Predictive process parameter selection for Selective Laser Melting Manufacturing: applications to high thermal conductivity alloys

There is growing interest in Laser Powder Bed Fusion (L-PBF) or Selective Laser Melting (SLM) manufacturing of high conductivity metals such as copper and refractory metals. SLM manufacturing of high thermal conductivity metals is particularly difficult. In case of refractory metals, the difficulty is amplified because of their high melting point and brittle behaviour. Rapid process development strategies are essential to identify suitable process parameters for achieving minimum porosities in these alloys, yet current strategies suffer from several limitations. We propose a simple approach for rapid process development using normalized process maps. Using plots of normalized energy density vs. normalized hatch spacing, we identify a wide processability window. This is further refined using analytical heat transfer models to predict melt pool size. Final optimization of the parameters is achieved by experiments based on statistical Design of Experiments concepts. In this article we demonstrate the use of our proposed approach for development of process parameters (hatch spacing, layer thickness, exposure time and point distance) for SLM manufacturing of molybdenum and aluminium. Relative densities of 97.4% and 99.7% are achieved using 200 W pulsed laser and 400 W continuous laser respectively, for molybdenum and aluminium, demonstrating the effectiveness of our approach for SLM processing of high conductivity materials

ngsLD: evaluating linkage disequilibrium using genotype likelihoods

MOTIVATION: Linkage disequilibrium measures the correlation between genetic loci and is highly informative for association mapping and population genetics. As many studies rely on called genotypes for estimating linkage disequilibrium, their results can be affected by data uncertainty, especially when employing a low read depth sequencing strategy. Furthermore, there is a manifest lack of tools for the analysis of large-scale, low-depth and short-read sequencing data from non-model organisms with limited sample sizes. RESULTS: ngsLD addresses these issues by estimating linkage disequilibrium directly from genotype likelihoods in a fast, reliable and user-friendly implementation. This method makes use of the full information available from sequencing data and provides accurate estimates of linkage disequilibrium patterns compared to approaches based on genotype calling. We conducted a case study to investigate how linkage disequilibrium decays over physical distance in two avian species. AVAILABILITY: The methods presented in this work were implemented in C/C and are freely available for non-commercial use from https://github.com/fgvieira/ngsLD

PILOT APPRAISAL OF VARIABLES AMONG MEXICAN-AMERICANS FOR SOCIAL NETWORKS ANALYSIS

poster abstractHispanics in the USA often suffer poor oral health. More appropriate solutions may be designed if we move beyond the simplistic interpretation of poor oral outcomes being associated with 1-2 variables, e.g., language; such an approach has failed to provide consistent interpretations, and offers no points for intervention. We propose to examine a constellation of variables interwoven into multilevel strategies under a new(er) paradigm, social network theories (http://cmol.nbi.dk/models/infoflow/infoflow.html). Objectives: To qualitatively identify domains of variables modulating oral health outcomes among 1st-2nd generation MexicanAmerican immigrants. Methods: Through key informant interviews, we ascertained KAB variables in immigrant families originating in Jalisco, Mexico. This community has had a strong, revolving presence for decades in a well-delimited location in Indianapolis, IN, around St. Patrick’s parish. We did not conduct clinical exams but used questions from American national surveys to document health perceptions, availability of dental services/insurance, presence of dental pain and impaired function in adults and children, and family structure and sociodemographic profiles during a Catholic festival (no incentives, no appointments). Data were content-analyzed. Results: Data were collected from 22 parent-child dyads (15 female adults, 7 male; mean age 24±6.3yrs; data from the oldest child and the interviewee). Frequencies of dental emergencies and acute problems varied markedly, with recurrence patterns. A minority exhibited consistent dental attendance, often enabled by public/private dental insurance. Time in the USA varied considerably, with 1st and 2nd generation immigrant parents and children sharing the household. Occupations ranged from manual to clerical, and education from elementary to college among adults. Conclusion: Interviews were feasible and acceptable, and the experience informed future fieldwork considerations. We are using the variables to design a social networks study to characterize the evolution of patterns between families in Indianapolis and among peers living in Jalisco, aiming to measure impacts ascribable to immigration along acculturation spectra

IoT focused VHF and UHF propagation study and comparisons

As the market for internet of things (IoT) is growing and due to Ofcom's decision to reassign parts of the very high frequency (VHF) spectrum in the UK for IoT use, a propagation study has been conducted using the newly released VHF spectrum and the currently commercially operated ultra-high frequency (UHF) spectrum, in order to compare and contrast the suitability of the VHF spectrum for IoT use. The authors conducted their study in a number of different environments (rural, suburban, urban and dense urban), with measurement equipment deployed in a manner suitable for a portable IoT use case. Results are presented in comparison to other propagation studies available in the literature and widely used propagation models such as the Hata model. Shadowing and noise are also measured and examined. It is found that current propagation models do not provide adequate predictions within the considered use case, but found it is possible to calculate log-distance based models that provide good predictions. Path-loss is found to be constantly lower at VHF than UHF, but radio frequency noise is consistently higher. The newly released spectrum is found to be suitable for IoT deployments in all the examined environments

Candidates for a possible third-generation gravitational wave detector: comparison of ring-Sagnac and sloshing-Sagnac speedmeter interferometers

Speedmeters are known to be quantum non-demolition devices and, by potentially providing sensitivity beyond the standard quantum limit, become interesting for third generation gravitational wave detectors. Here we introduce a new configuration, the sloshing-Sagnac interferometer, and compare it to the more established ring-Sagnac interferometer. The sloshing-Sagnac interferometer is designed to provide improved quantum noise limited sensitivity and lower coating thermal noise than standard position meter interferometers employed in current gravitational wave detectors. We compare the quantum noise limited sensitivity of the ring-Sagnac and the sloshing-Sagnac interferometers, in the frequency range, from 5 Hz to 100 Hz, where they provide the greatest potential benefit. We evaluate the improvement in terms of the unweighted noise reduction below the standard quantum limit, and by finding the range up to which binary black hole inspirals may be observed. The sloshing-Sagnac was found to give approximately similar or better sensitivity than the ring-Sagnac in all cases. We also show that by eliminating the requirement for maximally-reflecting cavity end mirrors with correspondingly-thick multi-layer coatings, coating noise can be reduced by a factor of approximately 2.2 compared to conventional interferometers

Large well-relaxed models of vitreous silica, coordination numbers and entropy

A Monte Carlo method is presented for the simulation of vitreous silica. Well-relaxed networks of vitreous silica are generated containing up to 300,000 atoms. The resulting networks, quenched under the BKS potential, display smaller bond-angle variations and lower defect concentrations, as compared to networks generated with molecular dynamics. The total correlation functions T(r) of our networks are in excellent agreement with neutron scattering data, provided that thermal effects and the maximum inverse wavelength used in the experiment are included in the comparison. A procedure commonly used in experiments to obtain coordination numbers from scattering data is to fit peaks in rT(r) with a gaussian. We show that this procedure can easily produce incorrect results. Finally, we estimate the configurational entropy of vitreous silica.Comment: 7 pages, 4 figures (two column version to save paper