10º N in Côte d’Ivoire and their respective colour notation by Munsell chart were used to generate prediction models. Multiple Linear Regression Analysis by Group was processed to identify clay, sand and silt contents in the soil based on color hue (2.5YR, 5YR, 7.5YR, and 10YR and Chroma (1, 2, 3, 4, 5, 6, 7, 8. The evaluation was conducted for each horizon coded as H1 (0-20 cm, H2 (20-60 cm, H3 (60-80 cm and H4 (80-150 cm and used as grouping variables. Highly significant (P< 0.001 models were identified for clay and sand. These models were used to estimate successfully clay and sand contents for other Ferralsol samples by comparing calculated and measured mean using the null hypothesis of difference and Tukey’s tests. They were accurate for at all depths, except 80 - 150 cm, for sand in 10YR soils. The method was deemed appropriate for in situ estimation of soil particle size contents in Ferralsol environment for improving reconnaissance agricultural soil surveys.

  10. Size-segregation in bedload transport: experiments at the particle scale and continuous modelling

    Science.gov (United States)

    Bel, Coraline; Kristina, Rorsman; Frey, Philippe

    2013-04-01

    Sediment transport plays a major role in the stability and the morphology of stream channels and has major consequences for environmental sustainability and in flood alleviation. Bedload, i.e. the transport of sediment remaining in contact with the streambed, should be considered from a granular point of view, and take into account not only the grain-fluid but also the grain-grain interactions. On the streambed, the wide range of grain sizes leads to size-segregation, especially to armouring, i.e. the building of a coarser layer on the surface of the bed. Segregation is also studied in industrial contexts often for non-desirable effects. Depending on the size-ratio, fine grains infiltrate spontaneously in between the coarser grains (spontaneous percolation), or smaller grains fall into the pores opened dynamically (kinetic sieving). This research is about the kinetic sieving process. The aim of this investigation is to test, against our experimental data, a continuum theoretical model for the segregation of binary mixtures based on a kinematic approach (Gray and Chugunov 2006). First, experiments were carried out to measure the evolution of the concentration over space and time in a binary flowing mixture. During those experiments, spherical glass beads of diameter 4 mm and 6 mm were entrained by a turbulent and supercritical water flow, down a steep (10%) narrow flume with a mobile bed under bedload equilibrium conditions. Experimental results have been compared to the model requiring as input the normal profiles of bead velocity and the sediment rates. A reasonable agreement was found between experimental and modelled concentration profiles. Gray, J. M. N. T., & Chugunov, V. A. (2006). Particle-size segregation and diffusive remixing in shallow granular avalanches. Journal of Fluid Mechanics, 569, 365-398.

  11. An explicit solution for calculating optimum spawning stock size from Ricker's stock recruitment model.

    Science.gov (United States)

    Scheuerell, Mark D

    2016-01-01

    Stock-recruitment models have been used for decades in fisheries management as a means of formalizing the expected number of offspring that recruit to a fishery based on the number of parents. In particular, Ricker's stock recruitment model is widely used due to its flexibility and ease with which the parameters can be estimated. After model fitting, the spawning stock size that produces the maximum sustainable yield (S MSY) to a fishery, and the harvest corresponding to it (U MSY), are two of the most common biological reference points of interest to fisheries managers. However, to date there has been no explicit solution for either reference point because of the transcendental nature of the equation needed to solve for them. Therefore, numerical or statistical approximations have been used for more than 30 years. Here I provide explicit formulae for calculating both S MSY and U MSY in terms of the productivity and density-dependent parameters of Ricker's model.

  12. Modeling the competition between antenna size mutant and wild type microalgae in outdoor mass culture.

    Science.gov (United States)

    de Mooij, Tim; Schediwy, Kira; Wijffels, René H; Janssen, Marcel

    2016-12-20

    Under high light conditions, microalgae are oversaturated with light which significantly reduces the light use efficiency. Microalgae with a reduced pigment content, antenna size mutants, have been proposed as a potential solution to increase the light use efficiency. The goal of this study was to investigate the competition between antenna size mutants and wild type microalgae in mass cultures. Using a kinetic model and literature-derived experimental data from wild type Chlorella sorokiniana, the productivity and competition of wild type cells and antenna size mutants were simulated. Cultivation was simulated in an outdoor microalgal raceway pond production system which was assumed to be limited by light only. Light conditions were based on a Mediterranean location (Tunisia) and a more temperate location (the Netherlands). Several wild type contamination levels were simulated in each mutant culture separately to predict the effect on the productivity over the cultivation time of a hypothetical summer season of 100days. The simulations demonstrate a good potential of antenna size reduction to increase the biomass productivity of microalgal cultures. However, it was also found that after a contamination with wild type cells the mutant cultures will be rapidly overgrown resulting in productivity loss. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. Evaluation of Mid-Size Male Hybrid III Models for use in Spaceflight Occupant Protection Analysis

    Science.gov (United States)

    Putnam, J.; Somers, J.; Wells, J.; Newby, N.; Currie-Gregg, N.; Lawrence, C.

    2016-01-01

    Introduction: In an effort to improve occupant safety during dynamic phases of spaceflight, the National Aeronautics and Space Administration (NASA) has worked to develop occupant protection standards for future crewed spacecraft. One key aspect of these standards is the identification of injury mechanisms through anthropometric test devices (ATDs). Within this analysis, both physical and computational ATD evaluations are required to reasonably encompass the vast range of loading conditions any spaceflight crew may encounter. In this study the accuracy of publically available mid-size male HIII ATD finite element (FE) models are evaluated within applicable loading conditions against extensive sled testing performed on their physical counterparts. Methods: A series of sled tests were performed at the Wright Patterson Air force Base (WPAFB) employing variations of magnitude, duration, and impact direction to encompass the dynamic loading range for expected spaceflight. FE simulations were developed to the specifications of the test setup and driven using measured acceleration profiles. Both fast and detailed FE models of the mid-size male HIII were ran to quantify differences in their accuracy and thus assess the applicability of each within this field. Results: Preliminary results identify the dependence of model accuracy on loading direction, magnitude, and rate. Additionally the accuracy of individual response metrics are shown to vary across each model within evaluated test conditions. Causes for model inaccuracy are identified based on the observed relationships. Discussion: Computational modeling provides an essential component to ATD injury metric evaluation used to ensure the safety of future spaceflight occupants. The assessment of current ATD models lays the groundwork for how these models can be used appropriately in the future. Identification of limitations and possible paths for improvement aid in the development of these effective analysis tools.

  14. Effect of pupil size on visual acuity in a laboratory model of pseudophakic monovision.

    Science.gov (United States)

    Kawamorita, Takushi; Uozato, Hiroshi; Handa, Tomoya; Ito, Misae; Shimizu, Kimiya

    2010-05-01

    To investigate the effect of pupil size on visual acuity in pseudophakic monovision. For the simulation, a modified Liou-Brennan model eye was used. The model eye was designed to include a centered optical system, corneal asphericity, an iris pupil, a Stiles-Crawford effect, an intraocular lens, and chromatic aberration. Calculation of the modulation transfer function (MTF) was performed with ZEMAX software. Visual acuity was estimated from the MTF and the retinal threshold curve. The sizes of the entrance pupil were 2.0, 2.5, 3.0, and 4.0 mm. Decreasing pupil diameter and increasing myopia progressively improved near visual acuity. For an entrance pupil size of 2.5 mm and a refractive error of -1.50 diopters, the logMAR value (Snellen; metric) in the non-dominant eye at 40 cm was 0.06 (20/23; 6/6.9). Knowledge of the patient's pupil diameter at near fixation can assist surgeons in determining the optimum degree of myopia for successful monovision.

  15. Sample Size Requirements for Estimation of Item Parameters in the Multidimensional Graded Response Model

    Directory of Open Access Journals (Sweden)

    Shengyu eJiang

    2016-02-01

    Full Text Available Likert types of rating scales in which a respondent chooses a response from an ordered set of response options are used to measure a wide variety of psychological, educational, and medical outcome variables. The most appropriate item response theory model for analyzing and scoring these instruments when they provide scores on multiple scales is the multidimensional graded response model (MGRM. A simulation study was conducted to investigate the variables that might affect item parameter recovery for the MGRM. Data were generated based on different sample sizes, test lengths, and scale intercorrelations. Parameter estimates were obtained through the flexiMIRT software. The quality of parameter recovery was assessed by the correlation between true and estimated parameters as well as bias and root- mean-square-error. Results indicated that for the vast majority of cases studied a sample size of N = 500 provided accurate parameter estimates, except for tests with 240 items when 1,000 examinees were necessary to obtain accurate parameter estimates. Increasing sample size beyond N = 1,000 did not increase the accuracy of MGRM parameter estimates.

  16. Optimal capacity and buffer size estimation under Generalized Markov Fluids Models and QoS parameters

    International Nuclear Information System (INIS)

    Bavio, José; Marrón, Beatriz

    2014-01-01

    Quality of service (QoS) for internet traffic management requires good traffic models and good estimation of sharing network resource. A link of a network processes all traffic and it is designed with certain capacity C and buffer size B. A Generalized Markov Fluid model (GMFM), introduced by Marrón (2011), is assumed for the sources because describes in a versatile way the traffic, allows estimation based on traffic traces, and also consistent effective bandwidth estimation can be done. QoS, interpreted as buffer overflow probability, can be estimated for GMFM through the effective bandwidth estimation and solving the optimization problem presented in Courcoubetis (2002), the so call inf-sup formulas. In this work we implement a code to solve the inf-sup problem and other optimization related with it, that allow us to do traffic engineering in links of data networks to calculate both, minimum capacity required when QoS and buffer size are given or minimum buffer size required when QoS and capacity are given

  17. Virus-sized colloid transport in a single pore: model development and sensitivity analysis.

    Science.gov (United States)

    Seetha, N; Mohan Kumar, M S; Majid Hassanizadeh, S; Raoof, Amir

    2014-08-01

    A mathematical model is developed to simulate the transport and deposition of virus-sized colloids in a cylindrical pore throat considering various processes such as advection, diffusion, colloid-collector surface interactions and hydrodynamic wall effects. The pore space is divided into three different regions, namely, bulk, diffusion and potential regions, based on the dominant processes acting in each of these regions. In the bulk region, colloid transport is governed by advection and diffusion whereas in the diffusion region, colloid mobility due to diffusion is retarded by hydrodynamic wall effects. Colloid-collector interaction forces dominate the transport in the potential region where colloid deposition occurs. The governing equations are non-dimensionalized and solved numerically. A sensitivity analysis indicates that the virus-sized colloid transport and deposition is significantly affected by various pore-scale parameters such as the surface potentials on colloid and collector, ionic strength of the solution, flow velocity, pore size and colloid size. The adsorbed concentration and hence, the favorability of the surface for adsorption increases with: (i) decreasing magnitude and ratio of surface potentials on colloid and collector, (ii) increasing ionic strength and (iii) increasing pore radius. The adsorbed concentration increases with increasing Pe, reaching a maximum value at Pe=0.1 and then decreases thereafter. Also, the colloid size significantly affects particle deposition with the adsorbed concentration increasing with increasing particle radius, reaching a maximum value at a particle radius of 100nm and then decreasing with increasing radius. System hydrodynamics is found to have a greater effect on larger particles than on smaller ones. The secondary minimum contribution to particle deposition has been found to increase as the favorability of the surface for adsorption decreases. The sensitivity of the model to a given parameter will be high if

  18. Confirmation of MRS/MPC transfer facility sizing using simulation modeling

    International Nuclear Information System (INIS)

    Houston, E.S.; Hadley, J.D.

    1994-01-01

    The Nuclear Waste Policy Act (NWPA) of 1982, as amended, requires the Department of Energy to begin receiving spent nuclear fuel (SNF) from utilities in January 1998. A repository will not be completed in time for the scheduled receipt of SNF. A Monitored Retrievable Storage (MRS) Facility is therefore a feasible solution to bridge the gap between the 1998 date for fuel acceptance and the startup of the repository. SNF will be stored temporarily at the MRS and later retrieved from storage and shipped to the repository. To simplify fuel handling and to standardize components, the multi-purpose canister (MPC) concept was investigated. The MPC would be a sealed, metallic canister containing multiple SNF assemblies in a dry inert environment. MPCs would be placed into different overpacks for transportation, storage, and disposal at the repository. The MRS transfer facility MPC and SNF throughput requirements, assumptions, and operating concepts were used to initially determine the size of the facility and the major equipment contained within the facility. This initial estimate was based on simplified calculation techniques. The adequacy of the design configurations were then confirmed using SLAM simulation modeling software. Modeling incorporates uncertainties in task durations, the effects of equipment reliability, availability of personnel and equipment, and system breakdowns. This paper describes how the model was developed and how it is used to verify the transfer facility size. It also illustrates how problems with the facility design, operational concepts, and staffing are identified with the results of the model

  19. Solar Desalination System Model for Sizing of Photovoltaic Reverse Osmosis (PVRO)

    KAUST Repository

    Habib, Abdulelah

    2015-06-28

    The focus of this paper is to optimize the solar energy utilization in the water desalination process. Due to variable nature of solar energy, new system design is needed to address this challenge. Here, reverse osmosis units, as the electrical loads, are considered as an ON/OFF units to track these solar energy variations. Reverse osmosis units are different in sizes and numbers. Various combinations of reverse osmosis units in size and capacity provide different water desalination system performances. To assess each scenario of reverse osmosis units, the total capital cost and operation and maintenance (O&M) cost are considered. The implemented optimization algorithm search all of the possible scenarios to find the best solution. This paper deploys the solar irradiance data which is provided from west coast (Red Sea) of Saudi Arabia for model construction and optimization algorithm implementation.

  20. Particle size distribution models of small angle neutron scattering pattern on ferro fluids

    International Nuclear Information System (INIS)

    Sistin Asri Ani; Darminto; Edy Giri Rachman Putra

    2009-01-01

    The Fe 3 O 4 ferro fluids samples were synthesized by a co-precipitation method. The investigation of ferro fluids microstructure is known to be one of the most important problems because the presence of aggregates and their internal structure influence greatly the properties of ferro fluids. The size and the size dispersion of particle in ferro fluids were determined assuming a log normal distribution of particle radius. The scattering pattern of the measurement by small angle neutron scattering were fitted by the theoretical scattering function of two limitation models are log normal sphere distribution and fractal aggregate. Two types of particle are detected, which are presumably primary particle of 30 Armstrong in radius and secondary fractal aggregate of 200 Armstrong with polydispersity of 0.47 up to 0.53. (author)

  1. Size influences the effect of hydrophobic nanoparticles on lung surfactant model systems.

    Science.gov (United States)

    Dwivedi, Mridula V; Harishchandra, Rakesh Kumar; Koshkina, Olga; Maskos, Michael; Galla, Hans-Joachim

    2014-01-07

    The alveolar lung surfactant (LS) is a complex lipid protein mixture that forms an interfacial monolayer reducing the surface tension to near zero values and thus preventing the lungs from collapse. Due to the expanding field of nanotechnology and the corresponding unavoidable exposure of human beings from the air, it is crucial to study the potential effects of nanoparticles (NPs) on the structural organization of the lung surfactant system. In the present study, we investigated both, the domain structure in pure DPPC monolayers as well as in lung surfactant model systems. In the pure lipid system we found that two different sized hydrophobic polymeric nanoparticles with diameter of ~12 nm and ~136 nm have contrasting effect on the functional and structural behavior. The small nanoparticles inserted into fluid domains at the LE-LC phase transition are not visibly disturbing the phase transition but disrupting the domain morphology of the LE phase. The large nanoparticles led to an expanded isotherm and to a significant decrease in the line tension and thus to a drastic disruption of the domain structures at a much lower number of nanoparticles with respect to the lipid. The surface activity of the model LS films again showed drastic variations due to presence of different sized NPs illustrated by the film balance isotherms and the atomic force microscopy. AFM revealed laterally profuse multilayer protrusion formation on compression but only in the presence of 136 nm sized nanoparticles. Moreover we investigated the vesicle insertion process into a preformed monolayer. A severe inhibition was observed only in the presence of ~136 nm NPs compared to minor effects in the presence of ~12 nm NPs. Our study clearly shows that the size of the nanoparticles made of the same material determines the interaction with biological membranes. Copyright © 2014 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  2. Finite size scaling of the Higgs-Yukawa model near the Gaussian fixed point

    Energy Technology Data Exchange (ETDEWEB)

    Chu, David Y.J.; Lin, C.J. David [National Chiao-Tung Univ., Hsinchu, Taiwan (China); Jansen, Karl [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Knippschild, Bastian [HISKP, Bonn (Germany); Nagy, Attila [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Humboldt-Univ. Berlin (Germany)

    2016-12-15

    We study the scaling properties of Higgs-Yukawa models. Using the technique of Finite-Size Scaling, we are able to derive scaling functions that describe the observables of the model in the vicinity of a Gaussian fixed point. A feasibility study of our strategy is performed for the pure scalar theory in the weak-coupling regime. Choosing the on-shell renormalisation scheme gives us an advantage to fit the scaling functions against lattice data with only a small number of fit parameters. These formulae can be used to determine the universality of the observed phase transitions, and thus play an essential role in future investigations of Higgs-Yukawa models, in particular in the strong Yukawa coupling region.

  3. A continuum-based model capturing size effects in polymer bonds

    International Nuclear Information System (INIS)

    Diebels, S; Johlitz, M; Steeb, H; Chatzouridou, A; Batal, J; Possart, W

    2007-01-01

    It is known from applications that the mechanical behaviour of polymer bonds does not only depend on the properties of the polymer itself but also on the substrate. Therefore, the mechanical behaviour, i.e. the stiffness, of a polymer joint becomes thickness dependent. In the present work we describe experiments performed on polymer joints and we develop a continuum-based model which is able to describe the experimentally observed size effects without suggesting the microstructure in detail. The continuum mechanical model is enhanced by a scalar-valued structure parameter which describes all the effects taking place in the boundary layer which arises near the substrate. It is shown that the model parameters can be determined on the basis of simple shear experiments performed on polymer layers of different thickness

  4. Modelling of Limestone Dissolution in Wet FGD Systems: The Importance of an Accurate Particle Size Distribution

    DEFF Research Database (Denmark)

    Kiil, Søren; Johnsson, Jan Erik; Dam-Johansen, Kim

    1999-01-01

    Danish limestone types with very different particle size distributions (PSDs). All limestones were of a high purity. Model predictions were found to be qualitatively in good agreement with experimental data without any use of adjustable parameters. Deviations between measurements and simulations were...... attributed primarily to the PSD measurements of the limestone particles, which were used as model inputs. The PSDs, measured using a laser diffrac-tion-based Malvern analyser, were probably not representative of the limestone samples because agglomeration phenomena took place when the particles were......In wet flue gas desulphurisation (FGD) plants, the most common sorbent is limestone. Over the past 25 years, many attempts to model the transient dissolution of limestone particles in aqueous solutions have been performed, due to the importance for the development of reliable FGD simu-lation tools...

  5. The bold and the beautiful. Influence of body size of televised media models on body dissatisfaction and actual food intake.

    Science.gov (United States)

    Anschutz, Doeschka J; Engels, Rutger C M E; Becker, Eni S; van Strien, Tatjana

    2008-11-01

    The effects of exposure to televised thin and average size models on body dissatisfaction and actual food intake were examined. Normal weight female students (N=104) were exposed to a 30-min movie clip featuring beautiful girls. Half of them viewed the movie clip in normal screen size (4:3) and the other half viewed the same movie clip in broad screen size (16:9), in which the body size of the actresses was slightly stretched breadthways. Actual food intake while watching and body dissatisfaction afterwards was examined. Additionally, restrained eating was assessed as a possible moderating variable. Two interaction effects were found between screen size and restrained eating on body dissatisfaction and actual food intake. Restrained eaters tended to feel worse and eat less in the average size condition compared to the thin model condition, whereas unrestrained eaters felt worse and ate less in the thin model condition compared to the average size condition. So, body size of televised images affected body dissatisfaction and food intake, differentially for restrained and unrestrained eaters. The screen sizes used correspond with widely used screen sizes nowadays enhancing the practical relevance of the study, since screen size might affect body dissatisfaction and food intake in daily life as well.

  6. Physical Model for Rapid and Accurate Determination of Nanopore Size via Conductance Measurement.

    Science.gov (United States)

    Wen, Chenyu; Zhang, Zhen; Zhang, Shi-Li

    2017-10-27

    Nanopores have been explored for various biochemical and nanoparticle analyses, primarily via characterizing the ionic current through the pores. At present, however, size determination for solid-state nanopores is experimentally tedious and theoretically unaccountable. Here, we establish a physical model by introducing an effective transport length, L eff , that measures, for a symmetric nanopore, twice the distance from the center of the nanopore where the electric field is the highest to the point along the nanopore axis where the electric field falls to e -1 of this maximum. By [Formula: see text], a simple expression S 0 = f (G, σ, h, β) is derived to algebraically correlate minimum nanopore cross-section area S 0 to nanopore conductance G, electrolyte conductivity σ, and membrane thickness h with β to denote pore shape that is determined by the pore fabrication technique. The model agrees excellently with experimental results for nanopores in graphene, single-layer MoS 2 , and ultrathin SiN x films. The generality of the model is verified by applying it to micrometer-size pores.

  7. Probabilistic finite-size transport models for fusion: Anomalous transport and scaling laws

    International Nuclear Information System (INIS)

    Milligen, B.Ph. van; Sanchez, R.; Carreras, B.A.

    2004-01-01

    Transport in fusion plasmas in the low confinement mode is characterized by several remarkable properties: the anomalous scaling of transport with system size, stiff (or 'canonical') profiles, power degradation, and rapid transport phenomena. The present article explores the possibilities of constructing a unified transport model, based on the continuous-time random walk, in which all these phenomena are handled adequately. The resulting formalism appears to be sufficiently general to provide a sound starting point for the development of a full-blown plasma transport code, capable of incorporating the relevant microscopic transport mechanisms, and allowing predictions of confinement properties

  8. Mathematical programming models for solving in equal-sized facilities layout problems. A genetic search method

    International Nuclear Information System (INIS)

    Tavakkoli-Moghaddam, R.

    1999-01-01

    This paper present unequal-sized facilities layout solutions generated by a genetic search program. named Layout Design using a Genetic Algorithm) 9. The generalized quadratic assignment problem requiring pre-determined distance and material flow matrices as the input data and the continuous plane model employing a dynamic distance measure and a material flow matrix are discussed. Computational results on test problems are reported as compared with layout solutions generated by the branch - and bound algorithm a hybrid method merging simulated annealing and local search techniques, and an optimization process of an enveloped block

  9. Steady-State Numerical Modeling of Size Effects in Wire Drawing

    DEFF Research Database (Denmark)

    Juul, Kristian Jørgensen; Nielsen, Kim Lau; Niordson, Christian Frithiof

    2016-01-01

    Wire drawing processes at micron scale receive increased interest as micro wires are increasingly required in micro electrical components. At the micron scale, size effects become important and have to be taken into consideration. The goal is to optimize the semi-cone angle of the tool in terms...... of drawing force. The present study employs a steady-state modelling technique that omits the transient regime, thus creating a basis for comprehensive parameter studies. The steady-state procedure is based on the streamline integration method presented by Dean and Hutchinson [1]. This approach allows...

  10. Modeling capsid kinetics assembly from the steady state distribution of multi-sizes aggregates

    Energy Technology Data Exchange (ETDEWEB)

    Hozé, Nathanaël; Holcman, David

    2014-01-24

    The kinetics of aggregation for particles of various sizes depends on their diffusive arrival and fusion at a specific nucleation site. We present here a mean-field approximation and a stochastic jump model for aggregates at equilibrium. This approach is an alternative to the classical Smoluchowski equations that do not have a close form and are not solvable in general. We analyze these mean-field equations and obtain the kinetics of a cluster formation. Our approach provides a simplified theoretical framework to study the kinetics of viral capsid formation, such as HIV from the self-assembly of the structural proteins Gag.

  11. Parameter Scaling for Epidemic Size in a Spatial Epidemic Model with Mobile Individuals.

    Directory of Open Access Journals (Sweden)

    Chiyori T Urabe

    Full Text Available In recent years, serious infectious diseases tend to transcend national borders and widely spread in a global scale. The incidence and prevalence of epidemics are highly influenced not only by pathogen-dependent disease characteristics such as the force of infection, the latent period, and the infectious period, but also by human mobility and contact patterns. However, the effect of heterogeneous mobility of individuals on epidemic outcomes is not fully understood. Here, we aim to elucidate how spatial mobility of individuals contributes to the final epidemic size in a spatial susceptible-exposed-infectious-recovered (SEIR model with mobile individuals in a square lattice. After illustrating the interplay between the mobility parameters and the other parameters on the spatial epidemic spreading, we propose an index as a function of system parameters, which largely governs the final epidemic size. The main contribution of this study is to show that the proposed index is useful for estimating how parameter scaling affects the final epidemic size. To demonstrate the effectiveness of the proposed index, we show that there is a positive correlation between the proposed index computed with the real data of human airline travels and the actual number of positive incident cases of influenza B in the entire world, implying that the growing incidence of influenza B is attributed to increased human mobility.

  12. Modelling the size and polydispersity of magnetic hybrid nanoparticles for luminescent sensing of oxygen

    International Nuclear Information System (INIS)

    Marín-Suárez, Marta; Arias-Martos, María C.; Fernández-Sánchez, Jorge F.; Fernández-Gutiérrez, Alberto; Galeano-Díaz, Teresa

    2013-01-01

    We report on a strategy to model both the size (d) and the polydispersity (PdI) of magnetic oxygen-sensitive nanoparticles with a typical size of 200 nm in order to increase the surface area. The strategy is based on experimental design and Response Surface Methodology. Nanoparticles were prepared by mini emulsion solvent evaporation of solutions of poly(styrene-co-maleic anhydride). Features of this strategy include (1) a quick selection of the most important variables that govern d and PdI; (2) a better understanding of the parameters that affect the performance of the polymer; and (3) optimized conditions for the synthesis of nanoparticles of targeted d and PdI. The results were used to produce nanoparticles in sizes that range from 100 to 300 nm and with small polydispersity. The addition of a platinum porphyrin complex that acts as a luminescent probe for oxygen and of magnetite (Fe 3 O 4 ) to the polymeric particles, did not affect d and PdI, thus demonstrating that this strategy simplifies their synthesis. The resulting luminescent and magnetic sensor nanoparticles respond to dissolved oxygen with sensitivity (Stern-Volmer constant) of around 35 bar −1 . (author)

  13. The Effect of Sterilization on Size and Shape of Fat Globules in Model Processed Cheese Samples

    Directory of Open Access Journals (Sweden)

    B. Tremlová

    2006-01-01

    Full Text Available Model cheese samples from 4 independent productions were heat sterilized (117 °C, 20 minutes after the melting process and packing with an aim to prolong their durability. The objective of the study was to assess changes in the size and shape of fat globules due to heat sterilization by using image analysis methods. The study included a selection of suitable methods of preparation mounts, taking microphotographs and making overlays for automatic processing of photographs by image analyser, ascertaining parameters to determine the size and shape of fat globules and statistical analysis of results obtained. The results of the experiment suggest that changes in shape of fat globules due to heat sterilization are not unequivocal. We found that the size of fat globules was significantly increased (p < 0.01 due to heat sterilization (117 °C, 20 min, and the shares of small fat globules (up to 500 μm2, or 100 μm2 in the samples of heat sterilized processed cheese were decreased. The results imply that the image analysis method is very useful when assessing the effect of technological process on the quality of processed cheese quality.

  14. An inverse modeling procedure to determine particle growth and nucleation rates from measured aerosol size distributions

    Directory of Open Access Journals (Sweden)

    B. Verheggen

    2006-01-01

    Full Text Available Classical nucleation theory is unable to explain the ubiquity of nucleation events observed in the atmosphere. This shows a need for an empirical determination of the nucleation rate. Here we present a novel inverse modeling procedure to determine particle nucleation and growth rates based on consecutive measurements of the aerosol size distribution. The particle growth rate is determined by regression analysis of the measured change in the aerosol size distribution over time, taking into account the effects of processes such as coagulation, deposition and/or dilution. This allows the growth rate to be determined with a higher time-resolution than can be deduced from inspecting contour plots ('banana-plots''. Knowing the growth rate as a function of time enables the evaluation of the time of nucleation of measured particles of a certain size. The nucleation rate is then obtained by integrating the particle losses from time of measurement to time of nucleation. The regression analysis can also be used to determine or verify the optimum value of other parameters of interest, such as the wall loss or coagulation rate constants. As an example, the method is applied to smog chamber measurements. This program offers a powerful interpretive tool to study empirical aerosol population dynamics in general, and nucleation and growth in particular.

  15. Impact of changing the measles vaccine vial size on Niger's vaccine supply chain: a computational model

    Science.gov (United States)

    2011-01-01

    Background Many countries, such as Niger, are considering changing their vaccine vial size presentation and may want to evaluate the subsequent impact on their supply chains, the series of steps required to get vaccines from their manufacturers to patients. The measles vaccine is particularly important in Niger, a country prone to measles outbreaks. Methods We developed a detailed discrete event simulation model of the vaccine supply chain representing every vaccine, storage location, refrigerator, freezer, and transport device (e.g., cold trucks, 4 × 4 trucks, and vaccine carriers) in the Niger Expanded Programme on Immunization (EPI). Experiments simulated the impact of replacing the 10-dose measles vial size with 5-dose, 2-dose and 1-dose vial sizes. Results Switching from the 10-dose to the 5-dose, 2-dose and 1-dose vial sizes decreased the average availability of EPI vaccines for arriving patients from 83% to 82%, 81% and 78%, respectively for a 100% target population size. The switches also changed transport vehicle's utilization from a mean of 58% (range: 4-164%) to means of 59% (range: 4-164%), 62% (range: 4-175%), and 67% (range: 5-192%), respectively, between the regional and district stores, and from a mean of 160% (range: 83-300%) to means of 161% (range: 82-322%), 175% (range: 78-344%), and 198% (range: 88-402%), respectively, between the district to integrated health centres (IHC). The switch also changed district level storage utilization from a mean of 65% to means of 64%, 66% and 68% (range for all scenarios: 3-100%). Finally, accounting for vaccine administration, wastage, and disposal, replacing the 10-dose vial with the 5 or 1-dose vials would increase the cost per immunized patient from $0.47US to $0.71US and $1.26US, respectively. Conclusions The switch from the 10-dose measles vaccines to smaller vial sizes could overwhelm the capacities of many storage facilities and transport vehicles as well as increase the cost per vaccinated child. PMID

  16. Impact of changing the measles vaccine vial size on Niger's vaccine supply chain: a computational model

    Directory of Open Access Journals (Sweden)

    Kenea Hailu

    2011-06-01

    Full Text Available Abstract Background Many countries, such as Niger, are considering changing their vaccine vial size presentation and may want to evaluate the subsequent impact on their supply chains, the series of steps required to get vaccines from their manufacturers to patients. The measles vaccine is particularly important in Niger, a country prone to measles outbreaks. Methods We developed a detailed discrete event simulation model of the vaccine supply chain representing every vaccine, storage location, refrigerator, freezer, and transport device (e.g., cold trucks, 4 × 4 trucks, and vaccine carriers in the Niger Expanded Programme on Immunization (EPI. Experiments simulated the impact of replacing the 10-dose measles vial size with 5-dose, 2-dose and 1-dose vial sizes. Results Switching from the 10-dose to the 5-dose, 2-dose and 1-dose vial sizes decreased the average availability of EPI vaccines for arriving patients from 83% to 82%, 81% and 78%, respectively for a 100% target population size. The switches also changed transport vehicle's utilization from a mean of 58% (range: 4-164% to means of 59% (range: 4-164%, 62% (range: 4-175%, and 67% (range: 5-192%, respectively, between the regional and district stores, and from a mean of 160% (range: 83-300% to means of 161% (range: 82-322%, 175% (range: 78-344%, and 198% (range: 88-402%, respectively, between the district to integrated health centres (IHC. The switch also changed district level storage utilization from a mean of 65% to means of 64%, 66% and 68% (range for all scenarios: 3-100%. Finally, accounting for vaccine administration, wastage, and disposal, replacing the 10-dose vial with the 5 or 1-dose vials would increase the cost per immunized patient from $0.47US to $0.71US and $1.26US, respectively. Conclusions The switch from the 10-dose measles vaccines to smaller vial sizes could overwhelm the capacities of many storage facilities and transport vehicles as well as increase the cost per

  17. Impact of changing the measles vaccine vial size on Niger's vaccine supply chain: a computational model.

    Science.gov (United States)

    Assi, Tina-Marie; Brown, Shawn T; Djibo, Ali; Norman, Bryan A; Rajgopal, Jayant; Welling, Joel S; Chen, Sheng-I; Bailey, Rachel R; Kone, Souleymane; Kenea, Hailu; Connor, Diana L; Wateska, Angela R; Jana, Anirban; Wisniewski, Stephen R; Van Panhuis, Willem G; Burke, Donald S; Lee, Bruce Y

    2011-06-02

    Many countries, such as Niger, are considering changing their vaccine vial size presentation and may want to evaluate the subsequent impact on their supply chains, the series of steps required to get vaccines from their manufacturers to patients. The measles vaccine is particularly important in Niger, a country prone to measles outbreaks. We developed a detailed discrete event simulation model of the vaccine supply chain representing every vaccine, storage location, refrigerator, freezer, and transport device (e.g., cold trucks, 4 × 4 trucks, and vaccine carriers) in the Niger Expanded Programme on Immunization (EPI). Experiments simulated the impact of replacing the 10-dose measles vial size with 5-dose, 2-dose and 1-dose vial sizes. Switching from the 10-dose to the 5-dose, 2-dose and 1-dose vial sizes decreased the average availability of EPI vaccines for arriving patients from 83% to 82%, 81% and 78%, respectively for a 100% target population size. The switches also changed transport vehicle's utilization from a mean of 58% (range: 4-164%) to means of 59% (range: 4-164%), 62% (range: 4-175%), and 67% (range: 5-192%), respectively, between the regional and district stores, and from a mean of 160% (range: 83-300%) to means of 161% (range: 82-322%), 175% (range: 78-344%), and 198% (range: 88-402%), respectively, between the district to integrated health centres (IHC). The switch also changed district level storage utilization from a mean of 65% to means of 64%, 66% and 68% (range for all scenarios: 3-100%). Finally, accounting for vaccine administration, wastage, and disposal, replacing the 10-dose vial with the 5 or 1-dose vials would increase the cost per immunized patient from $0.47US to $0.71US and $1.26US, respectively. The switch from the 10-dose measles vaccines to smaller vial sizes could overwhelm the capacities of many storage facilities and transport vehicles as well as increase the cost per vaccinated child.

  18. Modeling fractal structure of city-size distributions using correlation functions.

    Science.gov (United States)

    Chen, Yanguang

    2011-01-01

    Zipf's law is one the most conspicuous empirical facts for cities, however, there is no convincing explanation for the scaling relation between rank and size and its scaling exponent. Using the idea from general fractals and scaling, I propose a dual competition hypothesis of city development to explain the value intervals and the special value, 1, of the power exponent. Zipf's law and Pareto's law can be mathematically transformed into one another, but represent different processes of urban evolution, respectively. Based on the Pareto distribution, a frequency correlation function can be constructed. By scaling analysis and multifractals spectrum, the parameter interval of Pareto exponent is derived as (0.5, 1]; Based on the Zipf distribution, a size correlation function can be built, and it is opposite to the first one. By the second correlation function and multifractals notion, the Pareto exponent interval is derived as [1, 2). Thus the process of urban evolution falls into two effects: one is the Pareto effect indicating city number increase (external complexity), and the other the Zipf effect indicating city size growth (internal complexity). Because of struggle of the two effects, the scaling exponent varies from 0.5 to 2; but if the two effects reach equilibrium with each other, the scaling exponent approaches 1. A series of mathematical experiments on hierarchical correlation are employed to verify the models and a conclusion can be drawn that if cities in a given region follow Zipf's law, the frequency and size correlations will follow the scaling law. This theory can be generalized to interpret the inverse power-law distributions in various fields of physical and social sciences.

  19. Detailed measurements and modelling of thermo active components using a room size test facility

    DEFF Research Database (Denmark)

    Weitzmann, Peter; Svendsen, Svend

    2005-01-01

    measurements in an office sized test facility with thermo active ceiling and floor as well as modelling of similar conditions in a computer program designed for analysis of building integrated heating and cooling systems. A method for characterizing the cooling capacity of thermo active components is described...... based on measurements of the energy balance of the thermo active deck. A cooling capacity of around 60W/m² at a temperature difference of 10K between room and fluid temperature has been found. It is also shown, that installing a lowered acoustic ceiling covering around 50% of the ceiling surface area...... only causes a reduction in the cooling capacity of around 10%. At the same time, the simulation model is able to reproduce the results from the measurements. Especially the heat flows are well predicted with a deviation of only a few percent, while the temperatures are not as well predicted, though...

  20. Element size and other restrictions in finite-element modeling of reinforced concrete at elevated temperatures

    DEFF Research Database (Denmark)

    Carstensen, Josephine Voigt; Jomaas, Grunde; Pankaj, Pankaj

    2013-01-01

    One of the accepted approaches for postpeak finite-element modeling of RC comprises combining plain concrete, reinforcement, and interaction behaviors. In these, the postpeak strain-softening behavior of plain concrete is incorporated by the use of fracture energy concepts. This study attempts to...... variation in values. Application of the evaluated fracture energy values shows that these impose severe element size and reinforcement ratio limits. The effect of the limits is illustrated for a RC specimen. © 2013 American Society of Civil Engineers.......One of the accepted approaches for postpeak finite-element modeling of RC comprises combining plain concrete, reinforcement, and interaction behaviors. In these, the postpeak strain-softening behavior of plain concrete is incorporated by the use of fracture energy concepts. This study attempts...

  1. Electromagnetic properties and sizes of new vector mesons within the three-triplet model

    International Nuclear Information System (INIS)

    Govorkov, A.B.

    1976-01-01

    The new vector mesons psi(3095) and psi'(3684) are treated by analogy with the ω- and PHI-mesons, respectively, within the scheme of three triplets of the integer charge quarks-sakations. Their decay into the lepton pairs is calculated in the model of nonrelativistic harmonic oscillator. It appears that sizes of the new mesons decrease, and the effective mass of constituent quarks increases as compared with the corresponding quantities of the usual mesons. Within the vector meson dominence model the relation between the width of the transition psi → ν+γ and photoproduction cross section on nucleons is established and the estimate for the former is 3 keV

  2. Modelling the cutting edge radius size effect for force prediction in micro milling

    DEFF Research Database (Denmark)

    Bissacco, Giuliano; Hansen, Hans Nørgaard; Jan, Slunsky

    2008-01-01

    This paper presents a theoretical model for cutting force prediction in micro milling, taking into account the cutting edge radius size effect, the tool run out and the deviation of the chip flow angle from the inclination angle. A parameterization according to the uncut chip thickness to cutting...... edge radius ratio is used for the parameters involved in the force calculation. The model was verified by means of cutting force measurements in micro milling. The results show good agreement between predicted and measured forces. It is also demonstrated that the use of the Stabler's rule...... is a reasonable approximation and that micro end mill run out is effectively compensated by the deflections induced by the cutting forces....

  3. Mathematical modeling of pigment dispersion taking into account the full agglomerate particle size distribution

    DEFF Research Database (Denmark)

    Kiil, Søren

    2017-01-01

    The purpose of this work is to develop a mathematical model that can quantify the dispersion of pigments, with a focus on the mechanical breakage of pigment agglomerates. The underlying physical mechanism was assumed to be surface erosion of spherical pigment agglomerates. The full agglomerate......-based acrylic vehicle in a three-roll mill. When the linear rate of agglomerate surface erosion was taken to be proportional to the external agglomerate surface area, simulations of the volume-moment mean diameter over time were in good quantitative agreement with experimental data for all three pigments....... The only adjustable parameter used was an apparent rate constant for the linear agglomerate erosion rate. Model simulations, at selected values of time, for the full agglomerate particle size distribution were in good qualitative agreement with the measured values. A quantitative match of the experimental...

  4. Standardizing effect size from linear regression models with log-transformed variables for meta-analysis.

    Science.gov (United States)

    Rodríguez-Barranco, Miguel; Tobías, Aurelio; Redondo, Daniel; Molina-Portillo, Elena; Sánchez, María José

    2017-03-17

    Meta-analysis is very useful to summarize the effect of a treatment or a risk factor for a given disease. Often studies report results based on log-transformed variables in order to achieve the principal assumptions of a linear regression model. If this is the case for some, but not all studies, the effects need to be homogenized. We derived a set of formulae to transform absolute changes into relative ones, and vice versa, to allow including all results in a meta-analysis. We applied our procedure to all possible combinations of log-transformed independent or dependent variables. We also evaluated it in a simulation based on two variables either normally or asymmetrically distributed. In all the scenarios, and based on different change criteria, the effect size estimated by the derived set of formulae was equivalent to the real effect size. To avoid biased estimates of the effect, this procedure should be used with caution in the case of independent variables with asymmetric distributions that significantly differ from the normal distribution. We illustrate an application of this procedure by an application to a meta-analysis on the potential effects on neurodevelopment in children exposed to arsenic and manganese. The procedure proposed has been shown to be valid and capable of expressing the effect size of a linear regression model based on different change criteria in the variables. Homogenizing the results from different studies beforehand allows them to be combined in a meta-analysis, independently of whether the transformations had been performed on the dependent and/or independent variables.

  5. Urban Optimum Population Size and Development Pattern Based on Ecological Footprint Model: Case of Zhoushan, China

    Directory of Open Access Journals (Sweden)

    Yuan LU

    2016-09-01

    Full Text Available The agglomeration of population in the city can reflect the prosperity in the economy, society and culture. However, it has also brought a series of problems like environmental pollution, traffic congestion, housing shortage and jobs crisis. The results can be shown as the failure of urban comprehensive function, the decline of city benefits, and the contradiction between socioeconomic circumstance and ecosystem. Therefore, a reasonable population capacity, which is influenced by ecological resources, urban environment, geographical elements, social and economic factors, etc., is objectively needed. How to deal with the relationship between the utilization of natural capital and development of the city is extremely essential. This paper takes Zhoushan Island as an example, which is the fourth largest island off the coast of China. Firstly, the interactively influencing factors of urban optimal population are illustrated. And method is chosen to study the optimal population size. Secondly, based on the model of ecological footprint (EP, the paper calculates and analyzes the ecological footprint and ecological capacity of the Zhoushan Island, in order to explore the optimal population size of the city. Thirdly, analysis and evaluation of the resources and urban environment carrying capacity is made. Finally, the solution of the existing population problems and the suggestion for the future development pattern of the city are proposed in the urban eco-planning of Zhoushan Island. The main strategies can be summarized in two aspects: one is to reduce the ecological footprint, the other is to increase the ecological supply. The conclusion is that the current population of Zhoushan Island is far beyond the optimum population size calculated by the ecological footprint model. Therefore, sustainable development should be the guidance for urban planning in Zhoushan Island, and a low-carbon development pattern for the city is advocated.

