We develop a method for assessing uncertainty about quantities of interest using urban simulation models. The method is called Bayesian melding, and extends a previous method developed for macrolevel ...deterministic simulation models to agent-based stochastic models. It encodes all the available information about model inputs and outputs in terms of prior probability distributions and likelihoods, and uses Bayes’s theorem to obtain the resulting posterior distribution of any quantity of interest that is a function of model inputs and/or outputs. It is Monte Carlo based, and quite easy to implement. We applied it to the projection of future household numbers by traffic activity zone in Eugene-Springfield, Oregon, using the UrbanSim model developed at the University of Washington. We compared it with a simpler method that uses repeated runs of the model with fixed estimated inputs. We found that the simple repeated runs method gave distributions of quantities of interest that were too narrow, while Bayesian melding gave well calibrated uncertainty statements.
► Uncertainty in a combined land use and transportation model using Bayesian melding. ► Case study targets a controversy around the replacement of the Alaskan Way Viaduct. ► We analyze a predictive ...distribution of average commute times on 22 different routes. ► We compare two different policy scenarios including tearing down the viaduct. ► Hypothesis that removing the viaduct will increase travel times is not supported.
Uncertainty is inherent in major infrastructure projects, but public decision-making for such projects ignores it. We investigate the uncertainty about the future effects of tearing down the Alaskan Way Viaduct in downtown Seattle, using an integrated model of housing, jobs, land use and transportation, on outcomes including average commute times. Our methodology combines the urban simulation model UrbanSim with the regional transportation model. We assess uncertainty using Bayesian melding, yielding a full predictive distribution of average commute times on 22 different routes in 2020. Of these routes, 14 do not include the viaduct and eight do. For the 14 base routes that do not include the viaduct, the predictive distributions overlap substantially, and so there is no indication that removing the viaduct would increase commute times for these routes. For each of the eight routes that do include the viaduct, the 95% predictive interval for the difference in average travel times between the two scenarios includes zero, so there is not strong statistical support for the conclusion that removing the viaduct would lead to any increase in travel times. However, the median predicted increase is positive for each of these routes, with an average of 6
min, suggesting that there may be some measurable increase in travel time for drivers that use the viaduct as a core component of their commute.
Likelihood ratio tests in parametric mixture models suffer from several sources of instability, therefore tests against a nonparametric alternative are proposed. Their performance depends on the ...strategies for likelihood maximization. This article develops a fast and statistically powerful combination of methods under the null hypothesis and under the alternative hypothesis; the method also includes elimination of spurious components.
Modifying a strategy proposed by McLachlan, a sequence of such tests is applied for assessing the number of components and its performance is analyzed in a number of simulation studies in exponential mixture models. Although critical values have to be bootstrapped, the probability of overestimating is still bounded by the nominal level of the individual tests. Taking into account the number of components that can be reliably detected on the basis of a certain sample size, the proposed procedure yields the minimum number of components that is required for an adequate representation of the sample. It is compared to methods based on the Bayesian and the Akaike information criterion, and a recommendation is given to identify a range of meaningful model orders compatible with a given sample.
WEE1 regulates the cell cycle by inactivating cyclin dependent protein kinases (CDKs) via phosphorylation. In yeast and animal cells, CDC25 phosphatase dephosphorylates the CDK releasing cells into ...mitosis, but in plants, its role is less clear. Expression of fission yeast CDC25 (Spcdc25) in tobacco results in small cell size, premature flowering and increased shoot morphogenetic capacity in culture. When Arath;WEE1 is over-expressed in Arabidopsis, root apical meristem cell size increases, and morphogenetic capacity of cultured hypocotyls is reduced. However expression of Arath;WEE1 in tobacco plants resulted in precocious flowering and increased shoot morphogenesis of stem explants, and in BY2 cultures cell size was reduced. This phenotype is similar to expression of Spcdc25 and is consistent with a dominant negative effect on WEE1 action. Consistent with this putative mechanism, WEE1 protein levels fell and CDKB levels rose prematurely, coinciding with early mitosis. The phenotype is not due to sense-mediated silencing of WEE1, as overall levels of WEE1 transcript were not reduced in BY2 lines expressing Arath;WEE1. However the pattern of native WEE1 transcript accumulation through the cell cycle was altered by Arath;WEE1 expression, suggesting feedback inhibition of native WEE1 transcription.
Case 1-2010: Acute occlusion of abdominal aorta Sevcíková, Hana; Rozkos, Tomás; Hrubá, Iva ...
Acta medica Lékarskí fakulty Univerzity Karlovy v Hradci Králove,
2010, Letnik:
53, Številka:
2
Journal Article
Uncertainty in land use and transportation modeling has received increasing attention in the past few years. However, methods for quantifying uncertainty in such models are usually developed in an ...academic environment and in most cases do not reach users of official forecasts, such as planners and policymakers. In this paper, we describe the practical application of a methodology called Bayesian melding and its integration into the land-use forecast published by the Puget Sound Regional Council, a metropolitan planning organization. The method allows practitioners to assess uncertainty about forecasted quantities, such as households, population, and jobs, for each geographic unit. Users are provided with probability intervals around forecasts, which add value to model validation, scenario comparison, and external review and comment procedures. Practical issues such as how many runs to use or assessing uncertainty for aggregated regions are also discussed.
The propagation of arsenous acid−iodate reaction fronts of different net stoichiometries in externally applied dc electric fields is studied for a range of both electric field intensities and initial ...compositions of the reacting mixture (represented by the stoichiometric factor S 0). Regions of three different types of net stoichiometry in the parametric space ℰ/V vs S 0, where ℰ is the intensity of the applied electric field and V the reaction front propagation velocity, are determined both experimentally and by analyzing a reaction−diffusion−migration model that includes a realistic kinetic scheme of the reaction studied. Both agreement with and discrepancies between the theoretical predictions and experimental findings are discussed.
The emergence of wave patterns in chemical and biological systems is of interest for the understanding of development, differentiation, signaling, and other phenomena. In this work we report a new ...type of wave pattern - called the “global wave” - which was observed in populations of
Dictyostelium discoideum cells exposed to an excess of cyclic adenosine- 3′, 5′- monophosphate (cAMP) added to the supporting agar. It has been found that the addition of different amounts of cAMP to the agar leads to important deviations from the standard course of aggregation: (i) the formation and propagation of a global wave that has not been observed before; (ii) the delayed onset or absence of cAMP waves patterning; (iii) an atypical mechanism of cells clustering; and (iv) a faster or incomplete developmental cycle. We suggest that the global wave is a chemotactic response of the
Dictyostelium cells to a wave of the cAMP concentration.
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