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With the rapid development in sensor network technology, the complexity and diversity of application scenarios have put forward more and more new requirements for inductor–capacitor (LC) sensors, for instance, multi-parameter simultaneous monitoring. Here, the parity–time (PT) symmetry concept in quantum mechanics is applied to LC passive wireless sensing. Two or even three parameters can be monitored simultaneously by observing the frequency response of the reflection coefficient at the end of the readout circuit. In particular, for three-parameter detection, a novel detection method is studied to extract the three resonant frequencies of the system through the phase–frequency characteristics of the reflection coefficient, which has never appeared in the previous literature on PT symmetry. The changes in three resonant frequencies are in response to changes in the three parameters in the environment. We show theoretically and demonstrate experimentally that the PT-symmetric LC sensor can realize multi-parameter measurement using a series LCR circuit as the sensor and a symmetric adjustable LCR circuit as the readout circuit. Our work paves the way for applying PT symmetry in multi-parameter detection. [ABSTRACT FROM AUTHOR]

Large deformation phenomena in rock engineering are commonly key bottlenecks impeding engineering progress. Correspondingly, large deformation analysis in rock mechanics has a widespread impact on mechanism understanding, prevention, and control guidance. Various large deformation schemes broadly categorized as hypoelastic- and hyperelastic-based models exist in the literature and software. Without an understanding of the capabilities and demerits of these schemes, the diversity in choices inadvertently leads to pitfalls, placing engineering endeavors at a disadvantage. In this work, we review and compare the most prevalent schemes (including PK2-Green, Jaumann, Green–Naghdi, Truesdell, and hyperelastic-based schemes) from perspective of rock mechanics, with an emphasis on their application in rock engineering, and further develop a hyperelastic-based large deformation scheme (marked as Cauchy-Ln scheme) based on Cauchy stress and Hencky logarithm strain. The proposed model realizes the separation of material nonlinearity and geometry nonlinearity. Several typical large deformation phenomena in rock engineering are studied. The relationships between large deformation phenomena and large deformation analyses are clarified under different circumstances. Especially under large strain conditions, the PK2-Green scheme is enfeebled, and the hypoelastic-based scheme should be used with caution. For rock material with an apparent pressure-sensitive effect, the proposed Cauchy-Ln scheme is superior. Highlights: The connections between large deformation phenomenon and large deformation analysis are delineated. Prevalent large deformation schemes are compared from a rock mechanics perspective with an emphasis on application in rock engineering. A newly hyperelastic-based large deformation numerical model, enhancing compatibility with rocks, is developed. [ABSTRACT FROM AUTHOR]

What pupils learn in school should ideally be useful throughout their whole lives. It should help them in further studies, in working life, and when acting as responsible citizens in democratic society. This is challenging for all subjects, including technology. Technology develops fast. It is most likely that wheels, wedges, and inclined planes will be used in the future, but it is difficult to know which programming languages, sources of energy, and materials that will be relevant a few decades from now. This article describe how these problems are handled in international curricula and standards, and by Swedish teachers, teacher students, and teacher educators. In curricula they are seldom addressed explicitly, but handled by giving deliberately vague descriptions of what students are to learn. The interviewed teachers, teacher educators, and teacher students were unused to think about future-compliant or timeless knowledge. When prompted to do so during the interviews, they found it easier to describe timeless skills than timeless factual knowledge. Prominent among their suggestions were abilities related to engineering design processes, technical problem solving strategies, fundamentals of computer programming, and engineering mechanics. [ABSTRACT FROM AUTHOR]

The insulin‐degrading enzyme (IDE) plays a significant role in the degradation of the amyloid beta (Aβ), a peptide found in the brain regions of the patients with early Alzheimer's disease. Adenosine triphosphate (ATP) allosterically regulates the Aβ‐degrading activity of IDE. The present study investigates the electrostatic interactions between ATP‐IDE at the allosteric site of IDE, including thermostabilities/flexibilities of IDE residues, which have not yet been explored systematically. This study applies the quantum mechanics/molecular mechanics (QM/MM) to the proposed computational model for exploring electrostatic interactions between ATP and IDE. Molecular dynamic (MD) simulations are performed at different temperatures for identifying flexible and thermostable residues of IDE. The proposed computational model predicts QM/MM energy‐minimised structures providing the IDE residues (Lys530 and Asp385) with high binding affinities. Considering root mean square fluctuation values during the MD simulations at 300.00 K including heat‐shock temperatures (321.15 K and 315.15 K) indicates that Lys530 and Asp385 are also the thermostable residues of IDE, whereas Ser576 and Lys858 have high flexibilities with compromised thermostabilities. The present study sheds light on the phenomenon of biological recognition and interactions at the ATP‐binding domain, which may have important implications for pharmacological drug design. The proposed computational model may facilitate the development of allosteric IDE activators/inhibitors, which mimic ATP interactions. [ABSTRACT FROM AUTHOR]

