Spatiotemporal receptive fields: a dynamical model derived from cortical architectonics.
Krone, G; Mallot, H; Palm, G; Schüz, A
1986-01-22
We assume that the mammalian neocortex is built up out of some six layers which differ in their morphology and their external connections. Intrinsic connectivity is largely excitatory, leading to a considerable amount of positive feedback. The majority of cortical neurons can be divided into two main classes: the pyramidal cells, which are said to be excitatory, and local cells (most notably the non-spiny stellate cells), which are said to be inhibitory. The form of the dendritic and axonal arborizations of both groups is discussed in detail. This results in a simplified model of the cortex as a stack of six layers with mutual connections determined by the principles of fibre anatomy. This stack can be treated as a multi-input-multi-output system by means of the linear systems theory of homogeneous layers. The detailed equations for the simulation are derived in the Appendix. The results of the simulations show that the temporal and spatial behaviour of an excitation distribution cannot be treated separately. Further, they indicate specific processing in the different layers and some independence from details of wiring. Finally, the simulation results are applied to the theory of visual receptive fields. This yields some insight into the mechanisms possibly underlying hypercomplexity, putative nonlinearities, lateral inhibition, oscillating cell responses, and velocity-dependent tuning curves.
Hamker, Fred H; Wiltschut, Jan
2007-09-01
Most computational models of coding are based on a generative model according to which the feedback signal aims to reconstruct the visual scene as close as possible. We here explore an alternative model of feedback. It is derived from studies of attention and thus, probably more flexible with respect to attentive processing in higher brain areas. According to this model, feedback implements a gain increase of the feedforward signal. We use a dynamic model with presynaptic inhibition and Hebbian learning to simultaneously learn feedforward and feedback weights. The weights converge to localized, oriented, and bandpass filters similar as the ones found in V1. Due to presynaptic inhibition the model predicts the organization of receptive fields within the feedforward pathway, whereas feedback primarily serves to tune early visual processing according to the needs of the task.
Population Receptive Field Dynamics in Human Visual Cortex
Haak, Koen V.; Cornelissen, Frans W.; Morland, Antony B.
2012-01-01
Seminal work in the early nineties revealed that the visual receptive field of neurons in cat primary visual cortex can change in location and size when artificial scotomas are applied. Recent work now suggests that these single neuron receptive field dynamics also pertain to the neuronal population
Suder, Katrin; Funke, Klaus; Zhao, Yongqiang; Kerscher, Nicolas; Wennekers, Thomas; Wörgötter, Florentin
2002-06-01
We investigated how changes in the temporal firing rate of thalamocortical activity affect the spatiotemporal structure of receptive field (RF) subunits in cat primary visual cortex. Spike activity of 67 neurons (48 simple, 19 complex cells) was extracellulary recorded from area 17/18 of anesthetized and paralyzed cats. A total of 107 subfields (on/off) were mapped by applying a reverse correlation technique to the activity elicited by bright and dark rectangles flashed for 300 ms in a 20x10 grid. We found that the width of the (suprathreshold) discharge fields shrank on average by 22% during this 300-ms-long stimulus presentation time. Fifty-eight subfields (54%) shrank by more than 20% of peak width and only ten (less than 10%) showed a slight increase over time. The main size reduction took place 40-60 ms after response onset, which corresponded to the transition from transient peak firing to tonic visual activity in thalamocortical relay cells (TC). The experimentally obtained RFs were then fitted with the aid of a neural field model of the primary visual pathway. Assuming a Gaussian-shaped spatial sensitivity profile across the RF subfield width, the model allowed us to estimate the subthreshold RF (depolarization field, D-field) from the minimal discharge field (MDF). The model allowed us to test to what degree the temporal dynamics of thalamocortical activity contributes to the spatiotemporal changes of cortical RFs. To this end, we performed the fitting procedure either with a pure feedforward model or with a field model that also included intracortical feedback. Spatial and temporal parameters obtained from fits of the experimental RFs matched closely to those achieved by simulating a pure feedforward system with the field model but were not compatible with additional intracortical feedback. Thus, our results show that dot stimulation, which optimally excites thalamocortical cells, leads to a shrinkage with respect to the size of the RF subfield at the
Receptive field self-organization in a model of the fine structure in v1 cortical columns.
Lücke, Jörg
2009-10-01
We study a dynamical model of processing and learning in the visual cortex, which reflects the anatomy of V1 cortical columns and properties of their neuronal receptive fields. Based on recent results on the fine-scale structure of columns in V1, we model the activity dynamics in subpopulations of excitatory neurons and their interaction with systems of inhibitory neurons. We find that a dynamical model based on these aspects of columnar anatomy can give rise to specific types of computations that result in self-organization of afferents to the column. For a given type of input, self-organization reliably extracts the basic input components represented by neuronal receptive fields. Self-organization is very noise tolerant and can robustly be applied to different types of input. To quantitatively analyze the system's component extraction capabilities, we use two standard benchmarks: the bars test and natural images. In the bars test, the system shows the highest noise robustness reported so far. If natural image patches are used as input, self-organization results in Gabor-like receptive fields. In quantitative comparison with in vivo measurements, we find that the obtained receptive fields capture statistical properties of V1 simple cells that algorithms such as independent component analysis or sparse coding do not reproduce.
Joint Book Reading and Receptive Vocabulary: A Parallel Process Model
Meng, Christine
2016-01-01
The purpose of the present study was to understand the reciprocal, bidirectional longitudinal relation between joint book reading and English receptive vocabulary. To address the research goals, a nationally representative sample of Head Start children, the Head Start Family and Child Experiences Survey (2003 cohort), was used for analysis. The…
Analysis of a multiple reception model for processing images from the solid-state imaging camera
Yan, T.-Y.
1991-01-01
A detection model to identify the presence of Galileo optical communications from an Earth-based Transmitter (GOPEX) signal by processing multiple signal receptions extracted from the camera images is described. The model decomposes a multi-signal reception camera image into a set of images so that the location of the pixel being illuminated is known a priori and the laser can illuminate only one pixel at each reception instance. Numerical results show that if effects on the pointing error due to atmospheric refraction can be controlled to between 20 to 30 microrad, the beam divergence of the GOPEX laser should be adjusted to be between 30 to 40 microrad when the spacecraft is 30 million km away from Earth. Furthermore, increasing beyond 5 the number of receptions for processing will not produce a significant detection probability advantage.
Šulanová, Silvie
2009-01-01
Listening to music in the process of education is beneficial for a pupil only in case it is realized by means of active creativeness. To meet this requirement specific activities concerning music listening are applied in the framework of receptive music teaching. The dissertation proposes a so called dynamic model to function as an ideal solution to didactic transformation of music. The model enables to set up such classroom conditions in which pupils find it easier to observe elementary item...
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
The spatial-temporal response properties of some simple neurons in visual pathway arise basically prior to birth. In the absence of visual experience, how do these neurons develop in visual system? Based on Wimbauer network with delay, a four-layer feed-forward network model is proposed, which is characterized by modifying the Hebb learning rule through introducing the asymmetric time window of synaptic modification found recently in neurobiology. The model can not only generate by self-organization more diversified spatial-temporal response characteristics of neuronal receptive field than earlier models but also provide some explanations for the possible mechanism underlying the development of receptive fields of contrast polarity sensitive neurons found in visual system of vertebrate. Thus the proposed model may be more widely applicable than Linsker model and Wimbauer model.
Using the Receptivity model to uncover 'urine blindness': perceptions on the re-use of urine
Roma, E; Benoit, N.; Buckley, C.; Bell, S. J.
2013-01-01
Population growth, climatic changes and over-exploitation of natural resources are at the basis of the world’s food crisis, which counts almost one million people without sufficient food sustenance. These changes require novel environmental practices which are based on nutrient recovery and management in agriculture. This contribution analyses and discusses users’ perceptions on re-use of urine as fertilizer through the lenses of the Receptivity model. A search was performed on Scopus (as wel...
Dynamics of visual receptive fields in the macaque frontal eye field.
Mayo, J Patrick; DiTomasso, Amie R; Sommer, Marc A; Smith, Matthew A
2015-12-01
Neuronal receptive fields (RFs) provide the foundation for understanding systems-level sensory processing. In early visual areas, investigators have mapped RFs in detail using stochastic stimuli and sophisticated analytical approaches. Much less is known about RFs in prefrontal cortex. Visual stimuli used for mapping RFs in prefrontal cortex tend to cover a small range of spatial and temporal parameters, making it difficult to understand their role in visual processing. To address these shortcomings, we implemented a generalized linear model to measure the RFs of neurons in the macaque frontal eye field (FEF) in response to sparse, full-field stimuli. Our high-resolution, probabilistic approach tracked the evolution of RFs during passive fixation, and we validated our results against conventional measures. We found that FEF neurons exhibited a surprising level of sensitivity to stimuli presented as briefly as 10 ms or to multiple dots presented simultaneously, suggesting that FEF visual responses are more precise than previously appreciated. FEF RF spatial structures were largely maintained over time and between stimulus conditions. Our results demonstrate that the application of probabilistic RF mapping to FEF and similar association areas is an important tool for clarifying the neuronal mechanisms of cognition.
Reception analysis seen from the multiple mediation model: some issues for the debat
Directory of Open Access Journals (Sweden)
Guilermo Orozco
2008-12-01
Full Text Available This paper is an application of the "Multiple Mediation" Model, as it has been developing by the author during the last 10 years. The model is used as a way to substantiate a reconceptualization of different aspects of the television reception process. As understood by Orozco, it is continually under construction, and emerges from analysis made by different thinkers. Its formulation has been and will continue to be the outcome of much reflexivity between existing theoretical and epistemological assumptions (within the Cultural Studies and Critical Audience Research traditions and empirical, mostly qualitative, data.
Jalindre, Swaraj Sunil
Ink absorption performance in inkjet receptive coatings containing synthetic zeolite pigments was studied. Coating pigment pore and particle size distribution are the key parameters that influence in modifying media surface properties, thus affecting the rate of ink penetration and drying time (Scholkopf, et al. 2004). The primary objective of this study was: (1) to investigate the synthetic zeolite pigment effects on inkjet ink absorption, dynamic contact angle and printability, and (2) to evaluate these novel synthetic zeolite pigments in replacing the fumed silica pigments in conventional inkjet receptive coatings. In this research study, single pigment coating formulations (in equal P:B ratio) were prepared using microporous synthetic zeolite pigments (5A, Organophilic and 13X) and polyvinyl alcohol (PVOH) binder. The laboratory-coated samples were characterized for absorption, air permeance, roughness, drying time, wettability and print fidelity. Based on the rheological data, it was found that the synthetic zeolite formulated coatings depicted a Newtonian flow behavior at low shear; while the industry accepted fumed silica based coatings displayed a characteristically high pseudoplastic flow behavior. Our coated samples generated using microporous synthetic zeolite pigments produced low absorption, reduced wettability and accelerated ink drying characteristics. These characteristics were caused due to the synthetic zeolite pigments, which resulted in relatively closed surface structure coated samples. The research suggested that no single selected synthetic zeolite coating performed better than the conventional fumed silica based coatings. Experimental data also showed that there was no apparent relationship between synthetic zeolite pigment pore sizes and inkjet ink absorption. For future research, above coated samples should be evaluated for pore size distribution using Mercury Porosimeter, which quantifies surface porosity of coated samples. This presented
Receptivity, possibility, and democratic politics
Kompridis, Nikolas
2011-01-01
In this paper I present a model of receptivity that is composed of ontological and normative dimensions, which I argue answer to the critical-diagnostic and to the possibility-disclosing needs of democratic politics. I distinguish between ‘pre-reflective receptivity,’ understood ontologically as a condition of intelligibility, and ‘reflective receptivity,’ understood normatively as a condition of disclosing new possibilities.Keywords: receptivity; change; possibility; critique; reflective dis...
Blanc, F; François, V; Fabre, B; de la Cuadra, P; Lagrée, P-Y
2014-06-01
A simple analytical model for the interaction between a plane jet issued from a flue and a transverse acoustic disturbance is developed in this paper. The model is inspired by direct flow simulation results confronted to experimental data. The interaction is expected to take place in the vicinity of the separation points of the jet. The influence of the detailed geometry of the channel end on the jet receptivity is discussed, and more specifically the chamfer geometries found in flute-like musical instruments. The simplified model explains quite well the difference between the jet response of a flue with square edges compared to a chamfered flue exit. The effect of rounded, lip-like flue exit is not well captured by the model.
Moulin, Emmanuel; Grondel, Sébastien; Assaad, Jamal; Duquenne, Laurent
2008-12-01
The work described in this paper is intended to present a simple and efficient way of modeling a full Lamb wave emission and reception system. The emitter behavior and the Lamb wave generation are predicted using a two-dimensional (2D) hybrid finite element-normal mode expansion model. Then the receiver electrical response is obtained from a finite element computation with prescribed displacements. A numerical correction is applied to the 2D results in order to account for the in-plane radiation divergence caused by the finite length of the emitter. The advantage of this modular approach is that realistic configurations can be simulated without performing cumbersome modeling and time-consuming computations. It also provides insight into the physical interpretation of the results. A good agreement is obtained between predicted and measured signals. The range of application of the method is discussed.
Directory of Open Access Journals (Sweden)
Arthur M Jacobs
2015-04-01
Full Text Available A long tradition of research including classical rhetoric, aesthetics and poetics theory, formalism and structuralism, as well as current perspectives in (neurocognitive poetics has investigated structural and functional aspects of literature reception. Despite a wealth of literature published in specialised journals like Poetics, however, still little is known about how the brain processes and creates literary and poetic texts. Still, such stimulus material might be suited better than other genres for demonstrating the complexities with which our brain constructs the world in and around us, because it unifies thought and language, music and imagery in a clear, manageable way, most often with play, pleasure, and emotion (Schrott & Jacobs, 2011. In this paper, I discuss methods and models for investigating the neuronal and cognitive-affective bases of literary reading together with pertinent results from studies on poetics, text processing, emotion, or neuroaesthetics, and outline current challenges and future perspectives.
The Distancing-Embracing model of the enjoyment of negative emotions in art reception.
Menninghaus, Winfried; Wagner, Valentin; Hanich, Julian; Wassiliwizky, Eugen; Jacobsen, Thomas; Koelsch, Stefan
2017-02-20
Why are negative emotions so central in art reception far beyond tragedy? Revisiting classical aesthetics in light of recent psychological research, we present a novel model to explain this much-discussed (apparent) paradox. We argue that negative emotions are an important resource for the arts in general rather than a special license for exceptional art forms only. The underlying rationale is that negative emotions have been shown to be particularly powerful in securing attention, intense emotional involvement, and high memorability-and hence precisely in what artworks strive for. Two groups of processing mechanisms are identified that conjointly adopt the particular powers of negative emotions for art's purposes. The first group consists of psychological distancing mechanisms that are activated along with the cognitive schemata of art, representation, and fiction. These schemata imply personal safety and control over continuing or discontinuing exposure to artworks, thereby preventing negative emotions from becoming outright incompatible with expectations of enjoyment. This distancing sets the stage for a second group of processing components that allow art recipients to positively embrace the experiencing of negative emotions, thereby rendering art reception more intense, more interesting, more emotionally moving, more profound, and occasionally even more beautiful. These components include compositional interplays of positive and negative emotions, the effects of aesthetic virtues of using the media of (re)presentation (musical sound, words/language, color, shapes) on emotion perception, and meaning-making efforts. Moreover, our Distancing-Embracing model proposes that concomitant mixed emotions often help to integrate negative emotions into altogether pleasurable trajectories.
Perrone, John A.; Stone, Leland S.
1997-01-01
We have previously proposed a computational neural-network model by which the complex patterns of retinal image motion generated during locomotion (optic flow) can be processed by specialized detectors acting as templates for specific instances of self-motion. The detectors in this template model respond to global optic flow by sampling image motion over a large portion of the visual field through networks of local motion sensors with properties similar to neurons found in the middle temporal (MT) area of primate extrastriate visual cortex. The model detectors were designed to extract self-translation (heading), self-rotation, as well as the scene layout (relative distances) ahead of a moving observer, and are arranged in cortical-like heading maps to perform this function. Heading estimation from optic flow has been postulated by some to be implemented within the medial superior temporal (MST) area. Others have questioned whether MST neurons can fulfill this role because some of their receptive-field properties appear inconsistent with a role in heading estimation. To resolve this issue, we systematically compared MST single-unit responses with the outputs of model detectors under matched stimulus conditions. We found that the basic physiological properties of MST neurons can be explained by the template model. We conclude that MST neurons are well suited to support heading estimation and that the template model provides an explicit set of testable hypotheses which can guide future exploration of MST and adjacent areas within the primate superior temporal sulcus.
Lin, Chuan; Xu, Guili; Cao, Yijun; Liang, Chenghua; Li, Ya
2016-07-01
The responses of cortical neurons to a stimulus in a classical receptive field (CRF) can be modulated by stimulating the non-CRF (nCRF) of neurons in the primary visual cortex (V1). In the very early stages (at around 40 ms), a neuron in V1 exhibits strong responses to a small set of stimuli. Later, however (after 100 ms), the neurons in V1 become sensitive to the scene's global organization. As per these visual cortical mechanisms, a contour detection model based on the spatial summation properties is proposed. Unlike in previous studies, the responses of the nCRF to the higher visual cortex that results in the inhibition of the neuronal responses in the primary visual cortex by the feedback pathway are considered. In this model, the individual neurons in V1 receive global information from the higher visual cortex to participate in the inhibition process. Computationally, global Gabor energy features are involved, leading to the more coherent physiological characteristics of the nCRF. We conducted an experiment where we compared our model with those proposed by other researchers. Our model explains the role of the mutual inhibition of neurons in V1, together with an approach for object recognition in machine vision.
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Ana Calabrese
Full Text Available In the auditory system, the stimulus-response properties of single neurons are often described in terms of the spectrotemporal receptive field (STRF, a linear kernel relating the spectrogram of the sound stimulus to the instantaneous firing rate of the neuron. Several algorithms have been used to estimate STRFs from responses to natural stimuli; these algorithms differ in their functional models, cost functions, and regularization methods. Here, we characterize the stimulus-response function of auditory neurons using a generalized linear model (GLM. In this model, each cell's input is described by: 1 a stimulus filter (STRF; and 2 a post-spike filter, which captures dependencies on the neuron's spiking history. The output of the model is given by a series of spike trains rather than instantaneous firing rate, allowing the prediction of spike train responses to novel stimuli. We fit the model by maximum penalized likelihood to the spiking activity of zebra finch auditory midbrain neurons in response to conspecific vocalizations (songs and modulation limited (ml noise. We compare this model to normalized reverse correlation (NRC, the traditional method for STRF estimation, in terms of predictive power and the basic tuning properties of the estimated STRFs. We find that a GLM with a sparse prior predicts novel responses to both stimulus classes significantly better than NRC. Importantly, we find that STRFs from the two models derived from the same responses can differ substantially and that GLM STRFs are more consistent between stimulus classes than NRC STRFs. These results suggest that a GLM with a sparse prior provides a more accurate characterization of spectrotemporal tuning than does the NRC method when responses to complex sounds are studied in these neurons.
Gao, Kun; Yang, Hu; Chen, Xiaomei; Ni, Guoqiang
2008-03-01
Because of complex thermal objects in an infrared image, the prevalent image edge detection operators are often suitable for a certain scene and extract too wide edges sometimes. From a biological point of view, the image edge detection operators work reliably when assuming a convolution-based receptive field architecture. A DoG (Difference-of- Gaussians) model filter based on ON-center retinal ganglion cell receptive field architecture with artificial eye tremors introduced is proposed for the image contour detection. Aiming at the blurred edges of an infrared image, the subsequent orthogonal polynomial interpolation and sub-pixel level edge detection in rough edge pixel neighborhood is adopted to locate the foregoing rough edges in sub-pixel level. Numerical simulations show that this method can locate the target edge accurately and robustly.
Institute of Scientific and Technical Information of China (English)
杨谦; 齐翔林; 汪云九
2001-01-01
In order to probe into the self-organizing emergence of simple cell orientation selectivity,we tried to construct a neural network model that consists of LGN neurons and simple cells in visual cortex and obeys the Hebbian learning rule. We investigated the neural coding and representation of simple cells to a natural image by means of this model. The results show that the structures of their receptive fields are determined by the preferred orientation selectivity of simple cells.However, they are also decided by the emergence of self-organization in the unsupervision learning process. This kind of orientation selectivity results from dynamic self-organization based on the interactions between LGN and cortex.
Predicting Volleyball Serve-Reception
Paulo, Ana; Zaal, Frank T. J. M.; Fonseca, Sofia; Araújo, Duarte
2016-01-01
Serve and serve-reception performance have predicted success in volleyball. Given the impact of serve-reception on the game, we aimed at understanding what it is in the serve and receiver's actions that determines the selection of the type of pass used in serve-reception and its efficacy. Four high-level volleyball players received jump-float serves from four servers in two reception zones—zone 1 and 5. The ball and the receiver's head were tracked with two video cameras, allowing 3D world-coordinates reconstruction. Logistic-regression models were used to predict the type of pass used (overhand or underhand) and serve-reception efficacy (error, out, or effective) from variables related with the serve kinematics and related with the receiver's on-court positioning and movement. Receivers' initial position was different when in zone 1 and 5. This influenced the serve-related variables as well as the type of pass used. Strong predictors of using an underhand rather than overhand pass were higher ball contact of the server, reception in zone 1, receiver's initial position more to the back of the court and backward receiver movement. Receiver's larger longitudinal displacements and an initial position more to the back of the court had a strong relationship with the decreasing of the serve-reception efficacy. Receivers' positioning and movement were the factors with the largest impact on the type of pass used and the efficacy of the reception. Reception zone affected the variance in the ball's kinematics (with the exception of the ball's lateral displacement), as well as in the receivers' positioning (distances from the net and from the target). Also the reception zone was associated with the type of pass used by the receiver but not with reception efficacy. Given volleyball's rotation rule, the receiver needs to master receiving in the different reception zones; he/she needs to adapt to the diverse constraints of each zone to maintain performance efficacy. Thus
Predicting Volleyball Serve-reception
Directory of Open Access Journals (Sweden)
Ana Paulo
2016-11-01
Full Text Available Serve and serve-reception performance have predicted success in volleyball. Given the impact of serve-reception on the game, we aimed at understanding what it is in the serve and receiver’s actions that determines the selection of the type of pass used in serve-reception and its efficacy. Four high-level players received jump-float serves from four servers in two reception zones – zone 1 and 5. The ball and the receiver’s head were tracked with two video cameras, allowing 3D world-coordinates reconstruction. Logistic-regression models were used to predict the type of pass used (overhand or underhand and serve-reception efficacy (error, out, or effective from variables related with the serve kinematics and related with the receiver’s on-court positioning and movement. Receivers’ initial position was different when in zone 1 and 5. This influenced the serve-related variables as well as the type of pass used. Strong predictors of using an underhand rather than overhand pass were higher ball contact of the server, reception in zone 1, receiver’s initial position more to the back of the court and backward receiver movement. Receiver’s larger longitudinal displacements and an initial position more to the back of the court had a strong relationship with the decreasing of the serve-reception efficacy. Receivers’ positioning and movement were the factors with the largest impact on the type of pass used and the efficacy of the reception. Reception zone affected the variance in the ball’s kinematics (with the exception of the ball’s lateral displacement, as well as in the receivers’ positioning (distances from the net and from the target. Also the reception zone was associated with the type of pass used by the receiver but not with reception efficacy. Given volleyball’s rotation rule, the receiver needs to master receiving in the different reception zones; he/she needs to adapt to the diverse constraints of each zone to maintain
Dynamic Latent Classification Model
DEFF Research Database (Denmark)
Zhong, Shengtong; Martínez, Ana M.; Nielsen, Thomas Dyhre
as possible. Motivated by this problem setting, we propose a generative model for dynamic classification in continuous domains. At each time point the model can be seen as combining a naive Bayes model with a mixture of factor analyzers (FA). The latent variables of the FA are used to capture the dynamics...... in the process as well as modeling dependences between attributes....
Jacobs, Arthur M.
2015-01-01
A long tradition of research including classical rhetoric, esthetics and poetics theory, formalism and structuralism, as well as current perspectives in (neuro)cognitive poetics has investigated structural and functional aspects of literature reception. Despite a wealth of literature published in specialized journals like Poetics, however, still little is known about how the brain processes and creates literary and poetic texts. Still, such stimulus material might be suited better than other genres for demonstrating the complexities with which our brain constructs the world in and around us, because it unifies thought and language, music and imagery in a clear, manageable way, most often with play, pleasure, and emotion (Schrott and Jacobs, 2011). In this paper, I discuss methods and models for investigating the neuronal and cognitive-affective bases of literary reading together with pertinent results from studies on poetics, text processing, emotion, or neuroaesthetics, and outline current challenges and future perspectives. PMID:25932010
Jacobs, Arthur M
2015-01-01
A long tradition of research including classical rhetoric, esthetics and poetics theory, formalism and structuralism, as well as current perspectives in (neuro)cognitive poetics has investigated structural and functional aspects of literature reception. Despite a wealth of literature published in specialized journals like Poetics, however, still little is known about how the brain processes and creates literary and poetic texts. Still, such stimulus material might be suited better than other genres for demonstrating the complexities with which our brain constructs the world in and around us, because it unifies thought and language, music and imagery in a clear, manageable way, most often with play, pleasure, and emotion (Schrott and Jacobs, 2011). In this paper, I discuss methods and models for investigating the neuronal and cognitive-affective bases of literary reading together with pertinent results from studies on poetics, text processing, emotion, or neuroaesthetics, and outline current challenges and future perspectives.
Education and Technology Transfer Unit/ETT-EC
2004-01-01
Friday 15.10.2004 CERN 50th Anniversary articles will be sold in the Main Building, ground floor on Friday 15th October from 10h00 to 16h00. T-shirt, (S, M, L, XL) 20.- K-way (M, L, XL) 20.- Silk tie (2 models) 30.- Einstein tie 45.- Umbrella 20.- Caran d'Ache pen 5.- 50th Anniversary Pen 5.- Kit of Cartoon Album & Crayons 10.- All the articles are also available at the Reception Shop in Building 33 from Monday to Saturday between 08.30 and 17.00 hrs. Education and Technology Transfer Unit/ETT-EC
National Research Council Canada - National Science Library
Hyvärinen, Aapo; Hoyer, Patrik O
2001-01-01
The classical receptive fields of simple cells in the visual cortex have been shown to emerge from the statistical properties of natural images by forcing the cell responses to be maximally sparse, i.e...
Models for Dynamic Applications
DEFF Research Database (Denmark)
2011-01-01
be applied to formulate, analyse and solve these dynamic problems and how in the case of the fuel cell problem the model consists of coupledmeso and micro scale models. It is shown how data flows are handled between the models and how the solution is obtained within the modelling environment....
Directory of Open Access Journals (Sweden)
Jennifer Nedelsky
2011-12-01
Full Text Available Both judgment and receptivity are important to optimal politics, and both are important to each other. In making this argument, I use an Arendtian conception of judgment and take mindfulness as an example of receptivity. I argue that receptivity offers a needed dimension to addressing the puzzles of what makes Arendtian judgment possible, and that judgment provides a necessary complement to receptivity for action in the world. Exploring this complementary relation between judgment and receptivity also reveals a surprising similarity between what each offers to the practice of politics, in particular to freedom and the possibility of transformation. At the same time, I argue, these important contributions to politics are best understood and realized if judgment and receptivity are thought of as distinct forms of relating to the world.
The Receptive Side of Teaching
Hruska, Barbara
2008-01-01
When observing teachers in action, one is likely to witness explaining, modeling, managing, guiding, and encouraging. These expressive behaviors constitute a directive force moving outward from teacher to students. Though less visible to an outside observer, teaching also requires receptive skills, the ability to take in information by being fully…
Perrone, J. A.; Stone, L. S.
1998-01-01
We have proposed previously a computational neural-network model by which the complex patterns of retinal image motion generated during locomotion (optic flow) can be processed by specialized detectors acting as templates for specific instances of self-motion. The detectors in this template model respond to global optic flow by sampling image motion over a large portion of the visual field through networks of local motion sensors with properties similar to those of neurons found in the middle temporal (MT) area of primate extrastriate visual cortex. These detectors, arranged within cortical-like maps, were designed to extract self-translation (heading) and self-rotation, as well as the scene layout (relative distances) ahead of a moving observer. We then postulated that heading from optic flow is directly encoded by individual neurons acting as heading detectors within the medial superior temporal (MST) area. Others have questioned whether individual MST neurons can perform this function because some of their receptive-field properties seem inconsistent with this role. To resolve this issue, we systematically compared MST responses with those of detectors from two different configurations of the model under matched stimulus conditions. We found that the characteristic physiological properties of MST neurons can be explained by the template model. We conclude that MST neurons are well suited to support self-motion estimation via a direct encoding of heading and that the template model provides an explicit set of testable hypotheses that can guide future exploration of MST and adjacent areas within the superior temporal sulcus.
DEFF Research Database (Denmark)
Andreasen, Martin Møller; Meldrum, Andrew
This paper studies whether dynamic term structure models for US nominal bond yields should enforce the zero lower bound by a quadratic policy rate or a shadow rate specification. We address the question by estimating quadratic term structure models (QTSMs) and shadow rate models with at most four...
Eguchi, Akihiro; Neymotin, Samuel A; Stringer, Simon M
2014-01-01
Although many computational models have been proposed to explain orientation maps in primary visual cortex (V1), it is not yet known how similar clusters of color-selective neurons in macaque V1/V2 are connected and develop. In this work, we address the problem of understanding the cortical processing of color information with a possible mechanism of the development of the patchy distribution of color selectivity via computational modeling. Each color input is decomposed into a red, green, and blue representation and transmitted to the visual cortex via a simulated optic nerve in a luminance channel and red-green and blue-yellow opponent color channels. Our model of the early visual system consists of multiple topographically-arranged layers of excitatory and inhibitory neurons, with sparse intra-layer connectivity and feed-forward connectivity between layers. Layers are arranged based on anatomy of early visual pathways, and include a retina, lateral geniculate nucleus, and layered neocortex. Each neuron in the V1 output layer makes synaptic connections to neighboring neurons and receives the three types of signals in the different channels from the corresponding photoreceptor position. Synaptic weights are randomized and learned using spike-timing-dependent plasticity (STDP). After training with natural images, the neurons display heightened sensitivity to specific colors. Information-theoretic analysis reveals mutual information between particular stimuli and responses, and that the information reaches a maximum with fewer neurons in the higher layers, indicating that estimations of the input colors can be done using the output of fewer cells in the later stages of cortical processing. In addition, cells with similar color receptive fields form clusters. Analysis of spiking activity reveals increased firing synchrony between neurons when particular color inputs are presented or removed (ON-cell/OFF-cell).
Designing a Normed Receptive Vocabulary Test for Bilingual Populations: A Model from Welsh
Mueller Gathercole, Virginia C.; Thomas, Enlli Mon; Hughes, Emma
2008-01-01
The purpose of this paper is to propose an applied model for the assessment of bilingual children's language abilities with standardised tests. We discuss the purposes of such tests, especially in relation to vocabulary knowledge, and potential applications of test results for each of those purposes. The specific case to be examined here is that…
Image identification from brain activity using the population receptive field model
Zuiderbaan, Wietske; Harvey, Ben M.; Dumoulin, Serge O
2017-01-01
A goal of computational models is not only to explain experimental data but also to make new predictions. A current focus of computational neuroimaging is to predict features of the presented stimulus from measured brain signals. These computational neuroimaging approaches may be agnostic about the
DEFF Research Database (Denmark)
Ambjørn, Lone
2002-01-01
Sproglæringsteoretisk værktøj til udvikling af IT-støttede materialer og programmer inden for sproglig reception......Sproglæringsteoretisk værktøj til udvikling af IT-støttede materialer og programmer inden for sproglig reception...
2010-09-22
Photodetector which is cooled to 70 K with an onboard Stirling motor cooler . The camera has a sensitivity of 0.02 C at a temperature of 30 C...a Kemo VBF44 bandpass filter12. A new coordinate system was developed for studying this unconventional, vertically-mounted airfoil. The aircraft...psid, 16-bit, Pressure Systems scanner. The scanner was imbedded inside the model to reduce pressure lag time within the tubing. For all Cp flights
Data-driven modeling to assess receptivity for Rift Valley Fever virus.
Directory of Open Access Journals (Sweden)
Christopher M Barker
2013-11-01
Full Text Available Rift Valley Fever virus (RVFV is an enzootic virus that causes extensive morbidity and mortality in domestic ruminants in Africa, and it has shown the potential to invade other areas such as the Arabian Peninsula. Here, we develop methods for linking mathematical models to real-world data that could be used for continent-scale risk assessment given adequate data on local host and vector populations. We have applied the methods to a well-studied agricultural region of California with [Formula: see text]1 million dairy cattle, abundant and competent mosquito vectors, and a permissive climate that has enabled consistent transmission of West Nile virus and historically other arboviruses. Our results suggest that RVFV outbreaks could occur from February-November, but would progress slowly during winter-early spring or early fall and be limited spatially to areas with early increases in vector abundance. Risk was greatest in summer, when the areas at risk broadened to include most of the dairy farms in the study region, indicating the potential for considerable economic losses if an introduction were to occur. To assess the threat that RVFV poses to North America, including what-if scenarios for introduction and control strategies, models such as this one should be an integral part of the process; however, modeling must be paralleled by efforts to address the numerous remaining gaps in data and knowledge for this system.
Mismatch Receptive Fields in Mouse Visual Cortex.
Zmarz, Pawel; Keller, Georg B
2016-11-23
In primary visual cortex, a subset of neurons responds when a particular stimulus is encountered in a certain location in visual space. This activity can be modeled using a visual receptive field. In addition to visually driven activity, there are neurons in visual cortex that integrate visual and motor-related input to signal a mismatch between actual and predicted visual flow. Here we show that these mismatch neurons have receptive fields and signal a local mismatch between actual and predicted visual flow in restricted regions of visual space. These mismatch receptive fields are aligned to the retinotopic map of visual cortex and are similar in size to visual receptive fields. Thus, neurons with mismatch receptive fields signal local deviations of actual visual flow from visual flow predicted based on self-motion and could therefore underlie the detection of objects moving relative to the visual flow caused by self-motion. VIDEO ABSTRACT.
The challenge of audience reception: a developmental model for educational game engagement.
Sherry, John L
2013-01-01
According to educational gaming advocates, the engaging nature of games encourages sustained game play and enhanced attention to learning outcomes among players. Because children's and adolescents' play time varies by game genre, engagement with a game likely reflects the match between the genre and the player's preferences and needs. Youth learn which games are likely to promote satisfying psychological needs and yield positive experiences, which then informs their engagement with the games. A model is presented for research and development of educational games based on uses and gratifications theory from communication science, as well as developmental science and cognitive science findings. Copyright © 2013 Wiley Periodicals, Inc., A Wiley Company.
Sexual conflict over floral receptivity.
Lankinen, Asa; Hellriegel, Barbara; Bernasconi, Giorgina
2006-12-01
In flowering plants, the onset and duration of female receptivity vary among species. In several species the receptive structures wilt upon pollination. Here we explore the hypothesis that postpollination wilting may be influenced by pollen and serve as a general means to secure paternity of the pollen donor at the expense of female fitness. Taking a game-theoretical approach, we examine the potential for the evolution of a pollen-borne wilting substance, and for the coevolution of a defense strategy by the recipient plant. The model without defense predicts an evolutionarily stable strategy (ESS) for the production of wilting substance. The ESS value is highest when pollinator visiting rates are intermediate and when the probability that pollen from several donors arrives at the same time is low. This finding has general implications in that it shows that male traits to secure paternity also can evolve in species, such as plants, where mating is not strictly sequential. We further model coevolution of the wilting substance with the timing of stigma receptivity. We assume that pollen-receiving plants can reduce the costs induced by toxic pollen by delaying the onset of stigmatic receptivity. The model predicts a joint ESS, but no female counter-adaptation when the wilting substance is highly toxic. This indicates that toxicity affects the probability that a male manipulative trait stays beneficial (i.e., not countered by female defense) over evolutionary time. We discuss parallels to male induced changes in female receptivity known to occur in animals and the role of harm for the evolution of male manipulative adaptations.
Knowledge Model and Consumer Behavior in Delivery and Reception Gift Interpersonal
Directory of Open Access Journals (Sweden)
Jorge Aníbal Cruz Cárdenas
2011-05-01
Full Text Available The interpersonal giving and receiving of gifts implies a more complex purchasing process than the usual purchases of the consumer. It has two central factors, the giver and the receiver, each one with their own personal and psychological characteristics. These actors are influenced by external variables such as the relationship they maintain, the marketing variables and other variables not controlled by the enterprises, namely the economy, the culture, and the family. The purchasing process of gifts begins with the recognition of a necessity. Many times it develops with a high involvement of the giver and the receiver and it gets through with the impact of the gift in the relationship that they maintain. By using the most common variables of consumer behavior, the article interprets and analyzes the state of the existing knowledge and it proposes a possible research agenda. The article presents a behavior model adapted to the stimulus-consumer-response models and discusses the implication for the marketing practice.DOI:10.5585/remark.v10i1.2205
Salinelli, Ernesto
2014-01-01
This book provides an introduction to the analysis of discrete dynamical systems. The content is presented by an unitary approach that blends the perspective of mathematical modeling together with the ones of several discipline as Mathematical Analysis, Linear Algebra, Numerical Analysis, Systems Theory and Probability. After a preliminary discussion of several models, the main tools for the study of linear and non-linear scalar dynamical systems are presented, paying particular attention to the stability analysis. Linear difference equations are studied in detail and an elementary introduction of Z and Discrete Fourier Transform is presented. A whole chapter is devoted to the study of bifurcations and chaotic dynamics. One-step vector-valued dynamical systems are the subject of three chapters, where the reader can find the applications to positive systems, Markov chains, networks and search engines. The book is addressed mainly to students in Mathematics, Engineering, Physics, Chemistry, Biology and Economic...
Ghanem, Bernard
2013-01-01
This paper proposes the problem of modeling video sequences of dynamic swarms (DSs). We define a DS as a large layout of stochastically repetitive spatial configurations of dynamic objects (swarm elements) whose motions exhibit local spatiotemporal interdependency and stationarity, i.e., the motions are similar in any small spatiotemporal neighborhood. Examples of DS abound in nature, e.g., herds of animals and flocks of birds. To capture the local spatiotemporal properties of the DS, we present a probabilistic model that learns both the spatial layout of swarm elements (based on low-level image segmentation) and their joint dynamics that are modeled as linear transformations. To this end, a spatiotemporal neighborhood is associated with each swarm element, in which local stationarity is enforced both spatially and temporally. We assume that the prior on the swarm dynamics is distributed according to an MRF in both space and time. Embedding this model in a MAP framework, we iterate between learning the spatial layout of the swarm and its dynamics. We learn the swarm transformations using ICM, which iterates between estimating these transformations and updating their distribution in the spatiotemporal neighborhoods. We demonstrate the validity of our method by conducting experiments on real and synthetic video sequences. Real sequences of birds, geese, robot swarms, and pedestrians evaluate the applicability of our model to real world data. © 2012 Elsevier Inc. All rights reserved.
Byers, John A
2013-08-01
Dose-response curves of the effects of semiochemicals on neurophysiology and behavior are reported in many articles in insect chemical ecology. Most curves are shown in figures representing points connected by straight lines, in which the x-axis has order of magnitude increases in dosage vs. responses on the y-axis. The lack of regression curves indicates that the nature of the dose-response relationship is not well understood. Thus, a computer model was developed to simulate a flux of various numbers of pheromone molecules (10(3) to 5 × 10(6)) passing by 10(4) receptors distributed among 10(6) positions along an insect antenna. Each receptor was depolarized by at least one strike by a molecule, and subsequent strikes had no additional effect. The simulations showed that with an increase in pheromone release rate, the antennal response would increase in a convex fashion and not in a logarithmic relation as suggested previously. Non-linear regression showed that a family of kinetic formation functions fit the simulated data nearly perfectly (R(2) >0.999). This is reasonable because olfactory receptors have proteins that bind to the pheromone molecule and are expected to exhibit enzyme kinetics. Over 90 dose-response relationships reported in the literature of electroantennographic and behavioral bioassays in the laboratory and field were analyzed by the logarithmic and kinetic formation functions. This analysis showed that in 95% of the cases, the kinetic functions explained the relationships better than the logarithmic (mean of about 20% better). The kinetic curves become sigmoid when graphed on a log scale on the x-axis. Dose-catch relationships in the field are similar to dose-EAR (effective attraction radius, in which a spherical radius indicates the trapping effect of a lure) and the circular EARc in two dimensions used in mass trapping models. The use of kinetic formation functions for dose-response curves of attractants, and kinetic decay curves for
Heikkinen, Hanna; Sharifian, Fariba; Vigario, Ricardo; Vanni, Simo
2015-07-01
The blood oxygenation level-dependent (BOLD) response has been strongly associated with neuronal activity in the brain. However, some neuronal tuning properties are consistently different from the BOLD response. We studied the spatial extent of neural and hemodynamic responses in the primary visual cortex, where the BOLD responses spread and interact over much longer distances than the small receptive fields of individual neurons would predict. Our model shows that a feedforward-feedback loop between V1 and a higher visual area can account for the observed spread of the BOLD response. In particular, anisotropic landing of inputs to compartmental neurons were necessary to account for the BOLD signal spread, while retaining realistic spiking responses. Our work shows that simple dendrites can separate tuning at the synapses and at the action potential output, thus bridging the BOLD signal to the neural receptive fields with high fidelity.
Dynamic causal modelling revisited.
Friston, K J; Preller, Katrin H; Mathys, Chris; Cagnan, Hayriye; Heinzle, Jakob; Razi, Adeel; Zeidman, Peter
2017-02-17
This paper revisits the dynamic causal modelling of fMRI timeseries by replacing the usual (Taylor) approximation to neuronal dynamics with a neural mass model of the canonical microcircuit. This provides a generative or dynamic causal model of laminar specific responses that can generate haemodynamic and electrophysiological measurements. In principle, this allows the fusion of haemodynamic and (event related or induced) electrophysiological responses. Furthermore, it enables Bayesian model comparison of competing hypotheses about physiologically plausible synaptic effects; for example, does attentional modulation act on superficial or deep pyramidal cells - or both? In this technical note, we describe the resulting dynamic causal model and provide an illustrative application to the attention to visual motion dataset used in previous papers. Our focus here is on how to answer long-standing questions in fMRI; for example, do haemodynamic responses reflect extrinsic (afferent) input from distant cortical regions, or do they reflect intrinsic (recurrent) neuronal activity? To what extent do inhibitory interneurons contribute to neurovascular coupling? What is the relationship between haemodynamic responses and the frequency of induced neuronal activity? This paper does not pretend to answer these questions; rather it shows how they can be addressed using neural mass models of fMRI timeseries. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.
Receptive fields and visual representations
Watson, Andrew B.
1989-01-01
Efficient representation of images for human use requires an understanding of how the brain processes and represents visual information. Spatial imagery is represented in the brain in the receptive fields of visual neurons. Models of these neurons lead to models of image fidelity, and to digital implementations of these neural codes. This approach will be illustrated by two example codes. The advantages and difficulties of this approach will be discussed.
Malafeyev, O. A.; Nemnyugin, S. A.; Rylow, D.; Kolpak, E. P.; Awasthi, Achal
2017-07-01
The corruption dynamics is analyzed by means of the lattice model which is similar to the three-dimensional Ising model. Agents placed at nodes of the corrupt network periodically choose to perfom or not to perform the act of corruption at gain or loss while making decisions based on the process history. The gain value and its dynamics are defined by means of the Markov stochastic process modelling with parameters established in accordance with the influence of external and individual factors on the agent's gain. The model is formulated algorithmically and is studied by means of the computer simulation. Numerical results are obtained which demonstrate asymptotic behaviour of the corruption network under various conditions.
Directory of Open Access Journals (Sweden)
Sorin Dan ŞANDOR
2003-01-01
Full Text Available System Dynamics was introduced by Jay W. Forrester in the 1960s. Since then the methodology was adopted in many areas of natural or social sciences. This article tries to present briefly how this methodology works, both as Systems Thinking and as Modelling with Vensim computer software.
Dynamic modelling of windmills
DEFF Research Database (Denmark)
Akhmatov, Vladislav; Knudsen, Hans
1999-01-01
An empirical dynamic model of windmills is set up based on analysis of measured Fourier spectra of the active electric power from a wind farm. The model is based on the assumption that eigenswings of the mechanical construction of the windmills excited by the phenomenon of vortex tower interaction...... will be transferred through the shaft to the electrical generator and result in disturbances of the active electric power supplied by the windmills. The results of the model are found to be in agreement with measurements in the frequency range of the model that is from 0.1 to 10 Hz....
Armbruster, Benjamin
2011-01-01
We analyze random networks that change over time. First we analyze a dynamic Erdos-Renyi model, whose edges change over time. We describe its stationary distribution, its convergence thereto, and the SI contact process on the network, which has relevance for connectivity and the spread of infections. Second, we analyze the effect of node turnover, when nodes enter and leave the network, which has relevance for network models incorporating births, deaths, aging, and other demographic factors.
Institute of Scientific and Technical Information of China (English)
YANG; Qian(
2001-01-01
［1］Hubel, D. H.. Wiesel. T. N., Receptive fields of single neuron in the cat striate cortex, Journal of Physiology, 1959, 148:574-591.［2］Hubel. D. H.. Wiesel, T. N., Functional architecture macaque monkey visual cortexm, Proc. Roy. Soc. B, 1977, 198: 1-59.［3］Shou. T. D., Brain Mechanisms of Visual Information Processing (in Chinese), Shanghai: Shanghai Science-Technology and Education Press, 1997, 188-197.［4］Ferster, D., Chung, S., Wheat, H., Orientation selectivity of thalamic input to simple cells of cat visual cortex, Nature,1996, 380: 249-252.［5］Vidyasagar. T. R., Pei, X., Volgushev, M., Multiple mechanisms underlying the orientation selectivity of visual cortical neurons. TINS, 1996, 19: 272-277.［6］Artun, O. B., Shouval, H. Z., Cooper, L. N., The effect of dynamic synapses on spatiotemporal receptive fields in visual cortex, Proc. Natl. Acad. Sci. USA, 1998, 95:11999-12003.［7］Rolls, E. T.. Tovee, M. J., Sparseness of the neuronal representation of stimuli in the primate temporal visual cortex, J.Neurophysiology, 1995,73: 713-726.［8］Olshausen. B. A.. Field, D. J., Sparse coding with an overcomplete basis set: A strategy employed by V 1 ? Vision Research,1997.37: 3311-3325.［9］Bell. A. J., Sejnoswski, T. J., The "Independent components" of natural scenes are edge filters, Vision Research, 1997, 37:3327-3338.［10］Dan, Y., Atick, J. J., Reid, R. C., Efficient coding of natural scenes in the lateral geniculate nucleus: experimental test of a computational theory, Journal of Neuroscience, 1996, 16:3351-3362.［11］Field. D. J., Relations between the statistics of natural images and the response properties of cortical cells, Journal of the Optical Society of America A, 1987, 4: 2379-2394.［12］DeAngelis, G. C., Ohzawa, I., Freeman, R. D., Receptive filed dynamics in the central visual pathway, TINS, 1995,18:451-458.［13］Wang, Y. J., Qi, X. L., Chen, Y. Z., Simulations of receptive fields dynamics, TINS, 1996, 19: 385-386.
Modal aerosol dynamics modeling
Energy Technology Data Exchange (ETDEWEB)
Whitby, E.R.; McMurry, P.H.; Shankar, U.; Binkowski, F.S.
1991-02-01
The report presents the governing equations for representing aerosol dynamics, based on several different representations of the aerosol size distribution. Analytical and numerical solution techniques for these governing equations are also reviewed. Described in detail is a computationally efficient numerical technique for simulating aerosol behavior in systems undergoing simultaneous heat transfer, fluid flow, and mass transfer in and between the gas and condensed phases. The technique belongs to a general class of models known as modal aerosol dynamics (MAD) models. These models solve for the temporal and spatial evolution of the particle size distribution function. Computational efficiency is achieved by representing the complete aerosol population as a sum of additive overlapping populations (modes), and solving for the time rate of change of integral moments of each mode. Applications of MAD models for simulating aerosol dynamics in continuous stirred tank aerosol reactors and flow aerosol reactors are provided. For the application to flow aerosol reactors, the discussion is developed in terms of considerations for merging a MAD model with the SIMPLER routine described by Patankar (1980). Considerations for incorporating a MAD model into the U.S. Environmental Protection Agency's Regional Particulate Model are also described. Numerical and analytical techniques for evaluating the size-space integrals of the modal dynamics equations (MDEs) are described. For multimodal logonormal distributions, an analytical expression for the coagulation integrals of the MDEs, applicable for all size regimes, is derived, and is within 20% of accurate numerical evaluation of the same moment coagulation integrals. A computationally efficient integration technique, based on Gauss-Hermite numerical integration, is also derived.
Murawski, Jens; Kleine, Eckhard
2017-04-01
Sea ice remains one of the frontiers of ocean modelling and is of vital importance for the correct forecasts of the northern oceans. At large scale, it is commonly considered a continuous medium whose dynamics is modelled in terms of continuum mechanics. Its specifics are a matter of constitutive behaviour which may be characterised as rigid-plastic. The new developed sea ice dynamic module bases on general principles and follows a systematic approach to the problem. Both drift field and stress field are modelled by a variational property. Rigidity is treated by Lagrangian relaxation. Thus one is led to a sensible numerical method. Modelling fast ice remains to be a challenge. It is understood that ridging and the formation of grounded ice keels plays a role in the process. The ice dynamic model includes a parameterisation of the stress associated with grounded ice keels. Shear against the grounded bottom contact might lead to plastic deformation and the loss of integrity. The numerical scheme involves a potentially large system of linear equations which is solved by pre-conditioned iteration. The entire algorithm consists of several components which result from decomposing the problem. The algorithm has been implemented and tested in practice.
Dynamic wake meandering modeling
Energy Technology Data Exchange (ETDEWEB)
Larsen, Gunner C.; Aagaard Madsen, H.; Bingoel, F. (and others)
2007-06-15
We present a consistent, physically based theory for the wake meandering phenomenon, which we consider of crucial importance for the overall description of wind turbine loadings in wind farms. In its present version the model is confined to single wake situations. The model philosophy does, however, have the potential to include also mutual wake interaction phenomenons. The basic conjecture behind the dynamic wake meandering model is that wake transportation in the atmospheric boundary layer is driven by the large scale lateral- and vertical turbulence components. Based on this conjecture a stochastic model of the downstream wake meandering is formulated. In addition to the kinematic formulation of the dynamics of the 'meandering frame of reference', models characterizing the mean wake deficit as well as the added wake turbulence, described in the meandering frame of reference, are an integrated part the model complex. For design applications, the computational efficiency of wake deficit prediction is a key issue. Two computationally low cost models are developed for this purpose. The character of the added wake turbulence, generated by the up-stream turbine in the form of shed and trailed vorticity, has been approached by analytical as well as by numerical studies. The dynamic wake meandering philosophy has been verified by comparing model predictions with extensive full-scale measurements. These comparisons have demonstrated good agreement, both qualitatively and quantitatively, concerning both flow characteristics and turbine load characteristics. Contrary to previous attempts to model wake loading, the dynamic wake meandering approach opens for a unifying description in the sense that turbine power and load aspects can be treated simultaneously. This capability is a direct and attractive consequence of the model being based on the underlying physical process, and it potentially opens for optimization of wind farm topology, of wind farm operation as
Dynamic wake meandering modeling
DEFF Research Database (Denmark)
Larsen, Gunner Chr.; Madsen Aagaard, Helge; Bingöl, Ferhat;
, are an integrated part the model complex. For design applications, the computational efficiency of wake deficit prediction is a key issue. Two computationally low cost models are developed for this purpose. The character of the added wake turbulence, generated by the up-stream turbine in the form of shed......We present a consistent, physically based theory for the wake meandering phenomenon, which we consider of crucial importance for the overall description of wind turbine loadings in wind farms. In its present version the model is confined to single wake situations. The model philosophy does, however......, have the potential to include also mutual wake interaction phenomenons. The basic conjecture behind the dynamic wake meandering model is that wake transportation in the atmospheric boundary layer is driven by the large scale lateral- and vertical turbulence components. Based on this conjecture...
