Microstress in the matrix of a melt‐infiltrated SiC/SiC ceramic matrix composite

Microstress in the SiC: Si matrix of a ceramic matrix composite (CMC) has been characterized, using Raman spectroscopy. The matrix of the composite was manufactured using liquid melt infiltration, and has about 20% unreacted free silicon. During the processing of the composite, the unreacted free silicon expands 11 vol% when transforming from liquid to solid. This crystallization expansion creates compressive microstress in the silicon phase of the matrix, which ranges from 2.4 to 3.1 GPa, and tensile microstress in the SiC of the matrix which ranges from 0.24 to 0.75 GPa. The microstress varies significantly with position, following a normal distribution.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138911/1/jace15038_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/138911/2/jace15038.pd

Forest cover estimation in Ireland using radar remote sensing: a comparative analysis of forest cover assessment methodologies

Quantification of spatial and temporal changes in forest cover is an essential component of forest monitoring programs. Due to its cloud free capability, Synthetic Aperture Radar (SAR) is an ideal source of information on forest dynamics in countries with near-constant cloud-cover. However, few studies have investigated the use of SAR for forest cover estimation in landscapes with highly sparse and fragmented forest cover. In this study, the potential use of L-band SAR for forest cover estimation in two regions (Longford and Sligo) in Ireland is investigated and compared to forest cover estimates derived from three national (Forestry2010, Prime2, National Forest Inventory), one pan-European (Forest Map 2006) and one global forest cover (Global Forest Change) product. Two machine-learning approaches (Random Forests and Extremely Randomised Trees) are evaluated. Both Random Forests and Extremely Randomised Trees classification accuracies were high (98.1–98.5%), with differences between the two classifiers being minimal (<0.5%). Increasing levels of post classification filtering led to a decrease in estimated forest area and an increase in overall accuracy of SAR-derived forest cover maps. All forest cover products were evaluated using an independent validation dataset. For the Longford region, the highest overall accuracy was recorded with the Forestry2010 dataset (97.42%) whereas in Sligo, highest overall accuracy was obtained for the Prime2 dataset (97.43%), although accuracies of SAR-derived forest maps were comparable. Our findings indicate that spaceborne radar could aid inventories in regions with low levels of forest cover in fragmented landscapes. The reduced accuracies observed for the global and pan-continental forest cover maps in comparison to national and SAR-derived forest maps indicate that caution should be exercised when applying these datasets for national reporting

Ultraviolet Curing of Highly Loaded Ceramic Suspensions for Stereolithography of Ceramics

Ceramic green bodies can be created using stereolithography methods where a ceramic slip consisting of 45-55 vlo ceramic powder is dispersed within an ultraviolet-curable aqueous acrylamide solution. Two ceramic materials were investigated: silica [Si02] for investment casting purposes, and alumina [AI203] for structural parts. After mixing the powders in the curable solution, the ceramic slip is tape cast onto a substrate for cure under a high intensity ultraviolet lamp (220-450 nm) at different exposure times. The materials systems were evaluated at different solids loadings (10-50 v/o) for cure thickness and viscosity control. Silica had a cure depth of 330 f.lm at a solids loading of 55 vlo, and at 50 vlo, alumina had a cure depth of 300 f.lm. Preliminary work utilizing scattering theory revealed the cure depth is controlled by the particle size and the refractive index difference between the ceramic and ultraviolet solution. The refractive index difference is the dominating factor. Two particle size distributions of alumina were used to more accurately determine the effect of particle size.Mechanical Engineerin

Scattering of ultraviolet radiation in turbid suspensions

A Beer’s law expression for the penetration depth of ultraviolet radiation in a concentrated suspension of scattering particles is used to model the depth of cure for a suspension of ceramic particles in a medium of photocurable monomers. The cure depth is predominantly controlled by the square of the refractive index difference between the ceramic particles and the medium, Δn2 = (np−n0)2Δn2=(np−n0)2. A secondary effect on the cure depth is the ratio of the interparticle spacing to the ultraviolet wavelength. Theoretical results agree with experimental data for 0.40–0.50 volume fraction ceramic-filled suspensions. © 1997 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71270/2/JAPIAU-81-6-2538-1.pd

Porous Ceramics by Photopolymerization with Terpene–Acrylate Vehicles

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94486/1/jace5444.pd

Estimating Influenza Vaccine Efficacy From Challenge and Community-based Study Data

