Li, Jicun; Wang, Feng
2016-07-01
The effects of decoupling the water-water and water-solute interactions are studied with selected mono-valent ions as the solute. Using the ion-water cross terms developed for the BLYPSP-4F water model, we replaced the water potential with WAIL, TIP4P, and TIP3P without changing the ion-water parameters. When the adaptive force matching (AFM) derived BLYPSP-4F model is replaced by the other AFM derived WAIL model, the difference in ion properties, such as hydration free energies, radial distribution functions, relative diffusion constants, is negligible, demonstrating the feasibility for combining AFM parameters from different sources. Interestingly, when the AFM-derived ion-water cross-terms are used with a non-AFM based water model, only small changes in the ion properties are observed. The final combined models with TIP3P or TIP4P water reproduce the salt hydration free energies within 6% of experiments. The feasibility of combining AFM models with other non-AFM models is of significance since such combinations allow more complex systems to be studied without specific parameterization. In addition, the study suggests an interesting prospect of reusing the cross-terms when a part of a general force field is replaced with a different model. The prevailing practice, which is to re-derive all cross-terms with combining rules, may not have been optimal.
Bento, M C; Santos, N M C
2008-01-01
A simple model of quintessential inflation with the modified exponential potential $e^{-\\alpha \\phi} [A+(\\phi-\\phi_0)^2]$ is analyzed in the braneworld context. Considering reheating via instant preheating, we conclude that the model exhibits transient acceleration at late times for $0.96 \\lesssim A \\alpha^2 \\lesssim 1.26$ and $271 \\lesssim \\phi_0 \\alpha \\lesssim 273$, while permanent acceleration is obtained for $2.3\\times10^{-8} \\lesssim A \\alpha^2 \\lesssim 0.98$ and $255 \\lesssim \\phi_0 \\alpha \\lesssim 273$. The steep parameter $\\alpha$ is constrained to be in the range $5.3 \\lesssim \\alpha \\lesssim 10.8$.
Two Simple Models for Fracking
Norris, Jaren Quinn
Recent developments in fracking have enable the recovery of oil and gas from tight shale reservoirs. These developments have also made fracking one of the most controversial environmental issues in the United States. Despite the growing controversy surrounding fracking, there is relatively little publicly available research. This dissertation introduces two simple models for fracking that were developed using techniques from non-linear and statistical physics. The first model assumes that the volume of induced fractures must be equal to the volume of injected fluid. For simplicity, these fractures are assumed to form a spherically symmetric damage region around the borehole. The predicted volumes of water necessary to create a damage region with a given radius are in good agreement with reported values. The second model is a modification of invasion percolation which was previously introduced to model water flooding. The reservoir rock is represented by a regular lattice of local traps that contain oil and/or gas separated by rock barriers. The barriers are assumed to be highly heterogeneous and are assigned random strengths. Fluid is injected from a central site and the weakest rock barrier breaks allowing fluid to flow into the adjacent site. The process repeats with the weakest barrier breaking and fluid flowing to an adjacent site each time step. Extensive numerical simulations were carried out to obtain statistical properties of the growing fracture network. The network was found to be fractal with fractal dimensions differing slightly from the accepted values for traditional percolation. Additionally, the network follows Horton-Strahler and Tokunaga branching statistics which have been used to characterize river networks. As with other percolation models, the growth of the network occurs in bursts. These bursts follow a power-law size distribution similar to observed microseismic events. Reservoir stress anisotropy is incorporated into the model by assigning
Simple inhomogeneous cosmological (toy) models
I., Eddy G Chirinos; Zimdahl, Winfried
2016-01-01
Based on the Lema\\^itre-Tolman-Bondi (LTB) metric we consider two flat inhomogeneous big-bang models. We aim at clarifying, as far as possible analytically, basic features of the dynamics of the simplest inhomogeneous models and to point out the potential usefulness of exact inhomogeneous solutions as generalizations of the homogeneous configurations of the cosmological standard model. We discuss explicitly partial successes but also potential pitfalls of these simplest models. Although primarily seen as toy models, the relevant free parameters are fixed by best-fit values using the Joint Light-curve Analysis (JLA)-sample data. On the basis of a likelihood analysis we find that a local hump provides a better description of the observations than a local void. Future redshift-drift measurements are discussed as a promising tool to discriminate between inhomogeneous configurations and the $\\Lambda$CDM model.
Simple models of firms emergence
Weisbuch, Gérard; Mangalagiu, Diana; Ben-Av, Radel; Solomon, Sorin
2008-09-01
We present a dynamical model of the emergence of firms as opposed to a flat labour market where entrepreneurs would recruit workers for each business opportunity. The model uses a preferential choice of partners based on previous collaborations experience. A sharp transition in the parameter space separates an ordered regime, where preferential links establish, from a disordered regime corresponding to a fast turnover of employees.
Ohta, Takao; Sano, Masaki
2015-01-01
Based on symmetry consideration of migration and shape deformations, we formulate phenomenologically the dynamics of cell crawling in two dimensions. Forces are introduced to change the cell shape. The shape deformations induce migration of the cell on a substrate. For time-independent forces we show that not only a stationary motion but also a limit cycle oscillation of the migration velocity and the shape occurs as a result of nonlinear coupling between different deformation modes. Time-dependent forces are generated in a stochastic manner by utilizing the so-called coherence resonance of an excitable system. The present coarse-grained model has a flexibility that it can be applied, e.g., both to keratocyte cells and to Dictyostelium cells, which exhibit quite different dynamics from each other. The key factors for the motile behavior inherent in each cell type are identified in our model.
Ohta, T.; Tarama, M.; Sano, M.
2016-04-01
Based on symmetry consideration of migration and shape deformations, we formulate phenomenologically the dynamics of cell crawling in two dimensions. Forces are introduced to change the cell shape. The shape deformations induce migration of the cell on a substrate. For time-independent forces we show that not only a stationary motion but also a limit cycle oscillation of the migration velocity and the shape occurs as a result of nonlinear coupling between different deformation modes. Time-dependent forces are generated in a stochastic manner by utilizing the so-called coherence resonance of an excitable system. The present coarse-grained model has a flexibility that it can be applied, e.g., both to keratocyte cells and to Dictyostelium cells, which exhibit quite different dynamics from each other. The key factors for the motile behavior inherent in each cell type are identified in our model.
Evaluation of help model replacement codes
Energy Technology Data Exchange (ETDEWEB)
Whiteside, Tad [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Hang, Thong [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Flach, Gregory [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)
2009-07-01
This work evaluates the computer codes that are proposed to be used to predict percolation of water through the closure-cap and into the waste containment zone at the Department of Energy closure sites. This work compares the currently used water-balance code (HELP) with newly developed computer codes that use unsaturated flow (Richards’ equation). It provides a literature review of the HELP model and the proposed codes, which result in two recommended codes for further evaluation: HYDRUS-2D3D and VADOSE/W. This further evaluation involved performing actual simulations on a simple model and comparing the results of those simulations to those obtained with the HELP code and the field data. From the results of this work, we conclude that the new codes perform nearly the same, although moving forward, we recommend HYDRUS-2D3D.
A simple probabilistic model of multibody interactions in proteins
DEFF Research Database (Denmark)
Johansson, Kristoffer Enøe; Hamelryck, Thomas
2013-01-01
predictions. Our coarse-grained model is compared to state-of-art methods that use full atomic detail. This article illustrates how the use of simple probabilistic models can lead to new opportunities in the treatment of nonlocal interactions in knowledge-based protein structure prediction and design....... beyond pairwise interactions have been described, the formulation of a general multibody potential is seen as intractable due to the perceived limited amount of data. In this article, we show that it is possible to formulate a probabilistic model of higher order interactions in proteins, without...... arbitrarily limiting the number of contacts. The success of this approach is based on replacing a naive table-based approach with a simple hierarchical model involving suitable probability distributions and conditional independence assumptions. The model captures the joint probability distribution of an amino...
Simple models of evolution and extinction
Newman, M E J
1999-01-01
This article gives a brief introduction to the mathematical modeling of large-scale biological evolution and extinction. We give three examples of simple models in this field: the coevolutionary avalanche model of Bak and Sneppen, the environmental stress model of Newman, and the increasing fitness model of Sibani, Schmidt, and Alstrom. We describe the features of real evolution which these models are intended to explain and compare the results of simulations against data drawn from the fossil record.
Directory of Open Access Journals (Sweden)
S. Radhakrishnan
2014-03-01
Full Text Available The fishmeal replaced with Spirulina platensis, Chlorella vulgaris and Azolla pinnata and the formulated diet fed to Macrobrachium rosenbergii postlarvae to assess the enhancement ability of non-enzymatic antioxidants (vitamin C and E, enzymatic antioxidants (superoxide dismutase (SOD and catalase (CAT and lipid peroxidation (LPx were analysed. In the present study, the S. platensis, C. vulgaris and A. pinnata inclusion diet fed groups had significant (P < 0.05 improvement in the levels of vitamins C and E in the hepatopancreas and muscle tissue. Among all the diets, the replacement materials in 50% incorporated feed fed groups showed better performance when compared with the control group in non-enzymatic antioxidant activity. The 50% fishmeal replacement (best performance diet fed groups taken for enzymatic antioxidant study, in SOD, CAT and LPx showed no significant increases when compared with the control group. Hence, the present results revealed that the formulated feed enhanced the vitamins C and E, the result of decreased level of enzymatic antioxidants (SOD, CAT and LPx revealed that these feeds are non-toxic and do not produce any stress to postlarvae. These ingredients can be used as an alternative protein source for sustainable Macrobrachium culture.
From Complex to Simple: Interdisciplinary Stochastic Models
Mazilu, D. A.; Zamora, G.; Mazilu, I.
2012-01-01
We present two simple, one-dimensional, stochastic models that lead to a qualitative understanding of very complex systems from biology, nanoscience and social sciences. The first model explains the complicated dynamics of microtubules, stochastic cellular highways. Using the theory of random walks in one dimension, we find analytical expressions…
A Study of Simple Diffraction Models
DEFF Research Database (Denmark)
Agerkvist, Finn
In this paper two simple methods for cabinet edge diffraction are examined. Calculations with both models are compared with more sophisticated theoretical models and with measured data. The parameters involved are studied and their importance for normal loudspeaker box designs is examined....
SIMPLE LATTICE BOLTZMANN MODEL FOR TRAFFIC FLOWS
Institute of Scientific and Technical Information of China (English)
Yan Guangwu; Hu Shouxin
2000-01-01
A lattice Boltzmann model with 5-bit lattice for traffic flows is proposed.Using the Chapman-Enskog expansion and multi-scale technique,we obtain the higher-order moments of equilibrium distribution function.A simple traffic light problem is simulated by using the present lattice Boltzmann model,and the result agrees well with analytical solution.
Estimation for the simple linear Boolean model
2006-01-01
We consider the simple linear Boolean model, a fundamental coverage process also known as the Markov/General/infinity queue. In the model, line segments of independent and identically distributed length are located at the points of a Poisson process. The segments may overlap, resulting in a pattern of "clumps"-regions of the line that are covered by one or more segments-alternating with uncovered regions or "spacings". Study and application of the model have been impeded by the difficult...
A simple model for turbulence intermittencies
Rimbert, Nicolas
2009-01-01
Whether turbulence intermittencies shall be described by a log-Poisson, a log-stable pdf or other distributions is still debated nowadays. In this paper, a bridge between polymer physics, self-avoiding walk and random vortex stretching is established which may help in getting a new insight on this topics. Actually a very simple relationship between stability index of the stable law and the well known Flory exponent stemming from polymer physics is established. Moreover the scaling of turbulence intermittencies with Reynolds number is also obtained and the overall picture is very close to Tennekes' simple model for the fine scale structure of turbulence [Phys. Fluids, 11, 3 (1968)] : vortex tubes of Kolmogorov length width are bend by bigger vortices of Taylor length scale. This thus results in both a simple and sound model with no fitting parameter needed.
Simple model of stacking-fault energies
DEFF Research Database (Denmark)
Stokbro, Kurt; Jacobsen, Lærke Wedel
1993-01-01
-density calculations of stacking-fault energies, and gives a simple way of understanding the calculated energy contributions from the different atomic layers in the stacking-fault region. The two parameters in the model describe the relative energy contributions of the s and d electrons in the noble and transition......A simple model for the energetics of stacking faults in fcc metals is constructed. The model contains third-nearest-neighbor pairwise interactions and a term involving the fourth moment of the electronic density of states. The model is in excellent agreement with recently published local...... metals, and thereby explain the pronounced differences in energetics in these two classes of metals. The model is discussed in the framework of the effective-medium theory where it is possible to find a functional form for the pair potential and relate the contribution associated with the fourth moment...
A Simple Fuzzy Time Series Forecasting Model
DEFF Research Database (Denmark)
Ortiz-Arroyo, Daniel
2016-01-01
In this paper we describe a new ﬁrst order fuzzy time series forecasting model. We show that our automatic fuzzy partitioning method provides an accurate approximation to the time series that when combined with rule forecasting and an OWA operator improves forecasting accuracy. Our model does...... not attempt to provide the best results in comparison with other forecasting methods but to show how to improve ﬁrst order models using simple techniques. However, we show that our ﬁrst order model is still capable of outperforming some more complex higher order fuzzy time series models....
A simple model of direct gauge mediation
Energy Technology Data Exchange (ETDEWEB)
Zheng Sibo, E-mail: sibozheng.zju@gmail.com [Department of Physics, Chongqing University, Chongqing 401331 (China); Yu Yao [Department of Physics, Chongqing University, Chongqing 401331 (China)
2012-03-23
In the context of direct gauge mediation Wess-Zumino models are very attractive in supersymmetry model building. Besides the spontaneous supersymmetry and R-symmetry breaking, the problems of small gaugino mass as well as {mu} and B{mu} terms should be solved so as to achieve a viable model. In this Letter, we propose a simple model as an existence proof, in which all these subjects are realized simultaneously, with no need of fine tuning. This completion also implies that much of parameter space for direct gauge mediation can be directly explored at LHC.
Simple models for containment of a pandemic
Arino, Julien; Brauer, Fred; van den Driessche, P; Watmough, James; Wu, Jianhong
2006-01-01
Stochastic simulations of network models have become the standard approach to studying epidemics. We show that many of the predictions of these models can also be obtained from simple classical deterministic compartmental models. We suggest that simple models may be a better way to plan for a threatening pandemic with location and parameters as yet unknown, reserving more detailed network models for disease outbreaks already underway in localities where the social networks are well identified. We formulate compartmental models to describe outbreaks of influenza and attempt to manage a disease outbreak by vaccination or antiviral treatment. The models give an important prediction that may not have been noticed in other models, namely that the number of doses of antiviral treatment required is extremely sensitive to the number of initial infectives. This suggests that the actual number of doses needed cannot be estimated with any degree of reliability. The model is applicable to pre-epidemic vaccination, such as annual vaccination programs in anticipation of an ‘ordinary’ influenza outbreak with limited drift, and as a combination of treatment both before and during an epidemic. PMID:16849273
Cities in Space: Three Simple Models
Paul Krugman
1991-01-01
Urban agglomerations arise at least in part out of the interaction between economies of scale in production and market size effects. This paper develops a simple spatial framework to develop illustrative models of the determinants of urban location, of the number and size of cities, and of the degree of urbanization. A Central theme is the probable existence of multiple equilibria, and the dependence of the range of potential outcomes on a few key parameters.
Behaviour of Polariton in a Simple Model
Institute of Scientific and Technical Information of China (English)
WAN Shao-Long; MA Shuang-Ge; WANG Ke-Lin
2003-01-01
Behaviour of a simple model polariton system is restudied. The distribution of phonons in polariton never is sub-Poisson given by computation of the thermal counterpart of the Q parameter and the matrix m'3\\ The polariton complex as a whole shows non-classical behaviour below a threshold temperature, which depends on the photon-phonon coupling strength, when the distribution of phonons is always classical at any temperature.
FSM Model of a Simple Photovoltaic System
Directory of Open Access Journals (Sweden)
Martina Latkova
2015-01-01
Full Text Available The paper describes a simulation model of a simple photovoltaic system intended as a tool for testing the use of finite state machines for simulations representing a long-term operation of renewable energy sources. The mathematical model of the photovoltaic system is described first. Then it is used to build a finite state machine model that calculates a power output of the photovoltaic system for changing values of a solar irradiance and a temperature. Data measured on a real photovoltaic installation are used to verify modelâ€™s accuracy through its comparison with a previously created and verified Matlab model. The finite state machine model presented in this paper was created using Ptolemy II software.
Comprehensive Care For Joint Replacement Model - Provider Data
U.S. Department of Health & Human Services — Comprehensive Care for Joint Replacement Model - provider data. This data set includes provider data for two quality measures tracked during an episode of care:...
Chaos and irreversibility in simple model systems.
Hoover, Wm. G.; Posch, Harald A.
1998-06-01
The multifractal link between chaotic time-reversible mechanics and thermodynamic irreversibility is illustrated for three simple chaotic model systems: the Baker Map, the Galton Board, and many-body color conductivity. By scaling time, or the momenta, or the driving forces, it can be shown that the dissipative nature of the three thermostated model systems has analogs in conservative Hamiltonian and Lagrangian mechanics. Links between the microscopic nonequilibrium Lyapunov spectra and macroscopic thermodynamic dissipation are also pointed out. (c) 1998 American Institute of Physics.
A simple probabilistic model of multibody interactions in proteins.
Johansson, Kristoffer Enøe; Hamelryck, Thomas
2013-08-01
Protein structure prediction methods typically use statistical potentials, which rely on statistics derived from a database of know protein structures. In the vast majority of cases, these potentials involve pairwise distances or contacts between amino acids or atoms. Although some potentials beyond pairwise interactions have been described, the formulation of a general multibody potential is seen as intractable due to the perceived limited amount of data. In this article, we show that it is possible to formulate a probabilistic model of higher order interactions in proteins, without arbitrarily limiting the number of contacts. The success of this approach is based on replacing a naive table-based approach with a simple hierarchical model involving suitable probability distributions and conditional independence assumptions. The model captures the joint probability distribution of an amino acid and its neighbors, local structure and solvent exposure. We show that this model can be used to approximate the conditional probability distribution of an amino acid sequence given a structure using a pseudo-likelihood approach. We verify the model by decoy recognition and site-specific amino acid predictions. Our coarse-grained model is compared to state-of-art methods that use full atomic detail. This article illustrates how the use of simple probabilistic models can lead to new opportunities in the treatment of nonlocal interactions in knowledge-based protein structure prediction and design. Copyright © 2013 Wiley Periodicals, Inc., a Wiley company.
A simple model of eddy saturation
Marshall, D. P.; Ambaum, M.; Munday, D. R.; Novak, L.; Maddison, J. R.
2016-02-01
A simple model is developed for eddy saturation of the Antarctic Circumpolar Current (ACC): the relative insensitivity of its volume transport to the magnitude of the surface wind stress in ocean models with explicit eddies. The simple model solves prognostic equations for the ACC volume transport and the eddy energy, forming a 2-dimensional nonlinear dynamical system. In equilibrium, the volume transport is independent of the surface wind stress but scales with the bottom drag, whereas the eddy energy scales with the wind stress but is independent of bottom drag. The magnitude of the eddy energy is controlled by the zonal momentum balance between the surface wind stress and eddy form stress, whereas the baroclinic volume transport is controlled by the eddy energy balance between the mean-to-eddy energy conversion and bottom dissipation. The theoretical predictions are confirmed in eddy-resolving numerical calculations for an idealised reentrant channel. The results suggest that the rate of eddy energy dissipation has a strong impact not only the volume transport of the ACC, but also on global ocean stratification and heat content through the thermal wind relation. Moreover, a vital ingredient in this model is a relation between the eddy form stress and eddy energy derived in the eddy parameterisation framework of Marshall et al. (2012, J. Phys. Oceanogr.), offering the prospect of obtaining eddy saturation in ocean models with parameterised eddies.
Modeling reproductive decisions with simple heuristics
Directory of Open Access Journals (Sweden)
Peter Todd
2013-10-01
Full Text Available BACKGROUND Many of the reproductive decisions that humans make happen without much planning or forethought, arising instead through the use of simple choice rules or heuristics that involve relatively little information and processing. Nonetheless, these heuristic-guided decisions are typically beneficial, owing to humans' ecological rationality - the evolved fit between our constrained decision mechanisms and the adaptive problems we face. OBJECTIVE This paper reviews research on the ecological rationality of human decision making in the domain of reproduction, showing how fertility-related decisions are commonly made using various simple heuristics matched to the structure of the environment in which they are applied, rather than being made with information-hungry mechanisms based on optimization or rational economic choice. METHODS First, heuristics for sequential mate search are covered; these heuristics determine when to stop the process of mate search by deciding that a good-enough mate who is also mutually interested has been found, using a process of aspiration-level setting and assessing. These models are tested via computer simulation and comparison to demographic age-at-first-marriage data. Next, a heuristic process of feature-based mate comparison and choice is discussed, in which mate choices are determined by a simple process of feature-matching with relaxing standards over time. Parental investment heuristics used to divide resources among offspring are summarized. Finally, methods for testing the use of such mate choice heuristics in a specific population over time are then described.
Simple implementation of general dark energy models
Energy Technology Data Exchange (ETDEWEB)
Bloomfield, Jolyon K. [MIT Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, 77 Massachusetts Ave #37241, Cambridge, MA, 02139 (United States); Pearson, Jonathan A., E-mail: jolyon@mit.edu, E-mail: jonathan.pearson@durham.ac.uk [Centre for Particle Theory, Department of Mathematical Sciences, Durham University, South Road, Durham, DH1 3LE (United Kingdom)
2014-03-01
We present a formalism for the numerical implementation of general theories of dark energy, combining the computational simplicity of the equation of state for perturbations approach with the generality of the effective field theory approach. An effective fluid description is employed, based on a general action describing single-scalar field models. The formalism is developed from first principles, and constructed keeping the goal of a simple implementation into CAMB in mind. Benefits of this approach include its straightforward implementation, the generality of the underlying theory, the fact that the evolved variables are physical quantities, and that model-independent phenomenological descriptions may be straightforwardly investigated. We hope this formulation will provide a powerful tool for the comparison of theoretical models of dark energy with observational data.
A Simple HCCI Engine Model for Control
Energy Technology Data Exchange (ETDEWEB)
Killingsworth, N; Aceves, S; Flowers, D; Krstic, M
2006-06-29
The homogeneous charge compression ignition (HCCI) engine is an attractive technology because of its high efficiency and low emissions. However, HCCI lacks a direct combustion trigger making control of combustion timing challenging, especially during transients. To aid in HCCI engine control we present a simple model of the HCCI combustion process valid over a range of intake pressures, intake temperatures, equivalence ratios, and engine speeds. The model provides an estimate of the combustion timing on a cycle-by-cycle basis. An ignition threshold, which is a function of the in-cylinder motored temperature and pressure is used to predict start of combustion. This model allows the synthesis of nonlinear control laws, which can be utilized for control of an HCCI engine during transients.
Chaos from simple models to complex systems
Cencini, Massimo; Vulpiani, Angelo
2010-01-01
Chaos: from simple models to complex systems aims to guide science and engineering students through chaos and nonlinear dynamics from classical examples to the most recent fields of research. The first part, intended for undergraduate and graduate students, is a gentle and self-contained introduction to the concepts and main tools for the characterization of deterministic chaotic systems, with emphasis to statistical approaches. The second part can be used as a reference by researchers as it focuses on more advanced topics including the characterization of chaos with tools of information theor
Simple Models of Many-Fermion Systems
Maruhn, Joachim Alexander; Suraud, Eric
2010-01-01
The purpose of this book is to provide a pedestrians route to the physics of many-particle systems. The material is developed along simple and generic models which allow to illuminate the basic mechanisms beyond each approach and which apply to broad variety of systems in different areas of physics and chemistry. The book is sorted in steps of slowly increasing complexity of the models. Complementing numerical tools help to carry on where analytical methods reach their limits. They provide at the same time a useful training for the typical numerical methods in many-body physics. In order to confine the huge field, we shall focus the discussions on finite systems wherefrom we take the examples of applications. This covers nuclei, atoms, molecules and clusters. The idea of this book is to concentrate first on the generic, robust and simple, approaches and show how they apply to several domains across the specific disciplines. On the other hand, we aim to establish contact with actual research by carrying forth ...
Simple models for shear flow transition
Barkley, Dwight
2011-11-01
I will discuss recent developments in modeling transitional shear flows with simple two-variable models. Both pipe flow and plane Couette flow are considered. The essential insight is that most large-scale features of these shear flows can be traced to a change from excitability to bistability in the local dynamics. Models are presented in two variables, turbulence intensity and mean shear. A PDE model of pipe flow captures the essence of the puff-slug transition as a change from excitability to bistability. Extended models with turbulence as deterministic transient chaos or multiplicative noise reproduce almost all large-scale features of transitional pipe flow. In particular they capture metastable localized puffs, puff splitting, slugs, localized edge states, a continuous transition to sustained turbulence via spatiotemporal intermittency (directed percolation), and a subsequent increase in turbulence fraction towards uniform, featureless turbulence. A model that additionally takes into account the symmetries of plane Couette flow reproduces localized turbulence and periodic turbulent-laminar bands.
Simple nonlinear models suggest variable star universality
Lindner, John F; Kia, Behnam; Hippke, Michael; Learned, John G; Ditto, William L
2015-01-01
Dramatically improved data from observatories like the CoRoT and Kepler spacecraft have recently facilitated nonlinear time series analysis and phenomenological modeling of variable stars, including the search for strange (aka fractal) or chaotic dynamics. We recently argued [Lindner et al., Phys. Rev. Lett. 114 (2015) 054101] that the Kepler data includes "golden" stars, whose luminosities vary quasiperiodically with two frequencies nearly in the golden ratio, and whose secondary frequencies exhibit power-law scaling with exponent near -1.5, suggesting strange nonchaotic dynamics and singular spectra. Here we use a series of phenomenological models to make plausible the connection between golden stars and fractal spectra. We thereby suggest that at least some features of variable star dynamics reflect universal nonlinear phenomena common to even simple systems.
A simple model of bank bankruptcies
Aleksiejuk, Agata; Hołyst, Janusz A.
2001-10-01
Interbank deposits (loans and credits) are quite common in banking system all over the world. Such interbank co-operation is profitable for banks but it can also lead to collective financial failures. In this paper, we introduce a new model of directed percolation as a simple representation for contagion process and mass bankruptcies in banking systems. Directed connections that are randomly distributed between junctions of bank lattice simulate flows of money in our model. Critical values of a mean density of interbank connections as well as static and dynamic scaling laws for the statistics of avalanche bankruptcies are found. Results of computer simulations for the universal profile of bankruptcies spreading are in a qualitative agreement with the third wave of bank suspensions during The Great Depression in USA.
Genealogies in simple models of evolution
Brunet, Éric; Derrida, Bernard
2013-01-01
We review the statistical properties of the genealogies of a few models of evolution. In the asexual case, selection leads to coalescence times which grow logarithmically with the size of the population, in contrast with the linear growth of the neutral case. Moreover for a whole class of models, the statistics of the genealogies are those of the Bolthausen-Sznitman coalescent rather than the Kingman coalescent in the neutral case. For sexual reproduction in the neutral case, the time to reach the first common ancestors for the whole population and the time for all individuals to have all their ancestors in common are also logarithmic in the population size, as predicted by Chang in 1999. We discuss how these times are modified by introducing selection in a simple way.
Dreuw, Andreas; Wormit, Michael
2008-03-01
Recently, a mechanism for the energy-dependent component (qE) of non-photochemical quenching (NPQ), the fundamental photo-protection mechanism in green plants, has been suggested. Replacement of violaxanthin by zeaxanthin in the binding pocket of the major light harvesting complex LHC-II may be sufficient to invoke efficient chlorophyll fluorescence quenching. Our quantum chemical calculations, however, show that the excited state energies of violaxanthin and zeaxanthin are practically identical when their geometry is constrained to the naturally observed structure of violaxanthin in LHC-II. Therefore, since violaxanthin does not quench LHC-II, zeaxanthin should not either. This theoretical finding is nicely in agreement with experimental results obtained by femtosecond spectroscopy on LHC-II complexes containing violaxanthin or zeaxanthin.
Behaviour of ion velocity distributions for a simple collision model
St-Maurice, J.-P.; Schunk, R. W.
1974-01-01
Calculation of the ion velocity distributions for a weakly ionized plasma subjected to crossed electric and magnetic fields. An exact solution to Boltzmann's equation has been obtained by replacing the Boltzmann collision integral with a simple relaxation model. At altitudes above about 150 km, where the ion collision frequency is much less than the ion cyclotron frequency, the ion distribution takes the shape of a torus in velocity space for electric fields greater than 40 mV/m. This shape persists for one to two hours after application of the electric field. At altitudes where the ion collision and cyclotron frequencies are approximately equal (about 120 km), the ion velocity distribution is shaped like a bean for large electric field strengths. This bean-shaped distribution persists throughout the lifetime of ionospheric electric fields. These highly non-Maxwellian ion velocity distributions may have an appreciable affect on the interpretation of ion temperature measurements.
Zhang, Liang; Sun, Xiao-Gang; Yu, Cun-Tao; Chang, Qian; Qian, Xiang-Yang
2016-07-01
To retrospectively analyze the role of intercostal artery reconstruction in the spinal cord protection for patients undergoing extensive thoracoabdominal aortic aneurysm repair. From August 2007 to 2014, thoracoabdominal aortas (Crawford II) of 81 consecutive patients with mean age 39.4 ± 10.32 years were repaired. Seventy-three of these patients (90.12%) were diagnosed with aortic dissection in our group, 25 (30.86%) with Stanford type A dissection and 48 (59.26%) with Stanford B aortic dissection. All 25 patients with type A dissection have previously undergone surgical procedures which include Bentall's procedures in 11 cases, ascending aortic replacement in 6 cases, and total aortic arch replacement in 8 cases. All procedures were performed under profound hypothermia with interval cardiac arrest after making a thoracoabdominal incision. Extracorporeal circulation was instituted with 2 arterial cannulae and a single venous cannula in the right atrium. T6-T12 intercostal arteries and L1 and L2 lumbar arteries were formed to a neo-intercostal artery in place and were connected to an 8 mm branch for maintaining spinal cord blood perfusion. Visceral arteries were joined into a patch and anastomosed to the end of the main graft. The left renal artery was anastomosed to an 8 mm branch or joined to the patch. The other 10 mm branches were anastomosed to iliac arteries. With 100% follow-up, early mortality was 7.4%. Six deaths were recorded; 1 patient died of cerebral hemorrhage, 3 of renal failure, 1 of heart failure because of myocardial infarction, and the last one died from the rupture of celiac artery dissection. The rate of postoperative spinal cord deficits was 3.7%, 2 patients with paraplegia and 1 patient with paraparesis. None had bladder or rectum dysfunction. Neo-intercostal arteries were clogged in 12 patients within follow-up period and formed pseudoaneurysm in 2 patients with Marfan syndrome. The mean survival time in this group was 54.22 ± 3.03
Swarming behavior of simple model squirmers
Energy Technology Data Exchange (ETDEWEB)
Thutupalli, Shashi; Seemann, Ralf; Herminghaus, Stephan, E-mail: shashi.thutupalli@ds.mpg.de, E-mail: stephan.herminghaus@ds.mpg.de [Max Planck Institute for Dynamics and Self-Organization, Bunsenstrasse 10, 37073 Goettingen (Germany)
2011-07-15
We have studied experimentally the collective behavior of self-propelling liquid droplets, which closely mimic the locomotion of some protozoal organisms, the so-called squirmers. For the sake of simplicity, we concentrate on quasi-two-dimensional (2D) settings, although our swimmers provide a fully 3D propulsion scheme. At an areal density of 0.46, we find strong polar correlation of the locomotion velocities of neighboring droplets, which decays over less than one droplet diameter. When the areal density is increased to 0.78, distinct peaks show up in the angular correlation function, which point to the formation of ordered rafts. This shows that pronounced textures, beyond what has been seen in simulations so far, may show up in crowds of simple model squirmers, despite the simplicity of their (purely physical) mutual interaction.
A simple model for studying interacting networks
Liu, Wenjia; Jolad, Shivakumar; Schmittmann, Beate; Zia, R. K. P.
2011-03-01
Many specific physical networks (e.g., internet, power grid, interstates), have been characterized in considerable detail, but in isolation from each other. Yet, each of these networks supports the functions of the others, and so far, little is known about how their interactions affect their structure and functionality. To address this issue, we consider two coupled model networks. Each network is relatively simple, with a fixed set of nodes, but dynamically generated set of links which has a preferred degree, κ . In the stationary state, the degree distribution has exponential tails (far from κ), an attribute which we can explain. Next, we consider two such networks with different κ 's, reminiscent of two social groups, e.g., extroverts and introverts. Finally, we let these networks interact by establishing a controllable fraction of cross links. The resulting distribution of links, both within and across the two model networks, is investigated and discussed, along with some potential consequences for real networks. Supported in part by NSF-DMR-0705152 and 1005417.
Simple mathematical models of gene regulatory dynamics
Mackey, Michael C; Tyran-Kamińska, Marta; Zeron, Eduardo S
2016-01-01
This is a short and self-contained introduction to the field of mathematical modeling of gene-networks in bacteria. As an entry point to the field, we focus on the analysis of simple gene-network dynamics. The notes commence with an introduction to the deterministic modeling of gene-networks, with extensive reference to applicable results coming from dynamical systems theory. The second part of the notes treats extensively several approaches to the study of gene-network dynamics in the presence of noise—either arising from low numbers of molecules involved, or due to noise external to the regulatory process. The third and final part of the notes gives a detailed treatment of three well studied and concrete examples of gene-network dynamics by considering the lactose operon, the tryptophan operon, and the lysis-lysogeny switch. The notes contain an index for easy location of particular topics as well as an extensive bibliography of the current literature. The target audience of these notes are mainly graduat...
Simple models of assortment through environmental feedback.
Pepper, John W
2007-01-01
Social evolution depends critically on assortment, or segregation versus even mixing, between cooperators and noncooperators. Altruistic traits, which reduce the absolute fitness of their bearers, cannot evolve without positive assortment (excess segregation). The question of how positive assortment can arise has been controversial, but most evolutionary biologists believe that common descent is the only effective general mechanism. Here I investigate another recently proposed mechanism for generating nonrandom assortment, termed environmental feedback. This requires only that two forms of a trait affect the quality of the local environment differently in such a way that all individuals are more likely to leave low-quality locales. Experiments with simple computational models confirm that environmental feedback generates significant levels of genetic similarity among non-kin within locales. The mechanism is fairly general, and can under some conditions produce levels of genetic similarity comparable to those resulting from close genealogical relationship. Environmental feedback can also generate the negative assortment necessary for the evolution of spiteful traits. Environmental feedback is expected to create positive frequency-dependent selection, which thus favor any social trait that becomes common in the population. Results from this stylized model suggest that environmental feedback could be important in the evolution of both cooperation and spite, within as well as between species.
Replacement model of city bus: A dynamic programming approach
Arifin, Dadang; Yusuf, Edhi
2017-06-01
This paper aims to develop a replacement model of city bus vehicles operated in Bandung City. This study is driven from real cases encountered by the Damri Company in the efforts to improve services to the public. The replacement model propounds two policy alternatives: First, to maintain or keep the vehicles, and second is to replace them with new ones taking into account operating costs, revenue, salvage value, and acquisition cost of a new vehicle. A deterministic dynamic programming approach is used to solve the model. The optimization process was heuristically executed using empirical data of Perum Damri. The output of the model is to determine the replacement schedule and the best policy if the vehicle has passed the economic life. Based on the results, the technical life of the bus is approximately 20 years old, while the economic life is an average of 9 (nine) years. It means that after the bus is operated for 9 (nine) years, managers should consider the policy of rejuvenation.
Competition, coinfection and strain replacement in models of Bordetella pertussis.
Nicoli, Emily J; Ayabina, Diepreye; Trotter, Caroline L; Turner, Katherine M E; Colijn, Caroline
2015-08-01
Pertussis, or whooping cough, is an important respiratory infection causing considerable infant mortality worldwide. Recently, incidence has risen in countries with strong vaccine programmes and there are concerns about antigenic shift resulting in vaccine evasion. Interactions between pertussis and non-vaccine-preventable strains will play an important role in the evolution and population dynamics of pertussis. In particular, if we are to understand the role strain replacement plays in vaccinated settings, it will be essential to understand how strains or variants of pertussis interact. Here we explore under what conditions we would expect strain replacement to be of concern in pertussis. We develop a dynamic transmission model that allows for coinfection between Bordetella pertussis (the main causative agent of pertussis) and a strain or variant unaffected by the vaccine. We incorporate both neutrality (in the sense of ecological/population genetic neutrality) and immunity into the model, leaving the specificity of the immune response flexible. We find that strain replacement may be considerable when immunity is non-specific. This is in contrast to previous findings where neutrality was not considered. We conclude that the extent to which models reflect ecological neutrality can have a large impact on conclusions regarding strain replacement. This will likely have onward consequences for estimates of vaccine efficacy and cost-effectiveness.
A simple model of ostracism formation.
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Pilwon Kim
Full Text Available We study formation of ostracism in a society from a game theoretical perspective. The dynamics of group formation is complicated in that the choices of the individuals and the form of the groups mutually affect each other in the process. A suggested simple model shows that individual efforts to increase his/her own sense of belonging is responsible for both growth of groups and creation of an outcast. Once a person happens to get behind in synchronizing with others, tendency to alienate him may grow among others, possibly making him left out in the end. Alienating minority occurs even when there is a penalty for disliking and people are encouraged to favor others. Considering that the target is accidentally picked, we can understand ostracism as an inherent part of the group formation, rather than a result of specific discrepancy among people. Another finding is that a single individual who seeks for unconditional unification of the society ("philanthropist" likely invites his/her own isolation from the society, while the existence of such person generally promotes coalition of others.
A simple model of ostracism formation.
Kim, Pilwon
2014-01-01
We study formation of ostracism in a society from a game theoretical perspective. The dynamics of group formation is complicated in that the choices of the individuals and the form of the groups mutually affect each other in the process. A suggested simple model shows that individual efforts to increase his/her own sense of belonging is responsible for both growth of groups and creation of an outcast. Once a person happens to get behind in synchronizing with others, tendency to alienate him may grow among others, possibly making him left out in the end. Alienating minority occurs even when there is a penalty for disliking and people are encouraged to favor others. Considering that the target is accidentally picked, we can understand ostracism as an inherent part of the group formation, rather than a result of specific discrepancy among people. Another finding is that a single individual who seeks for unconditional unification of the society ("philanthropist") likely invites his/her own isolation from the society, while the existence of such person generally promotes coalition of others.
Simple models of the hydrofracture process
Marder, M.
2015-12-29
Hydrofracturing to recover natural gas and oil relies on the creation of a fracture network with pressurized water. We analyze the creation of the network in two ways. First, we assemble a collection of analytical estimates for pressure-driven crack motion in simple geometries, including crack speed as a function of length, energy dissipated by fluid viscosity and used to break rock, and the conditions under which a second crack will initiate while a first is running. We develop a pseudo-three-dimensional numerical model that couples fluid motion with solid mechanics and can generate branching crack structures not specified in advance. One of our main conclusions is that the typical spacing between fractures must be on the order of a meter, and this conclusion arises in two separate ways. First, it arises from analysis of gas production rates, given the diffusion constants for gas in the rock. Second, it arises from the number of fractures that should be generated given the scale of the affected region and the amounts of water pumped into the rock.
Simple model of the slingshot effect
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Gaetano Fiore
2016-07-01
Full Text Available We present a detailed quantitative description of the recently proposed “slingshot effect.” Namely, we determine a broad range of conditions under which the impact of a very short and intense laser pulse normally onto a low-density plasma (or matter locally completely ionized into a plasma by the pulse causes the expulsion of a bunch of surface electrons in the direction opposite to the one of propagation of the pulse, and the detailed, ready-for-experiments features of the expelled electrons (energy spectrum, collimation, etc. The effect is due to the combined actions of the ponderomotive force and the huge longitudinal field arising from charge separation. Our predictions are based on estimating 3D corrections to a simple, yet powerful plane 2-fluid magnetohydrodynamic (MHD model where the equations to be solved are reduced to a system of Hamilton equations in one dimension (or a collection of which become autonomous after the pulse has overcome the electrons. Experimental tests seem to be at hand. If confirmed by the latter, the effect would provide a new extraction and acceleration mechanism for electrons, alternative to traditional radio-frequency-based or Laser-Wake-Field ones.
A simple model of the slingshot effect
Fiore, Gaetano
2015-01-01
We present a detailed quantitative description of the recently proposed "slingshot effect" [Fiore, Fedele, De angelis 2014]. Namely, we determine a broad range of conditions under which the impact of a very short and intense laser pulse normally onto a plasma (or matter to be locally completely ionized into a plasma by the pulse) causes the expulsion of a bunch of surface electrons in the direction opposite to the one of propagation of the pulse, and the detailed, ready-for-experiments features of the expelled electrons (energy spectrum, collimation, etc). The effect is due to the combined actions of the ponderomotive force and the huge longitudinal field arising from charge separation. Our predictions are based on estimating 3D corrections to a simple, yet powerful plane magnetofluidodynamic model where the equations to be solved are reduced to a system of Hamilton equations in one dimension (or a collection of) which become autonomous after the pulse has overcome the electrons. Experimental tests seem to be...
Fleet Replacement Squadron consolidation : a cost model applied.
Maholchic, Robert M.
1991-01-01
The consolidation of Fleet Replacement Squadrons (FRS) represents one method of achieving planned force reductions. This thesis utilizes the Cost of Base Realignment Actions (COBRA) cost model to develop cost estimates for determination of the cost effective site location. The A-6 FRS consolidation is used as a case study. Data were compiled using completed Functional Wing studies as well as local information sources. A comparison between the cost estimates provided by the COBRA cost model fo...
Modeling dynamic recrystallization of olivine aggregates deformed in simple shear
Energy Technology Data Exchange (ETDEWEB)
Wenk, H.-R. [Department of Geology and Geophysics, University of California, Berkeley (United States); Tome, C. N. [Materials, Science and Technology Division, Los Alamos National Laboratory, Los Alamos, New Mexico (United States)
1999-11-10
Experiments by Zhang and Karato [1995] have shown that in simple shear dislocation creep of olivine at low strains, an asymmetric texture develops with a [100] maximum rotated away from the shear direction against the sense of shear. At large strain where recrystallization is pervasive, the texture pattern is symmetrical, and [100] is parallel to the shear direction. The deformation texture can be adequately modeled with a viscoplastic self-consistent polycrystal plasticity theory. This model can be expanded to include recrystallization, treating the process as a balance of boundary migration (growth of relatively underformed grains at the expense of highly deformed grains) and nucleation (strain-free nuclei replacing highly deformed grains). If nucleation dominates over growth, the model predicts a change from the asymmetric to the symmetric texture as recrystallization proceeds and stabilization in the ''easy slip'' orientation for the dominant (010)[100] slip system. This result is in accordance with the experiments and suggests that the most highly deformed orientation components dominate the recrystallization texture. The empirical model will be useful to simulate more adequately the development of anisotropy in the mantle where olivine is largely recrystallized. (c) 1999 American Geophysical Union.
Model for Quantitative Evaluation of Enzyme Replacement Treatment
Directory of Open Access Journals (Sweden)
Radeva B.
2009-12-01
Full Text Available Gaucher disease is the most frequent lysosomal disorder. Its enzyme replacement treatment was the new progress of modern biotechnology, successfully used in the last years. The evaluation of optimal dose of each patient is important due to health and economical reasons. The enzyme replacement is the most expensive treatment. It must be held continuously and without interruption. Since 2001, the enzyme replacement therapy with Cerezyme*Genzyme was formally introduced in Bulgaria, but after some time it was interrupted for 1-2 months. The dose of the patients was not optimal. The aim of our work is to find a mathematical model for quantitative evaluation of ERT of Gaucher disease. The model applies a kind of software called "Statistika 6" via the input of the individual data of 5-year-old children having the Gaucher disease treated with Cerezyme. The output results of the model gave possibilities for quantitative evaluation of the individual trends in the development of the disease of each child and its correlation. On the basis of this results, we might recommend suitable changes in ERT.
Simple Models for the Dynamic Modeling of Rotating Tires
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J.C. Delamotte
2008-01-01
Full Text Available Large Finite Element (FE models of tires are currently used to predict low frequency behavior and to obtain dynamic model coefficients used in multi-body models for riding and comfort. However, to predict higher frequency behavior, which may explain irregular wear, critical rotating speeds and noise radiation, FE models are not practical. Detailed FE models are not adequate for optimization and uncertainty predictions either, as in such applications the dynamic solution must be computed a number of times. Therefore, there is a need for simpler models that can capture the physics of the tire and be used to compute the dynamic response with a low computational cost. In this paper, the spectral (or continuous element approach is used to derive such a model. A circular beam spectral element that takes into account the string effect is derived, and a method to simulate the response to a rotating force is implemented in the frequency domain. The behavior of a circular ring under different internal pressures is investigated using modal and frequency/wavenumber representations. Experimental results obtained with a real untreaded truck tire are presented and qualitatively compared with the simple model predictions with good agreement. No attempt is made to obtain equivalent parameters for the simple model from the real tire results. On the other hand, the simple model fails to represent the correct variation of the quotient of the natural frequency by the number of circumferential wavelengths with the mode count. Nevertheless, some important features of the real tire dynamic behavior, such as the generation of standing waves and part of the frequency/wavenumber behavior, can be investigated using the proposed simplified model.
A simple analytic model of wormhole formations
Maeda, Hideki
2008-01-01
An explicit and simple solution representing the wormhole formation is presented. The spacetime is constructed by gluing the Minkowski and Roberts spacetimes at null hypersurfaces in a regular manner. The parameters in the Roberts solution are required to give the negative kinetic term for the massless scalar field. Although a curvature singularity appears at the moment of the wormhole formation, it disappears instantaneously. This instantaneous singularity is weak in the both senses of Tipler and Kr\\'{o}lak along radial causal geodesics.
Sucrose-replacement by rebaudioside a in a model beverage.
Majchrzak, Dorota; Ipsen, Annika; Koenig, Juergen
2015-09-01
Rebaudioside A (RA), a component of Stevia rebaudiana, is a non-caloric sweetener of natural origin, suitable to meet consumers' demand for sweet taste, but undesirable flavors were reported at high concentrations. Aim of this study was to create a model beverage (ice-tea) in which sucrose was replaced increasingly by RA to identify optimal sensory profile for consumer acceptance. Samples with 20 % and 40 % sucrose replacement by RA, respectively, showed very similar sensory profiles but were significantly higher in some flavor attributes, such as artificial sweetness, licorice-like and metallic, as well as in sweet and bitter aftertaste (p < 0.05) compared to the reference ice-tea. In both hedonic tests, preference and acceptance samples with RA have been judged as comparable to the reference despite perception of some undesirable notes. In view of the results of our study it can be stated that a replacement of 20 % or 40 % sucrose by RA in an ice-tea is achievable.
REPLACEMENT ANALYSIS FOR DEFECTED PRODUCTS: A SYSTEM DYNAMIC MODELING APPROACH
Directory of Open Access Journals (Sweden)
R. N. Mall
2012-07-01
Full Text Available The current growth in present time due to globalization of markets means more competition for companies especially those in developing economies that have limited analytical tools for business decisions. Market demand uncertainty affects the performance and behavior of the planning processes used by production to satisfy sales. This uncertainty and the resulting instability in the production schedules affect the relationships with the suppliers from whom the company purchases raw materials and component parts. In order to solve the problem, this research developed a SCM system dynamics model that helps business managers and researchers in SCM make better and informed decisions for close life cycle products. The work is focused on the study of behavior of replacement in a supply chain related to closed life-cycle products by system dynamics, that are goods produced and sold and if any defect is found the product is replaced. This study includes the effect of replacement in profit and other variables. This work also includes the development of a model in the system and validation of the model. In this model the relation of the variables like customer, demand, cost, price is studied and the work is focused that what will be the optimum value of the defected product. It has been assumed that if we want to decrease the defected product the cost of the production will increase and that will reduce the profit and if we want to increase the defect the no of customers will decrease and their demand will decrease and this will decrease the profit.
Understanding the tsunami with a simple model
Helene, O
2006-01-01
In this paper, we use the approximation of shallow water waves (Margaritondo G 2005 Eur. J. Phys. 26 401) to understand the behaviour of a tsunami in a variable depth. We deduce the shallow water wave equation and the continuity equation that must be satisfied when a wave encounters a discontinuity in the sea depth. A short explanation about how the tsunami hit the west coast of India is given based on the refraction phenomenon. Our procedure also includes a simple numerical calculation suitable for undergraduate students in physics and engineering.
Simple grading model for financial markets
Thuy Anh, Chu; Lan, Nguyen Tri; Viet, Nguyen Ai
2015-06-01
A simple way to estimate and grade a financial market by comparison the evolution process and the shape of distribution functions was proposed. In normal working state of financial market, the shape of distribution functions have one-peak form and change from Boltzmann-like to Gaussian-like distributions, while in risk moment might have two-peak form. The grad of financial markets was characterized by overlap area of initial and final distribution functions, and for risk degree by the separation between two shoulders of distribution function. The meaning of Levi tails of distribution and laws of general entropy and information was discussed.
AUTONOMOUS CT REPLACEMENT METHOD FOR THE SKULL PROSTHESIS MODELLING
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Marcelo Rudek
2015-12-01
Full Text Available The geometric modeling of prosthesis is a complex task from medical and engineering viewpoint. A method based on CT replacement is proposed in order to circumvent the related problems with the missing information to modeling. The method is based on digital image processing and swarm intelligence algorithm. In this approach, a missing region on the defective skull is represented by curvature descriptors. The main function of the descriptors is to simplify the skull’s contour geometry; and they are defined from the Cubic Bezier Curves using a meta-heuristic process for parameter’s estimation. The Artificial Bee Colony (ABC optimization technique is applied in order to evaluate the best solution. The descriptors from a defective CT slice image are the searching parameters in medical image databases, and a similar image, i.e. with similar descriptors, can be retrieval and used to replace the defective slice. Thus, a prosthesis piece is automatically modeled with information extracted from distinct skulls with similar anatomical characteristics.
A Simple Holographic Model of Nonlinear Conductivity
Horowitz, Gary T; Santos, Jorge E
2013-01-01
We present a simple analytic gravitational solution which describes the holographic dual of a 2+1-dimensional conductor which goes beyond the usual linear response. In particular it includes Joule heating. We find that the nonlinear frequency-dependent conductivity is a constant. Surprisingly, the pressure remains isotropic. We also apply an electric field to a holographic insulator and show that there is a maximum electric field below which it can remain an insulator. Above this critical value, we argue that it becomes a conductor due to pair creation of charged particles. Finally, we study 1+1 and 3+1 dimensional conductors at the nonlinear level; here exact solutions are not available and a perturbative analysis shows that the current becomes time dependent, but in a way that is captured by a time-dependent effective temperature.
Simple opdriftsbaserede modeller for Wave Star
DEFF Research Database (Denmark)
Kramer, Morten
Wave Star modellen er udarbejdet i programmeringssproget Delphi. Modellerne er en videre udarbejdelse af tidligere anvendte Excel-modeller. I forhold til Excelmodellerne udmærker de nye Dephi-modeller sig ved at beregningerne udføres mange gange hurtigere og modellerne kan håndtere lange tidsserier...
SAM: A Simple Averaging Model of Impression Formation
Lewis, Robert A.
1976-01-01
Describes the Simple Averaging Model (SAM) which was developed to demonstrate impression-formation computer modeling with less complex and less expensive procedures than are required by most established programs. (RC)
Comment on "a simple inflationary quintessential model"
Fernandez-Jambrina, L
2016-01-01
In [1] a new cosmological model is proposed with no big bang singularity in the past. This model starts with an inflationary era, follows with a stiff matter dominated period and evolves to accelerated expansion in an asymptotically de Sitter regime. We argue that the initial singularity is in fact no big bang but a directional singularity which cannot be reached by comoving observers but by observers with nonzero linear momentum. Hence, the time lapse from the initial singularity can be as long as desired depending on the linear momentum of the observer. This conclusion applies to similar inflationary models. This sort of cosmological singularities have been postulated also in other scenarios.
Simple model for river network evolution
Energy Technology Data Exchange (ETDEWEB)
Leheny, R.L. [The James Franck Institute and The Department of Physics, The University of Chicago, 5640 South Ellis Avenue, Chicago, Illinois 60637 (United States)
1995-11-01
We simulate the evolution of a drainage basin by erosion from precipitation and avalanching on hillslopes. The avalanches create a competition in growth between neighboring basins and play the central role in driving the evolution. The simulated landscapes form drainage systems that share many qualitative features with Glock`s model for natural network evolution and maintain statistical properties that characterize real river networks. We also present results from a second model with a modified, mass conserving avalanche scheme. Although the terrains from these two models are qualitatively dissimilar, their drainage networks share the same general evolution and statistical features.
Simple statistical model for branched aggregates
DEFF Research Database (Denmark)
Lemarchand, Claire; Hansen, Jesper Schmidt
2015-01-01
, given that it already has bonds with others. The model is applied here to asphaltene nanoaggregates observed in molecular dynamics simulations of Cooee bitumen. The variation with temperature of the probabilities deduced from this model is discussed in terms of statistical mechanics arguments......We propose a statistical model that can reproduce the size distribution of any branched aggregate, including amylopectin, dendrimers, molecular clusters of monoalcohols, and asphaltene nanoaggregates. It is based on the conditional probability for one molecule to form a new bond with a molecule....... The relevance of the statistical model in the case of asphaltene nanoaggregates is checked by comparing the predicted value of the probability for one molecule to have exactly i bonds with the same probability directly measured in the molecular dynamics simulations. The agreement is satisfactory...
