The influence of the precipitation rate on the properties of porous chromia

The properties were studied of heated (320°C) chromia samples, prepared by two precipitation methods: \ud \ud 1. (1) addition of ammonia to chromium salt solutions,\ud 2. (2) OH− formation in chromium salt solutions through hydrolysis of urea.\ud \ud Samples formed by means of the first method are macro or mesoporous and have a lower specific surface area (~200 m2·g−1) than those formed by urea hydrolysis (~300 m2·g−1). Only in the case of a very slow addition of the ammonia solution these properties of the chromia's become equal. Experiments show that the micro porous type samples with high surface area are only formed if the pH range 5.1 to 5.7 is passed slowly. The formation of polychromium complexes of uniform size is suggested.\ud \u

Complexity of Coalition Structure Generation

We revisit the coalition structure generation problem in which the goal is to partition the players into exhaustive and disjoint coalitions so as to maximize the social welfare. One of our key results is a general polynomial-time algorithm to solve the problem for all coalitional games provided that player types are known and the number of player types is bounded by a constant. As a corollary, we obtain a polynomial-time algorithm to compute an optimal partition for weighted voting games with a constant number of weight values and for coalitional skill games with a constant number of skills. We also consider well-studied and well-motivated coalitional games defined compactly on combinatorial domains. For these games, we characterize the complexity of computing an optimal coalition structure by presenting polynomial-time algorithms, approximation algorithms, or NP-hardness and inapproximability lower bounds

Transport of nonlinearly biodegradable contaminants in aquifers

This thesis deals with the transport behavior of nonlinearly biodegradable contaminants in aquifers. Such transport occurs during in situ bioremediation which is based on the injection of an electron acceptor or electron donor. The main interests in this thesis are the mutual influences of underlying processes, i.e. transport, adsorption and biodegradation, and their influence on in situ bioremediation performance. To gain insight in these influences, the processes in a homogeneous aquifer are studied. Subsequently, the effect of physical heterogeneity of an aquifer on the displacement of the biodegradable contaminant is examined.Considering a homogeneous aquifer, numerical simulations are performed to ascertain the effect of transport, adsorption and biodegradation on the displacement of the contaminant and of the electron acceptor or electron donor. In the initial phase, the developed numerical results are successfully described by first order degradation. In the final phase, the numerical results show a traveling wave behavior; the developed concentration fronts have constant front shapes and 'travel' with a constant velocity through the aquifer. This behavior is due to the balance between the steepening effect of nonlinear biodegradation and the spreading effect of dispersion. Because of this traveling wave behavior, semi-analytical solutions have been derived that satisfactorily approximate the numerical results. These semi-analytical solutions are used to assess the performance of the in situ bioremediation. If in situ bioremediation is applied to a polluted site, the electron acceptor injection concentration and the injection velocity will be the only manipulative properties. By varying these two properties, the in situ bioremediation performance can be influenced and optimized.To study a physical heterogeneous aquifer, the hydraulic conductivity is considered spatially variable and it is assumed to be a random space function. The effect of physical heterogeneity is determined using a Lagrangian stochastic approach. Results show that incorporation of physical heterogeneity leads to a spreading of the breakthrough curve of both the contaminant and the electron acceptor or electron donor. In case of a large degree of heterogeneity, i.e. a strongly heterogeneous aquifer, it is the heterogeneity which determines the shape of the breakthrough curve and not the dispersion or nonlinear biodegradation.</p

In Conversation with Mubin Shaikh: From Salafi Jihadist to Undercover Agent inside the "Toronto 18" Terrorist Group

This interview with former undercover agent Mubin Shaikh can help academics and security practitioners understand the key role played and the challenges faced by covert human intelligence sources within domestic terrorist groups. The interview highlights the identity crisis, the personal factors, and the allure of jihadi militancy that initially drove Shaikh to join a Salafi jihadist group. It investigates Shaikh’s process of disengagement from the Salafi jihadist belief system and his rediscovery of a moderate, inclusive, and benevolent form of Islam. It explores his work as an undercover agent for the Canadian Security Intelligence Service, the Royal Canadian Mounted Police, and the Integrated National Security Enforcement Team responsible for disrupting domestic terrorist groups. The “Toronto 18” terrorist cell, the key role played by undercover agents in preventing terrorist action, and the challenges posed by entrapment are also discussed

