Mechanical Problems Research Articles

Polar mesospheric ozone loss initiates downward coupling of solar signal in the Northern Hemisphere

Abstract Solar driven energetic particle precipitation (EPP) is an important factor in polar atmospheric ozone balance and has been linked to ground-level regional climate variability. However, the linking mechanism has remained ambiguous. The observed and simulated ground-level changes start well before the processes from the main candidate, the so-called EPP-indirect effect, would start. Here we show that initial reduction of polar mesospheric ozone and the resulting change in atmospheric heating rapidly couples to dynamics, transferring the signal downwards, shifting the tropospheric jet polewards. This pathway is not constrained to the polar vortex. Rather, a subtropical route initiated by a changing wind shear plays a key role. Our results show that the signal propagates downwards in timescales consistent with observed tropospheric level climatic changes linked to EPP. This pathway, from mesospheric ozone to regional climate, is independent of the EPP-indirect effect, and solves the long-standing mechanism problem for EPP effects on climate.

First Clinical Evidence About the Use of a New Silver-Coated Titanium Alloy Instrumentation to Counteract Surgical Site Infection at the Spine Level

Background: Surgical site infections (SSIs) following spinal instrumentation surgery are among the most concerning complications. This study is aimed at assessing the effectiveness of a new treatment approach for SSIs that includes a single-stage approach with the removal of the previous hardware, accurate debridement, and single-stage instrumentation using a silver fixation system (SFS) made of titanium alloy coated with silver (Norm Medical, Ankara, Turkey) by means of a retrospective observational study. Materials and Methods: The demographic data, type of surgery, comorbidities, pathogens, and treatment details of consecutive patients with an SSI who received the SFS between 2018 and 2021 were extracted from their medical records and analyzed. The patients treated with the SFS for primary pyogenic infections were excluded. The patients were re-evaluated at multiple endpoints in order to assess the rate of reinfection and the local and general complications. Results: Fifty-six patients were treated with the SFS and thirty-four patients met the inclusion criteria. Out of those 34 patients, the rate of infection recurrence or insurgence after the implantation of the SFS was 11.8%, with infection detected in 4 out of 34 cases and mechanical problems detected in 2 of the 34 cases (5.9%). The overall success rate in controlling infection recurrence or emergence was 88.2% (30 out of 34 cases). The overall survival rate of the SFS was 87%, 78%, and 71% at one, two, and three years, respectively. Conclusions: The surgical strategy with the SFS demonstrated promising outcomes in preventing infection recurrence or insurgence, with a low incidence of mechanical complications. However, further structured and comprehensive studies are essential for validating these initial findings.

Complex Rock Mechanics Problems and Risk Prevention Solutions

The emergence of rock mechanics was driven by the need to address stability issues in rock engineering and to examine conditions leading to rock failure [...]

Dunkl-Schrödinger equation in higher dimensions

Abstract This paper presents analytical solutions for eigenvalues and eigenfunctions of the Schrödinger equation in higher dimensions, incorporating the Dunkl operator. Two fundamental quantum mechanical problems are examined in their exact forms: the d-dimensional harmonic oscillator and the Coulomb potential. In order to obtain analytical solutions to these problems, both Cartesian and polar coordinate systems were employed. Firstly, the Dunkl-Schrödinger equation is derived in d-dimensional Cartesian coordinates, and then for the isotropic harmonic potential interaction, its solutions are given. Subsequently, using polar coordinates the angular and radial parts of the Dunkl-Schrödinger equation are obtained. It is demonstrated that the system permits the separation of variables in both coordinate systems, with the resulting separated solutions expressed through Laguerre and Jacobi polynomials. Then, the radial Dunkl-Schrödinger equation is solved using the isotropic harmonic, pseudoharmonic, and Coulomb potentials. The eigenstates and eigenvalues are obtained for each case and the behavior of the energy eigenvalue functions are illustrated graphically with the reduced probability densities.