Kurt Magnus (1912–2003) is one of the personalities who shaped research and teaching in applied mechanics during the 20th century. Through his work with his doctoral supervisor Max Schuler at the University of Göttingen, gyrodynamics became his most important field of work, which also led to his research in oscillations, multi‐body systems, and mechatronics. Magnus made significant contributions in all these fields. He was regarded as a gifted lecturer, and the close connection between scientific research and practical application was important to him. Life and scientific work of Kurt Magnus were, however, also characterized by his 7‐year deportation to the USSR in 1946. Despite this fate, he was able to continue his research under certain restrictions during this time. After returning to Germany, he became Professor of Mechanics at the University of Stuttgart in 1958. His appointment coincided with the gradual resumption of industrial activities in Germany in the field of gyro technology—activities that had come to a standstill at the end of World War II. In the years that followed, Magnus' institute became the scientific center for gyrodynamics in Germany. The activities of that time are reflected in a preserved collection of gyro instruments for research and teaching as well as in the co‐founding of an annual international conference on inertial technology, which continues to this day. Magnus' subsequent move to the Technical University of Munich in 1966 did nothing to change this. At that time, he was regarded as a doyen of gyro technology. After a short biography of Kurt Magnus, the paper addresses the recent revision and digitization of the gyro instrument collection and presents an outline of the history of the conference series providing details on how gyro technology has developed since his work in Stuttgart. [ABSTRACT FROM AUTHOR]

An editorial focuses on refining Biot elastic coefficients in poroelastic solids by addressing discrepancies between drained and undrained conditions. It proposes new formulas for these coefficients and evaluates their accuracy through numerical analysis of Berea sandstone under different conditions. It highlights theoretical corrections needed for accurate wave propagation modeling in fluid-saturated porous media.

Crack stress thresholds in rocks have long been a popular subject in rock mechanics and engineering research. In this study, the applicability of existing methods for determining the crack stress thresholds of granite and weakly cemented porous siltstone is investigated using step loading and unloading tests. In addition, a novel method for decomposing the volumetric strain into solid-phase linear elastic strain, gas-phase nonlinear elastic strain, and plastic volumetric strain is presented. A quantitative calculation method for determining these thresholds is proposed based on the evolution law of the gas-phase volumetric strain and the physical significance of crack stress thresholds. The initiation and termination points of the stationary stage of the gas-phase volumetric strain are determined as σ cc and σ ci ; the point at which the gas-phase strain changes from positive to negative is determined as σ cd . To validate the proposed method, statistical results of the existing methods after screening are compared with the results of the proposed method. The results show that the proposed method provides reasonable crack stress thresholds for siltstone and granite and is applicable to rocks with similar stress–strain behaviors. The proposed method offers the advantages of independence from other methods, suitability across high and low confining pressures, and the capability for the quantitative calculation and processing of numerous samples. [ABSTRACT FROM AUTHOR]

In this work, we employ the multiple scale method to introduce a novel analytical solution for an extended four-degrees-of-freedom dynamical system modeled on a swinging Atwood machine. We provide a methodology for obtaining the asymptotic solution up to the second-order approximation for both the swinging and modified swinging Atwood machine, demonstrating its solvability through the multiple scale approach. Subsequently, we present a comparative analysis of time histories between numerical and analytical solutions. These analytical solutions are of particular significance in applied mechanics, given their practical applications in parametric dynamical models grounded in the pendulum concept. [ABSTRACT FROM AUTHOR]

The study of wear is currently one of the most important aspects of applied mechanics. The damage caused by this phenomenon involves the total replacement of parts in devices ranging from industrial machinery to biomedical implants. The focus of these work is aimed at the analysis and prediction of mechanical wear in prostheses manufactured using UHMWPE materials and 316 LVM stainless steel by means of the finite element method using Abaqus® software V. 2020. The wear mechanism between the surfaces of the UHMWPE material specimen and a 316 LVM stainless steel specimen was modeled using Archard's wear theory to determine the parameters of damage, plastic deformation, and fatigue. The attrition process was discretized into several steps, including developing a program in Fortran code, and integrating a pre-established subroutine known as UMESHMOTION, followed by a Mesh update whenever contact nodes were deformed. For the simulation process, the variables of the thermal properties of conductivity, specific heat, and the parameters of the Johnson-Cook plastic model were taken into account. The simulation results were validated by laboratory tests. [ABSTRACT FROM AUTHOR]

In this paper, analytic solutions and dynamic properties of a variety of Boussinesq-type equations are established via the complete discrimination system for polynomial method. All the existing single traveling wave solutions to these equations as well as some new solutions are shown, and the Hamiltonian and topological properties to these equations are also presented. Considering the significance of the Boussinesq-type equations, our results would have wide applications in ocean engineering and fluid mechanics, like describing and predicting the solitary and periodic waves in various shallow water models. [ABSTRACT FROM AUTHOR]

The ongoing refinement of bearing capacity equations remains pivotal in soil mechanics and foundation engineering, reflecting its critical role in ensuring design efficacy and construction safety. This study conducts a thorough evaluation of classical bearing capacity methods—Terzaghi, Meyerhof, Vesic, and Hansen—and methods included in various design standards, such as EN1997:2004, prEN1997:2023, GEO, AASHTO, FHWA, and API. It explores the performance and applicability of these approaches, identifying areas for potential improvement. In response to identified challenges, the paper proposes the integration of a unified depth factor. This new factor is designed to be applicable across all N-terms, providing a more versatile and accurate tool for bearing capacity predictions. Unlike the original depth factors unique to each method, which may not fully address complex soil and footing conditions, the unified depth factor is developed to enhance prediction accuracy for a wide range of conditions, including both flexible and rigid footings under varying flow rules (ψ = 0 and ψ = φ). This depth factor corrects for modeling errors, emphasizing the importance of pairing the correct set of N-factors with their corresponding depth factor. By offering a singular depth factor that aligns with the outcomes of finite element analysis, this paper not only simplifies the computational process but also enhances the accuracy of bearing capacity predictions across a diverse range of soil conditions and footing types. The comparative analysis, based on finite element analysis, validates the proposed method's effectiveness, showcasing its potential to significantly refine foundation design practices by comparing it with both traditional and newly developed depth factors. [ABSTRACT FROM AUTHOR]

