Hasil untuk "Mechanics of engineering. Applied mechanics"

Đorđe Brašanac, Marko Kapeleti, Igor Zlatović et al.

<b>Background:</b> Previous research has identified center of mass vertical oscillation and leg stiffness as the most common variables differentiating Natural and Groucho running techniques. The aim was to assess the inter-session reliability and inter-technique sensitivity of synchronized inertial measurement units and contact grids in quantifying kinematic and kinetic differences between Natural and Groucho running techniques. <b>Methods:</b> Eleven physically active and healthy males ran at a speed 50% higher than transition speed. Two sessions for Natural and two for Groucho running were performed, each lasting 1 min. <b>Results:</b> Most variables exhibited a similar inter-session reliability across running techniques, except contact time and center of mass vertical displacement, ranging from moderate to good (ICC = 0.538–0.897). A statistically significant difference between running techniques was found for all variables (<i>p</i> < 0.05), except for contact time and center of mass vertical oscillation (<i>p</i> > 0.05), likely due to inconsistency in reliability depending on the running technique, which may have covered the underlying differences. <b>Conclusions:</b> We can conclude that the combination of synchronized inertial measurement units and contact grids showed potentially acceptable reliability and sufficient sensitivity to recognize and differentiate between Natural and Groucho running techniques. The results may contribute to a broader understanding of the differences between these two running techniques and encourage the increased use of these devices within therapeutic, recreational, and sports running contexts.

Enrique Pujada-Gamarra, Daniel Lavayen-Farfán, Davy Olivera-Oliva et al.

In recent years, ecofriendly and renewable energy solutions have gained relevance mainly to lessen the effects of climate change. Governments and companies across the world have commitments to reduce fuel consumption and emissions as part of the 2030 Sustainable Development Goals. Solar energy systems have great importance as a renewable energy source; however, they often have large space requirements to be effective, e.g., large areas covered by solar panels, as well as low efficiency and strong dependance on the weather. On the other hand, origami, the art of folding paper, can be a source of inspiration for new technologies and solutions for modern problems. In this paper, origami-inspired solar panels are presented as a potential solution for naval and mining operations. Prototype panels are manufactured based on the Miura-Ori pattern. Using this pattern, the photovoltaic modules can be folded by just one movement, thus reducing their footprint by up to 90%. The prototype photovoltaic modules are then tested on land and on board a vessel, where their efficiency and resistance can be tested. It is shown that naval and mining operations, where fuel consumption can be extremely high and available space is a major constraint, benefit greatly from this kind of development.

Marvin Wyrich, Lloyd Montgomery

A well-rounded software engineer is often defined by technical prowess and the ability to deliver on complex projects. However, the narrative around the ideal Software Engineering (SE) candidate is evolving, suggesting that there is more to the story. This article explores the non-technical aspects emphasized in SE job postings, revealing the sociotechnical and organizational expectations of employers. Our Thematic Analysis of 100 job postings shows that employers seek candidates who align with their sense of purpose, fit within company culture, pursue personal and career growth, and excel in interpersonal interactions. This study contributes to ongoing discussions in the SE community about the evolving role and workplace context of software engineers beyond technical skills. By highlighting these expectations, we provide relevant insights for researchers, educators, practitioners, and recruiters. Additionally, our analysis offers a valuable snapshot of SE job postings in 2023, providing a scientific record of prevailing trends and expectations.

Lotfi Ben Said, Ali Basem, Dheyaa J. Jasim et al.

The present study investigated the effect of heat flux frequency on doxorubicin adsorption by bio MOF11 biocarrier using molecular dynamics simulation. This simulation examined the effect of several heat flux frequencies (0.001, 0.002, 0.005, and 0.010 1/fs) on the quantity of drug particles absorbed, mean square displacement (MSD), diffusion coefficient, and interaction energy. The present outputs of simulations predicted the structural stability of the modeled MOF-drug system in 300 K. Also, simulation outputs predicted by frequency optimization, the adsorption of target drug inside MOF11 maximized, and efficiency of this sample in actual clinical applications, such as drug delivery process increased. Numerically, the optimum value of frequency was estimated to be 0.005 1/fs. Using this heat setting, the interaction energy between MOF 11 and the doxorubicin drug increased to −929.05 kcal/mol, and the number of penetrated drug particles inside MOF11 converged to 207 atoms. The results reveal that the MSD parameter reached 64.82 Å2 after 100000-time steps. By increasing frequency to 0.005 fs−1, this increased to 78.05 Å2. By increasing MSD parameter, the drug diffusion process effectively occurred, and the diffusion coefficient increased from 67.29 to 82.47 nm2/ns. It is expected that the findings of present investigation guide the design of more efficient drug delivery platforms, enhance drug-carrier interactions, improve manufacturing processes, and aid in developing novel nanomaterials with enhanced adsorption properties for various applications.