  6. Standardizing effect size from linear regression models with log-transformed variables for meta-analysis

    Directory of Open Access Journals (Sweden)

    Miguel Rodríguez-Barranco

    2017-03-01

    Full Text Available Abstract Background Meta-analysis is very useful to summarize the effect of a treatment or a risk factor for a given disease. Often studies report results based on log-transformed variables in order to achieve the principal assumptions of a linear regression model. If this is the case for some, but not all studies, the effects need to be homogenized. Methods We derived a set of formulae to transform absolute changes into relative ones, and vice versa, to allow including all results in a meta-analysis. We applied our procedure to all possible combinations of log-transformed independent or dependent variables. We also evaluated it in a simulation based on two variables either normally or asymmetrically distributed. Results In all the scenarios, and based on different change criteria, the effect size estimated by the derived set of formulae was equivalent to the real effect size. To avoid biased estimates of the effect, this procedure should be used with caution in the case of independent variables with asymmetric distributions that significantly differ from the normal distribution. We illustrate an application of this procedure by an application to a meta-analysis on the potential effects on neurodevelopment in children exposed to arsenic and manganese. Conclusions The procedure proposed has been shown to be valid and capable of expressing the effect size of a linear regression model based on different change criteria in the variables. Homogenizing the results from different studies beforehand allows them to be combined in a meta-analysis, independently of whether the transformations had been performed on the dependent and/or independent variables.

  7. Solar granulation and statistical crystallography: A modeling approach using size-shape relations

    Science.gov (United States)

    Noever, D. A.

    1994-01-01

    The irregular polygonal pattern of solar granulation is analyzed for size-shape relations using statistical crystallography. In contrast to previous work which has assumed perfectly hexagonal patterns for granulation, more realistic accounting of cell (granule) shapes reveals a broader basis for quantitative analysis. Several features emerge as noteworthy: (1) a linear correlation between number of cell-sides and neighboring shapes (called Aboav-Weaire's law); (2) a linear correlation between both average cell area and perimeter and the number of cell-sides (called Lewis's law and a perimeter law, respectively) and (3) a linear correlation between cell area and squared perimeter (called convolution index). This statistical picture of granulation is consistent with a finding of no correlation in cell shapes beyond nearest neighbors. A comparative calculation between existing model predictions taken from luminosity data and the present analysis shows substantial agreements for cell-size distributions. A model for understanding grain lifetimes is proposed which links convective times to cell shape using crystallographic results.

  8. Acoustic modeling and eigenanalysis of coupled rooms with a transparent coupling aperture of variable size

    Science.gov (United States)

    Shi, Shuangxia; Jin, Guoyong; Xiao, Bin; Liu, Zhigang

    2018-04-01

    This paper is concerned with the modeling and acoustic eigenanalysis of coupled spaces with a coupling aperture of variable size. A modeling method for this problem is developed based on the energy principle in combination with a 3D modified Fourier cosine series approach. Under this theoretical framework, the energy exchange property and acoustically transparent characteristics of the opening are taken into account via the inflow and outflow sound powers through the opening without any assumptions. The sound pressure in the subrooms is constructed in the form of the three-dimensional modified Fourier series with several auxiliary functions introduced to ensure the uniform convergence of the solution over the entire solution domain. The accuracy of the natural frequencies and mode shapes of three exemplary coupled rooms systems is verified against numerical data obtained by finite element method, with good agreement achieved. The present method offers a unified procedure for a variety of cases because the modification of any parameter from one case to another, such as the size and location of the coupling aperture, is as simple as modifying the material properties, requiring no changes to the solution procedures.

  9. Linked Gauss-Diffusion processes for modeling a finite-size neuronal network.

    Science.gov (United States)

    Carfora, M F; Pirozzi, E

    2017-11-01

    A Leaky Integrate-and-Fire (LIF) model with stochastic current-based linkages is considered to describe the firing activity of neurons interacting in a (2×2)-size feed-forward network. In the subthreshold regime and under the assumption that no more than one spike is exchanged between coupled neurons, the stochastic evolution of the neuronal membrane voltage is subject to random jumps due to interactions in the network. Linked Gauss-Diffusion processes are proposed to describe this dynamics and to provide estimates of the firing probability density of each neuron. To this end, an iterated integral equation-based approach is applied to evaluate numerically the first passage time density of such processes through the firing threshold. Asymptotic approximations of the firing densities of surrounding neurons are used to obtain closed-form expressions for the mean of the involved processes and to simplify the numerical procedure. An extension of the model to an (N×N)-size network is also given. Histograms of firing times obtained by simulations of the LIF dynamics and numerical firings estimates are compared. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. Spreading Speed, Traveling Waves, and Minimal Domain Size in Impulsive Reaction–Diffusion Models

    KAUST Repository

    Lewis, Mark A.

    2012-08-15

    How growth, mortality, and dispersal in a species affect the species\\' spread and persistence constitutes a central problem in spatial ecology. We propose impulsive reaction-diffusion equation models for species with distinct reproductive and dispersal stages. These models can describe a seasonal birth pulse plus nonlinear mortality and dispersal throughout the year. Alternatively, they can describe seasonal harvesting, plus nonlinear birth and mortality as well as dispersal throughout the year. The population dynamics in the seasonal pulse is described by a discrete map that gives the density of the population at the end of a pulse as a possibly nonmonotone function of the density of the population at the beginning of the pulse. The dynamics in the dispersal stage is governed by a nonlinear reaction-diffusion equation in a bounded or unbounded domain. We develop a spatially explicit theoretical framework that links species vital rates (mortality or fecundity) and dispersal characteristics with species\\' spreading speeds, traveling wave speeds, as well as minimal domain size for species persistence. We provide an explicit formula for the spreading speed in terms of model parameters, and show that the spreading speed can be characterized as the slowest speed of a class of traveling wave solutions. We also give an explicit formula for the minimal domain size using model parameters. Our results show how the diffusion coefficient, and the combination of discrete- and continuous-time growth and mortality determine the spread and persistence dynamics of the population in a wide variety of ecological scenarios. Numerical simulations are presented to demonstrate the theoretical results. © 2012 Society for Mathematical Biology.

  11. Finite element modeling of grain size effects on the ultrasonic microstructural noise backscattering in polycrystalline materials.

    Science.gov (United States)

    Bai, X; Tie, B; Schmitt, J-H; Aubry, D

    2018-07-01

    The correlation between ultrasonic wave propagation and polycrystalline microstructures has significant implications in nondestructive evaluation. An original numerical approach using the finite element method to quantify in both time and frequency domains the ultrasonic noise scattering due to the elastic heterogeneity of polycrystalline microstructures is presented. Based on the reciprocity theorem, it allows the scattering evaluation using mechanical data recorded only on the boundary of polycrystal instead of within its volume and is applicable to any polycrystalline aggregate regardless of its crystallographic or morphological characteristics. Consequently it gives a more realistic and accurate access of polycrystalline microstructures than the classical analytical models developed under the assumption of single scattering and the Born approximation. The numerical approach is proposed within the same unified theoretical framework as the classical analytical models, so it is possible to validate it in the cases of idealized microstructures for which the considered analytical models remain relevant. As an original result, assuming single phase, untextured and equiaxed microstructures, two-dimensional (2D) theoretical formulas are developed and a frequency-dependent coefficient is found compared to the classical three-dimensional (3D) formulas. 2D numerical simulations are then performed for idealized microstructures composed of hexagonal grains with a uniform grain-size. Three grain sizes are considered herein and involve different scattering regions. Good comparisons are obtained between theoretical and numerical estimates of the backscattering coefficient, which validate the numerical approach. Effects of the grain boundary orientations are analyzed by modeling an irregular hexagonal grain morphology and a random grain morphology generated by an established Voronoi approach. The origin of the significant oscillation level of backscattering is then investigated

  12. Gas/particle partitioning, particle-size distribution of atmospheric polybrominated diphenyl ethers in southeast Shanghai rural area and size-resolved predicting model.

    Science.gov (United States)

    Su, Peng-Hao; Tomy, Gregg T; Hou, Chun-Yan; Yin, Fang; Feng, Dao-Lun; Ding, Yong-Sheng; Li, Yi-Fan

    2018-04-01

    A size-segregated gas/particle partitioning coefficient K Pi was proposed and evaluated in the predicting models on the basis of atmospheric polybrominated diphenyl ether (PBDE) field data comparing with the bulk coefficient K P . Results revealed that the characteristics of atmospheric PBDEs in southeast Shanghai rural area were generally consistent with previous investigations, suggesting that this investigation was representative to the present pollution status of atmospheric PBDEs. K Pi was generally greater than bulk K P , indicating an overestimate of TSP (the mass concentration of total suspended particles) in the expression of bulk K P . In predicting models, K Pi led to a significant shift in regression lines as compared to K P , thus it should be more cautious to investigate sorption mechanisms using the regression lines. The differences between the performances of K Pi and K P were helpful to explain some phenomenon in predicting investigations, such as P L 0 and K OA models overestimate the particle fractions of PBDEs and the models work better at high temperature than at low temperature. Our findings are important because they enabled an insight into the influence of particle size on predicting models. Copyright © 2018 Elsevier Ltd. All rights reserved.

  13. Nonlocal superelastic model of size-dependent hardening and dissipation in single crystal Cu-Al-Ni shape memory alloys.

    Science.gov (United States)

    Qiao, Lei; Rimoli, Julian J; Chen, Ying; Schuh, Christopher A; Radovitzky, Raul

    2011-02-25

    We propose a nonlocal continuum model to describe the size-dependent superelastic effect observed in recent experiments of single crystal Cu-Al-Ni shape memory alloys. The model introduces two length scales, one in the free energy and one in the dissipation, which account for the size-dependent hardening and dissipation in the loading and unloading response of micro- and nanopillars subject to compression tests. The information provided by the model suggests that the size dependence observed in the dissipation is likely to be associated with a nonuniform evolution of the distribution of the austenitic and martensitic phases during the loading cycle. © 2011 American Physical Society

  14. A mathematical model for the dynamic simulation of low size cogeneration gas turbines within smart microgrids

    International Nuclear Information System (INIS)

    Bracco, Stefano; Delfino, Federico

    2017-01-01

    Microturbines represent a suitable technology to be adopted in smart microgrids since they are characterized by affordable capital and maintenance costs, high reliability and flexibility, and low environmental impact; moreover, they can be fed by fossil fuels or biofuels. They can operate in cogeneration and trigeneration mode, thus permitting to attain high global efficiency values of the energy conversion system from primary energy to electrical and thermal energy; from the electrical point of view, microturbines can operate connected to the distribution grid but also in islanded mode, thus enabling their use in remote areas without electrification. The paper describes the mathematical model that has been developed to simulate in off-design and transient conditions the operation of a 65 kW el cogeneration microturbine installed within a smart microgrid. The dynamic simulation model is characterized by a flexible architecture that permits to simulate other different size single-shaft microturbines. The paper reports the main equations of the model, focusing on the architecture of the simulator and the microturbine control system; furthermore the most significant results derived from the validation phase are reported too, referring to the microturbine installed in the Smart Polygeneration Microgrid of the Savona Campus at the University of Genoa in Italy. - Highlights: • Dynamic simulation model of a cogeneration microturbine. • Off-design and transient performances of the microturbine. • Simulator validated on the Smart Polygeneration Microgrid at the Savona Campus.

  15. Finite-size effects in Luther-Emery phases of Holstein and Hubbard models

    Science.gov (United States)

    Greitemann, J.; Hesselmann, S.; Wessel, S.; Assaad, F. F.; Hohenadler, M.

    2015-12-01

    The one-dimensional Holstein model and its generalizations have been studied extensively to understand the effects of electron-phonon interaction. The half-filled case is of particular interest, as it describes a transition from a metallic phase with a spin gap due to attractive backscattering to a Peierls insulator with charge-density-wave order. Our quantum Monte Carlo results support the existence of a metallic phase with dominant power-law charge correlations, as described by the Luther-Emery fixed point. We demonstrate that for Holstein and also for purely fermionic models the spin gap significantly complicates finite-size numerical studies, and explains inconsistent previous results for Luttinger parameters and phase boundaries. On the other hand, no such complications arise in spinless models. The correct low-energy theory of the spinful Holstein model is argued to be that of singlet bipolarons with a repulsive, mutual interaction. This picture naturally explains the existence of a metallic phase, but also implies that gapless Luttinger liquid theory is not applicable.

  16. Comparison of Turbulence Models in Simulation of Flow in Small-Size Centrifugal Compressor

    Directory of Open Access Journals (Sweden)

    B. B. Novickii

    2015-01-01

    Full Text Available The aim of the work is the choice of turbulence model for the closure of the Reynoldsaveraged Navier-Stokes equations for calculation of the characteristics of small-size centrifugal compressor. To this were built three-dimensional sectors (as the compressor axisymmetric blade impeller and the diffuser of the centrifugal compressor on the basis of which they were created two grid models. The dimension of the grid model for the calculation models of turbulence komega and SST was 1.4 million. Elements and the dimensionless parameter y + does not exceed 2. turbulence model family k-epsilon model grid was also 1.4 million. Elements, and the dimensionless parameter y + was greater than 20, which corresponds to recommended values. The next part of the work was the task of boundary conditions required for the correct ca lculation. When the impeller inlet pawned pressure working fluid and the total temperature at the outlet and the gas flow rate through the stage. On the side faces sectors pawned boundary cond ition «Periodic», allowing everything except the wheel, but only axisymmetric part, which significantly reduces the required computational time and resources. Accounting clearance in addition to the meridional geometry construction additionally taken into account boundary condition «Counter Rotating Wall», which allows you to leave the domain in the rotating disc fixed coa ting.The next step was to analyze the results of these calculations, which showed that the turbulence model k-epsilon and RNG does not show the velocity vectors in the boundary layer, and "pushes" the flow from the blade using wall functions. At the core of the flow turbulence model k-omega shown for the undisturbed flow, which is not typical for the compressor working on predpompazhnom mode. For viscous gas diffuser vane for turbulence models SST, k-omega, RNG k-epsilon and has a similar character.The paper compares the characteristics of pressure centrifugal compressor

  17. Superior model for fault tolerance computation in designing nano-sized circuit systems

    Energy Technology Data Exchange (ETDEWEB)

    Singh, N. S. S., E-mail: narinderjit@petronas.com.my; Muthuvalu, M. S., E-mail: msmuthuvalu@gmail.com [Fundamental and Applied Sciences Department, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, Perak (Malaysia); Asirvadam, V. S., E-mail: vijanth-sagayan@petronas.com.my [Electrical and Electronics Engineering Department, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, Perak (Malaysia)

    2014-10-24

    As CMOS technology scales nano-metrically, reliability turns out to be a decisive subject in the design methodology of nano-sized circuit systems. As a result, several computational approaches have been developed to compute and evaluate reliability of desired nano-electronic circuits. The process of computing reliability becomes very troublesome and time consuming as the computational complexity build ups with the desired circuit size. Therefore, being able to measure reliability instantly and superiorly is fast becoming necessary in designing modern logic integrated circuits. For this purpose, the paper firstly looks into the development of an automated reliability evaluation tool based on the generalization of Probabilistic Gate Model (PGM) and Boolean Difference-based Error Calculator (BDEC) models. The Matlab-based tool allows users to significantly speed-up the task of reliability analysis for very large number of nano-electronic circuits. Secondly, by using the developed automated tool, the paper explores into a comparative study involving reliability computation and evaluation by PGM and, BDEC models for different implementations of same functionality circuits. Based on the reliability analysis, BDEC gives exact and transparent reliability measures, but as the complexity of the same functionality circuits with respect to gate error increases, reliability measure by BDEC tends to be lower than the reliability measure by PGM. The lesser reliability measure by BDEC is well explained in this paper using distribution of different signal input patterns overtime for same functionality circuits. Simulation results conclude that the reliability measure by BDEC depends not only on faulty gates but it also depends on circuit topology, probability of input signals being one or zero and also probability of error on signal lines.

  18. Use of statistical models based on radiographic measurements to predict oviposition date and clutch size in rock iguanas (Cyclura nubila)

    International Nuclear Information System (INIS)

    Alberts, A.C.

    1995-01-01

    The ability to noninvasively estimate clutch size and predict oviposition date in reptiles can be useful not only to veterinary clinicians but also to managers of captive collections and field researchers. Measurements of egg size and shape, as well as position of the clutch within the coelomic cavity, were taken from diagnostic radiographs of 20 female Cuban rock iguanas, Cyclura nubila, 81 to 18 days prior to laying. Combined with data on maternal body size, these variables were entered into multiple regression models to predict clutch size and timing of egg laying. The model for clutch size was accurate to 0.53 ± 0.08 eggs, while the model for oviposition date was accurate to 6.22 ± 0.81 days. Equations were generated that should be applicable to this and other large Cyclura species. © 1995 Wiley-Liss, Inc

  19. Forward modeling of inherent optical properties from flow cytometry estimates of particle size and refractive index.

    Science.gov (United States)

    Agagliate, Jacopo; Lefering, Ina; McKee, David

    2018-03-10

    A Mie-based forward modeling procedure was developed to reconstruct bulk inherent optical properties (IOPs) from particle size distributions (PSDs) and real refractive index distributions (PRIDs) obtained using a previously developed flow cytometric (FC) method [Appl. Opt.57, 1705 (2018)APOPAI0003-693510.1364/AO.57.001705]. Given the available PSDs, extrapolations for the particle fraction outside the detection limits of the method and a complex refractive index input (with real part n r directly estimated and imaginary part n i adapted from the literature separately for organic and inorganic components), the model produces volume scattering functions that are integrated to produce scattering and backscattering coefficients, and absorption efficiencies that are used to calculate absorption coefficients. The procedure was applied to PSDs and PRIDs derived from natural samples retrieved in UK coastal waters and analyzed using a CytoSense flow cytometer (CytoBuoy b.v., The Netherlands). Optical closure analysis was carried out between reconstructed IOPs and in situ IOPs measured using an ac-9 spectrophotometer and a BB9 backscattering meter (WET Labs Inc., OR) in the same waters. The procedure is shown to achieve broad agreement with particulate scattering (b p ) and backscattering (b bp ) [root mean square percentage error (RMS%E): 35.3% and 44.5%, respectively) and to a lesser degree with backscattering ratio (b˜ bp ) (RMS%E: 77%). The procedure, however, generally overestimated particulate absorption (a p ) (RMS%E: 202.3%). This degree of closure was dependent on applying recently developed scattering error corrections to both absorption and attenuation in situ measurements. Not only do these results indirectly validate the FC method as a useful tool for PSD and PRID determination in natural particle populations, they also suggest that Mie theory may be a sufficient model for bulk IOP determination, with previously reported difficulties potentially being caused by

  20. Integrating citizen-science data with movement models to estimate the size of a migratory golden eagle population

    Science.gov (United States)

    Andrew J. Dennhardt; Adam E. Duerr; David Brandes; Todd E. Katzner

    2015-01-01

    Estimating population size is fundamental to conservation and management. Population size is typically estimated using survey data, computer models, or both. Some of the most extensive and often least expensive survey data are those collected by citizen-scientists. A challenge to citizen-scientists is that the vagility of many organisms can complicate data collection....

  1. The bold and the beautiful. Influence of body size of televised media models on body dissatisfaction and actual food intake

    NARCIS (Netherlands)

    Anschutz, Doeschka J; Engels, Rutger C M E; Becker, Eni S; van Strien, Tatjana

    2008-01-01

    The effects of exposure to televised thin and average size models on body dissatisfaction and actual food intake were examined. Normal weight female students (N=104) were exposed to a 30-min movie clip featuring beautiful girls. Half of them viewed the movie clip in normal screen size (4:3) and the

  2. GPU-based ultra-fast dose calculation using a finite size pencil beam model

    Science.gov (United States)

    Gu, Xuejun; Choi, Dongju; Men, Chunhua; Pan, Hubert; Majumdar, Amitava; Jiang, Steve B.

    2009-10-01

    Online adaptive radiation therapy (ART) is an attractive concept that promises the ability to deliver an optimal treatment in response to the inter-fraction variability in patient anatomy. However, it has yet to be realized due to technical limitations. Fast dose deposit coefficient calculation is a critical component of the online planning process that is required for plan optimization of intensity-modulated radiation therapy (IMRT). Computer graphics processing units (GPUs) are well suited to provide the requisite fast performance for the data-parallel nature of dose calculation. In this work, we develop a dose calculation engine based on a finite-size pencil beam (FSPB) algorithm and a GPU parallel computing framework. The developed framework can accommodate any FSPB model. We test our implementation in the case of a water phantom and the case of a prostate cancer patient with varying beamlet and voxel sizes. All testing scenarios achieved speedup ranging from 200 to 400 times when using a NVIDIA Tesla C1060 card in comparison with a 2.27 GHz Intel Xeon CPU. The computational time for calculating dose deposition coefficients for a nine-field prostate IMRT plan with this new framework is less than 1 s. This indicates that the GPU-based FSPB algorithm is well suited for online re-planning for adaptive radiotherapy.

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

    Science.gov (United States)

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

    2014-01-01

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

  4. Coupling SPH and thermochemical models of planets: Methodology and example of a Mars-sized body

    Science.gov (United States)

    Golabek, G. J.; Emsenhuber, A.; Jutzi, M.; Asphaug, E. I.; Gerya, T. V.

    2018-02-01

    Giant impacts have been suggested to explain various characteristics of terrestrial planets and their moons. However, so far in most models only the immediate effects of the collisions have been considered, while the long-term interior evolution of the impacted planets was not studied. Here we present a new approach, combining 3-D shock physics collision calculations with 3-D thermochemical interior evolution models. We apply the combined methods to a demonstration example of a giant impact on a Mars-sized body, using typical collisional parameters from previous studies. While the material parameters (equation of state, rheology model) used in the impact simulations can have some effect on the long-term evolution, we find that the impact angle is the most crucial parameter for the resulting spatial distribution of the newly formed crust. The results indicate that a dichotomous crustal pattern can form after a head-on collision, while this is not the case when considering a more likely grazing collision. Our results underline that end-to-end 3-D calculations of the entire process are required to study in the future the effects of large-scale impacts on the evolution of planetary interiors.

  5. The Modelled Raindrop Size Distribution of Skudai, Peninsular Malaysia, Using Exponential and Lognormal Distributions

    Science.gov (United States)

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

    2014-01-01

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

  6. Modeling optical properties of human skin using Mie theory for particles with different size distributions and refractive indices.

    Science.gov (United States)

    Bhandari, A; Hamre, B; Frette, Ø; Stamnes, K; Stamnes, J J

    2011-07-18

    We used size distributions of volume equivalent spherical particles with complex refractive index to model the inherent optical properties (IOPs) in four different layers of human skin at ten different wavelengths in the visible and near-infrared spectral bands. For each layer, we first computed the size-averaged absorption coefficient, scattering coefficient, and asymmetry factor for the collection of particles in a host medium using Mie theory and compared these IOPs in each layer with those obtained from a bio-optical model (BOM). This procedure was repeated, using an optimization scheme, until satisfactory agreement was obtained between the IOPs obtained from the particle size distribution and those given by the BOM. The size distribution as well as the complex refractive index of the particles, obtained from this modeling exercise, can be used to compute the phase matrix, which is an essential input to model polarized light transport in human skin tissue.

  7. State-space modeling of population sizes and trends in Nihoa Finch and Millerbird

    Science.gov (United States)

    Gorresen, P. Marcos; Brinck, Kevin W.; Camp, Richard J.; Farmer, Chris; Plentovich, Sheldon M.; Banko, Paul C.

    2016-01-01

    Both of the 2 passerines endemic to Nihoa Island, Hawai‘i, USA—the Nihoa Millerbird (Acrocephalus familiaris kingi) and Nihoa Finch (Telespiza ultima)—are listed as endangered by federal and state agencies. Their abundances have been estimated by irregularly implemented fixed-width strip-transect sampling from 1967 to 2012, from which area-based extrapolation of the raw counts produced highly variable abundance estimates for both species. To evaluate an alternative survey method and improve abundance estimates, we conducted variable-distance point-transect sampling between 2010 and 2014. We compared our results to those obtained from strip-transect samples. In addition, we applied state-space models to derive improved estimates of population size and trends from the legacy time series of strip-transect counts. Both species were fairly evenly distributed across Nihoa and occurred in all or nearly all available habitat. Population trends for Nihoa Millerbird were inconclusive because of high within-year variance. Trends for Nihoa Finch were positive, particularly since the early 1990s. Distance-based analysis of point-transect counts produced mean estimates of abundance similar to those from strip-transects but was generally more precise. However, both survey methods produced biologically unrealistic variability between years. State-space modeling of the long-term time series of abundances obtained from strip-transect counts effectively reduced uncertainty in both within- and between-year estimates of population size, and allowed short-term changes in abundance trajectories to be smoothed into a long-term trend.

  8. Insights into plant size-density relationships from models and agricultural crops.

    Science.gov (United States)

    Deng, Jianming; Zuo, Wenyun; Wang, Zhiqiang; Fan, Zhexuan; Ji, Mingfei; Wang, Genxuan; Ran, Jinzhi; Zhao, Changming; Liu, Jianquan; Niklas, Karl J; Hammond, Sean T; Brown, James H

    2012-05-29

    There is general agreement that competition for resources results in a tradeoff between plant mass, M, and density, but the mathematical form of the resulting thinning relationship and the mechanisms that generate it are debated. Here, we evaluate two complementary models, one based on the space-filling properties of canopy geometry and the other on the metabolic basis of resource use. For densely packed stands, both models predict that density scales as M(-3/4), energy use as M(0), and total biomass as M(1/4). Compilation and analysis of data from 183 populations of herbaceous crop species, 473 stands of managed tree plantations, and 13 populations of bamboo gave four major results: (i) At low initial planting densities, crops grew at similar rates, did not come into contact, and attained similar mature sizes; (ii) at higher initial densities, crops grew until neighboring plants came into contact, growth ceased as a result of competition for limited resources, and a tradeoff between density and size resulted in critical density scaling as M(-0.78), total resource use as M(-0.02), and total biomass as M(0.22); (iii) these scaling exponents are very close to the predicted values of M(-3/4), M(0), and M(1/4), respectively, and significantly different from the exponents suggested by some earlier studies; and (iv) our data extend previously documented scaling relationships for trees in natural forests to small herbaceous annual crops. These results provide a quantitative, predictive framework with important implications for the basic and applied plant sciences.

  9. Insights into plant size-density relationships from models and agricultural crops

    Science.gov (United States)

    Deng, Jianming; Zuo, Wenyun; Wang, Zhiqiang; Fan, Zhexuan; Ji, Mingfei; Wang, Genxuan; Ran, Jinzhi; Zhao, Changming; Liu, Jianquan; Niklas, Karl J.; Hammond, Sean T.; Brown, James H.

    2012-01-01

    There is general agreement that competition for resources results in a tradeoff between plant mass, M, and density, but the mathematical form of the resulting thinning relationship and the mechanisms that generate it are debated. Here, we evaluate two complementary models, one based on the space-filling properties of canopy geometry and the other on the metabolic basis of resource use. For densely packed stands, both models predict that density scales as M−3/4, energy use as M0, and total biomass as M1/4. Compilation and analysis of data from 183 populations of herbaceous crop species, 473 stands of managed tree plantations, and 13 populations of bamboo gave four major results: (i) At low initial planting densities, crops grew at similar rates, did not come into contact, and attained similar mature sizes; (ii) at higher initial densities, crops grew until neighboring plants came into contact, growth ceased as a result of competition for limited resources, and a tradeoff between density and size resulted in critical density scaling as M−0.78, total resource use as M−0.02, and total biomass as M0.22; (iii) these scaling exponents are very close to the predicted values of M−3/4, M0, and M1/4, respectively, and significantly different from the exponents suggested by some earlier studies; and (iv) our data extend previously documented scaling relationships for trees in natural forests to small herbaceous annual crops. These results provide a quantitative, predictive framework with important implications for the basic and applied plant sciences. PMID:22586097

  10. Mathematical human body models representing a mid size male and a small female for frontal, lateral and rearward impact loading

    NARCIS (Netherlands)

    Happee, R.; Morsink, P.L.J.; Lange, R. de; Bours, R.; Ridella, S.; Nayef, A.; Hoof, J. van

    2000-01-01

    A human body model representing a mid size male has been presented at the 1998 STAPP conference. A combination of modeling techniques was applied using rigid bodies for most segments, but describing the thorax as a deformable structure. In this paper, this modeling strategy was employed to also

  11. An adaptive artificial neural network model for sizing stand-alone photovoltaic systems: Application for isolated sites in Algeria

    International Nuclear Information System (INIS)

    Mellit, A.; Benghanem, M.; Hadj Arab, A.; Guessoum, G.

    2004-07-01

    In this paper we investigate, by using an adaptive Artificial Neural Network (ANN), in order to find a suitable model for sizing Stand-Alone Photovoltaic (SAPV) systems, based on a minimum of input data. This model combines Radial Basis Function (RBF) network and Infinite Impulse Response (IIR) filter in order to accelerate the convergence of the network. For the sizing of a photovoltaic (PV) system, we need to determine the optimal sizing coefficients (K PV , K B . These coefficients allow us to determine the number of solar panels and storage batteries necessary to satisfy a given consumption, especially in isolated sites where the global solar radiation data is not always available and which are considered the most important parameters for sizing a PV system. Obtained results by classical models (analytical, numerical, analytical- numerical, B-spline function) and new models like feed-forward (MLP), radial basis function (RBF), MLP-IIR and RBF-IIR have been compared with experimental sizing coefficients in order to illustrate the accuracy of the results of the new developed model. This model has been trained by using 200 known optimal sizing coefficients corresponding to 200 locations in Algeria. In this way, the adaptive model was trained to accept and even handle a number of unusual cases, the unknown validation sizing coefficients set produced very set accurate estimation and a correlation coefficient of 98% was obtained between the calculated and that estimated by the RBF-IIR model. This result indicates that the proposed method can be successfully used for the estimation of optimal sizing coefficients of SAPV systems for any locations in Algeria, but the methodology can be generalized using different locations over the world. (author)

  12. A global off-line model of size-resolved aerosol microphysics: I. Model development and prediction of aerosol properties

    Directory of Open Access Journals (Sweden)

    D. V. Spracklen

    2005-01-01

    Full Text Available A GLObal Model of Aerosol Processes (GLOMAP has been developed as an extension to the TOMCAT 3-D Eulerian off-line chemical transport model. GLOMAP simulates the evolution of the global aerosol size distribution using a sectional two-moment scheme and includes the processes of aerosol nucleation, condensation, growth, coagulation, wet and dry deposition and cloud processing. We describe the results of a global simulation of sulfuric acid and sea spray aerosol. The model captures features of the aerosol size distribution that are well established from observations in the marine boundary layer and free troposphere. Modelled condensation nuclei (CN>3nm vary between about 250–500 cm-3 in remote marine boundary layer regions and are generally in good agreement with observations. Modelled continental CN concentrations are lower than observed, which may be due to lack of some primary aerosol sources or the neglect of nucleation mechanisms other than binary homogeneous nucleation of sulfuric acid-water particles. Remote marine CN concentrations increase to around 2000–10 000 cm (at standard temperature and pressure in the upper troposphere, which agrees with typical observed vertical profiles. Cloud condensation nuclei (CCN at 0.2% supersaturation vary between about 1000 cm-3 in polluted regions and between 10 and 500 cm-3 in the remote marine boundary layer. New particle formation through sulfuric acid-water binary nucleation occurs predominantly in the upper troposphere, but the model results show that these particles contribute greatly to aerosol concentrations in the marine boundary layer. For this sulfur-sea salt system it is estimated that sea spray emissions account for only ~10% of CCN in the tropical marine boundary layer, but between 20 and 75% in the mid-latitude Southern Ocean. In a run with only natural sulfate and sea salt emissions the global mean surface CN concentration is more than 60% of that from a run with 1985 anthropogenic

  13. Multiple Size Group Modeling of Polydispersed Bubbly Flow in the Mold: An Analysis of Turbulence and Interfacial Force Models

    Science.gov (United States)

    Liu, Zhongqiu; Qi, Fengsheng; Li, Baokuan; Jiang, Maofa

    2015-04-01

    An inhomogeneous Multiple Size Group (MUSIG) model based on the Eulerian-Eulerian approach has been developed to describe the polydispersed bubbly flow inside the continuous-casting mold. A laboratory scale mold has been simulated using four different turbulence closure models (modified k - ɛ, RNG k - ɛ, k - ω, and SST) with the purpose of critically comparing their predictions of bubble Sauter mean diameter distribution with previous experimental data. Furthermore, the influences of all the interfacial momentum transfer terms including drag force, lift force, virtual mass force, wall lubrication force, and turbulent dispersion force are investigated. The breakup and coalescence effects of the bubbles are modeled according to the bubble breakup by the impact of turbulent eddies while for bubble coalescence by the random collisions driven by turbulence and wake entrainment. It has been found that the modified k - ɛ model shows better agreement than other models in predicting the bubble Sauter mean diameter profiles. Further, simulations have also been performed to understand the sensitivity of different interfacial forces. The appropriate drag force coefficient, lift force coefficient, virtual mass force coefficient, and turbulent dispersion force coefficient are chosen in accordance with measurements of water model experiments. However, the wall lubrication force does not have much effect on the current polydispersed bubbly flow system. Finally, the MUSIG model is then used to estimate the argon bubble diameter in the molten steel of the mold. The argon bubble Sauter mean diameter generated in molten steel is predicted to be larger than air bubbles in water for the similar conditions.

  14. Modeling of magnetic fields on a cylindrical surface and associated parameter estimation for development of a size sensor

    International Nuclear Information System (INIS)

    Zhang, Song; Rajamani, Rajesh

    2016-01-01

    This paper develops analytical sensing principles for estimation of circumferential size of a cylindrical surface using magnetic sensors. An electromagnet and magnetic sensors are used on a wearable band for measurement of leg size. In order to enable robust size estimation during rough real-world use of the wearable band, three estimation algorithms are developed based on models of the magnetic field variation over a cylindrical surface. The magnetic field models developed include those for a dipole and for a uniformly magnetized cylinder. The estimation algorithms used include a linear regression equation, an extended Kalman filter and an unscented Kalman filter. Experimental laboratory tests show that the size sensor in general performs accurately, yielding sub-millimeter estimation errors. The unscented Kalman filter yields the best performance that is robust to bias and misalignment errors. The size sensor developed herein can be used for monitoring swelling due to fluid accumulation in the lower leg and a number of other biomedical applications. (paper)

  15. Rheotaxis performance increases with group size in a coupled phase model with sensory noise. The effects of noise and group size on rheotaxis

    Science.gov (United States)

    Chicoli, A.; Bak-Coleman, J.; Coombs, S.; Paley, D. A.

    2015-12-01

    Many fish exhibit rheotaxis, a behavior in which fish orient themselves relative to flow. Rheotaxis confers many benefits, including energetic cost savings and interception of drifting prey. Despite the fact that most species of fish school during at least some portion of their life, little is known about the importance of rheotactic behavior to schooling fish and, conversely, how the presence of nearby conspecifics affects rheotactic behavior. Understanding how rheotaxis is modified by social factors is thus of ecological importance. Here we present a mathematical model in the form of an all-to-all, coupled-oscillator framework over the non-Euclidean space of fish orientations to model group rheotactic behavior. Individuals in the model measure the orientation of their neighbors and the flow direction relative to their own orientation. These measures are corrupted by sensory noise. We study the effect of sensory noise and group size on internal (i.e., within the school) and external (i.e., with the flow) disagreement in orientation. We find that under noisy environmental conditions, increased group size improves rheotaxis. Results of this study have implications for understanding animal behavior, as well as for potential applications in bio-inspired engineering.

  16. Finite-size, chemical-potential and magnetic effects on the phase transition in a four-fermion interacting model

    Energy Technology Data Exchange (ETDEWEB)

    Correa, E.B.S. [Universidade Federal do Sul e Sudeste do Para, Instituto de Ciencias Exatas, Maraba (Brazil); Centro Brasileiro de Pesquisas Fisicas-CBPF/MCTI, Rio de Janeiro (Brazil); Linhares, C.A. [Universidade do Estado do Rio de Janeiro, Instituto de Fisica, Rio de Janeiro (Brazil); Malbouisson, A.P.C. [Centro Brasileiro de Pesquisas Fisicas-CBPF/MCTI, Rio de Janeiro (Brazil); Malbouisson, J.M.C. [Universidade Federal da Bahia, Instituto de Fisica, Salvador (Brazil); Santana, A.E. [Universidade de Brasilia, Instituto de Fisica, Brasilia, DF (Brazil)

    2017-04-15

    We study effects coming from finite size, chemical potential and from a magnetic background on a massive version of a four-fermion interacting model. This is performed in four dimensions as an application of recent developments for dealing with field theories defined on toroidal spaces. We study effects of the magnetic field and chemical potential on the size-dependent phase structure of the model, in particular, how the applied magnetic field affects the size-dependent critical temperature. A connection with some aspects of the hadronic phase transition is established. (orig.)

  17. Simultaneously simulating the scattering properties of nonspherical aerosol particles with different sizes by the MRTD scattering model.

    Science.gov (United States)

    Hu, Shuai; Gao, Taichang; Li, Hao; Chen, Ming; Zhang, Feng; Yang, Bo

    2017-07-24

    In order to improve the computational efficiency of multi-resolution time domain (MRTD) scattering model, a multi-size synchronous-computational scheme (MSCS) is proposed. By using MSCS, the scattering properties of the particles with different sizes can be simultaneously calculated by MRTD model in one wave-particle interaction simulation. In this model, the pulse plane wave with a wide spectrum is taken as the incident light, and the light scattering simulation for particles with different sizes is transformed into the scattering calculation for a size-fixed particle at different wavelengths. To guarantee the stability and precision of the improved MRTD (IMRTD) model, the method to design model's input parameters, such as the spatial resolution, discrete time interval and pulse width, is proposed. To validate the accuracy of IMRTD model, its results are compared with those of Mie and T-Matrix theory, and the influence of spatial resolution on the precision of IMRTD is analyzed as well. At last, model's computational efficiency is also discussed. The simulation results show that, IMRTD method can calculate the scattering parameters of particles with different sizes simultaneously and accurately, where, in case that the pulse width is 5.56 × 10 -8 ns, and the radius of the size-fixed particle is 0.5μm (its size parameter is 6.28), light scattering process by particles with size parameters up to 12.56 can be successfully simulated. With the increasing of spatial resolution, the simulation accuracy is improved for all particles, and the improvement for large particles is more notable than that for small ones. It can also be found that the computational efficiency of IMRTD is much higher than that of traditional version.

  18. Plume Aerosol Size Distribution Modeling and Comparisons to PrAIRie2005 Field Study Data

    Science.gov (United States)

    Cho, S.; Liggio, J.; Makar, P.; Li, S.; Racinthe, J.

    2006-12-01

    As part of the analysis phase of the PrAIRie2005 field study, the effects of different Edmonton-area emission sources on local air-quality are being examined. Four large coal-fired power-plants are located to the West of the city. Here, the effects of these power-plants on urban and regional air-quality will be examined, using both plume and regional air-quality models. During the last few decades, coal-fired power plants have been found to be as a major source of pollution, affecting public-health. According to NACEC (North American Commission for Environmental Corporation, 2001)'s report, 46 of the top 50 air polluters in North America were power plants. The importance of such sources has resulted in several attempts to improve understanding of the basic formation mechanisms of plume particulate matter. Sulphur dioxide contributes to acidifying emissions and to the production of secondary acidic aerosols that have been linked to a number of serious human health problems, acid rain and visibility (Seinfeld and Pandis, 1998; Hidy, 1984; Wilson and McMurray, 1981). Primary particulate matter originating directly from coal-fired power plants may also increase secondary particulate mass by providing a surface for sulphuric acid absorption . Environment Canada's PrAIRie2005 field study between August 12th and September 7th, 2005 included overflights and downwind measurements near the Edmonton powerplants (Wabamun, Sundance, Keephills and Genesee). The data collected consisted of particle size distributions, ozone, NOX, total mass and the chemical composition of fine particles. In order to investigate and improve our understanding of the formation mechanisms and physical properties of power-plant-generated aerosols in the Edmonton area, the Plume Aerosol Microphysical (PAM) model has been employed. This model accounts for gas-phase chemistry, aerosol microphysical processes (i.e. homogeneous/heterogeneous nucleation, condensation/evaporation and coagulation) and

  19. Simulation studies of optimum energies for DXA: dependence on tissue type, patient size and dose model

    International Nuclear Information System (INIS)

    Michael, G. J.; Henderson, C. J.

    1999-01-01

    Dual-energy x-ray absorptiometry (DXA) is a well established technique for measuring bone mineral density (BMD). However, in recent years DXA is increasingly being used to measure body composition in terms of fat and fat-free mass. DXA scanners must also determine the soft tissue baseline value from soft-tissue-only regions adjacent to bone. The aim of this work is to determine, using computer simulations, the optimum x- ray energies for a number of dose models, different tissues, i.e. bone mineral, average soft tissue, lean soft tissue and fat; and a range of anatomical sites and patient sizes. Three models for patient dose were evaluated total beam energy, entrance exposure and absorbed dose calculated by Monte Carlo modelling. A range of tissue compositions and thicknesses were chosen to cover typical patient variations for the three sites femoral neck, PA spine and lateral spine. In this work, the optimisation of the energies is based on (1) the uncertainty that arises from the quantum statistical nature of the number of x-rays recorded by the detector, and (2) the radiation dose received by the patient. This study has deliberately not considered other parameters such as detector response, electronic noise, x-ray tube heat load etc, because these are technology dependent parameters, not ones that are inherent to the measuring technique. Optimisation of the energies is achieved by minimisation of the product of variance of density measurement and dose which is independent of the absolute intensities of the x-ray beams. The results obtained indicate that if solving for bone density, then E-low in the range 34 to 42 keV, E-high in the range 100 to 200 keV and incident intensity ratio (low energy/high energy) in the range 3 to 10 is a reasonable compromise for the normal range of patient sizes. The choice of energies is complicated by the fact that the DXA unit must also solve for fat and lean soft tissue in soft- tissue-only regions adjacent to the bone. In this

  20. A Parametric Sizing Model for Molten Regolith Electrolysis Reactors to Produce Oxygen from Lunar Regolith

    Science.gov (United States)

    Schreiner, Samuel S.; Dominguez, Jesus A.; Sibille, Laurent; Hoffman, Jeffrey A.

