Journal articles: 'Pulsed flow'

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Ho, Viet Luan, Robert M. Dorrell, Gareth M. Keevil, Robert E. Thomas, Alan D. Burns, Jaco H. Baas, and William D. McCaffrey. "Dynamics and deposition of sediment-bearing multi-pulsed flows and geological implication." Journal of Sedimentary Research 89, no. 11 (November 26, 2019): 1127–39. http://dx.doi.org/10.2110/jsr.2019.62.

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ABSTRACT Previous studies on dilute, multi-pulsed, subaqueous saline flows have demonstrated that pulses will inevitably advect forwards to merge with the flow front. On the assumption that pulse merging occurs in natural-scale turbidity currents, it was suggested that multi-pulsed turbidites that display vertical cycles of coarsening and fining would transition laterally to single-pulsed, normally graded turbidites beyond the point of pulse merging. In this study, experiments of dilute, single- and multi-pulsed sediment-bearing flows (turbidity currents) are conducted to test the linkages between downstream flow evolution and associated deposit structure. Experimental data confirm that pulse merging occurs in laboratory-scale turbidity currents. However, only a weak correspondence was seen between longitudinal variations in the internal flow dynamics and the vertical structure of deposits; multi-pulsed deposits were documented, but transitioned to single-pulsed deposits before the pulse merging point. This early transition is attributed to rapid sedimentation-related depletion of the coarser-grained suspended fraction in the laboratory setting, whose absence may have prevented the distal development of multi-pulsed deposits; this factor complicates estimation of the transition point in natural-scale turbidite systems.

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Zhao, Zi-Jie, Y. D. Cui, Jiun-Ming Li, Jian-Guo Zheng, and B. C. Khoo. "On the boundary flow using pulsed nanosecond DBD plasma actuators." Modern Physics Letters B 32, no. 12n13 (May 10, 2018): 1840035. http://dx.doi.org/10.1142/s0217984918400353.

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Our previous studies in quiescent air environment [Z. J. Zhao et al., AIAA J. 53(5) (2015) 1336; J. G. Zheng et al., Phys. Fluids 26(3) (2014) 036102] reveal experimentally and numerically that the shock wave generated by the nanosecond pulsed plasma is fundamentally a microblast wave. The shock-induced burst perturbations (overpressure and induced velocity) are found to be restricted to a very narrow region (about 1 mm) behind the shock front and last only for a few microseconds. These results indicate that the pulsed nanosecond dielectric barrier discharge (DBD) plasma actuator has stronger local effects in time and spatial domain. In this paper, we further investigate the effects of pulsed plasma on the boundary layer flow over a flat plate. The present investigation reveals that the nanosecond pulsed plasma actuator generates intense perturbations and tends to promote the laminar boundary over a flat plate to turbulent flow. The heat effect after the pulsed plasma discharge was observed in the external flow, lasting a few milliseconds for a single pulse and reaching a quasi-stable state for multi-pulses.

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Krueger, Paul S., Ali A. Moslemi, J. Tyler Nichols, Ian K. Bartol, and William J. Stewart. "Vortex Rings in Bio-Inspired and Biological Jet Propulsion." Advances in Science and Technology 58 (September 2008): 237–46. http://dx.doi.org/10.4028/www.scientific.net/ast.58.237.

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Pulsed-jets are commonly used for aquatic propulsion, such as squid and jellyfish locomotion. The sudden ejection of a jet with each pulse engenders the formation of a vortex ring through the roll-up of the jet shear layer. If the pulse is too long, the vortex ring will stop forming and the remainder of the pulse is ejected as a trailing jet. Recent results from mechanical pulsedjets have demonstrated that vortex rings lead to thrust augmentation through the acceleration of additional ambient fluid. This benefit is most pronounced for short pulses without trailing jets. Simulating vehicle motion by introducing background co-flow surrounding the jet has shown that vortex ring formation can be interrupted, but only if the co-flow is sufficiently fast. Recent in situ measurements on squid have captured vortical flows similar to those observed in the laboratory, suggesting thrust augmentation may play a role in their swimming performance. Likewise, recent measurements with a mechanical self-propelled pulsed-jet vehicle (“robosquid”) have shown a cruise-speed advantage obtained by pulsing.

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Su, Zhi, Haohua Zong, Hua Liang, Jun Li, and Xiancong Chen. "Characteristics of a dielectric barrier discharge plasma actuator driven by pulsed-DC high voltage." Journal of Physics D: Applied Physics 55, no. 7 (November 12, 2021): 075203. http://dx.doi.org/10.1088/1361-6463/ac30bc.

