Statistics-based investigation on typhoon transition modeling
Zhang, Shuoyun; Nishijima, Kazuyoshi
The present study revisits the statistical modeling of typhoon transition. The objective of the study is to provide insights on plausible statistical typhoon transition models based on extensive statistical analysis. First, the correlation structures of the typhoon transition are estimated in terms...
Correlation-based Transition Modeling for External Aerodynamic Flows
Medida, Shivaji
Conventional turbulence models calibrated for fully turbulent boundary layers often over-predict drag and heat transfer on aerodynamic surfaces with partially laminar boundary layers. A robust correlation-based model is developed for use in Reynolds-Averaged Navier-Stokes simulations to predict laminar-to-turbulent transition onset of boundary layers on external aerodynamic surfaces. The new model is derived from an existing transition model for the two-equation k-omega Shear Stress Transport (SST) turbulence model, and is coupled with the one-equation Spalart-Allmaras (SA) turbulence model. The transition model solves two transport equations for intermittency and transition momentum thickness Reynolds number. Experimental correlations and local mean flow quantities are used in the model to account for effects of freestream turbulence level and pressure gradients on transition onset location. Transition onset is triggered by activating intermittency production using a vorticity Reynolds number criterion. In the new model, production and destruction terms of the intermittency equation are modified to improve consistency in the fully turbulent boundary layer post-transition onset, as well as ensure insensitivity to freestream eddy viscosity value specified in the SA model. In the original model, intermittency was used to control production and destruction of turbulent kinetic energy. Whereas, in the new model, only the production of eddy viscosity in SA model is controlled, and the destruction term is not altered. Unlike the original model, the new model does not use an additional correction to intermittency for separation-induced transition. Accuracy of drag predictions are improved significantly with the use of the transition model for several two-dimensional single- and multi-element airfoil cases over a wide range of Reynolds numbers. The new model is able to predict the formation of stable and long laminar separation bubbles on low-Reynolds number airfoils that
3D CFD computations of transitional flows using DES and a correlation based transition model
Sørensen, Niels N.
process can be important for the aerodynamic performance. Today, the most widespread approach is to use fully turbulent computations, where the transitional process is ignored and the entire boundary layer on the wings or airfoils is handled by the turbulence model. The correlation based transition model...... has lately shown promising results, and the present paper describes the application of the model to predict the drag and shedding frequency for flow around a cylinder from sub to super-critical Reynolds numbers. Additionally, the model is applied to the flow around the DU-96 airfoil, at high angles of...
Seyfert, Cornelia; Krumbein, Andreas
2013-01-01
The γ -Re θt model, a parallelizable, correlation-based, transition transport model was implemented into the DLR TAU code. Its capability to predict transition has been investigated at one-element airfoils, such as Somers NLF(1)-0416 airfoil and a transonic airfoil of Messerschmidt-Bölkow-Blohm. The influence of relevant input parameters is discussed in terms of predicted transition locations and skin friction coefficient distributions. The standard transition prediction approach in the DLR T...
von Essen, C; Mallonn, M; Tingley, B; Marcussen, M
2016-01-01
The transit timing variation technique (TTV) has been widely used to detect and characterize multiple planetary systems. Due to the observational biases imposed mainly by the photometric conditions and instrumentation and the high signal-to-noise required to produce primary transit observations, ground-based data acquired using small telescopes limit the technique to the follow-up of hot Jupiters. However, space-based missions such as Kepler and CoRoT have already revealed that hot Jupiters are mainly found in single systems. Thus, it is natural to question ourselves if we are properly using the observing time at hand carrying out such follow-ups, or if the use of medium-to-low quality transit light curves, combined with current standard techniques of data analysis, could be playing a main role against exoplanetary search via TTVs. The purpose of this work is to investigate to what extent ground-based observations treated with current modelling techniques are reliable to detect and characterize additional pla...
Resilience-based application of state-and-transition models
We recommend that several conceptual modifications be incorporated into the state-and-transition model (STM) framework to: 1) explicitly link this framework to the concept of ecological resilience, 2) direct management attention away from thresholds and toward the maintenance of state resilience, an...
Soerensen, Niels N.
2009-07-15
The report describes the application of the correlation based transition model of Menter et. al. [1, 2] to the cylinder drag crisis and the stalled flow over an DU-96-W-351 airfoil using the DES methodology. When predicting the flow over airfoils and rotors, the laminar-turbulent transition process can be important for the aerodynamic performance. Today, the most widespread approach is to use fully turbulent computations, where the transitional process is ignored and the entire boundary layer on the wings or airfoils is handled by the turbulence model. The correlation based transition model has lately shown promising results, and the present paper describes the application of the model to predict the drag and shedding frequency for flow around a cylinder from sub to super-critical Reynolds numbers. Additionally, the model is applied to the flow around the DU-96 airfoil, at high angles of attack. (au)
Development and validation of a transition model based on a mechanical approximation
Vizinho, R; Silvestre, M
2015-01-01
A new 3D transition turbulence model, more accurate and faster than an empirical transition model, is proposed. The model is based on the calculation of the pre-transitional u'v' due to mean flow shear. The present transition model is fully described and verified against eight benchmark test cases. Computations are performed for the ERCOFTAC flat-plate T3A, T3C and T3L test cases. Further, the model is validated for bypass, cross-flow and separation induced transition and compared with empirical transition models. The model presents very good results for bypass transition under zero-pressure gradient and with pressure gradient flow conditions. Also the model is able to correctly predict separation induced transition. However, for very low speed and low free-stream turbulence intensity the model delays separation induced transition onset. The model also shows very good results for transition under complex cross-flow conditions in three-dimensional geometries. The 3D tested case was the 6:1 prolate-spheroid und...
Optimisation of timetable-based, stochastic transit assignment models based on MSA
Nielsen, Otto Anker; Frederiksen, Rasmus Dyhr
2006-01-01
(CRM), such a large-scale transit assignment model was developed and estimated. The Stochastic User Equilibrium problem was solved by the Method of Successive Averages (MSA). However, the model suffered from very large calculation times. The paper focuses on how to optimise transit assignment models...
A Trust Transitivity Model Based-on Dempster-Shafer Theory
Xiang Qiu
2010-09-01
Full Text Available With the expansion of the Internet, Trust has attracted the attention of more and more researchers. This paper focuses on the trust transitivity problem and proposes a trust transitivity model based on Dempster-Shafer Theory. In our model, we show two types of trust relationship: Identity Trust and Behavior Trust based on Directness Trust and Recommendation Trust. Then we build the trust transitivity network and propose the trustworthiness propagation and combination rules. Finally, we propose a method for transforming the triple of evidence theory to a simple result in order to select the trust entity easily. We also use the nearness degree to analyze the transitivity rationality and show how to use the trust transitivity model by a shopping scenario in TaoBao and illustrate its legitimacy
Rail Transit Normality Passenger Flow Forecasting ModelBased on PSO-SMO
SongsongPang; Jianchu Kang; Yan Zhang
2012-01-01
With the increasing problems occurred frequently in traffic jams and accidents, increasing attention has been paid for the forecast for the rail transit passenger flow. Meanwhile, the ability to correctly predict the normality transit passenger flow plays a vital role for the analysis of large-scale events, weather and other unusual factors' impacts on passengers. In this paper, based on PSO-SMO (Particle Swarm Optimization-Sequential Minimal Optimization), a rail transit normality passenger flow forecasting model can be presented as follows. Firstly, a specific model can be built in use of the SMO algorithm. And then, combination of the model built above, the method of PSO-CV (Cross Validation) is introduced to optimize parameters. Finally, the model with optimal parameters extracts the training sample characteristics and the prediction passenger flow can be output. The results show that more than 80% of the data points' prediction relative error are less than 10%, certificating the validity of the model.
Equilibrium model and algorithm of urban transit assignment based on augmented network
无
2009-01-01
The passenger flow assignment problem for the urban transit network is relatively complicated due to the complexity of the network structure and many factors influencing the passengers’ route and line choices. In the past three decades, many models have been proposed to solve the passenger flow assignment problem. However, the common-line problem remains challenging in transit flow assignment. In this paper, the characteristics of the urban transit network is analysed and a new technique of augmented network is proposed to represent the urban transit system. The purpose is to eliminate the complex common-line problem when modeling transit passenger flow assignment. Through this augmentation technique, the urban transit system can be represented by an augmented network-it then behaves like a simple network and can be used as a generalized network for traffic assignment or network analysis. This paper presents a user equilibrium model for the urban transit assignment problem based on such a technique. A numerical example is also provided to illustrate the approach.
Dynamic Schedule-Based Assignment Model for Urban Rail Transit Network with Capacity Constraints
Baoming Han
2015-01-01
Full Text Available There is a great need for estimation of passenger flow temporal and spatial distribution in urban rail transit network. The literature review indicates that passenger flow assignment models considering capacity constraints with overload delay factor for in-vehicle crowding are limited in schedule-based network. This paper proposes a stochastic user equilibrium model for solving the assignment problem in a schedule-based rail transit network with considering capacity constraint. As splitting the origin-destination demands into the developed schedule expanded network with time-space paths, the model transformed into a dynamic schedule-based assignment model. The stochastic user equilibrium conditions can be equivalent to the equilibrium passenger overload delay with crowding penalty in the transit network. The proposal model can estimate the path choice probability according to the equilibrium condition when passengers minimize their perceptive cost in a schedule-based network. Numerical example in Beijing urban rail transit (BURT network is used to demonstrate the performance of the model and estimate the passenger flow temporal and spatial distribution more reasonably and dynamically with train capacity constraints.
3D CFD computations of trasitional flows using DES and a correlation based transition model
Sørensen, Niels N.; Bechmann, Andreas; Zahle, Frederik
2011-01-01
The present article describes the application of the correlation based transition model of Menter et al. in combination with the Detached Eddy Simulation (DES) methodology to two cases with large degree of flow separation typically considered difficult to compute. Firstly, the flow is computed over...
Liechty, Derek S.; Lewis, Mark
2010-01-01
A new method of treating electronic energy level transitions as well as linking ionization to electronic energy levels is proposed following the particle-based chemistry model of Bird. Although the use of electronic energy levels and ionization reactions in DSMC are not new ideas, the current method of selecting what level to transition to, how to reproduce transition rates, and the linking of the electronic energy levels to ionization are, to the author s knowledge, novel concepts. The resulting equilibrium temperatures are shown to remain constant, and the electronic energy level distributions are shown to reproduce the Boltzmann distribution. The electronic energy level transition rates and ionization rates due to electron impacts are shown to reproduce theoretical and measured rates. The rates due to heavy particle impacts, while not as favorable as the electron impact rates, compare favorably to values from the literature. Thus, these new extensions to the particle-based chemistry model of Bird provide an accurate method for predicting electronic energy level transition and ionization rates in gases.
Csank, Jeffrey T.; Stueber, Thomas J.
2012-01-01
An inlet system is being tested to evaluate methodologies for a turbine based combined cycle propulsion system to perform a controlled inlet mode transition. Prior to wind tunnel based hardware testing of controlled mode transitions, simulation models are used to test, debug, and validate potential control algorithms. One candidate simulation package for this purpose is the High Mach Transient Engine Cycle Code (HiTECC). The HiTECC simulation package models the inlet system, propulsion systems, thermal energy, geometry, nozzle, and fuel systems. This paper discusses the modification and redesign of the simulation package and control system to represent the NASA large-scale inlet model for Combined Cycle Engine mode transition studies, mounted in NASA Glenn s 10- by 10-Foot Supersonic Wind Tunnel. This model will be used for designing and testing candidate control algorithms before implementation.
Modeling of metamagnetism in metallic-based materials with first-order transitions
Yi Jin, E-mail: yijin@gwmail.gwu.edu [Institute for Magnetics Research, George Washington University, Washington DC 20052 (United States); Gu Shuo; Della Torre, Edward; Bennett, Lawrence H. [Institute for Magnetics Research, George Washington University, Washington DC 20052 (United States); Provenzano, Virgil [Metallurgy Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States)
2012-05-01
During the past decade, the magnetic properties of metallic-based materials with first-order transitions have been extensively studied, motivated in part by the observation of large magnetocaloric effect (MCE) peaks displayed by these materials near room temperature. These large peaks are believed to be the result of the materials' magnetic properties at the metamagnetic region, characterized by (i) the thermal-induced transition from the ferromagnetic state (FM) to the paramagnetic state (PM) near the Curie temperature (T{sub C}) and (ii) the field-induced transition from PM state to FM state above T{sub C}. We developed a phenomenological model that utilizes the materials' mixed-state probability function to model the materials' complex hysteretic and properties at metamagnetic region. The approximate probability functions are obtained from the first and second derivatives of the magnetization curve. The probability functions are used to separate the materials' magnetization into a FM state component and a PM state component. The applicability of the model is demonstrated for a metallic-based metamagnetic material, Gd{sub 5}Si{sub 2}Ge{sub 2} compound, where the modeled behaviors show remarkable agreement with the experimental data at the metamagnetic region and provide new physical insights in this mixed-state region. Specifically, in the region of metamagnetic transition, the PM state component is non-reversible and is a function of the FM state component.
Semiempirical Modeling of Reset Transitions in Unipolar Resistive-Switching based Memristors
R. Picos
2015-06-01
Full Text Available We have measured the transition process from the high to low resistivity states, i.e., the reset process of resistive switching based memristors based on Ni/HfO2/Si-n+ structures, and have also developed an analytical model for their electrical characteristics. When the characteristic curves are plotted in the current-voltage (I-V domain a high variability is observed. In spite of that, when the same curves are plotted in the charge-flux domain (Q-phi, they can be described by a simple model containing only three parameters: the charge (Qrst and the flux (rst at the reset point, and an exponent, n, relating the charge and the flux before the reset transition. The three parameters can be easily extracted from the Q-phi plots. There is a strong correlation between these three parameters, the origin of which is still under study.
Analysis of phase transition points for a two-color agent-based model
Shin, J. K.; Jung, P. S.
2013-04-01
The agent-based model treated in the present study describes dynamics of two types of population in a gravity-like potential field. In previous studies, the model was known to exhibit various spatiotemporal patterns on two-dimensioanl lattice systems. However, the patterns were classified depending purely on eye observations, and the underlying dynamics of these patterns were not fully explored. It remained a question to be answered if these eye observation-based classifications could be confirmed by any analytical means. To pursue the question, we first suggest several analytic quantities, such as convergence time steps and reaction speed, to replace the eye observations. As a result, we show that a phase diagram can be reasonably drawn on the contour diagram of the time steps. In addition, we find a power-law scaling in the reaction speed, confirming that a phase transition really is involved there. Next, as a main part of the present study, we apply analytical methods to calculate two important phase transition points from the system. The results from the analytical approach agreed well with the numerically obtained phase transition points from the agent-based model. In general, the paper serves as an example study of estimating global phenomena of complex systems in terms of local parameters of the system.
Analysis of Phase Transition in Traffic Flow based on a New Model of Driving Decision
Different driving decisions will cause different processes of phase transition in traffic flow. To reveal the inner mechanism, this paper built a new cellular automaton (CA) model, based on the driving decision (DD). In the DD model, a driver's decision is divided into three stages: decision-making, action, and result. The acceleration is taken as a decision variable and three core factors, i.e. distance between adjacent vehicles, their own velocity, and the preceding vehicle's velocity, are considered. Simulation results show that the DD model can simulate the synchronized flow effectively and describe the phase transition in traffic flow well. Further analyses illustrate that various density will cause the phase transition and the random probability will impact the process. Compared with the traditional NaSch model, the DD model considered the preceding vehicle's velocity, the deceleration limitation, and a safe distance, so it can depict closer to the driver preferences on pursuing safety, stability and fuel-saving and has strong theoretical innovation for future studies. (interdisciplinary physics and related areas of science and technology)
Analysis of Phase Transition in Traffic Flow based on a New Model of Driving Decision
Peng, Yu; Shang, Hua-Yan; Lu, Hua-Pu
2011-07-01
Different driving decisions will cause different processes of phase transition in traffic flow. To reveal the inner mechanism, this paper built a new cellular automaton (CA) model, based on the driving decision (DD). In the DD model, a driver's decision is divided into three stages: decision-making, action, and result. The acceleration is taken as a decision variable and three core factors, i.e. distance between adjacent vehicles, their own velocity, and the preceding vehicle's velocity, are considered. Simulation results show that the DD model can simulate the synchronized flow effectively and describe the phase transition in traffic flow well. Further analyses illustrate that various density will cause the phase transition and the random probability will impact the process. Compared with the traditional NaSch model, the DD model considered the preceding vehicle's velocity, the deceleration limitation, and a safe distance, so it can depict closer to the driver preferences on pursuing safety, stability and fuel-saving and has strong theoretical innovation for future studies.
Mechanism-based model of a mass rapid transit system: A perspective
Legara, Erika Fille; Khoon, Lee Kee; Guang, Hung Gih; Monterola, Christopher
2015-01-01
In this paper, we discuss our findings on the spatiotemporal dynamics within the mass rapid transit (MRT) system of Singapore. We show that the trip distribution of Origin-Destination (OD) station pairs follows a power-law, implying the existence of critical OD pairs. We then present and discuss the empirically validated agent-based model (ABM) we have developed. The model allows recreation of the observed statistics and the setting up of various scenarios and their effects on the system, such as increasing the commuter population and the propagation of travel delays within the transportation network. The proposed model further enables identification of bottlenecks that can cause the MRT to break down, and consequently provide foresight on how such disruptions can possibly be managed. This can potentially provide a versatile approach for transport planners and government regulators to make quantifiable policies that optimally balance cost and convenience as a function of the number of the commuting public.
A Low-Carbon-Based Bilevel Optimization Model for Public Transit Network
Xu Sun
2013-01-01
Full Text Available To satisfy the demand of low-carbon transportation, this paper studies the optimization of public transit network based on the concept of low carbon. Taking travel time, operation cost, energy consumption, pollutant emission, and traffic efficiency as the optimization objectives, a bilevel model is proposed in order to maximize the benefits of both travelers and operators and minimize the environmental cost. Then the model is solved with the differential evolution (DE algorithm and applied to a real network of Baoji city. The results show that the model can not only ensure the benefits of travelers and operators, but can also reduce pollutant emission and energy consumption caused by the operations of buses, which reflects the concept of low carbon.
ARX-NNPLS Model Based Optimization Strategy and Its Application in Polymer Grade Transition Process
费正顺; 胡斌; 叶鲁彬; 梁军
2012-01-01
Since it is often difficult to build differential algebraic equations (DAEs) for chemical processes, a new data-based modeling approach is proposed using ARX (AutoRegressive with eXogenous inputs) combined with neural network under partial least squares framework (ARX-NNPLS), in which less specific knowledge of the process is required but the input and output data. To represent the dynamic and nonlinear behavior of the process, the ARX combined with neural network is used in the partial least squares (PLS) inner model between input and output latent variables. In the proposed dynamic optimization strategy based on the ARX-NNPLS model, neither parameterization nor iterative solving process for DAEs is needed as the ARX-NNPLS model gives a proper representation for the dynamic behavior of the process, and the computing time is greatly reduced compared to conventional control vector parameterization method. To demonstrate the ARX-NNPLS model based optimization strategy, the polyethylene grade transition in gas phase fluidized-bed reactor is taken into account. The optimization results show that the final optimal trajectory of quality index determined by the new approach moves faster to the target values and the computing time is much less.
Baumgart, Diane; Perino, Daniel M.
The guide, developed by the Secondary Transition and Employment Project (STEP) in Idaho, describes a rationale and model for implementing secondary/vocational assessment of students with disabilities that is integrated with curriculum and transition strategies. Assessment and curricular strategies are particularly intended for students in rural…
Willatzen, M
2004-05-01
A comparison between three mathematical models frequently used in flow acoustics is presented and discussed with respect to ultrasonic flow-meter performance based on the transit-time method. The flow-meter spoolpiece geometry is assumed to be a cylindrical pipe. Semi-analytical calculations employing the Frobenius power series expansion method are shown for the cases of a constant-, linear-, parabolic-, and cubic-flow profiles although the Frobenius method presented can be applied to any smooth flow profile. It is shown that the so-called deviation of measurement, often used as a measure of the flow-meter accuracy, is strongly dependent on the acoustic mode excited and the flow profile. Furthermore, differences with respect to deviation of measurement results exist among the three mathematical models analyzed. PMID:15110538
Development of a transient boiling transition analysis method based on a film flow model
A new single-channel, transient boiling transition (BT) prediction method based on a film flow model has been developed for a core thermal-hydraulic code. This method could predict onset and location of dryout and rewetting under transient conditions mechanically based on the dryout criterion and with consideration of the spacer effect. The developed method was applied to analysis of steady-state and transient BT experiments using BWR fuel bundle mock-ups for verification. Comparisons between calculated results and experimental data showed that the developed method tended to predict occurrence of rewetting earlier, however, onset time of BT and maximum rod surface temperature were well predicted within 0.6 s and 20degC, respectively. Moreover, it was confirmed that consideration of the spacer effect on liquid film flow rate on the rod surface was required to predict dryout phenomena accurately under transient conditions. (author)
Agent based models of language competition: macroscopic descriptions and order-disorder transitions
Vazquez, F.; Castelló, X.; San Miguel, M.
2010-04-01
We investigate the dynamics of two agent based models of language competition. In the first model, each individual can be in one of two possible states, either using language X or language Y, while the second model incorporates a third state XY, representing individuals that use both languages (bilinguals). We analyze the models on complex networks and two-dimensional square lattices by analytical and numerical methods, and show that they exhibit a transition from one-language dominance to language coexistence. We find that the coexistence of languages is more difficult to maintain in the bilinguals model, where the presence of bilinguals facilitates the ultimate dominance of one of the two languages. A stability analysis reveals that the coexistence is more unlikely to happen in poorly connected than in fully connected networks, and that the dominance of just one language is enhanced as the connectivity decreases. This dominance effect is even stronger in a two-dimensional space, where domain coarsening tends to drive the system towards language consensus.
Agent Based Models of Language Competition: Macroscopic descriptions and Order-Disorder transitions
Vazquez, F; Miguel, M San
2010-01-01
We investigate the dynamics of two agent based models of language competition. In the first model, each individual can be in one of two possible states, either using language $X$ or language $Y$, while the second model incorporates a third state XY, representing individuals that use both languages (bilinguals). We analyze the models on complex networks and two-dimensional square lattices by analytical and numerical methods, and show that they exhibit a transition from one-language dominance to language coexistence. We find that the coexistence of languages is more difficult to maintain in the Bilinguals model, where the presence of bilinguals in use facilitates the ultimate dominance of one of the two languages. A stability analysis reveals that the coexistence is more unlikely to happen in poorly-connected than in fully connected networks, and that the dominance of only one language is enhanced as the connectivity decreases. This dominance effect is even stronger in a two-dimensional space, where domain coar...
Agent based models of language competition: macroscopic descriptions and order–disorder transitions
We investigate the dynamics of two agent based models of language competition. In the first model, each individual can be in one of two possible states, either using language X or language Y, while the second model incorporates a third state XY, representing individuals that use both languages (bilinguals). We analyze the models on complex networks and two-dimensional square lattices by analytical and numerical methods, and show that they exhibit a transition from one-language dominance to language coexistence. We find that the coexistence of languages is more difficult to maintain in the bilinguals model, where the presence of bilinguals facilitates the ultimate dominance of one of the two languages. A stability analysis reveals that the coexistence is more unlikely to happen in poorly connected than in fully connected networks, and that the dominance of just one language is enhanced as the connectivity decreases. This dominance effect is even stronger in a two-dimensional space, where domain coarsening tends to drive the system towards language consensus
An Extensible Dialogue Script for a Robot Based on Unification of State-Transition Models
Yosuke Matsusaka
2010-01-01
development of communication function of the robot. Compared to previous extension-by-connection method used in behavior-based communication robot developments, the extension-by-unification method has the ability to decompose the script into components. The decomposed components can be recomposed to build a new application easily. In this paper, first we, explain a reformulation we have applied to the conventional state-transition model. Second, we explain a set of algorithms to decompose, recompose, and detect the conflict of each component. Third, we explain a dialogue engine and a script management server we have developed. The script management server has a function to propose reusable components to the developer in real time by implementing the conflict detection algorithm. The dialogue engine SEAT (Speech Event-Action Translator has flexible adapter mechanism to enable quick integration to robotic systems. We have confirmed that by the application of three robots, development efficiency has improved by 30%.
