Cement-aggregate compatibility and structure property relationships including modelling
Jennings, H.M.; Xi, Y.
1993-07-15
The role of aggregate, and its interface with cement paste, is discussed with a view toward establishing models that relate structure to properties. Both short (nm) and long (mm) range structure must be considered. The short range structure of the interface depends not only on the physical distribution of the various phases, but also on moisture content and reactivity of aggregate. Changes that occur on drying, i.e. shrinkage, may alter the structure which, in turn, feeds back to alter further drying and shrinkage. The interaction is dynamic, even without further hydration of cement paste, and the dynamic characteristic must be considered in order to fully understand and model its contribution to properties. Microstructure and properties are two subjects which have been pursued somewhat separately. This review discusses both disciplines with a view toward finding common research goals in the future. Finally, comment is made on possible chemical reactions which may occur between aggregate and cement paste.
NASA Astrophysics Data System (ADS)
Van Geel, P. J.; Roy, S. D.
2002-09-01
A residual non-aqueous phase liquid (NAPL) present in the vadose zone can act as a contaminant source for many years as the compounds of concern partition to infiltrating groundwater and air contained in the soil voids. Current pressure-saturation-relative permeability relationships do not include a residual NAPL saturation term in their formulation. This paper presents the results of series of two- and three-phase pressure cell experiments conducted to evaluate the residual NAPL saturation and its impact on the pressure-saturation relationship. A model was proposed to incorporate a residual NAPL saturation term into an existing hysteretic three-phase parametric model developed by Parker and Lenhard [Water Resour. Res. 23(12) (1987) 2187], Lenhard and Parker [Water Resour. Res. 23(12) (1987) 2197] and Lenhard [J. Contam. Hydrol. 9 (1992) 243]. The experimental results indicated that the magnitude of the residual NAPL saturation was a function of the maximum total liquid saturation reached and the water saturation. The proposed model to incorporate a residual NAPL saturation term is similar in form to the entrapment model proposed by Parker and Lenhard, which was based on an expression presented by Land [Soc. Pet. Eng. J. (June 1968) 149].
NASA Astrophysics Data System (ADS)
Tesemma, Z. K.; Wei, Y.; Peel, M. C.; Western, A. W.
2015-06-01
Anthropogenic climate change is projected to enrich the atmosphere with carbon dioxide, change vegetation dynamics and influence the availability of water at the catchment scale. This study combines a nonlinear model for estimating changes in leaf area index (LAI) due to climatic fluctuations with the variable infiltration capacity (VIC) hydrological model to improve catchment streamflow prediction under a changing climate. The combined model was applied to 13 gauged sub-catchments with different land cover types (crop, pasture and tree) in the Goulburn-Broken catchment, Australia, for the "Millennium Drought" (1997-2009) relative to the period 1983-1995, and for two future periods (2021-2050 and 2071-2100) and two emission scenarios (Representative Concentration Pathway (RCP) 4.5 and RCP8.5) which were compared with the baseline historical period of 1981-2010. This region was projected to be warmer and mostly drier in the future as predicted by 38 Coupled Model Intercomparison Project Phase 5 (CMIP5) runs from 15 global climate models (GCMs) and for two emission scenarios. The results showed that during the Millennium Drought there was about a 29.7-66.3 % reduction in mean annual runoff due to reduced precipitation and increased temperature. When drought-induced changes in LAI were included, smaller reductions in mean annual runoff of between 29.3 and 61.4 % were predicted. The proportional increase in runoff due to modeling LAI was 1.3-10.2 % relative to not including LAI. For projected climate change under the RCP4.5 emission scenario, ignoring the LAI response to changing climate could lead to a further reduction in mean annual runoff of between 2.3 and 27.7 % in the near-term (2021-2050) and 2.3 to 23.1 % later in the century (2071-2100) relative to modeling the dynamic response of LAI to precipitation and temperature changes. Similar results (near-term 2.5-25.9 % and end of century 2.6-24.2 %) were found for climate change under the RCP8.5 emission scenario
Ozbilgin, M.M.; Dickerman, D.C.
1984-01-01
The two-dimensional finite-difference model for simulation of groundwater flow was modified to enable simulation of surface-water/groundwater interactions during periods of low streamflow. Changes were made to the program code in order to calculate surface-water heads for, and flow either to or from, contiguous surface-water bodies; and to allow for more convenient data input. Methods of data input and output were modified and entries (RSORT and HDRIVER) were added to the COEF and CHECKI subroutines to calculate surface-water heads. A new subroutine CALC was added to the program which initiates surface-water calculations. If CALC is not specified as a simulation option, the program runs the original version. The subroutines which solve the ground-water flow equations were not changed. Recharge, evapotranspiration, surface-water inflow, number of wells, pumping rate, and pumping duration can be varied for any time period. The Manning formula was used to relate stream depth and discharge in surface-water streams. Interactions between surface water and ground water are represented by the leakage term in the ground-water flow and surface-water mass balance equations. Documentation includes a flow chart, data deck instructions, input data, output summary, and program listing. Numerical results from the modified program are in good agreement with published analytical results. (USGS)
An Integrated Biochemistry Laboratory, Including Molecular Modeling
NASA Astrophysics Data System (ADS)
Hall, Adele J. Wolfson Mona L.; Branham, Thomas R.
1996-11-01
) experience with methods of protein purification; (iii) incorporation of appropriate controls into experiments; (iv) use of basic statistics in data analysis; (v) writing papers and grant proposals in accepted scientific style; (vi) peer review; (vii) oral presentation of results and proposals; and (viii) introduction to molecular modeling. Figure 1 illustrates the modular nature of the lab curriculum. Elements from each of the exercises can be separated and treated as stand-alone exercises, or combined into short or long projects. We have been able to offer the opportunity to use sophisticated molecular modeling in the final module through funding from an NSF-ILI grant. However, many of the benefits of the research proposal can be achieved with other computer programs, or even by literature survey alone. Figure 1.Design of project-based biochemistry laboratory. Modules (projects, or portions of projects) are indicated as boxes. Each of these can be treated independently, or used as part of a larger project. Solid lines indicate some suggested paths from one module to the next. The skills and knowledge required for protein purification and design are developed in three units: (i) an introduction to critical assays needed to monitor degree of purification, including an evaluation of assay parameters; (ii) partial purification by ion-exchange techniques; and (iii) preparation of a grant proposal on protein design by mutagenesis. Brief descriptions of each of these units follow, with experimental details of each project at the end of this paper. Assays for Lysozyme Activity and Protein Concentration (4 weeks) The assays mastered during the first unit are a necessary tool for determining the purity of the enzyme during the second unit on purification by ion exchange. These assays allow an introduction to the concept of specific activity (units of enzyme activity per milligram of total protein) as a measure of purity. In this first sequence, students learn a turbidimetric assay
Dynamic stall simulation including turbulence modeling
Allet, A.; Halle, S.; Paraschivoiu, I.
1995-09-01
The objective of this study is to investigate the two-dimensional unsteady flow around an airfoil undergoing a Darrieus motion in dynamic stall conditions. For this purpose, a numerical solver based on the solution of the Reynolds-averaged Navier-Stokes equations expressed in a streamfunction-vorticity formulation in a non-inertial frame of reference was developed. The governing equations are solved by the streamline upwind Petrov-Galerkin finite element method (FEM). Temporal discretization is achieved by second-order-accurate finite differences. The resulting global matrix system is linearized by the Newton method and solved by the generalized minimum residual method (GMRES) with an incomplete triangular factorization preconditioning (ILU). Turbulence effects are introduced in the solver by an eddy viscosity model. The investigation centers on an evaluation of the possibilities of several turbulence models, including the algebraic Cebeci-Smith model (CSM) and the nonequilibrium Johnson-King model (JKM). In an effort to predict dynamic stall features on rotating airfoils, first the authors present some testing results concerning the performance of both turbulence models for the flat plate case. Then, computed flow structure together with aerodynamic coefficients for a NACA 0015 airfoil in Darrieus motion under stall conditions are presented.
SEEPAGE MODEL FOR PA INCLUDING DRIFT COLLAPSE
C. Tsang
2004-09-22
The purpose of this report is to document the predictions and analyses performed using the seepage model for performance assessment (SMPA) for both the Topopah Spring middle nonlithophysal (Tptpmn) and lower lithophysal (Tptpll) lithostratigraphic units at Yucca Mountain, Nevada. Look-up tables of seepage flow rates into a drift (and their uncertainty) are generated by performing numerical simulations with the seepage model for many combinations of the three most important seepage-relevant parameters: the fracture permeability, the capillary-strength parameter 1/a, and the percolation flux. The percolation flux values chosen take into account flow focusing effects, which are evaluated based on a flow-focusing model. Moreover, multiple realizations of the underlying stochastic permeability field are conducted. Selected sensitivity studies are performed, including the effects of an alternative drift geometry representing a partially collapsed drift from an independent drift-degradation analysis (BSC 2004 [DIRS 166107]). The intended purpose of the seepage model is to provide results of drift-scale seepage rates under a series of parameters and scenarios in support of the Total System Performance Assessment for License Application (TSPA-LA). The SMPA is intended for the evaluation of drift-scale seepage rates under the full range of parameter values for three parameters found to be key (fracture permeability, the van Genuchten 1/a parameter, and percolation flux) and drift degradation shape scenarios in support of the TSPA-LA during the period of compliance for postclosure performance [Technical Work Plan for: Performance Assessment Unsaturated Zone (BSC 2002 [DIRS 160819], Section I-4-2-1)]. The flow-focusing model in the Topopah Spring welded (TSw) unit is intended to provide an estimate of flow focusing factors (FFFs) that (1) bridge the gap between the mountain-scale and drift-scale models, and (2) account for variability in local percolation flux due to
An Integrated Biochemistry Laboratory, Including Molecular Modeling
NASA Astrophysics Data System (ADS)
Hall, Adele J. Wolfson Mona L.; Branham, Thomas R.
1996-11-01
) experience with methods of protein purification; (iii) incorporation of appropriate controls into experiments; (iv) use of basic statistics in data analysis; (v) writing papers and grant proposals in accepted scientific style; (vi) peer review; (vii) oral presentation of results and proposals; and (viii) introduction to molecular modeling. Figure 1 illustrates the modular nature of the lab curriculum. Elements from each of the exercises can be separated and treated as stand-alone exercises, or combined into short or long projects. We have been able to offer the opportunity to use sophisticated molecular modeling in the final module through funding from an NSF-ILI grant. However, many of the benefits of the research proposal can be achieved with other computer programs, or even by literature survey alone. Figure 1.Design of project-based biochemistry laboratory. Modules (projects, or portions of projects) are indicated as boxes. Each of these can be treated independently, or used as part of a larger project. Solid lines indicate some suggested paths from one module to the next. The skills and knowledge required for protein purification and design are developed in three units: (i) an introduction to critical assays needed to monitor degree of purification, including an evaluation of assay parameters; (ii) partial purification by ion-exchange techniques; and (iii) preparation of a grant proposal on protein design by mutagenesis. Brief descriptions of each of these units follow, with experimental details of each project at the end of this paper. Assays for Lysozyme Activity and Protein Concentration (4 weeks) The assays mastered during the first unit are a necessary tool for determining the purity of the enzyme during the second unit on purification by ion exchange. These assays allow an introduction to the concept of specific activity (units of enzyme activity per milligram of total protein) as a measure of purity. In this first sequence, students learn a turbidimetric assay
Seepage Model for PA Including Dift Collapse
G. Li; C. Tsang
2000-12-20
The purpose of this Analysis/Model Report (AMR) is to document the predictions and analysis performed using the Seepage Model for Performance Assessment (PA) and the Disturbed Drift Seepage Submodel for both the Topopah Spring middle nonlithophysal and lower lithophysal lithostratigraphic units at Yucca Mountain. These results will be used by PA to develop the probability distribution of water seepage into waste-emplacement drifts at Yucca Mountain, Nevada, as part of the evaluation of the long term performance of the potential repository. This AMR is in accordance with the ''Technical Work Plan for Unsaturated Zone (UZ) Flow and Transport Process Model Report'' (CRWMS M&O 2000 [153447]). This purpose is accomplished by performing numerical simulations with stochastic representations of hydrological properties, using the Seepage Model for PA, and evaluating the effects of an alternative drift geometry representing a partially collapsed drift using the Disturbed Drift Seepage Submodel. Seepage of water into waste-emplacement drifts is considered one of the principal factors having the greatest impact of long-term safety of the repository system (CRWMS M&O 2000 [153225], Table 4-1). This AMR supports the analysis and simulation that are used by PA to develop the probability distribution of water seepage into drift, and is therefore a model of primary (Level 1) importance (AP-3.15Q, ''Managing Technical Product Inputs''). The intended purpose of the Seepage Model for PA is to support: (1) PA; (2) Abstraction of Drift-Scale Seepage; and (3) Unsaturated Zone (UZ) Flow and Transport Process Model Report (PMR). Seepage into drifts is evaluated by applying numerical models with stochastic representations of hydrological properties and performing flow simulations with multiple realizations of the permeability field around the drift. The Seepage Model for PA uses the distribution of permeabilities derived from air injection testing in niches and in the cross drift to
Including eddies in global ocean models
NASA Astrophysics Data System (ADS)
Semtner, Albert J.; Chervin, Robert M.
The ocean is a turbulent fluid that is driven by winds and by surface exchanges of heat and moisture. It is as important as the atmosphere in governing climate through heat distribution, but so little is known about the ocean that it remains a “final frontier” on the face of the Earth. Many ocean currents are truly global in extent, such as the Antarctic Circumpolar Current and the “conveyor belt” that connects the North Atlantic and North Pacific oceans by flows around the southern tips of Africa and South America. It has long been a dream of some oceanographers to supplement the very limited observational knowledge by reconstructing the currents of the world ocean from the first principles of physics on a computer. However, until very recently, the prospect of doing this was thwarted by the fact that fluctuating currents known as “mesoscale eddies” could not be explicitly included in the calculation.
Seven challenges for metapopulation models of epidemics, including households models.
Ball, Frank; Britton, Tom; House, Thomas; Isham, Valerie; Mollison, Denis; Pellis, Lorenzo; Scalia Tomba, Gianpaolo
2015-03-01
This paper considers metapopulation models in the general sense, i.e. where the population is partitioned into sub-populations (groups, patches,...), irrespective of the biological interpretation they have, e.g. spatially segregated large sub-populations, small households or hosts themselves modelled as populations of pathogens. This framework has traditionally provided an attractive approach to incorporating more realistic contact structure into epidemic models, since it often preserves analytic tractability (in stochastic as well as deterministic models) but also captures the most salient structural inhomogeneity in contact patterns in many applied contexts. Despite the progress that has been made in both the theory and application of such metapopulation models, we present here several major challenges that remain for future work, focusing on models that, in contrast to agent-based ones, are amenable to mathematical analysis. The challenges range from clarifying the usefulness of systems of weakly-coupled large sub-populations in modelling the spread of specific diseases to developing a theory for endemic models with household structure. They include also developing inferential methods for data on the emerging phase of epidemics, extending metapopulation models to more complex forms of human social structure, developing metapopulation models to reflect spatial population structure, developing computationally efficient methods for calculating key epidemiological model quantities, and integrating within- and between-host dynamics in models. PMID:25843386
Modeling Emergent Macrophyte Distributions: Including Sub-dominant Species
Mixed stands of emergent vegetation are often present following drawdowns but models of wetland plant distributions fail to include subdominant species when predicting distributions. Three variations of a spatial plant distribution cellular automaton model were developed to explo...
Dynamic hysteresis modeling including skin effect using diffusion equation model
NASA Astrophysics Data System (ADS)
Hamada, Souad; Louai, Fatima Zohra; Nait-Said, Nasreddine; Benabou, Abdelkader
2016-07-01
An improved dynamic hysteresis model is proposed for the prediction of hysteresis loop of electrical steel up to mean frequencies, taking into account the skin effect. In previous works, the analytical solution of the diffusion equation for low frequency (DELF) was coupled with the inverse static Jiles-Atherton (JA) model in order to represent the hysteresis behavior for a lamination. In the present paper, this approach is improved to ensure the reproducibility of measured hysteresis loops at mean frequency. The results of simulation are compared with the experimental ones. The selected results for frequencies 50 Hz, 100 Hz, 200 Hz and 400 Hz are presented and discussed.
A model for heterogeneous materials including phase transformations
Addessio, F.L.; Clements, B.E.; Williams, T.O.
2005-04-15
A model is developed for particulate composites, which includes phase transformations in one or all of the constituents. The model is an extension of the method of cells formalism. Representative simulations for a single-phase, brittle particulate (SiC) embedded in a ductile material (Ti), which undergoes a solid-solid phase transformation, are provided. Also, simulations for a tungsten heavy alloy (WHA) are included. In the WHA analyses a particulate composite, composed of tungsten particles embedded in a tungsten-iron-nickel alloy matrix, is modeled. A solid-liquid phase transformation of the matrix material is included in the WHA numerical calculations. The example problems also demonstrate two approaches for generating free energies for the material constituents. Simulations for volumetric compression, uniaxial strain, biaxial strain, and pure shear are used to demonstrate the versatility of the model.
Wang, Jing; Lu, Bin; Zan, Ruiguang; Chai, Jing; Ma, Wei; Jin, Wei; Duan, Rongyao; Luo, Jing; Murphy, Robert W; Xiao, Heng; Chen, Ziming
2016-01-01
The phylogenetic relationships of Asian schilbid catfishes of the genera Clupisoma, Ailia, Horabagrus, Laides and Pseudeutropius are poorly understood, especially those of Clupisoma. Herein, we reconstruct the phylogeny of 38 species of catfishes belonging to 28 genera and 14 families using the concatenated mitochondrial genes COI, cytb, and 16S rRNA, as well as the nuclear genes RAG1 and RAG2. The resulting phylogenetic trees consistently place Clupisoma as the sister taxon of Laides, and the five representative Asian schilbid genera form two monophyletic groups with the relationships (Ailia (Laides, Clupisoma)) and (Horabagrus, Pseudeutropius). The so-called "Big Asia" lineage relates distantly to African schilbids. Independent analyses of the mitochondrial and nuclear DNA data yield differing trees for the two Asian schilbid groups. Analyses of the mitochondrial gene data support a sister-group relationship for (Ailia (Laides, Clupisoma)) and the Sisoroidea and a sister-taxon association of (Horabagrus, Pseudeutropius) and the Bagridae. In contrast, analyses of the combined nuclear data indicate (Ailia (Laides, Clupisoma)) to be the sister group to (Horabagrus, Pseudeutropius). Our results indicate that the Horabagridae, recognized by some authors as consisting of Horabagrus, Pseudeutropius and Clupisoma does not include the latter genus. We formally erect a new family, Ailiidae fam. nov. for a monophyletic Asian group comprised of the genera Ailia, Laides and Clupisoma. PMID:26751688
Zan, Ruiguang; Chai, Jing; Ma, Wei; Jin, Wei; Duan, Rongyao; Luo, Jing; Murphy, Robert W.; Xiao, Heng; Chen, Ziming
2016-01-01
The phylogenetic relationships of Asian schilbid catfishes of the genera Clupisoma, Ailia, Horabagrus, Laides and Pseudeutropius are poorly understood, especially those of Clupisoma. Herein, we reconstruct the phylogeny of 38 species of catfishes belonging to 28 genera and 14 families using the concatenated mitochondrial genes COI, cytb, and 16S rRNA, as well as the nuclear genes RAG1 and RAG2. The resulting phylogenetic trees consistently place Clupisoma as the sister taxon of Laides, and the five representative Asian schilbid genera form two monophyletic groups with the relationships (Ailia (Laides, Clupisoma)) and (Horabagrus, Pseudeutropius). The so-called “Big Asia” lineage relates distantly to African schilbids. Independent analyses of the mitochondrial and nuclear DNA data yield differing trees for the two Asian schilbid groups. Analyses of the mitochondrial gene data support a sister-group relationship for (Ailia (Laides, Clupisoma)) and the Sisoroidea and a sister-taxon association of (Horabagrus, Pseudeutropius) and the Bagridae. In contrast, analyses of the combined nuclear data indicate (Ailia (Laides, Clupisoma)) to be the sister group to (Horabagrus, Pseudeutropius). Our results indicate that the Horabagridae, recognized by some authors as consisting of Horabagrus, Pseudeutropius and Clupisoma does not include the latter genus. We formally erect a new family, Ailiidae fam. nov. for a monophyletic Asian group comprised of the genera Ailia, Laides and Clupisoma. PMID:26751688
Modeling heart rate variability including the effect of sleep stages
NASA Astrophysics Data System (ADS)
Soliński, Mateusz; Gierałtowski, Jan; Żebrowski, Jan
2016-02-01
We propose a model for heart rate variability (HRV) of a healthy individual during sleep with the assumption that the heart rate variability is predominantly a random process. Autonomic nervous system activity has different properties during different sleep stages, and this affects many physiological systems including the cardiovascular system. Different properties of HRV can be observed during each particular sleep stage. We believe that taking into account the sleep architecture is crucial for modeling the human nighttime HRV. The stochastic model of HRV introduced by Kantelhardt et al. was used as the initial starting point. We studied the statistical properties of sleep in healthy adults, analyzing 30 polysomnographic recordings, which provided realistic information about sleep architecture. Next, we generated synthetic hypnograms and included them in the modeling of nighttime RR interval series. The results of standard HRV linear analysis and of nonlinear analysis (Shannon entropy, Poincaré plots, and multiscale multifractal analysis) show that—in comparison with real data—the HRV signals obtained from our model have very similar properties, in particular including the multifractal characteristics at different time scales. The model described in this paper is discussed in the context of normal sleep. However, its construction is such that it should allow to model heart rate variability in sleep disorders. This possibility is briefly discussed.
Modeling heart rate variability including the effect of sleep stages.
Soliński, Mateusz; Gierałtowski, Jan; Żebrowski, Jan
2016-02-01
We propose a model for heart rate variability (HRV) of a healthy individual during sleep with the assumption that the heart rate variability is predominantly a random process. Autonomic nervous system activity has different properties during different sleep stages, and this affects many physiological systems including the cardiovascular system. Different properties of HRV can be observed during each particular sleep stage. We believe that taking into account the sleep architecture is crucial for modeling the human nighttime HRV. The stochastic model of HRV introduced by Kantelhardt et al. was used as the initial starting point. We studied the statistical properties of sleep in healthy adults, analyzing 30 polysomnographic recordings, which provided realistic information about sleep architecture. Next, we generated synthetic hypnograms and included them in the modeling of nighttime RR interval series. The results of standard HRV linear analysis and of nonlinear analysis (Shannon entropy, Poincaré plots, and multiscale multifractal analysis) show that-in comparison with real data-the HRV signals obtained from our model have very similar properties, in particular including the multifractal characteristics at different time scales. The model described in this paper is discussed in the context of normal sleep. However, its construction is such that it should allow to model heart rate variability in sleep disorders. This possibility is briefly discussed. PMID:26931582
A coke oven model including thermal decomposition kinetics of tar
Munekane, Fuminori; Yamaguchi, Yukio; Tanioka, Seiichi
1997-12-31
A new one-dimensional coke oven model has been developed for simulating the amount and the characteristics of by-products such as tar and gas as well as coke. This model consists of both heat transfer and chemical kinetics including thermal decomposition of coal and tar. The chemical kinetics constants are obtained by estimation based on the results of experiments conducted to investigate the thermal decomposition of both coal and tar. The calculation results using the new model are in good agreement with experimental ones.
A sonic boom propagation model including mean flow atmospheric effects
NASA Astrophysics Data System (ADS)
Salamone, Joe; Sparrow, Victor W.
2012-09-01
This paper presents a time domain formulation of nonlinear lossy propagation in onedimension that also includes the effects of non-collinear mean flow in the acoustic medium. The model equation utilized is an augmented Burgers equation that includes the effects of nonlinearity, geometric spreading, atmospheric stratification, and also absorption and dispersion due to thermoviscous and molecular relaxation effects. All elements of the propagation are implemented in the time domain and the effects of non-collinear mean flow are accounted for in each term of the model equation. Previous authors have presented methods limited to showing the effects of wind on ray tracing and/or using an effective speed of sound in their model equation. The present work includes the effects of mean flow for all terms included in the augmented Burgers equation with all of the calculations performed in the time-domain. The capability to include the effects of mean flow in the acoustic medium allows one to make predictions more representative of real-world atmospheric conditions. Examples are presented for nonlinear propagation of N-waves and shaped sonic booms. [Work supported by Gulfstream Aerospace Corporation.
Models of Spectral Galaxy Evolution including the effects of Dust
NASA Astrophysics Data System (ADS)
Möller, C. S.; Fritze-v. Alvensleben, U.; Fricke, K. J.
To analyse the effects of dust to the UV emission in various galaxy types we present our evolutionary synthesis models which includes dust absorption in a chemically consistent way. The time and redshift evolution of the extinction is based on the evolution of the gas content and metallicity. Comparing our model SED's with templates from Kennicutt's and Kinney et al.'s atlas we show the detailed agreement with integrated spectra of galaxies and point out the importance of aperture effects. We are able to predict the UV fluxes for different galaxy types. Combined with a cosmological model we show the differences in the evolutionary and k-corrections comparing models with and without dust.
Estimation of nonlinear pilot model parameters including time delay.
NASA Technical Reports Server (NTRS)
Schiess, J. R.; Roland, V. R.; Wells, W. R.
1972-01-01
Investigation of the feasibility of using a Kalman filter estimator for the identification of unknown parameters in nonlinear dynamic systems with a time delay. The problem considered is the application of estimation theory to determine the parameters of a family of pilot models containing delayed states. In particular, the pilot-plant dynamics are described by differential-difference equations of the retarded type. The pilot delay, included as one of the unknown parameters to be determined, is kept in pure form as opposed to the Pade approximations generally used for these systems. Problem areas associated with processing real pilot response data are included in the discussion.
The forecast model of relationship commitment.
Lemay, Edward P
2016-07-01
Four studies tested the forecast model of relationship commitment, which posits that forecasts of future relationship satisfaction determine relationship commitment and prorelationship behavior in romantic relationships independently of other known predictors and partially explain the effects of these other predictors. This model was supported in 2 cross-sectional studies, a daily report study, and a study using behavioral observation, informant, and longitudinal methods. Across these studies, forecasts of future relationship satisfaction predicted relationship commitment and prorelationship behavior during relationship conflict and partially explained the effects of relationship satisfaction, quality of alternatives, and investment size. These results suggest that representations of the future have a prominent role in interpersonal processes. (PsycINFO Database Record PMID:27183320
Comprehensive modeling of electrostatically actuated MEMS beams including uncertainty quantification
NASA Astrophysics Data System (ADS)
Snow, Michael G.
MEMS switches have offered dramatic improvements in the performance of RF systems. However, difficulties with reliability has slowed the adoption of MEMS switches in RF systems. These reliability issues are partly due to the poor manufacturing tolerances endemic to MEMS manufacturing processes. These manufacturing tolerances may cause significant variations in performance characteristics. This work focuses on electrostatically actuated MEMS beam capacitive shunt switches. A non-linear dynamic model for these switches was developed. The model accounts for a variety of physical effects including; beam stretching, residual stress, non-rigid boundary conditions, initial curvature, electrostatic fringing field, finite electrodes, squeeze film damping, and distributed contact. The effects of uncertain parameters on the outputs of the model are discovered through response surface based uncertainty quantification techniques. The model accurately predicts the actuation voltages and switching times of these MEMS switches as well as the effects of uncertain parameters. The derived model is widely applicable and accuratly reproduces the results of other models in the literature. Future researchers will be able to rapidly iterate designs and accurately understand the behavior of these switches.
A model of Barchan dunes including lateral shear stress.
Schwämmle, V; Herrmann, H J
2005-01-01
Barchan dunes are found where sand availability is low and wind direction quite constant. The two dimensional shear stress of the wind field and the sand movement by saltation and avalanches over a barchan dune are simulated. The model with one dimensional shear stress is extended including surface diffusion and lateral shear stress. The resulting final shape is compared to the results of the model with a one dimensional shear stress and confirmed by comparison to measurements. We found agreement and improvements with respect to the model with one dimensional shear stress. Additionally, a characteristic edge at the center of the windward side is discovered which is also observed for big barchans. Diffusion effects reduce this effect for small dunes. PMID:15688141
A comparison of models for supernova remnants including cosmic rays
NASA Astrophysics Data System (ADS)
Kang, Hyesung; Drury, L. O'C.
1992-11-01
A simplified model which can follow the dynamical evolution of a supernova remnant including the acceleration of cosmic rays without carrying out full numerical simulations has been proposed by Drury, Markiewicz, & Voelk in 1989. To explore the accuracy and the merits of using such a model, we have recalculated with the simplified code the evolution of the supernova remnants considered in Jones & Kang, in which more detailed and accurate numerical simulations were done using a full hydrodynamic code based on the two-fluid approximation. For the total energy transferred to cosmic rays the two codes are in good agreement, the acceleration efficiency being the same within a factor of 2 or so. The dependence of the results of the two codes on the closure parameters for the two-fluid approximation is also qualitatively similar. The agreement is somewhat degraded in those cases where the shock is smoothed out by the cosmic rays.
A Prediction Model for Chronic Kidney Disease Includes Periodontal Disease
Fisher, Monica A.; Taylor, George W.
2009-01-01
Background An estimated 75% of the seven million Americans with moderate-to-severe chronic kidney disease are undiagnosed. Improved prediction models to identify high-risk subgroups for chronic kidney disease enhance the ability of health care providers to prevent or delay serious sequelae, including kidney failure, cardiovascular disease, and premature death. Methods We identified 11,955 adults ≥18 years of age in the Third National Health and Nutrition Examination Survey. Chronic kidney disease was defined as an estimated glomerular filtration rate of 15 to 59 ml/minute/1.73 m2. High-risk subgroups for chronic kidney disease were identified by estimating the individual probability using β coefficients from the model of traditional and non-traditional risk factors. To evaluate this model, we performed standard diagnostic analyses of sensitivity, specificity, positive predictive value, and negative predictive value using 5%, 10%, 15%, and 20% probability cutoff points. Results The estimated probability of chronic kidney disease ranged from virtually no probability (0%) for an individual with none of the 12 risk factors to very high probability (98%) for an older, non-Hispanic white edentulous former smoker, with diabetes ≥10 years, hypertension, macroalbuminuria, high cholesterol, low high-density lipoprotein, high C-reactive protein, lower income, and who was hospitalized in the past year. Evaluation of this model using an estimated 5% probability cutoff point resulted in 86% sensitivity, 85% specificity, 18% positive predictive value, and 99% negative predictive value. Conclusion This United States population–based study suggested the importance of considering multiple risk factors, including periodontal status, because this improves the identification of individuals at high risk for chronic kidney disease and may ultimately reduce its burden. PMID:19228085
NASA Astrophysics Data System (ADS)
Stravs, L.; Brilly, M.
2009-04-01
Good and accurate long-term low flow forecasting is important in the fields of sustainable water management, water rights, water supply management, industrial use of freshwater, optimization of the reservoir operations for the production of electric energy and other water-related disciplines. Today, low flow forecasting is usually performed as an integrated part of calibrated rainfall-runoff models, but in our research we developed two types of simple empirical 7-day ahead low flow forecasting models by using the M5 machine learning method for the generation of regression and model trees. Development of the first type of models was based solely on the application of the M5 machine learning method (1-, 2-, 3-, 4-, 5-, 6-and 7-day lead time low flow forecasting model trees were developed from using only past flow data and then combined to produce 7-day ahead forecast curve), while the development of the other type of models included the conceptual knowledge of linear reservoir recession functions AND application of the M5 machine learning method (we modelled the streamflow recession coefficient k as a function of the flow rate at which the 7-day low flow forecast is made and the decrease in the flow rate from the previous day). Both types of 7-day ahead low flow forecasting models were developed by using the same type and amount of data and were built for the Podhom gauging station on the Radovna River and the Medvode gauging station on the Sora River (both are Slovenian tributaries of the Sava River, which itself is a Danube River tributary). The results were compared and tested both visually and numerically.
A constitutive model for the forces of a magnetic bearing including eddy currents
NASA Technical Reports Server (NTRS)
Taylor, D. L.; Hebbale, K. V.
1993-01-01
A multiple magnet bearing can be developed from N individual electromagnets. The constitutive relationships for a single magnet in such a bearing is presented. Analytical expressions are developed for a magnet with poles arranged circumferencially. Maxwell's field equations are used so the model easily includes the effects of induced eddy currents due to the rotation of the journal. Eddy currents must be included in any dynamic model because they are the only speed dependent parameter and may lead to a critical speed for the bearing. The model is applicable to bearings using attraction or repulsion.
Kinetic models of gene expression including non-coding RNAs
NASA Astrophysics Data System (ADS)
Zhdanov, Vladimir P.
