WorldWideScience

Sample records for modeling strategy depends

  1. Dependability breakeven point mathematical model for production - quality strategy support

    Science.gov (United States)

    Vilcu, Adrian; Verzea, Ion; Chaib, Rachid

    2016-08-01

    This paper connects the field of dependability system with the production-quality strategies through a new mathematical model based on breakeven points. The novelties consist in the identification of the parameters of dependability system which, in safety control, represents the degree to which an item is capable of performing its required function at any randomly chosen time during its specified operating period disregarding non-operation related influences, as well as the analysis of the production-quality strategies, defining a mathematical model based on a new concept - dependability breakeven points, model validation on datasets and shows the practical applicability of this new approach.

  2. Performance analysis of a dependable scheduling strategy based on a fault-tolerant grid model

    Institute of Scientific and Technical Information of China (English)

    WANG Yuanzhuo; LIN Chuang; YANG Yang; SHAN Zhiguang

    2007-01-01

    The grid provides an integrated computer platform composed of differentiated and distributed systems.These resources are dynamic and heterogeneous.In this paper,a novel fault-tolerant grid-scheduling model is pre sented based on Stochastic Petri Nets (SPN) to assure the heterogeneity and dynamism of the grid system.Also,a new grid-scheduling strategy,the dependable strategy for the shortest expected accomplishing time (DSEAT),is put forward,in which the dependability factor is introduced in the task-dispatching strategy.In the end,the performance of the scheduling strategy based on the fault-tolerant gridscheduling model is analyzed by an software package,named SPNP.The numerical results show that dynamic resources will increase the response time for all classes of tasks in differing degrees.Compared with shortest expected accomplishing time (SEAT) strategy,the DSEAT strategy can reduce the negative effects of dynamic and autonomic resources to some extent so as to guarantee a high quality of service (QoS).

  3. State-Dependent Impulsive Control Strategies for a Tumor-Immune Model

    Directory of Open Access Journals (Sweden)

    Kwang Su Kim

    2016-01-01

    Full Text Available Controlling the number of tumor cells leads us to expect more efficient strategies for treatment of tumor. Towards this goal, a tumor-immune model with state-dependent impulsive treatments is established. This model may give an efficient treatment schedule to control tumor’s abnormal growth. By using the Poincaré map and analogue of Poincaré criterion, some conditions for the existence and stability of a positive order-1 periodic solution of this model are obtained. Moreover, we carry out numerical simulations to illustrate the feasibility of our main results and compare fixed-time impulsive treatment effects with state-dependent impulsive treatment effects. The results of our simulations say that, in determining optimal treatment timing, the model with state-dependent impulsive control is more efficient than that with fixed-time impulsive control.

  4. Effect of positional dependence and alignment strategy on modeling transcription factor binding sites

    Directory of Open Access Journals (Sweden)

    Quader Saad

    2012-07-01

    Full Text Available Abstract Background Many consensus-based and Position Weight Matrix-based methods for recognizing transcription factor binding sites (TFBS are not well suited to the variability in the lengths of binding sites. Besides, many methods discard known binding sites while building the model. Moreover, the impact of Information Content (IC and the positional dependence of nucleotides within an aligned set of TFBS has not been well researched for modeling variable-length binding sites. In this paper, we propose ML-Consensus (Mixed-Length Consensus: a consensus model for variable-length TFBS which does not exclude any reported binding sites. Methods We consider Pairwise Score (PS as a measure of positional dependence of nucleotides within an alignment of TFBS. We investigate how the prediction accuracy of ML-Consensus is affected by the incorporation of IC and PS with a particular binding site alignment strategy. We perform cross-validations for datasets of six species from the TRANSFAC public database, and analyze the results using ROC curves and the Wilcoxon matched-pair signed-ranks test. Results We observe that the incorporation of IC and PS in ML-Consensus results in statistically significant improvement in the prediction accuracy of the model. Moreover, the existence of a core region among the known binding sites (of any length is witnessed by the pairwise coexistence of nucleotides within the core length. Conclusions These observations suggest the possibility of an efficient multiple sequence alignment algorithm for aligning TFBS, accommodating known binding sites of any length, for optimal (or near-optimal TFBS prediction. However, designing such an algorithm is a matter of further investigation.

  5. A Holling Type II Pest and Natural Enemy Model with Density Dependent IPM Strategy

    Directory of Open Access Journals (Sweden)

    Xia Wang

    2017-01-01

    Full Text Available Resource limitations and density dependent releasing of natural enemies during the pest control and integrated pest management will undoubtedly result in nonlinear impulsive control. In order to investigate the effects of those nonlinear control strategies on the successful pest control, we have proposed a pest-natural enemy system concerning integrated pest management with density dependent instant killing rate and releasing rate. In particular, the releasing rate depicts how the number of natural enemy populations released was guided by their current density at the fixed moment. The threshold condition which ensures the existence and global stability of pest-free periodic solution has been discussed first, and the effects of key parameters on the threshold condition reveal that reducing the pulse period does not always benefit pest control; that is, frequent releasing of natural enemies may not be beneficial to the eradication of pests when the density dependent releasing method has been implemented. Moreover, the forward and backward bifurcations could occur once the pest-free periodic solution becomes unstable, and the system could exist with very complex dynamics. All those results confirm that the control actions should be carefully designed once the nonlinear impulsive control measures have been taken for pest management.

  6. Livelihood strategies, environmental dependency and rural poverty

    DEFF Research Database (Denmark)

    Walelign, Solomon Zena

    2016-01-01

    This article attempts to explore the nexus between rural households’ environmental dependency, poverty and livelihood strategies. Households’ income from each livelihood activities formed the basis for categorizing households according to livelihood strategies. The principal component analysis......, agglomerative hierarchical and the k-means cluster analysis were employed to determine the four livelihood clusters and to assign households to the identified livelihood strategies. Households’ environmental dependency, poverty and asset holding were compared across the strategies, and the determinants...... of livelihood choice were analyzed using multinomial logit model. The results indicate the existence of marked differences in environmental dependency, rural poverty and asset endowments across the livelihood groups. Household’s total saving, access to credit, production implements, business cost, exposure...

  7. Multijam Solutions in Traffic Models with Velocity-Dependent Driver Strategies

    DEFF Research Database (Denmark)

    Carter, Paul; Christiansen, Peter Leth; Gaididei, Yuri B.

    2014-01-01

    The optimal-velocity follow-the-leader model is augmented with an equation that allows each driver to adjust their target headway according to the velocity difference between the driver and the car in front. In this more detailed model, which is investigated on a ring, stable and unstable...

  8. Reduced motivation in the BACHD rat model of Huntington disease is dependent on the choice of food deprivation strategy.

    Directory of Open Access Journals (Sweden)

    Erik Karl Håkan Jansson

    Full Text Available Huntington disease (HD is an inherited neurodegenerative disease characterized by motor, cognitive, psychiatric and metabolic symptoms. Animal models of HD show phenotypes that can be divided into similar categories, with the metabolic phenotype of certain models being characterized by obesity. Although interesting in terms of modeling metabolic symptoms of HD, the obesity phenotype can be problematic as it might confound the results of certain behavioral tests. This concerns the assessment of cognitive function in particular, as tests for such phenotypes are often based on food depriving the animals and having them perform tasks for food rewards. The BACHD rat is a recently established animal model of HD, and in order to ensure that behavioral characterization of these rats is done in a reliable way, a basic understanding of their physiology is needed. Here, we show that BACHD rats are obese and suffer from discrete developmental deficits. When assessing the motivation to lever push for a food reward, BACHD rats were found to be less motivated than wild type rats, although this phenotype was dependent on the food deprivation strategy. Specifically, the phenotype was present when rats of both genotypes were deprived to 85% of their respective free-feeding body weight, but not when deprivation levels were adjusted in order to match the rats' apparent hunger levels. The study emphasizes the importance of considering metabolic abnormalities as a confounding factor when performing behavioral characterization of HD animal models.

  9. Joining or opting out of a Lotka-Volterra game between predators and prey: does the best strategy depend on modelling energy lost and gained?

    Science.gov (United States)

    Staňková, Kateřina; Abate, Alessandro; Sabelis, Maurice W; Buša, Ján; You, Li

    2013-12-06

    Apart from interacting, prey and predators may also avoid each other by moving into refuges where they lack food, yet survive by switching to an energy-saving physiological state. Lotka-Volterra models of predator-prey interactions ignore this option. Therefore, we have modelled this game of 'joining versus opting out' by extending Lotka-Volterra models to include portions of populations not in interaction and with different energy dynamics. Given this setting, the prey's decisions to join or to opt out influence those of the predator and vice versa, causing the set of possible strategies to be complex and large. However, using game theory, we analysed and published two models showing (i) which strategies are best for the prey population given the predator's strategy, and (ii) which are best for prey and predator populations simultaneously. The predicted best strategies appear to match empirical observations on plant-inhabiting predator and prey mites. Here, we consider a plausible third model that does not take energy dynamics into account, but appears to yield contrasting predictions. This supports our assumption to extend Lotka-Volterra models with 'interaction-dependent' energy dynamics, but more work is required to prove that it is essential and that what is best for the population is also best for the individual.

  10. Mobility-dependent selection of competing strategy associations

    Science.gov (United States)

    Dobrinevski, Alexander; Alava, Mikko; Reichenbach, Tobias; Frey, Erwin

    2014-01-01

    Standard models of population dynamics focus on the interaction, survival, and extinction of the competing species individually. Real ecological systems, however, are characterized by an abundance of species (or strategies, in the terminology of evolutionary-game theory) that form intricate, complex interaction networks. The description of the ensuing dynamics may be aided by studying associations of certain strategies rather than individual ones. Here we show how such a higher-level description can bear fruitful insight. Motivated from different strains of colicinogenic Escherichia coli bacteria, we investigate a four-strategy system which contains a three-strategy cycle and a neutral alliance of two strategies. We find that the stochastic, spatial model exhibits a mobility-dependent selection of either the three-strategy cycle or of the neutral pair. We analyze this intriguing phenomenon numerically and analytically.

  11. SURF Model Calibration Strategy

    Energy Technology Data Exchange (ETDEWEB)

    Menikoff, Ralph [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-03-10

    SURF and SURFplus are high explosive reactive burn models for shock initiation and propagation of detonation waves. They are engineering models motivated by the ignition & growth concept of high spots and for SURFplus a second slow reaction for the energy release from carbon clustering. A key feature of the SURF model is that there is a partial decoupling between model parameters and detonation properties. This enables reduced sets of independent parameters to be calibrated sequentially for the initiation and propagation regimes. Here we focus on a methodology for tting the initiation parameters to Pop plot data based on 1-D simulations to compute a numerical Pop plot. In addition, the strategy for tting the remaining parameters for the propagation regime and failure diameter is discussed.

  12. A strategy model for management

    DEFF Research Database (Denmark)

    Friis, Ole Uhrskov; Holmgren, Jens; Eskildsen, Jacob Kjær

    2016-01-01

    Purpose: Developing a strategy model which explains what organisations should focus on in their strategy work, both in terms of the environment as well as how the strategy is implemented. In addition, the purpose is to demonstrate how this can influence and improve the organisations’ performance...

  13. Modeling Dependencies in Critical Infrastructures

    NARCIS (Netherlands)

    Nieuwenhuijs, A.H.; Luiijf, H.A.M.; Klaver, M.H.A.

    2009-01-01

    This paper describes a model for expressing critical infrastructure dependencies. The model addresses the limitations of existing approaches with respect to clarity of definition, support for quality and the influence of operating states of critical infrastructures and environmental factors.

  14. Search Strategy for the Standard Model Higgs Boson in the $H \\to ZZ^{(*)} \\to 4\\mu$ Decay Channel using $M(4\\mu)$-Dependent Cuts

    CERN Document Server

    Abdullin, Salavat; Bartalini, Paolo; Cavanaugh, Richard; Drozdetsky, A AN; Korytov, Andrey; Mitselmakher, Guenakh; Pakhotin, Yuriy; Scurlock, Bobby; Sherstnev, Alexander

    2007-01-01

    We present a strategy for a Higgs-boson search in its four-muon decay channel Hmu. The method is based on using optimized, smooth M(4mu)-dependent cuts that automatically ensure an optimal signal-to-background ratio for any mass at which the Higgs boson might appear. The Higgs boson then manifests itself as a 4mu resonance-like peak over the continuum M(mu) distribution and can be searched for using various statistical techniques. The most important theoretical and instrumental systematic errors as well as the fact that the search is conducted in a broad range of M(4mu) invariant masses (110-600 GeV/c^2) are taken into account.

  15. Modelling strategy report

    Energy Technology Data Exchange (ETDEWEB)

    Smith, P.A. [SAM Switzerland GmbH (Switzerland); Brommundt, J.; Mayer, G. [AF-Consult Switzerland Ltd, Baden (Switzerland)] [and others

    2012-01-15

    This report presents a preliminary plan for the development and application of models for the probabilistic sensitivity analyses and the deterministic calculation cases that will be used to analyse scenarios in the 2012 safety case. The plan addresses both groundwater flow modelling and radionuclide transport modelling, primarily of the repository near field and of the geosphere. It also addresses the measures that will be applied during the implementation and documentation of the calculations that will contribute to the quality assurance of the safety case. It is expected that this plan will be refined and amended as experience is gained during the carrying out of the work. (orig.)

  16. Optimal Strategy and Business Models

    DEFF Research Database (Denmark)

    Johnson, Peter; Foss, Nicolai Juul

    2016-01-01

    , it is possible to formalize useful notions of a business model, resources, and competitive advantage. The business model that underpins strategy may be seen as a set of constraints on resources that can be interpreted as controls in optimal control theory. Strategy then might be considered to be the control......This study picks up on earlier suggestions that control theory may further the study of strategy. Strategy can be formally interpreted as an idealized path optimizing heterogeneous resource deployment to produce maximum financial gain. Using standard matrix methods to describe the firm Hamiltonian...... variable of firm path, suggesting in turn that the firm's business model is the codification of the application of investment resources used to control the strategic path of value realization....

  17. Succes on the International Market Depends on Brand Strategy

    OpenAIRE

    Victor Danciu

    2006-01-01

    Brand strategy is vital for the succes of the company on the international market. Identity and positionning are critical in order to develop a succesufull brand strategy. These two very important dimensions of any strategy of brand are accompanying every strategical option. Creating and launching new brands depend on the strategic process of the new product development. The new brands aim at acquiring strategic advantages which are associated with the enlargement of the competenc...

  18. Learning strategies: a synthesis and conceptual model

    Science.gov (United States)

    Hattie, John A. C.; Donoghue, Gregory M.

    2016-08-01

    The purpose of this article is to explore a model of learning that proposes that various learning strategies are powerful at certain stages in the learning cycle. The model describes three inputs and outcomes (skill, will and thrill), success criteria, three phases of learning (surface, deep and transfer) and an acquiring and consolidation phase within each of the surface and deep phases. A synthesis of 228 meta-analyses led to the identification of the most effective strategies. The results indicate that there is a subset of strategies that are effective, but this effectiveness depends on the phase of the model in which they are implemented. Further, it is best not to run separate sessions on learning strategies but to embed the various strategies within the content of the subject, to be clearer about developing both surface and deep learning, and promoting their associated optimal strategies and to teach the skills of transfer of learning. The article concludes with a discussion of questions raised by the model that need further research.

  19. Models for dependent time series

    CERN Document Server

    Tunnicliffe Wilson, Granville; Haywood, John

    2015-01-01

    Models for Dependent Time Series addresses the issues that arise and the methodology that can be applied when the dependence between time series is described and modeled. Whether you work in the economic, physical, or life sciences, the book shows you how to draw meaningful, applicable, and statistically valid conclusions from multivariate (or vector) time series data.The first four chapters discuss the two main pillars of the subject that have been developed over the last 60 years: vector autoregressive modeling and multivariate spectral analysis. These chapters provide the foundational mater

  20. TREAT Modeling and Simulation Strategy

    Energy Technology Data Exchange (ETDEWEB)

    DeHart, Mark David [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2015-09-01

    This report summarizes a four-phase process used to describe the strategy in developing modeling and simulation software for the Transient Reactor Test Facility. The four phases of this research and development task are identified as (1) full core transient calculations with feedback, (2) experiment modeling, (3) full core plus experiment simulation and (4) quality assurance. The document describes the four phases, the relationship between these research phases, and anticipated needs within each phase.

  1. Modeling local dependence in longitudinal IRT models

    DEFF Research Database (Denmark)

    Larsen, Maja Olsbjerg; Christensen, Karl Bang

    2015-01-01

    Measuring change in a latent variable over time is often done using the same instrument at several time points. This can lead to dependence between responses across time points for the same person yielding within person correlations that are stronger than what can be attributed to the latent...... variable. Ignoring this can lead to biased estimates of changes in the latent variable. In this paper we propose a method for modeling local dependence in the longitudinal 2PL model. It is based on the concept of item splitting, and makes it possible to correctly estimate change in the latent variable....

  2. Network Strategies in the Voter Model

    CERN Document Server

    Javarone, Marco Alberto

    2013-01-01

    We study a simple voter model with two competing parties. In particular, we represent the case of political elections, where people can choose to support one of the two competitors or to remain neutral. People interact in a social network and their opinion depends on those of their neighbors. Therefore, people may change opinion over time, i.e., they can support one competitor or none. The two competitors try to gain the people's consensus by interacting with their neighbors and also with other people. In particular, competitors define temporal connections, following a strategy, to interact with people they do not know, i.e., with all the people that are not their neighbors. We analyze the proposed model to investigate which network strategies are more advantageous, for the competitors, in order to gain the popular consensus. As result, we found that the best network strategy depends on the topology of the social network. Finally, we investigate how the charisma of competitors affects the outcomes of the prop...

  3. Succes on the International Market Depends on Brand Strategy

    Directory of Open Access Journals (Sweden)

    Victor Danciu

    2006-10-01

    Full Text Available Brand strategy is vital for the succes of the company on the international market. Identity and positionning are critical in order to develop a succesufull brand strategy. These two very important dimensions of any strategy of brand are accompanying every strategical option. Creating and launching new brands depend on the strategic process of the new product development. The new brands aim at acquiring strategic advantages which are associated with the enlargement of the competence field of the company and the differentiation over existing brands. In its turn, the extension of the brand is a strategic alternative which aims at the transfer or the relaunching of the existing brands. The companies which are following the geocentric strategy need global brands. Only the companies which succesfully overcome the numerous restrictions of the global strategy development are able to get good results. Apple is a good example of a brand strategy that gained a unique position on the global market and continues to help holding it.

  4. Telecommunication companies strategy depending on their stage of development

    Directory of Open Access Journals (Sweden)

    G. I. Tamoshina

    2012-01-01

    Full Text Available Telecommunication branch has an especial function in the economic of the country, because it major function is ensuring of the society's needs in information transmission. Depending on the companies' development degree on the market and also on the presence of the powerful local rival on the territory, the operator corresponds with definite group. The central strategy 4P (product, price, promotion, place adopts to the tasks which are actual for the concrete group.

  5. Boolean Queries and Term Dependencies in Probabilistic Retrieval Models.

    Science.gov (United States)

    Croft, W. Bruce

    1986-01-01

    Proposes approach to integrating Boolean and statistical systems where Boolean queries are interpreted as a means of specifying term dependencies in relevant set of documents. Highlights include series of retrieval experiments designed to test retrieval strategy based on term dependence model and relation of results to other work. (18 references)…

  6. Language Learning Strategies and Its Training Model

    Science.gov (United States)

    Liu, Jing

    2010-01-01

    This paper summarizes and reviews the literature regarding language learning strategies and it's training model, pointing out the significance of language learning strategies to EFL learners and an applicable and effective language learning strategies training model, which is beneficial both to EFL learners and instructors, is badly needed.

  7. Business model or strategy: which comes first?

    DEFF Research Database (Denmark)

    Friis, Jesper Deleuran; Lueg, Rainer; Mayanja, Remmy

    2015-01-01

    There is an ongoing debate on how the concepts of strategy and business models relate to each other. Specifically, it is a puzzle whether business models determine strategies, or whether strategies precede business models (Seddon et al., 2004). Based on recent conceptual considerations (Cavalcante...... et al., 2011), the authors attempt to solve this puzzle by considering their mutual influence at different stages of the company’s business lifecycle. For that, the auhors use Scandinavian Software Company (SSC) as a case study. The initial idea of a business model is shown to shape SSC’s strategy...... in the birth phase. It is then argued that this relationship changed as SSC entered its growth phase and met competition, and the product market strategy determined the change in the business model. The researchers contribute to the currently underexplored dynamic relationship of business models and strategies...

  8. Mining Social Entrepreneurship Strategies Using Topic Modeling.

    Science.gov (United States)

    Chandra, Yanto; Jiang, Li Crystal; Wang, Cheng-Jun

    2016-01-01

    Despite the burgeoning research on social entrepreneurship (SE), SE strategies remain poorly understood. Drawing on extant research on the social activism and social change, empowerment and SE models, we explore, classify and validate the strategies used by 2,334 social entrepreneurs affiliated with the world's largest SE support organization, Ashoka. The results of the topic modeling of the social entrepreneurs' strategy profiles reveal that they employed a total of 39 change-making strategies that vary across resources (material versus symbolic strategies), specificity (general versus specific strategies), and mode of participation (mass versus elite participation strategies); they also vary across fields of practice and time. Finally, we identify six meta-SE strategies-a reduction from the 39 strategies-and identify four new meta-SE strategies (i.e., system reform, physical capital development, evidence-based practices, and prototyping) that have been overlooked in prior SE research. Our findings extend and deepen the research into SE strategies and offer a comprehensive model of SE strategies that advances theory, practice and policy making.

  9. Mining Social Entrepreneurship Strategies Using Topic Modeling.

    Directory of Open Access Journals (Sweden)

    Yanto Chandra

    Full Text Available Despite the burgeoning research on social entrepreneurship (SE, SE strategies remain poorly understood. Drawing on extant research on the social activism and social change, empowerment and SE models, we explore, classify and validate the strategies used by 2,334 social entrepreneurs affiliated with the world's largest SE support organization, Ashoka. The results of the topic modeling of the social entrepreneurs' strategy profiles reveal that they employed a total of 39 change-making strategies that vary across resources (material versus symbolic strategies, specificity (general versus specific strategies, and mode of participation (mass versus elite participation strategies; they also vary across fields of practice and time. Finally, we identify six meta-SE strategies-a reduction from the 39 strategies-and identify four new meta-SE strategies (i.e., system reform, physical capital development, evidence-based practices, and prototyping that have been overlooked in prior SE research. Our findings extend and deepen the research into SE strategies and offer a comprehensive model of SE strategies that advances theory, practice and policy making.

  10. Context dependent DNA evolutionary models

    DEFF Research Database (Denmark)

    Jensen, Jens Ledet

    This paper is about stochastic models for the evolution of DNA. For a set of aligned DNA sequences, connected in a phylogenetic tree, the models should be able to explain - in probabilistic terms - the differences seen in the sequences. From the estimates of the parameters in the model one can...

  11. Business model or strategy: which comes first?

    DEFF Research Database (Denmark)

    Friis, Jesper Deleuran; Lueg, Rainer; Mayanja, Remmy;

    2015-01-01

    in the birth phase. It is then argued that this relationship changed as SSC entered its growth phase and met competition, and the product market strategy determined the change in the business model. The researchers contribute to the currently underexplored dynamic relationship of business models and strategies...

  12. Performance of hedging strategies in interval models

    NARCIS (Netherlands)

    Roorda, Berend; Engwerda, Jacob; Schumacher, J.M.

    2005-01-01

    For a proper assessment of risks associated with the trading of derivatives, the performance of hedging strategies should be evaluated not only in the context of the idealized model that has served as the basis of strategy development, but also in the context of other models. In this paper we consid

  13. Modeling and Generating Strategy Games Mechanics

    DEFF Research Database (Denmark)

    Mahlmann, Tobias

    of the game is, how players may manipulate the game world, etc. We present the Strategy Games Description Language (SGDL), a tree-based approach to model the game mechanics of strategy games. SGDL allows game designers to rapid prototype their game ideas with the help of our customisable game engine. We...... present several example games to demonstrate the capabilities of the language and how to model common strategy game elements. Furthermore, we present methods to procedurally generate and evaluate game mechanics modelled in SGDL in terms of enjoyability. We argue that an evolutionary process can be used......Strategy games are a popular genre of games with a long history, originating from games like Chess or Go. The first strategy games were published as “Kriegspiele” (engl. wargames) in the late 18th century, intended for the education of young cadets. Since then strategy games were refined...

  14. CLASSICAL RISK MODEL WITH THRESHOLD DIVIDEND STRATEGY

    Institute of Scientific and Technical Information of China (English)

    Zhou Ming; Guo Junyi

    2008-01-01

    In this article, a threshold dividend strategy is used for classical risk model.Under this dividend strategy, certain probability of ruin, which occurs in case of constant barrier strategy, is avoided. Using the strong Markov property of the surplus process and the distribution of the deficit in classical risk model, the survival probability for this model is derived, which is more direct than that in Asmussen(2000, P195, Proposition 1.10). The occupation time of non-dividend of this model is also discussed by means of Martingale method.

  15. Telestroke network business model strategies.

    Science.gov (United States)

    Fanale, Christopher V; Demaerschalk, Bart M

    2012-10-01

    Our objective is to summarize the evidence that supports the reliability of telemedicine for diagnosis and efficacy in acute stroke treatment, identify strategies for funding the development of a telestroke network, and to present issues with respect to economic sustainability, cost effectiveness, and the status of reimbursement for telestroke. Copyright © 2012 National Stroke Association. Published by Elsevier Inc. All rights reserved.

  16. Modeling Business Strategy: A Consumer Value Perspective

    OpenAIRE

    Svee, Eric-Oluf; Giannoulis, Constantinos; Zdravkovic, Jelena

    2011-01-01

    Part 3: Business Modeling; International audience; Business strategy lays out the plan of an enterprise to achieve its vision by providing value to its customers. Typically, business strategy focuses on economic value and its relevant exchanges with customers and does not directly address consumer values. However, consumer values drive customers’ choices and decisions to use a product or service, and therefore should have a direct impact on business strategy. This paper explores whether and h...

  17. The challenges of automobile-dependent urban transport strategy

    Directory of Open Access Journals (Sweden)

    Jovanović Miomir

    2015-01-01

    Full Text Available The fundamental aims of sustainable urban development and the pro-automobile oriented economic development are on a collision course. It is obvious that automobile-dependent urban development is under heavy/powerful influence of the automobile lobby (automobile and oil industries, along with construction. In this domain famous land-use-transportation studies (or ‘grand transportation studies’ are, unfortunately, still prevailing - a vicious circle of self-fulfilling prophecy of congestion, road building, sprawl, congestion and more road building. Until recently, it was commonly thought that investment in public transport was not economically sustainable and that focusing on the development of the automobile industry and financing the construction of roadways stimulated economic growth. In this paper we clearly show that automobile industry is now overcapitalized, less profitable than many other industries (and may become even less profitable in the future, that transport market is characterized with huge distortions (more than a third of motor-vehicle use can be explained by underpriced driving, while new road investment does not have a major impact on economic growth (especially in a region with an already well-developed infrastructure, and that pro-automobile transport strategy inexorably incurs harmful global, regional and local ecological consequences. [Projekat Ministarstva nauke Republike Srbije, br. 37010

  18. Control strategy of hand movement depends on target redundancy.

    Science.gov (United States)

    Togo, Shunta; Yoshioka, Toshinori; Imamizu, Hiroshi

    2017-03-31

    Reaching toward a point target has been intensively studied in human motor control. However, little is known about reaching toward a redundant target, such as grasping a bar, in which the grasping point is irrelevant to the achievement of a task. We examined whether humans could solve the target-redundancy and control problems in a serial fashion or control their body without solving the target-redundancy problem. We equalized the target ranges between two reaching tasks: a point-to-point reaching task without target-redundancy and a point-to-bar reaching task with target-redundancy. In the both tasks, we measured hand viscoelasticity at movement end as parameters that reflect the adopted control strategy. As a result, the hand viscoelasticity in the point-to-bar reaching task was smaller than that in the point-to-point reaching task, even under the same kinematics. These results indicate that the hand viscoelasticity was modulated depending on the target-redundancy. Moreover, it is suggested that a human reaches toward a redundant target by effectively utilizing information of target redundancy rather than explicitly solving the target-redundancy problem.

  19. Limited dependent variable models for panel data

    NARCIS (Netherlands)

    Charlier, E.

    1997-01-01

    Many economic phenomena require limited variable models for an appropriate treatment. In addition, panel data models allow the inclusion of unobserved individual-specific effects. These models are combined in this thesis. Distributional assumptions in the limited dependent variable models are

  20. SOFT MODELLING AND SIMULATION IN STRATEGY

    Directory of Open Access Journals (Sweden)

    Luciano Rossoni

    2006-06-01

    Full Text Available A certain resistance on the part of the responsible controllers for the strategy exists, in using techniques and tools of modeling and simulation. Many find them excessively complicated, already others see them as rigid and mathematical for excessively for the use of strategies in uncertain and turbulent environments. However, some interpretative boarding that take care of, in part exist, the necessities of these borrowers of decision. The objective of this work is to demonstrate of a clear and simple form, some of the most powerful boarding, methodologies and interpretative tools (soft of modeling and simulation in the business-oriented area of strategy. We will define initially, what they are on models, simulation and some aspects to the modeling and simulation in the strategy area. Later we will see some boarding of modeling soft, that they see the modeling process much more of that simply a mechanical process, therefore, as seen for Simon, the human beings rationally are limited and its decisions are influenced by a series of questions of subjective character, related to the way where it is inserted. Keywords: strategy, modeling and simulation, soft systems methodology, cognitive map, systems dynamics.

  1. Performance Study on Priority Strategies for WDM Packet Switches under Long-Range Dependent Traffic

    Institute of Scientific and Technical Information of China (English)

    Chia-Wei; Yu; Chao-Chih; Chang; Shou-Kuo; Shao; Jingshown; Wu

    2003-01-01

    The impact of long-range dependent (LRD) traffic on the buffer management schemes for WDM packet switches is studied by simulation. The different priority strategies are compared. The principles of efficient strategy design are also presented.

  2. Wind farm models and control strategies

    Energy Technology Data Exchange (ETDEWEB)

    Soerensen, Poul; Hansen, Anca D.; Iov, F.; Blaabjerg, F.; Donovan, M.H.

    2005-08-01

    This report describes models and control strategies for 3 different concepts of wind farms. Initially, the potential in improvement of grid integration, structural loads and energy production is investigated in a survey of opportunities. Then simulation models are described, including wind turbine models for a fixed speed wind turbine with active stall control and a variable speed wind turbine with doubly-fed induction generator. After that, the 3 wind farm concepts and control strategies are described. The 3 concepts are AC connected doubly fed turbines, AC connected active stall turbines and DC connected active stall turbines. Finally, some simulation examples and conclusions are presented. (au)

  3. Testing Strategies for Model-Based Development

    Science.gov (United States)

    Heimdahl, Mats P. E.; Whalen, Mike; Rajan, Ajitha; Miller, Steven P.

    2006-01-01

    This report presents an approach for testing artifacts generated in a model-based development process. This approach divides the traditional testing process into two parts: requirements-based testing (validation testing) which determines whether the model implements the high-level requirements and model-based testing (conformance testing) which determines whether the code generated from a model is behaviorally equivalent to the model. The goals of the two processes differ significantly and this report explores suitable testing metrics and automation strategies for each. To support requirements-based testing, we define novel objective requirements coverage metrics similar to existing specification and code coverage metrics. For model-based testing, we briefly describe automation strategies and examine the fault-finding capability of different structural coverage metrics using tests automatically generated from the model.

  4. Supply chain strategies, issues and models

    CERN Document Server

    Ramanathan, Ramakrishnan

    2014-01-01

    In the 21st century, supply chain operations and relationships among supply chain partners have become highly challenging, necessitating new approaches, e.g., the development of new models. Supply Chain Strategies, Issues and Models discusses supply chain issues and models with examples from actual industrial cases. Expert authors with a wide spectrum of knowledge working in various areas of supply chain management from various geographical locations offer refreshing, novel and insightful ideas and address possible solutions using established theories and models. Supply Chain Strategies, Issues and Models features studies that have used mathematical modeling, statistical analyses and also descriptive qualitative studies. The chapters cover many relevant themes related to supply chains and logistics including supply chain complexity, information sharing, quality (six sigma), electronic Kanbans, inventory models, scheduling, purchasing and contracts. To facilitate easy reading, the chapters that deal with suppl...

  5. Time-adaptive versus history-adaptive strategies for multicriterion routing in stochastic time-dependent networks

    DEFF Research Database (Denmark)

    Pretolani, Daniele; Nielsen, Lars Relund; Andersen, Kim Allan;

    We compare two different models for multicriterion routing in stochastic time-dependent networks: the  classic "time-adaptive'' route choice and the more flexible "history-adaptive'' route choice. We point out some interesting properties of the sets of efficient solutions ("strategies'') found...... under the two models. We also suggest possible directions for improving computational techniques....

  6. Hydrologic modeling strategy for the Islamic Republic of Mauritania, Africa

    Science.gov (United States)

    Friedel, Michael J.

    2008-01-01

    The government of Mauritania is interested in how to maintain hydrologic balance to ensure a long-term stable water supply for minerals-related, domestic, and other purposes. Because of the many complicating and competing natural and anthropogenic factors, hydrologists will perform quantitative analysis with specific objectives and relevant computer models in mind. Whereas various computer models are available for studying water-resource priorities, the success of these models to provide reliable predictions largely depends on adequacy of the model-calibration process. Predictive analysis helps us evaluate the accuracy and uncertainty associated with simulated dependent variables of our calibrated model. In this report, the hydrologic modeling process is reviewed and a strategy summarized for future Mauritanian hydrologic modeling studies.

  7. Evolution of learned strategy choice in a frequency-dependent game.

    Science.gov (United States)

    Katsnelson, Edith; Motro, Uzi; Feldman, Marcus W; Lotem, Arnon

    2012-03-22

    In frequency-dependent games, strategy choice may be innate or learned. While experimental evidence in the producer-scrounger game suggests that learned strategy choice may be common, a recent theoretical analysis demonstrated that learning by only some individuals prevents learning from evolving in others. Here, however, we model learning explicitly, and demonstrate that learning can easily evolve in the whole population. We used an agent-based evolutionary simulation of the producer-scrounger game to test the success of two general learning rules for strategy choice. We found that learning was eventually acquired by all individuals under a sufficient degree of environmental fluctuation, and when players were phenotypically asymmetric. In the absence of sufficient environmental change or phenotypic asymmetries, the correct target for learning seems to be confounded by game dynamics, and innate strategy choice is likely to be fixed in the population. The results demonstrate that under biologically plausible conditions, learning can easily evolve in the whole population and that phenotypic asymmetry is important for the evolution of learned strategy choice, especially in a stable or mildly changing environment.

  8. Wind farm models and control strategies

    DEFF Research Database (Denmark)

    Sørensen, Poul Ejnar; Hansen, Anca Daniela; Iov, F.;

    2005-01-01

    models for a fixed speed wind turbine with active stall control and a variable speed wind turbine with doubly-fed induction generator. After that, the 3 wind farm concepts and control strategies are described.The 3 concepts are AC connected doubly fed turbines, AC connected active stall turbines and DC......This report describes models and control strategies for 3 different concepts of wind farms. Initially, the potential in improvement of grid integration, structural loads and energy production is investigated in a survey of opportunities. Then simulationmodels are described, including wind turbine...

  9. Pseudoabsence generation strategies for species distribution models.

    Directory of Open Access Journals (Sweden)

    Brice B Hanberry

    Full Text Available BACKGROUND: Species distribution models require selection of species, study extent and spatial unit, statistical methods, variables, and assessment metrics. If absence data are not available, another important consideration is pseudoabsence generation. Different strategies for pseudoabsence generation can produce varying spatial representation of species. METHODOLOGY: We considered model outcomes from four different strategies for generating pseudoabsences. We generating pseudoabsences randomly by 1 selection from the entire study extent, 2 a two-step process of selection first from the entire study extent, followed by selection for pseudoabsences from areas with predicted probability <25%, 3 selection from plots surveyed without detection of species presence, 4 a two-step process of selection first for pseudoabsences from plots surveyed without detection of species presence, followed by selection for pseudoabsences from the areas with predicted probability <25%. We used Random Forests as our statistical method and sixteen predictor variables to model tree species with at least 150 records from Forest Inventory and Analysis surveys in the Laurentian Mixed Forest province of Minnesota. CONCLUSIONS: Pseudoabsence generation strategy completely affected the area predicted as present for species distribution models and may be one of the most influential determinants of models. All the pseudoabsence strategies produced mean AUC values of at least 0.87. More importantly than accuracy metrics, the two-step strategies over-predicted species presence, due to too much environmental distance between the pseudoabsences and recorded presences, whereas models based on random pseudoabsences under-predicted species presence, due to too little environmental distance between the pseudoabsences and recorded presences. Models using pseudoabsences from surveyed plots produced a balance between areas with high and low predicted probabilities and the strongest

  10. Selection Strategies for Social Influence in the Threshold Model

    Science.gov (United States)

    Karampourniotis, Panagiotis; Szymanski, Boleslaw; Korniss, Gyorgy

    The ubiquity of online social networks makes the study of social influence extremely significant for its applications to marketing, politics and security. Maximizing the spread of influence by strategically selecting nodes as initiators of a new opinion or trend is a challenging problem. We study the performance of various strategies for selection of large fractions of initiators on a classical social influence model, the Threshold model (TM). Under the TM, a node adopts a new opinion only when the fraction of its first neighbors possessing that opinion exceeds a pre-assigned threshold. The strategies we study are of two kinds: strategies based solely on the initial network structure (Degree-rank, Dominating Sets, PageRank etc.) and strategies that take into account the change of the states of the nodes during the evolution of the cascade, e.g. the greedy algorithm. We find that the performance of these strategies depends largely on both the network structure properties, e.g. the assortativity, and the distribution of the thresholds assigned to the nodes. We conclude that the optimal strategy needs to combine the network specifics and the model specific parameters to identify the most influential spreaders. Supported in part by ARL NS-CTA, ARO, and ONR.

  11. Inventive city-regions: path dependence and creative knowledge strategies

    NARCIS (Netherlands)

    Bontje, M.; Musterd, S.; Pelzer, P.

    2011-01-01

    Virtually every city and region in West and Central Europe has developed policies and strategies to attract, retain and encourage creative industries and knowledge-intensive services. Since most of these cities and regions tend to see a creative knowledge economy as 'the best bet for the future', on

  12. Models of the Sociocultural Strategies of Today's College Students

    Science.gov (United States)

    Gritsenko, G. D.; Maslova, T. F.

    2013-01-01

    Survey data suggest that there are several models of sociocultural strategy used by Russian students, each with a specific hierarchy of values. A typical model is the traditionalist strategy, although the achievement-oriented strategy is also quite widespread.

  13. Modelling emergent trophic strategies in plankton

    DEFF Research Database (Denmark)

    Andersen, Ken Haste; Aksnes, Dag L.; Berge, Terje;

    2015-01-01

    Plankton are typically divided into phytoplankton and zooplankton in marine ecosystem models. Yet, most protists in the photic zone engage in some degree of phagotrophy, and it has been suggested that trophic strategy is really a continuum between pure phototrophs (phytoplankton) and pure...... phagotrophs (unicellular zooplankton). Such a continuum of trophic strategies is well represented by trait-based modelling techniques. A key model ingredient is the size of individual cells, as size constrains affinities for nutrient uptake, photosynthesis and active encounter with other cells. We outline...... a general trait-based model of a unicellular planktonic organism where size is a central trait and where nutrient uptake, photosynthesis and phagotrophy are determined by investments into these functions and by the physical constraints imposed by organism size. This framework provides simple predictions...

  14. Persistence Modeling for Assessing Marketing Strategy Performance

    NARCIS (Netherlands)

    M.G. Dekimpe (Marnik); D.M. Hanssens (Dominique)

    2003-01-01

    textabstractThe question of long-run market response lies at the heart of any marketing strategy that tries to create a sustainable competitive advantage for the firm or brand. A key challenge, however, is that only short-run results of marketing actions are readily observable. Persistence modeling

  15. Persistence Modeling for Assessing Marketing Strategy Performance

    NARCIS (Netherlands)

    M.G. Dekimpe (Marnik); D.M. Hanssens (Dominique)

    2003-01-01

    textabstractThe question of long-run market response lies at the heart of any marketing strategy that tries to create a sustainable competitive advantage for the firm or brand. A key challenge, however, is that only short-run results of marketing actions are readily observable. Persistence modeling

  16. Individual Hearing Loss: Characterization, Modelling, Compensation Strategies

    DEFF Research Database (Denmark)

    Santurette, Sébastien; Dau, Torsten; Christensen-Dalsgaard, Jakob;

    2016-01-01

    account for such individual differences, which make it challenging to find adequate compensation strategies in hearing devices. How to characterize, model, and compensate for individual hearing loss were the main topics of the fifth International Symposium on Auditory and Audiological Research (ISAAR...

  17. A Pareto Improving Strategy for the Time-Dependent Morning Commute Problem

    OpenAIRE

    Garcia, Reinaldo Crispiniano

    1999-01-01

    This dissertation describes a strategy which makes all commuters better off (i.e. a Pareto effecient strategy) for the time-dependent morning commute problem, even if the collected revenues are not returned to the population of commuters. The proposed strategy will apply road pricing as a tool for congestion management, a practice usually called congestion pricing. 

  18. The Strategies of Modeling in Biology Education

    Science.gov (United States)

    Svoboda, Julia; Passmore, Cynthia

    2013-01-01

    Modeling, like inquiry more generally, is not a single method, but rather a complex suite of strategies. Philosophers of biology, citing the diverse aims, interests, and disciplinary cultures of biologists, argue that modeling is best understood in the context of its epistemic aims and cognitive payoffs. In the science education literature, modeling has been discussed in a variety of ways, but often without explicit reference to the diversity of roles models play in scientific practice. We aim to expand and bring clarity to the myriad uses of models in science by presenting a framework from philosopher of biology Jay Odenbaugh that describes five pragmatic strategies of model use in the biological sciences. We then present illustrative examples of each of these roles from an empirical study of an undergraduate biological modeling curriculum, which highlight how students used models to help them frame their research question, explore ideas, and refine their conceptual understanding in an educational setting. Our aim is to begin to explicate the definition of modeling in science in a way that will allow educators and curriculum developers to make informed choices about how and for what purpose modeling enters science classrooms.

  19. Exploring the Interconnectedness among Strategy Development, Shared Mental Models, Organisational Learning and Organisational Change

    Science.gov (United States)

    Malan, Renee

    2011-01-01

    The cognitive psychological processes related to learning and change behaviour are factors that impact on organisational strategy development. Strategy development is dependent on strategic thinking that is reciprocally influenced by shared mental models, organisational learning and organisational change. Although strategy development, shared…

  20. Exploring the Interconnectedness among Strategy Development, Shared Mental Models, Organisational Learning and Organisational Change

    Science.gov (United States)

    Malan, Renee

    2011-01-01

    The cognitive psychological processes related to learning and change behaviour are factors that impact on organisational strategy development. Strategy development is dependent on strategic thinking that is reciprocally influenced by shared mental models, organisational learning and organisational change. Although strategy development, shared…

  1. Temperature dependent extension of a hysteresis model

    OpenAIRE

    Sixdenier, Fabien; MESSAL, Oualid; Hilal, Alaa; Martin, Christian; Raulet, Marie-Ange

    2015-01-01

    International audience; Some soft magnetic materials (like ferrites but not only) are strongly dependent of the temperature. In order to predict their behaviour in electrical devices, engineers need hysteresis models able to take into account the temperature. This paper is an attempt to take into account the temperature in an existing model of hysteresis through its parameters. Variations of some parameters are issued from Weiss’s works and others have to be fitted numerically. Simulation res...

  2. Environmental dependence in the ellipsoidal collapse model

    CERN Document Server

    Desjacques, Vincent

    2007-01-01

    N-body simulations have demonstrated a correlation between the properties of haloes and their environment. In this paper, we assess whether the ellipsoidal collapse model can produce a similar dependence. First, we explore the statistical correlation that originates from Gaussian initial conditions. We derive analytic expressions for a number of joint statistics of the shear tensor and estimate the sensitivity of the local characteristics of the shear to the global geometry of the large scale environment. Next, we concentrate on the dynamical aspect of the environmental dependence using a simplified model that takes into account the interaction between a collapsing halo and its environment. We find that the tidal force exerted by the surrounding mass distribution causes haloes embedded in overdense regions to virialize earlier. An effective density threshold whose shape depends on the large scale density provides a good description of this environmental effect. We show that, using this approach, a correlation...

  3. Impact of coverage-dependent marginal costs on optimal HPV vaccination strategies.

    Science.gov (United States)

    Ryser, Marc D; McGoff, Kevin; Herzog, David P; Sivakoff, David J; Myers, Evan R

    2015-06-01

    The effectiveness of vaccinating males against the human papillomavirus (HPV) remains a controversial subject. Many existing studies conclude that increasing female coverage is more effective than diverting resources into male vaccination. Recently, several empirical studies on HPV immunization have been published, providing evidence of the fact that marginal vaccination costs increase with coverage. In this study, we use a stochastic agent-based modeling framework to revisit the male vaccination debate in light of these new findings. Within this framework, we assess the impact of coverage-dependent marginal costs of vaccine distribution on optimal immunization strategies against HPV. Focusing on the two scenarios of ongoing and new vaccination programs, we analyze different resource allocation policies and their effects on overall disease burden. Our results suggest that if the costs associated with vaccinating males are relatively close to those associated with vaccinating females, then coverage-dependent, increasing marginal costs may favor vaccination strategies that entail immunization of both genders. In particular, this study emphasizes the necessity for further empirical research on the nature of coverage-dependent vaccination costs.

  4. Impact of coverage-dependent marginal costs on optimal HPV vaccination strategies

    Directory of Open Access Journals (Sweden)

    Marc D. Ryser

    2015-06-01

    Full Text Available The effectiveness of vaccinating males against the human papillomavirus (HPV remains a controversial subject. Many existing studies conclude that increasing female coverage is more effective than diverting resources into male vaccination. Recently, several empirical studies on HPV immunization have been published, providing evidence of the fact that marginal vaccination costs increase with coverage. In this study, we use a stochastic agent-based modeling framework to revisit the male vaccination debate in light of these new findings. Within this framework, we assess the impact of coverage-dependent marginal costs of vaccine distribution on optimal immunization strategies against HPV. Focusing on the two scenarios of ongoing and new vaccination programs, we analyze different resource allocation policies and their effects on overall disease burden. Our results suggest that if the costs associated with vaccinating males are relatively close to those associated with vaccinating females, then coverage-dependent, increasing marginal costs may favor vaccination strategies that entail immunization of both genders. In particular, this study emphasizes the necessity for further empirical research on the nature of coverage-dependent vaccination costs.

  5. Integrating models that depend on variable data

    Science.gov (United States)

    Banks, A. T.; Hill, M. C.

    2016-12-01

    Models of human-Earth systems are often developed with the goal of predicting the behavior of one or more dependent variables from multiple independent variables, processes, and parameters. Often dependent variable values range over many orders of magnitude, which complicates evaluation of the fit of the dependent variable values to observations. Many metrics and optimization methods have been proposed to address dependent variable variability, with little consensus being achieved. In this work, we evaluate two such methods: log transformation (based on the dependent variable being log-normally distributed with a constant variance) and error-based weighting (based on a multi-normal distribution with variances that tend to increase as the dependent variable value increases). Error-based weighting has the advantage of encouraging model users to carefully consider data errors, such as measurement and epistemic errors, while log-transformations can be a black box for typical users. Placing the log-transformation into the statistical perspective of error-based weighting has not formerly been considered, to the best of our knowledge. To make the evaluation as clear and reproducible as possible, we use multiple linear regression (MLR). Simulations are conducted with MatLab. The example represents stream transport of nitrogen with up to eight independent variables. The single dependent variable in our example has values that range over 4 orders of magnitude. Results are applicable to any problem for which individual or multiple data types produce a large range of dependent variable values. For this problem, the log transformation produced good model fit, while some formulations of error-based weighting worked poorly. Results support previous suggestions fthat error-based weighting derived from a constant coefficient of variation overemphasizes low values and degrades model fit to high values. Applying larger weights to the high values is inconsistent with the log

  6. Drosophila as a model for context-dependent tumorigenesis.

    Science.gov (United States)

    Tipping, Marla; Perrimon, Norbert

    2014-01-01

    Drosophila can exhibit classic hallmarks of cancer, such as evasion of apoptosis, sustained proliferation, metastasis, prolonged survival, genome instability, and metabolic reprogramming, when cancer-related genes are perturbed. In the last two decades, studies in flies have identified several tumor suppressor and oncogenes. However, the greatest strength of the fly lies in its ability to model cancer hallmarks in a variety of tissue types, which enables the study of context-dependent tumorigenesis. We review the organs and tissues that have been used to model tumor formation, and propose new strategies to maximize the potential of Drosophila in cancer research.

  7. Donations and dependence: Individual contributor strategies in house elections.

    Science.gov (United States)

    Heerwig, Jennifer A

    2016-11-01

    Despite the importance of individual contributors to financing federal candidates, past work has largely neglected this crucial financial constituency in favor of research on corporate and trade political action committees (PACs). By contrast, in this study I offer the first analysis of aggregate contributions from the population of individual contributors to House candidates. Using an original big dataset constructed from over fifteen million Federal Election Commission (FEC) disclosure records, I identify individual contributors (rather than contributions) and trace the variation in their strategies across types of House candidates. I distinguish between frequent donors, who are theorized to have more contact with members of Congress, versus infrequent donors in these elections. I find evidence that the character of aggregate donations from repeat donors is more access-oriented even while controlling for other salient candidate characteristics. Funds from infrequent donors, in contrast, appear more ideologically motivated. By also examining the percentage of funds that House candidates receive from repeat donors, I show that the fundraising coalitions of candidates may reproduce reliance on more access-oriented, repeat donors despite the influx of dollars from infrequent donors. I suggest that my findings provide a persuasive case for re-evaluating the diversity of roles individual contributors play in the campaign finance system, and for systematically analyzing variation in contributor strategies. Copyright © 2016 Elsevier Inc. All rights reserved.

  8. Politeness Strategies Used in Requests--A Cybernetic Model.

    Science.gov (United States)

    Kitao, Kenji

    This paper discusses a cybernetic model of politeness strategies used in the process of making a request. The concept of systems, cybernetic models, and politeness strategies are reviewed, and the way they work together in the proposed model is examined. Politeness strategies are communication strategies used to change behavior enough to achieve…

  9. Error handling strategies in multiphase inverse modeling

    Energy Technology Data Exchange (ETDEWEB)

    Finsterle, S.; Zhang, Y.

    2010-12-01

    Parameter estimation by inverse modeling involves the repeated evaluation of a function of residuals. These residuals represent both errors in the model and errors in the data. In practical applications of inverse modeling of multiphase flow and transport, the error structure of the final residuals often significantly deviates from the statistical assumptions that underlie standard maximum likelihood estimation using the least-squares method. Large random or systematic errors are likely to lead to convergence problems, biased parameter estimates, misleading uncertainty measures, or poor predictive capabilities of the calibrated model. The multiphase inverse modeling code iTOUGH2 supports strategies that identify and mitigate the impact of systematic or non-normal error structures. We discuss these approaches and provide an overview of the error handling features implemented in iTOUGH2.

  10. A Simulation Model for Evaluating Distributed Systems Dependability

    CERN Document Server

    Dobre, Ciprian; Cristea, Valentin

    2012-01-01

    In this paper we present a new simulation model designed to evaluate the dependability in distributed systems. This model extends the MONARC simulation model with new capabilities for capturing reliability, safety, availability, security, and maintainability requirements. The model has been implemented as an extension of the multithreaded, process oriented simulator MONARC, which allows the realistic simulation of a wide-range of distributed system technologies, with respect to their specific components and characteristics. The extended simulation model includes the necessary components to inject various failure events, and provides the mechanisms to evaluate different strategies for replication, redundancy procedures, and security enforcement mechanisms, as well. The results obtained in simulation experiments presented in this paper probe that the use of discrete-event simulators, such as MONARC, in the design and development of distributed systems is appealing due to their efficiency and scalability.

  11. A heuristic model of alcohol dependence.

    Directory of Open Access Journals (Sweden)

    Zhen Qi

    Full Text Available BACKGROUND: Substance dependence poses a critical health problem. Sadly, its neurobiological mechanisms are still unclear, and this lack of real understanding is reflected in insufficient treatment options. It has been hypothesized that alcohol effects are due to an imbalance between neuroexcitatory and neuroinhibitory amino acids. However, glutamate and GABA interact with other neurotransmitters, which form a complicated network whose functioning evades intuition and should be investigated systemically with methods of biomedical systems analysis. METHODS AND RESULTS: We present a heuristic model of neurotransmitters that combines a neurochemical interaction matrix at the biochemical level with a mobile describing the balances between pairs of neurotransmitters at the physiological and behavioral level. We investigate the effects of alcohol on the integrated neurotransmitter systems at both levels. The model simulation results are consistent with clinical and experimental observations. The model demonstrates that the drug diazepam for symptoms of alcohol withdrawal effectively reduces the imbalances between neurotransmitters. Moreover, the acetylcholine signal is suggested as a novel target for treatment of symptoms associated with alcohol withdrawal. CONCLUSIONS: Efficient means of integrating clinical symptoms across multiple levels are still scarce and difficult to establish. We present a heuristic model of systemic neurotransmitter functionality that permits the assessment of genetic, biochemical, and pharmacological perturbations. The model can serve as a tool to represent clinical and biological observations and explore various scenarios associated with alcohol dependence and its treatments. It also is very well suited for educational purposes.

  12. Colour dependence of zodiacal light models

    Science.gov (United States)

    Giese, R. H.; Hanner, M. S.; Leinert, C.

    1973-01-01

    Colour models of the zodiacal light in the ecliptic have been calculated for both dielectric and metallic particles in the sub-micron and micron size range. Two colour ratios were computed, a blue ratio and a red ratio. The models with a size distribution proportional to s to the -2.5 power ds (where s is the particle radius) generally show a colour close to the solar colour and almost independent of elongation. Especially in the blue colour ratio there is generally no significant dependence on the lower cutoff size (0.1-1 micron). The main feature of absorbing particles is a reddening at small elongations. The models for size distributions proportional to s to the -4 power ds show larger departures from solar colour and more variation with model parameters. Colour measurements, including red and near infra-red, therefore are useful to distinguish between flat and steep size spectra and to verify the presence of slightly absorbing particles.

  13. Inflation and the Scale Dependent Spectral Index: Prospects and Strategies

    CERN Document Server

    Adshead, Peter; Pritchard, Jonathan; Loeb, Abraham

    2010-01-01

    We consider the running of the spectral index as a probe of both inflation itself, and of the overall evolution of the very early universe. Surveying a collection of simple single field inflationary models, we confirm that the magnitude of the running is relatively consistent, unlike the tensor amplitude, which varies by orders of magnitude. Given this target, we confirm that the running is potentially detectable by future large scale structure or 21 cm observations, but that only the most futuristic measurements can distinguish between these models on the basis of their running. For any specified inflationary scenario, the combination of the running index and unknown post-inflationary expansion history induces a theoretical uncertainty in the predicted value of the spectral index. This effect can easily dominate the statistical uncertainty with which Planck and its successors are expected to measure the spectral index. More positively, upcoming cosmological experiments thus provide an intriguing probe of phy...

  14. Combined optimization model for sustainable energization strategy

    Science.gov (United States)

    Abtew, Mohammed Seid

    Access to energy is a foundation to establish a positive impact on multiple aspects of human development. Both developed and developing countries have a common concern of achieving a sustainable energy supply to fuel economic growth and improve the quality of life with minimal environmental impacts. The Least Developing Countries (LDCs), however, have different economic, social, and energy systems. Prevalence of power outage, lack of access to electricity, structural dissimilarity between rural and urban regions, and traditional fuel dominance for cooking and the resultant health and environmental hazards are some of the distinguishing characteristics of these nations. Most energy planning models have been designed for developed countries' socio-economic demographics and have missed the opportunity to address special features of the poor countries. An improved mixed-integer programming energy-source optimization model is developed to address limitations associated with using current energy optimization models for LDCs, tackle development of the sustainable energization strategies, and ensure diversification and risk management provisions in the selected energy mix. The Model predicted a shift from traditional fuels reliant and weather vulnerable energy source mix to a least cost and reliable modern clean energy sources portfolio, a climb on the energy ladder, and scored multifaceted economic, social, and environmental benefits. At the same time, it represented a transition strategy that evolves to increasingly cleaner energy technologies with growth as opposed to an expensive solution that leapfrogs immediately to the cleanest possible, overreaching technologies.

  15. Implementation Strategies for Orbital-dependent Density Functionals

    Science.gov (United States)

    Bento, Marsal E.; Vieira, Daniel

    2016-12-01

    The development of density functional theory (DFT) has been focused primarily on two main pillars: (1) the pursuit of more accurate exchange-correlation (XC) density functionals; (2) the feasibility of computational implementation when dealing with many-body systems. In this context, this work is aimed on using one-dimensional quantum systems as theoretical laboratories to investigate the implementation of orbital functionals (OFs) of density. By definition, OFs are those which depend only implicitly on the density, via an explicit formulation in terms of Kohn-Sham orbitals. Typical examples are the XC functionals arising from the Perdew-Zunger self-interaction correction (PZSIC). Formally, via Kohn-Sham equations, the implementation of OFs must be performed by means of the optimized effective potential method (OEP), which is known by requiring an excessive computational effort even when dealing with few electrons systems. Here, we proceed a systematical investigation aiming to simplify or avoid the OEP procedure, taking as reference the implementation of the PZSIC correction applied to one-dimensional Hubbard chains.

  16. Mass communication and development: impact depends on strategies.

    Science.gov (United States)

    Wete, F N

    1988-01-01

    Development scholars are moving toward an emphasis on noneconomic factors (social values, social advancement, equality, individual freedom) and their interactions with labor, capital, and technology. People are now conceptualized as the agents of change, and they in turn must be convinced of the need for change. This new approach implies a need for a review of the role of mass communication in development. A central question is whether development makes possible mass communication development or do improved mass communication facilities--and the resulting increase in the flow of information--make possible economic and social development. Although there have undoubtedly been incidents in which self-serving politicians have used mass communication to oppress the masses, the mass media has the potential to be a powerful force in the education of the society, the sharing of consciousness, the creation of nationhood, and the promotion of socioeconomic development. Mass communication is, for example, vital in the development approach that accords importance to self-sufficiency at the village level. The mass media can be used in such cases to transmit information of a background nature to a group or community about their expressed needs and to disseminate innovations that may need these needs. In the final analysis, mass media's role in development depends on the media's messages reaching the target audiences. This underscores the importance of analyzing in advance who will be the recipients of a mass media campaign and encouraging community involvement in communications planning.

  17. Implementation Strategies for Orbital-dependent Density Functionals

    Science.gov (United States)

    Bento, Marsal E.; Vieira, Daniel

    2016-10-01

    The development of density functional theory (DFT) has been focused primarily on two main pillars: (1) the pursuit of more accurate exchange-correlation (XC) density functionals; (2) the feasibility of computational implementation when dealing with many-body systems. In this context, this work is aimed on using one-dimensional quantum systems as theoretical laboratories to investigate the implementation of orbital functionals (OFs) of density. By definition, OFs are those which depend only implicitly on the density, via an explicit formulation in terms of Kohn-Sham orbitals. Typical examples are the XC functionals arising from the Perdew-Zunger self-interaction correction (PZSIC). Formally, via Kohn-Sham equations, the implementation of OFs must be performed by means of the optimized effective potential method (OEP), which is known by requiring an excessive computational effort even when dealing with few electrons systems. Here, we proceed a systematical investigation aiming to simplify or avoid the OEP procedure, taking as reference the implementation of the PZSIC correction applied to one-dimensional Hubbard chains.

