The books Fractional Calculus with Applications in Mechanics: Vibrations and Diffusion Processes and Fractional Calculus with Applications in Mechanics: Wave Propagation, Impact and Variational ...Principles contain various applications of fractional calculus to the fields of classical mechanics. Namely, the books study problems in fields such as viscoelasticity of fractional order, lateral vibrations of a rod of fractional order type, lateral vibrations of a rod positioned on fractional order viscoelastic foundations, diffusion-wave phenomena, heat conduction, wave propagation, forced oscillations of a body attached to a rod, impact and variational principles of a Hamiltonian type. The books will be useful for graduate students in mechanics and applied mathematics, as well as for researchers in these fields. Part 1 of this book presents an introduction to fractional calculus. Chapter 1 briefly gives definitions and notions that are needed later in the book and Chapter 2 presents definitions and some of the properties of fractional integrals and derivatives. Part 2 is the central part of the book. Chapter 3 presents the analysis of waves in fractional viscoelastic materials in infinite and finite spatial domains. In Chapter 4, the problem of oscillations of a translatory moving rigid body, attached to a heavy, or light viscoelastic rod of fractional order type, is studied in detail. In Chapter 5, the authors analyze a specific engineering problem of the impact of a viscoelastic rod against a rigid wall. Finally, in Chapter 6, some results for the optimization of a functional containing fractional derivatives of constant and variable order are presented.
In this paper, the effects of Eu, Nd doping, and Eu–Nd co-doping on the stability, magnetic and optical properties of monolayer MoS2 are investigated by the density functional theory based on the ...first principle's calculations. It was found that the Eu–Nd co-doped monolayer MoS2 is more stable than other considered doping structures. After the introduction of Eu and Nd atoms, the band gap are decreased to different degrees, indicating that the doping is favorable to the electronic jump, which might enhances the conductivity of the system. All doped systems exhibit magnetic properties. In addition, the absorption spectra of all doped systems show significant red-shift compared with those of pure monolayer MoS2, indicating that the doping improves the absorption capacity in visible light. These results might provide theoretical guidance for the design of novel monolayer MoS2 semiconductor materials.
•First Inner Mongolia has rich rare earth mineral resources, and rare earth elements can change the electronic structure and magnetic properties of the material, thus improving the conductivity, magnetic properties, optical properties and so on.•Secondly, MoS2 is a popular material at the forefront, and with its special layered structure and unique properties, it is widely used in electronic devices, catalysts, biomedicine and other fields.•Finally, the band gap of monolayer MoS2 is significantly changed after doping with rare earth elements, and there are multiple impurity energy levels (ILS) within the band gap, which is helpful for electron excited leaps.•Moreover, all doped systems showed magnetic properties.
Negative thermal expansion (NTE) is crucial for controlling the thermomechanical properties of functional materials, albeit being relatively rare. This study reports a giant NTE (αV∼−9.2 ⋅ 10−5 K−1, ...100–200 K; αV∼−3.7 ⋅ 10−5 K−1, 200–650 K) observed in NaB(CN)4, showcasing interesting ultralight properties. A comprehensive investigation involving synchrotron X‐ray diffraction, Raman spectroscopy, and first‐principles calculations has been conducted to explore the thermal expansion mechanism. The findings indicate that the low‐frequency phonon modes play a primary role in NTE, and non‐rigid vibration modes with most negative Grüneisen parameters are the key contributing factor to the giant NTE observed in NaB(CN)4. This work presents a new material with giant NTE and ultralight mass density, providing insights for the understanding and design of novel NTE materials.
NaB(CN)4 exhibits a giant negative thermal expansion behaviour (αV∼−9.24 ⋅ 10−5 K−1, 100–200 K; αV∼−3.7 ⋅ 10−5 K−1, 200–650 K) with interesting ultralight mass density properties. Non‐rigid vibrational modes, characterized by a maximum negative Gruneisen parameter, play a key factor in the generation of the giant NTE observed in NaB(CN)4.
