112 results on '"Pulsed mode"'
Search Results
2. Membrane free alkaline sono-electrolysis for hydrogen production: An experimental approach.
- Author
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Merabet, Nour Hane and Kerboua, Kaouther
- Subjects
- *
HYDROGEN production , *NICKEL electrodes , *WATER electrolysis , *IONIC conductivity , *ELECTROLYTIC cells , *ELECTROLYSIS - Abstract
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]
- Published
- 2024
- Full Text
- View/download PDF
3. A Model Describing the Process of the Electrodeposition of Zinc Loose Deposits in Pulsed Current Modes.
- Author
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Nikitin, V. S., Ostanina, T. N., Rudoy, V. M., and Ostanin, N. I.
- Subjects
- *
ELECTROPLATING , *DENDRITES , *DENSITY , *ELECTROLYSIS - Abstract
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]
- Published
- 2023
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- View/download PDF
4. Heating Dynamics of the Active Region of High-Power Semiconductor Lasers (λ = 1060 nm) with an Ultra-Wide Aperture (800 µm) in the Quasi-CW Mode.
- Author
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Shashkin, I. S., Rybkin, A. D., Kryuchkov, V. A., Kazakova, A. E., Romanovich, D. N., Rudova, N. A., Slipchenko, S. O., and Pikhtin, N. A.
- Abstract
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]- Published
- 2023
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5. Phonophoresis treatment of subacromial impingement syndrome: Pulsed or continuous: A randomized-controlled clinical trial.
- Author
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Kelle, Bayram, Deniz, Volkan, and Ortaç, Emine Aygül
- Abstract
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]
- Published
- 2023
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6. On the Dynamics of the Development and the Results of the Action of Electric Discharge in an Aquatic Environment.
- Author
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Khlyustova, A. V., Sirotkin, N. A., Agafonov, A. V., Stepovich, M. A., and Shipko, M. N.
- Abstract
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]
- Published
- 2023
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7. TECHNOLOGIES OF REPAIRING CATHODE UNIT OF ELECTRON BEAM GUN WITH THE USE OF ELECTRON BEAM WELDING.
- Author
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Zagornikov, V. I., Nesterenkov, V. M., Orsa, Yu. V., and Ignatenko, A. M.
- Subjects
ELECTRON beam welding ,ELECTRON gun ,WELDING defects ,ELECTRON beams ,CATHODES ,BRAZING ,BRAZED joints - Abstract
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]
- Published
- 2023
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8. UV-LED TECHNOLOGY: THE FUTURE OF SAFE AND SUSTAINABLE WATER DISINFECTION.
- Author
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Ångbäck, Ida, Persson, Kenneth M., and Paul, Catherine
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LIGHT emitting diodes ,SUSTAINABILITY ,DRINKING water ,WATER disinfection - Abstract
Copyright of Vatten is the property of Foreningen Vatten and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2021
9. Laboratory and Numerical Study of the Peculiarities of Sea Surface Cooling in Coastal Waters.
- Author
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Kupriyanova, A. E. and Gritsenko, V. A.
- Subjects
- *
TERRITORIAL waters , *SALINE waters , *CHEMICAL stability , *BUOYANCY , *SEAWATER - Abstract
The initial phases of penetration of cold waters from the sea surface into the depth are analyzed within a study of the process of sea surface cooling. The phases of immersion of small volumes of water with negative buoyancy, reaching the bottom, and propagation along the bottom slope have been studied in laboratory experiment and numerical simulation. The interaction between two small volumes of salt water, which sequentially originate in the surface freshwater layer, during their immersion and subsequent propagation along the bottom slope is described in detail. Laboratory experiments have shown that the second of two water spots, equal in volumes and negative buoyancy, always reaches the first one during propagation along the bottom slope. A phenomenological explanation of this fact is suggested. The images of individual phases of the water-spot propagation show quite long-term stability of laminar structure of tracers inside the water spots. The simulation allows distinguishing two characteristic phases (advective and viscous) of interaction between two water spots. The experimental and simulation results allow us to suggest the general scheme of the negative-buoyancy water dynamics in coastal waters. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
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10. Optimization of pulsed-mode ultrasound assisted extraction of bioactive compounds from pomegranate peel using response surface methodology.
- Author
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Kumar, Ankit and Srinivasa Rao, Pavuluri
- Subjects
BIOACTIVE compounds ,EXTRACTION (Chemistry) ,POMEGRANATE ,FLAVONOIDS ,PHENOLS - Abstract
In this study, a pulsed mode ultrasound assisted extraction was performed for the extraction of bioactive compounds from Pomegranate (Punica granatum L.) peel. Box-Behnken experimental design combined with response surface methodology, was applied for the optimization of process conditions. The independent variables investigated were ultrasound amplitude (50–80%), sonication time (5–15 min), duty cycle (0.2–0.8), and methanol concentration (30–70%) to maximize the yield of total phenolic content, flavonoid content, total condensed and hydrolysable tannin (TCT and THT respectively), and antioxidant activity (DPPH and FRAP). The experimental results were fitted to quadratic models, and statistical analysis in terms of multiple regression, and analysis of variation was carried out for each response variable. The optimum predicted values of the response variables were obtained at 70% methanol concentration, 12.8 min of sonication treatment at a duty cycle of 0.58, and 80% ultrasound amplitude. A comparative analysis at optimized condition showed better recovery of bioactive compounds in pulsed mode, compared to continuous mode of sonication. Correlation analysis of the response variables was done to find the associations among the variables. Multivariate analysis using principal component analysis, and hierarchical cluster analysis was done for better understanding of interactions among experimental treatments and responses. [ABSTRACT FROM AUTHOR]
- Published
- 2020
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11. Stability of Ion Flow and Role of Boundary Conditions in a Simplified Model of the E × B Plasma Accelerator with a Uniform Electron Mobility.
- Author
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Romadanov, I. V., Smolyakov, A. I., Sorokina, E. A., Andreev, V. V., and Marusov, N. A.
- Abstract
Resistive oscillations of axial plasma with ionization effects are analyzed in configuration similar to the Hall effect thrusters. From analysis of stationary equations we have identified different types of the steady-state plasma flow profiles and use these solutions as initial conditions in time-dependent initial value simulations. We have identified unstable regimes with intrinsic oscillations, as well as stable regions without oscillations. It was found that nonlinear oscillations may exist in different form depending on the range of plasma parameters. Single mode coherent, multi-mode with nonlinear harmonics, and incoherent (stochastic) mode regimes were identified. We have further investigated the role of boundary conditions on the characteristics of nonlinear oscillations. [ABSTRACT FROM AUTHOR]
- Published
- 2020
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12. FEATURES OF APPLYING ELECTRON BEAM WELDING IN MANUFACTURE OF THE CATHODE ASSEMBLY OF THE ELECTRON GUN.
- Author
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Nesterenkov, V. M., Zagornikov, V. I., Orsa, Yu. V., and Ignatenko, O. M.