  18. COMMUNICATION STRATEGY ABOUT BUSINESS MODELS: STAKEHOLDERS PERSPECTIVE

    Directory of Open Access Journals (Sweden)

    Bojoagă Alexandru

    2013-07-01

    Full Text Available Organizations inform stakeholders about their current and future activities, processes, created value, strategic intentions, and other information that may influence the established relationships. Organizations choose to communicate with stakeholders by different means and in varied ways. The annual report represents a way of communicating between companies and their stakeholders, and it is offering comprehensive information about how companies operates and creates value. The business model is an emerging concept in management literature and practice. The concept describes the logic by which a organization creates, maintains and delivers value for its stakeholders. Through annual reports organisations can communicate to stakeholders information about their business models.We investigated how information about business models is explicitly communicated through annual reports, and how this information is reffering to stakeholders. Our paper aims to reveal which stakeholders are more often mentioned when organizations are communicating about business models through annual reports. This approach shows the attention degree given by organizations to stakeholders. We perceived this from a strategic point of view, as a strategic signal. Thus, we considered if the stakeholder is mentioned more frequent in the communicated message it has a greater role in communication strategy about business model. We conducted an exploratory research and have realized a content analysis.The analysed data consist in over a thousand annual reports from 96 organizations. We analysed the informations transmitted by organizations through annual reports. The annual reports were for a time period of 12 years. Most of the selected companies are multi-business, and are operating in different industries. The results show the stakeholder’s hierarchy based on how often they were mentioned in the communicated messages about business models through annual reports. Based on our

  19. Behaviorally Modeling Games of Strategy Using Descriptive Q-learning

    Science.gov (United States)

    2013-01-01

    REPORT Behaviorally Modeling Games of Strategy Using Descriptive Q-learning 14. ABSTRACT 16. SECURITY CLASSIFICATION OF: Modeling human decision making... Games of Strategy Using Descriptive Q-learning Report Title ABSTRACT Modeling human decision making in strategic problem domains is challenging with...an unknown automated opponent. Behaviorally Modeling Games of Strategy Using Descriptive Q-learning Roi Ceren Department of Computer Science

  20. Constitutive model with time-dependent deformations

    DEFF Research Database (Denmark)

    Krogsbøll, Anette

    1998-01-01

    are common in time as well as size. This problem is adressed by means of a new constitutive model for soils. It is able to describe the behavior of soils at different deformation rates. The model defines time-dependent and stress-related deformations separately. They are related to each other and they occur......In many geological and Engineering problems it is necessary to transform information from one scale to another. Data collected at laboratory scale are often used to evaluate field problems on a much larger scale. This is certainly true for geological problems where extreme scale differences...... simultanelously. The model is based on concepts from elasticity and viscoplasticity theories. In addition to Hooke's law for the elastic behavior, the framework for the viscoplastic behavior consists, in the general case (two-dimensional or three-dimensional), of a yield surface, an associated flow rule...

  1. Individual Hearing Loss: Characterization, Modelling, Compensation Strategies

    DEFF Research Database (Denmark)

    Santurette, Sébastien; Dau, Torsten; Christensen-Dalsgaard, Jakob

    2016-01-01

    It is well-established that hearing loss does not only lead to a reduction of hearing sensitivity. Large individual differences are typically observed among listeners with hearing impairment in a wide range of suprathreshold auditory measures. In many cases, audiometric thresholds cannot fully...... account for such individual differences, which make it challenging to find adequate compensation strategies in hearing devices. How to characterize, model, and compensate for individual hearing loss were the main topics of the fifth International Symposium on Auditory and Audiological Research (ISAAR...

  2. Complex networks repair strategies: Dynamic models

    Science.gov (United States)

    Fu, Chaoqi; Wang, Ying; Gao, Yangjun; Wang, Xiaoyang

    2017-09-01

    Network repair strategies are tactical methods that restore the efficiency of damaged networks; however, unreasonable repair strategies not only waste resources, they are also ineffective for network recovery. Most extant research on network repair focuses on static networks, but results and findings on static networks cannot be applied to evolutionary dynamic networks because, in dynamic models, complex network repair has completely different characteristics. For instance, repaired nodes face more severe challenges, and require strategic repair methods in order to have a significant effect. In this study, we propose the Shell Repair Strategy (SRS) to minimize the risk of secondary node failures due to the cascading effect. Our proposed method includes the identification of a set of vital nodes that have a significant impact on network repair and defense. Our identification of these vital nodes reduces the number of switching nodes that face the risk of secondary failures during the dynamic repair process. This is positively correlated with the size of the average degree and enhances network invulnerability.

  3. An Optimal Number-Dependent Preventive Maintenance Strategy for Offshore Wind Turbine Blades Considering Logistics

    Directory of Open Access Journals (Sweden)

    Mahmood Shafiee

    2013-01-01

    Full Text Available In offshore wind turbines, the blades are among the most critical and expensive components that suffer from different types of damage due to the harsh maritime environment and high load. The blade damages can be categorized into two types: the minor damage, which only causes a loss in wind capture without resulting in any turbine stoppage, and the major (catastrophic damage, which stops the wind turbine and can only be corrected by replacement. In this paper, we propose an optimal number-dependent preventive maintenance (NDPM strategy, in which a maintenance team is transported with an ordinary or expedited lead time to the offshore platform at the occurrence of the Nth minor damage or the first major damage, whichever comes first. The long-run expected cost of the maintenance strategy is derived, and the necessary conditions for an optimal solution are obtained. Finally, the proposed model is tested on real data collected from an offshore wind farm database. Also, a sensitivity analysis is conducted in order to evaluate the effect of changes in the model parameters on the optimal solution.

  4. Animal models of alcohol and drug dependence

    Directory of Open Access Journals (Sweden)

    Cleopatra S. Planeta

    2013-01-01

    Full Text Available Drug addiction has serious health and social consequences. In the last 50 years, a wide range of techniques have been developed to model specific aspects of drug-taking behaviors and have greatly contributed to the understanding of the neurobiological basis of drug abuse and addiction. In the last two decades, new models have been proposed in an attempt to capture the more genuine aspects of addiction-like behaviors in laboratory animals. The goal of the present review is to provide an overview of the preclinical procedures used to study drug abuse and dependence and describe recent progress that has been made in studying more specific aspects of addictive behavior in animals.

  5. The Modeling Strategies for Open Software Architecture of Robot Controller

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Although the modeling technologies for open robot controllers have been discussed widely, not much literature is devoted to the actual general modeling principles and strategies. The reason is that many researches focus on specific application fields. This paper accommodates for this lacuna and provides some general modeling principles and strategies. At last, the actual new modeling method -Hierarchical Object-Oriented Petri net (HOONet) which has been proved to be an effective modeling methodology, is used to illustrate the modeling strategies.

  6. Flavour Dependent Gauged Radiative Neutrino Mass Model

    CERN Document Server

    Baek, Seungwon; Yagyu, Kei

    2015-01-01

    We propose a one-loop induced radiative neutrino mass model with anomaly free flavour dependent gauge symmetry: $\\mu$ minus $\\tau$ symmetry $U(1)_{\\mu-\\tau}$. A neutrino mass matrix satisfying current experimental data can be obtained by introducing a weak isospin singlet scalar boson that breaks $U(1)_{\\mu-\\tau}$ symmetry, an inert doublet scalar field, and three right-handed neutrinos in addition to the fields in the standard model. We find that a characteristic structure appears in the neutrino mass matrix: two-zero texture form which predicts three non-zero neutrino masses and three non-zero CP-phases which can be determined five well measured experimental inputs of two squared mass differences and three mixing angles. Furthermore, it is clarified that only the inverted mass hierarchy is allowed in our model. In a favored parameter set from the neutrino sector, the discrepancy in the muon anomalous magnetic moment between the experimental data and the the standard model prediction can be explained by the ...

  7. Intralimb compensation strategy depends on the nature of joint perturbation in human hopping.

    Science.gov (United States)

    Chang, Young-Hui; Roiz, Ronald A; Auyang, Arick G

    2008-01-01

    Due to the well-described spring-mass dynamics of bouncing gaits, human hopping is a tractable model for elucidating basic neuromuscular compensation principles. We tested whether subjects would employ a multi-joint or single-joint response to stabilize leg stiffness while wearing a spring-loaded ankle-foot orthosis (AFO) that applied localized resistive and assistive torques to the ankle. We analyzed kinematics and kinetics data from nine subjects hopping in place on one leg, at three frequencies (2.2, 2.4, and 2.8Hz) and three orthosis conditions (freely articulating AFO, AFO with plantarflexion resistance, and AFO with plantarflexion assistance). Leg stiffness was invariant across AFO conditions, however, compensation strategy depended upon the nature of the applied load. Biological ankle stiffness increased in response to a resistive load at twice the rate that it decreased with an assitive load. Ankle adjustments alone fully compensated for an assistive load with no net change in combined (biological plus applied) total ankle stiffness (p > or =0.133). In contrast, a resistive load resulted in a 7.4-9.0% increase in total ankle stiffness across frequencies and a concomitant 10-15% increase in knee joint stiffness at each frequency (pcompensation strategies that are specific to the nature of the joint loading.

  8. Bayesian Network Models for Local Dependence among Observable Outcome Variables

    Science.gov (United States)

    Almond, Russell G.; Mulder, Joris; Hemat, Lisa A.; Yan, Duanli

    2009-01-01

    Bayesian network models offer a large degree of flexibility for modeling dependence among observables (item outcome variables) from the same task, which may be dependent. This article explores four design patterns for modeling locally dependent observations: (a) no context--ignores dependence among observables; (b) compensatory context--introduces…

  9. Model for Dynamic Multiple of CPPI Strategy

    Directory of Open Access Journals (Sweden)

    Guangyuan Xing

    2014-01-01

    Full Text Available Focusing on the parameter “Multiple” of CPPI strategy, this study proposes a dynamic setting model of multiple for gap risk management purpose. First, CPPI gap risk is measured as the probability that the value loss of active asset exceeds its allowed maximum drop determined by a given multiple setting. Moreover, according to the statistical estimation using SV-EVT approach, a dynamic choice of multiple is detailed as a function of time-varying asset volatility, expected loss, and the possibility of occurrence of extreme events in the active asset returns illustrated empirically on Shanghai composite index data. This study not only enriches the literature of dynamic proportion portfolio insurance, but also provides a practical reference for CPPI investors to choose a moderate risky exposure achieving gap risk management, which promotes CPPI’s application in emerging capital market.

  10. State impulsive control strategies for a two-languages competitive model with bilingualism and interlinguistic similarity

    Science.gov (United States)

    Nie, Lin-Fei; Teng, Zhi-Dong; Nieto, Juan J.; Jung, Il Hyo

    2015-07-01

    For reasons of preserving endangered languages, we propose, in this paper, a novel two-languages competitive model with bilingualism and interlinguistic similarity, where state-dependent impulsive control strategies are introduced. The novel control model includes two control threshold values, which are different from the previous state-dependent impulsive differential equations. By using qualitative analysis method, we obtain that the control model exhibits two stable positive order-1 periodic solutions under some general conditions. Moreover, numerical simulations clearly illustrate the main theoretical results and feasibility of state-dependent impulsive control strategies. Meanwhile numerical simulations also show that state-dependent impulsive control strategy can be applied to other general two-languages competitive model and obtain the desired result. The results indicate that the fractions of two competitive languages can be kept within a reasonable level under almost any circumstances. Theoretical basis for finding a new control measure to protect the endangered language is offered.

  11. Matching Heterogenous Open Innovation Strategies with Business Model Dimensions

    OpenAIRE

    Saebi, Tina; Foss, Nicolai Juul

    2014-01-01

    Research on open innovation suggests that companies benefit differentially from adopting open innovation strategies; however, it is unclear why this is so. One possible explanation is that companies' business models are not attuned to open strategies. Accordingly, we propose a contingency model of open business models by systematically linking open innovation strategies to core business model dimensions, notably the content, structure, and governance of transactions. We further illustrate a c...

  12. Dividend-Reinsurance Strategy in the Sparre Andersen Model

    Institute of Scientific and Technical Information of China (English)

    Ji Yang TAN; Lin XIAO; Shao Yue LIU; Xiang Qun YANG

    2013-01-01

    In this paper,we introduce a reinsurance strategy into the Sparre Andersen risk model with a horizon dividend barrier,which is named dividend-reinsurance strategy.It is shown that the value function of the new strategy far exceeds that of the optimal barrier strategy (even that of the optimal dividend strategy).Some results on the advantages of the new strategy are obtained,and the methods for computing the value functions are provided.Numerical illustrations for Erlang (2) and compound Poisson risk models are also given.

  13. Precommitted Investment Strategy versus Time-Consistent Investment Strategy for a Dual Risk Model

    Directory of Open Access Journals (Sweden)

    Lidong Zhang

    2014-01-01

    Full Text Available We are concerned with optimal investment strategy for a dual risk model. We assume that the company can invest into a risk-free asset and a risky asset. Short-selling and borrowing money are allowed. Due to lack of iterated-expectation property, the Bellman Optimization Principle does not hold. Thus we investigate the precommitted strategy and time-consistent strategy, respectively. We take three steps to derive the precommitted investment strategy. Furthermore, the time-consistent investment strategy is also obtained by solving the extended Hamilton-Jacobi-Bellman equations. We compare the precommitted strategy with time-consistent strategy and find that these different strategies have different advantages: the former can make value function maximized at the original time t=0 and the latter strategy is time-consistent for the whole time horizon. Finally, numerical analysis is presented for our results.

  14. Reproductive experience does not persistently alter prefrontal cortical-dependent learning but does alter strategy use dependent on estrous phase.

    Science.gov (United States)

    Workman, Joanna L; Crozier, Tamara; Lieblich, Stephanie E; Galea, Liisa A M

    2013-08-01

    Reproductive experiences in females comprise substantial hormonal and experiential changes and can exert long lasting changes in cognitive function, stress physiology, and brain plasticity. The goal of this research was to determine whether prior reproductive experience could alter a prefrontal-cortical dependent form of learning (strategy set shifting) in an operant box. In this study, female Sprague-Dawley rats were mated and mothered once or twice to produce either primiparous or biparous dams, respectively. Age-matched nulliparous controls (reproductively-naïve females with no exposure to pup cues) were also used. Maternal behaviors were also assessed to determine whether these factors would predict cognitive flexibility. For strategy set shifting, rats were trained in a visual-cue discrimination task on the first day and on the following day, were required to switch to a response strategy to obtain a reward. We also investigated a simpler form of behavioral flexibility (reversal learning) in which rats were trained to press a lever on one side of the box the first day, and on the following day, were required to press the opposite lever to obtain a reward. Estrous phase was determined daily after testing. Neither parity nor estrous phase altered total errors or trials to reach criterion in either the set-shifting or reversal-learning tasks, suggesting that PFC-dependent cognitive performance remains largely stable after 1 or 2 reproductive experiences. However, parity and estrous phase interacted to alter the frequency of particular error types, with biparous rats in estrus committing more perseverative but fewer regressive errors during the set-shifting task. This suggests that parity and estrous phase interfere with the ability to disengage from a previously used, but no longer relevant strategy. These data also suggest that parity alters the behavioral sensitivity to ovarian hormones without changing overall performance.

  15. Learning Style Factor of Field Dependence/Independence and Problem Solving Strategies of Hmong Refugee Students.

    Science.gov (United States)

    Worthley, Karin Marie Evenson

    This research examined the learning style factor of field dependence/independence and the problem solving strategies of Hmong male refugee students 17 years old and older who were attending or planning to attend post secondary education institutions in Wisconsin and Minnesota. The research was conducted from July 1986 to July 1987 to test two…

  16. Modelling combat strategies in fungal mycelia.

    Science.gov (United States)

    Boswell, Graeme P

    2012-07-07

    Fungal mycelia have a well-established role in nutrient cycling and are widely used as agents in biological control and in the remediation of polluted landscapes. Competition and combat between different fungal communities is common in these contexts and its outcome impacts on local biodiversity and the success of such biotechnological applications. In this investigation a mathematical model representing mycelia as a system of partial differential equations is used to simulate combat between two fungal colonies growing into a nutrient-free domain. The resultant equations are integrated numerically and the model simulates well-established outcomes of combat between fungal communities. The outcome of pairwise combat is shown to depend on numerous factors including the suppression of advancing hyphae in rivals, the degradation of a rival's established biomass and the utilization and redistribution of available nutrient resources. It is demonstrated how non-transitive hierarchies in fungal communities can be established through switching mechanisms, mirroring observations reported in experimental studies, and how specialized defensive structures can emerge through changes in the redistribution of internal resources.

  17. Modeling local item dependence with the hierarchical generalized linear model.

    Science.gov (United States)

    Jiao, Hong; Wang, Shudong; Kamata, Akihito

    2005-01-01

    Local item dependence (LID) can emerge when the test items are nested within common stimuli or item groups. This study proposes a three-level hierarchical generalized linear model (HGLM) to model LID when LID is due to such contextual effects. The proposed three-level HGLM was examined by analyzing simulated data sets and was compared with the Rasch-equivalent two-level HGLM that ignores such a nested structure of test items. The results demonstrated that the proposed model could capture LID and estimate its magnitude. Also, the two-level HGLM resulted in larger mean absolute differences between the true and the estimated item difficulties than those from the proposed three-level HGLM. Furthermore, it was demonstrated that the proposed three-level HGLM estimated the ability distribution variance unaffected by the LID magnitude, while the two-level HGLM with no LID consideration increasingly underestimated the ability variance as the LID magnitude increased.

  18. Context-dependent competition in a model gut bacterial community.

    Directory of Open Access Journals (Sweden)

    Eric J de Muinck

    Full Text Available Understanding the ecological processes that generate complex community structures may provide insight into the establishment and maintenance of a normal microbial community in the human gastrointestinal tract, yet very little is known about how biotic interactions influence community dynamics in this system. Here, we use natural strains of Escherichia coli and a simplified model microbiota to demonstrate that the colonization process on the strain level can be context dependent, in the sense that the outcome of intra-specific competition may be determined by the composition of the background community. These results are consistent with previous models for competition between organisms where one competitor has adapted to low resource environments whereas the other is optimized for rapid reproduction when resources are abundant. The genomic profiles of E. coli strains representing these differing ecological strategies provide clues for deciphering the genetic underpinnings of niche adaptation within a single species. Our findings extend the role of ecological theory in understanding microbial systems and the conceptual toolbox for describing microbial community dynamics. There are few, if any, concrete examples of context-dependent competition on a single trophic level. However, this phenomenon can have potentially dramatic effects on which bacteria will successfully establish and persist in the gastrointestinal system, and the principle should be equally applicable to other microbial ecosystems.

  19. Abrupt Strategy Change Underlies Gradual Performance Change: Bayesian Hierarchical Models of Component and Aggregate Strategy Use.

    Science.gov (United States)

    Wynton, Sarah K A; Anglim, Jeromy

    2017-04-10

    While researchers have often sought to understand the learning curve in terms of multiple component processes, few studies have measured and mathematically modeled these processes on a complex task. In particular, there remains a need to reconcile how abrupt changes in strategy use can co-occur with gradual changes in task completion time. Thus, the current study aimed to assess the degree to which strategy change was abrupt or gradual, and whether strategy aggregation could partially explain gradual performance change. It also aimed to show how Bayesian methods could be used to model the effect of practice on strategy use. To achieve these aims, 162 participants completed 15 blocks of practice on a complex computer-based task-the Wynton-Anglim booking (WAB) task. The task allowed for multiple component strategies (i.e., memory retrieval, information reduction, and insight) that could also be aggregated to a global measure of strategy use. Bayesian hierarchical models were used to compare abrupt and gradual functions of component and aggregate strategy use. Task completion time was well-modeled by a power function, and global strategy use explained substantial variance in performance. Change in component strategy use tended to be abrupt, whereas change in global strategy use was gradual and well-modeled by a power function. Thus, differential timing of component strategy shifts leads to gradual changes in overall strategy efficiency, and this provides one reason for why smooth learning curves can co-occur with abrupt changes in strategy use. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

  20. Identifying strategy use in category learning tasks: a case for more diagnostic data and models.

    Science.gov (United States)

    Donkin, Chris; Newell, Ben R; Kalish, Mike; Dunn, John C; Nosofsky, Robert M

    2015-07-01

    The strength of conclusions about the adoption of different categorization strategies-and their implications for theories about the cognitive and neural bases of category learning-depend heavily on the techniques for identifying strategy use. We examine performance in an often-used "information-integration" category structure and demonstrate that strategy identification is affected markedly by the range of models under consideration, the type of data collected, and model-selection techniques. We use a set of 27 potential models that represent alternative rule-based and information-integration categorization strategies. Our experimental paradigm includes the presentation of nonreinforced transfer stimuli that improve one's ability to discriminate among the predictions of alternative models. Our model-selection techniques incorporate uncertainty in the identification of individuals as either rule-based or information-integration strategy users. Based on this analysis we identify 48% of participants as unequivocally using an information-integration strategy. However, adopting the standard practice of using a restricted set of models, restricted data, and ignoring the degree of support for a particular strategy, we would typically conclude that 89% of participants used an information-integration strategy. We discuss the implications of potentially erroneous strategy identification for the security of conclusions about the categorization capabilities of various participant and patient groups.

  1. Modelling strategies for controlling SARS outbreaks.

    Science.gov (United States)

    Gumel, Abba B.; Ruan, Shigui; Day, Troy; Watmough, James; Brauer, Fred; van den Driessche, P.; Gabrielson, Dave; Bowman, Chris; Alexander, Murray E.; Ardal, Sten; Wu, Jianhong; Sahai, Beni M.

    2004-01-01

    Severe acute respiratory syndrome (SARS), a new, highly contagious, viral disease, emerged in China late in 2002 and quickly spread to 32 countries and regions causing in excess of 774 deaths and 8098 infections worldwide. In the absence of a rapid diagnostic test, therapy or vaccine, isolation of individuals diagnosed with SARS and quarantine of individuals feared exposed to SARS virus were used to control the spread of infection. We examine mathematically the impact of isolation and quarantine on the control of SARS during the outbreaks in Toronto, Hong Kong, Singapore and Beijing using a deterministic model that closely mimics the data for cumulative infected cases and SARS-related deaths in the first three regions but not in Beijing until mid-April, when China started to report data more accurately. The results reveal that achieving a reduction in the contact rate between susceptible and diseased individuals by isolating the latter is a critically important strategy that can control SARS outbreaks with or without quarantine. An optimal isolation programme entails timely implementation under stringent hygienic precautions defined by a critical threshold value. Values below this threshold lead to control, but those above are associated with the incidence of new community outbreaks or nosocomial infections, a known cause for the spread of SARS in each region. Allocation of resources to implement optimal isolation is more effective than to implement sub-optimal isolation and quarantine together. A community-wide eradication of SARS is feasible if optimal isolation is combined with a highly effective screening programme at the points of entry. PMID:15539347

  2. [Study of defense styles, defenses and coping strategies in alcohol-dependent population].

    Science.gov (United States)

    Ribadier, A; Varescon, I

    2017-05-01

    Defense mechanisms have been seen to greatly change over time and across different definitions made by different theoretical currents. Recently with the definition provided by the DSM IV, defense mechanisms have integrated the concept of coping as a defensive factor. These mechanisms are no longer considered just through a psychodynamic approach but also through a cognitive and behavioral one. In recent years, new theories have therefore integrated these two components of the defensive operation. According to Chabrol and Callahan (2013), defense mechanisms precede coping strategies. In individuals with psychopathological disorders, these authors indicate a relative stability of these mechanisms. Also, we asked about the presence of unique characteristics among people with alcohol dependence. Indeed, studies conducted with people with alcohol dependence highlight the presence of a neurotic defense style and some highly immature defenses (projection, acting out, splitting and somatization). In terms of coping strategies, persons with alcohol dependence preferentially use avoidant strategies and strategies focused on emotion. However, although several studies have been conducted to assess coping strategies and defense styles within a population of individuals with an alcohol problem, at the present time none of them has taken into account all these aspects of defense mechanisms. The aim of this study is therefore to study the defenses and defense styles and coping strategies in an alcohol-dependent population. This multicenter study (3 CHU, 1 center of supportive care and prevention in addiction and 1 clinic) received a favorable opinion of an Institutional Review Board (IRB Registration #: 00001072). Eighty alcohol-dependent individuals responded to a questionnaire assessing sociodemographic characteristics and elements related to the course of consumption. Coping strategies were assessed by means of a questionnaire validated in French: the Brief Cope. The Defense

  3. Step-up fecal microbiota transplantation strategy: a pilot study for steroid-dependent ulcerative colitis.

    Science.gov (United States)

    Cui, Bota; Li, Pan; Xu, Lijuan; Zhao, Youquan; Wang, Huiquan; Peng, Zhaoyuan; Xu, Hai'e; Xiang, Jie; He, Zhi; Zhang, Ting; Nie, Yongzhan; Wu, Kaichun; Fan, Daiming; Ji, Guozhong; Zhang, Faming

    2015-09-12

    The strategy of using fecal microbiota transplantation (FMT) for refractory ulcerative colitis (UC) remains unclear if single FMT failed to induce remission. This study aimed to evaluate the efficacy and safety of a designed step-up FMT strategy for the steroid-dependent UC. Fifteen patients with steroid-dependent UC were enrolled, and treated with step-up FMT strategy. Follow-up clinical data was collected for a minimum of 3 months. Fecal microbiota composition before and post FMT of patients and related donors were analyzed by 16S rRNA sequencing. Eight of fourteen (57.1 %) patients achieved clinical improvement and were able to discontinue steroids following step-up FMT. One patient was lost to follow-up. Among the 8 patients who responded, five (35.7 %) received one FMT therapy, one (7.1 %) received two FMTs, and two (14.2 %) received two FMTs plus a scheduled course of steroids. Four (28.6 %) of the 8 patients who responded maintained long-term remission during follow-up (3-18 months). Six patients (42.9 %) failed to meet the criteria of clinical improvement and maintained steroid dependence, though three experienced transient or partial improvement. Microbiota analysis showed that FMT altered the composition greatly, and a microbiota composition highly similar to that of the donor emerged in the patients with successful treatment. No severe adverse events occurred during treatment and follow-up. Step-up FMT strategy shows promise as a therapeutic strategy for patients with steroid-dependent UC, likely due to the successful restructuring of gut microbial composition. ClinicalTrials.gov, Number NCT01790061.

  4. Quantitative Index and Abnormal Alarm Strategy Using Sensor-Dependent Vibration Data for Blade Crack Identification in Centrifugal Booster Fans

    Directory of Open Access Journals (Sweden)

    Jinglong Chen

    2016-05-01

    Full Text Available Centrifugal booster fans are important equipment used to recover blast furnace gas (BFG for generating electricity, but blade crack faults (BCFs in centrifugal booster fans can lead to unscheduled breakdowns and potentially serious accidents, so in this work quantitative fault identification and an abnormal alarm strategy based on acquired historical sensor-dependent vibration data is proposed for implementing condition-based maintenance for this type of equipment. Firstly, three group dependent sensors are installed to acquire running condition data. Then a discrete spectrum interpolation method and short time Fourier transform (STFT are applied to preliminarily identify the running data in the sensor-dependent vibration data. As a result a quantitative identification and abnormal alarm strategy based on compound indexes including the largest Lyapunov exponent and relative energy ratio at the second harmonic frequency component is proposed. Then for validation the proposed blade crack quantitative identification and abnormality alarm strategy is applied to analyze acquired experimental data for centrifugal booster fans and it has successfully identified incipient blade crack faults. In addition, the related mathematical modelling work is also introduced to investigate the effects of mistuning and cracks on the vibration features of centrifugal impellers and to explore effective techniques for crack detection.

  5. Household Livelihood Strategies and Dependence on Agriculture in the Mountainous Settlements in the Three Gorges Reservoir Area, China

    Directory of Open Access Journals (Sweden)

    Dingde Xu

    2015-04-01

    Full Text Available This study explores the extent to which farmers in the Three Gorges Reservoir area remain highly dependent on agriculture despite rapid urbanization and industrialization. The study focuses on the factors that determine a household’s choice of livelihood strategy, with a particular focus on the production of and dependence on agricultural products. Using a sustainable livelihoods approach and survey data from farmers in the Three Gorges Reservoir area in China, the study provides a descriptive statistical analysis and ordinal logistic regression model that shows that close to 56% of households exhibit a low dependence on agriculture. The following variables had a significant influence on livelihood strategy: the maximum years of education of any household member; the age of the household head; the number of laborers in a household; household location; and formal and informal social networks. Regardless of whether the household had children, house value and fixed assets had no significant influence on livelihood strategy. According to the analysis results, we put forward the suggestions that government departments increase investment in infrastructure and make loan policies more favorable for farmers so as to encourage rural able-person to use their social networks to actively establish businesses at migrant destinations.

  6. Quantitative Index and Abnormal Alarm Strategy Using Sensor-Dependent Vibration Data for Blade Crack Identification in Centrifugal Booster Fans.

    Science.gov (United States)

    Chen, Jinglong; Sun, Hailiang; Wang, Shuai; He, Zhengjia

    2016-05-09

    Centrifugal booster fans are important equipment used to recover blast furnace gas (BFG) for generating electricity, but blade crack faults (BCFs) in centrifugal booster fans can lead to unscheduled breakdowns and potentially serious accidents, so in this work quantitative fault identification and an abnormal alarm strategy based on acquired historical sensor-dependent vibration data is proposed for implementing condition-based maintenance for this type of equipment. Firstly, three group dependent sensors are installed to acquire running condition data. Then a discrete spectrum interpolation method and short time Fourier transform (STFT) are applied to preliminarily identify the running data in the sensor-dependent vibration data. As a result a quantitative identification and abnormal alarm strategy based on compound indexes including the largest Lyapunov exponent and relative energy ratio at the second harmonic frequency component is proposed. Then for validation the proposed blade crack quantitative identification and abnormality alarm strategy is applied to analyze acquired experimental data for centrifugal booster fans and it has successfully identified incipient blade crack faults. In addition, the related mathematical modelling work is also introduced to investigate the effects of mistuning and cracks on the vibration features of centrifugal impellers and to explore effective techniques for crack detection.

  7. Evaluation of targeted influenza vaccination strategies via population modeling.

    Directory of Open Access Journals (Sweden)

    John Glasser

    Full Text Available BACKGROUND: Because they can generate comparable predictions, mathematical models are ideal tools for evaluating alternative drug or vaccine allocation strategies. To remain credible, however, results must be consistent. Authors of a recent assessment of possible influenza vaccination strategies conclude that older children, adolescents, and young adults are the optimal targets, no matter the objective, and argue for vaccinating them. Authors of two earlier studies concluded, respectively, that optimal targets depend on objectives and cautioned against changing policy. Which should we believe? METHODS AND FINDINGS: In matrices whose elements are contacts between persons by age, the main diagonal always predominates, reflecting contacts between contemporaries. Indirect effects (e.g., impacts of vaccinating one group on morbidity or mortality in others result from off-diagonal elements. Mixing matrices based on periods in proximity with others have greater sub- and super-diagonals, reflecting contacts between parents and children, and other off-diagonal elements (reflecting, e.g., age-independent contacts among co-workers, than those based on face-to-face conversations. To assess the impact of targeted vaccination, we used a time-usage study's mixing matrix and allowed vaccine efficacy to vary with age. And we derived mortality rates either by dividing observed deaths attributed to pneumonia and influenza by average annual cases from a demographically-realistic SEIRS model or by multiplying those rates by ratios of (versus adding to them differences between pandemic and pre-pandemic mortalities. CONCLUSIONS: In our simulations, vaccinating older children, adolescents, and young adults averts the most cases, but vaccinating either younger children and older adults or young adults averts the most deaths, depending on the age distribution of mortality. These results are consistent with those of the earlier studies.

  8. A Model of Dynamic Strategy-Making

    DEFF Research Database (Denmark)

    Andersen, Torben Juul; Hallin, Carina Antonia; Li, Xin

    The organizational capacity to cope with unexpected changes remains a fundamental challenge in strategy as global competition and technological innovation increase environmental uncertainty. Conventional strategy-making is often conceived as a sequential linear process where we see it as a non......-linear interaction between top-down and bottom-up mechanisms dealing with multiple actions taken throughout the organization over time. It is driven by intension but with a flexible balance between centralized (planned) and decentralized (spontaneous) activities. We adopt the principles of complementary Yin...

  9. Toward an Integrative Model of Global Business Strategy

    DEFF Research Database (Denmark)

    Li, Xin

    fragmentation-integration-fragmentation-integration upward spiral. In response to the call for integrative approach to strategic management research, we propose an integrative model of global business strategy that aims at integrating not only strategy and IB but also the different paradigms within the strategy......In this paper, we first review the development of the strategy field by introducing Hoskisson et al.’s (1999) notion of ‘swings of a pendulum’. With problematization of this notion, we then offer an alternative interpretation of the advancement of strategy knowledge, namely, a recursive...

  10. Coastline modelling for nourishment strategy evaluation

    NARCIS (Netherlands)

    Huisman, B.J.A.; Wang, Z.B.; De Ronde, J.G.; Stronkhorst, J.; Sprengers, C.J.

    2013-01-01

    Coastal zone managers in the Netherlands require new dedicated tools for the assessment of the long-term impacts of coastal maintenance policies. The policies need to be evaluated on the impacts on multiple coastal functions in order to be able to optimize the performance of such strategies. This pa

  11. Nine Strategies for Growing into Kirkpatrick's Model.

    Science.gov (United States)

    Wilburn, Kathleen M.; Wilburn, H. Ralph

    1998-01-01

    Presents nine strategies for gathering information on training effectiveness via: telephone, e-mail, mail-in survey, postcards, online bulletin board, a visit to the human resources department, the strategic plan, focus group, and end-of-course evaluations. (AEF)

  12. Continuous-Time Modeling with Spatial Dependence

    NARCIS (Netherlands)

    Oud, J.H.L.; Folmer, H.; Patuelli, R.; Nijkamp, P.

    2012-01-01

    (Spatial) panel data are routinely modeled in discrete time (DT). However, compelling arguments exist for continuous-time (CT) modeling of (spatial) panel data. Particularly, most social processes evolve in CT, so that statistical analysis in DT is an oversimplification, gives an incomplete

  13. Continuous-Time Modeling with Spatial Dependence

    NARCIS (Netherlands)

    Oud, J.; Folmer, H.; Patuelli, R.; Nijkamp, P.

    (Spatial) panel data are routinely modeled in discrete time (DT). However, compelling arguments exist for continuous-time (CT) modeling of (spatial) panel data. Particularly, most social processes evolve in CT, so that statistical analysis in DT is an oversimplification, gives an incomplete

  14. MODEL PERANGKAT PEMBELAJARAN MENULIS BIOGRAFI DENGAN STRATEGI BELAJAR KUANTUM

    Directory of Open Access Journals (Sweden)

    Sukirno Sukirno

    2016-02-01

    Full Text Available Instructional Model to Teach Biography Writing using Quantum Teaching-learning Strategies. The study was aimed at developing a model for the teaching of biography writing using quantum learning strategy. To devise the model, three main steps were taken: pre-development of the model, development of the model, and examination of the effectiveness of the model. The research re­sults are three models: 1 syllabus and evaluation system for the teaching of biography writing, 2 learn­ing materials and VCD, and 3 teaching scenario. Quantitative data analysis shows that the three models have a relatively high degree of effectiveness. In addition, there is a significant difference between the pre-test and post-test scores on biography writing ability using quantum learning strategy (p < .001. So, it can be concluded that the three models of learning sets are effective and have significant effects on the improvement of biography writing ability of the students.

  15. Dynamical Analysis of a Pest Management Model with Saturated Growth Rate and State Dependent Impulsive Effects

    Directory of Open Access Journals (Sweden)

    Wencai Zhao

    2013-01-01

    Full Text Available A new pest management mathematical model with saturated growth is proposed. The integrated pest management (IPM strategy by introducing two state dependent pulses into the model is considered. Firstly, we analyze singular points of the model qualitatively and get the condition for focus point. Secondly, by using geometry theory of impulsive differential equation, the existence and stability of periodic solution of the system are discussed. Lastly, some examples and numerical simulations are given to illustrate our results.

  16. A literature review on growth models and strategies: The missing link in entrepreneurial growth

    Directory of Open Access Journals (Sweden)

    Syed Fida Hussain Shah

    2013-08-01

    Full Text Available This study focuses on the importance of growth models, growth strategies, role of knowledge management system in the formulation of effective strategy for the enterprises following growth. Choice of an appropriate growth strategy is at the heart of any successful entrepreneurial venture. Selection of a strategy may be effective for one entrepreneur while it is not for other. Choice of Growth Strategy depends on various different factors, organisational context and environment which may vary from enterprise to enterprise. Resource based view is very important consideration for the entrepreneurs on the path of growth. Evaluation of all kind of resources helps them to grow their enterprises successfully. Selection of an appropriate growth strategy allows the entrepreneurs in overcoming growth challenges and avoiding the growth reversals and setbacks.

  17. Optimal harvesting for an age-dependent n-dimensional food chain model

    Institute of Scientific and Technical Information of China (English)

    LUO Zhi-xue; DU Ming-yin

    2008-01-01

    This paper is concerned with optimal harvesting policy for an age-dependent n-dimensional food chain model. The existence and uniqueness of non-negative solution of the system are proved using the fixed point theorem. By Mazur's theorem, the existence of optimal control strategy is demonstrated and optimality conditions derived by means of normal cone.

  18. OPTIMAL CONTROL PROBLEM FOR A PERIODIC PREDATOR-PREY MODEL WITH AGE-DEPENDENCE

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    In this paper,we investigate optimal policy for periodic predator-prey system with age-dependence.Namely,we consider the model with periodic vital rates and initial distribution.The existence of optimal control strategy is discussed by Mazur's theorem and optimality condition is derived by means of normal cone.

  19. Technology Marketing using PCA , SOM, and STP Strategy Modeling

    OpenAIRE

    Sunghae Jun

    2011-01-01

    Technology marketing is a total processing about identifying and meeting the technological needs of human society. Most technology results exist in intellectual properties like patents. In our research, we consider patent document as a technology. So patent data are analyzed by Principal Component Analysis (PCA) and Self Organizing Map (SOM) for STP(Segmentation, Targeting, and Positioning) strategy modeling. STP is a popular approach for developing marketing strategies. We use STP strategy m...

  20. Optimal control of an influenza model with seasonal forcing and age-dependent transmission rates.

    Science.gov (United States)

    Lee, Jeehyun; Kim, Jungeun; Kwon, Hee-Dae

    2013-01-21

    This study considers an optimal intervention strategy for influenza outbreaks. Variations in the SEIAR model are considered to include seasonal forcing and age structure, and control strategies include vaccination, antiviral treatment, and social distancing such as school closures. We formulate an optimal control problem by minimizing the incidence of influenza outbreaks while considering intervention costs. We examine the effects of delays in vaccine production, seasonal forcing, and age-dependent transmission rates on the optimal control and suggest some optimal strategies through numerical simulations.

  1. The spin dependent odderon in the diquark model

    CERN Document Server

    Szymanowski, Lech

    2016-01-01

    In this short note, we report a di-quark model calculation for the spin dependent odderon and demonstrate that the asymmetrical color source distribution in the transverse plane of a transversely polarized hadron plays an essential role in yielding the spin dependent odderon. This calculation confirms the earlier finding that the spin dependent odderon is closely related to the parton orbital angular momentum.

  2. Health benefit modelling and optimization of vehicular pollution control strategies

    Science.gov (United States)

    Sonawane, Nayan V.; Patil, Rashmi S.; Sethi, Virendra

    2012-12-01

    This study asserts that the evaluation of pollution reduction strategies should be approached on the basis of health benefits. The framework presented could be used for decision making on the basis of cost effectiveness when the strategies are applied concurrently. Several vehicular pollution control strategies have been proposed in literature for effective management of urban air pollution. The effectiveness of these strategies has been mostly studied as a one at a time approach on the basis of change in pollution concentration. The adequacy and practicality of such an approach is studied in the present work. Also, the assessment of respective benefits of these strategies has been carried out when they are implemented simultaneously. An integrated model has been developed which can be used as a tool for optimal prioritization of various pollution management strategies. The model estimates health benefits associated with specific control strategies. ISC-AERMOD View has been used to provide the cause-effect relation between control options and change in ambient air quality. BenMAP, developed by U.S. EPA, has been applied for estimation of health and economic benefits associated with various management strategies. Valuation of health benefits has been done for impact indicators of premature mortality, hospital admissions and respiratory syndrome. An optimization model has been developed to maximize overall social benefits with determination of optimized percentage implementations for multiple strategies. The model has been applied for sub-urban region of Mumbai city for vehicular sector. Several control scenarios have been considered like revised emission standards, electric, CNG, LPG and hybrid vehicles. Reduction in concentration and resultant health benefits for the pollutants CO, NOx and particulate matter are estimated for different control scenarios. Finally, an optimization model has been applied to determine optimized percentage implementation of specific

  3. Technology Marketing using PCA , SOM, and STP Strategy Modeling

    Directory of Open Access Journals (Sweden)

    Sunghae Jun

    2011-01-01

    Full Text Available Technology marketing is a total processing about identifying and meeting the technological needs of human society. Most technology results exist in intellectual properties like patents. In our research, we consider patent document as a technology. So patent data are analyzed by Principal Component Analysis (PCA and Self Organizing Map (SOM for STP(Segmentation, Targeting, and Positioning strategy modeling. STP is a popular approach for developing marketing strategies. We use STP strategy modeling for technology marketing. Also PCA and SOM are used to analyze patent data in STP modeling. To verify improved performance of our study, we make experiments using patent data from USPTO.

  4. A Romanian energy system model and a nuclear reduction strategy

    DEFF Research Database (Denmark)

    Gota, Dan-Ioan; Lund, Henrik; Miclea, Liviu

    2011-01-01

    This paper presents a model of the Romanian energy system with the purpose of providing a tool for the analysis of future sustainable energy strategies. The model represents the total national energy system and is detailed to the level of hourly demand and production in order to be able to analyse...... the consequences of adding fluctuating renewable energy sources to the system. The model has been implemented into the EnergyPLAN tool and has been validated in order to determine if it can be used as a reference model for other simulations. In EnergyPLAN, two different future strategy scenarios for the Romanian...... energy system are compared to the actual data of Romania of year 2008. First, a comparison is made between the 2008 model and the 2013 strategy scenario corresponding to the grid of the Romanian transmission system operator (TSO) Transelectrica. Then, a comparison is made to a second strategy scenario...

  5. Model strategy for village development in the Czech Republic

    Directory of Open Access Journals (Sweden)

    Ladislav ROLÍNEK

    2015-03-01

    Full Text Available The model strategies discussed in this article represent different ways of possible village development in the Czech Republic. We used typologies of strategies from business strategic management for their definition. Twenty municipalities, where structured interviews were carried out with their mayors, were chosen randomly from among 100 villages where a questionnaire survey was conducted in 2012 (Faltová Leitmanová, et al., 2012. Based on the qualitative analysis of the structured interview summaries, eight model strategies were ascertained. These include integration strategy, service differentiation, spending cuts, usage of municipal property, stabilization of village population, business support, fundraising, and identification of the inhabitants with the village (village pride. The most commonly applied model strategy is integration, followed by village population stabilization.

  6. Fixed transaction costs and modelling limited dependent variables

    NARCIS (Netherlands)

    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.

  7. Comparing Two Strategies to Model Uncertainties in Structural Dynamics

    Directory of Open Access Journals (Sweden)

    Rubens Sampaio

    2010-01-01

    Full Text Available In the modeling of dynamical systems, uncertainties are present and they must be taken into account to improve the prediction of the models. Some strategies have been used to model uncertainties and the aim of this work is to discuss two of those strategies and to compare them. This will be done using the simplest model possible: a two d.o.f. (degrees of freedom dynamical system. A simple system is used because it is very helpful to assure a better understanding and, consequently, comparison of the strategies. The first strategy (called parametric strategy consists in taking each spring stiffness as uncertain and a random variable is associated to each one of them. The second strategy (called nonparametric strategy is more general and considers the whole stiffness matrix as uncertain, and associates a random matrix to it. In both cases, the probability density functions either of the random parameters or of the random matrix are deduced from the Maximum Entropy Principle using only the available information. With this example, some important results can be discussed, which cannot be assessed when complex structures are used, as it has been done so far in the literature. One important element for the comparison of the two strategies is the analysis of the samples spaces and the how to compare them.

  8. Porter's Model of Generic Competitive Strategies

    OpenAIRE

    Orges Ormanidhi; Omer Stringa

    2008-01-01

    A firm's competitive behavior is an important topic for practitioners, theorists, and policy makers. Among the explanations of firms' behavior is Michael Porter's model. We have presented this model along with some alternative approaches: Structure-Conduct-Performance, the New Industrial Organization and Game Theory, the Resource-Based Perspective, and Market Process Economics. These approaches are discussed in terms of their relations, similarities, and differences relative to Porter's model...

  9. An epidemiological model with vaccination strategies

    Science.gov (United States)

    Prates, Dérek B.; Silva, Jaqueline M.; Gomes, Jessica L.; Kritz, Maurício V.

    2016-06-01

    Mathematical models can be widely found in the literature describing epidemics. The epidemical models that use differential equations to represent mathematically such description are especially sensible to parameters. This work analyze a variation of the SIR model when applied to a epidemic scenario including several aspects, as constant vaccination, pulse vaccination, seasonality, cross-immunity factor, birth and dead rate. The analysis and results are performed through numerical solutions of the model and a special attention is given to the discussion generated by the paramenters variation.

  10. Modeling Cycle Dependence in Credit Insurance

    Directory of Open Access Journals (Sweden)

    Anisa Caja

    2014-03-01

    Full Text Available Business and credit cycles have an impact on credit insurance, as they do on other businesses. Nevertheless, in credit insurance, the impact of the systemic risk is even more important and can lead to major losses during a crisis. Because of this, the insurer surveils and manages policies almost continuously. The management actions it takes limit the consequences of a downturning cycle. However, the traditional modeling of economic capital does not take into account this important feature of credit insurance. This paper proposes a model aiming to estimate future losses of a credit insurance portfolio, while taking into account the insurer’s management actions. The model considers the capacity of the credit insurer to take on less risk in the case of a cycle downturn, but also the inverse, in the case of a cycle upturn; so, losses are predicted with a more dynamic perspective. According to our results, the economic capital is over-estimated when not considering the management actions of the insurer.

  11. A framework for electric vehicle charging strategy optimization tested for travel demand generated by an activity-based model

    OpenAIRE

    Usman, Muhammad; Knapen, Luk; Kochan, Bruno; Yasar, Ansar; Bellemans, Tom; Janssens, Davy; WETS, Geert

    2015-01-01

    This paper presents the cost optimization model which plans a charging strategy for an electric vehicle. In case of time dependent electric prices an intelligent planner is required which plans the charging strategy only at cheaper moments and places to keep the vehicle charged enough to complete its scheduled travels. This model estimates the required charging energy to travel by the electric vehicle. Then using the time dependent electric prices and available power at each pe...

  12. An Object Extraction Model Using Association Rules and Dependence Analysis

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Extracting objects from legacy systems is a basic step insystem's obje ct-orientation to improve the maintainability and understandability of the syst e ms. A new object extraction model using association rules an d dependence analysis is proposed. In this model data are classified by associat ion rules and the corresponding operations are partitioned by dependence analysis.

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

    NARCIS (Netherlands)

    Külske, Christof

    1998-01-01

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

  14. A novel dependency language model for information retrieval

    Institute of Scientific and Technical Information of China (English)

    CAI Ke-ke; BU Jia-jun; CHEN Chun; QIU Guang

    2007-01-01

    This paper explores the application of term dependency in information retrieval (IR) and proposes a novel dependency retrieval model. This retrieval model suggests an extension to the existing language modeling (LM) approach to IR by introducing dependency models for both query and document. Relevance between document and query is then evaluated by reference to the Kullback-Leibler divergence between their dependency models. This paper introduces a novel hybrid dependency structure, which allows integration of various forms of dependency within a single framework. A pseudo relevance feedback based method is also introduced for constructing query dependency model. The basic idea is to use query-relevant top-ranking sentences extracted from the top documents at retrieval time as the augmented representation of query, from which the relationships between query terms are identified. A Markov Random Field (MRF) based approach is presented to ensure the relevance of the extracted sentences,which utilizes the association features between query terms within a sentence to evaluate the relevance of each sentence. This dependency retrieval model was compared with other traditional retrieval models. Experiments indicated that it produces significant improvements in retrieval effectiveness.

  15. Concurrent Lexicalized Dependency Parsing The ParseTalk Model

    CERN Document Server

    Broeker, N; Schacht, S; Broeker, Norbert; Hahn, Udo; Schacht, Susanne

    1994-01-01

    A grammar model for concurrent, object-oriented natural language parsing is introduced. Complete lexical distribution of grammatical knowledge is achieved building upon the head-oriented notions of valency and dependency, while inheritance mechanisms are used to capture lexical generalizations. The underlying concurrent computation model relies upon the actor paradigm. We consider message passing protocols for establishing dependency relations and ambiguity handling.

  16. Brain activation pattern depends on the strategy chosen by zebra finches to solve an orientation task.

    Science.gov (United States)

    Mayer, Uwe; Bischof, Hans-Joachim

    2012-02-01

    Zebra finches (Taeniopygia guttata) were trained to find food in one of four feeders on the floor of an aviary. This feeder was always in the same place during training and was additionally marked by a distinct pattern. In the test trial the distinctly patterned feeder was interchanged with one of the other feeders, so that the birds had to decide to use either the pattern or the original location for finding food. Half of the birds used one strategy and half used the other. According to the strategy applied, different brain areas were activated, as demonstrated by c-Fos immunohistochemistry. The hippocampus was activated when spatial cues were used, while in birds orienting using the pattern of the feeder, part of the collothalamic (tectofugal) visual system showed stronger activation. The visual wulst of the lemnothalamic (thalamofugal) visual system was activated with both strategies, indicating an involvement in both spatial and pattern-directed orientation. Because the experimental situation was the same for all zebra finches, the activation pattern was only dependent on the strategy that was voluntarily chosen by each of the birds.

  17. Modelling Strategies for Functional Magnetic Resonance Imaging

    DEFF Research Database (Denmark)

    Madsen, Kristoffer Hougaard

    2009-01-01

    This thesis collects research done on several models for the analysis of functional magnetic resonance neuroimaging (fMRI) data. Several extensions for unsupervised factor analysis type decompositions including explicit delay modelling as well as handling of spatial and temporal smoothness...

  18. Sample bias from different recruitment strategies in a randomised controlled trial for alcohol dependence.

    Science.gov (United States)

    Morley, Kirsten C; Teesson, Maree; Sannibale, Claudia; Haber, Paul S

    2009-05-01

    Participants may be recruited from diverse sources for randomised controlled trials (RCT) of treatments for alcohol dependence. A mixed recruitment strategy might facilitate recruitment and increase generalisability at the expense of introducing systematic selection bias. The current study aims to compare the effects of recruitment method on socio-demographics, baseline illness characteristics, treatment retention and treatment outcome measures. A secondary analysis from a previous 12 week RCT of naltrexone, acamprosate and placebo for alcohol dependence was conducted. Participants (n = 169) were obtained via four channels of recruitment including in-patient and outpatient referral, live media and print media solicitation. Baseline parameters, retention in treatment and treatment outcomes were compared in these groups. Relative to in-patient subjects, those recruited via live and print media had significantly lower scores on taking steps, less in-patient rehabilitation admissions and less previous abstinence before entering the trial. Subjects recruited via print media had significantly lower scores of alcohol dependence relative to all other modes recruitment. There were no differences between recruitment strategies on treatment retention or compliance. At outcome, no significant effect of recruitment method was detected. These results suggest that different recruitment methods may be sourcing subjects with different baseline characteristics of illness. Nonetheless, these differences did not significantly impact on treatment retention or outcome, suggesting that in this population it was appropriate to recruit subjects from mixed sources.

  19. Temperate heath plant response to dry conditions depends on growth strategy and less on physiology

    DEFF Research Database (Denmark)

    Albert, Kristian Rost; Kongstad, J.; Schmidt, I. K.

    2012-01-01

    The evidence that is currently available demonstrates that future changes in precipitation patterns will affect plant carbon uptake. However, the outcome in terms of success, productivity and fecundity depends upon individual species and different responses of various growth forms. Examination...... of these differences in response in dry versus rewetting conditions can be used to highlight the limitations coherent in different strategies adopted by, for example, evergreen shrubs and grasses. We investigated the leaf-level photosynthetic performance, leaf C, N and d13C along with vegetation cover and biomass...... rewetting increased leaf nitrogen and photosynthesis in the grass much more than for the dwarf shrub. These different strategies may have a considerable impact on carbon uptake and on the ability of a species to compete, as future climatic changes are likely to extend the summer drought period together...

  20. Modeling cancer progression via pathway dependencies.

    Directory of Open Access Journals (Sweden)

    Elena J Edelman

    2008-02-01

    Full Text Available Cancer is a heterogeneous disease often requiring a complexity of alterations to drive a normal cell to a malignancy and ultimately to a metastatic state. Certain genetic perturbations have been implicated for initiation and progression. However, to a great extent, underlying mechanisms often remain elusive. These genetic perturbations are most likely reflected by the altered expression of sets of genes or pathways, rather than individual genes, thus creating a need for models of deregulation of pathways to help provide an understanding of the mechanisms of tumorigenesis. We introduce an integrative hierarchical analysis of tumor progression that discovers which a priori defined pathways are relevant either throughout or in particular steps of progression. Pathway interaction networks are inferred for these relevant pathways over the steps in progression. This is followed by the refinement of the relevant pathways to those genes most differentially expressed in particular disease stages. The final analysis infers a gene interaction network for these refined pathways. We apply this approach to model progression in prostate cancer and melanoma, resulting in a deeper understanding of the mechanisms of tumorigenesis. Our analysis supports previous findings for the deregulation of several pathways involved in cell cycle control and proliferation in both cancer types. A novel finding of our analysis is a connection between ErbB4 and primary prostate cancer.

  1. Field dependence and verbalized strategies on the portable rod-and-frame test by depressed outpatients and normal controls.

    Science.gov (United States)

    Calamari, E; Pini, M; Puleggio, A

    2000-12-01

    This study examined the relationships between scores on the cognitive style of field dependence-independence and verbalized strategies on the Portable Rod-and-Frame Test for normal and psychopathological outpatients. We attempted to verify (a) Manning's hypothesis (1991) of a correspondence between scores on field dependence and external strategies (reference to the visual field) and scores on field independence and internal strategies (reference to the body) on perceptual tasks, and (b) a tendency of depressed persons to score as field dependent, and (c) use of external verbalized strategies. A total of 50 depressed outpatients and 50 normal controls were administered the test and requested to report the strategy they had employed to solve the problem. Contrary to Manning's findings, no significant relationship was found between cognitive style and verbalized strategies in the total sample. Depressed outpatients classified as internal scored significantly higher on the Group Embedded Figures Test but appeared more field dependent on the Rod-and-Frame Test. Moreover, only for the former test did depressed outpatients score more field-dependent than controls. Finally, no significant relationship was found between the diagnosis of depression and use of external strategies; however, field dependence and the use of external strategies on the Rod-and-Frame Test were associated with more severe depressive symptoms measured by the D scale of the MMPI-2. Further research is needed to assess the role of premorbid personality structures of depression in subjective and objective aspects of Rod-and-Frame Test performance.

  2. Fuzzy Control Strategies in Human Operator and Sport Modeling

    CERN Document Server

    Ivancevic, Tijana T; Markovic, Sasa

    2009-01-01

    The motivation behind mathematically modeling the human operator is to help explain the response characteristics of the complex dynamical system including the human manual controller. In this paper, we present two different fuzzy logic strategies for human operator and sport modeling: fixed fuzzy-logic inference control and adaptive fuzzy-logic control, including neuro-fuzzy-fractal control. As an application of the presented fuzzy strategies, we present a fuzzy-control based tennis simulator.

  3. Towards Economic Models for MOOC Pricing Strategy Design

    OpenAIRE

    Jia, Yongzheng; Song, Zhengyang; Bai, Xiaolan; Xu, Wei

    2017-01-01

    MOOCs have brought unprecedented opportunities of making high-quality courses accessible to everybody. However, from the business point of view, MOOCs are often challenged for lacking of sustainable business models, and academic research for marketing strategies of MOOCs is also a blind spot currently. In this work, we try to formulate the business models and pricing strategies in a structured and scientific way. Based on both theoretical research and real marketing data analysis from a MOOC ...

  4. The transverse momentum dependent distribution functions in the bag model

    Energy Technology Data Exchange (ETDEWEB)

    Avakian, Harut; Efremov, Anatoly; Schweitzer, Peter; Yuan, Feng

    2010-01-29

    Leading and subleading twist transverse momentum dependent parton distribution functions (TMDs) are studied in a quark model framework provided by the bag model. A complete set of relations among different TMDs is derived, and the question is discussed how model-(in)dependent such relations are. A connection of the pretzelosity distribution and quark orbital angular momentum is derived. Numerical results are presented, and applications for phenomenology discussed. In particular, it is shown that in the valence-x region the bag model supports a Gaussian Ansatz for the transverse momentum dependence of TMDs.

  5. Transverse momentum dependent distribution functions in the bag model

    Energy Technology Data Exchange (ETDEWEB)

    Avakian, Harut A. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Efremov, A. V. [Joint Inst. for Nuclear Research (JINR), Dubna (Russian Federation); Schweitzer, P. [Univ. of Connecticut, Storrs, CT (United States); Yuan, F. [Brookhaven National Lab. (BNL), Upton, NY (United States). RIKEN Research Center; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2010-04-01

    Leading and subleading twist transverse momentum dependent parton distribution functions (TMDs) are studied in a quark model framework provided by the bag model. A complete set of relations among different TMDs is derived, and the question is discussed how model-(in)dependent such relations are. A connection of the pretzelosity distribution and quark orbital angular momentum is derived. Numerical results are presented, and applications for phenomenology discussed. In particular, it is shown that in the valence-x region the bag model supports a Gaussian Ansatz for the transverse momentum dependence of TMDs.

  6. Modeling Light-Dependent Biofilm Morphology

    Science.gov (United States)

    Kernan, Chase; Huang, Jean; Christianson, Rebecca

    2013-03-01

    Bacterial aggregates on submerged substrates can produce complex biofilm morphologies that are subject to environmental and metabolic factors. We develop a reductionistic cellular automata model of these structures with the intent of guiding experimentation and explaining prior results. We focus on reproducing the columnar and ``mushroom'' phases of aerobic R. palustris and light-sensitive anaerobic R. palustris, respectively. This light sensitivity requires the novel inclusion of a characteristic light penetration depth in addition to surface tension and media penetration parameters. We quantitatively divide this parameter space into roughly four morphological phases--columnar, mushroom, uniform, and irregular--by examining the resultant convexity defect distribution, horizontal correlation, and coverage as a function of height. Finally, we both validate experimental evidence of these phases and suggest new parameter regimes to investigate empirically.

  7. A Model for Contract Bid Markup Strategies

    Institute of Scientific and Technical Information of China (English)

    LI Yong-ping; CHEN Rong-qiu; ZHOU Shao-fu

    2001-01-01

    This paper presents a bid model which can be readily implemented in a competitive bid environment within the construction industry. Competitive bid situations involve a multiplicity of criteria. In this paper, 31 criteria, which effect optimum estimation, are considered. The model is based on CBR, the database of past completed bids, and information associated with successful bids. CBR is considered the best method because of the complexity of the construction domain and the wealth of information that the contractors possessed on past bids.

  8. A vaccination strategy to SEIR-CA model

    Science.gov (United States)

    Almuzakki, Muhammad Zaki; Nuraini, Nuning

    2016-04-01

    A combination between Susceptible-Exposed-Infected-Removed (SEIR) model and Cellular Automaton (CA) called SEIR-CA model has been proposed to simulate spreading diseases through populations. We make an improvement to the parameter which describe the impact of neighborhood in CA system. We also propose a vaccination strategy to the model. Three examples are given to illustrate the model. The first one shows that the previously established SEIR-CA model does not work properly in a population with randomly distributed individuals. After an improvement to the neighborhood impact parameter has been made, the model works properly in a population with randomly distributed individuals and it is shown in the second example. The last example shows the spreading mechanisms with a chosen vaccination strategy. We also show that the vaccination strategy can reduce the number of infected individuals and can suppress the spread of the diseases.

  9. Integration Strategies for Efficient Multizone Chemical Kinetics Models

    Energy Technology Data Exchange (ETDEWEB)

    McNenly, M J; Havstad, M A; Aceves, S M; Pitz, W J

    2009-10-15

    Three integration strategies are developed and tested for the stiff, ordinary differential equation (ODE) integrators used to solve the fully coupled multizone chemical kinetics model. Two of the strategies tested are found to provide more than an order of magnitude of improvement over the original, basic level of usage for the stiff ODE solver. One of the faster strategies uses a decoupled, or segregated, multizone model to generate an approximate Jacobian. This approach yields a 35-fold reduction in the computational cost for a 20 zone model. Using the same approximate Jacobian as a preconditioner for an iterative Krylov-type linear system solver, the second improved strategy achieves a 75-fold reduction in the computational cost for a 20 zone model. The faster strategies achieve their cost savings with no significant loss of accuracy. The pressure, temperature and major species mass fractions agree with the solution from the original integration approach to within six significant digits; and the radical mass fractions agree with the original solution to within four significant digits. The faster strategies effectively change the cost scaling of the multizone model from cubic to quadratic, with respect to the number of zones. As a consequence of the improved scaling, the 40 zone model offers more than a 250-fold cost savings over the basic calculation.