Charpentier, Arthur; Durand, Marilou
2015-07-01
In this paper, we investigate questions arising in Parsons and Geist (Bull Seismol Soc Am 102:1-11, 2012). Pseudo causal models connecting magnitudes and waiting times are considered, through generalized regression. We do use conditional model (magnitude given previous waiting time, and conversely) as an extension to joint distribution model described in Nikoloulopoulos and Karlis (Environmetrics 19: 251-269, 2008). On the one hand, we fit a Pareto distribution for earthquake magnitudes, where the tail index is a function of waiting time following previous earthquake; on the other hand, waiting times are modeled using a Gamma or a Weibull distribution, where parameters are functions of the magnitude of the previous earthquake. We use those two models, alternatively, to generate the dynamics of earthquake occurrence, and to estimate the probability of occurrence of several earthquakes within a year or a decade.
Structural dynamic modifications via models
Indian Academy of Sciences (India)
T K Kundra
2000-06-01
Structural dynamic modification techniques attempt to reduce dynamic design time and can be implemented beginning with spatial models of structures, dynamic test data or updated models. The models assumed in this discussion are mathematical models, namely mass, stiffness, and damping matrices of the equations of motion of a structure. These models are identified/extracted from dynamic test data viz. frequency response functions (FRFs). Alternatively these models could have been obtained by adjusting or updating the finite element model of the structure in the light of the test data. The methods of structural modification for getting desired dynamic characteristics by using modifiers namely mass, beams and tuned absorbers are discussed.
Bioinspired Haircell Receptive Sensors
2009-07-23
DAPAR program manager Dr. Hylton. The new objective copes better with navy’s immediate interests, (ii) Station keeping was later aborted after some...alien to our human experience such as, for example, sensitivities in the infrared and ultrasound , electro-magnetic reception, and strain detection
Diversity Networking Reception
2014-03-01
Join us at the APS Diversity Reception to relax, network with colleagues, and learn about programs and initiatives for women, underrepresented minorities, and LGBT physicists. You'll have a great time meeting friends in a supportive environment and making connections.
A computational theory of visual receptive fields.
Lindeberg, Tony
2013-12-01
A receptive field constitutes a region in the visual field where a visual cell or a visual operator responds to visual stimuli. This paper presents a theory for what types of receptive field profiles can be regarded as natural for an idealized vision system, given a set of structural requirements on the first stages of visual processing that reflect symmetry properties of the surrounding world. These symmetry properties include (i) covariance properties under scale changes, affine image deformations, and Galilean transformations of space-time as occur for real-world image data as well as specific requirements of (ii) temporal causality implying that the future cannot be accessed and (iii) a time-recursive updating mechanism of a limited temporal buffer of the past as is necessary for a genuine real-time system. Fundamental structural requirements are also imposed to ensure (iv) mutual consistency and a proper handling of internal representations at different spatial and temporal scales. It is shown how a set of families of idealized receptive field profiles can be derived by necessity regarding spatial, spatio-chromatic, and spatio-temporal receptive fields in terms of Gaussian kernels, Gaussian derivatives, or closely related operators. Such image filters have been successfully used as a basis for expressing a large number of visual operations in computer vision, regarding feature detection, feature classification, motion estimation, object recognition, spatio-temporal recognition, and shape estimation. Hence, the associated so-called scale-space theory constitutes a both theoretically well-founded and general framework for expressing visual operations. There are very close similarities between receptive field profiles predicted from this scale-space theory and receptive field profiles found by cell recordings in biological vision. Among the family of receptive field profiles derived by necessity from the assumptions, idealized models with very good qualitative
Comparing different dynamic stall models
Energy Technology Data Exchange (ETDEWEB)
Holierhoek, J.G. [Unit Wind Energy, Energy research Centre of the Netherlands, ZG, Petten (Netherlands); De Vaal, J.B.; Van Zuijlen, A.H.; Bijl, H. [Aerospace Engineering, Delft University of Technology, Delft (Netherlands)
2012-07-16
The dynamic stall phenomenon and its importance for load calculations and aeroelastic simulations is well known. Different models exist to model the effect of dynamic stall; however, a systematic comparison is still lacking. To investigate if one is performing better than another, three models are used to simulate the Ohio State University measurements and a set of data from the National Aeronautics and Space Administration Ames experimental study of dynamic stall and compare results. These measurements were at conditions and for aerofoils that are typical for wind turbines, and the results are publicly available. The three selected dynamic stall models are the ONERA model, the Beddoes-Leishman model and the Snel model. The simulations show that there are still significant differences between measurements and models and that none of the models is significantly better in all cases than the other models. Especially in the deep stall regime, the accuracy of each of the dynamic stall models is limited.
Campagnoli, Patrizia; Petris, Giovanni
2009-01-01
State space models have gained tremendous popularity in as disparate fields as engineering, economics, genetics and ecology. Introducing general state space models, this book focuses on dynamic linear models, emphasizing their Bayesian analysis. It illustrates the fundamental steps needed to use dynamic linear models in practice, using R package.
Predicting Volleyball Serve-Reception
Paulo, Ana; Zaal, Frank T J M; Fonseca, Sofia; Araujo, Duarte
2016-01-01
Serve and serve-reception performance have predicted success in volleyball. Given the impact of serve-reception on the game, we aimed at understanding what it is in the serve and receiver's actions that determines the selection of the type of pass used in serve-reception and its efficacy. Four
Predicting Volleyball Serve-Reception
Paulo, Ana; Zaal, Frank T J M; Fonseca, Sofia; Araujo, Duarte
2016-01-01
Serve and serve-reception performance have predicted success in volleyball. Given the impact of serve-reception on the game, we aimed at understanding what it is in the serve and receiver's actions that determines the selection of the type of pass used in serve-reception and its efficacy. Four high-
Modelling dynamic roughness during floods
Paarlberg, Andries; Dohmen-Janssen, Catarine M.; Hulscher, Suzanne J.M.H.; Termes, A.P.P.
2007-01-01
In this paper, we present a dynamic roughness model to predict water levels during floods. Hysteresis effects of dune development are explicitly included. It is shown that differences between the new dynamic roughness model, and models where the roughness coefficient is calibrated, are most
Friston, K J; Harrison, L; Penny, W
2003-08-01
In this paper we present an approach to the identification of nonlinear input-state-output systems. By using a bilinear approximation to the dynamics of interactions among states, the parameters of the implicit causal model reduce to three sets. These comprise (1) parameters that mediate the influence of extrinsic inputs on the states, (2) parameters that mediate intrinsic coupling among the states, and (3) [bilinear] parameters that allow the inputs to modulate that coupling. Identification proceeds in a Bayesian framework given known, deterministic inputs and the observed responses of the system. We developed this approach for the analysis of effective connectivity using experimentally designed inputs and fMRI responses. In this context, the coupling parameters correspond to effective connectivity and the bilinear parameters reflect the changes in connectivity induced by inputs. The ensuing framework allows one to characterise fMRI experiments, conceptually, as an experimental manipulation of integration among brain regions (by contextual or trial-free inputs, like time or attentional set) that is revealed using evoked responses (to perturbations or trial-bound inputs, like stimuli). As with previous analyses of effective connectivity, the focus is on experimentally induced changes in coupling (cf., psychophysiologic interactions). However, unlike previous approaches in neuroimaging, the causal model ascribes responses to designed deterministic inputs, as opposed to treating inputs as unknown and stochastic.
Florian Ion Tiberiu Petrescu; Relly Victoria Virgil Petrescu
2016-01-01
Otto engine dynamics are similar in almost all common internal combustion engines. We can speak so about dynamics of engines: Lenoir, Otto, and Diesel. The dynamic presented model is simple and original. The first thing necessary in the calculation of Otto engine dynamics, is to determine the inertial mass reduced at the piston. One uses then the Lagrange equation. Kinetic energy conservation shows angular speed variation (from the shaft) with inertial masses. One uses and elastic constant of...
利于Logistic模型分析安康旅游接待量%Analysis of Logistic model of the number of tourist reception in Ankang
Institute of Scientific and Technical Information of China (English)
赵临龙; 武海辉
2016-01-01
By usingthe method of Logistic model to forecast the trend of block type,2001-2014 benefits of tourism Ankang original data and modified data analysis,given the formula to predict the amount of Ankang tourism,Ankang tourism reception and get maximum value for prediction of the amount of 30000000 people.%利用趋势预测阻滞型的Logistic模型，对2001-2014年安康旅游产业旅游效益原始数据和修正数据进行分析，给出安康旅游接待量的预测公式，并且得到安康旅游接待量的最大预测值为年3000万人次。
Prediction Model of TPC Reception Iron Amount Based on PCA-GA-BP%基于PCA-GA-BP的TPC受铁量预测模型
Institute of Scientific and Technical Information of China (English)
黄颖雷; 刘业峰; 黄辉; 郑秉霖
2009-01-01
Prediction problem of torpedo ladle car (TPC) actual reception iron amount under the blast furnace is discussed,which has an important function to coordinate molten iron balance,decrease exchanging bottles,reduce temperature loss and raise TPC utilization.A prediction model of TPC reception iron amount based on PCA-GA-BP is proposed.The principle component analysis is used to select the most relevant process features and to eliminate the correlations of the input variables.Back-propagation neural network is used to characterize the nonlinearity and accuracy.Genetic algorithm is employed to optimize the parameters and structure of the BP neural network by improving GA fitness function.Experiment results through the actual production data of an enterprise show the prediction rationality and validity,and the prediction accuracy of TiC actual reception iron amount is increased.%预测鱼雷罐车(TPC)在高炉的实际受铁量,时协调铁水平衡、减少兑罐次数和温降损失,保证高炉出铁安全,提高TPC利用率具有重要作用.采用主成分分析(PCA)提取过程特征参数,并剔除相关冗余信息;BP神经网络用来逼近受铁量预测这一非线性过程;改进了遗传算法(GA)的适应度函数,并精确给定BP神经网络的权值和阈值,进而建立了基于PCA-GA-BP的TPC受铁量预测模型.采用某钢铁企业实际生产数据运算,结果表明模型合理、有效,提高了鱼雷罐车(TPC)受铁量预测准确性.
Institute of Scientific and Technical Information of China (English)
汤漩
2013-01-01
In the process of shield-tunnel construction, risk research & monitoring on shield departure & reception can decrease accidences and damages effectively. According to risk identification, risk factors evaluation, risk monitoring indexes and the confirmation of grading reference range, a pre-warning method of shied departure & reception is formed on the basis of dynamic risk monitoring indexes. Practice in projects shows that this kind of dynamic risk pre-warning method can detect risk condition in time during construction, provide good conditions for risk prevention and emergency response and obtain great application effects finally.% 在盾构法隧道施工工程中，对盾构进出洞施工风险进行研究和监控，能有效地减少工程事故损失。通过盾构进出洞施工风险辨识、风险因素评价和监控指标项及其分级基准范围的确定，形成了一种基于监控指标动态监控的盾构进出洞施工风险预警方法，在工程应用中能及时监控风险情况，为风险防范和应急处理创造良好条件，取得较好的应用效果。
Computer Modelling of Dynamic Processes
Directory of Open Access Journals (Sweden)
B. Rybakin
2000-10-01
Full Text Available Results of numerical modeling of dynamic problems are summed in the article up. These problems are characteristic for various areas of human activity, in particular for problem solving in ecology. The following problems are considered in the present work: computer modeling of dynamic effects on elastic-plastic bodies, calculation and determination of performances of gas streams in gas cleaning equipment, modeling of biogas formation processes.
Institute of Scientific and Technical Information of China (English)
彭建明; 李荣英; 李戈; 王艳芳
2011-01-01
目的:研究阳春砂花粉活力和柱头可授性在开花散粉后的动态变化规律,为提高阳春砂仁坐果率提供基础资料.方法:在景洪市基诺族乡、景哈哈尼族乡和药植所云南分所园内选取10 ～ 30个花序,观察其的开花动态,并用悬滴法检测花粉活力(每次用3朵花),用MTT法测定柱头的可授性(用标记的10 ～30个花序的柱头).结果:阳春砂一个花序自第一朵开放到最后一朵开完需要3 ～ 9d.单花花期一般为1d；花粉在上午11:00以前均保持较高地萌发率,到中午11:00以后花粉活力下降,18:00仍有萌发能力；不同地区柱头可授性差异明显,花序上部小花柱头可授性比下部小花的高,不同花期柱头可授性变化不大.结论:景哈乡阳春砂柱头可授性比基诺乡的高,云南分所园内橡胶树下为最低.%Objective; Testing the dynamic changes of pollen viability and stigma receptivity after flowering, to provide a basis information on increasing fruit set of Amomum villosum. Method; Selecting 10-30 flowers In an inflorescence in Jingha village, Jinuo village and under robber - forest of Yunnan Branch, Institute of midic-inal Plant, observed floral dynamic, detected pollen viability with the hanging drop method ( three flowers each time) and stigma receptivity with the MTT method (10 -30 Stigmas each time) . Result; The Inflorescence flowering since the first flower opening to the last one in an inflorescence of Amomum villosum takes 3 to 9 days, the life span of a flower is generallyl day; Pollen viability in the morning before 11: 00 am maintain a high germination rate , then the pollen viability decrease after 11: 00 am, the pollen viability still has some germination rate till 6: 00 pm; Stigma receptivity of different regions is significantly different, flower stigma receptivity of the upper Inflorescence is higher than the lower part of Inflorescence, stigma receptivity has no change in different flowering period
Launch Vehicle Dynamics Demonstrator Model
1963-01-01
Launch Vehicle Dynamics Demonstrator Model. The effect of vibration on launch vehicle dynamics was studied. Conditions included three modes of instability. The film includes close up views of the simulator fuel tank with and without stability control. [Entire movie available on DVD from CASI as Doc ID 20070030984. Contact help@sti.nasa.gov
Generative models of conformational dynamics.
Langmead, Christopher James
2014-01-01
Atomistic simulations of the conformational dynamics of proteins can be performed using either Molecular Dynamics or Monte Carlo procedures. The ensembles of three-dimensional structures produced during simulation can be analyzed in a number of ways to elucidate the thermodynamic and kinetic properties of the system. The goal of this chapter is to review both traditional and emerging methods for learning generative models from atomistic simulation data. Here, the term 'generative' refers to a model of the joint probability distribution over the behaviors of the constituent atoms. In the context of molecular modeling, generative models reveal the correlation structure between the atoms, and may be used to predict how the system will respond to structural perturbations. We begin by discussing traditional methods, which produce multivariate Gaussian models. We then discuss GAMELAN (GRAPHICAL MODELS OF ENERGY LANDSCAPES), which produces generative models of complex, non-Gaussian conformational dynamics (e.g., allostery, binding, folding, etc.) from long timescale simulation data.
Fractal Models of Earthquake Dynamics
Bhattacharya, Pathikrit; Kamal,; Samanta, Debashis
2009-01-01
Our understanding of earthquakes is based on the theory of plate tectonics. Earthquake dynamics is the study of the interactions of plates (solid disjoint parts of the lithosphere) which produce seismic activity. Over the last about fifty years many models have come up which try to simulate seismic activity by mimicking plate plate interactions. The validity of a given model is subject to the compliance of the synthetic seismic activity it produces to the well known empirical laws which describe the statistical features of observed seismic activity. Here we present a review of two such models of earthquake dynamics with main focus on a relatively new model namely The Two Fractal Overlap Model.
Dynamic programming models and applications
Denardo, Eric V
2003-01-01
Introduction to sequential decision processes covers use of dynamic programming in studying models of resource allocation, methods for approximating solutions of control problems in continuous time, production control, more. 1982 edition.
Directory of Open Access Journals (Sweden)
Johanna Ross
2012-06-01
Full Text Available Valikuvõimalus (Option to Choose is a 1978 novel by the prolific Estonian writer Aimée Beekman. The novel tells the story of Regina, a schoolteacher approaching her thirtieth birthday who feels the need to start a family. Not able to find a suitable husband, she marries the village drunkard but, to ensure her children will be healthy, she decides to procreate with other men, alpha-males with clean medical records. This article tries to map the tumultuous dynamics of the reception of the novel and to explain it in terms of the rhetorical ethics developed by James Phelan. The first part of the article, “A story of a freakish unwoman”, describes the first wave of reception. Reviewers were almost unanimously hostile and the novel was declared a failure. This can be explained by the unavoidable intertwining of the ethical and aesthetic aspects of any given literary work. Largely due to the social conventions in Estonia in the 1970s, the scheming protagonist was considered cold and almost inhuman. Thus the outraged reviewers were more inclined to judge the entire book negatively. This is contrasted by the more open-minded German reception (the translation was published in 1983, where Regina was often described as a pleasant and adventurous young woman. The second part of the article, “A model novel full of spirit”, describes a change in the reception. At the end of the decade, a boom in “everyday novels” emerged in Estonia. Due to thematic similarities, Option to Choose was often compared to them: many of these books featured young women who faced problems with weak, uneducated men, often alcoholics, and tried different strategies to deal with the situation. However, the everyday novels were generally considered simplistic and vulgar. Against that background, the model-like, conceptual nature of Option to Choose became evident and appreciated. Using Phelan’s terms, the novel was now rightly perceived as a didactic rather than mimetic
Galeazzi, Juan M; Navajas, Joaquín; Mender, Bedeho M W; Quian Quiroga, Rodrigo; Minini, Loredana; Stringer, Simon M
2016-01-01
Neurons have been found in the primate brain that respond to objects in specific locations in hand-centered coordinates. A key theoretical challenge is to explain how such hand-centered neuronal responses may develop through visual experience. In this paper we show how hand-centered visual receptive fields can develop using an artificial neural network model, VisNet, of the primate visual system when driven by gaze changes recorded from human test subjects as they completed a jigsaw. A camera mounted on the head captured images of the hand and jigsaw, while eye movements were recorded using an eye-tracking device. This combination of data allowed us to reconstruct the retinal images seen as humans undertook the jigsaw task. These retinal images were then fed into the neural network model during self-organization of its synaptic connectivity using a biologically plausible trace learning rule. A trace learning mechanism encourages neurons in the model to learn to respond to input images that tend to occur in close temporal proximity. In the data recorded from human subjects, we found that the participant's gaze often shifted through a sequence of locations around a fixed spatial configuration of the hand and one of the jigsaw pieces. In this case, trace learning should bind these retinal images together onto the same subset of output neurons. The simulation results consequently confirmed that some cells learned to respond selectively to the hand and a jigsaw piece in a fixed spatial configuration across different retinal views.
Building dynamic spatial environmental models
Karssenberg, D.J.
2003-01-01
An environmental model is a representation or imitation of complex natural phenomena that can be discerned by human cognitive processes. This thesis deals with the type of environmental models referred to as dynamic spatial environmental models. The word spatial refers to the geographic domain whi
Dynamical models of the Galaxy
Directory of Open Access Journals (Sweden)
McMillan P.J.
2012-02-01
Full Text Available I discuss the importance of dynamical models for exploiting survey data, focusing on the advantages of “torus” models. I summarize a number of applications of these models to the study of the Milky Way, including the determination of the peculiar Solar velocity and investigation of the Hyades moving group.
Vision Integration Model of Receptive Field and Its Application%感受野视觉特征整合模型及应用
Institute of Scientific and Technical Information of China (English)
章健; 赵冰; 李永强; 常奇峰; 逯鹏
2013-01-01
采用基本ICA模拟视觉感知机制对自然图像分解得到的图像基函数在空间排列上是混乱的,这与视觉生理机制相互矛盾.模拟视皮层感受野间的信息整合机制,建立了新的计算模型.针对基于内容的图像故障区域检测问题,提出了相应的高效率少样本检测算法.首先,以列车正常和故障图像序列作为训练数据,利用拓扑ICA方法学习图像基函数,由此得到的独立分量系数作为神经元响应,然后模拟同步振荡机制选择响应强烈的神经元,输出其对应的内容,最后通过自动对比实现图像故障区域的快速定位.实验结果表明,与传统方法相比较,引入视觉信息整合机制的新模型及其算法能够提高故障检测率.%The visual information in the brain is passed layer by layer. Almost all the visual signals from the retina go through the receptive field of the primary visual cortex (V1 area) and pass on to a more advanced visual cortex after processing. The receptive field of V1 is mainly responsible for extracting the image shape, direction, color and other information, with the spatial domain of locality, time and frequency domain direction and choice, as well as sparse response characteristics. From the view of natural image statistics, Independent Component Analysis (ICA) is one of the main methods to model early computational vision. However, the space arrangement of basic functions (independent components of natural image) decomposed by basic ICA is chaotic and their amplitudes are uncertainty. This decomposition result is contradicted with physiological mechanisms of vision. So, a new computational model is proposed to simulate two important mechanisms of vision which are visual cortex receptive field topology construct and synchronous oscillation among neuron group. To solve the problem of train image fault detection, a new algorithm was proposed based on above compute model. The experiment results show that, the new
DEFF Research Database (Denmark)
Knudsen, Torben
2011-01-01
The purpose with this deliverable 2.5 is to use fresh experimental data for validation and selection of a flow model to be used for control design in WP3-4. Initially the idea was to investigate the models developed in WP2. However, in the project it was agreed to include and focus on a additive...... model turns out not to be useful for prediction of the flow. Moreover, standard Box Jenkins model structures and multiple output auto regressive models proves to be superior as they can give useful predictions of the flow....
Predictive models of forest dynamics.
Purves, Drew; Pacala, Stephen
2008-06-13
Dynamic global vegetation models (DGVMs) have shown that forest dynamics could dramatically alter the response of the global climate system to increased atmospheric carbon dioxide over the next century. But there is little agreement between different DGVMs, making forest dynamics one of the greatest sources of uncertainty in predicting future climate. DGVM predictions could be strengthened by integrating the ecological realities of biodiversity and height-structured competition for light, facilitated by recent advances in the mathematics of forest modeling, ecological understanding of diverse forest communities, and the availability of forest inventory data.
Adams, Neil S.; Bollenbacher, Gary
1992-01-01
This report discusses the development and underlying mathematics of a rigid-body computer model of a proposed cryogenic on-orbit liquid depot storage, acquisition, and transfer spacecraft (COLD-SAT). This model, referred to in this report as the COLD-SAT dynamic model, consists of both a trajectory model and an attitudinal model. All disturbance forces and torques expected to be significant for the actual COLD-SAT spacecraft are modeled to the required degree of accuracy. Control and experimental thrusters are modeled, as well as fluid slosh. The model also computes microgravity disturbance accelerations at any specified point in the spacecraft. The model was developed by using the Boeing EASY5 dynamic analysis package and will run on Apollo, Cray, and other computing platforms.
Invariance of visual operations at the level of receptive fields.
Lindeberg, Tony
2013-01-01
The brain is able to maintain a stable perception although the visual stimuli vary substantially on the retina due to geometric transformations and lighting variations in the environment. This paper presents a theory for achieving basic invariance properties already at the level of receptive fields. Specifically, the presented framework comprises (i) local scaling transformations caused by objects of different size and at different distances to the observer, (ii) locally linearized image deformations caused by variations in the viewing direction in relation to the object, (iii) locally linearized relative motions between the object and the observer and (iv) local multiplicative intensity transformations caused by illumination variations. The receptive field model can be derived by necessity from symmetry properties of the environment and leads to predictions about receptive field profiles in good agreement with receptive field profiles measured by cell recordings in mammalian vision. Indeed, the receptive field profiles in the retina, LGN and V1 are close to ideal to what is motivated by the idealized requirements. By complementing receptive field measurements with selection mechanisms over the parameters in the receptive field families, it is shown how true invariance of receptive field responses can be obtained under scaling transformations, affine transformations and Galilean transformations. Thereby, the framework provides a mathematically well-founded and biologically plausible model for how basic invariance properties can be achieved already at the level of receptive fields and support invariant recognition of objects and events under variations in viewpoint, retinal size, object motion and illumination. The theory can explain the different shapes of receptive field profiles found in biological vision, which are tuned to different sizes and orientations in the image domain as well as to different image velocities in space-time, from a requirement that the
Berg, van den, Aad; Meester, R.; White, Damien
1997-01-01
Consider an ordinary Boolean model, that is, a homogeneous Poisson point process in Rd, where the points are all centres of random balls with i.i.d. radii. Now let these points move around according to i.i.d. stochastic processes. It is not hard to show that at each xed time t we again have a Boolean model with the original distribution. Hence if the original model is supercritical then, for any t, the probability of having an unbounded occupied component at time t equals 1. We show that unde...
Modelling group dynamic animal movement
DEFF Research Database (Denmark)
Langrock, Roland; Hopcraft, J. Grant C.; Blackwell, Paul G.
2014-01-01
Group dynamic movement is a fundamental aspect of many species' movements. The need to adequately model individuals' interactions with other group members has been recognised, particularly in order to differentiate the role of social forces in individual movement from environmental factors. However......, to date, practical statistical methods which can include group dynamics in animal movement models have been lacking. We consider a flexible modelling framework that distinguishes a group-level model, describing the movement of the group's centre, and an individual-level model, such that each individual...... makes its movement decisions relative to the group centroid. The basic idea is framed within the flexible class of hidden Markov models, extending previous work on modelling animal movement by means of multi-state random walks. While in simulation experiments parameter estimators exhibit some bias...
Gabora, Liane
2008-01-01
EVOC (for EVOlution of Culture) is a computer model of culture that enables us to investigate how various factors such as barriers to cultural diffusion, the presence and choice of leaders, or changes in the ratio of innovation to imitation affect the diversity and effectiveness of ideas. It consists of neural network based agents that invent ideas for actions, and imitate neighbors' actions. The model is based on a theory of culture according to which what evolves through culture is not memes or artifacts, but the internal models of the world that give rise to them, and they evolve not through a Darwinian process of competitive exclusion but a Lamarckian process involving exchange of innovation protocols. EVOC shows an increase in mean fitness of actions over time, and an increase and then decrease in the diversity of actions. Diversity of actions is positively correlated with population size and density, and with barriers between populations. Slowly eroding borders increase fitness without sacrificing diver...
Swimmers’ Collective Dynamics Modelization
Ferré Porta, Guillem
2011-01-01
English: We describe a new model in order to study the properties of collections of self-propelled particles swimming in a two-dimensional fluid. Our model consist in two types of particles, the first interacting with each other with a soft potential and thus representing the fluid while the second type are self-propelled particles of biological nature capable of changing its orientation following the velocity field of the fluid. The results of the simulations show how a super-diffusive regim...
Model of THz Magnetization Dynamics
Bocklage, Lars
2016-01-01
Magnetization dynamics can be coherently controlled by THz laser excitation, which can be applied in ultrafast magnetization control and switching. Here, transient magnetization dynamics are calculated for excitation with THz magnetic field pulses. We use the ansatz of Smit and Beljers, to formulate dynamic properties of the magnetization via partial derivatives of the samples free energy density, and extend it to solve the Landau-Lifshitz-equation to obtain the THz transients of the magnetization. The model is used to determine the magnetization response to ultrafast multi- and single-cycle THz pulses. Control of the magnetization trajectory by utilizing the THz pulse shape and polarization is demonstrated. PMID:26956997
Modeling Internet Topology Dynamics
Haddadi, H.; Uhlig, S.; Moore, A.; Mortier, R.; Rio, M.
Despite the large number of papers on network topology modeling and inference, there still exists ambiguity about the real nature of the Internet AS and router level topology. While recent findings have illustrated the inaccuracies in maps inferred from BGP peering and traceroute measurements, exist
Vehicle dynamics modeling and simulation
Schramm, Dieter; Bardini, Roberto
2014-01-01
The authors examine in detail the fundamentals and mathematical descriptions of the dynamics of automobiles. In this context different levels of complexity will be presented, starting with basic single-track models up to complex three-dimensional multi-body models. A particular focus is on the process of establishing mathematical models on the basis of real cars and the validation of simulation results. The methods presented are explained in detail by means of selected application scenarios.
Institute of Scientific and Technical Information of China (English)
张雅荣; 宛涛; 蔡萍; 伊卫东
2012-01-01
Flowering dynamic was observed in test field, pollen viability of Artemisia frigida Willd. Was evaluated with TTC method, and stigma receptivity of Artemisia frigida Willd. Was evaluated with benzidine-H2O2 method. The results showed that flowers in inflorescence of Artemisia frigida Willd. Bloomed from up to down and outer florets bloomed before others, then middle florets bloomed later. The pollen viability of Artemisia frigida Willd. Was lower at initial stage, higher on the 2nd or 3rd day after flowering, and then reduced evidently, but a few pollen viability still existed until inflorescence withered. The life-span of pollen was about 20 days. The stigma receptivity of outer female flowers appeared on the first flowering day, and lasted longer, the highest on the 2nd or 3rd day after flowering. The stigma receptivity of middle flowers appeared latter than the outer female flowers, but the stigma receptivity were highest on the 2nd or 3rd day after flowering and lasted longer. The best stage of stigma receptivity and pollination was on the 2nd or 3rd day after flowering.%在试验地观察了冷蒿的开花动态,用TTC法测定了冷蒿花序花粉的活力,采用联苯胺—过氧化氢法测定了其柱头的可授性.结果表明,冷蒿花序的开花顺序是自上而下的,小花的开放是自外轮至中央小花.冷蒿的花粉活力在盛花期开花之初很低,第2～3d花粉活力较高,随后活力明显下降,但直至其花序枯萎,少量的花粉仍具有部分活力.花粉寿命较长,约为20d.冷蒿边缘雌花柱头的可授性在开花当天就具有,并且持续时间较长,在第2～3d可授性最强.中央两性小花柱头可授性要稍晚于边缘小花,但是在开花后第2～3d可授性也达到最高,其可授性时间也较长.柱头可授性的最佳时期为开花后第2～3d.冷蒿的最佳授粉期在开花后2～3d左右.
Dynamic Characteristics and Models
DEFF Research Database (Denmark)
Pedersen, Lars
2007-01-01
Vibration levels of flooring-systems are generally difficult to predict. Nevertheless an estimate may be needed for flooring-systems that are prone to vibrate to actions of humans in motion (e.g. grandstands, footbridges or long-span office floors). One reason for the difficulties...... and the paper therefore looks into this mechanism which is done by carrying out controlled modal identification tests on a test floor. The paper describes the experimental investigations and the basic principles adopted for modal identification. Since there is an interest in being able to model the scenario...
Directory of Open Access Journals (Sweden)
Bernd Rupp
Full Text Available MHC class II molecules (MHC II play a pivotal role in the cell-surface presentation of antigens for surveillance by T cells. Antigen loading takes place inside the cell in endosomal compartments and loss of the peptide ligand rapidly leads to the formation of a non-receptive state of the MHC molecule. Non-receptiveness hinders the efficient loading of new antigens onto the empty MHC II. However, the mechanisms driving the formation of the peptide inaccessible state are not well understood. Here, a combined approach of experimental site-directed mutagenesis and computational modeling is used to reveal structural features underlying "non-receptiveness." Molecular dynamics simulations of the human MHC II HLA-DR1 suggest a straightening of the α-helix of the β1 domain during the transition from the open to the non-receptive state. The movement is mostly confined to a hinge region conserved in all known MHC molecules. This shift causes a narrowing of the two helices flanking the binding site and results in a closure, which is further stabilized by the formation of a critical hydrogen bond between residues αQ9 and βN82. Mutagenesis experiments confirmed that replacement of either one of the two residues by alanine renders the protein highly susceptible. Notably, loading enhancement was also observed when the mutated MHC II molecules were expressed on the surface of fibroblast cells. Altogether, structural features underlying the non-receptive state of empty HLA-DR1 identified by theoretical means and experiments revealed highly conserved residues critically involved in the receptiveness of MHC II. The atomic details of rearrangements of the peptide-binding groove upon peptide loss provide insight into structure and dynamics of empty MHC II molecules and may foster rational approaches to interfere with non-receptiveness. Manipulation of peptide loading efficiency for improved peptide vaccination strategies could be one of the applications profiting
Energy Technology Data Exchange (ETDEWEB)
Pfeffer, A; Das, S; Lawless, D; Ng, B
2006-10-10
Many dynamic systems involve a number of entities that are largely independent of each other but interact with each other via a subset of state variables. We present global/local dynamic models (GLDMs) to capture these kinds of systems. In a GLDM, the state of an entity is decomposed into a globally influenced state that depends on other entities, and a locally influenced state that depends only on the entity itself. We present an inference algorithm for GLDMs called global/local particle filtering, that introduces the principle of reasoning globally about global dynamics and locally about local dynamics. We have applied GLDMs to an asymmetric urban warfare environment, in which enemy units form teams to attack important targets, and the task is to detect such teams as they form. Experimental results for this application show that global/local particle filtering outperforms ordinary particle filtering and factored particle filtering.
A dynamical model of terrorism
Directory of Open Access Journals (Sweden)
Firdaus Udwadia
2006-01-01
Full Text Available This paper develops a dynamical model of terrorism. We consider the population in a given region as being made up of three primary components: terrorists, those susceptible to both terrorist and pacifist propaganda, and nonsusceptibles, or pacifists. The dynamical behavior of these three populations is studied using a model that incorporates the effects of both direct military/police intervention to reduce the terrorist population, and nonviolent, persuasive intervention to influence the susceptibles to become pacifists. The paper proposes a new paradigm for studying terrorism, and looks at the long-term dynamical evolution in time of these three population components when such interventions are carried out. Many important features—some intuitive, others not nearly so—of the nature of terrorism emerge from the dynamical model proposed, and they lead to several important policy implications for the management of terrorism. The different circumstances in which nonviolent intervention and/or military/police intervention may be beneficial, and the specific conditions under which each mode of intervention, or a combination of both, may be useful, are obtained. The novelty of the model presented herein is that it deals with the time evolution of terrorist activity. It appears to be one of the few models that can be tested, evaluated, and improved upon, through the use of actual field data.
2009-01-01
At a reception on 28 January, the CERN management presented their best wishes for 2009 to politicians and representatives of the administrations in the local area, and diplomats representing CERN’s Member States, Observer States and other countries.
Experimental Modeling of Dynamic Systems
DEFF Research Database (Denmark)
Knudsen, Morten Haack
2006-01-01
An engineering course, Simulation and Experimental Modeling, has been developed that is based on a method for direct estimation of physical parameters in dynamic systems. Compared with classical system identification, the method appears to be easier to understand, apply, and combine with physical...
Nonlinear Dynamic Model Explains The Solar Dynamic
Kuman, Maria
Nonlinear mathematical model in torus representation describes the solar dynamic. Its graphic presentation shows that without perturbing force the orbits of the planets would be circles; only perturbing force could elongate the circular orbits into ellipses. Since the Hubble telescope found that the planetary orbits of other stars in the Milky Way are also ellipses, powerful perturbing force must be present in our galaxy. Such perturbing force is the Sagittarius Dwarf Galaxy with its heavy Black Hole and leftover stars, which we see orbiting around the center of our galaxy. Since observations of NASA's SDO found that magnetic fields rule the solar activity, we can expect when the planets align and their magnetic moments sum up, the already perturbed stars to reverse their magnetic parity (represented graphically as periodic looping through the hole of the torus). We predict that planets aligned on both sides of the Sun, when their magnetic moments sum-up, would induce more flares in the turbulent equatorial zone, which would bulge. When planets align only on one side of the Sun, the strong magnetic gradient of their asymmetric pull would flip the magnetic poles of the Sun. The Sun would elongate pole-to-pole, emit some energy through the poles, and the solar activity would cease. Similar reshaping and emission was observed in stars called magnetars and experimentally observed in super-liquid fast-spinning Helium nanodroplets. We are certain that NASA's SDO will confirm our predictions.
Directory of Open Access Journals (Sweden)
Florian Ion Tiberiu Petrescu
2016-03-01
Full Text Available Otto engine dynamics are similar in almost all common internal combustion engines. We can speak so about dynamics of engines: Lenoir, Otto, and Diesel. The dynamic presented model is simple and original. The first thing necessary in the calculation of Otto engine dynamics, is to determine the inertial mass reduced at the piston. One uses then the Lagrange equation. Kinetic energy conservation shows angular speed variation (from the shaft with inertial masses. One uses and elastic constant of the crank shaft, k. Calculations should be made for an engine with a single cylinder. Finally it makes a dynamic analysis of the mechanism with discussion and conclusions. The ratio between the crank length r and the length of the connecting-rod l is noted with landa. When landa increases the mechanism dynamics is deteriorating. For a proper operation is necessary the reduction of the ratio landa, especially if we want to increase the engine speed. We can reduce the acceleration values by reducing the dimensions r and l.
Losada Rodríguez, Juan Manuel; Herrero Romero, María
2012-01-01
Background and Aims Stigmatic receptivity plays a clear role in pollination dynamics; however, little is known about the factors that confer to a stigma the competence to be receptive for the germination of pollen grains. In this work, a developmental approach is used to evaluate the acquisition of stigmatic receptivity and its relationship with a possible change in arabinogalactan-proteins (AGPs). Methods Flowers of the domestic apple, Malus × domestica, were assessed for their capacity ...
Business model dynamics and innovation
DEFF Research Database (Denmark)
Cavalcante, Sergio Andre; Kesting, Peter; Ulhøi, John Parm
2011-01-01
Purpose – This paper aims to discuss the need to dynamize the existing conceptualization of business model, and proposes a new typology to distinguish different types of business model change. Design/methodology/approach – The paper integrates basic insights of innovation, business process...... and routine research into the concept of business model. The main focus of the paper is on strategic and terminological issues. Findings – The paper offers a new, process-based conceptualization of business model, which recognizes and integrates the role of individual agency. Based on this, it distinguishes...... and specifies four different types of business model change: business model creation, extension, revision, and termination. Each type of business model change is associated with specific challenges. Practical implications – The proposed typology can serve as a basis for developing a management tool to evaluate...
DYNAMIC TEACHING RATIO PEDAGOGIC MODEL
Directory of Open Access Journals (Sweden)
Chen Jiaying
2010-11-01
Full Text Available This paper outlines an innovative pedagogic model, Dynamic Teaching Ratio (DTR Pedagogic Model, for learning design and teaching strategy aimed at the postsecondary technical education. The model draws on the theory of differential learning, which is widely recognized as an important tool for engaging students and addressing the individual needs of all students. The DTR model caters to the different abilities, interest or learning needs of students and provides different learning approaches based on a student’s learning ability. The model aims to improve students’ academic performance through increasing the lecturer-to-student ratio in the classroom setting. An experimental case study on the model was conducted and the outcome was favourable. Hence, a large-scale implementation was carried out upon the successful trial run. The paper discusses the methodology of the model and its application through the case study and the large-scale implementation.
DYNAMIC MODELING OF METAMORPHIC MECHANISM
Institute of Scientific and Technical Information of China (English)
无
2003-01-01
The concept of metamorphic mechanism is put forward according to the change of configurations from one state to another. Different configurations of metamorphic mechanism are described through the method of Huston lower body arrays. Kinematics analyses for metamorphic mechanism with generalized topological structure, including the velocity, angular velocity, acceleration and angular acceleration, are given. Dynamic equations for an arbitrary configuration, including close-loop constraints, are formed by using Kane's equations. For an arbitrary metamorphic mechanism, the transformation matrix of generalized speeds between configuration (*)and(*)+1 is obtained for the first time. Furthermore, configuration-complete dynamic modeling of metamorphic mechanism including all configurations is completely established.
Stochastic Model of Microtubule Dynamics
Hryniv, Ostap; Martínez Esteban, Antonio
2017-10-01
We introduce a continuous time stochastic process on strings made of two types of particle, whose dynamics mimics that of microtubules in a living cell. The long term behaviour of the system is described in terms of the velocity v of the string end. We show that v is an analytic function of its parameters and study its monotonicity properties. We give a complete characterisation of the phase diagram of the model and derive several criteria of the growth (v>0) and the shrinking (v<0) regimes of the dynamics.
Dynamical Modelling of Meteoroid Streams
Clark, David; Wiegert, P. A.
2012-10-01
Accurate simulations of meteoroid streams permit the prediction of stream interaction with Earth, and provide a measure of risk to Earth satellites and interplanetary spacecraft. Current cometary ejecta and meteoroid stream models have been somewhat successful in predicting some stream observations, but have required questionable assumptions and significant simplifications. Extending on the approach of Vaubaillon et al. (2005)1, we model dust ejection from the cometary nucleus, and generate sample particles representing bins of distinct dynamical evolution-regulating characteristics (size, density, direction, albedo). Ephemerides of the sample particles are integrated and recorded for later assignment of frequency based on model parameter changes. To assist in model analysis we are developing interactive software to permit the “turning of knobs” of model parameters, allowing for near-real-time 3D visualization of resulting stream structure. With this tool, we will revisit prior assumptions made, and will observe the impact of introducing non-uniform cometary surface attributes and temporal activity. The software uses a single model definition and implementation throughout model verification, sample particle bin generation and integration, and analysis. It supports the adjustment with feedback of both independent and independent model values, with the intent of providing an interface supporting multivariate analysis. Propagations of measurement uncertainties and model parameter precisions are tracked rigorously throughout. We maintain a separation of the model itself from the abstract concepts of model definition, parameter manipulation, and real-time analysis and visualization. Therefore we are able to quickly adapt to fundamental model changes. It is hoped the tool will also be of use in other solar system dynamics problems. 1 Vaubaillon, J.; Colas, F.; Jorda, L. (2005) A new method to predict meteor showers. I. Description of the model. Astronomy and
Dynamic Model of Mesoscale Eddies
Dubovikov, Mikhail S.
2003-04-01
Oceanic mesoscale eddies which are analogs of well known synoptic eddies (cyclones and anticyclones), are studied on the basis of the turbulence model originated by Dubovikov (Dubovikov, M.S., "Dynamical model of turbulent eddies", Int. J. Mod. Phys.B7, 4631-4645 (1993).) and further developed by Canuto and Dubovikov (Canuto, V.M. and Dubovikov, M.S., "A dynamical model for turbulence: I. General formalism", Phys. Fluids8, 571-586 (1996a) (CD96a); Canuto, V.M. and Dubovikov, M.S., "A dynamical model for turbulence: II. Sheardriven flows", Phys. Fluids8, 587-598 (1996b) (CD96b); Canuto, V.M., Dubovikov, M.S., Cheng, Y. and Dienstfrey, A., "A dynamical model for turbulence: III. Numerical results", Phys. Fluids8, 599-613 (1996c)(CD96c); Canuto, V.M., Dubovikov, M.S. and Dienstfrey, A., "A dynamical model for turbulence: IV. Buoyancy-driven flows", Phys. Fluids9, 2118-2131 (1997a) (CD97a); Canuto, V.M. and Dubovikov, M.S., "A dynamical model for turbulence: V. The effect of rotation", Phys. Fluids9, 2132-2140 (1997b) (CD97b); Canuto, V.M., Dubovikov, M.S. and Wielaard, D.J., "A dynamical model for turbulence: VI. Two dimensional turbulence", Phys. Fluids9, 2141-2147 (1997c) (CD97c); Canuto, V.M. and Dubovikov, M.S., "Physical regimes and dimensional structure of rotating turbulence", Phys. Rev. Lett. 78, 666-669 (1997d) (CD97d); Canuto, V.M., Dubovikov, M.S. and Dienstfrey, A., "Turbulent convection in a spectral model", Phys. Rev. Lett. 78, 662-665 (1997e) (CD97e); Canuto, V.M. and Dubovikov, M.S., "A new approach to turbulence", Int. J. Mod. Phys.12, 3121-3152 (1997f) (CD97f); Canuto, V.M. and Dubovikov, M.S., "Two scaling regimes for rotating Raleigh-Benard convection", Phys. Rev. Letters78, 281-284, (1998) (CD98); Canuto, V.M. and Dubovikov, M.S., "A dynamical model for turbulence: VII. The five invariants for shear driven flows", Phys. Fluids11, 659-664 (1999a) (CD99a); Canuto, V.M., Dubovikov, M.S. and Yu, G., "A dynamical model for turbulence: VIII. IR and UV
Dynamic queuing transmission model for dynamic network loading
DEFF Research Database (Denmark)
Raovic, Nevena; Nielsen, Otto Anker; Prato, Carlo Giacomo
2017-01-01
This paper presents a new macroscopic multi-class dynamic network loading model called Dynamic Queuing Transmission Model (DQTM). The model utilizes ‘good’ properties of the Dynamic Queuing Model (DQM) and the Link Transmission Model (LTM) by offering a DQM consistent with the kinematic wave theory...... and allowing for the representation of multiple vehicle classes, queue spillbacks and shock waves. The model assumes that a link is split into a moving part plus a queuing part, and p that traffic dynamics are given by a triangular fundamental diagram. A case-study is investigated and the DQTM is compared...
Relating structure and dynamics in organisation models
Jonkers, C.M.; Treur, J.
To understand how an organisational structure relates to dynamics is an interesting fundamental challenge in the area of social modelling. Specifications of organisational structure usually have a diagrammatic form that abstracts from more detailed dynamics. Dynamic properties of agent systems,
Dynamics Modeling of Heavy Special Driving Simulator
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
Based on the dynamical characteristic parameters of the real vehicle, the modeling approach and procedure of dynamics of vehicles are expatiated. The layout of vehicle dynamics is proposed, and the sub-models of the diesel engine, drivetrain system and vehicle multi-body dynamics are introduced. Finally, the running characteristic data of the virtual and real vehicles are compared, which shows that the dynamics model is similar closely to the real vehicle system.
Enhanced AIS receiver design for satellite reception
Clazzer, Federico; Lázaro, Francisco; Plass, Simon
2016-12-01
The possibility to detect Automatic Identification System (AIS) messages from low earth orbit (LEO) satellites paves the road for a plurality of new and unexplored services. Besides worldwide tracking of vessels, maritime traffic monitoring, analysis of vessel routes employing big data, and oceans monitoring are just few of the fields, where satellite-aided AIS is beneficial. Designed for ship-to-ship communication and collision avoidance, AIS satellite reception performs poorly in regions with a high density of vessels. This calls for the development of advanced satellite AIS receivers able to improve the decoding capabilities. In this context, our contribution focuses on the introduction of a new enhanced AIS receiver design and its performance evaluation. The enhanced receiver makes use of a coherent receiver for the low signal-to-noise ratio (SNR) region, while for medium to high SNRs, a differential Viterbi receiver is used. Additional novelty of our work is in the exploitation of previously decoded packets from one vessel that is still under the LEO reception range, to improve the vessel detection probability. The assessment of the performance against a common receiver is done making the use of a simple and tight model of the medium access (MAC) layer and the multi-packet reception (MPR) matrix for physical layer (PHY) representation. Performance results show the benefits of such enhanced receiver, especially when it is bundled with successive interference cancellation (SIC).
Models of ungulate population dynamics
Directory of Open Access Journals (Sweden)
L. L. Eberhardt
1991-10-01
Full Text Available A useful theory for analyzing ungulate population dynamics is available in the form of equations based on the work of A. J. Lotka. Because the Leslie matrix model yields identical results and is widely known, it is convenient to label the resulting equations as the "Lotka-Leslie" model. The approach is useful for assessing population trends and attempting to predict the outcomes of various management actions. A broad list of applications to large mammals, and two examples specific to caribou are presented with a simple spreadsheet approach to calculations.
Numerical Simulation of Receptivity for a Transition Experiment
Collis, S. Scott; Joslin, R. D. (Technical Monitor)
2000-01-01
The cost of fuel to overcome turbulence induced viscous drag on a commercial airplane constitutes a significant fraction of the operating cost of an airline. Achieving laminar flow and maintaining it over a large portion of the wing can significantly reduce the viscous drag, and hence the cost. Design of such laminar-flow-control wings and their practical operation requires the ability to accurately and reliably predict the transition from laminar to turbulent flow. The transition process begins with the conversion of environmental and surface disturbances into the instability waves of the flow by a process called receptivity. The goal of the current research project has been to improve the prediction of transition through a better understanding of the physics of receptivity. The initial objective of this work was to investigate the specific stability and receptivity characteristics of a particular experimental investigation of boundary layer receptivity at NASA Langley. Some simulation results using direct solutions of the linearized Navier-Stokes equations which modeled this experiment where presented in the 1999 APS DFD meeting. However, based on these initial investigations, it became clear that to cover the vast receptivity parameter space required for a practical transition prediction tool, more efficient methods would be required. Thus, the focus of this research was shifted from modeling this particular experiment to formulating and developing new techniques that could efficiently yet accurately predict receptivity for a wide range of disturbance conditions.
DEFF Research Database (Denmark)
Mathieu, David
to set the question of meaning as a central issue in media studies, an issue that appears to be missing from current understandings of social media in which audiences are often reduced to a single reality or simply ignored as an empirical reality. Knowing about the meanings produced and circulated...... on social media can help us better understand the participatory media culture that has established itself over the past decade. To properly address the question of meaning, however, reception research needs to be adapted to the current media landscape. Taking my point of departure in the multi...... (motivation, comprehension, discrimination, position, implementation) for their relevance and explanatory power in today’s media landscape, suggesting new interpretations and new formulations. A revision of reception research does not only concern the notion of reception itself, but also that of the text...
A Companion to Classical Receptions
Directory of Open Access Journals (Sweden)
A. De Villiers
2012-03-01
Full Text Available This recent addition to the excellent Blackwell Companions series looks at the various forms of classical reception currently being researched as well as those deemed to have future importance. The diversity and volume of the themes and approaches contained in this book are truly impressive. As Hardwick and Stray state in their introduction, this collection “has been constructed on the basis that the activators of reception are many and varied and that we all gain from encountering examples from outside our own immediate areas of knowledge” (p. 4. Throughout the book they stay true to this motto and traditional approaches to classical reception are not given prominence over more recent (sometimes contentious approaches such as film studies, cultural politics and photography. The same goes for the various cultures involved and there is even a chapter on Greek drama in South Africa.
Dynamical model of brushite precipitation
Oliveira, Cristina; Georgieva, Petia; Rocha, Fernando; Ferreira, António; Feyo de Azevedo, Sebastião
2007-07-01
The objectives of this work are twofold. From academic point of view the aim is to build a dynamical macro model to fit the material balance and explain the main kinetic mechanisms that govern the transformation of the hydroxyapatite (HAP) into brushite and the growth of brushite, based on laboratory experiments and collected database. From practical point of view, the aim is to design a reliable process simulator that can be easily imbedded in industrial software for model driven monitoring, optimization and control purposes. Based upon a databank of laboratory measurements of the calcium concentration in solution (on-line) and the particle size distribution (off-line) a reliable dynamical model of the dual nature of brushite particle formation for a range of initial concentrations of the reagents was derived as a system of ordinary differential equations of time. The performance of the model is tested with respect to the predicted evolution of mass of calcium in solution and the average (in mass) particle size along time. Results obtained demonstrate a good agreement between the model time trajectories and the available experimental data for a number of different initial concentrations of reagents.
A rational fraction polynomials model to study vertical dynamic wheel-rail interaction
Correa, N.; Vadillo, E. G.; Santamaria, J.; Gómez, J.
2012-04-01
This paper presents a model designed to study vertical interactions between wheel and rail when the wheel moves over a rail welding. The model focuses on the spatial domain, and is drawn up in a simple fashion from track receptances. The paper obtains the receptances from a full track model in the frequency domain already developed by the authors, which includes deformation of the rail section and propagation of bending, elongation and torsional waves along an infinite track. Transformation between domains was secured by applying a modified rational fraction polynomials method. This obtains a track model with very few degrees of freedom, and thus with minimum time consumption for integration, with a good match to the original model over a sufficiently broad range of frequencies. Wheel-rail interaction is modelled on a non-linear Hertzian spring, and consideration is given to parametric excitation caused by the wheel moving over a sleeper, since this is a moving wheel model and not a moving irregularity model. The model is used to study the dynamic loads and displacements emerging at the wheel-rail contact passing over a welding defect at different speeds.