Zhang Yingshuai, Yang Yiyong, Cheng Jia et al.

When the human body experiences heat stress beyond the normal range, it may affect health and work efficiency to a certain extent. This study aimed to investigate the effectiveness of cold stimulation on Dazhui point (GV14), bilateral Xinshu points (B15), bilateral Danshu points (B19), and bilateral Quchi points (LI11) in the body to relieve heat strain in a high-temperature environment. The experiment results showed that the skin temperature (Tskin), tympanic temperature (Tty), heart rate (HR), the physiological strain index based on heart rate (PSIHR), thermal sensation (TS), and thermal comfort (TC) of the participants with acupoints cold stimulation were better than those without acupoints cold stimulation (p < 0.05). Tskin decreased by an average of 0.04 ± 0.46Ԩ. Tty decreased by an average of 0.08 ± 0.21Ԩ. The study concluded that cold stimulation at acupoints could reduce the heat strain and improve the thermal comfort of the human body.

E. T. Wang, H. N. Wang, F. Song et al.

Abstract This study provides a general analytical approach to predict the stresses and displacements of deep noncircular tunnels excavated in saturated elastic ground, considering the hydro-mechanical coupling, the interaction between rock and liner, and arbitrary tunnel shapes. The complex variable theory is innovatively extended to solve the seepage fields for noncircular supported tunnels in both surrounding rocks and liner fields. After that, coupled hydro-mechanical solutions of stresses and displacements can be determined by considering the influence of seepage flow on the mechanical responses. Furthermore, stability analyses of supported tunnels are conducted in the hydro-mechanical coupled framework, incorporating the effect of seepage flow. As a verification, a good agreement is observed between stress and displacement fields obtained from the current analytical solutions and numerical simulations. Then, parametric analyses are performed to assess how variations in tunnel shape, liner permeability, and liner thickness influence the mechanical behaviours of supported tunnels. Meanwhile, by employing the Mohr–Coulomb strength criterion, an expression of equivalent stress is proposed to assess the potential failure behaviour of supported tunnels in the entire process of excavation and operation stages. This study provides high potential of application to a number of relevant case studies, such as tunnelling below the water table.

Johan Cederbladh, Antonio Cicchetti

In this paper we discuss the growing need for system behaviour to be validated and verified (V&V'ed) early in model-based systems engineering. Several aspects push companies towards integration of techniques, methods, and processes that promote specific and general V&V activities earlier to support more effective decision-making. As a result, there are incentives to introduce new technologies to remain competitive with the recently drastic changes in system complexity and heterogeneity. Performing V&V early on in development is a means of reducing risk for later error detection while moving key activities earlier in a process. We present a summary of the literature on early V&V and position existing challenges regarding potential solutions and future investigations. In particular, we reason that the software engineering community can act as a source for inspiration as many emerging technologies in the software domain are showing promise in the wider systems domain, and there already exist well formed methods for early V&V of software behaviour in the software modelling community. We conclude the paper with a road-map for future research and development for both researchers and practitioners to further develop the concepts discussed in the paper.

Javad Ghorbanian, Nicholas Casaprima, Audrey Olivier

In recent years, neural networks (NNs) have become increasingly popular for surrogate modeling tasks in mechanics and materials modeling applications. While traditional NNs are deterministic functions that rely solely on data to learn the input--output mapping, casting NN training within a Bayesian framework allows to quantify uncertainties, in particular epistemic uncertainties that arise from lack of training data, and to integrate a priori knowledge via the Bayesian prior. However, the high dimensionality and non-physicality of the NN parameter space, and the complex relationship between parameters (NN weights) and predicted outputs, renders both prior design and posterior inference challenging. In this work we present a novel BNN training scheme based on anchored ensembling that can integrate a priori information available in the function space, from e.g. low-fidelity models. The anchoring scheme makes use of low-rank correlations between NN parameters, learnt from pre-training to realizations of the functional prior. We also perform a study to demonstrate how correlations between NN weights, which are often neglected in existing BNN implementations, is critical to appropriately transfer knowledge between the function-space and parameter-space priors. Performance of our novel BNN algorithm is first studied on a small 1D example to illustrate the algorithm's behavior in both interpolation and extrapolation settings. Then, a thorough assessment is performed on a multi--input--output materials surrogate modeling example, where we demonstrate the algorithm's capabilities both in terms of accuracy and quality of the uncertainty estimation, for both in-distribution and out-of-distribution data.