Robust Quantum-Based Interatomic Potentials for Multiscale Modeling in Transition Metals
Moriarty, J A; Benedict, L X; Glosli, J N; Hood, R Q; Orlikowski, D A; Patel, M V; Soderlind, P; Streitz, F H; Tang, M; Yang, L H
2005-09-27
First-principles generalized pseudopotential theory (GPT) provides a fundamental basis for transferable multi-ion interatomic potentials in transition metals and alloys within density-functional quantum mechanics. In the central bcc metals, where multi-ion angular forces are important to materials properties, simplified model GPT or MGPT potentials have been developed based on canonical d bands to allow analytic forms and large-scale atomistic simulations. Robust, advanced-generation MGPT potentials have now been obtained for Ta and Mo and successfully applied to a wide range of structural, thermodynamic, defect and mechanical properties at both ambient and extreme conditions. Selected applications to multiscale modeling discussed here include dislocation core structure and mobility, atomistically informed dislocation dynamics simulations of plasticity, and thermoelasticity and high-pressure strength modeling. Recent algorithm improvements have provided a more general matrix representation of MGPT beyond canonical bands, allowing improved accuracy and extension to f-electron actinide metals, an order of magnitude increase in computational speed for dynamic simulations, and the development of temperature-dependent potentials.
Sumangala Patil; P.Nagaraju; Somashekar Deasi
2012-01-01
This paper suggests an approach to software system architecture specification based on behavior models. The behavior of the system is defined as an event occurring probability and time. The behavior ofthe system over a time of stationary Markov process is completely characterized by the one step transition matrix, the matrix of instantaneous transition rates. Given the element of the appropriative matrix, it is possible to calculate probability of event of the process.
Coordinated scheduling model for intermodal transit hubs based on GI/MK/1 queuing system
贾洪飞; 曹雄赳; 杨丽丽
2015-01-01
Coordinated scheduling of multimode plays a pivotal role in the rapid gathering and dissipating of passengers in transport hubs. Based on the survey data, the whole-day reaching time distribution at transfer points of passengers from the dominant mode to the connecting mode was achieved. AGI/MK/1 bulk service queuing system was constituted by putting the passengers’ reaching time distribution as the input and the connecting mode as the service institution. Through queuing theory, the relationship between average queuing length under steady-state and headway of the connecting mode was achieved. By putting the minimum total cost of system as optimization objective, the headway as decision variable, a coordinated scheduling model of multimode in intermodal transit hubs was established. At last, a dynamic scheduling strategy was generated to cope with the unexpected changes of the dominant mode. The instance analysis indicates that this model can significantly reduce passengers’ queuing time by approximately 17% with no apparently increase in departure frequency, which provides a useful solution for the coordinated scheduling of different transport modes in hubs.
UTM: Universal Transit Modeller
Deeg, Hans J.
2014-12-01
The Universal Transit Modeller (UTM) is a light-curve simulator for all kinds of transiting or eclipsing configurations between arbitrary numbers of several types of objects, which may be stars, planets, planetary moons, and planetary rings. A separate fitting program, UFIT (Universal Fitter) is part of the UTM distribution and may be used to derive best fits to light-curves for any set of continuously variable parameters. UTM/UFIT is written in IDL code and its source is released in the public domain under the GNU General Public License.
HMX, RDX and NTO based cast-cured plastic bounded explosive (PBX) are widely used in insensitive ammunitions. Designing modern warheads needs robust and reliable models to compute shock ignition and detonation propagation inside PBX. Comparing to a pressed PBX, a cast-cured PBX is not porous and the hot-spots are mainly located at the grain-binder interface leading to a different burning behavior during shock-to-detonation transition. Here, we review the shock-to-detonation transition (SDT) and its modeling for cast-cured PBX containing HMX, RDX and NTO. Future direction is given in conclusion.
Baudin, G.; Roudot, M.; Genetier, M.; Mateille, P.; Lefrançois, A.
2014-05-01
HMX, RDX and NTO based cast-cured plastic bounded explosive (PBX) are widely used in insensitive ammunitions. Designing modern warheads needs robust and reliable models to compute shock ignition and detonation propagation inside PBX. Comparing to a pressed PBX, a cast-cured PBX is not porous and the hot-spots are mainly located at the grain-binder interface leading to a different burning behavior during shock-to-detonation transition. Here, we review the shock-to-detonation transition (SDT) and its modeling for cast-cured PBX containing HMX, RDX and NTO. Future direction is given in conclusion.
Economic Growth Models Transition
Coralia Angelescu
2006-03-01
Full Text Available The transitional recession in countries of Eastern Europe has been much longer than expected. The legacy and recent policy mistakes have both contributed to the slow progress. As structural reforms and gradual institution building have taken hold, the post-socialist economics have started to recover, with some leading countries building momentum toward faster growth. There is a possibility that in wider context of globalization several of these emerging market economies will be able to catch up with the more advanced industrial economies in a matter of one or two generations. Over the past few years, most candidate countries have made progress in the transition to a competitive market economy, macroeconomic stabilization and structural reform. However their income levels have remained far below those in the Member States. Measured by per capita income in purchasing power standards, there has been a very limited amount of catching up over the past fourteen years. Prior, the distinctions between Solow-Swan model and endogenous growth model. The interdependence between transition and integration are stated in this study. Finally, some measures of macroeconomic policy for sustainable growth are proposed in correlation with real macroeconomic situation of the Romanian economy. Our study would be considered the real convergence for the Romanian economy and the recommendations for the adequate policies to achieve a fast real convergence and sustainable growth.
Economic Growth Models Transition
Coralia Angelescu
2006-01-01
Full Text Available The transitional recession in countries of Eastern Europe has been much longer than expected. The legacy and recent policy mistakes have both contributed to the slow progress. As structural reforms and gradual institution building have taken hold, the post-socialist economics have started to recover, with some leading countries building momentum toward faster growth. There is a possibility that in wider context of globalization several of these emerging market economies will be able to catch up with the more advanced industrial economies in a matter of one or two generations. Over the past few years, most candidate countries have made progress in the transition to a competitive market economy, macroeconomic stabilization and structural reform. However their income levels have remained far below those in the Member States. Measured by per capita income in purchasing power standards, there has been a very limited amount of catching up over the past fourteen years. Prior, the distinctions between Solow-Swan model and endogenous growth model. The interdependence between transition and integration are stated in this study. Finally, some measures of macroeconomic policy for sustainable growth are proposed in correlation with real macroeconomic situation of the Romanian economy. Our study would be considered the real convergence for the Romanian economy and the recommendations for the adequate policies to achieve a fast real convergence and sustainable growth.
YE Bin; GAO Cai; YANG Suo; LIU Xiang-nong; JIANG Bin
2012-01-01
To investigate the enthalpy relaxation behavior of maltitol glass system,differential scanning calorimetry (DSC) was used to obtain the specific heat capacity[Cp(T)] near the glass transition temperature(Tg) at different cooling rates ranged between 1 and 20 K/min.Three phenomenological models of enthalpy relaxation,ToolNarayanaswamy-Moynihan(TNM) model,Adam-Gibbs-Vogel(AGV) model and Gómez Ribelles(GR) model,were used to simulate the experimental data.The models' parameters were obtained via a curve-fitting method.The results indicate that TNM and AGV models gave the almost identical prediction powers and can reproduce the curves of experimental Cp(T) very well.However,the prediction power of GR model evolved from configurational entropy approach is not so good as those of TNM and AGV models.In particular,the metastable limit state parameter(δ) introduced by Gómez Ribelles has insignificant effect on the enthalpy relaxation of the small molecular hydrogen-bonding glass system.
Research on Public Transit Network Hierarchy Based on Residential Transit Trip Distance
Gao Jian
2012-01-01
Full Text Available To the problem of being lack of transit network hierarchy theory, a research on public transit network hierarchy optimization based on residential transit trip distance is conducted. Firstly, the hierarchy standard of transit network is given, in addition, both simulating electron cloud model and Rayleigh distribution model are used to fit the residential transit trip distance. Secondly, from the view of balance between supply and demand, the hierarchy step of transit network based on residential transit trip distance is proposed. Then, models of transit’s supply turnover and demand turnover are developed. Finally, the method and models are applied into transit network optimization of Baoding, Hebei, China.
Determination of Scheduled Travel Time for a Fixed Transit Route Based on Multistate Model
Shukai Chen; Daniel Jian Sun; and Rui Xue
2016-01-01
In order to provide the guideline for bus drivers to adjust speed to minimize scheduled deviation, the method for setting bus scheduled travel time is proposed. Firstly, multistate model is introduced to fit historical travel time data and identify different service states. Based on the calibrated travel time distribution parameters, an optimization model is proposed, followed by a Monte Carlo ( MC) simulation based genetic algorithm ( GA) procedure to obtain the optimal scheduled time. A case study from a fixed bus route from Shenzhen is used to demonstrate the model applicability. The sensitivity analysis is conducted to study the effects of parameters setting on optimal slack time for each segment. The results show that multistate model fits travel time under peak hours better than Lognormal distribution, and the length of scheduled travel time basically reflects travel time reliability.
姚向明; 赵鹏; 禹丹丹
2015-01-01
The major objective of this work was to establish a structural state-space model to estimate the dynamic origin-destination(O-D) matrices for urban rail transit network, using in- and out-flows at each station from automatic fare collection(AFC) system as the real time observed passenger flow counts. For lacking of measurable passenger flow information, the proposed model employs priori O-D matrices and travel time distribution from historical travel records in AFC system to establish the dynamic system equations. An arriving rate based on travel time distribution is defined to identify the dynamic interrelations between time-varying O-D flows and observed flows, which greatly decreases the computational complexity and improve the model’s applicability for large-scale network. This methodology is tested in a real transit network from Beijing subway network in China through comparing the predicted matrices with the true matrices. Case study results indicate that the proposed model is effective and applicative for estimating dynamic O-D matrices for large-scale rail transit network.
姚向明; 赵鹏; 禹丹丹
2015-01-01
The major objective of this work was to establish a structural state-space model to estimate the dynamic origin-destination (O-D) matrices for urban rail transit network, using in- and out-flows at each station from automatic fare collection (AFC) system as the real time observed passenger flow counts. For lacking of measurable passenger flow information, the proposed model employs priori O-D matrices and travel time distribution from historical travel records in AFC system to establish the dynamic system equations. An arriving rate based on travel time distribution is defined to identify the dynamic interrelations between time-varying O-D flows and observed flows, which greatly decreases the computational complexity and improve the model’s applicability for large-scale network. This methodology is tested in a real transit network from Beijing subway network in China through comparing the predicted matrices with the true matrices. Case study results indicate that the proposed model is effective and applicative for estimating dynamic O-D matrices for large-scale rail transit network.
A Gaussian Model-Based Probabilistic Approach for Pulse Transit Time Estimation.
Jang, Dae-Geun; Park, Seung-Hun; Hahn, Minsoo
2016-01-01
In this paper, we propose a new probabilistic approach to pulse transit time (PTT) estimation using a Gaussian distribution model. It is motivated basically by the hypothesis that PTTs normalized by RR intervals follow the Gaussian distribution. To verify the hypothesis, we demonstrate the effects of arterial compliance on the normalized PTTs using the Moens-Korteweg equation. Furthermore, we observe a Gaussian distribution of the normalized PTTs on real data. In order to estimate the PTT using the hypothesis, we first assumed that R-waves in the electrocardiogram (ECG) can be correctly identified. The R-waves limit searching ranges to detect pulse peaks in the photoplethysmogram (PPG) and to synchronize the results with cardiac beats--i.e., the peaks of the PPG are extracted within the corresponding RR interval of the ECG as pulse peak candidates. Their probabilities of being the actual pulse peak are then calculated using a Gaussian probability function. The parameters of the Gaussian function are automatically updated when a new pulse peak is identified. This update makes the probability function adaptive to variations of cardiac cycles. Finally, the pulse peak is identified as the candidate with the highest probability. The proposed approach is tested on a database where ECG and PPG waveforms are collected simultaneously during the submaximal bicycle ergometer exercise test. The results are promising, suggesting that the method provides a simple but more accurate PTT estimation in real applications. PMID:25420274
Challal Mouloud
2016-01-01
Full Text Available In this paper, an equivalent circuit model (ECM for a defected ground structure (DGS pattern is proposed and evaluated for designing a compact low-pass filter (LPF. The proposed ECM is based on microstrip lines and microstrip-slotline transitions. Every slotlines of the DGS unit are modeled by ideals transmission lines of characteristic impedance and electrical length. Comparison between full-wave EM and circuit simulations illustrates the validity of the proposed ECM.
Lemoine, Pablo D; Cordovez, Juan Manuel; Zambrano, Juan Manuel; Sarmiento, Olga L; Meisel, Jose D; Valdivia, Juan Alejandro; Zarama, Roberto
2016-07-01
The effect of transport infrastructure on walking is of interest to researchers because it provides an opportunity, from the public policy point of view, to increase physical activity (PA). We use an agent based model (ABM) to examine the effect of transport infrastructure on walking. Particular relevance is given to assess the effect of the growth of the Bus Rapid Transit (BRT) system in Bogotá on walking. In the ABM agents are assigned a home, work location, and socioeconomic status (SES) based on which they are assigned income for transportation. Individuals must decide between the available modes of transport (i.e., car, taxi, bus, BRT, and walking) as the means of reaching their destination, based on resources and needed travel time. We calibrated the model based on Bogota's 2011 mobility survey. The ABM results are consistent with previous empirical findings, increasing BRT access does indeed increase the number of minutes that individuals walk for transportation, although this effect also depends on the availability of other transport modes. The model indicates a saturation process: as more BRT lanes are added, the increment in minutes walking becomes smaller, and eventually the walking time decreases. Our findings on the potential contribution of the expansion of the BRT system to walking for transportation suggest that ABMs may prove helpful in designing policies to continue promoting walking. PMID:27012602
J. M. Carcione
2014-06-01
Full Text Available The Earth crust presents two dissimilar rheological behaviours depending on the in-situ stress-temperature conditions. The upper, cooler, part is brittle while deeper zones are ductile. Seismic waves may reveal the presence of the transition but a proper characterization is required. We first obtain a stress–strain relation including the effects of shear seismic attenuation and ductility due to shear deformations and plastic flow. The anelastic behaviour is based on the Burgers mechanical model to describe the effects of seismic attenuation and steady-state creep flow. The shear Lamé constant of the brittle and ductile media depends on the in-situ stress and temperature through the shear viscosity, which is obtained by the Arrhenius equation and the octahedral stress criterion. The P- and S-wave velocities decrease as depth and temperature increase due to the geothermal gradient, an effect which is more pronounced for shear waves. We then obtain the P-S and SH equations of motion recast in the velocity-stress formulation, including memory variables to avoid the computation of time convolutions. The equations correspond to isotropic anelastic and inhomogeneous media and are solved by a direct grid method based on the Runge–Kutta time stepping technique and the Fourier pseudospectral method. The algorithm is tested with success against known analytical solutions for different shear viscosities. A realistic example illustrates the computation of surface and reverse-VSP synthetic seismograms in the presence of an abrupt brittle-ductile transition.
This work aims to study effects of toroidal flow on the L-H transition phenomenon in tokamak plasmas using bifurcation concept. Two-field (thermal and particle) transport equations with both neoclassical and turbulent effects included are solved simultaneously. The transport suppression mechanism used in this work is flow shear, which is assumed to affect only the turbulent transport. The flow shear can be calculated from the force balance equation with toroidal flow as a main contributor. The toroidal velocity profile is calculated using three different models. The first model is an empirical model in which the velocity is dependent on local ion temperature. The second model is based on neoclassical toroidal viscosity theory in which the velocity is driven by ion temperature gradient. In the third model, the velocity is dependent on current density flow in plasma. The two transport equations are solved both analytically and numerically using MATLAB to study the criteria for H-mode formation, pedestal width and its dynamics. The results from three toroidal velocity models are compared and analyzed with respect to bifurcation behavior and plasma performance.
By utilizing a two-step process to express the charge generation and separation mechanism of the transition metal oxides (TMOs) interconnector layer, a numerical model was proposed for tandem organic light emitting diodes (OLEDs) with a TMOs thin film as the interconnector layer. This model is valid not only for an n-type TMOs interconnector layer, but also for a p-type TMOs interconnector layer. Based on this model, the influences of different carrier injection barriers at the interface of the electrode/organic layer on the charge generation ability of interconnector layers were studied. In addition, the distribution characteristics of carrier concentration, electric field intensity and potential in the device under different carrier injection barriers were studied. The results show that when keeping one carrier injection barrier as a constant while increasing another carrier injection barrier, carriers injected into the device were gradually decreased, the carrier generation ability of the interconnector layer was gradually reduced, the electric field intensity at the interface of the organic/electrode was gradually enhanced, and the electric field distribution became nearly linear: the voltage drops in two light units gradually became the same. Meanwhile, the carrier injection ability decreased as another carrier injection barrier increased. The simulation results agree with the experimental data. The obtained results can provide us with a deep understanding of the work mechanism of TMOs-based tandem OLEDs. (semiconductor devices)
SU-E-T-05: A 2D EPID Transit Dosimetry Model Based On An Empirical Quadratic Formalism
Tan, Y [University of Glasgow, Glasgow, Scotland (United Kingdom); National University Cancer Institute (Singapore); Metwaly, M; Glegg, M [Beatson West of Scotland Cancer Centre, Glasgow, Scotland (United Kingdom); Baggarley, S [National University Cancer Institute (Singapore); Elliott, A [University of Glasgow, Glasgow, Scotland (United Kingdom)
2014-06-01
Purpose: To describe a 2D electronic portal imaging device (EPID) transit dosimetry model, based on an empirical quadratic formalism, that can predict either EPID or in-phantom dose distribution for comparisons with EPID captured image or treatment planning system (TPS) dose respectively. Methods: A quadratic equation can be used to relate the reduction in intensity of an exit beam to the equivalent path length of the attenuator. The calibration involved deriving coefficients from a set of dose planes measured for homogeneous phantoms with known thicknesses under reference conditions. In this study, calibration dose planes were measured with EPID and ionisation chamber (IC) in water for the same reference beam (6MV, 100mu, 20×20cm{sup 2}) and set of thicknesses (0–30cm). Since the same calibration conditions were used, the EPID and IC measurements can be related through the quadratic equation. Consequently, EPID transit dose can be predicted from TPS exported dose planes and in-phantom dose can be predicted using EPID distribution captured during treatment as an input. The model was tested with 4 open fields, 6 wedge fields, and 7 IMRT fields on homogeneous and heterogeneous phantoms. Comparisons were done using 2D absolute gamma (3%/3mm) and results were validated against measurements with a commercial 2D array device. Results: The gamma pass rates for comparisons between EPID measured and predicted ranged from 93.6% to 100.0% for all fields and phantoms tested. Results from this study agreed with 2D array measurements to within 3.1%. Meanwhile, comparisons in-phantom between TPS computed and predicted ranged from 91.6% to 100.0%. Validation with 2D array device was not possible for inphantom comparisons. Conclusion: A 2D EPID transit dosimetry model for treatment verification was described and proven to be accurate. The model has the advantage of being generic and allows comparisons at the EPID plane as well as multiple planes in-phantom.
Phenotypic transition maps of 3D breast acini obtained by imaging-guided agent-based modeling
Tang, Jonathan; Enderling, Heiko; Becker-Weimann, Sabine; Pham, Christopher; Polyzos, Aris; Chen, Chen-Yi; Costes, Sylvain V
2011-02-18
We introduce an agent-based model of epithelial cell morphogenesis to explore the complex interplay between apoptosis, proliferation, and polarization. By varying the activity levels of these mechanisms we derived phenotypic transition maps of normal and aberrant morphogenesis. These maps identify homeostatic ranges and morphologic stability conditions. The agent-based model was parameterized and validated using novel high-content image analysis of mammary acini morphogenesis in vitro with focus on time-dependent cell densities, proliferation and death rates, as well as acini morphologies. Model simulations reveal apoptosis being necessary and sufficient for initiating lumen formation, but cell polarization being the pivotal mechanism for maintaining physiological epithelium morphology and acini sphericity. Furthermore, simulations highlight that acinus growth arrest in normal acini can be achieved by controlling the fraction of proliferating cells. Interestingly, our simulations reveal a synergism between polarization and apoptosis in enhancing growth arrest. After validating the model with experimental data from a normal human breast line (MCF10A), the system was challenged to predict the growth of MCF10A where AKT-1 was overexpressed, leading to reduced apoptosis. As previously reported, this led to non growth-arrested acini, with very large sizes and partially filled lumen. However, surprisingly, image analysis revealed a much lower nuclear density than observed for normal acini. The growth kinetics indicates that these acini grew faster than the cells comprising it. The in silico model could not replicate this behavior, contradicting the classic paradigm that ductal carcinoma in situ is only the result of high proliferation and low apoptosis. Our simulations suggest that overexpression of AKT-1 must also perturb cell-cell and cell-ECM communication, reminding us that extracellular context can dictate cellular behavior.
Modelling the transition from cost-based to bid-based pricing in a deregulated electricity-market
Alberta is a province in western Canada with a deregulated electricity-market. Market clearing prices for most hours reflect the cost of either coal-fired or gas-fired thermal generation. Whenever there is a chronic shortage of generation or even a temporary one due to an outage, prices can be bid much higher than fuel costs would suggest. The province of British Columbia borders Alberta to the west and its electric utility, BC Hydro, has a history of trade with the utilities in Alberta. BC Hydro has predominantly hydroelectric resources and large storage reservoirs. Prior to Alberta's deregulation in 1996, BC Hydro was able to enter into mutually beneficial load-factoring contracts with the Alberta utilities. Now, as long as the transmission is available, BC Hydro can buy low priced off-peak coal-fired energy and sell into the high priced periods without having to share the benefits. BC Hydro uses a combination of econometric and Monte Carlo modelling to simulate hourly price-duration curves for Alberta that capture both cost-based and bid-based characteristics. This approach provides a good fit with the stochastic dynamic programming model that BC Hydro has developed for its mid-term hydro scheduling
Fragmentation transitions in multistate voter models
Böhme, Gesa A.; Gross, Thilo
2012-06-01
Adaptive models of opinion formation among humans can display a fragmentation transition, where a social network breaks into disconnected components. Here we investigate this transition in a class of models with arbitrary number of opinions. In contrast to previous work we do not assume that opinions are equidistant or arranged on a one-dimensional conceptual axis. Our investigation reveals detailed analytical results on fragmentations in a three-opinion model, which are confirmed by agent-based simulations. Furthermore, we show that in certain models the number of opinions can be reduced without affecting the fragmentation points.
Phase Transitions in Models of Bird Flocking
Christodoulidi, H; Bountis, T
2013-01-01
The aim of the present paper is to elucidate the transition from collective to random behavior exhibited by various mathematical models of bird flocking. In particular, we compare Vicsek's model [Viscek et al., Phys. Rev. Lett. 75, 1226 -- 1229 (1995)] with one based on topological considerations. The latter model is found to exhibit a first order phase transition from flocking to decoherence, as the 'noise parameter' of the problem is increased, whereas Viscek's model gives a second order transition. Refining the topological model in such a way that birds are influenced mostly by the birds in front of them, less by the ones at their sides and not at all by those behind them (because they do not see them), we find a behavior that lies in between the two models. Finally, we propose a novel mechanism for preserving the flock's cohesion, without imposing artificial boundary conditions or attracting forces.
