bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of the Pendular State on the Collapse of Granular Columns
Authors: Artoni R. , Gabrieli F. , Santomaso A. , Cola S.
Published: January 2023

Granular materials exhibit special phase transitions between different mechanical states. They behave like solids or fluids when particular conditions occur. Generally, the presence of water in the granular medium greatly affects mechanical stability, as well as jamming and blockage in dynamic phenomena, even in very small amounts. In this work the triggering and the stopping of flow was studied with regards to granular column collapse experiments. Glass beads of different grain-size were mixed with liquids of different surface tension values. The amount of liquid was varied from 0 to 5% in order to maintain the pendular state. The material was first poured in a rectangular box and then allowed to flow by removing a lateral wall. The movement of the mass was captured by a high-speed CCD camera. Repose angles, run-out and slope height were measured in order to explore the effect of the different initial dry and wet conditions on the profile evolution.

DEM numerical simulations were also carried out in a 1:1 scale reproducing the same experimental configuration and conditions. The classical Discrete Element model with spring dashpot at the normal contact was coupled with a capillary attraction force based on the minimum energy approach. Using DEM, the effect of liquid content and liquid surface tension were also evaluated. A good agreement between experiments and DEM simulations was found with respect to the kinematic and the final slope profile. In particular, both the techniques highlight the effect of the liquid that reduces the run-out distance and time even for small liquid contents. This work demonstrates the suitability of the DEM approach for the study of wet granular materials in static as well as in dynamic conditions.
Investigation of Dynamic Behaviour of a Particle-loaded Single Fibre Using Discrete Element Methods
Authors: Yang M. , Li S.Q. , Liu G. , Marshall J. S.
Published: January 2023

In this paper, starting from JKR adhesive contact theory, a multi-time discrete element method is used to investigate the dynamic particle capture process of a single loaded fibre. The dynamic variation of capture efficiency as well as the influence of the dendrite structure on the dynamic behaviour is discussed. The capture process can roughly be divided into two stages: an initial bare fibre stage and a particle-loaded fibre stage. In the initial stage, the deposited particles only cause a little additional blocking area in contrast to that of the bare fibre, since the ratio of the volume of deposited particles to fibre volume is less than 0.02. In the loaded fibre stage, the forming dendrites of particle on fibre play a dominate role in the capture. Both blocking area and dendrite length increase with the loaded number, leading to a power-law relationship between them. The effects of the particle dendrite growth on the efficiency are also studied. At the early stage, the dendrite dynamic variations, mainly bending, collapsing and breaking off, causes the efficiency rise, by spreading the dendrites from fibre front to side. When the deposited particles exceeds a certain amount, it eventually limit the length of dendrites and hence the blocking area.
Numerical Simulation of the Collapse of Granular Columns Using DEM
Authors: Zhao T. , Houlsby G.T. , Utili S.
Published: January 2023

In this paper, the collapse of plain strain dry granular columns was investigated by means of 3D DEM (Discrete Element Method) simulations. In the literature, 2D DEM analyses have been previously performed and showed to be unable to replicate the experimentally observed mass flow and final run-out distances. This is mainly due to the inability of 2D simulations to replicate the three dimensional motion of real particles. Spherical particles and a simple contact model based on linear springs, dashpots and frictional sliders were employed in the presented simulations. A rolling resistance model governed by two micromechanical parameters was added in order to indirectly account for the effect of particle non-sphericity on the angular moment equilibrium of the granular assembly. Calibration of the rolling resistance model leads to predictions of run-out distances in quantitative agreement with the available experimental data.
Three Dimensional DEM/CFD Analysis of Segregation During Silo Filling with Binary Mixtures of Different Particle Sizes
Authors: Wu C.-Y. , Guo Y.
Published: January 2023

Silos are widely used structures for storing bulk materials that generally consist of particles of different size and densities. These bulk materials are prone to segregation during silo filling and discharge, which can create serious problems in product quality control. In this study, segregation behaviour during silo filling with binary mixtures of particles of different sizes and densities in air is explored using a coupled Discrete Element Method and Computational Fluid Dynamics (DEM/CFD) in 3D. The effects of air current, fines mass fraction and silo venting design on the segregation behaviour are examined. It has been found that the presence of air generally augments the segregation tendency. Four mechanisms of segregation (air impediment, air entrainment, embedment and percolation) have been identified as the dominant mechanisms of segregation in silo filling with particles of different sizes and densities. However, the segregation patterns (i.e. the distribution of fine concentrations) depend on the filling processes.
Micromechanical Study on Shear Wave Velocity of Granular Materials Using Discrete Element Methods
Authors: Xu X. , Ling D. , Cheng Y. P. , Chen Y.
Published: January 2023