  10. Strategy renewal through business model innovation

    DEFF Research Database (Denmark)

    Holm, Anna; Ulhøi, John Parm

    2011-01-01

    The newspaper industry is presently under pressure in at least two important ways. First, their previous business models, based on paper-based newspapers, subscription fees and sales of advertising space are threatened by new internet-based technologies. Second, the hitherto monopoly held...... by leading newspapers. More specifically, we review how changes introduced during the on-going development of digital platforms have affected the dominant business model and its key components at the leading newspaper industry players in Denmark, and whether those changes have improved their situation...

  11. Strategy renewal through business model innovation

    DEFF Research Database (Denmark)

    Holm, Anna; Ulhøi, John Parm

    2011-01-01

    The newspaper industry is presently under pressure in at least two important ways. First, their previous business models, based on paper-based newspapers, subscription fees and sales of advertising space are threatened by new internet-based technologies. Second, the hitherto monopoly held...... by leading newspapers. More specifically, we review how changes introduced during the on-going development of digital platforms have affected the dominant business model and its key components at the leading newspaper industry players in Denmark, and whether those changes have improved their situation...

  12. Computational and Modeling Strategies for Cell Motility

    Science.gov (United States)

    Wang, Qi; Yang, Xiaofeng; Adalsteinsson, David; Elston, Timothy C.; Jacobson, Ken; Kapustina, Maryna; Forest, M. Gregory

    A predictive simulation of the dynamics of a living cell remains a fundamental modeling and computational challenge. The challenge does not even make sense unless one specifies the level of detail and the phenomena of interest, whether the focus is on near-equilibrium or strongly nonequilibrium behavior, and on localized, subcellular, or global cell behavior. Therefore, choices have to be made clear at the outset, ranging from distinguishing between prokaryotic and eukaryotic cells, specificity within each of these types, whether the cell is "normal," whether one wants to model mitosis, blebs, migration, division, deformation due to confined flow as with red blood cells, and the level of microscopic detail for any of these processes. The review article by Hoffman and Crocker [48] is both an excellent overview of cell mechanics and an inspiration for our approach. One might be interested, for example, in duplicating the intricate experimental details reported in [43]: "actin polymerization periodically builds a mechanical link, the lamellipodium, connecting myosin motors with the initiation of adhesion sites, suggesting that the major functions driving motility are coordinated by a biomechanical process," or to duplicate experimental evidence of traveling waves in cells recovering from actin depolymerization [42, 35]. Modeling studies of lamellipodial structure, protrusion, and retraction behavior range from early mechanistic models [84] to more recent deterministic [112, 97] and stochastic [51] approaches with significant biochemical and structural detail. Recent microscopic-macroscopic models and algorithms for cell blebbing have been developed by Young and Mitran [116], which update cytoskeletal microstructure via statistical sampling techniques together with fluid variables. Alternatively, whole cell compartment models (without spatial details) of oscillations in spreading cells have been proposed [35, 92, 109] which show positive and negative feedback

  13. Dependence of Two-proton Radioactivity on Nuclear Pairing Models

    CERN Document Server

    Oishi, Tomohiro; Pastore, Alessandro

    2016-01-01

    The sensitivity of two-proton emitting decays to the nuclear pairing correlation is discussed within a time-dependent three-body model. We focus on the $^6$Be nucleus assuming $\\alpha + p + p$ configuration, and its decay process is described as a time-evolution of the three-body resonance state. A noticeable model-dependence of two-proton decay width is found by utilizing schematic density-dependent contact (SDDC) and the finite-range Minnesota pairing models. The model-dependence with the SDDC pairing interaction can be understood from the density distribution of the resonance state, which reflects a synergy of participating interactions. Our result suggests that two-proton decay width may be a suitable reference quantity to sophisticate the nuclear pairing model beyond the nucleon driplines.

  14. ROBUST INTERNAL MODEL CONTROL STRATEGY BASED PID CONTROLLER FOR BLDCM

    Directory of Open Access Journals (Sweden)

    A.PURNA CHANDRA RAO

    2010-11-01

    Full Text Available All the closed loop control system requires the controller for improvement of transient response of the error signal. Though the tuning of PID controller in real time is bit difficult and moreover it lacks the disturbance rejection capability. This paper presents a tuning of PID parameters based on internal model strategy. The advantageous of the proposed control strategy is well described in the paper. To test the validity of the proposed control, it is implemented in brushless dc motor drive. The mathematical model of brushless dc motor (BLDC is presented for control design. In addition the robustness of the control strategy is discussed. The proposed control strategy possesses good transient responses and good load disturbance response. In addition, the proposed control strategy possesses good tracking ability. To test the effectiveness of the proposed strategy, the BLDC is represented in transfer function model and later implemented in test system. The results are presented to validate the proposed control strategy for BLDC drive.

  15. Dependence structure of the commodity and stock markets, and relevant multi-spread strategy

    Science.gov (United States)

    Kim, Min Jae; Kim, Sehyun; Jo, Yong Hwan; Kim, Soo Yong

    2011-10-01

    Understanding the dependence structure between the commodity and stock markets is a crucial issue in constructing a portfolio. It can also help us to discover new opportunities to implement spread trading using multiple assets classified in the two different markets. This study analyzed the dependence structure of the commodity and stock markets using the random matrix theory technique and network analysis. Our results show that the stock and commodity markets must be handled as completely separated asset classes except for the oil and gold markets, so the performance enhancement of the mean-variance portfolio is significant as expected. In light of the fact that WTI 1 month futures and four oil-related stocks are strongly correlated, they were selected as basic ingredients to complement the multi-spread convergence trading strategy using a machine learning technique called the AdaBoost algorithm. The performance of this strategy for non-myopic investors, who can endure short-term loss, can be enhanced significantly on a risk measurement basis.

  16. An Integrative Model of Internationalization Strategies

    DEFF Research Database (Denmark)

    Li, Xin; Gammelgaard, Jens

    2014-01-01

    Purpose – This paper aims to critically review the ownership, location and internalization (OLI) model and the Uppsala internationalization process (UIP) framework. We suggest that the inclusion of concepts such as corporate entrepreneurship, host country institutions and regulatory focus...... choice with regard to internationalization. Practical implications – Regulatory focus theory originates from managerial psychology. The model is, therefore, relevant for managers, and it shows how the outcomes and processes of corporate entrepreneurial activity should manifest themselves in managerial...... decision-making related to further internationalization. The strength of host country institutions also affects such decision-making. Originality/value – This paper is the first to present the concept of regulatory focus in relation to firm internationalization. In addition, it shows that most...

  17. Modeling strategy for clinched joints in assemblies

    Science.gov (United States)

    Breda, A.; Coppieters, S.; Debruyne, D.

    2016-08-01

    Clinching is a mechanical joining technique which involves severe local plastic deformation of two or more metal sheet parts resulting in a permanent mechanical interlock. Today, it is a reliable joining technique used in automotive, HVAC and general steel constructions whilst still gaining interest. As it is not computationally feasible to include detailed sub models of these type of joints in FE simulations of real-life clinched assemblies, this paper proposes a methodology to represent these connections with simplified elements. In order to calibrate the parameters governing the equivalent model, a simple shear lap and pullout test is used. This methodology is applied to clinched configurations and validated using a modified Arcan test in which both shear and pull-out loads are considered.

  18. Continuum modeling of rate-dependent granular flows in SPH

    Science.gov (United States)

    Hurley, Ryan C.; Andrade, José E.

    2016-09-01

    We discuss a constitutive law for modeling rate-dependent granular flows that has been implemented in smoothed particle hydrodynamics (SPH). We model granular materials using a viscoplastic constitutive law that produces a Drucker-Prager-like yield condition in the limit of vanishing flow. A friction law for non-steady flows, incorporating rate-dependence and dilation, is derived and implemented within the constitutive law. We compare our SPH simulations with experimental data, demonstrating that they can capture both steady and non-steady dynamic flow behavior, notably including transient column collapse profiles. This technique may therefore be attractive for modeling the time-dependent evolution of natural and industrial flows.

  19. Continuum modeling of rate-dependent granular flows in SPH

    Science.gov (United States)

    Hurley, Ryan C.; Andrade, José E.

    2017-01-01

    We discuss a constitutive law for modeling rate-dependent granular flows that has been implemented in smoothed particle hydrodynamics (SPH). We model granular materials using a viscoplastic constitutive law that produces a Drucker-Prager-like yield condition in the limit of vanishing flow. A friction law for non-steady flows, incorporating rate-dependence and dilation, is derived and implemented within the constitutive law. We compare our SPH simulations with experimental data, demonstrating that they can capture both steady and non-steady dynamic flow behavior, notably including transient column collapse profiles. This technique may therefore be attractive for modeling the time-dependent evolution of natural and industrial flows.

  20. Dose-Dependent Mutation Rates Determine Optimum Erlotinib Dosing Strategies for EGFR Mutant Non-Small Cell Lung Cancer Patients.

    Directory of Open Access Journals (Sweden)

    Lin L Liu

    Full Text Available The advent of targeted therapy for cancer treatment has brought about a paradigm shift in the clinical management of human malignancies. Agents such as erlotinib used for EGFR-mutant non-small cell lung cancer or imatinib for chronic myeloid leukemia, for instance, lead to rapid tumor responses. Unfortunately, however, resistance often emerges and renders these agents ineffective after a variable amount of time. The FDA-approved dosing schedules for these drugs were not designed to optimally prevent the emergence of resistance. To this end, we have previously utilized evolutionary mathematical modeling of treatment responses to elucidate the dosing schedules best able to prevent or delay the onset of resistance. Here we expand on our approaches by taking into account dose-dependent mutation rates at which resistant cells emerge. The relationship between the serum drug concentration and the rate at which resistance mutations arise can lead to non-intuitive results about the best dose administration strategies to prevent or delay the emergence of resistance.We used mathematical modeling, available clinical trial data, and different considerations of the relationship between mutation rate and drug concentration to predict the effectiveness of different dosing strategies.We designed several distinct measures to interrogate the effects of different treatment dosing strategies and found that a low-dose continuous strategy coupled with high-dose pulses leads to the maximal delay until clinically observable resistance. Furthermore, the response to treatment is robust against different assumptions of the mutation rate as a function of drug concentration.For new and existing targeted drugs, our methodology can be employed to compare the effectiveness of different dose administration schedules and investigate the influence of changing mutation rates on outcomes.

  1. Handling the Dependence of Claim Severities with Copula Models

    Directory of Open Access Journals (Sweden)

    Yulia Resti

    2010-01-01

    Full Text Available Problem statement: Several studies have been carried out on the modeling of claim severity data in actuarial literature as well as in insurance practice. Since it is well established that the claim cost distributions generally have positive support and are positively skewed, the regression models of Gamma and Lognormal have been used by practitioners for modeling claim severities. However, the fitting of claim severities via regression models assumes that the claim types are independent. Approach: In this study, independent assumption between claim types will be investigated as we will consider three types of Malaysian motor insurance claims namely Third Party Body Injury (TPBI, Third Party Property Damage (TPPD and Own Damage (OD and applied the normal, t, Frank and Clayton copulas for modeling dependence structures between these claim types. Results: The AIC and BIC indicated that the Clayton is the best copula for modeling dependence between TPBI and OD claims and between TPPD and OD claims, whereas the t-copula is the best copula for modeling dependence between TPBI and TPPD claims. Conclusion: This study modeled the dependence between insurance claim types using copulas on the Malaysian motor insurance claim severity data. The main advantage of using copula is that each marginal distribution can be specified independently based on the distribution of individual variable and then joined by the copula which takes into account the dependence between these variables. Based on the results, the estimated of copula parameter for claim severities indicate that the dependence between claim types is significant.

  2. DREAM/calsenilin/KChIP3 modulates strategy selection and estradiol-dependent learning and memory.

    Science.gov (United States)

    Tunur, Tumay; Stelly, Claire E; Schrader, Laura Ann

    2013-11-18

    Downstream regulatory element antagonist modulator (DREAM)/calsenilin(C)/K⁺ channel interacting protein 3 (KChIP3) is a multifunctional Ca²⁺-binding protein highly expressed in the hippocampus that inhibits hippocampus-sensitive memory and synaptic plasticity in male mice. Initial studies in our lab suggested opposing effects of DR/C/K3 expression in female mice. Fluctuating hormones that occur during the estrous cycle may affect these results. In this study, we hypothesized that DR/C/K3 interacts with 17β-estradiol, the primary estrogen produced by the ovaries, to play a role in hippocampus function. We investigated the role of estradiol and DR/C/K3 in learning strategy in ovariectomized (OVX) female mice. OVX WT and DR/C/K3 knockout (KO) mice were given three injections of vehicle (sesame oil) or 17β-estradiol benzoate (0.25 mg in 100 mL sesame oil) 48, 24, and 2 h before training and testing. DR/C/K3 and estradiol had a time-dependent effect on strategy use in the female mice. Male KO mice exhibited enhanced place strategy relative to WT 24 h after pre-exposure. Fear memory formation was significantly reduced in intact female KO mice relative to intact WT mice, and OVX reduced fear memory formation in the WT, but had no effect in the KO mice. Long-term potentiation in hippocampus slices from female mice was enhanced by circulating ovarian hormones in both WT and DR/C/K3 KO mice. Paired-pulse depression was not affected by ovarian hormones but was reduced in DR/C/K3 KO mice. These results provide the first evidence that DR/C/K3 plays a timing-dependent role in estradiol regulation of learning, memory, and plasticity.

  3. A strategy for eliciting antibodies against cryptic, conserved, conformationally dependent epitopes of HIV envelope glycoprotein.

    Directory of Open Access Journals (Sweden)

    Hanna C Kelker

    Full Text Available BACKGROUND: Novel strategies are needed for the elicitation of broadly neutralizing antibodies to the HIV envelope glycoprotein, gp120. Experimental evidence suggests that combinations of antibodies that are broadly neutralizing in vitro may protect against challenge with HIV in nonhuman primates, and a small number of these antibodies have been selected by repertoire sampling of B cells and by the fractionation of antiserum from some patients with prolonged disease. Yet no additional strategies for identifying conserved epitopes, eliciting antibodies to these epitopes, and determining whether these epitopes are accessible to antibodies have been successful to date. The defining of additional conserved, accessible epitopes against which one can elicit antibodies will increase the probability that some may be the targets of broadly neutralizing antibodies. METHODOLOGY/PRINCIPAL FINDINGS: We postulate that additional cryptic epitopes of gp120 are present, against which neutralizing antibodies might be elicited even though these antibodies are not elicited by gp120, and that many of these epitopes may be accessible to antibodies should they be formed. We demonstrate a strategy for eliciting antibodies in mice against selected cryptic, conformationally dependent conserved epitopes of gp120 by immunizing with multiple identical copies of covalently linked peptides (MCPs. This has been achieved with MCPs representing 3 different domains of gp120. We show that some cryptic epitopes on gp120 are accessible to the elicited antibodies, and some epitopes in the CD4 binding region are not accessible. The antibodies bind to gp120 with relatively high affinity, and bind to oligomeric gp120 on the surface of infected cells. CONCLUSIONS/SIGNIFICANCE: Immunization with MCPs comprised of selected peptides of HIV gp120 is able to elicit antibodies against conserved, conformationally dependent epitopes of gp120 that are not immunogenic when presented as gp120. Some

  4. A Structural Equation Approach to Models with Spatial Dependence

    NARCIS (Netherlands)

    Oud, J.H.L.; Folmer, H.

    2008-01-01

    We introduce the class of structural equation models (SEMs) and corresponding estimation procedures into a spatial dependence framework. SEM allows both latent and observed variables within one and the same (causal) model. Compared with models with observed variables only, this feature makes it poss

  5. A structural equation approach to models with spatial dependence

    NARCIS (Netherlands)

    Oud, J.H.L.; Folmer, H.

    2008-01-01

    We introduce the class of structural equation models (SEMs) and corresponding estimation procedures into a spatial dependence framework. SEM allows both latent and observed variables within one and the same (causal) model. Compared with models with observed variables only, this feature makes it poss

  6. Motion depending on the strategies of players enhances cooperation in a co-evolutionary prisoner's dilemma game

    Energy Technology Data Exchange (ETDEWEB)

    Cheng Hongyan; Li Haihong; Dai Qionglin; Zhu Yun; Yang Junzhong, E-mail: hycheng@bupt.edu.cn [School of Science, Beijing University of Posts and Telecommunications, Beijing 100876 (China)

    2010-12-15

    In the evolution of cooperation, the motion of players plays an important role. In this paper, we incorporate, into an evolutionary prisoner dilemma's game on networks, a new factor that cooperators and defectors move with different probabilities. By investigating the dependence of the cooperator frequency on the moving probabilities of cooperators and defectors, {mu}{sub c} and {mu}{sub d}, we find that cooperation is greatly enhanced in the parameter regime of {mu}{sub c}<{mu}{sub d}. The snapshots of strategy pattern and the evolutions of cooperator clusters and defector clusters reveal that either the fast motion of defectors or the slow motion of cooperators always favors the formation of large cooperator clusters. The model is investigated on different types of networks such as square lattices, Erdoes-Renyi networks and scale-free networks and with different types of strategy-updating rules such as the richest-following rule and the Fermi rule. The numerical results show that the observed phenomena are robust to different networks and to different strategy-updating rules.

  7. Modeling Stakeholder/Value Dependency through Mean Failure Cost

    Energy Technology Data Exchange (ETDEWEB)

    Aissa, Anis Ben [University of Tunis, Belvedere, Tunisia; Abercrombie, Robert K [ORNL; Sheldon, Frederick T [ORNL; Mili, Ali [New Jersey Insitute of Technology

    2010-01-01

    In an earlier series of works, Boehm et al. discuss the nature of information system dependability and highlight the variability of system dependability according to stakeholders. In a recent paper, the dependency patterns of this model are analyzed. In our recent works, we presented a stakeholder dependent quantitative security model, where we quantify security for a given stakeholder by the mean of the loss incurred by the stakeholder as a result of security threats. We show how this mean can be derived from the security threat configuration (represented as a vector of probabilities that reflect the likelihood of occurrence of the various security threats). We refer to our security metric as MFC, for Mean Failure Cost. In this paper, we analyze Boehm's model from the standpoint of the proposed metric, and show whether, to what extent, and how our metric addresses the issues raised by Boehm's Stakeholder/Value definition of system dependability.

  8. A strategy for developing a hammerhead ribozyme for selective RNA cleavage depending on substitutional RNA editing.

    Science.gov (United States)

    Fukuda, Masatora; Kurihara, Kei; Tanaka, Yasuyoshi; Deshimaru, Masanobu

    2012-09-01

    Substitutional RNA editing plays a crucial role in the regulation of biological processes. Cleavage of target RNA that depends on the specific site of substitutional RNA editing is a useful tool for analyzing and regulating intracellular processes related to RNA editing. Hammerhead ribozymes have been utilized as small catalytic RNAs for cleaving target RNA at a specific site and may be used for RNA-editing-specific RNA cleavage. Here we reveal a design strategy for a hammerhead ribozyme that specifically recognizes adenosine to inosine (A-to-I) and cytosine to uracil (C-to-U) substitutional RNA-editing sites and cleaves target RNA. Because the hammerhead ribozyme cleaves one base upstream of the target-editing site, the base that pairs with the target-editing site was utilized for recognition. RNA-editing-specific ribozymes were designed such that the recognition base paired only with the edited base. These ribozymes showed A-to-I and C-to-U editing-specific cleavage activity against synthetic serotonin receptor 2C and apolipoprotein B mRNA fragments in vitro, respectively. Additionally, the ribozyme designed for recognizing A-to-I RNA editing at the Q/R site on filamin A (FLNA) showed editing-specific cleavage activity against physiologically edited FLNA mRNA extracted from cells. We demonstrated that our strategy is effective for cleaving target RNA in an editing-dependent manner. The data in this study provided an experimental basis for the RNA-editing-dependent degradation of specific target RNA in vivo.

  9. MODEL MEKANISME ADMINISTRATIF TERINTEGRASIPADA IMPLEMENTASI STRATEGI DI LEVEL UNIT BISNIS STRATEGIS

    Directory of Open Access Journals (Sweden)

    Dwi Sulistiani

    2014-11-01

    Full Text Available Tulisan ini menindaklanjuti pandangan terpadu tentang elemen penting dari tiga mekanisme administratif: struktur organisasi, sistem kontrol dan manajer yang berkaitan dengan perbedaan dalam strategi kompetitif SBU (strategic business unit.Tulisan ini berdasarkan penelitian Govindarajan (1988 yang mencoba menemukan model untuk implementasi beragam strategi SBU yang dijalankan oleh korporasi berbeda. Hasilnya ditemukan bahwa lokus kontrol internal manajerial yang tinggi dan emphasis yang rendah pada pemenuhan sebuah budget berhubungan dengan kinerja tinggi dalam SBU yang menjalankan strategi diferensiasi. Hasil berbasis analisis sistem menunjukkan bahwa ketika gaya evaluatif budget, desentralisasi dan lokus kontrol berhubungan untuk memenuhi kebutuhan strategi SBU, maka dihasilkan kinerja superior. Kesesuaian sistem ini adalah sangat kuat antar SBU diferensiasi, tapi tidak begitu kuat antar unit low cost

  10. VEHICLE SIMULATION MODEL FOR DEVELOPING AN INTELLIGENT SLOPE SHIFT STRATEGY

    Institute of Scientific and Technical Information of China (English)

    Jin Hui; Ge Anlin

    2004-01-01

    With the rapid development of electronics and the growing demand for higher vehicle performance,intelligent shift technology is becoming increasingly important,and it promises to be a developing trend in vehicle automatic transmissions.A new simulation model is presented,which includes engine,powertrain,tire and vehicle dynamics models.Based on the model,simulation experiments are conducted to investigate the slope shift strategy.The data and conclusions obtained from the simulations are valuable contributions to the development of an intelligent slope shift strategy.

  11. A Multilevel Testlet Model for Dual Local Dependence

    Science.gov (United States)

    Jiao, Hong; Kamata, Akihito; Wang, Shudong; Jin, Ying

    2012-01-01

    The applications of item response theory (IRT) models assume local item independence and that examinees are independent of each other. When a representative sample for psychometric analysis is selected using a cluster sampling method in a testlet-based assessment, both local item dependence and local person dependence are likely to be induced.…

  12. EMPIRICAL LIKELIHOOD FOR LINEAR MODELS UNDER m-DEPENDENT ERRORS

    Institute of Scientific and Technical Information of China (English)

    QinYongsong; JiangBo; LiYufang

    2005-01-01

    In this paper,the empirical likelihood confidence regions for the regression coefficient in a linear model are constructed under m-dependent errors. It is shown that the blockwise empirical likelihood is a good way to deal with dependent samples.

  13. A model of plant strategies in fluvial hydrosystems

    NARCIS (Netherlands)

    Bornette, G.; Tabacchi, E.; Hupp, C.; Puijalon, S.; Rostan, J.C.

    2008-01-01

    1. We propose a model of plant strategies in temperate fluvial hydrosystems that considers the hydraulic and geomorphic features that control plant recruitment, establishment and growth in river floodplains. 2. The model describes first how the disturbance gradient and the grain-size of the river be

  14. Student Models of Learning and Their Impact on Study Strategies

    Science.gov (United States)

    Ferla, Johan; Valcke, Martin; Schuyten, Gilberte

    2009-01-01

    This study aims to identify student models of learning (sets of "intra-student" cognitions about learning) and to investigate their effect on study strategies. A two-step cluster analysis identified four student models of learning, representing students' self-efficacy beliefs, learning conceptions, attributions for academic performance…

  15. On the Temperature Dependence of the UNIQUAC/UNIFAC Models

    DEFF Research Database (Denmark)

    Skjold-Jørgensen, Steen; Rasmussen, Peter; Fredenslund, Aage

    1980-01-01

    Local composition models for the description of the properties of liquid mixtures do not in general give an accurate representation of excess Gibbs energy and excess enthalpy simultaneously. The introduction of temperature dependent interaction parameters leads to considerable improvements...

  16. An efficient finite-difference strategy for sensitivity analysis of stochastic models of biochemical systems.

    Science.gov (United States)

    Morshed, Monjur; Ingalls, Brian; Ilie, Silvana

    2017-01-01

    Sensitivity analysis characterizes the dependence of a model's behaviour on system parameters. It is a critical tool in the formulation, characterization, and verification of models of biochemical reaction networks, for which confident estimates of parameter values are often lacking. In this paper, we propose a novel method for sensitivity analysis of discrete stochastic models of biochemical reaction systems whose dynamics occur over a range of timescales. This method combines finite-difference approximations and adaptive tau-leaping strategies to efficiently estimate parametric sensitivities for stiff stochastic biochemical kinetics models, with negligible loss in accuracy compared with previously published approaches. We analyze several models of interest to illustrate the advantages of our method.

  17. Directed sample interrogation utilizing an accurate mass exclusion-based data-dependent acquisition strategy (AMEx).

    Science.gov (United States)

    Rudomin, Emily L; Carr, Steven A; Jaffe, Jacob D

    2009-06-01

    The ability to perform thorough sampling is of critical importance when using mass spectrometry to characterize complex proteomic mixtures. A common approach is to reinterrogate a sample multiple times by LC-MS/MS. However, the conventional data-dependent acquisition methods that are typically used in proteomics studies will often redundantly sample high-intensity precursor ions while failing to sample low-intensity precursors entirely. We describe a method wherein the masses of successfully identified peptides are used to generate an accurate mass exclusion list such that those precursors are not selected for sequencing during subsequent analyses. We performed multiple concatenated analytical runs to sample a complex cell lysate, using either accurate mass exclusion-based data-dependent acquisition (AMEx) or standard data-dependent acquisition, and found that utilization of AMEx on an ESI-Orbitrap instrument significantly increases the total number of validated peptide identifications relative to a standard DDA approach. The additional identified peptides represent precursor ions that exhibit low signal intensity in the sample. Increasing the total number of peptide identifications augmented the number of proteins identified, as well as improved the sequence coverage of those proteins. Together, these data indicate that using AMEx is an effective strategy to improve the characterization of complex proteomic mixtures.

  18. The role of grazer predation strategies in the dynamics of consumer-resource based ecological models

    Science.gov (United States)

    Cropp, Roger; Moroz, Irene; Norbury, John

    2017-07-01

    We analyse a simple plankton system to provide a heuristic for more complex models such as Dynamic Green Ocean Models (DGOMs). Zooplankton foraging is either by generalist grazers that consume whatever they bump into or specialist grazers that actively seek particular prey. The zooplankton may further be classified as either facultative grazers that can survive on any of their prey or obligate grazers that depend on the presence of specific prey. A key result is that different prey dependencies can result in dramatically different impacts of grazing strategies on system outcomes. The grazing strategy can determine whether a system with obligate grazers will be stable, have regular, predictable cycles or be chaotic. Conversely, whether facultative zooplankton functioned as specialist or generalist grazers makes no qualitative difference to the dynamics of the system. These results demonstrate that the effect of different grazing strategies can be critically dependent on the grazer's dependency on specific prey. Great care must be taken when choosing functional forms for population interactions in DGOMs, particularly in scenarios such as climate change where parameters such as mortality and growth coefficients may change. A robust theoretical framework supporting model development and analysis is key to understanding how such choices can affect model properties and hence predictions.

  19. Cluster-size dependent randomization traffic flow model

    Institute of Scientific and Technical Information of China (English)

    Gao Kun; Wang Bing-Hong; Fu Chuan-Ji; Lu Yu-Feng

    2007-01-01

    In order to exhibit the meta-stable states, several slow-to-start rules have been investigated as modification to Nagel-Schreckenberg (NS) model. These models can reproduce some realistic phenomena which are absent in the original NS model. But in these models, the size of cluster is still not considered as a useful parameter. In real traffic,the slow-to-start motion of a standing vehicle often depends on the degree of congestion which can be measured by the clusters'size. According to this idea, we propose a cluster-size dependent slow-to-start model based on the speeddependent slow-to-start rule (VDR) model. It gives expected results through simulations. Comparing with the VDR model, our new model has a better traffic efficiency and shows richer complex characters.

  20. Generalized linear models for categorical and continuous limited dependent variables

    CERN Document Server

    Smithson, Michael

    2013-01-01

    Introduction and OverviewThe Nature of Limited Dependent VariablesOverview of GLMsEstimation Methods and Model EvaluationOrganization of This BookDiscrete VariablesBinary VariablesLogistic RegressionThe Binomial GLMEstimation Methods and IssuesAnalyses in R and StataExercisesNominal Polytomous VariablesMultinomial Logit ModelConditional Logit and Choice ModelsMultinomial Processing Tree ModelsEstimation Methods and Model EvaluationAnalyses in R and StataExercisesOrdinal Categorical VariablesModeling Ordinal Variables: Common Practice versus Best PracticeOrdinal Model AlternativesCumulative Mod

  1. Detecting Character Dependencies in Stochastic Models of Evolution.

    Science.gov (United States)

    Chakrabarty, Deeparnab; Kannan, Sampath; Tian, Kevin

    2016-03-01

    Stochastic models of biological evolution generally assume that different characters (runs of the stochastic process) are independent and identically distributed. In this article we determine the asymptotic complexity of detecting dependence for some fairly general models of evolution, but simple models of dependence. A key difference from much of the previous work is that our algorithms work without knowledge of the tree topology. Specifically, we consider various stochastic models of evolution ranging from the common ones used by biologists (such as Cavender-Farris-Neyman and Jukes-Cantor models) to very general ones where evolution of different characters can be governed by different transition matrices on each edge of the evolutionary tree (phylogeny). We also consider several models of dependence between two characters. In the most specific model, on each edge of the phylogeny the joint distribution of the dependent characters undergoes a perturbation of a fixed magnitude, in a fixed direction from what it would be if the characters were evolving independently. More general dependence models don't require such a strong "signal." Instead they only require that on each edge, the perturbation of the joint distribution has a significant component in a specific direction. Our main results are nearly tight bounds on the induced or operator norm of the transition matrices that would allow us to detect dependence efficiently for most models of evolution and dependence that we consider. We make essential use of a new concentration result for multistate random variables of a Markov random field on arbitrary trivalent trees: We show that the random variable counting the number of leaves in any particular state has variance that is subquadratic in the number of leaves.

  2. Modelling temperature and concentration dependent solid/liquid interfacial energies

    Science.gov (United States)

    Lippmann, Stephanie; Jung, In-Ho; Paliwal, Manas; Rettenmayr, Markus

    2016-01-01

    Models for the prediction of the solid/liquid interfacial energy in pure substances and binary alloys, respectively, are reviewed and extended regarding the temperature and concentration dependence of the required thermodynamic entities. A CALPHAD-type thermodynamic database is used to introduce temperature and concentration dependent melting enthalpies and entropies for multicomponent alloys in the temperature range between liquidus and solidus. Several suitable models are extended and employed to calculate the temperature and concentration dependent interfacial energy for Al-FCC with their respective liquids and compared with experimental data.

  3. A DEM contact model for history-dependent powder flows

    Science.gov (United States)

    Hashibon, Adham; Schubert, Raphael; Breinlinger, Thomas; Kraft, Torsten

    2016-11-01

    Die filling is an important part of the powder handling process chain that greatly influences the characteristic structure and properties of the final part. Predictive modelling and simulation of the die-filling process can greatly contribute to the optimization of the part and the whole production procedure, e.g. by predicting the resulting powder compaction structure as a function of filling process parameters. The rheology of powders can be very difficult to model especially if heterogeneous agglomeration or time-dependent consolidation effects occur. We present a new discrete element contact force model that enables modelling complex powder flow characteristics including direct time-dependent consolidation effects and load history-dependent cohesion to describe the filling process of complex, difficult to handle powders. The model is demonstrated for simple flow and an industrial powder flow.

  4. Strategy Guideline: Modeling Enclosure Design in Above-Grade Walls

    Energy Technology Data Exchange (ETDEWEB)

    Lstiburek, J. [Building Science Corporation, Westford, MA (United States); Ueno, K. [Building Science Corporation, Westford, MA (United States); Musunuru, S. [Building Science Corporation, Westford, MA (United States)

    2016-02-24

    The Strategy Guideline describes how to model and interpret results of models for above grade walls. The Measure Guideline analyzes the failure thresholds and criteria for above grade walls. A library of above-grade walls with historically successful performance was used to calibrate WUFI (Warme Und Feuchte Instationar) software models. The information is generalized for application to a broad population of houses within the limits of existing experience.

  5. Strategy Dependent Swimming Dynamics Change among a Predatory Algae Species with Different Strains

    Science.gov (United States)

    Katz, Joseph; Sheng, Jian; Malkiel, Edwin; Adolf, Jason; Place, Allen

    2008-11-01

    Digital holographic microscopic cinematography is used for measuring the 3D, time resolved, swimming behavior of toxic and non-toxic strains the marine dinoflagellate Karlodinium veneficum. We focus on the response of predators of the same species, but with different predation strategy, to the presence of prey, Storeatula major. Experiments are performed in a 3x3 mm cuvette, at densities extending to 100,000 cells/ml. Holograms are recorded at 60fps and at 20X magnification. In each case, we simultaneously track 200-500 cells in the 3mm deep sample, at a spatial resolution of 0.4x0.4x2 μm. We show that responses are largely dependent on the predation strategy. K. veneficum 2064, a toxic mixotroph, slows down and decreases the helix radius and clusters around the prey. Conversely, MD5, a non-toxic, autotrophic-like strain is completely oblivious to prey. Strain 1974, which is toxic and twice as motile, shows heterotrophic-like responses with characteristics of an active hunter. Also, on going spectral analysis of the 3-D motion provides quantitative insight on the swimming dynamics of microorganisms.

  6. Bias associated with failing to incorporate dependence on event history in Markov models.

    Science.gov (United States)

    Bentley, Tanya G K; Kuntz, Karen M; Ringel, Jeanne S

    2010-01-01

    When using state-transition Markov models to simulate risk of recurrent events over time, incorporating dependence on higher numbers of prior episodes can increase model complexity, yet failing to capture this event history may bias model outcomes. This analysis assessed the tradeoffs between model bias and complexity when evaluating risks of recurrent events in Markov models. The authors developed a generic episode/relapse Markov cohort model, defining bias as the percentage change in events prevented with 2 hypothetical interventions (prevention and treatment) when incorporating 0 to 9 prior episodes in relapse risk versus a model with 10 such episodes. Magnitude and sign of bias were evaluated as a function of event and recovery risks, disease-specific mortality, and risk function. Bias was positive in the base case for a prevention strategy, indicating that failing to fully incorporate dependence on event history overestimated the prevention's predicted impact. For treatment, the bias was negative, indicating an underestimated benefit. Bias approached zero as the number of tracked prior episodes increased, and the average bias over 10 tracked episodes was greater with the exponential compared with linear functions of relapse risk and with treatment compared with prevention strategies. With linear and exponential risk functions, absolute bias reached 33% and 78%, respectively, in prevention and 52% and 85% in treatment. Failing to incorporate dependence on prior event history in subsequent relapse risk in Markov models can greatly affect model outcomes, overestimating the impact of prevention and treatment strategies by up to 85% and underestimating the impact in some treatment models by up to 20%. When at least 4 prior episodes are incorporated, bias does not exceed 26% in prevention or 11% in treatment.

  7. Survey of E-Commerce Modeling and Optimization Strategies

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Electronic commerce is impacting almost all commercial activities. The resulting emerging commercial activities bring with them many new modeling and optimization problems. This survey reviews pioneering works in this new area, covering topics in advertising strategy, web page design, automatic pricing, auction methods, brokerage strategy, and customer behavior analysis. Mathematical models for problems in these areas and their solution algorithms are discussed. In addition to presenting and commenting on these works, we also discuss possible extensions and related problems. The objective of this survey is to encourage more researchers to pay attention to this emerging area.

  8. The Effectiveness of Window Presentation Strategy and Cognitive Style of Field Dependence Status on Learning from Mediated Instructions.

    Science.gov (United States)

    Ikegulu, Patricia R.; Ikegulu, T. Nelson

    The primary purpose of this article is to review the literature on research studies conducted in the last five years on the effectiveness of window presentation strategies and the cognitive dependence status of field-dependent/independent (FD/FI) learners in a computer-mediated instruction (CMI). Secondary to this purpose is to summarize research…

  9. The Effects of Field Dependent/Independent Style Awareness on Learning Strategies and Outcomes in an Instructional Hypermedia Module

    Science.gov (United States)

    Fyle, Clifford Omodele

    2009-01-01

    The purpose of this study was to examine whether field-dependent/independent style awareness affects learning outcomes and learning strategies used in a hypermedia instructional module. Field-dependent/independent style was measured using the Global Embedded Figures Test. Style awareness meant that students were provided with information and…

  10. Majority-vote model on Opinion-Dependent Networks

    CERN Document Server

    Lima, F W S

    2013-01-01

    We study a nonequilibrium model with up-down symmetry and a noise parameter $q$ known as majority-vote model of M.J. Oliveira $1992$ on opinion-dependent network or Stauffer-Hohnisch-Pittnauer networks. By Monte Carlo simulations and finite-size scaling relations the critical exponents $\\beta/\

  11. Characterization of Models for Time-Dependent Behavior of Soils

    DEFF Research Database (Denmark)

    Liingaard, Morten; Augustesen, Anders; Lade, Poul V.

    2004-01-01

      Different classes of constitutive models have been developed to capture the time-dependent viscous phenomena ~ creep, stress relaxation, and rate effects ! observed in soils. Models based on empirical, rheological, and general stress-strain-time concepts have been studied. The first part is a r...

  12. Exploring Term Dependences in Probabilistic Information Retrieval Model.

    Science.gov (United States)

    Cho, Bong-Hyun; Lee, Changki; Lee, Gary Geunbae

    2003-01-01

    Describes a theoretic process to apply Bahadur-Lazarsfeld expansion (BLE) to general probabilistic models and the state-of-the-art 2-Poisson model. Through experiments on two standard document collections, one in Korean and one in English, it is demonstrated that incorporation of term dependences using BLE significantly contributes to performance…

  13. Model-driven dependability assessment of software systems

    CERN Document Server

    Bernardi, Simona; Petriu, Dorina C

    2013-01-01

    In this book, the authors present cutting-edge model-driven techniques for modeling and analysis of software dependability. Most of them are based on the use of UML as software specification language. From the software system specification point of view, such techniques exploit the standard extension mechanisms of UML (i.e., UML profiling). UML profiles enable software engineers to add non-functional properties to the software model, in addition to the functional ones. The authors detail the state of the art on UML profile proposals for dependability specification and rigorously describe the t

  14. A Dependent Hidden Markov Model of Credit Quality

    Directory of Open Access Journals (Sweden)

    Małgorzata Wiktoria Korolkiewicz

    2012-01-01

    Full Text Available We propose a dependent hidden Markov model of credit quality. We suppose that the "true" credit quality is not observed directly but only through noisy observations given by posted credit ratings. The model is formulated in discrete time with a Markov chain observed in martingale noise, where "noise" terms of the state and observation processes are possibly dependent. The model provides estimates for the state of the Markov chain governing the evolution of the credit rating process and the parameters of the model, where the latter are estimated using the EM algorithm. The dependent dynamics allow for the so-called "rating momentum" discussed in the credit literature and also provide a convenient test of independence between the state and observation dynamics.

  15. pH-dependent coarse-grained model of peptides

    CERN Document Server

    Enciso, Marta; Site, Luigi Delle

    2012-01-01

    We propose a coarse-grained modeling strategy for peptides where the effect of changes of the pH can be efficiently described. The idea is based on modeling the effects of the pH value on the main driving interactions using reference data from atomistic simulations and experimental databases and transferring its main physical features to the coarse-grained resolution according the principle of consistency across the scales. After refining the coarse-grained model appropriately this was achieved by finding a unique set of parameters for the coarse-grained model that, when applied to peptides with different sequences and experimental properties, reproduces the experimental and atomistic data of reference. We used the such parametrized model for performing several numerical tests to check the universality of the model. We have tried systems with rather different response to pH variations, showing a highly satisfactory performance of the model.

  16. On a Class of Dual Risk Model with Dependence based on the FGM Copula

    Directory of Open Access Journals (Sweden)

    Hua Dong

    2010-12-01

    Full Text Available In this paper, we consider an extension to a dual model under a barrier strategy, in which the innovation sizes depend on the innovation time via the FGM copula. We first derive a renewal equation for the expected total discounted dividends until ruin. Some differential equations and closed-form expressions are given for exponential innovation sizes. Then the optimal dividend barrier and the Laplace transform of the time to ruin are considered. Finally, a numerical example is given.

  17. A SIRS epidemic model with infection-age dependence

    Science.gov (United States)

    Zhang, Zhonghua; Peng, Jigen

    2007-07-01

    Based on J. Mena-Lorca and H.W. Hethcote's epidemic model, a SIRS epidemic model with infection-age-dependent infectivity and general nonlinear contact rate is formulated. Under general conditions, the unique existence of its global positive solutions is obtained. Moreover, under more general assumptions than the existing, the existence and asymptotical stability of its equilibria are discussed. In the end, the condition on the stability of endemic equilibrium is verified by a special model.

  18. Study of Simplification of Markov Model for Analyzing System Dependability

    Energy Technology Data Exchange (ETDEWEB)

    Son, Gwang Seop; Kim, Dong Hoon; Choi, Jong Gyun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2015-05-15

    In this paper, we introduce the simplification methodology of the Markov model for analyzing system dependability using system failure rate concept. This system failure rate is the probability that the system is failed or unavailable given that the system was as good as at this time. Using this parameter, the Markov model of sub system can be replaced to the system failure rate and then this parameter just is considered in the Markov model of whole system. In this paper, we proposed the method to simplify the Markov model in complex system architecture. We define the system failure rate and using this parameter, the Markov model of system could be simplified.

  19. Capturing Multivariate Spatial Dependence: Model, Estimate and then Predict

    OpenAIRE

    Cressie, Noel; Burden, Sandy; Davis, Walter; Krivitsky, Pavel N.; Mokhtarian, Payam; Suesse, Thomas; Zammit-Mangion, Andrew

    2015-01-01

    Physical processes rarely occur in isolation, rather they influence and interact with one another. Thus, there is great benefit in modeling potential dependence between both spatial locations and different processes. It is the interaction between these two dependencies that is the focus of Genton and Kleiber's paper under discussion. We see the problem of ensuring that any multivariate spatial covariance matrix is nonnegative definite as important, but we also see it as a means to an end. Tha...

  20. Modeling the Dependency Structure of Integrated Intensity Processes.

    Directory of Open Access Journals (Sweden)

    Yong-Ki Ma

    Full Text Available This paper studies an important issue of dependence structure. To model this structure, the intensities within the Cox processes are driven by dependent shot noise processes, where jumps occur simultaneously and their sizes are correlated. The joint survival probability of the integrated intensities is explicitly obtained from the copula with exponential marginal distributions. Subsequently, this result can provide a very useful guide for credit risk management.

  1. Thermo-Chemical Modelling Strategies for the Pultrusion Process

    DEFF Research Database (Denmark)

    Baran, Ismet; Hattel, Jesper Henri; Tutum, Cem Celal

    2013-01-01

    In the present study, three dimensional (3D) numerical modeling strategies of a thermosetting pultrusion process are investigated considering both transient and steady state approaches. For the transient solution, an unconditionally stable alternating direction implicit Douglas-Gunn (ADI-DG) sche...

  2. Current Models and Innovative Strategies in Management Education in China.

    Science.gov (United States)

    Wang, Zhong-Ming

    1999-01-01

    Current models of management education in China include national training, on-the-job technical training, and the national master's of business administration supervisory committee. Effective strategies being used include teamwork, process skills, action learning, cross-cultural management learning, and competency-based management development. (SK)

  3. The Creative Music Strategy: A Seven-Step Instructional Model

    Science.gov (United States)

    Robinson, Nathalie G.; Bell, Cindy L.; Pogonowski, Lenore

    2011-01-01

    The creative music strategy is a dynamic and flexible seven-step model for guiding general music students through the music concepts of improvisation and composition, followed by critical reflection. These are musical behaviors that cultivate the development of our students' deeper conceptual understandings and music independence by helping them…

  4. Temperature dependence of heterogeneous nucleation: Extension of the Fletcher model

    Science.gov (United States)

    McGraw, Robert; Winkler, Paul; Wagner, Paul

    2015-04-01

    Recently there have been several cases reported where the critical saturation ratio for onset of heterogeneous nucleation increases with nucleation temperature (positive slope dependence). This behavior contrasts with the behavior observed in homogeneous nucleation, where a decreasing critical saturation ratio with increasing nucleation temperature (negative slope dependence) seems universal. For this reason the positive slope dependence is referred to as anomalous. Negative slope dependence is found in heterogeneous nucleation as well, but because so few temperature-dependent measurements have been reported, it is not presently clear which slope condition (positive or negative) will become more frequent. Especially interesting is the case of water vapor condensation on silver nanoparticles [Kupc et al., AS&T 47: i-iv, 2013] where the critical saturation ratio for heterogeneous nucleation onset passes through a maximum, at about 278K, with higher (lower) temperatures showing the usual (anomalous) temperature dependence. In the present study we develop an extension of Fletcher's classical, capillarity-based, model of heterogeneous nucleation that explicitly resolves the roles of surface energy and surface entropy in determining temperature dependence. Application of the second nucleation theorem, which relates temperature dependence of nucleation rate to cluster energy, yields both necessary and sufficient conditions for anomalous temperature behavior in the extended Fletcher model. In particular it is found that an increasing contact angle with temperature is a necessary, but not sufficient, condition for anomalous temperature dependence to occur. Methods for inferring microscopic contact angle and its temperature dependence from heterogeneous nucleation probability measurements are discussed in light of the new theory.

  5. USING COPULAS TO MODEL DEPENDENCE IN SIMULATION RISK ASSESSMENT

    Energy Technology Data Exchange (ETDEWEB)

    Dana L. Kelly

    2007-11-01

    Typical engineering systems in applications with high failure consequences such as nuclear reactor plants often employ redundancy and diversity of equipment in an effort to lower the probability of failure and therefore risk. However, it has long been recognized that dependencies exist in these redundant and diverse systems. Some dependencies, such as common sources of electrical power, are typically captured in the logic structure of the risk model. Others, usually referred to as intercomponent dependencies, are treated implicitly by introducing one or more statistical parameters into the model. Such common-cause failure models have limitations in a simulation environment. In addition, substantial subjectivity is associated with parameter estimation for these models. This paper describes an approach in which system performance is simulated by drawing samples from the joint distributions of dependent variables. The approach relies on the notion of a copula distribution, a notion which has been employed by the actuarial community for ten years or more, but which has seen only limited application in technological risk assessment. The paper also illustrates how equipment failure data can be used in a Bayesian framework to estimate the parameter values in the copula model. This approach avoids much of the subjectivity required to estimate parameters in traditional common-cause failure models. Simulation examples are presented for failures in time. The open-source software package R is used to perform the simulations. The open-source software package WinBUGS is used to perform the Bayesian inference via Markov chain Monte Carlo sampling.

  6. Micromechanical modeling of rate-dependent behavior of Connective tissues.

    Science.gov (United States)

    Fallah, A; Ahmadian, M T; Firozbakhsh, K; Aghdam, M M

    2017-03-07

    In this paper, a constitutive and micromechanical model for prediction of rate-dependent behavior of connective tissues (CTs) is presented. Connective tissues are considered as nonlinear viscoelastic material. The rate-dependent behavior of CTs is incorporated into model using the well-known quasi-linear viscoelasticity (QLV) theory. A planar wavy representative volume element (RVE) is considered based on the tissue microstructure histological evidences. The presented model parameters are identified based on the available experiments in the literature. The presented constitutive model introduced to ABAQUS by means of UMAT subroutine. Results show that, monotonic uniaxial test predictions of the presented model at different strain rates for rat tail tendon (RTT) and human patellar tendon (HPT) are in good agreement with experimental data. Results of incremental stress-relaxation test are also presented to investigate both instantaneous and viscoelastic behavior of connective tissues.

  7. Reasoning About Strategies: On the Model-Checking Problem

    CERN Document Server

    Mogavero, Fabio; Perelli, Giuseppe; Vardi, Moshe Y

    2011-01-01

    In open systems verification, to formally check for reliability, one needs an appropriate formalism to model the interaction between agents and express the correctness of the system no matter how the environment behaves. An important contribution in this context is given by modal logics for strategic ability, in the setting of multi-agent games, such as ATL, ATL*, and the like. Recently, Chatterjee, Henzinger, and Piterman introduced Strategy Logic (CHP-SL), with the aim of getting a powerful framework for reasoning explicitly about strategies. CHP-SL is obtained by using first-order quantifications over strategies and it has been investigated in the setting of two-agents turned-based games, where a non-elementary model-checking algorithm has been provided. While CHP-SL is a very expressive logic, we claim that it does not fully capture the strategic aspects of multi-agent systems. In this paper, we introduce and study a more general strategy logic, denoted SL, for reasoning about strategies in multi-agent co...

  8. On the Markov-dependent risk model with tax

    Institute of Scientific and Technical Information of China (English)

    PENG Xing-chun; WANG Wen-yuan; HU Yi-jun

    2015-01-01

    In this paper we consider the Markov-dependent risk model with tax payments in which the claim occurrence, the claim amount as well as the tax rate are controlled by an irreducible discrete-time Markov chain. Systems of integro-diff erential equations satisfied by the expected discounted tax payments and the non-ruin probability in terms of the ruin probabilities under the Markov-dependent risk model without tax are established. The analytical solutions of the systems of integro-diff erential equations are also obtained by the iteration method.

  9. Modelling Difficulties and Their Overcoming Strategies in the Solution of a Modelling Problem

    Science.gov (United States)

    Dede, Ayse Tekin

    2016-01-01

    The purpose of the study is to reveal the elementary mathematics student teachers' difficulties encountered in the solution of a modelling problem, the strategies to overcome those difficulties and whether the strategies worked or not. Nineteen student teachers solved the modelling problem in their four or five-person groups, and the video records…

  10. Models, measurement, and strategies in developing critical-thinking skills.

    Science.gov (United States)

    Brunt, Barbara A

    2005-01-01

    Health care professionals must use critical-thinking skills to solve increasingly complex problems. Educators need to help nurses develop their critical-thinking skills to maintain and enhance their competence. This article reviews various models of critical thinking, as well as methods used to evaluate critical thinking. Specific educational strategies to develop nurses' critical-thinking skills are discussed. Additional research studies are needed to determine how the process of nursing practice can nurture and develop critical-thinking skills, and which strategies are most effective in developing and evaluating critical thinking.

  11. Performance deterioration modeling and optimal preventive maintenance strategy under scheduled servicing subject to mission time

    Directory of Open Access Journals (Sweden)

    Li Dawei

    2014-08-01

    Full Text Available Servicing is applied periodically in practice with the aim of restoring the system state and prolonging the lifetime. It is generally seen as an imperfect maintenance action which has a chief influence on the maintenance strategy. In order to model the maintenance effect of servicing, this study analyzes the deterioration characteristics of system under scheduled servicing. And then the deterioration model is established from the failure mechanism by compound Poisson process. On the basis of the system damage value and failure mechanism, the failure rate refresh factor is proposed to describe the maintenance effect of servicing. A maintenance strategy is developed which combines the benefits of scheduled servicing and preventive maintenance. Then the optimization model is given to determine the optimal servicing period and preventive maintenance time, with an objective to minimize the system expected life-cycle cost per unit time and a constraint on system survival probability for the duration of mission time. Subject to mission time, it can control the ability of accomplishing the mission at any time so as to ensure the high dependability. An example of water pump rotor relating to scheduled servicing is introduced to illustrate the failure rate refresh factor and the proposed maintenance strategy. Compared with traditional methods, the numerical results show that the failure rate refresh factor can describe the maintenance effect of servicing more intuitively and objectively. It also demonstrates that this maintenance strategy can prolong the lifetime, reduce the total lifetime maintenance cost and guarantee the dependability of system.

  12. Model selection in systems biology depends on experimental design.

    Science.gov (United States)

    Silk, Daniel; Kirk, Paul D W; Barnes, Chris P; Toni, Tina; Stumpf, Michael P H

    2014-06-01

    Experimental design attempts to maximise the information available for modelling tasks. An optimal experiment allows the inferred models or parameters to be chosen with the highest expected degree of confidence. If the true system is faithfully reproduced by one of the models, the merit of this approach is clear - we simply wish to identify it and the true parameters with the most certainty. However, in the more realistic situation where all models are incorrect or incomplete, the interpretation of model selection outcomes and the role of experimental design needs to be examined more carefully. Using a novel experimental design and model selection framework for stochastic state-space models, we perform high-throughput in-silico analyses on families of gene regulatory cascade models, to show that the selected model can depend on the experiment performed. We observe that experimental design thus makes confidence a criterion for model choice, but that this does not necessarily correlate with a model's predictive power or correctness. Finally, in the special case of linear ordinary differential equation (ODE) models, we explore how wrong a model has to be before it influences the conclusions of a model selection analysis.

  13. Modeling Responses of Leafy Spurge Dispersal to Control Strategies

    Institute of Scientific and Technical Information of China (English)

    Zewei Miao

    2007-01-01

    Leafy spurge (Euphorbia esula L.) has substantial negative effects on grassland biodiversity, productivity, and economic benefit in North America.To predict these negative impacts, we need an appropriate plant-spread model which can simulate the response of an invading population to different control strategies.In this study, using a stochastic map lattice approach we generated a spatially explicitly stochastic process-based model to simulate dispersal trajectories of leafy spurge under various control scenarios.The model integrated dispersal curve, propagule pressure, and population growth of leafy spurge at local and short-temporal scales to capture spread features of leafy spurge at large spatial and long-temporal scales.Our results suggested that narrow-, medium-, and fat-tailed kernels did not differ In their ability to predict spread, in contrast to previous works.For all kernels, Allee effects were significantly present and could explain the lag phase (three decades)before leafy spurge spread accelerated.When simulating from the initial stage of introduction, Allee effects were critical in predicting spread rate of leafy spurge, because the prediction could be seriously affected by the low density period of leafy spurge community.No Allee effects models were not able to simulate spread rate well in this circumstance.When applying control strategies to the current diatribution, Allee effects could stop the spread of leafy spurge; no Allee effects models, however, were able to slow but not stop the spread.The presence of Allee effects had significant ramifications on the efficiencies of control strategies.For both Allee and no Allee effects models, the later that control strategies were implemented, the more effort had to be input to achieve similar control results.

  14. Optimization model of vaccination strategy for dengue transmission

    Science.gov (United States)

    Widayani, H.; Kallista, M.; Nuraini, N.; Sari, M. Y.

    2014-02-01

    Dengue fever is emerging tropical and subtropical disease caused by dengue virus infection. The vaccination should be done as a prevention of epidemic in population. The host-vector model are modified with consider a vaccination factor to prevent the occurrence of epidemic dengue in a population. An optimal vaccination strategy using non-linear objective function was proposed. The genetic algorithm programming techniques are combined with fourth-order Runge-Kutta method to construct the optimal vaccination. In this paper, the appropriate vaccination strategy by using the optimal minimum cost function which can reduce the number of epidemic was analyzed. The numerical simulation for some specific cases of vaccination strategy is shown.

  15. Model-Based Dependability Analysis of Physical Systems with Modelica

    Directory of Open Access Journals (Sweden)

    Andrea Tundis

    2017-01-01

    Full Text Available Modelica is an innovative, equation-based, and acausal language that allows modeling complex physical systems, which are made of mechanical, electrical, and electrotechnical components, and evaluates their design through simulation techniques. Unfortunately, the increasing complexity and accuracy of such physical systems require new, more powerful, and flexible tools and techniques for evaluating important system properties and, in particular, the dependability ones such as reliability, safety, and maintainability. In this context, the paper describes some extensions of the Modelica language to support the modeling of system requirements and their relationships. Such extensions enable the requirement verification analysis through native constructs in the Modelica language. Furthermore, they allow exporting a Modelica-based system design as a Bayesian Network in order to analyze its dependability by employing a probabilistic approach. The proposal is exemplified through a case study concerning the dependability analysis of a Tank System.

  16. Condition dependence of reproductive strategy and the benefits of polyandry in a viviparous lizard.

    Science.gov (United States)

    Eizaguirre, Christophe; Laloi, David; Massot, Manuel; Richard, Murielle; Federici, Pierre; Clobert, Jean

    2007-02-07

    Species in which males do not contribute to reproduction beyond the provision of sperm offer good opportunities to study the potential genetic benefits that females can obtain from polyandry. Here, we report the results of a study examining the relationships between polyandry and components of female fitness in the common lizard (Lacerta vivipara). We found that polyandrous females produce larger clutches than monandrous females. Polyandrous females also lose fewer offspring during the later stages of gestation and at birth, but we did not find any relationship between polyandry and physical characteristics of viable neonates. Our results were consistent with the predictions of the intrinsic male quality hypothesis, while inbreeding avoidance and genetic incompatibility avoidance might also explain some part of the variation observed in clutch size. Moreover, the benefits of polyandry appeared to depend on female characteristics, as revealed by an interaction between reproductive strategy and female length on reproductive success. Thus, all females did not benefit equally from mating with multiple males, which could explain why polyandry and monandry coexist.

  17. Strategies for successful recombinant expression of disulfide bond-dependent proteins in Escherichia coli

    Directory of Open Access Journals (Sweden)

    de Marco Ario

    2009-05-01

    Full Text Available Abstract Bacteria are simple and cost effective hosts for producing recombinant proteins. However, their physiological features may limit their use for obtaining in native form proteins of some specific structural classes, such as for instance polypeptides that undergo extensive post-translational modifications. To some extent, also the production of proteins that depending on disulfide bridges for their stability has been considered difficult in E. coli. Both eukaryotic and prokaryotic organisms keep their cytoplasm reduced and, consequently, disulfide bond formation is impaired in this subcellular compartment. Disulfide bridges can stabilize protein structure and are often present in high abundance in secreted proteins. In eukaryotic cells such bonds are formed in the oxidizing environment of endoplasmic reticulum during the export process. Bacteria do not possess a similar specialized subcellular compartment, but they have both export systems and enzymatic activities aimed at the formation and at the quality control of disulfide bonds in the oxidizing periplasm. This article reviews the available strategies for exploiting the physiological mechanisms of bactera to produce properly folded disulfide-bonded proteins.

  18. Strategy Guideline. Modeling Enclosure Design in Above-Grade Walls

    Energy Technology Data Exchange (ETDEWEB)

    Lstiburek, J. [Building Science Corporation, Westford, MA (United States); Ueno, K. [Building Science Corporation, Westford, MA (United States); Musunuru, S. [Building Science Corporation, Westford, MA (United States)

    2016-02-01

    The Strategy Guideline, written by the U.S. Department of Energy's research team Building Science Corporation, 1) describes how to model and interpret results of models for above-grade walls, and 2) analyzes the failure thresholds and criteria for above-grade walls. A library of above-grade walls with historically successful performance was used to calibrate WUFI (Wärme und Feuchte instationär) software models. The information is generalized for application to a broad population of houses within the limits of existing experience.

  19. Deficit Prevention: Budget Control Model for Enrollment-Dependent Colleges.

    Science.gov (United States)

    Townsley, Michael K.

    1994-01-01

    An ongoing system of short-term budget controls that test actual performance against budget forecasts is essential for enrollment-dependent independent colleges. The budget control model presented here is a tool to inform the management continuously of changes in the all-important tuition revenue stream. (Author/MSE)

  20. Temperature dependence of bag pressure from quasiparticle model

    Science.gov (United States)

    Prasad, N.; Singh, C. P.

    2001-03-01

    A quasiparticle model with effective thermal gluon and quark masses is used to derive a temperature /T- and baryon chemical potential /μ-dependent bag constant /B(μ,T). Consequences of such a bag constant are obtained on the equation of state (EOS) for a deconfined quark-gluon plasma (QGP).

  1. Temperature dependence of electronic heat capacity in Holstein model

    CERN Document Server

    Fialko, N S; Lakhno, V D

    2015-01-01

    The dynamics of charge migration was modeled to calculate temperature dependencies of its thermodynamic equilibrium values such as energy and electronic heat capacity in homogeneous adenine fragments. The energy varies from nearly polaron one at T~0 to midpoint of the conductivity band at high temperatures. The peak on the graph of electronic heat capacity is observed at the polaron decay temperature.

  2. Model Transformation for a System of Systems Dependability Safety Case

    Science.gov (United States)

    Murphy, Judy; Driskell, Steve

    2011-01-01

    The presentation reviews the dependability and safety effort of NASA's Independent Verification and Validation Facility. Topics include: safety engineering process, applications to non-space environment, Phase I overview, process creation, sample SRM artifact, Phase I end result, Phase II model transformation, fault management, and applying Phase II to individual projects.

