26,152 research outputs found

    Long fluid filled bags suspended by line forces

    Get PDF
    A previous analysis of fluid filled storage bags is extended to the case of a long fluid filled cylindrical membrane supported by uniform line loads. Cross-sectional shape, stiffness of the support system and stress resultants in the membrane are determined. The application of the numerical results to problems arising in the design of nonrigid airships is discussed

    Ionosphere/microwave beam interaction study

    Get PDF
    A solar power satellite microwave power density of 20mw sq cm was confirmed as the level where nonlinear interactions may occur in the ionosphere, particularly at 100 km altitude. Radio wave heating at this altitude, produced at the Arecibo Observatory, yielded negative results for radio wave heating of an underdense ionosphere. Overdense heating produced striations in the ionosphere which may cause severe radio frequency interference problems under certain conditions. The effects of thermal self-focusing are shown to be limited severely geographically. The aspect sensitivity of field-aligned striations makes interference-free regions above magnetic latitude about 60 deg. A test program is proposed to simulate the interaction of the SPS beam with the ionosphere, to measure the effects of the interaction on the ionosphere and on communication and navigation systems, and to interpret the results

    Above and below the water: Social/ecological transformation in northwest Newfoundland

    Get PDF
    Marine fisheries and fishing societies develop around the resources provided by a particular ecosystem. As they exploit these resources, fisheries transform the ecosystem, which pushes fishery and society to adapt in turn. This process is illustrated by fisheries, ecological and social data tracking dramatic changes on Newfoundland\u27s Northern Peninsula and its adjacent marine ecosystem, the northern Gulf of St. Lawrence. There a longstanding fishery for cod and other groundfish collapsed in the 1990s, and was replaced by fisheries targeting invertebrates. The new invertebrate fisheries have different socioeconomic characteristics than the former groundfish fisheries. The shift in target species reflects deep ecological changes that were underway at least a decade before official recognition of the crisis. Our analysis of biological data reveals that the main ecological changes occurred during “the glory years” of the 1980s, when Newfoundland\u27s domestic fisheries were at their peak. Overfishing and interactions with adverse climatic conditions drove the changes. As the ecosystem transformed, human population declined due to outmigration, and social indicators show signs of distress. Accounts by outport residents paint a generational picture of social change

    Leveraging the fully integrated supply chain

    Get PDF
    Thesis (M. Eng. in Logistics)--Massachusetts Institute of Technology, Engineering Systems Division, 2004."June 2004."Includes bibliographical references (leaves 65-69).(cont.) in the success of Lucent's turnaround and, from the patterns that emerge, a basis for a new holistic framework for designing and leveraging an integrated supply chain is offered. This framework suggests that attaining competitive advantage from supply chain capabilities lies in a firm's ability to incorporate corporate culture, leadership style, organization structure and both inter and intra tier governance methods into it's supply chain design in order to enable an integrated and extended organization where the channel expert can be identified and engaged in decision making in a natural, real-time and organic process.Over the past three years, in response to dramatic changes in the telecommunications industry, Lucent Technologies has realigned its corporate strategy from being a provider of manufacturing excellence to one of supply chain excellence. Supported by this realignment, Lucent has recently returned to profitability after eleven consecutive losing quarters, and has posted dramatic improvements in financial, operational and customer satisfaction metrics. Lucent's new strategy is focused on leveraging its supply chain capabilities to create a new extended enterprise that is both customer and supplier intimate, and operates as a broad reaching cross-functional Supply Chain Networks (SCN) organization. Pivotal to the success of this realignment was extending the scope of Lucent's supply chain activities, both internally and externally to the company. Internally, Lucent integrated such non-traditional SCM activities as sales, product design, and margin management into its newly created SCN organization. Externally, by outsourcing virtually all of its manufacturing, and much of the associated supplier management, to Electronics Manufacturing Services (EMS) partners, Lucent became responsible for the orchestration of an extended multi-tier supply chain that integrated abilities and expertise of functional teams within Lucent and within its EMS partners, raw component suppliers and customers. In this thesis, the Supply Chain Networks transformation at Lucent is examined in the broader context of the changes that took place in Lucent's: organizational model; leadership team; corporate culture; customer and supplier relationships; operations; and market space. The change that was effected in each of these areas is reviewed for its roleby Duncan M.L. Scholtz.M.Eng.in Logistic

