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For structural design purposes, human-induced loads on pedestrian systems can be described by several simplified (i.e., deterministic equivalent-force models) or more complex computational approaches. Among others, the Spring-Mass-Damper (SMD), Single Degree of Freedom (SDOF) model has been elaborated by several researchers to describe single pedestrians (or groups) in the form of equivalent body mass m, spring stiffness k and damping coefficient c. For all these literature SMD formulations, it is proved that the biodynamic features of walking pedestrians can be realistically reproduced, with high computational efficiency for vibration serviceability assessment of those pedestrian systems mostly sensitive to human-induced loads (i.e., with vibration frequency f1 < 8 Hz). Besides, the same SMD proposals are characterized by mostly different theoretical and experimental assumptions for calibration. On the practical side, strongly different SMD input parameters can thus be obtained for a given pedestrian. This paper focuses on a selection of literature on SMD models, especially on their dynamic effects on different structural floor systems. Four different floors are explored (F#1 and F#2 made of concrete, F#3 and F#4 of glass), with high- or low-frequency, and/or high- (>1/130th) or low- (1/4th) mass ratio, compared to the occupant. Normal walking scenarios with frequency in the range fp = 1.5–2 Hz are taken into account for a total of 100 dynamic simulations. The quantitative comparison of typical structural performance indicators for vibration serviceability assessment (i.e., acceleration peak, RMS, CREST) shows significant sensitivity to input SMD assumptions. Most importantly, the sensitivity of structural behaviours is observed for low-frequency systems, as expected, but also for low-mass structures, which (as in the case of glazed floor solutions) can be characterized by the use of lightweight modular units with relatively high vibration frequency. As such, major attention can be required for their vibrational analysis and assessment.

We construct Functional Connectivity Networks (FCN) from resting state fMRI (rsfMRI) recordings towards the classification of brain activity between healthy and schizophrenic subjects using a publicly available dataset (the COBRE dataset) of 145 subjects (74 healthy controls and 71 schizophrenic subjects). First, we match the anatomy of the brain of each individual to the Desikan- Killiany brain atlas. Then, we use the conventional approach of correlating the parcellated time series to construct FCN and ISOMAP, a nonlinear manifold learning algorithm to produce low-dimensional embeddings of the correlation matrices. For the classification analysis, we computed five key local graph-theoretic measures of the FCN and used the LASSO and Random Forest (RF) algorithms for feature selection. For the classification we used standard linear Support Vector Machines. The classification performance is tested by a double cross-validation scheme [consisting of an outer and an inner loop of “Leave one out” cross-validation (LOOCV)]. The standard cross-correlation methodology produced a classification rate of 73.1%, while ISOMAP resulted in 79.3%, thus providing a simpler model with a smaller number of features as chosen from LASSO and RF, namely the participation coefficient of the right thalamus and the strength of the right lingual gyrus.

Among the different welding technologies, portable welding guns are one of the most critical devices in relation to human exposure to electromagnetic fields. This paper focuses on medium frequency (MF) direct current guns proposing two actions aimed to the mitigation of the magnetic field generated during the welding process. The first action consists in the adoption of a passive shield for the on-board MF transformer. The analysis points out that the transformer alone produces a magnetic field that can exceed the prescribed limits. Therefore, a suitable mitigation system is identified. The second action aims to mitigate the predominant magnetic field that is generated by the electrodes of the welding gun. The analysis of the field waveforms shows that the rise time of the welding current pulse is the main parameter affecting the exposure index. The effect of the increase of the rise time is investigated through experimental and numerical analyses. The results prove that a small increase of the rise time causes a significant reduction of the exposure level. It is noteworthy that the two mitigation actions can be adopted on both existing and newly developed welding guns as they do not require any structural modification of the welding device.

We address a numerical methodology for the approximation of coarse-grained stable and unstable manifolds of saddle equilibria/stationary states of multiscale/stochastic systems for which a macroscopic description does not exist analytically in a closed form. Thus, the underlying hypothesis is that we have a detailed microscopic simulator (Monte Carlo, molecular dynamics, agent-based model etc.) that describes the dynamics of the subunits of a complex system (or a black-box large-scale simulator) but we do not have explicitly available a dynamical model in a closed form that describes the emergent coarse-grained/macroscopic dynamics. Our numerical scheme is based on the equation-free multiscale framework, and it is a three-tier procedure including (a) the convergence on the coarse-grained saddle equilibrium, (b) its coarse-grained stability analysis, and (c) the approximation of the local invariant stable and unstable manifolds; the later task is achieved by the numerical solution of a set of homological/functional equations for the coefficients of a polynomial approximation of the manifolds.

