Academic literature on the topic 'Dynamical NO-models'
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Journal articles on the topic "Dynamical NO-models"
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Davis, A. C., M. D. Freeman, and A. J. Macfarlane. "Dynamical generation in non-compact σ-models: A No-Go theorem." Nuclear Physics B 258 (1985): 393–409. http://dx.doi.org/10.1016/0550-3213(85)90619-4.
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Montalva-Medel, Marco, Thomas Ledger, Gonzalo A. Ruz, and Eric Goles. "Lac Operon Boolean Models: Dynamical Robustness and Alternative Improvements." Mathematics 9, no. 6 (March 11, 2021): 600. http://dx.doi.org/10.3390/math9060600.
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In Veliz-Cuba and Stigler 2011, Boolean models were proposed for the lac operon in Escherichia coli capable of reproducing the operon being OFF, ON and bistable for three (low, medium and high) and two (low and high) parameters, representing the concentration ranges of lactose and glucose, respectively. Of these 6 possible combinations of parameters, 5 produce results that match with the biological experiments of Ozbudak et al., 2004. In the remaining one, the models predict the operon being OFF while biological experiments show a bistable behavior. In this paper, we first explore the robustness of two such models in the sense of how much its attractors change against any deterministic update schedule. We prove mathematically that, in cases where there is no bistability, all the dynamics in both models lack limit cycles while, when bistability appears, one model presents 30% of its dynamics with limit cycles while the other only 23%. Secondly, we propose two alternative improvements consisting of biologically supported modifications; one in which both models match with Ozbudak et al., 2004 in all 6 combinations of parameters and, the other one, where we increase the number of parameters to 9, matching in all these cases with the biological experiments of Ozbudak et al., 2004.
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WANG, LIANCHENG. "GLOBAL DYNAMICAL ANALYSIS OF HIV MODELS WITH TREATMENTS." International Journal of Bifurcation and Chaos 22, no. 09 (September 2012): 1250227. http://dx.doi.org/10.1142/s0218127412502276.
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In this paper, we study HIV mathematical models with treatments. Two models with RT inhibitor and HIV protease inhibitor are studied. Local and global analysis is carried out. By identifying a critical number [Formula: see text] for both treatments, we show that if the treatment is at least [Formula: see text] effective, then the uninfected steady state P0 is the only equilibrium in the feasible region, and P0 is globally asymptotically stable. Therefore, no HIV infection persists and infected T cells and HIV virus are cleared over time. However, if the treatment is not effective enough, i.e. less than [Formula: see text], then a unique infected steady state P* emerges in the interior of the feasible region. P0 becomes unstable and the system is uniformly persistent. Therefore, HIV infection persists. In this case, the unique infected steady state can be either stable or unstable. We show that it is locally stable only for r (the proliferation rate of T cells) small or large and unstable for some intermediate values. Global stability result is established for small values of r. Numerical simulation shows that once P* becomes unstable, periodic solution appears.
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Karpechko, Alexey Yu, and Elisa Manzini. "Arctic Stratosphere Dynamical Response to Global Warming." Journal of Climate 30, no. 17 (September 2017): 7071–86. http://dx.doi.org/10.1175/jcli-d-16-0781.1.
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The role of stationary planetary waves in the dynamical response of the Arctic winter stratosphere circulation to global warming is investigated here by analyzing simulations performed with atmosphere-only models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) driven by prescribed sea surface temperatures (SSTs). Climate models often simulate dynamical warming of the Arctic stratosphere as a response to global warming in association with a strengthening of the deep branch of the Brewer–Dobson circulation; however, until now, no satisfactory mechanism for such a response has been suggested. This study focuses on December–February (DJF) because this is the period when the troposphere and stratosphere are strongly coupled. When forced by increased SSTs, all the models analyzed here simulate Arctic stratosphere dynamical warming, mostly due to increased upward propagation of quasi-stationary wavenumber 1, as diagnosed by the meridional eddy heat flux. Further, it is shown that the stratospheric warming and increased wave flux to the stratosphere are related to the strengthening of the zonal winds in subtropics and midlatitudes near the tropopause. Evidence presented in this paper corroborate climate model simulations of future stratospheric changes and suggest a dynamical warming of the Arctic polar vortex as the most likely response to global warming.
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Mangan, N. M., J. N. Kutz, S. L. Brunton, and J. L. Proctor. "Model selection for dynamical systems via sparse regression and information criteria." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 473, no. 2204 (August 2017): 20170009. http://dx.doi.org/10.1098/rspa.2017.0009.
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We develop an algorithm for model selection which allows for the consideration of a combinatorially large number of candidate models governing a dynamical system. The innovation circumvents a disadvantage of standard model selection which typically limits the number of candidate models considered due to the intractability of computing information criteria. Using a recently developed sparse identification of nonlinear dynamics algorithm, the sub-selection of candidate models near the Pareto frontier allows feasible computation of Akaike information criteria (AIC) or Bayes information criteria scores for the remaining candidate models. The information criteria hierarchically ranks the most informative models, enabling the automatic and principled selection of the model with the strongest support in relation to the time-series data. Specifically, we show that AIC scores place each candidate model in the strong support , weak support or no support category. The method correctly recovers several canonical dynamical systems, including a susceptible-exposed-infectious-recovered disease model, Burgers’ equation and the Lorenz equations, identifying the correct dynamical system as the only candidate model with strong support.
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Samland, M., and G. Hensler. "Chemo-Dynamical Models and the Star Formation History of Galaxies." Symposium - International Astronomical Union 171 (1996): 23–27. http://dx.doi.org/10.1017/s0074180900232117.
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Sandage (1986) showed what the star formation rate (SFR) of galaxies of different Hubble type might look like. His curves are based on the study of Gallagher et al. (1984), who determined the SFR at three different epochs of galactic evolution. Sandage's figure establishes a connection of SFR and Hubble type but, as was already mentioned by Sandage, it “contains no physics”. In order to explore the background of this connection, however, it is necessary either to improve the observations or to model the evolution of galaxies self-consistently. However, the results of modelling the SFR are not reliable, if simplified models are used, which only describe some structural properties of galaxies. It is necessary to apply self-consistent models which take into consideration all relevant interaction processes between the gaseous and stellar components of a galaxy. Such models can be checked by comparison with observations like density and abundance distributions, star-gas content, velocities, velocity dispersions, mass-luminosity relations and age distributions of stars. A detailed model will show, whether the initial conditions, the feedback mechanisms during the evolution or the environment determine the evolution of a galaxy.
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DelSole, Timothy, and Arindam Banerjee. "Statistical Seasonal Prediction Based on Regularized Regression." Journal of Climate 30, no. 4 (February 2, 2017): 1345–61. http://dx.doi.org/10.1175/jcli-d-16-0249.1.
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Abstract This paper proposes a regularized regression procedure for finding a predictive relation between one variable and a field of other variables. The procedure estimates a linear prediction model under the constraint that the regression coefficients have smooth spatial structure. The smoothness constraint is imposed using a novel approach based on the eigenvectors of the Laplace operator over the domain, which results in a constrained optimization problem equivalent to either ridge regression or least absolute shrinkage and selection operator (LASSO) regression, which can be solved by standard numerical software. In addition, this paper explores an unconventional procedure whereby regression models are estimated from dynamical model output and then verified against observations—the reverse of the traditional order. The methodology is illustrated by constructing statistical prediction models of summer Texas-area temperature based on concurrent Pacific sea surface temperature (SST). None of the regularized regression models have statistically significant skill when estimated from observations. In contrast, when estimated from dynamical model output, the regression models have skill with respect to dynamical model data because of the substantially larger sample size available from dynamical model output. In addition, the regression models estimated from dynamical model data can predict observed anomalies with significant skill, even though no observations were used directly to estimate the regression models. The results indicate that dynamical models had no significant skill because they could not accurately predict the SST itself, not because they could not capture realistic SST teleconnections.
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Wybo, M., and H. Dejonghe. "Proper motions: what dynamical information can we easily extract from them?" Symposium - International Astronomical Union 153 (1993): 347–48. http://dx.doi.org/10.1017/s007418090012354x.
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Zhao, Xia-Xia, and Jian-Zhong Wang. "Dynamical Behaviors of Rumor Spreading Model with Control Measures." Abstract and Applied Analysis 2014 (2014): 1–11. http://dx.doi.org/10.1155/2014/247359.