- Subjects
ELECTRON beam welding ,ELECTRON beams ,ELECTRON gun ,WELDED joints ,MANUFACTURING processes ,CONSTRUCTION materials - Abstract
The efficiency of using electron beam welding in producing permanent joints of structural materials of all thicknesses and shapes is well-known. The work for the first time considers the possibility of using electron beam welding for the production of high-precision parts of optical system in cathode unit, providing the necessary parameters and their joining with electron beam gun insulator in future. The use of electron beam welding at the final stage of manufacturing cathode unit opens the opportunity of minimizing the number of further technological operations. It is noted that to create the welding technology, in which the operation of welding would become a final assembly operation, the development of new designs of welded joints and schemes for assembly of cathode unit are required. Due to a correct design of welding units and compliance with the accuracy of assembling for welding, it became possible to preserve geometric dimensions after electron beam welding and to provide the operational reliability of the design as a whole. 5 Ref., 6 Figures. [ABSTRACT FROM AUTHOR]
- Published
- 2020
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13. A Study on the Stability of Water-Gated Organic Field-Effect-Transistors Based on a Commercial p-Type Polymer
- Author
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Rosaria Anna Picca, Kyriaki Manoli, Eleonora Macchia, Angelo Tricase, Cinzia Di Franco, Gaetano Scamarcio, Nicola Cioffi, and Luisa Torsi
- Subjects
poly-3-hexylthiophene ,electrolyte-gated OFET ,degradation ,pulsed mode ,biosensors ,Chemistry ,QD1-999 - Abstract
Robust electrolyte-gated organic field-effect-transistors (OFETs) are particularly needed for the development of biosensing devices. However, when a FET biosensor operates in aqueous environments or even in real biological fluids, some critical issues may arise due to the possible lack of environmental long-term and/or operational stability. An important source of instability is associated with the degradation of the organic electronic channel materials such as for instance, poly-3-hexylthiophene (P3HT), a benchmark commercially available p-type organic semiconductor. In this work, the investigation of critical parameters, such as the control over spurious electrochemical phenomena as well as the operating conditions that can affect water-gated OFETs lifetime, is reported, together with a proposed modeling of the P3HT stability curve over 1 week in water. The investigation of possible morphological/chemical modifications occurring at the polymer surface after operating in water for 2 weeks was carried out. Moreover, it is proven how the addition of a gel layer can extend the P3HT based water-gated OFET shelf life up to 2 months.
- Published
- 2019
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14. Working process calculation of the control circuit for pulsed operation regime of the MPD accelerator
- Author
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Tashayev, Yuriy
- Subjects
discharge current ,pulse shape ,Morgan scheme ,дискретные плазменные образования ,pulsed mode ,плазменные ускорители ,схема Моргана ,plasma accelerators ,discrete plasma formations ,импульсный режим ,разрядный ток ,форма импульса - Abstract
A circuit for controlling the discharge current of an MPD accelerator based on the Morgan circuit is considered. It is shown that theoretically operation regime of the accelerator, depending on the parameters of the circuit, can be stationary, modulation, and pulsed. The necessary condition for the accelerator operation in the periodic mode is established. Calculations of the pulse shape of the discharge current are carried out. The experimentally observed pulse forms are compared with the calculated ones., Рассмотрена схема управления током разряда МПД-ускорителя, основанная на схеме Моргана. Теоретически показано, что режим работы ускорителя в зависимости от параметров схемы может быть стационарным, модуляционным и импульсным. Найдено необходимое условие работы ускорителя в периодическом режиме. Проведены расчеты формы импульса разрядного тока. Найдено условие перехода от модуляционного режима к импульсному. Экспериментально наблюдаемые формы импульсов сравниваются с расчетными.
- Published
- 2023
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15. Effect of Parameters of Pulsed Potential Mode on Concentration Changes in the Bulk Loose Zinc Deposit and Its Properties.
- Author
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Nikitin, V. S., Ostanina, T. N., and Rudoi, V. M.
- Subjects
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ZINC , *CRYSTAL growth , *ANODES , *CATHODES , *DENDRITIC crystals , *ELECTROLYSIS - Abstract
It is shown that the parameters of pulsed potential modes (pulse-on and pulse-off times) have a pronounced effect on the growth dynamics and properties of loose metal deposits in the cases that the process proceeds under the conditions of non-steady-state diffusion. It is proposed to use a ratio between the cathodic and anodic charges in a cycle as a parameter that characterizes the concentration changes. By varying the parameters of pulsed potential, zinc deposits of various morphology can be obtained: from compact deposits to highly porous deposits that consist of branched dendritic particles. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
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16. Influence of the Design Features of a Piezoelectric Transducer on Probing Signal Duration.
- Author
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Konovalov, R. S., Konovalov, S. I., and Kuz’menko, A. G.
- Subjects
- *
PIEZOELECTRIC transducers , *MICROELECTROMECHANICAL systems - Abstract
A piezoelectric transducer in the form of a damped plate radiating into steel through a system of transition layers is considered. The algorithm for calculating the frequency response of the transducer is described, and its pulsed operation mode is investigated. A voltage pulse in the form of a half sine wave at the plate’s antiresonance frequency is selected as an electrical excitation signal. Some materials used for manufacturing certain transducer design elements are considered. Based on estimative calculations of the geometrical thicknesses of layers actually encountered in the practice of ultrasonic testing, their wave thicknesses are chosen. The data obtained is used to determine the shape of the emitter output signal. Calculations are carried out in a wide range of specific acoustic impedances of the wear plate. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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17. Nitriding of Stainless Steel in Electron-Beam Plasma in the Pulsed and DC Generation Modes.
- Author
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Gavrilov, N. V., Mamaev, A. S., and Chukin, A. V.
- Abstract
The influence of electron-beam parameters on the thickness and phase composition of a hardened layer formed upon the nitriding of austenitic stainless steel 12Cr18Ni10Ti in plasma produced by a beam in a low-pressure (3 Pa) nitrogen--argon mixture is studied. The results obtained in the DC and pulse-periodic modes of beam generation with the same mean current and electron energy are compared. In this case the negative bias voltage applied to the samples is 100 V. The nitriding temperature of 400°C is maintained at a mean beam current of 2.6 A and various combinations of frequency (100--500 Hz) and current pulse durations (0.1-0.3 ms) with an amplitude of 80 A. The mean ion-plasma current densities in the DC and pulsed modes are close in magnitude (2-3 mA/cm² at 400°C). The high pulsed ion-current density (35-70 mA/cm²) creates conditions under which the surface sputtering rate during the pulse exceeds the growth rate of the nitrided layer. The nitriding of steel in the pulsed and DC modes over four hours gives the same result. Hardened layers with a thickness of 7-8 µm and a microhardness of the surface component of 15 ± 1 GPa in which the main phase is a supersaturated nitrogen solid solution (expanded austenite) are formed. A possible explanation is that nitriding in an electron-beam plasma proceeds mainly under the action of long-lived active neutral nitrogen particles rather than as a result of ion bombardment. [ABSTRACT FROM AUTHOR]
- Published
- 2017
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18. Definition of the influence of pulsed deposition modes on the electrochromic properties of Ni(OH)2-polyvinyl alcohol films
- Author
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Valerii Kotok and Vadym Kovalenko
- Subjects
Materials science ,pulsed mode ,nickel hydroxide ,Analytical chemistry ,Energy Engineering and Power Technology ,chemistry.chemical_element ,engineering.material ,composite coating ,Polyvinyl alcohol ,Industrial and Manufacturing Engineering ,law.invention ,chemistry.chemical_compound ,Coating ,law ,Management of Technology and Innovation ,electrochromism ,T1-995 ,Industry ,Electrical and Electronic Engineering ,Technology (General) ,Applied Mathematics ,Mechanical Engineering ,HD2321-4730.9 ,Cathode ,Computer Science Applications ,Nickel ,polyvinyl alcohol ,chemistry ,Control and Systems Engineering ,Electrochromism ,Electrode ,engineering ,electrodeposition ,Deposition (chemistry) ,Current density - Abstract
In this work, the influence of some types of the pulsed deposition mode of electrochromic films from aqueous solutions of nickel nitrate with the addition of polyvinyl alcohol was investigated. Glass coated with a fluorine-doped tin oxide film was used as the basis for deposition. The deposition of nickel (II) hydroxide – polyvinyl alcohol electrochromic films was carried out in three pulsed modes: –0.2mA/cm2×5s, 0mA/cm2×5s (10minutes); –0.5mA/cm2×2s, 0mA/cm2×8s (10minutes); –1mA/cm2×1s, 0mA/cm2×9s. In this case, the amount of electricity used for the formation of thin-film electrodes was the same for all samples. The resulting films showed dramatic differences in electrochemical, optical, and quality characteristics. The sample obtained in the mode of the highest cathode current density and the duration of the no-current condition (1mA/cm2×1s, 0mA/cm2×9s) had the worst specific capacity and optical characteristics. This sample was characterized by the highest number of coating defects and color non-uniformity as well. The sample, which was obtained at average current densities (–0.5mA/cm2×2s, 0mA/cm2×8s), had the highest specific characteristics among the electrodes in the series. The coating was uniform and solid. Also, this sample had the greatest stability of the coloration depth value, which varied from 79.1 to 78.1% (first to fifth cycles). The sample obtained in the mode –0.2mA/cm2×5s, 0mA/cm2×5s showed moderate specific indicators, however, there were some coating defects. According to the results obtained, a mechanism was proposed that explained the differences in the characteristics of thin-film electrodes formed in different modes. This mechanism consists of changing the time of non-stationary processes and the distribution of the current density with a change in the value of the deposition current density, the duration of the cathode period, and the no-current condition.