2011-03-01
In cells, genes are transcribed into mRNAs, and the latter are translated into proteins. Due to the feedbacks between these processes, the kinetics of gene expression may be complex even in the simplest genetic networks. The corresponding models have already been reviewed in the literature. A new avenue in this field is related to the recognition that the conventional scenario of gene expression is fully applicable only to prokaryotes whose genomes consist of tightly packed protein-coding sequences. In eukaryotic cells, in contrast, such sequences are relatively rare, and the rest of the genome includes numerous transcript units representing non-coding RNAs (ncRNAs). During the past decade, it has become clear that such RNAs play a crucial role in gene expression and accordingly influence a multitude of cellular processes both in the normal state and during diseases. The numerous biological functions of ncRNAs are based primarily on their abilities to silence genes via pairing with a target mRNA and subsequently preventing its translation or facilitating degradation of the mRNA-ncRNA complex. Many other abilities of ncRNAs have been discovered as well. Our review is focused on the available kinetic models describing the mRNA, ncRNA and protein interplay. In particular, we systematically present the simplest models without kinetic feedbacks, models containing feedbacks and predicting bistability and oscillations in simple genetic networks, and models describing the effect of ncRNAs on complex genetic networks. Mathematically, the presentation is based primarily on temporal mean-field kinetic equations. The stochastic and spatio-temporal effects are also briefly discussed.
Progress Towards an LES Wall Model Including Unresolved Roughness
NASA Astrophysics Data System (ADS)
Craft, Kyle; Redman, Andrew; Aikens, Kurt
2015-11-01
Wall models used in large eddy simulations (LES) are often based on theories for hydraulically smooth walls. While this is reasonable for many applications, there are also many where the impact of surface roughness is important. A previously developed wall model has been used primarily for jet engine aeroacoustics. However, jet simulations have not accurately captured thick initial shear layers found in some experimental data. This may partly be due to nozzle wall roughness used in the experiments to promote turbulent boundary layers. As a result, the wall model is extended to include the effects of unresolved wall roughness through appropriate alterations to the log-law. The methodology is tested for incompressible flat plate boundary layers with different surface roughness. Correct trends are noted for the impact of surface roughness on the velocity profile. However, velocity deficit profiles and the Reynolds stresses do not collapse as well as expected. Possible reasons for the discrepancies as well as future work will be presented. This work used the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by National Science Foundation grant number ACI-1053575. Computational resources on TACC Stampede were provided under XSEDE allocation ENG150001.
Development of an Aeroelastic Analysis Including a Viscous Flow Model
NASA Technical Reports Server (NTRS)
Keith, Theo G., Jr.; Bakhle, Milind A.
2001-01-01
Under this grant, Version 4 of the three-dimensional Navier-Stokes aeroelastic code (TURBO-AE) has been developed and verified. The TURBO-AE Version 4 aeroelastic code allows flutter calculations for a fan, compressor, or turbine blade row. This code models a vibrating three-dimensional bladed disk configuration and the associated unsteady flow (including shocks, and viscous effects) to calculate the aeroelastic instability using a work-per-cycle approach. Phase-lagged (time-shift) periodic boundary conditions are used to model the phase lag between adjacent vibrating blades. The direct-store approach is used for this purpose to reduce the computational domain to a single interblade passage. A disk storage option, implemented using direct access files, is available to reduce the large memory requirements of the direct-store approach. Other researchers have implemented 3D inlet/exit boundary conditions based on eigen-analysis. Appendix A: Aeroelastic calculations based on three-dimensional euler analysis. Appendix B: Unsteady aerodynamic modeling of blade vibration using the turbo-V3.1 code.
Polarimetric Models of Circumstellar Discs Including Aggregate Dust Grains
NASA Astrophysics Data System (ADS)
Mohan, Mahesh
output files and to apply a size distribution to the data. The second circumstellar disc investigated is the debris disc of the M dwarf star AU Mic. The disc was modelled, using the radiative transfer code Hyperion, based on F606W (HST) and JHK0-band (Keck II) scattered light observations and F606Wband polarized light observations. Initially, the disc is modelled as a two component structure using two grain types: compact silicate grains and porous dirty ice water. Both models are able to reproduce the observed SED and the F606W and H-band surface brightness profiles, but are unable to fit the observed F606W degree of polarization. Therefore, a more complex/realistic grain model was examined (ballistic aggregate particles). In addition, recent millimetre observations suggest the existence of a planetesimal belt < 3 AU from the central star. This belt is included in the BAM2 model and was successful in fitting the observed SED, F606W and H-band surface brightness and F606W polarization. These results demonstrate the limitations of spherical grain models and indicate the importance of modelling more realistic dust grains.
A model for including thermal conduction in molecular dynamics simulations
NASA Technical Reports Server (NTRS)
Wu, Yue; Friauf, Robert J.
1989-01-01
A technique is introduced for including thermal conduction in molecular dynamics simulations for solids. A model is developed to allow energy flow between the computational cell and the bulk of the solid when periodic boundary conditions cannot be used. Thermal conduction is achieved by scaling the velocities of atoms in a transitional boundary layer. The scaling factor is obtained from the thermal diffusivity, and the results show good agreement with the solution for a continuous medium at long times. The effects of different temperature and size of the system, and of variations in strength parameter, atomic mass, and thermal diffusivity were investigated. In all cases, no significant change in simulation results has been found.
Configuration based Collisional-Radiative Model including configuration interaction
NASA Astrophysics Data System (ADS)
Busquet, Michel
2007-11-01
Atomic levels mixing through Configuration Interaction (CI) yields important effects. It transfers oscillator strengthes from allowed lines to forbidden lines, and produces strong shift and broadening of line arrays, although the total emissivity is almost insensitive to CI, being proportional to the average wave number. However for hi Z material, like Xe or Sn (potential xuv-ray source for micro-lithography), a non-LTE calculation accounting for all relevant levels wiill be untractable with billions of states. The model we constructed, CAVCRM (caf'e-crème), is a non-LTE C.R.M. where states are configurations but it includes C.I. to give full richness of spectral quantities, using the latest version of the HULLAC-v9 suite of codes and our newly developped algorithm for large set of states with as many as 50,000 states [1]. [1] M.Klapisch et al, this conference
Modeling potentiometric measurements in topological insulators including parallel channels
NASA Astrophysics Data System (ADS)
Hong, Seokmin; Diep, Vinh; Datta, Supriyo; Chen, Yong P.
2012-08-01
The discovery of spin-polarized states at the surface of three-dimensional topological insulators (TI) like Bi2Te3 and Bi2Se3 motivates intense interests in possible electrical measurements demonstrating unique signatures of these unusual states. Here we show that a three-terminal potentiometric set-up can be used to probe them by measuring the voltage change of a detecting magnet upon reversing its magnetization. We present numerical results using a nonequilibrium Green's function (NEGF)-based model to show the corresponding signal quantitatively in various transport regimes. We then provide an analytical expression for the resistance (the measured voltage difference divided by an applied current) that agrees with NEGF results well in both ballistic and diffusive limits. This expression is applicable to TI surface states, two-dimensional electrons with Rashba spin-split bands, and any combination of multiple channels, including bulk parallel states in TI, which makes it useful in analyzing experimental results.
A new solar cycle model including meridional circulation
NASA Technical Reports Server (NTRS)
Wang, Y.-M.; Sheeley, N. R., Jr.; Nash, A. G.
1991-01-01
A kinematic model is presented for the solar cycle which includes not only the transport of magnetic flux by supergranular diffusion and a poleward bulk flow at the sun's surface, but also the effects of turbulent diffusion and an equatorward 'return flow' beneath the surface. As in the earlier models of Babcock and Leighton, the rotational shearing of a subsurface poloidal field generates toroidal flux that erupts at the surface in the form of bipolar magnetic regions. However, such eruptions do not result in any net loss of toroidal flux from the sun (as assumed by Babcock and Leighton); instead, the large-scale toroidal field is destroyed both by 'unwinding' as the local poloidal field reverses its polarity, and by diffusion as the toroidal flux is transported equatorward by the subsurface flow and merged with its opposite hemisphere counterpart. The inclusion of meridional circulation allows stable oscillations of the magnetic field, accompanied by the equatorward progression of flux eruptions, to be achieved even in the absence of a radial gradient in the angular velocity. An illustrative case in which a subsurface flow speed of order 1 m/s and subsurface diffusion rate of order 10 sq km/s yield 22-yr oscillations in qualitative agreement with observations.
Goldilocks models of higher-dimensional inflation (including modulus stabilization)
NASA Astrophysics Data System (ADS)
Burgess, C. P.; Enns, Jared J. H.; Hayman, Peter; Patil, Subodh P.
2016-08-01
We explore the mechanics of inflation within simplified extra-dimensional models involving an inflaton interacting with the Einstein-Maxwell system in two extra dimensions. The models are Goldilocks-like inasmuch as they are just complicated enough to include a mechanism to stabilize the extra-dimensional size (or modulus), yet simple enough to solve explicitly the full extra-dimensional field equations using only simple tools. The solutions are not restricted to the effective 4D regime with H ll mKK (the latter referring to the characteristic mass splitting of the Kaluza-Klein excitations) because the full extra-dimensional Einstein equations are solved. This allows an exploration of inflationary physics in a controlled calculational regime away from the usual four-dimensional lamp-post. The inclusion of modulus stabilization is important because experience with string models teaches that this is usually what makes models fail: stabilization energies easily dominate the shallow potentials required by slow roll and so open up directions to evolve that are steeper than those of the putative inflationary direction. We explore (numerically and analytically) three representative kinds of inflationary scenarios within this simple setup. In one the radion is trapped in an inflaton-dependent local minimum whose non-zero energy drives inflation. Inflation ends as this energy relaxes to zero when the inflaton finds its own minimum. The other two involve power-law scaling solutions during inflation. One of these is a dynamical attractor whose features are relatively insensitive to initial conditions but whose slow-roll parameters cannot be arbitrarily small; the other is not an attractor but can roll much more slowly, until eventually transitioning to the attractor. The scaling solutions can satisfy H > mKK, but when they do standard 4D fluctuation calculations need not apply. When in a 4D regime the solutions predict η simeq 0 and so r simeq 0.11 when ns simeq 0.96 and so
Energy loss in a partonic transport model including bremsstrahlung processes
Fochler, Oliver; Greiner, Carsten; Xu Zhe
2010-08-15
A detailed investigation of the energy loss of gluons that traverse a thermal gluonic medium simulated within the perturbative QCD-based transport model BAMPS (a Boltzmann approach to multiparton scatterings) is presented in the first part of this work. For simplicity the medium response is neglected in these calculations. The energy loss from purely elastic interactions is compared with the case where radiative processes are consistently included based on the matrix element by Gunion and Bertsch. From this comparison, gluon multiplication processes gg{yields}ggg are found to be the dominant source of energy loss within the approach employed here. The consequences for the quenching of gluons with high transverse momentum in fully dynamic simulations of Au+Au collisions at the BNL Relativistic Heavy Ion Collider (RHIC) energy of {radical}(s)=200A GeV are discussed in the second major part of this work. The results for central collisions as discussed in a previous publication are revisited, and first results on the nuclear modification factor R{sub AA} for noncentral Au+Au collisions are presented. They show a decreased quenching compared to central collisions while retaining the same shape. The investigation of the elliptic flow v{sub 2} is extended up to nonthermal transverse momenta of 10 GeV, exhibiting a maximum v{sub 2} at roughly 4 to 5 GeV and a subsequent decrease. Finally the sensitivity of the aforementioned results on the specific implementation of the effective modeling of the Landau-Pomeranchuk-Migdal (LPM) effect via a formation-time-based cutoff is explored.
Modelers and policymakers : improving the relationships.
Karas, Thomas H.
2004-06-01
On April 22 and 23, 2004, a diverse group of 14 policymakers, modelers, analysts, and scholars met with some 22 members of the Sandia National Laboratories staff to explores ways in which the relationships between modelers and policymakers in the energy and environment fields (with an emphasis on energy) could be made more productive for both. This report is not a transcription of that workshop, but draws very heavily on its proceedings. It first describes the concept of modeling, the varying ways in which models are used to support policymaking, and the institutional context for those uses. It then proposes that the goal of modelers and policymakers should be a relationship of mutual trust, built on a foundation of communication, supported by the twin pillars of policy relevance and technical credibility. The report suggests 20 guidelines to help modelers improve the relationship, followed by 10 guidelines to help policymakers toward the same goal.
Evaluation of annual, global seismicity forecasts, including ensemble models
NASA Astrophysics Data System (ADS)
Taroni, Matteo; Zechar, Jeremy; Marzocchi, Warner
2013-04-01
In 2009, the Collaboratory for the Study of the Earthquake Predictability (CSEP) initiated a prototype global earthquake forecast experiment. Three models participated in this experiment for 2009, 2010 and 2011—each model forecast the number of earthquakes above magnitude 6 in 1x1 degree cells that span the globe. Here we use likelihood-based metrics to evaluate the consistency of the forecasts with the observed seismicity. We compare model performance with statistical tests and a new method based on the peer-to-peer gambling score. The results of the comparisons are used to build ensemble models that are a weighted combination of the individual models. Notably, in these experiments the ensemble model always performs significantly better than the single best-performing model. Our results indicate the following: i) time-varying forecasts, if not updated after each major shock, may not provide significant advantages with respect to time-invariant models in 1-year forecast experiments; ii) the spatial distribution seems to be the most important feature to characterize the different forecasting performances of the models; iii) the interpretation of consistency tests may be misleading because some good models may be rejected while trivial models may pass consistency tests; iv) a proper ensemble modeling seems to be a valuable procedure to get the best performing model for practical purposes.
Probabilistic constitutive relationships for cyclic material strength models
NASA Technical Reports Server (NTRS)
Boyce, L.; Chamis, C. C.
1988-01-01
A methodology is developed that provides a probabilistic treatment for the lifetime of structural components of aerospace propulsion systems subjected to fatigue. Material strength degradation models, based on primitive variables, include both a fatigue strength reduction model and a fatigue crack growth model. Probabilistic analysis is based on simulation, and both maximum entropy and maximum penalized likelihood methods are used for the generation of probability density functions. The resulting constitutive relationships are included in several computer programs.
Constitutive modelling of evolving flow anisotropy including distortional hardening
Pietryga, Michael P.; Vladimirov, Ivaylo N.; Reese, Stefanie
2011-05-04
The paper presents a new constitutive model for anisotropic metal plasticity that takes into account the expansion or contraction (isotropic hardening), translation (kinematic hardening) and change of shape (distortional hardening) of the yield surface. The experimentally observed region of high curvature ('nose') on the yield surface in the loading direction and flattened shape in the reverse loading direction are modelled here by means of the concept of directional distortional hardening. The modelling of directional distortional hardening is accomplished by means of an evolving fourth-order tensor. The applicability of the model is illustrated by fitting experimental subsequent yield surfaces at finite plastic deformation. Comparisons with test data for aluminium low and high work hardening alloys display a good agreement between the simulation results and the experimental data.
Phase relationship in three-phase composites which include a void phase
NASA Technical Reports Server (NTRS)
Price, H. L.; Nelson, J. B.
1976-01-01
The paper shows the relationship among polymer, particles, and voids in a three-phase composite and how some of the properties of a composite may be changed by changing the proportions of the phases. The three-phase composite is an aggregate of microspheres bonded together with a small amount of polymer which may not form a continuous matrix. The void space (third phase) is obtained by limiting the amount of polymer which is mixed with the microspheres. A ternary phase diagram is used to show the proportional relationship among the three phases, with each apex representing a volume fraction of unity for a constituent while the side opposite the apex represents a volume fraction of zero for that constituent. The vertical dimension represents some composite property such as density or strength. The effect of composition on composite properties is shown by plotting them on a binary phase diagram which represents a perpendicular plane coincident with the 0.60 volume fraction microsphere line.
Laminated core modeling under rotational excitations including eddy currents and hysteresis
Bottauscio, Oriano; Chiampi, Mario
2001-06-01
This article presents a numerical model for the electromagnetic analysis of hysteretic-laminated cores under rotational excitations. The computational approach is based on the finite element solution of a two-dimensional field magnetic problem in a homogeneous structure, where the skin effect due to macroscopic eddy currents in the lamination depth is included through a generalized dynamic constitutive relationship between B and H. The proposed model, after validation, is applied to the analysis of a laminated disk, evaluating the effects of the supply frequency and distorsion on power losses and B{endash}H loops. {copyright} 2001 American Institute of Physics.
NASA Trapezoidal Wing Computations Including Transition and Advanced Turbulence Modeling
NASA Technical Reports Server (NTRS)
Rumsey, C. L.; Lee-Rausch, E. M.
2012-01-01
Flow about the NASA Trapezoidal Wing is computed with several turbulence models by using grids from the first High Lift Prediction Workshop in an effort to advance understanding of computational fluid dynamics modeling for this type of flowfield. Transition is accounted for in many of the computations. In particular, a recently-developed 4-equation transition model is utilized and works well overall. Accounting for transition tends to increase lift and decrease moment, which improves the agreement with experiment. Upper surface flap separation is reduced, and agreement with experimental surface pressures and velocity profiles is improved. The predicted shape of wakes from upstream elements is strongly influenced by grid resolution in regions above the main and flap elements. Turbulence model enhancements to account for rotation and curvature have the general effect of increasing lift and improving the resolution of the wing tip vortex as it convects downstream. However, none of the models improve the prediction of surface pressures near the wing tip, where more grid resolution is needed.
Modeling Insurgent Dynamics Including Heterogeneity. A Statistical Physics Approach
NASA Astrophysics Data System (ADS)
Johnson, Neil F.; Manrique, Pedro; Hui, Pak Ming
2013-05-01
Despite the myriad complexities inherent in human conflict, a common pattern has been identified across a wide range of modern insurgencies and terrorist campaigns involving the severity of individual events—namely an approximate power-law x - α with exponent α≈2.5. We recently proposed a simple toy model to explain this finding, built around the reported loose and transient nature of operational cells of insurgents or terrorists. Although it reproduces the 2.5 power-law, this toy model assumes every actor is identical. Here we generalize this toy model to incorporate individual heterogeneity while retaining the model's analytic solvability. In the case of kinship or team rules guiding the cell dynamics, we find that this 2.5 analytic result persists—however an interesting new phase transition emerges whereby this cell distribution undergoes a transition to a phase in which the individuals become isolated and hence all the cells have spontaneously disintegrated. Apart from extending our understanding of the empirical 2.5 result for insurgencies and terrorism, this work illustrates how other statistical physics models of human grouping might usefully be generalized in order to explore the effect of diverse human social, cultural or behavioral traits.
Mechanical Modeling of Foods Including Fracture and Simulation of Food Compression
NASA Astrophysics Data System (ADS)
Morimoto, Masamichi; Mizunuma, Hiroshi; Sonomura, Mitsuhiro; Kohyama, Kaoru; Ogoshi, Hiro
2008-07-01
The purposes of this research are to simulate the swallowing of foods, and to investigate the relationship between the rheological properties of foods and the swallowing. Here we proposed the mechanical modeling of foods, and simulated the compression test using the finite element method. A linear plasticity model was applied as the rheological model of the foods, and two types of computational elements were used to simulate the fracture behavior. The compression tests with a wedged plunger were simulated for tofu, banana, and biscuit, and were compared with the experimental results. Other than the homogeneous food model, the simulations were conducted for the multi-layer models. Reasonable agreements on the behaviors of compression and fracture were obtained between the simulations and the experiments including the reaction forces on the plunger.
Digital elevation model visibility including Earth's curvature and atmosphere refraction
NASA Astrophysics Data System (ADS)
Santossilva, Ewerton; Vieiradias, Luiz Alberto
1990-03-01
There are some instances in which the Earth's curvature and the atmospheric refraction, optical or electronic, are important factors when digital elevation models are used for visibility calculations. This work deals with this subject, suggesting a practical approach to solve this problem. Some examples, from real terrain data, are presented. The equipment used was an IBM-PC like computer with a SITIM graphic card.
Modeling shelter-in-place including sorption on indoor surfaces
Chan, Wanyu R.; Price, Phillip N.; Gadgil, Ashok J.; Nazaroff, William W.; Loosmore, Gwen A.; Sugiyama, Gayle A.
2003-11-01
Intentional or accidental large-scale airborne toxic releases (e.g. terrorist attacks or industrial accidents) can cause severe harm to nearby communities. As part of an emergency response plan, shelter-in-place (SIP) can be an effective response option, especially when evacuation is infeasible. Reasonably tight building envelopes provide some protection against exposure to peak concentrations when toxic release passes over an area. They also provide some protection in terms of cumulative exposure, if SIP is terminated promptly after the outdoor plume has passed. The purpose of this work is to quantify the level of protection offered by existing houses, and the importance of sorption/desorption to and from surfaces on the effectiveness of SIP. We examined a hypothetical chlorine gas release scenario simulated by the National Atmospheric Release Advisory Center (NARAC). We used a standard infiltration model to calculate the distribution of time dependent infiltration rates within each census tract. Large variation in the air tightness of dwellings makes some houses more protective than others. Considering only the median air tightness, model results showed that if sheltered indoors, the total population intake of non-sorbing toxic gas is only 50% of the outdoor level 4 hours from the start of the release. Based on a sorption/desorption model by Karlsson and Huber (1996), we calculated that the sorption process would further lower the total intake of the population by an additional 50%. The potential benefit of SIP can be considerably higher if the comparison is made in terms of health effects because of the non-linear acute effect dose-response curve of many chemical warfare agents and toxic industrial substances.
Comparison of Joint Modeling Approaches Including Eulerian Sliding Interfaces
Lomov, I; Antoun, T; Vorobiev, O
2009-12-16
Accurate representation of discontinuities such as joints and faults is a key ingredient for high fidelity modeling of shock propagation in geologic media. The following study was done to improve treatment of discontinuities (joints) in the Eulerian hydrocode GEODYN (Lomov and Liu 2005). Lagrangian methods with conforming meshes and explicit inclusion of joints in the geologic model are well suited for such an analysis. Unfortunately, current meshing tools are unable to automatically generate adequate hexahedral meshes for large numbers of irregular polyhedra. Another concern is that joint stiffness in such explicit computations requires significantly reduced time steps, with negative implications for both the efficiency and quality of the numerical solution. An alternative approach is to use non-conforming meshes and embed joint information into regular computational elements. However, once slip displacement on the joints become comparable to the zone size, Lagrangian (even non-conforming) meshes could suffer from tangling and decreased time step problems. The use of non-conforming meshes in an Eulerian solver may alleviate these difficulties and provide a viable numerical approach for modeling the effects of faults on the dynamic response of geologic materials. We studied shock propagation in jointed/faulted media using a Lagrangian and two Eulerian approaches. To investigate the accuracy of this joint treatment the GEODYN calculations have been compared with results from the Lagrangian code GEODYN-L which uses an explicit treatment of joints via common plane contact. We explore two approaches to joint treatment in the code, one for joints with finite thickness and the other for tight joints. In all cases the sliding interfaces are tracked explicitly without homogenization or blending the joint and block response into an average response. In general, rock joints will introduce an increase in normal compliance in addition to a reduction in shear strength. In the
A Model for Axial Magnetic Bearings Including Eddy Currents
NASA Technical Reports Server (NTRS)
Kucera, Ladislav; Ahrens, Markus
1996-01-01
This paper presents an analytical method of modelling eddy currents inside axial bearings. The problem is solved by dividing an axial bearing into elementary geometric forms, solving the Maxwell equations for these simplified geometries, defining boundary conditions and combining the geometries. The final result is an analytical solution for the flux, from which the impedance and the force of an axial bearing can be derived. Several impedance measurements have shown that the analytical solution can fit the measured data with a precision of approximately 5%.
Finite difference modeling of rotor flows including wake effects
NASA Technical Reports Server (NTRS)
Caradonna, F. X.; Desopper, A.; Tung, C.
1982-01-01
Rotary wing finite difference methods are investigated. The main concern is the specification of boundary conditions to properly account for the effect of the wake on the blade. Examples are given of an approach where wake effects are introduced by specifying an equivalent angle of attack. An alternate approach is also given where discrete vortices are introduced into the finite difference grid. The resulting computations of hovering and high advance ratio cases compare well with experiment. Some consideration is also given to the modeling of low to moderate advance ratio flows.
Relationship of sea level muon charge ratio to primary composition including nuclear target effects
NASA Technical Reports Server (NTRS)
Goned, A.; Shalaby, M.; Salem, A. M.; Roushdy, M.
1985-01-01
The discrepancy between the muon charge ratio observed at low energies and that calculated using pp data is removed by including nuclear target effects. Calculations at high energies show that the primary iron spectrum is expected to change slope from 2 to 2.2 to 2.4 to 2.5 for energies approx. 4 x 10 to the 3 GeV/nucleon if scaling features continue to the highest energies.
A Generic Model of Dyadic Social Relationships
Favre, Maroussia; Sornette, Didier
2015-01-01
We introduce a model of dyadic social interactions and establish its correspondence with relational models theory (RMT), a theory of human social relationships. RMT posits four elementary models of relationships governing human interactions, singly or in combination: Communal Sharing, Authority Ranking, Equality Matching, and Market Pricing. To these are added the limiting cases of asocial and null interactions, whereby people do not coordinate with reference to any shared principle. Our model is rooted in the observation that each individual in a dyadic interaction can do either the same thing as the other individual, a different thing or nothing at all. To represent these three possibilities, we consider two individuals that can each act in one out of three ways toward the other: perform a social action X or Y, or alternatively do nothing. We demonstrate that the relationships generated by this model aggregate into six exhaustive and disjoint categories. We propose that four of these categories match the four relational models, while the remaining two correspond to the asocial and null interactions defined in RMT. We generalize our results to the presence of N social actions. We infer that the four relational models form an exhaustive set of all possible dyadic relationships based on social coordination. Hence, we contribute to RMT by offering an answer to the question of why there could exist just four relational models. In addition, we discuss how to use our representation to analyze data sets of dyadic social interactions, and how social actions may be valued and matched by the agents. PMID:25826403
A generic model of dyadic social relationships.
Favre, Maroussia; Sornette, Didier
2015-01-01
We introduce a model of dyadic social interactions and establish its correspondence with relational models theory (RMT), a theory of human social relationships. RMT posits four elementary models of relationships governing human interactions, singly or in combination: Communal Sharing, Authority Ranking, Equality Matching, and Market Pricing. To these are added the limiting cases of asocial and null interactions, whereby people do not coordinate with reference to any shared principle. Our model is rooted in the observation that each individual in a dyadic interaction can do either the same thing as the other individual, a different thing or nothing at all. To represent these three possibilities, we consider two individuals that can each act in one out of three ways toward the other: perform a social action X or Y, or alternatively do nothing. We demonstrate that the relationships generated by this model aggregate into six exhaustive and disjoint categories. We propose that four of these categories match the four relational models, while the remaining two correspond to the asocial and null interactions defined in RMT. We generalize our results to the presence of N social actions. We infer that the four relational models form an exhaustive set of all possible dyadic relationships based on social coordination. Hence, we contribute to RMT by offering an answer to the question of why there could exist just four relational models. In addition, we discuss how to use our representation to analyze data sets of dyadic social interactions, and how social actions may be valued and matched by the agents. PMID:25826403
Global model including multistep ionizations in helium plasmas
NASA Astrophysics Data System (ADS)
Oh, Seungju; Lee, Hyo-Chang; Chung, Chin-Wook
2015-09-01
Particle and power balance equations including stepwise ionizations are derived and solved in helium plasma. In the balance equations, two metastable states (23S1 in singlet and 21S1 triplet) are considered and followings are obtained. The plasma density linearly increases and electron temperature is relatively in constant value against the absorbed power. It is also found that the contribution to multi-step ionization respect to the single-step ionization is in the range of 8% - 23%, as the gas pressure increases from 10 mTorr to 100 mTorr. There has little variation in the collisional energy loss per electron-ion pair created (Ec). These results indicate that the stepwise ionizations are the minor effect in case of the helium plasma compared to argon plasma. This is because that helium gas has very small collisional cross sections and higher inelastic collision threshold energy resulting in the little variations for the collisional energy loss per electron-ion pair created.
Building Customer Relationships: A Model for Vocational Education and Training Delivery.
ERIC Educational Resources Information Center
Jarratt, Denise G.; Murphy, Tom; Lowry, Diannah
1997-01-01
Review of the theory of relational marketing and interviews with training providers identified a training delivery model that includes elements of trust and commitment, investment by relationship partners, and knowledge exchange, supporting relationship longevity. (SK)
Supervisor's Interactive Model of Organizational Relationships
ERIC Educational Resources Information Center
O'Reilly, Frances L.; Matt, John; McCaw, William P.
2014-01-01
The Supervisor's Interactive Model of Organizational Relationships (SIMOR) integrates two models addressed in the leadership literature and then highlights the importance of relationships. The Supervisor's Interactive Model of Organizational Relationships combines the modified Hersey and Blanchard model of situational leadership, the…
A Probabilistic Model of Phonological Relationships from Contrast to Allophony
ERIC Educational Resources Information Center
Hall, Kathleen Currie
2009-01-01
This dissertation proposes a model of phonological relationships, the Probabilistic Phonological Relationship Model (PPRM), that quantifies how predictably distributed two sounds in a relationship are. It builds on a core premise of traditional phonological analysis, that the ability to define phonological relationships such as contrast and…
A Mercury orientation model including non-zero obliquity and librations
NASA Astrophysics Data System (ADS)
Margot, Jean-Luc
2009-12-01
Planetary orientation models describe the orientation of the spin axis and prime meridian of planets in inertial space as a function of time. The models are required for the planning and execution of Earth-based or space-based observational work, e.g. to compute viewing geometries and to tie observations to planetary coordinate systems. The current orientation model for Mercury is inadequate because it uses an obsolete spin orientation, neglects oscillations in the spin rate called longitude librations, and relies on a prime meridian that no longer reflects its intended dynamical significance. These effects result in positional errors on the surface of ~1.5 km in latitude and up to several km in longitude, about two orders of magnitude larger than the finest image resolution currently attainable. Here we present an updated orientation model which incorporates modern values of the spin orientation, includes a formulation for longitude librations, and restores the dynamical significance to the prime meridian. We also use modern values of the orbit normal, spin axis orientation, and precession rates to quantify an important relationship between the obliquity and moment of inertia differences.
A simple model clarifies the complicated relationships of complex networks
NASA Astrophysics Data System (ADS)
Zheng, Bojin; Wu, Hongrun; Kuang, Li; Qin, Jun; Du, Wenhua; Wang, Jianmin; Li, Deyi
2014-08-01
Real-world networks such as the Internet and WWW have many common traits. Until now, hundreds of models were proposed to characterize these traits for understanding the networks. Because different models used very different mechanisms, it is widely believed that these traits origin from different causes. However, we find that a simple model based on optimisation can produce many traits, including scale-free, small-world, ultra small-world, Delta-distribution, compact, fractal, regular and random networks. Moreover, by revising the proposed model, the community-structure networks are generated. By this model and the revised versions, the complicated relationships of complex networks are illustrated. The model brings a new universal perspective to the understanding of complex networks and provide a universal method to model complex networks from the viewpoint of optimisation.
A simple model clarifies the complicated relationships of complex networks
Zheng, Bojin; Wu, Hongrun; Kuang, Li; Qin, Jun; Du, Wenhua; Wang, Jianmin; Li, Deyi
2014-01-01
Real-world networks such as the Internet and WWW have many common traits. Until now, hundreds of models were proposed to characterize these traits for understanding the networks. Because different models used very different mechanisms, it is widely believed that these traits origin from different causes. However, we find that a simple model based on optimisation can produce many traits, including scale-free, small-world, ultra small-world, Delta-distribution, compact, fractal, regular and random networks. Moreover, by revising the proposed model, the community-structure networks are generated. By this model and the revised versions, the complicated relationships of complex networks are illustrated. The model brings a new universal perspective to the understanding of complex networks and provide a universal method to model complex networks from the viewpoint of optimisation. PMID:25160506
Modeling time-lagged reciprocal psychological empowerment-performance relationships.
Maynard, M Travis; Luciano, Margaret M; D'Innocenzo, Lauren; Mathieu, John E; Dean, Matthew D
2014-11-01
Employee psychological empowerment is widely accepted as a means for organizations to compete in increasingly dynamic environments. Previous empirical research and meta-analyses have demonstrated that employee psychological empowerment is positively related to several attitudinal and behavioral outcomes including job performance. While this research positions psychological empowerment as an antecedent influencing such outcomes, a close examination of the literature reveals that this relationship is primarily based on cross-sectional research. Notably, evidence supporting the presumed benefits of empowerment has failed to account for potential reciprocal relationships and endogeneity effects. Accordingly, using a multiwave, time-lagged design, we model reciprocal relationships between psychological empowerment and job performance using a sample of 441 nurses from 5 hospitals. Incorporating temporal effects in a staggered research design and using structural equation modeling techniques, our findings provide support for the conventional positive correlation between empowerment and subsequent performance. Moreover, accounting for the temporal stability of variables over time, we found support for empowerment levels as positive influences on subsequent changes in performance. Finally, we also found support for the reciprocal relationship, as performance levels were shown to relate positively to changes in empowerment over time. Theoretical and practical implications of the reciprocal psychological empowerment-performance relationships are discussed. (PsycINFO Database Record (c) 2014 APA, all rights reserved). PMID:25111249
Couple Infertility: From the Perspective of the Close-Relationship Model.
ERIC Educational Resources Information Center
Higgins, Barbara S.
1990-01-01
Presents Close-Relationship Model as comprehensive framework in which to examine interrelated nature of causes and effects of infertility on marital relationship. Includes these factors: physical and psychological characteristics of both partners; joint, couple characteristics; physical and social environment; and relationship itself. Discusses…
Similitude requirements and scaling relationships as applied to model testing
NASA Technical Reports Server (NTRS)
Wolowicz, C. H.; Brown, J. S., Jr.; Gilbert, W. P.
