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Abstract: The results of analyzing the statistical characteristics of the weighting vector of an adaptive antenna array tuned according to the Hebb algorithm, which is one of the classical learning algorithms used for tuning of artificial neural networks, are presented. The analysis is performed with consideration for fluctuations of the weighting vector. It is shown that fluctuations lead to distortions of the antenna-array output signal and to the mismatch effect (the presence of the residual power at the antenna output) that arises owing to fluctuations of weighting coefficients. In an adaptive antenna array tuned according to the Hebb algorithm, the overcompensation effect is not observed.

In contrast to reported hydrosilanes with alkyl and aromatic substituents at the silicon atom, 2-furyl-, di(2-furyl)- and tri(2-furyl)silanes undergo dehydrocondensation with water, while di(2-furyl)silane also undergoes this reaction with ethanol in the absence of catalyst. The structures of 2-furyl-, di(2-furyl)- and tri(2-furyl)silane were studied by electron diffraction.

The mechanism of reaction of 2,4-dichloro-1,5-pentanediones with ammonia has been studied. Intramolecular cyclization of the intermediate resulting from nucleophilic attack at the carbonyl group can occur in two ways, depending on the reaction conditions, either at the a-chloromethylene fragment or at the second carbonyl group, leading to the formation of 2-aroylpyrroles or 3-chloropyridines, respectively. In reactions with thio- and phenylthiourea both chlorophenacyl fragments are involved, resulting in the formation of di(2-amino-4-arylthiazolyl-5)methanes.

An x-ray diffraction investigation of 2-benzoyl-5-phenylpyrrole, whose molecules are combined as dimers in the crystal, has been carried out. The bond lengths and angles have been presented.

The author compares two widely used types of adaptive antenna arrays with linear limitation in the principal maximum of the directivity pattern and quadratic limitation of the absolute value of the weight-factor vector in the antenna channels in the reception of correlated interfering signals.

Under the influence of ammonia or ammonium acetate, a-a'-dichloro-substituted 1,5-diketones undergo heterocyclization to give ß-chloropyridines or 2-benzoylpyrrole derivatives. The structure of the final product depends on the reagent and the character of the substituent in the 3 position of the starting dichloro diketones.

The chlorinated diketones (II) are cyclized with ammonium acetate to give the pyridines (III), whereas cyclization with ammonia produces (III), together with the pyrroles (V).

The hydrolysis of tris(2‐furyl)silane (I) in aqueous dimethylformamide solution gives the disiloxane (II).

Chlorination of the dione (I) affords a mixture of the mono‐, di‐ and trichloro derivatives (III), (IV) and (V).