Ultrasonic effects on electroorganic processes. Part 17. Product selectivity control in cathodic reduction of acrylonitrile

Product selectivity for adiponitrile, which was formed as the corresponding hydrodimeric product along with propionitrile as the hydromonomeric product in the cathodic reduction of acrylonitrile, was significantly increased under ultrasonic irradiation with an intensity above the ultrasonic cavitation threshold. This ultrasonic effect is rationalized as due to mass transport promotion of acrylonitrile molecules to the cathode surface from the bulk electrolytic solution by high speed jet streams caused by the cavitation. A mechanism for the ultrasonic effect is discussed in detail on the basis of the reaction pathway of the hydrodimerization of acrylonitrile.     

Ultrasonic effects on electroorganic processes. Part 27. Electroreduction of acrylonitrile at suspended lead particle-electrode

Ultrasonic effect on the electroreduction of acrylonitrile at suspended lead particle-electrode was examined. The product selectivity for adiponitrile, which was formed as the corresponding hydrodimeric product along with propionitrile as the hydromonomeric one in the cathodic reduction of acrylonitrile, was increased by addition of lead particles as a particle-electrode, and moreover the selectivity was further increased under ultrasonication. This ultrasonic effect is rationalized as due to not only mass transport of lead particles to the feeder cathode but also an increase in the effective surface area of particle-electrode by ultrasonic dispersion. A mechanism for the ultrasonic effect is discussed in detail on the basis of the reaction system.     

Ultrasonic effects on electroorganic processes. Part 14. Indirect electroreduction of benzyl chlorides with anthracene redox-mediatory system

Ultrasonic effects were observed in the indirect electroreduction of benzyl chlorides with a radical anion mediator electrogenerated from anthracene. Both the current efficiency for the toluenes formed and the current density (reaction rate) at a working electrode were significantly increased in potential-controlled electrolysis under ultrasonic irradiation (20 kHz). These effects are important from a practical aspect and are rationalized as being due to mass transport promotion caused by ultrasonic cavitation. Although the efficiency could be also increased in the direct electroreduction in the absence of the mediator under irradiation, the current density was only slightly increased.     

Ultrasonic effects on electroorganic processes Part 6. Formation of cupric carboxylates at a reactive copper anode in carboxylic acid solutions

Current efficiency for the formation of highly soluble cupric acetate at a reactive (consumable) copper anode in an acetic acid solution was increased almost independently of current density under ultrasonic irradiation. On the other hand, the efficiency for sparingly soluble cupric oxalate depended complicatedly on current density. At a low current density region less than 4 mA cm(-2), ultrasonic irradiation caused an increase in the current efficiency, while at higher current densities no ultrasonic effect was observed because of the formation of a rigid oxalate film on the anode surface. This paper is the first report of ultrasonic effects on an electrochemical reaction at a reactive (consumable) anode which is stoichiometrically involved in the reaction leading to the formation of products derived from anode metal.     

Ultrasonic effects on electroorganic processes--Part 20. Photocatalytic oxidation of aliphatic alcohols in aqueous suspension of TiO2 powder

Ultrasonic effects in a suspension system were examined using the photocatalytic oxidation of 2-propanol to acetone and of ethanol to acetaldehyde in the aqueous suspension of TiO2 powder as a model reaction. The formation rate of acetone was significantly increased under ultrasonic irradiation. The oxidation reaction under ultrasonic irradiation was affected in a different manner from that in silence by reaction conditions such as ultrasonic power, stirring speed, amount of TiO2, concentration of 2-propanol, and pretreatment of the TiO2 powder. Furthermore, it was also observed that the particle size of the TiO2 photocatalyst powder was increased due to the particle agglomeration by ultrasonic irradiation, and consequently it was suggested that ultrasound activates the surface of the catalyst. These results are discussed on the basis of not only the activation of the photocatalyst but also ultrasonic enhancement of mass transport of 2-propanol molecules.     

