Spin Polarization of Quasi Two-Dimensional Hole Systems

In quasi two-dimensional (2D) hole systems with an effective spin j=3/2, heavy hole-light hole splitting results in a quantization of angular momentum perpendicular to the 2D plane. The spin polarization of quasi 2D hole systems due to an in-plane magnetic field B thus competes with the heavy hole-light hole splitting. As a result, the spin polarization of hole systems is very different from the spin polarization of j=1/2 electron systems. In particular, it is shown that the spin polarization of quasi 2D heavy hole systems can change its sign at a finite value of B.Comment: 4 pages, 2 figure

Boundedness in a fully parabolic chemotaxis system with nonlinear diffusion and sensitivity, and logistic source

In this paper we study the zero-flux chemotaxis-system \begin{equation*} \begin{cases} u_{ t}=\nabla \cdot ((u+1)^{m-1} \nabla u-(u+1)^\alpha \chi(v)\nabla v) + ku-\mu u^2 & x\in \Omega, t>0, \\ v_{t} = \Delta v-vu & x\in \Omega, t>0,\\ \end{cases} \end{equation*} $\Omega$ being a bounded and smooth domain of $\mathbb{R}^n$, $n\geq 1$, and where $m,k \in \mathbb{R}$, $\mu>0$ and $\alpha < \frac{m+1}{2}$. For any $v\geq 0$ the chemotactic sensitivity function is assumed to behave as the prototype $\chi(v) = \frac{\chi_0}{(1+av)^2}$, with $a\geq 0$ and $\chi_0>0$. We prove that for nonnegative and sufficiently regular initial data $u(x,0)$ and $v(x,0),$ the corresponding initial-boundary value problem admits a global bounded classical solution provided $\mu$ is large enough

Spin angular impulse due to spin-dependent reflection off a barrier

The spin-dependent elastic reflection of quasi two-dimensional electrons from a lateral impenetrable barrier in the presence of band-structure spin-orbit coupling results in a spin angular impulse exerted on the electrons which is proportional to the nontrivial difference between the electrons' momentum and velocity. Even for an unpolarized incoming beam we find that the spin angular impulse is nonzero when averaged over all components of the reflected beam. We present a detailed analysis of the kinematics of this process.Comment: 4 pages, 2 figures, final versio

Financial development, economic growth and corporate governance : paper presented at the First Annual Seminar on New Development Finance held at the Goethe University of Frankfurt, September 22 - October 3, 1997

During the last years the relationship between financial development and economic growth has received widespread attention in the literature on growth and development. This paper summarises in its first part the results of this research, stressing the growth-enhancing effects of an increased interpersonal re-allocation of resources promoted by financial development. The second part of the paper seeks to identify the determinants of financial development based on Diamond's theory of financial intermediation as delegated monitoring. The analysis shows that the quality of corporate governance of banks is the key factor in financial system development. Accordingly, financial sector reforms in developing countries will only succeed if they strengthen the corporate governance of financial institutions. In this area, financial institution building has an important contribution to make. Paper presented at the First Annual Seminar on New Development Finance held at the Goethe University of Frankfurt, September 22 - October 3, 199

AC logic flip-flop circuits Patent

Bistable multivibrator circuits operating at high speed and low power dissipatio

Transport user benefits calculation with the “Rule of a Half” for travel demand models with constraints

The importance of user benefits in transport projects assessments is well-known by transport planners and economists. Generally they have the greatest impact on the result of costbenefit analysis. It is common practice to adopt the consumer surplus measure for calculating transport user benefits. Normally the well-known “Rule of a Half”, as a practical approximation for the integral of the demand curve, is used to determine the change of consumer surplus. In this paper we enter into the question of whether the Rule of a Half is valid in the case of travel demand models with multiple constraints. Such models are often used for travel demand modeling of large-scale areas. The most discussed and well-known model in transport modeling field is the doubly constrained gravity model. Beside this model with inelastic constraints there are also more flexible models with elastic constraints. The theoretical analysis in this paper provides a mathematical proof for the validity of the concept of the Rule of a Half for travel demand models with multiple elastic and inelastic constraints. In this case the Rule of a Half is also a correct approximation of the change of consumer surplus

Error estimates for the finite element approximation of bilinear boundary control problems

In this article a special class of nonlinear optimal control problems involving a bilinear term in the boundary condition is studied. These kind of problems arise for instance in the identification of an unknown space-dependent Robin coefficient from a given measurement of the state, or when the Robin coefficient can be controlled in order to reach a desired state. To this end, necessary and sufficient optimality conditions are derived and several discretization approaches for the numerical solution the optimal control problem are investigated. Considered are both a full discretization and the postprocessing approach meaning that we compute an improved control by a pointwise evaluation of the first-order optimality condition. For both approaches finite element error estimates are shown and the validity of these results is confirmed by numerical experiments.Comment: 39 pages, 1 figur

Orthogonal Wavelets via Filter Banks: Theory and Applications

Wavelets are used in many applications, including image processing, signal analysis and seismology. The critical problem is the representation of a signal using a small number of computable functions, such that it is represented in a concise and computationally efficient form. It is shown that wavelets are closely related to filter banks (sub band filtering) and that there is a direct analogy between multiresolution analysis in continuous time and a filter bank in discrete time. This provides a clear physical interpretation of the approximation and detail spaces of multiresolution analysis in terms of the frequency bands of a signal. Only orthogonal wavelets, which are derived from orthogonal filter banks, are discussed. Several examples and applications are considered