Abdulla Mubaah , Siva Priya Thiagarajah

It is estimated that the cumulative of Electric Vehicles (EVs) will reach 85 million by 2030. EV batteries that have degraded to80% of their initial capacity no longer provide the required efficiency for EV, resulting in anincreasing amount of batteries being discarded and stored in warehouses instead of being recycled. The cost of this storage after its End of Life (EOL) adds to the initial cost of the EV. There is amounting environmental pressure to re-purposethese discarded batteriesin other applications, such as energy arbitrage and peak shaving, such that the initial cost of the EV be reduced. This work presents a feasibility study that allows discarded EV batteries to be repurposed batteries to providepeak shaving in a mid-tier data centre with an area size of 465 m2. A comparison of the cost during peak hours shows that the repurposed batteries can be used as a reliable power supply source to reduce the reliance of data centres on grid power during peak hours. Results showed that the use of these repurposed batteries alsoachieved a higher cost savings as compared to using brand new Lithium Ionbattery over a period of 10 years. Areliability study alsoshows that the repurposed battery system and brand new battery system performs atpar, when the data centre draws power from the grid during peak hours. The study concludes that power supply system in data centres that uses repurposed batteriesto achievepeak shaving is a cost effective, green solution that should be implemented. In the larger picture,the reusability of the EV batteriesis expected toreduce the initial price of the EV cars,allowing a larger market penetration and thus ensuring the sustainability of the EV car industry. Reusing the stored batteries also reduces environmental issues related to Lithium miningfor brand new batteries, such as mining pollution and fresh water shortage.

Lulin Fan, Lulin Fan, Tongjun Xu et al.

Micro-structured targets can be employed to enhance the coupling of laser energy to the high energy density plasma. Here we report on experimental measurement of enhanced proton beam energy from laser-driven micro-wire array (MWA) targets along the backward direction. An ultra-intense (∼2×1020W/cm2) laser pulse of ∼ 40 fs pulse duration interacts with the MWA structure and induces large population of energetic electrons. The enhanced sheath field efficiently accelerates protons both transversely and longitudinally. The spectrometers record proton cut-off energy of around 16 MeV and temperature 813keV along the backward direction, which is 20%−60% higher than that of a flat target under commensurate laser conditions. Comparison with particle-in-cell simulations suggests that the enhancement originates from the increased temperature and population of the hot electrons within the micro-wires. These measurements provide a direct probe of the high energy density plasma condition in laser-driven solid targets and a useful benchmark for further studies on laser-driven micro-structured targets.

Paweł Dłużewski, Horacio Antuúnez

The problem of dislocation motion in monocrystals is faced in the framework of the continuum theory of dislocations. The presented approach is based on the defects balance law. A constitutive model is formulated which relates the driving forces with the dislocation velocity. The model makes use of the relations between the plastic deformation tensor and the tensor of dislocation density. Given a crystal under certain boundary and initial conditions, the evolution of both dislocation field and elastic-plastic deformations is obtained by solving the coupled system of equations resulting from the equilibrium equation and the dislocation balance for each time step. The set of equations is discretized by the finite element method. As an example the movement of an edge dislocation field inducing shear band deformation in a monocrystal is considered.

Jie Chen, Heng Zhou

Nuralin Beket, Galiev Manarbek, Kubasheva Zhanna et al.

Soil preparation with single-operation serial machine-tractor units requires multiple passes over the field, which leads to excessive soil compaction and loss of fertile layer, increased consumption of fuel and lubricants. The use of machines with dynamic tillage tools to prepare the soil for sowing allows regulation of soil pulverization intensity and performing a technological operation in one pass. The aim of the research is to study the possibilities of a combined approach to graded tillage, combining static and dynamic tillage tools. The main disadvantages of tiller are poor penetration ability, high metal and energy consumption. The authors found that the rational joint use of static and dynamic tillage tool in the cultivator for graded soil treatment may reduce the energy consumption for the top layer cultivating by 1.5 times. Such aspects, as the degree of influence of the parameters and operating modes of the tiller on the specific energy consumption of processing, soil pulverization intensity and degree of the content of erosion-hazardous particles in the upper layer are revealed, design and operating parameters of the combined cultivator and its tillage tools are substantiated.