Shear wave velocity is a key parameter to evaluate the engineering properties of granular materials, like sand. It is generally obtained using piezoelectric transducers in various laboratory tests. The micromechanical study on shear wave velocity has become increasingly important to understand the microscopic mechanism of variation of the mechanical properties, as well as to bridge its micro- and macro-scale mechanisms. In this paper, both shear vibration and torsional vibration for shear wave propagation in DEM are implemented by applying a velocity pulse to the transmitter in a certain direction and monitoring the corresponding average velocity of the receiver. The cross-correlation analysis is adopted due to its superiority of both determining the travel time and identifying similarities between two signals. The shear wave velocity is calculated using the wave travel time and the distance of the travel path, in exactly the same way as in laboratory tests. On the basis of systematic parametric studies, reasonable values for the main parameters are proposed, including excitation frequency, excitation amplitude, size of transmitter and receiver as well as damp. For example, it is found that the appropriate excitation amplitude should be chosen on the basis of avoiding the generation of frictional work. The numerical methods are verified through the outcomes of even-particle assemblies for both regular and random packing, and also compared with the results from various homogenization techniques.
Base Metals
Authors: Mudd Gavin M. , Weng Zhehan
Published: January 2023

The base metals copper, lead, nickel and zinc provide a range of crucial functions in modern technology, products and infrastructure. While mineral resources are effectively non-renewable and arguably finite, ongoing growth in production rates raises important questions about the long-term sustainability of base metals mining. This chapter presents a thorough review of the base metals sector of the global mining industry, with a particular focus on detailed data sets on reported economic mineral resources and key production trends, especially declining ore grades and increasing mine waste. The resource data are then compared with available national or global estimates of base metal resources. A review of the energy and greenhouse gas emissions (GGE) intensity of base metals mining is then presented, demonstrating that there is an inverse relationship between ore grade and energy/GGE intensity. Given that ore grades for all base metals are in gradual decline globally, this presents significant upward pressure on the future energy/GGE intensity of base metals production. In addition, other crucial issues may also affect base metals production, such as acid and metalliferous drainage, water resources impacts, mine waste management, economic conditions and wealth sharing. The chapter presents a detailed and comprehensive review of the current status of the base metals sector, showing that there is ample room for optimism from a resource perspective, but this needs to be tempered with the reality of the growing effort and risks involved in production.
Gold
Authors: Stacey Julie L.
Published: January 2023

Gold has held a special place in society since its discovery. Its first recorded use was over 6000 years ago. Gold is one of the 10 rarest elements on Earth, and yet historically, over 80% of gold produced has been used for discretionary purposes, including non-essential applications such as jewellery. In its massive state, gold is largely inert and non-reactive, making it durable and tarnish resistant. It is highly malleable and ductile, and can be beaten into microscopically thin sheets, with 1 ounce (28g) of gold able to be drawn into a wire 80km in length. At nanoparticle size, however, gold displays fundamentally different properties, and serves as a highly effective catalyst, with significant biocompatibility characteristics as well. In the context of sustainable development, gold mining has massive negative environmental and social consequences, and yet has also fuelled the economic development of many countries. The application of specifically gold nanoparticles to sustainable development efforts is highly promising. Gold in nanotechnology is being used in pollution control measures, to reduce energy consumption, in nanotechnology for electronic applications, and in diagnostic and treatment options for a range of global health conditions including cancer and HIV/AIDS. With more gold available above ground than in the unmined reserves, improved recycling efforts and the release of the vast stocks could substantially fuel progress towards achieving a sustainable future.
Phosphorus
Authors: Neset Tina-Simone S.
Published: January 2023

Phosphorus is essential for all life, and global food production is dependent on it. The main source of phosphorus, phosphate rock, is, however, a finite resource, that accumulated over millions of years and is thus the object of an ongoing debate regarding the long-term development of phosphorus supplies. Most of the phosphorus mined from phosphate rock is used in the production of mineral fertilisers. The next major industrial application is in detergents. The use of phosphorus in fertilisers makes this element a key focus of global food security.
Uranium
Authors: Mudd Gavin M.
Published: January 2023

The major greenhouse gas emissions from coal combustion are leading certain people to argue for uranium mining and nuclear power to meet these challenges. Although there is considerable rhetoric around promoting nuclear power as ‘green’ owing to its relatively lower greenhouse intensity compared with fossil fuels, a careful study of the data is required to understand properly the sustainability of uranium mining and nuclear power, and whether it can or should have a role in future energy supply scenarios. This chapter presents detailed research and analysis on uranium mining, focusing on known economic resources, production, and energy and greenhouse aspects. Overall, the chapter raises fundamental issues concerning the long-term sustainability of uranium mining and nuclear power, and documents the energy and greenhouse intensity of uranium production within the nuclear fuel chain.
Chemicals from Biomass
Authors: Scott Janet L. , Unali Gianfranco
Published: January 2023

Producing chemicals from renewable bioresources has the potential to address issues of growing scarcity (or awareness of scarcity) of fossil carbon feedstocks, in addition to mitigating geopolitical tensions associated with uneven distribution of these resources. However, the use of a range of bio-based feedstocks, which are likely to be dependent on local resources and to differ from region to region or even from season to season, presents challenges to an industry accustomed to relatively homogeneous, oil- and gas-based feedstocks. This material inhomogeneity also provides opportunities and access to a range of highly functionalised molecules. Bulk sources of bio-based chemicals include sugars and polysaccharides, lignin and fats and oils, and these are summarised. Details of some commercial, or near to commercial, bio-based chemicals are presented and two large classes of chemical products, solvents and surfactants, are discussed in more detail.
Carbon Dioxide Utilisation in the Production of Chemicals, Fuels and Materials
Authors: Aresta Michele , Stufano Paolo
Published: January 2023

