40 CFR Table 2 to Subpart Dddd of... - Model Rule-Emission Limitations
2010-07-01
... Compliance Times for Commercial and Industrial Solid Waste Incineration Units that Commenced Construction On... averaging time And determining compliance using this method Cadmium 0.004 milligrams per dry standard cubic... this part) Carbon monoxide 157 parts per million by dry volume 3-run average (1 hour minimum sample...
40 CFR Table 2 to Subpart Ffff of... - Model Rule-Emission Limitations
2010-07-01
... Compliance Times for Other Solid Waste Incineration Units That Commenced Construction On or Before December 9... micrograms per dry standard cubic meter 3-run average (1 hour minimum sample time per run) Method 29 of appendix A of this part. 2. Carbon monoxide 40 parts per million by dry volume 3-run average (1 hour...
Directory of Open Access Journals (Sweden)
Oleg Svatos
2013-01-01
Full Text Available In this paper we analyze complexity of time limits we can find especially in regulated processes of public administration. First we review the most popular process modeling languages. There is defined an example scenario based on the current Czech legislature which is then captured in discussed process modeling languages. Analysis shows that the contemporary process modeling languages support capturing of the time limit only partially. This causes troubles to analysts and unnecessary complexity of the models. Upon unsatisfying results of the contemporary process modeling languages we analyze the complexity of the time limits in greater detail and outline lifecycles of a time limit using the multiple dynamic generalizations pattern. As an alternative to the popular process modeling languages there is presented PSD process modeling language, which supports the defined lifecycles of a time limit natively and therefore allows keeping the models simple and easy to understand.
Limits with modeling data and modeling data with limits
Directory of Open Access Journals (Sweden)
Lionello Pogliani
2006-01-01
Full Text Available Modeling of the solubility of amino acids and purine and pyrimidine bases with a set of sixteen molecular descriptors has been thoroughly analyzed to detect and understand the reasons for anomalies in the description of this property for these two classes of compounds. Unsatisfactory modeling can be ascribed to incomplete collateral data, i.e, to the fact that there is insufficient data known about the behavior of these compounds in solution. This is usually because intermolecular forces cannot be modeled. The anomalous modeling can be detected from the rather large values of the standard deviation of the estimates of the whole set of compounds, and from the unsatisfactory modeling of some of the subsets of these compounds. Thus the detected abnormalities can be used (i to get an idea about weak intermolecular interactions such as hydration, self-association, the hydrogen-bond phenomena in solution, and (ii to reshape the molecular descriptors with the introduction of parameters that allow better modeling. This last procedure should be used with care, bearing in mind that the solubility phenomena is rather complex.
Setting limits on supersymmetry using simplified models
Gutschow, C.
2012-01-01
Experimental limits on supersymmetry and similar theories are difficult to set because of the enormous available parameter space and difficult to generalize because of the complexity of single points. Therefore, more phenomenological, simplified models are becoming popular for setting experimental limits, as they have clearer physical implications. The use of these simplified model limits to set a real limit on a concrete theory has not, however, been demonstrated. This paper recasts simplified model limits into limits on a specific and complete supersymmetry model, minimal supergravity. Limits obtained under various physical assumptions are comparable to those produced by directed searches. A prescription is provided for calculating conservative and aggressive limits on additional theories. Using acceptance and efficiency tables along with the expected and observed numbers of events in various signal regions, LHC experimental results can be re-cast in this manner into almost any theoretical framework, includ...
Hanford defined waste model limitations and improvements
International Nuclear Information System (INIS)
HARMSEN, R.W.
1999-01-01
Recommendation 93-5 Implementation Plan, Milestone 5,6.3.1.i requires issuance of this report which addresses ''updates to the tank contents model''. This report summarizes the review of the Hanford Defined Waste, Revision 4, model limitations and provides conclusions and recommendations for potential updates to the model
Modelling of particles collection by vented limiters
International Nuclear Information System (INIS)
Tsitrone, E.; Pegourie, B.; Granata, G.
1995-01-01
This document deals with the use of vented limiters for the collection of neutral particles in Tore Supra. The model developed for experiments is presented together with its experimental validation. Some possible improvements to the present limiter are also proposed. (TEC). 5 refs., 3 figs
Matrix model calculations beyond the spherical limit
International Nuclear Information System (INIS)
Ambjoern, J.; Chekhov, L.; Kristjansen, C.F.; Makeenko, Yu.
1993-01-01
We propose an improved iterative scheme for calculating higher genus contributions to the multi-loop (or multi-point) correlators and the partition function of the hermitian one matrix model. We present explicit results up to genus two. We develop a version which gives directly the result in the double scaling limit and present explicit results up to genus four. Using the latter version we prove that the hermitian and the complex matrix model are equivalent in the double scaling limit and that in this limit they are both equivalent to the Kontsevich model. We discuss how our results away from the double scaling limit are related to the structure of moduli space. (orig.)
Computer modelling of superconductive fault current limiters
Energy Technology Data Exchange (ETDEWEB)
Weller, R.A.; Campbell, A.M.; Coombs, T.A.; Cardwell, D.A.; Storey, R.J. [Cambridge Univ. (United Kingdom). Interdisciplinary Research Centre in Superconductivity (IRC); Hancox, J. [Rolls Royce, Applied Science Division, Derby (United Kingdom)
1998-05-01
Investigations are being carried out on the use of superconductors for fault current limiting applications. A number of computer programs are being developed to predict the behavior of different `resistive` fault current limiter designs under a variety of fault conditions. The programs achieve solution by iterative methods based around real measured data rather than theoretical models in order to achieve accuracy at high current densities. (orig.) 5 refs.
Animal models of preeclampsia; uses and limitations.
LENUS (Irish Health Repository)
McCarthy, F P
2012-01-31
Preeclampsia remains a leading cause of maternal and fetal morbidity and mortality and has an unknown etiology. The limited progress made regarding new treatments to reduce the incidence and severity of preeclampsia has been attributed to the difficulties faced in the development of suitable animal models for the mechanistic research of this disease. In addition, animal models need hypotheses on which to be based and the slow development of testable hypotheses has also contributed to this poor progress. The past decade has seen significant advances in our understanding of preeclampsia and the development of viable reproducible animal models has contributed significantly to these advances. Although many of these models have features of preeclampsia, they are still poor overall models of the human disease and limited due to lack of reproducibility and because they do not include the complete spectrum of pathophysiological changes associated with preeclampsia. This review aims to provide a succinct and comprehensive assessment of current animal models of preeclampsia, their uses and limitations with particular attention paid to the best validated and most comprehensive models, in addition to those models which have been utilized to investigate potential therapeutic interventions for the treatment or prevention of preeclampsia.
Limit Cycles in Predator-Prey Models
Puchuri Medina, Liliana
2017-01-01
The classic Lotka-Volterra model belongs to a family of differential equations known as “Generalized Lotka-Volterra”, which is part of a classification of four models of quadratic fields with center. These models have been studied to address the Hilbert infinitesimal problem, which consists in determine the number of limit cycles of a perturbed hamiltonian system with center. In this work, we first present an alternative proof of the existence of centers in Lotka-Volterra predator-prey models...
Limited Commitment Models of the Labour Market
Jonathan Thomas; Tim Worrall
2007-01-01
We present an overview of models of long-term self-enforcing labour con- tracts in which risk-sharing is the dominant motive for contractual solutions. A base model is developed which is sufficiently general to encompass the two-agent problem central to most of the literature, including variable hours. We consider two-sided limited commitment and look at its implications for aggregate labour market variables. We consider the implications for empirical testing and the available empirical evide...
The Peierls model: Progress and limitations
International Nuclear Information System (INIS)
Schoeck, Gunther
2005-01-01
The basic features of the Peierls model are reviewed. The original model is based on the concept of balance of stresses in 1D and has serious limitations. These limitations can be overcome by a treatment as a variational problem on the energy level in 2D. The fundamental equations are given and applications to determine displacement profiles for dislocations and their dissociations are discussed. When the core misfit has a planar extension and the misfit energy in the glide plane - the γ-surface - is determined from ab initio methods, very reliable core configurations can be determined. For dislocations along close-packed lattice directions the misfit energy can be obtained by a summing procedure using Euler coordinates. When these dislocations are dissociated multiple equilibrium configurations with different splitting widths can exist, but the values of energy difference in between - the Peierls energy - are too small to be determined reliably, considering the simplifying assumptions of the model
London limit for lattice model of superconductor
International Nuclear Information System (INIS)
Ktitorov, S.A.
2004-01-01
The phenomenological approach to the strong-bond superconductor, which is based on the Ginzburg-Landau equation in the London limit, is considered. The effect of the crystalline lattice discreteness on the superconductors electromagnetic properties is studied. The classic problems on the critical current and magnetic field penetration are studied within the frames of the lattice model for thin superconducting films. The dependence of the superconducting current on the thin film order parameter is obtained. The critical current dependence on the degree of deviation from the continual approximation is calculated [ru
Model unspecific search in CMS. Model unspecific limits
Energy Technology Data Exchange (ETDEWEB)
Knutzen, Simon; Albert, Andreas; Duchardt, Deborah; Hebbeker, Thomas; Lieb, Jonas; Meyer, Arnd; Pook, Tobias; Roemer, Jonas [III. Physikalisches Institut A, RWTH Aachen University (Germany)
2016-07-01
The standard model of particle physics is increasingly challenged by recent discoveries and also by long known phenomena, representing a strong motivation to develop extensions of the standard model. The amount of theories describing possible extensions is large and steadily growing. In this presentation a new approach is introduced, verifying if a given theory beyond the standard model is consistent with data collected by the CMS detector without the need to perform a dedicated search. To achieve this, model unspecific limits on the number of additional events above the standard model expectation are calculated in every event class produced by the MUSiC algorithm. Furthermore, a tool is provided to translate these results into limits on the signal cross section of any theory. In addition to the general procedure, first results and examples are shown using the proton-proton collision data taken at a centre of mass energy of 8 TeV.
Toward Modeling Limited Plasticity in Ceramic Materials
National Research Council Canada - National Science Library
Grinfeld, Michael; Schoenfeld, Scott E; Wright, Tim W
2008-01-01
The characteristic features of many armor-related ceramic materials are the anisotropy on the micro-scale level and the very limited, though non-vanishing, plasticity due to limited number of the planes for plastic slip...
MODELLING OF DYNAMIC SPEED LIMITS USING THE MODEL PREDICTIVE CONTROL
Directory of Open Access Journals (Sweden)
Andrey Borisovich Nikolaev
2017-09-01
Full Text Available The article considers the issues of traffic management using intelligent system “Car-Road” (IVHS, which consist of interacting intelligent vehicles (IV and intelligent roadside controllers. Vehicles are organized in convoy with small distances between them. All vehicles are assumed to be fully automated (throttle control, braking, steering. Proposed approaches for determining speed limits for traffic cars on the motorway using a model predictive control (MPC. The article proposes an approach to dynamic speed limit to minimize the downtime of vehicles in traffic.
Model for movement of molten limiter material during the ISX-B beryllium limiter experiment
International Nuclear Information System (INIS)
Langley, R.A.; England, A.C.; Edmonds, P.H.; Hogan, J.T.; Neilson, G.H.
1986-01-01
A model is proposed for the movement and erosion of limiter material during the Beryllium Limiter Experiment performed on the ISX-B Tokamak. This model is consistent with observed experimental results and plasma operational characteristics. Conclusions drawn from the model can provide an understanding of erosion mechanisms, thereby contributing to the development of future design criteria. (author)
Limitations of the Revised DREAM Model
Breivik, Stian
2012-01-01
Master's thesis in Environmental Technology DREAM (Dose-related Risk and Exposure Assessment Model) is a risk assessment tool for modeling offshore waste discharge to the marine environment. The drilling waste model was developed through the joint industrial project ERMS (Environmental Risk Management System). The method follows a PEC/PNEC (Predicted Environmental Concentration / Predicted no Effect Concentration) approach as to determine an EIF (Environmental Impact Factor) fo...
Animal models of osteoporosis - necessity and limitations
Directory of Open Access Journals (Sweden)
Turner A. Simon
2001-06-01
Full Text Available There is a great need to further characterise the available animal models for postmenopausal osteoporosis, for the understanding of the pathogenesis of the disease, investigation of new therapies (e.g. selective estrogen receptor modulators (SERMs and evaluation of prosthetic devices in osteoporotic bone. Animal models that have been used in the past include non-human primates, dogs, cats, rodents, rabbits, guinea pigs and minipigs, all of which have advantages and disadvantages. Sheep are a promising model for various reasons: they are docile, easy to handle and house, relatively inexpensive, available in large numbers, spontaneously ovulate, and the sheep's bones are large enough to evaluate orthopaedic implants. Most animal models have used females and osteoporosis in the male has been largely ignored. Recently, interest in development of appropriate prosthetic devices which would stimulate osseointegration into osteoporotic, appendicular, axial and mandibular bone has intensified. Augmentation of osteopenic lumbar vertebrae with bioactive ceramics (vertebroplasty is another area that will require testing in the appropriate animal model. Using experimental animal models for the study of these different facets of osteoporosis minimizes some of the difficulties associated with studying the disease in humans, namely time and behavioral variability among test subjects. New experimental drug therapies and orthopaedic implants can potentially be tested on large numbers of animals subjected to a level of experimental control impossible in human clinical research.
Animal models of contraception: utility and limitations
Directory of Open Access Journals (Sweden)
Liechty ER
2015-04-01
Full Text Available Emma R Liechty,1 Ingrid L Bergin,1 Jason D Bell2 1Unit for Laboratory Animal Medicine, 2Program on Women's Health Care Effectiveness Research, Department of Obstetrics and Gynecology, University of Michigan, Ann Arbor, MI, USA Abstract: Appropriate animal modeling is vital for the successful development of novel contraceptive devices. Advances in reproductive biology have identified novel pathways for contraceptive intervention. Here we review species-specific anatomic and physiologic considerations impacting preclinical contraceptive testing, including efficacy testing, mechanistic studies, device design, and modeling off-target effects. Emphasis is placed on the use of nonhuman primate models in contraceptive device development. Keywords: nonhuman primate, preclinical, in vivo, contraceptive devices
Animal models of asthma: utility and limitations
Directory of Open Access Journals (Sweden)
Aun MV
2017-11-01
Full Text Available Marcelo Vivolo Aun,1,2 Rafael Bonamichi-Santos,1,2 Fernanda Magalhães Arantes-Costa,2 Jorge Kalil,1 Pedro Giavina-Bianchi1 1Clinical Immunology and Allergy Division, Department of Internal Medicine, University of São Paulo School of Medicine, São Paulo, Brazil, 2Laboratory of Experimental Therapeutics (LIM20, Department of Internal Medicine, University of Sao Paulo, Sao Paulo, Brazil Abstract: Clinical studies in asthma are not able to clear up all aspects of disease pathophysiology. Animal models have been developed to better understand these mechanisms and to evaluate both safety and efficacy of therapies before starting clinical trials. Several species of animals have been used in experimental models of asthma, such as Drosophila, rats, guinea pigs, cats, dogs, pigs, primates and equines. However, the most common species studied in the last two decades is mice, particularly BALB/c. Animal models of asthma try to mimic the pathophysiology of human disease. They classically include two phases: sensitization and challenge. Sensitization is traditionally performed by intraperitoneal and subcutaneous routes, but intranasal instillation of allergens has been increasingly used because human asthma is induced by inhalation of allergens. Challenges with allergens are performed through aerosol, intranasal or intratracheal instillation. However, few studies have compared different routes of sensitization and challenge. The causative allergen is another important issue in developing a good animal model. Despite being more traditional and leading to intense inflammation, ovalbumin has been replaced by aeroallergens, such as house dust mites, to use the allergens that cause human disease. Finally, researchers should define outcomes to be evaluated, such as serum-specific antibodies, airway hyperresponsiveness, inflammation and remodeling. The present review analyzes the animal models of asthma, assessing differences between species, allergens and routes
Overcoming some limitations of imprecise reliability models
DEFF Research Database (Denmark)
Kozine, Igor; Krymsky, Victor
2011-01-01
The application of imprecise reliability models is often hindered by the rapid growth in imprecision that occurs when many components constitute a system and by the fact that time to failure is bounded from above. The latter results in the necessity to explicitly introduce an upper bound on time ...
Limiting assumptions in molecular modeling: electrostatics.
Marshall, Garland R
2013-02-01
Molecular mechanics attempts to represent intermolecular interactions in terms of classical physics. Initial efforts assumed a point charge located at the atom center and coulombic interactions. It is been recognized over multiple decades that simply representing electrostatics with a charge on each atom failed to reproduce the electrostatic potential surrounding a molecule as estimated by quantum mechanics. Molecular orbitals are not spherically symmetrical, an implicit assumption of monopole electrostatics. This perspective reviews recent evidence that requires use of multipole electrostatics and polarizability in molecular modeling.
Limitations of the biopsychosocial model in psychiatry
Directory of Open Access Journals (Sweden)
Benning TB
2015-05-01
Full Text Available Tony B Benning Maple Ridge Mental Health Centre, Maple Ridge, BC, Canada Abstract: A commitment to an integrative, non-reductionist clinical and theoretical perspective in medicine that honors the importance of all relevant domains of knowledge, not just “the biological,” is clearly evident in Engel’s original writings on the biopsychosocial model. And though this model’s influence on modern psychiatry (in clinical as well as educational settings has been significant, a growing body of recent literature is critical of it - charging it with lacking philosophical coherence, insensitivity to patients’ subjective experience, being unfaithful to the general systems theory that Engel claimed it be rooted in, and engendering an undisciplined eclecticism that provides no safeguards against either the dominance or the under-representation of any one of the three domains of bio, psycho, or social. Keywords: critique of biopsychosocial psychiatry, integrative psychiatry, George Engel
Fixed transaction costs and modelling limited dependent variables
Hempenius, A.L.
1994-01-01
As an alternative to the Tobit model, for vectors of limited dependent variables, I suggest a model, which follows from explicitly using fixed costs, if appropriate of course, in the utility function of the decision-maker.
Limit on mass differences in the Weinberg model
Veltman, M.J.G.
1977-01-01
Within the Weinberg model mass differences between members of a multiplet generate further mass differences between the neutral and charged vector bosons. The experimental situation on the Weinberg model leads to an upper limit of about 800 GeV on mass differences within a multiplet. No limit on the
Atterberg Limits Prediction Comparing SVM with ANFIS Model
Directory of Open Access Journals (Sweden)
Mohammad Murtaza Sherzoy
2017-03-01
Full Text Available Support Vector Machine (SVM and Adaptive Neuro-Fuzzy inference Systems (ANFIS both analytical methods are used to predict the values of Atterberg limits, such as the liquid limit, plastic limit and plasticity index. The main objective of this study is to make a comparison between both forecasts (SVM & ANFIS methods. All data of 54 soil samples are used and taken from the area of Peninsular Malaysian and tested for different parameters containing liquid limit, plastic limit, plasticity index and grain size distribution and were. The input parameter used in for this case are the fraction of grain size distribution which are the percentage of silt, clay and sand. The actual and predicted values of Atterberg limit which obtained from the SVM and ANFIS models are compared by using the correlation coefficient R2 and root mean squared error (RMSE value. The outcome of the study show that the ANFIS model shows higher accuracy than SVM model for the liquid limit (R2 = 0.987, plastic limit (R2 = 0.949 and plastic index (R2 = 0966. RMSE value that obtained for both methods have shown that the ANFIS model has represent the best performance than SVM model to predict the Atterberg Limits as a whole.
Scaling limit for the Derezi\\'nski-G\\'erard model
OHKUBO, Atsushi
2010-01-01
We consider a scaling limit for the Derezi\\'nski-G\\'erard model. We derive an effective potential by taking a scaling limit for the total Hamiltonian of the Derezi\\'nski-G\\'erard model. Our method to derive an effective potential is independent of whether or not the quantum field has a nonnegative mass. As an application of our theory developed in the present paper, we derive an effective potential of the Nelson model.
Countercurrent flow limitation model for RELAP5/MOD3
International Nuclear Information System (INIS)
Riemke, R.A.
1991-01-01
This paper reports on a countercurrent flow limitation model incorporated into the RELAP5/MOD3 system transient analysis code. The model is implemented in a manner similar to the RELAP5 chocking model. Simulations using air/water flooding test problem demonstrate the ability of the code to significantly improve its comparison to data when a flooding correlation is used
Modelling of density limit phenomena in toroidal helical plasmas
International Nuclear Information System (INIS)
Itoh, Kimitaka; Itoh, Sanae-I.
2001-01-01
The physics of density limit phenomena in toroidal helical plasmas based on an analytic point model of toroidal plasmas is discussed. The combined mechanism of the transport and radiation loss of energy is analyzed, and the achievable density is derived. A scaling law of the density limit is discussed. The dependence of the critical density on the heating power, magnetic field, plasma size and safety factor in the case of L-mode energy confinement is explained. The dynamic evolution of the plasma energy and radiation loss is discussed. Assuming a simple model of density evolution, of a sudden loss of density if the temperature becomes lower than critical value, then a limit cycle oscillation is shown to occur. A condition that divides the limit cycle oscillation and the complete radiation collapse is discussed. This model seems to explain the density limit oscillation that has been observed on the Wendelstein 7-AS (W7-AS) stellarator. (author)
Modelling of density limit phenomena in toroidal helical plasmas
International Nuclear Information System (INIS)
Itoh, K.; Itoh, S.-I.
2000-03-01
The physics of density limit phenomena in toroidal helical plasmas based on an analytic point model of toroidal plasmas is discussed. The combined mechanism of the transport and radiation loss of energy is analyzed, and the achievable density is derived. A scaling law of the density limit is discussed. The dependence of the critical density on the heating power, magnetic field, plasma size and safety factor in the case of L-mode energy confinement is explained. The dynamic evolution of the plasma energy and radiation loss is discussed. Assuming a simple model of density evolution, of a sudden loss of density if the temperature becomes lower than critical value, then a limit cycle oscillation is shown to occur. A condition that divides the limit cycle oscillation and the complete radiation collapse is discussed. This model seems to explain the density limit oscillation that has been observed on the W7-AS stellarator. (author)
A predictive model for the tokamak density limit
International Nuclear Information System (INIS)
Teng, Q.; Brennan, D. P.; Delgado-Aparicio, L.; Gates, D. A.; Swerdlow, J.; White, R. B.
2016-01-01
We reproduce the Greenwald density limit, in all tokamak experiments by using a phenomenologically correct model with parameters in the range of experiments. A simple model of equilibrium evolution and local power balance inside the island has been implemented to calculate the radiation-driven thermo-resistive tearing mode growth and explain the density limit. Strong destabilization of the tearing mode due to an imbalance of local Ohmic heating and radiative cooling in the island predicts the density limit within a few percent. Furthermore, we found the density limit and it is a local edge limit and weakly dependent on impurity densities. Our results are robust to a substantial variation in model parameters within the range of experiments.
Model studies of limitation of carbon dioxide emissions reduction
International Nuclear Information System (INIS)
1992-01-01
The report consists of two papers concerning mitigation of CO 2 emissions in Sweden, ''Limitation of carbon dioxide emissions. Socio-economic effects and the importance of international coordination'', and ''Model calculations for Sweden's energy system with carbon dioxide limitations''. Separate abstracts were prepared for both of the papers
Flux-limited diffusion models in radiation hydrodynamics
International Nuclear Information System (INIS)
Pomraning, G.C.; Szilard, R.H.
1993-01-01
The authors discuss certain flux-limited diffusion theories which approximately describe radiative transfer in the presence of steep spatial gradients. A new formulation is presented which generalizes a flux-limited description currently in widespread use for large radiation hydrodynamic calculations. This new formation allows more than one Case discrete mode to be described by a flux-limited diffusion equation. Such behavior is not extant in existing formulations. Numerical results predicted by these flux-limited diffusion models are presented for radiation penetration into an initially cold halfspace. 37 refs., 5 figs
Weak diffusion limits of dynamic conditional correlation models
DEFF Research Database (Denmark)
Hafner, Christian M.; Laurent, Sebastien; Violante, Francesco
The properties of dynamic conditional correlation (DCC) models are still not entirely understood. This paper fills one of the gaps by deriving weak diffusion limits of a modified version of the classical DCC model. The limiting system of stochastic differential equations is characterized...... by a diffusion matrix of reduced rank. The degeneracy is due to perfect collinearity between the innovations of the volatility and correlation dynamics. For the special case of constant conditional correlations, a non-degenerate diffusion limit can be obtained. Alternative sets of conditions are considered...
MODELLING OF CONCENTRATION LIMITS BASED ON NEURAL NETWORKS.
Directory of Open Access Journals (Sweden)
A. L. Osipov
2017-02-01
Full Text Available We study the forecasting model with the concentration limits is-the use of neural network technology. The software for the implementation of these models. It is shown that the efficiency of the system in the experimental material.
Modelling the influence of silicon and phosphorus limitation on the ...
African Journals Online (AJOL)
In the model, toxin production was related to C cell–1 and triggered by nutrient stress, defined by low values of the carbon-based cell quota of the limiting nutrient. The study therefore suggests that simple models, based on easily measured quantities, are capable of simulating Pseudo-nitzschia growth and toxin production.
Limitations of JEDI Models | Jobs and Economic Development Impact Models |
Group's IMPLAN accounting software. For JEDI, these are updated every two years for the best available -output modeling remains a widely used methodology for measuring economic development activity. Definition definition of the geographic area under consideration. Datasets of multipliers from IMPLAN are available at
Stochastic Modeling and Deterministic Limit of Catalytic Surface Processes
DEFF Research Database (Denmark)
Starke, Jens; Reichert, Christian; Eiswirth, Markus
2007-01-01
Three levels of modeling, microscopic, mesoscopic and macroscopic are discussed for the CO oxidation on low-index platinum single crystal surfaces. The introduced models on the microscopic and mesoscopic level are stochastic while the model on the macroscopic level is deterministic. It can......, such that in contrast to the microscopic model the spatial resolution is reduced. The derivation of deterministic limit equations is in correspondence with the successful description of experiments under low-pressure conditions by deterministic reaction-diffusion equations while for intermediate pressures phenomena...
Functional State Modelling of Cultivation Processes: Dissolved Oxygen Limitation State
Directory of Open Access Journals (Sweden)
Olympia Roeva
2015-04-01
Full Text Available A new functional state, namely dissolved oxygen limitation state for both bacteria Escherichia coli and yeast Saccharomyces cerevisiae fed-batch cultivation processes is presented in this study. Functional state modelling approach is applied to cultivation processes in order to overcome the main disadvantages of using global process model, namely complex model structure and a big number of model parameters. Alongwith the newly introduced dissolved oxygen limitation state, second acetate production state and first acetate production state are recognized during the fed-batch cultivation of E. coli, while mixed oxidative state and first ethanol production state are recognized during the fed-batch cultivation of S. cerevisiae. For all mentioned above functional states both structural and parameter identification is here performed based on experimental data of E. coli and S. cerevisiae fed-batch cultivations.
On the limits of application of the Stephens model
International Nuclear Information System (INIS)
Issa, A.; Piepenbring, R.
1977-01-01
The limits of the rotation alignment model of Stephens are studied. The conditions of applicability of the assumption of constant j for a unique parity isolated sub-shell (extended to N=4 and N=3) are discussed and explanations are given. A correct treatment of the eigenstates of the intrinsic motion allows however a simple extension of the model to non-isolated sub-shells without enlarging the basis of diagonalisation [fr
Experimental limits from ATLAS on Standard Model Higgs production.
ATLAS, collaboration
2012-01-01
Experimental limits from ATLAS on Standard Model Higgs production in the mass range 110-600 GeV. The solid curve reflects the observed experimental limits for the production of a Higgs of each possible mass value (horizontal axis). The region for which the solid curve dips below the horizontal line at the value of 1 is excluded with a 95% confidence level (CL). The dashed curve shows the expected limit in the absence of the Higgs boson, based on simulations. The green and yellow bands correspond (respectively) to 68%, and 95% confidence level regions from the expected limits. Higgs masses in the narrow range 123-130 GeV are the only masses not excluded at 95% CL
Limited Area Forecasting and Statistical Modelling for Wind Energy Scheduling
DEFF Research Database (Denmark)
Rosgaard, Martin Haubjerg
forecast accuracy for operational wind power scheduling. Numerical weather prediction history and scales of atmospheric motion are summarised, followed by a literature review of limited area wind speed forecasting. Hereafter, the original contribution to research on the topic is outlined. The quality...... control of wind farm data used as forecast reference is described in detail, and a preliminary limited area forecasting study illustrates the aggravation of issues related to numerical orography representation and accurate reference coordinates at ne weather model resolutions. For the o shore and coastal...... sites studied limited area forecasting is found to deteriorate wind speed prediction accuracy, while inland results exhibit a steady forecast performance increase with weather model resolution. Temporal smoothing of wind speed forecasts is shown to improve wind power forecast performance by up to almost...
Usefulness and limitations of global flood risk models
Ward, Philip; Jongman, Brenden; Salamon, Peter; Simpson, Alanna; Bates, Paul; De Groeve, Tom; Muis, Sanne; Coughlan de Perez, Erin; Rudari, Roberto; Mark, Trigg; Winsemius, Hessel
2016-04-01
Global flood risk models are now a reality. Initially, their development was driven by a demand from users for first-order global assessments to identify risk hotspots. Relentless upward trends in flood damage over the last decade have enhanced interest in such assessments. The adoption of the Sendai Framework for Disaster Risk Reduction and the Warsaw International Mechanism for Loss and Damage Associated with Climate Change Impacts have made these efforts even more essential. As a result, global flood risk models are being used more and more in practice, by an increasingly large number of practitioners and decision-makers. However, they clearly have their limits compared to local models. To address these issues, a team of scientists and practitioners recently came together at the Global Flood Partnership meeting to critically assess the question 'What can('t) we do with global flood risk models?'. The results of this dialogue (Ward et al., 2013) will be presented, opening a discussion on similar broader initiatives at the science-policy interface in other natural hazards. In this contribution, examples are provided of successful applications of global flood risk models in practice (for example together with the World Bank, Red Cross, and UNISDR), and limitations and gaps between user 'wish-lists' and model capabilities are discussed. Finally, a research agenda is presented for addressing these limitations and reducing the gaps. Ward et al., 2015. Nature Climate Change, doi:10.1038/nclimate2742
Singular limit analysis of a model for earthquake faulting
DEFF Research Database (Denmark)
Bossolini, Elena; Brøns, Morten; Kristiansen, Kristian Uldall
2017-01-01
In this paper we consider the one dimensional spring-block model describing earthquake faulting. By using geometric singular perturbation theory and the blow-up method we provide a detailed description of the periodicity of the earthquake episodes. In particular, the limit cycles arise from...
Homogeneous axisymmetric model with a limitting stiff equation of state
International Nuclear Information System (INIS)
Korkina, M.P.; Martynenko, V.G.
1976-01-01
A solution is obtained for Einstein's equations in which all metric coefficients are time functions for a limiting stiff equation of the substance state. Thr solution describes a homogeneous cosmological model with cylindrical symmetry. It is shown that the same metrics can be induced by a massless scalar only time-dependent field. Analysis of this solution is presented
The limitations of applying rational decision-making models to ...
African Journals Online (AJOL)
The aim of this paper is to show the limitations of rational decision-making models as applied to child spacing and more specifically to the use of modern methods of contraception. In the light of factors known to influence low uptake of child spacing services in other African countries, suggestions are made to explain the ...
Totally Asymmetric Limit for Models of Heat Conduction
De Carlo, Leonardo; Gabrielli, Davide
2017-08-01
We consider one dimensional weakly asymmetric boundary driven models of heat conduction. In the cases of a constant diffusion coefficient and of a quadratic mobility we compute the quasi-potential that is a non local functional obtained by the solution of a variational problem. This is done using the dynamic variational approach of the macroscopic fluctuation theory (Bertini et al. in Rev Mod Phys 87:593, 2015). The case of a concave mobility corresponds essentially to the exclusion model that has been discussed in Bertini et al. (J Stat Mech L11001, 2010; Pure Appl Math 64(5):649-696, 2011; Commun Math Phys 289(1):311-334, 2009) and Enaud and Derrida (J Stat Phys 114:537-562, 2004). We consider here the convex case that includes for example the Kipnis-Marchioro-Presutti (KMP) model and its dual (KMPd) (Kipnis et al. in J Stat Phys 27:6574, 1982). This extends to the weakly asymmetric regime the computations in Bertini et al. (J Stat Phys 121(5/6):843-885, 2005). We consider then, both microscopically and macroscopically, the limit of large externalfields. Microscopically we discuss some possible totally asymmetric limits of the KMP model. In one case the totally asymmetric dynamics has a product invariant measure. Another possible limit dynamics has instead a non trivial invariant measure for which we give a duality representation. Macroscopically we show that the quasi-potentials of KMP and KMPd, which are non local for any value of the external field, become local in the limit. Moreover the dependence on one of the external reservoirs disappears. For models having strictly positive quadratic mobilities we obtain instead in the limit a non local functional having a structure similar to the one of the boundary driven asymmetric exclusion process.
A simple shear limited, single size, time dependent flocculation model
Kuprenas, R.; Tran, D. A.; Strom, K.
2017-12-01
This research focuses on the modeling of flocculation of cohesive sediment due to turbulent shear, specifically, investigating the dependency of flocculation on the concentration of cohesive sediment. Flocculation is important in larger sediment transport models as cohesive particles can create aggregates which are orders of magnitude larger than their unflocculated state. As the settling velocity of each particle is determined by the sediment size, density, and shape, accounting for this aggregation is important in determining where the sediment is deposited. This study provides a new formulation for flocculation of cohesive sediment by modifying the Winterwerp (1998) flocculation model (W98) so that it limits floc size to that of the Kolmogorov micro length scale. The W98 model is a simple approach that calculates the average floc size as a function of time. Because of its simplicity, the W98 model is ideal for implementing into larger sediment transport models; however, the model tends to over predict the dependency of the floc size on concentration. It was found that the modification of the coefficients within the original model did not allow for the model to capture the dependency on concentration. Therefore, a new term within the breakup kernel of the W98 formulation was added. The new formulation results is a single size, shear limited, and time dependent flocculation model that is able to effectively capture the dependency of the equilibrium size of flocs on both suspended sediment concentration and the time to equilibrium. The overall behavior of the new model is explored and showed align well with other studies on flocculation. Winterwerp, J. C. (1998). A simple model for turbulence induced flocculation of cohesive sediment. .Journal of Hydraulic Research, 36(3):309-326.
New limit on logotropic unified dark energy models
Directory of Open Access Journals (Sweden)
V.M.C. Ferreira
2017-07-01
Full Text Available A unification of dark matter and dark energy in terms of a logotropic perfect dark fluid has recently been proposed, where deviations with respect to the standard ΛCDM model are dependent on a single parameter B. In this paper we show that the requirement that the linear growth of cosmic structures on comoving scales larger than 8h−1Mpc is not significantly affected with respect to the standard ΛCDM result provides the strongest limit to date on the model (B<6×10−7, an improvement of more than three orders of magnitude over previous upper limits on the value of B. We further show that this limit rules out the logotropic Unified Dark Energy model as a possible solution to the small scale problems of the ΛCDM model, including the cusp problem of Dark Matter halos or the missing satellite problem, as well as the original version of the model where the Planck energy density was taken as one of the two parameters characterizing the logotropic dark fluid.
The Particle-Matrix model: limitations and further improvements needed
DEFF Research Database (Denmark)
Cepuritis, Rolands; Jacobsen, Stefan; Spangenberg, Jon
According to the Particle-Matrix Model (PMM) philosophy, the workability of concrete dependson the properties of two phases and the volumetric ratio between them: the fluid matrix phase (≤0.125 mm) and the solid particle phase (> 0.125 mm). The model has been successfully appliedto predict concrete...... workability for different types of concrete, but has also indicated that somepotential cases exist when its application is limited. The paper presents recent studies onimproving the method by analysing how the PMM one-point flow parameter λQ can beexpressed by rheological models (Bingham and Herschel-Bulkley)....
Psychosocial Pain Management Moderation: The Limit, Activate, and Enhance Model.
Day, Melissa A; Ehde, Dawn M; Jensen, Mark P
2015-10-01
There is a growing emphasis in the pain literature on understanding the following second-order research questions: Why do psychosocial pain treatments work? For whom do various treatments work? This critical review summarizes research that addresses the latter question and proposes a moderation model to help guide future research. A theoretical moderation framework for matching individuals to specific psychosocial pain interventions has been lacking. However, several such frameworks have been proposed in the broad psychotherapy and implementation science literature. Drawing on these theories and adapting them specifically for psychosocial pain treatment, here we propose a Limit, Activate, and Enhance model of pain treatment moderation. This model is unique in that it includes algorithms not only for matching treatments on the basis of patient weaknesses but also for directing patients to interventions that build on their strengths. Critically, this model provides a basis for specific a priori hypothesis generation, and a selection of the possible hypotheses drawn from the model are proposed and discussed. Future research considerations are presented that could refine and expand the model based on theoretically driven empirical evidence. The Limit, Activate, and Enhance model presented here is a theoretically derived framework that provides an a priori basis for hypothesis generation regarding psychosocial pain treatment moderators. The model will advance moderation research via its unique focus on matching patients to specific treatments that (1) limit maladaptive responses, (2) activate adaptive responses, and (3) enhance treatment outcomes based on patient strengths and resources. Copyright © 2015 American Pain Society. Published by Elsevier Inc. All rights reserved.
Abilities and limitations in the use of regional climate models
Energy Technology Data Exchange (ETDEWEB)
Koeltzov, Morten Andreas Oedegaard
2012-11-01
In order to say something about the effect of climate change at the regional level, one takes in use regional climate models. In these models the thesis introduce regional features, which are not included in the global climate models (which are basically in climate research). Regional models can provide good and useful climate projections that add more value than the global climate models, but also introduces an uncertainty in the calculations. How should this uncertainty affect the use of regional climate models?The most common methodology for calculating potential future climate developments are based on different scenarios of possible emissions of greenhouse gases. These scenarios operates as global climate models using physical laws and calculate possible future developments. This is considered mathematical complexed and processes with limited supercomputing capacity calculates the global models for the larger scale of the climate system. To study the effects of climate change are regional details required and the regional models used therefore in a limited area of the climate system. These regional models are driven by data from the global models and refines and improves these data. Impact studies can then use the data from the regional models or data which are further processed to provide more local details using geo-statistical methods. In the preparation of the climate projections is there a minimum of 4 sources of uncertainty. This uncertainty is related to the provision of emission scenarios of greenhouse gases, uncertainties related to the use of global climate models, uncertainty related to the use of regional climate models and the uncertainty of internal variability in the climate system. This thesis discusses the use of regional climate models, and illustrates how the regional climate model adds value to climate projections, and at the same time introduce uncertainty in the calculations. It discusses in particular the importance of the choice of
Probabilistic models of population evolution scaling limits, genealogies and interactions
Pardoux, Étienne
2016-01-01
This expository book presents the mathematical description of evolutionary models of populations subject to interactions (e.g. competition) within the population. The author includes both models of finite populations, and limiting models as the size of the population tends to infinity. The size of the population is described as a random function of time and of the initial population (the ancestors at time 0). The genealogical tree of such a population is given. Most models imply that the population is bound to go extinct in finite time. It is explained when the interaction is strong enough so that the extinction time remains finite, when the ancestral population at time 0 goes to infinity. The material could be used for teaching stochastic processes, together with their applications. Étienne Pardoux is Professor at Aix-Marseille University, working in the field of Stochastic Analysis, stochastic partial differential equations, and probabilistic models in evolutionary biology and population genetics. He obtai...
Animal models of enterovirus 71 infection: applications and limitations
2014-01-01
Human enterovirus 71 (EV71) has emerged as a neuroinvasive virus that is responsible for several outbreaks in the Asia-Pacific region over the past 15 years. Appropriate animal models are needed to understand EV71 neuropathogenesis better and to facilitate the development of effective vaccines and drugs. Non-human primate models have been used to characterize and evaluate the neurovirulence of EV71 after the early outbreaks in late 1990s. However, these models were not suitable for assessing the neurovirulence level of the virus and were associated with ethical and economic difficulties in terms of broad application. Several strategies have been applied to develop mouse models of EV71 infection, including strategies that employ virus adaption and immunodeficient hosts. Although these mouse models do not closely mimic human disease, they have been applied to determine the pathogenesis of and treatment and prevention of the disease. EV71 receptor-transgenic mouse models have recently been developed and have significantly advanced our understanding of the biological features of the virus and the host-parasite interactions. Overall, each of these models has advantages and disadvantages, and these models are differentially suited for studies of EV71 pathogenesis and/or the pre-clinical testing of antiviral drugs and vaccines. In this paper, we review the characteristics, applications and limitation of these EV71 animal models, including non-human primate and mouse models. PMID:24742252
The spatial limitations of current neutral models of biodiversity.
Directory of Open Access Journals (Sweden)
Rampal S Etienne
Full Text Available The unified neutral theory of biodiversity and biogeography is increasingly accepted as an informative null model of community composition and dynamics. It has successfully produced macro-ecological patterns such as species-area relationships and species abundance distributions. However, the models employed make many unrealistic auxiliary assumptions. For example, the popular spatially implicit version assumes a local plot exchanging migrants with a large panmictic regional source pool. This simple structure allows rigorous testing of its fit to data. In contrast, spatially explicit models assume that offspring disperse only limited distances from their parents, but one cannot as yet test the significance of their fit to data. Here we compare the spatially explicit and the spatially implicit model, fitting the most-used implicit model (with two levels, local and regional to data simulated by the most-used spatially explicit model (where offspring are distributed about their parent on a grid according to either a radially symmetric Gaussian or a 'fat-tailed' distribution. Based on these fits, we express spatially implicit parameters in terms of spatially explicit parameters. This suggests how we may obtain estimates of spatially explicit parameters from spatially implicit ones. The relationship between these parameters, however, makes no intuitive sense. Furthermore, the spatially implicit model usually fits observed species-abundance distributions better than those calculated from the spatially explicit model's simulated data. Current spatially explicit neutral models therefore have limited descriptive power. However, our results suggest that a fatter tail of the dispersal kernel seems to improve the fit, suggesting that dispersal kernels with even fatter tails should be studied in future. We conclude that more advanced spatially explicit models and tools to analyze them need to be developed.
Numerical models for fluid-grains interactions: opportunities and limitations
Esteghamatian, Amir; Rahmani, Mona; Wachs, Anthony
2017-06-01
In the framework of a multi-scale approach, we develop numerical models for suspension flows. At the micro scale level, we perform particle-resolved numerical simulations using a Distributed Lagrange Multiplier/Fictitious Domain approach. At the meso scale level, we use a two-way Euler/Lagrange approach with a Gaussian filtering kernel to model fluid-solid momentum transfer. At both the micro and meso scale levels, particles are individually tracked in a Lagrangian way and all inter-particle collisions are computed by a Discrete Element/Soft-sphere method. The previous numerical models have been extended to handle particles of arbitrary shape (non-spherical, angular and even non-convex) as well as to treat heat and mass transfer. All simulation tools are fully-MPI parallel with standard domain decomposition and run on supercomputers with a satisfactory scalability on up to a few thousands of cores. The main asset of multi scale analysis is the ability to extend our comprehension of the dynamics of suspension flows based on the knowledge acquired from the high-fidelity micro scale simulations and to use that knowledge to improve the meso scale model. We illustrate how we can benefit from this strategy for a fluidized bed, where we introduce a stochastic drag force model derived from micro-scale simulations to recover the proper level of particle fluctuations. Conversely, we discuss the limitations of such modelling tools such as their limited ability to capture lubrication forces and boundary layers in highly inertial flows. We suggest ways to overcome these limitations in order to enhance further the capabilities of the numerical models.
Legal weight truck cask model impact limiter response
International Nuclear Information System (INIS)
Meinert, N.M.; Shappert, L.B.
1989-01-01
Dynamic and quasi-static quarter-scale model testing was performed to supplement the analytical case presented in the Nuclear Assurance Corporation Legal Weight Truck (NAC LWT) cask transport licensing application. Four successive drop tests from 9.0 meters (30 feet) onto an unyielding surface and one 1.0-meter (40-inch) drop onto a scale mild steel pin 3.8 centimeters (1.5 inches) in diameter, corroborated the impact limiter design and structural analyses presented in the licensing application. Quantitative measurements, made during drop testing, support the impact limiter analyses. High-speed photography of the tests confirm that only a small amount of energy is elastically stored in the aluminum honeycomb and that oblique drop slapdown is not significant. The qualitative conclusion is that the limiter protected LWT cask will not sustain permanent structural damage and containment will be maintained, subsequent to a hypothetical accident, as shown by structural analyses
Two-phase-flow models and their limitations
International Nuclear Information System (INIS)
Ishii, M.; Kocamustafaogullari, G.
1982-01-01
An accurate prediction of transient two-phase flow is essential to safety analyses of nuclear reactors under accident conditions. The fluid flow and heat transfer encountered are often extremely complex due to the reactor geometry and occurrence of transient two-phase flow. Recently considerable progresses in understanding and predicting these phenomena have been made by a combination of rigorous model development, advanced computational techniques, and a number of small and large scale supporting experiments. In view of their essential importance, the foundation of various two-phase-flow models and their limitations are discussed in this paper
Non compact continuum limit of two coupled Potts models
International Nuclear Information System (INIS)
Vernier, Éric; Jacobsen, Jesper Lykke; Saleur, Hubert
2014-01-01
We study two Q-state Potts models coupled by the product of their energy operators, in the regime 2 3 (2) vertex model. It corresponds to a selfdual system of two antiferromagnetic Potts models, coupled ferromagnetically. We derive the Bethe ansatz equations and study them numerically for two arbitrary twist angles. The continuum limit is shown to involve two compact bosons and one non compact boson, with discrete states emerging from the continuum at appropriate twists. The non compact boson entails strong logarithmic corrections to the finite-size behaviour of the scaling levels, an understanding of which allows us to correct an earlier proposal for some of the critical exponents. In particular, we infer the full set of magnetic scaling dimensions (watermelon operators) of the Potts model. (paper)
Space-Charge-Limited Emission Models for Particle Simulation
Verboncoeur, J. P.; Cartwright, K. L.; Murphy, T.
2004-11-01
Space-charge-limited (SCL) emission of electrons from various materials is a common method of generating the high current beams required to drive high power microwave (HPM) sources. In the SCL emission process, sufficient space charge is extracted from a surface, often of complicated geometry, to drive the electric field normal to the surface close to zero. The emitted current is highly dominated by space charge effects as well as ambient fields near the surface. In this work, we consider computational models for the macroscopic SCL emission process including application of Gauss's law and the Child-Langmuir law for space-charge-limited emission. Models are described for ideal conductors, lossy conductors, and dielectrics. Also considered is the discretization of these models, and the implications for the emission physics. Previous work on primary and dual-cell emission models [Watrous et al., Phys. Plasmas 8, 289-296 (2001)] is reexamined, and aspects of the performance, including fidelity and noise properties, are improved. Models for one-dimensional diodes are considered, as well as multidimensional emitting surfaces, which include corners and transverse fields.
Accuracy limit of rigid 3-point water models
Izadi, Saeed; Onufriev, Alexey V.
2016-08-01
Classical 3-point rigid water models are most widely used due to their computational efficiency. Recently, we introduced a new approach to constructing classical rigid water models [S. Izadi et al., J. Phys. Chem. Lett. 5, 3863 (2014)], which permits a virtually exhaustive search for globally optimal model parameters in the sub-space that is most relevant to the electrostatic properties of the water molecule in liquid phase. Here we apply the approach to develop a 3-point Optimal Point Charge (OPC3) water model. OPC3 is significantly more accurate than the commonly used water models of same class (TIP3P and SPCE) in reproducing a comprehensive set of liquid bulk properties, over a wide range of temperatures. Beyond bulk properties, we show that OPC3 predicts the intrinsic charge hydration asymmetry (CHA) of water — a characteristic dependence of hydration free energy on the sign of the solute charge — in very close agreement with experiment. Two other recent 3-point rigid water models, TIP3PFB and H2ODC, each developed by its own, completely different optimization method, approach the global accuracy optimum represented by OPC3 in both the parameter space and accuracy of bulk properties. Thus, we argue that an accuracy limit of practical 3-point rigid non-polarizable models has effectively been reached; remaining accuracy issues are discussed.
Testing of materials and scale models for impact limiters
International Nuclear Information System (INIS)
Maji, A.K.; Satpathi, D.; Schryer, H.L.
1991-01-01
Aluminum Honeycomb and Polyurethane foam specimens were tested to obtain experimental data on the material's behavior under different loading conditions. This paper reports the dynamic tests conducted on the materials and on the design and testing of scale models made out of these open-quotes Impact Limiters,close quotes as they are used in the design of transportation casks. Dynamic tests were conducted on a modified Charpy Impact machine with associated instrumentation, and compared with static test results. A scale model testing setup was designed and used for preliminary tests on models being used by current designers of transportation casks. The paper presents preliminary results of the program. Additional information will be available and reported at the time of presentation of the paper
Low-energy limit of the extended Linear Sigma Model
Energy Technology Data Exchange (ETDEWEB)
Divotgey, Florian [Johann Wolfgang Goethe-Universitaet, Institut fuer Theoretische Physik, Frankfurt am Main (Germany); Kovacs, Peter [Wigner Research Center for Physics, Hungarian Academy of Sciences, Institute for Particle and Nuclear Physics, Budapest (Hungary); GSI Helmholtzzentrum fuer Schwerionenforschung, ExtreMe Matter Institute, Darmstadt (Germany); Giacosa, Francesco [Johann Wolfgang Goethe-Universitaet, Institut fuer Theoretische Physik, Frankfurt am Main (Germany); Jan-Kochanowski University, Institute of Physics, Kielce (Poland); Rischke, Dirk H. [Johann Wolfgang Goethe-Universitaet, Institut fuer Theoretische Physik, Frankfurt am Main (Germany); University of Science and Technology of China, Interdisciplinary Center for Theoretical Study and Department of Modern Physics, Hefei, Anhui (China)
2018-01-15
The extended Linear Sigma Model is an effective hadronic model based on the linear realization of chiral symmetry SU(N{sub f}){sub L} x SU(N{sub f}){sub R}, with (pseudo)scalar and (axial-)vector mesons as degrees of freedom. In this paper, we study the low-energy limit of the extended Linear Sigma Model (eLSM) for N{sub f} = flavors by integrating out all fields except for the pions, the (pseudo-)Nambu-Goldstone bosons of chiral symmetry breaking. The resulting low-energy effective action is identical to Chiral Perturbation Theory (ChPT) after choosing a representative for the coset space generated by chiral symmetry breaking and expanding it in powers of (derivatives of) the pion fields. The tree-level values of the coupling constants of the effective low-energy action agree remarkably well with those of ChPT. (orig.)
Animal models of myasthenia gravis: utility and limitations
Mantegazza, Renato; Cordiglieri, Chiara; Consonni, Alessandra; Baggi, Fulvio
2016-01-01
Myasthenia gravis (MG) is a chronic autoimmune disease caused by the immune attack of the neuromuscular junction. Antibodies directed against the acetylcholine receptor (AChR) induce receptor degradation, complement cascade activation, and postsynaptic membrane destruction, resulting in functional reduction in AChR availability. Besides anti-AChR antibodies, other autoantibodies are known to play pathogenic roles in MG. The experimental autoimmune MG (EAMG) models have been of great help over the years in understanding the pathophysiological role of specific autoantibodies and T helper lymphocytes and in suggesting new therapies for prevention and modulation of the ongoing disease. EAMG can be induced in mice and rats of susceptible strains that show clinical symptoms mimicking the human disease. EAMG models are helpful for studying both the muscle and the immune compartments to evaluate new treatment perspectives. In this review, we concentrate on recent findings on EAMG models, focusing on their utility and limitations. PMID:27019601
Sum rule limitations of kinetic particle-production models
International Nuclear Information System (INIS)
Knoll, J.; CEA Centre d'Etudes Nucleaires de Grenoble, 38; Guet, C.
1988-04-01
Photoproduction and absorption sum rules generalized to systems at finite temperature provide a stringent check on the validity of kinetic models for the production of hard photons in intermediate energy nuclear collisions. We inspect such models for the case of nuclear matter at finite temperature employed in a kinetic regime which copes those encountered in energetic nuclear collisions, and find photon production rates which significantly exceed the limits imposed by the sum rule even under favourable concession. This suggests that coherence effects are quite important and the production of photons cannot be considered as an incoherent addition of individual NNγ production processes. The deficiencies of present kinetic models may also apply for the production of probes such as the pion which do not couple perturbatively to the nuclear currents. (orig.)
Toward a mechanistic modeling of nitrogen limitation for photosynthesis
Xu, C.; Fisher, R. A.; Travis, B. J.; Wilson, C. J.; McDowell, N. G.
2011-12-01
The nitrogen limitation is an important regulator for vegetation growth and global carbon cycle. Most current ecosystem process models simulate nitrogen effects on photosynthesis based on a prescribed relationship between leaf nitrogen and photosynthesis; however, there is a large amount of variability in this relationship with different light, temperature, nitrogen availability and CO2 conditions, which can affect the reliability of photosynthesis prediction under future climate conditions. To account for the variability in nitrogen-photosynthesis relationship under different environmental conditions, in this study, we developed a mechanistic model of nitrogen limitation for photosynthesis based on nitrogen trade-offs among light absorption, electron transport, carboxylization and carbon sink. Our model shows that strategies of nitrogen storage allocation as determined by tradeoff among growth and persistence is a key factor contributing to the variability in relationship between leaf nitrogen and photosynthesis. Nitrogen fertilization substantially increases the proportion of nitrogen in storage for coniferous trees but much less for deciduous trees, suggesting that coniferous trees allocate more nitrogen toward persistence compared to deciduous trees. The CO2 fertilization will cause lower nitrogen allocation for carboxylization but higher nitrogen allocation for storage, which leads to a weaker relationship between leaf nitrogen and maximum photosynthesis rate. Lower radiation will cause higher nitrogen allocation for light absorption and electron transport but less nitrogen allocation for carboxylyzation and storage, which also leads to weaker relationship between leaf nitrogen and maximum photosynthesis rate. At the same time, lower growing temperature will cause higher nitrogen allocation for carboxylyzation but lower allocation for light absorption, electron transport and storage, which leads to a stronger relationship between leaf nitrogen and maximum
Matrix models, Argyres-Douglas singularities and double scaling limits
International Nuclear Information System (INIS)
Bertoldi, Gaetano
2003-01-01
We construct an N = 1 theory with gauge group U(nN) and degree n+1 tree level superpotential whose matrix model spectral curve develops an Argyres-Douglas singularity. The calculation of the tension of domain walls in the U(nN) theory shows that the standard large-N expansion breaks down at the Argyres-Douglas points, with tension that scales as a fractional power of N. Nevertheless, it is possible to define appropriate double scaling limits which are conjectured to yield the tension of 2-branes in the resulting N = 1 four dimensional non-critical string theories as proposed by Ferrari. (author)
Animal models of GM2 gangliosidosis: utility and limitations
Directory of Open Access Journals (Sweden)
Lawson CA
2016-07-01
Full Text Available Cheryl A Lawson,1,2 Douglas R Martin2,3 1Department of Pathobiology, 2Scott-Ritchey Research Center, 3Department of Anatomy, Physiology and Pharmacology, Auburn University College of Veterinary Medicine, Auburn, AL, USA Abstract: GM2 gangliosidosis, a subset of lysosomal storage disorders, is caused by a deficiency of the glycohydrolase, β-N-acetylhexosaminidase, and includes the closely related Tay–Sachs and Sandhoff diseases. The enzyme deficiency prevents the normal, stepwise degradation of ganglioside, which accumulates unchecked within the cellular lysosome, particularly in neurons. As a result, individuals with GM2 gangliosidosis experience progressive neurological diseases including motor deficits, progressive weakness and hypotonia, decreased responsiveness, vision deterioration, and seizures. Mice and cats are well-established animal models for Sandhoff disease, whereas Jacob sheep are the only known laboratory animal model of Tay–Sachs disease to exhibit clinical symptoms. Since the human diseases are relatively rare, animal models are indispensable tools for further study of pathogenesis and for development of potential treatments. Though no effective treatments for gangliosidoses currently exist, animal models have been used to test promising experimental therapies. Herein, the utility and limitations of gangliosidosis animal models and how they have contributed to the development of potential new treatments are described. Keywords: GM2 gangliosidosis, Tay–Sachs disease, Sandhoff disease, lysosomal storage disorder, sphingolipidosis, brain disease
Animal models of GM2 gangliosidosis: utility and limitations
Lawson, Cheryl A; Martin, Douglas R
2016-01-01
GM2 gangliosidosis, a subset of lysosomal storage disorders, is caused by a deficiency of the glycohydrolase, β-N-acetylhexosaminidase, and includes the closely related Tay–Sachs and Sandhoff diseases. The enzyme deficiency prevents the normal, stepwise degradation of ganglioside, which accumulates unchecked within the cellular lysosome, particularly in neurons. As a result, individuals with GM2 gangliosidosis experience progressive neurological diseases including motor deficits, progressive weakness and hypotonia, decreased responsiveness, vision deterioration, and seizures. Mice and cats are well-established animal models for Sandhoff disease, whereas Jacob sheep are the only known laboratory animal model of Tay–Sachs disease to exhibit clinical symptoms. Since the human diseases are relatively rare, animal models are indispensable tools for further study of pathogenesis and for development of potential treatments. Though no effective treatments for gangliosidoses currently exist, animal models have been used to test promising experimental therapies. Herein, the utility and limitations of gangliosidosis animal models and how they have contributed to the development of potential new treatments are described. PMID:27499644
The limitations of mathematical modeling in high school physics education
Forjan, Matej
The theme of the doctoral dissertation falls within the scope of didactics of physics. Theoretical analysis of the key constraints that occur in the transmission of mathematical modeling of dynamical systems into field of physics education in secondary schools is presented. In an effort to explore the extent to which current physics education promotes understanding of models and modeling, we analyze the curriculum and the three most commonly used textbooks for high school physics. We focus primarily on the representation of the various stages of modeling in the solved tasks in textbooks and on the presentation of certain simplifications and idealizations, which are in high school physics frequently used. We show that one of the textbooks in most cases fairly and reasonably presents the simplifications, while the other two half of the analyzed simplifications do not explain. It also turns out that the vast majority of solved tasks in all the textbooks do not explicitly represent model assumptions based on what we can conclude that in high school physics the students do not develop sufficiently a sense of simplification and idealizations, which is a key part of the conceptual phase of modeling. For the introduction of modeling of dynamical systems the knowledge of students is also important, therefore we performed an empirical study on the extent to which high school students are able to understand the time evolution of some dynamical systems in the field of physics. The research results show the students have a very weak understanding of the dynamics of systems in which the feedbacks are present. This is independent of the year or final grade in physics and mathematics. When modeling dynamical systems in high school physics we also encounter the limitations which result from the lack of mathematical knowledge of students, because they don't know how analytically solve the differential equations. We show that when dealing with one-dimensional dynamical systems
Force Limited Random Vibration Test of TESS Camera Mass Model
Karlicek, Alexandra; Hwang, James Ho-Jin; Rey, Justin J.
2015-01-01
The Transiting Exoplanet Survey Satellite (TESS) is a spaceborne instrument consisting of four wide field-of-view-CCD cameras dedicated to the discovery of exoplanets around the brightest stars. As part of the environmental testing campaign, force limiting was used to simulate a realistic random vibration launch environment. While the force limit vibration test method is a standard approach used at multiple institutions including Jet Propulsion Laboratory (JPL), NASA Goddard Space Flight Center (GSFC), European Space Research and Technology Center (ESTEC), and Japan Aerospace Exploration Agency (JAXA), it is still difficult to find an actual implementation process in the literature. This paper describes the step-by-step process on how the force limit method was developed and applied on the TESS camera mass model. The process description includes the design of special fixtures to mount the test article for properly installing force transducers, development of the force spectral density using the semi-empirical method, estimation of the fuzzy factor (C2) based on the mass ratio between the supporting structure and the test article, subsequent validating of the C2 factor during the vibration test, and calculation of the C.G. accelerations using the Root Mean Square (RMS) reaction force in the spectral domain and the peak reaction force in the time domain.
Scrape-off layer based modelling of the density limit in beryllated JET limiter discharges
International Nuclear Information System (INIS)
Borrass, K.; Campbell, D.J.; Clement, S.; Vlases, G.C.
1993-01-01
The paper gives a scrape-off layer based interpretation of the density limit in beryllated JET limiter discharges. In these discharges, JET edge parameters show a complicated time evolution as the density limit is approached and the limit is manifested as a non-disruptive density maximum which cannot be exceeded by enhanced gas puffing. The occurrence of Marfes, the manner of density control and details of recycling are essential elements of the interpretation. Scalings for the maximum density are given and compared with JET data. The relation to disruptive density limits, previously observed in JET carbon limiter discharges, and to density limits in divertor discharges is discussed. (author). 18 refs, 10 figs, 1 tab
Limiting fragmentation in a thermal model with flow
Energy Technology Data Exchange (ETDEWEB)
Kumar Tiwari, Swatantra; Sahoo, Raghunath [Indian Institute of Technology Indore, Discipline of Physics, School of Basic Sciences, Simrol, Indore (India)
2016-12-15
The property of limiting fragmentation of various observables such as rapidity distributions (dN/dy), elliptic flow (v{sub 2}), average transverse momentum (left angle p{sub T} right angle) etc. of charged particles is observed when they are plotted as a function of rapidity (y) shifted by the beam rapidity (y{sub beam}) for a wide range of energies from AGS to RHIC. Limiting fragmentation (LF) is a well-studied phenomenon as observed in various collision energies and colliding systems experimentally. It is very interesting to verify this phenomenon theoretically. We study such a phenomenon for pion rapidity spectra using our hydrodynamic-like model where the collective flow is incorporated in a thermal model in the longitudinal direction. Our findings advocate the observation of extended longitudinal scaling in the rapidity spectra of pions from AGS to lower RHIC energies, while it is observed to be violated at top RHIC and LHC energies. Prediction of LF hypothesis for Pb+Pb collisions at √(s{sub NN}) = 5.02 TeV is given. (orig.)
