Non-Extensive Bose-Einstein Condensation Model

The imperfect Boson gas supplemented with a gentle repulsive interaction is completely solved. In particular it is proved that it has non-extensive Bose-Einstein condensation, i.e., there is condensation without macroscopic occupation of the ground state (k=0) level

Analysis of a Model for Ship Maneuvering

We analyze numerically and theoretically steady states and bifurcations in a model for ship maneuvering provided by MARIN, and in a simplified model that combines rudder and propeller into an abstract ‘thruster’. Steady states in the model correspond to circular motion of the ship and we compute the corresponding radii. We non-dimensionalize the models and thereby remove a number of parameters, so that, due to a scaling symmetry, only the rudder (or thruster) angle remains as a free parameter. Using ‘degree theory’, we show that a slight modification of the model pos- sesses at least one steady state for each angle and find certain constraints on the possible steady state configuration. We show that straight motion is unstable for the Hamburg test case and use numerical continuation and bifurcation software to compute a number of curves of states together with their stability, and the corresponding radii of the ship motion. In particular, straight forward motion can be stabilised by increasing the rudder size parameter, and the smallest possible radius is ∼ 119 m. These analyses illustrate methods and tools from dynamical systems theory that can be used to analyse a model without simulation. Compared with simulations, the numerical bifurcation analysis is much less time consuming. We have implemented the model in MATLAB and the bifurcation software AUTO

Sharpness versus robustness of the percolation transition in 2D contact processes

We study versions of the contact process with three states, and with infections occurring at a rate depending on the overall infection density. Motivated by a model described in [17] for vegetation patterns in arid landscapes, we focus on percolation under invariant measures of such processes. We prove that the percolation transition is sharp (for one of our models this requires a reasonable assumption). This is shown to contradict a form of 'robust critical behaviour' with power law cluster size distribution for a range of parameter values, as suggested in [17].Comment: 31 pages, to appear in Stochastic Processes and their Application

The Canonical Perfect Bose Gas in Casimir Boxes

We study the problem of Bose-Einstein condensation in the perfect Bose gas in the canonical ensemble, in anisotropically dilated rectangular parallelpipeds (Casimir boxes). We prove that in the canonical ensemble for these anisotropic boxes there is the same type of generalized Bose-Einstein condensation as in the grand-canonical ensemble for the equivalent geometry. However the amount of condensate in the individual states is different in some cases and so are the fluctuations.Comment: 23 page

Large deviations for ideal quantum systems

We consider a general d-dimensional quantum system of non-interacting particles, with suitable statistics, in a very large (formally infinite) container. We prove that, in equilibrium, the fluctuations in the density of particles in a subdomain of the container are described by a large deviation function related to the pressure of the system. That is, untypical densities occur with a probability exponentially small in the volume of the subdomain, with the coefficient in the exponent given by the appropriate thermodynamic potential. Furthermore, small fluctuations satisfy the central limit theorem.Comment: 28 pages, LaTeX 2

Pedagogies of Optimism: Teaching to ‘look forward’ in activating welfare programmes in the Netherlands

In the context of the Dutch welfare state, precarisation entails particular pedagogies: citizens are taught how to feel about being insecure through the techniques of (1) accepting; (2) controlling; and (3) imagining. Welfare activation thus focuses on teaching citizens to accept their precarious position, to embrace it and to prepare for its continuation while remaining optimistic about its discontinuation. Perhaps cruelly, then, the state teaches citizens to develop optimism towards certain imagined futures while at the same time acknowledging the unattainability of these futures. Importantly, case managers in Dutch welfare offices are often precarious themselves too, making the affective labour they perform both difficult and essential for themselves. Contemporary activation and workfare programmes are therefore best understood as characterised by insecurity and precarisation on both the receiving and the providing end of state–citizen encounters