- Published
- 2021
19. Closure of skin incision by dual wavelength (980 and 1064 nm) laser application.
- Author
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Uba, Abdullahi Ibrahim, Tabakoglu, Haşim Ozgur, Abdullahi, Umar Aliyu, and Sani, Musbahu Muhammad
- Subjects
- *
SURGICAL site , *LASER therapy , *CONTINUOUS wave lasers , *LASER welding , *WOUND healing - Abstract
Thermal effect of dual wavelength (980 and 1064 nm) laser application in skin incision closure was assessed on 18 male and female Wister rats. 1-cm-long incisions were made on the shaved dorsal region of 220–250 g animals. The incisions were closed by laser irradiation at 1 W and exposure time, 5 seconds in continuous-wave mode (CW) and 1 W and exposure time, 10 seconds in pulsed mode to deliver total energies of 5 J and 10 J per spot onto the incisions, respectively. Animals from each group were sacrificed at 0th, 4th, and 7th days and the skin samples of the weld area were excised for histological analysis using Hematoxylin and Eosin (H & E) stain. Mean thermally altered area (TAA) of CW-mode laser-treated groups was found to increase significantly (p< 0.05) compared with pulsed mode laser treated group at 0th and 4th days post-irradiation while no significant difference (p> 0.05) was statistically found at 7th day post-irradiation. Moreover, tighter closure was observed with CW group at 7th day post-irradiation. We thus conclude that 1 W, 5 J for 5 seconds CW mode laser application of 980 and 1064 nm combined beam form in skin incision closure was found to have absolute wound healing capability with minimal thermal alteration.ABSTRACT FROM PUBLISHERCopyright of Journal of Cosmetic & Laser Therapy is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
20. InAs‐based quantum cascade lasers emitting close to 25 µm.
- Author
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Loghmari, Z., Bahriz, M., Meguekam, A., Teissier, R., and Baranov, A.N.
- Abstract
Indium arsenide (InAs)‐based quantum cascade lasers (QCLs) operating close to 25 µm are reported. Thick n‐doped InAs cladding layers were used for optical confinement. Fabry–Perot lasers exhibited a threshold current density as low as 1.1 kA/cm2 in pulsed mode at 80 K. The lasers operated in this regime up to 240 K, where the threshold current density increased up to 1.7 kA/cm2. These are the lowest threshold current densities for QCLs operating above 20 µm. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
21. Performance optimization of water-jet assisted underwater laser cutting of AISI 304 stainless steel sheet.
- Author
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Mullick, Suvradip, Madhukar, Yuvraj K., Roy, Subhransu, and Nath, Ashish K.
- Subjects
- *
WATER jets , *UNDERWATER welding & cutting , *LASER beam cutting , *STAINLESS steel sheets , *ELECTRONIC modulation , *EXPERIMENTAL design - Abstract
Recent development of water-jet assisted underwater laser cutting has shown some advantages over the gas assisted underwater laser cutting, as it produces much less turbulence, gas bubble and aerosols, resulting in a more gentle process. However, this process has relatively low efficiency due to different losses in water. Scattering is reported to be a dominant loss mechanism, which depends on the growth of vapor layer at cut front and its removal by water-jet. Present study reports improvement in process efficiency by reducing the scattering loss using modulated laser power. Judicious control of laser pulse on- and off-time could improve process efficiency through restricting the vapor growth and its effective removal by water-jet within the laser on- and off-time, respectively. Effects of average laser power, duty cycle and modulation frequency on specific energy are studied to get an operating zone for maximum efficiency. Next, the variation in laser cut quality with different process parameters are studied within this operating zone using Design of experiment (DOE). Response surface methodology (RSM) is used by implementing three level Box-Behnken design to optimize the variation in cut quality, and to find out the optimal process parameters for desired quality. Various phenomena and material removal mechanism involved in this process are also discussed. [ABSTRACT FROM AUTHOR]
- Published
- 2016
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22. On some paradoxes in the analysis of pulsed operation mode of acoustic transducers by the method of integral transformations.
- Author
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Balabaev, S. and Ivina, N.
- Subjects
- *
ACOUSTIC transducers , *WAVENUMBER - Abstract
Reasons for the appearance of 'precursors' and 'tails' in the analysis of pulsed operation mode of acoustic transducers by the method of integral transformations are considered. It is emphasized that the reason is the impossibility to make an accurate allowance for the actual dependence of the complex wave number on frequency over the entire frequency range. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
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23. Equipment for electric arc metallizing with pulsed discharge of the air-spraying jet.
- Author
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Royanov, V. A. and Bovikov, V. I.