MODELING THE TRANSITION CURVE ON A LIMITED TERAIN
Directory of Open Access Journals (Sweden)
V. D. Borisenko
2017-04-01
rectilinear and circular rail track in a region of a limited size has been proved. Originality. A method for geometric modelling of transition curves between a rectilinear and circular section of a railway track is developed in conditions of limited terrain size, on which rails are laid. The transition curve is represented in the natural parameterization, using the cubic dependence of the curvature distribution on the length of its arc. Practical value. The proposed method of modelling the transition curves in conditions of limited terrain size allows obtaining these curves with a high accuracy in a wide range of geometric parameters of rectilinear and circular sections of the railway track and a parameter that acts as a constraint in the modelling of the transition curve. The method can be recommended in the practice of building railways.
Specialists without spirit: limitations of the mechanistic biomedical model.
Hewa, S; Hetherington, R W
1995-06-01
This paper examines the origin and the development of the mechanistic model of the human body and health in terms of Max Weber's theory of rationalization. It is argued that the development of Western scientific medicine is a part of the broad process of rationalization that began in sixteenth century Europe as a result of the Reformation. The development of the mechanistic view of the human body in Western medicine is consistent with the ideas of calculability, predictability, and control-the major tenets of the process of rationalization as described by Weber. In recent years, however, the limitations of the mechanistic model have been the topic of many discussions. George Engel, a leading advocate of general systems theory, is one of the leading proponents of a new medical model which includes the general quality of life, clean environment, and psychological, or spiritual stability of life. The paper concludes with consideration of the potential of Engel's proposed new model in the context of the current state of rationalization in modern industrialized society.
European Continental Scale Hydrological Model, Limitations and Challenges
Rouholahnejad, E.; Abbaspour, K.
2014-12-01
The pressures on water resources due to increasing levels of societal demand, increasing conflict of interest and uncertainties with regard to freshwater availability create challenges for water managers and policymakers in many parts of Europe. At the same time, climate change adds a new level of pressure and uncertainty with regard to freshwater supplies. On the other hand, the small-scale sectoral structure of water management is now reaching its limits. The integrated management of water in basins requires a new level of consideration where water bodies are to be viewed in the context of the whole river system and managed as a unit within their basins. In this research we present the limitations and challenges of modelling the hydrology of the continent Europe. The challenges include: data availability at continental scale and the use of globally available data, streamgauge data quality and their misleading impacts on model calibration, calibration of large-scale distributed model, uncertainty quantification, and computation time. We describe how to avoid over parameterization in calibration process and introduce a parallel processing scheme to overcome high computation time. We used Soil and Water Assessment Tool (SWAT) program as an integrated hydrology and crop growth simulator to model water resources of the Europe continent. Different components of water resources are simulated and crop yield and water quality are considered at the Hydrological Response Unit (HRU) level. The water resources are quantified at subbasin level with monthly time intervals for the period of 1970-2006. The use of a large-scale, high-resolution water resources models enables consistent and comprehensive examination of integrated system behavior through physically-based, data-driven simulation and provides the overall picture of water resources temporal and spatial distribution across the continent. The calibrated model and results provide information support to the European Water
Modelling the bioconversion of cellulose into microbial products: rate limitations
Energy Technology Data Exchange (ETDEWEB)
Asenjo, J A
1984-12-01
The direct bioconversion of cellulose into microbial products carried out as a simultaneous saccharification and fermentation has a strong effect on the rates of cellulose degradation because cellobiose and glucose inhibition of the reaction are circumvented. A general mathematical model of the kinetics of this bioconversion has been developed. Its use in representing aerobic systems and in the analysis of the kinetic limitations has been investigated. Simulations have been carried out to find the rate limiting steps in slow fermentations and in rapid ones as determined by the specific rate of product formation. The requirements for solubilising and depolymerising enzyme activities (cellulase and cellobiase) in these systems has been determined. The activity that have been obtained for fungal cellulases are adequate for the kinetic requirements of the fastest fermentative strains. The results also show that for simultaneous bioconversions where strong cellobiose and glucose inhibition is overcome, no additional cellobiase is necessary to increase the rate of product formation. These results are useful for the selection of cellolytic micro-organisms and in the determination of enzymes to be cloned in recombinant strains. 17 references.
Directory of Open Access Journals (Sweden)
Wenjun Huang
2017-01-01
Full Text Available Mechanical extending limit in horizontal drilling means the maximum horizontal extending length of a horizontal well under certain ground and down-hole mechanical constraint conditions. Around this concept, the constrained optimization model of mechanical extending limits is built and simplified analytical results for pick-up and slack-off operations are deduced. The horizontal extending limits for kinds of tubular strings under different drilling parameters are calculated and drawn. To improve extending limits, an optimal design model of drill strings is built and applied to a case study. The results indicate that horizontal extending limits are underestimated a lot when the effects of friction force on critical helical buckling loads are neglected. Horizontal extending limits firstly increase and tend to stable values with vertical depths. Horizontal extending limits increase faster but finally become smaller with the increase of horizontal pushing forces for tubular strings of smaller modulus-weight ratio. Sliding slack-off is the main limit operation and high axial friction is the main constraint factor constraining horizontal extending limits. A sophisticated installation of multiple tubular strings can greatly inhibit helical buckling and increase horizontal extending limits. The optimal design model is called only once to obtain design results, which greatly increases the calculation efficiency.
A quantum relativistic integrable model as the continuous limit of the six-vertex model
International Nuclear Information System (INIS)
Zhou, Y.K.
1992-01-01
The six-vertex model in two-dimensional statistical mechanics is used to construct the L-matrix of a one-dimensional quantum relativistic integrable model through a continuous limit. This is the first step to extend the method used earlier by the author to construct quantum completely integrable systems from other well-known two-dimensional vertex models. (orig.)
Analytic Models of Brown Dwarfs and the Substellar Mass Limit
Directory of Open Access Journals (Sweden)
Sayantan Auddy
2016-01-01
Full Text Available We present the analytic theory of brown dwarf evolution and the lower mass limit of the hydrogen burning main-sequence stars and introduce some modifications to the existing models. We give an exact expression for the pressure of an ideal nonrelativistic Fermi gas at a finite temperature, therefore allowing for nonzero values of the degeneracy parameter. We review the derivation of surface luminosity using an entropy matching condition and the first-order phase transition between the molecular hydrogen in the outer envelope and the partially ionized hydrogen in the inner region. We also discuss the results of modern simulations of the plasma phase transition, which illustrate the uncertainties in determining its critical temperature. Based on the existing models and with some simple modification, we find the maximum mass for a brown dwarf to be in the range 0.064M⊙–0.087M⊙. An analytic formula for the luminosity evolution allows us to estimate the time period of the nonsteady state (i.e., non-main-sequence nuclear burning for substellar objects. We also calculate the evolution of very low mass stars. We estimate that ≃11% of stars take longer than 107 yr to reach the main sequence, and ≃5% of stars take longer than 108 yr.
A unified model of density limit in fusion plasmas
Zanca, P.; Sattin, F.; Escande, D. F.; Pucella, G.; Tudisco, O.
2017-05-01
In this work we identify by analytical and numerical means the conditions for the existence of a magnetic and thermal equilibrium of a cylindrical plasma, in the presence of Ohmic and/or additional power sources, heat conduction and radiation losses by light impurities. The boundary defining the solutions’ space having realistic temperature profile with small edge value takes mathematically the form of a density limit (DL). Compared to previous similar analyses the present work benefits from dealing with a more accurate set of equations. This refinement is elementary, but decisive, since it discloses a tenuous dependence of the DL on the thermal transport for configurations with an applied electric field. Thanks to this property, the DL scaling law is recovered almost identical for two largely different devices such as the ohmic tokamak and the reversed field pinch. In particular, they have in common a Greenwald scaling, linearly depending on the plasma current, quantitatively consistent with experimental results. In the tokamak case the DL dependence on any additional heating approximately follows a 0.5 power law, which is compatible with L-mode experiments. For a purely externally heated configuration, taken as a cylindrical approximation of the stellarator, the DL dependence on transport is found stronger. By adopting suitable transport models, DL takes on a Sudo-like form, in fair agreement with LHD experiments. Overall, the model provides a good zeroth-order quantitative description of the DL, applicable to widely different configurations.
Peak-counts blood flow model-errors and limitations
International Nuclear Information System (INIS)
Mullani, N.A.; Marani, S.K.; Ekas, R.D.; Gould, K.L.
1984-01-01
The peak-counts model has several advantages, but its use may be limited due to the condition that the venous egress may not be negligible at the time of peak-counts. Consequently, blood flow measurements by the peak-counts model will depend on the bolus size, bolus duration, and the minimum transit time of the bolus through the region of interest. The effect of bolus size on the measurement of extraction fraction and blood flow was evaluated by injecting 1 to 30ml of rubidium chloride in the femoral vein of a dog and measuring the myocardial activity with a beta probe over the heart. Regional blood flow measurements were not found to vary with bolus sizes up to 30ml. The effect of bolus duration was studied by injecting a 10cc bolus of tracer at different speeds in the femoral vein of a dog. All intravenous injections undergo a broadening of the bolus duration due to the transit time of the tracer through the lungs and the heart. This transit time was found to range from 4-6 second FWHM and dominates the duration of the bolus to the myocardium for up to 3 second injections. A computer simulation has been carried out in which the different parameters of delay time, extraction fraction, and bolus duration can be changed to assess the errors in the peak-counts model. The results of the simulations show that the error will be greatest for short transit time delays and for low extraction fractions
Flux limitation in ultrafiltration: Osmotic pressure model and gel layer model
Wijmans, J.G.; Nakao, S.; Smolders, C.A.
1984-01-01
The characteristic permeate flux behaviour in ultrafiltration, i.e., the existence of a limiting flux which is independent of applied pressure and membrane resistance and a linear plot of the limiting flux versus the logarithm of the feed concentration, is explained by the osmotic pressure model. In
About dynamic model of limiting fragmentation of heavy nuclei
International Nuclear Information System (INIS)
Kuchin, I.A.
2001-01-01
Full text: As is known, during last years defined progress in understanding of static aspect of a dynamic structure organization of massive nuclei was reached. The offered model of a 'crystalline' structure of the nucleus generalizes drop, shell and cluster models in a natural way. Now increased interest induces the phenomenon of limiting fragmentation of heavy nuclei. There is a hope, that clearing up the general regularities of a soft disintegration of the massive nuclei on nucleons, component it, in a broad range of high energies can give a valuable information about dynamics of origin of nuclear structures and nature of their qualitative difference from a quark system structure, i.e. from nucleons. The key for understanding the indicated phenomenon can be it's study in connection with other aspects of disintegration of the nuclei - Coulomb and diffraction dissociation, fission etc. The sequential analysis of all these a processes from a single point of view is possible only within the framework of results and methods of the dynamic system theory. The purpose of the present research is clearing up a possibility to understand the nature of limiting fragmentation as a consequence of development of dynamic instability in a system of the nuclei as a result of ions interaction at high energy. In the analysis we based on data of the phenomenological analysis of heavy ion interactions at ultra-relativistic energies obtained by many authors for a number of years. As a result we came to a conclusion about general stochastic nature of an investigated phenomenon. In it development the fragmentation passes three different stages. On the first there is a process of preparation of chaos at a quantum level in an outcome of a Coulomb dissociation of the approaching nuclei and isotopic recharge of their nucleons, carrying a random character. A dominant here - viscous dissociation of nuclei under an operation of Coulomb forces. (A two body initial state). Then the multiparticle
Bayesian inference for partially identified models exploring the limits of limited data
Gustafson, Paul
2015-01-01
Introduction Identification What Is against Us? What Is for Us? Some Simple Examples of Partially Identified ModelsThe Road Ahead The Structure of Inference in Partially Identified Models Bayesian Inference The Structure of Posterior Distributions in PIMs Computational Strategies Strength of Bayesian Updating, Revisited Posterior MomentsCredible Intervals Evaluating the Worth of Inference Partial Identification versus Model Misspecification The Siren Call of Identification Comp
Experimental modeling of eddy currents and deflections for tokamak limiters
International Nuclear Information System (INIS)
Hua, T.Q.; Knott, M.J.; Turner, L.R.; Wehrle, R.B.
1986-01-01
In this study, experiments were performed to investigate deflection, current, and material stress in cantilever beams with the Fusion ELectromagnetic Induction eXperiment (FELIX) at the Argonne National Laboratory. Since structures near the plasma are typically cantilevered, the beams provide a good model for the limiter blades of a tokamak fusion reactor. The test pieces were copper, aluminum, phosphor bronze, and brass cantilever beams, clamped rigidly at one end with a nonconducting support frame inside the FELIX test volume. The primary data recorded as functions of time were the beam deflection measured with a noncontact electro-optical device, the total eddy current measured with a Rogowski coil and linking through a central hole in the beam, and the material stress extracted from strain gauges. Measurements of stress and deflection were taken at selected positions along the beam. The extent of the coupling effect depends on several factors. These include the size, the electrical and mechanical properties of the beam, segmenting of the beam, the decay rate of the dipole field, and the strength of the solenoid field
Cerebral radiation necrosis: limits and prospects of experimental models
International Nuclear Information System (INIS)
Lefaix, J.L.
1992-01-01
Cerebral radiation necrosis is the major CNS hazard of clinical treatment therapy involving delivery of high doses of radiation to the brain. It is generally irreversible and frequently leads to death from brain necrosis. Necrosis has been reported with total doses of 60 Gy, delivered in conventional fractions. Symptoms depend upon the volume of brain irradiated and are frequently those of an intracranial mass and may be present as an area of gliosis or frank necrosis. Possible causes include some direct effect of radiation on glial cells, vascular changes and the action of an immunological mechanism. The weight of evidence suggests that demyelination is important in the early delayed reaction, and that vascular changes gradually become more important in the late delayed reactions, from several months to years after treatment. The advent of sophisticated radiographic technologies such as computed tomography, magnetic resonance imaging and spectroscopy, and positron emission tomography have facilitated serial non invasive examination of morphologic or physiologic parameters within the brain after irradiation. Limits and prospects of these technologies are reviewed in experimental animal models of late radiation injuries of the brain, which were carried out in many species ranging from mouse to monkey
2011-10-11
... Airworthiness Directives; Viking Air Limited Model DHC-3 (Otter) Airplanes With Supplemental Type Certificate.... That AD applies to Viking Air Limited Model DHC-3 (Otter) airplanes equipped with a Honeywell TPE331... limitations and marking the airspeed indicator accordingly for Viking Air Limited Model DHC-3 (Otter...
Habitat modelling limitations - Puck Bay, Baltic Sea - a case study
Directory of Open Access Journals (Sweden)
Jan Marcin Węsławski
2013-02-01
Full Text Available The Natura 2000 sites and the Coastal Landscape Park in a shallow marine bay in the southern Baltic have been studied in detail for the distribution of benthic macroorganisms, species assemblages and seabed habitats. The relatively small Inner Puck Bay (104.8 km2 is one of the most thoroughly investigated marine areas in the Baltic: research has been carried out there continuously for over 50 years. Six physical parameters regarded as critically important for the marine benthos (depth, minimal temperature, maximum salinity, light, wave intensity and sediment type were summarized on a GIS map showing unified patches of seabed and the near-bottom water conditions. The occurrence of uniform seabed forms is weakly correlated with the distributions of individual species or multi-species assemblages. This is partly explained by the characteristics of the local macrofauna, which is dominated by highly tolerant, eurytopic species with opportunistic strategies. The history and timing of the assemblage formation also explains this weak correlation. The distribution of assemblages formed by long-living, structural species (Zostera marina and other higher plants shows the history of recovery following earlier disturbances. In the study area, these communities are still in the stage of recovery and recolonization, and their present distribution does not as yet match the distribution of the physical environmental conditions favourable to them. Our results show up the limitations of distribution modelling in coastal waters, where the history of anthropogenic disturbances can distort the picture of the present-day environmental control of biota distributions.
Truong, Sandra K; McCormick, Ryan F; Mullet, John E
2017-01-01
Bioenergy sorghum is targeted for production in water-limited annual cropland therefore traits that improve plant water capture, water use efficiency, and resilience to water deficit are necessary to maximize productivity. A crop modeling framework, APSIM, was adapted to predict the growth and biomass yield of energy sorghum and to identify potentially useful traits for crop improvement. APSIM simulations of energy sorghum development and biomass accumulation replicated results from field experiments across multiple years, patterns of rainfall, and irrigation schemes. Modeling showed that energy sorghum's long duration of vegetative growth increased water capture and biomass yield by ~30% compared to short season crops in a water-limited production region. Additionally, APSIM was extended to enable modeling of VPD-limited transpiration traits that reduce crop water use under high vapor pressure deficits (VPDs). The response of transpiration rate to increasing VPD was modeled as a linear response until a VPD threshold was reached, at which the slope of the response decreases, representing a range of responses to VPD observed in sorghum germplasm. Simulation results indicated that the VPD-limited transpiration trait is most beneficial in hot and dry regions of production where crops are exposed to extended periods without rainfall during the season or to a terminal drought. In these environments, slower but more efficient transpiration increases biomass yield and prevents or delays the exhaustion of soil water and onset of leaf senescence. The VPD-limited transpiration responses observed in sorghum germplasm increased biomass accumulation by 20% in years with lower summer rainfall, and the ability to drastically reduce transpiration under high VPD conditions could increase biomass by 6% on average across all years. This work indicates that the productivity and resilience of bioenergy sorghum grown in water-limited environments could be further enhanced by development
Geometrical Modeling of Woven Fabrics Weavability-Limit New Relationships
Directory of Open Access Journals (Sweden)
Dalal Mohamed
2017-03-01
Full Text Available The weavability limit and tightness for 2D and 3D woven fabrics is an important factor and depends on many geometric parameters. Based on a comprehensive review of the literature on textile fabric construction and property, and related research on fabric geometry, a study of the weavability limit and tightness relationships of 2D and 3D woven fabrics was undertaken. Experiments were conducted on a representative number of polyester and cotton woven fabrics which have been woven in our workshop, using three machines endowed with different insertion systems (rapier, projectiles and air jet. Afterwards, these woven fabrics have been analyzed in the laboratory to determine their physical and mechanical characteristics using air permeability-meter and KES-F KAWABATA Evaluation System for Fabrics. In this study, the current Booten’s weavability limit and tightness relationships based on Ashenhurst’s, Peirce’s, Love’s, Russell’s, Galuszynskl’s theory and maximum-weavability is reviewed and modified as new relationships to expand their use to general cases (2D and 3D woven fabrics, all fiber materiel, all yarns etc…. The theoretical relationships were examined and found to agree with experimental results. It was concluded that the weavability limit and tightness relationships are useful tools for weavers in predicting whether a proposed fabric construction was weavable and also in predicting and explaining their physical and mechanical properties.
Transgenic mouse models of hormonal mammary carcinogenesis: advantages and limitations.
Kirma, Nameer B; Tekmal, Rajeshwar R
2012-09-01
Mouse models of breast cancer, especially transgenic and knockout mice, have been established as valuable tools in shedding light on factors involved in preneoplastic changes, tumor development and malignant progression. The majority of mouse transgenic models develop estrogen receptor (ER) negative tumors. This is seen as a drawback because the majority of human breast cancers present an ER positive phenotype. On the other hand, several transgenic mouse models have been developed that produce ER positive mammary tumors. These include mice over-expressing aromatase, ERα, PELP-1 and AIB-1. In this review, we will discuss the value of these models as physiologically relevant in vivo systems to understand breast cancer as well as some of the pitfalls involving these models. In all, we argue that the use of transgenic models has improved our understanding of the molecular aspects and biology of breast cancer. Copyright © 2011 Elsevier Ltd. All rights reserved.
Limitations of sorption isotherms on modeling groundwater contaminant transport
International Nuclear Information System (INIS)
Silva, Eduardo Figueira da
2007-01-01
Design and safety assessment of radioactive waste repositories, as well as remediation of radionuclide contaminated groundwater require the development of models capable of accurately predicting trace element fate and transport. Adsorption of trace radionuclides onto soils and groundwater is an important mechanism controlling near- and far- field transport. Although surface complexation models (SCMs) can better describe the adsorption mechanisms of most radionuclides onto mineral surfaces by directly accounting for variability of system properties and mineral surface properties, isotherms are still used to model contaminant transport in groundwater, despite the much higher system dependence. The present work investigates differences between transport model results based on these two approaches for adsorption modeling. A finite element transport model is used for the isotherm model, whereas the computer program PHREEQC is used for the SCM approach. Both models are calibrated for a batch experiment, and one-dimensional transport is simulated using the calibrated parameters. At the lower injected concentrations there are large discrepancies between SCM and isotherm transport predictions, with the SCM presenting much longer tails on the breakthrough curves. Isotherms may also provide non-conservative results for time to breakthrough and for maximum concentration in a contamination plume. Isotherm models are shown not to be robust enough to predict transport behavior of some trace elements, thus discouraging their use. The results also illustrate the promise of the SCM modeling approach in safety assessment and environmental remediation applications, also suggesting that independent batch sorption measurements can be used, within the framework of the SCM, to produce a more versatile and realistic groundwater transport model for radionuclides which is capable of accounting more accurately for temporal and spatial variations in geochemical conditions. (author)
Stochastic Modeling and Deterministic Limit of Catalytic Surface Processes
DEFF Research Database (Denmark)
Starke, Jens; Reichert, Christian; Eiswirth, Markus
2007-01-01
of stochastic origin can be observed in experiments. The models include a new approach to the platinum phase transition, which allows for a unification of existing models for Pt(100) and Pt(110). The rich nonlinear dynamical behavior of the macroscopic reaction kinetics is investigated and shows good agreement...
Modelling of Microbiological Influenced Corrosion – Limitations and Perspectives
DEFF Research Database (Denmark)
Skovhus, Torben Lund; Taylor, Christopher; Eckert, Rickard
of corrosion relative to asset integrity, operators commonly use models to support decision-making. The models use qualitative, semi-quantitative or quantitative measures to help predict the rate of degradation caused by MIC and other threats. A new model that links MIC in topsides oil processing systems...... modeling tools to industry in the shortest development time. ICME development would couple our current understanding of MIC, as represented in models, with experimental data, to build a digital “twin” for optimizing performance of engineering systems, whether in the design phase or operations. Since...... functional groups of microorganisms on reaction kinetics or the significance of microbial growth kinetics on corrosion. The ability to accurately predict MIC initiation and growth is hampered by knowledge gaps regarding environmental conditions affect corrosion under biofilms. In order to manage the threat...
Quasi-neutral limit for a model of viscous plasma
Czech Academy of Sciences Publication Activity Database
Feireisl, Eduard; Zhang, P.
2010-01-01
Roč. 197, č. 1 (2010), s. 271-295 ISSN 0003-9527 R&D Projects: GA ČR GA201/08/0315 Institutional research plan: CEZ:AV0Z10190503 Keywords : Navier-Stokes- Poisson system * quasi-neutral limit * viscous plasma Subject RIV: BA - General Mathematics Impact factor: 2.277, year: 2010 http://link.springer.com/article/10.1007%2Fs00205-010-0317-7
Introduction to thermodynamics of spin models in the Hamiltonian limit
Energy Technology Data Exchange (ETDEWEB)
Berche, Bertrand [Groupe M, Laboratoire de Physique des Materiaux, UMR CNRS No 7556, Universite Henri Poincare, Nancy 1, BP 239, F-54506 Vandoeuvre les Nancy, (France); Lopez, Alexander [Instituto Venezolano de Investigaciones CientIficas, Centro de Fisica, Carr. Panamericana, km 11, Altos de Pipe, Aptdo 21827, 1020-A Caracas, (Venezuela)
2006-01-01
A didactic description of the thermodynamic properties of classical spin systems is given in terms of their quantum counterpart in the Hamiltonian limit. Emphasis is on the construction of the relevant Hamiltonian and the calculation of thermal averages is explicitly done in the case of small systems described, in Hamiltonian field theory, by small matrices. The targeted students are those of a graduate statistical physics course.
A mechanistic nitrogen limitation model for CLM(ED)
Ali, A. A.; Xu, C.; McDowell, N. G.; Rogers, A.; Wullschleger, S. D.; Fisher, R.; Vrugt, J. A.
2014-12-01
Photosynthetic capacity is a key plant trait that determines the rate of photosynthesis; however, in Earth System Models it is either a fixed value or derived from a linear function of leaf nitrogen content. A mechanistic leaf nitrogen allocation model have been developed for a DOE-sponsored Community Land Model coupled to the Ecosystem Demography model (CLM-ED) to predict the photosynthetic capacity [Vc,max25 (μmol CO2 m-2 s-1)] under different environmental conditions at the global scale. We collected more than 800 data points of photosynthetic capacity (Vc,max25) for 124 species from 57 studies with the corresponding leaf nitrogen content and environmental conditions (temperature, radiation, humidity and day length) from literature and the NGEE arctic site (Barrow). Based on the data, we found that environmental control of Vc,max25 is about 4 times stronger than the leaf nitrogen content. Using the Markov-Chain Monte Carlo simulation approach, we fitted the collected data to our newly developed nitrogen allocation model, which predict the leaf nitrogen investment in different components including structure, storage, respiration, light capture, carboxylation and electron transport at different environmental conditions. Our results showed that our nitrogen allocation model explained 52% of variance in observed Vc,max25 and 65% variance in observed Jmax25 using a single set of fitted model parameters for all species. Across the growing season, we found that the modeled Vc,max25 explained 49% of the variability in measured Vc,max25. In the context of future global warming, our model predicts that a temperature increase by 5oC and the doubling of atmospheric carbon dioxide reduced the Vc,max25 by 5%, 11%, respectively.
The Leaky Dielectric Model as a Weak Electrolyte Limit of an Electrodiffusion Model
Mori, Yoichiro; Young, Yuan-Nan
2017-11-01
The Taylor-Melcher (TM) model is the standard model for the electrohydrodynamics of poorly conducting leaky dielectric fluids under an electric field. The TM model treats the fluid as an ohmic conductor, without modeling ion dynamics. On the other hand, electrodiffusion models, which have been successful in describing electokinetic phenomena, incorporates ionic concentration dynamics. Mathematical reconciliation between electrodiffusion and the TM models has been a major issue for electrohydrodynamic theory. Here, we derive the TM model from an electrodiffusion model where we explicitly model the electrochemistry of ion dissociation. We introduce salt dissociation reaction in the bulk and take the limit of weak salt dissociation (corresponding to poor conductors in the TM model.) Assuming small Debye length we derive the TM model with or without the surface charge advection term depending upon the scaling of relevant dimensionless parameters. Our analysis also gives a description of the ionic concentration distribution within the Debye layer, which hints at possible scenarios for electrohydrodynamic singularity formation. In our analysis we also allow for a jump in voltage across the liquid interface which causes a drifting velocity for a liquid drop under an electric field. YM is partially supported by NSF-DMS-1516978 and NSF-DMS-1620316. YNY is partially supported by NSF-DMS-1412789 and NSF-DMS-1614863.
Imperfect Preventive Maintenance Model Study Based On Reliability Limitation
Directory of Open Access Journals (Sweden)
Zhou Qian
2016-01-01
Full Text Available Effective maintenance is crucial for equipment performance in industry. Imperfect maintenance conform to actual failure process. Taking the dynamic preventive maintenance cost into account, the preventive maintenance model was constructed by using age reduction factor. The model regards the minimization of repair cost rate as final target. It use allowed smallest reliability as the replacement condition. Equipment life was assumed to follow two parameters Weibull distribution since it was one of the most commonly adopted distributions to fit cumulative failure problems. Eventually the example verifies the rationality and benefits of the model.
Modelling across bioreactor scales: methods, challenges and limitations
DEFF Research Database (Denmark)
Gernaey, Krist
that it is challenging and expensive to acquire experimental data of good quality that can be used for characterizing gradients occurring inside a large industrial scale bioreactor. But which model building methods are available? And how can one ensure that the parameters in such a model are properly estimated? And what......Scale-up and scale-down of bioreactors are very important in industrial biotechnology, especially with the currently available knowledge on the occurrence of gradients in industrial-scale bioreactors. Moreover, it becomes increasingly appealing to model such industrial scale systems, considering...
The Limitations of Applying Rational Decision-Making Models
African Journals Online (AJOL)
decision-making models as applied to child spacing and more. specificaDy to the use .... also assumes that the individual operates as a rational decision- making organism in ..... work involves: Motivation; Counselling; Distribution ofIEC mate-.
CheckMATE 2: From the model to the limit
Dercks, Daniel; Desai, Nishita; Kim, Jong Soo; Rolbiecki, Krzysztof; Tattersall, Jamie; Weber, Torsten
2017-12-01
We present the latest developments to the CheckMATE program that allows models of new physics to be easily tested against the recent LHC data. To achieve this goal, the core of CheckMATE now contains over 60 LHC analyses of which 12 are from the 13 TeV run. The main new feature is that CheckMATE 2 now integrates the Monte Carlo event generation via MadGraph5_aMC@NLO and Pythia 8. This allows users to go directly from a SLHA file or UFO model to the result of whether a model is allowed or not. In addition, the integration of the event generation leads to a significant increase in the speed of the program. Many other improvements have also been made, including the possibility to now combine signal regions to give a total likelihood for a model.
The Model Identification Test: A Limited Verbal Science Test
McIntyre, P. J.
1972-01-01
Describes the production of a test with a low verbal load for use with elementary school science students. Animated films were used to present appropriate and inappropriate models of the behavior of particles of matter. (AL)
Advances and Limitations of Disease Biogeography Using Ecological Niche Modeling.
Escobar, Luis E; Craft, Meggan E
2016-01-01
Mapping disease transmission risk is crucial in public and animal health for evidence based decision-making. Ecology and epidemiology are highly related disciplines that may contribute to improvements in mapping disease, which can be used to answer health related questions. Ecological niche modeling is increasingly used for understanding the biogeography of diseases in plants, animals, and humans. However, epidemiological applications of niche modeling approaches for disease mapping can fail to generate robust study designs, producing incomplete or incorrect inferences. This manuscript is an overview of the history and conceptual bases behind ecological niche modeling, specifically as applied to epidemiology and public health; it does not pretend to be an exhaustive and detailed description of ecological niche modeling literature and methods. Instead, this review includes selected state-of-the-science approaches and tools, providing a short guide to designing studies incorporating information on the type and quality of the input data (i.e., occurrences and environmental variables), identification and justification of the extent of the study area, and encourages users to explore and test diverse algorithms for more informed conclusions. We provide a friendly introduction to the field of disease biogeography presenting an updated guide for researchers looking to use ecological niche modeling for disease mapping. We anticipate that ecological niche modeling will soon be a critical tool for epidemiologists aiming to map disease transmission risk, forecast disease distribution under climate change scenarios, and identify landscape factors triggering outbreaks.
Interaction of tide and salinity barrier: Limitation of numerical model
Directory of Open Access Journals (Sweden)
Suphat Vongvisessomjai1
2008-07-01
Full Text Available Nowadays, the study of interaction of the tide and the salinity barrier in an estuarine area is usually accomplished vianumerical modeling, due to the speed and convenience of modern computers. However, numerical models provide littleinsight with respect to the fundamental physical mechanisms involved. In this study, it is found that all existing numericalmodels work satisfactorily when the barrier is located at some distance far from upstream and downstream boundary conditions.Results are considerably underestimate reality when the barrier is located near the downstream boundary, usually theriver mouth. Meanwhile, this analytical model provides satisfactory output for all scenarios. The main problem of thenumerical model is that the effects of barrier construction in creation of reflected tide are neglected when specifying thedownstream boundary conditions; the use of the boundary condition before construction of the barrier which are significantlydifferent from those after the barrier construction would result in an error outputs. Future numerical models shouldattempt to account for this deficiency; otherwise, using this analytical model is another choice.
A diffusion-limited reaction model for self-propagating Al/Pt multilayers with quench limits
Kittell, D. E.; Yarrington, C. D.; Hobbs, M. L.; Abere, M. J.; Adams, D. P.
2018-04-01
A diffusion-limited reaction model was calibrated for Al/Pt multilayers ignited on oxidized silicon, sapphire, and tungsten substrates, as well as for some Al/Pt multilayers ignited as free-standing foils. The model was implemented in a finite element analysis code and used to match experimental burn front velocity data collected from several years of testing at Sandia National Laboratories. Moreover, both the simulations and experiments reveal well-defined quench limits in the total Al + Pt layer (i.e., bilayer) thickness. At these limits, the heat generated from atomic diffusion is insufficient to support a self-propagating wave front on top of the substrates. Quench limits for reactive multilayers are seldom reported and are found to depend on the thermal properties of the individual layers. Here, the diffusion-limited reaction model is generalized to allow for temperature- and composition-dependent material properties, phase change, and anisotropic thermal conductivity. Utilizing this increase in model fidelity, excellent overall agreement is shown between the simulations and experimental results with a single calibrated parameter set. However, the burn front velocities of Al/Pt multilayers ignited on tungsten substrates are over-predicted. Possible sources of error are discussed and a higher activation energy (from 41.9 kJ/mol.at. to 47.5 kJ/mol.at.) is shown to bring the simulations into agreement with the velocity data observed on tungsten substrates. This higher activation energy suggests an inhibited diffusion mechanism present at lower heating rates.
Geometrical Optimization Approach to Isomerization: Models and Limitations.
Chang, Bo Y; Shin, Seokmin; Engel, Volker; Sola, Ignacio R
2017-11-02
We study laser-driven isomerization reactions through an excited electronic state using the recently developed Geometrical Optimization procedure. Our goal is to analyze whether an initial wave packet in the ground state, with optimized amplitudes and phases, can be used to enhance the yield of the reaction at faster rates, driven by a single picosecond pulse or a pair of femtosecond pulses resonant with the electronic transition. We show that the symmetry of the system imposes limitations in the optimization procedure, such that the method rediscovers the pump-dump mechanism.
Toward a mechanistic modeling of nitrogen limitation on vegetation dynamics.
Directory of Open Access Journals (Sweden)
Chonggang Xu
Full Text Available Nitrogen is a dominant regulator of vegetation dynamics, net primary production, and terrestrial carbon cycles; however, most ecosystem models use a rather simplistic relationship between leaf nitrogen content and photosynthetic capacity. Such an approach does not consider how patterns of nitrogen allocation may change with differences in light intensity, growing-season temperature and CO(2 concentration. To account for this known variability in nitrogen-photosynthesis relationships, we develop a mechanistic nitrogen allocation model based on a trade-off of nitrogen allocated between growth and storage, and an optimization of nitrogen allocated among light capture, electron transport, carboxylation, and respiration. The developed model is able to predict the acclimation of photosynthetic capacity to changes in CO(2 concentration, temperature, and radiation when evaluated against published data of V(c,max (maximum carboxylation rate and J(max (maximum electron transport rate. A sensitivity analysis of the model for herbaceous plants, deciduous and evergreen trees implies that elevated CO(2 concentrations lead to lower allocation of nitrogen to carboxylation but higher allocation to storage. Higher growing-season temperatures cause lower allocation of nitrogen to carboxylation, due to higher nitrogen requirements for light capture pigments and for storage. Lower levels of radiation have a much stronger effect on allocation of nitrogen to carboxylation for herbaceous plants than for trees, resulting from higher nitrogen requirements for light capture for herbaceous plants. As far as we know, this is the first model of complete nitrogen allocation that simultaneously considers nitrogen allocation to light capture, electron transport, carboxylation, respiration and storage, and the responses of each to altered environmental conditions. We expect this model could potentially improve our confidence in simulations of carbon-nitrogen interactions and the
Measures and limits of models of fixation selection.
Directory of Open Access Journals (Sweden)
Niklas Wilming
Full Text Available Models of fixation selection are a central tool in the quest to understand how the human mind selects relevant information. Using this tool in the evaluation of competing claims often requires comparing different models' relative performance in predicting eye movements. However, studies use a wide variety of performance measures with markedly different properties, which makes a comparison difficult. We make three main contributions to this line of research: First we argue for a set of desirable properties, review commonly used measures, and conclude that no single measure unites all desirable properties. However the area under the ROC curve (a classification measure and the KL-divergence (a distance measure of probability distributions combine many desirable properties and allow a meaningful comparison of critical model performance. We give an analytical proof of the linearity of the ROC measure with respect to averaging over subjects and demonstrate an appropriate correction of entropy-based measures like KL-divergence for small sample sizes in the context of eye-tracking data. Second, we provide a lower bound and an upper bound of these measures, based on image-independent properties of fixation data and between subject consistency respectively. Based on these bounds it is possible to give a reference frame to judge the predictive power of a model of fixation selection. We provide open-source python code to compute the reference frame. Third, we show that the upper, between subject consistency bound holds only for models that predict averages of subject populations. Departing from this we show that incorporating subject-specific viewing behavior can generate predictions which surpass that upper bound. Taken together, these findings lay out the required information that allow a well-founded judgment of the quality of any model of fixation selection and should therefore be reported when a new model is introduced.
Toward a mechanistic modeling of nitrogen limitation on vegetation dynamics.
Xu, Chonggang; Fisher, Rosie; Wullschleger, Stan D; Wilson, Cathy J; Cai, Michael; McDowell, Nate G
2012-01-01
Nitrogen is a dominant regulator of vegetation dynamics, net primary production, and terrestrial carbon cycles; however, most ecosystem models use a rather simplistic relationship between leaf nitrogen content and photosynthetic capacity. Such an approach does not consider how patterns of nitrogen allocation may change with differences in light intensity, growing-season temperature and CO(2) concentration. To account for this known variability in nitrogen-photosynthesis relationships, we develop a mechanistic nitrogen allocation model based on a trade-off of nitrogen allocated between growth and storage, and an optimization of nitrogen allocated among light capture, electron transport, carboxylation, and respiration. The developed model is able to predict the acclimation of photosynthetic capacity to changes in CO(2) concentration, temperature, and radiation when evaluated against published data of V(c,max) (maximum carboxylation rate) and J(max) (maximum electron transport rate). A sensitivity analysis of the model for herbaceous plants, deciduous and evergreen trees implies that elevated CO(2) concentrations lead to lower allocation of nitrogen to carboxylation but higher allocation to storage. Higher growing-season temperatures cause lower allocation of nitrogen to carboxylation, due to higher nitrogen requirements for light capture pigments and for storage. Lower levels of radiation have a much stronger effect on allocation of nitrogen to carboxylation for herbaceous plants than for trees, resulting from higher nitrogen requirements for light capture for herbaceous plants. As far as we know, this is the first model of complete nitrogen allocation that simultaneously considers nitrogen allocation to light capture, electron transport, carboxylation, respiration and storage, and the responses of each to altered environmental conditions. We expect this model could potentially improve our confidence in simulations of carbon-nitrogen interactions and the vegetation
Toward a Mechanistic Modeling of Nitrogen Limitation on Vegetation Dynamics
Xu, Chonggang; Fisher, Rosie; Wullschleger, Stan D.; Wilson, Cathy J.; Cai, Michael; McDowell, Nate G.
2012-01-01
Nitrogen is a dominant regulator of vegetation dynamics, net primary production, and terrestrial carbon cycles; however, most ecosystem models use a rather simplistic relationship between leaf nitrogen content and photosynthetic capacity. Such an approach does not consider how patterns of nitrogen allocation may change with differences in light intensity, growing-season temperature and CO2 concentration. To account for this known variability in nitrogen-photosynthesis relationships, we develop a mechanistic nitrogen allocation model based on a trade-off of nitrogen allocated between growth and storage, and an optimization of nitrogen allocated among light capture, electron transport, carboxylation, and respiration. The developed model is able to predict the acclimation of photosynthetic capacity to changes in CO2 concentration, temperature, and radiation when evaluated against published data of Vc,max (maximum carboxylation rate) and Jmax (maximum electron transport rate). A sensitivity analysis of the model for herbaceous plants, deciduous and evergreen trees implies that elevated CO2 concentrations lead to lower allocation of nitrogen to carboxylation but higher allocation to storage. Higher growing-season temperatures cause lower allocation of nitrogen to carboxylation, due to higher nitrogen requirements for light capture pigments and for storage. Lower levels of radiation have a much stronger effect on allocation of nitrogen to carboxylation for herbaceous plants than for trees, resulting from higher nitrogen requirements for light capture for herbaceous plants. As far as we know, this is the first model of complete nitrogen allocation that simultaneously considers nitrogen allocation to light capture, electron transport, carboxylation, respiration and storage, and the responses of each to altered environmental conditions. We expect this model could potentially improve our confidence in simulations of carbon-nitrogen interactions and the vegetation feedbacks
Coherent states and classical limit of algebraic quantum models
International Nuclear Information System (INIS)
Scutaru, H.
1983-01-01
The algebraic models for collective motion in nuclear physics belong to a class of theories the basic observables of which generate selfadjoint representations of finite dimensional, real Lie algebras, or of the enveloping algebras of these Lie algebras. The simplest and most used for illustrations model of this kind is the Lipkin model, which is associated with the Lie algebra of the three dimensional rotations group, and which presents all characteristic features of an algebraic model. The Lipkin Hamiltonian is the image, of an element of the enveloping algebra of the algebra SO under a representation. In order to understand the structure of the algebraic models the author remarks that in both classical and quantum mechanics the dynamics is associated to a typical algebraic structure which we shall call a dynamical algebra. In this paper he shows how the constructions can be made in the case of the algebraic quantum systems. The construction of the symplectic manifold M can be made in this case using a quantum analog of the momentum map which he defines
Assessing the limitations of the Banister model in monitoring training
Hellard, Philippe; Avalos, Marta; Lacoste, Lucien; Barale, Frédéric; Chatard, Jean-Claude; Millet, Grégoire P.
2006-01-01
The aim of this study was to carry out a statistical analysis of the Banister model to verify how useful it is in monitoring the training programmes of elite swimmers. The accuracy, the ill-conditioning and the stability of this model were thus investigated. Training loads of nine elite swimmers, measured over one season, were related to performances with the Banister model. Firstly, to assess accuracy, the 95% bootstrap confidence interval (95% CI) of parameter estimates and modelled performances were calculated. Secondly, to study ill-conditioning, the correlation matrix of parameter estimates was computed. Finally, to analyse stability, iterative computation was performed with the same data but minus one performance, chosen randomly. Performances were significantly related to training loads in all subjects (R2= 0.79 ± 0.13, P < 0.05) and the estimation procedure seemed to be stable. Nevertheless, the 95% CI of the most useful parameters for monitoring training were wide τa =38 (17, 59), τf =19 (6, 32), tn =19 (7, 35), tg =43 (25, 61). Furthermore, some parameters were highly correlated making their interpretation worthless. The study suggested possible ways to deal with these problems and reviewed alternative methods to model the training-performance relationships. PMID:16608765
Some Limits Using Random Slope Models to Measure Academic Growth
Directory of Open Access Journals (Sweden)
Daniel B. Wright
2017-11-01
Full Text Available Academic growth is often estimated using a random slope multilevel model with several years of data. However, if there are few time points, the estimates can be unreliable. While using random slope multilevel models can lower the variance of the estimates, these procedures can produce more highly erroneous estimates—zero and negative correlations with the true underlying growth—than using ordinary least squares estimates calculated for each student or school individually. An example is provided where schools with increasing graduation rates are estimated to have negative growth and vice versa. The estimation is worse when the underlying data are skewed. It is recommended that there are at least six time points for estimating growth if using a random slope model. A combination of methods can be used to avoid some of the aberrant results if it is not possible to have six or more time points.
Confidence limits for data mining models of options prices
Healy, J. V.; Dixon, M.; Read, B. J.; Cai, F. F.
2004-12-01
Non-parametric methods such as artificial neural nets can successfully model prices of financial options, out-performing the Black-Scholes analytic model (Eur. Phys. J. B 27 (2002) 219). However, the accuracy of such approaches is usually expressed only by a global fitting/error measure. This paper describes a robust method for determining prediction intervals for models derived by non-linear regression. We have demonstrated it by application to a standard synthetic example (29th Annual Conference of the IEEE Industrial Electronics Society, Special Session on Intelligent Systems, pp. 1926-1931). The method is used here to obtain prediction intervals for option prices using market data for LIFFE “ESX” FTSE 100 index options ( http://www.liffe.com/liffedata/contracts/month_onmonth.xls). We avoid special neural net architectures and use standard regression procedures to determine local error bars. The method is appropriate for target data with non constant variance (or volatility).
Limit Stress Spline Models for GRP Composites | Ihueze | Nigerian ...
African Journals Online (AJOL)
Spline functions were established on the assumption of three intervals and fitting of quadratic and cubic splines to critical stress-strain responses data. Quadratic ... of data points. Spline model is therefore recommended as it evaluates the function at subintervals, eliminating the error associated with wide range interpolation.
Random fluid limit of an overloaded polling model
M. Frolkova (Masha); S.G. Foss (Sergey); A.P. Zwart (Bert)
2014-01-01
htmlabstractIn the present paper, we study the evolution of an overloaded cyclic polling model that starts empty. Exploiting a connection with multitype branching processes, we derive fluid asymptotics for the joint queue length process. Under passage to the fluid dynamics, the server switches
Random fluid limit of an overloaded polling model
M. Frolkova (Masha); S.G. Foss (Sergey); A.P. Zwart (Bert)
2013-01-01
htmlabstractIn the present paper, we study the evolution of an~overloaded cyclic polling model that starts empty. Exploiting a~connection with multitype branching processes, we derive fluid asymptotics for the joint queue length process. Under passage to the fluid dynamics, the server switches
Evidence, models, conservation programs and limits to management
Nichols, J.D.
2012-01-01
Walsh et al. (2012) emphasized the importance of obtaining evidence to assess the effects of management actions on state variables relevant to objectives of conservation programs. They focused on malleefowl Leipoa ocellata, ground-dwelling Australian megapodes listed as vulnerable. They noted that although fox Vulpes vulpes baiting is the main management action used in malleefowl conservation throughout southern Australia, evidence of the effectiveness of this action is limited and currently debated. Walsh et al. (2012) then used data from 64 sites monitored for malleefowl and foxes over 23 years to assess key functional relationships relevant to fox control as a conservation action for malleefowl. In one set of analyses, Walsh et al. (2012) focused on two relationships: fox baiting investment versus fox presence, and fox presence versus malleefowl population size and rate of population change. Results led to the counterintuitive conclusion that increases in investments in fox control produced slight decreases in malleefowl population size and growth. In a second set of analyses, Walsh et al. (2012) directly assessed the relationship between investment in fox baiting and malleefowl population size and rate of population change. This set of analyses showed no significant relationship between investment in fox population control and malleefowl population growth. Both sets of analyses benefited from the incorporation of key environmental covariates hypothesized to influence these management relationships. Walsh et al. (2012) concluded that "in most situations, malleefowl conservation did not effectively benefit from fox baiting at current levels of investment." In this commentary, I discuss the work of Walsh et al. (2012) using the conceptual framework of structured decision making (SDM). In doing so, I accept their analytic results and associated conclusions as accurate and discuss basic ideas about evidence, conservation and limits to management.
76 FR 31800 - Airworthiness Directives; Viking Air Limited Model DHC-3 (Otter) Airplanes
2011-06-02
... Airworthiness Directives; Viking Air Limited Model DHC-3 (Otter) Airplanes AGENCY: Federal Aviation... INFORMATION: Discussion Recent analysis by the FAA on the Viking Air Limited Model DHC-3 (Otter) airplanes... new airworthiness directive (AD): 2011-12-02 Viking Aircraft Limited: Amendment 39-16709; Docket No...
Little Higgs model limits from LHC - Input for Snowmass 2013
International Nuclear Information System (INIS)
Reuter, Juergen; Tonini, Marco; Vries, Maikel de
2013-07-01
The status of the most prominent model implementations of the Little Higgs paradigm, the Littlest Higgs with and without discrete T parity as well as the Simplest Little Higgs are reviewed. For this, we are taking into account a fit to 21 electroweak precision observables from LEP, SLC, Tevatron together with the full 25 fb -1 of Higgs data reported from ATLAS and CMS at Moriond 2013. We also - focusing on the Littlest Higgs with T parity - include an outlook on corresponding direct searches at the 8 TeV LHC and their competitiveness with the EW and Higgs data regarding their exclusion potential. This contribution to the Snowmass procedure serves as a guideline which regions in parameter space of Little Higgs models are still compatible for the upcoming LHC runs and future experiments at the energy frontier. For this we propose two different benchmark scenarios for the Littlest Higgs with T parity, one with heavy mirror quarks, one with light ones.
The Limit Deposit Velocity model, a new approach
Directory of Open Access Journals (Sweden)
Miedema Sape A.
2015-12-01
Full Text Available In slurry transport of settling slurries in Newtonian fluids, it is often stated that one should apply a line speed above a critical velocity, because blow this critical velocity there is the danger of plugging the line. There are many definitions and names for this critical velocity. It is referred to as the velocity where a bed starts sliding or the velocity above which there is no stationary bed or sliding bed. Others use the velocity where the hydraulic gradient is at a minimum, because of the minimum energy consumption. Most models from literature are one term one equation models, based on the idea that the critical velocity can be explained that way.
Staying Connected: Sustaining Collaborative Care Models with Limited Funding.
Johnston, Brenda J; Peppard, Lora; Newton, Marian
2015-08-01
Providing psychiatric services in the primary care setting is challenging. The multidisciplinary, coordinated approach of collaborative care models (CCMs) addresses these challenges. The purpose of the current article is to discuss the implementation of a CCM at a free medical clinic (FMC) where volunteer staff provide the majority of services. Essential components of CCMs include (a) comprehensive screening and assessment, (b) shared development and communication of care plans among providers and the patient, and (c) care coordination and management. Challenges to implementing and sustaining a CCM at a FMC in Virginia attempting to meet the medical and psychiatric needs of the underserved are addressed. Although the CCM produced favorable outcomes, sustaining the model long-term presented many challenges. Strategies for addressing these challenges are discussed. Copyright 2015, SLACK Incorporated.
Toward a Mechanistic Modeling of Nitrogen Limitation on Vegetation Dynamics
Xu, Chonggang; Fisher, Rosie; Wullschleger, Stan D.; Wilson, Cathy J.; Cai, Michael; McDowell, Nate G.
2012-01-01
Nitrogen is a dominant regulator of vegetation dynamics, net primary production, and terrestrial carbon cycles; however, most ecosystem models use a rather simplistic relationship between leaf nitrogen content and photosynthetic capacity. Such an approach does not consider how patterns of nitrogen allocation may change with differences in light intensity, growing-season temperature and CO(2) concentration. To account for this known variability in nitrogen-photosynthesis relationships, we deve...
Little Higgs model limits from LHC - Input for Snowmass 2013
Energy Technology Data Exchange (ETDEWEB)
Reuter, Juergen; Tonini, Marco; Vries, Maikel. de
2013-07-15
The status of the most prominent model implementations of the Little Higgs paradigm, the Littlest Higgs with and without discrete T parity as well as the Simplest Little Higgs are reviewed. For this, we are taking into account a fit to 21 electroweak precision observables from LEP, SLC, Tevatron together with the full 25 fb{sup -1} of Higgs data reported from ATLAS and CMS at Moriond 2013. We also - focusing on the Littlest Higgs with T parity - include an outlook on corresponding direct searches at the 8 TeV LHC and their competitiveness with the EW and Higgs data regarding their exclusion potential. This contribution to the Snowmass procedure serves as a guideline which regions in parameter space of Little Higgs models are still compatible for the upcoming LHC runs and future experiments at the energy frontier. For this we propose two different benchmark scenarios for the Littlest Higgs with T parity, one with heavy mirror quarks, one with light ones.
Dental Care Coverage and Use: Modeling Limitations and Opportunities
Moeller, John F.; Chen, Haiyan
2014-01-01
Objectives. We examined why older US adults without dental care coverage and use would have lower use rates if offered coverage than do those who currently have coverage. Methods. We used data from the 2008 Health and Retirement Study to estimate a multinomial logistic model to analyze the influence of personal characteristics in the grouping of older US adults into those with and those without dental care coverage and dental care use. Results. Compared with persons with no coverage and no dental care use, users of dental care with coverage were more likely to be younger, female, wealthier, college graduates, married, in excellent or very good health, and not missing all their permanent teeth. Conclusions. Providing dental care coverage to uninsured older US adults without use will not necessarily result in use rates similar to those with prior coverage and use. We have offered a model using modifiable factors that may help policy planners facilitate programs to increase dental care coverage uptake and use. PMID:24328635
Projective limits of state spaces III. Toy-models
Lanéry, Suzanne; Thiemann, Thomas
2018-01-01
In this series of papers, we investigate the projective framework initiated by Kijowski (1977) and Okołów (2009, 2014, 2013) [1,2], which describes the states of a quantum theory as projective families of density matrices. A short reading guide to the series can be found in Lanéry (2016). A strategy to implement the dynamics in this formalism was presented in our first paper Lanéry and Thiemann (2017) (see also Lanéry, 2016, section 4), which we now test in two simple toy-models. The first one is a very basic linear model, meant as an illustration of the general procedure, and we will only discuss it at the classical level. In the second one, we reformulate the Schrödinger equation, treated as a classical field theory, within this projective framework, and proceed to its (non-relativistic) second quantization. We are then able to reproduce the physical content of the usual Fock quantization.
On the limits of application of the nolocal quark model
International Nuclear Information System (INIS)
Efimov, G.V.; Ivanov, M.A.; Novitsyn, E.A.; Ryabtsev, A.D.
1983-01-01
The possibility of application of the nolocal quark model (NQM) to the physics of mesons, containin charmed quarks, is considered. A method for description of states with identical quantum numbers is suggested. I' order to distinguish between such states different quark currents are introduced with additional condition of ''o thogonality'' implied. The latter allows one to neglect nondiagonal off-shell matrix elements in compositeness conditi ' for coupling constants. In the framework of NQM with ditional assumptions mentioned several decay widths of vector charmonium states have been computed, namely lepton c widths of J/psi(3100), psi'(3685) and psi(3770) an the decay width into charmed D-mesons psi(3770) → D nti D. It is shown that the two-parametric freedom of the m del is not sufficient to fit the experimental data. It is co'cluded that the revision of basic concepts of NQM is nec ssary in physics of mesons containing c-quarks
Achieving the physical limits of the bounded-storage model
International Nuclear Information System (INIS)
Mandayam, Prabha; Wehner, Stephanie
2011-01-01
Secure two-party cryptography is possible if the adversary's quantum storage device suffers imperfections. For example, security can be achieved if the adversary can store strictly less then half of the qubits transmitted during the protocol. This special case is known as the bounded-storage model, and it has long been an open question whether security can still be achieved if the adversary's storage were any larger. Here, we answer this question positively and demonstrate a two-party protocol which is secure as long as the adversary cannot store even a small fraction of the transmitted pulses. We also show that security can be extended to a larger class of noisy quantum memories.
COUNTERCURRENT FLOW LIMITATION EXPERIMENTS AND MODELING FOR IMPROVED REACTOR SAFETY
International Nuclear Information System (INIS)
Vierow, Karen
2008-01-01
This project is investigating countercurrent flow and 'flooding' phenomena in light water reactor systems to improve reactor safety of current and future reactors. To better understand the occurrence of flooding in the surge line geometry of a PWR, two experimental programs were performed. In the first, a test facility with an acrylic test section provided visual data on flooding for air-water systems in large diameter tubes. This test section also allowed for development of techniques to form an annular liquid film along the inner surface of the 'surge line' and other techniques which would be difficult to verify in an opaque test section. Based on experiences in the air-water testing and the improved understanding of flooding phenomena, two series of tests were conducted in a large-diameter, stainless steel test section. Air-water test results and steam-water test results were directly compared to note the effect of condensation. Results indicate that, as for smaller diameter tubes, the flooding phenomena is predominantly driven by the hydrodynamics. Tests with the test sections inclined were attempted but the annular film was easily disrupted. A theoretical model for steam venting from inclined tubes is proposed herein and validated against air-water data. Empirical correlations were proposed for air-water and steam-water data. Methods for developing analytical models of the air-water and steam-water systems are discussed, as is the applicability of the current data to the surge line conditions. This report documents the project results from July 1, 2005 through June 30, 2008
Determining passive cooling limits in CPV using an analytical thermal model
Gualdi, Federico; Arenas, Osvaldo; Vossier, Alexis; Dollet, Alain; Aimez, Vincent; Arès, Richard
2013-09-01
We propose an original thermal analytical model aiming to predict the practical limits of passive cooling systems for high concentration photovoltaic modules. The analytical model is described and validated by comparison with a commercial 3D finite element model. The limiting performances of flat plate cooling systems in natural convection are then derived and discussed.
Turning limited experimental information into 3D models of RNA.
Flores, Samuel Coulbourn; Altman, Russ B
2010-09-01
Our understanding of RNA functions in the cell is evolving rapidly. As for proteins, the detailed three-dimensional (3D) structure of RNA is often key to understanding its function. Although crystallography and nuclear magnetic resonance (NMR) can determine the atomic coordinates of some RNA structures, many 3D structures present technical challenges that make these methods difficult to apply. The great flexibility of RNA, its charged backbone, dearth of specific surface features, and propensity for kinetic traps all conspire with its long folding time, to challenge in silico methods for physics-based folding. On the other hand, base-pairing interactions (either in runs to form helices or isolated tertiary contacts) and motifs are often available from relatively low-cost experiments or informatics analyses. We present RNABuilder, a novel code that uses internal coordinate mechanics to satisfy user-specified base pairing and steric forces under chemical constraints. The code recapitulates the topology and characteristic L-shape of tRNA and obtains an accurate noncrystallographic structure of the Tetrahymena ribozyme P4/P6 domain. The algorithm scales nearly linearly with molecule size, opening the door to the modeling of significantly larger structures.
New limits on coupled dark energy model after Planck 2015
Li, Hang; Yang, Weiqiang; Wu, Yabo; Jiang, Ying
2018-06-01
We used the Planck 2015 cosmic microwave background anisotropy, baryon acoustic oscillation, type-Ia supernovae, redshift-space distortions, and weak gravitational lensing to test the model parameter space of coupled dark energy. We assumed the constant and time-varying equation of state parameter for dark energy, and treated dark matter and dark energy as the fluids whose energy transfer was proportional to the combined term of the energy densities and equation of state, such as Q = 3 Hξ(1 +wx) ρx and Q = 3 Hξ [ 1 +w0 +w1(1 - a) ] ρx, the full space of equation of state could be measured when we considered the term (1 +wx) in the energy exchange. According to the joint observational constraint, the results showed that wx = - 1.006-0.027+0.047 and ξ = 0.098-0.098>+0.026 for coupled dark energy with a constant equation of state, w0 = -1.076-0.076+0.085, w1 = - 0.069-0.319+0.361, and ξ = 0.210-0.210+0.048 for a variable equation of state. We did not get any clear evidence for the coupling in the dark fluids at 1 σ region.
The spherical limit of the n-vector model and correlation inequaljties
International Nuclear Information System (INIS)
Angelescu, N.; Bundaru, M.; Costache, G.
1978-08-01
The asymptotics of the state of the n-vector model with a finite number of spins in the spherical limit is studied. Besides rederiving the limit free energy, corresponding to a generalized spherical model (with ''spherical constraint'' at every site), we obtain also the limit of the correlation functions, which allow a precise definition of the state of the latter model. Correlation inequalities are proved for ferromagnetic interactions in the asymptotic regime. In particular, it is shown that the generalized spherical model fulfills the expected Griffiths' type inequalities, differing in this respect from the spherical model with overall constraint. (author)
Sargsyan, K.; Safta, C.; Debusschere, B.; Najm, H.
2010-12-01
Uncertainty quantification in complex climate models is challenged by the sparsity of available climate model predictions due to the high computational cost of model runs. Another feature that prevents classical uncertainty analysis from being readily applicable is bifurcative behavior in climate model response with respect to certain input parameters. A typical example is the Atlantic Meridional Overturning Circulation. The predicted maximum overturning stream function exhibits discontinuity across a curve in the space of two uncertain parameters, namely climate sensitivity and CO2 forcing. We outline a methodology for uncertainty quantification given discontinuous model response and a limited number of model runs. Our approach is two-fold. First we detect the discontinuity with Bayesian inference, thus obtaining a probabilistic representation of the discontinuity curve shape and location for arbitrarily distributed input parameter values. Then, we construct spectral representations of uncertainty, using Polynomial Chaos (PC) expansions on either side of the discontinuity curve, leading to an averaged-PC representation of the forward model that allows efficient uncertainty quantification. The approach is enabled by a Rosenblatt transformation that maps each side of the discontinuity to regular domains where desirable orthogonality properties for the spectral bases hold. We obtain PC modes by either orthogonal projection or Bayesian inference, and argue for a hybrid approach that targets a balance between the accuracy provided by the orthogonal projection and the flexibility provided by the Bayesian inference - where the latter allows obtaining reasonable expansions without extra forward model runs. The model output, and its associated uncertainty at specific design points, are then computed by taking an ensemble average over PC expansions corresponding to possible realizations of the discontinuity curve. The methodology is tested on synthetic examples of
The Ising model in the scaling limit as model for the description of elementary particles
International Nuclear Information System (INIS)
Weinzierl, W.
