Robust Segmentation of Voxel Shapes using Medial Surfaces

We present a new patch-type segmentation method for 3D voxel shapes based on the medial surface, also called surface skeleton. The boundaries of the simplified fore- and background skeletons map one-to-one to increasingly fuzzy, soft convex, respectively concave, edges of the shape. Using this property, we build a method for segmentation of 3D shapes which has several desirable properties. Our method robustly segments both noisy shapes and shapes with soft edges which vanish over low-curvature regions. As the segmentation is based on the skeleton, it reflects the symmetry of the input shape. Finally, multiscale segmentations can be obtained by varying the simplification level of the skeleton. We present a voxel-based implementation of our approach and demonstrate it on several examples.

Patch-type Segmentation of Voxel Shapes using Simplified Surface Skeletons

We present a new method for decomposing a 3D voxel shape into disjoint segments using the shape’s simplified surface-skeleton. The surface skeleton of a shape consists of 2D manifolds inside its volume. Each skeleton point has a maximally inscribed ball that touches the boundary in at least two contact points. A key observation is that the boundaries of the simplified fore- and background skeletons map one-to-one to increasingly fuzzy, soft convex, respectively concave, edges of the shape. Using this property, we build a method for segmentation of 3D shapes which has several desirable properties. Our method segments both noisy shapes and shapes with soft edges which vanish over low-curvature regions. Multiscale segmentations can be obtained by varying the simplification level of the skeleton. We present a voxel-based implementation of our approach and illustrate it on several realistic examples.

Polygyny and HIV in Malawi

We review the relationship between polygyny and HIV and identify a positive individual-level correlation, and a negative ecological correlation. We subsequently examine two mechanisms that contribute to the individual-level correlation. First, we find that men in polygynous marriages have more extramarital sex than men in monogamous unions (both in terms of self reports and in terms of spousal reports of the suspicion of adultery). Second, we find evidence of adverse selection of HIV positive women into polygynous unions via an investigation of the relationship between marriage order and polygyny status. We conclude with reflections about possible explanations for the distinct individual and ecological correlations.AIDS/HIV, Malawi, marriage, polygyny, sexual behavior, Sub-Saharan Africa, widowhood

Security risk assessment and protection in the chemical and process industry

This article describes a security risk assessment and protection methodology that was developed for use in the chemical- and process industry in Belgium. The approach of the method follows a risk-based approach that follows desing principles for chemical safety. That approach is beneficial for workers in the chemical industry because they recognize the steps in this model from familiar safety models .The model combines the rings-of-protection approach with generic security practices including: management and procedures, security technology (e.g. CCTV, fences, and access control), and human interactions (pro-active as well as re-active). The method is illustrated in a case-study where a practical protection plan was developed for an existing chemical company. This chapter demonstrates that the method is useful for similar chemical- and process industrial activities far beyond the Belgian borders, as well as for cross-industrial security protection. This chapter offers an insight into how the chemical sector protects itself on the one hand, and an insight into how security risk management can be practiced on the other hand

Analysis of Boolean Equation Systems through Structure Graphs

We analyse the problem of solving Boolean equation systems through the use of structure graphs. The latter are obtained through an elegant set of Plotkin-style deduction rules. Our main contribution is that we show that equation systems with bisimilar structure graphs have the same solution. We show that our work conservatively extends earlier work, conducted by Keiren and Willemse, in which dependency graphs were used to analyse a subclass of Boolean equation systems, viz., equation systems in standard recursive form. We illustrate our approach by a small example, demonstrating the effect of simplifying an equation system through minimisation of its structure graph

Structural Analysis of Boolean Equation Systems

We analyse the problem of solving Boolean equation systems through the use of structure graphs. The latter are obtained through an elegant set of Plotkin-style deduction rules. Our main contribution is that we show that equation systems with bisimilar structure graphs have the same solution. We show that our work conservatively extends earlier work, conducted by Keiren and Willemse, in which dependency graphs were used to analyse a subclass of Boolean equation systems, viz., equation systems in standard recursive form. We illustrate our approach by a small example, demonstrating the effect of simplifying an equation system through minimisation of its structure graph

Design and Analysis of Computer Center Management System

S příchodem internetu se začínaly objevovat nové typy webových aplikací a systémů, které byly vytvořené na standardních technologiích, a proto jsou dostupné na většině uživatelských počítačů. Bez těchto systémů si v dnešní době nedokážeme svět ani představit. Mezi uživateli a vývojáři si získali velkou oblibu a jsou vyvíjeny jak pro internetové aplikace, tak i pro firemní intranetové aplikace. Vzhledem k příchodu objektově orientovaného návrhu a návrhových vzorů je důležité si tyto moderní vývojové nástroje otestovat na vývoji informačního systému. Právě touto problematikou se zabývá tato práce. Vyvíjím informační systém pro správu počítačového centra, který slouží k lepší přehlednosti a správě firem.With arrival of the internet new types of easily accesible web applications and systems developed on standard technologies have begun to emerge. Nowadays we cannot even imagine the world without these systems. They have garnished massive popularity among users and developers while being created for the internet applications as well as corporate intranet applications. Considering an emergence of object oriented desing and design patterns it is important to test these modern tools on developement of an information system. This thesis acts just this problem. I develope computer center managment system, which serves for better management of firms.

Tree rules in probabilistic transition system specifications with negative and quantitative premises

Probabilistic transition system specifications (PTSSs) in the ntmufnu/ntmuxnu format provide structural operational semantics for Segala-type systems that exhibit both probabilistic and nondeterministic behavior and guarantee that isimilarity is a congruence.Similar to the nondeterministic case of rule format tyft/tyxt, we show that the well-foundedness requirement is unnecessary in the probabilistic setting. To achieve this, we first define an extended version of the ntmufnu/ntmuxnu format in which quantitative premises and conclusions include nested convex combinations of distributions. This format also guarantees that bisimilarity is a congruence. Then, for a given (possibly non-well-founded) PTSS in the new format, we construct an equivalent well-founded transition system consisting of only rules of the simpler (well-founded) probabilistic ntree format. Furthermore, we develop a proof-theoretic notion for these PTSSs that coincides with the existing stratification-based meaning in case the PTSS is stratifiable. This continues the line of research lifting structural operational semantic results from the nondeterministic setting to systems with both probabilistic and nondeterministic behavior.Comment: In Proceedings EXPRESS/SOS 2012, arXiv:1208.244