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School of Computing Research Colloquia - 2013/2014              

Research Colloquia: Characterizing and Exploiting Heterogeneity for Enhancing Energy-Efficiency of Cloud Datacenters
Ismael Solis Moreno, Distributed Systems and Services research theme, School of Computing
School of Computing Staff Room (E.C. Stoner level 9)
11.30am, Friday 9 May 2014

Abstract: Cloud Computing environments are composed of large and power-consuming datacenters designed to support the elasticity required by their customers. The adoption of Cloud Computing is rapidly growing since it promises cost reductions for customers in comparison with permanent investments in traditional datacenters. However, for Cloud providers, energy consumption represents a serious problem since they have to deal with the increasing demand and diverse Quality of Service requirements. Contemporary energy-efficient Cloud approaches exploit the advantages of virtualization to maximize the use of physical resources and minimize the number of active servers.

A major problem not considered by current Cloud resource management schemes is that of the inherent heterogeneity of customer, workload and server types in multi-tenant environments. This is an issue when improving energy-efficiency, as co-location of specific workload types may result in strong contention for the physical resources. This then affects the resource consumption patterns and therefore the energy-efficiency of virtualized servers. In addition, because of the on-demand self-service characteristic of the Cloud model, different types of customers tend to highly overestimate the amount of required resources. This creates a non-negligible amount of underutilized servers that affects the energy-efficiency of the datacenter.

This thesis analyzes a production Cloud environment to determine the characteristics of the heterogeneous customer, workload and server types, and proposes a novel way to exploit such heterogeneity in order to improve energy-efficiency through two mechanisms. The first improves energy-efficiency by co-locating diverse workload types according to the minimum level of produced interference in a heterogeneous pool of servers. The second mitigates the waste generated by customer overestimation by dynamically overallocating resources based on heterogeneous customer profiles and the levels of produced interference. The evaluation of the proposed mechanisms demonstrates that considering the heterogeneity of elements in a Cloud environment supports the effective improvement of the datacenter energy-efficiency and the performance of individual workloads.

Research Colloquia: Cartographic Information Visualization
Jason Dykes, School of Informatics, City University
School of Computing Staff Room (E.C. Stoner level 9)
11.30am, Friday 16 May 2014

Abstract: Work at the giCentre at City University London creatively explores interactions between Cartography - the development and study of symbolised depictions of geographical settings, and Information Visualization - the use of physical space in graphics to represent non-spatial relationships.

This seminar will focus on recent work in which we develop novel maps and graphics by adding structure to geographic representations to help with comparison and geography to non-spatial representations to reveal geographic relationships.

These partial geographies are used amongst other things to track 21st century bicycles and 19th century migrants, present the UK census on a single page, provide an exploratory public-facing interface to data on local government service provision and reveal bias in London's local elections as giCentre ideas and applications for making sense of masses of data are showcased.

Fri 23rd May No Colloquium

Research Colloquia: User interfaces for navigating gigapixel images
Roy Ruddle, Applied Computing in Biology, Medicine and Health research theme, School of Computing
School of Computing Staff Room (E.C. Stoner level 9)
11.30am, Friday 30 May 2014

Abstract: In many disciplines people need to navigate large visualizations to analyze data, and our work focuses on a specific aspect of this – visualizing gigapixel medical images. In this talk, I will describe the design and evaluation of user interfaces for navigating such images. The interfaces are novel because they exploit a gigantic ‘thumbnail’ overview that breaks existing design guidelines to let users navigate gigapixel images quickly and accurately. Our evaluations involved images that are orders of magnitude larger than those used in any previous study.

Research Colloquia: Mobility diversity for robots
Daniel Bonilla Licea, School of Electronic & Electrical Engineering
School of Computing Staff Room (E.C. Stoner level 9)
11.30am, Friday 6 June 2014

Abstract: Communication systems are a very important part of mobile robots. By using communication systems robot can explore areas which are dangerous or inaccessible to humans and send to a base station (BS) sensors measurements and other relevant information. Another popular application is the surveillance of a place by a robot it can patrol some area and send periodically photographs and videos to a surveillance center.

The transmission of the data from the robot to the BS will suffer from the impairments of the wireless channel. Among these impairments we have the small scale fading. Since the robot may operate indoors or in places with rich scattering the small scale fading will affect the robot's communications. It is therefore very important that the robot's communications systems include some form of diversity techniques to combat fading. To solve the problem we could just apply all the classical theory for diversity, select one of the many techniques presented in the literature (e.g., selection combining, maximum ration combining, etc.). Nevertheless, robotic communications are not a classical problem, the key differences of robotic communications with all other wireless communications areas are that the transceiver knows its physical position and can control it, i.e., it can move to wherever it wants. These particular abilities and the fact that the small scale fading differ from position to position enables the use of a new diversity technique.

The mobility diversity is a new kind of diversity still in an early stage of development. This class of diversity consists in moving the robot (and in consequence its transceiver) to different locations (which experience different fading) in order to find a position with high channel gain. This kind of techniques presents a compromise: the more the robot moves the more it improves the channel gain but it also expends more mechanical energy. Therefore, smart algorithms are required.

Research Colloquia: Twitter: metrics, models and data
Jonathan Ward, School of Mathematics
School of Computing Staff Room (E.C. Stoner level 9)
11.30am, Friday 13 June 2014

Abstract: The widespread adoption of the social media platform Twitter has created an unprecedented volume of data concerning peoples' communication patterns, their social networks and also their attitudes and opinions towards current events. This has proved valuable to media agencies, who use data analytics and social network analysis to provide insights to clients by, for example, identifying influential consumers that can be engaged in real-time. Evolving graph centrality metrics are particularly suitable for this task since they account for the effects resulting from the rapid pace of communication in Twitter. In this talk I will give an overview of one such metric, known as `communicability', with examples of applications to Twitter data. I will also discuss a simple model of Twitter user behaviour that illustrates how the content of some tweets can become extremely widespread.