A note on the cathodic processes during electrolytic coloration of alkali halides

By using optical and scanning electron microscope techniques it has been shown that prior to electrolytic coloration of KBr the ionic transport taking place in the crystal leads to the formation of a new alkali metal cathode. Electrons emitted from this cathode and injected into the crystal create F-center.^{4, 5}     

The effects of anodic and cathodic processes on the characteristics of ceramic coatings formed on titanium alloy through the MAO coating technology

This paper reports on the investigation into the effects of the different anodic j_a and cathodic j_c current densities on the variations of the anodic and cathodic processes and the associated changes in the characteristics of the coatings synthesized on Ti-6Al-4V alloy substrate by microarc oxidation technique. The coated samples were subjected to coating thickness and cross-section fracture observation. Phase and elemental composition at different depth of the coatings were evaluated through X-ray diffraction and energy dispersive spectrum analyses. The experimental results indicate that the increase of j_a leads to the increasing slope of anodic voltage U₊ versus oxidation time plots, the larger coating thickness and the more coarse surface morphology of MAO coatings; while the aggrandizement of the cathodic process results in the lower growth rate and more uniform structure of coatings. The changes of the elements distribution from the interface towards the coating surface with variation of j_a and j_c are affected by the Ti anodic dissolution and the electromigration of electriferous particles, such as Al(OH)₄⁻, in electrolytes.     

Wave processes in media with hysteretic nonlinearity. Part I

Two phenomenological models of hysteretic equations of state for media with imperfect elasticity are described and compared. On the basis of these equations, a theoretical study of nonlinear effects caused by the acoustic wave propagation in an unbounded medium is performed. The profiles, parameters, and spectra of waves are determined. The distinctive features of nonlinear wave processes in such media are revealed, so that these features can be used to choose the appropriate hysteretic equation of state for analytically describing the experimental data.     

Ultrasonic effects on titanium tanning of leather

The effects of ultrasound on titanium tanning of leather were investigated. Either 20 or 40 kHz ultrasound was applied to the titanium tanning of pigskins. Five different treatment conditions were carried out and the effects were examined, such as leather shrinkage temperature (T(s)), titanium content and titanium distribution in the leather. Overall heat loading was carefully controlled. Results showed that 20 kHz ultrasound effectively improves titanium agent penetration into the hide and increases the leather's shrinkage temperature. Doubling the frequency to 40 kHz produced negligible enhancements. An impressive 105.6 degrees C T(s) was achieved using 20 kHz ultrasound pretreatment of the tanning liquor followed by 20 kHz ultrasound in the tanning mixture (liquor plus pigskins) in a special salt-free medium. Finally, using a unique ultrasonic tanning drum with 26.5 kHz ultrasound, the T(s) reached a record level of 106.5 degrees C, a value not achieved in conventional (no ultrasound) titanium tanning. The ultrasonic effects on titanium tanning of leather are judged to make a superior mineral tanned leather.     

Active control of double-glazed windows. Part II: Feedback control

This paper describes an experimental investigation of an actively controlled double-glazed window. It is the second of two companion papers of which the first treated results obtained employing adaptive feedforward control. Herein, the outcome using adaptive feedback control is presented. This adaptive feedback controller has been tested in different configurations, i.e. fully and partially connected controllers. The differences between fully connected controllers with few filter coefficients and partially connected controllers with many filter coefficients are discussed. Additionally, tests with different traffic noise examples have been performed showing the ability of the actively controlled window to enhance protection against traffic noise.     

Nonperturbative effects on factorization in high-momentum processes

It is pointed out that the usual demonstrations within QCD perturbation theory of factorization at high-momentum transfers are incomplete when nonperturbative instanton effects are incorporated in a dilute gas approximation. The apparent violation of factorization does not vanish at large Q².     

Nonlinear wave processes in a plasma with stationary random irregularities. Part II

We analyze the influence of large-scale random irregularities of a medium on nonlinear wave interactions. First, we study three-wave interactions in an equilibrium medium, and then we consider the problems of stabilizing the explosive instability in the presence of random irregularities. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 50, No. 1, pp. 54–71, January 2007     

Nonlinear wave processes in a plasma with stationary random irregularities. Part I

In this review comprising two papers, we discuss the results of studying the influence of random irregularities of a medium on nonlinear wave interactions. In this paper representing the first part of the review, we summarize the results of studying the mean fields of interacting waves in the presence of three-dimensional random irregularities and discuss the basic approximations within the framework of which these results are obtained. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 49, No. 11, pp. 977–1001, November 2006.     

