A Posteriori Probabilistic Bounds of Convex Scenario Programs with Validation Tests

Scenario programs have established themselves as efficient tools towards decision-making under uncertainty. To assess the quality of scenario-based solutions a posteriori, validation tests based on Bernoulli trials have been widely adopted in practice. However, to reach a theoretically reliable judgement of risk, one typically needs to collect massive validation samples. In this work, we propose new a posteriori bounds for convex scenario programs with validation tests, which are dependent on both realizations of support constraints and performance on out-of-sample validation data. The proposed bounds enjoy wide generality in that many existing theoretical results can be incorporated as particular cases. To facilitate practical use, a systematic approach for parameterizing a posteriori probability bounds is also developed, which is shown to possess a variety of desirable properties allowing for easy implementations and clear interpretations. By synthesizing comprehensive information about support constraints and validation tests, improved risk evaluation can be achieved for randomized solutions in comparison with existing a posteriori bounds. Case studies on controller design of aircraft lateral motion are presented to validate the effectiveness of the proposed a posteriori bounds

Eliciting Public Preferences For Managing Cultural Heritage Sites: Evidence from a Case study on the Temples Of Paestum

This paper discusses ways of improving the management of cultural heritage sites and cities, focusing on new forms of involvement and public participation based on public preferences’ elicitation. The problem of city governance and of the appropriate level of democratic participation needs an integrated approach, capable of bridging the practice of urban design, conservation of the built environment and decision-making support system. This paper reports results from a survey using conjoint choice approach questions to elicit people’s preferences for cultural heritage management strategies for an outstanding world heritage site: the Temples of Paestum, in Italy. The potential of the above-mentioned methodologies’ within the current cultural heritage research scenario is also discussed.

Rethinking Secure Precoding via Interference Exploitation: A Smart Eavesdropper Perspective

Based on the concept of constructive interference (CI), multiuser interference (MUI) has recently been shown to be beneficial for communication secrecy. A few CI-based secure precoding algorithms have been proposed that use both the channel state information (CSI) and knowledge of the instantaneous transmit symbols. In this paper, we examine the CI-based secure precoding problem with a focus on smart eavesdroppers that exploit statistical information gleaned from the precoded data for symbol detection. Moreover, the impact of correlation between the main and eavesdropper channels is taken into account. We first modify an existing CI-based preocding scheme to better utilize the destructive impact of the interference. Then, we point out the drawback of both the existing and the new modified CI-based precoders when faced with a smart eavesdropper. To address this deficiency, we provide a general principle for precoder design and then give two specific design examples. Finally, the scenario where the eavesdropper's CSI is unavailable is studied. Numerical results show that although our modified CI-based precoder can achieve a better energy-secrecy trade-off than the existing approach, both have a limited secrecy benefit. On the contrary, the precoders developed using the new CI-design principle can achieve a much improved trade-off and significantly degrade the eavesdropper's performance

Advances in Stability of Composite Airframe Structures Regarding Collapse, Robust Design and Dynamic Loading

European aircraft industry demands for reduced development and operating costs, by 20% and 50% in the short and long term, respectively. Structural weight reduction by exploitation of structural reserves in composite aerospace structures contributes to this aim, however, it requires accurate and experimentally validated stability analysis of real structures under realistic loading conditions. This paper presents new achievements from the area of computational and experimental stability research of composite aerospace structures which contribute to that field. The first two topics focus on stringer stiffened panels and the last one on imperfection sensitive unstiffened cylinders. Section 1 presents selected results achieved in the finished EU project COCOMAT, which deals with an accurate and reliable simulation of collapse. The main objective of COCOMAT is a future design scenario which exploits considerable reserves in fibre composite fuselage structures by accurate simulation of collapse. The project results comprise an experimental data base, improved slow and fast computational tools as well as design guidelines. In today’s design process dynamic loading, e.g. due to gusts or landing impact, is assumed to be uncritical, since the dynamic process increases buckling stability. Section 2 shows that rapidly applied loading of stiffened panels can yield critical dynamic behavior in the postbuckling regime. When applying the new design philosophy it has either to be assured that these critical interactions do not occur under the loading velocities to be expected, or they have to be taken into consideration. Section 3 presents a recently developed approach for unstiffened shells which are usually susceptible to imperfections. This robust design approach is based on a single buckle as the worst imperfection mode leading directly to the load carrying capacity of a cylinder. It also promises to improve the knock-down factors which are according the current guidelines very conservative. Future work should facilitate full applicability of the analysis methods in preliminary design. For that purpose speed of the collapse analysis of stiffened panels needs to be increased and for collapse simulation degradation must be taken into account. The application field of the robust design method should be widened towards imperfection sensitive stiffened shells (skin-dominant designs)

Comparative study of two laparoscopic instrument tracker designs for motion analysis and image-guided surgery: a technical evaluation

Laparoscopic instrument tracking systems are a key element in image-guided interventions, which requires high accuracy to be used in a real surgical scenario. In addition, these systems are a suitable option for objective assessment of laparoscopic technical skills based on instrument motion analysis. This study presents a new approach that improves the accuracy of a previously presented system, which applies an optical pose tracking system to laparoscopic practice. A design enhancement of the artificial markers placed on the laparoscopic instrument as well as an improvement of the calibration process are presented as a means to achieve more accurate results. A technical evaluation has been performed in order to compare the accuracy between the previous design and the new approach. Results show a remarkable improvement in the fluctuation error throughout the measurement platform. Moreover, the accumulated distance error and the inclination error have been improved. The tilt range covered by the system is the same for both approaches, from 90º to 7.5º. The relative position error is better for the new approach mainly at close distances to the camera syste