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Rumor has no basis in fact and flies around. And in general, it is propagated for a certain motivation, either for business, economy, or pleasure. It is found that the web does expose us to more rumor and increase the speed of the rumors spread. Corresponding to these new ways of spreading, the government should carry out some measures, such as issuing message by media, punishing the principal spreader, and enhancing management of the internet. In order to assess these measures, dynamical models without and with control measures are established. Firstly, for two models, equilibria and the basic reproduction number of models are discussed. More importantly, numerical simulation is implemented to assess control measures of rumor spread between individuals-to-individuals and medium-to-individuals. Finally, it is found that the amount of message released by government has the greatest influence on the rumor spread. The reliability of government and the cognizance ability of the public are more important. Besides that, monitoring the internet to prevent the spread of rumor is more important than deleting messages in media which already existed. Moreover, when the minority of people are punished, the control effect is obvious.
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Mamon, G. A., A. Cava, A. Biviano, A. Moretti, B. Poggianti, and D. Bettoni. "Structural and dynamical modeling of WINGS clusters." Astronomy & Astrophysics 631 (November 2019): A131. http://dx.doi.org/10.1051/0004-6361/201935081.
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The orbital shapes of galaxies of different classes are a probe of their formation and evolution. The Bayesian MAMPOSSt mass-orbit modeling algorithm is used to jointly fit the distribution of elliptical, spiral-irregular, and lenticular galaxies in projected phase space, on three pseudo-clusters (built by stacking the clusters after re-normalizing their positions and velocities) of 54 regular clusters from the Wide-field Nearby Galaxy-clusters Survey (WINGS), with at least 30 member velocities. Our pseudo-clusters (i.e., stacks) contain nearly 5000 galaxies with available velocities and morphological types. Thirty runs of MAMPOSSt with different priors are presented. The highest MAMPOSSt likelihoods are obtained for generalized Navarro-Frenk-White (NFW) models with steeper inner slope, free-index Einasto models, and double NFW models for the cluster and the brightest cluster galaxy. However, there is no strong Bayesian evidence for a steeper profile than the NFW model. The mass concentration matches the predictions from cosmological simulations. Ellipticals usually best trace the mass distribution while S0s are close. Spiral galaxies show increasingly elongated orbits at increasing radii, as do S0s on two stacks, and ellipticals on one stack. The inner orbits of all three types in the three stacks are consistent with isotropy. Spiral galaxies should transform rapidly into early-types given their much larger extent in clusters. Elongated outer orbits are expected for the spirals, a consequence of their recent radial infall into the cluster. The less elongated orbits we find for early-types could be related to the longer time spent by these galaxies in the cluster. We demonstrate that two-body relaxation is too slow to explain the inner isotropy of the early types, which suggests that inner isotropy is the consequence of violent relaxation during major cluster mergers or dynamical friction and tidal braking acting on subclusters. We propose that the inner isotropy of the short-lived spirals is a selection effect of spirals passing only once through pericenter before being transformed into early-type morphologies.
Dissertations / Theses on the topic "Dynamical NO-models"
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Claesson, Daniel. "Improved Experimental Agreement of Ionization and Pressure Peak Location by Adding a Dynamical NO-Model." Thesis, Linköping University, Department of Electrical Engineering, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-2462.
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Modelling combustion engines is an important tool in engine research. Development and modelling of ionization current has potential in developing virtual pressure sensors based on ionization measurements. Previous models has problem when predicting the true relationshipbetween the pressure peak location and ionization peak location, and both too early and too late predictions has been observed. An explanation for these discrepancies are provided and a model where the experimental mismatch has been reduced to less than one CAD is also presented. This is well within the measurement uncertainty.
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Sardanyés, i. Cayuela Josep. "Dynamics, evolution and information in nonlinear dynamical systems of replicators." Doctoral thesis, Universitat Pompeu Fabra, 2009. http://hdl.handle.net/10803/7182.
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En aquesta tesi he investigat diversos camps de la biologia que podrien englobar-se en la disciplina general dels sistemes no lineals de replicadors. Els treballs presentats en aquesta tesis investiguen diversos fenomens dinàmics i processos evolutius per virus de RNA, pels anomenats hipercicles i per models generals de replicadors antagonistes. Específicament he investigat les anomenades quasiespècies, utilitzades per a modelitzar poblacions de RNA. Els treballs sobre hipercicles exploren diversos fenomens previs a l'origen de la vida i a l'aparició de la primera cèl.lula vivent. Mitjançant models ecològics com també utilitzant diferents eines computacionals he estudiat l'anomenada hipòtesi de la Reina Roja per entitats replicadores simples amb mutació. Aquests estudis tenen un interès en el contexte de l'evolució prebiòtica i l'ecologia teòrica.In this thesis I have investigated several fields of biology that can be classified in the general subject of replicator nonlinear systems. The works presented in the thesis investigate several dynamical phenomena and evolutionary processes for RNA viruses, for hypercycles and for general models on antagonistic replicator dynamics. I have specifically investigated the dynamics of so-called quasispecies, used for the modelization of RNA populations. The works on hypercycles explore several phenomena related to previous events to the origin of life and to the appearance of the first living cell. By means of some ecologically-based mathematical models as well as of some computational models we also investigate the so-called Red Queen hypothesis for small, replicating-mutating entities. These studies are of interest in the context of prebiotic evolution and theoretical ecology.
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Canales, Cristian M. "Population structure and spatio-temporal modelling of biological attributes and population dynamic of nylon shrimp (Heterocarpus reedi) off central Chile (25°-36°S) = Estructura poblacional y modelamiento espacio-temporal de los atributos biológicos y la dinámica poblacional del camarón nailon Heterocarpus reedi (Decapoda, Caridea) frente a Chile central (25°-36°S)." Doctoral thesis, Universitat de Barcelona, 2016. http://hdl.handle.net/10803/400612.
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The population structure of fishery resources and the impact of environmental factors over its productivity are important processes to be considered in fisheries management. Environmental factors could determine both, the success of larval drift as the population spatial structure and its changes of biomass. Considering this, two key elements in the adequate, sustained exploitation of any fishery should be considered; the biological attributes of the species and how these vary over time and space. Research is needed to obtain a more thorough understanding of these effects, how they vary, and how they relate to environmental factors. However, spatial processes rarely constitute an explicit consideration in the evaluation and management of marine invertebrate populations, but this is particularly important in processes in which larval drift acts as one of the main mechanisms of population expansion. The ecological concept metapopulation is widely used and accepted for understanding low-mobility marine populations, and its implications for fishery management purposes should be considered.
In this work we show the environmental effect over distribution, abundance and spatial structure of nylon shrimp population (Heterocarpus reedi) off central Chile (25°-37°S) from trawling surveys carried out between 1996 and 2011. Environmental variables considered where sea surface concentration of chlorophyll-a and dissolved organic matter. Results show a geographical separation in population around 32°S. Shrimp density is higher in the southern zone, where concentration of chlorophyll-a and dissolved organic matter are high due to presence of river tributaries and coastal upwelling zones. In this area, the bulk of the adult population is concentrated, which could act as "source" population and thereby its influence on larval drift could explain both, the preponderance of juveniles in the northern area as the
smallest size of its population (“pseudo-sink” population). In the southern area, a process of spatial and bathymetric expansion had driven the increase in population size over time, where the colonization and individual somatic growth had been the main mechanisms. We found that periods of good environmental conditions explain high densities of shrimp with a delay of two years, which might be related mainly with larval survival and enhanced recruitment and somatic growth.
In order to do a cross check of this proposal, and based on a complementary information source, 17 years of biological data collected from nylon shrimp fishery off central Chile were analyzed. We analyze these data using generalized linear models and determine the factors responsible for changes in carapace length, body weight, maturity, and sex ratio. better physical conditions and reproductive attributes of H. reedi south of 32°S would be related with the best environmental and food conditions at this zone. For example, individuals are larger, females are longer at first maturity (CL50%), and mature females are less prevalent. We outline a theoretical foundation that can guide future research on H. reedi. We also suggest that future conservation measures consider biological attributes within a spatial context.