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Abstract Dielectric barrier discharge using pulsed-DC high voltage (pulsed-DC DBD) have been proven to be capable of effectively reducing skin friction drag in turbulent boundary layers with limited power consumption, thus producing significant net power savings. In this work, the characteristics of pulsed-DC DBD, including power consumption, induced flow structure, thermal effect, and body force, are investigated sequentially. Both the power consumption and pressure waves produced by pulsed-DC DBD are similar to that of DBD using nanosecond pulses (ns-DBD), whereas the wall-bounded jet structure resembles that of DBD using sinusoidal high voltage (ac-DBD). A curved wall jet is induced at a small pulse width, which turns into a straight one due to the combined effect of momentum and thermal addition when the pulse width increases. With increasing pulse width, the induced body force goes up while the thermal effect weakens. Although pulse frequency has no impact on the wall-bounded jet topology, the body force increases with pulse frequency because of the enhanced energy entrainment. With these results, four parameters that affect the performance of pulsed-DC DBD are extracted, including the pulse leading edge, pulse width, frequency, and amplitude, which lays the foundation for the optimization of pulsed-DC DBD.

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Pakhomov, M. A., and V. I. Terekhov. "RANS Simulation of the Effect of Pulse Form on Fluid Flow and Convective Heat Transfer in an Intermittent Round Jet Impingement." Energies 13, no. 15 (August 4, 2020): 4025. http://dx.doi.org/10.3390/en13154025.

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The of effect pulse form (rectangular, sinusoidal and triangular) on the fluid flow and heat transfer of an intermittent jet impingement was studied numerically. It was shown in a non-steady-state jet, both an increase and decrease in heat transfer are possible compared with steady-state jet for all investigated pulse forms. For small distances between the pipe edge and obstacle (H/D ≤ 6) in the pulsed jet, heat transfer around the stagnation point increases with increasing pulse frequency, while for H/D > 8 an increase in frequency causes a heat transfer decrease. A growth in the Reynolds number causes a decrease in heat transfer, and data for all frequencies approach the steady-state flow regime. The numerical model is compared with the experimental results. Satisfactory agreement on the influence of the form and frequency of pulses on heat transfer for the pulsed jet on the obstacle surface is obtained.

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Pratomo, Hariyo P. S., and Klaus Bremhorst. "Velocity Statistics of a Fully Pulsed Round Jet in Streamwise Direction." Applied Mechanics and Materials 534 (February 2014): 117–23. http://dx.doi.org/10.4028/www.scientific.net/amm.534.117.

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In this paper, statistical quantities of a fully pulsed round jet along the jet centerline are reported. A range of the Reynolds (1.5 x 104 < Re < 4 x 104) and Strouhal (0.0064 < St < 0.0076) numbers is used to generate the jet. Physically this unsteady jet produces a series of distinct pulses due to the excitations. The mechanically excitations lead to the appearance of pulse dominated and high turbulence steady jet region in which their existence is of a strong dependence on the level of the controlled parameters. After the pulse merging completes the pulsed jet alters to a self-preserving steady jet with a significantly higher turbulence intensity. Under a constant mass flow rate the pulsed jet tends to be more fluctuating at a less intense pulsation thus permitting the endurance of the normalized periodic component and a more rapid velocity decay in the pulse-dominated region.

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Zhao, Heqian, Huaizhong Shi, Zhongwei Huang, Zhenliang Chen, Ziang Gu, and Fei Gao. "Mechanism of Cuttings Removing at the Bottom Hole by Pulsed Jet." Energies 15, no. 9 (May 3, 2022): 3329. http://dx.doi.org/10.3390/en15093329.

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Vibration drilling technology induced by hydraulic pulse can assist the bit in breaking rock at deep formation. Simultaneously, the pulsed jet generated by the hydraulic pulse promotes removal of the cuttings from the bottom hole. Nowadays, the cuttings removal mechanism of the pulsed jet is not clear, which causes cuttings to accumulate at the bottom hole and increases the risk of repeated cutting. In this paper, a pressure-flow rate fluctuation model is established to analyze the fluctuation characteristics of the pulsed jet at the bottom hole. Based on the model, the effects of displacement, well depth, drilling fluid viscosity, and flow area of the pulsed jet tool on the feature of instantaneous flow at the bottom hole are discussed. The results show that the pulsed jet causes flow rate and pressure to fluctuate at the bottom hole. When the displacement changes from 20 L/s to 40 L/s in a 2000 m well, the pulsed jet generates a flow rate fluctuation of 4–9 L/s and pressure fluctuation of 0.1–0.5 MPa at the bottom hole. With the flow area of the tool increasing from 2 cm2 to 4 cm2, the amplitude of flow rate fluctuation decreases by 72.5%, and the amplitude of pressure fluctuation decreases by more than 60%. Combined with the fluctuation feature of the flow field and the water jet attenuation law at the bottom hole, the force acting on the cuttings under the pulsed jet is derived. It is found that flow rate fluctuation improves the mechanical state of cuttings and is beneficial for cuttings tumbled off the bottom hole. This research provides theoretical guidance for pulsed jet cuttings cleaning at the bottom hole.

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Heath, Martha E., and Susan Bleck GIBBS. "High-voltage pulsed galvanic stimulation: effects of frequency of current on blood flow in the human calf muscle." Clinical Science 82, no. 6 (June 1, 1992): 607–13. http://dx.doi.org/10.1042/cs0820607.