Dynamic pricing models for electronic business
Indian Academy of Sciences (India)
Y Narahari; C V L Raju; K Ravikumar; Sourabh Shah
2005-04-01
Dynamic pricing is the dynamic adjustment of prices to consumers depending upon the value these customers attribute to a product or service. Today’s digital economy is ready for dynamic pricing; however recent research has shown that the prices will have to be adjusted in fairly sophisticated ways, based on sound mathematical models, to derive the beneﬁts of dynamic pricing. This article attempts to survey different models that have been used in dynamic pricing. We ﬁrst motivate dynamic pricing and present underlying concepts, with several examples, and explain conditions under which dynamic pricing is likely to succeed. We then bring out the role of models in computing dynamic prices. The models surveyed include inventory-based models, data-driven models, auctions, and machine learning. We present a detailed example of an e-business market to show the use of reinforcement learning in dynamic pricing.
Receptivity to alcohol marketing predicts initiation of alcohol use.
Henriksen, Lisa; Feighery, Ellen C; Schleicher, Nina C; Fortmann, Stephen P
2008-01-01
This longitudinal study examined the influence of alcohol advertising and promotions on the initiation of alcohol use. A measure of receptivity to alcohol marketing was developed from research about tobacco marketing. Recall and recognition of alcohol brand names were also examined. Data were obtained from in-class surveys of sixth, seventh, and eighth graders at baseline and 12-month follow-up. Participants who were classified as never drinkers at baseline (n = 1,080) comprised the analysis sample. Logistic regression models examined the association of advertising receptivity at baseline with any alcohol use and current drinking at follow-up, adjusting for multiple risk factors, including peer alcohol use, school performance, risk taking, and demographics. At baseline, 29% of never drinkers either owned or wanted to use an alcohol branded promotional item (high receptivity), 12% students named the brand of their favorite alcohol ad (moderate receptivity), and 59% were not receptive to alcohol marketing. Approximately 29% of adolescents reported any alcohol use at follow-up; 13% reported drinking at least 1 or 2 days in the past month. Never drinkers who reported high receptivity to alcohol marketing at baseline were 77% more likely to initiate drinking by follow-up than those were not receptive. Smaller increases in the odds of alcohol use at follow-up were associated with better recall and recognition of alcohol brand names at baseline. Alcohol advertising and promotions are associated with the uptake of drinking. Prevention programs may reduce adolescents' receptivity to alcohol marketing by limiting their exposure to alcohol ads and promotions and by increasing their skepticism about the sponsors' marketing tactics.
Modelling of the Manifold Filling Dynamics
DEFF Research Database (Denmark)
Hendricks, Elbert; Chevalier, Alain Marie Roger; Jensen, Michael
1996-01-01
Mean Value Engine Models (MVEMs) are dynamic models which describe dynamic engine variable (or state) responses on time scales slightly longer than an engine event. This paper describes a new model of the intake manifold filling dynamics which is simple and easy to calibrate for use in engine con...
Multiscale modeling of pedestrian dynamics
Cristiani, Emiliano; Tosin, Andrea
2014-01-01
This book presents mathematical models and numerical simulations of crowd dynamics. The core topic is the development of a new multiscale paradigm, which bridges the microscopic and macroscopic scales taking the most from each of them for capturing the relevant clues of complexity of crowds. The background idea is indeed that most of the complex trends exhibited by crowds are due to an intrinsic interplay between individual and collective behaviors. The modeling approach promoted in this book pursues actively this intuition and profits from it for designing general mathematical structures susceptible of application also in fields different from the inspiring original one. The book considers also the two most traditional points of view: the microscopic one, in which pedestrians are tracked individually, and the macroscopic one, in which pedestrians are assimilated to a continuum. Selected existing models are critically analyzed. The work is addressed to researchers and graduate students.
DYNAMICAL MODEL OF ELECTROMAGNETIC DRIVE
Directory of Open Access Journals (Sweden)
Trunev A. P.
2016-02-01
Full Text Available The article discusses the dynamic model of the rocket motor electromagnetic type, consisting of a source of electromagnetic waves of radio frequency band and a conical cavity in which electromagnetic waves are excited. The processes of excitation of electromagnetic oscillations in a cavity with conducting walls, as well as the waves of the YangMills field have been investigated. Multi-dimensional transient numerical model describing the processes of establishment of electromagnetic oscillations in a cavity with the conducting wall was created Separately, the case of standing waves in the cavity with conducting walls been tested. It is shown that the oscillation mode in the conducting resonator different from that in an ideal resonator, both in the steady and unsteady processes. The mechanism of formation of traction for the changes in the space-time metric, the contribution of particle currents, the Yang-Mills and electromagnetic field proposed. It is shown that the effect of the Yang-Mills field calls change the dielectric properties of vacuum, which leads to a change in capacitance of the resonator. Developed a dynamic model, which enables optimal traction on a significant number of parameters. It was found that the thrust increases in the Yang-Mills field parameters near the main resonance frequency. In the presence of thermal fluctuations and the Yang-Mills field as well the traction force changes sign, indicating the presence of various oscillation modes
Communication from Goods Reception services
2007-01-01
Members of the personnel are invited to take note that only parcels corresponding to official orders or contracts will be handled at CERN. Individuals are not authorised to have private merchandise delivered to them at CERN and private deliveries will not be accepted by the Goods Reception services. Thank you for your understanding.
Eigenvalue dynamics for multimatrix models
de Mello Koch, Robert; Gossman, David; Nkumane, Lwazi; Tribelhorn, Laila
2017-07-01
By performing explicit computations of correlation functions, we find evidence that there is a sector of the two matrix model defined by the S U (2 ) sector of N =4 super Yang-Mills theory that can be reduced to eigenvalue dynamics. There is an interesting generalization of the usual Van der Monde determinant that plays a role. The observables we study are the Bogomol'nyi-Prasad-Sommerfield operators of the S U (2 ) sector and include traces of products of both matrices, which are genuine multimatrix observables. These operators are associated with supergravity solutions of string theory.
Eigenvalue Dynamics for Multimatrix Models
Koch, Robert de Mello; Nkumane, Lwazi; Tribelhorn, Laila
2016-01-01
By performing explicit computations of correlation functions, we find evidence that there is a sector of the two matrix model defined by the $SU(2)$ sector of ${\\cal N}=4$ super Yang-Mills theory, that can be reduced to eigenvalue dynamics. There is an interesting generalization of the usual Van der Monde determinant that plays a role. The observables we study are the BPS operators of the $SU(2)$ sector and include traces of products of both matrices, which are genuine multi matrix observables. These operators are associated to supergravity solutions of string theory.
Bayesian Estimation of Categorical Dynamic Factor Models
Zhang, Zhiyong; Nesselroade, John R.
2007-01-01
Dynamic factor models have been used to analyze continuous time series behavioral data. We extend 2 main dynamic factor model variations--the direct autoregressive factor score (DAFS) model and the white noise factor score (WNFS) model--to categorical DAFS and WNFS models in the framework of the underlying variable method and illustrate them with…
Emsellem, E; Bacon, R; Emsellem, Eric; Dejonghe, Herwig; Bacon, Roland
1998-01-01
We present new dynamical models of the S0 galaxy N3115, making use of the available published photometry and kinematics as well as of two-dimensional TIGER spectrography. We first examined the kinematics in the central 40 arcsec in the light of two integral f(E,J) models. Jeans equations were used to constrain the mass to light ratio, and the central dark mass whose existence was suggested by previous studies. The even part of the distribution function was then retrieved via the Hunter & Qian formalism. We thus confirmed that the velocity and dispersion profiles in the central region could be well fit with a two-integral model, given the presence of a central dark mass of ~10^9 Msun. However, no two integral model could fit the h_3 profile around a radius of 25 arcsec where the outer disc dominates the surface brightness distribution. Three integral analytical models were therefore built using a Quadratic Programming technique. These models showed that three integral components do indeed provide a reasona...
Energy Technology Data Exchange (ETDEWEB)
Cipiti, Benjamin B. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2017-03-01
The Co-Decontamination (CoDCon) Demonstration project is designed to test the separation of a mixed U and Pu product from dissolved spent nuclear fuel. The primary purpose of the project is to quantify the accuracy and precision to which a U/Pu mass ratio can be achieved without removing a pure Pu product. The system includes an on-line monitoring system using spectroscopy to monitor the ratios throughout the process. A dynamic model of the CoDCon flowsheet and on-line monitoring system was developed in order to expand the range of scenarios that can be examined for process control and determine overall measurement uncertainty. The model development and initial results are presented here.
Characterizing and modeling citation dynamics
Eom, Young-Ho; 10.1371/journal.pone.0024926
2011-01-01
Citation distributions are crucial for the analysis and modeling of the activity of scientists. We investigated bibliometric data of papers published in journals of the American Physical Society, searching for the type of function which best describes the observed citation distributions. We used the goodness of fit with Kolmogorov-Smirnov statistics for three classes of functions: log-normal, simple power law and shifted power law. The shifted power law turns out to be the most reliable hypothesis for all citation networks we derived, which correspond to different time spans. We find that citation dynamics is characterized by bursts, usually occurring within a few years since publication of a paper, and the burst size spans several orders of magnitude. We also investigated the microscopic mechanisms for the evolution of citation networks, by proposing a linear preferential attachment with time dependent initial attractiveness. The model successfully reproduces the empirical citation distributions and accounts...
基于蛙眼R3细胞感受野模型的运动滤波方法%Motion Filtering by Modelling R3 Cell0s Receptive Field in Frog Eyes
Institute of Scientific and Technical Information of China (English)
李智勇; 何霜; 刘俊敏; 李仁发
2015-01-01
视觉感受野(Visual receptive field)模型作为生物视觉感知计算的基础单元,在整个生物视觉信息加工过程中发挥着重要作用。借鉴具有运动视觉特长的生物感受野特性研究高效的运动视觉计算技术,是一种潜在可行的方法。本文基于蛙眼R3细胞感受野,在高斯差分模型(Difference of Gaussians, DOG)的基础上引入时间和空间各向异性的运动视觉表达方式,提出一种基于蛙眼R3细胞的不对称各向异性感受野(Asymmetric anisotropy receptive field, AARF)模型,表达蛙类视觉系统对运动目标敏感的视觉时空特征。基于该运动视觉模型,进一步提出了一种面向序列图像运动目标分析的蛙眼时空运动滤波算子(Frog-based spatio-temporal motion filter, FSTMF),以实现运动目标准确检测与分析。实验结果表明,该方法具有使序列图像背景模糊、动态目标突显的滤波效果,既符合蛙眼视觉背景模糊而前景清晰的特性,也为下一步运动目标的准确检测实现了高效的预处理。%As a basic unit of biological visual perception computing, the visual receptive field plays a significant role in the whole process of biological visual information processing. It is a potentially feasible method for further study of eﬃcient computing technology based on motion visual characteristic from biological receptive field. Inspired by frog eye0s R3 cell receptive field, this study introduces a spatio-temporal anisotropy motion visual presentation to the difference of Gaussians (DOG) model. Thus, an asymmetric anisotropy receptive field (AARF) model is presented. This model can express frog visual system0s spatio-temporal characteristic which is sensitive to moving visual targets. Based on the motion visual model, a frog-based spatio-temporal motion filter (FSTMF) is further proposed, which aims at accurate moving object detection and analysis in sequential images and videos. The experimental results
Tal Caspi; Wander Lowie
2013-01-01
Many studies have shown that the transfer of receptive L2 vocabulary into production is far from linear, whether production is elicited by a task or spontaneous. The nature and causes of this gap between receptive and productive vocabulary knowledge have been widely debated. This article attempts a novel approach to this topic by investigating vocabulary knowledge development in a detailed case study. Four knowledge levels of ESL vocabulary are traced across time during a 36-week period of in...
About the Bakhtinian Thought: A Reception of Receptions
Directory of Open Access Journals (Sweden)
Renata Coelho Marchezan
2013-06-01
Full Text Available There are several receptions of the Bakhtinian work: those which situate it in a cultural and historical perspective, making it possible to understand the context inherent to it, the interchanges with which it was instituted and its development paths; those which separately take one or other of its ideas, and those which search to infer a less or more systemized framework from it in order to consider a specific object. When we concentrate on those last ones and on the field of studies about language, we examine the receptions of the Bakhtinian thought as a pragmatics, a sociolinguistics, a semiotics, a social theory, a theory of the discourse. The perspective of this branch of instruction is the one on which we lastly focus in order to reflect upon some of its fundamental basis.
Dynamical Modeling of Mars' Paleoclimate
Richardson, Mark I.
2004-01-01
This report summarizes work undertaken under a one-year grant from the NASA Mars Fundamental Research Program. The goal of the project was to initiate studies of the response of the Martian climate to changes in planetary obliquity and orbital elements. This work was undertaken with a three-dimensional numerical climate model based on the Geophysical Fluid Dynamics Laboratory (GFDL) Skyhi General Circulation Model (GCM). The Mars GCM code was adapted to simulate various obliquity and orbital parameter states. Using a version of the model with a basic water cycle (ice caps, vapor, and clouds), we examined changes in atmospheric water abundances and in the distribution of water ice sheets on the surface. This work resulted in a paper published in the Journal of Geophysical Research - Planets. In addition, the project saw the initial incorporation of a regolith water transport and storage scheme into the model. This scheme allows for interaction between water in the pores of the near subsurface (<3m) and the atmosphere. This work was not complete by the end of the one-year grant, but is now continuing within the auspices of a three-year grant of the same title awarded by the Mars Fundamental Research Program in late 2003.
Wind Farm Decentralized Dynamic Modeling With Parameters
DEFF Research Database (Denmark)
Soltani, Mohsen; Shakeri, Sayyed Mojtaba; Grunnet, Jacob Deleuran;
2010-01-01
Development of dynamic wind flow models for wind farms is part of the research in European research FP7 project AEOLUS. The objective of this report is to provide decentralized dynamic wind flow models with parameters. The report presents a structure for decentralized flow models with inputs from...
Dynamical model for virus spread
Camelo-Neto, G
1995-01-01
The steady state properties of the mean density population of infected cells in a viral spread is simulated by a general forest fire like cellular automaton model with two distinct populations of cells ( permissive and resistant ones) and studied in the framework of the mean field approximation. Stochastic dynamical ingredients are introduced in this model to mimic cells regeneration (with probability {\\it p}) and to consider infection processes by other means than contiguity (with probability {\\it f}). Simulations are carried on a L \\times L square lattice considering the eight first neighbors. The mean density population of infected cells (D_i) is measured as function of the regeneration probability {\\it p}, and analyzed for small values of the ratio {\\it f/p } and for distinct degrees of the cell resistance. The results obtained by a mean field like approach recovers the simulations results. The role of the resistant parameter R (R \\geq 2) on the steady state properties is investigated and discussed in com...
Characterizing and modeling citation dynamics.
Directory of Open Access Journals (Sweden)
Young-Ho Eom
Full Text Available Citation distributions are crucial for the analysis and modeling of the activity of scientists. We investigated bibliometric data of papers published in journals of the American Physical Society, searching for the type of function which best describes the observed citation distributions. We used the goodness of fit with Kolmogorov-Smirnov statistics for three classes of functions: log-normal, simple power law and shifted power law. The shifted power law turns out to be the most reliable hypothesis for all citation networks we derived, which correspond to different time spans. We find that citation dynamics is characterized by bursts, usually occurring within a few years since publication of a paper, and the burst size spans several orders of magnitude. We also investigated the microscopic mechanisms for the evolution of citation networks, by proposing a linear preferential attachment with time dependent initial attractiveness. The model successfully reproduces the empirical citation distributions and accounts for the presence of citation bursts as well.
Relating structure and dynamics in organisation models
Jonkers, C.M.; Treur, J.
2008-01-01
To understand how an organisational structure relates to dynamics is an interesting fundamental challenge in the area of social modelling. Specifications of organisational structure usually have a diagrammatic form that abstracts from more detailed dynamics. Dynamic properties of agent systems, on t
Modelling the dynamics of youth subcultures
Holme, P; Holme, Petter; Gronlund, Andreas
2005-01-01
What are the dynamics behind youth subcultures such as punk, hippie, or hip-hop cultures? How does the global dynamics of these subcultures relate to the individual's search for a personal identity? We propose a simple dynamical model to address these questions and find that only a few assumptions of the individual's behaviour are necessary to regenerate known features of youth culture.
Dynamic stall model for wind turbine airfoils
DEFF Research Database (Denmark)
Larsen, J.W.; Nielsen, S.R.K.; Krenk, Steen
2007-01-01
A model is presented for aerodynamic lift of wind turbine profiles under dynamic stall. The model combines memory delay effects under attached flow with reduced lift due to flow separation under dynamic stall conditions. The model is based on a backbone curve in the form of the static lift...... conditions, nonstationary effects are included by three mechanisms: a delay of the lift coefficient of fully attached flow via a second-order filter, a delay of the development of separation represented via a first-order filter, and a lift contribution due to leading edge separation also represented via...... during dynamic stall conditions. The proposed model is compared with five other dynamic stall models including, among others, the Beddoes-Leishman model and the ONERA model. It is demonstrated that the proposed model performs equally well or even better than more complicated models and that the included...
Model dynamics for quantum computing
Tabakin, Frank
2017-08-01
A model master equation suitable for quantum computing dynamics is presented. In an ideal quantum computer (QC), a system of qubits evolves in time unitarily and, by virtue of their entanglement, interfere quantum mechanically to solve otherwise intractable problems. In the real situation, a QC is subject to decoherence and attenuation effects due to interaction with an environment and with possible short-term random disturbances and gate deficiencies. The stability of a QC under such attacks is a key issue for the development of realistic devices. We assume that the influence of the environment can be incorporated by a master equation that includes unitary evolution with gates, supplemented by a Lindblad term. Lindblad operators of various types are explored; namely, steady, pulsed, gate friction, and measurement operators. In the master equation, we use the Lindblad term to describe short time intrusions by random Lindblad pulses. The phenomenological master equation is then extended to include a nonlinear Beretta term that describes the evolution of a closed system with increasing entropy. An external Bath environment is stipulated by a fixed temperature in two different ways. Here we explore the case of a simple one-qubit system in preparation for generalization to multi-qubit, qutrit and hybrid qubit-qutrit systems. This model master equation can be used to test the stability of memory and the efficacy of quantum gates. The properties of such hybrid master equations are explored, with emphasis on the role of thermal equilibrium and entropy constraints. Several significant properties of time-dependent qubit evolution are revealed by this simple study.
An immune based dynamic intrusion detection model
Institute of Scientific and Technical Information of China (English)
LI Tao
2005-01-01
With the dynamic description method for self and antigen, and the concept of dynamic immune tolerance for lymphocytes in network-security domain presented in this paper, a new immune based dynamic intrusion detection model (Idid) is proposed. In Idid, the dynamic models and the corresponding recursive equations of the lifecycle of mature lymphocytes, and the immune memory are built. Therefore, the problem of the dynamic description of self and nonself in computer immune systems is solved, and the defect of the low efficiency of mature lymphocyte generating in traditional computer immune systems is overcome. Simulations of this model are performed, and the comparison experiment results show that the proposed dynamic intrusion detection model has a better adaptability than the traditional methods.
Workflow-Based Dynamic Enterprise Modeling
Institute of Scientific and Technical Information of China (English)
黄双喜; 范玉顺; 罗海滨; 林慧萍
2002-01-01
Traditional systems for enterprise modeling and business process control are often static and cannot adapt to the changing environment. This paper presents a workflow-based method to dynamically execute the enterprise model. This method gives an explicit representation of the business process logic and the relationships between the elements involved in the process. An execution-oriented integrated enterprise modeling system is proposed in combination with other enterprise views. The enterprise model can be established and executed dynamically in the actual environment due to the dynamic properties of the workflow model.
Dynamical model of the kinesin protein motor
Nesterov, Alexander I; Ramírez, Mónica F
2016-01-01
We model and simulate the stepping dynamics of the kinesin motor including electric and mechanical forces, environmental noise, and the complicated potentials produced by tracking and neighboring protofilaments. Our dynamical model supports the hand-over-hand mechanism of the kinesin stepping. Our theoretical predictions and numerical simulations include the off-axis displacements of the kinesin heads while the steps are performed. The results obtained are in a good agreement with recent experiments on the kinesin dynamics.
A simplified model of software project dynamics
Ruiz Carreira, Mercedes; Ramos Román, Isabel; Toro Bonilla, Miguel
2001-01-01
The simulation of a dynamic model for software development projects (hereinafter SDPs) helps to investigate the impact of a technological change, of different management policies, and of maturity level of organisations over the whole project. In the beginning of the 1990s, with the appearance of the dynamic model for SDPs by Abdel-Hamid and Madnick [Software Project Dynamics: An Integrated Approach, Prentice-Hall, Englewood Cliffs, NJ, 1991], a significant advance took place in the field of p...
A rational fraction polynomials model to study vertical dynamic wheel-rail interaction
Correa García, Nekane; García Vadillo, Ernesto; Santamaría Manrique, Javier; Gómez López, Josu
2012-01-01
This paper presents a model designed to study vertical interactions between wheel and rail when the wheel moves over a rail welding. The model focuses on the spatial domain, and is drawn up in a simple fashion from track receptances. The paper obtains the receptances from a full track model in the frequency domain already developed by the authors, which includes deformation of the rail section and propagation of bending, elongation and torsional waves along an infinite track. Transformation b...
Explicit models for dynamic software
Bosloper, Ivor; Siljee, Johanneke; Nijhuis, Jos; Nord, R; Medvidovic, N; Krikhaar, R; Khrhaar, R; Stafford, J; Bosch, J
2006-01-01
A key aspect in creating autonomous dynamic software systems is the possibility of reasoning about properties of runtime variability and dynamic behavior, e.g. when and how to reconfigure the system. Currently these properties are often not made explicit in the software architecture. We argue that
Explicit models for dynamic software
Bosloper, Ivor; Siljee, Johanneke; Nijhuis, Jos; Nord, R; Medvidovic, N; Krikhaar, R; Khrhaar, R; Stafford, J; Bosch, J
2006-01-01
A key aspect in creating autonomous dynamic software systems is the possibility of reasoning about properties of runtime variability and dynamic behavior, e.g. when and how to reconfigure the system. Currently these properties are often not made explicit in the software architecture. We argue that h
Comparative dynamics in a health investment model.
Eisenring, C
1999-10-01
The method of comparative dynamics fully exploits the inter-temporal structure of optimal control models. I derive comparative dynamic results in a simplified demand for health model. The effect of a change in the depreciation rate on the optimal paths for health capital and investment in health is studied by use of a phase diagram.
Dynamic Heat Transfer Model of Refrigerated Foodstuff
DEFF Research Database (Denmark)
Cai, Junping; Risum, Jørgen; Thybo, Claus
2006-01-01
their temperature relation. This paper discusses the dynamic heat transfer model of foodstuff inside the display cabinet, one-dimensional dynamic model is developed, and the Explicit Finite Difference Method is applied, to handle the unsteady heat transfer problem with phase change, as well as time varying boundary...
System dynamics modelling of situation awareness
CSIR Research Space (South Africa)
Oosthuizen, R
2015-11-01
Full Text Available . The feedback loops and delays in the Command and Control system also contribute to the complex dynamic behavior. This paper will build on existing situation awareness models to develop a System Dynamics model to support a qualitative investigation through...
The Challenges to Coupling Dynamic Geospatial Models
Energy Technology Data Exchange (ETDEWEB)
Goldstein, N
2006-06-23
Many applications of modeling spatial dynamic systems focus on a single system and a single process, ignoring the geographic and systemic context of the processes being modeled. A solution to this problem is the coupled modeling of spatial dynamic systems. Coupled modeling is challenging for both technical reasons, as well as conceptual reasons. This paper explores the benefits and challenges to coupling or linking spatial dynamic models, from loose coupling, where information transfer between models is done by hand, to tight coupling, where two (or more) models are merged as one. To illustrate the challenges, a coupled model of Urbanization and Wildfire Risk is presented. This model, called Vesta, was applied to the Santa Barbara, California region (using real geospatial data), where Urbanization and Wildfires occur and recur, respectively. The preliminary results of the model coupling illustrate that coupled modeling can lead to insight into the consequences of processes acting on their own.
Hydration dynamics near a model protein surface
Energy Technology Data Exchange (ETDEWEB)
Russo, Daniela; Hura, Greg; Head-Gordon, Teresa
2003-09-01
The evolution of water dynamics from dilute to very high concentration solutions of a prototypical hydrophobic amino acid with its polar backbone, N-acetyl-leucine-methylamide (NALMA), is studied by quasi-elastic neutron scattering and molecular dynamics simulation for both the completely deuterated and completely hydrogenated leucine monomer. We observe several unexpected features in the dynamics of these biological solutions under ambient conditions. The NALMA dynamics shows evidence of de Gennes narrowing, an indication of coherent long timescale structural relaxation dynamics. The translational water dynamics are analyzed in a first approximation with a jump diffusion model. At the highest solute concentrations, the hydration water dynamics is significantly suppressed and characterized by a long residential time and a slow diffusion coefficient. The analysis of the more dilute concentration solutions takes into account the results of the 2.0M solution as a model of the first hydration shell. Subtracting the first hydration layer based on the 2.0M spectra, the translational diffusion dynamics is still suppressed, although the rotational relaxation time and residential time are converged to bulk-water values. Molecular dynamics analysis shows spatially heterogeneous dynamics at high concentration that becomes homogeneous at more dilute concentrations. We discuss the hydration dynamics results of this model protein system in the context of glassy systems, protein function, and protein-protein interfaces.
Active vision and receptive field development in evolutionary robots.
Floreano, Dario; Suzuki, Mototaka; Mattiussi, Dario
2005-01-01
In this paper, we describe the artificial evolution of adaptive neural controllers for an outdoor mobile robot equipped with a mobile camera. The robot can dynamically select the gazing direction by moving the body and/or the camera. The neural control system, which maps visual information to motor commands, is evolved online by means of a genetic algorithm, but the synaptic connections (receptive fields) from visual photoreceptors to internal neurons can also be modified by Hebbian plasticity while the robot moves in the environment. We show that robots evolved in physics-based simulations with Hebbian visual plasticity display more robust adaptive behavior when transferred to real outdoor environments as compared to robots evolved without visual plasticity. We also show that the formation of visual receptive fields is significantly and consistently affected by active vision as compared to the formation of receptive fields with grid sample images in the environment of the robot. Finally, we show that the interplay between active vision and receptive field formation amounts to the selection and exploitation of a small and constant subset of visual features available to the robot.
Dynamic Factor Models for the Volatility Surface
DEFF Research Database (Denmark)
van der Wel, Michel; Ozturk, Sait R.; Dijk, Dick van
The implied volatility surface is the collection of volatilities implied by option contracts for different strike prices and time-to-maturity. We study factor models to capture the dynamics of this three-dimensional implied volatility surface. Three model types are considered to examine desirable...... features for representing the surface and its dynamics: a general dynamic factor model, restricted factor models designed to capture the key features of the surface along the moneyness and maturity dimensions, and in-between spline-based methods. Key findings are that: (i) the restricted and spline......-based models are both rejected against the general dynamic factor model, (ii) the factors driving the surface are highly persistent, (iii) for the restricted models option Delta is preferred over the more often used strike relative to spot price as measure for moneyness....
Comprehensive Survey on Dynamic Graph Models
Directory of Open Access Journals (Sweden)
Aya Zaki
2016-02-01
Full Text Available Most of the critical real-world networks are con-tinuously changing and evolving with time. Motivated by the growing importance and widespread impact of this type of networks, the dynamic nature of these networks have gained a lot of attention. Because of their intrinsic and special characteristics, these networks are best represented by dynamic graph models. To cope with their evolving nature, the representation model must keep the historical information of the network along with its temporal time. Storing such amount of data, poses many problems from the perspective of dynamic graph data management. This survey provides an in-depth overview on dynamic graph related problems. Novel categorization and classification of the state of the art dynamic graph models are also presented in a systematic and comprehensive way. Finally, we discuss dynamic graph processing including the output representation of its algorithms.
Modelling the dynamics of turbulent floods
Mei, Z; Li, Z; Li, Zhenquan
1999-01-01
Consider the dynamics of turbulent flow in rivers, estuaries and floods. Based on the widely used k-epsilon model for turbulence, we use the techniques of centre manifold theory to derive dynamical models for the evolution of the water depth and of vertically averaged flow velocity and turbulent parameters. This new model for the shallow water dynamics of turbulent flow: resolves the vertical structure of the flow and the turbulence; includes interaction between turbulence and long waves; and gives a rational alternative to classical models for turbulent environmental flows.
Flapping Wing Flight Dynamic Modeling
2011-08-22
von Karman, T. and Burgers, J. M., Gerneral Aerodynamic Theory - Perfect Fluids , Vol. II, Julius Springer , Berlin, 1935. [24] Pesavento, U. and Wang...L., Methods of Analytical Dynamics , McGraw-Hill Book Company, New York, 1970. [34] Deng, X., Schenato, L., Wu, W. C., and Sastry, S. S., Flapping...Micro air vehicle- motivated computational biomechanics in bio ights: aerodynamics, ight dynamics and maneuvering stability, Acta Mechanica
Institute of Scientific and Technical Information of China (English)
孔韦韦; 雷英杰; 雷阳; 李卫忠
2011-01-01
To the multi-sensor image fusion problem,a technique for image fusion based on non-subsampled contourlet transform（NSCT） domain receptive field model is presented.Firstly,by using NSCT,multi-scale and multi-direction sparse decomposition of source images are performed.Then,an improved receptive field model is utilized to achieve the fusion of the low frequency sub-images.In addition,the course of the high frequency sub-images fusion can be completed by using the model of adaptive unit-fast-linking pulse coupled neural network.Finally,the final fused image can be gained by adopting inverse NSCT to all sub-images.The simulation experimental results show the effectiveness of the proposed technique.%针对多传感器图像融合问题,提出了一种基于非下采样轮廓波变换域感受野模型的图像融合方法.首先,采用非下采样轮廓波变换对源图像进行多尺度、多方向稀疏分解;然后,对低频子图像采用改进型感受野模型进行融合,高频子图像则采用自适应Unit-Fast-Linking脉冲耦合神经网络模型进行融合;最后,将各子图像进行非下采样轮廓波逆变换,得到最终融合图像.仿真实验表明了所提出方法的有效性.
Institute of Scientific and Technical Information of China (English)
徐建武; 王红星; 孙晓明; 刘军
2012-01-01
In single-beam transmission and reception free-space optical communication (FSO) systems, the intensity scintillation obeys the negative exponential distribution in weak turbulence while in strong turbulence it obeys logarithm normal distribution, which is universally accepted at present. Because the Gamma-Gamma distribution can describe both weak turbulence and strong turbulence, it becomes the hot spot recently. By extending them to multiple-beam transmission and reception FSO systems, the intensity scintillation's probability density distribution functions are deduced and the channel models are established based on these distributions respectively. At last, the analysis of the influences of communication range, laser wavelength, receiving aperture as well as transmission and receiving antenna numbers on the channel model based on the negative exponential distribution and the simulations are detailedly done. All of these benefit theoretical research and design of the multiple-beam transmission and reception FSO systems.%在单光束发射和接收无线光通信(FSO)系统中,目前人们普遍接受的是光强闪烁在强湍流下服从负指数分布,在弱湍流下服从对数正态分布,而在强弱湍流下都适用的Gamma-Gamma分布则是研究的热点.在这几种分布的基础上,将它们推广到多光束发射和接收FSO系统,分别推导出了基于对数正态分布、负指数分布以及Gamma-Gamma分布的多光束发射和接收FSO系统的光强闪烁概率密度分布函数,建立起多光束发射和接收系统光强闪烁信道模型,并对基于负指数分布的多光束信道模型与通信距离、激光波长、接收孔径以及收发天线数目等参数的相互关系进行了具体的仿真分析.这对多光束发射和接收FSO系统的理论分析和系统设计具有一定的指导意义.
Modeling Mitochondrial Bioenergetics with Integrated Volume Dynamics
Bazil, Jason N.; Buzzard, Gregery T.; Ann E Rundell
2010-01-01
Author Summary Mathematically modeling biological systems challenges our current understanding of the physical and biochemical events contributing to the observed dynamics. It requires careful consideration of hypothesized mechanisms, model development assumptions and details regarding the experimental conditions. We have adopted a modeling approach to translate these factors that explicitly considers the thermodynamic constraints, biochemical states and reaction mechanisms during model devel...
Dynamical CP violation in composite Higgs models
Hashimoto, S.; Inagaki, Tomohiro; Muta, Taizo
1993-01-01
The dynamical origin of the CP violation in electroweak theory is investigated in composite Higgs models. The mechanism of the spontaneous CP violation proposed in other context by Dashen is adopted to construct simple models of the dynamical CP violation. Within the models the size of the neutron electric dipole moment is estimated and the constraint on the $\\varepsilon$-parameter in K-meson decays is discussed.
Very Large System Dynamics Models - Lessons Learned
Energy Technology Data Exchange (ETDEWEB)
Jacob J. Jacobson; Leonard Malczynski
2008-10-01
This paper provides lessons learned from developing several large system dynamics (SD) models. System dynamics modeling practice emphasize the need to keep models small so that they are manageable and understandable. This practice is generally reasonable and prudent; however, there are times that large SD models are necessary. This paper outlines two large SD projects that were done at two Department of Energy National Laboratories, the Idaho National Laboratory and Sandia National Laboratories. This paper summarizes the models and then discusses some of the valuable lessons learned during these two modeling efforts.
Comparing models of Red Knot population dynamics
McGowan, Conor
2015-01-01
Predictive population modeling contributes to our basic scientific understanding of population dynamics, but can also inform management decisions by evaluating alternative actions in virtual environments. Quantitative models mathematically reflect scientific hypotheses about how a system functions. In Delaware Bay, mid-Atlantic Coast, USA, to more effectively manage horseshoe crab (Limulus polyphemus) harvests and protect Red Knot (Calidris canutus rufa) populations, models are used to compare harvest actions and predict the impacts on crab and knot populations. Management has been chiefly driven by the core hypothesis that horseshoe crab egg abundance governs the survival and reproduction of migrating Red Knots that stopover in the Bay during spring migration. However, recently, hypotheses proposing that knot dynamics are governed by cyclical lemming dynamics garnered some support in data analyses. In this paper, I present alternative models of Red Knot population dynamics to reflect alternative hypotheses. Using 2 models with different lemming population cycle lengths and 2 models with different horseshoe crab effects, I project the knot population into the future under environmental stochasticity and parametric uncertainty with each model. I then compare each model's predictions to 10 yr of population monitoring from Delaware Bay. Using Bayes' theorem and model weight updating, models can accrue weight or support for one or another hypothesis of population dynamics. With 4 models of Red Knot population dynamics and only 10 yr of data, no hypothesis clearly predicted population count data better than another. The collapsed lemming cycle model performed best, accruing ~35% of the model weight, followed closely by the horseshoe crab egg abundance model, which accrued ~30% of the weight. The models that predicted no decline or stable populations (i.e. the 4-yr lemming cycle model and the weak horseshoe crab effect model) were the most weakly supported.
A Stochastic Cobweb Dynamical Model
Directory of Open Access Journals (Sweden)
Serena Brianzoni
2008-01-01
_,__0__1, and the forward predictor with probability (1−, so that the expected price at time is a random variable and consequently the dynamics describing the price evolution in time is governed by a stochastic dynamical system. The dynamical system becomes a Markov process when the memory rate vanishes. In particular, we study the Markov chain in the cases of discrete and continuous time. Using a mixture of analytical tools and numerical methods, we show that, when prices take discrete values, the corresponding Markov chain is asymptotically stable. In the case with continuous prices and nonnecessarily zero memory rate, numerical evidence of bounded price oscillations is shown. The role of the memory rate is studied through numerical experiments, this study confirms the stabilizing effects of the presence of resistant memory.
Modeling the Dynamics of an Information System
Directory of Open Access Journals (Sweden)
Jacek Unold
2003-11-01
Full Text Available The article concentrates on the nature of a social subsystem of an information system. It analyzes the nature of information processes of collectivity within an IS and introduces a model of IS dynamics. The model is based on the assumption that a social subsystem of an information system works as a nonlinear dynamic system. The model of IS dynamics is verified on the indexes of the stock market. It arises from the basic assumption of the technical analysis of the markets, that is, the index chart reflects the play of demand and supply, which in turn represents the crowd sentiment on the market.
Structural Dynamics Model of a Cartesian Robot
1985-10-01
34 D FILE COPY AD-A198 053 *.CC Technical Report 1009 Structural Dynamics Model of a Cartesian Robot "DTIC SELEC T E 0 Alfonso Garcia Reynoso MIT...COVERED Structural Dynamics Model of a Cartesian Robot technical report G. PERFORMING ORG. REPORT NUM9ER 7. AUTHO0R(@) S. CONTRACT On GRANT NUMSER...8217 %S S Structural Dynamics Model of a Cartesian Robot by Alfonso Garcia Reynoso BSME Instituto Tecnol6gico de Veracruz (1967) MSME Instituto Tecnol6gico
Equivalent dynamic model of DEMES rotary joint
Zhao, Jianwen; Wang, Shu; Xing, Zhiguang; McCoul, David; Niu, Junyang; Huang, Bo; Liu, Liwu; Leng, Jinsong
2016-07-01
The dielectric elastomer minimum energy structure (DEMES) can realize large angular deformations by a small voltage-induced strain of the dielectric elastomer (DE), so it is a suitable candidate to make a rotary joint for a soft robot. Dynamic analysis is necessary for some applications, but the dynamic response of DEMESs is difficult to model because of the complicated morphology and viscoelasticity of the DE film. In this paper, a method composed of theoretical analysis and experimental measurement is presented to model the dynamic response of a DEMES rotary joint under an alternating voltage. Based on measurements of equivalent driving force and damping of the DEMES, the model can be derived. Some experiments were carried out to validate the equivalent dynamic model. The maximum angle error between model and experiment is greater than ten degrees, but it is acceptable to predict angular velocity of the DEMES, therefore, it can be applied in feedforward-feedback compound control.
Modeling microbial growth and dynamics.
Esser, Daniel S; Leveau, Johan H J; Meyer, Katrin M
2015-11-01
Modeling has become an important tool for widening our understanding of microbial growth in the context of applied microbiology and related to such processes as safe food production, wastewater treatment, bioremediation, or microbe-mediated mining. Various modeling techniques, such as primary, secondary and tertiary mathematical models, phenomenological models, mechanistic or kinetic models, reactive transport models, Bayesian network models, artificial neural networks, as well as agent-, individual-, and particle-based models have been applied to model microbial growth and activity in many applied fields. In this mini-review, we summarize the basic concepts of these models using examples and applications from food safety and wastewater treatment systems. We further review recent developments in other applied fields focusing on models that explicitly include spatial relationships. Using these examples, we point out the conceptual similarities across fields of application and encourage the combined use of different modeling techniques in hybrid models as well as their cross-disciplinary exchange. For instance, pattern-oriented modeling has its origin in ecology but may be employed to parameterize microbial growth models when experimental data are scarce. Models could also be used as virtual laboratories to optimize experimental design analogous to the virtual ecologist approach. Future microbial growth models will likely become more complex to benefit from the rich toolbox that is now available to microbial growth modelers.
Institute of Scientific and Technical Information of China (English)
刘庆富; 邢世其; 代大海; 王雪松
2011-01-01
收发隔离是困扰转发式干扰机研制的瓶颈问题,研究收发同时工作中的收发隔离问题对于解决SAR干扰机中方位向欺骗干扰效果以及对抗脉间波形捷变的SAR(Synthetic Aperture Radar)ECCM(Electronic Counter-Counter Measures)具有重要意义.在此背景下,本文利用数学级数概念建立了同时收发体制下,干扰机收发信号的耦合模型,并结合LFM(Linear Frequency Modulation)信号的时频特性和波形补偿实现了耦合信号中有用信号和干扰分量的滤波分离.基于实测雷达数据的实验验证以及相应的仿真结果均验证了本文方法的有效性.%The isolation between the transmitted signal and the reception one of SAR(Synthetic Aperture Radar) jammer is a bottleneck for many DRFM(Digital Radio Frequency Memory) based jammers. This problem is especially important for SAR azimuth deceptive jamming and also for measures against waveform agile SAR ECCM( Electronic Counter-Couter Measures) where SAR jammers need to receive and transmit signal simultaneously within the same pulse. In order to get the jammer's coupling signal model caused by isolation problem, the mathematical series are employed to describe the specific working process of SAR jammer.Considering the LFM(Linear Frequency Modulation) signal's time-frequency property and its non-ideal waveform in real application,a method to decouple LFM's time-frequency coupling and also to compensate the non-ideal waveform is proposed here,which makes the harmful trans-reception coupling component and the useful received signal much easier to be 'distinguished. This suggests that the jammer's trans-reception isolation problem can be solved in a much easier way now by only employing filtering and other signal processing technologies. Finally, our method is proved both by the simulation and the data analysis to be effective.
Forecasting house prices in the 50 states using Dynamic Model Averaging and Dynamic Model Selection
DEFF Research Database (Denmark)
Bork, Lasse; Møller, Stig Vinther
2015-01-01
We examine house price forecastability across the 50 states using Dynamic Model Averaging and Dynamic Model Selection, which allow for model change and parameter shifts. By allowing the entire forecasting model to change over time and across locations, the forecasting accuracy improves...
Phone Routing using the Dynamic Memory Model
DEFF Research Database (Denmark)
Bendtsen, Claus Nicolaj; Krink, Thiemo
2002-01-01
In earlier studies a genetic algorithm (GA) extended with the dynamic memory model has shown remarkable performance on real-world-like problems. In this paper we experiment with routing in communication networks and show that the dynamic memory GA performs remarkable well compared to ant colony o...
System Dynamics Modelling for a Balanced Scorecard
DEFF Research Database (Denmark)
Nielsen, Steen; Nielsen, Erland Hejn
2008-01-01
Purpose - To construct a dynamic model/framework inspired by a case study based on an international company. As described by the theory, one of the main difficulties of BSC is to foresee the time lag dimension of different types of indicators and their combined dynamic effects. Design/methodology...
Nonlinear dynamic phenomena in the beer model
DEFF Research Database (Denmark)
Mosekilde, Erik; Laugesen, Jakob Lund
2007-01-01
The production-distribution system or "beer game" is one of the most well-known system dynamics models. Notorious for the complex dynamics it produces, the beer game has been used for nearly five decades to illustrate how structure generates behavior and to explore human decision making. Here we...
Note from the Goods Reception services
FI Department
2008-01-01
Members of the personnel are invited to take note that only parcels corresponding to official orders or contracts will be handled at CERN. Individuals are not authorised to have private merchandise delivered to them at CERN and private deliveries will not be accepted by the Goods Reception services. Goods Reception Services
Morning Receptions in a Danish ECE Context
DEFF Research Database (Denmark)
Kornerup, Ida; Gravgaard, Mette Lykke
2017-01-01
This paper focus on a special pedagogical context; morning receptions as a learning environment. The studies of mornings are part of a 3 year long research project in which different types of learning environments were investigated. Few studies have researched morning receptions in this perspecti...
THE AUDIT OF RECEPTION PROCESS
Directory of Open Access Journals (Sweden)
Dorina MOCUŢA
2013-01-01
Full Text Available The object of study case is to analyze the quality of the logistics department, focusing on the audit process. Purpose of this paper is to present the advantages resulting from the systematic audit processes and methods of analysis and improvement of nonconformities found. The case study is realised at SC Miele Tehnica SRL Brasov, twelfth production line, and the fourth from outside Germany. The specific objectives are: clarifying the concept of audit quality, emphasizing requirements ISO 19011:2003 "Guidelines for auditing quality management systems and / or environment" on audits; cchieving quality audit and performance analysis; improved process performance reception materials; compliance with legislation and auditing standards applicable in EU and Romania.
A new dynamics model for traffic flow
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
As a study method of traffic flow, dynamics models were developedand applied in the last few decades. However, there exist some flaws in most existing models. In this note, a new dynamics model is proposed by using car-following theory and the usual connection method of micro-macro variables, which can overcome some ubiquitous problems in the existing models. Numerical results show that the new model can very well simulate traffic flow conditions, such as congestion, evacuation of congestion, stop-and-go phenomena and phantom jam.
MODELING MICROBUBBLE DYNAMICS IN BIOMEDICAL APPLICATIONS
Institute of Scientific and Technical Information of China (English)
CHAHINE Georges L.; HSIAO Chao-Tsung
2012-01-01
Controlling mierobubble dynamics to produce desirable biomedical outcomes when and where necessary and avoid deleterious effects requires advanced knowledge,which can be achieved only through a combination of experimental and numerical/analytical techniques.The present communication presents a multi-physics approach to study the dynamics combining viscousinviseid effects,liquid and structure dynamics,and multi bubble interaction.While complex numerical tools are developed and used,the study aims at identifying the key parameters influencing the dynamics,which need to be included in simpler models.
Airship dynamics modeling: A literature review
Li, Yuwen; Nahon, Meyer; Sharf, Inna
2011-04-01
The resurgence of airships has created a need for dynamics models and simulation capabilities adapted to these lighter-than-air vehicles. However, the modeling techniques for airship dynamics have lagged behind and are less systematic than those for fixed-wing aircraft. A state-of-the-art literature review is presented on airship dynamics modeling, aiming to provide a comprehensive description of the main problems in this area and a useful source of references for researchers and engineers interested in modern airship applications. The references are categorized according to the major topics in this area: aerodynamics, flight dynamics, incorporation of structural flexibility, incorporation of atmospheric turbulence, and effects of ballonets. Relevant analytical, numerical, and semi-empirical techniques are discussed, with a particular focus on how the main differences between lighter-than-air and heavier-than-air aircraft have been addressed in the modeling. Directions are suggested for future research on each of these topics.
Computational fluid dynamics modeling in yarn engineering
CSIR Research Space (South Africa)
Patanaik, A
2011-07-01
Full Text Available This chapter deals with the application of computational fluid dynamics (CFD) modeling in reducing yarn hairiness during the ring spinning process and thereby “engineering” yarn with desired properties. Hairiness significantly affects the appearance...
Molecular dynamics model of dimethyl ether
Energy Technology Data Exchange (ETDEWEB)
Lin, B.; Halley, W.J. [Univ. of Minnesota, Minneapolis, MN (United States)
1995-11-02
We report a molecular dynamics model of the monomeric liquid dimethyl ether. The united atom approach is used to treat CH{sub 3} groups as point source centers. Partial charges are derived from the experimental dipole moment. Harmonic force constants are used for intramolecular interactions, and their values are so chosen that the model`s fundamental frequencies agree with experimental results. Because we are interested in solvation properties, the model contains flexible molecules, allowing molecular distortion and internal dynamical quantities. We report radial distribution functions and the static structure factors as well as some dynamical quantities such as the dynamical structure factor, infrared absorption, and Raman scattering spectra. Calculated results agree reasonably well with experimental and other simulation results. 25 refs., 8 figs., 1 tab.
Stochastic population dynamic models as probability networks
M.E. and D.C. Lee. Borsuk
2009-01-01
The dynamics of a population and its response to environmental change depend on the balance of birth, death and age-at-maturity, and there have been many attempts to mathematically model populations based on these characteristics. Historically, most of these models were deterministic, meaning that the results were strictly determined by the equations of the model and...
System Identification by Dynamic Factor Models
C. Heij (Christiaan); W. Scherrer; M. Destler
1996-01-01
textabstractThis paper concerns the modelling of stochastic processes by means of dynamic factor models. In such models the observed process is decomposed into a structured part called the latent process, and a remainder that is called noise. The observed variables are treated in a symmetric way, so
Damping mechanisms and models in structural dynamics
DEFF Research Database (Denmark)
Krenk, Steen
2002-01-01
Several aspects of damping models for dynamic analysis of structures are investigated. First the causality condition for structural response is used to identify rules for the use of complex-valued frequency dependent material models, illustrated by the shortcomings of the elastic hysteretic model...
Bayesian semiparametric dynamic Nelson-Siegel model
C. Cakmakli
2011-01-01
This paper proposes the Bayesian semiparametric dynamic Nelson-Siegel model where the density of the yield curve factors and thereby the density of the yields are estimated along with other model parameters. This is accomplished by modeling the error distributions of the factors according to a Diric
Probabilistic Modeling in Dynamic Information Retrieval
Sloan, M. C.
2016-01-01
Dynamic modeling is used to design systems that are adaptive to their changing environment and is currently poorly understood in information retrieval systems. Common elements in the information retrieval methodology, such as documents, relevance, users and tasks, are dynamic entities that may evolve over the course of several interactions, which is increasingly captured in search log datasets. Conventional frameworks and models in information retrieval treat these elements as static, or only...
Categorically distinct types of receptive fields in early visual cortex.
Talebi, Vargha; Baker, Curtis L
2016-05-01
In the visual cortex, distinct types of neurons have been identified based on cellular morphology, response to injected current, or expression of specific markers, but neurophysiological studies have revealed visual receptive field (RF) properties that appear to be on a continuum, with only two generally recognized classes: simple and complex. Most previous studies have characterized visual responses of neurons using stereotyped stimuli such as bars, gratings, or white noise and simple system identification approaches (e.g., reverse correlation). Here we estimate visual RF models of cortical neurons using visually rich natural image stimuli and regularized regression system identification methods and characterize their spatial tuning, temporal dynamics, spatiotemporal behavior, and spiking properties. We quantitatively demonstrate the existence of three functionally distinct categories of simple cells, distinguished by their degree of orientation selectivity (isotropic or oriented) and the nature of their output nonlinearity (expansive or compressive). In addition, these three types have differing average values of several other properties. Cells with nonoriented RFs tend to have smaller RFs, shorter response durations, no direction selectivity, and high reliability. Orientation-selective neurons with an expansive output nonlinearity have Gabor-like RFs, lower spontaneous activity and responsivity, and spiking responses with higher sparseness. Oriented RFs with a compressive nonlinearity are spatially nondescript and tend to show longer response latency. Our findings indicate multiple physiologically defined types of RFs beyond the simple/complex dichotomy, suggesting that cortical neurons may have more specialized functional roles rather than lying on a multidimensional continuum.
Identification and Modelling of Linear Dynamic Systems
Directory of Open Access Journals (Sweden)
Stanislav Kocur
2006-01-01
Full Text Available System identification and modelling are very important parts of system control theory. System control is only as good as good is created model of system. So this article deals with identification and modelling problems. There are simple classification and evolution of identification methods, and then the modelling problem is described. Rest of paper is devoted to two most known and used models of linear dynamic systems.
Ovarian fluid of receptive females enhances sperm velocity
Gasparini, Clelia; Andreatta, Gabriele; Pilastro, Andrea
2012-05-01
The females of several internal fertilizers are able to store sperm for a long time, reducing the risk of sperm limitation. However, it also means that males can attempt to mate outside females' receptive period, potentially increasing the level of sperm competition and exacerbating sexual conflict over mating. The guppy ( Poecilia reticulata), an internally fertilizing fish, is a model system of such competition and conflict. Female guppies accept courtship and mate consensually only during receptive periods of the ovarian cycle but receive approximately one (mostly forced) mating attempt per minute both during and outside their sexually receptive phase. In addition, females can store viable sperm for months. We expected that guppy females would disfavour sperm received during their unreceptive period, possibly by modulating the quality and/or quantity of the components present in the ovarian fluid (OF) over the breeding cycle. Ovarian fluid has been shown to affect sperm velocity, a determinant of sperm competition success in this and other fishes. We found that in vitro sperm velocity is slower in OF collected from unreceptive females than in OF from receptive females. Visual stimulation with a potential partner prior to collection did not significantly affect in vitro sperm velocity. These results suggest that sperm received by unreceptive females may be disfavoured as sperm velocity likely affects the migration process and the number of sperm that reach storage sites.
A stochastic model of human gait dynamics
Ashkenazy, Yosef; M. Hausdorff, Jeffrey; Ch. Ivanov, Plamen; Eugene Stanley, H.
2002-12-01
We present a stochastic model of gait rhythm dynamics, based on transitions between different “neural centers”, that reproduces distinctive statistical properties of normal human walking. By tuning one model parameter, the transition (hopping) range, the model can describe alterations in gait dynamics from childhood to adulthood-including a decrease in the correlation and volatility exponents with maturation. The model also generates time series with multifractal spectra whose broadness depends only on this parameter. Moreover, we find that the volatility exponent increases monotonically as a function of the width of the multifractal spectrum, suggesting the possibility of a change in multifractality with maturation.