1979-01-01
The similitude requirements for the most general test conditions are presented. These similitude requirements are considered in relation to the scaling relationships, test technique, test conditions (including supersonic flow), and test objectives. Particular emphasis is placed on satisfying the various similitude requirements for incompressible and compressible flow conditions. For free flying models tests, the test velocities for incompressible flow are scaled from Froude number similitude requirements and those for compressible flow are scaled from Mach number similitude requirements. The limitations of various test techniques are indicated, with emphasis on the free flying model.
NASA Astrophysics Data System (ADS)
Mayes, M. A.; Wang, G.; Tang, G.; Xu, X.; Jagadamma, S.
2013-12-01
Carbon cycle models are traditionally parameterized with ad hoc soil pools, empirical decay constants and first-order decomposition as a function of substrate supply. Decomposition of vegetative and faunal inputs, however, involves enzymatically-facilitated depolymerization by the microbial community. Traditional soil models are calibrated to match existing distribution of soil carbon, but they are not parameterized to predict the response of soil carbon to climate change due to microbial community shifts or physiological changes, i.e., acclimation. As an example, we will show how the temperature sensitivity of carbon use efficiency can influence the decomposition of different substrates and affect the release of CO2 from soil organic matter. Acclimation to warmer conditions could also involve shifts in microbial community composition or function, e.g., fungi: bacteria ratio shift. Experimental data is needed to decide how to parameterize models to accommodate functional or compositional changes. We will explore documented cases of microbial acclimation to warming, discuss methods to include microbial acclimation in carbon cycle models, and explore the need for additional experimental data to validate the next generation of microbially-facilitated carbon cycle models.
NASA Technical Reports Server (NTRS)
Hambric, Stephen A.; Hanford, Amanda D.; Shepherd, Micah R.; Campbell, Robert L.; Smith, Edward C.
2010-01-01
A computational approach for simulating the effects of rolling element and journal bearings on the vibration and sound transmission through gearboxes has been demonstrated. The approach, using ARL/Penn State s CHAMP methodology, uses Component Mode Synthesis of housing and shafting modes computed using Finite Element (FE) models to allow for rapid adjustment of bearing impedances in gearbox models. The approach has been demonstrated on NASA GRC s test gearbox with three different bearing configurations: in the first condition, traditional rolling element (ball and roller) bearings were installed, and in the second and third conditions, the traditional bearings were replaced with journal and wave bearings (wave bearings are journal bearings with a multi-lobed wave pattern on the bearing surface). A methodology for computing the stiffnesses and damping in journal and wave bearings has been presented, and demonstrated for the journal and wave bearings used in the NASA GRC test gearbox. The FE model of the gearbox, along with the rolling element bearing coupling impedances, was analyzed to compute dynamic transfer functions between forces applied to the meshing gears and accelerations on the gearbox housing, including several locations near the bearings. A Boundary Element (BE) acoustic model was used to compute the sound radiated by the gearbox. Measurements of the Gear Mesh Frequency (GMF) tones were made by NASA GRC at several operational speeds for the rolling element and journal bearing gearbox configurations. Both the measurements and the CHAMP numerical model indicate that the journal bearings reduce vibration and noise for the second harmonic of the gear meshing tones, but show no clear benefit to using journal bearings to reduce the amplitudes of the fundamental gear meshing tones. Also, the numerical model shows that the gearbox vibrations and radiated sound are similar for journal and wave bearing configurations.
ERIC Educational Resources Information Center
Fanti, Kostas A.; Henrich, Christopher C.; Brookmeyer, Kathryn A.; Kuperminc, Gabriel P.
2008-01-01
The present study includes externalizing problems, internalizing problems, mother-adolescent relationship quality, and father-adolescent relationship quality in the same structural equation model and tests the longitudinal reciprocal association among all four variables over a 1-year period. A transactional model in which adolescents'…
Farrance, Ian; Frenkel, Robert
2014-01-01
The Guide to the Expression of Uncertainty in Measurement (usually referred to as the GUM) provides the basic framework for evaluating uncertainty in measurement. The GUM however does not always provide clearly identifiable procedures suitable for medical laboratory applications, particularly when internal quality control (IQC) is used to derive most of the uncertainty estimates. The GUM modelling approach requires advanced mathematical skills for many of its procedures, but Monte Carlo simulation (MCS) can be used as an alternative for many medical laboratory applications. In particular, calculations for determining how uncertainties in the input quantities to a functional relationship propagate through to the output can be accomplished using a readily available spreadsheet such as Microsoft Excel. The MCS procedure uses algorithmically generated pseudo-random numbers which are then forced to follow a prescribed probability distribution. When IQC data provide the uncertainty estimates the normal (Gaussian) distribution is generally considered appropriate, but MCS is by no means restricted to this particular case. With input variations simulated by random numbers, the functional relationship then provides the corresponding variations in the output in a manner which also provides its probability distribution. The MCS procedure thus provides output uncertainty estimates without the need for the differential equations associated with GUM modelling. The aim of this article is to demonstrate the ease with which Microsoft Excel (or a similar spreadsheet) can be used to provide an uncertainty estimate for measurands derived through a functional relationship. In addition, we also consider the relatively common situation where an empirically derived formula includes one or more ‘constants’, each of which has an empirically derived numerical value. Such empirically derived ‘constants’ must also have associated uncertainties which propagate through the functional
Validation of gyrokinetic modelling of light impurity transport including rotation in ASDEX Upgrade
NASA Astrophysics Data System (ADS)
Casson, F. J.; McDermott, R. M.; Angioni, C.; Camenen, Y.; Dux, R.; Fable, E.; Fischer, R.; Geiger, B.; Manas, P.; Menchero, L.; Tardini, G.; the ASDEX Upgrade Team
2013-06-01
Upgraded spectroscopic hardware and an improved impurity concentration calculation allow accurate determination of boron density in the ASDEX Upgrade tokamak. A database of boron measurements is compared to quasilinear and nonlinear gyrokinetic simulations including Coriolis and centrifugal rotational effects over a range of H-mode plasma regimes. The peaking of the measured boron profiles shows a strong anti-correlation with the plasma rotation gradient, via a relationship explained and reproduced by the theory. It is demonstrated that the rotodiffusive impurity flux driven by the rotation gradient is required for the modelling to reproduce the hollow boron profiles at higher rotation gradients. The nonlinear simulations validate the quasilinear approach, and, with the addition of perpendicular flow shear, demonstrate that each symmetry breaking mechanism that causes momentum transport also couples to rotodiffusion. At lower rotation gradients, the parallel compressive convection is required to match the most peaked boron profiles. The sensitivities of both datasets to possible errors is investigated, and quantitative agreement is found within the estimated uncertainties. The approach used can be considered a template for mitigating uncertainty in quantitative comparisons between simulation and experiment.
A Relationship-Building Model for the Web Retail Marketplace.
ERIC Educational Resources Information Center
Wang, Fang; Head, Milena; Archer, Norm
2000-01-01
Discusses the effects of the Web on marketing practices. Introduces the concept and theory of relationship marketing. The relationship network concept, which typically is only applied to the business-to-business market, is discussed within the business-to-consumer market, and a new relationship-building model for the Web marketplace is proposed.…
Modeling species-abundance relationships in multi-species collections
Peng, S.; Yin, Z.; Ren, H.; Guo, Q.
2003-01-01
Species-abundance relationship is one of the most fundamental aspects of community ecology. Since Motomura first developed the geometric series model to describe the feature of community structure, ecologists have developed many other models to fit the species-abundance data in communities. These models can be classified into empirical and theoretical ones, including (1) statistical models, i.e., negative binomial distribution (and its extension), log-series distribution (and its extension), geometric distribution, lognormal distribution, Poisson-lognormal distribution, (2) niche models, i.e., geometric series, broken stick, overlapping niche, particulate niche, random assortment, dominance pre-emption, dominance decay, random fraction, weighted random fraction, composite niche, Zipf or Zipf-Mandelbrot model, and (3) dynamic models describing community dynamics and restrictive function of environment on community. These models have different characteristics and fit species-abundance data in various communities or collections. Among them, log-series distribution, lognormal distribution, geometric series, and broken stick model have been most widely used.
NASA Astrophysics Data System (ADS)
Gabrielle, B.; Gagnaire, N.; Massad, R.; Prieur, V.; Python, Y.
2012-04-01
. Compared to the standard methodology currently used in LCA, based on fixed emissions for N2O, the use of model-derived estimates leads to a 10 to 40% reduction in the overall life-cycle GHG emissions of biofuels. This emphasizes the importance of regional factors in the relationship between agricultural inputs and emissions (altogether with biomass yields) in the outcome of LCAs. When excluding indirect land-use change effects (iLUC), 1st generation pathways enabled GHG savings ranging from 50 to 73% compared to fossile-derived equivalents, while this figure reached 88% for 2nd generation bioethanol from miscanthus. Including iLUC reduced the savings to less than 5% for bio-diesel from rapeseed, 10 to 45% for 1st generation bioethanol and to 60% for miscanthus. These figures apply to the year 2007 and should be extended to a larger number of years, but the magnitude of N2O emissions was similar between 2007, 2008 and 2009 over the Ile de France region.
The Lag Model, a Turbulence Model for Wall Bounded Flows Including Separation
NASA Technical Reports Server (NTRS)
Olsen, Michael E.; Coakley, Thomas J.; Kwak, Dochan (Technical Monitor)
2001-01-01
A new class of turbulence model is described for wall bounded, high Reynolds number flows. A specific turbulence model is demonstrated, with results for favorable and adverse pressure gradient flowfields. Separation predictions are as good or better than either Spalart Almaras or SST models, do not require specification of wall distance, and have similar or reduced computational effort compared with these models.
Data Base Design Using Entity-Relationship Models.
ERIC Educational Resources Information Center
Davis, Kathi Hogshead
1983-01-01
The entity-relationship (ER) approach to database design is defined, and a specific example of an ER model (personnel-payroll) is examined. The requirements for converting ER models into specific database management systems are discussed. (Author/MSE)
Constitutive Relationships and Models in Continuum Theories of Multiphase Flows. [conferences
NASA Technical Reports Server (NTRS)
Decker, Rand (Editor)
1989-01-01
In April, 1989, a workshop on constitutive relationships and models in continuum theories of multiphase flows was held at NASA's Marshall Space Flight Center. Topics of constitutive relationships for the partial or per phase stresses, including the concept of solid phase pressure are discussed. Models used for the exchange of mass, momentum, and energy between the phases in a multiphase flow are also discussed. The program, abstracts, and texts of the presentations from the workshop are included.
Draft: Modeling Two-Phase Flow in Porous Media Including Fluid-Fluid Interfacial Area
Crandall, Dustin; Niessner, Jennifer; Hassanizadeh, S Majid
2008-01-01
We present a new numerical model for macro-scale twophase flow in porous media which is based on a physically consistent theory of multi-phase flow.The standard approach for modeling the flow of two fluid phases in a porous medium consists of a continuity equation for each phase, an extended form of Darcy’s law as well as constitutive relationships for relative permeability and capillary pressure. This approach is known to have a number of important shortcomings and, in particular, it does not account for the presence and role of fluid - fluid interfaces. An alternative is to use an extended model which is founded on thermodynamic principles and is physically consistent. In addition to the standard equations, the model uses a balance equation for specific interfacial area. The constitutive relationship for capillary pressure involves not only saturation, but also specific interfacial area. We show how parameters can be obtained for the alternative model using experimental data from a new kind of flow cell and present results of a numerical modeling study
Modeling rainfall-runoff relationship using multivariate GARCH model
NASA Astrophysics Data System (ADS)
Modarres, R.; Ouarda, T. B. M. J.
2013-08-01
The traditional hydrologic time series approaches are used for modeling, simulating and forecasting conditional mean of hydrologic variables but neglect their time varying variance or the second order moment. This paper introduces the multivariate Generalized Autoregressive Conditional Heteroscedasticity (MGARCH) modeling approach to show how the variance-covariance relationship between hydrologic variables varies in time. These approaches are also useful to estimate the dynamic conditional correlation between hydrologic variables. To illustrate the novelty and usefulness of MGARCH models in hydrology, two major types of MGARCH models, the bivariate diagonal VECH and constant conditional correlation (CCC) models are applied to show the variance-covariance structure and cdynamic correlation in a rainfall-runoff process. The bivariate diagonal VECH-GARCH(1,1) and CCC-GARCH(1,1) models indicated both short-run and long-run persistency in the conditional variance-covariance matrix of the rainfall-runoff process. The conditional variance of rainfall appears to have a stronger persistency, especially long-run persistency, than the conditional variance of streamflow which shows a short-lived drastic increasing pattern and a stronger short-run persistency. The conditional covariance and conditional correlation coefficients have different features for each bivariate rainfall-runoff process with different degrees of stationarity and dynamic nonlinearity. The spatial and temporal pattern of variance-covariance features may reflect the signature of different physical and hydrological variables such as drainage area, topography, soil moisture and ground water fluctuations on the strength, stationarity and nonlinearity of the conditional variance-covariance for a rainfall-runoff process.
The Effects of Time-Limitations and Peer Relationships on Adult Student Learning: A Causal Model.
ERIC Educational Resources Information Center
Lundberg, Carol
Using data from 4,644 undergraduates, this study tested a causal model identifying effects of social integration, age, and time limiting characteristics on adult student learning. Time limiting characteristics included such constraints as off-campus responsibilities and relationships. Educationally related peer relationships were the strongest…
Examining the Relationship between Physical Models and Students' Science Practices
NASA Astrophysics Data System (ADS)
Miller, Alison Riley
Scientists engage with practices like model development and use, data analysis and interpretation, explanation construction, and argumentation in order to expand the frontiers of science, so it can be inferred that students' engagement with science practices may help them deepen their own science understanding. As one of three dimensions on which the Next Generation Science Standards is built, science practices are recognized as an important component of science instruction. However, the contexts in which these practices happen are under-researched. Furthermore, research on science practices among students tends to focus on one or two practices in isolation when, in reality, students and scientists tend to engage with multiple overlapping practices. This study focused on identifying and characterizing multiple science practices as eighth and ninth-grade Earth Science students participated in a small group collaborative problem solving activity both with and without the use of a physical model. This study found a range of sophistication in the observed science practices as well as a relationship between the frequency of those practices and the accuracy of the groups' outcomes. Based on this relationship, groups were assigned to one of three categories. Further analysis revealed that model use varied among the three categories of groups. Comparisons across these three group categories suggest that there may be a bootstrapping relationship between students' engagement with science practices and the development of their content understanding. This metaphor of bootstrapping is used to represent how students may develop deeper science content understanding through engagement with science practices and concurrently develop greater facility with science practices as they learn science content. Implications are presented for curriculum designers, teachers and teacher educators. These include recommendations for curriculum design that encourage structured opportunities for
Relationships among certain joint constitutive models.
Segalman, Daniel Joseph; Starr, Michael James
2004-09-01
In a recent paper, Starr and Segalman demonstrated that any Masing model can be represented as a parallel-series Iwan model. A preponderance of the constitutive models that have been suggested for simulating mechanical joints are Masing models, and the purpose of this discussion is to demonstrate how the Iwan representation of those models can yield insight into their character. In particular, this approach can facilitate a critical comparison among numerous plausible constitutive models. It is explicitly shown that three-parameter models such as Smallwood's (Ramberg-Osgood) calculate parameters in such a manner that macro-slip is not an independent parameter, yet the model admits macro-slip. The introduction of a fourth parameter is therefore required. It is shown that when a macro-slip force is specified for the Smallwood model the result is a special case of the Segalman four-parameter model. Both of these models admit a slope discontinuity at the inception of macro-slip. A five-parameter model that has the beneficial features of Segalman's four-parameter model is proposed. This model manifests a force-displacement curve having a continuous first derivative.
PAL-DS MODEL: THE PAL MODEL INCLUDING DEPOSITION AND SEDIMENTATION. USER'S GUIDE
PAL is an acronym for an air quality model which applies a Gaussian plume diffusion algorithm to point, area, and line sources. The model is available from the U.S. Environmental Protection Agency and can be used for estimating hourly and short-term average concentrations of non-...
Modeling of microstructure property relationships in titanium-aluminum-vanadium
NASA Astrophysics Data System (ADS)
Tiley, Jaimie Scott
Fuzzy logic neural network models were developed to predict the room temperature tensile behavior of Ti-6Al-4V. This involved the development of a database relating microstructure to properties. This necessitated establishing heat treatment processes to develop microstructural features, mechanical testing of samples, creating rigorous stereology procedures, developing numerical models to predict mechanical behavior, and determining trends and inter-relationships relating microstructural features to mechanical properties. Microstructural features were developed using a Gleeble(TM) 1500 Thermal-mechanical simulator. Samples were obtained from mill annealed plate material and both alpha + beta forged and beta forged materials. A total of 72 samples were beta solutionized and heat treated using different heating and cooling conditions. Rigorous stereology procedures were developed to characterize the important microstructural features. The features included Widmanstatten alpha lath thickness, volume fraction of total alpha, volume fraction of Widmanstatten alpha, grain boundary alpha thickness, mean edge length, colony scale factor, and prior beta grain size factor. Chemical composition was also determined using standard chemical analysis and microscopy techniques. The samples were tested for yield strength, ultimate tensile strength, and elongation at room temperature. Results from the tests and the characterization were used to develop fuzzy logic neural network models to predict the mechanical behaviors and develop relationships between the microstructural features (using CubiCalc RTC(TM)). Results were compared to standard multi-variable regression models. The fuzzy logic neural network models were able to predict the yield, and ultimate tensile strength, within acceptable error ranges with a limited number of input data samples. The models also predicted the elongation values but with larger errors. Of particular importance, the models identified the importance of
Modeling the Relationship between Prosodic Sensitivity and Early Literacy
ERIC Educational Resources Information Center
Holliman, Andrew; Critten, Sarah; Lawrence, Tony; Harrison, Emily; Wood, Clare; Hughes, David
2014-01-01
A growing literature has demonstrated that prosodic sensitivity is related to early literacy development; however, the precise nature of this relationship remains unclear. It has been speculated in recent theoretical models that the observed relationship between prosodic sensitivity and early literacy might be partially mediated by children's…
Extension of the ADC Charge-Collection Model to Include Multiple Junctions
NASA Technical Reports Server (NTRS)
Edmonds, Larry D.
2011-01-01
The ADC model is a charge-collection model derived for simple p-n junction silicon diodes having a single reverse-biased p-n junction at one end and an ideal substrate contact at the other end. The present paper extends the model to include multiple junctions, and the goal is to estimate how collected charge is shared by the different junctions.
Modelling Mediterranean agro-ecosystems by including agricultural trees in the LPJmL model
NASA Astrophysics Data System (ADS)
Fader, M.; von Bloh, W.; Shi, S.; Bondeau, A.; Cramer, W.
2015-11-01
In the Mediterranean region, climate and land use change are expected to impact on natural and agricultural ecosystems by warming, reduced rainfall, direct degradation of ecosystems and biodiversity loss. Human population growth and socioeconomic changes, notably on the eastern and southern shores, will require increases in food production and put additional pressure on agro-ecosystems and water resources. Coping with these challenges requires informed decisions that, in turn, require assessments by means of a comprehensive agro-ecosystem and hydrological model. This study presents the inclusion of 10 Mediterranean agricultural plants, mainly perennial crops, in an agro-ecosystem model (Lund-Potsdam-Jena managed Land - LPJmL): nut trees, date palms, citrus trees, orchards, olive trees, grapes, cotton, potatoes, vegetables and fodder grasses. The model was successfully tested in three model outputs: agricultural yields, irrigation requirements and soil carbon density. With the development presented in this study, LPJmL is now able to simulate in good detail and mechanistically the functioning of Mediterranean agriculture with a comprehensive representation of ecophysiological processes for all vegetation types (natural and agricultural) and in a consistent framework that produces estimates of carbon, agricultural and hydrological variables for the entire Mediterranean basin. This development paves the way for further model extensions aiming at the representation of alternative agro-ecosystems (e.g. agroforestry), and opens the door for a large number of applications in the Mediterranean region, for example assessments of the consequences of land use transitions, the influence of management practices and climate change impacts.
Modelling Mediterranean agro-ecosystems by including agricultural trees in the LPJmL model
NASA Astrophysics Data System (ADS)
Fader, M.; von Bloh, W.; Shi, S.; Bondeau, A.; Cramer, W.
2015-06-01
Climate and land use change in the Mediterranean region is expected to affect natural and agricultural ecosystems by decreases in precipitation, increases in temperature as well as biodiversity loss and anthropogenic degradation of natural resources. Demographic growth in the Eastern and Southern shores will require increases in food production and put additional pressure on agro-ecosystems and water resources. Coping with these challenges requires informed decisions that, in turn, require assessments by means of a comprehensive agro-ecosystem and hydrological model. This study presents the inclusion of 10 Mediterranean agricultural plants, mainly perennial crops, in an agro-ecosystem model (LPJmL): nut trees, date palms, citrus trees, orchards, olive trees, grapes, cotton, potatoes, vegetables and fodder grasses. The model was successfully tested in three model outputs: agricultural yields, irrigation requirements and soil carbon density. With the development presented in this study, LPJmL is now able to simulate in good detail and mechanistically the functioning of Mediterranean agriculture with a comprehensive representation of ecophysiological processes for all vegetation types (natural and agricultural) and in a consistent framework that produces estimates of carbon, agricultural and hydrological variables for the entire Mediterranean basin. This development pave the way for further model extensions aiming at the representation of alternative agro-ecosystems (e.g. agroforestry), and opens the door for a large number of applications in the Mediterranean region, for example assessments on the consequences of land use transitions, the influence of management practices and climate change impacts.
Including operational data in QMRA model: development and impact of model inputs.
Jaidi, Kenza; Barbeau, Benoit; Carrière, Annie; Desjardins, Raymond; Prévost, Michèle
2009-03-01
A Monte Carlo model, based on the Quantitative Microbial Risk Analysis approach (QMRA), has been developed to assess the relative risks of infection associated with the presence of Cryptosporidium and Giardia in drinking water. The impact of various approaches for modelling the initial parameters of the model on the final risk assessments is evaluated. The Monte Carlo simulations that we performed showed that the occurrence of parasites in raw water was best described by a mixed distribution: log-Normal for concentrations > detection limit (DL), and a uniform distribution for concentrations < DL. The selection of process performance distributions for modelling the performance of treatment (filtration and ozonation) influences the estimated risks significantly. The mean annual risks for conventional treatment are: 1.97E-03 (removal credit adjusted by log parasite = log spores), 1.58E-05 (log parasite = 1.7 x log spores) or 9.33E-03 (regulatory credits based on the turbidity measurement in filtered water). Using full scale validated SCADA data, the simplified calculation of CT performed at the plant was shown to largely underestimate the risk relative to a more detailed CT calculation, which takes into consideration the downtime and system failure events identified at the plant (1.46E-03 vs. 3.93E-02 for the mean risk). PMID:18957777
Models of Shared Leadership: Evolving Structures and Relationships.
ERIC Educational Resources Information Center
Hallinger, Philip; Richardson, Don
1988-01-01
Explores potential changes in the power relationships among teachers and principals. Describes and analyzes the following models of teacher decision-making: (1) Instructional Leadership Teams; (2) Principals' Advisory Councils; (3) School Improvement Teams; and (4) Lead Teacher Committees. (FMW)
Including latent and sensible heat fluxes from sea spray in global weather and climate models
NASA Astrophysics Data System (ADS)
Copsey, Dan
2016-04-01
Most standard weather and climate models calculate interfacial latent (evaporation) and sensible heat fluxes over the ocean based on parameterisations of atmospheric turbulence, using the wave state only in the calculation of surface roughness length. They ignore latent and sensible heat fluxes generated by sea spray, which is an acceptable assumption at low wind speeds. However at high wind speeds (> 15 m/s) a significant amount of sea spray is generated from the sea surface which, while airborne, cools to an equilibrium temperature, absorbs heat and releases moisture before re-impacting the sea surface. This could impact, for example, the total heat loss from the Southern Ocean (which is anomalously warm in Met Office coupled models) or the accuracy of tropical cyclone forecasts. A modified version of the Fairall sea spray parameterisation scheme has been tested in the Met Office Unified Model including the JULES surface exchange model in both climate and NWP mode. The fast part of the scheme models the temperature change of the droplets to an equilibrium temperature and the slow part of the scheme models the evaporation and heat absorption while the droplets remain airborne. Including this scheme in the model cools and moistens the near surface layers of the atmosphere during high wind events, including tropical cyclones. Sea spray goes on to increase the convection intensity and precipitation near the high wind events in the model.
Modification of TOUGH2 to Include the Dusty Gas Model for Gas Diffusion
WEBB, STEPHEN W.
2001-10-01
The GEO-SEQ Project is investigating methods for geological sequestration of CO{sub 2}. This project, which is directed by LBNL and includes a number of other industrial, university, and national laboratory partners, is evaluating computer simulation methods including TOUGH2 for this problem. The TOUGH2 code, which is a widely used code for flow and transport in porous and fractured media, includes simplified methods for gas diffusion based on a direct application of Fick's law. As shown by Webb (1998) and others, the Dusty Gas Model (DGM) is better than Fick's Law for modeling gas-phase diffusion in porous media. In order to improve gas-phase diffusion modeling for the GEO-SEQ Project, the EOS7R module in the TOUGH2 code has been modified to include the Dusty Gas Model as documented in this report. In addition, the liquid diffusion model has been changed from a mass-based formulation to a mole-based model. Modifications for separate and coupled diffusion in the gas and liquid phases have also been completed. The results from the DGM are compared to the Fick's law behavior for TCE and PCE diffusion across a capillary fringe. The differences are small due to the relatively high permeability (k = 10{sup -11} m{sup 2}) of the problem and the small mole fraction of the gases. Additional comparisons for lower permeabilities and higher mole fractions may be useful.
ERIC Educational Resources Information Center
Mendonça, Paula Cristina Cardoso; Justi, Rosária
2013-01-01
Some studies related to the nature of scientific knowledge demonstrate that modelling is an inherently argumentative process. This study aims at discussing the relationship between modelling and argumentation by analysing data collected during the modelling-based teaching of ionic bonding and intermolecular interactions. The teaching activities…
ERIC Educational Resources Information Center
Cheng, Meng-Fei; Lin, Jang-Long
2015-01-01
Understanding the nature of models and engaging in modeling practice have been emphasized in science education. However, few studies discuss the relationships between students' views of scientific models and their ability to develop those models. Hence, this study explores the relationship between students' views of scientific models and their…
McGill, M J; Hart, W D; McKay, J A; Spinhirne, J D
1999-10-20
Previous modeling of the performance of spaceborne direct-detection Doppler lidar systems assumed extremely idealized atmospheric models. Here we develop a technique for modeling the performance of these systems in a more realistic atmosphere, based on actual airborne lidar observations. The resulting atmospheric model contains cloud and aerosol variability that is absent in other simulations of spaceborne Doppler lidar instruments. To produce a realistic simulation of daytime performance, we include solar radiance values that are based on actual measurements and are allowed to vary as the viewing scene changes. Simulations are performed for two types of direct-detection Doppler lidar system: the double-edge and the multichannel techniques. Both systems were optimized to measure winds from Rayleigh backscatter at 355 nm. Simulations show that the measurement uncertainty during daytime is degraded by only approximately 10-20% compared with nighttime performance, provided that a proper solar filter is included in the instrument design. PMID:18324169
Gleeson, Michael R.; Sheridan, John T.
2009-09-15
The photochemical processes present during free-radical-based holographic grating formation are examined. A kinetic model is presented, which includes, in a more nearly complete and physically realistic way, most of the major photochemical and nonlocal photopolymerization-driven diffusion effects. These effects include: (i) non-steady-state kinetics (ii) spatially and temporally nonlocal polymer chain growth (iii) time varying photon absorption (iv) diffusion controlled viscosity effects (v) multiple termination mechanisms, and (vi) inhibition. The convergence of the predictions of the resulting model is then examined. Comparisons with experimental results are carried out in Part II of this series of papers [J. Opt. Soc. Am. B 26, 1746 (2009)].
SAMI2-PE: A model of the ionosphere including multistream interhemispheric photoelectron transport
NASA Astrophysics Data System (ADS)
Varney, R. H.; Swartz, W. E.; Hysell, D. L.; Huba, J. D.
2012-06-01
In order to improve model comparisons with recently improved incoherent scatter radar measurements at the Jicamarca Radio Observatory we have added photoelectron transport and energy redistribution to the two dimensional SAMI2 ionospheric model. The photoelectron model uses multiple pitch angle bins, includes effects associated with curved magnetic field lines, and uses an energy degradation procedure which conserves energy on coarse, non-uniformly spaced energy grids. The photoelectron model generates secondary electron production rates and thermal electron heating rates which are then passed to the fluid equations in SAMI2. We then compare electron and ion temperatures and electron densities of this modified SAMI2 model with measurements of these parameters over a range of altitudes from 90 km to 1650 km (L = 1.26) over a 24 hour period. The new electron heating model is a significant improvement over the semi-empirical model used in SAMI2. The electron temperatures above the F-peak from the modified model qualitatively reproduce the shape of the measurements as functions of time and altitude and quantitatively agree with the measurements to within ˜30% or better during the entire day, including during the rapid temperature increase at dawn.
Bordas, R.; Gillow, K.; Lou, Q.; Efimov, I. R.; Gavaghan, D.; Kohl, P.; Grau, V.; Rodriguez, B.
2011-01-01
The function of the ventricular specialized conduction system in the heart is to ensure the coordinated electrical activation of the ventricles. It is therefore critical to the overall function of the heart, and has also been implicated as an important player in various diseases, including lethal ventricular arrhythmias such as ventricular fibrillation and drug-induced torsades de pointes. However, current ventricular models of electrophysiology usually ignore, or include highly simplified representations of the specialized conduction system. Here, we describe the development of a image-based, species-consistent, anatomically-detailed model of rabbit ventricular electrophysiology that incorporates a detailed description of the free-running part of the specialized conduction system. Techniques used for the construction of the geometrical model of the specialized conduction system from a magnetic resonance dataset and integration of the system model into a ventricular anatomical model, developed from the same dataset, are described. Computer simulations of rabbit ventricular electrophysiology are conducted using the novel anatomical model and rabbit-specific membrane kinetics to investigate the importance of the components and properties of the conduction system in determining ventricular function under physiological conditions. Simulation results are compared to panoramic optical mapping experiments for model validation and results interpretation. Full access is provided to the anatomical models developed in this study. PMID:21672547
Robust Programming Problems Based on the Mean-Variance Model Including Uncertainty Factors
NASA Astrophysics Data System (ADS)
Hasuike, Takashi; Ishii, Hiroaki
2009-01-01
This paper considers robust programming problems based on the mean-variance model including uncertainty sets and fuzzy factors. Since these problems are not well-defined problems due to fuzzy factors, it is hard to solve them directly. Therefore, introducing chance constraints, fuzzy goals and possibility measures, the proposed models are transformed into the deterministic equivalent problems. Furthermore, in order to solve these equivalent problems efficiently, the solution method is constructed introducing the mean-absolute deviation and doing the equivalent transformations.
NASA Technical Reports Server (NTRS)
Entekhabi, D.; Eagleson, P. S.
1989-01-01
Parameterizations are developed for the representation of subgrid hydrologic processes in atmospheric general circulation models. Reasonable a priori probability density functions of the spatial variability of soil moisture and of precipitation are introduced. These are used in conjunction with the deterministic equations describing basic soil moisture physics to derive expressions for the hydrologic processes that include subgrid scale variation in parameters. The major model sensitivities to soil type and to climatic forcing are explored.
Tanner, Colby J.; Salali, Gul Deniz; Jackson, Andrew L.
2011-01-01
Dominance hierarchies pervade animal societies. Within a static social environment, in which group size and composition are unchanged, an individual's hierarchy rank results from intrinsic (e.g. body size) and extrinsic (e.g. previous experiences) factors. Little is known, however, about how dominance relationships are formed and maintained when group size and composition are dynamic. Using a fusion–fission protocol, we fused groups of previously isolated shore crabs (Carcinus maenas) into larger groups, and then restored groups to their original size and composition. Pre-fusion hierarchies formed independently of individuals' sizes, and were maintained within a static group via winner/loser effects. Post-fusion hierarchies differed from pre-fusion ones; losing fights during fusion led to a decline in an individual's rank between pre- and post-fusion conditions, while spending time being aggressive during fusion led to an improvement in rank. In post-fusion tanks, larger individuals achieved better ranks than smaller individuals. In conclusion, dominance hierarchies in crabs represent a complex combination of intrinsic and extrinsic factors, in which experiences from previous groups can carry over to affect current competitive interactions. PMID:21561961
Tanner, Colby J; Salali, Gul Deniz; Jackson, Andrew L
2011-12-23
Dominance hierarchies pervade animal societies. Within a static social environment, in which group size and composition are unchanged, an individual's hierarchy rank results from intrinsic (e.g. body size) and extrinsic (e.g. previous experiences) factors. Little is known, however, about how dominance relationships are formed and maintained when group size and composition are dynamic. Using a fusion-fission protocol, we fused groups of previously isolated shore crabs (Carcinus maenas) into larger groups, and then restored groups to their original size and composition. Pre-fusion hierarchies formed independently of individuals' sizes, and were maintained within a static group via winner/loser effects. Post-fusion hierarchies differed from pre-fusion ones; losing fights during fusion led to a decline in an individual's rank between pre- and post-fusion conditions, while spending time being aggressive during fusion led to an improvement in rank. In post-fusion tanks, larger individuals achieved better ranks than smaller individuals. In conclusion, dominance hierarchies in crabs represent a complex combination of intrinsic and extrinsic factors, in which experiences from previous groups can carry over to affect current competitive interactions. PMID:21561961
NASA Astrophysics Data System (ADS)
Hincapié, Doracelly; Ospina, Juan
2014-06-01
Recently, a mathematical model of pandemic influenza was proposed including typical control strategies such as antivirals, vaccination and school closure; and considering explicitly the effects of immunity acquired from the early outbreaks on the ulterior outbreaks of the disease. In such model the algebraic expression for the basic reproduction number (without control strategies) and the effective reproduction number (with control strategies) were derived and numerically estimated. A drawback of this model of pandemic influenza is that it ignores the effects of the differential susceptibility due to immunosuppression and the effects of the complexity of the actual contact networks between individuals. We have developed a generalized model which includes such effects of heterogeneity. Specifically we consider the influence of the air network connectivity in the spread of pandemic influenza and the influence of the immunosuppresion when the population is divided in two immune classes. We use an algebraic expression, namely the Tutte polynomial, to characterize the complexity of the contact network. Until now, The influence of the air network connectivity in the spread of pandemic influenza has been studied numerically, but not algebraic expressions have been used to summarize the level of network complexity. The generalized model proposed here includes the typical control strategies previously mentioned (antivirals, vaccination and school closure) combined with restrictions on travel. For the generalized model the corresponding reproduction numbers will be algebraically computed and the effect of the contact network will be established in terms of the Tutte polynomial of the network.