  3. A stochastic inventory model with stock dependent demand items

    Directory of Open Access Journals (Sweden)

    Lakdere Benkherouf

    2001-01-01

    Full Text Available In this paper, we propose a new continuous time stochastic inventory model for stock dependent demand items. We then formulate the problem of finding the optimal replenishment schedule that minimizes the total expected discounted costs over an infinite horizon as a Quasi-Variational Inequality (QVI problem. The QVI is shown to have a unique solution under some conditions.

  4. Numerical analysis of time-dependent Boussinesq models

    NARCIS (Netherlands)

    Houwen, P.J. van der; Mooiman, J.; Wubs, F.W.

    1991-01-01

    In this paper we analyse numerical models for time-dependent Boussinesq equations. These equations arise when so-called Boussinesq terms are introduced into the shallow water equations. We use the Boussinesq terms proposed by Katapodes and Dingemans. These terms generalize the constant depth terms g

  5. Efficiency of attack strategies on complex model and real-world networks

    CERN Document Server

    Bellingeri, Michele; Vincenzi, Simone

    2013-01-01

    We investigated the efficiency of attack strategies to network nodes when targeting several complex model and real-world networks. We tested 5 attack strategies, 3 of which were introduced in this work for the first time, to attack 3 model (Erdos and Renyi, Barabasi and Albert preferential attachment network, and scale-free network configuration models) and 3 real networks (Gnutella peer-to-peer network, email network of the University of Rovira i Virgili, and immunoglobulin interaction network). Nodes were removed sequentially according to the importance criterion defined by the attack strategy. We used the size of the largest connected component (LCC) as a measure of network damage. We found that the efficiency of attack strategies (fraction of nodes to be deleted for a given reduction of LCC size) depends on the topology of the network, although attacks based on the number of connections of a node and betweenness centrality were often the most efficient strategies. Sequential deletion of nodes in decreasin...

  6. Cyanobacterial Biofuels: Strategies and Developments on Network and Modeling.

    Science.gov (United States)

    Klanchui, Amornpan; Raethong, Nachon; Prommeenate, Peerada; Vongsangnak, Wanwipa; Meechai, Asawin

    Cyanobacteria, the phototrophic microorganisms, have attracted much attention recently as a promising source for environmentally sustainable biofuels production. However, barriers for commercial markets of cyanobacteria-based biofuels concern the economic feasibility. Miscellaneous strategies for improving the production performance of cyanobacteria have thus been developed. Among these, the simple ad hoc strategies resulting in failure to optimize fully cell growth coupled with desired product yield are explored. With the advancement of genomics and systems biology, a new paradigm toward systems metabolic engineering has been recognized. In particular, a genome-scale metabolic network reconstruction and modeling is a crucial systems-based tool for whole-cell-wide investigation and prediction. In this review, the cyanobacterial genome-scale metabolic models, which offer a system-level understanding of cyanobacterial metabolism, are described. The main process of metabolic network reconstruction and modeling of cyanobacteria are summarized. Strategies and developments on genome-scale network and modeling through the systems metabolic engineering approach are advanced and employed for efficient cyanobacterial-based biofuels production.

  7. Model predictive control power management strategies for HEVs: A review

    Science.gov (United States)

    Huang, Yanjun; Wang, Hong; Khajepour, Amir; He, Hongwen; Ji, Jie

    2017-02-01

    This paper presents a comprehensive review of power management strategy (PMS) utilized in hybrid electric vehicles (HEVs) with an emphasis on model predictive control (MPC) based strategies for the first time. Research on MPC-based power management systems for HEVs has intensified recently due to its many inherent merits. The categories of the existing PMSs are identified from the latest literature, and a brief study of each type is conducted. Then, the MPC approach is introduced and its advantages are discussed. Based on the acquisition method of driver behavior used for state prediction and the dynamic model used, the MPC is classified and elaborated. Factors that affect the performance of the MPC are put forward, including prediction accuracy, design parameters, and solvers. Finally, several important issues in the application of MPC-based power management strategies and latest developing trends are discussed. This paper not only provides a comprehensive analysis of MPC-based power management strategies for HEVs but also puts forward the future and emphasis of future study, which will promote the development of energy management controller with high performance and low cost for HEVs.

  8. A modeling strategy for G-protein coupled receptors

    Directory of Open Access Journals (Sweden)

    Anna Kahler

    2016-03-01

    Full Text Available Cell responses can be triggered via G-protein coupled receptors (GPCRs that interact with small molecules, peptides or proteins and transmit the signal over the membrane via structural changes to activate intracellular pathways. GPCRs are characterized by a rather low sequence similarity and exhibit structural differences even for functionally closely related GPCRs. An accurate structure prediction for GPCRs is therefore not straightforward. We propose a computational approach that relies on the generation of several independent models based on different template structures, which are subsequently refined by molecular dynamics simulations. A comparison of their conformational stability and the agreement with GPCR-typical structural features is then used to select a favorable model. This strategy was applied to predict the structure of the herpesviral chemokine receptor US28 by generating three independent models based on the known structures of the chemokine receptors CXCR1, CXCR4, and CCR5. Model refinement and evaluation suggested that the model based on CCR5 exhibits the most favorable structural properties. In particular, the GPCR-typical structural features, such as a conserved water cluster or conserved non-covalent contacts, are present to a larger extent in the model based on CCR5 compared to the other models. A final model validation based on the recently published US28 crystal structure confirms that the CCR5-based model is the most accurate and exhibits 80.8% correctly modeled residues within the transmembrane helices. The structural agreement between the selected model and the crystal structure suggests that our modeling strategy may also be more generally applicable to other GPCRs of unknown structure.

  9. Model dependence of the deuteron electric dipole moment

    Science.gov (United States)

    Gibson, B. F.; Afnan, I. R.

    2012-09-01

    Direct measurement of the electric dipole moment (EDM) of the neutron lies in the future; measurement of a nuclear EDM may well be obtained first. The deuteron is the one nucleus for which exact model calculations can easily be performed. In this report we explore the model dependence of deuteron EDM calculations. Using a separable potential formulation of the Hamiltonian, we examine the sensitivity of the deuteron EDM to variations in the nucleon-nucleon interaction, including contemporary potential models. We compare the full calculation with the result in the plane-wave approximation, explore the tensor force contribution to the model results, and examine the effects of short range repulsion that characterizes realistic, contemporary potential models of the deuteron. We find that separable potential model calculations will provide an adequate description of the deuteron EDM until such time as a measurement of better than 10% is achieved.

  10. Model dependence of the H2 electric dipole moment

    Science.gov (United States)

    Afnan, I. R.; Gibson, B. F.

    2010-12-01

    Background: Direct measurement of the electric dipole moment (EDM) of the neutron is in the future; measurement of a nuclear EDM may well come first. The deuteron is one nucleus for which exact model calculations are feasible. Purpose: We explore the model dependence of deuteron EDM calculations. Methods: Using a separable potential formulation of the Hamiltonian, we examine the sensitivity of the deuteron EDM to variation in the nucleon-nucleon interaction. We write the EDM as the sum of two terms, the first depending on the target wave function with plane-wave intermediate states, and the second depending on intermediate multiple scattering in the 3P1 channel, the latter being sensitive to the off-shell behavior of the 3P1 amplitude. Results: We compare the full calculation with the plane-wave approximation result, examine the tensor force contribution to the model results, and explore the effect of short-range repulsion found in realistic, contemporary potential models of the deuteron. Conclusions: Because one-pion exchange dominates the EDM calculation, separable potential model calculations will provide an adequate description of the H2 EDM until such time as a measurement better than 10% is obtained.

  11. Muscular strategy shift in human running: dependence of running speed on hip and ankle muscle performance.

    Science.gov (United States)

    Dorn, Tim W; Schache, Anthony G; Pandy, Marcus G

    2012-06-01

    Humans run faster by increasing a combination of stride length and stride frequency. In slow and medium-paced running, stride length is increased by exerting larger support forces during ground contact, whereas in fast running and sprinting, stride frequency is increased by swinging the legs more rapidly through the air. Many studies have investigated the mechanics of human running, yet little is known about how the individual leg muscles accelerate the joints and centre of mass during this task. The aim of this study was to describe and explain the synergistic actions of the individual leg muscles over a wide range of running speeds, from slow running to maximal sprinting. Experimental gait data from nine subjects were combined with a detailed computer model of the musculoskeletal system to determine the forces developed by the leg muscles at different running speeds. For speeds up to 7 m s(-1), the ankle plantarflexors, soleus and gastrocnemius, contributed most significantly to vertical support forces and hence increases in stride length. At speeds greater than 7 m s(-1), these muscles shortened at relatively high velocities and had less time to generate the forces needed for support. Thus, above 7 m s(-1), the strategy used to increase running speed shifted to the goal of increasing stride frequency. The hip muscles, primarily the iliopsoas, gluteus maximus and hamstrings, achieved this goal by accelerating the hip and knee joints more vigorously during swing. These findings provide insight into the strategies used by the leg muscles to maximise running performance and have implications for the design of athletic training programs.

  12. Strain Rate Dependent Modeling of Polymer Matrix Composites

    Science.gov (United States)

    Goldberg, Robert K.; Stouffer, Donald C.

    1999-01-01

    A research program is in progress to develop strain rate dependent deformation and failure models for the analysis of polymer matrix composites subject to high strain rate impact loads. Strain rate dependent inelastic constitutive equations have been developed to model the polymer matrix, and have been incorporated into a micromechanics approach to analyze polymer matrix composites. The Hashin failure criterion has been implemented within the micromechanics results to predict ply failure strengths. The deformation model has been implemented within LS-DYNA, a commercially available transient dynamic finite element code. The deformation response and ply failure stresses for the representative polymer matrix composite AS4/PEEK have been predicted for a variety of fiber orientations and strain rates. The predicted results compare favorably to experimentally obtained values.

  13. IP-Sat: Impact-Parameter dependent Saturation model; revised

    CERN Document Server

    Rezaeian, Amir H; Van de Klundert, Merijn; Venugopalan, Raju

    2013-01-01

    In this talk, we present a global analysis of available small-x data on inclusive DIS and exclusive diffractive processes, including the latest data from the combined HERA analysis on reduced cross sections within the Impact-Parameter dependent Saturation (IP-Sat) Model. The impact-parameter dependence of dipole amplitude is crucial in order to have a unified description of both inclusive and exclusive diffractive processes. With the parameters of model fixed via a fit to the high-precision reduced cross-section, we compare model predictions to data for the structure functions, the longitudinal structure function, the charm structure function, exclusive vector mesons production and Deeply Virtual Compton Scattering (DVCS). Excellent agreement is obtained for the processes considered at small x in a wide range of Q^2.

  14. Energy based model for temperature dependent behavior of ferromagnetic materials

    Science.gov (United States)

    Sah, Sanjay; Atulasimha, Jayasimha

    2017-03-01

    An energy based model for temperature dependent anhysteretic magnetization curves of ferromagnetic materials is proposed and benchmarked against experimental data. This is based on the calculation of macroscopic magnetic properties by performing an energy weighted average over all possible orientations of the magnetization vector. Most prior approaches that employ this method are unable to independently account for the effect of both inhomogeneity and temperature in performing the averaging necessary to model experimental data. Here we propose a way to account for both effects simultaneously and benchmark the model against experimental data from 5 K to 300 K for two different materials in both annealed (fewer inhomogeneities) and deformed (more inhomogeneities) samples. This demonstrates that this framework is well suited to simulate temperature dependent experimental magnetic behavior.

  15. Time-dependent Integrated Predictive Modeling of ITER Plasmas

    Institute of Scientific and Technical Information of China (English)

    R.V. Budny

    2007-01-01

    @@ Introduction Modeling burning plasmas is important for speeding progress toward practical Tokamak energy production. Examples of issues that can be elucidated by modelinginclude requirements for heating, fueling, torque, and current drive systems, design of diagnostics, and estimates of the plasma performance (e.g., fusion power production) in various plasma scenarios. The modeling should be time-dependent to demonstrate that burning plasmas can be created, maintained (controlled), and terminated successfully. The modeling also should be integrated to treat self-consistently the nonlinearities and strong coupling between the plasma, heating, current drive, confinement, and control systems.

  16. A model system to study antimicrobial strategies in endodontic biofilms

    Directory of Open Access Journals (Sweden)

    Carlos Estrela

    2009-04-01

    Full Text Available The purpose of this work was to develop a model system to study antimicrobial strategies in endodontic biofilms. Enterococcus faecalis suspension was colonized in 10 human root canals. Five milliliters of Brain Heart Infusion (BHI were mixed with 5 mL of the bacterial inoculums (E. faecalis and inoculated with sufficient volume to fill the root canal during 60 days. This procedure was repeated every 72 h, always using 24-h pure culture prepared and adjusted to No. 1 MacFarland turbidity standard. Biofilm formation was analyzed by scanning electron microscopy (SEM. E. faecalis consistently adhered to collagen structure, colonized dentin surface, progressed towards the dentinal tubules and formed a biofilm. The proposed biofilm model seems to be viable for studies on antimicrobial strategies, and allows for a satisfactory colonization time of selected bacterial species with virulence and adherence properties.

  17. RAS-MAPK dependence underlies a rational polytherapy strategy in EML4-ALK–positive lung cancer

    Science.gov (United States)

    Hrustanovic, Gorjan; Olivas, Victor; Pazarentzos, Evangelos; Tulpule, Asmin; Asthana, Saurabh; Blakely, Collin M; Okimoto, Ross A; Lin, Luping; Neel, Dana S; Sabnis, Amit; Flanagan, Jennifer; Chan, Elton; Varella-Garcia, Marileila; Aisner, Dara L; Vaishnavi, Aria; Ou, Sai-Hong I; Collisson, Eric A; Ichihara, Eiki; Mack, Philip C; Lovly, Christine M; Karachaliou, Niki; Rosell, Rafael; Riess, Jonathan W; Doebele, Robert C; Bivona, Trever G

    2016-01-01

    One strategy for combating cancer-drug resistance is to deploy rational polytherapy up front that suppresses the survival and emergence of resistant tumor cells. Here we demonstrate in models of lung adenocarcinoma harboring the oncogenic fusion of ALK and EML4 that the GTPase RAS–mitogen-activated protein kinase (MAPK) pathway, but not other known ALK effectors, is required for tumor-cell survival. EML4-ALK activated RAS-MAPK signaling by engaging all three major RAS isoforms through the HELP domain of EML4. Reactivation of the MAPK pathway via either a gain in the number of copies of the gene encoding wild-type K-RAS (KRASWT) or decreased expression of the MAPK phosphatase DUSP6 promoted resistance to ALK inhibitors in vitro, and each was associated with resistance to ALK inhibitors in individuals with EML4-ALK–positive lung adenocarcinoma. Upfront inhibition of both ALK and the kinase MEK enhanced both the magnitude and duration of the initial response in preclinical models of EML4-ALK lung adenocarcinoma. Our findings identify RAS-MAPK dependence as a hallmark of EML4-ALK lung adenocarcinoma and provide a rationale for the upfront inhibition of both ALK and MEK to forestall resistance and improve patient outcomes. PMID:26301689

  18. A Dynamic Approach to Modeling Dependence Between Human Failure Events

    Energy Technology Data Exchange (ETDEWEB)

    Boring, Ronald Laurids [Idaho National Laboratory

    2015-09-01

    In practice, most HRA methods use direct dependence from THERP—the notion that error be- gets error, and one human failure event (HFE) may increase the likelihood of subsequent HFEs. In this paper, we approach dependence from a simulation perspective in which the effects of human errors are dynamically modeled. There are three key concepts that play into this modeling: (1) Errors are driven by performance shaping factors (PSFs). In this context, the error propagation is not a result of the presence of an HFE yielding overall increases in subsequent HFEs. Rather, it is shared PSFs that cause dependence. (2) PSFs have qualities of lag and latency. These two qualities are not currently considered in HRA methods that use PSFs. Yet, to model the effects of PSFs, it is not simply a matter of identifying the discrete effects of a particular PSF on performance. The effects of PSFs must be considered temporally, as the PSFs will have a range of effects across the event sequence. (3) Finally, there is the concept of error spilling. When PSFs are activated, they not only have temporal effects but also lateral effects on other PSFs, leading to emergent errors. This paper presents the framework for tying together these dynamic dependence concepts.

  19. Vaccination strategies for SEIR models using feedback linearization. Preliminary results

    CERN Document Server

    De la Sen, M; Alonso-Quesada, S

    2011-01-01

    A linearization-based feedback-control strategy for a SEIR epidemic model is discussed. The vaccination objective is the asymptotically tracking of the removed-by-immunity population to the total population while achieving simultaneously the remaining population (i.e. susceptible plus infected plus infectious) to asymptotically tend to zero. The disease controlpolicy is designed based on a feedback linearization technique which provides a general method to generate families of vaccination policies with sound technical background.

  20. Site investigations: Strategy for rock mechanics site descriptive model

    Energy Technology Data Exchange (ETDEWEB)

    Andersson, Johan [JA Streamflow AB, Aelvsjoe (Sweden); Christiansson, Rolf [Swedish Nuclear Fuel and Waste Management Co., Stockholm (Sweden); Hudson, John [Rock Engineering Consultants, Welwyn Garden City (United Kingdom)

    2002-05-01

    As a part of the planning work for the Site Investigations, SKB has developed a Rock Mechanics Site Descriptive Modelling Strategy. Similar strategies are being developed for other disciplines. The objective of the strategy is that it should guide the practical implementation of evaluating site specific data during the Site Investigations. It is also understood that further development may be needed. This methodology enables the crystalline rock mass to be characterised in terms of the quality at different sites, for considering rock engineering constructability, and for providing the input to numerical models and performance assessment calculations. The model describes the initial stresses and the distribution of deformation and strength properties of the intact rock, of fractures and fracture zones, and of the rock mass. The rock mass mechanical properties are estimated by empirical relations and by numerical simulations. The methodology is based on estimation of mechanical properties using both empirical and heroretical/numerical approaches; and estimation of in situ rock stress using judgement and numerical modelling, including the influence of fracture zones. These approaches are initially used separately, and then combined to produce the required characterisation estimates. The methodology was evaluated with a Test Case at the Aespoe Hard Rock Laboratory in Sweden. The quality control aspects are an important feature of the methodology: these include Protocols to ensure the structure and coherence of the procedures used, regular meetings to enhance communication, feedback from internal and external reviewing, plus the recording of an audit trail of the development steps and decisions made. The strategy will be reviewed and, if required, updated as appropriate.

  1. Stimulus-dependent maximum entropy models of neural population codes.

    Science.gov (United States)

    Granot-Atedgi, Einat; Tkačik, Gašper; Segev, Ronen; Schneidman, Elad

    2013-01-01

    Neural populations encode information about their stimulus in a collective fashion, by joint activity patterns of spiking and silence. A full account of this mapping from stimulus to neural activity is given by the conditional probability distribution over neural codewords given the sensory input. For large populations, direct sampling of these distributions is impossible, and so we must rely on constructing appropriate models. We show here that in a population of 100 retinal ganglion cells in the salamander retina responding to temporal white-noise stimuli, dependencies between cells play an important encoding role. We introduce the stimulus-dependent maximum entropy (SDME) model-a minimal extension of the canonical linear-nonlinear model of a single neuron, to a pairwise-coupled neural population. We find that the SDME model gives a more accurate account of single cell responses and in particular significantly outperforms uncoupled models in reproducing the distributions of population codewords emitted in response to a stimulus. We show how the SDME model, in conjunction with static maximum entropy models of population vocabulary, can be used to estimate information-theoretic quantities like average surprise and information transmission in a neural population.

  2. Stimulus-dependent maximum entropy models of neural population codes.

    Directory of Open Access Journals (Sweden)

    Einat Granot-Atedgi

    Full Text Available Neural populations encode information about their stimulus in a collective fashion, by joint activity patterns of spiking and silence. A full account of this mapping from stimulus to neural activity is given by the conditional probability distribution over neural codewords given the sensory input. For large populations, direct sampling of these distributions is impossible, and so we must rely on constructing appropriate models. We show here that in a population of 100 retinal ganglion cells in the salamander retina responding to temporal white-noise stimuli, dependencies between cells play an important encoding role. We introduce the stimulus-dependent maximum entropy (SDME model-a minimal extension of the canonical linear-nonlinear model of a single neuron, to a pairwise-coupled neural population. We find that the SDME model gives a more accurate account of single cell responses and in particular significantly outperforms uncoupled models in reproducing the distributions of population codewords emitted in response to a stimulus. We show how the SDME model, in conjunction with static maximum entropy models of population vocabulary, can be used to estimate information-theoretic quantities like average surprise and information transmission in a neural population.

  3. Geometry-dependent distributed polarizability models for the water molecule

    Energy Technology Data Exchange (ETDEWEB)

    Loboda, Oleksandr; Ingrosso, Francesca; Ruiz-López, Manuel F.; Millot, Claude [Université de Lorraine, SRSMC UMR 7565, Vandoeuvre-les-Nancy F-54506 (France); CNRS, SRSMC UMR 7565, Vandoeuvre-les-Nancy F-54506 (France); Szalewicz, Krzysztof [Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716 (United States)

    2016-01-21

    Geometry-dependent distributed polarizability models have been constructed by fits to ab initio calculations at the coupled cluster level of theory with up to noniterative triple excitations in an augmented triple-zeta quality basis set for the water molecule in the field of a point charge. The investigated models include (i) charge-flow polarizabilities between chemically bonded atoms, (ii) isotropic or anisotropic dipolar polarizabilities on oxygen atom or on all atoms, and (iii) combinations of models (i) and (ii). For each model, the polarizability parameters have been optimized to reproduce the induction energy of a water molecule polarized by a point charge successively occupying a grid of points surrounding the molecule. The quality of the models is ascertained by examining their ability to reproduce these induction energies as well as the molecular dipolar and quadrupolar polarizabilities. The geometry dependence of the distributed polarizability models has been explored by changing bond lengths and HOH angle to generate 125 molecular structures (reduced to 75 symmetry-unique ones). For each considered model, the distributed polarizability components have been fitted as a function of the geometry by a Taylor expansion in monomer coordinate displacements up to the sum of powers equal to 4.

  4. Dependability modeling and assessment in UML-based software development.

    Science.gov (United States)

    Bernardi, Simona; Merseguer, José; Petriu, Dorina C

    2012-01-01

    Assessment of software nonfunctional properties (NFP) is an important problem in software development. In the context of model-driven development, an emerging approach for the analysis of different NFPs consists of the following steps: (a) to extend the software models with annotations describing the NFP of interest; (b) to transform automatically the annotated software model to the formalism chosen for NFP analysis; (c) to analyze the formal model using existing solvers; (d) to assess the software based on the results and give feedback to designers. Such a modeling→analysis→assessment approach can be applied to any software modeling language, be it general purpose or domain specific. In this paper, we focus on UML-based development and on the dependability NFP, which encompasses reliability, availability, safety, integrity, and maintainability. The paper presents the profile used to extend UML with dependability information, the model transformation to generate a DSPN formal model, and the assessment of the system properties based on the DSPN results.

  5. Research on Dependable Ionizing Radiation Protection based on Model i*

    Directory of Open Access Journals (Sweden)

    Tan Hai

    2013-07-01

    Full Text Available The software’s unreliability mostly attributes to an erroneous analysis on the requirements done at the beginning. In this paper, we apply the tool of i* frame requirement modeling and build early requirement model against ionizing radiation. After finding out possible risks and corresponding solutions during the process of modeling analysis, we propose reasoning models against ionizing radiation. The radiation protection system  with  the  above models  can  figure out  the  purpose  of agents  related  to radiant source and provide normal service even when the environment software system is being interfered. It can serve the ecological and economical society with stability and development.  The model is divided into several sections. Section 1 gives the outline of the dependant software. Section 2 illustrates the  i* frame  technology. Section 3, 4 and 5 cover the topic of dependant security requirement analysis, SD&SR model on ionizing radiation respectively. Section 6 gives the conclusion.

  6. Anomalous scaling in an age-dependent branching model.

    Science.gov (United States)

    Keller-Schmidt, Stephanie; Tuğrul, Murat; Eguíluz, Víctor M; Hernández-García, Emilio; Klemm, Konstantin

    2015-02-01

    We introduce a one-parametric family of tree growth models, in which branching probabilities decrease with branch age τ as τ(-α). Depending on the exponent α, the scaling of tree depth with tree size n displays a transition between the logarithmic scaling of random trees and an algebraic growth. At the transition (α=1) tree depth grows as (logn)(2). This anomalous scaling is in good agreement with the trend observed in evolution of biological species, thus providing a theoretical support for age-dependent speciation and associating it to the occurrence of a critical point.

  7. Several Strategies on 3D Modeling of Manmade Objects

    Institute of Scientific and Technical Information of China (English)

    SHAO Zhenfeng; LI Deren; CHENG Qimin

    2004-01-01

    Several different strategies of 3D modeling are adopted for different kinds of manmade objects. Firstly, for those manmade objects with regular structure, if 2D information is available and elevation information can be obtained conveniently, then 3D modeling of them can be executed directly. Secondly, for those manmade objects with complicated structure comparatively and related stereo images pair can be acquired, in the light of topology-based 3D model we finish 3D modeling of them by integrating automatic and semi-automatic object extraction. Thirdly, for the most complicated objects whose geometrical information cannot be got from stereo images pair completely, we turn to topological 3D model based on CAD.

  8. Influence of the management strategy model on estimating water system performance under climate change

    Science.gov (United States)

    Francois, Baptiste; Hingray, Benoit; Creutin, Jean-Dominique; Hendrickx, Frederic

    2015-04-01

    The performance of water systems used worldwide for the management of water resources is expected to be influenced by future changes in regional climates and water uses. Anticipating possible performance changes of a given system requires a modeling chain simulating its management. Operational management is usually not trivial especially when several conflicting objectives have to be accounted for. Management models are therefore often a crude representation of the real system and they only approximate its performance. Estimated performance changes are expected to depend on the management model used, but this is often not assessed. This communication analyzes the influence of the management strategy representation on the performance of an Alpine reservoir (Serre-Ponçon, South-East of France) for which irrigation supply, hydropower generation and recreational activities are the main objectives. We consider three ways to construct the strategy named as clear-, short- and far-sighted management. They are based on different forecastability degrees of seasonal inflows into the reservoir. The strategies are optimized using a Dynamic Programming algorithm (deterministic for clear-sighted and implicit stochastic for short- and far-sighted). System performance is estimated for an ensemble of future hydro-meteorological projections obtained in the RIWER2030 research project (http://www.lthe.fr/RIWER2030/) from a suite of climate experiments from the EU - ENSEMBLES research project. Our results show that changes in system performance is much more influenced by changes in hydro-meteorological variables than by the choice of strategy modeling. They also show that a simple strategy representation (i.e. clear-sighted management) leads to similar estimates of performance modifications than those obtained with a representation supposedly closer to real world (i.e. the far-sighted management). The Short-Sighted management approach lead to significantly different results, especially

  9. MODEL PEMBELAJARAN DILEMA MORAL DAN KONTEMPLASI DENGAN STRATEGI KOOPERATIF

    Directory of Open Access Journals (Sweden)

    C. Asri Budiningsih

    2013-09-01

    Full Text Available Penelitian ini bertujuan untuk mengetahui keefektifan model Pembelajaran Dilema Moral, Kontemplasi, dan Strategi Kooperatif. Penelitian tindakan kelas dilakukan di Prodi Teknologi Pendidikan FIP-UNY. Subjek penelitian 37 orang mahasiswa. Tindakan dilakukan dalam dua siklus masing-masing terdiri atas empat kali tatap muka. Data tentang proses pembelajaran, kerjasama mahasiswa, situasi yang berpengaruh terhadap upaya peningkatan kualitas pembelajaran, penalaran moral, dan keimanan mahasiswa, digali melalui pengamatan, tes penalaran moral yang diadaptasi dari Kohlberg, tes perkembangan iman yang diadaptasi dari Fowler, panduan kontemplasi, angket terbuka, dan cerita-cerita dilema moral. Analisis data dilakukan secara kuantitatif dan kualitatif. Hasil penelitian menunjukkan bahwa (1 model pembelajaran terintegrasi mampu meningkatkan penalaran moral, dan keimanan mahasiswa, sehingga tidak ada lagi penalaran moral responden yang berada pada tahap II, 24,3% meningkat dari tahap II ke tahap III, 32,43% meningkat dari tahap III ke tahap IV dan 2,7% meningkat dari tahap IV ke tahap V, 48,65% meningkat dari tahap III ke tahap IV, dan 5,4% meningkat dari tahap IV ke tahap V. Penggunaan strategi kooperatif membuat mahasiswa mampu melakukan kerjasama di dalam kelompok; 35,13% mahasiswa dalam kategori sangat baik, 56,76% dalam kategori baik, dan 8,1% dalam kategori sedang. Kata kunci       :           model pembelajaran dilema moral, kontemplasi, strategi kooperatif, penalaran moral, keimanan

  10. Application Server Aging Model and Multi-Level Rejuvenation Strategy Using Semi-Markov Process

    Institute of Scientific and Technical Information of China (English)

    ZHAO Tianhai; QI Yong; SHEN Junyi; HOU Di; ZHENG Xiaomei; LIU Liang

    2006-01-01

    Aiming at the characteristic of the dependency between the application components and the application server platform, a rejuvenation strategy with two different levels of rejuvenation granularities is put forward in this paper including the application component rejuvenation and the application server system rejuvenation. The availability and maintenance cost functions are obtained by means of establishing the application server aging model and the boundary condition of the optimal rejuvenation time is analyzed. Theory analysis indicates that the two-level rejuvenation strategy is superior to the traditional single level one. Finally, evaluation experiments are carried out and numerical result shows that compared with the traditional rejuvenation policy, the rejuvenation strategy proposed in this paper can further increase availability of the application server and reduce maintenance cost.

  11. Multiaxial Temperature- and Time-Dependent Failure Model

    Science.gov (United States)

    Richardson, David; McLennan, Michael; Anderson, Gregory; Macon, David; Batista-Rodriquez, Alicia

    2003-01-01

    A temperature- and time-dependent mathematical model predicts the conditions for failure of a material subjected to multiaxial stress. The model was initially applied to a filled epoxy below its glass-transition temperature, and is expected to be applicable to other materials, at least below their glass-transition temperatures. The model is justified simply by the fact that it closely approximates the experimentally observed failure behavior of this material: The multiaxiality of the model has been confirmed (see figure) and the model has been shown to be applicable at temperatures from -20 to 115 F (-29 to 46 C) and to predict tensile failures of constant-load and constant-load-rate specimens with failure times ranging from minutes to months..

  12. Three New Probabilistic Models for Dependency Parsing An Exploration

    CERN Document Server

    Eisner, J

    1997-01-01

    After presenting a novel O(n^3) parsing algorithm for dependency grammar, we develop three contrasting ways to stochasticize it. We propose (a) a lexical affinity model where words struggle to modify each other, (b) a sense tagging model where words fluctuate randomly in their selectional preferences, and (c) a generative model where the speaker fleshes out each word's syntactic and conceptual structure without regard to the implications for the hearer. We also give preliminary empirical results from evaluating the three models' parsing performance on annotated Wall Street Journal training text (derived from the Penn Treebank). In these results, the generative (i.e., top-down) model performs significantly better than the others, and does about equally well at assigning part-of-speech tags.

  13. Neutrino flavor instabilities in a time-dependent supernova model

    Directory of Open Access Journals (Sweden)

    Sajad Abbar

    2015-12-01

    Full Text Available A dense neutrino medium such as that inside a core-collapse supernova can experience collective flavor conversion or oscillations because of the neutral-current weak interaction among the neutrinos. This phenomenon has been studied in a restricted, stationary supernova model which possesses the (spatial spherical symmetry about the center of the supernova and the (directional axial symmetry around the radial direction. Recently it has been shown that these spatial and directional symmetries can be broken spontaneously by collective neutrino oscillations. In this letter we analyze the neutrino flavor instabilities in a time-dependent supernova model. Our results show that collective neutrino oscillations start at approximately the same radius in both the stationary and time-dependent supernova models unless there exist very rapid variations in local physical conditions on timescales of a few microseconds or shorter. Our results also suggest that collective neutrino oscillations can vary rapidly with time in the regimes where they do occur which need to be studied in time-dependent supernova models.

  14. Modeling of time dependent subsidence for coal and ore deposits

    Institute of Scientific and Technical Information of China (English)

    Ryszard Hejmanowski

    2015-01-01

    Coal and ore underground mining generates subsidence and deformation of the land surface. Those defor-mations may cause damage to buildings and infrastructures. The environmental impact of subsidence will not be accepted in the future by the society in many countries. Especially there, where the mining regions are densely urbanized, the acceptance of the ground deformations decreases every year. The only solution is to limit the subsidence or its impact on the infrastructure. The first is not rentable for the mining industry, the second depends on the precise subsidence prediction and good preventing management involved in the mining areas. The precision of the subsidence prediction depends strictly on the mathematical model of the deformation phenomenon and on the uncertainty of the input data. The subsidence prediction in the geological conditions of the raw materials used to be made on the basis of numerical modeling or the stochastic models. A modified solution of the stochastic model by Knothe will be presented in the paper. The author focuses on the precise description of the deposit shape and on the time dependent displacements of the rock mass. A two parameters’ time function has been introduced in the algorithm.

  15. Some vaccination strategies for the SEIR epidemic model. Preliminary results

    CERN Document Server

    De la Sen, M; Alonso-Quesada, S

    2011-01-01

    This paper presents a vaccination-based control strategy for a SEIR (susceptible plus infected plus infectious plus removed populations) propagation disease model. The model takes into account the total population amounts as a refrain for the illness transmission since its increase makes more difficult contacts among susceptible and infected. The control objective is the asymptotically tracking of the removed-by-immunity population to the total population while achieving simultaneously the remaining population (i.e. susceptible plus infected plus infectious) to asymptotically tend to zero.

  16. A latitude-dependent wind model for Mira's cometary head

    CERN Document Server

    Raga, A C; De Colle, F; Esquivel, A; Kajdic, P; Rodríguez-González, A; Velázquez, P F

    2008-01-01

    We present a 3D numerical simulation of the recently discovered cometary structure produced as Mira travels through the galactic ISM. In our simulation, we consider that Mira ejects a steady, latitude-dependent wind, which interacts with a homogeneous, streaming environment. The axisymmetry of the problem is broken by the lack of alignment between the direction of the relative motion of the environment and the polar axis of the latitude-dependent wind. With this model, we are able to produce a cometary head with a ``double bow shock'' which agrees well with the structure of the head of Mira's comet. We therefore conclude that a time-dependence in the ejected wind is not required for reproducing the observed double bow shock.

  17. Model inadequacy and mistaken inferences of trait-dependent speciation.

    Science.gov (United States)

    Rabosky, Daniel L; Goldberg, Emma E

    2015-03-01

    Species richness varies widely across the tree of life, and there is great interest in identifying ecological, geographic, and other factors that affect rates of species proliferation. Recent methods for explicitly modeling the relationships among character states, speciation rates, and extinction rates on phylogenetic trees- BiSSE, QuaSSE, GeoSSE, and related models-have been widely used to test hypotheses about character state-dependent diversification rates. Here, we document the disconcerting ease with which neutral traits are inferred to have statistically significant associations with speciation rate. We first demonstrate this unfortunate effect for a known model assumption violation: shifts in speciation rate associated with a character not included in the model. We further show that for many empirical phylogenies, characters simulated in the absence of state-dependent diversification exhibit an even higher Type I error rate, indicating that the method is susceptible to additional, unknown model inadequacies. For traits that evolve slowly, the root cause appears to be a statistical framework that does not require replicated shifts in character state and diversification. However, spurious associations between character state and speciation rate arise even for traits that lack phylogenetic signal, suggesting that phylogenetic pseudoreplication alone cannot fully explain the problem. The surprising severity of this phenomenon suggests that many trait-diversification relationships reported in the literature may not be real. More generally, we highlight the need for diagnosing and understanding the consequences of model inadequacy in phylogenetic comparative methods.

  18. The Role of Learning Strategies in Second Language Acquisition: A Model for Research in Listening Comprehension

    Science.gov (United States)

    1987-06-01

    role of learning strategies in second language acquisition . While strategies used in acquiring productive language skills are discussed briefly, the...comprehensions. Keywords: Learning strategies, English as a second language, Second language acquisition , Basic skills, Research model.

  19. Modeling Coherent Strategies for the Sustainable Development Goals

    Science.gov (United States)

    Walsh, B.; Obersteiner, M.; Herrero, M.; Riahi, K.; Fritz, S.; van Vuuren, D.; Havlik, P.

    2016-12-01

    The Sustainable Development Goals (SDGs) call for a comprehensive new approach to development rooted in planetary boundaries, equity and inclusivity. Societies have largely responded to this call with siloed strategies capable of making progress on selected subsets of these goals. However, agendas crafted specifically to alleviate poverty, hunger, deforestation, biodiversity loss, or other ills may doom the SDG agenda, as policies and strategies designed to accomplish one or several goals can impede and in some cases reverse progress toward others at national, regional, and global levels. We adopt a comprehensive modeling approach to understand the basis for tradeoffs among environmental conservation initiatives (goals 13-15) and food prices (goal 2). We show that such tradeoffs are manifestations of policy-driven pressure in land (i.e. agricultural and environmental) systems. By reducing total land system pressure, Sustainable Consumption and Production (SCP, goal 12) policies minimize tradeoffs and should therefore be regarded as necessary conditions for achieving multiple SDGs. SDG strategies constructed around SCP policies escape problem-shifting, which has long placed global development and conservation agendas at odds. We expect that this and future systems analyses will allow policymakers to negotiate tradeoffs and exploit synergies as they assemble sustainable development strategies equal in scope to the ambition of the SDGs.

  20. Web malware spread modelling and optimal control strategies

    Science.gov (United States)

    Liu, Wanping; Zhong, Shouming

    2017-02-01

    The popularity of the Web improves the growth of web threats. Formulating mathematical models for accurate prediction of malicious propagation over networks is of great importance. The aim of this paper is to understand the propagation mechanisms of web malware and the impact of human intervention on the spread of malicious hyperlinks. Considering the characteristics of web malware, a new differential epidemic model which extends the traditional SIR model by adding another delitescent compartment is proposed to address the spreading behavior of malicious links over networks. The spreading threshold of the model system is calculated, and the dynamics of the model is theoretically analyzed. Moreover, the optimal control theory is employed to study malware immunization strategies, aiming to keep the total economic loss of security investment and infection loss as low as possible. The existence and uniqueness of the results concerning the optimality system are confirmed. Finally, numerical simulations show that the spread of malware links can be controlled effectively with proper control strategy of specific parameter choice.

  1. Active control strategy on a catenary-pantograph validated model

    Science.gov (United States)

    Sanchez-Rebollo, C.; Jimenez-Octavio, J. R.; Carnicero, A.

    2013-04-01

    Dynamic simulation methods have become essential in the design process and control of the catenary-pantograph system, overall since high-speed trains and interoperability criteria are getting very trendy. This paper presents an original hardware-in-the-loop (HIL) strategy aimed at integrating a multicriteria active control within the catenary-pantograph dynamic interaction. The relevance of HIL control systems applied in the frame of the pantograph is undoubtedly increasing due to the recent and more demanding requirements for high-speed railway systems. Since the loss of contact between the catenary and the pantograph leads to arcing and electrical wear, and too high contact forces cause mechanical wear of both the catenary wires and the strips of the pantograph, not only prescribed but also economic and performance criteria ratify such a relevance. Different configurations of the proportional-integral-derivative (PID) controller are proposed and applied to two different plant systems. Since this paper is mainly focused on the control strategy, both plant systems are simulation models though the methodology is suitable for a laboratory bench. The strategy of control involves a multicriteria optimisation of the contact force and the consumption of the energy supplied by the control force, a genetic algorithm has been applied for this purpose. Thus, the PID controller is fitted according to these conflicting objectives and tested within a nonlinear lumped model and a nonlinear finite element model, being the last one validated against the European Standard EN 50318. Finally, certain tests have been accomplished in order to analyse the robustness of the control strategy. Particularly, the relevance or the plant simulation, the running speed and the instrumentation time delay are studied in this paper.

  2. Population Modeling Approach to Optimize Crop Harvest Strategy. The Case of Field Tomato

    Directory of Open Access Journals (Sweden)

    Maarten L. A. T. M. Hertog

    2017-04-01

    Full Text Available In this study, the aim is to develop a population model based approach to optimize fruit harvesting strategies with regard to fruit quality and its derived economic value. This approach was applied to the case of tomato fruit harvesting under Vietnamese conditions. Fruit growth and development of tomato (cv. “Savior” was monitored in terms of fruit size and color during both the Vietnamese winter and summer growing seasons. A kinetic tomato fruit growth model was applied to quantify biological fruit-to-fruit variation in terms of their physiological maturation. This model was successfully calibrated. Finally, the model was extended to translate the fruit-to-fruit variation at harvest into the economic value of the harvested crop. It can be concluded that a model based approach to the optimization of harvest date and harvest frequency with regard to economic value of the crop as such is feasible. This approach allows growers to optimize their harvesting strategy by harvesting the crop at more uniform maturity stages meeting the stringent retail demands for homogeneous high quality product. The total farm profit would still depend on the impact a change in harvesting strategy might have on related expenditures. This model based harvest optimisation approach can be easily transferred to other fruit and vegetable crops improving homogeneity of the postharvest product streams.

  3. A Composite Model Predictive Control Strategy for Furnaces

    Institute of Scientific and Technical Information of China (English)

    Hao Zang; Hongguang Li; Jingwen Huang; Jia Wang

    2014-01-01

    Tube furnaces are essential and primary energy intensive facilities in petrochemical plants. Operational optimi-zation of furnaces could not only help to improve product quality but also benefit to reduce energy consumption and exhaust emission. Inspired by this idea, this paper presents a composite model predictive control (CMPC) strategy, which, taking advantage of distributed model predictive control architectures, combines tracking nonlinear model predictive control and economic nonlinear model predictive control metrics to keep process running smoothly and optimize operational conditions. The control ers connected with two kinds of communi-cation networks are easy to organize and maintain, and stable to process interferences. A fast solution algorithm combining interior point solvers and Newton's method is accommodated to the CMPC realization, with reason-able CPU computing time and suitable online applications. Simulation for industrial case demonstrates that the proposed approach can ensure stable operations of furnaces, improve heat efficiency, and reduce the emission effectively.

  4. Five-factor model personality traits in opioid dependence

    Directory of Open Access Journals (Sweden)

    Nordvik Hilmar

    2007-08-01

    Full Text Available Abstract Background Personality traits may form a part of the aetiology of opioid dependence. For instance, opioid dependence may result from self-medication in emotionally unstable individuals, or from experimenting with drugs in sensation seekers. The five factor model (FFM has obtained a central position in contemporary personality trait theory. The five factors are: Neuroticism, Extraversion, Openness to Experience, Agreeableness and Conscientiousness. Few studies have examined whether there is a distinct personality pattern associated with opioid dependence. Methods We compared FFM personality traits in 65 opioid dependent persons (mean age 27 years, 34% females in outpatient counselling after a minimum of 5 weeks in buprenorphine replacement therapy, with those in a non-clinical, age- and sex-matched sample selected from a national database. Personality traits were assessed by a Norwegian version of the Revised NEO Personality Inventory (NEO PI-R, a 240-item self-report questionnaire. Cohen's d effect sizes were calculated for the differences in personality trait scores. Results The opioid-dependent sample scored higher on Neuroticism, lower on Extraversion and lower on Conscientiousness (d = -1.7, 1.2 and 1.7, respectively than the controls. Effects sizes were small for the difference between the groups in Openness to experience scores and Agreeableness scores. Conclusion We found differences of medium and large effect sizes between the opioid dependent group and the matched comparison group, suggesting that the personality traits of people with opioid dependence are in fact different from those of non-clinical peers.

  5. Models for electricity market efficiency and bidding strategy analysis

    Science.gov (United States)

    Niu, Hui

    This dissertation studies models for the analysis of market efficiency and bidding behaviors of market participants in electricity markets. Simulation models are developed to estimate how transmission and operational constraints affect the competitive benchmark and market prices based on submitted bids. This research contributes to the literature in three aspects. First, transmission and operational constraints, which have been neglected in most empirical literature, are considered in the competitive benchmark estimation model. Second, the effects of operational and transmission constraints on market prices are estimated through two models based on the submitted bids of market participants. Third, these models are applied to analyze the efficiency of the Electric Reliability Council Of Texas (ERCOT) real-time energy market by simulating its operations for the time period from January 2002 to April 2003. The characteristics and available information for the ERCOT market are considered. In electricity markets, electric firms compete through both spot market bidding and bilateral contract trading. A linear asymmetric supply function equilibrium (SFE) model with transmission constraints is proposed in this dissertation to analyze the bidding strategies with forward contracts. The research contributes to the literature in several aspects. First, we combine forward contracts, transmission constraints, and multi-period strategy (an obligation for firms to bid consistently over an extended time horizon such as a day or an hour) into the linear asymmetric supply function equilibrium framework. As an ex-ante model, it can provide qualitative insights into firms' behaviors. Second, the bidding strategies related to Transmission Congestion Rights (TCRs) are discussed by interpreting TCRs as linear combination of forwards. Third, the model is a general one in the sense that there is no limitation on the number of firms and scale of the transmission network, which can have

  6. In silico models of alcohol dependence and treatment

    Directory of Open Access Journals (Sweden)

    Boris eKovatchev

    2012-02-01

    Full Text Available In this paper we view alcohol dependence and the response to treatment as a recurrent bio-behavioral process developing in time and propose formal models of this process combining behavior and biology in silico. The behavioral components of alcohol dependence and treatment are formally described by a stochastic process of human behavior, which serves as an event generator challenging the metabolic system. The biological component is driven by the biochemistry of alcohol intoxication described by deterministic models of ethanol pharmacodynamics and pharmacokintetics to enable simulation of drinking addiction in humans. Derived from the known physiology of ethanol and the literature of both ethanol intoxication and ethanol absorption, the different models are distilled into a minimal model (as simple as the complexity of the data allows that can represent any specific patient. We use these modeling and simulation techniques to explain responses to placebo and ondansetron treatment observed in clinical studies. Specifically, the response to placebo was explained by a reduction of the probability of environmental reinforcement, while the effect of ondansetron was explained by a gradual decline in the degree of ethanol-induced neuromodulation. Further, we use in silico experiments to study critical transitions in blood alcohol levels after specific average number of drinks per day, and propose the existence of two critical thresholds in the human - one at 5 and another at 11 drinks/day - at which the system shifts from stable to critical and to super critical state indicating a state of alcohol addiction. The advantages of such a model-based investigation are that 1 the process of instigation of alcohol dependence and its treatment can be deconstructed into meaningful steps, which allow for individualized treatment tailoring, and 2 physiology and behavior can be quantified in different (animal or human studies and then the results can be integrated

  7. Spatial scale dependency of the modelled climatic response to deforestation

    OpenAIRE

    Longobardi, P.; Montenegro, A.; H. Beltrami; M. Eby

    2012-01-01

    Deforestation is associated with increased atmospheric CO2 and alterations to the surface energy and mass balances that can lead to local and global climate changes. Previous modelling studies show that the global surface air temperature (SAT) response to deforestation depends on latitude, with most simulations showing that high latitude deforestation results in cooling, low latitude deforestation causes warming and that the mid latitude response is mixed. T...

  8. Anomalous scaling in an age-dependent branching model

    OpenAIRE

    Keller-Schmidt, Stephanie; Tugrul, Murat; Eguíluz, Víctor M; Hernández-García, Emilio; Klemm, Konstantin

    2015-01-01

    We introduce a one-parametric family of tree growth models, in which branching probabilities decrease with branch age $\\tau$ as $\\tau^{-\\alpha}$. Depending on the exponent $\\alpha$, the scaling of tree depth with tree size $n$ displays a transition between the logarithmic scaling of random trees and an algebraic growth. At the transition ($\\alpha=1$) tree depth grows as $(\\log n)^2$. This anomalous scaling is in good agreement with the trend observed in evolution of biological species, thus p...

  9. Drosophila as a Model for Context-Dependent Tumorigenesis

    OpenAIRE

    2014-01-01

    Drosophila can exhibit classic hallmarks of cancer, such as evasion of apoptosis, sustained proliferation, metastasis, prolonged survival, genome instability, and metabolic reprogramming, when cancer-related genes are perturbed. In the last two decades, studies in flies have identified several tumor suppressor and oncogenes. However, the greatest strength of the fly lies in its ability to model cancer hallmarks in a variety of tissue types, which enables the study of context-dependent tumorig...

  10. Anomalous scaling in an age-dependent branching model

    OpenAIRE

    Keller-Schmidt, Stephanie; Tugrul, Murat; Eguíluz, Víctor M.; Hernández-García, Emilio; Klemm, Konstantin

    2010-01-01

    We introduce a one-parametric family of tree growth models, in which branching probabilities decrease with branch age $\\tau$ as $\\tau^{-\\alpha}$. Depending on the exponent $\\alpha$, the scaling of tree depth with tree size $n$ displays a transition between the logarithmic scaling of random trees and an algebraic growth. At the transition ($\\alpha=1$) tree depth grows as $(\\log n)^2$. This anomalous scaling is in good agreement with the trend observed in evolution of biological species, thus p...

  11. Time-dependent models of dense PDRs with complex molecules

    OpenAIRE

    Morata, O.; Herbst, E.

    2008-01-01

    We present a study of the chemistry of a dense photon-dominated region (PDR) using a time-dependent chemical model. Our major interest is to study the spatial distribution of complex molecules such as hydrocarbons and cyanopolyynes in the cool dense material bordering regions where star formation has taken place. Our standard model uses a homogeneous cloud of density 2x10e4 cm-3 and temperature T=40 K, which is irradiated by a far-ultraviolet radiation field of intermediate intensity, given b...

  12. Modified 'Joyce model' of opioid dependence/withdrawal.

    Science.gov (United States)

    Raffa, Robert B; Tallarida, Ronald J

    2006-12-03

    By comprehensive and detailed measurement of the time course of withdrawal signs in rats, Joyce et al. (J. Theo. Biol. 240:531-537, 2006) recently provided a creative quantitative model of the onset of drug dependence based on the requirement of protein synthesis. Because the initial model fit the data imperfectly over the full time course, those authors postulated that additional features would be needed. We report excellent fit of the data (R(2)=0.96) by adding: (1) a transient early phase, and (2) a delay in the buildup of protein.

  13. HZEFRG1: An energy-dependent semiempirical nuclear fragmentation model

    Science.gov (United States)

    Townsend, Lawrence W.; Wilson, John W.; Tripathi, Ram K.; Norbury, John W.; Badavi, Francis F.; Khan, Ferdous

    1993-01-01

    Methods for calculating cross sections for the breakup of high-energy heavy ions by the combined nuclear and coulomb fields of the interacting nuclei are presented. The nuclear breakup contributions are estimated with an abrasion-ablation model of heavy ion fragmentation that includes an energy-dependent, mean free path. The electromagnetic dissociation contributions arising from the interacting coulomb fields are estimated by using Weizsacker-Williams theory extended to include electric dipole and electric quadrupole contributions. The complete computer code that implements the model is included as an appendix. Extensive comparisons of cross section predictions with available experimental data are made.

  14. Terminal-Dependent Statistical Inference for the FBSDEs Models

    Directory of Open Access Journals (Sweden)

    Yunquan Song

    2014-01-01

    Full Text Available The original stochastic differential equations (OSDEs and forward-backward stochastic differential equations (FBSDEs are often used to model complex dynamic process that arise in financial, ecological, and many other areas. The main difference between OSDEs and FBSDEs is that the latter is designed to depend on a terminal condition, which is a key factor in some financial and ecological circumstances. It is interesting but challenging to estimate FBSDE parameters from noisy data and the terminal condition. However, to the best of our knowledge, the terminal-dependent statistical inference for such a model has not been explored in the existing literature. We proposed a nonparametric terminal control variables estimation method to address this problem. The reason why we use the terminal control variables is that the newly proposed inference procedures inherit the terminal-dependent characteristic. Through this new proposed method, the estimators of the functional coefficients of the FBSDEs model are obtained. The asymptotic properties of the estimators are also discussed. Simulation studies show that the proposed method gives satisfying estimates for the FBSDE parameters from noisy data and the terminal condition. A simulation is performed to test the feasibility of our method.

  15. A Temperature-Dependent Battery Model for Wireless Sensor Networks

    Directory of Open Access Journals (Sweden)

    Leonardo M. Rodrigues

    2017-02-01

    Full Text Available Energy consumption is a major issue in Wireless Sensor Networks (WSNs, as nodes are powered by chemical batteries with an upper bounded lifetime. Estimating the lifetime of batteries is a difficult task, as it depends on several factors, such as operating temperatures and discharge rates. Analytical battery models can be used for estimating both the battery lifetime and the voltage behavior over time. Still, available models usually do not consider the impact of operating temperatures on the battery behavior. The target of this work is to extend the widely-used Kinetic Battery Model (KiBaM to include the effect of temperature on the battery behavior. The proposed Temperature-Dependent KiBaM (T-KiBaM is able to handle operating temperatures, providing better estimates for the battery lifetime and voltage behavior. The performed experimental validation shows that T-KiBaM achieves an average accuracy error smaller than 0.33%, when estimating the lifetime of Ni-MH batteries for different temperature conditions. In addition, T-KiBaM significantly improves the original KiBaM voltage model. The proposed model can be easily adapted to handle other battery technologies, enabling the consideration of different WSN deployments.

  16. A Temperature-Dependent Battery Model for Wireless Sensor Networks.

    Science.gov (United States)

    Rodrigues, Leonardo M; Montez, Carlos; Moraes, Ricardo; Portugal, Paulo; Vasques, Francisco

    2017-02-22

    Energy consumption is a major issue in Wireless Sensor Networks (WSNs), as nodes are powered by chemical batteries with an upper bounded lifetime. Estimating the lifetime of batteries is a difficult task, as it depends on several factors, such as operating temperatures and discharge rates. Analytical battery models can be used for estimating both the battery lifetime and the voltage behavior over time. Still, available models usually do not consider the impact of operating temperatures on the battery behavior. The target of this work is to extend the widely-used Kinetic Battery Model (KiBaM) to include the effect of temperature on the battery behavior. The proposed Temperature-Dependent KiBaM (T-KiBaM) is able to handle operating temperatures, providing better estimates for the battery lifetime and voltage behavior. The performed experimental validation shows that T-KiBaM achieves an average accuracy error smaller than 0.33%, when estimating the lifetime of Ni-MH batteries for different temperature conditions. In addition, T-KiBaM significantly improves the original KiBaM voltage model. The proposed model can be easily adapted to handle other battery technologies, enabling the consideration of different WSN deployments.

  17. A Temperature-Dependent Battery Model for Wireless Sensor Networks

    Science.gov (United States)

    Rodrigues, Leonardo M.; Montez, Carlos; Moraes, Ricardo; Portugal, Paulo; Vasques, Francisco

    2017-01-01

    Energy consumption is a major issue in Wireless Sensor Networks (WSNs), as nodes are powered by chemical batteries with an upper bounded lifetime. Estimating the lifetime of batteries is a difficult task, as it depends on several factors, such as operating temperatures and discharge rates. Analytical battery models can be used for estimating both the battery lifetime and the voltage behavior over time. Still, available models usually do not consider the impact of operating temperatures on the battery behavior. The target of this work is to extend the widely-used Kinetic Battery Model (KiBaM) to include the effect of temperature on the battery behavior. The proposed Temperature-Dependent KiBaM (T-KiBaM) is able to handle operating temperatures, providing better estimates for the battery lifetime and voltage behavior. The performed experimental validation shows that T-KiBaM achieves an average accuracy error smaller than 0.33%, when estimating the lifetime of Ni-MH batteries for different temperature conditions. In addition, T-KiBaM significantly improves the original KiBaM voltage model. The proposed model can be easily adapted to handle other battery technologies, enabling the consideration of different WSN deployments. PMID:28241444

  18. Characterization of Models for Time-Dependent Behavior of Soils

    DEFF Research Database (Denmark)

    Liingaard, Morten; Augustesen, Anders; Lade, Poul V.

    2004-01-01

      Different classes of constitutive models have been developed to capture the time-dependent viscous phenomena ~ creep, stress relaxation, and rate effects ! observed in soils. Models based on empirical, rheological, and general stress-strain-time concepts have been studied. The first part...... is a review of the empirical relations, which apply only to problems of specific boundary conditions and frequently involve natural time alone. The second part deals with different rheological models used for describing the viscous effects in the field of solid mechanics. The rheological models are typically...... developed for metals and steel but are, to some extent, used to characterize time effects in geomaterials. The third part is a review of constitutive laws that describe not only viscous effects but also the inviscid ( rate-independent) behavior of soils, in principle, under any possible loading condition...

  19. The transition model test for serial dependence in mixed-effects models for binary data

    DEFF Research Database (Denmark)

    Breinegaard, Nina; Rabe-Hesketh, Sophia; Skrondal, Anders

    2016-01-01

    Generalized linear mixed models for longitudinal data assume that responses at different occasions are conditionally independent, given the random effects and covariates. Although this assumption is pivotal for consistent estimation, violation due to serial dependence is hard to assess by model...... the targeted root mean squared error of approximation (TRSMEA) as a measure of the population misfit due to serial dependence....

  20. Modelling vaccination strategies against foot-and-mouth disease

    Science.gov (United States)

    Keeling, M. J.; Woolhouse, M. E. J.; May, R. M.; Davies, G.; Grenfell, B. T.

    2003-01-01

    Vaccination has proved a powerful defence against a range of infectious diseases of humans and animals. However, its potential to control major epidemics of foot-and-mouth disease (FMD) in livestock is contentious. Using an individual farm-based model, we consider either national prophylactic vaccination campaigns in advance of an outbreak, or combinations of reactive vaccination and culling strategies during an epidemic. Consistent with standard epidemiological theory, mass prophylactic vaccination could reduce greatly the potential for a major epidemic, while the targeting of high-risk farms increases efficiency. Given sufficient resources and preparation, a combination of reactive vaccination and culling might control ongoing epidemics. We also explore a reactive strategy, `predictive' vaccination, which targets key spatial transmission loci and can reduce markedly the long tail that characterizes many FMD epidemics. These analyses have broader implications for the control of human and livestock infectious diseases in heterogeneous spatial landscapes.

  1. Using Cotton Model Simulations to Estimate Optimally Profitable Irrigation Strategies

    Science.gov (United States)

    Mauget, S. A.; Leiker, G.; Sapkota, P.; Johnson, J.; Maas, S.

    2011-12-01

    In recent decades irrigation pumping from the Ogallala Aquifer has led to declines in saturated thickness that have not been compensated for by natural recharge, which has led to questions about the long-term viability of agriculture in the cotton producing areas of west Texas. Adopting irrigation management strategies that optimize profitability while reducing irrigation waste is one way of conserving the aquifer's water resource. Here, a database of modeled cotton yields generated under drip and center pivot irrigated and dryland production scenarios is used in a stochastic dominance analysis that identifies such strategies under varying commodity price and pumping cost conditions. This database and analysis approach will serve as the foundation for a web-based decision support tool that will help producers identify optimal irrigation treatments under specified cotton price, electricity cost, and depth to water table conditions.

  2. Solvable time-dependent models in quantum mechanics

    Science.gov (United States)

    Cordero-Soto, Ricardo J.

    In the traditional setting of quantum mechanics, the Hamiltonian operator does not depend on time. While some Schrodinger equations with time-dependent Hamiltonians have been solved, explicitly solvable cases are typically scarce. This thesis is a collection of papers in which this first author along with Suslov, Suazo, and Lopez, has worked on solving a series of Schrodinger equations with a time-dependent quadratic Hamiltonian that has applications in problems of quantum electrodynamics, lasers, quantum devices such as quantum dots, and external varying fields. In particular the author discusses a new completely integrable case of the time-dependent Schrodinger equation in Rn with variable coefficients for a modified oscillator, which is dual with respect to the time inversion to a model of the quantum oscillator considered by Meiler, Cordero-Soto, and Suslov. A second pair of dual Hamiltonians is found in the momentum representation. Our examples show that in mathematical physics and quantum mechanics a change in the direction of time may require a total change of the system dynamics in order to return the system back to its original quantum state. The author also considers several models of the damped oscillators in nonrelativistic quantum mechanics in a framework of a general approach to the dynamics of the time-dependent Schrodinger equation with variable quadratic Hamiltonians. The Green functions are explicitly found in terms of elementary functions and the corresponding gauge transformations are discussed. The factorization technique is applied to the case of a shifted harmonic oscillator. The time-evolution of the expectation values of the energy related operators is determined for two models of the quantum damped oscillators under consideration. The classical equations of motion for the damped oscillations are derived for the corresponding expectation values of the position operator. Finally, the author constructs integrals of motion for several models

  3. [Participation as Target of Social Medicine and Nursing Care: - Legal Definition of Long-Term Care Dependency - Strategies to Prevent Long-Term Care Dependency].

