Effetto di mineralogia e granulometria sul comportamento di transizione di miscele di sabbia.

Il comportamento di transizione è stato identificato per diverse tipologie di terreno, dai terreni con lacuna granulometrica a limi e sabbie ben gradate. Tale comportamento è caratterizzato dall’esistenza di percorsi di compressione non convergenti e dalla non unicità della linea di stato critico, con localizzazione fortemente dipendente dalla densità iniziale dei campioni. Sebbene in letteratura tale comportamento sia stato inizialmente attribuito a terreni di granulometria intermedia, è stato mostrato come questo sembrerebbe manifestarsi anche in presenza di terreni aventi granulometria mista, con lacuna granulometrica o ben gradati, e per miscele composte da particelle di diversa natura o diversa mineralogia. La diversa tipologia di terreni in cui tale comportamento è stato osservato evidenzia l’elevata difficoltà nell’individuazione dei fattori chiave che lo determinano. Uno studio recente ha mostrato la mancata convergenza dei percorsi di compressione per alcune miscele di sabbia create artificialmente utilizzando materiali di differente mineralogia: sabbia di quarzo e sabbia carbonatica. Con lo scopo di verificare l’effetto della composizione mineralogica, delle dimensioni e resistenza relative dei grani e natura delle particelle sul manifestarsi o meno del comportamento di transizione, la presente nota approfondisce i risultati del precedente studio utilizzando miscele di sabbia caratterizzate da proporzioni variabili delle componenti mineralogiche e granulometriche

The shear stiffness characteristics of four Eocene-to-Jurassic UK stiff clays

A large proportion of the southern UK is underlain by stiff clays. Improving their geotechnical characterisation is important for many current and future infrastructure projects. This paper presents an integrated study of the complex stiffness behaviour of four key medium-plasticity, highly overconsolidated strata: the Gault, Kimmeridge, Oxford and London clays. The latter were deposited between the Jurassic and the Eocene under broadly similar marine conditions. Coordinated programmes of advanced static and dynamic laboratory measurements have been undertaken on high-quality samples, concentrating on samples taken from similar depths at inland sites and including triaxial and hollow cylinder stress path experiments employing high-resolution local strain, multi-axial bender element and resonant column techniques. A new approach was employed to interpret the hollow cylinder experiments and the laboratory measurements are examined in combination with independent field shear wave data. The clays' stiffness characteristics are shown to be markedly anisotropic, pressure dependent and highly non-linear. Synthesis allows key conclusions to be drawn regarding: the relative reliability of alternative measurement approaches; the potential spread of stiffness behaviours between the clays; and whether the clays' varying geological ages and burial depths have any systematic influence on their stiffness characteristics. The results have important geotechnical engineering implications

The role of particle mineralogy in mixtures of sands

Several recent studies on mixtures of sands of different granulometries and/or mineralogies have focused on the key factors that might lead the behaviour to change from transitional to not transitional, where a transitional behaviour is characterised by non-convergent compression paths and critical state lines that might be non-unique. The authors present a review of mixtures of different soils showing a complex pattern of compression and shearing behaviour in which transitional behaviour can be caused by relatively small varia- tions to the proportion or nature of soil particles. Laboratory investigations, carried out by means of oedometer tests, have confirmed the role of the mineralogy of the matrix composed by larger grains. This determines the mode of behaviour so that, if there is a strong and stiff matrix made of quartz sand particles, which are either larger than or at least of similar size to the other component, then non-convergent compression paths are likely to occur, no matter whether particle breakage occurs or not

Crossing Over from Attractive to Repulsive Interactions in a Tunneling Bosonic Josephson Junction

We explore the interplay between tunneling and interatomic interactions in the dynamics of a bosonic Josephson junction. We tune the scattering length of an atomic $^{39}$K Bose-Einstein condensate confined in a double-well trap to investigate regimes inaccessible to other superconducting or superfluid systems. In the limit of small-amplitude oscillations, we study the transition from Rabi to plasma oscillations by crossing over from attractive to repulsive interatomic interactions. We observe a critical slowing down in the oscillation frequency by increasing the strength of an attractive interaction up to the point of a quantum phase transition. With sufficiently large initial oscillation amplitude and repulsive interactions the system enters the macroscopic quantum self-trapping regime, where we observe coherent undamped oscillations with a self-sustained average imbalance of the relative well population. The exquisite agreement between theory and experiments enables the observation of a broad range of many body coherent dynamical regimes driven by tunable tunneling energy, interactions and external forces, with applications spanning from atomtronics to quantum metrology.Comment: 10 pages, 8 figures, supplemental materials are include