The paper presents a novel algorithm for the development of stability charts. The second-order differential homogeneous equation describing a double salient reluctance machine with a capacitance connected to its stator winding is transformed into hill's equation. The circuit components are the stator coil time-varying inductance of a double salient reluctance machine, capacitance and resistance. All these are modeled by hill's equation. The double salient reluctance machine acts as an energy conversion system. The maximum and minimum inductance of the energy conversion system is measured in laboratory by inductance, capacitance, and resistance (LCR) meter. These values help to determine the inductance modulation index. The inductance modulation indetx, the characteristic constant and the characteristic parameter obtained from modeling equations are used in the MATLAB/Simulink model. The MATLAB/Simulink simulations generate stable and unstable oscillations to form stability charts. The proposed stability charts are in good agreement with the Ince-Stritt stability chart, which is widely applied in physics, mechanics and in electrical engineering, especially where the state of stability of a system or an electric oscillatory circuit is to be determined. [ABSTRACT FROM AUTHOR]

A new moment-resisting mass timber connection was designed based on the principles of force equilibrium in applied mechanics. The connection configuration utilizing two mechanically fastened threaded steel rods embedded into the end of a glulam beam section was experimentally investigated in this study. A gradually increasing transverse load was applied to the free end of a cantilevered beam, causing a bending moment on the beam-end connection until failure. Four different connection configurations were examined, each replicated twice to verify results. The beam connection parameters investigated were rod anchorage length (200 and 250 mm) and square washer size (38.1 and 50.8 mm). Test results show that increasing the washer size increased the connection bending strength by increments more significantly than those due to increasing the rod anchorage length. However, the connection configurations with the smaller-size washer, which failed mainly due to wood crushing under the washer, had higher ductility ratios than those with the larger-size washer, which failed due to steel rod yielding. In a real-life scenario, a structural element such as a glulam beam is usually loaded to approximately 50% to 70% of its design capacity, considering a reasonable margin of safety. The study estimates a maximum possible bending moment utilization factor for the strongest connection configuration that ranged between 34% and 48% compared to the maximum moment resistance of a supported glulam beam spanning an average length of 4.0 m to 6.0 m (a common span length in framed timber buildings) and has a cross-section size same as the one utilized in this study. This utilization factor is quite large for a timber connection, and thus, confirms a considerable moment-resisting capability of the new configuration developed in this study. [ABSTRACT FROM AUTHOR]

Stress and deformation analysis of a cavity in an infinite/finite medium is a fundamental applied mechanics problem of interest in multiple physics and engineering disciplines. This paper develops a complete semianalytical solution for the cylindrical cavity expansion in nonassociated Mohr–Coulomb materials, by using the graphical approach and Lagrangian formulation of the cavity boundary value problem (through tracing the responses of a single material point at the cavity wall). The novelty of the new solution framework lies not only in the relaxation of the stringent intermediacy assumption for the vertical stress as usually adopted in the previous analyses, but also in the comprehensive consideration of nonhydrostatic initial stress conditions via arbitrary values of K0 (the coefficient of earth pressure at rest defined as the ratio between the horizontal and vertical initial stresses). The essence of the so-called graphical method, i.e., the unique geometrical analysis and tracking of the deviatoric stress trajectory, is fulfilled by leveraging the deformation requirement that during cavity expansion the progressive development of the radial and tangential strains must maintain to be compressive and tensile, respectively. With the incorporation of the radial equilibrium condition, the problem is formulated to solve a single first-order differential equation for the internal cavity pressure with respect to a pivotal auxiliary variable, for all the distinct scenarios of K0 being covered. Some selected results are presented for the calculated cavity pressure-expansion curve and limit cavity pressure through an example analysis. The definitive semianalytical solution proposed will be not only substantially advancing the current state of knowledge on the fundamental cavity expansion theory, but also able to serve as a unique benchmark for truly verifying the correctness and capability of the classical cornered Mohr–Coulomb constitutive model built in commercial finite element programs. [ABSTRACT FROM AUTHOR]

In recent years, flexible functional materials have attracted increasing interest, but there is a lack of designing mechanisms of flexibility design with superstructures. In traditional engineering mechanics, the maximum bending strain (MBS) was considered universal for describing the bendable properties of a given material, leading to the universal designing method of lowering the dimension such as thin membranes designed flexible functional materials. In this work, the MBS was found only applicable for materials with uniformly distributed Poisson's ratio, while the MBS increases with the thickness of the given material in case there is a variation Poisson's ratio in different areas. This means the MBS can be enhanced by certain Poisson's ratio design in the future to achieve better flexibility of thick materials. Here, the macroscopic freestanding inorganic functional BaTiO3:Sm3+ (BTO:S) nanofiber membranes, which have a nonconstant Poisson's ratio response on stress/strain for creating nonuniformly distributed Poisson's ratio, were proven applicable for designing larger MBS and lower Young's modulus for flexible functional materials. [ABSTRACT FROM AUTHOR]