Modelling total duration of traffic incidents including incident detection and recovery time.
Tavassoli Hojati, Ahmad; Ferreira, Luis; Washington, Simon; Charles, Phil; Shobeirinejad, Ameneh
2014-10-01
Traffic incidents are key contributors to non-recurrent congestion, potentially generating significant delay. Factors that influence the duration of incidents are important to understand so that effective mitigation strategies can be implemented. To identify and quantify the effects of influential factors, a methodology for studying total incident duration based on historical data from an 'integrated database' is proposed. Incident duration models are developed using a selected freeway segment in the Southeast Queensland, Australia network. The models include incident detection and recovery time as components of incident duration. A hazard-based duration modelling approach is applied to model incident duration as a function of a variety of factors that influence traffic incident duration. Parametric accelerated failure time survival models are developed to capture heterogeneity as a function of explanatory variables, with both fixed and random parameters specifications. The analysis reveals that factors affecting incident duration include incident characteristics (severity, type, injury, medical requirements, etc.), infrastructure characteristics (roadway shoulder availability), time of day, and traffic characteristics. The results indicate that event type durations are uniquely different, thus requiring different responses to effectively clear them. Furthermore, the results highlight the presence of unobserved incident duration heterogeneity as captured by the random parameter models, suggesting that additional factors need to be considered in future modelling efforts. PMID:24974360
Magnetofluid Simulations of the Global Solar Wind Including Pickup Ions and Turbulence Modeling
NASA Technical Reports Server (NTRS)
Goldstein, Melvyn L.; Usmanov, Arcadi V.; Matthaeus, William H.
2011-01-01
I will describe a three-dimensional magnetohydrodynamic model of the solar wind that takes into account turbulent heating of the wind by velocity and magnetic fluctuations as well as a variety of effects produced by interstellar pickup protons. In this report, the interstellar pickup protons are treated as one fluid and the protons and electrons are treated together as a second fluid. The model equations include a Reynolds decomposition of the plasma velocity and magnetic field into mean and fluctuating quantities, as well as energy transfer from interstellar pickup protons to solar wind protons that results in the deceleration of the solar wind. The model is used to simulate the global steady-state structure of the solar wind in the region from 0.3 to 100 AU. Where possible, the model is compared with Voyager data. Initial results from generalization to a three-fluid model is described elsewhere in this session.
A statistical model including age to predict passenger postures in the rear seats of automobiles.
Park, Jangwoon; Ebert, Sheila M; Reed, Matthew P; Hallman, Jason J
2016-06-01
Few statistical models of rear seat passenger posture have been published, and none has taken into account the effects of occupant age. This study developed new statistical models for predicting passenger postures in the rear seats of automobiles. Postures of 89 adults with a wide range of age and body size were measured in a laboratory mock-up in seven seat configurations. Posture-prediction models for female and male passengers were separately developed by stepwise regression using age, body dimensions, seat configurations and two-way interactions as potential predictors. Passenger posture was significantly associated with age and the effects of other two-way interaction variables depended on age. A set of posture-prediction models are presented for women and men, and the prediction results are compared with previously published models. This study is the first study of passenger posture to include a large cohort of older passengers and the first to report a significant effect of age for adults. The presented models can be used to position computational and physical human models for vehicle design and assessment. Practitioner Summary: The significant effects of age, body dimensions and seat configuration on rear seat passenger posture were identified. The models can be used to accurately position computational human models or crash test dummies for older passengers in known rear seat configurations. PMID:26328769
Working models of attachment and attribution processes in intimate relationships.
Collins, Nancy L; Ford, Máire B; Guichard, AnaMarie C; Allard, Lisa M
2006-02-01
Two studies examined the link between working models of attachment and social construal processes in romantic relationships. In Study 1, individuals high in attachment-related anxiety responded to hypothetical partner transgressions by endorsing relationship-threatening attributions, experiencing emotional distress, and endorsing behavioral intentions that were likely to result in conflict. These effects emerged after controlling for pessimistic explanatory style, depressed mood, and self-esteem. In addition, the association between anxiety and emotional distress was mediated by attributions and attachment-related needs. In Study 2, anxious individuals endorsed relationship-threatening attributions for their partner's transgressions but less so for their partner's positive behaviors, and these effects occurred primarily among those in unhappy relationships. In contrast, avoidant individuals endorsed pessimistic attributions for their partner's positive behavior but less so for their partner's transgressions, and these effects occurred regardless of their level of relationship satisfaction. PMID:16382082
Markovits, Henry; Benenson, Joyce F; Kramer, Donald L
2003-01-01
This study examined internal representations of food sharing in 589 children and adolescents (8-19 years of age). Questionnaires, depicting a variety of contexts in which one person was asked to share a resource with another, were used to examine participants' expectations of food-sharing behavior. Factors that were varied included the value of the resource, the relation between the two depicted actors, the quality of this relation, and gender. Results indicate that internal models of food-sharing behavior showed systematic patterns of variation, demonstrating that individuals have complex contextually based internal models at all ages, including the youngest. Examination of developmental changes in use of individual patterns is consistent with the idea that internal models reflect age-specific patterns of interactions while undergoing a process of progressive consolidation. PMID:14669890
Horiuchi, Masahisa; Nakakuma, Miwa; Arimura, Emi; Ushikai, Miharu; Yoshida, Goichiro
2015-01-01
The food habit is involved in the onset and development of lifestyle-related diseases. In this review I would like to describe a historical case of vitamin B1 deficiency, as well as our case study of fatty acid metabolism abnormality due to carnitine deficiency. In history, the army and navy personnel in Japan at the end of the 19th century received food rations based on a high-carbohydrate diet including white rice, resulting in the onset of beriberi. An epidemiological study by Kenkan Takaki revealed the relationship between the onset of beriberi and rice intake. Then, Takaki was successful in preventing the onset of beriberi by changing the diet. However, the primary cause had yet to be elucidated. Finally, Christian Eijkman established an animal model of beriberi (chickens) showing peripheral neuropathy, and he identified the existence of an anti-beriberi substance, vitamin B1. This is an example of the successful control of a disease by integrating the results of epidemiological and experimental studies. In our study using a murine model of fatty acid metabolism abnormality caused by carnitine deficiency, cardiac abnormality and fatty liver developed depending on the amount of dietary fat. In addition, the mice showed disturbance of orexin neuron activity related to the sleep-arousal system, which is involved in fatigue symptoms under fasting condition, one of the states showing enhanced fatty acid metabolism. These findings suggest that fatty acid toxicity is enhanced when the mice are more dependent on fatty acid metabolism. Almost simultaneously, a human epidemiological study showed that narcolepsy, which is caused by orexin system abnormality, is associated with the polymorphism of the gene coding for carnitine palmitoyltransferase 1B, which is involved in carnitine metabolism. To understand the pathological mechanism of fatty acid toxicity, not only an experimental approach using animal models, but also an epidemiological approach is necessary. The
Exploring Third-Grade Student Model-Based Explanations about Plant Relationships within an Ecosystem
NASA Astrophysics Data System (ADS)
Zangori, Laura; Forbes, Cory T.
2015-12-01
Elementary students should have opportunities to develop scientific models to reason and build understanding about how and why plants depend on relationships within an ecosystem for growth and survival. However, scientific modeling practices are rarely included within elementary science learning environments and disciplinary content is often treated as discrete pieces separate from scientific practice. Elementary students have few, if any, opportunities to reason about how individual organisms, such as plants, hold critical relationships with their surrounding environment. The purpose of this design-based research study is to build a learning performance to identify and explore the third-grade students' baseline understanding of and their reasoning about plant-ecosystem relationships when engaged in the practices of modeling. The developed learning performance integrated scientific content and core scientific activity to identify and measure how students build knowledge about the role of plants in ecosystems through the practices of modeling. Our findings indicate that the third-grade students' ideas about plant growth include abiotic and biotic relationships. Further, they used their models to reason about how and why these relationships were necessary to maintain plant stasis. However, while the majority of the third-grade students were able to identify and reason about plant-abiotic relationships, a much smaller group reasoned about plant-abiotic-animal relationships. Implications from the study suggest that modeling serves as a tool to support elementary students in reasoning about system relationships, but they require greater curricular and instructional support in conceptualizing how and why ecosystem relationships are necessary for plant growth and development. This paper is based on data from a doctoral dissertation. An earlier version of this paper was presented at the 2015 international conference for the National Association for Research in Science
NASA Technical Reports Server (NTRS)
Kelly, Jeff; Betts, Juan Fernando; Fuller, Chris
2000-01-01
The study of normal impedance of perforated plate acoustic liners including the effect of bias flow was studied. Two impedance models were developed by modeling the internal flows of perforate orifices as infinite tubes with the inclusion of end corrections to handle finite length effects. These models assumed incompressible and compressible flows, respectively, between the far field and the perforate orifice. The incompressible model was used to predict impedance results for perforated plates with percent open areas ranging from 5% to 15%. The predicted resistance results showed better agreement with experiments for the higher percent open area samples. The agreement also tended to deteriorate as bias flow was increased. For perforated plates with percent open areas ranging from 1% to 5%, the compressible model was used to predict impedance results. The model predictions were closer to the experimental resistance results for the 2% to 3% open area samples. The predictions tended to deteriorate as bias flow was increased. The reactance results were well predicted by the models for the higher percent open area, but deteriorated as the percent open area was lowered (5%) and bias flow was increased. A fit was done on the incompressible model to the experimental database. The fit was performed using an optimization routine that found the optimal set of multiplication coefficients to the non-dimensional groups that minimized the least squares slope error between predictions and experiments. The result of the fit indicated that terms not associated with bias flow required a greater degree of correction than the terms associated with the bias flow. This model improved agreement with experiments by nearly 15% for the low percent open area (5%) samples when compared to the unfitted model. The fitted model and the unfitted model performed equally well for the higher percent open area (10% and 15%).
Evaluating Modeled Variables Included in the NOAA Water Vapor Flux Tool
NASA Astrophysics Data System (ADS)
Darby, L. S.; White, A. B.; Coleman, T.
2015-12-01
The NOAA/ESRL/Physical Sciences Division has a Water Vapor Flux Tool showing observed and forecast meteorological variables related to heavy precipitation. Details about this tool will be presented in a companion paper by White et al. (2015, this conference). We evaluate 3-hr precipitation forecasts from four models (the HRRR, HRRRexp, RAP, and RAPexp) that were added to the tool in Dec. 2014. The Rapid Refresh (RAP) and the High-Resolution Rapid Refresh (HRRR) models are run operationally by NOAA, are initialized hourly, and produce forecasts out to 15 hours. The RAP and HRRR have experimental versions (RAPexp and HRRRexp, respectively) that are run near-real time at the NOAA/ESRL/Global Systems Division. Our analysis of eight rain days includes atmospheric river events in Dec. 2014 and Feb. 2015. We evaluate the forecasts using observations at two sites near the California coast - Bodega Bay (BBY, 15 m ASL) and Cazadero (CZC, 478 m ASL), and an inland site near Colfax, CA (CFC, 643 m ASL). Various criteria were used to evaluate the forecasts. (1) The Pielke criteria: we compare the RMSE and unbiased RMSE of the model output to the standard deviation of the observations, and we compare the standard deviation of the model output to the standard deviation of the observations; (2) we compare the modeled 24-hr precipitation to the observed 24-hr precipitation; and (3) we assess the correlation coefficient between the modeled and observed precipitation. Based on these criteria, the RAP slightly outperformed the other models. Only the RAP and the HRRRexp had forecasts that met the Pielke criteria. All of the models were able to predict the observed 24-hour precipitation, within 10%, in only 8-16% of their forecasts. All models achieved a correlation coefficient value above the 90th percentile in 12.5% of their forecasts. The station most likely to have a forecast that met any of the criteria was the inland mountain station CFC; the least likely was the coastal mountain
Hierarchical longitudinal models of relationships in social networks
Paul, Sudeshna; O’Malley, A. James
2013-01-01
Summary Motivated by the need to understand the dynamics of relationship formation and dissolution over time in real-world social networks we develop a new longitudinal model for transitions in the relationship status of pairs of individuals (“dyads”). We first specify a model for the relationship status of a single dyad and then extend it to account for important inter-dyad dependencies (e.g., transitivity – “a friend of a friend is a friend”) and heterogeneity. Model parameters are estimated using Bayesian analysis implemented via Markov chain Monte Carlo. We use the model to perform novel analyses of two diverse longitudinal friendship networks: an excerpt of the Teenage Friends and Lifestyle Study (a moderately sized network) and the Framingham Heart Study (FHS) (a large network). PMID:24729637
MEMLS3&a: Microwave Emission Model of Layered Snowpacks adapted to include backscattering
NASA Astrophysics Data System (ADS)
Proksch, M.; Mätzler, C.; Wiesmann, A.; Lemmetyinen, J.; Schwank, M.; Löwe, H.; Schneebeli, M.
2015-08-01
The Microwave Emission Model of Layered Snowpacks (MEMLS) was originally developed for microwave emissions of snowpacks in the frequency range 5-100 GHz. It is based on six-flux theory to describe radiative transfer in snow including absorption, multiple volume scattering, radiation trapping due to internal reflection and a combination of coherent and incoherent superposition of reflections between horizontal layer interfaces. Here we introduce MEMLS3&a, an extension of MEMLS, which includes a backscatter model for active microwave remote sensing of snow. The reflectivity is decomposed into diffuse and specular components. Slight undulations of the snow surface are taken into account. The treatment of like- and cross-polarization is accomplished by an empirical splitting parameter q. MEMLS3&a (as well as MEMLS) is set up in a way that snow input parameters can be derived by objective measurement methods which avoid fitting procedures of the scattering efficiency of snow, required by several other models. For the validation of the model we have used a combination of active and passive measurements from the NoSREx (Nordic Snow Radar Experiment) campaign in Sodankylä, Finland. We find a reasonable agreement between the measurements and simulations, subject to uncertainties in hitherto unmeasured input parameters of the backscatter model. The model is written in Matlab and the code is publicly available for download through the following website: http://www.iapmw.unibe.ch/research/projects/snowtools/memls.html.
Diehl, S; Zambrano, J; Carlsson, B
2016-01-01
A reduced model of a completely stirred-tank bioreactor coupled to a settling tank with recycle is analyzed in its steady states. In the reactor, the concentrations of one dominant particulate biomass and one soluble substrate component are modelled. While the biomass decay rate is assumed to be constant, growth kinetics can depend on both substrate and biomass concentrations, and optionally model substrate inhibition. Compressive and hindered settling phenomena are included using the Bürger-Diehl settler model, which consists of a partial differential equation. Steady-state solutions of this partial differential equation are obtained from an ordinary differential equation, making steady-state analysis of the entire plant difficult. A key result showing that the ordinary differential equation can be replaced with an approximate algebraic equation simplifies model analysis. This algebraic equation takes the location of the sludge-blanket during normal operation into account, allowing for the limiting flux capacity caused by compressive settling to easily be included in the steady-state mass balance equations for the entire plant system. This novel approach grants the possibility of more realistic solutions than other previously published reduced models, comprised of yet simpler settler assumptions. The steady-state concentrations, solids residence time, and the wastage flow ratio are functions of the recycle ratio. Solutions are shown for various growth kinetics; with different values of biomass decay rate, influent volumetric flow, and substrate concentration. PMID:26476681
MEMLS3&a: Microwave Emission Model of Layered Snowpacks adapted to include backscattering
NASA Astrophysics Data System (ADS)
Proksch, M.; Mätzler, C.; Wiesmann, A.; Lemmetyinen, J.; Schwank, M.; Löwe, H.; Schneebeli, M.
2015-03-01
The Microwave Emission Model of Layered Snowpacks (MEMLS) was originally developed for microwave emissions of snowpacks in the frequency range 5-100 GHz. It is based on six-flux theory to describe radiative transfer in snow including absorption, multiple volume scattering, radiation trapping due to internal reflection and a combination of coherent and incoherent superposition of reflections between horizontal layer interfaces. Here we introduce MEMLS3&a, an extension of MEMLS, which includes a backscatter model for active microwave remote sensing of snow. The reflectivity is decomposed into diffuse and specular components. Slight undulations of the snow surface are taken into account. The treatment of like and cross polarization is accomplished by an empirical splitting parameter q. MEMLS3&a (as well as MEMLS) is set up in a way that snow input parameters can be derived by objective measurement methods which avoids fitting procedures of the scattering efficiency of snow, required by several other models. For the validation of the model we have used a combination of active and passive measurements from the NoSREx campaign in Sodankylä, Finland. We find a reasonable agreement between the measurements and simulations, subject to uncertainties in hitherto unmeasured input parameters of the backscatter model. The model is written in MATLAB and the code is publicly available for download through the following website: http://www.iapmw.unibe.ch/research/projects/snowtools/memls.html.
A Multivariate Model of Parent-Adolescent Relationship Variables in Early Adolescence
ERIC Educational Resources Information Center
McKinney, Cliff; Renk, Kimberly
2011-01-01
Given the importance of predicting outcomes for early adolescents, this study examines a multivariate model of parent-adolescent relationship variables, including parenting, family environment, and conflict. Participants, who completed measures assessing these variables, included 710 culturally diverse 11-14-year-olds who were attending a middle…
Marsolat, F; De Marzi, L; Pouzoulet, F; Mazal, A
2016-01-21
In proton therapy, the relative biological effectiveness (RBE) depends on various types of parameters such as linear energy transfer (LET). An analytical model for LET calculation exists (Wilkens' model), but secondary particles are not included in this model. In the present study, we propose a correction factor, L sec, for Wilkens' model in order to take into account the LET contributions of certain secondary particles. This study includes secondary protons and deuterons, since the effects of these two types of particles can be described by the same RBE-LET relationship. L sec was evaluated by Monte Carlo (MC) simulations using the GATE/GEANT4 platform and was defined by the ratio of the LET d distributions of all protons and deuterons and only primary protons. This method was applied to the innovative Pencil Beam Scanning (PBS) delivery systems and L sec was evaluated along the beam axis. This correction factor indicates the high contribution of secondary particles in the entrance region, with L sec values higher than 1.6 for a 220 MeV clinical pencil beam. MC simulations showed the impact of pencil beam parameters, such as mean initial energy, spot size, and depth in water, on L sec. The variation of L sec with these different parameters was integrated in a polynomial function of the L sec factor in order to obtain a model universally applicable to all PBS delivery systems. The validity of this correction factor applied to Wilkens' model was verified along the beam axis of various pencil beams in comparison with MC simulations. A good agreement was obtained between the corrected analytical model and the MC calculations, with mean-LET deviations along the beam axis less than 0.05 keV μm(-1). These results demonstrate the efficacy of our new correction of the existing LET model in order to take into account secondary protons and deuterons along the pencil beam axis. PMID:26732530
NASA Astrophysics Data System (ADS)
Marsolat, F.; De Marzi, L.; Pouzoulet, F.; Mazal, A.
2016-01-01
In proton therapy, the relative biological effectiveness (RBE) depends on various types of parameters such as linear energy transfer (LET). An analytical model for LET calculation exists (Wilkens’ model), but secondary particles are not included in this model. In the present study, we propose a correction factor, L sec, for Wilkens’ model in order to take into account the LET contributions of certain secondary particles. This study includes secondary protons and deuterons, since the effects of these two types of particles can be described by the same RBE-LET relationship. L sec was evaluated by Monte Carlo (MC) simulations using the GATE/GEANT4 platform and was defined by the ratio of the LET d distributions of all protons and deuterons and only primary protons. This method was applied to the innovative Pencil Beam Scanning (PBS) delivery systems and L sec was evaluated along the beam axis. This correction factor indicates the high contribution of secondary particles in the entrance region, with L sec values higher than 1.6 for a 220 MeV clinical pencil beam. MC simulations showed the impact of pencil beam parameters, such as mean initial energy, spot size, and depth in water, on L sec. The variation of L sec with these different parameters was integrated in a polynomial function of the L sec factor in order to obtain a model universally applicable to all PBS delivery systems. The validity of this correction factor applied to Wilkens’ model was verified along the beam axis of various pencil beams in comparison with MC simulations. A good agreement was obtained between the corrected analytical model and the MC calculations, with mean-LET deviations along the beam axis less than 0.05 keV μm-1. These results demonstrate the efficacy of our new correction of the existing LET model in order to take into account secondary protons and deuterons along the pencil beam axis.
AIR POLLUTION MODELS AS DESCRIPTORS OF CAUSE-EFFECT RELATIONSHIPS
The problem of air pollution modeling is treated beginning from a philosophical standpoint, in which a model is viewed as a universal statement and a complementary set of singular statements from which specific cause-effect relationships are deduced; proceeding to the formulation...
Exploring Third-Grade Student Model-Based Explanations about Plant Relationships within an Ecosystem
ERIC Educational Resources Information Center
Zangori, Laura; Forbes, Cory T.
2015-01-01
Elementary students should have opportunities to develop scientific models to reason and build understanding about how and why plants depend on relationships within an ecosystem for growth and survival. However, scientific modeling practices are rarely included within elementary science learning environments and disciplinary content is often…
ERIC Educational Resources Information Center
Kilic, Abdurrahman
2012-01-01
In this study, the relationship of values in elementary school 4th grade Social Studies textbook with the attainments and their level of being included in student workbook are tried to be determined. Case study, which is a qualitative research method, was applied for this research. To collect data, document analysis technique, which is among the…
The Effects of Including Non-Thermal Particles in Flare Loop Models
NASA Astrophysics Data System (ADS)
Reeves, K. K.; Winter, H. D.; Larson, N. L.
2012-05-01
In this work, we use HyLoop (Winter et al. 2011), a loop model that can incorporate the effects of both MHD and non-thermal particle populations, to simulate soft X-ray emissions in various situations. First of all, we test the effect of acceleration location on the emission in several XRT filters by simulating a series of post flare loops with different injection points for the non-thermal particle beams. We use an injection distribution peaked at the loop apex to represent a direct acceleration model, and an injection distribution peaked at the footpoints to represent the Alfvén wave interaction model. We find that footpoint injection leads to several early peaks in the apex-to-footpoint emission ratio. Second, we model a loop with cusp-shaped geometry based on the eruption model developed byLin & Forbes (2000) and Reeves & Forbes (2005a), and find that early in the flare, emission in the loop footpoints is much brighter in the XRT filters if non-thermal particles are included in the calculation. Finally, we employ a multi-loop flare model to simulate thermal emission and compare with a previous model where a semi-circular geometry was used (Reeves et al. 2007). We compare the Geostationary Operational Environmental Satellite (GOES) emission from the two models and find that the cusp-shaped geometry leads to a smaller GOES class flare.
Safe distance car-following model including backward-looking and its stability analysis
NASA Astrophysics Data System (ADS)
Yang, Da; Jin, Peter Jing; Pu, Yun; Ran, Bin
2013-03-01
The focus of this paper is the car-following behavior including backward-looking, simply called the bi-directional looking car-following behavior. This study is motivated by the potential changes of the physical properties of traffic flow caused by the fast developing intelligent transportation system (ITS), especially the new connected vehicle technology. Existing studies on this topic focused on general motors (GM) models and optimal velocity (OV) models. The safe distance car-following model, Gipps' model, which is more widely used in practice have not drawn too much attention in the bi-directional looking context. This paper explores the property of the bi-directional looking extension of Gipps' safe distance model. The stability condition of the proposed model is derived using the linear stability theory and is verified using numerical simulations. The impacts of the driver and vehicle characteristics appeared in the proposed model on the traffic flow stability are also investigated. It is found that taking into account the backward-looking effect in car-following has three types of effect on traffic flow: stabilizing, destabilizing and producing non-physical phenomenon. This conclusion is more sophisticated than the study results based on the OV bi-directional looking car-following models. Moreover, the drivers who have the smaller reaction time or the larger additional delay and think the other vehicles have larger maximum decelerations can stabilize traffic flow.
Taber, L A; Shi, Y; Yang, L; Bayly, P V
2011-01-01
Much is known about the biophysical mechanisms involved in cell crawling, but how these processes are coordinated to produce directed motion is not well understood. Here, we propose a new hypothesis whereby local cytoskeletal contraction generates fluid flow through the lamellipodium, with the pressure at the front of the cell facilitating actin polymerization which pushes the leading edge forward. The contraction, in turn, is regulated by stress in the cytoskeleton. To test this hypothesis, finite element models for a crawling cell are presented. These models are based on nonlinear poroelasticity theory, modified to include the effects of active contraction and growth, which are regulated by mechanical feedback laws. Results from the models agree reasonably well with published experimental data for cell speed, actin flow, and cytoskeletal deformation in migrating fish epidermal keratocytes. The models also suggest that oscillations can occur for certain ranges of parameter values. PMID:21765817
A consistent model of electroweak data including Z → b overlineb and Z → c overlinec
NASA Astrophysics Data System (ADS)
Agashe, K.; Graesser, M.; Hinchliffe, I.; Suzuki, M.
1996-02-01
We have performed an overall fit to the electroweak data with the generation blind U(1) extension of the Standard Model. As input data for fitting we have included the asymmetry parameters, the partial decay widths of Z, neutrino scattering, and atomic parity violation. The QCD coupling αs has been constrained to the world average obtained from all data except the Z width. On the basis of our fit we have constructed a viable gauge model that not only explains Rb and Rc but also provides a much better overall fit to the data than the Standard Model. Despite its phenomenological viability, our model is unfortunately not simple from the theoretical viewpoint. Atomic parity violation experiments strongly disfavor more aesthetically appealing alternatives that can be grand unified.
Multifluid Simulations of the Global Solar Wind Including Pickup Ions and Turbulence Modeling
NASA Technical Reports Server (NTRS)
Goldstein, Melvyn L.; Usmanov, A. V.
2011-01-01
I will describe a three-dimensional magnetohydrodynamic model of the solar wind that takes into account turbulent heating of the wind by velocity and magnetic fluctuations as well as a variety of effects produced by interstellar pickup protons. The interstellar pickup protons are treated in the model as one fluid and the protons and electrons are treated together as a second fluid. The model equations include a Reynolds decomposition of the plasma velocity and magnetic field into mean and fluctuating quantities, as well as energy transfer from interstellar pickup protons to solar wind protons that results in the deceleration of the solar wind. The model is used to simulate the global steady-state structure of the solar wind in the region from 0.3 to 100 AU. The simulation assumes that the background magnetic field on the Sun is either a dipole (aligned or tilted with respect to the solar rotation axis) or one that is deduced from solar magnetograms.
Global Reference Atmospheric Models, Including Thermospheres, for Mars, Venus and Earth
NASA Technical Reports Server (NTRS)
Justh, Hilary L.; Justus, C. G.; Keller, Vernon W.
2006-01-01
This document is the viewgraph slides of the presentation. Marshall Space Flight Center's Natural Environments Branch has developed Global Reference Atmospheric Models (GRAMs) for Mars, Venus, Earth, and other solar system destinations. Mars-GRAM has been widely used for engineering applications including systems design, performance analysis, and operations planning for aerobraking, entry descent and landing, and aerocapture. Preliminary results are presented, comparing Mars-GRAM with measurements from Mars Reconnaissance Orbiter (MRO) during its aerobraking in Mars thermosphere. Venus-GRAM is based on the Committee on Space Research (COSPAR) Venus International Reference Atmosphere (VIRA), and is suitable for similar engineering applications in the thermosphere or other altitude regions of the atmosphere of Venus. Until recently, the thermosphere in Earth-GRAM has been represented by the Marshall Engineering Thermosphere (MET) model. Earth-GRAM has recently been revised. In addition to including an updated version of MET, it now includes an option to use the Naval Research Laboratory Mass Spectrometer Incoherent Scatter Radar Extended Model (NRLMSISE-00) as an alternate thermospheric model. Some characteristics and results from Venus-GRAM and Earth-GRAM thermospheres are also presented.
Ikenaka, Yoshinori; Nakayama, Shouta M. M.; Mizukawa, Hazuki; Aoyama, Yoshiko; Ishizuka, Mayumi; Taira, Kumiko
2015-01-01
Neonicotinoid insecticides are nicotinic acetylcholine receptor agonists used worldwide. Their environmental health effects including neurotoxicity are of concern. We previously determined a metabolite of acetamiprid, N-desmethyl-acetamiprid in the urine of a patient, who exhibited some typical symptoms including neurological findings. We sought to investigate the association between urinary N-desmethyl-acetamiprid and the symptoms by a prevalence case-control study. Spot urine samples were collected from 35 symptomatic patients of unknown origin and 50 non-symptomatic volunteers (non-symptomatic group, NSG, 4–87 year-old). Patients with recent memory loss, finger tremor, and more than five of six symptoms (headache, general fatigue, palpitation/chest pain, abdominal pain, muscle pain/weakness/spasm, and cough) were in the typical symptomatic group (TSG, n = 19, 5–69 year-old); the rest were in the atypical symptomatic group (ASG, n = 16, 5–78 year-old). N-desmethyl-acetamiprid and six neonicotinoids in the urine were quantified by liquid chromatography-tandem mass spectrometry. The detection of N-desmethyl-acetamiprid was the most frequent and highest in TSG (47.4%, 6.0 ppb (frequency, maximum)), followed by in ASG (12.5%, 4.4 ppb) and in NSG (6.0%, 2.2 ppb), however acetamiprid was not detected. Thiamethoxam was detected in TSG (31.6%, 1.4 ppb), in ASG (6.3%, 1.9 ppb), but not in NSG. Nitenpyram was detected in TSG (10.5%, 1.2 ppb), in ASG (6.3%, not quantified) and in NSG (2.0%, not quantified). Clothianidin was only detected in ASG (6.3%, not quantified), and in NSG (2.0%, 1.6 ppb). Thiacloprid was detected in ASG (6.3%, 0.1 ppb). The cases in TSG with detection of N-desmethyl-acetamiprid and thiamethoxam were aged 5 to 62 years and 13 to 62 years, respectively. Detection of N-desmethyl-acetamiprid was associated with increased prevalence of the symptoms (odds ratio: 14, 95% confidence interval: 3.5–57). Urinary N-desmethyl-acetamiprid can be used as a
Marfo, Jemima Tiwaa; Fujioka, Kazutoshi; Ikenaka, Yoshinori; Nakayama, Shouta M M; Mizukawa, Hazuki; Aoyama, Yoshiko; Ishizuka, Mayumi; Taira, Kumiko
2015-01-01
Neonicotinoid insecticides are nicotinic acetylcholine receptor agonists used worldwide. Their environmental health effects including neurotoxicity are of concern. We previously determined a metabolite of acetamiprid, N-desmethyl-acetamiprid in the urine of a patient, who exhibited some typical symptoms including neurological findings. We sought to investigate the association between urinary N-desmethyl-acetamiprid and the symptoms by a prevalence case-control study. Spot urine samples were collected from 35 symptomatic patients of unknown origin and 50 non-symptomatic volunteers (non-symptomatic group, NSG, 4-87 year-old). Patients with recent memory loss, finger tremor, and more than five of six symptoms (headache, general fatigue, palpitation/chest pain, abdominal pain, muscle pain/weakness/spasm, and cough) were in the typical symptomatic group (TSG, n = 19, 5-69 year-old); the rest were in the atypical symptomatic group (ASG, n = 16, 5-78 year-old). N-desmethyl-acetamiprid and six neonicotinoids in the urine were quantified by liquid chromatography-tandem mass spectrometry. The detection of N-desmethyl-acetamiprid was the most frequent and highest in TSG (47.4%, 6.0 ppb (frequency, maximum)), followed by in ASG (12.5%, 4.4 ppb) and in NSG (6.0%, 2.2 ppb), however acetamiprid was not detected. Thiamethoxam was detected in TSG (31.6%, 1.4 ppb), in ASG (6.3%, 1.9 ppb), but not in NSG. Nitenpyram was detected in TSG (10.5%, 1.2 ppb), in ASG (6.3%, not quantified) and in NSG (2.0%, not quantified). Clothianidin was only detected in ASG (6.3%, not quantified), and in NSG (2.0%, 1.6 ppb). Thiacloprid was detected in ASG (6.3%, 0.1 ppb). The cases in TSG with detection of N-desmethyl-acetamiprid and thiamethoxam were aged 5 to 62 years and 13 to 62 years, respectively. Detection of N-desmethyl-acetamiprid was associated with increased prevalence of the symptoms (odds ratio: 14, 95% confidence interval: 3.5-57). Urinary N-desmethyl-acetamiprid can be used as a
Henkel, Marius; Schmidberger, Anke; Vogelbacher, Markus; Kühnert, Christian; Beuker, Janina; Bernard, Thomas; Schwartz, Thomas; Syldatk, Christoph; Hausmann, Rudolf
2014-08-01
The production of rhamnolipid biosurfactants by Pseudomonas aeruginosa is under complex control of a quorum sensing-dependent regulatory network. Due to a lack of understanding of the kinetics applicable to the process and relevant interrelations of variables, current processes for rhamnolipid production are based on heuristic approaches. To systematically establish a knowledge-based process for rhamnolipid production, a deeper understanding of the time-course and coupling of process variables is required. By combining reaction kinetics, stoichiometry, and experimental data, a process model for rhamnolipid production with P. aeruginosa PAO1 on sunflower oil was developed as a system of coupled ordinary differential equations (ODEs). In addition, cell density-based quorum sensing dynamics were included in the model. The model comprises a total of 36 parameters, 14 of which are yield coefficients and 7 of which are substrate affinity and inhibition constants. Of all 36 parameters, 30 were derived from dedicated experimental results, literature, and databases and 6 of them were used as fitting parameters. The model is able to describe data on biomass growth, substrates, and products obtained from a reference batch process and other validation scenarios. The model presented describes the time-course and interrelation of biomass, relevant substrates, and products on a process level while including a kinetic representation of cell density-dependent regulatory mechanisms. PMID:24770383
Modeling tether-ballast asteroid diversion systems, including tether mass and elasticity
NASA Astrophysics Data System (ADS)
French, David B.; Mazzoleni, Andre P.