Theoretical Study on the Generation Mechanism of Intermediates During Discharge/Charge Processes in Lithium‐Air Batteries

AbstractIn this paper, molecular dynamics (MD) was used to investigate the problem of the generation mechanism of product intermediates in the aprotic electrolyte in lithium‐air batteries. Through the utilisation of simulations of the electrolyte system, molecular orbitals of the electrolyte, thermodynamic analysis of the product intermediates' reactions, the Li+ solvation structure, the electrochemical stability of the electrolyte, the Li+ and O2‐ diffusion coefficients, and the Gibb's free energy of the Li+‐O2‐ and Li+‐C2O62− were investigated in detail. The results show that the Li+ coordination structure was a contact ion pair (CIP) structure, and the formation of a 5‐coordination structure with oxygen atoms was lower in energy and more stable in structure. The TEGDME‐LiTFSI electrolyte was the most stable in electrochemistry. The Gibbs free energy of the generated Li+‐O2− and Li+‐C2O62‐ was negative, indicating that the reaction can proceed spontaneously at ambient temperature. The intermediate products were present in the electrolyte in the form of [Li(solvent)n+‐O2‐] and [Li(solvent)n+‐C2O62‐]. The study of the mechanism of product intermediates in the lithium‐air battery is important for scholars to analyze the product growth pathway and improve the battery performance.

Refining boundary value problems in non-local micropolar mechanics

Refining boundary value problems in non-local micropolar mechanics

Cross-Platform Advertising Integration Strategies from a Brand Communication Perspective Research

With the rapid development of digitalization and multi-media environment, cross-platform advertising integration has gradually become an important way of brand communication. From the perspective of brand communication and based on the significance of cross-platform advertising integration, this study puts forward the strategies of improving laws and regulations and regulatory mechanisms, strengthening R&D investment in data privacy and security protection, and cultivating and introducing composite talents in response to the problems of unsound laws, regulations and regulatory mechanisms, outstanding data privacy and security issues, and the lack of composite talents that exist in the cross-platform advertising integration, which provides a new perspective on the construction of the theoretical system of cross-platform advertising integration, and also provides a reference for brand communication practice in the digital era. It provides a new perspective for the construction of the theoretical system of cross-platform advertising integration, and also provides a reference for the communication practice of brands in the digital era.

Numerical Solutions of Certain Time-Independent Quantum Mechanics Problems by Using the Python Environment

This paper discussed the digitization of some analytical solutions of the fundamental equation of non-relativistic quantum mechanics, the Schrödinger equation, in the Python programming environment. The main objective of the work is to automate the solution of several known analytically solvable problems of quantum mechanics and ensure their use in more complex problems. For this purpose, the Python programming environment was chosen, which, due to the large number of libraries and flexibility, is currently widely used in solving physical and mathematical problems. In the program we propose, which is available on the GitHub platform, it is solved easily. The problem of determining the probability of the spatial distribution of an electron in a hydrogen-like atom is discussed. The Schrödinger equation is presented in the spherical coordinate system. The wave function, describing the electron's state, quantized energy values, and probability density, is derived analytically. A recursive function was written in Python to handle the series coefficients defining the wave function. Utilizing relevant libraries, the resulting program constructs electron spatial distribution functions for different excitation levels. The paper then examines two one-dimensional tunneling scenarios and provides the tunneling coefficients in analytical form. A Python program was developed to plot the dependence of these coefficients on the particle's coordinate and energy. All the code is available on GitHub.

Enhanced Entanglement in the Measurement-Altered Quantum Ising Chain

Understanding the influence of measurements on the properties of many-body systems is a fundamental problem in quantum mechanics and for quantum technologies. This paper explores how a finite density of stochastic local measurement modifies a given state’s entanglement structure. Considering various measurement protocols, we explore the typical quantum correlations of their associated projected ensembles arising from the ground state of the quantum Ising model. Using large-scale numerical simulations, we demonstrate substantial differences among inequivalent measurement protocols. Surprisingly, we observe that forced on-site measurements can enhance both bipartite and multipartite entanglement. We present a phenomenological toy model and perturbative calculations to analytically support these results. Furthermore, we extend these considerations to the non-Hermitian Ising model, naturally arising in optically monitored systems, and we show that its qualitative entanglement features are not altered by a finite density of projective measurements. Overall, these results reveal a complex phenomenology where local quantum measurements do not simply disentangle degrees of freedom, but may actually strengthen the entanglement in the system.

