Hasil untuk "Mechanics of engineering. Applied mechanics"

Shimul Akhanjee

The statistical mechanics of particles that populate indistinguishable energy states is explored. In particular, the mathematical treatment of the microstates differs from conventional statistical mechanics where the energy levels or states are universally treated as distinguishable, and differentiated by unique quantum numbers, or addressed by distinct spatial locations. Results from combinatorial counting problems are adapted to derive exact distribution functions for both classical and quantum particles at high degeneracy levels. Classical particles exhibit a definitive glass transition, similar to supercooled liquids where where the configurational entropy vanishes below a finite temperature $T_K$.

Chichkhede S., Mahapatra D., Sanyal S. et al.

The dynamic behaviour of a rotating Timoshenko functionally graded (FG) beam is investigated, with material properties varying along the height of the beam according to a power-law distribution. The study investigates how key parameters such as the power-law index, rotational speed, slenderness ratio, and various functionally graded material (FGM) compositions affect the dynamic response of the beam. The governing equations, which incorporate shear deformation and rotary inertia effects, are formulated and solved using the B-spline collocation method. The results provide critical insights into how these parameters affect the natural properties of FG beams, contributing to optimization and development for the design of advanced rotating structures in engineering applications.

Mauricio da Silva Moreira, Carlos Eduardo Marcos Guilherme, João Henrique Corrêa de Souza et al.

This article presents a numerical study encompassing the mechanical behavior prediction during the roll bending process applied to four distinct profiles of extruded 6061-T6 aluminum, considering different radii of curvature. The numerical simulations were conducted using the ANSYS® software, based on the finite element method, adopting the three-dimensional SOLID187 finite element. The employed computational model was developed and validated by Moreira et al. [1]. The obtained results demonstrate consistent patterns regarding stresses and displacements for the different radii of curvature. As the radius of curvature decreases, the von Mises stress tends to increase, approaching the material's strength limit. This phenomenon is critical for identifying points of maximum stress and ensuring adequate safety margins to prevent structural failures. Displacements along the profiles were also monitored, providing relevant information about its evolution at different radii of curvature and allowing curve fitting for these displacements in each profile investigated. Therefore, these consistent patterns observed can help to determine the direct influence of curvature on resulting defects, contributing to an in-depth understanding of the mechanical behavior of these profiles.

Ali Rehman, Ma Chau Khun, Dolat Khan et al.

With the significant advancements in nanofluids, the fields of fluid dynamics and thermal management have experienced further development. Due to their enhanced thermal properties and capacity for customization to specific applications, nanofluids present a viable option for improving the efficacy and efficiency of various technological and industrial processes. The objective of this research article is to investigate the heat transfer properties of a blood-based steady laminar mixed convection flow of nanofluid over perpendicular stretched sheets. The non-Newtonian nanofluid's unique thermal properties, attributable to carbon nanotubes (CNTs), render it a suitable medium for enhancing heat transfer in biomedical applications. The flow model equations, one for momentum and another for energy, are transformed into a set of nonlinear ordinary differential equations through the application of appropriate similarity transformations. The governing nonlinear equations are solved semi-numerically using the Homotopy Analysis Method. This method is effective for obtaining series solutions to highly nonlinear differential equations. The Homotopy Analysis Method, developed by Shijun Liao in the 1990s, has applications in numerous disciplines of science and engineering. Several significant factors, including Local Grashof number, couple stress parameter, nanoparticle volume fraction, thermal radiation parameter, temperature exponent, and Prandtl number, are investigated, and their impact on the temperature and velocity profiles is examined. The study also considers the Nusselt number and skin friction coefficient. The results demonstrate that the addition of CNTs significantly increases heat transfer efficiency, thereby enhancing cooling in biological domains. This study contributes to our understanding of heat transfer enhancement in blood-based nanofluids with carbon nanotubes and provides important new insights for the development and improvement of thermal control systems in biomedical engineering. Furthermore, the findings of this study may inform the development of novel strategies to improve the efficacy of heat exchangers and cooling devices in medical applications.

