Search results for " Mechanical engineering"
showing 10 items of 623 documents
Estimates for Divergence Velocities of Axially Moving Orthotropic Thin Plates
2014
Some models for axially moving orthotropic thin plates are investigated analytically via methods of complex analysis to derive estimates for critical plate velocities. Linearised Kirchhoff plate theory is used, and the energy forms of steady-state models are considered with homogeneous and inhomogeneous tension profiles in the cross direction of the plate. With the help of the energy forms, some limits for the divergence velocity of the plate are found analytically. In numerical examples, the derived lower limits for the divergence velocity are analysed for plates with small flexural rigidity. peerReviewed
Fast 3D Ray Tracing for Indoor Coverage Solutions
2016
Optimal wireless indoor network planning requires huge number of iterations and evaluations of indoor coverage for each antenna location until an optimal solution is reached. Consequently, accurate and scalable calculation of power strength for indoor scenarios becomes necessary. The contribution in this paper is to reduce the complexity of 3D ray tracing for deterministic indoor power prediction. In order to achieve that while preserving the accuracy, image theory with feasible reflection volume as preprocessing approach is introduced. This proposed algorithm stores the image, its feasible reflection volume and valid area of receiving points. Significant complexity reduction is achieved by…
The importance of OER in engineering education
2017
The problem of education is a very important one and occupies an increasingly wider register among educational specialists, who see these changes directly related to current generations of students. It speaks increasingly more and more about the desire of young people to learn when they want, how they want and how much they want, in their own way, without any constraints imposed by fixed educational program, established by teachers, according to their idea how to go on an educational route. In this context, open education provides crucial support of any person who is interested, and covered a complete and appropriate educational needs, in connection with time and availability of the person.…
Study regarding the physical-mechanical properties of knits for garments – pilling performance
2017
The effect of the pilling degradation results is an important decreasing in garment quality and a negative influence on the user’s comfort to wear. There are a lot factors, such as the yarn spinning system, fabric geometry and finishing operation, which affect the pilling performance. This research paper presents the investigation of fabric surface concerning pilling formation, especially knits, influenced by the fibrous composition. As samples were used knitted fabric panels, obtained from carded yarns, with fibers composition like cotton, wool or mixed one. Regarding fabric geometry 3 types were used – single jersey, 2x2 rib and moss stitch. In order to establish which of the yarns are mo…
A comparative molecular dynamics-phase-field modeling approach to brittle fracture
2016
Abstract In this work, a novel comparative method for highly brittle materials such as aragonite crystals is proposed, which provides an efficient and accurate in-sight understanding for multi-scale fracture modeling. In particular, physically-motivated molecular dynamics (MD) simulations are performed to model quasi-static brittle crack propagation on the nano-scale and followingly compared to macroscopic modeling of fracture using the phase-field modeling (PFM) technique. A link between the two modeling schemes is later proposed by deriving PFM parameters from the MD atomistic simulations. Thus, in this combined approach, MD simulations provide a more realistic meaning and physical estima…
Channel Occupancy-Based Dynamic Spectrum Leasing in Multichannel CRNs: Strategies and Performance Evaluation
2016
Spectrum leasing has been proposed as an effective approach for enabling more flexible spectrum utilization in CRNs. In CRNs, a primary network (PN) which consists of multiple primary users (PUs) can lease part of the licensed spectrum to secondary users (SUs) in exchange for operational benefits. The focus of this study is to investigate how and to what extent the PN allows spectrum leasing in CRNs, considering the QoS requirements of the PN and the secondary network (SN). Correspondingly, we propose two dynamic spectrum leasing strategies, which can improve the QoS performance of SUs while ensuring sufficient remuneration for PUs. In order to dynamically adjust the portion of leased bandw…
Dynamic Shakedown Sensitivity Analysis by Means of a Probabilistic Approach
2017
The shakedown limit load multiplier problem for elastic plastic structures subjected to a combination of fixed and seismic loads is treated. In particular, reference is firstly made to the unrestricted dynamic shakedown theory. The relevant seismic load history is modeled as a repeated one and, with reference to classically damped structures, appropriate modal analyses are utilized. With the aim of evaluating the reliability of the results arising from the application of the cited theory, a recent probabilistic approach is also utilized. This approach adopts the Monte Carlo method in order to define the necessary seismic acceleration histories and finally compute the related shakedown limit…
Investigation of buckling characteristics of cracked variable stiffness composite plates by an eXtended Ritz approach
2021
Abstract Variable Angle Tow (VAT) composite plates are characterized by in-plane variable stiffness properties, which opens to new concepts of stiffness tailoring and optimization to achieve higher structural performance for advanced lightweight structures where damage tolerance consideration are often mandatory. In this paper, a single-domain eXtended Ritz formulation is proposed to study the buckling behaviour of variable stiffness laminated cracked plates. The plate behaviour is described by the first order shear deformation theory whose generalized displacements, namely reference plane translations and rotations, are expressed via suitable admissible trial functions. These consist of a …
The benefits of inclusive education: new challenges for university teachers
2017
Inclusive education is a child’s right, not a privilege. The amount of current attention given to children and to childhood is unprecedented. In a world affected by financial crises, attitudes about children’s needs are very important. Recent years have seen innovations in the focus of research, as political moves that challenge the ways different children have been excluded and silenced. Inclusive education is a real and urgent need for all educational systems around the world. Inside our university, the Teachers Training Department needs to take serious measures to create a professional environment for all the students involved in the initial training for becoming teachers at all levels. …
Solid State Joining of Thin Hybrid Sandwiches Made of Steel and Polymer: a Feasibility Study
2020
Abstract The growing demand for more environmentally friendly vehicles has led to an increased use of light materials in the transportation industry with the aim to reduce structural weight, fuel consumption, and gas emissions, thereby boosting cost-effectiveness and recyclable properties. Complex multi-material steel-based components would allow to improve mechanical properties and minimize weight even further. In particular, new sandwich materials made by steel outer skins and a polymeric internal layer seems very promising for obtaining mechanical performance and lightness at the same time. Unfortunately, traditional welding techniques, like arc welding, laser welding, and resistance spo…