5,954 research outputs found

    The Leadership Development Experiences of Church Denomination Executives

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    Leadership development through experiences is thought to be one of the most effective approaches in the development of leaders. Exploring the types of experiences of executive church leaders adds to the body of leadership development research focused on leadership lessons, and reveals the contexts through which these experiences were formed. this study applies a phenomenological approach to capture the essence of the leadership development experiences of several bishops within a single African American denomination. Six major themes emerged as important elements of their collective experience. these findings suggest that leadership development experiences for executive church leaders should include ministry venture creation, the use of relevant and real cases, and mentoring relationships

    Langley Mach 4 scramjet test facility

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    An engine test facility was constructed at the NASA Langley Research Center in support of a supersonic combustion ramjet (scramjet) technology development program. Hydrogen combustion in air with oxygen replenishment provides simulated air at Mach 4 flight velocity, pressure, and true total temperature for an altitude range from 57,000 to 86,000 feet. A facility nozzle with a 13 in square exit produces a Mach 3.5 free jet flow for engine propulsion tests. The facility is described and calibration results are presented which demonstrate the suitability of the test flow for conducting scramjet engine research

    Global surface slopes and roughness of the Moon from the Lunar Orbiter Laser Altimeter

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    The acquisition of new global elevation data from the Lunar Orbiter Laser Altimeter, carried on the Lunar Reconnaissance Orbiter, permits quantification of the surface roughness properties of the Moon at unprecedented scales and resolution. We map lunar surface roughness using a range of parameters: median absolute slope, both directional (along-track) and bidirectional (in two dimensions); median differential slope; and Hurst exponent, over baselines ranging from ~17 m to ~2.7 km. We find that the lunar highlands and the mare plains show vastly different roughness properties, with subtler variations within mare and highlands. Most of the surface exhibits fractal-like behavior, with a single or two different Hurst exponents over the given baseline range; when a transition exists, it typically occurs near the 1 km baseline, indicating a significant characteristic spatial scale for competing surface processes. The Hurst exponent is high within the lunar highlands, with a median value of 0.95, and lower in the maria (with a median value of 0.76). The median differential slope is a powerful tool for discriminating between roughness units and is useful in characterizing, among other things, the ejecta surrounding large basins, particularly Orientale, as well as the ray systems surrounding young, Copernican-age craters. In addition, it allows a quantitative exploration on mare surfaces of the evolution of surface roughness with age

    Beam energy measurement at linear colliders using spin precession

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    Linear collider designs foresee some bends of about 5-10 mrad. The spin precession angle of one TeV electrons on 10 mrad bend is 23.2 rad and it changes proportional to the energy. Measurement of the spin direction using Compton scattering of laser light on electrons before and after the bend allows determining the beam energy with an accuracy about of 10^{-5}. In this paper the principle of the method, the procedure of the measurement and possible errors are discussed. Some remarks about importance of plasma focusing effects in the method of beam energy measurement using Moller scattering are given.Comment: 7 pages, Latex, 4 figures(.eps). In v.3 corresponds to journal publication. Talk at 26-th Advanced ICFA Beam Dynamic Workshop on Nanometre-Size Colliding Beams (Nanobeam2002), Lausanne, Switzerland, Sept 2-6, 200

    The role of epidemiology in food safety issues in governmental decisions and actions

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    Since the President announced the Food Safety Initiative in 1997. numerous multi-agency initiatives, work groups, and committees have been established. Each group is struggling to gather science-based data to make regulatory and policy decisions and to guide strategic planning efforts. In many cases. there are little or no data available. Innovative and creative approaches are needed to address multi-disciplinary strategic goals in food safety and to fill knowledge gaps