1981-01-01
In this thesis a possible way is stepped over which starts from the derivation of a quantum field theory from simplest statistical degrees of freedom, as for instance in a two-level system. On a model theory, the Ising model in (1+1) dimensions the idea is explained. In this model theory two particle-interpretable quantum fields arise which can be constructed by a basic field which parametrizes the local dynamics in a simplest way. This so called proliferation is further examined. For the proliferation of the basic field a conserved quantity, a kind of parity is necessary. The stability of both particle fields is a consequence of this conservation law. For the identification of the ''particle-interpretable'' fields the propagators of the order and disorder parameter field are calculated and discussed. An effective Hamiltonian in this particle fields is calculated. As further aspect of this transition from the statistical system to quantum field theory the dimensional transmutation and the closely to this connected mass renormalization is examined. The relation between spin systems in the critical region and fermionic field theories is explained. Thereby it results that certain fermionic degrees of freedom of the spin system vanish in the scaling limit. The ''macroscopically'' relevant degrees of freedom constitute a relativistic Majorana field. (orig./HSI) [de
The Hintermann-Merlini-Baxter-Wu and the infinite-coupling-limit Ashkin-Teller models
Energy Technology Data Exchange (ETDEWEB)
Huang Yuan, E-mail: huangy22@mail.ustc.edu.cn [Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Deng Youjin, E-mail: yjdeng@ustc.edu.cn [Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Jacobsen, Jesper Lykke, E-mail: jacobsen@lpt.ens.fr [Laboratoire de Physique Theorique, Ecole Normale Superieure, 24 rue Lhomond, 75231 Paris (France); Universite Pierre et Marie Curie, 4 place Jussieu, 75252 Paris (France); Salas, Jesus, E-mail: jsalas@math.uc3m.es [Grupo de Modelizacion, Simulacion Numerica y Matematica Industrial, Universidad Carlos III de Madrid, Avda. de la Universidad 30, 28911 Leganes (Spain); Grupo de Teorias de Campos y Fisica Estadistica, Instituto Gregorio Millan, Universidad Carlos III de Madrid, Unidad asociada al IEM-CSIC, Madrid (Spain)
2013-03-11
We show how the Hintermann-Merlini-Baxter-Wu model (which is a generalization of the well-known Baxter-Wu model to a general Eulerian triangulation) can be mapped onto a particular infinite-coupling-limit of the Ashkin-Teller model. We work out some mappings among these models, also including the standard and mixed Ashkin-Teller models. Finally, we compute the phase diagram of the infinite-coupling-limit Ashkin-Teller model on the square, triangular, hexagonal, and kagome lattices.
Application of MCAM in generating Monte Carlo model for ITER port limiter
International Nuclear Information System (INIS)
Lu Lei; Li Ying; Ding Aiping; Zeng Qin; Huang Chenyu; Wu Yican
2007-01-01
On the basis of the pre-processing and conversion functions supplied by MCAM (Monte-Carlo Particle Transport Calculated Automatic Modeling System), this paper performed the generation of ITER Port Limiter MC (Monte-Carlo) calculation model from the CAD engineering model. The result was validated by using reverse function of MCAM and MCNP PLOT 2D cross-section drawing program. the successful application of MCAM to ITER Port Limiter demonstrates that MCAM is capable of dramatically increasing the efficiency and accuracy to generate MC calculation models from CAD engineering models with complex geometry comparing with the traditional manual modeling method. (authors)
The Benefits and Limitations of Hydraulic Modeling for Ordinary High Water Mark Delineation
2016-02-01
between two cross sections, the HEC-RAS model will not show it. If there is a sudden drop in the channel, such as a waterfall or steep rapids, the...ER D C/ CR RE L TR -1 6- 1 Wetland Regulatory Assistance Program (WRAP) The Benefits and Limitations of Hydraulic Modeling for Ordinary...client/default. Wetland Regulatory Assistance Program (WRAP) ERDC/CRREL TR-16-1 February 2016 The Benefits and Limitations of Hydraulic Modeling
Modeling the evolution of natural cliffs subject to weathering. 1, Limit analysis approach
Utili, Stefano; Crosta, Giovanni B.
2011-01-01
Retrogressive landsliding evolution of natural slopes subjected to weathering has been modeled by assuming Mohr-Coulomb material behavior and by using an analytical method. The case of weathering-limited slope conditions, with complete erosion of the accumulated debris, has been modeled. The limit analysis upper-bound method is used to study slope instability induced by a homogeneous decrease of material strength in space and time. The only assumption required in the model concerns the degree...
Central Limit Theorem for Exponentially Quasi-local Statistics of Spin Models on Cayley Graphs
Reddy, Tulasi Ram; Vadlamani, Sreekar; Yogeshwaran, D.
2018-04-01
Central limit theorems for linear statistics of lattice random fields (including spin models) are usually proven under suitable mixing conditions or quasi-associativity. Many interesting examples of spin models do not satisfy mixing conditions, and on the other hand, it does not seem easy to show central limit theorem for local statistics via quasi-associativity. In this work, we prove general central limit theorems for local statistics and exponentially quasi-local statistics of spin models on discrete Cayley graphs with polynomial growth. Further, we supplement these results by proving similar central limit theorems for random fields on discrete Cayley graphs taking values in a countable space, but under the stronger assumptions of α -mixing (for local statistics) and exponential α -mixing (for exponentially quasi-local statistics). All our central limit theorems assume a suitable variance lower bound like many others in the literature. We illustrate our general central limit theorem with specific examples of lattice spin models and statistics arising in computational topology, statistical physics and random networks. Examples of clustering spin models include quasi-associated spin models with fast decaying covariances like the off-critical Ising model, level sets of Gaussian random fields with fast decaying covariances like the massive Gaussian free field and determinantal point processes with fast decaying kernels. Examples of local statistics include intrinsic volumes, face counts, component counts of random cubical complexes while exponentially quasi-local statistics include nearest neighbour distances in spin models and Betti numbers of sub-critical random cubical complexes.
Friction induced hunting limit cycles : a comparison between the LuGre and switch friction model
Hensen, R.H.A.; Molengraft, van de M.J.G.; Steinbuch, M.
2003-01-01
In this paper, friction induced limit cycles are predicted for a simple motion system consisting of a motor-driven inertia subjected to friction and a PID-controlled regulator task. The two friction models used, i.e., (i) the dynamic LuGre friction model and (ii) the static switch friction model,
DEFF Research Database (Denmark)
Ragush, Colin M.; Gentleman, Wendy C.; Hansen, Lisbeth Truelstrup
2018-01-01
Presented here is a mechanistic model of the biological dynamics of the photic zone of a single-cell arctic waste stabilization pond (WSP) for the prediction of oxygen concentration and the removal of oxygen-demanding substances. The model is an exploratory model to assess the limiting environmen...
Directory of Open Access Journals (Sweden)
O. H. Kapitonov
2010-05-01
Full Text Available A mathematical model of coulostatic relaxation of the potential for solid metallic electrode was presented. The solution in the case of limiting diffusion current was obtained. On the basis of this model the technique of concentration measurements for heavy metal ions in diluted solutions was suggested. The model adequacy was proved by experimental data.
2011-07-25
... Conditions No. 25-441-SC] Special Conditions: Gulfstream Model GVI Airplane; Limit Engine Torque Loads for... for transport category airplanes. These design features include engine size and the potential torque... engine mounts and the supporting structures must be designed to withstand a ``limit engine torque load...
Yin, X.; Harbinson, J.; Struik, P.
2009-01-01
We describe an extended Farquhar, Von Caemmerer and Berry (FvCB) model for the RuBP regeneration-limited or electron transport-limited steady-state C3 photosynthesis. Analytical algorithms are presented to account for (i) the effects of Photosystem (PS) I and II photochemical efficiencies and of
Dacuñ a, Javier; Salleo, Alberto
2011-01-01
We have developed and have applied a mobility edge model that takes drift and diffusion currents to characterize the space-charge-limited current in organic semiconductors into account. The numerical solution of the drift-diffusion equation allows
Large-n limit of the Heisenberg model: The decorated lattice and the disordered chain
International Nuclear Information System (INIS)
Khoruzhenko, B.A.; Pastur, L.A.; Shcherbina, M.V.
1989-01-01
The critical temperature of the generalized spherical model (large-component limit of the classical Heisenberg model) on a cubic lattice, whose every bond is decorated by L spins, is found. When L → ∞, the asymptotics of the temperature is T c ∼ aL -1 . The reduction of the number of spherical constraints for the model is found to be fairly large. The free energy of the one-dimensional generalized spherical model with random nearest neighbor interaction is calculated
GA-4/GA-9 honeycomb impact limiter tests and analytical model
International Nuclear Information System (INIS)
Koploy, M.A.; Taylor, C.S.
1991-01-01
General Atomics (GA) has a test program underway to obtain data on the behavior of a honeycomb impact limiter. The program includes testing of small samples to obtain basic information, as well as testing of complete 1/4-scale impact limiters to obtain load-versus-deflection curves for different crush orientations. GA has used the test results to aid in the development of an analytical model to predict the impact limiter loads. The results also helped optimize the design of the impact limiters for the GA-4 and GA-9 Casks
Decay constants in the heavy quark limit in models a la Bakamjian and Thomas
International Nuclear Information System (INIS)
Morenas, V.; Le Yaouanc, A.; Oliver, L.; Pene, O.; Raynal, J.C.
1997-07-01
In quark models a la Bakamjian and Thomas, that yield covariance and Isgur-Wise scaling of form factors in the heavy quark limit, the decay constants f (n) and f 1/2 (n) of S-wave and P-wave mesons composed of heavy and light quarks are computed. Different Ansaetze for the dynamics of the mass operator at rest are discussed. Using phenomenological models of the spectrum with relativistic kinetic energy and regularized short distance part the decay constants in the heavy quark limit are calculated. The convergence of the heavy quark limit sum rules is also studied. (author)
A model for the derivation of new transport limits for non-fixed contamination
International Nuclear Information System (INIS)
Thierfeldt, S.; Lorenz, B.; Hesse, J.
2004-01-01
The IAEA Regulations for the Safe Transport of Radioactive Material contain requirements for contamination limits on packages and conveyances used for the transport of radioactive material. Current contamination limits for packages and conveyances under routine transport conditions have been derived from a model proposed by Fairbairn more than 40 years ago. This model has proven effective if used with pragmatism, but is based on very conservative as well as extremely simple assumptions which is in no way appropriate any more and which is not compatible with ICRP recommendations regarding radiation protection standards. Therefore, a new model has now been developed which reflects all steps of the transport process. The derivation of this model has been fostered by the IAEA by initiating a Co-ordinated Research Project. The results of the calculations using this model could be directly applied as new nuclide specific transport limits for the non-fixed contamination
A model for the derivation of new transport limits for non-fixed contamination
Energy Technology Data Exchange (ETDEWEB)
Thierfeldt, S. [Brenk Systemplanung GmbH, Aachen (Germany); Lorenz, B. [GNS Gesellschaft fuer Nuklearservice, Essen (Germany); Hesse, J. [RWE Power AG, Essen (Germany)
2004-07-01
The IAEA Regulations for the Safe Transport of Radioactive Material contain requirements for contamination limits on packages and conveyances used for the transport of radioactive material. Current contamination limits for packages and conveyances under routine transport conditions have been derived from a model proposed by Fairbairn more than 40 years ago. This model has proven effective if used with pragmatism, but is based on very conservative as well as extremely simple assumptions which is in no way appropriate any more and which is not compatible with ICRP recommendations regarding radiation protection standards. Therefore, a new model has now been developed which reflects all steps of the transport process. The derivation of this model has been fostered by the IAEA by initiating a Co-ordinated Research Project. The results of the calculations using this model could be directly applied as new nuclide specific transport limits for the non-fixed contamination.
Gauge Group Contraction of Electroweak Model and its Natural Energy Limits
Directory of Open Access Journals (Sweden)
Nikolai A. Gromov
2015-09-01
Full Text Available The low and higher energy limits of the Electroweak Model are obtained from first principles of gauge theory. Both limits are given by the same contraction of the gauge group, but for the different consistent rescalings of the field space. Mathematical contraction parameter in both cases is interpreted as energy. The very weak neutrino-matter interaction is explained by zero tending contraction parameter, which depends on neutrino energy. The second consistent rescaling corresponds to the higher energy limit of the Electroweak Model. At the infinite energy all particles lose masses, electroweak interactions become long-range and are mediated by the neutral currents. The limit model represents the development of the early Universe from the Big Bang up to the end of the first second.
Natural limits of electroweak model as contraction of its gauge group
International Nuclear Information System (INIS)
Gromov, N A
2015-01-01
The low and higher energy limits of the electroweak model are obtained from the first principles of gauge theory. Both limits are given by the same contraction of the gauge group, but for the different consistent rescalings of the field space. Mathematical contraction parameter in both cases is interpreted as energy. Very weak neutrino–matter interactions are explained by zero tending contraction parameter, which depends on neutrino energy. The second consistent rescaling corresponds to the higher energy limit of the electroweak model. At the infinite energy all particles lose mass, electroweak interactions become long-range and are mediated by neutral currents. The limit model represents the development of the early Universe from the big bang up to the end of the first second. (paper)
Importance of fish behaviour in modelling conservation problems: food limitation as an example
Steven Railsback; Bret Harvey
2011-01-01
Simulation experiments using the inSTREAM individual-based brown trout Salmo trutta population model explored the role of individual adaptive behaviour in food limitation, as an example of how behaviour can affect managersâ understanding of conservation problems. The model includes many natural complexities in habitat (spatial and temporal variation in characteristics...
Central limit theorems for a class of irreducible multicolor urn models
Indian Academy of Sciences (India)
Central limit theorem; Markov chains; martingale; urn models. 1. Introduction. In this article we are going to ... multicolor urn model is vastly different from the Markov chain evolving according to the transition matrix equal to the ...... /2 contribute a random variable less in absolute value than const. { sup n0≤n<∞. ∥. ∥. ∥. ∥.
Construction of quantized gauge fields: continuum limit of the Abelian Higgs model in two dimensions
International Nuclear Information System (INIS)
Seiler, E.
1981-01-01
The author proves the existence of the continuum limit of the two-dimensional Higgs model for two cases: External gauge fields that are Hoelder continuous and may be non-Abelian, and the fully quantized Abelian model. In the latter case all Wightman axioms are verified except clustering. Important ingredients are a universal diamagnetic bound and correlation inequalities. (Auth.)
Yin, X.; Oijen, van M.; Schapendonk, A.H.C.M.
2004-01-01
The widely used steady-state model of Farquhar et al. (Planta 149: 78-90, 1980) for C-3 photosynthesis was developed on the basis of linear whole-chain (non-cyclic) electron transport. In this model, calculation of the RuBP-regeneration limited CO2-assimilation rate depends on whether it is
Large-N limit of the two-Hermitian-matrix model by the hidden BRST method
International Nuclear Information System (INIS)
Alfaro, J.
1993-01-01
This paper discusses the large-N limit of the two-Hermitian-matrix model in zero dimensions, using the hidden Becchi-Rouet-Stora-Tyutin method. A system of integral equations previously found is solved, showing that it contained the exact solution of the model in leading order of large N
The limiting behavior of the estimated parameters in a misspecified random field regression model
DEFF Research Database (Denmark)
Dahl, Christian Møller; Qin, Yu
This paper examines the limiting properties of the estimated parameters in the random field regression model recently proposed by Hamilton (Econometrica, 2001). Though the model is parametric, it enjoys the flexibility of the nonparametric approach since it can approximate a large collection of n...
Oscillating in synchrony with a metronome: serial dependence, limit cycle dynamics, and modeling.
Torre, Kjerstin; Balasubramaniam, Ramesh; Delignières, Didier
2010-07-01
We analyzed serial dependencies in periods and asynchronies collected during oscillations performed in synchrony with a metronome. Results showed that asynchronies contain 1/f fluctuations, and the series of periods contain antipersistent dependence. The analysis of the phase portrait revealed a specific asymmetry induced by synchronization. We propose a hybrid limit cycle model including a cycle-dependent stiffness parameter provided with fractal properties, and a parametric driving function based on velocity. This model accounts for most experimentally evidenced statistical features, including serial dependence and limit cycle dynamics. We discuss the results and modeling choices within the framework of event-based and emergent timing.
Double scaling limit in O(N) vector models in D dimensions
International Nuclear Information System (INIS)
Di Vecchia, P.; Kato, M.; Ohta, N.
1991-03-01
Using the standard 1/N expansion, we study O(N) vector models in D dimensions with an arbitrary potential. We limit ourselves to renormalizable theories. We show that there exists a value of the coupling constant corresponding to a critical point and that a double scaling limit can be performed as in D=0 and in the case of matrix models in D=0,1. For D=1 the theory is renormalizable with an arbitrary potential and we find in general a hierarchy of critical theories labelled by an integer k. The universal partition function obtained in the double scaling limit is constructed. Finally we show that the critical behaviour of those models is the same as a branched polymer model recently constructed by Ambjoern, Durhuus and Jonsson. (orig.)
Mathematical interpretation of Brownian motor model: Limit cycles and directed transport phenomena
Yang, Jianqiang; Ma, Hong; Zhong, Suchuang
2018-03-01
In this article, we first suggest that the attractor of Brownian motor model is one of the reasons for the directed transport phenomenon of Brownian particle. We take the classical Smoluchowski-Feynman (SF) ratchet model as an example to investigate the relationship between limit cycles and directed transport phenomenon of the Brownian particle. We study the existence and variation rule of limit cycles of SF ratchet model at changing parameters through mathematical methods. The influences of these parameters on the directed transport phenomenon of a Brownian particle are then analyzed through numerical simulations. Reasonable mathematical explanations for the directed transport phenomenon of Brownian particle in SF ratchet model are also formulated on the basis of the existence and variation rule of the limit cycles and numerical simulations. These mathematical explanations provide a theoretical basis for applying these theories in physics, biology, chemistry, and engineering.
Emergence of nutrient limitation in tropical dry forests: hypotheses from simulation models
Medvigy, D.; Waring, B. G.; Xu, X.; Trierweiler, A.; Werden, L. K.; Wang, G.; Zhu, Q.; Powers, J. S.
2017-12-01
It is unclear to what extent tropical dry forest productivity may be limited by nutrients. Direct assessment of nutrient limitation through fertilization experiments has been rare, and paradigms pertaining to other ecosystems may not extend to tropical dry forests. For example, because dry tropical forests have a lower water supply than moist tropical forests, dry forests can have lower decomposition rates, higher soil carbon and nitrogen concentrations, and a more open nitrogen cycle than moist forests. We used a mechanistic, numerical model to generate hypotheses about nutrient limitation in tropical dry forests. The model dynamically couples ED2 (vegetation dynamics), MEND (biogeochemistry), and N-COM (plant-microbe competition for nutrients). Here, the MEND-component of the model has been extended to include nitrogen (N) and phosphorus (P) cycles. We focus on simulation of sixteen 25m x 25m plots in Costa Rica where a fertilization experiment has been underway since 2015. Baseline simulations are characterized by both nitrogen and phosphorus limitation of vegetation. Fertilization with N and P increased vegetation biomass, with N fertilization having a somewhat stronger effect. Nutrient limitation was also sensitive to climate and was more pronounced during drought periods. Overflow respiration was identified as a key process that mitigated nutrient limitation. These results suggest that, despite often having richer soils than tropical moist forests, tropical dry forests can also become nutrient-limited. If the climate becomes drier in the next century, as is expected for Central America, drier soils may decrease microbial activity and exacerbate nutrient limitation. The importance of overflow respiration underscores the need for appropriate treatment of microbial dynamics in ecosystem models. Ongoing and new nutrient fertilization experiments will present opportunities for testing whether, and how, nutrient limitation may indeed be emerging in tropical dry
Fatigue and Serviceability Limit State Model Basis for Assessment of Offshore Wind Energy Converters
DEFF Research Database (Denmark)
Thöns, Sebastian; Faber, M. H.; Rücker, W.
2012-01-01
, a probabilistic model is derived on the basis of literature review and measurement data from a prototype Multibrid M5000 support structure. The sensitivity study is based on the calculation of a nonlinear coefficient of correlation in conjunction with predetermined designs of experiments. This is conducted......This paper develops the models for the structural performance of the loading and probabilistic characterization for the fatigue and the serviceability limit states for the support structure of offshore wind energy converters. These models and a sensitivity study are part of a risk based assessment...... as the starting point for the development of the structural performance and loading models. With these models introduced in detail, several modeling aspects for both limit states are analyzed. This includes analyses of the influence on the hot spot stresses by applying a contact formulation for the pile guide...
A Study on Stability of Limit Cycle Walking Model with Feet: Parameter Study
Yonggwon Jeon; Youn-sik Park; Youngjin Park
2013-01-01
In this paper, two kinds of feet, namely, curved and flat feet, are added to limit cycle walking model to investigate its stability properties. Although both models are already proposed and are investigated, most previous works are focused on efficiency and gait behaviors. Only the stability properties of the simplest walking model conceived Garcia et al. are well defined. Therefore, there is still a need for a precise research on the effect of feet, especially in the view of local stability,...
Exotic Homoclinic Surface of a Saddle-Node Limit Cycle in a Leech Neuron Model
Yooer, Chi-Feng; Wei, Fang; Xu, Jian-Xue; Zhang, Xin-Hua
2011-03-01
We carry out numerical and theoretical investigations on the global unstable invariant set (manifold) of a saddle-node limit cycle in a leech heart interneuron model. The corresponding global bifurcation is accompanied by an explosion of secondary bifurcations of limit cycles and the emergence of loop-shaped bifurcation structures. The dynamical behaviors of the trajectories of the invariant set are very complicated and can only be partially explained by existing theories.
Effect of model choice and sample size on statistical tolerance limits
International Nuclear Information System (INIS)
Duran, B.S.; Campbell, K.
1980-03-01
Statistical tolerance limits are estimates of large (or small) quantiles of a distribution, quantities which are very sensitive to the shape of the tail of the distribution. The exact nature of this tail behavior cannot be ascertained brom small samples, so statistical tolerance limits are frequently computed using a statistical model chosen on the basis of theoretical considerations or prior experience with similar populations. This report illustrates the effects of such choices on the computations
Predicting the weathering of fuel and oil spills: A diffusion-limited evaporation model.
Kotzakoulakis, Konstantinos; George, Simon C
2018-01-01
The majority of the evaporation models currently available in the literature for the prediction of oil spill weathering do not take into account diffusion-limited mass transport and the formation of a concentration gradient in the oil phase. The altered surface concentration of the spill caused by diffusion-limited transport leads to a slower evaporation rate compared to the predictions of diffusion-agnostic evaporation models. The model presented in this study incorporates a diffusive layer in the oil phase and predicts the diffusion-limited evaporation rate. The information required is the composition of the fluid from gas chromatography or alternatively the distillation data. If the density or a single viscosity measurement is available the accuracy of the predictions is higher. Environmental conditions such as water temperature, air pressure and wind velocity are taken into account. The model was tested with synthetic mixtures, petroleum fuels and crude oils with initial viscosities ranging from 2 to 13,000 cSt. The tested temperatures varied from 0 °C to 23.4 °C and wind velocities from 0.3 to 3.8 m/s. The average absolute deviation (AAD) of the diffusion-limited model ranged between 1.62% and 24.87%. In comparison, the AAD of a diffusion-agnostic model ranged between 2.34% and 136.62% against the same tested fluids. Copyright © 2017 Elsevier Ltd. All rights reserved.
Detailed analysis of the continuum limit of a supersymmetric lattice model in 1D
International Nuclear Information System (INIS)
Huijse, L
2011-01-01
We present a full identification of lattice model properties with their field theoretical counterparts in the continuum limit for a supersymmetric model for itinerant spinless fermions on a one-dimensional chain. The continuum limit of this model is described by an N=(2,2) superconformal field theory (SCFT) with central charge c = 1. We identify states and operators in the lattice model with fields in the SCFT and we relate boundary conditions on the lattice to sectors in the field theory. We use the dictionary we develop in this paper to give a pedagogical explanation of a powerful tool to study supersymmetric models based on spectral flow (Huijse 2008 Phys. Rev. Lett. 101 146406). Finally, we employ the developed machinery to explain numerically observed properties of the particle density on the open chain presented in Beccaria and De Angelis (2005 Phys. Rev. Lett. 94 100401)
Capacity Prediction Model Based on Limited Priority Gap-Acceptance Theory at Multilane Roundabouts
Directory of Open Access Journals (Sweden)
Zhaowei Qu
2014-01-01
Full Text Available Capacity is an important design parameter for roundabouts, and it is the premise of computing their delay and queue. Roundabout capacity has been studied for decades, and empirical regression model and gap-acceptance model are the two main methods to predict it. Based on gap-acceptance theory, by considering the effect of limited priority, especially the relationship between limited priority factor and critical gap, a modified model was built to predict the roundabout capacity. We then compare the results between Raff’s method and maximum likelihood estimation (MLE method, and the MLE method was used to predict the critical gaps. Finally, the predicted capacities from different models were compared, with the observed capacity by field surveys, which verifies the performance of the proposed model.
Pulses in the Zero-Spacing Limit of the GOY Model
DEFF Research Database (Denmark)
Andersen, Ken Haste; Jensen, M.H.; Nielsen, J.L.
2000-01-01
We study the propagation of localised disturbances in a turbulent, but momentarily quiescent and unforced shell model (an approximation of the Navier-Stokes equations on a set of exponentially spaced momentum shells). These disturbances represent bursts of turbulence travelling down the inertial...... range, which is thought to be responsible for the intermittency observed in turbulence. Starting from the GOY shell model, we go to the limit where the distance between succeeding shells approaches zero ("the zero spacing limit") and helicity conservation is retained. We obtain a discrete field theory...... which is numerically shown to have pulse solutions travelling with constant speed and with unchanged form. We give numerical evidence that the model might even be exactly integrable, although the continuum limit seems to be singular and the pulses show an unusual super exponential decay to zero as exp...
One-dimensional fluid model for transport in divertor and limiter tokamak scrape-off layers
International Nuclear Information System (INIS)
Lipschultz, B.
1983-11-01
Single-fluid transport in the plasma scrape-off layer is modeled for poloidal divertor and mechanically limited discharges. This numerical model is one-dimensional along a field line and time-independent. Conductive and convective transport, as well as impurity and neutral source (sink) terms are included. A simple shooting method technique is used for obtaining solutions. Results are shown for the case of the proposed Alcator DCT tokamak
The quasi-invariant limit for a kinetic model of sociological collective behavior
Boudin , Laurent; Salvarani , Francesco
2009-01-01
International audience; The paper is devoted to the study of the asymptotic behaviour of a kinetic model proposed to forecast the phenomenon of opinion formation, with both effect of self-thinking and compromise between individuals. By supposing that the effects of self-thinking and compromise are very weak, we deduce, asymptotically, some simpler models who lose the kinetic structure. We explicitly characterize the asymptotic state of the limiting equation and study the speed of convergence ...
User Guide for GoldSim Model to Calculate PA/CA Doses and Limits
International Nuclear Information System (INIS)
Smith, F.
2016-01-01
A model to calculate doses for solid waste disposal at the Savannah River Site (SRS) and corresponding disposal limits has been developed using the GoldSim commercial software. The model implements the dose calculations documented in SRNL-STI-2015-00056, Rev. 0 ''Dose Calculation Methodology and Data for Solid Waste Performance Assessment (PA) and Composite Analysis (CA) at the Savannah River Site''.
User Guide for GoldSim Model to Calculate PA/CA Doses and Limits
Energy Technology Data Exchange (ETDEWEB)
Smith, F. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)
2016-10-31
A model to calculate doses for solid waste disposal at the Savannah River Site (SRS) and corresponding disposal limits has been developed using the GoldSim commercial software. The model implements the dose calculations documented in SRNL-STI-2015-00056, Rev. 0 “Dose Calculation Methodology and Data for Solid Waste Performance Assessment (PA) and Composite Analysis (CA) at the Savannah River Site”.
Model predictive control for power flows in networks with limited capacity
DEFF Research Database (Denmark)
Biegel, Benjamin; Stoustrup, Jakob; Bendtsen, Jan Dimon
2012-01-01
this problem can be formulated as an optimization problem, leading directly to the design of a model predictive controller. Using this scheme, we are able to incorporate predictions of future consumption and exploit knowledge of link limitations such that the intelligent consumers are utilized ahead of time......We consider an interconnected network of consumers powered through an electrical grid of limited capacity. A subset of the consumers are intelligent consumers and have the ability to store energy in a controllable fashion; they can be filled and emptied as desired under power and capacity...... limitations. We address the problem of maintaining power balance between production and consumption using the intelligent consumers to ensure smooth power consumption from the grid. Further, certain capacity limitations to the links interconnecting the consumers must be honored. In this paper, we show how...
Reversible thermal fusing model of carbon black current-limiting thermistors
International Nuclear Information System (INIS)
Martin, James E.; Heaney, Michael B.
2000-01-01
Composites of carbon black particles in polyethylene exhibit an unusually rapid increase in resistivity as the applied electric field is increased, making this material commercially useful as current-limiting thermistors, also known as automatically resettable fuses. In this application the composite is in series with the circuit it is protecting: at low applied voltages the circuit is the load, but at high applied voltages the composite becomes the load, limiting the current to the circuit. We present a simple model of this behavior in terms of a network of nonlinear resistors. Each resistor has a resistance that depends explicitly and reversibly on its instantaneous power dissipation. This model predicts that in the soft fusing, or current-limiting, regime, where the current through the composite decreases with increasing voltage, a platelike dissipation instability develops normal to the applied field, in agreement with experimental observations, which is solely due to fluctuations in the microstructure
Petersson, K M; Nichols, T E; Poline, J B; Holmes, A P
1999-01-01
Functional neuroimaging (FNI) provides experimental access to the intact living brain making it possible to study higher cognitive functions in humans. In this review and in a companion paper in this issue, we discuss some common methods used to analyse FNI data. The emphasis in both papers is on assumptions and limitations of the methods reviewed. There are several methods available to analyse FNI data indicating that none is optimal for all purposes. In order to make optimal use of the methods available it is important to know the limits of applicability. For the interpretation of FNI results it is also important to take into account the assumptions, approximations and inherent limitations of the methods used. This paper gives a brief overview over some non-inferential descriptive methods and common statistical models used in FNI. Issues relating to the complex problem of model selection are discussed. In general, proper model selection is a necessary prerequisite for the validity of the subsequent statistical inference. The non-inferential section describes methods that, combined with inspection of parameter estimates and other simple measures, can aid in the process of model selection and verification of assumptions. The section on statistical models covers approaches to global normalization and some aspects of univariate, multivariate, and Bayesian models. Finally, approaches to functional connectivity and effective connectivity are discussed. In the companion paper we review issues related to signal detection and statistical inference. PMID:10466149
Prediction of phenanthrene uptake by plants with a partition-limited model
International Nuclear Information System (INIS)
Zhu, Lizhong; Gao, Yanzheng
2004-01-01
The performance of a partition-limited model on prediction of phenanthrene uptake by a wide variety of plant species was evaluated using a greenhouse study. The model predictions of root or shoot concentrations for tested plant species were all within an order of magnitude of the observed values. Modeled root concentrations appeared to be more accurate than modeled shoot concentrations. The differences of simulated and experimented concentrations of phenanthrene in roots and shoots of three representative plant species, including ryegrass, flowering Chinese cabbage, and three-colored amaranth, were less than 81% for roots and 103% for shoots. Results are promising in that the α pt values of the partition-limited model for root uptake of phenanthrene correlate well with root lipid contents. Additionally, a significantly positive correlation is also observed between root concentration factors (RCFs, defined as the ratio of contaminant concentrations in root and in soil on a dry weight basis) of phenanthrene and root lipid contents. Results from this study suggest that the partition-limited model may have potential applications for predicting the plant PAH concentration in contaminated sites
Limits of performance for the model reduction problem of hidden Markov models
Kotsalis, Georgios
2015-12-15
We introduce system theoretic notions of a Hankel operator, and Hankel norm for hidden Markov models. We show how the related Hankel singular values provide lower bounds on the norm of the difference between a hidden Markov model of order n and any lower order approximant of order n̂ < n.
Limits of performance for the model reduction problem of hidden Markov models
Kotsalis, Georgios; Shamma, Jeff S.
2015-01-01
We introduce system theoretic notions of a Hankel operator, and Hankel norm for hidden Markov models. We show how the related Hankel singular values provide lower bounds on the norm of the difference between a hidden Markov model of order n and any lower order approximant of order n̂ < n.
Annealed central limit theorems for the ising model on random graphs
Giardinà, C.; Giberti, C.; van der Hofstad, R.W.; Prioriello, M.L.
2016-01-01
The aim of this paper is to prove central limit theorems with respect to the annealed measure for the magnetization rescaled by √N of Ising models on random graphs. More precisely, we consider the general rank-1 inhomogeneous random graph (or generalized random graph), the 2-regular configuration
Ha, Minsu; Nehm, Ross H.; Urban-Lurain, Mark; Merrill, John E.
2011-01-01
Our study explored the prospects and limitations of using machine-learning software to score introductory biology students' written explanations of evolutionary change. We investigated three research questions: 1) Do scoring models built using student responses at one university function effectively at another university? 2) How many human-scored…
A two-queue model with alternating limited service and state-dependent setups
Winands, E.M.M.; Adan, I.J.B.F.; Houtum, van G.J.J.A.N.; Papadopoulos, C.T.
2005-01-01
We consider a two-queue model with state-dependent setups, in which a single server alternately serves the two queues. The high-priority queue is served exhaustively, whereas the low-priority queue is served according to the k-limited strategy. We obtain the transforms of the queue length and
The role of extreme drought events in modelling the distribution of beech at its xeric limit
Rasztovits, Ervin; Berki, Imre; Eredics, Attila; Móricz, Norbert
2014-05-01
Context: Projections of species distribution models (SDMs) for future climate conditions are based on long term mean climate data. For management and conservation issues SDMs have been extensively used, but it is not tested whether models that are successful in predicting current distributions are equally powerful in predicting distributions under future climates. Methods: Observations after 2003 confirms that extreme drought events played an important role in driving beech mortality at low-elevation xeric limits. The objective of this study was (1) to set up a simple extreme drought event based vitality model (EDM) using sanitary logging information as a proxy of vitality response of beech and (2) to compare the spatial pattern of the predicted vitality loss provided by the EDM with the distribution limits of the SDMs for three terms (2025, 2050 and 2100) in Hungary to assess model performance. Results: Prediction for vitality loss for 2025 obtained from the EDM was in agreement with those of the SDM, but for the end of the century the EDM predicted a more serious decline in almost all regions of Hungary. Conclusion: The result of the comparison suggests that the increasing frequency and severity of extremes might play a more important role in limiting the distribution of beech in the future near to the xeric limit than long-term means.
Analyses of gust fronts by means of limited area NWP model outputs
Czech Academy of Sciences Publication Activity Database
Kašpar, Marek
67-68, - (2003), s. 559-572 ISSN 0169-8095 R&D Projects: GA ČR GA205/00/1451 Institutional research plan: CEZ:AV0Z3042911 Keywords : gust front * limited area NWP model * output Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 1.012, year: 2003
DEFF Research Database (Denmark)
Frutiger, Jerome; Abildskov, Jens; Sin, Gürkan
2015-01-01
Flammability data is needed to assess the risk of fire and explosions. This study presents a new group contribution (GC) model to predict the upper flammability limit UFL oforganic chemicals. Furthermore, it provides a systematic method for outlier treatment inorder to improve the parameter...
Scrape-off model and pumped-limiter design for reversed-field pinches (RFP)
International Nuclear Information System (INIS)
Embrechts, M.J.; Bathke, C.G.; Krakowski, R.A.
1983-01-01
In order to develop a better understanding of the plasma/first-wall interaction in an RFP configuration, the models being developed to describe edgeplasma and scrapeoff regions for the tokamak have been adopted. Specifically, a scrapeoff model similar to the one developed and used for the tokamak FED design is used to model the parameter range where pumped limiters may be applied to the compact RFP. The one-dimensional, steady-state heat and particle equations are solved in the scrapeoff layer for an RFP geometry, assuming equal electron and ion temperature and density, convective transport along field lines, and Bohm-like diffusion. All charge-exchange and radiation effects are assumed to take place in the region between plasma and scrapeoff layer, and only a specific fraction of the total plasma energy will enter the scrapeoff layer in the form of conduction and convection. A simplified recycling model based on an effective recycling coefficient is used. For a given particle and energy flux entering the scrapeoff and for specified relationships between the particle flux and the energy flux near the first wall, the temperature and density profiles in the scrapeoff layer region are determined. The shape of the limiter surface is determined iteratively for a specified number of poloidal limiters by specifying a constant (design) heat flux for the limiter surfaces
Suchetana, Bihu; Rajagopalan, Balaji; Silverstein, JoAnn
2017-11-15
A regression tree-based diagnostic approach is developed to evaluate factors affecting US wastewater treatment plant compliance with ammonia discharge permit limits using Discharge Monthly Report (DMR) data from a sample of 106 municipal treatment plants for the period of 2004-2008. Predictor variables used to fit the regression tree are selected using random forests, and consist of the previous month's effluent ammonia, influent flow rates and plant capacity utilization. The tree models are first used to evaluate compliance with existing ammonia discharge standards at each facility and then applied assuming more stringent discharge limits, under consideration in many states. The model predicts that the ability to meet both current and future limits depends primarily on the previous month's treatment performance. With more stringent discharge limits predicted ammonia concentration relative to the discharge limit, increases. In-sample validation shows that the regression trees can provide a median classification accuracy of >70%. The regression tree model is validated using ammonia discharge data from an operating wastewater treatment plant and is able to accurately predict the observed ammonia discharge category approximately 80% of the time, indicating that the regression tree model can be applied to predict compliance for individual treatment plants providing practical guidance for utilities and regulators with an interest in controlling ammonia discharges. The proposed methodology is also used to demonstrate how to delineate reliable sources of demand and supply in a point source-to-point source nutrient credit trading scheme, as well as how planners and decision makers can set reasonable discharge limits in future. Copyright © 2017 Elsevier B.V. All rights reserved.
A composite state method for ensemble data assimilation with multiple limited-area models
Directory of Open Access Journals (Sweden)
Matthew Kretschmer
2015-04-01
Full Text Available Limited-area models (LAMs allow high-resolution forecasts to be made for geographic regions of interest when resources are limited. Typically, boundary conditions for these models are provided through one-way boundary coupling from a coarser resolution global model. Here, data assimilation is considered in a situation in which a global model supplies boundary conditions to multiple LAMs. The data assimilation method presented combines information from all of the models to construct a single ‘composite state’, on which data assimilation is subsequently performed. The analysis composite state is then used to form the initial conditions of the global model and all of the LAMs for the next forecast cycle. The method is tested by using numerical experiments with simple, chaotic models. The results of the experiments show that there is a clear forecast benefit to allowing LAM states to influence one another during the analysis. In addition, adding LAM information at analysis time has a strong positive impact on global model forecast performance, even at points not covered by the LAMs.
DEFF Research Database (Denmark)
Buchholz, Jörg
2007-01-01
Masked thresholds were measured for a single test reflection, masked by the direct sound, as a function of the reflection delay. This was done for diotic as well as for dichotic stimulus presentations and all stimuli were presented via headphones. The input signal was a 200-ms long broadband noise......, such as normalized cross-correlation models (e.g., Bernstein et al., 1999, JASA, pp. 870-876), the power-addition model (Zurek, 1979, JASA, pp. 1750-1757), or Equalization-Cancellation-based models (e.g., Breebaart et al., 2001, JASA, pp. 1074-1088), cannot account for the psychoacoustical data. The present talk...
Ultimate Limit State Model Basis for Assessment of Offshore Wind Energy Converters
DEFF Research Database (Denmark)
Thöns, Sebastian; Faber, M. H.; Rücker, W.
2012-01-01
then in combina-tion with the ultimate limit state requirements leads to the specific constitutive relations. As a result finite element models based on shell elements incorporating a structural and a loading model are introduced and described in detail. Applying these models the ultimate capacity of the support...... on the basis of literature review and measurement data from a prototype Multibrid M5000 support structure. In combination with the developed structural and loading models, sensitivity analyses in regard to the responses are peiformed to enhance the understanding and to refine the developed models. To this end...... variables on the responses including nonlinearity the refinement of the model is performed on a quantitative basis....
International Nuclear Information System (INIS)
Kim, Man Cheol; Jang, Seung Cheol; Ha, Jae Joo
2007-01-01
It is generally known that software reliability growth models such as the Jelinski-Moranda model and the Goel-Okumoto's Non-Homogeneous Poisson Process (NHPP) model cannot be applied to safety-critical software due to a lack of software failure data. In this paper, by applying two of the most widely known software reliability growth models to sample software failure data, we demonstrate the possibility of using the software reliability growth models to prove the high reliability of safety-critical software. The high sensitivity of a piece of software's reliability to software failure data, as well as a lack of sufficient software failure data, is also identified as a possible limitation when applying the software reliability growth models to safety-critical software
International Nuclear Information System (INIS)
Webb, G.A.M.; Grimwood, P.D.
1976-12-01
This report describes an oceanographic model which has been developed for the use in calculating the capacity of the oceans to accept radioactive wastes. One component is a relatively short-term diffusion model which is based on that described in an earlier report (Webb et al., NRPB-R14(1973)), but which has been generalised to some extent. Another component is a compartment model which is used to calculate long-term widespread water concentrations. This addition overcomes some of the short comings of the earlier diffusion model. Incorporation of radioactivity into deep ocean sediments is included in this long-term model as a removal mechanism. The combined model is used to provide a conservative (safe) estimate of the maximum concentrations of radioactivity in water as a function of time after the start of a continuous disposal operation. These results can then be used to assess the limiting capacity of an ocean to accept radioactive waste. (author)
New self-limiting assembly model for Si quantum rings on Si(100).
Yu, L W; Chen, K J; Song, J; Xu, J; Li, W; Li, X F; Wang, J M; Huang, X F
2007-04-20
We propose a new self-limiting assembly model for Si quantum rings on Si(100) where the ring's formation and evolution are driven by a growth-etching competition mechanism. The as-grown ring structure in a plasma enhanced chemical vapor deposition system has excellent rotational symmetry and superior morphology with a typical diameter, edge width, and height of 150-300, 10, and 5 nm, respectively. Based on this model, the size and morphology can be controlled well by simply tuning the timing procedure. We suggest that this growth model is not limited to certain material system, but provides a general scheme to control and tailor the self-assembly nanostructures into the desired size, shape, and complexity.
Stochastic models for structured populations scaling limits and long time behavior
Meleard, Sylvie
2015-01-01
In this contribution, several probabilistic tools to study population dynamics are developed. The focus is on scaling limits of qualitatively different stochastic individual based models and the long time behavior of some classes of limiting processes. Structured population dynamics are modeled by measure-valued processes describing the individual behaviors and taking into account the demographic and mutational parameters, and possible interactions between individuals. Many quantitative parameters appear in these models and several relevant normalizations are considered, leading to infinite-dimensional deterministic or stochastic large-population approximations. Biologically relevant questions are considered, such as extinction criteria, the effect of large birth events, the impact of environmental catastrophes, the mutation-selection trade-off, recovery criteria in parasite infections, genealogical properties of a sample of individuals. These notes originated from a lecture series on Structured P...
Bernhardt, Paul W; Wang, Huixia Judy; Zhang, Daowen
2014-01-01
Models for survival data generally assume that covariates are fully observed. However, in medical studies it is not uncommon for biomarkers to be censored at known detection limits. A computationally-efficient multiple imputation procedure for modeling survival data with covariates subject to detection limits is proposed. This procedure is developed in the context of an accelerated failure time model with a flexible seminonparametric error distribution. The consistency and asymptotic normality of the multiple imputation estimator are established and a consistent variance estimator is provided. An iterative version of the proposed multiple imputation algorithm that approximates the EM algorithm for maximum likelihood is also suggested. Simulation studies demonstrate that the proposed multiple imputation methods work well while alternative methods lead to estimates that are either biased or more variable. The proposed methods are applied to analyze the dataset from a recently-conducted GenIMS study.
Modelling transport-limited discharge capacity of lithium-sulfur cells
International Nuclear Information System (INIS)
Zhang, Teng; Marinescu, Monica; Walus, Sylwia; Offer, Gregory J.
2016-01-01
Highlights: • We modelled the rate capability of a Li-S cell based on mass-transport limitation • The model predicts a discharged Li-S cell to regain capacity upon short relaxation • Modelled rate capability and capacity recovery effect validated with measurements - Abstract: Lithium-sulfur (Li-S) battery could bring a step-change in battery technology with a potential specific energy density of 500 - 600 Wh/kg. A key challenge for further improving the specific energy-density of Li-S cells is to understand the mechanisms behind reduced sulfur utilisation at low electrolyte loadings and high discharge currents. While several Li-S models have been developed to explore the discharge mechanisms of Li-S cells, they so far fail to capture the discharge profiles at high currents. In this study, we propose that the slow ionic transport in concentrated electrolyte is limiting the rate capability of Li-S cells. This transport-limitation mechanism is demonstrated through a one-dimensional Li-S model which qualitatively captures the discharge capacities of a sulfolane-based Li-S cell at different currents. Furthermore, our model predicts that a discharged Li-S cell is able regain some capacity with a short period of relaxation. This capacity recovery phenomenon is validated experimentally for different discharge currents and relaxation durations. The transport-limited discharge behavior of Li-S cells highlights the importance of optimizing the electrolyte loading and electrolyte transport property in Li-S cells.
Nitrogen limitation on land: how can it occur in Earth system models?
Thomas, R Quinn; Brookshire, E N Jack; Gerber, Stefan
2015-05-01
The representation of the nitrogen (N) cycle in Earth system models (ESMs) is strongly motivated by the constraint N poses on the sequestration of anthropogenic carbon (C). Models typically implement a stoichiometric relationship between C and N in which external supply and assimilation by organisms are adjusted to maintain their internal stoichiometry. N limitation of primary productivity thus occurs if the N supply from uptake and fixation cannot keep up with the construction of tissues allowed by C assimilation. This basic approach, however, presents considerable challenges in how to faithfully represent N limitation. Here, we review how N limitation is currently implemented and evaluated in ESMs and highlight challenges and opportunities in their future development. At or near steady state, N limitation is governed by the magnitude of losses from the plant-unavailable pool vs. N fixation and there are considerable differences in how models treat both processes. In nonsteady-state systems, the accumulation of N in pools with slow turnover rates reduces N available for plant uptake and can be challenging to represent when initializing ESM simulations. Transactional N limitation occurs when N is incorporated into various vegetation and soil pools and becomes available to plants only after it is mineralized, the dynamics of which depends on how ESMs represent decomposition processes in soils. Other challenges for ESMs emerge when considering seasonal to interannual climatic oscillations as they create asynchronies between C and N demand, leading to transient alternations between N surplus and deficit. Proper evaluation of N dynamics in ESMs requires conceptual understanding of the main levers that trigger N limitation, and we highlight key measurements and observations that can help constrain these levers. Two of the biggest challenges are the mechanistic representation of plant controls on N availability and turnover, including N fixation and organic matter
Limitations to the use of two-dimensional thermal modeling of a nuclear waste repository
International Nuclear Information System (INIS)
Davis, B.W.
1979-01-01
Thermal modeling of a nuclear waste repository is basic to most waste management predictive models. It is important that the modeling techniques accurately determine the time-dependent temperature distribution of the waste emplacement media. Recent modeling studies show that the time-dependent temperature distribution can be accurately modeled in the far-field using a 2-dimensional (2-D) planar numerical model; however, the near-field cannot be modeled accurately enough by either 2-D axisymmetric or 2-D planar numerical models for repositories in salt. The accuracy limits of 2-D modeling were defined by comparing results from 3-dimensional (3-D) TRUMP modeling with results from both 2-D axisymmetric and 2-D planar. Both TRUMP and ADINAT were employed as modeling tools. Two-dimensional results from the finite element code, ADINAT were compared with 2-D results from the finite difference code, TRUMP; they showed almost perfect correspondence in the far-field. This result adds substantially to confidence in future use of ADINAT and its companion stress code ADINA for thermal stress analysis. ADINAT was found to be somewhat sensitive to time step and mesh aspect ratio. 13 figures, 4 tables
A Study on Stability of Limit Cycle Walking Model with Feet: Parameter Study
Directory of Open Access Journals (Sweden)
Yonggwon Jeon
2013-01-01
Full Text Available In this paper, two kinds of feet, namely, curved and flat feet, are added to limit cycle walking model to investigate its stability properties. Although both models are already proposed and are investigated, most previous works are focused on efficiency and gait behaviors. Only the stability properties of the simplest walking model conceived Garcia et al. are well defined. Therefore, there is still a need for a precise research on the effect of feet, especially in the view of local stability, bifurcation route to chaos, global stability, falling boundary and energy balance line. Therefore, this article revisits the stability analysis of limit cycle walking model with various foot shape. To analyze the effects of feet, we re-derive the equation of motion of modified models by adding one more parameter of foot shape than the simplest walking model. Also, the falling boundary and energy balance line of modified models are derived to get proper initial conditions for stable walking and to explain global stability. Simulation results show us that the curved feet can enlarge both stable walking range and area of basin of attraction while the case of flat feet depends on foot shape parameter.
Modeling T-cell proliferation: an investigation of the consequences of the Hayflick limit.
Pilyugin, S; Mittler, J; Antia, R
1997-05-07
Somatic cells, including immune cells such as T-cells have a limited capacity for proliferation and can only replicate for a finite number of generations (known as the Hayflick limit) before dying. In this paper we use mathematical models to investigate the consequences of introducing a Hayflick limit on the dynamics of T-cells stimulated with specific antigen. We show that while the Hayflick limit does not alter the dynamics of T-cell response to antigen over the short term, it may have a profound effect on the long-term immune response. In particular we show that over the long term the Hayflick limit may be important in determining whether an immune response can be maintained to a persistent antigen (or parasite). The eventual outcome is determined by the magnitude of the Hayflick limit, the extent to which antigen reduces the input of T-cells from the thymus, and the rate of antigen-induced proliferation of T-cells. Counter to what might be expected we show that the persistence of an immune response (immune memory) requires the density of persistent antigen to be less than a defined threshold value. If the amount of persistent antigen (or parasite) is greater than this threshold value then immune memory will be relatively short lived. The consequences of this threshold for persistent mycobacterial and HIV infections and for the generation of vaccines are discussed.
On the zero mass limit of the non linear sigma model in four dimensions
International Nuclear Information System (INIS)
Gomes, M.; Koeberle, R.
The existence of the zero mass limit for the non-linear sigma-model in four dimensions is shown to all orders in renormalized perturbation theory. The main ingredient in the proof is the imposition of many current axial vector Ward identities and the tool used is Lowenstein's momentum-space subtraction procedure. Instead of introducing anisotropic symmetry breaking mass terms, which do not vanish in the symmetry limit, it is necessary to allow for 'soft' anisotropic derivative coupling in order to obtain the correct Ward indentities [pt
Model of alpha particle diffusion in the outer limiter shadow of TFTR
International Nuclear Information System (INIS)
Wang, S.; Academia Sinica, Hefei, Anhui; Zweben, S.J.
1996-05-01
A new code, Monte Carlo Collisional Stochastic Orbit Retracing (MCCSOR), has been developed to model the alpha particle loss signal as measured by the outer midplane scintillator detector in TFTR. The shadowing effects due to the outer limiters and the detector itself have been included, along with a pitch angle scattering and stochastic ripple diffusion. Shadowing by the outer limiters has a strong effect on both the magnitude and pitch angle distribution of the calculated loss. There is at least qualitative agreement between the calculated results and the experimental data
SU(6) quadrupole phonon model for even and odd nuclei and the SU(3) limit
Energy Technology Data Exchange (ETDEWEB)
Paar, V; Brant, S [Zagreb Univ. (Yugoslavia). Prirodoslovno Matematicki Fakultet; Canto, L F [Rio de Janeiro Univ. (Brazil). Inst. de Fisica; Leander, G [Lund Inst. of Tech. (Sweden). Dept. of Mathematical Physics; Oak Ridge National Lab., TN (USA)); Vouk, M [Zagreb Univ. (Yugoslavia). Computing Centre SRCE
1982-04-05
Analogous to the equivalence between the SU(6) quadrupole-phonon model (TQM) and the interacting boson model (IBM), the equivalence is pointed out for odd systems between the SU(6) particle quadrupole-phonon coupling model (PTQM) and the interacting boson-fermion model (IBFM). PTQM is formulated starting from the Dyson representation for the odd system. Different aspects of the SU(3) limit of TQM and PTQM are studied; the quadrupole-phonon block structure of rotational bands in even and odd nuclei and analytic expressions based on the coherent state; signature effects generated in PTQM; electromagnetic properties and correction factors for PTQM; overlaps of the PTQM analogs of Nilsson states with Coriolis-coupled Nilsson states and the relation to the rotational model representation.
Exploring the limits of the ``SNB'' multi-group diffusion nonlocal model
Brodrick, Jonathan; Ridgers, Christopher; Kingham, Robert
2014-10-01
A correct treatment of nonlocal transport in the presence of steep temperature gradients found in laser and inertial fusion plasmas has long been highly desirable over the use of an ad-hoc flux limiter. Therefore, an implementation of the ``SNB'' nonlocal model (G P Schurtz, P D Nicolaï & M Busquet, Phys. Plas. 7, 4238 (2000)) has been benchmarked against a fully-implicit kinetic code: IMPACT. A variety of scenarios, including relaxation of temperature sinusoids and Gaussians in addition to continuous laser heating have been investigated. Results highlight the effect of neglecting electron inertia (∂f1/∂ t) as well as question the feasibility of a nonlocal model that does not continuously track the evolution of the distribution function. Deviations from the Spitzer electric fields used in the model across steep gradients are also investigated. Regimes of validity for such a model are identified and discussed, and possible improvements to the model are suggested.
Continuous limit of a crowd motion and herding model: Analysis and numerical simulations
Pietschmann, Jan-Frederik
2011-11-01
In this paper we study the continuum limit of a cellular automaton model used for simulating human crowds with herding behaviour. We derive a system of non-linear partial differential equations resembling the Keller-Segel model for chemotaxis, however with a non-monotone interaction. The latter has interesting consequences on the behaviour of the model\\'s solutions, which we highlight in its analysis. In particular we study the possibility of stationary states, the formation of clusters and explore their connection to congestion. We also introduce an efficient numerical simulation approach based on an appropriate hybrid discontinuous Galerkin method, which in particular allows flexible treatment of complicated geometries. Extensive numerical studies also provide a better understanding of the strengths and shortcomings of the herding model, in particular we examine trapping effects of crowds behind nonconvex obstacles. © American Institute of Mathematical Sciences.
Photometric Modeling of a Cometary Nucleus: Taking Hapke Modeling to the Limit
Buratti, B. J.; Hicks, M. D.; Soderblom, L.; Hillier, J.; Britt, D.
2002-01-01
In the past two decades, photometric models developed by Bruce Hapke have been fit to a wide range of bodies in the Solar System: The Moon, Mercury, several asteroids, and many icy and rocky satellites. These models have enabled comparative descriptions of the physical attributes of planetary surfaces, including macroscopic roughness, particle size and size-distribution, the single scattering albedo, and the compaction state of the optically active portion of the regolith. One challenging type of body to observe and model, a cometary nucleus, awaited the first space based mission to obtain images unobscured by coma. The NASA-JPL Deep Space 1 Mission (DS1) encountered the short-period Jupiter-family comet 19/P Borrelly on September 22, 2001, about 8 days after perihelion. Prior to its closest approach of 2171 km, the remote-sensing package on the spacecraft obtained 25 CCD images of the comet, representing the first closeup, unobscured view of a comet's nucleus. At closest approach, corresponding to a resolution of 47 meters per pixel, the intensity of the coma was less than 1% of that of the nucleus. An unprecedented range of high solar phase angles (52-89 degrees), viewing geometries that are in general attainable only when a comet is active, enabled the first quantitative and disk-resolved modeling of surface photometric physical parameters.
A fully-online Neuro-Fuzzy model for flow forecasting in basins with limited data
Ashrafi, Mohammad; Chua, Lloyd Hock Chye; Quek, Chai; Qin, Xiaosheng
2017-02-01
Current state-of-the-art online neuro fuzzy models (NFMs) such as DENFIS (Dynamic Evolving Neural-Fuzzy Inference System) have been used for runoff forecasting. Online NFMs adopt a local learning approach and are able to adapt to changes continuously. The DENFIS model however requires upper/lower bound for normalization and also the number of rules increases monotonically. This requirement makes the model unsuitable for use in basins with limited data, since a priori data is required. In order to address this and other drawbacks of current online models, the Generic Self-Evolving Takagi-Sugeno-Kang (GSETSK) is adopted in this study for forecast applications in basins with limited data. GSETSK is a fully-online NFM which updates its structure and parameters based on the most recent data. The model does not require the need for historical data and adopts clustering and rule pruning techniques to generate a compact and up-to-date rule-base. GSETSK was used in two forecast applications, rainfall-runoff (a catchment in Sweden) and river routing (Lower Mekong River) forecasts. Each of these two applications was studied under two scenarios: (i) there is no prior data, and (ii) only limited data is available (1 year for the Swedish catchment and 1 season for the Mekong River). For the Swedish Basin, GSETSK model results were compared to available results from a calibrated HBV (Hydrologiska Byråns Vattenbalansavdelning) model. For the Mekong River, GSETSK results were compared against the URBS (Unified River Basin Simulator) model. Both comparisons showed that results from GSETSK are comparable with the physically based models, which were calibrated with historical data. Thus, even though GSETSK was trained with a very limited dataset in comparison with HBV or URBS, similar results were achieved. Similarly, further comparisons between GSETSK with DENFIS and the RBF (Radial Basis Function) models highlighted further advantages of GSETSK as having a rule-base (compared to
Juckett, D A
1987-03-01
A model is presented which proposes a specific cause-and-effect relationship between a limited cell division potential and the maximum lifespan of humans and other mammals. It is based on the clonal succession hypothesis of Kay which states that continually replicating cell beds (e.g. bone marrow, intestinal crypts, epidermis) could be composed of cells with short, well-defined division potentials. In this model, the cells of these beds are proposed to exist in an ordered hierarchy which establishes a specific sequence for cell divisions throughout the organism's lifespan. The depletion of division potential at all hierarchical levels leads to a loss of bed function and sets an intrinsic limit to species longevity. A specific hierarchy for cell proliferation is defined which allows the calculation of time to bed depletion and, ultimately, to organism mortality. The model allows the existence of a small number (n) of critical cell beds within the organism and defines organism death as the inability of any one of these beds to produce cells. The model is consistent with all major observations related to cellular and organismic aging. In particular, it links the PDLs (population doubling limit) observed for various species to their mean lifespan; it explains the slow decline in PDL as a function of age of the donor; it establishes a thermodynamically stable maximum lifespan for a disease-free population; and it can explain why tissue transplants outlive donors or hosts.
Ogden, F. L.
2017-12-01
HIgh performance computing and the widespread availabilities of geospatial physiographic and forcing datasets have enabled consideration of flood impact predictions with longer lead times and more detailed spatial descriptions. We are now considering multi-hour flash flood forecast lead times at the subdivision level in so-called hydroblind regions away from the National Hydrography network. However, the computational demands of such models are high, necessitating a nested simulation approach. Research on hyper-resolution hydrologic modeling over the past three decades have illustrated some fundamental limits on predictability that are simultaneously related to runoff generation mechanism(s), antecedent conditions, rates and total amounts of precipitation, discretization of the model domain, and complexity or completeness of the model formulation. This latter point is an acknowledgement that in some ways hydrologic understanding in key areas related to land use, land cover, tillage practices, seasonality, and biological effects has some glaring deficiencies. This presentation represents a review of what is known related to the interacting effects of precipitation amount, model spatial discretization, antecedent conditions, physiographic characteristics and model formulation completeness for runoff predictions. These interactions define a region in multidimensional forcing, parameter and process space where there are in some cases clear limits on predictability, and in other cases diminished uncertainty.
Colombant, Denis; Manheimer, Wallace; Busquet, Michel
2004-11-01
A simple steady-state model using flux-limiters by Day et al [1] showed that temperature profiles could formally be double-valued. Stability of temperature profiles in laser-driven temperature fronts using delocalization models was also discussed by Prasad and Kershaw [2]. We have observed steepening of the front and flattening of the maximum temperature in laser-driven implosions [3]. Following the simple model first proposed in [1], we solve for a two-boundary value steady-state heat flow problem for various non-local heat transport models. For the more complicated models [4,5], we obtain the steady-state solution as the asymptotic limit of the time-dependent solution. Solutions will be shown and compared for these various models. 1.M.Day, B.Merriman, F.Najmabadi and R.W.Conn, Contrib. Plasma Phys. 36, 419 (1996) 2.M.K.Prasad and D.S.Kershaw, Phys. Fluids B3, 3087 (1991) 3.D.Colombant, W.Manheimer and M.Busquet, Bull. Amer. Phys. Soc. 48, 326 (2003) 4.E.M.Epperlein and R.W.Short, Phys. Fluids B3, 3092 (1991) 5.W.Manheimer and D.Colombant, Phys. Plasmas 11, 260 (2004)
Global constraints on Z2 fluxes in two different anisotropic limits of a hypernonagon Kitaev model
Kato, Yasuyuki; Kamiya, Yoshitomo; Nasu, Joji; Motome, Yukitoshi
2018-05-01
The Kitaev model is an exactly-soluble quantum spin model, whose ground state provides a canonical example of a quantum spin liquid. Spin excitations from the ground state are fractionalized into emergent matter fermions and Z2 fluxes. The Z2 flux excitation is pointlike in two dimensions, while it comprises a closed loop in three dimensions because of the local constraint for each closed volume. In addition, the fluxes obey global constraints involving (semi)macroscopic number of fluxes. We here investigate such global constraints in the Kitaev model on a three-dimensional lattice composed of nine-site elementary loops, dubbed the hypernonagon lattice, whose ground state is a chiral spin liquid. We consider two different anisotropic limits of the hypernonagon Kitaev model where the low-energy effective models are described solely by the Z2 fluxes. We show that there are two kinds of global constraints in the model defined on a three-dimensional torus, namely, surface and volume constraints: the surface constraint is imposed on the even-odd parity of the total number of fluxes threading a two-dimensional slice of the system, while the volume constraint is for the even-odd parity of the number of the fluxes through specific plaquettes whose total number is proportional to the system volume. In the two anisotropic limits, therefore, the elementary excitation of Z2 fluxes occurs in a pair of closed loops so as to satisfy both two global constraints as well as the local constraints.
