Singularly Perturbed Control Systems with Noncompact Fast Variable

We deal with a singularly perturbed optimal control problem with slow and fast variable depending on a parameter {\epsilon}. We study the asymptotic, as {\epsilon} goes to 0, of the corresponding value functions, and show convergence, in the sense of weak semilimits, to sub and supersolution of a suitable limit equation containing the effective Hamiltonian. The novelty of our contribution is that no compactness condition are assumed on the fast variable. This generalization requires, in order to perform the asymptotic proce- dure, an accurate qualitative analysis of some auxiliary equations posed on the space of fast variable. The task is accomplished using some tools of Weak KAM theory, and in particular the notion of Aubry set

Euler reflexion formulas for motivic multiple zeta functions

We introduce a new notion of \boxast-product of two integrable series with coefficients in distinct Grothendieck rings of algebraic varieties, preserving the integrability and commuting with the limit of rational series. In the same context, we define a motivic multiple zeta function with respect to an ordered family of regular functions, which is integrable and connects closely to Denef-Loeser's motivic zeta functions. We also show that the \boxast-product is associative in the class of motivic multiple zeta functions. Furthermore, a version of the Euler reflexion formula for motivic zeta functions is nicely formulated to deal with the \boxast-product and motivic multiple zeta functions, and it is proved using the theory of arc spaces. As an application, taking the limit for the motivic Euler reflexion formula we recover the well known motivic Thom-Sebastiani theorem.Comment: To appear in Journal of Algebraic Geometr

Characterization And Flammability Of Ethylene Vinyl Acetate (Eva)/Zeolite Composites

This thesis describes the fabrication, characterization and properties of natural zeolite as filler in ethylene vinyl acetate (EVA) composites. One of the main objectives of this research is to determine the effect of zeolite loading on properties of EVA matrix composites. EVA composites at different loading of zeolite (5-25 vol. %) were prepared using Thermo Haake Polydrive internal mixer and were then compression molded according to standard test specimen. Tensile test and dynamic mechanical analysis (DMA) were performed to characterize the mechanical properties of EVA/zeolite composites. The tensile test can also be explained from the analysis of Scanning Electron Microscopy (SEM) micrograph of the tensile fractured surfaces. Besides, the influences of surface modifications on the properties of EVA/zeolite composites were also investigated. The interfacial interactions between EVA and zeolite were modified by crosslinking of EVA with dicumyl peroxide (DCP); cation exchange method using organic surfactant (octadecylamine) and also silane treatment using 3-aminopropyltriethoxysilane (AMPTES). In addition, Fourier Transform Infra red (FTIR) spectra analyses were performed in order to study the interaction between the composites and functional group of the surface modifiers. The application of surface modifications was proved to enhance the mechanical and morphological properties of EVA/zeolite composites. Thermal properties of the composites were also characterized by means of thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Intumescent flame retardant system consisting of ammonium polyphosphate (APP)/ pentaerythritol (PER) was used to enhance the thermal properties and fire retardancy of EVA/zeolite composites. The mechanical properties examined by tensile test indicated that the introduction of both flame retardants lead to deterioration of tensile strength and elongation at break of EVA/zeolite composites. However, the tensile modulus of the composites was significantly enhanced attributed to the rigidity of APP particles. The results of DSC and TGA showed that both types of flame retardants have the ability to enhance the thermal stability of EVA/zeolite composites. Meanwhile the results of vertical burning testing (UL-94-V) and limiting oxygen index (LOI) measurement revealed that the flame retardants could also reduce the flammability of the composites by achieving V-0 UL94-v rating and increased LOI value, respectively

VIRTUAL TEAMS IN THE DIGITAL AGE

Abstract: The world, nowadays, is closer and closer thanks to information communication technology (ICT). Actually, virtual teams are considered as a great way to connect people and bring advantages to organizations. From the existing literature, it is expected to extend knowledge about two big issues: the global virtual teams and ICT, as well as their benefits and drawbacks. For doing so, many academic and scientific journals are used for the purposes of summarizing and synthesizing. This study is secondary research combining some practices to explore the issue. On the one hand, virtual teams enable to cooperate with members from different geography and time zones. On the other hand, organizations have to deal with many challenges when applying them. Two typical examples of a reputable global brand and the success of a national company are presented to explain this issue, including IBM Company in the USA and FPT Group in Vietnam. By identifying the pros and cons, organizations can suggest suitable solutions to manage and establish their teams in a better way.Keywords: information communication technology, virtual teams, virtual working, team management, multinational team

