Belgium’s position in world trade

The objective of the article is to give a general overview of the position that Belgium occupies in the world trade stakes and its ability to adjust in response to changes in the international environment. Over the last two decades, world trade has expanded considerably, buoyed up by the rapid growth of new economic centres, the advanced economies generally having seen a drop in their market share. However, the growth in Belgium’s exports has lagged behind the average for twelve European countries going through the same major changes ; and the loss of market share has been higher than the average. A classical econometric analysis of price competitiveness shows up the limited role of relative export prices as a determinant in gains/losses of market share. This finding mainly reflects the fact that prices are largely fixed on international markets, producers cannot adjust their export prices according to the costs that they have to bear. In this context, a reasonable development of production costs, and with stronger reason wage costs, is essential in order to ensure the continuity of export activities. Beyond relative price effects, it is necessary to take into account structural elements in order to explain changes in market share. From this standpoint, it appears that the type of production has a crucial role to play. Faced with competition from emerging economies, Belgium’s external trade performance in the case of standardised products has been well below world demand. On the other hand, high-value-added products or those of a highly innovative nature or with a high research content are the ones that enable it to maintain or improve on its position in global trade. Export activities and innovation share some common features, not least because they are concentrated in the hands of a small number of large enterprises. In view of the high foreign market entry costs, the best performing firms are the ones that tend to be the exporters. However, factors such as the innovative nature of products on offer can of course influence the likelihood of success on foreign markets. Here, innovation efforts by Belgian firms are not creating enough opportunities for marketing new products. Yet, it is most certainly goods with a high value added or highly innovative products that Belgium will be able to count on to ensure sustainable economic development and to support the prosperity of its people.competitiveness, market share, export price, innovation, R&D

Collision-Induced Decay of Metastable Baby Skyrmions

Many extensions of the standard model predict heavy metastable particles which may be modeled as solitons (skyrmions of the Higgs field), relating their particle number to a winding number. Previous work has shown that the electroweak interactions admit processes in which these solitons decay, violating standard model baryon number. We motivate the hypothesis that baryon-number-violating decay is a generic outcome of collisions between these heavy particles. We do so by exploring a 2+1 dimensional theory which also possesses metastable skyrmions. We use relaxation techniques to determine the size, shape and energy of static solitons in their ground state. These solitons could decay by quantum mechanical tunneling. Classically, they are metastable: only a finite excitation energy is required to induce their decay. We attempt to induce soliton decay in a classical simulation by colliding pairs of solitons. We analyze the collision of solitons with varying inherent stabilities and varying incident velocities and orientations. Our results suggest that winding-number violating decay is a generic outcome of collisions. All that is required is sufficient (not necessarily very large) incident velocity; no fine-tuning of initial conditions is required.Comment: 24 pages, 7 figures, latex. Very small changes onl

Power dependent switching of nonlinear trapping by local photonic potentials

We study experimentally and numerically the nonlinear scattering of wave packets by local multi-site guiding centers embedded in a continuous dielectric medium, as a function of the input power and angle of incidence. The extent of trapping into the linear modes of different sites is manipulated as a function of both the input power and incidence angle, demonstrating power-controlled switching of nonlinear trapping by local photonic potentials.Comment: Submitted to Optics Letter

Automated real-time stress monitoring of police horses using wearable technology

Mounted police horses and riders are repeatedly subjected to demanding and stressful situations. Intensive selection and training of police horses is required to ensure performance, safety and welfare of the horses and their riders. At the mounted police in Brussels, Belgium, the selection of police horses is mainly based on intuition built upon previous experience which makes it a subjective decision. Although this decision mostly leads to good results, sometimes horses are purchased that turn out to be unsuited for the mounted police. Including an objective measure when evaluating the longer term suitability of candidate police horses could help the mounted police to further improve their selection procedure for police horses. This study investigated the potential of real-time stress detection as a measure to evaluate the longer term suitability of police horses. Four experimental protocols were developed in consultation with the mounted police and were performed by 17 horse-rider pairs. The horses were divided into four categories according to their experience and suitability as police horses: good beginner, bad beginner, good experienced and bad experienced. The relative stress of the horses was monitored with wearable technology during every protocol. For one protocol, the time percentage spent over 20% relative stress by the horse was found to be significantly lower for good compared to bad beginner horses (p-value = 0.0277). In conclusion this study demonstrated that real-time stress detection with wearable technology in mounted police horses provides information on the longer term suitability of police horses

The field theory of Skyrme lattices in quantum Hall ferromagnets

We report the application of the nonlinear $\sigma$ model to study the multi-skyrmion problem in the quantum Hall ferromagnet system. We show that the ground state of the system can be described by a ferromagnet triangular Skyrme lattice near $\nu=1$ where skyrmions are extremely dilute. We find a transition into antiferromagnet square lattice by increasing the skyrmion density and therefore $|\nu-1|$. We investigate the possibility that the square Skyrme lattice deforms to a single skyrmion with the same topological charge when the Zeeman energy is extremely smaller than the Coulomb energy. We explicitly show that the energy of a skyrmion with charge two is less than the energy of two skyrmions each with charge one when $g \leq g_c$. By taking the quantum fluctuations into account, we also argue the possibility of the existence of a non-zero temperature Kosterlitz-Thouless and a superconductor-insulator phase transition.Comment: 17 page

