Acceleration of electrocatalytic reactions by pulsation of potential: Oxidation of formic acid on Pt and Pt/Pbads electrodes

Pulsating potential electrolysis has been applied to one typical electrocatalytic reaction ie, the oxidation of formic acid on platinum and platinum partially covered by lead adatoms electrodes. It has been found that much higher average cds can be obtained with such regimes than in constant potential electrolysis. The effect can be of considerable interest for the application in electrochemical power sources. An analysis of the mechanism of effects of pulsating potentials has been given. A calculated frequency dependence of the average current density is in agreement with experimental one for both electrodes.     

Plastic-bonded electrodes for nickelcadmium accumulators. X. The nature of the second discharge step of nickel oxide electrodes

The second discharge step of nickel oxide accumulator electrodes is suppressed in the presence of a Teflon binder and/or cobalt, cerium, or manganese hydroxide, whereas the first discharge step increases. This behaviour is discussed in terms of ohmic resistance effects and semiconducting properties of the active material.     

Prediction and measurement of crystal size distributions for size-dependent growth

Predictions of size distributions, mean sizes and coefficients of variation in mixed-suspension mixed-product removal crystallizers are presented for the case when crystal growth rate is given by the expression G = G⁰ (1 + γL)^b as suggested by Abegg, Stevens and Larson (ASL). Crystal size distributions were measured at three scales of operation (1, 5 and 30 1.) for a system which exhibits size-dependent growth (potash alum/water). Experimental median sizes were in good agreement with the predictions and coefficients of variation significantly greater than 50% were obtained. The observed variation of crystal growth rate with size however was only moderately well represented by the ASL equation.     

Konstruktion und experimentelle Untersuchung des Arbeitsdiagrammes einer Einphase-Ausgleichswelle

Übersicht Zunächst werden Formeln für den Motorstrom in Zusammenhang mit der Einphasen-Ausgleichswelle gegeben; weiter wird gezeigt, wie die Motor-Arbeitsdiagramme konstruiert werden können, d. h. entweder mit Hilfe der berechneten Parameter oder mit Hilfe der durch Experimente erhaltenen Angaben.Mit 10 Textabbildungen.     

Trapping and recombination processes via deep level T3 in semi-insulating gallium arsenide

Trapping and recombination of free carriers by deep level T₃ has been studied. Occupancy of the level by electrons and dynamics of its filling and emptying as a function of illumination with monoenergetic photons in 0.69–1.55 eV range has been monitored by the thermally stimulated currents method. We have found that level T₃ behaves more like a recombination center than like an ordinary electron trap. Besides trapping free electrons from conduction band, this trap can also communicate with valence band, trapping holes. The capture cross section for trapping a hole is estimated to be comparable or even larger than the capture cross section for trapping an electron. However, in many experimental conditions free electrons are generated more abundantly than free holes, and free carrier mobility and thermal velocity are both much higher for electrons than for holes. Therefore, electron trapping often prevails, so that this frequently detected defect, has been up to now most often perceived as a deep electron trap.     

Stochastic LQ-optimal control for 2-D systems

Stochastic LQ-optimal control problem is solved for linear 2-D systems via 2-D polynomial techniques. All stabilizing controllers are parameterized and then minimizing one is obtained. Its transfer function results from two 2-D spectral factorizations and a couple of linear equations in formal power series. A practically useful sub-optimal controller is also considered that results from truncated spectral factorizations and a couple of 2-D polynomial equations.