2014-10-01
The risk of an impact between a large asteroid and the Earth has been significant enough to attract the attention of many researchers. This paper focuses on a mitigation technique that involves the use of a long tether and ballast mass to divert an asteroid. When such a tether is modeled as massless and inelastic, results show that the method may be viable for diverting asteroids away from a collision with the Earth; the next step towards demonstrating the viability of the approach is to conduct a study which uses a more realistic tether model. This paper presents such a study, in which the tether models include tether mass and elasticity. These models verify that a tether-ballast system is capable of diverting Earth-threatening asteroids. Detailed parametric studies are presented which illustrate how system performance depends on tether mass and elasticity. Also, case studies are presented which show how more realistic models can aid in the design of tether-ballast asteroid mitigation systems. Key findings include the dangers imposed by periods during which the tether goes slack and ways to preclude this.
A structural model for the in vivo human cornea including collagen-swelling interaction.
Cheng, Xi; Petsche, Steven J; Pinsky, Peter M
2015-08-01
A structural model of the in vivo cornea, which accounts for tissue swelling behaviour, for the three-dimensional organization of stromal fibres and for collagen-swelling interaction, is proposed. Modelled as a binary electrolyte gel in thermodynamic equilibrium, the stromal electrostatic free energy is based on the mean-field approximation. To account for active endothelial ionic transport in the in vivo cornea, which modulates osmotic pressure and hydration, stromal mobile ions are shown to satisfy a modified Boltzmann distribution. The elasticity of the stromal collagen network is modelled based on three-dimensional collagen orientation probability distributions for every point in the stroma obtained by synthesizing X-ray diffraction data for azimuthal angle distributions and second harmonic-generated image processing for inclination angle distributions. The model is implemented in a finite-element framework and employed to predict free and confined swelling of stroma in an ionic bath. For the in vivo cornea, the model is used to predict corneal swelling due to increasing intraocular pressure (IOP) and is adapted to model swelling in Fuchs' corneal dystrophy. The biomechanical response of the in vivo cornea to a typical LASIK surgery for myopia is analysed, including tissue fluid pressure and swelling responses. The model provides a new interpretation of the corneal active hydration control (pump-leak) mechanism based on osmotic pressure modulation. The results also illustrate the structural necessity of fibre inclination in stabilizing the corneal refractive surface with respect to changes in tissue hydration and IOP. PMID:26156299
Buckley, Lauren B; Waaser, Stephanie A; MacLean, Heidi J; Fox, Richard
2011-12-01
Thermal constraints on development are often invoked to predict insect distributions. These constraints tend to be characterized in species distribution models (SDMs) by calculating development time based on a constant lower development temperature (LDT). Here, we assessed whether species-specific estimates of LDT based on laboratory experiments can improve the ability of SDMs to predict the distribution shifts of six U.K. butterflies in response to recent climate warming. We find that species-specific and constant (5 degrees C) LDT degree-day models perform similarly at predicting distributions during the period of 1970-1982. However, when the models for the 1970-1982 period are projected to predict distributions in 1995-1999 and 2000-2004, species-specific LDT degree-day models modestly outperform constant LDT degree-day models. Our results suggest that, while including species-specific physiology in correlative models may enhance predictions of species' distribution responses to climate change, more detailed models may be needed to adequately account for interspecific physiological differences. PMID:22352161
A structural model for the in vivo human cornea including collagen-swelling interaction
Cheng, Xi; Petsche, Steven J.; Pinsky, Peter M.
2015-01-01
A structural model of the in vivo cornea, which accounts for tissue swelling behaviour, for the three-dimensional organization of stromal fibres and for collagen-swelling interaction, is proposed. Modelled as a binary electrolyte gel in thermodynamic equilibrium, the stromal electrostatic free energy is based on the mean-field approximation. To account for active endothelial ionic transport in the in vivo cornea, which modulates osmotic pressure and hydration, stromal mobile ions are shown to satisfy a modified Boltzmann distribution. The elasticity of the stromal collagen network is modelled based on three-dimensional collagen orientation probability distributions for every point in the stroma obtained by synthesizing X-ray diffraction data for azimuthal angle distributions and second harmonic-generated image processing for inclination angle distributions. The model is implemented in a finite-element framework and employed to predict free and confined swelling of stroma in an ionic bath. For the in vivo cornea, the model is used to predict corneal swelling due to increasing intraocular pressure (IOP) and is adapted to model swelling in Fuchs' corneal dystrophy. The biomechanical response of the in vivo cornea to a typical LASIK surgery for myopia is analysed, including tissue fluid pressure and swelling responses. The model provides a new interpretation of the corneal active hydration control (pump-leak) mechanism based on osmotic pressure modulation. The results also illustrate the structural necessity of fibre inclination in stabilizing the corneal refractive surface with respect to changes in tissue hydration and IOP. PMID:26156299
A numerical model including PID control of a multizone crystal growth furnace
NASA Technical Reports Server (NTRS)
Panzarella, Charles H.; Kassemi, Mohammad
1992-01-01
This paper presents a 2D axisymmetric combined conduction and radiation model of a multizone crystal growth furnace. The model is based on a programmable multizone furnace (PMZF) designed and built at NASA Lewis Research Center for growing high quality semiconductor crystals. A novel feature of this model is a control algorithm which automatically adjusts the power in any number of independently controlled heaters to establish the desired crystal temperatures in the furnace model. The control algorithm eliminates the need for numerous trial and error runs previously required to obtain the same results. The finite element code, FIDAP, used to develop the furnace model, was modified to directly incorporate the control algorithm. This algorithm, which presently uses PID control, and the associated heat transfer model are briefly discussed. Together, they have been used to predict the heater power distributions for a variety of furnace configurations and desired temperature profiles. Examples are included to demonstrate the effectiveness of the PID controlled model in establishing isothermal, Bridgman, and other complicated temperature profies in the sample. Finally, an example is given to show how the algorithm can be used to change the desired profile with time according to a prescribed temperature-time evolution.
Modeling of single char combustion, including CO oxidation in its boundary layer
Lee, C.H.; Longwell, J.P.; Sarofim, A.F.
1994-10-25
The combustion of a char particle can be divided into a transient phase where its temperature increases as it is heated by oxidation, and heat transfer from the surrounding gas to an approximately constant temperature stage where gas phase reaction is important and which consumes most of the carbon and an extinction stage caused by carbon burnout. In this work, separate models were developed for the transient heating where gas phase reactions were unimportant and for the steady temperature stage where gas phase reactions were treated in detail. The transient char combustion model incorporates intrinsic char surface production of CO and CO{sub 2}, internal pore diffusion and external mass and heat transfer. The model provides useful information for particle ignition, burning temperature profile, combustion time, and carbon consumption rate. A gas phase reaction model incorporating the full set of 28 elementary C/H/O reactions was developed. This model calculated the gas phase CO oxidation reaction in the boundary layer at particle temperatures of 1250 K and 2500 K by using the carbon consumption rate and the burning temperature at the pseudo-steady state calculated from the temperature profile model but the transient heating was not included. This gas phase model can predict the gas species, and the temperature distributions in the boundary layer, the CO{sub 2}/CO ratio, and the location of CO oxidation. A mechanistic heat and mass transfer model was added to the temperature profile model to predict combustion behavior in a fluidized bed. These models were applied to data from the fluidized combustion of Newlands coal char particles. 52 refs., 60 figs.
Modifying a telerobotic system to include robotic operation by means of dynamic modeling
Corbett, G.K.; Jansen, J.F.; Kress, R.L.; Noakes, M.W.
1989-01-01
The goal of this study was to implement a robotic mode for the Advanced Servomanipulator (ASM), a six-degree-of-freedom master/slave teleoperator. To implement a robotic mode on a system designed for teleoperation, the effects of any change in the control schemes must be completely understood. One way to study the impact of potential modifications is to develop a model of the system. This approach is the one taken in this study. A detailed full-arm model was developed by first creating a model for individual joints of the manipulator and then incorporating each of the joint models into a single full-arm model, including link inertias and kinematic cross-coupling. Parameters were identified for each joint model to provide a match between simulated and actual responses to a pulse input. The full-arm model was tested by comparing the simulated and actual response of the ASM to simultaneous sine-wave inputs to each joint, using the model parameters identified on a joint-by-joint basis. The full-arm model was able to characterize effectively the ASM system response for the inputs studied. Robotic-mode control algorithms were tested on both the individual-joint and full-arm models. The results of these simulations indicate that a simplified master/slave control structure is the best candidate for robotic operation. This control structure was added to the ASM. Experimental results demonstrate that the ASM system is capable of repeatable robotic operation. The robotic-mode man-machine interface and data handling system are described in this paper. 12 refs., 3 figs.
Including Finite Surface Span Effects in Empirical Jet-Surface Interaction Noise Models
NASA Technical Reports Server (NTRS)
Brown, Clifford A.
2016-01-01
The effect of finite span on the jet-surface interaction noise source and the jet mixing noise shielding and reflection effects is considered using recently acquired experimental data. First, the experimental setup and resulting data are presented with particular attention to the role of surface span on far-field noise. These effects are then included in existing empirical models that have previously assumed that all surfaces are semi-infinite. This extended abstract briefly describes the experimental setup and data leaving the empirical modeling aspects for the final paper.
Bongers, Mathilda L; de Ruysscher, Dirk; Oberije, Cary; Lambin, Philippe; Uyl-de Groot, Carin A; Coupé, V M H
2016-01-01
With the shift toward individualized treatment, cost-effectiveness models need to incorporate patient and tumor characteristics that may be relevant to treatment planning. In this study, we used multistate statistical modeling to inform a microsimulation model for cost-effectiveness analysis of individualized radiotherapy in lung cancer. The model tracks clinical events over time and takes patient and tumor features into account. Four clinical states were included in the model: alive without progression, local recurrence, metastasis, and death. Individual patients were simulated by repeatedly sampling a patient profile, consisting of patient and tumor characteristics. The transitioning of patients between the health states is governed by personalized time-dependent hazard rates, which were obtained from multistate statistical modeling (MSSM). The model simulations for both the individualized and conventional radiotherapy strategies demonstrated internal and external validity. Therefore, MSSM is a useful technique for obtaining the correlated individualized transition rates that are required for the quantification of a microsimulation model. Moreover, we have used the hazard ratios, their 95% confidence intervals, and their covariance to quantify the parameter uncertainty of the model in a correlated way. The obtained model will be used to evaluate the cost-effectiveness of individualized radiotherapy treatment planning, including the uncertainty of input parameters. We discuss the model-building process and the strengths and weaknesses of using MSSM in a microsimulation model for individualized radiotherapy in lung cancer. PMID:25732723
NASA Astrophysics Data System (ADS)
Gasheva, L. M.; Kalinkova, G.; Minkov, E.; Krestev, V.
1984-03-01
Employing IR spectroscopy some technological models of amoxicillin trihydrate, included in ethyl-, methyl-, carboxymethyl- and methylhydroxyethyl-cellulose have been studied. Interactions were established only between amoxicillin trihydrate and ethylcellulose. The IR absorption spectra suggest a H-bonded antibiotic with hydroxyl groups in the ethylcellulose molecule. The IR spectral differences observed are not due to polymorphic transformation; this was proved by X-ray powder diffraction.
Modeling and controller design of a wind energy conversion system including a matrix converter
NASA Astrophysics Data System (ADS)
Barakati, S. Masoud
In this thesis, a grid-connected wind-energy converter system including a matrix converter is proposed. The matrix converter, as a power electronic converter, is used to interface the induction generator with the grid and control the wind turbine shaft speed. At a given wind velocity, the mechanical power available from a wind turbine is a function of its shaft speed. Through the matrix converter, the terminal voltage and frequency of the induction generator is controlled, based on a constant V/f strategy, to adjust the turbine shaft speed and accordingly, control the active power injected into the grid to track maximum power for all wind velocities. The power factor at the interface with the grid is also controlled by the matrix converter to either ensure purely active power injection into the grid for optimal utilization of the installed wind turbine capacity or assist in regulation of voltage at the point of connection. Furthermore, the reactive power requirements of the induction generator are satisfied by the matrix converter to avoid use of self-excitation capacitors. The thesis addresses two dynamic models: a comprehensive dynamic model for a matrix converter and an overall dynamical model for the proposed wind turbine system. The developed matrix converter dynamic model is valid for both steady-state and transient analyses, and includes all required functions, i.e., control of the output voltage, output frequency, and input displacement power factor. The model is in the qdo reference frame for the matrix converter input and output voltage and current fundamental components. The validity of this model is confirmed by comparing the results obtained from the developed model and a simplified fundamental-frequency equivalent circuit-based model. In developing the overall dynamic model of the proposed wind turbine system, individual models of the mechanical aerodynamic conversion, drive train, matrix converter, and squirrel-cage induction generator are developed
Personality, relationship conflict, and teamwork-related mental models.
Vîrgă, Delia; Curşeu, Petru Lucian; CurŞeu, Petru Lucian; Maricuţoiu, Laurenţiu; Sava, Florin A; Macsinga, Irina; Măgurean, Silvia
2014-01-01
This study seeks to explore whether neuroticism, agreeableness, and conscientiousness moderate the influence of relationship conflict experienced in groups on changes in group members' evaluative cognitions related to teamwork quality (teamwork-related mental models). Data from 216 students, nested in 48 groups were analyzed using a multilevel modeling approach. Our results show that the experience of relationship conflict leads to a negative shift from the pre-task to the post-task teamwork-related mental models. Moreover, the results indicate that conscientiousness buffered the negative association between relationship conflict and the change in teamwork-related mental models. Our results did not support the hypothesized moderating effect of agreeableness and show that the detrimental effect of relationship conflict on the shift in teamwork-related mental models is accentuated for group members scoring low rather than high on neuroticism. These findings open new research venues for exploring the association between personality, coping styles and change in teamwork-related mental models. PMID:25372143
Personality, Relationship Conflict, and Teamwork-Related Mental Models
Vîrgă, Delia; CurŞeu, Petru Lucian; Maricuţoiu, Laurenţiu; Sava, Florin A.; Macsinga, Irina; Măgurean, Silvia
2014-01-01
This study seeks to explore whether neuroticism, agreeableness, and conscientiousness moderate the influence of relationship conflict experienced in groups on changes in group members' evaluative cognitions related to teamwork quality (teamwork-related mental models). Data from 216 students, nested in 48 groups were analyzed using a multilevel modeling approach. Our results show that the experience of relationship conflict leads to a negative shift from the pre-task to the post-task teamwork-related mental models. Moreover, the results indicate that conscientiousness buffered the negative association between relationship conflict and the change in teamwork-related mental models. Our results did not support the hypothesized moderating effect of agreeableness and show that the detrimental effect of relationship conflict on the shift in teamwork-related mental models is accentuated for group members scoring low rather than high on neuroticism. These findings open new research venues for exploring the association between personality, coping styles and change in teamwork-related mental models. PMID:25372143
A full model for simulation of electrochemical cells including complex behavior
NASA Astrophysics Data System (ADS)
Esperilla, J. J.; Félez, J.; Romero, G.; Carretero, A.
This communication presents a model of electrochemical cells developed in order to simulate their electrical, chemical and thermal behavior showing the differences when thermal effects are or not considered in the charge-discharge process. The work presented here has been applied to the particular case of the Pb,PbSO 4|H 2SO 4 (aq)|PbO 2,Pb cell, which forms the basis of the lead-acid batteries so widely used in the automotive industry and as traction batteries in electric or hybrid vehicles. Each half-cell is considered independently in the model. For each half-cell, in addition to the main electrode reaction, a secondary reaction is considered: the hydrogen evolution reaction in the negative electrode and the oxygen evolution reaction in the positive. The equilibrium potential is calculated with the Nernst equation, in which the activity coefficients are fitted to an exponential function using experimental data. On the other hand, the two main mechanisms that produce the overpotential are considered, that is the activation or charge transfer and the diffusion mechanisms. First, an isothermal model has been studied in order to show the behavior of the main phenomena. A more complex model has also been studied including thermal behavior. This model is very useful in the case of traction batteries in electric and hybrid vehicles where high current intensities appear. Some simulation results are also presented in order to show the accuracy of the proposed models.
Producing high-accuracy lattice models from protein atomic coordinates including side chains.
Mann, Martin; Saunders, Rhodri; Smith, Cameron; Backofen, Rolf; Deane, Charlotte M
2012-01-01
Lattice models are a common abstraction used in the study of protein structure, folding, and refinement. They are advantageous because the discretisation of space can make extensive protein evaluations computationally feasible. Various approaches to the protein chain lattice fitting problem have been suggested but only a single backbone-only tool is available currently. We introduce LatFit, a new tool to produce high-accuracy lattice protein models. It generates both backbone-only and backbone-side-chain models in any user defined lattice. LatFit implements a new distance RMSD-optimisation fitting procedure in addition to the known coordinate RMSD method. We tested LatFit's accuracy and speed using a large nonredundant set of high resolution proteins (SCOP database) on three commonly used lattices: 3D cubic, face-centred cubic, and knight's walk. Fitting speed compared favourably to other methods and both backbone-only and backbone-side-chain models show low deviation from the original data (~1.5 Å RMSD in the FCC lattice). To our knowledge this represents the first comprehensive study of lattice quality for on-lattice protein models including side chains while LatFit is the only available tool for such models. PMID:22934109
Producing High-Accuracy Lattice Models from Protein Atomic Coordinates Including Side Chains
Mann, Martin; Saunders, Rhodri; Smith, Cameron; Backofen, Rolf; Deane, Charlotte M.
2012-01-01
Lattice models are a common abstraction used in the study of protein structure, folding, and refinement. They are advantageous because the discretisation of space can make extensive protein evaluations computationally feasible. Various approaches to the protein chain lattice fitting problem have been suggested but only a single backbone-only tool is available currently. We introduce LatFit, a new tool to produce high-accuracy lattice protein models. It generates both backbone-only and backbone-side-chain models in any user defined lattice. LatFit implements a new distance RMSD-optimisation fitting procedure in addition to the known coordinate RMSD method. We tested LatFit's accuracy and speed using a large nonredundant set of high resolution proteins (SCOP database) on three commonly used lattices: 3D cubic, face-centred cubic, and knight's walk. Fitting speed compared favourably to other methods and both backbone-only and backbone-side-chain models show low deviation from the original data (~1.5 Å RMSD in the FCC lattice). To our knowledge this represents the first comprehensive study of lattice quality for on-lattice protein models including side chains while LatFit is the only available tool for such models. PMID:22934109
RELAP5-3D Code Includes Athena Features and Models
Richard A. Riemke; Cliff B. Davis; Richard R. Schultz
2006-07-01
Version 2.3 of the RELAP5-3D computer program includes all features and models previously available only in the ATHENA version of the code. These include the addition of new working fluids (i.e., ammonia, blood, carbon dioxide, glycerol, helium, hydrogen, lead-bismuth, lithium, lithium-lead, nitrogen, potassium, sodium, and sodium-potassium) and a magnetohydrodynamic model that expands the capability of the code to model many more thermal-hydraulic systems. In addition to the new working fluids along with the standard working fluid water, one or more noncondensable gases (e.g., air, argon, carbon dioxide, carbon monoxide, helium, hydrogen, krypton, nitrogen, oxygen, sf6, xenon) can be specified as part of the vapor/gas phase of the working fluid. These noncondensable gases were in previous versions of RELAP5- 3D. Recently four molten salts have been added as working fluids to RELAP5-3D Version 2.4, which has had limited release. These molten salts will be in RELAP5-3D Version 2.5, which will have a general release like RELAP5-3D Version 2.3. Applications that use these new features and models are discussed in this paper.
RELAP5-3D Code Includes ATHENA Features and Models
Riemke, Richard A.; Davis, Cliff B.; Schultz, Richard R.
2006-07-01
Version 2.3 of the RELAP5-3D computer program includes all features and models previously available only in the ATHENA version of the code. These include the addition of new working fluids (i.e., ammonia, blood, carbon dioxide, glycerol, helium, hydrogen, lead-bismuth, lithium, lithium-lead, nitrogen, potassium, sodium, and sodium-potassium) and a magnetohydrodynamic model that expands the capability of the code to model many more thermal-hydraulic systems. In addition to the new working fluids along with the standard working fluid water, one or more noncondensable gases (e.g., air, argon, carbon dioxide, carbon monoxide, helium, hydrogen, krypton, nitrogen, oxygen, SF{sub 6}, xenon) can be specified as part of the vapor/gas phase of the working fluid. These noncondensable gases were in previous versions of RELAP5-3D. Recently four molten salts have been added as working fluids to RELAP5-3D Version 2.4, which has had limited release. These molten salts will be in RELAP5-3D Version 2.5, which will have a general release like RELAP5-3D Version 2.3. Applications that use these new features and models are discussed in this paper. (authors)
Double-gate junctionless transistor model including short-channel effects
NASA Astrophysics Data System (ADS)
Paz, B. C.; Ávila-Herrera, F.; Cerdeira, A.; Pavanello, M. A.
2015-05-01
This work presents a physically based model for double-gate junctionless transistors (JLTs), continuous in all operation regimes. To describe short-channel transistors, short-channel effects (SCEs), such as increase of the channel potential due to drain bias, carrier velocity saturation and mobility degradation due to vertical and longitudinal electric fields, are included in a previous model developed for long-channel double-gate JLTs. To validate the model, an analysis is made by using three-dimensional numerical simulations performed in a Sentaurus Device Simulator from Synopsys. Different doping concentrations, channel widths and channel lengths are considered in this work. Besides that, the series resistance influence is numerically included and validated for a wide range of source and drain extensions. In order to check if the SCEs are appropriately described, besides drain current, transconductance and output conductance characteristics, the following parameters are analyzed to demonstrate the good agreement between model and simulation and the SCEs occurrence in this technology: threshold voltage (VTH), subthreshold slope (S) and drain induced barrier lowering.
Model of accelerating voltage pulse in DARHT-2 including Metglas saturation
NASA Astrophysics Data System (ADS)
Genoni, Thomas; Hughes, Thomas; Thoma, Carsten
2003-10-01
The DARHT-2 facility (Los Alamos National Laboratory) accelerates a 2 microsecond electron beam using a series of inductive accelerating cells. The cell inductance is provided by large Metglas cores, which are driven by a pulse-forming network (PFN). We have developed a model for this circuit which includes the nonlinear and spatially varying behavior of the Metglas. Data from experiments in which a capacitor was discharged through a Metglas core are used to develop a hysteresis model, based on the Hodgdon [Ref.1] theory of ferromagnetic materials. The resulting model is used in calculations of the output of the DARHT PFN, and comparison is made to experiments in which the PFN was terminated in a dummy resistive load. 1. M. L. Hodgdon, "Mathematical Theory and Calculations of Magnetic Hysteresis Curves", IEEE Trans. Magn., v. MAG-24, n. 6, pp. 3120-2, Nov. 1988.
Modeling relationships between use and nonuse values for surface water quality: A meta-analysis
NASA Astrophysics Data System (ADS)
Johnston, Robert J.; Besedin, Elena Y.; Wardwell, Ryan F.
2003-12-01
This paper describes a meta-analysis conducted to estimate relationships between the nonuse components of WTP for surface water quality improvements and a combination of resource, context, and study design attributes, where these attributes include estimated use values for identical improvements. Results are contrasted across four different statistical approaches: ordinary least squares, weighted least squares, multilevel models, and simultaneous equation models. Findings illustrate robust, systematic relationships between a variety of attributes and estimated nonuse WTP, in addition to a systematic empirical relationship between use and nonuse values. Results are promising with regard to the ability of meta-analysis to synthesize information regarding nonuse WTP for water quality improvements and to reveal relationships unapparent from individual stated preference models.
SPheno 3.1: extensions including flavour, CP-phases and models beyond the MSSM
NASA Astrophysics Data System (ADS)
Porod, W.; Staub, F.
2012-11-01
We describe recent extensions of the program SPhenoincluding flavour aspects, CP-phases, R-parity violation and low energy observables. In case of flavour mixing all masses of supersymmetric particles are calculated including the complete flavour structure and all possible CP-phases at the 1-loop level. We give details on implemented seesaw models, low energy observables and the corresponding extension of the SUSY Les Houches Accord. Moreover, we comment on the possibilities to include MSSM extensions in SPheno. Catalogue identifier: ADRV_v2_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADRV_v2_0.html Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 154062 No. of bytes in distributed program, including test data, etc.: 1336037 Distribution format: tar.gz Programming language: Fortran95. Computer: PC running under Linux, should run in every Unix environment. Operating system: Linux, Unix. Classification: 11.6. Catalogue identifier of previous version: ADRV_v1_0 Journal reference of previous version: Comput. Phys. Comm. 153(2003)275 Does the new version supersede the previous version?: Yes Nature of problem: The first issue is the determination of the masses and couplings of supersymmetric particles in various supersymmetric models, the R-parity conserved MSSM with generation mixing and including CP-violating phases, various seesaw extensions of the MSSM and the MSSM with bilinear R-parity breaking. Low energy data on Standard Model fermion masses, gauge couplings and electroweak gauge boson masses serve as constraints. Radiative corrections from supersymmetric particles to these inputs must be calculated. Theoretical constraints on the soft SUSY breaking parameters from a high scale theory are imposed and the parameters at the electroweak scale are obtained from the
Utilization of hierarchical, stochastic relationship modeling for Hangul character recognition.
Kang, Kyung-Won; Kim, Jin H
2004-09-01
In structural character recognition, a character is usually viewed as a set of strokes and the spatial relationships between them. Therefore, strokes and their relationships should be properly modeled for effective character representation. For this purpose, we propose a modeling scheme by which strokes as well as relationships are stochastically represented by utilizing the hierarchical characteristics of target characters. A character is defined by a multivariate random variable over the components and its probability distribution is learned from a training data set. To overcome difficulties of the learning due to the high order of the probability distribution (a problem of curse of dimensionality), the probability distribution is factorized and approximated by a set of lower-order probability distributions by applying the idea of relationship decomposition recursively to components and subcomponents. Based on the proposed method, a handwritten Hangul (Korean) character recognition system is developed. Recognition experiments conducted on a public database show the effectiveness of the proposed relationship modeling. The recognition accuracy increased by 5.5 percent in comparison to the most successful system ever reported. PMID:15742893
Dimer linkage structure in retroviruses: models that include both duplex and quadruplex domains.
Zarudnaya, M I; Kolomiets, I M; Potyahaylo, A L; Hovorun, D M
2005-01-01
Genome of all known retroviruses consists of two identical molecules of RNA, which are non-covalently linked. The most stable contact site between two RNA molecules is located near their 5' ends. The molecular interactions in the dimer linkage structure (DLS) in mature virions are currently unknown. Recently we suggested that the dimer linkage structure in human immunodeficiency virus 1 (HIV-1) contains both duplex and quadruplex domains and proposed a model of DLS in HIV-1Mal (Central African virus). In this paper we showed that similar models can be also built for HIV- 1Lai, a representative of the North-American and European viruses. One of the double-stranded domains in the model structures represents either an extended duplex formed by different pathways (through base pair melting and subsequent reannealing or by a recombination mechanism) or kissing loop complex. The quadruplexes contain both G- and mixed tetrads, for example, G.C.G.C or A.U.A.U. Phylogenetic analysis of 350 isolates from NCBI database showed that similar models of DLS are predictable practically for all HIV-1 isolates surveyed. A model of dimer linkage structure in Moloney murine sarcoma virus (MuSV) is also presented. The structure includes a duplex formed by the palindromic sequences and several quadruplexes. PMID:16335231
NASA Technical Reports Server (NTRS)
Stolarski, R. S.; Douglass, A. R.
1986-01-01
Models of stratospheric photochemistry are generally tested by comparing their predictions for the composition of the present atmosphere with measurements of species concentrations. These models are then used to make predictions of the atmospheric sensitivity to perturbations. Here the problem of the sensitivity of such a model to chlorine perturbations ranging from the present influx of chlorine-containing compounds to several times that influx is addressed. The effects of uncertainties in input parameters, including reaction rate coefficients, cross sections, solar fluxes, and boundary conditions, are evaluated using a Monte Carlo method in which the values of the input parameters are randomly selected. The results are probability distributions for present atmosheric concentrations and for calculated perturbations due to chlorine from fluorocarbons. For more than 300 Monte Carlo runs the calculated ozone perturbation for continued emission of fluorocarbons at today's rates had a mean value of -6.2 percent, with a 1-sigma width of 5.5 percent. Using the same runs but only allowing the cases in which the calculated present atmosphere values of NO, NO2, and ClO at 25 km altitude fell within the range of measurements yielded a mean ozone depletion of -3 percent, with a 1-sigma deviation of 2.2 percent. The model showed a nonlinear behavior as a function of added fluorocarbons. The mean of the Monte Carlo runs was less nonlinear than the model run using mean value of the input parameters.
Multiple tail models including inverse measures for structural design under uncertainties
NASA Astrophysics Data System (ADS)
Ramu, Palaniappan
Sampling-based reliability estimation with expensive computer models may be computationally prohibitive due to a large number of required simulations. One way to alleviate the computational expense is to extrapolate reliability estimates from observed levels to unobserved levels. Classical tail modeling techniques provide a class of models to enable this extrapolation using asymptotic theory by approximating the tail region of the cumulative distribution function (CDF). This work proposes three alternate tail extrapolation techniques including inverse measures that can complement classical tail modeling. The proposed approach, multiple tail models, applies the two classical and three alternate extrapolation techniques simultaneously to estimate inverse measures at the extrapolation regions and use the median as the best estimate. It is observed that the range of the five estimates can be used as a good approximation of the error associated with the median estimate. Accuracy and computational efficiency are competing factors in selecting sample size. Yet, as our numerical studies reveal, the accuracy lost to the reduction of computational power is very small in the proposed method. The method is demonstrated on standard statistical distributions and complex engineering examples.
Modeling the relationship between land use and surface water quality.
