PBF-LB Process-Induced Regular Cavities for Lightweight AlSi10Mg Structures

In powder bed fusion with laser beam (PBF-LB), two process-induced defects by pore formation are known: local spherical pores by the keyhole effect and geometrically undefined pores caused by lack of fusion. Both pore types are heterogeneously distributed and can be used for lightweight or damping design applications. The achievable porosity is limited to around 13%. This article presents a novel process-controlled method enabling the targeted and reproducible manufacturing of solid parts with regularly distributed cavities, currently up to 60% porosity in AlSi10Mg, using the balling effect. This eliminates the need for time-consuming digital pre-processing work.

Mitigating Display Fragmentation in the Electronic Health Record with the MedWISER Composable Approach: A Mixed Methods Design (Preprint)

BACKGROUND Navigational complexity can present formidable challenges for electronic health record (EHR) users. The fragmented design of conventional EHRs can contribute to increased cognitive load for clinician users and poor fit-to-task. First, the ‘keyhole effect’ describes the phenomenon in which due to the large volume of information and limited screen size, users cannot see all information on the same screen (like only seeing part of a large room through a small keyhole). Needed information is spread across several screens, creating fragmented displays and information. This can increase cognitive load – or the use of limited working memory resources – as users must navigate to a screen, identify useful information, and then hold that information in working memory as they navigate to another screen. For clinicians navigating EHRs, this has consequences for patient care as cognitive resources (perception, attention, and memory) are known to be limited. As clinicians expend more cognitive resources navigating and processing information from an EHR, they have fewer cognitive resources for patient care tasks and diagnostic reasoning, leading to possible error. Additionally, two key contextual factors in healthcare settings need to be addressed by EHRs to enable better fit-to-task: (1) clinicians often communicate information via patient records, thus the EHR needs to facilitate that communication; and (2) physicians are prone to interruptions as part of their workflow, which can lead to errors or omissions in perceiving information. Reducing fragmentation in EHR design has the potential to reduce cognitive load and enhance fit-to-task for clinician users. OBJECTIVE Introduce a novel composable approach to EHR design implemented as MedWISER, a composable system where users can freely assemble needed information on the same screen, thus reducing fragmentation. This study protocol introduces methods by which to assess MedWISER’s potential to address the keyhole effect and poor fit-to-task problems by reducing cognitive load, enhancing communication, and mitigating the impact of workflow interruptions. METHODS This multi-study project will involve qualitative and quantitative methods to evaluate how conventional EHRs and the composable approach affect clinician performance. Methods include think-aloud protocols, task completion, simulation studies, screen capture and eye tracking, and interviews and surveys. Key measures include time to complete tasks, error detection/omission, completeness of information review, and gaze direction. Subjects will be clinicians from large university hospital settings. RESULTS This project is supported by the Agency for Healthcare Research and Quality. Data collection and analysis is anticipated to conclude in Spring 2021. CONCLUSIONS Together these studies allow investigators to successfully investigate a range of challenges and contexts associated with EHR design, cognitive load, safety, and fit-to-task and evaluate the usefulness of the composable EHR design in meeting them. CLINICALTRIAL The following is not a clinical trial.

Steel Sheets Laser Lap Joint Welding—Process Analysis

This article presents the results of steel-sheet lap-joint-welding using laser beam radiation. The use of a laser beam and keyhole effect for deep material penetration in lap joint welding was presented. Thermodynamic mechanism of laser welding is related to material properties and process parameters. Estimation of welding parameters and joint properties’ analysis was performed through numerical simulation. The article presents a possibility of modeling laser lap-joint welding by using Simufact Welding software based on Marc solver and thermo-mechanical solution. Numerical calculation was performed for surface and conical volumetric heat sources simulating laser absorption and keyhole effect during steel sheet welding. Thermo-mechanical results of fusion zone (FZ), heat-affected zone (HAZ) and phase transformations calculated in numerical simulation were analyzed. The welding parameters for partial sealed joint penetration dedicated for gas piping installations were estimated from the numerical analysis. Low-carbon constructional steel was used for numerical and experimental analyses. A trial joint based on the estimated parameters was prepared by using a CO2 laser. Numerical and experimental results in the form of hardness distributions and weld geometry were compared. Metallographic analysis of the obtained weld was presented, including crystallographic structures and inclusions in the cross section of the joint.

