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The structural characteristics of loose zinc deposits obtained in pulse-potential modes are calculated using a phenomenological model. Increasing the duty cycle leads to intensified anodic dissolution during pauses and obtaining of denser deposits, due to the formation of dendrites with fewer tips, yet, a larger diameter as compared to the deposits obtained in the potentiostatic mode. The linear dependence of the diameter of the tips of dendrites forming a loose zinc deposit on the duty cycle is found. There is a critical time corresponding to the achievement of zero deposit growth rate when the metal deposited during the pulse will completely dissolve during the pause. [ABSTRACT FROM AUTHOR]

The present paper deals with hydrogen generation using sono-electrolysis. The experimental investigation is based on a parametric study of water electrolysis system according to the nature of the dissolved salt KOH/NaOH, the concentration of salt in the electrolyte, the temperatures of the electrolyte and the bath (27, 40, 45, 50, 55 and 60 °C), and the nature of the electrode (stainless steel 304, nickel, nickel foam and graphite). Two electrolyzer designs were adopted, namely Hoffmann cell and H-cell. The parametric study revealed the optimum configuration under silent conditions, before integrating the ultrasound power both in continuous and pulsed modes, in order to assess its effect on the energy efficiency of the process and the kinetics of hydrogen production. Under optimal conditions of electrolyte and electrode material, i.e., in KOH electrolyte using nickel foam electrodes, the integration of continuous ultrasound resulted in an increase of 7.78% in the cell current under ambient temperature, corresponding to 64% reduction in the bubble resistance. With the same configuration, the effect of sonication was negligible at the optimal solution temperature of 45 °C, while room temperature operation of the sono-electrolyzer conducted to a better performance than under silent conditions. Finally, continuous sonication mode led to the most performant operation with all the studied configurations, both kinetically and energetically, as compared to pulsed mode. • The geometry of the electrolytic cell controls the ionic transport between both anodic and cathodic compartments. • The effect of the electrolyte in sono-electrolysis is related to surface tension and ionic conductivity. • Heterogeneous solid liquid acoustic cavitation controls the kinetics of H 2 production by sono-electrolysis using nickel foam. • Continuous sono-electrolysis using KOH and nickel foam leads to 64% reductio of the bubble resistance. • Continuous sonication is the optimal mode in sono-electrolysis, both kinetically and energetically. [ABSTRACT FROM AUTHOR]

A phenomenological model describing the change in the structural characteristics of loose zinc deposits obtained in pulsed current modes is presented. Comparison of experimental data on the structural properties of deposits with the results of model calculations indicates the adequacy of the model. To describe the features of the dendritic deposit growth and to determine the duration of the homogeneous structure formation in pulsed modes, the concept of critical thickness is introduced, at which a sharp change in the loose deposit density occurs. The dependence of the zinc deposit critical thickness on the pulse duty ratio under pulsed current modes is determined. The increasing of the pulse duty ratio leads to denser deposits with rounded dendrite shapes and fewer growth points, as compared with the deposit obtained in galvanostatic mode. [ABSTRACT FROM AUTHOR]

An approach is developed to study temporal behavior of the active region overheating in high-power semiconductor lasers (λ = 1060 nm) with an ultrawide aperture (800 μm) operating in a quasi-continuous regime of pumping by current pulses with an amplitude of 21 A, a duration of 1 ms, and a repetition rate of 10 Hz. The approach is based on measuring the lasing dynamics with spectral selection. The lasing spectrum analysis shows that the region of the rising edge, where the amplitude of the current pulse increases, is characterized by a maximum red-shift rate of 30 nm ms–1, which is due to both thermal and nonthermal effects. The pulse region corresponding to a constant pump current amplitude is characterized only by a thermal red shift of the lasing spectrum long-wavelength edge at a rate of ~1 nm ms–1. The obtained experimental active region overheating is 2.78°C for the constant pump current amplitude range, which agrees with the calculated overheating of 3.08°C for the pump conditions under study. [ABSTRACT FROM AUTHOR]

