Tachyonic Teleparallel Dark Energy

Teleparallel gravity is an equivalent formulation of general relativity in which instead of the Ricci scalar $R$, one uses the torsion scalar $T$ for the Lagrangian density. Recently teleparallel dark energy has been proposed by Geng et al. in (Geng et al., 2011). They have added quintessence scalar field, allowing also a non-minimal coupling with gravity in the Lagrangian of teleparallel gravity and found that such a non-minimally coupled quintessence theory has a richer structure than the same one in the frame work of general relativity. In the present work we are interested in tachyonic teleparallel dark energy in which scalar field is responsible for dark energy in the frame work of torsion gravity. We find that such a non-minimally coupled tachyon gravity can realize the crossing of the phantom divide line for the effective equation of state. Using the numerical calculations we display such a behavior of the model explicitly.Comment: 12 pages, 4 figures, accepted for publication in Astrophysics and Space Scienc

Non-minimally Coupled Quintom Model Inspired by String Theory

In this paper we consider a quintom model of dark energy with a single scalar field $T$ given by a Lagrangian which inspired by tachyonic Lagrangian in string theory. We consider non-minimal coupling of tachyon field to the scalar curvature, then we obtain the equation of state (EoS), and the condition required for the model parameters when $\omega$ crosses over -1.Comment: 8 pages, 2 figure

Reheating in nonminimal derivative coupling model

We consider a model with nonminimal derivative coupling of inflaton to gravity. The reheating process during rapid oscillation of the inflaton is studied and the reheating temperature is obtained. Behaviors of the inflaton and produced radiation in this era are discussed.Comment: 16 pages, 5 figures; discussions added; accepted by JCA

The relationship between motivating tasks and academic resiliency: The mediating role of mastery goals and perceived competence

Background and Objectives:In academic situations, having the opportunity to succeed and rebuild learning increases students' self-confidence in achieving success. Teaching such learners the path to progress and showing the results of hard work makes them strive to master the learning situation. The result is a sense of control and autonomy along with a sense of value. Such instance causes the learner to insist, commit, and work harder without fear of failure to achieve success. Therefore, the importance of the present study is to theoretically determine and discover the model or how to place individual and environmental factors affecting academic resilience. From a practical point of view, this study aims to clarify the importance of individual and environmental factors affecting resilience in education. The aim of this study was to explore the relationship between motivating tasks and academic resiliency and Also determination mediating role of mastery goals and perceived competence. Methods: The present study utilizes a correlational research method using causal relationship modeling methods. The research method applied to this study was structural equation modeling. The target population of the study comprised Tehran universities students who were studying at education and psychology faculties in the academic year of 2014-2015. The sample consisted of 414 students who were selected by random cluster sampling method. In other words, the sampling unit was the classes rather than the individuals. The instruments used in this study were: Classroom Goals Structures, Achievement Goal Orientation, Perceived Competence Scale and Academic Resiliency Questionnaire.   Findings: The results revealed that motivating tasks has direct effect to predict academic resiliency. Furthermore, mastery goals and perceived competence mediated the relationship of motivating tasks with academic resiliency. Discussion and implications of the results are presented in the study. Conclusion: Based on this, it can be concluded that the setting of attractive and motivating tasks leads to the adoption of goals of mastery, self -esteem and control over the learning position of learners. Based on research results, the assignment variable as an extrinsic variable directly affects the resilience variable (dependent variable) and also through intermediate variables (proficiency goals and competency perception). In addition, the significance of the error estimation of each of the constructs shows that other external factors can also affect the relationship of the variables of this study with academic resilience. Based on this, it is suggested that other factors such as internal or external motivation and functional goals by learners be investigated as variables affecting the structural model. In order to apply the results of this research, it is recommended that academic centers be designed in such a way that learners face attractive and challenging tasks and provide them with the opportunity to succeed and experience a sense of competence.   ===================================================================================== COPYRIGHTS  ©2020 The author(s). This is an open access article distributed under the terms of the Creative Commons Attribution (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, as long as the original authors and source are cited. No permission is required from the authors or the publishers.  ====================================================================================

Kuksa*: Self-Adaptive Microservices in Automotive Systems

In pervasive dynamic environments, vehicles connect to other objects to send operational data and receive updates so that vehicular applications can provide services to users on demand. Automotive systems should be self-adaptive, thereby they can make real-time decisions based on changing operating conditions. Emerging modern solutions, such as microservices could improve self-adaptation capabilities and ensure higher levels of quality performance in many domains. We employed a real-world automotive platform called Eclipse Kuksa to propose a framework based on microservices architecture to enhance the self-adaptation capabilities of automotive systems for runtime data analysis. To evaluate the designed solution, we conducted an experiment in an automotive laboratory setting where our solution was implemented as a microservice-based adaptation engine and integrated with other Eclipse Kuksa components. The results of our study indicate the importance of design trade-offs for quality requirements' satisfaction levels of each microservices and the whole system for the optimal performance of an adaptive system at runtime

Three-dimensionally printed polycaprolactone/multicomponent bioactive glass scaffolds for potential application in bone tissue engineering

Over the last years, three-dimensional (3D) printing has been successfully applied to produce suitable substitutes for treating bone defects. In this work, 3D printed composite scaffolds of polycaprolactone (PCL) and strontium (Sr)- and cobalt (Co)-doped multi-component melt-derived bioactive glasses (BGs) were prepared for bone tissue engineering strategies. For this purpose, 30 of as-prepared BG particles (size <38 μm) were incorporated into PCL, and then the obtained composite mix was introduced into a 3D printing machine to fabricate layer-by-layer porous structures with the size of 12 � 12 � 2 mm3. The scaffolds were fully characterized through a series of physico-chemical and biological assays. Adding the BGs to PCL led to an improvement in the compressive strength of the fabricated scaffolds and increased their hydrophilicity. Furthermore, the PCL/BG scaffolds showed apatite-forming ability (i.e., bioactivity behavior) after being immersed in simulated body fluid (SBF). The in vitro cellular examinations revealed the cytocompatibility of the scaffolds and confirmed them as suitable substrates for the adhesion and proliferation of MG-63 osteosarcoma cells. In conclusion, 3D printed composite scaffolds made of PCL and Sr- and Co-doped BGs might be potentially-beneficial bone replacements, and the achieved results motivate further research on these materials. © 2020 Amirhosein Fathi et al., published by De Gruyter 2020

Phantom Divide Crossing with General Non-minimal Kinetic Coupling

We propose a model of dark energy consists of a single scalar field with a general non-minimal kinetic couplings to itself and to the curvature. We study the cosmological dynamics of the equation of state in this setup. The coupling terms have the form $\xi_{1} R f(\phi)\partial_{\mu}\phi\partial^{\mu}\phi$ and $\xi_{2} R_{\mu\nu}f(\phi)\partial^{\mu}\phi\partial^{\nu}\phi$ where $\xi_{1}$ and $\xi_{2}$ are coupling parameters and their dimensions depend on the type of function $f(\phi)$. We obtain the conditions required for phantom divide crossing and show numerically that a cosmological model with general non-minimal derivative coupling to the scalar and Ricci curvatures can realize such a crossing.Comment: 12 pages, 4 figures. Accepted for publication in Gen. Rel. Grav. arXiv admin note: substantial text overlap with arXiv:1105.4967, arXiv:1201.1627, and with arXiv:astro-ph/0610092 by other author