Catanzarite, Joseph; Burke, Christopher J.; Li, Jie; Seader, Shawn; Haas, Michael R.; Batalha, Natalie; Henze, Christopher; Christiansen, Jessie; Kepler Project, NASA Advanced Supercomputing Division
2016-06-01
The Kepler Mission is developing an Analytic Completeness Model (ACM) to estimate detection completeness contours as a function of exoplanet radius and period for each target star. Accurate completeness contours are necessary for robust estimation of exoplanet occurrence rates.The main components of the ACM for a target star are: detection efficiency as a function of SNR, the window function (WF) and the one-sigma depth function (OSDF). (Ref. Burke et al. 2015). The WF captures the falloff in transit detection probability at long periods that is determined by the observation window (the duration over which the target star has been observed). The OSDF is the transit depth (in parts per million) that yields SNR of unity for the full transit train. It is a function of period, and accounts for the time-varying properties of the noise and for missing or deweighted data.We are performing flux-level transit injection (FLTI) experiments on selected Kepler target stars with the goal of refining and validating the ACM. “Flux-level” injection machinery inserts exoplanet transit signatures directly into the flux time series, as opposed to “pixel-level” injection, which inserts transit signatures into the individual pixels using the pixel response function. See Jie Li's poster: ID #2493668, "Flux-level transit injection experiments with the NASA Pleiades Supercomputer" for details, including performance statistics.Since FLTI is affordable for only a small subset of the Kepler targets, the ACM is designed to apply to most Kepler target stars. We validate this model using “deep” FLTI experiments, with ~500,000 injection realizations on each of a small number of targets and “shallow” FLTI experiments with ~2000 injection realizations on each of many targets. From the results of these experiments, we identify anomalous targets, model their behavior and refine the ACM accordingly.In this presentation, we discuss progress in validating and refining the ACM, and we
Soil, resilience, and state and transition models
State and transition models are based on the assumption that less resilient systems are more susceptible to state changes. The objective of this paper is to show how two different types of soil properties contribute to resilience through their direct and indirect effects on ecosystem processes, and ...
Transition times in the Landau-Zener model
Vitanov, N. V.
1998-01-01
This paper presents analytic formulas for various transition times in the Landau-Zener model. Considerable differences are found between the transition times in the diabatic and adiabatic bases, and between the jump time (the time for which the transition probability rises to the region of its asymptotic value) and the relaxation time (the characteristic damping time of the oscillations which appear in the transition probability after the crossing). These transition times have been calculated...
Korang-Yeboah, Maxwell; Rahman, Ziyaur; Shah, Dhaval A; Khan, Mansoor A
2016-01-01
Variations in the solid state form of a pharmaceutical solid have profound impact on the product quality and clinical performance. Quantitative models that allow rapid and accurate determination of polymorphic changes in pharmaceutical products are essential in ensuring product quality throughout its lifecycle. This study reports the development and validation of chemometric models of Raman and near infrared spectroscopy (NIR) for quantifying the extent of pseudopolymorphic transitions of theophylline in extended release formulations. The chemometric models were developed using sample matrices consisting of the commonly used excipients and at the ratios in commercially available products. A combination of scatter removal (multiplicative signal correction and standard normal variate) and derivatization (Savitzky-Golay second derivative) algorithm were used for data pretreatment. Partial least squares and principal component regression models were developed and their performance assessed. Diagnostic statistics such as the root mean square error, correlation coefficient, bias and Q(2) were used as parameters to test the model fit and performance. The models developed had a good fit and performance as shown by the values of the diagnostic statistics. The model diagnostic statistics were similar for MSC-SG and SNV-SG treated spectra. Similarly, PLSR and PCR models had comparable performance. Raman chemometric models were slightly better than their corresponding NIR model. The Raman and NIR chemometric models developed had good accuracy and precision as demonstrated by closeness of the predicted values for the independent observations to the actual TMO content hence the developed models can serve as useful tools in quantifying and controlling solid state transitions in extended release theophylline products. PMID:26852844
Linking Complexity and Sustainability Theories: Implications for Modeling Sustainability Transitions
Camaren Peter; Mark Swilling
2014-01-01
In this paper, we deploy a complexity theory as the foundation for integration of different theoretical approaches to sustainability and develop a rationale for a complexity-based framework for modeling transitions to sustainability . We propose a framework based on a comparison of complex systemsâ€™ properties that characterize the different theories that deal with transitions to sustainability. We argue that adopting a complexity theory based approach for modeling transitions requires going...
White, Toby A; Erosheva, Elena A
2013-09-10
Latent class transition models track how individuals move among latent classes through time, traditionally assuming a complete set of observations for each individual. In this paper, we develop group-based latent class transition models that allow for staggered entry and exit, common in surveys with rolling enrollment designs. Such models are conceptually similar to, but structurally distinct from, pattern mixture models of the missing data literature. We employ group-based latent class transition modeling to conduct an in-depth data analysis of recent trends in chronic disability among the U.S. elderly population. Using activities of daily living data from the National Long-Term Care Survey (NLTCS), 1982-2004, we estimate model parameters using the expectation-maximization algorithm, implemented in SAS PROC IML. Our findings indicate that declines in chronic disability prevalence, observed in the 1980s and 1990s, did not continue in the early 2000s as previous NLTCS cross-sectional analyses have indicated. PMID:23553714
Transition matrix model for evolutionary game dynamics
Ermentrout, G. Bard; Griffin, Christopher; Belmonte, Andrew
2016-03-01
We study an evolutionary game model based on a transition matrix approach, in which the total change in the proportion of a population playing a given strategy is summed directly over contributions from all other strategies. This general approach combines aspects of the traditional replicator model, such as preserving unpopulated strategies, with mutation-type dynamics, which allow for nonzero switching to unpopulated strategies, in terms of a single transition function. Under certain conditions, this model yields an endemic population playing non-Nash-equilibrium strategies. In addition, a Hopf bifurcation with a limit cycle may occur in the generalized rock-scissors-paper game, unlike the replicator equation. Nonetheless, many of the Folk Theorem results are shown to hold for this model.
Yue Ting; Wang Lixin; Ai Junqiang
2013-01-01
This article investigates gain self-scheduled H∞ robust control system design for a tailless folding-wing morphing aircraft in the wing shape varying process.During the wing morphing phase,the aircraft's dynamic response will be governed by time-varying aerodynamic forces and moments.Nonlinear dynamic equations of the morphing aircraft are linearized by using Jacobian linearization approach,and a linear parameter varying (LPV) model of the morphing aircraft in wing folding is obtained.A multi-loop controller for the morphing aircraft is formulated to guarantee stability for the wing shape transition process.The proposed controller uses a set of inner-loop gains to provide stability using classical techniques,whereas a gain self-scheduled H∞ outer-loop controller is devised to guarantee a specific level of robust stability and performance for the time-varying dynamics.The closed-loop simulations show that speed and altitude vary slightly during the whole wing folding process,and they converge rapidly after the process ends.This proves that the gain self-scheduled H∞ robust controller can guarantee a satisfactory dynamic performance for the morphing aircraft during the whole wing shape transition process.Finally,the flight control system's robustness for the wing folding process is verified according to uncertainties of the aerodynamic parameters in the nonlinear model.
Meĭgal, A Iu; Voroshilov, A S
2009-01-01
Interferential electromyogram (iEMG) was analyzed in healthy newborn infants (n=29) during the first 24 hours of life as a model of transition from hypogravity (intrauterine immersion) to the Earth's gravity (postnatal period). Nonlinear instruments of iEMG analysis (correlation dimension, entropy and fractal dimension) reflected the complexity, chaotic character and predictability of signals from the leg and arm antagonistic muscles. Except for m. gastrocnemius, in all other musles iEMG fractal dimension was shown to grow as the postnatal period extended. Low fractal and correlation dimensions and entropy marked flexor muscles, particularly against low iEMG amplitude suggesting a better congenital programming for the flexors as compared to the extensors. It is concluded that the early ontogenesis model can be practicable in studying the evolution and states of antigravity functions. PMID:20169733
Phase transitions in paradigm shift models.
Huiseung Chae
Full Text Available Two general models for paradigm shifts, deterministic propagation model (DM and stochastic propagation model (SM, are proposed to describe paradigm shifts and the adoption of new technological levels. By defining the order parameter m based on the diversity of ideas, Δ, it is studied when and how the phase transition or the disappearance of a dominant paradigm occurs as a cost C in DM or an innovation probability α in SM increases. In addition, we also investigate how the propagation processes affect the transition nature. From analytical calculations and numerical simulations m is shown to satisfy the scaling relation m=1-f(C/N for DM with the number of agents N. In contrast, m in SM scales as m=1-f(α(aN.
Sullivan model for wetting transition in closed system
The wetting transition in a closed system is analytically discussed based on the Sullivan model. In order to have a wetting transition in the system the wall potential must have intermediate strength. The wetting transition is first order for the finite system, while it becomes of second order for the infinite one. In addition, the temperature TW of the wetting transition becomes lower as the separation of the two walls decreases. (author). 8 refs, 5 figs
Sebok, Angelia; Wickens, Christopher; Sargent, Robert
2015-01-01
One human factors challenge is predicting operator performance in novel situations. Approaches such as drawing on relevant previous experience, and developing computational models to predict operator performance in complex situations, offer potential methods to address this challenge. A few concerns with modeling operator performance are that models need to realistic, and they need to be tested empirically and validated. In addition, many existing human performance modeling tools are complex and require that an analyst gain significant experience to be able to develop models for meaningful data collection. This paper describes an effort to address these challenges by developing an easy to use model-based tool, using models that were developed from a review of existing human performance literature and targeted experimental studies, and performing an empirical validation of key model predictions.
Phase transitions in algebraic cluster models
Complete text of publication follows. There has been much interest recently in phase transitions in various nuclear systems. The phases are defined as (local) minima of the potential energy surface (PES) defined in terms of parameters characterizing the nuclear system. Phase transitions occur when some relevant parameter is changed gradually and the system moves from one phase to another one. In the analysis of such systems the key questions are the number of phases and the order of phase transition between them. Algebraic nuclear structure models are especially interesting from the phase transition point of view, because the different phases may be characterized by different symmetries of the system. Much work has been done recently on models based on the interacting boson approximation (IBA). In these studies the potential energy surface is constructed from the algebraic Hamiltonian by its geometric mapping using the coherent state formalism. Inspired by these studies we performed a similar analysis of a family of algebraic cluster models based on the semimicroscopic algebraic cluster model (SACM). This model has two dynamical symmetries: the SU(3) and SO(4) limits are believed to correspond to vibration around a spherical equilibrium shape and static dipole deformation, respectively. The semimicroscopic nature of this model is reflected by the fact that a fully antisymmetrized microscopic model space is combined with a phenomenologic Hamiltonian that describes excitations of the (typically) two-cluster system. The microscopic model space is necessary to take into account the Pauli exclusion principle acting between the nucleons of the closely interacting clusters. In practice this means that the number of excitation quanta in the relative motion of the clusters has to exceed a certain number n0 characterizing the system. This is clearly a novelty with respect to other algebraic models, and it complicates the formalism considerably. We thus introduced as a
Image-based modeling of the flow transition from a Berea rock matrix to a propped fracture
Sanematsu, P.; Willson, C. S.; Thompson, K. E.
2013-12-01
In the past decade, new technologies and advances in horizontal hydraulic fracturing to extract oil and gas from tight rocks have raised questions regarding the physics of the flow and transport processes that occur during production. Many of the multi-dimensional details of flow from the rock matrix into the fracture and within the proppant-filled fracture are still unknown, which leads to unreliable well production estimations. In this work, we use x-ray computed micro tomography (XCT) to image 30/60 CarboEconoprop light weight ceramic proppant packed between berea sandstone cores (6 mm in diameter and ~2 mm in height) under 4000 psi (~28 MPa) loading stress. Image processing and segmentation of the 6 micron voxel resolution tomography dataset into solid and void space involved filtering with anisotropic diffusion (AD), segmentation using an indicator kriging (IK) algorithm, and removal of noise using a remove islands and holes program. Physically-representative pore network structures were generated from the XCT images, and a representative elementary volume (REV) was analyzed using both permeability and effective porosity convergence. Boundary conditions were introduced to mimic the flow patterns that occur when fluid moves from the matrix into the proppant-filled fracture and then downstream within the proppant-filled fracture. A smaller domain, containing Berea and proppants close to the interface, was meshed using an in-house unstructured meshing algorithm that allows different levels of refinement. Although most of this domain contains proppants, the Berea section accounted for the majority of the elements due to mesh refinement in this region of smaller pores. A finite element method (FEM) Stokes flow model was used to provide more detailed insights on the flow transition from rock matrix to fracture. Results using different pressure gradients are used to describe the flow transition from the Berea rock matrix to proppant-filled fracture.
Zero-based budgeting eases the transition to specialty capitation.
1999-02-01
Zero-based budgeting--a simple payment methodology for specialists still transitioning to capitation--is being touted as preferable to the popular contact cap model. Here's how it works. PMID:10350830
Linking Complexity and Sustainability Theories: Implications for Modeling Sustainability Transitions
Camaren Peter
2014-03-01
Full Text Available In this paper, we deploy a complexity theory as the foundation for integration of different theoretical approaches to sustainability and develop a rationale for a complexity-based framework for modeling transitions to sustainability. We propose a framework based on a comparison of complex systems’ properties that characterize the different theories that deal with transitions to sustainability. We argue that adopting a complexity theory based approach for modeling transitions requires going beyond deterministic frameworks; by adopting a probabilistic, integrative, inclusive and adaptive approach that can support transitions. We also illustrate how this complexity-based modeling framework can be implemented; i.e., how it can be used to select modeling techniques that address particular properties of complex systems that we need to understand in order to model transitions to sustainability. In doing so, we establish a complexity-based approach towards modeling sustainability transitions that caters for the broad range of complex systems’ properties that are required to model transitions to sustainability.
Development and Maintenance of a GIS-based Transit Model Database%基于GIS的公交模型数据库构建及维护
张天然
2014-01-01
道路网络的修改直接影响公共交通线路数据的同步更新维护，大大增加了维护的工作量和复杂性。通过分析常用交通规划软件公交模型数据库的特点，研究基于动态分段技术的公交模型数据库结构。分别设计和开发了公交模型数据库的自动创建以及在不同路网间采用GIS方法进行移植的软件工具。探讨公交线路自动创建和移植的功能、算法流程、软件开发，并应用于大型工程项目。该软件工具的应用实现了公交模型数据和道路网络模型数据独立编辑，在提高工作效率的同时大大降低了维护模型和数据库的复杂性。%Alteration in roadway network directly affects the synchronization of transit line data, and there-fore significantly increases the workload and complexity of maintenance. By analyzing the characteristics of transit model database for several commonly used transportation planning software packages, this paper studies the structure of the dynamic segmentation-based transit model database. The paper develops soft-ware tools for automatic creation and transfer of transit model database among different roadway networks using the GIS. The functionalities, algorithm flowchart, and software development are discussed. Applica-tion of such software tools in large projects can separately edit transit model data and roadway network model data, hence significantly improves the efficiency and reducing the complexity for maintaining the models and databases.
Tsai, Y.; Turnbull, S.; Zia, A.
2015-12-01
In rural areas where farming competes with urban development and environmental amenities, urban and forest transitions occur simultaneously at different locales with different rates due to the underlying socio-economic shifts. Here we develop an interactive land use transition agent-based model (ILUTABM) in which farmers' land use decisions are made contingent on expansion and location choices of urban businesses and urban residences, as well as farmers' perceived ecosystem services produced by their land holdings. The ILUTABM simulates heterogeneity in land use decisions at parcel levels by differentiating decision making processes for agricultural and urban landowners. Landowners are simulated to make land-use transition decisions as bounded rational agents that maximize their partial expected utility functions under different underlying socio-economic conditions given the category of a landowner and the spatial characteristics of the landowner's landholdings. The ILUTABM is parameterized by spatial data sets such as National Land Cover Database (NLCD), zoning, parcels, property prices, US census, farmers surveys, building/facility characteristics, soil, slope and elevation. We then apply the ILUTABM to the rural Vermont landscape, located in the Northeast Arm District of Lake Champlain and the downstream sub-watersheds of Missisquoi River, to generate phase transitions of rural land towards urban land near peri-urban areas and towards forest land near financially stressed farmlands during 2001-2051. Possible tipping point trajectories of rural land towards regional forest or urban transition are simulated under three socio-economic scenarios: business as usual (ILUTABM calibrated to 2011 NLCD), increased incentives for conservation easements, and increased incentives for attracting urban residences and businesses.
Modelling of phase transitions: do it yourself
We present the basics of a powerful contemporary statistical mechanical technique that can be used by students to explore first-order phase transitions by themselves and for models of their own construction. The technique is a generalization of the well-known Peierls argument and is applicable to various models on a lattice. We illustrate the technique with the help of two simple models that were recently used to simulate phase transitions on surfaces. (paper)
Modelling of phase transitions: do it yourself
Medved', I.; Huckaby, D. A.; Trník, A.; Valovičová, L'
2013-01-01
We present the basics of a powerful contemporary statistical mechanical technique that can be used by students to explore first-order phase transitions by themselves and for models of their own construction. The technique is a generalization of the well-known Peierls argument and is applicable to various models on a lattice. We illustrate the technique with the help of two simple models that were recently used to simulate phase transitions on surfaces.
Marchant, Robert; Berrıo, Juan Carlos; Behling, Hermann; Boom, Arnoud; Hooghiemstra, Henry
2006-01-01
Colombian vegetation, at the ecological level of the biome, is reconstructed at six sites using pollen data assigned a priori to plant functional types and biomes. The chosen sites incorporate four savanna sites (Laguna Sardinas, Laguna Angel, El Pin˜al and Laguna Carimagua), a site on the transition between savanna and Amazon rainforest (Loma Linda) and a site within the Amazon rainforest (Pantano de Monica). The areal extent of tropical moist forest, tropical dry forest and steppe have been...
基于RFM模型的通勤人群公交忠诚度研究%Commuters' Loyalty to Public Transit Based on RFM Model
孙世超; 杨东援
2015-01-01
Based on the data collected from commuters'transit usage questionnaire in Shanghai, this paper analyzes commuters'loyalty to public transit by the use of RFM model in marketing and some relevant statistical approaches. The definition and classification of the"loyalty"are discussed from two dimensions which can be denoted as"behavioral loyalty"and"attitudinal loyalty". Combined with theories on service level of bus transit, customer satisfaction and loyalty, the distribution of the interviewed commuter's loyalty to public transit in Shanghai is given under the two dimensions. Then, casual model is also conducted to analyze the influence factor of the"loyalty". The results indicate that about 33% interviewed commuters who had shown a high-intensity usage of bus transit may transferred to other transport modes and the"loyalty"is influenced by age, education, ticket price, bus waiting time, stability of travel time and crowding.%以上海市通勤人群公交使用情况问卷调查数据为依托,运用营销学领域中识别顾客忠诚度的RFM模型及相关统计学方法,从"行为忠诚"与"态度忠诚"两方面探讨乘客公交忠诚度的界定与划分,并结合公交服务质量,顾客满意度和顾客忠诚度的相关理论,重点分析上海市通勤人群公交忠诚度的分布情况,并在此基础上建立公交忠诚度影响因素分析模型.结果表明,约1/3受访者虽然目前表现出高强度的公交使用行为,但未来有向公共系统外的其他交通方式转移趋势和风险,而公交使用的态度忠诚度主要受年龄、教育背景、轨道交通票价、公交候车时间、行程时间稳定性及公交车厢拥挤程度影响.
Using Transiting Planets to Model Starspot Evolution
Davenport, James R A; Hawley, Suzanne L
2014-01-01
Photometry from Kepler has revealed the presence of cool starspots on the surfaces of thousands of stars, presenting a wide range of spot morphologies and lifetimes. Understanding the lifetime and evolution of starspots across the main sequence reveals critical information about the strength and nature of stellar dynamos. We probe the dynamo by modeling the starspot properties over time using Kepler light curves. In particular, we use planetary systems like Kepler 17 that show in-transit starspot crossing features. Spot-occulting transits probe smaller-scale starspot features on the stellar surface along a fixed latitude region. Our approach is novel in modeling both the in- and out-of transit light curve features, allowing us to break fundamental degeneracies between spot size, latitude, and contrast. With continuous monitoring from Kepler we are able to observe small changes in the positions and sizes of spots from many transits, spanning 4 years of data. Additionally, for stars without transiting planets l...
Modeling Network Transition Constraints with Hypergraphs
Harrod, Steven
2011-01-01
Discrete time dynamic graphs are frequently used to model multicommodity flows or activity paths through constrained resources, but simple graphs fail to capture the interaction effects of resource transitions. The resulting schedules are not operationally feasible, and return inflated objective...
Evolutionary modelling of transitions to sustainable development
This thesis has examined how evolutionary economics can contribute to modelling the micromechanisms that underlie transitions towards sustainable development. In general, transitions are fundamental or structural system changes. They involve, or even require, escaping lock-in of dominant, environmentally unsustainable technologies, introducing major technical or social innovations, and changing prevailing social practices and structures. Due to the complexity of socioeconomic interactions, it is not always possible to identify, and thus target with appropriate policy instruments, causes of specific unsustainable patterns of behaviour. Formal modelling exercises can help improve our understanding of the interaction of various transition mechanisms which are otherwise difficult to grasp intuitively. They allow exploring effects of policy interventions in complex systems. However, existing models of transitions focus on social phenomena and seldom address economic problems. As opposed, mainstream (neoclassical) economic models of technological change do not account for social interactions, and changing heterogeneity of users and their perspectives - even though all of these can influence the direction of innovations and patterns of socio-technological development. Evolutionary economics offers an approach that goes beyond neoclassical economics - in the sense of employing more realistic assumptions regarding the behaviour and heterogeneity of consumers, firms and investors. It can complement current transition models by providing them with a better understanding of associated economic dynamics. In this thesis, formal models were proposed to illustrate the usefulness of a range of evolutionary-economic techniques for modelling transitions. Modelling exercises aimed to explain the core properties of socio-economic systems, such as lock-in, path-dependence, coevolution, group selection and recombinant innovation. The studies collected in this dissertation illustrate that
Evolutionary modelling of transitions to sustainable development
Safarzynska, K.
2010-01-20
This thesis has examined how evolutionary economics can contribute to modelling the micromechanisms that underlie transitions towards sustainable development. In general, transitions are fundamental or structural system changes. They involve, or even require, escaping lock-in of dominant, environmentally unsustainable technologies, introducing major technical or social innovations, and changing prevailing social practices and structures. Due to the complexity of socioeconomic interactions, it is not always possible to identify, and thus target with appropriate policy instruments, causes of specific unsustainable patterns of behaviour. Formal modelling exercises can help improve our understanding of the interaction of various transition mechanisms which are otherwise difficult to grasp intuitively. They allow exploring effects of policy interventions in complex systems. However, existing models of transitions focus on social phenomena and seldom address economic problems. As opposed, mainstream (neoclassical) economic models of technological change do not account for social interactions, and changing heterogeneity of users and their perspectives - even though all of these can influence the direction of innovations and patterns of socio-technological development. Evolutionary economics offers an approach that goes beyond neoclassical economics - in the sense of employing more realistic assumptions regarding the behaviour and heterogeneity of consumers, firms and investors. It can complement current transition models by providing them with a better understanding of associated economic dynamics. In this thesis, formal models were proposed to illustrate the usefulness of a range of evolutionary-economic techniques for modelling transitions. Modelling exercises aimed to explain the core properties of socio-economic systems, such as lock-in, path-dependence, coevolution, group selection and recombinant innovation. The studies collected in this dissertation illustrate that
Introducing Opportunity-based Entrepreneurship in a Transition Economy
Perunovic, Zoran
2005-01-01
This paper confronts necessity-based and opportunity-based entrepreneurial concepts in the transition of developing economies. The author constructs a research model and conducts field research (using Serbia as a case study) to explore how different personal and regional characteristics can favou...
Transitivity reinforcement in the coevolving voter model
Malik, Nishant; Lee, Hsuan-Wei; Mucha, Peter J
2016-01-01
One of the fundamental structural properties of many networks is triangle closure. Whereas the influence of this transitivity on a variety of contagion dynamics has been previously explored, existing models of coevolving or adaptive network systems use rewiring rules that randomize away this important property. In contrast, we study here a modified coevolving voter model dynamics that explicitly reinforces and maintains such clustering. Employing extensive numerical simulations, we establish that the transitions and dynamical states observed in coevolving voter model networks without clustering are altered by reinforcing transitivity in the model. We then use a semi-analytical framework in terms of approximate master equations to predict the dynamical behaviors of the model for a variety of parameter settings.
Microsimulation, CGE and macro modelling for transition and developing economies
Davis, James B.
2004-01-01
Alternative approaches to modelling distributional and welfare effects of changes in policy and the economic environment in developing and transition countries are surveyed. Microsimulations range from pure accounting approaches to models with behavioural equations based on econometric estimates and various dynamic models. Microsimulation accounting models are key to analysing the impact effects of tax and benefit changes and are becoming widespread. Computable general equilibrium (CGE) model...
