Finite-Element Analysis of Shear-off Failure of Keyed Dry Joints in Precast Concrete Segmental Bridges

This article has been made available through the Brunel Open Access Publishing Fund.The structural behaviour of precast concrete segmental bridges is largely dependent on the behaviour of the joints between segments. The current practice is to use small keys that are usually unreinforced, distributed over the height of the web and the flange of concrete segments and these keys are normally dry. In this study, a numerical analysis model was established based on ABAQUS finite element code to investigate structural behaviour of keyed dry joints under direct shear. The concrete damage plasticity model along with the pseudo-damping scheme were incorporated to analyse the system for microcracks and to stabilize the solution, respectively. The numerical model is calibrated by full-scale experimental results published elsewhere. It was found that the predicted ultimate load, cracking evolution history, and final crack pattern agree reasonably well with experiment results. The validated numerical model was then employed for parametric study on factors affecting shear behaviour of keyed dry joints, in this case confining pressure. It has been found that shear capacity predicted by AASHTO diverges from that predicted by numerical analysis at high confining pressure because the contribution of friction in the total shear capacity reduces with the increase in confining pressure. Hence, it is recommended to reduce the friction coefficient used in AASHTO code when high confining pressure is applied. Moreover, the propagation of inclined crack is arrested at high confining pressure due to the fact that the fracture propagation direction is governed by the criterion of the maximum energy release rate

Serological Prevalence of Schistosoma japonicum in Mobile Populations in Previously Endemic but Now Non-Endemic Regions of China: A Systematic Review and Meta-Analysis.

Background: Schistosomiasis japonica has been resurging in certain areas of China where its transmission was previously well controlled or interrupted. Several factors may be contributing to this, including mobile populations, which if infected, may spread the disease. A wide range of estimates have been published for S. japonicum infections in mobile populations, and a synthesis of these data will elucidate the relative risk presented from these groups. Methods: A literature search for publications up to Oct 31, 2014 on S. japonicum infection in mobile populations in previously endemic but now non-endemic regions was conducted using four bibliographic databases: China National Knowledge Infrastructure, WanFang, VIP Chinese Journal Databases, and PubMed. A meta-analysis was conducted by pooling one arm binary data with MetaAnalyst Beta 3.13. The protocol is available on PROSPERO (No. CRD42013005967). Results: A total of 41 studies in Chinese met the inclusion criteria, covering seven provinces of China. The time of post-interruption surveillance ranged from the first year to the 31st year. After employing a random-effects model, from 1992 to 2013 the pooled seroprevalence ranged from 0.9% (95% CI: 0.5-1.6%) in 2003 to 2.3% (95% CI: 1.5-3.4) in 1995; from the first year after the disease had been interrupted to the 31st year, the pooled seroprevalence ranged from 0.6% (95% CI: 0.2-2.1%) in the 27th year to 4.0% (95%CI: 1.3-11.3%) in the second year. The pooled seroprevalence in mobile populations each year was significantly lower than among the residents of endemic regions, whilst four papers reported a lower level of infection in the mobile populations than in the local residents out of only 13 papers which included this data. Conclusions: The re-emergence of S. japonicum in areas which had previously interrupted transmission might be due to other factors, although risk from re-introduction from mobile populations could not be excluded

Bayesian nonparametric models for biomedical data analysis

In this dissertation, we develop nonparametric Bayesian models for biomedical data analysis. In particular, we focus on inference for tumor heterogeneity and inference for missing data. First, we present a Bayesian feature allocation model for tumor subclone reconstruction using mutation pairs. The key innovation lies in the use of short reads mapped to pairs of proximal single nucleotide variants (SNVs). In contrast, most existing methods use only marginal reads for unpaired SNVs. In the same context of using mutation pairs, in order to recover the phylogenetic relationship of subclones, we then develop a Bayesian treed feature allocation model. In contrast to commonly used feature allocation models, we allow the latent features to be dependent, using a tree structure to introduce dependence. Finally, we propose a nonparametric Bayesian approach to monotone missing data in longitudinal studies with non-ignorable missingness. In contrast to most existing methods, our method allow for incorporating information from auxiliary covariates and is able to capture complex structures among the response, missingness and auxiliary covariates. Our models are validated through simulation studies and are applied to real-world biomedical datasets.Statistic