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1. Twelve healthy subjects received high-voltage pulsed galvanic stimulation (115–475V d.c.) delivered in separate treatments of 2, 32 and 128 pulses/s for 10 min at the subject's maximum tolerable voltage while calf muscle blood flow was measured by non-invasive Whitney strain-gauge venous occlusion plethysmography. 2. The high-voltage pulsed galvanic stimulation was administered with negative polarity by an intermittent mode of 30 s on, 30 s off. Measurements of calf muscle blood flow were made during each 30 s period when the stimulus was off. The effect of one 30 s maximum isometric contraction of the calf muscles on blood flow was used as a standard for evaluating the effectiveness of high-voltage pulsed galvanic stimulation on calf muscle blood flow. 3. Significant (paired t-tests; P < 0.05) increases in calf muscle blood flow over the preceding baseline levels occurred for the isometric contraction (322%) and for frequencies of 2 pulses/s (33.5%) and 128 pulses/s (13.36%), but not for a frequency of 32 pulses at which calf muscle blood flow increased in only six of 12 subjects. The mean increases in calf muscle blood flow at 2 and 128 pulses/s represented 11.63% and 4.0%, respectively, of that resulting from the isometric contraction. 4. A clear positive correlation between voltage level and the magnitude of increase in calf muscle blood flow was demonstrated but differed for each frequency used. 5. It is concluded that high-voltage pulsed galvanic stimulation results in a measurable increase in calf muscle blood flow when it is applied at frequencies of 2 or 128 pulses/s on intermittent mode and at maximum tolerable voltages, but the magnitude of the increase in blood flow is small compared with that stimulated by a maximal isometric contraction.

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Stessel, Richard Ian. "Controlling Pulsed Incompressible Flow." Journal of Energy Engineering 118, no. 1 (April 1992): 1–17. http://dx.doi.org/10.1061/(asce)0733-9402(1992)118:1(1).

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Legallais, C., Ph Morinière, A. Fournier, and M. Y. Jaffrin. "PULSED FLOW CASCADE FILTRATION." ASAIO Journal 42, no. 2 (March 1996): 1. http://dx.doi.org/10.1097/00002480-199603000-00003.

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Legallais, C., Ph Morini??re, A. Fournier, and M. Y. Jaffrin. "PULSED FLOW CASCADE FILTRATION." ASAIO Journal 42, no. 2 (April 1996): 1. http://dx.doi.org/10.1097/00002480-199604000-00003.

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LEGALLAIS, CÉCILE, PHILIPPE MORINIÈRE, ALBERT FOURNIER, and MICHEL YVES JAFFRIN. "Pulsed Flow Cascade Filtration." ASAIO JOURNAL 42, no. 5 (September 1996): M463–467. http://dx.doi.org/10.1097/00002480-199609000-00031.

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13

Khabarov, Kirill, Messan Nouraldeen, Sergei Tikhonov, Anna Lizunova, Alexey Efimov, and Victor Ivanov. "Modification of Aerosol Gold Nanoparticles by Nanosecond Pulsed-Periodic Laser Radiation." Nanomaterials 11, no. 10 (October 13, 2021): 2701. http://dx.doi.org/10.3390/nano11102701.

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This study investigates the processes of interaction of nanosecond pulsed-periodic laser radiation with the flow of aerosol agglomerates of gold nanoparticles synthesized in a spark discharge. Nanoparticles in a gas flow are spatially separated nano-objects whose interaction with each other and with the walls of an experimental cell was insignificant. Therefore, the energy absorbed by nanoparticles was used only for their own heating with further shape and size modification and on heat transfer to the surrounding gas. In the research, we used laser radiation with wavelengths of 527 and 1053 nm at pulse energies up to 900 µJ and pulse repetition rates up to 500 Hz. The dynamics of changes in the nanoparticles size during their sintering process depending on the laser pulses energy is characterized by an S-shaped shrinkage curve. Complete sintering of the initial agglomerates with their transformation into spherical nanoparticles is achieved by a series of impacting laser pulses. The result of nanoparticles’ laser modification is largely determined by the pulse energy and the efficiency of the nanoparticles’ radiation absorption.

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Khabarov, Kirill, Messan Nouraldeen, Sergei Tikhonov, Anna Lizunova, Alexey Efimov, and Victor Ivanov. "Modification of Aerosol Gold Nanoparticles by Nanosecond Pulsed-Periodic Laser Radiation." Nanomaterials 11, no. 10 (October 13, 2021): 2701. http://dx.doi.org/10.3390/nano11102701.

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This study investigates the processes of interaction of nanosecond pulsed-periodic laser radiation with the flow of aerosol agglomerates of gold nanoparticles synthesized in a spark discharge. Nanoparticles in a gas flow are spatially separated nano-objects whose interaction with each other and with the walls of an experimental cell was insignificant. Therefore, the energy absorbed by nanoparticles was used only for their own heating with further shape and size modification and on heat transfer to the surrounding gas. In the research, we used laser radiation with wavelengths of 527 and 1053 nm at pulse energies up to 900 µJ and pulse repetition rates up to 500 Hz. The dynamics of changes in the nanoparticles size during their sintering process depending on the laser pulses energy is characterized by an S-shaped shrinkage curve. Complete sintering of the initial agglomerates with their transformation into spherical nanoparticles is achieved by a series of impacting laser pulses. The result of nanoparticles’ laser modification is largely determined by the pulse energy and the efficiency of the nanoparticles’ radiation absorption.