Urban drainage models - making uncertainty analysis simple
DEFF Research Database (Denmark)
Vezzaro, Luca; Mikkelsen, Peter Steen; Deletic, Ana;
2012-01-01
There is increasing awareness about uncertainties in modelling of urban drainage systems and, as such, many new methods for uncertainty analyses have been developed. Despite this, all available methods have limitations which restrict their widespread application among practitioners. Here, a modif...... probability distributions (often used for sensitivity analyses) and prediction intervals. To demonstrate the new method, it is applied to a conceptual rainfall-runoff model using a dataset collected from Melbourne, Australia....
Statistical tests of simple earthquake cycle models
DeVries, Phoebe M. R.; Evans, Eileen L.
2016-12-01
A central goal of observing and modeling the earthquake cycle is to forecast when a particular fault may generate an earthquake: a fault late in its earthquake cycle may be more likely to generate an earthquake than a fault early in its earthquake cycle. Models that can explain geodetic observations throughout the entire earthquake cycle may be required to gain a more complete understanding of relevant physics and phenomenology. Previous efforts to develop unified earthquake models for strike-slip faults have largely focused on explaining both preseismic and postseismic geodetic observations available across a few faults in California, Turkey, and Tibet. An alternative approach leverages the global distribution of geodetic and geologic slip rate estimates on strike-slip faults worldwide. Here we use the Kolmogorov-Smirnov test for similarity of distributions to infer, in a statistically rigorous manner, viscoelastic earthquake cycle models that are inconsistent with 15 sets of observations across major strike-slip faults. We reject a large subset of two-layer models incorporating Burgers rheologies at a significance level of α = 0.05 (those with long-term Maxwell viscosities ηM 4.6 × 1020 Pa s) but cannot reject models on the basis of transient Kelvin viscosity ηK. Finally, we examine the implications of these results for the predicted earthquake cycle timing of the 15 faults considered and compare these predictions to the geologic and historical record.
Perspectives for computational modeling of cell replacement for neurological disorders
Directory of Open Access Journals (Sweden)
James B Aimone
2013-11-01
Full Text Available Mathematical modeling of anatomically-constrained neural networks has provided significant insights regarding the response of networks to neurological disorders or injury. A logical extension of these models is to incorporate treatment regimens to investigate network responses to intervention. The addition of nascent neurons from stem cell precursors into damaged or diseased tissue has been used as a successful therapeutic tool in recent decades. Interestingly, models have been developed to examine the incorporation of new neurons into intact adult structures, particularly the dentate granule neurons of the hippocampus. These studies suggest that the unique properties of maturing neurons can impact circuit behavior in unanticipated ways. In this perspective, we review the current status of models used to examine damaged CNS structures with particular focus on cortical damage due to stroke. Secondly, we suggest that computational modeling of cell replacement therapies can be made feasible by implementing approaches taken by current models of adult neurogenesis. The development of these models is critical for generating hypotheses regarding transplant therapies and improving outcomes by tailoring transplants to desired effects.
Perspectives for computational modeling of cell replacement for neurological disorders
Energy Technology Data Exchange (ETDEWEB)
Aimone, James B.; Weick, Jason P.
2013-01-01
Mathematical modeling of anatomically-constrained neural networks has provided significant insights regarding the response of networks to neurological disorders or injury. A logical extension of these models is to incorporate treatment regimens to investigate network responses to intervention. The addition of nascent neurons from stem cell precursors into damaged or diseased tissue has been used as a successful therapeutic tool in recent decades. Interestingly, models have been developed to examine the incorporation of new neurons into intact adult structures, particularly the dentate granule neurons of the hippocampus. These studies suggest that the unique properties of maturing neurons, can impact circuit behavior in unanticipated ways. In this perspective, we review the current status of models used to examine damaged CNS structures with particular focus on cortical damage due to stroke. Secondly, we suggest that computational modeling of cell replacement therapies can be made feasible by implementing approaches taken by current models of adult neurogenesis. The development of these models is critical for generating hypotheses regarding transplant therapies and improving outcomes by tailoring transplants to desired effects.
Perspectives for computational modeling of cell replacement for neurological disorders
Energy Technology Data Exchange (ETDEWEB)
Aimone, James B. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Weick, Jason P. [Univ. of New Mexico, Albuquerque, NM (United States)
2013-01-01
In mathematical modeling of anatomically-constrained neural networks we provide significant insights regarding the response of networks to neurological disorders or injury. Furthermore, a logical extension of these models is to incorporate treatment regimens to investigate network responses to intervention. The addition of nascent neurons from stem cell precursors into damaged or diseased tissue has been used as a successful therapeutic tool in recent decades. Interestingly, models have been developed to examine the incorporation of new neurons into intact adult structures, particularly the dentate granule neurons of the hippocampus. These studies suggest that the unique properties of maturing neurons, can impact circuit behavior in unanticipated ways. In this perspective, we review the current status of models used to examine damaged CNS structures with particular focus on cortical damage due to stroke. Secondly, we suggest that computational modeling of cell replacement therapies can be made feasible by implementing approaches taken by current models of adult neurogenesis. The development of these models is critical for generating hypotheses regarding transplant therapies and improving outcomes by tailoring transplants to desired effects.
Simple model to study heterogeneous electrocatalysts
Franco-Junior, Edison; Lopes, Ana Carolina G.; Suffredini, Hugo B.; Homem-de-Mello, Paula
2015-01-01
New electrocatalyst materials have been proposed to increase the performance of fuel cells. Experimental studies show that Pt and Pb metallic and oxide materials are quite efficient in the oxidation of alcohols and small organic molecules such as formic acid in advanced fuel cells. This work proposes a model for studying morphologically heterogeneous catalysts through quantum chemistry methods such as density functional calculations. For testing the model, we have experimentally studied the adsorption of small organic molecules, namely formic acid and methanol, on Pt and Pb electrodes. All methodologies we have tested can be employed for this kind of study, but M06 functional results correlate best with previous simulations of homogeneous catalysts and with experimental data obtained for homogeneous and heterogeneous electrodes. Our model indicates that the presence of a Pt-Pb interface is responsible for higher adsorption energies of these molecules, most likely due to the orientation of the organic molecules that should facilitate the oxidation process.
A simple nonlocal model for exchange.
Janesko, Benjamin G
2009-12-21
This work presents a new nonlocal model for the exchange energy density. The model is obtained from the product of the Kohn-Sham one-particle density matrix used to construct exact [Hartree-Fock-like (HF)] exchange, and an approximate density matrix used to construct local spin-density approximation (LSDA) exchange. The proposed exchange energy density has useful formal properties, including correct spin and coordinate scaling and the correct uniform limit. It can readily be evaluated in finite basis sets, with a computational scaling intermediate between HF exchange and semilocal quantities such as the noninteracting kinetic energy density. Applications to representative systems indicate that its properties are typically intermediate between HF and LSDA exchange, and often similar to global hybrids of HF and LSDA exchange. The model is proposed as a novel "Rung 3.5" ingredient for constructing approximate exchange-correlation functionals.
A simple model of bedform migration
DEFF Research Database (Denmark)
Bartholdy, Jesper; Ernstsen, Verner Brandbyge; Flemming, Burg W
2010-01-01
A model linking subaqueous dune migration to the effective (grain related) shear stress is calibrated by means of flume data for bedform dimensions and migration rates. The effective shear stress is calculated on the basis of a new method assuming a near-bed layer above the mean bed level in which...
Urban drainage models - making uncertainty analysis simple
DEFF Research Database (Denmark)
Vezzaro, Luca; Mikkelsen, Peter Steen; Deletic, Ana
2012-01-01
There is increasing awareness about uncertainties in modelling of urban drainage systems and, as such, many new methods for uncertainty analyses have been developed. Despite this, all available methods have limitations which restrict their widespread application among practitioners. Here, a modif...
A Study of Simple Diffraction Models
DEFF Research Database (Denmark)
Agerkvist, Finn
1997-01-01
Three different models for calculating edge diffraction are examined. The methods of Vanderkooy, Terai and Biot & Tolstoy are compared with measurements. Although a good agreement is obtained, the measurements also show that none of the methods work completely satisfactorily. The desired properties...
Simple models of human brain functional networks.
Vértes, Petra E; Alexander-Bloch, Aaron F; Gogtay, Nitin; Giedd, Jay N; Rapoport, Judith L; Bullmore, Edward T
2012-04-10
Human brain functional networks are embedded in anatomical space and have topological properties--small-worldness, modularity, fat-tailed degree distributions--that are comparable to many other complex networks. Although a sophisticated set of measures is available to describe the topology of brain networks, the selection pressures that drive their formation remain largely unknown. Here we consider generative models for the probability of a functional connection (an edge) between two cortical regions (nodes) separated by some Euclidean distance in anatomical space. In particular, we propose a model in which the embedded topology of brain networks emerges from two competing factors: a distance penalty based on the cost of maintaining long-range connections; and a topological term that favors links between regions sharing similar input. We show that, together, these two biologically plausible factors are sufficient to capture an impressive range of topological properties of functional brain networks. Model parameters estimated in one set of functional MRI (fMRI) data on normal volunteers provided a good fit to networks estimated in a second independent sample of fMRI data. Furthermore, slightly detuned model parameters also generated a reasonable simulation of the abnormal properties of brain functional networks in people with schizophrenia. We therefore anticipate that many aspects of brain network organization, in health and disease, may be parsimoniously explained by an economical clustering rule for the probability of functional connectivity between different brain areas.
Simple supersymmetric strongly coupled preon model
Fajfer, S.; Tadić, D.
1988-08-01
This supersymmetric-SU(5) composite model is a natural generalization of the usual strong-coupling models. Preon superfields are in representations 5* and 10. The product representations 5*×10, 5×10, 5×5, and 5*×5 contain only those strongly hypercolor bound states which are needed in the standard electroweak theory. There are no superfluous quarklike states. The neutrino is massless. Only one strongly hypercolor bound singlet (10×10*) can exist as a free particle. At higher energies one should expect to see a plethora of new particles. Grand unification happens at the scale M~1014 GeV. Cabibbo mixing can be incorporated by using a transposed Kobayashi-Maskawa mixing matrix.
Complex Behaviors of a Simple Traffic Model
Institute of Scientific and Technical Information of China (English)
GAO Xing-Ru
2006-01-01
In this paper, we propose a modified traffic model in which a single car moves through a sequence of traffic lights controlled by a step function instead of a sine function. In contrast to the previous work [Phys. Rev. E 70 (2004)016107], we have investigated in detail the dependence of the behavior on four parameters, ω, α, η, and a1, and given three kinds of bifurcation diagrams, which show three kinds of complex behaviors. We have found that in this model there are chaotic and complex periodic motions, as well as special singularities. We have also analyzed the characteristic of the complex period motion and the essential feature of the singularity.
Simple model of a coherent molecular photocell
Ernzerhof, Matthias; Bélanger, Marc-André; Mayou, Didier; Nemati Aram, Tahereh
2016-04-01
Electron transport in molecular electronic devices is often dominated by a coherent mechanism in which the wave function extends from the left contact over the molecule to the right contact. If the device is exposed to light, photon absorption in the molecule might occur, turning the device into a molecular photocell. The photon absorption promotes an electron to higher energy levels and thus modifies the electron transmission probability through the device. A model for such a molecular photocell is presented that minimizes the complexity of the problem while providing a non-trivial description of the device mechanism. In particular, the role of the molecule in the photocell is investigated. It is described within the Hückel method and the source-sink potential approach [F. Goyer, M. Ernzerhof, and M. Zhuang, J. Chem. Phys. 126, 144104 (2007)] is used to eliminate the contacts in favor of complex-valued potentials. Furthermore, the photons are explicitly incorporated into the model through a second-quantized field. This facilitates the description of the photon absorption process with a stationary state calculation, where eigenvalues and eigenvectors are determined. The model developed is applied to various generic molecular photocells.
Simple predictions from multifield inflationary models.
Easther, Richard; Frazer, Jonathan; Peiris, Hiranya V; Price, Layne C
2014-04-25
We explore whether multifield inflationary models make unambiguous predictions for fundamental cosmological observables. Focusing on N-quadratic inflation, we numerically evaluate the full perturbation equations for models with 2, 3, and O(100) fields, using several distinct methods for specifying the initial values of the background fields. All scenarios are highly predictive, with the probability distribution functions of the cosmological observables becoming more sharply peaked as N increases. For N=100 fields, 95% of our Monte Carlo samples fall in the ranges ns∈(0.9455,0.9534), α∈(-9.741,-7.047)×10-4, r∈(0.1445,0.1449), and riso∈(0.02137,3.510)×10-3 for the spectral index, running, tensor-to-scalar ratio, and isocurvature-to-adiabatic ratio, respectively. The expected amplitude of isocurvature perturbations grows with N, raising the possibility that many-field models may be sensitive to postinflationary physics and suggesting new avenues for testing these scenarios.
Life cycle optimization of automobile replacement: model and application.
Kim, Hyung Chul; Keoleian, Gregory A; Grande, Darby E; Bean, James C
2003-12-01
Although recent progress in automotive technology has reduced exhaust emissions per mile for new cars, the continuing use of inefficient, higher-polluting old cars as well as increasing vehicle miles driven are undermining the benefits of this progress. As a way to address the "inefficient old vehicle" contribution to this problem, a novel life cycle optimization (LCO) model is introduced and applied to the automobile replacement policy question. The LCO model determines optimal vehicle lifetimes, accounting for technology improvements of new models while considering deteriorating efficiencies of existing models. Life cycle inventories for different vehicle models that represent materials production, manufacturing, use, maintenance, and end-of-life environmental burdens are required as inputs to the LCO model. As a demonstration, the LCO model was applied to mid-sized passenger car models between 1985 and 2020. An optimization was conducted to minimize cumulative carbon monoxide (CO), non-methane hydrocarbon (NMHC), oxides of nitrogen (NOx), carbon dioxide (CO2), and energy use over the time horizon (1985-2020). For CO, NMHC, and NOx pollutants with 12000 mi of annual mileage, automobile lifetimes ranging from 3 to 6 yr are optimal for the 1980s and early 1990s model years while the optimal lifetimes are expected to be 7-14 yr for model year 2000s and beyond. On the other hand, a lifetime of 18 yr minimizes cumulative energy and CO2 based on driving 12000 miles annually. Optimal lifetimes are inversely correlated to annual vehicle mileage, especially for CO, NMHC, and NOx emissions. On the basis of the optimization results, policies improving durability of emission controls, retiring high-emitting vehicles, and improving fuel economies are discussed.
A simple model for pediment formation.
Mercier, Jonathan; Braun, Jean; Guillocheau, François; Robin, Cecile; Simon, Brendan
2016-04-01
Pediments are very flat and smooth erosive surfaces, connected to higher relief by a scarp, that covers up to two thirds of the Earth's surface. A physical mechanism to explain their formation remains elusive. Commonly accepted hypotheses include: (1) the widening of an incised river network (lateral corrasion of Gilbert, 1877), (2) sheetflow erosion, (3) subsurface weathering and exhumation (Strudley et al, 2006) and (4) slope retreat, usually at the base of an escarpment (King, 1949), potentially helped by flexural isostatic rebound (Pelletier, 2010). Here we explore the third hypothesis, which we believe applies mostly in regions characterised by intense rainfall where deep weathering profiles are commonly observed. In this study, using a new coupled model of groundwater flow and surface erosion, we highlight the critical impact of the geometry of the water table and of the unsaturated zone within a weathering profile to explain its evolution through time. The model is calibrated and used to explain the formation of pediments as the product of a dynamical balance between weathering front propagation and surface erosion. We also explore the effects of abrupt changes in rainfall intensity and base level drop on the geometry of the predicted pediments.
Solution profiles for some simple combustion models
Energy Technology Data Exchange (ETDEWEB)
Bebernes, J.; Eberly, D.; Fulks, W.
1986-01-01
In this paper, the shape (solution profile) of the solutions of the Gelfand problem and the perturbed Gelfand problem are studied. Both of these models play a fundamental role in the mathematical theory of thermal explosions for finite rigid and gaseous systems. For rigid systems the physical processes are determined by a pointwise balance between chemical heat addition and heat loss by conduction. During the inductive period, with a duration measured by the conduction time scale of the bounding container, the heat released by the chemical reaction is redistributed by thermal conduction. As the temperature of the container increases, the reaction rate grows dramatically. Eventually, the characteristic time for heat release becomes significantly smaller than the conduction time in a well-defined hot spot embedded in the system. Then the heat released is used almost entirely to increase the hot-spot temperature. The purpose of this paper is to show that both models detect this hot-spot development in a very precise manner. This hot-spot development had previously been detected only numerically.
Simple model of a cooling tower plume
Jan, Cizek; Jiri, Nozicka
2016-06-01
This article discusses the possibilities in the area of modeling of the so called cooling tower plume emergent at operating evaporating cooling systems. As opposed to recent publication, this text focuses on the possibilities of a simplified analytic description of the whole problem where this description shall - in the future - form the base of a calculation algorithms enabling to simulate the efficiency of systems reducing this cooling tower plume. The procedure is based on the application of basic formula for the calculation of the velocity and concentration fields in the area above the cooling tower. These calculation is then used to determine the form and the total volume of the plume. Although this approach does not offer more exact results, it can provide a basic understanding of the impact of individual quantities relating to this problem.
Simple Analytic Models of Gravitational Collapse
Energy Technology Data Exchange (ETDEWEB)
Adler, R.
2005-02-09
Most general relativity textbooks devote considerable space to the simplest example of a black hole containing a singularity, the Schwarzschild geometry. However only a few discuss the dynamical process of gravitational collapse, by which black holes and singularities form. We present here two types of analytic models for this process, which we believe are the simplest available; the first involves collapsing spherical shells of light, analyzed mainly in Eddington-Finkelstein coordinates; the second involves collapsing spheres filled with a perfect fluid, analyzed mainly in Painleve-Gullstrand coordinates. Our main goal is pedagogical simplicity and algebraic completeness, but we also present some results that we believe are new, such as the collapse of a light shell in Kruskal-Szekeres coordinates.
A Simple General Model of Evolutionary Dynamics
Thurner, Stefan
Evolution is a process in which some variations that emerge within a population (of, e.g., biological species or industrial goods) get selected, survive, and proliferate, whereas others vanish. Survival probability, proliferation, or production rates are associated with the "fitness" of a particular variation. We argue that the notion of fitness is an a posteriori concept in the sense that one can assign higher fitness to species or goods that survive but one can generally not derive or predict fitness per se. Whereas proliferation rates can be measured, fitness landscapes, that is, the inter-dependence of proliferation rates, cannot. For this reason we think that in a physical theory of evolution such notions should be avoided. Here we review a recent quantitative formulation of evolutionary dynamics that provides a framework for the co-evolution of species and their fitness landscapes (Thurner et al., 2010, Physica A 389, 747; Thurner et al., 2010, New J. Phys. 12, 075029; Klimek et al., 2009, Phys. Rev. E 82, 011901 (2010). The corresponding model leads to a generic evolutionary dynamics characterized by phases of relative stability in terms of diversity, followed by phases of massive restructuring. These dynamical modes can be interpreted as punctuated equilibria in biology, or Schumpeterian business cycles (Schumpeter, 1939, Business Cycles, McGraw-Hill, London) in economics. We show that phase transitions that separate phases of high and low diversity can be approximated surprisingly well by mean-field methods. We demonstrate that the mathematical framework is suited to understand systemic properties of evolutionary systems, such as their proneness to collapse, or their potential for diversification. The framework suggests that evolutionary processes are naturally linked to self-organized criticality and to properties of production matrices, such as their eigenvalue spectra. Even though the model is phrased in general terms it is also practical in the sense
Squeal noise in simple numerical brake models
Oberst, S.; Lai, J. C. S.
2015-09-01
Since the early 1920s, automotive disc brake squeal has caused warranty issues and customer dissatisfaction. Despite a good deal of progress achieved, predicting brake squeal propensity is as difficult as ever as not all mechanisms and interactions are known owing to their highly fugitive complex nature. In recent years, research has been focused on the prediction of unstable vibration modes by the complex eigenvalue analysis (CEA) for the mode-coupling type of instability. There has been very limited consideration given to the calculation of the acoustic radiation properties due to friction contact between a pad and a rotor. Recent analyses using a forced response analysis with harmonic contact pressure excitation indicates negative dissipated energy at some pad eigenfrequencies predicted to be stable by the CEA. A transient nonlinear time domain analysis with no external excitation indicates that squeal could develop at these eigenfrequencies. Here, the acoustic radiation characteristics of those pad modes are determined by analysing the acoustic power levels and radiation efficiencies of simplified brake models in the form of a pad rubbing on a plate or on a disc using the acoustic boundary element method based on velocities extracted from the forced response analysis. Results show that unstable pad modes trigger unstable disc vibrations resulting in instantaneous mode squeal similar to those observed experimentally. Changes in the radiation efficiency with pressure variations are smaller than those with friction coefficient variations and are caused by the phase difference of the velocities out-of-plane vibration between the pad and the disc.
Institute of Scientific and Technical Information of China (English)
BAI Yuan; CHEN Hai-yan; ZONG Gang-jun; JIANG Hai-bing; LI Wei-ping; WU Hong; ZHAO Xian-xian; QIN Yong-wen
2010-01-01
Background Valve replacement or repair Is recommended in patients with tricuspid regurgitation when deterioration of their clinical status occurs as a consequence of right ventricular dysfunction. Percutaneous valve replacement was developed in recent years. To investigate the feasibility, effectiveness and long-term results of percutaneous tricuspid valve replacement, an experimental model with tricuspid regurgitation is needed. We developed a simple and reproducible percutaneous approach for the creation of tricuspid regurgitation in sheep.Methods A specially designed grasping forceps were used to grasp chordae tendineae or the tricuspid valve leaflets through a catheter. Transcatheter creation of tricuspid regurgitation was performed on 7 healthy sheep. These sheep were followed up shortly after the procedure and at 6th month post-procedure with echocardiography. Additionally, all the sheep were sacrificed for anatomic evaluation at 6th month after the procedure.Results Creation of tricuspid regurgitation was successfully accomplished in all sheep. Necropsy confirmed that damage was done to the tricuspid valve apparatus in all animals (tearing of the anterior leaflet of the tricuspid valve in five animals and posterior leaflet of the tricuspid valve in two animals). At the six-month follow-up, there was no significant increase in the right ventricle dimension and ejection fraction measured by echocardiography. Autopsy examinations demonstrated the tearing of tricuspid valve leaflets.Conclusions The creation of an animal model of tricuspid regurgitation via a percutaneous approach using forceps to sever one or more tricuspid leaflets is feasible and will allow investigation of devices designed replace the tricuspid valve via a percutaneous approach. Despite significant tricuspid regurgitation, the hemodynamics did not change during the follow-up period in this model.
Simple neoclassical point model for transport and scaling in EBT
Energy Technology Data Exchange (ETDEWEB)
Hedrick, C.L.; Jaeger, E.F.; Spong, D.A.; Guest, G.E.; Krall, N.A.; McBride, J.B.; Stuart, G.W.
1977-04-01
A simple neoclassical point model is presented for the ELMO Bumpy Torus experiment. Solutions for steady state are derived. Comparison with experimental observations is made and reasonable agreement is obtained.
Simple model of photo acoustic system for greenhouse effect
Fukuhara, Akiko; Ogawa, Naohisa
2010-01-01
The simple theoretical basis for photo acoustic (PA) system for studying infrared absorption properties of greenhouse gases is constructed. The amplitude of sound observed in PA depends on the modulation frequency of light pulse. Its dependence can be explained by our simple model. According to this model, sound signal has higher harmonics. The theory and experiment are compared in third and fifth harmonics by spectrum analysis. The theory has the analogy with electric circuits. This analogy helps students for understanding the PA system.
Drift Intermittent Synchronization and Controllability in a Simple Model
Institute of Scientific and Technical Information of China (English)
XIE Bai-Song; YU Ming-Young
2005-01-01
A simple model of three coupled oscillators as an approximation of main modes behaviors in a spatial extended system is proposed. Multi-looping generalized synchronization and drift intermittent lag phase synchronization phenomena are found in this simple model. For a certain of parameters in which chaotic-like intermittent behavior exhibit the amplitudes and phases of three modes are controlled to be synchronized states via coupling them with an external periodic mode.
Combinatorial structures to modeling simple games and applications
Molinero, Xavier
2017-09-01
We connect three different topics: combinatorial structures, game theory and chemistry. In particular, we establish the bases to represent some simple games, defined as influence games, and molecules, defined from atoms, by using combinatorial structures. First, we characterize simple games as influence games using influence graphs. It let us to modeling simple games as combinatorial structures (from the viewpoint of structures or graphs). Second, we formally define molecules as combinations of atoms. It let us to modeling molecules as combinatorial structures (from the viewpoint of combinations). It is open to generate such combinatorial structures using some specific techniques as genetic algorithms, (meta-)heuristics algorithms and parallel programming, among others.
Identifiability of causal effect for a simple causal model
Institute of Scientific and Technical Information of China (English)
郑忠国; 张艳艳; 童行伟
2002-01-01
Counterfactual model is put forward to discuss the causal inference in the directed acyclic graph and its corresponding identifiability is thus studied with the ancillary information based on conditional independence. It is shown that the assumption of ignorability can be expanded to the assumption of replaceability,under which the causal efiects are identifiable.
Application of Simple CFD Models in Smoke Ventilation Design
DEFF Research Database (Denmark)
Brohus, Henrik; Nielsen, Peter Vilhelm; la Cour-Harbo, Hans
2004-01-01
The paper examines the possibilities of using simple CFD models in practical smoke ventilation design. The aim is to assess if it is possible with a reasonable accuracy to predict the behaviour of smoke transport in case of a fire. A CFD code mainly applicable for “ordinary” ventilation design...... is used for the examination. The CFD model is compared with benchmark tests and results from a special application fire simulation CFD code. Apart from benchmark tests two practical applications are examined in shape of modelling a fire in a theatre and a double façade, respectively. The simple CFD model...... uses a standard k-ε turbulence model. Simulations comprise both steady-state and dynamic approaches. Several boundary conditions are tested. Finally, the paper discusses the prospects of simple CFD models in smoke ventilation design including the inherent limitations....
An accurate and simple large signal model of HEMT
DEFF Research Database (Denmark)
Liu, Qing
1989-01-01
A large-signal model of discrete HEMTs (high-electron-mobility transistors) has been developed. It is simple and suitable for SPICE simulation of hybrid digital ICs. The model parameters are extracted by using computer programs and data provided by the manufacturer. Based on this model, a hybrid...
Simple Model of Shape Evolution of Desiccated Colloidal Sessile Drop
Tarasevich, Yu. Yu.; Vodolazskaya, I. V.; Isakova, O. P.
2011-01-01
We propose simple model of colloidal sessile drop desiccation. The model describes correctly both evolution of the phase boundary between sol and gel inside such a drop and the final shape of the dried film (deposit). The model is based on mass conservation and natural assumption that deposit (gel phase) prevents flows and evaporation.
Diagnosing declining grassland wader populations using simple matrix models
Klok, Chris; Roodbergen, Maja; Hemerik, Lia
2009-01-01
Many populations of wader species have shown a strong decline in number in Western-Europe in recent years. The use of simple population models such as matrix models can contribute to conserve these populations by identifying the most profitable management measures. Parameterization of such models is
A simple capacitor model for radio emission associated with earthquakes
Institute of Scientific and Technical Information of China (English)
Ares de Parga Gonzalo; Ram(I)rez-Rojas Alejandro
2004-01-01
In this brief report we propose a simple model based on the properties of an electric capacitor under short-circuit conditions as a possible mechanism of radio emissions associated with earthquakes. This model can be considered as complementary to other models concerning the same problem.
Replaceable Substructures for Efficient Part-Based Modeling
Liu, Han
2015-05-01
A popular mode of shape synthesis involves mixing and matching parts from different objects to form a coherent whole. The key challenge is to efficiently synthesize shape variations that are plausible, both locally and globally. A major obstacle is to assemble the objects with local consistency, i.e., all the connections between parts are valid with no dangling open connections. The combinatorial complexity of this problem limits existing methods in geometric and/or topological variations of the synthesized models. In this work, we introduce replaceable substructures as arrangements of parts that can be interchanged while ensuring boundary consistency. The consistency information is extracted from part labels and connections in the original source models. We present a polynomial time algorithm that discovers such substructures by working on a dual of the original shape graph that encodes inter-part connectivity. We demonstrate the algorithm on a range of test examples producing plausible shape variations, both from a geometric and from a topological viewpoint. © 2015 The Author(s) Computer Graphics Forum © 2015 The Eurographics Association and John Wiley & Sons Ltd. Published by John Wiley & Sons Ltd.
A new model to predict acute kidney injury requiring renal replacement therapy after cardiac surgery
Pannu, Neesh; Graham, Michelle; Klarenbach, Scott; Meyer, Steven; Kieser, Teresa; Hemmelgarn, Brenda; Ye, Feng; James, Matthew
2016-01-01
and validated a practical and accurate risk prediction model for acute kidney injury requiring renal replacement therapy after cardiac surgery based on routinely available preoperative clinical and laboratory data. The prediction model can be easily applied at the bedside and provides a simple and interpretable estimation of risk. PMID:27297813
Emulation of MIROC5 with a simple climate model
Ishizaki, Yasuhiro; Emori, Seita; Shiogama, Hideo; Takahashi, Kiyoshi; Yokohata, Tokuta; Yoshimori, Masakazu
2014-05-01
We developed a simple climate model based on MAGICC6, and investigated the ability of the simple climate model to emulate global mean surface air temperature (SAT) changes of an atmosphere-ocean general circulation model (MIROC5) in the twenty-first century in representative concentration pathways (RCPs). Some previous research indicated that climate sensitivity, ocean vertical diffusion and forcing of anthropogenic aerosols (direct and indirect effects of sulfate aerosol, black carbon and organic carbon) are important factors to emulate global mean SAT changes of atmosphere-ocean general circulation models CMIP3. We therefore estimate these important parameters in the simple climate model using a Metropolis-Hastings Markov chain Monte Carlo (MCMC) approach. The estimated values of the important parameters by the MCMC are physically valid, and our simple climate model can successfully emulate global mean SAT changes of MIROC5 in RCPs with the estimated parameters by the MCMC approach. In addition, we estimated the relative contributions f each important parameter in sensitivity experiments, in which we change the value of an important parameter from the estimated one by the MCMC to the default value of MAGICC6. As a result, we found that the estimation of climate sensitivity is the most important factor for the emulation of the AOGCM, and the stimation of ocean vertical diffusion is also important factor. Although the estimations of the anthropogenic aerosols forcing are very important for the emulation of the AOGCM in the twenty century, the influence of them on the emulation of the AOGCM in the twenty first century is very small. This is because emissions of anthropogenic aerosols are projected to decrease in the twenty first century, and relative contributions of the forcing of anthropogenic aerosols also decrease. Carbon cycle models are not incorporated into our simple climate model yet. A sophisticated carbon cycle model is required to be incorporated into
Enzyme replacement therapy in a mouse model of aspartylglycosaminuria.
Dunder, U; Kaartinen, V; Valtonen, P; Väänänen, E; Kosma, V M; Heisterkamp, N; Groffen, J; Mononen, I
2000-02-01
Aspartylglycosaminuria (AGU), the most common lysosomal disorder of glycoprotein degradation, is caused by deficient activity of glycosylasparaginase (AGA). AGA-deficient mice share most of the clinical, biochemical and histopathologic characteristics of human AGU disease. In the current study, recombinant human AGA administered i.v. to adult AGU mice disappeared from the systemic circulation of the animals in two phases predominantly into non-neuronal tissues, which were rapidly cleared from storage compound aspartylglucosamine. Even a single AGA injection reduced the amount of aspartylglucosamine in the liver and spleen of AGU mice by 90% and 80%, respectively. Quantitative biochemical analyses along with histological and immunohistochemical studies demonstrated that the pathophysiologic characteristics of AGU were effectively corrected in non-neuronal tissues of AGU mice during 2 wk of AGA therapy. At the same time, AGA activity increased to 10% of that in normal brain tissue and the accumulation of aspartylglucosamine was reduced by 20% in total brain of the treated animals. Immunohistochemical studies suggested that the corrective enzyme was widely distributed within the brain tissue. These findings suggest that AGU may be correctable by enzyme therapy.-Dunder, U., Kaartinen, V., Valtonen, P., Väänänen, E., Kosma, V.-M., Heisterkamp, N., Groffen, J., Mononen, I. Enzyme replacement therapy in a mouse model of aspartylglycosaminuria.
Application of Simple CFD Models in Smoke Ventilation Design
DEFF Research Database (Denmark)
Brohus, Henrik; Nielsen, Peter Vilhelm; la Cour-Harbo, Hans
2004-01-01
The paper examines the possibilities of using simple CFD models in practical smoke ventilation design. The aim is to assess if it is possible with a reasonable accuracy to predict the behaviour of smoke transport in case of a fire. A CFD code mainly applicable for “ordinary” ventilation design...... uses a standard k-ε turbulence model. Simulations comprise both steady-state and dynamic approaches. Several boundary conditions are tested. Finally, the paper discusses the prospects of simple CFD models in smoke ventilation design including the inherent limitations....
SIMPLE MODEL FOR THE INPUT IMPEDANCE OF RECTANGULAR MICROSTRIP ANTENNA
Directory of Open Access Journals (Sweden)
Celal YILDIZ
1998-03-01
Full Text Available A very simple model for the input impedance of a coax-fed rectangular microstrip patch antenna is presented. It is based on the cavity model and the equivalent resonant circuits. The theoretical input impedance results obtained from this model are in good agreement with the experimental results available in the literature. This model is well suited for computer-aided design (CAD.
A simple spatiotemporal chaotic Lotka-Volterra model
Energy Technology Data Exchange (ETDEWEB)
Sprott, J.C. [Department of Physics, University of Wisconsin, 1150 University Avenue, Madison, WI 53706 (United States)] e-mail: sprott@physics.wisc.edu; Wildenberg, J.C. [Department of Physics, University of Wisconsin, 1150 University Avenue, Madison, WI 53706 (United States)] e-mail: jcwildenberg@wisc.edu; Azizi, Yousef [Institute for Advanced Studies in Basic Sciences, Zanjan (Iran, Islamic Republic of)] e-mail: joseph_azizi@yahoo.com
2005-11-01
A mathematically simple example of a high-dimensional (many-species) Lotka-Volterra model that exhibits spatiotemporal chaos in one spatial dimension is described. The model consists of a closed ring of identical agents, each competing for fixed finite resources with two of its four nearest neighbors. The model is prototypical of more complicated models in its quasiperiodic route to chaos (including attracting 3-tori), bifurcations, spontaneous symmetry breaking, and spatial pattern formation.
A Simple Model of Hox Genes: Bone Morphology Demonstration
Shmaefsky, Brian
2008-01-01
Visual demonstrations of abstract scientific concepts are effective strategies for enhancing content retention (Shmaefsky 2004). The concepts associated with gene regulation of growth and development are particularly complex and are well suited for teaching with visual models. This demonstration provides a simple and accurate model of Hox gene…
A Simple Mechanical Model for the Isotropic Harmonic Oscillator
Nita, Gelu M.
2010-01-01
A constrained elastic pendulum is proposed as a simple mechanical model for the isotropic harmonic oscillator. The conceptual and mathematical simplicity of this model recommends it as an effective pedagogical tool in teaching basic physics concepts at advanced high school and introductory undergraduate course levels. (Contains 2 figures.)
CONSISTENCY OF LS ESTIMATOR IN SIMPLE LINEAR EV REGRESSION MODELS
Institute of Scientific and Technical Information of China (English)
Liu Jixue; Chen Xiru
2005-01-01
Consistency of LS estimate of simple linear EV model is studied. It is shown that under some common assumptions of the model, both weak and strong consistency of the estimate are equivalent but it is not so for quadratic-mean consistency.
Least squares estimation in a simple random coefficient autoregressive model
DEFF Research Database (Denmark)
Johansen, Søren; Lange, Theis
2013-01-01
The question we discuss is whether a simple random coefficient autoregressive model with infinite variance can create the long swings, or persistence, which are observed in many macroeconomic variables. The model is defined by yt=stρyt−1+εt,t=1,…,n, where st is an i.i.d. binary variable with p=P(...
Least squares estimation in a simple random coefficient autoregressive model
DEFF Research Database (Denmark)
Johansen, Søren; Lange, Theis
2013-01-01
The question we discuss is whether a simple random coefficient autoregressive model with infinite variance can create the long swings, or persistence, which are observed in many macroeconomic variables. The model is defined by yt=stρyt−1+εt,t=1,…,n, where st is an i.i.d. binary variable with p=P(...
Simple Models Create Steep Learning Curves in Academic Design Studio
DEFF Research Database (Denmark)
Hansen, Peter Lundsgaard; Dam, Torben; Le Goffic, Virginie Corinne
2014-01-01
This paper presents an easily adaptable, very learning-efficient and solution-oriented design studio method: ‘the simple model method’. On a practical level it solves well known problems that occur when teaching design studios. On a theoretical level it suggests a ‘third way’ of bridging design......, their supervisors and other actors. The simple model is a non-verbal agent. However, due to its simplicity it enables verbalization supporting a solution-focused design studio teaching strategy. The simple model method is presented through a specific design studio course undertaken at the University of Copenhagen...... theory positions normally regarded as mutually incompatible. The method is the result of years of ‘trial and error’ design studio teaching at the University of Copenhagen, triangulated with academic design theory research. Research based design studio teaching poses a fundamental pedagogical challenge...
A simple model for strong ground motions and response spectra
Safak, Erdal; Mueller, Charles; Boatwright, John
1988-01-01
A simple model for the description of strong ground motions is introduced. The model shows that response spectra can be estimated by using only four parameters of the ground motion, the RMS acceleration, effective duration and two corner frequencies that characterize the effective frequency band of the motion. The model is windowed band-limited white noise, and is developed by studying the properties of two functions, cumulative squared acceleration in the time domain, and cumulative squared amplitude spectrum in the frequency domain. Applying the methods of random vibration theory, the model leads to a simple analytical expression for the response spectra. The accuracy of the model is checked by using the ground motion recordings from the aftershock sequences of two different earthquakes and simulated accelerograms. The results show that the model gives a satisfactory estimate of the response spectra.
General autocatalytic theory and simple model of financial markets
Thuy Anh, Chu; Lan, Nguyen Tri; Viet, Nguyen Ai
2015-06-01
The concept of autocatalytic theory has become a powerful tool in understanding evolutionary processes in complex systems. A generalization of autocatalytic theory was assumed by considering that the initial element now is being some distribution instead of a constant value as in traditional theory. This initial condition leads to that the final element might have some distribution too. A simple physics model for financial markets is proposed, using this general autocatalytic theory. Some general behaviours of evolution process and risk moment of a financial market also are investigated in framework of this simple model.
Evolution of species from Darwin theory: A simple model
Moret, M. A.; Pereira, H. B. B.; Monteiro, S. L.; Galeão, A. C.
2012-04-01
Evolution of species is a complex phenomenon. Some theoretical models take into account evolution of species, like the Bak-Sneppen model that obtain punctuated equilibrium from self-organized criticality and the Penna model for biological aging that consists in a bit-string model subjected to aging, reproduction and death. In this work we propose a simple model to study different scenarios used to simulate the evolution of species. This model is based on Darwin's ideas of evolution. The present findings show that punctuated equilibria and stasis seem to be obtained directly from the mutation, selection of parents and the genetic crossover, and are very close to the fossil data analysis.
Ramirez, Pedro T.; Pareja, Rene; Rendón, Gabriel J.; Millan, Carlos; Frumovitz, Michael; Schmeler, Kathleen M.
2014-01-01
The standard treatment for women with early-stage cervical cancer (IA2-IB1) remains radical hysterectomy with pelvic lymphadenectomy. In select patients interested in future fertility, the option of radical trachelectomy with pelvic lymphadenectomy is also considered a viable option. The possibility of less radical surgery may be appropriate not only for patients desiring to preserve fertility but also for all patients with low-risk early-stage cervical cancer. Recently, a number of studies have explored less radical surgical options for early-stage cervical cancer, including simple hysterectomy, simple trachelectomy, and cervical conization with or without sentinel lymph node biopsy and pelvic lymph node dissection. Such options may be available for patients with low-risk early-stage cervical cancer. Criteria that define this low-risk group include: squamous carcinoma, adenocarcinoma, or adenosquamous carcinoma, tumor size <2 cm, stromal invasion <10mm, and no lymph-vascular space invasion. In this report, we provide a review of the existing literature on the conservative management of cervical cancer and describe ongoing multi-institutional trials evaluating the role of conservative surgery in selected patients with early-stage cervical cancer. PMID:24041877
Perching Dynamics and Development of a Simple Model
Puopolo, Michael; Jacob, Jamey; Reynolds, Ryan
2013-11-01
Aerodynamicists with a vision for bird-like aircraft have been forced to develop new ways of modeling extremely agile flight systems, and in recent years there has been a growing variety of creative approaches that incorporate computer methods, empirical data, and unsteady flow theory. However, there remains a lack of simple and easily transferable models that can be used to predict and control motion of a fixed-wing, perching aircraft in the low Reynolds number flow regime. The authors have developed a simple dynamic model for a perching vehicle with a common fixed wing configuration that uses only input of the system design parameters, in addition to other relevant widely available information, and does not rely on wind tunnel measurements, CFD analysis or other rigorous forms of system identification. The resulting model is presented with a comparison of model simulations to flight data from a perching UAV.
Simple model for low-frequency guitar function
DEFF Research Database (Denmark)
Christensen, Ove; Vistisen, Bo B.
1980-01-01
The frequency response of sound pressure and top plate mobility is studied around the two first resonances of the guitar. These resonances are shown to result from a coupling between the fundamental top plate mode and the Helmholtz resonance of the cavity. A simple model is proposed for low...
Specific heat of the simple-cubic Ising model
Feng, X.; Blöte, H.W.J.
2010-01-01
We provide an expression quantitatively describing the specific heat of the Ising model on the simple-cubic lattice in the critical region. This expression is based on finite-size scaling of numerical results obtained by means of a Monte Carlo method. It agrees satisfactorily with series expansions
A simple statistical signal loss model for deep underground garage
DEFF Research Database (Denmark)
Nguyen, Huan Cong; Gimenez, Lucas Chavarria; Kovacs, Istvan
2016-01-01
In this paper we address the channel modeling aspects for a deep-indoor scenario with extreme coverage conditions in terms of signal losses, namely underground garage areas. We provide an in-depth analysis in terms of path loss (gain) and large scale signal shadowing, and a propose simple...
Thermodynamics of a Simple Three-Dimensional DNA Hairpin Model
Kremer, Kellan; Boggess, Erin; Mask, Walker; Saucedo, Tony; Hansen, JJ; Appelgate, Ian; Jurgensen, Taylor; Santos, Aaron
2016-01-01
We characterize the equation of state for a simple three-dimensional DNA hairpin model using a Metropolis Monte Carlo algorithm. This algorithm was run at constant temperature and fixed separation between the terminal ends of the strand. From the equation of state, we compute the compressibility, thermal expansion coefficient, and specific heat along with adiabatic path.
Natural products--a simple model to explain chemical diversity.
Firn, Richard D; Jones, Clive G
2003-08-01
A simple evolutionary model is presented which explains why organisms produce so many natural products, why so many have low biological activity, why enzymes involved in natural product synthesis have the properties they do and why natural product metabolism is shaped as it is.
Simple model with damping of the mode-coupling instability
Energy Technology Data Exchange (ETDEWEB)
Pestrikov, D.V. [AN SSSR, Novosibirsk (Russian Federation). Inst. Yadernoj Fiziki
1996-08-01
In this paper we use a simple model to study the suppression of the transverse mode-coupling instability. Two possibilities are considered. One is due to the damping of particular synchrobetatron modes, and another - due to Landau damping, caused by the nonlinearity of betatron oscillations. (author)
40 CFR 80.42 - Simple emissions model.
2010-07-01
...) REGULATION OF FUELS AND FUEL ADDITIVES Reformulated Gasoline § 80.42 Simple emissions model. (a) VOC... (as measured under § 80.46) ETOH = Oxygen content of the fuel in question in the form of ethanol, in... weights than ethanol shall be evaluated as if it were in the form of ethanol. Oxygen in the form of...
Simple model on collisionless thin-shell instability growth
Doria, Domenico; Dieckmann, Mark E
2016-01-01
The manuscript discusses a simple model on the Thin Shell Instability (TSI) growth phenomenon at early stage, by only imposing the fulfillment of conservation laws; and in particular just applying the laws of mass and linear momentum conservation, without taking into account the energy partitioning inside the thin shell.
Modelling, Construction, and Testing of a Simple HTS Machine Demonstrator
DEFF Research Database (Denmark)
Jensen, Bogi Bech; Abrahamsen, Asger Bech
2011-01-01
This paper describes the construction, modeling and experimental testing of a high temperature superconducting (HTS) machine prototype employing second generation (2G) coated conductors in the field winding. The prototype is constructed in a simple way, with the purpose of having an inexpensive w...
Simple Regge pole model for Compton scattering of protons
Energy Technology Data Exchange (ETDEWEB)
Saleem, M.; Fazal-e-Aleem
1978-08-01
It is shown that by a phenomenological choice of the residue functions, the differential cross section for ..gamma.. p ..-->.. ..gamma.. p, including the very recent measurements up to /sup -/t=4.3 (GeV/c)/sup 2/, can be explained at all measured energies greater than 2 GeV with simple Regge pole model.
A Simple Cloud Reflectance Model for Ship Tracks in Clouds
1991-11-01
A Simple Cloud Reflectance Model 01 for Ship Tracks in Clouds I OTIOSt 9L1, FIF MAR 16 1992J R. A. Siquig Forecast Guidance and Naval Systems...because of increased absorption. Note that this is based on the results for four wavelengths. Because of the undulatory nature of the imaginary part of
A Simple Double-Source Model for Interference of Capillaries
Hou, Zhibo; Zhao, Xiaohong; Xiao, Jinghua
2012-01-01
A simple but physically intuitive double-source model is proposed to explain the interferogram of a laser-capillary system, where two effective virtual sources are used to describe the rays reflected by and transmitted through the capillary. The locations of the two virtual sources are functions of the observing positions on the target screen. An…
Optimizing model. 1. Insemination, replacement, seasonal production and cash flow.
Delorenzo, M.A.; Spreen, T.H.; Bryan, G.R.; Beede, D.K.; Arendonk, van J.A.M.
1992-01-01
Dynamic programming to solve the Markov decision process problem of optimal insemination and replacement decisions was adapted to address large dairy herd management decision problems in the US. Expected net present values of cow states (151,200) were used to determine the optimal policy. States
Modeling Outcome of Patients on Renal Replacement Therapy
Y.S. Liem (Ylian Serina)
2008-01-01
textabstractThe incidence of end-stage renal disease is increasing and therefore, the number of patients requiring renal replacement therapy (RRT), renal dialysis or renal transplantation (RTx), has been rising. The various forms of RRT are associated with differences in survival and quality of life
Optimizing model. 1. Insemination, replacement, seasonal production and cash flow.
Delorenzo, M.A.; Spreen, T.H.; Bryan, G.R.; Beede, D.K.; Arendonk, van J.A.M.
1992-01-01
Dynamic programming to solve the Markov decision process problem of optimal insemination and replacement decisions was adapted to address large dairy herd management decision problems in the US. Expected net present values of cow states (151,200) were used to determine the optimal policy. States wer
Beyond harmonic sounds in a simple model for birdsong production
Amador, Ana; Mindlin, Gabriel B.
2008-12-01
In this work we present an analysis of the dynamics displayed by a simple bidimensional model of labial oscillations during birdsong production. We show that the same model capable of generating tonal sounds can present, for a wide range of parameters, solutions which are spectrally rich. The role of physiologically sensible parameters is discussed in each oscillatory regime, allowing us to interpret previously reported data.
Simple Model for the Mechanics of Spider Webs
Aoyanagi, Yuko; Okumura, Ko
2010-01-01
We propose a simple model to describe spider orb webs. The model has a formal analytical solution when no thread elements are broken. When the radial threads are sufficiently strong compared to the spiral threads, the model is free of stress concentrations even when a few spiral threads are broken. This is in contrast with what occurs in common elastic materials. According to our model, spiders can increase the number of spiral threads to make a dense web (to catch small insects) or adjust the number of radial threads (to adapt to environmental conditions or reduce the cost of making the web) without reducing the damage tolerance of the web.
Simple Predictive Models for Saturated Hydraulic Conductivity of Technosands
DEFF Research Database (Denmark)
Arthur, Emmanuel; Razzaghi, Fatemeh; Møldrup, Per
2012-01-01
Accurate estimation of saturated hydraulic conductivity (Ks) of technosands (gravel-free, coarse sands with negligible organic matter content) is important for irrigation and drainage management of athletic fields and golf courses. In this study, we developed two simple models for predicting Ks......-connectivity parameter (m) obtained for pure coarse sand after fitting to measured Ks data was 1.68 for both models and in good agreement with m values obtained from recent solute and gas diffusion studies. Both the modified K-C and R-C models are easy to use and require limited parameter input, and both models gave...
Jalvingh, A.W.; Dijkhuizen, A.A.; Arendonk, van J.A.M.
1992-01-01
A dynamic probabilistic model has been designed for the personal computer to determine the technical and economic consequences of various biological variables and management strategies concerning reproduction and replacement in swine. In it, the Markov chain approach is used to simulate herd
A simple one-dimensional model for urban canopy flows
Cheng, Wai Chi; Porté-Agel, Fernando
2016-04-01
In urban canopy parameterizations, an urban canopy is usually modelled as a drag force on the flow, and the turbulent shear stress is parametrized by various methods. One of the most common methods to parametrize the turbulent shear stress in urban canopies is to use a mixing length (lm) model. Different mixing length models have been proposed in the literature, and recent direct numerical simulation and large-eddy simulation (LES) studies have shown that these models underpredict the value of lm in urban canopies. The high value of lm in the canopies is in fact related to the turbulence generated at the high-shear region near the top of the canopy, which is similar to that in a plane mixing layer. By considering this effect, a new simple mixing length model is proposed based on physical arguments. The results of the new lm model and the previous models are compared with the LES results of flows within and above uniform cube arrays of different densities. The comparison clearly demonstrates the better performance of the new model in predicting the wind profiles especially near the top of the urban canopies. For the drag coefficient (Cd) representing an urban canopy, previous studies found that its value depends on the building density. Here, a simple model for Cd is suggested by considering the spatial distribution of mean wind within canopies of different building densities. The model prediction is found to agree reasonably well with the LES results.
A simple oblique dip model for geomagnetic micropulsations
Directory of Open Access Journals (Sweden)
J. A. Lawrie
Full Text Available It is pointed out that simple models adopted so far have tended to neglect the obliquity of the magnetic field lines entering the Earth's surface. A simple alternative model is presented, in which the ambient field lines are straight, but enter wedge shaped boundaries at half a right-angle. The model is illustrated by assuming an axially symmetric, compressional, impulse type disturbance at the outer boundary, all other boundaries being assumed to be perfectly conducting. The numerical method used is checked from the instant the excitation ceases, by an analytical method. The first harmonic along field lines is found to be of noticeable size, but appears to be mainly due to coupling with the fundamental, and with the first harmonic across field lines.
Key words. Magnetospheric physics (MHD waves and instabilities.
A simple method for modeling dye-sensitized solar cells
Energy Technology Data Exchange (ETDEWEB)
Son, Min-Kyu [Department of Electrical Engineering, Pusan National University, San 30, Jangjeon-Dong, Geumjeong-Gu, Busan, 609-735 (Korea, Republic of); Seo, Hyunwoong [Graduate School of Information Science and Electrical Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, 819-0395 (Japan); Center of Plasma Nano-interface Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, 819-0395 (Japan); Lee, Kyoung-Jun; Kim, Soo-Kyoung; Kim, Byung-Man; Park, Songyi; Prabakar, Kandasamy [Department of Electrical Engineering, Pusan National University, San 30, Jangjeon-Dong, Geumjeong-Gu, Busan, 609-735 (Korea, Republic of); Kim, Hee-Je, E-mail: heeje@pusan.ac.kr [Department of Electrical Engineering, Pusan National University, San 30, Jangjeon-Dong, Geumjeong-Gu, Busan, 609-735 (Korea, Republic of)
2014-03-03
Dye-sensitized solar cells (DSCs) are photoelectrochemical photovoltaics based on complicated electrochemical reactions. The modeling and simulation of DSCs are powerful tools for evaluating the performance of DSCs according to a range of factors. Many theoretical methods are used to simulate DSCs. On the other hand, these methods are quite complicated because they are based on a difficult mathematical formula. Therefore, this paper suggests a simple and accurate method for the modeling and simulation of DSCs without complications. The suggested simulation method is based on extracting the coefficient from representative cells and a simple interpolation method. This simulation method was implemented using the power electronic simulation program and C-programming language. The performance of DSCs according to the TiO{sub 2} thickness was simulated, and the simulated results were compared with the experimental data to confirm the accuracy of this simulation method. The suggested modeling strategy derived the accurate current–voltage characteristics of the DSCs according to the TiO{sub 2} thickness with good agreement between the simulation and the experimental results. - Highlights: • Simple modeling and simulation method for dye-sensitized solar cells (DSCs). • Modeling done using a power electronic simulation program and C-programming language. • The performance of DSC according to the TiO{sub 2} thickness was simulated. • Simulation and experimental performance of DSCs were compared. • This method is suitable for accurate simulation of DSCs.
