Waves in charged thin plates

The spectrum of bending waves of a thin conducting plate bearing an electric charge is investigated. It is proved that there exists a critical value of the field upon exceeding which bending instability of the plate occurs.     

The effect of modification technology on the pyroelectric properties of polymer-piezoceramic composites

The pyroelectric properties of polymer-pyroceramic composites with components premodified under the action of a barrier discharge plasma and the pyroelectric properties of composites crystallized under the simultaneous action of a barrier discharge plasma and temperature are studied. It is shown that the plasma-assisted crystallization technology is more efficient for improving the pyroelectric properties of the composites. Plasma-assisted crystallization provides a high and stable pyroelectric state if the activation energy of the local levels formed in the quasi-bandgap of the polymer phase is higher than the deorientation energy of the domains of the pyrophase of the composite.     

Phonon drag of electrons in Ag<Subscript>2</Subscript>S

The temperature dependences of the heat-conductivity coefficient χ and the thermopower 6h of Ag₂S are investigated in the range of 4.2–300 K. It is found that the value of 6h sharply increases (6h ∞ T^-3) with decreasing T at T < 100 K and passes through a maximum at 16–18 K. The heat-conductivity coefficient passes through a maximum at ≈30 K. The sharp increase in 6h is found to be caused by the effect of long-wavelength-phonon drag of electrons. It is shown that the shift of the 6h and χ peaks, as well as the temperature dependence of the phonon thermopower 6h_ph ∞ T^-3, agrees with the Herring theory.     

The effects of defects on electrical properties of Ag<Subscript>2</Subscript>S at phase transition

The temperature dependences of electrical conductivity σ(T) and the Hall coefficient R(T) in Ag₂S at the phase transition have been studied. Qualitative discrepancies in the changes in σ(T) and R(T) in the case of phase transition have been revealed; i.e., σ increases by several orders of magnitude while R decreases by a factor of 3–4. This is interpreted in the context of a model with two types of charge carriers and with variation in the band parameters and the concentration of defects formed at the phase transition taken into account.     

Absolute negative resistance and multivaluedness on current-voltage characteristics of tunnel diodes

The effect of external perturbations of large amplitude in the form of a coherent signal or noise on the behavior of dynamic and static current-voltage (I–V) characteristics of tunnel diodes has been experimentally investigated. It is shown that, when an appropriate frequency is chosen, an increase in the amplitude of the external coherent signal leads to the occurrence of multivaluedness and absolute negative resistance on the I–V characteristics of tunnel diodes. The noise effect suppresses the N-type negative differential resistance on the I–V characteristics of tunnel diodes and significantly distorts these characteristics. A possible mechanism of the occurrence of absolute negative resistance is proposed.     

Recombination instability and double S-switching in <Emphasis Type="Italic">p</Emphasis>-Ge(Au)

We report on the experimental investigation of p-Ge(Au) samples and compare the results qualitatively to a one-dimensional theoretical model describing the recombination instability of current in gold-compensated germanium in a two-parameter (voltage-emission) space. Experiments showed the existence of three regimes of the system functioning in the parametric space. The second S-switching region was found on the current-voltage characteristic, which is probably related to a noise-induced nonequilibrium phase transition.     

Comments on “H2-optimal zeros”

It is shown that Theorem 2.1 from the above paper by Kubamba-Meerkov (1994) is the interpretation of the classical result on the Rayleigh quotient     

A Strategy for Controlling Groundwater Depletion in the Sa'dah Plain,Yemen

Over-exploitation of the groundwater resources is the major problem leading to groundwater depletion in the Sa'dah Plain, one of the major semi-arid highland basins of Yemen. Groundwater-irrigated agriculture is the chief economic activity in the Plain. Consequently, depletion places socioeconomic development in jeopardy. Owing to the lack of institutional arrangements and management instruments, government intervention is not likely to alleviate the crisis. One non-governmental approach that takes advantage of the existing local sociopolitical structure and customary law would be to adopt an annual abstraction quota. Approaching the crisis at a grass-roots level and relying on the conformity of the local citizens with customary law are the main characteristics of this strategy, the optimum objective of which is sustainable utilization of water resources.