Nonequilibrium processes in condensed media. Part 2. Structural instability induced by shock loading

In the first part of the work, we described our concept of shock wave processes, which is based on nonlocal nonequilibrium transport theory, and an associated mathematical elastoplastic wave model that allows for inertial properties, structural changes, and variation in mechanical properties of solid-state materials under shock loading. In the second part of the work, it is demonstrated that the energy exchange between the scales of dynamic deformation is defined by the relation between the characteristics measurable in real time: the mesoscale mass velocity variation and the mass velocity defect due to loss of the energy expended in structure formation. An internal criterion is found for the transition of a dynamically deformed material to structural instability.     

Ultrasonic frequency effects on the removal of Microcystis aeruginosa

Algae bloom in source water causes high chemical consumption and deteriorates water quality in waterworks. This paper studied the ultrasonic removal of Microcystis aeruginosa. The results showed that algae cells could be effectively removed by sonication and gas vesicle collapse was the main mechanism. The ultrasonic algae removal followed the first order reaction with a rate constant of 0.023 min(-1) (80 W, 80 kHz). Higher ultrasound frequency benefited algae removal; the algae removal rate constant was 0.114 min(-1) at 1320 kHz and 0.0224 min(-1) at 20 kHz (80 W). Higher ultrasound power also accelerated algae removal; the algae removal rate constant was 0.023 min(-1) at 80 W and 0.007 min(-1) at 32 W (80 kHz). However, high ultrasound power and long irradiation caused microcystins to increase. 80 W, 80 kHz sonication for 5 min increased the extracellular microcystins concentration from 0.87 microg/L to 3.11 microg/L. Sound frequency had little impact on the microcystins release. The chlorophyll a concentration initially decreased and then stabilized after 5 min of sonication.     

Ultrasonic irradiation effects on electrochemical synthesis of ZnO nanostructures

In the present article, electrochemical synthesis of ZnO nanostructures in presence of ultrasonic irradiation is investigated. The ultrasonic bath use for synthesis is calibrated using hydrophone method so that its frequency and acoustic power were obtained. From the results of the experimentation the role of ultrasonic irradiation in synthesis of ZnO nanoparticles is discussed. Diameter of the ZnO nanoparticles produced in the electrolyte was compared and investigated in absence and presence of the ultrasonic irradiation utilizing UV–visible photo-spectrometer. Then electrodeposited ZnO layer on the ITO glass as cathode’s surface in absence and presence of the ultrasonic irradiation were studied by UV–visible photo-spectrometer and field emission scanning electron microscopy (FE-SEM) and the results were compared. FE-SEM micrographs show, higher growth of nanosheets on the cathode electrode in presence of ultrasonic irradiation. Experiment shows synthesis of ZnO nanoparticles in presence of the ultrasonic irradiation happen 10 times faster.     

Nonequilibrium processes in condensed media: Part 1. Experimental studies in light of nonlocal transport theory

Based on experimental research in shock loading of solid-state materials it is shown that among the important dynamic characteristics of the process, like spatial-temporal mass velocity profiles of shock waves, are the mass velocity variation, velocity defect, and structural instability threshold recorded in real time. Analysis of these characteristics depending on the strain rate, target thickness, and structural state of material demonstrates that conventional approaches of continuum mechanics fail to provide their adequate interpretation and simulation of shock wave processes. A new concept of shock wave processes in condensed media is proposed. The concept, being based on nonlocal nonequilibrium transport theory, allows describing the transition from elastic to hydrodynamic response of a medium depending on the loading rate and time. A nonstationary elastoplastic wave model is proposed for describing the relaxation of an elastic precursor and formation of a retarded plastic front during the wave propagation in a medium with regard to structural evolution. Analysis of the experimental data shows that the division of stresses and strains into elastic and plastic components is incorrect for shock loading.     

Coherent control of interference processes in radiative decays

Possibility of coherent control of spontaneous emission from four- and five-level system in the laser radiation field is studied. The four-level system consists of two levels resonantly driven by laser radiation where either of levels may decay to a separate level. For such a system, we show that the presence of the second decay channel may deteriorate the destructive interference occurring in case of one decay channel because of Autler-Townes effect. The five-level diagram represents two two-level resonantly driven systems with the upper levels decaying to a common level. For this diagram, interference between the two decay channels takes place and it is partially or completely destructive or constructive depending on the initial conditions and on the mutual orientation of the transition dipole moments. It is shown that population transfer takes place by the same quantum vacuum via spontaneous emission. The populations are shown to have damping oscillatory nature.