Optimization models in a transition economy
Sergienko, Ivan V; Koshlai, Ludmilla
2014-01-01
This book opens new avenues in understanding mathematical models within the context of a transition economy. The exposition lays out the methods for combining different mathematical structures and tools to effectively build the next model that will accurately reflect real world economic processes. Mathematical modeling of weather phenomena allows us to forecast certain essential weather parameters without any possibility of changing them. By contrast, modeling of transition economies gives us the freedom to not only predict changes in important indexes of all types of economies, but also to influence them more effectively in the desired direction. Simply put: any economy, including a transitional one, can be controlled. This book is useful to anyone who wants to increase profits within their business, or improve the quality of their family life and the economic area they live in. It is beneficial for undergraduate and graduate students specializing in the fields of Economic Informatics, Economic Cybernetic...
Modelling the energy transition in cities
Huber, Felix [Wuppertal Univ. (Germany). Dept. of Civil Engineering; Schwarze, Bjoern; Spiekermann, Klaus; Wegener, Michael [Spiekermann und Wegener Urban and Regional Research, Dortmund (Germany)
2013-09-01
The history of cities is a history of energy transitions. In the medieval city heating and cooking occurred with wood and peat. The growth of the industrial city in the 19th century was built on coal and electricity. The sprawling metropolis of the 20th century was made possible by oil and gas. How will the city of the 21st century look after the next energy transition from fossil to renewable energy? This paper reports on the extension of an urban land-use transport interaction model to a model of the energy transition in the Ruhr Area, a five-million agglomeration in Germany. The paper presents the planned model extensions and how they are to be integrated into the model and shows first preliminary results.
Operationalizing resilience using state and transition models
In management, restoration, and policy contexts, the notion of resilience can be confusing. Systematic development of conceptual models of ecological state change (state transition models; STMs) can help overcome semantic confusion and promote a mechanistic understanding of resilience. Drawing on ex...
Fragmentation transitions in multi-state voter models
Böhme, Gesa A
2012-01-01
Adaptive models of opinion formation among humans can display a fragmentation transition, where a social network breaks into disconnected components. Here, we investigate this transition in a class of models with arbitrary number of opinions. In contrast to previous work we do not assume that opinions are equidistant or arranged on a one-dimensional conceptual axis. Our investigation reveals detailed analytical results on fragmentations in a three-opinion model, which are confirmed by agent-based simulations. Furthermore, we show that in certain models the number of opinions can be reduced without affecting the fragmentation points.
Introducing Opportunity-based Entrepreneurship in a Transition Economy
Perunovic, Zoran
2005-01-01
This paper confronts necessity-based and opportunity-based entrepreneurial concepts in the transition of developing economies. The author constructs a research model and conducts field research (using Serbia as a case study) to explore how different personal and regional characteristics can favour...... possible entrepreneurial settings for a selected town or region, and four strategies for introducing the opportunity-based entrepreneurship are given. In the most general sense, this paper strives to encourage discussion about national systems of innovation as a complementary and/or dominant catch......-up strategy for transition and developing economies....
A Model of Mental State Transition Network
Xiang, Hua; Jiang, Peilin; Xiao, Shuang; Ren, Fuji; Kuroiwa, Shingo
Emotion is one of the most essential and basic attributes of human intelligence. Current AI (Artificial Intelligence) research is concentrating on physical components of emotion, rarely is it carried out from the view of psychology directly(1). Study on the model of artificial psychology is the first step in the development of human-computer interaction. As affective computing remains unpredictable, creating a reasonable mental model becomes the primary task for building a hybrid system. A pragmatic mental model is also the fundament of some key topics such as recognition and synthesis of emotions. In this paper a Mental State Transition Network Model(2) is proposed to detect human emotions. By a series of psychological experiments, we present a new way to predict coming human's emotions depending on the various current emotional states under various stimuli. Besides, people in different genders and characters are taken into consideration in our investigation. According to the psychological experiments data derived from 200 questionnaires, a Mental State Transition Network Model for describing the transitions in distribution among the emotions and relationships between internal mental situations and external are concluded. Further more the coefficients of the mental transition network model were achieved. Comparing seven relative evaluating experiments, an average precision rate of 0.843 is achieved using a set of samples for the proposed model.
Numerical study on a disordered model for DNA denaturation transition
Coluzzi, Barbara
2005-01-01
We study numerically a disordered version of the model for DNA denaturation transition (DSAW-DNA) consisting of two interacting SAWs in 3d, which undergoes a first order transition in the homogeneous case. The two possible values eAT and eGC of the interactions between base pairs are taken as quenched random variables distributed with equal probability along the chain. We measure quantities averaged over disorder such as the energy density, the specific heat and the probability distribution o...
Sugiyama, Mayu; Saitou, Takashi; Kurokawa, Hiroshi; Sakaue-Sawano, Asako; Imamura, Takeshi; Miyawaki, Atsushi; Iimura, Tadahiro
2014-12-01
In multicellular organism development, a stochastic cellular response is observed, even when a population of cells is exposed to the same environmental conditions. Retrieving the spatiotemporal regulatory mode hidden in the heterogeneous cellular behavior is a challenging task. The G1/S transition observed in cell cycle progression is a highly stochastic process. By taking advantage of a fluorescence cell cycle indicator, Fucci technology, we aimed to unveil a hidden regulatory mode of cell cycle progression in developing zebrafish. Fluorescence live imaging of Cecyil, a zebrafish line genetically expressing Fucci, demonstrated that newly formed notochordal cells from the posterior tip of the embryonic mesoderm exhibited the red (G1) fluorescence signal in the developing notochord. Prior to their initial vacuolation, these cells showed a fluorescence color switch from red to green, indicating G1/S transitions. This G1/S transition did not occur in a synchronous manner, but rather exhibited a stochastic process, since a mixed population of red and green cells was always inserted between newly formed red (G1) notochordal cells and vacuolating green cells. We termed this mixed population of notochordal cells, the G1/S transition window. We first performed quantitative analyses of live imaging data and a numerical estimation of the probability of the G1/S transition, which demonstrated the existence of a posteriorly traveling regulatory wave of the G1/S transition window. To obtain a better understanding of this regulatory mode, we constructed a mathematical model and performed a model selection by comparing the results obtained from the models with those from the experimental data. Our analyses demonstrated that the stochastic G1/S transition window in the notochord travels posteriorly in a periodic fashion, with doubled the periodicity of the neighboring paraxial mesoderm segmentation. This approach may have implications for the characterization of the
Mayu Sugiyama
2014-12-01
Full Text Available In multicellular organism development, a stochastic cellular response is observed, even when a population of cells is exposed to the same environmental conditions. Retrieving the spatiotemporal regulatory mode hidden in the heterogeneous cellular behavior is a challenging task. The G1/S transition observed in cell cycle progression is a highly stochastic process. By taking advantage of a fluorescence cell cycle indicator, Fucci technology, we aimed to unveil a hidden regulatory mode of cell cycle progression in developing zebrafish. Fluorescence live imaging of Cecyil, a zebrafish line genetically expressing Fucci, demonstrated that newly formed notochordal cells from the posterior tip of the embryonic mesoderm exhibited the red (G1 fluorescence signal in the developing notochord. Prior to their initial vacuolation, these cells showed a fluorescence color switch from red to green, indicating G1/S transitions. This G1/S transition did not occur in a synchronous manner, but rather exhibited a stochastic process, since a mixed population of red and green cells was always inserted between newly formed red (G1 notochordal cells and vacuolating green cells. We termed this mixed population of notochordal cells, the G1/S transition window. We first performed quantitative analyses of live imaging data and a numerical estimation of the probability of the G1/S transition, which demonstrated the existence of a posteriorly traveling regulatory wave of the G1/S transition window. To obtain a better understanding of this regulatory mode, we constructed a mathematical model and performed a model selection by comparing the results obtained from the models with those from the experimental data. Our analyses demonstrated that the stochastic G1/S transition window in the notochord travels posteriorly in a periodic fashion, with doubled the periodicity of the neighboring paraxial mesoderm segmentation. This approach may have implications for the characterization of
Phase transitions in algebraic cluster models
We study the phase transitions of two algebraic cluster models, which have similar interactions, but differ from each other in their model spaces. The semimicroscopical model incorporates the Pauli exclusion principle, while the phenomenological one does not. The appearance of the quasidynamical SU(3) symmetry is also investigated in the presence of an explicitly symmetry-breaking interaction. Examples of binary cluster configurations with two, one, or zero closed-shell clusters are studied
Germany's abandonment of nuclear energy in favour of renewables is confronting the country's power supply with new challenges. First and foremost, the current subsidies for renewable energy must be radically reformed so that low-emission technologies can be integrated into the market as rapidly as possible. In the absence of such a reform there is a real danger that competition in the electricity market will increasingly be stifled. Without competition, however, the innovation and efficiency increases which are crucial to the success of Germany's new energy policy will not be possible. Essential as it is to promote renewable energy, there must also be ongoing development of the electricity market. This could be achieved by putting a price on security of supply, with the resulting revenues contributing to financing the necessary reserve capacity. An integrated option market model builds on the existing structures of an energy-only market and offers a framework for gradual development. The market design proposed contains both renewable energies and fossil fuel power stations. Technologies for electricity generation from replenishable resources should in future be temporarily subsidised by a premium over the market price to be awarded by auction.
Phase Transition in Hierarchy Model of Bonabeau
Stauffer, Dietrich
The model of Bonabeau explains the emergence of social hierarchies from the memory of fights in an initially egalitarian society. Introducing a feedback from the social inequality into the probability to win a fight, we find a sharp transition between an egalitarian society at low population density and a hierarchical society at high population density.
A model of interband radiative transition
Dittrich, Jaroslav; Exner, Pavel; Hirokawa, M.
2004-01-01
Roč. 56, č. 3 (2004), s. 753-786. ISSN 0025-5645 R&D Projects: GA AV ČR IAA1048101; GA MŠk ME 482 Institutional research plan: CEZ:AV0Z1048901 Keywords : radiative transition * two-band model Subject RIV: BE - Theoretical Physics Impact factor: 0.366, year: 2004
Juan Luis Rubio Mayoral
2015-05-01
Full Text Available This research aims at determining the basis of the model of public University emerged from the conditions of the transition to democracy and its relationship with the reform policies that have occurred since then. The method used is based on the analysis of the legislation along with the parliamentary debates, studies and reports that during the legislative procedure, and after its implementation, were carried out by various agencies. In addition to research, monographs and scientific articles, newspapers and other media were utilized. The main sources derive from legal and documentary nature, making use of the testimonies collected in interviews proposed to some responsibles for the management of University life. The application of the essence of democracy for the development of the ideas of freedom and autonomy recognized in the Spanish Constitution of 1978 at University as valid for their models of Government is the relevant conclusion; in addition, it needs to develop systems capable of ensuring efficiency in the management of the knowledge and in the decision-making. According to the constitutional system it could allow to transform them into institutions capable of ensuring the best training, the generation and application of knowledge as a basis for the future. How to reference this article Rubio Mayoral, J. L. (2015. Sobre los modelos de universidad en la política educativa de la Transición española. Herencia y génesis de sus bases (1976-1982. Espacio, Tiempo y Educación, 2(2, 125-153. doi: http://dx.doi.org/10.14516/ete.2015.002.002.007
A dynamical model for plasma confinement transitions
Pilarczyk, Paweł; García, Luis; Carreras, Benjamin A.; Llerena, Irene
2012-03-01
A three-equation model describing the evolution of the turbulence level, averaged shear flow and sheared zonal flow is analyzed using topological properties of the asymptotic solutions. An exploration in parameter space is done, identifying the attractor sets, which are fixed points and limit cycles. Then a more detailed analysis of all Morse sets is conducted using topological-combinatorial computations. This model allows the description of different types of transitions to improved plasma confinement regimes.
A dynamical model for plasma confinement transitions
A three-equation model describing the evolution of the turbulence level, averaged shear flow and sheared zonal flow is analyzed using topological properties of the asymptotic solutions. An exploration in parameter space is done, identifying the attractor sets, which are fixed points and limit cycles. Then a more detailed analysis of all Morse sets is conducted using topological-combinatorial computations. This model allows the description of different types of transitions to improved plasma confinement regimes. (paper)
Phase Transitions in Delaunay Potts Models
Adams, Stefan; Eyers, Michael
2016-01-01
We establish phase transitions for certain classes of continuum Delaunay multi-type particle systems (continuum Potts models) with infinite range repulsive interaction between particles of different type. In one class of the Delaunay Potts models studied the repulsive interaction is a triangle (multi-body) interaction whereas in the second class the interaction is between pairs (edges) of the Delaunay graph. The result for the edge model is an extension of finite range results in Bertin et al. (J Stat Phys 114(1-2):79-100, 2004) for the Delaunay graph and in Georgii and Häggström (Commun Math Phys 181:507-528, 1996) for continuum Potts models to an infinite range repulsion decaying with the edge length. This is a proof of an old conjecture of Lebowitz and Lieb. The repulsive triangle interactions have infinite range as well and depend on the underlying geometry and thus are a first step towards studying phase transitions for geometry-dependent multi-body systems. Our approach involves a Delaunay random-cluster representation analogous to the Fortuin-Kasteleyn representation of the Potts model. The phase transitions manifest themselves in the percolation of the corresponding random-cluster model. Our proofs rely on recent studies (Dereudre et al. in Probab Theory Relat Fields 153:643-670, 2012) of Gibbs measures for geometry-dependent interactions.
Satoshi Nori
2015-03-01
Full Text Available Previously, we described the safety and therapeutic potential of neurospheres (NSs derived from a human induced pluripotent stem cell (iPSC clone, 201B7, in a spinal cord injury (SCI mouse model. However, several safety issues concerning iPSC-based cell therapy remain unresolved. Here, we investigated another iPSC clone, 253G1, that we established by transducing OCT4, SOX2, and KLF4 into adult human dermal fibroblasts collected from the same donor who provided the 201B7 clone. The grafted 253G1-NSs survived, differentiated into three neural lineages, and promoted functional recovery accompanied by stimulated synapse formation 47 days after transplantation. However, long-term observation (for up to 103 days revealed deteriorated motor function accompanied by tumor formation. The tumors consisted of Nestin+ undifferentiated neural cells and exhibited activation of the OCT4 transgene. Transcriptome analysis revealed that a heightened mesenchymal transition may have contributed to the progression of tumors derived from grafted cells.
Nils Pharo
2004-01-01
Full Text Available This paper presents a conceptual model of information behaviour. The model is part of the Search Situation Transition method schema. The method schema is developed to discover and analyse interplay between phenomena traditionally analysed as factors influencing either information retrieval or information seeking. In this paper the focus is on the model's five main categories: the work task, the searcher, the social/organisational environment, the search task, and the search process. In particular, the search process and its sub-categories search situation and transition and the relationship between these are discussed. To justify the method schema an empirical study was designed according to the schema's specifications. In the paper a subset of the study is presented analysing the effects of work tasks on Web information searching. Findings from this small-scale study indicate a strong relationship between the work task goal and the level of relevance used for judging resources during search processes.
Culture in Transition: A learning model
Baca, Susan
2010-01-01
This paper addresses the problem of resistance to attempted changes in organizational culture, particularly those involving diversity, by 1) identifying precisely what is meant by organizational as opposed to societal culture, 2) developing a theoretical model of learning useful in contexts of...... organizational transition, and 3) demonstrating the efficacy of the model by using it to explain empirical research findings. It is argued that learning new cultural currency involves the use of active intelligence to locate and answer relevant questions, and further that this process requires the interplay of...... spare capacity, desire, focus, and information. By integrating the element of culture, both in the organizational sense and that pertaining to diversity, otherwise overseen aspects of transition are brought into view, with the potential of reducing stress and increasing job satisfaction. The model is...
Employment, Production and Consumption model: Patterns of phase transitions
Lavička, H.; Lin, L.; Novotný, Jan
2010-01-01
Roč. 389, č. 8 (2010), s. 1708-1720. ISSN 0378-4371 Institutional research plan: CEZ:AV0Z10480505 Keywords : EPC * Agent based model * Phase transition Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 1.521, year: 2010
A MATLAB GUI to study Ising model phase transition
Thornton, Curtislee; Datta, Trinanjan
We have created a MATLAB based graphical user interface (GUI) that simulates the single spin flip Metropolis Monte Carlo algorithm. The GUI has the capability to study temperature and external magnetic field dependence of magnetization, susceptibility, and equilibration behavior of the nearest-neighbor square lattice Ising model. Since the Ising model is a canonical system to study phase transition, the GUI can be used both for teaching and research purposes. The presence of a Monte Carlo code in a GUI format allows easy visualization of the simulation in real time and provides an attractive way to teach the concept of thermal phase transition and critical phenomena. We will also discuss the GUI implementation to study phase transition in a classical spin ice model on the pyrochlore lattice.
Structural transition models for a class or irreversible aggregates
A progress report on two recent theoretical approaches proposed to understand the physics of irreversible fractal aggregates showing up a structural transition from a rather dense to a more multibranched growth is presented. In the first approach the transition is understood by solving the Poisson equation on a squared lattice. The second approach is based on the discretization of the Biharmonic equation. Within these models the transition appears when the growth velocity at the fractal surface presents a minimum. The effects of the surrounding medium and geometrical constraints for the seed particles are considered. By using the optical diffraction method, the structural transition is further characterized by a decrease in the fractal dimension for this peculiar class of aggregates. (author). 17 refs, 4 figs
Phase transitions in a lattice population model
We introduce a model for a population on a lattice with diffusion and birth/death according to 2A→3A and A→Φ for a particle A. We find that the model displays a phase transition from an active to an absorbing state which is continuous in 1 + 1 dimensions and of first-order in higher dimensions in agreement with the mean field equation. For the (1 + 1)-dimensional case, we examine the critical exponents and a scaling function for the survival probability and show that it belongs to the universality class of directed percolation. In higher dimensions, we look at the first-order phase transition by plotting a histogram of the population density and use the presence of phase coexistence to find an accurate value for the critical point in 2 + 1 dimensions
Using Transiting Planets to Model Starspot Evolution
Davenport, James R. A.; Hebb, Leslie; Hawley, Suzanne L.
2014-01-01
Photometry from Kepler has revealed the presence of cool starspots on the surfaces of thousands of stars, presenting a wide range of spot morphologies and lifetimes. Understanding the lifetime and evolution of starspots across the main sequence reveals critical information about the strength and nature of stellar dynamos. We probe the dynamo by modeling the starspot properties over time using Kepler light curves. In particular, we use planetary systems like Kepler 17 that show in-transit star...
Modeling the polycentric transition of cities
Louf, Rémi; Barthelemy, Marc
2013-01-01
Empirical evidence suggest that most urban systems experience a transition from a monocentric to a polycentric organisation as they grow and expand. We propose here a stochastic, out-of-equilibrium model of the city which explains the appearance of subcenters as an effect of traffic congestion. We show that congestion triggers the unstability of the monocentric regime, and that the number of subcenters and the total commuting distance within a city scale sublinearly with its population, predi...
The Work of Cultural Transition: An Emerging Model
Ryba, Tatiana V.; Stambulova, Natalia B.; Ronkainen, Noora J.
2016-01-01
In today’s uncertain, fluid job market, transnational mobility has intensified. Though the concept of cultural transition is increasingly used in sport and career research, insight into the processes of how individuals produce their own development through work and relationships in shifting cultural patterns of meaning remains limited. The transnational industry of sports, in which athletes’ psychological adjustment to cultural transitions has implications for both performance and meaningful life, serves as a backdrop for this article. This study applied the life story method to interviews with 15 professional and semi-professional athletes, focusing particularly on the cultural transition aspect of their transnational athletic careers. The aims of the study were to identify the developmental tasks of cultural transitions and strategies/mechanisms through which cultural transitions were enacted. Three underlying mechanisms of the transition process that assisted athletic career adaptability were social repositioning, negotiation of cultural practices, and meaning reconstruction. Based on the data analyses, a temporal model of cultural transition is proposed. The results of this research provide professionals working in the fields of career counseling and migrant support with a content framework for enhancing migrant workers’ adaptabilities and psychological wellbeing. PMID:27047436
Andrew J. Filardo
1998-01-01
This paper discusses a practical estimation issue for time-varying transition probability (TVTP) Markov switching models. Time-varying transition probabilities allow researchers to capture important economic behavior that may be missed using constant (or fixed) transition probabilities. Despite its use, Hamilton’s (1989) filtering method for estimating fixed transition probability Markov switching models may not apply to TVTP models. This paper provides a set of sufficient conditions to justi...
Bieda, Boguslaw, E-mail: bbieda@zarz.agh.edu.pl
2013-01-01
The paper is concerned with application and benefits of MC simulation proposed for estimating the life of a modern municipal solid waste (MSW) landfill. The software Crystal Ball Registered-Sign (CB), simulation program that helps analyze the uncertainties associated with Microsoft Registered-Sign Excel models by MC simulation, was proposed to calculate the transit time contaminants in porous media. The transport of contaminants in soil is represented by the one-dimensional (1D) form of the advection-dispersion equation (ADE). The computer program CONTRANS written in MATLAB language is foundation to simulate and estimate the thickness of landfill compacted clay liner. In order to simplify the task of determining the uncertainty of parameters by the MC simulation, the parameters corresponding to the expression Z2 taken from this program were used for the study. The tested parameters are: hydraulic gradient (HG), hydraulic conductivity (HC), porosity (POROS), linear thickness (TH) and diffusion coefficient (EDC). The principal output report provided by CB and presented in the study consists of the frequency chart, percentiles summary and statistics summary. Additional CB options provide a sensitivity analysis with tornado diagrams. The data that was used include available published figures as well as data concerning the Mittal Steel Poland (MSP) S.A. in Krakow, Poland. This paper discusses the results and show that the presented approach is applicable for any MSW landfill compacted clay liner thickness design. -- Highlights: Black-Right-Pointing-Pointer Numerical simulation of waste in porous media is proposed. Black-Right-Pointing-Pointer Statistic outputs based on correct assumptions about probability distribution are presented. Black-Right-Pointing-Pointer The benefits of a MC simulation are examined. Black-Right-Pointing-Pointer The uniform probability distribution is studied. Black-Right-Pointing-Pointer I report a useful tool applied to determine the life of a
The paper is concerned with application and benefits of MC simulation proposed for estimating the life of a modern municipal solid waste (MSW) landfill. The software Crystal Ball® (CB), simulation program that helps analyze the uncertainties associated with Microsoft® Excel models by MC simulation, was proposed to calculate the transit time contaminants in porous media. The transport of contaminants in soil is represented by the one-dimensional (1D) form of the advection–dispersion equation (ADE). The computer program CONTRANS written in MATLAB language is foundation to simulate and estimate the thickness of landfill compacted clay liner. In order to simplify the task of determining the uncertainty of parameters by the MC simulation, the parameters corresponding to the expression Z2 taken from this program were used for the study. The tested parameters are: hydraulic gradient (HG), hydraulic conductivity (HC), porosity (POROS), linear thickness (TH) and diffusion coefficient (EDC). The principal output report provided by CB and presented in the study consists of the frequency chart, percentiles summary and statistics summary. Additional CB options provide a sensitivity analysis with tornado diagrams. The data that was used include available published figures as well as data concerning the Mittal Steel Poland (MSP) S.A. in Kraków, Poland. This paper discusses the results and show that the presented approach is applicable for any MSW landfill compacted clay liner thickness design. -- Highlights: ► Numerical simulation of waste in porous media is proposed. ► Statistic outputs based on correct assumptions about probability distribution are presented. ► The benefits of a MC simulation are examined. ► The uniform probability distribution is studied. ► I report a useful tool applied to determine the life of a modern MSW landfill.