Dang, Cuong Cao; Le, Vinh Sy; Gascuel, Olivier; Hazes, Bart; Le, Quang Si
2014-10-24
Amino acid replacement rate matrices are a crucial component of many protein analysis systems such as sequence similarity search, sequence alignment, and phylogenetic inference. Ideally, the rate matrix reflects the mutational behavior of the actual data under study; however, estimating amino acid replacement rate matrices requires large protein alignments and is computationally expensive and complex. As a compromise, sub-optimal pre-calculated generic matrices are typically used for protein-based phylogeny. Sequence availability has now grown to a point where problem-specific rate matrices can often be calculated if the computational cost can be controlled. The most time consuming step in estimating rate matrices by maximum likelihood is building maximum likelihood phylogenetic trees from protein alignments. We propose a new procedure, called FastMG, to overcome this obstacle. The key innovation is the alignment-splitting algorithm that splits alignments with many sequences into non-overlapping sub-alignments prior to estimating amino acid replacement rates. Experiments with different large data sets showed that the FastMG procedure was an order of magnitude faster than without splitting. Importantly, there was no apparent loss in matrix quality if an appropriate splitting procedure is used. FastMG is a simple, fast and accurate procedure to estimate amino acid replacement rate matrices from large data sets. It enables researchers to study the evolutionary relationships for specific groups of proteins or taxa with optimized, data-specific amino acid replacement rate matrices. The programs, data sets, and the new mammalian mitochondrial protein rate matrix are available at http://fastmg.codeplex.com.
A simple model of scientific progress - with examples
Scorzato, Luigi
2016-01-01
One of the main goals of scientific research is to provide a description of the empirical data which is as accurate and comprehensive as possible, while relying on as few and simple assumptions as possible. In this paper, I propose a definition of the notion of "few and simple assumptions" that is not affected by known problems. This leads to the introduction of a simple model of scientific progress that is based only on empirical accuracy and conciseness. An essential point in this task is the understanding of the role played by "measurability" in the formulation of a scientific theory. This is the key to prevent artificially concise formulations. The model is confronted here with many possible objections and with challenging cases of real progress. Although I cannot exclude that the model might have some limitations, it includes all the cases of genuine progress examined here, and no spurious one. In this model, I stress the role of the "state of the art", which is the collection of all the theories that ar...
Thermal margin comparison between DAM and simple model
Energy Technology Data Exchange (ETDEWEB)
Cha, Jeonghun; Yook, Daesik [Korea Institute of Nuclear Safety, Daejeon (Korea, Republic of)
2017-01-15
The nuclear industry in Korea, has considered using a detail analysis model (DAM), which described each rod, to get more thermal margin with the design a dry storage facility for nuclear spent fuel (NSF). A DAM is proposed and a thermal analysis to determine the cladding integrity is performed using test conditions with a homogenized NSF assembly analysis model(Simple model). The result show that according to USA safety criteria, temperature of canister surface has to keep below 500 K in normal condition and 630 K in excess condition. A commercial Computational Fluid Dynamics (CFD) called ANSYS Fluent version 14.5 was used.
Simple model of capillary condensation in cylindrical pores
Szybisz, Leszek; Urrutia, Ignacio
2002-11-01
A simple model based on an approximation of the dropletlike model is formulated for studying adsorption of fluids into cylindrical pores. This model yields a nearly universal description of capillary condensation transitions for noble gases confined by alkali metals. The system's thermodynamical behavior is predicted from the values of two dimensionless parameters: D* (the reduced asymptotic strength of the fluid-adsorber interaction, a function of temperature) and R* (the reduced radius of the pore). The phenomenon of hysteresis inherently related to capillary condensation is discussed. The connection to a previously proposed universality for cylindrical pores is also established.
Complex Dynamics of Discrete SEIS Models with Simple Demography
Directory of Open Access Journals (Sweden)
Hui Cao
2011-01-01
Full Text Available We investigate bifurcations and dynamical behaviors of discrete SEIS models with exogenous reinfections and a variety of treatment strategies. Bifurcations identified from the models include period doubling, backward, forward-backward, and multiple backward bifurcations. Multiple attractors, such as bistability and tristability, are observed. We also estimate the ultimate boundary of the infected regardless of initial status. Our rigorously mathematical analysis together with numerical simulations show that epidemiological factors alone can generate complex dynamics, though demographic factors only support simple equilibrium dynamics. Our model analysis supports and urges to treat a fixed percentage of exposed individuals.
Note: A simple model for thermal management in solenoids.
McIntosh, E M; Ellis, J
2013-11-01
We describe a model of the dynamical temperature evolution in a solenoid winding. A simple finite element analysis is calibrated by accurately measuring the thermally induced resistance change of the solenoid, thus obviating the need for accurate knowledge of the mean thermal conductivity of the windings. The model predicts quasi thermal runaway for relatively modest current increases from the normal operating conditions. We demonstrate the application of this model to determine the maximum current that can be safely applied to solenoids used for helium spin-echo measurements.
Linking Simple Economic Theory Models and the Cointegrated Vector AutoRegressive Model
DEFF Research Database (Denmark)
Møller, Niels Framroze
This paper attempts to clarify the connection between simple economic theory models and the approach of the Cointegrated Vector-Auto-Regressive model (CVAR). By considering (stylized) examples of simple static equilibrium models, it is illustrated in detail, how the theoretical model and its...
Denotational Semantics of a Simple Model of Eiffel
Institute of Scientific and Technical Information of China (English)
瞿裕忠; 王志坚; 等
1995-01-01
A simple abstract model of Eiffel is introduced,and its denotational semantics is defined using VDM style.A static analysis approach is presented to treat multiple inheritance and renaming mechanism.Within the framework of denotational semantics introduced in this paper,the key features of Eiffel,such as identification,classification,multiple inheritance,polymorphism and dynamic binding,can be adequately characterized.
Magnetic reversals in a simple model of magnetohydrodynamics.
Benzi, Roberto; Pinton, Jean-François
2010-07-09
We study a simple magnetohydrodynamical approach in which hydrodynamics and MHD turbulence are coupled in a shell model, with given dynamo constraints in the large scales. We consider the case of a low Prandtl number fluid for which the inertial range of the velocity field is much wider than that of the magnetic field. Random reversals of the magnetic field are observed and it shown that the magnetic field has a nontrivial evolution--linked to the nature of the hydrodynamics turbulence.
A Simple Model for Oxygen Conduction in Some Perovskite Compounds
Totsuji, Chieko
1996-01-01
A simple model for oxygen ion conduction in perovskite compounds is proposed. The potential for an oxygen ion is calculated as the sum of the long range Coulomb potential and short range repulsive potential in a cubic lattice. The activation energy is estimated as the difference in the values of potential at the barrier and at the stable site. When appropriate conditions are satisfied, the activation energy has a minimum as a function of lattice constant in accordance with recent experiments.
Electromagnetic Radiation and Motion of Dust Particle A Simple Model
Klacka, J
2000-01-01
A simple model for motion of dust particle (meteoroid) under the action of (solar) electromagnetic radiation is presented. The particle of the form of plane mirror is taken into account and exact analytical results are presented. As for long-term orbital evolution, particle may spiral outwards the central body (Sun); initial conditions are important. As a consequence, motion of real dust particles may differ from that generally considered.
Towards a Simple Constitutive Model for Bread Dough
Tanner, Roger I.
2008-07-01
Wheat flour dough is an example of a soft solid material consisting of a gluten (rubbery) network with starch particles as a filler. The volume fraction of the starch filler is high-typically 60%. A computer-friendly constitutive model has been lacking for this type of material and here we report on progress towards finding such a model. The model must describe the response to small strains, simple shearing starting from rest, simple elongation, biaxial straining, recoil and various other transient flows. A viscoelastic Lodge-type model involving a damage function. which depends on strain from an initial reference state fits the given data well, and it is also able to predict the thickness at exit from dough sheeting, which has been a long-standing unsolved puzzle. The model also shows an apparent rate-dependent yield stress, although no explicit yield stress is built into the model. This behaviour agrees with the early (1934) observations of Schofield and Scott Blair on dough recoil after unloading.
Climate stability and sensitivity in some simple conceptual models
Energy Technology Data Exchange (ETDEWEB)
Bates, J. Ray [University College Dublin, Meteorology and Climate Centre, School of Mathematical Sciences, Dublin (Ireland)
2012-02-15
A theoretical investigation of climate stability and sensitivity is carried out using three simple linearized models based on the top-of-the-atmosphere energy budget. The simplest is the zero-dimensional model (ZDM) commonly used as a conceptual basis for climate sensitivity and feedback studies. The others are two-zone models with tropics and extratropics of equal area; in the first of these (Model A), the dynamical heat transport (DHT) between the zones is implicit, in the second (Model B) it is explicitly parameterized. It is found that the stability and sensitivity properties of the ZDM and Model A are very similar, both depending only on the global-mean radiative response coefficient and the global-mean forcing. The corresponding properties of Model B are more complex, depending asymmetrically on the separate tropical and extratropical values of these quantities, as well as on the DHT coefficient. Adopting Model B as a benchmark, conditions are found under which the validity of the ZDM and Model A as climate sensitivity models holds. It is shown that parameter ranges of physical interest exist for which such validity may not hold. The 2 x CO{sub 2} sensitivities of the simple models are studied and compared. Possible implications of the results for sensitivities derived from GCMs and palaeoclimate data are suggested. Sensitivities for more general scenarios that include negative forcing in the tropics (due to aerosols, inadvertent or geoengineered) are also studied. Some unexpected outcomes are found in this case. These include the possibility of a negative global-mean temperature response to a positive global-mean forcing, and vice versa. (orig.)
Predicting human walking gaits with a simple planar model.
Martin, Anne E; Schmiedeler, James P
2014-04-11
Models of human walking with moderate complexity have the potential to accurately capture both joint kinematics and whole body energetics, thereby offering more simultaneous information than very simple models and less computational cost than very complex models. This work examines four- and six-link planar biped models with knees and rigid circular feet. The two differ in that the six-link model includes ankle joints. Stable periodic walking gaits are generated for both models using a hybrid zero dynamics-based control approach. To establish a baseline of how well the models can approximate normal human walking, gaits were optimized to match experimental human walking data, ranging in speed from very slow to very fast. The six-link model well matched the experimental step length, speed, and mean absolute power, while the four-link model did not, indicating that ankle work is a critical element in human walking models of this type. Beyond simply matching human data, the six-link model can be used in an optimization framework to predict normal human walking using a torque-squared objective function. The model well predicted experimental step length, joint motions, and mean absolute power over the full range of speeds.
Simple Numerical Model to Simulate Penetration Testing in Unsaturated Soils
Directory of Open Access Journals (Sweden)
Jarast S. Pegah
2016-01-01
Full Text Available Cone penetration test in unsaturated sand is modelled numerically using Finite Element Method. Simple elastic-perfectly plastic Mohr-Coulomb constitutive model is modified with an apparent cohesion to incorporate the effect of suction on cone resistance. The Arbitrary Lagrangian-Eulerian (ALE remeshing algorithm is also implemented to avoid mesh distortion problem due to the large deformation in the soil around the cone tip. The simulated models indicate that the cone resistance was increased consistently under higher suction or lower degree of saturation. Sensitivity analysis investigating the effect of input soil parameters on the cone tip resistance shows that unsaturated soil condition can be adequately modelled by incorporating the apparent cohesion concept. However, updating the soil stiffness by including a suction-dependent effective stress formula in Mohr-Coulomb material model does not influence the cone resistance significantly.
A simple statistical signal loss model for deep underground garage
DEFF Research Database (Denmark)
Nguyen, Huan Cong; Gimenez, Lucas Chavarria; Kovacs, Istvan
2016-01-01
In this paper we address the channel modeling aspects for a deep-indoor scenario with extreme coverage conditions in terms of signal losses, namely underground garage areas. We provide an in-depth analysis in terms of path loss (gain) and large scale signal shadowing, and a propose simple...... propagation model which can be used to predict cellular signal levels in similar deep-indoor scenarios. The proposed frequency-independent floor attenuation factor (FAF) is shown to be in range of 5.2 dB per meter deep....
Autocorrelation and regularization in digital images. II - Simple image models
Jupp, David L. B.; Strahler, Alan H.; Woodcock, Curtis E.
1989-01-01
The variogram function used in geostatistical analysis is a useful statistic in the analysis of remotely sensed images. Using the results derived by Jupp et al. (1988), the basic second-order, or covariance, properties of scenes modeled by simple disks of varying size and spacing after imaging into disk-shaped pixels are analyzed to explore the relationship betwee image variograms and discrete object scene structure. The models provide insight into the nature of real images of the earth's surface and the tools for a complete analysis of the more complex case of three-dimensional illuminated discrete-object images.
A Simple Hybrid Model for Short-Term Load Forecasting
Directory of Open Access Journals (Sweden)
Suseelatha Annamareddi
2013-01-01
Full Text Available The paper proposes a simple hybrid model to forecast the electrical load data based on the wavelet transform technique and double exponential smoothing. The historical noisy load series data is decomposed into deterministic and fluctuation components using suitable wavelet coefficient thresholds and wavelet reconstruction method. The variation characteristics of the resulting series are analyzed to arrive at reasonable thresholds that yield good denoising results. The constitutive series are then forecasted using appropriate exponential adaptive smoothing models. A case study performed on California energy market data demonstrates that the proposed method can offer high forecasting precision for very short-term forecasts, considering a time horizon of two weeks.
Modeling and simulation of a simple glass window
Energy Technology Data Exchange (ETDEWEB)
Ismail, K.A.R. [FEM-UNICAMP, Campinas (Brazil). Depto de Engenharia Termica e de Fluidos; Henriquez, J.R. [UFPE, Recife, PE (Brazil). Depto de Engenharia Mecanica
2003-11-01
This paper presents a mathematical model with numerical simulations of the heat transfer across a simple glass window. The model is two-dimensional, transient based upon the energy equation with a source term to account for the solar radiation absorbed through the glass sheet. Variable incident solar radiation and external ambient temperature are considered in the numerical simulations. The governing equations and the associated boundary conditions are discretized by the finite difference approach and the ADI scheme. Numerical simulations are realized for the cases of clear and absorbing glass to show the effect of the glass thickness on the total heat gain, the solar heat gain and the shading coefficient. (author)
Simple micromechanical model of protein crystals for their mechanical characterizations
Directory of Open Access Journals (Sweden)
Na S.
2010-06-01
Full Text Available Proteins have been known to perform the excellent mechanical functions and exhibit the remarkable mechanical properties such as high fracture toughness in spider silk protein [1]. This indicates that the mechanical characterization of protein molecules and/or crystals is very essential to understand such remarkable mechanical function of protein molecules. In this study, for gaining insight into mechanical behavior of protein crystals, we developed the micromechanical model by using the empirical potential field prescribed to alpha carbon atoms of a protein crystal in a unit cell. We consider the simple protein crystals for their mechanical behavior under tensile loading to be compared with full atomic models
A simple application of FIC to model selection
Wiggins, Paul A
2015-01-01
We have recently proposed a new information-based approach to model selection, the Frequentist Information Criterion (FIC), that reconciles information-based and frequentist inference. The purpose of this current paper is to provide a simple example of the application of this criterion and a demonstration of the natural emergence of model complexities with both AIC-like ($N^0$) and BIC-like ($\\log N$) scaling with observation number $N$. The application developed is deliberately simplified to make the analysis analytically tractable.
Chaos and complexity in a simple model of production dynamics
Directory of Open Access Journals (Sweden)
I. Katzorke
2000-01-01
Full Text Available We consider complex dynamical behavior in a simple model of production dynamics, based on the Wiendahl’s funnel approach. In the case of continuous order flow a model of three parallel funnels reduces to the one-dimensional Bernoulli-type map, and demonstrates strong chaotic properties. The optimization of production costs is possible with the OGY method of chaos control. The dynamics changes drastically in the case of discrete order flow. We discuss different dynamical behaviors, the complexity and the stability of this discrete system.
IMPROVING 9-INTERSECTION MODEL BY REPLACING THE COMPLEMENT WITH VORONOI REGION
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
9-intersection model is the most popular framework used for formalizing the spatial relations between two spatial objects A and B. It transforms the topological relation ships between two simple spatial objects A and B into point-set topology problem in terms of the intersections of A's boundary ( A), interior (A0) and exterior (A - ) with B's bound ary ( B),interior (B0) and exterior (B-). It is shown in this paper that there exist some limitations of the original 9-intersection model due to its definition of an object's exterior as its complement,and it is difficult to distinguish different disjoint relations and relations be tween complex objects with holes, difficult or even impossible to compute the intersections with the two object' s complements ( A ∩ B -, A0 ∩ B -, A - ∩ B, A- ∩ B0 and A - ∩ B - )since the complements are infinitive. The authors suggest to re-define the exterior of spa tial object by replacing the complement with its Voronoi region. A new Voronoi-based 9-in- tersection (VNI) is proposed and used for formalizing topological relations between spatial objects. By improving the 9-interscetion model, it is now possible to distinguish disjoint rela tions and to deal with objects with boles. Also it is possible to compute the exterior-based in tersections and manipulate spatial relations with the VNI.
Directory of Open Access Journals (Sweden)
Pawlowski Marcin
2012-11-01
Full Text Available Abstract Background Computational models of protein structures were proved to be useful as search models in Molecular Replacement (MR, a common method to solve the phase problem faced by macromolecular crystallography. The success of MR depends on the accuracy of a search model. Unfortunately, this parameter remains unknown until the final structure of the target protein is determined. During the last few years, several Model Quality Assessment Programs (MQAPs that predict the local accuracy of theoretical models have been developed. In this article, we analyze whether the application of MQAPs improves the utility of theoretical models in MR. Results For our dataset of 615 search models, the real local accuracy of a model increases the MR success ratio by 101% compared to corresponding polyalanine templates. On the contrary, when local model quality is not utilized in MR, the computational models solved only 4.5% more MR searches than polyalanine templates. For the same dataset of the 615 models, a workflow combining MR with predicted local accuracy of a model found 45% more correct solution than polyalanine templates. To predict such accuracy MetaMQAPclust, a “clustering MQAP” was used. Conclusions Using comparative models only marginally increases the MR success ratio in comparison to polyalanine structures of templates. However, the situation changes dramatically once comparative models are used together with their predicted local accuracy. A new functionality was added to the GeneSilico Fold Prediction Metaserver in order to build models that are more useful for MR searches. Additionally, we have developed a simple method, AmIgoMR (Am I good for MR?, to predict if an MR search with a template-based model for a given template is likely to find the correct solution.
A simple conceptual model of abrupt glacial climate events
Braun, H; Christl, M; Chialvo, D R
2008-01-01
Here we use a very simple conceptual model in an attempt to reduce essential parts of the complex nonlinearity of abrupt glacial climate changes (the so-called Dansgaard-Oeschger events) to a few simple principles, namely (i) a threshold process, (ii) an overshooting in the stability of the system and (iii) a millennial-scale relaxation. By comparison with a so-called Earth system model of intermediate complexity (CLIMBER-2), in which the events represent oscillations between two climate states corresponding to two fundamentally different modes of deep-water formation in the North Atlantic, we demonstrate that the conceptual model captures fundamental aspects of the nonlinearity of the events in that model. We use the conceptual model in order to reproduce and reanalyse nonlinear resonance mechanisms that were already suggested in order to explain the characteristic time scale of Dansgaard-Oeschger events. In doing so we identify a new form of stochastic resonance (i.e. an overshooting stochastic resonance) a...
Simple inflationary quintessential model. II. Power law potentials
de Haro, Jaume; Amorós, Jaume; Pan, Supriya
2016-09-01
The present work is a sequel of our previous work [Phys. Rev. D 93, 084018 (2016)] which depicted a simple version of an inflationary quintessential model whose inflationary stage was described by a Higgs-type potential and the quintessential phase was responsible due to an exponential potential. Additionally, the model predicted a nonsingular universe in past which was geodesically past incomplete. Further, it was also found that the model is in agreement with the Planck 2013 data when running is allowed. But, this model provides a theoretical value of the running which is far smaller than the central value of the best fit in ns , r , αs≡d ns/d l n k parameter space where ns, r , αs respectively denote the spectral index, tensor-to-scalar ratio and the running of the spectral index associated with any inflationary model, and consequently to analyze the viability of the model one has to focus in the two-dimensional marginalized confidence level in the allowed domain of the plane (ns,r ) without taking into account the running. Unfortunately, such analysis shows that this model does not pass this test. However, in this sequel we propose a family of models runs by a single parameter α ∈[0 ,1 ] which proposes another "inflationary quintessential model" where the inflation and the quintessence regimes are respectively described by a power law potential and a cosmological constant. The model is also nonsingular although geodesically past incomplete as in the cited model. Moreover, the present one is found to be more simple compared to the previous model and it is in excellent agreement with the observational data. In fact, we note that, unlike the previous model, a large number of the models of this family with α ∈[0 ,1/2 ) match with both Planck 2013 and Planck 2015 data without allowing the running. Thus, the properties in the current family of models compared to its past companion justify its need for a better cosmological model with the successive
Simple queueing model applied to the city of Portland
Energy Technology Data Exchange (ETDEWEB)
Simon, P.M.; Nagel, K. [Los Alamos National Lab., NM (United States)]|[Santa Fe Inst., NM (United States)
1998-07-31
The authors present a simple traffic micro-simulation model that models the effects of capacity cut-off, i.e. the effect of queue built-up when demand is exceeding capacity, and queue spillback, i.e. the effect that queues can spill back across intersections when a congested link is filled up. They derive the model`s fundamental diagrams and explain it. The simulation is used to simulate traffic on the emme/2 network of the Portland (Oregon) metropolitan region (20,000 links). Demand is generated by a simplified home-to-work assignment which generates about half a million trips for the AM peak. Route assignment is done by iterative feedback between micro-simulation and router. Relaxation of the route assignment for the above problem can be achieved within about half a day of computing time on a desktop workstation.
A Simple Pile-up Model for Time Series Analysis
Sevilla, Diego J. R.
2017-07-01
In this paper, a simple pile-up model is presented. This model calculates the probability P(n| N) of having n counts if N particles collide with a sensor during an exposure time. Through some approximations, an analytic expression depending on only one parameter is obtained. This parameter characterizes the pile-up magnitude, and depends on features of the instrument and the source. The statistical model obtained permits the determination of probability distributions of measured counts from the probability distributions of incoming particles, which is valuable for time series analysis. Applicability limits are discussed, and an example of the improvement that can be achieved in the statistical analysis considering the proposed pile-up model is shown by analyzing real data.
A Simple Model for Assessment of Anti-Toxin Antibodies
Directory of Open Access Journals (Sweden)
Alex Skvortsov
2013-01-01
Full Text Available The toxins associated with infectious diseases are potential targets for inhibitors which have the potential for prophylactic or therapeutic use. Many antibodies have been generated for this purpose, and the objective of this study was to develop a simple mathematical model that may be used to evaluate the potential protective effect of antibodies. This model was used to evaluate the contributions of antibody affinity and concentration to reducing antibody-receptor complex formation and internalization. The model also enables prediction of the antibody kinetic constants and concentration required to provide a specified degree of protection. We hope that this model, once validated experimentally, will be a useful tool for in vitro selection of potentially protective antibodies for progression to in vivo evaluation.
A Simple Model for Assessment of Anti-Toxin Antibodies
Skvortsov, Alex; Gray, Peter
2013-01-01
The toxins associated with infectious diseases are potential targets for inhibitors which have the potential for prophylactic or therapeutic use. Many antibodies have been generated for this purpose, and the objective of this study was to develop a simple mathematical model that may be used to evaluate the potential protective effect of antibodies. This model was used to evaluate the contributions of antibody affinity and concentration to reducing antibody-receptor complex formation and internalization. The model also enables prediction of the antibody kinetic constants and concentration required to provide a specified degree of protection. We hope that this model, once validated experimentally, will be a useful tool for in vitro selection of potentially protective antibodies for progression to in vivo evaluation. PMID:23862138
A new simple dynamo model for stellar activity cycle
Yokoi, Nobumitsu; Pipin, Valery; Hamba, Fujihiro
2016-01-01
A new simple dynamo model for stellar activity cycle is proposed. By considering an inhomogeneous mean flow effect on turbulence, it is shown that turbulent cross helicity (velocity--magnetic-field correlation) should enter the expression of turbulent electromotive force as the coupling coefficient for the mean absolute vorticity. The inclusion of the cross-helicity effect makes the present model different from the current $\\alpha$--$\\Omega$-type models mainly in two points. First, in addition to the usual $\\alpha$ (helicity effect) and $\\beta$ (turbulent magnetic diffusivity), we consider the $\\gamma$ coefficient (cross-helicity effect). Second, unlike the $\\alpha$ and $\\beta$ coefficients, which are often treated as an adjustable parameter in the current studies, the spatiotemporal evolution of $\\gamma$ coefficient should be solved simultaneously with the mean magnetic-field equations. The basic scenario for the stellar activity cycle in the present model is as follows: In the presence of turbulent cross he...
A Simple Model of Low-scale Direct Gauge Mediation
Csáki, C; Terning, J; Cs\\'aki, Csaba; Shirman, Yuri; Terning, John
2007-01-01
We construct a calculable model of low-energy direct gauge mediation making use of the metastable supersymmetry breaking vacua recently discovered by Intriligator, Seiberg and Shih. The standard model gauge group is a subgroup of the global symmetries of the SUSY breaking sector and messengers play an essential role in dynamical SUSY breaking: they are composites of a confining gauge theory, and the holomorphic scalar messenger mass appears as a consequence of the confining dynamics. The SUSY breaking scale is around 100 TeV nevertheless the model is calculable. The minimal non-renormalizable coupling of the Higgs to the DSB sector leads in a simple way to a mu-term, while the B-term arises at two-loop order resulting in a moderately large tan beta. A novel feature of this class of models is that some particles from the dynamical SUSY breaking sector may be accessible at the LHC.
A Simple Model for Nonlinear Confocal Ultrasonic Beams
Institute of Scientific and Technical Information of China (English)
ZHANG Dong; ZHOU Lin; SI Li-Sheng; GONG Xiu-Fen
2007-01-01
@@ A confocally and coaxially arranged pair of focused transmitter and receiver represents one of the best geometries for medical ultrasonic imaging and non-invasive detection. We develop a simple theoretical model for describing the nonlinear propagation of a confocal ultrasonic beam in biological tissues. On the basis of the parabolic approximation and quasi-linear approximation, the nonlinear Khokhlov-Zabolotskaya-Kuznetsov (KZK) equation is solved by using the angular spectrum approach. Gaussian superposition technique is applied to simplify the solution, and an analytical solution for the second harmonics in the confocal ultrasonic beam is presented.Measurements are performed to examine the validity of the theoretical model. This model provides a preliminary model for acoustic nonlinear microscopy.
A Simple Generative Model of Collective Online Behaviour
Gleeson, James P; Onnela, Jukka-Pekka; Porter, Mason A; Reed-Tsochas, Felix
2013-01-01
Human activities---from voter mobilization to political protests---increasingly take place in online environments, providing novel opportunities for relating individual behaviours to population-level outcomes. The recent availability of data sets that capture the behaviour of individuals participating in online social systems has driven the emerging field of computational social science, as large-scale empirical data sets enable the development of detailed computational models of individual and collective behaviour. Given the inherent limitations of observational data, it is crucial to investigate the extent to which models of collective dynamics can distinguish between different individual-level mechanisms. Here we introduce a simple generative model for the collective behaviour of millions of social networking site users who are deciding between different software applications. Our model incorporates two distinct components: one is associated with recent decisions of users, and the other reflects the cumula...
A Simple Model of Wings in Heavy-Ion Collisions
Parikh, Aditya
2015-01-01
We create a simple model of heavy ion collisions independent of any generators as a way of investigating a possible source of the wings seen in data. As a first test, we reproduce a standard correlations plot to verify the integrity of the model. We then proceed to test whether an η dependent v2 could be a source of the wings and take projections along multiple Δφ intervals and compare with data. Other variations of the model are tested by having dN/dφ and v2 depend on η as well as including pions and protons into the model to make it more realistic. Comparisons with data seem to indicate that an η dependent v2 is not the main source of the wings.
Technical Note: The Simple Diagnostic Photosynthesis and Respiration Model (SDPRM
Directory of Open Access Journals (Sweden)
B. Badawy
2012-10-01
Full Text Available We present a Simple Diagnostic Photosynthesis and Respiration Model (SDPRM that has been developed based on pre-existing formulations. The photosynthesis model is based on the light use efficiency logic, suggested by Monteith1977, for calculating the Gross Primary Production (GPP while the ecosystem respiration (R_{eco} model is based on the formulations introduced by Lloyd1994 and modified by Reichstein2003. SDPRM is driven by satellite-derived fAPAR (fraction of Absorbed Photosynthetically Active Radiation and climate data from NCEP/NCAR. The model estimates 3-hourly values of GPP for seven major biomes and daily R_{eco}. The motivation is to provide a-priori fields of surface CO_{2} fluxes with fine temporal and spatial scales, and their derivatives with respect to adjustable model parameters, for atmospheric CO_{2} inversions. The estimated fluxes from SDPRM showed that the model is capable of producing flux estimates consistent with the ones inferred from atmospheric CO_{2} inversion or simulated from process-based models. In this Technical Note, different analyses were carried out to test the sensitivity of the estimated fluxes of GPP and R_{eco} to their driving forces. The spatial patterns of the climatic controls (temperature, precipitation, water on the interannual variability of GPP are consistent with previous studies even though SDPRM has a very simple structure and few adjustable parameters, and hence it is much easier to modify than more sophisticated process-based models used in these previous studies. According to SDPRM, the results show that temperature is a limiting factor for the interannual variability of R_{eco} over the cold boreal forest, while precipitation is the main limiting factor of R_{eco} over the tropics and the southern hemisphere, consistent with previous regional studies.
Karttunen, L
1996-01-01
This paper introduces to the finite-state calculus a family of directed replace operators. In contrast to the simple replace expression, UPPER -> LOWER, defined in Karttunen (ACL-95), the new directed version, UPPER @-> LOWER, yields an unambiguous transducer if the lower language consists of a single string. It transduces the input string from left to right, making only the longest possible replacement at each point. A new type of replacement expression, UPPER @-> PREFIX ... SUFFIX, yields a transducer that inserts text around strings that are instances of UPPER. The symbol ... denotes the matching part of the input which itself remains unchanged. PREFIX and SUFFIX are regular expressions describing the insertions. Expressions of the type UPPER @-> PREFIX ... SUFFIX may be used to compose a deterministic parser for a ``local grammar'' in the sense of Gross (1989). Other useful applications of directed replacement include tokenization and filtering of text streams.
Analyses of Tsunami Events using Simple Propagation Models
Chilvery, Ashwith Kumar; Tan, Arjun; Aggarwal, Mohan
2012-03-01
Tsunamis exhibit the characteristics of ``canal waves'' or ``gravity waves'' which belong to the class of ``long ocean waves on shallow water.'' The memorable tsunami events including the 2004 Indian Ocean tsunami and the 2011 Pacific Ocean tsunami off the coast of Japan are analyzed by constructing simple tsunami propagation models including the following: (1) One-dimensional propagation model; (2) Two-dimensional propagation model on flat surface; (3) Two-dimensional propagation model on spherical surface; and (4) A finite line-source model on two-dimensional surface. It is shown that Model 1 explains the basic features of the tsunami including the propagation speed, depth of the ocean, dispersion-less propagation and bending of tsunamis around obstacles. Models 2 and 3 explain the observed amplitude variations for long-distance tsunami propagation across the Pacific Ocean, including the effect of the equatorial ocean current on the arrival times. Model 3 further explains the enhancement effect on the amplitude due to the curvature of the Earth past the equatorial distance. Finally, Model 4 explains the devastating effect of superposition of tsunamis from two subduction event, which struck the Phuket region during the 2004 Indian Ocean tsunami.
A simple model linking galaxy and dark matter evolution
Energy Technology Data Exchange (ETDEWEB)
Birrer, Simon; Lilly, Simon; Amara, Adam; Paranjape, Aseem; Refregier, Alexandre, E-mail: simon.birrer@phys.ethz.ch, E-mail: simon.lilly@phys.ethz.ch [Institute for Astronomy, Department of Physics, ETH Zurich, Wolfgang-Pauli-Strasse 27, 8093 Zurich (Switzerland)
2014-09-20
We construct a simple phenomenological model for the evolving galaxy population by incorporating predefined baryonic prescriptions into a dark matter hierarchical merger tree. The model is based on the simple gas-regulator model introduced by Lilly et al., coupled with the empirical quenching rules of Peng et al. The simplest model already does quite well in reproducing, without re-adjusting the input parameters, many observables, including the main sequence sSFR-mass relation, the faint end slope of the galaxy mass function, and the shape of the star forming and passive mass functions. Similar to observations and/or the recent phenomenological model of Behroozi et al., which was based on epoch-dependent abundance-matching, our model also qualitatively reproduces the evolution of the main sequence sSFR(z) and SFRD(z) star formation rate density relations, the M{sub s} – M{sub h} stellar-to-halo mass relation, and the SFR – M{sub h} relation. Quantitatively the evolution of sSFR(z) and SFRD(z) is not steep enough, the M{sub s} – M{sub h} relation is not quite peaked enough, and, surprisingly, the ratio of quenched to star forming galaxies around M* is not quite high enough. We show that these deficiencies can simultaneously be solved by ad hoc allowing galaxies to re-ingest some of the gas previously expelled in winds, provided that this is done in a mass-dependent and epoch-dependent way. These allow the model galaxies to reduce an inherent tendency to saturate their star formation efficiency, which emphasizes how efficient galaxies around M* are in converting baryons into stars and highlights the fact that quenching occurs at the point when galaxies are rapidly approaching the maximum possible efficiency of converting baryons into stars.
Modeling neuron selectivity over simple midlevel features for image classification.
Shu Kong; Zhuolin Jiang; Qiang Yang
2015-08-01
We now know that good mid-level features can greatly enhance the performance of image classification, but how to efficiently learn the image features is still an open question. In this paper, we present an efficient unsupervised midlevel feature learning approach (MidFea), which only involves simple operations, such as k-means clustering, convolution, pooling, vector quantization, and random projection. We show this simple feature can also achieve good performance in traditional classification task. To further boost the performance, we model the neuron selectivity (NS) principle by building an additional layer over the midlevel features prior to the classifier. The NS-layer learns category-specific neurons in a supervised manner with both bottom-up inference and top-down analysis, and thus supports fast inference for a query image. Through extensive experiments, we demonstrate that this higher level NS-layer notably improves the classification accuracy with our simple MidFea, achieving comparable performances for face recognition, gender classification, age estimation, and object categorization. In particular, our approach runs faster in inference by an order of magnitude than sparse coding-based feature learning methods. As a conclusion, we argue that not only do carefully learned features (MidFea) bring improved performance, but also a sophisticated mechanism (NS-layer) at higher level boosts the performance further.
Response of Simple, Model Systems to Extreme Conditions
Energy Technology Data Exchange (ETDEWEB)
Ewing, Rodney C. [Univ. of Michigan, Ann Arbor, MI (United States); Lang, Maik [Univ. of Michigan, Ann Arbor, MI (United States)
2015-07-30
The focus of the research was on the application of high-pressure/high-temperature techniques, together with intense energetic ion beams, to the study of the behavior of simple oxide systems (e.g., SiO_{2}, GeO_{2}, CeO_{2}, TiO_{2}, HfO_{2}, SnO_{2}, ZnO and ZrO_{2}) under extreme conditions. These simple stoichiometries provide unique model systems for the analysis of structural responses to pressure up to and above 1 Mbar, temperatures of up to several thousands of kelvin, and the extreme energy density generated by energetic heavy ions (tens of keV/atom). The investigations included systematic studies of radiation- and pressure-induced amorphization of high P-T polymorphs. By studying the response of simple stoichiometries that have multiple structural “outcomes”, we have established the basic knowledge required for the prediction of the response of more complex structures to extreme conditions. We especially focused on the amorphous state and characterized the different non-crystalline structure-types that result from the interplay of radiation and pressure. For such experiments, we made use of recent technological developments, such as the perforated diamond-anvil cell and in situ investigation using synchrotron x-ray sources. We have been particularly interested in using extreme pressures to alter the electronic structure of a solid prior to irradiation. We expected that the effects of modified band structure would be evident in the track structure and morphology, information which is much needed to describe theoretically the fundamental physics of track-formation. Finally, we investigated the behavior of different simple-oxide, composite nanomaterials (e.g., uncoated nanoparticles vs. core/shell systems) under coupled, extreme conditions. This provided insight into surface and boundary effects on phase stability under extreme conditions.
Comparison of Simple Versus Performance-Based Fall Prediction Models
Directory of Open Access Journals (Sweden)
Shekhar K. Gadkaree BS
2015-05-01
Full Text Available Objective: To compare the predictive ability of standard falls prediction models based on physical performance assessments with more parsimonious prediction models based on self-reported data. Design: We developed a series of fall prediction models progressing in complexity and compared area under the receiver operating characteristic curve (AUC across models. Setting: National Health and Aging Trends Study (NHATS, which surveyed a nationally representative sample of Medicare enrollees (age ≥65 at baseline (Round 1: 2011-2012 and 1-year follow-up (Round 2: 2012-2013. Participants: In all, 6,056 community-dwelling individuals participated in Rounds 1 and 2 of NHATS. Measurements: Primary outcomes were 1-year incidence of “any fall” and “recurrent falls.” Prediction models were compared and validated in development and validation sets, respectively. Results: A prediction model that included demographic information, self-reported problems with balance and coordination, and previous fall history was the most parsimonious model that optimized AUC for both any fall (AUC = 0.69, 95% confidence interval [CI] = [0.67, 0.71] and recurrent falls (AUC = 0.77, 95% CI = [0.74, 0.79] in the development set. Physical performance testing provided a marginal additional predictive value. Conclusion: A simple clinical prediction model that does not include physical performance testing could facilitate routine, widespread falls risk screening in the ambulatory care setting.
Comparison of Simple Versus Performance-Based Fall Prediction Models
Directory of Open Access Journals (Sweden)
Shekhar K. Gadkaree BS
2015-05-01
Full Text Available Objective: To compare the predictive ability of standard falls prediction models based on physical performance assessments with more parsimonious prediction models based on self-reported data. Design: We developed a series of fall prediction models progressing in complexity and compared area under the receiver operating characteristic curve (AUC across models. Setting: National Health and Aging Trends Study (NHATS, which surveyed a nationally representative sample of Medicare enrollees (age ≥65 at baseline (Round 1: 2011-2012 and 1-year follow-up (Round 2: 2012-2013. Participants: In all, 6,056 community-dwelling individuals participated in Rounds 1 and 2 of NHATS. Measurements: Primary outcomes were 1-year incidence of “ any fall ” and “ recurrent falls .” Prediction models were compared and validated in development and validation sets, respectively. Results: A prediction model that included demographic information, self-reported problems with balance and coordination, and previous fall history was the most parsimonious model that optimized AUC for both any fall (AUC = 0.69, 95% confidence interval [CI] = [0.67, 0.71] and recurrent falls (AUC = 0.77, 95% CI = [0.74, 0.79] in the development set. Physical performance testing provided a marginal additional predictive value. Conclusion: A simple clinical prediction model that does not include physical performance testing could facilitate routine, widespread falls risk screening in the ambulatory care setting.
The two capacitor problem revisited: simple harmonic oscillator model approach
Lee, Keeyung
2012-01-01
The well-known two-capacitor problem, in which exactly half the stored energy disappears when a charged capacitor is connected to an identical capacitor is discussed based on the mechanical harmonic oscillator model approach. In the mechanical harmonic oscillator model, it is shown first that \\emph {exactly half} the work done by a constant applied force is dissipated irrespective of the form of dissipation mechanism when the system comes to a new equilibrium after a constant force is abruptly applied. This model is then applied to the energy loss mechanism in the capacitor charging problem or the two-capacitor problem. This approach allows a simple explanation of the energy dissipation mechanism in these problems and shows that the dissipated energy should always be \\emph {exactly half} the supplied energy whether that is caused by the Joule heat or by the radiation. This paper which provides a simple treatment of the energy dissipation mechanism in the two-capacitor problem is suitable for all undergraduate...
A simple stationary semi-analytical wake model
DEFF Research Database (Denmark)
Larsen, Gunner Chr.
-uniform mean wind field, although the modelling of the individual stationary wake flow fields includes non-linear terms. The simulation of the individual wake contributions are based on an analytical solution of the thin shear layer approximation of the NS equations. The wake flow fields are assumed......We present an idealized simple, but fast, semi-analytical algorithm for computation of stationary wind farm wind fields with a possible potential within a multi-fidelity strategy for wind farm topology optimization. Basically, the model considers wakes as linear perturbations on the ambient non...... rotationally symmetric, and the rotor inflow fields are consistently assumed uniform. Expansion of stationary wake fields is believed to be significantly affected by meandering of wake deficits as e.g. described by the Dynamic Wake Meandering model. In the present context, this effect is approximately...
A Simple Model of the Variability of Soil Depths
Directory of Open Access Journals (Sweden)
Fang Yu
2017-06-01
Full Text Available Soil depth tends to vary from a few centimeters to several meters, depending on many natural and environmental factors. We hypothesize that the cumulative effect of these factors on soil depth, which is chiefly dependent on the process of biogeochemical weathering, is particularly affected by soil porewater (i.e., solute transport and infiltration from the land surface. Taking into account evidence for a non-Gaussian distribution of rock weathering rates, we propose a simple mathematical model to describe the relationship between soil depth and infiltration flux. The model was tested using several areas in mostly semi-arid climate zones. The application of this model demonstrates the use of fundamental principles of physics to quantify the coupled effects of the five principal soil-forming factors of Dokuchaev.
A simple model for skewed species-lifetime distributions
Murase, Yohsuke
2010-06-11
A simple model of a biological community assembly is studied. Communities are assembled by successive migrations and extinctions of species. In the model, species are interacting with each other. The intensity of the interaction between each pair of species is denoted by an interaction coefficient. At each time step, a new species is introduced to the system with randomly assigned interaction coefficients. If the sum of the coefficients, which we call the fitness of a species, is negative, the species goes extinct. The species-lifetime distribution is found to be well characterized by a stretched exponential function with an exponent close to 1/2. This profile agrees not only with more realistic population dynamics models but also with fossil records. We also find that an age-independent and inversely diversity-dependent mortality, which is confirmed in the simulation, is a key mechanism accounting for the distribution. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.
Speciation and Extinction in a simple model of evolution
Head, D A
1996-01-01
We introduce a simple model of macro-coevolution which allows the branching and termination of species lines and also incorporates external influences to the ecosystem. The strength of the external influences and the likelihood of speciation and extinction are defined from the fitness landscapes by two new parameters, $\\delta g$ and $\\delta s$. Results from numerical simulations show that the total number of species fluctuates about a natural system size $N_{\\infty}$. We present a mean-field theory which predicts $N_{\\infty}\\propto(K-1)\\delta s/\\delta g^{2}$, where $K-1$ is the system connectivity and $\\delta s$ is small. This result compares well with the numerical simulations. For large $\\delta s$, we demonstrate why this expression changes to $N_{\\infty}\\propto(K-1)\\delta s^{2}/\\delta g^{2}$. We compare the model to the fossil record, and comment on the role of ecological niches in models of evolution.
Describing pulsar wind nebulae with a simple leptonic model
Energy Technology Data Exchange (ETDEWEB)
Hahn, Joachim; Hoppe, Stefan; Domainko, Wilfried; Hofmann, Werner [Max-Planck-Institut fuer Kernphysik, Heidelberg (Germany); Egberts, Kathrin [Institut fuer Astro- und Teilchenphysik, Leopold-Franzens-Universitaet Innsbruck (Austria)
2010-07-01
In recent years, Cherenkov telescopes like e.g. H.E.S.S. have identified a large number of very-high-energy (VHE) gamma-ray sources as Pulsar wind nebulae (PWNe). The VHE-gamma-ray emission shows a rich diversity of spectral and spatial morphologies. Theoretical models can help to understand and interprete the observed source properties. A simple semi-analytical leptonic model describing VHE gamma-ray emission from PWNe is presented. It assumes diffusion with radiative cooling as the transport mechanism for electrons and their interaction with radiative and interstellar magnetic fields as the origin of electromagnetic radiation. In the framework of this model, spectral and spatial properties of the expected VHE gamma-ray emission from single PWNe may be estimated.
A simple model of multiphoton micromachining in silk hydrogels
Applegate, Matthew B.; Alonzo, Carlo; Georgakoudi, Irene; Kaplan, David L.; Omenetto, Fiorenzo G.
2016-06-01
High resolution three-dimensional voids can be directly written into transparent silk fibroin hydrogels using ultrashort pulses of near-infrared (NIR) light. Here, we propose a simple finite-element model that can be used to predict the size and shape of individual features under various exposure conditions. We compare predicted and measured feature volumes for a wide range of parameters and use the model to determine optimum conditions for maximum material removal. The simplicity of the model implies that the mechanism of multiphoton induced void creation in silk is due to direct absorption of light energy rather than diffusion of heat or other photoproducts, and confirms that multiphoton absorption of NIR light in silk is purely a 3-photon process.
Encouraging moderation: Clues from a simple model of ideological conflict
Marvel, Seth A; Papush, Anna; Strogatz, Steven H
2012-01-01
Some of the most pivotal moments in intellectual history occur when a new ideology sweeps through a society, supplanting an established system of beliefs in a rapid revolution of thought. Yet in many cases the new ideology is as extreme as the old. Why is it then that moderate positions so rarely prevail? Here, in the context of a simple model of opinion spreading, we test seven plausible strategies for deradicalizing a society and find that only one of them significantly expands the moderate subpopulation without risking its extinction in the process.
Encouraging moderation: clues from a simple model of ideological conflict.
Marvel, Seth A; Hong, Hyunsuk; Papush, Anna; Strogatz, Steven H
2012-09-14
Some of the most pivotal moments in intellectual history occur when a new ideology sweeps through a society, supplanting an established system of beliefs in a rapid revolution of thought. Yet in many cases the new ideology is as extreme as the old. Why is it then that moderate positions so rarely prevail? Here, in the context of a simple model of opinion spreading, we test seven plausible strategies for deradicalizing a society and find that only one of them significantly expands the moderate subpopulation without risking its extinction in the process.
Simple Models Create Steep Learning Curves in Academic Design Studio
DEFF Research Database (Denmark)
Hansen, Peter Lundsgaard; Dam, Torben; Le Goffic, Virginie Corinne
2014-01-01
theory positions normally regarded as mutually incompatible. The method is the result of years of ‘trial and error’ design studio teaching at the University of Copenhagen, triangulated with academic design theory research. Research based design studio teaching poses a fundamental pedagogical challenge......, as it must combine skill-based design practice with academic-explicated theories and methods. The vehicle in the development of the simple model method is overcoming the challenge of ensuring that a group of students with various backgrounds and cultures can produce specific and consistent design proposals...
SWIM: A Simple Model to Generate Small Mobile Worlds
Mei, Alessandro
2008-01-01
This paper presents small world in motion (SWIM), a new mobility model for ad-hoc networking. SWIM is relatively simple, is easily tuned by setting just a few parameters, and generates traces that look real--synthetic traces have the same statistical properties of real traces. SWIM shows both experimentally and theoretically the presence of the power law and exponential decay dichotomy of inter-contact times, and, most importantly, our experiments show that it can predict very accurately the performance of forwarding protocols.
Technical Note: The Simple Diagnostic Photosynthesis and Respiration Model (SDPRM
Directory of Open Access Journals (Sweden)
B. Badawy
2013-10-01
Full Text Available We present a Simple Diagnostic Photosynthesis and Respiration Model (SDPRM that has been developed based on pre-existing formulations. The photosynthesis model is based on the light use efficiency logic for calculating the gross primary production (GPP, while the ecosystem respiration (Reco is a modified version of an Arrhenius-type equation. SDPRM is driven by satellite-derived fAPAR (fraction of Absorbed Photosynthetically Active Radiation and climate data from the National Center for Environmental Prediction/National Center for Atmospheric Research Reanalysis (NCEP/NCAR. The model estimates 3-hourly values of GPP for seven major biomes and daily Reco. The motivation is to provide a priori fields of surface CO2 fluxes with fine temporal and spatial scales for atmospheric CO2 inversions. The estimated fluxes from SDPRM showed that the model is capable of producing flux estimates consistent with the ones inferred from atmospheric CO2 inversion or simulated from process-based models. In this Technical Note, different analyses were carried out to test the sensitivity of the estimated fluxes of GPP and CO2 to their driving forces. The spatial patterns of the climatic controls (temperature, precipitation, water on the interannual variability of GPP are consistent with previous studies, even though SDPRM has a very simple structure and few adjustable parameters and hence it is much easier to modify in an inversion than more sophisticated process-based models. In SDPRM, temperature is a limiting factor for the interannual variability of Reco over cold boreal forest, while precipitation is the main limiting factor of Reco over the tropics and the southern hemisphere, consistent with previous regional studies.
Uranus evolution models with simple thermal boundary layers
Nettelmann, N.; Wang, K.; Fortney, J. J.; Hamel, S.; Yellamilli, S.; Bethkenhagen, M.; Redmer, R.
2016-09-01
The strikingly low luminosity of Uranus (Teff ≃ Teq) constitutes a long-standing challenge to our understanding of Ice Giant planets. Here we present the first Uranus structure and evolution models that are constructed to agree with both the observed low luminosity and the gravity field data. Our models make use of modern ab initio equations of state at high pressures for the icy components water, methane, and ammonia. Proceeding step by step, we confirm that adiabatic models yield cooling times that are too long, even when uncertainties in the ice:rock ratio (I:R) are taken into account. We then argue that the transition between the ice/rock-rich interior and the H/He-rich outer envelope should be stably stratified. Therefore, we introduce a simple thermal boundary and adjust it to reproduce the low luminosity. Due to this thermal boundary, the deep interior of the Uranus models are up to 2-3 warmer than adiabatic models, necessitating the presence of rocks in the deep interior with a possible I:R of 1 × solar. Finally, we allow for an equilibrium evolution (Teff ≃ Teq) that begun prior to the present day, which would therefore no longer require the current era to be a "special time" in Uranus' evolution. In this scenario, the thermal boundary leads to more rapid cooling of the outer envelope. When Teff ≃ Teq is reached, a shallow, subadiabatic zone in the atmosphere begins to develop. Its depth is adjusted to meet the luminosity constraint. This work provides a simple foundation for future Ice Giant structure and evolution models, that can be improved by properly treating the heat and particle fluxes in the diffusive zones.
A simple physical model for deep moonquake occurrence times
Weber, R.C.; Bills, B.G.; Johnson, C.L.
2010-01-01
The physical process that results in moonquakes is not yet fully understood. The periodic occurrence times of events from individual clusters are clearly related to tidal stress, but also exhibit departures from the temporal regularity this relationship would seem to imply. Even simplified models that capture some of the relevant physics require a large number of variables. However, a single, easily accessible variable - the time interval I(n) between events - can be used to reveal behavior not readily observed using typical periodicity analyses (e.g., Fourier analyses). The delay-coordinate (DC) map, a particularly revealing way to display data from a time series, is a map of successive intervals: I(n+. 1) plotted vs. I(n). We use a DC approach to characterize the dynamics of moonquake occurrence. Moonquake-like DC maps can be reproduced by combining sequences of synthetic events that occur with variable probability at tidal periods. Though this model gives a good description of what happens, it has little physical content, thus providing only little insight into why moonquakes occur. We investigate a more mechanistic model. In this study, we present a series of simple models of deep moonquake occurrence, with consideration of both tidal stress and stress drop during events. We first examine the behavior of inter-event times in a delay-coordinate context, and then examine the output, in that context, of a sequence of simple models of tidal forcing and stress relief. We find, as might be expected, that the stress relieved by moonquakes influences their occurrence times. Our models may also provide an explanation for the opposite-polarity events observed at some clusters. ?? 2010.
Simple predictive electron transport models applied to sawtoothing plasmas
Kim, D.; Merle, A.; Sauter, O.; Goodman, T. P.
2016-05-01
In this work, we introduce two simple transport models to evaluate the time evolution of electron temperature and density profiles during sawtooth cycles (i.e. over a sawtooth period time-scale). Since the aim of these simulations is to estimate reliable profiles within a short calculation time, two simplified ad-hoc models have been developed. The goal for these models is to rely on a few easy-to-check free parameters, such as the confinement time scaling factor and the profiles’ averaged scale-lengths. Due to the simplicity and short calculation time of the models, it is expected that these models can also be applied to real-time transport simulations. We show that it works well for Ohmic and EC heated L- and H-mode plasmas. The differences between these models are discussed and we show that their predictive capabilities are similar. Thus only one model is used to reproduce with simulations the results of sawtooth control experiments on the TCV tokamak. For the sawtooth pacing, the calculated time delays between the EC power off and sawtooth crash time agree well with the experimental results. The map of possible locking range is also well reproduced by the simulation.
