2,196 research outputs found
PESI - a taxonomic backbone for Europe
No full textThis is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
The attached file is the published version of the article.NHM Repositor
Bounded Decentralised Coordination over Multiple Objectives
No full textWe propose the bounded multi-objective max-sum algorithm (B-MOMS), the first decentralised coordination algorithm for multi-objective optimisation problems. B-MOMS extends the max-sum message-passing algorithm for decentralised coordination to compute bounded approximate solutions to multi-objective decentralised constraint optimisation problems (MO-DCOPs). Specifically, we prove the optimality of B-MOMS in acyclic constraint graphs, and derive problem dependent bounds on its approximation ratio when these graphs contain cycles. Furthermore, we empirically evaluate its performance on a multi-objective extension of the canonical graph colouring problem. In so doing, we demonstrate that, for the settings we consider, the approximation ratio never exceeds 2, and is typically less than 1.5 for less-constrained graphs. Moreover, the runtime required by B-MOMS on the problem instances we considered never exceeds 30 minutes, even for maximally constrained graphs with agents. Thus, B-MOMS brings the problem of multi-objective optimisation well within the boundaries of the limited capabilities of embedded agents
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The geology of the Backbone Ridge area, Llano and Burnet counties, Texas
No full texttextThe purpose of the author is to present a geological survey of the Backbone Ridge area in Burnet and Llano counties, Texas. During the summer of 1947 while enrolled in a geologic field course in McCullough County, it was noted that a new classification of the Cambrian and Ordovician formations In central Texas had been presented In the literature. It was noted at the same time that the Paleozoic rocks of the Llano uplift are more highly faulted than had been shown on previous geologic maps of the region. The writer concluded from field observations that the Backbone Ridge area was more complexly faulted then had been previously shown, and it was decided to test this conclusion by making a detailed geologic map of the area using the stratigraphic subdivisions recently established by Bridge, Barnes, and Cloud. A detailed study was made of these subdivisions and a large number of the type sections were visited. It was necessary to study the complete geologic history of the region in order that the events which involved the complex structural pattern and the present physiographic forms might be properly understood. The material contained in this report consists of data obtained from the literature and from field observations which were made in the area during the months of June and July of 1948.Earth and Planetary Science
The Economics of the Internet Backbone
No full textThis paper discusses the economics of the Internet backbone. The author discusses competition on the Internet backbone as well as relevant competition policy issues. In particular, he shows how public protocols, ease of entry, very fast network expansion, connections by the same Internet Service Provider ('ISP') to multiple backbones (ISP multi-homing), and connections by the same large web site to multiple ISPs (customer multi-homing) enhance price competition and make it very unlikely that any firm providing Internet backbone connectivity would find it profitable to degrade or sever interconnection with other backbones in an attempt to monopolize the Internet backbone.Technology and Industry, Regulatory Reform
Sampling ISP backbone topologies
No full textLarge computer networks are too large to emulate or actually reproduce in conventional lab environments. Graph generation/reduction techniques have been a valuable tool to solve this limitation. However, current techniques focus on local features (e.g. router out-degree, clustering coefficient, traffic difference between edges for building a hierarchy) that do not preserve router-level backbone geographical/hierarchical features or the end-to-end delay between any arbitrary points. This letter proposes a geographical-based reduction mechanism that enables emulation in lab settings while preserving the global features of typical backbone networks. The performance evaluation is based on six inferred ISP backbone maps.</p
A baseline for dimensioning the Unisource FastPacket backbone for LAN interconnect services
No full textUnisource Business Networks is the international service provider of three European PTT's. One of the services that Unisource offers its business customers is LAN interconnect. The backbone on which this service is delivered is a StrataCom IPX FastPacket backbone, with a congestion management system called ForeSight. ForeSight does not rely on end-user response to congestion notification, which is a great advantage when comparing to the CCITT defined standards. But ForeSight not only throttles end-users when there is congestion in the backbone, it also speeds them up when there is bandwidth free. The research that this report describes mainly focuses on three questions. First Unisource wants to have a dimensioning of the backbone with minimum risk of FastPacket loss. Second, ForeSight uses a lot of parameters that may influence the performance of PVC's, ports and the whole system. We need to standardise these parameters as much as possible to keep the backbone manageable, without losing a lot of performance. The last main question is to give some options for improving the dimensioning of the backbone in future. The baseline may be a safe dimensioning, but we need to develop a method which allows Unisource to take more risk and thus to decrease the backbone cost…Applied SciencesElectrical EngineeringTelecommunications and Traffic Control Systems Grou
Visualizing the Marrow of Science
No full textThis study proposes a new methodology that allows for
the generation of scientograms of major scientific domains,
constructed on the basis of cocitation of Institute
of Scientific Information categories, and pruned using
PathfinderNetwork, with a layout determined by algorithms
of the spring-embedder type (Kamada–Kawai),
then corroborated structurally by factor analysis. We
present the complete scientogram of the world for the
