The effect of tempering parameters on the hardness and precipitation characteristics of quenched and tempered RQT701 steel plate.

Reheated quenched and tempered 701 steel (RQT701) is a high strength low alloy martensitic grade commonly used in the earth moving and construction industries. The aim of this project was to investigate the tempering response of RQT701 steel at 580, 600 and 620 °C for between 1 and 100 hours. Steel plate, of composition 0.17C, 0.29Cr and 0.53Mo (all wt. %) and 15 mm thickness, was supplied in the as-quenched condition. It was found that the as-quenched condition (water cooled from 925 °C at 60 °C-s, surface measurement) consisted of autotempered martensite with a hardness of 430 HV. Ice water quenching was tested and did not have any effect on the tempering response past 30 minutes. Hardness measurements on samples tempered between 1 and 4 hours showed an increase of approximately 10 HV between 2 and 3 hours. Particle analysis using SEM images revealed the average precipitate equivalent circle diameter to increase from 45 to 71 nm, the number density to decrease from 63 to 52 per μm2, and the volume fraction of precipitates to increase from 0.017 to 0.022 %. The results suggest that the formation of very fine M2C, in combination with cementite, cause the secondary hardening peak

An Affine-Invariant Sampler for Exoplanet Fitting and Discovery in Radial Velocity Data

Markov Chain Monte Carlo (MCMC) proves to be powerful for Bayesian inference and in particular for exoplanet radial velocity fitting because MCMC provides more statistical information and makes better use of data than common approaches like chi-square fitting. However, the non-linear density functions encountered in these problems can make MCMC time-consuming. In this paper, we apply an ensemble sampler respecting affine invariance to orbital parameter extraction from radial velocity data. This new sampler has only one free parameter, and it does not require much tuning for good performance, which is important for automatization. The autocorrelation time of this sampler is approximately the same for all parameters and far smaller than Metropolis-Hastings, which means it requires many fewer function calls to produce the same number of independent samples. The affine-invariant sampler speeds up MCMC by hundreds of times compared with Metropolis-Hastings in the same computing situation. This novel sampler would be ideal for projects involving large datasets such as statistical investigations of planet distribution. The biggest obstacle to ensemble samplers is the existence of multiple local optima; we present a clustering technique to deal with local optima by clustering based on the likelihood of the walkers in the ensemble. We demonstrate the effectiveness of the sampler on real radial velocity data.Comment: 24 pages, 7 figures, accepted to Ap

Collaborative research: ITR: global multi-scale kinetic simulations of the earth's magnetosphere using parallel discrete event simulation

Issued as final reportNational Science Foundation (U.S.

A Guide to Delineate the Logic of Neurovascular Signaling in the Brain

The neurovascular system may be viewed as a distributed nervous system within the brain. It transforms local neuronal activity into a change in the tone of smooth muscle that lines the walls of arterioles and microvessels. We review the current state of neurovascular coupling, with an emphasis on signaling molecules that convey information from neurons to neighboring vessels. At the level of neocortex, this coupling is mediated by: (i) a likely direct interaction with inhibitory neurons, (ii) indirect interaction, via astrocytes, with excitatory neurons, and (iii) fiber tracts from subcortical layers. Substantial evidence shows that control involves competition between signals that promote vasoconstriction versus vasodilation. Consistent with this picture is evidence that, under certain circumstances, increased neuronal activity can lead to vasoconstriction rather than vasodilation. This confounds naïve interpretations of functional brain images. We discuss experimental approaches to detect signaling molecules in vivo with the goal of formulating an empirical basis for the observed logic of neurovascular control

An Analysis of Costs and Health Co-Benefits for a U.S. Power Plant Carbon Standard

Reducing carbon dioxide (CO2) emissions from power plants can have important “co-benefits” for public health by reducing emissions of air pollutants. Here, we examine the costs and health co-benefits, in monetary terms, for a policy that resembles the U.S. Environmental Protection Agency’s Clean Power Plan. We then examine the spatial distribution of the co-benefits and costs, and the implications of a range of cost assumptions in the implementation year of 2020. Nationwide, the total health co-benefits were $29 billion 2010 USD (95$2.3 to $68 billion), and net co-benefits under our central cost case were$12 billion (95% CI: -$15 billion to$51 billion). Net co-benefits for this case in the implementation year were positive in 10 of the 14 regions studied. The results for our central case suggest that all but one region should experience positive net benefits within 5 years after implementation