167,636 research outputs found

    High Resolution Imaging Systems For Spin-Stabilized Probe Spacecraft

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    A novel design for a high-resolution imaging system which includes on-board data editing and optical navigation, suggests high quality images can be acquired from spin-stabilized spacecraft oriented towards high velocity, short duration planetary missions ("Probes"). The approach to designing imaging systems requires that mission objectives be met within the physical and fiscal constraints imposed by the spacecraft and mission design. Severe constraints imposed on a Comet Halley probe (for example, 57km/sec encounter velocity with a small, 10km diameter, object coupled with a great uncertainty in encounter time and distance, were overcome by innovative use of existing technology. Such designs suggest that 3-axis stabilization or non-spinning platforms are not necessary to acquire high resolution, high quality planetary images

    High Resolution Imaging Systems For Spin-Stabilized Probe Spacecraft

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    A novel design for a high-resolution imaging system which includes on-board data editing and optical navigation, suggests high quality images can be acquired from spin-stabilized spacecraft oriented towards high velocity, short duration planetary missions ("Probes"). The approach to designing imaging systems requires that mission objectives be met within the physical and fiscal constraints imposed by the spacecraft and mission design. Severe constraints imposed on a Comet Halley probe (for example, 57km/sec encounter velocity with a small, 10km diameter, object coupled with a great uncertainty in encounter time and distance, were overcome by innovative use of existing technology. Such designs suggest that 3-axis stabilization or non-spinning platforms are not necessary to acquire high resolution, high quality planetary images

    Federal Workforce: Sustained Attention to Human Capital Leading Practices Can Help Improve Agency Performance

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    [Excerpt] A careful consideration of federal pay is an essential part of fiscal stewardship and is necessary to support the recruitment and retention of a talented, agile, and high-performing federal workforce. High-performing organizations have found that the life-cycle of human capital management activities—including workforce planning, recruitment, on-boarding, compensation, engagement, succession planning, and retirement programs—need to be aligned for the cost-effective achievement of an organization’s mission. However, despite some improvements, strategic human capital management—and more specifically, skills gaps in mission critical occupations—continues to be a GAO high-risk area. This testimony is based on a body of GAO work primarily issued between June 2012 and March 2017. It focuses on (1) lessons learned in creating a more market driven, results-oriented approach to federal pay, and (2) opportunities, in addition to pay and benefits, that OPM and agencies could use to be more competitive in the labor market and address skills gaps

    Evaluating Mission-Critical Self-Adaptive Software Systems: A Testing-Based Approach

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    Self-adaptive software is a closed-loop system that tries to manage, direct, or regulate its own behavior dynamically. Such a system aims at providing an automated and systematic approach to handling the increasing complexity of operation management. Mission-critical systems (e.g., e-business and telecommunication systems) are usually large, complex, and distributed. These systems must preserve their Quality of Service (QoS) at runtime under highly dynamic and non-deterministic conditions; therefore, they are suitable candidates for being equipped with self-adaptive capabilities. Although significant efforts have been devoted to modeling, designing, developing and deploying self-adaptive software since a decade ago, there is still a lack of well-established concrete processes for evaluating such systems. This dissertation proposes a systematic evaluation process for mission-critical self-adaptive software systems. The process is a well-defined testing approach that needs a post-mortem analysis, takes the quantified QoS requirements as inputs, and comprises two main phases: i) conducting system-level testing, and ii) evaluating QoS requirements satisfaction. The process uses Service Level Agreements (SLAs) as quantified QoS requirements, and consequently as the adaptation requirements of mission-critical systems. Adaptation requirements are specific types of requirements used to engineer self-adaptive software. Moreover, for the first phase, the dissertation discusses the uniqueness and necessity of conducting system-level load and stress testing on a self-adaptive software system, for collecting runtime QoS data. In the second phase, the process makes use of utility functions to generate a single value indicating the QoS satisfaction of the evaluated system. The dissertation mainly focuses on evaluating the performance, availability and reliability characteristics of QoS. An open source service-oriented Voice over IP (VoIP) application was selected as a case study. The VoIP application was transformed into a self-adaptive software system with various types of adaptation mechanisms. A set of empirical experiments was performed on the developed self-adaptive VoIP application, and the proposed process was adopted for evaluating the effectiveness of different adaptation mechanisms. To this end, the dissertation defines a sample SLA for the VoIP application, presents a report on the load and stress testing performed on the self-adaptive VoIP application, and presents a set of utility functions for evaluation. The experiments illustrate the validity, reliability, flexibility, and cost of the proposed evaluation process. In sum, this dissertation introduces a novel evaluation process for mission-critical self-adaptive software systems, and shows that the proposed process can help researchers to systematically evaluate their self-adaptive systems

    Mixed Initiative Systems for Human-Swarm Interaction: Opportunities and Challenges

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    Human-swarm interaction (HSI) involves a number of human factors impacting human behaviour throughout the interaction. As the technologies used within HSI advance, it is more tempting to increase the level of swarm autonomy within the interaction to reduce the workload on humans. Yet, the prospective negative effects of high levels of autonomy on human situational awareness can hinder this process. Flexible autonomy aims at trading-off these effects by changing the level of autonomy within the interaction when required; with mixed-initiatives combining human preferences and automation's recommendations to select an appropriate level of autonomy at a certain point of time. However, the effective implementation of mixed-initiative systems raises fundamental questions on how to combine human preferences and automation recommendations, how to realise the selected level of autonomy, and what the future impacts on the cognitive states of a human are. We explore open challenges that hamper the process of developing effective flexible autonomy. We then highlight the potential benefits of using system modelling techniques in HSI by illustrating how they provide HSI designers with an opportunity to evaluate different strategies for assessing the state of the mission and for adapting the level of autonomy within the interaction to maximise mission success metrics.Comment: Author version, accepted at the 2018 IEEE Annual Systems Modelling Conference, Canberra, Australi

    When situativity meets objectivity in peer-production of knowledge:the case of the WikiRate platform

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    PurposeThe purpose of this paper is to further the debate on Knowledge Artefacts (KAs), by presenting the design of WikiRate, a Collective Awareness platform whose goal is to support a wider public contributing to the generation of knowledge on environmental, social and governance (ESG) performance of companies.Design/methodology/approachThe material presented in the paper comes from the first-hand experience of the authors as part of the WikiRate design team. This material is reflexively discussed using concepts from the field of science and technology studies.FindingsUsing the concept of the “funnel of interest”, the authors discuss how the design of a KA like WikiRate relies on the designers’ capacity to translate general statements into particular design solutions. The authors also show how this funnelling helps understanding the interplay between situativity and objectivity in a KA. The authors show how WikiRate is a peer-production platform based on situativity, which requires a robust level of objectivity for producing reliable knowledge about the ESG performance of companies.Originality/valueThis paper furthers the debate on KAs. It presents a relevant design example and offers in the discussion a set of design and community building recommendations to practitioners
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