696
Online searching with an autonomous robot
We discuss online strategies for visibility-based searching for an object hidden behind a corner, using Kurt3D, a real autonomous mobile robot. This task is closely related to a number of well-studied problems. Our robot uses a three-dimensional laser scanner in a stop, scan, plan, go fashion for building a virtual three-dimensional environment. Besides planning trajectories and avoiding obstacles, Kurt3D is capable of identifying objects like a chair. We derive a practically useful and asymptotically optimal strategy that guarantees a competitive ratio of 2, which differs remarkably from the well-studied scenario without the need of stopping for surveying the environment. Our strategy is used by Kurt3D, documented in a separate video.
1585010
Exact and Approximation Algorithms for Computing the Dilation Spectrum of Paths, Trees, and Cycles
Let G be a graph embedded in Euclidean space. For any two vertices of G their dilation denotes the length of a shortest connecting path in G, divided by their Euclidean distance. In this paper we study the spectrum of the dilation, over all pairs of vertices of G. For paths, trees, and cycles in 2D we present O(n3/2+e) randomized algorithms that compute, for a given value κ ≥ 1, the exact number of vertex pairs of dilation > κ. Then we present deterministic algorithms that approximate the number of vertex pairs of dilation > κ up to an 1+η factor. They run in time O(n log2n) for chains and cycles, and in time O(n log3n) for trees, in any constant dimension.
6552276
On the geometric dilation of closed curves, graphs, and point sets
Let G be an embedded planar graph whose edges are curves. The detour between two points p and q (on edges or vertices) of G is the ratio between the length of a shortest path connecting p and q in G and their Euclidean distance |pq|. The maximum detour over all pairs of points is called the geometric dilation δ(G). 
 
Ebbers-Baumann, Grune and Klein have shown that every finite point set is contained in a planar graph whose geometric dilation is at most 1.678, and some point sets require graphs with dilation δ ≥ π/2 ≈ 1.57. They conjectured that the lower bound is not tight. 
 
We use new ideas like the halving pair transformation, a disk packing result and arguments from convex geometry, to prove this conjecture. The lower bound is improved to (1 + 10-11) π/2. The proof relies on halving pairs, pairs of points dividing a given closed curve C in two parts of equal length, and their minimum and maximum distances h and H. Additionally, we analyze curves of constant halving distance (h = H), examine the relation of h to other geometric quantities and prove some new dilation bounds.
18735413
Service and commodity based electronic intermediaries: a comparative analysis
The theoretical literature concerning supply chain intermediation is surveyed to develop a framework of five intermediary states. Data collected on 134 electronic intermediaries are employed to explore correlations between intermediation states, growth strategies and firm profitability, in a sample representing both service based and commodity based intermediaries. The study finds a positive relationship between more capital intensive states of intermediation and profitability. In addition, we find a higher use of acquisitions as growth mechanisms in service based intermediaries, and a greater use of joint ventures as growth mechanisms within commodity based portals.
8529966
Graphische Datenverarbeitung
2107176
A Hybrid Web-Based Toolkit for Human Modeling
Modern web-based Scientific Visualization applications try to overcome common limitations imposed by limited internet bandwidth, server bottlenecks or network latency. A further aspect is the desire to gain platform independence by solely using instruments which are platform independent by conception: the programming language Java, the Virtual Reality Modeling Language (VRML), or the 3D API Java3D.We present a prototype of a hybrid web-based Scientific Visualization system which makes use of the increasing computational power of modern desktop workstations and personal computers on the client side, and the superior performance provided by a powerful machine on the server side. In order to achieve high interaction rates and to balance computational load the user can dynamically assign selected tasks to his client or to the server.Within the scientific field of human modeling we have implemented a hybrid web-based toolkit for the modeling of human muscles and skin. Our application allows the on-line generation and manipulation of three-dimensional implicit muscle models in a heterogeneous network and it offers various parameters to adjust computation and response time versus rendering quality.