Carbon dioxide is accumulating in the atmosphere as the natural carbon cycle is not able to absorb the anthropogenic CO2, despite the latter representing roughly 3% of the natural cycled amount. The influence of its growing concentration on possible climate change is of grave concern. Strategies for reducing its emission to the atmosphere are under urgent evaluation. The capture from point-concentrated sources is an option that can separate CO2 from flue gases; the captured CO2 can be either disposed of in natural fields (CCS) or used (CCU). CCS is site specific (existence of suited natural sites), requires large amounts of energy and comes with a high economic cost, but has the potential for disposing of large volumes of CO2. CCU can recycle carbon and contribute to avoiding fossil carbon extraction. The conversion of CO2 has different energy requirements depending on the nature of the chemicals derived from it; if the entire molecule is fixed into a compound (organic or inorganic, molecular or polymeric), the energy requirements are lower than if it is converted into energy-rich species such as fuels. This option requires that perennial primary energy sources (mainly solar and wind energy) are used for the conversion of CO2. In a changing paradigm of use of primary energy sources, the conversion of large volumes of CO2 is possible. This chapter presents the available opportunities of using CO2 as a source of carbon for making specialty and bulk molecular compounds, fuels or materials. The last use encompasses organic polymers such as polycarbonates, polyurethanes, urea-derived polymers, polyolefins and inorganic carbonates.
Carbon Dioxide in the Manufacture of Plastics
Authors: Jones Matthew D.
Published: January 2023

In the dawn of a sustainable economy, the formation of sustainable polymers from CO2 will be a cornerstone of such a movement. One of the most promising (both academically and industrially) systems is the copolymerisation of CO2 with epoxides to generate polycarbonates. This chapter introduces the rationale behind such and introduces some of the important catalytic developments in this area. Various metal centres (zinc, aluminium, cobalt and chromium) have all been employed – each metal initiator is discussed in turn. Finally, the chapter concludes with two areas of current/future research – ambient-pressure initiators and new epoxides – which show that the future is bright for such polymeric materials.
Materials for Water Splitting
Authors: Symes Mark D. , Cronin Leroy
Published: January 2023

The goal of sustainable water splitting is to generate hydrogen and oxygen from water using only renewable energy inputs. The hydrogen can then be stored and recombined with oxygen later, giving energy and water as the only products. Hence water splitting can be seen as an environmentally friendly way of turning intermittent energy sources such as solar power and wind energy into storable fuels. As the dissociation of water into H2 and O2 does not happen spontaneously, energy must be supplied for this reaction to occur. In this chapter, we investigate materials that facilitate the splitting of water into hydrogen and oxygen, paying particular attention to those that use only Earth-abundant elements, as opposed to rare or expensive constituents such as platinum.
Materials Used in Membranes for Water Purification and Recycling
Authors: Zhu Xiaoying , Wee Kin-Ho , Bai Renbi
Published: January 2023

In this chapter, the materials that can be used to fabricate membranes for water purification and recycling are briefly reviewed. Owing to its high effectiveness, freedom from chemical addition, simple system configuration and small footprint, membrane separation or membrane filtration has increasingly become the choice for water treatment technology and will continue to do so in the future. Materials for membrane fabrication can be classified into organic and inorganic. Base organic or polymeric materials that are commonly used to make pressure-driven membranes, including microfiltration, ultrafiltration, nanofiltration, and reverse osmosis, or electrical-driven membranes, such as ion-exchange membranes, are presented. Subsequently, polymer-based composite membranes consisting of two or more different kinds of polymers are discussed. Then, surface modification methods with functional materials to improve the performance of polymeric membranes or augment those base membranes with new properties are reviewed. Finally, inorganic materials and methods for inorganic membrane fabrication are briefly introduced.
Sewage and Sewage Sludge Treatment
Authors: Cartmell Elise
Published: January 2023

Sewage from properties and industries which are connected to the public sewerage system are treated by physical, chemical and biological sewage treatment processes to protect human health and the environment. In this chapter the conveyance of sewage to treatment works by combined or foul sewers is described. The subsequent preliminary treatment, primary sedimentation and biological secondary treatment stages are highlighted together with the consent standards required. The resulting sludge produced from these processes is treated using physical thickening and dewatering stages together with biological anaerobic digestion or composting processes which are further described in this chapter.
Air Pollution: Sources, Concentrations and Measurements
Authors: Harrison Roy M.
Published: January 2023

In this chapter, the basic concepts of particulate and gaseous, and primary and secondary pollutants are introduced. Consideration is then made of the sources, properties and measurement of the following specific air pollutants: sulfur dioxide, suspended particulate matter, oxides of nitrogen, carbon monoxide, hydrocarbons, ozone and peroxyacetyl nitrate. The determinants of airborne concentrations are considered and a brief section describes the principles of air quality management. Finally, the importance of indoor air quality is highlighted and a brief introduction is given of an international perspective on pollutant concentrations.
Control of Pollutant Emissions from Road Transport
Authors: Holman Claire
Published: January 2023