Poisson-Boltzmann theory of charged colloids: limits of the cell model for salty suspensions
International Nuclear Information System (INIS)
Denton, A R
2010-01-01
Thermodynamic properties of charge-stabilized colloidal suspensions and polyelectrolyte solutions are commonly modelled by implementing the mean-field Poisson-Boltzmann (PB) theory within a cell model. This approach models a bulk system by a single macroion, together with counterions and salt ions, confined to a symmetrically shaped, electroneutral cell. While easing numerical solution of the nonlinear PB equation, the cell model neglects microion-induced interactions and correlations between macroions, precluding modelling of macroion ordering phenomena. An alternative approach, which avoids the artificial constraints of cell geometry, exploits the mapping of a macroion-microion mixture onto a one-component model of pseudo-macroions governed by effective interparticle interactions. In practice, effective-interaction models are usually based on linear-screening approximations, which can accurately describe strong nonlinear screening only by incorporating an effective (renormalized) macroion charge. Combining charge renormalization and linearized PB theories, in both the cell model and an effective-interaction (cell-free) model, we compute osmotic pressures of highly charged colloids and monovalent microions, in Donnan equilibrium with a salt reservoir, over a range of concentrations. By comparing predictions with primitive model simulation data for salt-free suspensions, and with predictions from nonlinear PB theory for salty suspensions, we chart the limits of both the cell model and linear-screening approximations in modelling bulk thermodynamic properties. Up to moderately strong electrostatic couplings, the cell model proves accurate for predicting osmotic pressures of deionized (counterion-dominated) suspensions. With increasing salt concentration, however, the relative contribution of macroion interactions to the osmotic pressure grows, leading predictions from the cell and effective-interaction models to deviate. No evidence is found for a liquid
DEFF Research Database (Denmark)
Panovska, S.; Korte, M.; Finlay, Chris
2015-01-01
orientation is highlighted by inconsistencies in the West Pacific and Australian sediment records in CALS10k.1b model. Great care must also be taken to assess uncertainties associated with both paleomagnetic and age data and to evaluate the effects of poor data distribution. New consistently allocated....... This would be facilitated by realistic and globally consistent data and age uncertainties from the paleomagnetic community....
Directory of Open Access Journals (Sweden)
Roger Martin-Clouaire
Full Text Available Many farming-system studies have investigated the design and evaluation of crop-management practices with respect to economic performance and reduction in environmental impacts. In contrast, little research has been devoted to analysing these practices in terms of matching the recurrent context-dependent demand for resources (labour in particular with those available on the farm. This paper presents Dhivine, a simulation model of operational management of grape production at the vineyard scale. Particular attention focuses on representing a flexible plan, which organises activities temporally, the resources available to the vineyard manager and the process of scheduling and executing the activities. The model relies on a generic production-system ontology used in several agricultural production domains. The types of investigations that the model supports are briefly illustrated. The enhanced realism of the production-management situations simulated makes it possible to examine and understand properties of resource-constrained work-organisation strategies and possibilities for improving them.
Entry limitations and heterogeneous tolerances in a Schelling-like segregation model
International Nuclear Information System (INIS)
Radi, Davide; Gardini, Laura
2015-01-01
In this paper we consider a Schelling-type segregation model with two groups of agents that differ in some aspects, such as religion, political affiliation or color of skin. The first group is identified as the local population, while the second group is identified as the newcomers, whose members want to settle down in the city or country, or more generally a system, already populated by members of the local population. The members of the local population have a limited tolerance towards newcomers. On the contrary, some newcomers, but not all of them, may stand the presence of any amount of members of the local population. The heterogeneous, and partially limited, levels of tolerance trigger an entry and exit dynamics into and from the system of the members of the two groups based on their satisfaction with the number of members of the other group into the system. This entry/exit dynamics is described by a continuous piecewise-differentiable map in two dimensions. The dynamics of the model is characterized by smooth bifurcations as well as by border collision bifurcations. A combination of analytical results and numerical analysis are the main tools used to describe the quite complicated local and global dynamics of the model. The investigation reveals that two factors are the main elements that preclude integration. The first one is a low level of tolerance of the members of the two populations. The second one is an excessive and unbalanced level of tolerance between the two populations. In this last case, to facilitate the integration between members of the two groups, we impose an entry-limitation policy represented by the imposition of a maximum number of newcomers allowed to enter the system. The investigation of the dynamics reveals that the entry-limitation policy is useful to promote integration as it limits the negative effects due to excessive and unbalanced levels of tolerance.
Cellular modelling of river catchments and reaches: Advantages, limitations and prospects
Coulthard, T. J.; Hicks, D. M.; Van De Wiel, M. J.
2007-10-01
The last decade has witnessed the development of a series of cellular models that simulate the processes operating within river channels and drive their geomorphic evolution. Their proliferation can be partly attributed to the relative simplicity of cellular models and their ability to address some of the shortcomings of other numerical models. By using relaxed interpretations of the equations determining fluid flow, cellular models allow rapid solutions of water depths and velocities. These can then be used to drive (usually) conventional sediment transport relations to determine erosion and deposition and alter the channel form. The key advance of using these physically based yet simplified approaches is that they allow us to apply models to a range of spatial scales (1-100 km 2) and time periods (1-100 years) that are especially relevant to contemporary management and fluvial studies. However, these approaches are not without their limitations and technical problems. This paper reviews the findings of nearly 10 years of research into modelling fluvial systems with cellular techniques, principally focusing on improvements in routing water and how fluvial erosion and deposition (including lateral erosion) are represented. These ideas are illustrated using sample simulations of the River Teifi, Wales. A detailed case study is then presented, demonstrating how cellular models can explore the interactions between vegetation and the morphological dynamics of the braided Waitaki River, New Zealand. Finally, difficulties associated with model validation and the problems, prospects and future issues important to the further development and application of these cellular fluvial models are outlined.
Limit Theory for Panel Data Models with Cross Sectional Dependence and Sequential Exogeneity.
Kuersteiner, Guido M; Prucha, Ingmar R
2013-06-01
The paper derives a general Central Limit Theorem (CLT) and asymptotic distributions for sample moments related to panel data models with large n . The results allow for the data to be cross sectionally dependent, while at the same time allowing the regressors to be only sequentially rather than strictly exogenous. The setup is sufficiently general to accommodate situations where cross sectional dependence stems from spatial interactions and/or from the presence of common factors. The latter leads to the need for random norming. The limit theorem for sample moments is derived by showing that the moment conditions can be recast such that a martingale difference array central limit theorem can be applied. We prove such a central limit theorem by first extending results for stable convergence in Hall and Hedye (1980) to non-nested martingale arrays relevant for our applications. We illustrate our result by establishing a generalized estimation theory for GMM estimators of a fixed effect panel model without imposing i.i.d. or strict exogeneity conditions. We also discuss a class of Maximum Likelihood (ML) estimators that can be analyzed using our CLT.
Numerical modelling of pump limiter biasing on TEXTOR-94 and Tore Supra
International Nuclear Information System (INIS)
Gerhauser, H.; Claassen, H.A.; Mank, G.; Zagorski, R.; Loarer, T.; Gunn, J.; Boucher, C.
2002-01-01
The two-dimensional multifluid code TECXY has been used to model the biasing (with respect to the first wall) of the toroidal belt limiter ALT-II on the tokamak TEXTOR-94 and of the new toroidal pump limiter being installed on Tore Supra tokamak in the framework of the CIEL project. It is well known that the edge flow pattern can be influenced by the poloidal electric drifts from imposing radial electric fields. The modelling with TECXY introduces imprinted bias currents in the scrape-off layer (SOL) for the case of negative (limiter) biasing, and imprinted bias potentials for the case of positive biasing. This allowed us to simulate sufficiently well the experimental I-V characteristics for either biasing of ALT-II and also reproduced the essential features and trends of the observed plasma profiles in the SOL of TEXTOR-94. For negative biasing a moderate improvement of the pumping exhaust efficiency can be achieved in the case of TEXTOR. For Tore Supra, however, only a negligible improvement of the limiter performance with biasing can be predicted, which is explained by the relatively weak drift flows in Tore Supra. (author)
SITE-94. CAMEO: A model of mass-transport limited general corrosion of copper canisters
International Nuclear Information System (INIS)
Worgan, K.J.; Apted, M.J.
1996-12-01
This report describes the technical basis for the CAMEO code, which models the general, uniform corrosion of a copper canister either by transport of corrodants to the canister, or by transport of corrosion products away from the canister. According to the current Swedish concept for final disposal of spent nuclear fuels, extremely long containment times are achieved by thick (60-100 mm) copper canisters. Each canister is surrounded by a compacted bentonite buffer, located in a saturated, crystalline rock at a depth of around 500 m below ground level. Three diffusive transport-limited cases are identified for general, uniform corrosion of copper: General corrosion rate-limited by diffusive mass-transport of sulphide to the canister surface under reducing conditions; General corrosion rate-limited by diffusive mass-transport of oxygen to the canister surface under mildly oxidizing conditions; General corrosion rate-limited by diffusive mass-transport of copper chloride away from the canister surface under highly oxidizing conditions. The CAMEO code includes general corrosion models for each of the above three processes. CAMEO is based on the well-tested CALIBRE code previously developed as a finite-difference, mass-transfer analysis code for the SKI to evaluate long-term radionuclide release and transport in the near-field. A series of scoping calculations for the general, uniform corrosion of a reference copper canister are presented
Alternative model of space-charge-limited thermionic current flow through a plasma
Campanell, M. D.
2018-04-01
It is widely assumed that thermionic current flow through a plasma is limited by a "space-charge-limited" (SCL) cathode sheath that consumes the hot cathode's negative bias and accelerates upstream ions into the cathode. Here, we formulate a fundamentally different current-limited mode. In the "inverse" mode, the potentials of both electrodes are above the plasma potential, so that the plasma ions are confined. The bias is consumed by the anode sheath. There is no potential gradient in the neutral plasma region from resistivity or presheath. The inverse cathode sheath pulls some thermoelectrons back to the cathode, thereby limiting the circuit current. Thermoelectrons entering the zero-field plasma region that undergo collisions may also be sent back to the cathode, further attenuating the circuit current. In planar geometry, the plasma density is shown to vary linearly across the electrode gap. A continuum kinetic planar plasma diode simulation model is set up to compare the properties of current modes with classical, conventional SCL, and inverse cathode sheaths. SCL modes can exist only if charge-exchange collisions are turned off in the potential well of the virtual cathode to prevent ion trapping. With the collisions, the current-limited equilibrium must be inverse. Inverse operating modes should therefore be present or possible in many plasma devices that rely on hot cathodes. Evidence from past experiments is discussed. The inverse mode may offer opportunities to minimize sputtering and power consumption that were not previously explored due to the common assumption of SCL sheaths.
High-energy neutrino background: Limitations on models of deuterium production
International Nuclear Information System (INIS)
Eichler, D.
1979-01-01
It is pointed out that Epstein's model for deuterium production via high-energy spallation reactions produces high-energy neutrinos in sufficient quantity to stand out above those that are produced by cosmic-ray interactions in the Earth's atmosphere. That the Reines experiment detected neutrinos of atmospheric origin without detecting any cosmic component restricts deuterium production by spallation reactions to very high redshifts (z> or approx. =300). Improved neutrino experiments may be able to push these limits back to recombination
Comparison of the CREATE-L plasma response model with TCV limited discharges
International Nuclear Information System (INIS)
Villone, F.; Vyas, P.; Lister, J.B.; Albanese, R.
1997-02-01
Experiments have been performed on the TCV tokamak to evaluate the response of Ohmic-, L-Mode, limited, vertically unstable plasmas to changes in all the poloidal field coil voltages. The resulting closed loop plasma responses have been compared with the CREATE-L linearised MHD equilibrium model of TCV. All the responses in both the time domain and the frequency domain show excellent agreement both for directly measured quantities and for derived parameters which can be used as feedback variables. No modifications to the CREATE-L model were made to achieve this quality of agreement, indicating that the underlaying physical assumptions are appropriate. (author) 20 figs., 6 tabs., 16 refs
Comparison of the CREATE-L plasma response model with TCV limited discharges
International Nuclear Information System (INIS)
Villone, F.; Vyas, P.; Lister, J.B.; Albanese, R.
1997-01-01
Experiments have been performed on the TCV tokamak to evaluate the response of ohmic, L mode, limited, vertically unstable plasmas to changes in all the poloidal field coil voltages. The resulting closed loop plasma responses have been compared with the CREATE-L linearized MHD equilibrium model of the TCV tokamak. All the responses in both the time domain and the frequency domain show excellent agreement both for directly measured quantities and for derived parameters. No modifications to the CREATE-L model were made to achieve this quality of agreement, indicating that the underlying physical assumptions are appropriate. (author). 17 refs, 20 figs
Hopf Bifurcation of a Delayed Epidemic Model with Information Variable and Limited Medical Resources
Directory of Open Access Journals (Sweden)
Caijuan Yan
2014-01-01
Full Text Available We consider SIR epidemic model in which population growth is subject to logistic growth in absence of disease. We get the condition for Hopf bifurcation of a delayed epidemic model with information variable and limited medical resources. By analyzing the corresponding characteristic equations, the local stability of an endemic equilibrium and a disease-free equilibrium is discussed. If the basic reproduction ratio ℛ01, we obtain sufficient conditions under which the endemic equilibrium E* of system is locally asymptotically stable. And we also have discussed the stability and direction of Hopf bifurcations. Numerical simulations are carried out to explain the mathematical conclusions.
Numerical Modeling of Limiting Oxygen Index Apparatus for Film Type Fuels
Directory of Open Access Journals (Sweden)
Amit Kumar
2012-12-01
Full Text Available A detailed three-dimensional numerical model is used to compute the flow pattern and the flame behavior of thin solid fuels in a rectangular column that resembles a standard Limiting Oxygen Index (LOI device. The model includes full Navier-Stokes equations for mixed buoyant-forced flow and finite rate combustion and pyrolysis reactions so that the sample LOI can be computed to study the effect of feeding flow rate, sample width and gravity levels. In addition to the above parameters, the sample location in the column and the column cross-sectional area are also investigated on their effect on the ambient air entrainment from the top.
Cold aqueous planetary geochemistry with FREZCHEM from modeling to the search for life at the limits
Marion, Giles M
2007-01-01
This book explicitly investigates issues of astrobiological relevance in the context of cold aqueous planetary geochemistry. At the core of the technical chapters is the FREZCHEM model, initially developed over many years by one of the authors to quantify aqueous electrolyte properties and chemical thermodynamics at subzero temperatures. FREZCHEM, of general relevance to biogeochemists and geochemical modelers, cold planetary scientists, physicochemists and chemical engineers, is subsequently applied to the exploration of biogeochemical applications to solar systems bodies in general, and to speculations about the limits for life in cold environments in particular.
Testing the limits of the 'joint account' model of genetic information: a legal thought experiment.
Foster, Charles; Herring, Jonathan; Boyd, Magnus
2015-05-01
We examine the likely reception in the courtroom of the 'joint account' model of genetic confidentiality. We conclude that the model, as modified by Gilbar and others, is workable and reflects, better than more conventional legal approaches, both the biological and psychological realities and the obligations owed under Articles 8 and 10 of the European Convention on Human Rights (ECHR). Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.
Global dynamics in a stoichiometric food chain model with two limiting nutrients.
Chen, Ming; Fan, Meng; Kuang, Yang
2017-07-01
Ecological stoichiometry studies the balance of energy and multiple chemical elements in ecological interactions to establish how the nutrient content affect food-web dynamics and nutrient cycling in ecosystems. In this study, we formulate a food chain with two limiting nutrients in the form of a stoichiometric population model. A comprehensive global analysis of the rich dynamics of the targeted model is explored both analytically and numerically. Chaotic dynamic is observed in this simple stoichiometric food chain model and is compared with traditional model without stoichiometry. The detailed comparison reveals that stoichiometry can reduce the parameter space for chaotic dynamics. Our findings also show that decreasing producer production efficiency may have only a small effect on the consumer growth but a more profound impact on the top predator growth. Copyright © 2017 Elsevier Inc. All rights reserved.
On determining the prediction limits of mathematical models for time series
International Nuclear Information System (INIS)
Peluso, E.; Gelfusa, M.; Lungaroni, M.; Talebzadeh, S.; Gaudio, P.; Murari, A.; Contributors, JET
2016-01-01
Prediction is one of the main objectives of scientific analysis and it refers to both modelling and forecasting. The determination of the limits of predictability is an important issue of both theoretical and practical relevance. In the case of modelling time series, reached a certain level in performance in either modelling or prediction, it is often important to assess whether all the information available in the data has been exploited or whether there are still margins for improvement of the tools being developed. In this paper, an information theoretic approach is proposed to address this issue and quantify the quality of the models and/or predictions. The excellent properties of the proposed indicator have been proved with the help of a systematic series of numerical tests and a concrete example of extreme relevance for nuclear fusion.
Abellán-Nebot, J. V.; Liu, J.; Romero, F.
2009-11-01
The State Space modelling approach has been recently proposed as an engineering-driven technique for part quality prediction in Multistage Machining Processes (MMP). Current State Space models incorporate fixture and datum variations in the multi-stage variation propagation, without explicitly considering common operation variations such as machine-tool thermal distortions, cutting-tool wear, cutting-tool deflections, etc. This paper shows the limitations of the current State Space model through an experimental case study where the effect of the spindle thermal expansion, cutting-tool flank wear and locator errors are introduced. The paper also discusses the extension of the current State Space model to include operation variations and its potential benefits.
Continuous limit of a crowd motion and herding model: Analysis and numerical simulations
Pietschmann, Jan-Frederik; Markowich, Peter Alexander; Burger, Martin
2011-01-01
In this paper we study the continuum limit of a cellular automaton model used for simulating human crowds with herding behaviour. We derive a system of non-linear partial differential equations resembling the Keller-Segel model for chemotaxis, however with a non-monotone interaction. The latter has interesting consequences on the behaviour of the model's solutions, which we highlight in its analysis. In particular we study the possibility of stationary states, the formation of clusters and explore their connection to congestion. We also introduce an efficient numerical simulation approach based on an appropriate hybrid discontinuous Galerkin method, which in particular allows flexible treatment of complicated geometries. Extensive numerical studies also provide a better understanding of the strengths and shortcomings of the herding model, in particular we examine trapping effects of crowds behind nonconvex obstacles. © American Institute of Mathematical Sciences.
Lefkimmiatis, Stamatios; Maragos, Petros; Papandreou, George
2009-08-01
We present an improved statistical model for analyzing Poisson processes, with applications to photon-limited imaging. We build on previous work, adopting a multiscale representation of the Poisson process in which the ratios of the underlying Poisson intensities (rates) in adjacent scales are modeled as mixtures of conjugate parametric distributions. Our main contributions include: 1) a rigorous and robust regularized expectation-maximization (EM) algorithm for maximum-likelihood estimation of the rate-ratio density parameters directly from the noisy observed Poisson data (counts); 2) extension of the method to work under a multiscale hidden Markov tree model (HMT) which couples the mixture label assignments in consecutive scales, thus modeling interscale coefficient dependencies in the vicinity of image edges; 3) exploration of a 2-D recursive quad-tree image representation, involving Dirichlet-mixture rate-ratio densities, instead of the conventional separable binary-tree image representation involving beta-mixture rate-ratio densities; and 4) a novel multiscale image representation, which we term Poisson-Haar decomposition, that better models the image edge structure, thus yielding improved performance. Experimental results on standard images with artificially simulated Poisson noise and on real photon-limited images demonstrate the effectiveness of the proposed techniques.
Omrani, H.; Drobinski, P.; Dubos, T.
2009-09-01
In this work, we consider the effect of indiscriminate nudging time on the large and small scales of an idealized limited area model simulation. The limited area model is a two layer quasi-geostrophic model on the beta-plane driven at its boundaries by its « global » version with periodic boundary condition. This setup mimics the configuration used for regional climate modelling. Compared to a previous study by Salameh et al. (2009) who investigated the existence of an optimal nudging time minimizing the error on both large and small scale in a linear model, we here use a fully non-linear model which allows us to represent the chaotic nature of the atmosphere: given the perfect quasi-geostrophic model, errors in the initial conditions, concentrated mainly in the smaller scales of motion, amplify and cascade into the larger scales, eventually resulting in a prediction with low skill. To quantify the predictability of our quasi-geostrophic model, we measure the rate of divergence of the system trajectories in phase space (Lyapunov exponent) from a set of simulations initiated with a perturbation of a reference initial state. Predictability of the "global", periodic model is mostly controlled by the beta effect. In the LAM, predictability decreases as the domain size increases. Then, the effect of large-scale nudging is studied by using the "perfect model” approach. Two sets of experiments were performed: (1) the effect of nudging is investigated with a « global » high resolution two layer quasi-geostrophic model driven by a low resolution two layer quasi-geostrophic model. (2) similar simulations are conducted with the two layer quasi-geostrophic LAM where the size of the LAM domain comes into play in addition to the first set of simulations. In the two sets of experiments, the best spatial correlation between the nudge simulation and the reference is observed with a nudging time close to the predictability time.
Synthesizing modeling of power generation and power limits in energy systems
International Nuclear Information System (INIS)
Sieniutycz, Stanislaw
2015-01-01
Applying the common mathematical procedure of thermodynamic optimization the paper offers a synthesizing or generalizing modeling of power production in various energy generators, such as thermal, solar and electrochemical engines (fuel cells). Static and dynamical power systems are investigated. Dynamical models take into account the gradual downgrading of a resource, caused by power delivery. Analytical modeling includes conversion efficiencies expressed in terms of driving fluxes. Products of efficiencies and driving fluxes determine the power yield and power maxima. While optimization of static systems requires using of differential calculus and Lagrange multipliers, dynamic optimization involves variational calculus and dynamic programming. In reacting mixtures balances of mass and energy serve to derive power yield in terms of an active part of chemical affinity. Power maximization approach is also applied to fuel cells treated as flow engines driven by heat flux and fluxes of chemical reagents. The results of power maxima provide limiting indicators for thermal, solar and SOFC generators. They are more exact than classical reversible limits of energy transformation. - Highlights: • Systematic evaluation of power limits by optimization. • Common thermodynamic methodology for engine systems. • Original, in-depth study of power maxima. • Inclusion of fuel cells to a class of thermodynamic power systems
Limitations of demand- and pressure-driven modeling for large deficient networks
Braun, Mathias; Piller, Olivier; Deuerlein, Jochen; Mortazavi, Iraj
2017-10-01
The calculation of hydraulic state variables for a network is an important task in managing the distribution of potable water. Over the years the mathematical modeling process has been improved by numerous researchers for utilization in new computer applications and the more realistic modeling of water distribution networks. But, in spite of these continuous advances, there are still a number of physical phenomena that may not be tackled correctly by current models. This paper will take a closer look at the two modeling paradigms given by demand- and pressure-driven modeling. The basic equations are introduced and parallels are drawn with the optimization formulations from electrical engineering. These formulations guarantee the existence and uniqueness of the solution. One of the central questions of the French and German research project ResiWater is the investigation of the network resilience in the case of extreme events or disasters. Under such extraordinary conditions where models are pushed beyond their limits, we talk about deficient network models. Examples of deficient networks are given by highly regulated flow, leakage or pipe bursts and cases where pressure falls below the vapor pressure of water. These examples will be presented and analyzed on the solvability and physical correctness of the solution with respect to demand- and pressure-driven models.
PROBLEMS AND LIMITATIONS OF SATELLITE IMAGE ORIENTATION FOR DETERMINATION OF HEIGHT MODELS
Directory of Open Access Journals (Sweden)
K. Jacobsen
2017-05-01
Full Text Available The usual satellite image orientation is based on bias corrected rational polynomial coefficients (RPC. The RPC are describing the direct sensor orientation of the satellite images. The locations of the projection centres today are without problems, but an accuracy limit is caused by the attitudes. Very high resolution satellites today are very agile, able to change the pointed area over 200km within 10 to 11 seconds. The corresponding fast attitude acceleration of the satellite may cause a jitter which cannot be expressed by the third order RPC, even if it is recorded by the gyros. Only a correction of the image geometry may help, but usually this will not be done. The first indication of jitter problems is shown by systematic errors of the y-parallaxes (py for the intersection of corresponding points during the computation of ground coordinates. These y-parallaxes have a limited influence to the ground coordinates, but similar problems can be expected for the x-parallaxes, determining directly the object height. Systematic y-parallaxes are shown for Ziyuan-3 (ZY3, WorldView-2 (WV2, Pleiades, Cartosat-1, IKONOS and GeoEye. Some of them have clear jitter effects. In addition linear trends of py can be seen. Linear trends in py and tilts in of computed height models may be caused by limited accuracy of the attitude registration, but also by bias correction with affinity transformation. The bias correction is based on ground control points (GCPs. The accuracy of the GCPs usually does not cause some limitations but the identification of the GCPs in the images may be difficult. With 2-dimensional bias corrected RPC-orientation by affinity transformation tilts of the generated height models may be caused, but due to large affine image deformations some satellites, as Cartosat-1, have to be handled with bias correction by affinity transformation. Instead of a 2-dimensional RPC-orientation also a 3-dimensional orientation is possible, respecting the
Problems and Limitations of Satellite Image Orientation for Determination of Height Models
Jacobsen, K.
2017-05-01
The usual satellite image orientation is based on bias corrected rational polynomial coefficients (RPC). The RPC are describing the direct sensor orientation of the satellite images. The locations of the projection centres today are without problems, but an accuracy limit is caused by the attitudes. Very high resolution satellites today are very agile, able to change the pointed area over 200km within 10 to 11 seconds. The corresponding fast attitude acceleration of the satellite may cause a jitter which cannot be expressed by the third order RPC, even if it is recorded by the gyros. Only a correction of the image geometry may help, but usually this will not be done. The first indication of jitter problems is shown by systematic errors of the y-parallaxes (py) for the intersection of corresponding points during the computation of ground coordinates. These y-parallaxes have a limited influence to the ground coordinates, but similar problems can be expected for the x-parallaxes, determining directly the object height. Systematic y-parallaxes are shown for Ziyuan-3 (ZY3), WorldView-2 (WV2), Pleiades, Cartosat-1, IKONOS and GeoEye. Some of them have clear jitter effects. In addition linear trends of py can be seen. Linear trends in py and tilts in of computed height models may be caused by limited accuracy of the attitude registration, but also by bias correction with affinity transformation. The bias correction is based on ground control points (GCPs). The accuracy of the GCPs usually does not cause some limitations but the identification of the GCPs in the images may be difficult. With 2-dimensional bias corrected RPC-orientation by affinity transformation tilts of the generated height models may be caused, but due to large affine image deformations some satellites, as Cartosat-1, have to be handled with bias correction by affinity transformation. Instead of a 2-dimensional RPC-orientation also a 3-dimensional orientation is possible, respecting the object height
WCSPH with Limiting Viscosity for Modeling Landslide Hazard at the Slopes of Artificial Reservoir
Directory of Open Access Journals (Sweden)
Sauro Manenti
2018-04-01
Full Text Available This work illustrated an application of the FOSS code SPHERA v.8.0 (RSE SpA, Milano, Italy to the simulation of landslide hazard at the slope of a water basin. SPHERA is based on the weakly compressible SPH method (WCSPH and holds a mixture model, consistent with the packing limit of the Kinetic Theory of Granular Flow (KTGF, which was previously tested for simulating two-phase free-surface rapid flows involving water-sediment interaction. In this study a limiting viscosity parameter was implemented in the previous formulation of the mixture model to limit the growth of the apparent viscosity, thus saving computational time while preserving the solution accuracy. This approach is consistent with the experimental behavior of high polymer solutions for which an almost constant value of viscosity may be approached at very low deformation rates near the transition zone of elastic–plastic regime. In this application, the limiting viscosity was used as a numerical parameter for optimization of the computation. Some preliminary tests were performed by simulating a 2D erosional dam break, proving that a proper selection of the limiting viscosity leads to a considerable drop of the computational time without altering significantly the numerical solution. SPHERA was then validated by simulating a 2D scale experiment reproducing the early phase of the Vajont landslide when a tsunami wave was generated that climbed the opposite mountain side with a maximum run-up of about 270 m. The obtained maximum run-up was very close to the experimental result. Influence of saturation of the landslide material below the still water level was also accounted, showing that the landslide dynamics can be better represented and the wave run-up can be properly estimated.
Species distribution modeling in regions of high need and limited data: waterfowl of China
Prosser, Diann J.; Ding, Changqing; Erwin, R. Michael; Mundkur, Taej; Sullivan, Jeffery D.; Ellis, Erle C.
2018-01-01
BackgroundA number of conservation and societal issues require understanding how species are distributed on the landscape, yet ecologists are often faced with a lack of data to develop models at the resolution and extent desired, resulting in inefficient use of conservation resources. Such a situation presented itself in our attempt to develop waterfowl distribution models as part of a multi-disciplinary team targeting the control of the highly pathogenic H5N1 avian influenza virus in China.MethodsFaced with limited data, we built species distribution models using a habitat suitability approach for China’s breeding and non-breeding (hereafter, wintering) waterfowl. An extensive review of the literature was used to determine model parameters for habitat modeling. Habitat relationships were implemented in GIS using land cover covariates. Wintering models were validated using waterfowl census data, while breeding models, though developed for many species, were only validated for the one species with sufficient telemetry data available.ResultsWe developed suitability models for 42 waterfowl species (30 breeding and 39 wintering) at 1 km resolution for the extent of China, along with cumulative and genus level species richness maps. Breeding season models showed highest waterfowl suitability in wetlands of the high-elevation west-central plateau and northeastern China. Wintering waterfowl suitability was highest in the lowland regions of southeastern China. Validation measures indicated strong performance in predicting species presence. Comparing our model outputs to China’s protected areas indicated that breeding habitat was generally better covered than wintering habitat, and identified locations for which additional research and protection should be prioritized.ConclusionsThese suitability models are the first available for many of China’s waterfowl species, and have direct utility to conservation and habitat planning and prioritizing management of critically
Learning to Recognize Actions From Limited Training Examples Using a Recurrent Spiking Neural Model
Panda, Priyadarshini; Srinivasa, Narayan
2018-01-01
A fundamental challenge in machine learning today is to build a model that can learn from few examples. Here, we describe a reservoir based spiking neural model for learning to recognize actions with a limited number of labeled videos. First, we propose a novel encoding, inspired by how microsaccades influence visual perception, to extract spike information from raw video data while preserving the temporal correlation across different frames. Using this encoding, we show that the reservoir generalizes its rich dynamical activity toward signature action/movements enabling it to learn from few training examples. We evaluate our approach on the UCF-101 dataset. Our experiments demonstrate that our proposed reservoir achieves 81.3/87% Top-1/Top-5 accuracy, respectively, on the 101-class data while requiring just 8 video examples per class for training. Our results establish a new benchmark for action recognition from limited video examples for spiking neural models while yielding competitive accuracy with respect to state-of-the-art non-spiking neural models. PMID:29551962
A Reduced Model for Salt-Finger Convection in the Small Diffusivity Ratio Limit
Directory of Open Access Journals (Sweden)
Jin-Han Xie
2017-01-01
Full Text Available A simple model of nonlinear salt-ﬁnger convection in two dimensions is derived and studied. The model is valid in the limit of a small solute to heat diffusivity ratio and a large density ratio, which is relevant to both oceanographic and astrophysical applications. Two limits distinguished by the magnitude of the Schmidt number are found. For order one Schmidt numbers, appropriate for astrophysical applications, a modiﬁed Rayleigh–Bénard system with large-scale damping due to a stabilizing temperature is obtained. For large Schmidt numbers, appropriate for the oceanic setting, the model combines a prognostic equation for the solute ﬁeld and a diagnostic equation for inertia-free momentum dynamics. Two distinct saturation regimes are identiﬁed for the second model: the weakly driven regime is characterized by a large-scale ﬂow associated with a balance between advection and linear instability, while the strongly-driven regime produces multiscale structures, resulting in a balance between energy input through linear instability and energy transfer between scales. For both regimes, we analytically predict and numerically conﬁrm the dependence of the kinetic energy and salinity ﬂuxes on the ratio between solutal and thermal Rayleigh numbers. The spectra and probability density functions are also computed.
Limited sampling strategy models for estimating the AUC of gliclazide in Chinese healthy volunteers.
Huang, Ji-Han; Wang, Kun; Huang, Xiao-Hui; He, Ying-Chun; Li, Lu-Jin; Sheng, Yu-Cheng; Yang, Juan; Zheng, Qing-Shan
2013-06-01
The aim of this work is to reduce the cost of required sampling for the estimation of the area under the gliclazide plasma concentration versus time curve within 60 h (AUC0-60t ). The limited sampling strategy (LSS) models were established and validated by the multiple regression model within 4 or fewer gliclazide concentration values. Absolute prediction error (APE), root of mean square error (RMSE) and visual prediction check were used as criterion. The results of Jack-Knife validation showed that 10 (25.0 %) of the 40 LSS based on the regression analysis were not within an APE of 15 % using one concentration-time point. 90.2, 91.5 and 92.4 % of the 40 LSS models were capable of prediction using 2, 3 and 4 points, respectively. Limited sampling strategies were developed and validated for estimating AUC0-60t of gliclazide. This study indicates that the implementation of an 80 mg dosage regimen enabled accurate predictions of AUC0-60t by the LSS model. This study shows that 12, 6, 4, 2 h after administration are the key sampling times. The combination of (12, 2 h), (12, 8, 2 h) or (12, 8, 4, 2 h) can be chosen as sampling hours for predicting AUC0-60t in practical application according to requirement.
Modeling the 2016-2017 Yemen Cholera Outbreak with the Impact of Limited Medical Resources.
He, Daihai; Wang, Xueying; Gao, Daozhou; Wang, Jin
2018-05-01
We present a mathematical model to investigate the transmission dynamics of the 2016-2017 Yemen Cholera Outbreak. Our model describes the interaction between the human hosts and the pathogenic bacteria, under the impact of limited medical resources. We fit our model to Yemen epidemic data published by the World Health Organization, at both the country and regional levels. We find that the Yemen cholera outbreak is shaped by the interplay of environmental, socioeconomic, and climatic factors. Our results suggest that improvement of the public health system and strategic implementation of control measures with respect to time and location are key to future cholera prevention and intervention in Yemen. Copyright © 2018. Published by Elsevier Ltd.
The implementation of a toroidal limiter model into the gyrokinetic code ELMFIRE
Energy Technology Data Exchange (ETDEWEB)
Leerink, S.; Janhunen, S.J.; Kiviniemi, T.P.; Nora, M. [Euratom-Tekes Association, Helsinki University of Technology (Finland); Heikkinen, J.A. [Euratom-Tekes Association, VTT, P.O. Box 1000, FI-02044 VTT (Finland); Ogando, F. [Universidad Nacional de Educacion a Distancia, Madrid (Spain)
2008-03-15
The ELMFIRE full nonlinear gyrokinetic simulation code has been developed for calculations of plasma evolution and dynamics of turbulence in tokamak geometry. The code is applicable for calculations of strong perturbations in particle distribution function, rapid transients and steep gradients in plasma. Benchmarking against experimental reflectometry data from the FT2 tokamak is being discussed and in this paper a model for comparison and studying poloidal velocity is presented. To make the ELMFIRE code suitable for scrape-off layer simulations a simplified toroidal limiter model has been implemented. The model is be discussed and first results are presented. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
3D Modeling and Simulation for Electromagnetic Non-Destructive Testing- Problems and Limitations
International Nuclear Information System (INIS)
Ilham Mukriz Zainal Abidin; Nurul Ain Ahmad Latif
2011-01-01
Non-Destructive Testing (NDT) plays a critical role in nuclear power plants (NPPs) for life cycle management; such testing requires specialists with various NDT related expertise with specific equipment. This paper will discuss the importance of 3D modeling and simulation for electromagnetic NDT for critical and complex components in terms of engineering reasoning and physical trials. Results from simulation are presented which show the link established between the measurements and information relating to defects, such as 3D shape, size and location, which facilitates not only forward problem but also inverse modeling involving experimental system specification and configuration; and pattern recognition for 3D defect information. Subsequently, the problems and limitations pertinent to 3D modeling and simulation are then highlighted and areas of improvement are discussed. (author)
Final Progress Report on Model-Based Diagnosis of Soil Limitations to Forest Productivity
Energy Technology Data Exchange (ETDEWEB)
Luxmoore, R.J.
2004-08-30
This project was undertaken in support of the forest industry to link modeling of nutrients and productivity with field research to identify methods for enhancing soil quality and forest productivity and for alleviating soil limitations to sustainable forest productivity. The project consisted of a series of related tasks, including (1) simulation of changes in biomass and soil carbon with nitrogen fertilization, (2) development of spreadsheet modeling tools for soil nutrient availability and tree nutrient requirements, (3) additional modeling studies, and (4) evaluation of factors involved in the establishment and productivity of southern pine plantations in seasonally wet soils. This report also describes the two Web sites that were developed from the research to assist forest managers with nutrient management of Douglas-fir and loblolly pine plantations.
A locational gaming model with CO2 emission tax and limits
International Nuclear Information System (INIS)
Yu, Z.; Preckel, P.V.; Nderitu, G.; Sparrow, F.T.
2001-01-01
This paper presents a locational (spatial) gaming model with CO 2 emission and transmission capacity limits. It is developed for simulating strategic behavior of electricity producers in deregulated electricity markets. The model has multiple players, each maximizing their individual profit with a CO 2 emission tax included to reflect the societal cost of environment damages caused by CO 2 emission from different locations. In the paper, the multiple-producer profits are converted into a set of Lagrangian functions with power production and supply as the primary control variables, resulting in a set of unconstrained, individual profit maximization equations. The Karush-Kuhn-Tucker necessary conditions are then derived and solved simultaneously incorporating Cournot gaming strategy. Case studies show the successful application of the model. (author)
Behrman, K. D.; Johnson, M. V. V.; Atwood, J. D.; Norfleet, M. L.
2016-12-01
Recent algal blooms in Western Lake Erie Basin (WLEB) have renewed scientific community's interest in developing process based models to better understand and predict the drivers of eutrophic conditions in the lake. At the same time, in order to prevent future blooms, farmers, local communities and policy makers are interested in developing spatially explicit nutrient and sediment management plans at various scales, from field to watershed. These interests have fueled several modeling exercises intended to locate "hotspots" in the basin where targeted adoption of additional agricultural conservation practices could provide the most benefit to water quality. The models have also been used to simulate various scenarios representing potential agricultural solutions. The Soil and Water Assessment Tool (SWAT) and its sister model, the Agricultural Policy Environmental eXtender (APEX), have been used to simulate hydrology of interacting land uses in thousands of scientific studies around the world. High performance computing allows SWAT and APEX users to continue to improve and refine the model specificity to make predictions at small-spatial scales. Consequently, data inputs and calibration/validation data are now becoming the limiting factor to model performance. Water quality data for the tributaries and rivers that flow through WLEB is spatially and temporally limited. Land management data, including conservation practice and nutrient management data, are not publicly available at fine spatial and temporal scales. Here we show the data uncertainties associated with modeling WLEB croplands at a relatively large spatial scale (HUC-4) using site management data from over 1,000 farms collected by the Conservation Effects Assessment Project (CEAP). The error associated with downscaling this data to the HUC-8 and HUC-12 scale is shown. Simulations of spatially explicit dynamics can be very informative, but care must be taken when policy decisions are made based on models
International Nuclear Information System (INIS)
Qin Shaojin; Yu Lu.
1996-03-01
The critical exponent of the momentum distribution near k F , 3k F and 5k F are studied numerically for one-dimensional U → ∞ Hubbard model, using finite size systems and extrapolating them to the thermodynamic limit. Results at k F agree with earlier calculations, while at 3k F exponents less than 1 are obtained for finite size systems with extrapolation to 1 (regular behaviour) in the thermodynamic limit, in contrast to earlier analytic prediction 9/8. The distribution is regular at 5k F even for finite systems. The singularity near 3k F is interpreted as due to low energy excitations near 3k F in finite systems. (author). 18 refs, 4 figs, 1 tab
Breakdown of quasiparticle picture in the low-density limit of the 1D Hubbard model
International Nuclear Information System (INIS)
Qin Shaojin; Qian Tiezheng; Su Zhaobin
1995-03-01
Using the finite-size scaling of results obtained by exact diagonalization, we study the low-density limit of the one-dimensional Hubbard model. Calculating the quasiparticle weight, we demonstrate that for a given particle number N and system size L, there always exists a crossover point U c separating the Fermi-liquid (U c ) and non-Fermi-liquid (U > U c ) regimes (U is the Hubbard repulsion). We find that for a fixed N, U c is inversely proportional to L, keeping U c L/t constant (with t as the hopping integral), as L is large enough. It follows that in the low-density (in fact vanishing density) limit L → ∞, U c → 0, so the system is always in non-Fermi-liquid regime as long as U > 0. We show that our numerical results are consistent with the Bethe ansatz solution. (author). 11 refs, 3 figs
Modeling the impact of iron and phosphorus limitations on nitrogen fixation in the Atlantic Ocean
Directory of Open Access Journals (Sweden)
R. R. Hood
2007-07-01
Full Text Available The overarching goal of this study is to simulate subsurface N* (sensu, Gruber and Sarmiento, 1997; GS97 anomaly patterns in the North Atlantic Ocean and determine the basin wide rates of N_{2}-fixation that are required to do so. We present results from a new Atlantic implementation of a coupled physical-biogeochemical model that includes an explicit, dynamic representation of N_{2}-fixation with light, nitrogen, phosphorus and iron limitations, and variable stoichiometric ratios. The model is able to reproduce nitrogen, phosphorus and iron concentration variability to first order. The latter is achieved by incorporating iron deposition directly into the model's detrital iron compartment which allows the model to reproduce sharp near surface gradients in dissolved iron concentration off the west coast of Africa and deep dissolved iron concentrations that have been observed in recent observational studies. The model can reproduce the large scale N* anomaly patterns but requires relatively high rates of surface nitrogen fixation to do so (1.8×10^{12} moles N yr^{−1} from 10° N–30° N, 3.4×10^{12} moles N yr^{−1} from 25° S–65° N. In the model the surface nitrogen fixation rate patterns are not co-located with subsurface gradients in N*. Rather, the fixed nitrogen is advected away from its source prior to generating a subsurface N* anomaly. Changes in the phosphorus remineralization rate (relative to nitrogen linearly determine the surface nitrogen fixation rate because they change the degree of phosphorus limitation, which is the dominant limitation in the Atlantic in the model. Phosphorus remineralization rate must be increased by about a factor of 2 (relative to nitrogen in order to generate subsurface N* anomalies that are comparable to the observations. We conclude that N_{2}-fixation rate estimates for the Atlantic (and globally may need to be revised upward, which
Limits of Risk Predictability in a Cascading Alternating Renewal Process Model.
Lin, Xin; Moussawi, Alaa; Korniss, Gyorgy; Bakdash, Jonathan Z; Szymanski, Boleslaw K
2017-07-27
Most risk analysis models systematically underestimate the probability and impact of catastrophic events (e.g., economic crises, natural disasters, and terrorism) by not taking into account interconnectivity and interdependence of risks. To address this weakness, we propose the Cascading Alternating Renewal Process (CARP) to forecast interconnected global risks. However, assessments of the model's prediction precision are limited by lack of sufficient ground truth data. Here, we establish prediction precision as a function of input data size by using alternative long ground truth data generated by simulations of the CARP model with known parameters. We illustrate the approach on a model of fires in artificial cities assembled from basic city blocks with diverse housing. The results confirm that parameter recovery variance exhibits power law decay as a function of the length of available ground truth data. Using CARP, we also demonstrate estimation using a disparate dataset that also has dependencies: real-world prediction precision for the global risk model based on the World Economic Forum Global Risk Report. We conclude that the CARP model is an efficient method for predicting catastrophic cascading events with potential applications to emerging local and global interconnected risks.
Strifler, Lisa; Cardoso, Roberta; McGowan, Jessie; Cogo, Elise; Nincic, Vera; Khan, Paul A; Scott, Alistair; Ghassemi, Marco; MacDonald, Heather; Lai, Yonda; Treister, Victoria; Tricco, Andrea C; Straus, Sharon E
2018-04-13
To conduct a scoping review of knowledge translation (KT) theories, models and frameworks that have been used to guide dissemination or implementation of evidence-based interventions targeted to prevention and/or management of cancer or other chronic diseases. We used a comprehensive multistage search process from 2000-2016, which included traditional bibliographic database searching, searching using names of theories, models and frameworks, and cited reference searching. Two reviewers independently screened the literature and abstracted data. We found 596 studies reporting on the use of 159 KT theories, models or frameworks. A majority (87%) of the identified theories, models or frameworks were used in five or fewer studies, with 60% used once. The theories, models and frameworks were most commonly used to inform planning/design, implementation and evaluation activities, and least commonly used to inform dissemination and sustainability/scalability activities. Twenty-six were used across the full implementation spectrum (from planning/design to sustainability/scalability) either within or across studies. All were used for at least individual-level behavior change, while 48% were used for organization-level, 33% for community-level and 17% for system-level change. We found a significant number of KT theories, models and frameworks with a limited evidence base describing their use. Copyright © 2018. Published by Elsevier Inc.
Animal models and therapeutic molecular targets of cancer: utility and limitations
Directory of Open Access Journals (Sweden)
Cekanova M
2014-10-01
Full Text Available Maria Cekanova, Kusum Rathore Department of Small Animal Clinical Sciences, College of Veterinary Medicine, The University of Tennessee, Knoxville, TN, USA Abstract: Cancer is the term used to describe over 100 diseases that share several common hallmarks. Despite prevention, early detection, and novel therapies, cancer is still the second leading cause of death in the USA. Successful bench-to-bedside translation of basic scientific findings about cancer into therapeutic interventions for patients depends on the selection of appropriate animal experimental models. Cancer research uses animal and human cancer cell lines in vitro to study biochemical pathways in these cancer cells. In this review, we summarize the important animal models of cancer with focus on their advantages and limitations. Mouse cancer models are well known, and are frequently used for cancer research. Rodent models have revolutionized our ability to study gene and protein functions in vivo and to better understand their molecular pathways and mechanisms. Xenograft and chemically or genetically induced mouse cancers are the most commonly used rodent cancer models. Companion animals with spontaneous neoplasms are still an underexploited tool for making rapid advances in human and veterinary cancer therapies by testing new drugs and delivery systems that have shown promise in vitro and in vivo in mouse models. Companion animals have a relatively high incidence of cancers, with biological behavior, response to therapy, and response to cytotoxic agents similar to those in humans. Shorter overall lifespan and more rapid disease progression are factors contributing to the advantages of a companion animal model. In addition, the current focus is on discovering molecular targets for new therapeutic drugs to improve survival and quality of life in cancer patients. Keywords: mouse cancer model, companion animal cancer model, dogs, cats, molecular targets
Dickson, Robert P; Hotchkin, David L; Lamm, Wayne JE; Hinkson, Carl; Pierson, David J; Glenny, Robb W; Rubinson, Lewis
2013-01-01
Objective To adapt an animal model of acute lung injury for use as a standard protocol for a screening, initial evaluation of limited function, or “surge,” ventilators for use in mass casualty scenarios. Design Prospective, experimental animal study. Setting University research laboratory. Subjects 12 adult pigs. Interventions 12 spontaneously breathing pigs (6 in each group) were subjected to acute lung injury/acute respiratory distress syndrome (ALI/ARDS) via pulmonary artery infusion of oleic acid. Following development of respiratory failure, animals were mechanically ventilated with a limited function ventilator (Simplified Automatic Ventilator [SAVe] I or II; Automedx) for one hour or until the ventilator could not support the animal. The limited function ventilator was then exchanged for a full function ventilator (Servo 900C; Siemens). Measurements and Main Results Reliable and reproducible levels of ALI/ARDS were induced. The SAVe I was unable to adequately oxygenate 5 animals, with PaO2 (52.0 ± 11.1 torr) compared to the Servo (106.0 ± 25.6 torr; p=0.002). The SAVe II was able to oxygenate and ventilate all 6 animals for one hour with no difference in PaO2 (141.8 ± 169.3 torr) compared to the Servo (158.3 ± 167.7 torr). Conclusions We describe a novel in vivo model of ALI/ARDS that can be used to initially screen limited function ventilators considered for mass respiratory failure stockpiles, and is intended to be combined with additional studies to defintively assess appropriateness for mass respiratory failure. Specifically, during this study we demonstrate that the SAVe I ventilator is unable to provide sufficient gas exchange, while the SAVe II, with several more functions, was able to support the same level of hypoxemic respiratory failure secondary to ALI/ARDS for one hour. PMID:21187747
Analysis of enamel development using murine model systems: approaches and limitations.
Directory of Open Access Journals (Sweden)
Megan K Pugach
2014-09-01
Full Text Available A primary goal of enamel research is to understand and potentially treat or prevent enamel defects related to amelogenesis imperfecta (AI. Rodents are ideal models to assist our understanding of how enamel is formed because they are easily genetically modified, and their continuously erupting incisors display all stages of enamel development and mineralization. While numerous methods have been developed to generate and analyze genetically modified rodent enamel, it is crucial to understand the limitations and challenges associated with these methods in order to draw appropriate conclusions that can be applied translationally, to AI patient care. We have highlighted methods involved in generating and analyzing rodent enamel and potential approaches to overcoming limitations of these methods: 1 generating transgenic, knockout and knockin mouse models, and 2 analyzing rodent enamel mineral density and functional properties (structure, mechanics of mature enamel. There is a need for a standardized workflow to analyze enamel phenotypes in rodent models so that investigators can compare data from different studies. These methods include analyses of gene and protein expression, developing enamel histology, enamel pigment, degree of mineralization, enamel structure and mechanical properties. Standardization of these methods with regard to stage of enamel development and sample preparation is crucial, and ideally investigators can use correlative and complementary techniques with the understanding that developing mouse enamel is dynamic and complex.
Low Mach and Peclet number limit for a model of stellar tachocline and upper radiative zones
Directory of Open Access Journals (Sweden)
Donatella Donatelli
2016-09-01
Full Text Available We study a hydrodynamical model describing the motion of internal stellar layers based on compressible Navier-Stokes-Fourier-Poisson system. We suppose that the medium is electrically charged, we include energy exchanges through radiative transfer and we assume that the system is rotating. We analyze the singular limit of this system when the Mach number, the Alfven number, the Peclet number and the Froude number approache zero in a certain way and prove convergence to a 3D incompressible MHD system with a stationary linear transport equation for transport of radiation intensity. Finally, we show that the energy equation reduces to a steady equation for the temperature corrector.
Mass Limit for the standard model Higgs boson with the full LEP I ALEPH data sample
Buskulic, Damir; Décamp, D; Ghez, P; Goy, C; Lees, J P; Lucotte, A; Minard, M N; Nief, J Y; Odier, P; Pietrzyk, B; Casado, M P; Chmeissani, M; Crespo, J M; Delfino, M C; Efthymiopoulos, I; Fernández, E; Fernández-Bosman, M; Garrido, L; Juste, A; Martínez, M; Orteu, S; Padilla, C; Park, I C; Pascual, A; Perlas, J A; Riu, I; Sánchez, F; Teubert, F; Colaleo, A; Creanza, D; De Palma, M; Gelao, G; Girone, M; Iaselli, Giuseppe; Maggi, G; Maggi, M; Marinelli, N; Nuzzo, S; Ranieri, A; Raso, G; Ruggieri, F; Selvaggi, G; Silvestris, L; Tempesta, P; Zito, G; Huang, X; Lin, J; Ouyang, Q; Wang, T; Xie, Y; Xu, R; Xue, S; Zhang, J; Zhang, L; Zhao, W; Alemany, R; Bazarko, A O; Bonvicini, G; Cattaneo, M; Comas, P; Coyle, P; Drevermann, H; Forty, Roger W; Frank, M; Hagelberg, R; Harvey, J; Janot, P; Jost, B; Kneringer, E; Knobloch, J; Lehraus, Ivan; Lutters, G; Martin, E B; Mato, P; Minten, Adolf G; Miquel, R; Mir, L M; Moneta, L; Oest, T; Pacheco, A; Pusztaszeri, J F; Ranjard, F; Rensing, P E; Rolandi, Luigi; Schlatter, W D; Schmelling, M; Schmitt, M; Schneider, O; Tejessy, W; Tomalin, I R; Venturi, A; Wachsmuth, H W; Wagner, A; Ajaltouni, Ziad J; Barrès, A; Boyer, C; Falvard, A; Gay, P; Guicheney, C; Henrard, P; Jousset, J; Michel, B; Monteil, S; Montret, J C; Pallin, D; Perret, P; Podlyski, F; Proriol, J; Rosnet, P; Rossignol, J M; Fearnley, Tom; Hansen, J B; Hansen, J D; Hansen, J R; Hansen, P H; Nilsson, B S; Rensch, B; Wäänänen, A; Kyriakis, A; Markou, C; Simopoulou, Errietta; Siotis, I; Vayaki, Anna; Zachariadou, K; Blondel, A; Bonneaud, G R; Brient, J C; Bourdon, P; Rougé, A; Rumpf, M; Valassi, Andrea; Verderi, M; Videau, H L; Candlin, D J; Parsons, M I; Focardi, E; Parrini, G; Corden, M; Georgiopoulos, C H; Jaffe, D E; Antonelli, A; Bencivenni, G; Bologna, G; Bossi, F; Campana, P; Capon, G; Casper, David William; Chiarella, V; Felici, G; Laurelli, P; Mannocchi, G; Murtas, F; Murtas, G P; Passalacqua, L; Pepé-Altarelli, M; Curtis, L; Dorris, S J; Halley, A W; Knowles, I G; Lynch, J G; O'Shea, V; Raine, C; Reeves, P; Scarr, J M; Smith, K; Teixeira-Dias, P; Thompson, A S; Thomson, F; Thorn, S; Turnbull, R M; Becker, U; Geweniger, C; Graefe, G; Hanke, P; Hansper, G; Hepp, V; Kluge, E E; Putzer, A; Schmidt, M; Sommer, J; Stenzel, H; Tittel, K; Werner, S; Wunsch, M; Abbaneo, D; Beuselinck, R; Binnie, David M; Cameron, W; Dornan, Peter J; Moutoussi, A; Nash, J; Sedgbeer, J K; Stacey, A M; Williams, M D; Dissertori, G; Girtler, P; Kuhn, D; Rudolph, G; Betteridge, A P; Bowdery, C K; Colrain, P; Crawford, G; Finch, A J; Foster, F; Hughes, G; Sloan, Terence; Williams, M I; Galla, A; Giehl, I; Greene, A M; Kleinknecht, K; Quast, G; Renk, B; Rohne, E; Sander, H G; Van Gemmeren, P; Zeitnitz, C; Aubert, Jean-Jacques; Bencheikh, A M; Benchouk, C; Bonissent, A; Bujosa, G; Calvet, D; Carr, J; Diaconu, C A; Etienne, F; Konstantinidis, N P; Payre, P; Rousseau, D; Talby, M; Sadouki, A; Thulasidas, M; Trabelsi, K; Aleppo, M; Ragusa, F; Abt, I; Assmann, R W; Bauer, C; Blum, Walter; Dietl, H; Dydak, Friedrich; Ganis, G; Gotzhein, C; Jakobs, K; Kroha, H; Lütjens, G; Lutz, Gerhard; Männer, W; Moser, H G; Richter, R H; Rosado-Schlosser, A; Schael, S; Settles, Ronald; Seywerd, H C J; Saint-Denis, R; Wiedenmann, W; Wolf, G; Boucrot, J; Callot, O; Choi, Y; Cordier, A; Davier, M; Duflot, L; Grivaz, J F; Heusse, P; Höcker, A; Jacquet, M; Kim, D W; Le Diberder, F R; Lefrançois, J; Lutz, A M; Nikolic, I A; Park, H J; Schune, M H; Simion, S; Veillet, J J; Videau, I; Zerwas, D; Azzurri, P; Bagliesi, G; Batignani, G; Bettarini, S; Bozzi, C; Calderini, G; Carpinelli, M; Ciocci, M A; Ciulli, V; Dell'Orso, R; Fantechi, R; Ferrante, I; Foà, L; Forti, F; Giassi, A; Giorgi, M A; Gregorio, A; Ligabue, F; Lusiani, A; Marrocchesi, P S; Messineo, A; Palla, Fabrizio; Rizzo, G; Sanguinetti, G; Sciabà, A; Spagnolo, P; Steinberger, Jack; Tenchini, Roberto; Tonelli, G; Vannini, C; Verdini, P G; Walsh, J; Blair, G A; Bryant, L M; Cerutti, F; Chambers, J T; Gao, Y; Green, M G; Medcalf, T; Perrodo, P; Strong, J A; Von Wimmersperg-Töller, J H; Botterill, David R; Clifft, R W; Edgecock, T R; Haywood, S; Maley, P; Norton, P R; Thompson, J C; Wright, A E; Bloch-Devaux, B; Colas, P; Emery, S; Kozanecki, Witold; Lançon, E; Lemaire, M C; Locci, E; Marx, B; Pérez, P; Rander, J; Renardy, J F; Roussarie, A; Schuller, J P; Schwindling, J; Trabelsi, A; Vallage, B; Black, S N; Dann, J H; Johnson, R P; Kim, H Y; Litke, A M; McNeil, M A; Taylor, G; Booth, C N; Boswell, R; Brew, C A J; Cartwright, S L; Combley, F; Köksal, A; Lehto, M H; Newton, W M; Reeve, J; Thompson, L F; Böhrer, A; Brandt, S; Büscher, V; Cowan, G D; Grupen, Claus; Minguet-Rodríguez, J A; Rivera, F; Saraiva, P; Smolik, L; Stephan, F; Apollonio, M; Bosisio, L; Della Marina, R; Giannini, G; Gobbo, B; Musolino, G; Rothberg, J E; Wasserbaech, S R; Armstrong, S R; Elmer, P; Feng, Z; Ferguson, D P S; Gao, Y S; González, S; Grahl, J; Greening, T C; Hayes, O J; Hu, H; McNamara, P A; Nachtman, J M; Orejudos, W; Pan, Y B; Saadi, Y; Scott, I J; Walsh, A M; Wu Sau Lan; Wu, X; Yamartino, J M; Zheng, M; Zobernig, G
1996-01-01
background from the electroweak process e+e- --> l+ l- q qbar. This search results in a 95% C.L. lower limit on the Higgs boson mass of $63.9$~\\Gcs. The reaction e+e- --> HZ* is used to search for the standard model Higgs boson in the H nu nubar and the H l+ l- channels. The data sample corresponds to about 4.5 million hadronic Z decays collected by the ALEPH experiment at LEP from 1989 to 1995 at centre-of-mass energies at and around the Z peak. Three candidate events are found in the H mu+ mu- channel, in agreement with the expected
New limits on the mass of neutral Higgses in general models
International Nuclear Information System (INIS)
Comelli, D.
1996-07-01
In general electroweak models with weakly coupled (and otherwise arbitrary) Higgs sector there always exists in the spectrum a scalar state with mass controlled by the electroweak scale. A new and simple recipe to compute an analytical tree-level upper bound on the mass of this light scalar is given. We compare this new bound with similar ones existing in the literature and show how to extract extra information on heavier neutral scalars in the spectrum from the interplay of independent bounds. Production of these states at future colliders is addressed and the implications for the decoupling limit in which only one Higgs is expected to remain light are discussed. (orig.)
International Nuclear Information System (INIS)
Schlesinger, T.; Silverman, I.; Shapira, M.
1996-01-01
Ionizing radiation may cause immediate and/or delayed biological damages to the body of the exposed person and/or his/her progeny. The exposure may be caused by an external source or may arise due to internal contamination by a radioactive material. In order to prevent such exposure, or to reduce the probability that it will occur, national authorities and international organizations that are engaged in radiation safety and protection have set limits for the exposure to ionizing radiation from either source. The sensitivity of the body to ionizing radiation usually decreases with age. For this reason and due to the limited possibilities to control the exposure of the general public, different limits have been set for for occupational exposure and for the exposure of members of the public of different age groups. The general principles of these limits and guidelines for their calculations are set by the International Commission on Radiological Protection (ICRP) and published in the Annals of the ICRP. The basic philosophy of the Commission, which includes the principles of justification, optimization and dose limits, the basic radiobiological models, and the distinction between stochastic and non-stochastic effects has been presented in its publication no. 26 . Based on this philosophy, the Commission issued between 1979 and 1988 a series of publications followed by annexes and addenda known as publication no. 30 . This series presented models describing the metabolism of radioactive materials which enter the body by inhalation and ingestion, the transfer of such materials from the respiratory tract and the gastrointestinal tract to the blood, and from there to the body organs and the excretion of the material from the body. This series presented also values for biokinetic parameters of these systems and transfer paths, and methods for calculating limits on intake which ensure that the exposure from internal contamination will not exceed the dose limits set by the
Energy Technology Data Exchange (ETDEWEB)
Schlesinger, T; Silverman, I; Shapira, M [Israel Atomic Energy Commission, Yavne (Israel). Soreq Nuclear Research Center
1996-12-01
Ionizing radiation may cause immediate and/or delayed biological damages to the body of the exposed person and/or his/her progeny. The exposure may be caused by an external source or may arise due to internal contamination by a radioactive material. To prevent such exposure, or to reduce the probability that it will occur, national authorities and international organizations engaged in radiation safety and protection have set limits for the exposure to ionizing radiation from either source. The sensitivity of the body to ionizing radiation usually decreases with age. For this reason and due to the limited possibilities to control the exposure of the general public, different limits have been set for for occupational exposure and for the exposure of members of the public of different age groups. The general principles of these limits and guidelines for their calculations are set by the International Commission on Radiological Protection (ICRP) and published in the Annals of the ICRP. The basic philosophy of the Commission, which includes the principles of justification, optimization and dose limits, the basic radiobiological models, and the distinction between stochastic and non-stochastic effects has been presented in its publication no. 26. Based on this philosophy, the Commission issued between 1979 and 1988 a series of publications followed by annexes and addenda known as publication no. 30. This series presented models describing the metabolism of radioactive materials which enter the body by inhalation and ingestion, the transfer of such materials from the respiratory tract and the gastrointestinal tract to the blood, and from there to the body organs and the excretion of the material from the body. This series presented also values for biokinetic parameters of these systems and transfer paths, and methods for calculating limits on intake which ensure that the exposure from internal contamination will not exceed the dose limits set.
