Antenna pattern synthesis based on optimization in a probabilistic sense

Antenna optimization theory is usually formulated on the premise that all parameters could be adjusted with unlimited accuracy. Since no practical antenna can be built with absolute precision, only optimization in some probabilistic sense of a random performance index appears to be meaningful. The method also generalizes and gives meaning to the concept of regularization used by others. An approximate solution to the probability distribution of the random performance index is obtained. From this several possible senses of optimization may be defined. Several examples in the synthesis of a two-dimensional secant pattern are studied in detail. In general, it may be impractical to build an array with deterministically optimum currents but also next to impossible to even compute the currents accurately. A detailed numerical analysis is given to show possible sources of errors.     

Multiple scattering of EM waves by spheres part II--Numerical and experimental results

In [8], both low- and high-frequency solutions to the two-sphere problem were presented in a form suitable for efficient computer solution, Here, numerical results are presented using a method which has enabled the first appearance of reliable results for the scattered field from two spheres of radii larger than one wavelength and as large as ten or more. Radar cross sections (RCS) are computed for numerous configurations of two spheres of various materials. Results for scattering by three collinear spheres are also given. An experimental program was undertaken and is briefly described. Whenever possible, these results are compared with the theory. In all cases the agreement is excellent. Depolarization due to multiple scattering is also investigated, revealing some interesting effects and practical applications to scattering range calibration.     

Dimensions of creativity in children's drawings: A social-validation study.

Creative drawings of 3 preschool girls (3 and 5 yrs old) were modified using reinforcement procedures in a multiple baseline design. Clear changes were produced in the diversity of color and form. When selected drawings were shown to adult judges, higher ratings of creativity were given for drawings with increased form diversity but not for drawings with increased color diversity. Results are discussed in terms of the role of social validation in defining and encouraging creativity. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Infantile trauma, genetic factors, and adult temperament.

"This investigation was concerned with the effects of infantile trauma upon adult temperament, the influence of genetic factors upon temperament, and the possibility of an interaction between early experience and gene structure in their influence upon adult behavior." With mice as the Ss, evidence was obtained which indicated that: genetic factors influence emotionality, timidity, and motility in mice; infantile trauma influences emotionality; and there is an interaction effect of genetic and traumatic factors on timidity. The results are related to Freudian theory. (20 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A probabilistic approach to large circular and spherical arrays

Antenna arrays with elements distributed at random in a three-dimensional space are studied. Arbitrary excitation and nonisotropic elements are considered. The distribution of the sidelobe level below a certain value for all directions of observation, as well as other probabilistic properties are determined approximately. These general results are then applied to circular and spherical arrays. In particular, for the latter case, conical log-spiral antennas are considered in some detail. It is found that for large arrays with high resolution, the required number of elements can be several orders of magnitude smaller than what is commonly required on the basis of one element per(lambda/2)^{2}Finally, a few experiments simulated by the Monte Carlo method were conducted and excellent agreements with theory have been found in all cases.     

A study of space-tapered arrays

Previous works on nonuniformly spaced arrays are first critically reviewed, then an exhaustive study of a few small arrays is made. The results reveal that among a large number of possible element arrangements, only very few yield reasonably low sidelobe level. Although the majority of these few arrays are characterized by space-tapering, an overwhelming number of space-tapered arrays do not have low sidelobe level. Some statistical studies are made in order to relate the sidelobe level to the element arrangement. Finally, in the light of rather complete information of these arrays, a comparative study is made on some designs which are proposed by a few authors. The results show that none of them are truly optimum.     

A kinetic model for continuous-flow stirred biological reactors

A kinetic model is proposed to describe the mechanisms of substrate removal in continuous-flow, stirred bioteactors for bacterial autocatalytic reactions. A lumped parameter, defined as the average number of contacts between microorganisms and limiting substrate per unit time per unit of biomass, is used to study the overall effect of mixing on reactor performance. Under all the conditions studied, the overall effect is such that the larger the value of the parameter the better the reactor performance. The influence of formation and decomposition of cell-substrate intermediate on substrate removal is also presented.