Strength and failure characteristics of marble spheres subjected to paired point loads

Failure of irregular rock samples may provide implications in the rapid estimation of rock strength, which is imperative in rock engineering practice. In this work, analytical, experimental and numerical investigations were carried out to study the mechanical properties and failure characteristics of rock spheres under paired point loads. Analytical solutions indicted that with the increase in sample size (contact angle) and decrease in Poisson's ratio, the uneven tensile stress in theta direction decreased. Then laboratory experiments were carried out to investigate the load characteristics and failure mode of spherical marble samples with different sizes subjected to a pair of diametral point loads. The discrete element method (DEM) was adopted to study the failure process of rock spheres. The effect of the sphere diameter on the point load contact angle was examined in terms of peak load, crushed zone distribution and energy dissipation. Experimental and numerical results showed that the samples primarily fail in tension, with crushed zones formed at both loading points. With increase in the sample size, the contact angle, crushed area and total work increase. As the specimen diameter increases from 30 mm to 50 mm, the peak load on the specimen increases from 3.6 kN to 8.8 kN, and the percentage of crushed zone (ratio of crushing zone to sample radius, d/r) increased from 0.191 to 0.262. The results of the study have implications for understanding the failure of irregular rock specimens under point loading conditions and their size effects

Multi-view 3D Face Reconstruction Based on Flame

At present, face 3D reconstruction has broad application prospects in various fields, but the research on it is still in the development stage. In this paper, we hope to achieve better face 3D reconstruction quality by combining multi-view training framework with face parametric model Flame, propose a multi-view training and testing model MFNet (Multi-view Flame Network). We build a self-supervised training framework and implement constraints such as multi-view optical flow loss function and face landmark loss, and finally obtain a complete MFNet. We propose innovative implementations of multi-view optical flow loss and the covisible mask. We test our model on AFLW and facescape datasets and also take pictures of our faces to reconstruct 3D faces while simulating actual scenarios as much as possible, which achieves good results. Our work mainly addresses the problem of combining parametric models of faces with multi-view face 3D reconstruction and explores the implementation of a Flame based multi-view training and testing framework for contributing to the field of face 3D reconstruction

Design and assessment of a reconfigurable behavioral assistive robot: a pilot study

IntroductionFor patients with functional motor disorders of the lower limbs due to brain damage or accidental injury, restoring the ability to stand and walk plays an important role in clinical rehabilitation. Lower limb exoskeleton robots generally require patients to convert themselves to a standing position for use, while being a wearable device with limited movement distance.MethodsThis paper proposes a reconfigurable behavioral assistive robot that integrates the functions of an exoskeleton robot and an assistive standing wheelchair through a novel mechanism. The new mechanism is based on a four-bar linkage, and through simple and stable conformal transformations, the robot can switch between exoskeleton state, sit-to-stand support state, and wheelchair state. This enables the robot to achieve the functions of assisted walking, assisted standing up, supported standing and wheelchair mobility, respectively, thereby meeting the daily activity needs of sit-to-stand transitions and gait training. The configuration transformation module controls seamless switching between different configurations through an industrial computer. Experimental protocols have been developed for wearable testing of robotic prototypes not only for healthy subjects but also for simulated hemiplegic patients.ResultsThe experimental results indicate that the gait tracking effect during robot-assisted walking is satisfactory, and there are no sudden speed changes during the assisted standing up process, providing smooth support to the wearer. Meanwhile, the activation of the main force-generating muscles of the legs and the plantar pressure decreases significantly in healthy subjects and simulated hemiplegic patients wearing the robot for assisted walking and assisted standing-up compared to the situation when the robot is not worn.DiscussionThese experimental findings demonstrate that the reconfigurable behavioral assistive robot prototype of this study is effective, reducing the muscular burden on the wearer during walking and standing up, and provide effective support for the subject's body. The experimental results objectively and comprehensively showcase the effectiveness and potential of the reconfigurable behavioral assistive robot in the realms of behavioral assistance and rehabilitation training

Privacy-Preserving Aggregation in Federated Learning: A Survey

Over the recent years, with the increasing adoption of Federated Learning (FL) algorithms and growing concerns over personal data privacy, Privacy-Preserving Federated Learning (PPFL) has attracted tremendous attention from both academia and industry. Practical PPFL typically allows multiple participants to individually train their machine learning models, which are then aggregated to construct a global model in a privacy-preserving manner. As such, Privacy-Preserving Aggregation (PPAgg) as the key protocol in PPFL has received substantial research interest. This survey aims to fill the gap between a large number of studies on PPFL, where PPAgg is adopted to provide a privacy guarantee, and the lack of a comprehensive survey on the PPAgg protocols applied in FL systems. In this survey, we review the PPAgg protocols proposed to address privacy and security issues in FL systems. The focus is placed on the construction of PPAgg protocols with an extensive analysis of the advantages and disadvantages of these selected PPAgg protocols and solutions. Additionally, we discuss the open-source FL frameworks that support PPAgg. Finally, we highlight important challenges and future research directions for applying PPAgg to FL systems and the combination of PPAgg with other technologies for further security improvement.Comment: 20 pages, 10 figure