- Subjects
ELECTRIC arc ,ELECTRIC discharges ,JETS (Fluid dynamics) ,DATA analysis ,ELECTRIC power consumption ,COMPRESSED air - Abstract
The results of a review of literature data show that electric arc metallizing systems are characterized by high consumption of compressed air. Spraying is accompanied by the high-intensity interaction of the spraying air jet with the liquid metal of the molten ends of the electrodes, leading to rapid burnout of the alloying elements. The intensity of the oxidation reaction depends on the heat resistance of the sprayed material, the dispersion of the particles, the affinity of the components for oxygen and the technological parameters of the coatings. In order to reduce the oxidation effect, it is proposed to use a pulsed air-spraying jet. To solve this problem, experiments were carried out to develop appropriate equipment for the EN-17 stationary electric arc metallizing system characterized by the pulsed discharge of the air-spraying jet in the range 0–130 Hz. The experimental results show that the spraying jet is pulsed with temporary breaks. When using circular cross sections, the pulse smoothly becomes larger. The application of the right-angled section results in the pulse shape increasing at a higher rate. The experimental results show that the oxidation effect of the air-spraying jet is reduced. It is also shown that the optimum frequency resulting in improved properties of the coating is in the range 40–80 Hz. [ABSTRACT FROM PUBLISHER]
- Published
- 2016
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24. Определение влияния импульсных режимов осаждения на электрохромные свойства пленок Ni(OH)2-поливиниловый спирт
- Subjects
поливиниловый спирт ,электроосаждение ,pulsed mode ,nickel hydroxide ,композитное покрытие ,гидроксид никеля ,імпульсний режим ,композитне покриття ,composite coating ,електроосадження ,полівініловий спирт ,polyvinyl alcohol ,электрохромизм ,гідроксид нікелю ,electrodeposition ,electrochromism ,импульсный режим ,електрохромізм - Abstract
In this work, the influence of some types of the pulsed deposition mode of electrochromic films from aqueous solutions of nickel nitrate with the addition of polyvinyl alcohol was investigated. Glass coated with a fluorine-doped tin oxide film was used as the basis for deposition. The deposition of nickel (II) hydroxide – polyvinyl alcohol electrochromic films was carried out in three pulsed modes: –0.2 mA/cm2×5 s, 0 mA/cm2×5 s (10 minutes); –0.5 mA/cm2×2 s, 0 mA/cm2×8 s (10 minutes); –1 mA/cm2×1 s, 0 mA/cm2×9 s. In this case, the amount of electricity used for the formation of thin-film electrodes was the same for all samples. The resulting films showed dramatic differences in electrochemical, optical, and quality characteristics. The sample obtained in the mode of the highest cathode current density and the duration of the no-current condition (1 mA/cm2×1 s, 0 mA/cm2×9 s) had the worst specific capacity and optical characteristics. This sample was characterized by the highest number of coating defects and color non-uniformity as well. The sample, which was obtained at average current densities (–0.5 mA/cm2×2 s, 0 mA/cm2×8 s), had the highest specific characteristics among the electrodes in the series. The coating was uniform and solid. Also, this sample had the greatest stability of the coloration depth value, which varied from 79.1 to 78.1 % (first to fifth cycles). The sample obtained in the mode –0.2 mA/cm2×5 s, 0 mA/cm2×5 s showed moderate specific indicators, however, there were some coating defects. According to the results obtained, a mechanism was proposed that explained the differences in the characteristics of thin-film electrodes formed in different modes. This mechanism consists of changing the time of non-stationary processes and the distribution of the current density with a change in the value of the deposition current density, the duration of the cathode period, and the no-current condition., В работе было исследовано влияние некоторых режимов импульсного режима нанесения электрохромных пленок из водных растворов нитрата никеля с добавкой поливинилового спирта. В качестве основ для осаждения использовали стекло, покрытое пленкой оксида олова допированного фтором. Осаждение электрохромных пленок гидроксид никеля (II) – поливиниловый спирт было проведено в трех импульсных режимах: –0,2 мА/см2×5с, 0мА/см2 ×5с (10минут); –0,5мА/см2×2с, 0мА/см2×8с (10минут); –1мА/см2×1с, 0мА/см2×9с. При этом количество электричества, которое пошло на формирование тонкопленочных электродов было одинаковым для всех образцов. Полученные пленки показали кардинальные отличия в электрохимических, оптических и качественных характеристиках. Образец, полученный в режиме наибольшей катодной плотности тока и длительности бестоковой паузы (1мА/см2×1с, 0мА/см2×9с), имел наихудшие удельные емкостные и оптические характеристики. Также этот образец характеризовался наибольшим количеством дефектов покрытия и неравномерностью цвета. Образец, который был получен при средних плотностях токов (–0,5мА/см2×2с, 0мА/см2×8с), имел самые высокие удельные характеристики среди электродов серии. Покрытие было равномерное и сплошное. Также данный образец имел наибольшую стабильность величины глубины затемнения, которая менялась с 79,1 до 78,1% (первый-пятый циклы). Образец полученный в режиме –0,2мА/см2×5с, 0мА/см2×5 с продемонстрировал средние удельные показатели, однако при этом имели место дефекты покрытия. Согласно полученным результатам, был предположен механизм, который объясняет отличия характеристик тонкопленочных электродов, сформированных в разных режимах. Этот механизм заключается в изменении времени нестационарных процессов и распределении плотности тока при изменении величины плотности тока осаждения, длительности катодного периода и бестоковой паузы, Було досліджено вплив деяких режимів імпульсного режиму нанесення електрохромних плівок з водних розчинів нітрату нікелю з добавкою полівінілового спирту. У якості основи для осадження використовували скло, покрите плівкою оксиду олова допованого фтором. Осадження електрохромних плівок гідроксиду нікелю (II) – полівініловий спирт було проведено в трьох імпульсних режимах: –0,2мА/см2×5с, 0 мА/см2×5с (10хвилин); –0,5мА/см2×2с, 0мА/см2×8 з (10хвилин); –1мА/см2×1с, 0мА/см2×9с. При цьому кількість електрики, яка пішла на формування тонкоплівкових електродів, була однаковою для всіх зразків. Отримані плівки показали кардинальні відмінності в електрохімічних, оптичних і якісних характеристиках. Зразок, отриманий в режимі максимальної катодної густини струму і тривалості безструмової паузи (1мА/см2×1с, 0мА/см2×9с), мав найгірші питомі ємкісні і оптичні характеристики. Також цей зразок характеризувався найбільшою кількістю дефектів покриття і нерівномірністю кольору. Зразок, який був отриманий при середніх щільності струмів (–0,5мА/см2×2с, 0мА/см2×8с), мав найвищі питомі характеристики серед електродів серії. Покриття було рівномірне і суцільне. Також даний зразок мав найбільшу стабільність величини глибини затемнення, яка змінювалася з 79,1 до 78,1% (перший-п'ятий цикли). Зразок, отриманий в режимі –0,2мА/см2×5с, 0мА/см2×5с, продемонстрував середні питомі показники, однак при цьому мали місце дефекти покриття. Згідно з отриманими результатами, був припущений механізм, який пояснює відмінності характеристик тонкоплівкових електродів, сформованих в різних режимах. Цей механізм полягає в зміні часу нестаціонарних процесів і розподілі щільності струму при зміні величини густини струму осадження, тривалості катодного періоду і безструмової паузи
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- 2021
25. Photoionization of cobalt impurities in zinc oxide.
- Author
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Ivanov, Vitalii Yu., Godlewski, Marek, and Dejneka, Alexander
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- *
PHOTODISSOCIATION , *FIELD ionization , *ZINC oxide , *PHOTOIONIZATION , *ELECTRON spin - Abstract
Electron Spin Resonance investigations allow to attribute a broad absorption band below the band-to-band transition of ZnO:Co to photoionization transitions of Co-ions. This absorption, with the onset at about 2.4-2.6 eV, is due to cobalt recharging, as concluded from the photo-ESR and pulsed ESR experiments. In these experiments light sensitive ESR signals of Co2+ and shallow donor are observed. Their response to light favors cobalt 2+ to 3+ photoionization. [ABSTRACT FROM AUTHOR]
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- 2015
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26. APPLICATION OF PULSE ATOMIZING JET IN ELECTRIC ARC METALLIZING.
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ROYANOV, V. A. and BOBIKOV, V. I.