    2015-01-01

    We present a parametric sizing model for a Molten Electrolysis Reactor that produces oxygen and molten metals from lunar regolith. The model has a foundation of regolith material properties validated using data from Apollo samples and simulants. A multiphysics simulation of an MRE reactor is developed and leveraged to generate a vast database of reactor performance and design trends. A novel design methodology is created which utilizes this database to parametrically design an MRE reactor that 1) can sustain the required mass of molten regolith, current, and operating temperature to meet the desired oxygen production level, 2) can operate for long durations via joule heated, cold wall operation in which molten regolith does not touch the reactor side walls, 3) can support a range of electrode separations to enable operational flexibility. Mass, power, and performance estimates for an MRE reactor are presented for a range of oxygen production levels. The effects of several design variables are explored, including operating temperature, regolith type/composition, batch time, and the degree of operational flexibility.

  1. Mixed modeling and sample size calculations for identifying housekeeping genes.

    Science.gov (United States)

    Dai, Hongying; Charnigo, Richard; Vyhlidal, Carrie A; Jones, Bridgette L; Bhandary, Madhusudan

    2013-08-15

    Normalization of gene expression data using internal control genes that have biologically stable expression levels is an important process for analyzing reverse transcription polymerase chain reaction data. We propose a three-way linear mixed-effects model to select optimal housekeeping genes. The mixed-effects model can accommodate multiple continuous and/or categorical variables with sample random effects, gene fixed effects, systematic effects, and gene by systematic effect interactions. We propose using the intraclass correlation coefficient among gene expression levels as the stability measure to select housekeeping genes that have low within-sample variation. Global hypothesis testing is proposed to ensure that selected housekeeping genes are free of systematic effects or gene by systematic effect interactions. A gene combination with the highest lower bound of 95% confidence interval for intraclass correlation coefficient and no significant systematic effects is selected for normalization. Sample size calculation based on the estimation accuracy of the stability measure is offered to help practitioners design experiments to identify housekeeping genes. We compare our methods with geNorm and NormFinder by using three case studies. A free software package written in SAS (Cary, NC, U.S.A.) is available at http://d.web.umkc.edu/daih under software tab. Copyright © 2013 John Wiley & Sons, Ltd.

  2. Partner Influence in Diet and Exercise Behaviors: Testing Behavior Modeling, Social Control, and Normative Body Size

    Science.gov (United States)

    Ciciurkaite, Gabriele; Brady, Christy Freadreacea; Garcia, Justin

    2016-01-01

    Previous research has documented social contagion in obesity and related health behaviors, but less is known about the social processes underlying these patterns. Focusing on married or cohabitating couples, we simultaneously explore three potential social mechanisms influencing obesity: normative body size, social control, and behavior modeling. We analyze the association between partner characteristics and the obesity-related health behaviors of focal respondents, comparing the effects of partners’ body type, partners’ attempts to manage respondents’ eating behaviors, and partners’ own health behaviors on respondents’ health behaviors (physical activity, fruit and vegetable consumption, and fast food consumption). Data on 215 partners are extracted from a larger study of social mechanisms of obesity in family and community contexts conducted in 2011 in the United States. Negative binomial regression models indicate that partner behavior is significantly related to respondent behavior (p social control in this sample, though generalizations about the relevance of these processes may be inappropriate. These results underscore the importance of policies and interventions that target dyads and social groups, suggesting that adoption of exercise or diet modifications in one individual is likely to spread to others, creating a social environment characterized by mutual reinforcement of healthy behavior. PMID:28033428

  3. Finite-size behaviour of generalized susceptibilities in the whole phase plane of the Potts model

    Science.gov (United States)

    Pan, Xue; Zhang, Yanhua; Chen, Lizhu; Xu, Mingmei; Wu, Yuanfang

    2018-01-01

    We study the sign distribution of generalized magnetic susceptibilities in the temperature-external magnetic field plane using the three-dimensional three-state Potts model. We find that the sign of odd-order susceptibility is opposite in the symmetric (disorder) and broken (order) phases, but that of the even-order one remains positive when it is far away from the phase boundary. When the critical point is approached from the crossover side, negative fourth-order magnetic susceptibility is observable. It is also demonstrated that non-monotonic behavior occurs in the temperature dependence of the generalized susceptibilities of the energy. The finite-size scaling behavior of the specific heat in this model is mainly controlled by the critical exponent of the magnetic susceptibility in the three-dimensional Ising universality class. Supported by Fund Project of National Natural Science Foundation of China (11647093, 11405088, 11521064), Fund Project of Sichuan Provincial Department of Education (16ZB0339), Fund Project of Chengdu Technological University (2016RC004) and the Major State Basic Research Development Program of China (2014CB845402)

  4. Flocculation of Clay Colloids Induced by Model Polyelectrolytes: Effects of Relative Charge Density and Size.

    Science.gov (United States)

    Sakhawoth, Yasine; Michot, Laurent J; Levitz, Pierre; Malikova, Natalie

    2017-10-06

    Flocculation and its tuning are of utmost importance in the optimization of several industrial protocols in areas such as purification of waste water and civil engineering. Herein, we studied the polyelectrolyte-induced flocculation of clay colloids on a model system consisting of purified clay colloids of well-defined size fractions and ionene polyelectrolytes presenting regular and tunable chain charge density. To characterize ionene-induced clay flocculation, we turned to the combination of light absorbance (turbidity) and ζ-potential measurements, as well as adsorption isotherms. Our model system allowed us to identify the exact ratio of positive and negative charges in clay-ionene mixtures, the (c+/c-) ratio. For all samples studied, the onset of efficient flocculation occurred consistently at c+/c- ratios significantly below 1, which indicated the formation of highly ionene-deficient aggregates. At the same time, the ζ-potential measurements indicated an apparent zero charge on such aggregates. Thus, the ζ-potential values could not provide the stoichiometry inside the clay-ionene aggregates. The early onset of flocculation in clay-ionene mixtures is reminiscent of the behavior of multivalent salts and contrasts that of monovalent salts, for which a large excess amount of ions is necessary to achieve flocculation. Clear differences in the flocculation behavior are visible as a function of the ionene charge density, which governs the conformation of the ionene chains on the clay surface. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Study on the combined influence of battery models and sizing strategy for hybrid and battery-based electric vehicles

    DEFF Research Database (Denmark)

    Pinto, Cláudio; Barreras, Jorge V.; de Castro, Ricardo

    2017-01-01

    This paper presents a study of the combined influence of battery models and sizing strategy for hybrid and battery-based electric vehicles. In particular, the aim is to find the number of battery (and supercapacitor) cells to propel a light vehicle to run two different standard driving cycles....... Three equivalent circuit models are considered to simulate the battery electrical performance: linear static, non-linear static and non-linear with first-order dynamics. When dimensioning a battery-based vehicle, less complex models may lead to a solution with more battery cells and higher costs....... Despite the same tendency, when a hybrid vehicle is taken into account, the influence of the battery models is dependent on the sizing strategy. In this work, two sizing strategies are evaluated: dynamic programming and filter-based. For the latter, the complexity of the battery model has a clear...

  6. Modeling grain size adjustments in the downstream reach following run-of-river development

    Science.gov (United States)

    Fuller, Theodore K.; Venditti, Jeremy G.; Nelson, Peter A.; Palen, Wendy J.

    2016-04-01

    Disruptions to sediment supply continuity caused by run-of-river (RoR) hydropower development have the potential to cause downstream changes in surface sediment grain size which can influence the productivity of salmon habitat. The most common approach to understanding the impacts of RoR hydropower is to study channel changes in the years following project development, but by then, any impacts are manifest and difficult to reverse. Here we use a more proactive approach, focused on predicting impacts in the project planning stage. We use a one-dimensional morphodynamic model to test the hypothesis that the greatest risk of geomorphic change and impact to salmon habitat from a temporary sediment supply disruption exists where predevelopment sediment supply is high and project design creates substantial sediment storage volume. We focus on the potential impacts in the reach downstream of a powerhouse for a range of development scenarios that are typical of projects developed in the Pacific Northwest and British Columbia. Results indicate that increases in the median bed surface size (D50) are minor if development occurs on low sediment supply streams (<1 mm for supply rates 1 × 10-5 m2 s-1 or lower), and substantial for development on high sediment supply streams (8-30 mm for supply rates between 5.5 × 10-4 and 1 × 10-3 m2 s-1). However, high sediment supply streams recover rapidly to the predevelopment surface D50 (˜1 year) if sediment supply can be reestablished.

  7. Improvement to microphysical schemes in WRF Model based on observed data, part I: size distribution function

    Science.gov (United States)

    Shan, Y.; Eric, W.; Gao, L.; Zhao, T.; Yin, Y.

    2015-12-01

    In this study, we have evaluated the performance of size distribution functions (SDF) with 2- and 3-moments in fitting the observed size distribution of rain droplets at three different heights. The goal is to improve the microphysics schemes in meso-scale models, such as Weather Research and Forecast (WRF). Rain droplets were observed during eight periods of different rain types at three stations on the Yellow Mountain in East China. The SDF in this study were M-P distribution with a fixed shape parameter in Gamma SDF(FSP). Where the Gamma SDFs were obtained with three diagnosis methods with the shape parameters based on Milbrandt (2010; denoted DSPM10), Milbrandt (2005; denoted DSPM05) and Seifert (2008; denoted DSPS08) for solving the shape parameter(SSP) and Lognormal SDF. Based on the preliminary experiments, three ensemble methods deciding Gamma SDF was also developed and assessed. The magnitude of average relative error caused by applying a FSP was 10-2 for fitting 0-order moment of the observed rain droplet distribution, and the magnitude of average relative error changed to 10-1 and 100 respectively for 1-4 order moments and 5-6 order moments. To different extent, DSPM10, DSPM05, DSPS08, SSP and ensemble methods could improve fitting accuracies for 0-6 order moments, especially the one coupling SSP and DSPS08 methods, which provided a average relative error 6.46% for 1-4 order moments and 11.90% for 5-6 order moments, respectively. The relative error of fitting three moments using the Lognormal SDF was much larger than that of Gamma SDF. The threshold value of shape parameter ranged from 0 to 8, because values beyond this range could cause overflow in the calculation. When average diameter of rain droplets was less than 2mm, the possibility of unavailable shape parameter value(USPV) increased with a decreasing droplet size. There was strong sensitivity of moment group in fitting accuracy. When ensemble method coupling SSP and DSPS08 was used, a better fit

  8. The origin of felsic microgranitoid enclaves: Insights from plagioclase crystal size distributions and thermodynamic models

    Science.gov (United States)

    Alves, Adriana; Pereira, Giovanna de Souza; Janasi, Valdecir de Assis; Higgins, Michael; Polo, Liza Angelica; Juriaans, Orlando Stanley; Ribeiro, Bruno Vieira

    2015-12-01

    Magma mixing is widely recognized in contemporary petrology as one of the primary igneous processes. Microgranitoid enclaves (MEs) are considered to be remnants of such mixing processes, and the term has a well-established genetic implication. However, microgranitoid enclaves span a wide range of compositions, and felsic varieties are also frequently reported. Nd-Sr isotope and textural data from felsic microgranitoid enclaves (FMEs), mafic microgranitoid enclaves (MMEs) and host granites from the Salto pluton, Itu Granitic Province, show that the cm-sized MMEs are dioritic, have medium-grained igneous textures and xenocrysts of alkali feldspar and quartz. The FMEs are cm- to meter-sized, have spheric shapes, show corrugated contacts with the host granites, and have resorbed feldspars and deformed quartz crystals interpreted as xenocrysts set in a fine-grained groundmass. Compared to the host granites, both MME and FME samples have increased FeO, MgO, TiO2, P2O5 and Zr contents, but their Sr and Nd isotope signatures are identical: FME 87Sr/86Sri = 0.7088-0.7063, εNdi = - 10.0 to - 10.2; MME 87Sr/86Sri = 0.7070, εNdi = - 10.5; host granite 87Sr/86Sri 0.7056-0.7060, εNdi = - 10.2 to - 10.3. These indicate that the enclaves derive from a similar source, although the melts from which they formed were probably hotter and chemically more primitive than their host granites. Crystal size distributions (CSDs) of plagioclase in samples drilled from rinds and cores of three FMEs show that the rind samples are systematically finer-grained than the samples from the cores, which indicates that the FMEs cooled inwards and contradict interpretations that the FMEs are autoliths. Thermal modeling suggests that a slightly more primitive, hotter magma would be thermally equilibrated with an evolved resident melt within weeks after mixing/mingling. Upon thermal equilibrium, the FMEs would have an increased crystal cargo, and the resulting touching framework would impart a solid

  9. Tree Size Inequality Reduces Forest Productivity: An Analysis Combining Inventory Data for Ten European Species and a Light Competition Model.

    Science.gov (United States)

    Bourdier, Thomas; Cordonnier, Thomas; Kunstler, Georges; Piedallu, Christian; Lagarrigues, Guillaume; Courbaud, Benoit

    2016-01-01

    Plant structural diversity is usually considered as beneficial for ecosystem functioning. For instance, numerous studies have reported positive species diversity-productivity relationships in plant communities. However, other aspects of structural diversity such as individual size inequality have been far less investigated. In forests, tree size inequality impacts directly tree growth and asymmetric competition, but consequences on forest productivity are still indeterminate. In addition, the effect of tree size inequality on productivity is likely to vary with species shade-tolerance, a key ecological characteristic controlling asymmetric competition and light resource acquisition. Using plot data from the French National Geographic Agency, we studied the response of stand productivity to size inequality for ten forest species differing in shade tolerance. We fitted a basal area stand production model that included abiotic factors, stand density, stand development stage and a tree size inequality index. Then, using a forest dynamics model we explored whether mechanisms of light interception and light use efficiency could explain the tree size inequality effect observed for three of the ten species studied. Size inequality negatively affected basal area increment for seven out of the ten species investigated. However, this effect was not related to the shade tolerance of these species. According to the model simulations, the negative tree size inequality effect could result both from reduced total stand light interception and reduced light use efficiency. Our results demonstrate that negative relationships between size inequality and productivity may be the rule in tree populations. The lack of effect of shade tolerance indicates compensatory mechanisms between effect on light availability and response to light availability. Such a pattern deserves further investigations for mixed forests where complementarity effects between species are involved. When studying the

  10. Mathematical model parameters for describing the particle size spectra of knife-milled corn stover

    Energy Technology Data Exchange (ETDEWEB)

    Bitra, V.S.P [University of Tennessee; Womac, A.R. [University of Tennessee; Yang, Y.T. [University of Tennessee; Miu, P.I. [University of Tennessee; Igathanathane, C. [Mississippi State University (MSU)

    2009-09-01

    Particle size distributions of Corn stover (Zea mays L.) created by a knife mill were determined using integral classifying screens with sizes from 12.7 to 50.8 mm, operating at speeds from 250 to 500 rpm, and mass input rates ranging from 1 to 9 kg min_1. Particle distributions were classified using American Society of Agricultural and Biological Engineers (ASABE) standardised sieves for forage analysis that incorporated a horizontal sieving motion. The sieves were made from machined-aluminium with their thickness proportional to the sieve opening dimensions. A wide range of analytical descriptors that could be used to mathematically represent the range of particle sizes in the distributions were examined. The correlation coefficients between geometric mean length and screen size, feed rate, and speed were 0.980, 0.612, and _0.027, respectively. Screen size and feed rate directly influenced particle size, whereas operating speed had a weak indirect relation with particle size. The Rosin Rammler equation fitted the chopped corn stover size distribution data with coefficient of determination (R2) > 0.978. This indicated that particle size distribution of corn stover was well-fit by the Rosin Rammler function. This can be attributed to the fact that Rosin Rammler expression was well suited to the skewed distribution of particle sizes. Skewed distributions occurred when significant quantities of particles, either finer or coarser, existed or were removed from region of the predominant size. The mass relative span was slightly greater than 1, which indicated that it was a borderline narrow to wide distribution of particle sizes. The uniformity coefficient was <4.0 for 19.0 50.8 mm screens, which indicated particles of relatively uniform size. Knife mill chopping of corn stover produced fine-skewed mesokurtic particles with 12.7 50.8 mm screens. Size-related parameters, namely, geometric mean length, Rosin Rammler size parameter, median length, effective length, and

  11. Prey size and availability limits maximum size of rainbow trout in a large tailwater: insights from a drift-foraging bioenergetics model

    Science.gov (United States)

    Dodrill, Michael J.; Yackulic, Charles B.; Kennedy, Theodore A.; Haye, John W

    2016-01-01

    The cold and clear water conditions present below many large dams create ideal conditions for the development of economically important salmonid fisheries. Many of these tailwater fisheries have experienced declines in the abundance and condition of large trout species, yet the causes of these declines remain uncertain. Here, we develop, assess, and apply a drift-foraging bioenergetics model to identify the factors limiting rainbow trout (Oncorhynchus mykiss) growth in a large tailwater. We explored the relative importance of temperature, prey quantity, and prey size by constructing scenarios where these variables, both singly and in combination, were altered. Predicted growth matched empirical mass-at-age estimates, particularly for younger ages, demonstrating that the model accurately describes how current temperature and prey conditions interact to determine rainbow trout growth. Modeling scenarios that artificially inflated prey size and abundance demonstrate that rainbow trout growth is limited by the scarcity of large prey items and overall prey availability. For example, shifting 10% of the prey biomass to the 13 mm (large) length class, without increasing overall prey biomass, increased lifetime maximum mass of rainbow trout by 88%. Additionally, warmer temperatures resulted in lower predicted growth at current and lower levels of prey availability; however, growth was similar across all temperatures at higher levels of prey availability. Climate change will likely alter flow and temperature regimes in large rivers with corresponding changes to invertebrate prey resources used by fish. Broader application of drift-foraging bioenergetics models to build a mechanistic understanding of how changes to habitat conditions and prey resources affect growth of salmonids will benefit management of tailwater fisheries.

  12. Sample Size and Statistical Conclusions from Tests of Fit to the Rasch Model According to the Rasch Unidimensional Measurement Model (Rumm) Program in Health Outcome Measurement.

    Science.gov (United States)

    Hagell, Peter; Westergren, Albert

    Sample size is a major factor in statistical null hypothesis testing, which is the basis for many approaches to testing Rasch model fit. Few sample size recommendations for testing fit to the Rasch model concern the Rasch Unidimensional Measurement Models (RUMM) software, which features chi-square and ANOVA/F-ratio based fit statistics, including Bonferroni and algebraic sample size adjustments. This paper explores the occurrence of Type I errors with RUMM fit statistics, and the effects of algebraic sample size adjustments. Data with simulated Rasch model fitting 25-item dichotomous scales and sample sizes ranging from N = 50 to N = 2500 were analysed with and without algebraically adjusted sample sizes. Results suggest the occurrence of Type I errors with N less then or equal to 500, and that Bonferroni correction as well as downward algebraic sample size adjustment are useful to avoid such errors, whereas upward adjustment of smaller samples falsely signal misfit. Our observations suggest that sample sizes around N = 250 to N = 500 may provide a good balance for the statistical interpretation of the RUMM fit statistics studied here with respect to Type I errors and under the assumption of Rasch model fit within the examined frame of reference (i.e., about 25 item parameters well targeted to the sample).

  13. An extended steepness model for leg-size determination based on Dachsous/Fat trans-dimer system.

    Science.gov (United States)

    Yoshida, Hiroshi; Bando, Tetsuya; Mito, Taro; Ohuchi, Hideyo; Noji, Sumihare

    2014-03-11

    What determines organ size has been a long-standing biological question. Lawrence et al. (2008) proposed the steepness hypothesis suggesting that the protocadherin Dachsous/Fat (Ds/Ft) system may provide some measure of dimension to the cells in relation to the gradient. In this paper we extended the model as a means of interpreting experimental results in cricket leg regeneration. We assumed that (1) Ds/Ft trans-heterodimers or trans-homodimers are redistributed during cell division, and (2) growth would cease when a differential of the dimer across each cell decreases to a certain threshold. We applied our model to simulate the results obtained by leg regeneration experiments in a cricket model. The results were qualitatively consistent with the experimental data obtained for cricket legs by RNA interference methodology. Using our extended steepness model, we provided a molecular-based explanation for leg size determination even in intercalary regeneration and for organ size determination.

  14. Meta-Analysis of Effect Sizes Reported at Multiple Time Points Using General Linear Mixed Model

    Science.gov (United States)

    Musekiwa, Alfred; Manda, Samuel O. M.; Mwambi, Henry G.; Chen, Ding-Geng

    2016-01-01

    Meta-analysis of longitudinal studies combines effect sizes measured at pre-determined time points. The most common approach involves performing separate univariate meta-analyses at individual time points. This simplistic approach ignores dependence between longitudinal effect sizes, which might result in less precise parameter estimates. In this paper, we show how to conduct a meta-analysis of longitudinal effect sizes where we contrast different covariance structures for dependence between effect sizes, both within and between studies. We propose new combinations of covariance structures for the dependence between effect size and utilize a practical example involving meta-analysis of 17 trials comparing postoperative treatments for a type of cancer, where survival is measured at 6, 12, 18 and 24 months post randomization. Although the results from this particular data set show the benefit of accounting for within-study serial correlation between effect sizes, simulations are required to confirm these results. PMID:27798661

  15. Evaluation of borate bioactive glass scaffolds with different pore sizes in a rat subcutaneous implantation model.

    Science.gov (United States)

    Deliormanli, Aylin M; Liu, Xin; Rahaman, Mohamed N

    2014-01-01

    Borate bioactive glass has been shown to convert faster and more completely to hydroxyapatite and enhance new bone formation in vivo when compared to silicate bioactive glass (such as 45S5 and 13-93 bioactive glass). In this work, the effects of the borate glass microstructure on its conversion to hydroxyapatite (HA) in vitro and its ability to support tissue ingrowth in a rat subcutaneous implantation model were investigated. Bioactive borate glass scaffolds, designated 13-93B3, with a grid-like microstructure and pore widths of 300, 600, and 900 µm were prepared by a robocasting technique. The scaffolds were implanted subcutaneously for 4 weeks in Sprague Dawley rats. Silicate 13-93 glass scaffolds with the same microstructure were used as the control. The conversion of the scaffolds to HA was studied as a function of immersion time in a simulated body fluid. Histology and scanning electron microscopy were used to evaluate conversion of the bioactive glass implants to hydroxyapatite, as well as tissue ingrowth and blood vessel formation in the implants. The pore size of the scaffolds was found to have little effect on tissue infiltration and angiogenesis after the 4-week implantation.

  16. A size dependent dynamic model for piezoelectric nanogenerators: effects of geometry, structural and environmental parameters

    Science.gov (United States)

    Sadeghzadeh, Sadegh; Farshad Mir Saeed Ghazi, Seyyed

    2018-03-01

    Piezoelectric Nanogenerator (PENG) is one of the novel energy harvester systems that recently, has been a subject of interest for researchers. By the use of nanogenerators, it’s possible to harvest different forms of energy in the environment like mechanical vibrations and generate electricity. The structure of a PENG consists of vertical arrays of nanowires between two electrodes. In this paper, dynamic analysis of a PENG is studied numerically. The modified couple stress theory which includes one length scale material parameter is used to study the size-dependent behavior of PENGs. Then, by application of a complete form of linear hybrid piezoelectric—pyroelectric equations, and using the Euler-Bernoulli beam model, the equations of motion has been derived. Generalized Differential Quadrature (GDQ) method was employed to solve the equations of motion. The effect of damping ratio, temperature rise, excitation frequency and length scale parameter was studied. It was found that the PENG voltage maximizes at the resonant frequency of nanowire. The temperature rise has a significant effect on PENG’s efficiency. When temperature increases about 10 {{K}}, the maximum voltage increases about 26%. Increasing the damping ratio, the maximum voltage decreases gradually.

  17. Estimating Divergence Time and Ancestral Effective Population Size of Bornean and Sumatran Orangutan Subspecies Using a Coalescent Hidden Markov Model

    DEFF Research Database (Denmark)

    Mailund, Thomas; Dutheil, Julien; Hobolth, Asger

    2011-01-01

    event has occurred to split them apart. The size of these segments of constant divergence depends on the recombination rate, but also on the speciation time, the effective population size of the ancestral population, as well as demographic effects and selection. Thus, inference of these parameters may......, and the ancestral effective population size. The model is efficient enough to allow inference on whole-genome data sets. We first investigate the power and consistency of the model with coalescent simulations and then apply it to the whole-genome sequences of the two orangutan sub-species, Bornean (P. p. pygmaeus......) and Sumatran (P. p. abelii) orangutans from the Orangutan Genome Project. We estimate the speciation time between the two sub-species to be thousand years ago and the effective population size of the ancestral orangutan species to be , consistent with recent results based on smaller data sets. We also report...

  18. Finite-size effects for anisotropic 2D Ising model with various boundary conditions

    Science.gov (United States)

    Izmailian, N. Sh

    2012-12-01

    We analyze the exact partition function of the anisotropic Ising model on finite M × N rectangular lattices under four different boundary conditions (periodic-periodic (pp), periodic-antiperiodic (pa), antiperiodic-periodic (ap) and antiperiodic-antiperiodic (aa)) obtained by Kaufman (1949 Phys. Rev. 76 1232), Wu and Hu (2002 J. Phys. A: Math. Gen. 35 5189) and Kastening (2002 Phys. Rev. E 66 057103)). We express the partition functions in terms of the partition functions Zα, β(J, k) with (α, β) = (0, 0), (1/2, 0), (0, 1/2) and (1/2, 1/2), J is an interaction coupling and k is an anisotropy parameter. Based on such expressions, we then extend the algorithm of Ivashkevich et al (2002 J. Phys. A: Math. Gen. 35 5543) to derive the exact asymptotic expansion of the logarithm of the partition function for all boundary conditions mentioned above. Our result is f = fbulk + ∑∞p = 0fp(ρ, k)S-p - 1, where f is the free energy of the system, fbulk is the free energy of the bulk, S = MN is the area of the lattice and ρ = M/N is the aspect ratio. All coefficients in this expansion are expressed through analytical functions. We have introduced the effective aspect ratio ρeff = ρ/sinh 2Jc and show that for pp and aa boundary conditions all finite size correction terms are invariant under the transformation ρeff → 1/ρeff. This article is part of ‘Lattice models and integrability’, a special issue of Journal of Physics A: Mathematical and Theoretical in honour of F Y Wu's 80th birthday.

  19. Effective site-energy model: A thermodynamic approach applied to size-mismatched alloys

    Science.gov (United States)

    Berthier, F.; Creuze, J.; Legrand, B.

    2017-06-01

    We present a novel energetic model that takes into account atomistic relaxations to describe the thermodynamic properties of AcB1 -c binary alloys. It requires the calculation of the energies on each site of a random solid solution after relaxation as a function of both the local composition and the nominal concentration. These site energies are obtained by molecular static simulations using N -body interatomic potentials derived from the second-moment approximation (SMA) of the tight-binding scheme. This new model allows us to determine the effective pair interactions (EPIs) that drive the short-range order (SRO) and to analyze the relative role of the EPIs' contribution to the mixing enthalpy, with respect to the contribution due to the lattice mismatch between the constituents. We apply this formalism to Au-Ni and Ag-Cu alloys, both of them tending to phase separate in the bulk and exhibiting a large size mismatch. Rigid-lattice Monte Carlo (MC) simulations lead to phase diagrams that are in good agreement with both those obtained by off-lattice SMA-MC simulations and the experimental ones. While the phase diagrams of Au-Ni and Ag-Cu alloys are very similar, we show that phase separation is mainly driven by the elastic contribution for Au-Ni and by the EPIs' contribution for Ag-Cu. Furthermore, for Au-Ni, the analysis of the SRO shows an inversion between the tendency to order and the tendency to phase separate as a function of the concentration.

  20. Modelling of size effects on behavior of thin sheet metals for bipolar plate manufacturing

    OpenAIRE

    Koç, Muammer; Mahabunphachai, Sasawat

    2013-01-01

    The grain-to-feature size ratio in micro-forming processes is predicted to have a vital impact on the material behavior in addition to the well-known effect of the grain size itself as manifested by the Hall-Petch relation. In this study, the "size effects" on the material flow curve of thin sheet metals under hydraulic bulge testing conditions were investigated. The ratio of the sheet thickness to the material grain size (N = t0/d) was used as a parameter to characterize the interactive effe...

  1. Using multi-theory model to predict initiation and sustenance of small portion size consumption among college students

    OpenAIRE

    Manoj Sharma; Hannah Priest Catalano; Vinayak K. Nahar; Vimala Lingam; Paul Johnson; M. Allison Ford

    2016-01-01

    Background: Consumption of large portion sizes is contributing to overweight and obesity.College students are a vulnerable group in this regard. The purpose of this study was to use multi-theory model (MTM) to predict initiation and sustenance of small portion size consumption in college students. Methods: A total of 135 students at a large Southern US University completed a 35-item valid (face, content, and construct) and reliable (internally consistent) survey electronically in a cross-sect...

  2. Application of a droplet evaporation model to aerodynamic size measurement of drug aerosols generated by a vibrating mesh nebulizer.

    Science.gov (United States)

    Rao, Nagaraja; Kadrichu, Nani; Ament, Brian

    2010-10-01

    Droplet evaporation has been known to bias cascade impactor measurement of aerosols generated by jet nebulizers. Previous work suggests that vibrating mesh nebulizers behave differently from jet nebulizers. Unlike jet nebulizers, vibrating mesh nebulizers do not rely on compressed air to generate droplets. However, entrained air is still required to transport the generated droplets through the cascade impactor during measurement. The mixing of the droplet and entrained air streams, and heat and mass transfer occurring downstream determines the final aerosol size distribution actually measured by the cascade impactor. This study is aimed at quantifying the effect of these factors on droplet size measurements for the case of vibrating mesh nebulizers. A simple droplet evaporation model has been applied to investigate aerodynamic size measurement of drug aerosol droplets produced by a proprietary vibrating mesh nebulizer. The droplet size measurement system used in this study is the Next Generation Impactor (NGI) cascade impactor. Comparison of modeling results with experiment indicates that droplet evaporation remains a significant effect when sizing aerosol generated by a vibrating mesh nebulizer. Results from the droplet evaporation model shows that the mass median aerodynamic diameter (MMAD) measured by the NGI is strongly influenced not only by the initial droplet size, but also by factors such as the temperature and humidity of entrained air, the nebulizer output rate, and the entrained air flow rate. The modeling and experimental results indicate that the influence of these variables on size measurements may be reduced significantly by refrigerating the impactor down to 5°C prior to measurement. The same data also support the conclusion that for the case of nebulized drug solutions, laser diffraction spectrometry provides a meaningful droplet sizing approach, that is simpler and less susceptible to such droplet evaporation artifacts.

  3. Using multi-theory model to predict initiation and sustenance of small portion size consumption among college students.

    Science.gov (United States)

    Sharma, Manoj; Catalano, Hannah Priest; Nahar, Vinayak K; Lingam, Vimala; Johnson, Paul; Ford, M Allison

    2016-01-01

    Consumption of large portion sizes is contributing to overweight and obesity.College students are a vulnerable group in this regard. The purpose of this study was to use multi-theory model (MTM) to predict initiation and sustenance of small portion size consumption in college students. A total of 135 students at a large Southern US University completed a 35-item valid (face, content, and construct) and reliable (internally consistent) survey electronically in a cross-sectional design. The main outcome measures were intention to start eating small portion sizes and continuing to eat small portion sizes. Only those students who ate large portion sizes during the past 24 hours were included. Step wise multiple regression showed that initiation of small portion size consumption was explained by participatory dialogue (advantages outweighing disadvantages), behavioral confidence, age, and gender (adjusted R(2) = 0.37, P emotional transformation, changes in social environment, and race were the significant predictors (adjusted R(2) = 0.20, P < 0.001). Whites were less likely to sustain small portion size change than other races (β = -0.269, 95% CI = -0.97 - -0.26). Based on this study's findings, MTM appears to be a robust theoretical framework for predicting small portion size consumption behavior change. Interventions in this regard need to be designed.

  4. Population size dependence of fitness effect distribution and substitution rate probed by biophysical model of protein thermostability.

    Science.gov (United States)

    Goldstein, Richard A

    2013-01-01

    The predicted effect of effective population size on the distribution of fitness effects and substitution rate is critically dependent on the relationship between sequence and fitness. This highlights the importance of using models that are informed by the molecular biology, biochemistry, and biophysics of the evolving systems. We describe a computational model based on fundamental aspects of biophysics, the requirement for (most) proteins to be thermodynamically stable. Using this model, we find that differences in population size have minimal impact on the distribution of population-scaled fitness effects, as well as on the rate of molecular evolution. This is because larger populations result in selection for more stable proteins that are less affected by mutations. This reduction in the magnitude of the fitness effects almost exactly cancels the greater selective pressure resulting from the larger population size. Conversely, changes in the population size in either direction cause transient increases in the substitution rate. As differences in population size often correspond to changes in population size, this makes comparisons of substitution rates in different lineages difficult to interpret.

  5. Classifying and modeling setups and cleanings in lot sizing and scheduling

    NARCIS (Netherlands)

    Stefansdottir, Bryndis; Grunow, Martin; Akkerman, Renzo

    2017-01-01

    Much attention in the lot sizing and scheduling literature has been focused on reducing the number and size of setups. Cleanings, in contrast, remain a key cost driver in large parts of the process industries such as the food and pharmaceutical sectors. Here, quality and safety considerations lead

  6. Local existence for a general model of size-dependent population dynamics

    Directory of Open Access Journals (Sweden)

    Nobuyuki Kato

    1997-01-01

    Full Text Available We shall investigate a size structured population dynamics with aging and birth functions having general forms. The growth rate we deal with depends not only on the size but also on time. We show the existence of a local solution and continuous dependence on the initial data, which shows the uniqueness of the solution as well.

  7. A quantitative test of the size efficiency hypothesis by means of a physiologically structured model

    NARCIS (Netherlands)

    Hülsmann, S.; Rinke, K.; Mooij, W.M.

    2005-01-01

    According to the size-efficiency hypothesis (SEH) larger bodied cladocerans are better competitors for food than small bodied species. In environments with fish, however, the higher losses of the large bodied species due to size-selective predation may shift the balance in favor of the small bodied

  8. Model independent determination of colloidal silica size distributions via analytical ultracentrifugation

    NARCIS (Netherlands)

    Planken, K.L.|info:eu-repo/dai/nl/304841099; Kuipers, B.W.M.|info:eu-repo/dai/nl/304841110; Philipse, A.P.|info:eu-repo/dai/nl/073532894

    2008-01-01

    We report a method to determine the particle size distribution of small colloidal silica spheres via analytical ultracentrifugation and show that the average particle size, variance, standard deviation, and relative polydispersity can be obtained from a single sedimentation velocity (SV) analytical

  9. On the Size Dependences of the Metallic Nanoparticle Evaporation and Sublimation Heats: Thermodynamics and Atomistic Modeling

    Science.gov (United States)

    Bembel, A. G.

    2017-02-01

    Size dependences of the nanocrystal sublimation and the evaporation heats of the corresponding nanodrops are investigated using the isothermal molecular dynamics and the tight-binding potential (on examples of Ni and Au nanoparticles). Results of computer simulation demonstrating linear dependences of the evaporation and sublimation heats on the particle reciprocal radius are compared with results of thermodynamic calculations as well as with experimental data for bulk phases of the same metals. It has been found that the size dependences of the evaporation and sublimation heats are directly related with the behavior of the size dependence of the melting heat that in its turn correlates with structural transformations in nanoparticles induced by the change of their size. The conclusion is drawn that there is some characteristic nanoparticle size (of the order of 1 nm) at which its crystal and liquid states become indistinguishable.

  10. Population size dependence of fitness effect distribution and substitution rate probed by biophysical model of protein thermostability

    OpenAIRE

    Goldstein, R. A.

    2013-01-01

    The predicted effect of effective population size on the distribution of fitness effects and substitution rate is critically dependent on the relationship between sequence and fitness. This highlights the importance of using models that are informed by the molecular biology, biochemistry, and biophysics of the evolving systems. We describe a computational model based on fundamental aspects of biophysics, the requirement for (most) proteins to be thermodynamically stable. Using this model, we ...

  11. Evaluating targets and trade-offs among fisheries and conservation objectives using a multispecies size spectrum model

    DEFF Research Database (Denmark)

    Blanchard, J.L.; Andersen, Ken Haste; Scott, F.

    2014-01-01

    Marine environmental management policies seek to ensure that fishing impacts on fished populations and other components of the ecosystem are sustainable, to simultaneously meet objectives for fisheries and conservation. For example, in Europe, targets for (i) biodiversity, (ii) food web structure...... by knowledge on the consequences of alternate management actions. We develop, calibrate and apply a multispecies size spectrum model of the North Sea fish community to assess the response of populations and the community to fishing. The model predicts species' size distributions, abundance, productivity...... populations at FMSY than if status quo (2010) fishing rates are maintained. The probability of achieving a food web target was 60% under both scenarios in spite of major community restructuring revealed by other indicators of community size structure. Synthesis and applications. Our model can be applied...

  12. Particle-size dependent effects in the Balb/c murine model of inhalational melioidosis

    Directory of Open Access Journals (Sweden)

    Richard eThomas

    2012-07-01

    Full Text Available Deposition of Burkholderia pseudomallei within either the lungs or nasal passages of the Balb/c murine model resulted in different infection kinetics. The infection resulting from the inhalation of B. pseudomallei within a 12 um particle aerosol was prolonged compared to a 1 um particle aerosol with a mean time-to-death (MTD of 73.8 ± 11.3 h and 174.7 ± 14.9 h respectively. Inhalation of B. pseudomallei within 1 um or 12 um particle aerosols resulted in a median lethal dose (MLD of 4 and 12 cfu respectively. The 12 mm particle inhalational infection was characterised by involvement of the respiratory epithelium and inflammation of the neurological path leading from the olfactory epithelium to the olfactory bulb (100%, culminating in abscessation of the brain (33%. Initial involvement of the upper respiratory tract lymphoid tissues (nasal-associated lymphoid tissue and cervical lymph nodes was observed in both the 1 and 12 um particle inhalational infections (80-85%. Necrotising alveolitis and bronchiolitis were evident in both inhalational infections however lung pathology was greater after inhalation of the 1 mm particle aerosol with pronounced involvement of the mediastinal lymph node (50%. Terminal disease was characterised by bacteraemia in both inhalational infections with dissemination to the spleen, liver, kidneys and thymus. Treatment with co-trimoxazole was more effective than treatment with doxycycline irrespective of the size of the particles inhaled. Doxycycline was more effective against the 12 um particle inhalational infection as evidenced by increased time to death. However, both treatment regimes exhibited significant relapse when therapy was discontinued with massive enlargement and abscessation of the lungs, spleen and cervical lymph nodes observed.

  13. Modelling and simulation of size selectivity in diamond mesh trawl cod-ends

    DEFF Research Database (Denmark)

    Herrmann, Bent

    of the fishing gear. The cod-end is the rearmost part of a trawl where catch accumulates and in which most of the size selection is known to take place. To date, the main method used to assess the selectivity of trawl cod-ends has been to run sea trials followed by statistical analysis of the obtained......Within many fisheries there is a widespread discard of fish. Furthermore, there are several fisheries where fish are caught before reaching the optimal size, leading to an adverse exploitation of the resources. One way to achieve a more optimal exploitation is to improve the size selectivity...

  14. A joint model of mode and shipment size choice using the first generation of Commodity Flow Survey Public Use Microdata

    Directory of Open Access Journals (Sweden)

    Monique Stinson

    2017-12-01

    Full Text Available A behavior-based supply chain and freight transportation model was developed and implemented for the Maricopa Association of Governments (MAG and Pima Association of Governments (PAG. This innovative, data-driven modeling system simulates commodity flows to, from and within Phoenix and Tucson Megaregion and is used for regional planning purposes. This paper details the logistics choice component of the system and describes the position and functioning of this component in the overall framework. The logistics choice model uses a nested logit formulation to evaluate mode choice and shipment size jointly. Modeling decisions related to integrating this component within the overall framework are discussed. This paper also describes practical insights gained from using the 2012 Commodity Flow Survey Public Use Microdata (released in 2015, which was the principal data source used to estimate the joint shipment size-mode choice nested logit model. Finally, the validation effort and related lessons learned are described.

  15. MinSORTING: an Excel macro for modelling sediment composition and grain-size distribution

    Science.gov (United States)

    Resentini, Alberto; Malusà, Marco G.; Garzanti, Eduardo

    2013-04-01

    Detrital mineral analyses are gaining increasing attention in the geosciences as new single-grain analytical techniques are constantly improving their resolution, and consequently widening their range of application, including sedimentary petrology, tectonic geomorphology and archaeology (Mange and Wright, 2007; von Eynatten and Dunkl, 2012). We present here MinSORTING, a new tool to quickly predict the size distribution of various minerals and rock fragments in detrital sediments, based on the physical laws that control sedimentation by tractive wind or water currents (Garzanti et al., 2008). The input values requested by the software are the sediment mean size, sorting, fluid type (seawater, freshwater, air) and standard sediment composition chosen from a given array including nine diverse tectonic settings. MinSORTING calculates the bulk sediment density and the settling velocity. The mean size of each single detrital component, assumed as lognormally-distributed, is calculated from its characteristic size-shift with respect to bulk sediment mean size, dependent in turn on its density and shape. The final output of MinSORTING is the distribution of each single detrital mineral in each size classes (at the chosen 0.25, 0.5 or 1 phi intervals). This allows geochronolgists to select the most suitable grain size of sediment to be sampled in the field, as well as the most representative size-window for analysis. Also, MinSORTING provides an estimate of the volume/weight of the fractions not considered in both sizes finer and coarser than the selected size-window. A beta version of the software is available upon request from: alberto.resentini@unimib.it Mange, M., and Wright, D. (eds), 2007. Heavy minerals in use. Developments in Sedimentology Series, 58. Elsevier, Amsterdam. Garzanti, E., Andò, S., Vezzoli, G., 2008. Settling-equivalence of detrital minerals and grain-size dependence of sediment composition. Earth and Planetary Science Letters 273, 138-151. von

  16. Modeling of flow stress size effect based on variation of dislocation substructure in micro-tension of pure nickel

    Science.gov (United States)

    Wang, Chuanjie; Liu, Huan; Zhang, Ying; Chen, Gang; Li, Yujie; Zhang, Peng

    2017-12-01

    Micro-forming is one promising technology for manufacturing micro metal parts. However, the traditional metal-forming theories fail to analyze the plastic deformation behavior in micro-scale due to the size effect arising from the part geometry scaling down from macro-scale to micro-scale. To reveal the mechanism of plastic deformation behavior size effect in micro-scale, the geometrical parameters and the induced variation of microstructure by them need to be integrated in the developed constitutive models considering the free surface effect. In this research, the variations of dislocation cell diameter with original grain size, strain and location (surface grain or inner grain) are derived according the previous research data. Then the overall flow stress of the micro specimen is determined by employing the surface layer model and the relationship between dislocation cell diameter and the flow stress. This new developed constitutive model considers the original grain size, geometrical dimension and strain simultaneously. The flow stresses in micro-tensile tests of thin sheets are compared with calculated results using the developed constitutive model. The calculated and experimental results match well. Thus the validity of the developed constitutive model is verified.

