Curvature continuous offset approximation based on circle approximation using quadratic Bézier biarcs

We present a method for G² end-point interpolation of offset curves using rational Bézier curves. The method is based on a G² end-point interpolation of circular arcs using quadratic Bézier biarcs. We also prove the invariance of the Hausdorff distance between two compatible curves under convolution. Using this result, we obtain the exact Hausdorff distance between an offset curve and its approximation by our method. We present the approximation algorithm and give numerical examples.     

Recommendations for mass spectrometry data quality metrics for open access data (corollary to the Amsterdam principles)

Policies supporting the rapid and open sharing of proteomic data are being implemented by the leading journals in the field. The proteomics community is taking steps to ensure that data are made publicly accessible and are of high quality, a challenging task that requires the development and deployment of methods for measuring and documenting data quality metrics. On September 18, 2010, the U.S. National Cancer Institute (NCI) convened the "International Workshop on Proteomic Data Quality Metrics" in Sydney, Australia, to identify and address issues facing the development and use of such methods for open access proteomics data. The stakeholders at the workshop enumerated the key principles underlying a framework for data quality assessment in mass spectrometry data that will meet the needs of the research community, journals, funding agencies, and data repositories. Attendees discussed and agreed up on two primary needs for the wide use of quality metrics: (i) an evolving list of comprehensive quality metrics and (ii) standards accompanied by software analytics. Attendees stressed the importance of increased education and training programs to promote reliable protocols in proteomics. This workshop report explores the historic precedents, key discussions, and necessary next steps to enhance the quality of open access data. By agreement, this article is published simultaneously in Proteomics, Proteomics Clinical Applications, Journal of Proteome Research, and Molecular and Cellular Proteomics, as a public service to the research community. The peer review process was a coordinated effort conducted by a panel of referees selected by the journals.     

A multiple-vendor single-buyer integrated inventory model with a variable number of vendors

Supply chain management is concerned with the coordination of material and information flows in multi-stage production systems. A closer look at the literature reveals that previous research on the coordination of multi-stage production systems has predominantly focused on the sales side of the supply chain, whereas problems that arise on the supply side have often been neglected. This article closes this gap by studying the coordination of a supplier network in an integrated inventory model. Specifically, we consider a buyer sourcing a product from heterogeneous suppliers and tackle both the supplier selection and lot size decision with the objective to minimise total system costs. First, we provide mathematical formulations for the problem under study, and then suggest a two-stage solution procedure to derive a solution. Numerical studies indicate that our solution procedure reduces the total number of supplier combinations that have to be tested for optimality, and that it may support initiatives which aim on increasing the efficiency of the supply chain as a heuristic planning tool.     

A variational approach to vesicle membrane reconstruction from fluorescence imaging

Biological applications like vesicle membrane analysis involve the precise segmentation of 3D structures in noisy volumetric data, obtained by techniques like magnetic resonance imaging (MRI) or laser scanning microscopy (LSM). Dealing with such data is a challenging task and requires robust and accurate segmentation methods. In this article, we propose a novel energy model for 3D segmentation fusing various cues like regional intensity subdivision, edge alignment and orientation information. The uniqueness of the approach consists in the definition of a new anisotropic regularizer, which accounts for the unbalanced slicing of the measured volume data, and the generalization of an efficient numerical scheme for solving the arising minimization problem, based on linearization and fixed-point iteration. We show how the proposed energy model can be optimized globally by making use of recent continuous convex relaxation techniques. The accuracy and robustness of the presented approach are demonstrated by evaluating it on multiple real data sets and comparing it to alternative segmentation methods based on level sets. Although the proposed model is designed with focus on the particular application at hand, it is general enough to be applied to a variety of different segmentation tasks.     

Clusteranalyse von Smart-Meter-Daten

The introduction of smart meter technology is a great challenge for the German energy industry. It requires not only large investments in the communication and metering infrastructure, but also a redesign of traditional business processes. The newly incurring costs cannot be fully passed on to the end customers. One option to counterbalance these expenses is to exploit the newly generated smart metering data for the creation of new services and improved processes. For instance, performing a cluster analysis of smart metering data focused on the customers?? time-based consumption behavior allows for a detailed customer segmentation. In the article we present a cluster analysis performed on real-world consumption data from a smart meter project conducted by a German regional utilities company. We show how to integrate a cluster analysis approach into a business intelligence environment and evaluate this artifact as defined by design science. We discuss the results of the cluster analysis and highlight options to apply them to segment-specific tariff design.     

Guiding the evolution of product-line configurations

Software and Systems Modeling - A product line is an approach for systematically managing configuration options of customizable systems, usually by means of features. Products are generated for...     

Modeling discrete event systems with state-dependent deterministic service times

In this paper extensions to the numerical solution method of deterministic and stochastic Petri nets (DSPNs) are introduced in order to cope with deterministic transitions with marking-dependent firing delays. The basic idea lies in scaling each row of the generator matrix of the Markov chain subordinated to a deterministic transition with marking-dependent firing delay by the delay value corresponding to this marking. Computational formulas of this solution method are implemented in the software package DSPNexpress which completely automates the solution process of DSPNs. The extended modeling power of DSPNs is illustrated by a single-server queuing system with Poisson arrivals, degradable deterministic service requirements, and finite capacity. Christoph Lindemann was supported by the Federal Ministry for Research and Technology of Germany (BMFT) and by the German Research Council (DFG) under grants ITR9003 and Ho 1257/2-1, respectively. Reinhard German was supported by Siemens Corporate Research and Development and by a doctoral fellowship from the German Research Council (DFG) under grant Ho 1257/1-2.     

Subcomplete generalizations of graph isomorphism

We present eight group-theoretic problems in NP one of which is a reformulation of graph isomorphism. We give technical evidence that none of the problems is NP-complete, and give polynomial time reductions among the problems. There is a good possibility that seven of these problems are harder than graph isomorphism (relative to polynomial time reduction), so that they might be examples of natural problems of intermediate difficulty, situated properly between the class of NP-complete problems and the class P of problems decidable in deterministic polynomial time. Because of strong structural similarity, two of the apparently harder problems can be interpreted as generalized isomorphism and generalized automorphism, respectively. Whether these problems ultimately prove to be harder than graph isomorphism seems to depend, in part, on the open problem whether every permutation group of degree n arises as the automorphism group of a combinatorial structure of size polynomial in n. Finally, we give an O(n² · k) algorithm for constructing the centralizer of a permutation group of degree n presented by a generating set of k permutations. Note that we may assume that k is O(n · log n), without loss of generality. This problem is a special case of one of the harder group-theoretic problems. From the method of constructing the centralizer, we recover results about the group-theoretic structure of the centralizer. Furthermore, applying our algorithm for intersecting with a normalizing permutation group, we show how to find the center of a permutation group of degree n in O(n⁶) steps, having constructed the centralizer of the group first.