Identification of shallow sea models

In this paper we consider a parameter estimation procedure for shallow sea models. The method is formulated as a minimization problem. An adjoint model is used to calculate the gradient of the criterion which is to be minimized. In order to obtain a robust estimation method, the uncertainty of the open boundary conditions can be taken into acoount by allowing random noise inputs to act on the open boundaries. This method avoids the possibility that boundary errors are interpreted by the estimation procedure as parameter fluctuations. We apply the parameter estimation method to identify a shallow sea model of the entire European continental shelf. First, a space-varying bottom friction coefficient is estimated simultaneously with the depth. The second application is the estimation of the parameterization of the wind stress coefficient as a function of the wind velocity. Finally, an uncertain open boundary condition is included. It is shown that in this case the parameter estimation procedure does become more robust and produces more realistic estimates. Furthermore, an estimate of the open boundary conditions is also obtained

Lessons from two Dutch projects for the introduction of computers in schools

The systematic introduction of computers in schools for general secondary education in The Netherlands started in the early 1980s. Initially, the Dutch government experimented in 1983 with a project in 100 lower general secondary schools limited in scope to gain experience with educational computer use (100-school project). In the period 1985¿1989 the government implemented a second stimulation project focused at all lower secondary schools: New Information Technology in Secondary Education. This project consisted of the provision of hardware and courseware to all general secondary schools, organizing nationwide in-service teacher training, and the intensifying of software development.\ud \ud With respect to the 100-school project the question was whether there would be any differences in computer implementation and problems with computer use at schools in the 100-school project as compared to other schools which could only profit in the second promotional program.\ud \ud The question addressed for the second promotional program concerns the use of software packages and courseware which were provided to all schools for general education during the NIVO-project.\ud \ud An important conclusion for The Netherlands is, that the provision of hardware, software and in-service training was adequate to introduce computer education (called: information and computer literacy) as a new subject in nearly all lower secondary schools. But the set of stimulation activities does not seem to be adequate or sufficient to realize the integration of computer use in existing subjects

One-dimensional models for atoms in strong magnetic fields, II: Anti-Symmetry in the Landau Levels

Electrons in strong magnetic fields can be described by one-dimensional models in which the Coulomb potential and interactions are replaced by regularizations associated with the lowest Landau band. For a large class of models of these type, we show that the maximum number of electrons that can be bound is less than a Z + Z f(Z). The function f(Z) represents a small non-linear growth which is quadratic in log Z when the magnetic field strength grows polynomially with the nuclear charge Z. In contrast to earlier work, the models considered here include those arising from realistic cases in which the full trial wave function for N-electrons is the product of an N-electron trial function in one-dimension and an antisymmetric product of states in the lowest Landau level.Comment: Submitted to special issue of J. Stat. Phys. in honor of E. Lieb's 70th birthday. (latex, 25 pages

Multi-period conditional distribution functions for heteroscedastic models with applications to VaR.

For a GARCH(1,1) process, we study the large deviation asymptotics at the horizon k and their consequences for extreme quantile estimation. The results are relevant for the estimation of multi-period Value at Risk and prove that the heuristic “square k” rule used in financial risk management is false in the context of GARCH processes.GARCH models – Large deviation probabilities – Laplace integrals – Value at risk.

The relation between problem areas and stages of computer implementation

Although during the last decade the number of computers at secondary schools has increased considerably in many countries, only a small percentage of teachers are using computers for instructional purposes. In the COMPED study principals, computer coordinators and teachers were asked to indicate the obstacles which are hampering the introduction of computers in their school and classroom practice.\ud \ud The results which are based on data from France, Japan, the Netherlands and USA, show that the most important problems are: lack of hardware, software, knowledge and time. These problems in implementing computers in education are at the same time the most important reasons why non-users do not use computers for instructional purposes. A comparison between the relative most intensive computer-using schools and the less intensive users shows that both groups have mostly the same problems as mentioned before. Besides, schools with a high level of computer use have more often than other schools overcome organizational problems

Semi-classical spectral estimates for Schr\"odinger operators at a critical level. Case of a degenerate maximum of the potential

We study the semi-classical trace formula at a critical energy level for a Schr\"odinger operator on $\mathbb{R}^{n}$. We assume here that the potential has a totally degenerate critical point associated to a local maximum. The main result, which establishes the contribution of the associated equilibrium in the trace formula, is valid for all time in a compact subset of $\mathbb{R}$ and includes the singularity in $t=0$. For these new contributions the asymptotic expansion involves the logarithm of the parameter $h$. Depending on an explicit arithmetic condition on the dimension and the order of the critical point, this logarithmic contribution can appear in the leading term.Comment: 27 pages, perhaps to be revise

VAR FOR QUADRATIC PORTFOLIO'S WITH GENERALIZED LAPLACE DISTRIBUTED RETURNS

This paper is concerned with the e±cient analytical computation of Value-at-Risk (VaR) for portfolios of assets depending quadratically on a large number of joint risk factors that follows a multivariate Generalized Laplace Distribution. Our approach is designed to supplement the usual Monte-Carlo techniques, by providing an asymptotic formula for the quadratic portfolio's cumulative distribution function, together with explicit error-estimates. The application of these methods is demonstrated using some financial applications examples.

Status of introductory computer education in the Netherlands: results of a survey

The International Association for the Evaluation of Educational Achievement (IEA) is conducting an international comparative study on educational computer use in more than 20 countries. This paper analyzes some of the Dutch results of the IEA survey on the use of computers in lower secondary schools. The findings show that at present computers are mainly used for introductory computer courses, but that the integration of computers into existing subjects is still limited. The main problems identified in the study are: insufficient availability of courseware and hardware, time constraints and a high need for teacher training