Applicability of an orthogonal cutting slip-line field model for the microscale

Mechanical micromachining is a very flexible and widely exploited process, but its knowledge should still be improved since several incompletely explained phenomena affect the microscale chip removal. Several models have been developed to describe the machining process, but only some of them consider a rounded edge tool, which is a typical condition in micromachining. Among these models, the Waldorf’s slip-line field model for the macroscale allows to separately evaluate shearing and ploughing force components in orthogonal cutting conditions; therefore, it is suitable to predict cutting forces when a large ploughing action occurs, as in micromachining. This study aims at demonstrating how this model is suitable also for micromachining conditions. To achieve this goal, a clear and repeatable procedure has been developed for objectively validating its force prediction performance at low uncut chip thickness (less than 50 mm) and relatively higher cutting edge radius. The proposed procedure makes the model generally applicable after a suitable and nonextensive calibration campaign. This article shows how calibration experiments can be selected among the available cutting trial database based on the model force prediction capability. Final validation experiments have been used to show how the model is robust to a cutting speed variation even if the cutting speed is not among the model quantities. A suitable set-up, especially designed for microturning conditions, has been used to measure forces and chip thickness. Tests have been performed on 6082-T6 Aluminum alloy with different cutting speeds and different ratios between uncut chip thickness and cutting edge radius

Performance evaluation of polymer-filled metal fused filament fabrication tooling for profile extrusion

The application of additive manufacturing (AM) for tooling in the mould and die industry brings a disruptive potential in process performance, design flexibility and product enhancements. Maturing of existing AM technologies and emerging technologies such as metal-fused filament fabrication (metal FFF) can further support the applicability of AM tooling in polymer profile extrusion. This study provides a complete characterization of metal FFF 17–4 PH stainless-steel die inserts and evaluates their applicability in a polymer extrusion process chain. The presented experimental assessment pivots on the metrological characterization of the produced inserts and the impact of the insert characteristics on the final extrudates’ product. Considering a conventionally manufactured benchmark insert, produced via subtractive methods (CNC machining and electrical discharge machining), comparable results for AM tools in terms of extrudates’ quality and process repeatability are presented. It was found that despite significant higher average surface parameters for AM insert tools (Sa = 2–9 μm vs. Sa = 0.3–0.9 μm for dies manufactured by machining), a much smaller difference was observed in the resulting quality of polymer extrudates’ product. The roughness generation effect of polymer profile extrusion based on the different dies’ internal surface roughness topography and the effect on extrudates product was evaluated. Three-dimensional average roughness Sa on acrylonitrile butadiene styrene extrudate surfaces obtained from conventionally machined dies was in the range of 0.3 μm. For extrudates obtained from additively manufactured dies, their Sa was in the rage of 0.5 μm (despite the much higher surface roughness of FFF dies compared to machined dies). The results confirm that with suitable extrudates’ product requirement, it is feasible to apply metal FFF as the selected manufacturing method for tooling in polymer profile extrusion

On the temperature behavior of shunt-leakage currents in Cu(In,Ga)Se2 solar cells: The role of grain boundaries and rear Schottky contact

By comparing simulated and measured dark current-voltage (I-V) characteristics of CIGS cells at different temperatures, we investigate the temperature behavior of the shunt leakage current, and find that it can be explained by large donor trap concentrations at grain boundaries (GBs), and by a Schottky barrier at the backside contact where the GBs meets the anode metallization. We studied the I-V characteristics in the temperature range 280 K - 160 K achieving good fits of the measured I-V curves, especially for reverse bias and low forward bias, where the shunt leakage current dominates. The most important parameters determining the shunt leakage current value and its temperature dependence are the peak energy and density of the GB donor distribution, which control the inversion of GBs and the pinning of Fermi level at the anode/GB contact

