Transverse Circular Holes in Cylindrical Tubes Loaded in Traction and in Flexion: A New Analytical Approximation of the Stress Concentration Factor

This paper presents an analytic formula for the theoretical stress concentration factor kt for cylindrical tubes with transverse circular holes, loaded in traction or in flexion. The study is based on modern finite element (FEM) techniques, which allow for appreciating with great accuracy the phenomenon of stress concentration. A comparison between the FEM results of this paper and those that were obtained by the existing analytic formulas shows the need of an update, as some discrepancies may be noticed. Our results are the fruit of a wide campaign of numerical FEM simulations that have been conducted analyzing numerous geometric configurations of the tube. Moreover, these configurations are defined in a wider two-dimensional (2-D) domain than the one valid for previous analytic formulas published in literature. Finally, these FEM results have been approximated with great accuracy by means of a fourth degree double polynomial regression that led to the new analytic formula that is proposed in this paper

Delirium symptoms duration and mortality in SARS-COV2 elderly: results of a multicenter retrospective cohort study

BACKGROUND: Since the occurrence of the SARS-COV2 pandemic, there has been an increasing interest in investigating the epidemiology of delirium. Delirium is frequent in SARS-COV2 patients and it is associated with increased mortality; however, no information is available on the association between delirium duration in SARS-COV2 patients and related outcomes. AIMS: The aim of this study is to investigate the association between the duration of delirium symptoms and in-hospital mortality in older patients with SARS-COV2 infection. METHODS: Retrospective cohort study of patients 65 years of age and older with SARS-CoV 2 infection admitted to two acute geriatric wards and one rehabilitation ward. Delirium symptoms duration was assessed retrospectively with a chart-based validated method. In-hospital mortality was ascertained via medical records. RESULTS: A total of 241 patients were included. The prevalence of delirium on admission was 16%. The median number of days with delirium symptoms was 4 (IQR 2–6.5) vs. 0 (IQR 0–2) in patients with and without delirium on admission. In the multivariable Cox regression model, each day with a delirium symptom in a patient with the same length of stay was associated with a 10% increase in in-hospital mortality (Hazard ratio 1.1, 95% Confidence interval 1.01–1.2; p = 0.03). Other variables associated with increased risk of in-hospital death were age, comorbidity, CPAP, CRP levels and total number of drugs on admission. CONCLUSIONS: The study supports the necessity to establish protocols for the monitoring and management of delirium during emergency conditions to allow an appropriate care for older patients. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s40520-021-01899-8

Books’ Impact in Digital Social Reading: Towards a Conceptual and Methodological Framework

The aim of this panel is to debate the challenges and opportunities offered by online reviews for measuring the impact that books can have on readers (Boot and Koolen, 2020). The focus is specifically on culture- and language- specificity, thus we will compare insights from the analysis of Korean, English, Italian, German, and Dutch reviews. Digital social reading platforms – like Goodreads, Lovelybooks, or Naver Books – host millions of reviews and, thus, offer unique possibilities for research into literature, reading, and reader response (Rebora et al., 2021; Walsh and Antoniak, 2021). Computational tools are especially relevant, given the large amount of available data, but finding associations between textual features, cultural conventions (e.g. genre), and cognitive, affective, and aesthetic responses is not a straightforward task (Koolen et al., 2020; Pianzola et al., 2020). By comparing research done with different platforms, datasets, and languages, we aim at improving the methods that we employ, in a dialogue involving both data-driven insight and theoretical reflection on literature and readers. Questions that we will address are: what aspects of a book’s impact on readers can reviews help us to measure? What are the limitations of online book reviews for studying impact? How do we know to what extent these review texts reflect the actual reading experiences? What are unwanted, confounding influences (e.g. reviewers projecting a favourable self-image, socially desired responses, aspects of identity formation, fake reviews). How do online book reviews differ from experimentally controlled gathering of reader responses (lab studies, questionnaires, psychologically validated scales) (Lendvai et al., 2020)? How do platforms for reviewing and social interactions around books influence reviewers and their perceptions? How do reviewers compare to other readers? To answer such questions, we will present four case studies dealing with different languages and cultures, followed by an open discussion of the results and methods, reflecting on their generalizability, efficacy and limitations

Study of an intrinsically safe infrastructure for training and research on nuclear technologies