Essays on public policy and labor economics

The majority of insured Americans obtain health insurance coverage through employment as a non-portable fringe benefit. The link between health insurance coverage and employment could have potential important implica- tions on workers’ labor market decisions. My dissertation consists of three chapters that contribute to the understanding of the interaction between health insurance and workers’ job mobility. My first chapter studies the effect of the state dependent coverage man- dates on the job mobility of young adults. Prior to the Affordable Care Act, many states had already implemented insurance mandates that extended the age that young adults could gain access to parental health insurance, an alternative insurance source which is not contingent on employment. If young workers with employer-sponsored insurance (ESI) are locked into less preferred jobs for fear of losing health benefits, expanded dependent coverage is expected to reduce the job lock and increase mobility. Expanded eligibility could also decrease mobility among those who are pushed out of a better matched but uninsured job in search of access to ESI (job push). Using Survey of Income and Program Participation (SIPP) 2000-2010 data, the impact of the state mandates on job mobility is identified by a triple-difference framework that exploits the state level dependent coverage variations in eligibility criteria, mandate implementation states, and mandate implementation time. Results show that expanded dependent coverage led to a 5% decrease in the mobility of workers with no ESI (job push). I find no evidence of reduced job lock. The second chapter of my dissertation extends the analysis of my first chapter to the Affordable Care Act (ACA) Dependent Coverage Mandate. The ACA Dependent Coverage Mandate was passed on March 23rd, 2010, and became effective on September 23, 2010. The mandate requires that health insurance plans that provide dependent coverage must cover dependents until the age of 26. Using SIPP 2008-2013 data, and both difference-in-difference framework and regression discontinuity design, I find consistent evidence of reduced job push and no evidence of reduced job lock. The estimated reduced job push is larger than the state analysis. The third chapter studies the impact of the ACA Medicaid expansion on childless adults’ job mobility. The ACA Medicaid expansion raised the Medi- caid income eligibility threshold to 138% of the Federal Poverty Line (FPL) for everyone including childless adults who were not the traditional beneficiaries of the Medicaid. 32 states adopted the expansion while 19 states opted out. The reform could potentially increase childless adults’ job mobility if they are “locked” in their jobs for fear of losing employer-sponsored health insurance. Using the 2011-2016 basic monthly Current Population Survey (CPS), this paper tests this hypothesis by comparing the job mobility of childless adults in expansion states to those residing in non-expansion states, before and after the expansion. Results show the existence of “job lock” effect: the ACA Medicaid expansion increased the childless adults’ job mobility by 7% - 9%, and the increase comes entirely from job-to-job transitions. I find no evidence of the “employment lock”: the availability of Medicaid did not cause childless adults to be more likely to become unemployed or leave the labor force.Economic

The Role of Innovation in Inventory Turnover Performance

How a firm utilizes technological innovation to improve operations management is an important research question in today's knowledge economy but lacks empirical evidence in the literature. We use a dataset of all non-service U.S. public firms from 1976 to 2005 to examine how a firm's innovation performance is associated with its inventory turnover performance. In particular, we measure a firm's innovation performance by the ratio of its patents (either citations or counts) to its research and development (R&D) expenditure. Our fixed-effect panel regression results indicate a positive relation between innovation performance and inventory turnover ratio, and such a relation varies across industries. By differentiating process and product innovation according to patent usages, we find that process innovation has a consistent and long-lasting effect, whereas product innovation has an immediate but short-lasting effect. We also find supporting evidence for industry spillovers by showing that firms in a more innovative industry are likely to better manage their inventory performance. Our results confirm the benefit of using innovation in logistics and operations management and point to the strategic importance of integrating technology and operations management.postprin