Tong, Susanna T Y; Chen, Wenli
2002-12-01
It is widely known that watershed hydrology is dependent on many factors, including land use, climate, and soil conditions. But the relative impacts of different types of land use on the surface water are yet to be ascertained and quantified. This research attempted to use a comprehensive approach to examine the hydrologic effects of land use at both a regional and a local scale. Statistical and spatial analyses were employed to examine the statistical and spatial relationships of land use and the flow and water quality in receiving waters on a regional scale in the State of Ohio. Besides, a widely accepted watershed-based water quality assessment tool, the Better Assessment Science Integrating Point and Nonpoint Sources (BASINS), was adopted to model the plausible effects of land use on water quality in a local watershed in the East Fork Little Miami River Basin. The results from the statistical analyses revealed that there was a significant relationship between land use and in-stream water quality, especially for nitrogen, phosphorus and Fecal coliform. The geographic information systems (GIS) spatial analyses identified the watersheds that have high levels of contaminants and percentages of agricultural and urban lands. Furthermore, the hydrologic and water quality modeling showed that agricultural and impervious urban lands produced a much higher level of nitrogen and phosphorus than other land surfaces. From this research, it seems that the approach adopted in this study is comprehensive, covering both the regional and local scales. It also reveals that BASINS is a very useful and reliable tool, capable of characterizing the flow and water quality conditions for the study area under different watershed scales. With little modification, these models should be able to adapt to other watersheds or to simulate other contaminants. They also can be used to study the plausible impacts of global environmental change. In addition, the information on the hydrologic
Venetsanos, A G; Bartzis, J G; Würtz, J; Papailiou, D D
2003-04-25
A two-dimensional shallow layer model has been developed to predict dense gas dispersion, under realistic conditions, including complex features such as two-phase releases, obstacles and inclined ground. The model attempts to predict the time and space evolution of the cloud formed after a release of a two-phase pollutant into the atmosphere. The air-pollutant mixture is assumed ideal. The cloud evolution is described mathematically through the Cartesian, two-dimensional, shallow layer conservation equations for mixture mass, mixture momentum in two horizontal directions, total pollutant mass fraction (vapor and liquid) and mixture internal energy. Liquid mass fraction is obtained assuming phase equilibrium. Account is taken in the conservation equations for liquid slip and eventual liquid rainout through the ground. Entrainment of ambient air is modeled via an entrainment velocity model, which takes into account the effects of ground friction, ground heat transfer and relative motion between cloud and surrounding atmosphere. The model additionally accounts for thin obstacles effects in three ways. First a stepwise description of the obstacle is generated, following the grid cell faces, taking into account the corresponding area blockage. Then obstacle drag on the passing cloud is modeled by adding flow resistance terms in the momentum equations. Finally the effect of extra vorticity generation and entrainment enhancement behind obstacles is modeled by adding locally into the entrainment formula without obstacles, a characteristic velocity scale defined from the obstacle pressure drop and the local cloud height.The present model predictions have been compared against theoretical results for constant volume and constant flux gravity currents. It was found that deviations of the predicted cloud footprint area change with time from the theoretical were acceptably small, if one models the frictional forces between cloud and ambient air, neglecting the Richardson
Duan, Aiguo; Zhang, Jianguo; Zhang, Xiongqing; He, Caiyun
2015-01-01
In this study, seven popular equations, including 3-parameter Weibull, 2-parameter Weibull, Gompertz, Logistic, Mitscherlich, Korf and R distribution, were used to model stand diameter distributions for exploring the relationship between the equations' inflection point attributes and model accuracy. A database comprised of 146 diameter frequency distributions of Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) plantations was used to demonstrate model fitting and comparison. Results showed that the inflection points of the stand diameter cumulative percentage distribution ranged from 0.4 to 0.6, showing a 1/2 close rule. The equation's inflection point attribute was strongly related to its model accuracy. Equation with an inflection point showed much higher accuracy than that without an inflection point. The larger the effective inflection point interval of the fitting curve of the equation was, and the closer the inflection point was to 0.5 for the equations with fixed inflection points, the higher the equation's accuracy was. It could be found that the equation's inflection point had close relationship with skewness of diameter distribution and stand age, stand density, which provided a scientific basis for model selection of a stand diameter distribution for Chinese fir plantations and other tree species. PMID:26016995
Duan, Aiguo; Zhang, Jianguo; Zhang, Xiongqing; He, Caiyun
2015-01-01
In this study, seven popular equations, including 3-parameter Weibull, 2-parameter Weibull, Gompertz, Logistic, Mitscherlich, Korf and R distribution, were used to model stand diameter distributions for exploring the relationship between the equations’ inflection point attributes and model accuracy. A database comprised of 146 diameter frequency distributions of Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) plantations was used to demonstrate model fitting and comparison. Results showed that the inflection points of the stand diameter cumulative percentage distribution ranged from 0.4 to 0.6, showing a 1/2 close rule. The equation’s inflection point attribute was strongly related to its model accuracy. Equation with an inflection point showed much higher accuracy than that without an inflection point. The larger the effective inflection point interval of the fitting curve of the equation was, and the closer the inflection point was to 0.5 for the equations with fixed inflection points, the higher the equation’s accuracy was. It could be found that the equation’s inflection point had close relationship with skewness of diameter distribution and stand age, stand density, which provided a scientific basis for model selection of a stand diameter distribution for Chinese fir plantations and other tree species. PMID:26016995
NASA Technical Reports Server (NTRS)
Tournier, Jean-Michel; El-Genk, Mohamed S.
1995-01-01
A two-dimensional Heat Pipe Transient Analysis Model, 'HPTAM,' was developed to simulate the transient operation of fully-thawed heat pipes and the startup of heat pipes from a frozen state. The model incorporates: (a) sublimation and resolidification of working fluid; (b) melting and freezing of the working fluid in the porous wick; (c) evaporation of thawed working fluid and condensation as a thin liquid film on a frozen substrate; (d) free-molecule, transition, and continuum vapor flow regimes, using the Dusty Gas Model; (e) liquid flow and heat transfer in the porous wick; and (f) thermal and hydrodynamic couplings of phases at their respective interfaces. HPTAM predicts the radius of curvature of the liquid meniscus at the liquid-vapor interface and the radial location of the working fluid level (liquid or solid) in the wick. It also includes the transverse momentum jump condition (capillary relationship of Pascal) at the liquid-vapor interface and geometrically relates the radius of curvature of the liquid meniscus to the volume fraction of vapor in the wick. The present model predicts the capillary limit and partial liquid recess (dryout) in the evaporator wick, and incorporates a liquid pooling submodel, which simulates accumulation of the excess liquid in the vapor core at the condenser end.
An extended gene protein/products boolean network model including post-transcriptional regulation
2014-01-01
Background Networks Biology allows the study of complex interactions between biological systems using formal, well structured, and computationally friendly models. Several different network models can be created, depending on the type of interactions that need to be investigated. Gene Regulatory Networks (GRN) are an effective model commonly used to study the complex regulatory mechanisms of a cell. Unfortunately, given their intrinsic complexity and non discrete nature, the computational study of realistic-sized complex GRNs requires some abstractions. Boolean Networks (BNs), for example, are a reliable model that can be used to represent networks where the possible state of a node is a boolean value (0 or 1). Despite this strong simplification, BNs have been used to study both structural and dynamic properties of real as well as randomly generated GRNs. Results In this paper we show how it is possible to include the post-transcriptional regulation mechanism (a key process mediated by small non-coding RNA molecules like the miRNAs) into the BN model of a GRN. The enhanced BN model is implemented in a software toolkit (EBNT) that allows to analyze boolean GRNs from both a structural and a dynamic point of view. The open-source toolkit is compatible with available visualization tools like Cytoscape and allows to run detailed analysis of the network topology as well as of its attractors, trajectories, and state-space. In the paper, a small GRN built around the mTOR gene is used to demonstrate the main capabilities of the toolkit. Conclusions The extended model proposed in this paper opens new opportunities in the study of gene regulation. Several of the successful researches done with the support of BN to understand high-level characteristics of regulatory networks, can now be improved to better understand the role of post-transcriptional regulation for example as a network-wide noise-reduction or stabilization mechanisms. PMID:25080304
Mating programs including genomic relationships
Technology Transfer Automated Retrieval System (TEKTRAN)
Computer mating programs have helped breeders minimize pedigree inbreeding and avoid recessive defects by mating animals with parents that have fewer common ancestors. With genomic selection, breed associations, AI organizations, and on-farm software providers could use new programs to minimize geno...
Dissecting the two models of TCR structure-function relationships.
Cohn, Melvin
2016-08-01
There are only two comprehensive models attempting to account for the TCR structure-function relationships, referred to as the Standard or Centric model (Model I) and the Tritope model (Model II). This essay is written to analyze comparatively the two formulations of restrictive reactivity, stressing in particular the logic of each. Model I is essentially built on an analogy between the TCR and the BCR. Given a TCR with only one combining site (paratope), restrictive recognition requires that its ligand be viewed as a composite structure between the peptide and restricting element. It is this relationship that entrains a set of correlates that makes Model I untenable. Model II is predicated on the postulate that the recognition of the allele-specific determinants expressed by MHC-encoded restricting elements (R) is germline encoded and selected, whereas the recognition of peptide (P) is somatically encoded and selected. These selective pressures must operate on definable structures and this, in turn, necessitates a multiply recognitive T cell antigen receptor (TCR) with independent anti-R and anti-P paratopes that function coherently to signal restrictive reactivity. The consequences of this "two repertoire" postulate give us a concept of TCR structure quite distinct from that at present generally accepted, as well as a surprising relationship between numbers of functional TCR V gene segments and allele-specific determinants in the species. In the end, both models must deal with the relationship between the epitope-paratope interaction(s) and the signals to the T cell necessary for its differentiation and function. PMID:27114367
Neural network modelling of non-linear hydrological relationships
NASA Astrophysics Data System (ADS)
Abrahart, R. J.; See, L. M.
2007-09-01
Two recent studies have suggested that neural network modelling offers no worthwhile improvements in comparison to the application of weighted linear transfer functions for capturing the non-linear nature of hydrological relationships. The potential of an artificial neural network to perform simple non-linear hydrological transformations under controlled conditions is examined in this paper. Eight neural network models were developed: four full or partial emulations of a recognised non-linear hydrological rainfall-runoff model; four solutions developed on an identical set of inputs and a calculated runoff coefficient output. The use of different input combinations enabled the competencies of solutions developed on a reduced number of parameters to be assessed. The selected hydrological model had a limited number of inputs and contained no temporal component. The modelling process was based on a set of random inputs that had a uniform distribution and spanned a modest range of possibilities. The initial cloning operations permitted a direct comparison to be performed with the equation-based relationship. It also provided more general information about the power of a neural network to replicate mathematical equations and model modest non-linear relationships. The second group of experiments explored a different relationship that is of hydrological interest; the target surface contained a stronger set of non-linear properties and was more challenging. Linear modelling comparisons were performed against traditional least squares multiple linear regression solutions developed on identical datasets. The reported results demonstrate that neural networks are capable of modelling non-linear hydrological processes and are therefore appropriate tools for hydrological modelling.
Boullata, Joseph I; Holcombe, Beverly; Sacks, Gordon; Gervasio, Jane; Adams, Stephen C; Christensen, Michael; Durfee, Sharon; Ayers, Phil; Marshall, Neil; Guenter, Peggi
2016-08-01
Parenteral nutrition (PN) is a high-alert medication with a complex drug use process. Key steps in the process include the review of each PN prescription followed by the preparation of the formulation. The preparation step includes compounding the PN or activating a standardized commercially available PN product. The verification and review, as well as preparation of this complex therapy, require competency that may be determined by using a standardized process for pharmacists and for pharmacy technicians involved with PN. An American Society for Parenteral and Enteral Nutrition (ASPEN) standardized model for PN order review and PN preparation competencies is proposed based on a competency framework, the ASPEN-published interdisciplinary core competencies, safe practice recommendations, and clinical guidelines, and is intended for institutions and agencies to use with their staff. PMID:27317615
Hadden, Benjamin W; Smith, C Veronica; Webster, Gregory D
2014-02-01
Although research has examined associations between attachment dimensions and relationship outcomes, theory has ignored how these associations change over time in adult romantic relationships. We proposed the Temporal Adult Romantic Attachment (TARA) model, which predicts that the negative associations between anxious and avoidant attachment on one hand and relationship satisfaction and commitment on the other will be more negative as relationship durations increase. Meta-analyses largely confirmed that negative associations between both insecure attachment dimensions and both relationship outcomes were more negative among longer relationship durations in cross-sectional samples. We also explored gender differences in these associations. The present review not only integrates the literature on adult attachment and romantic relationship satisfaction/commitment but also highlights the importance of relationship duration as a key moderator of the associations among these variables. We discuss the broad implications of these effects and our meta-analytic findings for the TARA model, attachment theory, and romantic relationships. PMID:24026179
Modeling the Relationships between Subdimensions of Environmental Literacy
ERIC Educational Resources Information Center
Genc, Murat; Akilli, Mustafa
2016-01-01
The aim of this study is to demonstrate the relationships between subdimensions of environmental literacy using Structural Equation Modeling (SEM). The study was conducted by the analysis of students' answers to questionnaires data using SEM. Initially, Kaiser-Meyer-Olkin and Bartlett's tests were done to test appropriateness of subdimensions to…
Cultivating Knowledge Sharing through the Relationship Management Maturity Model
ERIC Educational Resources Information Center
Martin, Valerie A.; Hatzakis, Tally; Lycett, Mark; Macredie, Robert
2005-01-01
Purpose: The purpose of this paper is to present the development of the relationship management maturity model (RMMM), the output of an initiative aimed at bridging the gap between business units and the IT organisation. It does this through improving and assessing knowledge sharing between business and IT staff in Finco, a large financial…
Aging and Interdependence: A Theoretical Model for Close Relationships.
ERIC Educational Resources Information Center
Blieszner, Rosemary
This paper demonstrates the utility of interdependence theory for understanding older persons' social relationships. Using friendship as an exemplary case, a model of expectations for and reactions to social exchanges is described. Exchanges which are perceived to be motivated by obligation are distinguished from those which are perceived to…
Violence in Young Adolescents' Relationships: A Path Model
ERIC Educational Resources Information Center
Josephson, Wendy L.; Proulx, Jocelyn B.
2008-01-01
A structural equation model based on social cognitive theory was used to predict relationship violence from young adolescents' knowledge, self-efficacy, attitudes, and alternative conflict strategies (n = 143 male and 147 female grade 7-9 students). A direct causal effect was supported for violence-tolerant attitudes and psychologically aggressive…
NASA Technical Reports Server (NTRS)
Free, April M.; Flowers, George T.; Trent, Victor S.
1993-01-01
Auxiliary bearings are a critical feature of any magnetic bearing system. They protect the soft iron core of the magnetic bearing during an overload or failure. An auxiliary bearing typically consists of a rolling element bearing or bushing with a clearance gap between the rotor and the inner race of the support. The dynamics of such systems can be quite complex. It is desired to develop a rotor-dynamic model and assess the dynamic behavior of a magnetic bearing rotor system which includes the effects of auxiliary bearings. Of particular interest is the effects of introducing sideloading into such a system during failure of the magnetic bearing. A model is developed from an experimental test facility and a number of simulation studies are performed. These results are presented and discussed.
A model for Huanglongbing spread between citrus plants including delay times and human intervention
NASA Astrophysics Data System (ADS)
Vilamiu, Raphael G. d'A.; Ternes, Sonia; Braga, Guilherme A.; Laranjeira, Francisco F.
2012-09-01
The objective of this work was to present a compartmental deterministic mathematical model for representing the dynamics of HLB disease in a citrus orchard, including delay in the disease's incubation phase in the plants, and a delay period on the nymphal stage of Diaphorina citri, the most important HLB insect vector in Brazil. Numerical simulations were performed to assess the possible impacts of human detection efficiency of symptomatic plants, as well as the influence of a long incubation period of HLB in the plant.
NASA Astrophysics Data System (ADS)
Printsypar, G.; Iliev, O.; Rief, S.
2011-12-01
Paper production is a challenging problem which attracts attention of many scientists. The process which is of our interest takes place in the pressing section of a paper machine. The paper layer is dried by means of the pressing it against fabrics, i.e. press felts. The paper-felt sandwich is transported through the press nips at high speed (for more details see [3]). Since the natural drainage of water in the felts is much longer than the drying in the pressing section we include in the consideration the dynamic capillary effect. The dynamic capillary pressure-saturation relation proposed by Hassanizadeh and Gray (see [2]) is adopted for the pressing process. One of the other issues which is taken into account while modeling the pressing section is the appearance of fully saturated regions. We include in consideration two flow regimes: the one-phase water flow and the two-phase air-water flow. It leads to a free boundary problem. We also account for the complexity of the paper-felt sandwich porous structure. Apart from the two flow regimes the computational domain is divided by layers into nonoverlapping subdomains. Then, the system of equations describing transport processes in the pressing section is stated taking into account all these features. The presented model is discretized by the finite volume method. We carry out some numerical experiments for different configurations of the pressing section (roll press, shoe press) and for parameters which are typical for paper-felt sandwich during the paper production process. The experiments show that the dynamic capillary effect has a significant influence on the distribution of pressure even for small values of the material coefficient (see Fig. 1). The obtained results are in agreement with laboratory experiment performed in [1], which states that the distribution of the pressure is not symmetric with the maximum value occurring in front of the center of the pressing nip and the minimum value less than entry
DEVELOPMENT OF A PRODUCT MODEL FOR CUT-AND-COVER TUNNELS INCLUDING DEGRADATIONS
NASA Astrophysics Data System (ADS)
Aruga, Takashi; Yabuki, Nobuyoshi; Arai, Yasushi
Cut-and-Cover tunnels are constructed on site. The various conditions of environments and techniques of construction make a significant influence on the quality of the tunnel. It is extremely difficult to rebuild the tunnel even if a structural trouble is found once the construction is completed. Thus, suitable maintenance is needed to ensure the tunnel is in a healthy condition. To execute better maintenance, the information on design and construction of the tunnel is vital for inspection of degradation, estimation of occurrence factors and planning of repair or refurbishing works. In this paper, we developed a product model for representing cut-and-cover tunnels including degradations for effective information use in maintenance work. As its first step, we investigated the characteristics of cut-and-cover tunnels and degradations about reinforced concrete members and developed a conceptual model. Then, we implemented the conceptual product model by expanding Industry Foundation Classes (IFC). Finally, we verified the product model by applying it to a simple tunnel.
A multiscale model for glioma spread including cell-tissue interactions and proliferation.
Engwer, Christian; Knappitsch, Markus; Surulescu, Christina
2016-04-01
Glioma is a broad class of brain and spinal cord tumors arising from glia cells, which are the main brain cells that can develop into neoplasms. They are highly invasive and lead to irregular tumor margins which are not precisely identifiable by medical imaging, thus rendering a precise enough resection very difficult. The understanding of glioma spread patterns is hence essential for both radiological therapy as well as surgical treatment. In this paper we propose a multiscale model for glioma growth including interactions of the cells with the underlying tissue network, along with proliferative effects. Our current accounting for two subpopulations of cells to accomodate proliferation according to the go-or-grow dichtomoty is an extension of the setting in [16]. As in that paper, we assume that cancer cells use neuronal fiber tracts as invasive pathways. Hence, the individual structure of brain tissue seems to be decisive for the tumor spread. Diffusion tensor imaging (DTI) is able to provide such information, thus opening the way for patient specific modeling of glioma invasion. Starting from a multiscale model involving subcellular (microscopic) and individual (mesoscale) cell dynamics, we perform a parabolic scaling to obtain an approximating reaction-diffusion-transport equation on the macroscale of the tumor cell population. Numerical simulations based on DTI data are carried out in order to assess the performance of our modeling approach. PMID:27105989
Studies of Arctic stratospheric ozone in a 2-D model including some effects of zonal asymmetries
Isaksen, I.S.A.; Rognerud, B.; Stordal, F. ); Coffey, M.T.; Mankin, W.G. )
1990-03-01
A two-dimensional (2-D) zonally averaged chemistry-transport model of the stratosphere has been extended to include some zonally asymmetric effects to study the chemically disturbed conditions in the Arctic winter during the occurrence of polar stratospheric clouds (PSCs). The model allows air parcels that have been in PSCs in the polar night to be exposed to sunlight during the passage south through a wave trough. Large enhancements of ClO are estimated as well as significant ozone reductions, most pronounced around the 20 km height level. The ozone depletions maximize in late March, about one month after the cease in PSC activity in the model, and amount to 5-8% in column ozone at 70{degree}N. In agreement with column measurements made from the DC-8, the model estimates an increase in the columns of HNO{sub 3} and ClONO{sub 2}, and a decrease in the HCl column within the polar vortex.
Habitability of super-Earth planets around other suns: models including Red Giant Branch evolution.
von Bloh, W; Cuntz, M; Schröder, K-P; Bounama, C; Franck, S
2009-01-01
The unexpected diversity of exoplanets includes a growing number of super-Earth planets, i.e., exoplanets with masses of up to several Earth masses and a similar chemical and mineralogical composition as Earth. We present a thermal evolution model for a 10 Earth-mass planet orbiting a star like the Sun. Our model is based on the integrated system approach, which describes the photosynthetic biomass production and takes into account a variety of climatological, biogeochemical, and geodynamical processes. This allows us to identify a so-called photosynthesis-sustaining habitable zone (pHZ), as determined by the limits of biological productivity on the planetary surface. Our model considers solar evolution during the main-sequence stage and along the Red Giant Branch as described by the most recent solar model. We obtain a large set of solutions consistent with the principal possibility of life. The highest likelihood of habitability is found for "water worlds." Only mass-rich water worlds are able to realize pHZ-type habitability beyond the stellar main sequence on the Red Giant Branch. PMID:19630504
A laboratory model of the aortic root flow including the coronary arteries
NASA Astrophysics Data System (ADS)
Querzoli, Giorgio; Fortini, Stefania; Espa, Stefania; Melchionna, Simone
2016-08-01
Cardiovascular flows have been extensively investigated by means of in vitro models to assess the prosthetic valve performances and to provide insight into the fluid dynamics of the heart and proximal aorta. In particular, the models for the study of the flow past the aortic valve have been continuously improved by including, among other things, the compliance of the vessel and more realistic geometries. The flow within the sinuses of Valsalva is known to play a fundamental role in the dynamics of the aortic valve since they host a recirculation region that interacts with the leaflets. The coronary arteries originate from the ostia located within two of the three sinuses, and their presence may significantly affect the fluid dynamics of the aortic root. In spite of their importance, to the extent of the authors' knowledge, coronary arteries were not included so far when modeling in vitro the transvalvular aortic flow. We present a pulse duplicator consisting of a passively pulsing ventricle, a compliant proximal aorta, and coronary arteries connected to the sinuses of Valsalva. The coronary flow is modulated by a self-regulating device mimicking the physiological mechanism, which is based on the contraction and relaxation of the heart muscle during the cardiac cycle. Results show that the model reproduces satisfyingly the coronary flow. The analysis of the time evolution of the velocity and vorticity fields within the aortic root reveals the main characteristics of the backflow generated through the aorta in order to feed the coronaries during the diastole. Experiments without coronary flow have been run for comparison. Interestingly, the lifetime of the vortex forming in the sinus of Valsalva during the systole is reduced by the presence of the coronaries. As a matter of fact, at the end of the systole, that vortex is washed out because of the suction generated by the coronary flow. Correspondingly, the valve closure is delayed and faster compared to the case with
Rivas, Elena; Lang, Raymond; Eddy, Sean R
2012-02-01
The standard approach for single-sequence RNA secondary structure prediction uses a nearest-neighbor thermodynamic model with several thousand experimentally determined energy parameters. An attractive alternative is to use statistical approaches with parameters estimated from growing databases of structural RNAs. Good results have been reported for discriminative statistical methods using complex nearest-neighbor models, including CONTRAfold, Simfold, and ContextFold. Little work has been reported on generative probabilistic models (stochastic context-free grammars [SCFGs]) of comparable complexity, although probabilistic models are generally easier to train and to use. To explore a range of probabilistic models of increasing complexity, and to directly compare probabilistic, thermodynamic, and discriminative approaches, we created TORNADO, a computational tool that can parse a wide spectrum of RNA grammar architectures (including the standard nearest-neighbor model and more) using a generalized super-grammar that can be parameterized with probabilities, energies, or arbitrary scores. By using TORNADO, we find that probabilistic nearest-neighbor models perform comparably to (but not significantly better than) discriminative methods. We find that complex statistical models are prone to overfitting RNA structure and that evaluations should use structurally nonhomologous training and test data sets. Overfitting has affected at least one published method (ContextFold). The most important barrier to improving statistical approaches for RNA secondary structure prediction is the lack of diversity of well-curated single-sequence RNA secondary structures in current RNA databases. PMID:22194308
Including sugar cane in the agro-ecosystem model ORCHIDEE-STICS
NASA Astrophysics Data System (ADS)
Valade, A.; Vuichard, N.; Ciais, P.; Viovy, N.
2010-12-01
With 4 million ha currently grown for ethanol in Brazil only, approximately half the global bioethanol production in 2005 (Smeets 2008), and a devoted land area expected to expand globally in the years to come, sugar cane is at the heart of the biofuel debate. Indeed, ethanol made from biomass is currently the most widespread option for alternative transportation fuels. It was originally promoted as a carbon neutral energy resource that could bring energy independence to countries and local opportunities to farmers, until attention was drawn to its environmental and socio-economical drawbacks. It is still not clear to which extent it is a solution or a contributor to climate change mitigation. Dynamic Global Vegetation models can help address these issues and quantify the potential impacts of biofuels on ecosystems at scales ranging from on-site to global. The global agro-ecosystem model ORCHIDEE describes water, carbon and energy exchanges at the soil-atmosphere interface for a limited number of natural and agricultural vegetation types. In order to integrate agricultural management to the simulations and to capture more accurately the specificity of crops' phenology, ORCHIDEE has been coupled with the agronomical model STICS. The resulting crop-oriented vegetation model ORCHIDEE-STICS has been used so far to simulate temperate crops such as wheat, corn and soybean. As a generic ecosystem model, each grid cell can include several vegetation types with their own phenology and management practices, making it suitable to spatial simulations. Here, ORCHIDEE-STICS is altered to include sugar cane as a new agricultural Plant functional Type, implemented and parametrized using the STICS approach. An on-site calibration and validation is then performed based on biomass and flux chamber measurements in several sites in Australia and variables such as LAI, dry weight, heat fluxes and respiration are used to evaluate the ability of the model to simulate the specific
NASA Astrophysics Data System (ADS)
Cardoso Mendonça, Paula Cristina; Justi, Rosária
2013-09-01
Some studies related to the nature of scientific knowledge demonstrate that modelling is an inherently argumentative process. This study aims at discussing the relationship between modelling and argumentation by analysing data collected during the modelling-based teaching of ionic bonding and intermolecular interactions. The teaching activities were planned from the transposition of the main modelling stages that constitute the 'Model of Modelling Diagram' so that students could experience each of such stages. All the lessons were video recorded and their transcriptions supported the elaboration of case studies for each group of students. From the analysis of the case studies, we identified argumentative situations when students performed all of the modelling stages. Our data show that the argumentative situations were related to sense making, articulating and persuasion purposes, and were closely related to the generation of explanations in the modelling processes. They also show that representations are important resources for argumentation. Our results are consistent with some of those already reported in the literature regarding the relationship between modelling and argumentation, but are also divergent when they show that argumentation is not only related to the model evaluation phase.
Lee, H.J.; Syvitski, J.P.M.; Parker, G.; Orange, Daniel L.; Locat, J.; Hutton, E.W.H.; Imran, J.
2002-01-01
Migrating sediment waves have been reported in a variety of marine settings, including submarine levee-fan systems, floors of fjords, and other basin or continental slope environments. Examination of such wave fields reveals nine diagnostic characteristics. When these characteristics are applied to several features previously attributed to submarine landslide deformation, they suggest that the features should most likely be reinterpreted as migrating sediment-wave fields. Sites that have been reinterpreted include the 'Humboldt slide' on the Eel River margin in northern California, the continental slope in the Gulf of Cadiz, the continental shelf off the Malaspina Glacier in the Gulf of Alaska, and the Adriatic shelf. A reassessment of all four features strongly suggests that numerous turbidity currents, separated by intervals of ambient hemipelagic sedimentation, deposited the wave fields over thousands of years. A numerical model of hyperpycnal discharge from the Eel River, for example, shows that under certain alongshore-current conditions, such events can produce turbidity currents that flow across the 'Humboldt slide', serving as the mechanism for the development of migrating sediment waves. Numerical experiments also demonstrate that where a series of turbidity currents flows across a rough seafloor (i.e. numerical steps), sediment waves can form and migrate upslope. Hemipelagic sedimentation between turbidity current events further facilitates the upslope migration of the sediment waves. Physical modelling of turbidity currents also confirms the formation and migration of seafloor bedforms. The morphologies of sediment waves generated both numerically and physically in the laboratory bear a strong resemblance to those observed in the field, including those that were previously described as submarine landslides.
Jet Noise Modeling for Coannular Nozzles Including the Effects of Chevrons
NASA Technical Reports Server (NTRS)
Stone, James R.; Krejsa, Eugene A.; Clark, Bruce J.
2003-01-01
Development of good predictive models for jet noise has always been plagued by the difficulty in obtaining good quality data over a wide range of conditions in different facilities.We consider such issues very carefully in selecting data to be used in developing our model. Flight effects are of critical importance, and none of the means of determining them are without significant problems. Free-jet flight simulation facilities are very useful, and can provide meaningful data so long as they can be analytically transformed to the flight frame of reference. In this report we show that different methodologies used by NASA and industry to perform this transformation produce very different results, especially in the rear quadrant; this compels us to rely largely on static data to develop our model, but we show reasonable agreement with simulated flight data when these transformation issues are considered. A persistent problem in obtaining good quality data is noise generated in the experimental facility upstream of the test nozzle: valves, elbows, obstructions, and especially the combustor can contribute significant noise, and much of this noise is of a broadband nature, easily confused with jet noise. Muffling of these sources is costly in terms of size as well as expense, and it is particularly difficult in flight simulation facilities, where compactness of hardware is very important, as discussed by Viswanathan (Ref. 13). We feel that the effects of jet density on jet mixing noise may have been somewhat obscured by these problems, leading to the variable density exponent used in most jet noise prediction procedures including our own. We investigate this issue, applying Occam s razor, (e.g., Ref. 14), in a search for the simplest physically meaningful model that adequately describes the observed phenomena. In a similar vein, we see no reason to reject the Lighthill approach; it provides a very solid basis upon which to build a predictive procedure, as we believe we
Boundary element modeling of earthquake site effects including the complete incident wavefield
NASA Astrophysics Data System (ADS)
Kim, Kyoung-Tae
Numerical modeling of earthquake site effects in realistic, three-dimensional structures, including high frequencies, low surface velocities and surface topography, has not been possible simply because the amount of computer memory constrains the number of grid points available. In principle, this problem is reduced in the Boundary Element Method (BEM) since only the surface of the velocity discontinuity is discretized; wave propagation both inside and outside this boundary is computed analytically. Equivalent body forces are determined on the boundary by solving a matrix equation containing frequency-domain displacement and stress Green's functions from every point on the boundary to every other point. This matrix problem has imposed a practical limit on the size or maximum frequency of previous BEM models. Although the matrix can be quite large, it also seems to be fairly sparse. We have used iterative matrix algorithms of the PETSc package and direct solution algorithms of the ScaLAPACK on the massively parallel supercomputers at Cornell, San Diego and Michigan. Preconditioning has been applied using blockwise ILU decomposition for the iterative approach or LU decomposition for the direct approach. The matrix equation is solved using the GMRES method for the iterative approach and a tri-diagonal solver for the direct approach. Previous BEM applications typically have assumed a single, incident plane wave. However, it is clear that for more realistic ground motion simulations, we need to consider the complete incident wavefield. If we assume that the basin or three-dimensional structure of interest is embedded in a surrounding plane-layered medium, we may use the propagator matrix method to solve for the displacements and stresses at depth on the boundary. This is done in the frequency domain with integration over wavenumber so that all P, S, mode conversions, reverberations and surface waves are included. The Boundary Element Method succeeds in modeling
Expanded rock blast modeling capabilities of DMC{_}BLAST, including buffer blasting
Preece, D.S.; Tidman, J.P.; Chung, S.H.
1996-12-31
A discrete element computer program named DMC{_}BLAST (Distinct Motion Code) has been under development since 1987 for modeling rock blasting. This program employs explicit time integration and uses spherical or cylindrical elements that are represented as circles in 2-D. DMC{_}BLAST calculations compare favorably with data from actual bench blasts. The blast modeling capabilities of DMC{_}BLAST have been expanded to include independently dipping geologic layers, top surface, bottom surface and pit floor. The pit can also now be defined using coordinates based on the toe of the bench. A method for modeling decked explosives has been developed which allows accurate treatment of the inert materials (stemming) in the explosive column and approximate treatment of different explosives in the same blasthole. A DMC{_}BLAST user can specify decking through a specific geologic layer with either inert material or a different explosive. Another new feature of DMC{_}BLAST is specification of an uplift angle which is the angle between the normal to the blasthole and a vector defining the direction of explosive loading on particles adjacent to the blasthole. A buffer (choke) blast capability has been added for situations where previously blasted material is adjacent to the free face of the bench preventing any significant lateral motion during the blast.
Dynamic modelling and analysis of multi-machine power systems including wind farms
NASA Astrophysics Data System (ADS)
Tabesh, Ahmadreza
2005-11-01
This thesis introduces a small-signal dynamic model, based on a frequency response approach, for the analysis of a multi-machine power system with special focus on an induction machine based wind farm. The proposed approach is an alternative method to the conventional eigenvalue analysis method which is widely employed for small-signal dynamic analyses of power systems. The proposed modelling approach is successfully applied and evaluated for a power system that (i) includes multiple synchronous generators, and (ii) a wind farm based on either fixed-speed, variable-speed, or doubly-fed induction machine based wind energy conversion units. The salient features of the proposed method, as compared with the conventional eigenvalue analysis method, are: (i) computational efficiency since the proposed method utilizes the open-loop transfer-function matrix of the system, (ii) performance indices that are obtainable based on frequency response data and quantitatively describe the dynamic behavior of the system, and (iii) capability to formulate various wind energy conversion unit, within a wind farm, in a modular form. The developed small-signal dynamic model is applied to a set of multi-machine study systems and the results are validated based on comparison (i) with digital time-domain simulation results obtained from PSCAD/EMTDC software tool, and (ii) where applicable with eigenvalue analysis results.
Wang, Y. T.; Xu, L. X.; Gui, Y. X.