  17. Does company size matter? Validation of an integrative model of safety behavior across small and large construction companies.

    Science.gov (United States)

    Guo, Brian H W; Yiu, Tak Wing; González, Vicente A

    2018-02-01

    Previous safety climate studies primarily focused on either large construction companies or the construction industry as a whole, while little is known about whether company size has significant effects on workers' understanding of safety climate measures and relationships between safety climate factors and safety behavior. Thus, this study aims to: (a) test the measurement equivalence (ME) of a safety climate measure across workers from small and large companies; (b) investigate if company size alters the causal structure of the integrative model developed by Guo, Yiu, and González (2016). Data were collected from 253 construction workers in New Zealand using a safety climate measure. This study used multi-group confirmatory factor analyses (MCFA) to test the measurement equivalence of the safety climate measure and structure invariance of the integrative model. Results indicate that workers from small and large companies understood the safety climate measure in a similar manner. In addition, it was suggested that company size does not change the causal structure and mediational processes of the integrative model. Both measurement equivalence of the safety climate measure and structural invariance of the integrative model were supported by this study. Practical applications: Findings of this study provided strong support for a meaningful use of the safety climate measure across construction companies in different sizes. Safety behavior promotion strategies designed based on the integrative model may be well suited for both large and small companies. Copyright © 2017 National Safety Council and Elsevier Ltd. All rights reserved.

  18. Can the business model of Handelsbanken be an archetype for small and medium sized banks? A comparative case study

    DEFF Research Database (Denmark)

    Kousgaard Larsen, Morten; Lange Nissen, Jacob; Lueg, Rainer

    2014-01-01

    The Danish Banking sector faces increasing requirements regarding regulation and profitability, which especially threatens small- and medium sized banks. This study analyzes whether the successful business model of Handelsbanken (‘The Handelsbanken Way’) to banking in regard to the needed...... strengthening of the financial and non-financial position can serve as a blueprint for small- and medium sized banks. We conduct a comparative case study by interviewing Handelsbanken and the disguised ‘Danish Local Bank’ (DLB), where the DLB is a representative example of a small- and medium sized Danish bank...... advantages of ‘The Handelsbanken Way’, this study suggests that the financially troubled small- and medium sized banks in Denmark will not necessarily benefit from the tactical choice of decentralization unless they incorporate specific adjustments. This study contribute to the existing theory concerning...

  19. A Note on the Power Provided by Sibships of Sizes 2, 3, and 4 in Genetic Covariance Modeling of a Codominant QTL.

    NARCIS (Netherlands)

    Dolan, C.V.; Boomsma, D.I.; Neale, M.C.

    1999-01-01

    The contribution of size 3 and size 4 sibships to power in covariance structure modeling of a codominant QTL is investigated. Power calculations are based on the noncentral chi-square distribution. Sixteen sets of parameter values are considered. Results indicate that size 3 and size 4 sibships

  20. Modelling gastric evacuation without meal size as a variable. A model applicable for the estimation of daily ration of cod (Gadus morhua L.) in the field

    DEFF Research Database (Denmark)

    Temming, Axel; Andersen, Niels Gerner

    1994-01-01

    S=stomach content, T=time after ingestion, R and B=constants. This model allows for various curve shapes, including linear (B=O) and exponential (B=1), and the curve shape (B) was estimated from the data. Meal size was included in the model by modifying the constant R=R′ × MD, with M=meal size...... in weight and D=constant. When meal size was included in the model, the resulting B values were strongly dependent on the food type and the estimated D values were negatively correlated with B: capelin, B=1.37, D= -1.16; herring, B=0.84, D= -0.57; and prawn, B=0.35, D= -0.14. When meal size was excluded...

  1. Modeling the X-ray Process, and X-ray Flaw Size Parameter for POD Studies

    Science.gov (United States)

    Koshti, Ajay M.

    2014-01-01

    Nondestructive evaluation (NDE) method reliability can be determined by a statistical flaw detection study called probability of detection (POD) study. In many instances, the NDE flaw detectability is given as a flaw size such as crack length. The flaw is either a crack or behaving like a crack in terms of affecting the structural integrity of the material. An alternate approach is to use a more complex flaw size parameter. The X-ray flaw size parameter, given here, takes into account many setup and geometric factors. The flaw size parameter relates to X-ray image contrast and is intended to have a monotonic correlation with the POD. Some factors such as set-up parameters, including X-ray energy, exposure, detector sensitivity, and material type that are not accounted for in the flaw size parameter may be accounted for in the technique calibration and controlled to meet certain quality requirements. The proposed flaw size parameter and the computer application described here give an alternate approach to conduct the POD studies. Results of the POD study can be applied to reliably detect small flaws through better assessment of effect of interaction between various geometric parameters on the flaw detectability. Moreover, a contrast simulation algorithm for a simple part-source-detector geometry using calibration data is also provided for the POD estimation.

  2. Size- and concentration-dependent deposition of fluorescent silica colloids in saturated sand columns: transport experiments and modeling.

    Science.gov (United States)

    Vitorge, Elsa; Szenknect, Stéphanie; Martins, Jean M F; Gaudet, Jean-Paul

    2013-08-01

    This study investigates the size and concentration effects on the transport of silica colloids in columns of sandy aquifer material. Colloid transport experiments were performed with specifically developed fluorescent labeled silica colloids in columns of a repacked natural porous medium under hydro-geochemical conditions representative of sandy aquifers. Breakthrough curves and vertical deposition profiles of colloids were measured for various colloid concentrations and sizes. The results showed that for a given colloid concentration injected, deposition increased when increasing the size of the colloids. For a given colloid size, retention was also shown to be highly concentration-dependent with a non-monotonous pattern presenting low and high concentration specificities. Deposition increases when increasing both size and injected concentration, until a threshold concentration is reached, above which retention decreases, thus increasing colloid mobility. Results observed above the threshold concentration agree with a classical blocking mechanism typical of a high concentration regime. Results observed at lower colloid concentrations were not modeled with a classical blocking model and a depth- and time-dependent model with a second order kinetic law was necessary to correctly fit the experimental data in the entire range of colloid concentrations with a single set of parameters for each colloidal size. The colloid deposition mechanisms occuring at low concentrations were investigated through a pore structure analysis carried out with Mercury Intrusion Porosimetry and image analysis. The determined pore size distribution permitted estimation of the maximal retention capacity of the natural sand as well as some low flow zones. Altogether, these results stress the key role of the pore space geometry of the sand in controlling silica colloids deposition under hydro-geochemical conditions typical of sandy aquifers. Our results also showed originally that colloid

  3. Effect of exogenous progesterone on embryo size and ewe uterine gene expression in an ovine 'dam size' model of maternal constraint.

    Science.gov (United States)

    Fermin, Lisanne M; Pain, Sarah J; Morel, Patrick C H; Gedye, Kristene R; Kenyon, Paul R; Blair, Hugh T

    2017-11-21

    Progesterone (P4), acting via its receptor, regulates uterine function and histotroph production, which are crucial to embryo growth. This study aimed to examine exogenous P4 effects on embryo size and differential endometrial gene expression at Day 19 of gestation using a 'dam size' sheep model of maternal constraint. Purebred Suffolk (S, genotypically large) embryos were transferred into recipient groups of Cheviot (C, genotypically small) or Suffolk ewes that had, or had not, been pre-treated with P4 from Days 0 to 6 of pregnancy. At Day 19S embryos were collected from four experimental groups: P4 pretreated S ewes (SP4; n=5), untreated S ewes (SnP4; n=15), P4 pretreated C ewes (CP4; n=7) and untreated C ewes (CnP4; n=21). Day-19 embryos from CP4 ewes were larger (P0.05) to embryos from SnP4 and SP4 ewes. Expression of mucin 1 (MUC1) and prostaglandin-endoperoxide synthase 2 (PTGS2) was upregulated in uterine horns ipsilateral to the corpus luteum from CP4 ewes. Prostaglandin receptor (PGR), MUC1 and PTGS2 expression was upregulated, whilst cathepsin L (CTSL) and radical S-adenosyl methionine domain-containing 2 (RSAD2) expression was downregulated in the ipsilateral horn of SP4 ewes. This suggests that pretreating ewes with exogenous P4 may alleviate early pregnancy maternal constraint via mechanisms that alter uterine function. However, further research is required to investigate the timing of P4 administration and its impact on conception rates.

  4. How does dietary particle size affect carnivore gastrointestinal transit: A dog model.

    Science.gov (United States)

    De Cuyper, A; Hesta, M; Tibosch, S; Wanke, C; Clauss, M; Janssens, G P J

    2018-04-01

    The effect of dietary particle size on gastrointestinal transit in carnivores has not been studied and might offer more insight into their digestive physiology. This study evaluated the effect of two dietary particle sizes (fine = 7.8 mm vs. coarse = 13 mm) of chunked day-old chicks on transit parameters in dogs. Six beagle dogs were fed both dietary treatments in a crossover design of 7 days with transit testing on the fifth day. Transit parameters were assessed using two markers, that is a wireless motility capsule (IntelliCap ® ) and titanium oxide (TiO 2 ). Dietary particle size did not affect gastric emptying time (GRT), small bowel transit time (SBTT), colonic transit time (CTT) and total transit time (aTTT) of the capsule (p > .05). There was no effect of dietary particle size on TiO 2 mean retention time (MRT) (p > .05). The time of last TiO 2 excretion (MaxRT) differed (p = .013) between diets, being later for the coarse diet. Both MRT (R = 0.617, p = .032) and MaxRT (R = 0.814; p = .001) were positively correlated to aTTT. The ratio MRT/aTTT tended towards a difference between diets (p = .059) with the coarse diet exceeding fine diet values. Results show that the difference between capsule measurements and TiO 2 is larger for the fine than the coarse diet suggesting that the capsule becomes more accurate when dietary particle size approaches marker size. Dietary particle size might have affected transit parameters but differences are too small to claim major physiological consequences. © 2017 Blackwell Verlag GmbH.

  5. A Conceptual Model for Assessing the Minimum Size Area for an Area-Wide Integrated Pest Management Program

    Directory of Open Access Journals (Sweden)

    Hugh J. Barclay

    2011-01-01

    Full Text Available A conceptual model was developed based on the two basic spatial elements of area-wide integrated pest management (AW-IPM, a core area and a buffer zone, to determine the minimum size of the protected area for the program to be technically feasible and economically justifiable. The model consisted of a biological part (insect dispersal and an economic part. The biological part used random walks and diffusion equations to describe insect dispersal and to determine the minimum width of the buffer zone required to protect the core area from immigration of pests from outside. In the economic part, the size of the core area was calculated to determine the point at which the revenues from the core area equal the control costs. This model will need to be calibrated and validated for each species and geographic location. Tsetse flies and the Mediterranean fruit fly are used as case studies to illustrate the model.

  6. DLNA: a simple one-dimensional dynamical model as a possible interpretation of fragment size distribution in nuclear multifragmentation

    International Nuclear Information System (INIS)

    Lacroix, D.; Dayras, R.

    1996-08-01

    The possibility of interpreting multifragmentation data obtained from heavy-ion collisions at intermediate energies, by a new type of model: the DLNA (Dynamical Limited Nuclear Aggregation) is discussed. This model is connected to a more general class of models presenting Self-Organization Criticality (SOC). It is shown that the fragment size distributions exhibit a power-law dependence comparable to those obtained in second-order phase transition or percolation models. Fluctuations in term of scaled-factorial moments and cumulants are also studied: no signal of intermittency is seen. (K.A.)

  7. Co-word Maps and Topic Modeling: A Comparison Using Small and Medium-Sized Corpora (n

    NARCIS (Netherlands)

    Leydesdorff, Loet; Nerghes, A.

    2016-01-01

    Induced by “big data,” “topic modeling” has become an attractive alternative to mapping co-words in terms of co-occurrences and co-absences using network techniques. Does topic modeling provide an alternative for co-word mapping in research practices using moderately sized document collections? We

  8. Finite-size effects for the gap in the excitation spectrum of the one-dimensional Hubbard model

    NARCIS (Netherlands)

    Colomé-Tatché, M.; Matveenko, S.I.; Shlyapnikov, G.V.

    2010-01-01

    We study finite-size effects for the gap of the quasiparticle excitation spectrum in the weakly interacting regime one-dimensional Hubbard model with on-site attraction. Two types of corrections to the result of the thermodynamic limit are obtained. Aside from a power law (conformal) correction due

  9. CONFRONTING STANDARD MODELS OF PROTO-PLANETARY DISKS WITH NEW MID-INFRARED SIZES FROM THE KECK INTERFEROMETER

    Energy Technology Data Exchange (ETDEWEB)

    Millan-Gabet, Rafael [California Institute of Technology, NASA Exoplanet Science Institute, Pasadena, CA 91125 (United States); Che, Xiao; Monnier, John D.; Aarnio, Alicia N. [University of Michigan Astronomy Department, 1085 S. University Avenue 303B West Hall University of Michigan, Ann Arbor, MI 48109-1107 (United States); Sitko, Michael L.; Day, Amanda N. [Department of Physics, University of Cincinnati, Cincinnati OH 45221 (United States); Russell, Ray W. [The Aerospace Corporation, Los Angeles, CA 90009 (United States); Grady, Carol A. [Eureka Scientific, 2452 Delmer, Suite 100, Oakland, CA 96002 (United States); Perry, R. B. [NASA Langley Research Center, MS 160, Hampton, VA 23681 (United States); Harries, Tim J. [Department of Physics and Astronomy, University of Exeter, Stocker Road, Exeter EX4 4QL (United Kingdom); Colavita, Mark M. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Wizinowich, Peter L.; Ragland, Sam; Woillez, Julien, E-mail: R.Millan-Gabet@caltech.edu [Keck Observatory, 65-1120 Mamalahoa Hwy, Kamuela, HI 96743 (United States)

    2016-08-01

    We present near- and mid-infrared (MIR) interferometric observations made with the Keck Interferometer Nuller and near-contemporaneous spectro-photometry from the infrared telescope facilities (IRTFs) of 11 well-known young stellar objects, several of which were observed for the first time in these spectral and spatial resolution regimes. With au-level spatial resolution, we first establish characteristic sizes of the infrared emission using a simple geometrical model consisting of a hot inner rim and MIR disk emission. We find a high degree of correlation between the stellar luminosity and the MIR disk sizes after using near-infrared data to remove the contribution from the inner rim. We then use a semi-analytical physical model to also find that the very widely used “star + inner dust rim + flared disk” class of models strongly fails to reproduce the spectral energy distribution (SED) and spatially resolved MIR data simultaneously; specifically a more compact source of MIR emission is required than results from the standard flared disk model. We explore the viability of a modification to the model whereby a second dust rim containing smaller dust grains is added, and find that the 2-rim model leads to significantly improved fits in most cases. This complexity is largely missed when carrying out SED modeling alone, although detailed silicate feature fitting by McClure et al. recently came to a similar conclusion. As has been suggested recently by Menu et al., the difficulty in predicting MIR sizes from the SED alone might hint at “transition disk”-like gaps in the inner au; however, the relatively high correlation found in our MIR disk size versus stellar luminosity relation favors layered disk morphologies and points to missing disk model ingredients instead.

  10. Moderately thin advertising models are optimal, most of the time: Moderation of the quadratic effect of model body-size on ad attitude by fashion leadership

    NARCIS (Netherlands)

    Janssen, D.M.; Paas, L.J.

    2014-01-01

    The authors hypothesize and find that an advertising model's body size has an inverted U-shaped relationship with ad attitude in the apparel product category, in which moderately thin advertising models are optimal. They assess the moderating effect of consumers' fashion leadership on this quadratic

  11. A Hot Spots Ignition Probability Model for Low-Velocity Impacted Explosive Particles Based on the Particle Size and Distribution

    Directory of Open Access Journals (Sweden)

    Hong-fu Guo

    2017-01-01

    Full Text Available Particle size and distribution play an important role in ignition. The size and distribution of the cyclotetramethylene tetranitramine (HMX particles were investigated by Laser Particle Size Analyzer Malvern MS2000 before experiment and calculation. The mean size of particles is 161 μm. Minimum and maximum sizes are 80 μm and 263 μm, respectively. The distribution function is like a quadratic function. Based on the distribution of micron scale explosive particles, a microscopic model is established to describe the process of ignition of HMX particles under drop weight. Both temperature of contact zones and ignition probability of powder explosive can be predicted. The calculated results show that the temperature of the contact zones between the particles and the drop weight surface increases faster and higher than that of the contact zones between two neighboring particles. For HMX particles, with all other conditions being kept constant, if the drop height is less than 0.1 m, ignition probability will be close to 0. When the drop heights are 0.2 m and 0.3 m, the ignition probability is 0.27 and 0.64, respectively, whereas when the drop height is more than 0.4 m, ignition probability will be close to 0.82. In comparison with experimental results, the two curves are reasonably close to each other, which indicates our model has a certain degree of rationality.

  12. Constitutive modeling of rate dependence and microinertia effects in porous-plastic materials with multi-sized voids (MSVs)

    KAUST Repository

    Liu, Jinxing

    2012-11-27

    Micro-voids of varying sizes exist in most metals and alloys. Both experiments and numerical studies have demonstrated the critical influence of initial void sizes on void growth. The classical Gurson-Tvergaard-Needleman model summarizes the influence of voids with a single parameter, namely the void-volume fraction, excluding any possible effects of the void-size distribution. We extend our newly proposed model including the multi-sized void (MSV) effect and the void-interaction effect for the capability of working for both moderate and high loading rate cases, where either rate dependence or microinertia becomes considerable or even dominant. Parametric studies show that the MSV-related competitive mechanism among void growth leads to the dependence of the void growth rate on void size, which directly influences the void\\'s contribution to the total energy composition. We finally show that the stress-strain constitutive behavior is also affected by this MSV-related competitive mechanism. The stabilizing effect due to rate sensitivity and microinertia is emphasized. © 2013 IOP Publishing Ltd.

  13. Improving Genetic Evaluation of Litter Size Using a Single-step Model

    DEFF Research Database (Denmark)

    Guo, Xiangyu; Christensen, Ole Fredslund; Ostersen, Tage

    A recently developed single-step method allows genetic evaluation based on information from phenotypes, pedigree and markers simultaneously. This paper compared reliabilities of predicted breeding values obtained from single-step method and the traditional pedigree-based method for two litter size...... traits, total number of piglets born (TNB), and litter size at five days after birth (Ls 5) in Danish Landrace and Yorkshire pigs. The results showed that the single-step method combining phenotypic and genotypic information provided more accurate predictions than the pedigree-based method, not only...

  14. Comparative study of economics of different models of family size biogas plants for state of Punjab, India

    International Nuclear Information System (INIS)

    Singh, K. Jatinder; Sooch, Sarbjit Singh

    2004-01-01

    Biogas, the end product of anaerobic digestion of cattle dung, can successfully supplement the cooking fuels in the countryside areas of India, where the raw material needed for its production is plentifully available. Because of the lack of awareness regarding selection of a suitable model and size of biogas plant, the full potential of the biogas producing material is not harnessed, and the economic viability of biogas technology is rendered doubtful. To facilitate this decision making, the economics of family size biogas plants, i.e. with capacity from 1 to 6 m 3 , was studied, and three prevalent models, viz. KVIC, Janta and Deenbandu, were compared. Calculations for installation cost and annual operational cost were made for the state of Punjab, India, where the hydraulic retention time is 40 days, and current market prices were taken into account. Comparison of the economics revealed that the cost of installation and annual operational cost of each capacity were higher for the KVIC model, followed by the Janta and then the Deenbandhu model. Irrespective of the model, as the capacity of the biogas plant increases, the installation, as well as the annual operational cost increase proportionately. With increase in capacity, the payback period decreased exponentially with the exponential character being highest for the KVIC model, followed by the Janta and then the Deenbandhu model. However, on the basis of comparative economics, the Deenbandhu model was found to be the cheapest and most viable model of biogas plant

  15. Iron Oxide Nanoparticles: Tunable Size Synthesis and Analysis in Terms of the Core-Shell Structure and Mixed Coercive Model

    Science.gov (United States)

    Phong, P. T.; Oanh, V. T. K.; Lam, T. D.; Phuc, N. X.; Tung, L. D.; Thanh, Nguyen T. K.; Manh, D. H.

    2017-04-01

    Iron oxide nanoparticles (NPs) are currently a very active research field. To date, a comprehensive study of iron oxide NPs is still lacking not only on the size dependence of structural phases but also in the use of an appropriate model. Herein, we report on a systematic study of the structural and magnetic properties of iron oxide NPs prepared by a co-precipitation method followed by hydrothermal treatment. X-ray diffraction and transmission electron microscopy reveal that the NPs have an inverse spinel structure of iron oxide phase (Fe3O4) with average crystallite sizes ( D XRD) of 6-19 nm, while grain sizes ( D TEM) are of 7-23 nm. In addition, the larger the particle size, the closer the experimental lattice constant value is to that of the magnetite structure. Magnetic field-dependent magnetization data and analysis show that the effective anisotropy constants of the Fe3O4 NPs are about five times larger than that of their bulk counterpart. Particle size ( D) dependence of the magnetization and the non-saturating behavior observed in applied fields up to 50 kOe are discussed using the core-shell structure model. We find that with decreasing D, while the calculated thickness of the shell of disordered spins ( t ˜ 0.3 nm) remains almost unchanged, the specific surface areas S a increases significantly, thus reducing the magnetization of the NPs. We also probe the coercivity of the NPs by using the mixed coercive Kneller and Luborsky model. The calculated results indicate that the coercivity rises monotonously with the particle size, and are well matched with the experimental ones.

  16. Effects of copepod size on fish growth: A model based on data for North Sea sandeel

    DEFF Research Database (Denmark)

    Deurs, Mikael van; Jørgensen, C.; Fiksen, Ø.

    2015-01-01

    mechanistic models from relevant data: (1) a model of the bioenergetics and stomach filling/evacuation dynamics, and (2) a Holling type II functional response model that encompasses visual range from basic principles. The model predicts that going from a situation where large Calanus copepods (2 mm) dominate...

  17. Positive global solutions for a general model of size-dependent population dynamics

    Directory of Open Access Journals (Sweden)

    Nobuyuki Kato

    2000-01-01

    have the growth rate depending on the size and time. The local existence and uniqueness of the solution have been shown by Kato and Torikata (1997. Here, we discuss the positivity of the solution and global existence as well as L ∞ solutions.

  18. A random regression model in analysis of litter size in pigs | Lukovi& ...

    African Journals Online (AJOL)

    The eigenvalues of covariance functions showed that between 10 and 15% of genetic variability was explained by the individual genetic curve of sows in the DS2. This proportion was mainly covered by linear and quadratic coefficients. Results suggest that RRM could be used for genetic analysis of litter size. South African ...

  19. Systematic Modelling and Crystal Size Distribution Control for Batch Crystallization Processes

    DEFF Research Database (Denmark)

    Abdul Samad, Noor Asma Fazli; Singh, Ravendra; Sin, Gürkan

    Crystallization processes form an important class of separation methods that are frequently used in the chemical, the pharmaceutical and the food industry. The specifications of the crystal product are usually given in terms of crystal size, shape and purity. In order to predict the desired cryst...

  20. Multivariate models for prediction of rheological characteristics of filamentous fermentation broth from the size distribution

    DEFF Research Database (Denmark)

    Petersen, Nanna; Stocks, S.; Gernaey, Krist

    2008-01-01

    The main purpose of this article is to demonstrate that principal component analysis (PCA) and partial least squares regression (PLSR) can be used to extract information from particle size distribution data and predict rheological properties. Samples from commercially relevant Aspergillus oryzae ...

  1. Modelling Inter-Particle Forces and Resulting Agglomerate Sizes in Cement-Based Materials

    DEFF Research Database (Denmark)

    Kjeldsen, Ane Mette; Geiker, Mette Rica

    2005-01-01

    The theory of inter-particle forces versus external shear in cement-based materials is reviewed. On this basis, calculations on maximum agglomerate size present after the combined action of superplasticizers and shear are carried out. Qualitative experimental results indicate that external shear...

  2. Modeling the competition between antenna size mutant and wild type microalgae in outdoor mass culture

    NARCIS (Netherlands)

    Mooij, de Tim; Schediwy, Kira; Wijffels, René H.; Janssen, Marcel

    2016-01-01

    Under high light conditions, microalgae are oversaturated with light which significantly reduces the light use efficiency. Microalgae with a reduced pigment content, antenna size mutants, have been proposed as a potential solution to increase the light use efficiency. The goal of this study was

  3. Competition and brood reduction: testing alternative models of clutch-size evolution in parasitoids

    NARCIS (Netherlands)

    Pexton, J.J.; Boer, J.P.; Heimpel, G.E.; Vet, L.E.M.; Whitfield, J.; Ode, P.J.

    2009-01-01

    Competition between siblings occurs in many taxa including parasitoid wasps. Larvae of solitary species eliminate competitors by engaging in aggressive behavior, thus restricting brood size to a single individual. In gregarious species, more than one offspring can develop per host. There are 2

  4. Modeling grain-size dependent bias in estimating forest area: a regional application

    Science.gov (United States)

    Daolan Zheng; Linda S. Heath; Mark J. Ducey

    2008-01-01

    A better understanding of scaling-up effects on estimating important landscape characteristics (e.g. forest percentage) is critical for improving ecological applications over large areas. This study illustrated effects of changing grain sizes on regional forest estimates in Minnesota, Wisconsin, and Michigan of the USA using 30-m land-cover maps (1992 and 2001)...

  5. Sizing of photovoltaic system coupled with hydrogen/oxygen storage based on the ORIENTE model

    Energy Technology Data Exchange (ETDEWEB)

    Darras, C.; Sailler, S.; Thibault, C.; Muselli, M.; Poggi, P. [University of Corsica, UMR CNRS SPE 6134, Route des Sanguinaires, F-20000 Ajaccio (France); Hoguet, J.C.; Melscoet, S. [HELION Hydrogen Power, Domaine du Petit Arbois - Batiment Jules Verne, BP 71, 13545 Aix en Provence (France); Pinton, E.; Grehant, S. [Commissariat a l' Energie Atomique (CEA/LITEN), 17 rue des Martyrs, 38 054 Grenoble Cedex 9 (France); Gailly, F.; Turpin, C.; Astier, S.; Fontes, G. [Universite de Toulouse, INP, UPS, LAPLACE (Laboratoire Plasma et Conversion d' Energie), ENSEEIHT, 2 rue Charles Camichel, BP 7122, F-31071 Toulouse Cedex 7 (France); CNRS, LAPLACE, F-31071 Toulouse (France)

    2010-04-15

    PEPITE is a project funded by the French ANR PAN-H research program. This project concerns, among various other tasks, a demonstration of a weather station electricity supply with help of a PV/FC/EL hybrid system located at the CEA center of Cadarache (France). To design a relevant sizing for this demonstration system, a complete sizing tool has been developed via a new numerical optimizing code named ORIENTE. It uses Matlab software based on sequential running time. The demonstration system will be composed of a PV array, a PEM fuel cell system and a PEM electrolyzer, batteries, storage tanks for H{sub 2}, O{sub 2} and H{sub 2}O, as well as associated converters. This paper presents the obtained optimal sizing curves for the hybrid system (P{sub pv} [kWp], Q{sub H{sub 2}}{sub max} [kg]) by taking into account the predefined constant load (6.5 kW) functioning 24/24 hours and the system energy balance for a loss-of-load probability LLP = 0. These results give the sizes of each subsystem and will make possible to build the best energy flows control mode. (author)

  6. Early outcome in renal transplantation from large donors to small and size-matched recipients - a porcine experimental model

    DEFF Research Database (Denmark)

    Ravlo, Kristian; Chhoden, Tashi; Søndergaard, Peter

    2012-01-01

    Kidney transplantation from a large donor to a small recipient, as in pediatric transplantation, is associated with an increased risk of thrombosis and DGF. We established a porcine model for renal transplantation from an adult donor to a small or size-matched recipient with a high risk of DGF...... and studied GFR, RPP using MRI, and markers of kidney injury within 10 h after transplantation. After induction of BD, kidneys were removed from ∼63-kg donors and kept in cold storage for ∼22 h until transplanted into small (∼15 kg, n = 8) or size-matched (n = 8) recipients. A reduction in GFR was observed...

  7. Advanced model for poly dispersion in size in boiling flows; Modelisation avancee de la polydispersion en taille des ecoulements bouillants

    Energy Technology Data Exchange (ETDEWEB)

    Ruyer, P.; Seiler, N. [Institut de Radioprotection et Surete Nucleaire Cadarache, 13 - Saint Paul lez Durance (France)

    2009-07-01

    This work has been performed within the Institut de Radioprotection et de Surete Nucleaire that leads research programs concerning safety analysis of nuclear power plants. During a LOCA (Loss Of Coolant Accident), in-vessel pressure decreases and temperature increases, leading to the onset of nucleate boiling. The present study focuses on the numerical simulation of the local topology of the boiling flow. There is experimental evidence of a local and statistical large spectrum of possible bubble sizes. The relative importance of the correct description of this poly-dispersion in size is due to the dependency of (i) main hydrodynamic forces, as well as of (ii) transfer area with respect to the individual bubble size. We study the corresponding CFD model in the framework of an ensemble averaged description of the dispersed two-phase flow. The transport equations of the main statistical moment densities of the population size distribution are derived and models for the mass, momentum and heat transfers at the bubble scale as well as for bubble coalescence are achieved. This model introduced within NEPTUNE-CFD code of the NEPTUNE thermal-hydraulic platform, a joint project of CEA, EDF, IRSN and AREVA-NP, has been tested on boiling flows obtained on the DEBORA facility of the CEA at Grenoble. These numerical simulations provide a validation, check the meshing convergence as well as the impact of the various phenomena onto the local flow topology prediction. (authors)

  8. A framework for analysis of abortive colony size distributions using a model of branching processes in irradiated normal human fibroblasts.

    Science.gov (United States)

    Sakashita, Tetsuya; Hamada, Nobuyuki; Kawaguchi, Isao; Ouchi, Noriyuki B; Hara, Takamitsu; Kobayashi, Yasuhiko; Saito, Kimiaki

    2013-01-01

    Clonogenicity gives important information about the cellular reproductive potential following ionizing irradiation, but an abortive colony that fails to continue to grow remains poorly characterized. It was recently reported that the fraction of abortive colonies increases with increasing dose. Thus, we set out to investigate the production kinetics of abortive colonies using a model of branching processes. We firstly plotted the experimentally determined colony size distribution of abortive colonies in irradiated normal human fibroblasts, and found the linear relationship on the log-linear or log-log plot. By applying the simple model of branching processes to the linear relationship, we found the persistent reproductive cell death (RCD) over several generations following irradiation. To verify the estimated probability of RCD, abortive colony size distribution (≤ 15 cells) and the surviving fraction were simulated by the Monte Carlo computational approach for colony expansion. Parameters estimated from the log-log fit demonstrated the good performance in both simulations than those from the log-linear fit. Radiation-induced RCD, i.e. excess probability, lasted over 16 generations and mainly consisted of two components in the early (probability over 5 generations, whereas abortive colony size distribution was robust against it. These results suggest that, whereas short-term RCD is critical to the abortive colony size distribution, long-lasting RCD is important for the dose response of the surviving fraction. Our present model provides a single framework for understanding the behavior of primary cell colonies in culture following irradiation.

  9. Effect of Finite Particle Size on Convergence of Point Particle Models in Euler-Lagrange Multiphase Dispersed Flow

    Science.gov (United States)

    Nili, Samaun; Park, Chanyoung; Haftka, Raphael T.; Kim, Nam H.; Balachandar, S.

    2017-11-01

    Point particle methods are extensively used in simulating Euler-Lagrange multiphase dispersed flow. When particles are much smaller than the Eulerian grid the point particle model is on firm theoretical ground. However, this standard approach of evaluating the gas-particle coupling at the particle center fails to converge as the Eulerian grid is reduced below particle size. We present an approach to model the interaction between particles and fluid for finite size particles that permits convergence. We use the generalized Faxen form to compute the force on a particle and compare the results against traditional point particle method. We apportion the different force components on the particle to fluid cells based on the fraction of particle volume or surface in the cell. The application is to a one-dimensional model of shock propagation through a particle-laden field at moderate volume fraction, where the convergence is achieved for a well-formulated force model and back coupling for finite size particles. Comparison with 3D direct fully resolved numerical simulations will be used to check if the approach also improves accuracy compared to the point particle model. Work supported by the U.S. Department of Energy, National Nuclear Security Administration, Advanced Simulation and Computing Program, as a Cooperative Agreement under the Predictive Science Academic Alliance Program, under Contract No. DE-NA0002378.

  10. The Effect of Small Sample Size on Measurement Equivalence of Psychometric Questionnaires in MIMIC Model: A Simulation Study

    Directory of Open Access Journals (Sweden)

    Jamshid Jamali

    2017-01-01

    Full Text Available Evaluating measurement equivalence (also known as differential item functioning (DIF is an important part of the process of validating psychometric questionnaires. This study aimed at evaluating the multiple indicators multiple causes (MIMIC model for DIF detection when latent construct distribution is nonnormal and the focal group sample size is small. In this simulation-based study, Type I error rates and power of MIMIC model for detecting uniform-DIF were investigated under different combinations of reference to focal group sample size ratio, magnitude of the uniform-DIF effect, scale length, the number of response categories, and latent trait distribution. Moderate and high skewness in the latent trait distribution led to a decrease of 0.33% and 0.47% power of MIMIC model for detecting uniform-DIF, respectively. The findings indicated that, by increasing the scale length, the number of response categories and magnitude DIF improved the power of MIMIC model, by 3.47%, 4.83%, and 20.35%, respectively; it also decreased Type I error of MIMIC approach by 2.81%, 5.66%, and 0.04%, respectively. This study revealed that power of MIMIC model was at an acceptable level when latent trait distributions were skewed. However, empirical Type I error rate was slightly greater than nominal significance level. Consequently, the MIMIC was recommended for detection of uniform-DIF when latent construct distribution is nonnormal and the focal group sample size is small.

  11. Estimating the accuracy of optic nerve sheath diameter measurement using a pocket-sized, handheld ultrasound on a simulation model.

    Science.gov (United States)

    Johnson, Garrett G R J; Zeiler, Frederick A; Unger, Bertram; Hansen, Gregory; Karakitsos, Dimitrios; Gillman, Lawrence M

    2016-12-01

    Ultrasound measurement of optic nerve sheath diameter (ONSD) appears to be a promising, rapid, non-invasive bedside tool for identification of elevated intra-cranial pressure. With improvements in ultrasound technology, machines are becoming smaller; however, it is unclear if these ultra-portable handheld units have the resolution to make these measurements precisely. In this study, we estimate the accuracy of ONSD measurement in a pocket-sized ultrasound unit. Utilizing a locally developed, previously validated model of the eye, ONSD was measured by two expert observers, three times with two machines and on five models with different optic nerve sheath sizes. A pocket ultrasound (Vscan, GE Healthcare) and a standard portable ultrasound (M-Turbo, SonoSite) were used to measure the models. Data was analyzed by Bland-Altman plot and intra-class correlation coefficient (ICC). The ICC between raters for the SonoSite was 0.878, and for the Vscan was 0.826. The between-machine agreement ICC was 0.752. Bland-Altman agreement analysis between the two ultrasound methods showed an even spread across the range of sheath sizes, and that the Vscan tended to read on average 0.33 mm higher than the SonoSite for each measurement, with a standard deviation of 0.65 mm. Accurate ONSD measurement may be possible utilizing pocket-sized, handheld ultrasound devices despite their small screen size, lower resolution, and lower probe frequencies. Further study in human subjects is warranted for all newer handheld ultrasound models as they become available on the market.

  12. Modeling the growth and decline of pathogen effective population size provides insight into epidemic dynamics and drivers of antimicrobial resistance.

    Science.gov (United States)

    Volz, Erik M; Didelot, Xavier

    2018-02-07

    Non-parametric population genetic modeling provides a simple and flexible approach for studying demographic history and epidemic dynamics using pathogen sequence data. Existing Bayesian approaches are premised on stochastic processes with stationary increments which may provide an unrealistic prior for epidemic histories which feature extended period of exponential growth or decline. We show that non-parametric models defined in terms of the growth rate of the effective population size can provide a more realistic prior for epidemic history. We propose a non-parametric autoregressive model on the growth rate as a prior for effective population size, which corresponds to the dynamics expected under many epidemic situations. We demonstrate the use of this model within a Bayesian phylodynamic inference framework. Our method correctly reconstructs trends of epidemic growth and decline from pathogen genealogies even when genealogical data is sparse and conventional skyline estimators erroneously predict stable population size. We also propose a regression approach for relating growth rates of pathogen effective population size and time-varying variables that may impact the replicative fitness of a pathogen. The model is applied to real data from rabies virus and Staphylococcus aureus epidemics. We find a close correspondence between the estimated growth rates of a lineage of methicillin-resistant S. aureus and population-level prescription rates of β-lactam antibiotics. The new models are implemented in an open source R package called skygrowth which is available at https://github.com/mrc-ide/skygrowth. © The Author(s) 2018. Published by Oxford University Press, on behalf of the Society of Systematic Biologists.

  13. A Comparison of Airborne Laser Scanning and Image Point Cloud Derived Tree Size Class Distribution Models in Boreal Ontario

    Directory of Open Access Journals (Sweden)

    Margaret Penner

    2015-11-01

    Full Text Available Airborne Laser Scanning (ALS metrics have been used to develop area-based forest inventories; these metrics generally include estimates of stand-level, per hectare values and mean tree attributes. Tree-based ALS inventories contain desirable information on individual tree dimensions and how much they vary within a stand. Adding size class distribution information to area-based inventories helps to bridge the gap between area- and tree-based inventories. This study examines the potential of ALS and stereo-imagery point clouds to predict size class distributions in a boreal forest. With an accurate digital terrain model, both ALS and imagery point clouds can be used to estimate size class distributions with comparable accuracy. Nonparametric imputations were generally superior to parametric imputations; this may be related to the limitation of using a unimodal Weibull function on a relatively small prediction unit (e.g., 400 m2.

  14. Incorporation of the Pore Size Variation to Modeling of the Elastic Behavior of Metallic Open-Cell Foams

    Directory of Open Access Journals (Sweden)

    Ćwieka K.

    2017-03-01

    Full Text Available In the present paper we present the approach for modeling of the elastic behavior of open-cell metallic foams concerning non-uniform pore size distribution. This approach combines design of foam structures and numerical simulations of compression tests using finite element method (FEM. In the design stage, Laguerre-Voronoi tessellations (LVT were performed on several sets of packed spheres with defined variation of radii, bringing about a set of foam structures with porosity ranging from 74 to 98% and different pore size variation quantified by the coefficient of pore volume variation, CV(V, from 0.5 to 2.1. Each structure was numerically subjected to uni-axial compression test along three directions within the elastic region. Basing on the numerical response, the effective Young’s modulus, Eeff, was calculated for each structure. It is shown that the Eeff is not only dependent on the porosity but also on the pore size variation.

  15. Travel demand modeling for the small and medium sized MPOs in Illinois.

    Science.gov (United States)

    2011-09-01

    Travel demand modeling is an important tool in the transportation planning community. It helps forecast travel : characteristics into the future at various planning levels such as state, region and corridor. Using travel demand : modeling to evaluate...

  16. A Constrained Maximization Model for inspecting the impact of leaf shape on optimal leaf size and stoma resistance

    Science.gov (United States)

    Ding, J.; Johnson, E. A.; Martin, Y. E.

    2017-12-01

    Leaf is the basic production unit of plants. Water is the most critical resource of plants. Its availability controls primary productivity of plants by affecting leaf carbon budget. To avoid the damage of cavitation from lowering vein water potential t caused by evapotranspiration, the leaf must increase the stomatal resistance to reduce evapotranspiration rate. This comes at the cost of reduced carbon fixing rate as increasing stoma resistance meanwhile slows carbon intake rate. Studies suggest that stoma will operate at an optimal resistance to maximize the carbon gain with respect to water. Different plant species have different leaf shapes, a genetically determined trait. Further, on the same plant leaf size can vary many times in size that is related to soil moisture, an indicator of water availability. According to metabolic scaling theory, increasing leaf size will increase total xylem resistance of vein, which may also constrain leaf carbon budget. We present a Constrained Maximization Model of leaf (leaf CMM) that incorporates metabolic theory into the coupling of evapotranspiration and carbon fixation to examine how leaf size, stoma resistance and maximum net leaf primary productivity change with petiole xylem water potential. The model connects vein network structure to leaf shape and use the difference between petiole xylem water potential and the critical minor vein cavitation forming water potential as the budget. The CMM shows that both maximum net leaf primary production and optimal leaf size increase with petiole xylem water potential while optimal stoma resistance decreases. Narrow leaf has overall lower optimal leaf size and maximum net leaf carbon gain and higher optimal stoma resistance than those of broad leaf. This is because with small width to length ratio, total xylem resistance increases faster with leaf size. Total xylem resistance of narrow leaf increases faster with leaf size causing higher average and marginal cost of xylem water

  17. Hierarchical modelling of temperature and habitat size effects on population dynamics of North Atlantic cod

    DEFF Research Database (Denmark)

    Mantzouni, Irene; Sørensen, Helle; O'Hara, Robert B.

    2010-01-01

    and Beverton and Holt stock–recruitment (SR) models were extended by applying hierarchical methods, mixed-effects models, and Bayesian inference to incorporate the influence of these ecosystem factors on model parameters representing cod maximum reproductive rate and carrying capacity. We identified...... the pattern of temperature effects on cod productivity at the species level and estimated SR model parameters with increased precision. Temperature impacts vary geographically, being positive in areas where temperatures are...