Point fixed glass facade systems have been used to fulfill the requirements for high transèarency in modern structures, technological developments in glass production lead to an extent worldwide use. Nevertheless, structural designers face a void in regard to standardization for the current design practices, even for typical loads. Moreover, the overall response under seismic actions is not yet fully studied. This paper explores the seismic performance of bolted point fixed laminated glass facades fixed with stainless steel spider arms. The study focused on the dissipative capacity of the system, and the influence of the spider clearances on the installation phase to accommodate the lateral drift, by allowing horizontal translation of the panels for in-plane loads. The characterization involves numerical models developed in ABAQUS software, benchmarked with ongoing experimental research.

The present manuscript deals with the seismic vulnerability assessment of existing masonry churches, which is a fundamental process for risk and consequent prioritization analyses, as well as application of effective retrofitting strategies. In the past, different approaches with various levels of accuracy and application ranges have been developed to assess the vulnerability to damage of such structures in case of seismic events. Based on the classification provided in the Italian Guidelines for the Cultural Heritage, in this paper a review of seismic vulnerability assessment methodologies for existing masonry churches is presented. The main goal of the current study is to provide a critical comparative overview about these procedures, highlighting the main issues related to the application of each detail level. Moreover, particular attention is focused on the applications present in literature, allowing for the definition of a potential systematic procedure for smart management policy aimed at preserving cultural, architectural and historical heritage.

We investigate a behavioral epidemic model including a partially effective vaccination at all ages. The vaccination is information-dependent, in the sense that the vaccination rate of susceptibles depends on the current and the past information available about the disease prevalence in the population. The weight given to the past history is described by an exponential kernel. The proposed model presents both the possibility of backward bifurcation and that of oscillations triggered by behavioral memory. Furthermore, a forward hysteresis scenario may take place where multiple endemic states are possible when the basic reproduction number P 0 is greater than one. Finally, a stable endemic state may destabilize via Hopf bifurcation not only when P 0 > 1 but also when P 0 1 , depending on the interplay between some relevant information-related parameters.

The paper presents a general theoretical framework to investigate the dynamic behavior of rotating doubly-curved shell structures made of Functionally Graded Materials (FGMs). A clear advancement of the present formulation is the possibility to apply a rotating speed (angular velocity) about a general axis of the global reference system. It is important to underline that this aspect is innovative with respect to the previous studies proposed in the literature, in which the angular velocity is only applied about the revolution axis the shell. Furthermore, several Higher-order Shear Deformation Theories (HSDTs) are used to investigate the problem at issue. The results of various numerical applications are presented to discuss the effect of the choice of the axis of rotation, as well as the geometric features of the shells, on the dynamic response of the structures. In particular, the analyses are performed to evaluate the critical value of rotating speed, which define the stiffness reduction of the structure. A five-parameter power law is developed to define the variation of the mechanical properties of the FGMs along the thickness of the structures. The accuracy of the current formulation, which includes the effects of both Coriolis and centripetal accelerations, is verified by means of the comparison with the results available in the literature. The solutions are carried out numerically by means of an efficient tool that allows to solve the strong formulation of the governing equations.

The Seismic Microzonation of level 3 (SM3) is nowadays a world-wide accepted tool for the mitigation of seismic risk. The SM3 is a complex process involving different disciplines ranging from Geology and Applied Seismology to Structural and Geotechnical Engineering. The outcome of a SM3 is presented on a zoning map in terms of a selected ground shaking intensity parameter and susceptibility to main ground instability (soil liquefaction, settlements, landslides, fault ruptures). In an advanced SM3 study for a given area, four main interdisciplinary steps can be recognized: (1) definition of the reference input motions, (2) construction of the subsoil model, (3) performing of numerical analyses and computing of amplification factors, (4) identification of zones with different geotechnical hazard potential and drawing up of the SM3 map. After the 2016–2017 Central Italy seismic sequence, intensive studies have been performed to obtain SM3 maps in 137 municipalities most damaged by the earthquakes. The aim of these studies has been to obtain a clear background on site effects to perform a correct reconstruction of the municipalities. In the paper, main results and critical issues of the above-mentioned steps of SM3 procedure are discussed together with some remarks on the use of SM3 output in supporting seismic design for reconstruction.