Carmelo R. Cartiere

Quantum computing (QC) represents the future of computing systems, but the tools for reasoning about the quantum model of computation, in which the laws obeyed are those on the quantum mechanical scale, are still a mix of linear algebra and Dirac notation; two subjects more suitable for physicists, rather than computer scientists and software engineers. On this ground, we believe it is possible to provide a more intuitive approach to thinking and writing about quantum computing systems, in order to simplify the design of quantum algorithms and the development of quantum software. In this paper, we move the first step in such direction, introducing a specification language as the tool to represent the operations of a quantum computer via axiomatic definitions, by adopting the same symbolisms and reasoning principles used by formal methods in software engineering. We name this approach formal quantum software engineering (F-QSE). This work assumes familiarity with the basic principles of quantum mechanics (QM), with the use of Zed (Z) which is a formal language of software engineering (SE), and with the notation and techniques of first-order logic (FOL) and functional programming (FP).

Rodrigo Henrique Barbosa Monteiro, Maurício Ronny de Almeida Souza, Sandro Ronaldo Bezerra Oliveira et al.

Gamification has been used to motivate and engage participants in software engineering education and practice activities. There is a significant demand for empirical studies for the understanding of the impacts and efficacy of gamification. However, the lack of standard procedures and models for the evaluation of gamification is a challenge for the design, comparison, and report of results related to the assessment of gamification approaches and its effects. The goal of this study is to identify models and strategies for the evaluation of gamification reported in the literature. To achieve this goal, we conducted a systematic mapping study to investigate strategies for the evaluation of gamification in the context of software engineering. We selected 100 primary studies on gamification in software engineering (from 2011 to 2020). We categorized the studies regarding the presence of evaluation procedures or models for the evaluation of gamification, the purpose of the evaluation, the criteria used, the type of data, instruments, and procedures for data analysis. Our results show that 64 studies report procedures for the evaluation of gamification. However, only three studies actually propose evaluation models for gamification. We observed that the evaluation of gamification focuses on two aspects: the evaluation of the gamification strategy itself, related to the user experience and perceptions; and the evaluation of the outcomes and effects of gamification on its users and context. The most recurring criteria for the evaluation are 'engagement', 'motivation', 'satisfaction', and 'performance'. Finally, the evaluation of gamification requires a mix of subjective and objective inputs, and qualitative and quantitative data analysis approaches. Depending of the focus of the evaluation (the strategy or the outcomes), there is a predominance of a type of data and analysis.

Oleg G. Kharlanov, Boris S. Shvetsov, Vladimir V. Rylkov et al.

Memristors are among the most promising elements for modern microelectronics, having unique properties such as quasi-continuous change of conductance and long-term storage of resistive states. However, identifying the physical mechanisms of resistive switching and evolution of conductive filaments in such structures still remains a major challenge. In this work, aiming at a better understanding of these phenomena, we experimentally investigate an unusual effect of enhanced conductive filament stability in memristors with copper filaments under the applied voltage and present a simplified theoretical model of the effect of a quantum current through a filament on its shape. Our semi-quantitative, continuous model predicts, indeed, that for a thin filament, the "quantum pressure" exerted on its walls by the recoil of charge carriers can well compete with the surface tension and crucially affect the evolution of the filament profile at the voltages around 1V. At lower voltages, the quantum pressure is expected to provide extra stability to the filaments supporting quantized conductance, which we also reveal experimentally using a novel methodology focusing on retention statistics. Our results indicate that the recoil effects could potentially be important for resistive switching in memristive devices with metallic filaments and that taking them into account in rational design of memristors could help achieve their better retention and plasticity characteristics.