Finally, in order to contrast different hypotheses of population structure and spatial connectivity proposed along this work, we proposed a length-based population model and analyzed the biologic and fishery information available since 1945 under three hypotheses, based on the connectivity rate of two subpopulations located to the north and south of 32°S. The results show that, statistically, several hypotheses can be used to explain the data. The most likely hypothesis is that of a metapopulation in which the south zone acts as a source population (reproductive refuge) and determines, partially or totally, the arrival of recruits in the north zone, thereby explaining the population increase over the last decade. According to our study, empirical evidence will strengthen the hypothesis of spatial connectivity and, given
the implications for managing the fishery of this resource, special attention should be paid to the biological-fishery conditions recorded south of 32°S, caution in its exploitation levels and consider this zone as reproductive refuge of nylon shrimp.L'estructura poblacional dels recursos pesquers i l'impacte dels factors ambientals sobre la productivitat són processos importants a tenir en compte per a la gestió de les seves pesqueries. Els factors ambientals poden determinar l'èxit de la deriva larvària, l'estructura espacial de la població, així com les variacions de la biomassa. Tenint en compte aquests aspectes, s’haurien de considerar dos elements clau per a una explotació adequada i sostinguda de qualsevol pesqueria: les característiques biològiques de les espècies i com aquestes poden variar en el temps i en l’espai, essent necessària la millora de la comprensió d'aquests efectes, com varien, i com es relacionen amb els factors ambientals. No obstant això, els processos espacials rarament són considerats explícitament en la valoració i gestió de les poblacions d'invertebrats marins, més quan aquests aspectes són particularment importants en els processos de deriva larval actuant de principal mecanisme d'expansió d'una població. El concepte ecològic de metapopulations és àmpliament utilitzat i acceptat per a la comprensió de les poblacions marines de baixa mobilitat, i les seves implicacions haurien de ser considerades a la gestió pesquera. En aquest treball es demostra l'efecte del medi en la distribució, abundància i estructura espacial de la població de la espècie de crustaci decàpode Heterocarpus reedi anomenada a Xile en castellà com a “Camarón nailon”. S’ha mostrejat aquesta espècie a a la zona central de Xile (25 ° - 37 ° S) a partir de la informació obtinguda en campanyes oceanogràfiques de pesca d'arrossegament fets entre els anys 1996 i el 2011, així com de les característiques de l’aigua superficial (concentració de clorofil·la α i de la matèria orgànica dissolta). Els resultats van mostrar una separació geogràfica de la població a 32 ° S, on la densitat de gambes és més gran, així com també la concentració de clorofil·la α i la dissolució de matèria orgànica, això darrer degut segurament a la presència d'afluents dels rius i zones d'aflorament costaner. En aquesta zona es concentra la major part de la població adulta i podria actuar com a població “font” i la seva influència en la deriva larvària explicaria tant la preponderància de juvenils en la zona nord així com una població menys abundant (població “pseudo-sumider”). A la zona sud, l'augment de mida de la població s'explica per un procés d'expansió espacial i batimètric a traves del temps, on la colonització i el creixement somàtic dels individus serien els principals mecanismes. Els períodes de condicions ambientals favorables explicarien les altes densitats de individus de l’espècie niló dos anys després. Aquestes condicions ambientals favorables podrien estar principalment relacionades amb la supervivència de les larves, l'èxit dels processos de reclutament i el posterior creixement somàtic. D'altra banda, i amb l’objectiu de fer una verificació dels resultats dalt explicats, i basant-se en una font d'informació complementària, es van analitzar 17 anys de dades biològiques recollides en mostrejos pesquers del “camaron nylon” davant de la costa central de Xile. Es van analitzar aquestes dades utilitzant models lineals generalitzats (GLM) per tal de determinar els factors responsables dels canvis en la longitud del cefalotòrax, el pes del cos, la maduresa sexual i la proporció de sexes. Es va determinar una notable heterogeneïtat espacial en les característiques biològiques dels individus de H. reedi. Els individus en millor condició es van trobar al sud de la latitud de 32 ° S i aquesta millor condició es va relacionar amb les millors condicions ambientals i de menjar en aquesta zona. Per exemple, els individus són més grans, les femelles assoleixen abans el tamany de primera maduresa (CL50%), i les femelles madures són menys freqüents. Amb aquests resultats es presenta una base teòrica que pot guiar la recerca sobre les poblacions de H. reedi tenint en compte les consideracions espacials en les futures mesures de conservació. Finalment, per poder comparar diferents hipòtesis sobre l'estructura de la població i connectivitat espacial proposades al llarg d'aquest treball, es presenta un model de població basat en la talla i s’ha analitzat la informació biològica i pesquera disponible des de 1945. S’han tingut en compte tres hipòtesis en funció de la taxa de connectivitat de les dues subpoblacions, es a dir, les situades al nord i al sud de 32 ° S. Els resultats van mostrar que, estadísticament, diverses hipòtesi es poden fer servir per a explicar les dades disponibles. La hipòtesi més versemblant és la d'una metapoblació en la qual la zona sud actua com a població font o refugi reproductiu. Aquesta població determina parcialment o totalment l'arribada de reclutes a la zona nord i podria explicar l'augment d'aquesta població trobat a l'última dècada. Segons el nostre estudi, la hipòtesi de connectivitat espacial ha de ser contrastada només amb l'evidència empírica. Tenint en compte les implicacions per a la gestió pesquera, s’hauria de prestar una especial atenció a les condicions biològico-pesqueres que es registren al sud de 32 ° S, tenir especial precaució als nivells d'explotació pesquera i considerar aquesta zona (sud del 32 ° S) com a refugi reproductiu a Xile de l’espècie H. reedi.
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Cyriac, Praveen. "Tone mapping based on natural image statistics and visual perception models." Doctoral thesis, Universitat Pompeu Fabra, 2017. http://hdl.handle.net/10803/402574.
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Les tècniques d'imatge d'alt rang dinàmic (HDR) potencialment permeten la captura i l'emmagatzematge de tota la informació de llum en una escena. No obstant això, els dispositius comuns de visualització són limitats en termes de les seves capacitats de contrast i brillantor, per tant, les imatges HDR han de ser mapejades tonalment abans de presentar-les en un dispositiu de visualització per assegurar que es reprodueix l'aspecte original de l'escena. En aquesta tesi, es prenen dos enfocaments del problema de mapeig tonal. En primer lloc, es desenvolupa un marc general per a la millora de qualsevol imatge mapejada tonalment mitjançant la reducció de la distància a la corresponent imatge HDR en termes d'una mètrica perceptiva no local. La distància es redueix al mínim per mitjà d'un algoritme de descens de gradient. En segon lloc, es desenvolupa un operador de mapeig tonal (TMO) en temps real que s'adapta bé a les estadístiques d'escenes naturals, i concorda amb els nous descobriments psicofísics i dades neurofísiques. Determinem les correctes adaptacions no lineals necessàries per als nostres resultats de mapeig tonal per tal d'obtenir l'aparença òptima en diferents condicions de visualització, a través d'experiments psicofísics i desenvolupar un mètode automàtic per poder predir dades experimentals. El nostre TMO produeix resultats d'aspecte natural, sense cap tipus d'artefactes espacials o temporals. Els tests de preferència dels usuaris mostren que el nostre mètode obté millors resultats en comparació amb les tècniques més recents. El TMO és ràpid i podria ser implementat en el hardware de la càmera. Pot ser utilitzat per al monitoratge de càmeres HDR en pantalles regulars, com a substitut de la correcció gamma, i com una manera de proporcionar al colorista amb contingut que té alhora un aspecte natural i una aparença nítida i clara.High Dynamic Range (HDR) imaging techniques potentially allow for the capture and storage of the full information of light in a scene. However, common display devices are limited in terms of their contrast and brightness capabilities, thus HDR images must be tone mapped before presentation on a display device to ensure that the original appearance of the scene is reproduced. In this thesis, we take two approaches to the tone mapping problem. First, we develop a general framework for improving any tone mapped image by reducing the distance with the corresponding HDR image in terms of a non-local perceptual metric. The distance is minimized by means of a gradient descent algorithm. Second, we develop a real-time Tone Mapping Operator (TMO) that is well suited to the statistics of natural scenes, and is in keeping with new psychophysical findings and neurophysical data. We determine the adequate non-linear adjustments needed for our tone mapping results to look best in different viewing conditions through a psychophysical experiment and develop an automatic method that can predict the experimental data. Our TMO produces results that look natural, without any spatio-temporal artifacts. User preference tests show that our method outperforms state of the art approaches. The TMO is fast and could be implemented on camera hardware. It can be used for on-set monitoring of HDR cameras on regular displays, as a substitute for gamma correction, and as a way of providing the colorist with content that is both natural looking and has a crisp and clear appearance.
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"Wavelet transformers, multiresolution dynamical models, and multigrid estimation algorithms." Laboratory for Information and Decision Systems, Massachusetts Institute of Technology], 1989. http://hdl.handle.net/1721.1/3147.
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A.S. Willsky ... [et al.].Caption title. "1990 IFAC World Congress"--Leaf 1.
Includes bibliographical references.
Supported in part by the Air Force Office of Scientific Research. AFOSR-88-0032 Supported in part by the National Science Foundation. ECS-8700903 Supported in part by the US Army Research Office. DAAL03-86-K-0171 Supported in part by CNRS. GO134
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Hsieh, Yun Jung, and 謝昀容. "Integrating Opinion Dynamics and Innovation Diffusion Models to Analyze the ‘Best Game No One Played’ Phenomenon." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/44p9z6.