Sonja M. Hyrynsalmi, Grischa Liebel, Ronnie de Souza Santos et al.

The discipline of software engineering (SE) combines social and technological dimensions. It is an interdisciplinary research field. However, interdisciplinary research submitted to software engineering venues may not receive the same level of recognition as more traditional or technical topics such as software testing. For this paper, we conducted an online survey of 73 SE researchers and used a mixed-method data analysis approach to investigate their challenges and recommendations when publishing interdisciplinary research in SE. We found that the challenges of publishing interdisciplinary research in SE can be divided into topic-related and reviewing-related challenges. Furthermore, while our initial focus was on publishing interdisciplinary research, the impact of current reviewing practices on marginalized groups emerged from our data, as we found that marginalized groups are more likely to receive negative feedback. In addition, we found that experienced researchers are less likely to change their research direction due to feedback they receive. To address the identified challenges, our participants emphasize the importance of highlighting the impact and value of interdisciplinary work for SE, collaborating with experienced researchers, and establishing clearer submission guidelines and new interdisciplinary SE publication venues. Our findings contribute to the understanding of the current state of the SE research community and how we could better support interdisciplinary research in our field.

Marc Bruni, Fabio Gabrielli, Mohammad Ghafari et al.

Prompt engineering reduces reasoning mistakes in Large Language Models (LLMs). However, its effectiveness in mitigating vulnerabilities in LLM-generated code remains underexplored. To address this gap, we implemented a benchmark to automatically assess the impact of various prompt engineering strategies on code security. Our benchmark leverages two peer-reviewed prompt datasets and employs static scanners to evaluate code security at scale. We tested multiple prompt engineering techniques on GPT-3.5-turbo, GPT-4o, and GPT-4o-mini. Our results show that for GPT-4o and GPT-4o-mini, a security-focused prompt prefix can reduce the occurrence of security vulnerabilities by up to 56%. Additionally, all tested models demonstrated the ability to detect and repair between 41.9% and 68.7% of vulnerabilities in previously generated code when using iterative prompting techniques. Finally, we introduce a "prompt agent" that demonstrates how the most effective techniques can be applied in real-world development workflows.

Anil Chikkanna, Kuchangi Venkatappa Manjunath, Kumaraswamy Jayappa et al.

Conventional machining techniques struggle to effectively process these materials. To overcome these challenges, advanced methods like wire electric discharge machining (EDM) are being explored for cutting electrically conductive composites. This study aims to investigate the impact of various chill materials (Mild Steel, Cast Iron, Stainless Steel, and Copper), cutting parameters (Pulse On, Pulse Off time, and Current), and the weight percentage of Boron Carbide on two crucial aspects: Metal Removal Rate (MRR) and Surface Roughness (SR) of Aluminum-Boron Carbide (Al-B4C) chilled composites. By conducting ANOVA analysis, researchers seek to determine the individual and combined effects of these process variables on MRR and SR. Additionally, scanning electron microscopic analysis is employed to gain insights into the microstructure and quality of the machined surfaces. It's noteworthy that composites prepared using Cu-chill plates exhibit exceptional resistance to the machining process due to their superior mechanical properties, followed by SS-chill, CI-chill, and MS-chill. The thermal conductivity of the chill materials on solidified composites plays a pivotal role in influencing machinability and surface roughness. While the weight percentage of B4C has a lesser impact on machinability studies, it significantly affects the surface finish of the machined surface.

