Asano et al. [JoCG 2011] proposed an open problem of computing the minimum enclosing circle of a set of n points in R2 given in a read-only array in sub-quadratic time. We show that Megiddo’s prune and search algorithm for computing the minimum radius circle enclosing the given points can be tailored to work in a read-only environment in O(n1+ ) time using O(logn) extra space, where is a positi...

In this paper we present a decremental algorithm for maintaining of minimum rank hyperpaths in a directed hypergraph from a source vertex s to all other vertices, under the assumption of unit hyperedge weights. Given a hypergraph H with n vertices and m hyperedges, the total time needed to perform a sequence of m hyperedge deletions is O(n Size(H)), where Size(H) is the sum of the sizes of the ...

We give algorithms for the directed minimum odd or even cut problem and certain generalizations. Our algorithms improve on the previous best ones of Goemans and Ramakrishnan by a factor of O(n) (here n is the size of the ground vertex set). Our improvements apply among others to the minimum directed Todd or T-even cut and to the directed minimum Steiner cut problems. The (slightly more general)...

Deterministic fully dynamic graph algorithms are presented for con-nectivity and minimum spanning forest. For connectivity, starting with no edges, the amortized cost for maintaining a spanning forest is O(log 2 n) per update, i.e. per edge insertion or deletion. Deciding connectivity between any two given vertices is done in O(log n= log log n) time. This matches the previous best randomized b...

Let N be a single-source single-sink ow network with n nodes, m arcs, and positive arc costs. We present a pseudo-polynomial algorithm that computes a maximum ow of minimum cost for N in time O(3=4 m p log n), where is the cost of the ow. This improves upon previously known methods for networks where the minimum cost of the ow is small. We also show an application of our ow algorithm to a well-...

We present a new channel routing algorithm in the knock-knee mode that produces for dense problems area-optimal layouts with minimum total wire length and O(n) bends (n number of nets), where the total number of bends is at most d ? 2 (d density) more than the minimum. The running time is O(n). It thus improves the algorithm in 3] that determines area-optimal layouts with minimum total wire len...

The minimum feature size of a planar straight-line graph is the minimum distance between a vertex and a nonincident edge. When a polygon is partitioned into a mesh, the degradation is the ratio of original to final minimum feature size. We show that some planar straight-line graphs cannot be triangulated with constant degradation, even with an unbounded number of Steiner points and triangles. T...

We study the maximum flow problem in an undirected planar network with both edge and vertex capacities (EVC-network). A previous study reduces the minimum cut problem in an undirected planar EVC-network to the minimum edge-cut problem in another planar network with edge capacity only (EC-network), thus the minimum-cut or the maximum flow value can be computed in O(n log n) time. Based on this r...

A new optimization algorithm, the guided simulated annealing method, for use in X-ray crystallographic studies is presented. In the traditional simulated annealing method, the search for the global minimum of a cost function is only determined by the ratio of energy change to the temperature. This method designs a new quality function to guide the search for a minimum. Using a multiresolution p...

In this letter, we summarize initial results showing how solar cycle variations of the thermosphere modify the composition and intensity of ion upflows at high geomagnetic latitudes. Using an improved version of the one-dimensional hydrodynamic polar wind model developed by Gombosi et al. (1985), we obtain H + and O + vertical flow profiles using different thermospheric states corresponding to ...