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碩士長庚大學
資訊工程學系
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Opinion dynamics models have a tendency to overemphasize inter-agent communication, while innovation diffusion models tend to overstate the threshold settings of individual agents. To study the diffusion process with new products as well as interactions involving agent attitudes, an opinion dynamics model was combined with an innovation diffusion model in order to simulate a situation in which consumers rely on their social networks when deciding whether or not to accept a controversial product. Four social networks are used to analyze interactions between agent attitudes and individual agent thresholds: scale-free, small world, random, and cellular automata. Agents in the proposed model have both thresholds and attitudes that change over time based on interactions with other agents. Sensitivity analyses using different simulation parameters are used to discuss situations in which consumers are more likely to accept new products. Results indicate that average-of-threshold was the most sensitive parameter for all four social network types, with average-of-attitude and max-opinion-distance moderately sensitive. In simulations involving opinion dynamics diffusion, results from a series of simulation experiments indicate that the proposed model performed well with complex networks in different situations.
Books on the topic "Dynamical NO-models"
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Tosaka, Hiroyuki. Chiken mizu junkan no sūri: Ryūiki mizu kankyō no kaisekihō = Geosphere environmental fluid flows : theories, models and applications. Tōkyō: Tōkyō Daigaku Shuppankai, 2006.
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Nonlinear Dynamics in Physiology: A State-space Approach. World Scientific Publishing Company, 2006.
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United States. National Aeronautics and Space Administration., ed. [An investigation of the dynamical evolution of photoplanetary nebulae]: [annual status report, no. 1, 1 Nov. 1992-31 October, 1993]. [Washington, DC: National Aeronautics and Space Administration, 1994.
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Tibaldi, Stefano, and Franco Molteni. Atmospheric Blocking in Observation and Models. Oxford University Press, 2018. http://dx.doi.org/10.1093/acrefore/9780190228620.013.611.
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The atmospheric circulation in the mid-latitudes of both hemispheres is usually dominated by westerly winds and by planetary-scale and shorter-scale synoptic waves, moving mostly from west to east. A remarkable and frequent exception to this “usual” behavior is atmospheric blocking. Blocking occurs when the usual zonal flow is hindered by the establishment of a large-amplitude, quasi-stationary, high-pressure meridional circulation structure which “blocks” the flow of the westerlies and the progression of the atmospheric waves and disturbances embedded in them. Such blocking structures can have lifetimes varying from a few days to several weeks in the most extreme cases. Their presence can strongly affect the weather of large portions of the mid-latitudes, leading to the establishment of anomalous meteorological conditions. These can take the form of strong precipitation episodes or persistent anticyclonic regimes, leading in turn to floods, extreme cold spells, heat waves, or short-lived droughts. Even air quality can be strongly influenced by the establishment of atmospheric blocking, with episodes of high concentrations of low-level ozone in summer and of particulate matter and other air pollutants in winter, particularly in highly populated urban areas.Atmospheric blocking has the tendency to occur more often in winter and in certain longitudinal quadrants, notably the Euro-Atlantic and the Pacific sectors of the Northern Hemisphere. In the Southern Hemisphere, blocking episodes are generally less frequent, and the longitudinal localization is less pronounced than in the Northern Hemisphere.Blocking has aroused the interest of atmospheric scientists since the middle of the last century, with the pioneering observational works of Berggren, Bolin, Rossby, and Rex, and has become the subject of innumerable observational and theoretical studies. The purpose of such studies was originally to find a commonly accepted structural and phenomenological definition of atmospheric blocking. The investigations went on to study blocking climatology in terms of the geographical distribution of its frequency of occurrence and the associated seasonal and inter-annual variability. Well into the second half of the 20th century, a large number of theoretical dynamic works on blocking formation and maintenance started appearing in the literature. Such theoretical studies explored a wide range of possible dynamic mechanisms, including large-amplitude planetary-scale wave dynamics, including Rossby wave breaking, multiple equilibria circulation regimes, large-scale forcing of anticyclones by synoptic-scale eddies, finite-amplitude non-linear instability theory, and influence of sea surface temperature anomalies, to name but a few. However, to date no unique theoretical model of atmospheric blocking has been formulated that can account for all of its observational characteristics.When numerical, global short- and medium-range weather predictions started being produced operationally, and with the establishment, in the late 1970s and early 1980s, of the European Centre for Medium-Range Weather Forecasts, it quickly became of relevance to assess the capability of numerical models to predict blocking with the correct space-time characteristics (e.g., location, time of onset, life span, and decay). Early studies showed that models had difficulties in correctly representing blocking as well as in connection with their large systematic (mean) errors.Despite enormous improvements in the ability of numerical models to represent atmospheric dynamics, blocking remains a challenge for global weather prediction and climate simulation models. Such modeling deficiencies have negative consequences not only for our ability to represent the observed climate but also for the possibility of producing high-quality seasonal-to-decadal predictions. For such predictions, representing the correct space-time statistics of blocking occurrence is, especially for certain geographical areas, extremely important.
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Boydstun, Amber E., and Annelise Russell. From Crisis to Stasis: Media Dynamics and Issue Attention in the News. Oxford University Press, 2016. http://dx.doi.org/10.1093/acrefore/9780190228637.013.56.
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Media coverage does not ebb and flow. Rather, media coverage rapidly moves from crisis to stasis and back again. The result of these attention dynamics is news reporting that is disproportional to the breadth and pace of policy problems in the world, where some balloon in the news beyond expectations and others fade quickly (or never make the news at all). These patterns of news coverage result from the powerful role that momentum plays in the news-generation process. Forces of positive feedback drive news outlets to chase each new hot story quickly, while negative feedback forces drive news outlets to stay locked onto a hot story at hand. Together, these forces drive news coverage to lurch and fixate, lurch and fixate, again and again. Thus, although previous research has conceived of the news-generation process functioning either as a “patrol” system (where news outlets act as sentinels, tracking each policy problem as it unfolds in the world) or as an “alarm” system (where news outlets move in quick bursts from one policy problem to the next, with little to no in-depth coverage), both these previous models tell only half the story. Rather, the news-generation process is best understood through the alarm/patrol hybrid model, where news outlets often lurch from one hot item to the next but sometimes become entrenched in an unfolding storyline. The alarm/patrol hybrid model helps explain the particular phenomenon of “media storms” that can occur, where a sudden surge in media attention can vault a previously ignored issue into the center of public and political attention; think of the Catholic priest abuse scandal, or the scene in Ferguson, Missouri, after Michael Brown’s death. The lurching/fixating dynamics of media attention have far-ranging implications for citizen information and political response, contributing to a wider system of disproportionate information processing where some topics are attended to and others are largely ignored. In particular, because policymakers take so many of their cues from the news, it is likely the case that the lurching/fixating patterns of our media system exacerbate the punctuated patterns of government in turn.
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Kling, David W. A History of Christian Conversion. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780195320923.001.0001.
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Conversion has played a central role in the history of Christianity. In this first in-depth and wide-ranging narrative history, David W. Kling examines the dynamic of individuals, families, and people groups who turn to the Christian faith. Global in reach, this book progresses from early Christian beginnings in the Roman world to Christianity’s expansion into Europe, the Americas, China, India, and Africa. Although conversion is often associated with a particular strand of modern Christianity (evangelical) and a particular type of experience (sudden, overwhelming), it is, when examined over two millennia, a phenomenon far more complex than any one-dimensional profile would suggest. No single, unitary paradigm defines conversion, and no easily demonstrable process accounts for why people convert to Christianity. Rather, a multiplicity of factors—historical, personal, social, geographical, theological, psychological, and cultural—shape the converting process. A History of Christian Conversion not only narrates the conversions of select individuals and peoples. It also engages current theories and models to explain conversion and examines recurring themes in the converting process: gender, agency, motivation, testimony, coercion, self-identity, “true” conversion, music, communication, the body, and divine presence. Accessible to scholars, students, and those with a general interest in conversion, Kling’s book is, to date, the most satisfying and comprehensive account of conversion in Christian history; this major work will become a standard must-read in conversion studies.
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Xue, Yongkang, Yaoming Ma, and Qian Li. Land–Climate Interaction Over the Tibetan Plateau. Oxford University Press, 2017. http://dx.doi.org/10.1093/acrefore/9780190228620.013.592.