Image based simulation of one-dimensional compression tests on carbonate sand

High factors of safety and conservative methods are commonly used on foundation design on shelly carbonate soils. A better understanding of the behavior of this material is, thus, critical for more sustainable approaches for the design of a number of offshore structures and submarine pipelines. In particular, understanding the physical phenomena taking place at the microscale has the potential to spur the development of robust computational methods. In this study, a one-dimensional compression test was performed inside an X-ray scanner to obtain 3D images of the evolving internal structure of a shelly carbonate sand. A preliminary inspection of the images through five loading increments has shown that the grains rearrange under loading and in some cases cracks develop at the contacts. In order to replicate of the experiments in the numerical domain, the 3D image of the soil prior to loading was imported into a micro Finite Element (µFE) framework. This image-based modelling tool enables measurements of the contact force and stress map inside the grains while making use of the real microstructure of the soil. The potential of the µFE model to contribute insights into yield initiation within the grain is demonstrated here. This is of particular interest to better understand the breakage of shelly grains underpinning their highly compressive behavior

Pseudorehearsal in value function approximation

Catastrophic forgetting is of special importance in reinforcement learning, as the data distribution is generally non-stationary over time. We study and compare several pseudorehearsal approaches for Q-learning with function approximation in a pole balancing task. We have found that pseudorehearsal seems to assist learning even in such very simple problems, given proper initialization of the rehearsal parameters

Improvements in depressive symptoms following a brief relationship intervention

In the United States, 21 million adults are diagnosed with depression. Couple therapy effectively treats depression, however, couples encounter access barriers. The Relationship Checkup is an assessment and feedback intervention delivered in participants\u27 homes. The current study examines changes in relationship satisfaction and depressive symptoms, and moderators and mechanisms of change in a community sample (N = 85 couples). Changes in depressive symptoms and satisfaction, and the association between changes in satisfaction and depressive symptoms were examined with multilevel modeling. Depressive symptoms (Cohen\u27s d = 0.36) and satisfaction (d = 1.43) improved from baseline to 1-month follow-up, with greater declines in depression (d = 0.44) for those with more severe symptoms. Increases in satisfaction were associated with decreases in depressive symptoms (d = 0.23), and decreases in depressive symptoms were associated with increases in satisfaction (d = 0.33). Individuals with depression and relationship distress may be well served by this intervention. © 2023 The Authors. Journal of Marital and Family Therapy published by Wiley Periodicals LLC on behalf of American Association for Marriage and Family Therapy

The use and misuse of the SCOFF screening measure over two decades: a systematic literature review

Purpose The SCOFF questionnaire was designed as a simple, memorable screening tool to raise suspicion that a person might have an eating disorder. It is over 20 years since the creation of the SCOFF, during which time it has been widely used. Considering this, we wish to review the use of the SCOFF in peer-reviewed scientific journals, and to assess whether it is being used appropriately in the manner in which it was originally devised and tested. Methods The Preferred Reporting Items for a Systematic Review and Meta-analysis (PRISMA) guidelines were followed, and all search strategies and methods were determined before the onset of the study. PubMed and Wiley Online Library were searched using the terms SCOFF and eating. Two reviewers were involved in the reviewing process. Criteria for appropriate use of the SCOFF were formalised with the tool’s original authors. Results 180 articles were included in the final review. 48 articles had used the SCOFF appropriately, 117 articles inappropriately and 15 articles had been mixed in the appropriateness of their use. Conclusion This systematic review highlights the inappropriate use of the SCOFF in diverse languages and settings. When used correctly the SCOFF has made a significant contribution to the understanding of eating disorders and its simplicity has been applauded and led to widespread use. However in over two-thirds of studies, the use of the SCOFF was inappropriate and the paper highlights how and in what way it was misused, Guidelines for the appropriate use of the SCOFF are stated. Future validation and avenues of research are suggested. Level of evidence Level I