Xiuting Sun, Jian Xu, Zhifeng Qi

By the biological construction of a bird neck, a bionic bird-neck multilevel rigid-flexible structure is proposed and some biometric properties are explained. The proposed structure can flexibly deform in six directions, which inspires the study of its mechanical properties for flexible deformations. First, the structural configuration and composition are determined based on the study of the anatomical characteristics of the woodpeckers. Since the skeletons and muscles have very different values for the elasticity modulus and the deformation is mostly dependent on the muscle tension, the bionic structure consists of rigid units and bio-syncretic components. For combined deformations, the mechanical model is established by the connectivity matrix to describe the connection of each level. Second, based on the principle of minimum potential energy, an integral form-finding method is proposed for flexible combination deformations. All of the integral forms obtained with the theoretical analysis are compared with the results with Finite Element Analysis. The structural parameters of the bionic structure were then tightly fixed to the actual shape of the bird's neck and the corresponding overall form took on an ''S'' shape, which perfectly matched the construction of the bird's neck. In addition, for the pre-deformation form, by analyzing the potential energy of the bionic structure, due to the adjustable dynamic stiffness property, an explanation is provided for the significant dynamic stability of the bird neck in bending. This study not only proposes a bionic rigid-flexible structure with high spatial accessibility but also explains biological properties of a bird neck based on the study of its mechanics characteristics. Based on the modeling and the mechanical properties of the bionic structure in flexible spatial combination deformations, the multi-steady state, and the variable dynamic stiffness, the bird-neck bionic rigid-flexible structure has significant applications such as aeronautical deployable systems, manipulator positioning, and dynamic stability fields.

Sayan Chatterjee, Ching Louis Liu, Gareth Rowland et al.

The increasing popularity of AI, particularly Large Language Models (LLMs), has significantly impacted various domains, including Software Engineering. This study explores the integration of AI tools in software engineering practices within a large organization. We focus on ANZ Bank, which employs over 5000 engineers covering all aspects of the software development life cycle. This paper details an experiment conducted using GitHub Copilot, a notable AI tool, within a controlled environment to evaluate its effectiveness in real-world engineering tasks. Additionally, this paper shares initial findings on the productivity improvements observed after GitHub Copilot was adopted on a large scale, with about 1000 engineers using it. ANZ Bank's six-week experiment with GitHub Copilot included two weeks of preparation and four weeks of active testing. The study evaluated participant sentiment and the tool's impact on productivity, code quality, and security. Initially, participants used GitHub Copilot for proposed use-cases, with their feedback gathered through regular surveys. In the second phase, they were divided into Control and Copilot groups, each tackling the same Python challenges, and their experiences were again surveyed. Results showed a notable boost in productivity and code quality with GitHub Copilot, though its impact on code security remained inconclusive. Participant responses were overall positive, confirming GitHub Copilot's effectiveness in large-scale software engineering environments. Early data from 1000 engineers also indicated a significant increase in productivity and job satisfaction.

Carmine Maria Pappalardo, Filippo Califano, Sefika Ipek Lok et al.

This paper is the first part of a two-part research work aimed at performing a systematic computational and experimental analysis of the principal data-driven identification procedures based on the Observer/Kalman Filter Identification Methods (OKID) and the Numerical Algorithms for Subspace State-Space System Identification (N4SID). Considering the approach proposed in this work, the state-space model of a mechanical system can be identified with the OKID and N4SID methods. Additionally, the second-order configuration-space dynamical model of the mechanical system of interest can be estimated with the MKR (Mass, Stiffness, and Damping matrices) and PDC (Proportional Damping Coefficients) techniques. In particular, this first paper concentrates on the description of the fundamental analytical methods and computational algorithms employed in this study. In this investigation, numerical and experimental analyses of two fundamental time-domain system identification techniques are performed. To this end, the main variants of the OKID and the N4SID methods are examined in this study. These two families of numerical methods allow for identifying a first-order state-space model of a given dynamical system by directly starting from the time-domain experimental data measured in input and output to the system of interest. The basic steps of the system identification numerical procedures mentioned before are described in detail in the paper. As discussed in the manuscript, from the identified first-order state-space dynamical models obtained using the OKID and N4SID methods, a second-order configuration-space mechanical model of the dynamic system under consideration can be subsequently obtained by employing another identification algorithm described in this work and referred to as the MKR method. Furthermore, by using the second-order dynamical model obtained from experimental data, and considering the hypothesis of proportional damping, an effective technique referred to as the PDC method is also introduced in this investigation to calculate an improved estimation of the identified damping coefficients. In this investigation, a numerical and experimental comparison between the OKID methods and the N4SID algorithms is proposed. Both families of methodologies allow for performing the time-domain state-space system identification, namely, they lead to an estimation of the state, input influence, output influence, and direct transmission matrices that define the dynamic behavior of a mechanical system. Additionally, a least-square approach based on the PDC method is employed in this work for reconstructing an improved estimation of the damping matrix starting from a triplet of estimated mass, stiffness, and damping matrices of a linear dynamical system obtained using the MKR identification procedure. The mathematical background thoroughly analyzed in this first research work serves to pave the way for the applications presented and discussed in the second research paper.

