#### Schedule 2008-2009

### Schedule 2009-2010

### 1st semester (Sept 2009-Jan 2010)

##### October, 8

15:45-16:45, Room H-327, Citadel Building

Speakers:

**1. Philip Hölzenspies **on
**Towards Platforms - How to run applications that do not
yet exist
**

In Embedded Systems, power is a very scarce resource. Both the diversity of applications and the demand for integration into single appliances increase, despite of power problems. Power consumption can be reduced by specializing chips, whereas integration increases when generalizing them. This is why Multi-Processor System-on-Chips (MPSoCs) have become popular; flexibility and integration by offering several processors, all with their own specialization, in a single chip. We like to look at MPSoCs as platforms, but - especially when real-time constraints are involved - the assignment of tasks to processors is a design-time process. This means that two applications that require the same resource can not be run simultaneously and that when a resource becomes faulty, a set of applications can no longer run. This talk is about a way to loosen this constraint, by means of a heuristic approach to run-time resource assignment.

2. Denis Miretskiy

2. Denis Miretskiy

cancelled

### Poster

##### November, 12

15:45-16:45, Room 2126, Zilverling Building

Speakers:

**1. Didit Adytia** on
**
Variational Boussinesq Model for Simulation of Tsunamis and Coastal Waves**

We describe the basic ideas of a so-called Variational Boussinesq
Model (VBM) which is based on the Hamiltonian structure of gravity
surface waves. By using a rather simple approach to prescribe the
profile of the vertical fluid potential in the expression for the
kinetic energy, we obtain a set of dynamic equations extended with one
additional elliptic equation for the amplitude of the vertical profile.
All expressions in the energy contain at most first order derivatives,
which makes a numerical implementation with finite elements relatively
easy. The applicability of the code is illustrated for two different
applications. One application deals with tsunami simulation with study
case a historical tsunami on July 2006 in Pangandaran, Indonesia.
Another application deals with simulation of coastal waves entering the
small harbour of Cilacap on the south-coast of Java, Indonesia.
The approach is to investigate a resonance problem in the harbour.

**2. Matthijs Bomhoff **on **Space-efficient
Recognition of Perfect Elimination Bipartite Graphs
**

### Poster

##### December, 10

15:45-16:45, Room H-327, Citadel Building

Cancelled

##### January, 14

15:45-16:45, Room H-327, Citadel Building

Speakers:

**1. Sid Visser** on
**
Modeling the Neocortex with Meso-scale Models and Population Models**

Models of the brain yield new physiological insights as well as a better understanding of the brain and related disorders, e.g. epilepsy and Parkinson’s disease. A large model, having a detailed description of all neurons, is developed and numerically analyzed. Typical types of behavior, like oscillations and travelling waves, are observed. A different model, consisting of two delayed differential equations with two different delays, is derived that qualitatively captures the behavior of the detailed model. This model is then analyzed by construction of a bifurcation diagram that provides new insights in the dependence of both models on certain parameters.

**2. Bob Peeters** on
**
A Conservative Numerical Scheme for Hydrostatic Flow in Isentropic Coordinates**

Within this project we try to construct new numerical schemes that aim to improve current ensemble forecasting models for climate. Most contemporary climate models conserve energy and potential vor- ticity in the case of no forcing and dissipation. What’s missing in most cases, however, is a consistent discretization of the phase space structure. Constructing conservative Eulerian schemes is highly non- trivial. We take a different route and start with the equations for a hydrostatic atmosphere in isentropic coordinates. In absence of forcing and friction, entropy is conserved on infinitesimal fluid parcels. De- composing the atmosphere into a finite number of air particles is the key ingredient for a conservative numerical scheme.

### Poster

### 2nd semester (Feb 2010-July 2010)

##### February, 11

15:45-16:45, Room H-327, Citadel Building

Speakers:

**1. Peter Vanberkel** on
**
Modelling Hospital Patient Mix Decisions**

Dutch hospitals are becoming more focused in the types of treatments they want to provide to patients. To achieve these targets for each treatment type, hospitals can choose to attract only certain patient classes to the hospital. The actual treatment types required by a patient class are subject to randomness. Furthermore, the number of patients in a patient class is unknown and evolves over time. In this presentation we discuss models to determine, based on given targets, which patient classes to attract to the hospital and when to do so.