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ELECTRIC welding ,DYNAMIC pressure ,ELECTRIC arc ,STATIC pressure ,MICROSTRUCTURE - Abstract
The paper presents the results of investigation of pulse atomizing air jet application in electric arc metallizing. To ensure the pulsed mode, the respective device was developed allowing control of outflowing of a jet with frequency within 0-130 Hz. Oscillograms of variation of dynamic pressure are given. Dependence of pulse atomizing air jet on frequency of closing the spray gun nozzle channel is shown. Coating microstructures are given. Influence of pulsation frequency on composition of coatings spray-deposited with PP-MM-2 wire is shown. 15 Ref., 6 Figures. [ABSTRACT FROM AUTHOR]
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- 2014
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27. Diode-End-Pumped Midinfrared Multiwavelength Er:Pr:GGG Laser.
- Author
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Zhenyu You, Yan Wang, Jinlong Xu, Zhaojie Zhu, Jianfu Li, and Chaoyang Tu
- Abstract
We report a diode-end-pumped midinfrared multiwavelength Er:Pr:GGG laser, generating the output powers of 324 and 354 mW in CW and pulsed modes, respectively. The slope efficiencies of CW and pulsed modes are 15.18% and 16.06%, respectively. Compared with Er:GGG, the laser properties of Er:Pr:GGG are much better and the self-termination bottleneck is broken successfully. The transverse beam profile and spectra of Er:Pr:GGG laser are measured and the relationship between lasing wavelengths and operating temperature in the triwavelength emission state are also studied. The Er:Pr:GGG crystal is a potential midinfrared laser gain medium in medical and military application. [ABSTRACT FROM PUBLISHER]
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- 2014
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28. Linear IFMIF Prototype Accelerator (LIPAc): Installation activities for Phase-B beam commissioning in Rokkasho
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Ivan Moya, Atsushi Kasugai, Takayuki Kikuchi, Keishi Sakamoto, Antti Jokinen, Juan Knaster, Yoshikazu Okumura, M. Weber, Giuseppe Pruneri, Guy Phillips, Philippe Cara, David Jimenez, Keitaro Kondo, M. Perez, Masao Komata, Masayoshi Sugimoto, Benoit Bolzon, Sunao Maebara, Dominique Gex, Ryo Ichimiya, Y. Ikeda, R. Heidinger, J.-M. Ayala, Francesco Scantamburlo, Ivan Podadera, Shinobu Nishimura, Hervé Dzitko, Alvaro Marqueta, Takashi Ebisawa, Shigeru O‘hira, Yosuke Hirata, Takahiro Shinya, and Enrico Fagotti
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Physics ,Nuclear and High Energy Physics ,Materials Science (miscellaneous) ,Nuclear engineering ,Beam commissioning ,RF power amplifier ,Phase (waves) ,01 natural sciences ,lcsh:TK9001-9401 ,010305 fluids & plasmas ,Low energy ,Nuclear Energy and Engineering ,Duty cycle ,0103 physical sciences ,Neutron source ,Pulsed mode ,lcsh:Nuclear engineering. Atomic power ,010306 general physics ,Beam (structure) - Abstract
The construction of the Linear IFMIF Prototype Accelerator (LIPAc) is in progress in order to demonstrate the feasibility of the low energy section of an IFMIF deuteron accelerator up to 9 MeV with a beam current of 125 mA in CW. The next milestone of the project is the so-called Phase-B beam commissioning, and one of the missions is to demonstrate the acceleration of the proton beam up to 2.5 MeV or the deuteron beam up to 5.0 MeV in pulsed mode with a low duty cycle of 0.1% through RFQ. Most of the components and subsystems necessary for Phase-B were delivered by 2016 under the responsibility of Fusion for Energy (F4E) as in-kind contributions of several European institutes, namely CEA (France), CIEMAT (Spain), INFN (Italy), and SCK-CEN (Belgium), and QST is in charge of the installation of the delivered equipment. The installation and check-out of the RFQ subsystem and the RF power system was completed by July 2017, and the RF conditioning of the RFQ cavity started. Also, the installation and the check-out of the important sub-systems for Phase-B, namely MEBT and beam diagnostics, have been completed. Keywords: IFMIF, LIPAc, RFQ, Accelerator, Deuteron, Neutron source
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- 2018
29. Pulsed modes of the formation of multilayer char structures on the surface of fire-retardant intumescent paints.
- Author
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Krupkin, V., Mokhin, G., and Khalturinskii, N.
- Abstract
A mathematical model of the propagation of the front of decomposition of active fire-retardant intumescent paints in pulsed mode is developed. A hypothesis explaining the mechanism of the experimen-tally observed pulsed modes of decomposition front propagation by the existence of an exothermic step in the decomposition reaction, leading to the self-acceleration of the reaction and rapid burnout of the reacting substance layer, is suggested. A theory of the propagation of the decomposition front in the pulsed mode based on a minimum number of empirical parameters obtainable from experiment is developed. Based on numerical simulation results, formulas are derived for predicting the time history of the thickness of the char structure and the time during which the fire-retardant composition can protect the object from fire. These formulas can be used to calculate the desired thickness of the fire-retardant coating that would withstand a fire or a thermal agent of given intensity for a desired time. [ABSTRACT FROM AUTHOR]
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- 2013
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30. Modeling and Simulation Methodology for SOA-Aware Circuit Design in DC and Pulsed-Mode Operation of HV MOSFETs.
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Khandelwal, Sourabh, Sharma, Surya, Chauhan, Yogesh Singh, Gneiting, Thomas, and Fjeldly, Tor A.
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METAL oxide semiconductor field-effect transistors , *MATHEMATICAL models , *COMPUTER simulation , *INTEGRATED circuit design , *SEMICONDUCTOR optical amplifiers , *DIRECT currents , *HIGH voltages - Abstract
In this paper, we present a modeling and simulation methodology for safe-operating-area (SOA)-aware circuit design in dc and pulsed-mode operation of high-voltage MOSFETs (HV MOSFETs). The developed methodology gives an accurate description of the SOA of devices under dc and, more importantly, transient inputs, taking into account the width and duty-cycle of the pulse. To the best of the authors' knowledge, this is the first time such a methodology integrated with circuit design tools is presented. It is shown through simulation of standard circuits of HV MOSFETs that the proposed methodology avoids overdesigns and enables circuit designers to use the high-voltage technology to its full potential. [ABSTRACT FROM PUBLISHER]
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- 2013
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31. Multiharmonic Volterra Model Dedicated to the Design of Wideband and Highly Efficient GaN Power Amplifiers.
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Demenitroux, Wilfried, Maziere, Christophe, Gatard, Emmanuel, Dellier, Stéphane, Campovecchio, Michel, and Quere, Raymond
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- *
POWER amplifiers , *BROADBAND communication systems , *GALLIUM nitride , *COMPUTER-aided design , *TRANSISTORS , *VOLTERRA series , *MATHEMATICAL models ,DESIGN & construction - Abstract
This paper presents a complete validation of the new behavioral model called the multiharmonic Volterra (MHV) model for designing wideband and highly efficient power amplifiers with packaged transistors in computer-aided design (CAD) software. The proposed model topology is based on the principle of the harmonic superposition introduced by the Agilent X-parameters, which is combined with the dynamic Volterra theory to give an MHV model that can handle short-term memory effects. The MHV models of 10- and 100-W packaged GaN transistors have been extracted from time-domain load–pull measurements under continuous wave and pulsed modes, respectively. Both MHV models have been implemented into CAD software to design 10- and 85-W power amplifiers in L- and S-bands. Finally, the first power amplifier exhibited mean measured values of 10-W output power and 65% power-added efficiency over 36% bandwidth centered at 2.2 GHz, while the second one exhibited 85-W output power and 65% drain efficiency over 50% bandwidth centered at 1.6 GHz. [ABSTRACT FROM PUBLISHER]
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- 2012
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32. Drop-coated metal-oxide gas sensor on polyimide foil with reduced power consumption for wireless applications
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Courbat, J., Briand, D., Yue, L., Raible, S., and de Rooij, N.F.