Erectile dysfunction (ED) predominantly affects men in their 40–70s and can lead to poor quality of life. One option for ED treatment is surgical implantation of an inflatable penile prosthesis (IPP). However, they can be associated with negative outcomes including infection, migration or fibrosis. To improve outcomes, the interaction between the IPP device and surrounding tissues needs further investigation and this could be achieved using pre-clinical testbeds, but they need to be informed by extensive tissue testing. In this study, an experimental approach is adopted to characterise the mechanics of horse penile tissue and establish a testing protocol for penile tissue. The whole penis segments were tested in plate compression tests to obtain whole penis behaviour which is necessary for validation of a pre-clinical testbed, whilst tensile and compression tests were performed on individual penile tissues, namely corpus cavernosa and tunica albuginea. The second part of the paper deals with the development of a computational model employing an inverse finite element approach to estimate the material parameters of each tissue layer. These material parameters are in good agreement with the experimental results obtained from the individual tissue layers and whole organ tissue tests. This paper presents the first study proposing realistic nonlinear elastic material parameters for penile tissues and offers a validated testbed for IPPs. Erectile Dysfunction (ED) affects over half the male population aged 40–70 potentially leading to poor quality of life. Patients not responding to conventional treatments of ED, are advised to use penile prostheses which can create an erection using implanted inflatable cylinders. A significant drawback of such prostheses, however, is the substantial tissue damage they can induce during their usage. Preclinical testbeds, including computational and bench-top models, could offer an efficient means of improving device designs to mitigate this damage but such testbeds require extensive knowledge of penile tissue properties. In this study, the authors determine penile tissue mechanics and apply an inverse FE approach to characterise the penile material properties required to validate preclinical models of the penis. [Display omitted] [ABSTRACT FROM AUTHOR]

Numerical methods have been extensively applied to fracture mechanics, while they cannot simulate the problems without the mechanical models or constitutive equations. Artificial neural networks (ANNs) can be utilized to predict complex fracture problems, but these approaches require large amounts of data for the training. Therefore, in this paper, to combine the advantages of the numerical methods and the ANNs, an improved back propagation neural network (BPNN) is proposed by introducing the enrichment used in the numerical methods into the activation function utilized in the neural networks. The enrichment is able to represent the crack tip field which can accelerate the convergence. At the field near the crack tip, the improved BP solution can converge to the analytical solutions which validate the high accuracy of the proposed method. Without sufficient data, especially the data are missing in the near field of the crack tip, the improved BP method can also achieve high accuracy and convergence, while the conventional BP method may not converge to the predetermined error bound. Numerical simulations of the quasi‐static and fatigue crack problems demonstrate that the improved BP method can accurately predict the crack propagation and its growth rate with relatively little data. [ABSTRACT FROM AUTHOR]

Block theory, which successfully applies the geometric topology method to the field of rock mass stability analysis, is very suitable for analyzing the problem of local block stability caused by the cutting of structural planes (discontinuities) in engineering rock mass. It is a rare original theory in rock mechanics and engineering. However, compared with the completeness, progressiveness, and originality of the theory, the application of block theory in engineering is not widespread enough. Combining the authors' long-term experience in fundamental research and engineering applications of block theory, this work first clarifies the differences in the connotation of block analysis before and after the excavation of rock masses. This difference reflects the main ideas of using block theory for engineering applications and also reflects the different focuses of block theory application at different construction stages. Furthermore, it is pointed out that before and after excavation, the core tasks are "block prediction-support drafting" and "block determination-support verification", respectively. Before the excavation of the rock mass, the main tasks are to group and combine discontinuities, distinguish removable blocks and key blocks based on the whole-space stereographic projection (WSSP) for different discontinuity combinations, estimate the size and shape of unlocated blocks, analyze block stability, and draft support design parameters. After the excavation of the rock mass, the main tasks include analyzing the shape of the located block, analyzing the stability of the block, and verifying the support design parameters for rock blocks. Finally, combined with engineering cases, the key technical issues and work ideas in engineering applications were analyzed, such as how to estimate the size of the unlocated blocks, how to sort out the support-required blocks from key blocks, and how to draft or verify support parameters. The work is of great significance for the application and promotion of block theory in engineering. Highlights: Different connotations of block analysis before and after rock excavation are clarified. Before rock excavation, the core tasks are "block prediction-support drafting". After excavation, the core tasks are "block determination-support verification". Some key issues are discussed, such as distinguishing the support-required block. [ABSTRACT FROM AUTHOR]

Accurate estimates of momentum flux through the air-sea interface at very high wind speeds are important for predicting tropical cyclone intensities. To estimate the air-sea momentum flux under the long-fetch condition (20 m fetch) at very high wind speeds using a laboratory tank, a simple momentum flux measurement method using only four water-level gauges is conducted based on the momentum budget method. The air-water momentum flux under long-fetch conditions at very high wind speeds was measured in a typhoon simulation tank at the Research Institute of Applied Mechanics, Kyushu University. The verification was performed using previous values estimated by the eddy correlation method in a typhoon simulation tank at Kyoto University, Japan. The results showed good correlation between the values of momentum flux measured by the present momentum budget method and the other methods. The drag coefficient at very high wind speeds (41 m/s) under long-fetch conditions leveled off, as well as under the short-fetch condition (4.5 m and 6.5 m fetch). Moreover, a very weak relationship was found between the drag coefficient and the fetch. Since the maximum fetch in the present laboratory experiments is 20 m, the future field observation with the longer fetch condition will be needed for applying the results to oceans. [ABSTRACT FROM AUTHOR]

