Continuum Analysis Research Articles

3D slope stability analysis of a limestone quarry expansion in Northern Italy

Slope stability is a crucial aspect in case in quarrying, both in term of legal and technical restrictions. The availability of data regarding the rock mass characterization is not sufficient to guarantee a satisfactory stability analysis, which must be assessed by means of more accurate procedures. Limit equilibrium analyses have been used since many decades, as they can give satisfactory results for simple cases, such as planar or wedge blocks. Nevertheless, when dealing with more complex cases, such as opencast quarries and mines, where the slope geometry consists on several benches plunging in different directions, this simplified approach cannot give a satisfactory answer. In this scenario, numerical models can return a much more complete and accurate assessment of the overall stability. The paper describes a possible approach to evaluate the stability of the slopes of a limestone opencast quarry in Northern Italy. The country is experiencing a growing demand of limestone for the production of cement for the construction sector and this determined the need to expand the previous exploitations. Since the quarry experienced several expansion plans throughout the years, several site investigation campaigns have been carried out and the results were not always consistent with each other. Starting from the two most recent rock mass characterizations and by using 3D numerical models, the overall stability has been simulated by means of continuum and discontinuum analyses, to obtain a reproduction of the real episodes of instabilities that occurred in the past. The implementation of models with reliable data is essential to obtain results that are comparable with the reality: this would allow to proceed more effectively and safely with the exploitation of the future slopes.

DEVELOPMENT OF COARSE-GRAINED MODELS OF LIQUID WATER BY DEEP NEURAL NETWORKS FOR SIMULATING ACOUSTIC VIBRATIONS OF NANOSTRUCTURES IN AQUEOUS ENVIRONMENT

Molecular-level simulation can effectively complement continuum analysis for the study on the damping mechanisms of acoustic vibrations of nanostructures in aqueous environment, which is central to the applications of nanostructures in high-sensitivity sensing and detection. It is highly desirable to develop coarse-grained (CG) water models that can accurately reproduce the density, compressibility, and viscosity of water simultaneously, for the molecular simulations of vibrations of nanostructures in water at affordable computational cost. In this work, the CG water models based on Lennard-Jones potential have been developed with each CG particle representing three and four water molecules. The deep neural networks have been trained using the data generated by CG molecular-dynamics simulations and used to solve the inverse problem of parameterization of the CG force fields for the target properties of water. As compared with many other existing CG models, the proposed CG water models are advantageous in terms of the ability to accurately predict the experimentally measured density, compressibility, and viscosity of water simultaneously, which is essentially important for the faithful molecular-level descriptions of the damping effect of the surrounding water on mechanical vibrations of nanostructures. Further comparisons suggest that the proposed three-to-one CG water model is a preferable option for molecular simulations of vibrations of nanostructures in water, due to its more accurate descriptions of target water properties.

Suspended water nanodroplets evaporation and its deviation from continuum estimations

Although droplets evaporation is fundamental to many applications and phenomena, accurate prediction of their evaporation trajectory is still a technological gap today. This is even more so for nanodroplets when compared to the macro-sized droplets. Since it is technically challenging to observe real nanodroplets evaporation today, this contribution uses full atomistic molecular dynamics simulations to observe and quantify suspended water nanodroplets evaporation. There are two main findings to this contribution. First, it is shown in detail that continuum analysis significantly over predicts the evaporation rate of nanodroplets. This makes continuum analysis unsuitable to predict water nanodroplets’ behavior. Secondly, this contribution illustrates the use of data-driven approach that can be used for nanodroplets evaporation behavior prediction, instead of running full atomistic molecular dynamics simulations for every different condition, which can be prohibitively expensive. The paper hopes to encourage scientists working in similar field to share their MD results for nanodroplets evaporation to build a data-driven model that could be used to predict nanodroplets evaporation trajectory at a fraction of the cost of full-scale MD simulations.