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The Tibetan Plateau (TP) is the largest and highest plateau on Earth. Due to its elevation, it receives much more downward shortwave radiation than other areas, which results in very strong diurnal and seasonal changes of the surface energy components and other meteorological variables, such as surface temperature and the convective atmospheric boundary layer. With such unique land process conditions on a distinct geomorphic unit, the TP has been identified as having the strongest land/atmosphere interactions in the mid-latitudes.Three major TP land/atmosphere interaction issues are presented in this article: (1) Scientists have long been aware of the role of the TP in atmospheric circulation. The view that the TP’s thermal and dynamic forcing drives the Asian monsoon has been prevalent in the literature for decades. In addition to the TP’s topographic effect, diagnostic and modeling studies have shown that the TP provides a huge, elevated heat source to the middle troposphere, and that the sensible heat pump plays a major role in the regional climate and in the formation of the Asian monsoon. Recent modeling studies, however, suggest that the south and west slopes of the Himalayas produce a strong monsoon by insulating warm and moist tropical air from the cold and dry extratropics, so the TP heat source cannot be considered as a factor for driving the Indian monsoon. The climate models’ shortcomings have been speculated to cause the discrepancies/controversies in the modeling results in this aspect. (2) The TP snow cover and Asian monsoon relationship is considered as another hot topic in TP land/atmosphere interaction studies and was proposed as early as 1884. Using ground measurements and remote sensing data available since the 1970s, a number of studies have confirmed the empirical relationship between TP snow cover and the Asian monsoon, albeit sometimes with different signs. Sensitivity studies using numerical modeling have also demonstrated the effects of snow on the monsoon but were normally tested with specified extreme snow cover conditions. There are also controversies regarding the possible mechanisms through which snow affects the monsoon. Currently, snow is no longer a factor in the statistic prediction model for the Indian monsoon prediction in the Indian Meteorological Department. These controversial issues indicate the necessity of having measurements that are more comprehensive over the TP to better understand the nature of the TP land/atmosphere interactions and evaluate the model-produced results. (3) The TP is one of the major areas in China greatly affected by land degradation due to both natural processes and anthropogenic activities. Preliminary modeling studies have been conducted to assess its possible impact on climate and regional hydrology. Assessments using global and regional models with more realistic TP land degradation data are imperative.Due to high elevation and harsh climate conditions, measurements over the TP used to be sparse. Fortunately, since the 1990s, state-of-the-art observational long-term station networks in the TP and neighboring regions have been established. Four large field experiments since 1996, among many observational activities, are presented in this article. These experiments should greatly help further research on TP land/atmosphere interactions.
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Hupaniittu, Outi, and Ulla-Maija Peltonen, eds. Arkistot ja kulttuuriperintö. SKS Finnish Literature Society, 2021. http://dx.doi.org/10.21435/tl.268.
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Archives and the Cultural Heritage The edited volume Archives and the Cultural Heritage focuses on archives as institutions and to their tense relationship with archives as material. These dynamics are discussed in respect of the past, the present, and the future. The focus lies in the mechanisms the Finnish archive institutions have utilised when taking part in forming the cultural heritage and in debating the importance of the private archives in society. Within social sciences and history from the early 1990s onwards, the effects of globalisation have been seen as a new focal point for research. Momentarily, the archives saw the same paradigm shift as the focus of the archival studies proceeded from state to society. This brought forth the notion that the values of society are reflected in the acquisition of archival material. This archival turn draws attention to the archives as entities formed by cultural practices. The volume discusses cultural heritage within Finnish archives with diverse perspectives and from various time periods. The key concepts are cultural heritage and archives – both as institution and as material. Articles review the formation of archival collections spanning from the 19th to the 21st century and highlight that the archives have never been neutral or objective actors; rather, they have always been an active process of remembering and forgetting, a matter of inclusion and exclusion. The focus is on private archives and on the choices that guided the creation of the archives and the cultural perceptions and power structures associated with them. Although private archives have considerable social and research value, and although their material complements the picture of society provided by documentary data produced by public administrations, they have only risen to the theoretical discussions in the 21st century. The authors consider what has happened before the material ends up in the archive, what happens in the archive and what can be deduced from this. It shows how archival solutions manifest themselves, how they have influenced research and how they still affect it. One of the key questions is whose past has been preserved and whose is deemed worthy of preservation. Under what conditions have the permanently preserved documents been selected and how can they be accessed? In addition, the volume pays attention to whose documents have been ignored or forgotten, as well as to the networks and power of the individuals within the archival institution and to the politics of memory. The Archives and the Cultural Heritage is an opening to a discussion on the mechanisms, practices and goals of Finnish archival activities. It challenges archival organisations to reflect on their own operating models and to make visible their own conscious or unconscious choices. It raises awareness of the formation of the Finnish documentary cultural heritage, produces new information about private archives and participates in the scientific debate on the changing significance of archives in society. The volume is related to the Academy of Finland research project “Making and Interpreting National Pasts – Role of Finnish Archives as Networks of Power and Sites of Memory” (no 25257, 2011–2014/2019), University of Turku. Project partners Finnish Literature Society (SKS) and Society of Swedish Literature in Finland (SLS).
Book chapters on the topic "Dynamical NO-models"
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Lindelauf, Roy. "Nuclear Deterrence in the Algorithmic Age: Game Theory Revisited." In NL ARMS, 421–36. The Hague: T.M.C. Asser Press, 2020. http://dx.doi.org/10.1007/978-94-6265-419-8_22.
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AbstractCommonly used game and decision theoretic models fail to explain the empirics of deterrence. This has unjustly led many theorists to criticize the (rationality and other) assumptions underpinning of such models. No serious game theorist will contend that his theoretic model will possibly take account of all the peculiarities involved in decision making and therefore be an accurate model of such situations. Games are an aid to thinking about some of the aspects of the broader situation. Game theory models prescribe what a decision maker ought to do in a given situation, not what a decision maker actually does. To maintain nuclear strategic stability, it is of paramount importance to understand the dynamical interplay between all players involved in decision making processes with regard to nuclear strategy. History has shown some progress in understanding nuclear deterrence by the use of initial game- and decision theoretic models to alleviate the burden of human cognitive biases. Since it is highly likely that (semi-)autonomous systems will in some way participate in the future nuclear strategic landscape, combined with the fact that the nuclear deterrent decision-cycle will also be based on algorithmic analysis, rational deterrence theory is and should be an integral element of strategic thinking about nuclear deterrence. That, or it might as well be game over.
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Simner, Ben, Shaked Flur, Christopher Pulte, Alasdair Armstrong, Jean Pichon-Pharabod, Luc Maranget, and Peter Sewell. "ARMv8-A System Semantics: Instruction Fetch in Relaxed Architectures." In Programming Languages and Systems, 626–55. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-44914-8_23.
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AbstractComputing relies on architecture specifications to decouple hardware and software development. Historically these have been prose documents, with all the problems that entails, but research over the last ten years has developed rigorous and executable-as-test-oracle specifications of mainstream architecture instruction sets and “user-mode” concurrency, clarifying architectures and bringing them into the scope of programming-language semantics and verification. However, the system semantics, of instruction-fetch and cache maintenance, exceptions and interrupts, and address translation, remains obscure, leaving us without a solid foundation for verification of security-critical systems software.In this paper we establish a robust model for one aspect of system semantics: instruction fetch and cache maintenance for ARMv8-A. Systems code relies on executing instructions that were written by data writes, e.g. in program loading, dynamic linking, JIT compilation, debugging, and OS configuration, but hardware implementations are often highly optimised, e.g. with instruction caches, linefill buffers, out-of-order fetching, branch prediction, and instruction prefetching, which can affect programmer-observable behaviour. It is essential, both for programming and verification, to abstract from such microarchitectural details as much as possible, but no more. We explore the key architecture design questions with a series of examples, discussed in detail with senior Arm staff; capture the architectural intent in operational and axiomatic semantic models, extending previous work on “user-mode” concurrency; make these models executable as test oracles for small examples; and experimentally validate them against hardware behaviour (finding a bug in one hardware device). We thereby bring these subtle issues into the mathematical domain, clarifying the architecture and enabling future work on system software verification.
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Braak, Daniel. "What Kind of Insight Provide Analytical Solutions of Quantum Models?" In International Symposium on Mathematics, Quantum Theory, and Cryptography, 5–6. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-5191-8_2.
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Abstract There are several concepts of what constitutes the analytical solution of a quantum model, as opposed to the mere “numerically exact” one. This applies even if one considers only the determination of the discrete spectrum of the corresponding Hamiltonian, setting aside such important questions as the asymptotic dynamics for long times. In the simplest case, the spectrum can be given in closed form, the eigenvalues $$E_{j}, j=0,\ldots ,N\le \infty $$ read $$E_{j} =f(j,\{p_{k}\})$$, where f is a known function of the label $$j\in \mathbb {N}_{0}$$ and the $$\{p_k\}$$ are a set of numbers parameterizing the Hamilton operator. This kind of solution exists only in cases where the classical limit of the model is Liouville-integrable. Some quantum-mechanical many-body systems allow the determination of the spectrum in terms of auxiliary parameters $$[\{k_j\},\{n_l\}]$$ as $$E(\{n_l\}) = f(\{k_{j}(\{n_{l}\})\})$$ where the $$\{k_{j}(\{n_{l}\})\}$$ satisfy a coupled set of transcendental equations, following from a certain ansatz for the eigenfunctions. These systems (integrable in the sense of Yang-Baxter (Eckle 2019)) may have a Hilbert space dimension growing exponentially with the system size L, i.e., $$N\sim e^{L}$$. The simple enumeration of the energies with the label j is replaced by the multi-index $$\{n_{l}\}$$. Although no priori knowledge about the spectrum is available, its statistical properties can be computed exactly (Berry and Tabor 1977). Other integrable and also non-integrable models exist where N depends polynomially on L and the energies $$E_j$$ are the zeroes of an analytically computable transcendental function, the so-called G-function $$G(E,\{p_k\})$$ (Braak 2013a, 2016), which is proportional to the spectral determinant. Although no closed formula for $$E_j$$ as function of the index j exists, detailed qualitative insight into the distribution of the eigenvalues can be obtained (Braak 2013b). Possible applications of these concepts to information compression and cryptography are outlined.
