Acoustooptical processor for radio signals with discrete frequency modulation

A study is made of a processor for pulsed radio signals with discrete frequency modulation, where the frequency varies discontinuously within a pulse and takes on N different values. The spectral components are separated with an acoustooptic spectrum analyzer whose spectral plane is imaged onto a linear charged-coupled photodetector by means of a planar (one-dimensional) spatial converter made of optical fibers. In the imaging, the spectral components of the signal injected into the fiber are transposed by a special arrangement (permutation) of the fibers. The charge-coupled detector, which operates in the time-delay and accumulation mode, detects the spectral components and sums them with the required delay, and thereby compresses the signal and separates it from the noise. The compression factor is limited by the value of N and can be several hundred. Results of experimental investigations of a prototype of the processor are presented. Pis’ma Zh. Tekh. Fiz. 23, 12–19 (January 26, 1997)     

Parametric Method of Fault Location in Distribution Networks

A method for determining the distance to a fault (l) is suggested for medium-voltage distribution networks. The method is based on allocating the upper natural frequency (f ₂) due to the discharge of the capacitance of the damaged phase in the transient process of earth connection. The allocated frequency and frequency response l = (f ₂) calculated for the damaged line are used to locate the fault.     

Charge Transport Properties of Lightly-Doped Cuprates: Behavior of the Hall Coefficient

Behavior of _ab (T) and R _H(T) is presented for LSCO and YBCO single crystals in the lightly hole-doped antiferromagnetic region, with an emphasis on the R _H(T) data. In both systems, R _H is virtually constant at moderate temperatures and tends to increase at low temperatures. Since essentially the same behavior of _ab (T) and R _H(T) is observed in both LSCO and YBCO, we discuss that the in-plane charge transport properties are universal among the cuprates in the lightly-doped regime and that the R _H(T) data we obtained represent the genuine behavior of the Hall effect in this regime.     

Transient behavior of a few dies on an elastic half-space

Summary An asymptotic approach to dynamic interaction between a few distant dies and an elastic half-space is proposed. The transient motion of the dies under low-frequency vertical load is under consideration. The explicit expression for the fundamental singular solution of Lamb's problem is used to derive the boundary integral equation of contact. Then this equation is asymptotically simplified and solved numerically in combination with equations of motion of the dies.Equations obtained in the asymptotic limit describe both the die-medium dynamic interaction and the interaction between dies through the elastic medium. These equations take into account the energy dissipation phenomenon associated with energy transfer deep into the medium by outgoing elastic waves, of so called geometrical damping.Equations proposed are asymptotically correct within the corresponding range of parameters, as such improving the state-of-the-art.