Crack mediated dislocation activities in Al/Ti nanolayered composites: an atomistic study

In this work, to understand crack propagation in Al/Ti nanolayered composites, a series of molecular dynamic simulations were performed with crack in different layers of the nanolayered composites and subjected to mode I loading. Nanolayered composite with a crack in Al layer, and monolithic Al show ductile fracture behavior that occurs by nucleation of Shockley partial dislocation at the crack tip. On the other hand, the fracture behavior in nanolayered composites with a crack in Ti shows crack bowing which is similar to the brittle fracture, and subsequent crack trapping at the interface. However, monolithic Ti shows typical cleavage fracture followed by activation of basal and pyramidal slip that blunts the crack leading to ductile fracture. When the crack is in the Ti layer, the other Ti layers in a nanolayered composite deform by prismatic and pyramidal slip. However, the Ti layer deforms only via slip on prismatic planes when the crack is in the Al layer. Critical strain energy release rate G c based continuum analysis predicts the fracture mode in monolithic Ti correctly, but it fails to predict the fracture mode in monolithic Al and nanolayered composites with crack in the Al layer. It is found that the G c determined based on external loading is marginally higher when the crack is in the Al layer as compared against the case when the crack is in the Ti layer. The G c value for the basal and pyramidal slip in Ti is higher than the G c value for cleavage. This poses an interesting phenomenon since the G c in monolithic Al is found to be much lower than that of monolithic Ti. The reason is attributed to the constrained plasticity in the presence of an Al/Ti interface.

Non-continuum effects on a squeezed gas film in a two-dimensional acoustic resonator

We study the effect of gas rarefaction and wall confinement on the propagation of vibroacoustic disturbances in a microchannel, generated by non-uniform (localized) time-harmonic oscillations of one of the channel walls. The problem is studied in the entire range of gas rarefaction rates, combining continuum and free-molecular limit analyses with direct simulation Monte Carlo calculations. Gas rarefaction is found to strongly increase the signal decay rate, varying between a slowly decaying propagating wave parallel to the channel walls at continuum conditions, to a near-source confined acoustic perturbation in the free-molecular regime. The impact of the stationary scattering wall is examined in detail, and the effect of replacing between fully diffuse and specular boundary reflections is found to slightly reduce the decay rate of the signal. The frequency dependence of the force generated by the gas film on the channel walls is calculated. Here, gas rarefaction smooths the transition between resonance and antiresonance behaviours observed in the continuum regime. A model set-up of a fully specular channel with a point delta source is examined, for which closed-form expressions are found for the effect of the stationary wall on the hydrodynamic perturbations and the acoustic force. These expressions assist in rationalizing the fundamental effect of the scattering wall on the system response.

Highlights of pion and kaon structure from continuum analyses

One of the biggest challenges in contemporary physics is understanding the origin and dynamics of the internal structure of hadrons which, at a fundamental level, is described by quantum chromodynamics (QCD). Taking great prominence amongst hadrons are pions and kaons which, despite being the lightest hadrons in nature, their very existence is intimately connected to those mechanisms responsible for almost all of the mass of the visible matter. In this manuscript we discuss many aspects of the pion and kaon structure via light front wave functions and generalized parton distributions, and a collection of other distributions and structural properties that are inferred therefrom.

Family Caregiving for People Living With Dementia During COVID-19: A Thematic Analysis.

This study examines the experiences and needs of family caregivers (FCGs) for people living with dementia (PLWD) during the coronavirus disease 2019 (COVID-19) pandemic. Six focus groups were conducted with 21 FCGs from across the care continuum and thematic analysis was used to illuminate FCGs descriptions of their experiences and needs. Three main themes were identified that highlight the disruption the pandemic caused for FCGs: changes in the caregiving role, information use and needs, and mental and physical health outcomes. To better support FCGs during COVID-19 and future public health emergencies, we recommend that (a) information is accessible, specific, and centralized; (b) resources are tailored to the caregiving dyad (FCG and PLWD) and creatively adapted to public health restrictions; and (c) opportunities for the caregiving dyad to receive physical, social, and emotional engagement and support are maintained.

Ionic Transport in Electrostatic Janus Membranes. An Explicit Solvent Molecular Dynamic Simulation.