Integration of Dynamic Models in Range Operations
Bardina, Jorge; Thirumalainambi, Rajkumar
2004-01-01
This work addresses the various model interactions in real-time to make an efficient internet based decision making tool for Shuttle launch. The decision making tool depends on the launch commit criteria coupled with physical models. Dynamic interaction between a wide variety of simulation applications and techniques, embedded algorithms, and data visualizations are needed to exploit the full potential of modeling and simulation. This paper also discusses in depth details of web based 3-D graphics and applications to range safety. The advantages of this dynamic model integration are secure accessibility and distribution of real time information to other NASA centers.
Long-term dynamics simulation: Modeling requirements
Energy Technology Data Exchange (ETDEWEB)
Morched, A.S.; Kar, P.K.; Rogers, G.J.; Morison, G.K. (Ontario Hydro, Toronto, ON (Canada))
1989-12-01
This report details the required performance and modelling capabilities of a computer program intended for the study of the long term dynamics of power systems. Following a general introduction which outlines the need for long term dynamic studies, the modelling requirements for the conduct of such studies is discussed in detail. Particular emphasis is placed on models for system elements not normally modelled in power system stability programs, which will have a significant impact in the long term time frame of minutes to hours following the initiating disturbance. The report concludes with a discussion of the special computational and programming requirements for a long term stability program. 43 refs., 36 figs.
Uncertainty and Sensitivity in Surface Dynamics Modeling
Kettner, Albert J.; Syvitski, James P. M.
2016-05-01
Papers for this special issue on 'Uncertainty and Sensitivity in Surface Dynamics Modeling' heralds from papers submitted after the 2014 annual meeting of the Community Surface Dynamics Modeling System or CSDMS. CSDMS facilitates a diverse community of experts (now in 68 countries) that collectively investigate the Earth's surface-the dynamic interface between lithosphere, hydrosphere, cryosphere, and atmosphere, by promoting, developing, supporting and disseminating integrated open source software modules. By organizing more than 1500 researchers, CSDMS has the privilege of identifying community strengths and weaknesses in the practice of software development. We recognize, for example, that progress has been slow on identifying and quantifying uncertainty and sensitivity in numerical modeling of earth's surface dynamics. This special issue is meant to raise awareness for these important subjects and highlight state-of-the-art progress.
The future dynamic world model
Karr, Thomas J.
2014-10-01
Defense and security forces exploit sensor data by means of a model of the world. They use a world model to geolocate sensor data, fuse it with other data, navigate platforms, recognize features and feature changes, etc. However, their need for situational awareness today exceeds the capabilities of their current world model for defense operations, despite the great advances of sensing technology in recent decades. I review emerging technologies that may enable a great improvement in the spatial and spectral coverage, the timeliness, and the functional insight of their world model.
Brand Equity Evolution: a System Dynamics Model
Directory of Open Access Journals (Sweden)
Edson Crescitelli
2009-04-01
Full Text Available One of the greatest challenges in brand management lies in monitoring brand equity over time. This paper aimsto present a simulation model able to represent this evolution. The model was drawn on brand equity concepts developed by Aaker and Joachimsthaler (2000, using the system dynamics methodology. The use ofcomputational dynamic models aims to create new sources of information able to sensitize academics and managers alike to the dynamic implications of their brand management. As a result, an easily implementable model was generated, capable of executing continuous scenario simulations by surveying casual relations among the variables that explain brand equity. Moreover, the existence of a number of system modeling tools will allow extensive application of the concepts used in this study in practical situations, both in professional and educational settings
Dynamic stiffness model of spherical parallel robots
Cammarata, Alessandro; Caliò, Ivo; D`Urso, Domenico; Greco, Annalisa; Lacagnina, Michele; Fichera, Gabriele
2016-12-01
A novel approach to study the elastodynamics of Spherical Parallel Robots is described through an exact dynamic model. Timoshenko arches are used to simulate flexible curved links while the base and mobile platforms are modelled as rigid bodies. Spatial joints are inherently included into the model without Lagrangian multipliers. At first, the equivalent dynamic stiffness matrix of each leg, made up of curved links joined by spatial joints, is derived; then these matrices are assembled to obtain the Global Dynamic Stiffness Matrix of the robot at a given pose. Actuator stiffness is also included into the model to verify its influence on vibrations and modes. The latter are found by applying the Wittrick-Williams algorithm. Finally, numerical simulations and direct comparison to commercial FE results are used to validate the proposed model.
Stirling Engine Dynamic System Modeling
Nakis, Christopher G.
2004-01-01
The Thermo-Mechanical systems branch at the Glenn Research Center focuses a large amount time on Stirling engines. These engines will be used on missions where solar power is inefficient, especially in deep space. I work with Tim Regan and Ed Lewandowski who are currently developing and validating a mathematical model for the Stirling engines. This model incorporates all aspects of the system including, mechanical, electrical and thermodynamic components. Modeling is done through Simplorer, a program capable of running simulations of the model. Once created and then proven to be accurate, a model is used for developing new ideas for engine design. My largest specific project involves varying key parameters in the model and quantifying the results. This can all be done relatively trouble-free with the help of Simplorer. Once the model is complete, Simplorer will do all the necessary calculations. The more complicated part of this project is determining which parameters to vary. Finding key parameters depends on the potential for a value to be independently altered in the design. For example, a change in one dimension may lead to a proportional change to the rest of the model, and no real progress is made. Also, the ability for a changed value to have a substantial impact on the outputs of the system is important. Results will be condensed into graphs and tables with the purpose of better communication and understanding of the data. With the changing of these parameters, a more optimal design can be created without having to purchase or build any models. Also, hours and hours of results can be simulated in minutes. In the long run, using mathematical models can save time and money. Along with this project, I have many other smaller assignments throughout the summer. My main goal is to assist in the processes of model development, validation and testing.
Haptics-based dynamic implicit solid modeling.
Hua, Jing; Qin, Hong
2004-01-01
This paper systematically presents a novel, interactive solid modeling framework, Haptics-based Dynamic Implicit Solid Modeling, which is founded upon volumetric implicit functions and powerful physics-based modeling. In particular, we augment our modeling framework with a haptic mechanism in order to take advantage of additional realism associated with a 3D haptic interface. Our dynamic implicit solids are semi-algebraic sets of volumetric implicit functions and are governed by the principles of dynamics, hence responding to sculpting forces in a natural and predictable manner. In order to directly manipulate existing volumetric data sets as well as point clouds, we develop a hierarchical fitting algorithm to reconstruct and represent discrete data sets using our continuous implicit functions, which permit users to further design and edit those existing 3D models in real-time using a large variety of haptic and geometric toolkits, and visualize their interactive deformation at arbitrary resolution. The additional geometric and physical constraints afford more sophisticated control of the dynamic implicit solids. The versatility of our dynamic implicit modeling enables the user to easily modify both the geometry and the topology of modeled objects, while the inherent physical properties can offer an intuitive haptic interface for direct manipulation with force feedback.
Synaptic dynamics: linear model and adaptation algorithm.
Yousefi, Ali; Dibazar, Alireza A; Berger, Theodore W
2014-08-01
In this research, temporal processing in brain neural circuitries is addressed by a dynamic model of synaptic connections in which the synapse model accounts for both pre- and post-synaptic processes determining its temporal dynamics and strength. Neurons, which are excited by the post-synaptic potentials of hundred of the synapses, build the computational engine capable of processing dynamic neural stimuli. Temporal dynamics in neural models with dynamic synapses will be analyzed, and learning algorithms for synaptic adaptation of neural networks with hundreds of synaptic connections are proposed. The paper starts by introducing a linear approximate model for the temporal dynamics of synaptic transmission. The proposed linear model substantially simplifies the analysis and training of spiking neural networks. Furthermore, it is capable of replicating the synaptic response of the non-linear facilitation-depression model with an accuracy better than 92.5%. In the second part of the paper, a supervised spike-in-spike-out learning rule for synaptic adaptation in dynamic synapse neural networks (DSNN) is proposed. The proposed learning rule is a biologically plausible process, and it is capable of simultaneously adjusting both pre- and post-synaptic components of individual synapses. The last section of the paper starts with presenting the rigorous analysis of the learning algorithm in a system identification task with hundreds of synaptic connections which confirms the learning algorithm's accuracy, repeatability and scalability. The DSNN is utilized to predict the spiking activity of cortical neurons and pattern recognition tasks. The DSNN model is demonstrated to be a generative model capable of producing different cortical neuron spiking patterns and CA1 Pyramidal neurons recordings. A single-layer DSNN classifier on a benchmark pattern recognition task outperforms a 2-Layer Neural Network and GMM classifiers while having fewer numbers of free parameters and
Dynamics modeling and simulation of flexible airships
Li, Yuwen
The resurgence of airships has created a need for dynamics models and simulation capabilities of these lighter-than-air vehicles. The focus of this thesis is a theoretical framework that integrates the flight dynamics, structural dynamics, aerostatics and aerodynamics of flexible airships. The study begins with a dynamics model based on a rigid-body assumption. A comprehensive computation of aerodynamic effects is presented, where the aerodynamic forces and moments are categorized into various terms based on different physical effects. A series of prediction approaches for different aerodynamic effects are unified and applied to airships. The numerical results of aerodynamic derivatives and the simulated responses to control surface deflection inputs are verified by comparing to existing wind-tunnel and flight test data. With the validated aerodynamics and rigid-body modeling, the equations of motion of an elastic airship are derived by the Lagrangian formulation. The airship is modeled as a free-free Euler-Bernoulli beam and the bending deformations are represented by shape functions chosen as the free-free normal modes. In order to capture the coupling between the aerodynamic forces and the structural elasticity, local velocity on the deformed vehicle is used in the computation of aerodynamic forces. Finally, with the inertial, gravity, aerostatic and control forces incorporated, the dynamics model of a flexible airship is represented by a single set of nonlinear ordinary differential equations. The proposed model is implemented as a dynamics simulation program to analyze the dynamics characteristics of the Skyship-500 airship. Simulation results are presented to demonstrate the influence of structural deformation on the aerodynamic forces and the dynamics behavior of the airship. The nonlinear equations of motion are linearized numerically for the purpose of frequency domain analysis and for aeroelastic stability analysis. The results from the latter for the
Model Reduction of Nonlinear Fire Dynamics Models
Lattimer, Alan Martin
2016-01-01
Due to the complexity, multi-scale, and multi-physics nature of the mathematical models for fires, current numerical models require too much computational effort to be useful in design and real-time decision making, especially when dealing with fires over large domains. To reduce the computational time while retaining the complexity of the domain and physics, our research has focused on several reduced-order modeling techniques. Our contributions are improving wildland fire reduced-order mod...
Lagache, Jean-Marie; Assaf, Samir; Schulte, Christian
2008-02-01
The present study addresses the modal synthesis of dynamic responses or receptances, which can be considered as a major issue in vibratory or acoustic design. A new method termed "method of orthocomplement" offers to increase the accuracy of modal superposition. Two apparently independent domains are considered: first, the numerical control of round-off errors in finite-dimensional models; second, the regularization of modal boundary discontinuities in infinite-dimensional formulations. Concerning the finite-dimensional systems, using the proposed method in conjunction with pseudo-inversion theorems, proves that "inertia relief corrections" remedy modal truncation problems in singular floating systems, just as static corrections do for simply supported systems. The proof is based on hitherto unpublished expressions of inertial contributions in terms of orthogonal projectors. It is worth noting that such expressions present by themselves some technical interest. Modal formulae being delivered in closed form, a thorough analysis of errors becomes possible. Special "spectrograms" are introduced to appraise the convergence of ordinary or modified modal sums. When applied to infinite-dimensional modal boundary discontinuities, the method of orthocomplement eliminates the Gibbs oscillations that affect the ordinary spectral sums, and produces the same corrected formulae as it did for finite-dimensional examples. Effective solutions for the computation of vibratory or acoustic boundary receptances, are developed in that way. The paper once again illustrates how orthogonal projectors can contribute to the determination of static corrections. Future applications to coupling problems, model reduction and modal synthesis are briefly presented at the end of the text.
Forecasting with Dynamic Regression Models
Pankratz, Alan
2012-01-01
One of the most widely used tools in statistical forecasting, single equation regression models is examined here. A companion to the author's earlier work, Forecasting with Univariate Box-Jenkins Models: Concepts and Cases, the present text pulls together recent time series ideas and gives special attention to possible intertemporal patterns, distributed lag responses of output to input series and the auto correlation patterns of regression disturbance. It also includes six case studies.
Online Learning of Industrial Manipulators' Dynamics Models
DEFF Research Database (Denmark)
Polydoros, Athanasios
2017-01-01
The robotics industry has introduced light-weight compliant manipulators to increase the safety during human-robot interaction. This characteristic is achieved by replacing the stiff actuators of the traditional robots with compliant ones which creates challenges in the analytical derivation...... of the dynamics models. Those mainly derive from physics-based methods and thus they are based on physical properties which are hard to be calculated. In this thesis, is presented, a novel online machine learning approach which is able to model both inverse and forward dynamics models of industrial manipulators...
A stochastic evolutionary model for survival dynamics
Fenner, Trevor; Loizou, George
2014-01-01
The recent interest in human dynamics has led researchers to investigate the stochastic processes that explain human behaviour in different contexts. Here we propose a generative model to capture the essential dynamics of survival analysis, traditionally employed in clinical trials and reliability analysis in engineering. In our model, the only implicit assumption made is that the longer an actor has been in the system, the more likely it is to have failed. We derive a power-law distribution for the process and provide preliminary empirical evidence for the validity of the model from two well-known survival analysis data sets.
Cellular automata modeling of pedestrian's crossing dynamics
Institute of Scientific and Technical Information of China (English)
张晋; 王慧; 李平
2004-01-01
Cellular automata modeling techniques and the characteristics of mixed traffic flow were used to derive the 2-dimensional model presented here for simulation of pedestrian's crossing dynamics.A conception of "stop point" is introduced to deal with traffic obstacles and resolve conflicts among pedestrians or between pedestrians and the other vehicles on the crosswalk.The model can be easily extended,is very efficient for simulation of pedestrian's crossing dynamics,can be integrated into traffic simulation software,and has been proved feasible by simulation experiments.
Dynamical modelling of coordinated multiple robot systems
Hayati, Samad
1987-01-01
The state of the art in the modeling of the dynamics of coordinated multiple robot manipulators is summarized and various problems related to this subject are discussed. It is recognized that dynamics modeling is a component used in the design of controllers for multiple cooperating robots. As such, the discussion addresses some problems related to the control of multiple robots. The techniques used to date in the modeling of closed kinematic chains are summarized. Various efforts made to date for the control of coordinated multiple manipulators is summarized.
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.
Quantum Dynamics of the HMF Model
Plestid, Ryan; Mahon, Perry; O'Dell, Duncan
2016-01-01
We study the dynamics of the quantized Hamiltonian Mean Field (HMF) model assuming a gas of bosons in the large N limit. We characterize the full set of stationary states, and study the dynamics of the model numerically focussing on competition between classical and quantum effects. We make contact with the existing literature on the HMF model as a classical system, and stress universal features which can be inferred in the semi-classical limit.In particular we show that the characteristic ch...
Towards Disaggregate Dynamic Travel Forecasting Models
Institute of Scientific and Technical Information of China (English)
Moshe Ben-Akiva; Jon Bottom; Song Gao; Haris N. Koutsopoulos; Yang Wen
2007-01-01
The authors argue that travel forecasting models should be dynamic and disaggregate in their representation of demand, supply, and supply-demand interactions, and propose a framework for such models.The proposed framework consists of disaggregate activity-based representation of travel choices of individual motorists on the demand side integrated with disaggregate dynamic modeling of network performance,through vehicle-based traffic simulation models on the supply side. The demand model generates individual members of the population and assigns to them socioeconomic characteristics. The generated motorists maintain these characteristics when they are loaded on the network by the supply model. In an equilibrium setting, the framework lends itself to a fixed-point formulation to represent and resolve demand-supply interactions. The paper discusses some of the remaining development challenges and presents an example of an existing travel forecasting model system that incorporates many of the proposed elements.
Dynamical effects of overparametrization in nonlinear models
Aguirre, Luis Antonio; Billings, S. A.
1995-01-01
This paper is concemed with dynamical reconstruction for nonlinear systems. The effects of the driving function and of the complexity of a given representation on the bifurcation patter are investigated. It is shown that the use of different driving functions to excite the system may yield models with different bifurcation patterns. The complexity of the reconstructions considered is quantified by the embedding dimension and the number of estimated parameters. In this respect it appears that models which reproduce the original bifurcation behaviour are of limited complexity and that excessively complex models tend to induce ghost bifurcations and spurious dynamical regimes. Moreover, some results suggest that the effects of overparametrization on the global dynamical behaviour of a nonlinear model may be more deleterious than the presence of moderate noise levels. In order to precisely quantify the complexity of the reconstructions, global polynomials are used although the results are believed to apply to a much wider class of representations including neural networks.
Dynamic optimization deterministic and stochastic models
Hinderer, Karl; Stieglitz, Michael
2016-01-01
This book explores discrete-time dynamic optimization and provides a detailed introduction to both deterministic and stochastic models. Covering problems with finite and infinite horizon, as well as Markov renewal programs, Bayesian control models and partially observable processes, the book focuses on the precise modelling of applications in a variety of areas, including operations research, computer science, mathematics, statistics, engineering, economics and finance. Dynamic Optimization is a carefully presented textbook which starts with discrete-time deterministic dynamic optimization problems, providing readers with the tools for sequential decision-making, before proceeding to the more complicated stochastic models. The authors present complete and simple proofs and illustrate the main results with numerous examples and exercises (without solutions). With relevant material covered in four appendices, this book is completely self-contained.
MODELS FOR NETWORK DYNAMICS - A MARKOVIAN FRAMEWORK
LEENDERS, RTAJ
1995-01-01
A question not very often addressed in social network analysis relates to network dynamics and focuses on how networks arise and change. It alludes to the idea that ties do not arise or vanish randomly, but (partly) as a consequence of human behavior and preferences. Statistical models for modeling
Dynamic modeling of the INAPRO aquaponic system
Karimanzira, Divas; Keesman, Karel J.; Kloas, Werner; Baganz, Daniela; Rauschenbach, Thomas
2016-01-01
The use of modeling techniques to analyze aquaponics systems is demonstrated with an example of dynamic modeling for the production of Nile tilapia (Oreochromis niloticus) and tomatoes (Solanum lycopersicon) using the innovative double recirculating aquaponic system ASTAF-PRO. For the management and
Dynamic spatial panels : models, methods, and inferences
Elhorst, J. Paul
This paper provides a survey of the existing literature on the specification and estimation of dynamic spatial panel data models, a collection of models for spatial panels extended to include one or more of the following variables and/or error terms: a dependent variable lagged in time, a dependent
A Discrete Dynamical Model of Signed Partitions
Directory of Open Access Journals (Sweden)
G. Chiaselotti
2013-01-01
Full Text Available We use a discrete dynamical model with three evolution rules in order to analyze the structure of a partially ordered set of signed integer partitions whose main properties are actually not known. This model is related to the study of some extremal combinatorial sum problems.
A system dynamics model for communications networks
Awcock, A. J.; King, T. E. G.
1985-09-01
An abstract model of a communications network in system dynamics terminology is developed as implementation of this model by a FORTRAN program package developed at RSRE is discussed. The result of this work is a high-level simulation package in which the performance of adaptive routing algorithms and other network controls may be assessed for a network of arbitrary topology.
Concept-Oriented Modeling of Dynamic Behavior
Breedveld, P.C.; Borutzky, Wolfgang
2011-01-01
This chapter introduces the reader to the concept-oriented approach to modeling that clearly separates ideal concepts from the physical components of a system when modeling its dynamic behavior for a specific problem context. This is done from a port-based point of view for which the domain-independ
A dynamical model for the Utricularia trap
Llorens, Coraline; Argentina, Médéric; Bouret, Yann; Marmottant, Philippe; Vincent, Olivier
2012-01-01
We propose a model that captures the dynamics of a carnivorous plant, Utricularia inflata. This plant possesses tiny traps for capturing small aquatic animals. Glands pump water out of the trap, yielding a negative pressure difference between the plant and its surroundings. The trap door is set into a meta-stable state and opens quickly as an extra pressure is generated by the displacement of a potential prey. As the door opens, the pressure difference sucks the animal into the trap. We write an ODE model that captures all the physics at play. We show that the dynamics of the plant is quite similar to neuronal dynamics and we analyse the effect of a white noise on the dynamics of the trap. PMID:22859569
Adaptation dynamics of the quasispecies model
Indian Academy of Sciences (India)
Kavita Jain
2008-08-01
We study the adaptation dynamics of an initially maladapted population evolving via the elementary processes of mutation and selection. The evolution occurs on rugged fitness landscapes which are defined on the multi-dimensional genotypic space and have many local peaks separated by low fitness valleys. We mainly focus on the Eigen’s model that describes the deterministic dynamics of an infinite number of self-replicating molecules. In the stationary state, for small mutation rates such a population forms a quasispecies which consists of the fittest genotype and its closely related mutants. The quasispecies dynamics on rugged fitness landscape follow a punctuated (or step-like) pattern in which a population jumps from a low fitness peak to a higher one, stays there for a considerable time before shifting the peak again and eventually reaches the global maximum of the fitness landscape. We calculate exactly several properties of this dynamical process within a simplified version of the quasispecies model.
Adaptation dynamics of the quasispecies model
Jain, Kavita
2009-02-01
We study the adaptation dynamics of an initially maladapted population evolving via the elementary processes of mutation and selection. The evolution occurs on rugged fitness landscapes which are defined on the multi-dimensional genotypic space and have many local peaks separated by low fitness valleys. We mainly focus on the Eigen's model that describes the deterministic dynamics of an infinite number of self-replicating molecules. In the stationary state, for small mutation rates such a population forms a {\\it quasispecies} which consists of the fittest genotype and its closely related mutants. The quasispecies dynamics on rugged fitness landscape follow a punctuated (or step-like) pattern in which a population jumps from a low fitness peak to a higher one, stays there for a considerable time before shifting the peak again and eventually reaches the global maximum of the fitness landscape. We calculate exactly several properties of this dynamical process within a simplified version of the quasispecies model.
Replicator-dynamics models of sexual conflict.
Kimura, Mariko; Ihara, Yasuo
2009-09-07
Evolutionary conflict between the sexes has been studied in various taxa and in various contexts. When the sexes are in conflict over mating rates, natural selection favors both males that induce higher mating rates and females that are more successful at resisting mating attempts. Such sexual conflict may result in an escalating coevolutionary arms race between males and females. In this article, we develop simple replicator-dynamics models of sexual conflict in order to investigate its evolutionary dynamics. Two specific models of the dependence of a female's fitness on her number of matings are considered: in model 1, female fitness decreases linearly with increasing number of matings and in model 2, there is an optimal number of matings that maximizes female fitness. For each of these models, we obtain the conditions for a coevolutionary process to establish costly male and female traits and examine under what circumstances polymorphism is maintained at equilibrium. Then we discuss how assumptions in previous models of sexual conflict are translated to fit to our model framework and compare our results with those of the previous studies. The simplicity of our models allows us to consider sexual conflict in various contexts within a single framework. In addition, we find that our model 2 shows more complicated evolutionary dynamics than model 1. In particular, the population exhibits bistability, where the evolutionary outcome depends on the initial state, only in model 2.
Cosmological model with dynamical curvature
Stichel, Peter C
2016-01-01
We generalize the recently introduced relativistic Lagrangian darkon fluid model (EPJ C (2015) 75:9) by starting with a self-gravitating geodesic fluid whose energy-momentum tensor is dust-like with a nontrivial energy flow. The corresponding covariant propagation and constraint equations are considered in a shear-free nonrelativistic limit whose analytic solutions determine the 1st-order relativistic correction to the spatial curvature. This leads to a cosmological model where the accelerated expansion of the Universe is driven by a time-dependent spatial curvature without the need for introducing any kind of dark energy. We derive the differential equation to be satisfied by the area distance for this model.
Modeling hybrid perovskites by molecular dynamics.
Mattoni, Alessandro; Filippetti, Alessio; Caddeo, Claudia
2017-02-01
The topical review describes the recent progress in the modeling of hybrid perovskites by molecular dynamics simulations. Hybrid perovskites and in particular methylammonium lead halide (MAPI) have a tremendous technological relevance representing the fastest-advancing solar material to date. They also represent the paradigm of an organic-inorganic crystalline material with some conceptual peculiarities: an inorganic semiconductor for what concerns the electronic and absorption properties with a hybrid and solution processable organic-inorganic body. After briefly explaining the basic concepts of ab initio and classical molecular dynamics, the model potential recently developed for hybrid perovskites is described together with its physical motivation as a simple ionic model able to reproduce the main dynamical properties of the material. Advantages and limits of the two strategies (either ab initio or classical) are discussed in comparison with the time and length scales (from pico to microsecond scale) necessary to comprehensively study the relevant properties of hybrid perovskites from molecular reorientations to electrocaloric effects. The state-of-the-art of the molecular dynamics modeling of hybrid perovskites is reviewed by focusing on a selection of showcase applications of methylammonium lead halide: molecular cations disorder; temperature evolution of vibrations; thermally activated defects diffusion; thermal transport. We finally discuss the perspectives in the modeling of hybrid perovskites by molecular dynamics.
Modeling hybrid perovskites by molecular dynamics
Mattoni, Alessandro; Filippetti, Alessio; Caddeo, Claudia
2017-02-01
The topical review describes the recent progress in the modeling of hybrid perovskites by molecular dynamics simulations. Hybrid perovskites and in particular methylammonium lead halide (MAPI) have a tremendous technological relevance representing the fastest-advancing solar material to date. They also represent the paradigm of an organic-inorganic crystalline material with some conceptual peculiarities: an inorganic semiconductor for what concerns the electronic and absorption properties with a hybrid and solution processable organic-inorganic body. After briefly explaining the basic concepts of ab initio and classical molecular dynamics, the model potential recently developed for hybrid perovskites is described together with its physical motivation as a simple ionic model able to reproduce the main dynamical properties of the material. Advantages and limits of the two strategies (either ab initio or classical) are discussed in comparison with the time and length scales (from pico to microsecond scale) necessary to comprehensively study the relevant properties of hybrid perovskites from molecular reorientations to electrocaloric effects. The state-of-the-art of the molecular dynamics modeling of hybrid perovskites is reviewed by focusing on a selection of showcase applications of methylammonium lead halide: molecular cations disorder; temperature evolution of vibrations; thermally activated defects diffusion; thermal transport. We finally discuss the perspectives in the modeling of hybrid perovskites by molecular dynamics.
Dispersive models describing mosquitoes’ population dynamics
Yamashita, W. M. S.; Takahashi, L. T.; Chapiro, G.
2016-08-01
The global incidences of dengue and, more recently, zica virus have increased the interest in studying and understanding the mosquito population dynamics. Understanding this dynamics is important for public health in countries where climatic and environmental conditions are favorable for the propagation of these diseases. This work is based on the study of nonlinear mathematical models dealing with the life cycle of the dengue mosquito using partial differential equations. We investigate the existence of traveling wave solutions using semi-analytical method combining dynamical systems techniques and numerical integration. Obtained solutions are validated through numerical simulations using finite difference schemes.
Induction generator models in dynamic simulation tools
DEFF Research Database (Denmark)
Knudsen, Hans; Akhmatov, Vladislav
1999-01-01
. It is found to be possible to include a transient model in dynamic stability tools and, then, obtain correct results also in dynamic tools. The representation of the rotating system influences on the voltage recovery shape which is an important observation in case of windmills, where a heavy mill is connected......For AC network with large amount of induction generators (windmills) the paper demonstrates a significant discrepancy in the simulated voltage recovery after fault in weak networks when comparing dynamic and transient stability descriptions and the reasons of discrepancies are explained...
Dynamics of the supermarket model
MacPhee, I M; Vachkovskaia, M
2010-01-01
We consider the long term behaviour of a Markov chain \\xi(t) on \\Z^N based on the N station supermarket model. Different routing policies for the supermarket model give different Markov chains. We show that for a general class of local routing policies, "join the least weighted queue" (JLW), the N one-dimensional components \\xi_i(t) can be partitioned into disjoint clusters C_k. Within each cluster C_k the "speed" of each component \\xi_j converges to a constant V_k and under certain conditions \\xi is recurrent in shape on each cluster. To establish these results we have assembled methods from two distinct areas of mathematics, semi-martingale techniques used for showing stability of Markov chains together with the theory of optimal flows in networks. As corollaries to our main result we obtain the stability classification of the supermarket model under any JLW policy and can explicitly compute the C_k and V_k for any instance of the model and specific JLW policy.
Intermittent rainfall in dynamic multimedia fate modeling.
Hertwich, E G
2001-03-01
It has been shown that steady-state multimedia models (level III fugacity models) lead to a substantial underestimate of air concentrations for chemicals with a low Henry's law constant (H multimedia models are used to estimate the spatial range or inhalation exposure. A dynamic model of pollutant fate is developed for conditions of intermittent rainfall to calculate the time profile of pollutant concentrations in different environmental compartments. The model utilizes a new, mathematically efficient approach to dynamic multimedia fate modeling that is based on the convolution of solutions to the initial conditions problem. For the first time, this approach is applied to intermittent conditions. The investigation indicates that the time-averaged pollutant concentrations under intermittent rainfall can be approximated by the appropriately weighted average of steady-state concentrations under conditions with and without rainfall.
Dynamic exponents for potts model cluster algorithms
Coddington, Paul D.; Baillie, Clive F.
We have studied the Swendsen-Wang and Wolff cluster update algorithms for the Ising model in 2, 3 and 4 dimensions. The data indicate simple relations between the specific heat and the Wolff autocorrelations, and between the magnetization and the Swendsen-Wang autocorrelations. This implies that the dynamic critical exponents are related to the static exponents of the Ising model. We also investigate the possibility of similar relationships for the Q-state Potts model.
The dynamic model of enterprise revenue management
Mitsel, A. A.; Kataev, M. Yu; Kozlov, S. V.; Korepanov, K. V.
2017-01-01
The article presents the dynamic model of enterprise revenue management. This model is based on the quadratic criterion and linear control law. The model is founded on multiple regression that links revenues with the financial performance of the enterprise. As a result, optimal management is obtained so as to provide the given enterprise revenue, namely, the values of financial indicators that ensure the planned profit of the organization are acquired.
Feature Extraction for Structural Dynamics Model Validation
Energy Technology Data Exchange (ETDEWEB)
Farrar, Charles [Los Alamos National Laboratory; Nishio, Mayuko [Yokohama University; Hemez, Francois [Los Alamos National Laboratory; Stull, Chris [Los Alamos National Laboratory; Park, Gyuhae [Chonnam Univesity; Cornwell, Phil [Rose-Hulman Institute of Technology; Figueiredo, Eloi [Universidade Lusófona; Luscher, D. J. [Los Alamos National Laboratory; Worden, Keith [University of Sheffield
2016-01-13
As structural dynamics becomes increasingly non-modal, stochastic and nonlinear, finite element model-updating technology must adopt the broader notions of model validation and uncertainty quantification. For example, particular re-sampling procedures must be implemented to propagate uncertainty through a forward calculation, and non-modal features must be defined to analyze nonlinear data sets. The latter topic is the focus of this report, but first, some more general comments regarding the concept of model validation will be discussed.
A Dynamic Model for Energy Structure Analysis
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
Energy structure is a complicated system concerning economic development, natural resources, technological innovation, ecological balance, social progress and many other elements. It is not easy to explain clearly the developmental mechanism of an energy system and the mutual relations between the energy system and its related environments by the traditional methods. It is necessary to develop a suitable dynamic model, which can reflect the dynamic characteristics and the mutual relations of the energy system and its related environments. In this paper, the historical development of China's energy structure was analyzed. A new quantitative analysis model was developed based on system dynamics principles through analysis of energy resources, and the production and consumption of energy in China and comparison with the world. Finally, this model was used to predict China's future energy structures under different conditions.
Dynamic Model Identification for Industrial Robots
Directory of Open Access Journals (Sweden)
Ngoc Dung Vuong
2009-12-01
Full Text Available In this paper, a systematic procedure for identifying the dynamics of industrialrobots is presented. Since joint friction can be highly nonlinearwith time varyingcharacteristics in the low speed region,a simple and yet effective scheme has been used toidentify the boundary velocity that separates this “dynamic” friction region from its staticregion. The robot’s dynamic model is then identified in this static region, where thenonlinnear friction model is reduced to the linear-in-parameter form. To overcome thedrawbacks of the least squares estimator, which does not take in any constraints, anonlinear optimization problem is formulated to guarantee the physical feasibility of theidentified parameters. The proposed procedure has been demonstrated on the first fourlinks of the Mitsubishi PA10 manipulator, an improved dynamic model was obtained andthe the effectiveness of the proposed identification procedure is demonstrated.
Dynamic Model for Life History of Scyphozoa.
Directory of Open Access Journals (Sweden)
Congbo Xie
Full Text Available A two-state life history model governed by ODEs is formulated to elucidate the population dynamics of jellyfish and to illuminate the triggering mechanism of its blooms. The polyp-medusa model admits trichotomous global dynamic scenarios: extinction, polyps survival only, and both survival. The population dynamics sensitively depend on several biotic and abiotic limiting factors such as substrate, temperature, and predation. The combination of temperature increase, substrate expansion, and predator diminishment acts synergistically to create a habitat that is more favorable for jellyfishes. Reducing artificial marine constructions, aiding predator populations, and directly controlling the jellyfish population would help to manage the jellyfish blooms. The theoretical analyses and numerical experiments yield several insights into the nature underlying the model and shed some new light on the general control strategy for jellyfish.
Modeling Of Ballistic Missile Dynamics
Directory of Open Access Journals (Sweden)
Salih Mahmoud Attiya
2013-05-01
Full Text Available Aerodynamic modeling of ballistic missile in pitch plane is performed and the open-loop transfer function related to the jet deflector angle as input and pitch rate, normal acceleration as output has been derived with certain acceptable assumptions. For typical values of ballistic missile parameters such as mass, velocity, altitude, moment of inertia, thrust, moment and lift coefficient show that, the step time response and frequency response of the missile is unstable. The steady state gain, damping ratio and undraped natural frequency depend on the missile parameters. To stabilize the missile a lead compensator must be added to the forward loop.
Dynamic modeling of solar dynamic components and systems
Hochstein, John I.; Korakianitis, T.
1992-09-01
The purpose of this grant was to support NASA in modeling efforts to predict the transient dynamic and thermodynamic response of the space station solar dynamic power generation system. In order to meet the initial schedule requirement of providing results in time to support installation of the system as part of the initial phase of space station, early efforts were executed with alacrity and often in parallel. Initially, methods to predict the transient response of a Rankine as well as a Brayton cycle were developed. Review of preliminary design concepts led NASA to select a regenerative gas-turbine cycle using a helium-xenon mixture as the working fluid and, from that point forward, the modeling effort focused exclusively on that system. Although initial project planning called for a three year period of performance, revised NASA schedules moved system installation to later and later phases of station deployment. Eventually, NASA selected to halt development of the solar dynamic power generation system for space station and to reduce support for this project to two-thirds of the original level.
Effects of spike-triggered negative feedback on receptive-field properties.
Urdapilleta, Eugenio; Samengo, Inés
2015-04-01
Sensory neurons are often described in terms of a receptive field, that is, a linear kernel through which stimuli are filtered before they are further processed. If information transmission is assumed to proceed in a feedforward cascade, the receptive field may be interpreted as the external stimulus' profile maximizing neuronal output. The nervous system, however, contains many feedback loops, and sensory neurons filter more currents than the ones representing the transduced external stimulus. Some of the additional currents are generated by the output activity of the neuron itself, and therefore constitute feedback signals. By means of a time-frequency analysis of the input/output transformation, here we show how feedback modifies the receptive field. The model is applicable to various types of feedback processes, from spike-triggered intrinsic conductances to inhibitory synaptic inputs from nearby neurons. We distinguish between the intrinsic receptive field (filtering all input currents) and the effective receptive field (filtering only external stimuli). Whereas the intrinsic receptive field summarizes the biophysical properties of the neuron associated to subthreshold integration and spike generation, only the effective receptive field can be interpreted as the external stimulus' profile maximizing neuronal output. We demonstrate that spike-triggered feedback shifts low-pass filtering towards band-pass processing, transforming integrator neurons into resonators. For strong feedback, a sharp resonance in the spectral neuronal selectivity may appear. Our results provide a unified framework to interpret a collection of previous experimental studies where specific feedback mechanisms were shown to modify the filtering properties of neurons.
Dynamical properties of the Rabi model
Hu, Binglu; Zhou, Huili; Chen, Shujie; Xianlong, Gao; Wang, Kelin
2017-02-01
We study the dynamical properties of the quantum Rabi model using a systematic expansion method. Based on the observation that the parity symmetry of the Rabi model is kept during evolution of the states, we decompose the initial state and the time-dependent one into positive and negative parity parts expanded by superposition of the coherent states. The evolutions of the corresponding positive and the negative parities are obtained, in which the expansion coefficients in the dynamical equations are known from the derived recurrence relation.
Dynamical Model of Weak Pion Production Reactions
Sato, T; Lee, T S H
2003-01-01
The dynamical model of pion electroproduction has been extended to investigate the weak pion production reactions. The predicted cross sections of neutrino-induced pion production reactions are in good agreement with the existing data. We show that the renormalized(dressed) axial N-$\\Delta$ form factor contains large dynamical pion cloud effects and this renormalization effects are crucial in getting agreement with the data. We conclude that the N-$\\Delta$ transitions predicted by the constituent quark model are consistent with the existing neutrino induced pion production data in the $\\Delta$ region.
Research on nonlinear stochastic dynamical price model
Energy Technology Data Exchange (ETDEWEB)
Li Jiaorui [Department of Applied Mathematics, Northwestern Polytechnical University, Xi' an 710072 (China); School of Statistics, Xi' an University of Finance and Economics, Xi' an 710061 (China)], E-mail: jiaoruili@mail.nwpu.edu.cn; Xu Wei; Xie Wenxian; Ren Zhengzheng [Department of Applied Mathematics, Northwestern Polytechnical University, Xi' an 710072 (China)
2008-09-15
In consideration of many uncertain factors existing in economic system, nonlinear stochastic dynamical price model which is subjected to Gaussian white noise excitation is proposed based on deterministic model. One-dimensional averaged Ito stochastic differential equation for the model is derived by using the stochastic averaging method, and applied to investigate the stability of the trivial solution and the first-passage failure of the stochastic price model. The stochastic price model and the methods presented in this paper are verified by numerical studies.
Dynamic model for the popularity of websites
Lee, Chang-Yong; Kim, Seungwhan
2002-03-01
In this paper, we have studied a dynamic model to explain the observed characteristics of websites in the World Wide Web. The dynamic model consists of the self-growth term for each website and the external force term acting on the website. With simulations of the model, we can explain most of the important characteristics of websites. These characteristics include a power-law distribution of the number of visitors to websites, fluctuation in the fractional growth of individual websites, and the relationship between the age and the popularity of the websites. We also investigated a few variants of the model and showed that the ingredients included in the model adequately explain the behavior of the websites.
Modelling environmental dynamics. Advances in goematic solutions
Energy Technology Data Exchange (ETDEWEB)
Paegelow, Martin [Toulouse-2 Univ., 31 (France). GEODE UMR 5602 CNRS; Camacho Olmedo, Maria Teresa (eds.) [Granada Univ (Spain). Dpto. de Analisis Geografico Regional y Geografia Fisica
2008-07-01
Modelling environmental dynamics is critical to understanding and predicting the evolution of the environment in response to the large number of influences including urbanisation, climate change and deforestation. Simulation and modelling provide support for decision making in environmental management. The first chapter introduces terminology and provides an overview of methodological modelling approaches which may be applied to environmental and complex dynamics. Based on this introduction this book illustrates various models applied to a large variety of themes: deforestation in tropical regions, fire risk, natural reforestation in European mountains, agriculture, biodiversity, urbanism, climate change and land management for decision support, etc. These case studies, provided by a large international spectrum of researchers and presented in a uniform structure, focus particularly on methods and model validation so that this book is not only aimed at researchers and graduates but also at professionals. (orig.)
Modeling emotional dynamics : currency versus field.
Energy Technology Data Exchange (ETDEWEB)
Sallach, D .L.; Decision and Information Sciences; Univ. of Chicago
2008-08-01
Randall Collins has introduced a simplified model of emotional dynamics in which emotional energy, heightened and focused by interaction rituals, serves as a common denominator for social exchange: a generic form of currency, except that it is active in a far broader range of social transactions. While the scope of this theory is attractive, the specifics of the model remain unconvincing. After a critical assessment of the currency theory of emotion, a field model of emotion is introduced that adds expressiveness by locating emotional valence within its cognitive context, thereby creating an integrated orientation field. The result is a model which claims less in the way of motivational specificity, but is more satisfactory in modeling the dynamic interaction between cognitive and emotional orientations at both individual and social levels.
Modeling dynamic functional connectivity using a wishart mixture model
DEFF Research Database (Denmark)
Nielsen, Søren Føns Vind; Madsen, Kristoffer Hougaard; Schmidt, Mikkel Nørgaard
2017-01-01
.e. the window length. In this work we use the Wishart Mixture Model (WMM) as a probabilistic model for dFC based on variational inference. The framework admits arbitrary window lengths and number of dynamic components and includes the static one-component model as a special case. We exploit that the WMM...
Modeling the dynamics of dissent
Lee, Eun; Lee, Sang Hoon
2016-01-01
We investigate opinion formation against authority in an authoritarian society composed of agents with different levels of authority. We explore a (symbolically) "right" opinion, held by lower-ranking, obedient, less authoritative people, spreading in an environment of a "wrong" opinion held by authoritative leaders. The mental picture would be that of a corrupt society where the ruled people revolts against authority, but it could be argued to hold in more general situations. In our model, agents can change their opinion depending on the relative authority to their neighbors and their own confidence level. In addition, with a certain probability, agents can override the authority to take the right opinion of a neighbor. Based on analytic derivation and numerical simulations, we observe that both the network structure and heterogeneity in authority, and their correlation significantly affect the possibility of the right opinion to spread in the population. In particular, the right opinion is suppressed when t...
Induction generator models in dynamic simulation tools
DEFF Research Database (Denmark)
Knudsen, Hans; Akhmatov, Vladislav
1999-01-01
For AC network with large amount of induction generators (windmills) the paper demonstrates a significant discrepancy in the simulated voltage recovery after fault in weak networks when comparing dynamic and transient stability descriptions and the reasons of discrepancies are explained. It is fo......For AC network with large amount of induction generators (windmills) the paper demonstrates a significant discrepancy in the simulated voltage recovery after fault in weak networks when comparing dynamic and transient stability descriptions and the reasons of discrepancies are explained....... It is found to be possible to include a transient model in dynamic stability tools and, then, obtain correct results also in dynamic tools. The representation of the rotating system influences on the voltage recovery shape which is an important observation in case of windmills, where a heavy mill is connected...
Han, Dahai; Liu, Yile; Zhang, Kai; Luo, Pengfei; Zhang, Min
2012-07-02
Diversity reception technology is introduced into ultraviolet communication area in this article with theory analysis and practical experiment. The idea of diversity reception was known as a critical effective method in wireless communication area that improves the Gain significantly especially for the multi-scattering channel. A theoretical modeling and simulation method are proposed to depict the principle and feasibility of diversity reception adopted in UV communication. Besides, an experimental test-bed using ultraviolet LED and dual receiver of photomultiplier tube is setup to characterize the effects of diversity receiving in non-line-of-sight (NLOS) ultraviolet communication system. The experiment results are compared with the theoretical ones to verify the accuracy of theoretical modeling and the effect of diversity reception. Equal gain combining (EGC) method was adopted as the diversity mechanism in this paper. The research results of theory and experiment provide insight into the channel characteristics and achievable capabilities of ultraviolet communication system with diversity receiving method.
Dynamic Model Averaging in Large Model Spaces Using Dynamic Occam’s Window*
Onorante, Luca; Raftery, Adrian E.
2015-01-01
Bayesian model averaging has become a widely used approach to accounting for uncertainty about the structural form of the model generating the data. When data arrive sequentially and the generating model can change over time, Dynamic Model Averaging (DMA) extends model averaging to deal with this situation. Often in macroeconomics, however, many candidate explanatory variables are available and the number of possible models becomes too large for DMA to be applied in its original form. We propose a new method for this situation which allows us to perform DMA without considering the whole model space, but using a subset of models and dynamically optimizing the choice of models at each point in time. This yields a dynamic form of Occam’s window. We evaluate the method in the context of the problem of nowcasting GDP in the Euro area. We find that its forecasting performance compares well with that of other methods. PMID:26917859
Knowledge Map: Mathematical Model and Dynamic Behaviors
Institute of Scientific and Technical Information of China (English)
Hai Zhuge; Xiang-Feng Luo
2005-01-01
Knowledge representation and reasoning is a key issue of the Knowledge Grid. This paper proposes a Knowledge Map (KM) model for representing and reasoning causal knowledge as an overlay in the Knowledge Grid. It extends Fuzzy Cognitive Maps (FCMs) to represent and reason not only simple cause-effect relations, but also time-delay causal relations, conditional probabilistic causal relations and sequential relations. The mathematical model and dynamic behaviors of KM are presented. Experiments show that, under certain conditions, the dynamic behaviors of KM can translate between different states. Knowing this condition, experts can control or modify the constructed KM while its dynamic behaviors do not accord with their expectation. Simulations and applications show that KM is more powerful and natural than FCM in emulating real world.
Dynamic landscape models of coevolutionary games
Richter, Hendrik
2016-01-01
Players of coevolutionary games may update not only their strategies but also their networks of interaction. Based on interpreting the payoff of players as fitness, dynamic landscape models are proposed. The modeling procedure is carried out for Prisoner's Dilemma (PD) and Snowdrift (SD) games that both use either birth-death (BD) or death-birth (DB) strategy updating. With the main focus on using dynamic fitness landscapes as an alternative tool for analyzing coevolutionary games, landscape measures such as modality, ruggedness and information content are computed and analyzed. In addition, fixation properties of the games and quantifiers characterizing the network of interaction are calculated numerically. Relations are established between landscape properties expressed by landscape measures and quantifiers of coevolutionary game dynamics such as fixation probabilities, fixation times and network properties
Hidden Symmetry of a Fluid Dynamical Model
Neves, C
2001-01-01
A connection between solutions of the relativistic d-brane system in (d+1) dimensions with the solutions of a Galileo invariant fluid in d-dimensions is by now well established. However, the physical nature of the light-cone gauge description of a relativistic membrane changes after the reduction to the fluid dynamical model since the gauge symmetry is lost. In this work we argue that the original gauge symmetry present in a relativistic d-brane system can be recovered after the reduction process to a d-dimensional fluid model. To this end we propose, without introducing Wess-Zumino fields, a gauge invariant theory of isentropic fluid dynamics and show that this symmetry corresponds to the invariance under local translation of the velocity potential in the fluid dynamics picture. We show that different but equivalent choices of the sympletic sector lead to distinct representations of the embedded gauge algebra.
Dynamics models of soil organic carbon
Institute of Scientific and Technical Information of China (English)
YANGLi-xia; PANJian-jun
2003-01-01
As the largest pool of terrestrial organic carbon, soils interact strongly with atmosphere composition, climate, and land change. Soil organic carbon dynamics in ecosystem plays a great role in global carbon cycle and global change. With development of mathematical models that simulate changes in soil organic carbon, there have been considerable advances in understanding soil organic carbon dynamics. This paper mainly reviewed the composition of soil organic matter and its influenced factors, and recommended some soil organic matter models worldwide. Based on the analyses of the developed results at home and abroad, it is suggested that future soil organic matter models should be developed toward based-process models, and not always empirical ones. The models are able to reveal their interaction between soil carbon systems, climate and land cover by technique and methods of GIS (Geographical Information System) and RS (Remote Sensing). These models should be developed at a global scale, in dynamically describing the spatial and temporal changes of soil organic matter cycle. Meanwhile, the further researches on models should be strengthen for providing theory basis and foundation in making policy of green house gas emission in China.
Human Muscle Fatigue Model in Dynamic Motions
Ma, Ruina; Bennis, Fouad; Ma, Liang
2012-01-01
Human muscle fatigue is considered to be one of the main reasons for Musculoskeletal Disorder (MSD). Recent models have been introduced to define muscle fatigue for static postures. However, the main drawbacks of these models are that the dynamic effect of the human and the external load are not taken into account. In this paper, each human joint is assumed to be controlled by two muscle groups to generate motions such as push/pull. The joint torques are computed using Lagrange's formulation to evaluate the dynamic factors of the muscle fatigue model. An experiment is defined to validate this assumption and the result for one person confirms its feasibility. The evaluation of this model can predict the fatigue and MSD risk in industry production quickly.
System and mathematical modeling of quadrotor dynamics
Goodman, Jacob M.; Kim, Jinho; Gadsden, S. Andrew; Wilkerson, Stephen A.
2015-05-01
Unmanned aerial systems (UAS) are becoming increasingly visible in our daily lives; and range in operation from search and rescue, monitoring hazardous environments, and to the delivery of goods. One of the most popular UAS are based on a quad-rotor design. These are typically small devices that rely on four propellers for lift and movement. Quad-rotors are inherently unstable, and rely on advanced control methodologies to keep them operating safely and behaving in a predictable and desirable manner. The control of these devices can be enhanced and improved by making use of an accurate dynamic model. In this paper, we examine a simple quadrotor model, and note some of the additional dynamic considerations that were left out. We then compare simulation results of the simple model with that of another comprehensive model.
Contact force models for multibody dynamics
Flores, Paulo
2016-01-01
This book analyzes several compliant contact force models within the context of multibody dynamics, while also revisiting the main issues associated with fundamental contact mechanics. In particular, it presents various contact force models, from linear to nonlinear, from purely elastic to dissipative, and describes their parameters. Addressing the different numerical methods and algorithms for contact problems in multibody systems, the book describes the gross motion of multibody systems by using a two-dimensional formulation based on the absolute coordinates and employs different contact models to represent contact-impact events. Results for selected planar multibody mechanical systems are presented and utilized to discuss the main assumptions and procedures adopted throughout this work. The material provided here indicates that the prediction of the dynamic behavior of mechanical systems involving contact-impact strongly depends on the choice of contact force model. In short, the book provides a comprehens...
Record Dynamics in the Parking Lot Model
DEFF Research Database (Denmark)
Sibani, Paolo; Boettcher, Stefan
2016-01-01
We study the aging dynamics in the parking lot model of granular relaxation with extensive numerical simulations. Our results reveal the log-Poisson statistics in the progression of intermittent events that lead to ever slower increases in the density. Defining clusters as domains of parked cars...
Modeling the Hydrogen Bond within Molecular Dynamics
Lykos, Peter
2004-01-01
The structure of a hydrogen bond is elucidated within the framework of molecular dynamics based on the model of Rahman and Stillinger (R-S) liquid water treatment. Thus, undergraduates are exposed to the powerful but simple use of classical mechanics to solid objects from a molecular viewpoint.
The Dynamic Mundell-Fleming Model Reconsidered
金子, 邦彦; Kaneko, Kunihiko
2003-01-01
In this paper we reconsider the dynamic Mundell-Fleming model of Sarno and Taylor (2002) by incorporating one of the recent New Keynesian ingredients. In an extended framework, we reconfirm that their results on the effects of an expansionary fiscal policy are robust. However, we also show that their results on the effects of an expansionary monetary policy should be modified.
Nearly Unbiased Estimationin Dynamic Panel Data Models
M.A. Carree (Martin)
2002-01-01
textabstractThis paper introduces two easy to calculate estimators with desirable properties for the autoregressive parameter in dynamic panel data models. The estimators are (nearly) unbiased and perform satisfactorily even for small samples in either the time-series or cross-section dimension.
Object Oriented Modelling and Dynamical Simulation
DEFF Research Database (Denmark)
Wagner, Falko Jens; Poulsen, Mikael Zebbelin
1998-01-01
This report with appendix describes the work done in master project at DTU.The goal of the project was to develop a concept for simulation of dynamical systems based on object oriented methods.The result was a library of C++-classes, for use when both building componentbased models and when...