  18. Population Balance Modeling of Polydispersed Bubbly Flow in Continuous-Casting Using Multiple-Size-Group Approach

    Science.gov (United States)

    Liu, Zhongqiu; Li, Linmin; Qi, Fengsheng; Li, Baokuan; Jiang, Maofa; Tsukihashi, Fumitaka

    2015-02-01

    A population balance model based on the multiple-size-group (MUSIG) approach has been developed to investigate the polydispersed bubbly flow inside the slab continuous-casting mold and bubble behavior including volume fraction, breakup, coalescence, and size distribution. The Eulerian-Eulerian approach is used to describe the equations of motion of the two-phase flow. All the non-drag forces (lift force, virtual mass force, wall lubrication force, and turbulent dispersion force) and drag force are incorporated in this model. Sato and Sekiguchi model is used to account for the bubble-induced turbulence. Luo and Svendsen model and Prince and Blanch model are used to describe the bubbles breakup and coalescence behavior, respectively. A 1/4th water model of the slab continuous-casting mold was applied to investigate the distribution and size of bubbles by injecting air through a circumferential inlet chamber which was made of the specially-coated samples of mullite porous brick, which is used for the actual upper nozzle. Against experimental data, numerical results showed good agreement for the gas volume fraction and local bubble Sauter mean diameter. The bubble Sauter mean diameter in the upper recirculation zone decreases with increasing water flow rate and increases with increasing gas flow rate. The distribution of bubble Sauter mean diameter along the width direction of the upper mold increases first, and then gradually decreases from the SEN to the narrow wall. Close agreements between the predictions and measurements demonstrate the capability of the MUSIG model in modeling bubbly flow inside the continuous-casting mold.

  19. Interplay of Natural Organic Matter with Flow Rate and Particle Size on Colloid Transport: Experimentation, Visualization, and Modeling.

    Science.gov (United States)

    Yang, Xinyao; Zhang, Yimeng; Chen, Fangmin; Yang, Yuesuo

    2015-11-17

    The investigation on factors that affect the impact of natural organic matter (NOM) on colloid transport in complex hydraulic flow systems remains incomplete. Using our previously established approach, the interplay of flow rate and particle size on the NOM effect was quantified, using flow rates of 1 and 2 mL/min and particle sizes of 50 and 200 nm to represent small nanoparticles (1-100 nm) and large non-nano-microspheres (100-1000 nm) in the low-flow groundwater environment. Latex particles, Suwannee River humic acid (SRHA), and iron oxide-coated sand were used as model particles, NOM, and the aquifer medium, respectively. The quantitative results show NOM blocked more sites for large particles at a high flow rate: 1 μg of SRHA blocked 5.95 × 10(9) microsphere deposition sites at 2 mL/min but only 7.38 × 10(8) nanoparticle deposition sites at 1 mL/min. The particle size effect dominated over the flow rate, and the overall effect of the two is antagonistic. Granule-scale visualization of the particle packing on the NOM-presented sand surface corroborates the quantification results, revealing a more dispersed status of large particles at a high flow rate. We interpret this phenomenon as a polydispersivity effect resulting from the differential size of the particles and NOM: high flow and a high particle size enlarge the ratio of particle-blocked to NOM-blocked areas and thus the NOM blockage. To our knowledge, this is the first model-assisted quantification on the interplay of NOM, flow rate, and particle size on colloid transport. These findings are significant for nanorisk assessment and nanoremediation practices.

  20. Sustainable Sizing.

    Science.gov (United States)

    Robinette, Kathleen M; Veitch, Daisy

    2016-08-01

    To provide a review of sustainable sizing practices that reduce waste, increase sales, and simultaneously produce safer, better fitting, accommodating products. Sustainable sizing involves a set of methods good for both the environment (sustainable environment) and business (sustainable business). Sustainable sizing methods reduce (1) materials used, (2) the number of sizes or adjustments, and (3) the amount of product unsold or marked down for sale. This reduces waste and cost. The methods can also increase sales by fitting more people in the target market and produce happier, loyal customers with better fitting products. This is a mini-review of methods that result in more sustainable sizing practices. It also reviews and contrasts current statistical and modeling practices that lead to poor fit and sizing. Fit-mapping and the use of cases are two excellent methods suited for creating sustainable sizing, when real people (vs. virtual people) are used. These methods are described and reviewed. Evidence presented supports the view that virtual fitting with simulated people and products is not yet effective. Fit-mapping and cases with real people and actual products result in good design and products that are fit for person, fit for purpose, with good accommodation and comfortable, optimized sizing. While virtual models have been shown to be ineffective for predicting or representing fit, there is an opportunity to improve them by adding fit-mapping data to the models. This will require saving fit data, product data, anthropometry, and demographics in a standardized manner. For this success to extend to the wider design community, the development of a standardized method of data collection for fit-mapping with a globally shared fit-map database is needed. It will enable the world community to build knowledge of fit and accommodation and generate effective virtual fitting for the future. A standardized method of data collection that tests products' fit methodically

  1. Selective Hydrogenation of Acrolein Over Pd Model Catalysts: Temperature and Particle-Size Effects.

    Science.gov (United States)

    O'Brien, Casey P; Dostert, Karl-Heinz; Schauermann, Swetlana; Freund, Hans-Joachim

    2016-10-24

    The selectivity in the hydrogenation of acrolein over Fe 3 O 4 -supported Pd nanoparticles has been investigated as a function of nanoparticle size in the 220-270 K temperature range. While Pd(111) shows nearly 100 % selectivity towards the desired hydrogenation of the C=O bond to produce propenol, Pd nanoparticles were found to be much less selective towards this product. In situ detection of surface species by using IR-reflection absorption spectroscopy shows that the selectivity towards propenol critically depends on the formation of an oxopropyl spectator species. While an overlayer of oxopropyl species is effectively formed on Pd(111) turning the surface highly selective for propenol formation, this process is strongly hindered on Pd nanoparticles by acrolein decomposition resulting in CO formation. We show that the extent of acrolein decomposition can be tuned by varying the particle size and the reaction temperature. As a result, significant production of propenol is observed over 12 nm Pd nanoparticles at 250 K, while smaller (4 and 7 nm) nanoparticles did not produce propenol at any of the temperatures investigated. The possible origin of particle-size dependence of propenol formation is discussed. This work demonstrates that the selectivity in the hydrogenation of acrolein is controlled by the relative rates of acrolein partial hydrogenation to oxopropyl surface species and of acrolein decomposition, which has significant implications for rational catalyst design. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Size dependent gold nanoparticle interaction at nano-micro interface using both monolayer and multilayer (tissue-like) cell models

    Science.gov (United States)

    Yohan, Darren; Yang, Celina; Lu, Xiaofeng; Chithrani, Devika B.

    2016-03-01

    Gold nanoparticles (GNPs) can be used as a model NP system to improve the interface between nanotechnology and medicine since their size and surface properties can be tailored easily. GNPs are being used as radiation dose enhancers and as drug carriers in cancer research. Hence, it is important to know the optimum NP size for uptake not only at monolayer level but also at tissue level. Once GNPs leave tumor vasculature, they enter the tumor tissue. Success of any therapeutic technique using NPs depends on how well NPs penetrate the tumor tissue and reach individual tumor cells. In this work, multicellular layers (MCLs) were grown to model the post-vascular tumor environment. GNPs of 20 nm and 50 nm diameters were used to elucidate the effects of size on the GNP penetration and distribution dynamics. Larger NPs (50 nm) were better at monolayer level, but smaller NPs (20 nm) were at tissue level. The MCLs exhibited a much more extensive extracellular matrix (ECM) than monolayer cell cultures. This increased ECM created a barrier for NP transport and ECM was also dependent on the tumor cell lines. Smaller NPs penetrated better compared to larger NPs. Transport of NPs was better in MDA-MB231 vs MCF-7. This MCL model tissue structures are better tools to optimize NP transport through tissue before using them in animal models. Based on our study, we believe that smaller NPs are better for improved outcome in future cancer therapeutics.

  3. Population size and stopover duration estimation using mark-resight data and Bayesian analysis of a superpopulation model.

    Science.gov (United States)

    Lyons, James E; Kendall, William L; Royle, J Andrew; Converse, Sarah J; Andres, Brad A; Buchanan, Joseph B

    2016-03-01

    We present a novel formulation of a mark-recapture-resight model that allows estimation of population size, stopover duration, and arrival and departure schedules at migration areas. Estimation is based on encounter histories of uniquely marked individuals and relative counts of marked and unmarked animals. We use a Bayesian analysis of a state-space formulation of the Jolly-Seber mark-recapture model, integrated with a binomial model for counts of unmarked animals, to derive estimates of population size and arrival and departure probabilities. We also provide a novel estimator for stopover duration that is derived from the latent state variable representing the interim between arrival and departure in the state-space model. We conduct a simulation study of field sampling protocols to understand the impact of superpopulation size, proportion marked, and number of animals sampled on bias and precision of estimates. Simulation results indicate that relative bias of estimates of the proportion of the population with marks was low for all sampling scenarios and never exceeded 2%. Our approach does not require enumeration of all unmarked animals detected or direct knowledge of the number of marked animals in the population at the time of the study. This provides flexibility and potential application in a variety of sampling situations (e.g., migratory birds, breeding seabirds, sea turtles, fish, pinnipeds, etc.). Application of the methods is demonstrated with data from a study of migratory sandpipers. © 2015, The International Biometric Society.

  4. Population size and stopover duration estimation using mark–resight data and Bayesian analysis of a superpopulation model

    Science.gov (United States)

    Lyons, James E.; Kendall, William L.; Royle, J. Andrew; Converse, Sarah J.; Andres, Brad A.; Buchanan, Joseph B.

    2016-01-01

    We present a novel formulation of a mark–recapture–resight model that allows estimation of population size, stopover duration, and arrival and departure schedules at migration areas. Estimation is based on encounter histories of uniquely marked individuals and relative counts of marked and unmarked animals. We use a Bayesian analysis of a state–space formulation of the Jolly–Seber mark–recapture model, integrated with a binomial model for counts of unmarked animals, to derive estimates of population size and arrival and departure probabilities. We also provide a novel estimator for stopover duration that is derived from the latent state variable representing the interim between arrival and departure in the state–space model. We conduct a simulation study of field sampling protocols to understand the impact of superpopulation size, proportion marked, and number of animals sampled on bias and precision of estimates. Simulation results indicate that relative bias of estimates of the proportion of the population with marks was low for all sampling scenarios and never exceeded 2%. Our approach does not require enumeration of all unmarked animals detected or direct knowledge of the number of marked animals in the population at the time of the study. This provides flexibility and potential application in a variety of sampling situations (e.g., migratory birds, breeding seabirds, sea turtles, fish, pinnipeds, etc.). Application of the methods is demonstrated with data from a study of migratory sandpipers.

  5. Usage of Parameterized Fatigue Spectra and Physics-Based Systems Engineering Models for Wind Turbine Component Sizing: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Parsons, Taylor; Guo, Yi; Veers, Paul; Dykes, Katherine; Damiani, Rick

    2016-01-26

    Software models that use design-level input variables and physics-based engineering analysis for estimating the mass and geometrical properties of components in large-scale machinery can be very useful for analyzing design trade-offs in complex systems. This study uses DriveSE, an OpenMDAO-based drivetrain model that uses stress and deflection criteria to size drivetrain components within a geared, upwind wind turbine. Because a full lifetime fatigue load spectrum can only be defined using computationally-expensive simulations in programs such as FAST, a parameterized fatigue loads spectrum that depends on wind conditions, rotor diameter, and turbine design life has been implemented. The parameterized fatigue spectrum is only used in this paper to demonstrate the proposed fatigue analysis approach. This paper details a three-part investigation of the parameterized approach and a comparison of the DriveSE model with and without fatigue analysis on the main shaft system. It compares loads from three turbines of varying size and determines if and when fatigue governs drivetrain sizing compared to extreme load-driven design. It also investigates the model's sensitivity to shaft material parameters. The intent of this paper is to demonstrate how fatigue considerations in addition to extreme loads can be brought into a system engineering optimization.

  6. Model selection for semiparametric marginal mean regression accounting for within-cluster subsampling variability and informative cluster size.

    Science.gov (United States)

    Shen, Chung-Wei; Chen, Yi-Hau

    2018-03-13

    We propose a model selection criterion for semiparametric marginal mean regression based on generalized estimating equations. The work is motivated by a longitudinal study on the physical frailty outcome in the elderly, where the cluster size, that is, the number of the observed outcomes in each subject, is "informative" in the sense that it is related to the frailty outcome itself. The new proposal, called Resampling Cluster Information Criterion (RCIC), is based on the resampling idea utilized in the within-cluster resampling method (Hoffman, Sen, and Weinberg, 2001, Biometrika 88, 1121-1134) and accommodates informative cluster size. The implementation of RCIC, however, is free of performing actual resampling of the data and hence is computationally convenient. Compared with the existing model selection methods for marginal mean regression, the RCIC method incorporates an additional component accounting for variability of the model over within-cluster subsampling, and leads to remarkable improvements in selecting the correct model, regardless of whether the cluster size is informative or not. Applying the RCIC method to the longitudinal frailty study, we identify being female, old age, low income and life satisfaction, and chronic health conditions as significant risk factors for physical frailty in the elderly. © 2018, The International Biometric Society.

  7. Global Stability of Multigroup SIRS Epidemic Model with Varying Population Sizes and Stochastic Perturbation around Equilibrium

    Directory of Open Access Journals (Sweden)

    Xiaoming Fan

    2014-01-01

    Full Text Available We discuss multigroup SIRS (susceptible, infectious, and recovered epidemic models with random perturbations. We carry out a detailed analysis on the asymptotic behavior of the stochastic model; when reproduction number ℛ0>1, we deduce the globally asymptotic stability of the endemic equilibrium by measuring the difference between the solution and the endemic equilibrium of the deterministic model in time average. Numerical methods are employed to illustrate the dynamic behavior of the model and simulate the system of equations developed. The effect of the rate of immunity loss on susceptible and recovered individuals is also analyzed in the deterministic model.

  8. Size dependent thermal hysteresis in spin crossover nanoparticles reflected within a Monte Carlo based Ising-like model

    International Nuclear Information System (INIS)

    Atitoaie, Alexandru; Tanasa, Radu; Enachescu, Cristian

    2012-01-01

    Spin crossover compounds are photo-magnetic bistable molecular magnets with two states in thermodynamic competition: the diamagnetic low-spin state and paramagnetic high-spin state. The thermal transition between the two states is often accompanied by a wide hysteresis, premise for possible application of these materials as recording media. In this paper we study the influence of the system's size on the thermal hysteresis loops using Monte Carlo simulations based on an Arrhenius dynamics applied for an Ising like model with long- and short-range interactions. We show that using appropriate boundary conditions it is possible to reproduce both the drop of hysteresis width with decreasing particle size, the hysteresis shift towards lower temperatures and the incomplete transition, as in the available experimental data. The case of larger systems composed by several sublattices is equally treated reproducing the shrinkage of the hysteresis loop's width experimentally observed. - Highlights: ► A study concerning size effects in spin crossover nanoparticles hysteresis is presented. ► An Ising like model with short- and long-range interactions and Arrhenius dynamics is employed. ► In open boundary system the hysteresis width decreases with particle size. ► With appropriate environment, hysteresis loop is shifted towards lower temperature and transition is incomplete.

  9. A convenient method and numerical tables for sample size determination in longitudinal-experimental research using multilevel models.

    Science.gov (United States)

    Usami, Satoshi

    2014-12-01

    Recent years have shown increased awareness of the importance of sample size determination in experimental research. Yet effective and convenient methods for sample size determination, especially in longitudinal experimental design, are still under development, and application of power analysis in applied research remains limited. This article presents a convenient method for sample size determination in longitudinal experimental research using a multilevel model. A fundamental idea of this method is transformation of model parameters (level 1 error variance [σ(2)], level 2 error variances [τ 00, τ 11] and its covariance [τ 01, τ 10], and a parameter representing experimental effect [δ]) into indices (reliability of measurement at the first time point [ρ 1], effect size at the last time point [Δ T ], proportion of variance of outcomes between the first and the last time points [k], and level 2 error correlation [r]) that are intuitively understandable and easily specified. To foster more convenient use of power analysis, numerical tables are constructed that refer to ANOVA results to investigate the influence on statistical power by respective indices.

  10. Multi-fractal measures of city-size distributions based on the three-parameter Zipf model

    International Nuclear Information System (INIS)

    Chen Yanguang; Zhou Yixing

    2004-01-01

    A multi-fractal framework of urban hierarchies is presented to address the rank-size distribution of cities. The three-parameter Zipf model based on a pair of exponential-type scaling laws is generalized to multi-scale fractal measures. Then according to the equivalent relationship between Zipf's law and Pareto distribution, a set of multi-fractal equations are derived using dual conversion and the Legendre transform. The US city population data coming from the 2000 census are employed to verify the multi-fractal models and the results are satisfying. The multi-fractal measures reveal some strange symmetry regularity of urban systems. While explaining partially the remains of the hierarchical step-like frequency distribution of city sizes suggested by central place theory, the mathematical framework can be interpreted with the entropy-maximizing principle and some related ideas from self-organization

  11. Modelling of coupled heat and electric field distribution during ohmic heating of solid foods with varying sizes

    DEFF Research Database (Denmark)

    Feyissa, Aberham Hailu; Bøknæs, Niels; Nielsen, P.L.

    Heat treatment is an important process in the manufacturing of a wide range of solid foods. When food products of different sizes (e.g. cooking of shrimps) are processed with the conventional thermal processes, the products are heated unevenly where the small bodies are overcooked and the large...... bodies are undercooked. Ohmic heating (OH) is one of the novel technologies potentially solving this problem. However, the ability to predict and optimize the resulting temperature profile in solid foods processed by OH rests on a better understanding of the fundamental aspects of OH and of the physical...... factors leading to variations and uncertainties in prediction of the right process parameters. The current work is focused on modelling of OH of solid food pieces of varying sizes cooked in one batch. A 3D mathematical model of coupled heat transfer and electric field during OH of shrimps has been...

  12. The Impact of EU Funds on the Development of a Business Model for Small and Medium-Sized Enterprises

    Directory of Open Access Journals (Sweden)

    Olinski Marian

    2016-09-01

    Full Text Available The purpose of this paper is to assess the impact of grants received by companies on the formation of a business model. The study covered micro, small and medium-sized enterprises based in rural areas, which received support in the form of investment grants within the Regional Operational Programmes 2007-2013 for northern Poland. The research was done using a direct survey method, and covered a total of 155 companies. The results of the study indicate that the grant obtained affected implicitly the modification of the business model elements that are placed on the left side of the template of the Business Model Canvas. However, the tendency of enterprises to undertake an innovative activity usually means changes in their business model both on the left and right side. The greatest strength of the dependence was observed in the case of relationship between the size of the company and changes in the model elements. Mediumsized enterprises were the most active in this respect, when compared to comparison to micro and small businesses, and changed the largest number of elements of the business model due to the obtained grant.

  13. Evaluation and modelling of the size fractionated aerosol particle number concentration measurements nearby a major road in Helsinki ─ Part I: Modelling results within the LIPIKA project

    Directory of Open Access Journals (Sweden)

    M. Ketzel

    2007-08-01

    Full Text Available A field measurement campaign was conducted near a major road "Itäväylä" in an urban area in Helsinki in 17–20 February 2003. Aerosol measurements were conducted using a mobile laboratory "Sniffer" at various distances from the road, and at an urban background location. Measurements included particle size distribution in the size range of 7 nm–10 μm (aerodynamic diameter by the Electrical Low Pressure Impactor (ELPI and in the size range of 3–50 nm (mobility diameter by Scanning Mobility Particle Sizer (SMPS, total number concentration of particles larger than 3 nm detected by an ultrafine condensation particle counter (UCPC, temperature, relative humidity, wind speed and direction, driving route of the mobile laboratory, and traffic density on the studied road. In this study, we have compared measured concentration data with the predictions of the road network dispersion model CAR-FMI used in combination with an aerosol process model MONO32. For model comparison purposes, one of the cases was additionally computed using the aerosol process model UHMA, combined with the CAR-FMI model. The vehicular exhaust emissions, and atmospheric dispersion and transformation of fine and ultrafine particles was evaluated within the distance scale of 200 m (corresponding to a time scale of a couple of minutes. We computed the temporal evolution of the number concentrations, size distributions and chemical compositions of various particle size classes. The atmospheric dilution rate of particles is obtained from the roadside dispersion model CAR-FMI. Considering the evolution of total number concentration, dilution was shown to be the most important process. The influence of coagulation and condensation on the number concentrations of particle size modes was found to be negligible on this distance scale. Condensation was found to affect the evolution of particle diameter in the two smallest particle modes. The assumed value of the concentration of

  14. The Critical Size Defect as an Experimental Model for Craniomaxillofacial Nonunions,

    Science.gov (United States)

    1985-01-01

    W W W W V W-- U U U U 50I defects in the humn skull do not spontaneously repair. In this ird, the regenerative capacity of the calvaria of...Graft Material. J. Periodont . Res. 8:229, 1973. 20. Friedenberg, Z.B. and Lawrence, R.R.: The Regeneration of Pone in Defects of Varying Size. Surg...100, 1982. 61. Turnbull, R.S. and Freenan, E.: Use of Wounds in the Parietal Bone of the Rat for Evaluating Hone Marrow for Grafting Into Periodontal

  15. The economic production lot size model extended to include more than one production rate

    DEFF Research Database (Denmark)

    Larsen, Christian

    2005-01-01

    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....

  16. Dietary red palm oil supplementation reduces myocardial infarct size in an isolated perfused rat heart model

    Directory of Open Access Journals (Sweden)

    Esterhuyse Adriaan J

    2010-06-01

    Full Text Available Abstract Background and Aims Recent studies have shown that dietary red palm oil (RPO supplementation improves functional recovery following ischaemia/reperfusion in isolated hearts. The main aim of this study was to investigate the effects of dietary RPO supplementation on myocardial infarct size after ischaemia/reperfusion injury. The effects of dietary RPO supplementation on matrix metalloproteinase-2 (MMP2 activation and PKB/Akt phosphorylation were also investigated. Materials and methods Male Wistar rats were divided into three groups and fed a standard rat chow diet (SRC, a SRC supplemented with RPO, or a SRC supplemented with sunflower oil (SFO, for a five week period, respectively. After the feeding period, hearts were excised and perfused on a Langendorff perfusion apparatus. Hearts were subjected to thirty minutes of normothermic global ischaemia and two hours of reperfusion. Infarct size was determined by triphenyltetrazolium chloride staining. Coronary effluent was collected for the first ten minutes of reperfusion in order to measure MMP2 activity by gelatin zymography. Results Dietary RPO-supplementation decreased myocardial infarct size significantly when compared to the SRC-group and the SFO-supplemented group (9.1 ± 1.0% versus 30.2 ± 3.9% and 27.1 ± 2.4% respectively. Both dietary RPO- and SFO-supplementation were able to decrease MMP2 activity when compared to the SRC fed group. PKB/Akt phosphorylation (Thr 308 was found to be significantly higher in the dietary RPO supplemented group when compared to the SFO supplemented group at 10 minutes into reperfusion. There was, however, no significant changes observed in ERK phosphorylation. Conclusions Dietary RPO-supplementation was found to be more effective than SFO-supplementation in reducing myocardial infarct size after ischaemia/reperfusion injury. Both dietary RPO and SFO were able to reduce MMP2 activity, which suggests that MMP2 activity does not play a major role in

  17. On the importance of accounting for competing risks in pediatric brain cancer: II. Regression modeling and sample size.

    Science.gov (United States)

    Tai, Bee-Choo; Grundy, Richard; Machin, David

    2011-03-15

    To accurately model the cumulative need for radiotherapy in trials designed to delay or avoid irradiation among children with malignant brain tumor, it is crucial to account for competing events and evaluate how each contributes to the timing of irradiation. An appropriate choice of statistical model is also important for adequate determination of sample size. We describe the statistical modeling of competing events (A, radiotherapy after progression; B, no radiotherapy after progression; and C, elective radiotherapy) using proportional cause-specific and subdistribution hazard functions. The procedures of sample size estimation based on each method are outlined. These are illustrated by use of data comparing children with ependymoma and other malignant brain tumors. The results from these two approaches are compared. The cause-specific hazard analysis showed a reduction in hazards among infants with ependymoma for all event types, including Event A (adjusted cause-specific hazard ratio, 0.76; 95% confidence interval, 0.45-1.28). Conversely, the subdistribution hazard analysis suggested an increase in hazard for Event A (adjusted subdistribution hazard ratio, 1.35; 95% confidence interval, 0.80-2.30), but the reduction in hazards for Events B and C remained. Analysis based on subdistribution hazard requires a larger sample size than the cause-specific hazard approach. Notable differences in effect estimates and anticipated sample size were observed between methods when the main event showed a beneficial effect whereas the competing events showed an adverse effect on the cumulative incidence. The subdistribution hazard is the most appropriate for modeling treatment when its effects on both the main and competing events are of interest. Copyright © 2011 Elsevier Inc. All rights reserved.

  18. Nano-sized fluorescent particles as new tracers for sentinel node detection: experimental model for decision of appropriate size and wavelength.

    Science.gov (United States)

    Nakajima, Morio; Takeda, Motohiro; Kobayashi, Masaki; Suzuki, Satoshi; Ohuchi, Noriaki

    2005-06-01

    The concepts of made-to-order and low-invasiveness medicines are becoming widely accepted. A treatment for cancer, with minimum invasive surgery and without lymph nodes dissection based on sentinel lymph node (SN) navigation surgery, would adhere to these concepts. Dyes and/or radioisotopes are employed for SN detection in standard methods, however, each detection method has advantages and disadvantages. To make up for the disadvantages, we aimed at developing a new non-invasive method using fluorescent beads of uniform nano-size that could efficiently visualize SN from outside the body, and conducted experiments to determine the appropriate size and fluorescent wavelength. We examined various bead sizes and fluorescent wavelengths. The sizes were 20, 40, 100 and 200 nm. The fluorescent peak wavelengths of the beads were yellow-green (515 nm), dark red (680 nm), far red (720 nm) and infrared (755 nm). The beads were subcutaneously injected into the foot pad of the hind leg of a rat, and followed by laser scanning of the inguinal area for fluorescence observation. The beads exhibited different times for the fluorescence detection according to their sizes and wavelength. The 40 nm beads were considered to be the most appropriate size for SN detection in rats. The wavelength of near infrared was effective for avoiding attenuation by the tissue. In conclusion, we confirmed that uniformly nano-sized fluorescent beads have the potential to be an alternative to existing tracers in the detection of the SN in animal experiments if we select the appropriate particle size and wavelength.

  19. Accurate modeling of size and strain broadening in the Rietveld refinement: The open-quotes double-Voigtclose quotes approach

    International Nuclear Information System (INIS)

    Balzar, D.; Ledbetter, H.

    1995-01-01

    In the open-quotes double-Voigtclose quotes approach, an exact Voigt function describes both size- and strain-broadened profiles. The lattice strain is defined in terms of physically credible mean-square strain averaged over a distance in the diffracting domains. Analysis of Fourier coefficients in a harmonic approximation for strain coefficients leads to the Warren-Averbach method for the separation of size and strain contributions to diffraction line broadening. The model is introduced in the Rietveld refinement program in the following way: Line widths are modeled with only four parameters in the isotropic case. Varied parameters are both surface- and volume-weighted domain sizes and root-mean-square strains averaged over two distances. Refined parameters determine the physically broadened Voigt line profile. Instrumental Voigt line profile parameters are added to obtain the observed (Voigt) line profile. To speed computation, the corresponding pseudo-Voigt function is calculated and used as a fitting function in refinement. This approach allows for both fast computer code and accurate modeling in terms of physically identifiable parameters

  20. Effect of particle size, polydispersity and polymer degradation on progesterone release from PLGA microparticles: Experimental and mathematical modeling.

    Science.gov (United States)

    Busatto, Carlos; Pesoa, Juan; Helbling, Ignacio; Luna, Julio; Estenoz, Diana

    2018-01-30

    Poly(lactic-co-glycolic acid) (PLGA) microparticles containing progesterone were prepared by the solvent extraction/evaporation and microfluidic techniques. Microparticles were characterized by their size distribution, encapsulation efficiency, morphology and thermal properties. The effect of particle size, polydispersity and polymer degradation on the in vitro release of the hormone was studied. A triphasic release profile was observed for larger microparticles, while smaller microspheres showed a biphasic release profile. This behavior is related to the fact that complete drug release was achieved in a few days for smaller microparticles, during which polymer degradation effects are still negligible. A mathematical model was developed that predicts the progesterone release profiles from different-sized PLGA microspheres. The model takes into account both the dissolution and diffusion of the drug in the polymeric matrix as well as the autocatalytic effect of polymer degradation. The model was adjusted and validated with novel experimental data. Simulation results are in very good agreement with experimental results. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Fitting macroevolutionary models to phylogenies: an example using vertebrate body sizes

    NARCIS (Netherlands)

    Mooers, Arne Ø.; Schluter, Dolph

    1998-01-01

    How do traits change through time and with speciation? We present a simple and generally applicable method for comparing various models of the macroevolution of traits within a maximum likelihood framework. We illustrate four such models: 1) variance among species accumulates in direct proportion to

  2. A disaggregate freight transport model of transport chain and shipment size choice

    NARCIS (Netherlands)

    Windisch, E.; De Jong, G.C.; Van Nes, R.; Hoogendoorn, S.P.

    2010-01-01

    The field of freight transport modelling is relatively young compared to passenger transport modelling. However, some key issues in freight policy, like growing freight shares on the road, advanced logistics concepts or emerging strict freight transport regulations, have been creating increasing

  3. Dynamic one-dimensional modeling of secondary settling tanks and design impacts of sizing decisions.

    Science.gov (United States)

    Li, Ben; Stenstrom, Michael K

    2014-03-01

    As one of the most significant components in the activated sludge process (ASP), secondary settling tanks (SSTs) can be investigated with mathematical models to optimize design and operation. This paper takes a new look at the one-dimensional (1-D) SST model by analyzing and considering the impacts of numerical problems, especially the process robustness. An improved SST model with Yee-Roe-Davis technique as the PDE solver is proposed and compared with the widely used Takács model to show its improvement in numerical solution quality. The improved and Takács models are coupled with a bioreactor model to reevaluate ASP design basis and several popular control strategies for economic plausibility, contaminant removal efficiency and system robustness. The time-to-failure due to rising sludge blanket during overloading, as a key robustness indicator, is analyzed to demonstrate the differences caused by numerical issues in SST models. The calculated results indicate that the Takács model significantly underestimates time to failure, thus leading to a conservative design. Copyright © 2013 Elsevier Ltd. All rights reserved.

  4. Bioartificial heart: a human-sized porcine model--the way ahead.

    Directory of Open Access Journals (Sweden)

    Alexander Weymann

    Full Text Available A bioartificial heart is a theoretical alternative to transplantation or mechanical left ventricular support. Native hearts decellularized with preserved architecture and vasculature may provide an acellular tissue platform for organ regeneration. We sought to develop a tissue-engineered whole-heart neoscaffold in human-sized porcine hearts.We decellularized porcine hearts (n = 10 by coronary perfusion with ionic detergents in a modified Langendorff circuit. We confirmed decellularization by histology, transmission electron microscopy and fluorescence microscopy, quantified residual DNA by spectrophotometry, and evaluated biomechanical stability with ex-vivo left-ventricular pressure/volume studies, all compared to controls. We then mounted the decellularized porcine hearts in a bioreactor and reseeded them with murine neonatal cardiac cells and human umbilical cord derived endothelial cells (HUVEC under simulated physiological conditions.Decellularized hearts lacked intracellular components but retained specific collagen fibers, proteoglycan, elastin and mechanical integrity; quantitative DNA analysis demonstrated a significant reduction of DNA compared to controls (82.6±3.2 ng DNA/mg tissue vs. 473.2±13.4 ng DNA/mg tissue, p<0.05. Recellularized porcine whole-heart neoscaffolds demonstrated re-endothelialization of coronary vasculature and measurable intrinsic myocardial electrical activity at 10 days, with perfused organ culture maintained for up to 3 weeks.Human-sized decellularized porcine hearts provide a promising tissue-engineering platform that may lead to future clinical strategies in the treatment of heart failure.

  5. A Conceptual Model for Spatial Grain Size Variability on the Surface of and within Beaches

    Directory of Open Access Journals (Sweden)

    Edith Gallagher

    2016-05-01

    Full Text Available Grain size on the surface of natural beaches has been observed to vary spatially and temporally with morphology and wave energy. The stratigraphy of the beach at Duck, North Carolina, USA was examined using 36 vibracores (~1–1.5 m long collected along a cross-shore beach profile. Cores show that beach sediments are finer (~0.3 mm and more uniform high up on the beach. Lower on the beach, with more swash and wave action, the sand is reworked, segregated by size, and deposited in layers and patches. At the deepest measurement sites in the swash (~−1.4 to −1.6 m NAVD88, which are constantly being reworked by the energetic shore break, there is a thick layer (60–80 cm of very coarse sediment (~2 mm. Examination of two large trenches showed that continuous layers of coarse and fine sands comprise beach stratigraphy. Thicker coarse layers in the trenches (above mean sea level are likely owing to storm erosion and storm surge elevating the shore break and swash, which act to sort the sediment. Those layers are buried as water level retreats, accretion occurs and the beach recovers from the storm. Thinner coarse layers likely represent similar processes acting on smaller temporal scales.

  6. Testing the robustness of deterministic models of optimal dynamic pricing and lot-sizing for deteriorating items under stochastic conditions

    DEFF Research Database (Denmark)

    Ghoreishi, Maryam

    2018-01-01

    Many models within the field of optimal dynamic pricing and lot-sizing models for deteriorating items assume everything is deterministic and develop a differential equation as the core of analysis. Two prominent examples are the papers by Rajan et al. (Manag Sci 38:240–262, 1992) and Abad (Manag...... Sci 42:1093–1104, 1996). To our knowledge, nobody has ever tested whether the optimal solutions obtained in those papers are valid if the real system is exposed to randomness: with regard to demand process as well as with regard to the deterioration process. The motivation is that although the real...

  7. Group size effects in two repeated game models of a global climate agreement

    Energy Technology Data Exchange (ETDEWEB)

    Helland, Leif

    2002-07-01

    What levels of total abatement can one hope for in a global climate agreement. Some potential answers to this question are provided by game theory. This working paper contains a critical discussion of two (prominent) game ,models that answer the question quite pessimistically. Both models take the n-person, infinitely repeated prisoner's dilemma game as their point of departure. The first model is a full information model and utilises the motion of a weakly re negotiation proof equilibrium. This results in the (maybe counterintuitive) prediction that an agreement that can provide high utility to the group will attract less total abatement than an agreement that can only provide low utility to the group. The second model assumes imperfect public information and utilises the notion of a trigger level equilibrium. This results in the (more intuitive) prediction that the level of total abatements will increase with improved verification techniques for a given player set. Still the level of total abatements decrease with an increasing player set for a given verification technique. Empirical implications of the two models are identified and it is argued that one should confront these with experimentally generated data in order to discriminate between the models. One reason for this is that historical data on abatement efforts in a global climate agreement do not exist since no such agreement has entered into force yet. (Author)

  8. Group size effects in two repeated game models of a global climate agreement

    International Nuclear Information System (INIS)

    Helland, Leif

    2002-01-01

    What levels of total abatement can one hope for in a global climate agreement. Some potential answers to this question are provided by game theory. This working paper contains a critical discussion of two (prominent) game ,models that answer the question quite pessimistically. Both models take the n-person, infinitely repeated prisoner's dilemma game as their point of departure. The first model is a full information model and utilises the motion of a weakly re negotiation proof equilibrium. This results in the (maybe counterintuitive) prediction that an agreement that can provide high utility to the group will attract less total abatement than an agreement that can only provide low utility to the group. The second model assumes imperfect public information and utilises the notion of a trigger level equilibrium. This results in the (more intuitive) prediction that the level of total abatements will increase with improved verification techniques for a given player set. Still the level of total abatements decrease with an increasing player set for a given verification technique. Empirical implications of the two models are identified and it is argued that one should confront these with experimentally generated data in order to discriminate between the models. One reason for this is that historical data on abatement efforts in a global climate agreement do not exist since no such agreement has entered into force yet. (Author)

  9. PhytoSFDM version 1.0.0: Phytoplankton Size and Functional Diversity Model

    Science.gov (United States)

    Acevedo-Trejos, Esteban; Brandt, Gunnar; Smith, S. Lan; Merico, Agostino

    2016-11-01

    Biodiversity is one of the key mechanisms that facilitate the adaptive response of planktonic communities to a fluctuating environment. How to allow for such a flexible response in marine ecosystem models is, however, not entirely clear. One particular way is to resolve the natural complexity of phytoplankton communities by explicitly incorporating a large number of species or plankton functional types. Alternatively, models of aggregate community properties focus on macroecological quantities such as total biomass, mean trait, and trait variance (or functional trait diversity), thus reducing the observed natural complexity to a few mathematical expressions. We developed the PhytoSFDM modelling tool, which can resolve species discretely and can capture aggregate community properties. The tool also provides a set of methods for treating diversity under realistic oceanographic settings. This model is coded in Python and is distributed as open-source software. PhytoSFDM is implemented in a zero-dimensional physical scheme and can be applied to any location of the global ocean. We show that aggregate community models reduce computational complexity while preserving relevant macroecological features of phytoplankton communities. Compared to species-explicit models, aggregate models are more manageable in terms of number of equations and have faster computational times. Further developments of this tool should address the caveats associated with the assumptions of aggregate community models and about implementations into spatially resolved physical settings (one-dimensional and three-dimensional). With PhytoSFDM we embrace the idea of promoting open-source software and encourage scientists to build on this modelling tool to further improve our understanding of the role that biodiversity plays in shaping marine ecosystems.

  10. Deformation and Recrystallization Behavior of the Cast Structure in Large Size, High Strength Steel Ingots: Experimentation and Modeling

    Science.gov (United States)

    Chadha, K.; Shahriari, D.; Tremblay, R.; Bhattacharjee, P. P.; Jahazi, M.

    2017-09-01

    Constitutive modeling of the ingot breakdown process of large size ingots of high strength steel was carried out through comprehensive thermomechanical processing using Gleeble 3800® thermomechanical simulator, finite element modeling (FEM), optical and electron back scatter diffraction (EBSD). For this purpose, hot compression tests in the range of 1473 K to 1323 K (1200 °C to 1050 °C) and strain rates of 0.25 to 2 s-1 were carried out. The stress-strain curves describing the deformation behavior of the dendritic microstructure of the cast ingot were analyzed in terms of the Arrhenius and Hansel-Spittel models which were implemented in Forge NxT 1.0® FEM software. The results indicated that the Arrhenius model was more reliable in predicting microstructure evolution of the as-cast structure during ingot breakdown, particularly the occurrence of dynamic recrystallization (DRX) process which was a vital parameter in estimating the optimum loads for forming of large size components. The accuracy and reliability of both models were compared in terms of correlation coefficient (R) and the average absolute relative error (ARRE).

  11. Lp-norm-residual constrained regularization model for estimation of particle size distribution in dynamic light scattering.

    Science.gov (United States)

    Zhu, Xinjun; Li, Jing; Thomas, John C; Song, Limei; Guo, Qinghua; Shen, Jin

    2017-07-01

    In particle size measurement using dynamic light scattering (DLS), noise makes the estimation of the particle size distribution (PSD) from the autocorrelation function data unreliable, and a regularization technique is usually required to estimate a reasonable PSD. In this paper, we propose an Lp-norm-residual constrained regularization model for the estimation of the PSD from DLS data based on the Lp norm of the fitting residual. Our model is a generalization of the existing, commonly used L2-norm-residual-based regularization methods such as CONTIN and constrained Tikhonov regularization. The estimation of PSDs by the proposed model, using different Lp norms of the fitting residual for p=1, 2, 10, and ∞, is studied and their performance is determined using simulated and experimental data. Results show that our proposed model with p=1 is less sensitive to noise and improves stability and accuracy in the estimation of PSDs for unimodal and bimodal systems. The model with p=1 is particularly applicable to the noisy or bimodal PSD cases.

  12. Main transition in the Pink membrane model: finite-size scaling and the influence of surface roughness.

    Science.gov (United States)

    Sadeghi, Sina; Vink, R L C

    2012-06-01

    We consider the main transition in single-component membranes using computer simulations of the Pink model [D. A. Pink et al., Biochemistry 19, 349 (1980)]. We first show that the accepted parameters of the Pink model yield a main transition temperature that is systematically below experimental values. This resolves an issue that was first pointed out by Corvera and co-workers [Phys. Rev. E 47, 696 (1993)]. In order to yield the correct transition temperature, the strength of the van der Waals coupling in the Pink model must be increased; by using finite-size scaling, a set of optimal values is proposed. We also provide finite-size scaling evidence that the Pink model belongs to the universality class of the two-dimensional Ising model. This finding holds irrespective of the number of conformational states. Finally, we address the main transition in the presence of quenched disorder, which may arise in situations where the membrane is deposited on a rough support. In this case, we observe a stable multidomain structure of gel and fluid domains, and the absence of a sharp transition in the thermodynamic limit.

  13. Path sets size, model specification, or model estimation: Which one matters most in predicting stochastic user equilibrium traffic flow?

    Directory of Open Access Journals (Sweden)

    Milad Haghani

    2016-06-01

    Further investigations with respect to the relative importance of STA model estimation (or equivalently, parameter calibration and model specification (or equivalently, error term formulation are also conducted. A paired combinatorial logit (PCL assignment model with an origin–destination-specific-parameter, along with a heuristic method of model estimation (calibration, is proposed. The proposed model cannot only accommodate the correlation between path utilities, but also accounts for the fact that travelling between different origin–destination (O–D pairs can correspond to different levels of stochasticity and choice randomness. Results suggest that the estimation of the stochastic user equilibrium (SUE models can affect the outcome of the flow prediction far more meaningfully than the complexity of the choice model (i.e., model specification.