Energy-Efficient-Homes : Designing energy-efficient architecture in an urban context

Zugl. erschienen in: Energy Efficient Housing for Iran : Pilot Buildings in Hashtgerd New Town. - Berlin: Universitätsverlag der TU Berlin, 2013 (Young Cities Research Paper Series ; 4) http://nbn-resolving.de/urn:nbn:de:kobv:83-opus-39369 Zugleich gedruckt veröffentlicht im Universitätsverlag der TU Berlin unter der ISBN 978-3-7983-2565-4.The concept for the Energy- Efficient- Homes is part of a holistic approach to develop urban structures with energy-saving features, high quality, low carbon emissions and affordable costs for middle and lower income classes. The process of developing this concept includes a design for energy-efficient housing in an Iranian new town project with potential for mitigation in the region and climate adaptation. The method of developing a spatial concept according to the energy-relevant aspects of urban and architectural morphology and integrating it into the socio-cultural context of the “Shahre Javan Community”, the pilot settlement in Hashtgerd New Town, is designed to provide an economic strategy for a practical basic energy standard that has been adapted to the region. The courtyard housing scheme of the Energy- Efficient- Homes shows a new development derived from the vernacular approach of spatial hierarchy considering the major morphological aspects of orientation and compactness. With the use of new technologies for energy efficiency, this basic standard of spatial organisation and design can also be upgraded to meet higher standards. The chosen research methodology for the Energy-Efficient-Homes is performed for a residential pilot project in the “Shahre Javan Community”. To ensure the appropriateness to the pilot project, the methods of research are integrated in a planning process. The method suitable for combining scientific and planning results is the research-by-design process. In a systematic work process, the findings of a general approach and specific design allow for the evaluation and definition of further steps. By applying this scenario-specific methodology for architectural and urban design supposition, that have been obtained from a general approach, to real planning situations, the assessment can be performed on different scales. Finally, the results gathered in the design process are used to revise the formulation of the initial approach. The findings of the design and research process for the Energy-Efficient-Homes are transferred to a final design proposal for an urban unit in the pilot area. By transforming the design and adaptation measures from the typological approach into a specific design scenario, the challenges for the practical application of such a general approach can be weighted and evaluated. Furthermore, the realistic scenario serves as a basis for cost estimations, energy simulations and constructional detailing. Architectural models and drawings are used to define a standard for materials and energy objectives. The definition of adaptive design measures out of the research and planning process and the identification of urban, architectural and technical elements for developing the Energy-Efficient-Homes led to a distinction between a Basic Principle and possible Upgrades. This categorisation helps to define different standards as well as a scientific basis for the planning process of energy-efficient housing in the region. The Basic Principle is the design strategy for energy-efficient architecture and urban design from a spatial approach without any additional technical demands. It contains all planning and design measures to increase energy efficiency through the spatial configuration, such as building orientation and compactness, site suitability and cultural context. It can be seen as a low-cost approach and defines a minimum standard for energy efficiency in the Middle East. The upgrading measures include possibilities to raise the standard of the basic principle. Supplementary technologies can be integrated into the spatial approach. Possible Upgrades include simple mechanical elements for light and energy guidance, such as sun-shutters, furthermore the use of the ground temperature by means of earth tubes and a concept of heat exchangers, and finally the application of higher technological materials, such as photovoltaic fabrics to generate supplementary energy. The measures are characterized by a planning dimension as well as a technological and economic dimension. The choice of upgrading measure is dependent on the economic and technological context. The upgrade defines the standard for maximum energy efficiency in the region

Multicriteria material selection for casing pipe in shale gas wells application.

The conventional method of casing selection is based on availability and/or order placement to manufacturers based on certain design specifications to meet the anticipated downhole conditions. This traditional approach is very much dependent on experience as well as constructing oil and gas wells at minimum budget. However, this material selection approach is very limited in meeting the requirement of shale gas wells. This study utilises the material performance indices and ANSYS Granta database to examine three different casing pipe buckling scenarios including the buckling with corrosion potentials and buckling with impact and long-term service temperature conditions. Consequently, numerical evaluations of the response of the selected casing materials established the stress, deformations, and safety factor for the first scenario (shale gas well with buckling tendencies). The significance of this new method is added advantage in terms of integrating materials' physicochemical, thermal and mechanical properties and the casing functional performance to establish ideal selection within the design space or requirements. Results obtained in this study shows that there are optional materials that outperform the most common casing grades (P110 &Q125) utilised in shale gas development in terms of both safety and cost. This study established a procedure between cost, safety, performance indices and materials' physical and mechanical properties for a typical well design scenario. This procedure will assist the design engineer justify the selection of a particular material(s) safely and technically for a given shale well casing application in future. In all the 10 materials investigated, even though the P110 (API casing grade) meets the buckling design scenario and widely used in shale gas well development, there are many alternative viable material candidate options that outperform P110 Grade with the best material candidate studied in this work being BS 145