PRIMA: general and precise neural network certification via scalable convex hull approximations

Formal verification of neural networks is critical for their safe adoption in real-world applications. However, designing a precise and scalable verifier which can handle different activation functions, realistic network architectures and relevant specifications remains an open and difficult challenge. In this paper, we take a major step forward in addressing this challenge and present a new verification framework, called PRIMA. PRIMA is both (i) general: it handles any non-linear activation function, and (ii) precise: it computes precise convex abstractions involving multiple neurons via novel convex hull approximation algorithms that leverage concepts from computational geometry. The algorithms have polynomial complexity, yield fewer constraints, and minimize precision loss. We evaluate the effectiveness of PRIMA on a variety of challenging tasks from prior work. Our results show that PRIMA is significantly more precise than the state-of-the-art, verifying robustness to input perturbations for up to 20%, 30%, and 34% more images than existing work on ReLU-, Sigmoid-, and Tanh-based networks, respectively. Further, PRIMA enables, for the first time, the precise verification of a realistic neural network for autonomous driving within a few minutes.

Superabsorption in an organic microcavity: Toward a quantum battery

In a major step toward the development of a quantum battery, superabsorption has been achieved in an organic microcavity.

Hydrogen Energy Demand Growth Prediction and Assessment (2021–2050) Using a System Thinking and System Dynamics Approach

Adoption of hydrogen energy as an alternative to fossil fuels could be a major step towards decarbonising and fulfilling the needs of the energy sector. Hydrogen can be an ideal alternative for many fields compared with other alternatives. However, there are many potential environmental challenges that are not limited to production and distribution systems, but they also focus on how hydrogen is used through fuel cells and combustion pathways. The use of hydrogen has received little attention in research and policy, which may explain the widely claimed belief that nothing but water is released as a by-product when hydrogen energy is used. We adopt systems thinking and system dynamics approaches to construct a conceptual model for hydrogen energy, with a special focus on the pathways of hydrogen use, to assess the potential unintended consequences, and possible interventions; to highlight the possible growth of hydrogen energy by 2050. The results indicate that the combustion pathway may increase the risk of the adoption of hydrogen as a combustion fuel, as it produces NOx, which is a key air pollutant that causes environmental deterioration, which may limit the application of a combustion pathway if no intervention is made. The results indicate that the potential range of global hydrogen demand is rising, ranging from 73 to 158 Mt in 2030, 73 to 300 Mt in 2040, and 73 to 568 Mt in 2050, depending on the scenario presented.

Large Scale Modelling of Damage and Failure of Nuclear Graphite Moderated Reactor

The UK Advanced Gas-Cooled reactors (AGRs) have cores made of graphite bricks with dual functions: as structural elements of the core, providing space for and separating fuel and control rods; and as moderator of the nuclear reaction. Nuclear graphite is a quasi-brittle material, where the dominant mechanism for failure is cracking. While cracking of isolated bricks is expected due to operation-induced changes in graphite microstructure and stress fields, these could be tolerated as far as the overall structural function of the core is maintained. Assessment of the whole core behaviour has been previously done with whole scale models where bricks have been considered as rigid body elements connected by elastic-brittle springs. This approach does not allow for the realistic assessment of the stresses in the bricks and associated brick cracking. Reported here are results from an ongoing project, which addresses this shortcoming. The proposed model uses deformable bricks with appropriate interactions, allowing for physically realistic whole core analysis. The results are focused on the damage that a graphite moderated reactor develops during a life cycle, how this affects the behaviour of the whole core, and how changes in bricks' behaviour impacts the core integrity. The proposed methodology is a major step towards high-fidelity assessment of AGRs' fitness for service, required for supporting continuous safe operation and life-extension decisions.

Edge Detection in Natural Scenes Inspired by the Speed Drawing Challenge

Edge detection is a major step in several computer vision applications. Edges define the shape of objects to be used in a recognition system, for example. In this work, we introduce an approach to edge detection inspired by a challenge for artists: the Speed Drawing Challenge. In this challenge, a person is asked to draw the same figure in different times (as 10[Formula: see text]min, 1[Formula: see text]min and 10[Formula: see text]s); at each time, different levels of details are drawn by the artist. In a short time stamp, just the major elements remain. This work proposes a new approach for producing images with different amounts of edges representing different levels of relevance. Our method uses superpixel to suppress image details, followed by Globalized Probability of Boundary (gPb) and Canny edge detection algorithms to create an image containing different number of edges. After that, an edge analysis step detects whose edges are the most relevant for the scene. The results are presented for the BSDS500 dataset and they are compared to other edge and contour detection algorithms by quantitative and qualitative means with very satisfactory results.