The Agile Alert System For Gamma-Ray Transients

In recent years, a new generation of space missions offered great opportunities of discovery in high-energy astrophysics. In this article we focus on the scientific operations of the Gamma-Ray Imaging Detector (GRID) onboard the AGILE space mission. The AGILE-GRID, sensitive in the energy range of 30 MeV-30 GeV, has detected many gamma-ray transients of galactic and extragalactic origins. This work presents the AGILE innovative approach to fast gamma-ray transient detection, which is a challenging task and a crucial part of the AGILE scientific program. The goals are to describe: (1) the AGILE Gamma-Ray Alert System, (2) a new algorithm for blind search identification of transients within a short processing time, (3) the AGILE procedure for gamma-ray transient alert management, and (4) the likelihood of ratio tests that are necessary to evaluate the post-trial statistical significance of the results. Special algorithms and an optimized sequence of tasks are necessary to reach our goal. Data are automatically analyzed at every orbital downlink by an alert pipeline operating on different timescales. As proper flux thresholds are exceeded, alerts are automatically generated and sent as SMS messages to cellular telephones, e-mails, and push notifications of an application for smartphones and tablets. These alerts are crosschecked with the results of two pipelines, and a manual analysis is performed. Being a small scientific-class mission, AGILE is characterized by optimization of both scientific analysis and ground-segment resources. The system is capable of generating alerts within two to three hours of a data downlink, an unprecedented reaction time in gamma-ray astrophysics.Comment: 34 pages, 9 figures, 5 table

Results on MOVPE SiGeSn deposition for the monolithic integration of III-V and IV elements in multi-junction solar cells

Abstract In order to produce a step forward towards the monolithic integration of III-V and IV compounds in multijunction solar cells, a first assessment of SiGeSn deposition in a metal organic vapour phase epitaxy (MOVPE) chamber also used for III-V growth has been carried out. The study brings insights on several aspects of the MOVPE SiGeSn growth in order to get a better control of SiGeSn composition and to obtain epitaxial layers with improved morphology. In particular, it is shown that the gas source Si2H6 is more influenced by the growth temperature compared to GeH4 and SnCl4, moreover, its competition with SnCl4 makes it difficult to incorporate Si in SiGeSn, as SnCl4 partial pressure is increased. SiGeSn morphology is shown to be strongly dependent on temperature, As carry-over and growth rate. A new growth model is introduced in order to explain the importance of the adatom bond lengths in inhibiting tin segregation when SiGeSn is grown at relatively high growth temperatures (>480 °C). In order to investigate the photovoltaic behaviour of SiGeSn, a single-junction GaAs/InGaP/SiGeSn/Ge functional device has been manufactured and characterized by external quantum efficiency (EQE) and current-voltage measurements. The experimental and the simulated EQE show the higher absorption coefficient of SiGeSn with respect to Ge, which allows using SiGeSn layers with a thickness three times lower than Ge to produce the same photovoltaic current

Late thrombosis of a Transcatheter aortic valve: the border between a proactive and reactive management

BACKGROUND: Valve thrombosis - either biological or mechanical - is proved to increase patient's morbidity and mortality. No consensus exist on the best management in such cases. CASE PRESENTATION: We report the case of a 69-year-old man presenting with a late thrombosis of a transcatheter aortic valve who was medically managed until he acutely worsened, developing myocardial ischemia and cardiogenic shock. CONCLUSION: This unlucky case raises a word of caution about the safety of a reactive management

P2393Diagnostic accuracy of coronary CT angiography performed in 100 consecutive patients with coronary stents using a novel whole-organ high-definition CT scanner

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Multimodal approach to predict neurological outcome after cardiac arrest: A single-center experience

Introduction: The aims of this study were to assess the concordance of different tools and to describe the accuracy of a multimodal approach to predict unfavorable neurological outcome (UO) in cardiac arrest patients. Methods: Retrospective study of adult (>18 years) cardiac arrest patients who underwent multimodal monitoring; UO was defined as cerebral performance category 3-5 at 3 months. Predictors of UO were neurological pupillary index (NPi) 64 2 at 24 h; highly malignant patterns on EEG (HMp) within 48 h; bilateral absence of N20 waves on somato-sensory evoked potentials; and neuron-specific enolase (NSE) > 75 \u3bcg/L. Time-dependent decisional tree (i.e., NPi on day 1; HMp on day 1-2; absent N20 on day 2-3; highest NSE) and classification and regression tree (CART) analysis were used to assess the prediction of UO. Results: Of 137 patients, 104 (73%) had UO. Abnormal NPi, HMp on day 1 or 2, the bilateral absence of N20 or NSE >75 mcg/L had a specificity of 100% to predict UO. The presence of abnormal NPi was highly concordant with HMp and high NSE, and absence of N20 or high NSE with HMp. However, HMp had weak to moderate concordance with other predictors. The time-dependent decisional tree approach identified 73/103 patients (70%) with UO, showing a sensitivity of 71% and a specificity of 100%. Using the CART approach, HMp on EEG was the only variable significantly associated with UO. Conclusions: This study suggests that patients with UO had often at least two predictors of UO, except for HMp. A multimodal time-dependent approach may be helpful in the prediction of UO after CA. EEG should be included in all multimodal prognostic models

