1,721,061 research outputs found
Minimizing the number of optical crossconnect ports in mesh networks based on bidirectional line-switched WDM self-healing ring protection
No full textThe design of survivable all-optical mesh networks based on bidirectional line-switched WDM (wavelength division multiplexed) self-healing rings (SHR/WDM) to provide full protection against any single line fault requires the solution of three sub-problems: determining the ring cover of the mesh topology, determining the routing of the working lightpaths (paths of light) between the node pairs that originate traffic demands, determining the allocation of the spare wavelengths in each ring required to protect every line in the mesh that supports traffic. A working lightpath can span over multiple rings, thus requiring one crossconnect I/O port at each node that connects two adjacent rings along its path. This paper addresses the problem of minimizing the total number of optical crossconnect I/O ports that are required in the mesh to support a set of traffic demands. The problem is solved under two design scenarios. In the first scenario we derive the minimum number of crossconnect ports necessary in a mesh network with a given ring cover and given routes for the working lightpaths. Once the number of crossconnect ports are minimized, the network total (working and protection) wavelength mileage is minimized by balancing the traffic in each ring. In the second scenario the ring cover, the routing for the working lightpaths and the spare wavelengths in each ring are first computed in such a way to minimize the total wavelength mileage. With this network configuration we then minimize the number of crossconnect ports. The presented solutions provide the designer with two alternative approaches that trade one cost function, i.e., the number of crossconnect ports, for the other, i.e., the total wavelength mileag
Optimal design of survivable mesh networks based on line switched WDM self-healing rings
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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
Multi-rate and multi-hop optical carriers in WDM ring
No full textBy means of optical transparency wavelength division multiplexing (WDM) networks with multi-rate transmissions are becoming a reality. The potential advantages of individually selecting the transmission rate for each lightpath are however not yet fully understood. A recent work studied for the first time multi-rate and multi-hop (M&M) networks in which tributary signals are transmitted over a concatenation of lightpaths, each one operating at its own transmission rate. The study revealed that the problem of designing M&M networks is NP-complete and optimal solutions are practically available only for small networks. The paper presents a heuristic algorithm for designing M&M ring networks that yields efficient sub-optimal solutions in polynomial time. The algorithm determines the rate for each lightpath taking into account a number of factors including the node's interface, amount of multiplexed traffic and cost of the network components. The potential advantages provided by the M&M network when compared to first generation optical networks (i.e., SONET/SDH), single- and multi-hop (constant bit rate) optical networks, are discussed in the paper and documented with numerical results. Presented results show that the network cost reduction achieved by the M&M design is a function of the cost ratio between the optical bandwidth (wavelengths) and the optical terminals
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Effects of design constraints on the total wavelength mileage in optical mesh networks with shared line protection
No full textA fundamental task of the optical layer in modern telecommunication systems consists of providing a fast protection mechanism against possible faults in the network. A particularly attractive protection technique in the optical layer is the so called shared line protection, in which network lines are protected using shared resources. A previous work of the authors formally describes the problem of minimizing the total wavelength mileage, or (lambda) -mileage, necessary in a Wavelength Routing network with arbitrary topology to provide shared line protection. This paper presents an efficient approach to solving the above wavelength mileage problem
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