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Constant Factor (constant + factor)
Selected AbstractsViking and native: re,thinking identity in the DanelawEARLY MEDIEVAL EUROPE, Issue 1 2002D.M. Hadley This paper addresses the impact of the Scandinavian settlements in England in the ninth and tenth centuries, and the role that ethnic identity and affiliation played in the society of the so,called Danelaw. It is argued that ethnic identity was not a constant factor, but one that only became relevant, at least in the evidence available to us, at certain times. It is suggested that the key to understanding expressions of ethnicity lies in the absorption of new ruling elites in northern and eastern England, and in subsequent political manoeuvring, rather than in the scale of the Scandinavian settlement. Indeed, the scale of the settlement does not easily explain most of our evidence, with the exception of some of the linguistic data. This paper stresses the importance of discussing the Scandinavian settlements not simply by reference to ethnic factors, but within the social and political context of early medieval society. [source] Efficient Delaunay-based localized routing for wireless sensor networksINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 7 2007Yu Wang Abstract Consider a wireless sensor network consisting of n wireless sensors randomly distributed in a two-dimensional plane. In this paper, we show that with high probability we can locally find a path for any pair of sensors such that the length of the path is no more than a constant factor of the minimum. By assuming each sensor knows its position, our new routing method decides where to forward the message purely based on the position of current node, its neighbours, and the positions of the source and the target. Our method is based on a novel structure called localized Delaunay triangulation and a geometric routing method that guarantees that the distance travelled by the packets is no more than a small constant factor of the minimum when the Delaunay triangulation of sensor nodes are known. Our experiments show that the delivery rates of existing localized routing protocols are increased when localized Delaunay triangulation is used instead of several previously proposed topologies, and our localized routing protocol based on Delaunay triangulation works well in practice. We also conducted extensive simulations of another localized routing protocol, face routing. The path found by this protocol is also reasonably good compared with previous one although it cannot guarantee a constant approximation on the length of the path travelled theoretically. Copyright © 2006 John Wiley & Sons, Ltd. [source] An improved direct labeling method for the max,flow min,cut computation in large hypergraphs and applicationsINTERNATIONAL TRANSACTIONS IN OPERATIONAL RESEARCH, Issue 1 2003Joachim Pistorius Algorithms described so far to solve the maximum flow problem on hypergraphs first necessitate the transformation of these hypergraphs into directed graphs. The resulting maximum flow problem is then solved by standard algorithms. This paper describes a new method that solves the maximum flow problem directly on hypergraphs, leading to both reduced run time and lower memory requirements. We compare our approach with a state,of,the,art algorithm that uses a transformation of the hypergraph into a directed graph and an augmenting path algorithm to compute the maximum flow on this directed graph: the run,time complexity as well as the memory space complexity are reduced by a constant factor. Experimental results on large hypergraphs from VLSI applications show that the run time is reduced, on average, by a factor approximately 2, while memory occupation is reduced, on average, by a factor of 10. This improvement is particularly interesting for very large instances, to be solved in practical applications. [source] A linear time algorithm for the reverse 1-median problem on a cycleNETWORKS: AN INTERNATIONAL JOURNAL, Issue 1 2006Rainer E. Burkard Abstract This article deals with the reverse 1-median problem on graphs with positive vertex weights. The problem is proved to be strongly NP -hard even in the case of bipartite graphs and not approximable within a constant factor (unless P = NP). Furthermore, a linear time algorithm for the reverse 1-median problem on a cycle with linear cost functions (RMC) is developed. It is also shown that there exists an integral optimal solution of RMC if the input data are integral. © 2006 Wiley Periodicals, Inc. NETWORKS, Vol. 48(1), 16-23 2006 [source] The ring grooming problemNETWORKS: AN INTERNATIONAL JOURNAL, Issue 3 2004Timothy Y. Chow Abstract The problem of minimizing the number of bidirectional SONET rings required to support a given traffic demand has been studied by several researchers. Here we study the related ring-grooming problem of minimizing the number of add/drop locations instead of the number of rings; in a number of situations this is a better approximation to the true equipment cost. Our main result is a new lower bound for the case of uniform traffic. This allows us to prove that a certain simple algorithm for uniform traffic is, in fact, a constant-factor approximation algorithm, and it also demonstrates that known lower bounds for the general problem,in particular, the linear programming relaxation,are not within a constant factor of the optimum. We also show that our results for uniform traffic extend readily to the more practically important case of quasi-uniform traffic. Finally, we show that if the number of nodes on the ring is fixed, then ring grooming is solvable in polynomial time; however, whether ring grooming is fixed-parameter tractable is still an open question. © 2004 Wiley Periodicals, Inc. NETWORKS, Vol. 44(3), 194,202 2004 [source] Zero dimensional exciton-polaritonsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 10 2006A. Baas The cover picture from the article [1] shows, in the left parts of the three diagrams, the measured photoluminescence intensity as a function of energy and emission angle for a 3 ,m (left diagram), 9 ,m (middle diagram) and 19 ,m-diameter quasi-circular mesa (right diagram). The white lines are the energy dispersions of 2D polariton modes. For clarity, intensities above 1485 meV have been multiplied by a constant factor, as indicated. The right parts of the diagrams contain intensity plots of the simulated polariton spectral