Sehrish Malik, Moeen Ali Naqvi, Leon Moonen

There is an increasing need to assess the correct behavior of self-adaptive and self-healing systems due to their adoption in critical and highly dynamic environments. However, there is a lack of systematic evaluation methods for self-adaptive and self-healing systems. We proposed CHESS, a novel approach to address this gap by evaluating self-adaptive and self-healing systems through fault injection based on chaos engineering (CE) [ arXiv:2208.13227 ]. The artifact presented in this paper provides an extensive overview of the use of CHESS through two microservice-based case studies: a smart office case study and an existing demo application called Yelb. It comes with a managing system service, a self-monitoring service, as well as five fault injection scenarios covering infrastructure faults and functional faults. Each of these components can be easily extended or replaced to adopt the CHESS approach to a new case study, help explore its promises and limitations, and identify directions for future research. Keywords: self-healing, resilience, chaos engineering, evaluation, artifact

Yue Zhang, Yunmeng Zhang, Jizhong Huang

Abstract Sandstone grottoes, with their elaborate carvings and decorations, hold high historic, artistic and scientific values and therefore constitute an important part of China’s stone cultural heritage. Although capillary water accounts for severe pathologies at the grottoes, so far there have been limited comprehensive investigations concerned with the capillary water absorption behavior of sandstones. Aiming at three significant and famous sites in China, i.e., Yungang Grottoes (YG), Dazu Rock Carvings (DZ) and Leshan Grand Buddha (LS), capillary water absorption tests were performed on samples from local sandstones. During the test, evolution of cumulative inflow was measured and variation in the height of capillary rise over time was also monitored by combining visual observation and infrared thermography. Scanning electron microscope and mercury intrusion porosimetry were adopted to characterize the pore structure. The results indicate that all the tested sandstones had a medium capacity of water uptake. Kinetics for capillary water absorption was the highest for LS sandstone and the lowest for DZ sandstone. Differences in macroscopic properties were contributed to microstructural features such as average pore diameter and pore size distribution. An irregular shaped water front was only observed in LS sandstone due to its heterogeneity. Infrared thermography provides an efficient and nondestructive way to detect the transition zone between wet and dry portions of the sample, which was not visible to the naked eyes. A proper understanding of the interaction of the sandstones with capillary water is essential for revealing the deterioration of grottoes and the underlying mechanisms.

Ossama Mokhiamar, Mostafa Ghoniem, Taher Awad

This work implements a fuzzy logic control (FLC) on a proposed new low-cost semi-active shock absorber to improve vehicle ride comfort. The ordinary passive shock absorber is replaced with a new apparatus consisting of a conventional hydraulic cylinder with a proportional throttle valve placed outside the cylinder between its ports. FLC is used to adjust the damping coefficient by regulating the valve opening region. The fuzzy logic controller is configured using acceleration driven damping (ADD) methodology. Inputs are the accelerations of the sprung and the un-sprung masses, while the opening region of the valve is the output of the controller. Simscape/Matlab is used to build the model of the suggested semi-active shock absorber. The magneto-rheological (MR) suspension system and the suggested semi-active shock absorber with artificial neural network (ANN) controller are provided for comparison purposes. The findings demonstrated superior performance for the suggested shock absorber controlled by FLC relative to other controllers and to the ordinary damper as well, with one fourth of the cost of the magneto-rheological (MR) damper.