Object Oriented Modelling and Dynamical Simulation
DEFF Research Database (Denmark)
Wagner, Falko Jens; Poulsen, Mikael Zebbelin
1998-01-01
This report with appendix describes the work done in master project at DTU.The goal of the project was to develop a concept for simulation of dynamical systems based on object oriented methods.The result was a library of C++-classes, for use when both building componentbased models and when...... onduction simulation experiments....
A Flight Dynamic Model of Aircraft Spinning
1990-06-01
Australia, Library Australian Airlines, Library Qantas Airways Limited Hawker de Havilland Aust. Pty Ltd, Victoria, Library Hawker de Havilland Aust. Pty...3. MARTIN, C.A. ; Modelling Aircraft Dynamics. ARL-AERO-TECH- MEMO-400 July 1988 4. HULTBERG, R.S. ; Rotary Balance Data and Analysis for the
Advances in Inventory Management: Dynamic Models
C. Pinçe (Çerağ)
2010-01-01
textabstractIn this study, we develop and analyze models incorporating some of the dynamic aspects of inventory systems. In particular, we focus on two major themes to be analyzed separately: nonstationarity in demand rate and unfixed purchasing prices. In the first part of the study, we consider a
A Dynamic Distribution Model for Combat Logistics
1999-11-23
develop a heuristic algorithm for a similar problem, only capacity expansion can occur in any amount (modeled with continuous variables) while in...and Rutenberg (1977) solve it with a heuristic algorithm . Our problem is also related to the dynamic facility location problem. This problem seeks to
A Stochastic Dynamic Model of Computer Viruses
Directory of Open Access Journals (Sweden)
Chunming Zhang
2012-01-01
Full Text Available A stochastic computer virus spread model is proposed and its dynamic behavior is fully investigated. Specifically, we prove the existence and uniqueness of positive solutions, and the stability of the virus-free equilibrium and viral equilibrium by constructing Lyapunov functions and applying Ito's formula. Some numerical simulations are finally given to illustrate our main results.
Modeling of Reactor Kinetics and Dynamics
Energy Technology Data Exchange (ETDEWEB)
Matthew Johnson; Scott Lucas; Pavel Tsvetkov
2010-09-01
In order to model a full fuel cycle in a nuclear reactor, it is necessary to simulate the short time-scale kinetic behavior of the reactor as well as the long time-scale dynamics that occur with fuel burnup. The former is modeled using the point kinetics equations, while the latter is modeled by coupling fuel burnup equations with the kinetics equations. When the equations are solved simultaneously with a nonlinear equation solver, the end result is a code with the unique capability of modeling transients at any time during a fuel cycle.
The quantum Rabi model: solution and dynamics
Xie, Qiongtao; Zhong, Honghua; Batchelor, Murray T.; Lee, Chaohong
2017-03-01
This article presents a review of recent developments on various aspects of the quantum Rabi model. Particular emphasis is given on the exact analytic solution obtained in terms of confluent Heun functions. The analytic solutions for various generalisations of the quantum Rabi model are also discussed. Results are also reviewed on the level statistics and the dynamics of the quantum Rabi model. The article concludes with an introductory overview of several experimental realisations of the quantum Rabi model. An outlook towards future developments is also given.
The quantum Rabi model: solution and dynamics
Xie, Qiongtao; Batchelor, Murray T; Lee, Chaohong
2016-01-01
This article presents a review of recent developments on various aspects of the quantum Rabi model. Particular emphasis is given on the exact analytic solution obtained in terms of confluent Heun functions. The analytic solutions for various generalisations of the quantum Rabi model are also discussed. Results are also reviewed on the level statistics and the dynamics of the quantum Rabi model. The article concludes with an introductory overview of several experimental realisations of the quantum Rabi model. An outlook towards future developments is also given.
Structural Equation Modeling of Travel Choice Dynamics
Golob, Thomas F.
1988-01-01
This research has two objectives. The first objective is to explore the use of the modeling tool called "latent structural equations" (structural equations with latent variables) in the general field of travel behavior analysis and the more specific field of dynamic analysis of travel behavior. The second objective is to apply a latent structural equation model in order to determine the causal relationships between income, car ownership, and mobility. Many transportation researchers ...
Dynamic inventory models: an illustrative case study
Directory of Open Access Journals (Sweden)
Adendorff, Kris
2014-10-01
Full Text Available The study revisits the subject matter of inventory control, a continual part of the activities of wide-ranging organisations internationally. The mathematical model is presented of a particular situation that deals with the regular acquisition of a material required for a production process in a volatile environment of varying demand and fluctuating price. The usual process dynamics are demonstrated against a background of diverse choices of probability density function. The model makes use of Normal and Weibull distributions.
Population mixture model for nonlinear telomere dynamics
Itzkovitz, Shalev; Shlush, Liran I.; Gluck, Dan; Skorecki, Karl
2008-12-01
Telomeres are DNA repeats protecting chromosomal ends which shorten with each cell division, eventually leading to cessation of cell growth. We present a population mixture model that predicts an exponential decrease in telomere length with time. We analytically solve the dynamics of the telomere length distribution. The model provides an excellent fit to available telomere data and accounts for the previously unexplained observation of telomere elongation following stress and bone marrow transplantation, thereby providing insight into the nature of the telomere clock.
Feature extraction for structural dynamics model validation
Energy Technology Data Exchange (ETDEWEB)
Hemez, Francois [Los Alamos National Laboratory; Farrar, Charles [Los Alamos National Laboratory; Park, Gyuhae [Los Alamos National Laboratory; Nishio, Mayuko [UNIV OF TOKYO; Worden, Keith [UNIV OF SHEFFIELD; Takeda, Nobuo [UNIV OF TOKYO
2010-11-08
This study focuses on defining and comparing response features that can be used for structural dynamics model validation studies. Features extracted from dynamic responses obtained analytically or experimentally, such as basic signal statistics, frequency spectra, and estimated time-series models, can be used to compare characteristics of structural system dynamics. By comparing those response features extracted from experimental data and numerical outputs, validation and uncertainty quantification of numerical model containing uncertain parameters can be realized. In this study, the applicability of some response features to model validation is first discussed using measured data from a simple test-bed structure and the associated numerical simulations of these experiments. issues that must be considered were sensitivity, dimensionality, type of response, and presence or absence of measurement noise in the response. Furthermore, we illustrate a comparison method of multivariate feature vectors for statistical model validation. Results show that the outlier detection technique using the Mahalanobis distance metric can be used as an effective and quantifiable technique for selecting appropriate model parameters. However, in this process, one must not only consider the sensitivity of the features being used, but also correlation of the parameters being compared.
Nonsmooth dynamics in spiking neuron models
Coombes, S.; Thul, R.; Wedgwood, K. C. A.
2012-11-01
Large scale studies of spiking neural networks are a key part of modern approaches to understanding the dynamics of biological neural tissue. One approach in computational neuroscience has been to consider the detailed electrophysiological properties of neurons and build vast computational compartmental models. An alternative has been to develop minimal models of spiking neurons with a reduction in the dimensionality of both parameter and variable space that facilitates more effective simulation studies. In this latter case the single neuron model of choice is often a variant of the classic integrate-and-fire model, which is described by a nonsmooth dynamical system. In this paper we review some of the more popular spiking models of this class and describe the types of spiking pattern that they can generate (ranging from tonic to burst firing). We show that a number of techniques originally developed for the study of impact oscillators are directly relevant to their analysis, particularly those for treating grazing bifurcations. Importantly we highlight one particular single neuron model, capable of generating realistic spike trains, that is both computationally cheap and analytically tractable. This is a planar nonlinear integrate-and-fire model with a piecewise linear vector field and a state dependent reset upon spiking. We call this the PWL-IF model and analyse it at both the single neuron and network level. The techniques and terminology of nonsmooth dynamical systems are used to flesh out the bifurcation structure of the single neuron model, as well as to develop the notion of Lyapunov exponents. We also show how to construct the phase response curve for this system, emphasising that techniques in mathematical neuroscience may also translate back to the field of nonsmooth dynamical systems. The stability of periodic spiking orbits is assessed using a linear stability analysis of spiking times. At the network level we consider linear coupling between voltage
Wilson Barbosa Neto; André Araujo; Guilherme Carvalho; Gabriela Celani
2014-01-01
The present paper describes an integrative design experiment in which different types of models were used in order to achieve a design that compromises aesthetics, lightness, fabrication, assembly and structural performance. It shows how an integrative aproach, through the use of both virtual and physical models, can provide valuable feedback in different phases of the design and fabrication process. It was possible to conclude that the design method used allowed solving many problems and had...
Direct modeling for computational fluid dynamics
Xu, Kun
2015-06-01
All fluid dynamic equations are valid under their modeling scales, such as the particle mean free path and mean collision time scale of the Boltzmann equation and the hydrodynamic scale of the Navier-Stokes (NS) equations. The current computational fluid dynamics (CFD) focuses on the numerical solution of partial differential equations (PDEs), and its aim is to get the accurate solution of these governing equations. Under such a CFD practice, it is hard to develop a unified scheme that covers flow physics from kinetic to hydrodynamic scales continuously because there is no such governing equation which could make a smooth transition from the Boltzmann to the NS modeling. The study of fluid dynamics needs to go beyond the traditional numerical partial differential equations. The emerging engineering applications, such as air-vehicle design for near-space flight and flow and heat transfer in micro-devices, do require further expansion of the concept of gas dynamics to a larger domain of physical reality, rather than the traditional distinguishable governing equations. At the current stage, the non-equilibrium flow physics has not yet been well explored or clearly understood due to the lack of appropriate tools. Unfortunately, under the current numerical PDE approach, it is hard to develop such a meaningful tool due to the absence of valid PDEs. In order to construct multiscale and multiphysics simulation methods similar to the modeling process of constructing the Boltzmann or the NS governing equations, the development of a numerical algorithm should be based on the first principle of physical modeling. In this paper, instead of following the traditional numerical PDE path, we introduce direct modeling as a principle for CFD algorithm development. Since all computations are conducted in a discretized space with limited cell resolution, the flow physics to be modeled has to be done in the mesh size and time step scales. Here, the CFD is more or less a direct
Davtyan, Aram; Voth, Gregory A.; Andersen, Hans C.
2016-12-01
We recently developed a dynamic force matching technique for converting a coarse-grained (CG) model of a molecular system, with a CG potential energy function, into a dynamic CG model with realistic dynamics [A. Davtyan et al., J. Chem. Phys. 142, 154104 (2015)]. This is done by supplementing the model with additional degrees of freedom, called "fictitious particles." In that paper, we tested the method on CG models in which each molecule is coarse-grained into one CG point particle, with very satisfactory results. When the method was applied to a CG model of methanol that has two CG point particles per molecule, the results were encouraging but clearly required improvement. In this paper, we introduce a new type (called type-3) of fictitious particle that exerts forces on the center of mass of two CG sites. A CG model constructed using type-3 fictitious particles (as well as type-2 particles previously used) gives a much more satisfactory dynamic model for liquid methanol. In particular, we were able to construct a CG model that has the same self-diffusion coefficient and the same rotational relaxation time as an all-atom model of liquid methanol. Type-3 particles and generalizations of it are likely to be useful in converting more complicated CG models into dynamic CG models.
Dynamic Intellectual Capital Model in a Company
Directory of Open Access Journals (Sweden)
Vladimir Shatrevich
2015-06-01
Full Text Available The aim of this paper is to indicate the relations between company’s value added (VA and intangible assets. Authors declare that Intellectual capital (IC is one of the most relevant intangibles for a company, and the concept with measurement, and the relation with value creation is necessary for modern markets. Since relationship between IC elements and VA are complicated, this paper is aimed to create a usable dynamic model for building company’s value added through intellectual capital. The model is incorporating that outputs from IC elements are not homogeneously received and made some contributions to dynamic nature of IC relation and VA. Variables that will help companies to evaluate contribution of each element of IC are added to the model. This paper emphasizes the importance of a company’s IC and the positive interaction between them in generating profits for company.
Dynamic Circuit Model for Spintronic Devices
Alawein, Meshal
2017-01-09
In this work we propose a finite-difference scheme based circuit model of a general spintronic device and benchmark it with other models proposed for spintronic switching devices. Our model is based on the four-component spin circuit theory and utilizes the widely used coupled stochastic magnetization dynamics/spin transport framework. In addition to the steady-state analysis, this work offers a transient analysis of carrier transport. By discretizing the temporal and spatial derivatives to generate a linear system of equations, we derive new and simple finite-difference conductance matrices that can, to the first order, capture both static and dynamic behaviors of a spintronic device. We also discuss an extension of the spin modified nodal analysis (SMNA) for time-dependent situations based on the proposed scheme.
Traffic flow dynamics data, models and simulation
Treiber, Martin
2013-01-01
This textbook provides a comprehensive and instructive coverage of vehicular traffic flow dynamics and modeling. It makes this fascinating interdisciplinary topic, which to date was only documented in parts by specialized monographs, accessible to a broad readership. Numerous figures and problems with solutions help the reader to quickly understand and practice the presented concepts. This book is targeted at students of physics and traffic engineering and, more generally, also at students and professionals in computer science, mathematics, and interdisciplinary topics. It also offers material for project work in programming and simulation at college and university level. The main part, after presenting different categories of traffic data, is devoted to a mathematical description of the dynamics of traffic flow, covering macroscopic models which describe traffic in terms of density, as well as microscopic many-particle models in which each particle corresponds to a vehicle and its driver. Focus chapters on ...
Dynamical Models of Dyadic Interactions with Delay
Bielczyk, Natalia; Płatkowski, Tadeusz
2012-01-01
When interpersonal interactions between individuals are described by the (discrete or continuous) dynamical systems, the interactions are usually assumed to be instantaneous: the rates of change of the actual states of the actors at given instant of time are assumed to depend on their states at the same time. In reality the natural time delay should be included in the corresponding models. We investigate a general class of linear models of dyadic interactions with a constant discrete time delay. We prove that in such models the changes of stability of the stationary points from instability to stability or vice versa occur for various intervals of the parameters which determine the intensity of interactions. The conditions guaranteeing arbitrary number (zero, one ore more) of switches are formulated and the relevant theorems are proved. A systematic analysis of all generic cases is carried out. It is obvious that the dynamics of interactions depend both on the strength of reactions of partners on their own sta...
Indonesia’s Electricity Demand Dynamic Modelling
Sulistio, J.; Wirabhuana, A.; Wiratama, M. G.
2017-06-01
Electricity Systems modelling is one of the emerging area in the Global Energy policy studies recently. System Dynamics approach and Computer Simulation has become one the common methods used in energy systems planning and evaluation in many conditions. On the other hand, Indonesia experiencing several major issues in Electricity system such as fossil fuel domination, demand - supply imbalances, distribution inefficiency, and bio-devastation. This paper aims to explain the development of System Dynamics modelling approaches and computer simulation techniques in representing and predicting electricity demand in Indonesia. In addition, this paper also described the typical characteristics and relationship of commercial business sector, industrial sector, and family / domestic sector as electricity subsystems in Indonesia. Moreover, it will be also present direct structure, behavioural, and statistical test as model validation approach and ended by conclusions.
Modeling epidemics dynamics on heterogenous networks.
Ben-Zion, Yossi; Cohen, Yahel; Shnerb, Nadav M
2010-05-21
The dynamics of the SIS process on heterogenous networks, where different local communities are connected by airlines, is studied. We suggest a new modeling technique for travelers movement, in which the movement does not affect the demographic parameters characterizing the metapopulation. A solution to the deterministic reaction-diffusion equations that emerges from this model on a general network is presented. A typical example of a heterogenous network, the star structure, is studied in detail both analytically and using agent-based simulations. The interplay between demographic stochasticity, spatial heterogeneity and the infection dynamics is shown to produce some counterintuitive effects. In particular it was found that, while movement always increases the chance of an outbreak, it may decrease the steady-state fraction of sick individuals. The importance of the modeling technique in estimating the outcomes of a vaccination campaign is demonstrated.
A dynamical model of non regulated markets
Schaale, A
1999-01-01
The main focus of this work is to understand the dynamics of non regulated markets. The present model can describe the dynamics of any market where the pricing is based on supply and demand. It will be applied here, as an example, for the German stock market presented by the Deutscher Aktienindex (DAX), which is a measure for the market status. The duality of the present model consists of the superposition of the two components - the long and the short term behaviour of the market. The long term behaviour is characterised by a stable development which is following a trend for time periods of years or even decades. This long term growth (or decline) is based on the development of fundamental market figures. The short term behaviour is described as a dynamical evaluation (trading) of the market by the participants. The trading process is described as an exchange between supply and demand. In the framework of this model there the trading is modelled by a system of nonlinear differential equations. The model also...
Fully Equipped Dynamic Model of a Bus
Directory of Open Access Journals (Sweden)
I. Kowarska
2014-01-01
Full Text Available Nowadays, the time to market a new vehicle is crucial for every company as it is easier to meet the customers’ needs and expectations. However, designing a new vehicle is a long process which needs to take into account different performances. The most difficult is to predict a dynamic behavior of a vehicle especially when such a big vehicles as urban buses are considered. Therefore, there is a necessity to use a virtual model to investigate different performances. However, there is a lack of urban bus models that can fully reflect a dynamic behavior of the bus. This paper presents a fully equipped urban bus model which can be used to study a dynamic behavior of such vehicles. The model is based on innovative technique called cosimulation, which connects different modeling techniques (3D and 1D. Such a technique allows performing different analyses that require small deformations and large translations and rotations in shorter time and automatic way. The work has been carried out in a project EUREKA CHASING.
Analysing the temporal dynamics of model performance for hydrological models
Reusser, D.E.; Blume, T.; Schaefli, B.; Zehe, E.
2009-01-01
The temporal dynamics of hydrological model performance gives insights into errors that cannot be obtained from global performance measures assigning a single number to the fit of a simulated time series to an observed reference series. These errors can include errors in data, model parameters, or m
Directory of Open Access Journals (Sweden)
Wilson Barbosa Neto
2014-12-01
Full Text Available The present paper describes an integrative design experiment in which different types of models were used in order to achieve a design that compromises aesthetics, lightness, fabrication, assembly and structural performance. It shows how an integrative aproach, through the use of both virtual and physical models, can provide valuable feedback in different phases of the design and fabrication process. It was possible to conclude that the design method used allowed solving many problems and had a significant impact in the resulting object.
Learning generative models of molecular dynamics.
Razavian, Narges Sharif; Kamisetty, Hetunandan; Langmead, Christopher J
2012-01-01
We introduce three algorithms for learning generative models of molecular structures from molecular dynamics simulations. The first algorithm learns a Bayesian-optimal undirected probabilistic model over user-specified covariates (e.g., fluctuations, distances, angles, etc). L1 regularization is used to ensure sparse models and thus reduce the risk of over-fitting the data. The topology of the resulting model reveals important couplings between different parts of the protein, thus aiding in the analysis of molecular motions. The generative nature of the model makes it well-suited to making predictions about the global effects of local structural changes (e.g., the binding of an allosteric regulator). Additionally, the model can be used to sample new conformations. The second algorithm learns a time-varying graphical model where the topology and parameters change smoothly along the trajectory, revealing the conformational sub-states. The last algorithm learns a Markov Chain over undirected graphical models which can be used to study and simulate kinetics. We demonstrate our algorithms on multiple molecular dynamics trajectories.
Switched Dynamical Latent Force Models for Modelling Transcriptional Regulation
López-Lopera, Andrés F
2015-01-01
In order to develop statistical approaches for transcription networks, statistical community has proposed several methods to infer activity levels of proteins, from time-series measurements of targets' expression levels. A few number of approaches have been proposed in order to outperform the representation of fast switching time instants, but computational overheads are significant due to complex inference algorithms. Using the theory related to latent force models (LFM), the development of this project provide a switched dynamical hybrid model based on Gaussian processes (GPs). To deal with discontinuities in dynamical systems (or latent driving force), an extension of the single input motif approach is introduced, that switches between different protein concentrations, and different dynamical systems. This creates a versatile representation for transcription networks that can capture discrete changes and non-linearities in the dynamics. The proposed method is evaluated on both simulated data and real data,...
Global Langevin model of multidimensional biomolecular dynamics
Schaudinnus, Norbert; Lickert, Benjamin; Biswas, Mithun; Stock, Gerhard
2016-11-01
Molecular dynamics simulations of biomolecular processes are often discussed in terms of diffusive motion on a low-dimensional free energy landscape F ( 𝒙 ) . To provide a theoretical basis for this interpretation, one may invoke the system-bath ansatz á la Zwanzig. That is, by assuming a time scale separation between the slow motion along the system coordinate x and the fast fluctuations of the bath, a memory-free Langevin equation can be derived that describes the system's motion on the free energy landscape F ( 𝒙 ) , which is damped by a friction field and driven by a stochastic force that is related to the friction via the fluctuation-dissipation theorem. While the theoretical formulation of Zwanzig typically assumes a highly idealized form of the bath Hamiltonian and the system-bath coupling, one would like to extend the approach to realistic data-based biomolecular systems. Here a practical method is proposed to construct an analytically defined global model of structural dynamics. Given a molecular dynamics simulation and adequate collective coordinates, the approach employs an "empirical valence bond"-type model which is suitable to represent multidimensional free energy landscapes as well as an approximate description of the friction field. Adopting alanine dipeptide and a three-dimensional model of heptaalanine as simple examples, the resulting Langevin model is shown to reproduce the results of the underlying all-atom simulations. Because the Langevin equation can also be shown to satisfy the underlying assumptions of the theory (such as a delta-correlated Gaussian-distributed noise), the global model provides a correct, albeit empirical, realization of Zwanzig's formulation. As an application, the model can be used to investigate the dependence of the system on parameter changes and to predict the effect of site-selective mutations on the dynamics.
Model for Dynamic Multiple of CPPI Strategy
Directory of Open Access Journals (Sweden)
Guangyuan Xing
2014-01-01
Full Text Available Focusing on the parameter “Multiple” of CPPI strategy, this study proposes a dynamic setting model of multiple for gap risk management purpose. First, CPPI gap risk is measured as the probability that the value loss of active asset exceeds its allowed maximum drop determined by a given multiple setting. Moreover, according to the statistical estimation using SV-EVT approach, a dynamic choice of multiple is detailed as a function of time-varying asset volatility, expected loss, and the possibility of occurrence of extreme events in the active asset returns illustrated empirically on Shanghai composite index data. This study not only enriches the literature of dynamic proportion portfolio insurance, but also provides a practical reference for CPPI investors to choose a moderate risky exposure achieving gap risk management, which promotes CPPI’s application in emerging capital market.
An introduction to modeling neuronal dynamics
Börgers, Christoph
2017-01-01
This book is intended as a text for a one-semester course on Mathematical and Computational Neuroscience for upper-level undergraduate and beginning graduate students of mathematics, the natural sciences, engineering, or computer science. An undergraduate introduction to differential equations is more than enough mathematical background. Only a slim, high school-level background in physics is assumed, and none in biology. Topics include models of individual nerve cells and their dynamics, models of networks of neurons coupled by synapses and gap junctions, origins and functions of population rhythms in neuronal networks, and models of synaptic plasticity. An extensive online collection of Matlab programs generating the figures accompanies the book. .
Critical behavior of a dynamical percolation model
Institute of Scientific and Technical Information of China (English)
YU Mei-Ling; XU Ming-Mei; LIU Zheng-You; LIU Lian-Shou
2009-01-01
The critical behavior of the dynamical percolation model, which realizes the molecular-aggregation conception and describes the crossover between the hadronic phase and the partonic phase, is studied in detail. The critical percolation distance for this model is obtained by using the probability P∞ of the appearance of an infinite cluster. Utilizing the finite-size scaling method the critical exponents γ/v and T are extracted from the distribution of the average cluster size and cluster number density. The influences of two model related factors, I.e. The maximum bond number and the definition of the infinite cluster, on the critical behavior are found to be small.
Polarizable water model for Dissipative Particle Dynamics
Pivkin, Igor; Peter, Emanuel
2015-11-01
Dissipative Particle Dynamics (DPD) is an efficient particle-based method for modeling mesoscopic behavior of fluid systems. DPD forces conserve the momentum resulting in a correct description of hydrodynamic interactions. Polarizability has been introduced into some coarse-grained particle-based simulation methods; however it has not been done with DPD before. We developed a new polarizable coarse-grained water model for DPD, which employs long-range electrostatics and Drude oscillators. In this talk, we will present the model and its applications in simulations of membrane systems, where polarization effects play an essential role.
DYNAMICS IN A CLASS OF NEURON MODELS
Institute of Scientific and Technical Information of China (English)
Wang Junping; Ruan Jiong
2009-01-01
In this paper, we investigate the dynamics in a class of discrete-time neuron mo-dels. The neuron model we discussed, defined by such periodic input-output mapping as a sinusoidal function, has a remarkably larger memory capacity than the conven-tional association system with the monotonous function. Our results show that the orbit of the model takes a conventional bifurcation route, from stable equilibrium, to periodicity, even to chaotic region. And the theoretical analysis is verified by numerical simulations.
Five challenges in modelling interacting strain dynamics
DEFF Research Database (Denmark)
Wikramaratna, Paul S; Kurcharski, Adam; Gupta, Sunetra
2015-01-01
Population epidemiological models where hosts can be infected sequentially by different strains have the potential to help us understand many important diseases. Researchers have in recent years started to develop and use such models, but the extra layer of complexity from multiple strains brings...... with it many technical challenges. It is therefore hard to build models which have realistic assumptions yet are tractable. Here we outline some of the main challenges in this area. First we begin with the fundamental question of how to translate from complex small-scale dynamics within a host to useful...... population models. Next we consider the nature of so-called “strain space”. We describe two key types of host heterogeneities, and explain how models could help generate a better understanding of their effects. Finally, for diseases with many strains, we consider the challenge of modelling how immunity...
Amendment to Validated dynamic flow model
DEFF Research Database (Denmark)
Knudsen, Torben
2011-01-01
The purpose of WP2 is to establish flow models relating the wind speed at turbines in a farm. Until now, active control of power reference has not been included in these models as only data with standard operation has been available. In this report the first data series with power reference...... excitations from the Thanet farm are used for trying to update some of the models discussed in D2.5. Because of very limited amount of data only simple dynamic transfer function models can be obtained. The three obtained data series are somewhat different. Only the first data set seems to have the front...... turbine in undisturbed flow. For this data set both the multiplicative model and in particular the simple first order transfer function model can predict the down wind wind speed from upwind wind speed and loading....
Structural system identification: Structural dynamics model validation
Energy Technology Data Exchange (ETDEWEB)
Red-Horse, J.R.
1997-04-01
Structural system identification is concerned with the development of systematic procedures and tools for developing predictive analytical models based on a physical structure`s dynamic response characteristics. It is a multidisciplinary process that involves the ability (1) to define high fidelity physics-based analysis models, (2) to acquire accurate test-derived information for physical specimens using diagnostic experiments, (3) to validate the numerical simulation model by reconciling differences that inevitably exist between the analysis model and the experimental data, and (4) to quantify uncertainties in the final system models and subsequent numerical simulations. The goal of this project was to develop structural system identification techniques and software suitable for both research and production applications in code and model validation.
t-GIS AND ENVIRONMENTAL DYNAMIC MODELS
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
Temporal geographic information system(t-GIS) is a kind of computer information system that can display,process and analyze the micro-format distribution of temporal-spatial information of real world.It includes both spatial geographic information and temporal information,and can analyze both the static geographic information and the dynamic geographic information.Three models based on t-GIS for environment dynamics,namely,the mechanism method,the experience method and the mixed method are given.t-GIS based on the environment dynamic model has more new functions than traditional GIS,such as fast I/O,inquiry,static/dynamic display and visible analysis of spatial and temporal sequence information,especially it can display the image of the evolution in the past,current and future environment through the extrapolation method within its defining region.The velocity for analogue display can be accelerated by setting up time-varying-area-function for position and attribute.Dynamic environmental information analysis systems based on t-GIS are applicable to almost all the fields related to management,display and analysis of local environmental dynamic information.For this reason,some considerations to construct distinct information systems have been enumerated in this paper,such as,the analysis information system for terrain evolution,the analysis information system for the condition of water and fertilizer of farmland,analysis and the evaluation information system for ecological environment,and the analysis information system for distribution changes of population of China,etc.
Directory of Open Access Journals (Sweden)
M. Theau.Clément
2015-09-01
Full Text Available Sexual receptivity of rabbit does at insemination greatly influences fertility and is generally induced by hormones or techniques known as “biostimulation”. Searching for more sustainable farming systems, an original alternative would be to utilise the genetic pathway to increase the does’receptivity. The purpose of the present study was to identify genetic and non-genetic factors that influence rabbit doe sexual receptivity, in the context of a divergent selection experiment over 1 generation. The experiment spanned 2 generations: the founder generation (G0 consisting of 140 rabbit does, and the G1 generation comprising 2 divergently selected lines (L and H lines with 70 does each and 2 successive batches from each generation. The selection rate of the G0 females to form the G1 lines was 24/140. The selection tests consisted of 16 to 18 successive receptivity tests at the rate of 3 tests per week. On the basis of 4716 tests from 275 females, the average receptivity was 56.6±48.2%. A batch effect and a test operator effect were revealed. The contribution of females to the total variance was 20.0%, whereas that of bucks was only 1.1%. Throughout the experiment, 18.2% of does expressed a low receptivity (< 34%, 50.7% a medium one and 33.1% a high one (>66%. Some does were frequently receptive, whereas others were rarely receptive. The repeatability of sexual receptivity was approximately 20%. The results confirmed the high variability of sexual receptivity of non-lactating rabbit does maintained without any biostimulation or hormonal treatment. A lack of selection response on receptivity was observed. Accordingly, the heritability of receptivity was estimated at 0.01±0.02 from an animal model and at 0.02±0.03 from a sire and dam model. The heritability of the average receptivity of a doe was calculated as 0.04. In agreement with the low estimated heritability, the heritability determined was no different from zero
Modelling Holocene peatland and permafrost dynamics with the LPJ-GUESS dynamic vegetation model
Chaudhary, Nitin; Miller, Paul A.; Smith, Benjamin
2016-04-01
Dynamic global vegetation models (DGVMs) are an important platform to study past, present and future vegetation patterns together with associated biogeochemical cycles and climate feedbacks (e.g. Sitch et al. 2008, Smith et al. 2001). However, very few attempts have been made to simulate peatlands using DGVMs (Kleinen et al. 2012, Tang et al. 2015, Wania et al. 2009a). In the present study, we have improved the peatland dynamics in the state-of-the-art dynamic vegetation model (LPJ-GUESS) in order to understand the long-term evolution of northern peatland ecosystems and to assess the effect of changing climate on peatland carbon balance. We combined a dynamic multi-layer approach (Frolking et al. 2010, Hilbert et al. 2000) with soil freezing-thawing functionality (Ekici et al. 2015, Wania et al. 2009a) in LPJ-GUESS. The new model is named LPJ-GUESS Peatland (LPJ-GUESS-P) (Chaudhary et al. in prep). The model was calibrated and tested at the sub-arctic mire in Stordalen, Sweden, and the model was able to capture the reported long-term vegetation dynamics and peat accumulation patterns in the mire (Kokfelt et al. 2010). For evaluation, the model was run at 13 grid points across a north to south transect in Europe. The modelled peat accumulation values were found to be consistent with the published data for each grid point (Loisel et al. 2014). Finally, a series of additional experiments were carried out to investigate the vulnerability of high-latitude peatlands to climate change. We find that the Stordalen mire will sequester more carbon in the future due to milder and wetter climate conditions, longer growing seasons, and the carbon fertilization effect. References: - Chaudhary et al. (in prep.). Modelling Holocene peatland and permafrost dynamics with the LPJ-GUESS dynamic vegetation model - Ekici A, et al. 2015. Site-level model intercomparison of high latitude and high altitude soil thermal dynamics in tundra and barren landscapes. The Cryosphere 9: 1343
Modeling of intensified high dynamic star tracker.
Yan, Jinyun; Jiang, Jie; Zhang, Guangjun
2017-01-23
An intensified high dynamic star tracker (IHDST) is a photoelectric instrument and stably outputs three-axis attitude for a spacecraft at very high angular velocity. The IHDST uses an image intensifier to multiply the incident starlight. Thus, high sensitivity of the star detection is achieved under short exposure time such that extremely high dynamic performance is achieved. The IHDST differs from a traditional star tracker in terms of the imaging process. Therefore, we establish a quantum transfer model of IHDST based on stochastic process theory. By this model, the probability distribution of the output quantum number is obtained accurately. Then, we introduce two-dimensional Lorentz functions to describe the spatial spreading process of the IHDST. Considering the interaction of these two processes, a complete star imaging model of IHDST is provided. Using this model, the centroiding accuracy of the IHDST is analyzed in detail. Accordingly, a working parameter optimizing strategy is developed for high centroiding accuracy and improved dynamic performance. Finally, the laboratory tests and the night sky experiment support the conclusions.
Simple mathematical models of gene regulatory dynamics
Mackey, Michael C; Tyran-Kamińska, Marta; Zeron, Eduardo S
2016-01-01
This is a short and self-contained introduction to the field of mathematical modeling of gene-networks in bacteria. As an entry point to the field, we focus on the analysis of simple gene-network dynamics. The notes commence with an introduction to the deterministic modeling of gene-networks, with extensive reference to applicable results coming from dynamical systems theory. The second part of the notes treats extensively several approaches to the study of gene-network dynamics in the presence of noise—either arising from low numbers of molecules involved, or due to noise external to the regulatory process. The third and final part of the notes gives a detailed treatment of three well studied and concrete examples of gene-network dynamics by considering the lactose operon, the tryptophan operon, and the lysis-lysogeny switch. The notes contain an index for easy location of particular topics as well as an extensive bibliography of the current literature. The target audience of these notes are mainly graduat...
A Typed Model for Dynamic Authorizations
Directory of Open Access Journals (Sweden)
Silvia Ghilezan
2016-02-01
Full Text Available Security requirements in distributed software systems are inherently dynamic. In the case of authorization policies, resources are meant to be accessed only by authorized parties, but the authorization to access a resource may be dynamically granted/yielded. We describe ongoing work on a model for specifying communication and dynamic authorization handling. We build upon the pi-calculus so as to enrich communication-based systems with authorization specification and delegation; here authorizations regard channel usage and delegation refers to the act of yielding an authorization to another party. Our model includes: (i a novel scoping construct for authorization, which allows to specify authorization boundaries, and (ii communication primitives for authorizations, which allow to pass around authorizations to act on a given channel. An authorization error may consist in, e.g., performing an action along a name which is not under an appropriate authorization scope. We introduce a typing discipline that ensures that processes never reduce to authorization errors, even when authorizations are dynamically delegated.
Dynamic description logic model for data integration
Institute of Scientific and Technical Information of China (English)
Guoshun HAO; Shilong MA; Yuefei SUI; Jianghua LV
2008-01-01
Data integration is the issue of retrieving and combining data residing at distributed and heterogeneous sources,and of providing users with transparent access without being aware of the details of the sources.Data integration is a very important issue because it deals with data infrastructure issues of coordinated computing systems.Despite its importance,the following key challenges make data integration one of the longest standing problems around:1) how to solve the system heterogeneity;2) how to build a global model;3) how to process queries automatically and correctly;and 4) how to solve semantic heterogeneity. This paper presents an extended dynamic description logic language to describe systems with dynamic actions.By this language,a-universal and unified model for relational database systems and a model for data integration are presented.This paper presents a universal and unified description logic model for relational databases.The model is universal because any relational database system can be automatically transformed to the model;it is unified because it integrates three essential components of relational databases together:description logic knowledge bases modeling the relational data,atomic modalities modeling the atomic relational operations,and combined modalities modeling the combined relational operations-queries. Furthermore,a description logic model for data integration is proposed which contains four layers of ontologies.Based on the model,a solution for each key challenge is proposed:a universal model eliminates system heterogeneity;a novel global model including three ontologies is proposed with some important benefits;a query process mechanism is provided by which user queries can be decomposed to queries over the sources;and for solving the semantic heterogeneity,this paper provides a framework under which semantic relations can be expressed and inferred. In summary,this paper presents a dynamic knowledge base framework by an extended
Dynamic mesh for TCAD modeling with ECORCE
Michez, A.; Boch, J.; Touboul, A.; Saigné, F.
2016-08-01
Mesh generation for TCAD modeling is challenging. Because densities of carriers can change by several orders of magnitude in thin areas, a significant change of the solution can be observed for two very similar meshes. The mesh must be defined at best to minimize this change. To address this issue, a criterion based on polynomial interpolation on adjacent nodes is proposed that adjusts accurately the mesh to the gradients of Degrees of Freedom. Furthermore, a dynamic mesh that follows changes of DF in DC and transient mode is a powerful tool for TCAD users. But, in transient modeling, adding nodes to a mesh induces oscillations in the solution that appears as spikes at the current collected at the contacts. This paper proposes two schemes that solve this problem. Examples show that using these techniques, the dynamic mesh generator of the TCAD tool ECORCE handle semiconductors devices in DC and transient mode.
Hamiltonian Dynamics of Cosmological Quintessence Models
Ivanov, Rossen I
2016-01-01
The time-evolution dynamics of two nonlinear cosmological real gas models has been reexamined in detail with methods from the theory of Hamiltonian dynamical systems. These examples are FRWL cosmologies, one based on a gas, satisfying the van der Waals equation and another one based on the virial expansion gas equation. The cosmological variables used are the expansion rate, given by the Hubble parameter, and the energy density. The analysis is aided by the existence of global first integral as well as several special (second) integrals in each case. In addition, the global first integral can serve as a Hamiltonian for a canonical Hamiltonian formulation of the evolution equations. The conserved quantities lead to the existence of stable periodic solutions (closed orbits) which are models of a cyclic Universe. The second integrals allow for explicit solutions as functions of time on some special trajectories and thus for a deeper understanding of the underlying physics. In particular, it is shown that any pos...
Multiscale Model Approach for Magnetization Dynamics Simulations
De Lucia, Andrea; Tretiakov, Oleg A; Kläui, Mathias
2016-01-01
Simulations of magnetization dynamics in a multiscale environment enable rapid evaluation of the Landau-Lifshitz-Gilbert equation in a mesoscopic sample with nanoscopic accuracy in areas where such accuracy is required. We have developed a multiscale magnetization dynamics simulation approach that can be applied to large systems with spin structures that vary locally on small length scales. To implement this, the conventional micromagnetic simulation framework has been expanded to include a multiscale solving routine. The software selectively simulates different regions of a ferromagnetic sample according to the spin structures located within in order to employ a suitable discretization and use either a micromagnetic or an atomistic model. To demonstrate the validity of the multiscale approach, we simulate the spin wave transmission across the regions simulated with the two different models and different discretizations. We find that the interface between the regions is fully transparent for spin waves with f...
Dynamic energy-demand models. A comparison
Energy Technology Data Exchange (ETDEWEB)
Yi, Feng [Department of Economics, Goeteborg University, Gothenburg (Sweden)
2000-04-01
This paper compares two second-generation dynamic energy demand models, a translog (TL) and a general Leontief (GL), in the study of price elasticities and factor substitutions of nine Swedish manufacturing industries: food, textiles, wood, paper, printing, chemicals, non-metallic minerals, base metals and machinery. Several model specifications are tested with likelihood ratio test. There is a disagreement on short-run adjustments; the TL model accepts putty-putty production technology of immediate adjustments, implying equal short- and long-run price elasticities of factors, while the GL model rejects immediate adjustments, giving out short-run elasticities quite different from the long-run. The two models also disagree in substitutability in many cases. 21 refs.
The dynamic radiation environment assimilation model (DREAM)
Energy Technology Data Exchange (ETDEWEB)
Reeves, Geoffrey D [Los Alamos National Laboratory; Koller, Josef [Los Alamos National Laboratory; Tokar, Robert L [Los Alamos National Laboratory; Chen, Yue [Los Alamos National Laboratory; Henderson, Michael G [Los Alamos National Laboratory; Friedel, Reiner H [Los Alamos National Laboratory
2010-01-01
The Dynamic Radiation Environment Assimilation Model (DREAM) is a 3-year effort sponsored by the US Department of Energy to provide global, retrospective, or real-time specification of the natural and potential nuclear radiation environments. The DREAM model uses Kalman filtering techniques that combine the strengths of new physical models of the radiation belts with electron observations from long-term satellite systems such as GPS and geosynchronous systems. DREAM includes a physics model for the production and long-term evolution of artificial radiation belts from high altitude nuclear explosions. DREAM has been validated against satellites in arbitrary orbits and consistently produces more accurate results than existing models. Tools for user-specific applications and graphical displays are in beta testing and a real-time version of DREAM has been in continuous operation since November 2009.
Identification of helicopter rotor dynamic models
Molusis, J. A.; Bar-Shalom, Y.; Warmbrodt, W.
1983-01-01
A recursive, extended Kalman-filter approach is applied to the identifiction of rotor damping levels of representative helicopter dynamic systems. The general formulation of the approach is presented in the context of a typically posed stochastic estimation problem, and the method is analytically applied to determining the damping levels of a coupled rotor-body system. The identified damping covergence characteristics are studied for sensitivity to both constant-coefficient and periodic-coefficient measurement models, process-noise covariance levels, and specified initial estimates of the rotor-system damping. A second application of the method to identifying the plant model for a highly damped, isolated flapping blade with a constant-coefficient state model (hover) and a periodic-coefficient state model (forward flight) is also investigated. The parameter-identification capability is evaluated for the effect of periodicity on the plant model coefficients and the influence of different measurement noise levels.
Dynamical symmetries of the shell model
Energy Technology Data Exchange (ETDEWEB)
Van Isacker, P
2000-07-01
The applications of spectrum generating algebras and of dynamical symmetries in the nuclear shell model are many and varied. They stretch back to Wigner's early work on the supermultiplet model and encompass important landmarks in our understanding of the structure of the atomic nucleus such as Racah's SU(2) pairing model and Elliot's SU(3) rotational model. One of the aims of this contribution has been to show the historical importance of the idea of dynamical symmetry in nuclear physics. Another has been to indicate that, in spite of being old, this idea continues to inspire developments that are at the forefront of today's research in nuclear physics. It has been argued in this contribution that the main driving features of nuclear structure can be represented algebraically but at the same time the limitations of the symmetry approach must be recognised. It should be clear that such approach can only account for gross properties and that any detailed description requires more involved numerical calculations of which we have seen many fine examples during this symposium. In this way symmetry techniques can be used as an appropriate starting point for detailed calculations. A noteworthy example of this approach is the pseudo-SU(3) model which starting from its initial symmetry Ansatz has grown into an adequate and powerful description of the nucleus in terms of a truncated shell model. (author)
A Model for Nonstationary Market Dynamics with Nontrivial Dynamical Scaling
Liu, Min; Bassler, Kevin E.
2008-03-01
In a recent empirical analysis of the Euro/Dollar exchange rate [Bassler, et al., PNAS 104, 17287 (2007)] it was found that during certain periods of the day the market returns scale with Hurst exponents H that are significantly different from 1/2. In some of these periods it is less than 1/2, while in others it is greater than 1/2. In this talk we will propose a possible origin for this behavior and other stylized market facts, including short time negative autocorrelations of returns, in terms of a nonstationary compound Poisson process with a time-dependent intensity rate function that results from a changing bid-ask spread in the microscopic market. The model correctly describes the dynamic scaling behavior of a simple reaction-diffusion model of a limit-order book. That model, like the Euro/Dollar exchange rate, has nonstationary return increments and a Hurst exponent H not equal to 1/2.
Simple Models for the Dynamic Modeling of Rotating Tires
Directory of Open Access Journals (Sweden)
J.C. Delamotte
2008-01-01
Full Text Available Large Finite Element (FE models of tires are currently used to predict low frequency behavior and to obtain dynamic model coefficients used in multi-body models for riding and comfort. However, to predict higher frequency behavior, which may explain irregular wear, critical rotating speeds and noise radiation, FE models are not practical. Detailed FE models are not adequate for optimization and uncertainty predictions either, as in such applications the dynamic solution must be computed a number of times. Therefore, there is a need for simpler models that can capture the physics of the tire and be used to compute the dynamic response with a low computational cost. In this paper, the spectral (or continuous element approach is used to derive such a model. A circular beam spectral element that takes into account the string effect is derived, and a method to simulate the response to a rotating force is implemented in the frequency domain. The behavior of a circular ring under different internal pressures is investigated using modal and frequency/wavenumber representations. Experimental results obtained with a real untreaded truck tire are presented and qualitatively compared with the simple model predictions with good agreement. No attempt is made to obtain equivalent parameters for the simple model from the real tire results. On the other hand, the simple model fails to represent the correct variation of the quotient of the natural frequency by the number of circumferential wavelengths with the mode count. Nevertheless, some important features of the real tire dynamic behavior, such as the generation of standing waves and part of the frequency/wavenumber behavior, can be investigated using the proposed simplified model.
Dual-scale multimedia dynamic synchronization model
Institute of Scientific and Technical Information of China (English)
李乃祥
2009-01-01
Multimedia synchronization is the key technology in application of distributed multimedia.Solution of synchronization conflicts insides and among streams as well as that of user interaction,synchronization granularity refinement and synchronization precision improvement remain great challenges although great efforts have been invested by the academic circle.The construction method of a dual-scale dynamic synchronous model of multimedia presented in this article realizes multimedia synchronization on two sca...
Dynamic Modelling of a modular robot finger
2014-01-01
New generations of dexterous robotic hands with high degrees of freedom, integrated advanced sensors, improving power-to-weight ratio, have shown great potential for performing complex tasks beyond simple grasping such as manipulation and gaiting. With the help of control strategies such as impedance and compliance control, together with various compensation methods, researchers have achieved some success in performing dexterous tasks with robotic hands. However, the lack of a dynamic model o...
Modeling of glutamate-induced dynamical patterns
DEFF Research Database (Denmark)
Faurby-Bentzen, Christian Krefeld; Zhabotinsky, A.M.; Laugesen, Jakob Lund
2009-01-01
Based on established physiological mechanisms, the paper presents a detailed computer model, which supports the hypothesis that temporal lobe epilepsy may be caused by failure of glutamate reuptake from the extracellular space. The elevated glutamate concentration causes an increased activation o...... of NMDA receptors in pyramidal neurons, which in turn leads to neuronal dynamics that is qualitatively identical to epileptiform activity. We identify by chaos analysis a surprising possibility that muscarinergic receptors can help the system out of a chaotic regime....
Molecular dynamics modelling of solidification in metals
Energy Technology Data Exchange (ETDEWEB)
Boercker, D.B.; Belak, J.; Glosli, J. [Lawrence Livermore National Lab., CA (United States)
1997-12-31
Molecular dynamics modeling is used to study the solidification of metals at high pressure and temperature. Constant pressure MD is applied to a simulation cell initially filled with both solid and molten metal. The solid/liquid interface is tracked as a function of time, and the data are used to estimate growth rates of crystallites at high pressure and temperature in Ta and Mg.
DYNAMIC FREE ENERGY HYSTERESIS MODEL IN MAGNETOSTRICTIVE ACTUATORS
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
A dynamic free energy hysteresis model in magnetostrictive actuators is presented. It is the free energy hysteresis model coupled to an ordinary different equation in an unusual way. According to its special structure, numerical implementation method of the dynamic model is provided. The resistor parameter in the dynamic model changes according to different frequency ranges. This makes numerical implementation results reasonable in the discussed operating frequency range. The validity of the dynamic free energy model is illustrated by comparison with experimental data.
Stochastic dynamic model of SARS spreading
Institute of Scientific and Technical Information of China (English)
SHI Yaolin
2003-01-01
Based upon the simulation of the stochastic process of infection, onset and spreading of each SARS patient, a system dynamic model of SRAS spreading is constructed. Data from Vietnam is taken as an example for Monte Carlo test. The preliminary results indicate that the time-dependent infection rate is the most important control factor for SARS spreading. The model can be applied to prediction of the course with fluctuations of the epidemics, if the previous history of the epidemics and the future infection rate under control measures are known.
A dynamical model for bark beetle outbreaks.
Křivan, Vlastimil; Lewis, Mark; Bentz, Barbara J; Bewick, Sharon; Lenhart, Suzanne M; Liebhold, Andrew
2016-10-21
Tree-killing bark beetles are major disturbance agents affecting coniferous forest ecosystems. The role of environmental conditions on driving beetle outbreaks is becoming increasingly important as global climatic change alters environmental factors, such as drought stress, that, in turn, govern tree resistance. Furthermore, dynamics between beetles and trees are highly nonlinear, due to complex aggregation behaviors exhibited by beetles attacking trees. Models have a role to play in helping unravel the effects of variable tree resistance and beetle aggregation on bark beetle outbreaks. In this article we develop a new mathematical model for bark beetle outbreaks using an analogy with epidemiological models. Because the model operates on several distinct time scales, singular perturbation methods are used to simplify the model. The result is a dynamical system that tracks populations of uninfested and infested trees. A limiting case of the model is a discontinuous function of state variables, leading to solutions in the Filippov sense. The model assumes an extensive seed-bank so that tree recruitment is possible even if trees go extinct. Two scenarios are considered for immigration of new beetles. The first is a single tree stand with beetles immigrating from outside while the second considers two forest stands with beetle dispersal between them. For the seed-bank driven recruitment rate, when beetle immigration is low, the forest stand recovers to a beetle-free state. At high beetle immigration rates beetle populations approach an endemic equilibrium state. At intermediate immigration rates, the model predicts bistability as the forest can be in either of the two equilibrium states: a healthy forest, or a forest with an endemic beetle population. The model bistability leads to hysteresis. Interactions between two stands show how a less resistant stand of trees may provide an initial toe-hold for the invasion, which later leads to a regional beetle outbreak in the
Conceptual Model of Dynamic Geographic Environment
Directory of Open Access Journals (Sweden)
Martínez-Rosales Miguel Alejandro
2014-04-01
Full Text Available In geographic environments, there are many and different types of geographic entities such as automobiles, trees, persons, buildings, storms, hurricanes, etc. These entities can be classified into two groups: geographic objects and geographic phenomena. By its nature, a geographic environment is dynamic, thus, it’s static modeling is not sufficient. Considering the dynamics of geographic environment, a new type of geographic entity called event is introduced. The primary target is a modeling of geographic environment as an event sequence, because in this case the semantic relations are much richer than in the case of static modeling. In this work, the conceptualization of this model is proposed. It is based on the idea to process each entity apart instead of processing the environment as a whole. After that, the so called history of each entity and its spatial relations to other entities are defined to describe the whole environment. The main goal is to model systems at a conceptual level that make use of spatial and temporal information, so that later it can serve as the semantic engine for such systems.
Directed network discovery with dynamic network modelling.
Anzellotti, Stefano; Kliemann, Dorit; Jacoby, Nir; Saxe, Rebecca
2017-05-01
Cognitive tasks recruit multiple brain regions. Understanding how these regions influence each other (the network structure) is an important step to characterize the neural basis of cognitive processes. Often, limited evidence is available to restrict the range of hypotheses a priori, and techniques that sift efficiently through a large number of possible network structures are needed (network discovery). This article introduces a novel modelling technique for network discovery (Dynamic Network Modelling or DNM) that builds on ideas from Granger Causality and Dynamic Causal Modelling introducing three key changes: (1) efficient network discovery is implemented with statistical tests on the consistency of model parameters across participants, (2) the tests take into account the magnitude and sign of each influence, and (3) variance explained in independent data is used as an absolute (rather than relative) measure of the quality of the network model. In this article, we outline the functioning of DNM, we validate DNM in simulated data for which the ground truth is known, and we report an example of its application to the investigation of influences between regions during emotion recognition, revealing top-down influences from brain regions encoding abstract representations of emotions (medial prefrontal cortex and superior temporal sulcus) onto regions engaged in the perceptual analysis of facial expressions (occipital face area and fusiform face area) when participants are asked to switch between reporting the emotional valence and the age of a face. Copyright © 2017 Elsevier Ltd. All rights reserved.