  14. Image-based reconstruction of three-dimensional myocardial infarct geometry for patient-specific modeling of cardiac electrophysiology

    Energy Technology Data Exchange (ETDEWEB)

    Ukwatta, Eranga, E-mail: eukwatt1@jhu.edu; Arevalo, Hermenegild; Pashakhanloo, Farhad; Prakosa, Adityo; Vadakkumpadan, Fijoy [Institute for Computational Medicine, Johns Hopkins University, Baltimore, Maryland 21205 and Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland 21205 (United States); Rajchl, Martin [Department of Computing, Imperial College London, London SW7 2AZ (United Kingdom); White, James [Stephenson Cardiovascular MR Centre, University of Calgary, Calgary, Alberta T2N 2T9 (Canada); Herzka, Daniel A.; McVeigh, Elliot [Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland 21205 (United States); Lardo, Albert C. [Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland 21205 and Division of Cardiology, Johns Hopkins Institute of Medicine, Baltimore, Maryland 21224 (United States); Trayanova, Natalia A. [Institute for Computational Medicine, Johns Hopkins University, Baltimore, Maryland 21205 (United States); Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland 21205 (United States); Department of Biomedical Engineering, Johns Hopkins Institute of Medicine, Baltimore, Maryland 21205 (United States)

    2015-08-15

    Purpose: Accurate three-dimensional (3D) reconstruction of myocardial infarct geometry is crucial to patient-specific modeling of the heart aimed at providing therapeutic guidance in ischemic cardiomyopathy. However, myocardial infarct imaging is clinically performed using two-dimensional (2D) late-gadolinium enhanced cardiac magnetic resonance (LGE-CMR) techniques, and a method to build accurate 3D infarct reconstructions from the 2D LGE-CMR images has been lacking. The purpose of this study was to address this need. Methods: The authors developed a novel methodology to reconstruct 3D infarct geometry from segmented low-resolution (Lo-res) clinical LGE-CMR images. Their methodology employed the so-called logarithm of odds (LogOdds) function to implicitly represent the shape of the infarct in segmented image slices as LogOdds maps. These 2D maps were then interpolated into a 3D image, and the result transformed via the inverse of LogOdds to a binary image representing the 3D infarct geometry. To assess the efficacy of this method, the authors utilized 39 high-resolution (Hi-res) LGE-CMR images, including 36 in vivo acquisitions of human subjects with prior myocardial infarction and 3 ex vivo scans of canine hearts following coronary ligation to induce infarction. The infarct was manually segmented by trained experts in each slice of the Hi-res images, and the segmented data were downsampled to typical clinical resolution. The proposed method was then used to reconstruct 3D infarct geometry from the downsampled images, and the resulting reconstructions were compared with the manually segmented data. The method was extensively evaluated using metrics based on geometry as well as results of electrophysiological simulations of cardiac sinus rhythm and ventricular tachycardia in individual hearts. Several alternative reconstruction techniques were also implemented and compared with the proposed method. Results: The accuracy of the LogOdds method in reconstructing 3D

  15. A framework for analysis of abortive colony size distributions using a model of branching processes in irradiated normal human fibroblasts.

    Directory of Open Access Journals (Sweden)

    Tetsuya Sakashita

    Full Text Available Clonogenicity gives important information about the cellular reproductive potential following ionizing irradiation, but an abortive colony that fails to continue to grow remains poorly characterized. It was recently reported that the fraction of abortive colonies increases with increasing dose. Thus, we set out to investigate the production kinetics of abortive colonies using a model of branching processes.We firstly plotted the experimentally determined colony size distribution of abortive colonies in irradiated normal human fibroblasts, and found the linear relationship on the log-linear or log-log plot. By applying the simple model of branching processes to the linear relationship, we found the persistent reproductive cell death (RCD over several generations following irradiation. To verify the estimated probability of RCD, abortive colony size distribution (≤ 15 cells and the surviving fraction were simulated by the Monte Carlo computational approach for colony expansion. Parameters estimated from the log-log fit demonstrated the good performance in both simulations than those from the log-linear fit. Radiation-induced RCD, i.e. excess probability, lasted over 16 generations and mainly consisted of two components in the early (<3 generations and late phases. Intriguingly, the survival curve was sensitive to the excess probability over 5 generations, whereas abortive colony size distribution was robust against it. These results suggest that, whereas short-term RCD is critical to the abortive colony size distribution, long-lasting RCD is important for the dose response of the surviving fraction.Our present model provides a single framework for understanding the behavior of primary cell colonies in culture following irradiation.

  16. Semivarying coefficient models for capture-recapture data: colony size estimation for the little penguin Eudyptula minor.

    Science.gov (United States)

    Stoklosa, Jakub; Dann, Peter; Huggins, Richard

    2014-09-01

    To accommodate seasonal effects that change from year to year into models for the size of an open population we consider a time-varying coefficient model. We fit this model to a capture-recapture data set collected on the little penguin Eudyptula minor in south-eastern Australia over a 25 year period using Jolly-Seber type estimators and nonparametric P-spline techniques. The time-varying coefficient model identified strong changes in the seasonal pattern across the years which we further examined using functional data analysis techniques. To evaluate the methodology we also conducted several simulation studies that incorporate seasonal variation. Copyright © 2014 Elsevier Inc. All rights reserved.

  17. Using Balls of Different Sports To Model the Variation of Atomic Sizes

    Science.gov (United States)

    Pinto, Gabriel

    1998-06-01

    In this article, an analogy is described about the order of magnitude of the variation of atomic sizes that can be used for discussion in introductory chemistry classes. The order of magnitude of this variation, involving microscopic magnitudes, is difficult for students to imagine. For the most part, the students are very familiar with the world of sports. In any case for example, the teacher can make use of the wide, informative coverage given to the olympic games or similar events, where different sports are televised in a few days. The radii of official balls for seven well-known sports are given, and students must assign an atom to each ball by using tabulated single-bond, covalent radii and by assigning the smallest ball (i.e., corresponding to ping-pong) to the smallest atom (i.e., hydrogen). The balls can also be used to show how the ionic radii change upon ionization.

  18. Size-dependent standard deviation for growth rates: Empirical results and theoretical modeling

    Science.gov (United States)

    Podobnik, Boris; Horvatic, Davor; Pammolli, Fabio; Wang, Fengzhong; Stanley, H. Eugene; Grosse, I.

    2008-05-01

    We study annual logarithmic growth rates R of various economic variables such as exports, imports, and foreign debt. For each of these variables we find that the distributions of R can be approximated by double exponential (Laplace) distributions in the central parts and power-law distributions in the tails. For each of these variables we further find a power-law dependence of the standard deviation σ(R) on the average size of the economic variable with a scaling exponent surprisingly close to that found for the gross domestic product (GDP) [Phys. Rev. Lett. 81, 3275 (1998)]. By analyzing annual logarithmic growth rates R of wages of 161 different occupations, we find a power-law dependence of the standard deviation σ(R) on the average value of the wages with a scaling exponent β≈0.14 close to those found for the growth of exports, imports, debt, and the growth of the GDP. In contrast to these findings, we observe for payroll data collected from 50 states of the USA that the standard deviation σ(R) of the annual logarithmic growth rate R increases monotonically with the average value of payroll. However, also in this case we observe a power-law dependence of σ(R) on the average payroll with a scaling exponent β≈-0.08 . Based on these observations we propose a stochastic process for multiple cross-correlated variables where for each variable (i) the distribution of logarithmic growth rates decays exponentially in the central part, (ii) the distribution of the logarithmic growth rate decays algebraically in the far tails, and (iii) the standard deviation of the logarithmic growth rate depends algebraically on the average size of the stochastic variable.

  19. Size distribution and concentrations of heavy metals in atmospheric aerosols originating from industrial emissions as predicted by the HYSPLIT model

    Science.gov (United States)

    Chen, Bing; Stein, Ariel F.; Maldonado, Pabla Guerrero; Sanchez de la Campa, Ana M.; Gonzalez-Castanedo, Yolanda; Castell, Nuria; de la Rosa, Jesus D.

    2013-06-01

    This study presents a description of the emission, transport, dispersion, and deposition of heavy metals contained in atmospheric aerosols emitted from a large industrial complex in southern Spain using the HYSPLIT model coupled with high- (MM5) and low-resolution (GDAS) meteorological simulations. The dispersion model was configured to simulate eight size fractions (17 μm) of metals based on direct measurements taken at the industrial emission stacks. Twelve stacks in four plants were studied and the stacks showed considerable differences for both emission fluxes and size ranges of metals. We model the dispersion of six major metals; Cr, Co, Ni, La, Zn, and Mo, which represent 77% of the total mass of the 43 measured elements. The prediction shows that the modeled industrial emissions produce an enrichment of heavy metals by a factor of 2-5 for local receptor sites when compared to urban and rural background areas in Spain. The HYSPLIT predictions based on the meteorological fields from MM5 show reasonable consistence with the temporal evolution of concentrations of Cr, Co, and Ni observed at three sites downwind of the industrial area. The magnitude of concentrations of metals at two receptors was underestimated for both MM5 (by a factor of 2-3) and GDAS (by a factor of 4-5) meteorological runs. The model prediction shows that heavy metal pollution from industrial emissions in this area is dominated by the ultra-fine (<0.66 μm) and fine (<2.5 μm) size fractions.

  20. Efficient Algorithm for Locating and Sizing Series Compensation Devices in Large Transmission Grids: Model Implementation (PART 1)

    Energy Technology Data Exchange (ETDEWEB)

    Frolov, Vladimir [Moscow Inst. of Physics and Technology (MIPT), Moscow (Russian Federation); Backhaus, Scott N. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Chertkov, Michael [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2014-01-14

    We explore optimization methods for planning the placement, sizing and operations of Flexible Alternating Current Transmission System (FACTS) devices installed to relieve transmission grid congestion. We limit our selection of FACTS devices to Series Compensation (SC) devices that can be represented by modification of the inductance of transmission lines. Our master optimization problem minimizes the l1 norm of the inductance modification subject to the usual line thermal-limit constraints. We develop heuristics that reduce this non-convex optimization to a succession of Linear Programs (LP) which are accelerated further using cutting plane methods. The algorithm solves an instance of the MatPower Polish Grid model (3299 lines and 2746 nodes) in 40 seconds per iteration on a standard laptop—a speed up that allows the sizing and placement of a family of SC devices to correct a large set of anticipated congestions. We observe that our algorithm finds feasible solutions that are always sparse, i.e., SC devices are placed on only a few lines. In a companion manuscript, we demonstrate our approach on realistically-sized networks that suffer congestion from a range of causes including generator retirement. In this manuscript, we focus on the development of our approach, investigate its structure on a small test system subject to congestion from uniform load growth, and demonstrate computational efficiency on a realistically-sized network.

  1. Modeling and Analysis of Size-Dependent Structural Problems by Using Low- Order Finite Elements with Strain Gradient Plasticity

    International Nuclear Information System (INIS)

    Park, Moon Shik; Suh, Yeong Sung; Song, Seung

    2011-01-01

    An elasto-plastic finite element method using the theory of strain gradient plasticity is proposed to evaluate the size dependency of structural plasticity that occurs when the configuration size decreases to micron scale. For this method, we suggest a low-order plane and three-dimensional displacement-based elements, eliminating the need for a high order, many degrees of freedom, a mixed element, or super elements, which have been considered necessary in previous researches. The proposed method can be performed in the framework of nonlinear incremental analysis in which plastic strains are calculated and averaged at nodes. These strains are then interpolated and differentiated for gradient calculation. We adopted a strain-gradient-hardening constitutive equation from the Taylor dislocation model, which requires the plastic strain gradient. The developed finite elements are tested numerically on the basis of typical size-effect problems such as micro-bending, micro-torsion, and micro-voids. With respect to the strain gradient plasticity, i.e., the size effects, the results obtained by using the proposed method, which are simple in their calculation, are in good agreement with the experimental results cited in previously published papers

  2. Multivariate modeling of complications with data driven variable selection: Guarding against overfitting and effects of data set size

    International Nuclear Information System (INIS)

    Schaaf, Arjen van der; Xu Chengjian; Luijk, Peter van; Veld, Aart A. van’t; Langendijk, Johannes A.; Schilstra, Cornelis

    2012-01-01

    Purpose: Multivariate modeling of complications after radiotherapy is frequently used in conjunction with data driven variable selection. This study quantifies the risk of overfitting in a data driven modeling method using bootstrapping for data with typical clinical characteristics, and estimates the minimum amount of data needed to obtain models with relatively high predictive power. Materials and methods: To facilitate repeated modeling and cross-validation with independent datasets for the assessment of true predictive power, a method was developed to generate simulated data with statistical properties similar to real clinical data sets. Characteristics of three clinical data sets from radiotherapy treatment of head and neck cancer patients were used to simulate data with set sizes between 50 and 1000 patients. A logistic regression method using bootstrapping and forward variable selection was used for complication modeling, resulting for each simulated data set in a selected number of variables and an estimated predictive power. The true optimal number of variables and true predictive power were calculated using cross-validation with very large independent data sets. Results: For all simulated data set sizes the number of variables selected by the bootstrapping method was on average close to the true optimal number of variables, but showed considerable spread. Bootstrapping is more accurate in selecting the optimal number of variables than the AIC and BIC alternatives, but this did not translate into a significant difference of the true predictive power. The true predictive power asymptotically converged toward a maximum predictive power for large data sets, and the estimated predictive power converged toward the true predictive power. More than half of the potential predictive power is gained after approximately 200 samples. Our simulations demonstrated severe overfitting (a predicative power lower than that of predicting 50% probability) in a number of small

  3. Observations and regional modeling of aerosol optical properties, speciation and size distribution over Northern Africa and western Europe

    Directory of Open Access Journals (Sweden)

    L. Menut

    2016-10-01

    Full Text Available The aerosol speciation and size distribution is modeled during the summer 2013 and over a large area encompassing Africa, Mediterranean and western Europe. The modeled aerosol is compared to available measurements such as the AERONET aerosol optical depth (AOD and aerosol size distribution (ASD and the EMEP network for surface concentrations of particulate matter PM2.5, PM10 and inorganic species (nitrate, sulfate and ammonium. The main goal of this study is to quantify the model ability to realistically model the speciation and size distribution of the aerosol. Results first showed that the long-range transport pathways are well reproduced and mainly constituted by mineral dust: spatial correlation is  ≈  0.9 for AOD and Ångström exponent, when temporal correlations show that the day-to-day variability is more difficult to reproduce. Over Europe, PM2.5 and PM10 have a mean temporal correlation of  ≈  0.4 but the lowest spatial correlation ( ≈  0.25 and 0.62, respectively, showing that the fine particles are not well localized or transported. Being short-lived species, the uncertainties on meteorology and emissions induce these lowest scores. However, time series of PM2.5 with the speciation show a good agreement between model and measurements and are useful for discriminating the aerosol composition. Using a classification from the south (Africa to the north (northern Europe, it is shown that mineral dust relative mass contribution decreases from 50 to 10 % when nitrate increases from 0 to 20 % and all other species, sulfate, sea salt, ammonium, elemental carbon, primary organic matter, are constant. The secondary organic aerosol contribution is between 10 and 20 % with a maximum at the latitude of the Mediterranean Sea (Spanish stations. For inorganic species, it is shown that nitrate, sulfate and ammonium have a mean temporal correlation of 0.25, 0.37 and 0.17, respectively. The spatial correlation is better (0

  4. Quantitative genetic analysis of brain size variation in sticklebacks: support for the mosaic model of brain evolution.

    Science.gov (United States)

    Noreikiene, Kristina; Herczeg, Gábor; Gonda, Abigél; Balázs, Gergely; Husby, Arild; Merilä, Juha

    2015-07-07

    The mosaic model of brain evolution postulates that different brain regions are relatively free to evolve independently from each other. Such independent evolution is possible only if genetic correlations among the different brain regions are less than unity. We estimated heritabilities, evolvabilities and genetic correlations of relative size of the brain, and its different regions in the three-spined stickleback (Gasterosteus aculeatus). We found that heritabilities were low (average h(2) = 0.24), suggesting a large plastic component to brain architecture. However, evolvabilities of different brain parts were moderate, suggesting the presence of additive genetic variance to sustain a response to selection in the long term. Genetic correlations among different brain regions were low (average rG = 0.40) and significantly less than unity. These results, along with those from analyses of phenotypic and genetic integration, indicate a high degree of independence between different brain regions, suggesting that responses to selection are unlikely to be severely constrained by genetic and phenotypic correlations. Hence, the results give strong support for the mosaic model of brain evolution. However, the genetic correlation between brain and body size was high (rG = 0.89), suggesting a constraint for independent evolution of brain and body size in sticklebacks. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  5. Mathematical Models of Electro-Magnetohydrodynamic Multiphase Flows Synthesis with Nano-Sized Hafnium Particles

    Directory of Open Access Journals (Sweden)

    Farooq Hussain

    2018-02-01

    Full Text Available The multiphase fluid flow under the influence of electro-magnetohydrodynamics (EHD is investigated in this study. The base fluid contains hafnium particles. Two illustrative models namely fluid phase and particulate phase are considered for three different geometries having great importance in both industrial and mechanical usage. The impact of pertinent parameters from different aspects is illustrated graphically with requisite discussion keeping in view their physical aspects. The stream lines are also erected to highlight their physical importance regarding the flow patterns. In addition, the paper is terminated by making a comparison with the existing literature as a limiting case of considered problem to confirm the validations of achieved results and hence found in excellent agreement. This model can be used to design and engineer for nozzle or diffuser type of injectors in the latest models of automobiles to improve their performance and reduce the consumption of fuel.

  6. Sufficient Sample Size and Power in Multilevel Ordinal Logistic Regression Models

    Directory of Open Access Journals (Sweden)

    Sabz Ali

    2016-01-01

    Full Text Available For most of the time, biomedical researchers have been dealing with ordinal outcome variable in multilevel models where patients are nested in doctors. We can justifiably apply multilevel cumulative logit model, where the outcome variable represents the mild, severe, and extremely severe intensity of diseases like malaria and typhoid in the form of ordered categories. Based on our simulation conditions, Maximum Likelihood (ML method is better than Penalized Quasilikelihood (PQL method in three-category ordinal outcome variable. PQL method, however, performs equally well as ML method where five-category ordinal outcome variable is used. Further, to achieve power more than 0.80, at least 50 groups are required for both ML and PQL methods of estimation. It may be pointed out that, for five-category ordinal response variable model, the power of PQL method is slightly higher than the power of ML method.

  7. Sufficient Sample Size and Power in Multilevel Ordinal Logistic Regression Models.

    Science.gov (United States)

    Ali, Sabz; Ali, Amjad; Khan, Sajjad Ahmad; Hussain, Sundas

    2016-01-01

    For most of the time, biomedical researchers have been dealing with ordinal outcome variable in multilevel models where patients are nested in doctors. We can justifiably apply multilevel cumulative logit model, where the outcome variable represents the mild, severe, and extremely severe intensity of diseases like malaria and typhoid in the form of ordered categories. Based on our simulation conditions, Maximum Likelihood (ML) method is better than Penalized Quasilikelihood (PQL) method in three-category ordinal outcome variable. PQL method, however, performs equally well as ML method where five-category ordinal outcome variable is used. Further, to achieve power more than 0.80, at least 50 groups are required for both ML and PQL methods of estimation. It may be pointed out that, for five-category ordinal response variable model, the power of PQL method is slightly higher than the power of ML method.

  8. A stochastic chemostat model with an inhibitor and noise independent of population sizes

    Science.gov (United States)

    Sun, Shulin; Zhang, Xiaolu

    2018-02-01

    In this paper, a stochastic chemostat model with an inhibitor is considered, here the inhibitor is input from an external source and two organisms in chemostat compete for a nutrient. Firstly, we show that the system has a unique global positive solution. Secondly, by constructing some suitable Lyapunov functions, we investigate that the average in time of the second moment of the solutions of the stochastic model is bounded for a relatively small noise. That is, the asymptotic behaviors of the stochastic system around the equilibrium points of the deterministic system are studied. However, the sufficient large noise can make the microorganisms become extinct with probability one, although the solutions to the original deterministic model may be persistent. Finally, the obtained analytical results are illustrated by computer simulations.

  9. Collision model for fully resolved simulations of flows laden with finite-size particles.

    Science.gov (United States)

    Costa, Pedro; Boersma, Bendiks Jan; Westerweel, Jerry; Breugem, Wim-Paul

    2015-11-01

    We present a collision model for particle-particle and particle-wall interactions in interface-resolved simulations of particle-laden flows. Three types of interparticle interactions are taken into account: (1) long- and (2) short-range hydrodynamic interactions, and (3) solid-solid contact. Long-range interactions are incorporated through an efficient and second-order-accurate immersed boundary method (IBM). Short-range interactions are also partly reproduced by the IBM. However, since the IBM uses a fixed grid, a lubrication model is needed for an interparticle gap width smaller than the grid spacing. The lubrication model is based on asymptotic expansions of analytical solutions for canonical lubrication interactions between spheres in the Stokes regime. Roughness effects are incorporated by making the lubrication correction independent of the gap width for gap widths smaller than ∼1% of the particle radius. This correction is applied until the particles reach solid-solid contact. To model solid-solid contact we use a variant of a linear soft-sphere collision model capable of stretching the collision time. This choice is computationally attractive because it allows us to reduce the number of time steps required for integrating the collision force accurately and is physically realistic, provided that the prescribed collision time is much smaller than the characteristic time scale of particle motion. We verified the numerical implementation of our collision model and validated it against several benchmark cases for immersed head-on particle-wall and particle-particle collisions, and oblique particle-wall collisions. The results show good agreement with experimental data.

  10. Size, Value and Business Cycle Variables. The Three-Factor Model and Future Economic Growth: Evidence from an Emerging Market

    Directory of Open Access Journals (Sweden)

    Fahad Ali

    2018-02-01

    Full Text Available The paper empirically investigates three different methods to construct factors and identifies some pitfalls that arise in the application of Fama-French’s three-factor model to the Pakistani stock returns. We find that the special features in Pakistan significantly affect size and value factors and also influence the explanatory power of the three-factor model. Additionally, the paper examines the ability of the three factors to predict the future growth of Pakistan’s economy. Using monthly data of both financial and non-financial companies between 2002 and 2016, the article empirically investigates and finds that: (1 size and book-to-market factors exist in the Pakistani stock market, two mimic portfolios SMB and HML generate a return of 9.15% and 12.27% per annum, respectively; (2 adding SMB and HML factors into the model meaningfully increases the explanatory power of the model; and (3 the model’s factors, except for value factor, predict future gross domestic product (GDP growth of Pakistan and remain robust. Our results are robust across sub-periods, risk regimes, and under three different methods of constructing the factors.

  11. A polymer, random walk model for the size-distribution of large DNA fragments after high linear energy transfer radiation

    Science.gov (United States)

    Ponomarev, A. L.; Brenner, D.; Hlatky, L. R.; Sachs, R. K.

    2000-01-01

    DNA double-strand breaks (DSBs) produced by densely ionizing radiation are not located randomly in the genome: recent data indicate DSB clustering along chromosomes. Stochastic DSB clustering at large scales, from > 100 Mbp down to random-walk, coarse-grained polymer model for chromatin is combined with a simple track structure model in Monte Carlo software called DNAbreak and is applied to data on alpha-particle irradiation of V-79 cells. The chromatin model neglects molecular details but systematically incorporates an increase in average spatial separation between two DNA loci as the number of base-pairs between the loci increases. Fragment-size distributions obtained using DNAbreak match data on large fragments about as well as distributions previously obtained with a less mechanistic approach. Dose-response relations, linear at small doses of high linear energy transfer (LET) radiation, are obtained. They are found to be non-linear when the dose becomes so large that there is a significant probability of overlapping or close juxtaposition, along one chromosome, for different DSB clusters from different tracks. The non-linearity is more evident for large fragments than for small. The DNAbreak results furnish an example of the RLC (randomly located clusters) analytic formalism, which generalizes the broken-stick fragment-size distribution of the random-breakage model that is often applied to low-LET data.

  12. IDENTIFYING DEFECT SIZE IN TWO DIMENSIONAL PLATES BASED ON BOUNDARY MEASUREMENTS USING REDUCED MODEL AND GENETIC ALGORITHM

    Directory of Open Access Journals (Sweden)

    BRAHIM BENAISSA

    2014-12-01

    Full Text Available ­In this study the proper orthogonal decomposition method is utilised as a model reduction technique in crack size estimation in a cracked plate under traction problem. The idea is to create a reduced model based on the results issued from finite element method, thus the crack size parameter is directly related to the boundary displacement obtained from the boundary nodes considered as sensor points. The inverse investigation is run using a genetic algorithm to minimization the error function expressed as the difference between data caused by the crack proposed by genetic algorithm in every individual and the one measured at the actual crack identity. The reduced model is validated by comparing the estimated structural response with the corresponding results from the finite element model. The effectiveness of the approach related to the used number of sensors is presented. Finally the stability of the method against uncertainty is tested by introducing different levels of white noise to the reference data.

  13. Cluster-size entropy in the Axelrod model of social influence: Small-world networks and mass media

    Science.gov (United States)

    Gandica, Y.; Charmell, A.; Villegas-Febres, J.; Bonalde, I.

    2011-10-01

    We study the Axelrod's cultural adaptation model using the concept of cluster-size entropy Sc, which gives information on the variability of the cultural cluster size present in the system. Using networks of different topologies, from regular to random, we find that the critical point of the well-known nonequilibrium monocultural-multicultural (order-disorder) transition of the Axelrod model is given by the maximum of the Sc(q) distributions. The width of the cluster entropy distributions can be used to qualitatively determine whether the transition is first or second order. By scaling the cluster entropy distributions we were able to obtain a relationship between the critical cultural trait qc and the number F of cultural features in two-dimensional regular networks. We also analyze the effect of the mass media (external field) on social systems within the Axelrod model in a square network. We find a partially ordered phase whose largest cultural cluster is not aligned with the external field, in contrast with a recent suggestion that this type of phase cannot be formed in regular networks. We draw a q-B phase diagram for the Axelrod model in regular networks.

  14. Whole body counter calibration using Monte Carlo modeling with an array of phantom sizes based on national anthropometric reference data

    Science.gov (United States)

    Shypailo, R. J.; Ellis, K. J.

    2011-05-01

    During construction of the whole body counter (WBC) at the Children's Nutrition Research Center (CNRC), efficiency calibration was needed to translate acquired counts of 40K to actual grams of potassium for measurement of total body potassium (TBK) in a diverse subject population. The MCNP Monte Carlo n-particle simulation program was used to describe the WBC (54 detectors plus shielding), test individual detector counting response, and create a series of virtual anthropomorphic phantoms based on national reference anthropometric data. Each phantom included an outer layer of adipose tissue and an inner core of lean tissue. Phantoms were designed for both genders representing ages 3.5 to 18.5 years with body sizes from the 5th to the 95th percentile based on body weight. In addition, a spherical surface source surrounding the WBC was modeled in order to measure the effects of subject mass on room background interference. Individual detector measurements showed good agreement with the MCNP model. The background source model came close to agreement with empirical measurements, but showed a trend deviating from unity with increasing subject size. Results from the MCNP simulation of the CNRC WBC agreed well with empirical measurements using BOMAB phantoms. Individual detector efficiency corrections were used to improve the accuracy of the model. Nonlinear multiple regression efficiency calibration equations were derived for each gender. Room background correction is critical in improving the accuracy of the WBC calibration.

  15. Open-Source Conceptual Sizing Models for the Hyperloop Passenger Pod

    Science.gov (United States)

    Chin, Jeffrey C.; Gray, Justin S.; Jones, Scott M.; Berton, Jeffrey J.

    2015-01-01

    Hyperloop is a new mode of transportation proposed as an alternative to California's high speed rail project, with the intended benefits of higher performance at lower overall costs. It consists of a passenger pod traveling through a tube under a light vacuum and suspended on air bearings. The pod travels up to transonic speeds resulting in a 35 minute travel time between the intended route from Los Angeles and San Francisco. Of the two variants outlined, the smaller system includes a 1.1 meter tall passenger capsule traveling through a 2.2 meter tube at 700 miles per hour. The passenger pod features water-based heat exchangers as well as an on-board compression system that reduces the aerodynamic drag as it moves through the tube. Although the original proposal looks very promising, it assumes that tube and pod dimensions are independently sizable without fully acknowledging the constraints of the compressor system on the pod geometry. This work focuses on the aerodynamic and thermodynamic interactions between the two largest systems; the tube and the pod. Using open-source toolsets, a new sizing method is developed based on one-dimensional thermodynamic relationships that accounts for the strong interactions between these sub-systems. These additional considerations require a tube nearly twice the size originally considered and limit the maximum pod travel speed to about 620 miles per hour. Although the results indicate that Hyperloop will need to be larger and slightly slower than originally intended, the estimated travel time only increases by approximately five minutes, so the overall performance is not dramatically affected. In addition, the proposed on-board heat exchanger is not an ideal solution to achieve reasonable equilibrium air temperatures within the tube. Removal of this subsystem represents a potential reduction in weight, energy requirements and complexity of the pod. In light of these finding, the core concept still remains a compelling

  16. Demographic population model for American shad: will access to additional habitat upstream of dams increase population sizes?

    Science.gov (United States)

    Harris, Julianne E.; Hightower, Joseph E.

    2012-01-01

    American shad Alosa sapidissima are in decline in their native range, and modeling possible management scenarios could help guide their restoration. We developed a density-dependent, deterministic, stage-based matrix model to predict the population-level results of transporting American shad to suitable spawning habitat upstream of dams on the Roanoke River, North Carolina and Virginia. We used data on sonic-tagged adult American shad and oxytetracycline-marked American shad fry both above and below dams on the Roanoke River with information from other systems to estimate a starting population size and vital rates. We modeled the adult female population over 30 years under plausible scenarios of adult transport, effective fecundity (egg production), and survival of adults (i.e., to return to spawn the next year) and juveniles (from spawned egg to age 1). We also evaluated the potential effects of increased survival for adults and juveniles. The adult female population size in the Roanoke River was estimated to be 5,224. With no transport, the model predicted a slow population increase over the next 30 years. Predicted population increases were highest when survival was improved during the first year of life. Transport was predicted to benefit the population only if high rates of effective fecundity and juvenile survival could be achieved. Currently, transported adults and young are less likely to successfully out-migrate than individuals below the dams, and the estimated adult population size is much smaller than either of two assumed values of carrying capacity for the lower river; therefore, transport is not predicted to help restore the stock under present conditions. Research on survival rates, density-dependent processes, and the impacts of structures to increase out-migration success would improve evaluation of the potential benefits of access to additional spawning habitat for American shad.

  17. Lattice model for amyloid peptides: OPEP force field parametrization and applications to the nucleus size of Alzheimer’s peptides

    Energy Technology Data Exchange (ETDEWEB)

    Tran, Thanh Thuy; Nguyen, Phuong H., E-mail: phuong.nguyen@ibpc.fr; Derreumaux, Philippe, E-mail: philippe.derreumaux@ibpc.fr [Laboratoire de Biochimie Théorique, UPR 9080, CNRS, Université Denis Diderot, Sorbonne Paris Cité IBPC, 13 rue Pierre et Marie Curie, 75005 Paris (France)

    2016-05-28

    Coarse-grained protein lattice models approximate atomistic details and keep the essential interactions. They are, therefore, suitable for capturing generic features of protein folding and amyloid formation at low computational cost. As our aim is to study the critical nucleus sizes of two experimentally well-characterized peptide fragments Aβ{sub 16−22} and Aβ{sub 37−42} of the full length Aβ{sub 1−42} Alzheimer’s peptide, it is important that simulations with the lattice model reproduce all-atom simulations. In this study, we present a comprehensive force field parameterization based on the OPEP (Optimized Potential for Efficient protein structure Prediction) force field for an on-lattice protein model, which incorporates explicitly the formation of hydrogen bonds and directions of side-chains. Our bottom-up approach starts with the determination of the best lattice force parameters for the Aβ{sub 16−22} dimer by fitting its equilibrium parallel and anti-parallel β-sheet populations to all-atom simulation results. Surprisingly, the calibrated force field is transferable to the trimer of Aβ{sub 16−22} and the dimer and trimer of Aβ{sub 37−42}. Encouraged by this finding, we characterized the free energy landscapes of the two decamers. The dominant structure of the Aβ{sub 16−22} decamer matches the microcrystal structure. Pushing the simulations for aggregates between 4-mer and 12-mer suggests a nucleus size for fibril formation of 10 chains. In contrast, the Aβ{sub 37−42} decamer is largely disordered with mixed by parallel and antiparallel chains, suggesting that the nucleus size is >10 peptides. Our refined force field coupled to this on-lattice model should provide useful insights into the critical nucleation number associated with neurodegenerative diseases.

  18. Finite-size effects on the chiral phase diagram of four-fermion models in four dimensions

    International Nuclear Information System (INIS)

    Abreu, L.M.; Malbouisson, A.P.C.; Malbouisson, J.M.C.; Santana, A.E.

    2009-01-01

    We study the size dependence of the dynamical symmetry breaking in the four-dimensional Nambu-Jona-Lasinio model. We show that the presence of boundaries reduces the chiral breaking region, and this effect is strengthened for a larger number of compactified dimensions. A critical value for the length of the compactified dimensions exists, below which the dynamical symmetry breaking is not possible. Considering finite temperature and chemical potential, the chiral phase structure for the system with compactified dimensions is obtained. A gradual decreasing of the chiral breaking region with increasing of chemical potential is found. Also, at fixed chemical potential, the decreasing of the size of the system changes the order of the chiral phase transition.

  19. Application of a validated gasification model to determine the impact of coal particle grinding size on carbon conversion

    KAUST Repository

    Kumar, Mayank

    2013-06-01

    In this paper, we describe the implementation of a comprehensive, previously validated multiscale model of entrained flow gasification to examine the impact of particle size on the gasification process in two different gasifier designs; the MHI and the GE gasifier. We show that the impact of the particle size depends on whether the char conversion process is kinetically limited or boundary layer diffusion-limited. Fine grinding helps accelerate char conversion under diffusion-control conditions, whereas the impact is not as noticeable under kinetic-control operation. The availability of particular gasification agents, namely O2 in the earlier sections of the gasifier or CO2 and H2O in the latter sections, as well as the temperature, are shown to have an impact on the relative importance of kinetics versus diffusion limitation. © 2013 Elsevier Ltd. All rights reserved.

  20. Collision model for fully resolved simulations of flows laden with finite-size particles

    NARCIS (Netherlands)

    Costa, P.; Boersma, B.J.; Westerweel, J.; Breugem, W.P.

    2015-01-01

    We present a collision model for particle-particle and particle-wall interactions in interface-resolved simulations of particle-laden flows. Three types of interparticle interactions are taken into account: (1) long- and (2) short-range hydrodynamic interactions, and (3) solid-solid contact.

  1. Development and Application of ANN Model for Worker Assignment into Virtual Cells of Large Sized Configurations

    International Nuclear Information System (INIS)

    Murali, R. V.; Fathi, Khalid; Puri, A. B.

    2010-01-01

    This paper presents an extended version of study already undertaken on development of an artificial neural networks (ANNs) model for assigning workforce into virtual cells under virtual cellular manufacturing systems (VCMS) environments. Previously, the same authors have introduced this concept and applied it to virtual cells of two-cell configuration and the results demonstrated that ANNs could be a worth applying tool for carrying out workforce assignments. In this attempt, three-cell configurations problems are considered for worker assignment task. Virtual cells are formed under dual resource constraint (DRC) context in which the number of available workers is less than the total number of machines available. Since worker assignment tasks are quite non-linear and highly dynamic in nature under varying inputs and conditions and, in parallel, ANNs have the ability to model complex relationships between inputs and outputs and find similar patterns effectively, an attempt was earlier made to employ ANNs into the above task. In this paper, the multilayered perceptron with feed forward (MLP-FF) neural network model has been reused for worker assignment tasks of three-cell configurations under DRC context and its performance at different time periods has been analyzed. The previously proposed worker assignment model has been reconfigured and cell formation solutions available for three-cell configuration in the literature are used in combination to generate datasets for training ANNs framework. Finally, results of the study have been presented and discussed.

  2. Size and Shape Dependence of Hydrophobic Hydration at the Level of Primitive Models

    Czech Academy of Sciences Publication Activity Database

    Vlček, Lukáš; Nezbeda, Ivo

    2002-01-01

    Roč. 4, č. 15 (2002), s. 3704-3711 ISSN 1463-9076 R&D Projects: GA AV ČR IAA4072908 Keywords : hydrophobic * hydration * modeling Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.838, year: 2002

  3. Investigations on the size of inhibitory region in selective tuning model of attention

    Czech Academy of Sciences Publication Activity Database

    Lukavský, Jiří

    2008-01-01

    Roč. 37, Supplement (2008), 53 s. [European Conferenceon Visual Perception ,. 24.08.2008-28.08.2008, Utrecht] R&D Projects: GA ČR GA406/07/1676 Institutional research plan: CEZ:AV0Z70250504 Keywords : attention * visual perception * inhibition model Subject RIV: AN - Psychology

  4. Understanding the Listening Process: Rethinking the "One Size Fits All" Model

    Science.gov (United States)

    Wolvin, Andrew

    2013-01-01

    Robert Bostrom's seminal contributions to listening theory and research represent an impressive legacy and provide listening scholars with important perspectives on the complexities of listening cognition and behavior. Bostrom's work provides a solid foundation on which to build models that more realistically explain how listeners function…

  5. Full activated sludge model no. 1 calibration experience at a medium-size WWTP in Mexico.

    Science.gov (United States)

    Fall, C; Loaiza-Navia, J; Esparza-Soto, M

    2009-01-01

    As part of the efforts done to introduce the practice of modeling in Latin America, this research carried out at the North-East WWTP of Monterrey represents the first comprehensive modeling case in Mexico. The main objective was to reproduce the organic carbon removal and sludge production rates of the plant, based on ASM1. Different intermediate studies were performed prior to the calibration of the model: influent characterization, tracer tests and hydraulics modeling, sludge settling tests and respirometry. Two fractionation methods (STOWA protocol and Influent-advisor) were compared, showing no equivalent patterns. A stepwise sequence of calibration was developed and successfully applied. The hydraulics of the reactors at the plant was reproduced by use of a series of 3 to 5 CSTRs. The waste and return activated sludge flowrates (Q(WAS) and Q(RAS)) were corrected based on the inorganic and total suspended solids mass balances. The Vesilind settling constants were measured (V(o) and r(hind)), while the flocculent zone settling parameter (r(floc)) was adjusted to calibrate the secondary clarifier. In ASM1, the adjusted parameters were the COD soluble inert fraction (frS(I)) and the particulate substrate fraction (FrX(S)). All other ASM1 parameters were kept at their default values. The steady-state calibrated model (in GPS-X) adequately described the quality of the effluent (carbon and nitrogen) as well as the sludge composition (M. Liquor and WAS). This case study provides voluntarily detailed data to allow its wide use for training and teaching purposes.

  6. Energy landscape of the finite-size mean-field 2-spin spherical model and topology trivialization.

    Science.gov (United States)

    Mehta, Dhagash; Hauenstein, Jonathan D; Niemerg, Matthew; Simm, Nicholas J; Stariolo, Daniel A

    2015-02-01

    Motivated by the recently observed phenomenon of topology trivialization of potential energy landscapes (PELs) for several statistical mechanics models, we perform a numerical study of the finite-size 2-spin spherical model using both numerical polynomial homotopy continuation and a reformulation via non-Hermitian matrices. The continuation approach computes all of the complex stationary points of this model while the matrix approach computes the real stationary points. Using these methods, we compute the average number of stationary points while changing the topology of the PEL as well as the variance. Histograms of these stationary points are presented along with an analysis regarding the complex stationary points. This work connects topology trivialization to two different branches of mathematics: algebraic geometry and catastrophe theory, which is fertile ground for further interdisciplinary research.

  7. Finding the right RoPax vessel size and freight price. A coste and mode choice model

    Energy Technology Data Exchange (ETDEWEB)

    Morales Fusco, P.; Grau Sala, M.; Sauri Marchan, S.

    2016-07-01

    Motorways of the sea operated as RoPax services are natural competitors with only-road freight haulage transportation. Cost, time and quality perceived are the determinants that make transporters and shippers use one route or another. This research considers the role that shipping companies and their ship deployment and pricing strategy have in the equation, as incentives for modal shift from road to sea. A model of the ships and transporter costs is developed considering different business models for the transporter (accompanied versus unaccompanied cargo) followed with a discrete choice model that, once calibrated, allows to test the influence that variables such as frequency, ship size and commercial speed might play into the competitiveness of a shipping line. As a result, different pricing strategies for the shipping line are developed and the characteristics of the optimal shipping line for each of them are found, to either maximize the profit of the shipping company or the modal shift. (Author)

  8. Experimentally Based Model to Size the Geometry of a New OWC Device, with Reference to the Mediterranean Sea Wave Environment

    Directory of Open Access Journals (Sweden)

    Piero Ruol

    2013-09-01

    Full Text Available This note presents the Seabreath wave energy converter, basically a multi-chamber floating oscillating water column device, and the lumped model used to size its chambers, the ducts and the turbine. The model is based on extensive testing carried out in the wave flume of the University of Padova using fixed and floating models with a dummy power take off and indirect measurement of the produced power. A map with the available energy in the Mediterranean Sea is also proposed, showing possible ideal application sites. The Seabreath is finally dimensioned for a quarter scale test application in the Adriatic Sea, with a 3 kW turbine, and a capacity factor of 40%.

  9. Evaluation of the Fluid Model Approach for the Sizing of Energy Storage in Wave-Wind Energy Systems

    Directory of Open Access Journals (Sweden)

    José A. Domínguez-Navarro

    2016-03-01

    Full Text Available The application of energy storage in offshore renewable generation systems allows managing the intrinsic uncertainty of the resources and improving the utilization factor of the electrical network. Optimal storage design algorithms generally have to evaluate the behavior of the whole system thousands times before converging to the optimal solution and the reliability of the results obviously depends on the quality of input data. On the other hand, the utilization of simplified storage models in the design stage can reduce the simulation time drastically, while still providing useful information. The goal of this paper is to evaluate the applicability of a methodology for sizing the energy storage system in a hybrid wind and wave farm, which is based on fluid models. The description and performance of this modeling approach will be introduced and compared to standard design procedures based on extensive simulations. Advantages and limitations of each approach will be underlined and the impact of input data quality will be discussed.

  10. Electronic business model for small- and medium-sized manufacturing enterprises (SME): a case study

    Science.gov (United States)

    Yuen, Karina; Chung, Walter W.

    2001-10-01

    This paper identifies three essential factors (information infrastructure, executive information system and a new manufacturing paradigm) that are used to support the development of a new business model for competitiveness. They facilitate changes in organization structure in support of business transformation. A SME can source a good manufacturing practice using a model of academic-university collaboration to gain competitive advantage in the e-business world. The collaboration facilitates the change agents to use information systems development as a vehicle to increase the capability of executives in using information and knowledge management to gain higher responsiveness and customer satisfaction. The case company is used to illustrate the application of a web-based executive information system to interface internal communications with external operation. It explains where a good manufacturing practice may be re-applied by other SMEs to acquire skills as a learning organization grows in an extended enterprise setting.

  11. Modeling the Collision Phenomena of Ø11X19 Size Rolls

    Directory of Open Access Journals (Sweden)

    Tiberiu Manescu jr.

