Eigenstructure Assignment for Linear Systems

The use of feedback (full state, output, and constrained output) is considered as a means of shaping the transient response of linear time invariant systems. The underlying importance of the eigenstructure (eigenvalues/eigenvectors) is highlighted. Also, the important results and techniques are presented along with a brief literature review. An extensive flight control example is presented which should give direction to the application of eigenstructure assignment in diverse areas.     

Quasi-parallel collisionless shocks

The magnetic field and plasma data from the ISEE 1, 2, and 3 spacecraft have greatly increased our knowledge of the quasi-parallel collisionless shock in space. Hybrid-code simulations have provided us with valuable insights into the physics of the quasi-parallel shock. Unfortunately, theoretical understanding of the nonlinear physics of the quasi-parallel shock is still in a qualitative stage of development. Generation of large-amplitude whistler waves and hydromagnetic waves observed in the quasi-parallel shock has been discussed either in terms of linear instabilities or qualitative nonlinear arguments. It appears that the ion reflection, ion heating, and leakage of the shock-heated downstream ions at the quasi-parallel shock can all be explained in terms of nonadiabatic scatterings of ions by the large-amplitude whistler-magnetosonic waves with frequencies near the ion gyrofrequency and wavelength near the ion inertial length. The nonadiabatic scattering is defined by the non-conservation of the magnetic moment. Future study of the quasi-parallel shock should focus on developing quantitative theoretical models for the nonlinear physical processes fundamental to the quasi-parallel shock.     

Dual-frequency distortion predictions for the Cutler VLF array

The VLF transmitting system in Cutler, ME currently broadcasts at one frequency through a two-element antenna system. This study investigates simultaneous operation at 24.0 and 17.8 kHz. Detailed nonlinear PSPICE models were generated for the system including the amplifier triodes, saturable dynamic-tuning reactors, and the closely-coupled antenna elements. The predicted behavior is in close agreement with available observations. Upper limits are placed on harmonic content, <-59.8 dBc, and intermodulation distortion, <-78 dBc.     

Experimental and theoretical investigations of vibration characteristics for GTE compressor blade

The tables of vibration modes for a blade obtained by the experimental method of holographic interferometry and systematized according to the number of nodal lines are presented. The graphical dependences of resonant frequencies that allow eliminating the vibration mode miss are presented. The vibration modes for a rectangular plate and a blade are compared. A technique of determining the resonant frequency for a missed harmonics is proposed.     

Magnetic Fields in Astrophysical Jets: From Launch to Termination

Long-lived, stable jets are observed in a wide variety of systems, from protostars, through Galactic compact objects to active galactic nuclei (AGN). Magnetic fields play a central role in launching, accelerating, and collimating the jets through various media. The termination of jets in molecular clouds or the interstellar medium deposits enormous amounts of mechanical energy and momentum, and their interactions with the external medium, as well, in many cases, as the radiation processes by which they are observed, are intimately connected with the magnetic fields they carry. This review focuses on the properties and structures of magnetic fields in long-lived jets, from their launch from rotating magnetized young stars, black holes, and their accretion discs, to termination and beyond. We compare the results of theory, numerical simulations, and observations of these diverse systems and address similarities and differences between relativistic and non-relativistic jets in protostellar versus AGN systems. On the observational side, we focus primarily on jets driven by AGN because of the strong observational constraints on their magnetic field properties, and we discuss the links between the physics of these jets on all scales.     

The White Sands Range and Range-Rate System

This paper discusses the concept, design, and design verification of the White Sands Range and Range-Rate System. Development of the system has been completed only through the design phase. The system is designed to meet requirements for high-accuracy midcourse tracking under severe target dynamics at the White Sands Missile Range. It is a multistatic Doppler and range tracker which operates at X band and incorporates transmitter, transponder, receiver, and baseline subsystems. The transmitter includes specially designed digital circuitry to synthesize test signals for target simulation during checkout of the system. The transponder signal is processed by a receiver which has been established theoretically to be the optimum realizable processor of continuous tracking data. The receiver incorporates specially designed carrier acquisition circuitry and digital VCO, and directly provides digital Doppler and tone phase data to facilitate real-time processing. The system utilizes data from other tracking systems at the Range for spatial acquisition, for aiding carrier acquisition in the receiver, and for resolving range ambiguities.     

Automatic Light Control Electro-Optical CCDTV Systems

For electro-optical TV systems, a simplified method of analysis has been developed for an automatic light control (ALC) loop preliminary ary design and performance trade-offs. With iris and shutter control mechanization incorporated, not only does the input light range increase, but the video response overshoot and settling time are reduced as well. This study shows that the appealing notion of heavily damped response is not often true, particularly in the realtime ime airto-ground surveillance of targets with varying backgrounds. In addition, with exponential and geometric feedback functions introduced, the resultant ALC dynamics are independent of the input light level. To verify the assumptions made and to demonstrate the feasibility of a working model, a complete system simulation is performed.     

Computation of aircraft geometric height under radar surveillance

A radar system for geometric height estimation of civil aircraft is described. The system consists of one standard or mode S secondary surveillance radar (SSR) and one omnidirectional antenna sited away from SSR under an airplane. The geometric height is derived by trilateration. Systematic errors are compensated for by deriving the profile of the effect on height measurements of the bias in range measurements. A curve-fitting technique is then used, which estimates both the geometric height and any non-zero systematic errors