2010-10-15
In this paper, we investigate the integrated Sachs-Wolfe effect in the quintessence cold dark matter model with constant equation of state and constant speed of sound in dark energy rest frame, including dark energy perturbation and its anisotropic stress. Comparing with the {Lambda}CDM model, we find that the integrated Sachs-Wolfe (ISW)-power spectrums are affected by different background evolutions and dark energy perturbation. As we change the speed of sound from 1 to 0 in the quintessence cold dark matter model with given state parameters, it is found that the inclusion of dark energy anisotropic stress makes the variation of magnitude of the ISW source uncertain due to the anticorrelation between the speed of sound and the ratio of dark energy density perturbation contrast to dark matter density perturbation contrast in the ISW-source term. Thus, the magnitude of the ISW-source term is governed by the competition between the alterant multiple of (1+3/2xc-circumflex{sub s}{sup 2}) and that of {delta}{sub de}/{delta}{sub m} with the variation of c-circumflex{sub s}{sup 2}.
Analytical model for radiative transfer including the effects of a rough material interface.
Giddings, Thomas E; Kellems, Anthony R
2016-08-20
The reflected and transmitted radiance due to a source located above a water surface is computed based on models for radiative transfer in continuous optical media separated by a discontinuous air-water interface with random surface roughness. The air-water interface is described as the superposition of random, unresolved roughness on a deterministic realization of a stochastic wave surface at resolved scales. Under the geometric optics assumption, the bidirectional reflection and transmission functions for the air-water interface are approximated by applying regular perturbation methods to Snell's law and including the effects of a random surface roughness component. Formal analytical solutions to the radiative transfer problem under the small-angle scattering approximation account for the effects of scattering and absorption as light propagates through the atmosphere and water and also capture the diffusive effects due to the interaction of light with the rough material interface that separates the two optical media. Results of the analytical models are validated against Monte Carlo simulations, and the approximation to the bidirectional reflection function is also compared to another well-known analytical model. PMID:27556978
A model of force balance in Jupiter's magnetodisc including hot plasma pressure anisotropy
NASA Astrophysics Data System (ADS)
Nichols, J. D.; Achilleos, N.; Cowley, S. W. H.
2015-12-01
We present an iterative vector potential model of force balance in Jupiter's magnetodisc that includes the effects of hot plasma pressure anisotropy. The fiducial model produces results that are consistent with Galileo magnetic field and plasma data over the whole radial range of the model. The hot plasma pressure gradient and centrifugal forces dominate in the regions inward of ˜20 RJ and outward of ˜50 RJ, respectively, while for realistic values of the pressure anisotropy, the anisotropy current is either the dominant component or at least comparable with the hot plasma pressure gradient current in the region in between. With the inclusion of hot plasma pressure anisotropy, the ˜1.2 and ˜2.7° shifts in the latitudes of the main oval and Ganymede footprint, respectively, associated with variations over the observed range of the hot plasma parameter Kh, which is the product of hot pressure and unit flux tube volume, are comparable to the shifts observed in auroral images. However, the middle magnetosphere is susceptible to the firehose instability, with peak equatorial values of βh∥e-βh⊥e≃1 - 2, for Kh=2.0 - 2.5 × 107 Pa m T-1. For larger values of Kh,βh∥e-βh⊥e exceeds 2 near ˜25 RJ and the model does not converge. This suggests that small-scale plasmoid release or "drizzle" of iogenic plasma may often occur in the middle magnetosphere, thus forming a significant mode of plasma mass loss, alongside plasmoids, at Jupiter.
Groundwater recharge in a hard rock aquifer: A conceptual model including surface-loading effects
NASA Astrophysics Data System (ADS)
Rodhe, Allan; Bockgård, Niclas
2006-11-01
SummaryThe groundwater level in a fractured rock aquifer in Sweden was found to respond quickly to rainfall, although the bedrock was covered by 10-m-thick till soil. A considerable portion of the response was caused by surface loading, i.e., by the weight increase of the soil due to the addition of water from precipitation, whereas the rest reflected recharge. The hypothesis that the bedrock aquifer was recharged by vertical flow from groundwater in the overlying soil was tested with a simple recharge model, in which the bedrock-groundwater levels were simulated from the soil-groundwater and estimated surface-loading variation. The model had three parameters: the ratio between the equivalent vertical hydraulic conductivity governing the recharge and the storage coefficient of the bedrock reservoir, the recession coefficient for the bedrock-groundwater level, and the bedrock-groundwater level at which the outflow ceases. The model could be reasonably well calibrated and validated to head observations in one of two boreholes. The fit to the seasonal variation was similar when calibrating the model with or without surface loading, but surface loading had to be included to properly simulate individual recharge events. The relative temporal variation in the fluxes could be determined by the calibration. The variation in the recharge was from -10% to +25% in relation to the mean flux. The variation in the discharge was only ±1%. By applying a storage coefficient of the reservoir of 5 × 10 -4, the simulated mean recharge was about 20 mm yr -1. The results support the hypothesis that the bedrock-groundwater at the site is fed by local recharge from the overlying soil aquifer.
Modelling and control of a microgrid including photovoltaic and wind generation
NASA Astrophysics Data System (ADS)
Hussain, Mohammed Touseef
Extensive increase of distributed generation (DG) penetration and the existence of multiple DG units at distribution level have introduced the notion of micro-grid. This thesis develops a detailed non-linear and small-signal dynamic model of a microgrid that includes PV, wind and conventional small scale generation along with their power electronics interfaces and the filters. The models developed evaluate the amount of generation mix from various DGs for satisfactory steady state operation of the microgrid. In order to understand the interaction of the DGs on microgrid system initially two simpler configurations were considered. The first one consists of microalternator, PV and their electronics, and the second system consists of microalternator and wind system each connected to the power system grid. Nonlinear and linear state space model of each microgrid are developed. Small signal analysis showed that the large participation of PV/wind can drive the microgrid to the brink of unstable region without adequate control. Non-linear simulations are carried out to verify the results obtained through small-signal analysis. The role of the extent of generation mix of a composite microgrid consisting of wind, PV and conventional generation was investigated next. The findings of the smaller systems were verified through nonlinear and small signal modeling. A central supervisory capacitor energy storage controller interfaced through a STATCOM was proposed to monitor and enhance the microgrid operation. The potential of various control inputs to provide additional damping to the system has been evaluated through decomposition techniques. The signals identified to have damping contents were employed to design the supervisory control system. The controller gains were tuned through an optimal pole placement technique. Simulation studies demonstrate that the STATCOM voltage phase angle and PV inverter phase angle were the best inputs for enhanced stability boundaries.
Relationship between X(5) models and the interacting boson model
Barea, Jose; Arias, Jose M.; Garcia-Ramos, Jose Enrique
2010-08-15
The connections between the X(5) models [the original X(5) using an infinite square well, X(5)-{beta}{sup 8}, X(5)-{beta}{sup 6}, X(5)-{beta}{sup 4}, and X(5)-{beta}{sup 2}], based on particular solutions of the geometrical Bohr Hamiltonian with harmonic potential in the {gamma} degree of freedom, and the interacting boson model (IBM) are explored. This work is the natural extension of the work presented in Garcia-Ramos and Arias, Phys. Rev. C 77, 054307 (2008) for the E(5) models. For that purpose, a quite general one- and two-body IBM Hamiltonian is used and a numerical fit to the different X(5) model energies is performed; then the obtained wave functions are used to calculate B(E2) transition rates. It is shown that within the IBM one can reproduce well the results for energies and B(E2) transition rates obtained with all these X(5) models, although the agreement is not so impressive as for the E(5) models. From the fitted IBM parameters the corresponding energy surface can be extracted and, surprisingly, only the X(5) case corresponds in the moderately large N limit to an energy surface very close to the one expected for a critical point, whereas the rest of models are situated a little further away.
Relationships between Visual Static Models and Students' Written Solutions to Fraction Tasks
ERIC Educational Resources Information Center
Anderson-Pence, Katie L.; Moyer-Packenham, Patricia S.; Westenskow, Arla; Shumway, Jessica; Jordan, Kerry
2014-01-01
The purpose of this study was to deconstruct the relationship between visual static models and students' written solutions to fraction problems using a large sample of students' solutions. Participants in the study included 162 third-grade and 209 fourth-grade students from 17 different classrooms. Students' written responses to…
The importance of including imperfect detection models in eDNA experimental design.
Willoughby, Janna R; Wijayawardena, Bhagya K; Sundaram, Mekala; Swihart, Robert K; DeWoody, J Andrew
2016-07-01
Environmental DNA (eDNA) is DNA that has been isolated from field samples, and it is increasingly used to infer the presence or absence of particular species in an ecosystem. However, the combination of sampling procedures and subsequent molecular amplification of eDNA can lead to spurious results. As such, it is imperative that eDNA studies include a statistical framework for interpreting eDNA presence/absence data. We reviewed published literature for studies that utilized eDNA where the species density was known and compared the probability of detecting the focal species to the sampling and analysis protocols. Although biomass of the target species and the volume per sample did not impact detectability, the number of field replicates and number of samples from each replicate were positively related to detection. Additionally, increased number of PCR replicates and increased primer specificity significantly increased detectability. Accordingly, we advocate for increased use of occupancy modelling as a method to incorporate effects of sampling effort and PCR sensitivity in eDNA study design. Based on simulation results and the hierarchical nature of occupancy models, we suggest that field replicates, as opposed to molecular replicates, result in better detection probabilities of target species. PMID:27037675
INTERIOR MODELS OF SATURN: INCLUDING THE UNCERTAINTIES IN SHAPE AND ROTATION
Helled, Ravit; Guillot, Tristan
2013-04-20
The accurate determination of Saturn's gravitational coefficients by Cassini could provide tighter constraints on Saturn's internal structure. Also, occultation measurements provide important information on the planetary shape which is often not considered in structure models. In this paper we explore how wind velocities and internal rotation affect the planetary shape and the constraints on Saturn's interior. We show that within the geodetic approach the derived physical shape is insensitive to the assumed deep rotation. Saturn's re-derived equatorial and polar radii at 100 mbar are found to be 54,445 {+-} 10 km and 60,365 {+-} 10 km, respectively. To determine Saturn's interior, we use one-dimensional three-layer hydrostatic structure models and present two approaches to include the constraints on the shape. These approaches, however, result in only small differences in Saturn's derived composition. The uncertainty in Saturn's rotation period is more significant: with Voyager's 10{sup h}39{sup m} period, the derived mass of heavy elements in the envelope is 0-7 M{sub Circled-Plus }. With a rotation period of 10{sup h}32{sup m}, this value becomes <4 M{sub Circled-Plus }, below the minimum mass inferred from spectroscopic measurements. Saturn's core mass is found to depend strongly on the pressure at which helium phase separation occurs, and is estimated to be 5-20 M{sub Circled-Plus }. Lower core masses are possible if the separation occurs deeper than 4 Mbar. We suggest that the analysis of Cassini's radio occultation measurements is crucial to test shape models and could lead to constraints on Saturn's rotation profile and departures from hydrostatic equilibrium.
A two-dimensional energy balance climate model including radiation and ice caps-albedo feedback
NASA Astrophysics Data System (ADS)
Yingyi, Chen; Jiping, Chao
1984-11-01
A simplified two-dimensional energy balance climate model including the solar and infrared radiation transports, the turbulent exchanges of heat in vertical and horizontal directions and the ice caps-albedo feedback is developed. The solutions show that if the atmosphere is considered as a grey body and the grey coefficient depends upon the distributions of absorption medium and cloudiness, both horizontal and vertical distribution of temperature are identical to the observation. On the other hand, comparing the models that the atmosphere is considered as a grey body with ones that the infrared radiation is parameterized as a linear function of temperature, as was considered by Budyko, Sellers(1969), then the results show that even though both of them can obtain the earth's surface temperature in agreement with the observation, the sensitivity of the climate to the changes of solar constant is very different. In the former case, the requirement for the ice edge to move southward from the normal 72°N to 50°N(i.e. where the glacial climate would take place) is that the solar constant should decrease by 13% to 16%. However, in the latter case, the climate is highly sensitive to the changes of solar radiation. In this case, the requirement of solar radiation occurring in the glacial climate should decrease by, 2% to 6%. According to the investigations mentioned above we must be careful when the parameterizations of the radiation and other processes are conducted in a climate model., otherwise the reliability of the results is suspicious.
Effects of neurosteroids on a model membrane including cholesterol: A micropipette aspiration study.
Balleza, Daniel; Sacchi, Mattia; Vena, Giulia; Galloni, Debora; Puia, Giulia; Facci, Paolo; Alessandrini, Andrea
2015-05-01
Amphiphilic molecules supposed to affect membrane protein activity could strongly interact also with the lipid component of the membrane itself. Neurosteroids are amphiphilic molecules that bind to plasma membrane receptors of cells in the central nervous system but their effect on membrane is still under debate. For this reason it is interesting to investigate their effects on pure lipid bilayers as model systems. Using the micropipette aspiration technique (MAT), here we studied the effects of a neurosteroid, allopregnanolone (3α,5α-tetrahydroprogesterone or Allo) and of one of its isoforms, isoallopregnanolone (3β,5α-tetrahydroprogesterone or isoAllo), on the physical properties of pure lipid bilayers composed by DOPC/bSM/chol. Allo is a well-known positive allosteric modulator of GABAA receptor activity while isoAllo acts as a non-competitive functional antagonist of Allo modulation. We found that Allo, when applied at nanomolar concentrations (50-200 nM) to a lipid bilayer model system including cholesterol, induces an increase of the lipid bilayer area and a decrease of the mechanical parameters. Conversely, isoAllo, decreases the lipid bilayer area and, when applied, at the same nanomolar concentrations, it does not affect significantly its mechanical parameters. We characterized the kinetics of Allo uptake by the lipid bilayer and we also discussed its aspects in relation to the slow kinetics of Allo gating effects on GABAA receptors. The overall results presented here show that a correlation exists between the modulation of Allo and isoAllo of GABAA receptor activity and their effects on a lipid bilayer model system containing cholesterol. PMID:25660752
Extending the actor-partner interdependence model to include cross-informant data.
van Dulmen, Manfred H M; Goncy, Elizabeth A
2010-12-01
This paper illustrates an extension of the APIM technique within a path analysis framework by using cross-informant data on the outcome variable. Data for the current study were derived from a sample of young adult heterosexual couples who had been in a romantic relationship for at least four months (N = 115 couples). The findings from the current study indicate that romantic relationship satisfaction is associated with externalizing behavior problems among both females and males, but that both dyadic data and cross-informant reports are needed to understand this association. Not considering dyadic or cross-informant data may lead to different, and potentially misleading, claims. The findings from the current study provide clear evidence that incorporating cross-informant data in dyadic data analyses provides important new insights into understanding the association between romantic relationship functioning and individual outcomes. PMID:20719376
[Relationship between two models of personality in old individuals].
Calvet, Benjamin; Bricaud, Magali; Clément, Jean-Pierre
2014-12-01
The relationships between the seven dimensions of the Cloninger psychobiological model and the five factors of the Costa and McCrae model were examined in 54 elderly subjects from the French general population. The dimensions of temperament (novelty seeking, harm avoidance, reward dependence) and character (determination, cooperation, transcendence) from the Cloninger's model were measured by the temperament and character inventory whereas the five factors of Costa and McCrae model (neuroticism, extraversion, openness to experience, agreeableness and conscientiousness) were evaluated using the NEO PI-R. Multiple regression analyses show that some dimensions of the temperament and character inventory predict some dimensions of the Big five and vice versa. Therefore we suggest that the Big five model could be related to brain monoaminergic activities. PMID:25515910
NASA Astrophysics Data System (ADS)
Mann, Matthew James
Rural and small schools have almost one-third of all public school enrollment in America, yet typically have the fewest financial and research based resources. Educational models have been developed with either the urban or suburban school in mind, and the rural school is often left with no other alternative except this paradigm. Rural based educational resources are rare and the ability to access these resources for rural school districts almost non-existent. Federal and state based education agencies provide some rural educational based programs, but have had virtually no success in answering rural school issues. With federal and state interest in science initiatives, the challenge that rural schools face weigh in. To align with that focus, this study examined Texas middle school student achievement in science and its relationship with school district enrollment size. This study involved a sequential transformative mixed methodology with the quantitative phase driving the second qualitative portion. The quantitative research was a non-experimental causal-comparative study conducted to determine whether there is a significant difference between student achievement on the 2010 Texas Assessment of Knowledge and Skills 8 th grade science results and school district enrollment size. The school districts were distributed into four categories by size including: a) small districts (32-550); b) medium districts (551-1500); c) large districts (1501-6000); and d) mega-sized districts (6001-202,773). A one-way analysis of variance (ANOVA) was conducted to compare the district averages from the 2010 TAKS 8th grade science assessment results and the four district enrollment groups. The second phase of the study was qualitative utilizing constructivism and critical theory to identify the issues facing rural and small school administrators concerning science based curriculum and development. These themes and issues were sought through a case study method and through use of semi
NASA Astrophysics Data System (ADS)
Segall, P.; Bradley, A. M.
2009-12-01
Seismic and geodetic observations indicate that slow-slip events (SSE) occur down-dip of locked megathrusts, in areas of high pore-pressure, p. We suggest that at low effective stress (σ -p) dilatancy stabilizes rate-weakening faults, whereas at higher (σ -p) thermal pressurization overwhelms dilatancy leading to dynamic slip. 2D simulations include rate-state (slip-law) friction with Linker-Dieterich normal stress effect, Segall-Rice dilatancy linked to state evolution, and heat and pore-fluid flow normal to the fault. The fault is loaded by down-dip slip at v∞ . We discretize the fault normal direction with log spacing, and employ explicit-implicit time integration to improve speed and accuracy. The governing equations involve numerous physical parameters, but relatively few non-dimensional groups. Ep={ɛ h}/ [2 {β (σ - p∞)}√ {{v{∞ }}/ {chyd}dc] and ET=({f_0Λ }/{2ρ cp})√ {{chydd_c v∞}}/{cth}2 represent dilatancy and shear heating efficiency, respectively. For a nominal set of parameters (given below), spatially uniform properties, and σ -p=1MPa, (Ep = 1.5 × 10-3, ET = 3 × 10-5), we find a series of propagating SSE, that are stabilized by dilatancy-induced drops in p at the rupture tips. For a broad range of parameters we observe slow-slip events driven by down-dip slip, with negative stress drop, as well as faster (but quasi-static) events that relax the accumulated stress. At 10 MPa effective stress, the models exhibit both SSE and dynamic ruptures. Following dynamic stress drops, a sequence of slow slip events is driven from the down-dip end of the fault, with generally increasing maximum slip-speeds. We also consider spatially variable (σ -p), ranging from 2 MPa down-dip to 10 MPa up-dip (with arctangent distribution such that 80% of the variation occurs across 20% of the fault), and uniform material properties. The models exhibit both SSE and dynamic events. Following a dynamic rupture there are initially no slow events, and the
Extending the Actor-Partner Interdependence Model to Include Cross-Informant Data
ERIC Educational Resources Information Center
van Dulmen, Manfred H. M.; Goncy, Elizabeth A.
2010-01-01
This paper illustrates an extension of the APIM technique within a path analysis framework by using cross-informant data on the outcome variable. Data for the current study were derived from a sample of young adult heterosexual couples who had been in a romantic relationship for at least four months (N = 115 couples). The findings from the current…
Fast hybrid SPECT simulation including efficient septal penetration modelling (SP-PSF).
Staelens, Steven; de Wit, Tim; Beekman, Freek
2007-06-01
Single photon emission computed tomography (SPECT) images are degraded by the detection of scattered photons and photons that penetrate the collimator septa. In this paper, a previously proposed Monte Carlo software that employs fast object scatter simulation using convolution-based forced detection (CFD) is extended towards a wide range of medium and high energy isotopes measured using various collimators. To this end, a fast method was developed for incorporating effects of septal penetrating (SP) photons. The SP contributions are obtained by calculating the object attenuation along the path from primary emission to detection followed by sampling a pre-simulated and scalable septal penetration point spread function (SP-PSF). We found that with only a very slight reduction in accuracy, we could accelerate the SP simulation by four orders of magnitude. To achieve this, we combined: (i) coarse sampling of the activity and attenuation distribution; (ii) simulation of the penetration only for a coarse grid of detector pixels followed by interpolation and (iii) neglection of SP-PSF elements below a certain threshold. By inclusion of this SP-PSF-based simulation it became possible to model both primary and septal penetrated photons while only 10% extra computation time was added to the CFD-based Monte Carlo simulator. As a result, a SPECT simulation of a patient-like distribution including SP now takes less than 5 s per projection angle on a dual processor PC. Therefore, the simulator is well-suited as an efficient projector for fully 3D model-based reconstruction or as a fast data-set generator for applications such as image processing optimization or observer studies. PMID:17505087
ERIC Educational Resources Information Center
Department of Defense, Washington, DC.
Updated Defense Economic Impact Modeling System (DEIMS) manpower data are provided. Skilled-labor demand by job categories and industrial sectors are estimated for 163 skill categories. Both defense and non-defense demands are presented for the years 1982 to 1987. The average annual percentage growth for the time period is also estimated. Data are…
NASA Astrophysics Data System (ADS)
Fitzenz, D. D.; Nyst, M.; Apel, E. V.; Muir-Wood, R.
2014-12-01
The recent Canterbury earthquake sequence (CES) renewed public and academic awareness concerning the clustered nature of seismicity. Multiple event occurrence in short time and space intervals is reminiscent of aftershock sequences, but aftershock is a statistical definition, not a label one can give an earthquake in real-time. Aftershocks are defined collectively as what creates the Omori event rate decay after a large event or are defined as what is taken away as "dependent events" using a declustering method. It is noteworthy that depending on the declustering method used on the Canterbury earthquake sequence, the number of independent events varies a lot. This lack of unambiguous definition of aftershocks leads to the need to investigate the amount of clustering inherent in "declustered" risk models. This is the task we concentrate on in this contribution. We start from a background source model for the Canterbury region, in which 1) centroids of events of given magnitude are distributed using a latin-hypercube lattice, 2) following the range of preferential orientations determined from stress maps and focal mechanism, 3) with length determined using the local scaling relationship and 4) rates from a and b values derived from the declustered pre-2010 catalog. We then proceed to create tens of thousands of realizations of 6 to 20 year periods, and we define criteria to identify which successions of events in the region would be perceived as a sequence. Note that the spatial clustering expected is a lower end compared to a fully uniform distribution of events. Then we perform the same exercise with rates and b-values determined from the catalog including the CES. If the pre-2010 catalog was long (or rich) enough, then the computed "stationary" rates calculated from it would include the CES declustered events (by construction, regardless of the physical meaning of or relationship between those events). In regions of low seismicity rate (e.g., Canterbury before
NASA Astrophysics Data System (ADS)
Höning, D.; Spohn, T.
2014-12-01
By harvesting solar energy and converting it to chemical energy, photosynthetic life plays an important role in the energy budget of Earth [2]. This leads to alterations of chemical reservoirs eventually affecting the Earth's interior [4]. It further has been speculated [3] that the formation of continents may be a consequence of the evolution life. A steady state model [1] suggests that the Earth without its biosphere would evolve to a steady state with a smaller continent coverage and a dryer mantle than is observed today. We present a model including (i) parameterized thermal evolution, (ii) continental growth and destruction, and (iii) mantle water regassing and outgassing. The biosphere enhances the production rate of sediments which eventually are subducted. These sediments are assumed to (i) carry water to depth bound in stable mineral phases and (ii) have the potential to suppress shallow dewatering of the underlying sediments and crust due to their low permeability. We run a Monte Carlo simulation for various initial conditions and treat all those parameter combinations as success which result in the fraction of continental crust coverage observed for present day Earth. Finally, we simulate the evolution of an abiotic Earth using the same set of parameters but a reduced rate of continental weathering and erosion. Our results suggest that the origin and evolution of life could have stabilized the large continental surface area of the Earth and its wet mantle, leading to the relatively low mantle viscosity we observe at present. Without photosynthetic life on our planet, the Earth would be geodynamical less active due to a dryer mantle, and would have a smaller fraction of continental coverage than observed today. References[1] Höning, D., Hansen-Goos, H., Airo, A., Spohn, T., 2014. Biotic vs. abiotic Earth: A model for mantle hydration and continental coverage. Planetary and Space Science 98, 5-13. [2] Kleidon, A., 2010. Life, hierarchy, and the
Conchúir, Shane Ó.; Der, Bryan S.; Drew, Kevin; Kuroda, Daisuke; Xu, Jianqing; Weitzner, Brian D.; Renfrew, P. Douglas; Sripakdeevong, Parin; Borgo, Benjamin; Havranek, James J.; Kuhlman, Brian; Kortemme, Tanja; Bonneau, Richard; Gray, Jeffrey J.; Das, Rhiju
2013-01-01
The Rosetta molecular modeling software package provides experimentally tested and rapidly evolving tools for the 3D structure prediction and high-resolution design of proteins, nucleic acids, and a growing number of non-natural polymers. Despite its free availability to academic users and improving documentation, use of Rosetta has largely remained confined to developers and their immediate collaborators due to the code’s difficulty of use, the requirement for large computational resources, and the unavailability of servers for most of the Rosetta applications. Here, we present a unified web framework for Rosetta applications called ROSIE (Rosetta Online Server that Includes Everyone). ROSIE provides (a) a common user interface for Rosetta protocols, (b) a stable application programming interface for developers to add additional protocols, (c) a flexible back-end to allow leveraging of computer cluster resources shared by RosettaCommons member institutions, and (d) centralized administration by the RosettaCommons to ensure continuous maintenance. This paper describes the ROSIE server infrastructure, a step-by-step ‘serverification’ protocol for use by Rosetta developers, and the deployment of the first nine ROSIE applications by six separate developer teams: Docking, RNA de novo, ERRASER, Antibody, Sequence Tolerance, Supercharge, Beta peptide design, NCBB design, and VIP redesign. As illustrated by the number and diversity of these applications, ROSIE offers a general and speedy paradigm for serverification of Rosetta applications that incurs negligible cost to developers and lowers barriers to Rosetta use for the broader biological community. ROSIE is available at http://rosie.rosettacommons.org. PMID:23717507
PORTNEUF VALLEY, IDAHO PM-10 DISPERSION MODEL INCLUDING SECONDARY CHEMICAL FORMATION
A dispersion modeling effort for the Portneuf Valley, Pocatello, Idaho PM-10 attainment demonstration is underway. The model will treat the secondary chemical formation process, primarily sulfate and nitrate formation under both the aqueous and gas phases. The model will simul...
Including Overweight or Obese Students in Physical Education: A Social Ecological Constraint Model
ERIC Educational Resources Information Center
Li, Weidong; Rukavina, Paul
2012-01-01
In this review, we propose a social ecological constraint model to study inclusion of overweight or obese students in physical education by integrating key concepts and assumptions from ecological constraint theory in motor development and social ecological models in health promotion and behavior. The social ecological constraint model proposes…
Extending Galactic Habitable Zone Modelling to Include the Emergence of Intelligent Life
NASA Astrophysics Data System (ADS)
Morrison, I. S.; Gowanlock, M. G.
2014-03-01
Previous studies of the Galactic Habitable Zone (GHZ) have been concerned with identifying those regions of the Galaxy that may favour the emergence of "complex life" - typically defined to be land-based life. A planet is deemed "habitable" if it meets a set of assumed criteria for supporting the emergence of such complex life. The notion of the GHZ, and the premise that sufficient chemical evolution is required for planet formation, was quantified by Gonzalez et al. (2001). This work was later broadened to include dangers to the formation and habitability of terrestrial planets by Lineweaver et al. (2004) and then studied using a Monte Carlo simulation on the resolution of individual stars in the previous work of Gowanlock et al. (2011). The model developed in the latter work considers the stellar number density distribution and formation history of the Galaxy, planet formation mechanisms and the hazards to planetary biospheres as a result of supernova sterilization events that take place in the vicinity of the planets. Based on timescales taken from the origin and evolution of complex life on Earth, the model suggests large numbers of potentially habitable planets exist in our Galaxy, with the greatest concentration likely being towards the inner Galaxy. In this work we extend the assessment of habitability to consider the potential for life to further evolve on habitable planets to the point of intelligence - which we term the propensity for the emergence of intelligent life. We assume the propensity is strongly influenced by the time durations available for evolutionary processes to proceed undisturbed by the "resetting" effect of nearby supernovae. The model of Gowanlock et al. (2011) is used to produce a representative population of habitable planets by matching major observable properties of the Milky Way. Account is taken of the birth and death dates of each habitable planet and the timing of supernova events in each planet's vicinity. The times between
Evaluation of an Impedance Model for Perforates Including the Effect of Bias Flow
NASA Technical Reports Server (NTRS)
Betts, J. F.; Follet, J. I.; Kelly, J. J.; Thomas, R. H.
2000-01-01
A new bias flow impedance model is developed for perforated plates from basic principles using as little empiricisms as possible. A quality experimental database was used to determine the predictive validity of the model. Results show that the model performs better for higher (15%) rather than lower (5%) percent open area (POA) samples. Based on the least squares ratio of numerical vs. experimental results, model predictions were on average within 20% and 30% for the higher and lower (POA), respectively. It is hypothesized on the work of other investigators that at lower POAs the higher fluid velocities in the perforate's orifices start forming unsteady vortices, which is not accounted for in our model. The numerical model, in general also underpredicts the experiments. It is theorized that the actual acoustic C(sub D) is lower than the measured raylometer C(sub D) used in the model. Using a larger C(sub D) makes the numerical model predict lower impedances. The frequency domain model derived in this paper shows very good agreement with another model derived using a time domain approach.
Including slot harmonics to mechanical model of two-pole induction machine with a force actuator
NASA Astrophysics Data System (ADS)
Sinervo, Anssi; Arkkio, Antero
2012-10-01
A simple mechanical model is identified for a two-pole induction machine that has a four-pole extra winding as a force actuator. The actuator can be used to suppress rotor vibrations. Forces affecting the rotor of the induction machine are separated into actuator force, purely mechanical force due to mass unbalance, and force caused by unbalanced magnetic pull from higher harmonics and unipolar flux. The force due to higher harmonics is embedded to the mechanical model. Parameters of the modified mechanical model are identified from measurements and the modifications are shown to be necessary. The force produced by the actuator is calculated using the mechanical model, direct flux measurements, and voltage and current of the force actuator. All three methods are shown to give matching results proving that the mechanical model can be used in vibration control. The test machine is shown to have time periodic behavior and discrete Fourier analysis is used to obtain time-invariant model parameters.
2010-01-01
Background The use of structural equation models for the analysis of recursive and simultaneous relationships between phenotypes has become more popular recently. The aim of this paper is to illustrate how these models can be applied in animal breeding to achieve parameterizations of different levels of complexity and, more specifically, to model phenotypic recursion between three calving traits: gestation length (GL), calving difficulty (CD) and stillbirth (SB). All recursive models considered here postulate heterogeneous recursive relationships between GL and liabilities to CD and SB, and between liability to CD and liability to SB, depending on categories of GL phenotype. Methods Four models were compared in terms of goodness of fit and predictive ability: 1) standard mixed model (SMM), a model with unstructured (co)variance matrices; 2) recursive mixed model 1 (RMM1), assuming that residual correlations are due to the recursive relationships between phenotypes; 3) RMM2, assuming that correlations between residuals and contemporary groups are due to recursive relationships between phenotypes; and 4) RMM3, postulating that the correlations between genetic effects, contemporary groups and residuals are due to recursive relationships between phenotypes. Results For all the RMM considered, the estimates of the structural coefficients were similar. Results revealed a nonlinear relationship between GL and the liabilities both to CD and to SB, and a linear relationship between the liabilities to CD and SB. Differences in terms of goodness of fit and predictive ability of the models considered were negligible, suggesting that RMM3 is plausible. Conclusions The applications examined in this study suggest the plausibility of a nonlinear recursive effect from GL onto CD and SB. Also, the fact that the most restrictive model RMM3, which assumes that the only cause of correlation is phenotypic recursion, performs as well as the others indicates that the phenotypic recursion
Facal, David; González-Barcala, Francisco-Javier
2016-01-01
Changes in respiratory function are common in older populations and affect quality of life, social relationships, cognitive function and functional capacity. This paper reviews evidence reported in medical and psychological journals between 2000 and 2014 concerning the impact of changes in respiratory function on daily living in older adults. A tentative model establishes relationships involving respiratory function, cognitive function and functional capacities. The conclusion stresses the need for both longitudinal studies, to establish causal pathways between respiratory function and psychosocial aspects in aging, and intervention studies. PMID:26593253
A model for multi-finger HBTs including current gain collapse effects
NASA Astrophysics Data System (ADS)
Garlapati, Akhil; Prasad, Sheila; Vempada, Pradeep; Munshi, Kambiz
2003-11-01
A common-emitter equivalent circuit model which represents both the self-heating and the current collapse as feedback from the collector current to the base-emitter voltage is developed for multi-finger InGaAs/GaAs HBTs. The modified Ebers-Moll model is verified by comparing the simulated and measured results. Good agreement is also achieved for the scattering parameters and I- V characteristics confirming the validity of the model for high frequency applications.
NASA Astrophysics Data System (ADS)
Hauser, H.; Melikhov, Y.; Jiles, D. C.
2007-10-01
Two recent theoretical hysteresis models (Jiles-Atherton model and energetic model) are examined with respect to their capability to describe the dependence of the magnetization on magnetic field, microstructure, and anisotropy. It is shown that the classical Rayleigh law for the behavior of magnetization at low fields and the Stoner-Wohlfarth theory of domain magnetization rotation in noninteracting magnetic single domain particles can be considered as limiting cases of a more general theoretical treatment of hysteresis in ferromagnetism.