    Science.gov (United States)

    Nüchtern, Elisabeth; Gansweid, Barbara; Gerber, Hans; von Mittelstaedt, Gert

    2017-01-01

    Objective: By the "Second Bill to Strengthen Long-Term Care", a new concept of long-term care dependency will be introduced, valid from 2017. Long-term care dependency according to Social Code XI will be defined covering more aspects than today. Therefore, the working group "Nursing Care" of the division "Social Medicine in Practice and Rehabilitation" in the German Society for Social Medicine and Prevention presents their results after working on the social medicine perspective of the definition and prevention of long-term care dependency. Methods: Both the definition and strategies to prevent long-term care dependency are systematically taken into consideration from the point of view of social medicine on the basis of the International Classification of Functioning, Disability and Health (ICF), as long-term care dependency means a defined condition of disability. Results: Both the current and the new concept of long-term care dependency focus activity limitations. The perspective of social medicine considers the interactions of health condition, its effects on daily activities and personal as well as environmental factors. From this point of view approaches for social benefits concerning prevention and rehabilitation can be identified systematically so as to work against the development and progression of long-term care dependency. The reference to the ICF can facilitate the communication between different professions. The new "graduation" of long-term care dependency would allow an international "translation" referring to the ICF. Conclusion: Experts from the field of social medicine as well as those of nursing care, care-givers and nursing researchers have in common the objective that persons in need of nursing care can participate in as many aspects of life of importance to them in an autonomous and self-determined way. The point of view of social medicine on long-term care dependency is fundamental for all occupational groups that are involved and for their

  4. An Effective Parameter Screening Strategy for High Dimensional Watershed Models

    Science.gov (United States)

    Khare, Y. P.; Martinez, C. J.; Munoz-Carpena, R.

    2014-12-01

    Watershed simulation models can assess the impacts of natural and anthropogenic disturbances on natural systems. These models have become important tools for tackling a range of water resources problems through their implementation in the formulation and evaluation of Best Management Practices, Total Maximum Daily Loads, and Basin Management Action Plans. For accurate applications of watershed models they need to be thoroughly evaluated through global uncertainty and sensitivity analyses (UA/SA). However, due to the high dimensionality of these models such evaluation becomes extremely time- and resource-consuming. Parameter screening, the qualitative separation of important parameters, has been suggested as an essential step before applying rigorous evaluation techniques such as the Sobol' and Fourier Amplitude Sensitivity Test (FAST) methods in the UA/SA framework. The method of elementary effects (EE) (Morris, 1991) is one of the most widely used screening methodologies. Some of the common parameter sampling strategies for EE, e.g. Optimized Trajectories [OT] (Campolongo et al., 2007) and Modified Optimized Trajectories [MOT] (Ruano et al., 2012), suffer from inconsistencies in the generated parameter distributions, infeasible sample generation time, etc. In this work, we have formulated a new parameter sampling strategy - Sampling for Uniformity (SU) - for parameter screening which is based on the principles of the uniformity of the generated parameter distributions and the spread of the parameter sample. A rigorous multi-criteria evaluation (time, distribution, spread and screening efficiency) of OT, MOT, and SU indicated that SU is superior to other sampling strategies. Comparison of the EE-based parameter importance rankings with those of Sobol' helped to quantify the qualitativeness of the EE parameter screening approach, reinforcing the fact that one should use EE only to reduce the resource burden required by FAST/Sobol' analyses but not to replace it.

  5. Hydrogeological modeling for improving groundwater monitoring network and strategies

    Science.gov (United States)

    Thakur, Jay Krishna

    2016-09-01

    The research aimed to investigate a new approach for spatiotemporal groundwater monitoring network optimization using hydrogeological modeling to improve monitoring strategies. Unmonitored concentrations were incorporated at different potential monitoring locations into the groundwater monitoring optimization method. The proposed method was applied in the contaminated megasite, Bitterfeld/Wolfen, Germany. Based on an existing 3-D geological model, 3-D groundwater flow was obtained from flow velocity simulation using initial and boundary conditions. The 3-D groundwater transport model was used to simulate transport of α-HCH with an initial ideal concentration of 100 mg/L injected at various hydrogeological layers in the model. Particle tracking for contaminant and groundwater flow velocity realizations were made. The spatial optimization result suggested that 30 out of 462 wells in the Quaternary aquifer (6.49 %) and 14 out of 357 wells in the Tertiary aquifer (3.92 %) were redundant. With a gradual increase in the width of the particle track path line, from 0 to 100 m, the number of redundant wells remarkably increased, in both aquifers. The results of temporal optimization showed different sampling frequencies for monitoring wells. The groundwater and contaminant flow direction resulting from particle tracks obtained from hydrogeological modeling was verified by the variogram modeling through α-HCH data from 2003 to 2009. Groundwater monitoring strategies can be substantially improved by removing the existing spatio-temporal redundancy as well as incorporating unmonitored network along with sampling at recommended interval of time. However, the use of this model-based method is only recommended in the areas along with site-specific experts' knowledge.

  6. Evolution of the social-learner-explorer strategy in an environmentally heterogeneous two-island model.

    Science.gov (United States)

    Aoki, Kenichi

    2010-09-01

    Social-learner-explorer (SE) is a learning strategy that combines accurate social learning with exploratory individual learning in that order. Arguably, it is one of the few plausible learning strategies that can support cumulative culture. We investigate numerically the factors that affect the evolution of SE in an environmentally heterogeneous two-island model. Conditions favorable to the evolution of SE include a small exogenous cost of social learning, the occurrence of migration after social learning but before individual learning, the ability to adaptively modify the behavioral phenotype in the postmigration environment (asymmetrical individual learning), and a relatively high migration rate. The implications of our model for the evolution of SE in humans are discussed. Of particular interest is the prediction that behaviors affecting fitness would have to be socially learned in the natal environment and then subsequently modified by individual learning in the postmigration environment, suggesting a life-cycle stage dependent reliance on the two types of learning.

  7. Bifurcation analysis of vertical transmission model with preventive strategy

    Directory of Open Access Journals (Sweden)

    Gosalamang Ricardo Kelatlhegile

    2016-07-01

    Full Text Available We formulate and analyze a deterministic mathematical model for the prevention of a disease transmitted horizontally and vertically in a population of varying size. The model incorporates prevention of disease on individuals at birth and adulthood and allows for natural recovery from infection. The main aim of the study is to investigate the impact of a preventive strategy applied at birth and at adulthood in reducing the disease burden. Bifurcation analysis is explored to determine existence conditions for establishment of the epidemic states. The results of the study showed that in addition to the disease-free equilibrium there exist multiple endemic equilibria for the model reproduction number below unity. These results may have serious implications on the design of intervention programs and public health policies. Numerical simulations were carried out to illustrate analytical results.

  8. Outcome modelling strategies in epidemiology: traditional methods and basic alternatives.

    Science.gov (United States)

    Greenland, Sander; Daniel, Rhian; Pearce, Neil

    2016-04-01

    Controlling for too many potential confounders can lead to or aggravate problems of data sparsity or multicollinearity, particularly when the number of covariates is large in relation to the study size. As a result, methods to reduce the number of modelled covariates are often deployed. We review several traditional modelling strategies, including stepwise regression and the 'change-in-estimate' (CIE) approach to deciding which potential confounders to include in an outcome-regression model for estimating effects of a targeted exposure. We discuss their shortcomings, and then provide some basic alternatives and refinements that do not require special macros or programming. Throughout, we assume the main goal is to derive the most accurate effect estimates obtainable from the data and commercial software. Allowing that most users must stay within standard software packages, this goal can be roughly approximated using basic methods to assess, and thereby minimize, mean squared error (MSE).

  9. A strategy to model nonmonotonic dose-response curve and estimate IC50.

    Science.gov (United States)

    Zhang, Hui; Holden-Wiltse, Jeanne; Wang, Jiong; Liang, Hua

    2013-01-01

    The half-maximal inhibitory concentration IC[Formula: see text] is an important pharmacodynamic index of drug effectiveness. To estimate this value, the dose response relationship needs to be established, which is generally achieved by fitting monotonic sigmoidal models. However, recent studies on Human Immunodeficiency Virus (HIV) mutants developing resistance to antiviral drugs show that the dose response curve may not be monotonic. Traditional models can fail for nonmonotonic data and ignore observations that may be of biologic significance. Therefore, we propose a nonparametric model to describe the dose response relationship and fit the curve using local polynomial regression. The nonparametric approach is shown to be promising especially for estimating the IC[Formula: see text] of some HIV inhibitory drugs, in which there is a dose-dependent stimulation of response for mutant strains. This model strategy may be applicable to general pharmacologic, toxicologic, or other biomedical data that exhibits a nonmonotonic dose response relationship for which traditional parametric models fail.

  10. Measures and models of nicotine dependence: positive reinforcement.

    Science.gov (United States)

    Glautier, Steven

    2004-06-01

    This paper addresses the problem of assessing nicotine dependence. The main objective is to develop theory-led suggestions for measures that will be relevant in the early phases of tobacco use, as well as in established smokers. Theoretical models of addiction falling into the general class of 'positive reinforcement theories' were identified and reviewed. From this review a number of drug effects and patterns of behaviour were distilled and categorized as either vulnerability or dependence indicators. A comparison of those features with the International Classification of Diseases (ICD-10) and Diagnostic and Statistical Manual (DSM-IV) diagnostic systems shows that neither system includes detailed assessment of vulnerability indicators. It is argued that measurement of vulnerability indicators, in addition to dependence indicators, may add to the predictive validity of assessments carried out in early career tobacco users, especially where there is limited evidence of established dependence. In addition, it is suggested that examination of measures that differentiate a subgroup of early career smokers termed 'rapid accelerators' may prove profitable and enable identification of the key parameters of nicotine reinforcement.

  11. Supplier Selection in Three Echelon Supply Chain & Vendor Managed Inventory Model Under Price Dependent Demand Condition

    Directory of Open Access Journals (Sweden)

    Mohammad Sohrabi

    2016-02-01

    Full Text Available This paper, considers the supplier selection in three echelon supply chain with Vendor Managed Inventory (VMI strategy under price dependent demand condition. As there is a lack of study on the supplier selection in VMI literature, this paper presents a VMI model in supply chain including multi supplier, one distributer and multi retailer that distributer selects suppliers. Two class models (traditional vs. VMI are presented and we compare them to study the impact of VMI on supply chain and supplier selection. As the proposed model is a NP-hard problem, a meta-heuristics namely Harmony Search is employed to optimize the proposed models. We show that how the VMI system can effect on supplier selection and can change the set of selected suppliers. Finally the conclusion and further studies are presented

  12. A continuous latitudinal energy balance model to explore non-uniform climate engineering strategies

    Science.gov (United States)

    Bonetti, F.; McInnes, C. R.

    2016-12-01

    Current concentrations of atmospheric CO2 exceed measured historical levels in modern times, largely attributed to anthropogenic forcing since the industrial revolution. The required decline in emissions rates has never been achieved leading to recent interest in climate engineering for future risk-mitigation strategies. Climate engineering aims to offset human-driven climate change. It involves techniques developed both to reduce the concentration of CO2 in the atmosphere (Carbon Dioxide Removal (CDR) methods) and to counteract the radiative forcing that it generates (Solar Radiation Management (SRM) methods). In order to investigate effects of SRM technologies for climate engineering, an analytical model describing the main dynamics of the Earth's climate has been developed. The model is a time-dependent Energy Balance Model (EBM) with latitudinal resolution and allows for the evaluation of non-uniform climate engineering strategies. A significant disadvantage of climate engineering techniques involving the management of solar radiation is regional disparities in cooling. This model offers an analytical approach to design multi-objective strategies that counteract climate change on a regional basis: for example, to cool the Artic and restrict undesired impacts at mid-latitudes, or to control the equator-to-pole temperature gradient. Using the Green's function approach the resulting partial differential equation allows for the computation of the surface temperature as a function of time and latitude when a 1% per year increase in the CO2 concentration is considered. After the validation of the model through comparisons with high fidelity numerical models, it will be used to explore strategies for the injection of the aerosol precursors in the stratosphere. In particular, the model involves detailed description of the optical properties of the particles, the wash-out dynamics and the estimation of the radiative cooling they can generate.

  13. Strong scale dependent bispectrum in the Starobinsky model of inflation

    CERN Document Server

    Arroja, Frederico

    2012-01-01

    We compute analytically the dominant contribution to the tree-level bispectrum in the Starobinsky model of inflation. In this model, the potential is vacuum energy dominated but contains a subdominant linear term which changes the slope abruptly at a point. We show that on large scales compared with the transition scale $k_0$ and in the equilateral limit the analogue of the non-linearity parameter scales as $(k/k_0)^2$, that is its amplitude decays for larger and larger scales until it becomes subdominant with respect to the usual slow-roll suppressed corrections. On small scales we show that the non-linearity parameter oscillates with angular frequency given by $3/k_0$ and its amplitude grows linearly towards smaller scales and can be large depending on the model parameters. We also compare our results with previous results in the literature.

  14. Modeling, dependence, classification, united statistical science, many cultures

    CERN Document Server

    Parzen, Emanuel

    2012-01-01

    Breiman (2001) proposed to statisticians awareness of two cultures: 1. Parametric modeling culture, pioneered by R.A.Fisher and Jerzy Neyman; 2. Algorithmic predictive culture, pioneered by machine learning research. Parzen (2001), as a part of discussing Breiman (2001), proposed that researchers be aware of many cultures, including the focus of our research: 3. Nonparametric, quantile based, information theoretic modeling. Our research seeks to unify statistical problem solving in terms of comparison density, copula density, measure of dependence, correlation, information, new measures (called LP score comoments) that apply to long tailed distributions with out finite second order moments. A very important goal is to unify methods for discrete and continuous random variables. We are actively developing these ideas, which have a history of many decades, since Parzen (1979, 1983) and Eubank et al. (1987). Our research extends these methods to modern high dimensional data modeling.

  15. Angular dependence models for radiance to flux conversion

    Science.gov (United States)

    Green, Richard N.; Suttles, John T.; Wielicki, Bruce A.

    1990-01-01

    Angular dependence models (ADM) used for converting the measured radiance to flux at the top of the atmosphere are reviewed, and emphasis is placed on the measure of their effectiveness and the implications of requiring the ADMs to satisfy reciprocity. The overall significance of the ADMs is figured out by analyzing the same satellite data with a single Lambertian model, single mean model, and the 12 Earth Radiation Budget Experiment (ERBE) ADMs. It is shown that the Lambertian ADM is inadequate, while the mean ADM results in nearly unbiased fluxes but creates substantial differences for individual pixel fluxes. The standard ERBE ADM works well except for a 10-pct to 15-pct albedo growth across the scan; a modified ADM based on the standard ERBE ADM but forced to satisfy the principle of reciprocity increases the limb brightening and reduces the albedo growth but does not improve the scanner and nonscanner intercomparison.

  16. A Computationally Efficient Aggregation Optimization Strategy of Model Predictive Control

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Model Predictive Control (MPC) is a popular technique and has been successfully used in various industrial applications. However, the big drawback of MPC involved in the formidable on-line computational effort limits its applicability to relatively slow and/or small processes with a moderate number of inputs. This paper develops an aggregation optimization strategy for MPC that can improve the computational efficiency of MPC. For the regulation problem, an input decaying aggregation optimization algorithm is presented by aggregating all the original optimized variables on control horizon with the decaying sequence in respect of the current control action.

  17. Analysis of local dependence and multidimensionality in graphical loglinear Rasch models

    DEFF Research Database (Denmark)

    Kreiner, Svend; Christensen, Karl Bang

    local independence; multidimensionality, differential item functioning; uniform local dependency and DIF; graphical Rasch models; loglinear Rasch models......local independence; multidimensionality, differential item functioning; uniform local dependency and DIF; graphical Rasch models; loglinear Rasch models...

  18. Analysis of Local Dependence and Multidimensionality in Graphical Loglinear Rasch Models

    DEFF Research Database (Denmark)

    Kreiner, Svend; Christensen, Karl Bang

    2004-01-01

    Local independence; Multidimensionality; Differential item functioning; Uniform local dependence and DIF; Graphical Rasch models; Loglinear Rasch model......Local independence; Multidimensionality; Differential item functioning; Uniform local dependence and DIF; Graphical Rasch models; Loglinear Rasch model...

  19. Filippov Ratio-Dependent Prey-Predator Model with Threshold Policy Control

    Directory of Open Access Journals (Sweden)

    Xianghong Zhang

    2013-01-01

    Full Text Available The Filippov ratio-dependent prey-predator model with economic threshold is proposed and studied. In particular, the sliding mode domain, sliding mode dynamics, and the existence of four types of equilibria and tangent points are investigated firstly. Further, the stability of pseudoequilibrium is addressed by using theoretical and numerical methods, and also the local sliding bifurcations including regular/virtual equilibrium bifurcations and boundary node bifurcations are studied. Finally, some global sliding bifurcations are addressed numerically. The globally stable touching cycle indicates that the density of pest population can be successfully maintained below the economic threshold level by designing suitable threshold policy strategies.

  20. Model Penjadwalan Batch Multi Item dengan Dependent Processing Time

    Directory of Open Access Journals (Sweden)

    Sukoyo Sukoyo

    2010-01-01

    Full Text Available This paper investigates a development of single machine batch scheduling for multi items with dependent processing time. The batch scheduling problem is to determine simultaneously number of batch (N, which item and its size allocated for each batch, and processing sequences of resulting batches. We use total actual flow time as the objective of schedule performance. The multi item batch scheduling problem could be formulated into a biner-integer nonlinear programming model because the number of batch should be in integer value, the allocation of items to resulting batch need binary values, and also there are some non-linearity on objective function and constraint due to the dependent processing time. By applying relaxation on the decision variable of number of batch (N as parameter, a heuristic procedure could be applied to find solution of the single machine batch scheduling problem for multi items.

  1. A context dependent pair hidden Markov model for statistical alignment

    CERN Document Server

    Arribas-Gil, Ana

    2011-01-01

    This article proposes a novel approach to statistical alignment of nucleotide sequences by introducing a context dependent structure on the substitution process in the underlying evolutionary model. We propose to estimate alignments and context dependent mutation rates relying on the observation of two homologous sequences. The procedure is based on a generalized pair-hidden Markov structure, where conditional on the alignment path, the nucleotide sequences follow a Markov distribution. We use a stochastic approximation expectation maximization (saem) algorithm to give accurate estimators of parameters and alignments. We provide results both on simulated data and vertebrate genomes, which are known to have a high mutation rate from CG dinucleotide. In particular, we establish that the method improves the accuracy of the alignment of a human pseudogene and its functional gene.

  2. Business Model Innovation Portfolio Strategy for Growth Under Product-Market Configurations

    National Research Council Canada - National Science Library

    Bert Verhoeven; Lester W Johnson

    2017-01-01

    Purpose: The research links three concepts: product market growth strategy, the magnitude of innovation and Business Model Innovation, merging them together into a dynamic Business Model Innovation strategy framework...

  3. An Empirical Comparison of Probability Models for Dependency Grammar

    CERN Document Server

    Eisner, J

    1997-01-01

    This technical report is an appendix to Eisner (1996): it gives superior experimental results that were reported only in the talk version of that paper. Eisner (1996) trained three probability models on a small set of about 4,000 conjunction-free, dependency-grammar parses derived from the Wall Street Journal section of the Penn Treebank, and then evaluated the models on a held-out test set, using a novel O(n^3) parsing algorithm. The present paper describes some details of the experiments and repeats them with a larger training set of 25,000 sentences. As reported at the talk, the more extensive training yields greatly improved performance. Nearly half the sentences are parsed with no misattachments; two-thirds are parsed with at most one misattachment. Of the models described in the original written paper, the best score is still obtained with the generative (top-down) "model C." However, slightly better models are also explored, in particular, two variants on the comprehension (bottom-up) "model B." The be...

  4. Spatially dependent polya tree modeling for survival data.

    Science.gov (United States)

    Zhao, Luping; Hanson, Timothy E

    2011-06-01

    With the proliferation of spatially oriented time-to-event data, spatial modeling in the survival context has received increased recent attention. A traditional way to capture a spatial pattern is to introduce frailty terms in the linear predictor of a semiparametric model, such as proportional hazards or accelerated failure time. We propose a new methodology to capture the spatial pattern by assuming a prior based on a mixture of spatially dependent Polya trees for the baseline survival in the proportional hazards model. Thanks to modern Markov chain Monte Carlo (MCMC) methods, this approach remains computationally feasible in a fully hierarchical Bayesian framework. We compare the spatially dependent mixture of Polya trees (MPT) approach to the traditional spatial frailty approach, and illustrate the usefulness of this method with an analysis of Iowan breast cancer survival data from the Surveillance, Epidemiology, and End Results (SEER) program of the National Cancer Institute. Our method provides better goodness of fit over the traditional alternatives as measured by log pseudo marginal likelihood (LPML), the deviance information criterion (DIC), and full sample score (FSS) statistics. © 2010, The International Biometric Society.

  5. The effects of field dependent/independent style awareness on learning strategies and outcomes in an instructional hypermedia module

    Science.gov (United States)

    Fyle, Clifford Omodele

    The purpose of this study was to examine whether field-dependent/independent style awareness affects learning outcomes and learning strategies used in a hypermedia instructional module. Field-dependent/independent style was measured using the Global Embedded Figures Test. Style awareness meant that students were provided with information and explanations about their individual cognitive styles and the learning strategies that accommodate those styles. The study entailed examining students' achievement in a multiple-choice test and performance in a design task, and also their navigation patterns as they studied a science-oriented Webquest. The sample consisted of 149 eighth-grade students in 10 sections of a science class taught by two teachers in a public middle school. A two-group posttest-only design on one factor (style awareness) was used. Sixty-eight students in five sections of the class were assigned to the treatment group (field dependent/independent style awareness) while the other 81 students in five sections were assigned to the control group (no field dependent/independent style awareness). The study took place over a period of 6 days. On the first day, students in the treatment group were first tested and debriefed on their individual styles. Next, all students in both the treatment and control groups studied the hypermedia instructional module (Webquest) over a period of two days. On the fourth and fifth days students worked on the performance tasks, and on the sixth day students took the multiple-choice test and students in the control group were tested and debriefed on their individual styles. The findings indicate that style awareness significantly influenced the learning strategies of field-dependent students as they studied and carried out learning tasks in the Webquest. Field-dependent students with style awareness used hypertext links and navigated the menu sequentially a greater number of times than their counterparts with no style awareness

  6. Alternative Models of Self-regulation and Implications for L2 Strategy Research

    Directory of Open Access Journals (Sweden)

    Jim Ranalli

    2012-12-01

    Full Text Available In this paper I discuss the proposal of Dörnyei and colleagues (Dörnyei, 2005; Tseng, Dörnyei, & Schmitt, 2006 to replace the construct of learning strategy with that of self-regulation and thus shift the research focus from specific strategic behaviors to a trait that is seen to underlie them. I argue that before doing so, we need a fuller understanding of what self-regulation entails and how it might intersect with traditional concerns of second language strategy research. To contribute to this understanding, I highlight alternative conceptualizations of self-regulation and then use data from my doctoral research to illustrate one in particular, the COPES model of self-regulated learning (Winne & Hadwin, 1998. This model’s explanatory power is contrasted with that of Dörnyei and colleagues’ conceptualization to show that, depending on the model one adopts, self-regulation is not only compatible with the study of specific strategies but useful for shedding new light on strategy research and integrating it with research in other related areas, such as L2 motivation.

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

    DEFF Research Database (Denmark)

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

    2017-01-01

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

  8. Fault evolution-test dependency modeling for mechanical systems

    Institute of Scientific and Technical Information of China (English)

    Xiao-dong TAN; Jian-lu LUO; Qing LI; Bing LU; Jing QIU

    2015-01-01

    Tracking the process of fault growth in mechanical systems using a range of tests is important to avoid catastrophic failures. So, it is necessary to study the design for testability (DFT). In this paper, to improve the testability performance of me-chanical systems for tracking fault growth, a fault evolution-test dependency model (FETDM) is proposed to implement DFT. A testability analysis method that considers fault trackability and predictability is developed to quantify the testability performance of mechanical systems. Results from experiments on a centrifugal pump show that the proposed FETDM and testability analysis method can provide guidance to engineers to improve the testability level of mechanical systems.

  9. Graphical models for inference under outcome-dependent sampling

    DEFF Research Database (Denmark)

    Didelez, V; Kreiner, S; Keiding, N

    2010-01-01

    a node for the sampling indicator, assumptions about sampling processes can be made explicit. We demonstrate how to read off such graphs whether consistent estimation of the association between exposure and outcome is possible. Moreover, we give sufficient graphical conditions for testing and estimating......We consider situations where data have been collected such that the sampling depends on the outcome of interest and possibly further covariates, as for instance in case-control studies. Graphical models represent assumptions about the conditional independencies among the variables. By including...

  10. A Neuronal Network Model for Context-Dependence of Pitch Change Perception

    Directory of Open Access Journals (Sweden)

    Chengcheng eHuang

    2015-08-01

    Full Text Available Many natural stimuli have perceptual ambiguities that can be cognitively resolved by the surrounding context. In audition, preceding context can bias the perception of speech and non-speech stimuli. Here, we develop a neuronal network model that can account for how context affects the perception of pitch change between a pair of successive complex tones. We focus especially on an ambiguous comparison -- listeners experience opposite percepts (either ascending or descending for an ambiguous tone pair depending on the spectral location of preceding context tones.We developed a recurrent, firing-rate network model, which detects frequency-change-direction of successively played stimuli and successfully accounts for the context-dependent perception demonstrated in behavioral experiments. The model consists of two tonotopically organized, excitatory populations, Eup and Edown, that respond preferentially to ascending or descending stimuli in pitch, respectively. These preferences are generated by an inhibitory population that provides inhibition asymmetric in frequency to the two populations; context dependence arises from slow facilitation of inhibition. We show that contextual influence depends on the spectral distribution of preceding tones and the tuning width of inhibitory neurons. Further, we demonstrate, using phase-space analysis, how the facilitated inhibition from previous stimuli and the waning inhibition from the just-preceding tone shape the competition between the Eup and Edown populations. In sum, our model accounts for contextual influences on the pitch change perception of an ambiguous tone pair by introducing a novel decoding strategy based on direction-selective units. The model’s network architecture and slow facilitating inhibition emerge as predictions of neuronal mechanisms for these perceptual dynamics. Since the model structure does not depend on the specific stimuli, we show that it generalizes to other contextual effects

  11. Striatal and hippocampal involvement in motor sequence chunking depends on the learning strategy.

    Science.gov (United States)

    Lungu, Ovidiu; Monchi, Oury; Albouy, Geneviève; Jubault, Thomas; Ballarin, Emanuelle; Burnod, Yves; Doyon, Julien

    2014-01-01

    Motor sequences can be learned using an incremental approach by starting with a few elements and then adding more as training evolves (e.g., learning a piano piece); conversely, one can use a global approach and practice the whole sequence in every training session (e.g., shifting gears in an automobile). Yet, the neural correlates associated with such learning strategies in motor sequence learning remain largely unexplored to date. Here we used functional magnetic resonance imaging to measure the cerebral activity of individuals executing the same 8-element sequence after they completed a 4-days training regimen (2 sessions each day) following either a global or incremental strategy. A network comprised of striatal and fronto-parietal regions was engaged significantly regardless of the learning strategy, whereas the global training regimen led to additional cerebellar and temporal lobe recruitment. Analysis of chunking/grouping of sequence elements revealed a common prefrontal network in both conditions during the chunk initiation phase, whereas execution of chunk cores led to higher mediotemporal activity (involving the hippocampus) after global than incremental training. The novelty of our results relate to the recruitment of mediotemporal regions conditional of the learning strategy. Thus, the present findings may have clinical implications suggesting that the ability of patients with lesions to the medial temporal lobe to learn and consolidate new motor sequences may benefit from using an incremental strategy.

  12. Striatal and hippocampal involvement in motor sequence chunking depends on the learning strategy.

    Directory of Open Access Journals (Sweden)

    Ovidiu Lungu

    Full Text Available Motor sequences can be learned using an incremental approach by starting with a few elements and then adding more as training evolves (e.g., learning a piano piece; conversely, one can use a global approach and practice the whole sequence in every training session (e.g., shifting gears in an automobile. Yet, the neural correlates associated with such learning strategies in motor sequence learning remain largely unexplored to date. Here we used functional magnetic resonance imaging to measure the cerebral activity of individuals executing the same 8-element sequence after they completed a 4-days training regimen (2 sessions each day following either a global or incremental strategy. A network comprised of striatal and fronto-parietal regions was engaged significantly regardless of the learning strategy, whereas the global training regimen led to additional cerebellar and temporal lobe recruitment. Analysis of chunking/grouping of sequence elements revealed a common prefrontal network in both conditions during the chunk initiation phase, whereas execution of chunk cores led to higher mediotemporal activity (involving the hippocampus after global than incremental training. The novelty of our results relate to the recruitment of mediotemporal regions conditional of the learning strategy. Thus, the present findings may have clinical implications suggesting that the ability of patients with lesions to the medial temporal lobe to learn and consolidate new motor sequences may benefit from using an incremental strategy.

  13. Dissociable contributions of the prefrontal cortex to hippocampus- and caudate nucleus-dependent virtual navigation strategies.

    Science.gov (United States)

    Dahmani, Louisa; Bohbot, Véronique D

    2015-01-01

    The hippocampus and the caudate nucleus are critical to spatial- and stimulus-response-based navigation strategies, respectively. The hippocampus and caudate nucleus are also known to be anatomically connected to various areas of the prefrontal cortex. However, little is known about the involvement of the prefrontal cortex in these processes. In the current study, we sought to identify the prefrontal areas involved in spatial and response learning. We used functional magnetic resonance imaging (fMRI) and voxel-based morphometry to compare the neural activity and grey matter density of spatial and response strategy users. Twenty-three healthy young adults were scanned in a 1.5 T MRI scanner while they engaged in the Concurrent Spatial Discrimination Learning Task, a virtual navigation task in which either a spatial or response strategy can be used. In addition to increased BOLD activity in the hippocampus, spatial strategy users showed increased BOLD activity and grey matter density in the ventral area of the medial prefrontal cortex, especially in the orbitofrontal cortex. On the other hand, response strategy users exhibited increased BOLD activity and grey matter density in the dorsal area of the medial prefrontal cortex. Given the prefrontal cortex's role in reward-guided decision-making, we discuss the possibility that the ventromedial prefrontal cortex, including the orbitofrontal cortex, supports spatial learning by encoding stimulus-reward associations, while the dorsomedial prefrontal cortex supports response learning by encoding action-reward associations.

  14. Performance deterioration modeling and optimal preventive maintenance strategy under scheduled servicing subject to mission time

    Institute of Scientific and Technical Information of China (English)

    Li Dawei; Zhang Zhihua; Zhong Qianghui; Zhai Yali

    2014-01-01

    Servicing is applied periodically in practice with the aim of restoring the system state and prolonging the lifetime. It is generally seen as an imperfect maintenance action which has a chief influ-ence on the maintenance strategy. In order to model the maintenance effect of servicing, this study analyzes the deterioration characteristics of system under scheduled servicing. And then the deterio-ration model is established from the failure mechanism by compound Poisson process. On the basis of the system damage value and failure mechanism, the failure rate refresh factor is proposed to describe the maintenance effect of servicing. A maintenance strategy is developed which combines the benefits of scheduled servicing and preventive maintenance. Then the optimization model is given to determine the optimal servicing period and preventive maintenance time, with an objective to minimize the sys-tem expected life-cycle cost per unit time and a constraint on system survival probability for the dura-tion of mission time. Subject to mission time, it can control the ability of accomplishing the mission at any time so as to ensure the high dependability. An example of water pump rotor relating to scheduled servicing is introduced to illustrate the failure rate refresh factor and the proposed maintenance strat-egy. Compared with traditional methods, the numerical results show that the failure rate refresh factor can describe the maintenance effect of servicing more intuitively and objectively. It also demonstrates that this maintenance strategy can prolong the lifetime, reduce the total lifetime maintenance cost and guarantee the dependability of system.

  15. Logical Reasoning versus Information Processing in the Dual-Strategy Model of Reasoning

    Science.gov (United States)

    Markovits, Henry; Brisson, Janie; de Chantal, Pier-Luc

    2017-01-01

    One of the major debates concerning the nature of inferential reasoning is between counterexample-based strategies such as mental model theory and statistical strategies underlying probabilistic models. The dual-strategy model, proposed by Verschueren, Schaeken, & d'Ydewalle (2005a, 2005b), which suggests that people might have access to both…

  16. A General Shear-Dependent Model for Thrombus Formation.

    Science.gov (United States)

    Yazdani, Alireza; Li, He; Humphrey, Jay D; Karniadakis, George Em

    2017-01-01

    Modeling the transport, activation, and adhesion of platelets is crucial in predicting thrombus formation and growth following a thrombotic event in normal or pathological conditions. We propose a shear-dependent platelet adhesive model based on the Morse potential that is calibrated by existing in vivo and in vitro experimental data and can be used over a wide range of flow shear rates ([Formula: see text]). We introduce an Eulerian-Lagrangian model where hemodynamics is solved on a fixed Eulerian grid, while platelets are tracked using a Lagrangian framework. A force coupling method is introduced for bidirectional coupling of platelet motion with blood flow. Further, we couple the calibrated platelet aggregation model with a tissue-factor/contact pathway coagulation cascade, representing the relevant biology of thrombin generation and the subsequent fibrin deposition. The range of shear rates covered by the proposed model encompass venous and arterial thrombosis, ranging from low-shear-rate conditions in abdominal aortic aneurysms and thoracic aortic dissections to thrombosis in stenotic arteries following plaque rupture, where local shear rates are extremely high.

  17. A time-dependent model for improved biogalvanic tissue characterisation.

    Science.gov (United States)

    Chandler, J H; Culmer, P R; Jayne, D G; Neville, A

    2015-10-01

    Measurement of the passive electrical resistance of biological tissues through biogalvanic characterisation has been proposed as a simple means of distinguishing healthy from diseased tissue. This method has the potential to provide valuable real-time information when integrated into surgical tools. Characterised tissue resistance values have been shown to be particularly sensitive to external load switching direction and rate, bringing into question the stability and efficacy of the technique. These errors are due to transient variations observed in measurement data that are not accounted for in current electrical models. The presented research proposes the addition of a time-dependent element to the characterisation model to account for losses associated with this transient behaviour. Influence of switching rate has been examined, with the inclusion of transient elements improving the repeatability of the characterised tissue resistance. Application of this model to repeat biogalvanic measurements on a single ex vivo human colon tissue sample with healthy and cancerous (adenocarcinoma) regions showed a statistically significant difference (p  0.05) between tissue types was found when measurements were subjected to the current model, suggesting that the proposed model may allow for improved biogalvanic tissue characterisation. Copyright © 2015 IPEM. Published by Elsevier Ltd. All rights reserved.

  18. Phenology as a strategy for carbon optimality: a global model

    Directory of Open Access Journals (Sweden)

    S. Caldararu

    2013-09-01

    Full Text Available Phenology is essential to our understanding of biogeochemical cycles and the climate system. We develop a global mechanistic model of leaf phenology based on the hypothesis that phenology is a strategy for optimal carbon gain at the canopy level so that trees adjust leaf gains and losses in response to environmental factors such as light, temperature and soil moisture, to achieve maximum carbon assimilation. We fit this model to five years of satellite observations of leaf area index (LAI using a Bayesian fitting algorithm. We show that our model is able to reproduce phenological patterns for all vegetation types and use it to explore variations in growing season length and the climate factors that limit leaf growth for different biomes. Phenology in wet tropical areas is limited by leaf age physiological constraints while at higher latitude leaf seasonality is limited by low temperature and light availability. Leaf growth in grassland regions is limited by water availability but often in combination with other factors. This model will advance the current understanding of phenology for ecosystem carbon models and our ability to predict future phenological behaviour.

  19. A Web of Drones: A 2040 Strategy to Reduce the United States Dependance on Space Based Capabilities

    Science.gov (United States)

    2015-02-17

    2040. On the Design of the Aircraft The drone is required to keep a payload airborne for 24 hours unrefueled and 5 days with refueling but without... Design of the Web The altitude of the drones and the distance between them are not set in stone. A denser web (more nodes, shorter distances between...AIR WAR COLLEGE AIR UNIVERSITY A WEB OF DRONES : A 2040 STRATEGY TO REDUCE THE UNITED STATES DEPENDANCE ON SPACE BASED CAPABILITIES by

  20. Fuzzy economic production quantity model with time dependent demand rate

    Directory of Open Access Journals (Sweden)

    Susanta Kumar Indrajitsingha

    2016-09-01

    Full Text Available Background: In this paper, an economic production quantity model is considered under a fuzzy environment. Both the demand cost and holding cost are considered using fuzzy pentagonal numbers. The Signed Distance Method is used to defuzzify the total cost function. Methods: The results obtained by these methods are compared with the help of a numerical example. Sensitivity analysis is also carried out to explore the effect of changes in the values of some of the system parameters. Results and conclusions: The fuzzy EPQ model with time dependent demand rate was presented together with the possible implementation. The behavior of changes in parameters was analyzed. The possible extension of the implementation of this method was presented.

  1. Isospin dependence of nuclear multifragmentation in statistical model

    Institute of Scientific and Technical Information of China (English)

    ZHANG Lei; XIE Dong-Zhu; ZHANG Yan-Ping; GAO Yuan

    2011-01-01

    The evolution of nuclear disintegration mechanisms with increasing excitation energy, from com- pound nucleus to multifragmentation, has been studied by using the Statistical Multifragmentation Model (SMM) within a micro-canonical ensemble. We discuss the observable characteristics as functions of excitation energy in multifragmentation, concentrating on the isospin dependence of the model in its decaying mechanism and break-up fragment configuration by comparing the A = 200, Z = 78 and A = 200, Z = 100 systems. The calculations indicate that the neutron-rich system (Z = 78) translates to a fission-like process from evaporation later than the symmetric nucleus at a lower excitation energy, but gets a larger average multiplicity as the excitation energy increases above 1.0 MeV/u.

  2. The pasta phase within density dependent hadronic models

    CERN Document Server

    Avancini, S S; Marinelli, J R; Peres-Menezes, D; Watanabe de Moraes, M M; Providência, C; Santos, A M

    2008-01-01

    In the present paper we investigate the onset of the pasta phase with different parametrisations of the density dependent hadronic model and compare the results with one of the usual parametrisation of the non-linear Walecka model. The influence of the scalar-isovector virtual delta meson is shown. At zero temperature two different methods are used, one based on coexistent phases and the other on the Thomas-Fermi approximation. At finite temperature only the coexistence phases method is used. npe matter with fixed proton fractions and in beta-equilibrium are studied. We compare our results with restrictions imposed on the the values of the density and pressure at the inner edge of the crust, obtained from observations of the Vela pulsar and recent isospin diffusion data from heavy-ion reactions, and with predictions from spinodal calculations.

  3. Micro-macro modelling of stress-dependent anisotropic magnetoresistance

    Energy Technology Data Exchange (ETDEWEB)

    Bartok, A; Daniel, L; Razek, A, E-mail: andras.bartok@lgep.supelec.fr, E-mail: laurent.daniel@u-psud.fr [Laboratoire de Genie Electrique de Paris (LGEP), CNRS (UMR 8507)-SUPELEC-UPMC Paris 6-Univ Paris-Sud 11, 11 rue Joliot-Curie, Plateau de Moulon, 91192 Gif-sur-Yvette (France)

    2011-04-06

    Anisotropic magnetoresistance (AMR) is the basic phenomenon of a spread class of sensors. AMR effect has a strong mechanical stress dependence. Micromagnetic simulations are often used for modelling the magnetoresistance of ferromagnetic materials, but these approaches do not allow us to investigate macroscopic effects (for example behaviour of a polycrystal under stress) due to the high number of interactions and degrees of freedom. On the other hand macroscopic phenomenological approaches fail in describing the main role of microstructure on the effective behaviour. In this work a micro-macro model is proposed to describe the effect of stress on the AMR in ferromagnetic polycrystals. Results are discussed and compared with experimental data from the literature.

  4. Recovery of time-dependent volatility in option pricing model

    Science.gov (United States)

    Deng, Zui-Cha; Hon, Y. C.; Isakov, V.

    2016-11-01

    In this paper we investigate an inverse problem of determining the time-dependent volatility from observed market prices of options with different strikes. Due to the non linearity and sparsity of observations, an analytical solution to the problem is generally not available. Numerical approximation is also difficult to obtain using most of the existing numerical algorithms. Based on our recent theoretical results, we apply the linearisation technique to convert the problem into an inverse source problem from which recovery of the unknown volatility function can be achieved. Two kinds of strategies, namely, the integral equation method and the Landweber iterations, are adopted to obtain the stable numerical solution to the inverse problem. Both theoretical analysis and numerical examples confirm that the proposed approaches are effective. The work described in this paper was partially supported by a grant from the Research Grant Council of the Hong Kong Special Administrative Region (Project No. CityU 101112) and grants from the NNSF of China (Nos. 11261029, 11461039), and NSF grants DMS 10-08902 and 15-14886 and by Emylou Keith and Betty Dutcher Distinguished Professorship at the Wichita State University (USA).

  5. A reliable facility location design model with site-dependent disruption in the imperfect information context.

    Science.gov (United States)

    Yun, Lifen; Wang, Xifu; Fan, Hongqiang; Li, Xiaopeng

    2017-01-01

    This paper proposes a reliable facility location design model under imperfect information with site-dependent disruptions; i.e., each facility is subject to a unique disruption probability that varies across the space. In the imperfect information contexts, customers adopt a realistic "trial-and-error" strategy to visit facilities; i.e., they visit a number of pre-assigned facilities sequentially until they arrive at the first operational facility or give up looking for the service. This proposed model aims to balance initial facility investment and expected long-term operational cost by finding the optimal facility locations. A nonlinear integer programming model is proposed to describe this problem. We apply a linearization technique to reduce the difficulty of solving the proposed model. A number of problem instances are studied to illustrate the performance of the proposed model. The results indicate that our proposed model can reveal a number of interesting insights into the facility location design with site-dependent disruptions, including the benefit of backup facilities and system robustness against variation of the loss-of-service penalty.

  6. Mobility dependent recombination models for organic solar cells

    Science.gov (United States)

    Wagenpfahl, Alexander

    2017-09-01

    Modern solar cell technologies are driven by the effort to enhance power conversion efficiencies. A main mechanism limiting power conversion efficiencies is charge carrier recombination which is a direct function of the encounter probability of both recombination partners. In inorganic solar cells with rather high charge carrier mobilities, charge carrier recombination is often dominated by energetic states which subsequently trap both recombination partners for recombination. Free charge carriers move fast enough for Coulomb attraction to be irrelevant for the encounter probability. Thus, charge carrier recombination is independent of charge carrier mobilities. In organic semiconductors charge carrier mobilities are much lower. Therefore, electrons and holes have more time react to mutual Coulomb-forces. This results in the strong charge carrier mobility dependencies of the observed charge carrier recombination rates. In 1903 Paul Langevin published a fundamental model to describe the recombination of ions in gas-phase or aqueous solutions, known today as Langevin recombination. During the last decades this model was used to interpret and model recombination in organic semiconductors. However, certain experiments especially with bulk-heterojunction solar cells reveal much lower recombination rates than predicted by Langevin. In search of an explanation, many material and device properties such as morphology and energetic properties have been examined in order to extend the validity of the Langevin model. A key argument for most of these extended models is, that electron and hole must find each other at a mutual spatial location. This encounter may be limited for instance by trapping of charges in trap states, by selective electrodes separating electrons and holes, or simply by the morphology of the involved semiconductors, making it impossible for electrons and holes to recombine at high rates. In this review, we discuss the development of mobility limited

  7. Comparison of strategies for model predictive control for home heating in future energy systems

    DEFF Research Database (Denmark)

    Vogler-Finck, Pierre Jacques Camille; Popovski, Petar; Wisniewski, Rafal

    2017-01-01

    Model predictive control is seen as one of the key future enabler in increasing energy efficiency in buildings. This paper presents a comparison of the performance of the control for different formulations of the objective function. This comparison is made in a simulation study on a single building...... using historical weather and power system data from Denmark. Trade-offs between energy consumption, comfort and incurred CO2 emissions depending on the chosen objective function are quantified, highlighting the need to carefully select the strategy used in future design and implementation, rather than...

  8. Two-strain Tuberculosis Transmission Model under Three Control Strategies

    Science.gov (United States)

    Rayhan, S. N.; Bakhtiar, T.; Jaharuddin

    2017-03-01

    In 1997, Castillo-Chavez and Feng developed a two-strain tuberculosis (TB) model, which is typical TB and resistant TB. Castillo-Chavez and Feng’s model was then subsequently developed by Jung et al. (2002) by adding two control variables. In this work, Jung et al.’s model was modified by introducing a new control variable so that there are three controls, namely chemoprophylaxis and two treatment strategies, with the application of three different scenarios related to the objective functional form and control application. Pontryagin maximum principle was applied to derive the differential equations system as a condition that must be satisfied by the optimal control variables. Furthermore, the fourth-order Runge-Kutta method was exploited to determine the numerical solution of the optimal control problem. In this numerical solution, it is shown that the controls treated on TB transmission model provide a good effect because latent and infected individuals are decreasing, and the number of individuals that is treated effectively is increasing.

  9. Modeling budgetary strategies in health policy, East and West.

    Science.gov (United States)

    Welsh, W A

    1983-01-01

    This essay has sought to develop a rationale for new approach to the formal modeling of intergovernmental budgetary relations. The focus has been on health care budgeting, and on evidence from centrally-planned systems in Eastern Europe. But it has been argued that the modeling strategy advanced here will have applicability across policy areas, and across types of political and economic systems. The description of developments in human service provision emphasized the growing complexity of policy activity along both vertical and horizontal dimensions, and the accompanying increase in competition and in strategic thinking as central elements of policy activity generally, and of intergovernmental budgetary relations specifically. It has been argued that these developments are observable not only in Western pluralist systems--where the adumbration of evidence makes it increasingly difficult to take exception to these generalizations--but also in highly-structured systems such as the communist-governed systems of Eastern Europe. The possibility that certain elements of human service policy activity are becoming increasingly similar across ideologically and structurally different system types has numerous significant implications worth exploring. The next step will be the testing of the full set of linear systems theory models with data from Eastern Europe. If these tests are encouraging, important methodological implications for the modeling of budgetary activity would seem to follow.

  10. New Hepatitis C Virus Drug Discovery Strategies and Model Systems

    Science.gov (United States)

    Hussain, Snawar; Barretto, Naina; Uprichard, Susan L

    2013-01-01

    Introduction Hepatitis C virus is a major cause of liver disease worldwide and the leading indication for liver transplantation in the United States. Current treatment options are expensive, not effective in all patients and are associated with serious side effects. While pre-clinical anti-HCV drug screening is still hampered by the lack of readily infectable small animal models, the development of cell culture HCV experimental model systems has driven a promising new wave of HCV antiviral drug discovery. Areas covered This review contains a concise overview of current HCV treatment options and limitations with a subsequent in-depth focus on the available experimental models and novel strategies that have and continue to enable important advances in HCV drug development. Expert opinion With a large cohort of chronically HCV infected patients progressively developing liver disease that puts them at risk for hepatocellular carcinoma and hepatic decompensation, there is an urgent need to develop effective therapeutics that are well-tolerated and effective in all patients and against all HCV genotypes. Significant advances in HCV experimental model development have expedited drug discovery; however, additional progress is needed. Importantly, the current trends and momentum in the field suggests that we will continue to overcome critical experimental challenges to reach this end goal. PMID:22861052

  11. Identifying of risks in pricing using a regression model of demand on price dependence

    Directory of Open Access Journals (Sweden)

    O.I. Yashkina

    2016-09-01

    risk of increasing or lowering prices. For each of the reference regression models of dependence of demand on price when using the research methods of the extremum optimal prices were obtained, through which businesses can count on the maximum price. Conclusions and direction of further researches. The results of the study provide the approach based on the existence of a regression of price elasticity of demand for the price of high-tech products which can be used as a tool for the assessment and prevention of risks in the pricing at all stages of the product life cycle. Methods of assessing risks of pricing and profit optimization for the regression demand on price allows companies with different pricing strategies, such as the strategy of «skimming» or a strategy to capture the market to assess the risks of pricing and optimal price at which it will receive the maximum profit. In order to confirm the findings of Methods of assessing risks of pricing and profit optimization for the regression of demand on price approbation of the theoretical results to actual data is required. The main task of approbation should be consider as getting the functions of price elasticity of demand, evaluating pricing risks and determining the optimal selling prices for different groups of new high-tech products.

  12. Soil mapping and processes models to support climate change mitigation and adaptation strategies: a review

    Science.gov (United States)

    Muñoz-Rojas, Miriam; Pereira, Paulo; Brevik, Eric; Cerda, Artemi; Jordan, Antonio

    2017-04-01

    As agreed in Paris in December 2015, global average temperature is to be limited to "well below 2 °C above pre-industrial levels" and efforts will be made to "limit the temperature increase to 1.5 °C above pre-industrial levels. Thus, reducing greenhouse gas emissions (GHG) in all sectors becomes critical and appropriate sustainable land management practices need to be taken (Pereira et al., 2017). Mitigation strategies focus on reducing the rate and magnitude of climate change by reducing its causes. Complementary to mitigation, adaptation strategies aim to minimise impacts and maximize the benefits of new opportunities. The adoption of both practices will require developing system models to integrate and extrapolate anticipated climate changes such as global climate models (GCMs) and regional climate models (RCMs). Furthermore, integrating climate models driven by socio-economic scenarios in soil process models has allowed the investigation of potential changes and threats in soil characteristics and functions in future climate scenarios. One of the options with largest potential for climate change mitigation is sequestering carbon in soils. Therefore, the development of new methods and the use of existing tools for soil carbon monitoring and accounting have therefore become critical in a global change context. For example, soil C maps can help identify potential areas where management practices that promote C sequestration will be productive and guide the formulation of policies for climate change mitigation and adaptation strategies. Despite extensive efforts to compile soil information and map soil C, many uncertainties remain in the determination of soil C stocks, and the reliability of these estimates depends upon the quality and resolution of the spatial datasets used for its calculation. Thus, better estimates of soil C pools and dynamics are needed to advance understanding of the C balance and the potential of soils for climate change mitigation. Here

  13. Incorporating Context Dependency of Species Interactions in Species Distribution Models.

    Science.gov (United States)

    Lany, Nina K; Zarnetske, Phoebe L; Gouhier, Tarik C; Menge, Bruce A

    2017-07-01

    Species distribution models typically use correlative approaches that characterize the species-environment relationship using occurrence or abundance data for a single species. However, species distributions are determined by both abiotic conditions and biotic interactions with other species in the community. Therefore, climate change is expected to impact species through direct effects on their physiology and indirect effects propagated through their resources, predators, competitors, or mutualists. Furthermore, the sign and strength of species interactions can change according to abiotic conditions, resulting in context-dependent species interactions that may change across space or with climate change. Here, we incorporated the context dependency of species interactions into a dynamic species distribution model. We developed a multi-species model that uses a time-series of observational survey data to evaluate how abiotic conditions and species interactions affect the dynamics of three rocky intertidal species. The model further distinguishes between the direct effects of abiotic conditions on abundance and the indirect effects propagated through interactions with other species. We apply the model to keystone predation by the sea star Pisaster ochraceus on the mussel Mytilus californianus and the barnacle Balanus glandula in the rocky intertidal zone of the Pacific coast, USA. Our method indicated that biotic interactions between P. ochraceus and B. glandula affected B. glandula dynamics across >1000 km of coastline. Consistent with patterns from keystone predation, the growth rate of B. glandula varied according to the abundance of P. ochraceus in the previous year. The data and the model did not indicate that the strength of keystone predation by P. ochraceus varied with a mean annual upwelling index. Balanus glandula cover increased following years with high phytoplankton abundance measured as mean annual chlorophyll-a. M. californianus exhibited the same

  14. Modeling posture-dependent leg actuation in sagittal plane locomotion

    Energy Technology Data Exchange (ETDEWEB)

    Schmitt, J [Department of Mechanical Engineering, Oregon State University, Corvallis, OR 97331 (United States); Clark, J, E-mail: schmitjo@engr.orst.ed [Department of Mechanical Engineering, Florida State University, Tallahassee, FL 32310 (United States)

    2009-12-15

    The spring loaded inverted pendulum template has been shown to accurately model the steady locomotion dynamics of a variety of running animals, and has served as the inspiration for an entire class of dynamic running robots. While the template models the leg dynamics by an energy-conserving spring, insects and animals have structures that dissipate, store and produce energy during a stance phase. Recent investigations into the spring-like properties of limbs, as well as animal response to drop-step perturbations, suggest that animals use their legs to manage energy storage and dissipation, and that this management is important for gait stability. In this paper, we extend our previous analysis of control of the spring loaded inverted pendulum template via changes in the leg touch-down angle to include energy variations during the stance phase. Energy variations are incorporated through leg actuation that varies the force-free leg length during the stance phase, yet maintains qualitatively correct force and velocity profiles. In contrast to the partially asymptotically stable gaits identified in previous analyses, incorporating energy and leg angle variations in this manner produces complete asymptotic stability. Drop-step perturbation simulations reveal that the control strategy is rather robust, with gaits recovering from drops of up to 30% of the nominal hip height.

  15. Tilted dipole model for bias-dependent photoluminescence pattern

    Energy Technology Data Exchange (ETDEWEB)

    Fujieda, Ichiro, E-mail: fujieda@se.ritsumei.ac.jp; Suzuki, Daisuke; Masuda, Taishi [Department of Electrical and Electronic Engineering, Ritsumeikan University, Kusatsu 525-8577 (Japan)

    2014-12-14

    In a guest-host system containing elongated dyes and a nematic liquid crystal, both molecules are aligned to each other. An external bias tilts these molecules and the radiation pattern of the system is altered. A model is proposed to describe this bias-dependent photoluminescence patterns. It divides the liquid crystal/dye layer into sub-layers that contain electric dipoles with specific tilt angles. Each sub-layer emits linearly polarized light. Its radiation pattern is toroidal and is determined by the tilt angle. Its intensity is assumed to be proportional to the power of excitation light absorbed by the sub-layer. This is calculated by the Lambert-Beer's Law. The absorption coefficient is assumed to be proportional to the cross-section of the tilted dipole moment, in analogy to the ellipsoid of refractive index, to evaluate the cross-section for each polarized component of the excitation light. Contributions from all the sub-layers are added to give a final expression for the radiation pattern. Self-absorption is neglected. The model is simplified by reducing the number of sub-layers. Analytical expressions are derived for a simple case that consists of a single layer with tilted dipoles sandwiched by two layers with horizontally-aligned dipoles. All the parameters except for the tilt angle can be determined by measuring transmittance of the excitation light. The model roughly reproduces the bias-dependent photoluminescence patterns of a cell containing 0.5 wt. % coumarin 6. It breaks down at large emission angles. Measured spectral changes suggest that the discrepancy is due to self-absorption and re-emission.

  16. Hybrid Model of the Context Dependent Vestibulo-Ocular Reflex: Implications for Vergence-Version Interactions

    Directory of Open Access Journals (Sweden)

    Mina eRanjbaran

    2015-02-01

    Full Text Available The vestibulo-ocular reflex (VOR is an involuntary eye movement evoked by head movements. It is also influenced by viewing distance. This paper presents a hybrid nonlinear bilateral model for the horizontal angular vestibulo-ocular reflex (AVOR in the dark. The model is based on known interconnections between saccadic burst circuits in the brainstem and ocular premotor areas in the vestibular nuclei during fast and slow phase intervals of nystagmus. We implemented a viable switching strategy for the timing of nystagmus events to allow emulation of real nystagmus data. The performance of the hybrid model is evaluated with simulations, and results are consistent with experimental observations. The hybrid model replicates realistic AVOR nystagmus patterns during sinusoidal or step head rotations in the dark and during interactions with vergence, e.g. fixation distance. By simply assigning proper nonlinear neural computations at the premotor level, the model replicates all reported experimental observations. This work sheds light on potential underlying neural mechanisms driving the context dependent AVOR and explains contradictory results in the literature. Moreover, context-dependent behaviors in more complex motor systems could also rely on local nonlinear neural computations.

  17. Hybrid model of the context dependent vestibulo-ocular reflex: implications for vergence-version interactions.

    Science.gov (United States)

    Ranjbaran, Mina; Galiana, Henrietta L

    2015-01-01

    The vestibulo-ocular reflex (VOR) is an involuntary eye movement evoked by head movements. It is also influenced by viewing distance. This paper presents a hybrid nonlinear bilateral model for the horizontal angular vestibulo-ocular reflex (AVOR) in the dark. The model is based on known interconnections between saccadic burst circuits in the brainstem and ocular premotor areas in the vestibular nuclei during fast and slow phase intervals of nystagmus. We implemented a viable switching strategy for the timing of nystagmus events to allow emulation of real nystagmus data. The performance of the hybrid model is evaluated with simulations, and results are consistent with experimental observations. The hybrid model replicates realistic AVOR nystagmus patterns during sinusoidal or step head rotations in the dark and during interactions with vergence, e.g., fixation distance. By simply assigning proper nonlinear neural computations at the premotor level, the model replicates all reported experimental observations. This work sheds light on potential underlying neural mechanisms driving the context dependent AVOR and explains contradictory results in the literature. Moreover, context-dependent behaviors in more complex motor systems could also rely on local nonlinear neural computations.

  18. Modeling and Correcting the Time-Dependent ACS PSF

    Science.gov (United States)

    Rhodes, Jason; Massey, Richard; Albert, Justin; Taylor, James E.; Koekemoer, Anton M.; Leauthaud, Alexie

    2006-01-01

    The ability to accurately measure the shapes of faint objects in images taken with the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope (HST) depends upon detailed knowledge of the Point Spread Function (PSF). We show that thermal fluctuations cause the PSF of the ACS Wide Field Camera (WFC) to vary over time. We describe a modified version of the TinyTim PSF modeling software to create artificial grids of stars across the ACS field of view at a range of telescope focus values. These models closely resemble the stars in real ACS images. Using 10 bright stars in a real image, we have been able to measure HST s apparent focus at the time of the exposure. TinyTim can then be used to model the PSF at any position on the ACS field of view. This obviates the need for images of dense stellar fields at different focus values, or interpolation between the few observed stars. We show that residual differences between our TinyTim models and real data are likely due to the effects of Charge Transfer Efficiency (CTE) degradation. Furthermore, we discuss stochastic noise that is added to the shape of point sources when distortion is removed, and we present MultiDrizzle parameters that are optimal for weak lensing science. Specifically, we find that reducing the MultiDrizzle output pixel scale and choosing a Gaussian kernel significantly stabilizes the resulting PSF after image combination, while still eliminating cosmic rays/bad pixels, and correcting the large geometric distortion in the ACS. We discuss future plans, which include more detailed study of the effects of CTE degradation on object shapes and releasing our TinyTim models to the astronomical community.

  19. Multimodal Sensing Strategy Using pH Dependent Fluorescence Switchable System

    Science.gov (United States)

    Muthurasu, A.; Ganesh, V.

    2016-12-01

    Biomolecules assisted preparation of fluorescent gold nanoparticles (FL–Au NPs) has been reported in this work using glucose oxidase enzyme as both reducing and stabilizing agent and demonstrated their application through multimodal sensing strategy for selective detection of cysteine (Cys). Three different methods namely fluorescence turn OFF–ON strategy, naked eye detection and electrochemical methods are used for Cys detection by employing FL–Au NPs as a common probe. In case of fluorescence turn–OFF method a strong interaction between Au NPs and thiol results in quenching of fluorescence due to replacement of glucose oxidase by Cys at neutral pH. Second mode is based on fluorescence switch–ON strategy where initial fluorescence is significantly quenched by either excess acid or base and further addition of Cys results in appearance of rosy-red and green fluorescence respectively. Visual colour change and fluorescence emission arises due to etching of Au atoms on the surface by thiol leading to formation of Au nanoclusters. Finally, electrochemical sensing of Cys is also carried out using cyclic voltammetry in 0.1 M PBS solution. These findings provide a suitable platform for Cys detection over a wide range of pH and concentration levels and hence the sensitivity can also be tuned accordingly.