The Relationship of Dental Anxiety, Behaviour, Temperament and Dental Caries in Children

The first dental examination is a major step that is affected by many factors and determines the dental treatment process. The main objective of this study was to evaluate the association of child temperament with child dental anxiety, parental dental anxiety, dental behaviour and dental caries. The study consisted of 100 children aged 3 to 6 who were attending their first dental examination and their accompanying parents. The Facial Image Scale (FIS), Frankl’s Behaviour Scale (FBS), Corah’s Dental Anxiety Scale (CDAS) and the Short Temperament Scale for Children (STSC) were used for assessment. The DMFT (decayed, missing and filled teeth) score of each child was recorded. Children who exhibited negative behaviour on the FBS had the highest rhythmicity scores (p = 0.008). The mean DMFT score of children in the rhythmicity temperamental dimension was relatively high (p = 0.008). The parents of children defined as negative on the FBS had high dental anxiety levels on CDAS (p < 0.001). Children whose parents had higher dental anxiety levels showed higher dental anxiety (p = 0.007). The success rate of dental treatment procedures may be increased by improving dentists’ knowledge of dental anxiety related to the child’s temperament and integrating parental support to reduce dental anxiety.

Rheological Behaviour of Cementitious Materials Incorporating Solid–Solid Phase Change Materials

Nowadays, thermal regulation of the indoor environment is mandatory to reduce greenhouse gas emissions. The incorporation of Phase Change Materials (PCMs) and especially solid–solid PCMs (s/s PCMs) into building materials can be a major step forward in reducing energy consumption. Such materials are used for their high latent heat to save and release heat during phase change. To integrate these products in the fabrication of cementitious materials, it is essential to predict their influence on the rheological behaviour of construction materials. In this work, rheological measurements were carried out on composite suspensions made of cement or mortar plus s/s PCMs. Results showed that the fitting of the Herschel–Bulkley model with a constant value of flow exponent was reliable. The s/s PCMs influenced the consistency and the yield strength values, with the yield strength value being only slightly affected. The adaptation of an existing viscosity model is proposed to predict the consistency value of suspensions. Finally, an innovative approach to predict the flow behaviour is proposed and we highlight the research needs to mainstream the use of s/s PCMs in construction materials.

A halogen budget of the bulk silicate Earth points to a history of early halogen degassing followed by net regassing

Halogens are important tracers of various planetary formation and evolution processes, and an accurate understanding of their abundances in the Earth’s silicate reservoirs can help us reconstruct the history of interactions among mantle, atmosphere, and oceans. The previous studies of halogen abundances in the bulk silicate Earth (BSE) are based on the assumption of constant ratios of element abundances, which is shown to result in a gross underestimation of the BSE halogen budget. Here we present a more robust approach using a log-log linear model. Using this method, we provide an internally consistent estimate of halogen abundances in the depleted mid-ocean ridge basalts (MORB)-source mantle, the enriched ocean island basalts (OIB)-source mantle, the depleted mantle, and BSE. Unlike previous studies, our results suggest that halogens in BSE are not more depleted compared to elements with similar volatility, thereby indicating sufficient halogen retention during planetary accretion. According to halogen abundances in the depleted mantle and BSE, we estimate that ∼87% of all stable halogens reside in the present-day mantle. Given our understanding of the history of mantle degassing and the evolution of crustal recycling, the revised halogen budget suggests that deep halogen cycle is characterized by efficient degassing in the early Earth and subsequent net regassing in the rest of Earth history. Such an evolution of deep halogen cycle presents a major step toward a more comprehensive understanding of ancient ocean alkalinity, which affects carbon partitioning within the hydrosphere, the stability of crustal and authigenic minerals, and the development of early life.

Academic Copyright, Open Access and the "Moral" Second Publication Right

The Green route to Open Access (OA), meaning the re-publication in OA venues of previously published works, can essentially be executed by contract and by copyright law. In theory, rights retention and contracts may allow authors to re-publish and communicate their works to the public, by means of license to publish agreements or specific addenda to copyright transfer agreements. But as a matter of fact, because authors lack bargaining power, they usually transfer all economic copyrights to publishers. Legislation, which overcomes the constraints of a contractual scheme where authors usually have less bargaining power, may deliver a (digital) second publication or communication right, which this paper discusses in the context of research publications. Outlining the historical and philosophical roots of the secondary publication right, the paper provocatively suggests that it has a “moral” nature that even makes it a shield for academic freedom as well as a major step forward in the overall development of OA.

A simulation approach for closed-loop control of coupled four tank system

The coupled tank system is the most widely used sub-component in chemical process industries. Fluid mixing is a major step in chemical processes that alters the material properties and cost. Fluid flow and its level regulation between several tanks are important control problems. As the first step, this paper addresses the level regulation problem using classical integer order proportional, derivative, integral (PID), fractional order PID controllers. As a second step, model-based robust fractional order controllers are derived using sliding mode approach in order to achieve the desired response, parameters of the proposed controllers are tuned using genetic algorithm. Finally, system performance under all variants of control schemes has been tested using numerical simulations.