Purpose. To formalize the design of the elastic element of the connection unit of a multi-axis vibrating machine with a plate, in the form of internal cutouts and autonomous jumpers. To obtain the dependence of the stiffness of the plate elastic element in the direction of transmitted vibration on the modulus of elasticity of the plate material, the cross-sectional area of an individual lintel, its length, width, and thickness. To determine the limiting values of the forcing forces of the machine that satisfy the stability conditions of the jumpers of the plate package according to Euler. Methodology. When creating the configuration of an elastic element in the form of longitudinal bridges of an even number and modeling the stiffness characteristic of the joint, the methods of applied mechanics and the theory of material resistance were used. Findings. The basic results of the work include mathematical and physical modeling of the characteristics of elasticity, stability, and mutual influences in the working and combined directions in relation to the connection points of multi-coordinate vibration machines, which are implemented through flat multi-section plate elements. Taken together, this makes it possible to create energy-efficient vibration machines, to increase the accuracy of the program movement of their working body, which in turn increases: the productivity of mining equipment – in the extraction of minerals, and their reliability – in the case of mechanical tests. Originality. It consists of the fact that for the first time the dependence of the stiffness of the plate elastic element in the direction of transmitted vibration on the modulus of elasticity of the plate material, the cross-sectional area of an individual lintel, its length, width, and thickness were obtained. It is shown that the stiffness of the plate in the conjugate direction is directly proportional to the material’s modulus of elasticity, the width of the lintel, its thickness cubed, and is inversely proportional to the length of the lintel in the third degree. It is established that in order to ensure the stability conditions of the lintels of the plate package with respect to the limiting values of the forces of the vibration exciters of the machine, there is their directly proportional dependence on the number of plates in the package, the modulus of elasticity of the material, the width of the lintel and the thickness of the plate in the third degree, and is inversely proportional to the length of the jumper in the square. Practical value. For the first time, a structural mechanical model of an elastic element has been proposed, represented by a plate divided by internal straight slots into external and internal lintels identical in width and length. A real plate connection unit has been created, and its experimental stiffness characteristics depending on the number of plates in the package are given. [ABSTRACT FROM AUTHOR]

Mastering the concept of distributed forces is vital for students who are pursuing a major involving engineering mechanics. Misconceptions related to distributed forces that are typically acquired in introductory Physics courses should be corrected to increase student success in subsequent mechanics coursework. The goal of this study was to develop and assess a guided instructional activity using augmented reality (AR) technology to improve undergraduate engineering students' understanding of distributed forces. The AR app was accompanied by a complementary activity to guide and challenge students to model objects as beams with progressively increasing difficulty. The AR tool allowed students to (a) model a tabletop as a beam with multiple distributed forces, (b) visualize the free body diagram, and (c) compute the external support reactions. To assess the effectiveness of the activity, 43 students were allocated to control and treatment groups using an experimental nonequivalent groups preactivity/postactivity test design. Of the 43 students, 35 participated in their respective activity. Students in the control group collaborated on traditional problem‐solving, while those in the treatment group engaged in a guided activity using AR. Students' knowledge of distributed forces was measured using their scores on a 10‐item test instrument. Analysis of covariance was utilized to analyze postactivity test scores by controlling for the preactivity test scores. The treatment group demonstrated a significantly greater improvement in postactivity test scores than that of the control group. The measured effect size was 0.13, indicating that 13% of the total variance in the postactivity test scores can be attributed to the activity. Though the effect size was small, the results suggest that a guided AR activity can be more effective in improving student learning outcomes than traditional problem‐solving. [ABSTRACT FROM AUTHOR]

Purpose: Balancing an asymmetrical rotor-bearing system is currently considered a topic of interest for applied mechanics, mainly due to the parametric excitation produced by the shaft asymmetry, which complicates the balancing procedure. Therefore, the development of novel techniques aimed at reducing the number of trial runs for balancing the rotor and decreasing the idle times is nowadays a topic driving several investigations around the world. In this work, a balancing method where the online parameter algebraic identification for the identification of the modal unbalance of an asymmetrical rotor-bearing system is presented. Methods: The mathematical model for the modal unbalance identification was obtained based on the dynamic behavior model of the multiple-degree-of-freedom asymmetrical rotor-bearing system obtained through the finite element method. The proposed identification model requires, in contrast to the conventional methods reported in the literature, the vibration response of one single node of the rotordynamic system as input data. Results: By applying the proposed methodology, an identification simplified model is obtained, which involves only the vibration modes to be balanced and allows using the conventional modal balancing (modal masses array). The proposed balancing method was numerically validated through the identification of the modal unbalance of an asymmetric rotor-bearing system with multiple inertial disks as well as discrete unbalance, and a reduction in the rotor vibration amplitude response of 90% was achieved for the first four vibration modes. The numerical results showed that a one single trial run is required to achieve the simultaneous balance of the four vibration modes. [ABSTRACT FROM AUTHOR]

The influence of the jet pressure ratio () in a nonisobaric supersonic jet of a vibrationally excited gas SF6 exhausting from a convergent axisymmetric nozzle 0.25 mm in diameter is studied numerically and experimentally. The experiments aimed at studying the gas-dynamic structure of the jets are performed in a specially designed jet setup of the Khristianovich Institute of Theoretical and Applied Mechanics of the Siberian Branch of the Russian Academy of Sciences. The numerical simulations are performed by solving two-dimensional Navier–Stokes equations within the framework of the ANSYS Fluent software and the thermally perfect gas model. The influence of excitation of vibrational degrees of freedom of the SF6 gas is studied in both an equilibrium gas and a vibrationally nonequilibrium gas. The nonequilibrium state of vibrational degrees of freedom is simulated with the use of a two-temperature model of relaxation flows. It is shown that the jet pressure ratio of the SF6 gas affects the cell length of the wave structure, which is responsible for the change in the vibrational relaxation rate. The coefficient of density amplitude reduction in gas-dynamic cells is derived as a function of the jet pressure ratio. [ABSTRACT FROM AUTHOR]