International Nuclear Information System (INIS)
Kim, Man Cheol; Jang, Seung Cheol; Ha, Jae Joo
2006-01-01
As digital systems are gradually introduced to nuclear power plants (NPPs), the need of quantitatively analyzing the reliability of the digital systems is also increasing. Kang and Sung identified (1) software reliability, (2) common-cause failures (CCFs), and (3) fault coverage as the three most critical factors in the reliability analysis of digital systems. For the estimation of the safety-critical software (the software that is used in safety-critical digital systems), the use of Bayesian Belief Networks (BBNs) seems to be most widely used. The use of BBNs in reliability estimation of safety-critical software is basically a process of indirectly assigning a reliability based on various observed information and experts' opinions. When software testing results or software failure histories are available, we can use a process of directly estimating the reliability of the software using various software reliability growth models such as Jelinski- Moranda model and Goel-Okumoto's nonhomogeneous Poisson process (NHPP) model. Even though it is generally known that software reliability growth models cannot be applied to safety-critical software due to small number of expected failure data from the testing of safety-critical software, we try to find possibilities and corresponding limitations of applying software reliability growth models to safety critical software
Shelomentsev, A. G.; Medvedev, M. A.; Berg, D. B.; Lapshina, S. N.; Taubayev, A. A.; Davletbaev, R. H.; Savina, D. V.
2017-12-01
Present study is devoted to the development of competition life cycle mathematical model in the closed business community with limited resources. Growth of each agent is determined by the balance of input and output resource flows: input (cash) flow W is covering the variable V and constant C costs and growth dA/dt of the agent's assets A. Value of V is proportional to assets A that allows us to write down a first order non-stationary differential equation of the agent growth. Model includes the number of such equations due to the number of agents. The amount of resources that is available for agents vary in time. The balances of their input and output flows are changing correspondingly to the different stages of the competition life cycle. According to the theory of systems, the most complete description of any object or process is the model of its life cycle. Such a model describes all stages of its development: from the appearance ("birth") through development ("growth") to extinction ("death"). The model of the evolution of an individual firm, not contradicting the economic meaning of events actually observed in the market, is the desired result from modern AVMs for applied use. With a correct description of the market, rules for participants' actions, restrictions, forecasts can be obtained, which modern mathematics and the economy can not give.
Directory of Open Access Journals (Sweden)
A. Loew
2013-09-01
Full Text Available Soil moisture is an essential climate variable (ECV of major importance for land–atmosphere interactions and global hydrology. An appropriate representation of soil moisture dynamics in global climate models is therefore important. Recently, a first multidecadal, observation-based soil moisture dataset has become available that provides information on soil moisture dynamics from satellite observations (ECVSM, essential climate variable soil moisture. The present study investigates the potential and limitations of this new dataset for several applications in climate model evaluation. We compare soil moisture data from satellite observations, reanalysis and simulations from a state-of-the-art land surface model and analyze relationships between soil moisture and precipitation anomalies in the different dataset. Other potential applications like model parameter optimization or model initialization are not investigated in the present study. In a detailed regional study, we show that ECVSM is capable to capture well the interannual and intraannual soil moisture and precipitation dynamics in the Sahelian region. Current deficits of the new dataset are critically discussed and summarized at the end of the paper to provide guidance for an appropriate usage of the ECVSM dataset for climate studies.
An improved model for nucleation-limited ice formation in living cells during freezing.
Directory of Open Access Journals (Sweden)
Jingru Yi
Full Text Available Ice formation in living cells is a lethal event during freezing and its characterization is important to the development of optimal protocols for not only cryopreservation but also cryotherapy applications. Although the model for probability of ice formation (PIF in cells developed by Toner et al. has been widely used to predict nucleation-limited intracellular ice formation (IIF, our data of freezing Hela cells suggest that this model could give misleading prediction of PIF when the maximum PIF in cells during freezing is less than 1 (PIF ranges from 0 to 1. We introduce a new model to overcome this problem by incorporating a critical cell volume to modify the Toner's original model. We further reveal that this critical cell volume is dependent on the mechanisms of ice nucleation in cells during freezing, i.e., surface-catalyzed nucleation (SCN and volume-catalyzed nucleation (VCN. Taken together, the improved PIF model may be valuable for better understanding of the mechanisms of ice nucleation in cells during freezing and more accurate prediction of PIF for cryopreservation and cryotherapy applications.
Flow-Through Stream Modeling with MODFLOW and MT3D: Certainties and Limitations.
Ben Simon, Rose; Bernard, Stéphane; Meurville, Charles; Rebour, Vincent
2015-01-01
This paper aims to assess MODFLOW and MT3D capabilities for simulating the spread of contaminants from a river exhibiting an unusual relationship with an alluvial aquifer, with the groundwater head higher than the river head on one side and lower on the other (flow-through stream). A series of simulation tests is conducted using a simple hypothetical model so as to characterize and quantify these limitations. Simulation results show that the expected contaminant spread could be achieved with a specific configuration composed of two sets of parameters: (1) modeled object parameters (hydraulic groundwater gradient, hydraulic conductivity values of aquifer and streambed), and (2) modeling parameters (vertical discretization of aquifer, horizontal refinement of stream modeled with River [RIV] package). The influence of these various parameters on simulation results is investigated, and potential complications and errors are identified. Contaminant spread from stream to aquifer is not always reproduced by MT3D due to the RIV package's inability to simulate lateral exchange fluxes between stream and aquifer. This paper identifies the need for a MODFLOW streamflow package allowing lateral stream-aquifer interactions and streamflow routine calculations. Such developments could be of particular interest for modeling contaminated flow-through streams. © 2015, National Ground Water Association.
Implications of emission zone limits for the Ruderman-Sutherland pulsar model
International Nuclear Information System (INIS)
Matese, J.J.; Whitmire, D.P.
1980-01-01
In the Ruderman-Sutherland (RS) pulsar model the frequency at which coherent radiation is emitted depends upon the source location, v=v (r). In the oblique rotator version of this model the time-averaged tangential velocities of the magnetosphere sources must increase linearly with radius, and this leads to a frequency-dependent aberration and retardation time delay in which higher frequencies lag behind lower frequencies. As previously noted by Cordes, within the context of a given model which specifies v (r), the absence of any anomalous time delay in dispersion measurements allows limits to be placed on the radial position of the source of a given frequency. In this paper we (a) give a time-delay analysis (similar to that of Cordes) appropriate for the RS model and show that existing dispersion measurements are incompatible with RS emission mechanism. If the basic RS emission mechanism is applicable to pulsars, we find that the most plausible modification consistent with the dispersion data is a reduction in the low-energy plasma density by a factor approx.10 -4 to 10 -5 . This has the effect of bringing the radio emission zone closer to the stellar surface, thereby making the model consistent with the dispersion data. In addition, this modification results in a significant decrease in the predicted maximum cone angle and an increase in the predicted maximum frequency by factors which bring these predictions more in line with observation. We also consider implications of a reduced plasma density for radio luminosity
International Nuclear Information System (INIS)
Parisot, M.
2011-01-01
This work is dedicated study of a problem resulting from plasma physics: the thermal transfer of electrons in a plasma close to equilibrium Maxwellian. Firstly, a dimensional study of the Vlasov-Fokker-Planck-Maxwell system is performed, allowing one hand to identify a physically relevant parameter of scale and also to define mathematically the contours of validity domain. The asymptotic regime called Spitzer-Harm is studied for a relatively general class of collision operator. The following part of this work is devoted to the derivation and study of the hydrodynamic limit of the system of Vlasov-Maxwell-Landau outside the strictly asymptotic. A model proposed by Schurtz and Nicolais located in this context and analyzed. The particularity of this model lies in the application of a delocalization operation in the heat flux. The link with non-local models of Luciani and Mora is established as well as mathematics properties as the principle of maximum and entropy dissipation. Then a formal derivation from the Vlasov equations with a simplified collision operator, is proposed. The derivation, inspired by the recent work of D. Levermore, involves decomposition methods according to the spherical harmonics and methods of closing called diffusion methods. A hierarchy of intermediate models between the kinetic equations and the hydrodynamic limit is described. In particular a new hydrodynamic system integro-differential by nature, is proposed. The Schurtz and Nicolai model appears as a simplification of the system resulting from the derivation, assuming a steady flow of heat. The above results are then generalized to account for the internal energy dependence which appears naturally in the equation establishment. The existence and uniqueness of the solution of the nonstationary system are established in a simplified framework. The last part is devoted was the implementation of a specific numerical scheme to solve these models. We propose a finite volume approach can be
Measuring and overcoming limits of the Saffman-Delbrück model for soap film viscosities.
Vivek, Skanda; Weeks, Eric R
2015-01-01
We observe tracer particles diffusing in soap films to measure the two-dimensional (2D) viscous properties of the films. Saffman-Delbrück type models relate the single-particle diffusivity to parameters of the film (such as thickness h) for thin films, but the relation breaks down for thicker films. Notably, the diffusivity is faster than expected for thicker films, with the crossover at h/d = 5.2 ± 0.9 using the tracer particle diameter d. This indicates a crossover from purely 2D diffusion to diffusion that is more three-dimensional. We demonstrate that measuring the correlations of particle pairs as a function of their separation overcomes the limitations of the Saffman-Delbrück model and allows one to measure the viscosity of a soap film for any thickness.
The fractional diffusion limit of a kinetic model with biochemical pathway
Perthame, Benoît; Sun, Weiran; Tang, Min
2018-06-01
Kinetic-transport equations that take into account the intracellular pathways are now considered as the correct description of bacterial chemotaxis by run and tumble. Recent mathematical studies have shown their interest and their relations to more standard models. Macroscopic equations of Keller-Segel type have been derived using parabolic scaling. Due to the randomness of receptor methylation or intracellular chemical reactions, noise occurs in the signaling pathways and affects the tumbling rate. Then comes the question to understand the role of an internal noise on the behavior of the full population. In this paper we consider a kinetic model for chemotaxis which includes biochemical pathway with noises. We show that under proper scaling and conditions on the tumbling frequency as well as the form of noise, fractional diffusion can arise in the macroscopic limits of the kinetic equation. This gives a new mathematical theory about how long jumps can be due to the internal noise of the bacteria.
Li, Shu-Bin; Cao, Dan-Ni; Dang, Wen-Xiu; Zhang, Lin
As a new cross-discipline, the complexity science has penetrated into every field of economy and society. With the arrival of big data, the research of the complexity science has reached its summit again. In recent years, it offers a new perspective for traffic control by using complex networks theory. The interaction course of various kinds of information in traffic system forms a huge complex system. A new mesoscopic traffic flow model is improved with variable speed limit (VSL), and the simulation process is designed, which is based on the complex networks theory combined with the proposed model. This paper studies effect of VSL on the dynamic traffic flow, and then analyzes the optimal control strategy of VSL in different network topologies. The conclusion of this research is meaningful to put forward some reasonable transportation plan and develop effective traffic management and control measures to help the department of traffic management.
A state of the art on the flooding phenomena and countercurrent flow limiting modeling
Energy Technology Data Exchange (ETDEWEB)
Jeong, Young Jong; Chang, Won Pyo [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)
1996-07-01
Countercurrent flow limiting phenomenon and its modeling for vertical and nearly horizontal pipes has been reviewed in two phase flow. A number of analytical and empirical model have been developed for flooding in the vertical pipes and annulars. These may be classified as stability theory, envelope theory, static equilibrium theory, slug formation theory, Wallis correlation, and Kutateladze correlation. The theories and empirical correlations are reviewed and comparison with the various experimental data. The scatter of the experimental data is large because of the different flooding condition and because of the influence of the experimental conditions. Application of flooding for PWR best estimate system codes is reviewed. The codes provide the user options to implement CCFL correlation for the specific geometry. The codes can accommodate generally Wallis, Kutateladze, or Bankoff correlation. 4 tabs., 36 figs., 52 refs. (Author).
Proposing a model for limiting earning management practices: The case of Jordanian listed firms
Directory of Open Access Journals (Sweden)
Dea’a Al-Deen Al-Sraheen
2016-11-01
Full Text Available The key objective of this paper is to propose a model for limiting earning management practices among manufacturing firms in Jordan. In order to do so, two independent variables are examined in this paper, namely, political influence and CEO Duality. Discretionary total accruals according to the modified Jones model (1991 was used in order to estimate the level of earnings management, which is the dependent variable. The sample comprised 64 companies for the financial year 2013. The results suggest that a positive and significant association existed among both political influence and CEO duality and earning management. This means that both independent variables exacerbated earnings management. Further research is required to determine what urgent legislation should be developed to restrict the presence of members who have political connections on the board of directors. Also, the need exists for the separation of roles of Chairman and CEO to ensure the independence and complying with the requirements of corporate governance.
From explicit to implicit normal mode initialization of a limited-area model
Energy Technology Data Exchange (ETDEWEB)
Bijlsma, S.J.
2013-02-15
In this note the implicit normal mode initialization of a limited-area model is discussed from a different point of view. To that end it is shown that the equations describing the explicit normal mode initialization applied to the shallow water equations in differentiated form on the sphere can readily be derived in normal mode space if the model equations are separable, but only in the case of stationary Rossby modes can be transformed into the implicit equations in physical space. This is a consequence of the simple relations between the components of the different modes in that case. In addition a simple eigenvalue problem is given for the frequencies of the gravity waves. (orig.)
A state of the art on the flooding phenomena and countercurrent flow limiting modeling
International Nuclear Information System (INIS)
Jeong, Young Jong; Chang, Won Pyo
1996-07-01
Countercurrent flow limiting phenomenon and its modeling for vertical and nearly horizontal pipes has been reviewed in two phase flow. A number of analytical and empirical model have been developed for flooding in the vertical pipes and annulars. These may be classified as stability theory, envelope theory, static equilibrium theory, slug formation theory, Wallis correlation, and Kutateladze correlation. The theories and empirical correlations are reviewed and comparison with the various experimental data. The scatter of the experimental data is large because of the different flooding condition and because of the influence of the experimental conditions. Application of flooding for PWR best estimate system codes is reviewed. The codes provide the user options to implement CCFL correlation for the specific geometry. The codes can accommodate generally Wallis, Kutateladze, or Bankoff correlation. 4 tabs., 36 figs., 52 refs. (Author)
Modeling of a Small Transportation Company’s Start-up with Limited Data during Economic Recession
Fang, Xiaoping; Ansell, Jonathan; Chen, Weiya
2014-01-01
This paper presents a modeling method for analyzing a small transportation company’s start-up and growth during a global economic crisis which had an impact on in China which is designed to help the owners make better investment and operating decisions with limited data. Since there is limited data, simple regression model and binary regression model failed to generate satisfactory results, so an additive periodic time series model was built to forecast business orders and income. Since the t...
International Nuclear Information System (INIS)
2017-01-01
This report focuses on studies of KIT-INE to derive a significantly improved description of the chemical behaviour of Americium and Plutonium in saline NaCl, MgCl 2 and CaCl 2 brine systems. The studies are based on new experimental data and aim at deriving reliable Am and Pu solubility limits for the investigated systems as well as deriving comprehensive thermodynamic model descriptions. Both aspects are of high relevance in the context of potential source term estimations for Americium and Plutonium in aqueous brine systems and related scenarios. Americium and Plutonium are long-lived alpha emitting radionuclides which due to their high radiotoxicity need to be accounted for in a reliable and traceable way. The hydrolysis of trivalent actinides and the effect of highly alkaline pH conditions on the solubility of trivalent actinides in calcium chloride rich brine solutions were investigated and a thermodynamic model derived. The solubility of Plutonium in saline brine systems was studied under reducing and non-reducing conditions and is described within a new thermodynamic model. The influence of dissolved carbonate on Americium and Plutonium solubility in MgCl 2 solutions was investigated and quantitative information on Am and Pu solubility limits in these systems derived. Thermodynamic constants and model parameter derived in this work are implemented in the Thermodynamic Reference Database THEREDA owned by BfS. According to the quality assurance approach in THEREDA, is was necessary to publish parts of this work in peer-reviewed scientific journals. The publications are focused on solubility experiments, spectroscopy of aquatic and solid species and thermodynamic data. (Neck et al., Pure Appl. Chem., Vol. 81, (2009), pp. 1555-1568., Altmaier et al., Radiochimica Acta, 97, (2009), pp. 187-192., Altmaier et al., Actinide Research Quarterly, No 2., (2011), pp. 29-32.).
Teal, Lorna R.; Marras, Stefano; Peck, Myron A.; Domenici, Paolo
2018-02-01
empirical relationships which can be found consistently within physiological data across the animal kingdom. The advantages of the DEB models are that they make use of the generalities found in terms of animal physiology and can therefore be applied to species for which little data or empirical observations are available. In addition, the limitations as well as useful potential refinements of these and other physiology-based modelling approaches are discussed. Inclusion of the physiological response of various life stages and modelling the patterns of extreme events observed in nature are suggested for future work.
Modelling inter-supply chain competition with resource limitation and demand disruption
Chen, Zhaobo; Teng, Chunxian; Zhang, Ding; Sun, Jiayi
2016-05-01
This paper proposes a comprehensive model for studying supply chain versus supply chain competition with resource limitation and demand disruption. We assume that there are supply chains with heterogeneous supply network structures that compete at multiple demand markets. Each supply chain is comprised of internal and external firms. The internal firms are coordinated in production and distribution and share some common but limited resources within the supply chain, whereas the external firms are independent and do not share the internal resources. The supply chain managers strive to develop optimal strategies in terms of production level and resource allocation in maximising their profit while facing competition at the end market. The Cournot-Nash equilibrium of this inter-supply chain competition is formulated as a variational inequality problem. We further study the case when there is demand disruption in the plan-execution phase. In such a case, the managers need to revise their planned strategy in order to maximise their profit with the new demand under disruption and minimise the cost of change. We present a bi-criteria decision-making model for supply chain managers and develop the optimal conditions in equilibrium, which again can be formulated by another variational inequality problem. Numerical examples are presented for illustrative purpose.
International Nuclear Information System (INIS)
Senf, Fabian; Altrock, Philipp M; Behn, Ulrich
2009-01-01
A finite array of N globally coupled Stratonovich models exhibits a continuous nonequilibrium phase transition. In the limit of strong coupling, there is a clear separation of timescales of centre of mass and relative coordinates. The latter relax very fast to zero and the array behaves as a single entity described by the centre of mass coordinate. We compute analytically the stationary probability distribution and the moments of the centre of mass coordinate. The scaling behaviour of the moments near the critical value of the control parameter a c (N) is determined. We identify a crossover from linear to square root scaling with increasing distance from a c . The crossover point approaches a c in the limit N→∞ which reproduces previous results for infinite arrays. Our results are obtained in both the Fokker-Planck and the Langevin approach and are corroborated by numerical simulations. For a general class of models we show that the transition manifold in the parameter space depends on N and is determined by the scaling behaviour near a fixed point of the stochastic flow.
Diagnosing phosphorus limitations in natural terrestrial ecosystems in carbon cycle models
Sun, Yan; Peng, Shushi; Goll, Daniel S.; Ciais, Philippe; Guenet, Bertrand; Guimberteau, Matthieu; Hinsinger, Philippe; Janssens, Ivan A.; Peñuelas, Josep; Piao, Shilong; Poulter, Benjamin; Violette, Aurélie; Yang, Xiaojuan; Yin, Yi; Zeng, Hui
2017-07-01
Most of the Earth System Models (ESMs) project increases in net primary productivity (NPP) and terrestrial carbon (C) storage during the 21st century. Despite empirical evidence that limited availability of phosphorus (P) may limit the response of NPP to increasing atmospheric CO2, none of the ESMs used in the previous Intergovernmental Panel on Climate Change assessment accounted for P limitation. We diagnosed from ESM simulations the amount of P need to support increases in carbon uptake by natural ecosystems using two approaches: the demand derived from (1) changes in C stocks and (2) changes in NPP. The C stock-based additional P demand was estimated to range between -31 and 193 Tg P and between -89 and 262 Tg P for Representative Concentration Pathway (RCP) 2.6 and RCP8.5, respectively, with negative values indicating a P surplus. The NPP-based demand, which takes ecosystem P recycling into account, results in a significantly higher P demand of 648-1606 Tg P for RCP2.6 and 924-2110 Tg P for RCP8.5. We found that the P demand is sensitive to the turnover of P in decomposing plant material, explaining the large differences between the NPP-based demand and C stock-based demand. The discrepancy between diagnosed P demand and actual P availability (potential P deficit) depends mainly on the assumptions about availability of the different soil P forms. Overall, future P limitation strongly depends on both soil P availability and P recycling on ecosystem scale.
Plot showing ATLAS limits on Standard Model Higgs production in the mass range 100-600 GeV
ATLAS Collaboration
2011-01-01
The combined upper limit on the Standard Model Higgs boson production cross section divided by the Standard Model expectation as a function of mH is indicated by the solid line. This is a 95% CL limit using the CLs method in the entire mass range. The dotted line shows the median expected limit in the absence of a signal and the green and yellow bands reflect the corresponding 68% and 95% expected
Plot showing ATLAS limits on Standard Model Higgs production in the mass range 110-150 GeV
ATLAS Collaboration
2011-01-01
The combined upper limit on the Standard Model Higgs boson production cross section divided by the Standard Model expectation as a function of mH is indicated by the solid line. This is a 95% CL limit using the CLs method in in the low mass range. The dotted line shows the median expected limit in the absence of a signal and the green and yellow bands reflect the corresponding 68% and 95% expected
Validation of a limited area model over Dome C, Antarctic Plateau, during winter
Energy Technology Data Exchange (ETDEWEB)
Gallee, Hubert; Gorodetskaya, Irina V. [Laboratoire de Glaciologie et de Geophysique de l' Environnement, CNRS, 54, rue Moliere, BP. 96, St Martin d' Heres Cedex (France)
2010-01-15
The limited area model MAR (Modele Atmospherique Regional) is validated over the Antarctic Plateau for the period 2004-2006, focussing on Dome C during the cold season. MAR simulations are made by initializing the model once and by forcing it through its lateral and top boundaries by the ECMWF operational analyses. Model outputs compare favourably with observations from automatic weather station (AWS), radiometers and atmospheric soundings. MAR is able to simulate the succession of cold and warm events which occur at Dome C during winter. Larger longwave downwelling fluxes (LWD) are responsible for higher surface air temperatures and weaker surface inversions during winter. Warm events are better simulated when the small Antarctic precipitating snow particles are taken into account in radiative transfer computations. MAR stratosphere cools during the cold season, with the coldest temperatures occurring in conjunction with warm events at the surface. The decrease of saturation specific humidity associated with these coldest temperatures is responsible for the formation of polar stratospheric clouds (PSCs) especially in August-September. PSCs then contribute to the surface warming by increasing the surface downwelling longwave flux. (orig.)
High-resolution surface analysis for extended-range downscaling with limited-area atmospheric models
Separovic, Leo; Husain, Syed Zahid; Yu, Wei; Fernig, David
2014-12-01
High-resolution limited-area model (LAM) simulations are frequently employed to downscale coarse-resolution objective analyses over a specified area of the globe using high-resolution computational grids. When LAMs are integrated over extended time frames, from months to years, they are prone to deviations in land surface variables that can be harmful to the quality of the simulated near-surface fields. Nudging of the prognostic surface fields toward a reference-gridded data set is therefore devised in order to prevent the atmospheric model from diverging from the expected values. This paper presents a method to generate high-resolution analyses of land-surface variables, such as surface canopy temperature, soil moisture, and snow conditions, to be used for the relaxation of lower boundary conditions in extended-range LAM simulations. The proposed method is based on performing offline simulations with an external surface model, forced with the near-surface meteorological fields derived from short-range forecast, operational analyses, and observed temperatures and humidity. Results show that the outputs of the surface model obtained in the present study have potential to improve the near-surface atmospheric fields in extended-range LAM integrations.
Modeling interfacial glass-water reactions: recent advances and current limitations
International Nuclear Information System (INIS)
Pierce, Eric M.; Frugier, Pierre; Criscenti, Louise J.; Kwon, Kideok D.; Kerisit, Sebastien N.
2014-01-01
Describing the reactions that occur at the glass-water interface and control the development of the altered layer constitutes one of the main scientific challenges impeding existing models from providing accurate radionuclide release estimates. Radionuclide release estimates are a critical component of the safety basis for geologic repositories. The altered layer (i.e., amorphous hydrated surface layer and crystalline reaction products) represents a complex region, both physically and chemically, sandwiched between two distinct boundaries-pristine glass surface at the inner most interface and aqueous solution at the outer most interface. Computational models, spanning different length and timescales, are currently being developed to improve our understanding of this complex and dynamic process with the goal of accurately describing the mesoscale changes that occur as the system evolves. These modeling approaches include geochemical simulations (i.e., classical reaction path simulations and glass reactivity in allowance for alteration layer simulations), Monte Carlo simulations, and molecular dynamics methods. Discussed in this manuscript are the advances and limitations of each modeling approach placed in the context of the glass-water reaction and how collectively these approaches provide insights into the mechanisms that control the formation and evolution of altered layers. New results are presented as examples of each approach. (authors)
Variable speed limit strategies analysis with link transmission model on urban expressway
Li, Shubin; Cao, Danni
2018-02-01
The variable speed limit (VSL) is a kind of active traffic management method. Most of the strategies are used in the expressway traffic flow control in order to ensure traffic safety. However, the urban expressway system is the main artery, carrying most traffic pressure. It has similar traffic characteristics with the expressways between cities. In this paper, the improved link transmission model (LTM) combined with VSL strategies is proposed, based on the urban expressway network. The model can simulate the movement of the vehicles and the shock wave, and well balance the relationship between the amount of calculation and accuracy. Furthermore, the optimal VSL strategy can be proposed based on the simulation method. It can provide management strategies for managers. Finally, a simple example is given to illustrate the model and method. The selected indexes are the average density, the average speed and the average flow on the traffic network in the simulation. The simulation results show that the proposed model and method are feasible. The VSL strategy can effectively alleviate traffic congestion in some cases, and greatly promote the efficiency of the transportation system.
Tomar, Dheeraj S; Weber, Valéry; Pettitt, B Montgomery; Asthagiri, D
2014-04-17
The hydration thermodynamics of the amino acid X relative to the reference G (glycine) or the hydration thermodynamics of a small-molecule analog of the side chain of X is often used to model the contribution of X to protein stability and solution thermodynamics. We consider the reasons for successes and limitations of this approach by calculating and comparing the conditional excess free energy, enthalpy, and entropy of hydration of the isoleucine side chain in zwitterionic isoleucine, in extended penta-peptides, and in helical deca-peptides. Butane in gauche conformation serves as a small-molecule analog for the isoleucine side chain. Parsing the hydrophobic and hydrophilic contributions to hydration for the side chain shows that both of these aspects of hydration are context-sensitive. Furthermore, analyzing the solute-solvent interaction contribution to the conditional excess enthalpy of the side chain shows that what is nominally considered a property of the side chain includes entirely nonobvious contributions of the background. The context-sensitivity of hydrophobic and hydrophilic hydration and the conflation of background contributions with energetics attributed to the side chain limit the ability of a single scaling factor, such as the fractional solvent exposure of the group in the protein, to map the component energetic contributions of the model-compound data to their value in the protein. But ignoring the origin of cancellations in the underlying components the group-transfer model may appear to provide a reasonable estimate of the free energy for a given error tolerance.
Image-based Modeling of PSF Deformation with Application to Limited Angle PET Data
Matej, Samuel; Li, Yusheng; Panetta, Joseph; Karp, Joel S.; Surti, Suleman
2016-01-01
The point-spread-functions (PSFs) of reconstructed images can be deformed due to detector effects such as resolution blurring and parallax error, data acquisition geometry such as insufficient sampling or limited angular coverage in dual-panel PET systems, or reconstruction imperfections/simplifications. PSF deformation decreases quantitative accuracy and its spatial variation lowers consistency of lesion uptake measurement across the imaging field-of-view (FOV). This can be a significant problem with dual panel PET systems even when using TOF data and image reconstruction models of the detector and data acquisition process. To correct for the spatially variant reconstructed PSF distortions we propose to use an image-based resolution model (IRM) that includes such image PSF deformation effects. Originally the IRM was mostly used for approximating data resolution effects of standard PET systems with full angular coverage in a computationally efficient way, but recently it was also used to mitigate effects of simplified geometric projectors. Our work goes beyond this by including into the IRM reconstruction imperfections caused by combination of the limited angle, parallax errors, and any other (residual) deformation effects and testing it for challenging dual panel data with strongly asymmetric and variable PSF deformations. We applied and tested these concepts using simulated data based on our design for a dedicated breast imaging geometry (B-PET) consisting of dual-panel, time-of-flight (TOF) detectors. We compared two image-based resolution models; i) a simple spatially invariant approximation to PSF deformation, which captures only the general PSF shape through an elongated 3D Gaussian function, and ii) a spatially variant model using a Gaussian mixture model (GMM) to more accurately capture the asymmetric PSF shape in images reconstructed from data acquired with the B-PET scanner geometry. Results demonstrate that while both IRMs decrease the overall uptake
International Nuclear Information System (INIS)
Plakida, N. M.; Anton, L.; Adam, S. . Department of Theoretical Physics, Horia Hulubei National Institute for Physics and Nuclear Engineering, PO Box MG-6, RO-76900 Bucharest - Magurele; RO); Adam, Gh. . Department of Theoretical Physics, Horia Hulubei National Institute for Physics and Nuclear Engineering, PO Box MG-6, RO-76900 Bucharest - Magurele; RO)
2001-01-01
A microscopical theory of superconductivity in the two-band singlet-hole Hubbard model, in the strong coupling limit in a paramagnetic state, is developed. The model Hamiltonian is obtained by projecting the p-d model to an asymmetric Hubbard model with the lower Hubbard subband occupied by one-hole Cu d-like states and the upper Hubbard subband occupied by two-hole p-d singlet states. The model requires two microscopical parameters only, the p-d hybridization parameter t and the charge-transfer gap Δ. It was previously shown to secure an appropriate description of the normal state properties of the high -T c cuprates. To treat rigorously the strong correlations, the Hubbard operator technique within the projection method for the Green function is used. The Dyson equation is derived. In the molecular field approximation, d-wave superconducting pairing of conventional hole (electron) pairs in one Hubbard subband is found, which is mediated by the exchange interaction given by the interband hopping, J ij = 4 (t ij ) 2 / Δ. The normal and anomalous components of the self-energy matrix are calculated in the self-consistent Born approximation for the electron-spin-fluctuation scattering mediated by kinematic interaction of the second order of the intraband hopping. The derived numerical and analytical solutions predict the occurrence of singlet d x 2 -y 2 -wave pairing both in the d-hole and singlet Hubbard subbands. The gap functions and T c are calculated for different hole concentrations. The exchange interaction is shown to be the most important pairing interaction in the Hubbard model in the strong correlation limit, while the spin-fluctuation coupling results only in a moderate enhancement of T c . The smaller weight of the latter comes from two specific features: its vanishing inside the Brillouin zone (BZ) along the lines, |k x | + |k y |=π pointing towards the hot spots and the existence of a small energy shell within which the pairing is effective. By
Deribe, Kebede; Cano, Jorge; Newport, Melanie J; Golding, Nick; Pullan, Rachel L; Sime, Heven; Gebretsadik, Abeba; Assefa, Ashenafi; Kebede, Amha; Hailu, Asrat; Rebollo, Maria P; Shafi, Oumer; Bockarie, Moses J; Aseffa, Abraham; Hay, Simon I; Reithinger, Richard; Enquselassie, Fikre; Davey, Gail; Brooker, Simon J
2015-01-01
Ethiopia is assumed to have the highest burden of podoconiosis globally, but the geographical distribution and environmental limits and correlates are yet to be fully investigated. In this paper we use data from a nationwide survey to address these issues. Our analyses are based on data arising from the integrated mapping of podoconiosis and lymphatic filariasis (LF) conducted in 2013, supplemented by data from an earlier mapping of LF in western Ethiopia in 2008-2010. The integrated mapping used woreda (district) health offices' reports of podoconiosis and LF to guide selection of survey sites. A suite of environmental and climatic data and boosted regression tree (BRT) modelling was used to investigate environmental limits and predict the probability of podoconiosis occurrence. Data were available for 141,238 individuals from 1,442 communities in 775 districts from all nine regional states and two city administrations of Ethiopia. In 41.9% of surveyed districts no cases of podoconiosis were identified, with all districts in Affar, Dire Dawa, Somali and Gambella regional states lacking the disease. The disease was most common, with lymphoedema positivity rate exceeding 5%, in the central highlands of Ethiopia, in Amhara, Oromia and Southern Nations, Nationalities and Peoples regional states. BRT modelling indicated that the probability of podoconiosis occurrence increased with increasing altitude, precipitation and silt fraction of soil and decreased with population density and clay content. Based on the BRT model, we estimate that in 2010, 34.9 (95% confidence interval [CI]: 20.2-51.7) million people (i.e. 43.8%; 95% CI: 25.3-64.8% of Ethiopia's national population) lived in areas environmentally suitable for the occurrence of podoconiosis. Podoconiosis is more widespread in Ethiopia than previously estimated, but occurs in distinct geographical regions that are tied to identifiable environmental factors. The resultant maps can be used to guide programme planning
Directory of Open Access Journals (Sweden)
Kebede Deribe
Full Text Available Ethiopia is assumed to have the highest burden of podoconiosis globally, but the geographical distribution and environmental limits and correlates are yet to be fully investigated. In this paper we use data from a nationwide survey to address these issues.Our analyses are based on data arising from the integrated mapping of podoconiosis and lymphatic filariasis (LF conducted in 2013, supplemented by data from an earlier mapping of LF in western Ethiopia in 2008-2010. The integrated mapping used woreda (district health offices' reports of podoconiosis and LF to guide selection of survey sites. A suite of environmental and climatic data and boosted regression tree (BRT modelling was used to investigate environmental limits and predict the probability of podoconiosis occurrence.Data were available for 141,238 individuals from 1,442 communities in 775 districts from all nine regional states and two city administrations of Ethiopia. In 41.9% of surveyed districts no cases of podoconiosis were identified, with all districts in Affar, Dire Dawa, Somali and Gambella regional states lacking the disease. The disease was most common, with lymphoedema positivity rate exceeding 5%, in the central highlands of Ethiopia, in Amhara, Oromia and Southern Nations, Nationalities and Peoples regional states. BRT modelling indicated that the probability of podoconiosis occurrence increased with increasing altitude, precipitation and silt fraction of soil and decreased with population density and clay content. Based on the BRT model, we estimate that in 2010, 34.9 (95% confidence interval [CI]: 20.2-51.7 million people (i.e. 43.8%; 95% CI: 25.3-64.8% of Ethiopia's national population lived in areas environmentally suitable for the occurrence of podoconiosis.Podoconiosis is more widespread in Ethiopia than previously estimated, but occurs in distinct geographical regions that are tied to identifiable environmental factors. The resultant maps can be used to guide
International Nuclear Information System (INIS)
Krutzik, Norbert J.; Eibl, Josef
2005-01-01
Shocks on building structures due to impact loads (drop of wreckage and heavy masses from accidents, transport operations, explosions, etc.), especially in case of a postulated aircraft crash, may lead to feasibility problems due to high-induced vibrations and large expenditures at safety-related systems accommodated inside the building structures. A rational and cost-effective qualification of the functionality of such systems requires the prediction of reliable information about the nature of structural responses induced by impact loading in the corresponding regions of the structure. The analytic derivation of realistic and reliable structural responses requires the application of adequate mathematical models and methods as well as a critical evaluation of all factors that influence the entire shock transmission path, from the area of impact to the site of installation of the affected component or system in the structure. Despite extensive studies and computational analyses of impact-induced shocks performed using finite element simulation method, limited and insufficient experimental results to date have precluded a complete investigation and clarification of several 'peculiarities' in the field of shock transmission in finite element models. This refers mainly to the divergence of results observed using FE models when not considering a the required FE element discretization ratio as well as to the attenuation and scatter behavior of the dynamic response results obtained for large building structures and given large distances between the load impact application areas and the component anchoring locations. The cause for such divergences are related to several up to now not clarified 'phenomena' of FE models especially the low-pass filtering effects and dispersion characteristics of FE models
Directory of Open Access Journals (Sweden)
Byunghun Choi
2016-04-01
Full Text Available Chinese responsibility for reducing Greenhouse Gas or carbon dioxide emission increases continuously. Chinese government suggested two targets; Alternative Fuel Vehicle output volume 500 thousand and AFV market share 5% by the end of 2011. However any of two targets did not come true. Therefore this study accessed the question, ‘why Chinese government initiative model for AFV promotion has been so poor?’ This study reviewed the transition process for AFV policies in China and made a structural analysis for three key policies since 2009. As a result the number of articles for related industries or factor endowments was relatively more than firm strategy or demand conditions. Also this study accessed the AFV strategy of Six SOEs from the perspective of social responsibility. Six SOEs have more concentrated on electric vehicle rather than hybrid vehicle with following the government leadership. However major EV or HEV models of them mostly were made by Joint Ventures being under control of foreign makers and the JVs have actually controlled over AFV business. So the limitation of Chinese government initiative model resulted from supplier-centric approach with targeting for public transportation and institution consumer, and it caused a failure to create the demand conditions of general customers.
Mégarbane, Bruno; Aslani, Arsia Amir; Deye, Nicolas; Baud, Frédéric J
2008-05-01
Hypotension, cardiac failure, QT interval prolongation, dysrhythmias, and conduction disturbances are common complications of overdoses with cardiotoxicants. Pharmacokinetic/pharmacodynamic (PK/PD) relationships are useful to assess diagnosis, prognosis, and treatment efficacy in acute poisonings. To review the utility and limits of PK/PD studies of cardiac toxicity. Discussion of various models, mainly those obtained in digitalis, cyanide, venlafaxine and citalopram poisonings. A sigmoidal E(max) model appears adequate to represent the PK/PD relationships in cardiotoxic poisonings. PK/PD correlations investigate the discrepancies between the time course of the effect magnitude and its evolving concentrations. They may help in understanding the mechanisms of occurrence as well as disappearance of a cardiotoxic effect. When data are sparse, population-based PK/PD modeling using computer-intensive algorithms is helpful to estimate population mean values of PK parameters as well as their individual variability. Further PK/PD studies are needed in medical toxicology to allow understanding of the meaning of blood toxicant concentration in acute poisonings and thus improve management.
The Poisson model limits in NBA basketball: Complexity in team sports
Martín-González, Juan Manuel; de Saá Guerra, Yves; García-Manso, Juan Manuel; Arriaza, Enrique; Valverde-Estévez, Teresa
2016-12-01
Team sports are frequently studied by researchers. There is presumption that scoring in basketball is a random process and that can be described using the Poisson Model. Basketball is a collaboration-opposition sport, where the non-linear local interactions among players are reflected in the evolution of the score that ultimately determines the winner. In the NBA, the outcomes of close games are often decided in the last minute, where fouls play a main role. We examined 6130 NBA games in order to analyze the time intervals between baskets and scoring dynamics. Most numbers of baskets (n) over a time interval (ΔT) follow a Poisson distribution, but some (e.g., ΔT = 10 s, n > 3) behave as a Power Law. The Poisson distribution includes most baskets in any game, in most game situations, but in close games in the last minute, the numbers of events are distributed following a Power Law. The number of events can be adjusted by a mixture of two distributions. In close games, both teams try to maintain their advantage solely in order to reach the last minute: a completely different game. For this reason, we propose to use the Poisson model as a reference. The complex dynamics will emerge from the limits of this model.
Rotary engine performance limits predicted by a zero-dimensional model
Bartrand, Timothy A.; Willis, Edward A.
1992-01-01
A parametric study was performed to determine the performance limits of a rotary combustion engine. This study shows how well increasing the combustion rate, insulating, and turbocharging increase brake power and decrease fuel consumption. Several generalizations can be made from the findings. First, it was shown that the fastest combustion rate is not necessarily the best combustion rate. Second, several engine insulation schemes were employed for a turbocharged engine. Performance improved only for a highly insulated engine. Finally, the variability of turbocompounding and the influence of exhaust port shape were calculated. Rotary engines performance was predicted by an improved zero-dimensional computer model based on a model developed at the Massachusetts Institute of Technology in the 1980's. Independent variables in the study include turbocharging, manifold pressures, wall thermal properties, leakage area, and exhaust port geometry. Additions to the computer programs since its results were last published include turbocharging, manifold modeling, and improved friction power loss calculation. The baseline engine for this study is a single rotor 650 cc direct-injection stratified-charge engine with aluminum housings and a stainless steel rotor. Engine maps are provided for the baseline and turbocharged versions of the engine.
Directory of Open Access Journals (Sweden)
Junlian Gao
2018-05-01
Full Text Available Across the world, human activity is approaching planetary boundaries. In northwest China, in particular, the coal industry and agriculture are competing for key limited inputs of land and water. In this situation, the traditional approach to planning the development of each sector independently fails to deliver sustainable solutions, as solutions made in sectorial ‘silos’ are often suboptimal for the entire economy. We propose a spatially detailed cost-minimizing model for coal and agricultural production in a region under constraints on land and water availability. We apply the model to the case study of Shanxi province, China. We show how such an integrated optimization, which takes maximum advantage of the spatial heterogeneity in resource abundance, could help resolve the conflicts around the water–food–energy (WFE nexus and assist in its management. We quantify the production-possibility frontiers under different water-availability scenarios and demonstrate that in water-scarce regions, like Shanxi, the production capacity and corresponding production solutions are highly sensitive to water constraints. The shadow prices estimated in the model could be the basis for intelligent differentiated water pricing, not only to enable the water-resource transfer between agriculture and the coal industry, and across regions, but also to achieve cost-effective WFE management.
Is sustainability achievable? Exploring the limits of sustainability with model systems.
Shastri, Yogendra; Diwekar, Urmila; Cabezas, Heriberto; Williamson, James
2008-09-01
Successful implementation of sustainability ideas in ecosystem management requires a basic understanding of the often nonlinear and nonintuitive relationships among different dimensions of sustainability, particularly the system-wide implications of human actions. This basic understanding further includes a sense of the time scale of possible future events and the limits of what is and is not likely to be possible. With this understanding, systematic approaches can then be used to develop policy guidelines for the system. This article presents an illustration of these ideas by analyzing an integrated ecological-economic-social model, which comprises various ecological (natural) and domesticated compartments representing species along with a macroeconomic price setting model. The stable and qualitatively realistic model is used to analyze different relevant scenarios. Apart from highlighting complex relationships within the system, it identifies potentially unsustainable future developments such as increased human per capita consumption rates. Dynamic optimization is then used to develop time-dependent policy guidelines for the unsustainable scenarios using objective functions that aim to minimize fluctuations in the system's Fisher information. The results can help to identify effective policy parameters and highlight the tradeoff between natural and domesticated compartments while managing such integrated systems. The results should also qualitatively guide further investigations in the area of system level studies and policy development.
CHOI, S.; Shi, Y.; Ni, X.; Simard, M.; Myneni, R. B.
2013-12-01
Sparseness in in-situ observations has precluded the spatially explicit and accurate mapping of forest biomass. The need for large-scale maps has raised various approaches implementing conjugations between forest biomass and geospatial predictors such as climate, forest type, soil property, and topography. Despite the improved modeling techniques (e.g., machine learning and spatial statistics), a common limitation is that biophysical mechanisms governing tree growth are neglected in these black-box type models. The absence of a priori knowledge may lead to false interpretation of modeled results or unexplainable shifts in outputs due to the inconsistent training samples or study sites. Here, we present a gray-box approach combining known biophysical processes and geospatial predictors through parametric optimizations (inversion of reference measures). Total aboveground biomass in forest stands is estimated by incorporating the Forest Inventory and Analysis (FIA) and Parameter-elevation Regressions on Independent Slopes Model (PRISM). Two main premises of this research are: (a) The Allometric Scaling and Resource Limitations (ASRL) theory can provide a relationship between tree geometry and local resource availability constrained by environmental conditions; and (b) The zeroth order theory (size-frequency distribution) can expand individual tree allometry into total aboveground biomass at the forest stand level. In addition to the FIA estimates, two reference maps from the National Biomass and Carbon Dataset (NBCD) and U.S. Forest Service (USFS) were produced to evaluate the model. This research focuses on a site-scale test of the biomass model to explore the robustness of predictors, and to potentially improve models using additional geospatial predictors such as climatic variables, vegetation indices, soil properties, and lidar-/radar-derived altimetry products (or existing forest canopy height maps). As results, the optimized ASRL estimates satisfactorily
Druhan, J. L.; Giannetta, M.; Sanford, R. A.
2017-12-01
In recent years, reactive transport principles have expanded from early applications, largely based in contaminant hydrology, to a wide range of biologically mediated redox environments including marine sedimentary diagenesis, terrestrial metal ore deposits, soils, and critical zone weathering profiles. A common observation across this diversity of systems is that they often function under energetically limited conditions in comparison to those typical of contaminated aquifers subject to engineered remediation techniques. As a result, the kinetic rate expressions traditionally employed within reactive transport frameworks to simulate microbially mediated redox transformations have required modification. This was recognized in a series of seminal papers by Jin and Bethke (2005, 2007) in which the authors expanded upon a Monod rate law to include a thermodynamic potential factor `Ft' which exerts a limitation on the overall rate based on the thermodynamic driving force of the electron transfer reaction. This new rate expression is now commonly implemented within many of the major reactive transport software packages, though appropriate application has yet to be thoroughly demonstrated. Notably, the characteristically large partitioning of stable isotopes during microbially mediated reactions, which is extensively utilized to identify and quantify these redox transformations, has yet to be simulated under conditions in which the Ft term may be expected to exert a significant mass dependent influence. Here, we develop a series of simplified simulations for the microbially mediated reduction of sulfate based on the datasets reported by Jin and Bethke, and apply appropriate mass-bias within the Ft term to consider the extent to which the resulting isotopic fractionation is consistent with that observed in energetically limited systems. We show that the Ft term can exert a significant influence on the observed fractionation factor under common environmental conditions
DEFF Research Database (Denmark)
Kilic, Onur Alper; Akkerman, Renzo; Grunow, Martin
2009-01-01
In the food industry products are usually characterized by their recipes, which are specified by various quality attributes. For end products, this is given by customer requirements, but for intermediate products, the recipes can be chosen in such a way that raw material procurement costs and pro...... with production and inventory planning, thereby considering the production and storage capacity limitations. The resulting model can be used to solve an important practical problem typical for many food processing industries.......In the food industry products are usually characterized by their recipes, which are specified by various quality attributes. For end products, this is given by customer requirements, but for intermediate products, the recipes can be chosen in such a way that raw material procurement costs...... and processing costs are minimized. However, this product selection process is bound by production and storage capacity limitations, such as the number and size of storage tanks or silos. In this paper, we present a mathematical programming approach that combines decision making on product selection...
Energy Technology Data Exchange (ETDEWEB)
Peng, Yan, E-mail: yanpengphy@163.com [School of Mathematical Sciences, Qufu Normal University, Qufu, Shandong 273165 (China); School of Mathematics and Computer Science, Shaanxi Sci-Tech University, Hanzhong, Shaanxi 723000 (China); Pan, Qiyuan, E-mail: panqiyuan@126.com [Department of Physics, Key Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of Education, Hunan Normal University, Changsha, Hunan 410081 (China); Liu, Yunqi, E-mail: liuyunqi@hust.edu.cn [School of Physics, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China)
2017-02-15
We investigate holographic phase transitions with dark matter sector in the AdS soliton background away from the probe limit. In cases of weak backreaction, we find that the larger coupling parameter α makes the gap of condensation shallower and the critical chemical potential keeps as a constant. In contrast, for very heavy backreaction, the dark matter sector could affect the critical chemical potential and the order of phase transitions. We also find the jump of the holographic topological entanglement entropy corresponds to a first order transition between superconducting states in this model with dark matter sector. More importantly, for certain sets of parameters, we observe novel phenomenon of retrograde condensation. In a word, the dark matter sector provides richer physics in the phase structure and the holographic superconductor properties are helpful in understanding dark matter.
Composite Estimation for Single-Index Models with Responses Subject to Detection Limits
Tang, Yanlin; Wang, Huixia Judy; Liang, Hua
2017-01-01
We propose a semiparametric estimator for single-index models with censored responses due to detection limits. In the presence of left censoring, the mean function cannot be identified without any parametric distributional assumptions, but the quantile function is still identifiable at upper quantile levels. To avoid parametric distributional assumption, we propose to fit censored quantile regression and combine information across quantile levels to estimate the unknown smooth link function and the index parameter. Under some regularity conditions, we show that the estimated link function achieves the non-parametric optimal convergence rate, and the estimated index parameter is asymptotically normal. The simulation study shows that the proposed estimator is competitive with the omniscient least squares estimator based on the latent uncensored responses for data with normal errors but much more efficient for heavy-tailed data under light and moderate censoring. The practical value of the proposed method is demonstrated through the analysis of a human immunodeficiency virus antibody data set.
Burgués, Javier; Jiménez-Soto, Juan Manuel; Marco, Santiago
2018-07-12
The limit of detection (LOD) is a key figure of merit in chemical sensing. However, the estimation of this figure of merit is hindered by the non-linear calibration curve characteristic of semiconductor gas sensor technologies such as, metal oxide (MOX), gasFETs or thermoelectric sensors. Additionally, chemical sensors suffer from cross-sensitivities and temporal stability problems. The application of the International Union of Pure and Applied Chemistry (IUPAC) recommendations for univariate LOD estimation in non-linear semiconductor gas sensors is not straightforward due to the strong statistical requirements of the IUPAC methodology (linearity, homoscedasticity, normality). Here, we propose a methodological approach to LOD estimation through linearized calibration models. As an example, the methodology is applied to the detection of low concentrations of carbon monoxide using MOX gas sensors in a scenario where the main source of error is the presence of uncontrolled levels of humidity. Copyright © 2018 Elsevier B.V. All rights reserved.
Theoretical limit of spatial resolution in diffuse optical tomography using a perturbation model
International Nuclear Information System (INIS)
Konovalov, A B; Vlasov, V V
2014-01-01
We have assessed the limit of spatial resolution of timedomain diffuse optical tomography (DOT) based on a perturbation reconstruction model. From the viewpoint of the structure reconstruction accuracy, three different approaches to solving the inverse DOT problem are compared. The first approach involves reconstruction of diffuse tomograms from straight lines, the second – from average curvilinear trajectories of photons and the third – from total banana-shaped distributions of photon trajectories. In order to obtain estimates of resolution, we have derived analytical expressions for the point spread function and modulation transfer function, as well as have performed a numerical experiment on reconstruction of rectangular scattering objects with circular absorbing inhomogeneities. It is shown that in passing from reconstruction from straight lines to reconstruction using distributions of photon trajectories we can improve resolution by almost an order of magnitude and exceed the accuracy of reconstruction of multi-step algorithms used in DOT. (optical tomography)
Calculation of hydrogen outgassing rate of LHD by recombination limited model
International Nuclear Information System (INIS)
Akaishi, K.; Nakasuga, M.
2002-04-01
To simulate hydrogen outgassing in the plasma vacuum vessel of LHD, the recombination limited model is presented, where the time evolution of hydrogen concentration in the wall of the plasma vacuum vessel is described by a one-dimensional diffusion equation. The hydrogen outgassing rates when the plasma vacuum vessel is pumped down at room temperature and baked at 100 degC are calculated as a function of pumping time. The calculation shows that the hydrogen outgassing rate of the plasma vacuum vessel can be reduced at least by one order of magnitude due to pumping and baking. This prediction is consistent with the recent result of outgassing reduction observed in the pumping-down and baking of the plasma vacuum vessel in LHD. (author)
Directory of Open Access Journals (Sweden)
Florencia Stelzer
2014-01-01
Full Text Available Executive functions (EF have been defined as a series of higher-order cognitive processes which allow the control of thought, behavior and affection according to the achievement of a goal. Such processes present a lengthy postnatal development which matures completely by the end of adolescence. In this article we make a review of some of the main models of EF development during childhood. The aim of this work is to describe the state of the art related to the topic, identifying the main theoretical difficulties and methodological limitations associated with the different proposed paradigms. Finally, some suggestions are given to cope with such difficulties, emphasizing that the development of an ontology of EF could be a viable alternative to counter them. We believe that futture researches should guide their efforts toward the development of that ontology.
International Nuclear Information System (INIS)
Peng, Yan; Pan, Qiyuan; Liu, Yunqi
2017-01-01
We investigate holographic phase transitions with dark matter sector in the AdS soliton background away from the probe limit. In cases of weak backreaction, we find that the larger coupling parameter α makes the gap of condensation shallower and the critical chemical potential keeps as a constant. In contrast, for very heavy backreaction, the dark matter sector could affect the critical chemical potential and the order of phase transitions. We also find the jump of the holographic topological entanglement entropy corresponds to a first order transition between superconducting states in this model with dark matter sector. More importantly, for certain sets of parameters, we observe novel phenomenon of retrograde condensation. In a word, the dark matter sector provides richer physics in the phase structure and the holographic superconductor properties are helpful in understanding dark matter.
Strzałka, Dominik; Dymora, Paweł; Mazurek, Mirosław
2018-02-01
In this paper we present some preliminary results in the field of computer systems management with relation to Tsallis thermostatistics and the ubiquitous problem of hardware limited resources. In the case of systems with non-deterministic behaviour, management of their resources is a key point that guarantees theirs acceptable performance and proper working. This is very wide problem that stands for many challenges in financial, transport, water and food, health, etc. areas. We focus on computer systems with attention paid to cache memory and propose to use an analytical model that is able to connect non-extensive entropy formalism, long-range dependencies, management of system resources and queuing theory. Obtained analytical results are related to the practical experiment showing interesting and valuable results.
Design and modeling of an SJ infrared solar cell approaching upper limit of theoretical efficiency
Sahoo, G. S.; Mishra, G. P.
2018-01-01
Recent trends of photovoltaics account for the conversion efficiency limit making them more cost effective. To achieve this we have to leave the golden era of silicon cell and make a path towards III-V compound semiconductor groups to take advantages like bandgap engineering by alloying these compounds. In this work we have used a low bandgap GaSb material and designed a single junction (SJ) cell with a conversion efficiency of 32.98%. SILVACO ATLAS TCAD simulator has been used to simulate the proposed model using both Ray Tracing and Transfer Matrix Method (under 1 sun and 1000 sun of AM1.5G spectrum). A detailed analyses of photogeneration rate, spectral response, potential developed, external quantum efficiency (EQE), internal quantum efficiency (IQE), short-circuit current density (JSC), open-circuit voltage (VOC), fill factor (FF) and conversion efficiency (η) are discussed. The obtained results are compared with previously reported SJ solar cell reports.
Directory of Open Access Journals (Sweden)
Yan Peng
2017-02-01
Full Text Available We investigate holographic phase transitions with dark matter sector in the AdS soliton background away from the probe limit. In cases of weak backreaction, we find that the larger coupling parameter α makes the gap of condensation shallower and the critical chemical potential keeps as a constant. In contrast, for very heavy backreaction, the dark matter sector could affect the critical chemical potential and the order of phase transitions. We also find the jump of the holographic topological entanglement entropy corresponds to a first order transition between superconducting states in this model with dark matter sector. More importantly, for certain sets of parameters, we observe novel phenomenon of retrograde condensation. In a word, the dark matter sector provides richer physics in the phase structure and the holographic superconductor properties are helpful in understanding dark matter.
Mass limit for the standard model Higgs boson with the full LEP I ALEPH data sample
Buskulic, D.; de Bonis, I.; Decamp, D.; Ghez, P.; Goy, C.; Lees, J.-P.; Lucotte, A.; Minard, M.-N.; Nief, J.-Y.; Odier, P.; Pietrzyk, B.; Casado, M. P.; Chmeissani, M.; Crespo, J. M.; Delfino, M.; Efthymiopoulos, I.; Fernandez, E.; Fernandez-Bosman, M.; Garrido, Ll.; Juste, A.; Martinez, M.; Orteu, S.; Padilla, C.; Park, I. C.; Pascual, A.; Perlas, J. A.; Riu, I.; Sanchez, F.; Teubert, F.; Colaleo, A.; Creanza, D.; de Palma, M.; Gelao, G.; Girone, M.; Iaselli, G.; Maggi, G.; Maggi, M.; Marinelli, N.; Nuzzo, S.; Ranieri, A.; Raso, G.; Ruggieri, F.; Selvaggi, G.; Silvestris, L.; Tempesta, P.; Zito, G.; Huang, X.; Lin, J.; Ouyang, Q.; Wang, T.; Xie, Y.; Xu, R.; Xue, S.; Zhang, J.; Zhang, L.; Zhao, W.; Alemany, R.; Bazarko, A. O.; Bonvicini, G.; Cattaneo, M.; Comas, P.; Coyle, P.; Drevermann, H.; Forty, R. W.; Frank, M.; Hagelberg, R.; Harvey, J.; Janot, P.; Jost, B.; Kneringer, E.; Knobloch, J.; Lehraus, I.; Lutters, G.; Martin, E. B.; Mato, P.; Minten, A.; Miquel, R.; Mir, Ll. M.; Moneta, L.; Oest, T.; Pacheco, A.; Pusztaszeri, J.-F.; Ranjard, F.; Rensing, P.; Rolandi, L.; Schlatter, D.; Schmelling, M.; Schmitt, M.; Schneider, O.; Tejessy, W.; Tomalin, I. R.; Venturi, A.; Wachsmuth, H.; Wagner, A.; Ajaltouni, Z.; Barrès, A.; Boyer, C.; Falvard, A.; Gay, P.; Guicheney, C.; Henrard, P.; Jousset, J.; Michel, B.; Monteil, S.; Montret, J.-C.; Pallin, D.; Perret, P.; Podlyski, F.; Proriol, J.; Rosnet, P.; Rossignol, J.-M.; Fearnley, T.; Hansen, J. B.; Hansen, J. D.; Hansen, J. R.; Hansen, P. H.; Nilsson, B. S.; Rensch, B.; Wäänänen, A.; Kyriakis, A.; Markou, C.; Simopoulou, E.; Siotis, I.; Vayaki, A.; Zachariadou, K.; Blondel, A.; Bonneaud, G.; Brient, J. C.; Bourdon, P.; Rougé, A.; Rumpf, M.; Valassi, A.; Verderi, M.; Videau, H.; Candlin, D. J.; Parsons, M. I.; Focardi, E.; Parrini, G.; Corden, M.; Georgiopoulos, C.; Jaffe, D. E.; Antonelli, A.; Bencivenni, G.; Bologna, G.; Bossi, F.; Campana, P.; Capon, G.; Casper, D.; Chiarella, V.; Felici, G.; Laurelli, P.; Mannocchi, G.; Murtas, F.; Murtas, G. P.; Passalacqua, L.; Pepe-Altarelli, M.; Curtis, L.; Dorris, S. J.; Halley, A. W.; Knowles, I. G.; Lynch, J. G.; O'Shea, V.; Raine, C.; Reeves, P.; Scarr, J. M.; Smith, K.; Teixeira-Dias, P.; Thompson, A. S.; Thomson, F.; Thorn, S.; Turnbull, R. M.; Becker, U.; Geweniger, C.; Graefe, G.; Hanke, P.; Hansper, G.; Hepp, V.; Kluge, E. E.; Putzer, A.; Schmidt, M.; Sommer, J.; Stenzel, H.; Tittel, K.; Werner, S.; Wunsch, M.; Abbaneo, D.; Beuselinck, R.; Binnie, D. M.; Cameron, W.; Dornan, P. J.; Moutoussi, A.; Nash, J.; Sedgbeer, J. K.; Stacey, A. M.; Williams, M. D.; Dissertori, G.; Girtler, P.; Kuhn, D.; Rudolph, G.; Betteridge, A. P.; Bowdery, C. K.; Colrain, P.; Crawford, G.; Finch, A. J.; Foster, F.; Hughes, G.; Sloan, T.; Williams, M. I.; Galla, A.; Giehl, I.; Greene, A. M.; Kleinknecht, K.; Quast, G.; Renk, B.; Rohne, E.; Sander, H.-G.; van Gemmeren, P.; Zeitnitz, C.; Aubert, J. J.; Bencheikh, A. M.; Benchouk, C.; Bonissent, A.; Bujosa, G.; Calvet, D.; Carr, J.; Diaconu, C.; Etienne, F.; Konstantinidis, N.; Payre, P.; Rousseau, D.; Talby, M.; Sadouki, A.; Thulasidas, M.; Trabelsi, K.; Aleppo, M.; Ragusa, F.; Abt, I.; Assmann, R.; Bauer, C.; Blum, W.; Dietl, H.; Dydak, F.; Ganis, G.; Gotzhein, C.; Jakobs, K.; Kroha, H.; Lütjens, G.; Lutz, G.; Männer, W.; Moser, H.-G.; Richter, R.; Rosado-Schlosser, A.; Schael, S.; Settles, R.; Seywerd, H.; Denis, R. St.; Wiedenmann, W.; Wolf, G.; Boucrot, J.; Callot, O.; Choi, Y.; Cordier, A.; Davier, M.; Duflot, L.; Grivaz, J.-F.; Heusse, Ph.; Höcker, A.; Jacquet, M.; Kim, D. W.; Le Diberder, F.; Lefrançois, J.; Lutz, A.-M.; Nikolic, I.; Park, H. J.; Schune, M.-H.; Simion, S.; Veillet, J.-J.; Videau, I.; Zerwas, D.; Azzurri, P.; Bagliesi, G.; Batignani, G.; Bettarini, S.; Bozzi, C.; Calderini, G.; Carpinelli, M.; Ciocci, M. A.; Ciulli, V.; Dell'Orso, R.; Fantechi, R.; Ferrante, I.; Foà, L.; Forti, F.; Giassi, A.; Giorgi, M. A.; Gregorio, A.; Ligabue, F.; Lusiani, A.; Marrocchesi, P. S.; Messineo, A.; Palla, F.; Rizzo, G.; Sanguinetti, G.; Sciabà, A.; Spagnolo, P.; Steinberger, J.; Tenchini, R.; Tonelli, G.; Vannini, C.; Verdini, P. G.; Walsh, J.; Blair, G. A.; Bryant, L. M.; Cerutti, F.; Chambers, J. T.; Gao, Y.; Green, M. G.; Medcalf, T.; Perrodo, P.; Strong, J. A.; von Wimmersperg-Toeller, J. H.; Botterill, D. R.; Clifft, R. W.; Edgecock, T. R.; Haywood, S.; Maley, P.; Norton, P. R.; Thompson, J. C.; Wright, A. E.; Bloch-Devaux, B.; Colas, P.; Emery, S.; Kozanecki, W.; Lançon, E.; Lemaire, M. C.; Locci, E.; Marx, B.; Perez, P.; Rander, J.; Renardy, J.-F.; Roussarie, A.; Schuller, J.-P.; Schwindling, J.; Trabelsi, A.; Vallage, B.; Black, S. N.; Dann, J. H.; Johnson, R. P.; Kim, H. Y.; Litke, A. M.; McNeil, M. A.; Taylor, G.; Booth, C. N.; Boswell, R.; Brew, C. A. J.; Cartwright, S.; Combley, F.; Koksal, A.; Letho, M.; Newton, W. M.; Reeve, J.; Thompson, L. F.; Böhrer, A.; Brandt, S.; Büscher, V.; Cowan, G.; Grupen, C.; Minguet-Rodriguez, J.; Rivera, F.; Saraiva, P.; Smolik, L.; Stephan, F.; Apollonio, M.; Bosisio, L.; Della Marina, R.; Giannini, G.; Gobbo, B.; Musolino, G.; Rothberg, J.; Wasserbaech, S.; Armstrong, S. R.; Elmer, P.; Feng, Z.; Ferguson, D. P. S.; Gao, Y. S.; González, S.; Grahl, J.; Greening, T. C.; Hayes, O. J.; Hu, H.; McNamara, P. A.; Nachtman, J. M.; Orejudos, W.; Pan, Y. B.; Saadi, Y.; Scott, I. J.; Walsh, A. M.; Lan Wu, Sau; Wu, X.; Yamartino, J. M.; Zheng, M.; Zobernig, G.; Aleph Collaboration
1996-02-01
The reaction e +e - → HZ ∗ is used to search for the standard model Higgs boson in the Hν overlineν and the Hℓ +ℓ - channels. The data sample corresponds to about 4.5 million hadronic Z decays collected by the ALEPH experiment at LEP from 1989 to 1995 at centre-of-mass energies at and around the Z peak. Three candidate events are found in the H μ+μ- channel, in agreement with the expected background from the electroweak process e +e -ℓ +ℓ -q overlineq. This search results in a 95% C.L. lower limit on the Higgs boson mass of 63.9 GeV/ c2.
