Alternating simulation and IOCO

We propose a symbolic framework called guarded labeled assignment systems or GLASs and show how GLASs can be used as a foundation for symbolic analysis of various aspects of formal specification languages. We define a notion of i/o-refinement over GLASs as an alternating simulation relation and provide formal proofs that relate i/o-refinement to ioco. We show that non-i/o-refinement reduces to a reachability problem and provide a translation from bounded non-i/o-refinement or bounded non-ioco to checking first-order assertions.     

Fast sequence segmentation using log-linear models

Sequence segmentation is a well-studied problem, where given a sequence of elements, an integer K, and some measure of homogeneity, the task is to split the sequence into K contiguous segments that are maximally homogeneous. A classic approach to find the optimal solution is by using a dynamic program. Unfortunately, the execution time of this program is quadratic with respect to the length of the input sequence. This makes the algorithm slow for a sequence of non-trivial length. In this paper we study segmentations whose measure of goodness is based on log-linear models, a rich family that contains many of the standard distributions. We present a theoretical result allowing us to prune many suboptimal segmentations. Using this result, we modify the standard dynamic program for 1D log-linear models, and by doing so reduce the computational time. We demonstrate empirically, that this approach can significantly reduce the computational burden of finding the optimal segmentation.     

Die oxidation von butadienstyrolkautschuk und daraus gewonnenem vulkanisat mit salpetersäure

The interaction between butadiene-styrene-rubber Bulex-1500 (a commercial product containing 25 to 30% of styrene links) and a vulcanisate based on it and nitric acid was studied. It was established that a measurable yield of several reaction products may be obtained: Butadiene-styrene-rubber yields oxidized rubber, polyfunctional oligomer, and oxalic acid; the vulcanisate yields oxidized vulcanisate, polyfunctional oligomer, and oxalic acid. The effect of the conditions of oxidation (particle size, time, temperature) on the yield of the reaction products was studied. The conditions needed to obtain optimum yield of a given reaction product were determined. The influence of the styrene links from the molecule of butadienestyrene-rubber on the yield was studied and a comparison with butadiene rubber was made. It was established that oxalic acid is a product of a number of oxidation-decomposition processes in nitric acid medium, and a scheme of its formation was suggested. It was proved that oxidation-decomposition processes and nitration occur simultaneously. It was suggested that the interaction of nitric acid with butadienestyrene-rubber and its vulcanisate may be used to utilize waste products obtained from them.     

Logic Program Synthesis as Problem Reduction Using Combining Forms

This paper presents an approach to inductive synthesis of logic programs from examples using problem decomposition and problem reduction principles. This is in contrast to the prevailing logic program induction paradigm, which relies on generalization of programs from examples. The problem reduction is accomplished as a constrained top-down search process, which eventually is to reach trivial problems.Our induction scheme applies a distinguished logic programming language in which programs are combined from elementary predicates by means of combinators conceived of as problem reduction operators including list recursion forms. The operator form admits inductive synthesis as a top-down piecewise composition of semantically meaningful program elements according to the compositional semantics principle and with appeals neither to special generalization mechanisms nor to alternative forms of resolution and unification, or predicate invention.The search space is reduced by subjecting the induction process to various constraints concerning syntactical form, modes, data types, and computational resources. This is illustrated in the paper with well-modedness constraints with the aim of synthesising well-moded, procedurally acceptable programs.Preliminary experiments with the proposed induction method lead us to tentatively conclude that the presented approach forms a viable alternative to the prevailing inductive logic programming methods applying generalization from examples.     

Overlapping community detection in labeled graphs

We present a new approach for the problem of finding overlapping communities in graphs and social networks. Our approach consists of a novel problem definition and three accompanying algorithms. We are particularly interested in graphs that have labels on their vertices, although our methods are also applicable to graphs with no labels. Our goal is to find k communities so that the total edge density over all k communities is maximized. In the case of labeled graphs, we require that each community is succinctly described by a set of labels. This requirement provides a better understanding for the discovered communities. The proposed problem formulation leads to the discovery of vertex-overlapping and dense communities that cover as many graph edges as possible. We capture these properties with a simple objective function, which we solve by adapting efficient approximation algorithms for the generalized maximum-coverage problem and the densest-subgraph problem. Our proposed algorithm is a generic greedy scheme. We experiment with three variants of the scheme, obtained by varying the greedy step of finding a dense subgraph. We validate our algorithms by comparing with other state-of-the-art community-detection methods on a variety of performance measures. Our experiments confirm that our algorithms achieve results of high quality in terms of the reported measures, and are practical in terms of performance.