Landlord and Tenant—Eviction—Presence of Vermin as Contructive Eviction

xv, 242 hlm.;14 x 21 c

Adsorption of Group-IV Elements on Graphene, Silicene, Germanene, Stanene: Dumbbell Formation

Silicene and germanene derivatives constructed from periodic dumbbell units play a crucial role in multilayers of these honeycomb structures. Using first-principles calculations based on density functional theory, here we investigate the dumbbell formation mechanisms and energetics of Group IV atoms adsorbed on graphene, silicene, germanene and stanene monolayer honeycomb structures. The stabilities of the binding structures are further confirmed by performing ab-initio molecular dynamics calculations at elevated temperatures, except for stanene which is subject to structural instability upon the adsorption of adatoms. Depending on the row number of the adatoms and substrates we find three types of binding structures, which lead to significant changes in the electronic, magnetic, and optical properties of substrates. In particular, Si, Ge and Sn adatoms adsorbed on silicene and germanene form dumbbell structures. Furthermore, dumbbell structures occur not only on single layer, monatomic honeycomb structures, but also on their compounds like SiC and SiGe. We show that the energy barrier to the migration of a dumbbell structure is low due to the concerted action of atoms. This renders dumbbells rather mobile on substrates to construct new single and multilayer Si and Ge phases.Comment: Accepted for publication in J. Phys. Chem.

Achieving the Impossible? Teaching Practice component of a Pre-service Distance English Language Teacher Training Program in Turkey

The aim of this article is to describe the model developed for the teaching practice component of the pre-service Distance English Language Teacher Training Program (DELTT) at Anadolu University, Eskişehir, Turkey. The steps taken to improve the model over a six-year period will be explained and the recent developments in the teaching practice area of the current program will be discussed in the light of recent research on learning and personal development. Lessons learned and the steps taken during this developmental process will be explored and recommendations for other programs concerned with the teaching practice component will be made

Discourses and Practices of Campus Food Sustainability at Concordia University

Discourses and Practices of Campus Food Sustainability at Concordia University Nil Alt Kecik Most North American universities employ transnational food service corporations to cater to predominantly residence populations. Known as the Big Three within the industrial food system, these corporations— Chartwells, Sodexho and Aramark—are the largest global food retailers. After Chartwell’s 13-year contract term at Concordia University ended, the university administration granted an exclusivity contract to Aramark in 2015. The university’s choice of food service provider, and its food procurement practices are in tension with Concordia’s discursive commitment to a ‘sustainable’ campus food system. Building on the epistemological tension between profit and sustainability, this study reviews the global commodity chain (GCC) framework, and its relevance for studying food system transformation through institutional consumption. The need to conceptualize GCCs as interlinked and complex flows of not only materials, but also of power, knowledge and discourse is the central theme. Grounded in this theme, the study looks at how the transition into food sustainability is governed and operationalized at Concordia. It is concluded that building direct producer-consumer relationships is more complicated than reflected with a linear supply chain imagery. At Concordia, subscription to this imagery muddles accountability and curtails the possibilities for alternatives

The bandstructure of gold from many-body perturbation theory

The bandstructure of gold is calculated using many-body perturbation theory (MBPT). Different approximations within the GW approach are considered. Standard single shot G0W0 corrections shift the unoccupied bands up by ~0.2 eV and the first sp-like occupied band down by ~0.4 eV, while leaving unchanged the 5d occupied bands. Beyond G0W0, quasiparticle self-consistency on the wavefunctions lowers the occupied 5d bands by 0.35 eV. Globally, many-body effects achieve an opening of the interband gap (5d-6sp gap) of 0.35 to 0.75 eV approaching the experimental results. Finally, the quasiparticle bandstructure is compared to the one obtained by the widely used HSE (Heyd, Scuseria, and Ernzerhof) hybrid functional

Density functional and dynamics study of the dissociative adsorption of hydrogen on

a b s t r a c t A first principles study is performed to investigate the adsorption characteristics of hydrogen on magnesium surface. Substitutional and on-surface adsorption energies are calculated for Mg (0 0 0 1) surface alloyed with the selected elements. To further analyze the hydrogen-magnesium interaction, first principles molecular dynamics method is used which simulates the behavior of H 2 at the surface. Also, charge density differences of substitutionally doped surface configurations were illustrated. Accordingly, Mo and Ni are among the elements yielding lower adsorption energies, which are found to be À9.2626 and À5.2995 eV for substitutionally alloyed surfaces, respectively. In light of the dynamic calculations, Co as an alloying element is found to have a splitting effect on H 2 in 50 fs, where the first hydrogen atom is taken inside the Mg substrate right after the decomposition and the other after 1300 fs. An interesting remark is that, elements which acquire higher chances of adsorption are also seen to be competent at dissociating the hydrogen molecule. Furthermore, charge density distributions support the results of molecular dynamics simulations, by verifying the distinguished effects of most of the 3d and 4d transition metals