Janus, or two-sided, charged membranes offer promise as ionic current rectifiers. In such systems, pores consisting of two regions of opposite charge can be used to generate a current from a gradient in salinity. The efficiency of nanoscale Janus pores increases dramatically as their diameter becomes smaller. However, little is known about the underlying transport processes, particularly under experimentally accessible conditions. In this work, we examine the molecular basis for rectification in Janus nanopores using an applied electric field. Molecular simulations with explicit water and ions are used to examine the structure and dynamics of all molecular species in aqueous electrolyte solutions. For several macroscopic observables, the results of such simulations are consistent with experimental observations on asymmetric membranes. Our analysis reveals a number of previously unknown features, including a pronounced local reorientation of water molecules in the pores, and a segregation of ionic species that had not been anticipated by previously reported continuum analyses of Janus pores. Using these insights, a model is proposed for ionic current rectification in which electric leakage at the pore entrance controls net transport.

Sustainability of Palliative Care Principles in the Surgical Intensive Care Unit Using a Multi-Faceted Integration Model.

Objective(s): Understanding patient goals of care is essential in any setting, and especially so in an urban, safety net trauma centers' Surgical Intensive Care Units (SICU). This underscores the need for implementation of palliative care principles and practices, such as identification of surrogate decision makers, goals-of-care discussions, and CPR directives, in the SICU. Methods: A pragmatic, quality improvement study utilizing a retrospective, pre- and post-intervention continuum analysis. Interventions included a surgeon champion, resident education, and an electronic medical record template, called the Advanced Care Planning (ACP) Note, for use on daily rounds. We reviewed the charts of all adults admitted to the SICU before, during, and after these interventions to identify the incidence of surrogate decision maker documentation by SICU residents. Results: There was an early and enthusiastic adoption in ACP note utilization by SICU residents over the study period. Rates of documenting surrogate decision makers increased throughout the study period (p < 0.0001). Having an ACP note in the chart was associated with significantly higher rates of documented surrogate decision makers (p < 0.0001). Conclusions: Through the integration of targeted education, standardization of an electronic medical record tool for palliative care documentation, and incorporation of palliative care goals into daily rounding ICU checklists, we significantly increased identification of surrogate decision makers in the SICU of our urban Level One trauma center. Chart review from one year post-intervention showed sustained commitment to the use of the ACP note and identification of surrogate decision makers.

Loss to Follow-Up and the Care Cascade for Cervical Cancer Care in Rural Guatemala: A Cross-Sectional Study.

PURPOSEMore than 80% of cervical cancer cases and deaths occur in low- and middle-income countries. Here, we analyze a large geographically extensive cross-sectional data set from the Western rural highlands of Guatemala. Our objective is to better characterize weak points in care along the cervical cancer care continuum and investigate sociodemographic and clinical correlates of loss to follow-up.METHODSWe conducted a retrospective review of electronic health records data from July 21, 2015, through December 10, 2020 for a cytology-based screening and cervical cancer treatment program. We used a care cascade analysis to characterize the progression of individuals through screening, confirmatory testing, and treatment. We examined demographic and clinical factors correlated with screening and loss to follow-up using multivariate logistic regression.RESULTSA total of 8,872 individuals were included in the analysis. Five thousand nine hundred thirteen cervical cancer screenings were conducted. 4.1% of all screening tests were abnormal, including 0.61% cervical intraepithelial neoplasia or overt cervical cancer. Care cascade analysis showed that 67% of eligible women accepted screening. Of those requiring confirmatory testing or treatment, 73% completed recommended follow-up. In adjusted multivariable analysis, prior history of sexual transmitted infection, prior experience with cervical cancer screening, older age, and current contraceptive use were associated with accepting screening. Age and contraceptive use were also associated with retention in care after a positive first screen.CONCLUSIONIn a large rural Guatemalan retrospective cohort, a care continuum analysis showed that both declining the opportunity to receive cervical cancer screening as well as declining confirmatory testing after a first positive screen were both important weak points along the care continuum. These data support the need for comprehensive and culturally appropriate initiatives to improve screening uptake and retention in care.