  20. Time-dependent models of dense PDRs with complex molecules

    CERN Document Server

    Morata, O

    2008-01-01

    We present a study of the chemistry of a dense photon-dominated region (PDR) using a time-dependent chemical model. Our major interest is to study the spatial distribution of complex molecules such as hydrocarbons and cyanopolyynes in the cool dense material bordering regions where star formation has taken place. Our standard model uses a homogeneous cloud of density 2x10e4 cm-3 and temperature T=40 K, which is irradiated by a far-ultraviolet radiation field of intermediate intensity, given by X=100. We find that over a range of times unsaturated hydrocarbons (e.g., C2H, C4H, C3H2) have relatively high fractional abundances in the more external layers of the PDR, whereas their abundances in the innermost layers are several orders of magnitudes lower. On the other hand, molecules that are typical of late-time chemistry are usually more abundant in the inner parts of the PDR. We also present results for models with different density, temperature, intensity of the radiation field and initial fractional abundance...

  1. A new model to predict weak-lensing peak counts II. Parameter constraint strategies

    CERN Document Server

    Lin, Chieh-An

    2015-01-01

    Peak counts have been shown to be an excellent tool to extract the non-Gaussian part of the weak lensing signal. Recently, we developped a fast stochastic forward model to predict weak-lensing peak counts. Our model is able to reconstruct the underlying distribution of observables for analyses. In this work, we explore and compare various strategies for constraining parameter using our model, focusing on the matter density $\\Omega_\\mathrm{m}$ and the density fluctuation amplitude $\\sigma_8$. First, we examine the impact from the cosmological dependency of covariances (CDC). Second, we perform the analysis with the copula likelihood, a technique which makes a weaker assumption compared to the Gaussian likelihood. Third, direct, non-analytic parameter estimations are applied using the full information of the distribution. Fourth, we obtain constraints with approximate Bayesian computation (ABC), an efficient, robust, and likelihood-free algorithm based on accept-reject sampling. We find that neglecting the CDC ...

  2. Structural models of vanadate-dependent haloperoxidases and their reactivity

    Indian Academy of Sciences (India)

    Mannar R Maurya

    2006-11-01

    Vanadium(V) complexes with hydrazone-based ONO and ONN donor ligands that partly model active-site structures of vanadate-dependent haloperoxidases have been reported. On reaction with [VO(acac)2] (Hacac = acetylacetone) under nitrogen, these ligands generally provide oxovanadium(IV) complexes [VO(ONO)X] (X = solvent or nothing) and [VO(acac)(ONN)], respectively. Under aerobic conditions, these oxovanadium(IV) species undergo oxidation to give oxovanadium(V), dioxovanadium (V) or -oxobis{oxovanadium(V)} species depending upon the nature of the ligand. Anionic and neutral dioxovanadium(V) complexes slowly deoxygenate in methanol to give monooxo complexes [VO(OMe)(MeOH)(ONO)]. The anionic complexes [VO2(ONO)]- can also be converted in situ on acidification to oxohydroxo complexes [VO(OH)(HONO)]+ and to peroxo complexes [VO(O2)(ONO)]-, and thus to the species assumed to be intermediates in the haloperoxidases activity of the enzymes. In the presence of catechol (H2cat) and benzohydroxamic acid (H2bha), oxovanadium (IV) complexes, [VO (acac)(ONN)] gave mixed-chelate oxovanadium(V) complexes [VO(cat)(ONN)] and [VO(bha)(ONN)] respectively. These complexes are not very stable in solution and slowly convert to the corresponding dioxo species [VO2(ONN)] as observed by 51V NMR and electronic absorption spectroscopic studies.

  3. Increased opioid dependence in a mouse model of panic disorder

    Directory of Open Access Journals (Sweden)

    Xavier Gallego

    2010-02-01

    Full Text Available Panic disorder is a highly prevalent neuropsychiatric disorder that shows co-occurrence with substance abuse. Here, we demonstrate that TrkC, the high affinity receptor for neurotrophin-3, is a key molecule involved in panic disorder and opiate dependence, using a transgenic mouse model (TgNTRK3. Constitutive TrkC overexpression in TgNTRK3 mice dramatically alters spontaneous firing rates of locus coeruleus neurons and the response of the noradrenergic system to chronic opiate exposure, possibly related to the altered regulation of neurotrophic peptides observed. Notably, TgNTRK3 locus coeruleus neurons showed an increased firing rate in saline-treated conditions and profound abnormalities in their response to met5-enkephalin. Behaviorally, chronic morphine administration induced a significantly increased withdrawal syndrome in TgNTRK3 mice. In conclusion, we show here that the NT-3/TrkC system is an important regulator of neuronal firing in locus coeruleus and could contribute to the adaptations of the noradrenergic system in response to chronic opiate exposure. Moreover, our results indicate that TrkC is involved in the molecular and cellular changes in noradrenergic neurons underlying both panic attacks and opiate dependence and support a functional endogenous opioid deficit in panic disorder patients.

  4. Iron chelation therapy in transfusion-dependent thalassemia patients: current strategies and future directions

    Directory of Open Access Journals (Sweden)

    Saliba AN

    2015-06-01

    Full Text Available Antoine N Saliba, Afif R Harb, Ali T Taher Department of Internal Medicine, Division of Hematology/Oncology, American University of Beirut, Beirut, Lebanon Abstract: Transfusional iron overload is a major target in the care of patients with transfusion-dependent thalassemia (TDT and other refractory anemias. Iron accumulates in the liver, heart, and endocrine organs leading to a wide array of complications. In this review, we summarize the characteristics of the approved iron chelators, deferoxamine, deferiprone, and deferasirox, and the evidence behind the use of each, as monotherapy or as part of combination therapy. We also review the different guidelines on iron chelation in TDT. This review also discusses future prospects and directions in the treatment of transfusional iron overload in TDT whether through innovation in chelation or other therapies, such as novel agents that improve transfusion dependence. Keywords: thalassemia, transfusion-dependent thalassemia, iron overload, iron chelation therapy, transfusion

  5. Prandtl-Ishlinskii hysteresis models for complex time dependent hysteresis nonlinearities

    OpenAIRE

    Al Janaideh, M.; Krejčí, P

    2012-01-01

    We introduce a new class of time dependent hysteresis models by combining the time dependent Prandtl–Ishlinskii model with functional nonlinearities. This combination improves the capability of the time dependent Prandtl–Ishlinskii model to characterize a class of complex time dependent hysteresis nonlinearities in smart actuators. The analytical inversion for the proposed time dependent hysteresis model is also presented in order to extend the inversion algorithm of the inverse time dependen...

  6. Determinations of from inclusive semileptonic decays with reduced model dependence.

    Science.gov (United States)

    Aubert, B; Barate, R; Boutigny, D; Couderc, F; Karyotakis, Y; Lees, J P; Poireau, V; Tisserand, V; Zghiche, A; Grauges, E; Palano, A; Pappagallo, M; Pompili, A; Chen, J C; Qi, N D; Rong, G; Wang, P; Zhu, Y S; Eigen, G; Ofte, I; Stugu, B; Abrams, G S; Battaglia, M; Best, D S; Brown, D N; Button-Shafer, J; Cahn, R N; Charles, E; Day, C T; Gill, M S; Gritsan, A V; Groysman, Y; Jacobsen, R G; Kadel, R W; Kadyk, J A; Kerth, L T; Kolomensky, Yu G; Kukartsev, G; Lynch, G; Mir, L M; Oddone, P J; Orimoto, T J; Pripstein, M; Roe, N A; Ronan, M T; Wenzel, W A; Barrett, M; Ford, K E; Harrison, T J; Hart, A J; Hawkes, C M; Morgan, S E; Watson, A T; Fritsch, M; Goetzen, K; Held, T; Koch, H; Lewandowski, B; Pelizaeus, M; Peters, K; Schroeder, T; Steinke, M; Boyd, J T; Burke, J P; Cottingham, W N; Walker, D; Cuhadar-Donszelmann, T; Fulsom, B G; Hearty, C; Knecht, N S; Mattison, T S; McKenna, J A; Khan, A; Kyberd, P; Saleem, M; Teodorescu, L; Blinov, A E; Blinov, V E; Bukin, A D; Druzhinin, V P; Golubev, V B; Kravchenko, E A; Onuchin, A P; Serednyakov, S I; Skovpen, Yu I; Solodov, E P; Yushkov, A N; Bondioli, M; Bruinsma, M; Chao, M; Curry, S; Eschrich, I; Kirkby, D; Lankford, A J; Lund, P; Mandelkern, M; Mommsen, R K; Roethel, W; Stoker, D P; Abachi, S; Buchanan, C; Foulkes, S D; Gary, J W; Long, O; Shen, B C; Wang, K; Zhang, L; del Re, D; Hadavand, H K; Hill, E J; MacFarlane, D B; Paar, H P; Rahatlou, S; Sharma, V; Berryhill, J W; Campagnari, C; Cunha, A; Dahmes, B; Hong, T M; Mazur, M A; Richman, J D; Beck, T W; Eisner, A M; Flacco, C J; Heusch, C A; Kroseberg, J; Lockman, W S; Nesom, G; Schalk, T; Schumm, B A; Seiden, A; Spradlin, P; Williams, D C; Wilson, M G; Albert, J; Chen, E; Dubois-Felsmann, G P; Dvoretskii, A; Hitlin, D G; Minamora, J S; Narsky, I; Piatenko, T; Porter, F C; Ryd, A; Samuel, A; Andreassen, R; Mancinelli, G; Meadows, B T; Sokoloff, M D; Blanc, F; Bloom, P C; Chen, S; Ford, W T; Hirschauer, J F; Kreisel, A; Nauenberg, U; Olivas, A; Ruddick, W O; Smith, J G; Ulmer, K A; Wagner, S R; Zhang, J; Chen, A; Eckhart, E A; Soffer, A; Toki, W H; Wilson, R J; Winklmeier, F; Zeng, Q; Altenburg, D D; Feltresi, E; Hauke, A; Spaan, B; Brandt, T; Dickopp, M; Klose, V; Lacker, H M; Nogowski, R; Otto, S; Petzold, A; Schubert, J; Schubert, K R; Schwierz, R; Sundermann, J E; Bernard, D; Bonneaud, G R; Grenier, P; Latour, E; Schrenk, S; Thiebaux, Ch; Vasileiadis, G; Verderi, M; Bard, D J; Clark, P J; Gradl, W; Muheim, F; Playfer, S; Xie, Y; Andreotti, M; Bettoni, D; Bozzi, C; Calabrese, R; Cibinetto, G; Luppi, E; Negrini, M; Piemontese, L; Anulli, F; Baldini-Ferroli, R; Calcaterra, A; de Sangro, R; Finocchiaro, G; Patteri, P; Peruzzi, I M; Piccolo, M; Zallo, A; Buzzo, A; Capra, R; Contri, R; Lo Vetere, M; Macri, M M; Monge, M R; Passaggio, S; Patrignani, C; Robutti, E; Santroni, A; Tosi, S; Brandenburg, G; Chaisanguanthum, K S; Morii, M; Wu, J; Dubitzky, R S; Langenegger, U; Marks, J; Schenk, S; Uwer, U; Bhimji, W; Bowerman, D A; Dauncey, P D; Egede, U; Flack, R L; Gaillard, J R; Nash, J A; Nikolich, M B; Vazquez, W Panduro; Chai, X; Charles, M J; Mader, W F; Mallik, U; Ziegler, V; Cochran, J; Crawley, H B; Dong, L; Eyges, V; Meyer, W T; Prell, S; Rosenberg, E I; Rubin, A E; Yi, J I; Schott, G; Arnaud, N; Davier, M; Giroux, X; Grosdidier, G; Höcker, A; Diberder, F Le; Lepeltier, V; Lutz, A M; Oyanguren, A; Petersen, T C; Pruvot, S; Rodier, S; Roudeau, P; Schune, M H; Stocchi, A; Wang, W F; Wormser, G; Cheng, C H; Lange, D J; Wright, D M; Bevan, A J; Chavez, C A; Forster, I J; Fry, J R; Gabathuler, E; Gamet, R; George, K A; Hutchcroft, D E; Parry, R J; Payne, D J; Schofield, K C; Touramanis, C; Di Lodovico, F; Menges, W; Sacco, R; Brown, C L; Cowan, G; Flaecher, H U; Green, M G; Hopkins, D A; Jackson, P S; McMahon, T R; Ricciardi, S; Salvatore, F; Brown, D N; Davis, C L; Allison, J; Barlow, N R; Barlow, R J; Chia, Y M; Edgar, C L; Kelly, M P; Lafferty, G D; Naisbit, M T; Williams, J C; Chen, C; Hulsbergen, W D; Jawahery, A; Kovalskyi, D; Lae, C K; Roberts, D A; Simi, G; Blaylock, G; Dallapiccola, C; Hertzbach, S S; Kofler, R; Li, X; Moore, T B; Saremi, S; Staengle, H; Willocq, S Y; Cowan, R; Koeneke, K; Sciolla, G; Sekula, S J; Spitznagel, M; Taylor, F; Yamamoto, R K; Kim, H; Patel, P M; Robertson, S H; Lazzaro, A; Lombardo, V; Palombo, F F; Bauer, J M; Cremaldi, L; Eschenburg, V; Godang, R; Kroeger, R; Reidy, J; Sanders, D A; Summers, D J; Zhao, H W; Brunet, S; Côté, D; Taras, P; Viaud, F B; Nicholson, H; Cavallo, N; De Nardo, G; Fabozzi, F; Gatto, C; Lista, L; Monorchio, D; Paolucci, P; Piccolo, D; Sciacca, C; Baak, M; Bulten, H; Raven, G; Snoek, H L; Wilden, L; Jessop, C P; LoSecco, J M; Allmendinger, T; Benelli, G; Gan, K K; Honscheid, K; Hufnagel, D; Jackson, P D; Kagan, H; Kass, R; Pulliam, T; Rahimi, A M; Ter-Antonyan, R; Wong, Q K; Blount, N L; Brau, J; Frey, R; Igonkina, O; Lu, M; Potter, C T; Rahmat, R; Sinev, N B; Strom, D; Strube, J; Torrence, E; Galeazzi, F; Margoni, M; Morandin, M; Posocco, M; Rotondo, M; Simonetto, F; Stroili, R; Voci, C; Benayoun, M; Chauveau, J; David, P; Del Buono, L; de la Vaissière, Ch; Hamon, O; Hartfiel, B L; John, M J J; Leruste, Ph; Malclès, J; Ocariz, J; Roos, L; Therin, G; Behera, P K; Gladney, L; Panetta, J; Biasini, M; Covarelli, R; Pacetti, S; Pioppi, M; Angelini, C; Batignani, G; Bettarini, S; Bucci, F; Calderini, G; Carpinelli, M; Cenci, R; Forti, F; Giorgi, M A; Lusiani, A; Marchiori, G; Morganti, M; Neri, N; Paoloni, E; Rama, M; Rizzo, G; Walsh, J; Haire, M; Judd, D; Wagoner, D E; Biesiada, J; Danielson, N; Elmer, P; Lau, Y P; Lu, C; Olsen, J; Smith, A J S; Telnov, A V; Bellini, F; Cavoto, G; D'Orazio, A; Di Marco, E; Faccini, R; Ferrarotto, F; Ferroni, F; Gaspero, M; Gioi, L Li; Mazzoni, M A; Morganti, S; Piredda, G; Polci, F; Tehrani, F Safai; Voena, C; Schröder, H; Waldi, R; Adye, T; De Groot, N; Franek, B; Gopal, G P; Olaiya, E O; Wilson, F F; Aleksan, R; Emery, S; Gaidot, A; Ganzhur, S F; Graziani, G; de Monchenault, G Hamel; Kozanecki, W; Legendre, M; Mayer, B; Vasseur, G; Yèche, Ch; Zito, M; Purohit, M V; Weidemann, A W; Wilson, J R; Abe, T; Allen, M T; Aston, D; Bartoldus, R; Berger, N; Boyarski, A M; Buchmueller, O L; Claus, R; Coleman, J P; Convery, M R; Cristinziani, M; Dingfelder, J C; Dong, D; Dorfan, J; Dujmic, D; Dunwoodie, W; Fan, S; Field, R C; Glanzman, T; Gowdy, S J; Hadig, T; Halyo, V; Hast, C; Hryn'ova, T; Innes, W R; Kelsey, M H; Kim, P; Kocian, M L; Leith, D W G S; Libby, J; Luitz, S; Luth, V; Lynch, H L; Marsiske, H; Messner, R; Muller, D R; O'Grady, C P; Ozcan, V E; Perazzo, A; Perl, M; Ratcliff, B N; Roodman, A; Salnikov, A A; Schindler, R H; Schwiening, J; Snyder, A; Stelzer, J; Su, D; Sullivan, M K; Suzuki, K; Swain, S K; Thompson, J M; Va'vra, J; van Bakel, N; Weaver, M; Weinstein, A J R; Wisniewski, W J; Wittgen, M; Wright, D H; Yarritu, A K; Yi, K; Young, C C; Burchat, P R; Edwards, A J; Majewski, S A; Petersen, B A; Roat, C; Ahmed, S; Alam, M S; Bula, R; Ernst, J A; Pan, B; Saeed, M A; Wappler, F R; Zain, S B; Bugg, W; Krishnamurthy, M; Spanier, S M; Eckmann, R; Ritchie, J L; Satpathy, A; Schwitters, R F; Izen, J M; Kitayama, I; Lou, X C; Ye, S; Bianchi, F; Bona, M; Gallo, F; Gamba, D; Bomben, M; Bosisio, L; Cartaro, C; Cossutti, F; Ricca, G Della; Dittongo, S; Grancagnolo, S; Lanceri, L; Vitale, L; Azzolini, V; Martinez-Vidal, F; Panvini, R S; Banerjee, Sw; Bhuyan, B; Brown, C M; Fortin, D; Hamano, K; Kowalewski, R; Nugent, I M; Roney, J M; Sobie, R J; Back, J J; Harrison, P F; Latham, T E; Mohanty, G B; Band, H R; Chen, X; Cheng, B; Dasu, S; Datta, M; Eichenbaum, A M; Flood, K T; Graham, M T; Hollar, J J; Johnson, J R; Kutter, P E; Li, H; Liu, R; Mellado, B; Mihalyi, A; Mohapatra, A K; Pan, Y; Pierini, M; Prepost, R; Tan, P; Wu, S L; Yu, Z; Neal, H

    2006-06-09

    We report two novel determinations of /|Vub/ with reduced model dependence, based on measurements of the mass distribution of the hadronic system in semileptonic B decays. Events are selected by fully reconstructing the decay of one B meson and identifying a charged lepton from the decay of the other B meson from Upsilon(4S)-->BB events. In one approach, we combine the inclusive B-->Xulambdav rate, integrated up to a maximum hadronic mass mXXsgamma photon energy spectrum. We obtain /Vub/=(4.43+/-0.38stat+/-0.25syst+/-0.29theo) x 10-3. In another approach we measure the total B-->Xulambdav rate over the full phase space and find /Vub/=(3.84+/-0.70stat+/-0.30syst+/-0.10theo) x 10-3.

  7. The Dependence of Global Ocean Modeling on Background Diapycnal Mixing

    Directory of Open Access Journals (Sweden)

    Zengan Deng

    2014-01-01

    Full Text Available The Argo-derived background diapycnal mixing (BDM proposed by Deng et al. (in publish is introduced to and applied in Hybrid Coordinate Ocean Model (HYCOM. Sensitive experiments are carried out using HYCOM to detect the responses of ocean surface temperature and Meridional Overturning Circulation (MOC to BDM in a global context. Preliminary results show that utilizing a constant BDM, with the same order of magnitude as the realistic one, may cause significant deviation in temperature and MOC. It is found that the dependence of surface temperature and MOC on BDM is prominent. Surface temperature is decreased with the increase of BDM, because diapycnal mixing can promote the deep cold water return to the upper ocean. Comparing to the control run, more striking MOC changes can be caused by the larger variation in BDM.

  8. Mathematical model of SPOC with a time dependent reactive field

    Energy Technology Data Exchange (ETDEWEB)

    Ohtaki, Masako [Department of Physics, School of Science and Engineering, Waseda University, Okubo, Shinjuku-ku, Tokyo 169-8555 (Japan)

    2006-03-21

    In general the muscle is in one of the two state possible states, relaxation or contraction. These contractions result from relative sliding of myosin and actin in the sarcomere, which is the contraction structure unit of skeletal muscle. The switching between two states is depending on the Ca2{sup +} concentrations. However another state has been detected between these two states. In the third state, that is SPontaneous Oscillatory Contraction (SPOC), sarcomere repeats contraction and extension spontaneously. Muscle fibers are composed of hundreds of sarcomeres in series and one sarcomea also is composed of hundreds of myosin. In microscopic, the force generated by actin and myosin interaction occurs stochastically. SPOC, however, is macroscopically observable and there are regular oscillations. To understand SPOC mechanism, we propose a model for SPOC based on chemical reaction including mechanical process.

  9. Mathematical model of SPOC with a time dependent reactive field

    Science.gov (United States)

    Ohtaki, Masako

    2006-03-01

    In general the muscle is in one of the two state possible states, relaxation or contraction. These contractions result from relative sliding of myosin and actin in the sarcomere, which is the contraction structure unit of skeletal muscle. The switching between two states is depending on the Ca2+ concentrations. However another state has been detected between these two states. In the third state, that is SPontaneous Oscillatory Contraction (SPOC), sarcomere repeats contraction and extension spontaneously. Muscle fibers are composed of hundreds of sarcomeres in series and one sarcomea also is composed of hundreds of myosin. In microscopic, the force generated by actin and myosin interaction occurs stochastically. SPOC, however, is macroscopically observable and there are regular oscillations. To understand SPOC mechanism, we propose a model for SPOC based on chemical reaction including mechanical process.

  10. Designing Mechatronic Products - Achieving Integration by Means of Modelling Dependencies

    DEFF Research Database (Denmark)

    Torry-Smith, Jonas

    The research carried out in this PhD thesis focuses on the integration phenomenon in the design of mechatronic products. It contributes to the understanding of the phenomenon and to conceptual modelling of mechatronic products. These products are perceived to have emerged as a consequence...... to be aware of when designing mechatronic products. The literature study shows that such a classification has not been attempted before. Without a classification to provide a basis for a structured search it is left to chance for the development team to discover potentially critical dependencies in due time....... A ‘Mechatronic Integration Concept’ is proposed aiming at operationalizing the use of the classification. The purpose is to facilitate discussions between engineers from different disciplines on matters that are important to clarify between the designers working on contributing with solutions to the product...

  11. Phase transition with an isospin dependent lattice gas model

    Energy Technology Data Exchange (ETDEWEB)

    Gulminelli, F. [Caen Univ., 14 (France). Lab. de Physique Corpusculaire; Chomaz, Ph. [Grand Accelerateur National d`Ions Lourds (GANIL), 14 - Caen (France)

    1998-10-01

    The nuclear liquid-gas phase transition is studied within an isospin dependent Lattice Gas Model in the canonical ensemble. Finite size effects on thermodynamical variables are analyzed by a direct calculation of the partition function, and it is shown that phase coexistence and phase transition are relevant concepts even for systems of a few tens of particles. Critical exponents are extracted from the behaviour of the fragment production yield as a function of temperature by means of a finite size scaling. The result is that in a finite system well defined critical signals can be found at supercritical (Kertesz line) as well as subcritical densities. For isospin asymmetric systems it is shown that, besides the modification of the critical temperature, isotopic distributions can provide an extra observable to identify and characterize the transition. (author) 21 refs.

  12. Nutrient-dependent/pheromone-controlled adaptive evolution: a model

    Directory of Open Access Journals (Sweden)

    James Vaughn Kohl

    2013-06-01

    Full Text Available Background: The prenatal migration of gonadotropin-releasing hormone (GnRH neurosecretory neurons allows nutrients and human pheromones to alter GnRH pulsatility, which modulates the concurrent maturation of the neuroendocrine, reproductive, and central nervous systems, thus influencing the development of ingestive behavior, reproductive sexual behavior, and other behaviors. Methods: This model details how chemical ecology drives adaptive evolution via: (1 ecological niche construction, (2 social niche construction, (3 neurogenic niche construction, and (4 socio-cognitive niche construction. This model exemplifies the epigenetic effects of olfactory/pheromonal conditioning, which alters genetically predisposed, nutrient-dependent, hormone-driven mammalian behavior and choices for pheromones that control reproduction via their effects on luteinizing hormone (LH and systems biology. Results: Nutrients are metabolized to pheromones that condition behavior in the same way that food odors condition behavior associated with food preferences. The epigenetic effects of olfactory/pheromonal input calibrate and standardize molecular mechanisms for genetically predisposed receptor-mediated changes in intracellular signaling and stochastic gene expression in GnRH neurosecretory neurons of brain tissue. For example, glucose and pheromones alter the hypothalamic secretion of GnRH and LH. A form of GnRH associated with sexual orientation in yeasts links control of the feedback loops and developmental processes required for nutrient acquisition, movement, reproduction, and the diversification of species from microbes to man. Conclusion: An environmental drive evolved from that of nutrient ingestion in unicellular organisms to that of pheromone-controlled socialization in insects. In mammals, food odors and pheromones cause changes in hormones such as LH, which has developmental affects on pheromone-controlled sexual behavior in nutrient-dependent reproductively

  13. Stimulus-dependent refractoriness in the Frankenhaeuser-Huxley model.

    Science.gov (United States)

    Morse, R P; Allingham, D; Stocks, N G

    2015-10-07

    Phenomenological neural models, such as the leaky integrate-and-fire model, normally have a fixed refractory time-course that is independent of the stimulus. The recovery of threshold following an action potential is typically based on physiological experiments that use a two-pulse paradigm in which the first pulse is suprathreshold and causes excitation and the second pulse is used to determine the threshold at various intervals following the first. In such experiments, the nerve is completely unstimulated between the two pulses. This contrasts the receptor stimuli in normal physiological systems and the electrical stimuli used by cochlear implants and other neural prostheses. A numerical study of the Frankenhaeuser-Huxley conductance-based model of nerve fibre was therefore undertaken to investigate the effect of stimulation on refractoriness. We found that the application of a depolarizing stimulus during the later part of what is classically regarded as the absolute refractory period could effectively prolong the absolute refractory period, while leaving the refractory time-constants and other refractory parameters largely unaffected. Indeed, long depolarizing pulses, which would have been suprathreshold if presented to a resting nerve fibre, appeared to block excitation indefinitely. Stimulation during what is classically regarded as the absolute refractory period can therefore greatly affect the temporal response of a nerve. We conclude that the classical definition of absolute refractory period should be refined to include only the initial period following an action potential when an ongoing stimulus would not affect threshold; this period was found to be about half as long as the classical absolute refractory period. We further conclude that the stimulus-dependent nature of the relative refractory period must be considered when developing a phenomenological nerve model for complex stimuli.

  14. Modelling polarization dependent absorption: The vectorial Lambert-Beer law

    Science.gov (United States)

    Franssens, G.

    2014-07-01

    The scalar Lambert-Beer law, describing the absorption of unpolarized light travelling through a linear non-scattering medium, is simple, well-known, and mathematically trivial. However, when we take the polarization of light into account and consider a medium with polarization dependent absorption, we now need a Vectorial Lambert-Beer Law (VLBL) to quantify this interaction. Such a generalization of the scalar Lambert-Beer law appears not to be readily available. A careful study of this topic reveals that it is not a trivial problem. We will see that the VLBL is not and cannot be a straightforward vectorized version of its scalar counterpart. The aim of the work is to present the general form of the VLBL and to explain how it arises. A reasonable starting point to derive the VLBL is the Vectorial Radiative Transfer Equation (VRTE), which models the absorption and scattering of (partially) polarized light travelling through a linear medium. When we turn off scattering, the VRTE becomes an infinitesimal model for the VLBL holding in the medium. By integrating this equation, we expect to find the VLBL. Surprisingly, this is not the end of the story. It turns out that light propagation through a medium with polarization-dependent absorption is mathematically not that trivial. The trickiness behind the VLBL can be understood in the following terms. The matrix in the VLBL, relating any input Stokes vector to the corresponding output Stokes vector, must necessarily be a Mueller matrix. The subset of invertible Mueller matrices forms a Lie group. It is known that this Lie group contains the ortho-chronous Lorentz group as a subgroup. The group manifold of this subgroup has a (well-known) non-trivial topology. Consequently, the manifold of the Lie group of Mueller matrices also has (at least the same, but likely a more general) non-trivial topology (the full extent of which is not yet known). The type of non-trivial topology, possessed by the manifold of (invertible

  15. Integrated crop pollination: Combining strategies to ensure stable and sustainable yields of pollination-dependent crops

    Science.gov (United States)

    Meeting the nutritional needs of our growing human population will be increasingly dependent on bees and other pollinators that provide the essential delivery of pollen to crop flowers during bloom. Honey bees have experienced population declines in some regions, and similar changes are evident for ...

  16. Development of new neurobiological strategies to treat patients with cocaine dependence

    NARCIS (Netherlands)

    Crunelle, C.L.

    2012-01-01

    Dopamine is a key neurotransmitter in the pathophysiology of substance dependence and low striatal dopamine D2 receptor availability is probably both a risk factor for and a consequence of repeated drug use. It was, therefore, hypothesized that increasing dopamine D2 receptor availability is a promi

  17. Toddler's self-regulation strategies in a challenge context are nap-dependent.

    Science.gov (United States)

    Miller, Alison L; Seifer, Ronald; Crossin, Rebecca; Lebourgeois, Monique K

    2015-06-01

    Early childhood represents a time of developmental changes in both sleep and self-regulation, a construct reflecting the ability to control one's behaviour, attention and emotions when challenged. Links between sleep and self-regulation processes have been proposed, but experimental evidence with young children is lacking. In the current study, we tested the effects of acute sleep restriction (nap deprivation) on toddlers' self-regulation. Healthy children (n = 12; four males; aged 30-36 months (33.9 ± 1.7)) slept on a strict schedule (verified with actigraphy and sleep diaries) for 5 days before each of two afternoon assessments following a nap and a no-nap condition (~11-day protocol). Children were videotaped while attempting an unsolvable puzzle, and 10 mutually exclusive self-regulation strategies were later coded. On average, children lost ~90 min of sleep on the no-nap versus the nap day. Nap deprivation resulted in moderate-to-large effects on self-regulation strategies, with decreases in scepticism (d = 0.77; 7% change), negative self-appraisal (d = 0.92; 5% change) and increases in physical self-soothing (d = 0.68; 10% change), focus on the puzzle piece that would not fit (perseveration; d = 0.50; 9% change) and insistence on completing the unsolvable puzzle (d = 0.91; 10% change). Results suggest that sleep serves an important role in the way that toddlers respond to challenging events in their daily lives. After losing daytime sleep, toddlers were less able to engage effectively in a difficult task and reverted to less mature self-regulation strategies than when they were well rested. Over time, chronically missed sleep may impair young children's self-regulation abilities, resulting in risk for social-emotional, behavioural and school problems.

  18. Hydrogeochemical site descriptive model - a strategy for the model development during site investigations

    Energy Technology Data Exchange (ETDEWEB)

    Smellie, John [Conterra AB, Uppsala (Sweden); Laaksoharju, Marcus [GeoPoint AB, Sollentuna (Sweden); Tullborg, Eva-Lena [Terralogica AB, Graabo (Sweden)

    2002-12-01

    In 2002, SKB commenced site characterisation investigations using deep boreholes at different sites. As an integral part of the planning work SKB has prepared a strategy to develop a Hydrogeochemical Site Descriptive Model; similar strategies have been developed for the other major geoscience disciplines. The main objectives of the Hydrogeochemical Site Descriptive Model are to describe the chemistry and distribution of the groundwater in the bedrock and overburden and the hydrogeochemical processes involved in its origin and evolution. This description is based primarily on measurements of the groundwater composition but incorporates the use of available geological and hydrogeological site descriptive models. The SKB hydrogeochemistry programme is planned to fulfil two basic requirements: 1) to provide representative and quality assured data for use as input parameter values in calculating long-term repository safety, and 2) to understand the present undisturbed hydrogeochemical conditions and how these conditions will change in the future. Parameter values for safety analysis include pH, Eh, S, SO{sub 4}, HCO{sub 3}, HPO{sub 4} and TDS (mainly cations), together with colloids, fulvic and humic acids, other organics, bacteria and nitrogen. These values will be used to characterise the groundwater environment at, above and below repository depths. In the hydrogeochemical site investigation programme the number and location of the sampling points will be constrained by: a) geology (e.g. topography, overburden types, bedrock structures etc), b) hydrogeology (e.g. groundwater recharge/discharge areas, residence times), c) reliability (e.g. undisturbed vs disturbed groundwater chemical conditions), and d) resources (e.g. number and type of samples, and also available personnel, may be restricted by budgetary and schedule concerns). Naturally a balance is required between these constraints and the scientific aims of the programme. The constraints should never

  19. Improved pump turbine transient behaviour prediction using a Thoma number-dependent hillchart model

    Science.gov (United States)

    Manderla, M.; Kiniger, K.; Koutnik, J.

    2014-03-01

    Water hammer phenomena are important issues for high head hydro power plants. Especially, if several reversible pump-turbines are connected to the same waterways there may be strong interactions between the hydraulic machines. The prediction and coverage of all relevant load cases is challenging and difficult using classical simulation models. On the basis of a recent pump-storage project, dynamic measurements motivate an improved modeling approach making use of the Thoma number dependency of the actual turbine behaviour. The proposed approach is validated for several transient scenarios and turns out to increase correlation between measurement and simulation results significantly. By applying a fully automated simulation procedure broad operating ranges can be covered which provides a consistent insight into critical load case scenarios. This finally allows the optimization of the closing strategy and hence the overall power plant performance.

  20. Disentangling density-dependent dynamics using full annual cycle models and Bayesian model weight updating

    Science.gov (United States)

    Robinson, Orin J.; McGowan, Conor; Devers, Patrick K.

    2017-01-01

    Density dependence regulates populations of many species across all taxonomic groups. Understanding density dependence is vital for predicting the effects of climate, habitat loss and/or management actions on wild populations. Migratory species likely experience seasonal changes in the relative influence of density dependence on population processes such as survival and recruitment throughout the annual cycle. These effects must be accounted for when characterizing migratory populations via population models.To evaluate effects of density on seasonal survival and recruitment of a migratory species, we used an existing full annual cycle model framework for American black ducks Anas rubripes, and tested different density effects (including no effects) on survival and recruitment. We then used a Bayesian model weight updating routine to determine which population model best fit observed breeding population survey data between 1990 and 2014.The models that best fit the survey data suggested that survival and recruitment were affected by density dependence and that density effects were stronger on adult survival during the breeding season than during the non-breeding season.Analysis also suggests that regulation of survival and recruitment by density varied over time. Our results showed that different characterizations of density regulations changed every 8–12 years (three times in the 25-year period) for our population.Synthesis and applications. Using a full annual cycle, modelling framework and model weighting routine will be helpful in evaluating density dependence for migratory species in both the short and long term. We used this method to disentangle the seasonal effects of density on the continental American black duck population which will allow managers to better evaluate the effects of habitat loss and potential habitat management actions throughout the annual cycle. The method here may allow researchers to hone in on the proper form and/or strength of

  1. A Model of How Motivational Strategies Related to the Expectative Component Affect Cognitive and Metacognitive Strategies

    Science.gov (United States)

    Suarez, Jose Manuel; Fernandez, Ana Patricia

    2011-01-01

    Introduction: The topic of self-regulated learning has provided very important information about students' acquisition of knowledge and competences. Traditional research has described the importance of several cognitive, metacognitive, resource control and motivational strategies. Nevertheless, motivational strategies have received less attention…

  2. Default risk modeling with position-dependent killing

    Science.gov (United States)

    Katz, Yuri A.

    2013-04-01

    Diffusion in a linear potential in the presence of position-dependent killing is used to mimic a default process. Different assumptions regarding transport coefficients, initial conditions, and elasticity of the killing measure lead to diverse models of bankruptcy. One “stylized fact” is fundamental for our consideration: empirically default is a rather rare event, especially in the investment grade categories of credit ratings. Hence, the action of killing may be considered as a small parameter. In a number of special cases we derive closed-form expressions for the entire term structure of the cumulative probability of default, its hazard rate, and intensity. Comparison with historical data on aggregate global corporate defaults confirms the validity of the perturbation method for estimations of long-term probability of default for companies with high credit quality. On a single company level, we implement the derived formulas to estimate the one-year likelihood of default of Enron on a daily basis from August 2000 to August 2001, three months before its default, and compare the obtained results with forecasts of traditional structural models.

  3. Cognitive endophenotypes, gene-environment interactions and experience-dependent plasticity in animal models of schizophrenia.

    Science.gov (United States)

    Burrows, Emma L; Hannan, Anthony J

    2016-04-01

    Schizophrenia is a devastating brain disorder caused by a complex and heterogeneous combination of genetic and environmental factors. In order to develop effective new strategies to prevent and treat schizophrenia, valid animal models are required which accurately model the disorder, and ideally provide construct, face and predictive validity. The cognitive deficits in schizophrenia represent some of the most debilitating symptoms and are also currently the most poorly treated. Therefore it is crucial that animal models are able to capture the cognitive dysfunction that characterizes schizophrenia, as well as the negative and psychotic symptoms. The genomes of mice have, prior to the recent gene-editing revolution, proven the most easily manipulable of mammalian laboratory species, and hence most genetic targeting has been performed using mouse models. Importantly, when key environmental factors of relevance to schizophrenia are experimentally manipulated, dramatic changes in the phenotypes of these animal models are often observed. We will review recent studies in rodent models which provide insight into gene-environment interactions in schizophrenia. We will focus specifically on environmental factors which modulate levels of experience-dependent plasticity, including environmental enrichment, cognitive stimulation, physical activity and stress. The insights provided by this research will not only help refine the establishment of optimally valid animal models which facilitate development of novel therapeutics, but will also provide insight into the pathogenesis of schizophrenia, thus identifying molecular and cellular targets for future preclinical and clinical investigations.

  4. Personality-dependent differences in problem-solving performance in a social context reflect foraging strategies.

    Science.gov (United States)

    Zandberg, Lies; Quinn, John L; Naguib, Marc; van Oers, Kees

    2017-01-01

    Individuals develop innovative behaviours to solve foraging challenges in the face of changing environmental conditions. Little is known about how individuals differ in their tendency to solve problems and in their subsequent use of this solving behaviour in social contexts. Here we investigated whether individual variation in problem-solving performance could be explained by differences in the likelihood of solving the task, or if they reflect differences in foraging strategy. We tested this by studying the use of a novel foraging skill in groups of great tits (Parus major), consisting of three naive individuals with different personality, and one knowledgeable tutor. We presented them with multiple, identical foraging devices over eight trials. Though birds of different personality type did not differ in solving latency; fast and slow explorers showed a steeper increase over time in their solving rate, compared to intermediate explorers. Despite equal solving potential, personality influenced the subsequent use of the skill, as well as the pay-off received from solving. Thus, variation in the tendency to solve the task reflected differences in foraging strategy among individuals linked to their personality. These results emphasize the importance of considering the social context to fully understand the implications of learning novel skills. Copyright © 2016 Elsevier B.V. All rights reserved.

  5. Extraversion differentiates between model-based and model-free strategies in a reinforcement learning task.

    Science.gov (United States)

    Skatova, Anya; Chan, Patricia A; Daw, Nathaniel D

    2013-01-01

    Prominent computational models describe a neural mechanism for learning from reward prediction errors, and it has been suggested that variations in this mechanism are reflected in personality factors such as trait extraversion. However, although trait extraversion has been linked to improved reward learning, it is not yet known whether this relationship is selective for the particular computational strategy associated with error-driven learning, known as model-free reinforcement learning, vs. another strategy, model-based learning, which the brain is also known to employ. In the present study we test this relationship by examining whether humans' scores on an extraversion scale predict individual differences in the balance between model-based and model-free learning strategies in a sequentially structured decision task designed to distinguish between them. In previous studies with this task, participants have shown a combination of both types of learning, but with substantial individual variation in the balance between them. In the current study, extraversion predicted worse behavior across both sorts of learning. However, the hypothesis that extraverts would be selectively better at model-free reinforcement learning held up among a subset of the more engaged participants, and overall, higher task engagement was associated with a more selective pattern by which extraversion predicted better model-free learning. The findings indicate a relationship between a broad personality orientation and detailed computational learning mechanisms. Results like those in the present study suggest an intriguing and rich relationship between core neuro-computational mechanisms and broader life orientations and outcomes.

  6. EW WEIGHT DEPENDENT ROUTING AND WAVELENGTH ASSIGNMENT STRATEGY FOR ALL OPTICAL NETWORKS IN ABSENCE OF WAVELENGTH CONVERTERS

    Directory of Open Access Journals (Sweden)

    Shilpa S. Patil

    2015-09-01

    Full Text Available In wavelength division multiplexed all optical networks; lightpath establishes a connection between sending and receiving nodes bypassing the electronic processing at intermediate nodes. One of the prime objectives of Routing and Wavelength Assignment (RWA problem is to maximize the number of connections efficiently by choosing the best routes. Although there are several algorithms available, improving the blocking performance in optical networks and finding optimal solutions for RWA problem has still remained a challenging issue. Wavelength conversion can be helpful in restricting the problem of wavelength continuity constraint but it increases complexity in the network. In this paper, we propose new weight dependent routing and wavelength assignment strategy for all optical networks without use of wavelength converters. Proposed weight function reduces blocking probability significantly, improving the network performance at various load conditions. Further, due to absence of wavelength converters, the cost and complexity of network reduces. Results show that the proposed strategy performs better than earlier reported methods.

  7. A copula method for modeling directional dependence of genes

    Directory of Open Access Journals (Sweden)

    Park Changyi

    2008-05-01

    Full Text Available Abstract Background Genes interact with each other as basic building blocks of life, forming a complicated network. The relationship between groups of genes with different functions can be represented as gene networks. With the deposition of huge microarray data sets in public domains, study on gene networking is now possible. In recent years, there has been an increasing interest in the reconstruction of gene networks from gene expression data. Recent work includes linear models, Boolean network models, and Bayesian networks. Among them, Bayesian networks seem to be the most effective in constructing gene networks. A major problem with the Bayesian network approach is the excessive computational time. This problem is due to the interactive feature of the method that requires large search space. Since fitting a model by using the copulas does not require iterations, elicitation of the priors, and complicated calculations of posterior distributions, the need for reference to extensive search spaces can be eliminated leading to manageable computational affords. Bayesian network approach produces a discretely expression of conditional probabilities. Discreteness of the characteristics is not required in the copula approach which involves use of uniform representation of the continuous random variables. Our method is able to overcome the limitation of Bayesian network method for gene-gene interaction, i.e. information loss due to binary transformation. Results We analyzed the gene interactions for two gene data sets (one group is eight histone genes and the other group is 19 genes which include DNA polymerases, DNA helicase, type B cyclin genes, DNA primases, radiation sensitive genes, repaire related genes, replication protein A encoding gene, DNA replication initiation factor, securin gene, nucleosome assembly factor, and a subunit of the cohesin complex by adopting a measure of directional dependence based on a copula function. We have compared

  8. Using the business excellence model to develop a strategy for a healthcare organisation.

    Science.gov (United States)

    Naylor, G

    1999-01-01

    This article examines the appropriateness of the Business Excellence Model in developing a strategy for Bolton Hospitals NHS Trust to measure organisational performance. The need for a strategy to measure organisational performance and to improve organisational performance was highlighted with the production of the Government White Paper, The New NHS: Modern and Dependable. At the heart of recommendations there is emphasis on improving quality and driving efficiency. Greater emphasis will be placed on organisations measuring their performance. By utilising the conceptual framework, which consisted of The European Foundation for Quality Management (EFQM) Model, it became evident that, although tools were in existence within Bolton Hospitals to measure organisational performance, several critical areas needed addressing. By addressing these key areas, the organisation could begin to work towards its goal of business excellence. The conclusions drawn from this project demonstrated that there was scope for Bolton Hospitals to improve on organisational performance. It was highlighted that the Trust was functioning well in some areas of the EFQM Model, but not in others. For Bolton Hospitals NHS Trust to improve organisational performance, the EFQM Model should be adopted.

  9. Directed Sample Interrogation Utilizing an Accurate Mass Exclusion-Based Data-Dependent Acquisition Strategy (AMEx)

    OpenAIRE

    Rudomin, Emily L.; Carr, Steven A.; Jaffe, Jacob D.

    2009-01-01

    The ability to perform thorough sampling is of critical importance when using mass spectrometry to characterize complex proteomic mixtures. A common approach is to re-interrogate a sample multiple times by LC-MS/MS. However, the conventional data-dependent acquisition methods that are typically used in proteomics studies will often redundantly sample high-intensity precursor ions while failing to sample low-intensity precursors entirely. We describe a method wherein the masses of successfully...

  10. Spatial scale dependency of the modelled climatic response to deforestation

    Directory of Open Access Journals (Sweden)

    P. Longobardi

    2012-10-01

    Full Text Available Deforestation is associated with increased atmospheric CO2 and alterations to the surface energy and mass balances that can lead to local and global climate changes. Previous modelling studies show that the global surface air temperature (SAT response to deforestation depends on latitude, with most simulations showing that high latitude deforestation results in cooling, low latitude deforestation causes warming and that the mid latitude response is mixed. These earlier conclusions are based on simulated large scale land cover change, with complete removal of trees from whole latitude bands. Using a global climate model we determine effects of removing fractions of 5% to 100% of forested areas in the high, mid and low latitudes. All high latitude deforestation scenarios reduce mean global SAT, the opposite occurring for low latitude deforestation, although a decrease in SAT is registered over low latitude deforested areas. Mid latitude SAT response is mixed. For all simulations deforested areas tend to become drier and have lower surface air temperature, although soil temperatures increase over deforested mid and low latitude grid cells. For high latitude deforestation fractions of 45% and above, larger net primary productivity, in conjunction with colder and drier conditions after deforestation, cause an increase in soil carbon large enough to generate a previously not reported net drawdown of CO2 from the atmosphere. Our results support previous indications of the importance of changes in cloud cover in the modelled temperature response to deforestation at low latitudes. They also show the complex interaction between soil carbon dynamics and climate and the role this plays on the climatic response to land cover change.

  11. Incorporating Pass-Phrase Dependent Background Models for Text-Dependent Speaker verification

    DEFF Research Database (Denmark)

    Sarkar, Achintya Kumar; Tan, Zheng-Hua

    2017-01-01

    -dependent. We show that the proposed method significantly reduces the error rates of text-dependent speaker verification for the non-target types: target-wrong and impostor-wrong while it maintains comparable TD-SV performance when impostors speak a correct utterance with respect to the conventional system...

  12. Irreversible prey diapause as an optimal strategy of a physiologically extended Lotka-Volterra model.

    Science.gov (United States)

    Staňková, Kateřina; Abate, Alessandro; Sabelis, Maurice W

    2013-03-01

    We propose an optimal control framework to describe intra-seasonal predator-prey interactions, which are characterized by a continuous-time dynamical model comprising predator and prey density, as well as the energy budget of the prey over the length of a season. The model includes a time-dependent decision variable for the prey, representing the portion of the prey population in time that is active, as opposed to diapausing (a state of physiological rest). The predator follows autonomous dynamics and accordingly it remains active during the season. The proposed model is a generalization of the classical Lotka-Volterra predator-prey model towards non-autonomous dynamics that furthermore includes the effect of an energy variable. The model has been inspired by a specific biological system of predatory mites (Acari: Phytoseiidae) and prey mites (so-called fruit-tree red spider mites) (Acari: Tetranychidae) that feed on leaves of apple trees--its parameters have been instantiated based on laboratory and field studies. The goal of the work is to understand the decisions of the prey mites to enter diapause (a state of physiological rest) given the dynamics of the predatory mites: this is achieved by solving an optimization problem hinging on the maximization of the prey population contribution to the next season. The main features of the optimal strategy for the prey are shown to be that (1) once in diapause, the prey does not become active again within the same season and hence diapause is an irreversible process; (2) for the vast majority of parameter space, the portion of prey individuals entering diapause within the season does not decrease in time; (3) with an increased number of predators, the optimal population strategy for the prey is to start diapause earlier and to enter diapause more gradually. This optimal population strategy will be studied for its ESS properties in a sequel to the work presented in this article.

  13. Strategies for fitting nonlinear ecological models in R, AD Model Builder, and BUGS

    Science.gov (United States)

    Bolker, Benjamin M.; Gardner, Beth; Maunder, Mark; Berg, Casper W.; Brooks, Mollie; Comita, Liza; Crone, Elizabeth; Cubaynes, Sarah; Davies, Trevor; de Valpine, Perry; Ford, Jessica; Gimenez, Olivier; Kéry, Marc; Kim, Eun Jung; Lennert-Cody, Cleridy; Magunsson, Arni; Martell, Steve; Nash, John; Nielson, Anders; Regentz, Jim; Skaug, Hans; Zipkin, Elise

    2013-01-01

    1. Ecologists often use nonlinear fitting techniques to estimate the parameters of complex ecological models, with attendant frustration. This paper compares three open-source model fitting tools and discusses general strategies for defining and fitting models. 2. R is convenient and (relatively) easy to learn, AD Model Builder is fast and robust but comes with a steep learning curve, while BUGS provides the greatest flexibility at the price of speed. 3. Our model-fitting suggestions range from general cultural advice (where possible, use the tools and models that are most common in your subfield) to specific suggestions about how to change the mathematical description of models to make them more amenable to parameter estimation. 4. A companion web site (https://groups.nceas.ucsb.edu/nonlinear-modeling/projects) presents detailed examples of application of the three tools to a variety of typical ecological estimation problems; each example links both to a detailed project report and to full source code and data.

  14. Quality Saving Mechanisms of Mitochondria during Aging in a Fully Time-Dependent Computational Biophysical Model.

    Science.gov (United States)

    Mellem, Daniel; Fischer, Frank; Jaspers, Sören; Wenck, Horst; Rübhausen, Michael

    2016-01-01

    Mitochondria are essential for the energy production of eukaryotic cells. During aging mitochondria run through various processes which change their quality in terms of activity, health and metabolic supply. In recent years, many of these processes such as fission and fusion of mitochondria, mitophagy, mitochondrial biogenesis and energy consumption have been subject of research. Based on numerous experimental insights, it was possible to qualify mitochondrial behaviour in computational simulations. Here, we present a new biophysical model based on the approach of Figge et al. in 2012. We introduce exponential decay and growth laws for each mitochondrial process to derive its time-dependent probability during the aging of cells. All mitochondrial processes of the original model are mathematically and biophysically redefined and additional processes are implemented: Mitochondrial fission and fusion is separated into a metabolic outer-membrane part and a protein-related inner-membrane part, a quality-dependent threshold for mitophagy and mitochondrial biogenesis is introduced and processes for activity-dependent internal oxidative stress as well as mitochondrial repair mechanisms are newly included. Our findings reveal a decrease of mitochondrial quality and a fragmentation of the mitochondrial network during aging. Additionally, the model discloses a quality increasing mechanism due to the interplay of the mitophagy and biogenesis cycle and the fission and fusion cycle of mitochondria. It is revealed that decreased mitochondrial repair can be a quality saving process in aged cells. Furthermore, the model finds strategies to sustain the quality of the mitochondrial network in cells with high production rates of reactive oxygen species due to large energy demands. Hence, the model adds new insights to biophysical mechanisms of mitochondrial aging and provides novel understandings of the interdependency of mitochondrial processes.

  15. Quality Saving Mechanisms of Mitochondria during Aging in a Fully Time-Dependent Computational Biophysical Model

    Science.gov (United States)

    Mellem, Daniel; Fischer, Frank; Jaspers, Sören; Wenck, Horst; Rübhausen, Michael

    2016-01-01

    Mitochondria are essential for the energy production of eukaryotic cells. During aging mitochondria run through various processes which change their quality in terms of activity, health and metabolic supply. In recent years, many of these processes such as fission and fusion of mitochondria, mitophagy, mitochondrial biogenesis and energy consumption have been subject of research. Based on numerous experimental insights, it was possible to qualify mitochondrial behaviour in computational simulations. Here, we present a new biophysical model based on the approach of Figge et al. in 2012. We introduce exponential decay and growth laws for each mitochondrial process to derive its time-dependent probability during the aging of cells. All mitochondrial processes of the original model are mathematically and biophysically redefined and additional processes are implemented: Mitochondrial fission and fusion is separated into a metabolic outer-membrane part and a protein-related inner-membrane part, a quality-dependent threshold for mitophagy and mitochondrial biogenesis is introduced and processes for activity-dependent internal oxidative stress as well as mitochondrial repair mechanisms are newly included. Our findings reveal a decrease of mitochondrial quality and a fragmentation of the mitochondrial network during aging. Additionally, the model discloses a quality increasing mechanism due to the interplay of the mitophagy and biogenesis cycle and the fission and fusion cycle of mitochondria. It is revealed that decreased mitochondrial repair can be a quality saving process in aged cells. Furthermore, the model finds strategies to sustain the quality of the mitochondrial network in cells with high production rates of reactive oxygen species due to large energy demands. Hence, the model adds new insights to biophysical mechanisms of mitochondrial aging and provides novel understandings of the interdependency of mitochondrial processes. PMID:26771181

  16. Quality Saving Mechanisms of Mitochondria during Aging in a Fully Time-Dependent Computational Biophysical Model.

    Directory of Open Access Journals (Sweden)

    Daniel Mellem

    Full Text Available Mitochondria are essential for the energy production of eukaryotic cells. During aging mitochondria run through various processes which change their quality in terms of activity, health and metabolic supply. In recent years, many of these processes such as fission and fusion of mitochondria, mitophagy, mitochondrial biogenesis and energy consumption have been subject of research. Based on numerous experimental insights, it was possible to qualify mitochondrial behaviour in computational simulations. Here, we present a new biophysical model based on the approach of Figge et al. in 2012. We introduce exponential decay and growth laws for each mitochondrial process to derive its time-dependent probability during the aging of cells. All mitochondrial processes of the original model are mathematically and biophysically redefined and additional processes are implemented: Mitochondrial fission and fusion is separated into a metabolic outer-membrane part and a protein-related inner-membrane part, a quality-dependent threshold for mitophagy and mitochondrial biogenesis is introduced and processes for activity-dependent internal oxidative stress as well as mitochondrial repair mechanisms are newly included. Our findings reveal a decrease of mitochondrial quality and a fragmentation of the mitochondrial network during aging. Additionally, the model discloses a quality increasing mechanism due to the interplay of the mitophagy and biogenesis cycle and the fission and fusion cycle of mitochondria. It is revealed that decreased mitochondrial repair can be a quality saving process in aged cells. Furthermore, the model finds strategies to sustain the quality of the mitochondrial network in cells with high production rates of reactive oxygen species due to large energy demands. Hence, the model adds new insights to biophysical mechanisms of mitochondrial aging and provides novel understandings of the interdependency of mitochondrial processes.

  17. Thiamin diphosphate-dependent enzymes: from enzymology to metabolic regulation, drug design and disease models.

    Science.gov (United States)

    Bunik, Victoria I; Tylicki, Adam; Lukashev, Nikolay V

    2013-12-01

    Bringing a knowledge of enzymology into research in vivo and in situ is of great importance in understanding systems biology and metabolic regulation. The central metabolic significance of thiamin (vitamin B1 ) and its diphosphorylated derivative (thiamin diphosphate; ThDP), and the fundamental differences in the ThDP-dependent enzymes of metabolic networks in mammals versus plants, fungi and bacteria, or in health versus disease, suggest that these enzymes are promising targets for biotechnological and medical applications. Here, the in vivo action of known regulators of ThDP-dependent enzymes, such as synthetic structural analogs of the enzyme substrates and thiamin, is analyzed in light of the enzymological data accumulated during half a century of research. Mimicking the enzyme-specific catalytic intermediates, the phosphonate analogs of 2-oxo acids selectively inhibit particular ThDP-dependent enzymes. Because of their selectivity, use of these compounds in cellular and animal models of ThDP-dependent enzyme malfunctions improves the validity of the model and its predictive power when compared with the nonselective and enzymatically less characterized oxythiamin and pyrithiamin. In vitro studies of the interaction of thiamin analogs and their biological derivatives with potential in vivo targets are necessary to identify and attenuate the analog selectivity. For both the substrate and thiamin synthetic analogs, in vitro reactivities with potential targets are highly relevant in vivo. However, effective concentrations in vivo are often higher than in vitro studies would suggest. The significance of specific inihibition of the ThDP-dependent enzymes for the development of herbicides, antibiotics, anticancer and neuroprotective strategies is discussed.

  18. A stochastic model updating strategy-based improved response surface model and advanced Monte Carlo simulation

    Science.gov (United States)

    Zhai, Xue; Fei, Cheng-Wei; Choy, Yat-Sze; Wang, Jian-Jun

    2017-01-01

    To improve the accuracy and efficiency of computation model for complex structures, the stochastic model updating (SMU) strategy was proposed by combining the improved response surface model (IRSM) and the advanced Monte Carlo (MC) method based on experimental static test, prior information and uncertainties. Firstly, the IRSM and its mathematical model were developed with the emphasis on moving least-square method, and the advanced MC simulation method is studied based on Latin hypercube sampling method as well. And then the SMU procedure was presented with experimental static test for complex structure. The SMUs of simply-supported beam and aeroengine stator system (casings) were implemented to validate the proposed IRSM and advanced MC simulation method. The results show that (1) the SMU strategy hold high computational precision and efficiency for the SMUs of complex structural system; (2) the IRSM is demonstrated to be an effective model due to its SMU time is far less than that of traditional response surface method, which is promising to improve the computational speed and accuracy of SMU; (3) the advanced MC method observably decrease the samples from finite element simulations and the elapsed time of SMU. The efforts of this paper provide a promising SMU strategy for complex structure and enrich the theory of model updating.

  19. Hydrogeochemical site descriptive model - a strategy for the model development during site investigations

    Energy Technology Data Exchange (ETDEWEB)

    Smellie, John [Conterra AB, Uppsala (Sweden); Laaksoharju, Marcus [GeoPoint AB, Sollentuna (Sweden); Tullborg, Eva-Lena [Terralogica AB, Graabo (Sweden)

    2002-12-01

    In 2002, SKB commenced site characterisation investigations using deep boreholes at different sites. As an integral part of the planning work SKB has prepared a strategy to develop a Hydrogeochemical Site Descriptive Model; similar strategies have been developed for the other major geoscience disciplines. The main objectives of the Hydrogeochemical Site Descriptive Model are to describe the chemistry and distribution of the groundwater in the bedrock and overburden and the hydrogeochemical processes involved in its origin and evolution. This description is based primarily on measurements of the groundwater composition but incorporates the use of available geological and hydrogeological site descriptive models. The SKB hydrogeochemistry programme is planned to fulfil two basic requirements: 1) to provide representative and quality assured data for use as input parameter values in calculating long-term repository safety, and 2) to understand the present undisturbed hydrogeochemical conditions and how these conditions will change in the future. Parameter values for safety analysis include pH, Eh, S, SO{sub 4}, HCO{sub 3}, HPO{sub 4} and TDS (mainly cations), together with colloids, fulvic and humic acids, other organics, bacteria and nitrogen. These values will be used to characterise the groundwater environment at, above and below repository depths. In the hydrogeochemical site investigation programme the number and location of the sampling points will be constrained by: a) geology (e.g. topography, overburden types, bedrock structures etc), b) hydrogeology (e.g. groundwater recharge/discharge areas, residence times), c) reliability (e.g. undisturbed vs disturbed groundwater chemical conditions), and d) resources (e.g. number and type of samples, and also available personnel, may be restricted by budgetary and schedule concerns). Naturally a balance is required between these constraints and the scientific aims of the programme. The constraints should never

  20. Modelling the ancestral sequence distribution and model frequencies in context-dependent models for primate non-coding sequences

    Directory of Open Access Journals (Sweden)

    Baele Guy

    2010-08-01

    Full Text Available Abstract Background Recent approaches for context-dependent evolutionary modelling assume that the evolution of a given site depends upon its ancestor and that ancestor's immediate flanking sites. Because such dependency pattern cannot be imposed on the root sequence, we consider the use of different orders of Markov chains to model dependence at the ancestral root sequence. Root distributions which are coupled to the context-dependent model across the underlying phylogenetic tree are deemed more realistic than decoupled Markov chains models, as the evolutionary process is responsible for shaping the composition of the ancestral root sequence. Results We find strong support, in terms of Bayes Factors, for using a second-order Markov chain at the ancestral root sequence along with a context-dependent model throughout the remainder of the phylogenetic tree in an ancestral repeats dataset, and for using a first-order Markov chain at the ancestral root sequence in a pseudogene dataset. Relaxing the assumption of a single context-independent set of independent model frequencies as presented in previous work, yields a further drastic increase in model fit. We show that the substitution rates associated with the CpG-methylation-deamination process can be modelled through context-dependent model frequencies and that their accuracy depends on the (order of the Markov chain imposed at the ancestral root sequence. In addition, we provide evidence that this approach (which assumes that root distribution and evolutionary model are decoupled outperforms an approach inspired by the work of Arndt et al., where the root distribution is coupled to the evolutionary model. We show that the continuous-time approximation of Hwang and Green has stronger support in terms of Bayes Factors, but the parameter estimates show minimal differences. Conclusions We show that the combination of a dependency scheme at the ancestral root sequence and a context-dependent

  1. Relationship between Business Strategy and Business Model Studied in a Sample of Service Companies

    Directory of Open Access Journals (Sweden)

    Slávik Štefan

    2016-12-01

    Full Text Available A business model and a business strategy are the basic conditions of a company existence. A business model describes and explains how a company works and makes money. A business strategy describes and explains how, where and for what purpose and goal a business model will be used. The research seeks to ascertain whether there is any measurable relationship between a strategy and a model. An identification of this relationship will deepen knowledge of strategic management of the company and it is a reason for further research on the nature of relationship between a model and a strategy.