Oscillations in a simple climate–vegetation model
Directory of Open Access Journals (Sweden)
J. Rombouts
2015-05-01
Full Text Available We formulate and analyze a simple dynamical systems model for climate–vegetation interaction. The planet we consider consists of a large ocean and a land surface on which vegetation can grow. The temperature affects vegetation growth on land and the amount of sea ice on the ocean. Conversely, vegetation and sea ice change the albedo of the planet, which in turn changes its energy balance and hence the temperature evolution. Our highly idealized, conceptual model is governed by two nonlinear, coupled ordinary differential equations, one for global temperature, the other for vegetation cover. The model exhibits either bistability between a vegetated and a desert state or oscillatory behavior. The oscillations arise through a Hopf bifurcation off the vegetated state, when the death rate of vegetation is low enough. These oscillations are anharmonic and exhibit a sawtooth shape that is characteristic of relaxation oscillations, as well as suggestive of the sharp deglaciations of the Quaternary. Our model's behavior can be compared, on the one hand, with the bistability of even simpler, Daisyworld-style climate–vegetation models. On the other hand, it can be integrated into the hierarchy of models trying to simulate and explain oscillatory behavior in the climate system. Rigorous mathematical results are obtained that link the nature of the feedbacks with the nature and the stability of the solutions. The relevance of model results to climate variability on various timescales is discussed.
A Simple and Accurate Closed-Form EGN Model Formula
Poggiolini, P; Carena, A; Forghieri, F
2015-01-01
The GN model of non-linear fiber propagation has been shown to overestimate the variance of non-linearity due to the signal Gaussianity approximation, leading to maximum reach predictions for typical optical systems which may be pessimistic by about 5% to 15%, depending on fiber type and system set-up. Various models have been proposed which improve over the GN model accuracy. One of them is the EGN model, which completely removes the Gaussianity approximation from all non-linear interference (NLI) components. The EGN model is, however, substantially more complex than the GN model. Recently, we proposed a simple closed-form formula which permits to approximate the EGN model, starting from the GN. It was however limited to all-identical, equispaced channels, and did not correct single-channel NLI (also called SCI). In this follow-up contribution, we propose an improved version which both allows to address non-identical channels and corrects the SCI contribution as well. Extensive simulative testing shows the n...
SREF - a Simple Removable Epoxy Foam decomposition chemistry model.
Energy Technology Data Exchange (ETDEWEB)
Hobbs, Michael L.
2003-12-01
A Simple Removable Epoxy Foam (SREF) decomposition chemistry model has been developed to predict the decomposition behavior of an epoxy foam encapsulant exposed to high temperatures. The foam is composed of an epoxy polymer, blowing agent, and surfactant. The model is based on a simple four-step mass loss model using distributed Arrhenius reaction rates. A single reaction was used to describe desorption of the blowing agent and surfactant (BAS). Three of the reactions were used to describe degradation of the polymer. The coordination number of the polymeric lattice was determined from the chemical structure of the polymer; and a lattice statistics model was used to describe the evolution of polymer fragments. The model lattice was composed of sites connected by octamethylcylotetrasiloxane (OS) bridges, mixed product (MP) bridges, and bisphenol-A (BPA) bridges. The mixed products were treated as a single species, but are likely composed of phenols, cresols, and furan-type products. Eleven species are considered in the SREF model - (1) BAS, (2) OS, (3) MP, (4) BPA, (5) 2-mers, (6) 3-mers, (7) 4-mers, (8) nonvolatile carbon residue, (9) nonvolatile OS residue, (10) L-mers, and (11) XL-mers. The first seven of these species (VLE species) can either be in the condensed-phase or gas-phase as determined by a vapor-liquid equilibrium model based on the Rachford-Rice equation. The last four species always remain in the condensed-phase. The 2-mers, 3-mers, and 4-mers are polymer fragments that contain two, three, or four sites, respectively. The residue can contain C, H, N, O, and/or Si. The L-mer fraction consists of polymer fragments that contain at least five sites (5-mer) up to a user defined maximum mer size. The XL-mer fraction consists of polymer fragments greater than the user specified maximum mer size and can contain the infinite lattice if the bridge population is less than the critical bridge population. Model predictions are compared to 133-thermogravimetric
Cavo-portal transposition in rat: a new simple model
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Andorno Enzo
2007-08-01
Full Text Available Abstract Background Liver transplantation in presence of diffuse portal vein thrombosis is possible by using caval blood as portal inflow, through cavo-portal transposition. However, clinical results are heterogeneous and experimental studies are needed, but similar hemodynamic conditions are difficult to obtain, especially in small animals. Herein we describe a new simple model of cavo-portal transposition in rat. Methods Spontaneous porto-systemic shunts are induced by subcutaneous transposition of the spleen. The presence of porto-caval shunts through the spleen permits the interruption of the main portal vein without splanchnic hemodynamic consequences. Cavo-portal transposition is achieved by anastomosing the inferior vena cava and the main portal vein after division of the pancreatic-duodenal vein. Results Selective angiography revealed total splanchnic blood diversion to the systemic venous circulation through the neoformed collaterals; macroscopical examination showed the absence of any signs of acute portal hypertension with normal liver and gut appearance. Conclusion This model of cavoportal transposition is simple, effective and it simulates the clinical hemodynamic condition since the porto-systemic shunts induced by splenic subcutaneous transposition correspond to the physiological inframesocolic collaterals during chronic portal thrombosis in man.
A simple model for behaviour change in epidemics
Directory of Open Access Journals (Sweden)
Brauer Fred
2011-02-01
Full Text Available Abstract Background People change their behaviour during an epidemic. Infectious members of a population may reduce the number of contacts they make with other people because of the physical effects of their illness and possibly because of public health announcements asking them to do so in order to decrease the number of new infections, while susceptible members of the population may reduce the number of contacts they make in order to try to avoid becoming infected. Methods We consider a simple epidemic model in which susceptible and infectious members respond to a disease outbreak by reducing contacts by different fractions and analyze the effect of such contact reductions on the size of the epidemic. We assume constant fractional reductions, without attempting to consider the way in which susceptible members might respond to information about the epidemic. Results We are able to derive upper and lower bounds for the final size of an epidemic, both for simple and staged progression models. Conclusions The responses of uninfected and infected individuals in a disease outbreak are different, and this difference affects estimates of epidemic size.
A simple model of hysteresis behavior using spreadsheet analysis
Ehrmann, A.; Blachowicz, T.
2015-01-01
Hysteresis loops occur in many scientific and technical problems, especially as field dependent magnetization of ferromagnetic materials, but also as stress-strain-curves of materials measured by tensile tests including thermal effects, liquid-solid phase transitions, in cell biology or economics. While several mathematical models exist which aim to calculate hysteresis energies and other parameters, here we offer a simple model for a general hysteretic system, showing different hysteresis loops depending on the defined parameters. The calculation which is based on basic spreadsheet analysis plus an easy macro code can be used by students to understand how these systems work and how the parameters influence the reactions of the system on an external field. Importantly, in the step-by-step mode, each change of the system state, compared to the last step, becomes visible. The simple program can be developed further by several changes and additions, enabling the building of a tool which is capable of answering real physical questions in the broad field of magnetism as well as in other scientific areas, in which similar hysteresis loops occur.
Wealth distribution of simple exchange models coupled with extremal dynamics
Bagatella-Flores, N.; Rodríguez-Achach, M.; Coronel-Brizio, H. F.; Hernández-Montoya, A. R.
2015-01-01
Punctuated Equilibrium (PE) states that after long periods of evolutionary quiescence, species evolution can take place in short time intervals, where sudden differentiation makes new species emerge and some species extinct. In this paper, we introduce and study the effect of punctuated equilibrium on two different asset exchange models: the yard sale model (YS, winner gets a random fraction of a poorer player's wealth) and the theft and fraud model (TF, winner gets a random fraction of the loser's wealth). The resulting wealth distribution is characterized using the Gini index. In order to do this, we consider PE as a perturbation with probability ρ of being applied. We compare the resulting values of the Gini index at different increasing values of ρ in both models. We found that in the case of the TF model, the Gini index reduces as the perturbation ρ increases, not showing dependence with the agents number. While for YS we observe a phase transition which happens around ρc = 0.79. For perturbations ρ increases (an extreme wealth condensation state), whereas for perturbations greater than or equal to ρc the Gini index becomes different to one, avoiding the system reaches this extreme state. We show that both simple exchange models coupled with PE dynamics give more realistic results. In particular for YS, we observe a power low decay of wealth distribution.
From innovation to diversification: a simple competitive model
Saracco, Fabio; Gabrielli, Andrea; Pietronero, Luciano
2015-01-01
Few attempts have been proposed in order to describe the statistical features and historical evolution of the export bipartite matrix countries/products. An important standpoint is the introduction of a products network, namely a hierarchical forest of products that models the formation and the evolution of commodities. In the present article, we propose a simple dynamical model where countries compete with each other to acquire the ability to produce and export new products. Countries will have two possibilities to expand their export: innovating, i.e. introducing new goods, namely new nodes in the product networks, or copying the productive process of others, i.e. occupying a node already present in the same network. In this way, the topology of the products network and the country-product matrix evolve simultaneously, driven by the countries push toward innovation.
A Simple Model for Identifying Critical Structures in Atrial Fibrillation
Christensen, Kim; Peters, Nicholas S
2014-01-01
Atrial fibrillation (AF) is the most common abnormal heart rhythm and the single biggest cause of stroke. Ablation, destroying regions of the atria, is applied largely empirically and can be curative but with a disappointing clinical success rate. We design a simple model of activation wavefront propagation on a structure mimicking the branching network architecture of heart muscle and show how AF emerges spontaneously as age-related parameters change. We identify regions responsible for the initiation and maintenance of AF, the ablation of which terminates AF. The simplicity of the model allows us to calculate analytically the risk of arrhythmia. This analytical result allows us to locate the transition in parameter space and highlights that the transition from regular to fibrillatory behaviour is a finite-size effect present in systems of any size. These clinically testable predictions might inform ablation therapies and arrhythmic risk assessment.
A simple model for doublet bands in doubly odd nuclei
Energy Technology Data Exchange (ETDEWEB)
Yoshinaga, N. [Saitama University, Department of Physics, Saitama City (Japan); Higashiyama, K. [Chiba Institute of Technology, Department of Physics, Narashino, Chiba (Japan); University of Tokyo, Department of Physics, Hongo, Tokyo (Japan)
2006-11-15
Nuclear structure of doublet bands in doubly odd nuclei with mass A {proportional_to} 130 is investigated within the framework of a simple model where the even-even core couples with a neutron and a proton in intruder orbitals through a quadrupole-quadrupole interaction. The model reproduces quite well the energy levels of doublet bands and electromagnetic transitions. The staggering of the ratios B(M1;I{yields}I-1)/B(E2;I{yields}I-2) of the yrast bands turns out to be described by the chopsticks-like motion of two angular momenta of the unpaired neutron and the unpaired proton when they are weakly coupled with the core. (orig.)
Fermionic dark matter in a simple t-channel model
Energy Technology Data Exchange (ETDEWEB)
Goyal, Ashok; Kumar, Mukesh [National Institute for Theoretical Physics, School of Physics and Mandelstam Institute for Theoretical Physics, University of the Witwatersrand, Johannesburg, Wits 2050 (South Africa)
2016-11-02
We consider a fermionic dark matter (DM) particle in renormalizable Standard Model (SM) gauge interactions in a simple t-channel model. The DM particle interactions with SM fermions is through the exchange of scalar and vector mediators which carry colour or lepton number. In the case of coloured mediators considered in this study, we find that if the DM is thermally produced and accounts for the observed relic density almost the entire parameter space is ruled out by the direct detection observations. The bounds from the monojet plus missing energy searches at the Large Hadron Collider are less stringent in this case. In contrast for the case of Majorana DM, we obtain strong bounds from the monojet searches which rule out DM particles of mass less than about a few hundred GeV for both the scalar and vector mediators.
Dynamical phase transition in a simple model of competing shops
Lambert, Gaultier; Bertin, Eric
2011-01-01
We consider a simple model in which a set of agents randomly visit one of two competing shops selling the same perishable products (typically food). The satisfaction of agents with respect to a given store is related to the freshness of the previously bought products. Agents then choose with a higher probability the store they are most satisfied with. Studying the model both through numerical simulations and mean-field analytical methods, we find a rich behaviour with continuous and discontinuous phase transitions between a symmetric phase where both stores maintain the same level of activity, and a phase with broken symmetry where one of the two shops attracts more customers than the other.
Simple computer model for the quantum Zeno effect
Wallace, D
2000-01-01
This paper presents a simple model for repeated measurement of a quantum system: the evolution of a free particle, simulated by discretising the particle's position. This model is easily simulated by computer and provides a useful arena to investigate the effects of measurement upon dynamics, in particular the slowing of evolution due to measurement (the `quantum Zeno effect'). The results of this simulation are discussed for two rather different sorts of measurement process, both of which are (simplified forms of) measurements used in previous simulations of position measurement. A number of interesting results due to measurement are found, and the investigation casts some light on previous disagreements about the presence or absence of the Zeno effect.
A Simple Singlet Fermionic Dark-Matter Model Revisited
Institute of Scientific and Technical Information of China (English)
QIN Hong-Yi; WANG Wen-Yu; XIONG Zhao-Hua
2011-01-01
We evaluate the spin-independent elastic dark matter-nucleon scattering cross section in the framework of the simple singlet fermionic dark matter extension of the standard model and constrain the model parameter space with the following considerations:(i) new dark matter measurement,in which,apart from WMAP and CDMS,the results from the XENON experiment are also used in constraining the model;(ii) new fitted value of the quark fractions in nucleons,in which the updated value of fTs from the recent lattice simulation is much smaller than the previous one and may reduce the scattering rate significantly;(iii) new dark matter annihilation channels,in which the scenario where top quark and Higgs pairs produced by dark matter annihilation was not included in the previous works.We find that unlike in the minimal supersymmetric standard model,the cross section is just reduced by a factor of about 1/4 and dark matter lighter than 100 GeV is not favored by the WMAP,CDMS and XENON experiments.It is well known that about 20％ of the energy density of the Universe[1] is composed of dark matter (DM).Probing the properties of DM and searching for DM candidates are the most important motivations for the research of new physics beyond the standard model (SM).%We evaluate the spin-independent elastic dark matter-nucleon scattering cross section in the framework of the simple singlet fermionic dark matter extension of the standard model and constrain the model parameter space with the following considerations: (I) new dark matter measurement, in which, apart from WMAP and CDMS, the results from the XENON experiment are also used in constraining the model; (ii) new fitted value of the quark fractions in nucleons, in which the updated value of fT8 from the recent lattice simulation is much smaller than the previous one and may reduce the scattering rate significantly; (Hi) new dark matter annihilation channels, in which the scenario where top quark and Higgs pairs produced by dark
SPUF - a simple polyurethane foam mass loss and response model.
Energy Technology Data Exchange (ETDEWEB)
Hobbs, Michael L.; Lemmon, Gordon H.
2003-07-01
A Simple PolyUrethane Foam (SPUF) mass loss and response model has been developed to predict the behavior of unconfined, rigid, closed-cell, polyurethane foam-filled systems exposed to fire-like heat fluxes. The model, developed for the B61 and W80-0/1 fireset foam, is based on a simple two-step mass loss mechanism using distributed reaction rates. The initial reaction step assumes that the foam degrades into a primary gas and a reactive solid. The reactive solid subsequently degrades into a secondary gas. The SPUF decomposition model was implemented into the finite element (FE) heat conduction codes COYOTE [1] and CALORE [2], which support chemical kinetics and dynamic enclosure radiation using 'element death.' A discretization bias correction model was parameterized using elements with characteristic lengths ranging from 1-mm to 1-cm. Bias corrected solutions using the SPUF response model with large elements gave essentially the same results as grid independent solutions using 100-{micro}m elements. The SPUF discretization bias correction model can be used with 2D regular quadrilateral elements, 2D paved quadrilateral elements, 2D triangular elements, 3D regular hexahedral elements, 3D paved hexahedral elements, and 3D tetrahedron elements. Various effects to efficiently recalculate view factors were studied -- the element aspect ratio, the element death criterion, and a 'zombie' criterion. Most of the solutions using irregular, large elements were in agreement with the 100-{micro}m grid-independent solutions. The discretization bias correction model did not perform as well when the element aspect ratio exceeded 5:1 and the heated surface was on the shorter side of the element. For validation, SPUF predictions using various sizes and types of elements were compared to component-scale experiments of foam cylinders that were heated with lamps. The SPUF predictions of the decomposition front locations were compared to the front locations
Simple model for multiple-choice collective decision making.
Lee, Ching Hua; Lucas, Andrew
2014-11-01
We describe a simple model of heterogeneous, interacting agents making decisions between n≥2 discrete choices. For a special class of interactions, our model is the mean field description of random field Potts-like models and is effectively solved by finding the extrema of the average energy E per agent. In these cases, by studying the propagation of decision changes via avalanches, we argue that macroscopic dynamics is well captured by a gradient flow along E. We focus on the permutation symmetric case, where all n choices are (on average) the same, and spontaneous symmetry breaking (SSB) arises purely from cooperative social interactions. As examples, we show that bimodal heterogeneity naturally provides a mechanism for the spontaneous formation of hierarchies between decisions and that SSB is a preferred instability to discontinuous phase transitions between two symmetric points. Beyond the mean field limit, exponentially many stable equilibria emerge when we place this model on a graph of finite mean degree. We conclude with speculation on decision making with persistent collective oscillations. Throughout the paper, we emphasize analogies between methods of solution to our model and common intuition from diverse areas of physics, including statistical physics and electromagnetism.
Fire, ice, water, and dirt: A simple climate model
Kroll, John
2017-07-01
A simple paleoclimate model was developed as a modeling exercise. The model is a lumped parameter system consisting of an ocean (water), land (dirt), glacier, and sea ice (ice) and driven by the sun (fire). In comparison with other such models, its uniqueness lies in its relative simplicity yet yielding good results. For nominal values of parameters, the system is very sensitive to small changes in the parameters, yielding equilibrium, steady oscillations, and catastrophes such as freezing or boiling oceans. However, stable solutions can be found, especially naturally oscillating solutions. For nominally realistic conditions, natural periods of order 100kyrs are obtained, and chaos ensues if the Milankovitch orbital forcing is applied. An analysis of a truncated system shows that the naturally oscillating solution is a limit cycle with the characteristics of a relaxation oscillation in the two major dependent variables, the ocean temperature and the glacier ice extent. The key to getting oscillations is having the effective emissivity decreasing with temperature and, at the same time, the effective ocean albedo decreases with increasing glacier extent. Results of the original model compare favorably to the proxy data for ice mass variation, but not for temperature variation. However, modifications to the effective emissivity and albedo can be made to yield much more realistic results. The primary conclusion is that the opinion of Saltzman [Clim. Dyn. 5, 67-78 (1990)] is plausible that the external Milankovitch orbital forcing is not sufficient to explain the dominant 100kyr period in the data.
BRS structure of simple model of cosmological constant and cosmology
Mori, Taisaku; Nitta, Daisuke; Nojiri, Shin'ichi
2017-07-01
In Mod. Phys. Lett. A 31, 1650213 (2016, 10.1142/S0217732316502138), Nojiri proposed a simple model in order to solve one of the problems related to the cosmological constant. The model is induced from a topological field theory, and the model has an infinite number of BRS symmetries. The BRS symmetries are, in general, spontaneously broken, however. We investigate the BRS symmetry in detail and show that there is one and only one BRS symmetry which is not broken, and the unitarity can be guaranteed. In the model, the quantum problem of the vacuum energy, which may be identified with the cosmological constant, reduces to the classical problem of the initial condition. We investigate the cosmology given by the model and specify the region of the initial conditions, which could be consistent with the evolution of the Universe. We also show that there is a stable solution describing the de Sitter space-time, which may explain the accelerating expansion in the current Universe.
Uranus evolution models with simple thermal boundary layers
Nettelmann, N; Fortney, J J; Hamel, S; Yellamilli, S; Bethkenhagen, M; Redmer, R
2016-01-01
The strikingly low luminosity of Uranus (Teff ~ Teq) constitutes a long-standing challenge to our understanding of Ice Giant planets. Here we present the first Uranus structure and evolution models that are constructed to agree with both the observed low luminosity and the gravity field data. Our models make use of modern ab initio equations of state at high pressures for the icy components water, methane, and ammonia. Proceeding step by step, we confirm that adiabatic models yield cooling times that are too long, even when uncertainties in the ice:rock ratio (I:R) are taken into account. We then argue that the transition between the ice/rock-rich interior and the H/He-rich outer envelope should be stably stratified. Therefore, we introduce a simple thermal boundary and adjust it to reproduce the low luminosity. Due to this thermal boundary, the deep interior of the Uranus models are up to 2--3 warmer than adiabatic models, necessitating the presence of rocks in the deep interior with a possible I:R of $1\\tim...
Simple models for quorum sensing: Nonlinear dynamical analysis
Chiang, Wei-Yin; Li, Yue-Xian; Lai, Pik-Yin
2011-10-01
Quorum sensing refers to the change in the cooperative behavior of a collection of elements in response to the change in their population size or density. This behavior can be observed in chemical and biological systems. These elements or cells are coupled via chemicals in the surrounding environment. Here we focus on the change of dynamical behavior, in particular from quiescent to oscillatory, as the cell population changes. For instance, the silent behavior of the elements can become oscillatory as the system concentration or population increases. In this work, two simple models are constructed that can produce the essential representative properties in quorum sensing. The first is an excitable or oscillatory phase model, which is probably the simplest model one can construct to describe quorum sensing. Using the mean-field approximation, the parameter regime for quorum sensing behavior can be identified, and analytical results for the detailed dynamical properties, including the phase diagrams, are obtained and verified numerically. The second model consists of FitzHugh-Nagumo elements coupled to the signaling chemicals in the environment. Nonlinear dynamical analysis of this mean-field model exhibits rich dynamical behaviors, such as infinite period bifurcation, supercritical Hopf, fold bifurcation, and subcritical Hopf bifurcations as the population parameter changes for different coupling strengths. Analytical result is obtained for the Hopf bifurcation phase boundary. Furthermore, two elements coupled via the environment and their synchronization behavior for these two models are also investigated. For both models, it is found that the onset of oscillations is accompanied by the synchronized dynamics of the two elements. Possible applications and extension of these models are also discussed.
Simple models for studying complex spatiotemporal patterns of animal behavior
Tyutyunov, Yuri V.; Titova, Lyudmila I.
2017-06-01
Minimal mathematical models able to explain complex patterns of animal behavior are essential parts of simulation systems describing large-scale spatiotemporal dynamics of trophic communities, particularly those with wide-ranging species, such as occur in pelagic environments. We present results obtained with three different modelling approaches: (i) an individual-based model of animal spatial behavior; (ii) a continuous taxis-diffusion-reaction system of partial-difference equations; (iii) a 'hybrid' approach combining the individual-based algorithm of organism movements with explicit description of decay and diffusion of the movement stimuli. Though the models are based on extremely simple rules, they all allow description of spatial movements of animals in a predator-prey system within a closed habitat, reproducing some typical patterns of the pursuit-evasion behavior observed in natural populations. In all three models, at each spatial position the animal movements are determined by local conditions only, so the pattern of collective behavior emerges due to self-organization. The movement velocities of animals are proportional to the density gradients of specific cues emitted by individuals of the antagonistic species (pheromones, exometabolites or mechanical waves of the media, e.g., sound). These cues play a role of taxis stimuli: prey attract predators, while predators repel prey. Depending on the nature and the properties of the movement stimulus we propose using either a simplified individual-based model, a continuous taxis pursuit-evasion system, or a little more detailed 'hybrid' approach that combines simulation of the individual movements with the continuous model describing diffusion and decay of the stimuli in an explicit way. These can be used to improve movement models for many species, including large marine predators.
Addor, Nans; Clark, Martyn P.; Mizukami, Naoki
2017-04-01
-HMS and the second group three models generated using FUSE. All models are driven by CMIP5 model runs bias-corrected and downscaled. We explore whether the range of outcomes projected by the first group can be captured by the second group, i.e. whether a flexible modeling framework like FUSE can replace a small ensemble of hydrological models typically used for impact modeling. We envision that flexible modeling frameworks will allow us to provide more reliable and more tractable estimates of the uncertainty in hydrological projections, and to progressively move toward large ensembles of hydrological models.
Wind Power Curve Modeling in Simple and Complex Terrain
Energy Technology Data Exchange (ETDEWEB)
Bulaevskaya, V. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Wharton, S. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Irons, Z. [Enel Green Power North America, Andover, MA (United States); Qualley, G. [Pentalum, Colleyville, TX (United States)
2015-02-09
Our previous work on wind power curve modeling using statistical models focused on a location with a moderately complex terrain in the Altamont Pass region in northern California (CA). The work described here is the follow-up to that work, but at a location with a simple terrain in northern Oklahoma (OK). The goal of the present analysis was to determine the gain in predictive ability afforded by adding information beyond the hub-height wind speed, such as wind speeds at other heights, as well as other atmospheric variables, to the power prediction model at this new location and compare the results to those obtained at the CA site in the previous study. While we reach some of the same conclusions at both sites, many results reported for the CA site do not hold at the OK site. In particular, using the entire vertical profile of wind speeds improves the accuracy of wind power prediction relative to using the hub-height wind speed alone at both sites. However, in contrast to the CA site, the rotor equivalent wind speed (REWS) performs almost as well as the entire profile at the OK site. Another difference is that at the CA site, adding wind veer as a predictor significantly improved the power prediction accuracy. The same was true for that site when air density was added to the model separately instead of using the standard air density adjustment. At the OK site, these additional variables result in no significant benefit for the prediction accuracy.
Prometheus payment model: application to hip and knee replacement surgery.
Rastogi, Amita; Mohr, Beth A; Williams, Jeffery O; Soobader, Mah-Jabeen; de Brantes, Francois
2009-10-01
The Prometheus Payment Model offers a potential solution to the failings of the current fee-for-service system and various forms of capitation. At the core of the Prometheus model are evidence-informed case rates (ECRs), which include a bundle of typical services that are informed by evidence and/or expert opinion as well as empirical data analysis, payment based on the severity of patients, and allowances for potentially avoidable complications (PACs) and other provider-specific variations in payer costs. We outline the methods and findings of the hip and knee arthroplasty ECRs with an emphasis on PACs. Of the 2076 commercially insured patients undergoing hip arthroplasty in our study, PAC costs totaled $7.8 million (14% of total costs; n = 699 index PAC stays). Similarly, PAC costs were $12.7 million (14% of total costs; n = 897 index PAC stays) for 3403 patients undergoing knee arthroplasty. By holding the providers clinically and financially responsible for PACs, and by segmenting and quantifying the type of PACs generated during and after the procedure, the Prometheus model creates an opportunity for providers to focus on the reduction of PACs, including readmissions, making the data actionable and turn the waste related to PAC costs into potential savings.
Simple mixing model for pressurized thermal shock applications
Energy Technology Data Exchange (ETDEWEB)
Chexal, B.; Chao, J.; Nickell, R.; Griesbach, T. (Electric Power Research Inst., Palo Alto, CA (USA))
1983-02-01
The phenomenon of fluid/thermal mixing in the cold leg and downcomer of a Pressurized Water Reactor (PWR) has been a critical issue related to the concern of pressurized thermal shock. The question of imperfect mixing arises when the possibility of cold emergency core cooling water contacting the vessel wall during an overcooling transient could produce thermal stresses large enough to initiate a flaw in a radiation embrittled vessel wall. The temperature of the fluid in contact with the vessel wall is crucial to a determination of vessel integrity since temperature affects both the stresses and the material toughness of the vessel material. A simple mixing model is described which was developed as part of the EPRI pressurized thermal shock program for evaluation of reactor vessel integrity.
Nonequilibrium Anderson model made simple with density functional theory
Kurth, S.; Stefanucci, G.
2016-12-01
The single-impurity Anderson model is studied within the i-DFT framework, a recently proposed extension of density functional theory (DFT) for the description of electron transport in the steady state. i-DFT is designed to give both the steady current and density at the impurity, and it requires the knowledge of the exchange-correlation (xc) bias and on-site potential (gate). In this work we construct an approximation for both quantities which is accurate in a wide range of temperatures, gates, and biases, thus providing a simple and unifying framework to calculate the differential conductance at negligible computational cost in different regimes. Our results mark a substantial advance for DFT and may inform the construction of functionals applicable to other correlated systems.
Simple brane-world inflationary models — An update
Okada, Nobuchika; Okada, Satomi
2016-05-01
In the light of the Planck 2015 results, we update simple inflationary models based on the quadratic, quartic, Higgs and Coleman-Weinberg potentials in the context of the Randall-Sundrum brane-world cosmology. Brane-world cosmological effect alters the inflationary predictions of the spectral index (ns) and the tensor-to-scalar ratio (r) from those obtained in the standard cosmology. In particular, the tensor-to-scalar ratio is enhanced in the presence of the 5th dimension. In order to maintain the consistency with the Planck 2015 results for the inflationary predictions in the standard cosmology, we find a lower bound on the five-dimensional Planck mass (M5). On the other hand, the inflationary predictions laying outside of the Planck allowed region can be pushed into the allowed region by the brane-world cosmological effect with a suitable choice of M5.
A Simple Hubbard Model for the Excited States of Dibenzoterrylene
Sadeq, Z S
2016-01-01
We use a simple Hubbard model to characterize the electronic excited states of the dibenzoterrylene (DBT) molecule; we compute the excited state transition energies and oscillator strengths from the ground state to several singlet excited states. We consider the lowest singlet and triplet states of the molecule, examine their wavefunctions, and compute the density correlation functions that describe these states. We find that the DBT ground state is mostly a closed shell singlet with very slight radical character. We predict a relatively small singlet-triplet splitting of 0.75 eV, which is less than the mid-sized -acenes but larger than literature predictions for this state; this is because the Hubbard interaction makes a very small correction to the singlet and triplet states.
Hopf bifurcation for simple food chain model with delay
Directory of Open Access Journals (Sweden)
Mario Cavani
2009-06-01
Full Text Available In this article we consider a chemostat-like model for a simple food chain where there is a well stirred nutrient substance that serves as food for a prey population of microorganisms, which in turn, is the food for a predator population of microorganisms. The nutrient-uptake of each microorganism is of Holling type I (or Lotka-Volterra form. We show the existence of a global attractor for solutions of this system. Also we show that the positive globally asymptotically stable equilibrium point of the system undergoes a Hopf bifurcation when the dynamics of the microorganisms at the bottom of the chain depends on the history of the prey population by means of a distributed delay that takes an average of the microorganism in the middle of the chain.
A model theoretic Baire category theorem for simple theories
Shami, Ziv
2009-01-01
We define the class of $\\tilde\\tau_{low}^f$-sets. This is a class of type-definable sets defined in terms of forking by low formulas. We prove a model theoretic Baire category theorem for $\\tilde\\tau_{low}^f$-sets in a countable simple theory in which the extension property is first-order and show some of its applications. A typical application is the following. Let $T$ be a countable theory with the wnfcp (weak nonfinite cover property) and assume for every non-algebraic $a$ there exists a non-algebraic $a'\\acl(a)$ such that $SU(a')<\\omega$. Then there exists a weakly-minimal formula with parameters.
A Simple Model for the Evolution of Evolution
Fussy, S; Schwabl, H; Fussy, Siegfried; Groessing, Gerhard; Schwabl, Herbert
1997-01-01
A simple model of macroevolution is proposed exhibiting both the property of punctuated equilibrium and the dynamics of potentialities for different species to evolve towards increasingly higher complexity. It is based on the phenomenon of "fractal evolution" which has been shown to constitute a fundamental property of nonlinear discretized systems with one memory- or random-based feedback loop. The latter involves a basic "cognitive" function of each species given by the power of distinction of states within some predefined resolution. The introduction of a realistic background noise limiting the range of the feedback operation yields a pattern signature in fitness space with a distribution of temporal boost/mutation distances according to a randomized devil's staircase function. Introducing a further level in the hierarchy of the system's rules, the possibility of an adaptive evolutionary change of the resolution itself is implemented, thereby providing a time-dependent measure of the species' cognitive abi...
Simple brane-world inflationary models: an update
Okada, Nobuchika
2015-01-01
In the light of the Planck 2015 results, we update simple inflationary models based on the quadratic, quartic, Higgs and Coleman-Weinberg potentials in the context of the Randall-Sundrum brane-world cosmology. Brane-world cosmological effect alters the inflationary predictions of the spectral index ($n_s$) and the tensor-to-scalar ratio ($r$) from those obtained in the standard cosmology. In particular, the tensor-to-scalar ratio is enhanced in the presence of the 5th dimension. In order to maintain the consistency with the Planck 2015 results for the inflationary predictions in the standard cosmology, we find a lower bound on the five-dimensional Planck mass. On the other hand, the inflationary predictions laying outside of the Planck allowed region can be pushed into the allowed region by the brane-world cosmological effect.
DEFF Research Database (Denmark)
Kristensen, Anders Ringgaard; Søllested, Thomas Algot
2004-01-01
that really uses all these methodological improvements. In this paper, the biological model describing the performance and feed intake of sows is presented. In particular, estimation of herd specific parameters is emphasized. The optimization model is described in a subsequent paper......Several replacement models have been presented in literature. In other applicational areas like dairy cow replacement, various methodological improvements like hierarchical Markov processes and Bayesian updating have been implemented, but not in sow models. Furthermore, there are methodological...... improvements like multi-level hierarchical Markov processes with decisions on multiple time scales, efficient methods for parameter estimations at herd level and standard software that has been hardly implemented at all in any replacement model. The aim of this study is to present a sow replacement model...
A simple physical model predicts small exon length variations.
Directory of Open Access Journals (Sweden)
2006-04-01
Full Text Available One of the most common splice variations are small exon length variations caused by the use of alternative donor or acceptor splice sites that are in very close proximity on the pre-mRNA. Among these, three-nucleotide variations at so-called NAGNAG tandem acceptor sites have recently attracted considerable attention, and it has been suggested that these variations are regulated and serve to fine-tune protein forms by the addition or removal of a single amino acid. In this paper we first show that in-frame exon length variations are generally overrepresented and that this overrepresentation can be quantitatively explained by the effect of nonsense-mediated decay. Our analysis allows us to estimate that about 50% of frame-shifted coding transcripts are targeted by nonsense-mediated decay. Second, we show that a simple physical model that assumes that the splicing machinery stochastically binds to nearby splice sites in proportion to the affinities of the sites correctly predicts the relative abundances of different small length variations at both boundaries. Finally, using the same simple physical model, we show that for NAGNAG sites, the difference in affinities of the neighboring sites for the splicing machinery accurately predicts whether splicing will occur only at the first site, splicing will occur only at the second site, or three-nucleotide splice variants are likely to occur. Our analysis thus suggests that small exon length variations are the result of stochastic binding of the spliceosome at neighboring splice sites. Small exon length variations occur when there are nearby alternative splice sites that have similar affinity for the splicing machinery.
A SIMPLE EXPERIMENTAL MODEL OF HEAT SHOCK RESPONSE IN RATS
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Tufi Neder Meyer
1998-10-01
Full Text Available Objective: To obtain a simple model for the elicitation of the heat shock response in rats. Design: Laboratory study. Setting: University research laboratories. Sample: Seventy-nine adult male albino rats (weight range 200 g to 570 g. Procedures: Exposure to heat stress by heating animals in a warm bath for 5 min after their rectal temperatures reached 107.60 F (420 C. Liver and lung samples were collected for heat-shock protein 70 (HSP70 detection (Western analysis. Results: Western analysis was positive for HSP70 in the liver and in the lungs of heated animals. There was a temporal correlation between heating and HSP70 detection: it was strongest 1 day after heating and reduced afterwards. No heated animals died. Conclusion: These data show that heating rats in a warm (45o C bath, according to parameters set in this model, elicits efficiently the heat shock response.OBJETIVO: Obter um modelo simples para tentar esclarecer a resposta ao choque térmico em ratos. LOCAL: Laboratório de pesquisa da Universidade. MÉTODO: Amostra: 79 ratos albinos, adultos, entre 200g a 570g. Procedimentos: Exposição ao calor, em banho quente, por 5 minutos, após a temperatura retal chegar a 42 graus centigrados. Biópsias de fígado e pulmão foram obtidas para detectar a proteina 70 (HSP 70, pelo "Western blot". RESULTADOS: As análises foram positivas nos animais aquecidos, com uma correlação entre aquecimento e constatação da HSP 70. Foi mais elevada no primeiro dia e não houve óbitos nos animais aquecidos. CONCLUSÃO: Os ratos aquecidos a 45 graus centígrados respondem eficientemente ao choque térmico.
Test Driven Development: Lessons from a Simple Scientific Model
Clune, T. L.; Kuo, K.
2010-12-01
In the commercial software industry, unit testing frameworks have emerged as a disruptive technology that has permanently altered the process by which software is developed. Unit testing frameworks significantly reduce traditional barriers, both practical and psychological, to creating and executing tests that verify software implementations. A new development paradigm, known as test driven development (TDD), has emerged from unit testing practices, in which low-level tests (i.e. unit tests) are created by developers prior to implementing new pieces of code. Although somewhat counter-intuitive, this approach actually improves developer productivity. In addition to reducing the average time for detecting software defects (bugs), the requirement to provide procedure interfaces that enable testing frequently leads to superior design decisions. Although TDD is widely accepted in many software domains, its applicability to scientific modeling still warrants reasonable skepticism. While the technique is clearly relevant for infrastructure layers of scientific models such as the Earth System Modeling Framework (ESMF), numerical and scientific components pose a number of challenges to TDD that are not often encountered in commercial software. Nonetheless, our experience leads us to believe that the technique has great potential not only for developer productivity, but also as a tool for understanding and documenting the basic scientific assumptions upon which our models are implemented. We will provide a brief introduction to test driven development and then discuss our experience in using TDD to implement a relatively simple numerical model that simulates the growth of snowflakes. Many of the lessons learned are directly applicable to larger scientific models.
A simple, mass balance model of carbon flow in a controlled ecological life support system
Garland, Jay L.
1989-01-01
Internal cycling of chemical elements is a fundamental aspect of a Controlled Ecological Life Support System (CELSS). Mathematical models are useful tools for evaluating fluxes and reservoirs of elements associated with potential CELSS configurations. A simple mass balance model of carbon flow in CELSS was developed based on data from the CELSS Breadboard project at Kennedy Space Center. All carbon reservoirs and fluxes were calculated based on steady state conditions and modelled using linear, donor-controlled transfer coefficients. The linear expression of photosynthetic flux was replaced with Michaelis-Menten kinetics based on dynamical analysis of the model which found that the latter produced more adequate model output. Sensitivity analysis of the model indicated that accurate determination of the maximum rate of gross primary production is critical to the development of an accurate model of carbon flow. Atmospheric carbon dioxide was particularly sensitive to changes in photosynthetic rate. The small reservoir of CO2 relative to large CO2 fluxes increases the potential for volatility in CO2 concentration. Feedback control mechanisms regulating CO2 concentration will probably be necessary in a CELSS to reduce this system instability.
Simple Model for Identifying Critical Regions in Atrial Fibrillation
Peters, Nicholas S.
2015-01-01
Atrial fibrillation (AF) is the most common abnormal heart rhythm and the single biggest cause of stroke. Ablation, destroying regions of the atria, is applied largely empirically and can be curative but with a disappointing clinical success rate. We design a simple model of activation wave front propagation on an anisotropic structure mimicking the branching network of heart muscle cells. This integration of phenomenological dynamics and pertinent structure shows how AF emerges spontaneously when the transverse cell-to-cell coupling decreases, as occurs with age, beyond a threshold value. We identify critical regions responsible for the initiation and maintenance of AF, the ablation of which terminates AF. The simplicity of the model allows us to calculate analytically the risk of arrhythmia and express the threshold value of transversal cell-to-cell coupling as a function of the model parameters. This threshold value decreases with increasing refractory period by reducing the number of critical regions which can initiate and sustain microreentrant circuits. These biologically testable predictions might inform ablation therapies and arrhythmic risk assessment. PMID:25635565
Simple Electromagnetic Modeling of Small Airplanes: Neural Network Approach
Directory of Open Access Journals (Sweden)
P. Tobola
2009-04-01
Full Text Available The paper deals with the development of simple electromagnetic models of small airplanes, which can contain composite materials in their construction. Electromagnetic waves can penetrate through the surface of the aircraft due to the specific electromagnetic properties of the composite materials, which can increase the intensity of fields inside the airplane and can negatively influence the functionality of the sensitive avionics. The airplane is simulated by two parallel dielectric layers (the left-hand side wall and the right-hand side wall of the airplane. The layers are put into a rectangular metallic waveguide terminated by the absorber in order to simulate the illumination of the airplane by the external wave (both of the harmonic nature and pulse one. Thanks to the simplicity of the model, the parametric analysis can be performed, and the results can be used in order to train an artificial neural network. The trained networks excel in further reduction of CPU-time demands of an airplane modeling.
A Simple Disk Wind Model for Broad Absorption Line Quasars
Higginbottom, N; Long, K S; Sim, S A; Matthews, J H
2013-01-01
Approximately 20% of quasi-stellar objects (QSOs) exhibit broad, blue-shifted absorption lines in their ultraviolet spectra. Such features provide clear evidence for significant outflows from these systems, most likely in the form of accretion disk winds. These winds may represent the "quasar" mode of feedback that is often invoked in galaxy formation/evolution models, and they are also key to unification scenarios for active galactic nuclei (AGN) and QSOs. To test these ideas, we construct a simple benchmark model of an equatorial, biconical accretion disk wind in a QSO and use a Monte Carlo ionization/radiative transfer code to calculate the ultraviolet spectra as a function of viewing angle. We find that for plausible outflow parameters, sightlines looking directly into the wind cone do produce broad, blue-shifted absorption features in the transitions typically seen in broad absorption line QSOs. However, our benchmark model is intrinsically X-ray weak in order to prevent overionization of the outflow, an...
Simple models for estimating dementia severity using machine learning.
Shankle, W R; Mania, S; Dick, M B; Pazzani, M J
1998-01-01
Estimating dementia severity using the Clinical Dementia Rating (CDR) Scale is a two-stage process that currently is costly and impractical in community settings, and at best has an interrater reliability of 80%. Because staging of dementia severity is economically and clinically important, we used Machine Learning (ML) algorithms with an Electronic Medical Record (EMR) to identify simpler models for estimating total CDR scores. Compared to a gold standard, which required 34 attributes to derive total CDR scores, ML algorithms identified models with as few as seven attributes. The classification accuracy varied with the algorithm used with naïve Bayes giving the highest. (76%) The mildly demented severity class was the only one with significantly reduced accuracy (59%). If one groups the severity classes into normal, very mild-to-mildly demented, and moderate-to-severely demented, then classification accuracies are clinically acceptable (85%). These simple models can be used in community settings where it is currently not possible to estimate dementia severity due to time and cost constraints.
Insights from simple models for surface states in nanostructures
Boykin, Timothy B.; Klimeck, Gerhard
2017-03-01
Surface passivation is of great technological importance due to the increasing miniaturisation of electronic devices. It has been known for many years that under certain conditions surface states can form; when they do so in a quantum well (QW) the result is an unbound (i.e., evanescent) state in the QW. Such surface states are generally undesirable, so a good physical understanding of them is important. A simple single-p-orbital valence band model is used with two types of surface passivation to examine surface states in a QW: (1) an energy upshift added to the terminal atoms; and (2) explicit passivation by an s-orbital on each end of the QW. These models show these unbound/evanescent QW states can occur in both models; that in them the wavefunction is bound to the terminal atoms; and that the existence of these states is connected to the effective valence-band offset between the terminal atoms and the bulk QW.
A simple model of optimal population coding for sensory systems.
Doi, Eizaburo; Lewicki, Michael S
2014-08-01
A fundamental task of a sensory system is to infer information about the environment. It has long been suggested that an important goal of the first stage of this process is to encode the raw sensory signal efficiently by reducing its redundancy in the neural representation. Some redundancy, however, would be expected because it can provide robustness to noise inherent in the system. Encoding the raw sensory signal itself is also problematic, because it contains distortion and noise. The optimal solution would be constrained further by limited biological resources. Here, we analyze a simple theoretical model that incorporates these key aspects of sensory coding, and apply it to conditions in the retina. The model specifies the optimal way to incorporate redundancy in a population of noisy neurons, while also optimally compensating for sensory distortion and noise. Importantly, it allows an arbitrary input-to-output cell ratio between sensory units (photoreceptors) and encoding units (retinal ganglion cells), providing predictions of retinal codes at different eccentricities. Compared to earlier models based on redundancy reduction, the proposed model conveys more information about the original signal. Interestingly, redundancy reduction can be near-optimal when the number of encoding units is limited, such as in the peripheral retina. We show that there exist multiple, equally-optimal solutions whose receptive field structure and organization vary significantly. Among these, the one which maximizes the spatial locality of the computation, but not the sparsity of either synaptic weights or neural responses, is consistent with known basic properties of retinal receptive fields. The model further predicts that receptive field structure changes less with light adaptation at higher input-to-output cell ratios, such as in the periphery.
Selection of an appropriately simple storm runoff model
Directory of Open Access Journals (Sweden)
A. I. J. M. van Dijk
2009-09-01
Full Text Available Alternative conceptual storm runoff models, including several published ones, were evaluated against storm flow time series for 260 catchments in Australia (23–1902 km^{2}. The original daily streamflow data was separated into baseflow and storm flow components and from these, event rainfall and storm flow totals were estimated. For each tested model structure, the number of free parameters was reduced in stages. The appropriate balance between simplicity and explanatory power was decided based on Aikake's Final Prediction Error Criterion and evidence of parameter equivalence. The majority of catchments showed storm recession half-times in the order of a day, with more rapid drainage in dry catchments. Overland and channel travel time did not appear to be an important driver of storm flow recession. A storm runoff model with two free parameters (one related to storm event size, the other to antecedent baseflow and a fixed initial loss of 12 mm provided the optimal model structure. The optimal model had some features similar to the Soil Conservation Service Curve Number technique, but performed an average 12 to 19% better. The non-linear relationship between event rainfall and event runoff may be associated with saturated area expansion during storms and/or the relationship between storm event size and peak rainfall intensity. Antecedent baseflow was a strong predictor of runoff response. A simple conceptual relationship between groundwater storage and saturated catchment area proved adequate and produced realistic estimates of saturated area of <0.1% for the driest and >5% for the wettest catchments.
Continuum fusion solutions for replacement target models in electro-optic detection.
Schaum, Alan
2014-05-01
The additive target model is used routinely in the statistical detection of opaque targets, despite its phenomenological inaccuracy. The more appropriate replacement target model is seldom used, because the standard method for producing a detection algorithm from it proves to be intractable, unless narrow restrictions are imposed. Now, the recently developed continuum fusion (CF) methodology allows an expanded solution set to the general replacement target problem. It also provides a mechanism for producing approximate solutions for the standard approach. We illustrate the principles of CF by using them to generate both types of answers for the correct detection model.
Spin decoherence in electron storage rings. More from a simple model
Energy Technology Data Exchange (ETDEWEB)
Barber, D.P. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Heinemann, K. [The Univ. of New Mexico, Albuquerque, NM (United States). Dept. of Mathematics and Statistics
2015-06-15
This is an addendum to the paper ''Some models of spin coherence and decoherence in storage rings'' by one of the authors (K. Heinemann, DESY Report 97-166 (1997)), in which spin diffusion in simple electron storage rings is studied. In particular, we illustrate in a compact way, namely that the exact formalism of this article delivers a rate of depolarisation which can differ from that obtained by the conventional treatments of spin diffusion which rely on the use of the derivative ∂n/∂η. As a vehicle we consider a ring with a Siberian Snake and electron polarisation in the plane of the ring. For this simple setup with its one-dimensional spin motion, we avoid having to deal directly with the Bloch equation for the polarisation density. Our treatment, which is deliberately pedagogical, shows that the use of ∂n/∂η provides a very good approximation to the rate of spin depolarisation in the model considered. But it then shows that the exact rate of depolarisation can be obtained by replacing ∂n/∂η by another derivative, while giving a heuristic justification for the new derivative.
A Simple Hydraulic Analog Model of Oxidative Phosphorylation.
Willis, Wayne T; Jackman, Matthew R; Messer, Jeffrey I; Kuzmiak-Glancy, Sarah; Glancy, Brian
2016-06-01
Mitochondrial oxidative phosphorylation is the primary source of cellular energy transduction in mammals. This energy conversion involves dozens of enzymatic reactions, energetic intermediates, and the dynamic interactions among them. With the goal of providing greater insight into the complex thermodynamics and kinetics ("thermokinetics") of mitochondrial energy transduction, a simple hydraulic analog model of oxidative phosphorylation is presented. In the hydraulic model, water tanks represent the forward and back "pressures" exerted by thermodynamic driving forces: the matrix redox potential (ΔGredox), the electrochemical potential for protons across the mitochondrial inner membrane (ΔGH), and the free energy of adenosine 5'-triphosphate (ATP) (ΔGATP). Net water flow proceeds from tanks with higher water pressure to tanks with lower pressure through "enzyme pipes" whose diameters represent the conductances (effective activities) of the proteins that catalyze the energy transfer. These enzyme pipes include the reactions of dehydrogenase enzymes, the electron transport chain (ETC), and the combined action of ATP synthase plus the ATP-adenosine 5'-diphosphate exchanger that spans the inner membrane. In addition, reactive oxygen species production is included in the model as a leak that is driven out of the ETC pipe by high pressure (high ΔGredox) and a proton leak dependent on the ΔGH for both its driving force and the conductance of the leak pathway. Model water pressures and flows are shown to simulate thermodynamic forces and metabolic fluxes that have been experimentally observed in mammalian skeletal muscle in response to acute exercise, chronic endurance training, and reduced substrate availability, as well as account for the thermokinetic behavior of mitochondria from fast- and slow-twitch skeletal muscle and the metabolic capacitance of the creatine kinase reaction.
A simple model of the anthropogenically forced CO2 cycle
Directory of Open Access Journals (Sweden)
W. Weber
2015-10-01
Full Text Available From basic physical assumptions we derive a simple linear model of the global CO2 cycle without free parameters. It yields excellent agreement with the observations reported by the carbon dioxide information analysis center (CDIAC as time series of atmospheric CO2 growth, of sinks in the ocean and of absorption by the biosphere. The agreement extends from the year 1850 until present (2013. Based on anthropogenic CO2 emission scenarios until 2150, future atmospheric CO2 concentrations are calculated. As the model shows, and depending on the emission scenario, the airborne fraction of CO2 begins to decrease in the year ~ 2050 and becomes negative at the latest in ~ 2130. At the same time the concentration of the atmospheric CO2 will reach a maximum between ~ 500 and ~ 900 ppm. As a consequence, increasing anthropogenic CO2 emissions will make the ocean and the biosphere the main reservoirs of anthropogenic CO2 in the long run. Latest in about 150 years, anthropogenic CO2 emission will no longer increase the CO2 content of the atmosphere.
A simple model of the chaotic eccentricity of Mercury
Boué, Gwenaël; Farago, François
2012-01-01
Mercury's eccentricity is chaotic and can increase so much that collisions with Venus or the Sun become possible (Laskar, 1989, 1990, 1994, 2008, Batygin & Laughlin, 2008, Laskar & Gastineau, 2009). This chaotic behavior results from an intricate network of secular resonances, but in this paper, we show that a simple integrable model with only one degree of freedom is actually able to reproduce the large variations in Mercury's eccentricity, with the correct amplitude and timescale. We show that this behavior occurs in the vicinity of the separatrices of the resonance g1-g5 between the precession frequencies of Mercury and Jupiter. However, the main contribution does not come from the direct interaction between these two planets. It is due to the excitation of Venus' orbit at Jupiter's precession frequency g5. We use a multipolar model that is not expanded with respect to Mercury's eccentricity, but because of the proximity of Mercury and Venus, the Hamiltonian is expanded up to order 20 and more in t...
A simple model for the magnetoelectric interaction in multiferroics
Calderon, C. J.; Barberis, G. E.
2010-03-01
The (anti)ferromagnetic and ferroelectric transitions in some magnetoelectric compounds seem to be strongly correlated. Even for systems that do not show spontaneous ferroelectricity such as the LiMPO4 (M = Mn, Fe, Co, Ni) compounds, the coupling between magnetic and electric degrees of freedom is evident experimentally. Here, we present a simple numerical calculation to simulate this coupling that leads to the two transitions. We assume a magnetic sublattice consisting of magnetic moments coupled to a separated non-magnetic sublattice consisting of classical electric dipoles. The coupling between them is realized using the phenomenological spin - lattice Hamiltonian method, where the magnetic moment in each site of the lattice is coupled to strains, and the minimum of energy obtained through the Monte Carlo method. In the simplest version, the magnetic system is 2D Ising (anti)ferromagnetic lattice, with nearest neighbors interactions only, and the electric moments are non-coupled, permanent moments. Within this approximation, the second order magnetic transition induces ferroelectricity in the electric dipoles. We show that these calculations can be extended to other magnetic systems, (x-y model and 3D Heisenberg) with coupling to the electric moments will, so they can be applied to model realistic systems such as the olivines mentioned above.