Roadmap on energy harvesting materials

Ambient energy harvesting has great potential to contribute to sustainable development and address growing environmental challenges. Converting waste energy from energy-intensive processes and systems (e.g. combustion engines and furnaces) is crucial to reducing their environmental impact and achieving net-zero emissions. Compact energy harvesters will also be key to powering the exponentially growing smart devices ecosystem that is part of the Internet of Things, thus enabling futuristic applications that can improve our quality of life (e.g. smart homes, smart cities, smart manufacturing, and smart healthcare). To achieve these goals, innovative materials are needed to efficiently convert ambient energy into electricity through various physical mechanisms, such as the photovoltaic effect, thermoelectricity, piezoelectricity, triboelectricity, and radiofrequency wireless power transfer. By bringing together the perspectives of experts in various types of energy harvesting materials, this Roadmap provides extensive insights into recent advances and present challenges in the field. Additionally, the Roadmap analyses the key performance metrics of these technologies in relation to their ultimate energy conversion limits. Building on these insights, the Roadmap outlines promising directions for future research to fully harness the potential of energy harvesting materials for green energy anytime, anywhere

Philanthropic Behaviour of Quebecers

Residents of Quebec give less, on average, than those in all other provinces. They also volunteer, on average, the least when compared to time donated in other provinces. Why? This paper empirically examines and compares the giving and volunteering behaviour of Quebecers to that of other Canadians, with the aim of addressing this question. The most recent General Social Survey - Giving Volunteering and Participation (GSS GVP 2013) and Tobit procedure are employed to conduct the analysis. I find that once I control for demographic and socio-economic characteristics, Quebecers behave similarly to others when it comes to money and time donations, except for total volunteering hours. The key factors that seem to explain why the average giving is so much lower in Quebec are that they have the lowest proportion of religious individuals across provinces and that they are in the lower half of low disposable household income when comparing across provinces

Philanthropic Behaviour of Quebecers

Residents of Québec typically give less money and volunteer less time compared to residents of all other provinces. This article employs the most recent General Social Survey: Giving, Volunteering and Participating (2013) data set and Tobit procedures and finds that Quebeckers give less money largely because of smaller endowments of two important determinants, religiosity and household income. Once demographic and socioeconomic characteristics are controlled, Quebeckers’ financial donations are comparable to those of residents of Ontario and Atlantic Canada and exceed those of residents of British Columbia. Quebeckers moreover are similar to others when it comes to volunteering for religious organizations, but they volunteer significantly less than others for secular organizations, which cannot be explained in this article.Typiquement, les résidents du Québec donnent moins d’argent et consacrent moins de temps au bénévolat que les résidents des autres provinces. Cet article, en recourant aux données provenant de la dernière « Enquête sociale générale : dons, bénévolat et participation, 2013 » et au modèle Tobit, conclut que les Québécois donnent moins d’argent en grande partie parce qu’ils ont des lacunes dans deux domaines importants, à savoir la religiosité et le revenu du ménage. Cependant, après un contrôle des caractéristiques démographiques et socioéconomiques, on constate que les dons de la part des Québécois sont au fait comparables à ceux des résidents de l’Ontario et des provinces de l’Atlantique et supérieures à ceux des résidents de la Colombie-Britannique. D’autre part, les Québécois sont comparables aux résidents des autres provinces pour ce qui est du bénévolat dans les organismes religieux, mais ils font beaucoup moins de bénévolat dans les organismes séculaires, fait que cet article ne parvient pas à expliquer.

Achieving Long-Cycle-Life Zinc-Ion Batteries through a Zincophilic Prussian Blue Analogue Interphase

The practical application of rechargeable aqueous zinc-ion batteries (ZIBs) has been severely hindered by detrimental dendrite growth, uncontrollable hydrogen evolution, and unfavorable side reactions occurring at the Zn metal anode. Here, we applied a Prussian blue analogue (PBA) material K2Zn3(Fe(CN)6)2 as an artificial solid electrolyte interphase (SEI), by which the plentiful -C≡N- ligands at the surface and the large channels in the open framework structure can operate as a highly zincophilic moderator and ion sieve, inducing fast and uniform nucleation and deposition of Zn. Additionally, the dense interface effectively prevents water molecules from approaching the Zn surface, thereby inhibiting the hydrogen-evolution-resultant side reactions and corrosion. The highly reversible Zn plating/stripping is evidenced by an elevated Coulombic efficiency of 99.87% over 600 cycles in a Zn/Cu cell and a prolonged lifetime of 860 h at 5 mA cm−2, 2 mAh cm−2 in a Zn/Zn symmetric cell. Furthermore, the PBA-coated Zn anode ensures the excellent rate and cycling performance of an α-MnO2/Zn full cell. This work provides a simple and effective solution for the improvement of the Zn anode, advancing the commercialization of aqueous ZIBs