Расчет температурных полей на основе конечно-элементной модели процесса аддитивного синтеза изделия

The work is devoted to the creation of a hybrid finite element model of the process of additive synthesis of a product by the Wire Arc Additive Manufacturing/3D Metal Print method, supplemented by a block of wave strain hardening of the synthesized product. The main result obtained is the proposed original approach to the mathematical modeling of fundamentally new processes of synthesis and hardening of a wide range of products manufactured from various materials in the form of wire, which can be extended to the entire class of additive synthesis processes with periodic or post-processing. The main feature of the approach is the hybridization of calculation models, while, unlike known solutions, significant attention is paid to the processes of exchange and transmission of information between the models of synthesis and hardening processes. A distinctive feature of the hybrid model is the need for a periodic exchange of information on the geometric and temperature parameters of the synthesized areas at a specific point in time. The novelty of the hybrid model is in the application of coordinated approaches to solving thermal and mechanical problems in a three-dimensional formulation in the ANSYS environment, taking into account the natural dynamic heat flows that form in the synthesized product and the installation table modeled by the finite element method. Calculation of continuously changing dynamic temperature fields in the synthesized product with additional optimization and visualization capabilities is an important structural part of the model. The studies performed allowed us to identify a significant range of the ratio of the product and table volumes 30 ≤ Vс/Vи ≤ 100 and patterns in the formation of temperature fields when changing the table parameters.

A Mechanical Hackathon Co-developed with Industry

Hackathons have become a very popular activity in the software domain. These activities give students a chance to work in teams to address challenging, real-world, software design problems in a fast-paced and time-bound environment. This limited duration has both positives (e.g. students can experience the entire design-build-test process during a 2-day event), and negatives (e.g. students may be “hacking” code together instead of following a more rigorous design process); but if designed well can give students a meaningful design experience which develops their empathy, self-efficacy, and sense of belonging. To date, however, these events have typically stayed within the software domain where the cycles of building and testing can happen very rapidly. This paper describes an extra-curricular activity, co-developed with industry, which provided an opportunity for undergraduate students to design, build, and test solutions to a challenging real-world, mechanical problem sourced from an industry partner. This activity was offered as a pilot to approximately 40 students over a weekend in fall 2023 as part of a larger industry “Innovation Challenge” where the majority of students at the challenge were working on a related software problem from the same industry partner.

The effects of conical singularity and the Wu–Yang magnetic monopole on the thermodynamic properties of a harmonic oscillator interacting with a potential

Abstract This paper investigates the thermodynamic properties of the harmonic oscillator system in a conical singularities background. Moreover, we incorporate a Wu-Yang magnetic monopole (WYMM) and inverse square potential into the quantum system and analyze the resulting effects. Using analytical methods, we derive the energy eigenvalues and study the thermodynamic properties, such as the partition function, Helmholtz free energy, Gibbs's free energy and specific heat capacity at finite temperature $T \neq 0$. Our findings demonstrate that these physical parameters are influenced by the topological parameter, strength of WYMM and potential parameters. These results provide valuable insights into the interplay between thermodynamic properties of a quantum mechanical problem and the gravitational effects.

A Novel Slime Mould Multiverse Algorithm for Global Optimization and Mechanical Engineering Design Problems