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Coussement, Axel, O. Gicquel, and G. Degrez. "Large eddy simulation of a pulsed jet in cross-flow." Journal of Fluid Mechanics 695 (February 7, 2012): 1–34. http://dx.doi.org/10.1017/jfm.2011.539.

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AbstractThis study quantifies the mixing that results from a pulsed jet in cross-flow in the near jet region. By large eddy simulation computations, it also helps to understand the physical phenomena involved in the formation of the pulsed jet in cross-flow. The boundary conditions of the jet inlet are implemented via a Navier–Stokes characteristic boundary condition coupled with a Fourier series development. The signals used to pulse the jet inlet are a square or a sine wave. A new way of characterizing the mixing is introduced with the goal of easily interpreting and quantifying the complicated mixing process involved in a pulsed jet in cross-flow flow fields. Different flow configurations, pulsed and non-pulsed, are computed and compared, keeping the root mean square value of the signal constant. This comparison not only allows the characterization of the mixing but also illustrates some of the properties of the mixing characterization.

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Min, Min, Shuiting Ding, Xiao Yu, Shijian Zhang, Haowen Zhong, Gennady Efimovich Remnev, Xiaoyun Le, and Yu Zhou. "Investigation of the Effects of an Intense Pulsed Ion Beam on the Surface Melting of IN718 Superalloy Prepared with Selective Laser Melting." Metals 10, no. 9 (September 2, 2020): 1178. http://dx.doi.org/10.3390/met10091178.

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Intense pulsed ion beam irradiation on IN718 superalloy prepared with selective laser melting as an after-treatment for surface melting is introduced. It is demonstrated that intense pulsed ion beam composed of protons and carbon ions, with a maximum current density of 200 A/cm2 and a pulse length of 80 ns, can induce surface melting and the surface roughness changes significantly due to the generation of micro-defects and the flow of the molten surface. Irradiation experiments and thermal field simulation revealed that the energy density of the ion beam plays a predominant role in the irradiation effect—with low energy density, the flow of molten surface is too weak to smooth the fluctuations on the surface. With high energy density, the surface can be effectively melted and smoothened while micro-defects, such as craters, may be generated and can be flattened by an increased number of pulses. The research verified that for the surface melting with intense pulsed ion beam (IPIB), higher energy density should be used for stronger surface fluidity and a greater pulse number is also required for the curing of surface micro-defects.

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Hermet, Florian, Nicolas Binder, Jérémie Gressier, and Gonzalo Sáez-Mischlich. "Pulsed Flow Turbine Design Recommendations." International Journal of Turbomachinery, Propulsion and Power 6, no. 3 (July 8, 2021): 24. http://dx.doi.org/10.3390/ijtpp6030024.

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A preliminary analysis of turbine design, fit for pulsed flow, is proposed in this paper. It focuses on an academic 2D configuration using inviscid flows, since pressure loads due to wave propagation are several orders of magnitude higher than friction and viscous effects do not significantly impinge on the inviscid part, as previously shown by Hermet, 2021. As such, a large parametric study was carried out using the design of experiments methodology. A performance indicator adapted to unsteady environment is carefully defined before detailing the factors chosen for the design of experiments. Since the number of factors is substantial, a screening design to identify the factors influence on the output is first established. The non-influential factors are then omitted in a more quantitative study of the output law. The surface response calculation allows determining the factor level favouring the best output. Consequently, the main trends in the turbine design driven by a pulsed flow can be stated.

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Aouidef, A., C. Normand, A. Stegner, and J. E. Wesfreid. "Centrifugal instability of pulsed flow." Physics of Fluids 6, no. 11 (November 1994): 3665–76. http://dx.doi.org/10.1063/1.868423.

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Aouidef, A., C. Normand, and J. E. Wesfreid. "Coriolis instability of pulsed flow." Physics of Fluids 7, no. 9 (September 1995): 2230–42. http://dx.doi.org/10.1063/1.868471.

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Caprihan, Arvind. "4621234 Pulsed NMR flow measurement." Magnetic Resonance Imaging 5, no. 3 (January 1987): I. http://dx.doi.org/10.1016/0730-725x(87)90029-4.

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Hollister, L. S., and D. Grujic. "Pulsed channel flow in Bhutan." Geological Society, London, Special Publications 268, no. 1 (2006): 415–23. http://dx.doi.org/10.1144/gsl.sp.2006.268.01.19.

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Zhang, Qian, Zhiheng Liu, Deling Lin, Yuzhe Hu, Borui Zheng, and Taifei Zhao. "Analysis of discharge characteristics of pulsed plasma power source in the microsecond scale." Journal of Physics: Conference Series 2313, no. 1 (July 1, 2022): 012023. http://dx.doi.org/10.1088/1742-6596/2313/1/012023.