Road transport emissions have been controlled in the EU for over four decades. Large reductions in nitrogen oxides (NOx), carbon monoxide (CO) and hydrocarbons (HC) have occurred since the early 1990s when three-way catalysts were first widely fitted to new cars. Since then there has been a series of increasingly stringent and mandatory exhaust emission limits introduced, as well as new requirements to reduce road transport carbon dioxide (CO2) emissions. Both have been, and remain challenges for the motor industry. The emissions legislation has gradually evolved to reduce the real-world performance of road vehicles, but there is evidence that more needs to be done. Ambient concentrations of NO2 and particulate matter (PM) remain a concern in many urban areas. This chapter discusses the roles of engine technology, exhaust after-treatment and alternative fuels, as well the quality of conventional fuels to reduce emissions.
Climate Change
Authors: Shine Keith P.
Published: January 2023

This chapter presents a broad overview of understanding of climate change over the past century or so, together with a discussion of some of the uncertainties. It provides a background to the developments in understanding of climate change, presents evidence that climate has changed and assesses the mechanisms that cause climate change, with a particular emphasis on those due to human activity. The concepts underlying climate modelling are introduced and results are then presented that strongly support the view that human activity has played a major role in the observed climate change over the past fifty years. Possible changes in climate over the coming century are then discussed.
Health Effects of Environmental Chemicals
Authors: DELGADO-Saborit Juana Maria , Harrison ROY M.
Published: January 2023

This chapter reviews some of the ways that catastrophic or more incidental local exposures, as well as generalised chronic exposures to environmental pollutants can result in adverse effects on human health. The causes leading to the catastrophic and incidental exposures are associated with human actions, such as poor process management, inadequate maintenance programmes, wrong labelling and handling of toxic materials, and fraudulent practices. The generalised chronic exposure to traditional air pollutants, pesticides and endocrine disrupters is linked to our current standard of living, since they are associated with road traffic, industrial processes, and increased production of foodstuffs. The main pathways of exposure to contaminants are: (i) ingestion of pesticides and other chemical residues in food and water; and (ii) inhalation of pollutants associated with road vehicles and the indoor environment. Growing evidence is now available for specific chemicals acting as endocrine disruptors and possibly affecting human reproductive health, fertility, behaviour, growth and development. Currently, new concerns are also arising over exposures to novel nanomaterials. Increased understanding of total exposure, individual susceptibility, and source apportionment will help understand the link between chemicals exposure and related health effects, and will facilitate the adoption of appropriate control measures.
The Legal Control of Pollution
Authors: Macrory Richard , Howarth William
Published: January 2023

Recognising the uniqueness of any system of national law seeking to address pollution control, this chapter provides a selective account of the laws of the United Kingdom, and particularly England, in relation to environmental quality. Following introductory observations on the relatively long history of the UK in respect of industrial pollution control legislation and the contemporary significance of membership of the European Union, the chapter outlines the purposes and mechanisms of environmental law and the sources of law and institutional responsibilities as these arise in national law, EU law and under international law. This provides a basis for more detailed consideration of key areas, encompassing private rights and civil remedies, and consideration of four legal models for pollution regulation: concerning statutory nuisances; water pollution and water quality law; the integration of pollution control and environmental permitting; and procedural environmental rights. The chapter concludes with observations on the future of pollution control law, recognising the limitations of what has been achieved by past environmental laws and offering reflections on the challenges which lie ahead.
Edible Nanostructures: Introduction
Authors: Marangoni Alejandro G. , Pink David A.
Published: January 2023

Interest in soft materials has experienced tremendous growth in the past decade. This stems from the fact that such materials include many important industrial products, such as plastics, foods and lubricants. This chapter provides a brief overview of the subject.
Fat Nanostructure
Authors: O'sullivan Chloe , Acevedo Nuria , Peyronel Fernanda , Marangoni Alejandro G.
Published: January 2023

Fat is made up of a mixture of triacylglycerol molecules (TAGs) – three fatty acids esterified to a glycerol backbone. The solid material is structured by a fraction of high melting point TAGs, which form a crystal network that traps the low melting TAGs within. Characterization of that crystal network is an important tool to understand fat properties and functionality. This chapter will cover fat crystal structure using a bottom-up approach, from TAG molecules to space-filling network. Emphasis will be on the fat crystal nanoscale, a level which was recently isolated and characterized, and how nano-sized crystalline structures fit into the larger network. Finally, the effect of composition and crystallization conditions on crystal structure and bulk physicochemical properties will be examined, to understand how processing conditions can be used to target functionality.
Imaging Nanostucture
Authors: Smith Alexandra K.
Published: January 2023

