A well-conditioned combined field integral equation for electromagnetic scattering

This paper aims to address two issues of integral equations for the scattering of time-harmonic electromagnetic waves by a perfect electric conductor with Lipschitz continuous boundary: resonant instability and dense discretization breakdown. The remedy to resonant instability is a combined field integral equation, and dense discretization breakdown is eliminated by means of operator preconditioning. The exterior traces of single and double layer potentials are complemented by their interior counterparts of a pure imaginary wave number. We derive the corresponding variational formulation in the natural trace space for electromagnetic fields and establish its well-posedness for all wave numbers. A Galerkin discretization scheme is employed using conforming edge boundary elements on dual meshes, which produces well-conditioned discrete linear systems of the variational formulation. Some numerical results are also provided to support the numerical analysis.Comment: 6 figure

Road Vehicle Functional Safety in Ground-Level Radiation Environments

This presentation gives an overview of the natural space radiation environment, the ground-level radiation environment, and single-event effects (SEEs). We then discuss the impact of SEEs for road vehicle functional safety and issues with commercial electronic components in these high-reliability systems. Finally, we introduce some forward-looking concepts that the radiation effects and automotive electronics communities will have to address as aggressive technology insertion continues

Ceramic Matrix Composite (CMC) Thermal Protection Systems (TPS) and Hot Structures for Hypersonic Vehicles

Thermal protection systems (TPS) and hot structures are required for a range of hypersonic vehicles ranging from ballistic reentry to hypersonic cruise vehicles, both within Earth's atmosphere and non-Earth atmospheres. The focus of this paper is on air breathing hypersonic vehicles in the Earth's atmosphere. This includes single-stage to orbit (SSTO), two-stage to orbit (TSTO) accelerators, access to space vehicles, and hypersonic cruise vehicles. This paper will start out with a brief discussion of aerodynamic heating and thermal management techniques to address the high heating, followed by an overview of TPS for rocket-launched and air-breathing vehicles. The argument is presented that as we move from rocket-based vehicles to air-breathing vehicles, we need to move away from the insulated airplane approach used on the Space Shuttle Orbiter to a wide range of TPS and hot structure approaches. The primary portion of the paper will discuss issues and design options for CMC TPS and hot structure components, including leading edges, acreage TPS, and control surfaces. The current state-of-the-art will be briefly discussed for some of the components. The two primary technical challenges impacting the use of CMC TPS and hot structures for hypersonic vehicles are environmental durability and fabrication, and will be discussed briefly

Emerging Trustworthiness Issues in Distributed Learning Systems

A distributed learning system allocates learning processes onto several workstations to enable faster learning algorithms. Federated Learning (FL) is an increasingly popular type of distributed learning which allows mutually untrusted clients to collaboratively train a common machine learning model without sharing their private/proprietary training data with each other. In this dissertation, we aim to address emerging trustworthiness issues in distributed learning systems, particularly in the field of FL. First, we tackle the issue of robustness in FL and demonstrate its susceptibility by presenting a comprehensive analysis of the various poisoning attacks and defensive aggregation rules proposed in the literature and connecting them under a common framework. To address this issue, we propose Federated Rank Learning (FRL) which reduces the space of client updates from a continuous space of float numbers in standard FL to a discrete space of integer values, limiting the adversary\u27s options for poisoning attacks. Next, we address the privacy concerns in FL, including access privacy and data privacy. An adversarial server in FL gets information about the data distribution of a target client by monitoring either I) local updates that the target submits throughout the FL training or II) the access pattern of the target, which can be privacy sensitive in many real-world scenarios. To preserve access privacy, we design Heterogeneous Private Information Retrieval (HPIR), which allows clients to fetch their specific model parameters from untrusted servers without leaking any information. We believe that HPIR will enable new application scenarios for private distributed learning systems, as well as improve the usability of some of the known applications of PIR. To preserve data privacy, we show that local rankings leak less information about private training data. We conduct a comprehensive investigation on the privacy of rankings in FRL to measure data leakage compared to weight parameter updates in standard FL in presence of the state-of-the-art white-box membership inference attack. Finally, we address the issue of fairness in FL where a single model cannot represent all clients equally due to heterogeneity in their data distributions. To alleviate this issue, we propose Equal and Equitable Federated Learning (E2FL). E2FL produces fair federated learning models by preserving both equity and equality among the participating clients based on learning on parameter rankings where multiple global models are learned so that each group of clients can benefit from their personalized model

Identity management and e-learning standards for promoting the sharing of contents and services in higher education