The Latent Absolute Advantage Of The Comparative Advantage In Theories Of International Trade

The absolute advantage and comparative advantage are the basic concepts of the international economics. Up till now, the popular understanding about them is that absolute advantage is the special case of the comparative advantage. This view has been dominant in all books related to the field of international economics. However, the comparative advantage by nature is the absolute advantage. Generally, comparative advantage is only particular case of absolute advantage. In other words, comparative advantage has the latent absolute advantage. It is the opposite view of the traditional one on absolute and comparative advantage in the field of international trade theories and it constructs the content of this paper

Magneto-transport and localization in disordered systems with local superconductive attraction

Motivated by the intriguing features of the insulating regime close to an SIT, I carry out a systematic study of magnetoresistance, elucidating a variety of approach that influence it. In Chapter 2 I introduce a model of hard-core bosons on a two dimensional honeycomb lattice in a magnetic field, as motivated by recent experiments on structured films [38, 39]. This aims at explaining several key features observed in the activated magneto-transport in those experiments. Taking into account long range Coulomb interactions among the bosons, I study the crossover from strong to weak localization of those excitations and how it is affected by a magnetic field. An effective mobility edge in the excitation spectrum of the insulating Bose glass is identified as the (intensive) energy scale at which excitations become nearly delocalized. Within the forward scattering approximation in the bosonic hopping I find the effective mobility edge to oscillate periodically with the magnetic flux per plaquette [51]. Furthermore, I contrast the magnetoresistance in bosonic and fermionic systems, and thus show convincingly that the magneto-oscillations seen in experiments of SIT systems reflect the physics of localized electron pairs, i.e a Bose glass rather than a Fermi insulator. The bosonic magneto-oscillations start with an increase of the mobility edge (and thus of resistance) with applied flux, as opposed to the equivalent fermionic problem. The amplitude of the oscillations is much more substantial in bosons than in fermions. Bosons exhibit a single hump per flux period, while fermion characteristics undergo two humps. Those are identical for non-interacting fermions, but Coulomb correlations are shown to lead to systematic deviations from this statistical period doubling. In this approach, only bosonic degrees of freedom are considered. It thus cannot cover the wide range of fields often explored in experiments, where field-induced pair breaking processes certainly take place and are relevant. Therefore, in Chapter 3 I introduce a microscopic model taking both bosonic and fermionic degrees of freedom into account. This model is then used to study the magnetic field driven crossover from pair to single electron regimes and the corresponding resistive transport. This study is motivated by the above mentioned experiments observing a strong magnetoresistance peak on the insulating side of the SIT which reflects that crossover. Assuming Mott variable range hopping transport, the pair-to-single crossover in transport is driven by the crossover in the characteristic temperature scale TM governing the stretched exponential growth of the resistance R(T) for pairs and single electrons. Within this work, I consider a system of electrons on a square lattice, subject to strong onsite disorder, a local pairing attraction, a magnetic field, and nearest neighbor hopping. The tuning parameter, the magnetic field, enters both by a (spatially) isotropic Zeeman depairing term and an anisotropic orbital effect proportional to the perpendicular component of the field incorporated via the complex phase of the hoppings. I found that the former leads to a strong effect on the density of state which causes and dominates the crossover, and thus the magnetoresistance peak. The orbital effect captures the effect of the quantum interference of different types of carriers. It further enhances the peak as the field orientation changes. I also discuss the effect of including Coulomb interactions into this theory. Having pointed out the peculiarity of two dimensional disordered systems which are marginal in terms of single-particle localization, and in view of our finding of the effective mobility edge above, I address the question of whether Coulomb interactions can give rise to a genuine mobility edge in electronic systems in two dimensions. In Chapter 4 with Coulomb interactions being treated at a more quantum level (but still approximately) within a Hartree-Fock treatment, I carry out a numerical study aiming at addressing the possibility of an interaction-induced delocalization effect. This setting focuses on the multiplicity of electron species, or valley degeneracy, that Punnoose and Finkel'stein [11, 52] predicted to cause delocalization in two dimensional interacting electron system. As I will discuss, by looking at the density-density correlation function, the system with multiple species behaves differently from the system with single species. In the former, the two-stage scale-dependent behavior of the correlation function reflects the scale-dependent resistance predicted in Punnoose and Finkel'stein's renormalization group equations