  2. Dengue Virus Utilizes a Novel Strategy for Translation Initiation When Cap-Dependent Translation Is Inhibited

    OpenAIRE

    Edgil, Dianna; Polacek, Charlotta; Harris, Eva

    2006-01-01

    Viruses have developed numerous mechanisms to usurp the host cell translation apparatus. Dengue virus (DEN) and other flaviviruses, such as West Nile and yellow fever viruses, contain a 5′ m7GpppN-capped positive-sense RNA genome with a nonpolyadenylated 3′ untranslated region (UTR) that has been presumed to undergo translation in a cap-dependent manner. However, the means by which the DEN genome is translated effectively in the presence of capped, polyadenylated cellular mRNAs is unknown. Th...

  3. Probabilistic Inference: Task Dependency and Individual Differences of Probability Weighting Revealed by Hierarchical Bayesian Modeling.

    Science.gov (United States)

    Boos, Moritz; Seer, Caroline; Lange, Florian; Kopp, Bruno

    2016-01-01

    Cognitive determinants of probabilistic inference were examined using hierarchical Bayesian modeling techniques. A classic urn-ball paradigm served as experimental strategy, involving a factorial two (prior probabilities) by two (likelihoods) design. Five computational models of cognitive processes were compared with the observed behavior. Parameter-free Bayesian posterior probabilities and parameter-free base rate neglect provided inadequate models of probabilistic inference. The introduction of distorted subjective probabilities yielded more robust and generalizable results. A general class of (inverted) S-shaped probability weighting functions had been proposed; however, the possibility of large differences in probability distortions not only across experimental conditions, but also across individuals, seems critical for the model's success. It also seems advantageous to consider individual differences in parameters of probability weighting as being sampled from weakly informative prior distributions of individual parameter values. Thus, the results from hierarchical Bayesian modeling converge with previous results in revealing that probability weighting parameters show considerable task dependency and individual differences. Methodologically, this work exemplifies the usefulness of hierarchical Bayesian modeling techniques for cognitive psychology. Theoretically, human probabilistic inference might be best described as the application of individualized strategic policies for Bayesian belief revision.

  4. A Conceptual Model For Effluent-Dependent Riverine Environments

    Science.gov (United States)

    Murphy, M. T.; Meyerhoff, R. D.; Osterkamp, W. R.; Smith, E. L.; Hawkins, R. H.

    2001-12-01

    The Arid West Water Quality Research Project (WQRP) is a multi-year, EPA-funded scientific endeavor directed by the Pima County, Wastewater Management Department in southern Arizona and focussed upon several interconnected ecological questions. These questions are crucial to water quality management in the arid and semi arid western US. A key component has been the ecological, hydrological and geomorphological investigation of habitat created by the discharge of treated effluent into ephemeral streams. Such environments are fundamentally different from the dry streams or rivers they displace; however, they are clearly not the perennial streams they superficially resemble. Under Arizona State regulations, such streams can bear the use designation of "Effluent Dependent Waters," or EDWs. Before this investigation, a hydrological/ecological conceptual model for these unique ecosystems had not been published. We have constructed one for general review that is designed to direct future work in the WQRP. The project investigated ten representative, yet contrasting EDW sites distributed throughout arid areas of the western US, to gather both historical and reconnaissance level field data, including in-stream and riparian, habitat and morphometric fluvial data. In most cases, the cross sectional area of the prior channel is oversized relative to the discharge of the introduced effluent. Where bed control is absent, the channels are incised downstream of the discharge point, further suggesting a disequilibrium between the channel and the regulated effluent flow. Several of the studied stream systems primarily convey storm water and are aggradational, exhibiting braided or anastomizing channels, high energy bedforms, and spatially dynamic interfluves. Active channels are formed in response to individual storm events and can be highly dynamic in both location and cross-sectional morphology. This poses a geomorphological challenge in the selection of a discharge point. We

  5. Neural Network Inverse Model Control Strategy: Discrete-Time Stability Analysis for Relative Order Two Systems

    Directory of Open Access Journals (Sweden)

    M. A. Hussain

    2014-01-01

    Full Text Available This paper discusses the discrete-time stability analysis of a neural network inverse model control strategy for a relative order two nonlinear system. The analysis is done by representing the closed loop system in state space format and then analyzing the time derivative of the state trajectory using Lyapunov’s direct method. The analysis shows that the tracking output error of the states is confined to a ball in the neighborhood of the equilibrium point where the size of the ball is partly dependent on the accuracy of the neural network model acting as the controller. Simulation studies on the two-tank-in-series system were done to complement the stability analysis and to demonstrate some salient results of the study.

  6. Dynamics of a Market Share Model for Enterprises with Coopetition Strategy

    Directory of Open Access Journals (Sweden)

    Mingxia Zhao

    2013-01-01

    Full Text Available A deterministic model is used to study the change of the market share with coopetition strategy for enterprises. The model takes into consideration both coopetition enterprises and other enterprises, and the coopetition threshold R0 is identified and global dynamics are completely determined by R0. It shows that R0 is a global threshold parameter in the sense that if R01, there is a unique coopetition equilibrium which is globally attractive with some conditions, and thus the market share of coopetition enterprises tends to a steady state value. By some sensitivity analysis of R0 on parameters, we conclude that the size of the coopetition threshold R0 and coopetition equilibrium depended on the cooperation competitiveness of coopetition enterprises.

  7. A Mixed-Effects Model with Different Strategies for Modeling Volume in Cunninghamia lanceolata Plantations.

    Directory of Open Access Journals (Sweden)

    Mei Guangyi

    Full Text Available A systematic evaluation of nonlinear mixed-effect taper models for volume prediction was performed. Of 21 taper equations with fewer than 5 parameters each, the best 4-parameter fixed-effect model according to fitting statistics was then modified by comparing its values for the parameters total height (H, diameter at breast height (DBH, and aboveground height (h to modeling data. Seven alternative prediction strategies were compared using the best new equation in the absence of calibration data, which is often unavailable in forestry practice. The results of this study suggest that because calibration may sometimes be a realistic option, though it is rarely used in practical applications, one of the best strategies for improving the accuracy of volume prediction is the strategy with 7 calculated total heights of 3, 6 and 9 trees in the largest, smallest and medium-size categories, respectively. We cannot use the average trees or dominant trees for calculating the random parameter for further predictions. The method described here will allow the user to make the best choices of taper type and the best random-effect calculated strategy for each practical application and situation at tree level.

  8. A Mixed-Effects Model with Different Strategies for Modeling Volume in Cunninghamia lanceolata Plantations.

    Science.gov (United States)

    Guangyi, Mei; Yujun, Sun; Hao, Xu; de-Miguel, Sergio

    2015-01-01

    A systematic evaluation of nonlinear mixed-effect taper models for volume prediction was performed. Of 21 taper equations with fewer than 5 parameters each, the best 4-parameter fixed-effect model according to fitting statistics was then modified by comparing its values for the parameters total height (H), diameter at breast height (DBH), and aboveground height (h) to modeling data. Seven alternative prediction strategies were compared using the best new equation in the absence of calibration data, which is often unavailable in forestry practice. The results of this study suggest that because calibration may sometimes be a realistic option, though it is rarely used in practical applications, one of the best strategies for improving the accuracy of volume prediction is the strategy with 7 calculated total heights of 3, 6 and 9 trees in the largest, smallest and medium-size categories, respectively. We cannot use the average trees or dominant trees for calculating the random parameter for further predictions. The method described here will allow the user to make the best choices of taper type and the best random-effect calculated strategy for each practical application and situation at tree level.

  9. Strategies for 4-D Regional Modeling of Water Vapour Using GPS

    Institute of Scientific and Technical Information of China (English)

    S. H. Skone; S.M. Shrestha

    2003-01-01

    Global Positioning System (GPS) signals experience ranging errors due to propagation through the neutral atmosphere. These range delays consist of a hydrostatic component, dependent on air pressure and temperature, and a wet delay dependent on water vapour pressure and temperature.Range delays arising from the hydrostatic component can be computed with accuracies of a few millimeters using existing models, provided that surface barometric or meteorological data are available. By using a regional network of GPS reference stations, it is possible to recover estimates of the Slant Wet Delay to all satellites in view. Observations of the Slant Wet Delay (SWD) can be used to model the vertical and horizontal structure of water vapour over a local area. These techniques are based on a tomographic approach using the SWD as input observables, where 4-D models of the wet refractivity may be derived. This method allows improved resolution of water vapour estimates for precise positioning applications and assimilation into Numerical Weather Predictions (NWP). In this paper we present strategies for real-time modeling of wet refractivity, with simulations and preliminary results of data processing for a regional GPS network in Southern California.

  10. Time Dependent Hadronic Modeling of Flat Spectrum Radio Quasars

    CERN Document Server

    Diltz, Christopher; Fossati, Giovanni

    2015-01-01

    We introduce a new time-dependent lepto-hadronic model for blazar emission that takes into account the radiation emitted by secondary particles, such as pions and muons, from photo hadronic interactions. Starting from a baseline parameter set guided by a fit to the spectral energy distribution of the blazar 3C 279, we perform a parameter study to investigate the effects of perturbations of the input parameters to mimic different flaring events to study the resulting lightcurves in the optical, X-ray, high energy (HE: E > 100 MeV) and very-high-energy (VHE: E > 100 GeV) gamma-rays as well as the neutrino emission associated with charged-pion and muon decay. We find that flaring events from an increase in the efficiency of Fermi II acceleration will produce a positive correlation between all bandpasses and a marked plateau in the HE gamma-ray lightcurve. We also predict a distinctive dip in the HE lightcurve for perturbations caused by a change in the proton injection spectral index. These plateaus / dips could...

  11. Collagen model peptides: Sequence dependence of triple-helix stability.

    Science.gov (United States)

    Persikov, A V; Ramshaw, J A; Brodsky, B

    2000-01-01

    The triple helix is a specialized protein motif, found in all collagens as well as in noncollagenous proteins involved in host defense. Peptides will adopt a triple-helical conformation if the sequence contains its characteristic features of Gly as every third residue and a high content of Pro and Hyp residues. Such model peptides have proved amenable to structural studies by x-ray crystallography and NMR spectroscopy, suitable for thermodynamic and kinetic analysis, and a valuable tool in characterizing the binding activities of the collagen triple helix. A systematic approach to understanding the amino acid sequence dependence of the collagen triple helix has been initiated, based on a set of host-guest peptides of the form, (Gly-Pro-Hyp)(3)-Gly-X-Y-(Gly-Pro-Hyp)(4). Comparison of their thermal stabilities has led to a propensity scale for the X and Y positions, and the additivity of contributions of individual residues is now under investigation. The local and global stability of the collagen triple helix is normally modulated by the residues in the X and Y positions, with every third position occupied by Gly in fibril-forming collagens. However, in collagen diseases, such as osteogenesis imperfecta, a single Gly may be substituted by another residue. Host-guest studies where the Gly is replaced by various amino acids suggest that the identity of the residue in the Gly position affects the degree of destabilization and the clinical severity of the disease.

  12. Solvent-Dependent Pyranopterin Cyclization in Molybdenum Cofactor Model Complexes.

    Science.gov (United States)

    Williams, Benjamin R; Gisewhite, Douglas; Kalinsky, Anna; Esmail, Alisha; Burgmayer, Sharon J Nieter

    2015-09-08

    The conserved pterin dithiolene ligand that coordinates molybdenum (Mo) in the cofactor (Moco) of mononuclear Mo enzymes can exist in both a tricyclic pyranopterin dithiolene form and as a bicyclic pterin-dithiolene form as observed in protein crystal structures of several bacterial molybdoenzymes. Interconversion between the tricyclic and bicyclic forms via pyran scission and cyclization has been hypothesized to play a role in the catalytic mechanism of Moco. Therefore, understanding the interconversion between the tricyclic and bicyclic forms, a type of ring-chain tautomerism, is an important aspect of study to understand its role in catalysis. In this study, equilibrium constants (K(eq)) as well as enthalpy, entropy, and free energy values are obtained for pyran ring tautomerism exhibited by two Moco model complexes, namely, (Et4N)[Tp*Mo(O)(S2BMOPP)] (1) and (Et4N)[Tp*Mo(O)(S2PEOPP)] (2), as a solvent-dependent equilibrium process. Keq values obtained from (1)H NMR data in seven deuterated solvents show a correlation between solvent polarity and tautomer form, where solvents with higher polarity parameters favor the pyran form.

  13. Energy-Dependent Octagonal Lattice Boltzmann Modeling for Compressible Flows

    Science.gov (United States)

    Pavlo, Pavol; Vahala, Linda; Vahala, George

    2000-10-01

    There has been much interest in thermal lattice Boltzmann modeling (TLBM) for compressible flows because of their inherent parallelizeability. Instead of applying CFD techniques to the nonlinear conservation equations, one instead solves a linear BGK kinetic equation. To reduce storage requirements, the velocity space is discretized and lattice geometries are so chosen to minimize the number of degrees of freedom that must be retained in the Chapman-Enskog recovery of the original macroscopic equations. The simplest (and most efficient) TLBM runs at a CFL=1, so that no numerical diffusion or dissipation is introduced. The algorithm involves Lagrangian streaming (shift operator) and purely local operations. Because of the underlying discrete lattice symmetry, the relaxation distributions cannot be Maxwellian and hence the inherent numerical instability problem in TLBM. We are investigating the use of energy-dependent lattices so as to allow simulation of problems of interest in divertor physics, The appeal of TLBM is that it can provide a unified representation for both strongly collisional (‘fluid’) and weakly collisional (‘Monte Carlo’) regimes. Moreover, our TLBM code is more efficiently solved on mulit-PE platforms than the corresponding CFD codes and is readily extended to 3D. MHD can also be handled by TLBM.

  14. A tuned mesh-generation strategy for image representation based on data-dependent triangulation.

    Science.gov (United States)

    Li, Ping; Adams, Michael D

    2013-05-01

    A mesh-generation framework for image representation based on data-dependent triangulation is proposed. The proposed framework is a modified version of the frameworks of Rippa and Garland and Heckbert that facilitates the development of more effective mesh-generation methods. As the proposed framework has several free parameters, the effects of different choices of these parameters on mesh quality are studied, leading to the recommendation of a particular set of choices for these parameters. A mesh-generation method is then introduced that employs the proposed framework with these best parameter choices. This method is demonstrated to produce meshes of higher quality (both in terms of squared error and subjectively) than those generated by several competing approaches, at a relatively modest computational and memory cost.

  15. Optimal Investment Strategy for an Insurer under Mean-Variance in a Dependent Risk Model%保险公司在风险相依模型中均值-方差准则下的最优投资策略*

    Institute of Scientific and Technical Information of China (English)

    谷爱玲; 李仲飞; 申曙光

    2013-01-01

    研究了具有两个业务部门的保险公司的最优投资问题,其中每个业务部门的盈余过程由二维的Lévy过程描述。保险公司可将其盈余投资于金融市场,其中金融市场由一个无风险资产和两个具有风险相关性的风险资产组成,而且风险资产的价格过程由二维的Lévy过程所驱动。文中讨论了两个优化问题。一个是基准问题,即选择适当的投资策略使保险公司的终端财富与一个基准值之差的平方期望最小;另一个是均值-方差(M-V)问题,即在保险公司终端财富给定的情形下,选择适当的投资策略使终端财富的方差最小。利用动态规划的方法,得到第一个优化问题的最优投资策略和最优值函数的解析式。结合第一个优化问题的结果,利用对偶定理得到第二个优化问题的最优投资策略和有效前沿。%Two optimal investment problems for an insurer with two business lines are considered,where each business line's risk process is modeled by two-dimensional Lévy process.It is assumed that the in-surer can invest its surplus in a risk-free asset and two risky assets,where the risky assets'price processes are described by a two-dimensional Lévy process.A benchmark problem and a mean-variance problem are discussed.The first problem is to choose the optimal investment strategy to minimize the expected quadratic distance of the risk reserve to a given benchmark;the second problem is to minimize the vari-ance of the terminal wealth when the expected terminal reserve is given.By employing stochastic dynamic programming approach,the explicit expressions of the optimal investment strategy and the optimal value function are derived for the first problem;with the results of the first problem and the duality theory,the optimal investment strategy and the efficient frontier for the second problem are derived.

  16. What is strategy? The concept and model for its application in the Czech security strategy

    Directory of Open Access Journals (Sweden)

    Jan Ludvík

    2011-06-01

    Full Text Available The article conceptually explains the notion of strategy. Drawing on its understanding by well-established authorities like Carl von Clausewitz, Basil Liddel Hart, André Beaufre, or Colin Gray, the authors discuss strengths and weaknesses of various views. Furthermore, the article employs Arthur Lykke’s definition of strategy to demonstrate various conceptual requirements. Strategy is thus perceived as the relationship among means, ends, and ways. Crucial implications for a development of the Czech strategic documents are further examined. The article argues that, the vital importance of coherent interconnection of all the afore-mentioned parts of the strategy has been so far neglected in this process. It is suggested that particular attention should be paid to the clear formulation of a goal, which is the prerequisite for any meaningful strategy. However, any goals must be developed with the close relation to the available or potentially attainable resources, and purposeful ways how to employ them. The whole process is best described as the hermeneutic circle.

  17. Probabilistic inference: Task dependency and individual differences of probability weighting revealed by hierarchical Bayesian modelling

    Directory of Open Access Journals (Sweden)

    Moritz eBoos

    2016-05-01

    Full Text Available Cognitive determinants of probabilistic inference were examined using hierarchical Bayesian modelling techniques. A classic urn-ball paradigm served as experimental strategy, involving a factorial two (prior probabilities by two (likelihoods design. Five computational models of cognitive processes were compared with the observed behaviour. Parameter-free Bayesian posterior probabilities and parameter-free base rate neglect provided inadequate models of probabilistic inference. The introduction of distorted subjective probabilities yielded more robust and generalizable results. A general class of (inverted S-shaped probability weighting functions had been proposed; however, the possibility of large differences in probability distortions not only across experimental conditions, but also across individuals, seems critical for the model’s success. It also seems advantageous to consider individual differences in parameters of probability weighting as being sampled from weakly informative prior distributions of individual parameter values. Thus, the results from hierarchical Bayesian modelling converge with previous results in revealing that probability weighting parameters show considerable task dependency and individual differences. Methodologically, this work exemplifies the usefulness of hierarchical Bayesian modelling techniques for cognitive psychology. Theoretically, human probabilistic inference might be best described as the application of individualized strategic policies for Bayesian belief revision.

  18. Activation and inflammation markers in HIV-1-infected patients in dependency of treatment strategies

    Directory of Open Access Journals (Sweden)

    R Ehret

    2012-11-01

    Full Text Available Purpose of the study: HIV-1-infected patients have elevated levels of immune activation and systemic inflammatory markers which are partially strong predictors of disease progression or are associated with increased cardiovascular risk. The dependency of anti-retroviral treatment (ART, the usage of NNRTI or PI-based and the application of non-nuc regimens is analysed here on the basis of a dataset (Chronic Inflammation Dependency on TREatment: CIDRE cohort from 1500 patients in Berlin. Methods: In a retrospective analysis we compared relative CD4+ cell counts, viral load, relative CD8+CD38+DR-and CD3+DR+cells, concentration of high-sensitivity C-reactive protein (hsCRP and interleukin-6 (IL-6 in therapy-naïve or treated patients dependent on usage or non-usage of NUCs, PI or NNRTI. Statistics were performed with R (R Core Team; 2012; R: A language and environment for statistical computing using Wilcoxon rank sum test in two-sided analysis. Summary of results: As to expect, ART-naïve patients (n=190 had significantly higher viral loads and lower CD4+cell counts (p: both<0.05 and showed higher activation levels than treated patient (CD8+CD38+DR- and CD3+DR+both<0.05. But no significant difference was calculated for hsCRP or IL-6. Nuc-sparing regimen (n=46 did not show any distinction compared to nuc-containing therapies (n=1249 for the analysed parameters. Significant differences were detected for PI-regimen (n=711 with lower CD4+ cell counts and higher activation (CD8+38+DR-, CD3+DR+ and IL-6 (p: all<0.05 but not for hsCRP (p=0.39. The opposite was true for NNRTI-based therapies (n=445 with higher CD4+ cell percentages and lower activation and inflammation markers (p: all<0.05 and as well no difference in hsCRP (p=0.97 compared with all other treated patients. Conclusions: The lack of differences between therapy-naïve patients and patients on ART for inflammation markers may be due to the relative good immunological state of the first group

  19. Dependence in probabilistic modeling, Dempster-Shafer theory, and probability bounds analysis.

    Energy Technology Data Exchange (ETDEWEB)

    Oberkampf, William Louis; Tucker, W. Troy (Applied Biomathematics, Setauket, NY); Zhang, Jianzhong (Iowa State University, Ames, IA); Ginzburg, Lev (Applied Biomathematics, Setauket, NY); Berleant, Daniel J. (Iowa State University, Ames, IA); Ferson, Scott (Applied Biomathematics, Setauket, NY); Hajagos, Janos (Applied Biomathematics, Setauket, NY); Nelsen, Roger B. (Lewis & Clark College, Portland, OR)

    2004-10-01

    This report summarizes methods to incorporate information (or lack of information) about inter-variable dependence into risk assessments that use Dempster-Shafer theory or probability bounds analysis to address epistemic and aleatory uncertainty. The report reviews techniques for simulating correlated variates for a given correlation measure and dependence model, computation of bounds on distribution functions under a specified dependence model, formulation of parametric and empirical dependence models, and bounding approaches that can be used when information about the intervariable dependence is incomplete. The report also reviews several of the most pervasive and dangerous myths among risk analysts about dependence in probabilistic models.

  20. Time-dependent evolution of rock slopes by a multi-modelling approach

    Science.gov (United States)

    Bozzano, F.; Della Seta, M.; Martino, S.

    2016-06-01

    This paper presents a multi-modelling approach that incorporates contributions from morpho-evolutionary modelling, detailed engineering-geological modelling and time-dependent stress-strain numerical modelling to analyse the rheological evolution of a river valley slope over approximately 102 kyr. The slope is located in a transient, tectonically active landscape in southwestern Tyrrhenian Calabria (Italy), where gravitational processes drive failures in rock slopes. Constraints on the valley profile development were provided by a morpho-evolutionary model based on the correlation of marine and river strath terraces. Rock mass classes were identified through geomechanical parameters that were derived from engineering-geological surveys and outputs of a multi-sensor slope monitoring system. The rock mass classes were associated to lithotechnical units to obtain a high-resolution engineering-geological model along a cross section of the valley. Time-dependent stress-strain numerical modelling reproduced the main morpho-evolutionary stages of the valley slopes. The findings demonstrate that a complex combination of eustatism, uplift and Mass Rock Creep (MRC) deformations can lead to first-time failures of rock slopes when unstable conditions are encountered up to the generation of stress-controlled shear zones. The multi-modelling approach enabled us to determine that such complex combinations may have been sufficient for the first-time failure of the S. Giovanni slope at approximately 140 ka (MIS 7), even without invoking any trigger. Conversely, further reactivations of the landslide must be related to triggers such as earthquakes, rainfall and anthropogenic activities. This failure involved a portion of the slope where a plasticity zone resulted from mass rock creep that evolved with a maximum strain rate of 40% per thousand years, after the formation of a river strath terrace. This study demonstrates that the multi-modelling approach presented herein is a useful

  1. A numerical strategy for modelling rotating stall in core compressors

    Science.gov (United States)

    Vahdati, M.

    2007-03-01

    The paper will focus on one specific core-compressor instability, rotating stall, because of the pressing industrial need to improve current design methods. The determination of the blade response during rotating stall is a difficult problem for which there is no reliable procedure. During rotating stall, the blades encounter the stall cells and the excitation depends on the number, size, exact shape and rotational speed of these cells. The long-term aim is to minimize the forced response due to rotating stall excitation by avoiding potential matches between the vibration modes and the rotating stall pattern characteristics. Accurate numerical simulations of core-compressor rotating stall phenomena require the modelling of a large number of bladerows using grids containing several tens of millions of points. The time-accurate unsteady-flow computations may need to be run for several engine revolutions for rotating stall to get initiated and many more before it is fully developed. The difficulty in rotating stall initiation arises from a lack of representation of the triggering disturbances which are inherently present in aeroengines. Since the numerical model represents a symmetric assembly, the only random mechanism for rotating stall initiation is provided by numerical round-off errors. In this work, rotating stall is initiated by introducing a small amount of geometric mistuning to the rotor blades. Another major obstacle in modelling flows near stall is the specification of appropriate upstream and downstream boundary conditions. Obtaining reliable boundary conditions for such flows can be very difficult. In the present study, the low-pressure compression (LPC) domain is placed upstream of the core compressor. With such an approach, only far field atmospheric boundary conditions are specified which are obtained from aircraft speed and altitude. A chocked variable-area nozzle, placed after the last compressor bladerow in the model, is used to impose boundary

  2. Lattice Discrete Particle Model (LDPM) for pressure-dependent inelasticity in granular rocks

    CERN Document Server

    Ashari, Shiva Esna; Cusatis, Gianluca

    2016-01-01

    This paper deals with the formulation, calibration, and validation of a Lattice Discrete Particle Model (LDPM) for the simulation of the pressure-dependent inelastic response of granular rocks. LDPM is formulated in the framework of discrete mechanics and it simulates the heterogeneous deformation of cemented granular systems by means of discrete compatibility/equilibrium equations defined at the grain scale. A numerical strategy is proposed to generate a realistic microstructure based on the actual grain size distribution of a sandstone and the capabilities of the method are illustrated with reference to the particular case of Bleurswiller sandstone, i.e. a granular rock that has been extensively studied at the laboratory scale. LDPM micromechanical parameters are calibrated based on evidences from triaxial experiments, such as hydrostatic compression, brittle failure at low confinement and plastic behavior at high confinement. Results show that LDPM allows exploring the effect of fine-scale heterogeneity on...

  3. Input-dependent wave attenuation in a critically-balanced model of cortex.

    Directory of Open Access Journals (Sweden)

    Xiao-Hu Yan

    Full Text Available A number of studies have suggested that many properties of brain activity can be understood in terms of critical systems. However it is still not known how the long-range susceptibilities characteristic of criticality arise in the living brain from its local connectivity structures. Here we prove that a dynamically critically-poised model of cortex acquires an infinitely-long ranged susceptibility in the absence of input. When an input is presented, the susceptibility attenuates exponentially as a function of distance, with an increasing spatial attenuation constant (i.e., decreasing range the larger the input. This is in direct agreement with recent results that show that waves of local field potential activity evoked by single spikes in primary visual cortex of cat and macaque attenuate with a characteristic length that also increases with decreasing contrast of the visual stimulus. A susceptibility that changes spatial range with input strength can be thought to implement an input-dependent spatial integration: when the input is large, no additional evidence is needed in addition to the local input; when the input is weak, evidence needs to be integrated over a larger spatial domain to achieve a decision. Such input-strength-dependent strategies have been demonstrated in visual processing. Our results suggest that input-strength dependent spatial integration may be a natural feature of a critically-balanced cortical network.

  4. Extraversion differentiates between model-based and model-free strategies in a reinforcement learning task

    Directory of Open Access Journals (Sweden)

    Anya eSkatova

    2013-09-01

    Full Text Available Prominent computational models describe a neural mechanism for learning from reward prediction errors, and it has been suggested that variations in this mechanism are reflected in personality factors such as trait extraversion. However, although trait extraversion has been linked to improved reward learning, it is not yet known whether this relationship is selective for the particular computational strategy associated with error-driven learning, known as model-free reinforcement learning, versus another strategy, model-based learning, which the brain is also known to employ. In the present study we test this relationship by examining whether humans’ scores on an extraversion scale predict individual differences in the balance between model-based and model-free learning strategies in a sequentially structured decision task designed to distinguish between them. In previous studies with this task, participants have shown a combination of both types of learning, but with substantial individual variation in the balance between them. In the current study, extraversion predicted worse behavior across both sorts of learning. However, the hypothesis that extraverts would be selectively better at model-free reinforcement learning held up among a subset of the more engaged participants, and overall, higher task engagement was associated with a more selective pattern by which extraversion predicted better model-free learning. The findings indicate a relationship between a broad personality orientation and detailed computational learning mechanisms. Results like those in the present study suggest an intriguing and rich relationship between core neuro-computational mechanisms and broader life orientations and outcomes.

  5. Identifying Multiple Levels of Discussion-Based Teaching Strategies for Constructing Scientific Models

    Science.gov (United States)

    Williams, Grant; Clement, John

    2015-01-01

    This study sought to identify specific types of discussion-based strategies that two successful high school physics teachers using a model-based approach utilized in attempting to foster students' construction of explanatory models for scientific concepts. We found evidence that, in addition to previously documented dialogical strategies that teachers utilize to engage students in effectively communicating their scientific ideas in class, there is a second level of more cognitively focused model-construction-supporting strategies that these teachers utilized in attempting to foster students' learning. A further distinction between macro and micro strategy levels within the set of cognitive strategies is proposed. The relationships between the resulting three levels of strategies are portrayed in a diagramming system that tracks discussions over time. The study attempts to contribute to a clearer understanding of how discussion-leading strategies may be used to scaffold the development of conceptual understanding.

  6. Strategies and models for agricultural sustainability in developing Asian countries.

    Science.gov (United States)

    Kesavan, P C; Swaminathan, M S

    2008-02-27

    The green revolution of the 1960s and 1970s which resulted in dramatic yield increases in the developing Asian countries is now showing signs of fatigue in productivity gains. Intensive agriculture practiced without adherence to the scientific principles and ecological aspects has led to loss of soil health, and depletion of freshwater resources and agrobiodiversity. With progressive diversion of arable land for non-agricultural purposes, the challenge of feeding the growing population without, at the same time, annexing more forestland and depleting the rest of life is indeed daunting. Further, even with food availability through production/procurement, millions of marginal farming, fishing and landless rural families have very low or no access to food due to lack of income-generating livelihoods. Approximately 200 million rural women, children and men in India alone fall in this category. Under these circumstances, the evergreen revolution (pro-nature, pro-poor, pro-women and pro-employment/livelihood oriented ecoagriculture) under varied terms are proposed for achieving productivity in perpetuity. In the proposed 'biovillage paradigm', eco-friendly agriculture is promoted along with on- and non-farm eco-enterprises based on sustainable management of natural resources. Concurrently, the modern ICT-based village knowledge centres provide time- and locale-specific, demand-driven information needed for evergreen revolution and ecotechnologies. With a system of 'farm and marine production by masses', the twin goals of ecoagriculture and eco-livelihoods are addressed. The principles, strategies and models of these are briefly discussed in this paper.

  7. Neural underpinnings of decision strategy selection: a review and a theoretical model

    Directory of Open Access Journals (Sweden)

    Szymon Wichary

    2016-11-01

    Full Text Available In multi-attribute choice, decision makers use various decision strategies to arrive at the final choice. What are the neural mechanisms underlying decision strategy selection? The first goal of this paper is to provide a literature review on the neural underpinnings and cognitive models of decision strategy selection and thus set the stage for a unifying neurocognitive model of this process. The second goal is to outline such a unifying, mechanistic model that can explain the impact of noncognitive factors (e.g. affect, stress on strategy selection. To this end, we review the evidence for the factors influencing strategy selection, the neural basis of strategy use and the cognitive models explaining this process. We also present the neurocognitive Bottom-Up Model of Strategy Selection (BUMSS. The model assumes that the use of the rational, normative Weighted Additive strategy and the boundedly rational heuristic Take The Best can be explained by one unifying, neurophysiologically plausible mechanism, based on the interaction of the frontoparietal network, orbitofrontal cortex, anterior cingulate cortex and the brainstem nucleus locus coeruleus. According to BUMSS, there are three processes that form the bottom-up mechanism of decision strategy selection and lead to the final choice: 1 cue weight computation, 2 gain modulation, and 3 weighted additive evaluation of alternatives. We discuss how these processes might be implemented in the brain, and how this knowledge allows us to formulate novel predictions linking strategy use and neurophysiological indices.

  8. Neural Underpinnings of Decision Strategy Selection: A Review and a Theoretical Model

    Science.gov (United States)

    Wichary, Szymon; Smolen, Tomasz

    2016-01-01

    In multi-attribute choice, decision makers use decision strategies to arrive at the final choice. What are the neural mechanisms underlying decision strategy selection? The first goal of this paper is to provide a literature review on the neural underpinnings and cognitive models of decision strategy selection and thus set the stage for a neurocognitive model of this process. The second goal is to outline such a unifying, mechanistic model that can explain the impact of noncognitive factors (e.g., affect, stress) on strategy selection. To this end, we review the evidence for the factors influencing strategy selection, the neural basis of strategy use and the cognitive models of this process. We also present the Bottom-Up Model of Strategy Selection (BUMSS). The model assumes that the use of the rational Weighted Additive strategy and the boundedly rational heuristic Take The Best can be explained by one unifying, neurophysiologically plausible mechanism, based on the interaction of the frontoparietal network, orbitofrontal cortex, anterior cingulate cortex and the brainstem nucleus locus coeruleus. According to BUMSS, there are three processes that form the bottom-up mechanism of decision strategy selection and lead to the final choice: (1) cue weight computation, (2) gain modulation, and (3) weighted additive evaluation of alternatives. We discuss how these processes might be implemented in the brain, and how this knowledge allows us to formulate novel predictions linking strategy use and neural signals. PMID:27877103

  9. Statistical modelling of spatio-temporal dependencies in NGS data

    NARCIS (Netherlands)

    Ranciati, Saverio

    2016-01-01

    Next-generation sequencing (NGS) heeft zich snel gevestigd als de huidige standaard in de genetische analyse. Deze omschakeling van microarray naar NGS vereist nieuwe statistische strategieën om de onderzoeksvragen aan te pakken. Ten eerste, NGS data bestaat uit discrete waarnemingen, meestal gekenm

  10. Can neuromuscular fatigue explain running strategies and performance in ultra-marathons?: the flush model.

    Science.gov (United States)

    Millet, Guillaume Y

    2011-06-01

    While the industrialized world adopts a largely sedentary lifestyle, ultra-marathon running races have become increasingly popular in the last few years in many countries. The ability to run long distances is also considered to have played a role in human evolution. This makes the issue of ultra-long distance physiology important. In the ability to run multiples of 10 km (up to 1000 km in one stage), fatigue resistance is critical. Fatigue is generally defined as strength loss (i.e. a decrease in maximal voluntary contraction [MVC]), which is known to be dependent on the type of exercise. Critical task variables include the intensity and duration of the activity, both of which are very specific to ultra-endurance sports. They also include the muscle groups involved and the type of muscle contraction, two variables that depend on the sport under consideration. The first part of this article focuses on the central and peripheral causes of the alterations to neuromuscular function that occur in ultra-marathon running. Neuromuscular function evaluation requires measurements of MVCs and maximal electrical/magnetic stimulations; these provide an insight into the factors in the CNS and the muscles implicated in fatigue. However, such measurements do not necessarily predict how muscle function may influence ultra-endurance running and whether this has an effect on speed regulation during a real competition (i.e. when pacing strategies are involved). In other words, the nature of the relationship between fatigue as measured using maximal contractions/stimulation and submaximal performance limitation/regulation is questionable. To investigate this issue, we are suggesting a holistic model in the second part of this article. This model can be applied to all endurance activities, but is specifically adapted to ultra-endurance running: the flush model. This model has the following four components: (i) the ball-cock (or buoy), which can be compared with the rate of perceived

  11. Results of epidemic simulation modeling to evaluate strategies to control an outbreak of foot-and-mouth disease.

    Science.gov (United States)

    Bates, Thomas W; Thurmond, Mark C; Carpenter, Tim E

    2003-02-01

    To assess estimated effectiveness of control and eradication procedures for foot-and-mouth disease (FMD) in a region of California. 2,238 herds and 5 sale yards in Fresno, Kings, andTulare counties of California. A spatial stochastic model was used to simulate hypothetical epidemics of FMD for specified control scenarios that included a baseline eradication strategy mandated by USDA and supplemental control strategies of slaughter or vaccination of all animals within a specified distance of infected herds, slaughter of only high-risk animals identified by use of a model simulation, and expansion of infected and surveillance zones. Median number of herds affected varied from 1 to 385 (17% of all herds), depending on type of index herd and delay in diagnosis of FMD. Percentage of herds infected decreased from that of the baseline eradication strategy by expanding the designated infected area from 10 to 20 km (48%), vaccinating within a 50-km radius of an infected herd (41%), slaughtering the 10 highest-risk herds for each infected herd (39%), and slaughtering all animals within 5 km of an infected herd (24%). Results for the model provided a means of assessing the relative merits of potential strategies for control and eradication of FMD should it enter the US livestock population. For the study region, preemptive slaughter of highest-risk herds and vaccination of all animals within a specified distance of an infected herd consistently decreased size and duration of an epidemic, compared with the baseline eradication strategy.

  12. Strategies to Automatically Derive a Process Model from a Configurable Process Model Based on Event Data

    Directory of Open Access Journals (Sweden)

    Mauricio Arriagada-Benítez

    2017-10-01

    Full Text Available Configurable process models are frequently used to represent business workflows and other discrete event systems among different branches of large organizations: they unify commonalities shared by all branches and describe their differences, at the same time. The configuration of such models is usually done manually, which is challenging. On the one hand, when the number of configurable nodes in the configurable process model grows, the size of the search space increases exponentially. On the other hand, the person performing the configuration may lack the holistic perspective to make the right choice for all configurable nodes at the same time, since choices influence each other. Nowadays, information systems that support the execution of business processes create event data reflecting how processes are performed. In this article, we propose three strategies (based on exhaustive search, genetic algorithms and a greedy heuristic that use event data to automatically derive a process model from a configurable process model that better represents the characteristics of the process in a specific branch. These strategies have been implemented in our proposed framework and tested in both business-like event logs as recorded in a higher educational enterprise resource planning system and a real case scenario involving a set of Dutch municipalities.

  13. Lagrangian velocity statistics of directed launch strategies in a Gulf of Mexico model

    Directory of Open Access Journals (Sweden)

    M. Toner

    2004-01-01

    Full Text Available The spatial dependence of Lagrangian displacement and velocity statistics is studied in the context of a data assimilating numerical model of the Gulf Mexico. In the active eddy region of the Western Gulf, a combination of Eulerian and Lagrangian measures are used to locate strongly hyperbolic regions of the flow. The statistics of the velocity field sampled by sets of drifters launched specifically in these hyperbolic regions are compared to those produced by randomly chosen launch sites. The results show that particle trajectories initialized in hyperbolic regions preferentially sample a broader range of Eulerian velocities than do members of ensembles of randomly launched drifters. The velocity density functions produced by the directed launches compare well with Eulerian velocity pdfs. Implications for the development of launch strategies to improve Eulerian velocity field reconstruction from drifter data are discussed.

  14. A Moderated Mediation Model: Racial Discrimination, Coping Strategies, and Racial Identity among Black Adolescents

    Science.gov (United States)

    Seaton, Eleanor K.; Upton, Rachel; Gilbert, Adrianne; Volpe, Vanessa

    2014-01-01

    This study examined a moderated mediation model among 314 Black adolescents aged 13-18. The model included general coping strategies (e.g., active, distracting, avoidant, and support-seeking strategies) as mediators and racial identity dimensions (racial centrality, private regard, public regard, minority, assimilationist, and humanist ideologies)…

  15. A Moderated Mediation Model: Racial Discrimination, Coping Strategies, and Racial Identity among Black Adolescents

    Science.gov (United States)

    Seaton, Eleanor K.; Upton, Rachel; Gilbert, Adrianne; Volpe, Vanessa

    2014-01-01

    This study examined a moderated mediation model among 314 Black adolescents aged 13-18. The model included general coping strategies (e.g., active, distracting, avoidant, and support-seeking strategies) as mediators and racial identity dimensions (racial centrality, private regard, public regard, minority, assimilationist, and humanist ideologies)…

  16. Sales Training for Army Recruiter Success: Modeling the Sales Strategies and Skills of Excellent Recruiters

    Science.gov (United States)

    1987-11-01

    strategies used by excellent Army recruiters. Neurolinguistic programming (NLP) was used as the protocol for modeling performance and acquiring...Behavioral and Social Sciences 3001 Eisenhower Avenue, Alexandria, VA 22333-5600 10. PROGRAM ELEMENT. PROJECT. TASK ARE* 4 WORK UNIT...Modeling ’Expert knowledge,, Neurolinguistics Knowledge engineering; Recruiting Sales, &’ Sales cycle Sales skills Sales strategies 20

  17. Regression modeling strategies with applications to linear models, logistic and ordinal regression, and survival analysis

    CERN Document Server

    Harrell , Jr , Frank E

    2015-01-01

    This highly anticipated second edition features new chapters and sections, 225 new references, and comprehensive R software. In keeping with the previous edition, this book is about the art and science of data analysis and predictive modeling, which entails choosing and using multiple tools. Instead of presenting isolated techniques, this text emphasizes problem solving strategies that address the many issues arising when developing multivariable models using real data and not standard textbook examples. It includes imputation methods for dealing with missing data effectively, methods for fitting nonlinear relationships and for making the estimation of transformations a formal part of the modeling process, methods for dealing with "too many variables to analyze and not enough observations," and powerful model validation techniques based on the bootstrap.  The reader will gain a keen understanding of predictive accuracy, and the harm of categorizing continuous predictors or outcomes.  This text realistically...

  18. Development of a Pressure-Dependent Constitutive Model with Combined Multilinear Kinematic and Isotropic Hardening

    Science.gov (United States)

    Allen Phillip A.; Wilson, Christopher D.

    2003-01-01

    The development of a pressure-dependent constitutive model with combined multilinear kinematic and isotropic hardening is presented. The constitutive model is developed using the ABAQUS user material subroutine (UMAT). First the pressure-dependent plasticity model is derived. Following this, the combined bilinear and combined multilinear hardening equations are developed for von Mises plasticity theory. The hardening rule equations are then modified to include pressure dependency. The method for implementing the new constitutive model into ABAQUS is given.

  19. Path planning versus cue responding: a bio-inspired model of switching between navigation strategies.

    Science.gov (United States)

    Dollé, Laurent; Sheynikhovich, Denis; Girard, Benoît; Chavarriaga, Ricardo; Guillot, Agnès

    2010-10-01

    In this article, we describe a new computational model of switching between path-planning and cue-guided navigation strategies. It is based on three main assumptions: (i) the strategies are mediated by separate memory systems that learn independently and in parallel; (ii) the learning algorithms are different in the two memory systems-the cue-guided strategy uses a temporal-difference (TD) learning rule to approach a visible goal, whereas the path-planning strategy relies on a place-cell-based graph-search algorithm to learn the location of a hidden goal; (iii) a strategy selection mechanism uses TD-learning rule to choose the most successful strategy based on past experience. We propose a novel criterion for strategy selection based on the directions of goal-oriented movements suggested by the different strategies. We show that the selection criterion based on this "common currency" is capable of choosing the best among TD-learning and planning strategies and can be used to solve navigational tasks in continuous state and action spaces. The model has been successfully applied to reproduce rat behavior in two water-maze tasks in which the two strategies were shown to interact. The model was used to analyze competitive and cooperative interactions between different strategies during these tasks as well as relative influence of different types of sensory cues.

  20. A Cognitive Modeling Approach to Strategy Formation in Dynamic Decision Making.

    Science.gov (United States)

    Prezenski, Sabine; Brechmann, André; Wolff, Susann; Russwinkel, Nele

    2017-01-01

    Decision-making is a high-level cognitive process based on cognitive processes like perception, attention, and memory. Real-life situations require series of decisions to be made, with each decision depending on previous feedback from a potentially changing environment. To gain a better understanding of the underlying processes of dynamic decision-making, we applied the method of cognitive modeling on a complex rule-based category learning task. Here, participants first needed to identify the conjunction of two rules that defined a target category and later adapt to a reversal of feedback contingencies. We developed an ACT-R model for the core aspects of this dynamic decision-making task. An important aim of our model was that it provides a general account of how such tasks are solved and, with minor changes, is applicable to other stimulus materials. The model was implemented as a mixture of an exemplar-based and a rule-based approach which incorporates perceptual-motor and metacognitive aspects as well. The model solves the categorization task by first trying out one-feature strategies and then, as a result of repeated negative feedback, switching to two-feature strategies. Overall, this model solves the task in a similar way as participants do, including generally successful initial learning as well as reversal learning after the change of feedback contingencies. Moreover, the fact that not all participants were successful in the two learning phases is also reflected in the modeling data. However, we found a larger variance and a lower overall performance of the modeling data as compared to the human data which may relate to perceptual preferences or additional knowledge and rules applied by the participants. In a next step, these aspects could be implemented in the model for a better overall fit. In view of the large interindividual differences in decision performance between participants, additional information about the underlying cognitive processes from

  1. A Cognitive Modeling Approach to Strategy Formation in Dynamic Decision Making

    Science.gov (United States)

    Prezenski, Sabine; Brechmann, André; Wolff, Susann; Russwinkel, Nele

    2017-01-01

    Decision-making is a high-level cognitive process based on cognitive processes like perception, attention, and memory. Real-life situations require series of decisions to be made, with each decision depending on previous feedback from a potentially changing environment. To gain a better understanding of the underlying processes of dynamic decision-making, we applied the method of cognitive modeling on a complex rule-based category learning task. Here, participants first needed to identify the conjunction of two rules that defined a target category and later adapt to a reversal of feedback contingencies. We developed an ACT-R model for the core aspects of this dynamic decision-making task. An important aim of our model was that it provides a general account of how such tasks are solved and, with minor changes, is applicable to other stimulus materials. The model was implemented as a mixture of an exemplar-based and a rule-based approach which incorporates perceptual-motor and metacognitive aspects as well. The model solves the categorization task by first trying out one-feature strategies and then, as a result of repeated negative feedback, switching to two-feature strategies. Overall, this model solves the task in a similar way as participants do, including generally successful initial learning as well as reversal learning after the change of feedback contingencies. Moreover, the fact that not all participants were successful in the two learning phases is also reflected in the modeling data. However, we found a larger variance and a lower overall performance of the modeling data as compared to the human data which may relate to perceptual preferences or additional knowledge and rules applied by the participants. In a next step, these aspects could be implemented in the model for a better overall fit. In view of the large interindividual differences in decision performance between participants, additional information about the underlying cognitive processes from

  2. A Cognitive Modeling Approach to Strategy Formation in Dynamic Decision Making

    Directory of Open Access Journals (Sweden)

    Sabine Prezenski

    2017-08-01

    Full Text Available Decision-making is a high-level cognitive process based on cognitive processes like perception, attention, and memory. Real-life situations require series of decisions to be made, with each decision depending on previous feedback from a potentially changing environment. To gain a better understanding of the underlying processes of dynamic decision-making, we applied the method of cognitive modeling on a complex rule-based category learning task. Here, participants first needed to identify the conjunction of two rules that defined a target category and later adapt to a reversal of feedback contingencies. We developed an ACT-R model for the core aspects of this dynamic decision-making task. An important aim of our model was that it provides a general account of how such tasks are solved and, with minor changes, is applicable to other stimulus materials. The model was implemented as a mixture of an exemplar-based and a rule-based approach which incorporates perceptual-motor and metacognitive aspects as well. The model solves the categorization task by first trying out one-feature strategies and then, as a result of repeated negative feedback, switching to two-feature strategies. Overall, this model solves the task in a similar way as participants do, including generally successful initial learning as well as reversal learning after the change of feedback contingencies. Moreover, the fact that not all participants were successful in the two learning phases is also reflected in the modeling data. However, we found a larger variance and a lower overall performance of the modeling data as compared to the human data which may relate to perceptual preferences or additional knowledge and rules applied by the participants. In a next step, these aspects could be implemented in the model for a better overall fit. In view of the large interindividual differences in decision performance between participants, additional information about the underlying

  3. Modeling Earth's Disk-Integrated, Time-Dependent Spectrum: Applications to Directly Imaged Habitable Planets

    Science.gov (United States)

    Lustig-Yaeger, Jacob; Schwieterman, Edward; Meadows, Victoria; Fujii, Yuka; NAI Virtual Planetary Laboratory, ISSI 'The Exo-Cartography Inverse Problem'

    2016-10-01

    Earth is our only example of a habitable world and is a critical reference point for potentially habitable exoplanets. While disk-averaged views of Earth that mimic exoplanet data can be obtained by interplanetary spacecraft, these datasets are often restricted in wavelength range, and are limited to the Earth phases and viewing geometries that the spacecraft can feasibly access. We can overcome these observational limitations using a sophisticated UV-MIR spectral model of Earth that has been validated against spacecraft observations in wavelength-dependent brightness and phase (Robinson et al., 2011; 2014). This model can be used to understand the information content – and the optimal means for extraction of that information – for multi-wavelength, time-dependent, disk-averaged observations of the Earth. In this work, we explore key telescope parameters and observing strategies that offer the greatest insight into the wavelength-, phase-, and rotationally-dependent variability of Earth as if it were an exoplanet. Using a generalized coronagraph instrument simulator (Robinson et al., 2016), we synthesize multi-band, time-series observations of the Earth that are consistent with large space-based telescope mission concepts, such as the Large UV/Optical/IR (LUVOIR) Surveyor. We present fits to this dataset that leverage the rotationally-induced variability to infer the number of large-scale planetary surface types, as well as their respective longitudinal distributions and broadband albedo spectra. Finally, we discuss the feasibility of using such methods to identify and map terrestrial exoplanets surfaces with the next generation of space-based telescopes.

  4. Thermal site descriptive model. A strategy for the model development during site investigations - version 2

    Energy Technology Data Exchange (ETDEWEB)

    Back, Paer-Erik; Sundberg, Jan [Geo Innova AB (Sweden)

    2007-09-15

    This report presents a strategy for describing, predicting and visualising the thermal aspects of the site descriptive model. The strategy is an updated version of an earlier strategy applied in all SDM versions during the initial site investigation phase at the Forsmark and Oskarshamn areas. The previous methodology for thermal modelling did not take the spatial correlation fully into account during simulation. The result was that the variability of thermal conductivity in the rock mass was not sufficiently well described. Experience from earlier thermal SDMs indicated that development of the methodology was required in order describe the spatial distribution of thermal conductivity in the rock mass in a sufficiently reliable way, taking both variability within rock types and between rock types into account. A good description of the thermal conductivity distribution is especially important for the lower tail. This tail is important for the design of a repository because it affects the canister spacing. The presented approach is developed to be used for final SDM regarding thermal properties, primarily thermal conductivity. Specific objectives for the strategy of thermal stochastic modelling are: Description: statistical description of the thermal conductivity of a rock domain. Prediction: prediction of thermal conductivity in a specific rock volume. Visualisation: visualisation of the spatial distribution of thermal conductivity. The thermal site descriptive model should include the temperature distribution and thermal properties of the rock mass. The temperature is the result of the thermal processes in the repository area. Determination of thermal transport properties can be made using different methods, such as laboratory investigations, field measurements, modelling from mineralogical composition and distribution, modelling from density logging and modelling from temperature logging. The different types of data represent different scales, which has to be

  5. Dose-Dependent Model of Caffeine Effects on Human Vigilance during Total Sleep Deprivation

    Science.gov (United States)

    2014-05-20

    Dose-dependent model of caffeine effects on human vigilance during total sleep deprivation Sridhar Ramakrishnan a, Srinivas Laxminarayan a, Nancy J...We modeled the dose-dependent effects of caffeine on human vigilance. The model predicted the effects of both single and repeated caffeine doses...We developed and validated the model using two laboratory studies. Individual-specific caffeine models outperformed population-average models. a

  6. Nuclear mass dependence of chaotic dynamics in Ginocchio model

    CERN Document Server

    Yoshinaga, N; Shigehara, T; Yoshinaga, Naotaka; Yoshida, Nobuaki; Shigehara, Takaomi

    1995-01-01

    The chaotic dynamics in nuclear collective motion is studied in the framework of a schematic shell model which has only monopole and quadrupole degrees of freedom. The model is shown to reproduce the experimentally observed global trend toward less chaotic motion in heavier nuclei. The relation between current approach and the earlier studies with bosonic models is discussed.

  7. Temperature-dependent rate models of vascular cambium cell mortality

    Science.gov (United States)

    Matthew B. Dickinson; Edward A. Johnson

    2004-01-01

    We use two rate-process models to describe cell mortality at elevated temperatures as a means of understanding vascular cambium cell death during surface fires. In the models, cell death is caused by irreversible damage to cellular molecules that occurs at rates that increase exponentially with temperature. The models differ in whether cells show cumulative effects of...

  8. Thermodynamic Modeling as a Strategy for Casting High Alloy Steels

    Institute of Scientific and Technical Information of China (English)

    Peri Reddy V; S Raman Sankaranarayanan

    2009-01-01

    Strategies based on thermodynamic calculations can be used to overcome the problems associated with oxides encountered in steel plant operations, which can lead to certain difficulties in the process such as clogging of submerged entry nozzle during continuous casting. Approaches to producing high alloy steels by continuous casting have been taken. One of the strategies to avoid the oxidation of chromium is to add a small amount of other elements (subject to other constraints), which do not cause subsequent problems. The problem has been studied using the Thermo-CalcR software, with related databases; and the results obtained for different process conditions or generic com-positions have been presented.

  9. A dependence modelling study of extreme rainfall in Madeira Island

    Science.gov (United States)

    Gouveia-Reis, Délia; Guerreiro Lopes, Luiz; Mendonça, Sandra

    2016-08-01

    The dependence between variables plays a central role in multivariate extremes. In this paper, spatial dependence of Madeira Island's rainfall data is addressed within an extreme value copula approach through an analysis of maximum annual data. The impact of altitude, slope orientation, distance between rain gauge stations and distance from the stations to the sea are investigated for two different periods of time. The results obtained highlight the influence of the island's complex topography on the spatial distribution of extreme rainfall in Madeira Island.

  10. Modeling in the quality by design environment: Regulatory requirements and recommendations for design space and control strategy appointment.

    Science.gov (United States)

    Djuris, Jelena; Djuric, Zorica

    2017-06-01

    Mathematical models can be used as an integral part of the quality by design (QbD) concept throughout the product lifecycle for variety of purposes, including appointment of the design space and control strategy, continual improvement and risk assessment. Examples of different mathematical modeling techniques (mechanistic, empirical and hybrid) in the pharmaceutical development and process monitoring or control are provided in the presented review. In the QbD context, mathematical models are predominantly used to support design space and/or control strategies. Considering their impact to the final product quality, models can be divided into the following categories: high, medium and low impact models. Although there are regulatory guidelines on the topic of modeling applications, review of QbD-based submission containing modeling elements revealed concerns regarding the scale-dependency of design spaces and verification of models predictions at commercial scale of manufacturing, especially regarding real-time release (RTR) models. Authors provide critical overview on the good modeling practices and introduce concepts of multiple-unit, adaptive and dynamic design space, multivariate specifications and methods for process uncertainty analysis. RTR specification with mathematical model and different approaches to multivariate statistical process control supporting process analytical technologies are also presented. Copyright © 2017 Elsevier B.V. All rights reserved.

  11. A dependent stress-strength interference model based on mixed copula function

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Jian Xiong; An, Zong Wen; Liu, Bo [School of Mechatronics Engineering, Lanzhou University of Technology, Lanzhou (China)

    2016-10-15

    In the traditional Stress-strength interference (SSI) model, stress and strength must satisfy the basic assumption of mutual independence. However, a complex dependence between stress and strength exists in practical engineering. To evaluate structural reliability under the case that stress and strength are dependent, a mixed copula function is introduced to a new dependent SSI model. This model can fully characterize the dependence between stress and strength. The residual square sum method and genetic algorithm are also used to estimate the unknown parameters of the model. Finally, the validity of the proposed model is demonstrated via a practical case. Results show that traditional SSI model ignoring the dependence between stress and strength more easily overestimates product reliability than the new dependent SSI model.

  12. Siglec-F-dependent negative regulation of allergen-induced eosinophilia depends critically on the experimental model.

    Science.gov (United States)

    McMillan, Sarah J; Richards, Hannah E; Crocker, Paul R

    2014-07-01

    Siglec-8 and siglec-F are paralogous membrane proteins expressed on human and murine eosinophils respectively. They bind similar sialylated and sulphated glycans and mediate eosinophil apoptosis when cross-linked with antibodies or glycan ligands. In models of allergic eosinophilic airway inflammation, siglec-F was shown previously to be important for negatively regulating eosinophilia. It was proposed that this was due to siglec-F-dependent apoptosis, triggered via engagement with ligands that are upregulated on bronchial epithelium. Our aim was to further investigate the functions of siglec-F by comparing two commonly used models of ovalbumin-induced airway inflammation that differ in the dose and route of administration of ovalbumin. In confirmation of published results, siglec-F-deficient mice had enhanced lung tissue eosinophilia in response to intranasal ovalbumin delivered every other day. However, following aerosolised ovalbumin delivered daily, there was no influence of siglec-F deficiency on lung eosinophilia. Expression of siglec-F ligands in lung tissues was similar in both models of allergen induced inflammation. These data demonstrate that siglec-F-dependent regulation of eosinophilia is subtle and depends critically on the model used. The findings also indicate that mechanisms other than ligand-induced apoptosis may be important in siglec-F-dependent suppression of eosinophilia. Copyright © 2014 The Authors. Published by Elsevier B.V. All rights reserved.

  13. Application of adversarial risk analysis model in pricing strategies with remanufacturing

    Directory of Open Access Journals (Sweden)

    Liurui Deng

    2015-01-01

    Full Text Available Purpose: Purpose: This paper mainly focus on the application of adversarial risk analysis (ARA in pricing strategy with remanufacturing. We hope to obtain more realistic results than classical model. Moreover, we also wish that our research improve the development of ARA in pricing strategy of manufacturing or remanufacturing. Approach: In order to gain more actual research, combining adversarial risk analysis, we explore the pricing strategy with remanufacturing based on Stackelberg model. Especially, we build OEM’s 1-order ARA model and further study on manufacturers and remanufacturers’ pricing strategy. Findings: We find the OEM’s 1-order ARA model for the OEM’s product cost C. Besides, we get according manufacturers and remanufacturers’ pricing strategies. Besides, the pricing strategies based on 1-order ARA model have advantage over than the classical model regardless of OEMs and remanufacturers. Research implications: The research on application of ARA imply that we can get more actual results with this kind of modern risk analysis method and ARA can be extensively in pricing strategies of supply chain. Value: Our research improves the application of ARA in remanufacturing industry. Meanwhile, inspired by this analysis, we can also create different ARA models for different parameters. Furthermore, some results and analysis methods can be applied to other pricing strategies of supply chain.

  14. Gender-dependence of bone structure and properties in adult osteogenesis imperfecta murine model.

    Science.gov (United States)

    Yao, Xiaomei; Carleton, Stephanie M; Kettle, Arin D; Melander, Jennifer; Phillips, Charlotte L; Wang, Yong

    2013-06-01

    Osteogenesis imperfecta (OI) is a dominant skeletal disorder characterized by bone fragility and deformities. Though the oim mouse model has been the most widely studied of the OI models, it has only recently been suggested to exhibit gender-dependent differences in bone mineralization. To characterize the impact of gender on the morphometry/ultra-structure, mechanical properties, and biochemical composition of oim bone on the congenic C57BL/J6 background, 4-month-old oim/oim, +/oim, and wild-type (wt) female and male tibiae were evaluated using micro-computed tomography, three-point bending, and Raman spectroscopy. Dramatic gender differences were evident in both cortical and trabecular bone morphological and geometric parameters. Male mice had inherently more bone and increased moment of inertia than genotype-matched female counterparts with corresponding increases in bone biomechanical strength. The primary influence of gender was structure/geometry in bone growth and mechanical properties, whereas the mineral/matrix composition and hydroxyproline content of bone were influenced primarily by the oim collagen mutation. This study provides evidence of the importance of gender in the evaluation and interpretation of potential therapeutic strategies when using mouse models of OI.

  15. Strategies for tuning phonon transport in multilayered structures using a mismatch-based particle model

    Science.gov (United States)

    Le, Nam Q.; Duda, John C.; English, Timothy S.; Hopkins, Patrick E.; Beechem, Thomas E.; Norris, Pamela M.