In this paper we present a minimal integrated environment-economic growth model. The accumulations of capital and pollution are connected by reciprocal feedbacks. Pollution is an undesirable but inevitable by-product of production, whose efficiency is hindered by pollution. The nexus between pollution and production is embodied in a damage function. The evolution of capital is enriched by the specific technology adopted here, an S -shaped production function. The model dynamics is represented by a couple of nonlinear differential equations, whose long run behavior gives rise to multiple stationary points. A global analysis underlines the importance of a meditated choice of the relevant policy parameters. Pollution induced poverty traps emerge for low level of saving ratio and share of abated emission. Periodic behaviour of the economic and environmental variables represents an early signal of the imminent risk of being trapped in an unsatisfactory level of economic performance. Numerical examples corroborate the theoretical results of the paper.

Landslides in pyroclastic soils are among the most calamitous natural phenomena causing damage to people and territory every year. The mechanisms underpinning such landslides can be controlled by multiple factors, including site conditions and features of pyroclastic soils. Spatial variations of textural characteristics and related hydro-mechanical features in the overlain pyroclastic layers can yield to relevant effects on water infiltration, with potential formation of capillary barriers at the interface between different soil layers. A better knowledge of the key triggering factors, based on engineering-geological modeling, may be carried out through a detailed field and laboratory measurements, as well as performing numerical simulations. The area surrounding Palma Campania (Napoli, Italy) is largely affected by fast-moving landslides involving pyroclastic deposits. The volcanoclastic sequence is constituted upward by (white and grey) vesicular pumices and (black) dense scoriae levels, associated with the Somma-Vesuvius “Pomici di Base” Plinian eruption (22 ka). Stratigraphic sections along the carbonate slopes of Vallone Lupici reveal failure surfaces along various pyroclastic contact layers (white/gray vesicular pumice and dark dense scoria layers). Representative samples were collected at different stratigraphic heights and analyzed to define structural and textural characteristics; the obtained data were used as input parameters to perform 2D numerical simulations to explore the propagation of hydraulic front under different conditions of water flow (flow rate) and textural features of rocks. The obtained results allow us to put constrains on capillary barriers development in function of soils characteristic and rain fall intensity.

In the present paper, a concentrated-parameter model is presented, in order to simulate the behavior of a climatic chamber suitably designed for testing tracked and wheeled tractors. Reference is made to standard-severe winter conditions (–18°C), i.e., the tractor dissipates thermal power in a climatic chamber that reproduces winter temperature and humidity conditions. The software package Matlab-Simulink is utilized and the system under investigation consists of 5 blocks. The dynamic modeling first covers a 10 hours period to reach the prescribed conditions for the climatic test chamber. Then, after this preparation period, the tractor’s engine is supposed to work. The simulations show that higher values of the adduction coefficient are preferable since they allow obtaining quickly, and with a lower heating power, the desired comfort conditions for the machine’s cabin.

A large portion of the Italian building heritage is made of masonry construc-tions, which were erected in the first decades of the last century and were conceived to support gravitational loads only. Many research activities have been carried out in order to propose retrofitting techniques aimed at improving seismic behaviour of existing ma-sonry buildings. The present paper focuses on the CAM® reinforcing system. Such a retrofitting technique, which is widely used in Italy, consists in the application of pre-tensioned stainless steel ribbons on existing masonry walls, conferring to them addi-tional strength, ductility and beneficial confinement effects. The preliminary outcomes of a common research activity developed in cooperation between the University of Cam-pania “Luigi Vanvitelli”, the University of Palermo, the University of Messina and the EDILCAM® Sistemi Srl, aimed at setting up appropriate design criteria, are provided in this paper. In particular, the calibration procedure of a specific FEM numerical model developed by Abaqus is presented, which then has been applied to interpret the cyclic response of unreinforced and reinforced masonry walls previously tested in within the research project In.CAM.M.I.N.O.

The importance of internal environmental conditions in a wine cellar is well known and investigated. The process of wine preparation consists in several steps, where temperature and humidity play a fundamental role, since the quality of the final products is strongly affected by constant and suitable environmental conditions. However, various critical factors have emerged, such as mold growth or wine losses, where ventilation has proved to be insufficient or poorly designed. Considering these, the addiction of a mechanical ventilation system, consisting in a perforated tube provided by a small fan, has been considered to support the possible lack of natural ventilation. The comparison between the two cellar congurations has been carried out through CFD modeling of the indoor air and temperature distributions in the room, in two different periods of the year when the natural ventilation is differently performed.

In practice, structures of pallet racks are characterized by very wide options of beam-to-column connections. The up to date part of the standard Eurocode 3 considers details for the design of connections. However, experimental determination of the joint properties in steel pallet racks is the most reliable process, since it takes into account an inability to develop a general analytical model for the design of these connections. In this paper, a test procedure for the behavior of beam-to-column connections is presented and the results are analyzed according to the procedure defined in the relevant design codes. With aim to avoid expensive experiments to determine structural properties of different types of connections, a polynomial model and a corresponding numerical model were developed to be used for simulating the experiment. After verification, the developed analytical and numerical model can be applied for investigation of various combinations of beam-to-column connections.