    2011-09-01

    Full Text Available This paper presents a numerical comparison using dynamic modeling techniques, of physical phenomena occurring at collisions between two rollers in a lot of distinct situations: impact on the edge at angles of 0°, 10°, 20°, 30°, 40°, 50°, 60°, 70°, 80° and impact on generator. These situations occur frequently in the manufacturing process of small cylindrical rollers.

  12. BIM adoption within Australian Small and Medium-sized Enterprises (SMEs): an innovation diffusion model

    OpenAIRE

    M. Reza Hosseini; Saeed Banihashemi; Nicholas Chileshe; Mehran Oraee Namzadi; Chika Udaeja; Raufdeen Rameezdeen; Tammy McCuen

    2016-01-01

    Despite the envisaged benefits of BIM adoption for SMEs, BIM in SMEs has remained an underrepresented area within the available academic literature. This study proposes and draws upon a framework grounded on innovation diffusion theory (IDT) to provide an illuminating insight into the current state of BIM and the main barriers to BIM adoption within Australian SMEs. Based on analyses of 135 questionnaires completed by SMEs through partial least squares structural equation modelling (PLS-SEM) ...

  13. correction to numerica advection of moments of the particle size distribution in eulerian model

    Science.gov (United States)

    Chang, L.; Schwartz, S.; McGraw, B.; Lewis, E.

    2007-12-01

    Quadrature method of moments(QMOM) offers a alternative more efficient than sectional methods and more accurate than modal methods. If QMOM is incorporated into eulerian model, invalid moments set are produced by nonlinear transport methods when valid moments are transported as seperate tracers. A non-negative least squares (NNLS) soultion eliminates the problem without requiring modification of the transport algorithm. The evaluation of NNLS for two representative advection schemes in one dimension was done for 10E4 test cases.

  14. Finite-size effects and analytical modeling of electrostatic force microscopy applied to dielectric films.

    Science.gov (United States)

    Gomila, G; Gramse, G; Fumagalli, L

    2014-06-27

    A numerical analysis of the polarization force between a sharp conducting probe and a dielectric film of finite lateral dimensions on a metallic substrate is presented with the double objective of (i) determining the conditions under which the film can be approximated by a laterally infinite film and (ii) proposing an analytical model valid in this limit. We show that, for a given dielectric film, the critical diameter above which the film can be modeled as laterally infinite depends not only on the probe geometry, as expected, but mainly on the film thickness. In particular, for films with intermediate to large thicknesses (>100 nm), the critical diameter is nearly independent from the probe geometry and essentially depends on the film thickness and dielectric constant following a relatively simple phenomenological expression. For films that can be considered as laterally infinite, we propose a generalized analytical model valid in the thin-ultrathin limit (<20-50 nm) that reproduces the numerical calculations and the experimental data. Present results provide a general framework under which accurate quantification of electrostatic force microscopy measurements on dielectric films on metallic substrates can be achieved.

  15. Reliable calculation in probabilistic logic: Accounting for small sample size and model uncertainty

    Energy Technology Data Exchange (ETDEWEB)

    Ferson, S. [Applied Biomathematics, Setauket, NY (United States)

    1996-12-31

    A variety of practical computational problems arise in risk and safety assessments, forensic statistics and decision analyses in which the probability of some event or proposition E is to be estimated from the probabilities of a finite list of related subevents or propositions F,G,H,.... In practice, the analyst`s knowledge may be incomplete in two ways. First, the probabilities of the subevents may be imprecisely known from statistical estimations, perhaps based on very small sample sizes. Second, relationships among the subevents may be known imprecisely. For instance, there may be only limited information about their stochastic dependencies. Representing probability estimates as interval ranges on has been suggested as a way to address the first source of imprecision. A suite of AND, OR and NOT operators defined with reference to the classical Frochet inequalities permit these probability intervals to be used in calculations that address the second source of imprecision, in many cases, in a best possible way. Using statistical confidence intervals as inputs unravels the closure properties of this approach however, requiring that probability estimates be characterized by a nested stack of intervals for all possible levels of statistical confidence, from a point estimate (0% confidence) to the entire unit interval (100% confidence). The corresponding logical operations implied by convolutive application of the logical operators for every possible pair of confidence intervals reduces by symmetry to a manageably simple level-wise iteration. The resulting calculus can be implemented in software that allows users to compute comprehensive and often level-wise best possible bounds on probabilities for logical functions of events.

  16. Modeling and sizing optimization of hybrid photovoltaic/wind power generation system

    Science.gov (United States)

    Yazdanpanah, Mohammad-Ali

    2014-03-01

    The rapid industrialization and growth of world's human population have resulted in the unprecedented increase in the demand for energy and in particular electricity. Depletion of fossil fuels and impacts of global warming caused widespread attention using renewable energy sources, especially wind and solar energies. Energy security under varying weather conditions and the corresponding system cost are the two major issues in designing hybrid power generation systems. In this paper, the match evaluation method (MEM) is developed based on renewable energy supply/demand match evaluation criteria to size the proposed system in lowest cost. This work is undertaken with triple objective function: inequality coefficient, correlation coefficient, and annualized cost of system. It provides optimum capacity of as many numbers of supplies as required to match with a load demand in lowest investment, so it can handle large-scale design problems. Meteorological data were collected from the city of Zabol, located in south-east of Iran, as a case study. Six types of wind turbine and also six types of PV modules, with different output powers and costs, are considered for this optimization procedure. A battery storage system is used to even out irregularities in meteorological data. A multi-objective particle swarm optimization algorithm has been used for the prediction of an optimized set of design based on the MEM technique. The results of this study are valuable for evaluating the performance of future stand-alone hybrid power system. It is worth mentioning that the proposed methodology can be effectively employed for any composition of hybrid energy systems in any locations taking into account the meteorological data and the consumer's demand.

  17. Using grain-size characteristics to model soil water content: Application to dose-rate calculation for luminescence dating

    International Nuclear Information System (INIS)

    Nelson, Michelle S.; Rittenour, Tammy M.

    2015-01-01

    Soil moisture is an important factor for dose-rate determination in luminescence and other dating methods as soil water content impacts sediment bulk density, alters rates of chemical reactions and attenuates effective exposure to nuclear radiation from the surrounding sediments and incoming cosmic rays. Given its importance in dose-rate calculation, methods for measuring and modeling soil water content are discussed, with special focus on semi-arid environments and other situations where modern in situ values are unlikely to be representative of mean soil moisture conditions. We present an alternative method for calculating sediment water content based on grain-size characteristics using the freely available Rosetta Lite v.1.1 software. Modeled outputs include saturation, residual and other water retention curve (WRC) parameters. WRCs were generated from model outputs using the van Genuchten (1980) equation, and mean annual water state was determined using soil moisture regime maps and classifications. Dose-rate values using modeled outputs and laboratory-measured in situ and saturation water content are compared in a test case using Holocene alluvial sediments from Kanab Creek in southern Utah, USA. Best practices for how to estimate mean annual water state for different soil moisture regimes and past soil moisture content in situations where in situ values are not representative of the burial history are discussed. - Highlights: • Using grain size characteristics to generate water retention curves. • Saturation water content was estimated using laboratory and computer modeling. • In situ water content is compared with the model outputs. • Dose-rate variability with new water content estimates is evaluated.

  18. 3D printing for orthopedic applications: from high resolution cone beam CT images to life size physical models

    Science.gov (United States)

    Jackson, Amiee; Ray, Lawrence A.; Dangi, Shusil; Ben-Zikri, Yehuda K.; Linte, Cristian A.

    2017-03-01

    With increasing resolution in image acquisition, the project explores capabilities of printing toward faithfully reflecting detail and features depicted in medical images. To improve safety and efficiency of orthopedic surgery and spatial conceptualization in training and education, this project focused on generating virtual models of orthopedic anatomy from clinical quality computed tomography (CT) image datasets and manufacturing life-size physical models of the anatomy using 3D printing tools. Beginning with raw micro CT data, several image segmentation techniques including thresholding, edge recognition, and region-growing algorithms available in packages such as ITK-SNAP, MITK, or Mimics, were utilized to separate bone from surrounding soft tissue. After converting the resulting data to a standard 3D printing format, stereolithography (STL), the STL file was edited using Meshlab, Netfabb, and Meshmixer. The editing process was necessary to ensure a fully connected surface (no loose elements), positive volume with manifold geometry (geometry possible in the 3D physical world), and a single, closed shell. The resulting surface was then imported into a "slicing" software to scale and orient for printing on a Flashforge Creator Pro. In printing, relationships between orientation, print bed volume, model quality, material use and cost, and print time were considered. We generated anatomical models of the hand, elbow, knee, ankle, and foot from both low-dose high-resolution cone-beam CT images acquired using the soon to be released scanner developed by Carestream, as well as scaled models of the skeletal anatomy of the arm and leg, together with life-size models of the hand and foot.

  19. Excitation energy spectra of the Λc and Λb baryons in a finite-size diquark model

    Science.gov (United States)

    Kumakawa, Kento; Jido, Daisuke

    2017-12-01

    The excitation energies of the Λc and Λb baryons are investigated in a finite-size diquark potential model, in which the heavy baryons are treated as bound states of a charm quark and a scalar-isoscalar diquark. The diquark is considered as a sizable object. The quark-diquark interaction is calculated as a sum of the quark-quark interaction that is assumed to be half of the quark-antiquark interaction for the color singlet. The potential parameters in the quark-antiquark interaction are fixed so as to reproduce the charmonium spectrum. We find the diquark size to be 1.1 fm for the diquark mass 0.5 GeV/c2 to reproduce the 1p excitation energy of Λc. In this model, the Λc and Λb excitation spectra are reproduced well, while this model does not explain Λc(2765), whose isospin and spin-parity are still unknown. Thus, the detailed properties of Λc(2765) are very important to the presence of the diquark in heavy baryons as an effective constituent. We also discuss the Ξc spectrum with the scalar strange diquark.

  20. GOVERNMENT SIZE VERSUS GOVERNMENT EFFICIENCY IN A MODEL OF ECONOMIC GROWTH

    Directory of Open Access Journals (Sweden)

    Francisca Guedes de Oliveira

    2016-04-01

    Full Text Available We develop a Solow type growth model where firms produce a single homogenous good using labor, private capital and a public good. The "amount" of public good depends on current government spending and government quality. Quality is the result of the accumulation of public capital. Governments charge distortionary taxes and provide the public good, investing also in "quality" by accumulating public capital. We analyze how the composition of government spending between current expenditures and quality affects the equilibrium levels. We aim to understand the difference in terms of steady state levels between leviathan, quality driven and benevolent governments.

  1. An extended steepness model for leg-size determination based on Dachsous/Fat trans-dimer system

    OpenAIRE

    Hiroshi Yoshida; Tetsuya Bando; Taro Mito; Hideyo Ohuchi; Sumihare Noji

    2014-01-01

    What determines organ size has been a long-standing biological question. Lawrence et al. (2008) proposed the steepness hypothesis suggesting that the protocadherin Dachsous/Fat (Ds/Ft) system may provide some measure of dimension to the cells in relation to the gradient. In this paper we extended the model as a means of interpreting experimental results in cricket leg regeneration. We assumed that (1) Ds/Ft trans-heterodimers or trans-homodimers are redistributed during cell division, and (2)...

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

    Science.gov (United States)

    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

  3. Distribution and direct radiative forcing of carbonaceous and sulfate aerosols in an interactive size-resolving aerosol-climate model

    Science.gov (United States)

    Kim, Dongchul; Wang, Chien; Ekman, Annica M. L.; Barth, Mary C.; Rasch, Phil J.

    2008-08-01

    A multimode, two-moment aerosol model has been incorporated in the NCAR CAM3 to develop an interactive aerosol-climate model and to study the impact of anthropogenic aerosols on the global climate system. Currently, seven aerosol modes, namely three for external sulfate and one each for external black carbon (BC), external organic carbon (OC), sulfate/BC mixture (MBS; with BC core coated by sulfate shell), and sulfate/OC mixture (MOS; a uniform mixture of OC and sulfate) are included in the model. Both mass and number concentrations of each aerosol mode, as well as the mass of carbonaceous species in the mixed modes, are predicted by the model so that the chemical, physical, and radiative processes of various aerosols can be formulated depending on aerosol's size, chemical composition, and mixing state. Comparisons of modeled surface and vertical aerosol concentrations, as well as the optical depth of aerosols with available observations and previous model estimates, are in general agreement. However, some discrepancies do exist, likely caused by the coarse model resolution or the constant rates of anthropogenic emissions used to test the model. Comparing to the widely used mass-only method with prescribed geometric size of particles (one-moment scheme), the use of prognostic size distributions of aerosols based on a two-moment scheme in our model leads to a significant reduction in optical depth and thus the radiative forcing at the top of the atmosphere (TOA) of particularly external sulfate aerosols. The inclusion of two types of mixed aerosols alters the mass partitioning of carbonaceous and sulfate aerosol constituents: about 35.5%, 48.5%, and 32.2% of BC, OC, and sulfate mass, respectively, are found in the mixed aerosols. This also brings in competing effects in aerosol radiative forcing including a reduction in atmospheric abundance of BC and OC due to the shorter lifetime of internal mixtures (cooling), a mass loss of external sulfate to mixtures (warming

  4. Source apportionment of synchronously size segregated fine and coarse particulate matter, using an improved three-way factor analysis model.

    Science.gov (United States)

    Shi, Guo-Liang; Tian, Ying-Ze; Ye, Si; Peng, Xing; Xu, Jiao; Wang, Wei; Han, Bo; Feng, Yin-Chang

    2015-02-01

    Samples of PM₁₀ and PM₂.₅ were synchronously collected from a megacity in China (Chengdu) during the 2011 sampling campaign and then analyzed by an improved three-way factor analysis method based on ME2 (multilinear engine 2), to investigate the contributions and size distributions of the source categories for size segregated particulate matter (PM). Firstly, the synthetic test was performed to evaluate the accuracy of the improved three-way model. The same five source categories with slightly different source profiles were caught. The low AAE (average absolute error) values between the estimated and the synthetic source contributions (dust & coal combustion presented the highest percentage contributions, accounting for 58.20% (PM₁₀) and 53.73% (PM2.5); followed by vehicle exhaust & secondary organic carbon (18.45% for PM₁₀ and 21.63% for PM₂.₅), secondary sulfate and nitrate (17.06% for PM₁₀ and 20.91% for PM₂.₅) and cement dust (6.30% for PM₁₀ and 3.73% for PM₂.₅). The source profiles and contributions presented slightly different distributions for PM₁₀ and PM₂.₅, which could better reflect the actual situation. The findings based on the improved three-way factor analysis method may provide clear and deep insights into the sources of synchronously size-resolved PM. Copyright © 2014 Elsevier B.V. All rights reserved.

  5. Shape and size of methane bubbles in muddy aquatic sediments and their dependence on sediment fracture toughness: a modeling approach

    Science.gov (United States)

    Katsman, Regina

    2014-05-01

    Shallow gassy marine sediments abundantly found on continental margins of Israel and worldwide, are a source of a major concern for their contribution to the destabilization of coastal and marine infrastructure, air pollution, and global warming. Bubbles are different in the different sediment types. Size of the bubbles residing in the fine-grained muddy sediment exceeds significantly the grain size of sediment, and its shape can be approximated by a large oblate spheroid surrounded by sediment saturated with water. Experimental results indicate that bubble growth is accompanied by fracturing of the fine-grained muddy sediment. Modeling reveals that fracture toughness of the muddy sediments significantly affects bubble shape and size evolution prior its ascent. Small fracture toughness is responsible for generation of the small bubbles with highly asymmetric configuration and with fracturing concentrated mostly on the bubble head. In contrast, bigger fracture toughness is responsible for generation of the large, more symmetric bubbles. Moreover, growing bubble demonstrates a positive allometry resulting in a bigger rate of growth of its surface area that is responsible for the effectiveness of the solute supply from pore water to the bubble interior. This scaling demonstrates a strong correlation with sediment fracture toughness as well. Cross-section of the buoyant bubbles evolves from the elliptic profile to the one resembling an 'inverted tear drop'. Calculated bubbles characteristics in different sediments types demonstrate a good agreement with values reported in the literature.

  6. Optimized sizing model for renewable energy systems in rural areas; Modelo de dimensionamento otimizado para sistemas energeticos renovaveis em ambiente rurais

    Energy Technology Data Exchange (ETDEWEB)

    Nogueira, Carlos E.C. [UNIOESTE, Cascavel, PR (Brazil). Centro de Ciencias Exatas e Tecnologicas]. E-mail: cecn@correios.net.br; Zuern, Hans H. [Santa Catarina Univ., Florianopolis, SC (Brazil). Dept. de Engenharia Eletrica

    2005-05-15

    The purpose of this research was to develop a methodology for sizing integrated renewable energy systems, useful for rural areas, using simulation and optimization tools developed in MATLAB 6.0. The sizing model produces a system with minimum cost and high reliability level, based on the concept of loss of power supply probability (LPSP) for consecutive hours. An optimization model is presented and three different sizing scenarios are calculated and compared, showing flexibility in the elaboration of different project conceptions. The obtained results show a complete sizing of the energy conversion devices and a long-term cost evaluation. (author)

  7. A geological and hydrogeological assessment of the electrical conductivity information from the HiRES airborne geophysical survey of the Isle of Wight

    OpenAIRE

    Beamish, David; White, James C.

    2011-01-01

    A recent high resolution airborne geophysical survey across the Isle of Wight (IoW) and Lymington area has provided the first electromagnetic data across the relatively young geological formations characterising much of southern England. The multi-frequency data provide information on bulk electrical conductivity to depths of the order of 100 m. A GIS-based assessment of the electrical conductivity information in relation to bedrock geological classification has been conducted for the first t...

  8. Portion size

    Science.gov (United States)

    ... with hummus. To control your portion sizes when eating out, try these tips: Order the small size. Instead of a medium or large, ask for the smallest size. By eating a small hamburger instead of a large, you ...

  9. Optimization of low frequency sound absorption by cell size control and multiscale poroacoustics modeling

    Science.gov (United States)

    Park, Ju Hyuk; Yang, Sei Hyun; Lee, Hyeong Rae; Yu, Cheng Bin; Pak, Seong Yeol; Oh, Chi Sung; Kang, Yeon June; Youn, Jae Ryoun

    2017-06-01

    Sound absorption of a polyurethane (PU) foam was predicted for various geometries to fabricate the optimum microstructure of a sound absorbing foam. Multiscale numerical analysis for sound absorption was carried out by solving flow problems in representative unit cell (RUC) and the pressure acoustics equation using Johnson-Champoux-Allard (JCA) model. From the numerical analysis, theoretical optimum cell diameter for low frequency sound absorption was evaluated in the vicinity of 400 μm under the condition of 2 cm-80 K (thickness of 2 cm and density of 80 kg/m3) foam. An ultrasonic foaming method was employed to modulate microcellular structure of PU foam. Mechanical activation was only employed to manipulate the internal structure of PU foam without any other treatment. A mean cell diameter of PU foam was gradually decreased with increase in the amplitude of ultrasonic waves. It was empirically found that the reduction of mean cell diameter induced by the ultrasonic wave enhances acoustic damping efficiency in low frequency ranges. Moreover, further analyses were performed with several acoustic evaluation factors; root mean square (RMS) values, noise reduction coefficients (NRC), and 1/3 octave band spectrograms.

  10. Molecular finite-size effects in stochastic models of equilibrium chemical systems.

    Science.gov (United States)

    Cianci, Claudia; Smith, Stephen; Grima, Ramon

    2016-02-28

    The reaction-diffusion master equation (RDME) is a standard modelling approach for understanding stochastic and spatial chemical kinetics. An inherent assumption is that molecules are point-like. Here, we introduce the excluded volume reaction-diffusion master equation (vRDME) which takes into account volume exclusion effects on stochastic kinetics due to a finite molecular radius. We obtain an exact closed form solution of the RDME and of the vRDME for a general chemical system in equilibrium conditions. The difference between the two solutions increases with the ratio of molecular diameter to the compartment length scale. We show that an increase in the fraction of excluded space can (i) lead to deviations from the classical inverse square root law for the noise-strength, (ii) flip the skewness of the probability distribution from right to left-skewed, (iii) shift the equilibrium of bimolecular reactions so that more product molecules are formed, and (iv) strongly modulate the Fano factors and coefficients of variation. These volume exclusion effects are found to be particularly pronounced for chemical species not involved in chemical conservation laws. Finally, we show that statistics obtained using the vRDME are in good agreement with those obtained from Brownian dynamics with excluded volume interactions.

  11. BIM adoption within Australian Small and Medium-sized Enterprises (SMEs: an innovation diffusion model

    Directory of Open Access Journals (Sweden)

    M. Reza Hosseini

    2016-09-01

    Full Text Available Despite the envisaged benefits of BIM adoption for SMEs, BIM in SMEs has remained an underrepresented area within the available academic literature. This study proposes and draws upon a framework grounded on innovation diffusion theory (IDT to provide an illuminating insight into the current state of BIM and the main barriers to BIM adoption within Australian SMEs. Based on analyses of 135 questionnaires completed by SMEs through partial least squares structural equation modelling (PLS-SEM and grounded on the proposed framework, the current state of BIM adoption and barriers to BIM adoption for SMEs are discussed. The findings show that currently around 42% of Australian SMEs use BIM in Level 1 and Level 2 with only around 5% have tried Level 3. It comes to light that lack of knowledge within SMEs and across the construction supply chain is not a major barrier for Australian SMEs. In essence, the main barriers stem from the risks associated with an uncertain return on investment (ROI for BIM as perceived by key players in SMEs. The findings also show the validity of the framework proposed for explaining BIM adoption in Australian SMEs.

  12. Reduction of sample size requirements by bilateral versus unilateral research designs in animal models for cartilage tissue engineering.

    Science.gov (United States)

    Orth, Patrick; Zurakowski, David; Alini, Mauro; Cucchiarini, Magali; Madry, Henning

    2013-11-01

    Advanced tissue engineering approaches for articular cartilage repair in the knee joint rely on translational animal models. In these investigations, cartilage defects may be established either in one joint (unilateral design) or in both joints of the same animal (bilateral design). We hypothesized that a lower intraindividual variability following the bilateral strategy would reduce the number of required joints. Standardized osteochondral defects were created in the trochlear groove of 18 rabbits. In 12 animals, defects were produced unilaterally (unilateral design; n=12 defects), while defects were created bilaterally in 6 animals (bilateral design; n=12 defects). After 3 weeks, osteochondral repair was evaluated histologically applying an established grading system. Based on intra- and interindividual variabilities, required sample sizes for the detection of discrete differences in the histological score were determined for both study designs (α=0.05, β=0.20). Coefficients of variation (%CV) of the total histological score values were 1.9-fold increased following the unilateral design when compared with the bilateral approach (26 versus 14%CV). The resulting numbers of joints needed to treat were always higher for the unilateral design, resulting in an up to 3.9-fold increase in the required number of experimental animals. This effect was most pronounced for the detection of small-effect sizes and estimating large standard deviations. The data underline the possible benefit of bilateral study designs for the decrease of sample size requirements for certain investigations in articular cartilage research. These findings might also be transferred to other scoring systems, defect types, or translational animal models in the field of cartilage tissue engineering.

  13. Battery sizing for serial plug-in hybrid electric vehicles: A model-based economic analysis for Germany

    International Nuclear Information System (INIS)

    Ernst, Christian-Simon; Hackbarth, Andre; Madlener, Reinhard; Lunz, Benedikt; Uwe Sauer, Dirk; Eckstein, Lutz

    2011-01-01

    The battery size of a Plug-in Hybrid Electric Vehicle (PHEV) is decisive for the electrical range of the vehicle and crucial for the cost-effectiveness of this particular vehicle concept. Based on the energy consumption of a conventional reference car and a PHEV, we introduce a comprehensive total cost of ownership model for the average car user in Germany for both vehicle types. The model takes into account the purchase price, fixed annual costs and variable operating costs. The amortization time of a PHEV also depends on the recharging strategy (once a day, once a night, after each trip), the battery size, and the battery costs. We find that PHEVs with a 4 kWh battery and at current lithium-ion battery prices reach the break-even point after about 6 years (5 years when using the lower night-time electricity tariffs). With higher battery capacities the amortization time becomes significantly longer. Even for the small battery size and assuming the EU-15 electricity mix, a PHEV is found to emit only around 60% of the CO 2 emissions of a comparable conventional car. Thus, with the PHEV concept a cost-effective introduction of electric mobility and reduction of greenhouse gas emissions per vehicle can be reached. - Highlights: → Total cost of ownership of a PHEV and a conventional car are compared for the average German car user.→ PHEVs with a 4 kWh battery reach the break-even after 5-6 years at current Li-Ion battery prices.→ Even with a small battery, PHEVs emit about 40% less CO 2 emissions than the average conventional car.

  14. Modelling, sizing and testing a scroll expander for a waste heat recovery application on a gasoline engine

    Science.gov (United States)

    Legros, Arnaud; Guillaume, Ludovic; Diny, Mouad; Lemort, Vincent

    2015-08-01

    Waste heat recovery technologies in a mobile application emerge every time energy becomes a valuable resource. It has been the case in the 70s with oil crisis and it is starting to regain some interests now due to the continuously rising price of oil and due to the restrictive standards imposed by the different governments. This paper deals with the recovery on the exhaust gases of an internal combustion engine by using a Rankine system. The study focuses on the expander, which is one of the most important components of the system. The use of a scroll expander operating with steam is currently investigated through simulation and experimentation. This paper presents the modelling of a scroll expander. The model is a detailed model including various losses such as leakage, friction or under or over expansion. This model has been used to design and size a tailor-made scroll expander. This was necessary due to the small amount of expanders on the market and also to have a machine that fits our application. After designing the machine, a prototype has been built. It has also been tested on our prototype bench of waste heat recovery on a gasoline engine, by means of a Rankine cycle. Measured performance will be presented, analysed and compared to predictions by the model. The first results will be presented here and discussed in order to give recommendations for the design of next prototypes.

  15. Accuracy of the blob model for single flexible polymers inside nanoslits that are a few monomer sizes wide

    Science.gov (United States)

    Nikoofard, Narges; Hoseinpoor, S. Mohammad; Zahedifar, Mostafa

    2014-12-01

    The de Gennes' blob model is extensively used in different problems of polymer physics. This model is theoretically applicable when the number of monomers inside each blob is large enough. For confined flexible polymers, this requires the confining geometry to be much larger than the monomer size. In this paper, the opposite limit of polymer in nanoslits with one to several monomers width is studied, using molecular dynamics simulations. Extension of the polymer inside nanoslits, confinement force on the plates, and the effective spring constant of the confined polymer are investigated. Despite the theoretical limitations of the blob model, the simulation results are explained with the blob model very well. The agreement is observed for the static properties and the dynamic spring constant of the polymer. A theoretical description of the conditions under which the dynamic spring constant of the polymer is independent of the small number of monomers inside blobs is given. Our results on the limit of applicability of the blob model can be useful in the design of nanotechnology devices.

  16. Model-based measurement of food portion size for image-based dietary assessment using 3D/2D registration

    International Nuclear Information System (INIS)

    Chen, Hsin-Chen; Yue, Yaofeng; Sun, Mingui; Jia, Wenyan; Li, Zhaoxin; Sun, Yung-Nien; Fernstrom, John D

    2013-01-01

    Dietary assessment is important in health maintenance and intervention in many chronic conditions, such as obesity, diabetes and cardiovascular disease. However, there is currently a lack of convenient methods for measuring the volume of food (portion size) in real-life settings. We present a computational method to estimate food volume from a single photographic image of food contained on a typical dining plate. First, we calculate the food location with respect to a 3D camera coordinate system using the plate as a scale reference. Then, the food is segmented automatically from the background in the image. Adaptive thresholding and snake modeling are implemented based on several image features, such as color contrast, regional color homogeneity and curve bending degree. Next, a 3D model representing the general shape of the food (e.g., a cylinder, a sphere, etc) is selected from a pre-constructed shape model library. The position, orientation and scale of the selected shape model are determined by registering the projected 3D model and the food contour in the image, where the properties of the reference are used as constraints. Experimental results using various realistically shaped foods with known volumes demonstrated satisfactory performance of our image-based food volume measurement method even if the 3D geometric surface of the food is not completely represented in the input image. (paper)

  17. A Millimetre-Sized Robot Realized by a Piezoelectric Impact-Type Rotary Actuator and a Hardware Neuron Model

    Directory of Open Access Journals (Sweden)

    Minami Takato

    2014-07-01

    Full Text Available Micro-robotic systems are increasingly used in medicine and other fields requiring precision engineering. This paper proposes a piezoelectric impact-type rotary actuator and applies it to a millimetre-size robot controlled by a hardware neuron model. The rotary actuator and robot are fabricated by micro-electro-mechanical systems (MEMS technology. The actuator is composed of multilayer piezoelectric elements. The rotational motion of the rotor is generated by the impact head attached to the piezoelectric element. The millimetre-size robot is fitted with six legs, three on either side of the developed actuator, and can walk on uneven surfaces like an insect. The three leg parts on each side are connected by a linking mechanism. The control system is a hardware neuron model constructed from analogue electronic circuits that mimic the behaviour of biological neurons. The output signal ports of the controller are connected to the multilayer piezoelectric element. This robot system requires no specialized software programs or A/D converters. The rotation speed of the rotary actuator reaches 60 rpm at an applied neuron frequency of 25 kHz during the walking motion. The width, length and height of the robot are 4.0, 4.6 and 3.6 mm, respectively. The motion speed is 180 mm/min.

  18. Derivation of Physical and Optical Properties of Midlatitude Cirrus Ice Crystals for a Size-Resolved Cloud Microphysics Model

    Science.gov (United States)

    Fridlind, Ann M.; Atlas, Rachel; Van Diedenhoven, Bastiaan; Um, Junshik; McFarquhar, Greg M.; Ackerman, Andrew S.; Moyer, Elisabeth J.; Lawson, R. Paul

    2016-01-01

    Single-crystal images collected in mid-latitude cirrus are analyzed to provide internally consistent ice physical and optical properties for a size-resolved cloud microphysics model, including single-particle mass, projected area, fall speed, capacitance, single-scattering albedo, and asymmetry parameter. Using measurements gathered during two flights through a widespread synoptic cirrus shield, bullet rosettes are found to be the dominant identifiable habit among ice crystals with maximum dimension (Dmax) greater than 100µm. Properties are therefore first derived for bullet rosettes based on measurements of arm lengths and widths, then for aggregates of bullet rosettes and for unclassified (irregular) crystals. Derived bullet rosette masses are substantially greater than reported in existing literature, whereas measured projected areas are similar or lesser, resulting in factors of 1.5-2 greater fall speeds, and, in the limit of large Dmax, near-infrared single-scattering albedo and asymmetry parameter (g) greater by approx. 0.2 and 0.05, respectively. A model that includes commonly imaged side plane growth on bullet rosettes exhibits relatively little difference in microphysical and optical properties aside from approx. 0:05 increase in mid-visible g primarily attributable to plate aspect ratio. In parcel simulations, ice size distribution, and g are sensitive to assumed ice properties.

  19. Statistical topography as a mechanistic model for the geometry & size distribution of tidal mud puddles, Arctic melt ponds, & terrestrial lakes

    Science.gov (United States)

    Barry, Brendan

    2015-11-01

    Studies over the last decade have reported power law distributions for the sizes of terrestrial lakes & Arctic melt ponds, as well as relationships between their area & the fractal dimension of their contours. These systems are important for the climate system, in terms of carbon cycling & ice-albedo feedback, respectively; these distributions offer promise for improved quantification & description of their influence. However, a mechanistic explanation of their distribution is lacking, & both systems remain difficult to observe logistically. Here we report 1) a simple mechanistic model for the distribution of lakes & melt ponds, based on statistical topography, which neatly predicts their distribution & the relationship between area & fractal dimension, as well as 2) the existence of a similar phenomena in tidal mud flats. Data was collected at low tide in a tidal bed near Damariscotta, Maine, which reveals a power law size distribution over a large dynamic range & a well-defined compatible fractal dimension. This data set significantly extends the observed spatiotemporal range of such phenomena, & suggests this easily observable system may be an ideal model for lakes & melt ponds. MIT-WHOI Jiont Program, Physical Oceanography.

  20. Alveolar bone tissue engineering in critical-size defects of experimental animal models: a systematic review and meta-analysis.

    Science.gov (United States)

    Shanbhag, Siddharth; Pandis, Nikolaos; Mustafa, Kamal; Nyengaard, Jens R; Stavropoulos, Andreas

    2017-10-01

    Regeneration of large, 'critical-size' bone defects remains a clinical challenge. Bone tissue engineering (BTE) is emerging as a promising alternative to autogenous, allogeneic and biomaterial-based bone grafting. The objective of this systematic review was to answer the focused question: in animal models, do cell-based BTE strategies enhance regeneration in alveolar bone critical-size defects (CSDs), compared with grafting with only biomaterial scaffolds or autogenous bone? Following PRISMA guidelines, electronic databases were searched for controlled animal studies reporting maxillary or mandibular CSD and implantation of mesenchymal stem cells (MSCs) or osteoblasts (OBs) seeded on biomaterial scaffolds. A random effects meta-analysis was performed for the outcome histomorphometric new bone formation (%NBF). Thirty-six studies were included that reported on large- (monkeys, dogs, sheep, minipigs) and small-animal (rabbits, rats) models. On average, studies presented with an unclear-to-high risk of bias and short observation times. In most studies, MSCs or OBs were used in combination with alloplastic mineral-phase scaffolds. In five studies, cells were modified by ex vivo gene transfer of bone morphogenetic proteins (BMPs). The meta-analysis indicated statistically significant benefits in favour of: (1) cell-loaded vs. cell-free scaffolds [weighted mean difference (WMD) 15.59-49.15% and 8.60-13.85% NBF in large- and small-animal models, respectively]; and (2) BMP-gene-modified vs. unmodified cells (WMD 10.06-20.83% NBF in small-animal models). Results of cell-loaded scaffolds vs. autogenous bone were inconclusive. Overall, heterogeneity in the meta-analysis was high (I 2  > 90%). In summary, alveolar bone regeneration is enhanced by addition of osteogenic cells to biomaterial scaffolds. The direction and estimates of treatment effect are useful to predict therapeutic efficacy and guide future clinical trials of BTE. Copyright © 2016 John Wiley & Sons, Ltd

  1. Precise large deviations of aggregate claims in a size-dependent renewal risk model with stopping time claim-number process

    Directory of Open Access Journals (Sweden)

    Shuo Zhang

    2017-04-01

    Full Text Available Abstract In this paper, we consider a size-dependent renewal risk model with stopping time claim-number process. In this model, we do not make any assumption on the dependence structure of claim sizes and inter-arrival times. We study large deviations of the aggregate amount of claims. For the subexponential heavy-tailed case, we obtain a precise large-deviation formula; our method substantially relies on a martingale for the structure of our models.

  2. A statistical model for estimation of fish density including correlation in size, space, time and between species from research survey data.

    Directory of Open Access Journals (Sweden)

    J Rasmus Nielsen

    Full Text Available Trawl survey data with high spatial and seasonal coverage were analysed using a variant of the Log Gaussian Cox Process (LGCP statistical model to estimate unbiased relative fish densities. The model estimates correlations between observations according to time, space, and fish size and includes zero observations and over-dispersion. The model utilises the fact the correlation between numbers of fish caught increases when the distance in space and time between the fish decreases, and the correlation between size groups in a haul increases when the difference in size decreases. Here the model is extended in two ways. Instead of assuming a natural scale size correlation, the model is further developed to allow for a transformed length scale. Furthermore, in the present application, the spatial- and size-dependent correlation between species was included. For cod (Gadus morhua and whiting (Merlangius merlangus, a common structured size correlation was fitted, and a separable structure between the time and space-size correlation was found for each species, whereas more complex structures were required to describe the correlation between species (and space-size. The within-species time correlation is strong, whereas the correlations between the species are weaker over time but strong within the year.

  3. Modeling ferroelectric film properties and size effects from tetragonal interlayer in Hf1-xZrxO2 grains

    Science.gov (United States)

    Künneth, Christopher; Materlik, Robin; Kersch, Alfred

    2017-05-01

    Size effects from surface or interface energy play a pivotal role in stabilizing the ferroelectric phase in recently discovered thin film Zirconia-Hafnia. However, sufficient quantitative understanding has been lacking due to the interference with the stabilizing effect from dopants. For the important class of undoped Hf1-xZrxO2, a phase stability model based on free energy from Density functional theory (DFT) and surface energy values adapted to the sparse experimental and theoretical data has been successful to describe key properties of the available thin film data. Since surfaces and interfaces are prone to interference, the predictive capability of the model is surprising and directs to a hitherto undetected, underlying reason. New experimental data hint on the existence of an interlayer on the grain surface fixed in the tetragonal phase possibly shielding from external influence. To explore the consequences of such a mechanism, we develop an interface free energy model to include the fixed interlayer, generalize the grain model to include a grain radius distribution, calculate average polarization and permittivity, and compare the model with available experimental data. Since values for interface energies are sparse or uncertain, we obtain its values from minimizing the least square difference between predicted key parameters to experimental data in a global optimization. Since the detailed values for DFT energies depend on the chosen method, we repeat the search for different computed data sets and come out with quantitatively different but qualitatively consistent values for interface energies. The resulting values are physically very reasonable and the model is able to give qualitative prediction. On the other hand, the optimization reveals that the model is not able to fully capture the experimental data. We discuss possible physical effects and directions of research to possibly close this gap.

  4. Statistical methodology for discrete fracture model - including fracture size, orientation uncertainty together with intensity uncertainty and variability

    International Nuclear Information System (INIS)

    Darcel, C.; Davy, P.; Le Goc, R.; Dreuzy, J.R. de; Bour, O.

    2009-11-01

    Investigations led for several years at Laxemar and Forsmark reveal the large heterogeneity of geological formations and associated fracturing. This project aims at reinforcing the statistical DFN modeling framework adapted to a site scale. This leads therefore to develop quantitative methods of characterization adapted to the nature of fracturing and data availability. We start with the hypothesis that the maximum likelihood DFN model is a power-law model with a density term depending on orientations. This is supported both by literature and specifically here by former analyses of the SKB data. This assumption is nevertheless thoroughly tested by analyzing the fracture trace and lineament maps. Fracture traces range roughly between 0.5 m and 10 m - i e the usual extension of the sample outcrops. Between the raw data and final data used to compute the fracture size distribution from which the size distribution model will arise, several steps are necessary, in order to correct data from finite-size, topographical and sampling effects. More precisely, a particular attention is paid to fracture segmentation status and fracture linkage consistent with the DFN model expected. The fracture scaling trend observed over both sites displays finally a shape parameter k t close to 1.2 with a density term (α 2d ) between 1.4 and 1.8. Only two outcrops clearly display a different trend with k t close to 3 and a density term (α 2d ) between 2 and 3.5. The fracture lineaments spread over the range between 100 meters and a few kilometers. When compared with fracture trace maps, these datasets are already interpreted and the linkage process developed previously has not to be done. Except for the subregional lineament map from Forsmark, lineaments display a clear power-law trend with a shape parameter k t equal to 3 and a density term between 2 and 4.5. The apparent variation in scaling exponent, from the outcrop scale (k t = 1.2) on one side, to the lineament scale (k t = 2) on

  5. Validation of a new model for the sizing of denitrification reactors, by testing full-scale plants.

    Science.gov (United States)

    Raboni, M; Torretta, V

    2017-06-01

    A new deterministic model for the calculation of the specific denitrification rate (SDNR), useful for the design of pre-denitrification reactors, was tested on eight full-scale activated sludge plants. The model represents the SDNR at 20°C (SDNR 20°C ) as a function of the sludge loading in the denitrification reactor (F:M DEN ) and the residual dissolved oxygen in the denitrification reactor (DO DEN ). The results proved the ability of the model in calculating the SDNR 20°C . The model shows a lower degree of adaptability for small-sized plants. SDNR 20°C proved to have a strong sensitivity to DO DEN , mainly in correspondence with low DO concentrations (less than 2 mg L -1 ). The sensitivity decreases at greater DO values, but with a progressively less marked gradient, up to becoming weak only at DO concentrations greater than 0.4-0.5 mg L -1 , which are rarely found in full-scale plants. DO concentrations measured in real-scale facilities are mostly in the range 0.2-0.4 mg L -1 . These concentrations cause adverse effects on the kinetics of nitrogen removal, and consequently on the denitrification performance. Thus, minimizing DO in the pre-denitrification reactor is relevant. The sensitivity of SDNR 20°C to F:M DEN was less important, as it is characterized by a growing linear behaviour with a low slope.

  6. A conservative vapour intrusion screening model of oxygen-limited hydrocarbon vapour biodegradation accounting for building footprint size.

    Science.gov (United States)

    Knight, John H; Davis, Gregory B

    2013-12-01

    Petroleum hydrocarbon vapours pose a reduced risk to indoor air due to biodegradation processes where oxygen is available in the subsurface or below built structures. However, no previous assessment has been available to show the effects of a building footprint (slab size) on oxygen-limited hydrocarbon vapour biodegradation and the potential for oxygen to be present beneath the entire sub-slab region of a building. Here we provide a new, conservative and conceptually simple vapour screening model which links oxygen and hydrocarbon vapour transport and biodegradation in the vicinity and beneath an impervious slab. This defines when vapour risk is insignificant, or conversely when there is potential for vapour to contact the sub-slab of a building. The solution involves complex mathematics to determine the position of an unknown boundary interface between oxygen diffusing in from the ground surface and vapours diffusing upwards from a subsurface vapour source, but the mathematics reduces to a simple relationship between the vapour source concentration and the ratio of the half slab width and depth to the vapour source. Data from known field investigations are shown to be consistent with the model predictions. Examples of 'acceptable' slab sizes for vapour source depths and strengths are given. The predictions are conservative as an estimator of when petroleum hydrocarbon vapours might come in contact with a slab-on-ground building since additional sources of oxygen due to advective flow or diffusion through the slab are ignored. As such the model can be used for screening sites for further investigation. © 2013.

  7. The attention-weighted sample-size model of visual short-term memory: Attention capture predicts resource allocation and memory load.

