7,105 research outputs found
An Improved Upper Bound for the Ring Loading Problem
The Ring Loading Problem emerged in the 1990s to model an important special
case of telecommunication networks (SONET rings) which gained attention from
practitioners and theorists alike. Given an undirected cycle on nodes
together with non-negative demands between any pair of nodes, the Ring Loading
Problem asks for an unsplittable routing of the demands such that the maximum
cumulated demand on any edge is minimized. Let be the value of such a
solution. In the relaxed version of the problem, each demand can be split into
two parts where the first part is routed clockwise while the second part is
routed counter-clockwise. Denote with the maximum load of a minimum split
routing solution. In a landmark paper, Schrijver, Seymour and Winkler [SSW98]
showed that , where is the maximum demand value. They
also found (implicitly) an instance of the Ring Loading Problem with . Recently, Skutella [Sku16] improved these bounds by showing that , and there exists an instance with .
We contribute to this line of research by showing that . We
also take a first step towards lower and upper bounds for small instances
Ono: an open platform for social robotics
In recent times, the focal point of research in robotics has shifted from industrial ro- bots toward robots that interact with humans in an intuitive and safe manner. This evolution has resulted in the subfield of social robotics, which pertains to robots that function in a human environment and that can communicate with humans in an int- uitive way, e.g. with facial expressions. Social robots have the potential to impact many different aspects of our lives, but one particularly promising application is the use of robots in therapy, such as the treatment of children with autism. Unfortunately, many of the existing social robots are neither suited for practical use in therapy nor for large scale studies, mainly because they are expensive, one-of-a-kind robots that are hard to modify to suit a specific need. We created Ono, a social robotics platform, to tackle these issues. Ono is composed entirely from off-the-shelf components and cheap materials, and can be built at a local FabLab at the fraction of the cost of other robots. Ono is also entirely open source and the modular design further encourages modification and reuse of parts of the platform
On-board B-ISDN fast packet switching architectures. Phase 2: Development. Proof-of-concept architecture definition report
For the next-generation packet switched communications satellite system with onboard processing and spot-beam operation, a reliable onboard fast packet switch is essential to route packets from different uplink beams to different downlink beams. The rapid emergence of point-to-point services such as video distribution, and the large demand for video conference, distributed data processing, and network management makes the multicast function essential to a fast packet switch (FPS). The satellite's inherent broadcast features gives the satellite network an advantage over the terrestrial network in providing multicast services. This report evaluates alternate multicast FPS architectures for onboard baseband switching applications and selects a candidate for subsequent breadboard development. Architecture evaluation and selection will be based on the study performed in phase 1, 'Onboard B-ISDN Fast Packet Switching Architectures', and other switch architectures which have become commercially available as large scale integration (LSI) devices
An evolutionary approach to the optimisation of autonomous pod distribution for application in an urban transportation service
For autonomous vehicles (AVs), which when deployed in urban areas are called “pods”, to be used as part of a commercially viable low-cost urban transport system, they will need to operate efficiently. Among ways to achieve efficiency, is to minimise time vehicles are not serving users. To reduce the amount of wasted time, this paper presents a novel approach for distribution of AVs within an urban environment. Our approach uses evolutionary computation, in the form of a genetic algorithm (GA), which is applied to a simulation of an intelligent transportation service, operating in the city of Coventry, UK. The goal of the GA is to optimise distribution of pods, to reduce the amount of user waiting time. To test the algorithm, real-world transport data was obtained for Coventry, which in turn was processed to generate user demand patterns. Results from the study showed a 30% increase in the number of successful journeys completed in a 24 hours, compared to a random distribution. The implications of these findings could yield significant benefits for fleet management companies. These include increases in profits per day, a decrease in capital cost, and better energy efficiency. The algorithm could also be adapted to any service offering pick up and drop of points, including package delivery and transportation of goods
Managing Population and Workload Imbalance in Structured Overlays
Every day the number of data produced by networked devices increases. The current
paradigm is to offload the data produced to data centers to be processed. However as
more and more devices are offloading their data do cloud centers, accessing data becomes
increasingly more challenging. To combat this problem, systems are bringing data closer
to the consumer and distributing network responsibilities among the end devices. We are
witnessing a change in networking paradigm, where data storage and computation that
was once only handled in the cloud, is being processed by Internet of Things (IoT) and
mobile devices, thanks to the ever increasing technological capabilities of these devices.
One approach, leverages devices into a structured overlay network.
Structured Overlays are a common approach to address the organization and distri-
bution of data in peer-to-peer distributed systems. Due to their nature, indexing and
searching for elements of the system becomes trivial, thus structured overlays become
ideal building blocks of resource location based applications.
Such overlays assume that the data is distributed evenly over the peers, and that the
popularity of those data items is also evenly balanced. However in many systems, due to
many factors outside of the system domain, popularity may behave rather randomly, al-
lowing for some nodes to spare more resources looking for the popular items than others.
In this work we intend to exploit the properties of cluster-based structured overlays
propose to address this problem by improving a structure overlay with the mechanisms
to manage the population and workload imbalance and achieve more uniform use of
resources.
Our approach focus on implementing a Group-Based Distributed Hash Table (DHT)
capable of dynamically changing its groups to accommodate the changes in churn in the
network.
With the conclusion of our work we believe that we have indeed created a network
capable of withstanding high levels of churn, while ensuring fairness to all members of
the network.Todos os dias aumenta o número de dados produzidos por dispositivos em rede. O pa-
radigma atual é descarregar os dados produzidos para centros de dados para serem pro-
cessados. No entanto com o aumento do número de dispositivos a descarregar dados
para estes centros, o acesso aos dados torna-se cada vez mais desafiante. Para combater
este problema, os sistemas estão a aproximar os dados dos consumidores e a distribuir
responsabilidades de rede entre os dispositivos. Estamos a assistir a uma mudança no
paradigma de redes, onde o armazenamento de dados e a computação que antes eram da
responsabilidade dos centros de dados, está a ser processado por dispositivos móveis IoT,
graças às crescentes capacidades tecnológicas destes dispositivos. Uma abordagem, junta
os dispositivos em redes estruturadas.
As redes estruturadas são o meio mais comum de organizar e distribuir dados em
redes peer-to-peer. Gradas às suas propriedades, indexar e procurar por elementos torna-
se trivial, assim, as redes estruturadas tornam-se o bloco de construção ideal para sistemas
de procura de ficheiros.
Estas redes assumem que os dados estão distribuídos equitativamente por todos os
participantes e que todos esses dados são igualmente procurados. no entanto em muitos
sistemas, por factores externos a popularidade tem um comportamento volátil e imprevi-
sível sobrecarregando os participantes que guardam os dados mais populares.
Este trabalho tenta explorar as propriedades das redes estruturadas em grupo para
confrontar o problema, vamos equipar uma destas redes com os mecanismos necessários
para coordenar os participantes e a sua carga.
A nossa abordagem focasse na implementação de uma DHT baseado em grupos capaz
de alterar dinamicamente os grupos para acomodar as mudanças de membros da rede.
Com a conclusão de nosso trabalho, acreditamos que criamos uma rede capaz de
suportar altos níveis de instabilidade, enquanto garante justiça a todos os membros da
rede
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