Railway infrastructure operators need to push their network capacity up to their limits in high-traffic corridors. Virtual coupling is considered among the most relevant innovations to be studied within the European Horizon 2020 Shift2Rail Joint Undertaking as it can drastically reduce headways and thus increase the line capacity by allowing to dynamically connect two or more trains in a single convoy. This paper provides a proof of concept of Virtual coupling by introducing a specific operating mode within the European rail traffic management system/European train control system (ERTMS/ETCS) standard specification, and by defining a coupling control algorithm accounting for time-varying delays affecting the communication links. To that aim, we define one ploy to enrich the ERTMS/ETCS with Virtual coupling without changing its working principles and we borrow a numerical analysis methodology used to study platooning in the automotive field. The numerical analysis is also provided to support the proof of concept with quantitative results in a case-study simulation scenario.

We localize the sources of brain activity of children with epilepsy based on electroencephalograph (EEG) recordings acquired during a visual discrimination working memory task. For the numerical solution of the inverse problem, with the aid of age-specific MRI scans processed from a publicly available database, we use and compare three regularization numerical methods, namely the standardized low resolution brain electromagnetic tomography (sLORETA), the weighted minimum norm estimation (wMNE) and the dynamic statistical parametric mapping (dSPM). We show that all three methods provide the same spatio-temporal patterns of differences between the groups of epileptic and control children. In particular, our analysis reveals statistically significant differences between the two groups in regions of the parietal cortex indicating that these may serve as "biomarkers" for diagnostic purposes and ultimately localized treatment.

Large magnitude earthquakes have historically caused devastating damage to engineered structures as a result of permanent ground deformations induced by soil liquefaction (e.g. 1964 Niigata earthquake, 1995 Kobe earthquake, 2010–2011 Christchurch earthquakes). A relevant amount of such damages is directly connected to liquefaction induced lateral spreading. This paper deals with the capacity of concrete framed structures with shallow foundations to handle lateral spreading demands. A simplified force–displacement compatible model was developed to capture the loads on the shallow foundations and estimate the performance of the building. The key parameters of foundation embedment, foundation width and shear length of the pillar, as well as soil friction angle were identified as having a strong influence on the expected performance. The developed model was used to develop probabilistic fragility curves for a class of buildings representing two to five storeys reinforced concrete buildings. Field measurements from existing literature of the liquefaction induced lateral displacement demand from the the September 4, 2010 (Mw 7.1) and the February 22, 2011 (Mw 6.2) Canterbury (New Zealand) earthquakes along the Avon River were probabilistically quantified in relation to the distance from the river. Finally, the displacement demand and fragility curves were used to estimate the probability of exceeding the considered limit states as a function of the distance from the river.

Intact rock bridges have been recognised as of critical importance in the stability of rock slopes but still remain a poorly understood and challenging engineering problem both in respect to their measurement and their incorporation into design analyses. The objective of this paper is not to provide conclusive answers as to the definition and measurement of rock bridges, and the manner that they can be accounted for in rock slope stability analysis. Rather, we highlight important and as yet unanswered questions to allow review of fundamental rock bridge concepts and then proceed to provide new insight into how rock bridges may be incorporated into slope stability analysis. Early definitions of what constitute a rock bridge are somewhat limited, and the authors suggest that they could be improved by including important constraints such as “block forming potential” and “block kinematics”. In this context, this paper introduces an improved terminology (RBij) commonly used by the discrete fracture network (DFN) community to define rock bridge intensity relative to the sampling region. In rock engineering, the measurement of rock bridges is exacerbated by the fact that rock bridges are not visible unless the rock mass is exposed by human activities or by natural events such as rockfalls. This constitutes a major problem for engineering design scenarios, since it would not be possible to validate any assumption made with respect to extent of rock bridges without performing some form of field testing or back-analysis. The results of a of the Finite-Discrete numerical analysis are presented to support our conclusions with respect to the limitations current methods used to characterise rock bridge strength. The role of scale effects, block theory, kinematics and what we term “negative rock bridges” in stability analysis is discussed.

Detecting and tracking events from logging data is a critical element for security and system administrators and thus attracts more and more research efforts. However, there exists a major limitation in current processes of Event Logging analysis, related to the verbosity and language-dependence of messages produced by many logging systems. In this paper, a novel methodology was proposed to tackle this limitation by analysing event messages through a Natural Language Processing task in order to annotate them with semantic metadata. These metadata are further used to enable semantic searches or domain ontology population that help administrator to filter only relevant event and to correlate them for a prompt and efficient response and incident analysis.

