Pointing compensation system for spacecraft instruments

A closed loop system reduces pointing errors in one or more spacecraft instruments. Associated with each instrument is a electronics package (3) for commanding motion in that instrument and a pointing control system (5) for imparting motion in that instrument in response to a command (4) from the commanding package (3). Spacecraft motion compensation logic (25) compensates for instrument pointing errors caused by instrument-motion-induced spacecraft motion. Any finite number of instruments can be so compensated, by providing each pointing control system (5) and each commanding package (3), for the instruments desired to be compensated, with a link to the spacecraft motion compensation logic (25). The spacecraft motion compensation logic (25) is an electronic manifestation of the algebraic negative of a model of the dynamics of motion of the spacecraft. An example of a suitable model, and computer-simulated results, are presented

Design time detection of architectural mismatches in service oriented architectures

Service Oriented Architecture (SOA) is a software component paradigm that has the potential to allow for exible systems that are loosely coupled to each other. They are discoverable entities that may be bound to at run time by a client who is able to use the service correctly by referring to the service's description documents. Assumptions often have to be made in any design process if the problem domain is not fully speci ed. If those decisions are about the software architecture of that component and it is inserted into a system with di ering and incompatible assumptions then we say that an architectural mismatch exists. Architectural styles are a form of software reuse. They can simply be used by referring to a name such as \client-server" or \pipe and lter", where these names may conjure up topologies and expected properties in the architects mind. They can also however be more rigorously de ned given the right software environment. This can lead to a vocabulary of elements in the system, de ned properties of those elements along with rules and analysis to either show correctness of an implementation or reveal some emergent property of the whole. SOA includes a requirement that the service components make available descriptions of themselves, indicating how they are to be used. With this in mind and assuming we have a suitable description of the client application it should be the case that we can detect architectural mismatches when designing a new system. Here designing can range from organising a set of existing components into a novel con guration through to devising an entirely new set of components for an SOA. This work investigates the above statement using Web Services as the SOA implementation and found that, to a degree, the above statement is true. The only element of description required for a web service is the Web Service Description Language (WSDL) document and this does indeed allow the detection of a small number of mismatches when represented using our minimal web service architectural style. However from the literature we nd that the above mismatches are only a subset of those that we argue should be detectable. In response to this we produce an enhanced web service architectural style containing properties and analysis supporting the detection of this more complete set of mismatches and demonstrate its e ectiveness against a number of case studies.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Cyber-Physical Systems Design: Formal Foundations, Methods and Integrated Tool Chains

The engineering of dependable cyber-physical systems (CPSs) is inherently collaborative, demanding cooperation between diverse disciplines. A goal of current research is the development of integrated tool chains for model-based CPS design that support co-modelling, analysis, co-simulation, testing and implementation. We discuss the role of formal methods in addressing three key aspects of this goal: providing reasoning support for semantically heterogeneous models, managing the complexity and scale of design space exploration, and supporting traceability and provenance in the CPS design set. We briefly outline an approach to the development of such a tool chain based on existing tools and discuss ongoing challenges and open research questions in this area

Analysing Systems Interdependencies Using a Digital Twin

This work provides a first step towards next-generation systems engineering by demonstrating the feasibility of using a digital twin to generate new insight into systems relationships and interdependencies. This step required substantial interdisciplinary work and industry collaboration in order to examine the potential to combine a set of relevant analytical methods (e.g. BIM query, network analyses and multi-modelling). We assembled an experienced team (Imperial College London, University of Sheffield, Newcastle University), and worked closely with and used empirical data from a major project (Thames Tideway Tunnel). This first step delivers fundamental theoretical understanding that will support the use of the digital twin for systems analyses, and a practical contribution to the identification, prioritisation and management of interdependencies. The long-term ambition is to build the tools that decision makers need in order to understand infrastructure system interdependencies within and across project boundaries

Features of integrated model-based co-modelling and co-simulation technology

Given the considerable ongoing research interest in collaborative multidisciplinary modelling and co-simulation, it is worth considering the features of model-based techniques and tools that deliver benefits to cyber-physical systems developers. The European project “Integrated Tool Chain for Model-based Design of Cyber-Physical Systems” (INTO-CPS) has developed a well-founded tool chain for CPS design, based on the Functional Mock-up Interface standard, and supported by methodological guidance. The focus of the project has been on the delivery of a sound foundation, an open chain of compatible and usable tools, and a set of accessible guidelines that help users adapt the technology to their development needs

In the dedicated pursuit of dedicated capital: restoring an indigenous investment ethic to British capitalism

Tony Blair’s landslide electoral victory on May 1 (New Labour Day?) presents the party in power with a rare, perhaps even unprecedented, opportunity to revitalise and modernise Britain’s ailing and antiquated manufacturing economy.* If it is to do so, it must remain true to its long-standing (indeed, historic) commitment to restore an indigenous investment ethic to British capitalism. In this paper we argue that this in turn requires that the party reject the very neo-liberal orthodoxies which it offered to the electorate as evidence of its competence, moderation and ‘modernisation’, which is has internalised, and which it apparently now views as circumscribing the parameters of the politically and economically possible

Distance to health services influences insecticide-treated net possession and use among six to 59 month-old children in Malawi

<p>Abstract</p> <p>Background</p> <p>Health ministries and providers are rapidly scaling up insecticide-treated nets (ITN) distribution to control malaria, yet possession and proper use typically remain below targeted levels. In Malawi, health facilities (HFs) are currently the principal points of ITN distribution, making it important to understand how access to these ITN sources affects ownership, possession, and use. The authors evaluated the association between proximity to HFs and ITN possession or use among Malawian children six to 59 months of age.</p> <p>Methods</p> <p>A household malaria survey undertaken in eight districts of Malawi during 2007 was used to characterize ITN possession and use. The location of each respondent's household was geocoded as was those of Ministry of Health (MoH) HFs and other health centres. Euclidean distance from each household to the nearest HF was calculated. Patterns of net possession and use were determined through descriptive methods. The authors then analysed the significance of distance and ITN possession/use through standard statistical tests, including logistic regression.</p> <p>Results</p> <p>Median distance to HFs was greater among households that did not possess ITNs and did not use an ITN the previous evening. Descriptive statistical methods confirmed a pattern of decreasing ITN possession and use with increasing distance from HFs. Logistic regression showed the same statistically significant association of distance to HFs, even when controlling for age and gender of the child, ratio of nets to children in household, community net possession and use, and household material wealth.</p> <p>Conclusions</p> <p>Strategies that exclusively distribute ITNs through HFs are likely to be less effective in increasing possession and use in communities that are more distant from those health services. Health providers should look towards community-based distribution services that take ITNs directly to community members to more effectively scale up ITN possession and regular use aimed at protecting children from malaria.</p