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Zinn-Justin, Jean. "Critical dynamics and renormalization group (RG)." In Quantum Field Theory and Critical Phenomena, 875–98. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780198834625.003.0036.
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Time evolution, near a phase transition in the critical domain of critical systems not far from equilibrium, using a Langevin-type evolution is studied. Typical quantities of interest are relaxation rates towards equilibrium, time-dependent correlation functions and transport coefficients. The main motivation for such a study is that, in systems in which the dynamics is local (on short time-scales, a modification of a dynamic variable has an influence only locally in space) when the correlation length becomes large, a large time-scale emerges, which characterizes the rate of time evolution. This phenomenon called critical slowing down leads to universal behaviour and scaling laws for time-dependent quantities. In contrast with the situation in static critical phenomena, there is no clean and systematic derivation of the dynamical equations governing the time evolution in the critical domain, because often the time evolution is influenced by conservation laws involving the order parameter, or other variables like energy, momentum, angular momentum, currents and so on. Indeed, the equilibrium distribution does not determine the driving force in the Langevin equation, but only the dissipative couplings are generated by the derivative of the equilibrium Hamiltonian, and directly related to the static properties. The purely dissipative Langevin equation specifically discussed, corresponding to static models like the f4 field theory and two-dimensional models. Renormalization group (RG) equations are derived, and dynamical scaling relations established.
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Fogarty, Michael J., and Jeremy S. Collie. "Empirical Dynamic Modeling." In Fishery Ecosystem Dynamics, 251–68. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780198768937.003.0014.
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Empirical Dynamic Modeling offers a flexible complement to standard mechanistic modeling approaches. Because it makes no assumptions concerning the structural form of ecological processes, it can provide an effective approach to dealing with model uncertainty. The method uses non-linear, non-parametric models. It can accommodate a wide spectrum of dynamical behaviors and makes no equilibrium assumptions. The approach is predicated on the idea that within a time series of observations of an ecological variable (e.g. population or species abundance) is encoded information on the factors that have affected that variable over time (e.g. the effects of predators or prey, competitors, environmental change, etc.). The method employs state-space reconstruction to decode this embedded information, and applies nearest-neighbor and kernel regression methods of forecasting. Forecast skill is used directly as a criterion for model selection and validation. It has been proven effective in application to fisheries forecasting problems, often outperforming standard modeling approaches.
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Fogarty, Michael J., and Jeremy S. Collie. "Density-Dependent Population Growth." In Fishery Ecosystem Dynamics, 29–46. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780198768937.003.0003.
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The observation that no population can grow indefinitely and that most populations persist on ecological timescales implies that mechanisms of population regulation exist. Feedback mechanisms include competition for limited resources, cannibalism, and predation rates that vary with density. Density dependence occurs when per capita birth or death rates depend on population density. Density dependence is compensatory when the population growth rate decreases with population density and depensatory when it increases. The logistic model incorporates density dependence as a simple linear function. A population exhibiting logistic growth will reach a stable population size. Non-linear density-dependent terms can give rise to multiple equilibria. With discrete time models or time delays in density-dependent regulation, the approach to equilibrium may not be smooth—complex dynamical behavior is possible. Density-dependent feedback processes can compensate, up to a point, for natural and anthropogenic disturbances; beyond this point a population will collapse.
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Dyall, Kenneth G., and Knut Faegri. "Correlation Methods." In Introduction to Relativistic Quantum Chemistry. Oxford University Press, 2007. http://dx.doi.org/10.1093/oso/9780195140866.003.0018.
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It is well known from nonrelativistic quantum chemistry that mean-field methods, such as the Hartree–Fock (HF) model, provide mainly qualitative insights into the electronic structure and bonding of molecules. To obtain reliable results of “chemical accuracy” usually requires models that go beyond the mean field and account for electron correlation. There is no reason to expect that the mean-field approach should perform significantly better in this respect for the relativistic case, and so we are led to develop schemes for introducing correlation into our models for relativistic quantum chemistry. There is no fundamental change in the concept of correlation between relativistic and nonrelativistic quantum chemistry: in both cases, correlation describes the difference between a mean-field description, which forms the reference state for the correlation method, and the exact description. We can also define dynamical and nondynamical correlation in both cases. There is in fact no formal difference between a nonrelativistic spin–orbital-based formalism and a relativistic spinor-based formalism. Thus we should be able to transfer most of the schemes for post-Hartree–Fock calculations to a relativistic post-Dirac–Hartree–Fock model. Several such schemes have been implemented and applied in a range of calculations. The main technical differences to consider are those arising from having to deal with integrals that are complex, and the need to replace algorithms that exploit the nonrelativistic spin symmetry by schemes that use time-reversal and double-group symmetry. In addition to these technical differences, however, there are differences of content between relativistic and nonrelativistic methods. The division between dynamical and nondynamical correlation is complicated by the presence of the spin–orbit interaction, which creates near-degeneracies that are not present in the nonrelativistic theory. The existence of the negative-energy states of relativistic theory raise the question of whether they should be included in the correlation treatment. The first two sections of this chapter are devoted to a discussion of these issues. The main challenges in the rest of this chapter are to handle the presence of complex integrals and to exploit time-reversal symmetry.
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Raydugin, Yuri G. "Project System Dynamics." In Modern Risk Quantification in Complex Projects, 255–70. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780198844334.003.0017.
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The purpose of this chapter is to develop project system dynamic (SD) models that mirror non-linear Monte Carlo N-SCRA models of project Zemblanity. Only schedule part of risk exposure is considered. Required recalculations of parameters is undertaken. As these are no one-to-one relations between the parameters of the SD and Monte Carlo models, required assumptions are applied. These can be used for mutual calibrations of the two types of models. Two SD models are built that reflect on the project risk exposure before and after risk interaction addressing. Limitations of the project SD modelling are revealed. The SD modelling results demonstrate a good alignment of corresponding non-linear schedule and cost risk analysis (N-SCRA) and SD models. One additional SD model is built to explicitly demonstrate a contribution of risk compounding to overall project duration. The three workable SD models are available on the book’s companion website.
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Botsford, Louis W., J. Wilson White, and Alan Hastings. "Spatial population dynamics." In Population Dynamics for Conservation, 214–46. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780198758365.003.0009.
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This chapter considers populations structured in a different dimension: space. This begins by representing population dynamics with a spatial continuity equation (analogous to the M’Kendrick/von Foerster model for continuity in age or size). If organisms move at random, this motion can be approximated as diffusion. This proves useful for modeling spreading populations, such as the expansion of sea otter populations along the California coast. Adding directional advection represents a population in a flowing stream. Metapopulation models are then introduced using a simple model of the fraction of occupied patches; these are made more realistic by accounting for inter-patch distance using incidence function models. The next level of complexity is models with population dynamics in each patch. These are used to examine how metapopulations can persist as a network even if no patch would persist by itself. Finally, the consequences of synchrony (or lack thereof) among spatially separated populations is described.
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Pearson, Ronald K. "Linear Dynamic Models." In Discrete-time Dynamic Models. Oxford University Press, 1999. http://dx.doi.org/10.1093/oso/9780195121988.003.0004.