Purpose The purpose of this paper is to analyze the thermal and fluid dynamic behaviors of mixed convection in air because of the interaction between a buoyancy flow and a moving plate induced flow in a horizontal no parallel-plates channel to investigate the effects of the minimum channel spacing, wall heat flux, moving plate velocity and converging angle. Design/methodology/approach The horizontal channel is made up of an upper inclined plate heated at uniform wall heat flux and a lower adiabatic moving surface (belt). The belt moves from the minimum channel spacing section to the maximum channel spacing section at a constant velocity so that its effect interferes with the buoyancy effect. The numerical analysis is accomplished by means of the finite volume method, using the commercial code Fluent. Findings Results in terms of heated upper plate and moving lower plate temperatures and stream function fields are presented. The paper underlines the thermal and fluid dynamic differences when natural convection or mixed convection takes place, varying minimum channel spacing, wall heat flux, moving plate velocity and converging angle. Research limitations/implications The hypotheses on which the present analysis is based are two-dimensional, laminar and steady state flow and constant thermo physical properties with the Boussinesq approximation. The minimum distance between the upper heated plate of the channel and its lower adiabatic moving plate is 10 and 20 mm. The moving plate velocity varies in the range 0-1 m/s; the belt moves from the right reservoir to the left one. Three values of the uniform wall heat flux are considered, 30, 60 and 120 W/m2, whereas the inclination angle of the upper plate θ is 2° and 10°. Practical implications Mixed convection because of moving surfaces in channels is present in many industrial applications; examples of processes include continuous casting, extrusion of plastics and other polymeric materials, bonding, annealing and tempering, cooling and/or drying of paper and textiles, chemical catalytic reactors, nuclear waste repositories, petroleum reservoirs, composite materials manufacturing and many others. The investigated configuration is used in applications such as re-heating of billets in furnaces for hot rolling process, continuous extrusion of materials and chemical vapor deposition, and it could also be used in thermal control of electronic systems. Originality/value This paper evaluates the thermal and velocity fields to detect the maximum temperature location and the presence of fluid recirculation. The paper is useful to thermal designers.

We present a systematic approach to the construction of starting procedures for general linear methods (GLMs) of order p and stage order q = p . Order conditions for starting procedures based on the generalized Runge–Kutta (RK) are derived using the theory of rooted trees, elementary differentials, and elementary weights, and examples of generalized RK formulas are given up to the order p = 4 .

This paper introduces a study on twisted viscoelastic beams, having considered fractional calculus to capture the viscoelastic behaviour. Further another novelty of this paper is extending a recent numerical approach, labelled line elementless method (LEM), to viscoelastic beams. The latter does not require any discretization neither in the domain nor in the boundary. Some numerical applications have been reported to demonstrate the efficiency and accuracy of the method.

Linear friction welding (LFW) is a solid-state joining process used to weld non-axisymmetric components. Material joining is obtained through the reciprocating motion of two specimens undergoing an axial force. During this process, the heat source is determined by the frictional work transformed into heat. This results in a local softening of the material and plays a key role in the onset of the bonding conditions. In this paper, a critical analysis of the different approaches used to simulate the LFW processes is provided. The focus of the paper is the comparison of different modeling strategies and the most relevant outputs available, i.e. temperature, strain and stress distribution, material flow, axial shortening and residual stress. Major issues arising due to the complexity of the process are discussed, highlighting strengths and weaknesses of each approach.

International audience; We introduce a class of preconditioners for general sparse matrices based on the Birkhoff-von Neumann decomposition of doubly stochastic matrices. These precondi- tioners are aimed primarily at solving challenging linear systems with highly unstructured and indefinite coefficient matrices. We present some theoretical results and numerical experiments on linear systems from a variety of applications.; Nous introduisons une classe de préconditionnement pour matrices creuses générales fondées sur la décomposition de Birkhoff–von Neumann des matrices bistochastiques. Ces préconditionnements visent principalement à résoudre des systèmes linéaires difficiles dont les matrices sont non-structurées et non-définies. Nous présentons quelques résultats théoriques et des expériences numériques pour des systèmes linéaires issus de tout un ensemble d’applications.