Considering complementary relationship of evaporation in Budyko's hydrological model
NASA Astrophysics Data System (ADS)
Han, Songjun; Shao, Weiwei
2013-04-01
In Budyko's hydrological model, actual evaporation was partitioned from precipitation as a function of the relative magnitude of precipitation and potential evaporation. In practice, both Penman equation and Priestley-Taylor equation have been used to estimate the potential evaporation with same Budyko curve, and they are not distinguished under Budyko framework. Nevertheless, according to the complementary relationship of evaporation, the definitions of Penman equation and Priestley-Taylor equation are absolutely different. When water availability is not limited, evaporation occurs at Priestley-Taylor's evaporation (Ew, referred to as wet environment evaporation). As the surface dries without changing the available energy, the actual and Penman's potential evaporation (Epen) rates depart from Ew with opposite changes in fluxes. So the question is: what is the difference of the Budyko's hydrological model with potential evaporation estimated by Penman or Priestley-Taylor equation? How to consider the complementary relationship in Budyko framework? In this study, for both long-term (multiyear) and annual values on water balances in the 29 non-humid catchments in the middle Yellow River Basin of China, the performances of Budyko's hydrological model with potential evaporation estimated by Epen and Ew were distinguished and compared. The catchments with larger value of Ep/Ew (ratio of Penman potential evaporation to Priestley-Taylor evaporation) are characterized with smaller evaporation ratios. The value of Ep/Ew can be served as another variable besides dryness index to partition actual evaporation from precipitation. With Priestley-Taylor equation as energy supply, an empirical formula for the parameter of the Budyko in terms of Ep/Ew and curve is proposed. Therefore, the complementary relationship of evaporation should be considered in the Budyko framework.
A New Finite-Conductivity Droplet Evaporation Model Including Liquid Turbulence Effect
NASA Technical Reports Server (NTRS)
Balasubramanyam, M. S.; Chen, C. P.; Trinh, H. P.
2006-01-01
A new approach to account for finite thermal conductivity and turbulence effects within atomizing droplets of an evaporating spray is presented in this paper. The model is an extension of the T-blob and T-TAB atomization/spray model of Trinh and Chen [9]. This finite conductivity model is based on the two-temperature film theory in which the turbulence characteristics of the droplet are used to estimate the effective thermal diffusivity for the liquid-side film thickness. Both one-way and two-way coupled calculations were performed to investigate the performance cf this model against the published experimental data.
NASA Astrophysics Data System (ADS)
Gupta, Santosh Kumar
2015-12-01
2D Analytical model of the body center potential (BCP) in short channel junctionless Cylindrical Surrounding Gate (JLCSG) MOSFETs is developed using evanescent mode analysis (EMA). This model also incorporates the gate bias dependent inner and outer fringing capacitances due to the gate-source/drain fringing fields. The developed model provides results in good agreement with simulated results for variations of different physical parameters of JLCSG MOSFET viz. gate length, channel radius, doping concentration, and oxide thickness. Using the BCP, an analytical model for the threshold voltage has been derived and validated against results obtained from 3D device simulator.
Software Engineering Laboratory (SEL) relationships, models, and management rules
NASA Technical Reports Server (NTRS)
Decker, William; Hendrick, Robert; Valett, Jon D.
1991-01-01
Over 50 individual Software Engineering Laboratory (SEL) research results, extracted from a review of published SEL documentation, that can be applied directly to managing software development projects are captured. Four basic categories of results are defined and discussed - environment profiles, relationships, models, and management rules. In each category, research results are presented as a single page that summarizes the individual result, lists potential uses of the result by managers, and references the original SEL documentation where the result was found. The document serves as a concise reference summary of applicable research for SEL managers.
NASA Astrophysics Data System (ADS)
Canuto, V. M.
1994-06-01
The Reynolds numbers that characterize geophysical and astrophysical turbulence (Re approximately equals 108 for the planetary boundary layer and Re approximately equals 1014 for the Sun's interior) are too large to allow a direct numerical simulation (DNS) of the fundamental Navier-Stokes and temperature equations. In fact, the spatial number of grid points N approximately Re9/4 exceeds the computational capability of today's supercomputers. Alternative treatments are the ensemble-time average approach, and/or the volume average approach. Since the first method (Reynolds stress approach) is largely analytical, the resulting turbulence equations entail manageable computational requirements and can thus be linked to a stellar evolutionary code or, in the geophysical case, to general circulation models. In the volume average approach, one carries out a large eddy simulation (LES) which resolves numerically the largest scales, while the unresolved scales must be treated theoretically with a subgrid scale model (SGS). Contrary to the ensemble average approach, the LES+SGS approach has considerable computational requirements. Even if this prevents (for the time being) a LES+SGS model to be linked to stellar or geophysical codes, it is still of the greatest relevance as an 'experimental tool' to be used, inter alia, to improve the parameterizations needed in the ensemble average approach. Such a methodology has been successfully adopted in studies of the convective planetary boundary layer. Experienc e with the LES+SGS approach from different fields has shown that its reliability depends on the healthiness of the SGS model for numerical stability as well as for physical completeness. At present, the most widely used SGS model, the Smagorinsky model, accounts for the effect of the shear induced by the large resolved scales on the unresolved scales but does not account for the effects of buoyancy, anisotropy, rotation, and stable stratification. The latter phenomenon
An Effective Model to Increase Student Attitude and Achievement: Narrative Including Analogies
ERIC Educational Resources Information Center
Akkuzu, Nalan; Akcay, Husamettin
2011-01-01
This study describes the analogical models and narratives used to introduce and teach Grade 9 chemical covalent compounds which are relatively abstract and difficult for students. We explained each model's development during the lessons and analyzed understanding students derived from these learning materials. In this context, achievement,…
NASA Astrophysics Data System (ADS)
Neumann, R. B.; Cardon, Z. G.; Rockwell, F. E.; Teshera-Levye, J.; Zwieniecki, M.; Holbrook, N. M.
2013-12-01
The movement of water from moist to dry soil layers through the root systems of plants, referred to as hydraulic redistribution (HR), occurs throughout the world and is thought to influence carbon and water budgets and ecosystem functioning. The realized hydrologic, biogeochemical, and ecological consequences of HR depend on the amount of redistributed water, while the ability to assess these impacts requires models that correctly capture HR magnitude and timing. Using several soil types and two eco-types of Helianthus annuus L. in split-pot experiments, we examined how well the widely used HR modeling formulation developed by Ryel et al. (2002) could match experimental determination of HR across a range of water potential driving gradients. H. annuus carries out extensive nighttime transpiration, and though over the last decade it has become more widely recognized that nighttime transpiration occurs in multiple species and many ecosystems, the original Ryel et al. (2002) formulation does not include the effect of nighttime transpiration on HR. We developed and added a representation of nighttime transpiration into the formulation, and only then was the model able to capture the dynamics and magnitude of HR we observed as soils dried and nighttime stomatal behavior changed, both influencing HR.
NASA Technical Reports Server (NTRS)
Ukanwa, A. O.; Stermole, F. J.; Golden, J. O.
1972-01-01
Natural convection effects in phase change thermal control devices were studied. A mathematical model was developed to evaluate natural convection effects in a phase change test cell undergoing solidification. Although natural convection effects are minimized in flight spacecraft, all phase change devices are ground tested. The mathematical approach to the problem was to first develop a transient two-dimensional conduction heat transfer model for the solidification of a normal paraffin of finite geometry. Next, a transient two-dimensional model was developed for the solidification of the same paraffin by a combined conduction-natural-convection heat transfer model. Throughout the study, n-hexadecane (n-C16H34) was used as the phase-change material in both the theoretical and the experimental work. The models were based on the transient two-dimensional finite difference solutions of the energy, continuity, and momentum equations.
A Sheath Model for Negative Ion Sources Including the Formation of a Virtual Cathode
McAdams, R.; King, D. B.; Surrey, E.
2011-09-26
A one dimensional model of the sheath between the plasma and the wall in a negative ion source has been developed. The plasma consists of positive ions, electrons and negative ions. The model takes into account the emission of negative ions from the wall into the sheath and thus represents the conditions in a caesiated ion source with surface production of negative ions. At high current densities of the emitted negative ions, the sheath is unable to support the transport of all the negative ions to the plasma and a virtual cathode is formed. This model takes this into account and allows the calculation of the transported negative ions across the sheath with the virtual cathode. The model has been extended to allow the linkage between plasma conditions at the sheath edge and the plasma to be made. Comparisons are made between the results of the model and experimental measurements.
Simulated village locations in Thailand: A multi-scale model including a neural network approach
Malanson, George P.; Entwisle, Barbara
2010-01-01
The simulation of rural land use systems, in general, and rural settlement dynamics in particular has developed with synergies of theory and methods for decades. Three current issues are: linking spatial patterns and processes, representing hierarchical relations across scales, and considering nonlinearity to address complex non-stationary settlement dynamics. We present a hierarchical simulation model to investigate complex rural settlement dynamics in Nang Rong, Thailand. This simulation uses sub-models to allocate new villages at three spatial scales. Regional and sub-regional models, which involve a nonlinear space-time autoregressive model implemented in a neural network approach, determine the number of new villages to be established. A dynamic village niche model, establishing pattern-process link, was designed to enable the allocation of villages into specific locations. Spatiotemporal variability in model performance indicates the pattern of village location changes as a settlement frontier advances from rice-growing lowlands to higher elevations. Experiments results demonstrate this simulation model can enhance our understanding of settlement development in Nang Rong and thus gain insight into complex land use systems in this area. PMID:21399748
Simulated village locations in Thailand: A multi-scale model including a neural network approach.
Tang, Wenwu; Malanson, George P; Entwisle, Barbara
2009-04-01
The simulation of rural land use systems, in general, and rural settlement dynamics in particular has developed with synergies of theory and methods for decades. Three current issues are: linking spatial patterns and processes, representing hierarchical relations across scales, and considering nonlinearity to address complex non-stationary settlement dynamics. We present a hierarchical simulation model to investigate complex rural settlement dynamics in Nang Rong, Thailand. This simulation uses sub-models to allocate new villages at three spatial scales. Regional and sub-regional models, which involve a nonlinear space-time autoregressive model implemented in a neural network approach, determine the number of new villages to be established. A dynamic village niche model, establishing pattern-process link, was designed to enable the allocation of villages into specific locations. Spatiotemporal variability in model performance indicates the pattern of village location changes as a settlement frontier advances from rice-growing lowlands to higher elevations. Experiments results demonstrate this simulation model can enhance our understanding of settlement development in Nang Rong and thus gain insight into complex land use systems in this area. PMID:21399748
A feedback model for leukemia including cell competition and the action of the immune system
NASA Astrophysics Data System (ADS)
Balea, S.; Halanay, A.; Neamtu, M.
2014-12-01
A mathematical model, coupling the dynamics of short-term stem-like cells and mature leukocytes in leukemia with that of the immune system, is investigated. The model is described by a system of nine delay differential equations with nine delays. Three equilibrium points E0, E1, E2 are highlighted. The stability and the existence of the Hopf bifurcation for the equilibrium points are investigated. In the analysis of the model, the rate of asymmetric division and the rate of symmetric division are very important.
A physical-based pMOSFETs threshold voltage model including the STI stress effect
NASA Astrophysics Data System (ADS)
Wei, Wu; Gang, Du; Xiaoyan, Liu; Lei, Sun; Jinfeng, Kang; Ruqi, Han
2011-05-01
The physical threshold voltage model of pMOSFETs under shallow trench isolation (STI) stress has been developed. The model is verified by 130 nm technology layout dependent measurement data. The comparison between pMOSFET and nMOSFET model simulations due to STI stress was conducted to show that STI stress induced less threshold voltage shift and more mobility shift for the pMOSFET. The circuit simulations of a nine stage ring oscillator with and without STI stress proved about 11% improvement of average delay time. This indicates the importance of STI stress consideration in circuit design.
ERIC Educational Resources Information Center
Theiss, Jennifer A.; Knobloch, Leanne K.; Checton, Maria G.; Magsamen-Conrad, Kate
2009-01-01
We employed the relational turbulence model to identify (a) relationship characteristics associated with people's appraisals of hurtful messages, and (b) features of hurtful episodes and relationship characteristics that correspond with the directness of communication about hurt. We conducted a study in which 135 dating couples reported on their…
Progress in turbulence modeling for complex flow fields including effects of compressibility
NASA Technical Reports Server (NTRS)
Wilcox, D. C.; Rubesin, M. W.
1980-01-01
Two second-order-closure turbulence models were devised that are suitable for predicting properties of complex turbulent flow fields in both incompressible and compressible fluids. One model is of the "two-equation" variety in which closure is accomplished by introducing an eddy viscosity which depends on both a turbulent mixing energy and a dissipation rate per unit energy, that is, a specific dissipation rate. The other model is a "Reynolds stress equation" (RSE) formulation in which all components of the Reynolds stress tensor and turbulent heat-flux vector are computed directly and are scaled by the specific dissipation rate. Computations based on these models are compared with measurements for the following flow fields: (a) low speed, high Reynolds number channel flows with plane strain or uniform shear; (b) equilibrium turbulent boundary layers with and without pressure gradients or effects of compressibility; and (c) flow over a convex surface with and without a pressure gradient.
Allen, D.H.; Helms, K.L.E.; Hurtado, L.D.
1999-04-06
A model is developed herein for predicting the mechanical response of inelastic crystalline solids. Particular emphasis is given to the development of microstructural damage along grain boundaries, and the interaction of this damage with intragranular inelasticity caused by dislocation dissipation mechanisms. The model is developed within the concepts of continuum mechanics, with special emphasis on the development of internal boundaries in the continuum by utilizing a cohesive zone model based on fracture mechanics. In addition, the crystalline grains are assumed to be characterized by nonlinear viscoplastic mechanical material behavior in order to account for dislocation generation and migration. Due to the nonlinearities introduced by the crack growth and viscoplastic constitution, a numerical algorithm is utilized to solve representative problems. Implementation of the model to a finite element computational algorithm is therefore briefly described. Finally, sample calculations are presented for a polycrystalline titanium alloy with particular focus on effects of scale on the predicted response.
NASA Technical Reports Server (NTRS)
Holland, D. B.; Virgin, L. N.; Belvin, W. K.
2003-01-01
This paper presents a parameter study of the effect of boom axial loading on the global dynamics of a 2-meter solar sail scale model. The experimental model used is meant for building expertise in finite element analysis and experimental execution, not as a predecessor to any planned flight mission or particular design concept. The results here are to demonstrate the ability to predict and measure structural dynamics and mode shapes in the presence of axial loading.
Model and parameter uncertainty in IDF relationships under climate change
NASA Astrophysics Data System (ADS)
Chandra, Rupa; Saha, Ujjwal; Mujumdar, P. P.
2015-05-01
Quantifying distributional behavior of extreme events is crucial in hydrologic designs. Intensity Duration Frequency (IDF) relationships are used extensively in engineering especially in urban hydrology, to obtain return level of extreme rainfall event for a specified return period and duration. Major sources of uncertainty in the IDF relationships are due to insufficient quantity and quality of data leading to parameter uncertainty due to the distribution fitted to the data and uncertainty as a result of using multiple GCMs. It is important to study these uncertainties and propagate them to future for accurate assessment of return levels for future. The objective of this study is to quantify the uncertainties arising from parameters of the distribution fitted to data and the multiple GCM models using Bayesian approach. Posterior distribution of parameters is obtained from Bayes rule and the parameters are transformed to obtain return levels for a specified return period. Markov Chain Monte Carlo (MCMC) method using Metropolis Hastings algorithm is used to obtain the posterior distribution of parameters. Twenty six CMIP5 GCMs along with four RCP scenarios are considered for studying the effects of climate change and to obtain projected IDF relationships for the case study of Bangalore city in India. GCM uncertainty due to the use of multiple GCMs is treated using Reliability Ensemble Averaging (REA) technique along with the parameter uncertainty. Scale invariance theory is employed for obtaining short duration return levels from daily data. It is observed that the uncertainty in short duration rainfall return levels is high when compared to the longer durations. Further it is observed that parameter uncertainty is large compared to the model uncertainty.
NASA Astrophysics Data System (ADS)
Toyokuni, Genti; Takenaka, Hiroshi
2012-06-01
We propose a method for modeling global seismic wave propagation through an attenuative Earth model including the center. This method enables accurate and efficient computations since it is based on the 2.5-D approach, which solves wave equations only on a 2-D cross section of the whole Earth and can correctly model 3-D geometrical spreading. We extend a numerical scheme for the elastic waves in spherical coordinates using the finite-difference method (FDM), to solve the viscoelastodynamic equation. For computation of realistic seismic wave propagation, incorporation of anelastic attenuation is crucial. Since the nature of Earth material is both elastic solid and viscous fluid, we should solve stress-strain relations of viscoelastic material, including attenuative structures. These relations represent the stress as a convolution integral in time, which has had difficulty treating viscoelasticity in time-domain computation such as the FDM. However, we now have a method using so-called memory variables, invented in the 1980s, followed by improvements in Cartesian coordinates. Arbitrary values of the quality factor (Q) can be incorporated into the wave equation via an array of Zener bodies. We also introduce the multi-domain, an FD grid of several layers with different grid spacings, into our FDM scheme. This allows wider lateral grid spacings with depth, so as not to perturb the FD stability criterion around the Earth center. In addition, we propose a technique to avoid the singularity problem of the wave equation in spherical coordinates at the Earth center. We develop a scheme to calculate wavefield variables on this point, based on linear interpolation for the velocity-stress, staggered-grid FDM. This scheme is validated through a comparison of synthetic seismograms with those obtained by the Direct Solution Method for a spherically symmetric Earth model, showing excellent accuracy for our FDM scheme. As a numerical example, we apply the method to simulate seismic
Deuterium and oxygen 18 in precipitation: Isotropic model, including mixed cloud processes
Ciais, P.; Jouzel, J.
1994-08-01
Modeling the isotropic ratios of precipitation in cold regions meets the problem of `switching` from the vapor-liquid transition to the vapor-ice transition at the oneset of snow formation. The one-dimensional model (mixed cloud isotopic model (MCIM)) described in this paper focuses on the fractionation of water isotopes in mixed clouds, where both liquid droplets and ice crystals can coexist for a given range of temperatures. This feature is linked to the existence of specific saturation conditions within the cloud, allowing droplets to evaporate while the water vapor condensates onto ice crystals. The isotopic composition of the different airborne phases and the precipitation is calculated throughout the condensation history of an isolated air mass moving over the Antarctic ice sheet. The results of the MCIM are compared to surface snow data both for the isotopic ratios and the deuterium excesses. The sensitivity of the model is compared to previous one-dimensional models. Our main result is that accounting specifically for the microphysics of mixed stratiform clouds (Bergeron-Findesein process) does not invalidate the results of earlier modeling studies.
Including sugar cane in the agro-ecosystem model ORCHIDEE-STICS: calibration and validation
NASA Astrophysics Data System (ADS)
Valade, A.; Vuichard, N.; Ciais, P.; Viovy, N.
2011-12-01
Sugarcane is currently the most efficient bioenergy crop with regards to the energy produced per hectare. With approximately half the global bioethanol production in 2005, and a devoted land area expected to expand globally in the years to come, sugar cane is at the heart of the biofuel debate. Dynamic global vegetation models coupled with agronomical models are powerful and novel tools to tackle many of the environmental issues related to biofuels if they are carefully calibrated and validated against field observations. Here we adapt the agro-terrestrial model ORCHIDEE-STICS for sugar cane simulations. Observation data of LAI are used to evaluate the sensitivity of the model to parameters of nitrogen absorption and phenology, which are calibrated in a systematic way for six sites in Australia and La Reunion. We find that the optimal set of parameters is highly dependent on the sites' characteristics and that the model can reproduce satisfactorily the evolution of LAI. This careful calibration of ORCHIDEE-STICS for sugar cane biomass production for different locations and technical itineraries provides a strong basis for further analysis of the impacts of bioenergy-related land use change on carbon cycle budgets. As a next step, a sensitivity analysis is carried out to estimate the uncertainty of the model in biomass and carbon flux simulation due to its parameterization.
Breather solutions of a nonlinear DNA model including a longitudinal degree of freedom
NASA Astrophysics Data System (ADS)
Agarwal, J.; Hennig, D.
2003-05-01
We present a model of the DNA double helix assigning three degrees of freedom to each pair of nucleotides. The model is an extension of the Barbi-Cocco-Peyrard (BCP) model in the sense that the current model allows for longitudinal motions of the nucleotides parallel to the helix axis. The molecular structure of the double helix is modelled by a system of coupled oscillators. The nucleotides are represented by point masses and coupled via point-point interaction potentials. The latter describe the covalent and hydrogen bonds responsible for the secondary structure of DNA. We obtain breather solutions using an established method for the construction of breathers on nonlinear lattices starting from the anti-coupling limit. In order to apply this method we analyse the phonon spectrum of the linearised system corresponding to our model. The obtained breathing motion consists of a local opening and re-closing of base pairs combined with a local untwist of the helix. The motions in longitudinal direction are of much lower amplitudes than the radial and angular elongations.
A weighted network model for interpersonal relationship evolution
NASA Astrophysics Data System (ADS)
Hu, Bo; Jiang, Xin-Yu; Ding, Jun-Feng; Xie, Yan-Bo; Wang, Bing-Hong
2005-08-01
A simple model is proposed to mimic and study the evolution of interpersonal relationships in a student class. The small social group is simply assumed as an undirected and weighted graph, in which students are represented by vertices, and the depth of favor or disfavor between them are denoted by the corresponding edge weight. In our model, we find that the first impression between people has a crucial influence on the final status of student relations (i.e., the final distribution of edge weights). The system displays a phase transition in the final hostility proportion depending on the initial amity possibility. We can further define the strength of vertices to describe the individual popularity, which exhibits nonlinear evolution. Meanwhile, various nonrandom perturbations to the initial system have been investigated, and simulation results are in accord with common real-life observations.
Models of professional regulation: institutionalizing an agency relationship
2013-01-01
The regulation of medical practice can historically be understood as a second-level agency relationship whereby the state delegated authority to professional bodies to police the primary agency relationship between the individual physician and the patient. Borow, Levi and Glekin show how different national systems vary in the degree to which they insist on institutionally insulating the agency function from the promotion of private professional interests, and relate these variations to different models of the health care state. In fact these differences have even deeper roots in different “liberal” or “coordinated” varieties of capitalist political economies. Neither model is inherently more efficient than the other: what matters is the internal coherence or logic of these systems that conditions the expectations of actors in responding to particular challenges. The territory that Borow, Levi and Glekin have usefully mapped invites further exploration in this regard. This is a commentary on http://www.ijhpr.org/content/2/1/8. PMID:23537144
A two-phase solid/fluid model for dense granular flows including dilatancy effects
NASA Astrophysics Data System (ADS)
Mangeney, Anne; Bouchut, Francois; Fernandez-Nieto, Enrique; Koné, El-Hadj; Narbona-Reina, Gladys
2016-04-01
Describing grain/fluid interaction in debris flows models is still an open and challenging issue with key impact on hazard assessment [{Iverson et al.}, 2010]. We present here a two-phase two-thin-layer model for fluidized debris flows that takes into account dilatancy effects. It describes the velocity of both the solid and the fluid phases, the compression/dilatation of the granular media and its interaction with the pore fluid pressure [{Bouchut et al.}, 2016]. The model is derived from a 3D two-phase model proposed by {Jackson} [2000] based on the 4 equations of mass and momentum conservation within the two phases. This system has 5 unknowns: the solid and fluid velocities, the solid and fluid pressures and the solid volume fraction. As a result, an additional equation inside the mixture is necessary to close the system. Surprisingly, this issue is inadequately accounted for in the models that have been developed on the basis of Jackson's work [{Bouchut et al.}, 2015]. In particular, {Pitman and Le} [2005] replaced this closure simply by imposing an extra boundary condition at the surface of the flow. When making a shallow expansion, this condition can be considered as a closure condition. However, the corresponding model cannot account for a dissipative energy balance. We propose here an approach to correctly deal with the thermodynamics of Jackson's model by closing the mixture equations by a weak compressibility relation following {Roux and Radjai} [1998]. This relation implies that the occurrence of dilation or contraction of the granular material in the model depends on whether the solid volume fraction is respectively higher or lower than a critical value. When dilation occurs, the fluid is sucked into the granular material, the pore pressure decreases and the friction force on the granular phase increases. On the contrary, in the case of contraction, the fluid is expelled from the mixture, the pore pressure increases and the friction force diminishes. To
Genomic prediction of growth in pigs based on a model including additive and dominance effects.
Lopes, M S; Bastiaansen, J W M; Janss, L; Knol, E F; Bovenhuis, H
2016-06-01
Independent of whether prediction is based on pedigree or genomic information, the focus of animal breeders has been on additive genetic effects or 'breeding values'. However, when predicting phenotypes rather than breeding values of an animal, models that account for both additive and dominance effects might be more accurate. Our aim with this study was to compare the accuracy of predicting phenotypes using a model that accounts for only additive effects (MA) and a model that accounts for both additive and dominance effects simultaneously (MAD). Lifetime daily gain (DG) was evaluated in three pig populations (1424 Pietrain, 2023 Landrace, and 2157 Large White). Animals were genotyped using the Illumina SNP60K Beadchip and assigned to either a training data set to estimate the genetic parameters and SNP effects, or to a validation data set to assess the prediction accuracy. Models MA and MAD applied random regression on SNP genotypes and were implemented in the program Bayz. The additive heritability of DG across the three populations and the two models was very similar at approximately 0.26. The proportion of phenotypic variance explained by dominance effects ranged from 0.04 (Large White) to 0.11 (Pietrain), indicating that importance of dominance might be breed-specific. Prediction accuracies were higher when predicting phenotypes using total genetic values (sum of breeding values and dominance deviations) from the MAD model compared to using breeding values from both MA and MAD models. The highest increase in accuracy (from 0.195 to 0.222) was observed in the Pietrain, and the lowest in Large White (from 0.354 to 0.359). Predicting phenotypes using total genetic values instead of breeding values in purebred data improved prediction accuracy and reduced the bias of genomic predictions. Additional benefit of the method is expected when applied to predict crossbred phenotypes, where dominance levels are expected to be higher. PMID:26676611
Quantitative structure-(chromatographic) retention relationship models for dissociating compounds.
Kubik, Łukasz; Wiczling, Paweł
2016-08-01
The aim of this work was to develop mathematical models relating the hydrophobicity and dissociation constant of an analyte with its structure, which would be useful in predicting analyte retention times in reversed-phase liquid chromatography. For that purpose a large and diverse group of 115 drugs was used to build three QSRR models combining retention-related parameters (logkw-chromatographic measure of hydrophobicity, S-slope factor from Snyder-Soczewinski equation, and pKa) with structural descriptors calculated by means of molecular modeling for both dissociated and nondissociated forms of analytes. Lasso, Stepwise and PLS regressions were used to build statistical models. Moreover a simple QSRR equations based on lipophilicity and dissociation constant parameters calculated in the ACD/Labs software were proposed and compared with quantum chemistry-based QSRR equations. The obtained relationships were further used to predict chromatographic retention times. The predictive performances of the obtained models were assessed using 10-fold cross-validation and external validation. The QSRR equations developed were simple and were characterized by satisfactory predictive performance. Application of quantum chemistry-based and ACD-based descriptors leads to similar accuracy of retention times' prediction. PMID:26960942
Results of including geometric nonlinearities in an aeroelastic model of an F/A-18
NASA Technical Reports Server (NTRS)
Buttrill, Carey S.
1989-01-01
An integrated, nonlinear simulation model suitable for aeroelastic modeling of fixed-wing aircraft has been developed. While the author realizes that the subject of modeling rotating, elastic structures is not closed, it is believed that the equations of motion developed and applied herein are correct to second order and are suitable for use with typical aircraft structures. The equations are not suitable for large elastic deformation. In addition, the modeling framework generalizes both the methods and terminology of non-linear rigid-body airplane simulation and traditional linear aeroelastic modeling. Concerning the importance of angular/elastic inertial coupling in the dynamic analysis of fixed-wing aircraft, the following may be said. The rigorous inclusion of said coupling is not without peril and must be approached with care. In keeping with the same engineering judgment that guided the development of the traditional aeroelastic equations, the effect of non-linear inertial effects for most airplane applications is expected to be small. A parameter does not tell the whole story, however, and modes flagged by the parameter as significant also need to be checked to see if the coupling is not a one-way path, i.e., the inertially affected modes can influence other modes.
A model of protein translation including codon bias, nonsense errors, and ribosome recycling.
Gilchrist, Michael A; Wagner, Andreas
2006-04-21
We present and analyse a model of protein translation at the scale of an individual messenger RNA (mRNA) transcript. The model we develop is unique in that it incorporates the phenomena of ribosome recycling and nonsense errors. The model conceptualizes translation as a probabilistic wave of ribosome occupancy traveling down a heterogeneous medium, the mRNA transcript. Our results show that the heterogeneity of the codon translation rates along the mRNA results in short-scale spikes and dips in the wave. Nonsense errors attenuate this wave on a longer scale while ribosome recycling reinforces it. We find that the combination of nonsense errors and codon usage bias can have a large effect on the probability that a ribosome will completely translate a transcript. We also elucidate how these forces interact with ribosome recycling to determine the overall translation rate of an mRNA transcript. We derive a simple cost function for nonsense errors using our model and apply this function to the yeast (Saccharomyces cervisiae) genome. Using this function we are able to detect position dependent selection on codon bias which correlates with gene expression levels as predicted a priori. These results indirectly validate our underlying model assumptions and confirm that nonsense errors can play an important role in shaping codon usage bias. PMID:16171830
Kinetic modelling of anaerobic hydrolysis of solid wastes, including disintegration processes
García-Gen, Santiago; Sousbie, Philippe; Rangaraj, Ganesh; Lema, Juan M.; Rodríguez, Jorge; Steyer, Jean-Philippe; Torrijos, Michel
2015-01-15
Highlights: • Fractionation of solid wastes into readily and slowly biodegradable fractions. • Kinetic coefficients estimation from mono-digestion batch assays. • Validation of kinetic coefficients with a co-digestion continuous experiment. • Simulation of batch and continuous experiments with an ADM1-based model. - Abstract: A methodology to estimate disintegration and hydrolysis kinetic parameters of solid wastes and validate an ADM1-based anaerobic co-digestion model is presented. Kinetic parameters of the model were calibrated from batch reactor experiments treating individually fruit and vegetable wastes (among other residues) following a new protocol for batch tests. In addition, decoupled disintegration kinetics for readily and slowly biodegradable fractions of solid wastes was considered. Calibrated parameters from batch assays of individual substrates were used to validate the model for a semi-continuous co-digestion operation treating simultaneously 5 fruit and vegetable wastes. The semi-continuous experiment was carried out in a lab-scale CSTR reactor for 15 weeks at organic loading rate ranging between 2.0 and 4.7 g VS/L d. The model (built in Matlab/Simulink) fit to a large extent the experimental results in both batch and semi-continuous mode and served as a powerful tool to simulate the digestion or co-digestion of solid wastes.
A bone remodelling model including the effect of damage on the steering of BMUs.
Martínez-Reina, J; Reina, I; Domínguez, J; García-Aznar, J M
2014-04-01
Bone remodelling in cortical bone is performed by the so-called basic multicellular units (BMUs), which produce osteons after completing the remodelling sequence. Burger et al. (2003) hypothesized that BMUs follow the direction of the prevalent local stress in the bone. More recently, Martin (2007) has shown that BMUs must be somehow guided by microstructural damage as well. The interaction of both variables, strain and damage, in the guidance of BMUs has been incorporated into a bone remodelling model for cortical bone. This model accounts for variations in porosity, anisotropy and damage level. The bone remodelling model has been applied to a finite element model of the diaphysis of a human femur. The trajectories of the BMUs have been analysed throughout the diaphysis and compared with the orientation of osteons measured experimentally. Some interesting observations, like the typical fan arrangement of osteons near the periosteum, can be explained with the proposed remodelling model. Moreover, the efficiency of BMUs in damage repairing has been shown to be greater if BMUs are guided by damage. PMID:24445006
Naghavi, Nadia; Hosseini, Farideh S; Sardarabadi, Mohammad; Kalani, Hadi
2016-09-01
In this paper, an adaptive model for tumor induced angiogenesis is developed that integrates generation and diffusion of a growth factor originated from hypoxic cells, adaptive sprouting from a parent vessel, blood flow and structural adaptation. The proposed adaptive sprout spacing model (ASS) determines position, time and number of sprouts which are activated from a parent vessel and also the developed vascular network is modified by a novel sprout branching prediction algorithm. This algorithm couples local vascular endothelial growth factor (VEGF) concentrations, stresses due to the blood flow and stochastic branching to the structural reactions of each vessel segment in response to mechanical and biochemical stimuli. The results provide predictions for the time-dependent development of the network structure, including the position and diameters of each segment and the resulting distributions of blood flow and VEGF. Considering time delays between sprout progressions and number of sprouts activated at different time durations provides information about micro-vessel density in the network. Resulting insights could be useful for motivating experimental investigations of vascular pattern in tumor induced angiogenesis and development of therapies targeting angiogenesis. PMID:27179697