This work extends the applicability of local models for ductile fracture to large crack growth modelization for ductile tearing. This is done inserting a cohesive zone model whose constitutive law is identified in order to be consistent with the local model. The consistency is obtained through the cohesive law incremental construction which ensures the equivalence of the energy and of the mechanical response of the models. The extension of the applicability domain of the local modelization is enabled via the XFEM framework which allows for maintaining the mechanical energy during the crack extension step. This method permits also to introduce the cohesive zone model during the calculation without regards to the mesh of the structure for its maximal tensile stress. To apply the XFEM to ductile tearing, this method is extended to non linear problems (Updated Lagrangian Formulation, large scale yield plasticity). The cohesive zone model grows when the criterion defined in term of porosity, tested at the front of the cohesive crack front, is verified. The cohesive zone growth criterion is determined in order to model most of the damaging phase with the local model to ensure that the modelization takes into account the triaxiality ratio history accurately. The proposed method is applied to the Rousselier local model for ductile fracture in the XFEM framework of Cast3M, the FE software of the CEA. (author)
Dislocation dynamics modelling of the ductile-brittle-transition
Hennecke, Thomas; Haehner, Peter, E-mail: thomas.hennecke@tu-bs.de, E-mail: peter.haehner@jrc.nl [European Commission, DG Joint Research Centre, Institute for Energy, Westerduinweg 3, 1755 LE Petten (Netherlands)
2009-07-15
Many materials like silicon, tungsten or ferritic steels show a transition between high temperature ductile fracture with stable crack grow and high deformation energy absorption and low temperature brittle fracture in an unstable and low deformation mode, the ductile-brittle-transition. Especially in steels, the temperature transition is accompanied by a strong increase of the measured fracture toughness over a certain temperature range and strong scatter in the toughness data in this transition regime. The change in fracture modes is affected by dynamic interactions between dislocations and the inhomogeneous stress fields of notches and small cracks. In the present work a dislocation dynamics model for the ductile-brittle-transition is proposed, which takes those interactions into account. The model can explain an increase with temperature of apparent toughness in the quasi-brittle regime and different levels of scatter in the different temperature regimes. Furthermore it can predict changing failure sites in materials with heterogeneous microstructure. Based on the model, the effects of crack tip blunting, stress state, external strain rate and irradiation-induced changes in the plastic flow properties can be discussed.
Percolation-based precursors of transitions in extended systems
Rodríguez-Méndez, Víctor; Eguíluz M, Víctor M.; Hernández-García, Emilio; Ramasco, José J.
2016-07-01
Abrupt transitions are ubiquitous in the dynamics of complex systems. Finding precursors, i.e. early indicators of their arrival, is fundamental in many areas of science ranging from electrical engineering to climate. However, obtaining warnings of an approaching transition well in advance remains an elusive task. Here we show that a functional network, constructed from spatial correlations of the system’s time series, experiences a percolation transition way before the actual system reaches a bifurcation point due to the collective phenomena leading to the global change. Concepts from percolation theory are then used to introduce early warning precursors that anticipate the system’s tipping point. We illustrate the generality and versatility of our percolation-based framework with model systems experiencing different types of bifurcations and with Sea Surface Temperature time series associated to El Niño phenomenon.
Modeling the polycentric transition of cities
Louf, Rémi
2013-01-01
Empirical evidence suggest that most urban systems experience a transition from a monocentric to a polycentric organisation as they grow and expand. We propose here a stochastic, out-of-equilibrium model of the city which explains the appearance of subcenters as an effect of traffic congestion. We show that congestion triggers the unstability of the monocentric regime, and that the number of subcenters and the total commuting distance within a city scale sublinearly with its population, predictions which are in agreement with data gathered for around 9000 US cities between 1994 and 2010.
Modeling the Polycentric Transition of Cities
Louf, Rémi; Barthelemy, Marc
2013-11-01
Empirical evidence suggests that most urban systems experience a transition from a monocentric to a polycentric organization as they grow and expand. We propose here a stochastic, out-of-equilibrium model of the city, which explains the appearance of subcenters as an effect of traffic congestion. We show that congestion triggers the instability of the monocentric regime and that the number of subcenters and the total commuting distance within a city scale sublinearly with its population, predictions that are in agreement with data gathered for around 9000 U.S. cities between 1994 and 2010.
Mazzotti, Valerie L.; Plotner, Anthony J.
2016-01-01
Inadequate transition outcomes for youth with disabilities have produced a call for enhanced transition service delivery that includes implementation of evidence-based practices (EBPs). However, research indicates transition service providers still lack the knowledge and skills to effectively implement EBPs to ensure youth with disabilities…
Stochastic transition model for pedestrian dynamics
Schultz, Michael
2012-01-01
The proposed stochastic model for pedestrian dynamics is based on existing approaches using cellular automata, combined with substantial extensions, to compensate the deficiencies resulting of the discrete grid structure. This agent motion model is extended by both a grid-based path planning and mid-range agent interaction component. The stochastic model proves its capabilities for a quantitative reproduction of the characteristic shape of the common fundamental diagram of pedestrian dynamics...
AN AGENT-BASED SIMULATION ON MARKET CONSIDERING KNOWLEDGE TRANSITION AND SOCIAL IMPACT
Tieju Ma; Mina Ryoke; Yoshiteru Nakamori
2002-01-01
In this paper, an agent-based simulation about knowledge transition associated with social impact in market is introduced. In the simulation, the genetic algorithm is used to generate the next generation products and a dynamic social impact model is used to simulate how customers are influenced by other customers. The simulation and its results not only show some features and patterns of knowledge transition, but also explore and display some phenomena of business cultures. On the basis of the innovation model of knowledge-based economy, the transition between technical knowledge and products knowledge is discussed, and a fuzzy linear quantification model which can be used to simulate the transition is introduced.
Microscopic model of the glass transition and the glassy state
A microscopic model of the glass transition and the glassy state is presented. It is exactly solvable, and offers a unified view of the equilibrium and non-equilibrium aspects of the glass transition. It also provides a statistical-mechanical justification of the irreversible thermodynamic models of the glass transition proposed earlier. (author)
Estimating transition probabilities among everglades wetland communities using multistate models
Hotaling, A.S.; Martin, J.; Kitchens, W.M.
2009-01-01
In this study we were able to provide the first estimates of transition probabilities of wet prairie and slough vegetative communities in Water Conservation Area 3A (WCA3A) of the Florida Everglades and to identify the hydrologic variables that determine these transitions. These estimates can be used in management models aimed at restoring proportions of wet prairie and slough habitats to historical levels in the Everglades. To determine what was driving the transitions between wet prairie and slough communities we evaluated three hypotheses: seasonality, impoundment, and wet and dry year cycles using likelihood-based multistate models to determine the main driver of wet prairie conversion in WCA3A. The most parsimonious model included the effect of wet and dry year cycles on vegetative community conversions. Several ecologists have noted wet prairie conversion in southern WCA3A but these are the first estimates of transition probabilities among these community types. In addition, to being useful for management of the Everglades we believe that our framework can be used to address management questions in other ecosystems. ?? 2009 The Society of Wetland Scientists.
A Runway Configuration Management Model with Marginally Decreasing Transition Capacities
Christopher Weld
2010-01-01
Full Text Available The runway configuration management (RCM problem governs what combinations of airport runways are in use at a given time, and to what capacity. Runway configurations (groupings of runways operate under runway configuration capacity envelopes (RCCEs which limit arrival and departure capacities. The RCCE identifies unique capacity constraints based on which tarmacs are used for arrivals, departures, or both, and their direction of travel. When switching between RCCEs, some decrement in arrival and departure capacities is incurred by the transition. A previous RCM model (Frankovich et al., 2009 accounted for this cost through a required period of inactivity. In this paper, we instead focus on the introduction and assessment of a model capable of marginally decreasing RCCE capacities during configuration transitions. A transition penalty matrix is introduced, specifying the relative costs (in terms of accepted arrival and departure capacities for switching between RCCEs. The new model benefits from customizable transition penalties which more closely represent real-world conditions, at a reasonable computational cost.
Jamei, Masoud
2016-01-01
There is a renewed surge of interest in applications of physiologically-based pharmacokinetic (PBPK) models by the pharmaceutical industry and regulatory agencies. Developing PBPK models within a systems pharmacology context allows separation of the parameters pertaining to the animal or human body (the system) from that of the drug and the study design which is essential to develop generic drug-independent models used to extrapolate PK/PD properties in various healthy and patient populations...
PyTransit: Fast and Easy Exoplanet Transit Modelling in Python
Parviainen, Hannu
2015-01-01
We present a fast and user friendly exoplanet transit light curve modelling package PyTransit, implementing optimised versions of the Gimen\\'ez and the Mandel & Agol transit models. The package offers an object-oriented Python interface to access the two models implemented natively in Fortran with OpenMP parallelisation. A partial OpenCL version of the quadratic Mandel-Agol model is also included for GPU-accelerated computations. The aim of PyTransit is to facilitate the analysis of photometr...
Agents adopting agriculture : Modeling the agricultural transition
van der Vaart, Elske; de Boer, Bart; Hankel, Albert; Verheij, Bart; Nolfi, S; Baldassarre, G; Calabretta, R; Hallam, JCT; Marocco, D; Meyer, JA; Miglino, O; Parisi, D
2006-01-01
The question "What drove foragers to farm?" has drawn answers from many different disciplines, often in the form of verbal models. Here, we take one such model, that of the ideal free distribution, and implement it as an agent-based computer simulation. Populations distribute themselves according to
Kostić Marina
2014-01-01
Full Text Available Background/Aim. Recent studies have shown that biological treatments for rheumatoid arthritis can change the course of rheumatoid arthritis and improve functional ability of patients with rheumatoid arthritis. In spite of this fact, use of biological therapy is still limited by high prices of these medicines, especially in countries in socioeconomic transition. The aim of our study was to compare costeffectiveness of a combination of tocilizumab and methotrexate with methotrexate alone for rheumatoid arthritis in Serbia, a country in socioeconomic transition. Methods. For the purpose of our study we designed a Markov model using data on therapy efficacy from the available literature, and data on the costs of health states calculated from records of actual patients treated in the Clinical Center Kragujevac, Serbia. The duration of one cycle in our model was set at one month, and the time horizon was 480 months (40 years. The study was done from the social perspective, and all the costs and outcomes were discounted for 3% per year. Results. Treating rheumatoid arthritis with diseasemodifying antirheumatic drugs (DMARDs alone was more cost-effective in comparison with a combination of biologic treatment with tocilizumab and DMARDs. The total costs for treating a patient with DMARDs for one year were on average 261,945.42 RSD, or 2,497.70 Euro and the total costs for treatment with tocilizimab plus DMARDs were on average 1,959,217.44 RSD, or 18,659.20 Euro. However, these results are susceptible to changes in costs and treatment effects of tocilizumab in patients with more severe forms of rheumatoid arthritis. Conclusion. Our results show that the use of tocilizumab for rheumatoid arthrits in economic environment of Serbia is not cost-effective. Use of tocilizumab for treating rheumatoid arthritis can become affordable, if costs of its use become lower. In order to start using expensive biologic medicines in patients in transitional countries
Stochastic transition model for pedestrian dynamics
Schultz, Michael
2012-01-01
The proposed stochastic model for pedestrian dynamics is based on existing approaches using cellular automata, combined with substantial extensions, to compensate the deficiencies resulting of the discrete grid structure. This agent motion model is extended by both a grid-based path planning and mid-range agent interaction component. The stochastic model proves its capabilities for a quantitative reproduction of the characteristic shape of the common fundamental diagram of pedestrian dynamics. Moreover, effects of self-organizing behavior are successfully reproduced. The stochastic cellular automata approach is found to be adequate with respect to uncertainties in human motion patterns, a feature previously held by artificial noise terms alone.
The comfortable driving model revisited: traffic phases and phase transitions
We study the spatiotemporal patterns resulting from different boundary conditions for a microscopic traffic model and contrast them with empirical results. By evaluating the time series of local measurements, the local traffic states are assigned to the different traffic phases of Kerner’s three-phase traffic theory. For this classification we use the rule-based FOTO-method, which provides ‘hard’ rules for this assignment. Using this approach, our analysis shows that the model is indeed able to reproduce three qualitatively different traffic phases: free flow (F), synchronized traffic (S), and wide moving jams (J). In addition, we investigate the likelihood of transitions between the three traffic phases. We show that a transition from free flow to a wide moving jam often involves an intermediate transition: first from free flow to synchronized flow and then from synchronized flow to a wide moving jam. This is supported by the fact that the so-called F → S transition (from free flow to synchronized traffic) is much more likely than a direct F → J transition. The model under consideration has a functional relationship between traffic flow and traffic density. The fundamental hypothesis of the three-phase traffic theory, however, postulates that the steady states of synchronized flow occupy a two-dimensional region in the flow–density plane. Due to the obvious discrepancy between the model investigated here and the postulate of the three-phase traffic theory, the good agreement that we found could not be expected. For a more detailed analysis, we also studied vehicle dynamics at a microscopic level and provide a comparison of real detector data with simulated data of the identical highway segment. (paper)
Mott transition in the Hubbard model
In this article, the author discuss W. Kohn's criterion for a metal insulator transition, within the framework of a one-band Hubbard model. This and related ideas are applied to 1-dimensional Hubbard systems, and some interesting miscellaneous results discussed. The Jordan-Wigner transformation converting the two species of fermions to two species of hardcore bosons is performed in detail, and the extra phases arising from odd-even effects are explicitly derived. Bosons are shown to prefer zero flux (i.e., diamagnetism) and the corresponding happy fluxes: for the fermions identified. A curios result following from the interplay between orbital diamagnetism and spin polarization is highlighted. A spin-statistics like theorem, showing that the anticommutation relations between fermions of opposite spin are crucial to obtain the SU(2) invariance is pointed out
PyTransit: Fast and Easy Exoplanet Transit Modelling in Python
Parviainen, Hannu
2015-01-01
We present a fast and user friendly exoplanet transit light curve modelling package PyTransit, implementing optimised versions of the Gimen\\'ez and the Mandel & Agol transit models. The package offers an object-oriented Python interface to access the two models implemented natively in Fortran with OpenMP parallelisation. A partial OpenCL version of the quadratic Mandel-Agol model is also included for GPU-accelerated computations. The aim of PyTransit is to facilitate the analysis of photometric time series of exoplanet transits consisting of hundreds of thousands of datapoints, and of multi-passband transit light curves from spectrophotometric observations, as a part of a researcher's programming toolkit for building complex, problem-specific, analyses.
Comparison of several models of the laminar/turbulent transition
Fürst J.
2013-04-01
Full Text Available The contribution deals with modelling of the laminar/turbulent transition using several transition models. Transition models of various types were tested: a the model with the algebraic equation for the intermittency coefficient according to Straka and Pøíhoda; b the three-equation transition model with the transport equation for the energy of non-turbulent fluctuations proposed by Walters and Cokljat; c the γ-Reθ model with the transport equation forthe intermittency coefficient of Langtry and Menter. The transition models were compared by means of test cases covering both flat-plate boundary-layer flows with various free stream turbulence and the flow over an airfoil including the effect of foregoing wake on the transition. The agreement of numerical results with experimental data is in all cases quite satisfactory.
Min Yang; Dan Li; Wei Wang; Jingyao Zhao; Xuewu Chen
2013-01-01
Activity-travel behavior differs between women and men. Previous researches dealing with gender differences mainly focus on travel in itself rather than the interaction between time-use pattern and travel mode choice. Based on the activity-travel survey data of Suzhou, China, multigroup structural equation modeling is adopted to explore the reason for gender-based differences in mode choice through comparing the interactions among sociodemographics, time-use pattern, and mode choice. The resu...
Phase Transitions in Model Active Systems
Redner, Gabriel S.
The amazing collective behaviors of active systems such as bird flocks, schools of fish, and colonies of microorganisms have long amazed scientists and laypeople alike. Understanding the physics of such systems is challenging due to their far-from-equilibrium dynamics, as well as the extreme diversity in their ingredients, relevant time- and length-scales, and emergent phenomenology. To make progress, one can categorize active systems by the symmetries of their constituent particles, as well as how activity is expressed. In this work, we examine two categories of active systems, and explore their phase behavior in detail. First, we study systems of self-propelled spherical particles moving in two dimensions. Despite the absence of an aligning interaction, this system displays complex emergent dynamics, including phase separation into a dense active solid and dilute gas. Using simulations and analytic modeling, we quantify the phase diagram and separation kinetics. We show that this nonequilibrium phase transition is analogous to an equilibrium vapor-liquid system, with binodal and spinodal curves and a critical point. We also characterize the dense active solid phase, a unique material which exhibits the structural signatures of a crystalline solid near the crystal-hexatic transition point, as well as anomalous dynamics including superdiffusive motion on intermediate timescales. We also explore the role of interparticle attraction in this system. We demonstrate that attraction drastically changes the phase diagram, which contains two distinct phase-separated regions and is reentrant as a function of propulsion speed. We interpret this complex situation with a simple kinetic model, which builds from the observed microdynamics of individual particles to a full description of the macroscopic phase behavior. We also study active nematics, liquid crystals driven out of equilibrium by energy-dissipating active stresses. The equilibrium nematic state is unstable in these
Transit-Based Emergency Evacuation with Transit Signal Priority in Sudden-Onset Disaster
Ciyun Lin
2016-01-01
Full Text Available This study presents methods of transit signal priority without transit-only lanes for a transit-based emergency evacuation in a sudden-onset disaster. Arterial priority signal coordination is optimized when a traffic signal control system provides priority signals for transit vehicles along an evacuation route. Transit signal priority is determined by “transit vehicle arrival time estimation,” “queuing vehicle dissipation time estimation,” “traffic signal status estimation,” “transit signal optimization,” and “arterial traffic signal coordination for transit vehicle in evacuation route.” It takes advantage of the large capacities of transit vehicles, reduces the evacuation time, and evacuates as many evacuees as possible. The proposed methods were tested on a simulation platform with Paramics V6.0. To evaluate and compare the performance of transit signal priority, three scenarios were simulated in the simulator. The results indicate that the methods of this study can reduce the travel times of transit vehicles along an evacuation route by 13% and 10%, improve the standard deviation of travel time by 16% and 46%, and decrease the average person delay at a signalized intersection by 22% and 17% when the traffic flow saturation along an evacuation route is 0.81.0, respectively.
李柏洲; 赵健宇; 苏屹
2013-01-01
回顾了现有的研究成果,基于“组织学习—知识创造”与量子运动特征的隐喻提出“组织学习一知识创造”的能级跃迁过程模型,以知识积累、知识跃迁与知识衰减为阶段对能级跃迁机理进行分析.根据能级跃迁机理,针对SECI模型的不足对其进行量子化改进.同时,将渐进式学习与顿悟式学习相融合,建立跨层面组织学习的动态模型,用以解决沟通失衡、3C误区及组织学习陷阱等实际问题,验证了模型的价值性.%Based on the exiting literature,this paper constructs the level transition process model of "organizational learning-knowledge creation" in view of the metaphor between "organizational learning-knowledge creation" and characteristics of quantum' s motion,and also analyzes level transition' s mechanisms from the stages,namely knowledge accumulation,knowledge transition and knowledge attenuation.According to the level transition mechanism,this paper does quantization improvements aiming at improving the SECI model.At the same time,we combine incremental learning with insightful learning and construct the dynamic model of crosslevel organizational learning in order to solve some actual problems such as communication' s imbalance,the misunderstanding of 3C and organizational learning' s trap,proving the value of the model.
Time Varying Transition Probabilities for Markov Regime Switching Models
Bazzi, Marco; Blasques, Francisco; Koopman, Siem Jan; Lucas, Andre
2014-01-01
We propose a new Markov switching model with time varying probabilities for the transitions. The novelty of our model is that the transition probabilities evolve over time by means of an observation driven model. The innovation of the time varying probability is generated by the score of the predictive likelihood function. We show how the model dynamics can be readily interpreted. We investigate the performance of the model in a Monte Carlo study and show that the model is successful in estim...
Modeling continuum of epithelial mesenchymal transition plasticity.
Mandal, Mousumi; Ghosh, Biswajoy; Anura, Anji; Mitra, Pabitra; Pathak, Tanmaya; Chatterjee, Jyotirmoy
2016-02-01
Living systems respond to ambient pathophysiological changes by altering their phenotype, a phenomenon called 'phenotypic plasticity'. This program contains information about adaptive biological dynamism. Epithelial-mesenchymal transition (EMT) is one such process found to be crucial in development, wound healing, and cancer wherein the epithelial cells with restricted migratory potential develop motile functions by acquiring mesenchymal characteristics. In the present study, phase contrast microscopy images of EMT induced HaCaT cells were acquired at 24 h intervals for 96 h. The expression study of relevant pivotal molecules viz. F-actin, vimentin, fibronectin and N-cadherin was carried out to confirm the EMT process. Cells were intuitively categorized into five distinct morphological phenotypes. A population of 500 cells for each temporal point was selected to quantify their frequency of occurrence. The plastic interplay of cell phenotypes from the observations was described as a Markovian process. A model was formulated empirically using simple linear algebra, to depict the possible mechanisms of cellular transformation among the five phenotypes. This work employed qualitative, semi-quantitative and quantitative tools towards illustration and establishment of the EMT continuum. Thus, it provides a newer perspective to understand the embedded plasticity across the EMT spectrum. PMID:26762753
Understanding and surviving the transition to value-based oncology.
Cox, John V; Sprandio, John D; Barkley, Ronald
2013-01-01
This paper and the three presentations it supports are drawn from the theme of the 2012 Cancer Center Business Summit (CCBS): "Transitioning to Value-Based Oncology: Strategies to Survive and Thrive." The CCBS is a forum on oncology business innovation, and the principal question the organizers address each year is "What are the creative, innovative, and best business models and practices that are being conceived or piloted today that may provide a responsible and sustainable platform for the delivery of cancer care tomorrow?" At this moment in health care-when so much is in flux and new business models and solutions abound-the oncology sector has a solemn responsibility: to forge the business models and relationships that will help to define a new cancer care value proposition and a sustainable health care system of tomorrow for the benefit of the patients it serves to get it "right." PMID:23714548
An atom laser based on Raman transitions
Moy, G M; Savage, C M
1996-01-01
In this paper we present an atom laser scheme using a Raman transition for the output coupling of atoms. A beam of thermal atoms (bosons) in a metastable atomic state |1> are pumped into a multimode atomic cavity. This cavity is coupled through spontaneous emission to a single mode of another cavity for the ground atomic state, |2>. Above a certain threshold pumping rate a large number of atoms, N2, builds up in this single quantum state and transitions to the ground state of the cavity become enhanced by a factor (N2+1). Atoms in this state are then coupled to the outside of the cavity with a Raman transition. This changes the internal state of the atom and imparts a momentum kick, allowing the atoms to leave the system.
Xuan Yang
2015-01-01
Full Text Available This paper presents a geometric least square framework for deriving [0,1]-valued interval weights from interval fuzzy preference relations. By analyzing the relationship among [0,1]-valued interval weights, multiplicatively consistent interval judgments, and planes, a geometric least square model is developed to derive a normalized [0,1]-valued interval weight vector from an interval fuzzy preference relation. Based on the difference ratio between two interval fuzzy preference relations, a geometric average difference ratio between one interval fuzzy preference relation and the others is defined and employed to determine the relative importance weights for individual interval fuzzy preference relations. A geometric least square based approach is further put forward for solving group decision making problems. An individual decision numerical example and a group decision making problem with the selection of enterprise resource planning software products are furnished to illustrate the effectiveness and applicability of the proposed models.
Phase Transition in Distance-Based Phylogeny Reconstruction
Roch, Sebastien
2011-01-01
We introduce a new distance-based phylogeny reconstruction technique which provably achieves, at sufficiently short branch lengths, a logarithmic sequence-length requirement---improving significantly over previous polynomial bounds for distance-based methods and matching existing results for general methods. The technique is based on an averaging procedure that implicitly reconstructs ancestral sequences. In the same token, we extend previous results on phase transitions in phylogeny reconstruction to general time-reversible models. More precisely, we show that in the so-called Kesten-Stigum zone (roughly, a region of the parameter space where ancestral sequences are well approximated by "linear combinations" of the observed sequences) sequences of length $O(\\log n)$ suffice for reconstruction when branch lengths are discretized. Here $n$ is the number of extant species. Our results challenge, to some extent, the conventional wisdom that estimates of evolutionary distances alone carry significantly less infor...
Modelling the transition from a socialist to capitalist economic system
Kitov, Ivan
2005-01-01
The transition of several East and Central European countries and the countries of the Former Soviet Union from the socialist economic system to the capitalist one is studied. A recently developed microeconomic model for the personal income distribution and its evolution and a simple functional relationship between the rate of the per capita GDP growth and the attained level of the per capita GDP are used to describe the transition process. The developed transition model contains only three d...