Optical properties of single-layer and bilayer arsenene phases

An extensive investigation of the optical properties of single-layer buckled and washboard arsenene and their bilayers was performed, starting from layered three-dimensional crystalline phase of arsenic using density functional and many-body perturbation theories combined with random phase approximation. Electron-hole interactions were taken into account by solving the Bethe-Salpeter equation, suggesting first bound exciton energies on the order of 0.7 eV. Thus, many-body effects were found to be crucial for altering the optical properties of arsenene. The light absorption of single-layer and bilayer arsenene structures in general falls within the visible-ultraviolet spectral regime. Moreover, directional anisotropy, varying the number of layers, and applying homogeneous or uniaxial in-plane tensile strain were found to modify the optical properties of two-dimensional arsenene phases, which could be useful for diverse photovoltaic and optoelectronic applications. ©2016 American Physical Society

Stability of single-layer and multilayer arsenene and their mechanical and electronic properties

Using first-principles spin-polarized density functional theory, we carried out an analysis on the atomic structure, stability, energetics, and mechanical and electronic properties of single-layer structures of arsenene. These are buckled honeycomb, symmetric, and asymmetric washboard arsenene structures. Our analysis is extended to include layered three-dimensional crystalline phase of arsenic, as well as bilayer and trilayer structures to reveal dimensionality effects. The buckled honeycomb and symmetric washboard structures are shown to maintain their stability at high temperatures even when they are freestanding. As a manifestation of the confinement effect, the large fundamental band gap of single-layer phases decreases with increasing number of layers and eventually is closed. Concomitantly, lattice constants partially increase, while interlayer distances decrease. The effects of hybrid functional or self-energy corrections together with the spin-orbit coupling on the electronic structure of arsenene are crucial. The responses of direct and indirect band gaps to biaxial or uniaxial strain are rather complex and directional; while the fundamental band gap decreases and changes from indirect to direct with the biaxial strain applied to buckled arsenene, these effects are strongly directional for washboard arsenene. The width and the indirect/direct character of the band gap can be tuned by the number of layers, as well as by applied uniaxial/biaxial strain. ©2016 American Physical Society

DYNAMICS OF COMPOSITE MATERIALS CUTTING

S u m m a r y The paper presents stability analysis of milling process of epoxide polymer composite material with carbon fibres. In order to determine zones of stable milling , times series of cutting forces are applied. Next, recurrence quantification analysis is conducted which can define three stability indexes: recurrence rate, ratio of recurrence rate to determinism, and recurrence time. Finally, stability lobs diagram for the composite material is proposed. Keywords: milling stability, recurrence quantification analysis Dynamika skrawania materiałów kompozytowych S t r e s z c z e n i e W pracy zaprezentowano wyniki badania stabilności procesu frezowania kompozytu epoksydowo--polimerowego wzmacnianego włóknem węglowym. Określono obszary skrawania stabilnego. Prowadzono analizę przebiegów czasowych sił skrawania opartą na kwantyfikatorach wykresów rekurencyjnych. Stosowano trzy z nich: recurrence rate, proporcję recurrence rate i determinizmu oraz czas rekurencji. Opracowano wykres stabilności frezowania materiału kompozytowego. Słowa kluczowe: stabilność frezowania, wykresy rekurencyjn

GaN: From three- to two-dimensional single-layer crystal and its multilayer van der Waals solids

Three-dimensional (3D) GaN is a III-V compound semiconductor with potential optoelectronic applications. In this paper, starting from 3D GaN in wurtzite and zinc-blende structures, we investigated the mechanical, electronic, and optical properties of the 2D single-layer honeycomb structure of GaN (g-GaN) and its bilayer, trilayer, and multilayer van der Waals solids using density-functional theory. Based on high-temperature ab initio molecular-dynamics calculations, we first showed that g-GaN can remain stable at high temperature. Then we performed a comparative study to reveal how the physical properties vary with dimensionality. While 3D GaN is a direct-band-gap semiconductor, g-GaN in two dimensions has a relatively wider indirect band gap. Moreover, 2D g-GaN displays a higher Poisson ratio and slightly less charge transfer from cation to anion. In two dimensions, the optical-absorption spectra of 3D crystalline phases are modified dramatically, and their absorption onset energy is blueshifted. We also showed that the physical properties predicted for freestanding g-GaN are preserved when g-GaN is grown on metallic as well as semiconducting substrates. In particular, 3D layered blue phosphorus, being nearly lattice-matched to g-GaN, is found to be an excellent substrate for growing g-GaN. Bilayer, trilayer, and van der Waals crystals can be constructed by a special stacking sequence of g-GaN, and they can display electronic and optical properties that can be controlled by the number of g-GaN layers. In particular, their fundamental band gap decreases and changes from indirect to direct with an increasing number of g-GaN layers. © 2016 American Physical Society