In this paper, we present the status of identity management systems and e-learning standards across Europe, in order to promote the mobility and the sharing of contents and services in higher education institutions. With new requirements for authentication, authorization and identity management for Web applications, most higher education institutions implement several solutions to address these issues. At the first level, the adoption of directory Servers like LDAP, Active Directory and others, solve some problems of having multiple logins and passwords for authentication. The growing of Web applications like Learning management Systems, portals, Blogs, Wikis, and others, need a more effective way of identity management, providing security and accessibility. Web Single Sign-On (SSO) resolves some of these issues of identity management, because the authentication is managed centrally and the user can navigate through different Web applications using the same session. One example of a Web SSO system is the Central Authentication Systems (CAS). SSO systems provide an effective way to manage authentication and authorization inside institutions, but are restricted to the administrative domain of each institution. With the implementation of Bologna Process more students, lecturers and staff will be on mobility programs within European higher education institutions. The creation of identity management federations is mandatory to provide the mobility of users and to permit the exchange of contents and services between institutions. The creation of identities federations across Europe is been in discussion by TERENA (Trans-European Research and Education Networking Association) to provide a service federation like the EDUROAM WI-FI network that permits the mobility across Europe. This paper reports on some of the issues highlighted in the light of recent developments. To share contents and services within Europe, the adoption of standards is mandatory. IEEE LTSC (Learning Technology Standards Committee), IMS (IMS Global Learning, Inc) and ADL (Advanced Distributed Learning) are standards organizations that publish a set of standards to promote the interoperability, reusability and integration of e-learning contents and services. The most important standards that promote the sharing of contents and services across Europe are Sharable Content Object Reference Model (SCORM), IMS Digital Repositories Interoperability and IMS Learning Design. This paper presents the main features of e-learning standards and how it can be used in conjunction with identity management systems to create collaborative learning objects repositories to promote a more effective learning experience and a more competitive European space for higher education, with respect to the requirements of knowledge based societies

Programming with process groups: Group and multicast semantics

Process groups are a natural tool for distributed programming and are increasingly important in distributed computing environments. Discussed here is a new architecture that arose from an effort to simplify Isis process group semantics. The findings include a refined notion of how the clients of a group should be treated, what the properties of a multicast primitive should be when systems contain large numbers of overlapping groups, and a new construct called the causality domain. A system based on this architecture is now being implemented in collaboration with the Chorus and Mach projects

Discovery of Shared Semantic Spaces for Multiscene Video Query and Summarization.

The growing rate of public space CCTV installations has generated a need for automated methods for exploiting video surveillance data including scene understanding, query, behaviour annotation and summarization. For this reason, extensive research has been performed on surveillance scene understanding and analysis. However, most studies have considered single scenes, or groups of adjacent scenes. The semantic similarity between different but related scenes (e.g., many different traffic scenes of similar layout) is not generally exploited to improve any automated surveillance tasks and reduce manual effort. Exploiting commonality, and sharing any supervised annotations, between different scenes is however challenging due to: Some scenes are totally un-related -- and thus any information sharing between them would be detrimental; while others may only share a subset of common activities -- and thus information sharing is only useful if it is selective. Moreover, semantically similar activities which should be modelled together and shared across scenes may have quite different pixel-level appearance in each scene. To address these issues we develop a new framework for distributed multiple-scene global understanding that clusters surveillance scenes by their ability to explain each other's behaviours; and further discovers which subset of activities are shared versus scene-specific within each cluster. We show how to use this structured representation of multiple scenes to improve common surveillance tasks including scene activity understanding, cross-scene query-by-example, behaviour classification with reduced supervised labelling requirements, and video summarization. In each case we demonstrate how our multi-scene model improves on a collection of standard single scene models and a flat model of all scenes.Comment: Multi-Scene Traffic Behaviour Analysis ---- Accepted at IEEE Transactions on Circuits and Systems for Video Technolog

Strategies to address gender inequalities in Scottish schools: a review of the literature

This literature review forms the first part of a study of the strategies employed in Scottish schools to address gender inequalities in relation primarily to attainment. In undertaking this task, the intention is to build upon a number of previous investigations into the nature and causes of gender inequalities in schools. Some of these (Riddell, 1996; Osler et al, 2002; Lloyd, 2005) have considered gender and special educational needs; others have discussed gender at particular stages of schooling (Wilkinson et al, 1999; Croxford, 1999; Biggart, 2000); whilst a number of recent projects in the UK and in Scotland (Powney, 1996; Sukhnandan, 1999; Tinklin et al, 2001) have considered gender, attainment and/or achievement across the population and span of compulsory schooling. A recent nationally commissioned report (Younger, Warrington et al, 2005) has specifically investigated the issue of raising the attainment of boys. Together, these studies and others have established that there are gender inequalities both in the forms of participation in schooling and in its outcomes (albeit there is agreement that gender is not the only, nor even the main, source of inequality). Also available from this body of literature are analyses of causes of gender inequalities and debate about the strategies schools might adopt to address these inequalities. These strategies arise, in general, from understandings of the nature and causes of gender difference. There is, therefore, some contention here. A number of commentators argue that some of the strategies adopted by schools pathologise gender differences and hence reinforce particular forms of masculinity at the risk of suppressing, or marginalising, other forms, and at the expense of femininities. Evidence that there are gender inequalities in attainment in Scottish schools has been discussed in detail elsewhere. It will be reviewed briefly here and will be related to broader patterns of inequality, and in particular to social class. For this study, though, with its focus on school strategies, the debate about the causes of gendered outcomes is especially important and it will be treated in some depth and related to social class before the discussion moves on to consider the range of strategies employed in schools, as far as they are represented in the literature. The strategies to be considered encompass approaches to learning, teaching and assessment; aspects of classroom organisation; and school-wide issues such as staff development. All of these will be considered critically in the light of previous discussion of the causes of gender differences and their intersection by other, and arguably more influential, forms of identity