Food structure is based on a system of molecules that provide form and function. A better understanding of the arrangement of the underlying molecules that contribute to the macromolecular structure of natural foods leads to the ability to create novel food products. Microscopes give us the opportunity to image the basic architectural molecules and are tools that contribute to research into food structure. Imaging of food at a nanostructure level is possible by the use of the transmission electron microscope, the scanning electron microscope, and the atomic force microscope. The ability of these instruments to provide nanostructure resolution is based on design principles, and the quality of the preparation of the sample. The critical objective of sample preparation is to maintain the original properties of the biological material, whether it is native tissue or a complex emulsion. Only when the sample is prepared without distortion can the interpretation be considered valid. The researcher must understand the opportunities and limitations that come with each imaging method. Cryo-preparation methods are preferred for food imaging applications because freezing preserves water, fat, and air and the distribution of these constituents, which are major components in most food systems. Imaging methods must be complemented with other scientific methods to verify interpretation and eliminate bias. Correlated microscopy techniques are recommended.
Computer Simulation Techniques for Modelling Statics and Dynamics of Nanoscale Structures
Authors: Pink David A. , Razul M. Shajahan G. , Gordon T. , Quinn B. , MacDonald A. J.
Published: January 2023

This chapter describes computer simulation techniques that are used to model the statics and dynamics of nanoscale structures and their self-organized assemblies via their physical interactions. We describe some models which cannot be enabled without employing computer simulation but do not explicitly address models such as self-consistent field approaches or DLVO theory. The chapter is divided into four sections: introduction and background, atomic scale molecular dynamics, coarse-grained modelling and stochastic processes, and fluid flow. It is introduced via brief descriptions of protein folding and crystalline microscale structures in edible oils. A brief background to important aspects of statistical mechanics is followed by a description of atomic scale molecular dynamics. The spatial scale is then expanded and coarse-graining of atomic interactions is described. This leads into nanoscale systems and stochastic processes, and we describe the various applications of Monte Carlo techniques. The fourth section deals with fluid flow and we describe dissipative particle dynamics and, to a lesser extent, lattice-Boltzmann theory. In all sections we give steps to follow (recipes) in using these techniques. In addition, we give one or two examples of modelling and how computer simulation was used. Although our choices of methods and examples reflect our principal interests, we are not pushing for the use of one technique rather than another. We describe techniques which either continue to play fundamental roles in computer simulation of soft matter and fluids or are newer developments which have shown increased use in the last decade.
Anti-tumor effect of infant-derived Enterococcus via the inhibition of proliferation and inflammation as well as the promotion of apoptosis
Authors: Yang Qin , He Yao , Tian Linlin , Zhang Zhihong , Qiu Liang , Tao Xueying , Wei Hua
Published: January 2023

The oral administration of E. faecium WEFA23 effectively inhibited melanoma growth by inhibiting cell proliferation, promoting apoptosis and inhibiting tumor inflammation in mice.
Anti-glycation and anti-inflammatory activities of anthocyanins from purple vegetables
Authors: Gao Qingchao , Ma Rong , Shi Lu , Wang Shulin , Liang Ying , Zhang Zhiyong
Published: January 2023

Anthocyanins may be effective bioactive constituents to reduce the potential risk of chronic diseases induced by glycation and inflammation.
Synergistic or antagonistic antioxidant combinations – a case study exploring flavonoid-nitroxide hybrids
Authors: Larin Astrid C. R. , Pfrunder Michael C. , Mullen Kathleen M. , Wiedbrauk Sandra , Boase Nathan R. , Fairfull-Smith Kathryn E.
Published: January 2023

Flavonoid-nitroxide hybrids were prepared and displayed limited antioxidant protection, performing antagonistically compared to the individual components in a peroxyl radical scavenging assay.
Solvent-controlled synthesis of an Al12-oxo molecular ring and Al24-oxo truncated metallo-cube
Authors: Zou Ying , Lv Wei , Xue Zhen-Zhen , Li Jin-Hua , Li Xiao-Yu , Wang Guo-Ming
Published: January 2023

A highly symmetric Al24 cluster with truncated metallo-cube structure is reported. As one of 13 Archimedean polyhedra, Al24 is composed of eight Al3triangles and six Al8octagons. And the regulation from ringy Al12 to Al24 metallocage is realized.
Interface engineering of porous Co(OH)2/La(OH)3@Cu nanowire heterostructures for high efficiency hydrogen evolution and overall water splitting
Authors: Zhang Zhen , Wang Zhiqiang , Zhang Hang , Zhang Zikuan , Zhou Jingwei , Hou Ying , Liu Peizhi , Xu Bingshe , Zhang Haixia , Guo Junjie
Published: January 2023

The heterointerface strategy of cobalt hydroxide and lanthanum hydroxide enable excellent electrocatalytic water splitting performance and durability.
Rapid photo-oxidation reactions of imidazole derivatives accelerated by planar quinoid oxidation-state structures
Authors: Yu Yue , Wang Bohan , Chen Jianai , Dong Yujie , Zhan Wang , Zhang Shitong , Li Weijun , Yang Bing , Zhang Cheng , Ma Yuguang
Published: January 2023

Photo-oxidation reactions of imidazole derivatives accelerated by quinoid oxidation-state structures, which can be controlled by different linking types of arylamine groups.
Waterfall: Gozalandia. Distributed protocol with fast finality and proven safety and liveness
Authors: Grybniak Sergii , Leonchyk Yevhen , Mazurok Igor , Nashyvan Oleksandr , Shanin Ruslan
Published: January 2023