メッシュ制約型離散点法を用いた移動境界流れの数値解法の検討

Meshfree particle methods are known as a powerful tool for complex numerical continuum analyses, including migration or large deformation of boundaries. However, the methods commonly tend to need higher computational costs for stable stencil calculation than mesh-based methods because the computational points, called particles, are heterogeneously distributed in a domain. To overcome this issue, we developed the mesh-constrained discrete point (MCD) approach. The MCD method can perform the stencil calculation efficiently because of constraining the arrangement of discrete points (DPs) using simple background mesh systems such as the Cartesian grids. In this study, we further develop the MCD method to address moving boundary problems. In the developed formulation, the arrangements of DP positions and related calculation masks are updated every time that follows the moving boundary. The validity of the proposed method is investigated in a simple numerical example for a moving body in two-circular channels. The calculation masks for the DPs are adequately updated even when the moving boundary crosses the background mesh.

Evolution of structure of cohesive granular ensembles in compression

A small amount of cementation between particles drastically changes the mechanical response of a granular ensemble. Through a series of interrupted uniaxial compression tests inside the x-ray computed tomograph (XCT) on fine and coarse grained cemented sand specimens, a quantification of the behavior at both the continuum and particle scales is made. At the continuum length scale, displacements and porosity fields are examined. While at the particle scale, the coordination number, particle and contact fabric tensors, directional distribution of particles and contact normals are extracted and analyzed. Particle level phenomenology—at different stages of loading—such as breakage of bonds, formation of new contacts, manifest themselves at the ensemble scale in the form of bifurcation zones, which coalesce into split zones through the specimen. A new paradigm for the fabric tensor is also provided using principal component analysis. The results of the continuum and particle scale analysis are used to provide insights on the compression behavior of cemented sands.

Deeply Buried Nuclei in the Infrared-luminous Galaxies NGC 4418 and Arp 220. I. ALMA Observations at λ = 1.4–0.4 mm and Continuum Analysis

Abstract We observed with Atacama Large Millimeter/submillimeter Array three deeply buried nuclei in two galaxies, NGC 4418 and Arp 220, at ∼0.″2 resolution over a total bandwidth of 67 GHz in f rest = 215–697 GHz. Here we (1) introduce our program, (2) describe our data reduction method for wide-band, high-resolution imaging spectroscopy, (3) analyze in visibilities the compact nuclei with line forests, (4) develop a continuum-based estimation method of dust opacity and gas column density in heavily obscured nuclei, which uses the buried galactic nuclei (BGN) model and is sensitive to log ( N H 2 / cm − 2 ) ∼ 25–26 at λ ∼ 1 mm, and (5) present the continuum data and diagnosis of our targets. The three continuum nuclei have major-axis FWHMs of ∼0.″1–0.″3 (20–140 pc) aligned to their rotating nuclear disks of molecular gas. However, each nucleus is described better with two or three concentric components than with a single Gaussian. The innermost cores have sizes of 0.″05–0.″10 (8–40 pc), peak brightness temperatures of ∼100–500 K at 350 GHz, and more fractional flux at lower frequencies. The intermediate components correspond to the nuclear disks. They have axial ratios of ≈0.5 and hence inclinations ≳60°. The outermost elements include the bipolar outflow from Arp 220W. We estimate 1 mm dust opacity of τ d,1 mm ≈ 2.2, 1.2, and ≲0.4, respectively, for NGC 4418, Arp 220W, and Arp 220E. The first two correspond to log ( N H / cm − 2 ) ∼ 26 for conventional dust-opacity laws, and hence the nuclei are highly Compton thick.