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It was emphasized in Chapter 1 that low-order, linear time-invariant models provide the foundation for much intuition about dynamic phenomena in the real world. This chapter provides a brief review of the characteristics and behavior of linear models, beginning with these simple cases and then progressing to more complex examples where this intuition no longer holds: infinite-dimensional and time-varying linear models. In continuous time, infinite-dimensional linear models arise naturally from linear partial differential equations whereas in discrete time, infinite-dimensional linear models may be used to represent a variety of “slow decay” effects. Time-varying linear models are also extremely flexible: In the continuous-time case, many of the ordinary differential equations defining special functions (e.g., the equations defining Bessel functions) may be viewed as time-varying linear models; in the discrete case, the gamma function arises naturally as the solution of a time-varying difference equation. Sec. 2.1 gives a brief discussion of low-order, time-invariant linear dynamic models, using second-order examples to illustrate both the “typical” and “less typical” behavior that is possible for these models. One of the most powerful results of linear system theory is that any time-invariant linear dynamic system may be represented as either a moving average (i.e., convolution-type) model or an autoregressive one. Sec. 2.2 presents a short review of these ideas, which will serve to establish both notation and a certain amount of useful intuition for the discussion of NARMAX models presented in Chapter 4. Sec. 2.3 then briefly considers the problem of characterizing linear models, introducing four standard input sequences that are typical of those used in linear model characterization. These standard sequences are then used in subsequent chapters to illustrate differences between nonlinear model behavior and linear model behavior. Sec. 2.4 provides a brief introduction to infinite-dimensional linear systems, including both continuous-time and discrete-time examples. Sec. 2.5 provides a similar introduction to the subject of time-varying linear systems, emphasizing the flexibility of this class. Finally, Sec. 2.6 briefly considers the nature of linearity, presenting some results that may be used to define useful classes of nonlinear models.
Conference papers on the topic "Dynamical NO-models"
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Wang, Deshi, Xin Chen, Xindu Chen, Jun Yu, and Ji Zhou. "Dynamics of Mechanical Systems Solved by Quadratic Programming." In ASME 1994 Design Technical Conferences collocated with the ASME 1994 International Computers in Engineering Conference and Exhibition and the ASME 1994 8th Annual Database Symposium. American Society of Mechanical Engineers, 1994. http://dx.doi.org/10.1115/detc1994-0258.
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Abstract A new method for dynamics of mechanical systems has been established and the new use of the optimum software has been shown in this paper. Gauss’ principle in the theory of mechanics has been employed to transform the dynamical control and simulation into the quadratic programming problems, which makes it possible that the optimum software developed in CAD systems is applied to obtain the dynamics of mechanical systems. Such a method is significant for systems which contain complex motion and constraints, since there is no longer necessity of reducing the analytical dynamic models, which are tedious and even impossible to obtain. Morever, it gives a new way of applying the optimum software package. The dynamics of a robot with sliding and revolving joints has been demonstrated in detail.
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Elmegaard, Michael, Jan Ru¨bel, Mizuho Inagaki, Atsushi Kawamoto, and Jens Starke. "Equation-Free Continuation of Maximal Vibration Amplitudes in a Nonlinear Rotor-Bearing Model of a Turbocharger." In ASME 2009 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/detc2009-87339.
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Mechanical systems are typically described with finite element models resulting in high-dimensional dynamical systems. The high-dimensional space excludes the application of certain investigation methods like numerical continuation and bifurcation analysis to investigate the dynamical behaviour and its parameter dependence. Nevertheless, the dynamical behaviour usually lives on a low-dimensional manifold but typically no closed equations are available for the macroscopic quantities of interest. Therefore, an equation-free approach is suggested here to analyse and investigate the vibration behaviour of nonlinear rotating machinery. This allows then in the next step to optimize the rotor design specifications to reduce unbalance vibrations of a rotor-bearing system with nonlinear factors like the oil film dynamics. As an example we provide a simple model of a passenger car turbocharger where we investigate how the maximal vibration amplitude of the rotor depends on the viscosity of the oil used in the bearings.
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Xia, Z., and J. Tang. "Characterization of Structural Dynamics With Uncertainty by Using Gaussian Processes." In ASME 2011 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/detc2011-48804.
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An efficient way to capture the dynamic characteristics of structural systems with uncertainties has been an important and challenging subject. While such characterization is valuable for structural response predictions, it could be impractical in many application situations where a sufficiently large sample is expensive or unavailable. In this paper, Gaussian process regression models are employed to capture structural dynamical responses, especially responses with uncertainties. When Gaussian processes are used to make predictions for responses with uncertainties, the sampling costs can be significantly reduced because only a relatively small set of data points is needed. With no loss of generality, applications of Gaussian process regression models are introduced in conjunction with Monte Carlo sampling. This approach can be easily generalized to situations where data points are obtained by other sampling techniques.
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Jordy, Daniel E., and Mohammad I. Younis. "Characterization of the Dynamical Response of a Micromachined G-Sensor to Mechanical Shock Loading." In ASME 2007 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/detc2007-34843.
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Squeeze film damping has a significant effect on the dynamic response of MEMS devices that employ perforated microstructures with large planar areas and small gap widths separating them from the substrate. Perforations can alter the effect of squeeze film damping by allowing the gas underneath the device to easily escape, thereby lowering the damping. By decreasing the size of the holes, the damping increases and the squeeze film damping effect increases. This can be used to minimize the out-of-plane motion of the microstructures toward the substrate, thereby minimizing the possibility of contact and stiction. This paper aims to explore the use of the squeeze-film damping phenomenon as a way to mitigate shock and minimize the possibility of stiction and failure in this class of MEMS devices. As a case study, we consider a G-sensor, which is a sort of a threshold accelerometer, employed in an arming and fusing chip. We study the effect of changing the size of the perforation holes and the gap width separating the microstructure from the substrate. We use a multi-physics finite-element model built using the software ANSYS. First, a modal analysis is conducted to calculate the out-of-plane natural frequency of the G-sensor. Then, a squeeze-film damping finite-element model, for both the air underneath the structure and the flow of the air through the perforations, is developed and utilized to estimate the damping coefficients for several hole sizes. Results are shown for various models of squeeze-film damping assuming no holes, large holes, and assuming a finite pressure drop across the holes, which is the most accurate way of modeling. The extracted damping coefficients are then used in a transient structural-shock analysis. Finally, the transient shock analysis is used to determine the shock loads that induce contacts between the G-sensor and the underlying substrate. It is found that the threshold of shock to contact the substrate has increased significantly when decreasing the holes size or the gap width, which is very promising to help mitigate stiction in this class of devices, thereby improving their reliability.
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Schoen, Marco P., Sinchai Chinvorarat, and Chien-Hsun Kuo. "Eigensystem Realization With Modified Genetic Algorithm for System Identification of Noise Corrupted Processes." In ASME 2006 International Mechanical Engineering Congress and Exposition. ASMEDC, 2006. http://dx.doi.org/10.1115/imece2006-13409.
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The results of real world application of system identification (SI) algorithms are always affected by the process and measurement noise associated with the system to be identified and the measurement set-up. A small signal to noise ratio generally results into poor and sometimes unusable dynamical models. Missing system dynamics and characteristics in the inferred system model may cause undesirable and sometimes harmful control laws. Robust control is one avenue to avoid causing undesirable system performance due to the large model uncertainties. In this paper, an alternative approach is presented. In particular, a proof is given that no dynamic controller can reduce the noise influence in linear system identification. Eigensystem Realization Algorithms (ERA) used commonly in the Observer Kalman Filter Identification (OKID) algorithm allows for the discrimination between noise and system modes based on the magnitude of the singular values. Having a large noise content embedded in the input/output data is reflected by large singular values for the noise and system modes. This leaves them indistinguishable from each other. Hence the number and exact selection of the system modes using the traditional Eigensystem realization and the DC realization algorithm is impracticable. A new selection scheme is proposed for the Eigensystem realization portion of the OKID algorithm. The selection is done using a modified Genetic Algorithm (GA). The GA uses a cost function based on the step response, which is addition data to the random data collected from the experiment. The GA proposed adapts the probability density function for the selection scheme of the mating chromosomes based on the approximated cost gradient. Simulation results of the proposed algorithm in comparison with the traditional used method are presented. The results indicate an improved ability to extract system models from very noise data.
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Clavijo, Cristian E., Julie Crockett, and Daniel Maynes. "Analytical Model of Post-Impact Droplet Spreading on a Micro-Patterned Superhydrophobic Surface With Surface Slip." In ASME 2014 4th Joint US-European Fluids Engineering Division Summer Meeting collocated with the ASME 2014 12th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/fedsm2014-21648.
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Several analytical models exist to predict droplet impact behavior on superhydrophobic surfaces. However, no previous model has rigorously considered the effect of surface slip on droplet spreading and recoiling that is inherent in many superhydrophobic surfaces. This paper presents an analytical model that takes into account surface slip at the solid-fluid interface during droplet deformation. The effects of slip are captured in terms that model the kinetic energy and viscous dissipation and are compared to a classical energy conservation model given by Attane et al. and experimental data from Pearson et al. A range of slip lengths, Weber numbers, Ohnesorge numbers, and contact angles are investigated to characterize the effects of slip over the entire range of realizable conditions. We find that surface slip does not influence normalized maximum spread diameter for low We but can cause a significant increase for We > 100. Surface slip affects dynamical parameters more profoundly for low Oh numbers (0.002–0.01). Normalized residence time and rebound velocity increase as slip increases for the same range of We and Oh. The influence of slip is more significantly manifested on normalized rebound velocity than normalized maximum spread diameter. Contact angles in the range of 150°–180° do not affect impact dynamics significantly.