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Abstract The characteristics test of plasma discharge is an essential physical basis for studying plasma flow control. The power consumption of pulsed plasma aerodynamic actuation is 30% lower than when the actuation voltage is a continuous sine wave. This paper uses a self-developed pulsed plasma power source to superimpose DC. The power source conducts the discharge measurement on the sliding discharge plasma. The experimental results show that the power source effectively outputs 0-20 kV pulsed high voltage. The superimposed DC power source generates a negative DC high voltage, accelerating the drift speed of positive ions in the plasma and forming a stable and uniform surface discharge. But the essence of pulse discharge is still filamentary discharge. In a cycle, the plasma discharge is mainly concentrated on the rising edge of the pulse. In contrast, the pulse current is bipolar, and the negative pulse current has a more obvious growth trend, which is more effective for improving the flow control ability.

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Korolkov, O. E., M. A. Pakhomov, and V. V. Stolyarov. "The electroplastic effect in titanium alloys under tension." Industrial laboratory. Diagnostics of materials 88, no. 10 (October 25, 2022): 73–82. http://dx.doi.org/10.26896/1028-6861-2022-88-10-73-82.

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The electroplastic effect (EPE) is a phenomenon which consists in a decrease in the strain resistance and enhancing of the plasticity of metals under the effect of the electric current of a sufficiently high density [1]. The goal of the study is to compare the deformation behavior of single-phase commercially pure titanium Grade 4 and two-phase VT6 alloy under tension and external heating with introduction of a pulsed current. Current of various pulse ratio and density was supplied to the grips of the tensile testing machine from a pulse generator. To estimate the relative contribution of the electroplastic effect during passage of current to the reduction of flow stresses, the materials were also exposed to external heating. The microstructure of the samples in the sample head and in the vicinity of the fracture region in the longitudinal section was studied using optical microscopy. The electroplastic effect in the studied materials is manifested on the tensile curve through individual jumps in the downward flow stress at a high pulse ratio, whereas at a low current pulse ratio a decrease in the flow stress and strain hardening and increase in the plasticity are observed. It is shown that tension of the sample under the effect of current results in a greater decrease in the flow stresses than that observed under external heating at the same temperature for both materials. This confirms the athermal nature of the pulsed current effect. The critical density of the high pulse ratio current (q - 5000) capable of providing manifestation of the electroplastic effect is two times lower for a VT6 alloy than for pure titanium Grade 4. Under the same pulsed current modes, the flow stresses for VT6 decrease more than for Grade 4. Pulsed current of high pulse ratio caused an anomalous hardening effect in a VT6 alloy, but the physical nature of this effect requires an additional study. The pulsed current modes used in the study did not lead to any structural changes noticeable under optical magnification in the samples under tension, except for the disappearance of twins and separation of the impurity particles in Grade 4 and spheroidization of grains in VT6.

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Kandratsyeu, Aleh, Uladzimir Sabaleuski, Luis Redondo, and Andrei G. Pakhomov. "Four Channel 6.5 kV, 65 A, 100 ns–100 µs Generator with Advanced Control of Pulse and Burst Protocols for Biomedical and Biotechnological Applications." Applied Sciences 11, no. 24 (December 11, 2021): 11782. http://dx.doi.org/10.3390/app112411782.

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Pulsed electric fields in the sub-microsecond range are being increasingly used in biomedical and biotechnology applications, where the demand for high-voltage and high-frequency pulse generators with enhanced performance and pulse flexibility is pushing the limits of pulse power solid state technology. In the scope of this article, a new pulsed generator, which includes four independent MOSFET based Marx modulators, operating individually or combined, controlled from a computer user interface, is described. The generator is capable of applying different pulse shapes, from unipolar to bipolar pulses into biological loads, in symmetric and asymmetric modes, with voltages up to 6.5 kV and currents up to 65 A, in pulse widths from 100 ns to 100 µs, including short-circuit protection, current and voltage monitoring. This new scientific tool can open new research possibility due to the flexibility it provides in pulse generation, particularly in adjusting pulse width, polarity, and amplitude from pulse-to-pulse. It also permits operating in burst mode up to 5 MHz in four independent channels, for example in the application of synchronized asymmetric bipolar pulses, which is shown together with other characteristics of the generator.

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Zudov, Vladimir N., Pavel K. Tretyakov, and Andrey V. Tupikin. "Some Features of Pulse-Periodic Energy Supply in Supersonic Flow." Siberian Journal of Physics 5, no. 2 (July 1, 2010): 43–54. http://dx.doi.org/10.54362/1818-7919-2010-5-2-43-54.

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In the present work, the results of numerical and experimental investigations of supersonic flows with a localized energy supply are considered. The energy supply region (the heat source) was formed by the plasma created by a focused pulsed-periodic laser emission either by combustion in the separation zone upstream of the blunted body. The main attention is paid to the unsteady effects the role of which is determining at the integral flow structure formation. A physical model of energy source is formulated. The numerical and experimental data on the structure of the flow around the source and the characteristics of a thermal wake arising behind the source are compared. The energy pulses frequency and capacity are shown to determine the wake properties: the formation and development of subsonic regions, vortex structures, and reverse flow regions. It follows from an analysis of the aerodynamic drag variation at a flow with a thermal wake of the energy supply source around blunt bodies that the energy and pulse as well as its duration are the main parameters determining the efficiency of the frequency effect. A high sensitivity of the results to the physical model accepted in numerical investigation is shown. The pressure variation dynamics on a conical surface is presented versus the frequency of pulses. Comparison with experiment has shown a good quantitative agreement.