Пространственно-временной континуум в постмодернистской парадигме: Ж. Делез (1926–1995)

According to the author, J. Deleuze enriches the postmodern paradigm of space-time continuum analysis with original ideas about space, time, and duration (extension) as properties of the world. Psychologism in the interpretation of time-space is indicated. Time is interpreted as a relation, the sign of which is becoming. Attention is drawn to the fact that processality is provided by eventfulness; events have specific differences and act as neutral singularities that form history. It is noted that time is personal and events as signs and relationships are actualized in the time of the ego. The article reveals Deleuze's rationale for two times: one – present, the other – past and future; one – cyclical, the other – linear (the time of Chronos and the time of EON). It is emphasized that the present is an elusive being of the mind; it is the field of action of historical individuality, which is characterized by an infinity of analytical or synthetic propositions that are self-determined in space-time. The synthesis of time rests on habit, which is the basis of the passing present. Justifies the time memory. It is argued that the present for Deleuze is a simulacrum present in appearances; it dissolves in the past and future. The author reveals the philosopher's conviction in the subjectivity of time, which asserts the priority of the present as existing. The unconscious ends the history of time, shifting the center and periphery, which cease to exist. The influence of depth and distance on the perception of space is noted; time is perceived as an axis, as a form of mental activity, as a bundle of "I" and "My I", as an Affect. The dependence of individual perception on national and cultural affiliation was found. Attention is drawn to the incorporation of time - space into the spiritual world of man. The conclusion is made about the anthropological nature of the space-time continuum in Deleuze's epistemological constructions. Space-time is analyzed through the concepts that form the basis of Deleuze's philosophical discourse, as an attempt to go beyond the established ideas about the space-time continuum.

Fcc lattice, checkerboards, fractons, and quantum field theory

We consider XY-spin degrees of freedom on an FCC lattice, such that the system respects some subsystem global symmetry. We then gauge this global symmetry and study the corresponding $U(1)$ gauge theory on the FCC lattice. Surprisingly, this $U(1)$ gauge theory is dual to the original spin system. We also analyze a similar $\mathbb{Z}_N$ gauge theory on that lattice. All these systems are fractonic. The $U(1)$ theories are gapless and the $\mathbb{Z}_N$ theories are gapped. We analyze the continuum limits of all these systems and present free continuum Lagrangians for their low-energy physics. Our $\mathbb{Z}_2$ FCC gauge theory is the continuum limit of the well known checkerboard model of fractons. Our continuum analysis leads to a straightforward proof of the known fact that this theory is dual to two copies of the $\mathbb{Z}_2$ X-cube model. We find new models and new relations between known models. The $\mathbb{Z}_N$ FCC gauge theory can be realized by coupling three copies of an anisotropic model of lineons and planons to a certain exotic $\mathbb{Z}_2$ gauge theory. Also, although for $N=2$ this model is dual to two copies of the $\mathbb{Z}_2$ X-cube model, a similar statement is not true for higher $N$.

Multiscale calculation results of the flow behavior in micro/nano porous filtration membrane with the adsorbed layer-fluid interfacial slippage

The paper presents the multiscale calculation results for the multiscale flow in micro/nano porous filtration membranes where the adsorbed layer effect is involved, by considering the adsorbed layer-fluid interfacial slippage. The analysis consists of the molecular scale analysis for the adsorbed layer flow and the continuum analysis for the intermediate fluid flow. The calculation results are respectively compared with the classical flow theory calculations and those based on the solid layer assumption. The adsorbed layer flow rate is also compared with the flow rate of the intermediate continuum fluid. It is shown that for a strong fluid-pore wall interaction or for a large adsorbed layer-fluid interfacial slippage the adsorbed layer can be treated as a solid layer; otherwise it should be treated as a flowing layer. The large interfacial slippage results in the flow rate through the pore far greater than the classical Hagen-Poiseuille equation calculation; it largely propels the flow of the intermediate continuum fluid and makes the adsorbed layer flow negligible particularly for the medium and strong fluid-pore wall interactions. The increasing fluid-pore wall interaction strength significantly reduces the flow rate through the pore.

