314 research outputs found

    Marine Geodesy in the Department of Defense (USA)

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    Marine geodesy during and since World War II has occupied a significant place in the military whenever precise positioning or distance measurements were required. Applications of geodetic principles in coastal and deep ocean marine environments have been of perhaps greater importance to the Naval Oceanographic Office (NAVOCEANO) and the Defense Mapping Agency (DMA) in DoD. The Army Corps o f Engineers depends also on accurate geodetic control in the conduct of hydrographic survey and dredging operations in United States harbors and inland waterways. Accurate absolute positions are critical for Air Force global operations using electronic navigation systems referenced to the World Geodetic System (WGS). Even the Department of State depends on DMA and the National Ocean Service (NOS) for Doppler-derived island positions and computed geodesics to determine Exclusive Economic Zone (EEZ) 200-mile limits from continental baselines and median lines between U.S. and foreign territories. Other navigational problems demanding precise geodetic control are associated with radioactive waste disposal and missile-firing evaluations. The aim of this paper, therefore, is to review major marine geodetic requirements, relevant applications, and major developing systems, some o f which are being developed for DMA through the Naval Ocean Research and Development Activity (NORDA)

    Source unit organization of two topics:

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    Thesis (M.A.)--Boston University, 1946. This item was digitized by the Internet Archive

    Reliability and performance evaluation of systems containing embedded rule-based expert systems

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    A method for evaluating the reliability of real-time systems containing embedded rule-based expert systems is proposed and investigated. It is a three stage technique that addresses the impact of knowledge-base uncertainties on the performance of expert systems. In the first stage, a Markov reliability model of the system is developed which identifies the key performance parameters of the expert system. In the second stage, the evaluation method is used to determine the values of the expert system's key performance parameters. The performance parameters can be evaluated directly by using a probabilistic model of uncertainties in the knowledge-base or by using sensitivity analyses. In the third and final state, the performance parameters of the expert system are combined with performance parameters for other system components and subsystems to evaluate the reliability and performance of the complete system. The evaluation method is demonstrated in the context of a simple expert system used to supervise the performances of an FDI algorithm associated with an aircraft longitudinal flight-control system

    Analysis of existing mathematics textbooks for use in secondary schools.

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    Thesis (Ed.M.)--Boston University Thesis (M.A.)--Boston Universit

    Greased Lightning (GL-10) Flight Testing Campaign

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    Greased Lightning (GL-10) is an aircraft configuration that combines the characteristics of a cruise efficient airplane with the ability to perform vertical takeoff and landing (VTOL). This aircraft has been designed, fabricated and flight tested at the small unmanned aerial system (UAS) scale. This technical memorandum will document the procedures and findings of the flight test experiments. The GL-10 design utilized two key technologies to enable this unique aircraft design; namely, distributed electric propulsion (DEP) and inexpensive closed loop controllers. These technologies enabled the flight of this inherently unstable aircraft. Overall it has been determined thru flight test that a design that leverages these new technologies can yield a useful VTOL cruise efficient aircraft

    A Unique Conjunction: Evidence for Gynogenesis Accompanying Haplodiploid Sex Determination in the Australian Ant Myrmecia impaternata Taylor

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    Myrmecia impaternata is an allodiploid all-female species of hybrid origin. Its parental taxa are confirmed here to be M. banksi and M. pilosula. We suggest that its queens produce diploid female offspring by gynogenetic parthenogenesis, a process which requires interaction between unreduced maternal oocytes and allospecific sperm cells obtained by copulation with another related species. We propose that impaternata queens almost certainly mate for this purpose with males reared in impaternata nests from eggs laid by impaternata females. Because sex in ants is determined by haplodiploidy (males haploid, females diploid), we posit that these males would in fact not be technically conspecific with the females in whose reproductive systems they developed, since they would each carry the haploid genome of one or other of the hybridic parental species. They would therefore be individually identical karyologically to males of either M. banksi or M. pilosula and appropriately allospecific to M. impaternata. We postulate that, unlike all other known gynogens, M. impaternata would have no need to maintain parasitic affiliation or sympatry with free-living sperm-donor host species. Its queens are arguably able to produce the required allospecific males by accessing their own genomes. M. impaternata apparently originated by instantaneous speciation when individuals of its parental species first successfully hybridized

    Cloud System Evolution in the Trades (CSET): Following the Evolution of Boundary Layer Cloud Systems with the NSFNCAR GV

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    The Cloud System Evolution in the Trades (CSET) study was designed to describe and explain the evolution of the boundary layer aerosol, cloud, and thermodynamic structures along trajectories within the North Pacific trade winds. The study centered on seven round trips of the National Science FoundationNational Center for Atmospheric Research (NSFNCAR) Gulfstream V (GV) between Sacramento, California, and Kona, Hawaii, between 7 July and 9 August 2015. The CSET observing strategy was to sample aerosol, cloud, and boundary layer properties upwind from the transition zone over the North Pacific and to resample these areas two days later. Global Forecast System forecast trajectories were used to plan the outbound flight to Hawaii with updated forecast trajectories setting the return flight plan two days later. Two key elements of the CSET observing system were the newly developed High-Performance Instrumented Airborne Platform for Environmental Research (HIAPER) Cloud Radar (HCR) and the high-spectral-resolution lidar (HSRL). Together they provided unprecedented characterizations of aerosol, cloud, and precipitation structures that were combined with in situ measurements of aerosol, cloud, precipitation, and turbulence properties. The cloud systems sampled included solid stratocumulus infused with smoke from Canadian wildfires, mesoscale cloudprecipitation complexes, and patches of shallow cumuli in very clean environments. Ultraclean layers observed frequently near the top of the boundary layer were often associated with shallow, optically thin, layered veil clouds. The extensive aerosol, cloud, drizzle, and boundary layer sampling made over open areas of the northeast Pacific along 2-day trajectories during CSET will be an invaluable resource for modeling studies of boundary layer cloud system evolution and its governing physical processes

    A blinded, randomized, controlled trial assessing conservative management strategies for frozen shoulder

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    BACKGROUND: There is little evidence for the optimal form of nonoperative treatment in the management of frozen shoulder. This study assesses the efficacy of current physiotherapy strategies. METHODS: All primary care referrals of frozen shoulder to our physiotherapy department were included during a 12-month period. Of these referrals, 17% met the inclusion criteria for primary idiopathic frozen shoulder. The 75 patients were randomly assigned to 1 of 3 groups: group exercise class, individual physiotherapy, and home exercises alone. A single independent physiotherapist, who was blinded to the treatment groups, made all assessments. Range of motion, Constant score, Oxford Shoulder Score, Short Form 36, and Hospital Anxiety and Disability Scale (HADS) outcome measures were performed at baseline, 6 weeks, 6 months, and 1 year. RESULTS: The exercise class group improved from a mean Constant score of 39.8 at baseline to 71.4 at 6 weeks and 88.1 at 1 year. There was a significant improvement in shoulder symptoms on Oxford and Constant scores (P < .001). This improvement was greater than with individual physiotherapy or home exercises alone (P < .001). The improvement in range of motion was significantly greater in both physiotherapy groups over home exercises (P < .001). HADS scores significantly improved during the course of treatment (P < .001). The improvement in HADS anxiety score was significantly greater in both physiotherapy intervention groups than in home exercises alone. CONCLUSIONS: A hospital-based exercise class can produce a rapid recovery from a frozen shoulder with a minimum number of visits to the hospital and is more effective than individual physiotherapy or a home exercise program
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