The age limit for euthanasia requests in the Netherlands:a Delphi study among paediatric experts

BACKGROUND: The Dutch Euthanasia Act applies to patients 12 years and older, which makes euthanasia for minors younger than 12 legally impossible. The issue under discussion specifically regards the capacity of minors to request euthanasia.OBJECTIVE: Gain insight in paediatric experts' views about which criteria are important to assess capacity, from what age minors can meet those criteria, what an assessment procedure should look like and what role parents should have.METHODS: A Delphi study with 16 experts (paediatricians, paediatric nurses and paediatric psychologists) who work in Children Comfort Teams in Dutch academic hospitals. The questionnaire contained statements concerning criteria for capacity and procedural criteria. Consensus was defined as ≥80% agreement.RESULTS: The experts agreed that five criteria for capacity, found in a previous literature study, are all important. They agreed that some children between ages 9 and 11 could meet all the criteria. Consensus was reached for the statements that the entire medical team should be involved in the decision making and that a second independent expert must assess the case. Experts agreed that the parents' opinion is relevant and should always be taken into account, but it need not be decisive.CONCLUSION: This study shows that the age limit of 12 years in the Dutch Euthanasia Act is too strong according to paediatric experts. Letting go of the age limit or lowering the age limit combined with adequate capacity assessment for minors younger than 12 are options that should be discussed further.</p

Evolving Symbolic Controllers

International audienceThe idea of symbolic controllers tries to bridge the gap between the top-down manual design of the controller architecture, as advocated in Brooks' subsumption architecture, and the bottom-up designer-free approach that is now standard within the Evolutionary Robotics community. The designer provides a set of elementary behavior, and evolution is given the goal of assembling them to solve complex tasks. Two experiments are presented, demonstrating the efficiency and showing the recursiveness of this approach. In particular, the sensitivity with respect to the proposed elementary behaviors, and the robustness w.r.t. generalization of the resulting controllers are studied in detail

Nearly optimal solutions for the Chow Parameters Problem and low-weight approximation of halfspaces

The \emph{Chow parameters} of a Boolean function $f: \{-1,1\}^n \to \{-1,1\}$ are its $n+1$ degree-0 and degree-1 Fourier coefficients. It has been known since 1961 (Chow, Tannenbaum) that the (exact values of the) Chow parameters of any linear threshold function $f$ uniquely specify $f$ within the space of all Boolean functions, but until recently (O'Donnell and Servedio) nothing was known about efficient algorithms for \emph{reconstructing} $f$ (exactly or approximately) from exact or approximate values of its Chow parameters. We refer to this reconstruction problem as the \emph{Chow Parameters Problem.} Our main result is a new algorithm for the Chow Parameters Problem which, given (sufficiently accurate approximations to) the Chow parameters of any linear threshold function $f$, runs in time \tilde{O}(n^2)\cdot (1/\eps)^{O(\log^2(1/\eps))} and with high probability outputs a representation of an LTF $f'$ that is \eps-close to $f$. The only previous algorithm (O'Donnell and Servedio) had running time \poly(n) \cdot 2^{2^{\tilde{O}(1/\eps^2)}}. As a byproduct of our approach, we show that for any linear threshold function $f$ over $\{-1,1\}^n$, there is a linear threshold function $f'$ which is \eps-close to $f$ and has all weights that are integers at most \sqrt{n} \cdot (1/\eps)^{O(\log^2(1/\eps))}. This significantly improves the best previous result of Diakonikolas and Servedio which gave a \poly(n) \cdot 2^{\tilde{O}(1/\eps^{2/3})} weight bound, and is close to the known lower bound of $\max\{\sqrt{n},$ (1/\eps)^{\Omega(\log \log (1/\eps))}\} (Goldberg, Servedio). Our techniques also yield improved algorithms for related problems in learning theory

Optimalisatie van vraagarticulatie en kennisuitwisseling over de effecten van inundatie en waterberging (P2052) : eindrapport voor consortiumpartijen

Doel van dit project was om via een participatief proces de relevante kennisvragen te identificeren die in de praktijk spelen bij waterberging en deze te confronteren met specialistische kennis en met de praktijkervaring over bodem en water. Het proces werd uitgevoerd met partijen in een of meerdere stroomgebieden (Hoog-Nederland en Laag-Nederland) met alle betrokken partijen die met kennisvragen zitten t.a.v. inundatie-effecte