Year 2002. It integrates the natural sciences, the social
sciences, and arts and humanities. Its basic structure
and the essential relationships therein are revealed,
allowing us to simultaneously analyze the macrostructure,
microstructure, and marrow of worldwide scientific
output
CDS-based virtual backbone construction with guaranteed routing cost in wireless sensor networks
No full textInspired by the backbone concept in wired networks, virtual backbone is expected to bring substantial benefits to routing in wireless sensor networks (WSNs). Virtual backbone construction based on Connected Dominating Set (CDS) is a competitive approach among the existing methods used to establish virtual backbone in WSNs. Traditionally, CDS size was the only factor considered in the CDS-based approach. The motivation was that smaller CDS leads to simplified network maintenance. However, routing cost in terms of routing path length is also an important factor for virtual backbone construction. In our research, both of these two factors are taken into account. Specifically, we attempt to devise a polynomial-time constant-approximation algorithm that leads to a CDS with bounded CDS size and guaranteed routing cost. We prove that, under general graph model, there is no polynomial-time constant-approximation algorithm unless . Under Unit Disk Graph (UDG) model, we propose an innovative polynomial-time constant-approximation algorithm, GOC-MCDS-C, that produces a CDS whose size is within a constant factor from that of the minimum CDS. In addition, for each node pair and , there exists a routing path with all intermediate nodes in and path length at most , where is the length of the shortest path between and . Our theoretical analysis and simulation results show that the distributed version of the proposed algorithm, GOC-MCDS-D, outperforms the existing approache
Seamless transitions of multiple micro-grids between the backbone interconnected and the islanded operational modes
No full textThe traditional power system has been undergoing fundamental changes during the latest years. The developments in the field of renewable energy sources, as well as in the power electronics industry, acted as drivers aiding the establishment of micro-grids. Nowadays, power production is becoming more and more decentralized, therefore loads and consumers are powered via local generation avoiding the losses resulting from the transmission system. However, there is still a lot of research needed in the field of micro-grids, before they are mature enough to penetrate the conventional system at a large extent. This thesis aims to contribute to the further development of the field of micro-grids. The thesis focuses on a grid comprised of various micro-grids working in parallel. The micro-grids are interconnected through a low voltage backbone. Each micro-grid can operate either in islanded mode or connected to the backbone and working in parallel with other micro-grids. The main restriction that has to be respected is the lack of ICT equipment. Only local measurements are allowed and each of the interconnected micro-grids cannot acquire information for the rest of the micro-grids. Thus, the frequency of the system is the only communication signal and the main control variable. The frequency closely reflects the state of the system. The main component of each micro-grid is the converter of the battery energy storage system. Apart from that, each micro-grid consists of a PV system and a load, as well as the connection to the backbone. The key aspect is the lack of connection to the main grid. The backbone interconnected system can be perceived to be working in stand-alone mode. Within this regime, the question arises as to how to achieve seamless transitions of such a micro-grid between the islanded and the backbone interconnected operational modes. The literature shows many examples of such transitions of a micro-grid and the main grid. This thesis addresses the seamless mode switching issue in an extended grid comprised of parallel micro-grids and under the absence of a main conventional grid. The main aim of this thesis was to develop adequate controllers which would ensure seamless transitions of the previously described micro-grid between the islanded and the backbone interconnected operation. Nevertheless, in order to implement and test the efficiency of the controllers, the development of a base-model regulating the operation of the micro-grid both in islanded and in backbone interconnected mode was necessary. The respective controllers were developed in the PowerFactory simulation software and their efficiency was tested under different operational conditions, especially under extreme cases. The results were evaluated and conclusions were finally drawn.Electrical Engineering, Mathematics and Computer ScienceElectrical Sustainable Energ
The Backbone: Indeterminate Framework
No full textArchitecture often manifests itself for a multitude of decades in the built environment, as something that is static. It is in itself an end-result, often designed as a seamless whole, specifically applicable within the design of music venues. These are often iconic objects within city fabrics, sometimes only accessible by one specific target group. The spatial configuration and experiences within the building are staying the same during its lifespan. If our cities, environments, technologies, economies and even our own ideas, activities and (musical) preferences change constantly, why do we construct and design architecture still as something that is fixed, rigid, pre-established, and permanent? Can we create architecture which generates freedom and is open for interpretation, therefore responding to unforeseen activities? For the design of the music building, a framework is designed, which is indeterminate in its functions. The framework derives from a characteristic crane rail located in the Binckhorst, The Hague (Netherlands), which functions as the ''backbone'' of the whole project. It can be appropriated and used by different groups and (sub)cultures and host various activities. The framework is flexible and can grow over time in which there is not one particular end-result created. By doing this, the building is more resilient towards future societal changes.Architecture, Urbanism and Building Sciences | Public Buildin
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