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We develop a new k-means clustering algorithm for data streams, which we call StreamKM++. Our algorithm computes a small weighted sample of the data stream and solves the problem on the sample using the k-means++ algorithm [1]. To compute the small sample, we propose two new techniques. First, we use a non-uniform sampling approach similar to the k-means++(More)
We develop a new <it>k</it>-means clustering algorithm for data streams of points from a Euclidean space. We call this algorithm StreamKM++. Our algorithm computes a small weighted sample of the data stream and solves the problem on the sample using the <it>k</it>-means++ algorithm of Arthur and Vassilvitskii (SODA '07). To compute(More)
Gathering n mobile robots in one single point in the Euclidean plane is a widely studied problem from the area of robot formation problems. Classically, the robots are assumed to have no physical extent, and they are able to share a position with other robots. We drop these assumptions and investigate a similar problem for robots with (a spherical) extent:(More)
We make use of self-adaptation in a Differential Evolution algorithm and of the asynchronous island model to design a complex interplanetary trajectory touring the Galilean Jupiter moons (Io, Europa, Ganymede and Callisto) using the multiple gravity assist technique. Such a problem was recently the subject of an international competition organized by the(More)
This work presents an implementation of the asynchronous island model suitable for multi-objective evolutionary optimization on heterogeneous and large-scale computing platforms. The migration of individuals is regulated by the crowding comparison operator applied to the originating population during selection and to the receiving population augmented by(More)
A fast computation of the hypervolume has become a crucial component for the quality assessment and the performance of modern multi-objective evolutionary optimization algorithms. Albeit recent improvements , exact computation becomes quickly infeasible if the optimization problems scale in their number of objectives or size. To overcome this issue, we(More)
Psychotherapy research results are viewed under the aspect of relevance and irrelevance for psychotherapeutic practice. The difficulties to develop effective research designs for children, and adolescents are described, and possible research perspectives are developed for this complex domain. Especially the amount of variables in combination with(More)
We consider the interplanetary trajectory design problem posed by the 8th edition of the Global Trajectory Optimization Competition and present the end-to-end strategy developed by the team ACT-ISAS (a collaboration between the European Space Agency's Advanced Concepts Team and JAXA's Institute of Space and Astronautical Science). The resulting(More)
In the face of changes that characterise adolescence, a number of youth experience ill-being, as part of a normal developmental process. For some of them, however, this ill-being may represent early signs of a psychopathological process. Regarding depression and psychosis, such early signs are non-specific, which complicates and delays treatment. In(More)