In this paper, the authors provide estimates of 4 measures of vaccine efficacy for live, attenuated and inactivated influenza vaccine based on secondary analysis of 5 experimental influenza challenge studies in seronegative adults and community-based vaccine trials. The 4 vaccine efficacy measures are for susceptibility (VES), symptomatic illness given infection (VEP), infection and illness (VESP), and infectiousness (VEI). The authors also propose a combined (VEC) measure of the reduction in transmission in the entire population based on all of the above efficacy measures. Live influenza vaccine and inactivated vaccine provided similar protection against laboratory-confirmed infection (for live vaccine: VES  = 41%, 95% confidence interval (CI): 15, 66; for inactivated vaccine: VES  = 43%, 95% CI: 8, 79). Live vaccine had a higher efficacy for illness given infection (VEP  = 67%, 95% CI: 24, 100) than inactivated vaccine (VEP  = 29%, 95% CI: −19, 76), although the difference was not statistically significant. VESP for the live vaccine was higher than for the inactivated vaccine. VEI estimates were particularly low for these influenza vaccines. VESP and VEC can remain high for both vaccines, even when VEI is relatively low, as long as the other 2 measures of vaccine efficacy are relatively high

Microfabrication of Ceramics by Co-extrusion

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65777/1/j.1151-2916.1998.tb02307.x.pd

Commentary on the Integration of Model Sharing and Reproducibility Analysis to Scholarly Publishing Workflow in Computational Biomechanics

© 1964-2012 IEEE.Objective: The overall goal of this paper is to demonstrate that dissemination of models and analyses for assessing the reproducibility of simulation results can be incorporated in the scientific review process in biomechanics. Methods: As part of a special issue on model sharing and reproducibility in the IEEE Transactions on Biomedical Engineering, two manuscripts on computational biomechanics were submitted: Rajagopal et al., IEEE Trans. Biomed. Eng., 2016 and Schmitz and Piovesan, IEEE Trans. Biomed. Eng., 2016. Models used in these studies were shared with the scientific reviewers and the public. In addition to the standard review of the manuscripts, the reviewers downloaded the models and performed simulations that reproduced results reported in the studies. Results: There was general agreement between simulation results of the authors and those of the reviewers. Discrepancies were resolved during the necessary revisions. The manuscripts and instructions for download and simulation were updated in response to the reviewers' feedback; changes that may otherwise have been missed if explicit model sharing and simulation reproducibility analysis was not conducted in the review process. Increased burden on the authors and the reviewers, to facilitate model sharing and to repeat simulations, were noted. Conclusion: When the authors of computational biomechanics studies provide access to models and data, the scientific reviewers can download and thoroughly explore the model, perform simulations, and evaluate simulation reproducibility beyond the traditional manuscript-only review process. Significance: Model sharing and reproducibility analysis in scholarly publishing will result in a more rigorous review process, which will enhance the quality of modeling and simulation studies and inform future users of computational models

Evaluating Spillover Effects in Network-Based Studies In the Presence of Missing Outcomes

Estimating causal effects in the presence of spillover among individuals embedded within a social network is often challenging with missing information. The spillover effect is the effect of an intervention if a participant is not exposed to the intervention themselves but is connected to intervention recipients in the network. In network-based studies, outcomes may be missing due to the administrative end of a study or participants being lost to follow-up due to study dropout, also known as censoring. We propose an inverse probability censoring weighted (IPCW) estimator, which is an extension of an IPW estimator for network-based observational studies to settings where the outcome is subject to possible censoring. We demonstrated that the proposed estimator was consistent and asymptotically normal. We also derived a closed-form estimator of the asymptotic variance estimator. We used the IPCW estimator to quantify the spillover effects in a network-based study of a nonrandomized intervention with censoring of the outcome. A simulation study was conducted to evaluate the finite-sample performance of the IPCW estimators. The simulation study demonstrated that the estimator performed well in finite samples when the sample size and number of connected subnetworks (components) were fairly large. We then employed the method to evaluate the spillover effects of community alerts on self-reported HIV risk behavior among people who inject drugs and their contacts in the Transmission Reduction Intervention Project (TRIP), 2013 to 2015, Athens, Greece. Community alerts were protective not only for the person who received the alert from the study but also among others in the network likely through information shared between participants. In this study, we found that the risk of HIV behavior was reduced by increasing the proportion of a participant's immediate contacts exposed to community alerts

An objective frequency domain method for quantifying confined aquifer compressible storage using Earth and atmospheric tides

The groundwater hydraulic head response to the worldwide and ubiquitous atmospheric tide at 2 cycles per day (cpd) is a direct function of confined aquifer compressible storage. The ratio of the responses of hydraulic head to the atmospheric pressure change is a measure of aquifer barometric efficiency, from which formation compressibility and aquifer specific storage can be determined in situ rather than resorting to laboratory or aquifer pumping tests. The Earth tide also impacts the hydraulic head response at the same frequency, and a method is developed here to quantify and remove this interference. As a result, the barometric efficiency can be routinely calculated from 6-hourly hydraulic head, atmospheric pressure, and modeled Earth tide records where available for a minimum of 15 days duration. This new approach will be of critical importance in assessing worldwide problems of land subsidence or groundwater resource evaluation that both occur due to groundwater abstractio