We present a novel formulation of structural design optimization problems specifically tailored to be solved by qa. Structural design optimization aims to find the best, i.e., material-efficient yet high-performance, configuration of a structure. To this end, computational optimization strategies can be employed, where a recently evolving strategy based on quantum mechanical effects is qa. This approach requires the optimization problem to be present, e.g., as a qubo model. Thus, we develop a novel formulation of the optimization problem. The latter typically involves an analysis model for the component. Here, we use energy minimization principles that govern the behavior of structures under applied loads. This allows us to state the optimization problem as one overall minimization problem. Next, we map this to a qubo problem that can be immediately solved by qa. We validate the proposed approach using a size optimization problem of a compound rod under self-weight loading. To this end, we develop strategies to account for the limitations of currently available hardware. Remarkably, for small-scale problems, our approach showcases functionality on today's hardware such that this study can lay the groundwork for continued exploration of qa's impact on engineering design optimization problems. [ABSTRACT FROM AUTHOR]

Vocational school students are not only required to master competency skills but also cognitive skills. Engineering mechanics learning is a basic calculation lesson that students should master. This research aimed to develop and identify the effectiveness of Android-based virtual laboratory (V-lab) media to improve students’ cognitive skills in learning engineering mechanics at vocational school in Surakarta. The subjects comprised 70 students of first grade vocational school majoring in civil engineering in Surakarta. This research was a research and development (R&D) study to develop an Android-based virtual laboratory media. Testing the N-Gain analysis in the experimental and control classes was to determine the effectiveness of virtual laboratory media in improving students’ cognitive thinking skills. Data were obtained from questionnaires and pretest and post-test test sheets. The developed virtual laboratory media was considered ‘very appropriate’ by media, material, and practitioner experts. The average value of N-Gain for the experimental class was 78.19% which was included in the effective category. Meanwhile, in the control class, the average N-Gain value reached 54.07%, which was included in the less effective category. This indicates that the use of Android-based virtual laboratory media for learning is more effective than conventional learning media. [ABSTRACT FROM AUTHOR]

The Euler–Bernoulli beam bending theory in engineering mechanics assumes that the material behavior is isotropic elastic and that plane cross sections remain plane and rigid. It is well-known that this theory suffers from inconsistencies that, e.g., the shear strain is always vanishing, whereas the shear stress does not vanish. In recent work, consistent Euler–Bernoulli beam theories in classical and explicit gradient elasticities were accomplished by assuming the constitutive response to be anisotropic elastic, subject to internal constraints. This approach is extended in the present paper to get consistent Euler–Bernoulli beam theory for gradient elasticity based on Laplacians of stress and strain. The developed beam theory is employed to discuss bending of cantilever beams. [ABSTRACT FROM AUTHOR]

The value of Poisson's ratio is a crucial parameter in rock mechanics and engineering for both intact rock and rock mass. Poisson's ratio has not gotten the attention it merits compared to other essential mechanical characteristics of intact rock and rock mass. Limited relationships exist between rock mass classification systems (such as RMR, RMQR, Q, and GSI) and Poisson's ratio. This paper provides a comprehensive review of models proposed by various researchers for estimating Poisson's ratio for rock mass. The different methods are compared, and new general equations are derived. The results indicate that the Poisson's ratio value of rock mass is inversely proportional to its quality and strength and depends on the Poisson's ratio value of the intact rock. Specifically, a linear equation is obtained using the RMR or GSI system, showing that the Poisson's ratio increases as the quality and strength of the rock mass decrease. The Q system has a logarithmic link between the rock mass quality and Poisson's ratio. It should be noted that the derived equations are applicable only under the assumption of a homogeneous isotropic rock mass. [ABSTRACT FROM AUTHOR]

We describe the implementation of Critical Thinking Activities (CTA) designed to encourage 'critical thinking' in an undergraduate engineering Fluid Mechanics course. Critical thinking can be a vague term both difficult to grasp and even more so to measure. Using a longitudinal case study we analyse quantitative and qualitative data collected over three years to explore the overarching question: "how do we know students have thought critically?". We investigate and evaluate the quantitative data that emerged from students undertaking the CTA and the impact of this on their performance. The results indicate that students who performed well in the CTA achieved a final grade for the course of 5 or more (Credit, Distinction or High Distinction). Qualitative data from student feedback demonstrated that the CTA was a significant factor in reinforcing student learning, enabling us to identify areas of misconception and areas in which they could improve. While the study is situated in an engineering context at the University of Queensland, the paper is an exemplar of embedded and sustainable practice, is equally transferable to other disciplinary contexts. • Successful implementation of critical thinking activity (CTA). • CTA used problem-based-learning and reflection through integrated feedback loop. • Three year long studyshows significant impact on student learning • Method used is equally transferable to other disciplines. [ABSTRACT FROM AUTHOR]

Numerical simulation of rock fracture mechanics has been a major research interest and challenging area in the field of rock mechanics. Based on this background, a smooth particle dynamics numerical simulation method (RGIMP) is proposed to consider the failed material point. The RGIMP algorithm is simple in form, does not need to use multiple velocity fields, takes advantage of the stability of the GIMP itself, and simulates the brittle fracture process of the rock by the failure process of the material point, and the resulting cracks are displayed. The accuracy of the RGIMP algorithm was verified via uniaxial compressive numerical simulations of a single-cleft standard cube specimen, a double-cleft standard cube specimen, and a double-cleft Brazilian disk specimen. Our research results provide a reference for the application of smooth particle dynamics methods in rock mechanics engineering and an understanding of rock fracture mechanisms. [ABSTRACT FROM AUTHOR]