Limited ability driven phase transitions in the coevolution process in Axelrod's model
Wang, Bing; Han, Yuexing; Chen, Luonan; Aihara, Kazuyuki
2009-04-01
We study the coevolution process in Axelrod's model by taking into account of agents' abilities to access information, which is described by a parameter α to control the geographical range of communication. We observe two kinds of phase transitions in both cultural domains and network fragments, which depend on the parameter α. By simulation, we find that not all rewiring processes pervade the dissemination of culture, that is, a very limited ability to access information constrains the cultural dissemination, while an exceptional ability to access information aids the dissemination of culture. Furthermore, by analyzing the network characteristics at the frozen states, we find that there exists a stage at which the network develops to be a small-world network with community structures.
Limited ability driven phase transitions in the coevolution process in Axelrod's model
Energy Technology Data Exchange (ETDEWEB)
Wang Bing [ERATO Aihara Complexity Modelling Project, JST, Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Institute of Industrial Science, University of Tokyo, Tokyo (Japan)], E-mail: bingbignmath@gmail.com; Han Yuexing [Graduate School of Information System, University of Electro-Communications, 1-5-1 Chofugaoka, Chofu-Shi, Tokyo (Japan); Chen Luonan [Department of Electrical Engineering and Electronics, Osaka Sangyo University, Daito, Osaka 574-8530 (Japan); Aihara, Kazuyuki [ERATO Aihara Complexity Modelling Project, JST, Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Institute of Industrial Science, University of Tokyo, Tokyo (Japan)
2009-04-13
We study the coevolution process in Axelrod's model by taking into account of agents' abilities to access information, which is described by a parameter {alpha} to control the geographical range of communication. We observe two kinds of phase transitions in both cultural domains and network fragments, which depend on the parameter {alpha}. By simulation, we find that not all rewiring processes pervade the dissemination of culture, that is, a very limited ability to access information constrains the cultural dissemination, while an exceptional ability to access information aids the dissemination of culture. Furthermore, by analyzing the network characteristics at the frozen states, we find that there exists a stage at which the network develops to be a small-world network with community structures.
Composite Estimation for Single-Index Models with Responses Subject to Detection Limits
Tang, Yanlin
2017-11-03
We propose a semiparametric estimator for single-index models with censored responses due to detection limits. In the presence of left censoring, the mean function cannot be identified without any parametric distributional assumptions, but the quantile function is still identifiable at upper quantile levels. To avoid parametric distributional assumption, we propose to fit censored quantile regression and combine information across quantile levels to estimate the unknown smooth link function and the index parameter. Under some regularity conditions, we show that the estimated link function achieves the non-parametric optimal convergence rate, and the estimated index parameter is asymptotically normal. The simulation study shows that the proposed estimator is competitive with the omniscient least squares estimator based on the latent uncensored responses for data with normal errors but much more efficient for heavy-tailed data under light and moderate censoring. The practical value of the proposed method is demonstrated through the analysis of a human immunodeficiency virus antibody data set.
Directory of Open Access Journals (Sweden)
Franjo Šumanovac
2007-12-01
Full Text Available The block model in a homogenous environment can generally serve for presentation of some geological models: changes of facies, changes of rock compactness-fragmentation, underground cavities, bauxite deposits, etc. Therefore, on the block model of increased resistivities in a homogenous environment of low resistivity, the potentials of the electrical tomography method were tested for the purpose of their detection. Regarding potentials of block detection, resolution methods depend on: depth of block location, ratio between block resistivity and the environment in which it is located as well as applied survey geometry, i.e. electrode array. Thus the analyses carried out for the most frequently used electrode arrays in the investigations are the following: the Wenner, Wenner-Schlumberger, dipole-dipole and pole-pole arrays. For each array, maximum depths at which a block can be detected relative to the ratio between block resistivity and parent rock environment were analyzed. The results are shown in the two-dimensional graphs, where the ratio between the block resistivity and the environment is shown on the X-axis, and the resolution depth on the Y-axis, after which the curves defining the resolution limits were drawn. These graphs have a practical use, since they enable a fast, simple determination of potentials of the method application on a specific geological model.
Can limited area NWP and/or RCM models improve on large scales inside their domain?
Mesinger, Fedor; Veljovic, Katarina
2017-04-01
In a paper in press in Meteorology and Atmospheric Physics at the time this abstract is being written, Mesinger and Veljovic point out four requirements that need to be fulfilled by a limited area model (LAM), be it in NWP or RCM environment, to improve on large scales inside its domain. First, NWP/RCM model needs to be run on a relatively large domain. Note that domain size in quite inexpensive compared to resolution. Second, NWP/RCM model should not use more forcing at its boundaries than required by the mathematics of the problem. That means prescribing lateral boundary conditions only at its outside boundary, with one less prognostic variable prescribed at the outflow than at the inflow parts of the boundary. Next, nudging towards the large scales of the driver model must not be used, as it would obviously be nudging in the wrong direction if the nested model can improve on large scales inside its domain. And finally, the NWP/RCM model must have features that enable development of large scales improved compared to those of the driver model. This would typically include higher resolution, but obviously does not have to. Integrations showing improvements in large scales by LAM ensemble members are summarized in the mentioned paper in press. Ensemble members referred to are run using the Eta model, and are driven by ECMWF 32-day ensemble members, initialized 0000 UTC 4 October 2012. The Eta model used is the so-called "upgraded Eta," or "sloping steps Eta," which is free of the Gallus-Klemp problem of weak flow in the lee of the bell-shaped topography, seemed to many as suggesting the eta coordinate to be ill suited for high resolution models. The "sloping steps" in fact represent a simple version of the cut cell scheme. Accuracy of forecasting the position of jet stream winds, chosen to be those of speeds greater than 45 m/s at 250 hPa, expressed by Equitable Threat (or Gilbert) skill scores adjusted to unit bias (ETSa) was taken to show the skill at large scales
International Nuclear Information System (INIS)
Fouquet, Ch. de; Deraisme, J.; Bobbia, M.
2007-01-01
Geo-statistics is increasingly applied to the study of environmental risks in a variety of sectors, especially in the fields of soil decontamination and the evaluation of the risks due to air pollution. Geo-statistics offers a rigorous stochastic modeling approach that makes it possible to answer questions expressed in terms of uncertainty and risk. This article focusses on nonlinear geo-statistical methods, based on the Gaussian random function model, whose essential properties are summarised. We use two examples to characterize situations where direct and thus rapid methods provide appropriate solutions and cases that inevitably require more laborious simulation techniques. Exposure of the population of the Rouen metropolitan area to the risk of NO 2 pollution is assessed by simulations, but the surface area where the pollution exceeds the threshold limit can be easily estimated with nonlinear conditional expectation techniques. A second example is used to discuss the bias introduced by direct simulation, here of a percentile of daily SO 2 concentration for one year in the city of Le Havre; an operational solution is proposed. (authors)
Stirk, Emily R; Lythe, Grant; van den Berg, Hugo A; Hurst, Gareth A D; Molina-París, Carmen
2010-04-01
The limiting conditional probability distribution (LCD) has been much studied in the field of mathematical biology, particularly in the context of epidemiology and the persistence of epidemics. However, it has not yet been applied to the immune system. One of the characteristic features of the T cell repertoire is its diversity. This diversity declines in old age, whence the concepts of extinction and persistence are also relevant to the immune system. In this paper we model T cell repertoire maintenance by means of a continuous-time birth and death process on the positive integers, where the origin is an absorbing state. We show that eventual extinction is guaranteed. The late-time behaviour of the process before extinction takes place is modelled by the LCD, which we prove always exists for the process studied here. In most cases, analytic expressions for the LCD cannot be computed but the probability distribution may be approximated by means of the stationary probability distributions of two related processes. We show how these approximations are related to the LCD of the original process and use them to study the LCD in two special cases. We also make use of the large N expansion to derive a further approximation to the LCD. The accuracy of the various approximations is then analysed. (c) 2009 Elsevier Inc. All rights reserved.
Hindmarsh–Rose model: Close and far to the singular limit
Energy Technology Data Exchange (ETDEWEB)
Barrio, Roberto, E-mail: rbarrio@unizar.es [Departamento de Matemática Aplicada and IUMA, University of Zaragoza, E-50009 Zaragoza (Spain); Computational Dynamics group, University of Zaragoza, E-50009 Zaragoza (Spain); Ibáñez, Santiago, E-mail: mesa@uniovi.es [Departamento de Matemáticas, University of Oviedo, E-33007 Oviedo (Spain); Pérez, Lucía, E-mail: lpcuadrado@gmail.com [Departamento de Matemáticas, University of Oviedo, E-33007 Oviedo (Spain)
2017-02-12
Dynamics arising in the Hindmarsh–Rose model are considered from a novel perspective. We study qualitative changes that occur as the time scale of the slow variable increases taking the system far from the slow-fast scenario. We see how the structure of spike-adding still persists far from the singular case but the geometry of the bifurcations changes notably. Particular attention is paid to changes in the shape of the homoclinic bifurcation curves and the disappearance of Inclination-Flip codimension-two points. These transformations seem to be linked to the way in which the spike-adding takes place, the changing from fold/hom to fold/Hopf bursting behavior and also with the way in which the chaotic regions evolve as the time scale of the slow variable increases. - Highlights: • Dynamics arising in the Hindmarsh–Rose model are considered close and far to the singular limit. • The structure of spike-adding still persists far from the singular case but the geometry of the bifurcations changes notably. • The homoclinic bifurcation curves change their shape and some codimension-two points (Inclination-Flip) disappear. • The changes in the homoclinic curves are correlated with adjustments in the spike-adding process and in the chaotic regions.
Limit order book and its modeling in terms of Gibbs Grand-Canonical Ensemble
Bicci, Alberto
2016-12-01
In the domain of so called Econophysics some attempts have been already made for applying the theory of thermodynamics and statistical mechanics to economics and financial markets. In this paper a similar approach is made from a different perspective, trying to model the limit order book and price formation process of a given stock by the Grand-Canonical Gibbs Ensemble for the bid and ask orders. The application of the Bose-Einstein statistics to this ensemble allows then to derive the distribution of the sell and buy orders as a function of price. As a consequence we can define in a meaningful way expressions for the temperatures of the ensembles of bid orders and of ask orders, which are a function of minimum bid, maximum ask and closure prices of the stock as well as of the exchanged volume of shares. It is demonstrated that the difference between the ask and bid orders temperatures can be related to the VAO (Volume Accumulation Oscillator), an indicator empirically defined in Technical Analysis of stock markets. Furthermore the derived distributions for aggregate bid and ask orders can be subject to well defined validations against real data, giving a falsifiable character to the model.
Mode-coupling theory predictions for a limited valency attractive square well model
International Nuclear Information System (INIS)
Zaccarelli, E; Saika-Voivod, I; Moreno, A J; Nave, E La; Buldyrev, S V; Sciortino, F; Tartaglia, P
2006-01-01
Recently we have studied, using numerical simulations, a limited valency model, i.e. an attractive square well model with a constraint on the maximum number of bonded neighbours. Studying a large region of temperatures T and packing fractions φ, we have estimated the location of the liquid-gas phase separation spinodal and the loci of dynamic arrest, where the system is trapped in a disordered non-ergodic state. Two distinct arrest lines for the system are present in the system: a (repulsive) glass line at high packing fraction, and a gel line at low φ and T. The former is essentially vertical φ controlled), while the latter is rather horizontal (T controlled) in the φ-T) plane. We here complement the molecular dynamics results with mode coupling theory calculations, using the numerical structure factors as input. We find that the theory predicts a repulsive glass line-in satisfactory agreement with the simulation results-and an attractive glass line, which appears to be unrelated to the gel line
Energy Technology Data Exchange (ETDEWEB)
Cruz-Dombriz, Álvaro de la; Dunsby, Peter K.S.; Luongo, Orlando; Reverberi, Lorenzo, E-mail: alvaro.delacruzdombriz@uct.ac.za, E-mail: peter.dunsby@uct.ac.za, E-mail: luongo@na.infn.it, E-mail: lorenzo.reverberi@uct.ac.za [Department of Mathematics and Applied Mathematics, University of Cape Town, Rondebosch 7701, Cape Town (South Africa)
2016-12-01
The onset of dark energy domination depends on the particular gravitational theory driving the cosmic evolution. Model independent techniques are crucial to test the both the present ΛCDM cosmological paradigm and alternative theories, making the least possible number of assumptions about the Universe. In this paper we investigate whether cosmography is able to distinguish between different gravitational theories, by determining bounds on model parameters for three different extensions of General Relativity, namely quintessence, F (Τ) and f ( R ) gravitational theories. We expand each class of theories in powers of redshift z around the present time, making no additional assumptions. This procedure is an extension of previous work and can be seen as the most general approach for testing extended theories of gravity through the use of cosmography. In the case of F (Τ) and f ( R ) theories, we show that some assumptions on model parameters often made in previous works are superfluous or even unjustified. We use data from the Union 2.1 supernovae catalogue, baryonic acoustic oscillation data and H ( z ) differential age compilations, which probe cosmology on different scales of the cosmological evolution. We perform a Monte Carlo analysis using a Metropolis-Hastings algorithm with a Gelman-Rubin convergence criterion, reporting 1-σ and 2-σ confidence levels. To do so, we perform two distinct fits, assuming only data within z < 1 first and then without limitations in redshift. We obtain the corresponding numerical intervals in which coefficients span, and find that the data is compatible the ΛCDM limit of all three theories at the 1-σ level, while still compatible with quite a large portion of parameter space. We compare our results to the truncated ΛCDM paradigm, demonstrating that our bounds divert from the expectations of previous works, showing that the permitted regions of coefficients are significantly modified and in general widened with respect to
Watkins, Nicholas
2013-04-01
Stochastic modelling is of increasing importance, both specifically in climate science and more broadly across the whole of nonlinear geophysics. Traditionally, the noise components of such models would be spectrally white (delta-correlated) and Gaussian in amplitude, and their variance (first named by Fisher in 1918) would well characterise the likely size of fluctuations. Integration, for example in autoregressive models like AR(1), would redden a noise spectrum, while multiplication in turbulent cascades could greatly increase the range of fluctuation amplitudes, but such processes would still inherit aspects of their finite variance building blocks. In the 60s and 70s, however, Mandelbrot and others [see e.g. Watkins, GRL Frontiers, 2013] began to present evidence in nature for much stronger departures from Gaussianity (via very heavy tailed, infinite variance, distributions) and from white noise (through long range dependence (LRD) in time). He also observed intermittency, defined here as correlations between absolute magnitudes in some time series, in, for example, finance and turbulence. He proposed various models, including self-similar ones for heavy tails and LRD, and multifractal cascades for intermittency. In this presentation we compare contrasting types of model by looking at the "wild" events that they produce. The notion of a "wild" event can be made more precise in many ways, including by its duration in time, peak amplitude, and spatial extent. Our chosen measure will be the "burst", defined as the area of a time series above a fixed threshold. We will compare burst scaling in a self-similar, LRD, heavy tailed model (LFSM, e.g. Watkins et al, PRE, 2009] with our newer results for multifractal random walks [with M. Rypdal and O. Lovsletten], and for the heavy tailed extended version of the FARIMA (1,d,0) process, which combines long range dependence with the high frequency structure familiar from AR(1). We will also discuss the physical meaning of
Space-charge-limited-current diode model for amorphous silicon solar cell degradation
International Nuclear Information System (INIS)
Partain, L.D.
1987-01-01
A space-charge-limited-current (SCLI) diode model for trap controlled rectification in the dark is extended to a continuous trap distribution for p-i-n a-Si:H solar cells in the light. Light degradation, thermal annealing recovery, and 10% efficient device data are quantitatively fit with i layer, conduction electron concentrations between 1.95 (10 11 ) and 1.90 (10 12 ) cm -3 and band gap trap concentration densities between 7.66 (10 14 ) and 1.14 (10 18 ) cm -3 ev -1 for 0.2 to 0.5 eV below the conduction band edge (E/sub c/). Light exposure increased the trap density at 0.4 eV below E/sub c/ by a factor of 7. Annealing decreased the distance of the peak trap density from E/sub c/ by 0.2 eV. These results agree with trap distributions measured with field effect, DLTS, and ICTS and with theoretical models based on dangling bonds or on defect rearrangements. The model indicates that a minimum peak amplitude of 10 17 cm -3 eV -1 of trapping states is required at about 0.5 eV below E/sub c/ for high fill factors (FF) and open circuit voltages (V/sub oc/). Improved FF values of 0.76 are predicted for trap densities below 10 15 cm -3 eV -1 at 0.2 to 0.4 eV below E/sub c/. Increased V/sub oc/ values of 0.99 V are predicted for a peak trap density of 3.5 (10 17 ) cm -3 eV -1 at 0.5 eV below E/sub c/
Breton, S.; Casson, F. J.; Bourdelle, C.; Angioni, C.; Belli, E.; Camenen, Y.; Citrin, J.; Garbet, X.; Sarazin, Y.; Sertoli, M.; JET Contributors
2018-01-01
Heavy impurities, such as tungsten (W), can exhibit strongly poloidally asymmetric density profiles in rotating or radio frequency heated plasmas. In the metallic environment of JET, the poloidal asymmetry of tungsten enhances its neoclassical transport up to an order of magnitude, so that neoclassical convection dominates over turbulent transport in the core. Accounting for asymmetries in neoclassical transport is hence necessary in the integrated modeling framework. The neoclassical drift kinetic code, NEO [E. Belli and J. Candy, Plasma Phys. Controlled Fusion P50, 095010 (2008)], includes the impact of poloidal asymmetries on W transport. However, the computational cost required to run NEO slows down significantly integrated modeling. A previous analytical formulation to describe heavy impurity neoclassical transport in the presence of poloidal asymmetries in specific collisional regimes [C. Angioni and P. Helander, Plasma Phys. Controlled Fusion 56, 124001 (2014)] is compared in this work to numerical results from NEO. Within the domain of validity of the formula, the factor for reducing the temperature screening due to poloidal asymmetries had to be empirically adjusted. After adjustment, the modified formula can reproduce NEO results outside of its definition domain, with some limitations: When main ions are in the banana regime, the formula reproduces NEO results whatever the collisionality regime of impurities, provided that the poloidal asymmetry is not too large. However, for very strong poloidal asymmetries, agreement requires impurities in the Pfirsch-Schlüter regime. Within the JETTO integrated transport code, the analytical formula combined with the poloidally symmetric neoclassical code NCLASS [W. A. Houlberg et al., Phys. Plasmas 4, 3230 (1997)] predicts the same tungsten profile as NEO in certain cases, while saving a factor of one thousand in computer time, which can be useful in scoping studies. The parametric dependencies of the temperature
Day-Lewis, F. D.; Singha, K.; Binley, A.M.
2005-01-01
Geophysical imaging has traditionally provided qualitative information about geologic structure; however, there is increasing interest in using petrophysical models to convert tomograms to quantitative estimates of hydrogeologic, mechanical, or geochemical parameters of interest (e.g., permeability, porosity, water content, and salinity). Unfortunately, petrophysical estimation based on tomograms is complicated by limited and variable image resolution, which depends on (1) measurement physics (e.g., electrical conduction or electromagnetic wave propagation), (2) parameterization and regularization, (3) measurement error, and (4) spatial variability. We present a framework to predict how core-scale relations between geophysical properties and hydrologic parameters are altered by the inversion, which produces smoothly varying pixel-scale estimates. We refer to this loss of information as "correlation loss." Our approach upscales the core-scale relation to the pixel scale using the model resolution matrix from the inversion, random field averaging, and spatial statistics of the geophysical property. Synthetic examples evaluate the utility of radar travel time tomography (RTT) and electrical-resistivity tomography (ERT) for estimating water content. This work provides (1) a framework to assess tomograms for geologic parameter estimation and (2) insights into the different patterns of correlation loss for ERT and RTT. Whereas ERT generally performs better near boreholes, RTT performs better in the interwell region. Application of petrophysical models to the tomograms in our examples would yield misleading estimates of water content. Although the examples presented illustrate the problem of correlation loss in the context of near-surface geophysical imaging, our results have clear implications for quantitative analysis of tomograms for diverse geoscience applications. Copyright 2005 by the American Geophysical Union.
International Nuclear Information System (INIS)
Lapillonne, X.; Brunner, S.; Dannert, T.; Jolliet, S.; Marinoni, A.; Villard, L.; Goerler, T.; Jenko, F.; Merz, F.
2009-01-01
In the context of gyrokinetic flux-tube simulations of microturbulence in magnetized toroidal plasmas, different treatments of the magnetic equilibrium are examined. Considering the Cyclone DIII-D base case parameter set [Dimits et al., Phys. Plasmas 7, 969 (2000)], significant differences in the linear growth rates, the linear and nonlinear critical temperature gradients, and the nonlinear ion heat diffusivities are observed between results obtained using either an s-α or a magnetohydrodynamic (MHD) equilibrium. Similar disagreements have been reported previously [Redd et al., Phys. Plasmas 6, 1162 (1999)]. In this paper it is shown that these differences result primarily from the approximation made in the standard implementation of the s-α model, in which the straight field line angle is identified to the poloidal angle, leading to inconsistencies of order ε (ε=a/R is the inverse aspect ratio, a the minor radius and R the major radius). An equilibrium model with concentric, circular flux surfaces and a correct treatment of the straight field line angle gives results very close to those using a finite ε, low β MHD equilibrium. Such detailed investigation of the equilibrium implementation is of particular interest when comparing flux tube and global codes. It is indeed shown here that previously reported agreements between local and global simulations in fact result from the order ε inconsistencies in the s-α model, coincidentally compensating finite ρ * effects in the global calculations, where ρ * =ρ s /a with ρ s the ion sound Larmor radius. True convergence between local and global simulations is finally obtained by correct treatment of the geometry in both cases, and considering the appropriate ρ * →0 limit in the latter case.
Energy Technology Data Exchange (ETDEWEB)
Boerner, A. J. [Oak Ridge Institute for Science and Education (ORISE), Oak Ridge, TN (United States). Independent Environmental Assessment and Verification Program; Maldonado, D. G. [Oak Ridge Institute for Science and Education (ORISE), Oak Ridge, TN (United States). Independent Environmental Assessment and Verification Program; Hansen, Tom [Ameriphysics, LLC (United States)
2012-09-01
Environmental assessments and remediation activities are being conducted by the U.S. Department of Energy (DOE) at the Paducah Gaseous Diffusion Plant (PGDP), Paducah, Kentucky. The Oak Ridge Institute for Science and Education (ORISE), a DOE prime contractor, was contracted by the DOE Portsmouth/Paducah Project Office (DOE-PPPO) to conduct radiation dose modeling analyses and derive single radionuclide soil guidelines (soil guidelines) in support of the derivation of Authorized Limits (ALs) for 'DOE-Owned Property Outside the Limited Area' ('Property') at the PGDP. The ORISE evaluation specifically included the area identified by DOE restricted area postings (public use access restrictions) and areas licensed by DOE to the West Kentucky Wildlife Management Area (WKWMA). The licensed areas are available without restriction to the general public for a variety of (primarily) recreational uses. Relevant receptors impacting current and reasonably anticipated future use activities were evaluated. In support of soil guideline derivation, a Conceptual Site Model (CSM) was developed. The CSM listed radiation and contamination sources, release mechanisms, transport media, representative exposure pathways from residual radioactivity, and a total of three receptors (under present and future use scenarios). Plausible receptors included a Resident Farmer, Recreational User, and Wildlife Worker. single radionuclide soil guidelines (outputs specified by the software modeling code) were generated for three receptors and thirteen targeted radionuclides. These soil guidelines were based on satisfying the project dose constraints. For comparison, soil guidelines applicable to the basic radiation public dose limit of 100 mrem/yr were generated. Single radionuclide soil guidelines from the most limiting (restrictive) receptor based on a target dose constraint of 25 mrem/yr were then rounded and identified as the derived soil guidelines. An additional evaluation using the derived soil
International Nuclear Information System (INIS)
Boerner, A. J.
2012-01-01
Environmental assessments and remediation activities are being conducted by the U.S. Department of Energy (DOE) at the Paducah Gaseous Diffusion Plant (PGDP), Paducah, Kentucky. The Oak Ridge Institute for Science and Education (ORISE), a DOE prime contractor, was contracted by the DOE Portsmouth/Paducah Project Office (DOE-PPPO) to conduct radiation dose modeling analyses and derive single radionuclide soil guidelines (soil guidelines) in support of the derivation of Authorized Limits (ALs) for 'DOE-Owned Property Outside the Limited Area' ('Property') at the PGDP. The ORISE evaluation specifically included the area identified by DOE restricted area postings (public use access restrictions) and areas licensed by DOE to the West Kentucky Wildlife Management Area (WKWMA). The licensed areas are available without restriction to the general public for a variety of (primarily) recreational uses. Relevant receptors impacting current and reasonably anticipated future use activities were evaluated. In support of soil guideline derivation, a Conceptual Site Model (CSM) was developed. The CSM listed radiation and contamination sources, release mechanisms, transport media, representative exposure pathways from residual radioactivity, and a total of three receptors (under present and future use scenarios). Plausible receptors included a Resident Farmer, Recreational User, and Wildlife Worker. single radionuclide soil guidelines (outputs specified by the software modeling code) were generated for three receptors and thirteen targeted radionuclides. These soil guidelines were based on satisfying the project dose constraints. For comparison, soil guidelines applicable to the basic radiation public dose limit of 100 mrem/yr were generated. Single radionuclide soil guidelines from the most limiting (restrictive) receptor based on a target dose constraint of 25 mrem/yr were then rounded and identified as the derived soil guidelines. An additional evaluation using the derived soil
International Nuclear Information System (INIS)
Hiroshima, Fumio
2002-01-01
Scaling limits of the Hamiltonian H of a system of N charged particles coupled to a quantized radiation field are considered. Ultraviolet cutoffs, λ 1 ,...,λ N , are imposed on the radiation field and the Coulomb gauge is taken. It is the so-called Pauli-Fierz model in nonrelativistic quantum electrodynamics. We mainly consider two cases: (i) all the ultraviolet cutoffs are identical, λ 1 =···=λ N , (ii) supports of ultraviolet cutoffs have no intersection, supp λ i intersection supp λ j = null-set , i≠j. The Hamiltonian acts on L 2 (R dN )(multiply-in-circle sign)F, where F is a symmetric Fock space, and has the form H=H el (multiply-in-circle sign)1+B+1(multiply-in-circle sign)H quad . Here H el denotes a particle Hamiltonian, H quad a quadratic field operator, and B an interaction term. The scaling is introduced as H(κ)=H el (multiply-in-circle sign)1+κ l B+κ 2 1(multiply-in-circle sign)H quad , where κ is a scaling parameter and l≤2 a parameter of the scaling. Performing a mass renormalization we consider the scaling limit of H(κ) as κ→∞ in the strong resolvent sense. Then effective Hamiltonians H eff in L 2 (R dN ) infected with reaction of effect of the radiation field is derived. In particular (1) effective Hamiltonians with an effective potential for l=2, and (2) effective Hamiltonians with an observed mass for l=1, are obtained
Huizer, Daan; Huijbregts, Mark A J; van Rooij, Joost G M; Ragas, Ad M J
2014-08-01
The coherence between occupational exposure limits (OELs) and their corresponding biological limit values (BLVs) was evaluated for 2-propanol and acetone. A generic human PBPK model was used to predict internal concentrations after inhalation exposure at the level of the OEL. The fraction of workers with predicted internal concentrations lower than the BLV, i.e. the 'false negatives', was taken as a measure for incoherence. The impact of variability and uncertainty in input parameters was separated by means of nested Monte Carlo simulation. Depending on the exposure scenario considered, the median fraction of the population for which the limit values were incoherent ranged from 2% to 45%. Parameter importance analysis showed that body weight was the main factor contributing to interindividual variability in blood and urine concentrations and that the metabolic parameters Vmax and Km were the most important sources of uncertainty. This study demonstrates that the OELs and BLVs for 2-propanol and acetone are not fully coherent, i.e. enforcement of BLVs may result in OELs being violated. In order to assess the acceptability of this "incoherence", a maximum population fraction at risk of exceeding the OEL should be specified as well as a minimum level of certainty in predicting this fraction. Copyright © 2014 Elsevier Inc. All rights reserved.
Energy Technology Data Exchange (ETDEWEB)
Alwan, Aravind; Aluru, N.R.
2013-12-15
This paper presents a data-driven framework for performing uncertainty quantification (UQ) by choosing a stochastic model that accurately describes the sources of uncertainty in a system. This model is propagated through an appropriate response surface function that approximates the behavior of this system using stochastic collocation. Given a sample of data describing the uncertainty in the inputs, our goal is to estimate a probability density function (PDF) using the kernel moment matching (KMM) method so that this PDF can be used to accurately reproduce statistics like mean and variance of the response surface function. Instead of constraining the PDF to be optimal for a particular response function, we show that we can use the properties of stochastic collocation to make the estimated PDF optimal for a wide variety of response functions. We contrast this method with other traditional procedures that rely on the Maximum Likelihood approach, like kernel density estimation (KDE) and its adaptive modification (AKDE). We argue that this modified KMM method tries to preserve what is known from the given data and is the better approach when the available data is limited in quantity. We test the performance of these methods for both univariate and multivariate density estimation by sampling random datasets from known PDFs and then measuring the accuracy of the estimated PDFs, using the known PDF as a reference. Comparing the output mean and variance estimated with the empirical moments using the raw data sample as well as the actual moments using the known PDF, we show that the KMM method performs better than KDE and AKDE in predicting these moments with greater accuracy. This improvement in accuracy is also demonstrated for the case of UQ in electrostatic and electrothermomechanical microactuators. We show how our framework results in the accurate computation of statistics in micromechanical systems.
Dacuña, Javier
2011-11-28
We have developed and have applied a mobility edge model that takes drift and diffusion currents to characterize the space-charge-limited current in organic semiconductors into account. The numerical solution of the drift-diffusion equation allows the utilization of asymmetric contacts to describe the built-in potential within the device. The model has been applied to extract information of the distribution of traps from experimental current-voltage measurements of a rubrene single crystal from Krellner showing excellent agreement across several orders of magnitude in the current. Although the two contacts are made of the same metal, an energy offset of 580 meV between them, ascribed to differences in the deposition techniques (lamination vs evaporation) was essential to correctly interpret the shape of the current-voltage characteristics at low voltage. A band mobility of 0.13cm 2V-1s-1 for holes is estimated, which is consistent with transport along the long axis of the orthorhombic unit cell. The total density of traps deeper than 0.1 eV was 2.2×1016cm -3. The sensitivity analysis and error estimation in the obtained parameters show that it is not possible to accurately resolve the shape of the trap distribution for energies deeper than 0.3 eV or shallower than 0.1 eV above the valence-band edge. The total number of traps deeper than 0.3 eV, however, can be estimated. Contact asymmetry and the diffusion component of the current play an important role in the description of the device at low bias and are required to obtain reliable information about the distribution of deep traps. © 2011 American Physical Society.
International Nuclear Information System (INIS)
Alwan, Aravind; Aluru, N.R.
2013-01-01
This paper presents a data-driven framework for performing uncertainty quantification (UQ) by choosing a stochastic model that accurately describes the sources of uncertainty in a system. This model is propagated through an appropriate response surface function that approximates the behavior of this system using stochastic collocation. Given a sample of data describing the uncertainty in the inputs, our goal is to estimate a probability density function (PDF) using the kernel moment matching (KMM) method so that this PDF can be used to accurately reproduce statistics like mean and variance of the response surface function. Instead of constraining the PDF to be optimal for a particular response function, we show that we can use the properties of stochastic collocation to make the estimated PDF optimal for a wide variety of response functions. We contrast this method with other traditional procedures that rely on the Maximum Likelihood approach, like kernel density estimation (KDE) and its adaptive modification (AKDE). We argue that this modified KMM method tries to preserve what is known from the given data and is the better approach when the available data is limited in quantity. We test the performance of these methods for both univariate and multivariate density estimation by sampling random datasets from known PDFs and then measuring the accuracy of the estimated PDFs, using the known PDF as a reference. Comparing the output mean and variance estimated with the empirical moments using the raw data sample as well as the actual moments using the known PDF, we show that the KMM method performs better than KDE and AKDE in predicting these moments with greater accuracy. This improvement in accuracy is also demonstrated for the case of UQ in electrostatic and electrothermomechanical microactuators. We show how our framework results in the accurate computation of statistics in micromechanical systems
Vautard, Robert; Thais, Françoise; Tobin, Isabelle; Bréon, François-Marie; Devezeaux de Lavergne, Jean-Guy; Colette, Augustin; Yiou, Pascal; Ruti, Paolo Michele
2014-01-01
The rapid development of wind energy has raised concerns about environmental impacts. Temperature changes are found in the vicinity of wind farms and previous simulations have suggested that large-scale wind farms could alter regional climate. However, assessments of the effects of realistic wind power development scenarios at the scale of a continent are missing. Here we simulate the impacts of current and near-future wind energy production according to European Union energy and climate policies. We use a regional climate model describing the interactions between turbines and the atmosphere, and find limited impacts. A statistically significant signal is only found in winter, with changes within ±0.3 °C and within 0-5% for precipitation. It results from the combination of local wind farm effects and changes due to a weak, but robust, anticyclonic-induced circulation over Europe. However, the impacts remain much weaker than the natural climate interannual variability and changes expected from greenhouse gas emissions.
The square lattice Ising model on the rectangle II: finite-size scaling limit
Hucht, Alfred
2017-06-01
Based on the results published recently (Hucht 2017 J. Phys. A: Math. Theor. 50 065201), the universal finite-size contributions to the free energy of the square lattice Ising model on the L× M rectangle, with open boundary conditions in both directions, are calculated exactly in the finite-size scaling limit L, M\\to∞ , T\\to Tc , with fixed temperature scaling variable x\\propto(T/Tc-1)M and fixed aspect ratio ρ\\propto L/M . We derive exponentially fast converging series for the related Casimir potential and Casimir force scaling functions. At the critical point T=Tc we confirm predictions from conformal field theory (Cardy and Peschel 1988 Nucl. Phys. B 300 377, Kleban and Vassileva 1991 J. Phys. A: Math. Gen. 24 3407). The presence of corners and the related corner free energy has dramatic impact on the Casimir scaling functions and leads to a logarithmic divergence of the Casimir potential scaling function at criticality.
High-resolution digital 3D models of Algar do Penico Chamber: limitations, challenges, and potential
Directory of Open Access Journals (Sweden)
Ivo Silvestre M.Sc.
2015-01-01
Full Text Available The study of karst and its geomorphological structures is important for understanding the relationships between hydrology and climate over geological time. In that context, we conducted a terrestrial laser-scan survey to map geomorphological structures in the karst cave of Algar do Penico in southern Portugal. The point cloud data set obtained was used to generate 3D meshes with different levels of detail, allowing the limitations of mapping capabilities to be explored. In addition to cave mapping, the study focuses on 3D-mesh analysis, including the development of two algorithms for determination of stalactite extremities and contour lines, and on the interactive visualization of 3D meshes on the Web. Data processing and analysis were performed using freely available open-source software. For interactive visualization, we adopted a framework based on Web standards X3D, WebGL, and X3DOM. This solution gives both the general public and researchers access to 3D models and to additional data produced from map tools analyses through a web browser, without the need for plug-ins.
Julio Andre, Benavides; Cross, Paul C.; Luikart, Gordon; Scott, Creel
2014-01-01
Cross-species transmission (CST) of bacterial pathogens has major implications for human health, livestock, and wildlife management because it determines whether control actions in one species may have subsequent effects on other potential host species. The study of bacterial transmission has benefitted from methods measuring two types of genetic variation: variable number of tandem repeats (VNTRs) and single nucleotide polymorphisms (SNPs). However, it is unclear whether these data can distinguish between different epidemiological scenarios. We used a simulation model with two host species and known transmission rates (within and between species) to evaluate the utility of these markers for inferring CST. We found that CST estimates are biased for a wide range of parameters when based on VNTRs and a most parsimonious reconstructed phylogeny. However, estimations of CST rates lower than 5% can be achieved with relatively low bias using as low as 250 SNPs. CST estimates are sensitive to several parameters, including the number of mutations accumulated since introduction, stochasticity, the genetic difference of strains introduced, and the sampling effort. Our results suggest that, even with whole-genome sequences, unbiased estimates of CST will be difficult when sampling is limited, mutation rates are low, or for pathogens that were recently introduced.
Novick, Kimberly A; Miniat, Chelcy F; Vose, James M
2016-03-01
We merge concepts from stomatal optimization theory and cohesion-tension theory to examine the dynamics of three mechanisms that are potentially limiting to leaf-level gas exchange in trees during drought: (1) a 'demand limitation' driven by an assumption of optimal stomatal functioning; (2) 'hydraulic limitation' of water movement from the roots to the leaves; and (3) 'non-stomatal' limitations imposed by declining leaf water status within the leaf. Model results suggest that species-specific 'economics' of stomatal behaviour may play an important role in differentiating species along the continuum of isohydric to anisohydric behaviour; specifically, we show that non-stomatal and demand limitations may reduce stomatal conductance and increase leaf water potential, promoting wide safety margins characteristic of isohydric species. We used model results to develop a diagnostic framework to identify the most likely limiting mechanism to stomatal functioning during drought and showed that many of those features were commonly observed in field observations of tree water use dynamics. Direct comparisons of modelled and measured stomatal conductance further indicated that non-stomatal and demand limitations reproduced observed patterns of tree water use well for an isohydric species but that a hydraulic limitation likely applies in the case of an anisohydric species. Published 2015. This article is a US Government work and is in the public domain in the USA.
Screen-level non-GTS data assimilation in a limited-area mesoscale model
Directory of Open Access Journals (Sweden)
M. Milelli
2010-06-01
Full Text Available The forecast in areas of very complex topography, as for instance the Alpine region, is still a challenge even for the new generation of numerical weather prediction models which aim at reaching the km-scale. The problem is enhanced by a general lack of standard observations, which is even more evident over the southern side of the Alps. For this reason, it would be useful to increase the performance of the mathematical models by locally assimilating non-conventional data. Since in ARPA Piemonte there is the availability of a great number of non-GTS stations, it has been decided to assimilate the 2 m temperature, coming from this dataset, in the very-high resolution version of the COSMO model, which has a horizontal resolution of about 3 km, more similar to the average resolution of the thermometers. Four different weather situations have been considered, ranging from spring to winter, from cloudy to clear sky. The aim of the work is to investigate the effects of the assimilation of non-GTS data in order to create an operational very high-resolution analysis, but also to test the option of running in the future a very short-range forecast starting from these analyses (RUC or Rapid Update Cycle. The results, in terms of Root Mean Square Error, Mean Error and diurnal cycle of some surface variables such as 2 m temperature, 2 m relative humidity and 10 m wind intensity show a positive impact during the assimilation cycle which tends to dissipate a few hours after the end of it. Moreover, the 2 m temperature assimilation has a slightly positive or neutral impact on the vertical profiles of temperature, eventhough some calibration is needed for the precipitation field which is too much perturbed during the assimilation cycle, while it is unaffected in the forecast period. So the stability of the planetary boundary layer, on the one hand, has not been particularly improved by the new-data assimilation, but, on the other hand, it has not been destroyed
Directory of Open Access Journals (Sweden)
Feras Khalil
2011-01-01
Full Text Available The concept of physiologically based pharmacokinetic (PBPK modeling was introduced years ago, but it has not been practiced significantly. However, interest in and implementation of this modeling technique have grown, as evidenced by the increased number of publications in this field. This paper demonstrates briefly the methodology, applications, and limitations of PBPK modeling with special attention given to discuss the use of PBPK models in pediatric drug development and some examples described in detail. Although PBPK models do have some limitations, the potential benefit from PBPK modeling technique is huge. PBPK models can be applied to investigate drug pharmacokinetics under different physiological and pathological conditions or in different age groups, to support decision-making during drug discovery, to provide, perhaps most important, data that can save time and resources, especially in early drug development phases and in pediatric clinical trials, and potentially to help clinical trials become more “confirmatory” rather than “exploratory”.
Directory of Open Access Journals (Sweden)
D. S. Goll
2012-09-01
Full Text Available Terrestrial carbon (C cycle models applied for climate projections simulate a strong increase in net primary productivity (NPP due to elevated atmospheric CO_{2} concentration during the 21st century. These models usually neglect the limited availability of nitrogen (N and phosphorus (P, nutrients that commonly limit plant growth and soil carbon turnover. To investigate how the projected C sequestration is altered when stoichiometric constraints on C cycling are considered, we incorporated a P cycle into the land surface model JSBACH (Jena Scheme for Biosphere–Atmosphere Coupling in Hamburg, which already includes representations of coupled C and N cycles.
The model reveals a distinct geographic pattern of P and N limitation. Under the SRES (Special Report on Emissions Scenarios A1B scenario, the accumulated land C uptake between 1860 and 2100 is 13% (particularly at high latitudes and 16% (particularly at low latitudes lower in simulations with N and P cycling, respectively, than in simulations without nutrient cycles. The combined effect of both nutrients reduces land C uptake by 25% compared to simulations without N or P cycling. Nutrient limitation in general may be biased by the model simplicity, but the ranking of limitations is robust against the parameterization and the inflexibility of stoichiometry. After 2100, increased temperature and high CO_{2} concentration cause a shift from N to P limitation at high latitudes, while nutrient limitation in the tropics declines. The increase in P limitation at high-latitudes is induced by a strong increase in NPP and the low P sorption capacity of soils, while a decline in tropical NPP due to high autotrophic respiration rates alleviates N and P limitations. The quantification of P limitation remains challenging. The poorly constrained processes of soil P sorption and biochemical mineralization are identified as the main uncertainties in the strength of P limitation
3D MODELING OF INDUSTRIAL HERITAGE BUILDING USING COTSs SYSTEM: TEST, LIMITS AND PERFORMANCES
Directory of Open Access Journals (Sweden)
M. Piras
2017-08-01
Full Text Available The role of UAV systems in applied geomatics is continuously increasing in several applications as inspection, surveying and geospatial data. This evolution is mainly due to two factors: new technologies and new algorithms for data processing. About technologies, from some years ago there is a very wide use of commercial UAV even COTSs (Commercial On-The-Shelf systems. Moreover, these UAVs allow to easily acquire oblique images, giving the possibility to overcome the limitations of the nadir approach related to the field of view and occlusions. In order to test potential and issue of COTSs systems, the Italian Society of Photogrammetry and Topography (SIFET has organised the SBM2017, which is a benchmark where all people can participate in a shared experience. This benchmark, called “Photogrammetry with oblique images from UAV: potentialities and challenges”, permits to collect considerations from the users, highlight the potential of these systems, define the critical aspects and the technological challenges and compare distinct approaches and software. The case study is the “Fornace Penna” in Scicli (Ragusa, Italy, an inaccessible monument of industrial architecture from the early 1900s. The datasets (images and video have been acquired from three different UAVs system: Parrot Bebop 2, DJI Phantom 4 and Flytop Flynovex. The aim of this benchmark is to generate the 3D model of the “Fornace Penna”, making an analysis considering different software, imaging geometry and processing strategies. This paper describes the surveying strategies, the methodologies and five different photogrammetric obtained results (sensor calibration, external orientation, dense point cloud and two orthophotos, using separately – the single images and the frames extracted from the video – acquired with the DJI system.
D Modeling of Industrial Heritage Building Using COTSs System: Test, Limits and Performances
Piras, M.; Di Pietra, V.; Visintini, D.
2017-08-01
The role of UAV systems in applied geomatics is continuously increasing in several applications as inspection, surveying and geospatial data. This evolution is mainly due to two factors: new technologies and new algorithms for data processing. About technologies, from some years ago there is a very wide use of commercial UAV even COTSs (Commercial On-The-Shelf) systems. Moreover, these UAVs allow to easily acquire oblique images, giving the possibility to overcome the limitations of the nadir approach related to the field of view and occlusions. In order to test potential and issue of COTSs systems, the Italian Society of Photogrammetry and Topography (SIFET) has organised the SBM2017, which is a benchmark where all people can participate in a shared experience. This benchmark, called "Photogrammetry with oblique images from UAV: potentialities and challenges", permits to collect considerations from the users, highlight the potential of these systems, define the critical aspects and the technological challenges and compare distinct approaches and software. The case study is the "Fornace Penna" in Scicli (Ragusa, Italy), an inaccessible monument of industrial architecture from the early 1900s. The datasets (images and video) have been acquired from three different UAVs system: Parrot Bebop 2, DJI Phantom 4 and Flytop Flynovex. The aim of this benchmark is to generate the 3D model of the "Fornace Penna", making an analysis considering different software, imaging geometry and processing strategies. This paper describes the surveying strategies, the methodologies and five different photogrammetric obtained results (sensor calibration, external orientation, dense point cloud and two orthophotos), using separately - the single images and the frames extracted from the video - acquired with the DJI system.
Theoretical models of highly magnetic white dwarf stars that violate the Chandrasekhar Limit
Shah, Hridaya
2017-08-01
Until recently, white dwarf (WD) stars were believed to be no more massive than 1.44 solar masses (M ⊙ ). This belief has been changed now with the observations of over-luminous or 'peculiar' Type la supernovae that have lead researchers to hypothesize the existence of WDs in the mass range 2.4 - 2.8 M ⊙ . This discovery also raises some doubt over the reliability of the Type Ia supernova as a standard candle. It is thought that these super-massive WDs are their most likely progenitors and that they probably have a very strong magnetic field inside them. A degenerate electron gas in a magnetic field, such as that present inside this star, will be Landau quantized. Magnetic field changes the momentum space of electrons which in turn changes their density of states (DOS) and that in turn changes the equation of state (EoS) of matter inside the star, as opposed to that without a field. When this change in the DOS is taken into account and a link between the DOS and the EoS is established, as is done in this work, I find a physical reason behind the theoretical mass-radius (M-R) relations of a super-massive WD. I start with different equations of state with at most three Landau levels occupied and then construct stellar models of magnetic WDs (MWDs) using the same. I also show the M-R relations of these stars for a particular chosen value of maximum electron Fermi energy. Once a multiple Landau level system of electrons is considered, I find that it leads to such an EoS that gives multiple branches in the MR relations. Super-massive MWDs are obtained only when the Landau level occupancy is limited to just one level and some of the mass values fall within the mass range given above.
Piersma, Theunis
1987-01-01
This review examines the question whether the cumulative amount of benthic biomass removed by feeding shorebirds on a certain intertidal area is limited by the renewal rate of benthic food stocks. Limitations of current methods to estimate both predatory impact by shorebirds and harvestable benthic
Directory of Open Access Journals (Sweden)
Mathieu Legros
Full Text Available Recently there have been significant advances in research on genetic strategies to control populations of disease-vectoring insects. Some of these strategies use the gene drive properties of selfish genetic elements to spread physically linked anti-pathogen genes into local vector populations. Because of the potential of these selfish elements to spread through populations, control approaches based on these strategies must be carefully evaluated to ensure a balance between the desirable spread of the refractoriness-conferring genetic cargo and the avoidance of potentially unwanted outcomes such as spread to non-target populations. There is also a need to develop better estimates of the economics of such releases. We present here an evaluation of two such strategies using a biologically realistic mathematical model that simulates the resident Aedes aegypti mosquito population of Iquitos, Peru. One strategy uses the selfish element Medea, a non-limited element that could permanently spread over a large geographic area; the other strategy relies on Killer-Rescue genetic constructs, and has been predicted to have limited spatial and temporal spread. We simulate various operational approaches for deploying these genetic strategies, and quantify the optimal number of released transgenic mosquitoes needed to achieve definitive spread of Medea-linked genes and/or high frequencies of Killer-Rescue-associated elements. We show that for both strategies the most efficient approach for achieving spread of anti-pathogen genes within three years is generally to release adults of both sexes in multiple releases over time. Even though females in these releases should not transmit disease, there could be public concern over such releases, making the less efficient male-only release more practical. This study provides guidelines for operational approaches to population replacement genetic strategies, as well as illustrates the use of detailed spatial models to
Results on neutrinoless double beta decay search in GERDA. Background modeling and limit setting
Energy Technology Data Exchange (ETDEWEB)
Becerici Schmidt, Neslihan
2014-07-22
The search for the neutrinoless double beta decay (0νββ) process is primarily motivated by its potential of revealing the possible Majorana nature of the neutrino, in which the neutrino is identical to its antiparticle. It has also the potential to yield information on the intrinsic properties of neutrinos, if the underlying mechanism is the exchange of a light Majorana neutrino. The Gerda experiment is searching for 0νββ decay of {sup 76}Ge by operating high purity germanium (HPGe) detectors enriched in the isotope {sup 76}Ge (∝ 87%), directly in ultra-pure liquid argon (LAr). The first phase of physics data taking (Phase I) was completed in 2013 and has yielded 21.6 kg.yr of data. A background index of B∼10{sup -2} cts/(keV.kg.yr) at Q{sub ββ}=2039 keV has been achieved. A comprehensive background model of the Phase I energy spectrum is presented as the major topic of this dissertation. Decomposition of the background energy spectrum into the individual contributions from different processes provides many interesting physics results. The specific activity of {sup 39}Ar has been determined. The obtained result, A=(1.15±0.11) Bq/kg, is in good agreement with the values reported in literature. The contribution from {sup 42}K decays in LAr to the background spectrum has yielded a {sup 42}K({sup 42}Ar) specific activity of A=(106.2{sub -19.2}{sup +12.7}) μBq/kg, for which only upper limits exist in literature. The analysis of high energy events induced by α decays in the {sup 226}Ra chain indicated a total {sup 226}Ra activity of (3.0±0.9) μBq and a total initial {sup 210}Po activity of (0.18±0.01) mBq on the p{sup +} surfaces of the enriched semi-coaxial HPGe detectors. The half life of the two-neutrino double beta (2νββ) decay of {sup 76}Ge has been determined as T{sub 1/2}{sup 2ν}=(1.926±0.094).10{sup 21} yr, which is in good agreement with the result that was obtained with lower exposure and has been published by the Gerda collaboration
Results on neutrinoless double beta decay search in GERDA. Background modeling and limit setting
International Nuclear Information System (INIS)
Becerici Schmidt, Neslihan
2014-01-01
The search for the neutrinoless double beta decay (0νββ) process is primarily motivated by its potential of revealing the possible Majorana nature of the neutrino, in which the neutrino is identical to its antiparticle. It has also the potential to yield information on the intrinsic properties of neutrinos, if the underlying mechanism is the exchange of a light Majorana neutrino. The Gerda experiment is searching for 0νββ decay of 76 Ge by operating high purity germanium (HPGe) detectors enriched in the isotope 76 Ge (∝ 87%), directly in ultra-pure liquid argon (LAr). The first phase of physics data taking (Phase I) was completed in 2013 and has yielded 21.6 kg.yr of data. A background index of B∼10 -2 cts/(keV.kg.yr) at Q ββ =2039 keV has been achieved. A comprehensive background model of the Phase I energy spectrum is presented as the major topic of this dissertation. Decomposition of the background energy spectrum into the individual contributions from different processes provides many interesting physics results. The specific activity of 39 Ar has been determined. The obtained result, A=(1.15±0.11) Bq/kg, is in good agreement with the values reported in literature. The contribution from 42 K decays in LAr to the background spectrum has yielded a 42 K( 42 Ar) specific activity of A=(106.2 -19.2 +12.7 ) μBq/kg, for which only upper limits exist in literature. The analysis of high energy events induced by α decays in the 226 Ra chain indicated a total 226 Ra activity of (3.0±0.9) μBq and a total initial 210 Po activity of (0.18±0.01) mBq on the p + surfaces of the enriched semi-coaxial HPGe detectors. The half life of the two-neutrino double beta (2νββ) decay of 76 Ge has been determined as T 1/2 2ν =(1.926±0.094).10 21 yr, which is in good agreement with the result that was obtained with lower exposure and has been published by the Gerda collaboration. According to the model, the background in Q ββ ±5 keV window is resulting from close
Energy Technology Data Exchange (ETDEWEB)
Cole, Henry E.; Fullen, Robert E.
1980-09-01
This report reviews four of the major models used by the Department of Energy (DOE) for energy conservation analyses in the residential- and commercial-building sectors. The objective is to provide a critical analysis of how these models can serve as tools for DOE and its Conservation Policy Office in evaluating and quantifying their policy and program requirements. For this, the study brings together information on the models' analytical structure and their strengths and limitations in policy applications these are then employed to assess the most-effective role for each model in addressing future issues of buildings energy-conservation policy and analysis. The four models covered are: Oak Ridge Residential Energy Model; Micro Analysis of Transfers to Households/Comprehensive Human Resources Data System (MATH/CHRDS) Model; Oak Ridge Commercial Energy Model; and Brookhaven Buildings Energy Conservation Optimization Model (BECOM).
Alex Diego Souza Queiroz; Marilia Oliveira dos Reis; Joseilton Silveira da Rocha
2016-01-01
The objective of this study was to determine whether the decision-making models present in Prospect Theory and the theory of limited rationality could help managers of financial institutions identify and control the emotions and rational limitations involved in the credit granting process in the financial market. To this end, a study was carried out with 17 bank managers as experimental group and 31 other managers from different areas as control group. Adopting a quantitative approach to rese...
An analytical model for neutral and charged particles in closed pump limiter
International Nuclear Information System (INIS)
Tokar, M.Z.
1990-01-01
In number of modern tokamaks pump limiters are used for control of the edge plasma parameters. In thermonuclear reactor projects pump limiters are considered as a possible alternative or additional for divertor configuration of magnetic field method for unburnt fuel, helium ash and other impurity exhaust. From the point of view of limiter operation efficiency the dependence of neutral particle pressure P g in pumping system on the plasma parameters in the scrape-off layer (SOL) is of importance since an increase of P g will permit to decrease needed pump rate and facilitate solution of reactor technological problems. In connection with this the experimentally observed mode of closed pump limiter operation with strong neutral compression is of great interest. In such a mode P g sharply grows up when the SOL plasma density n s exceeds some critial level. (author) 6 refs., 2 figs
Pisano, Aurora; Weichert, Dieter
2015-01-01
Articles in this book examine various materials and how to determine directly the limit state of a structure, in the sense of limit analysis and shakedown analysis. Apart from classical applications in mechanical and civil engineering contexts, the book reports on the emerging field of material design beyond the elastic limit, which has further industrial design and technological applications. Readers will discover that “Direct Methods” and the techniques presented here can in fact be used to numerically estimate the strength of structured materials such as composites or nano-materials, which represent fruitful fields of future applications. Leading researchers outline the latest computational tools and optimization techniques and explore the possibility of obtaining information on the limit state of a structure whose post-elastic loading path and constitutive behavior are not well defined or well known. Readers will discover how Direct Methods allow rapid and direct access to requested information in...
Milne, R K; Yeo, G F; Edeson, R O; Madsen, B W
1988-04-22
Stochastic models of ion channels have been based largely on Markov theory where individual states and transition rates must be specified, and sojourn-time densities for each state are constrained to be exponential. This study presents an approach based on random-sum methods and alternating-renewal theory, allowing individual states to be grouped into classes provided the successive sojourn times in a given class are independent and identically distributed. Under these conditions Markov models form a special case. The utility of the approach is illustrated by considering the effects of limited time resolution (modelled by using a discrete detection limit, xi) on the properties of observable events, with emphasis on the observed open-time (xi-open-time). The cumulants and Laplace transform for a xi-open-time are derived for a range of Markov and non-Markov models; several useful approximations to the xi-open-time density function are presented. Numerical studies show that the effects of limited time resolution can be extreme, and also highlight the relative importance of the various model parameters. The theory could form a basis for future inferential studies in which parameter estimation takes account of limited time resolution in single channel records. Appendixes include relevant results concerning random sums and a discussion of the role of exponential distributions in Markov models.
Eckhart, V M; Geber, M A; Morris, W F; Fabio, E S; Tiffin, P; Moeller, D A
2011-10-01
Potential causes of species' geographic distribution limits fall into two broad classes: (1) limited adaptation across spatially variable environments and (2) limited opportunities to colonize unoccupied areas. Combining demographic studies, analyses of demographic responses to environmental variation, and species distribution models, we investigated the causes of range limits in a model system, the eastern border of the California annual plant Clarkia xantiana ssp. xantiana. Vital rates of 20 populations varied with growing season temperature and precipitation: fruit number and overwinter survival of 1-year-old seeds declined steeply, while current-year seed germination increased modestly along west-to-east gradients in decreasing temperature, decreasing mean precipitation, and increasing variation in precipitation. Long-term stochastic finite rate of increase, λ(s), exhibited a fourfold range and varied among geologic surface materials as well as with temperature and precipitation. Growth rate declined significantly toward the eastern border, falling below 1 in three of the five easternmost populations. Distribution models employing demographically important environmental variables predicted low habitat favorability beyond the eastern border. Models that filtered or weighted population presences by λ(s) predicted steeper eastward declines in favorability and assigned greater roles in setting the distribution to among-year variation in precipitation and to geologic surface material. These analyses reveal a species border likely set by limited adaptation to declining environmental quality.
Modeling Acceleration of a System of Two Objects Using the Concept of Limits
Sokolowski, Andrzej
2018-01-01
Traditional school laboratory exercises on a system of moving objects connected by strings involve deriving expressions for the system acceleration, a = (∑F )/m, and sketching a graph of acceleration vs. force. While being in the form of rational functions, these expressions present great opportunities for broadening the scope of the analysis by using a more sophisticated math apparatus—the concept of limits. Using the idea of limits allows for extending both predictions and explanations of this type of motion that are—according to Redish—essential goals of teaching physics. This type of analysis, known in physics as limiting case analysis, allows for generalizing inferences by evaluating or estimating values of algebraic functions based on its extreme inputs. In practice, such transition provides opportunities for deriving valid conclusions for cases when direct laboratory measurements are not possible. While using limits is common for scientists, the idea of applying limits in school practice is not visible, and testing students' ability in this area is also rare.
Monte Carlo modelling of impurity ion transport for a limiter source/sink
International Nuclear Information System (INIS)
Stangeby, P.C.; Farrell, C.; Hoskins, S.; Wood, L.
1988-01-01
In relating the impurity influx Φ I (0) (atoms per second) into a plasma from the edge to the central impurity ion density n I (0) (ions·m -3 ), it is necessary to know the value of τ I SOL , the average dwell time of impurity ions in the scrape-off layer. It is usually assumed that τ I SOL =L c /c s , the hydrogenic dwell time, where L c is the limiter connection length and c s is the hydrogenic ion acoustic speed. Monte Carlo ion transport results are reported here which show that, for a wall (uniform) influx, τ I SOL is longer than L c /c s , while for a limiter influx it is shorter. Thus for a limiter influx n I (0) is predicted to be smaller than the reference value. Impurities released from the limiter form ever large 'clouds' of successively higher ionization stages. These are reproduced by the Monte Carlo code as are the cloud shapes for a localized impurity injection far from the limiter. (author). 23 refs, 18 figs, 6 tabs
Utilization of the ICARUS model by the electricity authority of Cyprus and its limitations
International Nuclear Information System (INIS)
Stephanou, A.
1997-01-01
This report describes the principal uses of the ICARUS model at the Electricity Authority of Cyprus (EAC). The problems encountered in the application of the model at EAC are highlighted, together with some suggestions for future improvements of this model. (author)
Utilization of the ICARUS model by the electricity authority of Cyprus and its limitations
Energy Technology Data Exchange (ETDEWEB)
Stephanou, A [Electricity Authority of Cyprus, Nicosia (Cyprus)
1997-09-01
This report describes the principal uses of the ICARUS model at the Electricity Authority of Cyprus (EAC). The problems encountered in the application of the model at EAC are highlighted, together with some suggestions for future improvements of this model. (author).
