2,530 research outputs found

    Algebraic, geometric, and stochastic aspects of genetic operators

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    Genetic algorithms for function optimization employ genetic operators patterned after those observed in search strategies employed in natural adaptation. Two of these operators, crossover and inversion, are interpreted in terms of their algebraic and geometric properties. Stochastic models of the operators are developed which are employed in Monte Carlo simulations of their behavior

    Mycorrhizal colonization of Hypericum perforatum L. (Hypericaceae) on adjacent serpentine and granite outcrops on the Deer Isles, Maine, USA

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    Given the paucity of literature on plant-fungal interactions on serpentine soils and limited investigation of serpentine geoecology in eastern North America, we examined mycorrhizal colonization of Hypericum perforatum from adjacent serpentine and granite outcrops on the Deer Isles, ME to determine whether plants were differentially colonized based on substrate. We coincided our sampling with three phenologic stages of H. perforatum (preflowering, flowering, postflowering) to determine possible differences in colonization based on plant phenology. The levels of mycorrhizal colonization in H. perforatum were not significantly different between serpentine and granite sites, while levels of colonization in postflowering plants were significantly higher than in those at preflowering and flowering stages

    ORBIT: The Oregon Road Base Information Team, A Draft Summary Report

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    It is clear that transportation organizations across the nation are integrating GIS into operations at many different levels—from day to day use for data display, to full-scale enterprise level integration for operations, inventory management, research and a variety of other purposes. The cost of building and maintaining a current and accurate GIS database can be substantial within any given organization. For some smaller level organizations—small counties, cities or special districts, the cost of gathering data, organizing it and implementing systems within expensive software on an expensive operating platform can be downright discouraging. Also, as more complex data structures are accumulated a window for more comprehensive modeling and analysis of regional issues is opened. Each of these trends alone provide ample incentive to develop data standards that can be applied to all systems to facilitate data sharing between organizations for system development, system update, or project specific purposes. Taken together these trends provide an imperative to develop data-sharing standards

    Doing research in immigration removal centres: ethics, emotions and impact

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    Immigration Removal Centres (IRCs) are deeply contested institutions that rarely open their doors to independent research. In this article we discuss some of the complications we faced in conducting the first national study of everyday life in them. As we will set out, research relationships were difficult to forge due to low levels of trust, and unfamiliarity with academic research. At the same time, many participants had unrealistic expectations about our capacity to assist while most exhibited high levels of distress. We were not immune from the emotional burden of the field sites. Such matters were compounded by the limited amount of published information about life in IRCs and a lack of ethical guidelines addressing such places. Drawing on related literature from prison sociology, we use our experiences in IRCs to set out a methodological account of understanding, ethics, and impact within these complex sites

    Tailored Excitation for Multivariable Stability-Margin Measurement Applied to the X-31A Nonlinear Simulation

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    Safety and productivity of the initial flight test phase of a new vehicle have been enhanced by developing the ability to measure the stability margins of the combined control system and vehicle in flight. One shortcoming of performing this analysis is the long duration of the excitation signal required to provide results over a wide frequency range. For flight regimes such as high angle of attack or hypersonic flight, the ability to maintain flight condition for this time duration is difficult. Significantly reducing the required duration of the excitation input is possible by tailoring the input to excite only the frequency range where the lowest stability margin is expected. For a multiple-input/multiple-output system, the inputs can be simultaneously applied to the control effectors by creating each excitation input with a unique set of frequency components. Chirp-Z transformation algorithms can be used to match the analysis of the results to the specific frequencies used in the excitation input. This report discusses the application of a tailored excitation input to a high-fidelity X-31A linear model and nonlinear simulation. Depending on the frequency range, the results indicate the potential to significantly reduce the time required for stability measurement

    Immigration Detention: Perspectives from Maine Law Students Working on the Ground at the Laredo Detention Center in Texas

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    Since 2017, students enrolled in the University of Maine School of Law Refugee and Human Rights Clinic have traveled to Laredo, Texas to participate in a program, sponsored and run by the law firm Jones Day in collaboration with Texas RioGrande Legal Aid, to provide representation for women in the Laredo Detention Center. Alongside Jones Day attorneys, the students conduct client intake interviews, draft memos detailing each woman’s experiences and any potential legal claims, and assist in the representation of clients. This article will provide a glimpse into the experiences of three Maine Law student attorneys during their time in Laredo, Texas, and will survey issues in the contemporary immigration landscape: first, an overview of the political climate surrounding the immigration debate, current immigration trends, and statistical figures; second, stories providing context for why people are seeking to immigrate to the U.S., and the persecution and challenges faced by immigrant women; third, the shortage of representation for immigrants, whether detained or non-detained; and finally, one of the most challenging and poignant issues encountered by student attorneys participating in the Laredo Project—the separation of immigrant mothers from their children

    Welding the Space Station Common Module Prototype

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    The NASA Manned Space Flight program planned for the 1990\u27 s is directed towards the commercial use of space through development of large space structures serving a variety of missions. The diversity of the program, and the demands of the mission tasks requires a thorough understanding of the mission requirements and the requirements for subsystems which are readily adaptable to a wide range of applications. The heart of the NASA Space Station is the common module; a light weight, thin walled pressure vessel that can be configured for a wide range of functions: i.e., laboratories, manufacturing facilities, living quarters, and cargo carriers. Before the space station is placed in orbit, development articles must be built and tested, design issues must be resolved, manufacturing problems overcome and accurate cost information generated

    How do I sound to me? Perceived changes in communication in Parkinson's disease

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    Objective: To examine self and carer perceived changes in communication associated with Parkinson's disease and relate these to speech intelligibility, gender, age and other disease measures. Design: Cross-sectional survey of a hospital- and community-based sample of 176 people with Parkinson's disease and their carers using a questionnaire based on semantic differential techniques. Participants: One hundred and four people with Parkinson's disease with no history of communication difficulties prior to onset of their Parkinson's disease and 45 primary carers who returned completed questionnaires. Main outcome measures: Differences in ratings for `before' the onset of Parkinson's disease versus present status. Results: There was a strong perception of negative impact on communication between `before' and `now', irrespective of age and gender and largely independent of disease severity and duration, intelligibility and cognitive status. Activities of daily living (assessed by Unified Parkinson's Disease Rating Scale (UPDRS) II) and depression rating scale scores had the strongest association with change (adjusted R 2 0.27). There was a significant correlation between the rank order of perceived change in features examined in people with Parkinson's disease versus their carers, though in general carers rated change as having less impact. Conclusions: Parkinson's disease exercises a strong influence on communication even before apparent alterations to intelligibility or motor status
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