    Science.gov (United States)

    Smith, Philip L; Lilburn, Simon D; Corbett, Elaine A; Sewell, David K; Kyllingsbæk, Søren

    2016-09-01

    We investigated the capacity of visual short-term memory (VSTM) in a phase discrimination task that required judgments about the configural relations between pairs of black and white features. Sewell et al. (2014) previously showed that VSTM capacity in an orientation discrimination task was well described by a sample-size model, which views VSTM as a resource comprised of a finite number of noisy stimulus samples. The model predicts the invariance of [Formula: see text] , the sum of squared sensitivities across items, for displays of different sizes. For phase discrimination, the set-size effect significantly exceeded that predicted by the sample-size model for both simultaneously and sequentially presented stimuli. Instead, the set-size effect and the serial position curves with sequential presentation were predicted by an attention-weighted version of the sample-size model, which assumes that one of the items in the display captures attention and receives a disproportionate share of resources. The choice probabilities and response time distributions from the task were well described by a diffusion decision model in which the drift rates embodied the assumptions of the attention-weighted sample-size model. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

  8. Calibration of modelled mixing patterns in loess grain-size distributions: an example from the north-eastern margin of the Tibetan Plateau, China

    NARCIS (Netherlands)

    Vriend, M.G.A.; Prins, M.A.

    2005-01-01

    Genetically meaningful decomposition (unmixing) of sediment grain-size distributions is accomplished with the end-member modelling algorithm. Unmixing of the loess grain-size distributions of a Late Quaternary loess-palaeosol succession from the north-eastern Tibetan Plateau indicates that the loess

  9. Analysis of the grain size evolution for ferrite formation in Fe-C-Mn steels using a 3D model under a mixed-mode interface condition

    NARCIS (Netherlands)

    Fang, H.; Mecozzi, M.G.; Brück, E.H.; van der Zwaag, S.; van Dijk, N.H.

    2018-01-01

    A 3D model has been developed to predict the average ferrite grain size and grain size distribution for an austenite-to-ferrite phase transformation during continuous cooling of an Fe-C-Mn steel. Using a Voronoi construction to represent the austenite grains, the ferrite is assumed to nucleate at

  10. GI Joe or Average Joe? The impact of average-size and muscular male fashion models on men's and women's body image and advertisement effectiveness.

    Science.gov (United States)

    Diedrichs, Phillippa C; Lee, Christina

    2010-06-01

    Increasing body size and shape diversity in media imagery may promote positive body image. While research has largely focused on female models and women's body image, men may also be affected by unrealistic images. We examined the impact of average-size and muscular male fashion models on men's and women's body image and perceived advertisement effectiveness. A sample of 330 men and 289 women viewed one of four advertisement conditions: no models, muscular, average-slim or average-large models. Men and women rated average-size models as equally effective in advertisements as muscular models. For men, exposure to average-size models was associated with more positive body image in comparison to viewing no models, but no difference was found in comparison to muscular models. Similar results were found for women. Internalisation of beauty ideals did not moderate these effects. These findings suggest that average-size male models can promote positive body image and appeal to consumers. 2010 Elsevier Ltd. All rights reserved.

  11. Statistical methodology for discrete fracture model - including fracture size, orientation uncertainty together with intensity uncertainty and variability

    Energy Technology Data Exchange (ETDEWEB)

    Darcel, C. (Itasca Consultants SAS (France)); Davy, P.; Le Goc, R.; Dreuzy, J.R. de; Bour, O. (Geosciences Rennes, UMR 6118 CNRS, Univ. def Rennes, Rennes (France))

    2009-11-15

    Investigations led for several years at Laxemar and Forsmark reveal the large heterogeneity of geological formations and associated fracturing. This project aims at reinforcing the statistical DFN modeling framework adapted to a site scale. This leads therefore to develop quantitative methods of characterization adapted to the nature of fracturing and data availability. We start with the hypothesis that the maximum likelihood DFN model is a power-law model with a density term depending on orientations. This is supported both by literature and specifically here by former analyses of the SKB data. This assumption is nevertheless thoroughly tested by analyzing the fracture trace and lineament maps. Fracture traces range roughly between 0.5 m and 10 m - i e the usual extension of the sample outcrops. Between the raw data and final data used to compute the fracture size distribution from which the size distribution model will arise, several steps are necessary, in order to correct data from finite-size, topographical and sampling effects. More precisely, a particular attention is paid to fracture segmentation status and fracture linkage consistent with the DFN model expected. The fracture scaling trend observed over both sites displays finally a shape parameter k{sub t} close to 1.2 with a density term (alpha{sub 2d}) between 1.4 and 1.8. Only two outcrops clearly display a different trend with k{sub t} close to 3 and a density term (alpha{sub 2d}) between 2 and 3.5. The fracture lineaments spread over the range between 100 meters and a few kilometers. When compared with fracture trace maps, these datasets are already interpreted and the linkage process developed previously has not to be done. Except for the subregional lineament map from Forsmark, lineaments display a clear power-law trend with a shape parameter k{sub t} equal to 3 and a density term between 2 and 4.5. The apparent variation in scaling exponent, from the outcrop scale (k{sub t} = 1.2) on one side, to

  12. A corrected model for static and dynamic electromechanical instability of narrow nanotweezers: Incorporation of size effect, surface layer and finite dimensions

    Science.gov (United States)

    Koochi, Ali; Hosseini-Toudeshky, Hossein; Abadyan, Mohamadreza

    2018-03-01

    Herein, a corrected theoretical model is proposed for modeling the static and dynamic behavior of electrostatically actuated narrow-width nanotweezers considering the correction due to finite dimensions, size dependency and surface energy. The Gurtin-Murdoch surface elasticity in conjunction with the modified couple stress theory is employed to consider the coupling effect of surface stresses and size phenomenon. In addition, the model accounts for the external force corrections by incorporating the impact of narrow width on the distribution of Casimir attraction, van der Waals (vdW) force and the fringing field effect. The proposed model is beneficial for the precise modeling of the narrow nanotweezers in nano-scale.

  13. Design and modeling of compact-size environmental telemetry station based on passive optical sensors and fuzzy logic control

    Science.gov (United States)

    Mahmoud, Mohamed

    2003-04-01

    In today's life, remote environmental sensing via distributed and remote telemetry stations is a vital demand for pollution control and wildlife protection. However the high cost of sensors and their environmental ruggedness, engineering and equipments' cost, and the complex signal processing are restricting the spread of such technology. This paper is introducing the design and modelling of a compact size environmental telemetry station (CETS) based on passive optical sensors and Fuzzy logic control. Here, the cost reduction and size problems are solved by using the fiber Bragg gratings sensors that are able to detect a wide variety of environmental variables such as temperature, humidity, toxic gases, odours, chemical pollution, water dissolved toxins, level, pressure and many more. Also the complex signal processing problem is solved by using an array of fiber Bragg gratings sensors that coexist on a single fiber core, where their signals are multiplexed and processed in the optical domain without the need to analogue-to-digital conversion. The control and encoding problem is solved by using a Fuzzy logic control algorithm within an imbedded system fitted with a CCD sensor spectrometer.

  14. Kriging modeling and SPSA adjusting PID with KPWF compensator control of IPMC gripper for mm-sized objects

    Science.gov (United States)

    Chen, Yang; Hao, Lina; Yang, Hui; Gao, Jinhai

    2017-12-01

    Ionic polymer metal composite (IPMC) as a new smart material has been widely concerned in the micromanipulation field. In this paper, a novel two-finger gripper which contains an IPMC actuator and an ultrasensitive force sensor is proposed and fabricated. The IPMC as one finger of the gripper for mm-sized objects can achieve gripping and releasing motion, and the other finger works not only as a support finger but also as a force sensor. Because of the feedback signal of the force sensor, this integrated actuating and sensing gripper can complete gripping miniature objects in millimeter scale. The Kriging model is used to describe nonlinear characteristics of the IPMC for the first time, and then the control scheme called simultaneous perturbation stochastic approximation adjusting a proportion integration differentiation parameter controller with a Kriging predictor wavelet filter compensator is applied to track the gripping force of the gripper. The high precision force tracking in the foam ball manipulation process is obtained on a semi-physical experimental platform, which demonstrates that this gripper for mm-sized objects can work well in manipulation applications.

  15. Modified energy-deposition model, for the computation of the stopping-power ratio for small cavity sizes

    International Nuclear Information System (INIS)

    Janssens, A.C.A.

    1981-01-01

    This paper presents a modification to the Spencer-Attix theory, which allows application of the theory to larger cavity sizes. The modified theory is in better agreement with the actual process of energy deposition by delta rays. In the first part of the paper it is recalled how the Spencer-Attix theory can be derived from basic principles, which allows a physical interpretation of the theory in terms of a function describing the space and direction average of the deposited energy. A realistic model for the computation of this function is described and the resulting expression for the stopping-power ratio is calculated. For the comparison between the Spencer-Attix theory and this modified expression a correction factor to the ''Bragg-Gray inhomogeneous term'' has been defined. This factor has been computed as a function of cavity size for different source energies and mean excitation energies; thus, general properties of this factor have been elucidated. The computations have been extended to include the density effect. It has been shown that the computation of the inhomogeneous term can be performed for any expression describing the energy loss per unit distance of the electrons as a function of their energy. Thus an expression has been calculated which is in agreement with a quadratic range-energy relationship. In conclusion, the concrete procedure for computing the stopping-power ratio is reviewed

  16. Investigation of vertical size segregation in bedload sediment transport with a coupled fluid-discrete element model

    Directory of Open Access Journals (Sweden)

    Frey Philippe

    2017-01-01

    Full Text Available In order to gain understanding of kinetic sieving-type segregation in bedload sediment transport, numerical experiments of two-size particle mixtures were carried out, using a validated coupled fluid-discrete element model developed at Irstea. A 3D 10% steep domain consisting at initial time of a given number of layers of 4 mm particles deposited on top of a coarser 6 mm particle bed, was submitted to a turbulent and supercritical fluid shear flow (Shields numbers of 0.1 and 0.3. The elevation of the centre of mass of the infiltrated fine particles is observed to follow the same logarithmic decrease with time, whatever the initial number of fine layers. This decrease is steeper for a higher Shields number. The main result is that this typical behaviour is related at first order to the shear rate depth profile.

  17. Fuzzy model of relationship among economic performance, competitiveness and business ethics of small and medium-sized enterprises

    Directory of Open Access Journals (Sweden)

    Nina Bočková

    2012-01-01

    Full Text Available The objective of this article is to study the relations among financial indicators, competitiveness and business ethics of comparable small and medium-sized enterprises. A sample of 59 SMEs from the South Moravia region was chosen. All selected companies either produce or service electronics. This research is based on the application of scientific analysis, synthesis, induction, fuzzy logic and modeling. Information for this research was obtained from secondary information sources – Amadeus database, accounting statements and information from the register of companies. Each company is described by a set of 10 variables. Fuzzy sets and reasoning are ideal tools to cope with vague, ill-structured and uncertain scenarios which can be found frequently in business and economics. This is the main reason why fuzzy logic was used in this research. The paper is self-explanatory and no a prior knowledge of fuzzy reasoning is required.

  18. Initial stage sintering of polymer particles – Experiments and modelling of size-, temperature- and time-dependent contacts

    Directory of Open Access Journals (Sweden)

    Fuchs Regina

    2017-01-01

    Full Text Available The early-stage sintering of thin layers of micron-sized polystyrene (PS particles, at sintering temperatures near and above the glass transition temperature Tg (~ 100°C, is studied utilizing 3D tomography, nanoindentation and confocal microscopy. Our experimental results confirm the existence of a critical particle radius (rcrit ~ 1 μm below which surface forces need to be considered as additional driving force, on top of the usual surfacetension driven viscous flow sintering mechanism. Both sintering kinetics and mechanical properties of particles smaller than rcrit are dominated by contact deformation due to surface forces, so that sintering of larger particles is generally characterized by viscous flow. Consequently, smaller particles require shorter sintering. These experimental observations are supported by discrete particle simulations that are based on analytical models: for small particles, if only viscous sintering is considered, the model under-predicts the neck radius during early stage sintering, which confirms the need for an additional driving mechanism like elastic-plastic repulsion and surface forces that are both added to the DEM model.

  19. An Experimental Study of Lightning Overvoltages in Wind Turbine Generation Systems Using a Reduced-Size Model

    Science.gov (United States)

    Yamamoto, Kazuo; Noda, Taku; Yokoyama, Shigeru; Ametani, Akihiro

    Wind turbine generation systems are built at locations where few tall structures are found nearby so as to obtain good wind conditions, and thus, they are often struck by lightning. To promote wind power generation, lightning-protection methodologies for such wind turbine generation systems have to be established. This paper presents the result of an experimental study of lightning overvoltages in wind turbine generation systems using a reduced-size wind turbine model. Overvoltages observed at wavefronts of lightning surges are focused on in this study. In the experiments, lightning strokes to one of the blades and to the nacelle were considered, and voltages and currents at various positions of the wind turbine model were measured. The following points have been deduced from the results: (i) The voltage rise due to the tower footing resistance can cause a significant voltage difference between the tower foot and an incoming conductor led from a distant point. Also, a voltage difference between the bottom of down conductors installed inside the tower and an incoming conductor can be of significance. (ii) The lightning current flowing through the tower body induces voltages in main and control circuits which form loops, and the induced voltages can cause overvoltages and malfunctions. (iii) Traveling-wave phenomena in a wind turbine generation system for a lightning strike to the tip of a blade and to the nacelle have been made clear from the measured waveforms. This information can be used for developing an EMTP simulation model of wind turbine generation systems.

  20. A Sustainability-Oriented Multiobjective Optimization Model for Siting and Sizing Distributed Generation Plants in Distribution Systems

    Directory of Open Access Journals (Sweden)

    Guang Chen

    2013-01-01

    Full Text Available This paper proposes a sustainability-oriented multiobjective optimization model for siting and sizing DG plants in distribution systems. Life cycle exergy (LCE is used as a unified indicator of the entire system’s environmental sustainability, and it is optimized as an objective function in the model. Other two objective functions include economic cost and expected power loss. Chance constraints are used to control the operation risks caused by the uncertain power loads and renewable energies. A semilinearized simulation method is proposed and combined with the Latin hypercube sampling (LHS method to improve the efficiency of probabilistic load flow (PLF analysis which is repeatedly performed to verify the chance constraints. A numerical study based on the modified IEEE 33-node system is performed to verify the proposed method. Numerical results show that the proposed semilinearized simulation method reduces about 93.3% of the calculation time of PLF analysis and guarantees satisfying accuracy. The results also indicate that benefits for environmental sustainability of using DG plants can be effectively reflected by the proposed model which helps the planner to make rational decision towards sustainable development of the distribution system.

  1. A Life-Cycle Model of Human Social Groups Produces a U-Shaped Distribution in Group Size.

    Directory of Open Access Journals (Sweden)

    Gul Deniz Salali

    Full Text Available One of the central puzzles in the study of sociocultural evolution is how and why transitions from small-scale human groups to large-scale, hierarchically more complex ones occurred. Here we develop a spatially explicit agent-based model as a first step towards understanding the ecological dynamics of small and large-scale human groups. By analogy with the interactions between single-celled and multicellular organisms, we build a theory of group lifecycles as an emergent property of single cell demographic and expansion behaviours. We find that once the transition from small-scale to large-scale groups occurs, a few large-scale groups continue expanding while small-scale groups gradually become scarcer, and large-scale groups become larger in size and fewer in number over time. Demographic and expansion behaviours of groups are largely influenced by the distribution and availability of resources. Our results conform to a pattern of human political change in which religions and nation states come to be represented by a few large units and many smaller ones. Future enhancements of the model should include decision-making rules and probabilities of fragmentation for large-scale societies. We suggest that the synthesis of population ecology and social evolution will generate increasingly plausible models of human group dynamics.

  2. Modeling the Hydrological Cycle in the Atmosphere of Mars: Influence of a Bimodal Size Distribution of Aerosol Nucleation Particles

    Science.gov (United States)

    Shaposhnikov, Dmitry S.; Rodin, Alexander V.; Medvedev, Alexander S.; Fedorova, Anna A.; Kuroda, Takeshi; Hartogh, Paul

    2018-02-01

    We present a new implementation of the hydrological cycle scheme into a general circulation model of the Martian atmosphere. The model includes a semi-Lagrangian transport scheme for water vapor and ice and accounts for microphysics of phase transitions between them. The hydrological scheme includes processes of saturation, nucleation, particle growth, sublimation, and sedimentation under the assumption of a variable size distribution. The scheme has been implemented into the Max Planck Institute Martian general circulation model and tested assuming monomodal and bimodal lognormal distributions of ice condensation nuclei. We present a comparison of the simulated annual variations, horizontal and vertical distributions of water vapor, and ice clouds with the available observations from instruments on board Mars orbiters. The accounting for bimodality of aerosol particle distribution improves the simulations of the annual hydrological cycle, including predicted ice clouds mass, opacity, number density, and particle radii. The increased number density and lower nucleation rates bring the simulated cloud opacities closer to observations. Simulations show a weak effect of the excess of small aerosol particles on the simulated water vapor distributions.

  3. Assessing the impact of large-scale computing on the size and complexity of first-principles electromagnetic models

    International Nuclear Information System (INIS)

    Miller, E.K.

    1990-01-01

    There is a growing need to determine the electromagnetic performance of increasingly complex systems at ever higher frequencies. The ideal approach would be some appropriate combination of measurement, analysis, and computation so that system design and assessment can be achieved to a needed degree of accuracy at some acceptable cost. Both measurement and computation benefit from the continuing growth in computer power that, since the early 1950s, has increased by a factor of more than a million in speed and storage. For example, a CRAY2 has an effective throughput (not the clock rate) of about 10 11 floating-point operations (FLOPs) per hour compared with the approximate 10 5 provided by the UNIVAC-1. The purpose of this discussion is to illustrate the computational complexity of modeling large (in wavelengths) electromagnetic problems. In particular the author makes the point that simply relying on faster computers for increasing the size and complexity of problems that can be modeled is less effective than might be anticipated from this raw increase in computer throughput. He suggests that rather than depending on faster computers alone, various analytical and numerical alternatives need development for reducing the overall FLOP count required to acquire the information desired. One approach is to decrease the operation count of the basic model computation itself, by reducing the order of the frequency dependence of the various numerical operations or their multiplying coefficients. Another is to decrease the number of model evaluations that are needed, an example being the number of frequency samples required to define a wideband response, by using an auxiliary model of the expected behavior. 11 refs., 5 figs., 2 tabs

  4. Tyrosine-derived polycarbonate scaffolds for bone regeneration in a rabbit radius critical-size defect model

    International Nuclear Information System (INIS)

    Kim, Jinku; McBride, Sean; Donovan, Amy; Hollinger, Jeffrey O; Darr, Aniq; Magno, Maria Hanshella R

    2015-01-01

    The aim of the study was to determine bone regeneration in a rabbit radius critical-size defect (CSD) model using a specific polymer composition (E1001(1k)) from a library of tyrosine-derived polycarbonate scaffolds coated with a calcium phosphate (CP) formulation (E1001(1k) + CP) supplemented with recombinant human bone morphogenetic protein-2 (rhBMP-2). Specific doses of rhBMP-2 (0, 17, and 35 μg/scaffold) were used. E1001(1k) + CP scaffolds were implanted in unilateral segmental defects (15 mm length) in the radial diaphyses of New Zealand White rabbits. At 4 and 8 weeks post-implantation, bone regeneration was determined using micro-computed tomography (µCT), histology, and histomorphometry. The quantitative outcome data suggest that E1001(1k) + CP scaffolds with rhBMP-2 were biocompatible and promoted bone regeneration in segmental bone defects. Histological examination of the implant sites showed that scaffolds made of E1001(1k) + CP did not elicit adverse cellular or tissue responses throughout test periods up to 8 weeks. Noteworthy is that the incorporation of a very small amount of rhBMP-2 into the scaffolds (as low as 17 μg/defect site) promoted significant bone regeneration compared to scaffolds consisting of E1001(1k) + CP alone. This finding indicates that E1001(1k) + CP may be an effective platform for bone regeneration in a critical size rabbit radius segmental defect model, requiring only a minimal dose of rhBMP-2. (paper)

  5. Source attribution of aerosol size distributions and model evaluation using Whistler Mountain measurements and GEOS-Chem-TOMAS simulations

    Science.gov (United States)

    D'Andrea, S. D.; Ng, J. Y.; Kodros, J. K.; Atwood, S. A.; Wheeler, M. J.; Macdonald, A. M.; Leaitch, W. R.; Pierce, J. R.

    2016-01-01

    Remote and free-tropospheric aerosols represent a large fraction of the climatic influence of aerosols; however, aerosol in these regions is less characterized than those polluted boundary layers. We evaluate aerosol size distributions predicted by the GEOS-Chem-TOMAS global chemical transport model with online aerosol microphysics using measurements from the peak of Whistler Mountain, British Columbia, Canada (2182 m a.s.l., hereafter referred to as Whistler Peak). We evaluate the model for predictions of aerosol number, size, and composition during periods of free-tropospheric (FT) and boundary-layer (BL) influence at "coarse" 4° × 5° and "nested" 0.5° × 0.667° resolutions by developing simple FT/BL filtering techniques. We find that using temperature as a proxy for upslope flow (BL influence) improved the model-measurement comparisons. The best threshold temperature was around 2 °C for the coarse simulations and around 6 °C for the nested simulations, with temperatures warmer than the threshold indicating boundary-layer air. Additionally, the site was increasingly likely to be in cloud when the measured relative humidity (RH) was above 90 %, so we do not compare the modeled and measured size distributions during these periods. With the inclusion of these temperature and RH filtering techniques, the model-measurement comparisons improved significantly. The slope of the regression for N80 (the total number of particles with particle diameter, Dp, > 80 nm) in the nested simulations increased from 0.09 to 0.65, R2 increased from 0.04 to 0.46, and log-mean bias improved from 0.95 to 0.07. We also perform simulations at the nested resolution without Asian anthropogenic emissions and without biomass-burning emissions to quantify the contribution of these sources to aerosols at Whistler Peak (through comparison with simulations with these emissions on). The long-range transport of Asian anthropogenic aerosol was found to be significant throughout all particle

  6. Metastable configurations of a finite-size chain of classical spins within the one-dimensional chiral XY-model

    Energy Technology Data Exchange (ETDEWEB)

    Popov, Alexander P., E-mail: APPopov@mephi.ru [Department of Molecular Physics, National Research Nuclear University MEPhI, Kashirskoe shosse 31, 115409 Moscow (Russian Federation); Gloria Pini, Maria, E-mail: mariagloria.pini@isc.cnr.it [Istituto dei Sistemi Complessi del CNR (CNR-ISC), Unità di Firenze, Via Madonna del Piano 10, I-50019 Sesto Fiorentino (Italy); Rettori, Angelo [Dipartimento di Fisica ed Astronomia, Università di Firenze, Via G. Sansone 1, I-50019 Sesto Fiorentino (Italy)

    2016-03-15

    The metastable states of a finite-size chain of N classical spins described by the chiral XY-model on a discrete one-dimensional lattice are calculated by means of a general theoretical method recently developed by one of us. This method allows one to determine all the possible equilibrium magnetic states in an accurate and systematic way. The ground state of a chain consisting of N classical XY spins is calculated in the presence of (i) a symmetric ferromagnetic exchange interaction, favoring parallel alignment of nearest neighbor spins, (ii) a uniaxial anisotropy, favoring a given direction in the film plane, and (iii) an antisymmetric Dzyaloshinskii–Moriya interaction (DMI), favoring perpendicular alignment of nearest neighbor spins. In addition to the ground state with a non-uniform helical spin arrangement, which originates from the energy competition in the finite-size chain with open boundary conditions, we have found a considerable number of higher-energy equilibrium states. In the investigated case of a chain with N=10 spins and a DMI much smaller than the in-plane uniaxial anisotropy, it turns out that a metastable (unstable) state of the finite chain is characterized by a configuration where none (at least one) of the inner spins is nearly parallel to the hard axis. The role of the DMI is to establish a unique rotational sense for the helical ground state. Moreover, the number of both metastable and unstable equilibrium states is doubled with respect to the case of zero DMI. This produces modifications in the Peierls–Nabarro potential encountered by a domain wall during its displacement along the discrete spin chain. - Highlights: • A finite-size chain of N classical spins within the XY-chiral model is investigated. • Using a systematic theoretical method, all equilibrium states are calculated for N=10. • The ground state has a non-uniform helical order with unique rotational sense. • Metastable states contain a domain wall whose energy

  7. The difference of canine, first and second premolar tooth size resulted from cone beam computed tomography imaging with Moyers Prediction Table on the working study model

    Directory of Open Access Journals (Sweden)

    Julies Hariani Sugiaman

    2011-03-01

    Full Text Available Model study is one of the standard orthodontic components which is important for diagnosis and treatment plan, but in some patients with the high gag reflex, it will be difficult to get this kind of study models. The existence of a new device which is able to show the condition of patients' mouth in three space areas (axial, sagittal, and coronal is expected to be an alternative when a study model is difficult to get. The purpose of this study is to find out whether or not there are any differences on the size of canine's mesiodistal, first and second premolar resulted from CBCT imaging with Moyers analysis on the study models. The method of the research is comparative descriptive. Measurements are made on 10 CBCT imaging results and 10 study models. The mesiodistal size, the result of CBCT imaging is measured by the available computer program and also the mesiodistal size of the study models is measured using a sliding compass, and then the size of canines, first and second premolar teeth resulted from CBCT imaging are compared to the result of Moyers method analysis on the study models. The t-test is used to find out if there is a difference between teeth size value between the CBCT imaging with the study models. The significance is determined based on the p-value t table.

  8. A proposed adaptive step size perturbation and observation maximum power point tracking algorithm based on photovoltaic system modeling

    Science.gov (United States)

    Huang, Yu

    Solar energy becomes one of the major alternative renewable energy options for its huge abundance and accessibility. Due to the intermittent nature, the high demand of Maximum Power Point Tracking (MPPT) techniques exists when a Photovoltaic (PV) system is used to extract energy from the sunlight. This thesis proposed an advanced Perturbation and Observation (P&O) algorithm aiming for relatively practical circumstances. Firstly, a practical PV system model is studied with determining the series and shunt resistances which are neglected in some research. Moreover, in this proposed algorithm, the duty ratio of a boost DC-DC converter is the object of the perturbation deploying input impedance conversion to achieve working voltage adjustment. Based on the control strategy, the adaptive duty ratio step size P&O algorithm is proposed with major modifications made for sharp insolation change as well as low insolation scenarios. Matlab/Simulink simulation for PV model, boost converter control strategy and various MPPT process is conducted step by step. The proposed adaptive P&O algorithm is validated by the simulation results and detail analysis of sharp insolation changes, low insolation condition and continuous insolation variation.

  9. Multiscale modelling of vascular tumour growth in 3D: the roles of domain size and boundary conditions.

    Directory of Open Access Journals (Sweden)

    Holger Perfahl

    2011-04-01

    Full Text Available We investigate a three-dimensional multiscale model of vascular tumour growth, which couples blood flow, angiogenesis, vascular remodelling, nutrient/growth factor transport, movement of, and interactions between, normal and tumour cells, and nutrient-dependent cell cycle dynamics within each cell. In particular, we determine how the domain size, aspect ratio and initial vascular network influence the tumour's growth dynamics and its long-time composition. We establish whether it is possible to extrapolate simulation results obtained for small domains to larger ones, by constructing a large simulation domain from a number of identical subdomains, each subsystem initially comprising two parallel parent vessels, with associated cells and diffusible substances. We find that the subsystem is not representative of the full domain and conclude that, for this initial vessel geometry, interactions between adjacent subsystems contribute to the overall growth dynamics. We then show that extrapolation of results from a small subdomain to a larger domain can only be made if the subdomain is sufficiently large and is initialised with a sufficiently complex vascular network. Motivated by these results, we perform simulations to investigate the tumour's response to therapy and show that the probability of tumour elimination in a larger domain can be extrapolated from simulation results on a smaller domain. Finally, we demonstrate how our model may be combined with experimental data, to predict the spatio-temporal evolution of a vascular tumour.

  10. Importance of the surface size distribution of erodible material: an improvement on the Dust Entrainment And Deposition (DEAD) Model

    Science.gov (United States)

    Mokhtari, M.; Gomes, L.; Tulet, P.; Rezoug, T.

    2012-05-01

    This paper is based on dust aerosol cycle modelling in the atmospheric model ALADIN (Aire Limitée Adaptation dynamique Développement InterNational) coupled with the EXternalised SURFace scheme SURFEX. Its main goal is to create an appropriate mineral dust emission parameterization compatible with the global database of land surface parameters ECOCLIMAP, and the Food and Agriculture Organization (FAO) soil type database in SURFEX. An improvement on the Dust Entrainment And Deposition scheme (DEAD) is proposed in this paper by introducing the geographical variation of surface soil size distribution, the Marticorena and Bergametti (1995) formulation of horizontal saltation flux and the Shao et al. (1996) formulation of sandblasting efficiency α. To show the importance of the modifications introduced in the DEAD, both sensitivity and comparative studies are conducted in 0 dimensions (0-D) and then in 3 dimensions (3-D) between the old DEAD and the new DEAD. The results of the 0-D simulations indicate that the revised DEAD scheme represents the dust source emission better, particularly in the Bodélé depression, and provides a reasonable friction threshold velocity. In 3-D simulations, small differences are found between the DEAD and the revised DEAD for the simulated Aerosol Optical Depth (AOD) compared with the AErosol RObotic NETwork (AERONET) photometer measurements available in the African Monsoon Multidisciplinary Analyses (AMMA) databases. For the surface concentration, a remarkable improvement is noted for the revised DEAD scheme.

  11. Finite element modelling to assess the effect of surface mounted piezoelectric patch size on vibration response of a hybrid beam

    Science.gov (United States)

    Rahman, N.; Alam, M. N.

    2018-02-01

    Vibration response analysis of a hybrid beam with surface mounted patch piezoelectric layer is presented in this work. A one dimensional finite element (1D-FE) model based on efficient layerwise (zigzag) theory is used for the analysis. The beam element has eight mechanical and a variable number of electrical degrees of freedom. The beams are also modelled in 2D-FE (ABAQUS) using a plane stress piezoelectric quadrilateral element for piezo layers and a plane stress quadrilateral element for the elastic layers of hybrid beams. Results are presented to assess the effect of size of piezoelectric patch layer on the free and forced vibration responses of thin and moderately thick beams under clamped-free and clamped-clamped configurations. The beams are subjected to unit step loading and harmonic loading to obtain the forced vibration responses. The vibration control using in phase actuation potential on piezoelectric patches is also studied. The 1D-FE results are compared with the 2D-FE results.

  12. Quantitative structure-activity relationship (QSAR) models for polycyclic aromatic hydrocarbons (PAHs) dissipation in rhizosphere based on molecular structure and effect size.

    Science.gov (United States)

    Ma, Bin; Chen, Huaihai; Xu, Minmin; Hayat, Tahir; He, Yan; Xu, Jianming

    2010-08-01

    Rhizoremediation is a significant form of bioremediation for polycyclic aromatic hydrocarbons (PAHs). This study examined the role of molecular structure in determining the rhizosphere effect on PAHs dissipation. Effect size in meta-analysis was employed as activity dataset for building quantitative structure-activity relationship (QSAR) models and accumulative effect sizes of 16 PAHs were used for validation of these models. Based on the genetic algorithm combined with partial least square regression, models for comprehensive dataset, Poaceae dataset, and Fabaceae dataset were built. The results showed that information indices, calculated as information content of molecules based on the calculation of equivalence classes from the molecular graph, were the most important molecular structural indices for QSAR models of rhizosphere effect on PAHs dissipation. The QSAR model, based on the molecular structure indices and effect size, has potential to be used in studying and predicting the rhizosphere effect of PAHs dissipation. Copyright 2010 Elsevier Ltd. All rights reserved.

  13. Analysis of the Grain Size Evolution for Ferrite Formation in Fe-C-Mn Steels Using a 3D Model Under a Mixed-Mode Interface Condition

    Science.gov (United States)

    Fang, H.; Mecozzi, M. G.; Brück, E.; van der Zwaag, S.; van Dijk, N. H.

    2018-01-01

    A 3D model has been developed to predict the average ferrite grain size and grain size distribution for an austenite-to-ferrite phase transformation during continuous cooling of an Fe-C-Mn steel. Using a Voronoi construction to represent the austenite grains, the ferrite is assumed to nucleate at the grain corners and to grow as spheres. Classical nucleation theory is used to estimate the density of ferrite nuclei. By assuming a negligible partition of manganese, the moving ferrite-austenite interface is treated with a mixed-mode model in which the soft impingement of the carbon diffusion fields is considered. The ferrite volume fraction, the average ferrite grain size, and the ferrite grain size distribution are derived as a function of temperature. The results of the present model are compared with those of a published phase-field model simulating the ferritic microstructure evolution during linear cooling of an Fe-0.10C-0.49Mn (wt pct) steel. It turns out that the present model can adequately reproduce the phase-field modeling results as well as the experimental dilatometry data. The model presented here provides a versatile tool to analyze the evolution of the ferrite grain size distribution at low computational costs.

  14. Qualification of the Lasentec M600P Particle Size Analyzer and the Red Valve Model 1151 Pressure Sensor

    Energy Technology Data Exchange (ETDEWEB)

    JR Bontha; NG Colton; EA Daymo; TD Hylton; CK Bayne; TH May

    2000-01-28

    The Lasentec M600 in-line particle size analyzer was installed at Oak Ridge National Laboratory (ORNL) in August 1998 to support retrieval of the Gunite and Associated Tanks (GAAT). Before installation at ORNL, the sensor underwent validation testing at the Pacific Northwest National Laboratory (PNNL) Instrument Validation facility. Mechanically, the instrument worked well during validation testing and met all expectations. Operationally, much was learned about optimum ways to display and interpret the data. Slurry samples taken during the in-line tests at PNNL were shipped to the vendor for analysis with a benchtop Lasentec sensor. These experiments were performed to determine if off-line analyses yield particle size distributions similar to those generated by the in-line sensor. It was determined that the Lasentec sensor measures repeatable chord lengths as long as particles are ''presenter'' to the sensor window the same way. After the initial non-radioactive simulant testing at PNNL, the instrument was shipped for radioactive validation and acceptance testing in the Slurry Monitoring Test System (SMTS) connected to the Tank W-9 of the GAATs at ORNL. For all acceptance tests conducted at ORNL, the variation in the chord length distribution and the total particle count corresponded very well with the slurry density data as determined using an in-line Promass 63M Coriolis meter. Based on the performance results obtained, the Lasentec M600P FBRM is expected to meet the requirements for measuring the particle size distribution during the slurry transfer operations at Hanford and the Oak Ridge GAAT remediation project. The Red Valve pressure sensor was endorsed at the Hanford Site following instrument validation tests at PNNL and is currently in operation in the Tank 241-C-106 pump pit. While this instrument measures pressure within a transfer line, this type of pressure sensor could be configured to measure pressure drop over time. In turn, the

  15. Effect of roll compaction on granule size distribution of microcrystalline cellulose-mannitol mixtures: computational intelligence modeling and parametric analysis.

    Science.gov (United States)

    Kazemi, Pezhman; Khalid, Mohammad Hassan; Pérez Gago, Ana; Kleinebudde, Peter; Jachowicz, Renata; Szlęk, Jakub; Mendyk, Aleksander

    2017-01-01

    Dry granulation using roll compaction is a typical unit operation for producing solid dosage forms in the pharmaceutical industry. Dry granulation is commonly used if the powder mixture is sensitive to heat and moisture and has poor flow properties. The output of roll compaction is compacted ribbons that exhibit different properties based on the adjusted process parameters. These ribbons are then milled into granules and finally compressed into tablets. The properties of the ribbons directly affect the granule size distribution (GSD) and the quality of final products; thus, it is imperative to study the effect of roll compaction process parameters on GSD. The understanding of how the roll compactor process parameters and material properties interact with each other will allow accurate control of the process, leading to the implementation of quality by design practices. Computational intelligence (CI) methods have a great potential for being used within the scope of quality by design approach. The main objective of this study was to show how the computational intelligence techniques can be useful to predict the GSD by using different process conditions of roll compaction and material properties. Different techniques such as multiple linear regression, artificial neural networks, random forest, Cubist and k-nearest neighbors algorithm assisted by sevenfold cross-validation were used to present generalized models for the prediction of GSD based on roll compaction process setting and material properties. The normalized root-mean-squared error and the coefficient of determination ( R 2 ) were used for model assessment. The best fit was obtained by Cubist model (normalized root-mean-squared error =3.22%, R 2 =0.95). Based on the results, it was confirmed that the material properties (true density) followed by compaction force have the most significant effect on GSD.

  16. Modeling and optimization of effective parameters on the size of synthesized Fe{sub 3}O{sub 4} superparamagnetic nanoparticles by coprecipitation technique using response surface methodology

    Energy Technology Data Exchange (ETDEWEB)

    Ghazanfari, Mohammad Reza, E-mail: Ghazanfari.mr@gmail.com [Department of Materials Science and Engineering, Ferdowsi University of Mashhad, 9177948974 Mashhad (Iran, Islamic Republic of); Kashefi, Mehrdad, E-mail: m-kashefi@um.ac.ir [Department of Materials Science and Engineering, Ferdowsi University of Mashhad, 9177948974 Mashhad (Iran, Islamic Republic of); Jaafari, Mahmoud Reza [Biotechnology Research Center, Nanotechnology Research Center, School of Pharmacy, Mashhad University of Medical Sciences, Mashhad (Iran, Islamic Republic of)

    2016-05-01

    Generally, the statistical methods are defined as appropriate techniques to study the processes trends. In current research, the Fe{sub 3}O{sub 4} superparamagnetic nanoparticles were synthesized by coprecipitation method. In order to investigate the size properties of synthesized particles, the experimental design was done using central composite method (CCD) of response surface methodology (RSM) while the temperature, pH, and cation ratio of reaction were selected as influential factors. After particles synthesis based on designed runs, the different responses such as hydrodynamic size of particles (both freeze dried and air dried), size distribution, crystallite size, magnetic size, and zeta potential were evaluated by different techniques i.e. dynamic light scattering (DLS), X-ray diffraction (XRD), and vibrating sample magnetometer (VSM). Based on these results, the quadratic polynomial model was fitted for each response that could predict the response amounts. In following, the study of factors effects was carried out that showed the temperature, pH, and their interactions had higher effectiveness. Finally, by optimizing, it was clear that the minimum amounts of particle size (10.15 nm) and size distribution (13.01 nm) were reached in the minimum temperature (70 °C) and cation ratio (0.5) amounts and maximum pH amount (10.5). Moreover, the characterizations showed the particles size was about 10 nm while the amounts of M{sub s}, H{sub c}, and M{sub r} were equal to 60 (emu/g), 0.2 (Oe) and 0.22 (emu/g), respectively. - Highlights: • The Fe{sub 3}O{sub 4} nanoparticles were successfully synthesized by coprecipitation method. • By RSM technique, some predicted models were presented for particles size. • Temperature, pH and their interactions had most effectiveness on the particles size. • The drying techniques can effect on the size properties.

  17. A statistical model for estimation of fish density including correlation in size, space, time and between species from research survey data

    DEFF Research Database (Denmark)

    Nielsen, J. Rasmus; Kristensen, Kasper; Lewy, Peter

    2014-01-01

    Trawl survey data with high spatial and seasonal coverage were analysed using a variant of the Log Gaussian Cox Process (LGCP) statistical model to estimate unbiased relative fish densities. The model estimates correlations between observations according to time, space, and fish size and includes...

  18. Automated quantification and sizing of unbranched filamentous cyanobacteria by model-based object-oriented image analysis.

    Science.gov (United States)

    Zeder, Michael; Van den Wyngaert, Silke; Köster, Oliver; Felder, Kathrin M; Pernthaler, Jakob

    2010-03-01

    Quantification and sizing of filamentous cyanobacteria in environmental samples or cultures are time-consuming and are often performed by using manual or semiautomated microscopic analysis. Automation of conventional image analysis is difficult because filaments may exhibit great variations in length and patchy autofluorescence. Moreover, individual filaments frequently cross each other in microscopic preparations, as deduced by modeling. This paper describes a novel approach based on object-oriented image analysis to simultaneously determine (i) filament number, (ii) individual filament lengths, and (iii) the cumulative filament length of unbranched cyanobacterial morphotypes in fluorescent microscope images in a fully automated high-throughput manner. Special emphasis was placed on correct detection of overlapping objects by image analysis and on appropriate coverage of filament length distribution by using large composite images. The method was validated with a data set for Planktothrix rubescens from field samples and was compared with manual filament tracing, the line intercept method, and the Utermöhl counting approach. The computer program described allows batch processing of large images from any appropriate source and annotation of detected filaments. It requires no user interaction, is available free, and thus might be a useful tool for basic research and drinking water quality control.

  19. Physical models of size-dependent nanofilament formation and rupture in NiO resistive switching memories

    Energy Technology Data Exchange (ETDEWEB)

    Ielmini, D; Nardi, F; Cagli, C, E-mail: ielmini@elet.polimi.it [Dipartimento di Elettronica e Informazione-Politecnico di Milano and IU.NET, Piazza L. da Vinci 32, I-20133 Milano (Italy)

    2011-06-24

    NiO films display unipolar resistance switching characteristics, due to the electrically induced formation and rupture of nanofilaments. While the applicative interest for possible use in highly dense resistance switching memory (RRAM) is extremely high, switching phenomena pose strong fundamental challenges in understanding the physical mechanisms and models. This work addresses the set and reset mechanisms for the formation and rupture of nanofilaments in NiO RRAM devices. Reset is described in terms of thermally-accelerated diffusion and oxidation processes, and its resistance dependence is explained by size-dependent Joule heating and oxidation. The filament is described as a region with locally-enhanced doping, resulting in an insulator-metal transition driven by structural and chemical defects. The set mechanism is explained by a threshold switching effect, triggering chemical reduction and a consequent local increase of metallic doping. The possible use of the observed resistance-dependent reset and set parameters to improve the memory array operation and variability is finally discussed.

  20. Export Barriers for Small and Medium-sized Enterprises: A Literature Review based on Leonidou’s Model

    Directory of Open Access Journals (Sweden)

    Vijay Narayanan

    2015-06-01

    Full Text Available The purpose of this article is to understand the barriers faced by small and medium-sized enterprises in their path to internationalization. The intention of this paper is to provide an overview about the barriers faced by SMEs in their path to internationalization and discuss in detail different approaches taken by SMEs to overcome these barriers. This article is a literature review on the barriers faced by SMEs in internationalization and new approaches in this domain based on Leonidou’s (1995, 1998, 2004 model of export barrier classification. Modern approaches by SMEs are effective in handling most of the traditional challenges posed in internationalization. Firms have evolved in handling internal barriers by finding dynamic solutions from within. SMEs need support from governmental and policy makers to overcome external barriers. Indications on the work to be done in overcoming certain barriers which impede the internationalization of SMEs are more in the context of external barriers. The originality of this work is in creating a framework of barriers and finding solutions to some of the identified barriers.