The tensile properties and the deformation microstructure of pearlitic steel (0.8 wt % C) have been quantified in wires drawn to strains in the range from 3.7 to 5.4, having a flow stress in the ...range from 3.5 to 4.5 GPa. With increasing strain the interlamellar spacing (ILS) decreases from about 20 to 10 nm and the thickness of the cementite lamellae decreases from about 2 nm to about 0.7 nm, representing a structure, which breaks up at large strains, decomposes and releases carbon to the ferrite lamellae. The dislocation density increases continuously with strain and reaches about 5 × 1016 m−2 at a strain of 5.4; the dislocations are stored as threading dislocations, as dislocation tangles and as cell boundaries with low to medium misorientation angles. An analysis of the evolution of microstructure and strength with increasing strain suggests that dislocation-based plasticity is a dominating mechanism in the wire and three strengthening mechanisms are applied: boundary strengthening, dislocation strengthening and solid solution hardening with their relative contributions to the total flow stress which change as the strain is increased. Based on linear additivity good correspondence between the calculated and the measured flow stress is observed over the strain range 0–5.4. However at large strains beyond 3.7 deviations are observed which are discussed in terms of the applied strength-structure relationships.
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The microstructure and chemical composition of a 316L stainless steel prepared by selective laser melting have been characterized using electron backscatter diffraction, transmission electron ...microscopy and atom probe tomography (APT). A multi-scale microstructure in the 316L stainless steel was observed in the as-built samples, consisting of equiaxed and columnar grains, dislocation cell blocks, dislocation cells, individual dislocations and nano-sized particles. The misorientations across dislocation cells were determined based on local crystallographic orientation measurements using a Kikuchi pattern method. The dislocation cells have very small misorientation angles with an average angle of 0.9°, and are arranged to form dislocation cell-blocks with cell-block boundary misorientation angles generally larger than 2°. APT data reveal that alloying elements are evenly distributed in the matrix as well as a high nitrogen content in the as-built material. Based on quantification of the microstructural parameters, good agreement is achieved between the yield strength as calculated from a linear sum of different strengthening contributions, and the experimentally measured value, with significant contributions from dislocation strengthening and solid solution strengthening effects.
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Anisotropy in mechanical properties is one of the critical issues in metal additive manufacturing (AM) impeding the wider application of parts fabricated using this manufacturing technique. In this ...work, the anisotropy in mechanical properties of an AlSi10Mg alloy fabricated by AM was investigated in terms of grain morphology, microstructure and residual stress distribution, with a focus on changes occurring during post-AM heat treatment by isochronal annealing. It was found that microstructural inhomogeneity is the major factor that weakens the melt pool boundaries, and leads also to anisotropic mechanical properties. Volumes in the vicinity of melt pool boundaries are characterized by coarse Al–Si eutectic networks and high residual stresses, where the former are the main reason for the plastic anisotropy, and the latter increase the local strength. Post-AM heat treatment can alleviate the presence of anisotropy due to homogenization of the microstructure and a redistribution of residual stresses. The overall effect of heat treatment on mechanical strength is a balance between improvement through precipitation strengthening and weakening of grain boundary strengthening, solid solution strengthening and dislocation strengthening. Through an appropriate heat treatment process (annealing at 280 °C for 2 h), the anisotropy in mechanical properties can be effectively reduced and a good strength-elongation synergy can be obtained (strength of 350 MPa and elongation of ∼9%). This study provides new ideas for understanding and mitigating anisotropy of additively manufactured AlSi10Mg, and also has implications for the study of anisotropy of other materials.
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•The anisotropy in mechanical properties of an AlSi10Mg alloy fabricated by AM was investigated, with a focus on changes occurring during post-AM heat treatment by isochronal annealing.•Microstructural inhomogeneity is the major factor that weakens the melt pool boundaries, and leads also to anisotropic mechanical properties.•Post-AM heat treatment can alleviate the presence of anisotropy due to homogenization of the microstructure and a redistribution of residual stresses.•A good strength-elongation synergy can be obtained (strength of 350 MPa and elongation of ∼9%) through an appropriate heat treatment process.•Strengthening behavior of the samples before and after heat treatment was discussed considering solid solution strengthening, dislocation strengthening, grain boundary strengthening, and precipitation strengthening.
This work discusses the implementation, capabilities, and validation of Shift, a massively parallel Monte Carlo radiation transport package authored at Oak Ridge National Laboratory. Shift has been ...developed to scale well from laptops to small computing clusters to advanced supercomputers and includes features such as support for multiple geometry and physics engines, hybrid capabilities for variance reduction methods such as the Consistent Adjoint-Driven Importance Sampling methodology, advanced parallel decompositions, and tally methods optimized for scalability on supercomputing architectures. The scaling studies presented in this paper demonstrate good weak and strong scaling behavior for the implemented algorithms. Shift has also been validated and verified against various reactor physics benchmarks, including the Consortium for Advanced Simulation of Light Water Reactors' Virtual Environment for Reactor Analysis criticality test suite and several Westinghouse AP1000® problems presented in this paper. These benchmark results compare well to those from other contemporary Monte Carlo codes such as MCNP5 and KENO.