The New Heat Source Model of AZ31B Magnesium Alloy Laser-TIG Hybrid Welding

A new heat source model consisted of inverted conical heat source and rotary Gauss body heat source is established using the CAE software for the keyhole effect of laser-TIG hybrid welding. The inverted conical heat source is used for analyzing the wide upper part of weld pool due to the rapid heat up by the laser and arc. The rotary Gauss body heat source model is used for analyzing the long and narrow lower part of weld pool formed by the laser. The result showed that, compared with other single source mode, this new heat source model may get a better simulation of the weld pool morphology, especially the inflection point near the keyhole. It provides a new method to predict the morphology and size of the weld pool of magnesium alloy laser-TIG welding.

Induction-assisted laser welding taking into account phase changes

Purpose The paper aims to describe the modeling of the induction-assisted laser welding process taking into account the keyhole effect and phase changes in the material. Design/methodology/approach A sophisticated mathematical model of the above heat treatment process is presented, taking into account the above phenomena and all available nonlinearities of the material. Its numerical solution is carried out using the finite element method incorporating algorithms for the deformation of geometry and solution of the flow field. Findings Unlike various simplified models solved in the past, this approach incorporating a sophisticated model of heat transfer and flow of melt is able to reach a very accurate solution, differing only by a small error (not more than 8 per cent) from the experiment. Research limitations/implications The presented model does not consider several subtle phenomena related to the evaporation of metal after irradiation of the material by a laser beam. In fact, at the heated spot, all three phases of the material coexist. The evaporated metal forms a capillary leak off and forms a cloud above the spot of irradiation. Due to the absorption of laser power in this cloud, the process of heating decelerates, which leads to a decrease in the process efficiency. Practical implications The presented model and methodology of its solution may represent a basis for design of the process of laser welding. Originality/value The main value is the proposal of numerical model for solution a complex multiphysical model with respecting several physical phenomena whose results are available in a short time and still with a good agreement with the experimental verification.

SOLAR ABSORBER WITH A STRUCTURED SURFACE – A WAY TO INCREASE EFFICIENCY

The basic idea of a solar absorber’s thermal gain increase is the keyhole effect utilization during which the radiation is absorbed by multiple reflections on cavity walls. The lattice of pyramidal or conical cavities on the solar absorber surface can be formed to create a structured surface leading to its overall absorptivity increase and to a reduction of the surface absorptivity dependence on the solar radiation incident beam angle changes caused by the daily and annual solar cycles. This contribution concludes the results of simulations of the effect of cavity geometry, geographical position and absorber orientation on its thermal gain with respect to the technological manufacturability of cavities. Furthermore, the real construction of the absorber with a structured surface using laser welding and parallel hydroforming is briefly described.

Molecular epidemiology and clonality of Acinetobacter spp in a Lebanese hospital over a period of one year

Introduction: The worldwide emergence of antimicrobial resistance in Acinetobacter spp and their clonal dissemination call for the investigation into Acinetobacter spp epidemiology. Methodology: 100 nonrepetitive Acinetobacter spp isolates were recovered from patients admitted at Saint- George-Hospital-University-Medical-Center-Beirut, in a one-year period. Identification of the isolates was determined by the API20NE and confirmed by PCR amplification of blaOXA-51-like. Susceptibility to carbapenems and colistin were determined by the microdilution method and interpreted according to the CLSI, 2015.The β lactamase inhibitors: PBA, EDTA, and Cloxacillin were used for the detection of KPC, MBL and AmpC, respectively. ESBL producers were detected whenever a keyhole effect was observed between 3rd generation cephalosporin and Augmentin®. Simplex PCR was conducted for the genotypic detection of β lactamases. ERIC and 3LST-PCR were performed to determine the clonality of the isolates. Results: Our findings showed that 84% were carbapenem resistant. Only one isolate was resistant to colistin. Phenotypically, 23 were ESBL, 15 KPC, 5 AmpC, and 4 MBL producers. PCR analysis showed that 99%, 93%, 77% and 3 % of the isolates harbored blaOXA-51-like, blaADC, blaOXA-23-like, and blaOXA-40-like, respectively. ERIC-PCR analysis showed that A.baumannii isolates were clustered in 19 possibly related and 30 closely related subtypes. The 3-LST-PCR showed that 86.2% of the A.baumannii isolates pertained to the ICII (international clone II). Conclusion: Our study showed a predominance of OXA-23-like producers and dissemination of ICII. Inhibitor based method was shown not to be accurate for the prediction of carbapenemases in Acinetobacter spp. Infection control measures are needed for management of Acinetobacter spp infections.