Fast and simple model for atmospheric radiative transfer
Directory of Open Access Journals (Sweden)
F. C. Seidel
2010-05-01
Full Text Available Radiative transfer models (RTMs are of utmost importance for quantitative remote sensing, especially for compensating atmospheric perturbation. A persistent trade-off exists between approaches that prefer accuracy at the cost of computational complexity, versus those favouring simplicity at the cost of reduced accuracy. We propose an approach in the latter category, using analytical equations, parameterizations and a correction factor to efficiently estimate the effect of molecular multiple scattering. We discuss the approximations together with an analysis of the resulting performance and accuracy. The proposed Simple Model for Atmospheric Radiative Transfer (SMART decreases the calculation time by a factor of more than 25 in comparison to the benchmark RTM~6S on the same infrastructure. The approximative computation of the atmospheric reflectance factor by SMART has an uncertainty ranging from about 5% to 10% for nadir spaceborne and airborne observational conditions. The combination of a large solar zenith angle (SZA with high aerosol optical depth (AOD at low wavelengths lead to uncertainties of up to 15%. SMART can be used to simulate the hemispherical conical reflectance factor (HCRF for spaceborne and airborne sensors, as well as for the retrieval of columnar AOD.
A simple model of the anthropogenically forced CO2 cycle
Weber, W.; Lüdecke, H.-J.; Weiss, C. O.
2015-10-01
From basic physical assumptions we derive a simple linear model of the global CO2 cycle without free parameters. It yields excellent agreement with the observations reported by the carbon dioxide information analysis center (CDIAC) as time series of atmospheric CO2 growth, of sinks in the ocean and of absorption by the biosphere. The agreement extends from the year 1850 until present (2013). Based on anthropogenic CO2 emission scenarios until 2150, future atmospheric CO2 concentrations are calculated. As the model shows, and depending on the emission scenario, the airborne fraction of CO2 begins to decrease in the year ~ 2050 and becomes negative at the latest in ~ 2130. At the same time the concentration of the atmospheric CO2 will reach a maximum between ~ 500 and ~ 900 ppm. As a consequence, increasing anthropogenic CO2 emissions will make the ocean and the biosphere the main reservoirs of anthropogenic CO2 in the long run. Latest in about 150 years, anthropogenic CO2 emission will no longer increase the CO2 content of the atmosphere.
Linking Simple Economic Theory Models and the Cointegrated Vector AutoRegressive Model
DEFF Research Database (Denmark)
Møller, Niels Framroze
This paper attempts to clarify the connection between simple economic theory models and the approach of the Cointegrated Vector-Auto-Regressive model (CVAR). By considering (stylized) examples of simple static equilibrium models, it is illustrated in detail, how the theoretical model and its stru....... Further fundamental extensions and advances to more sophisticated theory models, such as those related to dynamics and expectations (in the structural relations) are left for future papers......This paper attempts to clarify the connection between simple economic theory models and the approach of the Cointegrated Vector-Auto-Regressive model (CVAR). By considering (stylized) examples of simple static equilibrium models, it is illustrated in detail, how the theoretical model and its......, it is demonstrated how other controversial hypotheses such as Rational Expectations can be formulated directly as restrictions on the CVAR-parameters. A simple example of a "Neoclassical synthetic" AS-AD model is also formulated. Finally, the partial- general equilibrium distinction is related to the CVAR as well...
A simple disc wind model for broad absorption line quasars
Higginbottom, N.; Knigge, C.; Long, K. S.; Sim, S. A.; Matthews, J. H.
2013-12-01
Approximately 20 per cent of quasi-stellar objects (QSOs) exhibit broad, blue-shifted absorption lines in their ultraviolet spectra. Such features provide clear evidence for significant outflows from these systems, most likely in the form of accretion disc winds. These winds may represent the `quasar' mode of feedback that is often invoked in galaxy formation/evolution models, and they are also key to unification scenarios for active galactic nuclei (AGN) and QSOs. To test these ideas, we construct a simple benchmark model of an equatorial, biconical accretion disc wind in a QSO and use a Monte Carlo ionization/radiative transfer code to calculate the ultraviolet spectra as a function of viewing angle. We find that for plausible outflow parameters, sightlines looking directly into the wind cone do produce broad, blue-shifted absorption features in the transitions typically seen in broad absorption line (BAL) QSOs. However, our benchmark model is intrinsically X-ray weak in order to prevent overionization of the outflow, and the wind does not yet produce collisionally excited line emission at the level observed in non-BAL QSOs. As a first step towards addressing these shortcomings, we discuss the sensitivity of our results to changes in the assumed X-ray luminosity and mass-loss rate, Ṁwind. In the context of our adopted geometry, Ṁwind ˜ Ṁacc is required in order to produce significant BAL features. The kinetic luminosity and momentum carried by such outflows would be sufficient to provide significant feedback.
Simple-Minded Models of Condensed Matter Systems.
Lammert, Paul Edward
understand the occurence of superconductivity in these compounds at unexpectedly high temperatures. Chapter 4 explores the question of whether the unusual molecular character of the fullerenes allows the fundamentally repulsive Coulomb interaction between electrons to give rise to an effective attraction near the Fermi surface, leading to a superconducting instability. Although such an effect was demonstrated in a perturbative Hubbard model calculation by Chakravarty et al., its origin and the significance of exotic correlation effects, such as spin-charge separation, in bringing it about remained obscure. A diagrammatic analysis is undertaken to elucidate these issues. The Hubbard model for pi electrons on a buckyball is an extreme simplification. A more sophisticated model which contains the dynamic metallic screening in a simple but qualitatively correct fashion is studied in Chapter 5. It is found that in low-order perturbation theory, the values of adjustable parameters required to produce an attractive Coulomb pseudopotential (mu^* < 0) are not greatly different than those for the Hubbard model. Chapter 6 examines the effects of (carbon) isotopic disorder on critical temperature shifts in the doped fullerenes, in an attempt to determine whether the electronic pairing scheme is able to explain the anomalous T_ {rm c} shifts which have been experimentally observed for intermediate substitution. Isotopic disorder leads to anisotropic changes in electronic hopping within a buckyball, slightly altering the binding energy. Thus, while isotopic disorder does tend to suppress T _{rm c} within this model, the effect is too slight to account for the experimental anomalies. (Abstract shortened by UMI.).
Simple models of two-dimensional information sources and codes
DEFF Research Database (Denmark)
Justesen, Jørn; Shtarkov, Y. M.
1998-01-01
We consider discrete random fields which have simple descriptions of rows and columns. We present constructions which combine high entropy with simple means of generating the fields and analyzing the probability distribution. Hidden state Markov sources are an essential tool in the construction...
Simple integer recourse models : convexity and convex approximations
Klein Haneveld, W.K.; Stougie, L.; van der Vlerk, M.H.
We consider the objective function of a simple recourse problem with fixed technology matrix and integer second-stage variables. Separability due to the simple recourse structure allows to study a one-dimensional version instead. Based on an explicit formula for the objective function, we derive a
Simple Integer Recourse Models : Convexity and Convex Approximations
Klein Haneveld, Willem K.; Stougie, L; van der Vlerk, Maarten H.
2004-01-01
We consider the objective function of a simple recourse problem with fixed technology matrix and integer second-stage variables. Separability due to the simple recourse structure allows to study a one-dimensional version instead. Based on an explicit formula for the objective function, we derive a
Multimedia Modeling of engineered Nanoparticles with SimpleBox4Nano: Model Definition and Evaluation
Meesters, J.; Koelmans, A.A.; Quik, J.T.K.; Hendriks, A.J.; Meent, van de D.
2014-01-01
Screening level models for environmental assessment of engineered nanoparticles (ENP) are not generally available. Here we present SimpleBox for Nano (SB4N) as the first model of this type, motivate its validity and evaluate it by comparisons with a known material flow model. SB4N expresses ENP tran
Multimedia Modeling of engineered Nanoparticles with SimpleBox4Nano: Model Definition and Evaluation
Meesters, J.; Koelmans, A.A.; Quik, J.T.K.; Hendriks, A.J.; Meent, van de D.
2014-01-01
Screening level models for environmental assessment of engineered nanoparticles (ENP) are not generally available. Here we present SimpleBox for Nano (SB4N) as the first model of this type, motivate its validity and evaluate it by comparisons with a known material flow model. SB4N expresses ENP
Simple Queueing Model Applied to the City of Portland
Simon, Patrice M.; Esser, Jörg; Nagel, Kai
We use a simple traffic micro-simulation model based on queueing dynamics as introduced by Gawron [IJMPC, 9(3):393, 1998] in order to simulate traffic in Portland/Oregon. Links have a flow capacity, that is, they do not release more vehicles per second than is possible according to their capacity. This leads to queue built-up if demand exceeds capacity. Links also have a storage capacity, which means that once a link is full, vehicles that want to enter the link need to wait. This leads to queue spill-back through the network. The model is compatible with route-plan-based approaches such as TRANSIMS, where each vehicle attempts to follow its pre-computed path. Yet, both the data requirements and the computational requirements are considerably lower than for the full TRANSIMS microsimulation. Indeed, the model uses standard emme/2 network data, and runs about eight times faster than real time with more than 100 000 vehicles simultaneously in the simulation on a single Pentium-type CPU. We derive the model's fundamental diagrams and explain it. The simulation is used to simulate traffic on the emme/2 network of the Portland (Oregon) metropolitan region (20 000 links). Demand is generated by a simplified home-to-work destination assignment which generates about half a million trips for the morning peak. Route assignment is done by iterative feedback between micro-simulation and router. An iterative solution of the route assignment for the above problem can be achieved within about half a day of computing time on a desktop workstation. We compare results with field data and with results of traditional assignment runs by the Portland Metropolitan Planning Organization. Thus, with a model such as this one, it is possible to use a dynamic, activities-based approach to transportation simulation (such as in TRANSIMS) with affordable data and hardware. This should enable systematic research about the coupling of demand generation, route assignment, and micro
Fluctuations, response, and resonances in a simple atmospheric model
Gritsun, Andrey; Lucarini, Valerio
2017-06-01
We study the response of a simple quasi-geostrophic barotropic model of the atmosphere to various classes of perturbations affecting its forcing and its dissipation using the formalism of the Ruelle response theory. We investigate the geometry of such perturbations by constructing the covariant Lyapunov vectors of the unperturbed system and discover in one specific case-orographic forcing-a substantial projection of the forcing onto the stable directions of the flow. This results into a resonant response shaped as a Rossby-like wave that has no resemblance to the unforced variability in the same range of spatial and temporal scales. Such a climatic surprise corresponds to a violation of the fluctuation-dissipation theorem, in agreement with the basic tenets of nonequilibrium statistical mechanics. The resonance can be attributed to a specific group of rarely visited unstable periodic orbits of the unperturbed system. Our results reinforce the idea of using basic methods of nonequilibrium statistical mechanics and high-dimensional chaotic dynamical systems to approach the problem of understanding climate dynamics.
Research Techniques Made Simple: Skin Carcinogenesis Models: Xenotransplantation Techniques.
Mollo, Maria Rosaria; Antonini, Dario; Cirillo, Luisa; Missero, Caterina
2016-02-01
Xenotransplantation is a widely used technique to test the tumorigenic potential of human cells in vivo using immunodeficient mice. Here we describe basic technologies and recent advances in xenotransplantation applied to study squamous cell carcinomas (SCCs) of the skin. SCC cells isolated from tumors can either be cultured to generate a cell line or injected directly into mice. Several immunodeficient mouse models are available for selection based on the experimental design and the type of tumorigenicity assay. Subcutaneous injection is the most widely used technique for xenotransplantation because it involves a simple procedure allowing the use of a large number of cells, although it may not mimic the original tumor environment. SCC cell injections at the epidermal-to-dermal junction or grafting of organotypic cultures containing human stroma have also been used to more closely resemble the tumor environment. Mixing of SCC cells with cancer-associated fibroblasts can allow the study of their interaction and reciprocal influence, which can be followed in real time by intradermal ear injection using conventional fluorescent microscopy. In this article, we will review recent advances in xenotransplantation technologies applied to study behavior of SCC cells and their interaction with the tumor environment in vivo.
A Simple Family of Models for Eccentric Keplerian Fluid Disks
Statler, T S
2001-01-01
In order to be in a long-lived configuration, the density in a fluid disk should be constant along streamlines to prevent compressional (PdV) work from being done cyclically around every orbit. In a pure Kepler potential, flow along aligned, elliptical streamlines of constant eccentricity will satisfy this condition. For most density profiles, differential precession driven by the pressure gradient will destroy the alignment; however, in the razor-thin approximation there is a family of simple equilibria in which the precession frequency is the same at all radii. These disks may therefore be long-lived at significant eccentricities. The density can be made axisymmetric as r goes to 0, while maintaining the precession rate, by relaxing the requirement of constancy along streamlines in an arbitrarily small transition region near the center. In the limit of small eccentricity, the models can be seen as acoustically perturbed axisymmetric disks, and the precession rate is shown to agree with linear theory. The pe...
Fluctuations, Response, and Resonances in a Simple Atmospheric Model
Gritsun, Andrey
2016-01-01
We study the response of a simple quasi-geostrophic barotropic model of the atmosphere to various classes of perturbations affecting its forcing and its dissipation using the formalism of the Ruelle response theory. We investigate the geometry of such perturbations using the covariant Lyapunov vectors on the unperturbed system and discover in one specific case - orographic forcing - a substantial projection of the perturbation onto the stable directions of the flow. As a result, we find a clear violation of the fluctuation-dissipation theorem, in agreement with the basic tenets of nonequilibrium statistical mechanics. This results into a very strong response in the form of a forced Rossby-like wave that has no resemblance to the natural variability in the same range of spatial and temporal scales. We further analyze such a feature and discover it can be interpreted as resonant response to a specific group of rarely visited unstable periodic orbits of the unperturbed system. Our results reinforce the idea of u...
An independent pair-link model of simple fluids
Bonneville, Richard
2016-01-01
A new approach to thermodynamics of simple fluids is presented. The partition function is first expressed in the reciprocal space, it is argued that the links (p,q) between 2 molecules can reasonably in the thermodynamical limit be considered as a set nearly independent objects characterized by the dynamical variables . It is then possible to derive an expression of the pair correlation function. The results, which are independent of the exact shape of the intermolecular potential, are applied to the simple case of hard sphere fluids.
Lin, Yi-Chung; Haftka, Raphael T; Queipo, Nestor V; Fregly, Benjamin J
2009-04-01
Computational speed is a major limiting factor for performing design sensitivity and optimization studies of total knee replacements. Much of this limitation arises from extensive geometry calculations required by contact analyses. This study presents a novel surrogate contact modeling approach to address this limitation. The approach involves fitting contact forces from a computationally expensive contact model (e.g., a finite element model) as a function of the relative pose between the contacting bodies. Because contact forces are much more sensitive to displacements in some directions than others, standard surrogate sampling and modeling techniques do not work well, necessitating the development of special techniques for contact problems. We present a computational evaluation and practical application of the approach using dynamic wear simulation of a total knee replacement constrained to planar motion in a Stanmore machine. The sample points needed for surrogate model fitting were generated by an elastic foundation (EF) contact model. For the computational evaluation, we performed nine different dynamic wear simulations with both the surrogate contact model and the EF contact model. In all cases, the surrogate contact model accurately reproduced the contact force, motion, and wear volume results from the EF model, with computation time being reduced from 13 min to 13 s. For the practical application, we performed a series of Monte Carlo analyses to determine the sensitivity of predicted wear volume to Stanmore machine setup issues. Wear volume was highly sensitive to small variations in motion and load inputs, especially femoral flexion angle, but not to small variations in component placements. Computational speed was reduced from an estimated 230 h to 4 h per analysis. Surrogate contact modeling can significantly improve the computational speed of dynamic contact and wear simulations of total knee replacements and is appropriate for use in design sensitivity
A modeling paradigm for interdisciplinary water resources modeling: Simple Script Wrappers (SSW)
Steward, David R.; Bulatewicz, Tom; Aistrup, Joseph A.; Andresen, Daniel; Bernard, Eric A.; Kulcsar, Laszlo; Peterson, Jeffrey M.; Staggenborg, Scott A.; Welch, Stephen M.
2014-05-01
Holistic understanding of a water resources system requires tools capable of model integration. This team has developed an adaptation of the OpenMI (Open Modelling Interface) that allows easy interactions across the data passed between models. Capabilities have been developed to allow programs written in common languages such as matlab, python and scilab to share their data with other programs and accept other program's data. We call this interface the Simple Script Wrapper (SSW). An implementation of SSW is shown that integrates groundwater, economic, and agricultural models in the High Plains region of Kansas. Output from these models illustrates the interdisciplinary discovery facilitated through use of SSW implemented models. Reference: Bulatewicz, T., A. Allen, J.M. Peterson, S. Staggenborg, S.M. Welch, and D.R. Steward, The Simple Script Wrapper for OpenMI: Enabling interdisciplinary modeling studies, Environmental Modelling & Software, 39, 283-294, 2013. http://dx.doi.org/10.1016/j.envsoft.2012.07.006 http://code.google.com/p/simple-script-wrapper/
Gauge Boson Mass Without a Higgs Field A Simple Model
Nicholson, A F; Nicholson, Angus F.; Kennedy, Dallas C.
1997-01-01
A simple, anomaly-free chiral gauge theory can be perturbatively quantized and renormalized in such a way as to generate fermion and gauge boson masses. This development exploits certain freedoms inherent in choosing the unperturbed Lagrangian and in the renormalization procedure. Apart from its intrinsic interest, such a mechanism might be employed in electroweak gauge theory to generate fermion and gauge boson masses without a Higgs sector.
Development and experimental validation of a finite element model of total ankle replacement.
Terrier, Alexandre; Larrea, Xabier; Guerdat, Jonas; Crevoisier, Xavier
2014-02-07
Total ankle replacement remains a less satisfactory solution compared to other joint replacements. The goal of this study was to develop and validate a finite element model of total ankle replacement, for future testing of hypotheses related to clinical issues. To validate the finite element model, an experimental setup was specifically developed and applied on 8 cadaveric tibias. A non-cemented press fit tibial component of a mobile bearing prosthesis was inserted into the tibias. Two extreme anterior and posterior positions of the mobile bearing insert were considered, as well as a centered one. An axial force of 2kN was applied for each insert position. Strains were measured on the bone surface using digital image correlation. Tibias were CT scanned before implantation, after implantation, and after mechanical tests and removal of the prosthesis. The finite element model replicated the experimental setup. The first CT was used to build the geometry and evaluate the mechanical properties of the tibias. The second CT was used to set the implant position. The third CT was used to assess the bone-implant interface conditions. The coefficient of determination (R-squared) between the measured and predicted strains was 0.91. Predicted bone strains were maximal around the implant keel, especially at the anterior and posterior ends. The finite element model presented here is validated for future tests using more physiological loading conditions.
Insights: Simple Models for Teaching Equilibrium and Le Chatelier's Principle.
Russell, Joan M.
1988-01-01
Presents three models that have been effective for teaching chemical equilibrium and Le Chatelier's principle: (1) the liquid transfer model, (2) the fish model, and (3) the teeter-totter model. Explains each model and its relation to Le Chatelier's principle. (MVL)
Ellimoottil, Chad; Ryan, Andrew M.; Hou, Hechuan; Dupree, James M.; Hallstrom, Brian; Miller, David C.
2017-01-01
Importance Under the Comprehensive Care for Joint Replacement (CJR) model, hospitals are held accountable for nearly all Medicare payments that occur during the initial hospitalization through 90-days post-discharge (i.e., episode of care). It is unknown whether unrelated expenditures resulting from this “broad” episode definition will impact participating hospital’s average 90-day episode payments. Objective To compare the CJR program’s broad episode definition to a clinically-narrow episode definition Design We identified Medicare claims for patients in Michigan who underwent joint replacement from 2011 through 2013. Using specifications from the CJR model and the clinically-narrow Hospital Compare payment measure, we constructed episodes of care and calculated 90-day episode payments. We then compared hospitals’ average 90-day episode payments using the two episode definitions and fit linear regression models to understand whether payment differences were associated with specific hospital characteristics (average CMS-HCC risk score, rural hospital status, joint replacement volume, percentage of Medicaid discharges, teaching hospital status, number of beds, percentage of joint replacements performed on African American patients and median income of the hospital’s county). Setting All Michigan hospitals located in metropolitan statistical areas Participants Medicare beneficiaries Main Outcome and Measure(s) The correlation and difference between average 90-day episode payments using the broad CJR model episode definition and the clinically-narrow Hospital Compare episode definition. Results We identified 23,251 joint replacement episodes. 90-day episode payments using the broad CJR episode definition ranged from $17,349 to $29,465 (mean: $22,122, standard deviation: $2,600). Episode payments were slightly lower (mean: $21,670) when the Hospital Compare episode definition was used. Both methods were strongly correlated (r=0.99, p<0.001). The average
2016-01-01
Camera traps are used to estimate densities or abundances using capture-recapture and, more recently, random encounter models (REMs). We deploy REMs to describe an invasive-native species replacement process, and to demonstrate their wider application beyond abundance estimation. The Irish hare Lepus timidus hibernicus is a high priority endemic of conservation concern. It is threatened by an expanding population of non-native, European hares L. europaeus, an invasive species of global import...
Model calculations of the relative effects of CFCs and their replacements on stratospheric ozone
Fisher, Donald A.; Hales, Charles H.; Filkin, David L.; Ko, Malcolm K. W.; Sze, N. Dak
1990-01-01
Because chlorine has been linked to the destruction of stratospheric ozone, the use of many fully halogenated compounds, such as the chlorofluorocarbons CFC-11 and -12, is restricted by international agreement. Hydrohalocarbons are under intensive development as replacements for CFCs. Because they contain hydrogen, these gases are susceptible to tropospheric destruction which significantly shortens their atmospheric lifetimes,. Model calculations show that chlorine-containing hydrohalocarbons have less effect on ozone, by an order of magnitude, than their regulated counterparts.
Keegan, Ronan M; Bibby, Jaclyn; Thomas, Jens; Xu, Dong; Zhang, Yang; Mayans, Olga; Winn, Martyn D; Rigden, Daniel J
2015-02-01
AMPLE clusters and truncates ab initio protein structure predictions, producing search models for molecular replacement. Here, an interesting degree of complementarity is shown between targets solved using the different ab initio modelling programs QUARK and ROSETTA. Search models derived from either program collectively solve almost all of the all-helical targets in the test set. Initial solutions produced by Phaser after only 5 min perform surprisingly well, improving the prospects for in situ structure solution by AMPLE during synchrotron visits. Taken together, the results show the potential for AMPLE to run more quickly and successfully solve more targets than previously suspected.
Computing the Electrokinetic Response with Simple Models via Eigenvalue Decomposition
Kuhlman, K. L.; Malama, B.
2010-12-01
The efficient solution of coupled hydrogeophysical problems both numerically and analytically is important to their use in parameter estimation. We present a general approach for decoupling the governing equations for groundwater flow and the associated electrokinetic problem. The approach can use either a symbolic or numerical eigenvector decomposition of the matrix that arises when writing the two equations in vector form. The two coupled problems, once uncoupled, can then be solved using any existing approaches for the simple non-coupled component problems. Solutions can be either analytic or numerical in nature with the effective parameters being computed in the decomposition. The final solution, in terms of the physical potentials of interest, is computed through a simple matrix multiplication. We solve the fully coupled electrokinetic problem (water flow driving electrical flow and electrical flow driving water flow) for a single layer using the Theis solution, and for multilayer problems using MODFLOW. The approach is quite general, with the main limitation being a required symmetry between the coupled processes in their differential equation (e.g., both processes must be governed by the diffusion equation). The solution obtained with this approach is shown to agree with that obtained by Malama et al. (2009). Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000
Knock Prediction Using a Simple Model for Ignition Delay
Kalghatgi, Gautam
2016-04-05
An earlier paper has shown the ability to predict the phasing of knock onset in a gasoline PFI engine using a simple ignition delay equation for an appropriate surrogate fuel made up of toluene and PRF (TPRF). The applicability of this approach is confirmed in this paper in a different engine using five different fuels of differing RON, sensitivity, and composition - including ethanol blends. An Arrhenius type equation with a pressure correction for ignition delay can be found from interpolation of previously published data for any gasoline if its RON and sensitivity are known. Then, if the pressure and temperature in the unburned gas can be estimated or measured, the Livengood-Wu integral can be estimated as a function of crank angle to predict the occurrence of knock. Experiments in a single cylinder DISI engine over a wide operating range confirm that this simple approach can predict knock very accurately. The data presented should enable engineers to study knock or other auto-ignition phenomena e.g. in premixed compression ignition (PCI) engines without explicit chemical kinetic calculations. © Copyright 2016 SAE International.
Building Mathematical Models of Simple Harmonic and Damped Motion.
Edwards, Thomas
1995-01-01
By developing a sequence of mathematical models of harmonic motion, shows that mathematical models are not right or wrong, but instead are better or poorer representations of the problem situation. (MKR)
A simple numerical model of a geometrically nonlinear Timoshenko beam
Keijdener, C.; Metrikine, A.
2015-01-01
In the original problem for which this model was developed, onedimensional flexible objects interact through a non-linear contact model. Due to the non-linear nature of the contact model, a numerical time-domain approach was adopted. One of the goals was to see if the coupling between axial and tran
Effect of Replacing Beef Fat with Chicken Skin on Some Properties of Model System Chicken Emulsions
Directory of Open Access Journals (Sweden)
Aslı Zungur
2015-12-01
Full Text Available Model system chicken emulsions were prepared by replacing 5, 10, 15 and 20 % beef fat with chicken skin. Moisture, protein, fat, ash and pH were determined in raw and heat processed emulsions. Emulsion samples were evaluated for cooking characteristics, TBA values and colour parameters (L*, a*, b*. Addition of chicken skin decreased fat content and increased moisture and protein content of emulsion samples. Chicken skin replacement significantly increased water holding capacity and cooking yield and decreased fluid release. Increasing chicken skin in formulation increased a* and b* values of emulsion samples. Therefore, adding of chicken skin instead of beef fat is useful in improving technological quality and producing low fat formulation.
A simple model of trees for unicellular maps
Chapuy, Guillaume; Fusy, Eric
2012-01-01
We consider unicellular maps, or polygon gluings, of fixed genus. A few years ago the first author gave a recursive bijection transforming unicellular maps into trees, explaining the presence of Catalan numbers in counting formulas for these objects. In this paper, we give another bijection that explicitly describes the "recursive part" of the first bijection. As a result we obtain a very simple description of unicellular maps as pairs made by a plane tree and a permutation-like structure. All the previously known formulas follow as an immediate corollary or easy exercise, thus giving a bijective proof for each of them, in a unified way. For some of these formulas, this is the first bijective proof, e.g. the Harer-Zagier recurrence formula, or the Lehman-Walsh/Goupil-Schaeffer formulas. Thanks to previous work of the second author this also leads us to a new expression for Stanley character polynomials, which evaluate irreducible characters of the symmetric group.
Anharmonic effects in simple physical models: introducing undergraduates to nonlinearity
Christian, J. M.
2017-09-01
Given the pervasive character of nonlinearity throughout the physical universe, a case is made for introducing undergraduate students to its consequences and signatures earlier rather than later. The dynamics of two well-known systems—a spring and a pendulum—are reviewed when the standard textbook linearising assumptions are relaxed. Some qualitative effects of nonlinearity can be anticipated from symmetry (e.g., inspection of potential energy functions), and further physical insight gained by applying a simple successive-approximation method that might be taught in parallel with courses on classical mechanics, ordinary differential equations, and computational physics. We conclude with a survey of how these ideas have been deployed on programmes at a UK university.
Denitrification in the root zone using a simple empirical model SimDen
DEFF Research Database (Denmark)
Vinther, Finn Pilgaard
2006-01-01
Only by knowing soil type and amount of nitrogen applied, an estimate of the annual denitrification can be obtained with the simple empirical model SimDen.......Only by knowing soil type and amount of nitrogen applied, an estimate of the annual denitrification can be obtained with the simple empirical model SimDen....
A simple model for sizing stand alone photovoltaic systems
Energy Technology Data Exchange (ETDEWEB)
Sidrach-de-Cardona, M. [Departamento Fisica Aplicada II, ETSI Informatica, Universidad de Malaga, 29071 Malaga (Spain); Mora Lopez, Ll. [Departamento Lenguajes y C. Computacion, ETSI Informatica, Universidad de Malaga, 29071 Malaga (Spain)
1998-08-24
We consider a general model for sizing a stand-alone photovoltaic system, using as energy input data the information available in any radiation atlas. The parameters of the model are estimated by multivariate linear regression. The results obtained from a numerical sizing method were used as initial input data to fit the model. The expression proposed allows us to determine the photovoltaic array size, with a coefficient of determination ranging from 0.94 to 0.98. System parameters and mean monthly values for daily global radiation on the solar modules surface are taken as independent variables in the model. It is also shown that the proposed model can be used with the same accuracy for other locations not considered in the estimation of the model
Simple model for fault-charged hydrothermal systems
Energy Technology Data Exchange (ETDEWEB)
Bodvarsson, G.S.; Miller, C.W.; Benson, S.M.
1981-06-01
A two-dimensional transient model of fault-charged hydrothermal systems has been developed. The model can be used to analyze temperature data from fault-charged hydrothermal systems, estimate the recharge rate from the fault, and determine how long the system has been under natural development. The model can also be used for theoretical studies of the development of fault-controlled hydrothermal systems. The model has been tentatively applied to the low-temperature hydrothermal system at Susanville, California. A resonable match was obtained with the observed temperature data, and a hot water recharge rate of 9 x 10{sup -6} m{sup 3}s/m was calculated.
Surface pressure model for simple delta wings at high angles of attack
Indian Academy of Sciences (India)
A A Pashilkar
2001-12-01
A new aerodynamic modelling approach is proposed for the longitudinal static characteristics of a simple delta wing. It captures the static variation of normal force and pitching moment characteristics throughout the angle of attack range. The pressure model is based on parametrizing the surface pressure distribution on a simple delta wing. The model is then extended to a wing/body combination where body-alone data are also available. The model is shown to be simple and consistent with experimental data. The pressure model can be used as a ﬁrst approximation for the load estimation on the delta wing at high angles of attack.
A numerical assessment of simple airblast models of impact airbursts
Collins, Gareth S.; Lynch, Elliot; McAdam, Ronan; Davison, Thomas M.
2017-08-01
Asteroids and comets 10-100 m in size that collide with Earth disrupt dramatically in the atmosphere with an explosive transfer of energy, caused by extreme air drag. Such airbursts produce a strong blastwave that radiates from the meteoroid's trajectory and can cause damage on the surface. An established technique for predicting airburst blastwave damage is to treat the airburst as a static source of energy and to extrapolate empirical results of nuclear explosion tests using an energy-based scaling approach. Here we compare this approach to two more complex models using the iSALE shock physics code. We consider a moving-source airburst model where the meteoroid's energy is partitioned as two-thirds internal energy and one-third kinetic energy at the burst altitude, and a model in which energy is deposited into the atmosphere along the meteoroid's trajectory based on the pancake model of meteoroid disruption. To justify use of the pancake model, we show that it provides a good fit to the inferred energy release of the 2013 Chelyabinsk fireball. Predicted overpressures from all three models are broadly consistent at radial distances from ground zero that exceed three times the burst height. At smaller radial distances, the moving-source model predicts overpressures two times greater than the static-source model, whereas the cylindrical line-source model based on the pancake model predicts overpressures two times lower than the static-source model. Given other uncertainties associated with airblast damage predictions, the static-source approach provides an adequate approximation of the azimuthally averaged airblast for probabilistic hazard assessment.
Describing dengue epidemics: Insights from simple mechanistic models
Aguiar, Maíra; Stollenwerk, Nico; Kooi, Bob W.
2012-09-01
We present a set of nested models to be applied to dengue fever epidemiology. We perform a qualitative study in order to show how much complexity we really need to add into epidemiological models to be able to describe the fluctuations observed in empirical dengue hemorrhagic fever incidence data offering a promising perspective on inference of parameter values from dengue case notifications.
Simple model of self-organized biological evolution
de Boer, Jan; Derrida, Bernard; Flyvbjerg, Henrik; Jackson, Andrew D.; Wettig, Tilo
1994-08-01
We give an exact solution of a recently proposed self-organized critical model of biological evolution. We show that the model has a power law distribution of durations of coevolutionary ``avalanches'' with a mean field exponent 3/2. We also calculate analytically the finite size effects which cut off this power law at times of the order of the system size.
A New Interpretation of Spontaneous Sway Measures Based on a Simple Model of Human Postural Control
National Research Council Canada - National Science Library
Maurer, Christoph; Peterka, Robert J
...) traces that closely resemble physiologically measured COP functions can be produced by an appropriate selection of model parameters in a simple feedback model of the human postural control system...
Simple Mathematical Models Do Not Accurately Predict Early SIV Dynamics
Directory of Open Access Journals (Sweden)
Cecilia Noecker
2015-03-01
Full Text Available Upon infection of a new host, human immunodeficiency virus (HIV replicates in the mucosal tissues and is generally undetectable in circulation for 1–2 weeks post-infection. Several interventions against HIV including vaccines and antiretroviral prophylaxis target virus replication at this earliest stage of infection. Mathematical models have been used to understand how HIV spreads from mucosal tissues systemically and what impact vaccination and/or antiretroviral prophylaxis has on viral eradication. Because predictions of such models have been rarely compared to experimental data, it remains unclear which processes included in these models are critical for predicting early HIV dynamics. Here we modified the “standard” mathematical model of HIV infection to include two populations of infected cells: cells that are actively producing the virus and cells that are transitioning into virus production mode. We evaluated the effects of several poorly known parameters on infection outcomes in this model and compared model predictions to experimental data on infection of non-human primates with variable doses of simian immunodifficiency virus (SIV. First, we found that the mode of virus production by infected cells (budding vs. bursting has a minimal impact on the early virus dynamics for a wide range of model parameters, as long as the parameters are constrained to provide the observed rate of SIV load increase in the blood of infected animals. Interestingly and in contrast with previous results, we found that the bursting mode of virus production generally results in a higher probability of viral extinction than the budding mode of virus production. Second, this mathematical model was not able to accurately describe the change in experimentally determined probability of host infection with increasing viral doses. Third and finally, the model was also unable to accurately explain the decline in the time to virus detection with increasing viral
A simple model of global cascades on random networks
Watts, Duncan J.
2002-04-01
The origin of large but rare cascades that are triggered by small initial shocks is a phenomenon that manifests itself as diversely as cultural fads, collective action, the diffusion of norms and innovations, and cascading failures in infrastructure and organizational networks. This paper presents a possible explanation of this phenomenon in terms of a sparse, random network of interacting agents whose decisions are determined by the actions of their neighbors according to a simple threshold rule. Two regimes are identified in which the network is susceptible to very large cascadesherein called global cascadesthat occur very rarely. When cascade propagation is limited by the connectivity of the network, a power law distribution of cascade sizes is observed, analogous to the cluster size distribution in standard percolation theory and avalanches in self-organized criticality. But when the network is highly connected, cascade propagation is limited instead by the local stability of the nodes themselves, and the size distribution of cascades is bimodal, implying a more extreme kind of instability that is correspondingly harder to anticipate. In the first regime, where the distribution of network neighbors is highly skewed, it is found that the most connected nodes are far more likely than average nodes to trigger cascades, but not in the second regime. Finally, it is shown that heterogeneity plays an ambiguous role in determining a system's stability: increasingly heterogeneous thresholds make the system more vulnerable to global cascades; but an increasingly heterogeneous degree distribution makes it less vulnerable.
Digital clocks: simple Boolean models can quantitatively describe circadian systems.
Akman, Ozgur E; Watterson, Steven; Parton, Andrew; Binns, Nigel; Millar, Andrew J; Ghazal, Peter
2012-09-07
The gene networks that comprise the circadian clock modulate biological function across a range of scales, from gene expression to performance and adaptive behaviour. The clock functions by generating endogenous rhythms that can be entrained to the external 24-h day-night cycle, enabling organisms to optimally time biochemical processes relative to dawn and dusk. In recent years, computational models based on differential equations have become useful tools for dissecting and quantifying the complex regulatory relationships underlying the clock's oscillatory dynamics. However, optimizing the large parameter sets characteristic of these models places intense demands on both computational and experimental resources, limiting the scope of in silico studies. Here, we develop an approach based on Boolean logic that dramatically reduces the parametrization, making the state and parameter spaces finite and tractable. We introduce efficient methods for fitting Boolean models to molecular data, successfully demonstrating their application to synthetic time courses generated by a number of established clock models, as well as experimental expression levels measured using luciferase imaging. Our results indicate that despite their relative simplicity, logic models can (i) simulate circadian oscillations with the correct, experimentally observed phase relationships among genes and (ii) flexibly entrain to light stimuli, reproducing the complex responses to variations in daylength generated by more detailed differential equation formulations. Our work also demonstrates that logic models have sufficient predictive power to identify optimal regulatory structures from experimental data. By presenting the first Boolean models of circadian circuits together with general techniques for their optimization, we hope to establish a new framework for the systematic modelling of more complex clocks, as well as other circuits with different qualitative dynamics. In particular, we anticipate
(Relatively) Simple Models of Flow in Complex Terrain
Taylor, Peter; Weng, Wensong; Salmon, Jim
2013-04-01
The term, "complex terrain" includes both topography and variations in surface roughness and thermal properties. The scales that are affected can differ and there are some advantages to modeling them separately. In studies of flow in complex terrain we have developed 2 D and 3 D models of atmospheric PBL boundary layer flow over roughness changes, appropriate for longer fetches than most existing models. These "internal boundary layers" are especially important for understanding and predicting wind speed variations with distance from shorelines, an important factor for wind farms around, and potentially in, the Great Lakes. The models can also form a base for studying the wakes behind woodlots and wind turbines. Some sample calculations of wind speed evolution over water and the reduced wind speeds behind an isolated woodlot, represented simply in terms of an increase in surface roughness, will be presented. Note that these models can also include thermal effects and non-neutral stratification. We can use the model to deal with 3-D roughness variations and will describe applications to both on-shore and off-shore situations around the Great Lakes. In particular we will show typical results for hub height winds and indicate the length of over-water fetch needed to get the full benefit of siting turbines over water. The linear Mixed Spectral Finite-Difference (MSFD) and non-linear (NLMSFD) models for surface boundary-layer flow over complex terrain have been extended to planetary boundary-layer flow over topography This allows for their use for larger scale regions and increased heights. The models have been applied to successfully simulate the Askervein hill experimental case and we will show examples of applications to more complex terrain, typical of some Canadian wind farms. Output from the model can be used as an alternative to MS-Micro, WAsP or other CFD calculations of topographic impacts for input to wind farm design software.
As Simple as Possible, But No Simpler: A Gentle Introduction to Simulation Modeling
2006-12-01
SIMPLE AS POSSIBLE, BUT NO SIMPLER: A GENTLE INTRODUCTION TO SIMULATION MODELING Paul J. Sánchez Operations Research Department Naval Postgraduate...Simple as Possible, But No Simpler: A Gentle Introduction to Simulation Modeling 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6...to mess things up. Simulation modeling involves a longer chain of inference than does analytical modeling, which is why we generally would prefer to
A simple forecasting model for industrial electric energy consumption
Energy Technology Data Exchange (ETDEWEB)
Al-Shehri, Abdallah [King Fahd Univ. of Petroleum and Minerals, Electrical Engineering Dept., Dhaharan (Saudi Arabia)
2000-07-01
A single-equation model is developed and employed for forecasting industrial electric energy consumption in the Saudi Consolidated Electric Company in the Eastern Province (SCECO-East) of Saudi Arabia. SCECO-East's industrial loads are composed mainly of oil-related and petrochemical industries. Even though industrial loads are generally characterised by their steadiness, the harsh weather conditions of the Eastern Province cause great variations in the industrial electric energy consumption at SCECO-East. The developed model reflects these variations. MATLAB is used to solve the model. (Author)
A simple model of money, credit and aggregate demand
Spencer Dale; Andrew Haldane
1993-01-01
The paper presents a theoretical model of how banks and the non-bank private sector respond to changes in monetary policy. Unlike many textbook models in which banks play no active role, the banking sector is recognised here as playing a key part in transmitting changes in monetary policy to the real economy. In a conventional IS/LM model, the impact of a change in monetary policy arises from the response of expenditure to changes in interest rates (the "monetary" channel). If, however, bank ...
Generic Graph Grammar: A Simple Grammar for Generic Procedural Modelling
DEFF Research Database (Denmark)
Christiansen, Asger Nyman; Bærentzen, Jakob Andreas
2012-01-01
in a directed cyclic graph. Furthermore, the basic productions are chosen such that Generic Graph Grammar seamlessly combines the capabilities of L-systems to imitate biological growth (to model trees, animals, etc.) and those of split grammars to design structured objects (chairs, houses, etc.). This results......Methods for procedural modelling tend to be designed either for organic objects, which are described well by skeletal structures, or for man-made objects, which are described well by surface primitives. Procedural methods, which allow for modelling of both kinds of objects, are few and usually...
Mathematical modeling of the evolution of a simple biological system
Digital Repository Service at National Institute of Oceanography (India)
Gonsalves, M.J.B.D.; Neetu, S.; Krishnan, K.P.; Attri, K.; LokaBharathi, P.A.
phytoplankton and bacteria compete for a given concentration of nitrate. Further experiments in chemostats or mesocosms would help understand and the growth kinetics or interactions in nature and add to the model. Acknowledgements The authors are grateful...
A simple model for the design of vertical tube absorbers
Energy Technology Data Exchange (ETDEWEB)
Patnaik, V.; Perez-Blanco, H. [Pennsylvania State Univ., University Park, PA (United States); Ryan, W.A. [Gas Research Inst., Chicago, IL (United States)
1993-08-01
The absorption of water vapor in aqueous solutions of lithium bromide is modelled for a falling-film, vertical-tube absorber. The model is based on the solution of three ordinary differential equations to calculate solution bulk and interface concentration and temperature distributions and the coolant temperature distribution. The heat and mass transfer coefficients employed in the equations are extracted from the literature. In this way, the model incorporates recent information on wavy-laminar flows. Under certain conditions, the solution exhibits instabilities in the entrance region of the absorber tube, which are corrected by the introduction of a dampening factor incorporating relevant thermophysical properties. The usefulness of the model for generating absorber performance charts is demonstrated.
There Is No Simple Model of the Plasma Membrane Organization
Bernardino de la Serna, Jorge; Schütz, Gerhard J.; Eggeling, Christian; Cebecauer, Marek
2016-01-01
Ever since technologies enabled the characterization of eukaryotic plasma membranes, heterogeneities in the distributions of its constituents were observed. Over the years this led to the proposal of various models describing the plasma membrane organization such as lipid shells, picket-and-fences, lipid rafts, or protein islands, as addressed in numerous publications and reviews. Instead of emphasizing on one model we in this review give a brief overview over current models and highlight how current experimental work in one or the other way do not support the existence of a single overarching model. Instead, we highlight the vast variety of membrane properties and components, their influences and impacts. We believe that highlighting such controversial discoveries will stimulate unbiased research on plasma membrane organization and functionality, leading to a better understanding of this essential cellular structure. PMID:27747212
A Simple Analytic ICP Model and Comparison to Experiment
Juliano, Daniel R.; Hayden, Douglas B.; Ruzic, David N.
1996-10-01
An analytic model is developed for a cylindrically symmetric inductively coupled plasma system in order to find the electron temperature and density distribution. Boltzmann's equation is solved by a computer code using a 2-term spherical harmonic expansion. Analytic results are compared to experimental measurements made with a Langmuir probe. The apparatus is a magnetron system (magnetron system donated by MRC) with an RF coil or other ionization source inserted between the target and substrate. Far from the target, the resulting plasma is dominated by this ionization source, so the plasma at the magnetron target is not accounted for in the analytic model. In the model, electric and magnetic fields from the RF coil are found as a function of position and the power deposition profile is calculated. Insights gained from this model have been used to guide research efforts in ionizing the sputter flux in the magnetron.
A Simple Structure Model for Enzyme Production by Phanerochaete chrysosporium
Institute of Scientific and Technical Information of China (English)
岑沛霖; 郑重鸣; FOOYinDin; JefferyPhilipObbard; 林建平
2003-01-01
In order to understand the behavior of ligninolytic enzyme production by white rot fungi Phanerochaete chrysosporium, study on time courses and a mathematical model for the production of lignin peroxidase (LiP) and manganese peroxidase (MnP) of the fungi was undertaken. Based on the Monod-Jacob operon model, the ligninolytic enzyme would be synthesized in the absence of a related repressor. The repressor is assumed to be active in the presence of ammonia nitrogen, and as combined as co-repressor, it causes the inhibition of enzyme synthesis. The model can explain the mechanism of extracellular ligninolytic enzyme production by white rot fungi. The results,as predicted by the model, correspond closely to those observed in experimental studies. In addition, some light is also shed on unmeasured variables, such as the concentrations of repressor and mRNA that are related to the enzyme synthesis.
Fast and simple model for atmospheric radiative transfer
Seidel, F.C.; Kokhanovsky, A.A.; Schaepman, M.E.
2010-01-01
Radiative transfer models (RTMs) are of utmost importance for quantitative remote sensing, especially for compensating atmospheric perturbation. A persistent trade-off exists between approaches that prefer accuracy at the cost of computational complexity, versus those favouring simplicity at the
There is no simple model of the plasma membrane organisation
Directory of Open Access Journals (Sweden)
Jorge Bernardino De La Serna
2016-09-01
Full Text Available Ever since technologies enabled the characterisation of eukaryotic plasma membranes, heterogeneities in the distributions of its constituents were observed. Over the years this led to the proposal of various models describing the plasma membrane organisation such as lipid shells, picket-and-fences, lipid rafts, or protein islands, as addressed in numerous publications and reviews. Instead of emphasising on one model we in this review give a brief overview over current models and highlight how current experimental work in one or the other way do not support the existence of a single overarching model. Instead, we highlight the vast variety of membrane properties and components, their influences and impacts. We believe that highlighting such controversial discoveries will stimulate unbiased research on plasma membrane organisation and functionality, leading to a better understanding of this essential cellular structure.
Simple model of self-organized biological evolution
Energy Technology Data Exchange (ETDEWEB)
de Boer, J.; Derrida, B.; Flyvbjerg, H.; Jackson, A.D.; Wettig, T. (Department of Physics, State University of New York at Stony Brook, Stony Brook, New York 11794-3800 (United States) The Isaac Newton Institute for Mathematical Sciences, 20 Clarkson Road, Cambridge, CB4 0EH (United Kingdom) Laboratoire de Physique Statistique, Ecole Normale Superieure, 24 rue Lhomond, F-75005 Paris (France) Service de Physique Theorique, Centre de Etudes Nucleaires de Saclay, F-91191, Gif-Sur-Yvette (France) CONNECT, The Niels Bohr Institute, Blegdamsvej 17, DK-2100 Copenhagen (Denmark))
1994-08-08
We give an exact solution of a recently proposed self-organized critical model of biological evolution. We show that the model has a power law distribution of durations of coevolutionary avalanches'' with a mean field exponent 3/2. We also calculate analytically the finite size effects which cut off this power law at times of the order of the system size.
A simple approach to adjust tidal forcing in fjord models
Hjelmervik, Karina; Kristensen, Nils Melsom; Staalstrøm, André; Røed, Lars Petter
2017-07-01
To model currents in a fjord accurate tidal forcing is of extreme importance. Due to complex topography with narrow and shallow straits, the tides in the innermost parts of a fjord are both shifted in phase and altered in amplitude compared to the tides in the open water outside the fjord. Commonly, coastal tide information extracted from global or regional models is used on the boundary of the fjord model. Since tides vary over short distances in shallower waters close to the coast, the global and regional tidal forcings are usually too coarse to achieve sufficiently accurate tides in fjords. We present a straightforward method to remedy this problem by simply adjusting the tides to fit the observed tides at the entrance of the fjord. To evaluate the method, we present results from the Oslofjord, Norway. A model for the fjord is first run using raw tidal forcing on its open boundary. By comparing modelled and observed time series of water level at a tidal gauge station close to the open boundary of the model, a factor for the amplitude and a shift in phase are computed. The amplitude factor and the phase shift are then applied to produce adjusted tidal forcing at the open boundary. Next, we rerun the fjord model using the adjusted tidal forcing. The results from the two runs are then compared to independent observations inside the fjord in terms of amplitude and phases of the various tidal components, the total tidal water level, and the depth integrated tidal currents. The results show improvements in the modelled tides in both the outer, and more importantly, the inner parts of the fjord.
Chemical association in simple models of molecular and ionic fluids. III. The cavity function
Zhou, Yaoqi; Stell, George
1992-01-01
Exact equations which relate the cavity function to excess solvation free energies and equilibrium association constants are rederived by using a thermodynamic cycle. A zeroth-order approximation, derived previously by us as a simple interpolation scheme, is found to be very accurate if the associative bonding occurs on or near the surface of the repulsive core of the interaction potential. If the bonding radius is substantially less than the core radius, the approximation overestimates the association degree and the association constant. For binary association, the zeroth-order approximation is equivalent to the first-order thermodynamic perturbation theory (TPT) of Wertheim. For n-particle association, the combination of the zeroth-order approximation with a ``linear'' approximation (for n-particle distribution functions in terms of the two-particle function) yields the first-order TPT result. Using our exact equations to go beyond TPT, near-exact analytic results for binary hard-sphere association are obtained. Solvent effects on binary hard-sphere association and ionic association are also investigated. A new rule which generalizes Le Chatelier's principle is used to describe the three distinct forms of behaviors involving solvent effects that we find. The replacement of the dielectric-continuum solvent model by a dipolar hard-sphere model leads to improved agreement with an experimental observation. Finally, equation of state for an n-particle flexible linear-chain fluid is derived on the basis of a one-parameter approximation that interpolates between the generalized Kirkwood superposition approximation and the linear approximation. A value of the parameter that appears to be near optimal in the context of this application is obtained from comparison with computer-simulation data.
Improved Analysis of Earth System Models and Observations using Simple Climate Models
Nadiga, Balasubramanya; Urban, Nathan
2017-04-01
First-principles-based Earth System Models (ESMs) are central to both improving our understanding of the climate system and developing climate projections. Nevertheless, given the diversity of climate simulated by the various ESMs and the intense computational burden associated with running such models, simple climate models (SCMs) are key to being able to compare ESMs and the climates they simulate in a dynamically meaningful fashion. We present some preliminary work along these lines. In an application of an SCM to compare different ESMs and observations, we demonstrate a deficiency in the commonly-used upwelling-diffusion (UD) energy balance model (EBM). When we consider the vertical distribution of ocean heat uptake, the lack of representation of processes such as deep water formation and subduction in the UD-EBM precludes a reasonable representation of the vertical distribution of heat uptake in that model. We then demonstrate how the problem can be remedied by introducing a parameterization of such processes in the UD-EBM. With further development, it is anticipated that this approach of ESM inter-comparison using simple physics-based models will lead to further insights into aspects of the climate response such as its stability and sensitivity, uncertainty and predictability, and underlying flow structure and topology.
A simple landslide model at a laboratory scale
Atmajati, Elisabeth Dian; Yuliza, Elfi; Habil, Husni; Sadisun, Imam Ahmad; Munir, Muhammad Miftahul; Khairurrijal
2017-07-01
Landslide, which is one of the natural disasters that occurs frequently, often causes very adverse effects. Landslide early warning systems, which are installed at prone areas, measure physical parameters closely related to landslides and give warning signals indicating that landslides would occur. To determine the critical values of the measured physical parameters or test the early warning system itself, a laboratory scale model of a rotational landslide was developed. This rotational landslide model had a size of 250×45×40 cm3 and was equipped with soil moisture sensors, accelerometers, and automated measurement system. The soil moisture sensors were used to determine the water content in soil sample. The accelerometers were employed to detect movements in x-, y-, and z-direction. Therefore, the flow and rotational landslides were expected to be modeled and characterized. The developed landslide model could be used to evaluate the effects of slope, soil type, and water seepage on the incidence of landslides. The present experiment showed that the model can show the occurrence of landslides. The presence of water seepage made the slope crack. As the time went by, the crack became bigger. After evaluating the obtained characteristics, the occurred landslide was the flow type. This landslide occurred when the soil sample was in a saturated condition with water. The soil movements in x-, y-, and z-direction were also observed. Further experiments should be performed to realize the rotational landslide.
A simple but realistic model for laser cladding
Energy Technology Data Exchange (ETDEWEB)
Picasso, M.; Marsden, C.F.; Wagniere, J.D.; Frenk, A.; Rappaz, M. (Ecole Polytechnique Federale de Lausanne (Switzerland))
1994-04-01
The steady development of high-power lasers has encouraged the industrial application of laser surface treatments. The aim of the laser-cladding process is to deposit a protective layer (from 0.1 to 1.5 mm) onto a workpiece and for the two to be joined by a fusion bond. A model which takes into account the main phenomena occurring during the laser-cladding process is proposed. For a given laser power, beam radius, powder jet geometry, and clad height, this model evaluates two other processing parameters, namely, the laser-beam velocity and the powder feed rate. It considers the interactions between the powder particles, the laser beam, and the molten pool. The laser power reaching the surface of the workpiece is estimated and, assuming this power is used to remelt the substrate with the clad having been predeposited, the melt-pool shape is computed using a three-dimensional (3-D) analytical model, which produces immediate results, even on personal computers. The predictions obtained with this numerical model are in good agreement with experimental results. Processing engineers may therefore use this model to choose the correct processing parameters and to establish cladding maps.