**2. Wenny Kristina** on
**
Wave Reflection over Slowly Varying Bathymetry modelled by Effective Boundary Conditions**

In tsunami simulations, the wave height near the shore is the most important aspect scientists would like to calculate accurately. Unfortunately, the present-day simulation tools still cannot calculate the waveheight near the shore accurately enough. One source of inaccuracy is the interaction of the incoming waves with the reflected waves from the coast. Besides, computing the details of run-up and run-down of waves on the shore is computationally very demanding and expensive since closer to the shore a finer computational resolution will be needed. Moreover, the modelling of the physical processes is bound to be rather rudimentary because many aspects of tsunami propagation, e.g. nonlinearity, dispersion, friction, etc., have to be considered. In this talk, an analytical expression for the reflection of a wave that travels over slowly varying bathymetry is derived by using the Wentzel-Kramer-Brillouin (WKB) approximation of the linear Shallow Water Equations. This solution is then used to model the effective boundary condition to be imposed in a zone before the shoreline.

### Poster

##### March, 11

15:45-16:45, Room H-327, Citadel Building

Speaker:

**1. Hanumant Singh Shekhawat** on
**
Computation of Chopped System Norm**

If system *G* represents the class of signals we are aiming for, then *L*^{2}-norm of the
optimal signal re-constructors over all samplers and holds require the norm computation of the
system *G* in the frequency range [ω,∞) instead of usual (−∞,∞). The
computation becomes more complicated if system *G* is allowed to have the poles not
only in the left half complex plane but also on the imaginary axis of the complex
plane. Hence a Lyapunov type answer is not applicable in this case. This talk is
about a method for efficient computation of *L*^{2}-norm of the system given in state
space form with poles in the left half plane as well as on the imaginary axis. The
relationship with *L*^{2}-norm of the stable system and *H*^{2}-norm of the system will also
be discussed.

### Poster

##### April, 8

15:45-16:45, Room H-327, Citadel Building

Speakers:

**1. Daniël Reijsbergen** on
**
Rare Event Simulation for Model Checking Highly Dependable Systems**

We are interested in estimating system failure probabilities in highly dependable systems, such as a telecommunications network or a nuclear power plant. Probabilities of interest could be system failure before some time bound or the time fraction that the system is down in equilibrium. Often, the models have state spaces that are too big to allow for iterative methods (e.g. Gauss-Seidel). Stochastic simulation is then typically used as the alternative. Obviously, in a highly dependable system, system failure is a rare event, so we need to apply efficient simulation techniques. We use Importance Sampling, i.e. we simulate under a new distribution which oversamples occurrence of the rare event. In this talk we explain why existing techniques fail in some situations and propose a new distribution for systems with high component repair rates.

**2. Julia Mikhal** on
**
Prediction of Shear Stress in Cerebral Aneurysms**

The prediction of blood flow inside aneurysms that can develop in a human brain is a field of intense research. It is important in relation to the growing medical need for an effective planning and execution of surgical intervention. The shear stress that occurs at the vessel walls of cerebral aneurysms is a key component for the prediction of the risk of their long-term rupture. The computational model for the simulation of blood flow through vessels in the human brain is formulated in terms of the incompressible Navier-Stokes equations in three-dimensional domains. We apply the immersed boundary method based on volume penalization to represent the complex shaped solid vessel walls of the aneurysm. In this presentation we focus on the flow near the boundaries, where the shear stress distribution appears as a reliable characteristic of the flow.

### Poster

##### May, 6

15:45-16:45, Room H-327, Citadel Building

Cancelled

##### June, 10

15:45-16:45, Room H-327, Citadel Building

Speaker:

**1. Lilya Ghazaryan** on
**Simulation of Impaction Filtration of Aerosol Droplets in Porous Media**

Driven by various applications, several approaches have been developed to determine the filtration efficiency of particulate filters. Our aim is to simulate the particle filtration efficiency of several basic structured porous media under a number of flow conditions and to quantify the role of the particle’s inertia on filtration. This is a steppingstone problem towards the analysis of realistic systems of porous filters.

Particle motion is governed by a variety of forces. Here, we focus on the dominant drag-force dynamics to quantify the filtration efficiency as a function of the droplet inertia, expressed in terms of its relaxation time. Filtration of a droplet is assumed to arise whenever this droplet hits the surface of the porous medium. The immersed boundary method is applied to capture the detailed particle motion in the gas flow through a complex porous medium. The flow field is calculated by solving the incompressible Navier-Stokes equations. For the particle phase the Lagrangian approach is used, in which we track the trajectories of a large number of particles embedded in the flow. The porous medium is formed by a staggered arrangement of square rods in 3D in order to develop and validate our approach.

### Poster

Designed by Free CSS Templates, Thanks to Dubai Villas