    Accuracy of the LEP Spectrometer Beam Orbit Monitors

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    At the LEP e+/e- collider, a spectrometer is used to determine the beam energy with a target accuracy of 10-4. The spectrometer measures the lattice dipole bending angle of the beam using six beam position monitors (BPMs). The required calibration error imposes a BPM accuracy of a 10-6 m corresponding to a relative electrical signal variation of 2. 10-5. The operating parameters have been compared with beam simulator results and non-linearBPM response simulations. The relative beam current variations between 0.02 and 0.03 and position changes of 0.1 mm during the fills of last year lead to uncertainties in the orbit measurements of well below 10-6 m. For accuracy tests absolute beam currents were varied by a factor of three. The environment magnetical field is introduced to correct orbit readings. The BPM linearity and calibration was checked using moveable supports and wire position sensors. The BPM triplet quantity is used to determine the orbit position monitors accuracy. The BPM triplet changed during the fills between 1 and 2 10-6 m RMS, which indicates a single BPM orbit determination accuracy between 1 and 1.5 10-6 m

    Astronomical Site Ranking Based on Tropospheric Wind Statistics

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    We present comprehensive and reliable statistics of high altitude wind speeds and the tropospheric flows at the location of five important astronomical observatories. Statistical analysis exclusively of high altitude winds point to La Palma as the most suitable site for adaptive optics, with a mean value of 22.13 m/s at the 200 mbar pressure level. La Silla is at the bottom of the ranking, with the largest average value 200 mbar wind speed(33.35 m/s). We have found a clear annual periodicity of high altitude winds for the five sites in study. We have also explored the connection of high to low altitude atmospheric winds as a first approach of the linear relationship between the average velocity of the turbulence and high altitude winds (Sarazin & Tokovinin 2001). We may conclude that high and low altitude winds show good linear relationships at the five selected sites. The highest correlation coefficients correspond to Paranal and San Pedro Martir, while La Palma and La Silla show similar high to low altitude wind connection. Mauna Kea shows the smallest degree of correlation, which suggests a weaker linear relationship. Our results support the idea of high altitude winds as a parameter for rank astronomical sites in terms of their suitability for adaptive optics, although we have no evidence for adopting the same linear coefficient at different sites. The final value of this linear coefficient at a particular site could drastically change the interpretation of high altitude wind speeds as a direct parameter for site characterization.Comment: 18 pages, 5 figures. Accepted in MNRA

    Performance of BPM Electronics for the LEP Spectrometer

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    At the LEP e+/e- collider at CERN, Geneva, a Spectrometer is used to determine the beam energy with a relative accuracy of 10-4. The Spectrometer measures the change in bending angle in a well-characterised dipole magnet as LEP is ramped. The beam trajectory is obtained using three beam position monitors (BPMs) on each side of the magnet. The error on each BPM measurement should not exceed 1 micron if the desired accuracy on the bending angle is to be reached. The BPMs used consist of an aluminium block with an elliptical aperture and four capacitive button pickup electrodes. The button signals are fed to customised electronics supplied by Bergoz. The electronics use time multiplexing of individual button signals through a single processing chain to optimise for long-term stability. We report on our experience of the performance of these electronics, describing measurements made with test signals and with beam. We have implemented a beam-based calibration procedure and have monitored the reproducibility of the measurements obtained over time. Measurements show that a relative accuracy better than 300 nm is achievable over a period of 1 hr

    LAGEOS geodetic analysis-SL7.1

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    Laser ranging measurements to the LAGEOS satellite from 1976 through 1989 are related via geodetic and orbital theories to a variety of geodetic and geodynamic parameters. The SL7.1 analyses are explained of this data set including the estimation process for geodetic parameters such as Earth's gravitational constant (GM), those describing the Earth's elasticity properties (Love numbers), and the temporally varying geodetic parameters such as Earth's orientation (polar motion and Delta UT1) and tracking site horizontal tectonic motions. Descriptions of the reference systems, tectonic models, and adopted geodetic constants are provided; these are the framework within which the SL7.1 solution takes place. Estimates of temporal variations in non-conservative force parameters are included in these SL7.1 analyses as well as parameters describing the orbital states at monthly epochs. This information is useful in further refining models used to describe close-Earth satellite behavior. Estimates of intersite motions and individual tracking site motions computed through the network adjustment scheme are given. Tabulations of tracking site eccentricities, data summaries, estimated monthly orbital and force model parameters, polar motion, Earth rotation, and tracking station coordinate results are also provided
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