Measurement and Identification of the Parameters of SPICE-Models of a Bipolar Transistor

A method of measuring and identifying the static parameters of a bipolar transistor is considered. The characteristic of the transistor, from which the parameters of the model are determined, is chosen depending on what group the calculated parameters belong to. The characteristics are measured in such a way that the equations of the model describing them can be reduced to the simplest form.     

Stabilizing the spectrum of a femtosecond Ti:Sapphire laser

A new scheme for stabilizing the beat frequency of the interacting longitudinal modes in a femtosecond Ti:sapphire laser (Femos-1) has been developed and experimentally studied. The stability and frequency spectrum of mode beats in a modified laser have been monitored. A short-term instability of the beat frequency does not exceed 4.8 × 10^?8 (τ = 10 s) over a time scale of 10 min. The laser linewidth in the regime of self-mode-locking is ≤3 Hz at a laser spectrum width of 20 nm.     

Wear resistance and structure–phase states in the surface of the welding-deposited coating on steel

The elemental and phase composition, the state of a defect substructure, and the tribological characteristics of the layer deposited on the surface of a low-carbon low-alloy steel by a welding method are studied. The deposited layer on the steel surface causes the formation of a multilayer structure, and the wear resistance of the deposited layer is found to increase.     

Selection of optimum spacing of channels for underground gasification of coal

Lyubertsy. Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 2, pp. 91–94, March–April, 1989.     

A diode-laser spectrometer for measuring ortho/para composition of water vapor

A diode laser spectrometer, which is ment for recording ortho-and paracomposition of water vapor in gas mixtures, is described. The studied mixture is probed by infrared radiation at frequencies of the resonance absorptions of ortho-and paramolecules of water (λ ≈ 1.85 μ m). The recording rate of spectral ortho-and paralines is 2 Hz, and the ortho/para composition is calculated in real time with respect to their integrated intensities. An accuracy of 1% is ensured in a 0.01- to 20-Torr partial pressure range for water vapor and in a 0- to 700-Torr partial pressure range for the buffer gas.     

New minimum distance bounds for certain binary linear codes

Let an [n, k, d]-code denote a binary linear code of length n, dimension k, and minimum distance at least d. Define d(n, k) as the maximum value of d for which there exists a binary linear [n, k, d]-code. T. Verhoeff (1989) has provided an updated table of bounds on d(n, k) for 1⩽k⩽n⩽127. The authors improve on some of the upper bounds given in that table by proving the nonexistence of codes with certain parameters     

Enumeration of Optimal Ternary Constant-Composition Codes

The problem of classification of optimal ternary constant-composition codes is considered. Using a combinatorial-computer method, the number of inequivalent codes is determined for 3 d n 10.