Leading Edge Estimation Errors

The leading edge estimator (LEE) of a pulse signal is defined as the instant at which a filtered version of the received noisy signal passes a preset threshold. A rigorous analysis for a rectangular pulse model of the signal results in an exact probability density function for the LEE, valid within the time interval of the leading edge of the filtered pulse. Possible occurrence of the threshold crossing outside of this interval is considered to be an anomalous estimate, since it leads to a gross error in comparison with the regular cases. It is found that the density function of the LEE error is asymmetrical and therefore biased, that the probability PA of anomalous estimation increases with the filter bandwidth, thus setting a well definable limit to the latter and that, for prespecified PA, the minimum bias and variance are proportional, respectively, to R-1 and R-2, minima being obtained by allowing for the largest bandwidth compatible with PA. On the other hand, for given bandwidth the variance decreases only as R-1. Here R is the signal-to-noise energy ratio. Results are presented in form of parameterized graphs.     

Radiation problems in manned spaceflight with a view towards the Space Station.

With the advent of a permanently manned Space Station, the longstanding problems of radiation protection in manned spaceflight have acquired an immediacy. This paper endeavors to emphasize the gaps of our knowledge which must be closed for effective radiation protection. The information that is required includes the accurate determination of the exposure inside the space station to the various components of the ionizing radiation, the evaluation of the biological importance of the different radiation qualities and the depth-dose distribution of the less penetrating component. There is also the possibility of an interaction with weightlessness. It is necessary to establish adequate radiation protection standards and a system of dosimetric surveillance. There is a need for studies of methods on the possibilities of hardening selective shielding of the space station. Spaceflight experiments, which might contribute to the solution of some of these problems are discussed.     

Comparison of resonant topologies in high-voltage DC applications

Because of their tolerance of transformer nonidealities, resonant converters are considered to be well-suited to high-voltage applications. The series and parallel resonant topologies, as well as a newly discovered hybrid resonant topology are compared for high-voltage applications. Design criteria which incorporate transformer nonidealities are developed and used in the construction of high voltage prototypes for each topology. It is found that the parallel topology leads to the lowest peak switch current and the most ideal behavior     

Causes of aircraft electrical failures

The results of a survey of data on failures of aircraft electronic and electrical components that was conducted to identify problematic components are reported. The motivation for the work was to determine priorities for future work on the development of accident investigation techniques for aircraft electrical components. The primary source of data was the Airforce Mishap Database, which is maintained by the Directorate of Aerospace Safety at Norton Air Force Base. Published data from the Air Force Avionics Integrity Program (AVIP) and Hughes Aircraft were also reviewed. Statistical data from these three sources are presented. Two major conclusions are that problems with interconnections are major contributors to aircraft electrical equipment failures, and that environmental factors, especially corrosion, are significant contributors to connector problems     

Beamspace ML bearing estimation incorporating low-angle geometry

A problem in low-angle radar tracking, namely, bearing estimation in the presence of a strong specular multipath component that arrives within the beamwidth of the direct path signal, is studied. Three-dimensional beamspace domain maximum likelihood (3D-BDML) is a computationally simple ML bearing estimation algorithm applicable in this scenario which operates in a 3-D beamspace. A variation of 3D-BDML incorporating the multipath geometry as a priori information is presented. In symmetric 3D-BDML the pointing angle of the center beam is equal to the bisector angle between the direct path ray and the image ray, which may be estimated a priori given only the radar height and the target range. The effect of the inclusion of a priori information on the performance of 3D-BDML is analyzed in terms of the dependence on the relative phase difference between the direct and specular path signals, the sensitivity to error in the bisector angle estimate, and the results of operation when no specular multipath component is present in the data. In addition, computationally simple schemes for coherently incorporating multifrequency data into 3D-BDML are investigated     

High performance magnetostrictive actuators

The application of magnetostriction in the design of a hybrid, electromechanical/hydraulic high-performance linear (large force and stroke) and/or rotational (large moment and angle) actuator is considered. The design concept combines the high power density of actuation possible with magnetostriction (approaching 0.1 HP/cm³ of the magnetostrictive material assuming 3 kHz excitation frequency) and the design flexibility of hydraulics. The objective of the research described was to validate the concept theoretically and to study alternatives and improvements. The system, as currently envisioned, offers very small packaging volume (approximately an order of magnitude smaller than conventional electromechanical systems), flexible packaging (relative location of the major system components is not critical), and easy control (precise control of actuation speed, quick reverse time, and inherent position lockup). The major technical problems associated with the design are outlined, and results of a computer simulation of a prototype actuator are presented     

Applications of aluminum-air batteries

Advances in aluminum-air batteries are described. These include alloys that show higher efficiencies and therefore lower hydrogen evolution, low-cost air cathodes that can be fabricated in production quantities, and methods for handling the aluminum hydroxide reaction product. Emphasis is placed on the advances in air cathodes. The application of this technology to new products and the implications for electric vehicles are discussed     

Energy and charge localization in irradiated DNA.

The relation between the site of energy deposition and the site of its biological action is an important question in radiobiology. Even at 77 degrees K, evidence is clear that these two sites must be separated since energy deposition is random but specific products are formed. Several processes that may contribute to this separation are: 1) hole migration and stabilization through deprotonation to give neutral oxidation product radicals; 2) electron trapping and transfer to form specific radical anions, possibly followed by protonation to give neutral reduction product radicals; and 3) recombination of spatially separated charges or radicals. These microscopic processes will be reviewed critically in an analysis using electron paramagnetic resonance spectroscopy (EPR) evidence for and against long-range transfer of energy and/or charge in frozen, hydrated DNA.     

Sequential ridge regression

A sequential algorithm which closely approximates ridge regression is introduced, and it is pointed out that the desired sequential ridge estimator can be obtained by properly choosing the free parameters of a startup technique for ordinary sequential least squares estimation. The derivation of this result is trivial; however, since no matrix inversions are needed for its implementation, this algorithm is of practical importance     

A target cueing and tracking system (TCATS) for smart videoprocessing

A smart system that uses state-of-the-art image processing techniques to detect and track targets moving in video or infrared imagery is presented. It is a general-purpose system that was developed to be independent of the application and the user interface. TCATS has successfully demonstrated a high detection capability and the ability to ignore exterior environmental conditions, such as cloud shadows moving through the scene, snow, blowing dust, rain and moderate camera motion. TCATS can handle many targets and retain the identity of each object from one frame to the next. Special rugged hardware has been developed to reduce the size, cost, and power consumption and to increase the processing rate, reliability, and environmental operating capability of the system. TCATS can be incorporated into an existing video assessment system without a major cost outlay intruder. The TCATS algorithms, custom-developed hardware, and preliminary field test results are described