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Wang, Xingxing, Adam Patel, and Alexey Shashurin. "Initial transient stage of pin-to-pin nanosecond repetitively pulsed discharges in air." Journal of Applied Physics 132, no. 1 (July 7, 2022): 013301. http://dx.doi.org/10.1063/5.0093794.

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In this work, evolution of parameters of nanosecond repetitively pulsed (NRP) discharges in pin-to-pin configuration in air was studied during the transient stage of initial 20 discharge pulses. Gas and plasma parameters in the discharge gap were measured using coherent microwave scattering, optical emission spectroscopy, and laser Rayleigh scattering for NRP discharges at repetition frequencies of 1, 10, and 100 kHz. Memory effects (when perturbations induced by the previous discharge pulse would not decay fully until the subsequent pulse) were detected for the repetition frequencies of 10 and 100 kHz. For 10 kHz NRP discharge, the discharge parameters experienced significant change after the first pulse and continued to substantially fluctuate between subsequent pulses due to rapid evolution of gas density and temperature during the 100 μs inter-pulse time caused by intense redistribution of the flow field in the gap on that time scale. For 100 kHz NRP discharge, the discharge pulse parameters reached a new steady-state at about five pulses after initiation. This new steady-state was associated with well-reproducible parameters between the discharge pulses and substantial reduction in breakdown voltage, discharge pulse energy, and electron number density in comparison to the first discharge pulse. For repetition frequencies 1–100 kHz considered in this work, the memory effects can be likely attributed to the reduction in gas number density and increase in the gas temperature that cannot fully recover to ambient conditions before subsequent discharge pulses.

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Riahi, Mehdi, Saïd Aniss, Mohamed Ouazzani Touhami, and Salah Skali Lami. "Stability of a Pulsed Taylor-Couette Flow in a Viscoelastic Fluid." Nihon Reoroji Gakkaishi 42, no. 5 (2015): 321–27. http://dx.doi.org/10.1678/rheology.42.321.

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Tortoli, P., R. S. Thompson, P. Berti, and F. Guidi. "Flow imaging with pulsed Doppler ultrasound and flow phantoms." IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control 46, no. 6 (November 1999): 1591–96. http://dx.doi.org/10.1109/58.808885.

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Nduom, Edjah K., Stuart Walbridge, and Russell R. Lonser. "Comparison of pulsed versus continuous convective flow for central nervous system tissue perfusion." Journal of Neurosurgery 117, no. 6 (December 2012): 1150–54. http://dx.doi.org/10.3171/2012.9.jns12506.

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Object Although pulsatile and continuous infusion paradigms have been described for convective delivery of drugs, the effectiveness and properties of each flow paradigm are unknown. To determine the effectiveness and properties of pulsatile and continuous convective infusion paradigms, the authors compared these convective flow methods in the gray and white matter of primates. Methods Six primates (Macaca mulatta) underwent convective infusion of Gd-DPTA (5 mM) into the cerebral gray matter (thalamus) or white matter (frontal lobe) using pulsed (intermittent pulses of 15 μl/min) or continuous (1 μl/min) convective flow. Results were assessed by clinical MRI and histological analyses. Results Distribution of Gd-DTPA infusate in gray and white matter by pulsed and continuous flow was clearly identified using MRI, which revealed that both convective flow methods demonstrated an increase in the volume of distribution (Vd) with increasing volume of infusion (Vi) in the surrounding gray and white matter. Although the mean (± SD) gray matter Vd:Vi ratio for the pulsed infusions (4.2 ± 0.5) was significantly lower than the mean Vd:Vi ratio for continuous infusions (5.4 ± 0.5; a 22% difference [p = 0.0006]), the difference between pulsed (3.8 ± 0.4) and continuous (4.3 ± 1.2) infusions in white matter was not significantly different (p = 0.3). Pulsed infusions were associated with more leakback (12.3% ± 6.4% of Vi) than continuous infusions (3.9% ± 7.8%), although this difference was not significant (p = 0.2). All animals tolerated the infusions and there was no histological evidence of tissue injury at the infusion sites. Conclusions Although pulsed and continuous infusion flow paradigms can be safely and effectively used for convective delivery into both gray and white matter, continuous infusion is associated with a higher Vd:Vi ratio than pulsatile infusion in gray matter. High rates of infusion (15 μl/min) can be used to deliver infusate without any significant leakback and without any clinical or histological evidence of injury.

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Ali, Syed Sadiq, Agus Arsad, Kenneth L. Roberts, and Mohammad Asif. "Effect of Inlet Flow Strategies on the Dynamics of Pulsed Fluidized Bed of Nanopowder." Nanomaterials 13, no. 2 (January 11, 2023): 304. http://dx.doi.org/10.3390/nano13020304.

