961 research outputs found
Small Engine Component Technology (SECT) studies
A study was conducted to identify component technology requirements for small, expendable gas turbine engines that would result in substantial improvements in performance and cost by the year 2000. A subsonic, 2600 nautical mile (4815 km) strategic cruise missile mission was selected for study. A baseline (state-of-the-art) engine and missile configuration were defined to evaluate the advanced technology engines. Two advanced technology engines were configured and evaluated using advanced component efficiencies and ceramic composite materials; a 22:1 overall pressure ratio, 3.85 bypass ratio twin-spool turbofan; and an 8:1 overall pressure, 3.66 bypass ratio, single-spool recuperated turbofan with 0.85 recuperator effectiveness. Results of mission analysis indicated a reduction in fuel burn of 38 and 47 percent compared to the baseline engine when using the advanced turbofan and recuperated turbofan, respectively. While use of either advanced engine resulted in approximately a 25 percent reduction in missile size, the unit life cycle (LCC) cost reduction of 56 percent for the advanced turbofan relative to the baseline engine gave it a decisive advantage over the recuperated turbofan with 47 percent LCC reduction. An additional range improvement of 10 percent results when using a 56 percent loaded carbon slurry fuel with either engine. These results can be realized only if significant progress is attained in the fields of solid lubricated bearings, small aerodynamic component performance, composite ceramic materials and integration of slurry fuels. A technology plan outlining prospective programs in these fields is presented
Ion-ion dynamic structure factor, acoustic modes and equation of state of two-temperature warm dense aluminum
The ion-ion dynamical structure factor and the equation of state of warm
dense aluminum in a two-temperature quasi-equilibrium state, with the electron
temperature higher than the ion temperature, are investigated using
molecular-dynamics simulations based on ion-ion pair potentials constructed
from a neutral pseudoatom model. Such pair potentials based on density
functional theory are parameter-free and depend directly on the electron
temperature and indirectly on the ion temperature, enabling efficient
computation of two-temperature properties. Comparison with ab initio
simulations and with other average-atom calculations for equilibrium aluminum
shows good agreement, justifying a study of quasi-equilibrium situations.
Analyzing the van Hove function, we find that ion-ion correlations vanish in a
time significantly smaller than the electron-ion relaxation time so that
dynamical properties have a physical meaning for the quasi-equilibrium state. A
significant increase in the speed of sound is predicted from the modification
of the dispersion relation of the ion acoustic mode as the electron temperature
is increased. The two-temperature equation of state including the free energy,
internal energy and pressure is also presented
Isochoric, isobaric and ultrafast conductivities of aluminum, lithium and carbon in the warm dense matter (WDM) regime
We study the conductivities of (i) the equilibrium isochoric state
(), (ii) the equilibrium isobaric state (),
and also the (iii) non-equilibrium ultrafast matter (UFM) state () with the ion temperature less than the the electron temperature
. Aluminum, lithium and carbon are considered, being increasingly complex
warm dense matter (WDM) systems, with carbon having transient covalent bonds.
First-principles calculations, i.e., neutral-pseudoatom (NPA) calculations and
density-functional theory (DFT) with molecular-dynamics (MD) simulations, are
compared where possible with experimental data to characterize and . The NPA are
closest to the available experimental data when compared to results from
DFT+MD, where simulations of about 64-125 atoms are typically used. The
published conductivities for Li are reviewed and the value at a temperature of
4.5 eV is examined using supporting X-ray Thomson scattering calculations. A
physical picture of the variations of with temperature and density
applicable to these materials is given. The insensitivity of to
below 10 eV for carbon, compared to Al and Li, is clarified.Comment: 10 figure
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Succession Planning Activities at a Rural Public Health Department
This qualitative case study utilized interviews and evaluation of publicallyavailable documents to investigate the process of succession planning in a moderately-sized public health office located in a metropolitan community in a frontier-rural state. Following analysis of the data, the results were compared to literature findings. Four public health directors, the County Health Officer and the Board of Health chairperson participated in the private, face-to-face interviews. These individuals were asked to participate because they have the ability to direct staff leadership development activities. A formal succession planning program did not exist at this agency; however, on an informal basis, leadership development was evident. Successes in promotion of leadership development included establishment of a cooperative and collegial work atmosphere. Barriers to the process of succession planning included a lack of stable funding, lack of understanding about the role of public health by the public, erosion of public health authority, inability to recruit trained personnel, low pay scales, and aging of the current workforce. The results of this study indicate that although formal succession planning programs may not exist within an agency, leadership development is still possible through proven adult education methods
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