A muscle fatigue identification method that integrates the multifractal of sEMG with LSTM is proposed. The MFDMA method was introduced to analyze and extract non-linear properties of sEMG. The significance of differences between the fatigue and non-fatigue states in terms of spectral width, Hurst index variation difference, and peak singularity index was determined using the t-test. A LSTM networks under the combined feature set comprising multiple fractals was built, and its recognition accuracy was 98.91%. The LSTM network model was found to be more accurate than other classification methods in identifying muscle fatigue under the same feature set. [ABSTRACT FROM AUTHOR]

The article "ON THE VORTEX IDENTIFICATION WITHIN A LINEAR BLADE CASCADE - AN EXPERIMENTAL RESEARCH" discusses the identification of vortical structures within a linear blade cascade using H criteria. The study examines the impact of the inlet flow angle on the velocity field and vortical structures, as well as the effect of the H threshold on vortex identification. The article provides insights into the complex flow through a turbine and the formation of vortices in blade cascades. The second article, "VR helicity density and its application in turbomachinery tip leakage flows" by Y. Tang and Y. Liu, explores the concept of VR helicity density and its relevance in turbomachinery tip leakage flows. The authors provide a detailed analysis of the topic, discussing the theoretical background and practical applications. This article is a valuable resource for researchers and professionals in the field of turbomachinery. [Extracted from the article]

This paper integrates and extends an earlier article presented at the 20th International Conference on Soil Mechanics and Geotechnical Engineering. The generation of a stiffened zone in the proximity of a geogrid is one of the primary mechanisms of mechanical stabilization of pavement unbound aggregate layers using geogrids. This paper focuses on the quantification of the stiffened zone through a local stiffness assessment using bender element (BE) sensors. Unbound aggregate base layers were constructed in a large-scale laboratory testbed. Geogrid-stabilized layers had geogrids with different-sized triangular apertures contributing to the geogrid-stiffened zone. Shear wave velocities were measured at three different heights using BE sensors, and the vertical stiffness profiles of the mechanically stabilized aggregate layers were evaluated. In addition, the conversion method between small-strain stiffness and large-strain stiffness was established from the repeated load triaxial tests with BE pairs to transform the vertical stiffness profile into that of the resilient modulus. Furthermore, dynamic cone penetration (DCP) and light-weight deflectometer (LWD) tests were performed at multiple locations into the stabilized and unstabilized unbound aggregates. From the large-scale experimental study, the local stiffness improvement owing to the geogrid enhancement was up to 16.2% in the vicinity of the geogrid location, and the extent of the local stiffened zone evaluated through various test methods was between 15.2 cm (6 in.) and 25.4 cm (10 in.) above the geogrid. [ABSTRACT FROM AUTHOR]

The utility of bioprosthetic heart valves (BHVs) is limited to certain patient populations because of their poor durability compared to mechanical prosthetic valves. Histological analysis of failed porcine BHVs suggests that degeneration of the tissue extracellular matrix (ECM), specifically the loss of proteoglycans and their glycosaminoglycans (GAGs), may lead to impaired mechanical performance, resulting in nucleation and propagation of tears and ultimately failure of the prosthetic. Several strategies have been proposed to address this deterioration, including novel chemical fixatives to stabilize ECM constituents and incorporation of small molecule inhibitors of catabolic enzymes implicated in the degeneration of the BHV ECM. Here, biomimetic proteoglycans (BPGs) were introduced into porcine aortic valves ex vivo and were shown to distribute throughout the valve leaflets. Incorporation of BPGs into the heart valve leaflet increased tissue overall GAG content. The presence of BPGs also significantly increased the micromodulus of the spongiosa layer within the BHV without compromising the chemical fixation process used to sterilize and strengthen the tissue prior to implantation. These findings suggest that a targeted approach for molecularly engineering valve leaflet ECM through the use of BPGs may be a viable way to improve the mechanical behavior and potential durability of BHVs. [ABSTRACT FROM AUTHOR]

In the present paper, motion trajectories corresponding to the working process for a multibody system, specifically a serial robot structure, have been studied. Within working processes, robots perform mechanical motions, where active forces are governed by laws of temporal variation, thus inducing higher-order accelerations in the mechanical system. These accelerations become essential in the analysis of acceleration energies. The study of advanced dynamics of multibody systems, often characterized by symmetry, is approached by applying differential and variational principles, frequently utilizing Lagrange-Euler equations, as well as Gibbs--Appell equations, where the central function is represented by the acceleration energy of first order. Considering these aspects, in this paper will be determined generalized inertia forces, as components in dynamic control functions of the mechanical systems. [ABSTRACT FROM AUTHOR]