Since the 1980s, a Business District is located in the eastern area of Naples. The first pioneer studies carried out in this area showed that a significant variability of site amplification can be predicted due to the morphology of seismic bedrock and to the presence of vanishing lenses of peat. More recently, the seismic vulnerability of the New Law Court was assessed adopting the hypothesis of 1D conditions for the seismic response analysis. This paper aims at verifying the reliability of this assumption, evaluating the 2D seismic site response of a representative geological section. Geotechnical characterization of the soil deposits has been carried out by integrating the available experimental data with literature data. Two suites of accelerograms have been considered as input motions, representative of ‘near field’ and ‘far field’ seismic events. Equivalent linear and non-linear 2D analyses have been carried out through a finite element and a finite difference code, respectively. Results provide insights on the non-linear soil behaviour of peat and allow for recognizing the limits and advantages of both adopted approaches. Finally, the comparison between the results of 2D and 1D analyses allows for highlighting the effects of focalization of seismic waves on the amplification of the ground motion at the surface.

The aim of the paper is to provide quantitative elements on the mechanisms that controlled the slope instabilities occurred after two major recent eruptions at Stromboli volcano (i.e. 2002-2003 and 2007). After a brief description of the geological setting and of the largest well documented instability phenomena on volcano flanks, the main objective is pursued using three-dimensional stress-strain analyses for modelling the effects of the magma intrusion on the stability of the volcano flank. Modelling is based on the results of an extensive geotechnical characterization of the volcaniclastic and lava materials. The numerical analyses investigate the influence of different paths and geometry of magma intrusion as well as the spatial variation of mechanical properties. As a result, favourable conditions for specific failure modes are identified. The stress-strain analyses show that magma intrusion can cause both a local failure of a wedge immediately downslope from the dyke or deep-seated movement involving large part of the slope; these two mechanisms were consistent with the deformative patterns observed during the 2007 and 2002-2003 eruptions, respectively. The magma thrust induces shear strains up to levels associated to appreciable grain crushing even below the sea level, where flow liquefaction can be invoked to explain the occurrence of past submarine slides. The submarine landslide is analysed by a combined finite element - limit equilibrium approach that demonstrates that instability conditions can develop if the loading exerted by the upper portion of the slope is sufficiently fast to produce undrained conditions. The analyses also support the hypothesis that at the 2002 subaerial failure occurred, due to combined effects of a magma mild thrust and the removal of the toe support caused by the preceding submarine slide. (C) 2019 Elsevier B.V. All rights reserved.

Combining the effects of transvascular and interstitial fluid movement with the structural mechanics of a tissue is necessary to properly analyze processes such as nutrient transport in a tumor cell. Furthermore, externally induced heat loads can play a role: for example, cryoablation can be performed by means of hypothermia and hyperthermia can be induced in order to treat some kinds of tumors such as liver tumor. Recently, the study of the effects of hypo-and hyperthermia on fluid flow and mass transport in biological systems by considering the fluid–structure interaction has gained researchers’ attention. In this paper, fluid flow in a tumor mass is analyzed at the macroscopic scale by considering the effects of both solid tissue deformation and temperature via hypo-and hyperthermia. Governing equations are averaged over a representative elementary volume of the living tissue, and written by means of the thermo-poroelasticity theory. Darcy’s law is used to describe fluid flow through the interstitial space, while transvascular transport is described with a generalized Starling’s law. The effects of hypo-and hyperthermia on the living tissue are included with a source term in the tissue momentum equation that considers thermal expansion. This term can be either negative or positive, i.e., hypo-or hyperthermia is herein considered. Governing equations with the appropriate boundary conditions are solved with the finite-element commercial code COMSOL Multiphysics in the steady-state regime. The numerical model is validated with analytical results from previously published results for an isothermal case. Results are presented in terms of pressure, velocity, and temperature fields for various thermal loads and the effects of hypo-and hyperthermia on various physical parameters are analyzed.

Thermal energy storage systems have increasingly attracted researchers and engineers in the last decades, not only because they permit to overcome the mismatch between thermal energy supply and demand in solar thermal systems, but also because they have the potential to improve the power grid reliability and flexibility, as they allow, for example, to store the heat or the cooling energy produced by residential electric heat pumps for a later use. In this context, this work analyses the cooling energy charging and discharging of two different cold thermal energy storage units, based on the use of a phase change material (PCM), by numerical simulation. One unit consists of an aluminum cylindrical container partially filled with a biological PCM. The other one is similar, with the only difference that it also includes an aluminum metal foam immersed in the PCM. Two different 2D axisymmetric models have been developed, both based on the effective heat capacity method in order to account for the PCM latent heat, for the numerical simulation of the two different units, and the numerical results are compared with experimental ones, obtained by means of a climatic chamber, in order to assess, in each case, the best set of the model arbitrary parameters among the considered ones. Moreover, for each simulation model, a sensitivity analysis is performed to show the effects of two arbitrary model parameters on the numerical results. Simulation results relative to the unit with only the PCM indicate that the cooling energy charging is most affected by conductive heat transfer, and in particular by the thermally resistive layer of solid PCM that forms at the lateral wall of the aluminum container, and that heat transfer by free convection plays a crucial role in the cooling energy discharging process. As concerns the unit with the PCM and the aluminum foam, numerical results show that the charging process and the discharging one are about four times and two times faster than without the foam, respectively. Furthermore, numerical results show that, with the employed aluminum foam, free convection within the PCM is negligible in both the cooling energy charging and discharging process.