Analysis of cone penetration in brittle liquefiable soils

The paper presents a comprehensive set of simulations of the cone penetration test with pore pressure measurements (CPTu test) in brittle, potentially liquefiable, soils using advanced numerical techniques. The large displacements and large deformations involved in the cone penetration problem are tackled using the Particle Finite Element Method, especially adapted for the analysis of coupled geotechnical problems (G-PFEM). A non-local regularization technique is adopted to prevent the pathological mesh dependence associated with continuum analysis of softening materials. Brittle soil behaviour is described using the CASM constitutive model. Undrained CPTu tests are simulated for a range of soils with different degree of brittleness. Effects of permeability, partial drainage and cone roughness are also explored. The results of the analyses are assessed in terms of the interpretation and classification procedures usually applied in practice. In addition, advantage is taken of the availability of a full numerical solution to explore aspects of soil response during penetration that are not possible when only global CPTu observations are available. The full set of numerical analyses have been able to capture the essential features of the problem and to provide useful insights into the effects of brittleness on the mechanisms and results of the CPTu test.

A Fully Integrated Arduino-Based System for the Application of Stretching Stimuli to Living Cells and Their Time-Lapse Observation: A Do-It-Yourself Biology Approach

Mechanobiology has nowadays acquired the status of a topic of fundamental importance in a degree in Biological Sciences. It is inherently a multidisciplinary topic where biology, physics and engineering competences are required. A course in mechanobiology should include lab experiences where students can appreciate how mechanical stimuli from outside affect living cell behaviour. Here we describe all the steps to build a cell stretcher inside an on-stage cell incubator. This device allows exposing living cells to a periodic mechanical stimulus similar to what happens in physiological conditions such as, for example, in the vascular system or in the lungs. The reaction of the cells to the periodic mechanical stretching represents a prototype of a mechanobiological signal integrated by living cells. We also provide the theoretical and experimental aspects related to the calibration of the stretcher apparatus at a level accessible to researchers not used to dealing with topics like continuum mechanics and analysis of deformations. We tested our device by stretching cells of two different lines, U87-MG and Balb-3T3 cells, and we analysed and discussed the effect of the periodic stimulus on both cell reorientation and migration. We also discuss the basic aspects related to the quantitative analysis of the reorientation process and of cell migration. We think that the device we propose can be easily reproduced at low-cost within a project-oriented course in the fields of biology, biotechnology and medical engineering.

Soil–Structure Interaction and Structural Design of Raft-Foundation and Reinforced Concrete Superstructure

Raft foundations can be analyzed using the conventional, Winkler, and continuum methods. In the conventional method, it is assumed that the raft is rigid and settles uniformly. In the Winkler method, commonly employed in structural analysis software packages, soil is represented by a series of springs. On the other hand, in computer-aided continuum analysis, soil below the raft is modeled using solid elements available in finite element–based software. In the present study, analyses of the raft as a single unit and the raft together with the superstructure as a combined unit are carried out separately for a wide range of soil strength parameters employing the Winkler and continuum methods. The results of the analyses and subsequent designs were compared for different models. The variations in the quantity of reinforcement required for the raft and superstructure, corresponding to changes in soil stiffness values in different modeling methods, are investigated. Useful recommendations are presented to increase the effectiveness of Winkler model for structural design. The need for modeling the raft and superstructure as a combined unit is also highlighted.

Scaled boundary polygon formula for Cosserat continuum and its verification

Cosserat continuum method can be used to solve stress concentration of holes. However, with the shape limitation of its elements, it is worthwhile to improve the element quality so that this method can be universal and feasible to complex situations. In this paper, a flexible polygonal Cosserat continuum analysis method is firstly deduced and numerically developed based on the theory of Scaled Boundary FEM. Stress concentration on the holes embedded in different structures is then investigated using the proposed method and verified against theoretical solution, which not only shows good agreement, but also reasonably weakens the stress concentration. The proposed method can closely replicate the theoretical solution for the case when the material is nearly incompressible (Poisson's ratio close to 0.5), also indicating the robustness of this method. Additionally, complex polygonal elements can be solved directly, coupling the quadtree and polygon discretization techniques seamlessly, wherein the efficiency and convenience are improved for processing complex geometries. The proposed method can provide important technical support for stress concentration analysis of structures with complex holes, and contribute to facilitating shape optimization of holes design.