This paper aims at the development and implementation of an algorithm for the treatment of damage and fracture in smooth particle hydrodynamic (SPH) method, where free surface, crack opening, including its propagation and branching is modelled by weakening the interparticle interactions combined with the visibility criterion. The model is consistent with classical continuum damage mechanics approach, but does not use an effective stress concept. It is a difficult task to model fracture leading to fragmentation in materials subjected to high-strain rates using continuum mechanics. Meshless methods such as SPH are well suited to be applied to fracture mechanics problems, since they are not prone to the problems associated with mesh tangling. The SPH momentum equation can be rearranged and expressed in terms of a particleparticle interaction area. Damage acts to reduce this area, which is ultimately set to zero, indicating material fracture. The first implementation of the model makes use of Cochran-Banner damage parameter evolution and incorporates a multiple bond break criterion for each neighbourhood of particles. This model implementation was verified in simulation of the onedimensional and three-dimensional flyer plate impact tests, where the results were compared to experimental data. The test showed that the model can recreate the phenomena associated with uniaxial spall to a high degree of accuracy. The model was then applied to orthotropic material formulation, combined with the failure modes typical for composites, and used for simulation of the hard projectile impact on composite target. [ABSTRACT FROM AUTHOR]

This article discusses the possibilities of estimation of safe sizes of integrity defects on the basis of risk criteria. Such defects occur at all stages of the lifetime of structures. In most cases the estimation of their hazard and determination of allowable sizes attract attention when the defects can lead to brittle or quasi-brittle fractures. In this case, the models of linear and nonlinear destruction mechanics are applied, when the defects are considered as internal elliptical or surface semielliptical cracks. The stochastic variety of shapes, sizes, locations, and orientations of defects has a significant influence on the failure mechanisms. Therefore, the probabilistic problem of estimating allowable sizes of defects according to the criteria of risk of failure is relevant. This paper examines a general approach to estimation of the hazards of defects according to risk criteria. Two formulations of the probabilistic problem of risk estimation are presented: on the basis of single-parameter and two-parameter failure criteria. The risk function is used as the calculated characteristic, represented as the probability of failure according to a given criterion. An equation of the risk function based on single-parameter failure criteria is presented. The main focus is on the probabilistic model based on the two-parameter Morozov failure criterion. This criterion provides a wide range of opportunities for analyzing various failure mechanisms with variations in the size of defects. An expression for the risk function based on the family of two-dimensional Lu–Bhattacharya probability distributions of Weibull type is derived. It is shown that correlations between failure mechanisms can significantly influence the probabilities of failure and, consequently, the allowable size of defects. [ABSTRACT FROM AUTHOR]

Multi‐fidelity models are of great importance due to their capability of fusing information coming from different numerical simulations, surrogates, and sensors. We focus on the approximation of high‐dimensional scalar functions with low intrinsic dimensionality. By introducing a low dimensional bias we can fight the curse of dimensionality affecting these quantities of interest, especially for many‐query applications. We seek a gradient‐based reduction of the parameter space through linear active subspaces or a nonlinear transformation of the input space. Then we build a low‐fidelity response surface based on such reduction, thus enabling nonlinear autoregressive multi‐fidelity Gaussian process regression without the need of running new simulations with simplified physical models. This has a great potential in the data scarcity regime affecting many engineering applications. In this work we present a new multi‐fidelity approach that involves active subspaces and the nonlinear level‐set learning method, starting from the preliminary analysis previously conducted (Romor F, Tezzele M, Rozza G. Proceedings in Applied Mathematics & Mechanics. Wiley Online Library; 2021). The proposed framework is tested on two high‐dimensional benchmark functions, and on a more complex car aerodynamics problem. We show how a low intrinsic dimensionality bias can increase the accuracy of Gaussian process response surfaces. [ABSTRACT FROM AUTHOR]

A description of a small icing wind tunnel designed for studying the icing processes at the Khristianovich Institute of Theoretical and Applied Mechanics of the Siberian Branch of the Russian Academy of Sciences is presented. The use of such a wind tunnel offers a possibility not only of studying the physical features of the icing process, but also of testing methods of anti-icing control, validating numerical methods used for calculating the icing processes, etc. [ABSTRACT FROM AUTHOR]

The corresponding author had the pleasure of attending an excellent symposium titled "Experimental and Theoretical Micro- and Nano-Mechanics: Honoring the Contributions of Prof. Kyung-Suk Kim" organized by Professors Ashraf Bastawros, Wendy Crone, Yanfei Gao, and Ruike (Renee) Zhao as part of the 2022 Society of Engineering Sciences Annual Technical Meeting held in College Station, TX on October 16-19, 2022. The symposium was held in honor of Prof. Kim's 70th Birthday and celebrated over 40 years of Prof. Kim's independent research achievements across several areas of Applied Mechanics. The present paper is dedicated to Prof. Kim, a great colleague at Brown University. We present a new formulation for the multilayer isogeometric Kirchhoff-Love (KL) shells, where the individual layers are assumed to interact through no-penetration and frictional contact. This work is largely motivated by the experiments and analysis presented in Poincloux et al. (2021, "Bending Response of a Book With Internal Friction," Phys. Rev. Lett., 126(21), p. 218004). We utilize a regularized version of Coulomb's friction law to model the tangential traction between the contacting shell surfaces. To ensure objectivity (i.e., reference-frame invariance) in the frictional model, we propose two different strategies to extrapolate the velocity vectors of the contact pair at the contact interface: (i) using the underlying KL kinematics of the individual shell layers and (ii) using the Taylor series-based extension from Kamensky et al. (2019, "Peridynamic Modeling of Frictional Contact," J. Peridyn. Nonlocal Model., 1(2), pp. 107-121). We compare the performance of both approaches through a numerical benchmark example. We then validate our multilayer shell formulation using the "bending response of a book with internal friction" experiments of Poincloux et al. (2021, "Bending Response of a Book With Internal Friction," Phys. Rev. Lett., 126(21), p. 218004). [ABSTRACT FROM AUTHOR]