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SURFACE coatings , *POLYIMIDES , *METALLIC oxides , *GAS detectors , *METAL foils , *ELECTRIC power consumption , *ELECTRONIC industries , *WIRELESS communications , *TRANSDUCERS - Abstract
Abstract: Highly miniaturized low-power drop-coated metal-oxide gas sensors on polyimide foil are presented. Drop-coating of SnO2-based material was successfully achieved on transducers as small as 15μm on polyimide, a substrate compatible with the printed electronics industry. The sensors showed a very good chemoresistive response when exposed to CO and NO2. The power consumptions of the sensors ranged from a minimum of 7.7mW for the smallest hotplate at 200°C to a maximum of 28.4mW for the largest device at 250°C in continuous mode of operation. In a pulsed mode, their consumption was reduced to the sub-milliwatt range for the 15μm wide heaters while keeping a good chemoresistive response, widening their use to low-power applications, such as for wireless systems. The sensors were interfaced to a custom-made electronic circuitry with a readout based on time-to-digital conversion to minimize the amount of electronic components and reduce the power consumption. The power consumption of the 15μm wide sensor was 680μW in pulsed mode, while the sensor system exhibited a total power consumption of 1.9mW. [Copyright &y& Elsevier]
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- 2012
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33. Towards an assessment of bone fracture healing using pulsed mode ultrasound.
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Qaddoumi, N., Al-Nashash, H., Sediq, A. Bin, Al-Shamsi, H., Al-Mehrizi, M., and Khalaf, K.
- Subjects
- *
BONE fractures , *HEALING , *BONE injuries , *ULTRASONIC imaging , *MATHEMATICAL models - Abstract
Healing rate of fractured bone differs from one patient to another which may lead to incorrect consequent medical procedures. Thus, quantitative assessment of bone healing after fracture becomes important. In this paper, we present a mathematical model which describes the interaction of a pulsed mode ultrasound waves with a multilayered biological structure. The model is applied to estimate the bone callus thickness and degree of hardness. Different frequencies are utilized to obtain highest measurement sensitivity and accuracy of callus thickness and degree of hardness. It is found that a transducer operating at 1 MHz has the highest sensitivity to the different phases of callus hardening. On the other hand, a 3 MHz transducer yields the highest sensitivity to the thickness of the callus layer. Thus, using both frequencies might prove to be useful for full quantitative assessment of the bone healing process. [ABSTRACT FROM AUTHOR]
- Published
- 2011
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34. Effects of processing parameters on laser cutting of aluminium–copper alloys using off-axial supersonic nozzles
- Author
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Riveiro, A., Quintero, F., Lusquiños, F., Comesaña, R., and Pou, J.
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- *
ALUMINUM-copper alloys , *SUPERSONIC nozzles , *INDUSTRIAL lasers , *EXPERIMENTS , *AEROSPACE engineering , *PULSE frequency modulation - Abstract
Abstract: Conventional laser cutting involves the utilization of converging coaxial nozzles to inject the assist gas used to remove the molten material. This processing system prevents the utilization of this technique to cut aluminium alloys for aerospace applications. The inefficient removal of molten material by the assist gas produces cuts with poor quality; very rough cuts, with a large amount of dross, and a large heat affected zone (HAZ) are obtained. An alternative to increase the assist gas performance is the utilization of off-axial supersonic nozzles. Removal of molten material is substantially increased and cuts with high quality are obtained. On the other hand, pulsed laser cutting offers superior results during the processing of high reflectivity materials as aluminium alloys. However, there are no experimental studies which explore the pulsed laser cutting of aluminium alloys by means of a cutting head assisted by an off-axis supersonic nozzle. The present work constitutes a quantitative experimental study to determine the influence of processing parameters on the cutting speed and quality criteria during processing by means of off-axial supersonic nozzles. Cutting experiments were performed in pulsed mode and the results explained under the basis of the molten material removal mechanisms. Performed experiments indicate a reduction in cutting speed as compared to continuous wave (CW) mode processing and the existence of two processing regimes as a function of the pulse frequency. Best results are obtained under the high pulse frequency one (f >100Hz) because the superior capabilities of molten material removal of the supersonic jets are completely exploited in this processing regime. [Copyright &y& Elsevier]
- Published
- 2011
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35. A Comparative Study on Cutting Electrodes for Batteries with Lasers.
- Author
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Luetke, Matthias, Franke, Volker, Techel, Anja, Himmer, Thomas, Klotzbach, Udo, Wetzig, Andreas, and Beyer, Eckhard
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ELECTRODES ,LASER beam cutting ,LITHIUM-ion batteries ,LASER ablation ,AUTOMOBILE industry ,COMPARATIVE studies - Abstract
Abstract: E-mobility is still one of the most discussed topics within the automotive industry. Electric powered vehicles can drive emissionfree and present consequently the future propulsion. Nearly all global players in the automotive industry are making great efforts to develop cost-efficient electric drives, which are suitable for series production. The national governments support this evolution progressively. For example the mobility research programme of the Federal Republic of Germany looks at the production of Li- Ion cells in its entirety. Within this programme the cutting of electrodes for Li-Ion cells by lasers is an issue, too. This paper provides a comparative study on cutting materials relevant for Li-Ion cells with beam sources operating in a cw mode and a pulsed mode respectively. [Copyright &y& Elsevier]
- Published
- 2011
- Full Text
- View/download PDF
36. Study of polycrystalline diamond deposition by continuous and pulsed discharges
- Author
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Cicala, G., Brescia, R., Nitti, M.A., Romeo, A., Altamura, D., Giannini, C., Capitelli, M., Spinelli, P., and Schutzmann, S.
- Subjects
- *
POLYCRYSTALS , *DIAMONDS , *THIN films , *PLASMA-enhanced chemical vapor deposition , *ELECTRIC discharges , *MICROWAVES , *INTERFEROMETRY - Abstract
Abstract: The effects of pulsed microwave discharges on the deposition and properties of a set of polycrystalline diamond films are investigated by varying the duty cycle at a fixed pulse frequency and keeping constant the peak microwave power at 1250W, the substrate temperature and the final film thickness. The deposition of polycrystalline diamond films obtained from highly diluted CH4 (1% CH4 in H2) gas mixtures was monitored by pyrometric interferometry technique. This analysis evidences that, in order to obtain the same thickness, the nucleation/deposition times and the process rates increase and decrease, respectively, by decreasing the pulse duration. Moreover, the influence of the variations of duty cycle on the deposition rates, the surface morphology, the optical properties (refractive index and extinction coefficient) and the crystallite orientations of the polycrystalline diamond films is investigated. [Copyright &y& Elsevier]
- Published
- 2010
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- View/download PDF
37. Formation of a pulsed electron beam in a plasmacathode system under forevacuum pressures.
- Author
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Medovnik, A. V., Burdovitsin, V. A., and Oks, E. M.