Energy Technology Data Exchange (ETDEWEB)
Keegan, Ronan M. [STFC Rutherford Appleton Laboratory, Didcot OX11 0FA (United Kingdom); Bibby, Jaclyn; Thomas, Jens [University of Liverpool, Liverpool L69 7ZB (United Kingdom); Xu, Dong [Sanford-Burnham Medical Research Institute, 10901 North Torrey Pines Road, La Jolla, CA 92037 (United States); Zhang, Yang [University of Michigan, Ann Arbor, MI 48109 (United States); Mayans, Olga [University of Liverpool, Liverpool L69 7ZB (United Kingdom); Winn, Martyn D. [Science and Technology Facilities Council Daresbury Laboratory, Warrington WA4 4AD (United Kingdom); Rigden, Daniel J., E-mail: drigden@liv.ac.uk [University of Liverpool, Liverpool L69 7ZB (United Kingdom); STFC Rutherford Appleton Laboratory, Didcot OX11 0FA (United Kingdom)
2015-02-01
Two ab initio modelling programs solve complementary sets of targets, enhancing the success of AMPLE with small proteins. AMPLE clusters and truncates ab initio protein structure predictions, producing search models for molecular replacement. Here, an interesting degree of complementarity is shown between targets solved using the different ab initio modelling programs QUARK and ROSETTA. Search models derived from either program collectively solve almost all of the all-helical targets in the test set. Initial solutions produced by Phaser after only 5 min perform surprisingly well, improving the prospects for in situ structure solution by AMPLE during synchrotron visits. Taken together, the results show the potential for AMPLE to run more quickly and successfully solve more targets than previously suspected.
Simple mathematical models for interacting wild and transgenic mosquito populations.
Li, Jia
2004-05-01
Two discrete-time models for interacting populations of wild and genetically altered mosquito are presented, where the genetically altered mosquitoes are grouped into a single population without distinguishing their zygosity. The birth and death rates for both populations are density-dependent, and the mating rates between the mosquitoes are assumed to be either constant or proportional to the total populations for the two models, respectively. The existence and stability of the boundary and positive equilibria are investigated. In particular, it is shown that bifurcations from both boundary and positive equilibria can appear for the model with proportional mating rates. Stable equilibria, periodic-doubling bifurcations, aperiodic oscillations, and chaotic behavior are all illustrated by numerical simulations.
Mass Extinction in a Simple Mathematical Biological Model
Tokita, K; Tokita, Kei; Yasutomi, Ayumu
1997-01-01
Introducing the effect of extinction into the so-called replicator equations in mathematical biology, we construct a general model of ecosystems. The present model shows mass extinction by its own extinction dynamics when the system initially has a large number of species ( diversity). The extinction dynamics shows several significant features such as a power law in basin size distribution, induction time, etc. The present theory can be a mathematical foundation of the species-area effect in the paleontologic theory for mass extinction.
Simple thermodynamic model for the hydrogen phase diagram
Magdǎu, Ioan B.; Marqués, Miriam; Borgulya, Balint; Ackland, Graeme J.
2017-03-01
We describe a classical thermodynamic model that reproduces the main features of the solid hydrogen phase diagram. In particular, we show how the general structure types, which are found by electronic structure calculations and the quantum nature of the protons, can also be understood from a classical viewpoint. The model provides a picture not only of crystal structure, but also for the anomalous melting curve and insights into isotope effects, liquid metallisation, and infrared activity. The existence of a classical picture for this most quantum of condensed matter systems provides a surprising extension of the correspondence principle of quantum mechanics, in particular the equivalent effects of classical and quantum uncertainty.
A simple flow-concentration modelling method for integrating water ...
African Journals Online (AJOL)
DRINIE
2003-07-03
Jul 3, 2003 ... a useful screening tool for identifying sites where, without reduction of pollution, the water ... or “Q-C” modelling method) developed to inter-relate water quality ..... Pretoria. 7/1-7/33. MALAN HL and DAY JA (2002a) Development of Numerical ... (1996) Trends in New Zealand's national river water quality.
Simple Model for Describing and Estimating Wind Turbine Dynamic Inflow
DEFF Research Database (Denmark)
Knudsen, Torben; Bak, Thomas
2013-01-01
Wind turbines operate with sudden change in pitch angle, rotor or wind speed. In such cases the wake behind the turbine, achieve steady state conditions only after a certain delay. This phenomenon is commonly called dynamic inflow. There are many models for dynamic inflow. The most accurate use a...
Development of simple kinetic models and parameter estimation for ...
African Journals Online (AJOL)
PANCHIGA
Key words: Exponential feed, growth modeling, Monod kinetic equation, Pichia pastoris, recombinant human ... Author(s) agree that this article remains permanently open access under the terms of the Creative Commons .... Methanol was the only energy and carbon source ..... A potential explanation for the decline in cell.
Fast and simple model for atmospheric radiative transfer
Seidel, F.C.; Kokhanovsky, A.A.; Schaepman, M.E.
2010-01-01
Radiative transfer models (RTMs) are of utmost importance for quantitative remote sensing, especially for compensating atmospheric perturbation. A persistent trade-off exists between approaches that prefer accuracy at the cost of computational complexity, versus those favouring simplicity at the cos
Production compilation : A simple mechanism to model complex skill acquisition
Taatgen, N.A.; Lee, F.J.
2003-01-01
In this article we describe production compilation, a mechanism for modeling skill acquisition. Production compilation has been developed within the ACT-Rational (ACT-R; J. R. Anderson, D. Bothell, M. D. Byrne, & C. Lebiere, 2002) cognitive architecture and consists of combining and specializing tas
A simple model for assessing utilisable streamflow allocations in the ...
African Journals Online (AJOL)
2006-07-03
Jul 3, 2006 ... It should be noted, however, that any water resource systems model is faced with the ... mendations made to decision makers (including water resource managers and river basin ... but should rather be viewed as a preliminary analysis method that can be used ..... some decision support information (Fig. 4).
A Survey of Combat Models for Use in CARF (Combat Active Replacement Factor) Value Generation
1985-03-01
requirements for the degree of MASTER OF SCIENCE IN CPERATIONS RESEARCH from the NAVAL POSTGRADUATE SCHOOL darch 1985 Author: tv Approved by :... - n Z ...GENERATION OF A WARTIME ACTIVE REPLACEMENT FACTOR (WARF) 65 A. THE PREPROCESSER ................. 66 B. THE COMBAT SAMPLE GEERATOR (COSAGE) MODEL 66 C. THE...en -T,, , -T T L T 17, V 7777% T -T T K 97 7 Ř 7 T W 71 T 7 - Z W.; ., . 7. , II. THE CARF GENERA7ION SYSTEM TODAY The previous and current CARF
Vinegar, A; Jepson, G W; Cisneros, M; Rubenstein, R; Brock, W J
2000-08-01
Most proposed replacements for Halon 1301 as a fire suppressant are halogenated hydrocarbons. The acute toxic endpoint of concern for these agents is cardiac sensitization. An approach is described that links the cardiac endpoint as assessed in dogs to a target arterial concentration in humans. Linkage was made using a physiologically based pharmacokinetic (PBPK) model. Monte Carlo simulations, which account for population variability, were used to establish safe exposure times at different exposure concentrations for Halon 1301 (bromotrifluoromethane), CF(3)I (trifluoroiodomethane), HFC-125 (pentafluoroethane), HFC-227ea (1,1,1,2,3,3,3-heptafluoropropane), and HFC-236fa (1,1,1,3,3,3-hexafluoropropane). Application of the modeling technique described here not only makes use of the conservative cardiac sensitization endpoint, but also uses an understanding of the pharmacokinetics of the chemical agents to better establish standards for safe exposure. The combined application of cardiac sensitization data and physiologically based modeling provides a quantitative approach, which can facilitate the selection and effective use of halon replacement candidates.
A field test of a simple stochastic radiative transfer model
Energy Technology Data Exchange (ETDEWEB)
Byrne, N. [Science Applications International Corp., San Diego, CA (United States)
1995-09-01
The problem of determining the effect of clouds on the radiative energy balance of the globe is of well-recognized importance. One can in principle solve the problem for any given configuration of clouds using numerical techniques. This knowledge is not useful however, because of the amount of input data and computer resources required. Besides, we need only the average of the resulting solution over the grid scale of a general circulation model (GCM). Therefore, we are interested in estimating the average of the solutions of such fine-grained problems using only coarse grained data, a science or art called stochastic radiation transfer. Results of the described field test indicate that the stochastic description is a somewhat better fit to the data than is a fractional cloud cover model, but more data are needed. 1 ref., 3 figs.
Engineering complex topological memories from simple Abelian models
Wootton, James R.; Lahtinen, Ville; Doucot, Benoit; Pachos, Jiannis K.
2011-09-01
In three spatial dimensions, particles are limited to either bosonic or fermionic statistics. Two-dimensional systems, on the other hand, can support anyonic quasiparticles exhibiting richer statistical behaviors. An exciting proposal for quantum computation is to employ anyonic statistics to manipulate information. Since such statistical evolutions depend only on topological characteristics, the resulting computation is intrinsically resilient to errors. The so-called non-Abelian anyons are most promising for quantum computation, but their physical realization may prove to be complex. Abelian anyons, however, are easier to understand theoretically and realize experimentally. Here we show that complex topological memories inspired by non-Abelian anyons can be engineered in Abelian models. We explicitly demonstrate the control procedures for the encoding and manipulation of quantum information in specific lattice models that can be implemented in the laboratory. This bridges the gap between requirements for anyonic quantum computation and the potential of state-of-the-art technology.
A Simple Model for Human and Nature Interaction
Motesharrei, S.; Rivas, J.; Kalnay, E.
2012-12-01
There are widespread concerns that current trends in population and resource-use are unsustainable, but the possibilities of an overshoot and collapse remain unclear and controversial. Collapses of civilizations have occurred many times in the past 5000 years, often followed by centuries of economic, intellectual, and population decline. Many different natural and social phenomena have been invoked to explain specific collapses, but a general explanation remains elusive. Two important features seem to appear across societies that have collapsed: Ecological Strain and Economic Stratification. Our new model (Human And Nature DYnamics, HANDY) has just four equations that describe the evolution of Elites, Commoners, Nature, and Wealth. Mechanisms leading to collapse are discussed and the measure "Carrying Capacity" is developed and defined. The model shows that societal collapse can happen due to either one of two independent factors: (1) over-consumption of natural resources, and/or (2) deep inequity between Elites and Commoners. The model also portrays two distinct types of collapse: (i) collapse followed by recovery of nature, and (ii) full collapse. The model suggests that the estimation of Carrying Capacity is a practical means for early detection of a collapse. Collapse can be avoided, and population can reach a sustainable equilibrium, if the rate of depletion of nature is reduced to a sustainable level, and if resources are distributed in a reasonably equitable fashion.; A type-ii (full) collapse is shown in this figure. With high inequality and high depletion, societies are doomed to collapse. Wealth starts to decrease when population rises above the carrying capacity. The large gap between carrying capacity and its maximum is a result of depletion factor being much larger than the sustainable limit. ; It is possible to overshoot, oscillate, and eventually converge to an equilibrium, even in an inequitable society. However, it requires policies that control
Simple Model with Time-Varying Fine-Structure ``Constant''
Berman, M. S.
2009-10-01
Extending the original version written in colaboration with L.A. Trevisan, we study the generalisation of Dirac's LNH, so that time-variation of the fine-structure constant, due to varying electrical and magnetic permittivities is included along with other variations (cosmological and gravitational ``constants''), etc. We consider the present Universe, and also an inflationary scenario. Rotation of the Universe is a given possibility in this model.
Caenorhabditis elegans: a simple nematode infection model for Penicillium marneffei.
Directory of Open Access Journals (Sweden)
Xiaowen Huang
Full Text Available Penicillium marneffei, one of the most important thermal dimorphic fungi, is a severe threat to the life of immunocompromised patients. However, the pathogenic mechanisms of P. marneffei remain largely unknown. In this work, we developed a model host by using nematode Caenorhabditis elegans to investigate the virulence of P. marneffei. Using two P. marneffei clinical isolate strains 570 and 486, we revealed that in both liquid and solid media, the ingestion of live P. marneffei was lethal to C. elegans (P<0.001. Meanwhile, our results showed that the strain 570, which can produce red pigment, had stronger pathogenicity in C. elegans than the strain 486, which can't produce red pigment (P<0.001. Microscopy showed the formation of red pigment and hyphae within C. elegans after incubation with P. marneffei for 4 h, which are supposed to be two contributors in nematodes killing. In addition, we used C. elegans as an in vivo model to evaluate different antifungal agents against P. marneffei, and found that antifungal agents including amphotericin B, terbinafine, fluconazole, itraconazole and voriconazole successfully prolonged the survival of nematodesinfected by P. marneffei. Overall, this alternative model host can provide us an easy tool to study the virulence of P. marneffei and screen antifungal agents.
Tanaka, H. L.
2003-06-01
In this study, a numerical simulation of the Arctic Oscillation (AO) is conducted using a simple barotropic model that considers the barotropic-baroclinic interactions as the external forcing. The model is referred to as a barotropic S model since the external forcing is obtained statistically from the long-term historical data, solving an inverse problem. The barotropic S model has been integrated for 51 years under a perpetual January condition and the dominant empirical orthogonal function (EOF) modes in the model have been analyzed. The results are compared with the EOF analysis of the barotropic component of the real atmosphere based on the daily NCEP-NCAR reanalysis for 50 yr from 1950 to 1999.According to the result, the first EOF of the model atmosphere appears to be the AO similar to the observation. The annular structure of the AO and the two centers of action at Pacific and Atlantic are simulated nicely by the barotropic S model. Therefore, the atmospheric low-frequency variabilities have been captured satisfactorily even by the simple barotropic model.The EOF analysis is further conducted to the external forcing of the barotropic S model. The structure of the dominant forcing shows the characteristics of synoptic-scale disturbances of zonal wavenumber 6 along the Pacific storm track. The forcing is induced by the barotropic-baroclinic interactions associated with baroclinic instability.The result suggests that the AO can be understood as the natural variability of the barotropic component of the atmosphere induced by the inherent barotropic dynamics, which is forced by the barotropic-baroclinic interactions. The fluctuating upscale energy cascade from planetary waves and synoptic disturbances to the zonal motion plays the key role for the excitation of the AO.
Pawlyk, Basil S; Smith, Alexander J; Buch, Prateek K; Adamian, Michael; Hong, Dong-Hyun; Sandberg, Michael A; Ali, Robin R; Li, Tiansen
2005-09-01
Retinitis pigmentosa GTPase regulator (RPGR) is a photoreceptor protein anchored in the connecting cilia by an RPGR-interacting protein (RPGRIP). Loss of RPGRIP causes Leber congenital amaurosis (LCA), a severe form of photoreceptor degeneration. The current study was an investigation of whether somatic gene replacement could rescue degenerating photoreceptors in a murine model of LCA due to a defect in RPGRIP. An RPGRIP expression cassette, driven by a mouse opsin promoter, was packaged into recombinant adeno-associated virus (AAV). The AAV vector was delivered into the right eyes of RPGRIP(-/-) mice by a single subretinal injection into the superior hemisphere. The left eyes received a saline injection as a control. Full-field electroretinograms (ERGs) were recorded from both eyes at 2, 3, 4, and 5 months after injection. After the final follow-up, retinas were analyzed by immunostaining or by light and electron microscopy. Delivery of the AAV vector led to RPGRIP expression and restoration of normal RPGR localization at the connecting cilia. Photoreceptor preservation was evident by a thicker cell layer and well-developed outer segments in the treated eyes. Rescue was more pronounced in the superior hemisphere coincident with the site of delivery. Functional preservation was demonstrated by ERG. AAV-mediated RPGRIP gene replacement preserves photoreceptor structure and function in a mouse model of LCA, despite ongoing cell loss at the time of intervention. These results indicate that gene replacement therapy may be effective in patients with LCA due to a defect in RPGRIP and suggest that further preclinical development of gene therapy for this disorder is warranted.
A simple model to estimate the optimal doping of p - Type oxide superconductors
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Adir Moysés Luiz
2008-12-01
Full Text Available Oxygen doping of superconductors is discussed. Doping high-Tc superconductors with oxygen seems to be more efficient than other doping procedures. Using the assumption of double valence fluctuations, we present a simple model to estimate the optimal doping of p-type oxide superconductors. The experimental values of oxygen content for optimal doping of the most important p-type oxide superconductors can be accounted for adequately using this simple model. We expect that our simple model will encourage further experimental and theoretical researches in superconducting materials.
Meesters, Johannes A J; Koelmans, Albert A; Quik, Joris T K; Hendriks, A Jan; van de Meent, Dik
2014-05-20
Screening level models for environmental assessment of engineered nanoparticles (ENP) are not generally available. Here, we present SimpleBox4Nano (SB4N) as the first model of this type, assess its validity, and evaluate it by comparisons with a known material flow model. SB4N expresses ENP transport and concentrations in and across air, rain, surface waters, soil, and sediment, accounting for nanospecific processes such as aggregation, attachment, and dissolution. The model solves simultaneous mass balance equations (MBE) using simple matrix algebra. The MBEs link all concentrations and transfer processes using first-order rate constants for all processes known to be relevant for ENPs. The first-order rate constants are obtained from the literature. The output of SB4N is mass concentrations of ENPs as free dispersive species, heteroaggregates with natural colloids, and larger natural particles in each compartment in time and at steady state. Known scenario studies for Switzerland were used to demonstrate the impact of the transport processes included in SB4N on the prediction of environmental concentrations. We argue that SB4N-predicted environmental concentrations are useful as background concentrations in environmental risk assessment.
Honda, Hidehito; Matsuka, Toshihiko; Ueda, Kazuhiro
2016-07-20
Some researchers on binary choice inference have argued that people make inferences based on simple heuristics, such as recognition, fluency, or familiarity. Others have argued that people make inferences based on available knowledge. To examine the boundary between heuristic and knowledge usage, we examine binary choice inference processes in terms of attribute substitution in heuristic use (Kahneman & Frederick, 2005). In this framework, it is predicted that people will rely on heuristic or knowledge-based inference depending on the subjective difficulty of the inference task. We conducted competitive tests of binary choice inference models representing simple heuristics (fluency and familiarity heuristics) and knowledge-based inference models. We found that a simple heuristic model (especially a familiarity heuristic model) explained inference patterns for subjectively difficult inference tasks, and that a knowledge-based inference model explained subjectively easy inference tasks. These results were consistent with the predictions of the attribute substitution framework. Issues on usage of simple heuristics and psychological processes are discussed.
Vibrational exciton-mediated quantum state transfert: a simple model
Pouthier, Vincent J C
2012-01-01
A communication protocol is proposed in which quantum state transfer is mediated by a vibrational exciton. We consider two distant molecular groups grafted on the sides of a lattice. These groups behave as two quantum computers where the information in encoded and received. The lattice plays the role of a communication channel along which the exciton propagates and interacts with a phonon bath. Special attention is paid for describing the system involving an exciton dressed by a single phonon mode. The Hamiltonian is thus solved exactly so that the relevance of the perturbation theory is checked. Within the nonadiabatic weak-coupling limit, it is shown that the system supports three quasi-degenerate states that define the relevant paths followed by the exciton to tunnel between the computers. When the model parameters are judiciously chosen, constructive interferences take place between these paths. Phonon-induced decoherence is minimized and a high-fidelity quantum state transfer occurs over a broad temperat...
Electromagnetic simulations of simple models of ferrite loaded kickers
Zannini, Carlo; Salvant, B; Metral, E; Rumolo, G
2010-01-01
The kickers are major contributors to the CERN SPS beam coupling impedance. As such, they may represent a limitation to increasing the SPS bunch current in the frame of an intensity upgrade of the LHC. In this paper, CST Particle Studio time domain electromagnetic simulations are performed to obtain the longitudinal and transverse impedances/wake potentials of simplified models of ferrite loaded kickers. The simulation results have been successfully compared with some existing analytical expressions. In the transverse plane, the dipolar and quadrupolar contributions to the wake potentials have been estimated from the results of these simulations. For some cases, simulations have also been benchmarked against measurements on PS kickers. It turns out that the large simulated quadrupolar contributions of these kickers could explain both the negative total (dipolar+quadrupolar) horizontal impedance observed in bench measurements and the positive horizontal tune shift measured with the SPS beam.
Ecological and Social Dynamics in Simple Models of Ecosystem Management
Directory of Open Access Journals (Sweden)
William Brock
1999-12-01
Full Text Available Simulation models were developed to explore and illustrate dynamics of socioecological systems. The ecosystem is a lake subject to phosphorus pollution. Phosphorus flows from agriculture to upland soils, to surface waters, where it cycles between water and sediments. The ecosystem is multistable, and moves among domains of attraction depending on the history of pollutant inputs. The alternative states yield different economic benefits. Agents form expectations about ecosystem dynamics, markets, and/or the actions of managers, and choose levels of pollutant inputs accordingly. Agents have heterogeneous beliefs and/or access to information. Their aggregate behavior determines the total rate of pollutant input. As the ecosystem changes, agents update their beliefs and expectations about the world they co-create, and modify their actions accordingly. For a wide range of scenarios, we observe irregular oscillations among ecosystem states and patterns of agent behavior. These oscillations resemble some features of the adaptive cycle of panarchy theory.
Bobrovskij, N. M.; Levashkin, D. G.; Bobrovskij, I. N.; Melnikov, P. A.; Lukyanov, A. A.
2017-01-01
Article is devoted the decision of basing holes machining accuracy problems of automatically replaceable cubical units (carriers) for reconfigurable manufacturing systems with low-waste production (RMS). Results of automatically replaceable units basing holes machining modeling on the basis of the dimensional chains analysis are presented. Influence of machining parameters processing on accuracy spacings on centers between basing apertures is shown. The mathematical model of carriers basing holes machining accuracy is offered.
A simple model for the location of Saturn's F ring
Benet, Luis; Jorba, Àngel
2017-03-01
In this paper, we introduce a simplified model to understand the location of Saturn's F ring. The model is a planar restricted five-body problem defined by the gravitational field of Saturn, including its second zonal harmonic J2, the shepherd moons Prometheus and Pandora, and Titan. We compute accurate long-time numerical integrations of (about 2.5 million) non-interacting test-particles initially located in the region between the orbits of Prometheus and Pandora, and address whether they escape or remain trapped in this region. We obtain a wide region of initial conditions of the test particles that remain confined. We consider a dynamical stability indicator for the test particles' motion defined by computing the ratio of the standard deviation over the average value of relevant dynamical quantities, in particular, for the mean-motion and the semi-major axis. This indicator separates clearly a subset of trapped initial conditions that appear as very localized stripes in the initial semi-major axis and eccentricity space for the most stable orbits. Retaining only these test particles, we obtain a narrow eccentric ring which displays sharp edges and collective alignment. The semi-major axis of the accumulation stripes of the stable ring-particles can be associated with resonances, mostly involving Prometheus' outer Lindblad and co-rotation resonances, but not exclusively. Pandora's inner Lindblad and co-rotation resonances as well as low-order three-body resonances typically coincide with gaps, i.e., regions of instabilities. Comparison of our results with the nominal data for the F ring shows some correspondence.
A very simple dynamic soil acidification model for scenario analyses and target load calculations
Posch, M.; Reinds, G.J.
2009-01-01
A very simple dynamic soil acidification model, VSD, is described, which has been developed as the simplest extension of steady-state models for critical load calculations and with an eye on regional applications. The model requires only a minimum set of inputs (compared to more detailed models) and
Tamburrino, Anna; Churchill, Madeline J; Wan, Oi W; Colino-Sanguino, Yolanda; Ippolito, Rossana; Bergstrand, Sofie; Wolf, Daniel A; Herz, Niculin J; Sconce, Michelle D; Björklund, Anders; Meshul, Charles K; Decressac, Mickael
2015-12-14
The early clinical trials using fetal ventral mesencephalic (VM) allografts in Parkinson's disease (PD) patients have shown efficacy (albeit not in all cases) and have paved the way for further development of cell replacement therapy strategies in PD. The preclinical work that led to these clinical trials used allografts of fetal VM tissue placed into 6-OHDA lesioned rats, while the patients received similar allografts under cover of immunosuppression in an α-synuclein disease state. Thus developing models that more faithfully replicate the clinical scenario would be a useful tool for the translation of such cell-based therapies to the clinic. Here, we show that while providing functional recovery, transplantation of fetal dopamine neurons into the AAV-α-synuclein rat model of PD resulted in smaller-sized grafts as compared to similar grafts placed into the 6-OHDA-lesioned striatum. Additionally, we found that cyclosporin treatment was able to promote the survival of the transplanted cells in this allografted state and surprisingly also provided therapeutic benefit in sham-operated animals. We demonstrated that delayed cyclosporin treatment afforded neurorestoration in three complementary models of PD including the Thy1-α-synuclein transgenic mouse, a novel AAV-α-synuclein mouse model, and the MPTP mouse model. We then explored the mechanisms for this benefit of cyclosporin and found it was mediated by both cell-autonomous mechanisms and non-cell autonomous mechanisms. This study provides compelling evidence in favor for the use of immunosuppression in all grafted PD patients receiving cell replacement therapy, regardless of the immunological mismatch between donor and host cells, and also suggests that cyclosporine treatment itself may act as a disease-modifying therapy in all PD patients.
Habitat connectivity and ecosystem productivity: implications from a simple model.
Cloern, J.E.
2007-01-01
The import of resources (food, nutrients) sustains biological production and food webs in resource-limited habitats. Resource export from donor habitats subsidizes production in recipient habitats, but the ecosystem-scale consequences of resource translocation are generally unknown. Here, I use a nutrient-phytoplankton-zooplankton model to show how dispersive connectivity between a shallow autotrophic habitat and a deep heterotrophic pelagic habitat can amplify overall system production in metazoan food webs. This result derives from the finite capacity of suspension feeders to capture and assimilate food particles: excess primary production in closed autotrophic habitats cannot be assimilated by consumers; however, if excess phytoplankton production is exported to food-limited heterotrophic habitats, it can be assimilated by zooplankton to support additional secondary production. Transport of regenerated nutrients from heterotrophic to autotrophic habitats sustains higher system primary production. These simulation results imply that the ecosystem-scale efficiency of nutrient transformation into metazoan biomass can be constrained by the rate of resource exchange across habitats and that it is optimized when the transport rate matches the growth rate of primary producers. Slower transport (i.e., reduced connectivity) leads to nutrient limitation of primary production in autotrophic habitats and food limitation of secondary production in heterotrophic habitats. Habitat fragmentation can therefore impose energetic constraints on the carrying capacity of aquatic ecosystems. The outcomes of ecosystem restoration through habitat creation will be determined by both functions provided by newly created aquatic habitats and the rates of hydraulic connectivity between them.
A Simple Evacuation Modeling and Simulation Tool for First Responders
Energy Technology Data Exchange (ETDEWEB)
Koch, Daniel B [ORNL; Payne, Patricia W [ORNL
2015-01-01
Although modeling and simulation of mass evacuations during a natural or man-made disaster is an on-going and vigorous area of study, tool adoption by front-line first responders is uneven. Some of the factors that account for this situation include cost and complexity of the software. For several years, Oak Ridge National Laboratory has been actively developing the free Incident Management Preparedness and Coordination Toolkit (IMPACT) to address these issues. One of the components of IMPACT is a multi-agent simulation module for area-based and path-based evacuations. The user interface is designed so that anyone familiar with typical computer drawing tools can quickly author a geospatially-correct evacuation visualization suitable for table-top exercises. Since IMPACT is designed for use in the field where network communications may not be available, quick on-site evacuation alternatives can be evaluated to keep pace with a fluid threat situation. Realism is enhanced by incorporating collision avoidance into the simulation. Statistics are gathered as the simulation unfolds, including most importantly time-to-evacuate, to help first responders choose the best course of action.
Predicting and understanding forest dynamics using a simple tractable model.
Purves, Drew W; Lichstein, Jeremy W; Strigul, Nikolay; Pacala, Stephen W
2008-11-04
The perfect-plasticity approximation (PPA) is an analytically tractable model of forest dynamics, defined in terms of parameters for individual trees, including allometry, growth, and mortality. We estimated these parameters for the eight most common species on each of four soil types in the US Lake states (Michigan, Wisconsin, and Minnesota) by using short-term (
Directory of Open Access Journals (Sweden)
A C T Vrancken
Full Text Available Since the treatment options for symptomatic total meniscectomy patients are still limited, an anatomically shaped, polycarbonate urethane (PCU, total meniscus replacement was developed. This study evaluates the in vivo performance of the implant in a goat model, with a specific focus on the implant location in the joint, geometrical integrity of the implant and the effect of the implant on synovial membrane and articular cartilage histopathological condition.The right medial meniscus of seven Saanen goats was replaced by the implant. Sham surgery (transection of the MCL, arthrotomy and MCL suturing was performed in six animals. The contralateral knee joints of both groups served as control groups. After three months follow-up the following aspects of implant performance were evaluated: implant position, implant deformation and the histopathological condition of the synovium and cartilage.Implant geometry was well maintained during the three month implantation period. No signs of PCU wear were found and the implant did not induce an inflammatory response in the knee joint. In all animals, implant fixation was compromised due to suture breakage, wear or elongation, likely causing the increase in extrusion observed in the implant group. Both the femoral cartilage and tibial cartilage in direct contact with the implant showed increased damage compared to the sham and sham-control groups.This study demonstrates that the novel, anatomically shaped PCU total meniscal replacement is biocompatible and resistant to three months of physiological loading. Failure of the fixation sutures may have increased implant mobility, which probably induced implant extrusion and potentially stimulated cartilage degeneration. Evidently, redesigning the fixation method is necessary. Future animal studies should evaluate the improved fixation method and compare implant performance to current treatment standards, such as allografts.
Azzopardi, George; Petkov, Nicolai
Simple cells in primary visual cortex are believed to extract local contour information from a visual scene. The 2D Gabor function (GF) model has gained particular popularity as a computational model of a simple cell. However, it short-cuts the LGN, it cannot reproduce a number of properties of real
Hip Joint Replacement Using Monofilament Polypropylene Surgical Mesh: An Animal Model
Directory of Open Access Journals (Sweden)
Jacek Białecki
2014-01-01
Full Text Available Hip joint dysplasia is a deformation of the articular elements (pelvic acetabulum, head of the femur, and/or ligament of the head of the femur leading to laxity of the hip components and dislocation of the femoral head from the pelvic acetabulum. Diagnosis is based on symptoms observed during clinical and radiological examinations. There are two treatment options: conservative and surgical. The classic surgical procedures are juvenile pubic symphysiodesis (JPS, triple pelvic osteotomy (TPO, total hip replacement (THR, and femoral head and neck resection (FHNE. The aim of this experiment was to present an original technique of filling the acetabulum with a polypropylene implant, resting the femoral neck directly on the mesh. The experiment was performed on eight sheep. The clinical value of the new surgical technique was evaluated using clinical, radiological, and histological methods. This technique helps decrease the loss of limb length by supporting the femoral neck on the mesh equivalent to the femoral head. It also reduces joint pain and leads to the formation of stable and mobile pseudarthrosis. The mesh manifested osteoprotective properties and enabled the formation of a stiff-elastic connection within the hip joint. The method is very cost-effective and the technique itself is simple to perform.
Hip joint replacement using monofilament polypropylene surgical mesh: an animal model.
Białecki, Jacek; Majchrzycki, Marian; Szymczak, Antoni; Klimowicz-Bodys, Małgorzata Dorota; Wierzchoś, Edward; Kołomecki, Krzysztof
2014-01-01
Hip joint dysplasia is a deformation of the articular elements (pelvic acetabulum, head of the femur, and/or ligament of the head of the femur) leading to laxity of the hip components and dislocation of the femoral head from the pelvic acetabulum. Diagnosis is based on symptoms observed during clinical and radiological examinations. There are two treatment options: conservative and surgical. The classic surgical procedures are juvenile pubic symphysiodesis (JPS), triple pelvic osteotomy (TPO), total hip replacement (THR), and femoral head and neck resection (FHNE). The aim of this experiment was to present an original technique of filling the acetabulum with a polypropylene implant, resting the femoral neck directly on the mesh. The experiment was performed on eight sheep. The clinical value of the new surgical technique was evaluated using clinical, radiological, and histological methods. This technique helps decrease the loss of limb length by supporting the femoral neck on the mesh equivalent to the femoral head. It also reduces joint pain and leads to the formation of stable and mobile pseudarthrosis. The mesh manifested osteoprotective properties and enabled the formation of a stiff-elastic connection within the hip joint. The method is very cost-effective and the technique itself is simple to perform.
Beer's-law-based, simple spectral model for direct normal and diffuse horizontal irradiance
Energy Technology Data Exchange (ETDEWEB)
Bird, R.E.
1982-12-01
A spectral model for cloudless days that uses simple mathematical expressions and tabulated look-up tables to generate direct normal and diffuse horizontal irradiance is presented. The model is based on modifications to previously published simple models and comparisons with rigorous radiative transfer codes. This model is expected to be more accurate and to be applicable to a broader range of atmospheric conditions than previous simple models. The prime significance of this model is its simplicity, which allows it to be used on small desk-top computers. The spctrum produced by this model is limited to 0.3 to 4.0 ..mu..m wavelength with an approximate resolution of 10 nm.
The Development Study of a Medical Ethics Education Program by Using Simple ISD Model.
Kim, Young Jon; Yoo, Hyoo Hyun; Joo, Chan Uhng
2011-09-01
Simple instructional systems design (ISD) model is based on a fast development, usability test, and continuos feedback, which are necessary for educational program development in medical school. This study aims to figure out the usability of Simple ISD model for a medical ethics education program by describing a developmental details of each phase and its evaluation results. Research has been conducted in two steps. First, while researchers participated in the program development by using Simple ISD model, we collected empirical data of each development activities. Second, the developed program was evaluated by students' web-based usability test, a 8-students' focus group interview and 5 faculty members' individual interviews in 4 domains; learning contents, instructional methods and strategies, achievement evaluation, and self-evaluation. Following the circular process of analysis, design, development, and usability test of Simple ISD model, a 10-week medical ethics program covering 9 instructional topics was developed. The average points of response on the developed medical ethics program in 2008 and 2009 are increased from 3.96 to 4.59 and 4.41, respectively. The prospects and limitations of the program are discussed. From a development study of the medical ethics program by using Simple ISD model, we could implement a more usable medical ethics program, and found 4 different usability of the Simple ISD model; the rapid development of educational program, program improvement by continuous feedback, faculty members' engagement in instructional design, and professional development of the faculty members.
Improved Analysis of Earth System Models and Observations using Simple Climate Models
Nadiga, B. T.; Urban, N. M.
2016-12-01
Earth system models (ESM) are the most comprehensive tools we have to study climate change and develop climate projections. However, the computational infrastructure required and the cost incurred in running such ESMs precludes direct use of such models in conjunction with a wide variety of tools that can further our understanding of climate. Here we are referring to tools that range from dynamical systems tools that give insight into underlying flow structure and topology to tools that come from various applied mathematical and statistical techniques and are central to quantifying stability, sensitivity, uncertainty and predictability to machine learning tools that are now being rapidly developed or improved. Our approach to facilitate the use of such models is to analyze output of ESM experiments (cf. CMIP) using a range of simpler models that consider integral balances of important quantities such as mass and/or energy in a Bayesian framework.We highlight the use of this approach in the context of the uptake of heat by the world oceans in the ongoing global warming. Indeed, since in excess of 90% of the anomalous radiative forcing due greenhouse gas emissions is sequestered in the world oceans, the nature of ocean heat uptake crucially determines the surface warming that is realized (cf. climate sensitivity). Nevertheless, ESMs themselves are never run long enough to directly assess climate sensitivity. So, we consider a range of models based on integral balances--balances that have to be realized in all first-principles based models of the climate system including the most detailed state-of-the art climate simulations. The models range from simple models of energy balance to those that consider dynamically important ocean processes such as the conveyor-belt circulation (Meridional Overturning Circulation, MOC), North Atlantic Deep Water (NADW) formation, Antarctic Circumpolar Current (ACC) and eddy mixing. Results from Bayesian analysis of such models using
The fermion content of the Standard Model from a simple world-line theory
Energy Technology Data Exchange (ETDEWEB)
Mansfield, Paul, E-mail: P.R.W.Mansfield@durham.ac.uk
2015-04-09
We describe a simple model that automatically generates the sum over gauge group representations and chiralities of a single generation of fermions in the Standard Model, augmented by a sterile neutrino. The model is a modification of the world-line approach to chiral fermions.
Boesten, J.J.T.I.; Stroosnijder, L.
1986-01-01
A simple parametric model is presented to estimate daily evaporation from fallow tilled soil under spring conditions in a temperate climate. In this model, cumulative actual evaporation during a drying cycle is directly proportional to the square root of cumulative potential evaporation. The model
A simple model of group selection that cannot be analyzed with inclusive fitness
M. van Veelen; S. Luo; B. Simon
2014-01-01
A widespread claim in evolutionary theory is that every group selection model can be recast in terms of inclusive fitness. Although there are interesting classes of group selection models for which this is possible, we show that it is not true in general. With a simple set of group selection models,
The fermion content of the Standard Model from a simple world-line theory
Directory of Open Access Journals (Sweden)
Paul Mansfield
2015-04-01
Full Text Available We describe a simple model that automatically generates the sum over gauge group representations and chiralities of a single generation of fermions in the Standard Model, augmented by a sterile neutrino. The model is a modification of the world-line approach to chiral fermions.
The modeling of the ENSO events with the help of a simple model
Stepanov, V N
2007-01-01
The Southern Oscillation (ENSO) is modelled with the help of a simple model representing a classical damped oscillator forced by external forcing. Eastern Pacific sea surface temperature (SST) and the mean equatorial Pacific thermocline depth correspond to the roles of momentum and position. The external forcing of the system is supplied by short-period meridional mass fluctuations in the Pacific sector of the Southern Ocean due to the joint effect of the atmospheric variability over the Antarctic Circumpolar Current (ACC), bottom topography and coastlines, and also by the variability of westerly winds in the tropics. Under such conditions the ENSO-like oscillations arise as a result of propagation of signals due to both initial signals appeared in the Southern Ocean and the tropical westerly wind anomaly, that propagate then across the equatorial Pacific by means of fast wave processes. The external forcings are the main factor in establishing the oscillation pattern.
Suported by Replacement Policy for Caching World-Wide Web Documents Based on Site-Graph Model
Institute of Scientific and Technical Information of China (English)
庄伟强; 胡敏; 王鼎兴; 郑纬民; 沈美明
2001-01-01
The hit rate, a major metric for evaluating proxy caches, is mostly limited by the replacementstrategy of proxy caches. However, in traditional proxy caches, the hit rate does not usually successfullypredict how well a proxy cache will perform because the proxy cache counts any hit in its caching space whichhas many pages without useful information, so its replacement strategy fails to determine which pages to keepand which to release. The proxy cache efficiency can be measured more accurately using the valid hit rateintroduced in this paper. An efficient replacement strategy based on the Site-Graph model for WWW(World-Wide Web) documents is also discussed in this paper. The model analyzes user access behavior as abasis for the replacement strategy. Simulation results demonstrate that the replacement strategy improvesproxy cache efficiency.``
Analysis of in vitro and in vivo function of total knee replacements using dynamic contact models
Zhao, Dong
Despite the high incidence of osteoarthritis in human knee joint, its causes remain unknown. Total knee replacement (TKR) has been shown clinically to be effective in restoring the knee function. However, wear of ultra-high molecular weight polyethylene has limited the longevity of TKRs. To address these important issues, it is necessary to investigate the in vitro and in vivo function of total knee replacements using dynamic contact models. A multibody dynamic model of an AMTI knee simulator was developed. Incorporating a wear prediction model into the contact model based on elastic foundation theory enables the contact surface to take into account creep and wear during the dynamic simulation. Comparisons of the predicted damage depth, area, and volume lost with worn retrievals from a physical machine were made to validate the model. In vivo tibial force distributions during dynamic and high flexion activities were investigated using the dynamic contact model. In vivo medial and lateral contact forces experienced by a well-aligned instrumented knee implant, as well as upper and lower bounds on contact pressures for a variety of activities were studied. For all activities, the predicted medial and lateral contact forces were insensitive to the selected material model. For this patient, the load split during the mid-stance phase of gait and during stair is more equal than anticipated. The external knee adduction torque has been proposed as a surrogate measure for medial compartment load during gait. However, a direct link between these two quantities has not been demonstrated using in vivo measurement of medial compartment load. In vivo data collected from a subject with an instrumented knee implant were analyzed to evaluate this link. The subject performed five different overground gait motions (normal, fast, slow, wide, and toe out) while instrumented implant, video motion, and ground reaction data were simultaneously collected. The high correlation coefficient
Xiao, Jianxi; Madhan, Balaraman; Li, Yingjie; Brodsky, Barbara; Baum, Jean
2011-01-01
Missense mutations, which replace one Gly with a larger residue in the repeating sequence of the type I collagen triple helix, lead to the hereditary bone disorder osteogenesis imperfecta (OI). Previous studies suggest that these mutations may interfere with triple-helix folding. NMR was used to investigate triple-helix formation in a series of model peptides where the residue replacing Gly, as well as the local sequence environment, was varied. NMR measurement of translational diffusion coef...
Three-dimensional force model of the low-back for simple computer programming.
Tracy, M F
1990-08-01
A three-dimensional static model is described to evaluate the forces on low-back muscles and on the spine during manual handling tasks and other forceful activities. It is simple to use either with a calculator or programmed onto a micro-computer, whilst being more accurate than existing simple models. Comparisons are made with a more sophisticated model that requires mathematical libraries and programming skills. As predictions are similar, so is the area of validity: the proposed model's accuracy is good for light tasks but poorer for strenuous ones.
Short, David
2008-01-01
The 45th Weather Squadron (45 WS) is replacing the Weather Surveillance Radar, Model 74C (WSR-74C) at Patrick Air Force Base (PAFB), with a Doppler, dual polarization radar, the Radtec 43/250. A new scan strategy is needed for the Radtec 43/250, to provide high vertical resolution data over the Kennedy Space Center (KSC) and Cape Canaveral Air Force Station (CCAFS) launch pads, while taking advantage of the new radar's advanced capabilities for detecting severe weather phenomena associated with convection within the 45 WS area of responsibility. The Applied Meteorology Unit (AMU) developed several scan strategies customized for the operational needs of the 45 WS. The AMU also developed a plan for evaluating the scan strategies in the period prior to operational acceptance, currently scheduled for November 2008.
A simple moisture advection model of specific humidity change over land in response to SST warming
Chadwick, Robin; Good, Peter; Willett, Kate
2017-04-01
A new, simple conceptual model of surface specific humidity change (∆q) over land has been developed, based on the effect of increased moisture advection from the oceans in response to sea surface temperature (SST) warming. In this model, future q over land is determined by scaling the present-day pattern of land q by the fractional increase in the oceanic moisture source. Simple model estimates agree well with climate model projections of future ∆q (mean spatial correlation coefficient 0.87), so ∆q over both land and ocean can be viewed primarily as a thermodynamic process controlled by SST warming. Precipitation change (∆P) is also affected by ∆q, and the new simple model can be included in a decomposition of tropical precipitation change, where it provides increased physical understanding of the processes that drive ∆P over land. Confidence in the thermodynamic part of extreme precipitation change over land is increased by this improved understanding, and this should scale approximately with Clausius-Clapeyron oceanic q increases under SST warming. Residuals between actual climate model ∆q and simple model estimates are often associated with regions of large circulation change, and can be thought of as the 'dynamical' part of specific humidity change. The simple model is used to explore inter-model uncertainty in ∆q, and there are substantial contributions to uncertainty from both the thermodynamic (simple model) and 'dynamical' (residual) terms. The largest cause of inter-model uncertainty within the thermodynamic term is uncertainty in the magnitude of global mean SST warming.
A Simple Mathematical Model for Standard Model of Elementary Particles and Extension Thereof
Sinha, Ashok
2016-03-01
An algebraically (and geometrically) simple model representing the masses of the elementary particles in terms of the interaction (strong, weak, electromagnetic) constants is developed, including the Higgs bosons. The predicted Higgs boson mass is identical to that discovered by LHC experimental programs; while possibility of additional Higgs bosons (and their masses) is indicated. The model can be analyzed to explain and resolve many puzzles of particle physics and cosmology including the neutrino masses and mixing; origin of the proton mass and the mass-difference between the proton and the neutron; the big bang and cosmological Inflation; the Hubble expansion; etc. A novel interpretation of the model in terms of quaternion and rotation in the six-dimensional space of the elementary particle interaction-space - or, equivalently, in six-dimensional spacetime - is presented. Interrelations among particle masses are derived theoretically. A new approach for defining the interaction parameters leading to an elegant and symmetrical diagram is delineated. Generalization of the model to include supersymmetry is illustrated without recourse to complex mathematical formulation and free from any ambiguity. This Abstract represents some results of the Author's Independent Theoretical Research in Particle Physics, with possible connection to the Superstring Theory. However, only very elementary mathematics and physics is used in my presentation.
Auger-Méthé, Marie; Field, Chris; Albertsen, Christoffer M; Derocher, Andrew E; Lewis, Mark A; Jonsen, Ian D; Mills Flemming, Joanna
2016-05-25
State-space models (SSMs) are increasingly used in ecology to model time-series such as animal movement paths and population dynamics. This type of hierarchical model is often structured to account for two levels of variability: biological stochasticity and measurement error. SSMs are flexible. They can model linear and nonlinear processes using a variety of statistical distributions. Recent ecological SSMs are often complex, with a large number of parameters to estimate. Through a simulation study, we show that even simple linear Gaussian SSMs can suffer from parameter- and state-estimation problems. We demonstrate that these problems occur primarily when measurement error is larger than biological stochasticity, the condition that often drives ecologists to use SSMs. Using an animal movement example, we show how these estimation problems can affect ecological inference. Biased parameter estimates of a SSM describing the movement of polar bears (Ursus maritimus) result in overestimating their energy expenditure. We suggest potential solutions, but show that it often remains difficult to estimate parameters. While SSMs are powerful tools, they can give misleading results and we urge ecologists to assess whether the parameters can be estimated accurately before drawing ecological conclusions from their results.
Sato, N.; Sellers, P. J.; Randall, D. A.; Schneider, E. K.; Shukla, J.; Kinter, J. L., III; Hou, Y.-T.; Albertazzi, E.
1989-01-01
The Simple Biosphere MOdel (SiB) of Sellers et al., (1986) was designed to simulate the interactions between the Earth's land surface and the atmosphere by treating the vegetation explicitly and relistically, thereby incorporating biophysical controls on the exchanges of radiation, momentum, sensible and latent heat between the two systems. The steps taken to implement SiB in a modified version of the National Meteorological Center's spectral GCM are described. The coupled model (SiB-GCM) was used with a conventional hydrological model (Ctl-GCM) to produce summer and winter simulations. The same GCM was used with a conventional hydrological model (Ctl-GCM) to produce comparable 'control' summer and winter variations. It was found that SiB-GCM produced a more realistic partitioning of energy at the land surface than Ctl-GCM. Generally, SiB-GCM produced more sensible heat flux and less latent heat flux over vegetated land than did Ctl-GCM and this resulted in the development of a much deeper daytime planetary boundary and reduced precipitation rates over the continents in SiB-GCM. In the summer simulation, the 200 mb jet stream and the wind speed at 850 mb were slightly weakened in the SiB-GCM relative to the Ctl-GCM results and equivalent analyses from observations.
Freeman, Brian M; Univers, Junior; Fisher, Richard K; Kirkpatrick, Stacy S; Klein, Frederick A; Freeman, Michael B; Mountain, Deidra J H; Grandas, Oscar H
2017-01-01
Androgen deficiency (AD) is associated with increased risk of vascular disease. Dysfunctional remodeling of the vessel wall and atypical proliferative potential of vascular smooth muscle cells (VSMCs) are fundamental processes in the development of intimal hyperplasia (IH). We have demonstrated an inverse relationship between dihydrotestosterone (DHT) levels, matrix metalloproteinase activity, and VSMC migration and proliferation in vitro. Here, we investigated the role of AD and testosterone (TST) replacement in IH development in an animal model of vascular injury to elucidate mechanisms modulated by AD that could be playing a role in the development of vascular pathogenesis. Aged orchiectomized male rats underwent TST supplementation via controlled release pellet (0.5-35 mg). Young adult and middle-age adult intact (MI) and orchiectomized placebo (Plac) groups served as controls. All groups underwent balloon angioplasty of the left common carotid at a 14-d post-TST. Carotid tissue was collected at a 14-d post-balloon angioplasty and subjected to morphologic and immunohistochemical analyses. Human male VSMCs were treated with DHT (0-3000 nM) for 24 h then subjected to quantitative PCR for gene expression analyses and costained for F-actin and G-actin for visualization of cytoskeletal organization. I:M ratio was increased in Plac, subphysiological, low-physiological, and high pharmacologic level TST animals compared with MI controls but was decreased with high-physiological TST supplementation. Injury-induced expression of previously defined matrix metalloproteinase remodeling enzymes was not significantly affected by TST status. Urotensin (UTS) receptor (UTSR) staining was low in injured vessels of all young adult intact, MI, and Plac controls but was significantly upregulated in all groups receiving exogenous TST supplementation, irrespective of dose. In vitro DHT exposure increased the expression of UTSR in VSMCs in a dose-dependent manner. However, this did
Modeling Impact of Urbanization in US Cities Using Simple Biosphere Model SiB2
Zhang, Ping; Bounoua, Lahouari; Thome, Kurtis; Wolfe, Robert
2016-01-01
We combine Landsat- and the Moderate Resolution Imaging Spectroradiometer (MODIS)-based products, as well as climate drivers from Phase 2 of the North American Land Data Assimilation System (NLDAS-2) in a Simple Biosphere land surface model (SiB2) to assess the impact of urbanization in continental USA (excluding Alaska and Hawaii). More than 300 cities and their surrounding suburban and rural areas are defined in this study to characterize the impact of urbanization on surface climate including surface energy, carbon budget, and water balance. These analyses reveal an uneven impact of urbanization across the continent that should inform upon policy options for improving urban growth including heat mitigation and energy use, carbon sequestration and flood prevention.
A simple geometrical model describing shapes of soap films suspended on two rings
Herrmann, Felix J.; Kilvington, Charles D.; Wildenberg, Rebekah L.; Camacho, Franco E.; Walecki, Wojciech J.; Walecki, Peter S.; Walecki, Eve S.
2016-09-01
We measured and analysed the stability of two types of soap films suspended on two rings using the simple conical frusta-based model, where we use common definition of conical frustum as a portion of a cone that lies between two parallel planes cutting it. Using frusta-based we reproduced very well-known results for catenoid surfaces with and without a central disk. We present for the first time a simple conical frusta based spreadsheet model of the soap surface. This very simple, elementary, geometrical model produces results surprisingly well matching the experimental data and known exact analytical solutions. The experiment and the spreadsheet model can be used as a powerful teaching tool for pre-calculus and geometry students.
Phenotypic evolutionary models in stem cell biology: replacement, quiescence, and variability.
Directory of Open Access Journals (Sweden)
Marc Mangel
Full Text Available Phenotypic evolutionary models have been used with great success in many areas of biology, but thus far have not been applied to the study of stem cells except for investigations of cancer. We develop a framework that allows such modeling techniques to be applied to stem cells more generally. The fundamental modeling structure is the stochastic kinetics of stem cells in their niche and of transit amplifying and fully differentiated cells elsewhere in the organism, with positive and negative feedback. This formulation allows graded signals to be turned into all or nothing responses, and shows the importance of looking beyond the niche for understanding how stem cells behave. Using the deterministic version of this framework, we show how competition between different stem cell lines can be analyzed, and under what circumstances stem cells in a niche will be replaced by other stem cells with different phenotypic characteristics. Using the stochastic version of our framework and state dependent life history theory, we show that the optimal behavior of a focal stem cell will involve long periods of quiescence and that a population of identical stem cells will show great variability in the times at which activity occurs; we compare our results with classic ones on quiescence and variability in the hematopoietic system.
Application of simple dynamic recurrent neural networks in solid granule flowrate modeling
Du, Yun; Sun, Huiqin; Tian, Qiang; Ren, Haiping; Zhang, Suying
2008-10-01
To build the solid granule flowrate model by the simple dynamic recurrent neural network (SRNN) is presented in this paper. Because of the dynamic recurrent neural network has the characteristic of intricate network structure and slow training algorithm rate, the simple recurrent neural network without the weight values on recursion layer is studied. The recurrent prediction error (RPE) learning algorithm for SRNN by adjustment the weight value and the threshold value is reduced. The modeling result of solid granule flowrate indicates that it has fast convergence rate and the high precision the model. It can be used on real time.
Yoshinaga, Natsuhiko
2017-10-01
In this review, we discuss recent developments in the theoretical models of self-propelled particles. We first summarize simple models, including active Brownian particles (ABPs), squirmers, and Janus particles (self-phoretic swimmers). We then consider the extension of these models in order to demonstrate the symmetry-breaking mechanism of the motion. Finally, we investigate the emergence of the rich collective behaviors of these models.
A Simple Model to Teach Business Cycle Macroeconomics for Emerging Market and Developing Economies
Duncan, Roberto
2015-01-01
The canonical neoclassical model is insufficient to understand business cycle fluctuations in emerging market and developing economies. The author reformulates the model proposed by Aguiar and Gopinath (2007) in a simple setting that can be used to teach business cycle macroeconomics for emerging market and developing economies at the…
How Long is my Toilet Roll?--A Simple Exercise in Mathematical Modelling
Johnston, Peter R.