Within European Partitioning & Transmutation research programs, infrastructures specifically dedicated to the study of fundamental reactor physics and engineering parameters of future fast-neutron-based reactors are very important, being some of these features not available in present zero-power prototypes. This presentation will illustrate the conceptual design of an Accelerator-Driven System with high safety standards, but ample flexibility for measurements. The design assumes as base option a 70MeV, 0.75mA proton cyclotron, as the one which will be installed at the INFN National Laboratory in Legnaro, Italy and a Beryllium target, with Helium gas as core coolant. Safety is guaranteed by limiting the thermal power to 200 kW, with a neutron multiplication coefficient around 0.94, loading the core with fuel containing Uranium enriched at 20% inserted in a solid-lead diffuser. The small decay heat can be passively removed by thermal radiation from the vessel. Such a system could be used to study, among others, some specific aspects of neutron diffusion in lead, beam-core coupling, target cooling and could serve as a training facility

Finite Element Analysis of Dynamically Loaded Journal Bearings: Influence of the Bolt Preload

An improved FEM model was developed to simulate the elastic behavior of a connecting rod bearing, accounting for the displacements caused by the tightening torque applied to the bolts that join the cap and the rod. These initial displacements are added to the pressure induced displacements, to enhance the solution of the elastohydrodynamic bearing lubrication problem. The big end bearing of a marine diesel engine was modeled and analyzed under combustion process loads and inertia loads using the Newton-Raphson method together with the Murty’s algorithm. Some important differences between these results and other results published for the same bearing without the bolt preload are identified and discussed.</jats:p

Steadily loaded journal bearings: Quasi-3D mass\u2013energy-conserving analysis

A finite-element approach to thermoelastohydrodynamic lubrication analysis is developed by extending a previous mass- and energy-conserving algorithm to include wall-convection boundary conditions, groove-mixing theory, and thermo-mechanical deformations. To this end, the cross-film-averaged energy equation is coupled with the heat conduction equations relevant to the bearing sleeve and the journal by fitting the temperature profile across the film thickness with a fourth-order polynomial. A finite-element condensation technique is used to reduce the unknowns in heat conduction equations in the bush and in the journal to the temperatures of the sleeve surface and journal axis, respectively. Applied to the analysis of steadily loaded journal bearings, the proposed method shows good agreement with published experimental results and incurs low computational cost

A Nonlinear Structure Based Elastohydrodynamic Analysis Method for Connecting Rod Big End Bearings of High Performance Engines

Big end bearings of connecting rods for high performance automotive engines are quite compliant and exhibit relatively large deformations at high rotation speed. Nowadays numerical simulation provides good estimate of tribological parameters for bearings operating in severe, but not extreme elastohydrodynamic lubrication conditions. At very high rotation speed regimes, reliable previsions are achieved only if an effort to increase the accuracy of structural modeling is accomplished. A finite element model able to account for the nonlinear friction controlled sliding phenomena occurring at the junction surface between the cap and the body of the rod has been developed. A new method to solve the coupled equations governing the interaction between the hydrodynamic fluid model and the nonlinear structural model of the connecting rod bearing is presented, together with a simple application example

Influence Of Some Design Parameters On The Thermal Performance Of Domestic Refrigerator Appliances

A one dimensional dynamic model of an active reciprocating magnetic regenerator (AMR) was developed and a parametric analysis on its behavior was carried out. The main hypothesis assumed in the 1D model are: ideal magneto caloric effect, no heat leakages outwards, constant fluid thermo physical properties, uniform temperature in both the solid matrix and in the fluid at each cross section of the AMR. The geometry of the AMR and a standard set of working conditions and parameters are defined according to the size and operating conditions of a prototype under construction at the University of Genoa. A parametric investigation is carried out, in order to evaluate the influence of the operating parameters operating frequency and fluid mass flow rate, that is the parameters that can be tuned in a given device. Simulations show that for a given temperature span (temperature difference between hot and cold thermal sources) these parameters can be tuned to obtain an optimal behavior

Prestazioni termiche ed energetiche di congelatori Hot-Wall: simulazione numerica e verifica sperimentale

none3A. REBORA; SENAREGA M.; TAGLIAFICO L.Rebora, Alessandro; Senarega, M.; Tagliafico, LUCA ANTONI