Modeling of Tunnel Concrete Lining under Fire and Explosion Damage

This paper presents studies that focus on fire and explosion-induced damage of tunnel structures by employing the Discrete Element Method (DEM). By assuming a two-dimensional aggregate distribution and reconstructing the digital representation of the experimental concrete blocks, a numerical model of the tunnel lining concrete was established in the PFC2D program. The temperature distribution and the shock wave pressure at the surface of the tunnel lining were obtained by using Fluent and LS-Dyna separately; the final damage simulation of concrete section under different conditions was carried out in PFC2D. The results showed that PFC2D cooperatively provided more accurate and effective modeling and visualization of impact damage of concrete blocks. The visualizations of damage indicated the degree of damage more clearly and more intuitively. These findings also provide a potential method for further study of the damage assessment for entire tunnel lining structures.

Remote expert elicitation to determine the prior probability distribution for Bayesian sample size determination in international randomized controlled trials: Bronchiolitis in Infants Placebo Versus Epinephrine and Dexamethasone (BIPED) Study

BackgroundBayesian methods are increasing in popularity in clinical research. The design of Bayesian clinical trials requires a prior distribution, which can be elicited from experts. Current elicitation approaches either use face-to-face sessions or expert surveys. In diseases with international differences in management, the elicitation exercise should recruit internationally, requiring expensive face-to-face sessions or surveys, which suffer low response rates. To address this, we developed a remote, real-time elicitation exercise to construct prior distributions. These elicited distributions were then used to determine the sample size of the Bronchiolitis in Infants with Placebo Versus Epinephrine and Dexamethasone (BIPED) Study, an international randomized controlled trial trial in the Pediatric Emergency Research Network (PERN). The BIPED study aims to determine whether the combination of epinephrine and dexamethasone, compared to placebo, is effective in reducing hospital admission for infants presenting with bronchiolitis to the emergency department.MethodsWe developed a web-based tool to support the elicitation of the probability of hospitalization for infants with bronchiolitis. Experts participated in online workshops to specify their individual prior distributions, which were aggregated using the equal-weighted linear pooling method. The Average Length Criterion determined the BIPED sample size.ResultsFifteen paediatric emergency medicine clinicians from Canada, USA, Australia and New Zealand participated in three workshops to provide their elicitied prior distributions. The elicited probability of admission for infants with bronchiolitis was slightly lower for those receiving epinephrine and dexamethasone compared to supportive care in the aggregate distribution. There were substantial differences in the individual beliefs but limited differences between North America and Australaisia. From this aggregate distribution, a sample size of 410 patients per arm results in an average 95% credible interval length of less than 9% and a relative predictive power of 90%.ConclusionRemote expert elicitation is a feasible, useful and practical tool to determine a prior distribution for international randomized controlled trials. Bayesian methods can then determine the trial sample size using these elicited prior distributions. The ease and low cost of remote expert elicitation means that this approach is suitable for future international randomized controlled trials.Trial Registration: clinicaltrials.gov Identifier: NCT03567473

The impacts of climate change on the availability of granular resources in the Inuvialuit Settlement Region, Northwest Territories

Physical community infrastructure is vulnerable to changes in permafrost regimes resulting from warming in Arctic environments. The vulnerability of community infrastructure is greatly exacerbated by factors related to the accessibility of aggregates that are used to insulate built form from the active layer of the permafrost. The abililty of communities to address stresses brought about by melting permafrost is a function of access to aggregates, the ability to transport them, and competition for gravel between users. In the Inuvialuit Settlement Region readily accessible aggregate is in short supply, and concerns about resource allocation pre-date current prognoses about the impact of global warming. The prospect is that while demand for gravel will increase as permafrost is degraded, competition from new activities along with degradation of winter roads may further stress supplies. This research project examines the manner in which institutional arrangements, the geography of aggregate distribution, transportation, and competition from emerging new activities exacerbate vulnerabilites associated with permafrost melt in the Inuvialuit Settlement Region.

The impacts of climate change on the availability of granular resources in the Inuvialuit Settlement Region, Northwest Territories

Physical community infrastructure is vulnerable to changes in permafrost regimes resulting from warming in Arctic environments. The vulnerability of community infrastructure is greatly exacerbated by factors related to the accessibility of aggregates that are used to insulate built form from the active layer of the permafrost. The abililty of communities to address stresses brought about by melting permafrost is a function of access to aggregates, the ability to transport them, and competition for gravel between users. In the Inuvialuit Settlement Region readily accessible aggregate is in short supply, and concerns about resource allocation pre-date current prognoses about the impact of global warming. The prospect is that while demand for gravel will increase as permafrost is degraded, competition from new activities along with degradation of winter roads may further stress supplies. This research project examines the manner in which institutional arrangements, the geography of aggregate distribution, transportation, and competition from emerging new activities exacerbate vulnerabilites associated with permafrost melt in the Inuvialuit Settlement Region.

Structure, spatial distribution and phenology of two Vochysiaceae species in Cerrado fragment in the Caatinga, Southern Ceará, Brazil

The family Vochysiaceae, representative for Brazilian Cerrado, does not stand out in Caatinga environments. Due to the lack of studies that address the behavior of species of this family in disjunct Cerrado environments, this study aimed to investigate structural, ecological and phenological aspects of Qualea parviflora and Callisthene fasciculata populations. The phytosociological and phenological surveys were carried out in a Cerrado enclave at Serra do Boqueirão, Lavras da Mangabeira municipality, Southern Ceará, Brazil. Twelve sampling units of 12.0 x 30 m (0.432 ha) were plotted randomly, including all living individuals with a ground level diameter ≥ 3 cm, also measuring total heights. For the evaluation of phenophases, the Fournier percentage was used, allowing the estimation of intensity of the phenophase in each individual through a semi-quantitative interval scale of five categories (0 to 4), 0 being equivalent to 0%; (1) 1 to 25%; (2) 26 to 50%; (3) 51 to 75% and (4) 76 to 100%. Each sample was composed of 103 and 78 individuals respectively in 66.6% and 91.6% of the plots, of Q. parviflora and C. fasciculata, respectively. The spatial distribution, measured by the Dispersion (ID) and Morisita (IM) indexes reached the values of 17.14 and 18.26 (ID) and 1.08 and 1.16 (IM), respectively, indicating that the species have an aggregate distribution. The phenophases generally correlated with all the climatic variables studied in the region such as rain and preciptation. All data and results presented here collaborate for future projects in the area.