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Tilbury, D. M., B. T. Felt, N. Kaciroti, L. Wang, and T. Tardif. "Dynamic Systems Modeling of Cortisol Stress Response." In ASME 2008 Dynamic Systems and Control Conference. ASMEDC, 2008. http://dx.doi.org/10.1115/dscc2008-2197.
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This paper presents preliminary results for using dynamic systems models to describe cortisol responses to stressful events. Linear, single-input single-output discrete-time models are used. Choices that must be made regarding interpolation and input modeling are discussed in some detail. Results are presented that indicate an impulse model for the stressful input gives a better fit than no input, and that logarithmic transformation of the data before model fitting gives no better results than using the raw data. The issue of stability of the resulting models is discussed. In addition, the paper discusses how the resulting dynamic systems models can be used for statistical analysis, as well as for predicting future stress responses.
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Ekeregbe, Merit P. "Model Prediction of Critical Gas Rate With Water-Cut Reversal Effect." In SPE Nigeria Annual International Conference and Exhibition. SPE, 2021. http://dx.doi.org/10.2118/208257-ms.
Full textAbstract:
Abstract Accurate prediction of gas critical rate is critical to the successful management of gas wells. This paper covers the prediction of gas critical rate and presents limitations of old models with gas condensate wells with water-cut reversal. Comparison of prediction methods or models with this new method will be explained using field data of condensate wells. The effect and relation of water-cut with critical gas rate determination will be presented and the best method that universally meets changing conditions of the well will be tested with field data. Any method that must be acceptable must meet the dynamics of the well. No static model can predict accurately a dynamic well and reservoir performance. The old models of critical gas rate prediction show a static outlook, probably see the beginning of the well-life and cannot predict correctly when the fluid phases change in gravity. The late life prediction of the well performance is much more critical than the early life when the well has sufficient energy. The production envelope is more critical at depletion than at when the reservoir energy just kick. Therefore, any model prediction must be dynamic. The results from the old models show that they fail the dynamic test of the well performance. This limitation makes those model unusable in a late life of the well when water cut increases. This study has revealed a method or a model for critical rate prediction that is accurate throughout the life of the well. The effect of water cut reversal is well tracked with this new model whereas the static nature of other models predicts a wrong minimum rate at a liquid load up rate. The field data reveals that the dynamic nature of well and reservoir performance can only be understood dynamically.
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Ekeregbe, Merit P. "Model Prediction of Critical Gas Rate with Water-Cut Reversal Effect." In SPE Annual Technical Conference and Exhibition. SPE, 2021. http://dx.doi.org/10.2118/205970-ms.
Full textAbstract:
Abstract Accurate prediction of gas critical rate is critical to the successful management of gas wells. This paper covers the prediction of gas critical rate and presents limitations of old models with gas condensate wells with water-cut reversal. Comparison of prediction methods or models with this new method will be explained using field data of condensate wells. The effect and relation of water-cut with critical gas rate determination will be presented and the best method that universally meets changing conditions of the well will be tested with field data. Any method that must be acceptable must meet the dynamics of the well. No static model can predict accurately a dynamic well and reservoir performance. The old models of critical gas rate prediction show a static outlook, probably see the beginning of the well-life and cannot predict correctly when the fluid phases change in gravity. The late life prediction of the well performance is much more critical than the early life when the well has sufficient energy. The production envelope is more critical at depletion than at when the reservoir energy just kick. Therefore, any model prediction must be dynamic. The results from the old models show that they fail the dynamic test of the well performance. This limitation makes those model unusable in a late life of the well when water cut increases. This study has revealed a method or a model for critical rate prediction that is accurate throughout the life of the well. The effect of water cut reversal is well tracked with this new model whereas the static nature of other models predicts a wrong minimum rate at a liquid load up rate. The field data reveals that the dynamic nature of well and reservoir performance can only be understood dynamically.
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Cao, Dongpu, Amir Khajepour, and Xubin Song. "Wheelbase Filtering and Characterization of Road Profiles for Vehicle Dynamics." In ASME 2010 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/detc2010-28062.
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Random road profiles and wheelbase filtering, both of which strongly affect vehicle dynamic performance characteristics, have been explored in many studies. These studies invariably focused on either characterizing road roughness or vehicle dynamics considering wheelbase filtering effect. No effort, however, has been attempted to characterize road roughness profiles upon considering vehicle wheelbase filtering effect, and then to investigate their combined roles on vehicle dynamic responses. In this study, characteristics of different random road profiles are investigated upon considering wheelbase filtering effect. Two vehicle models, including quarter-car and pitch-plane models, are then employed to analyze the combined influence of random road roughness and wheelbase filtering on vehicle dynamics. The simulation results reveal the significant difference between the characteristics of random road profiles with and without wheelbase filtering effect. The results further demonstrate that wheelbase filtering has a positive effect on vehicle vertical ride, with a negligible or small compromise on suspension travel and dynamic tire deflection.
Reports on the topic "Dynamical NO-models"
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Carney, Nancy, Tamara Cheney, Annette M. Totten, Rebecca Jungbauer, Matthew R. Neth, Chandler Weeks, Cynthia Davis-O'Reilly, et al. Prehospital Airway Management: A Systematic Review. Agency for Healthcare Research and Quality (AHRQ), June 2021. http://dx.doi.org/10.23970/ahrqepccer243.
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Objective. To assess the comparative benefits and harms across three airway management approaches (bag valve mask [BVM], supraglottic airway [SGA], and endotracheal intubation [ETI]) by emergency medical services in the prehospital setting, and how the benefits and harms differ based on patient characteristics, techniques, and devices. Data sources. We searched electronic citation databases (Ovid® MEDLINE®, CINAHL®, the Cochrane Central Register of Controlled Trials, the Cochrane Database of Systematic Reviews, and Scopus®) from 1990 to September 2020 and reference lists, and posted a Federal Register notice request for data. Review methods. Review methods followed Agency for Healthcare Research and Quality Evidence-based Practice Center Program methods guidance. Using pre-established criteria, studies were selected and dual reviewed, data were abstracted, and studies were evaluated for risk of bias. Meta-analyses using profile-likelihood random effects models were conducted when data were available from studies reporting on similar outcomes, with analyses stratified by study design, emergency type, and age. We qualitatively synthesized results when meta-analysis was not indicated. Strength of evidence (SOE) was assessed for primary outcomes (survival, neurological function, return of spontaneous circulation [ROSC], and successful advanced airway insertion [for SGA and ETI only]). Results. We included 99 studies (22 randomized controlled trials and 77 observational studies) involving 630,397 patients. Overall, we found few differences in primary outcomes when airway management approaches were compared. • For survival, there was moderate SOE for findings of no difference for BVM versus ETI in adult and mixed-age cardiac arrest patients. There was low SOE for no difference in these patients for BVM versus SGA and SGA versus ETI. There was low SOE for all three comparisons in pediatric cardiac arrest patients, and low SOE in adult trauma patients when BVM was compared with ETI. • For neurological function, there was moderate SOE for no difference for BVM compared with ETI in adults with cardiac arrest. There was low SOE for no difference in pediatric cardiac arrest for BVM versus ETI and SGA versus ETI. In adults with cardiac arrest, neurological function was better for BVM and ETI compared with SGA (both low SOE). • ROSC was applicable only in cardiac arrest. For adults, there was low SOE that ROSC was more frequent with SGA compared with ETI, and no difference for BVM versus SGA or BVM versus ETI. In pediatric patients there was low SOE of no difference for BVM versus ETI and SGA versus ETI. • For successful advanced airway insertion, low SOE supported better first-pass success with SGA in adult and pediatric cardiac arrest patients and adult patients in studies that mixed emergency types. Low SOE also supported no difference for first-pass success in adult medical patients. For overall success, there was moderate SOE of no difference for adults with cardiac arrest, medical, and mixed emergency types. • While harms were not always measured or reported, moderate SOE supported all available findings. There were no differences in harms for BVM versus SGA or ETI. When SGA was compared with ETI, there were no differences for aspiration, oral/airway trauma, and regurgitation; SGA was better for multiple insertion attempts; and ETI was better for inadequate ventilation. Conclusions. The most common findings, across emergency types and age groups, were of no differences in primary outcomes when prehospital airway management approaches were compared. As most of the included studies were observational, these findings may reflect study design and methodological limitations. Due to the dynamic nature of the prehospital environment, the results are susceptible to indication and survival biases as well as confounding; however, the current evidence does not favor more invasive airway approaches. No conclusion was supported by high SOE for any comparison and patient group. This supports the need for high-quality randomized controlled trials designed to account for the variability and dynamic nature of prehospital airway management to advance and inform clinical practice as well as emergency medical services education and policy, and to improve patient-centered outcomes.