Accelerator-based studies of intercombination transitions
Intercombination transitions in multiply-charged few-electron ions have been studied for a number of years now by a number of methods, including beam-foil spectroscopy. Only very recently it has been realized that the intrinsic properties of the beam-foil light source, in particular the time resolution, offer means to single out and measure such transitions from the multiline spectra of many-electron ions where the exploitation of other light sources has been less successful. Wavelengths and transition rates of these lines provide both a test of many-electron atomic theory and tools for plasma diagnostics. As examples, data on Mg-, Al- and Si-like ions of elements Ti-Zn are presented and compared with tokamak, laser-produced plasma and solar flare data. It turns out that the level of adequacy reached by the various theoretical approaches for predictions of wavelengths and transition probabilities in the individual isoelectronic sequences is very different. However, even calculational schemes which are successful for one sequence are much worse for others. The variety of isoelectronic sequences and the ranges of ionic charge for each of the sequences which are accessible at typical heavy-ion accelerator laboratories are outlined in order to encourage the use of existing facilities for this type of spectroscopy. (orig.)
"A Two-Stage Prediction Model for Web Page Transition"
Makoto Abe
2003-01-01
Utilizing data from a log file, a two-stage model for step-ahead web page prediction that permits adaptive page customization in real-time is proposed. The first stage predicts the next page of a viewer based on a variant of a Markov transition matrix computed from page sequences of other visitors who read the same pages as that viewer did thus far. The second stage re-analyzes the incorrect exit/continuation predictions of the first stage through data mining, incorporating the visitor's view...
Quantum Hall transitions: An exact theory based on conformal restriction
Bettelheim, E.; Gruzberg, I. A.; Ludwig, A. W. W.
2012-01-01
We revisit the problem of the plateau transition in the integer quantum Hall effect. Here we develop an analytical approach for this transition, based on the theory of conformal restriction. This is a mathematical theory that was recently developed within the context of the Schramm-Loewner evolution which describes the stochastic geometry of fractal curves and other stochastic geometrical fractal objects in 2D space. Observables elucidating the connection with the plateau transition include t...
Ground-Based Photometric Searches for Transiting Planets
Mazeh, Tsevi
2009-01-01
This paper reviews the basic technical characteristics of the ground-based photometric searches for transiting planets, and discusses a possible observational selection effect. I suggest that additional photometric observations of the already observed fields might discover new transiting planets with periods around 4-6 days. The set of known transiting planets support the intriguing correlation between the planetary mass and the orbital period suggested already in 2005.
Modelling and numerical simulation of liquid-vapor phase transitions
This work deals with the modelling and numerical simulation of liquid-vapor phase transition phenomena. The study is divided into two part: first we investigate phase transition phenomena with a Van Der Waals equation of state (non monotonic equation of state), then we adopt an alternative approach with two equations of state. In the first part, we study the classical viscous criteria for selecting weak solutions of the system used when the equation of state is non monotonic. Those criteria do not select physical solutions and therefore we focus a more recent criterion: the visco-capillary criterion. We use this criterion to exactly solve the Riemann problem (which imposes solving an algebraic scalar non linear equation). Unfortunately, this step is quite costly in term of CPU which prevent from using this method as a ground for building Godunov solvers. That is why we propose an alternative approach two equations of state. Using the least action principle, we propose a phase changing two-phase flow model which is based on the second thermodynamic principle. We shall then describe two equilibrium submodels issued from the relaxations processes when instantaneous equilibrium is assumed. Despite the weak hyperbolicity of the last sub-model, we propose stable numerical schemes based on a two-step strategy involving a convective step followed by a relaxation step. We show the ability of the system to simulate vapor bubbles nucleation. (author)
Bag constant and deconfinement phase transition in the nontopological soliton bag model
The effective potential in finite temperature and density nontopological soliton bag model is investigated. Based on this, the authors calculate the bag constant which depends on temperature and chemical potential. The property of deconfinement phase transition is analysed
d-Dimensional exactly solvable model for structural phase transition
The approximating Hamiltonian method is used to prove the exact solvability of a lattice type gphi4 model with the interacting constant g=lambda/N. The thermodynamical properties of the phase transition in this model is studied as well
Quantum Hall transitions: An exact theory based on conformal restriction
Bettelheim, E.; Gruzberg, I. A.; Ludwig, A. W. W.
2012-10-01
We revisit the problem of the plateau transition in the integer quantum Hall effect. Here we develop an analytical approach for this transition, and for other two-dimensional disordered systems, based on the theory of “conformal restriction.” This is a mathematical theory that was recently developed within the context of the Schramm-Loewner evolution which describes the “stochastic geometry” of fractal curves and other stochastic geometrical fractal objects in two-dimensional space. Observables elucidating the connection with the plateau transition include the so-called point-contact conductances (PCCs) between points on the boundary of the sample, described within the language of the Chalker-Coddington network model for the transition. We show that the disorder-averaged PCCs are characterized by a classical probability distribution for certain geometric objects in the plane (which we call pictures), occurring with positive statistical weights, that satisfy the crucial so-called restriction property with respect to changes in the shape of the sample with absorbing boundaries; physically, these are boundaries connected to ideal leads. At the transition point, these geometrical objects (pictures) become fractals. Upon combining this restriction property with the expected conformal invariance at the transition point, we employ the mathematical theory of “conformal restriction measures” to relate the disorder-averaged PCCs to correlation functions of (Virasoro) primary operators in a conformal field theory (of central charge c=0). We show how this can be used to calculate these functions in a number of geometries with various boundary conditions. Since our results employ only the conformal restriction property, they are equally applicable to a number of other critical disordered electronic systems in two spatial dimensions, including for example the spin quantum Hall effect, the thermal metal phase in symmetry class D, and classical diffusion in two
Mesoscale modeling of phase transition dynamics of thermoresponsive polymers
Li, Zhen; Li, Xuejin; Karniadakis, George Em
2015-01-01
We present a non-isothermal mesoscopic model for investigation of the phase transition dynamics of thermoresponsive polymers. Since this model conserves energy in the simulations, it is able to correctly capture not only the transient behavior of polymer precipitation from solvent, but also the energy variation associated with the phase transition process. Simulations provide dynamic details of the thermally induced phase transition and confirm two different mechanisms dominating the phase transition dynamics. A shift of endothermic peak with concentration is observed and the underlying mechanism is explored.
Transition to knowledge-based economy in Saudi Arabia
Nour, S.
2014-01-01
This paper discusses the progress in transition to knowledge-based economy in Saudi Arabia. As for the methodology, this paper uses updated secondary data obtained from different sources. It uses both descriptive and comparative approaches and uses the OECD definition of knowledge-based economy and the World Bank Knowledge Index (KI) and Knowledge Economy Index (KEI) and other indicators often used in the international literature to examine progress in transition to a knowledge-based economy ...
Thresholds and Smooth Transitions in Vector Autoregressive Models
Hubrich, Kirstin; Teräsvirta, Timo
This survey focuses on two families of nonlinear vector time series models, the family of Vector Threshold Regression models and that of Vector Smooth Transition Regression models. These two model classes contain incomplete models in the sense that strongly exogeneous variables are allowed in the...
Station Level Transit Ridership Direct Estimation Model Based on Precise Land Use%基于精细化用地的轨道客流直接估计模型
王淑伟; 孙立山; 郝思源; 荣建
2015-01-01
现有轨道客流直接估计模型中,对于用地的描述多基于人口、岗位分布、用地面积等概略数据,未能准确反映用地开发的多样性和复杂性,难以揭示用地混合开发对于居民出行的作用机理.本文采用北京市电子地图中的兴趣点(POI)数据表示用地信息,结合轨道站点多层次吸引范围划分,实现了轨道站点吸引范围内各类用地比例的精细化描述.通过将精细化用地信息与轨道站点乘降客流量进行回归分析,总结了用地、交通、区位因素对于轨道站点乘降客流的影响机理,建立了基于精细化用地的轨道站点客流估计模型.验证结果显示,模型对于本文所研究典型站点的预测精度达到预期,反映了用地与轨道客流之间的强相关性.%The existing transit ridership models describe land use with indexes such as population, employment and land use area, these indexes can' t describe the diversity and complexity of land use development, thus make it difficult to reveal the influence mechanism of mixed land use on travel demand. This paper quantifies the precise land use characteristics of Beijing transit station catchment areas using POIs (points of interest) extract from an electronic map. Through the regression analysis of precise land use and transit station boarding volume, a direct ridership model is built based on the influence mechanism analysis of land use, traffic and location factors on transit ridership. Following validation shows the prediction accuracy of the proposed model meets expectation, reveals the strong correlation between land use and transit ridership.
基于精细化用地的轨道客流直接估计模型%Station Level Transit Ridership Direct Estimation Model Based on Precise Land Use
王淑伟; 孙立山; 郝思源; 荣建
2015-01-01
现有轨道客流直接估计模型中,对于用地的描述多基于人口、岗位分布、用地面积等概略数据,未能准确反映用地开发的多样性和复杂性,难以揭示用地混合开发对于居民出行的作用机理.本文采用北京市电子地图中的兴趣点(POI)数据表示用地信息,结合轨道站点多层次吸引范围划分,实现了轨道站点吸引范围内各类用地比例的精细化描述.通过将精细化用地信息与轨道站点乘降客流量进行回归分析,总结了用地、交通、区位因素对于轨道站点乘降客流的影响机理,建立了基于精细化用地的轨道站点客流估计模型.验证结果显示,模型对于本文所研究典型站点的预测精度达到预期,反映了用地与轨道客流之间的强相关性.%The existing transit ridership models describe land use with indexes such as population, employment and land use area, these indexes can' t describe the diversity and complexity of land use development, thus make it difficult to reveal the influence mechanism of mixed land use on travel demand. This paper quantifies the precise land use characteristics of Beijing transit station catchment areas using POIs (points of interest) extract from an electronic map. Through the regression analysis of precise land use and transit station boarding volume, a direct ridership model is built based on the influence mechanism analysis of land use, traffic and location factors on transit ridership. Following validation shows the prediction accuracy of the proposed model meets expectation, reveals the strong correlation between land use and transit ridership.
Explosive Percolation: Unusual Transitions of a Simple Model
Bastas, Nikolaos; Giazitzidis, Paraskevas; Maragakis, Michael; Kosmidis, Kosmas
2014-01-01
In this paper we review the recent advances on explosive percolation, a very sharp phase transition first observed by Achlioptas et al. (Science, 2009). There a simple model was proposed, which changed slightly the classical percolation process so that the emergence of the spanning cluster is delayed. This slight modification turns out to have a great impact on the percolation phase transition. The resulting transition is so sharp that it was termed explosive, and it was at first considered t...
A model with simultaneous first and second order phase transitions
Messager, Alain; Nachtergaele, Bruno
2005-01-01
We introduce a two dimensional nonlinear XY model with a second order phase transition driven by spin waves, together with a first order phase transition in the bond variables between two bond ordered phases, one with local ferromagnetic order and another with local antiferromagnetic order. We also prove that at the transition temperature the bond-ordered phases coexist with a disordered phase as predicted by Domany, Schick and Swendsen. This last result generalizes the result of Shlosman and...
Phenomenological models of cosmic phase transitions. 2
Classical nucleation theory is applied to follow the thermal history of a homogeneous and isotropic universe during a first-order phase transition. The dependence of possible supercooling and reheating scenarios on the surface tension and growth velocity of bubbles is discussed. (author)
A model of interband radiative transition
Dittrich, Jaroslav; Exner, Pavel; Hirokawa, M.
2004-01-01
Roč. 56, č. 3 (2004), s. 753-786. ISSN 0025-5645 R&D Projects: GA MŠk ME 482 Keywords : radiative transition * crystal spectral band * decay law Subject RIV: BE - Theoretical Physics Impact factor: 0.366, year: 2004
Yujie Wei; Yongheng Jiang; Dexian Huang⁎
2014-01-01
This paper introduces a practical solving scheme of gradetransition trajectory optimization (GTTO) problems under typical certificate-checking–updating framework. Due to complicated kinetics of polymerization, differential/algebraic equations (DAEs) always cause great computational burden and system non-linearity usual y makes GTTO non-convex bearing multiple optima. Therefore, coupled with the three-stage decomposi-tion model, a three-section algorithm of dynamic programming (TSDP) is proposed based on the general iteration mechanism of iterative programming (IDP) and incorporated with adaptivegrid allocation scheme and heuristic modifications. The algorithm iteratively performs dynamic programming with heuristic modifications under constant calculation loads and adaptively allocates the valued computational resources to the regions that can further improve the optimality under the guidance of local error estimates. TSDP is finally compared with IDP and interior point method (IP) to verify its efficiency of computation.
On the phase transition nature in compressible Ising models
The phase transition phenomenon is analysed in a compressible ferromagnetic Ising model at null field, through the mean-field approximation. The model studied is d-dimensional under the magnetic point of view and one-dimensional under the elastic point of view. This is achieved keeping the compressive interactions among the ions and rejecting annealing forces completely. The exchange parameter J is linear and the elastic potential quadratic in relation to the microscopic shifts of the lattice. In the one-dimensional case, this model shows no phase transition. In the two-dimensional case, the role of the Si spin of the i-the ion is crucial: a) for spin 1/2 the transitions are of second order; b) for spin 1, desides the second order transitions there is a three-critical point and a first-order transitions line. (L.C.)
校园数据集成过渡模式研究与应用%Research and application of data integrated transition model based on campus network
郭政慧
2012-01-01
分析了校园网各业务系统的特点和软件架构模式,提出了利用面向服务架构实现数据集成的过渡方案.采用多粒度服务设计原则,将遗留系统封装成为服务构件.经过比较,选择统一的Web服务标准接口方式,并给出了校园网业务集成的步骤、方法,分析其可行性,并应用于具体实践中.%With the construction of information systems,there has been a wide variety of isolated applications.Based on this,this paper analyzes the characteristics of business systems and software architecture model,then proposes service-oriented architecture for business integration framework.Based on the principles of multi-granularity services,Legacy systems will be encapsulated as a web service component.Finally,the article describes the steps,methods,feasibility of the business integration on compus network.
Description of transitional nuclei in the sdg boson model
The study of the transitional nuclei in the framework of the sdg boson model was necessitated by recent measurements of E2 and E4 transitions in the Pt and Os isotopes which can not be explained in the sd boson models. It is shown how γ-unstable and triaxial shapes arise from special choices of sdg model Hamiltonians. Ways of limiting the number of free parameters through consistency and coherence conditions are also discussed. A satisfactory description of E2 and E4 properties is obtained for the Pt and Os nuclei, which also predicts dynamic shape transitions in these nuclei. 36 refs., 10 tabs., 12 figs
First-order transitions for very nonlinear sigma models
Enter, Aernout C.D. van; Shlosman, Senya B.
2005-01-01
In this contribution we discuss the occurrence of first-order transitions in temperature in various short-range lattice models with a rotation symmetry. Such transitions turn out to be widespread under the condition that the interaction potentials are sufficiently nonlinear.
An improved model for the transit entropy of monatomic liquids
Wallace, Duane C [Los Alamos National Laboratory; Chisolm, Eric D [Los Alamos National Laboratory; Bock, Nicolas [Los Alamos National Laboratory
2009-01-01
In the original formulation of V-T theory for monatomic liquid dynamics, the transit contribution to entropy was taken to be a universal constant, calibrated to the constant-volume entropy of melting. This model suffers two deficiencies: (a) it does not account for experimental entropy differences of {+-}2% among elemental liquids, and (b) it implies a value of zero for the transit contribution to internal energy. The purpose of this paper is to correct these deficiencies. To this end, the V-T equation for entropy is fitted to an overall accuracy of {+-}0.1% to the available experimental high temperature entropy data for elemental liquids. The theory contains two nuclear motion contributions: (a) the dominant vibrational contribution S{sub vib}(T/{theta}{sub 0}), where T is temperature and {theta}{sub 0} is the vibrational characteristic temperature, and (b) the transit contribution S{sub tr}(T/{theta}{sub tr}), where {theta}{sub tr} is a scaling temperature for each liquid. The appearance of a common functional form of S{sub tr} for all the liquids studied is a property of the experimental data, when analyzed via the V-T formula. The resulting S{sub tr} implies the correct transit contribution to internal energy. The theoretical entropy of melting is derived, in a single formula applying to normal and anomalous melting alike. An ab initio calculation of {theta}{sub 0}, based on density functional theory, is reported for liquid Na and Cu. Comparison of these calculations with the above analysis of experimental entropy data provides verification of V-T theory. In view of the present results, techniques currently being applied in ab initio simulations of liquid properties can be employed to advantage in the further testing and development of V-T theory.
Kostić Marina; Jovanović Snežana; Tomović Marina; Popović-Milenković Marija; Janković Slobodan M.
2014-01-01
Background/Aim. Recent studies have shown that biological treatments for rheumatoid arthritis can change the course of rheumatoid arthritis and improve functional ability of patients with rheumatoid arthritis. In spite of this fact, use of biological therapy is still limited by high prices of these medicines, especially in countries in socioeconomic transition. The aim of our study was to compare costeffectiveness of a combination of tocilizumab and methotr...
Least Expected Time Paths in Stochastic Schedule-Based Transit Networks
Dang Khoa Vo; Tran Vu Pham; Nguyen Huynh Tuong; Van Hoai Tran
2016-01-01
We consider the problem of determining a least expected time (LET) path that minimizes the number of transfers and the expected total travel time in a stochastic schedule-based transit network. A time-dependent model is proposed to represent the stochastic transit network where vehicle arrival times are fully stochastically correlated. An exact label-correcting algorithm is developed, based on a proposed dominance condition by which Bellman’s principle of optimality is valid. Experimental res...
An Anderson-like model of the QCD chiral transition
Giordano, Matteo; Pittler, Ferenc
2016-01-01
We study the problems of chiral symmetry breaking and eigenmode localisation in finite-temperature QCD by looking at the lattice Dirac operator as a random Hamiltonian. We recast the staggered Dirac operator into an unconventional three-dimensional Anderson Hamiltonian ("Dirac-Anderson Hamiltonian") carrying internal degrees of freedom, with disorder provided by the fluctuations of the gauge links. In this framework, we identify the features relevant to chiral symmetry restoration and localisation of the low-lying Dirac eigenmodes in the ordering of the local Polyakov lines, and in the related correlation between spatial links across time slices, thus tying the two phenomena to the deconfinement transition. We then build a toy model based on QCD and on the Dirac-Anderson approach, replacing the Polyakov lines with spin variables and simplifying the dynamics of the spatial gauge links, but preserving the above-mentioned relevant dynamical features. Our toy model successfully reproduces the main features of the...
Modeling Tiered Pricing in the Internet Transit Market
Valancius, Vytautas; Feamster, Nick; Johari, Ramesh; Vazirani, Vijay V
2011-01-01
ISPs are increasingly selling "tiered" contracts, which offer Internet connectivity to wholesale customers in bundles, at rates based on the cost of the links that the traffic in the bundle is traversing. Although providers have already begun to implement and deploy tiered pricing contracts, little is known about how such pricing affects ISPs and their customers. While contracts that sell connectivity on finer granularities improve market efficiency, they are also more costly for ISPs to implement and more difficult for customers to understand. In this work we present two contributions: (1) we develop a novel way of mapping traffic and topology data to a demand and cost model; and (2) we fit this model on three large real-world networks: an European transit ISP, a content distribution network, and an academic research network, and run counterfactuals to evaluate the effects of different pricing strategies on both the ISP profit and the consumer surplus. We highlight three core findings. First, ISPs gain most ...
Methanol Oxidation on Model Elemental and Bimetallic Transition Metal Surfaces
Tritsaris, G. A.; Rossmeisl, J.
2012-01-01
Direct methanol fuel cells are a key enabling technology for clean energy conversion. Using density functional theory calculations, we study the methanol oxidation reaction on model electrodes. We discuss trends in reactivity for a set of monometallic and bimetallic transition metal surfaces, fla...... active sites on the surface and to screen for novel bimetallic surfaces of enhanced activity. We suggest platinum copper surfaces as promising anode catalysts for direct methanol fuel cells....... and stepped, which includes platinum-based alloys with ruthenium, tin, and copper, as well as nonprecious alloys, overlayer structures, and modified edges. A common lower bound on the overpotential is estimated (ca. 0.3 V). A model for bifunctional alloys is employed to investigate the nature of the...
Prediction of Synchrostate Transitions in EEG Signals Using Markov Chain Models
Jamal, Wasifa; Oprescu, Ioana-Anastasia; Maharatna, Koushik
2014-01-01
This paper proposes a stochastic model using the concept of Markov chains for the inter-state transitions of the millisecond order quasi-stable phase synchronized patterns or synchrostates, found in multi-channel Electroencephalogram (EEG) signals. First and second order transition probability matrices are estimated for Markov chain modelling from 100 trials of 128-channel EEG signals during two different face perception tasks. Prediction accuracies with such finite Markov chain models for synchrostate transition are also compared, under a data-partitioning based cross-validation scheme.
Overlap and activity glass transitions in plaquette spin models with hierarchical dynamics
Turner, Robert M.; Jack, Robert L.; Garrahan, Juan P.
2015-08-01
We consider thermodynamic and dynamic phase transitions in plaquette spin models of glasses. The thermodynamic transitions involve coupled (annealed) replicas of the model. We map these coupled-replica systems to a single replica in a magnetic field, which allows us to analyze the resulting phase transitions in detail. For the triangular plaquette model (TPM), we find for the coupled-replica system a phase transition between high- and low-overlap phases, occurring at a coupling ɛ*(T ) , which vanishes in the low-temperature limit. Using computational path sampling techniques, we show that a single TPM also displays "space-time" transitions between active and inactive dynamical phases. These first-order dynamical transitions occur at a critical counting field sc(T ) ≳0 that appears to vanish at zero temperature in a manner reminiscent of the thermodynamic overlap transition. In order to extend the ideas to three dimensions, we introduce the square pyramid model, which also displays both overlap and activity transitions. We discuss a possible common origin of these various phase transitions, based on long-lived (metastable) glassy states.
Liquid-Liquid Phase Transition and Glass Transition in a Monoatomic Model System
Nicolas Giovambattista
2010-12-01
Full Text Available We review our recent study on the polyamorphism of the liquid and glass states in a monatomic system, a two-scale spherical-symmetric Jagla model with both attractive and repulsive interactions. This potential with a parametrization for which crystallization can be avoided and both the glass transition and the liquid-liquid phase transition are clearly separated, displays water-like anomalies as well as polyamorphism in both liquid and glassy states, providing a unique opportunity to study the interplay between the liquid-liquid phase transition and the glass transition. Our study on a simple model may be useful in understanding recent studies of polyamorphism in metallic glasses.