ICRF Faraday shield plasma sheath models: Low and high conductivity limits
International Nuclear Information System (INIS)
Whealton, J.H.; Ryan, P.M.; Raridon, R.J.
1989-01-01
Using a 2-D nonlinear formulation which explicitly considers the plasma edge near a Faraday shield in a self consistent manner, progress is indicated in the modeling of the ion motion for a Faraday shield concept and model suggested by Perkins. Several models are considered which may provide significant insight into the impurities generation for ICRH antennas. 6 refs., 8 figs
Marin, Pricila; Borba, Carlos Eduardo; Módenes, Aparecido Nivaldo; Espinoza-Quiñones, Fernando R; de Oliveira, Silvia Priscila Dias; Kroumov, Alexander Dimitrov
2014-01-01
Reactive blue 5G dye removal in a fixed-bed column packed with Dowex Optipore SD-2 adsorbent was modelled. Three mathematical models were tested in order to determine the limiting step of the mass transfer of the dye adsorption process onto the adsorbent. The mass transfer resistance was considered to be a criterion for the determination of the difference between models. The models contained information about the external, internal, or surface adsorption limiting step. In the model development procedure, two hypotheses were applied to describe the internal mass transfer resistance. First, the mass transfer coefficient constant was considered. Second, the mass transfer coefficient was considered as a function of the dye concentration in the adsorbent. The experimental breakthrough curves were obtained for different particle diameters of the adsorbent, flow rates, and feed dye concentrations in order to evaluate the predictive power of the models. The values of the mass transfer parameters of the mathematical models were estimated by using the downhill simplex optimization method. The results showed that the model that considered internal resistance with a variable mass transfer coefficient was more flexible than the other ones and this model described the dynamics of the adsorption process of the dye in the fixed-bed column better. Hence, this model can be used for optimization and column design purposes for the investigated systems and similar ones.
Directory of Open Access Journals (Sweden)
K. Ichii
2010-07-01
Full Text Available Terrestrial biosphere models show large differences when simulating carbon and water cycles, and reducing these differences is a priority for developing more accurate estimates of the condition of terrestrial ecosystems and future climate change. To reduce uncertainties and improve the understanding of their carbon budgets, we investigated the utility of the eddy flux datasets to improve model simulations and reduce variabilities among multi-model outputs of terrestrial biosphere models in Japan. Using 9 terrestrial biosphere models (Support Vector Machine – based regressions, TOPS, CASA, VISIT, Biome-BGC, DAYCENT, SEIB, LPJ, and TRIFFID, we conducted two simulations: (1 point simulations at four eddy flux sites in Japan and (2 spatial simulations for Japan with a default model (based on original settings and a modified model (based on model parameter tuning using eddy flux data. Generally, models using default model settings showed large deviations in model outputs from observation with large model-by-model variability. However, after we calibrated the model parameters using eddy flux data (GPP, RE and NEP, most models successfully simulated seasonal variations in the carbon cycle, with less variability among models. We also found that interannual variations in the carbon cycle are mostly consistent among models and observations. Spatial analysis also showed a large reduction in the variability among model outputs. This study demonstrated that careful validation and calibration of models with available eddy flux data reduced model-by-model differences. Yet, site history, analysis of model structure changes, and more objective procedure of model calibration should be included in the further analysis.
Ichii, K.; Suzuki, T.; Kato, T.; Ito, A.; Hajima, T.; Ueyama, M.; Sasai, T.; Hirata, R.; Saigusa, N.; Ohtani, Y.; Takagi, K.
2010-07-01
Terrestrial biosphere models show large differences when simulating carbon and water cycles, and reducing these differences is a priority for developing more accurate estimates of the condition of terrestrial ecosystems and future climate change. To reduce uncertainties and improve the understanding of their carbon budgets, we investigated the utility of the eddy flux datasets to improve model simulations and reduce variabilities among multi-model outputs of terrestrial biosphere models in Japan. Using 9 terrestrial biosphere models (Support Vector Machine - based regressions, TOPS, CASA, VISIT, Biome-BGC, DAYCENT, SEIB, LPJ, and TRIFFID), we conducted two simulations: (1) point simulations at four eddy flux sites in Japan and (2) spatial simulations for Japan with a default model (based on original settings) and a modified model (based on model parameter tuning using eddy flux data). Generally, models using default model settings showed large deviations in model outputs from observation with large model-by-model variability. However, after we calibrated the model parameters using eddy flux data (GPP, RE and NEP), most models successfully simulated seasonal variations in the carbon cycle, with less variability among models. We also found that interannual variations in the carbon cycle are mostly consistent among models and observations. Spatial analysis also showed a large reduction in the variability among model outputs. This study demonstrated that careful validation and calibration of models with available eddy flux data reduced model-by-model differences. Yet, site history, analysis of model structure changes, and more objective procedure of model calibration should be included in the further analysis.
Review and limitations of 3D plasma blob modeling with reduced collisional fluid equations
Energy Technology Data Exchange (ETDEWEB)
Angus, Justin R., E-mail: jangus@ucsd.edu [University of California, San Diego, La Jolla, CA (United States); Umansky, Maxim V. [Lawrence Livermore National Laboratory, Livermore, CA (United States); Krashenninikov, Sergei I. [University of California, San Diego, La Jolla, CA (United States)
2013-07-15
Recent 3D studies on plasma blobs (coherent structures found in the edge region of magnetic confinement devices) have demonstrated that the drift wave instability can strongly limit the blob’s coherency and cross field convective nature that is predicted by 2D theory. However, the dominant unstable drift wave modes that effect plasma blobs were found to exist in parameter regimes that only marginally satisfied several of the major assumptions considered for the validity of the reduced collisional fluid equations used in the study. Namely, the neglect of electron heat flow, finite electron mean free path effects, and thermal ions. A follow up study demonstrated how the drift wave instability might change if a set of equations that does not suffer from the limitations mentioned above were considered. In the present paper, the results of this later work are used to discuss the limitations on using the collisional fluid equations for 3D studies of plasma blobs.
DEFF Research Database (Denmark)
Merkey, Brian; Lardon, Laurent; Seoane, Jose Miguel
2011-01-01
Plasmid invasion in biofilms is often surprisingly limited in spite of the close contact of cells in a biofilm. We hypothesized that this poor plasmid spread into deeper biofilm layers is caused by a dependence of conjugation on the growth rate (relative to the maximum growth rate) of the donor......, we find that invasion of a resident biofilm is indeed limited when plasmid transfer depends on growth, but not so in the absence of growth dependence. Using sensitivity analysis we also find that parameters related to timing (i.e. a lag before the transconjugant can transfer, transfer proficiency...... and scan speed) and spatial reach (EPS yield, conjugal pilus length) are more important for successful plasmid invasion than the recipients' growth rate or the probability of segregational loss. While this study identifies one factor that can limit plasmid invasion in biofilms, the new individual...
Waves and solitons in the continuum limit of the Calogero-Sutherland model
Polychronakos, A P
1995-01-01
We examine a collection of classical particles interacting with inverse-square two-body potentials in the thermodynamic limit of finite particle density. We find explicit large-amplitude density waves and soliton solutions for the motion of the system. Waves can be constructed as coherent states of either solitons or phonons (small-amplitude waves). Therefore, either solitons or phonons can be considered as the fundamental excitations. The generic wave is shown to correspond to a two-band state in the quantum description of the system, while the limiting cases of solitons and phonons correspond to particle and hole excitations.
FEM-model of the Naesliden Mine: requirements and limitations at the outset of the project. [Sweden
Energy Technology Data Exchange (ETDEWEB)
Krauland, N.
1980-05-15
The design of any instrument depends entirely on the application planned for the instrument. This applies also to the FEM-representation of the Naesliden Mine. With reference to the aims of the project the requirements on the model are outlined with regard to - simulation of the mining process - modelling with special reference to the aims of the project - comparison of FEM-results with in situ observations to determine the validity of the model. The proposed model is two-dimensional and incorporates joint elements to simulate the weak alteration zone between orebody and sidewall rock. The remainder of the model exhibits linear elastic behaviour. This model is evaluated with respect to the given requirements. The limitations of the chosen model are outlined.
Product unit neural network models for predicting the growth limits of Listeria monocytogenes.
Valero, A; Hervás, C; García-Gimeno, R M; Zurera, G
2007-08-01
A new approach to predict the growth/no growth interface of Listeria monocytogenes as a function of storage temperature, pH, citric acid (CA) and ascorbic acid (AA) is presented. A linear logistic regression procedure was performed and a non-linear model was obtained by adding new variables by means of a Neural Network model based on Product Units (PUNN). The classification efficiency of the training data set and the generalization data of the new Logistic Regression PUNN model (LRPU) were compared with Linear Logistic Regression (LLR) and Polynomial Logistic Regression (PLR) models. 92% of the total cases from the LRPU model were correctly classified, an improvement on the percentage obtained using the PLR model (90%) and significantly higher than the results obtained with the LLR model, 80%. On the other hand predictions of LRPU were closer to data observed which permits to design proper formulations in minimally processed foods. This novel methodology can be applied to predictive microbiology for describing growth/no growth interface of food-borne microorganisms such as L. monocytogenes. The optimal balance is trying to find models with an acceptable interpretation capacity and with good ability to fit the data on the boundaries of variable range. The results obtained conclude that these kinds of models might well be very a valuable tool for mathematical modeling.
Fluid Limits for an ALOHA-type Model with Impatient Customers
M. Frolkova (Masha); A.P. Zwart (Bert); S.G. Foss (Sergey)
2012-01-01
htmlabstractIn the present paper we consider an ALOHA-type random-multiple-access protocol where users are allowed to renege before transmission completion. We focus on the scenario which leads to overload in the absence of impatience. Under mild assumptions, we show that the fluid limit of the
Real gas effects in mixing-limited diesel spray vaporization models
Luijten, C.C.M.; Kurvers, C.
2010-01-01
The maximum penetration length of the liquid phase in diesel sprays is of paramount importance in reducing diesel engine emissions. Quasi-steady liquid length values have been successfully correlated in the literature, assuming that mixing of fuel and air is the limiting step in the evaporation
Addressing water scarcity through limited irrigation cropping: Field experiments and modeling
Population growth in urbanizing areas such as the Front Range of Colorado has led to increased pressure to transfer water from agriculture to municipalities. In many cases this has led to complete dry up of productive irrigated lands. An option to complete dry-up is the practice of limited or defi...
Sprakel, J.H.B.; Besseling, N.A.M.; Cohen Stuart, M.A.; Leermakers, F.A.M.
2008-01-01
We introduce a simple thermodynamic argument for capillary adhesion forces, for various geometries, in the limit of saturation of the bulk phase. For one specific geometry (i.e., the sphere¿plate geometry such as that found in the colloidal probe AFM technique), we provide evidence of the validity
A numerical scheme for a kinetic model for mixtures in the diffusive limit using the moment method
Bondesan , Andrea; Boudin , Laurent; Grec , Bérénice
2018-01-01
In this article, we consider a multi-species kinetic model which leads to the Maxwell-Stefan equations under a standard diffusive scaling (small Knudsen and Mach numbers). We propose a suitable numerical scheme which approximates both the solution of the kinetic model in rarefied regime and the one in the diffusion limit. We prove some a priori estimates (mass conservation and nonnegativity) and well-posedness of the discrete problem. We also present numerical examples where we observe the as...
Pushing the pseudo-SU(3) model towards its limits: Excited bands in even-even Dy isotopes
International Nuclear Information System (INIS)
Vargas, Carlos E.; Hirsch, Jorge G.
2004-01-01
The energetics of states belonging to normal parity bands in even-even dysprosium isotopes, and their B(E2) transition strengths, are studied using an extended pseudo-SU(3) shell model. States with pseudospin 1 are added to the standard pseudospin 0 space, allowing for a proper description of known excited normal parity bands. A realistic Hamiltonian is employed. Both the success of model and its limitations are discussed
Modeling of a Small Transportation Company’s Start-Up with Limited Data during Economic Recession
Directory of Open Access Journals (Sweden)
Xiaoping Fang
2013-01-01
Full Text Available This paper presents a modeling method for analyzing a small transportation company’s start-up and growth during a global economic crisis which had an impact on China which is designed to help the owners make better investment and operating decisions with limited data. Since there is limited data, simple regression model and binary regression model failed to generate satisfactory results, so an additive periodic time series model was built to forecast business orders and income. Since the transportation market is segmented by business type and transportation distance, a polynomial model and logistic curve model were constructed to forecast the growth trend of each segmented transportation market, and the seasonal influence function was fitted by seasonal ratio method. Although both of the models produced satisfactory results and showed very nearly the same of goodness-of-fit in the sample, the logistic model presented better forecasting performance out of the sample therefore closer to the reality. Additionally, by checking the development trajectory of the case company’s business and the financial crisis in 2008, the modeling and analysis suggest that the sample company is affected by national macroeconomic factors such as GDP and import & export, and this effect comes with a time lag of one to two years.
International Nuclear Information System (INIS)
Attaway, S.W.; Yoshimura, H.R.
1989-01-01
Wood is often used as the energy absorbing material in impact limiters, because it begins to crush at low strains, then maintains a near constant crush stress up to nearly 60% volume reduction, and then locks up. Hill (Hill and Joseph, 1974) has performed tests that show that wood is an excellent absorber. However, wood's orthotropic behavior for large crush is difficult to model. In the past, analysts have used isotropic foam-like material models for modeling wood. A new finite element technique is presented in this paper that gives a better model of wood crush than the model currently in use. The orthotropic technique is based on locally isotropic, but globally orthotropic (LIGO) (Attaway, 1988) assumptions in which alternating layers of hard and soft crushable material are used. Each layer is isotropic; however, by alternating hard and soft thin layers, the resulting global behavior is orthotropic. In the remainder of this paper, the new technique for modeling orthotropic wood crush will be presented. The model is used to predict the crush behavior for different grain orientations of balsa wood. As an example problem, an impact limiter containing balsa wood as the crushable material is analyzed using both an isotropic model and the LIGO model
Rajesh VijayKumar Kherde; Dr. Priyadarshi. H. Sawant
2013-01-01
The evolution of Geographic information systems (GIS) facilitated the use digital terrain data for topography based hydrological modelling. The use of spatial data for hydrological modelling emerged from the great capability of GIS tools to store and handle the data associated hydro-morphology of the basin. These models utilize the spatially variable terrain data for converting rainfall into surface runoff.Manual map manipulation has always posed difficulty in analysing and designing large sc...
MESH-TO-BIM: FROM SEGMENTED MESH ELEMENTS TO BIM MODEL WITH LIMITED PARAMETERS
Directory of Open Access Journals (Sweden)
X. Yang
2018-05-01
Full Text Available Building Information Modelling (BIM technique has been widely utilized in heritage documentation and comes to a general term Historical/Heritage BIM (HBIM. The current HBIM project mostly employs the scan-to-BIM process to manually create the geometric model from the point cloud. This paper explains how it is possible to shape from the mesh geometry with reduced human involvement during the modelling process. Aiming at unbuilt heritage, two case studies are handled in this study, including a ruined Roman stone architectural and a severely damaged abbey. The pipeline consists of solid element modelling based on documentation data using Autodesk Revit, a common BIM platform, and the successive modelling from these geometric primitives using Autodesk Dynamo, a visual programming built-in plugin tool in Revit. The BIM-based reconstruction enriches the classic visual model from computer graphics approaches with measurement, semantic and additional information. Dynamo is used to develop a semi-automated function to reduce the manual process, which builds the final BIM model from segmented parametric elements directly. The level of detail (LoD of the final models is dramatically relevant with the manual involvement in the element creation. The proposed outline also presents two potential issues in the ongoing work: combining the ontology semantics with the parametric BIM model, and introducing the proposed pipeline into the as-built HBIM process.
Directory of Open Access Journals (Sweden)
G. M. S. ALVA
Full Text Available Brazilian Codes NBR 6118 and NBR 15575 provide practical values for interstory drift limits applied to conventional modeling in order to prevent negative effects in masonry infill walls caused by excessive lateral deformability, however these codes do not account for infill walls in the structural model. The inclusion of infill walls in the proposed model allows for a quantitative evaluation of structural stresses in these walls and an assessment of cracking in these elements (sliding shear diagonal tension and diagonal compression cracking. This paper presents the results of simulations of single-story one-bay infilled R/C frames. The main objective is to show how to check the serviceability limit states under lateral loads when the infill walls are included in the modeling. The results of numerical simulations allowed for an evaluation of stresses and the probable cracking pattern in infill walls. The results also allowed an identification of some advantages and limitations of the NBR 6118 practical procedure based on interstory drift limits.
Signature effect in the SU(3) limit of SU(6) particle-quadrupole phonon coupling model (PTQM)
International Nuclear Information System (INIS)
Paar, V.; Brant, S.
1981-09-01
Systematic deviations from the J(J + 1) energy rule in the SU(3) limit of PTQM are studied and interpreted in terms of signature from the rotational model. The signature effect, which is in the rotational mode introduced via the Coriolis force, is generated here by the correlation of PTQM. (author)
Proost, J. H.
Objective: Limited sampling models (LSM) for estimating AUC in therapeutic drug monitoring are usually validated in a separate group of patients, according to published guidelines. The aim of this study is to evaluate the validation of LSM by comparing independent validation with cross-validation
Huisman, Jef; Weissing, F.J.
Light is never distributed homogeneously since it forms a gradient over biomass. As a consequence, the common theories on nutrient competition are not applicable to competition for light. In this paper, we investigate a model for light-limited growth and competition among phytoplankton species in a
High temperature limit of the order parameter correlation functions in the quantum Ising model
Reyes, S. A.; Tsvelik, A. M.
2006-06-01
In this paper we use the exact results for the anisotropic two-dimensional Ising model obtained by Bugrii and Lisovyy [A.I. Bugrii, O.O. Lisovyy, Theor. Math. Phys. 140 (2004) 987] to derive the expressions for dynamical correlation functions for the quantum Ising model in one dimension at high temperatures.
High temperature limit of the order parameter correlation functions in the quantum Ising model
Energy Technology Data Exchange (ETDEWEB)
Reyes, S.A. [Department of Physics and Astronomy, SUNY at Stony Brook, Stony Brook, NY 11794-3840 (United States); Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, Upton, NY 11973-5000 (United States); Tsvelik, A.M. [Department of Physics and Astronomy, SUNY at Stony Brook, Stony Brook, NY 11794-3840 (United States) and Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, Upton, NY 11973-5000 (United States)]. E-mail tsvelik@bnl.gov
2006-06-12
In this paper we use the exact results for the anisotropic two-dimensional Ising model obtained by Bugrii and Lisovyy [A.I. Bugrii, O.O. Lisovyy, Theor. Math. Phys. 140 (2004) 987] to derive the expressions for dynamical correlation functions for the quantum Ising model in one dimension at high temperatures.
A multistate model to project elderly disability in case of limited data
van der Gaag, N.L.; Bijwaard, G.E.; de Beer, J.A.A.; Bonneux, L.
2015-01-01
Background : Prevalence of disability depends on when a person becomes disabled (disability incidence) and when he or she dies (mortality). Multistate projection models can take into account both underlying processes of disability prevalence. The application of these models, however, is often
Simplified prognostic model for critically ill patients in resource limited settings in South Asia
Haniffa, Rashan; Mukaka, Mavuto; Munasinghe, Sithum Bandara; de Silva, Ambepitiyawaduge Pubudu; Jayasinghe, Kosala Saroj Amarasiri; Beane, Abi; de Keizer, Nicolette; Dondorp, Arjen M.
2017-01-01
Background: Current critical care prognostic models are predominantly developed in high-income countries (HICs) and may not be feasible in intensive care units (ICUs) in lower-and middle-income countries (LMICs). Existing prognostic models cannot be applied without validation in LMICs as the
On looking into the Black Box: Prospects and Limits in the Search for Mental Models
1985-05-01
particularly in terms of the ways in which humans understand systems. Norman (19831 characterizes this understanding as messy, sloppy, incomplete, and...Kleinman, et al., 1971]). However, for tasks involving only monitoring [ Smallwood , 1967; Sheridan, 1970], especially when apparent discontinuities...18 Norman [1983] uses the word "conceptaalization" to characterize researchers’ models of humans’ mental models. This characterization serves to
The Limit Behavior of a Stochastic Logistic Model with Individual Time-Dependent Rates
Directory of Open Access Journals (Sweden)
Yilun Shang
2013-01-01
Full Text Available We investigate a variant of the stochastic logistic model that allows individual variation and time-dependent infection and recovery rates. The model is described as a heterogeneous density dependent Markov chain. We show that the process can be approximated by a deterministic process defined by an integral equation as the population size grows.
One-dimensional modelling of limit-cycle oscillation and H-mode power scaling
DEFF Research Database (Denmark)
Wu, Xingquan; Xu, Guosheng; Wan, Baonian
2015-01-01
To understand the connection between the dynamics of microscopic turbulence and the macroscale power scaling in the L-I-H transition in magnetically confined plasmas, a new time-dependent, one-dimensional (in radius) model has been developed. The model investigates the radial force balance equati...
Rajagopal, K. R.
2011-01-06
This paper is the first part of an extended program to develop a theory of fracture in the context of strain-limiting theories of elasticity. This program exploits a novel approach to modeling the mechanical response of elastic, that is non-dissipative, materials through implicit constitutive relations. The particular class of models studied here can also be viewed as arising from an explicit theory in which the displacement gradient is specified to be a nonlinear function of stress. This modeling construct generalizes the classical Cauchy and Green theories of elasticity which are included as special cases. It was conjectured that special forms of these implicit theories that limit strains to physically realistic maximum levels even for arbitrarily large stresses would be ideal for modeling fracture by offering a modeling paradigm that avoids the crack-tip strain singularities characteristic of classical fracture theories. The simplest fracture setting in which to explore this conjecture is anti-plane shear. It is demonstrated herein that for a specific choice of strain-limiting elasticity theory, crack-tip strains do indeed remain bounded. Moreover, the theory predicts a bounded stress field in the neighborhood of a crack-tip and a cusp-shaped opening displacement. The results confirm the conjecture that use of a strain limiting explicit theory in which the displacement gradient is given as a function of stress for modeling the bulk constitutive behavior obviates the necessity of introducing ad hoc modeling constructs such as crack-tip cohesive or process zones in order to correct the unphysical stress and strain singularities predicted by classical linear elastic fracture mechanics. © 2011 Springer Science+Business Media B.V.
On Looking into the Black Box: Prospects and Limits in the Search for Mental Models
Rouse, W. B.; Morris, N. M.
1984-01-01
To place the arguments advanced in this paper in alternative points of view with regard to mental models are reviewed. Use of the construct in areas such as neural information processing, manual control, decision making, problem solving, and cognitive science are discussed. Also reviewed are several taxonomies of mental models. The available empirical evidence for answering questions concerning the nature and usage of mental models is then discussed. A variety of studies are reviewed where the type and form of humans' knowledge have been manipulated. Also considered are numerous transfer of training studies whose results provide indirect evidence of the nature of mental models. The alternative perspectives considered and the spectrum of empirical evidence are combined to suggest a framework within which research on mental models can be viewed. By considering interactions of dimensions of this framework, the most salient unanswered questions can be identified.
Cost modelling in maintenance strategy optimisation for infrastructure assets with limited data
International Nuclear Information System (INIS)
Zhang, Wenjuan; Wang, Wenbin
2014-01-01
Our paper reports on the use of cost modelling in maintenance strategy optimisation for infrastructure assets. We present an original approach: the possibility of modelling even when the data and information usually required are not sufficient in quantity and quality. Our method makes use of subjective expert knowledge, and requires information gathered for only a small sample of assets to start with. Bayes linear methods are adopted to combine the subjective expert knowledge with the sample data to estimate the unknown model parameters of the cost model. When new information becomes available, Bayes linear methods also prove useful in updating these estimates. We use a case study from the rail industry to demonstrate our methods. The optimal maintenance strategy is obtained via simulation based on the estimated model parameters and the strategy with the least unit time cost is identified. When the optimal strategy is not followed due to insufficient funding, the future costs of recovering the degraded asset condition are estimated
Mathematical models of incompressible fluids as singular limits of complete fluid systems
Czech Academy of Sciences Publication Activity Database
Feireisl, Eduard
2010-01-01
Roč. 78, č. 2 (2010), s. 523-560 ISSN 1424-9286 R&D Projects: GA ČR GA201/08/0315 Institutional research plan: CEZ:AV0Z10190503 Keywords : scale analysis * Navier-Stokes-Fourier system * incompressible limit Subject RIV: BA - General Mathematics Impact factor: 0.933, year: 2010 http://link.springer.com/article/10.1007%2Fs00032-010-0128-1
Deribe, Kebede; Cano, Jorge; Newport, Melanie J.; Golding, Nick; Pullan, Rachel L.; Sime, Heven; Gebretsadik, Abeba; Assefa, Ashenafi; Kebede, Amha; Hailu, Asrat; Rebollo, Maria P.; Shafi, Oumer; Bockarie, Moses J.; Aseffa, Abraham; Hay, Simon I.
2015-01-01
Background\\ud \\ud Ethiopia is assumed to have the highest burden of podoconiosis globally, but the geographical distribution and environmental limits and correlates are yet to be fully investigated. In this paper we use data from a nationwide survey to address these issues.\\ud \\ud Methodology\\ud \\ud Our analyses are based on data arising from the integrated mapping of podoconiosis and lymphatic filariasis (LF) conducted in 2013, supplemented by data from an earlier mapping of LF in western Et...
Directory of Open Access Journals (Sweden)
Habtamu Yesigat Ayenew
2012-09-01
Full Text Available Resource allocation is a point of concern in small to large farms and is generally argued that small farmers in developing countries are “poor but efficient”, trying to allocate the limited resources to unlimited desires efficiently in the given production system in the light of their life-long experiences. The issue of market orientation in cattle fattening is basically challenged with the risks and uncertainties in the production and the market. Data were collected from 112 purposively selected fattening operator farmers from 3 districts and 6 peasant associations to see the risks. The data were analyzed through both descriptive and econometric statistical tools using STATA. Only about 13% of the respondents have participated in the farm business with own capital and the vast majority borrowed from Amhara Credit and Saving Association (ACSI through their cooperatives. It is found that production risks are limited while economic and market related risks play vital role in the farm operation. Duration of stay of the cattle, land holding of the household, distance to the development agent’s office and age of the household head increase the risk averse nature of the household and limit their participation in export market. In the other hand, frequency of fattening enhances the risk taking character of the households and their participation in the export of cattle. It is vital to enhance the institutional support from the public to enhance the gain from the fattening activity and market orientation of farming.
Generalized Veneziano model for pion scattering off isovector currents and the scaling limit
Rothe, H J; Rolhe, K D
1972-01-01
Starting from a local one-particle approximation scheme for the commutator of two conserved currents, the authors construct a generalized Veneziano model for pion scattering off neutral and charged isovector currents, satisfying the constraints of current conservation and current algebra. The model factorizes correctly on the leading Regge trajectories and incorporates the proper Regge behaviour for strong amplitudes. Fixed poles are found to be present in the s and t channels of the one- and two-current amplitudes. Furthermore, the model makes definite predictions about the structure of Schwinger terms and of the 'seagull' terms in the retarded commutator. (13 refs).
Nwosu, Cajethan M.; Ogbuka, Cosmas U.; Oti, Stephen E.
2017-08-01
This paper presents a control model design capable of inhibiting the phenomenal rise in the DC-link voltage during grid- fault condition in a variable speed wind turbine. Against the use of power circuit protection strategies with inherent limitations in fault ride-through capability, a control circuit algorithm capable of limiting the DC-link voltage rise which in turn bears dynamics that has direct influence on the characteristics of the rotor voltage especially during grid faults is here proposed. The model results so obtained compare favorably with the simulation results as obtained in a MATLAB/SIMULINK environment. The generated model may therefore be used to predict near accurately the nature of DC-link voltage variations during fault given some factors which include speed and speed mode of operation, the value of damping resistor relative to half the product of inner loop current control bandwidth and the filter inductance.
Neutron-skin thickness of finite nuclei in relativistic mean-field models with chiral limits
International Nuclear Information System (INIS)
Jiang Weizhou; Li Baoan; Chen Liewen
2007-01-01
We study several structure properties of finite nuclei using relativistic mean-field Lagrangians constructed according to the Brown-Rho scaling due to the chiral symmetry restoration at high densities. The models are consistent with current experimental constraints for the equations of state of symmetric matter at both normal and supranormal densities and of asymmetric matter at subsaturation densities. It is shown that these models can successfully describe the binding energies and charge radii of finite nuclei. Compared to calculations with usual relativistic mean-field models, these models give a reduced thickness of neutron skin in 208 Pb between 0.17 fm and 0.21 fm. The reduction of the predicted neutron skin thickness is found to be due to not only the softening of the symmetry energy but also the scaling property of ρ meson required by the partial restoration of chiral symmetry
A nested-grid limited-area model for short term weather forecasting
Wong, V. C.; Zack, J. W.; Kaplan, M. L.; Coats, G. D.
1983-01-01
The present investigation is concerned with a mesoscale atmospheric simulation system (MASS), incorporating the sigma-coordinate primitive equations. The present version of this model (MASS 3.0) has 14 vertical layers, with the upper boundary at 100 mb. There are 128 x 96 grid points in each layer. The earlier version of this model (MASS 2.0) has been described by Kaplan et al. (1982). The current investigation provides a summary of major revisions to that version and a description of the parameterization schemes which are presently included in the model. The planetary boundary layer (PBL) is considered, taking into account aspects of generalized similarity theory and free convection, the surface energy budget, the surface moisture budget, and prognostic equations for the depth h of the PBL. A cloud model is discussed, giving attention to stable precipitation, and cumulus convection.
DEFF Research Database (Denmark)
Bauer-Gottwein, Peter; Christiansen, Lars; Rosbjerg, Dan
2011-01-01
parameter uncertainty decreased significantly when TLRG data was included in the inversion. The forced infiltration experiment caused changes in unsaturated zone storage, which were monitored using TLRG and ground-penetrating radar. A numerical unsaturated zone model was subsequently conditioned on both......Coupled hydrogeophysical inversion emerges as an attractive option to improve the calibration and predictive capability of hydrological models. Recently, ground-based time-lapse relative gravity (TLRG) measurements have attracted increasing interest because there is a direct relationship between...
25-years three-fluid modeling-experience: successes and limits
International Nuclear Information System (INIS)
Kolev, N.I.
2004-01-01
The paper presents many examples of successful use of the three fluid processes modeling in 1D-networks, 3D-single volumes and 3D-boundary fitted volumes in the nuclear engineering. Fig. 1 shows 2700K hot molten aluminum oxide dropped in water and 3000K uranium oxide dropped in water as a demonstration for mathematical modeling of very complex real processes. (author)
Coherent density fluctuation model as a local-scale limit to ATDHF
International Nuclear Information System (INIS)
Antonov, A.N.; Petkov, I.Zh.; Stoitsov, M.V.
1985-04-01
The local scale transformation method is used for the construction of an Adiabatic Time-Dependent Hartree-Fock approach in terms of the local density distribution. The coherent density fluctuation relations of the model result in a particular case when the ''flucton'' local density is connected with the plane wave determinant model function be means of the local-scale coordinate transformation. The collective potential energy expression is obtained and its relation to the nuclear matter energy saturation curve is revealed. (author)
Neonatal disease environment limits the efficacy of retinal transplantation in the LCA8 mouse model
Cho, Seo-Hee; Song, Ji Yun; Shin, Jinyeon; Kim, Seonhee
2016-01-01
Background Mutations of Crb1 gene cause irreversible and incurable visual impairment in humans. This study aims to use an LCA8-like mouse model to identify host-mediated responses that might interfere with survival, retinal integration and differentiation of grafted cells during neonatal cell therapy. Methods Mixed retinal donor cells (1?~?2???104) isolated from neural retinas of neonatal eGFP transgenic mice were injected into the subretinal space of LCA8-like model neonatal mice. Markers of...
Technical challenges and limitations of current mouse models of ovarian cancer
Directory of Open Access Journals (Sweden)
Garson Kenneth
2012-11-01
Full Text Available Abstract The development of genetically engineered models (GEM of epithelial ovarian cancer (EOC has been very successful, with well validated models representing high grade and low grade serous adenocarcinomas and endometrioid carcinoma (EC. Most of these models were developed using technologies intended to target the ovarian surface epithelium (OSE, the cell type long believed to be the origin of EOC. More recent evidence has highlighted what is likely a more prevalent role of the secretory cell of the fallopian tube in the ontogeny of EOC, however none of the GEM of EOC have demonstrated successful targeting of this important cell type. The precise technologies exploited to develop the existing GEM of EOC are varied and carry with them advantages and disadvantages. The use of tissue specific promoters to model disease has been very successful, but the lack of any truly specific OSE or oviductal secretory cell promoters makes the outcomes of these models quite unpredictable. Effecting genetic change by the administration of adenoviral vectors expressing Cre recombinase may alleviate the perceived need for tissue specific promoters, however the efficiencies of infection of different cell types is subject to numerous biological parameters that may lead to preferential targeting of certain cell populations. One important future avenue of GEM of EOC is the evaluation of the role of genetic modifiers. We have found that genetic background can lead to contrasting phenotypes in one model of ovarian cancer, and data from other laboratories have also hinted that the exact genetic background of the model may influence the resulting phenotype. The different genetic backgrounds may modify the biology of the tumors in a manner that will be relevant to human disease, but they may also be modifying parameters which impact the response of the host to the technologies employed to develop the model.
Cressie, Noel; Calder, Catherine A; Clark, James S; Ver Hoef, Jay M; Wikle, Christopher K
2009-04-01
Analyses of ecological data should account for the uncertainty in the process(es) that generated the data. However, accounting for these uncertainties is a difficult task, since ecology is known for its complexity. Measurement and/or process errors are often the only sources of uncertainty modeled when addressing complex ecological problems, yet analyses should also account for uncertainty in sampling design, in model specification, in parameters governing the specified model, and in initial and boundary conditions. Only then can we be confident in the scientific inferences and forecasts made from an analysis. Probability and statistics provide a framework that accounts for multiple sources of uncertainty. Given the complexities of ecological studies, the hierarchical statistical model is an invaluable tool. This approach is not new in ecology, and there are many examples (both Bayesian and non-Bayesian) in the literature illustrating the benefits of this approach. In this article, we provide a baseline for concepts, notation, and methods, from which discussion on hierarchical statistical modeling in ecology can proceed. We have also planted some seeds for discussion and tried to show where the practical difficulties lie. Our thesis is that hierarchical statistical modeling is a powerful way of approaching ecological analysis in the presence of inevitable but quantifiable uncertainties, even if practical issues sometimes require pragmatic compromises.
Ruczyński, Ireneusz; Bartoń, Kamil A
2012-01-01
Sensory limitation plays an important role in the evolution of animal behaviour. Animals have to find objects of interest (e.g. food, shelters, predators). When sensory abilities are strongly limited, animals adjust their behaviour to maximize chances for success. Bats are nocturnal, live in complex environments, are capable of flight and must confront numerous perceptual challenges (e.g. limited sensory range, interfering clutter echoes). This makes them an excellent model for studying the role of compensating behaviours to decrease costs of finding resources. Cavity roosting bats are especially interesting because the availability of tree cavities is often limited, and their quality is vital for bats during the breeding season. From a bat's sensory point of view, cavities are difficult to detect and finding them requires time and energy. However, tree cavities are also long lasting, allowing information transfer among conspecifics. Here, we use a simple simulation model to explore the benefits of tree selection, memory and eavesdropping (compensation behaviours) to searches for tree cavities by bats with short and long perception range. Our model suggests that memory and correct discrimination of tree suitability are the basic strategies decreasing the cost of roost finding, whereas perceptual range plays a minor role in this process. Additionally, eavesdropping constitutes a buffer that reduces the costs of finding new resources (such as roosts), especially when they occur in low density. We conclude that natural selection may promote different strategies of roost finding in relation to habitat conditions and cognitive skills of animals.
Directory of Open Access Journals (Sweden)
Ireneusz Ruczyński
Full Text Available Sensory limitation plays an important role in the evolution of animal behaviour. Animals have to find objects of interest (e.g. food, shelters, predators. When sensory abilities are strongly limited, animals adjust their behaviour to maximize chances for success. Bats are nocturnal, live in complex environments, are capable of flight and must confront numerous perceptual challenges (e.g. limited sensory range, interfering clutter echoes. This makes them an excellent model for studying the role of compensating behaviours to decrease costs of finding resources. Cavity roosting bats are especially interesting because the availability of tree cavities is often limited, and their quality is vital for bats during the breeding season. From a bat's sensory point of view, cavities are difficult to detect and finding them requires time and energy. However, tree cavities are also long lasting, allowing information transfer among conspecifics. Here, we use a simple simulation model to explore the benefits of tree selection, memory and eavesdropping (compensation behaviours to searches for tree cavities by bats with short and long perception range. Our model suggests that memory and correct discrimination of tree suitability are the basic strategies decreasing the cost of roost finding, whereas perceptual range plays a minor role in this process. Additionally, eavesdropping constitutes a buffer that reduces the costs of finding new resources (such as roosts, especially when they occur in low density. We conclude that natural selection may promote different strategies of roost finding in relation to habitat conditions and cognitive skills of animals.
Limiting Global Warming to Well Below 2 °C: Energy System Modelling and Policy Development
DEFF Research Database (Denmark)
This book presents the energy system roadmaps necessary to limit global temperature increase to below 2°C, in order to avoid the catastrophic impacts of climate change. It provides a unique perspective on and critical understanding of the feasibility of a well-below-2°C world by exploring energy...... and at a global scale to offer scientific evidence to underpin complex policy decisions relating to climate change mitigation and interrelated issues like energy security and the energy–water nexus. It includes several chapters directly related to the Nationally Determined Contributions proposed in the context...
Kota, V. K. B.
General expression for the representation matrix elements in the SUsdg(3) limit of the sdg interacting boson model (sdgIBM) is derived that determine the scattering amplitude in the eikonal approximation for medium energy proton-nucleus scattering when the target nucleus is deformed and it is described by the SUsdg(3) limit. The SUsdg(3) result is generalized to two important situations: (i) when the target nucleus ground band states are described as states arising out of angular momentum projection from a general single Kπ = 0+ intrinsic state in sdg space; (ii) for rotational bands built on one-phonon excitations in sdgIBM.
International Nuclear Information System (INIS)
Sakimoto, P.J.
1985-01-01
Quasi-Stellar Objects (QSOs) are apparently the excessively bright nuclei of distant galaxies. They are thought to be powered by accretion disks surrounding supermassive black holes: however, proof of this presumption is hampered by major uncertainties in the viscous stress necessary for accretion to occur. Models generally assume an and hoc stress law which scales the stress with the total pressure. Near the black hole, radiation pressure dominates gas pressure; scaling the stress with the radiation pressure results in disk models that are thermally unstable and optically thin. This dissertation shows that a radiation pressure scaling for the stress is not possible if the viscosity is due to turbulent magnetic Maxwell stresses. The argument is one of internal self-consistency. First, four model accretion disks that bound the reasonably expected ranges of viscous stress scalings and vertical structures are constructed. Magnetic flux tubes of various initial field strengths are then placed within these models, nd their buoyancy is modeled numerically. In disks using the radiation pressure stress law scaling, low opacities allow rapid heat flow into the flux tubes: the tubes are extremely buoyant, and magnetic fields strong enough to provide the required stress cannot be retained. If an alternative gas pressure scaling for the stress is assumed, then the disks are optically thick; flux tubes have corresponding lower buoyancy, and magnetic fields strong enough to provide the stress can be retained for dynamically significant time periods
Thomas, Yoann; Dumas, Franck; Andréfouët, Serge
2016-12-01
The black-lip pearl oyster (Pinctada margaritifera) is cultured extensively to produce black pearls, especially in French Polynesia atoll lagoons. This aquaculture relies on spat collection, a process that experiences spatial and temporal variability and needs to be optimized by understanding which factors influence recruitment. Here, we investigate the sensitivity of P. margaritifera larval dispersal to both physical and biological factors in the lagoon of Ahe atoll. Coupling a validated 3D larval dispersal model, a bioenergetics larval growth model following the Dynamic Energy Budget (DEB) theory, and a population dynamics model, the variability of lagoon-scale connectivity patterns and recruitment potential is investigated. The relative contribution of reared and wild broodstock to the lagoon-scale recruitment potential is also investigated. Sensitivity analyses pointed out the major effect of the broodstock population structure as well as the sensitivity to larval mortality rate and inter-individual growth variability to larval supply and to the subsequent settlement potential. The application of the growth model clarifies how trophic conditions determine the larval supply and connectivity patterns. These results provide new cues to understand the dynamics of bottom-dwelling populations in atoll lagoons, their recruitment, and discuss how to take advantage of these findings and numerical models for pearl oyster management.
Planck limits on non-canonical generalizations of large-field inflation models
Energy Technology Data Exchange (ETDEWEB)
Stein, Nina K.; Kinney, William H., E-mail: ninastei@buffalo.edu, E-mail: whkinney@buffalo.edu [Dept. of Physics, University at Buffalo, the State University of New York, Buffalo, NY 14260-1500 (United States)
2017-04-01
In this paper, we consider two case examples of Dirac-Born-Infeld (DBI) generalizations of canonical large-field inflation models, characterized by a reduced sound speed, c {sub S} < 1. The reduced speed of sound lowers the tensor-scalar ratio, improving the fit of the models to the data, but increases the equilateral-mode non-Gaussianity, f {sup equil.}{sub NL}, which the latest results from the Planck satellite constrain by a new upper bound. We examine constraints on these models in light of the most recent Planck and BICEP/Keck results, and find that they have a greatly decreased window of viability. The upper bound on f {sup equil.}{sub NL} corresponds to a lower bound on the sound speed and a corresponding lower bound on the tensor-scalar ratio of r ∼ 0.01, so that near-future Cosmic Microwave Background observations may be capable of ruling out entire classes of DBI inflation models. The result is, however, not universal: infrared-type DBI inflation models, where the speed of sound increases with time, are not subject to the bound.
Brain in flames – animal models of psychosis: utility and limitations
Directory of Open Access Journals (Sweden)
Mattei D
2015-05-01
Full Text Available Daniele Mattei,1 Regina Schweibold,1,2 Susanne A Wolf1 1Department of Cellular Neuroscience, Max-Delbrueck-Center for Molecular Medicine, Berlin, Germany; 2Department of Neurosurgery, Helios Clinics, Berlin, Germany Abstract: The neurodevelopmental hypothesis of schizophrenia posits that schizophrenia is a psychopathological condition resulting from aberrations in neurodevelopmental processes caused by a combination of environmental and genetic factors which proceed long before the onset of clinical symptoms. Many studies discuss an immunological component in the onset and progression of schizophrenia. We here review studies utilizing animal models of schizophrenia with manipulations of genetic, pharmacologic, and immunological origin. We focus on the immunological component to bridge the studies in terms of evaluation and treatment options of negative, positive, and cognitive symptoms. Throughout the review we link certain aspects of each model to the situation in human schizophrenic patients. In conclusion we suggest a combination of existing models to better represent the human situation. Moreover, we emphasize that animal models represent defined single or multiple symptoms or hallmarks of a given disease. Keywords: inflammation, schizophrenia, microglia, animal models
Physical Limitations of Empirical Field Models: Force Balance and Plasma Pressure
International Nuclear Information System (INIS)
Sorin Zaharia; Cheng, C.Z.
2002-01-01
In this paper, we study whether the magnetic field of the T96 empirical model can be in force balance with an isotropic plasma pressure distribution. Using the field of T96, we obtain values for the pressure P by solving a Poisson-type equation (gradient) 2 P = (gradient) · (J x B) in the equatorial plane, and 1-D profiles on the Sun-Earth axis by integrating (gradient)P = J x B. We work in a flux coordinate system in which the magnetic field is expressed in terms of Euler potentials. Our results lead to the conclusion that the T96 model field cannot be in equilibrium with an isotropic pressure. We also analyze in detail the computation of Birkeland currents using the Vasyliunas relation and the T96 field, which yields unphysical results, again indicating the lack of force balance in the empirical model. The underlying reason for the force imbalance is likely the fact that the derivatives of the least-square fitted model B are not accurate predictions of the actual magnetospheric field derivatives. Finally, we discuss a possible solution to the problem of lack of force balance in empirical field models
Chung, Kun-Jen
2013-09-01
An inventory problem involves a lot of factors influencing inventory decisions. To understand it, the traditional economic production quantity (EPQ) model plays rather important role for inventory analysis. Although the traditional EPQ models are still widely used in industry, practitioners frequently question validities of assumptions of these models such that their use encounters challenges and difficulties. So, this article tries to present a new inventory model by considering two levels of trade credit, finite replenishment rate and limited storage capacity together to relax the basic assumptions of the traditional EPQ model to improve the environment of the use of it. Keeping in mind cost-minimisation strategy, four easy-to-use theorems are developed to characterise the optimal solution. Finally, the sensitivity analyses are executed to investigate the effects of the various parameters on ordering policies and the annual total relevant costs of the inventory system.
The Balance-of-Payments-Constrained Growth Model and the Limits to Export-Led Growth
Directory of Open Access Journals (Sweden)
Robert A. Blecker
2000-12-01
Full Text Available This paper discusses how A. P. Thirlwall's model of balance-of-payments-constrained growth can be adapted to analyze the idea of a "fallacy of composition" in the export-led growth strategy of many developing countries. The Deaton-Muellbauer model of the Almost Ideal Demand System (AIDS is used to represent the adding-up constraints on individual countries' exports, when they are all trying to export competing products to the same foreign markets (i.e. newly industrializing countries are exporting similar types of manufactured goods to the OECD countries. The relevance of the model to the recent financial crises in developing countries and policy alternatives for redirecting development strategies are also discussed.
International Nuclear Information System (INIS)
Smith, A C; Pei, X; Oliver, A; Husband, M; Rindfleisch, M
2012-01-01
A prototype resistive superconducting fault current limiter (SFCL) was developed using single-strand round magnesium diboride (MgB 2 ) wire. The MgB 2 wire was wound with an interleaved arrangement to minimize coil inductance and provide adequate inter-turn voltage withstand capability. The temperature profile from 30 to 40 K and frequency profile from 10 to 100 Hz at 25 K were tested and reported. The quench properties of the prototype coil were tested using a high current test circuit. The fault current was limited by the prototype coil within the first quarter-cycle. The prototype coil demonstrated reliable and repeatable current limiting properties and was able to withstand a potential peak current of 372 A for one second without any degradation of performance. A three-strand SFCL coil was investigated and demonstrated scaled-up current capacity. An analytical model to predict the behaviour of the prototype single-strand SFCL coil was developed using an adiabatic boundary condition on the outer surface of the wire. The predicted fault current using the analytical model showed very good correlation with the experimental test results. The analytical model and a finite element thermal model were used to predict the temperature rise of the wire during a fault. (paper)
Gomez-Ramirez, Jaime; Sanz, Ricardo
2013-09-01
One of the most important scientific challenges today is the quantitative and predictive understanding of biological function. Classical mathematical and computational approaches have been enormously successful in modeling inert matter, but they may be inadequate to address inherent features of biological systems. We address the conceptual and methodological obstacles that lie in the inverse problem in biological systems modeling. We introduce a full Bayesian approach (FBA), a theoretical framework to study biological function, in which probability distributions are conditional on biophysical information that physically resides in the biological system that is studied by the scientist. Copyright © 2013 Elsevier Ltd. All rights reserved.
Modelling internal migration in Kenya: an econometric analysis with limited data.
Barber, G M; Milne, W J
1988-09-01
"In this paper the determinants of internal migration in Kenya are analyzed on the basis of a human capital model. Explanatory variables included in the specification are both economic (wage rates and employment rates) and noneconomic (for example, population density and educational attainment). Also incorporated are variables which reflect intervening opportunities.... The econometric results show that destination variables are important determinants of internal migration, as is distance between the districts. Further, the variables for the intervening opportunities add significantly to the explanatory power of the model." excerpt
Hydrothermal models used to predict germination response in the field are usually parameterized with data from laboratory experiments that examine the full range of germination response to temperature and water potential. Inclusion of low water potential and high and low-temperature treatments, how...
On impossibility of limit cycles in certain two-dimensional countinuous-time growth models
Czech Academy of Sciences Publication Activity Database
Slobodyan, Sergey
2001-01-01
Roč. 5, č. 1 (2001), s. 33-40 ISSN 1081-1826 Institutional research plan: CEZ:AV0Z7085904 Keywords : growth model Subject RIV: BB - Applied Statistics, Operational Research Impact factor: 0.150, year: 2001
Broken-and-Intact Cell Model for Supercritical Fluid Extraction: Its Origin and Limits.
Czech Academy of Sciences Publication Activity Database
Sovová, Helena
2017-01-01
Roč. 129, SI (2017), s. 3-8 ISSN 0896-8446. [Iberoamerican Conference on Supercritical Fluids ProSCiba 2016 /4./. Vina del Mar, 28.03.2016-01.04.2016] Institutional support: RVO:67985858 Keywords : modelling * extraction kinetics * supercritical CO2 Subject RIV: CI - Industrial Chemistry, Chemical Engineering OBOR OECD: Chemical process engineering Impact factor: 2.991, year: 2016
Introduction. Use and Limitations of the Principal-Agent model in Studying the European Union
Delreux, Tom; Adriaensen, J.; Delreux, Tom; Adriaensen, Johan
2017-01-01
Given the omnipresence of delegation and control in the EU, the principal–agent model has become a popular analytical framework to study the design and effects of delegation and control. Yet, with the ascendance of governance as a mode of decision-making, the contemporary relevance of the
Directory of Open Access Journals (Sweden)
C. Santagati
2013-07-01
Full Text Available 3D reconstruction from images has undergone a revolution in the last few years. Computer vision techniques use photographs from data set collection to rapidly build detailed 3D models. The simultaneous applications of different algorithms (MVS, the different techniques of image matching, feature extracting and mesh optimization are inside an active field of research in computer vision. The results are promising: the obtained models are beginning to challenge the precision of laser-based reconstructions. Among all the possibilities we can mainly distinguish desktop and web-based packages. Those last ones offer the opportunity to exploit the power of cloud computing in order to carry out a semi-automatic data processing, thus allowing the user to fulfill other tasks on its computer; whereas desktop systems employ too much processing time and hard heavy approaches. Computer vision researchers have explored many applications to verify the visual accuracy of 3D model but the approaches to verify metric accuracy are few and no one is on Autodesk 123D Catch applied on Architectural Heritage Documentation. Our approach to this challenging problem is to compare the 3Dmodels by Autodesk 123D Catch and 3D models by terrestrial LIDAR considering different object size, from the detail (capitals, moldings, bases to large scale buildings for practitioner purpose.
Hofstra, Jorrit J; Vlaar, Alexander P; Cornet, Alexander D; Dixon, Barry; Roelofs, Joris J; Choi, Goda; van der Poll, Tom; Levi, Marcel; Schultz, Marcus J
BACKGROUND: Pulmonary coagulopathy may contribute to an adverse outcome in lung injury. We assessed the effects of local anticoagulant therapy on bronchoalveolar and systemic haemostasis in a rat model of endotoxemia-induced lung injury. METHODS: Male Sprague-Dawley rats were intravenously
Gholamhoseini, Alireza
2016-03-01
Relatively little research has been reported on the time-dependent in-service behavior of composite concrete slabs with profiled steel decking as permanent formwork and little guidance is available for calculating long-term deflections. The drying shrinkage profile through the thickness of a composite slab is greatly affected by the impermeable steel deck at the slab soffit, and this has only recently been quantified. This paper presents the results of long-term laboratory tests on composite slabs subjected to both drying shrinkage and sustained loads. Based on laboratory measurements, a design model for the shrinkage strain profile through the thickness of a slab is proposed. The design model is based on some modifications to an existing creep and shrinkage prediction model B3. In addition, an analytical model is developed to calculate the time-dependent deflection of composite slabs taking into account the time-dependent effects of creep and shrinkage. The calculated deflections are shown to be in good agreement with the experimental measurements.
On the Numerical Modeling of Fluid Instabilities in the Small-Amplitude Limit
Zalesak, Steven; Schmitt, A. J.; Velikovich, A. L.
2008-11-01
The problem we wish to address is that of accurately modeling the evolution of small-amplitude perturbations to a time- dependent flow, where the unperturbed flow itself exhibits large-amplitude temporal and spatial variations. In particular, we wish to accurately model the evolution of small-amplitude perturbations to an imploding ICF pellet, which is subject to both Richtmyer-Meshkov and Rayleigh-Taylor instabilities. This modeling is difficult despite the expected linear evolution of the perturbations themselves, because these perturbations are embedded in a highly nonlinear, strongly- shocked, and highly complex flow field which in and of itself stresses numerical computation capabilities, and whose simulation often employs numerical techniques which were not designed with the proper treatment of small-amplitude perturbations in mind. We will review some of the techniques that we have found to be of use toward this end, including the imposition of a ``differentiability condition'' on the component numerical algorithms of the codes which implement such modeling, the appropriate representation of interfaces in an Eulerian hydrodynamics context, and the role of exact energy conservation.
Limitations and possibilities of animal models for human allergenic risk evaluation
DEFF Research Database (Denmark)
Madsen, Charlotte Bernhard; Kroghsbo, Stine; Bøgh, Katrine Lindholm
2012-01-01
evaluation. One of the pitfalls may be the premise that an animal model needs to mimic the disease. Chemical contact sensitizers may be predicted in an animal test, the Local Lymph Node Assay (LLNA). This assay is based on detailed mechanistic knowledge of contact sensitization including knowledge on dose...
Heavy-traffic limits for polling models with exhaustive service and non-FCFS service orders
P. Vis (Petra); R. Bekker (Rene); R.D. van der Mei (Rob)
2015-01-01
htmlabstractWe study cyclic polling models with exhaustive service at each queue under a variety of non-FCFS (first-come-first-served) local service orders, namely last-come-first-served with and without preemption, random-order-of-service, processor sharing, the multi-class priority scheduling with
Defining the limits of homology modeling in information-driven protein docking
Garcia Lopes Maia Rodrigues, João; Melquiond, A S J; Karaca, E; Trellet, M; van Dijk, M; van Zundert, G C P; Schmitz, C; de Vries, S J; Bordogna, A; Bonati, L; Kastritis, P L; Bonvin, Alexandre M J J; Garcia Lopes Maia Rodrigues, João
2013-01-01
Information-driven docking is currently one of the most successful approaches to obtain structural models of protein interactions as demonstrated in the latest round of CAPRI. While various experimental and computational techniques can be used to retrieve information about the binding mode, the
Compressive system identification of LTI and LTV ARX models: The limited data set case
Sanandaij, B. M.; Vincent, T. L.; Wakin, M. B.; Toth, R.; Poolla, K.
2011-01-01
In this paper, we consider identifying Auto Regressive with eXternal input (ARX) models for both Linear Time-Invariant (LTI) and Linear Time-Variant (LTV) systems. We aim at doing the identification from the smallest possible number of observations. This is inspired by the field of Compressive
Glucose reactivity with filling materials as a limitation for using the glucose leakage model
Shemesh, H.; Souza, E.M.; Wu, M.K.; Wesselink, P.R.
2008-01-01
Aim To evaluate the reactivity of different endodontic materials and sealers with glucose and to asses the reliability of the glucose leakage model in measuring penetration of glucose through these materials. Methodology Ten uniform discs (radius 5 mm, thickness 2 mm) were made of each of the
Santagati, C.; Inzerillo, L.; Di Paola, F.
2013-07-01
3D reconstruction from images has undergone a revolution in the last few years. Computer vision techniques use photographs from data set collection to rapidly build detailed 3D models. The simultaneous applications of different algorithms (MVS), the different techniques of image matching, feature extracting and mesh optimization are inside an active field of research in computer vision. The results are promising: the obtained models are beginning to challenge the precision of laser-based reconstructions. Among all the possibilities we can mainly distinguish desktop and web-based packages. Those last ones offer the opportunity to exploit the power of cloud computing in order to carry out a semi-automatic data processing, thus allowing the user to fulfill other tasks on its computer; whereas desktop systems employ too much processing time and hard heavy approaches. Computer vision researchers have explored many applications to verify the visual accuracy of 3D model but the approaches to verify metric accuracy are few and no one is on Autodesk 123D Catch applied on Architectural Heritage Documentation. Our approach to this challenging problem is to compare the 3Dmodels by Autodesk 123D Catch and 3D models by terrestrial LIDAR considering different object size, from the detail (capitals, moldings, bases) to large scale buildings for practitioner purpose.
International Nuclear Information System (INIS)
Stacey, W. M.
2001-01-01
Several series of model problem calculations have been performed to investigate the predicted effect of pumping, divertor configuration and fueling on the maximum achievable density in diverted tokamaks. Density limitations due to thermal instabilities (confinement degradation and multifaceted axisymmetric radiation from the edge) and to divertor choking are considered. For gas fueling the maximum achievable density is relatively insensitive to pumping (on or off), to the divertor configuration (open or closed), or to the location of the gas injection, although the gas fueling rate required to achieve this maximum achievable density is quite sensitive to these choices. Thermal instabilities are predicted to limit the density at lower values than divertor choking. Higher-density limits are predicted for pellet injection than for gas fueling
DEFF Research Database (Denmark)
Bollerslev, Anne Mette; Nauta, Maarten; Hansen, Tina Beck
2017-01-01
Microbiological limits are widely used in food processing as an aid to reduce the exposure to hazardous microorganisms for the consumers. However, in pork, the prevalence and concentrations of Salmonella are generally low and microbiological limits are not considered an efficient tool to support...... for this purpose includes the dose-response relationship for Salmonella and a reduction factor to account for preparation of the fresh pork. By use of the risk model, it was estimated that the majority of salmonellosis cases, caused by the consumption of pork in Denmark, is caused by the small fraction of pork...... products that has enterococci concentrations above 5. log. CFU/g. This illustrates that our approach can be used to evaluate the potential effect of different microbiological limits and therefore, the perspective of this novel approach is that it can be used for definition of a risk-based microbiological...
Modelling of Split Condenser Heat Pump with Limited Set of Plate Heat Exchanger Dimensions
DEFF Research Database (Denmark)
Christensen, Stefan Wuust; Elmegaard, Brian; Markussen, Wiebke Brix
2017-01-01
in parallel to different temperature levels, whereas only one stream is heated in a THP. The length/width ratio of the plate heat exchangers on the high pressure side of a SCHP was investigated to find the optimal plate dimensions with respect to minimum area of the heat exchangers. The total heat exchanger...... area was found to decrease with an increasing length/width ratio of the plates. The marginal change in heat exchanger area was shown to be less significant for heat exchangers with high length/width ratios. In practice only a limited number of plate dimensions are available and feasible...... in the production. This was investigated to find the practical potential of a SCHP compared to a THP. Using plates optimized for a SCHP in a THP, the total required heat exchanger area increased by approximately 100% for the conditions investigated in this study, indicating that available plate dimensions influence...
Directory of Open Access Journals (Sweden)
Charles Knessl
2013-01-01
Full Text Available We consider two parallel queues, each with independent Poisson arrival rates, that are tended by a single server. The exponential server devotes all of its capacity to the longer of the queues. If both queues are of equal length, the server devotes ν of its capacity to the first queue and the remaining 1−ν to the second. We obtain exact integral representations for the joint probability distribution of the number of customers in this two-node network. Then we evaluate this distribution in various asymptotic limits, such as large numbers of customers in either/both of the queues, light traffic where arrivals are infrequent, and heavy traffic where the system is nearly unstable.
An analytical erosion model for divertor plates and limiter experiments in CHS
International Nuclear Information System (INIS)
Sagara, A.; Noda, N.; Akiyama, R.; Arimoto, H.; Idei, H.; Iguchi, H.; Kaneko, O.; Kohmoto, T.; Kubo, S.; Matsuoka, K.; Morita, S.; Motojima, O.; Nishimura, K.; Okamura, S.; Takahasi, C.; Takita, Y.; Yamada, I.; Matsunami, N.; Rice, J.; Yamada, H.; Shoji, T.; Ueda, M.
1992-01-01
A self-consistent analytical solution for net erosion of a divertor plate which is set perpendicular to magnetic field lines is presented. The primary flux profile of hydrogen and impurities except redepositing particles is externally given as well as the return ratio of sputtered atoms to the plate. In the direction along the divertor trace, all conditions are uniform. The ionization mean free path is assumed constant to simplify equations. The analytical solution is compared with net erosion experiments carried out in compact helical system (CHS) by exposing a graphite target to a neutral beam heated plasma column introduced perpendicularly to the target along the magnetic field lines through a 2 cm slit opend on a graphite limiter. After exposure to 98 discharges, the target surface is analyzed with Rutherford backscattering method. Deposition profiles of Ti and O impurities are very well explained with the analytical predictions. (orig.)
CEMENT TRANSPORTATION LIMITED-FLEET MODELING AND ASSIGNING TO RATED DEMANDS
Directory of Open Access Journals (Sweden)
Narjes MASHHADI BANDANI
2017-04-01
Full Text Available Transportation is an inseparable part of the supply chain, with a key role in product distribution. This role is highlighted when ratio of “the cost of transportation” to “the value of goods” such as cement is significant. Iran has recently become one of the main centers of cement production in the world. However, transportation is the most important challenge in cement distribution because of weak structure of the transportation fleet and its independent action. Independence of and lack of commitment on the part of transportation fleets to cement companies as well as lack of timely delivery due to shortage of transportation in some routes and seasons lead to customers` dissatisfaction and even market loss or lack of market development. One of the significant differences between the transportation system in Iran and that in developed countries is lack of complete productivity of the transportation fleet. It means that trucks are driver-based in Iran. This paper introduces a model considering some issues such as driver-based trucks, size of the transportation fleet based on the number of active trucks, and demand priorities in the cement company. Taking the relation between the number of active trucks and the cement company into account, this model assigns weekly demands to the transportation fleet. It also tries to minimize the delay to respond to demands and increases the efficiency of the transportation fleet. Finally, this current condition-based model is compared with two other models including “no constraints on different routes of trucks” as well as single-route model for trucks.