Aqueous zinc‐ion batteries (AZIBs) are an appealing battery system due to their low cost, intrinsic safety, and environmental‐friendliness, while their application is plagued by the obstacles from ...the cathode, electrolyte, and zinc anode. Summarizing the design principles and strategies toward the optimization of cathode, electrolyte, and zinc anode is crucial for the development of AZIBs. Herein, we present a comprehensive analysis of the design principles and promising strategies toward the improvement of AZIBs. Firstly, the various reaction mechanisms are summarized and the existing issues associated with the cathode, electrolyte, and zinc anode are discussed to guide the rational design of AZIBs. Subsequently, we provide an in‐depth and comprehensive discussion on the design principles and strategies for the electrodes/electrolyte/separator optimization, and analyze the advantages and disadvantages of various strategies. Importantly, the design principles and strategies of the newly appeared conversion‐type AZIBs, such as Zn‐S battery and Zn‐Se battery, are also discussed and analyzed. The effect of design strategies on the electrochemical performance and the relationship between the current issues and strategies are also unveiled in detail. Finally, some research trends and perspectives are provided for designing better AZIBs.
Aiming to better understand the reaction mechanism and various design principles towards the development of AZIBs, we present an overview of the zinc storage mechanisms and existing issues, and then offer an in‐depth discussion on the design principles and strategies for battery optimization, including the cathode, anode, and electrolyte. Finally, some constructive research perspectives have been provided for further development of AZIBs.
Refractory high-entropy alloys (RHEAs) have promising applications in industry due to their outstanding high-temperature properties, but most of them are brittle and poorly plastic formability at ...ambient temperature. Developing new ambient ductile RHEAs is a challenge in current materials research. In this work, an ambient ductility TiHfVNbTa alloy was prepared, and its microstructure, mechanical properties, phase stability, lattice distortion, and basic physical properties were investigated by combing experiments and density functional theory (DFT) calculations. The obtained results show that TiHfVNbTa alloy has excellent cold-rolled formability with >84% thickness reduction, no crack generation, and ultimate tensile strain up to >12% at ambient temperature. Besides, the tensile yield strength (hardness) of the alloy increases from 997 MPa (363 HV) in the annealed state to 1340 MPa (453 HV) in the 84% cold-rolled state, displaying work-hardening behavior. The TiHfVNbTa alloy has a single-phase solid solution body-centered cubic (BCC) structure, and no structural transformation occurs during rolling and tension, implying its good phase stability. Notably, the TiHfVNbTa alloy exhibits a higher specific yield stress and ductility compared to most RHEAs. DFT results reveal that the high strength is mainly contributed by severe lattice distortion. Hf and V elements are the major sources of lattice distortion. In addition, the physical properties such as metallic bonding, anisotropy and electronic structure are also analyzed based DFT calculations. The obtained results not only help to understand the material properties of TiHfVNbTa alloy, but also provide design guidelines for novel ductile RHEAs.
•Rolling and tension display that TiHfVNbTa has excellent ambient ductility and phase stability.•First time, solid solution strengthening is clarified by experiments and DFT calculations.•First time, lattice distortion is identified and evaluated for TiHfVNbTa alloy.•First time, Hf and V are identified as the key elements for the lattice distortion.•It provides new concept for designing ambient ductile refractory high-entropy alloys.
The author of the article has studied the scientific positions of scholars on understanding and classification of the principles of law. The characteristic features of the principles of preventive ...police activity have been distinguished. First of all, they are formed and developed in accordance with the contemporary requirements, expectations and needs of members of society and the state regarding the protection of their rights, freedoms and interests within the public and legal sphere; secondly, they determine the social purpose, nature, content and limits of preventive police activity; thirdly, it is obvious that all principles of preventive police activity form an objectively conditioned, normatively fixed, scientifically sound, relatively stable “coordinate system”, the elements of which do not act in isolation but, in a certain interdependence, do not contradict each other and have distinct character in the application of police preventive measures and the implementation of the preventive function by the agencies and units of the National Police of Ukraine.
The principles of preventive activities, depending on the method of their regulatory consolidation, are classified into: 1) general legal principles that determine the principles of formation and implementation of state policy in the field of national security; 2) basic principles that characterize the purposefulness, content and limits of police activity and are enshrined in the provisions of the Law of Ukraine “On the National Police”; 3) special principles that characterize the specificity of preventive police activity.
The principles of preventive police activity should be understood as objectively stipulated, pivotal, relatively stable, scientifically substantiated guiding principles, enshrined by the norms of national legislation and international legal acts, which are the basis for the activity of the National Police of Ukraine, as well as the authorized officials of its agencies and structural units carried out in the process of forecasting and preventing offenses through the use of preventive police measures permitted by national law, and complex of preventive actions.
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