9,214 research outputs found
Should we attempt global (inlet engine airframe) control design?
The feasibility of multivariable design of the entire airplane control system is briefly addressed. An intermediate step in that direction is to design a control for an inlet engine augmentor system by using multivariable techniques. The supersonic cruise large scale inlet research program is described which will provide an opportunity to develop, integrate, and wind tunnel test a control for a mixed compression inlet and variable cycle engine. The integrated propulsion airframe control program is also discussed which will introduce the problem of implementing MVC within a distributed processing avionics architecture, requiring real time decomposition of the global design into independent modules in response to hardware communication failures
High-speed civil transport flight- and propulsion-control technological issues
Technology advances required in the flight and propulsion control system disciplines to develop a high speed civil transport (HSCT) are identified. The mission and requirements of the transport and major flight and propulsion control technology issues are discussed. Each issue is ranked and, for each issue, a plan for technology readiness is given. Certain features are unique and dominate control system design. These features include the high temperature environment, large flexible aircraft, control-configured empennage, minimizing control margins, and high availability and excellent maintainability. The failure to resolve most high-priority issues can prevent the transport from achieving its goals. The flow-time for hardware may require stimulus, since market forces may be insufficient to ensure timely production. Flight and propulsion control technology will contribute to takeoff gross weight reduction. Similar technology advances are necessary also to ensure flight safety for the transport. The certification basis of the HSCT must be negotiated between airplane manufacturers and government regulators. Efficient, quality design of the transport will require an integrated set of design tools that support the entire engineering design team
Improving the Reliability and Modal Stability of High Power 870 nm AlGaAs CSP Laser Diodes for Applications to Free Space Communication Systems
The operating characteristics (power-current, beam divergence, etc.) and reliability assessment of high-power CSP lasers is discussed. The emission wavelength of these lasers was optimized at 860 to 880 nm. The operational characteristics of a new laser, the inverse channel substrate planar (ICSP) laser, grown by metalorganic chemical vapor deposition (MOCVD), is discussed and the reliability assessment of this laser is reported. The highlights of this study include a reduction in the threshold current value for the laser to 15 mA and a degradation rate of less than 2 kW/hr for the lasers operating at 60 mW of peak output power
Cavity-enhanced optical Hall effect in two-dimensional free charge carrier gases detected at terahertz frequencies
The effect of a tunable, externally coupled Fabry-P\'{e}rot cavity to
resonantly enhance the optical Hall effect signatures at terahertz frequencies
produced by a traditional Drude-like two-dimensional electron gas is shown and
discussed in this communication. As a result, the detection of optical Hall
effect signatures at conveniently obtainable magnetic fields, for example by
neodymium permanent magnets, is demonstrated. An AlInN/GaN-based high electron
mobility transistor structure grown on a sapphire substrate is used for the
experiment. The optical Hall effect signatures and their dispersions, which are
governed by the frequency and the reflectance minima and maxima of the
externally coupled Fabry-P\'{e}rot cavity, are presented and discussed. Tuning
the externally coupled Fabry-P\'{e}rot cavity strongly modifies the optical
Hall effect signatures, which provides a new degree of freedom for optical Hall
effect experiments in addition to frequency, angle of incidence and magnetic
field direction and strength
Propulsion/flight control integration technology (PROFIT) software system definition
The Propulsion Flight Control Integration Technology (PROFIT) program is designed to develop a flying testbed dedicated to controls research. The control software for PROFIT is defined. Maximum flexibility, needed for long term use of the flight facility, is achieved through a modular design. The Host program, processes inputs from the telemetry uplink, aircraft central computer, cockpit computer control and plant sensors to form an input data base for use by the control algorithms. The control algorithms, programmed as application modules, process the input data to generate an output data base. The Host program formats the data for output to the telemetry downlink, the cockpit computer control, and the control effectors. Two applications modules are defined - the bill of materials F-100 engine control and the bill of materials F-15 inlet control
Functional and Structural Biological Methods for Palytoxin Detection
Palytoxin (PLTX) and its analogues are marine polyethers identified in Palythoa and Zoanthus
corals, Ostreopsis dinoflagellates, and Trichodesmium cyanobacteria. Humans can be exposed
to these toxins by different routes with a series of adverse effects but the most severe risk is associated with poisonings by the consumption of edible marine organisms accumulating these toxins, as occurs in (sub)-tropical areas. In temperate areas, adverse effects ascribed to PLTXs have been recorded after inhalation of marine aerosols and/or cutaneous contact with seawater during Ostreopsis blooms, as well as during cleaning procedures of Palythoa-containing home aquaria. Besides instrumental analytical methods, in the last years a series of alternative or complementary methods based on biological/biochemical tools have been developed for the rapid and specific PLTX detection required for risk assessment. These methods are usually sensitive, cost- and time-effective, and do not require highly specialized operators. Among them, structural immunoassays and functional cellbased assays are reviewed. The availability of specific anti-PLTX antibodies allowed the development of different sensitive structural assays, suitable for its detection also in complex matrices, such as mussels. In addition, knowing the mechanism of PLTX action, a series of functional identification methods has been developed. Despite some of them being limited by matrix effects and specificity issues, biological methods for PLTX detection represent a feasible tool, suitable for rapid screening
High-power AlGaAs channeled substrate planar diode lasers for spaceborne communications
A high power channeled substrate planar AlGaAs diode laser with an emission wavelength of 8600 to 8800 A was developed. The optoelectronic behavior (power current, single spatial and spectral behavior, far field characteristics, modulation, and astigmatism properties) and results of computer modeling studies on the performance of the laser are discussed. Lifetest data on these devices at high output power levels is also included. In addition, a new type of channeled substrate planar laser utilizing a Bragg grating to stabilize the longitudinal mode was demonstrated. The fabrication procedures and optoelectronic properties of this new diode laser are described
Exploring Halo Substructure with Giant Stars: The Dynamics and Metallicity of the Dwarf Spheroidal in Bootes
We report the results of a spectroscopic study of the Bootes (Boo) dwarf
spheroidal (dSph) galaxy carried out with the WIYN telescope and the Hydra
multifiber spectrograph. Radial velocities have been measured for 58 Boo
candidate stars selected to have magnitudes and colors consistent with its red
and asymptotic giant branches. Within the 13' half-light radius, seven members
of Boo yield a systemic velocity of V_r=95.6+-3.4 km/s and a velocity
dispersion of 6.6+-2.3 km/s. This implies a mass on the order of 1 x 10^7
M_sun, similar to the inferred masses of other Galactic dSphs. Adopting a total
Boo luminosity of L=1.8 x 10^4 L_sun to 8.6 x 10^4 L_sun implies M/L ~ 610 to
130, making Boo, the most distorted known Milky Way dwarf galaxy, potentially
also the darkest. From the spectra of Boo member stars we estimate its
metallicity to be [Fe/H] ~ -2.5, which would make it the most metal poor dSph
known to date.Comment: Accepted for publication in ApJ Letter
Interplay of static and dynamic effects in 6He+ 238U Fusion
We investigate the influence of the neutron halo and the breakup channel in
6He + 238U fusion at near-barrier energies. To include static effects of the
2n-halo in 6He nuclei, we use a single-folding potential obtained from an
appropriate nucleon-238U interaction and a realistic 6He density. Dynamical
effects arising from the breakup process are then included through
coupled-channel calculations. These calculations suggest that static effects
dominate the cross section at energies above the Coulomb barrier, while the
sub-barrier fusion cross section appears to be determined by coupling to the
breakup channel. This last conclusion is uncertain due to the procedure
employed to measure the fusion cross-section.Comment: 13 pages, 4 figure
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