A METHOD FOR THERMAL HISTORY PREDICTION DURING ADDITIVE MANUFACTURING USING FAR-FIELD TEMPERATURE MEASUREMENTS

Directed Energy Deposition is a near net-shape, additive manufacturing process that uses high-energy lasers for powder melting and consolidation. While a detailed knowledge of the thermal histories of the process can help understand and ultimately predict the resulting microstructure, residual-stresses, and/or material properties of the component, experimental limitations usually restrict all temperature measurements to far-field locations. When fixed, these measurements become increasingly removed from the laser/material interactions as the build process unfolds. To help offset this limitation, a relatively straightforward method using finite-elements and a fixed far-field measurement was developed that considers experimental processing conditions such as a moving heat source and relevant (and evolving) boundary conditions to generate more complete thermal histories. In essence, an inverse problem was iteratively solved using a direct computational approach. Once validated, the model was then used over multiple depositions with the outcome discussed relative to the agreement and disparities in peak temperatures, heating, and cooling rates. The increasing importance of the growing surface area and evolving radiative and convective boundary conditions with each layer was clearly demonstrate

Empirical pseudopotential and full-Brillouin-zone k*p electronic structure of CdTe, HgTe and HgCdTe

Two alternative approximations of the electronic structure of CdTe and HgTe are proposed, both suited to the needs of accuracy and numerical efficiency of full-band carrier transport simulation: a local empirical pseudopotential (EPM) parametrization including relativistic corrections, and an original full- Brillouin-zone (FBZ) k.p model using two expansion points (C and W). The EPM and k.p band structures closely match the available experimental and ab initio information, complemented with the results of new density functional theory (DFT)-local density approximation (LDA) calculations, for the conduction and valence bands relevant in transport phenomena. The EPM description of the binary compounds, featuring transferable Te pseudopotentials, is the basis for a computation of the electronic structure of the ternary alloy HgCdTe in the framework of disorder-corrected virtual crystal approximation. The composition dependence of energy gaps, effective masses, and high-frequency dielectric constants are discussed and compared with available experimental data, and the novel FBZ approach is applied to the case of x = 0.

High-dimensional Exploratory Item Factor Analysis by A Metropolis–Hastings Robbins–Monro Algorithm

stochastic approximation, SA, item response theory, IRT, Markov chain Monte Carlo, MCMC, numerical integration, categorical factor analysis, latent variable modeling, structural equation modeling,

Critical care usage after major gastrointestinal and liver surgery: a prospective, multicentre observational study

Background Patient selection for critical care admission must balance patient safety with optimal resource allocation. This study aimed to determine the relationship between critical care admission, and postoperative mortality after abdominal surgery. Methods This prespecified secondary analysis of a multicentre, prospective, observational study included consecutive patients enrolled in the DISCOVER study from UK and Republic of Ireland undergoing major gastrointestinal and liver surgery between October and December 2014. The primary outcome was 30-day mortality. Multivariate logistic regression was used to explore associations between critical care admission (planned and unplanned) and mortality, and inter-centre variation in critical care admission after emergency laparotomy. Results Of 4529 patients included, 37.8% (n=1713) underwent planned critical care admissions from theatre. Some 3.1% (n=86/2816) admitted to ward-level care subsequently underwent unplanned critical care admission. Overall 30-day mortality was 2.9% (n=133/4519), and the risk-adjusted association between 30-day mortality and critical care admission was higher in unplanned [odds ratio (OR): 8.65, 95% confidence interval (CI): 3.51–19.97) than planned admissions (OR: 2.32, 95% CI: 1.43–3.85). Some 26.7% of patients (n=1210/4529) underwent emergency laparotomies. After adjustment, 49.3% (95% CI: 46.8–51.9%, P<0.001) were predicted to have planned critical care admissions, with 7% (n=10/145) of centres outside the 95% CI. Conclusions After risk adjustment, no 30-day survival benefit was identified for either planned or unplanned postoperative admissions to critical care within this cohort. This likely represents appropriate admission of the highest-risk patients. Planned admissions in selected, intermediate-risk patients may present a strategy to mitigate the risk of unplanned admission. Substantial inter-centre variation exists in planned critical care admissions after emergency laparotomies