This meta-analytic review is an update to the first meta-analysis of battering interventions (Babcock et al., 2004) and includes 59 studies that evaluated treatment efficacy for domestically violent ...men and women. The outcome literature of controlled quasi-experimental and experimental studies was reviewed to test the relative impact of Duluth, cognitive-behavioral therapy (CBT), and novel types of treatment on subsequent recidivism of violence. The first model examines studies comparing interventions to no treatment control conditions. The second model compares novel interventions to treatment as usual (i.e., the Duluth curriculum). Study design and type of treatment were tested as moderators in both models. Consistent with previous meta-analyses, effect sizes were in the small range, smaller in true experiments as compared to quasi-experimental designs when recidivism was based on partner or police reports. However, new experiments comparing novel treatments to the Duluth curriculum reveal effect sizes comparable to when comparing novel interventions to an untreated comparison group. Novel interventions, including Acceptance and Commitment Therapy and Circles of Peace had the largest effect sizes when put head-to-head with Duluth control groups. Future research directions include testing moderators and mechanisms of change of the battering interventions that work. Implications for evidence-based practice in criminal justice include broader implementation and continued testing of these novel interventions with demonstrated efficacy in stopping intimate partner violence.
•This review of 59 controlled outcome studies on battering interventions reveals small but significant effects on recidivism of physical abuse.•True experiments yield smaller effect sizes than do quasi-experimental studies.•The efficacy of “Other” interventions has improved whereas the efficacy for Duluth curriculum groups have not.•New interventions, including Acceptance and Commitment Therapy and Circles of Peace, outperform Duluth groups.•These efficacious interventions should be disseminated, implemented, and further tested for feasibility and effectivenss.
To estimate the relative risk (RR) of developing methicillin-resistant Staphylococcus aureus (MRSA) or vancomycin-resistant Enterococcus (VRE) colonization or infection within 30 days of ambulance ...transport.
We performed a retrospective cohort study of patients with a principal diagnosis of chest pain presenting to our emergency department (ED) over a 4-year period. Patients were included if they presented from and were discharged to nonhealthcare locations without being admitted. Encounters were stratified by arrival mechanism: ambulance versus private vehicle. We performed propensity score matching and multivariable logistic regression to estimate the RR for the primary outcome.
In total, 321,229 patients had ED encounters during the study period. After applying inclusion criteria and propensity score matching, there were 11,324 patients: 3,903 in the ambulance group and 7,421 in the unexposed group. Among them, 12 patients (0.11%) had the outcome of interest, including 9 (0.08%) with MRSA and 3 (0.03%) with VRE. The 30-day prevalence of MRSA or VRE was larger in the ambulance group than in the unexposed group: 8 (0.20%) and 4 (0.05%), respectively (P = .02). Patients who presented to the ED via ambulance were almost 4 times more likely to have MRSA or VRE within 30 days of their encounter (RR, 3.72; 95% CI, 1.09-12.71; P = .04).
Our cohort study is the first to demonstrate an association between ambulance exposure and pathogen incidence, representing the first step in evaluating medical-transport-associated infection burden to eventually develop interventions to address it.
Pearlitic steel wire, with a representative sub-100 nm lamellar structure, is the strongest mass-produced steel with an excellent combination of formability and strength. This overview summarises ...investigations of cold-drawn pearlitic steel wire in the last decades, covering the microstructural evolution and strengthening mechanisms. Based on quantitative structural parameters, this overview covers a quantitative and extensive analysis of structure–strength relationships. By focusing on the structure, challenges and future strategy are outlined to further improve the mechanical behaviour and performance of pearlitic steel wire to widen its use in society.
This is part of a thematic issue on Pearlitic Steel Wires.
VERA core simulator capabilities to predict spent fuel decay heat have been explored. The comparison with the Serpent2 and NEWT/TRITON sequence from the SCALE package, performed on the NPP Krško fuel ...test cases, has enabled independent verification of the successful implementation of the VERA depletion/decay calculation sequence applied on the extended nuclide set. Since the VERA is a 3-D core simulator, the focus in the rest of the paper was on the investigation of the 3-D effects and non-linearity of the soluble boron concentration averaging process, which are difficult to assess with most of available computational tools. A difference in the decay heat prediction between the 3-D and 2-D model approaches was analyzed. In addition, the impact of the Inconel grids on the decay heat was determined. Averaging the concentration of soluble boron over the fuel irradiation period has been found to be a viable approach, since it results in slight decay heat overprediction, which is considered conservative for most applications. Finally, demonstration on the Watts Bar Unit 1 cycle 1 depletion has shown formidable VERA capabilities to accurately predict spent fuel decay heat.
•Summarizes a realistic high burnup core design.•Used DOE tools to evaluate steady state and transient high burnup fuel performance.•Estimated total core mass susceptible to pulverization.•Evaluated ...pre-transient and transient fuel conditions (temperature and stress).
Vascular endothelial cells are highly glycolytic and consume relatively low amounts of oxygen (O₂) compared with other cells. We have confirmed that oxidative phosphorylation is not the main source ...of ATP generation in these cells. We also show that at a low O₂ concentration (<1%) endogenous NO plays a key role in preventing the accumulation of the a-subunit of hypoxia-inducible factor 1. At higher O₂ concentrations (1-3%) NO facilitates the production of mitochondrial reactive oxygen species. This production activates the AMP-activated protein kinase by a mechanism independent of nucleotide concentrations. Thus, the primary role of mitochondria in vascular endothelial cells may not be to generate ATP but, under the control of NO, to act as signaling organelles using either O₂ or O₂-derived species as signaling molecules. Diversion of O₂ away from endothelial cell mitochondria by NO might also facilitate oxygenation of vascular smooth muscle cells.
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