Gutierrez-Jurado, H. A.; Guan, H.; Wang, J.; Wang, H.; Bras, R. L.; Simmons, C. T.
2015-12-01
Quantification of evapotranspiration (ET) and its partition over regions of heterogeneous topography and canopy poses a challenge using traditional approaches. In this study, we report the results of a novel field experiment design guided by the Maximum Entropy Production model of ET (MEP-ET), formulated for estimating evaporation and transpiration from homogeneous soil and canopy. A catchment with complex terrain and patchy vegetation in South Australia was instrumented to measure temperature, humidity and net radiation at soil and canopy surfaces. Performance of the MEP-ET model to quantify transpiration and soil evaporation was evaluated during wet and dry conditions with independently and directly measured transpiration from sapflow and soil evaporation using the Bowen Ratio Energy Balance (BREB). MEP-ET transpiration shows remarkable agreement with that obtained through sapflow measurements during wet conditions, but consistently overestimates the flux during dry periods. However, an additional term introduced to the original MEP-ET model accounting for higher stomatal regulation during dry spells, based on differences between leaf and air vapor pressure deficits and temperatures, significantly improves the model performance. On the other hand, MEP-ET soil evaporation is in good agreement with that from BREB regardless of moisture conditions. The experimental design allows a plot and tree scale quantification of evaporation and transpiration respectively. This study confirms for the first time that the MEP-ET originally developed for homogeneous open bare soil and closed canopy can be used for modeling ET over heterogeneous land surfaces. Furthermore, we show that with the addition of an empirical function simulating the plants ability to regulate transpiration, and based on the same measurements of temperature and humidity, the method can produce reliable estimates of ET during both wet and dry conditions without compromising its parsimony.
Modelling the acid/base 1H NMR chemical shift limits of metabolites in human urine.
Tredwell, Gregory D; Bundy, Jacob G; De Iorio, Maria; Ebbels, Timothy M D
2016-01-01
Despite the use of buffering agents the 1 H NMR spectra of biofluid samples in metabolic profiling investigations typically suffer from extensive peak frequency shifting between spectra. These chemical shift changes are mainly due to differences in pH and divalent metal ion concentrations between the samples. This frequency shifting results in a correspondence problem: it can be hard to register the same peak as belonging to the same molecule across multiple samples. The problem is especially acute for urine, which can have a wide range of ionic concentrations between different samples. To investigate the acid, base and metal ion dependent 1 H NMR chemical shift variations and limits of the main metabolites in a complex biological mixture. Urine samples from five different individuals were collected and pooled, and pre-treated with Chelex-100 ion exchange resin. Urine samples were either treated with either HCl or NaOH, or were supplemented with various concentrations of CaCl 2 , MgCl 2 , NaCl or KCl, and their 1 H NMR spectra were acquired. Nonlinear fitting was used to derive acid dissociation constants and acid and base chemical shift limits for peaks from 33 identified metabolites. Peak pH titration curves for a further 65 unidentified peaks were also obtained for future reference. Furthermore, the peak variations induced by the main metal ions present in urine, Na + , K + , Ca 2+ and Mg 2+ , were also measured. These data will be a valuable resource for 1 H NMR metabolite profiling experiments and for the development of automated metabolite alignment and identification algorithms for 1 H NMR spectra.
Nitrogen leaching from N limited forest ecosystems: the MERLIN model applied to Gårdsjön, Sweden
Directory of Open Access Journals (Sweden)
O. J. Kjønaas
1998-01-01
Full Text Available Chronic deposition of inorganic nitrogen (N compounds from the atmosphere to forested ecosystems can alter the status of a forest ecosystem from N-limited towards N-rich, which may cause, among other things, increased leaching of inorganic N below the rooting zone. To assess the time aspects of excess N leaching, a process-oriented dynamic model, MERLIN (Model of Ecosystem Retention and Loss of Inorganic Nitrogen, was tested on an N-manipulated catchment at Gårdsjön, Sweden (NITREX project. Naturally generated mature Norway spruce dominates the catchment with Scots pine in drier areas. Since 1991, ammonium nitrate (NH4NO3 solution at a rate of about 35 kg N ha-1 yr-1 (250 mmol m-2 yr-1 has been sprinkled weekly, to simulate increased atmospheric N deposition. MERLIN describes C and N cycles, where rates of uptake and cycling between pools are governed by the C/N ratios of plant and soil pools. The model is calibrated through a hindcast period and then used to predict future trends. A major source of uncertainty in model calibration and prediction is the paucity of good historical information on the specific site and stand history over the hindcast period 1930 to 1990. The model is constrained poorly in an N-limited system. The final calibration, therefore, made use of the results from the 6-year N addition experiment. No independent data set was available to provide a test for the model calibration. The model suggests that most N deposition goes to the labile (LOM and refractory (ROM organic matter pools. Significant leaching is predicted to start as the C/N ratio in LOM is reduced from the 1990 value of 35 to <28. At ambient deposition levels, the system is capable of retaining virtually all incoming N over the next 50 years. Increased decomposition rates, however, could simulate nitrate leaching losses. The rate and capacity of N assimilation as well as the change in carbon dynamics are keys to ecosystem changes. Because the knowledge of
Directory of Open Access Journals (Sweden)
R. Ludwig
2003-01-01
Full Text Available Numerous applications of hydrological models have shown their capability to simulate hydrological processes with a reasonable degree of certainty. For flood modelling, the quality of precipitation data — the key input parameter — is very important but often remains questionable. This paper presents a critical review of experience in the EU-funded RAPHAEL project. Different meteorological data sources were evaluated to assess their applicability for flood modelling and forecasting in the Bavarian pre-alpine catchment of the Ammer river (709 km2, for which the hydrological aspects of runoff production are described as well as the complex nature of floods. Apart from conventional rain gauge data, forecasts from several Numerical Weather Prediction Models (NWP as well as rain radar data are examined, scaled and applied within the framework of a GIS-structured and physically based hydrological model. Multi-scenario results are compared and analysed. The synergetic approach leads to promising results under certain meteorological conditions but emphasises various drawbacks. At present, NWPs are the only source of rainfall forecasts (up to 96 hours with large spatial coverage and high temporal resolution. On the other hand, the coarse spatial resolution of NWP grids cannot yet address, adequately, the heterogeneous structures of orographic rainfields in complex convective situations; hence, a major downscaling problem for mountain catchment applications is introduced. As shown for two selected Ammer flood events, a high variability in prediction accuracy has still to be accepted at present. Sensitivity analysis of both meteo-data input and hydrological model performance in terms of process description are discussed and positive conclusions have been drawn for future applications of an advanced meteo-hydro model synergy. Keywords: RAPHAEL, modelling, forecasting, model coupling, PROMET-D, TOPMODEL
International Nuclear Information System (INIS)
Sazykina, Tatiana G.; Kryshev, Alexander I.
2016-01-01
A dynamic mathematical model is formulated, predicting the development of radiation effects in a generic animal population, inhabiting an elemental ecosystem ‘population-limiting resource’. Differential equations of the model describe the dynamic responses to radiation damage of the following population characteristics: gross biomass; intrinsic fractions of healthy and reversibly damaged tissues in biomass; intrinsic concentrations of the self-repairing pool and the growth factor; and amount of the limiting resource available in the environment. Analytical formulae are found for the steady states of model variables as non-linear functions of the dose rate of chronic radiation exposure. Analytical solutions make it possible to predict the expected severity of radiation effects in a model ecosystem, including such endpoints as morbidity, mortality, life shortening, biosynthesis, and population biomass. Model parameters are selected from species data on lifespan, physiological growth and mortality rates, and individual radiosensitivity. Thresholds for population extinction can be analytically calculated for different animal species, examples are provided for generic mice and wolf populations. The ecosystem model demonstrates a compensatory effect of the environment on the development of radiation effects in wildlife. The model can be employed to construct a preliminary scale ‘radiation exposure-population effects’ for different animal species; species can be identified, which are vulnerable at a population level to chronic radiation exposure. - Highlights: • Mathematical model is formulated predicting radiation effects in elemental ecosystem. • Analytical formulae are found for steady states of variables as functions of exposure. • Severity of radiation effects are calculated, including population extinction. • Model parameterization is made for generic mice and wolf populations.
Directory of Open Access Journals (Sweden)
Kaj Frick
2013-01-01
Full Text Available In the Nordic work environment model, health risks at work are mainly to be managed in cooperation with the employees and their representatives. The model is based on strong trade unions and is supported by the state through participatory rights and funding to produce and disseminate knowledge on risks and solutions. The model is evident in the large Swedish municipal sector with its strong unions and extensive social dialogue. However, municipal employees also face widespread risks, mainly from mental and physical overload. They led the costly wave of rising sickness absence from the late 1990s. Municipal (and other employers therefore attempt to reduce the absence. The rural municipality of Leksand started a project Hälsosam with the broad objectives to half the absence, implement a national agreement on better dialogue, make Leksand an attractive employer, and improve employee influence and work environment. The article’s objective is to use Hälsosam’s intervention project to explore the limits of what the Nordic work environment model can achieve against risks rooted in the employers’ prerogative of organizing, resourcing, and managing the operations that create the conditions at work. Hälsosam’s practice focused on sickness absence and the forms of the new national agreement. The absence was halved by reducing cases of long-term sickness. There was also workplace health promotion and the safety reps were supported through regular meetings. However, little was done to the extensive mental and physical overload revealed in a survey. Nor was the mandatory work environment management improved, as was ordered by the municipal council. This remained delegated to first-line managers who had a limited ability to handle work risks. This limited practice implemented Leksand’s political priority to reduce the absenteeism, while other objectives had less political support. The difficulties to improve the work environment and its management
Scrutinizing the alignment limit in two-Higgs-doublet models. II. mH=125 GeV
Bernon, Jérémy; Gunion, John F.; Haber, Howard E.; Jiang, Yun; Kraml, Sabine
2016-02-01
In the alignment limit of a multidoublet Higgs sector, one of the Higgs mass eigenstates aligns in field space with the direction of the scalar field vacuum expectation values, and its couplings approach those of the Standard Model (SM) Higgs boson. We consider C P -conserving two-Higgs-doublet models (2HDMs) of type I and type II near the alignment limit in which the heavier of the two C P -even Higgs bosons, H , is the SM-like state observed with a mass of 125 GeV, and the couplings of H to gauge bosons approach those of the SM. We review the theoretical structure and analyze the phenomenological implications of this particular realization of the alignment limit, where decoupling of the extra states cannot occur given that the lighter C P -even state h must, by definition, have a mass below 125 GeV. For the numerical analysis, we perform scans of the 2HDM parameter space employing the software packages 2hdmc and lilith, taking into account all relevant pre-LHC constraints, constraints from the measurements of the 125 GeV Higgs signal at the LHC, as well as the most recent limits coming from searches for other Higgs-like states. Implications for Run 2 at the LHC, including expectations for observing the other scalar states, are also discussed.
Lin, M. C.; Verboncoeur, J.
2016-10-01
A maximum electron current transmitted through a planar diode gap is limited by space charge of electrons dwelling across the gap region, the so called space charge limited (SCL) emission. By introducing a counter-streaming ion flow to neutralize the electron charge density, the SCL emission can be dramatically raised, so electron current transmission gets enhanced. In this work, we have developed a relativistic self-consistent model for studying the enhancement of maximum transmission by a counter-streaming ion current. The maximum enhancement is found when the ion effect is saturated, as shown analytically. The solutions in non-relativistic, intermediate, and ultra-relativistic regimes are obtained and verified with 1-D particle-in-cell simulations. This self-consistent model is general and can also serve as a comparison for verification of simulation codes, as well as extension to higher dimensions.
Where are all the gravastars? Limits upon the gravastar model from accreting black holes
Energy Technology Data Exchange (ETDEWEB)
Broderick, Avery E; Narayan, Ramesh [Institute for Theory and Computation, Harvard-Smithsonian Center for Astrophysics, MS 51, 60 Garden Street, Cambridge, MA 02138 (United States)
2007-02-07
The gravastar model, which postulates a strongly correlated thin shell of anisotropic matter surrounding a region of anti-de Sitter space, has been proposed as an alternative to black holes. We discuss constraints that present-day observations of well-known black hole candidates place on this model. We focus upon two black hole candidates known to have extraordinarily low luminosities: the supermassive black hole in the galactic centre, Sagittarius A*, and the stellar-mass black hole, XTE J1118 + 480. We find that the length scale for modifications of the type discussed in Chapline et al (2003 Int. J. Mod. Phys. 18 3587-90) must be sub-Planckian.
Mathematical analysis of an age-structured population model with space-limited recruitment.
Kamioka, Katumi
2005-11-01
In this paper, we investigate structured population model of marine invertebrate whose life stage is composed of sessile adults and pelagic larvae, such as barnacles contained in a local habitat. First we formulate the basic model as an Cauchy problem on a Banach space to discuss the existence and uniqueness of non-negative solution. Next we define the basic reproduction number R0 to formulate the invasion condition under which the larvae can successfully settle down in the completely vacant habitat. Subsequently we examine existence and stability of steady states. We show that the trivial steady state is globally asymptotically stable if R0 1. Furthermore, we show that a positive (non-trivial) steady state uniquely exists if R0 > 1 and it is locally asymptotically stable as far as absolute value of R0 - 1 is small enough.
Cosmological perturbations in the ΛCDM-like limit of a polytropic dark matter model
Kleidis, K.; Spyrou, N. K.
2017-10-01
It has recently been proposed that both dark matter (DM) and dark energy (DE) can be treated as a single component when they are considered in the context of a polytropic DM fluid with thermodynamical content. Depending on only one free parameter, that is, the polytropic exponent, - 0.103 law of conventional statistical physics. As a consequence, peculiar velocities in this model slightly increase instead of being redshifted away by cosmic expansion. This result might comprise a convenient probe of the polytropic DM model with Γ = 0. Even more importantly, however, upon consideration of scale-invariant metric perturbations, the spectrum of their rest-mass density counterparts exhibits an effective power-law dependence on the (physical) wavenumber, kph, of the form kph3+nseff, with the associated scalar spectral index, nseff, being equal to nseff = 0.970. This theoretical value reproduces the corresponding observational Planck result, that is, nsobs = 0.968 ± 0.006.
An Inventory Model with Time-Dependent Demand and Limited Storage Facility under Inflation
Directory of Open Access Journals (Sweden)
Neeraj Kumar
2012-01-01
Full Text Available The main objective of this paper is to develop a two-warehouse inventory model with partial backordering and Weibull distribution deterioration. We consider inflation and apply the discounted cash flow in problem analysis. The discounted cash flow (DCF and optimization framework are presented to derive the optimal replenishment policy that minimizes the total present value cost per unit time. When only rented or own warehouse model is considered, the present value of the total relevant cost is higher than the case when two-warehouse is considered. The results have been validated with the help of a numerical example. Sensitivity analysis with respect to various parameters is also performed. From the sensitivity analysis, we show that the total cost of the system is influenced by the deterioration rate, the inflation rate, and the backordering ratio.
Heart failure therapy at a crossroad: are there limits to the neurohormonal model?
Mehra, Mandeep R; Uber, Patricia A; Francis, Gary S
2003-05-07
The advent of neurohormonal blockade in heart failure (HF) has been an overwhelming success, but current evidence points to a ceiling effect as newer neurohormonal targets are exploited in an incremental manner. This has lead us to question whether the neurohormonal model of HF can be sustained by simply stacking multiple neurohormonal or cytokine blockers together as treatment. A unifying theme in some of these disparate trials relates to either a lack of efficacy or, more importantly, adversity resulting in regression of already achieved benefits. It is our contention that the available evidence has uncovered the remarkable complexity of interaction within the context of the neurohormonal construct. As we stand at a crossroad in HF and begin to fervently pursue non-neurohormonal therapeutic targets, we must also direct attention at navigating the multifaceted labyrinth of the neurohormonal model that has led to the current imbroglio.
Pushing the limits of Monte Carlo simulations for the three-dimensional Ising model
Ferrenberg, Alan M.; Xu, Jiahao; Landau, David P.
2018-04-01
While the three-dimensional Ising model has defied analytic solution, various numerical methods like Monte Carlo, Monte Carlo renormalization group, and series expansion have provided precise information about the phase transition. Using Monte Carlo simulation that employs the Wolff cluster flipping algorithm with both 32-bit and 53-bit random number generators and data analysis with histogram reweighting and quadruple precision arithmetic, we have investigated the critical behavior of the simple cubic Ising Model, with lattice sizes ranging from 163 to 10243. By analyzing data with cross correlations between various thermodynamic quantities obtained from the same data pool, e.g., logarithmic derivatives of magnetization and derivatives of magnetization cumulants, we have obtained the critical inverse temperature Kc=0.221 654 626 (5 ) and the critical exponent of the correlation length ν =0.629 912 (86 ) with precision that exceeds all previous Monte Carlo estimates.
Broken-and-Intact Cell Model for Supercritical Fluid Extraction: Its Origin and Limits.
Czech Academy of Sciences Publication Activity Database
Sovová, Helena
2017-01-01
Roč. 129, SI (2017), s. 3-8 ISSN 0896-8446. [Iberoamerican Conference on Supercritical Fluid s ProSCiba 2016 /4./. Vina del Mar, 28.03.2016-01.04.2016] Institutional support: RVO:67985858 Keywords : modelling * extraction kinetics * supercritical CO2 Subject RIV: CI - Industrial Chemistry, Chemical Engineering OBOR OECD: Chemical process engineering Impact factor: 2.991, year: 2016
A functional central limit theorem for a class of urn models
Indian Academy of Sciences (India)
Introduction. Consider a four-color urn model in which the replacement matrix is actually a stochastic matrix R as in ref. [4]. That is, we start with one ball of any color, which is the 0-th trial. Let Wn denote the column vector of the number of balls of the four colors up to the n-th trial, where the components of Wn are ...
Photoemission and the electronic properties of heavy fermions -- limitations of the Kondo model
International Nuclear Information System (INIS)
Joyce, J.J.; Arko, A.J.; Andrews, A.B.
1993-01-01
The electronic properties of Yb-based heavy fermions have been investigated by means of high resolution synchrotron radiation photoemission and compared with predictions of the Kondo model. The Yb heavy fermion photoemission spectra show massive disagreement with the Kondo model predictions (as calculated within the Gunnarsson-Schonhammer computational method). Moreover, the Yb heavy fermion photoemission spectra give very strong indications of core-like characteristics and compare favorable to purely divalent Yb metal and core-like Lu 4f levels. The heavy fermions YbCu 2 Si 2 , YbAgCu 4 and YbAl 3 were measured and shown to have lineshapes much broader and deeper in binding energy than predicted by the Kondo model. The lineshape of the bulk component of the 4f emission for these three heavy fermion materials was compared with that from Yb metal and the Lu 4f levels in LuAl 3 , the heavy fermion materials show no substantive spectroscopic differences from simple 4f levels observed in Yb metal and LuAl 3 . Also, the variation with temperature of the 4f fineshape was measured for Yb metal and clearly demonstrates that phonon broadening plays a major role in 4f level lineshape analysis and must be accounted for before considerations of correlated electron resonance effects are presumed to be at work
Tikhonov, Mikhail; Monasson, Remi
2018-01-01
Much of our understanding of ecological and evolutionary mechanisms derives from analysis of low-dimensional models: with few interacting species, or few axes defining "fitness". It is not always clear to what extent the intuition derived from low-dimensional models applies to the complex, high-dimensional reality. For instance, most naturally occurring microbial communities are strikingly diverse, harboring a large number of coexisting species, each of which contributes to shaping the environment of others. Understanding the eco-evolutionary interplay in these systems is an important challenge, and an exciting new domain for statistical physics. Recent work identified a promising new platform for investigating highly diverse ecosystems, based on the classic resource competition model of MacArthur. Here, we describe how the same analytical framework can be used to study evolutionary questions. Our analysis illustrates how, at high dimension, the intuition promoted by a one-dimensional (scalar) notion of fitness can become misleading. Specifically, while the low-dimensional picture emphasizes organism cost or efficiency, we exhibit a regime where cost becomes irrelevant for survival, and link this observation to generic properties of high-dimensional geometry.
Wu, Zhen; Liu, Yong; Liang, Zhongyao; Wu, Sifeng; Guo, Huaicheng
2017-06-01
Lake eutrophication is associated with excessive anthropogenic nutrients (mainly nitrogen (N) and phosphorus (P)) and unobserved internal nutrient cycling. Despite the advances in understanding the role of external loadings, the contribution of internal nutrient cycling is still an open question. A dynamic mass-balance model was developed to simulate and measure the contributions of internal cycling and external loading. It was based on the temporal Bayesian Hierarchical Framework (BHM), where we explored the seasonal patterns in the dynamics of nutrient cycling processes and the limitation of N and P on phytoplankton growth in hyper-eutrophic Lake Dianchi, China. The dynamic patterns of the five state variables (Chla, TP, ammonia, nitrate and organic N) were simulated based on the model. Five parameters (algae growth rate, sediment exchange rate of N and P, nitrification rate and denitrification rate) were estimated based on BHM. The model provided a good fit to observations. Our model results highlighted the role of internal cycling of N and P in Lake Dianchi. The internal cycling processes contributed more than external loading to the N and P changes in the water column. Further insights into the nutrient limitation analysis indicated that the sediment exchange of P determined the P limitation. Allowing for the contribution of denitrification to N removal, N was the more limiting nutrient in most of the time, however, P was the more important nutrient for eutrophication management. For Lake Dianchi, it would not be possible to recover solely by reducing the external watershed nutrient load; the mechanisms of internal cycling should also be considered as an approach to inhibit the release of sediments and to enhance denitrification. Copyright © 2017 Elsevier Ltd. All rights reserved.
Excessive folate synthesis limits lifespan in the C. elegans: E. coli aging model
Directory of Open Access Journals (Sweden)
Virk Bhupinder
2012-07-01
Full Text Available Abstract Background Gut microbes influence animal health and thus, are potential targets for interventions that slow aging. Live E. coli provides the nematode worm Caenorhabditis elegans with vital micronutrients, such as folates that cannot be synthesized by animals. However, the microbe also limits C. elegans lifespan. Understanding these interactions may shed light on how intestinal microbes influence mammalian aging. Results Serendipitously, we isolated an E. coli mutant that slows C. elegans aging. We identified the disrupted gene to be aroD, which is required to synthesize aromatic compounds in the microbe. Adding back aromatic compounds to the media revealed that the increased C. elegans lifespan was caused by decreased availability of para-aminobenzoic acid, a precursor to folate. Consistent with this result, inhibition of folate synthesis by sulfamethoxazole, a sulfonamide, led to a dose-dependent increase in C. elegans lifespan. As expected, these treatments caused a decrease in bacterial and worm folate levels, as measured by mass spectrometry of intact folates. The folate cycle is essential for cellular biosynthesis. However, bacterial proliferation and C. elegans growth and reproduction were unaffected under the conditions that increased lifespan. Conclusions In this animal:microbe system, folates are in excess of that required for biosynthesis. This study suggests that microbial folate synthesis is a pharmacologically accessible target to slow animal aging without detrimental effects.
Barber, Amelia E.; Norton, J. Paul; Wiles, Travis J.
2016-01-01
SUMMARY Urinary tract infections (UTIs) are some of the most common bacterial infections worldwide and are a source of substantial morbidity among otherwise healthy women. UTIs can be caused by a variety of microbes, but the predominant etiologic agent of these infections is uropathogenic Escherichia coli (UPEC). An especially troubling feature of UPEC-associated UTIs is their high rate of recurrence. This problem is compounded by the drastic increase in the global incidence of antibiotic-resistant UPEC strains over the past 15 years. The need for more-effective treatments for UTIs is driving research aimed at bettering our understanding of the virulence mechanisms and host-pathogen interactions that occur during the course of these infections. Surrogate models of human infection, including cell culture systems and the use of murine, porcine, avian, teleost (zebrafish), and nematode hosts, are being employed to define host and bacterial factors that modulate the pathogenesis of UTIs. These model systems are revealing how UPEC strains can avoid or overcome host defenses and acquire scarce nutrients while also providing insight into the virulence mechanisms used by UPEC within compromised individuals, such as catheterized patients. Here, we summarize our current understanding of UTI pathogenesis while also giving an overview of the model systems used to study the initiation, persistence, and recurrence of UTIs and life-threatening sequelae like urosepsis. Although we focus on UPEC, the experimental systems described here can also provide valuable insight into the disease processes associated with other bacterial pathogens both within the urinary tract and elsewhere within the host. PMID:26935136
Matsumoto, Tomotaka
2015-11-24
Recent studies suggest the existence of a stochasticity in gene expression (SGE) in many organisms, and its non-negligible effect on their phenotype and fitness. To date, however, how SGE affects the key parameters of population genetics are not well understood. SGE can increase the phenotypic variation and act as a load for individuals, if they are at the adaptive optimum in a stable environment. On the other hand, part of the phenotypic variation caused by SGE might become advantageous if individuals at the adaptive optimum become genetically less-adaptive, for example due to an environmental change. Furthermore, SGE of unimportant genes might have little or no fitness consequences. Thus, SGE can be advantageous, disadvantageous, or selectively neutral depending on its context. In addition, there might be a genetic basis that regulates magnitude of SGE, which is often referred to as “modifier genes,” but little is known about the conditions under which such an SGE-modifier gene evolves. In the present study, we conducted individual-based computer simulations to examine these conditions in a diploid model. In the simulations, we considered a single locus that determines organismal fitness for simplicity, and that SGE on the locus creates fitness variation in a stochastic manner. We also considered another locus that modifies the magnitude of SGE. Our results suggested that SGE was always deleterious in stable environments and increased the fixation probability of deleterious mutations in this model. Even under frequently changing environmental conditions, only very strong natural selection made SGE adaptive. These results suggest that the evolution of SGE-modifier genes requires strict balance among the strength of natural selection, magnitude of SGE, and frequency of environmental changes. However, the degree of dominance affected the condition under which SGE becomes advantageous, indicating a better opportunity for the evolution of SGE in different genetic
Theoretical model for a background noise limited laser-excited optical filter for doubled Nd lasers
Shay, Thomas M.; Garcia, Daniel F.
1990-01-01
A simple theoretical model for the calculation of the dependence of filter quantum efficiency versus laser pump power in an atomic Rb vapor laser-excited optical filter is reported. Calculations for Rb filter transitions that can be used to detect the practical and important frequency-doubled Nd lasers are presented. The results of these calculations show the filter's quantum efficiency versus the laser pump power. The required laser pump powers required range from 2.4 to 60 mW/sq cm of filter aperture.
The Limits of Acclimation of land plants in a Terrestrial Ecosystems Model
Kothavala, Zavareh
2014-05-01
In this study, we examine the role of the terrestrial carbon cycle and the ability of different plant types to acclimate to a changing climate at the centennial scale using a global ecosystems model with updated biogeochemical processes related to moisture, carbon, and nitrogen. Elevated level of atmospheric carbon dioxide (CO2) increases CO2 fertilization, resulting in more CO2 uptake by vegetation, whereas the concomitant warming increases autotrophic and heterotrophic respiration, releasing CO2 to the atmosphere. Additionally, warming will enhance photosynthesis if current temperatures are below the optimal temperature for plant growth, while it will reduce photosynthesis if current temperatures are above the optimal temperature for plant growth. We present a series of ensemble simulations to evaluate the ability of plants to acclimate to changing conditions over the last century and how this affects the terrestrial carbon sink. A set of experiments related to (a) the varying relationship between CO2 fertilization and the half saturation constant, (b) the factors related to gross primary productivity and maintenance respiration, and (c) the variables related to heterotrophic respiration, were conducted with thirteen plant functional types. The experiments were performed using the Terrestrial Ecosystem Model (TEM) with a present-day vegetation distribution without the effects of natural or human disturbance, and a closed Nitrogen cycle, at a half-degree resolution over the globe. The experiment design consisted of eight scenarios that are consistent with past and future ecosystem conditions, presented in other scientific studies. The significance of model trends related to runoff, soil moisture, soil carbon, Net Primary Productivity (NPP), crop yield, and Net Ecosystem Productivity (NEP) for different seasons, as well as surface temperature, precipitation, vapor pressure, and photosynthetically active radiation are analyzed for various ecosystems at the global
Ali Saif, M.; Gade, Prashant M.
2009-03-01
Pareto law, which states that wealth distribution in societies has a power-law tail, has been the subject of intensive investigations in the statistical physics community. Several models have been employed to explain this behavior. However, most of the agent based models assume the conservation of number of agents and wealth. Both these assumptions are unrealistic. In this paper, we study the limiting wealth distribution when one or both of these assumptions are not valid. Given the universality of the law, we have tried to study the wealth distribution from the asset exchange models point of view. We consider models in which (a) new agents enter the market at a constant rate (b) richer agents fragment with higher probability introducing newer agents in the system (c) both fragmentation and entry of new agents is taking place. While models (a) and (c) do not conserve total wealth or number of agents, model (b) conserves total wealth. All these models lead to a power-law tail in the wealth distribution pointing to the possibility that more generalized asset exchange models could help us to explain the emergence of a power-law tail in wealth distribution.
Kitta, Takeya; Kanno, Yukiko; Chiba, Hiroki; Higuchi, Madoka; Ouchi, Mifuka; Togo, Mio; Moriya, Kimihiko; Shinohara, Nobuo
2018-01-01
The functions of the lower urinary tract have been investigated for more than a century. Lower urinary tract symptoms, such as incomplete bladder emptying, weak urine stream, daytime urinary frequency, urgency, urge incontinence and nocturia after partial bladder outlet obstruction, is a frequent cause of benign prostatic hyperplasia in aging men. However, the pathophysiological mechanisms have not been fully elucidated. The use of animal models is absolutely imperative for understanding the pathophysiological processes involved in bladder dysfunction. Surgical induction has been used to study lower urinary tract functions of numerous animal species, such as pig, dog, rabbit, guinea pig, rat and mouse, of both sexes. Several morphological and functional modifications under partial bladder outlet obstruction have not only been observed in the bladder, but also in the central nervous system. Understanding the changes of the lower urinary tract functions induced by partial bladder outlet obstruction would also contribute to appropriate drug development for treating these pathophysiological conditions. In the present review, we discuss techniques for creating partial bladder outlet obstruction, the characteristics of several species, as well as issues of each model, and their translational value. © 2017 The Japanese Urological Association.
Damping at positive frequencies in the limit J⊥-->0 in the strongly correlated Hubbard model
Mohan, Minette M.
1992-08-01
I show damping in the two-dimensional strongly correlated Hubbard model within the retraceable-path approximation, using an expansion around dominant poles for the self-energy. The damping half-width ~J2/3z occurs only at positive frequencies ω>5/2Jz, the excitation energy of a pure ``string'' state of length one, where Jz is the Ising part of the superexchange interaction, and occurs even in the absence of spin-flip terms ~J⊥ in contrast to other theoretical treatments. The dispersion relation for both damped and undamped peaks near the upper band edge is found and is shown to have lost the simple J2/3z dependence characteristic of the peaks near the lower band edge. The position of the first three peaks near the upper band edge agrees well with numerical simulations on the t-J model. The weight of the undamped peaks near the upper band edge is ~J4/3z, contrasting with Jz for the weight near the lower band edge.
Numerical methods for limit problems in two-phase flow models
International Nuclear Information System (INIS)
Cordier, F.
2011-01-01
Numerical difficulties are encountered during the simulation of two-phase flows. Two issues are studied in this thesis: the simulation of phase transitions on one hand, and the simulation of both compressible and incompressible flows in the other hand. Un asymptotic study has shown that the loss of hyperbolicity of the bi fluid model was responsible for the difficulties encountered by the Roe scheme during the simulation of phase transitions. Robust and accurate polynomial schemes have thus been developed. To tackle the occasional lack of positivity of the solution, a numerical treatment based on adaptive diffusion was proposed and allowed to simulate with accuracy the test-cases of a boiling channel with creation of vapor and a tee-junction with separation of the phases. In a second part, an all-speed scheme for compressible and incompressible flows have been proposed. This pressure-based semi-implicit asymptotic preserving scheme is conservative, solves an elliptic equation on the pressure, and has been designed for general equations of state. The scheme was first developed for the full Euler equations and then extended to the Navier-Stokes equations. The good behaviour of the scheme in both compressible and incompressible regimes have been investigated. An extension of the scheme to the two-phase mixture model was implemented and demonstrated the ability of the scheme to simulate two-phase flows with phase change and a water-steam equation of state. (author) [fr
Modelling of Quench Limit for Steady State Heat Deposits in LHC Magnets
Bocian, D; Siemko, A
2008-01-01
A quench, the transition of a conductor from the superconducting to the normal conducting state, occurs irreversibly in the accelerator magnets if one of the three parameters: temperature, magnetic field or current density exceeds a critical value. Energy deposited in the superconductor by the particle beams provokes quenches detrimental for the accelerator operation. In particular if particles impacting on the vacuum chamber and their secondary showers depose energy in the magnet coils. The Large Hadron Collider (LHC) nominal beam intensity is 3.2 ldr 10^14 protons. A quench occurs if a fraction of the order of 10^7 protons per second is lost locally. A network model is used to simulate the thermodynamic behaviour of the magnets. The heat flow in the network model was validated with measurements performed in the CERN magnet test facility. A steady state heat flow was introduced in the coil by using the quench heaters implemented in the LHC magnets. The value of the heat source current is determined by the ne...
Energy Technology Data Exchange (ETDEWEB)
Kaasalainen, Touko; Lampinen, Anniina [University of Helsinki and Helsinki University Hospital, HUS Medical Imaging Center, Radiology, POB 340, Helsinki (Finland); University of Helsinki, Department of Physics, Helsinki (Finland); Palmu, Kirsi [University of Helsinki and Helsinki University Hospital, HUS Medical Imaging Center, Radiology, POB 340, Helsinki (Finland); School of Science, Aalto University, Department of Biomedical Engineering and Computational Science, Helsinki (Finland); Reijonen, Vappu; Kortesniemi, Mika [University of Helsinki and Helsinki University Hospital, HUS Medical Imaging Center, Radiology, POB 340, Helsinki (Finland); Leikola, Junnu [University of Helsinki and Helsinki University Hospital, Department of Plastic Surgery, Helsinki (Finland); Kivisaari, Riku [University of Helsinki and Helsinki University Hospital, Department of Neurosurgery, Helsinki (Finland)
2015-09-15
Medical professionals need to exercise particular caution when developing CT scanning protocols for children who require multiple CT studies, such as those with craniosynostosis. To evaluate the utility of ultra-low-dose CT protocols with model-based iterative reconstruction techniques for craniosynostosis imaging. We scanned two pediatric anthropomorphic phantoms with a 64-slice CT scanner using different low-dose protocols for craniosynostosis. We measured organ doses in the head region with metal-oxide-semiconductor field-effect transistor (MOSFET) dosimeters. Numerical simulations served to estimate organ and effective doses. We objectively and subjectively evaluated the quality of images produced by adaptive statistical iterative reconstruction (ASiR) 30%, ASiR 50% and Veo (all by GE Healthcare, Waukesha, WI). Image noise and contrast were determined for different tissues. Mean organ dose with the newborn phantom was decreased up to 83% compared to the routine protocol when using ultra-low-dose scanning settings. Similarly, for the 5-year phantom the greatest radiation dose reduction was 88%. The numerical simulations supported the findings with MOSFET measurements. The image quality remained adequate with Veo reconstruction, even at the lowest dose level. Craniosynostosis CT with model-based iterative reconstruction could be performed with a 20-μSv effective dose, corresponding to the radiation exposure of plain skull radiography, without compromising required image quality. (orig.)
Directory of Open Access Journals (Sweden)
Leonetti Davide
2018-01-01
Full Text Available Estimating and reducing uncertainty in fatigue test data analysis is a relevant task in order to assess the reliability of a structural connection with respect to fatigue. Several statistical models have been proposed in the literature with the aim of representing the stress range vs. endurance trend of fatigue test data under constant amplitude loading and the scatter in the finite and infinite life regions. In order to estimate the safety level of the connection also the uncertainty related to the amount of information available need to be estimated using the methods provided by the theory of statistic. The Bayesian analysis is employed to reduce the uncertainty due to the often small amount of test data by introducing prior information related to the parameters of the statistical model. In this work, the inference of fatigue test data belonging to cover plated steel beams is presented. The uncertainty is estimated by making use of Bayesian and frequentist methods. The 5% quantile of the fatigue life is estimated by taking into account the uncertainty related to the sample size for both a dataset containing few samples and one containing more data. The S-N curves resulting from the application of the employed methods are compared and the effect of the reduction of uncertainty in the infinite life region is quantified.
Gavagnin, Enrico; Yates, Christian A.
2018-03-01
Persistence of motion is the tendency of an object to maintain motion in a direction for short time scales without necessarily being biased in any direction in the long term. One of the most appropriate mathematical tools to study this behavior is an agent-based velocity-jump process. In the absence of agent-agent interaction, the mean-field continuum limit of the agent-based model (ABM) gives rise to the well known hyperbolic telegraph equation. When agent-agent interaction is included in the ABM, a strictly advective system of partial differential equations (PDEs) can be derived at the population level. However, no diffusive limit of the ABM has been obtained from such a model. Connecting the microscopic behavior of the ABM to a diffusive macroscopic description is desirable, since it allows the exploration of a wider range of scenarios and establishes a direct connection with commonly used statistical tools of movement analysis. In order to connect the ABM at the population level to a diffusive PDE at the population level, we consider a generalization of the agent-based velocity-jump process on a two-dimensional lattice with three forms of agent interaction. This generalization allows us to take a diffusive limit and obtain a faithful population-level description. We investigate the properties of the model at both the individual and population levels and we elucidate some of the models' key characteristic features. In particular, we show an intrinsic anisotropy inherent to the models and we find evidence of a spontaneous form of aggregation at both the micro- and macroscales.
Smith, B.; Wårlind, D.; Arneth, A.; Hickler, T.; Leadley, P.; Siltberg, J.; Zaehle, S.
2014-04-01
The LPJ-GUESS dynamic vegetation model uniquely combines an individual- and patch-based representation of vegetation dynamics with ecosystem biogeochemical cycling from regional to global scales. We present an updated version that includes plant and soil N dynamics, analysing the implications of accounting for C-N interactions on predictions and performance of the model. Stand structural dynamics and allometric scaling of tree growth suggested by global databases of forest stand structure and development were well reproduced by the model in comparison to an earlier multi-model study. Accounting for N cycle dynamics improved the goodness of fit for broadleaved forests. N limitation associated with low N-mineralisation rates reduces productivity of cold-climate and dry-climate ecosystems relative to mesic temperate and tropical ecosystems. In a model experiment emulating free-air CO2 enrichment (FACE) treatment for forests globally, N limitation associated with low N-mineralisation rates of colder soils reduces CO2 enhancement of net primary production (NPP) for boreal forests, while some temperate and tropical forests exhibit increased NPP enhancement. Under a business-as-usual future climate and emissions scenario, ecosystem C storage globally was projected to increase by ca. 10%; additional N requirements to match this increasing ecosystem C were within the high N supply limit estimated on stoichiometric grounds in an earlier study. Our results highlight the importance of accounting for C-N interactions in studies of global terrestrial N cycling, and as a basis for understanding mechanisms on local scales and in different regional contexts.
The Sznajd model with limited persuasion: competition between high-reputation and hesitant agents
International Nuclear Information System (INIS)
Crokidakis, Nuno; De Oliveira, Paulo Murilo Castro
2011-01-01
In this work we study a modified version of the two-dimensional Sznajd sociophysics model. In particular, we consider the effects of agents' reputations in the persuasion rules. In other words, a high-reputation group with a common opinion may convince its neighbors with probability p, which induces an increase of the group's reputation. On the other hand, there is always a probability q = 1 − p of the neighbors keeping their opinions, which induces a decrease of the group's reputation. These rules describe a competition between groups with high-reputation and hesitant agents, which makes the full-consensus states (with all spins pointing in one direction) more difficult to reach. As consequences, the usual phase transition does not occur for p c ∼ 0.69 and the system presents realistic democracy-like situations, where the majority of spins are aligned in a certain direction, for a wide range of parameters
The Sznajd model with limited persuasion: competition between high-reputation and hesitant agents
Crokidakis, Nuno; Murilo Castro de Oliveira, Paulo
2011-11-01
In this work we study a modified version of the two-dimensional Sznajd sociophysics model. In particular, we consider the effects of agents' reputations in the persuasion rules. In other words, a high-reputation group with a common opinion may convince its neighbors with probability p, which induces an increase of the group's reputation. On the other hand, there is always a probability q = 1 - p of the neighbors keeping their opinions, which induces a decrease of the group's reputation. These rules describe a competition between groups with high-reputation and hesitant agents, which makes the full-consensus states (with all spins pointing in one direction) more difficult to reach. As consequences, the usual phase transition does not occur for p < pc ~ 0.69 and the system presents realistic democracy-like situations, where the majority of spins are aligned in a certain direction, for a wide range of parameters.
Model-independent limits on four-fermion contact interactions at LC with polarization
International Nuclear Information System (INIS)
Pankov, A.A.; Paver, N.
1998-04-01
Fermion compositeness, and other types of new physics that can be described by the exchange of very massive particles, can manifest themselves as the result of an effective four-fermion contact interaction. In the case of the processes e + e - →μ + μ - , τ + τ - , b-bar b and c-bar c at future e + e - colliders with √s=0.5-1 TeV, we examine the sensitivity to four-fermion contact interactions of two new integrated observables, σ + and σ - , conveniently defined for such kind of analysis. We find that, if longitudinal polarization of the electron beam were available, these observables would offer the opportunity to separate the helicity cross sections and, in this way, to derive model-independent bounds on the relevant parameters. (author)
A model for electrochemical insertion limited by a phase transition process - eilpt
Directory of Open Access Journals (Sweden)
Adhoum N.
2003-01-01
Full Text Available This paper deals with electrochemical insertion into a cathodic material. New results on modeling of the influence of a solid phase transformation on the shape of voltamograms are presented. The original experiments concern the insertion of sodium into carbon during the cathodic reduction of molten NaF at 1020 °C, but in the present manuscript emphasis on the theoretical aspects of the work is put. Phase transformations during electrochemical insertion are taken into account, with various values for parameters such as the thermodynamic biphase equilibrium potential, the compared diffusion and phase transformation kinetics, and the electrode thickness. The voltamograms calculated present very specific features; some of them have already been observed experimentally in literature.
Convergence of discrete Aubry–Mather model in the continuous limit
Su, Xifeng; Thieullen, Philippe
2018-05-01
We develop two approximation schemes for solving the cell equation and the discounted cell equation using Aubry–Mather–Fathi theory. The Hamiltonian is supposed to be Tonelli, time-independent and periodic in space. By Legendre transform it is equivalent to find a fixed point of some nonlinear operator, called Lax-Oleinik operator, which may be discounted or not. By discretizing in time, we are led to solve an additive eigenvalue problem involving a discrete Lax–Oleinik operator. We show how to approximate the effective Hamiltonian and some weak KAM solutions by letting the time step in the discrete model tend to zero. We also obtain a selected discrete weak KAM solution as in Davini et al (2016 Invent. Math. 206 29–55), and show that it converges to a particular solution of the cell equation. In order to unify the two settings, continuous and discrete, we develop a more general formalism of the short-range interactions.
The sufferer as model in photojournalism: notes on the limit of identity
Directory of Open Access Journals (Sweden)
Angie Biondi
2011-06-01
Full Text Available Suffering has been caused by press photographs ever since the start of Modern times. Sufferers in galleries exhibit the marks of their misfortunes as a legitimate record of wars, attempts, diseases. Anchored on an acute indicial character, such images also constitute and intensify a complex field of visibility in which disputes and access or placement pacts come into action. The purpose of this text is to discuss the means for turning suffering into a classificationin which it associates the sufferer with a condition of belonging. Thus, tied to an identity, body and expression would serve solelythe conformation of an ethos, as an exemplary model of personage. In order to describe these strategies, we seek to reflect on affective experiences in this universe of images from the perspective of apossible encounter with what is singular, with any one subject, which is brought about by image.
Global high resolution versus Limited Area Model climate change projections over Europe
DEFF Research Database (Denmark)
Déqué, Michel; Jones, R. G.; Wild, M.
2005-01-01
the 2071-2100 and the 1961-1990 means is compared with the same diagnostic obtained with nine Regional Climate Models (RCM) all driven by the Hadley Centre atmospheric GCM. The seasonal mean response for 2m temperature and precipitation is investigated. For temperature, GCMs and RCMs behave similarly......, except that GCMs exhibit a larger spread. However, during summer, the spread of the RCMs - in particular in terms of precipitation - is larger than that of the GCMs. This indicates that the European summer climate is strongly controlled by parameterized physics and/or high-resolution processes...... errors are more spread. In addition, GCM precipitation response is slightly but significantly different from that of the RCMs....
Bosonization of the two-dimensional t-J model in the continuum limit
International Nuclear Information System (INIS)
Schmeltzer, D.; Bishop, A.R.
1996-01-01
The t-J model in two dimensions is bosonized using a set of N, coupled two-dimensional Fermi-surface patches. Ignoring tunneling between the patches, the coherent tunneling of holes and the superfluid phase are suppressed. Within this scheme the system remains in the normal phase when temperature T→0. The main feature of this construction is the absence of screening of the dissipative transversal gauge field generated by the spinons. This dissipative gauge field is responsible for the non-Fermi-liquid behavior, which is manifested in the free energy and single-particle Green function. The deviation from Fermi-liquid behavior is due to the U(1) gauge field, and at long distances a new exponent due to the holes is identified. Experimental consequences are discussed. copyright 1996 The American Physical Society
Energy Technology Data Exchange (ETDEWEB)
Toms, Andoni P. (Dept. of Radiology, The Norfolk and Norwich Univ. Hospital, Norwich, Norfolk (United Kingdom)); White, Lawrence M.; Bleakney, Robert R. (Dept. of Medical Imaging, Mount Sinai Hospital, Toronto, ON (Canada)); Kandel, Rita (Dept. of Pathology and Laboratory Medicine, Mount Sinai Hospital, Toronto, ON (Canada)); Noseworthy, Michael (Health Sciences Centre, Faculty of Health Sciences, McMaster Univ., Hamilton, ON (Canada)); Lee, Shepstone (Institute of Health, Univ. of East Anglia, Norwich, Norfolk (United Kingdom)); Blackstein, Martin E. (Dept. of Oncology, Mount Sinai Hospital, Toronto, ON (Canada)); Wunder, Jay (Musculoskeletal Oncology Unit, Mount Sinai Hospital, Toronto, ON (Canada))
2009-06-15
Background: Single slice dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) appears to provide perfusion data about sarcomas in vivo that correlate with tumor necrosis on equivalent pathological sections. However, sarcomas are heterogeneous and therefore single slice DCE-MRI may not correlate with total tumor necrosis. Purpose: To determine whether changes in pharmacokinetic modeling of DCE-MRI, during chemotherapy for primary bone sarcomas correlated with histological measures of total tumor necrosis. Material and Methods: Twelve patients with appendicular primary bone sarcomas were included in the study. Each patient had DCE-MRI before, and after completion, of pre-operative chemotherapy. The mean arterial slope (A), endothelial permeability coefficient (Ktrans), and extravascular extracellular volume (Ve) were derived from each data set using a modified two compartment pharmacokinetic model. Total tumor necrosis rates were compared with changes in A, Ktrans, and Ve. Results: Six patients had total tumor necrosis of =90% and six had a measure of <90%. The median percentage changes in A, Ktrans, and Ve for the =90% necrosis group were -52.5% (-83 to 6), -66% (-82 to 26), and 23.5% (-26 to 40), respectively. For the <90% necrosis group, A = - 35% (-75 to 132), Ktrans= - 53 (-66 to 149) and Ve= - 14.5% (-42 to 40). One patient with >90% necrosis had increases in all three measures. Comparison of the two groups generated P-values of 0.699 for A, 0.18 for Ktrans, and 0.31 for Ve. Conclusion: There was no statistically significant correlation between changes in pharmacokinetic perfusion parameters and total tumor necrosis. When using single slice DCE-MRI heterogeneous histology of primary bone sarcomas and repair mediated angiogenesis might both be confounding factors
Modeling the role of information and limited optimal treatment on disease prevalence.
Kumar, Anuj; Srivastava, Prashant K; Takeuchi, Yasuhiro
2017-02-07
Disease outbreaks induce behavioural changes in healthy individuals to avoid contracting infection. We first propose a compartmental model which accounts for the effect of individual's behavioural response due to information of the disease prevalence. It is assumed that the information is growing as a function of infective population density that saturates at higher density of infective population and depends on active educational and social programmes. Model analysis has been performed and the global stability of equilibrium points is established. Further, choosing the treatment (a pharmaceutical intervention) and the effect of information (a non-pharmaceutical intervention) as controls, an optimal control problem is formulated to minimize the cost and disease fatality. In the cost functional, the nonlinear effect of controls is accounted. Analytical characterization of optimal control paths is done with the help of Pontryagin's Maximum Principle. Numerical findings suggest that if only control via information is used, it is effective and economical for early phase of disease spread whereas treatment works well for long term control except for initial phase. Furthermore, we observe that the effect of information induced behavioural response plays a crucial role in the absence of pharmaceutical control. Moreover, comprehensive use of both the control interventions is more effective than any single applied control policy and it reduces the number of infective individuals and minimizes the economic cost generated from disease burden and applied controls. Thus, the combined effect of both the control policies is found more economical during the entire epidemic period whereas the implementation of a single policy is not found economically viable. Copyright © 2016 Elsevier Ltd. All rights reserved.
Risk model for suspected acute coronary syndrome is of limited value in an emergency department.
Mogensen, Christian Backer; Christiansen, Maja; Jørgensen, Jess Bjerre; Staehr, Peter Bisgaard
2015-10-01
Among patients with acute chest pain, acute coronary syndrome (ACS) is seen only in a minority of the patients, which raises the question, whether it is possible to separate a group with a high risk of ACS for admission to a cardiac care unit (CCU) from those with a low risk who would be treated at an emergency department (ED). The aim of this study was to describe a risk stratification model for a Danish context. This was a historic prospective cohort study of patients with suspicion of ACS. The patient was defined as a low-risk patient and admitted to the ED if: 1) electrocardiogram (ECG) was normal, 2) the patient did not have persisting chest pain and 3) there was no history of ischaemic heart disease, heart failure or cardioverter defibrillator. Otherwise, patients were admitted to the CCU. The primary outcome was whether the ACS diagnosis was confirmed or rejected. We included a total of 488 patients with suspicion of ACS, 50% of whom were low-risk patients. 17% had a verified ACS; 10% of those in the low-risk group and 24% of those in the high-risk group (p = 0.0001). Among the verified ACS cases, 71% went primarily to the CCU. The odds ratio for an ACS if assigned to the high-risk group was 3.0. Allocation to the high-risk group, male gender and age above 60 years was associated with a higher risk of ACS. For patients fulfilling the high-risk definition, sensitivity was 71%, specificity 55%, negative predictive value 90% and positive predictive value 24% for an ACS. The model for stratification separated patients into two equal groups, allocated 71% of all ACS directly to the CCU and could not be improved by any of the additional factors examined. Further development of referral strategies for chest pain patients is required. none. not relevant.
Peters, Andre; Durner, Wolfgang; Iden, Sascha C.
2017-04-01
Modeling water flow in the soil-plant-atmosphere continuum with the Richards equation requires a model for the sink term describing water uptake by plant roots. Despite recent progress in developing process-based models of water uptake by plant roots and water flow in aboveground parts of vegetation, effective models of root water uptake are widely applied and necessary for large-scale applications. Modeling root water uptake consists of three steps, (i) specification of the spatial distribution of potential uptake, (ii) reduction of uptake due to various stress sources, and (iii) enhancement of uptake in part of the simulation domain to describe compensation. We discuss the conceptual shortcomings of the frequently used root water uptake model of Feddes and suggest a simple but effective improvement of the model. The improved model parametrizes water stress in wet soil by a reduction scheme which is formulated as function of air content where water stress due to low soil water potential is described by the original approach of Feddes. The improved model is physically more consistent than Feddes' model because water uptake in wet soil is limited by aeration which is a function of water content. The suggested modification is particularly relevant for simulations in heterogeneous soils, because stress parameters are uniquely defined for the entire simulation domain, irrespective of soil texture. Numerical simulations of water flow and root water uptake in homogeneous and stochastic heterogeneous soils illustrate the effect of the new model on root water uptake and actual transpiration. For homogeneous fine-textured soils, root water uptake never achieves its potential rate. In stochastic heterogeneous soil, water uptake is more pronounced at the interfaces between fine and coarse regions which has potential implications for plant growth, nutrient uptake and depletion.
The Gap-Startle Paradigm for Tinnitus Screening in Animal Models: Limitations and Optimization
Lobarinas, Edward; Hayes, Sarah H.; Allman, Brian L.
2012-01-01
as assessed with the traditional BBN gap-startle paradigm, resulting in a false-positive screening for tinnitus. Thus, the present study identifies significant caveats of the traditional gap-startle paradigm, and describes experimental parameters using an airpuff startle stimulus which may help to limit the negative consequences of reduced startle reactivity following noise exposure, thereby allowing researchers to better screen for tinnitus in animals with hearing loss. PMID:22728305
International Nuclear Information System (INIS)
Jen Chunping; Tien Nengchuan
2010-01-01
Nuclides can move with groundwater either as solutes or colloids, where the latter mechanism generally results in much shorter traveling time as the nuclides interact strongly with solid phases, such as actinides. In the performance assessment, it is therefore essential to assess the relative importance of these two transport mechanisms for different nuclides. The relative importance of colloids depends on the nature and concentration of the colloids in groundwater. Plutonium (Pu), neptunium (Np), uranium (U) and americium (Am) are four nuclides of concern for the long-term emplacement of nuclear wastes at potential repository sites. These four actinides have a high potential for migrating if attached to iron oxide, clay or silica colloids in the groundwater.Strong sorption of the actinides by colloids in the groundwater may facilitate the transport of these nuclides along potential flow paths. The solubility-limited dissolution model can be used to assess the safety of the release of nuclear waste in geological disposal sites. Usually, it has been assumed that the solubility of the waste form is constant. If a nuclide reaches its solubility limit at an inner location near the waste form, it is unlikely that the same nuclide will reach its solubility limit at an outer location unless this nuclide has a parent nuclide. It is unlikely that the daughter nuclides will exceed their solubility limit due to decay of their parent nuclide. The present study investigates the effect of colloids on the transport of solubility-limited nuclides under the kinetic solubility-limited dissolution (KSLD) boundary condition in fractured media. The release rate of the nuclides is proportional to the difference between the saturation concentration and the inlet aqueous concentration of the nuclides. The presence of colloids decreases the aqueous concentration of nuclides and, thus, increases the release flux of nuclides from the waste form. (authors)
Katsukawa, Y.; Suematsu, Y.; Tsuneta, S.; Ichimoto, K.; Shimizu, T.
2011-09-01
HINODE, Japanese for "sunrise", is a spacecraft dedicated for observations of the Sun, and was launched in 2006 to study the Sun's magnetic fields and how their explosive energies propagate through the different atmospheric layers. The spacecraft carries the Solar Optical Telescope (SOT), which has a 50 cm diameter clear aperture and provides a continuous series of diffraction-limited visible light images from space. The telescope was developed through international collaboration between Japan and US. In order to achieve the diffraction-limited performance, thermal and structural modeling of the telescope was extensively used in its development phase to predict how the optical performance changes dependent on the thermal condition in orbit. Not only the modeling, we devoted many efforts to verify the optical performance in ground tests before the launch. The verification in the ground tests helped us to find many issues, such as temperature dependent focus shifts, which were not identified only through the thermal-structural modeling. Another critical issue was micro-vibrations induced by internal disturbances of mechanical gyroscopes and momentum wheels for attitude control of the spacecraft. Because the structural modeling was not accurate enough to predict how much the image quality was degraded by the micro-vibrations, we measured their transmission in a spacecraft-level test.
Michaud, Claude; Sannino, Nadine; Duboudin, Cédric; Baudier, François; Guillin, Caroline; Billondeau, Christine; Mansion, Sylvie
2014-01-01
The French "Hospitals, patients, health and territories" law of July 2009 created the Regional Health Project (PRS) to support regional health policy, and requires evaluation of these projects. The construction of these projects, which includes prevention planning, care planning, and medical and social welfare planning, presents an unprecedented complexity in France, where evaluation programmes are still in their infancy. To support future evaluations, the Franche-Comté Regional Health Agency (ARS FC), assisted by the expertise of EFECT Consultants, decided to reconstruct the PRS logic model. This article analyzes the advantages and limitations of this approach. The resulting logic model allows visualization of the strategy adopted to achieve the Franche-Comté PRS ambitions and expected results. The model highlights four main aspects of structural change to the health system, often poorly visible in PRS presentation documents. This model also establishes links with the usual public policy evaluation issues and facilitates their prioritization. This approach also provides a better understanding of the importance of analysis of the programme construction in order to be effective rather than direct analysis of the effects, which constitutes the natural tendency of current practice. The main controversial limit concerns the retrospective design of the PRS framework, both in terms of the reliability of interpretation and adoption by actors not directly involved in this initiative.
Bollerslev, Anne Mette; Nauta, Maarten; Hansen, Tina Beck; Aabo, Søren
2017-01-02
Microbiological limits are widely used in food processing as an aid to reduce the exposure to hazardous microorganisms for the consumers. However, in pork, the prevalence and concentrations of Salmonella are generally low and microbiological limits are not considered an efficient tool to support hygiene interventions. The objective of the present study was to develop an approach which could make it possible to define potential risk-based microbiological limits for an indicator, enterococci, in order to evaluate the risk from potential growth of Salmonella. A positive correlation between the concentration of enterococci and the prevalence and concentration of Salmonella was shown for 6640 pork samples taken at Danish cutting plants and retail butchers. The samples were collected in five different studies in 2001, 2002, 2010, 2011 and 2013. The observations that both Salmonella and enterococci are carried in the intestinal tract, contaminate pork by the same mechanisms and share similar growth characteristics (lag phase and maximum specific growth rate) at temperatures around 5-10°C, suggest a potential of enterococci to be used as an indicator of potential growth of Salmonella in pork. Elevated temperatures during processing will lead to growth of both enterococci and, if present, also Salmonella. By combining the correlation between enterococci and Salmonella with risk modelling, it is possible to predict the risk of salmonellosis based on the level of enterococci. The risk model used for this purpose includes the dose-response relationship for Salmonella and a reduction factor to account for preparation of the fresh pork. By use of the risk model, it was estimated that the majority of salmonellosis cases, caused by the consumption of pork in Denmark, is caused by the small fraction of pork products that has enterococci concentrations above 5logCFU/g. This illustrates that our approach can be used to evaluate the potential effect of different microbiological
Letting students discover the power, and the limits, of simple models: Coulomb's law
Bohacek, Peter; Vonk, Matthew; Dill, Joseph; Boehm, Emma
2017-09-01
The inverse-square law pops up all over. It's a simplified model of reality that describes light, sound, gravity, and static electricity. But when it's brought up in class, students are often just handed the equations. They rarely have an opportunity to discover Coulomb's law or Newton's law of gravitation for themselves. It's not hard to understand why. A quantitative demonstration of Coulomb's law can be difficult. The forces are smaller than many force sensors can measure and static electricity tends to be finicky. In addition, off-the-shelf units are expensive or difficult to use. As a result, many instructors skip this lab in favor of qualitative demonstrations or simulations. Adolf Cortel sought to remedy this by designing a straightforward experiment for measuring Coulomb's law using charged metalized-glass spheres (Christmas ornaments) and an electronic balance. Building on Cortel's design, we've made a series of video-based experiments that students can use to discover the relationships that underlie electric force.
Morison, K R; Hutchinson, C A
2009-01-01
The Weissler reaction in which iodide is oxidised to a tri-iodide complex (I(3)(-)) has been widely used for measurement of the intensity of ultrasonic and hydrodynamic cavitation. It was used in this work to compare ultrasonic cavitation at 24 kHz with hydrodynamic cavitation using two different devices, one a venturi and the other a sudden expansion, operated up to 8.7 bar. Hydrodynamic cavitation had a maximum efficiency of about 5 x 10(-11) moles of I(3)(-) per joule of energy compared with the maximum of almost 8 x 10(-11) mol J(-1) for ultrasonic cavitation. Hydrodynamic cavitation was found to be most effective at 10 degrees C compared with 20 degrees C and 30 degrees C and at higher upstream pressures. However, it was found that in hydrodynamic conditions, even without cavitation, I(3)(-) was consumed at a rapid rate leading to an equilibrium concentration. It was concluded that the Weissler reaction was not a good model reaction for the assessment of the effectiveness of hydrodynamic cavitation.
Risk model for suspected acute coronary syndrome is of limited value in an emergency department
DEFF Research Database (Denmark)
Mogensen, Christian Backer; Christiansen, Maja; Jørgensen, Jess Bjerre
2015-01-01
INTRODUCTION: Among patients with acute chest pain, acute coronary syndrome (ACS) is seen only in a minority of the patients, which raises the question, whether it is possible to separate a group with a high risk of ACS for admission to a cardiac care unit (CCU) from those with a low risk who would...... be treated at an emergency department (ED). The aim of this study was to describe a risk stratification model for a Danish context. METHODS: This was a historic prospective cohort study of patients with suspicion of ACS. The patient was defined as a low-risk patient and admitted to the ED if: 1....... RESULTS: We included a total of 488 patients with suspicion of ACS, 50% of whom were low-risk patients. 17% had a verified ACS; 10% of those in the low-risk group and 24% of those in the high-risk group (p = 0.0001). Among the verified ACS cases, 71% went primarily to the CCU. The odds ratio for an ACS...