Structural and Dimensional Analysis by Computed Tomography of a Multi Geometric Template Manufactured by Fused Deposition Modeling.

As a consequence of the development of AM, strategies have been developed to optimize the printing process, which focuses on reducing manufacturing time, such as using genetic algorithms (GAs), among others. The effect caused by the modification of path patterns is an effect of interest in two aspects: dimensional assurance focused on the compliance of the dimensions of the components in comparison with the digital design of the components, and the structural composition and resistance that the printing process itself can generate. This paper aims to present the effect of optimizing the path of fused filament fabrication (FFF) equipment on the dimensional finish and structural quality of a multi-geometric component using computed tomography. For this purpose, a template composed of 23 geometric elements, printed using FFF technology and PLA as the base material, is used. The results show an 11% reduction in the total process time required to print the component. The effect on the dimensional precision of different geometric elements was identified. In addition, it was possible to ensure that the structural quality of the multi-geometric component was not affected by the modification of the path required by the printing process.

Assessment of Gradient-Based Algorithm for Surface Determination in Multi-Material Gap Measurements by X ray Computed Tomography.

X-ray computed tomography is one of the most promising measurement techniques for the dimensional evaluation of industrial components. However, the inherent complexity of this technology also involves important challenges. One of them is to develop surface determination algorithms capable of providing measurement results with better accuracy in any situation-for example, for single and multi-material parts, inner and outer geometries, with and without image artefacts, etc.-and reducing user influence. The surface determination is particularly complex in the case of multi-material parts, especially when they are separated by small air gaps. In previous works, two gradient-based algorithms were presented, that showed less measurement variability throughout the whole part, and reduced the computational cost and operator influence compared to threshold-based algorithms. This work focuses on the evaluation of the performance of these algorithms when used in a scenario so complex that parts of it are made of one or more materials (metal-metal and polymer-metal) with gaps inside. For this purpose, a set of multi-material reference standards is used. The presented gradient-based algorithms show measurement errors comparable to commercial threshold-based algorithms, but with the capability of obtaining accurate measurements in smaller gaps, apart from reducing the user influence on the measurement process.

A Systematic Review and Meta-Analysis of the Effects of Food Safety and Hygiene Training on Food Handlers.

Foodborne diseases are a significant cause of morbidity and mortality worldwide. Studies have shown that the knowledge, attitude, and practices of food handlers are important factors in preventing foodborne illness. The purpose of this research is to assess the effects of training interventions on knowledge, attitude, and practice on food safety and hygiene among food handlers at different stages of the food supply chain. To this end, we conducted a systematic review and meta-analysis with close adherence to the PRISMA guidelines. We searched for training interventions among food handlers in five databases. Randomized control trials (RCT), quasi-RCTs, controlled before-after, and nonrandomized designs, including pre-post studies, were analyzed to allow a more comprehensive assessment. The meta-analysis was conducted using the random-effects model to calculate the effect sizes (Hedges's g) and 95% confidence interval (CI). Out of 1094 studies, 31 were included. Results showed an effect size of 1.24 (CI = 0.89-1.58) for knowledge, an attitude effect size of 0.28 (CI = 0.07-0.48), and an overall practice effect size of 0.65 (CI = 0.24-1.06). In addition, subgroups of self-reported practices and observed practices presented effect sizes of 0.80 (CI = 0.13-1.48) and 0.45 (CI = 0.15-0.76) respectively.

Assessing the Impact of Lean Healthcare on Inpatient Care: A Systematic Review.

Healthcare services are facing challenges in increasing their efficiency, quality of care, and coping with surges in demand. To this end, some hospitals have implemented lean healthcare. The aim of this systematic review is to evaluate the effects of lean healthcare (LH) interventions on inpatient care and determine whether patient flow and efficiency outcomes improve. The review was performed according to PRISMA. We used six databases to search for studies published from 2002 to 2019. Out of 5732 studies, 39 measuring one or more defined outcomes were included. Hospital length of stay (LOS) was measured in 23 studies, 16 of which reported a reduction, turnover time (TOT) decreased in six out of eight studies, while the turnaround time (TAT) and on-time starts (OTS) improved in all five and seven studies, respectively. Moreover, eight out of nine studies reported an earlier discharge time, and the boarding time decreased in all four cases. Meanwhile, the readmission rate did not increase in all nine studies. Lastly, staff and patient satisfaction improved in all eight studies. Our findings show that by focusing on reducing non-value-added activities, LH contributed to improving patient flow and efficiency within inpatient care.

Analysis of Surface Extraction Methods Based on Gradient Operators for Computed Tomography in Metrology Applications.

Among the multiple factors influencing the accuracy of Computed Tomography measurements, the surface extraction process is a significant contributor. The location of the surface for metrological applications is generally based on the definition of a gray value as a characteristic of similarity to define the regions of interest. A different approach is to perform the detection or location of the surface based on the discontinuity or gradient. In this paper, an adapted 3D Deriche algorithm based on gradient information is presented and compared with a previously developed adapted Canny algorithm for different surface types. Both algorithms have been applied to nine calibrated workpieces with different geometries and materials. Both the systematic error and measurement uncertainty have been determined. The results show a significant reduction of the deviations obtained with the Deriche-based algorithm in the dimensions defined by flat surfaces.

Experimental Approach for the Uncertainty Assessment of 3D Complex Geometry Dimensional Measurements Using Computed Tomography at the mm and Sub-mm Scales.

The dimensional verification of miniaturized components with 3D complex geometries is particularly challenging. Computed Tomography (CT) can represent a suitable alternative solution to micro metrology tools based on optical and tactile techniques. However, the establishment of CT systems' traceability when measuring 3D complex geometries is still an open issue. In this work, an alternative method for the measurement uncertainty assessment of 3D complex geometries by using CT is presented. The method is based on the micro-CT system Maximum Permissible Error (MPE) estimation, determined experimentally by using several calibrated reference artefacts. The main advantage of the presented method is that a previous calibration of the component by a more accurate Coordinate Measuring System (CMS) is not needed. In fact, such CMS would still hold all the typical limitations of optical and tactile techniques, particularly when measuring miniaturized components with complex 3D geometries and their inability to measure inner parts. To validate the presented method, the most accepted standard currently available for CT sensors, the Verein Deutscher Ingenieure/Verband Deutscher Elektrotechniker (VDI/VDE) guideline 2630-2.1 is applied. Considering the high number of influence factors in CT and their impact on the measuring result, two different techniques for surface extraction are also considered to obtain a realistic determination of the influence of data processing on uncertainty. The uncertainty assessment of a workpiece used for micro mechanical material testing is firstly used to confirm the method, due to its feasible calibration by an optical CMS. Secondly, the measurement of a miniaturized dental file with 3D complex geometry is carried out. The estimated uncertainties are eventually compared with the component's calibration and the micro manufacturing tolerances to demonstrate the suitability of the presented CT calibration procedure. The 2U/T ratios resulting from the validation workpiece are, respectively, 0.27 (VDI) and 0.35 (MPE), by assuring tolerances in the range of ± 20-30 µm. For the dental file, the EN < 1 value analysis is favorable in the majority of the cases (70.4%) and 2U/T is equal to 0.31 for sub-mm measurands (L < 1 mm and tolerance intervals of ± 40-80 µm).