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.     

Tellurium-rich growth and laser fabrication of lead-tin-telluride (Pb1−xSnxTe: 0.06<x<0.08)

Single crystals of Pb_1−x Sn_x Te (0.06<x<0.08) have been grown by using an ingot-nucleation technique from a Te-rich source. The as-grown crystals have a p-type carrier concentration around 10¹⁹ cm⁻³ and dislocation density as low as 10³ cm⁻². Diode lasers fabricated from these crystals have contact resistances of 2×10⁻⁵ Ω-cm² and a single-mode single-ended output power of 750 μW at heat sink temperatures around 15 K.     

Estimation for rotational processes with one degree of freedom--Part I: Introduction and continuous-time processes

A class of bilinear estimation problems involving single-degree-of-freedom rotation is formulated and resolved. Continuous-time problems are considered here, and discrete-time analogs will be studied in a second paper. Error criteria, probability densities, and optimal estimates on the circle are studied. An effective synthesis procedure for continuous-time estimation is provided, and a generalization to estimation on arbitrary Abelian Lie groups is included. Applications of these results to a number of practical problems including frequency demodulation will be considered in a third paper.     

A hybrid architecture for analog video broadcast and B-ISDNservices in customer premises networks

The use of SCM (subcarrier multiplexing) transmission to deliver broadcast analog video signals within a CPN (customer premises network) as an overlay to an all-digital B-ISDN (broadband integrated services digital network) is considered. The feasibility of a proposal where the analog and digital signals are carried on different wavelengths is shown. An architecture for an optical CPN, termed H-Bus and incorporating emerging broadband SONET and ATM (asynchronous transfer mode) standards, is taken as a baseline for the delivery of switched digital, two-way voice, data, and video services. An optical overlay for the distribution of analog, broadcast video services using subcarrier multiplexing is considered. Several key alternatives associated with the delivery of broadcast video services are assessed, including signal quality, number of simultaneous channels, number of user terminals to be served, and modulation format. These issues are considered in terms of their impact on the interface with the public local exchange network and on the complexity, topology, and cost of the CPN     

Roles of electron trapping and interface state generation ongate-induced drain leakage current in p-MOSFETs

The roles of electron trapping and of acceptor-type interface state generation (ΔD_it) in the off-state gate-induced drain leakage (GIDL) current in p-MOSFETs are studied. It is found that both trapped electrons and negatively charged acceptor-type interface states reduce the GIDL current at the high-surface-field region, in which GIDL is still governed by the band-to-band tunneling process. However, the neutral acceptor-type ΔD_it increases the GIDL current significantly at the low-surface-field region     

Symptoms and signs in diseases caused by mycoplasma pneumoniae in infants and small children (author's transl)

In 12 children aged 8 month to 5 years (in the average 2,3 years), respiratory illness caused by Mycoplasma pneumoniae, could be secured with microbiological methods (growth inhibition, cultivation). The most common clinical, roentgenological and laboratory signs are discussed. A disease from Mycoplasma pneumoniae should be assumed, when a child will begin to cough often with staccato attacks without apnoea at night and has temperature short time after adimission to a group. The findings by auscultation are small but the X-ray-picture is showing marked alterations. A precise diagnosis can be achieved only with microbiological examinations (serology or cultivation). When there are no symptoms and signs described above, the diseases caused by Mycoplasma pneumoniae can be detected only if Mycoplasma serology has become a routine laboratory task in institutions for paediatric bronchopneumology.     

Optical coherence tomography system with no high-precision scanning stage and stage controller

Optical coherence tomography (OCT) is a novel technique for noninvasive imaging based on the use of a low-coherence interferometer. Conventionally, obtaining high-resolution images requires the use of high-precision sample and scanning stages and a stage controller for simultaneous measurement of the refractive index and the thickness of an optical sample. However, in this study a novel optical-fiber-type OCT system is developed that does not need both a high-precision scanning stage and a stage controller. Additionally, two signal demodulation processes are described. Compared with that of conventional OCT systems, the current configuration eliminates the high-precision scanning stage and stage controller and is therefore cheaper and less complex. Also, this new technique could be applied to conventional OCTs in biotissue scanning.