The absorption inverse, studied in Jacobsen and Tien (2018) [13] , is a generalized inverse specifically introduced for the analysis of graphs with absorption. In this paper we consider numerical methods for the efficient computation of the absorption inverse and related quantities. Both direct and iterative methods are developed. We also consider different centrality measures for graphs with absorption, as well as fast updating/downdating techniques. Numerical experiments show that computations on graphs with up to 36 million edges can be performed quickly on a standard laptop.

In this paper, motivated by applications to multigrid, we present families of anisotropic, bivariate, interpolating and approximating subdivision schemes. We study the minimality and polynomial generation/reproduction properties of both families and Holder regularity of their prominent representatives. From the symbols of the proposed subdivision schemes, we define bivariate grid transfer operators for anisotropic multigrid methods. We link the generation/reproduction properties of subdivision to the convergence and optimality of the corresponding multigrid methods. We illustrate the performance of our subdivision based grid transfer operators on examples of anisotropic Laplacian and biharmonic problems.

The resolution of inverse problems is a quite common task in the diagnostic processes based on electromagnetic field measurements, in particular when internal characteristics of the object under test are to be estimated from external measurements. This class of problems are well known to be ill posed, and a number of different techniques have been proposed to make the estimation process reliable. In this paper, with reference to an application in the framework of low frequency magnetic fields measurements, the effects of different choices for the degrees of freedom are discussed, with the aim of improving the solution reliability.

Within the framework of the displacement-based virtual element method (VEM), namely, for plane elasticity, an important topic is the development of optimal techniques for the evaluation of the stress field. In fact, in the classical VEM formulation, the same projection operator used to approximate the strain field (and then evaluate the stiffness matrix) is employed to recover, via constitutive law, the stress field. Considering a first-order formulation, strains are locally mapped onto constant functions, and stresses are piecewise constant. However, the virtual displacements might engender more complex strain fields for polygons, which are not triangles. This leads to an undesirable loss of information with respect to the underlying virtual stress field. The recovery by compatibility in patches, originally proposed for finite element schemes, is here extended to VEM, aiming at mitigating such an effect. Stresses are recovered by minimizing the complementary energy of patches of elements over an assumed set of equilibrated stress modes. The procedure is simple, efficient, and can be readily implemented in existing codes. Numerical tests confirm the good performance of the proposed technique in terms of accuracy and indicate an increase of convergence rate with respect to the classical approach in many cases.

In the modelling of electromagnetic scattering in a Through-the-Wall environment large domains made by walls, and sparse targets are involved. Approximated models based on ray-tracing techniques are mostly employed to reduce computer times, although a more accurate response that takes account of all the interactions between walls and targets may be obtained with full-wave methods. In this work, the Cylindrical Wave Approach is employed, as full-wave technique for the modelling of Through-the-wall scenarios. The technique is mainly analytical, as targets with circular cross-section are modelled through expansions into cylindrical waves. However, through suitable rules, it is possible to approximate targets with cross-section of arbitrary shape through an arrangement of smaller circular cross-section cylinders. This may be applied, for example, to the modelling of pieces of furniture, as wall as to introduce further walls in the simulation domain.

We perform one and two-parameter numerical bifurcation analysis of a mechanotransduction model approximating the dynamics of mesenchymal stem cell differentiation into neurons, adipocytes, myocytes and osteoblasts. For our analysis, we use as bifurcation parameters the stiffness of the extracellular matrix and parameters linked with the positive feedback mechanisms that up-regulate the production of the YAP/TAZ transcriptional regulators (TRs) and the cell-substrate adhesion area. Our analysis reveals regimes of hysteresis and multistability, stable oscillations of the effective adhesion area, the YAP/TAZ TRs and the PPAR γ receptors associated with the adipogenic fate, as well as homoclinic bifurcations that interrupt high-amplitude oscillations abruptly. The two-parameter bifurcation analysis of the Andronov–Hopf points that give birth to the oscillating patterns predicts their existence for soft extracellular substrates ( 1 k P a ), a regime that favours the neurogenic and the adipogenic cell fate. Furthermore, in these regimes, the analysis reveals the presence of homoclinic bifurcations that result in the sudden loss of stable oscillations of the cell-substrate adhesion towards weaker adhesions and high expression levels of the gene encoding Tubulin beta-3 chain, thus favouring the phase transition from the adipogenic to the neurogenic fate.

