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81.
Given a most believed value for a quantity together with upper and lower possible deviations from that value, a rectangular distribution might be used to represent state-of-knowledge about the quantity. If the deviations are themselves known by probability distributions, and the value conditioned on the deviations is rectangular, then the marginal distribution of the value is determined by the distributions of the deviations. Here we show under quite general conditions that conversely, given the marginal distribution, the distributions of the deviations are uniquely determined. The case in which the marginal distribution is trapezoidal is studied in some detail. 相似文献
82.
This article introduces a new model for transaction prices in the presence of market microstructure noise in order to study the properties of the price process on two different time scales, namely, transaction time where prices are sampled with every transaction and tick time where prices are sampled with every price change. Both sampling schemes have been used in the literature on realized variance, but a formal investigation into their properties has been lacking. Our empirical and theoretical results indicate that the return dynamics in transaction time are very different from those in tick time and the choice of sampling scheme can therefore have an important impact on the properties of realized variance. For RV we find that tick time sampling is superior to transaction time sampling in terms of mean-squared-error, especially when the level of noise, number of ticks, or the arrival frequency of efficient price moves is low. Importantly, we show that while the microstructure noise may appear close to IID in transaction time, in tick time it is highly dependent. As a result, bias correction procedures that rely on the noise being independent, can fail in tick time and are better implemented in transaction time. 相似文献
83.
Henry J. Liu Peter E. D. Love Jim Smith Zahir Irani Nick Hajli Michael C. P. Sing 《生产规划与管理》2018,29(1):68-83
Public–Private Partnerships (PPPs) have become a critical vehicle for delivering infrastructure worldwide. Yet, the use of such a procurement strategy has received considerable criticism, as they have been prone to experiencing time/cost overruns and during their operation poorly managed. A key issue contributing to the poor performance of PPPs is the paucity of an effective and comprehensive performance measurement system. There has been a tendency for the performance of PPPs to be measured based on their ex-post criteria of time, cost and quality. Such criteria do not accommodate the complexities and lifecycle of an asset. In addressing this problem, the methodology of sequential triangulation is used to develop and examine the effectiveness of a ‘Process Management Life Cycle Performance Measurement System’. The research provides public authorities and private-sector entities embarking on PPPs with a robust mechanism to effectively measure, control and manage their projects’ life cycle performances, ensuring the assets are ‘future proofed’. 相似文献
84.
Scour (localized erosion by water) is an important risk to bridges, and hence many infrastructure networks, around the world. In Britain, scour has caused the failure of railway bridges crossing rivers in more than 50 flood events. These events have been investigated in detail, providing a data set with which we develop and test a model to quantify scour risk. The risk analysis is formulated in terms of a generic, transferrable infrastructure network risk model. For some bridge failures, the severity of the causative flood was recorded or can be reconstructed. These data are combined with the background failure rate, and records of bridges that have not failed, to construct fragility curves that quantify the failure probability conditional on the severity of a flood event. The fragility curves generated are to some extent sensitive to the way in which these data are incorporated into the statistical analysis. The new fragility analysis is tested using flood events simulated from a spatial joint probability model for extreme river flows for all river gauging sites in Britain. The combined models appear robust in comparison with historical observations of the expected number of bridge failures in a flood event. The analysis is used to estimate the probability of single or multiple bridge failures in Britain's rail network. Combined with a model for passenger journey disruption in the event of bridge failure, we calculate a system‐wide estimate for the risk of scour failures in terms of passenger journey disruptions and associated economic costs. 相似文献
85.
Simon French Nikolaos Argyris Stephanie M. Haywood Matthew C. Hort Jim Q. Smith 《Risk analysis》2019,39(1):9-16
In any crisis, there is a great deal of uncertainty, often geographical uncertainty or, more precisely, spatiotemporal uncertainty. Examples include the spread of contamination from an industrial accident, drifting volcanic ash, and the path of a hurricane. Estimating spatiotemporal probabilities is usually a difficult task, but that is not our primary concern. Rather, we ask how analysts can communicate spatiotemporal uncertainty to those handling the crisis. We comment on the somewhat limited literature on the representation of spatial uncertainty on maps. We note that many cognitive issues arise and that the potential for confusion is high. We note that in the early stages of handling a crisis, the uncertainties involved may be deep, i.e., difficult or impossible to quantify in the time available. In such circumstance, we suggest the idea of presenting multiple scenarios. 相似文献
86.
Erika Jiménez Vicky Brotherton Alison Gardner Nicola Wright Hannah Browne Nancy Esiovwa Minh Dang Emily Wyman Liana Bravo-Balsa Benjamin Lucas Mohsen Gul Elizabeth Such Zoe Trodd 《Children & Society》2023,37(1):216-234
This article discusses the unequal impact of Covid-19 on the lives of the children of survivors of modern slavery, child victims of exploitation and children at risk of exploitation in the UK. It draws on research that has analysed the risks and impacts of Covid-19 on victims and survivors of modern slavery. It explores how pandemic responses may have hindered these children's rights to education, food, safety, development and participation and representation in legal processes. It suggests that the pandemic should be used as an impetus to address inequalities that existed pre-Covid-19 and those that have been exacerbated by it. 相似文献
87.
88.
Susana Jiménez-Murcia Eva M. Álvarez-Moya Randy Stinchfield Fernando Fernández-Aranda Roser Granero Neus Aymamí Mónica Gómez-Peña Nuria Jaurrieta Francesca Bove José M. Menchón 《Journal of gambling studies / co-sponsored by the National Council on Problem Gambling and Institute for the Study of Gambling and Commercial Gaming》2010,26(2):235-248
We aimed to explore the association between age of onset of gambling problems and current psychopathological and clinical
status, personality profile and therapeutic outcome in a sample of pathological gamblers. A total of 904 consecutive pathological
gambling patients were administered several instruments about gambling behavior, psychopathology and personality. They received
a 4-month cognitive-behavioral group treatment. Information of dropouts and relapses during treatment was registered. Older
age of onset of gambling problems was associated with higher general psychopathology (SCL-90-R Paranoid Ideation, Psychoticism,
Depression; P < 0.015). Younger age of onset was related to greater severity of pathological gambling (P < 0.015), higher novelty seeking, and lower self-directedness (P < 0.015). No statistically significant association was found between age of onset and relapse and dropouts during treatment.
Age of onset of gambling problems seems to influence the clinical presentation of pathological gambling but not treatment
outcome. 相似文献
89.
90.
We propose a more efficient version of the slice sampler for Dirichlet process mixture models described by Walker (Commun.
Stat., Simul. Comput. 36:45–54, 2007). This new sampler allows for the fitting of infinite mixture models with a wide-range of prior specifications. To illustrate
this flexibility we consider priors defined through infinite sequences of independent positive random variables. Two applications
are considered: density estimation using mixture models and hazard function estimation. In each case we show how the slice
efficient sampler can be applied to make inference in the models. In the mixture case, two submodels are studied in detail.
The first one assumes that the positive random variables are Gamma distributed and the second assumes that they are inverse-Gaussian
distributed. Both priors have two hyperparameters and we consider their effect on the prior distribution of the number of
occupied clusters in a sample. Extensive computational comparisons with alternative “conditional” simulation techniques for
mixture models using the standard Dirichlet process prior and our new priors are made. The properties of the new priors are
illustrated on a density estimation problem. 相似文献