Self-Cohering an Airborne e Radio Camera

By distributing antenna elements or small subarrays throughout the skin of an aircraft, a large portion of the airframe can act as an electromagnetic transducer. The basic problem associated with such a design is that uncertainties in element locations due to the nonrigidness of the airframe induce phase errors. Self-cohering techniques are required to compensate for those errors. Four such techniques are presented here.     

A Microwave Feedback Radiometer

Two versions of a microwave feedback radiometer have been built and tested. One used an electromechanical feedback system; the other, an all-electronic system. The response of the servo loops proved to be fast enough and linear enough for almost any radiometer application. The rms noise fluctuation was the same as that of a Dicke radiometer. Stability was excellent even under adverse environmental conditions.     

The Engineer as a Radical?

Outdated and rigorous curricula are not only producing engineers unsuited to the challenges of the 1970's, but they are scaring off many of the most creative and intelligent students. Engineering education has become an endurance test; the excitement has been lost. Most students strive only to get out. Engineering schools have not yet realized the importance of the involvement of engineers in current environmental problems. They continue to present only the dry technical courses and seem unconcerned about the student's sense of social perspective or his motivation. This paper proposes a freshman awareness seminar plus project oriented learning in the following years as a remedy for this sad situation.     

Some early results of the keV plasma experiment on GEOS-1

Some preliminary new results are presented of the keV plasma experiment on GEOS-1. Electrons and ions have been observed to stream along the magnetic field lines in the dayside magnetosphere from the ionospheric side of the satellite towards the equatorial plane during magnetic storms, with streaming velocities corresponding to a kinetic energy of the order of a keV. The opposite streaming velocity has also been seen, but primarily in the ions only and with a smaller flux ratio for the two opposite directions along the field lines. The transition between the two opposite streaming directions, as seen by the satellite, has been found to occur even in a fraction of a second.In magnetic storm conditions azimuthal asymmetries in ion fluxes corresponding to electric field intensities of several tens of millivolts per meter have been observed.     

The Measurement of Echo Direction in a Phased-Array Radar

For a planar-array antenna with a monopulse feed horn, this study describes a simple algorithm for the determination of the direction of target echoes. Antenna pattern measurements of the array indicate that the direction sines of a received wavefront can be independently obtained with one simple relation between a normalized difference channel output and a direction sine. This paper determines the accuracy of the algorithm.     

Minimal-Order Models for False-Alarm Calculations on Sliding Windows

A procedure is developed to obtain practical numerical results in connection with the m-out-of-n sliding-window detection problem. This effort was motivated by difficulties with previous approaches involving approximation, Markov models, and Monte Carlo simulation. Generating-function methods were found to be unsatisfactory for window lengths greater than 6 due to their complexity. Instead, a Markov model is described that is then constructively reduced to the minimum number of state variables. The results are derived for binary strings with intersymbol correlation. Computational aids are discussed for obtaining design information, such as quantiles, from the minimal-order Markov models. Numerical results are given comparing the methods of the paper with a "jumping" window approximation for an 8/10 problem.     

A Unified Approach to Model-Reference Adaptive Systems Part I: Theory

A unified approach to model-reference adaptive control systems is presented. A linearized error equation for each adaptive system is derived about some operating point and converted into the standard form for plotting root loci. The contribution made here is to convert the selection of an adaptive technique and the choosing of adaptive coefficients for some desired system performance from a "mystical art" to standard control techniquess.     

Thrust modulation of solid propellant rockets by a fluidic vortex valve with secondary combustion

An analytical model for calculation of the thrust and pressure modulation of a solid propellant rocket by means of a fluidic vortex valve with secondary combustion has been developed. Thrust control by the vortex valve method was found superior to the axial injection of control flow. Addition of oxygen in the injected flow improves the energetic performance of the system as well as the thrust modulation capability. Experiments have been conducted using a mixture of nitrogen and oxygen as the injection gas. The two main parameters investigated in a series of experiments were the oxygen percentage in the injection gas and the ratio between the mass flow rates of the control gas and the solid propellant combustion products. The results show an increase of thrust by a factor of 2 for a 25% addition in mass flow rate by secondary injection at optimal conditions.     

On the stabilization of ribose by silicate minerals

The RNA-world theory hypothesizes that early Earth life was based on the RNA molecule. However, the notion that ribose, the sugar in RNA, is unstable still casts a serious doubt over this theory. Recently, it has been found that the silicate-mediated formose reaction facilitates the stabilization of ribose. Using accurate quantum chemical calculations, we determined the relative stability of the silicate complexes of arabinose, lyxose, ribose, and xylose with the intent to determine which would form predominantly from a formose-like reaction. Five stereoisomers were investigated for each complex. The stereoisomers of 2:1 ribose-silicate are the more stable ones, to the extent that the least stable of these is even more stable than the most stable stereoisomer of the other 2:1 sugar-silicate complexes. Thus, thermodynamically, a formose-like reaction in the presence of silicate minerals should preferentially form the silicate complex of ribose over the silicate complex of arabinose, lyxose, and xylose.