Accepted and presented at The Design of Medical Devices Conference (DMD2016)

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia and is a prognostic marker for stroke, heart failure, and even death Successful ablation therapy to terminate AF requires a highly reliable technique to determine ablation sites using raw intra-atrial electrograms of AF patients. Hence, there is a clear need for a robust spatiotemporal mapping technology that can accurately identify the rotor pivot points in a patient-specific manner, which is the motivation for this research. Recently, a novel entropy-based approach was used to identify the rotor pivot point using optical mapping data from rabbit heart [4]. This approach was also used to generate 3D Shannon entropy maps for a persistent AF patient using raw intra-atrial electrograms demonstrating the feasibility to identify rotor pivot points outside the pulmonary vein (PV) region. However, challenges still remain to robustly map and more precisely confirm the exact location of rotor pivot points for AF ablation. It is known that the DF of a rotor is the same throughout the entire spatial area occupied by the rotor and therefore cannot accurately identify the rotor pivot point. This method uses a Fourier transform to calculate the DF and is therefore limited to a single frequency. In contrast, we hypothesize that the chaotic nature of the rotor at the pivot point yields various frequency components. In this work, the authors propose and demonstrate a novel multiscale frequency (MSF) approach that takes into account the contribution from various frequencies to yield valuable information regarding the rotor pivot point, thus allowing for its identification. We validate the feasibility of this technique to identify the pivot point of rotors using optical mapping data from isolated rabbit hearts with induced ventricular tachycardia (VT). Methods Novel MSF Approach. Band-pass quadrature filters are robust for estimating local multiscale information, such as the energy, phase, radial frequency, and orientation/angular frequency. The Hilbert transform operation transforms a real-valued signal to analytic signal with no negative frequencies, and its utility with the quadrature filter can yield MSF information by weighting the various frequency components. In this work, eight log-Gabor/normal filters were designed and used with a relative filter bandwidth B of 2ͱ2, one octave apart as described in Ref. where q i is the output of the ith log-Gabor filter, and q 0 is the center frequency of the first log-Gabor filter Optical Mapping Data From Isolated Rabbit Hearts. Optical Optical mapping experiments were performed with IACUC approval on isolated rabbit hearts which were put in the Langendorffperfusion system, and voltage-sensitive dye di-4-ANEPPS (5 lg/mL) was added to the perfusate. After staining, 532 nm green laser was used to illuminate the epicardial surface of the heart. Fluorescence intensity was captured with two 12-bit CCD cameras, which run at 600 frames per second with 64 Â 64 pixel resolution. VT was induced via burst pacing, and phase movies of the rotors were obtained from optical mapping recordings. The phase movies from one rabbit heart with a known pivot point were used in this work, shown in Result

A systematic review investigating fatigue, psychological and cognitive impairment following TIA and minor stroke:protocol paper

Approximately 20,000 people have a transient ischemic attack (TIA) and 23,375 have a minor stroke in England each year. Fatigue, psychological and cognitive impairments are well documented post-stroke. Evidence suggests that TIA and minor stroke patients also experience these impairments; however, they are not routinely offered relevant treatment. This systematic review aims to: (1) establish the prevalence of fatigue, anxiety, depression, post-traumatic stress disorder (PTSD) and cognitive impairment following TIA and minor stroke and to investigate the temporal course of these impairments; (2) explore impact on quality of life (QoL), change in emotions and return to work; (3) identify where further research is required and to potentially inform an intervention study