- Subjects
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PARTICLE beams , *PLASMA electrodynamics , *PLASMA gases , *ELECTRON beams , *PARTICLES (Nuclear physics) - Abstract
Results of an experimental study of the features of the production of pulsed beams by a plasma electron source operating in the forevacuum pressure range (5–15 Pa) are presented. For this pressure range, the emission properties of the plasma are substantially affected by the backward ion flow generated in the regions of formation and transport of the electron beam. It has been shown that in experimental conditions the ratio of the current of backward ions to the current of the electron beam can reach 10%, which is an order of magnitude greater than the same parameter for electron sources operating in the pressure range that is conventional for devices of this type (0.01–0.1 Pa). The principal factors that impose an upper limit on the beam current in a plasma-cathode source are analyzed. [ABSTRACT FROM AUTHOR]
- Published
- 2010
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38. High‐performance operation of distributed feedback terahertz quantum cascade lasers.
- Author
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Li, Yuanyuan, Liu, Junqi, Liu, Fengqi, Zhang, Jinchuan, and Wang, Zhanguo
- Abstract
Carefully designed distributed feedback terahertz quantum cascade lasers based on surface metallic‐stripe grating structure are presented. Stable single‐mode emission with a side‐mode suppression ratio of >20 dB is obtained under all injection currents and operating temperatures. Maximum edge‐emitting power of 58 mW is realised in continuous‐wave mode. In pulsed mode, record output powers of 286 mW at 10 K and 82 mW at 77 K are achieved at 97.1 μm with a well‐shaped beam pattern. [ABSTRACT FROM AUTHOR]
- Published
- 2016
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39. Simulation of a high-voltage semiconductor resistor in development of power tab-shaped silicon resistors.
- Author
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Chibirkin, V., Geifman, E., and Batyaev, P.
- Abstract
The results of simulation, which is based on a mathematical model developed, and experimental studies of operation of a silicon resistor in strong electric fields and pulsed modes are given. Influence of the geometrical and electrophysical parameters of a resistive element and the measurement modes on the resistor parameters is studied. Original techniques for manufacturing PK-series silicon resistors with specified parameters and dependences are developed. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
40. Deposition of nanocrystalline diamond films in pulsed Ar/H2/CH4 microwave discharges
- Author
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Monéger, D., Bénédic, F., Azouani, R., Chelibane, F., Syll, O., Silva, F., and Gicquel, A.
- Subjects
- *
PULSED laser deposition , *NANOCRYSTALS , *DIAMONDS , *ARGON plasmas - Abstract
Abstract: The use of pulsed microwave discharges is examined as a way to improve nanocrystalline diamond film growth process, while maintaining small amounts of hydrogen in the argon-based gas mixture in order to ensure plasma stability. The effects of pulse repetition rate and duty cycle on the film properties are investigated, keeping a constant time-average microwave power of 500 W at 20,000 Pa. When the duty cycle is maintained at 50%, the best microstructure and topography properties are obtained at low pulse repetition rate (50 Hz), with a 10 nm grain size and a 25 nm Rms roughness, which is better by a factor of two than the values reached in conventional continuous mode while the growth rate is comparable. At low frequency (50 Hz), possible variations of duty cycle in the range 50–80% has only a weak influence, so that films with optimal properties and growth rate are always provided. Besides, the measured and calculated time-average gas temperature for pulsed discharges as a function of duty cycle, and for continuous plasmas, yield roughly constant and identical values close to 4000 K. This points out that no changes in the heating or cooling of the reactor walls and substrate are required when the pulsed mode is employed, even if the injected peak power may be greatly changed in order to keep constant time-average values. [Copyright &y& Elsevier]
- Published
- 2007
- Full Text
- View/download PDF
41. Inert gas cutting of titanium sheet with pulsed mode CO2 laser
- Author
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Rao, B. Tirumala, Kaul, Rakesh, Tiwari, Pragya, and Nath, A.K.
- Subjects
- *
LASERS , *RADIOACTIVITY , *NITROGEN , *DUTY , *NUCLEAR reactions - Abstract
Abstract: The present work aimed at studying the dynamic behavior of melt ejection in laser cutting of 1mm thick titanium sheet and to obtain dross-free cuts with minimum heat affected zone (HAZ). CO2 laser cutting of titanium sheet was carried out with continuous wave (CW) and pulsed mode laser operation with different shear gases namely argon, helium and nitrogen. Laser cutting with high frequency and low-duty cycle pulse mode operation produced dross-free cuts with no noticeable HAZ. Helium, because of its high heat convection and ability to generate high shear stress, produced laser-cuts with narrow HAZ and low dross, as compared to those produced with argon as the shear gas. Microscopic features of laser cut surfaces were analyzed and correlated with dynamic mechanism involved in laser cutting process. Process parameters for laser piercing, required for the initiation of fusion cut within the sheet, were also studied. Laser piercing requires either CW or high-duty cycle (>80%) pulse mode operation. [Copyright &y& Elsevier]
- Published
- 2005
- Full Text
- View/download PDF
42. Infrared fiber based on AgCl-AgBr and AgBr-TlI crystals to transfer thermal radiation in pulsed
- Author
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A. S. Shmygalev, B. P. Zhilkin, A. Turabi, and Alexandr Korsakov
- Subjects
History ,Materials science ,Infrared ,Analytical chemistry ,CONTINUOUS MODE ,BROMINE COMPOUNDS ,PULSED MODE ,Computer Science Applications ,Education ,INFRARED RADIATION ,CHLORINE COMPOUNDS ,SILVER HALIDES ,Thermal radiation ,RESEARCH SUBJECTS ,Fiber ,THALLIUM COMPOUNDS ,INFRARED FIBERS ,OPERATIONAL PARAMETERS ,ENERGY TRANSFER ,RESEARCH OBJECTIVES ,HEAT RADIATION ,OPTICAL FIBERS ,IR ENERGY - Abstract
The our research objective is to study IR energy transfer in pulsed and continuous mode through optical fibers produced from crystals of silver halide and a monovalent thallium solid solutions. It is assumed that the transfer of infrared radiation in the pulsed mode will significantly reduce losses. We designed the experimental setup, determined its operational parameters, and obtained the dependence of the detector's received radiation on the frequency of the pulses of thermal radiation. As a research subjects we used two different fibers compositions namely AgCl0.25Br0.75 and Ag0.95Tl0.05Br0.95I0.05. © Published under licence by IOP Publishing Ltd. Council on grants of the President of the Russian Federation: SP-2455.2018.1 The research has been supported by the grants of President of the Russian Federation SP-2455.2018.1.