    2012-04-01

    The performance of many micro- and nanoscale devices depends on the ability to control interfacial thermal transport, which is predominantly mediated by phonons in semiconductor systems. The phonon transmissivity at an interface is therefore a quantity of interest. In this work, an empirical model, termed the thermal mismatch model, is developed to predict transmissivity at ideal interfaces between semiconductor materials, producing an excellent agreement with molecular dynamics simulations of wave packets. To investigate propagation through multilayered structures, this thermal mismatch model is then incorporated into a simulation scheme that represents wave packets as particles, showing a good agreement with a similar scheme that used molecular dynamics simulations as input [P. K. Schelling and S. R. Phillpot, J. Appl. Phys. 93, 5377 (2003)]. With these techniques validated for both single interfaces and superlattices, they are further used to identify ways to tune the transmissivity of multilayered structures. It is shown that by introducing intermediate layers of certain atomic masses, the total transmissivity can either be systematically enhanced or reduced compared to that of a single interface. Thus, this model can serve as a computationally inexpensive means of developing strategies to control phonon transmissivity in applications that may benefit from either enhancement (e.g., microelectronics) or reduction (e.g., thermoelectrics) in thermal transport.

  16. A comparison of statistical selection strategies for univariate and bivariate log-linear models.

    Science.gov (United States)

    Moses, Tim; Holland, Paul W

    2010-11-01

    In this study, eight statistical selection strategies were evaluated for selecting the parameterizations of log-linear models used to model the distributions of psychometric tests. The selection strategies included significance tests based on four chi-squared statistics (likelihood ratio, Pearson, Freeman-Tukey, and Cressie-Read) and four additional strategies (Akaike information criterion (AIC), Bayesian information criterion (BIC), consistent Akaike information criterion (CAIC), and a measure attributed to Goodman). The strategies were evaluated in simulations for different log-linear models of univariate and bivariate test-score distributions and two sample sizes. Results showed that all eight selection strategies were most accurate for the largest sample size considered. For univariate distributions, the AIC selection strategy was especially accurate for selecting the correct parameterization of a complex log-linear model and the likelihood ratio chi-squared selection strategy was the most accurate strategy for selecting the correct parameterization of a relatively simple log-linear model. For bivariate distributions, the likelihood ratio chi-squared, Freeman-Tukey chi-squared, BIC, and CAIC selection strategies had similarly high selection accuracies.

  17. Dynamic Dependence Analysis : Modeling and Inference of Changing Dependence Among Multiple Time-Series

    Science.gov (United States)

    2009-06-01

    Carreras , and M. Collins. Structured prediction models via the matrix-tree theorem,. In EMNLP, 2007. 73, 74 [57] B. Korte and J. Vygen. Combinatorial...On lines and planes of closest fit to systems of points, 1901. 116 [75] J. Pers, M. Bon, and G. Vuckovic. CVBASE 06 dataset. In http://vision.fe.uni

  18. Sample-dependent phase transitions in disordered exclusion models

    Science.gov (United States)

    Enaud, C.; Derrida, B.

    2004-04-01

    We give numerical evidence that the location of the first-order phase transition between the low- and the high-density phases of the one-dimensional asymmetric simple exclusion process with open boundaries becomes sample dependent when quenched disorder is introduced for the hopping rates.

  19. Simulation of time-dependent Heisenberg models in one dimension

    DEFF Research Database (Denmark)

    Volosniev, A. G.; Hammer, H. -W.; Zinner, N. T.

    2016-01-01

    In this Letter, we provide a theoretical analysis of strongly interacting quantum systems confined by a time-dependent external potential in one spatial dimension. We show that such systems can be used to simulate spin chains described by Heisenberg Hamiltonians in which the exchange coupling...

  20. Regressor and random-effects dependencies in multilevel models

    NARCIS (Netherlands)

    Ebbes, P.; Bockenholt, U; Wedel, M.

    The objectives of this paper are (1) to review methods that can be used to test for different types of random effects and regressor dependencies, (2) to present results from Monte Carlo studies designed to investigate the performance of these methods, and (3) to discuss estimation methods that can

  1. Modeling Cognitive Strategies during Complex Task Performing Process

    Science.gov (United States)

    Mazman, Sacide Guzin; Altun, Arif

    2012-01-01

    The purpose of this study is to examine individuals' computer based complex task performing processes and strategies in order to determine the reasons of failure by cognitive task analysis method and cued retrospective think aloud with eye movement data. Study group was five senior students from Computer Education and Instructional Technologies…

  2. Generation of safe optimised execution strategies for uml models

    DEFF Research Database (Denmark)

    Herbert, Luke Thomas; Herbert-Hansen, Zaza Nadja Lee

    strategy which fully specifies, from any state in the system, the actions needed for an actor to achieve the optimal values of the quantitative goals. We show that our method is computationally feasible and apply it to an illustrative example featuring an industrial robot in the food industry. Our approach...

  3. Developing Argumentation Strategies in Electronic Dialogs: Is Modeling Effective?

    Science.gov (United States)

    Mayweg-Paus, Elisabeth; Macagno, Fabrizio; Kuhn, Deanna

    2016-01-01

    The study presented here examines how interacting with a more capable interlocutor influences use of argumentation strategies in electronic discourse. To address this question, 54 young adolescents participating in an intervention centered on electronic peer dialogs were randomly assigned to either an experimental or control condition. In both…

  4. An Integrative Model of Dynamic Strategy-Making

    DEFF Research Database (Denmark)

    Andersen, Torben Juul; Hallin, Carina Antonia; Li, Xin

    -linear interaction between top-down and bottom-up mechanisms dealing with multiple actions taken throughout the organization over time. It is driven by intension but with a flexible balance between centralized (planned) and decentralized (spontaneous) activities where strategy formulation and implementation interact...... top-down and bottom-up mechanisms shape sustainable strategic responses....

  5. Agent based models for testing city evacuation strategies under a flood event as strategy to reduce flood risk

    Science.gov (United States)

    Medina, Neiler; Sanchez, Arlex; Nokolic, Igor; Vojinovic, Zoran

    2016-04-01

    This research explores the uses of Agent Based Models (ABM) and its potential to test large scale evacuation strategies in coastal cities at risk from flood events due to extreme hydro-meteorological events with the final purpose of disaster risk reduction by decreasing human's exposure to the hazard. The first part of the paper corresponds to the theory used to build the models such as: Complex adaptive systems (CAS) and the principles and uses of ABM in this field. The first section outlines the pros and cons of using AMB to test city evacuation strategies at medium and large scale. The second part of the paper focuses on the central theory used to build the ABM, specifically the psychological and behavioral model as well as the framework used in this research, specifically the PECS reference model is cover in this section. The last part of this section covers the main attributes or characteristics of human beings used to described the agents. The third part of the paper shows the methodology used to build and implement the ABM model using Repast-Symphony as an open source agent-based modelling and simulation platform. The preliminary results for the first implementation in a region of the island of Sint-Maarten a Dutch Caribbean island are presented and discussed in the fourth section of paper. The results obtained so far, are promising for a further development of the model and its implementation and testing in a full scale city

  6. Multiple-membership multiple-classification models for social network and group dependences

    OpenAIRE

    Tranmer, Mark; Steel, David; Browne, William J

    2014-01-01

    The social network literature on network dependences has largely ignored other sources of dependence, such as the school that a student attends, or the area in which an individual lives. The multilevel modelling literature on school and area dependences has, in turn, largely ignored social networks. To bridge this divide, a multiple-membership multiple-classification modelling approach for jointly investigating social network and group dependences is presented. This allows social network and ...

  7. Onset of hippocampus-dependent memory impairments in 5XFAD transgenic mouse model of Alzheimer's disease.

    Science.gov (United States)

    Girard, Stéphane D; Jacquet, Marlyse; Baranger, Kévin; Migliorati, Martine; Escoffier, Guy; Bernard, Anne; Khrestchatisky, Michel; Féron, François; Rivera, Santiago; Roman, François S; Marchetti, Evelyne

    2014-07-01

    The 5XFAD mice are an early-onset transgenic model of Alzheimer's disease (AD) in which amyloid plaques are first observed between two and four months of age in the cortical layer five and in the subiculum of the hippocampal formation. Although cognitive alterations have been described in these mice, there are no studies that focused on the onset of hippocampus-dependent memory deficits, which are a hallmark of the prodromal stage of AD. To identify when the first learning and memory impairments appear, 5XFAD mice of two, four, and six months of age were compared with their respective wild-type littermates using the olfactory tubing maze, which is a very sensitive hippocampal-dependent task. Deficits in learning and memory started at four months with a substantial increase at six months of age while no olfactory impairments were observed. The volumetric study using magnetic resonance imaging of the whole brain and specific areas (olfactory bulb, striatum, and hippocampus) did not reveal neuro-anatomical difference. Slight memory deficits appeared at 4 months of age in correlation with an increased astrogliosis and amyloid plaque formation. This early impairment in learning and memory related to the hippocampal dysfunction is particularly suited to assess preclinical therapeutic strategies aiming to delay or suppress the onset of AD. © 2014 Wiley Periodicals, Inc.

  8. Time-Dependent Reliability Modeling and Analysis Method for Mechanics Based on Convex Process

    Directory of Open Access Journals (Sweden)

    Lei Wang

    2015-01-01

    Full Text Available The objective of the present study is to evaluate the time-dependent reliability for dynamic mechanics with insufficient time-varying uncertainty information. In this paper, the nonprobabilistic convex process model, which contains autocorrelation and cross-correlation, is firstly employed for the quantitative assessment of the time-variant uncertainty in structural performance characteristics. By combination of the set-theory method and the regularization treatment, the time-varying properties of structural limit state are determined and a standard convex process with autocorrelation for describing the limit state is formulated. By virtue of the classical first-passage method in random process theory, a new nonprobabilistic measure index of time-dependent reliability is proposed and its solution strategy is mathematically conducted. Furthermore, the Monte-Carlo simulation method is also discussed to illustrate the feasibility and accuracy of the developed approach. Three engineering cases clearly demonstrate that the proposed method may provide a reasonable and more efficient way to estimate structural safety than Monte-Carlo simulations throughout a product life-cycle.

  9. Dark energy models with time-dependent gravitational constant

    CERN Document Server

    Ray, S; Ray, Saibal; Mukhopadhyay, Utpal

    2005-01-01

    Two phenomenological models of $\\Lambda$, viz. $\\Lambda \\sim (\\dot a/a)^2$ and $\\Lambda \\sim \\ddot a/a$ are studied under the assumption that $G$ is a time-variable parameter. Both models show that $G$ is inversely proportional to time as suggested earlier by others including Dirac. The models considered here can be matched with observational results by properly tuning the parameters of the models. Our analysis shows that $\\Lambda \\sim \\ddot a/a$ model corresponds to a repulsive situation and hence correlates with the present status of the accelerating Universe. The other model $\\Lambda \\sim (\\dot a/a)^2$ is, in general, attractive in nature. Moreover, it is seen that due to the combined effect of time-variable $\\Lambda$ and $G$ the Universe evolved with acceleration as well as deceleration. This later one indicates a Big Crunch.

  10. Dark Energy Models with a Time-Dependent Gravitational Constant

    Science.gov (United States)

    Ray, Saibal; Mukhopadhyay, Utpal; Choudhury, S. B. Dutta

    Two phenomenological models of Λ, viz. Λ ˜ (˙ a/a)2 and Λ ˜ ḋ a/a, are studied under the assumption that G is a time-variable parameter. Both models show that G is inversely proportional to time, as suggested earlier by others, including Dirac. The models considered here can be matched with observational results by properly tuning the parameters of the models. Our analysis shows that the Λ ˜ ḋ a/a model corresponds to a repulsive situation and hence correlates with the present status of the accelerating Universe. The other model, Λ ˜ (˙ a/a)2, is in general attractive in nature. Moreover, it is seen that due to the combined effect of time-variable Λ and G the Universe evolved with acceleration as well as deceleration. Deceleration indicates a "big crunch".

  11. The transtheoretical model and substance dependence: theoretical and practical aspects

    OpenAIRE

    2009-01-01

    OBJECTIVE: This paper aims to present and discuss the Transtheoretical Model and its importance for the treatment of substance abuse disorders. METHOD: A literature review was made based on articles from the last 10 years in substance use with human subjects found in PubMed (Medline) and the Scientific Electronic Library Online, as well as on the main books written by the creators of the model. From the initial collection of articles related to the Transtheoretical Model, the University of Rh...

  12. Light-Front Spin-1 Model: Parameters Dependence

    CERN Document Server

    Mello, Clayton S; de Melo, J P B C; Frederico, T

    2015-01-01

    We study the structure of the $\\rho$-meson within a light-front model with constituent quark degrees of freedom. We calculate electroweak static observables: magnetic and quadrupole moments, decay constant and charge radius. The prescription used to compute the electroweak quantities is free of zero modes, which makes the calculation implicitly covariant. We compare the results of our model with other ones found in the literature. Our model parameters give a decay constant close to the experimental one.

  13. Local dependence in random graph models: characterization, properties and statistical inference.

    Science.gov (United States)

    Schweinberger, Michael; Handcock, Mark S

    2015-06-01

    Dependent phenomena, such as relational, spatial and temporal phenomena, tend to be characterized by local dependence in the sense that units which are close in a well-defined sense are dependent. In contrast with spatial and temporal phenomena, though, relational phenomena tend to lack a natural neighbourhood structure in the sense that it is unknown which units are close and thus dependent. Owing to the challenge of characterizing local dependence and constructing random graph models with local dependence, many conventional exponential family random graph models induce strong dependence and are not amenable to statistical inference. We take first steps to characterize local dependence in random graph models, inspired by the notion of finite neighbourhoods in spatial statistics and M-dependence in time series, and we show that local dependence endows random graph models with desirable properties which make them amenable to statistical inference. We show that random graph models with local dependence satisfy a natural domain consistency condition which every model should satisfy, but conventional exponential family random graph models do not satisfy. In addition, we establish a central limit theorem for random graph models with local dependence, which suggests that random graph models with local dependence are amenable to statistical inference. We discuss how random graph models with local dependence can be constructed by exploiting either observed or unobserved neighbourhood structure. In the absence of observed neighbourhood structure, we take a Bayesian view and express the uncertainty about the neighbourhood structure by specifying a prior on a set of suitable neighbourhood structures. We present simulation results and applications to two real world networks with 'ground truth'.

  14. Empirical angle-dependent Biot and MBA models for acoustic anisotropy in cancellous bone.

    Science.gov (United States)

    Lee, Kang Il; Hughes, E R; Humphrey, V F; Leighton, T G; Choi, Min Joo

    2007-01-01

    The Biot and the modified Biot-Attenborough (MBA) models have been found useful to understand ultrasonic wave propagation in cancellous bone. However, neither of the models, as previously applied to cancellous bone, allows for the angular dependence of acoustic properties with direction. The present study aims to account for the acoustic anisotropy in cancellous bone, by introducing empirical angle-dependent input parameters, as defined for a highly oriented structure, into the Biot and the MBA models. The anisotropy of the angle-dependent Biot model is attributed to the variation in the elastic moduli of the skeletal frame with respect to the trabecular alignment. The angle-dependent MBA model employs a simple empirical way of using the parametric fit for the fast and the slow wave speeds. The angle-dependent models were used to predict both the fast and slow wave velocities as a function of propagation angle with respect to the trabecular alignment of cancellous bone. The predictions were compared with those of the Schoenberg model for anisotropy in cancellous bone and in vitro experimental measurements from the literature. The angle-dependent models successfully predicted the angular dependence of phase velocity of the fast wave with direction. The root-mean-square errors of the measured versus predicted fast wave velocities were 79.2 m s(-1) (angle-dependent Biot model) and 36.1 m s(-1) (angle-dependent MBA model). They also predicted the fact that the slow wave is nearly independent of propagation angle for angles about 50 degrees , but consistently underestimated the slow wave velocity with the root-mean-square errors of 187.2 m s(-1) (angle-dependent Biot model) and 240.8 m s(-1) (angle-dependent MBA model). The study indicates that the angle-dependent models reasonably replicate the acoustic anisotropy in cancellous bone.

  15. Strain Rate Dependant Material Model for Orthotropic Metals

    Science.gov (United States)

    Vignjevic, Rade

    2016-08-01

    In manufacturing processes anisotropic metals are often exposed to the loading with high strain rates in the range from 102 s-1 to 106 s-1 (e.g. stamping, cold spraying and explosive forming). These types of loading often involve generation and propagation of shock waves within the material. The material behaviour under such a complex loading needs to be accurately modelled, in order to optimise the manufacturing process and achieve appropriate properties of the manufactured component. The presented research is related to development and validation of a thermodynamically consistent physically based constitutive model for metals under high rate loading. The model is capable of modelling damage, failure and formation and propagation of shock waves in anisotropic metals. The model has two main parts: the strength part which defines the material response to shear deformation and an equation of state (EOS) which defines the material response to isotropic volumetric deformation [1]. The constitutive model was implemented into the transient nonlinear finite element code DYNA3D [2] and our in house SPH code. Limited model validation was performed by simulating a number of high velocity material characterisation and validation impact tests. The new damage model was developed in the framework of configurational continuum mechanics and irreversible thermodynamics with internal state variables. The use of the multiplicative decomposition of deformation gradient makes the model applicable to arbitrary plastic and damage deformations. To account for the physical mechanisms of failure, the concept of thermally activated damage initially proposed by Tuller and Bucher [3], Klepaczko [4] was adopted as the basis for the new damage evolution model. This makes the proposed damage/failure model compatible with the Mechanical Threshold Strength (MTS) model Follansbee and Kocks [5], 1988; Chen and Gray [6] which was used to control evolution of flow stress during plastic deformation. In

  16. Modeling frequency dependence of GaAs MESFET characteristics

    Science.gov (United States)

    Conger, Jeff; Peczalski, Andrzej; Shur, Michael S.

    1994-01-01

    We present a new method of modeling the output conductance dispersion of GaAs MESFET's. High frequency model parameters are extracted and then used to model high frequency output conductance over a wide range of bias conditions. The model is then used to simulate and analyze the effect of output conductance dispersion on the performance of DCFL and SCFL logic gates. Whereas the DCFL performance is not significantly affected by the high frequency effects, the noise margin of SCFL decreases by almost a factor of 30% above 100 kHz, with an associated decrease in the voltage swing and gate delay.

  17. System theory and safety models in Swedish, UK, Dutch and Australian road safety strategies.

    Science.gov (United States)

    Hughes, B P; Anund, A; Falkmer, T

    2015-01-01

    Road safety strategies represent interventions on a complex social technical system level. An understanding of a theoretical basis and description is required for strategies to be structured and developed. Road safety strategies are described as systems, but have not been related to the theory, principles and basis by which systems have been developed and analysed. Recently, road safety strategies, which have been employed for many years in different countries, have moved to a 'vision zero', or 'safe system' style. The aim of this study was to analyse the successful Swedish, United Kingdom and Dutch road safety strategies against the older, and newer, Australian road safety strategies, with respect to their foundations in system theory and safety models. Analysis of the strategies against these foundations could indicate potential improvements. The content of four modern cases of road safety strategy was compared against each other, reviewed against scientific systems theory and reviewed against types of safety model. The strategies contained substantial similarities, but were different in terms of fundamental constructs and principles, with limited theoretical basis. The results indicate that the modern strategies do not include essential aspects of systems theory that describe relationships and interdependencies between key components. The description of these strategies as systems is therefore not well founded and deserves further development.

  18. Testing a social psychological model of strategy use with students of english as a foreign language.

    Science.gov (United States)

    Hsiao, Tsung-Yuan

    2004-12-01

    This replication study tested MacIntyre's Social Psychological Model of Strategy Use. Participants were 137 first-year college students (100 men and 37 women), all in their late teens or early 20s, learning English as a foreign language in a university in Taiwan. McIntyre specified three conditions for use of language-learning strategies in his model: awareness of the strategy, having a reason to use it, and not having a reason not to use it. Stepwise multiple regression analyses of data measured by Oxford's 50-item Strategy Inventory for Language Learning partially support this model because only Knowledge about the Strategy (representing the first condition) and Difficulty about Using It (representing the third condition) made significant independent contributions to the prediction of use of most of the 50 strategies. Close examination of the results poses questions about MacIntyre and Noels' thesis, as implied in their revised model, that reason to use the strategy and reason not to use the strategy are independent. The present replication suggests a need for further revision of the model. Use of methods more advanced than the multiple regression is recommended to test and refine the model.

  19. Agent-based models of strategies for the emergence and evolution of grammatical agreement.

    Science.gov (United States)

    Beuls, Katrien; Steels, Luc

    2013-01-01

    Grammatical agreement means that features associated with one linguistic unit (for example number or gender) become associated with another unit and then possibly overtly expressed, typically with morphological markers. It is one of the key mechanisms used in many languages to show that certain linguistic units within an utterance grammatically depend on each other. Agreement systems are puzzling because they can be highly complex in terms of what features they use and how they are expressed. Moreover, agreement systems have undergone considerable change in the historical evolution of languages. This article presents language game models with populations of agents in order to find out for what reasons and by what cultural processes and cognitive strategies agreement systems arise. It demonstrates that agreement systems are motivated by the need to minimize combinatorial search and semantic ambiguity, and it shows, for the first time, that once a population of agents adopts a strategy to invent, acquire and coordinate meaningful markers through social learning, linguistic self-organization leads to the spontaneous emergence and cultural transmission of an agreement system. The article also demonstrates how attested grammaticalization phenomena, such as phonetic reduction and conventionalized use of agreement markers, happens as a side effect of additional economizing principles, in particular minimization of articulatory effort and reduction of the marker inventory. More generally, the article illustrates a novel approach for studying how key features of human languages might emerge.

  20. Agent-based models of strategies for the emergence and evolution of grammatical agreement.

    Directory of Open Access Journals (Sweden)

    Katrien Beuls

    Full Text Available Grammatical agreement means that features associated with one linguistic unit (for example number or gender become associated with another unit and then possibly overtly expressed, typically with morphological markers. It is one of the key mechanisms used in many languages to show that certain linguistic units within an utterance grammatically depend on each other. Agreement systems are puzzling because they can be highly complex in terms of what features they use and how they are expressed. Moreover, agreement systems have undergone considerable change in the historical evolution of languages. This article presents language game models with populations of agents in order to find out for what reasons and by what cultural processes and cognitive strategies agreement systems arise. It demonstrates that agreement systems are motivated by the need to minimize combinatorial search and semantic ambiguity, and it shows, for the first time, that once a population of agents adopts a strategy to invent, acquire and coordinate meaningful markers through social learning, linguistic self-organization leads to the spontaneous emergence and cultural transmission of an agreement system. The article also demonstrates how attested grammaticalization phenomena, such as phonetic reduction and conventionalized use of agreement markers, happens as a side effect of additional economizing principles, in particular minimization of articulatory effort and reduction of the marker inventory. More generally, the article illustrates a novel approach for studying how key features of human languages might emerge.

  1. Strategy and the Learning Organization: A Maturity Model for the Formation of Strategy

    Science.gov (United States)

    Kenny, John

    2006-01-01

    Purpose: To develop a theoretical model for strategic change that links learning in an organization to the strategic process. Design/methodology/approach: The model was developed from a review of literature covering a range of areas including: management, strategic planning, psychology of learning and organizational learning. The process of…

  2. Modeling and temperature regulation of a thermally coupled reactor system via internal model control strategy

    Energy Technology Data Exchange (ETDEWEB)

    Lee, S.Y.; Coronella, C.J.; Bhadkamkar, A.S.; Seader, J.D. [Univ. of Utah, Salt Lake City, UT (United States). Dept. of Chemical and Fuels Engineering

    1993-12-01

    A two-stage, thermally coupled fluidized-bed reactor system has been developed for energy-efficient conversion of tar-sand bitumen to synthetic crude oil. Modeling and temperature control of a system are addressed in this study. A process model and transfer function are determined by a transient response technique and the reactor temperature are controlled by PI controllers with tuning settings determined by an internal model control (IMC) strategy. Using the IMC tuning method, sufficiently good control performance was experimentally observed without lengthy on-line tuning. It is shown that IMC strategy provides a means to directly use process knowledge to make a control decision. Although this control method allows for fine tuning by adjusting a single tuning parameter, it is not easy to determine the optimal value of this tuning parameter, which must be specified by the user. A novel method is presented to evaluate that parameter, which must be specified by the user. A novel method is presented to evaluate that parameter in this study. It was selected based on the magnitude of elements on the off-diagonal of the relative gain array to account for the effect of thermal coupling on control performance. It is shown that this method provides stable and fast control of reactor temperatures. By successfully decoupling the system, a simple method of extending the IMC tuning technique to multiinput/multioutput systems is obtained.

  3. Modelling Nonlinearities and Reference Dependence in General Practitioners' Income Preferences.

    Science.gov (United States)

    Holte, Jon Helgheim; Sivey, Peter; Abelsen, Birgit; Olsen, Jan Abel

    2016-08-01

    This paper tests for the existence of nonlinearity and reference dependence in income preferences for general practitioners. Confirming the theory of reference dependent utility within the context of a discrete choice experiment, we find that losses loom larger than gains in income for Norwegian general practitioners, i.e. they value losses from their current income level around three times higher than the equivalent gains. Our results are validated by comparison with equivalent contingent valuation values for marginal willingness to pay and marginal willingness to accept compensation for changes in job characteristics. Physicians' income preferences determine the effectiveness of 'pay for performance' and other incentive schemes. Our results may explain the relative ineffectiveness of financial incentive schemes that rely on increasing physicians' incomes. Copyright © 2015 John Wiley & Sons, Ltd.

  4. Model dependence of baryon decay enhancement by cosmic strings

    CERN Document Server

    Fewster, C J

    1993-01-01

    Cosmic strings arising from GUTs can catalyse baryon decay processes with strong interaction cross sections. We examine the mechanism by which the cross section is enhanced and find that it depends strongly on the details of the distribution of gauge fields within the string core. We propose a calculational scheme for estimating wavefunction amplification factors and also a physical understanding of the nature of the enhancement process.

  5. Cosmological Models with Time Dependent G and A Coupling Scalars

    Institute of Scientific and Technical Information of China (English)

    N.Ibotombi Singh; S.Kiranmla Chanu; S.Surendra Singh

    2009-01-01

    A cosmological model in which the universe has its critical density and gravitational constants generalized as coupling scalars in Einstein's theory is considered.A general method of solving the field equations is given.An exact solution for matter distribution in cosmological models satisfying G = Go(R/Ro)n is presented.Corresponding physical interpretations of the cosmological solutions are also discussed.

  6. Multiplicity Control in Structural Equation Modeling: Incorporating Parameter Dependencies

    Science.gov (United States)

    Smith, Carrie E.; Cribbie, Robert A.

    2013-01-01

    When structural equation modeling (SEM) analyses are conducted, significance tests for all important model relationships (parameters including factor loadings, covariances, etc.) are typically conducted at a specified nominal Type I error rate ([alpha]). Despite the fact that many significance tests are often conducted in SEM, rarely is…

  7. DYNAMIC MODELING STRATEGY FOR FLOW REGIME TRANSITION IN GAS-LIQUID TWO-PHASE FLOWS

    Energy Technology Data Exchange (ETDEWEB)

    X. Wang; X. Sun; H. Zhao

    2011-09-01

    In modeling gas-liquid two-phase flows, the concept of flow regime has been used to characterize the global interfacial structure of the flows. Nearly all constitutive relations that provide closures to the interfacial transfers in two-phase flow models, such as the two-fluid model, are often flow regime dependent. Currently, the determination of the flow regimes is primarily based on flow regime maps or transition criteria, which are developed for steady-state, fully-developed flows and widely applied in nuclear reactor system safety analysis codes, such as RELAP5. As two-phase flows are observed to be dynamic in nature (fully-developed two-phase flows generally do not exist in real applications), it is of importance to model the flow regime transition dynamically for more accurate predictions of two-phase flows. The present work aims to develop a dynamic modeling strategy for determining flow regimes in gas-liquid two-phase flows through the introduction of interfacial area transport equations (IATEs) within the framework of a two-fluid model. The IATE is a transport equation that models the interfacial area concentration by considering the creation and destruction of the interfacial area, such as the fluid particle (bubble or liquid droplet) disintegration, boiling and evaporation; and fluid particle coalescence and condensation, respectively. For the flow regimes beyond bubbly flows, a two-group IATE has been proposed, in which bubbles are divided into two groups based on their size and shape (which are correlated), namely small bubbles and large bubbles. A preliminary approach to dynamically identifying the flow regimes is provided, in which discriminators are based on the predicted information, such as the void fraction and interfacial area concentration of small bubble and large bubble groups. This method is expected to be applied to computer codes to improve their predictive capabilities of gas-liquid two-phase flows, in particular for the applications in

  8. DEPENDABLE PRIVACY REQUIREMENTS BY AGILE MODELED LAYERED SECURITY ARCHITECTURES – WEB SERVICES CASE STUDY

    Directory of Open Access Journals (Sweden)

    M.Upendra Kumar

    2011-07-01

    Full Text Available Software Engineering covers the definition of processes, techniques and models suitable for its environment to guarantee quality of results. An important design artifact in any software development project is the Software Architecture. Software Architecture’s important part is the set of architectural design rules. A primary goal of the architecture is to capture the architecture design decisions. An important part of these design decisions consists of architectural design rules In an MDA (Model-Driven Architecture context, the design of the system architecture is captured in the models of the system. MDA is known to be layered approach for modeling the architectural design rules and uses design patterns to improve the quality of software system. And to include the security to the software system, security patterns are introduced that offer security at the architectural level. More over, agile software development methods are used to build secure systems. There are different methods defined in agile development as extreme programming (XP, scrum, feature driven development (FDD, test driven development (TDD, etc. Agile processing is includes the phases as agile analysis, agile design and agile testing. These phases are defined in layers of MDA to provide security at the modeling level which ensures that security at the system architecture stage will improve the requirements for that system. Agile modeled Layered Security Architectures increase the dependability of the architecture in terms of privacy requirements. We validate this with a case study of dependability of privacy of Web Services Security Architectures, which helps for secure service oriented security architecture. In this paper the major part is given to model architectural design rules using MDA so that architects and developers are responsible to automatic enforcement on the detailed design and easy to understand and use by both of them. This MDA approach is implemented in use of

  9. A Comparison of Two Strategies for Building an Exposure Prediction Model.

    Science.gov (United States)

    Heiden, Marina; Mathiassen, Svend Erik; Garza, Jennifer; Liv, Per; Wahlström, Jens

    2016-01-01

    Cost-efficient assessments of job exposures in large populations may be obtained from models in which 'true' exposures assessed by expensive measurement methods are estimated from easily accessible and cheap predictors. Typically, the models are built on the basis of a validation study comprising 'true' exposure data as well as an extensive collection of candidate predictors from questionnaires or company data, which cannot all be included in the models due to restrictions in the degrees of freedom available for modeling. In these situations, predictors need to be selected using procedures that can identify the best possible subset of predictors among the candidates. The present study compares two strategies for selecting a set of predictor variables. One strategy relies on stepwise hypothesis testing of associations between predictors and exposure, while the other uses cluster analysis to reduce the number of predictors without relying on empirical information about the measured exposure. Both strategies were applied to the same dataset on biomechanical exposure and candidate predictors among computer users, and they were compared in terms of identified predictors of exposure as well as the resulting model fit using bootstrapped resamples of the original data. The identified predictors were, to a large part, different between the two strategies, and the initial model fit was better for the stepwise testing strategy than for the clustering approach. Internal validation of the models using bootstrap resampling with fixed predictors revealed an equally reduced model fit in resampled datasets for both strategies. However, when predictor selection was incorporated in the validation procedure for the stepwise testing strategy, the model fit was reduced to the extent that both strategies showed similar model fit. Thus, the two strategies would both be expected to perform poorly with respect to predicting biomechanical exposure in other samples of computer users.

  10. Consistently modeling the same movement strategy is more important than model skill level in observational learning contexts.

    Science.gov (United States)

    Buchanan, John J; Dean, Noah

    2014-02-01

    The experiment undertaken was designed to elucidate the impact of model skill level on observational learning processes. The task was bimanual circle tracing with a 90° relative phase lead of one hand over the other hand. Observer groups watched videos of either an instruction model, a discovery model, or a skilled model. The instruction and skilled model always performed the task with the same movement strategy, the right-arm traced clockwise and the left-arm counterclockwise around circle templates with the right-arm leading. The discovery model used several movement strategies (tracing-direction/hand-lead) during practice. Observation of the instruction and skilled model provided a significant benefit compared to the discovery model when performing the 90° relative phase pattern in a post-observation test. The observers of the discovery model had significant room for improvement and benefited from post-observation practice of the 90° pattern. The benefit of a model is found in the consistency with which that model uses the same movement strategy, and not within the skill level of the model. It is the consistency in strategy modeled that allows observers to develop an abstract perceptual representation of the task that can be implemented into a coordinated action. Theoretically, the results show that movement strategy information (relative motion direction, hand lead) and relative phase information can be detected through visual perception processes and be successfully mapped to outgoing motor commands within an observational learning context.

  11. ANALISIS DAN MODEL STRATEGI PENINGKATAN DAYA SAING PRODUK EDAMAME BEKU

    Directory of Open Access Journals (Sweden)

    Sandryas Alief Kurniasanti

    2015-03-01

    Full Text Available Jember regency is a agricultural and plantation central area. The soybean plant is principal commodity that competes fiercely with production of corn. PT Mitratani Dua Tujuh (PT MT 27 try to find new technology by processing edamame to frozen edamame that focus in the export market. The primary market of frozen edamame besides domestic market is Japan. The aim of this research is to analyze competitiveness and formulated the priority of competitiveness alternative strategy on frozen edamame product in PT MT 27. The research method used is the analysis of competitiveness by using revealed comparative advantage to know the export performance of the product on the world market then analyze a factor of competition by using Diamond Porter's Theory. Alternative strategies are resulted from the SWOT analysis and priorities are determined by using analytical hierarchy process from the expert source. The research results about alternative strategy priority to increase the competitiveness of frozen edamame products in PT MT 27 are: (1 market diversification, (2 product diversification, (3 improve cooperation overseas, (4 develop a research and development division, (5 develop corporate social responsibility, (6 proper financial management, and (7 to develop an agricultural area greenhouse-based to avoid bad weather as tropical country. Managerial implications of this research are expanding existing markets, and develop type of product produced to satisfy the export market and also savings cost production. Keywords: competitiveness, frozen edamame, Mitratani Dua Tujuh, competitiveness strategiesABSTRAKKabupaten Jember merupakan sentra  daerah pertanian dan perkebunan. Tanaman kedelai merupakan komoditas utama yang bersaing ketat dengan produksi jagung. PT Mitratani Dua Tujuh (PT MT 27 mencoba untuk mencari terobosan baru yaitu dengan mengolah edamame menjadi edamame beku siap makan. Pasar utama edamame beku ini selain pasar domestik adalah Jepang. Tujuan

  12. Compensatory motor control after stroke: an alternative joint strategy for object-dependent shaping of hand posture.

    Science.gov (United States)

    Raghavan, Preeti; Santello, Marco; Gordon, Andrew M; Krakauer, John W

    2010-06-01

    Efficient grasping requires planned and accurate coordination of finger movements to approximate the shape of an object before contact. In healthy subjects, hand shaping is known to occur early in reach under predominantly feedforward control. In patients with hemiparesis after stroke, execution of coordinated digit motion during grasping is impaired as a result of damage to the corticospinal tract. The question addressed here is whether patients with hemiparesis are able to compensate for their execution deficit with a qualitatively different grasp strategy that still allows them to differentiate hand posture to object shape. Subjects grasped a rectangular, concave, and convex object while wearing an instrumented glove. Reach-to-grasp was divided into three phases based on wrist kinematics: reach acceleration (reach onset to peak horizontal wrist velocity), reach deceleration (peak horizontal wrist velocity to reach offset), and grasp (reach offset to lift-off). Patients showed reduced finger abduction, proximal interphalangeal joint (PIP) flexion, and metacarpophalangeal joint (MCP) extension at object grasp across all three shapes compared with controls; however, they were able to partially differentiate hand posture for the convex and concave shapes using a compensatory strategy that involved increased MCP flexion rather than the PIP flexion seen in controls. Interestingly, shape-specific hand postures did not unfold initially during reach acceleration as seen in controls, but instead evolved later during reach deceleration, which suggests increased reliance on sensory feedback. These results indicate that kinematic analysis can identify and quantify within-limb compensatory motor control strategies after stroke. From a clinical perspective, quantitative study of compensation is important to better understand the process of recovery from brain injury. From a motor control perspective, compensation can be considered a model for how joint redundancy is exploited

  13. Strategies for water management. A global irrigation model

    OpenAIRE

    Nunes, Joao; Sousa, Miguel; Torres-Campos, Tiago; Pereira, Mariana

    2011-01-01

    This study focuses on the physical component of irrigation water management in regions where its scarcity is intensified by recent urban centre development, seeking not only the definition of strategies for major savings in consumption, but rather their inclusion in landscape principles for more sustainable urban design solutions.The (re)establishment of a close relation between water management and planting techniques (perpetuated in vernacular irrigation techniques) is quintessential. There...

  14. Dependency Modeling of a SOA Based System Through Colored Petri Nets

    Directory of Open Access Journals (Sweden)

    Pawan Kumar

    2016-09-01

    Full Text Available Dependency relationships play an important role in testing, maintenance and configuration management of software systems. The informal dependency representations fail to observe behavioral connections among subsystems and cause ambiguity in representing different types of dependency relationships. Therefore, dependency in a software system requires a formal and unambiguous representation so that its correct effects can be visualized. In this paper, we present a Colored Petri Net based dependency analysis of a Service Oriented Architecture (SOA based system that represents specification of dependency relationships and models the dependencies in a SOA based system at conceptual level. Different types of dependency relations are represented in a formal manner by using Service Algebra. A module SOA based system ‘Online Bookshop’ has been developed and used for the purpose of modeling and example demonstration. Such modeling can help in identification of inconsistency among services, and web services can be verified for safety and reliability.

  15. A Strategy Tackling Local Minimum of Direct Search Method in Modeling a Hydraulic Actuator

    Institute of Scientific and Technical Information of China (English)

    刘云山; 陈晓辉

    2013-01-01

    A strategy for attacking the local minimum problem of direct search method is developed for modeling a hydraulic actuator. The Nelder-Mead direct search method is combined with Ordinary Least Squares which can used to optimize the parameters which the model function is in linear with. The model fitting results show that this strategy can reach a solution more close to the global minimum than the Nelder-Mead direct search method used alone.

  16. Study on ABCD Analysis Technique for Business Models, business strategies, Operating Concepts & Business Systems

    OpenAIRE

    Aithal, Sreeramana

    2016-01-01

    Studying the implications of a business model, choosing success strategies, developing viable operational concepts or evolving a functional system, it is important to analyse it in all dimensions. For this purpose, various analysing techniques/frameworks are used. This paper is a discussion on how to use an innovative analysing framework called ABCD model on a given business model, or on a business strategy or a operational concept/idea or business system. Based on four constructs Advantages,...

  17. Adaptive hybrid optimization strategy for calibration and parameter estimation of physical models

    CERN Document Server

    Vesselinov, Velimir V

    2011-01-01

    A new adaptive hybrid optimization strategy, entitled squads, is proposed for complex inverse analysis of computationally intensive physical models. The new strategy is designed to be computationally efficient and robust in identification of the global optimum (e.g. maximum or minimum value of an objective function). It integrates a global Adaptive Particle Swarm Optimization (APSO) strategy with a local Levenberg-Marquardt (LM) optimization strategy using adaptive rules based on runtime performance. The global strategy optimizes the location of a set of solutions (particles) in the parameter space. The LM strategy is applied only to a subset of the particles at different stages of the optimization based on the adaptive rules. After the LM adjustment of the subset of particle positions, the updated particles are returned to the APSO strategy. The advantages of coupling APSO and LM in the manner implemented in squads is demonstrated by comparisons of squads performance against Levenberg-Marquardt (LM), Particl...

  18. Designing Multidimensional Policing Strategy And Organization: Towards A Synthesis Of Professional And Community Police Models

    Directory of Open Access Journals (Sweden)

    Suve Priit

    2015-06-01

    Full Text Available In this article we analyse professional police and community policing in view of professionalism, strategy and structures. We aim to find ways for synthesizing these models that are usually seen as incompatible. Unlike many earlier studies of police organizations or strategies, we view strategies in the organization at the corporate, functional and operational levels, and argue that by combining them with functional and divisional principles of structuring, it is possible to place professional strategy at the core of policing, while using the community policing strategy mainly as a component part of the strategy in the framework of divisional organization. This way it is possible to avoid the risk of alienating police from the community and to ensure the successful implementation of corporate strategy through providing professional police units that perform the narrow functions, with quick and adequate information from the community.

  19. Integrated Inventory Model for Deteriorating Items with Price-Dependent Demand under Quantity-Dependent Trade Credit

    Directory of Open Access Journals (Sweden)

    Karuppuchamy Annadurai

    2013-01-01

    Full Text Available This paper explores an integrated inventory model when the deterioration rate follows exponential distribution under trade credit. Here, it is assumed that demand rate is a function of selling price and the permissible delay in payment depends on the order quantity. In the model shortages are completely backlogged. The maximization of the total profit per unit of time is taken as the objective function to study the retailer’s optimal ordering policy. This paper also presents a practical application example where the proposed inventory model is utilized to support business decision making. Particularly, the model developed in the paper could be useful in the area of supply chain management. Finally, sensitivity analysis of the optimal solution with respect to major parameters is carried out. Our result illustrates that this model can be quite useful in determining the optimal ordering policy when the trade credit period is being analyzed.

  20. Isospin dependence of nuclear multifragmentation in statistical model

    Institute of Scientific and Technical Information of China (English)

    张蕾; 谢东珠; 张艳萍; 高远

    2011-01-01

    The evolution of nuclear disintegration mechanisms with increasing excitation energy, from compound nucleus to multifragmentation, has been studied by using the Statistical Multifragmentation Model (SMM) within a micro-canonical ensemble. We discuss the o

  1. Time-Dependent Stochastic Acceleration Model for the Fermi Bubbles

    CERN Document Server

    Sasaki, Kento; Terasawa, Toshio

    2015-01-01

    We study stochastic acceleration models for the Fermi bubbles. Turbulence is excited just behind the shock front via Kelvin-Helmholtz, Rayleigh-Taylor or Richtmyer-Meshkov instabilities, and plasma particles are continuously accelerated by the interaction with the turbulence. The turbulence gradually decays as it goes away from the shock fronts. Adopting a phenomenological model for the stochastic acceleration, we explicitly solve the temporal evolution of the particle energy distribution in the turbulence. Our results show that the spatial distribution of high-energy particles is different from those for a steady solution. We also show that the contribution of electrons escaped from the acceleration regions significantly softens the photon spectrum. The photon spectrum and surface brightness profile are reproduced by our models. If the escape efficiency is very high, the radio flux from the escaped low-energy electrons can be comparable to that of the WMAP haze. We also demonstrate hadronic models with the s...

  2. SHERLOCK: A quasi-model-independent new physics search strategy.

    Science.gov (United States)

    Knuteson, Bruce

    2000-04-01

    We develop a quasi-model-independent prescription for searching for physics responsible for the electroweak symmetry breaking in the Standard Model, and show a preliminary version of what we find when this prescription is applied to the DZero data.

  3. Assessing clustering strategies for Gaussian mixture filtering a subsurface contaminant model

    KAUST Repository

    Liu, Bo

    2016-02-03

    An ensemble-based Gaussian mixture (GM) filtering framework is studied in this paper in term of its dependence on the choice of the clustering method to construct the GM. In this approach, a number of particles sampled from the posterior distribution are first integrated forward with the dynamical model for forecasting. A GM representation of the forecast distribution is then constructed from the forecast particles. Once an observation becomes available, the forecast GM is updated according to Bayes’ rule. This leads to (i) a Kalman filter-like update of the particles, and (ii) a Particle filter-like update of their weights, generalizing the ensemble Kalman filter update to non-Gaussian distributions. We focus on investigating the impact of the clustering strategy on the behavior of the filter. Three different clustering methods for constructing the prior GM are considered: (i) a standard kernel density estimation, (ii) clustering with a specified mixture component size, and (iii) adaptive clustering (with a variable GM size). Numerical experiments are performed using a two-dimensional reactive contaminant transport model in which the contaminant concentration and the heterogenous hydraulic conductivity fields are estimated within a confined aquifer using solute concentration data. The experimental results suggest that the performance of the GM filter is sensitive to the choice of the GM model. In particular, increasing the size of the GM does not necessarily result in improved performances. In this respect, the best results are obtained with the proposed adaptive clustering scheme.

  4. Depth-color fusion strategy for 3-D scene modeling with Kinect.

    Science.gov (United States)

    Camplani, Massimo; Mantecon, Tomas; Salgado, Luis

    2013-12-01

    Low-cost depth cameras, such as Microsoft Kinect, have completely changed the world of human-computer interaction through controller-free gaming applications. Depth data provided by the Kinect sensor presents several noise-related problems that have to be tackled to improve the accuracy of the depth data, thus obtaining more reliable game control platforms and broadening its applicability. In this paper, we present a depth-color fusion strategy for 3-D modeling of indoor scenes with Kinect. Accurate depth and color models of the background elements are iteratively built, and used to detect moving objects in the scene. Kinect depth data is processed with an innovative adaptive joint-bilateral filter that efficiently combines depth and color by analyzing an edge-uncertainty map and the detected foreground regions. Results show that the proposed approach efficiently tackles main Kinect data problems: distance-dependent depth maps, spatial noise, and temporal random fluctuations are dramatically reduced; objects depth boundaries are refined, and nonmeasured depth pixels are interpolated. Moreover, a robust depth and color background model and accurate moving objects silhouette are generated.

  5. Towards the Accuracy of Cybernetic Strategy Planning Models: Causal Proof and Function Approximation

    Directory of Open Access Journals (Sweden)

    Christian A. Hillbrand

    2003-04-01

    Full Text Available All kind of strategic tasks within an enterprise require a deep understanding of its critical key success factors and their interrelations as well as an in-depth analysis of relevant environmental influences. Due to the openness of the underlying system, there seems to be an indefinite number of unknown variables influencing strategic goals. Cybernetic or systemic planning techniques try to overcome this intricacy by modeling the most important cause-and-effect relations within such a system. Although it seems to be obvious that there are specific influences between business variables, it is mostly impossible to identify the functional dependencies underlying such relations. Hence simulation or evaluation techniques based on such hypothetically assumed models deliver inaccurate results or fail completely. This paper addresses the need for accurate strategy planning models and proposes an approach to prove their cause-andeffect relations by empirical evidence. Based on this foundation an approach for the approximation of the underlying cause-andeffect function by the means of Artificial Neural Networks is developed.

  6. Progression to multi-scale models and the application to food system intervention strategies.

    Science.gov (United States)

    Gröhn, Yrjö T

    2015-02-01

    The aim of this article is to discuss how the systems science approach can be used to optimize intervention strategies in food animal systems. It advocates the idea that the challenges of maintaining a safe food supply are best addressed by integrating modeling and mathematics with biological studies critical to formulation of public policy to address these challenges. Much information on the biology and epidemiology of food animal systems has been characterized through single-discipline methods, but until now this information has not been thoroughly utilized in a fully integrated manner. The examples are drawn from our current research. The first, explained in depth, uses clinical mastitis to introduce the concept of dynamic programming to optimize management decisions in dairy cows (also introducing the curse of dimensionality problem). In the second example, a compartmental epidemic model for Johne's disease with different intervention strategies is optimized. The goal of the optimization strategy depends on whether there is a relationship between Johne's and Crohn's disease. If so, optimization is based on eradication of infection; if not, it is based on the cow's performance only (i.e., economic optimization, similar to the mastitis example). The third example focuses on food safety to introduce risk assessment using Listeria monocytogenes and Salmonella Typhimurium. The last example, practical interventions to effectively manage antibiotic resistance in beef and dairy cattle systems, introduces meta-population modeling that accounts for bacterial growth not only in the host (cow), but also in the cow's feed, drinking water and the housing environment. Each example stresses the need to progress toward multi-scale modeling. The article ends with examples of multi-scale systems, from food supply systems to Johne's disease. Reducing the consequences of foodborne illnesses (i.e., minimizing disease occurrence and associated costs) can only occur through an

  7. A Schematic Model For Density-Dependent Vector Meson Masses

    CERN Document Server

    Kim, Y; Brown, G E; Rho, M; Kim, Youngman; Rho, Mannque

    1999-01-01

    A schematic two-level model consisting of a "collective" bosonic state and an "elementary" meson is constructed that provides interpolation from a hadronic description (a la Rapp/Wambach) to B/R scaling for the description of properties of vector mesons in dense medium. The development is based on a close analogy to the degenerate schematic model of Brown for giant resonances in nuclei.

  8. Validation of simulation strategies for the flow in a model propeller turbine during a runaway event

    Science.gov (United States)

    Fortin, M.; Houde, S.; Deschênes, C.

    2014-03-01

    Recent researches indicate that the useful life of a turbine can be affected by transient events. This study aims to define and validate strategies for the simulation of the flow within a propeller turbine model in runaway condition. Using unsteady pressure measurements on two runner blades for validation, different strategies are compared and their results analysed in order to quantify their precision. This paper will focus on justifying the choice of the simulations strategies and on the analysis of preliminary results.

  9. Emerging organic contaminant removal depending on primary treatment and operational strategy in horizontal subsurface flow constructed wetlands: influence of redox.

    Science.gov (United States)

    Avila, Cristina; Reyes, Carolina; Bayona, Josep María; García, Joan

    2013-01-01

    This study aimed at assessing the influence of primary treatment (hydrolytic upflow sludge blanket (HUSB) reactor vs. conventional settling) and operational strategy (alternation of saturated/unsaturated phases vs. permanently saturated) on the removal of various emerging organic contaminants (i.e. ibuprofen, diclofenac, acetaminophen, tonalide, oxybenzone, bisphenol A) in horizontal subsurface flow constructed wetlands. For that purpose, a continuous injection experiment was carried out in an experimental treatment plant for 26 days. The plant had 3 treatment lines: a control line (settler-wetland permanently saturated), a batch line (settler-wetland operated with saturate/unsaturated phases) and an anaerobic line (HUSB reactor-wetland permanently saturated). In each line, wetlands had a surface area of 2.95 m(2), a water depth of 25 cm and a granular medium D(60) = 7.3 mm, and were planted with common reed. During the study period the wetlands were operated at a hydraulic and organic load of 25 mm/d and about 4.7 g BOD/m(2)d, respectively. The injection experiment delivered very robust results that show how the occurrence of higher redox potentials within the wetland bed promotes the elimination of conventional quality parameters as well as emerging microcontaminants. Overall, removal efficiencies were always greater for the batch line than for the control and anaerobic lines, and to this respect statistically significantly differences were found for ibuprofen, diclofenac, oxybenzone and bisphenol A. As an example, ibuprofen, whose major removal mechanism has been reported to be biodegradation under aerobic conditions, showed a higher removal in the batch line (85%) than in the control (63%) and anaerobic (52%) lines. Bisphenol A showed also a great dependence on the redox status of the wetlands, finding an 89% removal rate for the batch line, as opposed to the control and anaerobic lines (79 and 65%, respectively). Furthermore, diclofenac showed a greater

  10. Modeling Strategies: In Search of the Holy Grail.

    Science.gov (United States)

    Bollen, Kenneth A.

    2000-01-01

    Neither the four-step model nor the one-step procedure can actually tell whether the researcher has the right number of factors in structural equation modeling. In fact, for reasons discussed, a simple formulaic approach to the correct specification of models does not yet exist. (SLD)

  11. Prognosis Research Strategy (PROGRESS 3: prognostic model research.

    Directory of Open Access Journals (Sweden)

    Ewout W Steyerberg

    Full Text Available Prognostic models are abundant in the medical literature yet their use in practice seems limited. In this article, the third in the PROGRESS series, the authors review how such models are developed and validated, and then address how prognostic models are assessed for their impact on practice and patient outcomes, illustrating these ideas with examples.

  12. A descriptive ecosystem model - a strategy for model development during site investigations

    Energy Technology Data Exchange (ETDEWEB)

    Loefgren, Anders [Stockholm Univ. (Sweden). Dept. of Botany; Lindborg, Tobias [Swedish Nuclear Fuel and Waste Management Co., Stockholm (Sweden)

    2003-09-01

    This report describes a strategy for the development of a site descriptive model for the surface ecosystem on the potential deep repository sites. The surface ecosystem embraces many disciplines, and these have to be identified, described and integrated in order to construct a descriptive ecosystem model that describes and quantifies biotic and abiotic patterns and processes of importance for the ecosystem on the site. The descriptive model includes both present day conditions and historical information. The descriptive ecosystem model will be used to supply input data for the safety assessment and to serve as the baseline model for devising a monitoring program to detect short-term disturbances caused first by the site investigations and later by the construction of the deep repository. Furthermore, it will serve as a reference for future comparisons to determine more long-term effects or changes caused by the deep repository. The report adopts a non-site-specific approach focusing on the following aims: 1. To present and define the properties that will constitute the descriptive ecosystem model. 2. To present a methodology for determining those properties. 3. To describe and develop the framework for the descriptive ecosystem model by integrating the different properties. 4. To present vital data from other site descriptive models such as those for geology or hydrogeology that interacts with and affects the descriptive ecosystem model. The properties are described under four different sections: general physical properties of the landscape, the terrestrial system, the limnic system and the marine system. These headings are further subdivided into entities that integrate properties in relation to processes.

  13. Analyzing “Etka Chain Stores” Strategies and Proposing Optimal Strategies; Using SWOT Model based on Fuzzy Logic

    Directory of Open Access Journals (Sweden)

    Mohammad Aghaei

    2013-10-01

    Full Text Available To maintain and achieve optimal growth, development and to be more competitive, organizations need a comprehensive and coherent plan compatible with their objectives and goals which is called strategic planning. This research aims to analyse strategically “Etka Chain Stores” and to propose optimal strategies by using SWOT model and based on fuzzy logic. The scope of this research is limited to “Etka Chain stores in Tehran”. As instrumentation, a questioner, consisting of 138 questions, was used. The data have been extracted from interviews to managers and the expert in Etka Chain stores and from studying the available reports in the organization. Validity and reliability of research have been measured. The research consists of two main and four subsidiary questions and lacks hypothesis and regarding type of the objective, this research is an applied one and regarding the data gathering, it is experimental-descriptive and a case study. Analysing the data consists of five steps. In the first step, all the documents, interviews to organization experts and “Etka Chain stores” reports were analysed by tests and a list of environmental opportunities and threats together with strengths and weaknesses was prepared. In the second step, all the above-mentioned factors were screened and opportunities, threats, strengths and weaknesses were identified. In the third stage, by using key factors and SWOT model, the most suitable strategies for the company have been proposed. In the fifth step, an operational program is proposed. The findings of the research indicate that to be more competitive in key axis which includes customers, supply chain, expanses control, competitive smartness, human resources and operational productivity, the company should adopt suitable strategies. In this regard, the suitable strategies were identified, codified and proposed. In this research, planning a strategic management model, analysing value chain for spotting

  14. A strategy for Bayesian inference for computationally expensive models with application to the estimation of stem cell properties.

    Science.gov (United States)

    Overstall, Antony M; Woods, David C

    2013-06-01

    Bayesian inference is considered for statistical models that depend on the evaluation of a computationally expensive computer code or simulator. For such situations, the number of evaluations of the likelihood function, and hence of the unnormalized posterior probability density function, is determined by the available computational resource and may be extremely limited. We present a new example of such a simulator that describes the properties of human embryonic stem cells using data from optical trapping experiments. This application is used to motivate a novel strategy for Bayesian inference which exploits a Gaussian process approximation of the simulator and allows computationally efficient Markov chain Monte Carlo inference. The advantages of this strategy over previous methodology are that it is less reliant on the determination of tuning parameters and allows the application of model diagnostic procedures that require no additional evaluations of the simulator. We show the advantages of our method on synthetic examples and demonstrate its application on stem cell experiments.

  15. The structure of optimal time- and age-dependent harvesting in the Lotka-McKendrik population model.

    Science.gov (United States)

    Hritonenko, Natali; Yatsenko, Yuri

    2007-07-01

    The paper analyzes optimal harvesting of age-structured populations described by the Lotka-McKendrik model. It is shown that the optimal time- and age-dependent harvesting control involves only one age at natural conditions. This result leads to a new optimization problem with the time-dependent harvesting age as an unknown control. The integral Lotka model is employed to explicitly describe the time-varying age of harvesting. It is proven that in the case of the exponential discounting and infinite horizon the optimal strategy is a stationary solution with a constant harvesting age. A numeric example on optimal forest management illustrates the theoretical findings. Discussion and interpretation of the results are provided.

  16. Modeling Human Attention Allocation Strategies in Situations with Competing Criteria.

    Science.gov (United States)

    1981-10-01

    Depending upon the un- certainty, in general, one could request in- EST IAT1ON GEERATION CHOICE OF formation concerninz the range (the linear AN... Z . control of the spread of epidemics, monitor- 9. Jr two fire-fronts propogate with dif- ing the propogation of oil spills, chemical lerert

  17. The simulated features of heliospheric cosmic-ray modulation with a time-dependent drift model. III - General energy dependence

    Science.gov (United States)

    Potgieter, M. S.; Le Roux, J. A.

    1992-01-01

    The time-dependent cosmic-ray transport equation is solved numerically in an axially symmetric heliosphere. Gradient and curvature drifts are incorporated, together with an emulated wavy neutral sheet. This model is used to simulate heliospheric cosmic-ray modulation for the period 1985-1989 during which drifts are considered to be important. The general energy dependence of the modulation of Galactic protons is studied as predicted by the model for the energy range 1 MeV to 10 GeV. The corresponding instantaneous radial and latitudinal gradients are calculated, and it is found that, whereas the latitudinal gradients follow the trends in the waviness of the neutral sheet to a large extent for all energies, the radial gradients below about 200 MeV deviate from this general pattern. In particular, these gradients increase when the waviness decreases for the simulated period 1985-1987.3, after which they again follow the neutral sheet by increasing rapidly.

  18. Inequivalent models of irreversible dimer filling: ``Transition state'' dependence

    Science.gov (United States)

    Nord, R. S.; Evans, J. W.

    1990-12-01

    Irreversible adsorption of diatomics on crystalline surfaces is sometimes modeled as random dimer filling of adjacent pairs of sites on a lattice. We note that this process can be implemented in two distinct ways: (i) randomly pick adjacent pairs of sites, jj', and fill jj' only if both are empty (horizontal transition state); or (ii) randomly pick a single site, j, and if j and at least one neighbor are empty, then fill j and a randomly chosen empty neighbor (vertical transition state). Here it is instructive to consider processes which also include competitive random monomer filling of single sites. We find that although saturation (partial) coverages differ little between the models for pure dimer filling, there is a significant difference for comparable monomer and dimer filling rates. We present exact results for saturation coverage behavior for a linear lattice, and estimates for a square lattice. Ramifications for simple models of CO oxidation on surfaces are indicated.

  19. A Model for Geometry-Dependent Errors in Length Artifacts.

    Science.gov (United States)

    Sawyer, Daniel; Parry, Brian; Phillips, Steven; Blackburn, Chris; Muralikrishnan, Bala

    2012-01-01

    We present a detailed model of dimensional changes in long length artifacts, such as step gauges and ball bars, due to bending under gravity. The comprehensive model is based on evaluation of the gauge points relative to the neutral bending surface. It yields the errors observed when the gauge points are located off the neutral bending surface of a bar or rod but also reveals the significant error associated with out-of-straightness of a bar or rod even if the gauge points are located in the neutral bending surface. For example, one experimental result shows a length change of greater than 1.5 µm on a 1 m ball bar with an out-of-straightness of 0.4 mm. This and other results are in agreement with the model presented in this paper.

  20. A stochastic model of supercoiling-dependent transcription

    CERN Document Server

    Brackley, C A; Bentivogli, A; Corles, S; Gilber, N; Gonnella, G; Marenduzzo, D

    2016-01-01

    We propose a stochastic model for gene transcription coupled to DNA supercoiling, where we incorporate the experimental observation that polymerases create supercoiling as they unwind the DNA helix, and that these enzymes bind more favourably to regions where the genome is unwound. Within this model, we show that when the transcriptionally induced flux of supercoiling increases, there is a sharp crossover from a regime where torsional stresses relax quickly and gene transcription is random, to one where gene expression is highly correlated and tightly regulated by supercoiling. In the latter regime, the model displays transcriptional bursts, waves of supercoiling, and up-regulation of divergent or bidirectional genes. It also predicts that topological enzymes which relax twist and writhe should provide a pathway to down-regulate transcription. This article has been accepted for publication in Physical Review Letters, May 2016.