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The use of fluidization assistance can greatly enhance the fluidization hydrodynamics of powders that exhibit poor fluidization behavior. Compared to other assistance techniques, pulsed flow assistance is a promising technique for improving conventional fluidization because of its energy efficiency and ease of process implementation. However, the inlet flow configuration of pulsed flow can significantly affect the bed hydrodynamics. In this study, the conventional single drainage (SD) flow strategy was modified to purge the primary flow during the non-flow period of the pulse to eliminate pressure buildup in the inlet flow line while providing a second drainage path to the residual gas. The bed dynamics for both cases, namely, single drainage (SD) and modified double drainage (MDD), were carefully monitored by recording the overall and local pressure drop transients in different bed regions at two widely different pulsation frequencies of 0.05 and 0.25 Hz. The MDD strategy led to substantially faster bed dynamics and greater frictional pressure drop in lower bed regions with significantly mitigated segregation behavior. The spectral analysis of the local and global pressure transient data in the frequency domain revealed a pronounced difference between the two flow strategies. The application of the MDD inlet flow strategy eliminated the disturbances from the pulsed fluidized bed irrespective of the pulsation frequency.

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Stolyarov, Vladimir, Oleg Korolkov, Alexander Pesin, and George Raab. "Deformation Behavior under Tension with Pulse Current of Ultrafine-Grain and Coarse-Grain CP Titanium." Materials 16, no. 1 (December 25, 2022): 191. http://dx.doi.org/10.3390/ma16010191.

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The problem of the real existence of the electroplastic effect during deformation of metallic materials of different nature is still relevant. At the same time, the influence of structure refinement is not considered enough. In this work, the deformation behavior of ultrafine-grained (UFG) titanium Grade 4 is compared with that of coarse-grained (CG) titanium under tension with pulse current of the low duty cycle. The deformation curves of both structure states are presented for different regimes of pulsed current and thermal heating from an external source. Structure studies by optical and scanning electron microscopy, as well as microhardness measurements have been carried out. It is shown that Grade 4 titanium under tension accompanied by pulsed current exhibits electroplastic effect (EPE) in the form of a flow stress reduction. EPE in UFG state is much stronger than in CG state. An increase in the density and duration of the current pulse leads to a multiple decrease in the flow stresses in CG and UFG titanium. The contribution in the flow stress reduction from heating by an external source was less than that from tension with pulse current at the same temperatures. The impact of pulsed current during tension does not influence microhardness and grain size.

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32

Ravi Vishnu, P., W. B. Li, and K. E. Easterling. "Heat flow model for pulsed welding." Materials Science and Technology 7, no. 7 (July 1991): 649–59. http://dx.doi.org/10.1179/mst.1991.7.7.649.

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Bombardini, Tonino, Battista Borghi, Laura Lorenzini, Elettra Pignotti, and Gian Carlo Caroli. "Pulsed Venous Flow Pattern with Hemodilution." Vascular Surgery 35, no. 2 (March 2001): 123–29. http://dx.doi.org/10.1177/153857440103500207.

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Grant, I. "Flow Measurement By Pulsed Laser (Speckle)." Physics Bulletin 38, no. 5 (May 1987): 175–77. http://dx.doi.org/10.1088/0031-9112/38/5/023.

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35

Zakhmatov, V. D. "A pulsed gas-solid jet flow." Combustion, Explosion, and Shock Waves 30, no. 3 (May 1994): 326–30. http://dx.doi.org/10.1007/bf00789425.

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36

Wang, X. S., and M. J. Rhodes. "Using pulsed flow to overcome defluidization." Chemical Engineering Science 60, no. 18 (September 2005): 5177–81. http://dx.doi.org/10.1016/j.ces.2005.04.016.

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37

Zhang, Hongxin, Shaowen Chen, Yun Gong, and Songtao Wang. "A comparison of different unsteady flow control techniques in a highly loaded compressor cascade." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 233, no. 6 (April 18, 2018): 2051–65. http://dx.doi.org/10.1177/0954410018770492.

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A numerical research is applied to investigate the effect of controlling the flow separation in a certain highly loaded compressor cascade using different unsteady flow control techniques. Firstly, unsteady pulsed suction as a new novel unsteady flow control technique was proposed and compared to steady constant suction in the control of flow separation. A more exciting effect of controlling the flow separation and enhancing the aerodynamic performance for unsteady pulsed suction was obtained compared to steady constant suction with the same time-averaged suction flow rate. Simultaneously, with the view to further exploring the potential of unsteady flow control technique, unsteady pulsed suction, unsteady pulsed blowing, and unsteady synthetic jet (three unsteady flow control techniques) are analyzed comparatively in detail by the related unsteady aerodynamic parameters such as excitation location, frequency, and amplitude. The results show that unsteady pulsed suction shows greater advantage than unsteady pulsed blowing and unsteady synthetic jet in controlling the flow separation. Unsteady pulsed suction and unsteady synthetic jet have a wider range of excitation location obtaining positive effects than unsteady pulsed blowing. The ranges of excitation frequency and excitation amplitude for unsteady pulsed suction gaining favorable effects are both much wider than that of unsteady pulsed blowing and unsteady synthetic jet. The optimum frequencies of unsteady pulsed suction, unsteady pulsed blowing, and unsteady synthetic jet are found to be different, but these optimum frequencies are all an integer multiple of the natural frequency of vortex shedding. The total pressure loss coefficient is reduced by 16.98%, 16.55%, and 17.38%, respectively, when excitation location, frequency, and amplitude are all their own optimal values for unsteady pulsed suction, unsteady pulsed blowing, and unsteady synthetic jet. The optimum result of unsteady synthetic jet only slightly outperforms that of unsteady pulsed suction and unsteady pulsed blowing. But unfortunately, there is no advantage from the standpoint of overall efficiency for the optimum result of unsteady synthetic jet because the slight improvement has to require a greater power consumption than the unsteady pulsed suction and unsteady pulsed blowing methods.