An intermittency model for predicting roughness induced transition
Highlights: • A bypass transition model is extended to predict roughness induced transition. • Effective displacement of the wall origin serves as a framework to the modification. • The modification is capable of properly shifting the smooth wall transition onset. • Computational results obtain reasonable agreement with the data. - Abstract: An intermittency transport equation for RANS modeling, formulated in local variables, is extended for roughness-induced transition. To predict roughness effects in the fully turbulent boundary layer, published boundary conditions for k and ω are used. They depend on the equivalent sand-grain roughness height, and account for the effective displacement of wall distance origin. Similarly in our approach, wall distance in the transition model for smooth surfaces is modified by an effective origin, which depends on equivalent sand-grain roughness. Flat plate test cases are computed to show that the proposed model is able to predict transition onset in agreement with a data correlation of transition location versus roughness height, Reynolds number, and inlet turbulence intensity. Experimental data for turbine cascades are compared to the predicted results to validate the proposed model
We have developed an N-body interatomic potential, based on the second moment approximation of the tight-binding scheme, by fitting its four adjustable parameters to the cohesive energy, atomic volume, and elastic constants of hcp-Zr. We then showed that various properties of this potential compare favorably with those of zirconium in both the low temperatures hcp phase and the high temperature bcc phase. Such is the case in particular for the elastic constants, the phonon dispersion curves, the thermal expansion, and the melting temperature. We reproduced by molecular dynamics (MD) simulations on this potential the hcp/bcc phase transformation in both ways. It indeed occurs following the mechanism predicted by Burgers. We find a vibrational entropy of transformation equal to 0.13 kB. Our calculations suggest that in real zirconium the electronic contribution to the transformation entropy is important. We show that some interatomic potential lead to a higher value of the vibrational entropy in the hcp phase than in the bcc phase. We specified the dynamics of the vacancy migration in the bcc phase. The atomic jumps are almost exclusively nearest neighbour ones. The walk of the vacancy becomes strongly correlated at high temperatures. The vacancy jump frequency is very large and has a perfectly arrhenian behaviour. There is no evicence of a dynamical lowering of the vacancy migration barrier: the static and dynamic values of the vacancy migration energy are almost equal, both being unusually small (0.3 eV). The self diffusion coefficent of our model for the vacancy mechanism reproduces an anomalous fast diffusion close to that measured experimentally in bcc-Zr. In our model at high temperatures the time interval between successive jumps is almost equal to the time of flight. The migration events will therefore influence the formation of the vacancies
AN AGENT—BASED SIMULATION ON MARKET CONSIDERING KNOWLEDGE TRANSITION AND SOCIAL IMPACT
Tieju; MinaRyoke; 等
2002-01-01
In this paper,an agent-based simulation about knowledge transition associated with social impact in market is introduced.In the simulation,the genetic algorthm is used to generate the next generation products and a dynamic social impact model is used to simulate how customers are influenced by other customers.The simulation and its results not only show some features and patterns of knowlege transition,but also explore and display some phenomena of business cultures.On the basis of the innovation model of knowledge-based economy,the transition between technical knowledge and products knowledge is discussed,and a fuzzy linear quantification model which can be used to simulate the transition is introduced.
The Electroweak Phase Transition in the Inert Doublet Model
Blinov, Nikita; Stefaniak, Tim
2015-01-01
We study the strength of a first-order electroweak phase transition in the Inert Doublet Model (IDM), where particle dark matter (DM) is comprised of the lightest neutral inert Higgs boson. We improve over previous studies in the description and treatment of the finite-temperature effective potential and of the electroweak phase transition. We focus on a set of benchmark models inspired by the key mechanisms in the IDM leading to a viable dark matter particle candidate, and illustrate how to enhance the strength of the electroweak phase transition by adjusting the masses of the yet undiscovered IDM Higgs states. We argue that across a variety of DM masses, obtaining a strong enough first-order phase transition is a generic possibility in the IDM. We find that due to direct dark matter searches and collider constraints, a sufficiently strong transition and a thermal relic density matching the universal DM abundance is possible only in the Higgs funnel regime.
The electroweak phase transition in the Inert Doublet Model
Blinov, Nikita [Department of Physics, University of California Santa Cruz,1156 High St, Santa Cruz, CA 95064 (United States); Santa Cruz Institute for Particle Physics,1156 High St, Santa Cruz, CA 95064 (United States); Theory Department, TRIUMF,4004 Wesbrook Mall, Vancouver, BC V6T 2A3 (Canada); Department of Physics and Astronomy, University of British Columbia,Vancouver, BC V6T 1Z1 (Canada); Profumo, Stefano; Stefaniak, Tim [Department of Physics, University of California Santa Cruz,1156 High St, Santa Cruz, CA 95064 (United States); Santa Cruz Institute for Particle Physics,1156 High St, Santa Cruz, CA 95064 (United States)
2015-07-21
We study the strength of a first-order electroweak phase transition in the Inert Doublet Model (IDM), where particle dark matter (DM) is comprised of the lightest neutral inert Higgs boson. We improve over previous studies in the description and treatment of the finite-temperature effective potential and of the electroweak phase transition. We focus on a set of benchmark models inspired by the key mechanisms in the IDM leading to a viable dark matter particle candidate, and illustrate how to enhance the strength of the electroweak phase transition by adjusting the masses of the yet undiscovered IDM Higgs states. We argue that across a variety of DM masses, obtaining a strong enough first-order phase transition is a generic possibility in the IDM. We find that due to direct dark matter searches and collider constraints, a sufficiently strong transition and a thermal relic density matching the universal DM abundance is possible only in the Higgs funnel regime.
An Anderson-like model of the QCD chiral transition
Giordano, Matteo; Kovács, Tamás G.; Pittler, Ferenc
2016-06-01
We study the problems of chiral symmetry breaking and eigenmode localisation in finite-temperature QCD by looking at the lattice Dirac operator as a random Hamiltonian. We recast the staggered Dirac operator into an unconventional three-dimensional Anderson Hamiltonian ("Dirac-Anderson Hamiltonian") carrying internal degrees of freedom, with disorder provided by the fluctuations of the gauge links. In this framework, we identify the features relevant to chiral symmetry restoration and localisation of the low-lying Dirac eigenmodes in the ordering of the local Polyakov lines, and in the related correlation between spatial links across time slices, thus tying the two phenomena to the deconfinement transition. We then build a toy model based on QCD and on the Dirac-Anderson approach, replacing the Polyakov lines with spin variables and simplifying the dynamics of the spatial gauge links, but preserving the above-mentioned relevant dynamical features. Our toy model successfully reproduces the main features of the QCD spectrum and of the Dirac eigenmodes concerning chiral symmetry breaking and localisation, both in the ordered (deconfined) and disordered (confined) phases. Moreover, it allows us to study separately the roles played in the two phenomena by the diagonal and the off-diagonal terms of the Dirac-Anderson Hamiltonian. Our results support our expectation that chiral symmetry restoration and localisation of the low modes are closely related, and that both are triggered by the deconfinement transition.
Statistical Physics and Dynamical Systems: Models of Phase Transitions
Patwardhan, Ajay
2007-01-01
This paper explores the connection between dynamical system properties and statistical physics of ensembles of such systems. Simple models are used to give novel phase transitions; particularly for finite N particle systems with many physically interesting examples.
Phase transition in Potts model with invisible states
We study phase transition in the ferromagnetic Potts model with invisible states that are added as redundant states by mean-field calculation and Monte Carlo simulation. Invisible states affect the entropy and free energy, although they do not contribute to the internal energy. A second-order phase transition takes place at finite temperature in the standard q-state ferromagnetic Potts model on two-dimensional lattice for q=2,3, and 4. However, our present model on two-dimensional lattice undergoes a first-order phase transition with spontaneous q-fold symmetry breaking (q=2,3, and 4) due to entropy effect of invisible states. The model is fundamental for the analysis of a first-order phase transition with spontaneous discrete symmetry breaking. (author)
The folding transition state theory in simple model systems
Niewieczerzal, Szymon; Cieplak, Marek [Institute of Physics, Polish Academy of Sciences, 02-668 Warsaw (Poland)
2008-06-18
We present the results of an exact analysis of several model free energy landscapes of a protein to clarify the notion of the transition state and the physical meaning of the {phi} values determined in protein engineering experiments. We argue that a proper search strategy for the transition state in more realistic models should involve identification of a common part of various methods. Two of the models considered involve explicit conformations instead of just points on the free energy axis. These models are minimalistic as they are endowed only with five or 36 states to enumerate folding paths and to identify the transition state easily. Even though they display much of the two-state behavior, the {phi} values are found not to correspond to the conformation of the transition state.
The folding transition state theory in simple model systems
Niewieczerzał, Szymon; Cieplak, Marek
2008-06-01
We present the results of an exact analysis of several model free energy landscapes of a protein to clarify the notion of the transition state and the physical meaning of the phi values determined in protein engineering experiments. We argue that a proper search strategy for the transition state in more realistic models should involve identification of a common part of various methods. Two of the models considered involve explicit conformations instead of just points on the free energy axis. These models are minimalistic as they are endowed only with five or 36 states to enumerate folding paths and to identify the transition state easily. Even though they display much of the two-state behavior, the phi values are found not to correspond to the conformation of the transition state.
PYTRANSIT: fast and easy exoplanet transit modelling in PYTHON
Parviainen, Hannu
2015-07-01
We present a fast and user friendly exoplanet transit light-curve modelling package PYTRANSIT, implementing optimized versions of the Giménez and Mandel & Agol transit models. The package offers an object-oriented PYTHON interface to access the two models implemented natively in FORTRAN with OpenMP parallelization. A partial OpenCL version of the quadratic Mandel-Agol model is also included for GPU-accelerated computations. The aim of PYTRANSIT is to facilitate the analysis of photometric time series of exoplanet transits consisting of hundreds of thousands of data points, and of multipassband transit light curves from spectrophotometric observations, as a part of a researcher's programming toolkit for building complex, problem-specific analyses.
Integrability and Quantum Phase Transitions in Interacting Boson Models
Dukelsky, J; García-Ramos, J E; Pittel, S
2003-01-01
The exact solution of the boson pairing hamiltonian given by Richardson in the sixties is used to study the phenomena of level crossings and quantum phase transitions in the integrable regions of the sd and sdg interacting boson models.
Facilitating Transition to Team Based Design Education
Tollestrup, Christian
2014-01-01
supervisors and programme 3.Reflection of the role in a team, problem based project work 4.The level of information of special expectations from the Industrial Design program towards team and problem based project work. Results indicates that Class receiving the “Survival Kit” improved in the calibration...
Numerical model of post-DNB transition boiling heat transfer
In this paper a physical model for the transition boiling heat transfer is proposed. The corresponding mathematical descriptions are given in detail and the heat transfer characteristics of post-DNB transition boiling is analyzed. The numerical model of post-DNB transition boiling heat transfer is obtained as the empirical value of the coefficient is determined by the experimental data. The numerical model is compared with the experimental data of different parameters and other numerical models, and the statistical deviations are calculated. The calculating results of the numerical model in this paper show good agreement with the experimental data and the numerical model in this paper is with good applicability compared with other numerical models. (authors)
Bond-Ordering Model for the Glass Transition
Davatolhagh, Saeid; Patton, Bruce R.
2000-01-01
We consider the idea of bond ordering as a model for glass transition: a generic covalently bonded liquid may substantially reduce its energy through bond ordering, without undergoing significant structural order. This concept is developed for a model system using quantities such as a bond order parameter and susceptibility which provide new identification for calorimetric glass transition temperature. Monte Carlo simulation results exhibit bond ordering at intermediate temperatures uncorrela...
On the chiral phase transition in the linear sigma model
The Cornwall- Jackiw-Tomboulis (CJT) effective action for composite operators at finite temperature is used to investigate the chiral phase transition within the framework of the linear sigma model as the low-energy effective model of quantum chromodynamics (QCD). A new renormalization prescription for the CJT effective action in the Hartree-Fock (HF) approximation is proposed. A numerical study, which incorporates both thermal and quantum effect, shows that in this approximation the phase transition is of first order. However, taking into account the higher-loop diagrams contribution the order of phase transition is unchanged. (author)
Nuclear clocks based on resonant excitation of gamma-transitions
Peik, Ekkehard
2015-01-01
We review the ideas and concepts for a clock that is based on a radiative transition in the nucleus rather than in the electron shell. This type of clock offers advantages like an insensitivity against field-induced systematic frequency shifts and the opportunity to obtain high stability from interrogating many nuclei in the solid state. Experimental work concentrates on the low-energy (about 8 eV) isomeric transition in Th-229. We review the status of the experiments that aim at a direct optical observation of this transition and outline the plans for high-resolution laser spectroscopy experiments.
Percolation-based precursors of transitions in dynamical systems
Rodriguez Mendez, Victor Manuel; Eguiluz, Victor M.; Ramasco, Jose J.; Hernandez-Garcia, Emilio
2015-04-01
Transitions in complex dynamical systems are ubiquitous in nature. Finding leading indicators in such systems is a fundamental task in many areas of science, such as financial markets, the extinction of species or climate change studies. Here we propose a new framework to study systems close to a bifurcation point by analyzing topological properties, based on clusters and percolation, of functional networks defined from the time series. The use of networks allows us for a global parametrization of the system going far beyond simple two-point relations (classical correlations). The generality and versatility of the cluster-based method to forecast transitions is shown in two different kinds of data. In one hand, three theoretical dynamical systems displaying very different transitions and crossovers were used as a test bed. On the other hand, we have used the field of surface air temperature in the NINO 3.4 zone. In this new approach, critical transitions are identified before they occur.
Allosteric transition: a comparison of two models
Bindslev, Niels
2013-01-01
Introduction Two recent models are in use for analysis of allosteric drug action at receptor sites remote from orthosteric binding sites. One is an allosteric two-state mechanical model derived in 2000 by David Hall. The other is an extended operational model developed in 2007 by Arthur Christopo......Introduction Two recent models are in use for analysis of allosteric drug action at receptor sites remote from orthosteric binding sites. One is an allosteric two-state mechanical model derived in 2000 by David Hall. The other is an extended operational model developed in 2007 by Arthur...
The tax base in transition : the case of Bulgaria
Bogetic, Zeljko; Hillman, Arye L.
1994-01-01
The transition from socialism characteristically reduces existing tax revenues at the same time that it increases the need for government spending. An increasing need for revenue combined with an eroding tax base creates a transition-related fiscal gap and a challenge for tax policy. The solution, say the authors, is not to lay a heavier tax burden on new private firms. The issue is how to meet revenue needs without inhibiting private sector development. Large-scale tax evasion in the private...
Thermodynamics and phase transitions in the Overhauser model
Duffield, N.G.; Pule, J.V.
1989-01-01
The authors analyze the thermodynamics of the Overhauser model and demonstrate rigorously the existence of a phase transition. This is achieved by extending techniques previously developed to treat the BCS model in the quasi-spin formulation. Additionally, they compare the thermodynamics of the quasi-spin and full-trace BCS models. The results are identical up to a temperature rescaling.
Thermodynamics and phase transitions in the Overhauser model
Duffield, N. G.; Pulé, J. V.
1989-01-01
We analyze the thermodynamics of the Overhauser model and demonstrate rigorously the existence of a phase transition. This is achieved by extending techniques previously developed to treat the BCS model in the quasi-spin formulation. Additionally, we compare the thermodynamics of the quasi-spin and full-trace BCS models. The results are identical up to a temperature rescaling.
Phase Transition in Conditional Curie-Weiss Model
Opoku, Alex A; Ansah, Richard
2016-01-01
This paper proposes a conditional Curie-Weiss model as a model for opinion formation in a society polarized along two opinions, say opinions 1 and 2. The model comes with interaction strength $\\beta>0$ and bais $h$. Here the population in question is divided into three main groups, namely: Group one consisting of individuals who have decided on opinion 1. Let the proportion of this group be given by $s$. Group two consisting of individauls who have chosen opinion 2. Let $r$ be their proportion. Group three consisting of individuals who are yet to decide and they will decide based on their environmental conditions. Let $1-s-r$ be the proportion of this group. We show that the specific magnetization of the associated conditional Curie-Weiss model has a first order phase transition (discontinuous jump in specific magnetization) at $\\beta^*=\\left(1-s-r\\right)^{-1}$. It is also shown that not all the discontinuous jumps in magnetization will result in phase change. We point out how an extention of this model could...
Application of a Transition Transport Model to Industrially Relevant Aerodynamic Configurations
Seyfert, Cornelia
2011-01-01
The correlation-based γ-Reθt transition transport model has been implemented into a hybrid Reynolds-Averaged Navier-Stokes solver and evaluated on various basic test cases. The present work deals with the application of the γ-Reθt transition transport model to more complex and industrially relevant aerodynamic configurations. Results are shown for the computation of flow around a 2D high-lift airfoil and a 3D helicopter fuselage. The computed transition locations as well as the pressure an...
Phases and phase transitions in the algebraic microscopic shell model
Georgieva A. I.
2016-01-01
Full Text Available We explore the dynamical symmetries of the shell model number conserving algebra, which define three types of pairing and quadrupole phases, with the aim to obtain the prevailing phase or phase transition for the real nuclear systems in a single shell. This is achieved by establishing a correspondence between each of the pairing bases with the Elliott’s SU(3 basis that describes collective rotation of nuclear systems. This allows for a complete classification of the basis states of different number of particles in all the limiting cases. The probability distribution of the SU(3 basis states within theirs corresponding pairing states is also obtained. The relative strengths of dynamically symmetric quadrupole-quadrupole interaction in respect to the isoscalar, isovector and total pairing interactions define a control parameter, which estimates the importance of each term of the Hamiltonian in the correct reproduction of the experimental data for the considered nuclei.
Transition to knowledge-based economy in Saudi Arabia
Nour, S.
2014-01-01
This paper discusses the progress in transition to knowledge-based economy in Saudi Arabia. As for the methodology, this paper uses updated secondary data obtained from different sources. It uses both descriptive and comparative approaches and uses the OECD definition of knowledge-based economy and
A Smooth Transition GARCH-M Model
Tsatsura, Oleg
2010-01-01
Generalized autoregressive conditional heteroscedasticity in-mean model allows accounting for both time-varying variance and risk premium in financial time series data. This paper introduces an extension of this particular model with more flexible parameterization of the way variance enters the conditional mean equation, which allows for more complex dynamics in the time-varying risk premium. Paper presents model specification, criteria for hypothesis testing and develops an application for s...
On superradiant phase transitions and effective models in circuit QED
Circuit QED systems of artificial atoms interacting with microwaves have been proved to behave in many respects analogously to their counterparts with real atoms in cavity QED. However, it has been predicted recently that the analogy fails if a large number of (artificial) atoms couple strongly to the electromagnetic radiation: Whereas for real atoms a no-go theorem rules out the possibility of a superradiant quantum phase transition as the coupling is increased, the standard description of circuit QED systems by an effective model based on macroscopic quantities does allow it. We investigate the possibility of a superradiant quantum phase transition in circuit QED systems from a microscopic point of view. Our analysis shows that also circuit QED systems are subject to the no-go theorem. It hence restores the analogy of circuit QED and cavity QED and challenges the applicability of the standard description of circuit QED systems in the regime under concern. In the light of this analysis, the no-go theorem is scrutinized and confirmed in a way more adequate for realistic physical systems.
Model of transit time for SiGe HBT Collector junction depletion-layer
Hu Hui-Yong; Zhang He-Ming; Dai Xian-Ying; Jia Xin-Zhang; Cui Xiao-Ying; Wang Wei; Ou Jian-Feng; Wang Xi-Yuan
2005-01-01
The transit time through collector junction depletion-layer is an important parameter that influences AC gain and frequency performance. In SiGe heterojunction bipolar transistor (HBT) collector junction, the depletion-layer width is given in three cases. The models of collector depletion-layer transit time, considering the collector current densities and base extension effect, are established and simulated using MATLAB. The influence of the different collector j unction bias voltage, collector concentration of As or P dopant and collector width on collector junction transit time is quantitatively studied. When the collector junction bias voltage, collector doping concentration and collector width are large, the transit time is quite long. And, from the results of simulations, the influence of the collector depletion-layer transit time on frequency performance is considerable in SiGe HBT with a thin base, so it could not be ignored.
The γ-Reθ transition model of Menter et al. [Menter, F.R., Langtry, R.B., Volker, S., Huang, P.G., 2005. Transition modelling for general purpose CFD codes. ERCOFTAC International Symposium Engineering Turbulence Modelling and Measurements] is a highly generalized transport equation model in which it has been developed based on the concept of local variables compatible with modern CFD methods where the unstructured grid and the parallel computing technique are usually integrated in. To perform the prediction with this model, two essential parameters, Flength which is used to control the length of the transition region and Reθc which is used to control the onset of the transition location, must be specified to close the model. At present, both parameters are proprietary and their formulations are unpublished. For the first time here, the relations for both parameters are formulated by means of numerical experiments and analysis under the assumption of Reθc = Reθt corresponding with the bypass transition behavior. Based on this analysis, the optimized values of the parameters are found and their relations can be constructed as follows: Reθc = 803.73(Tu∞,le + 0.6067)-1.027 and Flength = 163 ln(Tu∞,le) + 3.625. The performance of this transition model is assessed by testing with the experimental cases of T3AM, T3A, and T3B. Detailed comparisons with the predicted results by the transition models of Suzen and Huang [Suzen, Y.B., Huang, P.G., 2000. Modeling of flow transition using an intermittency transport equation. J. Fluids Eng. 122, 273-284] and Lodefier et al. [Lodefier, K., Merci, B., De Langhe, C., Dick, E., 2003. Transition modelling with the SST turbulence model and intermittency transport equation. ASME Turbo Expo, Atlanta, GA, USA, June 16-19], and also with the predicted results by the k-ε model of Launder and Sharma [Launder, B.E., Sharma, B., 1974. Application of the energy dissipation model of turbulence to the calculation of flow near a
A College-Level Inquiry-Based Laboratory Activity on Transiting Planets
McConnell, Nicholas J.; Medling, Anne M.; Strubbe, Linda E.; Moth, Pimol; Montgomery, Ryan M.; Raschke, Lynne M.; Hunter, Lisa; Goza, Barbara
2010-01-01
We have designed an inquiry-based laboratory activity on transiting extrasolar planets for an introductory college-level astronomy class. The activity was designed with the intent of simultaneously teaching science process skills and factual content about transits and light curves. In the activity, groups of two to four students each formulate a specific science question and design and carry out an investigation using a table-top model of a star and orbiting planet. Each group then presents t...
TPmsm: Estimation of the Transition Probabilities in 3-State Models
Artur Araújo
2014-12-01
Full Text Available One major goal in clinical applications of multi-state models is the estimation of transition probabilities. The usual nonparametric estimator of the transition matrix for non-homogeneous Markov processes is the Aalen-Johansen estimator (Aalen and Johansen 1978. However, two problems may arise from using this estimator: first, its standard error may be large in heavy censored scenarios; second, the estimator may be inconsistent if the process is non-Markovian. The development of the R package TPmsm has been motivated by several recent contributions that account for these estimation problems. Estimation and statistical inference for transition probabilities can be performed using TPmsm. The TPmsm package provides seven different approaches to three-state illness-death modeling. In two of these approaches the transition probabilities are estimated conditionally on current or past covariate measures. Two real data examples are included for illustration of software usage.
Lifshitz transitions in magnetic phases of the periodic Anderson model
We investigate the reconstruction of a Fermi surface, which is called a Lifshitz transition, in magnetically ordered phases of the periodic Anderson model on a square lattice with a finite Coulomb interaction between f electrons. We apply the variational Monte Carlo method to the model by using the Gutzwiller wavefunctions for the paramagnetic, antiferromagnetic, ferromagnetic, and charge-density-wave states. We find that an antiferromagnetic phase is realized around half-filling and a ferromagnetic phase is realized when the system is far away from half-filling. In both magnetic phases, Lifshitz transitions take place. By analyzing the electronic states, we conclude that the Lifshitz transitions to large ordered-moment states can be regarded as itinerant-localized transitions of the f electrons. (author)
Free association transitions in models of cortical latching dynamics
Potts networks, in certain conditions, hop spontaneously from one discrete attractor state to another, a process we have called latching dynamics. When continuing indefinitely, latching can serve as a model of infinite recursion, which is nontrivial if the matrix of transition probabilities presents a structure, i.e. a rudimentary grammar. We show here, with computer simulations, that latching transitions cluster in a number of distinct classes: effectively random transitions between weakly correlated attractors; structured, history-dependent transitions between attractors with intermediate correlations; and oscillations between pairs of closely overlapping attractors. Each type can be described by a reduced set of equations of motion, which, once numerically integrated, matches simulations results. We propose that the analysis of such equations may offer clues on how to embed meaningful grammatical structures into more realistic models of specific recursive processes
Recurrence-based detection of the hyperchaos-chaos transition in an electronic circuit
Ngamga, E. J.; Buscarino, A.; Frasca, M.; Sciuto, G.; Kurths, J.; Fortuna, L.
2010-12-01
Some complex measures based on recurrence plots give evidence about hyperchaos-chaos transitions in coupled nonlinear systems [E. G. Souza et al., "Using recurrences to characterize the hyperchaos-chaos transition," Phys. Rev. E 78, 066206 (2008)]. In this paper, these measures are combined with a significance test based on twin surrogates to identify such a transition in a fourth-order Lorenz-like system, which is able to pass from a hyperchaotic to a chaotic behavior for increasing values of a single parameter. A circuit analog of the mathematical model has been designed and implemented and the robustness of the recurrence-based method on experimental data has been tested. In both the numerical and experimental cases, the combination of the recurrence measures and the significance test allows to clearly identify the hyperchaos-chaos transition.