Modeling the Dynamic Digestive System Microbiome
Directory of Open Access Journals (Sweden)
Anne M. Estes
2015-08-01
Full Text Available “Modeling the Dynamic Digestive System Microbiome” is a hands-on activity designed to demonstrate the dynamics of microbiome ecology using dried pasta and beans to model disturbance events in the human digestive system microbiome. This exercise demonstrates how microbiome diversity is influenced by: 1 niche availability and habitat space and 2 a major disturbance event, such as antibiotic use. Students use a pictorial key to examine prepared models of digestive system microbiomes to determine what the person with the microbiome “ate.” Students then model the effect of taking antibiotics by removing certain “antibiotic sensitive” pasta. Finally, they add in “environmental microbes” or “native microbes” to recolonize the digestive system, determine how resilient their model microbome community is to disturbance, and discuss the implications. Throughout the exercise, students discuss differences in the habitat space available and microbiome community diversity. This exercise can be modified to discuss changes in the microbiome due to diet shifts and the emergence of antibiotic resistance in more depth.
Dynamic model for the internal combustion engine
Energy Technology Data Exchange (ETDEWEB)
Rizzoni, G.
1986-01-01
Over the last decade there has been increasing interest in the application of control theory to passenger vehicles: stringent governmental regulations constraining fuel consumption and exhaust emissions have required a shift to integrated electronics controls. Unfortunately, the lack of robust global models for the dynamics of the IC engine has limited the application of the tools of control theory in this areas. This dissertation is devoted to the formulation of a robust model for the dynamics of the IC engine. The engine is viewed as a system with inputs given by cylinder pressure and net engine torque, and output corresponding to crankshaft angular acceleration. The model is well suited to closed loop engine and transmission control applications. The deterministic model provides a powerful tool for estimating average and instantaneous net engine torque based on a noncontacting measurement of crankshaft acceleration. The stochastic model explains cyclic pressure variations by an additive Gaussian WSS vector noise process. Further, it demonstrates that by means of a suitable linear transformation-invariant with load and RPM-, the noise process may be expressed in terms of a three-dimensional uncorrelated vector random process.
Directory of Open Access Journals (Sweden)
Catherine L Taylor
Full Text Available Receptive vocabulary develops rapidly in early childhood and builds the foundation for language acquisition and literacy. Variation in receptive vocabulary ability is associated with variation in children's school achievement, and low receptive vocabulary ability is a risk factor for under-achievement at school. In this study, bivariate and multivariate growth curve modelling was used to estimate trajectories of receptive vocabulary development in relation to a wide range of candidate child, maternal and family level influences on receptive vocabulary development from 4-8 years. The study sample comprised 4332 children from the first nationally representative Longitudinal Study of Australian Children (LSAC. Predictors were modeled as risk variables with the lowest level of risk as the reference category. In the multivariate model, risks for receptive vocabulary delay at 4 years, in order of magnitude, were: Maternal Non- English Speaking Background (NESB, low school readiness, child not read to at home, four or more siblings, low family income, low birthweight, low maternal education, maternal mental health distress, low maternal parenting consistency, and high child temperament reactivity. None of these risks were associated with a lower rate of growth from 4-8 years. Instead, maternal NESB, low school readiness and maternal mental health distress were associated with a higher rate of growth, although not sufficient to close the receptive vocabulary gap for children with and without these risks at 8 years. Socio-economic area disadvantage, was not a risk for low receptive vocabulary ability at 4 years but was the only risk associated with a lower rate of growth in receptive vocabulary ability. At 8 years, the gap between children with and without socio-economic area disadvantage was equivalent to eight months of receptive vocabulary growth. These results are consistent with other studies that have shown that social gradients in children
Taylor, Catherine L; Christensen, Daniel; Lawrence, David; Mitrou, Francis; Zubrick, Stephen R
2013-01-01
Receptive vocabulary develops rapidly in early childhood and builds the foundation for language acquisition and literacy. Variation in receptive vocabulary ability is associated with variation in children's school achievement, and low receptive vocabulary ability is a risk factor for under-achievement at school. In this study, bivariate and multivariate growth curve modelling was used to estimate trajectories of receptive vocabulary development in relation to a wide range of candidate child, maternal and family level influences on receptive vocabulary development from 4-8 years. The study sample comprised 4332 children from the first nationally representative Longitudinal Study of Australian Children (LSAC). Predictors were modeled as risk variables with the lowest level of risk as the reference category. In the multivariate model, risks for receptive vocabulary delay at 4 years, in order of magnitude, were: Maternal Non- English Speaking Background (NESB), low school readiness, child not read to at home, four or more siblings, low family income, low birthweight, low maternal education, maternal mental health distress, low maternal parenting consistency, and high child temperament reactivity. None of these risks were associated with a lower rate of growth from 4-8 years. Instead, maternal NESB, low school readiness and maternal mental health distress were associated with a higher rate of growth, although not sufficient to close the receptive vocabulary gap for children with and without these risks at 8 years. Socio-economic area disadvantage, was not a risk for low receptive vocabulary ability at 4 years but was the only risk associated with a lower rate of growth in receptive vocabulary ability. At 8 years, the gap between children with and without socio-economic area disadvantage was equivalent to eight months of receptive vocabulary growth. These results are consistent with other studies that have shown that social gradients in children's developmental outcomes
Taylor, Catherine L.; Christensen, Daniel; Lawrence, David; Mitrou, Francis; Zubrick, Stephen R.
2013-01-01
Receptive vocabulary develops rapidly in early childhood and builds the foundation for language acquisition and literacy. Variation in receptive vocabulary ability is associated with variation in children's school achievement, and low receptive vocabulary ability is a risk factor for under-achievement at school. In this study, bivariate and multivariate growth curve modelling was used to estimate trajectories of receptive vocabulary development in relation to a wide range of candidate child, maternal and family level influences on receptive vocabulary development from 4–8 years. The study sample comprised 4332 children from the first nationally representative Longitudinal Study of Australian Children (LSAC). Predictors were modeled as risk variables with the lowest level of risk as the reference category. In the multivariate model, risks for receptive vocabulary delay at 4 years, in order of magnitude, were: Maternal Non- English Speaking Background (NESB), low school readiness, child not read to at home, four or more siblings, low family income, low birthweight, low maternal education, maternal mental health distress, low maternal parenting consistency, and high child temperament reactivity. None of these risks were associated with a lower rate of growth from 4–8 years. Instead, maternal NESB, low school readiness and maternal mental health distress were associated with a higher rate of growth, although not sufficient to close the receptive vocabulary gap for children with and without these risks at 8 years. Socio-economic area disadvantage, was not a risk for low receptive vocabulary ability at 4 years but was the only risk associated with a lower rate of growth in receptive vocabulary ability. At 8 years, the gap between children with and without socio-economic area disadvantage was equivalent to eight months of receptive vocabulary growth. These results are consistent with other studies that have shown that social gradients in children's developmental
A Multiscale Model for Virus Capsid Dynamics
Directory of Open Access Journals (Sweden)
Changjun Chen
2010-01-01
Full Text Available Viruses are infectious agents that can cause epidemics and pandemics. The understanding of virus formation, evolution, stability, and interaction with host cells is of great importance to the scientific community and public health. Typically, a virus complex in association with its aquatic environment poses a fabulous challenge to theoretical description and prediction. In this work, we propose a differential geometry-based multiscale paradigm to model complex biomolecule systems. In our approach, the differential geometry theory of surfaces and geometric measure theory are employed as a natural means to couple the macroscopic continuum domain of the fluid mechanical description of the aquatic environment from the microscopic discrete domain of the atomistic description of the biomolecule. A multiscale action functional is constructed as a unified framework to derive the governing equations for the dynamics of different scales. We show that the classical Navier-Stokes equation for the fluid dynamics and Newton's equation for the molecular dynamics can be derived from the least action principle. These equations are coupled through the continuum-discrete interface whose dynamics is governed by potential driven geometric flows.
Dynamical models of happiness with fractional order
Song, Lei; Xu, Shiyun; Yang, Jianying
2010-03-01
This present study focuses on a dynamical model of happiness described through fractional-order differential equations. By categorizing people of different personality and different impact factor of memory (IFM) with different set of model parameters, it is demonstrated via numerical simulations that such fractional-order models could exhibit various behaviors with and without external circumstance. Moreover, control and synchronization problems of this model are discussed, which correspond to the control of emotion as well as emotion synchronization in real life. This study is an endeavor to combine the psychological knowledge with control problems and system theories, and some implications for psychotherapy as well as hints of a personal approach to life are both proposed.
Mathematical modeling and applications in nonlinear dynamics
Merdan, Hüseyin
2016-01-01
The book covers nonlinear physical problems and mathematical modeling, including molecular biology, genetics, neurosciences, artificial intelligence with classical problems in mechanics and astronomy and physics. The chapters present nonlinear mathematical modeling in life science and physics through nonlinear differential equations, nonlinear discrete equations and hybrid equations. Such modeling can be effectively applied to the wide spectrum of nonlinear physical problems, including the KAM (Kolmogorov-Arnold-Moser (KAM)) theory, singular differential equations, impulsive dichotomous linear systems, analytical bifurcation trees of periodic motions, and almost or pseudo- almost periodic solutions in nonlinear dynamical systems. Provides methods for mathematical models with switching, thresholds, and impulses, each of particular importance for discontinuous processes Includes qualitative analysis of behaviors on Tumor-Immune Systems and methods of analysis for DNA, neural networks and epidemiology Introduces...
Plausible cloth animation using dynamic bending model
Institute of Scientific and Technical Information of China (English)
Chuan Zhou; Xiaogang Jin; Charlie C.L. Wang; Jieqing Feng
2008-01-01
Simulating the mechanical behavior of a cloth is a very challenging and important problem in computer animation. The models of bending in most existing cloth simulation approaches are taking the assumption that the cloth is little deformed from a plate shape.Therefore, based on the thin-plate theory, these bending models do not consider the condition that the current shape of the cloth under large deformations cannot be regarded as the approximation to that before deformation, which leads to an unreal static bending. [This paper introduces a dynamic bending model which is appropriate to describe large out-plane deformations such as cloth buckling and bending, and develops a compact implementation of the new model on spring-mass systems. Experimental results show that wrinkles and folds generated using this technique in cloth simulation, can appear and vanish in a more natural way than other approaches.
Computational model of cellular metabolic dynamics
DEFF Research Database (Denmark)
Li, Yanjun; Solomon, Thomas; Haus, Jacob M
2010-01-01
: intracellular metabolite concentrations and patterns of glucose disposal. Model variations were simulated to investigate three alternative mechanisms to explain insulin enhancements: Model 1 (M.1), simple mass action; M.2, insulin-mediated activation of key metabolic enzymes (i.e., hexokinase, glycogen synthase......Identifying the mechanisms by which insulin regulates glucose metabolism in skeletal muscle is critical to understanding the etiology of insulin resistance and type 2 diabetes. Our knowledge of these mechanisms is limited by the difficulty of obtaining in vivo intracellular data. To quantitatively...... distinguish significant transport and metabolic mechanisms from limited experimental data, we developed a physiologically based, multiscale mathematical model of cellular metabolic dynamics in skeletal muscle. The model describes mass transport and metabolic processes including distinctive processes...
Modeling of Carrier Dynamics in Electroabsorption Modulators
DEFF Research Database (Denmark)
Højfeldt, Sune
2002-01-01
and a phenomenological model for the carrier sweep-out dynamics, we investigate all-optical wavelength conversion, all-optical signal regeneration, and all-optical demultiplexing. A detailed drift-diffusion type model for the sweerp-out of photo-excited carriers in electroabsorption modulators is presented. We use...... the model to calclulate absorption spectra and steady-state carrier distributions in different modulator structures. This allows us to investigate a number of important properties of electroabsorption modulators, such as the electroabsorption effect and th saturation properties. We also investigate...... the influence that carrier recapture has on the device properties, and we discuss the recapture process on a more fundamental level. The model is also used to investigate in detail the carrier sweep-out process in electroabsorption modulators. We investigate how the intrinsic-region width, the separate...
Random graph models for dynamic networks
Zhang, Xiao; Newman, M E J
2016-01-01
We propose generalizations of a number of standard network models, including the classic random graph, the configuration model, and the stochastic block model, to the case of time-varying networks. We assume that the presence and absence of edges are governed by continuous-time Markov processes with rate parameters that can depend on properties of the nodes. In addition to computing equilibrium properties of these models, we demonstrate their use in data analysis and statistical inference, giving efficient algorithms for fitting them to observed network data. This allows us, for instance, to estimate the time constants of network evolution or infer community structure from temporal network data using cues embedded both in the probabilities over time that node pairs are connected by edges and in the characteristic dynamics of edge appearance and disappearance. We illustrate our methods with a selection of applications, both to computer-generated test networks and real-world examples.
Advances in dynamic network modeling in complex transportation systems
Ukkusuri, Satish V
2013-01-01
This book focuses on the latest in dynamic network modeling, including route guidance and traffic control in transportation systems and other complex infrastructure networks. Covers dynamic traffic assignment, flow modeling, mobile sensor deployment and more.
Dynamic Modeling of the SMAP Rotating Flexible Antenna
Nayeri, Reza D.
2012-01-01
Dynamic model development in ADAMS for the SMAP project is explained: The main objective of the dynamic models are for pointing error assessment, and the control/stability margin requirement verifications
Dynamic Modeling of the SMAP Rotating Flexible Antenna
Nayeri, Reza D.
2012-01-01
Dynamic model development in ADAMS for the SMAP project is explained: The main objective of the dynamic models are for pointing error assessment, and the control/stability margin requirement verifications
OFFl Models: Novel Schema for Dynamical Modeling of Biological Systems.
Ogbunugafor, C Brandon; Robinson, Sean P
2016-01-01
Flow diagrams are a common tool used to help build and interpret models of dynamical systems, often in biological contexts such as consumer-resource models and similar compartmental models. Typically, their usage is intuitive and informal. Here, we present a formalized version of flow diagrams as a kind of weighted directed graph which follow a strict grammar, which translate into a system of ordinary differential equations (ODEs) by a single unambiguous rule, and which have an equivalent representation as a relational database. (We abbreviate this schema of "ODEs and formalized flow diagrams" as OFFL.) Drawing a diagram within this strict grammar encourages a mental discipline on the part of the modeler in which all dynamical processes of a system are thought of as interactions between dynamical species that draw parcels from one or more source species and deposit them into target species according to a set of transformation rules. From these rules, the net rate of change for each species can be derived. The modeling schema can therefore be understood as both an epistemic and practical heuristic for modeling, serving both as an organizational framework for the model building process and as a mechanism for deriving ODEs. All steps of the schema beyond the initial scientific (intuitive, creative) abstraction of natural observations into model variables are algorithmic and easily carried out by a computer, thus enabling the future development of a dedicated software implementation. Such tools would empower the modeler to consider significantly more complex models than practical limitations might have otherwise proscribed, since the modeling framework itself manages that complexity on the modeler's behalf. In this report, we describe the chief motivations for OFFL, carefully outline its implementation, and utilize a range of classic examples from ecology and epidemiology to showcase its features.
OFFl Models: Novel Schema for Dynamical Modeling of Biological Systems.
Directory of Open Access Journals (Sweden)
C Brandon Ogbunugafor
Full Text Available Flow diagrams are a common tool used to help build and interpret models of dynamical systems, often in biological contexts such as consumer-resource models and similar compartmental models. Typically, their usage is intuitive and informal. Here, we present a formalized version of flow diagrams as a kind of weighted directed graph which follow a strict grammar, which translate into a system of ordinary differential equations (ODEs by a single unambiguous rule, and which have an equivalent representation as a relational database. (We abbreviate this schema of "ODEs and formalized flow diagrams" as OFFL. Drawing a diagram within this strict grammar encourages a mental discipline on the part of the modeler in which all dynamical processes of a system are thought of as interactions between dynamical species that draw parcels from one or more source species and deposit them into target species according to a set of transformation rules. From these rules, the net rate of change for each species can be derived. The modeling schema can therefore be understood as both an epistemic and practical heuristic for modeling, serving both as an organizational framework for the model building process and as a mechanism for deriving ODEs. All steps of the schema beyond the initial scientific (intuitive, creative abstraction of natural observations into model variables are algorithmic and easily carried out by a computer, thus enabling the future development of a dedicated software implementation. Such tools would empower the modeler to consider significantly more complex models than practical limitations might have otherwise proscribed, since the modeling framework itself manages that complexity on the modeler's behalf. In this report, we describe the chief motivations for OFFL, carefully outline its implementation, and utilize a range of classic examples from ecology and epidemiology to showcase its features.
The Exactly Solvable Simplest Model for Queue Dynamics
Y. Sugiyama; Yamada, H.
1996-01-01
We present an exactly solvable model for queue dynamics. Our model is very simple but provides the essential property for such dynamics. As an example, the model has the traveling cluster solution as well as the homogeneous flow solution. The model is the limiting case of Optimal Velocity (OV) model, which is proposed for the car following model to induce traffic jam spontaneously.
A nonparametric dynamic additive regression model for longitudinal data
DEFF Research Database (Denmark)
Martinussen, Torben; Scheike, Thomas H.
2000-01-01
dynamic linear models, estimating equations, least squares, longitudinal data, nonparametric methods, partly conditional mean models, time-varying-coefficient models......dynamic linear models, estimating equations, least squares, longitudinal data, nonparametric methods, partly conditional mean models, time-varying-coefficient models...
Ableism and the Reception of Improvised Soundsinging
Tonelli, Christopher
2016-01-01
Soundsinging is one name for the practice of making music using an idiosyncratic palette of vocal and non-vocal oral techniques. This paper is concerned with the reception of soundsinging and, more specifically, with listeners whose reactions to soundsinging involve attempts to contain the practice.
The reception of relativity in the Netherlands
J. van Besouw; J. van Dongen
2013-01-01
This article reviews the early academic and public reception of Albert Einstein's theory of relativity in the Netherlands, particularly after Arthur Eddington's eclipse experiments of 1919. Initially, not much attention was given to relativity, as it did not seem an improvement over Hendrik A. Loren
The politics, science, and art of receptivity
Directory of Open Access Journals (Sweden)
Emily Beausoleil
2014-03-01
Full Text Available With so much attention on the issue of voice in democratic theory, the inverse question of how people come to listen remains a marginal one. Recent scholarship in affect and neuroscience reveals that cognitive and verbal strategies, while privileged in democratic politics, are often insufficient to cultivate the receptivity that constitutes the most basic premise of democratic encounters. This article draws on this scholarship and a recent case of forum theatre to examine the conditions of receptivity and responsiveness, and identify specific strategies that foster such conditions. It argues that the forms of encounter most effective in cultivating receptivity are those that move us via affective intensity within pointedly mediated contexts. It is this constellation of strategies—this strange marriage of immersion and mediation—that enabled this performance to surface latent memory, affect and bias, unsettle entrenched patterns of thought and behaviour, and provide the conditions for revisability. This case makes clear that to lie beyond the domain of cognitive and verbal processes is not to lie beyond potential intervention, and offers insight to how such receptivity might be achieved in political processes more broadly.
The reception of Cambodian refugees in France
Wijers, G.D.M.
2011-01-01
Cambodian refugees’ arrival in France has helped initiate an atypical political mobilization in the process of their reception. The French political power balance, the sociocultural “mood” (zeitgeist) and the “mediatization” of the Indochinese region have impacted on their resettlement and given the
Simulated Critical Differences for Speech Reception Thresholds
Pedersen, Ellen Raben; Juhl, Peter Møller
2017-01-01
Purpose: Critical differences state by how much 2 test results have to differ in order to be significantly different. Critical differences for discrimination scores have been available for several decades, but they do not exist for speech reception thresholds (SRTs). This study presents and discusses how critical differences for SRTs can be…
BVA and AWF hold parliamentary reception.
2016-07-02
After another successful Animal Welfare Foundation (AWF) Discussion Forum, BVA honorary member Neil Parish MP hosted an evening reception in the House of Commons' terrace pavilion on behalf of BVA and AWF. Felicity Quick, BVA media officer, reports on the event.
Measuring receptive collocational competence across proficiency levels
Directory of Open Access Journals (Sweden)
Déogratias Nizonkiza
2015-12-01
Full Text Available The present study investigates, (i English as Foreign Language (EFL learners’ receptive collocational knowledge growth in relation to their linguistic proficiency level; (ii how much receptive collocational knowledge is acquired as proficiency develops; and (iii the extent to which receptive knowledge of collocations of EFL learners varies across word frequency bands. A proficiency measure and a collocation test were administered to English majors at the University of Burundi. Results of the study suggest that receptive collocational competence develops alongside EFL learners’ linguistic proficiency; which lends empirical support to Gyllstad (2007, 2009 and Author (2011 among others, who reported similar findings. Furthermore, EFL learners’ collocations growth seems to be quantifiable wherein both linguistic proficiency level and word frequency occupy a crucial role. While more gains in terms of collocations that EFL learners could potentially add as a result of change in proficiency are found at lower levels of proficiency; collocations of words from more frequent word bands seem to be mastered first, and more gains are found at more frequent word bands. These results confirm earlier findings on the non-linearity nature of vocabulary growth (cf. Meara 1996 and the fundamental role played by frequency in word knowledge for vocabulary in general (Nation 1983, 1990, Nation and Beglar 2007, which are extended here to collocations knowledge.
Interrelating Reception and Expression in Speechreading Training.
van Uden, Antoine M. J.
1988-01-01
This paper identifies characteristics of poor speechreaders, defines developmental dyspraxia in profoundly hearing-impaired children, and outlines the speechreading process. An active training method is described in which expressive and receptive skills are integrated, by having hearing-impaired people speechread their own speech via videotape…
Language, gay pornography, and audience reception.
Leap, William L
2011-01-01
Erotic imagery is an important component of gay pornographic cinema, particularly, where work of audience reception is concerned. However, to assume the audience engagement with the films is limited solely to the erotic realm is to underestimate the workings of ideological power in the context and aftermath of reception. For example, the director of the film under discussion here (Men of Israel; Lucas, 2009b) intended to present an erotic celebration of the nation-state. Yet, most viewers ignore the particulars of context in their comments about audience reception, placing the "Israeli" narrative within a broader framework, using transnational rather than film-specific criteria to guide their "reading" of the Israeli-centered narrative. This article uses as its entry point the language that viewers employ when describing their reactions to Men of Israel on a gay video club's Web site; this article shows how the work of audience reception may draw attention to a film's erotic details while invoking social and political messages that completely reframe the film's erotic narrative.
Design of an Oscillator for Satellite Reception
Leong, F.H.E.H.C.
2007-01-01
This thesis presents research on an LC-oscillator for Ku-band (10.7-12.7GHz) satellite reception. The zero-IF receiver architecture, proposed in the joint project involving the University of Twente and NXP Research, requires a 11.7GHz quadrature oscillator that achieves a phase noise of -85dBc/Hz@10
Mathematical Modeling Social Responsibility for Dynamic Organizations
Directory of Open Access Journals (Sweden)
Farzaneh Chavoshbashi
2012-03-01
Full Text Available Dynamic organizations as accountable organizations, for transparency and accountability to its stakeholders to stakeholders for their toward performance there should express their commitment to social responsibility are through their values and ensure that this commitment throughout the organization are now and thus will have a social responsibility for their mutual benefit, so there is more and more coherent in their ethical approach takes advantage and the community and stakeholders and the organization will have better performance and strengths. Because of interest in social responsibility, in this paper dynamic model is presented for Corporate Social Responsibility of Bionic organization. Model presented a new model is inspired by chaos theory and natural systems theory based on bifurcation in creation to be all natural systems, realizing the value of responsibility as one of the fundamental values of social and institutional development that the relationship between business and work environment in the global market economy and range will be specified. First Social Responsibility factors identified, then experts and scholars determine the weight of the components and technical coefficient for modeling and paired comparison has been done using MATLAB mathematical Software.
Mathematical Model of Porous Medium Dynamics
Gerschuk, Peotr; Sapozhnikov, Anatoly
1999-06-01
Semiempirical model describing porous material strains under pulse mechanical and thermal loadings is proposed. Porous medium is considered as continuous one but with special form of pressure dependence upon strain. This model takes into account principal features of porous materials behavior which can be observed when the material is strained in dynamic and static experiments ( non-reversibility of large strains, nonconvexity of loading curve). Elastoplastic properties of porous medium, its damages when it is strained and dynamic fracture are also taken into account. Dispersion of unidirectional motion caused by medium heterogeneity (porousness) is taken into acount by introducing the physical viscosity depending upon pores size. It is supposed that at every moment of time pores are in equilibrium with pressure i.e. kinetic of pores collapse is not taken into account. The model is presented by the system of differential equations connecting pressure and energy of porous medium with its strain. These equations close system of equations of motion and continuity which then is integrated numerically. The proposed model has been tested on carbon materials and porous copper . Results of calculation of these materials shock compressing are in satisfactory agreement with experimental data. Results of calculation of thin plate with porous copper layer collision are given as an illustration.
MSMBuilder: Statistical Models for Biomolecular Dynamics.
Harrigan, Matthew P; Sultan, Mohammad M; Hernández, Carlos X; Husic, Brooke E; Eastman, Peter; Schwantes, Christian R; Beauchamp, Kyle A; McGibbon, Robert T; Pande, Vijay S
2017-01-10
MSMBuilder is a software package for building statistical models of high-dimensional time-series data. It is designed with a particular focus on the analysis of atomistic simulations of biomolecular dynamics such as protein folding and conformational change. MSMBuilder is named for its ability to construct Markov state models (MSMs), a class of models that has gained favor among computational biophysicists. In addition to both well-established and newer MSM methods, the package includes complementary algorithms for understanding time-series data such as hidden Markov models and time-structure based independent component analysis. MSMBuilder boasts an easy to use command-line interface, as well as clear and consistent abstractions through its Python application programming interface. MSMBuilder was developed with careful consideration for compatibility with the broader machine learning community by following the design of scikit-learn. The package is used primarily by practitioners of molecular dynamics, but is just as applicable to other computational or experimental time-series measurements. Copyright © 2017 Biophysical Society. Published by Elsevier Inc. All rights reserved.
A dynamic network model for interbank market
Xu, Tao; He, Jianmin; Li, Shouwei
2016-12-01
In this paper, a dynamic network model based on agent behavior is introduced to explain the formation mechanism of interbank market network. We investigate the impact of credit lending preference on interbank market network topology, the evolution of interbank market network and stability of interbank market. Experimental results demonstrate that interbank market network is a small-world network and cumulative degree follows the power-law distribution. We find that the interbank network structure keeps dynamic stability in the network evolution process. With the increase of bank credit lending preference, network clustering coefficient increases and average shortest path length decreases monotonously, which improves the stability of the network structure. External shocks are main threats for the interbank market and the reduction of bank external investment yield rate and deposits fluctuations contribute to improve the resilience of the banking system.
OFFl Models: Novel Schema for Dynamical Modeling of Biological Systems
2016-01-01
Flow diagrams are a common tool used to help build and interpret models of dynamical systems, often in biological contexts such as consumer-resource models and similar compartmental models. Typically, their usage is intuitive and informal. Here, we present a formalized version of flow diagrams as a kind of weighted directed graph which follow a strict grammar, which translate into a system of ordinary differential equations (ODEs) by a single unambiguous rule, and which have an equivalent representation as a relational database. (We abbreviate this schema of “ODEs and formalized flow diagrams” as OFFL.) Drawing a diagram within this strict grammar encourages a mental discipline on the part of the modeler in which all dynamical processes of a system are thought of as interactions between dynamical species that draw parcels from one or more source species and deposit them into target species according to a set of transformation rules. From these rules, the net rate of change for each species can be derived. The modeling schema can therefore be understood as both an epistemic and practical heuristic for modeling, serving both as an organizational framework for the model building process and as a mechanism for deriving ODEs. All steps of the schema beyond the initial scientific (intuitive, creative) abstraction of natural observations into model variables are algorithmic and easily carried out by a computer, thus enabling the future development of a dedicated software implementation. Such tools would empower the modeler to consider significantly more complex models than practical limitations might have otherwise proscribed, since the modeling framework itself manages that complexity on the modeler’s behalf. In this report, we describe the chief motivations for OFFL, carefully outline its implementation, and utilize a range of classic examples from ecology and epidemiology to showcase its features. PMID:27270918
Study of Endometrial Receptivity during Implantation in Implantation Dysfunction Mouse
Institute of Scientific and Technical Information of China (English)
Yan-juan LIU; Guang-ying HUANG; Ming-wei YANG; Fu-er LU
2008-01-01
Objective To establish the mice model of implantation dysfunction and to study the endometrial receptivity during implantation in implantation dysfunction mouse. Methods Sexually mature female virgin, Kunming mice were randomly assigned to the control group and the model group postcoitally. The model mice at 9 : 00 AM on d 4 of pregnancy(d 4) were injected subcutaneously with mifepristone. All animals were sacrificed at 9:00 PM on d 4 and their uterine horns were examined for the presence of implanted embryos. Histopathology of uterine endometrium was observed by light-microscope. The endometrial expressions of estrogen receptor (ER) and progesterone receptor (PR) assessed by immunnohistochemical SP method. The endometrial expressions of ER mRNA and PR mRNA were assessed by semi-quantitative reverse transcriptase polymerase chain reaction (RT-PCR).Results Compared with control group, implantation rates and average embryo number significently decreased in model group, the development of endometrium was inhibited. In model group, absorbency and area rate of ER and PR in the gland and stroma were lower than those in control group (P<0.05). Expressions of ER mRNA and PR mRNA in model uterus were significantly lower than those in the control.Conclusion The endometrial receptivity and implantation decreased in mifepristoneinduced implantation dysfunction mouse.
Dynamical model for Pion-Nucleon Bremsstrahlung
Mariano, A V
2000-01-01
A dynamical model based on effective Lagrangians is proposed to describe the bremsstrahlung reaction $ \\pi N \\to \\pi N \\gamma$ at low energies. The $\\Delta(1232)$ degrees of freedom are incorporated in a way consistent with both, electromagnetic gauge invariance and invariance under contact transformations. The model also includes the initial and final state rescattering of hadrons via a T-matrix with off-shell effects. The $\\pi N \\gamma$ differential cross sections are calculated using three different T-matrix models and the results are compared with the soft photon approximation, and with experimental data. The aim of this analysis is to test the off-shell behavior of the different T-matrices under consideration.
Dynamic model of Fast Breeder Test Reactor
Energy Technology Data Exchange (ETDEWEB)
Vaidyanathan, G., E-mail: vaidya@igcar.gov.i [Fast Reactor Technology Group, Indira Gandhi Center for Atomic Research, Kalpakkam (India); Kasinathan, N.; Velusamy, K. [Fast Reactor Technology Group, Indira Gandhi Center for Atomic Research, Kalpakkam (India)
2010-04-15
Fast Breeder Test Reactor (FBTR) is a 40 M Wt/13.2 MWe sodium cooled reactor operating since 1985. It is a loop type reactor. As part of the safety analysis the response of the plant to various transients is needed. In this connection a computer code named DYNAM was developed to model the reactor core, the intermediate heat exchanger, steam generator, piping, etc. This paper deals with the mathematical model of the various components of FBTR, the numerical techniques to solve the model, and comparison of the predictions of the code with plant measurements. Also presented is the benign response of the plant to a station blackout condition, which brings out the role of the various reactivity feedback mechanisms combined with a gradual coast down of reactor sodium flow.
Modelling Market Dynamics with a "Market Game"
Katahira, Kei; Chen, Yu
In the financial market, traders, especially speculators, typically behave as to yield capital gains by the difference between selling and buying prices. Making use of the structure of Minority Game, we build a novel market toy model which takes account of such the speculative mind involving a round-trip trade to analyze the market dynamics as a system. Even though the micro-level behavioral rules of players in this new model is quite simple, its macroscopic aggregational output has the reproducibility of the well-known stylized facts such as volatility clustering and heavy tails. The proposed model may become a new alternative bottom-up approach in order to study the emerging mechanism of those stylized qualitative properties of asset returns.
Dynamics of a Stochastic Intraguild Predation Model
Directory of Open Access Journals (Sweden)
Zejing Xing
2016-04-01
Full Text Available Intraguild predation (IGP is a widespread ecological phenomenon which occurs when one predator species attacks another predator species with which it competes for a shared prey species. The objective of this paper is to study the dynamical properties of a stochastic intraguild predation model. We analyze stochastic persistence and extinction of the stochastic IGP model containing five cases and establish the sufficient criteria for global asymptotic stability of the positive solutions. This study shows that it is possible for the coexistence of three species under the influence of environmental noise, and that the noise may have a positive effect for IGP species. A stationary distribution of the stochastic IGP model is established and it has the ergodic property, suggesting that the time average of population size with the development of time is equal to the stationary distribution in space. Finally, we show that our results may be extended to two well-known biological systems: food chains and exploitative competition.
Agent-based modeling and network dynamics
Namatame, Akira
2016-01-01
The book integrates agent-based modeling and network science. It is divided into three parts, namely, foundations, primary dynamics on and of social networks, and applications. The book begins with the network origin of agent-based models, known as cellular automata, and introduce a number of classic models, such as Schelling’s segregation model and Axelrod’s spatial game. The essence of the foundation part is the network-based agent-based models in which agents follow network-based decision rules. Under the influence of the substantial progress in network science in late 1990s, these models have been extended from using lattices into using small-world networks, scale-free networks, etc. The book also shows that the modern network science mainly driven by game-theorists and sociophysicists has inspired agent-based social scientists to develop alternative formation algorithms, known as agent-based social networks. The book reviews a number of pioneering and representative models in this family. Upon the gi...
Dynamic Process of Money Transfer Models
Wang, Y; Wang, Yougui; Ding, Ning
2005-01-01
We have studied numerically the statistical mechanics of the dynamic phenomena, including money circulation and economic mobility, in some transfer models. The models on which our investigations were performed are the basic model proposed by A. Dragulescu and V. Yakovenko [1], the model with uniform saving rate developed by A. Chakraborti and B.K. Chakrabarti [2], and its extended model with diverse saving rate [3]. The velocity of circulation is found to be inversely related with the average holding time of money. In order to check the nature of money transferring process in these models, we demonstrated the probability distributions of holding time. In the model with uniform saving rate, the distribution obeys exponential law, which indicates money transfer here is a kind of Poisson process. But when the saving rate is set diversely, the holding time distribution follows a power law. The velocity can also be deduced from a typical individual's optimal choice. In this way, an approach for building the micro-...
Mineral vein dynamics modelling (FRACS II)
Energy Technology Data Exchange (ETDEWEB)
Urai, J.; Virgo, S.; Arndt, M. [RWTH Aachen (Germany); and others
2016-08-15
The Mineral Vein Dynamics Modeling group ''FRACS'' started out as a team of 7 research groups in its first phase and continued with a team of 5 research groups at the Universities of Aachen, Tuebingen, Karlsruhe, Mainz and Glasgow during its second phase ''FRACS 11''. The aim of the group was to develop an advanced understanding of the interplay between fracturing, fluid flow and fracture healing with a special emphasis on the comparison of field data and numerical models. Field areas comprised the Oman mountains in Oman (which where already studied in detail in the first phase), a siliciclastic sequence in the Internal Ligurian Units in Italy (closed to Sestri Levante) and cores of Zechstein carbonates from a Lean Gas reservoir in Northern Germany. Numerical models of fracturing, sealing and interaction with fluid that were developed in phase I where expanded in phase 11. They were used to model small scale fracture healing by crystal growth and the resulting influence on flow, medium scale fracture healing and its influence on successive fracturing and healing, as well as large scale dynamic fluid flow through opening and closing fractures and channels as a function of fluid overpressure. The numerical models were compared with structures in the field and we were able to identify first proxies for mechanical vein-hostrock properties and fluid overpressures versus tectonic stresses. Finally we propose a new classification of stylolites based on numerical models and observations in the Zechstein cores and continued to develop a new stress inversion tool to use stylolites to estimate depth of their formation.
A dynamic model of the wormhole and the Multiverse model
Energy Technology Data Exchange (ETDEWEB)
Shatskii, A A; Kardashev, N S [Astro-Space Centre of the P. N. Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Novikov, I D [Russian Research Centre ' Kurchatov Institute' , Moscow (Russian Federation)
2008-05-31
An analytic solution methodology for general relativity (GR) equations describing the hypothetical phenomenon of wormholes is presented and the analysis of wormholes in terms of their physical properties is discussed. An analytic solution of the GR equations for static and dynamic spherically symmetric wormholes is given. The dynamic solution generally describes a 'traversable' wormhole, i.e., one allowing matter, energy, and information to pass through it. It is shown how the energy-momentum tensor of matter in a wormhole can be represented in a form allowing the GR equations to be solved analytically, which has a crucial methodological importance for analyzing the properties of the solution obtained. The energy-momentum tensor of wormhole matter is represented as a superposition of a spherically symmetric magnetic (or electric) field and negative-density dust matter, serving as exotic matter necessary for a 'traversable' wormhole to exist. The dynamics of the model are investigated. A similar model is considered (and analyzed in terms of inflation) for the Einstein equations with a {lambda} term. Superposing enough dust matter, a magnetic field, and a {lambda} term can produce a static solution, which turns out to be a spherical Multiverse model with an infinite number of wormhole-connected spherical universes. This Multiverse can have its total energy positive everywhere in space, and in addition can be out of equilibrium (i.e., dynamic). (methodological notes)
Idealized computational models for auditory receptive fields
National Research Council Canada - National Science Library
Lindeberg, Tony; Friberg, Anders
2015-01-01
.... For defining a time-frequency transformation of a purely temporal sound signal, it is shown that the framework allows for a new way of deriving the Gabor and Gammatone filters as well as a novel...
Modeling cell dynamics under mobile phone radiation.
Minelli, Tullio Antonio; Balduzzo, Maurizio; Milone, Francesco Ferro; Nofrate, Valentina
2007-04-01
Perturbations by pulse-modulated microwave radiation from GSM mobile phones on neuron cell membrane gating and calcium oscillations have been suggested as a possible mechanism underlying activation of brain states and electroencephalographic epiphenomena. As the employ of UMTS phones seems to reveal other symptoms, a unified phenomenological framework is needed. In order to explain possible effects of mobile phone radiation on cell oscillations, GSM and UMTS low-frequency envelopes have been detected, recorded and used as input in cell models. Dynamical systems endowed with contiguous regular and chaotic regimes suitable to produce stochastic resonance can both account for the perturbation of the neuro-electrical activity and even for the low intensity of the signal perceived by high sensitive subjects. Neuron models of this kind can be employed as a reductionist hint for the mentioned phenomenology. The Hindmarsh-Rose model exhibits frequency enhancement and regularization phenomena induced by weak GSM and UMTS. More realistic simulations of cell membrane gating and calcium oscillations have been performed with the help of an adaptation of the Chay-Keizer dynamical system. This scheme can explain the suspected subjective sensitivity to mobile phone signals under the thermal threshold, in terms of cell calcium regularity mechanisms. Concerning the two kinds of emission, the stronger occupation of the ELF band of last generation UMTS phones is compensated by lower power emitted.
Dynamical Vertex Approximation for the Hubbard Model
Toschi, Alessandro
A full understanding of correlated electron systems in the physically relevant situations of three and two dimensions represents a challenge for the contemporary condensed matter theory. However, in the last years considerable progress has been achieved by means of increasingly more powerful quantum many-body algorithms, applied to the basic model for correlated electrons, the Hubbard Hamiltonian. Here, I will review the physics emerging from studies performed with the dynamical vertex approximation, which includes diagrammatic corrections to the local description of the dynamical mean field theory (DMFT). In particular, I will first discuss the phase diagram in three dimensions with a special focus on the commensurate and incommensurate magnetic phases, their (quantum) critical properties, and the impact of fluctuations on electronic lifetimes and spectral functions. In two dimensions, the effects of non-local fluctuations beyond DMFT grow enormously, determining the appearance of a low-temperature insulating behavior for all values of the interaction in the unfrustrated model: Here the prototypical features of the Mott-Hubbard metal-insulator transition, as well as the existence of magnetically ordered phases, are completely overwhelmed by antiferromagnetic fluctuations of exponentially large extension, in accordance with the Mermin-Wagner theorem. Eventually, by a fluctuation diagnostics analysis of cluster DMFT self-energies, the same magnetic fluctuations are identified as responsible for the pseudogap regime in the holed-doped frustrated case, with important implications for the theoretical modeling of the cuprate physics.
Cortico-Cortical Receptive Field Estimates in Human Visual Cortex
Directory of Open Access Journals (Sweden)
Koen V Haak
2012-05-01
Full Text Available Human visual cortex comprises many visual areas that contain a map of the visual field (Wandell et al 2007, Neuron 56, 366–383. These visual field maps can be identified readily in individual subjects with functional magnetic resonance imaging (fMRI during experimental sessions that last less than an hour (Wandell and Winawer 2011, Vis Res 718–737. Hence, visual field mapping with fMRI has been, and still is, a heavily used technique to examine the organisation of both normal and abnormal human visual cortex (Haak et al 2011, ACNR, 11(3, 20–21. However, visual field mapping cannot reveal every aspect of human visual cortex organisation. For example, the information processed within a visual field map arrives from somewhere and is sent to somewhere, and visual field mapping does not derive these input/output relationships. Here, we describe a new, model-based analysis for estimating the dependence between signals in distinct cortical regions using functional magnetic resonance imaging (fMRI data. Just as a stimulus-referred receptive field predicts the neural response as a function of the stimulus contrast, the neural-referred receptive field predicts the neural response as a function of responses elsewhere in the nervous system. When applied to two cortical regions, this function can be called the cortico-cortical receptive field (CCRF. We model the CCRF as a Gaussian-weighted region on the cortical surface and apply the model to data from both stimulus-driven and resting-state experimental conditions in visual cortex.
Nonlocal Crowd Dynamics Models for several Populations
Colombo, Rinaldo M
2011-01-01
This paper develops the basic analytical theory related to some recently introduced crowd dynamics models. Where well posedness was known only locally in time, it is here extended to all of $\\reali^+$. The results on the stability with respect to the equations are improved. Moreover, here the case of several populations is considered, obtaining the well posedness of systems of multi-D non-local conservation laws. The basic analytical tools are provided by the classical Kruzkov theory of scalar conservation laws in several space dimensions.
Institute of Scientific and Technical Information of China (English)
GE Rong-Chun; LI Chuan-Feng; GUO Guang-Can
2012-01-01
We investigate the dynamics of entanglement,quantum correlation and classical correlation for the one-dimensional XY model in a transverse magnetic field.With the initial state polarized along the z axis,we find that the first maximum of the classical correlation between the nearest neighbor sites peaks around the critical point for large anisotropy parameter.It may indicate the quantum phase transition.For all kinds of correlation,we find that their behaviors between the nearest neighbor sites are significantly different from those of the next-nearestneighbor sites.
Schwinger model simulations with dynamical overlap fermions
Bietenholz, W; Volkholz, J
2007-01-01
We present simulation results for the 2-flavour Schwinger model with dynamical overlap fermions. In particular we apply the overlap hypercube operator at seven light fermion masses. In each case we collect sizable statistics in the topological sectors 0 and 1. Since the chiral condensate Sigma vanishes in the chiral limit, we observe densities for the microscopic Dirac spectrum, which have not been addressed yet by Random Matrix Theory (RMT). Nevertheless, by confronting the averages of the lowest eigenvalues in different topological sectors with chiral RMT in unitary ensemble we obtain -- for the very light fermion masses -- values for $\\Sigma$ that follow closely the analytical predictions in the continuum.
Schwinger model simulations with dynamical overlap fermions
Energy Technology Data Exchange (ETDEWEB)
Bietenholz, W. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Shcheredin, S. [Bielefeld Univ. (Germany). Fakultaet fuer Physik; Volkholz, J. [Humboldt-Universitaet, Berlin (Germany). Inst. fuer Physik
2007-11-15
We present simulation results for the 2-flavour Schwinger model with dynamical overlap fermions. In particular we apply the overlap hypercube operator at seven light fermion masses. In each case we collect sizable statistics in the topological sectors 0 and 1. Since the chiral condensate {sigma} vanishes in the chiral limit, we observe densities for the microscopic Dirac spectrum, which have not been addressed yet by Random Matrix Theory (RMT). Nevertheless, by confronting the averages of the lowest eigenvalues in different topological sectors with chiral RMT in unitary ensemble we obtain - for the very light fermion masses - values for {sigma} that follow closely the analytical predictions in the continuum. (orig.)
A Model for Dynamic Adaptive Coscheduling
Institute of Scientific and Technical Information of China (English)
LU Sanglu; ZHOU Xiaobo; XIE Li
1999-01-01
This paper proposes a dynamic adaptive coscheduling modelDASIC to take advantage of excess available resources in anetwork of workstations (NOW). Besides coscheduling related subtasksdynamically, DASIC can scale up or down the process space dependingupon the number of available processors on an NOW. Based on thedynamic idle processor group (IPG), DASIC employs three modules: thecoscheduling module, the scalable scheduling module and the loadbalancing module, and uses six algorithms to achieve scalability. Asimplified DASIC was also implemented, and experimental results arepresented in this paper, which show that it can maximize systemutilization, and achieve task parallelism as much as possible.
NONLOCAL CROWD DYNAMICS MODELS FOR SEVERAL POPULATIONS
Institute of Scientific and Technical Information of China (English)
Rinaldo M. Colombo; Magali Lécureux-Mercier
2012-01-01
This paper develops the basic analytical theory related to some recently introduced crowd dynamics models.Where well posedness was known only locally in time,it is here extended to all of R+.The results on the stability with respect to the equations are improved.Moreover,here the case of several populations is considered,obtaining the well posedness of systems of multi-D non-local conservation laws.The basic analytical tools are provided by the classical Kru(z)kov theory of scalar conservation laws in several space dimensions.
Computational fluid dynamics modelling in cardiovascular medicine.
Morris, Paul D; Narracott, Andrew; von Tengg-Kobligk, Hendrik; Silva Soto, Daniel Alejandro; Hsiao, Sarah; Lungu, Angela; Evans, Paul; Bressloff, Neil W; Lawford, Patricia V; Hose, D Rodney; Gunn, Julian P
2016-01-01
This paper reviews the methods, benefits and challenges associated with the adoption and translation of computational fluid dynamics (CFD) modelling within cardiovascular medicine. CFD, a specialist area of mathematics and a branch of fluid mechanics, is used routinely in a diverse range of safety-critical engineering systems, which increasingly is being applied to the cardiovascular system. By facilitating rapid, economical, low-risk prototyping, CFD modelling has already revolutionised research and development of devices such as stents, valve prostheses, and ventricular assist devices. Combined with cardiovascular imaging, CFD simulation enables detailed characterisation of complex physiological pressure and flow fields and the computation of metrics which cannot be directly measured, for example, wall shear stress. CFD models are now being translated into clinical tools for physicians to use across the spectrum of coronary, valvular, congenital, myocardial and peripheral vascular diseases. CFD modelling is apposite for minimally-invasive patient assessment. Patient-specific (incorporating data unique to the individual) and multi-scale (combining models of different length- and time-scales) modelling enables individualised risk prediction and virtual treatment planning. This represents a significant departure from traditional dependence upon registry-based, population-averaged data. Model integration is progressively moving towards 'digital patient' or 'virtual physiological human' representations. When combined with population-scale numerical models, these models have the potential to reduce the cost, time and risk associated with clinical trials. The adoption of CFD modelling signals a new era in cardiovascular medicine. While potentially highly beneficial, a number of academic and commercial groups are addressing the associated methodological, regulatory, education- and service-related challenges.
Dynamic HMM Model with Estimated Dynamic Property in Continuous Mandarin Speech Recognition
Institute of Scientific and Technical Information of China (English)
CHENFeili; ZHUJie
2003-01-01
A new dynamic HMM (hiddem Markov model) has been introduced in this paper, which describes the relationship between dynamic property and feature of space. The method to estimate the dynamic property is discussed in this paper, which makes the dynamic HMMmuch more practical in real time speech recognition. Ex-periment on large vocabulary continuous Mandarin speech recognition task has shown that the dynamic HMM model can achieve about 10% of error reduction both for tonal and toneless syllable. Estimated dynamic property can achieve nearly same (even better) performance than using extracted dynamic property.
Unsteady aerodynamics modeling for flight dynamics application
Wang, Qing; He, Kai-Feng; Qian, Wei-Qi; Zhang, Tian-Jiao; Cheng, Yan-Qing; Wu, Kai-Yuan
2012-02-01
In view of engineering application, it is practicable to decompose the aerodynamics into three components: the static aerodynamics, the aerodynamic increment due to steady rotations, and the aerodynamic increment due to unsteady separated and vortical flow. The first and the second components can be presented in conventional forms, while the third is described using a one-order differential equation and a radial-basis-function (RBF) network. For an aircraft configuration, the mathematical models of 6-component aerodynamic coefficients are set up from the wind tunnel test data of pitch, yaw, roll, and coupled yawroll large-amplitude oscillations. The flight dynamics of an aircraft is studied by the bifurcation analysis technique in the case of quasi-steady aerodynamics and unsteady aerodynamics, respectively. The results show that: (1) unsteady aerodynamics has no effect upon the existence of trim points, but affects their stability; (2) unsteady aerodynamics has great effects upon the existence, stability, and amplitudes of periodic solutions; and (3) unsteady aerodynamics changes the stable regions of trim points obviously. Furthermore, the dynamic responses of the aircraft to elevator deflections are inspected. It is shown that the unsteady aerodynamics is beneficial to dynamic stability for the present aircraft. Finally, the effects of unsteady aerodynamics on the post-stall maneuverability are analyzed by numerical simulation.
Complex networks repair strategies: Dynamic models
Fu, Chaoqi; Wang, Ying; Gao, Yangjun; Wang, Xiaoyang
2017-09-01
Network repair strategies are tactical methods that restore the efficiency of damaged networks; however, unreasonable repair strategies not only waste resources, they are also ineffective for network recovery. Most extant research on network repair focuses on static networks, but results and findings on static networks cannot be applied to evolutionary dynamic networks because, in dynamic models, complex network repair has completely different characteristics. For instance, repaired nodes face more severe challenges, and require strategic repair methods in order to have a significant effect. In this study, we propose the Shell Repair Strategy (SRS) to minimize the risk of secondary node failures due to the cascading effect. Our proposed method includes the identification of a set of vital nodes that have a significant impact on network repair and defense. Our identification of these vital nodes reduces the number of switching nodes that face the risk of secondary failures during the dynamic repair process. This is positively correlated with the size of the average degree and enhances network invulnerability.
Unsteady aerodynamics modeling for flight dynamics application
Institute of Scientific and Technical Information of China (English)
Qing Wang; Kai-Feng He; Wei-Qi Qian; Tian-Jiao Zhang; Yan-Qing Cheng; Kai-Yuan Wu
2012-01-01
In view of engineering application,it is practicable to decompose the aerodynamics into three components:the static aerodynamics,the aerodynamic increment due to steady rotations,and the aerodynamic increment due to unsteady separated and vortical flow.The first and the second components can be presented in conventional forms,while the third is described using a one-order differential equation and a radial-basis-function (RBF) network. For an aircraft configuration,the mathematical models of 6-component aerodynamic coefficients are set up from the wind tunnel test data of pitch,yaw,roll,and coupled yawroll large-amplitude oscillations.The flight dynamics of an aircraft is studied by the bifurcation analysis technique in the case of quasi-steady aerodynamics and unsteady aerodynamics,respectively.The results show that:(1) unsteady aerodynamics has no effect upon the existence of trim points,but affects their stability; (2) unsteady aerodynamics has great effects upon the existence,stability,and amplitudes of periodic solutions; and (3) unsteady aerodynamics changes the stable regions of trim points obviously.Furthermore,the dynamic responses of the aircraft to elevator deflections are inspected.It is shown that the unsteady aerodynamics is beneficial to dynamic stability for the present aircraft.Finally,the effects of unsteady aerodynamics on the post-stall maneuverability are analyzed by numerical simulation.
Modeling mitochondrial bioenergetics with integrated volume dynamics.
Directory of Open Access Journals (Sweden)
Jason N Bazil
2010-01-01
Full Text Available Mathematical models of mitochondrial bioenergetics provide powerful analytical tools to help interpret experimental data and facilitate experimental design for elucidating the supporting biochemical and physical processes. As a next step towards constructing a complete physiologically faithful mitochondrial bioenergetics model, a mathematical model was developed targeting the cardiac mitochondrial bioenergetic based upon previous efforts, and corroborated using both transient and steady state data. The model consists of several modified rate functions of mitochondrial bioenergetics, integrated calcium dynamics and a detailed description of the K(+-cycle and its effect on mitochondrial bioenergetics and matrix volume regulation. Model simulations were used to fit 42 adjustable parameters to four independent experimental data sets consisting of 32 data curves. During the model development, a certain network topology had to be in place and some assumptions about uncertain or unobserved experimental factors and conditions were explicitly constrained in order to faithfully reproduce all the data sets. These realizations are discussed, and their necessity helps contribute to the collective understanding of the mitochondrial bioenergetics.