A consensus protocol is a crucial mechanism of distributed networks by which nodes can coordinate their actions and the current state of data. This article describes a BlockDAG consensus algorithm based on the Proof of Stake approach. The protocol provides network participants with cross‐voting for the order of blocks, which, in the case of a fair vote, guarantees a quick consensus. Under conditions of dishonest behavior, cross‐voting ensures that violations will be quickly detected. In addition, the protocol assumes the existence of a Coordinating network containing information about the approved ordering, which qualitatively increases security and also serves to improve network synchronization.
Motion optimization for safe robot–environment interaction with force constraints
Authors: Guo Yi , Huang Haohui , Guan Xinping
Published: January 2023

Autonomous robotics working in the uncertain environment have drawn increasing interests from researchers. Here, an issue of online motion optimization under unknown environment is considered while preserving the safety and improving the flexible manoeuvrability of robot–environment interaction. This problem is addressed by improving the conventional dynamic movement primitives (DMPs) framework with force tracking constraints. First, an initial motion is learned through the DMPs. At the stage of skill generalization, a temporal coupling term combining with force constraints scheme which is inspired by the barrier Lyapunov function and finite‐time prescribed performance is deduced and adds to the original DMPs, so as to remain the contacting force staying within a predefined limit while aligning the motion along with surface of unknown environment adaptively. In this way, not only the contacting force can be guaranteed within a safe margin, but the shape of generalizing motion is preserved. Then the convergence and stability of the proposed DMPs are proved which is grounded on Laplace transformation‐based stability analysis to ensure the performance and safety. Finally, the proposed method is instantiated combined with conventional PID controller through the compared simulations to verify its effectiveness.
An efficient two‐stage algorithm for parameter identification of non‐linear state‐space models‐based on Gaussian process regression
Authors: Li Xiaonan , Ma Ping , Wu Zehua , Chao Tao , Yang Ming
Published: January 2023

This paper aims to improve the efficiency of parameter identification of the nonlinear state‐space model (SSM). The commonly used particle Markov chain Monte Carlo (PMCMC) method is time‐consuming. The surrogate model is a useful acceleration strategy, but it is expensive to establish a global high‐precision surrogate model. This paper proposes an efficient algorithm that gradually estimates the unknown parameters in two stages. In the first stage, a reduced region is established based on the latest method. We train a local Gaussian Process regression (GPR) of the likelihood function in the reduced region based on the optimum Latin hypercube design (OLHD). In the second stage, we identify the unknown parameters more accurately based on the MCMC method. When the proposal sample is in the reduced region, we use GPR to estimate the likelihood; otherwise, BPF is used to estimate the likelihood. The reduced region is usually the high probability density region, which is why the algorithm is efficient. It is proved that the acceptance rate of any two samples based on the proposed algorithm is theoretically convergent to that of the PMCMC algorithm. Two examples demonstrate that the proposed method performs well in accuracy and efficiency.
Operation and coordination control scheme of an enhanced AC–DC hybrid microgrid under abnormal distribution network
Authors: Du Yi , Sun Huadong , Zheng Chao
Published: January 2023

Considering that the AC–DC hybrid microgrid (HMG) is connected to the low‐voltage distribution network (DN) where voltage faults occur most commonly, the fault ride‐through (FRT) capability and power quality performance of the HMG under abnormal DN conditions have become a critical issue. In this paper, a decentralized coordination control scheme based on an improved topology is proposed for the grid‐interactive HMG to guarantee uninterrupted and high power‐quality operation during grid faults. The method of it includes: (1) a new HMG topology is presented by adding a series transformer (ST), which is inserted between the DN and HMG; (2) an improved coordination control strategy that considers the interaction between converters of the enhanced HMG. Based on the proposed method, the operation modes of the system are introduced, and the specific design process and small‐signal model analysis of the proposed control scheme are presented. Finally, the simulated and experimental results show that the proposed method can keep both AC and DC bus voltage stable and improve the fault ride‐through capability and power quality of the HMG under abnormal DN conditions.
Retracted: Smart optimal path with blockchain modelling in internet of things using enhanced K‐means clustering and advance encryption standard
Authors: Ismael Imran Inas , Mohammed Jameel Shymaa , Adnan Jaleel Refed
Published: January 2023

Retraction: [Inas Ismael Imran, Shymaa Mohammed Jameel, Refed Adnan Jaleel, Smart optimal path with blockchain modelling in internet of things using enhanced K‐means clustering and advance encryption standard, IET Software 2023 (https://doi.org/10.1049/sfw2.12095)].