2013-01-01
The simple question of how much paper is left on my toilet roll is studied from a mathematical modelling perspective. As is typical with applied mathematics, models of increasing complexity are introduced and solved. Solutions produced at each step are compared with the solution from the previous step. This process exposes students to the typical…
Introduction to Solar Motion Geometry on the Basis of a Simple Model
Khavrus, Vyacheslav; Shelevytsky, Ihor
2010-01-01
By means of a simple mathematical model developed by the authors, the apparent movement of the Sun can be studied for arbitrary latitudes. Using this model, it is easy to gain insight into various phenomena, such as the passage of the seasons, dependences of position and time of sunrise or sunset on a specific day of year, day duration for…
Comparison of different objective functions for parameterization of simple respiration models
M.T. van Wijk; B. van Putten; D.Y. Hollinger; A.D. Richardson
2008-01-01
The eddy covariance measurements of carbon dioxide fluxes collected around the world offer a rich source for detailed data analysis. Simple, aggregated models are attractive tools for gap filling, budget calculation, and upscaling in space and time. Key in the application of these models is their parameterization and a robust estimate of the uncertainty and reliability...
Abstracting and reasoning over ship trajectories and web data with the Simple Event Model (SEM)
W.R. van Hage; V. Malaisé; G.K.D. de Vries; A.Th. Schreiber; M.W. van Someren
2012-01-01
Bridging the gap between low-level features and semantics is a problem commonly acknowledged in the Multimedia community. Event modeling can fill this gap by representing knowledge about the data at different level of abstraction. In this paper we present the Simple Event Model (SEM) and its applica
Combining ship trajectories and semantics with the simple event model (SEM)
W.R. van Hage; V. Malaisé; G. de Vries; G. Schreiber; M. van Someren
2009-01-01
Bridging the gap between low-level features and semantics is a problem commonly acknowledged in the Multimedia community. Event modeling can fill the gap. In this paper we present the Simple Event Model (SEM) and its application in a Maritime Safety and Security use case about Situational Awareness.
DEFF Research Database (Denmark)
Sørensen, P. B.; Fauser, P.; Carlsen, L.
It is shown how diffusion and deposition of solids drive the flux of substance between the water column and the sediment. The generic compartment models (Mackay type) use a one box model for the sediment in order to keep the calculations simple. However, when diffusion needs to be included...
Grass Grows, the Cow Eats: A Simple Grazing Systems Model with Emergent Properties
Ungar, Eugene David; Seligman, Noam G.; Noy-Meir, Imanuel
2004-01-01
We describe a simple, yet intellectually challenging model of grazing systems that introduces basic concepts in ecology and systems analysis. The practical is suitable for high-school and university curricula with a quantitative orientation, and requires only basic skills in mathematics and spreadsheet use. The model is based on Noy-Meir's (1975)…
Modelling the phonotactic structure of natural language words with simple recurrent networks
Stoianov, [No Value; Nerbonne, J; Bouma, H; Coppen, PA; vanHalteren, H; Teunissen, L
1998-01-01
Simple Recurrent Networks (SRN) are Neural Network (connectionist) models able to process natural language. Phonotactics concerns the order of symbols in words. We continued an earlier unsuccessful trial to model the phonotactics of Dutch words with SRNs. In order to overcome the previously reported
Modelling the advance–retreat cycle of a tidewater glacier with simple sediment dynamics
Oerlemans, J.; Nick, Faezeh Maghami
2006-01-01
We present a simple coupled glacier-sediment model to simulate the evolution of a tidewater glacier. The model is based on a consideration of the total mass budget of a glacier, whereas ice mechanics are fully parameterized. The calving rate at the glacier terminus is assumed to be proportional to t
A Simple Model to Teach Business Cycle Macroeconomics for Emerging Market and Developing Economies
Duncan, Roberto
2015-01-01
The canonical neoclassical model is insufficient to understand business cycle fluctuations in emerging market and developing economies. The author reformulates the model proposed by Aguiar and Gopinath (2007) in a simple setting that can be used to teach business cycle macroeconomics for emerging market and developing economies at the…
Comparison of the indoor performance of 12 commercial PV products by a simple model
Apostolou, G.; Reinders, A.H.M.E.; Verwaal, M.
2016-01-01
This article presents a simple comparative model which has been developed for the estimation of the performance of photovoltaic (PV) products' cells in indoor environments. The model predicts the performance of PV solar cells, as a function of the distance from a spectrum of artificial (fluorescent
Comparison of the indoor performance of 12 commercial PV products by a simple model
Apostolou, G.; Reinders, A.H.M.E.; Verwaal, M.
2016-01-01
This article presents a simple comparative model which has been developed for the estimation of the performance of photovoltaic (PV) products' cells in indoor environments. The model predicts the performance of PV solar cells, as a function of the distance from a spectrum of artificial (fluorescent
Directory of Open Access Journals (Sweden)
Hideki Higashi
Full Text Available BACKGROUND: Osteoarthritis constitutes a major musculoskeletal burden for the aged Australians. Hip and knee replacement surgeries are effective interventions once all conservative therapies to manage the symptoms have been exhausted. This study aims to evaluate the cost-effectiveness of hip and knee replacements in Australia. To our best knowledge, the study is the first attempt to account for the dual nature of hip and knee osteoarthritis in modelling the severities of right and left joints separately. METHODOLOGY/PRINCIPAL FINDINGS: We developed a discrete-event simulation model that follows up the individuals with osteoarthritis over their lifetimes. The model defines separate attributes for right and left joints and accounts for several repeat replacements. The Australian population with osteoarthritis who were 40 years of age or older in 2003 were followed up until extinct. Intervention effects were modelled by means of disability-adjusted life-years (DALYs averted. Both hip and knee replacements are highly cost effective (AUD 5,000 per DALY and AUD 12,000 per DALY respectively under an AUD 50,000/DALY threshold level. The exclusion of cost offsets, and inclusion of future unrelated health care costs in extended years of life, did not change the findings that the interventions are cost-effective (AUD 17,000 per DALY and AUD 26,000 per DALY respectively. However, there was a substantial difference between hip and knee replacements where surgeries administered for hips were more cost-effective than for knees. CONCLUSIONS/SIGNIFICANCE: Both hip and knee replacements are cost-effective interventions to improve the quality of life of people with osteoarthritis. It was also shown that the dual nature of hip and knee OA should be taken into account to provide more accurate estimation on the cost-effectiveness of hip and knee replacements.
Directory of Open Access Journals (Sweden)
Dongha Lim
2014-01-01
Full Text Available Falls are a serious medical and social problem among the elderly. This has led to the development of automatic fall-detection systems. To detect falls, a fall-detection algorithm that combines a simple threshold method and hidden Markov model (HMM using 3-axis acceleration is proposed. To apply the proposed fall-detection algorithm and detect falls, a wearable fall-detection device has been designed and produced. Several fall-feature parameters of 3-axis acceleration are introduced and applied to a simple threshold method. Possible falls are chosen through the simple threshold and are applied to two types of HMM to distinguish between a fall and an activity of daily living (ADL. The results using the simple threshold, HMM, and combination of the simple method and HMM were compared and analyzed. The combination of the simple threshold method and HMM reduced the complexity of the hardware and the proposed algorithm exhibited higher accuracy than that of the simple threshold method.
mNos2 deletion and human NOS2 replacement in Alzheimer disease models.
Colton, Carol A; Wilson, Joan G; Everhart, Angela; Wilcock, Donna M; Puoliväli, Jukka; Heikkinen, Taneli; Oksman, Juho; Jääskeläinen, Olli; Lehtimäki, Kimmo; Laitinen, Teemu; Vartiainen, Nina; Vitek, Michael P
2014-08-01
Understanding the pathophysiologic mechanisms underlying Alzheimer disease relies on knowledge of disease onset and the sequence of development of brain pathologies. We present a comprehensive analysis of early and progressive changes in a mouse model that demonstrates a full spectrum of characteristic Alzheimer disease-like pathologies. This model demonstrates an altered immune redox state reminiscent of the human disease and capitalizes on data indicating critical differences between human and mouse immune responses, particularly in nitric oxide levels produced by immune activation of the NOS2 gene. Using the APPSwDI(+)/(+)mNos2(-/-) (CVN-AD) mouse strain, we show a sequence of pathologic events leading to neurodegeneration,which include pathologically hyperphosphorylated tau in the perforant pathway at 6 weeks of age progressing to insoluble tau, early appearance of β-amyloid peptides in perivascular deposits around blood vessels in brain regions known to be vulnerable to Alzheimer disease, and progression to damage and overt loss in select vulnerable neuronal populations in these regions. The role of species differences between hNOS2 and mNos2 was supported by generating mice in which the human NOS2 gene replaced mNos2. When crossed with CVN-AD mice, pathologic characteristics of this new strain (APPSwDI(+)/(-)/HuNOS2(tg+)/(+)/mNos2(-/-)) mimicked the pathologic phenotypes found in the CVN-AD strain.
Higher plant modelling for life support applications: first results of a simple mechanistic model
Hezard, Pauline; Dussap, Claude-Gilles; Sasidharan L, Swathy
2012-07-01
total biomass fresh weight during the full growth duration. The model predicts a growth with exponential rate at the beginning and then it becomes linear for the end of the growth; this follows rather accurately the experimental data. Even if this model is too simple to be realistic for more complex plants in changing environments, this is the first step for an integrated approach of plant growth accounting of architectural and mass transfer limitations.
Modeling Surface Climate in US Cities Using Simple Biosphere Model Sib2
Zhang, Ping; Bounoua, Lahouari; Thome, Kurtis; Wolfe, Robert; Imhoff, Marc
2015-01-01
We combine Landsat- and the Moderate Resolution Imaging Spectroradiometer (MODIS)-based products in the Simple Biosphere model (SiB2) to assess the effects of urbanized land on the continental US (CONUS) surface climate. Using National Land Cover Database (NLCD) Impervious Surface Area (ISA), we define more than 300 urban settlements and their surrounding suburban and rural areas over the CONUS. The SiB2 modeled Gross Primary Production (GPP) over the CONUS of 7.10 PgC (1 PgC= 10(exp 15) grams of Carbon) is comparable to the MODIS improved GPP of 6.29 PgC. At state level, SiB2 GPP is highly correlated with MODIS GPP with a correlation coefficient of 0.94. An increasing horizontal GPP gradient is shown from the urban out to the rural area, with, on average, rural areas fixing 30% more GPP than urbans. Cities built in forested biomes have stronger UHI magnitude than those built in short vegetation with low biomass. Mediterranean climate cities have a stronger UHI in wet season than dry season. Our results also show that for urban areas built within forests, 39% of the precipitation is discharged as surface runoff during summer versus 23% in rural areas.
SU(3)simple group model and single top production at the e-γ colliders
Institute of Scientific and Technical Information of China (English)
LIU Yao-Bei; WANG Xue-Lei; REN Xiao-Yan; CAO Yong-Hua
2008-01-01
In the framework of the SU(3) simple group model,we consider the single top quark production process e-γ→,νebt.We find that the correction effects on the process mainly come from the terms of the tree-level Wqq'couplings.In the reasonable parameter space of the SU(3) simple group model,the deviation of the total production cross section σtot from its SM value is larger than 5%,which might be detected in the future high energy linear e+e- coUider (LC) experiments.
A Simple Stream Water Quality Modelling Software for Educational and Training Purposes
Erturk, Ali
2010-01-01
Water quality models are important decision support system tools for water pollution control, study of the health of aquatic ecosystems and assessment of the effects of point and diffuse pollution. However, water quality models are usually comprehensive software, which are usually not easy to learn and apply. Thus extensive training is needed before scientists and engineers can use most of the water quality models effectively. In this study; a new, easy to use and simple stream water quality ...
Self-Organized Criticality in a Simple Neuron Model Based on Scale-Free Networks
Institute of Scientific and Technical Information of China (English)
LIN Min; WANG Gang; CHEN Tian-Lun
2006-01-01
A simple model for a set of interacting idealized neurons in scale-free networks is introduced. The basic elements of the model are endowed with the main features of a neuron function. We find that our model displays powerlaw behavior of avalanche sizes and generates long-range temporal correlation. More importantly, we find different dynamical behavior for nodes with different connectivity in the scale-free networks.
A simple model for the magnetocrystalline anisotropy in mixed ferrite nanoparticles
Energy Technology Data Exchange (ETDEWEB)
Biasi, R.S. de, E-mail: rsbiasi@ime.eb.br [Secao de Engenharia Mecanica e de Materiais, Instituto Militar de Engenharia, Pr. Gen. Tiburcio 80 SE/4, Urca, 22290-270 Rio de Janeiro, RJ (Brazil); Cardoso, L.H.G., E-mail: lh.cardoso@yahoo.com.br [Secao de Engenharia Mecanica e de Materiais, Instituto Militar de Engenharia, Pr. Gen. Tiburcio 80 SE/4, Urca, 22290-270 Rio de Janeiro, RJ (Brazil)
2012-09-15
A simple model, based on the relative occupancy of tetrahedral and octahedral sites by different cations, is proposed for the magnetocrystalline anisotropy of mixed ferrite nanoparticles. According to this model, the total magnetocrystalline anisotropy is the weighted average of the contributions of the anisotropies of Fe{sup 3+} and M{sup 2+} ions in A and B sites. The model predictions are confirmed in the case of cobalt-zinc ferrite.
A Mathematical Model of a Simple Amplifier Using a Ferroelectric Transistor
Sayyah, Rana; Hunt, Mitchell; MacLeod, Todd C.; Ho, Fat D.
2009-01-01
This paper presents a mathematical model characterizing the behavior of a simple amplifier using a FeFET. The model is based on empirical data and incorporates several variables that affect the output, including frequency, load resistance, and gate-to-source voltage. Since the amplifier is the basis of many circuit configurations, a mathematical model that describes the behavior of a FeFET-based amplifier will help in the integration of FeFETs into many other circuits.
Simple Model for Simulating Characteristics of River Flow Velocity in Large Scale
Directory of Open Access Journals (Sweden)
Husin Alatas
2015-01-01
Full Text Available We propose a simple computer based phenomenological model to simulate the characteristics of river flow velocity in large scale. We use shuttle radar tomography mission based digital elevation model in grid form to define the terrain of catchment area. The model relies on mass-momentum conservation law and modified equation of motion of falling body in inclined plane. We assume inelastic collision occurs at every junction of two river branches to describe the dynamics of merged flow velocity.
Simple Models and Methods for Estimating the UltrasonicReflectivity of Spot Welds
Energy Technology Data Exchange (ETDEWEB)
Davis, William B.
2006-10-15
This paper describes models and methods for estimating theacoustic reflectivity of the welded interfaces between spot-welded sheetsfrom normal-incidence pulse-echo ultrasound signals. The simple geometryof the problem allows an abstraction that does not resort to complex waveequations. Instead, a reflectivity model predicts the timing andamplitude of the echoes arriving at the probe. This reflectivity model isnested in a signal processing model; recovering reflectivity firstrequires deconvolution to recover discrete impulses from the probesignal, then processing these with the reflectivity model. Reflectivitymaps of spot welds generated with this model show promise for predictingweld quality.
The coupling of land surface models and hydrological models potentially improves the land surface representation, benefiting both the streamflow prediction capabilities as well as providing improved estimates of water and energy fluxes into the atmosphere. In this study, the simple biosphere model 2...
Energy Technology Data Exchange (ETDEWEB)
Boehm, B. [Technical Univ. of Denmark, Dept. of Mechanical Engineering, Kgs. Lyngby (Denmark); Larsen, H.V. [Risoe National Lab., System Analysis Dept., Roskilde (DK)
2004-12-01
The purpose of this research project has been to further develop and test simple (aggregated) models of district heating (DH) systems for simulation and operational optimization, and to investigate the influence of Load Management and Demand Side Management (DMS) on the total operational costs. The work is based on physical-mathematical modelling and simulation of DH systems, and is a continuation of previous EFP-96 work. In the present EFP-2001 project the goals have been to improve the Danish method of aggregation by addressing the problem of aggregation of pressure losses, and to test the methods on a much larger data set than in the EFP-1996 project. In order to verify the models it is crucial to have good data at disposal. Full information on the heat loads and temperatures not only at the DH plant but also at every consumer (building) is needed, and therefore only a few DH systems in Denmark can supply such data. (BA)
Ankle arthroplasty - total; Total ankle arthroplasty; Endoprosthetic ankle replacement; Ankle surgery ... You may not be able to have a total ankle replacement if you have had ankle joint infections in ...
Knee replacement is surgery for people with severe knee damage. Knee replacement can relieve pain and allow you to ... Your doctor may recommend it if you have knee pain and medicine and other treatments are not ...
Testosterone replacement attenuates mitochondrial damage in a rat model of myocardial infarction.
Wang, Fengyue; Yang, Jing; Sun, Junfeng; Dong, Yanli; Zhao, Hong; Shi, Hui; Fu, Lu
2015-05-01
Testosterone can affect cardiovascular disease, but its effects on mitochondrial dynamics in the post-infarct myocardium remain unclear. To observe the effects of testosterone replacement, a rat model of castration-myocardial infarction (MI) was established by ligating the left anterior descending coronary artery 2 weeks after castration with or without testosterone treatment. Expression of mitochondrial fission and fusion proteins was detected by western blot and immunofluorescence 14 days after MI. Cardiac function, myocardial inflammatory infiltration and fibrosis, cardiomyocyte apoptosis, mitochondrial microstructure, and ATP levels were also assessed. Compared with MI rats, castrated rats showed aggravated mitochondrial and myocardial insults, including mitochondrial swelling and disordered arrangement; loss of cristae, reduced mitochondrial length; decreased ATP levels; cardiomyocyte apoptosis; and impaired cardiac function. Results of western blotting analyses indicated that castration downregulated peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1A) and mitofusin 2, but upregulated dynamin-related protein 1. The results were also supported by results obtained using immunofluorescence. However, these detrimental effects were reversed by testosterone supplementation, which also elevated the upstream AMP-activated protein kinase (AMPK) activation of PGC1A. Thus, testosterone can protect mitochondria in the post-infarct myocardium, partly via the AMPK-PGC1A pathway, thereby decreasing mitochondrial dysfunction and cardiomyocyte apoptosis. The effects of testosterone were confirmed by the results of ELISA analyses.
Schäfer-Nolte, Franziska; Hennecke, Kathleen; Reimers, Kerstin; Schnabel, Reinhild; Allmeling, Christina; Vogt, Peter M; Kuhbier, Joern W; Mirastschijski, Ursula
2014-04-01
The aim of this study was to investigate biomechanical and immunogenic properties of spider silk meshes implanted as fascia replacement in a rat in vivo model. Meshes for hernia repair require optimal characteristics with regard to strength, elasticity, and cytocompatibility. Spider silk as a biomaterial with outstanding mechanical properties is potentially suitable for this application. Commercially available meshes used for hernia repair (Surgisis and Ultrapro) were compared with handwoven meshes manufactured from native dragline silk of Nephila spp. All meshes were tied onto the paravertebral fascia, whereas sham-operated rats were sutured without mesh implantation. After 4 or 14 days, 4 weeks, and 4 or 8 months, tissue samples were analyzed concerning inflammation and biointegration both by histological and biochemical methods and by biomechanical stability tests. Histological sections revealed rapid cell migration into the spider silk meshes with increased numbers of giant cells compared with controls with initial decomposition of silk fibers after 4 weeks. Four months postoperatively, spider silk was completely degraded with the formation of a stable scar verified by constant tensile strength values. Surgisis elicited excessive stability loss from day 4 to day 14 (P spider silk samples had the highest relative elongation (P spider silk meshes with good biocompatibility and beneficial mechanical properties seem superior to standard biological and synthetic meshes, implying an innovative alternative to currently used meshes for hernia repair.
Encoding Scratch and Scrape Features for Wear Modeling of Total Joint Replacements
Directory of Open Access Journals (Sweden)
Karen M. Kruger
2013-01-01
Full Text Available Damage to hard bearing surfaces of total joint replacement components typically includes both thin discrete scratches and broader areas of more diffuse scraping. Traditional surface metrology parameters such as average roughness or peak asperity height are not well suited to quantifying those counterface damage features in a manner allowing their incorporation into models predictive of polyethylene wear. A diffused lighting technique, which had been previously developed to visualize these microscopic damage features on a global implant level, also allows damaged regions to be automatically segmented. These global-level segmentations in turn provide a basis for performing high-resolution optical profilometry (OP areal scans, to quantify the microscopic-level damage features. Algorithms are here reported by means of which those imaged damage features can be encoded for input into finite element (FE wear simulations. A series of retrieved clinically failed implant femoral heads analyzed in this manner exhibited a wide range of numbers and severity of damage features. Illustrative results from corresponding polyethylene wear computations are also presented.
Damped and persistent oscillations in a simple model of cell crawling.
Bayly, Philip V; Taber, Larry A; Carlsson, Anders E
2012-06-07
A very simple, one-dimensional, discrete, autonomous model of cell crawling is proposed; the model involves only three or four coupled first-order differential equations. This form is sufficient to describe many general features of cell migration, including both steady forward motion and oscillatory progress. Closed-form expressions for crawling speeds and internal forces are obtained in terms of dimensionless parameters that characterize active intracellular processes and the passive mechanical properties of the cell. Two versions of the model are described: a basic cell model with simple elastic coupling between front and rear, which exhibits stable, steady forward crawling after initial transient oscillations have decayed, and a poroelastic model, which can exhibit oscillatory crawling in the steady state.
Otto Laporte Lecture: Fluid Dynamics Prize Talk: Simple Models for Turbulent Flows
Pope, Stephen B.
2009-11-01
We focus on the modeling of two turbulent flows: dispersion from a line source in grid turbulence; and, a lifted non-premixed turbulent jet flame. Stochastic Lagrangian models and PDF methods are described, and are shown to model these flows satisfactorily. For the line source, a Lagrangian approach is taken, with the Langevin equation modeling the velocity following a fluid particle, and with a simple relaxation model for the particle temperature. Comparison with experimental data shows that the resulting model describes accurately the dispersion from single and multiple line sources. These simple stochastic Lagrangian models are then applied to the much more challenging case of a lifted non-premixed jet flame. The stochastic Lagrangian models form the basis for a particle/mesh numerical method for solving a modeled transport equation for the Eulerian joint probability density function (PDF) of velocity and composition. The PDF calculations are in excellent agreement with the experimental data, and exhibit the observed extreme sensitivity of the flame to the temperature of the co-flow. The PDF model calculations presented clearly demonstrate that simple models can be very useful, even though aspects of their behavior may be inaccurate or incomplete. The shortcomings of the Langevin equation are examined, and more advanced models (designed to overcome some of these shortcomings) are described. These include models for fluid-particle acceleration, including the effects of intermittency; models accounting for mean shear, which are correct in the rapid- distortion limit; and models designed for use in conjunction with large-eddy simulations (LES).
A Simple Computer-Aided Three-Dimensional Molecular Modeling for the Octant Rule
Kang, Yinan; Kang, Fu-An
2011-01-01
The Moffitt-Woodward-Moscowitz-Klyne-Djerassi octant rule is one of the most successful empirical rules in organic chemistry. However, the lack of a simple effective modeling method for the octant rule in the past 50 years has posed constant difficulties for researchers, teachers, and students, particularly the young generations, to learn and…
Erratum: A Simple, Analytical Model of Collisionless Magnetic Reconnection in a Pair Plasma
Hesse, Michael; Zenitani, Seiji; Kuznetsova, Masha; Klimas, Alex
2011-01-01
The following describes a list of errata in our paper, "A simple, analytical model of collisionless magnetic reconnection in a pair plasma." It supersedes an earlier erratum. We recently discovered an error in the derivation of the outflow-to-inflow density ratio.
Antarctic ice volume for the last 740 ka calculated with a simple ice sheet model
Oerlemans, J.
2005-01-01
Fluctuations in the volume of the Antarctic ice sheet for the last 740 ka are calculated by forcing a simple ice sheet model with a sea-level history (from a composite deep sea δ18O record) and a temperature history (from the Dome C deuterium record). Antarctic ice volume reaches maximum values of a
Baudena, M.|info:eu-repo/dai/nl/340303867; Boni, G.; Ferraris, L.; von Hardenberg, J.; Provenzale, A.
2007-01-01
Vegetation in arid and semi-arid regions is affected by intermittent water availability. We discuss a simple stochastic model describing the coupled dynamics of soil moisture and vegetation, and study the effects of rainfall intermittency. Soil moisture dynamics is described by a ecohydrological box
Interaction of Simple Ions with Water: Theoretical Models for the Study of Ion Hydration
Gancheff, Jorge S.; Kremer, Carlos; Ventura, Oscar N.
2009-01-01
A computational experiment aimed to create and systematically analyze models of simple cation hydrates is presented. The changes in the structure (bond distances and angles) and the electronic density distribution of the solvent and the thermodynamic parameters of the hydration process are calculated and compared with the experimental data. The…
Simple Quantum Model of Learning Explains the Yerkes-Dodson Law in Psychology
Vol, E D
2012-01-01
We propose the simple model of learning based on which we derive and explain the Yerkes-Dodson law - one of the oldest laws of experimental psychology. The approach uses some ideas of quantum theory of open systems (QTOS) and develops the method of statistical description of psychological systems that was proposed by author earlier.
Using of Video Modeling in Teaching a Simple Meal Preparation Skill for Pupils of Down Syndrome
AL-Salahat, Mohammad Mousa
2016-01-01
The current study aimed to identify the impact of video modeling upon teaching three pupils with Down syndrome the skill of preparing a simple meal (sandwich), where the training was conducted in a separate classroom in schools of normal students. The training consisted of (i) watching the video of an intellectually disabled pupil, who is…
Validation of a simple model for the morphology of the T wave in unipolar electrograms
Potse, Mark; Vinet, Alain; Opthof, Tobias; Coronel, Ruben
2009-01-01
Potse M, Vinet A, Opthof T, Coronel R. Validation of a simple model for the morphology of the T wave in unipolar electrograms. Am J Physiol Heart Circ Physiol 297: H792-H801, 2009. First published May 22, 2009; doi: 10.1152/ajpheart.00064.2009.-Local unipolar electrograms (UEGs) permit assessment of
A simple and efficient parallel FFT algorithm using the BSP model
Bisseling, R.H.; Inda, M.A.
2000-01-01
In this paper we present a new parallel radix FFT algorithm based on the BSP model Our parallel algorithm uses the groupcyclic distribution family which makes it simple to understand and easy to implement We show how to reduce the com munication cost of the algorithm by a factor of three in the case
A simple model for Brownian motion leading to the Langevin equation
Grooth, de Bart G.
1999-01-01
A simple one-dimensional model is presented for the motion of a Brownian particle. It is shown how the collisions between a Brownian particle and its surrounding molecules lead to the Langevin equation, the power spectrum of the stochastic force, and the equipartition of kinetic energy.
[Structural models of simple sense organs by the example of first metazoans].
Aronova, M Z
2009-01-01
Basic variants of the evolutional program for formation of simple sensor system--structural models of gravitation receptor, organ of vision, chemoreceptor organ as well as of the nervous system at early stages of the metazoan phylogenesis--are considered from results of our own morphofunctional studies and literature data.
A simple model for atomic layer doped field-effect transistor (ALD-FET) electronic states
Energy Technology Data Exchange (ETDEWEB)
Mora R, M.E. [Centro de Investigaciones en Optica, Unidad Aguascalientes. Juan de Montoro 207, Zona Centro, 20000 Aguascalientes (Mexico); Gaggero S, L.M. [Escuela de Fisica, Universidad Autonoma de Zacatecas, Av. Preparatoria 301, 98060 Zacatecas (Mexico)
1998-12-31
We propose a simple potential model based on the Thomas-Fermi approximation to reproduce the main properties of the electronic structure of an atomic layer doped field effect transistor. Preliminary numerical results for a Si-based ALD-FET justify why bound electronic states are not observed in the experiment. (Author)
DYNAMIC SURFACE BOUNDARY-CONDITIONS - A SIMPLE BOUNDARY MODEL FOR MOLECULAR-DYNAMICS SIMULATIONS
JUFFER, AH; BERENDSEN, HJC
1993-01-01
A simple model for the treatment of boundaries in molecular dynamics simulations is presented. The method involves the positioning of boundary atoms on a surface that surrounds a system of interest. The boundary atoms interact with the inner region and represent the effect of atoms outside the surfa
Simple One-Dimensional Quantum-Mechanical Model for a Particle Attached to a Surface
Fernandez, Francisco M.
2010-01-01
We present a simple one-dimensional quantum-mechanical model for a particle attached to a surface. It leads to the Schrodinger equation for a harmonic oscillator bounded on one side that we solve in terms of Weber functions and discuss the behaviour of the eigenvalues and eigenfunctions. We derive the virial theorem and other exact relationships…
Examining the Simple View of Reading Model for United States High School Spanish Students
Sparks, Richard; Patton, Jon
2016-01-01
The Simple View of Reading (SVR) model, which posits that reading comprehension is the product of word decoding and language comprehension that make independent contributions to reading skill, has been found to explain the acquisition of first language (L1) reading and second language (L2) reading in young English language learners (ELLs).…
Simple Regge pole model for proton-proton elastic scattering at high energies
Energy Technology Data Exchange (ETDEWEB)
Saleem, M.; Fazal-e-Aleem
1979-06-01
It is shown that by a phenomemological choice of residue functions, the angular distribution in pp elastic scattering at high energies, including the most recent measurement at ..sqrt..s = 27.4 GeV with squared 4-momentum transfer, -t, extending up to 14 (GeV/c)/sup 2/, can be explained with simple Regge pole model.
DEFF Research Database (Denmark)
Hubalek, Friedrich; Posedel, Petra
We provide a simple explicit estimator for discretely observed Barndorff-Nielsen and Shephard models, prove rigorously consistency and asymptotic normality based on the single assumption that all moments of the stationary distribution of the variance process are finite, and give explicit expressi...
Simple One-Dimensional Quantum-Mechanical Model for a Particle Attached to a Surface
Fernandez, Francisco M.
2010-01-01
We present a simple one-dimensional quantum-mechanical model for a particle attached to a surface. It leads to the Schrodinger equation for a harmonic oscillator bounded on one side that we solve in terms of Weber functions and discuss the behaviour of the eigenvalues and eigenfunctions. We derive the virial theorem and other exact relationships…
van Dussen, Laura; Biegstraaten, Marieke; Dijkgraaf, Marcel Gw; Hollak, Carla Em
2014-07-24
Long-term complications and associated conditions of type 1 Gaucher Disease (GD) can include splenectomy, bone complications, pulmonary hypertension, Parkinson disease and malignancies. Enzyme replacement therapy (ERT) reverses cytopenia and reduces organomegaly. To study the effects of ERT on long-term complications and associated conditions, the course of Gaucher disease was modelled.
A simple model of bipartite cooperation for ecological and organizational networks.
Saavedra, Serguei; Reed-Tsochas, Felix; Uzzi, Brian
2009-01-22
In theoretical ecology, simple stochastic models that satisfy two basic conditions about the distribution of niche values and feeding ranges have proved successful in reproducing the overall structural properties of real food webs, using species richness and connectance as the only input parameters. Recently, more detailed models have incorporated higher levels of constraint in order to reproduce the actual links observed in real food webs. Here, building on previous stochastic models of consumer-resource interactions between species, we propose a highly parsimonious model that can reproduce the overall bipartite structure of cooperative partner-partner interactions, as exemplified by plant-animal mutualistic networks. Our stochastic model of bipartite cooperation uses simple specialization and interaction rules, and only requires three empirical input parameters. We test the bipartite cooperation model on ten large pollination data sets that have been compiled in the literature, and find that it successfully replicates the degree distribution, nestedness and modularity of the empirical networks. These properties are regarded as key to understanding cooperation in mutualistic networks. We also apply our model to an extensive data set of two classes of company engaged in joint production in the garment industry. Using the same metrics, we find that the network of manufacturer-contractor interactions exhibits similar structural patterns to plant-animal pollination networks. This surprising correspondence between ecological and organizational networks suggests that the simple rules of cooperation that generate bipartite networks may be generic, and could prove relevant in many different domains, ranging from biological systems to human society.
Rank Set Sampling in Improving the Estimates of Simple Regression Model
Directory of Open Access Journals (Sweden)
M Iqbal Jeelani
2015-04-01
Full Text Available In this paper Rank set sampling (RSS is introduced with a view of increasing the efficiency of estimates of Simple regression model. Regression model is considered with respect to samples taken from sampling techniques like Simple random sampling (SRS, Systematic sampling (SYS and Rank set sampling (RSS. It is found that R2 and Adj R2 obtained from regression model based on Rank set sample is higher than rest of two sampling schemes. Similarly Root mean square error, p-values, coefficient of variation are much lower in Rank set based regression model, also under validation technique (Jackknifing there is consistency in the measure of R2, Adj R2 and RMSE in case of RSS as compared to SRS and SYS. Results are supported with an empirical study involving a real data set generated of Pinus Wallichiana taken from block Langate of district Kupwara.
A simple, closed-form, mathematical model for gas exchange in microchannel artificial lungs.
Potkay, Joseph A
2013-06-01
Microfabrication techniques are attractive for constructing artificial lungs due to the ability to create features similar in size to those in the natural lung. However, a simple and intuitive mathematical model capable of accurately predicting the gas exchange performance of microchannel artificial lungs does not currently exist. Such a model is critical to understanding and optimizing these devices. Here, we describe a simple, closed-form mathematical model for gas exchange in microchannel artificial lungs and qualify it through application to experimental data from several research groups. We utilize lumped parameters and several assumptions to obtain a closed-form set of equations that describe gas exchange. This work is intended to augment computational models by providing a more intuitive, albeit potentially less accurate, understanding of the operation and trade-offs inherent in microchannel artificial lung devices.
Spectral Line-Shape Model to Replace the Voigt Profile in Spectroscopic Databases
Lisak, Daniel; Ngo, Ngoc Hoa; Tran, Ha; Hartmann, Jean-Michel
2014-06-01
The standard description of molecular line shapes in spectral databases and radiative transfer codes is based on the Voigt profile. It is well known that its simplified assumptions of absorber free motion and independence of collisional parameters from absorber velocity lead to systematic errors in analysis of experimental spectra, and retrieval of gas concentration. We demonstrate1,2 that the partially correlated quadratic speed-dependent hardcollision profile3. (pCqSDHCP) is a good candidate to replace the Voigt profile in the next generations of spectroscopic databases. This profile takes into account the following physical effects: the Doppler broadening, the pressure broadening and shifting of the line, the velocity-changing collisions, the speed-dependence of pressure broadening and shifting, and correlations between velocity- and phase/state-changing collisions. The speed-dependence of pressure broadening and shifting is incorporated into the pCqSDNGP in the so-called quadratic approximation. The velocity-changing collisions lead to the Dicke narrowing effect; however in many cases correlations between velocityand phase/state-changing collisions may lead to effective reduction of observed Dicke narrowing. The hard-collision model of velocity-changing collisions is also known as the Nelkin-Ghatak model or Rautian model. Applicability of the pCqSDHCP for different molecular systems was tested on calculated and experimental spectra of such molecules as H2, O2, CO2, H2O in a wide span of pressures. For all considered systems, pCqSDHCP is able to describe molecular spectra at least an order of magnitude better than the Voigt profile with all fitted parameters being linear with pressure. In the most cases pCqSDHCP can reproduce the reference spectra down to 0.2% or better, which fulfills the requirements of the most demanding remote-sensing applications. An important advantage of pCqSDHCP is that a fast algorithm for its computation was developedab4,5 and allows
A Push-Pull CORF Model of a Simple Cell with Antiphase Inhibition Improves SNR and Contour Detection
Azzopardi, George; Rodriguez-Sanchez, Antonio; Piater, Justus; Petkov, Nicolai
2014-01-01
We propose a computational model of a simple cell with push-pull inhibition, a property that is observed in many real simple cells. It is based on an existing model called Combination of Receptive Fields or CORF for brevity. A CORF model uses as afferent inputs the responses of model LGN cells with
Statistical power analysis a simple and general model for traditional and modern hypothesis tests
Murphy, Kevin R; Wolach, Allen
2014-01-01
Noted for its accessible approach, this text applies the latest approaches of power analysis to both null hypothesis and minimum-effect testing using the same basic unified model. Through the use of a few simple procedures and examples, the authors show readers with little expertise in statistical analysis how to obtain the values needed to carry out the power analysis for their research. Illustrations of how these analyses work and how they can be used to choose the appropriate criterion for defining statistically significant outcomes are sprinkled throughout. The book presents a simple and g
Half-lives for α and cluster radioactivity in a simple model
Zdeb, A.; Warda, M.; Pomorski, K.
2013-05-01
A simple phenomenological model based on the WKB theory for the evaluation of half-lives for α and cluster radioactivity is proposed. The model contains only one adjustable parameter, the nuclear radius constant, common for both kinds of decay and three additional hindrance factors for odd-even, even-odd and odd-odd nuclei. A good agreement with the experimental data is achieved.
Stock Exchange Competition in a Simple Model of Capital Market Equilibrium
Sofia B. Ramos; Ernst-Ludwig VON THADDEN
2003-01-01
This paper uses a simple model of mean-variance asset pricing with transaction costs to analyze one of the main empirical phenomena in stock market competition in the last years, the decrease of transaction costs. We endogenize transaction costs as variables strategically influenced by stock exchanges and model stock market integration as an increase in the correlation of the underlying stock market returns. Among other things, we find that market integration leads to a decrease of transactio...
Stellar and HI Mass Functions Predicted by a Simple Preheating Galaxy Formation Model
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
According to the new preheating mechanism of galaxy formation suggested by Mo et al., we construct a simple model of formation of disk galaxies within the current paradigm of galaxy formation. It incorporates preheating, gas cooling, bulge formation and star formation. The predicted stellar and HI mass functions of galaxies are discussed and compared with the observations. It is found that our model can roughly match both the observed galaxy luminosity function and the observed HI-mass function.
A Simple Model for the Non-Arrhenius Ionic Conductivity in Superionic Glasses
Indoh, Takaki; Aniya, Masaru; インドウ, タカキ; アニヤ, マサル; 犬童, 貴樹; 安仁屋, 勝
2010-01-01
Many superionic conducting glasses follow the Arrhenius type temperature dependence of ionic conductivity. However, in some superionic conductors it has been discovered that the conductivity deviate from the Arrhenius type behavior. In this paper, we present a simple model that describes the non-Arrhenius type ionic conductivity based on the Zwanzig model of diffusion. From the theory, the condition for the appearance of non-Arrhenius type ionic conductivity has been obtained.
Xiao, Jianxi; Madhan, Balaraman; Li, Yingjie; Brodsky, Barbara; Baum, Jean
2011-07-20
Missense mutations, which replace one Gly with a larger residue in the repeating sequence of the type I collagen triple helix, lead to the hereditary bone disorder osteogenesis imperfecta (OI). Previous studies suggest that these mutations may interfere with triple-helix folding. NMR was used to investigate triple-helix formation in a series of model peptides where the residue replacing Gly, as well as the local sequence environment, was varied. NMR measurement of translational diffusion coefficients allowed the identification of partially folded species. When Gly was replaced by Ala, the Ala residue was incorporated into a fully folded triple helix, whereas replacement of Gly by Ser or Arg resulted in the presence of some partially folded species, suggesting a folding barrier. Increasing the triple-helix stability of the sequence N-terminal to a Gly-to-Ser replacement allowed complete triple-helix folding, whereas with the substitution of Arg, with its large side chain, the peptide achieved full folding only after flexible residues were introduced N-terminal to the mutation site. These studies shed light on the factors important for accommodation of Gly mutations within the triple helix and may relate to the varying severity of OI.
Simple analytic functions for modeling three-dimensional flow in layered aquifers
Fitts, Charles R.
1989-05-01
Analytic functions are presented for modeling three-dimensional steady groundwater flow in stratified aquifers. The functions create discontinuity in the potential across an infinite plane while maintaining continuity of the potential gradient across the plane. These functions may be superimposed with other analytic functions to model three-dimensional flow in stratified aquifers under a variety of boundary conditions. An interface between two layers of different hydraulic conductivity, an impermeable boundary, or a thin leaky layer may be modeled using such functions. These functions are simple compared to functions for doublet distributions over finite plane panels and are suitable for efficient modeling.
Vaquerizo, Beatriz; Theriault-Lauzier, Pascal; Piazza, Nicolo
2015-12-01
Mitral regurgitation is the most prevalent valvular heart disease worldwide. Despite the widespread availability of curative surgical intervention, a considerable proportion of patients with severe mitral regurgitation are not referred for treatment, largely due to the presence of left ventricular dysfunction, advanced age, and comorbid illnesses. Transcatheter mitral valve replacement is a promising therapeutic alternative to traditional surgical valve replacement. The complex anatomical and pathophysiological nature of the mitral valvular complex, however, presents significant challenges to the successful design and implementation of novel transcatheter mitral replacement devices. Patient-specific 3-dimensional computer-based models enable accurate assessment of the mitral valve anatomy and preprocedural simulations for transcatheter therapies. Such information may help refine the design features of novel transcatheter mitral devices and enhance procedural planning. Herein, we describe a novel medical image-based processing tool that facilitates accurate, noninvasive assessment of the mitral valvular complex, by creating precise three-dimensional heart models. The 3-dimensional computer reconstructions are then converted to a physical model using 3-dimensional printing technology, thereby enabling patient-specific assessment of the interaction between device and patient. It may provide new opportunities for a better understanding of the mitral anatomy-pathophysiology-device interaction, which is of critical importance for the advancement of transcatheter mitral valve replacement.
Reversals of the solar magnetic dipole in the light of observational data and simple dynamo models
Moss, D; Sokoloff, D D; Hoeksema, J T
2013-01-01
Observations show that the photospheric solar magnetic dipole usually does not vanish during the inversion of the solar magnetic field, which occurs in each solar cycle. In contrast, mean-field solar dynamo models predict that the dipole field does become zero. In a recent paper Moss et al. (2013) suggested that this contradiction can be explained as a large-scale manifestation of small-scale magnetic fluctuations. Our aim is to confront this interpretation with the available observational data. Here we compare this interpretation with WSO (Wilcox Solar Observatory) photospheric magnetic field data in order to determine the amplitude of magnetic fluctuations required to explain the phenomenon and to compare the results with predictions from a simple dynamo model which takes fluctuations into account. We demonstrate that the WSO data concerning the magnetic dipole inversions are very similar indeed to the predictions of our very simple solar dynamo model, which includes both mean magnetic field and fluctuation...
PeptideBuilder: A simple Python library to generate model peptides
Directory of Open Access Journals (Sweden)
Matthew Z. Tien
2013-05-01
Full Text Available We present a simple Python library to construct models of polypeptides from scratch. The intended use case is the generation of peptide models with pre-specified backbone angles. For example, using our library, one can generate a model of a set of amino acids in a specific conformation using just a few lines of python code. We do not provide any tools for energy minimization or rotamer packing, since powerful tools are available for these purposes. Instead, we provide a simple Python interface that enables one to add residues to a peptide chain in any desired conformation. Bond angles and bond lengths can be manipulated if so desired, and reasonable values are used by default.
Simple Empirical Model for Identifying Rheological Properties of Soft Biological Tissues
Kobayashi, Yo; Miyashita, Tomoyuki; Fujie, Masakatsu G
2015-01-01
Understanding the rheological properties of soft biological tissue is a key issue for mechanical systems used in the healthcare field. We propose a simple empirical model using Fractional Dynamics and Exponential Nonlinearity (FDEN) to identify the rheological properties of soft biological tissue. The model is derived from detailed material measurements using samples isolated from porcine liver. We conducted dynamic viscoelastic and creep tests on liver samples using a rheometer. The experimental results indicated that biological tissue has specific properties: i) power law increases in storage elastic modulus and loss elastic modulus with the same slope; ii) power law gain decrease and constant phase delay in the frequency domain over two decades; iii) log-log scale linearity between time and strain relationships under constant force; and iv) linear and log scale linearity between strain and stress relationships. Our simple FDEN model uses only three dependent parameters and represents the specific propertie...
A simple model for predicting sprint-race times accounting for energy loss on the curve
Mureika, J. R.
1997-11-01
The mathematical model of J. Keller for predicting World Record race times, based on a simple differential equation of motion, predicted quite well the records of the day. One of its shortcoming is that it neglects to account for a sprinter's energy loss around a curve, a most important consideration particularly in the 200m--400m. An extension to Keller's work is considered, modeling the aforementioned energy loss as a simple function of the centrifugal force acting on the runner around the curve. Theoretical World Record performances for indoor and outdoor 200m are discussed, and the use of the model at 300m is investigated. Some predictions are made for possible 200m outdoor and indoor times as run by Canadian 100m WR holder Donovan Bailey, based on his 100m final performance at the 1996 Olympic Games in Atlanta.
A Simple Model for Predicting Sprint Race Times Accounting for Energy Loss on the Curve
Mureika, J R
1997-01-01
The mathematical model of J. Keller for predicting World Record race times, based on a simple differential equation of motion, predicted quite well the records of the day. One of its shortcoming is that it neglects to account for a sprinter's energy loss around a curve, a most important consideration particularly in the 200m--400m. An extension to Keller's work is considered, modeling the aforementioned energy loss as a simple function of the centrifugal force acting on the runner around the curve. Theoretical World Record performances for indoor and outdoor 200m are discussed, and the use of the model at 300m is investigated. Some predictions are made for possible 200m outdoor and indoor times as run by Canadian 100m WR holder Donovan Bailey, based on his 100m final performance at the 1996 Olympic Games in Atlanta.
A simple multistage closed-(box+reservoir model of chemical evolution
Directory of Open Access Journals (Sweden)
Caimmi R.
2011-01-01
Full Text Available Simple closed-box (CB models of chemical evolution are extended on two respects, namely (i simple closed-(box+reservoir (CBR models allowing gas outflow from the box into the reservoir (Hartwick 1976 or gas inflow into the box from the reservoir (Caimmi 2007 with rate proportional to the star formation rate, and (ii simple multistage closed-(box+reservoir (MCBR models allowing different stages of evolution characterized by different inflow or outflow rates. The theoretical differential oxygen abundance distribution (TDOD predicted by the model maintains close to a continuous broken straight line. An application is made where a fictitious sample is built up from two distinct samples of halo stars and taken as representative of the inner Galactic halo. The related empirical differential oxygen abundance distribution (EDOD is represented, to an acceptable extent, as a continuous broken line for two viable [O/H]-[Fe/H] empirical relations. The slopes and the intercepts of the regression lines are determined, and then used as input parameters to MCBR models. Within the errors (-+σ, regression line slopes correspond to a large inflow during the earlier stage of evolution and to low or moderate outflow during the subsequent stages. A possible inner halo - outer (metal-poor bulge connection is also briefly discussed. Quantitative results cannot be considered for applications to the inner Galactic halo, unless selection effects and disk contamination are removed from halo samples, and discrepancies between different oxygen abundance determination methods are explained.
Chen, Nan; Majda, Andrew J.
2017-01-01
The El Niño Southern Oscillation (ENSO) has significant impact on global climate and seasonal prediction. A simple modeling framework is developed here that automatically captures the statistical diversity of ENSO. First, a stochastic parameterization of the wind bursts including both westerly and easterly winds is coupled to a simple ocean–atmosphere model that is otherwise deterministic, linear, and stable. Second, a simple nonlinear zonal advection with no ad hoc parameterization of the background sea-surface temperature (SST) gradient and a mean easterly trade wind anomaly representing the multidecadal acceleration of the trade wind are both incorporated into the coupled model that enables anomalous warm SST in the central Pacific. Then a three-state stochastic Markov jump process is used to drive the wind burst activity that depends on the strength of the western Pacific warm pool in a simple and effective fashion. It allows the coupled model to simulate the quasi-regular moderate traditional El Niño, the super El Niño, and the central Pacific (CP) El Niño as well as the La Niña with realistic features. In addition to the anomalous SST, the Walker circulation anomalies at different ENSO phases all resemble those in nature. In particular, the coupled model succeeds in reproducing the observed episode during the 1990s, where a series of 5-y CP El Niños is followed by a super El Niño and then a La Niña. Importantly, both the variance and the non-Gaussian statistical features in different Niño regions spanning from the western to the eastern Pacific are captured by the coupled model. PMID:28137886
Energy Technology Data Exchange (ETDEWEB)
Svedmark, Per (Div. of Orthopedics, Dept. of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm (Sweden); Stockholm Spine Center, Lowenstromska Hospital, Stockholm (Sweden)), email: per.svedmark@spinecenter.se; Lundh, Fredrik; Olivecrona, Henrik (Div. of Orthopedics, Dept. of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm (Sweden)); Nemeth, Gunnar (Capio group, Stockholm (Sweden)); Noz, Marilyn E. (Dept. of Radiology, New York Univ. School of Medicine, New York (United States)); Maguire Jr, Gerald Q. (School of Information and Communication Technology, Royal Inst. of Technology, Kista (Sweden)); Zeleznik, Michael P. (Saya Systems Inc., Salt Lake City (United States))
2011-12-15
Background. Cervical total disc replacement (CTDR) is an alternative to anterior fusion. Therefore, it is desirable to have an accurate in vivo measurement of prosthetic kinematics and assessment of implant stability relative to the adjacent vertebrae. Purpose. To devise an in vivo CT-based method to analyze the kinematics of cervical total disc replacements (CTDR), specifically of two prosthetic components between two CT scans obtained under different conditions. Material and Methods. Nine patients with CTDR were scanned in flexion and extension of the cervical spine using a clinical CT scanner with a routine low-dose protocol. The flexion and extension CT volume data were spatially registered, and the prosthetic kinematics of two prosthetic components, an upper and a lower, was calculated and expressed in Euler angles and orthogonal linear translations relative to the upper component. For accuracy analysis, a cervical spine model incorporating the same disc replacement as used in the patients was also scanned and processed in the same manner. Results. Analysis of both the model and patients showed good repeatability, i.e. within 2 standard deviations of the mean using the 95% limits of agreement with no overlapping confidence intervals. The accuracy analysis showed that the median error was close to zero. Conclusion. The mobility of the cervical spine after total disc replacement can be effectively measured in vivo using CT. This method requires an appropriate patient positioning and scan parameters to achieve suitable image quality
Reeves, E A; Barton, D C; FitzPatrick, D P; Fisher, J
1998-01-01
As new methods of sterilization of the ultra-high molecular weight polyethylene (UHMWPE) component in knee replacements are introduced, reported incidents of delamination will decrease. The prediction of plastic strain accumulation and associated failure mechanisms will then become more important in knee replacement design. The finite element analysis reported in this paper aims to advance the modelling of strain accumulation in UHMWPE over repeated gait cycles and seeks to determine the effects of the knee replacement design variables of geometry and kinematics. Material testing was performed under cyclic and creep conditions to generate the elastic, viscoplastic material model that has been used in this time-dependent analysis. Non-conforming geometries were found to accumulate plastic strains at higher rates than conforming geometries. The anatomical motion known as rollback initially produced lower strain rates, but predictions of the long-term response indicated that designs which allow rollback may produce higher strains than static designs after only about a week of loading for a knee replacement patient.
Institute of Scientific and Technical Information of China (English)
ZHAO Chong-bin; Thomas POULET; Klaus REGENAUER-LIEB
2015-01-01
In order to simulate the instability phenomenon of a nonaqueous phase liquid (NAPL) dissolution front in a computational model, the intrinsic characteristic length is commonly used to determine the length scale at which the instability of the NAPL dissolution front can be initiated. This will require a huge number of finite elements if a whole NAPL dissolution system is simulated in the computational model. Even though modern supercomputers might be used to tackle this kind of NAPL dissolution problem, it can become prohibitive for commonly-used personal computers to do so. The main purpose of this work is to investigate whether or not the whole NAPL dissolution system of an annular domain can be replaced by a trapezoidal domain, so as to greatly reduce the requirements for computer efforts. The related simulation results have demonstrated that when the NAPL dissolution system under consideration is in a subcritical state, if the dissolution pattern around the entrance of an annulus domain is of interest, then a trapezoidal domain cannot be used to replace an annular domain in the computational simulation of the NAPL dissolution system. However, if the dissolution pattern away from the vicinity of the entrance of an annulus domain is of interest, then a trapezoidal domain can be used to replace an annular domain in the computational simulation of the NAPL dissolution system. When the NAPL dissolution system under consideration is in a supercritical state, a trapezoidal domain cannot be used to replace an annular domain in the computational simulation of the NAPL dissolution system.
Directory of Open Access Journals (Sweden)
E. Lokupitiya
2009-06-01
Full Text Available Croplands are man-made ecosystems that have high net primary productivity during the growing season of crops, thus impacting carbon and other exchanges with the atmosphere. These exchanges play a major role in nutrient cycling and climate change related issues. An accurate representation of crop phenology and physiology is important in land-atmosphere carbon models being used to predict these exchanges. To better estimate time-varying exchanges of carbon, water, and energy of croplands using the Simple Biosphere (SiB model, we developed crop-specific phenology models and coupled them to SiB. The coupled SiB-phenology model (SiBcrop replaces remotely-sensed NDVI information, on which SiB originally relied for deriving Leaf Area Index (LAI and the fraction of Photosynthetically Active Radiation (fPAR for estimating carbon dynamics. The use of the new phenology scheme within SiB substantially improved the prediction of LAI and carbon fluxes for maize, soybean, and wheat crops, as compared with the observed data at several AmeriFlux eddy covariance flux tower sites in the US mid continent region. SiBcrop better predicted the onset and end of the growing season, harvest, interannual variability associated with crop rotation, day time carbon uptake (especially for maize and day to day variability in carbon exchange. Biomass predicted by SiBcrop had good agreement with the observed biomass at field sites. In the future, we will predict fine resolution regional scale carbon and other exchanges by coupling SiBcrop with RAMS (the Regional Atmospheric Modeling System.