Managed Bumblebees Outperform Honeybees in Increasing Peach Fruit Set in China: Different Limiting Processes with Different Pollinators

© 2015 Zhang et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. http://creativecommons.org/licenses/by/4.0/ The file attached is the published version of the article

Atomic-scale coexistence of short-range magnetic order and superconductivity in Fe1+y_{1+y}Se0.1_{0.1}Te0.9_{0.9}

The ground state of the parent compounds of many high temperature superconductors is an antiferromagnetically (AFM) ordered phase, where superconductivity emerges when the AFM phase transition is suppressed by doping or application of pressure. This behaviour implies a close relation between the two orders. Understanding the interplay between them promises a better understanding of how the superconducting condensate forms from the AFM ordered background. Here we explore this relation in real space at the atomic scale using low temperature spin-polarized scanning tunneling microscopy (SP-STM) and spectroscopy. We investigate the transition from antiferromagnetically ordered $\mathrm{Fe}_{1+y}\mathrm{Te}$ via the spin glass phase in $\mathrm{Fe}_{1+y}\mathrm{Se}_{0.1}\mathrm{Te}_{0.9}$ to superconducting $\mathrm{Fe}_{1+y}\mathrm{Se}_{0.15}\mathrm{Te}_{0.85}$. In $\mathrm{Fe}_{1+y}\mathrm{Se}_{0.1}\mathrm{Te}_{0.9}$ we observe an atomic-scale coexistence of superconductivity and short-ranged bicollinear antiferromagnetic order.Comment: 7 pages, 6 figure

Spatial-Temporal Deep Embedding for Vehicle Trajectory Reconstruction from High-Angle Video

Spatial-temporal Map (STMap)-based methods have shown great potential to process high-angle videos for vehicle trajectory reconstruction, which can meet the needs of various data-driven modeling and imitation learning applications. In this paper, we developed Spatial-Temporal Deep Embedding (STDE) model that imposes parity constraints at both pixel and instance levels to generate instance-aware embeddings for vehicle stripe segmentation on STMap. At pixel level, each pixel was encoded with its 8-neighbor pixels at different ranges, and this encoding is subsequently used to guide a neural network to learn the embedding mechanism. At the instance level, a discriminative loss function is designed to pull pixels belonging to the same instance closer and separate the mean value of different instances far apart in the embedding space. The output of the spatial-temporal affinity is then optimized by the mutex-watershed algorithm to obtain final clustering results. Based on segmentation metrics, our model outperformed five other baselines that have been used for STMap processing and shows robustness under the influence of shadows, static noises, and overlapping. The designed model is applied to process all public NGSIM US-101 videos to generate complete vehicle trajectories, indicating a good scalability and adaptability. Last but not least, the strengths of the scanline method with STDE and future directions were discussed. Code, STMap dataset and video trajectory are made publicly available in the online repository. GitHub Link: shorturl.at/jklT0

The dynamothermal aureole of the Donqiao ophiolite (northern Tibet)

Metamorphic rocks found at the base of the Jurassic Donqiao ophiolite of northern Tibet are interpreted as a basal dynamothermal aureole produced during obduction of the massif. The rocks form a sequence some 8 m thick, varying from high-grade amphibolites at the contact with overlying harzburgites to greenschist facies metasedimentary rocks lower down. The mineral paragenesis is similar to other such aureoles, and indicates that temperatures in excess of 750°C may have been reached during metamorphism. The lack of high-pressure minerals suggests that the rocks were produced by subcretion in a relatively shallow dipping subduction zone. Ar-Ar geochronology on amphibole separates provides dates of 175-180 Ma for the displacement of the ophiolite, significantly older than the age of emplacement estimated from stratigraphic relationships. The ophiolite was clearly obducted very soon after its formation in a suprasubduction zone environment.published_or_final_versio