POROVISCOELASTICITY AND ANALYTICAL SOLUTIONS OF SELECTED PROBLEMS IN ENGINEERING

This study provides newly-derived analytical poroviscoelastic solutions for a number of practical and important engineering problems with various levels of material anisotropy: laboratory and field testing of cylinders (isotropy, transverse isotropy, and weak orthotropy), laboratory testing of rectangular strips (isotropy, transverse isotropy, and orthotropy), and wellbore drilling and tunnel excavation (isotropy and transverse isotropy). The solutions for these problems are crucial in many disciplines such as civil engineering, petroleum engineering, and biomechanics. The newly-derived solutions can be considered extensions of some existing analytical solutions to a higher degree of anisotropy. However, the importance of material anisotropy is self-evident in engineering applications since many bio- and geo-materials are intrinsically anisotropic and their mechanical anisotropy can significantly influence the material behavior as illustrated throughout this dissertation. The frequently-used assumption of material isotropy in poroviscoelasticity to simplify modeling and analysis is therefore no longer justified without thorough calibration and validation.More important, this study finally establishes the correspondence principle between poroviscoelasticity and poroelasticity with general anisotropy based on rigorous mathematical and physical considerations. The correspondence principle has been established not only in time domain but also in Laplace transform domain, for the general phenomenological formulation as well as for the micromechanical relations between material coefficients, and will be of fundamental importance in the study of poroviscoelasticity. In particular, using the correspondence principle, analytical poroelastic solutions in the Laplace transform domain with any degree of anisotropy can now be readily transferred to poroviscoelasticity and vice versa

Linear Approximation and Asymptotic Expansion of Solutions for a Nonlinear Carrier Wave Equation in an Annular Membrane with Robin-Dirichlet Conditions

This paper is devoted to the study of a nonlinear Carrier wave equation in an annular membrane associated with Robin-Dirichlet conditions. Existence and uniqueness of a weak solution are proved by using the linearization method for nonlinear terms combined with the Faedo-Galerkin method and the weak compact method. Furthermore, an asymptotic expansion of a weak solution of high order in a small parameter is established

Factors affecting learner’s satisfaction towards online learning during COVID-19 pandemic: A case study of Vietnam

Online learning is being considered a new model of knowledge exchange in modern education. In parallel with the incredible impacts of the global pandemic, this is considered an opportunity to promote the development of online learning globally. Therefore, this study proposed a research framework including four factors affecting learner satisfaction towards online learning during the COVID-19 pandemic at a university, which are system quality, service quality, transformational leadership, and self-efficacy. A questionnaire was conducted online to assess which 131 respondents were representative students from two large private universities in Da Nang: FPT University and Duy Tan University. The results from the regression analysis show that three factors have a positive impact on learner satisfaction during COVID-19. This study concludes that students at private universities in Da Nang prioritize system quality as the most significant factor in their satisfaction with the online learning system, followed by transformational leadership and the last one is self-efficacy. Therefore, it can be more strategic for private organizations, developers, software designers, or even transformation-trained trainers to be emphasized to build a system of processes for implementing online learning for students effectively

Application of value chain analysis in understanding the losses and wastes of cassava in Vietnam

To reduce post-harvest losses and foster development of cassava, it is necessary to evaluate the full range of activities required to bring fresh cassava root through different stages of production, processing, and marketing until it reaches the end-user. A Value Chain Analysis (VCA) provides the approach for such an understanding in that it is a process of tracing a product’s flow from the point of production to the point of consumption along with tracing the roles and relationships of different actors and stakeholder at different points in the value chain. This paper provides an overview of the main cassava value chains in Vietnam, and the extent and nature of losses and wastes in those value chains

Experimental observation of topological Fermi arcs in type-II Weyl semimetal MoTe2

Weyl semimetal is a new quantum state of matter [1-12] hosting the condensed matter physics counterpart of relativisticWeyl fermion [13] originally introduced in high energy physics. The Weyl semimetal realized in the TaAs class features multiple Fermi arcs arising from topological surface states [10, 11, 14-16] and exhibits novel quantum phenomena, e.g., chiral anomaly induced negative mag-netoresistance [17-19] and possibly emergent supersymmetry [20]. Recently it was proposed theoretically that a new type (type-II) of Weyl fermion [21], which does not have counterpart in high energy physics due to the breaking of Lorentz invariance, can emerge as topologically-protected touching between electron and hole pockets. Here, we report direct spectroscopic evidence of topological Fermi arcs in the predicted type-II Weyl semimetal MoTe2 [22-24]. The topological surface states are confirmed by directly observing the surface states using bulk-and surface-sensitive angle-resolved photoemission spectroscopy (ARPES), and the quasi-particle interference (QPI) pattern between the two putative Fermi arcs in scanning tunneling microscopy (STM). Our work establishes MoTe2 as the first experimental realization of type-II Weyl semimetal, and opens up new opportunities for probing novel phenomena such as exotic magneto-transport [21] in type-II Weyl semimetals.Comment: submitted on 01/29/2016. Nature Physics, in press. Spectroscopic evidence of the Fermi arcs from two complementary surface sensitive probes - ARPES and STS. A comparison of the calculated band structure for T_d and 1T' phase to identify the topological Fermi arcs in the T_d phase is also included in the supplementary informatio