Warnars, Spits
2010-01-01
Unified modelling language (UML) 2.0 introduced in 2002 has been developing and influencing object-oriented software engineering and has become a standard and reference for information system analysis and design modelling. There are many concepts and theories to model the information system or software application with UML 2.0, which can make ambiguities and inconsistencies for a novice to learn to how to model the system with UML especially with UML 2.0. This article will discuss how to model the simple software application by using some of the diagrams of UML 2.0 and not by using the whole diagrams as suggested by agile methodology. Agile methodology is considered as convenient for novices because it can deliver the information technology environment to the end-user quickly and adaptively with minimal documentation. It also has the ability to deliver best performance software application according to the customer's needs. Agile methodology will make simple model with simple documentation, simple team and si...
Simple dynamical models capturing the key features of the Central Pacific El Niño.
Chen, Nan; Majda, Andrew J
2016-10-18
The Central Pacific El Niño (CP El Niño) has been frequently observed in recent decades. The phenomenon is characterized by an anomalous warm sea surface temperature (SST) confined to the central Pacific and has different teleconnections from the traditional El Niño. Here, simple models are developed and shown to capture the key mechanisms of the CP El Niño. The starting model involves coupled atmosphere-ocean processes that are deterministic, linear, and stable. Then, systematic strategies are developed for incorporating several major mechanisms of the CP El Niño into the coupled system. First, simple nonlinear zonal advection with no ad hoc parameterization of the background SST gradient is introduced that creates coupled nonlinear advective modes of the SST. Secondly, due to the recent multidecadal strengthening of the easterly trade wind, a stochastic parameterization of the wind bursts including a mean easterly trade wind anomaly is coupled to the simple atmosphere-ocean processes. Effective stochastic noise in the wind burst model facilitates the intermittent occurrence of the CP El Niño with realistic amplitude and duration. In addition to the anomalous warm SST in the central Pacific, other major features of the CP El Niño such as the rising branch of the anomalous Walker circulation being shifted to the central Pacific and the eastern Pacific cooling with a shallow thermocline are all captured by this simple coupled model. Importantly, the coupled model succeeds in simulating a series of CP El Niño that lasts for 5 y, which resembles the two CP El Niño episodes during 1990-1995 and 2002-2006.
Hoede, C.; Zandvliet, H.J.W.
2008-01-01
In a recent paper Hoede and Zandvliet introduced the concept of gauging on an equation. This enables the simulation of more complex Ising models by the simple quadratic model. The possibility of simulating the simple cubic model was defended by calculating a sequence of approximations to the transit
Kalachev, L. V.
2016-06-01
We present a simple model of experimental setup for in vitro study of drug release from drug eluting stents and drug propagation in artificial tissue samples representing blood vessels. The model is further reduced using the assumption on vastly different characteristic diffusion times in the stent coating and in the artificial tissue. The model is used to derive a relationship between the times at which the measurements have to be taken for two experimental platforms, with corresponding artificial tissue samples made of different materials with different drug diffusion coefficients, to properly compare the drug release characteristics of drug eluting stents.
A simple model for /f-->d transitions of rare-earth ions in crystals
Duan, C. K.; Reid, M. F.
2003-02-01
Theoretical simulation and interpretation of f→ d transitions of rare earth ions in crystals are more difficult than for f→ f transitions, because f→ d transitions involve many more energy levels and are further complicated by strong vibronic transitions, so the experimental spectra contain many fewer resolvable peaks. In order to better understand the structure of the spectra, a simple model is developed to take into account the main interactions in the fN-1 d configuration. This model leads to quantum numbers characterizing the states and the associated transition selection rules. Relative transition intensities can be quantitatively estimated. The model is applied to Eu 2+ and Sm 3+ ions in crystals.
A SIMPLE CONSTITUTIVE MODEL FOR FERROELECTRIC CERAMICS UNDER ELECTRICAL/MECHANICAL LOADING
Institute of Scientific and Technical Information of China (English)
Yu Li; Yu Shouwen; Feng Xiqiao
2007-01-01
A simple phenomenological model is developed for describing the macroscopic constitutive response of ferroelectric materials based on consideration of the fact that domain switching is a progressive evolution process with loading. The volume fraction of domain switching is taken as an internal variable, which is derived from the domain nucleation theory. The proposed theory can simulate the dielectric hysteresis, reversed butterfly hysteresis, nonlinear strain-stress hysteresis, as well as electric displacement-stress relation of ferroelectric materials. Its comparison with experimental results and two other theoretical models reveals that the model presented can well predict the nonlinear hysteresis of ferroelectrics under electrical or mechanical loading.
A simple model of gas flow in a porous powder compact.
Energy Technology Data Exchange (ETDEWEB)
Shugard, Andrew D.; Robinson, David B.
2014-04-01
This report describes a simple model for ideal gas flow from a vessel through a bed of porous material into another vessel. It assumes constant temperature and uniform porosity. Transport is treated as a combination of viscous and molecular flow, with no inertial contribution (low Reynolds number). This model can be used to fit data to obtain permeability values, determine flow rates, understand the relative contributions of viscous and molecular flow, and verify volume calibrations. It draws upon the Dusty Gas Model and other detailed studies of gas flow through porous media.
A Simple Nonlinear Dynamic Model for Unemployment: Explaining the Spanish Case
Directory of Open Access Journals (Sweden)
João Ricardo Faria
2008-01-01
Full Text Available Spanish unemployment is characterized by three distinct regimes of low, medium, and high unemployment and by a fast transition between them. This paper presents a simple nonlinear dynamic model that is able to explain this behavior with multiple equilibria and jumps describing the transition between equilibria. The model has only a small number of parameters capturing the fundamentals of labor markets and macroeconomic and institutional factors. The model is capable of generating unemployment dynamics that encompass the “unique” natural rate hypothesis, the structuralist hypothesis, and the hysteresis hypothesis.
A Simple Model of Gas Flow in a Porous Powder Compact
Energy Technology Data Exchange (ETDEWEB)
Shugard, Andrew D. [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Robinson, David [Sandia National Lab. (SNL-CA), Livermore, CA (United States)
2012-07-01
This report describes a simple model for ideal gas flow from a vessel through a bed of porous material into another vessel. It assumes constant temperature and uniform porosity. Transport is treated as a combination of viscous and molecular flow, with no inertial contribution (low Reynolds number). This model can be used to fit data to obtain permeability values, determine flow rates, understand the relative contributions of viscous and molecular flow, and verify volume calibrations. It draws upon the Dusty Gas Model and other detailed studies of gas flow through porous media.
a Simple Evolutionary Model for Cancer Cell Population and its Implications on Cancer Therapy
Yao, Peng; Wen, Shutang; Li, Baoshun; Li, Yuxiao
We established a simple evolutionary model based on the cancer stem cell hypothesis. By taking cellular interactions into consideration, we introduced the evolutionary games theory into the quasispecies model. The fitness values are determined by both genotypes and cellular interactions. In the evolutionary model, a cancer cell population can evolve in different patterns. For single peak intrinsic fitness landscape, the evolution pattern can transit with increasing differentiation probability from malignant cells to benign cells in four different modes. For a large enough value of differentiation probability, the evolution is always the case that the malignant cells extinct ultimately, which might give some implications on cancer therapy.
Simple one-dimensional quantum-mechanical model for a particle attached to a surface
Energy Technology Data Exchange (ETDEWEB)
Fernandez, Francisco M, E-mail: fernande@quimica.unlp.edu.a [INIFTA (UNLP, CCT La Plata-CONICET), Division Quimica Teorica, Blvd 113 S/N, Sucursal 4, Casilla de Correo 16, 1900 La Plata (Argentina)
2010-07-15
We present a simple one-dimensional quantum-mechanical model for a particle attached to a surface. It leads to the Schroedinger equation for a harmonic oscillator bounded on one side that we solve in terms of Weber functions and discuss the behaviour of the eigenvalues and eigenfunctions. We derive the virial theorem and other exact relationships as well as the asymptotic behaviour of the eigenvalues. We calculate the zero-point energy for model parameters corresponding to H adsorbed on Pd(1 0 0). The model is suitable for an advanced undergraduate or graduate course on quantum mechanics.
A simple atmospheric boundary layer model applied to large eddy simulations of wind turbine wakes
DEFF Research Database (Denmark)
Troldborg, Niels; Sørensen, Jens Nørkær; Mikkelsen, Robert Flemming
2014-01-01
boundary type technique where volume forces are used to introduce wind shear and atmospheric turbulence. The application of the model for wake studies is demonstrated by combining it with the actuator line method, and predictions are compared with field measurements. Copyright © 2013 John Wiley & Sons, Ltd.......A simple model for including the influence of the atmospheric boundary layer in connection with large eddy simulations of wind turbine wakes is presented and validated by comparing computed results with measurements as well as with direct numerical simulations. The model is based on an immersed...
Oubei, Hassan M.
2017-06-16
In this Letter, we use laser beam intensity fluctuation measurements to model and describe the statistical properties of weak temperature-induced turbulence in underwater wireless optical communication (UWOC) channels. UWOC channels with temperature gradients are modeled by the generalized gamma distribution (GGD) with an excellent goodness of fit to the measured data under all channel conditions. Meanwhile, thermally uniform channels are perfectly described by the simple gamma distribution which is a special case of GGD. To the best of our knowledge, this is the first model that comprehensively describes both thermally uniform and gradient-based UWOC channels.
The problem with simple lumped parameter models: Evidence from tritium mean transit times
Stewart, Michael; Morgenstern, Uwe; Gusyev, Maksym; Maloszewski, Piotr
2017-04-01
Simple lumped parameter models (LPMs) based on assuming homogeneity and stationarity in catchments and groundwater bodies are widely used to model and predict hydrological system outputs. However, most systems are not homogeneous or stationary, and errors resulting from disregard of the real heterogeneity and non-stationarity of such systems are not well understood and rarely quantified. As an example, mean transit times (MTTs) of streamflow are usually estimated from tracer data using simple LPMs. The MTT or transit time distribution of water in a stream reveals basic catchment properties such as water flow paths, storage and mixing. Importantly however, Kirchner (2016a) has shown that there can be large (several hundred percent) aggregation errors in MTTs inferred from seasonal cycles in conservative tracers such as chloride or stable isotopes when they are interpreted using simple LPMs (i.e. a range of gamma models or GMs). Here we show that MTTs estimated using tritium concentrations are similarly affected by aggregation errors due to heterogeneity and non-stationarity when interpreted using simple LPMs (e.g. GMs). The tritium aggregation error series from the strong nonlinearity between tritium concentrations and MTT, whereas for seasonal tracer cycles it is due to the nonlinearity between tracer cycle amplitudes and MTT. In effect, water from young subsystems in the catchment outweigh water from old subsystems. The main difference between the aggregation errors with the different tracers is that with tritium it applies at much greater ages than it does with seasonal tracer cycles. We stress that the aggregation errors arise when simple LPMs are applied (with simple LPMs the hydrological system is assumed to be a homogeneous whole with parameters representing averages for the system). With well-chosen compound LPMs (which are combinations of simple LPMs) on the other hand, aggregation errors are very much smaller because young and old water flows are treated
Directory of Open Access Journals (Sweden)
Guy J. Abel
2013-12-01
Full Text Available Background: Population forecasts are widely used for public policy purposes. Methods to quantify the uncertainty in forecasts tend to ignore model uncertainty and to be based on a single model. Objective: In this paper, we use Bayesian time series models to obtain future population estimates with associated measures of uncertainty. The models are compared based on Bayesian posterior model probabilities, which are then used to provide model-averaged forecasts. Methods: The focus is on a simple projection model with the historical data representing population change in England and Wales from 1841 to 2007. Bayesian forecasts to the year 2032 are obtained based on a range of models, including autoregression models, stochastic volatility models and random variance shift models. The computational steps to fit each of these models using the OpenBUGS software via R are illustrated. Results: We show that the Bayesian approach is adept in capturing multiple sources of uncertainty in population projections, including model uncertainty. The inclusion of non-constant variance improves the fit of the models and provides more realistic predictive uncertainty levels. The forecasting methodology is assessed through fitting the models to various truncated data series.
DEFF Research Database (Denmark)
Ersboell, Mads; Vejlstrup, Niels; Nilsson, Jens Christian;
2013-01-01
BACKGROUND: Free pulmonary regurgitation (PR) after surgical correction of Tetralogy of Fallot (ToF) with transannular patching can lead to irreversible right ventricular (RV) failure. However, the optimal timing of valve replacement is still debated. METHODS AND RESULTS: Thirty six pigs were inc...
WORK GROUP DEVELOPMENT MODELS – THE EVOLUTION FROM SIMPLE GROUP TO EFFECTIVE TEAM
Directory of Open Access Journals (Sweden)
Raluca ZOLTAN
2016-02-01
Full Text Available Currently, work teams are increasingly studied by virtue of the advantages they have compared to the work groups. But a true team does not appear overnight but must complete several steps to overcome the initial stage of its existence as a group. The question that arises is at what point a simple group is turning into an effective team. Even though the development process of group into a team is not a linear process, the models found in the literature provides a rich framework for analyzing and identifying the features which group acquires over time till it become a team in the true sense of word. Thus, in this article we propose an analysis of the main models of group development in order to point out, even in a relative manner, the stage when the simple work group becomes an effective work team.
Simple versus complex models of trait evolution and stasis as a response to environmental change
Hunt, Gene; Hopkins, Melanie J.; Lidgard, Scott
2015-04-01
Previous analyses of evolutionary patterns, or modes, in fossil lineages have focused overwhelmingly on three simple models: stasis, random walks, and directional evolution. Here we use likelihood methods to fit an expanded set of evolutionary models to a large compilation of ancestor-descendant series of populations from the fossil record. In addition to the standard three models, we assess more complex models with punctuations and shifts from one evolutionary mode to another. As in previous studies, we find that stasis is common in the fossil record, as is a strict version of stasis that entails no real evolutionary changes. Incidence of directional evolution is relatively low (13%), but higher than in previous studies because our analytical approach can more sensitively detect noisy trends. Complex evolutionary models are often favored, overwhelmingly so for sequences comprising many samples. This finding is consistent with evolutionary dynamics that are, in reality, more complex than any of the models we consider. Furthermore, the timing of shifts in evolutionary dynamics varies among traits measured from the same series. Finally, we use our empirical collection of evolutionary sequences and a long and highly resolved proxy for global climate to inform simulations in which traits adaptively track temperature changes over time. When realistically calibrated, we find that this simple model can reproduce important aspects of our paleontological results. We conclude that observed paleontological patterns, including the prevalence of stasis, need not be inconsistent with adaptive evolution, even in the face of unstable physical environments.
Redesign of Industrial Column Flotation Circuits Based on a Simple Residence Time Distribution Model
2008-01-01
The potential for improved selectivity has made column flotation cells a popular choice for upgrading fine coal. Unfortunately, recent production data from full-scale column plants indicate that many industrial installations have failed to meet original expectations in terms of clean coal recovery. Theoretical studies performed using a simple dispersion model showed that this inherent shortcoming could be largely minimized by reconfiguring the columns to operate in series as a cell-to-cell ci...
A Model of Discrete-Continuum Time for a Simple Physical System
Directory of Open Access Journals (Sweden)
Karimov A. R.
2008-04-01
Full Text Available Proceeding from the assumption that the time flow of an individual object is a real physical value, in the framework of a physical kinetics approach we propose an analogy between time and temperature. The use of such an analogy makes it possible to work out a discrete-continuum model of time for a simple physical system. The possible physical properties of time for the single object and time for the whole system are discussed.
On complex Langevin dynamics and zeroes of the measure I: Formal proof and simple models
Aarts, Gert; Sexty, Denes; Stamatescu, Ion-Olimpiu
2016-01-01
In the complex Langevin approach to lattice simulations at nonzero density, zeroes of the fermion determinant lead to a meromorphic drift and hence a need to revisit the theoretical derivation. We discuss how poles in the drift affect the formal justification of the approach and then explore the various potential issues in simple models, in a manner that is applicable to heavy dense and full QCD.
Why simple regression models work so well describing 'risk behaviors' in the USA
Wallace, R.; R Fullilove
1999-01-01
The generalized anger created by individual experience of marginalization in the USA makes violent behavior frequent enough to become a 'typical' symbol, in the information-theoretic sense, for use in communicating along the damaged social networks of oppressed communities. Simple regression models relating violence and other risk behaviors to indices of relative deprivation emerge, after some mathematical development, as a natural consequence of this underlying dynamic, described elegantly b...
The effect of compression on tuning estimates in a simple nonlinear auditory filter model
DEFF Research Database (Denmark)
Marschall, Marton; MacDonald, Ewen; Dau, Torsten
2013-01-01
, there is evidence that human frequency-selectivity estimates depend on whether an iso-input or an iso-response measurement paradigm is used (Eustaquio-Martin et al., 2011). This study presents simulated tuning estimates using a simple compressive auditory filter model, the bandpass nonlinearity (BPNL), which......, then compression alone may explain a large part of the behaviorally observed differences in tuning between simultaneous and forward-masking conditions....
A simple model for 100 K-year oscillations in glaciation
Lindzen, R. S.
1986-01-01
A simple climatic model which produces glaciation cycles of 100 K periods in response to forcing by 20 K, 40 K, and 100 K periods is described. The model is based on Milankovitch's (1930) hypothesis that glaciation fluctuations are forced by orbital variation and the associated change in insolation. The sea ice/snow cover line for the model, and the relation between heat variations and the ice/snow line are analyzed. The sea ice/snow cover line for the model is between the pole and 53 deg latitude and the line's position is the forcing for the glaciation cycle. Examples of the model's response to forcing are presented and evaluated. The negative glaciation permitted by the model is studied. The role of CO2 feedback in the glaciation cycle is investigated.
Ellimoottil, Chad; Ryan, Andrew M; Hou, Hechuan; Dupree, James M; Hallstrom, Brian; Miller, David C
2017-01-01
Under the Comprehensive Care for Joint Replacement (CJR) model, hospitals are held accountable for nearly all Medicare payments that occur during the initial hospitalization until 90 days after hospital discharge (ie, the episode of care). It is not known whether unrelated expenditures resulting from this "broad" definition of an episode of care will affect participating hospitals' average episode-of-care payments. To compare the CJR program's broad definition of an episode of care with a clinically narrow definition of an episode of care. We identified Medicare claims for 23 251 patients in Michigan who were Medicare beneficiaries and who underwent joint replacement during the period from 2011 through 2013 at hospitals located in metropolitan statistical areas. Using specifications from the CJR model and the clinically narrow Hospital Compare payment measure, we constructed episodes of care and calculated 90-day episode payments. We then compared hospitals' average 90-day episode payments using the 2 definitions of an episode of care and fit linear regression models to understand whether payment differences were associated with specific hospital characteristics (average Centers for Medicare & Medicaid Services-hierarchical condition categories risk score, rural hospital status, joint replacement volume, percentage of Medicaid discharges, teaching hospital status, number of beds, percentage of joint replacements performed on African American patients, and median income of the hospital's county). We performed analyses from July 1 through October 1, 2015. The correlation and difference between average 90-day episode payments using the broad definition of an episode of care in the CJR model and the clinically narrow Hospital Compare definition of an episode of care. We identified 23 251 joint replacements (ie, episodes of care). The 90-day episode payments using the broad definition of the CJR model ranged from $17 349 to $29 465 (mean [SD] payment, $22 122
A simple regional coupled model experiment for summer-time climate simulation over southern Africa
Energy Technology Data Exchange (ETDEWEB)
Ratnam, J.V.; Behera, S.K. [Research Institute for Global Change, Yokohama, Kanagawa (Japan); Application Laboratory, Yokohama (Japan); Masumoto, Y. [Research Institute for Global Change, Yokohama, Kanagawa (Japan); Takahashi, K. [Application Laboratory, Yokohama (Japan); Earth Simulator Center, Yokohama (Japan); Yamagata, T. [Application Laboratory, Yokohama (Japan); The University of Tokyo, School of Science, Tokyo (Japan)
2012-11-15
The main aim of this paper is to evaluate the Advanced Research Weather Research and Forecasting (WRF) regional model in simulating the precipitation over southern Africa during austral summer. The model's ability to reproduce the southern African mean climate and its variability around this mean state was evaluated by using the two-tier approach of specifying sea surface temperature (SST) to WRF and by using the one-tier approach of coupling the WRF with a simple mixed-layer ocean model. The boundary conditions provided by the reanalysis-II data were used for the simulations. Model experiments were conducted for twelve austral summers from DJF1998-99 to DJF2009-10. The experiments using both the two-tier and one-tier approaches simulated the spatial and temporal distributions of the precipitation realistically. However, both experiments simulated negative biases over Mozambique. Furthermore, analysis of the wet and dry spells revealed that the one-tier approach is superior to the two-tier approach. Based on the analysis of the surface temperature and the zonal wind shear it is noted that the simple mixed-layer ocean model coupled to WRF can be effectively used in place of two-tier WRF to simulate the climate of southern Africa. This is an important result because specification of SST at higher temporal resolutions in the subtropics is the most difficult task in the two-tier approach for most regional prediction models. The one-tier approach with the simple mixed-layer model can effectively reduce the complicacy of finding good SST predictions. (orig.)
A Simple Model for Yielding and Strain Hardening in Glassy Polymers
Larson, Ron
2013-03-01
Strain hardening has long been an observed feature of polymer glasses in extension; explanations to date have often been phenomenological. Ediger and coworkers (Lee et al. Science 323, 231, 2009) have shown in experiments on PMMA glasses that, in addition to strain hardening, polymeric glasses show a remarkable non-monotonicity in the segmental relaxation time both in loading and unloading of stress. Here, we develop a simple constitutive equation that combines recent theories for yielding in simple glasses (Brader et al. PNAS, 106, 15186, 2009) to represent local segmental modes in the polymer, with a dumbbell model for the slow polymer relaxation modes. For a polymer glass under uniaxial loading, the model predicts that the liquefaction of the segmental modes permits strain hardening of the polymer modes to emerge, and once this emerges, it slows the deformation of the material under constant load enough to partially re-vitrify the segmental modes even though the sample remains under stress. In this way, the observed non-monotonicity in the segmental relaxation modes is produced. We show the extension of the work to simple shearing flows, and make (as yet) untested predictions about segmental relaxation rates in shear flows. We also show how to extend the model to include Rouse chain dynamics in place of the over-simplified dumbbell.
Abokifa, Ahmed A; Biswas, Pratim
2017-03-07
Partial replacement of lead service lines (LSLs) often results in the excessive long-term release of lead particulates due to the disturbance of pipe scale and galvanic corrosion. In this study, a modeling approach to simulate the release and transport of particulate and dissolved lead from full and partially replaced LSLs is developed. A mass-transfer model is coupled with a stochastic residential water demand generator to investigate the effect of normal household usage flow patterns on lead exposure. The model is calibrated by comparing simulation results against experimental measurements from pilot-scale setups where lead release under different flow rates and water chemistry scenarios was reported. Applying the model within a Monte Carlo simulation framework, partial replacement of the LSL was predicted to result in releasing spikes with significantly high concentrations of particulate lead (1011.9 ± 290.3 μg/L) that were five times higher than those released from the simulated full LSL. Sensitivity analysis revealed that the intensity of flow demands significantly affects particulate lead release, while dissolved lead levels are more dependent on the lengths of the stagnation periods. Preflushing of the LSL prior to regulatory sampling was found to underestimate the maximum monthly exposure to dissolved lead by 19%, while sampling at low flow rates (<5.2 LPM) was found to consistently suppress the high spikes induced by particulate lead mobilization.
Pawlyk, Basil S; Bulgakov, Oleg V; Liu, Xiaoqing; Xu, Xiaoyun; Adamian, Michael; Sun, Xun; Khani, Shahrokh C; Berson, Eliot L; Sandberg, Michael A; Li, Tiansen
2010-08-01
RPGR-interacting protein-1 (RPGRIP1) is localized in the photoreceptor-connecting cilium, where it anchors the RPGR (retinitis pigmentosa GTPase regulator) protein, and its function is essential for photoreceptor maintenance. Genetic defect in RPGRIP1 is a known cause of Leber congenital amaurosis (LCA), a severe, early-onset form of retinal degeneration. We evaluated the efficacy of replacement gene therapy in a murine model of LCA carrying a targeted disruption of RPGRIP1. The replacement construct, packaged in an adeno-associated virus serotype 8 (AAV8) vector, used a rhodopsin kinase gene promoter to drive RPGRIP1 expression. Both promoter and transgene were of human origin. After subretinal delivery of the replacement gene in the mutant mice, human RPGRIP1 was expressed specifically in photoreceptors, localized correctly in the connecting cilia, and restored the normal localization of RPGR. Electroretinogram and histological examinations showed better preservation of rod and cone photoreceptor function and improved photoreceptor survival in the treated eyes. This study demonstrates the efficacy of human gene replacement therapy and validates a gene therapy design for future clinical trials in patients afflicted with this condition. Our results also have therapeutic implications for other forms of retinal degenerations attributable to a ciliary defect.
Simple in vitro models can predict pulmonary toxicity of silver nanoparticles.
Braakhuis, Hedwig M; Giannakou, Christina; Peijnenburg, Willie J G M; Vermeulen, Jolanda; van Loveren, Henk; Park, Margriet V D Z
2016-08-01
To study the effects of nanomaterials after inhalation, a large number of in vitro lung models have been reported in literature. Although the in vitro models contribute to the reduction of animal studies, insufficient data exists to determine the predictive value of these in vitro models for the in vivo situation. The aim of this study was to determine the correlation between in vitro and in vivo data by comparing the dose metrics of silver nanoparticles in an in vitro lung model of increasing complexity to our previously published in vivo inhalation study. In vivo, the previously published study showed that the alveolar dose expressed as particle surface area is the most suitable dose metric to describe the toxicity of silver nanoparticles after inhalation. The results of the present study show that particle surface area is a suitable dose metric to describe the effects of silver nanoparticles when using a simple monolayer of lung epithelial cells. The dose metric shifted from particle surface area to particle mass when adding an increasing number of macrophages. In addition, a co-culture of endothelial cells, epithelial cells and macrophages on a Transwell® insert correlated less well to the in vivo results compared to the epithelial monolayer. We conclude that for studying the acute pulmonary toxicity of nanoparticles simple in vitro models using an epithelial monolayer better predict the in vivo response compared to complex co-culture models.
Directory of Open Access Journals (Sweden)
T. S. Steenhuis
1997-01-01
Full Text Available Agricultural tile drainage lines have been implicated as a source of pesticide contamination of surface waters. Field experiments were conducted and a simple model was developed to examine preferential transport of applied chemicals to agricultural tile lines. The conceptual model consists of two linear reservoirs, one near the soil surface and one near the tile drain. The connection between the two reservoirs is via preferential flow paths with very little interaction with the soil matrix. The model assumes that only part of the field contributes solutes to the tile drain. The model was evaluated with data from the field experiments in which chloride, 2,4-D, and atrazine concentrations were measured on eight tile-drained plots that were irrigated twice. Atrazine was applied two months prior to the experiment, 2,4-D was sprayed just before the first irrigation, and chloride before the second irrigation. All three chemicals were found in the tile effluent shortly after the rainfall began. Generally, the concentration increased with increased flow rates and decreased exponentially after the rainfall ceased. Although the simple model could simulate the observed chloride concentration patterns in the tile outflow for six of the eight plots, strict validation was not possible because of the difficulty with independent measurement of the data needed for a preferential flow model applied to field conditions. The results show that, to simulate pesticide concentration in tile lines, methods that can measure field averaged preferential flow characteristics need to be developed.
A simple model for screening the local impacts of atmospheric ammonia.
Theobald, M R; Bealey, W J; Tang, Y S; Vallejo, A; Sutton, M A
2009-11-15
The dry deposition of ammonia from the atmosphere to the surface can lead to eutrophication of sensitive ecosystems and acidification of the soil. A large proportion of the ammonia emitted from agricultural sources can be deposited within a few kilometres and, therefore, impacts of ammonia dry deposition often occur near to the source. To assess these impacts, short-range atmospheric dispersion models are often applied to simulate the emission, dispersion and deposition of ammonia. However, these models can be time-consuming to run and often require detailed input data and, therefore, for multiple assessments it is useful to have a method of screening to discard scenarios where impacts are expected to be negligible. The SCAIL model (Simple Calculation of Ammonia Impact Limits) has been developed for this purpose. SCAIL estimates the atmospheric concentration and dry deposition at the nearest edge of a sensitive ecosystem (receptor) downwind of an ammonia source. These estimates are calculated based on simple meteorological data, the emission rate of the source, land cover type and distance to the receptor. Analysis of the model predictions showed that uncertainty in the model input data leads to an uncertainty in concentration and dry deposition estimates of 25-30% and 40-45% respectively. Detailed atmospheric dispersion models will also have similar uncertainties since they use similar types of input data. Comparison of the concentration predictions with previous measurements made around eight farms showed that the model significantly underestimated concentrations although the model performance was similar to existing screening techniques. The measurement dataset was used to calibrate the SCAIL model which subsequently performed better, using independent verification data, than existing models calibrated in a similar way. The benefits of the SCAIL model are already being seen in the UK, where it is used to screen farms for potential impacts on statutory nature
MANEA MARINELA – DANIELA
2011-01-01
The term fair value is spread within the sphere of international standards without reference to any detailed guidance on how to apply. However, specialized tangible assets, which are rarely sold, the rule IAS 16 "Intangible assets " makes it possible to estimate fair value using an income approach or a replacement cost or depreciation. The following material is intended to identify potential modeling of fair value as an income-based approach, appealing to techniques used by professional evalu...
A simple dynamic model and transient simulation of the nuclear power reactor on microcomputers
Energy Technology Data Exchange (ETDEWEB)
Han, Yang Gee; Park, Cheol [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)
1997-12-31
A simple dynamic model is developed for the transient simulation of the nuclear power reactor. The dynamic model includes the normalized neutron kinetics model with reactivity feedback effects and the core thermal-hydraulics model. The main objective of this paper demonstrates the capability of the developed dynamic model to simulate various important variables of interest for a nuclear power reactor transient. Some representative results of transient simulations show the expected trends in all cases, even though no available data for comparison. In this work transient simulations are performed on a microcomputer using the DESIRE/N96T continuous system simulation language which is applicable to nuclear power reactor transient analysis. 3 refs., 9 figs. (Author)
The distribution of wealth in the presence of altruism for simple economic models
Rodriguez-Achach, M
2005-01-01
We study the effect of altruism in two simple asset exchange models: the yard sale model (winner gets a random fraction of the poorer player's wealth) and the theft and fraud model (winner gets a random fraction of the loser's wealth). We also introduce in these models the concept of bargaining efficiency, which makes the poorer trader more aggressive in getting a favorable deal thus augmenting his winning probabilities. The altruistic behavior is controlled by varying the number of traders that behave altruistically and by the degree of altruism that they show. The resulting wealth distribution is characterized using the Gini index. We compare the resulting values of the Gini index at different levels of altruism in both models. It is found that altruistic behavior does lead to a more equitable wealth distribution but only for unreasonable high values of altruism that are difficult to expect in a real economic system.
Simple metal model for predicting uptake and chemical processes in sewage-fed aquaculture ecosystem
DEFF Research Database (Denmark)
Azanu, David; Jorgensen, Sven Erik; Darko, Godfred;
2016-01-01
This paper shows how a model can be used as an experimental tool to assess the processes in aqua chemistry that should be included in the model. The STELLA software was used to study the uptake of Cd, Pb, Cr, Cu and Hg from sewage-fed aquaculture. Model calibration revealed that feeding rate of 15......% was the best, which is also in accordance to the fish growth. The ratio of fish food was also calibrated to be 70% due to a food chain in the water and 30% due to a food chain in the sediment. This gave the lowest uncertainty of the model. The simple metal model was working acceptably well for Pb, Cu and Cd...... but not working properly for chromium and mercury. Additional processes, including precipitation of chromium and bio-magnification of methylmercury were introduced to explain concentration of chromium and mercury in fish. Comparison of measured and predicted metal concentration used for validation gave a linear...
Addressing challenges in single species assessments via a simple state-space assessment model
DEFF Research Database (Denmark)
Nielsen, Anders
Single-species and age-structured fish stock assessments still remains the main tool for managing fish stocks. A simple state-space assessment model is presented as an alternative to (semi) deterministic procedures and the full parametric statistical catch at age models. It offers a solution...... of state-space assessment models is that they tend to be more conservative (react slower to changes) than the alternatives. A solution to this criticism is offered by introducing a mixture distribution for the transitions steps. The model presented is used for several commercially important stocks...... to some of the key challenges of these models. Compared to the deterministic procedures it solves a list of problems originating from falsely assuming that age classified catches are known without errors and allows quantification of uncertainties of estimated quantities of interest. Compared to full...
A New Simple Model for the Mushrooming Deformation of Projectile Impacting on A Deformable Target
Institute of Scientific and Technical Information of China (English)
Zhang Xiaoqing; Yang Guitong
2004-01-01
Based on Taylor's model and Hawkyard's model, a new simple model for the mushrooming deformation of projectile impacting on a deformable target is installed considering the penetration of the projectile to the deformable target. In the model, the following time-dependent variables are involved in: the extent and the particle velocity in the rigid zone; the extent, the cross-section area and the particle velocity in plastic zone; the velocity and depth of the penetrating of projectile to the target. Solving the set of equations, analytic solution is given. The profiles of deformed projectile and shape parameters for different initial impact velocities are shown. The duration time of deformation increases with increasing the impact velocity. The analytical results by using this model are coincident with experimental result.
New tools for Loop Quantum Gravity with applications to a simple model
Borja, Enrique F.; Díaz-Polo, Jacobo; Freidel, Laurent; Garay, Iñaki; Livine, Etera R.
2012-07-01
Loop Quantum Gravity is now a well established approach to quantum gravity. One of the main challenges still faced by the theory is constructing a consistent dynamics which would lead back to the standard dynamics of the gravitational field at large scales. Here we will review the recent U(N) framework for Loop Quantum Gravity and the new spinor representation (that provides a classical setting for the U(N) framework). Then, we will apply these techniques to a simple model in order to propose a dynamics for a symmetry reduced sector of the theory. Furthermore, we will explore certain analogies of this model with Loop Quantum Cosmology.
New tools for Loop Quantum Gravity with applications to a simple model
Borja, Enrique F; Freidel, Laurent; Garay, Iñaki; Livine, Etera R
2012-01-01
Loop Quantum Gravity is now a well established approach to quantum gravity. One of the main challenges still faced by the theory is constructing a consistent dynamics which would lead back to the standard dynamics of the gravitational field at large scales. Here we will review the recent U(N) framework for Loop Quantum Gravity and the new spinor representation (that provides a classical setting for the U(N) framework). Then, we will apply these techniques to a simple model in order to propose a dynamics for a symmetry reduced sector of the theory. Furthermore, we will explore certain analogies of this model with Loop Quantum Cosmology.
A simple branching model that reproduces language family and language population distributions
Schwämmle, Veit; de Oliveira, Paulo Murilo Castro
2009-07-01
Human history leaves fingerprints in human languages. Little is known about language evolution and its study is of great importance. Here we construct a simple stochastic model and compare its results to statistical data of real languages. The model is based on the recent finding that language changes occur independently of the population size. We find agreement with the data additionally assuming that languages may be distinguished by having at least one among a finite, small number of different features. This finite set is also used in order to define the distance between two languages, similarly to linguistics tradition since Swadesh.
A simple model for 1/f spectra in heart rate variability
Gleeson, James P.; Stefanovska, Aneta
2007-06-01
Heart rate variability (HRV) measures cycle-to-cycle correlations in the instantaneous oscillation period of the heart. In this paper it is shown that a simple model process, consisting of a sum of uncoupled sinusoidal oscillators with slightly different frequencies, has a HRV spectrum with a 1/f scaling over a range of frequencies. This implies that the appearance of 1/f HRV spectra in experiments should not be considered evidence of oscillator coupling or other more complex dynamics. The origin of the 1/f scaling in the model is examined analytically, and its dependence upon the sampling of low-amplitude fluctuations of the process is highlighted.
Kleidon, Axel
2016-04-01
The Earth is, undoubtedly, a vastly complex system that is shaped by a range of processes, from solar radiation to planetary motion, geochemical cycling, biotic and human activity, all interacting across a range of time scales to shape the emergent state of the system. The common approach to deal with modelling parts of or the whole Earth system is to build increasingly more comprehensive models, with higher resolutions, a greater range of processes, and a greater number of interactions being represented. Yet, this also yields increasingly incomprehensible models in which the underlying assumptions in the model parameterizations are obscured. I present an alternative approach to model the complex Earth system that focuses on fundamental physical constraints and that allows for insights from simple, back-of-the-envelope calculations. This approach is based on describing the Earth as a thermodynamic system with dynamics that are driven by energy conversions, and in which its complexity is dealt with by the assumption that the dynamics operate at their thermodynamic limit. It requires us to think of Earth system processes in terms of the energy that they convert, the origin of this energy, the interactions that result from the energy conversion, and how these factors shape the resulting thermodynamic limit. The behavior of the complex Earth system then becomes predictable by relatively simple means, not because we deal with a simple system, but because it is so complex that it is ultimately constrained by fundamental thermodynamic limits that can be derived by comparably simple means. I illustrate this approach with three examples, dealing with the hydrologic sensitivity to global warming, the surface energy balance partitioning on land at the diurnal scale, and the limits to wind power as renewable energy. Each example shows that the approach matches observations or complex climate models very well, highlighting that this approach provides a simple alternative to
Directory of Open Access Journals (Sweden)
V. Couvreur
2012-08-01
Full Text Available Many hydrological models including root water uptake (RWU do not consider the dimension of root system hydraulic architecture (HA because explicitly solving water flow in such a complex system is too time consuming. However, they might lack process understanding when basing RWU and plant water stress predictions on functions of variables such as the root length density distribution. On the basis of analytical solutions of water flow in a simple HA, we developed an "implicit" model of the root system HA for simulation of RWU distribution (sink term of Richards' equation and plant water stress in three-dimensional soil water flow models. The new model has three macroscopic parameters defined at the soil element scale, or at the plant scale, rather than for each segment of the root system architecture: the standard sink fraction distribution SSF, the root system equivalent conductance K_{rs} and the compensatory RWU conductance K_{comp}. It clearly decouples the process of water stress from compensatory RWU, and its structure is appropriate for hydraulic lift simulation. As compared to a model explicitly solving water flow in a realistic maize root system HA, the implicit model showed to be accurate for predicting RWU distribution and plant collar water potential, with one single set of parameters, in dissimilar water dynamics scenarios. For these scenarios, the computing time of the implicit model was a factor 28 to 214 shorter than that of the explicit one. We also provide a new expression for the effective soil water potential sensed by plants in soils with a heterogeneous water potential distribution, which emerged from the implicit model equations. With the proposed implicit model of the root system HA, new concepts are brought which open avenues towards simple and mechanistic RWU models and water stress functions operational for field scale water dynamics simulation.
Directory of Open Access Journals (Sweden)
V. Couvreur
2012-04-01
Full Text Available Many hydrological models including root water uptake (RWU do not consider the dimension of root system hydraulic architecture (HA because explicitly solving water flow in such a complex system is too much time consuming. However, they might lack process understanding when basing RWU and plant water stress predictions on functions of variables such as the root length density distribution. On the basis of analytical solutions of water flow in a simple HA, we developed an "implicit" model of the root system HA for simulation of RWU distribution (sink term of Richards' equation and plant water stress in three-dimensional soil water flow models. The new model has three macroscopic parameters defined at the soil element scale or at the plant scale rather than for each segment of the root architecture: the standard sink distribution SSD, the root system equivalent conductance K_{rs} and the compensatory conductance K_{comp}. It clearly decouples the process of water stress from compensatory RWU and its structure is appropriate for hydraulic lift simulation. As compared to a model explicitly solving water flow in a realistic maize root system HA, the implicit model showed to be accurate for predicting RWU distribution and plant collar water potential, with one single set of parameters, in contrasted water dynamics scenarios. For these scenarios, the computing time of the implicit model was a factor 28 to 214 shorter than that of the explicit one. We also provide a new expression for the effective soil water potential sensed by plants in soils with a heterogeneous water potential distribution, which emerged from the implicit model equations. With the proposed implicit model of the root system HA, new concepts are brought which open avenues towards simple and process understanding RWU models and water stress functions operational for field scale water dynamics simulation.
Indian Academy of Sciences (India)
MIN-T SAI LAI; SHIH-CHIH CHEN
2016-05-01
In this paper, a bivariate replacement policy (n, T) for a cumulative shock damage process is presented that included the concept of cumulative repair cost limit. The arrival shocks can be divided into two kinds of shocks. Each type-I shock causes a random amount of damage and these damages are additive. When the total damage exceeds a failure level, the system goes into serious failure. Type-II shock causes the system into minor failure and such a failure can be corrected by minimal repair. When a minor failure occurs, the repaircost will be evaluated and minimal repair is executed if the accumulated repair cost is less than a predetermined limit L. The system is replaced at scheduled time T, at n-th minor failure, or at serious failure. The long-term expected cost per unit time is derived using the expected costs as the optimality criterion. The minimum-cost policy is derived, and existence and uniqueness of the optimal n* and T* are proved. This bivariate optimal replacement policy (n, T) is showed to be better than the optimal T* and the optimal n* policy.
Simple to complex modeling of breathing volume using a motion sensor
John, Dinesh; Staudenmayer, John; Freedson, Patty
2013-01-01
Purpose To compare simple and complex modeling techniques to estimate categories of low, medium, and high ventilation (VE) from ActiGraph™ activity counts. Methods Vertical axis ActiGraph™ GT1M activity counts, oxygen consumption and VE were measured during treadmill walking and running, sports, household chores and labor-intensive employment activities. Categories of low (35.4 l/min) VEs were derived from activity intensity classifications (light 6.0 METs). We examined the accuracy of two simple techniques (multiple regression and activity count cut-point analyses) and one complex (random forest technique) modeling technique in predicting VE from activity counts. Results Prediction accuracy of the complex random forest technique was marginally better than the simple multiple regression method. Both techniques accurately predicted VE categories almost 80% of the time. The multiple regression and random forest techniques were more accurate (85 to 88%) in predicting medium VE. Both techniques predicted the high VE (70 to 73%) with greater accuracy than low VE (57 to 60%). Actigraph™ cut-points for light, medium and high VEs were 3660 cpm. Conclusions There were minor differences in prediction accuracy between the multiple regression and the random forest technique. This study provides methods to objectively estimate VE categories using activity monitors that can easily be deployed in the field. Objective estimates of VE should provide a better understanding of the dose–response relationship between internal exposure to pollutants and disease. PMID:23542491
Liquid-liquid critical point in a simple analytical model of water
Urbic, Tomaz
2016-10-01
A statistical model for a simple three-dimensional Mercedes-Benz model of water was used to study phase diagrams. This model on a simple level describes the thermal and volumetric properties of waterlike molecules. A molecule is presented as a soft sphere with four directions in which hydrogen bonds can be formed. Two neighboring waters can interact through a van der Waals interaction or an orientation-dependent hydrogen-bonding interaction. For pure water, we explored properties such as molar volume, density, heat capacity, thermal expansion coefficient, and isothermal compressibility and found that the volumetric and thermal properties follow the same trends with temperature as in real water and are in good general agreement with Monte Carlo simulations. The model exhibits also two critical points for liquid-gas transition and transition between low-density and high-density fluid. Coexistence curves and a Widom line for the maximum and minimum in thermal expansion coefficient divides the phase space of the model into three parts: in one part we have gas region, in the second a high-density liquid, and the third region contains low-density liquid.
Keeping it simple: a conceptual model of DOC dynamics in a subarctic alpine catchment
Lessels, J. S.; Tetzlaff, D.; Carey, S. K.; Soulsby, C.
2013-12-01
Understanding hydrological processes in subarctic alpine catchments characterised with discontinuous permafrost is important in order to understand carbon exports. Subarctic catchments have large storages of carbon in organic and permafrost soils. Active layer depth is one of the largest controlling factors of the release of dissolved organic carbon (DOC) due to its control on runoff pathways. Therefore, any change of this depth will affect the amount of DOC mobilised from these catchments. Simple low parameterised conceptual models offer the ability to characterise hydrological processes and linked DOC dynamics without introducing many of the uncertainties linked to high parameterised models. Lumped models can also be used to identify sources of DOC within catchments. Here, we investigate hydrological sources, flow pathways and consequently DOC dynamics in the Granger Basin, Canada, a subarctic alpine catchment using data collected from 2001 to 2008. The catchment is distinguished by aspect dependant discontinuous permafrost and seasonal frost, compounded further by differences in soil and vegetation types. Applying a simple low parameterised conceptual model allowed identification of the dominant flow paths of the main hydrological response units. The results showed that it was necessary to include active layer dynamics combined with aspect to represent the hydrological and DOC dynamics. The model provides information on the effect of climatic conditions on DOC releases. By identifying the key flow paths and relating these to spring freshet DOC exports over multiple years it is possible to gain an insight of the how climatic changes might affect hydrological processes within subarctic catchments.
A Simple Line Drawing Definition and Transfer Model for Facial Animation Generation
Directory of Open Access Journals (Sweden)
Qingxiang Wang
2013-11-01
Full Text Available The Line Drawing Animation is an active research area in Non-Photorealistic Rendering. Many researchs are focused on the skech abastract, like such as portrait drawing of human and animation generation. However most of the model are too complex to calculate or pay attention to the details which are not stable that are not suitable for realtime transfer for continuous sequence of video. This paper proposes a simple line drawing definition and transfer model with Bézier Curves and the core of the AAM fit parameters. The facial line drawings have seven basic emotions include neutral, happiness, anger, disgust, fear, sadness and surprised. Each of the drawing in a specific model is consisted of a same set of cubic Bézier curves. The proposed model is suitabl for shape conbination anmition. In the experiment, the AAM method is used to get the facial features of the face and then find the nearest combination of the emotion to transfer to the line drawing model. The result shows that the method is simple and fast. Only a few of the parameters are needed to transfer that is suitable to record and communication.
Simple cellular automaton model for traffic breakdown, highway capacity, and synchronized flow.
Kerner, Boris S; Klenov, Sergey L; Schreckenberg, Michael
2011-10-01
We present a simple cellular automaton (CA) model for two-lane roads explaining the physics of traffic breakdown, highway capacity, and synchronized flow. The model consists of the rules "acceleration," "deceleration," "randomization," and "motion" of the Nagel-Schreckenberg CA model as well as "overacceleration through lane changing to the faster lane," "comparison of vehicle gap with the synchronization gap," and "speed adaptation within the synchronization gap" of Kerner's three-phase traffic theory. We show that these few rules of the CA model can appropriately simulate fundamental empirical features of traffic breakdown and highway capacity found in traffic data measured over years in different countries, like characteristics of synchronized flow, the existence of the spontaneous and induced breakdowns at the same bottleneck, and associated probabilistic features of traffic breakdown and highway capacity. Single-vehicle data derived in model simulations show that synchronized flow first occurs and then self-maintains due to a spatiotemporal competition between speed adaptation to a slower speed of the preceding vehicle and passing of this slower vehicle. We find that the application of simple dependences of randomization probability and synchronization gap on driving situation allows us to explain the physics of moving synchronized flow patterns and the pinch effect in synchronized flow as observed in real traffic data.
Directory of Open Access Journals (Sweden)
Simonson Thomas
2008-10-01
Full Text Available Abstract Background Structure-based computational methods are needed to help identify and characterize protein-protein complexes and their function. For individual proteins, the most successful technique is homology modelling. We investigate a simple extension of this technique to protein-protein complexes. We consider a large set of complexes of known structures, involving pairs of single-domain proteins. The complexes are compared with each other to establish their sequence and structural similarities and the relation between the two. Compared to earlier studies, a simpler dataset, a simpler structural alignment procedure, and an additional energy criterion are used. Next, we compare the Xray structures to models obtained by threading the native sequence onto other, homologous complexes. An elementary requirement for a successful energy function is to rank the native structure above any threaded structure. We use the DFIREβ energy function, whose quality and complexity are typical of the models used today. Finally, we compare near-native models to distinctly non-native models. Results If weakly stable complexes are excluded (defined by a binding energy cutoff, as well as a few unusual complexes, a simple homology principle holds: complexes that share more than 35% sequence identity share similar structures and interaction modes; this principle was less clearcut in earlier studies. The energy function was then tested for its ability to identify experimental structures among sets of decoys, produced by a simple threading procedure. On average, the experimental structure is ranked above 92% of the alternate structures. Thus, discrimination of the native structure is good but not perfect. The discrimination of near-native structures is fair. Typically, a single, alternate, non-native binding mode exists that has a native-like energy. Some of the associated failures may correspond to genuine, alternate binding modes and/or native complexes that
A Simple, Analytical Model of Collisionless Magnetic Reconnection in a Pair Plasma
Hesse, Michael; Zenitani, Seiji; Kuznetova, Masha; Klimas, Alex
2011-01-01
A set of conservation equations is utilized to derive balance equations in the reconnection diffusion region of a symmetric pair plasma. The reconnection electric field is assumed to have the function to maintain the current density in the diffusion region, and to impart thermal energy to the plasma by means of quasi-viscous dissipation. Using these assumptions it is possible to derive a simple set of equations for diffusion region parameters in dependence on inflow conditions and on plasma compressibility. These equations are solved by means of a simple, iterative, procedure. The solutions show expected features such as dominance of enthalpy flux in the reconnection outflow, as well as combination of adiabatic and quasi-viscous heating. Furthermore, the model predicts a maximum reconnection electric field of E(sup *)=0.4, normalized to the parameters at the inflow edge of the diffusion region.
Institute of Scientific and Technical Information of China (English)
BAI Yuan; ZONG Gang-jun; WANG Yan-yan; JIANG Hai-bin; LI Wei-ping; WU Hong; ZHAO Xian-xian; QIN Yong-wen
2009-01-01
Background Percutaneous aortic valve replacement is a promising strategy in the treatment of patients with aortic valve stenosis. And many kinds of valved stents have been implanted in selected patients worldwide. However, the clinical experience is still limited. We developed a W-model valved stent and evaluated the feasibility and safety of percutaneous implantation of the device in the native aortic valve position.Methods A self expanding nitinol stent with W-model, containing porcine pericardium valves in its proximal part, was implanted in six sheep by means of a 14 French catheter through the right common lilac artery under guidance of fluoroscopy. During stent deployment the original aortic valve was pushed against the aortic wall by the self expanding force of the stent while the new valve was expanded. These sheep were followed up shortly after procedure with supra-aortic angiogram and left ventriculography. Additionally, one sheep was sacrificed after the procedure for anatomic evaluation.Results It was possible to replace the aortic valve in the beating heart in four sheep. The procedure failed in two sheep due to coronary orifice occlusion in one case and severe aortic valve regurgitation in the other case. One sheep was killed one hour after percutaneous aortic valve replacement for anatomic evaluation. There were no signs of damage of the aortic intima, or of obstruction of the coronary orifice.Conclusions Percutaneous aortic valve replacement with a W-model valved stent in the beating heart is possible. Further studies are mandatory to assess safety and efficacy of this kind of valved stent in larger sample size and by longer follow-up period.
A simple method for EEG guided transcranial electrical stimulation without models
Cancelli, Andrea; Cottone, Carlo; Tecchio, Franca; Truong, Dennis Q.; Dmochowski, Jacek; Bikson, Marom
2016-06-01
Objective. There is longstanding interest in using EEG measurements to inform transcranial Electrical Stimulation (tES) but adoption is lacking because users need a simple and adaptable recipe. The conventional approach is to use anatomical head-models for both source localization (the EEG inverse problem) and current flow modeling (the tES forward model), but this approach is computationally demanding, requires an anatomical MRI, and strict assumptions about the target brain regions. We evaluate techniques whereby tES dose is derived from EEG without the need for an anatomical head model, target assumptions, difficult case-by-case conjecture, or many stimulation electrodes. Approach. We developed a simple two-step approach to EEG-guided tES that based on the topography of the EEG: (1) selects locations to be used for stimulation; (2) determines current applied to each electrode. Each step is performed based solely on the EEG with no need for head models or source localization. Cortical dipoles represent idealized brain targets. EEG-guided tES strategies are verified using a finite element method simulation of the EEG generated by a dipole, oriented either tangential or radial to the scalp surface, and then simulating the tES-generated electric field produced by each model-free technique. These model-free approaches are compared to a ‘gold standard’ numerically optimized dose of tES that assumes perfect understanding of the dipole location and head anatomy. We vary the number of electrodes from a few to over three hundred, with focality or intensity as optimization criterion. Main results. Model-free approaches evaluated include (1) voltage-to-voltage, (2) voltage-to-current; (3) Laplacian; and two Ad-Hoc techniques (4) dipole sink-to-sink; and (5) sink to concentric. Our results demonstrate that simple ad hoc approaches can achieve reasonable targeting for the case of a cortical dipole, remarkably with only 2-8 electrodes and no need for a model of the head
Energy Technology Data Exchange (ETDEWEB)
Coste, P.; Bestion, D. [Commissariat a l Energie Atomique, Grenoble (France)
1995-09-01
This paper presents a simple modelling of mass diffusion effects on condensation. In presence of noncondensable gases, the mass diffusion near the interface is modelled using the heat and mass transfer analogy and requires normally an iterative procedure to calculate the interface temperature. Simplifications of the model and of the solution procedure are used without important degradation of the predictions. The model is assessed on experimental data for both film condensation in vertical tubes and direct contact condensation in horizontal tubes, including air-steam, Nitrogen-steam and Helium-steam data. It is implemented in the Cathare code, a french system code for nuclear reactor thermal hydraulics developed by CEA, EDF, and FRAMATOME.