Modeling mitochondrial bioenergetics with integrated volume dynamics.
Bazil, Jason N; Buzzard, Gregery T; Rundell, Ann E
2010-01-01
Mathematical models of mitochondrial bioenergetics provide powerful analytical tools to help interpret experimental data and facilitate experimental design for elucidating the supporting biochemical and physical processes. As a next step towards constructing a complete physiologically faithful mitochondrial bioenergetics model, a mathematical model was developed targeting the cardiac mitochondrial bioenergetic based upon previous efforts, and corroborated using both transient and steady state data. The model consists of several modified rate functions of mitochondrial bioenergetics, integrated calcium dynamics and a detailed description of the K(+)-cycle and its effect on mitochondrial bioenergetics and matrix volume regulation. Model simulations were used to fit 42 adjustable parameters to four independent experimental data sets consisting of 32 data curves. During the model development, a certain network topology had to be in place and some assumptions about uncertain or unobserved experimental factors and conditions were explicitly constrained in order to faithfully reproduce all the data sets. These realizations are discussed, and their necessity helps contribute to the collective understanding of the mitochondrial bioenergetics.
Computational social dynamic modeling of group recruitment.
Energy Technology Data Exchange (ETDEWEB)
Berry, Nina M.; Lee, Marinna; Pickett, Marc; Turnley, Jessica Glicken (Sandia National Laboratories, Albuquerque, NM); Smrcka, Julianne D. (Sandia National Laboratories, Albuquerque, NM); Ko, Teresa H.; Moy, Timothy David (Sandia National Laboratories, Albuquerque, NM); Wu, Benjamin C.
2004-01-01
The Seldon software toolkit combines concepts from agent-based modeling and social science to create a computationally social dynamic model for group recruitment. The underlying recruitment model is based on a unique three-level hybrid agent-based architecture that contains simple agents (level one), abstract agents (level two), and cognitive agents (level three). This uniqueness of this architecture begins with abstract agents that permit the model to include social concepts (gang) or institutional concepts (school) into a typical software simulation environment. The future addition of cognitive agents to the recruitment model will provide a unique entity that does not exist in any agent-based modeling toolkits to date. We use social networks to provide an integrated mesh within and between the different levels. This Java based toolkit is used to analyze different social concepts based on initialization input from the user. The input alters a set of parameters used to influence the values associated with the simple agents, abstract agents, and the interactions (simple agent-simple agent or simple agent-abstract agent) between these entities. The results of phase-1 Seldon toolkit provide insight into how certain social concepts apply to different scenario development for inner city gang recruitment.
Hybrid modeling and prediction of dynamical systems
Lloyd, Alun L.; Flores, Kevin B.
2017-01-01
Scientific analysis often relies on the ability to make accurate predictions of a system’s dynamics. Mechanistic models, parameterized by a number of unknown parameters, are often used for this purpose. Accurate estimation of the model state and parameters prior to prediction is necessary, but may be complicated by issues such as noisy data and uncertainty in parameters and initial conditions. At the other end of the spectrum exist nonparametric methods, which rely solely on data to build their predictions. While these nonparametric methods do not require a model of the system, their performance is strongly influenced by the amount and noisiness of the data. In this article, we consider a hybrid approach to modeling and prediction which merges recent advancements in nonparametric analysis with standard parametric methods. The general idea is to replace a subset of a mechanistic model’s equations with their corresponding nonparametric representations, resulting in a hybrid modeling and prediction scheme. Overall, we find that this hybrid approach allows for more robust parameter estimation and improved short-term prediction in situations where there is a large uncertainty in model parameters. We demonstrate these advantages in the classical Lorenz-63 chaotic system and in networks of Hindmarsh-Rose neurons before application to experimentally collected structured population data. PMID:28692642
Testing substellar models with dynamical mass measurements
Directory of Open Access Journals (Sweden)
Liu M.C.
2011-07-01
Full Text Available We have been using Keck laser guide star adaptive optics to monitor the orbits of ultracool binaries, providing dynamical masses at lower luminosities and temperatures than previously available and enabling strong tests of theoretical models. We have identified three specific problems with theory: (1 We find that model color–magnitude diagrams cannot be reliably used to infer masses as they do not accurately reproduce the colors of ultracool dwarfs of known mass. (2 Effective temperatures inferred from evolutionary model radii are typically inconsistent with temperatures derived from fitting atmospheric models to observed spectra by 100–300 K. (3 For the only known pair of field brown dwarfs with a precise mass (3% and age determination (≈25%, the measured luminosities are ~2–3× higher than predicted by model cooling rates (i.e., masses inferred from Lbol and age are 20–30% larger than measured. To make progress in understanding the observed discrepancies, more mass measurements spanning a wide range of luminosity, temperature, and age are needed, along with more accurate age determinations (e.g., via asteroseismology for primary stars with brown dwarf binary companions. Also, resolved optical and infrared spectroscopy are needed to measure lithium depletion and to characterize the atmospheres of binary components in order to better assess model deficiencies.
Greene, Clint A.; Dumoulin, Serge O.; Harvey, Ben M.; Ress, David
2014-01-01
Properties of human visual population receptive fields (pRFs) are currently estimated by performing measurements of visual stimulation using functional magnetic resonance imaging (fMRI), and then fitting the results using a predefined model shape for the pRF. Various models exist and different model
Dynamic Factor Method of Computing Dynamic Mathematical Model for System Simulation
Institute of Scientific and Technical Information of China (English)
老大中; 吴娟; 杨策; 蒋滋康
2003-01-01
The computational methods of a typical dynamic mathematical model that can describe the differential element and the inertial element for the system simulation are researched. The stability of numerical solutions of the dynamic mathematical model is researched. By means of theoretical analysis, the error formulas, the error sign criteria and the error relationship criterion of the implicit Euler method and the trapezoidal method are given, the dynamic factor affecting the computational accuracy has been found, the formula and the methods of computing the dynamic factor are given. The computational accuracy of the dynamic mathematical model like this can be improved by use of the dynamic factor.
Modeling Robot Dynamic Performance for Endpoint Force Control
1988-08-01
Task Dynamics 55 2.5.1 The Dynamic Workpiece Model 55 2.5.2 Adding Robot Dynamics 56 2.5.3 Adding Actuator Dynamics 56 Tabie I o iiau 6 2.6 Grip...motion control system. Robot dynamics couple with the task dynamics in a very complex way. When the robot makes contact with the environment, the impact...robot flexibility or actuator dynamics. 2.5.2 Adding Robot Dynamics Figure 2.29 shows the robot now represented by two lumped masses, as in the robot
A Simple General Model of Evolutionary Dynamics
Thurner, Stefan
Evolution is a process in which some variations that emerge within a population (of, e.g., biological species or industrial goods) get selected, survive, and proliferate, whereas others vanish. Survival probability, proliferation, or production rates are associated with the "fitness" of a particular variation. We argue that the notion of fitness is an a posteriori concept in the sense that one can assign higher fitness to species or goods that survive but one can generally not derive or predict fitness per se. Whereas proliferation rates can be measured, fitness landscapes, that is, the inter-dependence of proliferation rates, cannot. For this reason we think that in a physical theory of evolution such notions should be avoided. Here we review a recent quantitative formulation of evolutionary dynamics that provides a framework for the co-evolution of species and their fitness landscapes (Thurner et al., 2010, Physica A 389, 747; Thurner et al., 2010, New J. Phys. 12, 075029; Klimek et al., 2009, Phys. Rev. E 82, 011901 (2010). The corresponding model leads to a generic evolutionary dynamics characterized by phases of relative stability in terms of diversity, followed by phases of massive restructuring. These dynamical modes can be interpreted as punctuated equilibria in biology, or Schumpeterian business cycles (Schumpeter, 1939, Business Cycles, McGraw-Hill, London) in economics. We show that phase transitions that separate phases of high and low diversity can be approximated surprisingly well by mean-field methods. We demonstrate that the mathematical framework is suited to understand systemic properties of evolutionary systems, such as their proneness to collapse, or their potential for diversification. The framework suggests that evolutionary processes are naturally linked to self-organized criticality and to properties of production matrices, such as their eigenvalue spectra. Even though the model is phrased in general terms it is also practical in the sense
Radiative and dynamical modeling of Jupiter's atmosphere
Guerlet, Sandrine; Spiga, Aymeric
2016-04-01
Jupiter's atmosphere harbours a rich meteorology, with alternate westward and eastward zonal jets, waves signatures and long-living storms. Recent ground-based and spacecraft measurements have also revealed a rich stratospheric dynamics, with the observation of thermal signatures of planetary waves, puzzling meridional distribution of hydrocarbons at odds with predictions of photochemical models, and a periodic equatorial oscillation analogous to the Earth's quasi-biennal oscillation and Saturn's equatorial oscillation. These recent observations, along with the many unanswered questions (What drives and maintain the equatorial oscillations? How important is the seasonal forcing compared to the influence of internal heat? What is the large-scale stratospheric circulation of these giant planets?) motivated us to develop a complete 3D General Circulation Model (GCM) of Saturn and Jupiter. We aim at exploring the large-scale circulation, seasonal variability, and wave activity from the troposphere to the stratosphere of these giant planets. We will briefly present how we adapted our existing Saturn GCM to Jupiter. One of the main change is the addition of a stratospheric haze layer made of fractal aggregates in the auroral regions (poleward of 45S and 30N). This haze layer has a significant radiative impact by modifying the temperature up to +/- 15K in the middle stratosphere. We will then describe the results of radiative-convective simulations and how they compare to recent Cassini and ground-based temperature measurements. These simulations reproduce surprisingly well some of the observed thermal vertical and meridional gradients, but several important mismatches at low and high latitudes suggest that dynamics also plays an important role in shaping the temperature field. Finally, we will present full GCM simulations and discuss the main resulting features (waves and instabilities). We will also and discuss the impact of the choice of spatial resolution and
Quench dynamics of the anisotropic Heisenberg model.
Liu, Wenshuo; Andrei, Natan
2014-06-27
We develop an analytical approach for the study of the quench dynamics of the anisotropic Heisenberg model (XXZ model) on the infinite line. We present the exact time-dependent wave functions after a quench in an integral form for any initial state and for any anisotropy Δ by means of a generalized Yudson contour representation. We calculate the evolution of several observables from two particular initial states: starting from a local Néel state we calculate the time evolution of the antiferromagnetic order parameter-staggered magnetization; starting from a state with consecutive flipped spins (1) we calculate the evolution of the local magnetization and express it in terms of the propagation of magnons and bound state excitations, and (2) we predict the evolution of the induced spin currents. These predictions can be confronted with experiments in ultracold gases in optical lattices. We also show how the "string" solutions of Bethe ansatz equations emerge naturally from the contour approach.
Driven dynamics of simplified tribological models
Vanossi, A.; Braun, O. M.
2007-08-01
Over the last decade, remarkable developments in nanotechnology, notably the use of atomic and friction force microscopes (AFM/FFM), the surface-force apparatus (SFA) and the quartz-crystal microbalance (QCM), have provided the possibility to build experimental devices able to perform analysis on well-characterized materials at the nano- and microscale. Simultaneously, tremendous advances in computing hardware and methodology (molecular dynamics techniques and ab initio calculations) have dramatically increased the ability of theoreticians to simulate tribological processes, supplying very detailed information on the atomic scale for realistic sliding systems. This acceleration in experiments and computations, leading often to very detailed yet complex data, has deeply stimulated the search, rediscovery and implementation of simpler mathematical models such as the generalized Frenkel-Kontorova and Tomlinson models, capable of describing and interpreting, in a more immediate way, the essential physics involved in nonlinear sliding phenomena.
Organic production in a dynamic CGE model
DEFF Research Database (Denmark)
Jacobsen, Lars Bo
2004-01-01
Concerns about the impact of modern agriculture on the environment have in recent years led to an interest in supporting the development of organic farming. In addition to environmental benefits, the aim is to encourage the provision of other “multifunctional” properties of organic farming...... such as rural amenities and rural development that are spillover benefit additional to the supply of food. In this paper we further develop an existing dynamic general equilibrium model of the Danish economy to specifically incorporate organic farming. In the model and input-output data each primary...... to illustrate the working of our theory by constructing a long term forecast for the development of the Danish economy. Moreover we simulate the effect of the recent agreed 2003 reform of the common agricultural policy....
Dynamic modelling of packaging material flow systems.
Tsiliyannis, Christos A
2005-04-01
A dynamic model has been developed for reused and recycled packaging material flows. It allows a rigorous description of the flows and stocks during the transition to new targets imposed by legislation, product demand variations or even by variations in consumer discard behaviour. Given the annual reuse and recycle frequency and packaging lifetime, the model determines all packaging flows (e.g., consumption and reuse) and variables through which environmental policy is formulated, such as recycling, waste and reuse rates and it identifies the minimum number of variables to be surveyed for complete packaging flow monitoring. Simulation of the transition to the new flow conditions is given for flows of packaging materials in Greece, based on 1995--1998 field inventory and statistical data.
Nonsmooth mechanics models, dynamics and control
Brogliato, Bernard
2016-01-01
Now in its third edition, this standard reference is a comprehensive treatment of nonsmooth mechanical systems refocused to give more prominence to control and modelling. It covers Lagrangian and Newton–Euler systems, detailing mathematical tools such as convex analysis and complementarity theory. The ways in which nonsmooth mechanics influence and are influenced by well-posedness analysis, numerical analysis and simulation, modelling and control are explained. Contact/impact laws, stability theory and trajectory-tracking control are given in-depth exposition connected by a framework formed from complementarity systems and measure-differential inclusions. Links are established with electrical circuits with set-valued nonsmooth elements and with other nonsmooth dynamical systems like impulsive and piecewise linear systems. Nonsmooth Mechanics (third edition) has been substantially rewritten, edited and updated to account for the significant body of results that have emerged in the twenty-first century—incl...
Modeling quantum fluid dynamics at nonzero temperatures
Berloff, Natalia G.; Brachet, Marc; Proukakis, Nick P.
2014-03-01
The detailed understanding of the intricate dynamics of quantum fluids, in particular in the rapidly growing subfield of quantum turbulence which elucidates the evolution of a vortex tangle in a superfluid, requires an in-depth understanding of the role of finite temperature in such systems. The Landau two-fluid model is the most successful hydrodynamical theory of superfluid helium, but by the nature of the scale separations it cannot give an adequate description of the processes involving vortex dynamics and interactions. In our contribution we introduce a framework based on a nonlinear classical-field equation that is mathematically identical to the Landau model and provides a mechanism for severing and coalescence of vortex lines, so that the questions related to the behavior of quantized vortices can be addressed self-consistently. The correct equation of state as well as nonlocality of interactions that leads to the existence of the roton minimum can also be introduced in such description. We review and apply the ideas developed for finite-temperature description of weakly interacting Bose gases as possible extensions and numerical refinements of the proposed method. We apply this method to elucidate the behavior of the vortices during expansion and contraction following the change in applied pressure. We show that at low temperatures, during the contraction of the vortex core as the negative pressure grows back to positive values, the vortex line density grows through a mechanism of vortex multiplication. This mechanism is suppressed at high temperatures.
A Model of Project and Organisational Dynamics
Directory of Open Access Journals (Sweden)
Jenny Leonard
2012-04-01
Full Text Available The strategic, transformational nature of many information systems projects is now widely understood. Large-scale implementations of systems are known to require significant management of organisational change in order to be successful. Moreover, projects are rarely executed in isolation – most organisations have a large programme of projects being implemented at any one time. However, project and value management methodologies provide ad hoc definitions of the relationship between a project and its environment. This limits the ability of an organisation to manage the larger dynamics between projects and organisations, over time, and between projects. The contribution of this paper, therefore, is to use literature on organisational theory to provide a more systematic understanding of this area. The organisational facilitators required to obtain value from a project are categorised, and the processes required to develop those facilitators are defined. This formalisation facilitates generalisation between projects and highlights any time and path dependencies required in developing organisational facilitators. The model therefore has the potential to contribute to the development of IS project management theory within dynamic organisational contexts. Six cases illustrate how this model could be used.
Modeling habitat dynamics accounting for possible misclassification
Veran, Sophie; Kleiner, Kevin J.; Choquet, Remi; Collazo, Jaime; Nichols, James D.
2012-01-01
Land cover data are widely used in ecology as land cover change is a major component of changes affecting ecological systems. Landscape change estimates are characterized by classification errors. Researchers have used error matrices to adjust estimates of areal extent, but estimation of land cover change is more difficult and more challenging, with error in classification being confused with change. We modeled land cover dynamics for a discrete set of habitat states. The approach accounts for state uncertainty to produce unbiased estimates of habitat transition probabilities using ground information to inform error rates. We consider the case when true and observed habitat states are available for the same geographic unit (pixel) and when true and observed states are obtained at one level of resolution, but transition probabilities estimated at a different level of resolution (aggregations of pixels). Simulation results showed a strong bias when estimating transition probabilities if misclassification was not accounted for. Scaling-up does not necessarily decrease the bias and can even increase it. Analyses of land cover data in the Southeast region of the USA showed that land change patterns appeared distorted if misclassification was not accounted for: rate of habitat turnover was artificially increased and habitat composition appeared more homogeneous. Not properly accounting for land cover misclassification can produce misleading inferences about habitat state and dynamics and also misleading predictions about species distributions based on habitat. Our models that explicitly account for state uncertainty should be useful in obtaining more accurate inferences about change from data that include errors.
Microscopic to Macroscopic Dynamical Models of Sociality
Solis Salas, Citlali; Woolley, Thomas; Pearce, Eiluned; Dunbar, Robin; Maini, Philip; Social; Evolutionary Neuroscience Research Group (Senrg) Collaboration
To help them survive, social animals, such as humans, need to share knowledge and responsibilities with other members of the species. The larger their social network, the bigger the pool of knowledge available to them. Since time is a limited resource, a way of optimising its use is meeting amongst individuals whilst fulfilling other necessities. In this sense it is useful to know how many, and how often, early humans could meet during a given period of time whilst performing other necessary tasks, such as food gathering. Using a simplified model of these dynamics, which comprehend encounter and memory, we aim at producing a lower-bound to the number of meetings hunter-gatherers could have during a year. We compare the stochastic agent-based model to its mean-field approximation and explore some of the features necessary for the difference between low population dynamics and its continuum limit. We observe an emergent property that could have an inference in the layered structure seen in each person's social organisation. This could give some insight into hunter-gatherer's lives and the development of the social layered structure we have today. With support from the Mexican Council for Science and Technology (CONACyT), the Public Education Secretariat (SEP), and the Mexican National Autonomous University's Foundation (Fundacion UNAM).
DYNAMIC MODELLING OF VIBRATIONS ASSISTED DRILLING
Directory of Open Access Journals (Sweden)
Mathieu LADONNE
2015-05-01
Full Text Available The number of multi-materials staking configurations for aeronautical structures is increasing, with the evolution of composite and metallic materials. For drilling the fastening holes, the processes of Vibration Assisted Drilling (VAD expand rapidly, as it permits to improve reliability of drilling operations on multilayer structures. Among these processes of VAD, the solution with forced vibrations added to conventional feed to create a discontinuous cutting is the more developed in industry. The back and forth movement allows to improve the evacuation of chips by breaking it. This technology introduces two new operating parameters, the frequency and the amplitude of the oscillation. To optimize the process, the choice of those parameters requires first to model precisely the operation cutting and dynamics. In this paper, a kinematic modelling of the process is firstly proposed. The limits of the model are analysed through comparison between simulations and measurements. The proposed model is used to develop a cutting force model that allows foreseeing the operating conditions which ensure good chips breaking and tool life improvement.
Partially dynamic vehicle routing - models and algorithms
DEFF Research Database (Denmark)
Larsen, Allan; Madsen, Oli B.G.; Solomon, M.
2002-01-01
In this paper we propose a framework for dynamic routing systems based on their degree of dynamism. Next, we consider its impact on solution methodology and quality. Specifically, we introduce the Partially Dynamic Travelling Repairman Problem and describe several dynamic policies to minimize rou...
Dynamic hysteresis modeling including skin effect using diffusion equation model
Hamada, Souad; Louai, Fatima Zohra; Nait-Said, Nasreddine; Benabou, Abdelkader
2016-07-01
An improved dynamic hysteresis model is proposed for the prediction of hysteresis loop of electrical steel up to mean frequencies, taking into account the skin effect. In previous works, the analytical solution of the diffusion equation for low frequency (DELF) was coupled with the inverse static Jiles-Atherton (JA) model in order to represent the hysteresis behavior for a lamination. In the present paper, this approach is improved to ensure the reproducibility of measured hysteresis loops at mean frequency. The results of simulation are compared with the experimental ones. The selected results for frequencies 50 Hz, 100 Hz, 200 Hz and 400 Hz are presented and discussed.
Dynamic hysteresis modeling including skin effect using diffusion equation model
Energy Technology Data Exchange (ETDEWEB)
Hamada, Souad, E-mail: souadhamada@yahoo.fr [LSP-IE: Research Laboratory, Electrical Engineering Department, University of Batna, 05000 Batna (Algeria); Louai, Fatima Zohra, E-mail: fz_louai@yahoo.com [LSP-IE: Research Laboratory, Electrical Engineering Department, University of Batna, 05000 Batna (Algeria); Nait-Said, Nasreddine, E-mail: n_naitsaid@yahoo.com [LSP-IE: Research Laboratory, Electrical Engineering Department, University of Batna, 05000 Batna (Algeria); Benabou, Abdelkader, E-mail: Abdelkader.Benabou@univ-lille1.fr [L2EP, Université de Lille1, 59655 Villeneuve d’Ascq (France)
2016-07-15
An improved dynamic hysteresis model is proposed for the prediction of hysteresis loop of electrical steel up to mean frequencies, taking into account the skin effect. In previous works, the analytical solution of the diffusion equation for low frequency (DELF) was coupled with the inverse static Jiles-Atherton (JA) model in order to represent the hysteresis behavior for a lamination. In the present paper, this approach is improved to ensure the reproducibility of measured hysteresis loops at mean frequency. The results of simulation are compared with the experimental ones. The selected results for frequencies 50 Hz, 100 Hz, 200 Hz and 400 Hz are presented and discussed.
The Critical Reception of Lewis Nordan
DEFF Research Database (Denmark)
Bjerre, Thomas Ærvold
2010-01-01
The essay covers the critical reception of Mississippi-writer Lewis Nordan from his debut in 1983 to the boost in scholarly attention in the new millennium. The essay covers newspaper reviews but pays particular attention to the many academic essays that have placed Nordan as a writer in the sout...... in the southern literary tradition and have highlighted themes such as magical realism, the grotesque, race relations, music, and gender....
A Methodology for Conus APOE Reception Planning.
1982-09-01
Heizer , Ramon N. Chief, Supply Systems Branch, Dir- ectorate of Distribution, DCS/Logistics Operations , HQ AFLC, Wright-Patterson AFB OH. Personal inter...would be tasked to serve as aerial ports of embarkation for large quantities of per- sonnel and equipment. The managers must develop reception plans to...into a ’rough cut’ estimate of the workload based on an unconstrained flow through the -.i system. Based on this workload, the managers can develop a
Czech children's literature reception in Slovenia
Starc, Barbara
2016-01-01
This master’s degree thesis introduces the historical background of the Czech nation and the cultural contacts between Slovenes and Czechs. It outlines the development of the Czech young adult literature. In the thesis is qualitatively and quantitatively researched the reception of the Czech young adult literature. With a qualitative research it has been discovered how many young adult books have been translated from Czech into Slovene language, how many in different periods and which lit...
Dual-Antenna Microwave Reception Without Switching
Hartop, Robert W.
1994-01-01
Receiver remains connected to both antennas, transmitter switched to connect it to one or other. Combination of hybrid junction, circulators, and filter provides simultaneous reception paths from both antennas without significantly altering radiation patterns of antennas. Communication system considered for use in spacecraft and in which mechanical switch permitted on downlink but not on uplink. Applicable to terrestrial microwave communication stations subject to dual-antenna requirements.
Eugen Bleuler 150: Bleuler's reception of Freud.
Dalzell, Thomas G
2007-12-01
On the 150th anniversary of Eugen Bleuler's birth, this article examines his reception of Sigmund Freud and his use of Freudian theory to understand the symptoms of schizophrenia. In addition, in contrast to earlier interpretations of Bleuler's relationship with Freud in terms of an eventual personal and theoretical incompatibility, the article demonstrates that, although Bleuler did distance himself from the psychoanalytic movement, he remained consistent in his views on Freud's theories.
Rehabilitering og 'motion på recept'
DEFF Research Database (Denmark)
Larsen, Niels Sandholm; Larsen, Kristian
2008-01-01
I denne artikel vil vi søge at analysere fænomenerne 'rehabilitering' og 'motion på recept' med særlig fokus på relationerne til det, som vi efterfølgende betegner som medicinsk felt. Vi vil via en sociologisk optik beskrive og forklare opkomsten af rehabilitering som del af en række andre...... stridigheder og bevægelser i medicinsk felt. Vi vil i den forbindelse samtidig vise, at rehabilitering, og også det nye fænomen 'motion på recept', hverken kan forstås som en selvstændig substans eller som et isoleret fænomen. Rehabilitering og 'motion på recept' konstrueres som fænomener, der udgør et slags...... sociologisk analyse af nogle relativt upåagtede områder indenfor sundhedsområdet, og hensigten er at vise, at denne type praksisområder med fordel kan beskrives og forklares sociologisk. I Danmark ser vi aktuelt en genkomst eller opblomstring af fænomenet 'rehabilitering'. Rehabilitering beskrives i...
Modeling boreal fire and forest dynamics
de Groot, W. J.; McRae, D. J.; Cantin, A.
2009-04-01
The circumpolar boreal forest covers about 1.4 billion ha, representing 1/3 of global forest land. Approximately 2/3 of the boreal forest is located in Eurasia and the remainder in North America. Wildland fires annually burn an estimated 12-20 M ha across the entire boreal region, having a major influence on forest structure and composition. However, fire weather, fire behaviour, and fire ecology differ greatly between the boreal forests in eastern and western hemispheres, which have significant impact on tree survival, post-fire regeneration and forest succession. Every year, wildland fires in Canada and Alaska burn an average of 2-3 M ha, primarily by stand-replacing, high intensity crown fires. By comparison, Russian fires burn about 10-15 M ha annually, primarily by low to moderate intensity surface fires that cause minimal tree mortality. Fire weather conditions in the most fire prone regions of Russia are generally more severe than in similar regions of North America. Finally, the species composition of eastern and western boreal forests is also very different. Russian forests are dominated by larch (30%) and pine (28%) with lower components of spruce (14%) and poplar/birch hardwoods (18%) By contrast, Canadian forests are comprised mainly of spruce (35%), pine (22%), poplar/birch (16%), and fir (9%). All of these factors contribute to the variability in vegetation dynamics occurring within the circumpolar boreal region. This modeling study examines the interactions of fire weather, forest composition, fire behaviour, and fire ecology on forest vegetation dynamics within the boreal region. Similar active fire zones in western Canada and eastern Siberia were used as study sites. Historical weather data were collected for both locations and used to calculate fire weather data, which were used as primary driving variables for the Boreal Fire Effects model (BORFIRE). Fire behaviour was calculated in BORFIRE using data for major tree species at both study sites
Modelling Holocene peatland dynamics with an individual-based dynamic vegetation model
Chaudhary, Nitin; Miller, Paul A.; Smith, Benjamin
2017-05-01
Dynamic global vegetation models (DGVMs) are designed for the study of past, present and future vegetation patterns together with associated biogeochemical cycles and climate feedbacks. However, most DGVMs do not yet have detailed representations of permafrost and non-permafrost peatlands, which are an important store of carbon, particularly at high latitudes. We demonstrate a new implementation of peatland dynamics in a customized Arctic version of the LPJ-GUESS DGVM, simulating the long-term evolution of selected northern peatland ecosystems and assessing the effect of changing climate on peatland carbon balance. Our approach employs a dynamic multi-layer soil with representation of freeze-thaw processes and litter inputs from a dynamically varying mixture of the main peatland plant functional types: mosses, shrubs and graminoids. The model was calibrated and tested for a sub-Arctic mire in Stordalen, Sweden, and validated at a temperate bog site in Mer Bleue, Canada. A regional evaluation of simulated carbon fluxes, hydrology and vegetation dynamics encompassed additional locations spread across Scandinavia. Simulated peat accumulation was found to be generally consistent with published data and the model was able to capture reported long-term vegetation dynamics, water table position and carbon fluxes. A series of sensitivity experiments were carried out to investigate the vulnerability of high-latitude peatlands to climate change. We found that the Stordalen mire may be expected to sequester more carbon in the first half of the 21st century due to milder and wetter climate conditions, a longer growing season, and the CO2 fertilization effect, turning into a carbon source after mid-century because of higher decomposition rates in response to warming soils.
Bio-Inspired Neural Model for Learning Dynamic Models
Duong, Tuan; Duong, Vu; Suri, Ronald
2009-01-01
A neural-network mathematical model that, relative to prior such models, places greater emphasis on some of the temporal aspects of real neural physical processes, has been proposed as a basis for massively parallel, distributed algorithms that learn dynamic models of possibly complex external processes by means of learning rules that are local in space and time. The algorithms could be made to perform such functions as recognition and prediction of words in speech and of objects depicted in video images. The approach embodied in this model is said to be "hardware-friendly" in the following sense: The algorithms would be amenable to execution by special-purpose computers implemented as very-large-scale integrated (VLSI) circuits that would operate at relatively high speeds and low power demands.
Kaliuzny, M. P.; Bushuev, F. I.; Sibiriakova, Ye. S.; Shulga, O. V.; Shakun, L. S.; Bezrukovs, V.; Kulishenko, V. F.; Moskalenko, S. S.; Malynovsky, Ye. V.; Balagura, O. A.
2017-02-01
The results of the determination of the geostationary satellite "Eutelsat-13B" orbital position obtained during 2015-2016 years using European stations' network for reception of DVB-S signals from the satellite are presented. The network consists of five stations located in Ukraine and Latvia. The stations are equipped with a radio engineering complex developed by the RI "MAO". The measured parameter is a time difference of arrival (TDOA) of the DVB-S signals to the stations of the network. The errors of TDOA determination and satellite coordinates, obtained using a numerical model of satellite motion, are equal ±2.6 m and ±35 m respectively. Software implementation of the numerical model is taken from the free space dynamics library OREKIT.
Multiscale modeling with smoothed dissipative particle dynamics.
Kulkarni, Pandurang M; Fu, Chia-Chun; Shell, M Scott; Leal, L Gary
2013-06-21
In this work, we consider two issues related to the use of Smoothed Dissipative Particle Dynamics (SDPD) as an intermediate mesoscale model in a multiscale scheme for solution of flow problems when there are local parts of a macroscopic domain that require molecular resolution. The first is to demonstrate that SDPD with different levels of resolution can accurately represent the fluid properties from the continuum scale all the way to the molecular scale. Specifically, while the thermodynamic quantities such as temperature, pressure, and average density remain scale-invariant, we demonstrate that the dynamic properties are quantitatively consistent with an all-atom Lennard-Jones reference system when the SDPD resolution approaches the atomistic scale. This supports the idea that SDPD can serve as a natural bridge between molecular and continuum descriptions. In the second part, a simple multiscale methodology is proposed within the SDPD framework that allows several levels of resolution within a single domain. Each particle is characterized by a unique physical length scale called the smoothing length, which is inversely related to the local number density and can change on-the-fly. This multiscale methodology is shown to accurately reproduce fluid properties for the simple problem of steady and transient shear flow.
A dynamic model for railway freight overbooking
Institute of Scientific and Technical Information of China (English)
冯芬玲; 张佳琪; 郭晓峰
2015-01-01
In order to apply overbooking idea in Chinese railway freight industry to improve revenue, a Markov decision process (dynamic programming) model for railway freight reservation was formulated and the overbooking limit level was proposed as a control policy. However, computing the dynamic programming treatment needs six nested loops and this will be burdensome for real-world problems. To break through the calculation limit, the properties of value function were analyzed and the overbooking protection level was proposed to reduce the calculating quantity. The simulation experiments show that the overbooking protection level for the lower-fare class is higher than that for the higher-fare class, so the overbooking strategy is nested by fare class. Besides, by analyzing the influence on the overbooking strategy of freight arrival probability and cancellation probability, the proposed approach is efficient and also has a good application prospect in reality. Also, compared with the existing reservation (FCFS), the overbooking strategy performs better in the fields of vacancy reduction and revenue improvement.
Dynamical Models for Computer Viruses Propagation
Directory of Open Access Journals (Sweden)
José R. C. Piqueira
2008-01-01
Full Text Available Nowadays, digital computer systems and networks are the main engineering tools, being used in planning, design, operation, and control of all sizes of building, transportation, machinery, business, and life maintaining devices. Consequently, computer viruses became one of the most important sources of uncertainty, contributing to decrease the reliability of vital activities. A lot of antivirus programs have been developed, but they are limited to detecting and removing infections, based on previous knowledge of the virus code. In spite of having good adaptation capability, these programs work just as vaccines against diseases and are not able to prevent new infections based on the network state. Here, a trial on modeling computer viruses propagation dynamics relates it to other notable events occurring in the network permitting to establish preventive policies in the network management. Data from three different viruses are collected in the Internet and two different identification techniques, autoregressive and Fourier analyses, are applied showing that it is possible to forecast the dynamics of a new virus propagation by using the data collected from other viruses that formerly infected the network.
Modelling of the PELE fragmentation dynamics
Verreault, J.
2014-05-01
The Penetrator with Enhanced Lateral Effect (PELE) is a type of explosive-free projectile that undergoes radial fragmentation upon an impact with a target plate. This type of projectile is composed of a brittle cylindrical shell (the jacket) filled in its core with a material characterized with a large Poisson's ratio. Upon an impact with a target, the axial compression causes the filling to expand in the radial direction. However, due to the brittleness of the jacket material, very little radial deformation can occur which creates a radial stress between the two materials and a hoop stress in the jacket. Fragmentation of the jacket occurs if the hoop stress exceeds the material's ultimate stress. The PELE fragmentation dynamics is explored via Finite-Element Method (FEM) simulations using the Autodyn explicit dynamics hydrocode. The numerical results are compared with an analytical model based on wave interactions, as well as with the experimental investigation of Paulus and Schirm (1996). The comparison is based on the mechanical stress in the filling and the qualitative fragmentation of the jacket.
A dynamical model for competing opinions
Souza, S R
2012-01-01
We propose an opinion model based on agents located at the vertices of a regular lattice. Each agent has an independent opinion (among an arbitrary, but fixed, number of choices) and its own degree of conviction. The latter changes every time it interacts with another agent who has a different opinion. The dynamics leads to size distributions of clusters (made up of agents which have the same opinion and are located at contiguous spatial positions) which follow a power law, as long as the range of the interaction between the agents is not too short, i.e. the system self-organizes into a critical state. Short range interactions lead to an exponential cut off in the size distribution and to spatial correlations which cause agents which have the same opinion to be closely grouped. When the diversity of opinions is restricted to two, non-consensus dynamic is observed, with unequal population fractions, whereas consensus is reached if the agents are also allowed to interact with those which are located far from th...
Modelling the Congo basin ecosystems with a dynamic vegetation model
Dury, Marie; Hambuckers, Alain; Trolliet, Franck; Huynen, Marie-Claude; Haineaux, Damien; Fontaine, Corentin M.; Fayolle, Adeline; François, Louis
2014-05-01
The scarcity of field observations in some parts of the world makes difficult a deep understanding of some ecosystems such as humid tropical forests in Central Africa. Therefore, modelling tools are interesting alternatives to study those regions even if the lack of data often prevents sharp calibration and validation of the model projections. Dynamic vegetation models (DVMs) are process-based models that simulate shifts in potential vegetation and its associated biogeochemical and hydrological cycles in response to climate. Initially run at the global scale, DVMs can be run at any spatial scale provided that climate and soil data are available. In the framework of the BIOSERF project ("Sustainability of tropical forest biodiversity and services under climate and human pressure"), we use and adapt the CARAIB dynamic vegetation model (Dury et al., iForest - Biogeosciences and Forestry, 4:82-99, 2011) to study the Congo basin vegetation dynamics. The field campaigns have notably allowed the refinement of the vegetation representation from plant functional types (PFTs) to individual species through the collection of parameters such as the specific leaf area or the leaf C:N ratio of common tropical tree species and the location of their present-day occurrences from literature and available database. Here, we test the model ability to reproduce the present spatial and temporal variations of carbon stocks (e.g. biomass, soil carbon) and fluxes (e.g. gross and net primary productivities (GPP and NPP), net ecosystem production (NEP)) as well as the observed distribution of the studied species over the Congo basin. In the lack of abundant and long-term measurements, we compare model results with time series of remote sensing products (e.g. vegetation leaf area index (LAI), GPP and NPP). Several sensitivity tests are presented: we assess consecutively the impacts of the level at which the vegetation is simulated (PFTs or species), the spatial resolution and the initial land
Vortex dynamics in nonrelativistic Abelian Higgs model
Directory of Open Access Journals (Sweden)
A.A. Kozhevnikov
2015-11-01
Full Text Available The dynamics of the gauge vortex with arbitrary form of a contour is considered in the framework of the nonrelativistic Abelian Higgs model, including the possibility of the gauge field interaction with the fermion asymmetric background. The equations for the time derivatives of the curvature and the torsion of the vortex contour generalizing the Betchov–Da Rios equations in hydrodynamics, are obtained. They are applied to study the conservation of helicity of the gauge field forming the vortex, twist, and writhe numbers of the vortex contour. It is shown that the conservation of helicity is broken when both terms in the equation of the vortex motion are present, the first due to the exchange of excitations of the phase and modulus of the scalar field and the second one due to the coupling of the gauge field forming the vortex, with the fermion asymmetric background.
Opinion dynamics: models, extensions and external effects
Sîrbu, Alina; Servedio, Vito D P; Tria, Francesca
2016-01-01
Recently, social phenomena have received a lot of attention not only from social scientists, but also from physicists, mathematicians and computer scientists, in the emerging interdisciplinary field of complex system science. Opinion dynamics is one of the processes studied, since opinions are the drivers of human behaviour, and play a crucial role in many global challenges that our complex world and societies are facing: global financial crises, global pandemics, growth of cities, urbanisation and migration patterns, and last but not least important, climate change and environmental sustainability and protection. Opinion formation is a complex process affected by the interplay of different elements, including the individual predisposition, the influence of positive and negative peer interaction (social networks playing a crucial role in this respect), the information each individual is exposed to, and many others. Several models inspired from those in use in physics have been developed to encompass many of t...
Interpretation of test data with dynamic modeling
Energy Technology Data Exchange (ETDEWEB)
Biba, P. [Southern California Edison, San Clemente, CA (United States). San Onofre Nuclear Generating Station
1999-11-01
The in-service testing of many Important-to-safety components, such as valves, pumps, etc. is often performed while the plant is either shut-down or the particular system is in a test mode. Thus the test conditions may be different from the actual operating conditions under which the components would be required to operate. In addition, the components must function under various postulated accident scenarios, which can not be duplicated during plant normal operation. This paper deals with the method of interpretation of the test data by a dynamic model, which allows the evaluation of the many factors affecting the system performance, in order to assure component and system operability.
Molecular modelling and molecular dynamics of CFTR.
Callebaut, Isabelle; Hoffmann, Brice; Lehn, Pierre; Mornon, Jean-Paul
2017-01-01
The cystic fibrosis transmembrane conductance regulator (CFTR) protein is a member of the ATP-binding cassette (ABC) transporter superfamily that functions as an ATP-gated channel. Considerable progress has been made over the last years in the understanding of the molecular basis of the CFTR functions, as well as dysfunctions causing the common genetic disease cystic fibrosis (CF). This review provides a global overview of the theoretical studies that have been performed so far, especially molecular modelling and molecular dynamics (MD) simulations. A special emphasis is placed on the CFTR-specific evolution of an ABC transporter framework towards a channel function, as well as on the understanding of the effects of disease-causing mutations and their specific modulation. This in silico work should help structure-based drug discovery and design, with a view to develop CFTR-specific pharmacotherapeutic approaches for the treatment of CF in the context of precision medicine.
Probabilistic Model for Dynamic Signature Verification System
Directory of Open Access Journals (Sweden)
Chai Tong Yuen
2011-11-01
Full Text Available This study has proposed the algorithm for signature verification system using dynamic parameters of the signature: pen pressure, velocity and position. The system is proposed to read, analyze and verify the signatures from the SUSig online database. Firstly, the testing and reference samples will have to be normalized, re-sampled and smoothed through pre-processing stage. In verification stage, the difference between reference and testing signatures will be calculated based on the proposed thresholded standard deviation method. A probabilistic acceptance model has been designed to enhance the performance of the verification system. The proposed algorithm has reported False Rejection Rate (FRR of 14.8% and False Acceptance Rate (FAR of 2.64%. Meanwhile, the classification rate of the system is around 97%.
Dynamic object-oriented geospatial modeling
Directory of Open Access Journals (Sweden)
Tomáš Richta
2010-02-01
Full Text Available Published literature about moving objects (MO simplifies the problem to the representation and storage of moving points, moving lines, or moving regions. The main insufficiency of this approach is lack of MO inner structure and dynamics modeling – the autonomy of moving agent. This paper describes basics of the object-oriented geospatial methodology for modeling complex systems consisting of agents, which move within spatial environment. The main idea is that during the agent movement, different kinds of connections with other moving or stationary objects are established or disposed, based on some spatial constraint satisfaction or nonfulfilment respectively. The methodology is constructed with regard to following two main conditions – 1 the inner behavior of agents should be represented by any formalism, e.g. Petri net, finite state machine, etc., and 2 the spatial characteristic of environment should be supplied by any information system, that is able to store defined set of spatial types, and support defined set of spatial operations. Finally, the methodology is demonstrated on simple simulation model of tram transportation system.
A dynamic model of reasoning and memory.
Hawkins, Guy E; Hayes, Brett K; Heit, Evan
2016-02-01
Previous models of category-based induction have neglected how the process of induction unfolds over time. We conceive of induction as a dynamic process and provide the first fine-grained examination of the distribution of response times observed in inductive reasoning. We used these data to develop and empirically test the first major quantitative modeling scheme that simultaneously accounts for inductive decisions and their time course. The model assumes that knowledge of similarity relations among novel test probes and items stored in memory drive an accumulation-to-bound sequential sampling process: Test probes with high similarity to studied exemplars are more likely to trigger a generalization response, and more rapidly, than items with low exemplar similarity. We contrast data and model predictions for inductive decisions with a recognition memory task using a common stimulus set. Hierarchical Bayesian analyses across 2 experiments demonstrated that inductive reasoning and recognition memory primarily differ in the threshold to trigger a decision: Observers required less evidence to make a property generalization judgment (induction) than an identity statement about a previously studied item (recognition). Experiment 1 and a condition emphasizing decision speed in Experiment 2 also found evidence that inductive decisions use lower quality similarity-based information than recognition. The findings suggest that induction might represent a less cautious form of recognition. We conclude that sequential sampling models grounded in exemplar-based similarity, combined with hierarchical Bayesian analysis, provide a more fine-grained and informative analysis of the processes involved in inductive reasoning than is possible solely through examination of choice data.
CFD modeling of the IRIS pressurizer dynamic
Energy Technology Data Exchange (ETDEWEB)
Sanz, Ronny R.; Montesinos, Maria E.; Garcia, Carlos; Bueno, Elizabeth D.; Mazaira, Leorlen R., E-mail: rsanz@instec.cu, E-mail: mmontesi@instec.cu, E-mail: cgh@instec.cu, E-mail: leored1984@gmail.com [Instituto Superior de Tecnologias y Ciencias Aplicadas (InSTEC), La Habana (Cuba); Bezerra, Jair L.; Lira, Carlos A.B. Oliveira, E-mail: jair.lima@ufpe.br, E-mail: cabol@ufpe.br [Universida Federal de Pernambuco (UFPE), Recife, PE (Brazil). Dept. de Energia Nuclear
2015-07-01
Integral layout of nuclear reactor IRIS makes possible the elimination of the spray system, which is usually used to mitigate in-surge transient and also help to Boron homogenization. The study of transients with deficiencies in the Boron homogenization in this technology is very important, because they can cause disturbances in the reactor power and insert a strong reactivity in the core. The detailed knowledge of the behavior of multiphase multicomponent flows is challenging due to the complex phenomena and interactions at the interface. In this context, the CFD modeling is employed in the design of equipment in the nuclear industry as it allows predicting accidents or predicting their performance in dissimilar applications. The aim of the present research is to model the IRIS pressurizer's dynamic using the commercial CFD code CFX. A symmetric tri dimensional model equivalent to 1/8 of the total geometry was adopted to reduce mesh size and minimize processing time. The model considers the coexistence of four phases and also takes into account the heat losses. The relationships for interfacial mass, energy, and momentum transport are programmed and incorporated into CFX. Moreover, two subdomains and several additional variables are defined to monitoring the boron dilution sequences and condensation-evaporation rates in different control volumes. For transient states a non - equilibrium stratification in the pressurizer is considered. This paper discusses the model developed and the behavior of the system for representative transients sequences. The results of analyzed transients of IRIS can be applied to the design of pressurizer internal structures and components. (author)
An empirical model of tropical ocean dynamics
Energy Technology Data Exchange (ETDEWEB)
Newman, Matthew; Scott, James D. [University of Colorado, CIRES Climate Diagnostics Center, Boulder, CO (United States); NOAA Earth System Research Laboratory, Physical Sciences Division, Boulder, CO (United States); Alexander, Michael A. [NOAA Earth System Research Laboratory, Physical Sciences Division, Boulder, CO (United States)
2011-11-15
To extend the linear stochastically forced paradigm of tropical sea surface temperature (SST) variability to the subsurface ocean, a linear inverse model (LIM) is constructed from the simultaneous and 3-month lag covariances of observed 3-month running mean anomalies of SST, thermocline depth, and zonal wind stress. This LIM is then used to identify the empirically-determined linear dynamics with physical processes to gauge their relative importance to ENSO evolution. Optimal growth of SST anomalies over several months is triggered by both an initial SST anomaly and a central equatorial Pacific thermocline anomaly that propagates slowly eastward while leading the amplifying SST anomaly. The initial SST and thermocline anomalies each produce roughly half the SST amplification. If interactions between the sea surface and the thermocline are removed in the linear dynamical operator, the SST anomaly undergoes less optimal growth but is also more persistent, and its location shifts from the eastern to central Pacific. Optimal growth is also found to be essentially the result of two stable eigenmodes with similar structure but differing 2- and 4-year periods evolving from initial destructive to constructive interference. Variations among ENSO events could then be a consequence not of changing stability characteristics but of random excitation of these two eigenmodes, which represent different balances between surface and subsurface coupled dynamics. As found in previous studies, the impact of the additional variables on LIM SST forecasts is relatively small for short time scales. Over time intervals greater than about 9 months, however, the additional variables both significantly enhance forecast skill and predict lag covariances and associated power spectra whose closer agreement with observations enhances the validation of the linear model. Moreover, a secondary type of optimal growth exists that is not present in a LIM constructed from SST alone, in which initial SST
Pion production model - connection between dynamics and quark models
Energy Technology Data Exchange (ETDEWEB)
Lee, T.-S. H.; Sato, T.
2000-05-17
The authors discuss the difficulties in testing the hadron models by using the N{sup *} parameters extracted from the empirical amplitude analyses of the {pi}N and {gamma}N reaction data. As an alternative or perhaps a more advantageous approach, they present a Hamiltonian formulation that can relate the pion production dynamics and the constituent quark models of N{sup *} structure. The application of the approach in investigating the {Delta} and N{sup *}(S{sub 11}) excitations is reviewed. It is found that while the {Delta} excitation can be described satisfactory, the {pi}N scattering in S{sub 11} channel can not be described by the constituent quark models based on either the one-gluon-exchange or one-meson-exchange mechanisms. A phenomenological quark-quark potential has been constructed to reproduce the S{sub 11} amplitude.
Model Adequacy Checks for Discrete Choice Dynamic Models
Kheifets, Igor
2012-01-01
This paper proposes new parametric model adequacy tests for possibly nonlinear and nonstationary time series models with noncontinuous data distribution, which is often the case in applied work. In particular, we consider the correct specification of parametric conditional distributions in dynamic discrete choice models, not only of some particular conditional characteristics such as moments or symmetry. Knowing the true distribution is important in many circumstances, in particular to apply efficient maximum likelihood methods, obtain consistent estimates of partial effects and appropriate predictions of the probability of future events. We propose a transformation of data which under the true conditional distribution leads to continuous uniform iid series. The uniformity and serial independence of the new series is then examined simultaneously. The transformation can be considered as an extension of the integral transform tool for noncontinuous data. We derive asymptotic properties of such tests taking into...
Progress towards Continental River Dynamics modeling
Yu, Cheng-Wei; Zheng, Xing; Liu, Frank; Maidment, Daivd; Hodges, Ben
2017-04-01
The high-resolution National Water Model (NWM), launched by U.S. National Oceanic and Atmospheric Administration (NOAA) in August 2016, has shown it is possible to provide real-time flow prediction in rivers and streams across the entire continental United States. The next step for continental-scale modeling is moving from reduced physics (e.g. Muskingum-Cunge) to full dynamic modeling with the Saint-Venant equations. The Simulation Program for River Networks (SPRNT) provides a computational approach for the Saint-Venant equations, but obtaining sufficient channel bathymetric data and hydraulic roughness is seen as a critical challenge. However, recent work has shown the Height Above Nearest Drainage (HAND) method can be applied with the National Elevation Dataset (NED) to provide automated estimation of effective channel bathymetry suitable for large-scale hydraulic simulations. The present work examines the use of SPRNT with the National Hydrography Dataset (NHD) and HAND-derived bathymetry for automated generation of rating curves that can be compared to existing data. The approach can, in theory, be applied to every stream reach in the NHD and thus provide flood guidance where none is available. To test this idea we generated 2000+ rating curves in two catchments in Texas and Alabama (USA). Field data from the USGS and flood records from an Austin, Texas flood in May 2015 were used as validation. Large-scale implementation of this idea requires addressing several critical difficulties associated with numerical instabilities, including ill-posed boundary conditions generated in automated model linkages and inconsistencies in the river geometry. A key to future progress is identifying efficient approaches to isolate numerical instability contributors in a large time-space varying solution. This research was supported in part by the National Science Foundation under grant number CCF-1331610.
Dynamics in Higher Education Politics: A Theoretical Model
Kauko, Jaakko
2013-01-01
This article presents a model for analysing dynamics in higher education politics (DHEP). Theoretically the model draws on the conceptual history of political contingency, agenda-setting theories and previous research on higher education dynamics. According to the model, socio-historical complexity can best be analysed along two dimensions: the…
Urban eco-efficiency and system dynamics modelling
Energy Technology Data Exchange (ETDEWEB)
Hradil, P., Email: petr.hradil@vtt.fi
2012-06-15
Assessment of urban development is generally based on static models of economic, social or environmental impacts. More advanced dynamic models have been used mostly for prediction of population and employment changes as well as for other macro-economic issues. This feasibility study was arranged to test the potential of system dynamic modelling in assessing eco-efficiency changes during urban development. (orig.)
Maritime piracy situation modelling with dynamic Bayesian networks
CSIR Research Space (South Africa)
Dabrowski, James M
2015-05-01
Full Text Available A generative model for modelling maritime vessel behaviour is proposed. The model is a novel variant of the dynamic Bayesian network (DBN). The proposed DBN is in the form of a switching linear dynamic system (SLDS) that has been extended into a...
Linking spatial and dynamic models for traffic maneuvers
DEFF Research Database (Denmark)
Olderog, Ernst-Rüdiger; Ravn, Anders Peter; Wisniewski, Rafal
2015-01-01
For traffic maneuvers of multiple vehicles on highways we build an abstract spatial and a concrete dynamic model. In the spatial model we show the safety (collision freedom) of lane-change maneuvers. By linking the spatial and dynamic model via suitable refinements of the spatial atoms to distance...