The above article from IET Software, published online on 28 January 2023 in Wiley Online Library (wileyonlinelibrary.com), has been retracted by agreement between the Editor‐in‐Chief, Hana Chockler, the Institution of Engineering and Technology (the IET) and John Wiley and Sons Ltd. This article was published as part of a Guest Edited special issue. Following an investigation, the IET and the journal have determined that the article was not reviewed in line with the journal’s peer review standards and there is evidence that the peer review process of the special issue underwent systematic manipulation. Accordingly, we cannot vouch for the integrity or reliability of the content. As such we have taken the decision to retract the article. The authors have been informed of the decision to retract.
Impact of a new H/He equation of state on the evolution of massive brown dwarfs
Authors: Chabrier Gilles , Baraffe Isabelle , Phillips Mark , Debras Florian
Published: January 2023

We explored the impact of the latest equation of state (EOS) for dense hydrogen–helium mixtures, which takes into account the interactions between hydrogen and helium species during the evolution of very low-mass stars and brown dwarfs (BDs). These interactions modify the thermodynamic properties of the H/He mixture, notably the entropy, a quantity of prime importance for these fully convective bodies, but also the onset and the development of degeneracy throughout the body. This translates into a faster cooling rate, that is, cooler isentropes for a given mass and age, and thus larger BD masses and smaller radii for a given effective temperature and luminosity than the models based on previous EOSs. This means that objects of a given mass and age in the rangeM ≲ 0.1 M⊙,τ ≳ 108yr will have cooler effective temperatures and fainter luminosities. Confronting these new models with several observationally determined BD dynamical masses, we show that this improves the agreement between evolutionary models and observations and resolves at least part of the observed discrepancy between the properties of dynamical mass determinations and evolutionary models. A noticeable consequence of this improvement of the dense H/He EOS is that it yields a larger H-burning minimum mass, now found to be 0.075 M⊙(78.5 MJup) with the ATMO atmosphere models for solar metallicity. These updated BD models are made publicly available.
J-NEP: 60-band photometry and photometric redshifts for the James Webb Space Telescope North Ecliptic Pole Time-Domain Field
Authors: Hernán-Caballero A. , Willmer C. N. A. , Varela J. , López-Sanjuan C. , Marín-Franch A. , Vázquez Ramió H. , Civera T. , Ederoclite A. , Muniesa D. , Cenarro J. , Bonoli S. , Dupke R. , Lim J. , Chaves-Montero J. , Laur J. , Hernández-Monteagudo C. , Fernández-Ontiveros J. A. , Fernández-Soto A. , Díaz-García L. A. , González Delgado R. M. , Queiroz C. , Vílchez J. M. , Abramo R. , Alcaniz J. , Benítez N. , Carneiro S. , Cristóbal-Hornillos D. , Mendes de Oliveira C. , Moles M. , Sodré L. , Taylor K.
Published: January 2023

The Javalambre-Physics of the Accelerating Universe Astrophysical Survey (J-PAS) will observe approximately one-third of the northern sky with a set of 56 narrow-band filters using the dedicated 2.55 m Javalambre Survey Telescope (JST) at the Javalambre Astrophysical Observatory. Prior to the installation of the main camera, in order to demonstrate the scientific potential of J-PAS, two small surveys were performed with the single-CCD Pathfinder camera: miniJPAS (~1 deg2 along the Extended Groth Strip), and J-NEP (~0.3 deg2 around the JWST North Ecliptic Pole Time Domain Field), including all 56 J-PAS filters as well as u, g, r, and i. J-NEP is ~0.5–1.0 mag deeper than miniJPAS, providing photometry for 24,618 r-band-detected sources and photometric redshifts (photo-z) for the 6662 sources with r < 23. In this paper, we describe the photometry and photo-z of J-NEP and demonstrate a new method for the removal of systematic offsets in the photometry based on the median colours of galaxies, which we call ‘galaxy locus recalibration’. This method does not require spectroscopic observations except in a few reference pointings and, unlike previous methods, is directly applicable to the whole J-PAS survey. We use a spectroscopic sample of 787 galaxies to test the photo-z performance for J-NEP and in comparison to miniJPAS. We find that the deeper J-NEP observations result in a factor ~1.5–2 decrease in σNMAD (a robust estimate of the standard deviation of the photo-z error) and η (the outlier rate) relative to miniJPAS for r > 21.5 sources, but no improvement in brighter ones, which is probably because of systematic uncertainties. We find the same relation between σNMAD and odds in J-NEP and miniJPAS, which suggests that we will be able to predict the σNMAD of any set of J-PAS sources from their odds distribution alone, with no need for additional spectroscopy to calibrate the relation. We explore the causes of photo-z outliers and find that colour-space degeneracy at low S/N, photometry artefacts, source blending, and exotic spectra are the most important factors.
Understanding the TeV γ-ray emission surrounding the young massive star cluster Westerlund 1
Authors: Härer Lucia K. , Reville Brian , Hinton Jim , Mohrmann Lars , Vieu Thibault
Published: January 2023

Context. Young massive star clusters (YMCs) have increasingly become the focus of discussions on the origin of galactic cosmic rays (CRs). The proposition that CRs are accelerated inside superbubbles (SBs) blown by the strong winds of these clusters avoids issues faced by the standard paradigm of acceleration at supernova remnant shocks.

Aims. We provide an interpretation of the latest TeV γ-ray observations of the region around the YMC Westerlund 1 taken with the High Energy Stereoscopic System (H.E.S.S.) in terms of diffusive shock acceleration at the cluster wind termination shock, taking the spectrum and morphology of the emission into account. As Westerlund 1 is a prototypical example of a YMC, this study is relevant to the general question about the role of YMCs for the Galactic CR population.