The heat rejection of industrial plants is often made with evaporative condensers as their choice meets energy efficiency requirements. In this work some numerical simulations of the evaporative condenser heat and mass transfer processes were carried out at the tube scale: 2D and 3D approaches were performed using the Ansys Fluent R.16.2 (VOF model). The time resolved characteristics of the film flow process were studied and two different types of flow (stable film and drops mode) were investigated, by varying the water-to-air mass flow ratio. The decrease of the water-to-air mass flow ratio was found that led to the film break-up into droplets. An experimental test rig was designed and built up for future validation works and to give designers new relations to quantify heat transfer performance depending on real working conditions.

This paper presents a mathematical approach to model the effects of phenomena with random nature such as turbulence and fire-spotting into the existing wildfire simulators. The formulation proposes that the propagation of the fire-front is the sum of a drifting component (obtained from an existing wildfire simulator without turbulence and fire-spotting) and a random fluctuating component. The modelling of the random effects is embodied in a probability density function accounting for the fluctuations around the fire perimeter which is given by the drifting component. In past, this formulation has been applied to include these random effects into a wildfire simulator based on an Eulerian moving interface method, namely the Level Set Method (LSM), but in this paper the same formulation is adapted for a wildfire simulator based on a Lagrangian front tracking technique, namely the Discrete Event System Specification (DEVS). The main highlight of the present study is the comparison of the performance of a Lagrangian and an Eulerian moving interface method when applied to wild-land fire propagation. Simple idealised numerical experiments are used to investigate the potential applicability of the proposed formulation to DEVS and to compare its behaviour with respect to the LSM. The results show that DEVS based wildfire propagation model qualitatively improves its performance (e.g., reproducing flank and back fire, increase in fire spread due to pre-heating of the fuel by hot air and firebrands, fire propagation across no fuel zones, secondary fire generation, \dots). Though the results presented here are devoid of any validation exercise and provide only a proof of concept, they show a strong inclination towards an intended operational use. The existing LSM or DEVS based operational simulators like WRF-SFIRE and ForeFire respectively can serve as an ideal basis for the same., Accepted for publication in Commun. Nonlinear Sci. Numer. Simulat

In this paper, the frictional two-dimensional contact in the presence of a surface crack in a functionally graded coating substrate system is studied for rigid circular and flat stamps. A computational method based on finite difference (FD) is developed to evaluate the contact stresses and also the fracture parameters, which are KI and KII due to mixed mode fracture. The FD method applied here, uses a mapping technique which enable the analysis to consider any geometry of the punch and the crack. The Coulomb's dry friction law is considered in the contact area. The advantage of this study, compared to the efforts done by other researchers, is the ability to analysis a system with any arbitrary material properties distribution. Here, the elastic material properties distribution is estimated by TTO model which takes into account the interaction between the constituting phases as well, and the Poisson's ratio is assumed to be constant. The effect of material nonhomogeneity, the interaction of the constituting phases, the thickness of the graded coating layer, the size of the punch and the coefficient of friction is studied. In a general case, the findings of this research show that increasing the size of the punch, the coefficient of friction and the thickness of the graded layer increase the contact force and hence the contact stress; however, the interaction of the constituting phases does not have any effects on the contact parameters. In frictionless contact, the stress intensity factor is negative. In addition, increasing the coefficient of friction increases KI but decreases KII. These results are valid for any materials properties distribution.

We present a discrepancy-like stopping criterium for iterative regularization methods for the solution of linear discrete ill-posed problems. The presented criterium terminates the iterations of the iterative method when the residual norm of the computed solution becomes less or equal to the residual norm of a regularized Truncated Singular Value Decomposition (TSVD) solution. We present two algorithms for the automatic computation of the TSVD residual norm using the Discrete Picard Condition. The first algorithm uses the SVD coefficients while the second one uses the Fourier coefficients. In this work, we mainly focus on the Conjugate Gradient Least Squares method, but the proposed criterium can be used for terminating the iterations of any iterative regularization method. Many numerical tests on some selected one dimensional and image deblurring problems are presented and the results are compared with those obtained by state-of-the-art parameter selection rules. The numerical results show the efficiency and robustness of the proposed criterium.