Phase transitions in models of human cooperation
Perc, Matjaž
2016-08-01
If only the fittest survive, why should one cooperate? Why should one sacrifice personal benefits for the common good? Recent research indicates that a comprehensive answer to such questions requires that we look beyond the individual and focus on the collective behavior that emerges as a result of the interactions among individuals, groups, and societies. Although undoubtedly driven also by culture and cognition, human cooperation is just as well an emergent, collective phenomenon in a complex system. Nonequilibrium statistical physics, in particular the collective behavior of interacting particles near phase transitions, has already been recognized as very valuable for understanding counterintuitive evolutionary outcomes. However, unlike pairwise interactions among particles that typically govern solid-state physics systems, interactions among humans often involve group interactions, and they also involve a larger number of possible states even for the most simplified description of reality. Here we briefly review research done in the realm of the public goods game, and we outline future research directions with an emphasis on merging the most recent advances in the social sciences with methods of nonequilibrium statistical physics. By having a firm theoretical grip on human cooperation, we can hope to engineer better social systems and develop more efficient policies for a sustainable and better future.
Models for isostructural transitions and properties of SmS under pressure
One-dimensional phenomenological model of isostructural phase transition based on an assumption that the structure element may be in two states characterized by different compressibilities and dimensions. The system entropy, as in the Landau theory, is supposed by a polynom in relation to particle number density in the second state. The model permits to describe phase transitions in SmS determining phenomenological model parameters from the experiment. On the model base predicted is the necessity of another four phase transitions in SmS, three of second type: at 7.5, at +50.5 and 78.5 kbar and one - of first type at +68 kbar. The lattice parameter value SmS a0=5.97 A, observed under normal conditions, according to the model pertains to the mixture Smsub(0.814)sup(2+)Smsub(0.186)sup(3+)S, for Sm2+S shoued be observed a0=6.05 A
Selection Bias in Educational Transition Models: Theory and Empirical Evidence
Anders Holm; Mads Meier Jæger
2009-01-01
Most studies which use Mare’s (1980, 1981) seminal model of educational transitions find that the effect of family background variables decreases across educational transitions. Cameron and Heckman (1998, 2001) have argued that this “waning coefficients” phenomenon might be driven by selection on unobserved variables. This paper, first, analyzes theoretically how selection on unobserved variables leads to waning coefficients and, second, illustrates empirically how selection affects estimates...
Radiative transitions in mesons in a non relativistic quark model
Bonnaz, R.; Silvestre-Brac, B.; Gignoux, C.
2001-01-01
In the framework of the non relativistic quark model, an exhaustive study of radiative transitions in mesons is performed. The emphasis is put on several points. Some traditional approximations (long wave length limit, non relativistic phase space, dipole approximation for E1 transitions, gaussian wave functions) are analyzed in detail and their effects commented. A complete treatment using three different types of realistic quark-antiquark potential is made. The overall agreement with experi...
Chiral Transition Within Effective Quark Models under Strong Magnetic Fields
Garcia, Andre Felipe
2013-01-01
In the recently years it has been argued that spectators in heavy ion collisions are responsible for creating a strong magnetic field that could play an important role in the QCD phase transition. In this work we use the SU(2) Nambu--Jona-Lasinio (NJL) model in order to study the chiral transition in quark matter subject to a strong magnetic field. We show some results involving the breaking of chiral symmetry and its restoration at finite temperature and density.
A Human Breast Cell Model of Preinvasive to Invasive Transition
Rizki, Aylin; Weaver, Valerie M.; Lee, Sun-Young; Rozenberg, Gabriela I.; Chin, Koei; Myers, Connie A.; Bascom, Jamie L.; Mott, Joni D.; Semeiks, Jeremy R.; Grate, Leslie R.; Mian, I. Saira; Borowsky, Alexander D; Jensen, Roy A; Idowu, Michael O.; Chen, Fanqing
2008-01-01
A crucial step in human breast cancer progression is the acquisition of invasiveness. There is a distinct lack of human cell culture models to study the transition from preinvasive to invasive phenotype as it may occur “spontaneously” in vivo. To delineate molecular alterations important for this transition, we isolated human breast epithelial cell lines that showed partial loss of tissue polarity in three-dimensional reconstituted basement membrane cultures. These cells remained noninvasive;...
The electroweak phase transition in extended models
Espinosa, J R
1994-01-01
We study the possibility of relaxing the cosmological bound on the Higgs mass coming from the requirement of non-erasure of the baryon asymmetry by sphalerons. After reviewing the Standard Model case we obtain this bound in two extensions of it: 1) The Standard Model with an additional gauge singlet, and 2) The Minimal Supersymmetric Standard Model. Taking fully into account all experimental constraints and thermal screening effects we found that the situation can be slightly improved with respect to the Standard Model but only in case 1) a non negligible region in parameter space exists where the baryon washout is avoided and the experimental bounds evaded. (Talk given at the NATO Advanced Reseach Workshop: "Electroweak Physics and the early Universe", 23-25 March 1994, Sintra (Portugal).)
Diffraction model of a step-out transition
The diffraction model of a cavity, suggested by Lawson, Bane and Sands is generalized to a step out transition. Using this model, the high frequency impedance is calculated explicitly for the case that the transition step is small compared with the beam pipe radius. In the diffraction model for a small step out transition, the total energy is conserved, but, unlike the cavity case, the diffracted waves in the geometric shadow and the pipe region, in general, do not always carry equal energy. In the limit of small step sizes, the impedance derived from the diffraction model agrees with that found by Balakin, Novokhatsky and also Kheifets. This impedance can be used to compute the wake field of a round collimator whose half aperture is much larger than the bunch length, as existing in the SLC final focus
A general holographic metal/superconductor phase transition model
Peng, Yan
2014-01-01
We study the scalar condensation of a general holographic superconductor model in AdS black hole background away from the probe limit. We find the model parameters together with the scalar mass and backreaction can determine the order of phase transitions completely. In addition, we observe two types of discontinuities of the scalar operator in the case of first order phase transitions. We analyze in detail the effects of the scalar mass and backreaction on the formation of discontinuities and arrive at an approximate relation between the threshold model parameters. Furthermore, we obtain superconductor solutions corresponding to higher energy states and examine the stability of these superconductor solutions.
Phase Transitions in a Forest-Fire Model
Clar, Siegfried; Schenk, Klaus; Schwabl, Franz
1997-01-01
We investigate a forest-fire model with the density of empty sites as control parameter. The model exhibits three phases, separated by one first-order phase transition and one 'mixed' phase transition which shows critical behavior on only one side and hysteresis. The critical behavior is found to be that of the self-organized critical forest-fire model [B. Drossel and F. Schwabl, Phys. Rev. Lett. 69, 1629 (1992)], whereas in the adjacent phase one finds the spiral waves of the Bak et al. fore...
A model is developed to describe the transition of annular flow to intermittent flow in a vertical two-phase flow system. The instability of the disturbance wave, which is a dominant wave shape at the boundary between annular flow and intermittent flow, is considered as the governing mechanism and this instability is described by the concept of hyperbolicity breaking in the characteristic equation. The developed model is validated by comparing its predictions of gas superficial velocity for the transition with the experimental data available from the literature, and comparing those with the predictions of the other correlations. The comparison results show that the developed model gives better predictions for the transition condition than the existing correlations and the effects of fluid properties, geometry and liquid flow rate on the transition are well considered by the developed model. It is found that the predictions of the developed model have much smaller bias than those of the other correlations; the average of the prediction error is 3% for the present model. The standard deviation of the prediction errors of the present model reaches 28%, which is the smallest among the models compared here. Through the core uncovery experiments, it has been known that the low power and high power core boil-off patterns are observed in the high pressure core uncovery following a small-break loss-of-coolant accident. The developed model for the annular to intermittent flow regime transition was applied to the classification of low power boil-off and high power boil-off patterns. At first, the applicability of the developed criterion to the rod-bundle geometry is demonstrated using the flow pattern transition data taken by Bergles et al. and Venkateswararao. It is shown that the developed criterion well predicts the boundary between low power boil-off and high power boil-off through the comparisons of the predicted annular to intermittent flow transition conditions with
Numerical modelling of bypass transition in turbine cascades
Louda, P.; Příhoda, Jaromír; Kozel, K.
Budapest: Budapest University of Technology and Economics, 2015. [International Conference on Fluid Flow Technologies /16./. Budapest (HU), 01.09.2015-04.09.2015] R&D Projects: GA ČR GAP101/12/1271 Institutional support: RVO:61388998 Keywords : 3D turbine cascade * bypass transition model * EARSM turbulence model Subject RIV: BK - Fluid Dynamics
Dealing with selection bias in educational transition models
Holm, Anders; Jæger, Mads Meier
2011-01-01
This paper proposes the bivariate probit selection model (BPSM) as an alternative to the traditional Mare model for analyzing educational transitions. The BPSM accounts for selection on unobserved variables by allowing for unobserved variables which affect the probability of making educational...
On a Jaynes-Cummings type model with multiphoton transitions
The authors present a quantum electrodynamic model, soluble in the dipole and rotating wave approximation, for a three-level atom interacting with a two-mode resonant radiation field through the multiphoton transition mechanism. Population dynamics and photon statistics in this Jaynes-Cummings type model are examined. (author)
Conformational transitions in random heteropolymer models
Blavatska, Viktoria; Janke, Wolfhard
2014-01-01
We study the conformational properties of heteropolymers containing two types of monomers A and B, modeled as self-attracting self-avoiding random walks on a regular lattice. Such a model can describe in particular the sequences of hydrophobic and hydrophilic residues in proteins [K. F. Lau and K. A. Dill, Macromolecules 22, 3986 (1989)] and polyampholytes with oppositely charged groups [Y. Kantor and M. Kardar, Europhys. Lett. 28, 169 (1994)]. Treating the sequences of the two types of monomers as quenched random variables, we provide a systematic analysis of possible generalizations of this model. To this end we apply the pruned-enriched Rosenbluth chain-growth algorithm, which allows us to obtain the phase diagrams of extended and compact states coexistence as function of both the temperature and fraction of A and B monomers along the heteropolymer chain.
A collective model for transitional nuclei
The paper consists of the following sections: 1. Introduction; 2. The model (The quadrupole co-ordinates, the potential energy surface, the Hamilton operator, quadrupole moments, B(E2)-values and rms-radii); 3. The diagonalization of the collective Hamilton operator (The eigen-states of the five-dimensional oscillator, classification of the basis: R(5) is contained in R(3) and R(5) is contained in R(4) = SU(2) x SU(2), calculation of the matrix elements of H, convergence of the numerical procedure); 4. Application of the model (General remarks, typical spectra, selected spectra, conclusions); 5. The coupling of the giant-resonance states with the low-energy spectrum (The Hamilton operator, hydrodynamical model for the GR, the interaction Hamilton operator Hsub(DQ), the basis states for diagonalization, the dipole operator and the γ-absorption cross-section, results); 6. Summary. (author)
Models of agglomeration and glass transition
Kerner, Richard
2007-01-01
This book is for any physicist interested in new vistas in the domain of non-crystalline condensed matter, aperiodic and quasi-crystalline networks and especially glass physics and chemistry. Students with an elementary background in thermodynamics and statistical physics will find the book accessible. The physics of glasses is extensively covered, focusing on their thermal and mechanical properties, as well as various models leading to the formation of the glassy states of matter from overcooled liquids. The models of agglomeration and growth are also applied to describe the formation of quasicrystals, fullerenes and, in biology, to describe virus assembly pathways.
Kostyalik, Diána; Vas, Szilvia; Kátai, Zita; Kitka, Tamás; Gyertyán, István; Bagdy, Gyorgy; Tóthfalusi, László
2014-01-01
Background Shortened rapid eye movement (REM) sleep latency and increased REM sleep amount are presumed biological markers of depression. These sleep alterations are also observable in several animal models of depression as well as during the rebound sleep after selective REM sleep deprivation (RD). Furthermore, REM sleep fragmentation is typically associated with stress procedures and anxiety. The selective serotonin reuptake inhibitor (SSRI) antidepressants reduce REM sleep time and increas...
State-and-transition model archetypes: a global taxonomy of rangeland change
State and transition models (STMs) synthesize science-based and local knowledge to formally represent the dynamics of rangeland and other ecosystems. Mental models or concepts of ecosystem dynamics implicitly underlie all management decisions in rangelands and thus how people influence rangeland sus...
Electron radiative transitions in the fields of complex ions with heavy cores are under consideration. Theoretical models based on model electron density approximations make it possible to express all types of radiative frequency in terms of atomic electron density distribution with a close connection between a radiated frequency and effective radius of radiation. (author)
Phase Transition in a Sexual Age-Structured Model of Learning Foreign Languages
Schwämmle, V.
The understanding of language competition helps us to predict extinction and survival of languages spoken by minorities. A simple agent-based model of a sexual population, based on the Penna model, is built in order to find out under which circumstances one language dominates other ones. This model considers that only young people learn foreign languages. The simulations show a first order phase transition of the ratio between the number of speakers of different languages with the mutation rate as control parameter.
Diggle, Peter J
2007-01-01
Model-based geostatistics refers to the application of general statistical principles of modeling and inference to geostatistical problems. This volume provides a treatment of model-based geostatistics and emphasizes on statistical methods and applications. It also features analyses of datasets from a range of scientific contexts.
Andrea Chester; Lorelle Burton; Sophia Xenos; Karen Elgar; Bianca Denny
2013-01-01
Peer mentoring, presented as an inclusive teaching approach, embedded in the curriculum, has been successfully implemented to support first year student learning. Developing sustainable and scalable models for large first year cohorts, however, provides a challenge. The Transition in, Transition out model is a sustainable peer mentoring model supporting the transition of both first and final year students. The model has been implemented in two Australian psychology programs, one face-to-face ...
MRMaid, the web-based tool for designing multiple reaction monitoring (MRM) transitions.
Mead, Jennifer A; Bianco, Luca; Ottone, Vanessa; Barton, Chris; Kay, Richard G; Lilley, Kathryn S; Bond, Nicholas J; Bessant, Conrad
2009-04-01
Multiple reaction monitoring (MRM) of peptides uses tandem mass spectrometry to quantify selected proteins of interest, such as those previously identified in differential studies. Using this technique, the specificity of precursor to product transitions is harnessed for quantitative analysis of multiple proteins in a single sample. The design of transitions is critical for the success of MRM experiments, but predicting signal intensity of peptides and fragmentation patterns ab initio is challenging given existing methods. The tool presented here, MRMaid (pronounced "mermaid") offers a novel alternative for rapid design of MRM transitions for the proteomics researcher. The program uses a combination of knowledge of the properties of optimal MRM transitions taken from expert practitioners and literature with MS/MS evidence derived from interrogation of a database of peptide identifications and their associated mass spectra. The tool also predicts retention time using a published model, allowing ordering of transition candidates. By exploiting available knowledge and resources to generate the most reliable transitions, this approach negates the need for theoretical prediction of fragmentation and the need to undertake prior "discovery" MS studies. MRMaid is a modular tool built around the Genome Annotating Proteomic Pipeline framework, providing a web-based solution with both descriptive and graphical visualizations of transitions. Predicted transition candidates are ranked based on a novel transition scoring system, and users may filter the results by selecting optional stringency criteria, such as omitting frequently modified residues, constraining the length of peptides, or omitting missed cleavages. Comparison with published transitions showed that MRMaid successfully predicted the peptide and product ion pairs in the majority of cases with appropriate retention time estimates. As the data content of the Genome Annotating Proteomic Pipeline repository increases
Spin-state transition and phase separation in multi-orbital Hubbard model
Suzuki, Ryo; Watanabe, Tsutomu; Ishihara, Sumio
2009-01-01
We study spin-state transition and phase separation involving this transition based on the milti-orbital Hubbard model. Multiple spin states are realized by changing the energy separation between the two orbitals and the on-site Hund coupling. By utilizing the variational Monte-Carlo simulation, we analyze the electronic and magnetic structures in hole doped and undoped states. Electronic phase separation occurs between the low-spin band insulating state and the high-spin ferromagnetic metall...
Explosive percolation: Unusual transitions of a simple model
Bastas, N.; Giazitzidis, P.; Maragakis, M.; Kosmidis, K.
In this paper we review the recent advances in explosive percolation, a very sharp phase transition first observed by Achlioptas et al. (2009). There a simple model was proposed, which changed slightly the classical percolation process so that the emergence of the spanning cluster is delayed. This slight modification turns out to have a great impact on the percolation phase transition. The resulting transition is so sharp that it was termed explosive, and it was at first considered to be discontinuous. This surprising fact stimulated considerable interest in “Achlioptas processes”. Later work, however, showed that the transition is continuous (at least for Achlioptas processes on Erdös networks), but with very unusual finite size scaling. We present a review of the field, indicate open “problems” and propose directions for future research.
Stochastic User Equilibrium Assignment in Schedule-Based Transit Networks with Capacity Constraints
Wangtu Xu
2012-01-01
Full Text Available This paper proposes a stochastic user equilibrium (SUE assignment model for a schedule-based transit network with capacity constraint. We consider a situation in which passengers do not have the full knowledge about the condition of the network and select paths that minimize a generalized cost function encompassing five components: (1 ride time, which is composed of in-vehicle and waiting times, (2 overload delay, (3 fare, (4 transfer constraints, and (5 departure time difference. We split passenger demands among connections which are the space-time paths between OD pairs of the network. All transit vehicles have a fixed capacity and operate according to some preset timetables. When the capacity constraint of the transit line segment is reached, we show that the Lagrange multipliers of the mathematical programming problem are equivalent to the equilibrium passenger overload delay in the congested transit network. The proposed model can simultaneously predict how passengers choose their transit vehicles to minimize their travel costs and estimate the associated costs in a schedule-based congested transit network. A numerical example is used to illustrate the performance of the proposed model.
Transition to Community-Based Nursing Curriculum: Processes and Outcomes.
Edwards, Joellen B.; Alley, Nancy M.
2002-01-01
The East Tennessee State University nursing school's transition to a community-based nursing curriculum was built on five key concepts: (1) relevance and accountability to health and social needs; (2) meeting of basic health needs through teaching and learning; (3) community experiences throughout the curriculum; (4) interdisciplinary…
Korea : Transition to a Knowledge-Based Economy
World Bank
2000-01-01
The report reviews the economic transition in Korea, summarizing the challenge of the knowledge revolution, to the country's development strategy, and the analytical, and policy framework for a knowledge-based economy. It explores the needs to increase overall productivity, and areas of relative inefficiency, namely, inadequate conditions for generation of knowledge, and information; insuf...
Electrical Compact Modeling of Graphene Base Transistors
Sébastien Frégonèse
2015-11-01
Full Text Available Following the recent development of the Graphene Base Transistor (GBT, a new electrical compact model for GBT devices is proposed. The transistor model includes the quantum capacitance model to obtain a self-consistent base potential. It also uses a versatile transfer current equation to be compatible with the different possible GBT configurations and it account for high injection conditions thanks to a transit time based charge model. Finally, the developed large signal model has been implemented in Verilog-A code and can be used for simulation in a standard circuit design environment such as Cadence or ADS. This model has been verified using advanced numerical simulation.
Comparison of several models of the laminar/turbulent transition
Fürst, J.; Straka, P.; Příhoda, Jaromír; Šimurda, David
Liberec : Technical University of Liberec, 2013 - (Dančová, P.; Novotný, P.) ISBN 978-80-7372-912-7. ISSN 2100-014X. - (EPJ Web of Conferences. 45). [International Conference on Experimental Fluid Mechanics /7./. Hradec Králové (CZ), 20.11.2012-23.11.2012] R&D Projects: GA ČR(CZ) GAP101/10/1329; GA ČR GAP101/12/1271 Institutional support: RVO:61388998 Keywords : bypass transition * algebraic transition model * three-equation k-kL-omega model Subject RIV: BK - Fluid Dynamics
Phase transition of p-adic Ising λ-model
We consider an interaction of the nearest-neighbors and next nearest-neighbors for the mixed type p-adic λ-model with spin values (−1, +1) on a Cayley tree of order two. In the previous work we have proved the existence of the p-adic Gibbs measure for the model. In this work we have proved the existence of the phase transition occurs for the model
Phase transition of p-adic Ising λ-model
Dogan, Mutlay; Akın, Hasan [Department of Mathematics, Faculty of Education, Zirve University, Gaziantep, TR27260 (Turkey); Mukhamedov, Farrukh [Department of Computational & Theoretical Sciences Faculty of Science, International Islamic University Malaysia P.O. Box, 141, 25710, Kuantan Pahang (Malaysia)
2015-09-18
We consider an interaction of the nearest-neighbors and next nearest-neighbors for the mixed type p-adic λ-model with spin values (−1, +1) on a Cayley tree of order two. In the previous work we have proved the existence of the p-adic Gibbs measure for the model. In this work we have proved the existence of the phase transition occurs for the model.
Computable Equilibrium Modelling and Application to Economies in Transition
Erno Zalai
1998-01-01
This paper examines the development and implementation of computable general equilibrium (CGE) models and examines their application to economies undergoing transition. The generalised development of a CGE model is presented in terms of the series of 'building blocks' which comprise a typical CGE system, whilst the flexibility of the CGE approach is illustrated by comparison of two specific CGE models: the GEM-E3 framework, developed by a team of researchers, led by Professor Pantelis Capros,...
Comment on ``Jamming Percolation and Glass Transitions in Lattice Models.''
Jeng, M.; Schwarz, J. M.
2006-01-01
Toninelli, Biroli, and Fisher recently introduced the knights model, a correlated percolation system (Phys. Rev. Lett. 96, 035702 (2006)). They claimed to prove that the critical point of this model was the same as that for directed percolation, and then used this to show (assuming a conjecture about directed percolation, described later in a more detailed proof) that this model has a discontinuous phase transition with a diverging correlation length. However, there is an error in their work,...
Dynamical phase transitions in spin models and automata
Some of the models and methods developed in the study of the dynamics of spin models and automata are described. Special attention is given to the distance method which consists of comparing the time evolution of two configurations. The method is used to obtain the phase boundary between a frozen and a chaotic phase in the case of deterministic models. For stochastic systems the method is used to obtain dynamical phase transitions
Nuclear clocks based on resonant excitation of gamma-transitions
Peik, Ekkehard; Okhapkin, Maxim
2015-01-01
We review the ideas and concepts for a clock that is based on a radiative transition in the nucleus rather than in the electron shell. This type of clock offers advantages like an insensitivity against field-induced systematic frequency shifts and the opportunity to obtain high stability from interrogating many nuclei in the solid state. Experimental work concentrates on the low-energy (about 8 eV) isomeric transition in Th-229. We review the status of the experiments that aim at a direct opt...
Discontinuous transition of a multistage independent cascade model on networks
We propose a multistage version of the independent cascade model, which we call a multistage independent cascade (MIC) model, on networks. This model is parameterized by two probabilities: the probability T1 that a node adopting a fad increases the awareness of a neighboring susceptible node and the probability T2 that an adopter directly causes a susceptible node to adopt the fad. We formulate a tree approximation for the MIC model on an uncorrelated network with an arbitrary degree distribution pk. Applied on a random regular network with degree k = 6, this model exhibits a rich phase diagram, including continuous and discontinuous transition lines for fad percolation and a continuous transition line for the percolation of susceptible nodes. In particular, the percolation transition of fads is discontinuous (continuous) when T1 is larger (smaller) than a certain value. A similar discontinuous transition is observed in random graphs and scale-free networks. Furthermore, assigning a finite fraction of initial adopters dramatically changes the phase boundaries. (paper)
Engineering models of deflagration-to-detonation transition
Bdzil, J.B.; Son, S.F.
1995-07-01
For the past two years, Los Alamos has supported research into the deflagration-to-detonation transition (DDT) in damaged energetic materials as part of the explosives safety program. This program supported both a theory/modeling group and an experimentation group. The goal of the theory/modeling group was to examine the various modeling structures (one-phase models, two-phase models, etc.) and select from these a structure suitable to model accidental initiation of detonation in damaged explosives. The experimental data on low-velocity piston supported DDT in granular explosive was to serve as a test bed to help in the selection process. Three theoretical models have been examined in the course of this study: (1) the Baer-Nunziato (BN) model, (2) the Stewart-Prasad-Asay (SPA) model and (3) the Bdzil-Kapila-Stewart model. Here we describe these models, discuss their properties, and compare their features.