- Published
- 2019
43. Bubble deformation in the repetitive pulsed glycerin pulse forming line and its relation with the liquid breakdown
- Author
-
Baoliang Qian, Jiuyuan Geng, Xinbing Cheng, Xiao Yang, and Jianhua Yang
- Subjects
010302 applied physics ,Materials science ,Liquid dielectric ,General Physics and Astronomy ,Pulse forming line ,02 engineering and technology ,Deformation (meteorology) ,021001 nanoscience & nanotechnology ,01 natural sciences ,Energy storage ,lcsh:QC1-999 ,Electric field ,0103 physical sciences ,Breakdown voltage ,Pulsed mode ,Composite material ,0210 nano-technology ,lcsh:Physics ,Bubble deformation - Abstract
Glycerin is a promising liquid dielectric for pulsed power systems because of its high storage energy density and high resistivity. In order to further improve the energy storage density of glycerin, its breakdown characteristics should be investigated. In this paper, experiments are carried out to study the decline of the breakdown voltage of glycerin in a repetitive pulsed pulse forming line (PFL) in both the single pulse mode and the repetitive pulsed mode. It is shown that the breakdown voltage of the glycerin PFL is reduced by about 35% after 100 pulses in 10 s. The bubbles in glycerin are suspected to be an important factor affecting the breakdown characteristics. By using a high-speed camera, the deformation of bubbles (especially the height) is observed in the experiments and the deformation of bubbles is cumulative after multiple pulses. Experiments confirm that the bubbles’ height is influenced by factors including the electric field, pressure, and temperature. These experimental results demonstrate an important process of the liquid breakdown in the repetitive pulsed mode, which will be helpful to improve the breakdown characteristics of liquid dielectrics.Glycerin is a promising liquid dielectric for pulsed power systems because of its high storage energy density and high resistivity. In order to further improve the energy storage density of glycerin, its breakdown characteristics should be investigated. In this paper, experiments are carried out to study the decline of the breakdown voltage of glycerin in a repetitive pulsed pulse forming line (PFL) in both the single pulse mode and the repetitive pulsed mode. It is shown that the breakdown voltage of the glycerin PFL is reduced by about 35% after 100 pulses in 10 s. The bubbles in glycerin are suspected to be an important factor affecting the breakdown characteristics. By using a high-speed camera, the deformation of bubbles (especially the height) is observed in the experiments and the deformation of bubbles is cumulative after multiple pulses. Experiments confirm that the bubbles’ height is influenced by factors including the electric field, pressure, and temperature. These experimental results demonst...
- Published
- 2019
44. C-doped AlN/GaN HEMTs for High efficiency mmW applications
- Author
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Riad Kabouche, Malek Zegaoui, R. Pecheux, Farid Medjdoub, Etienne Okada, Institut d’Électronique, de Microélectronique et de Nanotechnologie - UMR 8520 (IEMN), Centrale Lille-Institut supérieur de l'électronique et du numérique (ISEN)-Université de Valenciennes et du Hainaut-Cambrésis (UVHC)-Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Université Polytechnique Hauts-de-France (UPHF), Thalès Optronique, Plateforme de Caractérisation Multi-Physiques - IEMN (PCMP - IEMN), Centrale Lille-Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Université Polytechnique Hauts-de-France (UPHF)-JUNIA (JUNIA), Université catholique de Lille (UCL)-Université catholique de Lille (UCL)-Centrale Lille-Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Université Polytechnique Hauts-de-France (UPHF)-JUNIA (JUNIA), Université catholique de Lille (UCL)-Université catholique de Lille (UCL), and Centrale Lille-Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Université Polytechnique Hauts-de-France (UPHF)-JUNIA (JUNIA)-Centrale Lille-Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Université Polytechnique Hauts-de-France (UPHF)-JUNIA (JUNIA)
- Subjects
010302 applied physics ,Materials science ,output power density and power added efficiency (PAE) ,Carbon doped ,Doping ,Gate length ,Analytical chemistry ,020206 networking & telecommunications ,Heterojunction ,02 engineering and technology ,High-electron-mobility transistor ,01 natural sciences ,7. Clean energy ,GaN ,0103 physical sciences ,0202 electrical engineering, electronic engineering, information engineering ,high electron mobility transistors (HEMTs) ,Pulsed mode ,[SPI.NANO]Engineering Sciences [physics]/Micro and nanotechnologies/Microelectronics ,Drain current ,Electron confinement - Abstract
We report on high power-added-efficiency using AlN/GaN heterostructure with a carbon doped buffer layer for millimeter wave applications (C-doped HEMTs). The carbon doped HEMTs show high electrical characteristics with a maximum drain current density ${{\mathbf{I}}}_{{{\mathbf{d}}}} $ of 1.5 A/mm, an extrinsic transconductance ${{\mathbf{G}}}_{{{\mathbf{m}}}} $ of 500 mS/mm and a maximum oscillation frequency ${{\mathbf{f}}}_{{{\mathbf{max}}}}$ above 200 GHz while using a gate length of 120 nm. The high RF performance obtained on the carbon doped HEMT combined to an excellent electron confinement under high bias enabled to achieve a state-of-the-art combination at 40 GHz of output power density (${{\mathbf{P}}}_{{{\mathbf{OUT}}}} ={{\mathbf{7W}}}/{{\mathbf{mm}}}$) and power added efficiency (PAE) above 50% up to ${{\mathbf{V}}}_{{{\mathbf{DS}}}} ={{\mathbf{25V}}}$ in pulsed mode.
- Published
- 2018
45. 1.8-W Room Temperature Pulsed Operation of Substrate-Emitting Quantum Cascade Lasers.
- Author
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Dan-Yang Yao, Jin-Chuan Zhang, Feng-Qi Liu, Zhi-Wei Jia, Fang-liang Yan, Li-Jun Wang, Jun-Qi Liu, and Zhan-Guo Wang
- Abstract
High-power broad area substrate-emitting distributed feedback (DFB) quantum cascade laser emitting at λ ~ 4.6 μm is reported. Proper second-order DFB grating coupling, low waveguide loss mechanism, and epilayer-down mounting bring about a high vertical radiative optical power. The maximum peak power is as high as 1.82 W at 20 °C and still 1.22 W at 50 °C operated in pulsed mode with a pulsed width of 1 μs and duty cycle of 0.2%. A single-lobed radiation far-field with a divergence angle of 7.9 ° in the ridge-width direction and two-lobed radiation far-field with a divergence angle of 0.61 ° in the cavity-length direction are achieved by depositing the high-reflection coatings on both facets. Robust single-mode emission is continuously tunable by the heat sink temperature up to 115 °C. [ABSTRACT FROM PUBLISHER]
- Published
- 2014
- Full Text
- View/download PDF
46. Terahertz quantum cascade lasers with >1 W output powers.
- Author
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Li, Lianhe, Chen, Li, Zhu, Jingxuan, Freeman, J., Dean, P., Valavanis, A., Davies, A.G., and Linfield, E.H.
- Abstract
Terahertz (THz) frequency quantum cascade lasers emitting peak powers of >1 W from a single facet in the pulsed mode are demonstrated. The active region is based on a bound‐to‐continuum transition with a one‐well injector, and is embedded into a surface‐plasmon waveguide. The lasers emit at a frequency of ∼3.4 THz and have a maximum operating temperature of 123 K. The maximum measured emitted powers are ∼1.01 W at 10 K and ∼420 mW at 77 K, with no correction made to allow for the optical collection efficiency of the apparatus. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
47. Ring laser having an output at a single frequency
- Author
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Hackell, Lloyd [Livermore, CA]
- Published
- 1991
48. High brilliance negative ion and neutral beam source
- Author
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Compton, Robert [Oak Ridge, TN]
- Published
- 1991
49. Apparatus for coating a surface with a metal utilizing a plasma source
- Author
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Galvin, James [Emeryville, CA]
- Published
- 1991
50. Fast pulsed excitation wiggler or undulator
- Author
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van Steenbergen, Arie [Shoreham, NY]
- Published
- 1990
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