    Ethnic identity and aspirations among rural Alaska youth

    Get PDF
    The villages of rural Alaska comprise one of the most exceptional, yet least visible, sociocultural environments in the United States They are geographically remote, and set off from the mainstream also by their unique Eskimo, Indian or Aleut cultures. At the same time many economic, legal and cultural connections pull these villages toward the dominant U.S. society, impelling continual and rapid social change. Our research focuses on adolescents growing up in this culturally complex and changing environment. We employ survey data from adolescents in 19 rural schools to explore relationships between ethnic identity and students\u27 expectations about moving away or attending college. Many students describe their ethnic identity as mixed, both Native and non-Native. On some key variables, the responses of mixed-identity students fall between those of Natives and non-Natives, supporting a theoretical conception of ethnicity as a matter of degree rather than category. Migration and college expectations vary with ethnic identity, but the college expectations/identity relationship fades when we adjust for other variables. Ethnicity affects expectations for the most part indirectly, through “cultural tool kit” variables including family role models and support. Gender differences in expectations, on the other hand, remain substantial even after adjusting for other variables

    Simulation verification techniques study. Subsystem simulation validation techniques

    Get PDF
    Techniques for validation of software modules which simulate spacecraft onboard systems are discussed. An overview of the simulation software hierarchy for a shuttle mission simulator is provided. A set of guidelines for the identification of subsystem/module performance parameters and critical performance parameters are presented. Various sources of reference data to serve as standards of performance for simulation validation are identified. Environment, crew station, vehicle configuration, and vehicle dynamics simulation software are briefly discussed from the point of view of their interfaces with subsystem simulation modules. A detailed presentation of results in the area of vehicle subsystems simulation modules is included. A list of references, conclusions and recommendations are also given

    Simulation verification techniques study: Simulation performance validation techniques document

    Get PDF
    Techniques and support software for the efficient performance of simulation validation are discussed. Overall validation software structure, the performance of validation at various levels of simulation integration, guidelines for check case formulation, methods for real time acquisition and formatting of data from an all up operational simulator, and methods and criteria for comparison and evaluation of simulation data are included. Vehicle subsystems modules, module integration, special test requirements, and reference data formats are also described

    Extending the Globular Cluster System-Halo Mass Relation to the Lowest Galaxy Masses

    Full text link
    High mass galaxies, with halo masses M2001010MM_{200} \ge 10^{10} M_{\odot}, reveal a remarkable near-linear relation between their globular cluster (GC) system mass and their host galaxy halo mass. Extending this relation to the mass range of dwarf galaxies has been problematic due to the difficulty in measuring independent halo masses. Here we derive new halo masses based on stellar and HI gas kinematics for a sample of nearby dwarf galaxies with GC systems. We find that the GC system mass--halo mass relation for galaxies populated by GCs holds from halo masses of M2001014MM_{200} \sim 10^{14} M_{\odot} down to below M200M_{200} 109M\sim 10^9 M_{\odot}, although there is a substantial increase in scatter towards low masses. In particular, three well-studied ultra diffuse galaxies, with dwarf-like stellar masses, reveal a wide range in their GC-to-halo mass ratios. We compare our GC system--halo mass relation to the recent model of El Badry et al., finding that their fiducial model does not reproduce our data in the low mass regime. This may suggest that GC formation needs to be more efficient than assumed in their model, or it may be due to the onset of stochastic GC occupation in low mass halos. Finally, we briefly discuss the stellar mass-halo mass relation for our low mass galaxies with GCs, and we suggest some nearby dwarf galaxies for which searches for GCs may be fruitful.Comment: 16 pages, 5 figures, accepted for publication in MNRA
    corecore