The Casimir energy of skyrmions in the 2+1-dimensional O(3)-model

One-loop quantum corrections to the classical vortices in 2+1 dimensional O(3)-models are evaluated. Skyrme and Zeeman potential terms are used to stabilize the size of topological solitons. Contributions from zero modes, bound-states and scattering phase-shifts are calculated for vortices with winding index n=1 and n=2. For both cases the S-matrix shows a pronounced series of resonances for magnon-vortex scattering in analogy to the well-established baryon resonances in hadron physics, while vortices with n>2 are already classically unstable against decay. The quantum corrections destabilize the classically bound n=2 configuration. Approximate independence of the results with respect to changes in the renormalization scale is demonstrated.Comment: 24 pages LaTeX, 14 figure

From Effective Lagrangians, to Chiral Bags, to Skyrmions with the Large-N_c Renormalization Group

We explicitly relate effective meson-baryon Lagrangian models, chiral bags, and Skyrmions in the following way. First, effective Lagrangians are constructed in a manner consistent with an underlying large-N_c QCD. An infinite set of graphs dress the bare Yukawa couplings at *leading* order in 1/N_c, and are summed using semiclassical techniques. What emerges is a picture of the large-N_c baryon reminiscent of the chiral bag: hedgehog pions for r > 1/\Lambda patched onto bare nucleon degrees of freedom for r < 1/\Lambda, where the ``bag radius'' 1/\Lambda is the UV cutoff on the graphs. Next, a novel renormalization group (RG) is derived, in which the bare Yukawa couplings, baryon masses and hyperfine baryon mass splittings run with \Lambda. Finally, this RG flow is shown to act as a *filter* on the renormalized Lagrangian parameters: when they are fine-tuned to obey Skyrme-model relations the continuum limit \Lambda --> \infty exists and is, in fact, a Skyrme model; otherwise there is no continuum limit.Comment: Figures included (separate file). This ``replaced'' version corrects the discussion of backwards-in-time baryon

Static solitons with non-zero Hopf number

We investigate a generalized non-linear O(3) $\sigma$-model in three space dimensions where the fields are maps $S^3 \mapsto S^2$. Such maps are classified by a homotopy invariant called the Hopf number which takes integer values. The model exhibits soliton solutions of closed vortex type which have a lower topological bound on their energies. We explicitly compute the fields for topological charge 1 and 2 and discuss their shapes and binding energies. The effect of an additional potential term is considered and an approximation is given for the spectrum of slowly rotating solitons.Comment: 13 pages, RevTeX, 7 Postscript figures, minor changes have been made, a reference has been corrected and a figure replace

Stress Urinary Incontinence in Women with a History of Gestational Diabetes Mellitus

ABSTRACT Objective: Stress urinary incontinence may serve as a barrier to lifestyle modification among women at high risk for diabetes, but the prevalence of stress urinary incontinence among women with histories of gestational diabetes mellitus (hGDM) is unknown. The purpose of this study was to examine the prevalence of stress incontinence among women with hGDM and to examine its association with their current physical activity. Methods: We surveyed women with hGDM within the past 5 years who were currently enrolled in a managed care plan (n = 228). In a cross-sectional analysis, self-reported weekly or more frequent stress incontinence was the primary independent variable and measures of physical activity and body mass index (BMI) were the outcomes of interest. We constructed multivariable models that adjusted for participant characteristics associated with the measure of incontinence or outcomes in bivariate analyses. Results: Of the 228 women with hGDM, 49% reported weekly or more frequent incontinence during pregnancy, and 28% reported that incontinence affected their activities during pregnancy. Fifty percent reported weekly or more frequent incontinence after delivery, with 27% reporting interference of incontinence with activity. Less than a third of women reported optimal physical activity, and 42% were obese. After adjustment for characteristics associated with measures of activity and incontinence, there was minimal association between levels of activity and stress urinary incontinence; similarly, there was no association between BMI and measures of stress incontinence. Conclusions: Stress urinary incontinence is common among women with hGDM but does not appear to be associated with physical activity levels or BMI.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/63394/1/jwh.2007.0616.pd

Saturation in Liquid/Gas Coalescence

The problem was to construct a mathematical model for a liquid/gas coalescer, in order that the model could be analyzed to find combinations of parameters that would minimize the effects of saturation. The team has developed three complementary models, each with different strengths and weaknesses so that, depending on the information desired, one model may be more useful than another. The three models are: 1. A continuum model giving a macroscopic description of the filter. The governing equations are derived from first-principle consider- ations of conservation of mass and momentum. Constitutive relations for this model are derived by considering the processes going on in the filter at a microscopic level. 2. A stochastic model based on a Markov Decision Process. Each droplet is modelled as a single entity that can merge or move stochastically. This leads to a Markov simulation of the filter and the computation of average quantities. 3. A Lattice-Boltzmann model. The droplets are modelled to interact with each other and with the filter, using a Boltzmann distribution for their speed. This simulates the hydrodynamic behaviour of the droplet inside the filter