P. Meriggi, G. de Felice, S. De Santis et al.

ABSTRACT The out-of-plane vulnerability of masonry walls plays a crucial role in the seismic response of existing structures. Depending upon mechanical properties and section morphology, collapse may occur by the onset of a mechanism or, as historic constructions often exhibit, leaf separation, disaggregation or sliding. In these latter cases, structural analyses based on rigid-body mechanics may overestimate the seismic capacity, thus resulting unconservative. The distinct element method (DEM), which represents masonry as an assembly of discrete blocks and nonlinear interfaces, could instead be used. Nevertheless, it is more complex and requires more input parameters, so it is still barely applied in engineering practice. In this paper, the seismic out-of-plane response of masonry walls was modelled with DEM. A shake table test on a two-leaf rubble stone masonry wall and a single-leaf wall in tuff blocks was simulated through nonlinear dynamic analyses. The mechanical properties of joints were calibrated on the basis of dynamic identification under low-intensity white noise input, leading to a good prediction of the seismic response. Then, they were further tuned based on the surveyed crack pattern for an improved matching between experimental results and numerical postdictions. Finally, the results provided by the limit analysis were discussed in the light of DEM simulations.

Christopher S. Timperley, Lauren Herckis, Claire Le Goues et al.

In recent years, many software engineering researchers have begun to include artifacts alongside their research papers. Ideally, artifacts, including tools, benchmarks, and data, support the dissemination of ideas, provide evidence for research claims, and serve as a starting point for future research. However, in practice, artifacts suffer from a variety of issues that prevent the realization of their full potential. To help the software engineering community realize the full potential of artifacts, we seek to understand the challenges involved in the creation, sharing, and use of artifacts. To that end, we perform a mixed-methods study including a survey of artifacts in software engineering publications, and an online survey of 153 software engineering researchers. By analyzing the perspectives of artifact creators, users, and reviewers, we identify several high-level challenges that affect the quality of artifacts including mismatched expectations between these groups, and a lack of sufficient reward for both creators and reviewers. Using Diffusion of Innovations as an analytical framework, we examine how these challenges relate to one another, and build an understanding of the factors that affect the sharing and success of artifacts. Finally, we make recommendations to improve the quality of artifacts based on our results and existing best practices.

Michel Destrade, Brian Mac Donald, Jerry Murphy et al.

The modelling of off-axis simple tension experiments on transversely isotropic nonlinearly elastic materials is considered. A testing protocol is proposed where normal force is applied to one edge of a rectangular specimen with the opposite edge allowed to move laterally but constrained so that no vertical displacement is allowed. Numerical simulations suggest that this deformation is likely to remain substantially homogeneous throughout the specimen for moderate deformations. It is therefore further proposed that such tests can be modelled adequately as a homogenous deformation consisting of a triaxial stretch accompanied by a simple shear. Thus the proposed test should be a viable alternative to the standard biaxial tests currently used as material characterisation tests for transversely isotropic materials in general and, in particular, for soft, biological tissue. A consequence of the analysis is a kinematical universal relation for off-axis testing that results when the strain-energy function is assumed to be a function of only one isotropic and one anisotropic invariant, as is typically the case. The universal relation provides a simple test of this assumption, which is usually made for mathematical convenience. Numerical simulations also suggest that this universal relation is unlikely to agree with experimental data and therefore that at least three invariants are necessary to fully capture the mechanical response of transversely isotropic materials.

Jean-Sebastien Spratt, Mauro Rodriguez, Kevin Schmidmayer et al.

Viscoelastic material properties at high strain rates are needed to model many biological and medical systems. Bubble cavitation can induce such strain rates, and the resulting bubble dynamics are sensitive to the material properties. Thus, in principle, these properties can be inferred via measurements of the bubble dynamics. Estrada et al. (2018) demonstrated such bubble-dynamic high-strain-rate rheometry by using least-squares shooting to minimize the difference between simulated and experimental bubble radius histories. We generalize their technique to account for additional uncertainties in the model, initial conditions, and material properties needed to uniquely simulate the bubble dynamics. Ensemble-based data assimilation minimizes the computational expense associated with the bubble cavitation model. We test an ensemble Kalman filter (EnKF), an iterative ensemble Kalman smoother (IEnKS), and a hybrid ensemble-based 4D--Var method (En4D--Var) on synthetic data, assessing their estimations of the viscosity and shear modulus of a Kelvin--Voigt material. Results show that En4D--Var and IEnKS provide better moduli estimates than EnKF. Applying these methods to the experimental data of Estrada et al. (2018) yields similar material property estimates to those they obtained, but provides additional information about uncertainties. In particular, the En4D--Var yields lower viscosity estimates for some experiments, and the dynamic estimators reveal a potential mechanism that is unaccounted for in the model, whereby the viscosity is reduced in some cases due to material damage occurring at bubble collapse.