Assessment of Sustainable Development

The objective of this paper is to introduce fuzzy set theory and develop fuzzy mathematical models to assess sustainable development based on context-dependent economic, ecological, and societal sustainability indicators. Membership functions are at the core of fuzzy models, and define the degree to which indicators contribute to development. Although a decision-making process regarding sustainable development is subjective, fuzzy set theory links human expectations about development, expressed in linguistic propositions, to numerical data, expressed in measurements of sustainability indicators. In the future, practical implementation of such models will be based on elicitation of expert knowledge to construct a membership function. The fuzzy models developed in this paper provide a novel approach to support decisions regarding sustainable development.agriculture;assessment;fuzzy set theory;sustainable development

Differential Cyclic Voltammetry - a Novel Technique for Selective and Simultaneous Detection using Redox Cycling Based Sensors

Redox cycling (RC) is an effect that is used to amplify electrochemical signals. However, traditional techniques such as cyclic voltammetry (CV) do not provide clear insight for a mixture of multiple redox couples while RC is applied. Thus, we have developed a new measurement technique which delivers electrochemical spectra of all reversible redox couples present based on concentrations and standard potentials. This technique has been named differential cyclic voltammetry (DCV). We have fabricated micrometer-sized interdigitated electrode (IDE) sensors to conduct DCV measurements in mixtures of 1mM catechol and 4mM [Ru(NH3)6]Cl3. To simulate the electrochemical behavior of these sensors we have also developed a finite element model (FEM) in Comsol®. The\ud experimental data corresponds to the calculated spectra obtained from simulations. Additionally, the measured spectra can be used to easily derive standard potentials and concentrations simultaneously and selectively.\u

Children's ability to generate novel actions

Social learning has given us insight into how children learn actions from others across different domains (e.g., actions on objects, pretend play, and tool use). However, little research exists to confirm whether young children can generate their own novel actions. Three different settings were chosen to offer a varied investigation of children’s ability to generate novel actions: generating multiple actions with novel objects; generating iconic gestures in order to communicate; and generating pretend actions using object substitution. Generating multiple actions with novel objects: The Unusual Box test was developed to investigate children’s ability to generate multiple actions with novel objects (Chapter 2). The Unusual Box test involves children playing with a wooden box that contains many different features (e.g., rings, stairs, strings), and five novel objects. The number of different actions performed on the box and with the objects (i.e., fluency) was used as a measure of their individual learning. Positive correlations between the fluency scores of 24 3- and 4-year-olds on the Unusual Box test and two existing measures of divergent thinking were found. Divergent thinking relates to the ability to think of multiple answers based on one premise. Furthermore, a large range of fluency scores indicated individual differences in children’s ability to generate multiple actions with novel objects. In addition, 16 2-year-olds were assessed on the Unusual Box test, twice two weeks apart, to investigate test-retest reliability and the possibility that the Unusual Box test could be used with children younger than 3 years. A strong positive correlation between the scores on the two assessments showed high test-retest reliability, while individual differences in fluency scores and the absence of a floor effect indicated that the Unusual Box test was usable in children from 2 years of age. Generating iconic gestures in order to communicate: Children’s ability to generate iconic gestures in order to communicate was assessed using a game to request stickers from an experimenter (N = 20, Chapter 3). In order to get a sticker children had to communicate to the experimenter which out of two objects they wanted (only one object had a sticker attached to it). Children’s use of speech or pointing was ineffective; therefore only generating an iconic gesture was sufficient to retrieve the sticker. Children generated a correct iconic gesture on 71% of the trials. These findings indicate that children generate their own iconic gestures in order to communicate; and that they understand the representational nature of iconic gestures, and use this in their own generation of iconic gestures. Generating pretend actions using object substitution: In order to determine whether children are able to generate their own object substitution actions and understand the representational nature of these actions, 45 3- and 4-year-olds were familiarized with the goal of a task through modelling actions. Children distinguished between the intentions of an experimenter to pretend, or try and perform a correct action. Children mainly imitated the pretend actions, while correcting the trying actions. Next, children were presented with objects for which they had to generate their own object substitution actions without being shown a model. When children had previously been shown pretend actions, children generated their own object substitution actions. This indicates that children generate their own object substitution actions, and that they understand the representational nature of these actions. An additional study with 34 3-year-olds, revealed no significant correlations between divergent thinking, inhibitory control, or children’s object substitution in a free play setting, and children’s ability to generate object substitution actions in the experimental setting