The slime mould optimization algorithm (SMA) is one of the well-established optimization algorithms with a superior performance in a variety of real-life optimization problems. The SMA has certain limitations that reduce the diversity and accuracy of solutions, raising the risk of premature convergence with an inadequate balance between its exploitation and exploration phases. In this study, a novel hybrid slime mould multi-verse algorithm (SMMVA) is proposed to improve the performance of SMA algorithm. The SMA and multi-verse optimization (MVO) algorithm hybrid is introduced while updating variation parameter through novel nonlinear convergence factor. The proposed algorithm balances the ability of the SMA algorithm to explore and exploit, boosts the global exploration capability and improves the accuracy, stability, and convergence speed. The performance of SMMVA algorithm is compared with 16 well-established and recently-published metaheuristic algorithms on 23 standard benchmark functions, CEC2017, CEC2022 test functions, five engineering design problems, and five UCI repository datasets. The statistical tests such as Friedman’s test, box plot comparison and Wilcoxon rank sum test are employed to verify the SMMVA’s stability and statistical superiority. The algorithm was tested on total 64 benchmark functions, achieving an overall success rate of 68.75% across 30 runs compared to the other counterparts. The results for the feature selection problem show that the proposed algorithm with k-nearest neighbour (KNN) classifier obtained more informative features with higher accuracy values. Thus, the proposed SMMVA algorithm is proven to perform excellent performance in solving optimization problems with better solution accuracy and promising prospect.

The influence of desalinization of reservoir rocks on their mechanical and filtration properties using the example of the Chayandinskoye field

Using the Independent Triaxial Loading Test System of the Institute for Problems in Mechanics of the Russian Academy of Sciences (TILTS), rock specimens from the core material of the reservoir of the Chayandinskoye oil and gas condensate field were tested in order to experimentally study the effect of desalinization of reservoir rocks on their deformation, strength and filtration characteristics. It has been shown that desalinization sharply increases the permeability of rocks. At the same time, the deformation and strength properties of the studied rocks change towards softening (with the exception of the angle of internal friction), nevertheless remaining quite high. Experiments on physical modeling of the process of reducing pressure at the bottom of a horizontal well using TILTS showed that a slight decrease in the elastic and strength properties of the reservoir rocks of the Chayandinskoye oil and gas condensate field after their desalinization should not affect the stability of the well walls. The results obtained allow us to draw an important practical conclusion that when operating a field at the stage of salt washing out due to water filtration during operation, one should not expect a significant increase in the risks associated with reservoir destruction and increased sand production.

Comparative study of state-of-the-art metaheuristics for solving constrained mechanical design optimization problems: experimental analyses and performance evaluations

Abstract Many challenges are involved in solving mechanical design optimization problems related to the real-world, such as conflicting objectives, assorted design variables, discrete search space, intuitive flaws, and many locally optimal solutions. A comparison of algorithms on a given set of problems can provide us with insights into their performance, finding the best one to use, and potential improvements needed in their mechanisms to ensure maximum performance. This motivated our attempts to comprehensively compare eight recent meta-heuristics on 15 mechanical engineering design problems. Algorithms considered are water wave optimizer (WWO), butterfly optimization algorithm (BOA), Henry gas solubility optimizer (HGSO), Harris Hawks optimizer (HHO), ant lion optimizer (ALO), whale optimization algorithm (WOA), sine–cosine algorithm (SCA) and dragonfly algorithm (DA). Comparative performance analysis is based on the solution trait obtained from statistical tests and convergence plots. The results demonstrate the wide range of adaptability of considered algorithms for future applications.

Deterministic interconversion of GHZ state and KLM state via Lie-transform-based pulse design in Rydberg atoms

Abstract Conversion between different types of entangled states is an interesting problem in quantum mechanics. But research on the conversion between Greenberger-Horne-Zeilinger (GHZ) state and Knill-Laflamme-Milburn (KLM) state in atomic system has not been reported. In this paper, we propose a scheme to realize the interconversion (one-step) between GHZ state and KLM state with Rydberg atoms. By utilizing Rydberg-mediated interactions, we simplify the system. By combining Lie-transform-based pulse design, the evolution path is built up to realize interconversion of GHZ state and KLM state. The numerical simulation result shows that the present scheme is robust against decoherence and operational imperfection.