density for cylindrical mesas of the same diameters, yielding very good quantitative agreement of the 0D polariton states in the circular mesas. This confirms the coexistence of 0D and 2D microcavity polaritons in these semiconductor structures. This paper is an invited presentation from the 8th International Workshop on Nonlinear Optics and Excitation Kinetics. Further articles from NOEKS 8 are published in phys. stat. sol. (c) 3, No. 7 (2006). [source] Quantitative evaluation of shunts in solar cells by lock-in thermographyPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 8 2003O. Breitenstein Abstract Infrared lock-in thermography allows to image shunts very sensitively in all kinds of solar cells and also to measure dark currents flowing in certain regions of the cell quantitatively. After a summary of the physical basis of lock-in thermography and its practical realization, four types of quantitative measurements are described: local I,V characteristics measured thermally up to a constant factor (LIVT); the quantitative measurement of the current through a local shunt; the evaluation of the influence of shunts on the efficiency of a cell as a function of the illumination intensity; and the mapping of the ideality factor n and the saturation current density J0 over the whole cell. The investigation of a typical multicrystalline solar cell shows that the shunts are predominantly responsible for deterioration of the low-light-level performance of the cell, and that variations of the injection current density related to crystal defects are predominantly determined by variation of J0 rather than of n. Copyright © 2003 John Wiley & Sons, Ltd. [source] Induced subgraphs with distinct sizesRANDOM STRUCTURES AND ALGORITHMS, Issue 1 2009Noga Alon Abstract We show that for every 0 < , < 1/2, there is an n0 = n0(,) such that if n > n0 then every n -vertex graph G of size at least and at most contains induced k -vertex subgraphs with at least 10,7k different sizes, for every . This is best possible, up to a constant factor. This is also a step toward a conjecture by Erd,s, Faudree, and Sós on the number of distinct pairs (|V (H)|,|E(H)|) of induced subgraphs of Ramsey graphs. © 2008 Wiley Periodicals, Inc. Random Struct. Alg., 2009 [source] A fast, scalable method for the parallel evaluation of distance-limited pairwise particle interactionsJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 13 2005David E. Shaw Abstract Classical molecular dynamics simulations of biological macromolecules in explicitly modeled solvent typically require the evaluation of interactions between all pairs of atoms separated by no more than some distance R, with more distant interactions handled using some less expensive method. Performing such simulations for periods on the order of a millisecond is likely to require the use of massive parallelism. The extent to which such simulations can be efficiently parallelized, however, has historically been limited by the time required for interprocessor communication. This article introduces a new method for the parallel evaluation of distance-limited pairwise particle interactions that significantly reduces the amount of data transferred between processors by comparison with traditional methods. Specifically, the amount of data transferred into and out of a given processor scales as O(R3/2p,1/2), where p is the number of processors, and with constant factors that should yield a substantial performance advantage in practice. © 2005 Wiley Periodicals, Inc. J Comput Chem 26: 1318,1328, 2005 [source] Rules, Red Tape, and Paperwork: The Archeology of State Control over MigrantsJOURNAL OF HISTORICAL SOCIOLOGY, Issue 1 2008DAVID COOK MARTÍN How and with what consequences did state control over migration become acceptable and possible after the Great War? Existing studies have centered on core countries of immigration and thus underestimate the degree to which legitimate state capacities have developed in a political field spanning sending and receiving countries with similar designs on the same international migrants. Relying on archival research, and an examination of the migratory field constituted by two quintessential emigration countries (Italy and Spain), and a traditional immigration country (Argentina) since the mid-nineteenth century, this article argues that widespread acceptance of migration control as an administrative domain rightfully under states' purview, and the development of attendant capacities have derived from legal, organizational, and administrative mechanisms crafted by state actors in response to the challenges posed by mass migration. Concretely, these countries codified migration and nationality laws, built, took over, and revamped migration-related organizations, and administratively encaged mobile people through official paperwork. The nature of efforts to evade official checks on mobility implicitly signaled the acceptance of migration control as a bona fide administrative domain. In more routine migration management, states legitimate capacity has had unforeseen intermediate- and long-term consequences such as the subjection of migrants (and, because of ius sanguinis nationality laws, sometimes their descendants) to other states' administrative influence and the generation of conditions for dual citizenship. Study findings challenge scholarship that implicitly views states as constant factors conditioning migration flows, rather than as developing institutions with historically variable regulatory abilities and legitimacy. It extends current work by specifying mechanism used by state actors to establish migration as an accepted administrative domain. [source] Area efficient layouts of the Batcher sorting networks ,NETWORKS: AN INTERNATIONAL JOURNAL, Issue 4 2001Shimon Even Abstract In the early 1980s, the grid area required by the sorting nets of Batcher for input vectors of length N was investigated by Thompson. He showed that the ,(N2) area was necessary and sufficient, but the hidden constant factors, both for the lower and upper bounds, were not discussed. In this paper, a lower bound of (N , 1)2/2 is proven, for the area required by any sorting network. Upper bounds of 4N2 and 3N2 are shown for the bitonic sorter and the odd,even sorter, respectively. In the layouts, which are presented to establish these upper bounds, slanted lines are used and there are no knock-knees. © 2001 John Wiley & Sons, Inc. [source] | ||||||||||||||||