1,720,983 research outputs found
Channel assignment with separation in wireless networks based on regular plane tessellations
No full textProc. of the 1st Advanced Research Workshop on Information Security in Wireless Networks (ARW),
NATO Security through Science Series D, vol. 13, éd. IOS Press, 2008
Allocating Servers in Infostations for On-Demand Communications
No full textGiven a set of service requests, each characterized by a temporal interval and a category, an integer k , and an integer h_c for each category c , the Server Allocation with Bounded Simultaneous Requests problem consists in assigning a server to each request in such a way thatat most k mutually simultaneous requests are assigned to the same server at the same time, out of which at most hc are of category c , and the minimum number of servers is used. Since this problem is computationally intractable, a 2-approximation on-line algorithm is exhibited which asymptotically gives a (2 - \frac{h}{k})-approximation, where h = \min \{ h_c \}. Generalizations of the problem are considered, where each request r is also characterized by a bandwidth rate wr, and the sum of the bandwidth rates of the simultaneous requests is bounded, and where each request is characterized also by a gender bandwidth. Such generalizations contain Bin-Packing and Multiprocessor Task scheduling as special cases, and they admit on-line algorithms providing constant approximations
Channel assignment on strongly-simplicial graphs
No full textGiven a vector ( 1 � 2�::: � t) of non increasing positive integers, and an undirected graph G = (V�E), an L ( 1 � 2�::: � t)-coloring of G is a function f from the vertex set V to a set of nonnegative integers such that jf(u) ; f(v)j i, if d(u � v) = i � 1 i t� where d(u � v) is the distance (i.e. the minimum number of edges) between the vertices u and v. This paper presents e cient algorithms for nding optimal L(1�:::�1)-colorings of trees and interval graphs. Moreover, e cient algorithms are also provided for nding approximate L ( 1 � 1�:::�1)-colorings of trees and interval graphs, as well as approximate L ( 1 � 2)colorings of unit interval graphs.
Optimal Multi-Channel Data Allocation with Flat Broadcast Per Channel.
No full textBroadcast is an efficient and scalable way of transmitting data to an unlimited number of clients that are listening to a channel. Cyclically broadcasting data over the channel is a basic scheduling technique, which is known as flat scheduling. When multiple channels are available, partitioning data among channels in an unbalanced way, depending on data popularities, is an allocation technique known as skewed allocation. In this paper, the problem of data broadcasting over multiple channels is considered assuming skewed data allocation to channels and flat data scheduling per channel, with the objective of minimizing the average waiting time of the clients. Several algorithms, based on dynamic programming, are presented which provide optimal solutions for N data items and K channels. Specifically, for data items with uniform lengths, an O(NK logN) time algorithm is proposed, which improves over the previously known O(N^2 K) time algorithm. When K ≤ 4, faster O(N) time algorithms are exhibited. Moreover, for data items with non-uniform lengths, it is shown that the problem is NP-hard when K = 2, and strong NP-hard for arbitrary K. In the former case, a pseudo-polynomial algorithm is discussed, whose time is O(NZ) where Z is the sum of the data lengths
Randomized Greedy Algorithms for the Hypergraph Partitioning Problem
No full text. We propose a series of randomized greedy construction schemes for the hypergraph partitioning problem. While the final results are inferior to those obtained by recent multi-level methods, the advantages of our greedy schemes are their simplicity and low computational complexity. The best greedy algorithms considered obtain low cut values and large standard deviations of the results. Therefore, when independent repetitions are considered, the quality of the best solution greatly improves and, in some cases, it is superior to the variable-depth Fiduccia-Mattheyses (FM) algorithm, for smaller CPU times. Furthermore, the algorithms can be used as building blocks in more complex schemes. For example, we successfully employ our greedy schemes to produce initial partitions for improvement-based heuristics. In particular, if FM is run starting from partitions generated by our greedy schemes, instead of random initial solutions, a significant improvement of the average solution quality is ac..
Scheduling data broadcasts on wireless channels: exact solutions and heuristics
No full textWe discuss the broadcasting problem of N data items over K wireless channels, under the assumptions of
skewed data allocation to channels and flat data scheduling per channel. Both the uniform and nonuniform
length cases are surveyed showing their exact and heuristic solutions, respectively. Two of the heuristic
methods are greedy and the third one is based on a dynamic programming procedure developed to solve a
simplified version of the problem. An experimental evaluation of our heuristics is presented and the quality
of the solutions generated is compared against a lower bound, which is derived by relaxing the problem
and then solving it optimally via a dynamic programming procedure developed in earlier sections
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
- …
