Nonlinear Optical Rectification of Confined Exciton in a ZnO/ZnMgO Strained Quantum Dot

Heavy hole exciton binding energies as functions of dot radius and the Mg alloy content in a ZnO/MgxZn1 – xO quantum dot are investigated. The effects of strain, including the hydrostatic and the biaxial strain, and the internal electric field, due to spontaneous and piezoelectric polarization are taken into account. Numerical calculations are performed using variational procedure within the single band effective mass approximation. The nonlinear optical rectification is investigated for different dot radius and the values of Mg alloy content in a ZnO/MgxZn1 – xO quantum dot taking into account the strain-induced piezoelectric effects. The results show that the resonant peak of the nonlinear optical rectification is blue shifted with the confinement effect and the Mg alloy content. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3026

A note on the index bundle over the moduli space of monopoles

Donaldson has shown that the moduli space of monopoles $M_k$ is diffeomorphic to the space \Rat_k of based rational maps from the two-sphere to itself. We use this diffeomorphism to give an explicit description of the bundle on \Rat_k obtained by pushing out the index bundle from $M_k$. This gives an alternative and more explicit proof of some earlier results of Cohen and Jones.Comment: 9 page

Nonlinear HControl with Delayed Measurements

This paper considers the nonlinear Hcontrol problem for systems subject to delayed measurements. Necessary and sufficient conditions for the solvability of the problem are presented. We employ the concept of an information state to achieve separation between estimation and control. In particular, the information state derived is no longer the ﲷorst case cost to come function. We also briefly discuss certainty equivalence for systems with delayed measurements

Robust Control of Set-Valued Discrete Time Dynamical Systems

This paper presents results obtained for the robust control of discrete time dynamical systems. The problem is formulated and solved using dynamic programming. Both necessary and sufficient conditions in terms of (stationary ) dynamic programming equalities are presented. The output feedback problem is solved using the concept of an information state, where a decoupling between estimation and control is obtained

Reduced Complexity Output Feedback Nonlinear HControllers and Relation to Certainty Equivalence

In this paper, we consider the problem of constructing reduced complexity controllers for output feedback nonlinear Hcontrol. We give sufficient conditions, under which the controllers so obtained, guarantee asymptotic stability of the closed-loop system when there are no exogenous inputs. The controllers obtained are non-optimal in general. However, in case optimality holds, we show that these controllers are in fact the certainty equivalence controllers

Information State for Robust Control of Set-Valued Discrete Time Systems

In this paper, we construct the information state for robust output feedback control of set-valued discrete time dynamical systems. The information state is obtained as the small noise limit of an appropriate risk-sensitive stochastic control problem. It is possible to obtain this limit by an extension of the Vardgan-Laplace lemma. Finally, the relationship between the information state, and the indicator function of feasible sets is examined

Cosmic cookery : making a stereoscopic 3D animated movie.

This paper describes our experience making a short stereoscopic movie visualizing the development of structure in the universe during the 13.7 billion years from the Big Bang to the present day. Aimed at a general audience for the Royal Society's 2005 Summer Science Exhibition, the movie illustrates how the latest cosmological theories based on dark matter and dark energy are capable of producing structures as complex as spiral galaxies and allows the viewer to directly compare observations from the real universe with theoretical results. 3D is an inherent feature of the cosmology data sets and stereoscopic visualization provides a natural way to present the images to the viewer, in addition to allowing researchers to visualize these vast, complex data sets. The presentation of the movie used passive, linearly polarized projection onto a 2m wide screen but it was also required to playback on a Sharp RD3D display and in anaglyph projection at venues without dedicated stereoscopic display equipment. Additionally lenticular prints were made from key images in the movie. We discuss the following technical challenges during the stereoscopic production process; 1) Controlling the depth presentation, 2) Editing the stereoscopic sequences, 3) Generating compressed movies in display speci¯c formats. We conclude that the generation of high quality stereoscopic movie content using desktop tools and equipment is feasible. This does require careful quality control and manual intervention but we believe these overheads are worthwhile when presenting inherently 3D data as the result is signi¯cantly increased impact and better understanding of complex 3D scenes

Vortices in magnetically coupled superconducting layered systems

Pancake vortices in stacks of thin superconducting films or layers are considered. It is stressed that in the absence of Josephson coupling topological restrictions upon possible configurations of vortices are removed and various examples of structures forbidden in bulk superconductors are given. In particular, it is shown that vortices may skip surface layers in samples of less than a certain size R_c which might be macroscopic. The Josephson coupling suppresses R_c estimates

Referencing practices in physical geography : how well do we cite what we write?

Accurate citation practices are important, from both an ethical and a scientific point of view. Using an easily reproducible, previously published method, we assess citation accuracy in 120 articles published in the first half of 2011 and listed under ‘Physical Geography’ in Thomson Reuters’ ISI Web of Knowledge Science Citation Index. Our results indicate that at least 19% of citations in physical geography do not provide clear support for the statements they are meant to support. These results are in line with previously published findings for ‘field-orientated’ sciences. We propose that both authors and editors help remedy this problem, by employing more rigorous writing and editing practices.University of Pretoria Research Development Programme (RDP) grant (grant number AOT380).http://ppg.sagepub.com/hb201

Hyperbolic Space Cosmologies

We present a systematic study of accelerating cosmologies obtained from M/string theory compactifications of hyperbolic spaces with time-varying volume. A set of vacuum solutions where the internal space is a product of hyperbolic manifolds is found to give qualitatively the same accelerating four-dimensional FLRW universe behavior as a single hyperbolic space. We also examine the possibility that our universe is a hyperbolic space and provide exact Milne type solutions, as well as intersecting S-brane solutions. When both the usual 4D spacetime and the m-dimensional internal space are hyperbolic, we find eternally accelerating cosmologies for $m\geq 7$, with and without form field backgrounds. In particular, the effective potential for a magnetic field background in the large 3 dimensions is positive definite with a local minimum and thus enhances the eternally accelerating expansion.Comment: 33 pages, 2 figures; v2 refs added; v3 minor change in text, JHEP versio