Academician of the All-Ukrainian Academy of Sciences Petro Mykhaylovych Suprunenko: Life and activity

The article updates the most significant information about the outstanding scientist-mechanic and railwayman of the first third of the 20th century Academician of the All-Ukrainian Academy of Sciences Petro Mykhaylovych Suprunenko (1893–1938). It is proven that his activities in the field of railway development are a significant contribution to the development of world science and technology. The main scientific works of the scientist and engineer are devoted to important problems of transport mechanics. He paid special attention to locomotive and wagon construction (he was a wagon designer). Wagons were built on the basis of a large amount of experimental material, which at one time received significant public resonance and scientific and technical recognition. It is emphasized that P. M. Suprunenko was one of the first railway engineers who proposed a scientific analysis of the interaction of the track with the rolling stock of railways. The article notes that today P. M. Suprunenko is mentioned very little, only fragments of his biography are described, only some of his scientific works are characterized. In the Institute of Transport Mechanics of the All-Ukrainian Academy of Sciences headed by him, the following research was successfully developed under his leadership: methodological problems of transport mechanics were highlighted in order to comprehensively solve the tasks of modernization of the railway industry; research of non-stationary dynamic processes of interaction of rolling stock (train) with the track system (especially the study of the resonance phenomenon); research of the theory of calculations of locomotive traction on railway tracks in order to optimize elements of transport mechanics and increase their efficiency, etc. The article describes in detail each of these areas of research by P. M. Suprunenko. In general, his research focused on problems of railway transport. In the field of train traction theory, P. M. Suprunenko created a number of new methods for graphical integration of differential equations of train motion, paid significant attention to improving existing ones and creating new devices designed to measure the characteristics of various processes occurring in rolling stock and tracks. The scientist's achievements in the initial period of railway transport construction in Ukraine, especially on the South-Western Railways, are confirmed. The article shows that the role of P. M. Suprunenko was in his scientific work as an "idea generator" and a leading theorist in combination with engineering activities.

APPROXIMATION OF FUNCTIONAL-ALGEBRAIC EIGENVALUE PROBLEMS

A new symmetric variational functional-algebraic formulation of the eigenvalue problem in the Hilbert space with linear dependence on the spectral parameter for a class of mathematical models of thin-walled structures with an attached oscillator is proposed. The existence of eigenvalues and eigenvectors is established. A new symmetric approximation of the problem in a finite-dimensional subspace with linear dependence on the spectral parameter is constructed. Error estimates of the approximate eigenvalues and eigenvectors are obtained. The theoretical results are illustrated on the example of the problem of structural mechanics.

The role played by scientific realism in the measurement problem of quantum mechanics

Many attempts have been made to characterise and solve the infamous measurement problem of quantum mechanics by advocating, implicitly or explicitly, different realist perspectives. As a result, we are still uncertain where this problem and its corresponding solution are to be located in the realism-antirealism debate. On the basis of a well-known characterisation of scientific realism, this paper intends to fill this gap by arguing that the quantum description of the processes involved in typical measurements is problematic from the standpoint of semantic realism, which is a necessary but not sufficient condition for fully-fledged scientific realism.

A shear and elongational decomposition approach of the rate-of-deformation tensor for non-Newtonian flows with mixed kinematics

We propose a novel approach for non-Newtonian viscoelastic steady flows based on a decomposition of the rate-of-deformation tensor which here, in a simplified version, leads to an anisotropic generalised Newtonian fluid-like model with separated treatment of kinematics pertaining to shear and extensional flows. Care is taken to assure that the approach is objective and does not introduce spurious effects due to dependence on a specific reference frame. This is done by separating the rate-of-deformation tensor into shear and elongational components, with the local scalar shear and elongation rates being the second invariant of each tensor separately, and by modifying the method used to separate the rate-of-deformation tensor so that it becomes independent of superimposed rigid rotations, thus satisfying the principle of material indifference. We assess the model with two test cases: planar contraction flow, often employed to evaluate numerical methods or constitutive equations and for which experimentally observed corner vortex enhancement and pressure drop increase are seldom found in numerical simulations; and flow past confined or unconfined cylinders, for which experiments indicate a drag increase due to elasticity and most predictions give a drag decrease. With our anisotropic model, incorporating additional elongational-flow-related terms, large vortices and accentuated pressure drop coefficients can be predicted for the contraction problem and enhanced drag coefficient for the cylinder problems. This is the first work where problems of non-Newtonian fluid mechanics are solved numerically with separation of strain rate into shear and elongational components.