A novel feature-based approach to characterize algorithm performance for the traveling salesperson problem

Meta-heuristics are frequently used to tackle NP-hard combinatorial optimization problems. With this paper we contribute to the understanding of the success of 2-opt based local search algorithms for solving the traveling salesperson problem (TSP). Although 2-opt is widely used in practice, it is hard to understand its success from a theoretical perspective. We take a statistical approach and examine the features of TSP instances that make the problem either hard or easy to solve. As a measure of problem difficulty for 2-opt we use the approximation ratio that it achieves on a given instance. Our investigations point out important features that make TSP instances hard or easy to be approximated by 2-opt.     

Disambiguating Visual Motion by Form-Motion Interaction—a Computational Model

The neural mechanisms underlying motion segregation and integration still remain unclear to a large extent. Local motion estimates often are ambiguous in the lack of form features, such as corners or junctions. Furthermore, even in the presence of such features, local motion estimates may be wrong if they were generated near occlusions or from transparent objects. Here, a neural model of visual motion processing is presented that involves early stages of the cortical dorsal and ventral pathways. We investigate the computational mechanisms of V1-MT feedforward and feedback processing in the perception of coherent shape motion. In particular, we demonstrate how modulatory MT-V1 feedback helps to stabilize localized feature signals at, e.g. corners, and to disambiguate initial flow estimates that signal ambiguous movement due to the aperture problem for single shapes. In cluttered environments with multiple moving objects partial occlusions may occur which, in turn, generate erroneous motion signals at points of overlapping form. Intrinsic-extrinsic region boundaries are indicated by local T-junctions of possibly any orientation and spatial configuration. Such junctions generate strong localized feature tracking signals that inject erroneous motion directions into the integration process. We describe a simple local mechanism of excitatory form-motion interaction that modifies spurious motion cues at T-junctions. In concert with local competitive-cooperative mechanisms of the motion pathway the motion signals are subsequently segregated into coherent representations of moving shapes. Computer simulations demonstrate the competency of the proposed neural model.     

When to use bit-wise neutrality

Representation techniques are important issues when designing successful evolutionary algorithms. Within this field the use of neutrality plays an important role. We examine the use of bit-wise neutrality introduced by Poli and López (2007) from a theoretical point of view and show that this mechanism only enhances mutation-based evolutionary algorithms if not the same number of genotypic bits for each phenotypic bit is used. Using different numbers of genotypic bits for the bits in the phenome we point out by rigorous runtime analyses that it may reduce the optimization time significantly.     

Modernisierung des Datenschutzes: Herausforderungen durch die Technik

Auf Einladung des Innenausschusses des Deutschen Bundestages fand am 5. M?rz 2007 eine ?ffentliche Anh?rung zum Thema der Modernisierung des Datenschutzes statt. Gegenstand waren Entschlie?ungsantr?ge der Fraktionen der FDP sowie von Bündnis90/Die Grünen zum Datenschutzaudit¹ sowie zum Scoring und zu Auskunftspflichten bei Datenschutzpannen.² Eingeladen war auch der Landesbeauftragte für den Datenschutz Mecklenburg Vorpommern, dessen schriftliche Analyse wir mit den Schwerpunkten der Herausforderungen durch die Technik und des Datenschutzaudits abdrucken.     

On the algebraic identifiability of finite impulse response channels driven by linearly precoded signals

It is common in wireless communications to perform some form of linear precoding operation on the source signal prior to transmission over a channel. Although the traditional reason for precoding is to improve the performance of the communication system, this paper draws attention to the fact that the receiver can identify the impulse response of the channel without any prior knowledge of the transmitted signal simply by solving a system of polynomial equations. Since different precoders lead to different systems of equations, this paper addresses the fundamental issue of determining which classes of linear precoders lead to a system of equations having a unique solution. In doing so, basic properties of polynomial equations which are useful for studying other identifiability issues commonly encountered in engineering and the applied sciences are presented.     

TimeLapseAnalyzer: multi-target analysis for live-cell imaging and time-lapse microscopy

The direct observation of cells over time using time-lapse microscopy can provide deep insights into many important biological processes. Reliable analyses of motility, proliferation, invasive potential or mortality of cells are essential to many studies involving live cell imaging and can aid in biomarker discovery and diagnostic decisions. Given the vast amount of image- and time-series data produced by modern microscopes, automated analysis is a key feature to capitalize the potential of time-lapse imaging devices. To provide fast and reproducible analyses of multiple aspects of cell behaviour, we developed TimeLapseAnalyzer. Apart from general purpose image enhancements and segmentation procedures, this extensible, self-contained, modular cross-platform package provides dedicated modalities for fast and reliable analysis of multi-target cell tracking, scratch wound healing analysis, cell counting and tube formation analysis in high throughput screening of live-cell experiments. TimeLapseAnalyzer is freely available (MATLAB, Open Source) at http://www.informatik.uni-ulm.de/ni/mitarbeiter/HKestler/tla.     

Simulating protection rackets: a case study of the Sicilian Mafia

Protection racketeering groups are powerful, deeply entrenched in multiple societies across the globe, and they harm the societies and economies in which they operate in multiple ways. These reasons make their dynamics important to understand and an objective of both scientific and application-oriented interest. Legal and social norm-based approaches arguably play significant roles in influencing protection racket dynamics. We propose an agent-based simulation model, the Palermo Scenario, to enrich our understanding of these influences and to test the effect of different policies on protection racket dynamics. Our model integrates the legal and the social norm-based approaches and uses a complex normative agent architecture that enables the analysis of both agents’ behaviours and mental normative representations driving behaviour. We demonstrate the usefulness of the model and the benefits of using this complex normative architecture through a case study of the Sicilian Mafia.