Methods. We generated model γ-ray spectra, characterised particle propagation inside the SB based on the advection, diffusion, and cooling timescales, and constrained key parameters of the system. We considered hadronic emission from proton-proton interaction and subsequent pion decay and leptonic emission from inverse Compton scattering on all relevant photon fields, including the cosmic microwave background, diffuse and dust-scattered starlight, and the photon field of Westerlund 1 itself. The effect of the magnetic field on cooling and propagation is discussed. Klein-Nishina effects are found to be important in determining the spectral evolution of the electron population.

Results. A leptonic origin of the bulk of the observed γ-rays is preferable. The model is energetically plausible, consistent with the presence of a strong shock, and allows for the observed energy-independent morphology. The hadronic model faces two main issues: confinement of particles to the emission region, and an unrealistic energy requirement.
A flux globalization based well-balanced path-conservative central-upwind scheme for the shallow water flows in channels
Authors: Chen Yiming , Kurganov Alexander , Na Mingye
Published: January 2023

We develop a flux globalization based well-balanced (WB) path-conservative central-upwind (PCCU) scheme for the one-dimensional shallow water flows in channels. Challenges in developing numerical methods for the studied system are mainly related to the presence of nonconservative terms modeling the flow when the channel width and bottom topography are discontinuous. We use the path-conservative technique to treat these nonconservative product terms and implement this technique within the flux globalization framework, for which the friction and aforementioned nonconservative terms are incorporated into the global flux: This results in a quasi-conservative system, which is numerically solved using the Riemann-problem-solver-free central-upwind scheme. The WB property of the resulting scheme (that is, its ability to exactly preserve both still- and moving-water equilibria at the discrete level) is ensured by performing piecewise linear reconstruction for the equilibrium variables rather than the conservative variables, and then evaluating the global flux using the obtained point values of the equilibrium quantities. The robustness and excellent performance of the proposed flux globalization based WB PCCU scheme are demonstrated in several numerical examples with both continuous and discontinuous channel width and bottom topography. In these examples, we clearly demonstrate the advantage of the proposed scheme over its simpler counterparts.
Besteht der Bedarf zur Gründung einer Nachwuchsorganisation „Young DGN“ innerhalb der Deutschen Gesellschaft für Nuklearmedizin (DGN)? Ergebnisse einer webbasierten Umfrage in der deutschen Nuklearmedizin 2021/2022
Authors: Sahin Yasemin Aylin , Eilsberger Friederike , Einspänner Eric , Kunz Johannes , Spreckelmeyer Sarah , Luster Markus , Brenner Winfried , Kläsner Benjamin , Holzgreve Adrien
Published: January 2023

Ziel In zahlreichen medizinischen Fachgesellschaften bilden
dedizierte Nachwuchsorganisationen eine wichtige Grundlage der Nachwuchsarbeit. In der
Deutschen Gesellschaft für Nuklearmedizin (DGN) war eine derartige Nachwuchsorganisation
bisher nicht vorhanden. Ziel dieser Arbeit war daher eine Bedarfserhebung unter allen
nuklearmedizinischen Berufsgruppen in Deutschland hinsichtlich Gründung und möglicher
Ausgestaltung einer Nachwuchsorganisation der DGN („Young DGN“).

Methoden Es wurde von einer seitens der DGN beauftragten
Initiativgruppe aus jungen DGN-Mitgliedern ein Fragebogen mit 18 Fragen entwickelt. Der
Fragebogen wurde zunächst als PDF am 10.12.2021 per E-Mail an die Mitglieder des
DGN-Hochschulausschusses verschickt. Als Online-Survey wurde der Fragbogen dann zu 4 weiteren
Zeitpunkten zwischen dem 23.12.2021 und dem 18.03.2022 per E-Mail über den DGN-eBrief und am
23.02.2022 per E-Mail über den Verteiler des Berufsverbandes Deutscher Nuklearmediziner (BDN)
verschickt.

Ergebnis Die Umfrage schloss am 31.03.2022 mit 111 Antworten (104
Online-Surveys, 7 PDF). Der Altersmedian der Teilnehmenden lag bei 32,5 Jahren (20–80 Jahre).
86% der Teilnehmenden gaben an, Interesse an einer Young DGN zu haben, wovon 67% zu einer
aktiven Mitarbeit bereit waren. 79% gaben an, dass die Nuklearmedizin für sie ein spannendes
Fach sei. 96% äußerten Interesse an Fortbildungsprogrammen, 60% an einem Mentoring-Programm.
75% denken, dass eine Young DGN die Sichtbarkeit des Faches verbessern könnte.

Schlussfolgerung Die Gründung einer Nachwuchsorganisation „Young
DGN“ findet großen Anklang unter den nuklearmedizinischen Berufsgruppen in Deutschland. Ein
Großteil der Umfrageteilnehmenden kann sich vorstellen, an dieser mitzuwirken. Besonderer
Konsens fand sich bei dem Wunsch nach einer Ausweitung des Fortbildungsangebotes.