Objectives: This study aims to compare the effectiveness of pulsed and continuous modes of therapeutic ultrasound (US) for phonophoresis in the treatment of subacromial impingement syndrome (SAIS). Patients and methods: Between April 2019 and January 2021, a total of 66 patients with SAIS (17 males, 49 females; mean age: 48.2±8.6 years; range, 19 to 64 years) were included. The patients were randomized to the phonophoresis with continuous mode group (n=22), phonophoresis with pulsed mode group (n=22), and phonophoresis with sham US group (n=22). Five grams of ibuprofen phonophoresis was applied in five sessions per week for three weeks for all groups. Primary outcomes were pain intensity as assessed by the Visual Analog Scale (VAS) and shoulder functions by the short version of Disabilities of the Arm, Shoulder and Hand Questionnaire (QuickDASH). The secondary outcome was the quality of life as assessed by the Nottingham Health Profile (NHP). All patients were evaluated at pre-treatment, post-treatment, and at three months after the end of the treatment. Results: There was a significant improvement in pain during activity, shoulder function, and quality of life after treatment in phonophoresis with continuous and pulsed modes compared to phonophoresis with sham US (p<0.05). Phonophoresis with continuous mode was superior to other groups in reducing pain at rest (p<0.05). Changes between pre-treatment and the three-month follow-up showed a significant improvement in pain during activity and shoulder functions in phonophoresis with continuous and pulsed modes, compared to phonophoresis with sham US (p<0.05). Phonophoresis with pulsed mode was more effective than the other interventions in improving quality of life during the same period (p<0.05). Conclusion: Despite a significant change in phonophoresis with continuous and pulsed modes, it is more pronounced for rest pain in the early period in continuous mode and for quality of life during follow-up in pulsed mode. [ABSTRACT FROM AUTHOR]

The properties of synthesized nanostructured materials are determined by the methods of their preparation. The combination of electric discharges with liquid is a new tool for the synthesis of pure structures but the conditions for obtaining structures play an important role as in the case of traditional synthesis methods. In this work, the electrical and emission characteristics of a low-temperature direct-current plasma in contact with water at currents of 0.25 and 0.80 A are studied. The values of the power (energy) of single discharges are calculated. It is established that this type of discharge burns in the pulsed mode. The value of the discharge current affects the frequency of occurrence of discharges and the energy of a single discharge. It is shown that low-temperature underwater plasma is an effective tool for the synthesis of nanocomposites based on metal oxides, the precursors of which are metal electrodes. The emission spectroscopy method is used to study the emission spectra of underwater plasma. The sputtering of electrodes during plasma combustion is established. X-ray phase analysis shows that the phase composition of the resulting products is determined by the strength of the plasma current. The formation of oxides and hydroxides of Ni and Cr with different valences of metal ions is found. [ABSTRACT FROM AUTHOR]

The elements of repair technology of electron beam welding in the manufacture of a metal-ceramic cathode unit of a powerful welding electron beam gun are considered. A low degree of heat generation at the place of weld overlapping inherent in electron beam welding reduces the risk of buckling parts being joined and provides the maximum compliance with the required sizes of the unit. The need in repair of the cathode unit was determined by the cases of supplying imported insulators with defects in the form of deviations of a thickness from 0.5 to 1.0 mm in the wall of the metal flange («collar») in the brazed joint with the insulator. It was necessary to eliminate the consequences of a violation of the mechanical treatment of the insulator collar after brazing. The possible ways and schemes of repair technologies of such units are shown that allow avoiding the rejection of valuable parts and transferring them to the category of those subjected to restoration. The presented repair technologies involve the use of circumferential insertsbandages of different configuration for two variants to eliminate welding defects associated both with local repair of the edge as well as with repair of its quite elongated areas. Due to a correct choice of the shape of repair inserts, the use of some technological methods and observance of the accuracy of assembly and the sequence of repair welding, it became possible to preserve geometric dimensions and to ensure the functionality of the welded assembly as a whole. 6 Ref., 6 Tabl., 6 Fig. [ABSTRACT FROM AUTHOR]

The elements of repair technology of electron beam welding in the manufacture of a metal-ceramic cathode unit of a powerful welding electron beam gun are considered. A low degree of heat generation at the place of weld overlapping inherent in electron beam welding reduces the risk of buckling parts being joined and provides the maximum compliance with the required sizes of the unit. The need in repair of the cathode unit was determined by the cases of supplying imported insulators with defects in the form of deviations of a thickness from 0.5 to 1.0 mm in the wall of the metal flange ("collar") in the brazed joint with the insulator. It was necessary to eliminate the consequences of a violation of the mechanical treatment of the insulator collar after brazing. The possible ways and schemes of repair technologies of such units are shown that allow avoiding the rejection of valuable parts and transferring them to the category of those subjected to restoration. The presented repair technologies involve the use of circumferential inserts-bandages of different configuration for two variants to eliminate welding defects associated both with local repair of the edge as well as with repair of its quite elongated areas. Due to a correct choice of the shape of repair inserts, the use of some technological methods and observance of the accuracy of assembly and the sequence of repair welding, it became possible to preserve geometric dimensions and to ensure the functionality of the welded assembly as a whole. [ABSTRACT FROM AUTHOR]

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