Jiu WANG, Rong LIN, Xiaofeng CHEN et al.

Body injury criterion is the basis of aircraft seat and restraint system design. On the base of statistics on 559 autopsies involved in fatal general aircraft accidents in Federal Aviation Administration's autopsy database, an analysis was performed to confirm the frequency and fatal risk in these aircraft accidents. Concerning different tolerance against impact of various body regions, the General Injury Criterion (GIC) was proposed to address the application in aviation, trying to provide an evaluation index for design and test of aircraft seat and restrain system. In union of seat dynamic test of a certain light amphibious aircraft for the airworthiness certification, the finite element model of the test was analyzed, and GIC was used to assess severe injury risk corresponding to various seat positions forward and backward. The assessment provides references in confirming testing condition of seat installed test.

Sompop Jarungthammachote

In S-CO2 recompression Brayton cycle, use of intercooling is a way to improve the cycle efficiency. However, it may decrease the efficiency due to increase of heat rejection. In this work, two S-CO2 recompression Brayton cycles are investigated using the thermodynamic model. The first cycle has intercoolings in a main compression and a recompression process (MCRCIC) and the second cycle has an intercooling in only the recompression process (RCIC). The thermal efficiencies of both cycles are compared with that of S-CO2 recompression Brayton cycle with intercooling in the main compression process (MCIC). Effects of a split fraction (SF) and a ratio of pressure ratio of the recompression (RPRRC) on the thermal efficiencies of MCRCIC and RCIC are also studied. The study results show that the intercooling of recompressor in MCRCIC and RCIC can reduce the compression power. However, it also rejects heat from the cycle and this leads to increasing added heat in the heater. The thermal efficiency of MCRCIC and RCIC are, then, lower than that of the MCIC. For the effects of RPRRC and SF to the thermal efficiency of the cycles, in general, when RPRRC increases, the thermal efficiency decreases due to increasing rejected heat. The increase in SF causes increasing thermal efficiency of the cycles and the thermal efficiency, then, decrease when SF is beyond the optimal value.

Galal M. Moatimid, Fawzy M.F. Elsabaa, Marwa H. Zekry

The current article is concerned with a comprehensive investigation in achieving approximate solutions of coupled nonlinear oscillations with high nonlinearity. These equations are highly nonlinear second-order ordinary differential equations. Via a coupling of the Homotopy perturbation method and Laplace transforms, which is so-called the He-Laplace method, traditional approximate solutions involving the secular terms are accomplished. On the other hand, in order to cancel the secular terms, an expanded frequency technique is adapted to accomplish periodic approximate solutions. Therefore, a nonlinear frequency, for each differential equation, is achieved. Furthermore, for more convenience, these solutions are pictured to indicate their behavior. The multiple time-scales with the aid of the Homotopy concept are utilized to judge the stability criteria. The analyses reveal the resonance as well as the non-resonant cases. Additionally, numerical calculations are carried out, graphically, to address the regions that guaranteed the bounded solutions. It is found that the latter method, is the most powerful mathematical tool in extracting the stability analysis of the considered system.