Agent Based Modeling on Organizational Dynamics of Terrorist Network
Bo Li; Duoyong Sun; Renqi Zhu; Ze Li
2015-01-01
Modeling organizational dynamics of terrorist network is a critical issue in computational analysis of terrorism research. The first step for effective counterterrorism and strategic intervention is to investigate how the terrorists operate with the relational network and what affects the performance. In this paper, we investigate the organizational dynamics by employing a computational experimentation methodology. The hierarchical cellular network model and the organizational dynamics model ...
Production TTR modeling and dynamic buckling analysis
Institute of Scientific and Technical Information of China (English)
Hugh Liu; John Wei; Edward Huang
2013-01-01
In a typical tension leg platform (TLP) design,the top tension factor (TTF),measuring the top tension of a top tensioned riser (TTR) relative to its submerged weight in water,is one of the most important design parameters that has to be specified properly.While a very small TTF may lead to excessive vortex induced vibration (ⅤⅣ),clashing issues and possible compression close to seafloor,an unnecessarily high TTF may translate into excessive riser cost and vessel payload,and even has impacts on the TLP sizing and design in general.In the process of a production TTR design,it is found that its outer casing can be subjected to compression in a worst-case scenario with some extreme metocean and hardware conditions.The present paper shows how finite element analysis (FEA) models using beam elements and two different software packages (Flexcom and ABAQUS) are constructed to simulate the TTR properly,and especially the pipe-in-pipe effects.An ABAQUS model with hybrid elements (beam elements globally + shell elements locally) can be used to investigate how the outer casing behaves under compression.It is shown for the specified TTR design,even with its outer casing being under some local compression in the worst-case scenario,dynamic buckling would not occur; therefore the TTR design is adequate.
Supercomputer modeling of volcanic eruption dynamics
Energy Technology Data Exchange (ETDEWEB)
Kieffer, S.W. [Arizona State Univ., Tempe, AZ (United States); Valentine, G.A. [Los Alamos National Lab., NM (United States); Woo, Mahn-Ling [Arizona State Univ., Tempe, AZ (United States)
1995-06-01
Our specific goals are to: (1) provide a set of models based on well-defined assumptions about initial and boundary conditions to constrain interpretations of observations of active volcanic eruptions--including movies of flow front velocities, satellite observations of temperature in plumes vs. time, and still photographs of the dimensions of erupting plumes and flows on Earth and other planets; (2) to examine the influence of subsurface conditions on exit plane conditions and plume characteristics, and to compare the models of subsurface fluid flow with seismic constraints where possible; (3) to relate equations-of-state for magma-gas mixtures to flow dynamics; (4) to examine, in some detail, the interaction of the flowing fluid with the conduit walls and ground topography through boundary layer theory so that field observations of erosion and deposition can be related to fluid processes; and (5) to test the applicability of existing two-phase flow codes for problems related to the generation of volcanic long-period seismic signals; (6) to extend our understanding and simulation capability to problems associated with emplacement of fragmental ejecta from large meteorite impacts.
Modeling Dynamic Evolution of Online Friendship Network
Institute of Scientific and Technical Information of China (English)
吴联仁; 闫强
2012-01-01
In this paper,we study the dynamic evolution of friendship network in SNS (Social Networking Site).Our analysis suggests that an individual joining a community depends not only on the number of friends he or she has within the community,but also on the friendship network generated by those friends.In addition,we propose a model which is based on two processes:first,connecting nearest neighbors;second,strength driven attachment mechanism.The model reflects two facts:first,in the social network it is a universal phenomenon that two nodes are connected when they have at least one common neighbor;second,new nodes connect more likely to nodes which have larger weights and interactions,a phenomenon called strength driven attachment (also called weight driven attachment).From the simulation results,we find that degree distribution P(k),strength distribution P(s),and degree-strength correlation are all consistent with empirical data.
Divisional and hierarchical innervations of G.gecko's toes to motion and reception
Institute of Scientific and Technical Information of China (English)
GUO Ce; CAI Lei; XIE HeRui; WANG ZhouYi; DAI ZhenDong; SUN JiuRong
2009-01-01
As a member of robot families,climbing robots have become one of the research hot-spots in the robotic field recently and Gekko gecko (G gecko) has been broadly seen as an ideal model for climbing robot development.But for gecko-mimic robots,one of the key problems is how to design the robot's foot.In this paper,(1) high-speed camera recording and electrophysiological method are used to observe motion patterns of G gecko's foot when it climbs on different oriented surfaces;(2) nerve innerrations of gecko's toes to motion and reception are studied.It is found that the five toes of the G gecko can be divided into two motion and reception divisions,and also its motion and reception are modulated and controlled hierarchically.The results provide important information and exclusive ideas for the foot design and control algorithm of gecko-mimic robots.
[Reception in the hospital environment: perspectives of companions of hospitalized patients].
Prochnow, Adelina Giacomelli; dos Santos, José Luis Guedes; Pradebon, Vania Marta; Schimith, Maria Denise
2009-03-01
Reception procedures are one of the main guidelines concerning the health care production, even though the studies on this subject are focused upon primary health care. This paper aimed to understand the way reception is experienced by the companions of hospitalized patients and discuss their difficulties while accompanying the patients in a hospital environment. This is a qualitative study, conducted with 77 companions of patients hospitalized in a university hospital in the state of Rio Grande do Sul, Brazil. Data were collected through interviews and examined by the content analysis. According to the companions' perceptions, the reception procedure is associated to clarifying rules and routines, as well as meals delivery; the main difficulties were related to the physical structure and the noise in the hospital environment. A need for reconsidering the established models for health assistance is pointed, as well as the importance of improving health care practices based on light technology.
Nonlinear dynamics new directions models and applications
Ugalde, Edgardo
2015-01-01
This book, along with its companion volume, Nonlinear Dynamics New Directions: Theoretical Aspects, covers topics ranging from fractal analysis to very specific applications of the theory of dynamical systems to biology. This second volume contains mostly new applications of the theory of dynamical systems to both engineering and biology. The first volume is devoted to fundamental aspects and includes a number of important new contributions as well as some review articles that emphasize new development prospects. The topics addressed in the two volumes include a rigorous treatment of fluctuations in dynamical systems, topics in fractal analysis, studies of the transient dynamics in biological networks, synchronization in lasers, and control of chaotic systems, among others. This book also: · Develops applications of nonlinear dynamics on a diversity of topics such as patterns of synchrony in neuronal networks, laser synchronization, control of chaotic systems, and the study of transient dynam...
A Dynamic Travel Time Estimation Model Based on Connected Vehicles
Directory of Open Access Journals (Sweden)
Daxin Tian
2015-01-01
Full Text Available With advances in connected vehicle technology, dynamic vehicle route guidance models gradually become indispensable equipment for drivers. Traditional route guidance models are designed to direct a vehicle along the shortest path from the origin to the destination without considering the dynamic traffic information. In this paper a dynamic travel time estimation model is presented which can collect and distribute traffic data based on the connected vehicles. To estimate the real-time travel time more accurately, a road link dynamic dividing algorithm is proposed. The efficiency of the model is confirmed by simulations, and the experiment results prove the effectiveness of the travel time estimation method.
Approximate group context tree: applications to dynamic programming and dynamic choice models
Belloni, Alexandre
2011-01-01
The paper considers a variable length Markov chain model associated with a group of stationary processes that share the same context tree but potentially different conditional probabilities. We propose a new model selection and estimation method, develop oracle inequalities and model selection properties for the estimator. These results also provide conditions under which the use of the group structure can lead to improvements in the overall estimation. Our work is also motivated by two methodological applications: discrete stochastic dynamic programming and dynamic discrete choice models. We analyze the uniform estimation of the value function for dynamic programming and the uniform estimation of average dynamic marginal effects for dynamic discrete choice models accounting for possible imperfect model selection. We also derive the typical behavior of our estimator when applied to polynomially $\\beta$-mixing stochastic processes. For parametric models, we derive uniform rate of convergence for the estimation...
Follistatin is critical for mouse uterine receptivity and decidualization.
Fullerton, Paul T; Monsivais, Diana; Kommagani, Ramakrishna; Matzuk, Martin M
2017-06-13
Embryo implantation remains a significant challenge for assisted reproductive technology, with implantation failure occurring in ∼50% of in vitro fertilization attempts. Understanding the molecular mechanisms underlying uterine receptivity will enable the development of new interventions and biomarkers. TGFβ family signaling in the uterus is critical for establishing and maintaining pregnancy. Follistatin (FST) regulates TGFβ family signaling by selectively binding TGFβ family ligands and sequestering them. In humans, FST is up-regulated in the decidua during early pregnancy, and women with recurrent miscarriage have lower endometrial expression of FST during the luteal phase. Because global knockout of Fst is perinatal lethal in mice, we generated a conditional knockout (cKO) of Fst in the uterus using progesterone receptor-cre to study the roles of uterine Fst during pregnancy. Uterine Fst-cKO mice demonstrate severe fertility defects and deliver only 2% of the number of pups delivered by control females. In Fst-cKO mice, the uterine luminal epithelium does not respond properly to estrogen and progesterone signals and remains unreceptive to embryo attachment by continuing to proliferate and failing to differentiate. The uterine stroma of Fst-cKO mice also responds poorly to artificial decidualization, with lower levels of proliferation and differentiation. In the absence of uterine FST, activin B expression and signaling are up-regulated, and bone morphogenetic protein (BMP) signals are impaired. Our findings support a model in which repression of activin signaling by FST enables uterine receptivity by preserving critical BMP signaling.
Health-reception of newly arrived documented migrants in Europe—why, whom, what and how?
DEFF Research Database (Denmark)
Frederiksen, Hanne Winther
2013-01-01
address the existing health inequities, nor determining factors of migrant health, including barriers to access health services’.1 Two recent Danish documents highlight these aspects in relation to the health-reception of migrants. A report from the Ministry of Social Affairs and Integration concludes...... Danish health-reception model, using a more systematic approach based on a close cooperation between social and health sectors.3 With this development, we wish to initiate a European public health debate about how to assess and meet the health needs of newly arrived long-term documented migrants...
Bayesian Estimation of Random Coefficient Dynamic Factor Models
Song, Hairong; Ferrer, Emilio
2012-01-01
Dynamic factor models (DFMs) have typically been applied to multivariate time series data collected from a single unit of study, such as a single individual or dyad. The goal of DFMs application is to capture dynamics of multivariate systems. When multiple units are available, however, DFMs are not suited to capture variations in dynamics across…
Energy Technology Data Exchange (ETDEWEB)
Davtyan, Aram; Dama, James F.; Voth, Gregory A. [Department of Chemistry, The James Franck Institute, Institute for Biophysical Dynamics, and Computation Institute, The University of Chicago, Chicago, Illinois 60637 (United States); Andersen, Hans C., E-mail: hca@stanford.edu [Department of Chemistry, Stanford University, Stanford, California 94305 (United States)
2015-04-21
Coarse-grained (CG) models of molecular systems, with fewer mechanical degrees of freedom than an all-atom model, are used extensively in chemical physics. It is generally accepted that a coarse-grained model that accurately describes equilibrium structural properties (as a result of having a well constructed CG potential energy function) does not necessarily exhibit appropriate dynamical behavior when simulated using conservative Hamiltonian dynamics for the CG degrees of freedom on the CG potential energy surface. Attempts to develop accurate CG dynamic models usually focus on replacing Hamiltonian motion by stochastic but Markovian dynamics on that surface, such as Langevin or Brownian dynamics. However, depending on the nature of the system and the extent of the coarse-graining, a Markovian dynamics for the CG degrees of freedom may not be appropriate. In this paper, we consider the problem of constructing dynamic CG models within the context of the Multi-Scale Coarse-graining (MS-CG) method of Voth and coworkers. We propose a method of converting a MS-CG model into a dynamic CG model by adding degrees of freedom to it in the form of a small number of fictitious particles that interact with the CG degrees of freedom in simple ways and that are subject to Langevin forces. The dynamic models are members of a class of nonlinear systems interacting with special heat baths that were studied by Zwanzig [J. Stat. Phys. 9, 215 (1973)]. The properties of the fictitious particles can be inferred from analysis of the dynamics of all-atom simulations of the system of interest. This is analogous to the fact that the MS-CG method generates the CG potential from analysis of equilibrium structures observed in all-atom simulation data. The dynamic models generate a non-Markovian dynamics for the CG degrees of freedom, but they can be easily simulated using standard molecular dynamics programs. We present tests of this method on a series of simple examples that demonstrate that
Further Results on Dynamic Additive Hazard Rate Model
Directory of Open Access Journals (Sweden)
Zhengcheng Zhang
2014-01-01
Full Text Available In the past, the proportional and additive hazard rate models have been investigated in the works. Nanda and Das (2011 introduced and studied the dynamic proportional (reversed hazard rate model. In this paper we study the dynamic additive hazard rate model, and investigate its aging properties for different aging classes. The closure of the model under some stochastic orders has also been investigated. Some examples are also given to illustrate different aging properties and stochastic comparisons of the model.
MULTI-FLEXIBLE SYSTEM DYNAMIC MODELING THEORY AND APPLICATION
Institute of Scientific and Technical Information of China (English)
仲昕; 周兵; 杨汝清
2001-01-01
The flexible body modeling theory was demonstrated. An example of modeling a kind of automobile's front suspension as a multi-flexible system was shown. Finally, it shows that the simulation results of multi-flexible dynamic model more approach the road test data than those of multi-rigid dynamic model do. Thus, it is fully testified that using multi-flexible body theory to model is necessary and effective.
Mice endometrium receptivity in early pregnancy is impaired by maternal hyperinsulinemia
Li, Runqin; Wu, Juan; He, Junlin; Wang, Yingxiong; Liu, Xueqing; Chen, Xuemei; Tong, Chao; Ding, Yubin; Su, Yan; Chen, Wenqi; Zhang, Chen; Gao, Rufei
2017-01-01
Previous studies have investigated the lower embryo implantation rates in women with polycystic ovary syndrome, obesity and type 2 diabetes, and specifically the association between the abnormal oocyte and embryo and hyperinsulinemia. The importance of hyperinsulinemia on maternal endometrium receptivity remains to be elucidated. The present study used a hyperinsulinemic mouse model to determine whether hyperinsulinemia may affect endometrial receptivity. An insulin intervention mouse model was first established. The serum levels of insulin, progesterone and estradiol were subsequently detected by ELISA assay analysis. The number of implantation sites was recorded using Trypan blue dye and the morphology of mice uteri was investigated using hematoxylin and eosin staining. The expression levels of molecular markers associated with endometrial receptivity were detected by reverse transcription-quantitative polymerase chain reaction, western blotting and immunohistochemistry analyses. Finally, the importance of mechanistic target of rapamycin (mTOR) expression following insulin treatment was determined. Mice treated with insulin developed insulin resistance and hyperinsulinemia. The number of implantation sites following insulin treatment did not differ between the control and insulin-treated groups. Additionally, no significant morphological alterations in mice uteri between control and insulin-treated groups were observed. However, the expression levels of estrogen receptor (Esr) 1, Esr2, progesterone receptor and homeobox A10 associated with endometrial receptivity, were imbalanced during endometrium receptivity when maternal hyperinsulinemia was induced. Western blot analysis revealed that expression levels of endometrial phosphorylated (p)-mTOR and p-ribosomal protein S6 kinase β-1 were significantly greater in the insulin-treated group. These results demonstrated that although an embryo may implant into endometrium, mice endometrium receptivity in early
A dynamic model reduction algorithm for atmospheric chemistry models
Santillana, Mauricio; Le Sager, Philippe; Jacob, Daniel J.; Brenner, Michael
2010-05-01
Understanding the dynamics of the chemical composition of our atmosphere is essential to address a wide range of environmental issues from air quality to climate change. Current models solve a very large and stiff system of nonlinear advection-reaction coupled partial differential equations in order to calculate the time evolution of the concentration of over a hundred chemical species. The numerical solution of this system of equations is difficult and the development of efficient and accurate techniques to achieve this has inspired research for the past four decades. In this work, we propose an adaptive method that dynamically adjusts the chemical mechanism to be solved to the local environment and we show that the use of our approach leads to accurate results and considerable computational savings. Our strategy consists of partitioning the computational domain in active and inactive regions for each chemical species at every time step. In a given grid-box, the concentration of active species is calculated using an accurate numerical scheme, whereas the concentration of inactive species is calculated using a simple and computationally inexpensive formula. We demonstrate the performance of the method by application to the GEOS-Chem global chemical transport model.
Analysing the temporal dynamics of model performance for hydrological models
Directory of Open Access Journals (Sweden)
D. E. Reusser
2008-11-01
Full Text Available The temporal dynamics of hydrological model performance gives insights into errors that cannot be obtained from global performance measures assigning a single number to the fit of a simulated time series to an observed reference series. These errors can include errors in data, model parameters, or model structure. Dealing with a set of performance measures evaluated at a high temporal resolution implies analyzing and interpreting a high dimensional data set. This paper presents a method for such a hydrological model performance assessment with a high temporal resolution and illustrates its application for two very different rainfall-runoff modeling case studies. The first is the Wilde Weisseritz case study, a headwater catchment in the eastern Ore Mountains, simulated with the conceptual model WaSiM-ETH. The second is the Malalcahuello case study, a headwater catchment in the Chilean Andes, simulated with the physics-based model Catflow. The proposed time-resolved performance assessment starts with the computation of a large set of classically used performance measures for a moving window. The key of the developed approach is a data-reduction method based on self-organizing maps (SOMs and cluster analysis to classify the high-dimensional performance matrix. Synthetic peak errors are used to interpret the resulting error classes. The final outcome of the proposed method is a time series of the occurrence of dominant error types. For the two case studies analyzed here, 6 such error types have been identified. They show clear temporal patterns which can lead to the identification of model structural errors.
Analysing the temporal dynamics of model performance for hydrological models
Directory of Open Access Journals (Sweden)
E. Zehe
2009-07-01
Full Text Available The temporal dynamics of hydrological model performance gives insights into errors that cannot be obtained from global performance measures assigning a single number to the fit of a simulated time series to an observed reference series. These errors can include errors in data, model parameters, or model structure. Dealing with a set of performance measures evaluated at a high temporal resolution implies analyzing and interpreting a high dimensional data set. This paper presents a method for such a hydrological model performance assessment with a high temporal resolution and illustrates its application for two very different rainfall-runoff modeling case studies. The first is the Wilde Weisseritz case study, a headwater catchment in the eastern Ore Mountains, simulated with the conceptual model WaSiM-ETH. The second is the Malalcahuello case study, a headwater catchment in the Chilean Andes, simulated with the physics-based model Catflow. The proposed time-resolved performance assessment starts with the computation of a large set of classically used performance measures for a moving window. The key of the developed approach is a data-reduction method based on self-organizing maps (SOMs and cluster analysis to classify the high-dimensional performance matrix. Synthetic peak errors are used to interpret the resulting error classes. The final outcome of the proposed method is a time series of the occurrence of dominant error types. For the two case studies analyzed here, 6 such error types have been identified. They show clear temporal patterns, which can lead to the identification of model structural errors.
BUILDING MATHEMATICAL MODELS IN DYNAMIC PROGRAMMING
Directory of Open Access Journals (Sweden)
LIANA RODICA PATER
2012-05-01
Full Text Available In short, we can say that dynamic programming is a method of optimization of systems, using their mathematical representation in phases or sequences or as we say, periods. Such systems are common in economic studies at the implementation of programs on the most advanced techniques, such as for example that involving cosmic navigation. Another concept that is involved in the study of dynamic programs is the economic horizon (number of periods or phases that a dynamic program needs. This concept often leads to the examination of the convergence of certain variables on infinite horizon. In many cases from the real economy by introducing updating, dynamic programs can be made convergent.
Hybrid Dynamical Systems Modeling, Stability, and Robustness
Goebel, Rafal; Teel, Andrew R
2012-01-01
Hybrid dynamical systems exhibit continuous and instantaneous changes, having features of continuous-time and discrete-time dynamical systems. Filled with a wealth of examples to illustrate concepts, this book presents a complete theory of robust asymptotic stability for hybrid dynamical systems that is applicable to the design of hybrid control algorithms--algorithms that feature logic, timers, or combinations of digital and analog components. With the tools of modern mathematical analysis, Hybrid Dynamical Systems unifies and generalizes earlier developments in continuous-time and discret
Dynamical Models For Prices With Distributed Delays
Directory of Open Access Journals (Sweden)
Mircea Gabriela
2015-06-01
Full Text Available In the present paper we study some models for the price dynamics of a single commodity market. The quantities of supplied and demanded are regarded as a function of time. Nonlinearities in both supply and demand functions are considered. The inventory and the level of inventory are taken into consideration. Due to the fact that the consumer behavior affects commodity demand, and the behavior is influenced not only by the instantaneous price, but also by the weighted past prices, the distributed time delay is introduced. The following kernels are taken into consideration: demand price weak kernel and demand price Dirac kernel. Only one positive equilibrium point is found and its stability analysis is presented. When the demand price kernel is weak, under some conditions of the parameters, the equilibrium point is locally asymptotically stable. When the demand price kernel is Dirac, the existence of the local oscillations is investigated. A change in local stability of the equilibrium point, from stable to unstable, implies a Hopf bifurcation. A family of periodic orbits bifurcates from the positive equilibrium point when the time delay passes through a critical value. The last part contains some numerical simulations to illustrate the effectiveness of our results and conclusions.
Dynamical Models of Terrestrial Planet Formation
Lunine, Jonathan I; Raymond, Sean N; Morbidelli, Alessandro; Quinn, Thomas; Graps, Amara
2009-01-01
We review the problem of the formation of terrestrial planets, with particular emphasis on the interaction of dynamical and geochemical models. The lifetime of gas around stars in the process of formation is limited to a few million years based on astronomical observations, while isotopic dating of meteorites and the Earth-Moon system suggest that perhaps 50-100 million years were required for the assembly of the Earth. Therefore, much of the growth of the terrestrial planets in our own system is presumed to have taken place under largely gas-free conditions, and the physics of terrestrial planet formation is dominated by gravitational interactions and collisions. The earliest phase of terrestrial-planet formation involve the growth of km-sized or larger planetesimals from dust grains, followed by the accumulations of these planetesimals into ~100 lunar- to Mars-mass bodies that are initially gravitationally isolated from one-another in a swarm of smaller planetesimals, but eventually grow to the point of sig...
Modelling dynamics with context-free grammars
García-Huerta, Juan-M.; Jiménez-Hernández, Hugo; Herrera-Navarro, Ana-M.; Hernández-Díaz, Teresa; Terol-Villalobos, Ivan
2014-03-01
This article presents a strategy to model the dynamics performed by vehicles in a freeway. The proposal consists on encode the movement as a set of finite states. A watershed-based segmentation is used to localize regions with high-probability of motion. Each state represents a proportion of a camera projection in a two-dimensional space, where each state is associated to a symbol, such that any combination of symbols is expressed as a language. Starting from a sequence of symbols through a linear algorithm a free-context grammar is inferred. This grammar represents a hierarchical view of common sequences observed into the scene. Most probable grammar rules express common rules associated to normal movement behavior. Less probable rules express themselves a way to quantify non-common behaviors and they might need more attention. Finally, all sequences of symbols that does not match with the grammar rules, may express itself uncommon behaviors (abnormal). The grammar inference is built with several sequences of images taken from a freeway. Testing process uses the sequence of symbols emitted by the scenario, matching the grammar rules with common freeway behaviors. The process of detect abnormal/normal behaviors is managed as the task of verify if any word generated by the scenario is recognized by the grammar.
Front Office and Reception; An Approach to Front Office and Reception Training.
Hotel and Catering Industry Training Board, Wembley (England).
This manual is concerned with the tasks and training needs of front office personnel in hotels. After discussion of selection and qualifications of such personnel, the perfect receptionist is described in terms of personality, appearance, and deportment. Then follows a detailed listing of tasks--basic tasks, such as reception, bookkeeping, cash,…
Strand, Paul S.; Pula, Kacy; Parks, Craig D.; Cerna, Sandra
2011-01-01
The present study utilized a short-term longitudinal research design to model the relationship between shyness-anxiousness and receptive language skills. Hypotheses regarding the direction of the causal relationship, mediation, and moderation were evaluated. Subjects included 340 Head Start attendees from primarily English- and Spanish-speaking…
Strand, Paul S.; Pula, Kacy; Parks, Craig D.; Cerna, Sandra
2011-01-01
The present study utilized a short-term longitudinal research design to model the relationship between shyness-anxiousness and receptive language skills. Hypotheses regarding the direction of the causal relationship, mediation, and moderation were evaluated. Subjects included 340 Head Start attendees from primarily English- and Spanish-speaking…
Optimum spatiotemporal receptive fields for vision in dim light.
Klaus, Andreas; Warrant, Eric J
2009-04-22
Many nocturnal insects depend on vision for daily life and have evolved different strategies to improve their visual capabilities in dim light. Neural summation of visual signals is one strategy to improve visual performance, and this is likely to be especially important for insects with apposition compound eyes. Here we develop a model to determine the optimum spatiotemporal sampling of natural scenes at gradually decreasing light levels. Image anisotropy has a strong influence on the receptive field properties predicted to be optimal at low light intensities. Spatial summation between visual channels is predicted to extend more strongly in the direction with higher correlations between the input signals. Increased spatiotemporal summation increases signal-to-noise ratio at low frequencies but sacrifices signal-to-noise ratio at higher frequencies. These results, while obtained from a model of the insect visual system, are likely to apply to visual systems in general.
An individual-based model of zebrafish population dynamics accounting for energy dynamics.
Directory of Open Access Journals (Sweden)
Rémy Beaudouin
Full Text Available Developing population dynamics models for zebrafish is crucial in order to extrapolate from toxicity data measured at the organism level to biological levels relevant to support and enhance ecological risk assessment. To achieve this, a dynamic energy budget for individual zebrafish (DEB model was coupled to an individual based model of zebrafish population dynamics (IBM model. Next, we fitted the DEB model to new experimental data on zebrafish growth and reproduction thus improving existing models. We further analysed the DEB-model and DEB-IBM using a sensitivity analysis. Finally, the predictions of the DEB-IBM were compared to existing observations on natural zebrafish populations and the predicted population dynamics are realistic. While our zebrafish DEB-IBM model can still be improved by acquiring new experimental data on the most uncertain processes (e.g. survival or feeding, it can already serve to predict the impact of compounds at the population level.
Area Logistics System Based on System Dynamics Model
Institute of Scientific and Technical Information of China (English)
GUI Shouping; ZHU Qiang; LU Lifang
2005-01-01
At present, there are few effective ways to analyze area logistics systems. This paper uses system dynamics to analyze the area logistics system and establishes a system dynamics model for the area logistics system based on the characteristics of the area logistics system and system dynamics. Numerical simulations with the system dynamic model were used to analyze a logistic system. Analysis of the Guangzhou economy shows that the model can reflect the actual state of the system objectively and can be used to make policy and harmonize environment.
Intervention for mixed receptive-expressive language impairment: a review
National Research Council Canada - National Science Library
Boyle, James; McCartney, Elspeth; O'Hare, Anne; Law, James
2010-01-01
... difficulties as well as adverse outcomes for language development and academic progress. This paper considers underlying explanations that may account for receptive-expressive language impairment...
A review of dynamics modelling of friction wedge suspensions
Wu, Qing; Cole, Colin; Spiryagin, Maksym; Sun, Yan Quan
2014-11-01
Three-piece bogies with friction wedge suspensions are the most widely used bogies in heavy haul trains. Fiction wedge suspensions play a key role in these wagon systems. This article reviews current techniques in dynamic modelling of friction wedge suspension with various motivations: to improve dynamic models of friction wedge suspensions so as to improve general wagon dynamics simulations; to seek better friction wedge suspension models for wagon stability assessments in complex train systems; to improve the modelling of other friction devices, such as friction draft gear. Relevant theories and friction wedge suspension models developed by using commercial simulation packages and in-house simulation packages are reviewed.
Dynamical Widom-Rowlinson Model and Its Mesoscopic Limit
Finkelshtein, Dmitri; Kondratiev, Yuri; Kutoviy, Oleksandr; Oliveira, Maria João
2015-01-01
We consider the non-equilibrium dynamics for the Widom-Rowlinson model (without hard-core) in the continuum. The Lebowitz-Penrose-type scaling of the dynamics is studied and the system of the corresponding kinetic equations is derived. In the space-homogeneous case, the equilibrium points of this system are described. Their structure corresponds to the dynamical phase transition in the model. The bifurcation of the system is shown.
Dynamical model of electroweak pion production in the resonance region
Sato, T; Kubodera, K; Lee, T S H
2006-01-01
In this report, we will briefly review the dynamical model of pion electroweak production reactions in the $\\Delta$ resonance region and report on our study of neutrino-nucleus reactions based on this model.
An integrated dynamic model of a flexible wind turbine
Bongers, Peter M. M.; Bierbooms, Wim A. A.; Dijkstra, Sjoerd; Vanholten, Theo
1990-06-01
A model to study the dynamic behavior of flexible wind turbines was developed. The different subsystems of the wind turbine are individually modeled with about the same degree of accuracy. The aerodynamic part describes wind shear, gravity effects, unsteady effects, and dynamic inflow. The rotor blades are provided with degrees of freedom in lag and flap directions. The tower construction is modeled including the first bending mode. The first torsional mode of the transmission is included in the model. The model of synchronous generator with dc link consists of a nonlinear fourth order model, including saturation effects. The different models of the subsystems are coupled into one integrated dynamic model which is implemented as simulation code in the DUWECS (Delf University Wind Energy Converter Simulation Package) program. The DUWECS program is developed in such a manner that it is an easy to handle tool for the study of the dynamic features of wind turbine systems.
Werner Sombart and his reception in Italy
Directory of Open Access Journals (Sweden)
Simona Pisanelli
2015-03-01
Full Text Available This article intends to focus on the difficulty encountered by Werner Sombart’s works in gaining a hearing in various Italian intellectual circuits. As is well known, Sombart belonged to the German Historical School of economics, sharing with other scholars of that school the same problems in getting his work known in Italy. Our aim is to explain the reason for this hostile reception. First of all, we will analyze the factors which generally hindered the spread of the German Historical School in Italy, recognizing in economists like Francesco Ferrara, Idealists like Benedetto Croce and Marxists like Antonio Labriola some of its strongest opponents. We will dwell on the cases of Gustav Schmoller and Max Weber, in order to give two representative examples of the slow and complicated Italian reception of methodological approaches and analytical perspectives which characterized the scientific experience of the German Historical School. Secondly, we will try to show why Sombart was even less appreciated than other German social scientists, giving the reasons that attracted severe criticism from economists, economic historians and sociologists towards his interdisciplinary approach in the analysis of modern capitalism. Finally, we will show the reasons of the contemporary rediscovery of Sombart and of his works.
Ibrahimagic, Amela; Zunic, Lejla Junuzovic; Rasidovic, Mirsada; Radic, Bojan; Kantic, Ahmet
2016-12-01
Aging, as an irrepressible biological process involves a series of physiological and pathological changes. The main aim of this study was to examine the correlation and predictability of receptive vocabulary and cognitive functioning of elderly people with anamnestic variables: chronological age, sex, level of formal education, marital status, years of work and retirement and years spent in an institution for the elderly. The sample of participants consisted of 120 elderly people, average age was 78 years, placed in institutional care for elderly people in four cities in Bosnia and Herzegovina. It was three groups of variables: anamnestic, receptive vocabulary assessment, and cognitive assessments. A Montreal Cognitive Assessment Scale (MoCA) was used for the assessment of cognitive abilities. In order to estimate the receptive vocabulary Peabody Picture Vocabulary Test (PPVT-III-HR) was used. Results of multiple regression analysis show that part of the variance of receptive language which is explained by the model (anamnestic variables) was 44.0% and of cognitive functioning was 33.7%. The biggest single contribution to explaining the development of receptive vocabulary was given by predictor variable of college education (β = 0.417) then variable university education (β = 0.293), while the smallest single contribution was given by variable secondary education (β = 0.167). The biggest single contribution to explaining the results of tests of cognitive function was given by predictor variable College education (β = 0.328) and variable unskilled (β = -0.229), which has a negative effect on the increase in recent cognitive functioning. Anamnestic variables were valid predictors of receptive vocabulary and cognitive functioning of elderly people. The highest individual contribution was given by variables describing the level of formal education of elderly.
Estimation of Spatial Dynamic Nonparametric Durbin Models with Fixed Effects
Qian, Minghui; Hu, Ridong; Chen, Jianwei
2016-01-01
Spatial panel data models have been widely studied and applied in both scientific and social science disciplines, especially in the analysis of spatial influence. In this paper, we consider the spatial dynamic nonparametric Durbin model (SDNDM) with fixed effects, which takes the nonlinear factors into account base on the spatial dynamic panel…
A NEW SOLUTION MODEL OF NONLINEAR DYNAMIC LEAST SQUARE ADJUSTMENT
Institute of Scientific and Technical Information of China (English)
陶华学; 郭金运
2000-01-01
The nonlinear least square adjustment is a head object studied in technology fields. The paper studies on the non-derivative solution to the nonlinear dynamic least square adjustment and puts forward a new algorithm model and its solution model. The method has little calculation load and is simple. This opens up a theoretical method to solve the linear dynamic least square adjustment.
Wind speed dynamical model in a wind farm
DEFF Research Database (Denmark)
Soleimanzadeh, Maryam; Wisniewski, Rafal
2010-01-01
, the dynamic model for wind flow will be established. The state space variables are determined based on a fine mesh defined for the farm. The end goal of this method is to assist the development of a dynamical model of a wind farm that can be engaged for better wind farm control strategies....
Modelling Seasonal Carbon Dynamics on Fen Peatlands
Giebels, Michael; Beyer, Madlen; Augustin, Jürgen; Roppel, Mario; Juszczak, Radoszlav; Serba, Tomasz
2010-05-01
In Germany more than 99 % of fens have lost their carbon and nutrient sink function due to heavy drainage and agricultural land use especially during the last decades and thus resulted in compression and heavy peat loss (CHARMAN 2002; JOOSTEN & CLARKE 2002; SUCCOW & JOOSTEN 2001; AUGUSTIN et al. 1996; KUNTZE 1993). Therefore fen peatlands play an important part (4-5 %) in the national anthropogenic trace gas budget. But only a small part of drained and agricultural used fens in NE Germany can be restored. Knowledge of the influence of land use to trace gas exchange is important for mitigation of the climate impact of the anthropogenic peatland use. We study carbon exchanges between soil and atmosphere on several fen peatland use areas at different sites in NE-Germany. Our research covers peatlands of supposed strongly climate forcing land use (cornfield and intensive pasture) and of probably less forcing, alternative types (meadow and extensive pasture) as well as rewetted (formerly drained) areas and near-natural sites like a low-degraded fen and a wetted alder woodland. We measured trace gas fluxes with manual and automatic chambers in periodic routines since spring 2007. The used chamber technique bases on DROESLER (2005). In total we now do research at 22 sites situated in 5 different locations covering agricultural, varying states of rewetted and near-natural treatments. We present results of at least 2 years of measurements on our site of varying types of agricultural land use. There we found significant differences in the annual carbon balances depending on the genesis of the observed sites and the seasonal dynamics. Annual balances were constructed by applying single respiration and photosynthesis CO2 models for each measurement campaign. These models were based on LLOYD-TAYLOR (1994) and Michaelis-Menten-Kinetics respectively. Crosswise comparison of different site treatments combined with the seasonal environmental observations give good hints for the
Costs and effects of chlamydial screening : Dynamic versus static modeling
Welte, R; Postma, M; Leidl, R; Kretzschmar, M
2005-01-01
Objective: The objective of this study was to assess the impact of modeling type on the economic evaluation of screening programs for asymptomatic Chlamydia trachomatis infections. Study: We compared a stochastic network simulation model (dynamic model) with a decision analysis model (static model)
Costs and effects of chlamydial screening : Dynamic versus static modeling
Welte, R; Postma, M; Leidl, R; Kretzschmar, M
2005-01-01
Objective: The objective of this study was to assess the impact of modeling type on the economic evaluation of screening programs for asymptomatic Chlamydia trachomatis infections. Study: We compared a stochastic network simulation model (dynamic model) with a decision analysis model (static model)
Dynamic modelling of an electromechanical valve using frequency response data
Miller, R L; Smith, D. L.
1986-01-01
Dynamic modelling of electromechanical parts is often accomplished by conducting an analysis from first physical principles. While this is always a useful effort for physical insight, it may lead to transfer function models which are unnecessarily complex. This paper presents a supplementary dynamic modelling method based on frequency response data. The method is applied to modelling of a globe valve use for water flow control Naval Postgraduate School, Monterey, CA. http://archive.org/...
Directory of Open Access Journals (Sweden)
Xu Liu
2015-01-01
Full Text Available Unsteady aerodynamic system modeling is widely used to solve the dynamic stability problems encountering aircraft design. In this paper, single degree-of-freedom (SDF vibration model and forced simple harmonic motion (SHM model for dynamic derivative prediction are developed on the basis of modified Etkin model. In the light of the characteristics of SDF time domain solution, the free vibration identification methods for dynamic stability parameters are extended and applied to the time domain numerical simulation of blunted cone calibration model examples. The dynamic stability parameters by numerical identification are no more than 0.15% deviated from those by experimental simulation, confirming the correctness of SDF vibration model. The acceleration derivatives, rotary derivatives, and combination derivatives of Army-Navy Spinner Rocket are numerically identified by using unsteady N-S equation and solving different SHV patterns. Comparison with the experimental result of Army Ballistic Research Laboratories confirmed the correctness of the SHV model and dynamic derivative identification. The calculation result of forced SHM is better than that by the slender body theory of engineering approximation. SDF vibration model and SHM model for dynamic stability parameters provide a solution to the dynamic stability problem encountering aircraft design.
Dynamics of mathematical models in biology bringing mathematics to life
Zazzu, Valeria; Guarracino, Mario
2016-01-01
This volume focuses on contributions from both the mathematics and life science community surrounding the concepts of time and dynamicity of nature, two significant elements which are often overlooked in modeling process to avoid exponential computations. The book is divided into three distinct parts: dynamics of genomes and genetic variation, dynamics of motifs, and dynamics of biological networks. Chapters included in dynamics of genomes and genetic variation analyze the molecular mechanisms and evolutionary processes that shape the structure and function of genomes and those that govern genome dynamics. The dynamics of motifs portion of the volume provides an overview of current methods for motif searching in DNA, RNA and proteins, a key process to discover emergent properties of cells, tissues, and organisms. The part devoted to the dynamics of biological networks covers networks aptly discusses networks in complex biological functions and activities that interpret processes in cells. Moreover, chapters i...
Benchmarking novel approaches for modelling species range dynamics.
Zurell, Damaris; Thuiller, Wilfried; Pagel, Jörn; Cabral, Juliano S; Münkemüller, Tamara; Gravel, Dominique; Dullinger, Stefan; Normand, Signe; Schiffers, Katja H; Moore, Kara A; Zimmermann, Niklaus E
2016-08-01
Increasing biodiversity loss due to climate change is one of the most vital challenges of the 21st century. To anticipate and mitigate biodiversity loss, models are needed that reliably project species' range dynamics and extinction risks. Recently, several new approaches to model range dynamics have been developed to supplement correlative species distribution models (SDMs), but applications clearly lag behind model development. Indeed, no comparative analysis has been performed to evaluate their performance. Here, we build on process-based, simulated data for benchmarking five range (dynamic) models of varying complexity including classical SDMs, SDMs coupled with simple dispersal or more complex population dynamic models (SDM hybrids), and a hierarchical Bayesian process-based dynamic range model (DRM). We specifically test the effects of demographic and community processes on model predictive performance. Under current climate, DRMs performed best, although only marginally. Under climate change, predictive performance varied considerably, with no clear winners. Yet, all range dynamic models improved predictions under climate change substantially compared to purely correlative SDMs, and the population dynamic models also predicted reasonable extinction risks for most scenarios. When benchmarking data were simulated with more complex demographic and community processes, simple SDM hybrids including only dispersal often proved most reliable. Finally, we found that structural decisions during model building can have great impact on model accuracy, but prior system knowledge on important processes can reduce these uncertainties considerably. Our results reassure the clear merit in using dynamic approaches for modelling species' response to climate change but also emphasize several needs for further model and data improvement. We propose and discuss perspectives for improving range projections through combination of multiple models and for making these approaches
Dynamical systems and spherically symmetric cosmological models
He, Yanjing
2006-06-01
In this thesis we present a study of the timelike self-similar spherically symmetric cosmological models with two scalar fields with exponential potentials. We first define precisely the timelike self-similar spherically symmetric (TSS) spacetimes. We write the TSS metric in a conformally isometric form in a coordinate system adapted to the geometry of the spacetime manifold. In this coordinate system, both the metric functions of the TSS spacetimes and the potential functions of the scalar fields can be simplified to four undetermined functions of a single coordinate. As a result, the Einstein field equations reduce to an autonomous system of first-order ODEs and polynomial constraints in terms of these undetermined functions. By introducing new bounded variables as well as a new independent variable and solving the constraints, we are able to apply the theory of dynamical systems to study the properties of the TSS solutions. By finding invariant sets and associated monotonic functions, by applying the LaSalle Invariance Principle and the Monotonicity Principle, by applying the [straight phi] t -connected property of a limit set, and using other theorems, we prove that all of the TSS trajectories are heteroclinic trajectories. In addition, we conduct numerical simulations to confirm and support the qualitative analysis. We obtain all possible types of TSS solutions, by analyzing the qualitative behavior of the original system of ODES from those of the reduced one. We obtain asymptotic expressions for the TSS solutions (e.g., the asymptotic expressions for the metric functions, the source functions and the Ricci scalar). In particular, self-similar flat Friedmann-Robertson-Walker spacetimes are examined in order to obtain insights into the issues related to the null surface in general TSS spacetimes in these coordinates. A discussion of the divergence of the spacetime Ricci scalar and the possible extension of the TSS solutions across the null boundary is presented
Automatic code generation from the OMT-based dynamic model
Energy Technology Data Exchange (ETDEWEB)
Ali, J.; Tanaka, J.
1996-12-31
The OMT object-oriented software development methodology suggests creating three models of the system, i.e., object model, dynamic model and functional model. We have developed a system that automatically generates implementation code from the dynamic model. The system first represents the dynamic model as a table and then generates executable Java language code from it. We used inheritance for super-substate relationships. We considered that transitions relate to states in a state diagram exactly as operations relate to classes in an object diagram. In the generated code, each state in the state diagram becomes a class and each event on a state becomes an operation on the corresponding class. The system is implemented and can generate executable code for any state diagram. This makes the role of the dynamic model more significant and the job of designers even simpler.
Gradient dynamics models for liquid films with soluble surfactant
Thiele, Uwe; Pismen, Len M
2016-01-01
In this paper we propose equations of motion for the dynamics of liquid films of surfactant suspensions that consist of a general gradient dynamics framework based on an underlying energy functional. This extends the gradient dynamics approach to dissipative non-equilibrium thin film systems with several variables, and casts their dynamic equations into a form that reproduces Onsager's reciprocity relations. We first discuss the general form of gradient dynamics models for an arbitrary number of fields and discuss simple well-known examples with one or two fields. Next, we develop the gradient dynamics (three field) model for a thin liquid film covered by soluble surfactant and discuss how it automatically results in consistent convective (driven by pressure gradients, Marangoni forces and Korteweg stresses), diffusive, adsorption/desorption, and evaporation fluxes. We then show that in the dilute limit, the model reduces to the well-known hydrodynamic form that includes Marangoni fluxes due to a linear equat...
Dynamics models and modeling of tree stand development
Directory of Open Access Journals (Sweden)
M. V. Rogozin
2015-04-01
Full Text Available Brief analysis of scientific works in Russia and in the CIS over the past 100 years. Logical and mathematical models consider the conceptual and show some of the results of their verification. It was found that the models include different laws and the parameters, the sum of which allows you to divide them into four categories: models of static states, development models, models of care for the natural forest and models of cultivation. Each category has fulfilled and fulfills its tasks in economic management. Thus, the model states in statics (table traverse growth played a prominent role in figuring out what may be the most productive (full stands in different regions of the country. However, they do not answer the question of what the initial states lead to the production of complete stands. In a study of the growth of stands used system analysis, and it is observed dominance of works studying static state, snatched from the biological time. Therefore, the real drama of the growth of stands remained almost unexplored. It is no accident there were «chrono-forestry» «plantation forestry» and even «non-traditional forestry», where there is a strong case of a number of new concepts of development stands. That is quite in keeping with Kuhn (Kuhn, 2009 in the forestry crisis began – there were alternative theories and coexist conflicting scientific schools. To develop models of stand development, it is proposed to use a well-known method of repeated observations within 10–20 years, in conjunction with the explanation of the history of the initial density. It mounted on the basis of studying the dynamics of its indicators: the trunk, crown overlap coefficient, the sum of volumes of all crowns and the relative length of the crown. According to these indicators, the researcher selects natural series of development stands with the same initial density. As a theoretical basis for the models it is possible to postulate the general properties of
Multicomponent aerosol dynamics model UHMA: model development and validation
Directory of Open Access Journals (Sweden)
H. Korhonen
2004-01-01
Full Text Available A size-segregated aerosol dynamics model UHMA (University of Helsinki Multicomponent Aerosol model was developed for studies of multicomponent tropospheric aerosol particles. The model includes major aerosol microphysical processes in the atmosphere with a focus on new particle formation and growth; thus it incorporates particle coagulation and multicomponent condensation, applying a revised treatment of condensation flux onto free molecular regime particles and the activation of nanosized clusters by organic vapours (Nano-Köhler theory, as well as recent parameterizations for binary H2SO4-H2O and ternary H2SO4-NH3-H2O homogeneous nucleation and dry deposition. The representation of particle size distribution can be chosen from three sectional methods: the hybrid method, the moving center method, and the retracking method in which moving sections are retracked to a fixed grid after a certain time interval. All these methods can treat particle emissions and atmospheric transport consistently, and are therefore suitable for use in large scale atmospheric models. In a test simulation against an accurate high resolution solution, all the methods showed reasonable treatment of new particle formation with 20 size sections although the hybrid and the retracking methods suffered from artificial widening of the distribution. The moving center approach, on the other hand, showed extra dents in the particle size distribution and failed to predict the onset of detectable particle formation. In a separate test simulation of an observed nucleation event, the model captured the key qualitative behaviour of the system well. Furthermore, its prediction of the organic volume fraction in newly formed particles, suggesting values as high as 0.5 for 3–4 nm particles and approximately 0.8 for 10 nm particles, agrees with recent indirect composition measurements.
Multicomponent aerosol dynamics model UHMA: model development and validation
Directory of Open Access Journals (Sweden)
H. Korhonen
2004-01-01
Full Text Available A size-segregated aerosol dynamics model UHMA (University of Helsinki Multicomponent Aerosol model was developed for studies of multicomponent tropospheric aerosol particles. The model includes major aerosol microphysical processes in the atmosphere with a focus on new particle formation and growth; thus it incorporates particle coagulation and multicomponent condensation, applying a revised treatment of condensation flux onto free molecular regime particles and the activation of nanosized clusters by organic vapours (Nano-Köhler theory, as well as recent parameterizations for binary H_{2}SO_{4}–H_{2}O and ternary H_{2}SO_{4}–NH_{3}-H_{2}O homogeneous nucleation and dry deposition. The representation of particle size distribution can be chosen from three sectional methods: the hybrid method, the moving center method, and the retracking method in which moving sections are retracked to a fixed grid after a certain time interval. All these methods can treat particle emissions and transport consistently, and are therefore suitable for use in large scale atmospheric models. In a test simulation against an accurate high resolution solution, all the methods showed reasonable treatment of new particle formation with 20 size sections although the hybrid and the retracking methods suffered from artificial widening of the distribution. The moving center approach, on the other hand, showed extra dents in the particle size distribution and failed to predict the onset of detectable particle formation. In a separate test simulation of an observed nucleation event, the model captured the key qualitative behaviour of the system well. Furthermore, its prediction of the organic volume fraction in newly formed particles, suggesting values as high as 0.5 for 3–4 nm particles and approximately 0.8 for 10 nm particles, agrees with recent indirect composition measurements.
Multicomponent aerosol dynamics model UHMA: model development and validation
Korhonen, H.; Lehtinen, K. E. J.; Kulmala, M.
2004-05-01
A size-segregated aerosol dynamics model UHMA (University of Helsinki Multicomponent Aerosol model) was developed for studies of multicomponent tropospheric aerosol particles. The model includes major aerosol microphysical processes in the atmosphere with a focus on new particle formation and growth; thus it incorporates particle coagulation and multicomponent condensation, applying a revised treatment of condensation flux onto free molecular regime particles and the activation of nanosized clusters by organic vapours (Nano-Köhler theory), as well as recent parameterizations for binary H2SO4-H2O and ternary H2SO4-NH3-H2O homogeneous nucleation and dry deposition. The representation of particle size distribution can be chosen from three sectional methods: the hybrid method, the moving center method, and the retracking method in which moving sections are retracked to a fixed grid after a certain time interval. All these methods can treat particle emissions and atmospheric transport consistently, and are therefore suitable for use in large scale atmospheric models. In a test simulation against an accurate high resolution solution, all the methods showed reasonable treatment of new particle formation with 20 size sections although the hybrid and the retracking methods suffered from artificial widening of the distribution. The moving center approach, on the other hand, showed extra dents in the particle size distribution and failed to predict the onset of detectable particle formation. In a separate test simulation of an observed nucleation event, the model captured the key qualitative behaviour of the system well. Furthermore, its prediction of the organic volume fraction in newly formed particles, suggesting values as high as 0.5 for 3-4 nm particles and approximately 0.8 for 10 nm particles, agrees with recent indirect composition measurements.
Research on Dynamic Model's Building of Active Magnetic Suspension Systems
Institute of Scientific and Technical Information of China (English)
SHI Jian; YAN Guo-zheng; LI Li-chuan; WANG Kun-dong
2006-01-01
An experimental method is introduced in this paper to build the dynamics of AMSS (the active magnetic suspension system), which doesn't depend on system's physical parameters. The rotor can be reliably suspended under the unit feedback control system designed with the primary dynamic model obtained. Online identification in frequency domain is processed to give the precise model. Comparisons show that the experimental method is much closer to the precise model than the theoretic method based on magnetic circuit law. So this experimental method is a good choice to build the primary dynamic model of AMSS.
Multiscale mathematical modeling and simulation of cellular dynamical process.
Nakaoka, Shinji
2014-01-01
Epidermal homeostasis is maintained by dynamic interactions among molecules and cells at different spatiotemporal scales. Mathematical modeling and simulation is expected to provide clear understanding and precise description of multiscaleness in tissue homeostasis under systems perspective. We introduce a stochastic process-based description of multiscale dynamics. Agent-based modeling as a framework of multiscale modeling to achieve consistent integration of definitive subsystems is proposed. A newly developed algorithm that particularly aims to perform stochastic simulations of cellular dynamical process is introduced. Finally we review applications of multiscale modeling and quantitative study to important aspects of epidermal and epithelial homeostasis.
Dynamic root uptake model for neutral lipophilic organics
DEFF Research Database (Denmark)
Trapp, Stefan
2002-01-01
and output to stem with the transpiration stream plus first-order metabolism and dilution by exponential growth. For chemicals with low or intermediate lipophilicity (log Kow , 2), there was no relevant difference between dynamic model and equilibrium approach. For lipophilic compounds, the dynamic model...... approach. Very lipophilic compounds (e.g., DDT) diffuse very slowly into plant tissue, so they are likely to remain in the peel of root vegetables. In addition, a dynamic (steady-state) flux model for uptake with transpiration water into thick roots is presented. The model considers input from soil...
DYNAMIC SOFTWARE AVAILABILITY MODEL WITH REJUVENATION
National Research Council Canada - National Science Library
Dohi, Tadashi; Okamura, Hiroyuki
2016-01-01
In this paper we consider an operational software system with multi-stage degradation levels due to software aging, and derive the optimal dynamic software rejuvenation policy maximizing the steady...