Yuanran Zhu

We propose a unified framework to study the turbulent transport problem from the perspective of nonequilibrium statistical mechanics. By combining Krarichnan's turbulence thermalization assumption and Ruelle's recent work on nonequilibrium statistical mechanics settings for fluids, we show that the equation for viscous fluid can be viewed as the non-canonical Hamiltonian system perturbed by different thermostats. This allows an analogy between the viscous fluid and the nonequilibrium heat conduction model where the Fourier modes can be regarded as the ''particles''. With this framework, we reformulate the dispersion of Lagrangian particles in turbulence as a nonequilibrium transport problem. We also derive the first and the second generalized fluctuation-dissipation relations for the Lagrangian particle using respectively the path-integral technique and the Mori-Zwanzig equation. The obtained theoretical results can be used predict the dispersion of the Lagrangian particle in a general nonequilibrium.

Dulaji Hidellaarachchi, John Grundy, Rashina Hoda et al.

Requirements Engineering (RE)-related activities require high collaboration between various roles in software engineering (SE), such as requirements engineers, stakeholders, developers, etc. Their demographics, views, understanding of technologies, working styles, communication and collaboration capabilities make RE highly human dependent. Identifying how "human aspects" such as motivation, domain knowledge, communication skills, personality, emotions, culture, etc. might impact RE-related activities would help us improve the RE and SE in general. This study aims to better understand current industry perspectives on the influence of human aspects on RE-related activities, specifically focusing on motivation and personality by targeting software practitioners involved in RE-related activities. Our findings indicate that software practitioners consider motivation, domain knowledge, attitude, communication skills and personality as highly important human aspects when involved in RE-related activities. A set of factors were identified as software practitioners motivational factors when involved in RE-related activities and identified important personality characteristics to have when involved in RE. We also identified factors that made individuals less effective when involved in RE-related activities and obtained an initial idea on measuring individuals performance when involved in RE. The findings from our study suggest various areas needing more investigation, and we summarise a set of key recommendations for further research.

Matthew Grasinger, Kaushik Dayal, Gal deBotton et al.

Constitutive modeling of dielectric elastomers has been of long standing interest in mechanics. Over the last two decades rigorous constitutive models have been developed that couple the electrical response of these polymers with large deformations characteristic of soft solids. A drawback of these models is that unlike classic models of rubber elasticity they do not consider the coupled electromechanical response of single polymer chains which must be treated using statistical mechanics. The objective of this paper is to compute the stretch and polarization of single polymer chains subject to a fixed force and fixed electric field using statistical mechanics. We assume that the dipoles induced by the applied electric field at each link do not interact with each other and compute the partition function using standard techniques. We then calculate the stretch and polarization by taking appropriate derivatives of the partition function and obtain analytical results in various limits. We also perform Markov chain Monte Carlo simulations using the Metropolis and umbrella sampling methods, as well as develop a new sampling method which improves convergence by exploiting a symmetry inherent in dielectric polymer chains. The analytical expressions are shown to agree with the Monte Carlo results over a range of forces and electric fields. Our results complement recent work on the statistical mechanics of electro-responsive chains which obtains analytical expressions in a different ensemble.

Isaque Alves, Carla Rocha

The constant changes in the software industry, practices, and methodologies impose challenges to teaching and learning current software engineering concepts and skills. DevOps is particularly challenging because it covers technical concepts, such as pipeline automation, and non-technical ones, such as team roles and project management. The present study investigates a course setup to introduce these concepts to software engineering undergraduates. We designed the course by employing coding to associate DevOps concepts to Agile, Lean, and Open source practices and tools. We present the main aspects of this project-oriented DevOps course, with 240 students enrolled in it since its first offering in 2016. We conducted an empirical study, with both a quantitative and qualitative analysis, to evaluate this project-oriented course setup. We collected the data from the projects repository and students perceptions from a questionnaire. We mined 148 repositories (corresponding to 72 projects) and obtained 86 valid responses to the questionnaire. We also mapped the concepts which are more challenging to students learn from experience. The results evidence that first-hand experience facilitates the comprehension of DevOps concepts and enriches classes discussions. We present a set of lessons learned, which may help professors better design and conduct project-oriented courses to cover DevOps concepts.