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38

Wan, Tao, Takashi Naoe, Hiroyuki Kogawa, Masatoshi Futakawa, Hironari Obayashi, and Toshinobu Sasa. "Numerical Study on the Potential of Cavitation Damage in a Lead–Bismuth Eutectic Spallation Target." Materials 12, no. 4 (February 25, 2019): 681. http://dx.doi.org/10.3390/ma12040681.

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To perform basic Research and Development for future Accelerator-driven Systems (ADSs), Japan Proton Accelerator Research Complex (J-PARC) will construct an ADS target test facility. A Lead–Bismuth Eutectic (LBE) spallation target will be installed in the target test facility and bombarded by pulsed proton beams (250 kW, 400 MeV, 25 Hz, and 0.5 ms pulse duration). To realize the LBE spallation target, cavitation damage due to pressure changes in the liquid metal should be determined, preliminarily, because such damage is considered to be very critical, from the viewpoint of target safety and lifetime. In this study, cavitation damage due to pressure waves caused by pulsed proton beam injection and turbulent liquid metal flow, were studied, numerically, from the viewpoint of single cavitation bubble dynamics. Specifically, the threshold of cavitation and effects of flow speed fluctuation on cavitation bubble dynamics, in an orifice structure, were investigated in the present work. The results showed that the LBE spallation target did not undergo cavitation damage, under normal nominal operation conditions, mainly because of the long pulse duration of the pulsed proton beam and the low liquid metal flow velocity. Nevertheless, the possibility of cavitation damage in the orifice structure, under certain extreme transient LBE flow conditions, cannot be neglected.

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CHAINE, ALINE, CAROLINE LEVY, BERNARD LACOUR, CHRISTOPHE RIEDEL, and FRÉDÉRIC CARLIN. "Decontamination of Sugar Syrup by Pulsed Light." Journal of Food Protection 75, no. 5 (May 1, 2012): 913–17. http://dx.doi.org/10.4315/0362-028x.jfp-11-342.

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The pulsed light produced by xenon flash lamps was applied to 65 to 67 °Brix sugar syrups artificially contaminated with suspensions of Saccharomyces cerevisiae and with spores of Bacillus subtilis, Geobacillus stearothermophilus, Alicyclobacillus acidoterrestris, and Aspergillus niger. The emitted pulsed light contained 18.5% UV radiation. At least 3-log reductions of S. cerevisiae, B. subtilis, G. stearothermophilus, and A. acidoterrestris suspended in 3-mm-deep volumes of sugar syrup were obtained with a fluence of the incident pulsed light equal to or less than 1.8 J/cm2, and the same results were obtained for B. subtilis and A. acidoterrestris suspended in 10-mm-deep volumes of sugar syrup. A. niger spores would require a more intense treatment; for instance, the maximal log reduction was close to 1 with a fluence of the incident pulsed light of 1.2 J/cm2. A flowthrough reactor with a flow rate of 320 ml/min and a flow gap of 2.15 mm was designed for pulsed light treatment of sugar syrup. Using this device, a 3-log reduction of A. acidoterrestris spores was obtained with 3 to 4 pulses of incident pulsed light at 0.91 J/cm2 per sugar syrup volume.

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Wang, Chengze, Huawei Lu, Xiaozhi Kong, Shiqi Wang, Dongzhi Ren, and Tianshuo Huang. "Effects of Pulsed Jet Intensities on the Performance of the S-Duct." Aerospace 10, no. 2 (February 15, 2023): 184. http://dx.doi.org/10.3390/aerospace10020184.

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The high curvature of modern S-ducts causes a strong secondary flow, which seriously affects the uniformity of the compressor inlet flow. In this study, the flow control method of a pulsed jet was applied in the S-duct at an incoming Mach number of 0.4. The jet holes were with an angle of 45° and were symmetrically distributed on the upper wall. Three jet intensities of 0.16%, 0.24%, and 0.31% were simulated using the unsteady Reynolds-averaged Navier–Stokes equations (URANS) and were validated by experiments. The mechanism of the pulsed jet, with respect to controlling the flow separation in the S-duct, was analyzed through secondary flow behaviors and boundary layer characteristics. The results indicated that the radial and axial pressure gradients were crucial to the formation of the large-scale vortices and reversed fluids in the S-duct. The pulsed jets were found to resist the adverse pressure gradient by exciting the turbulent kinetic energy of the boundary layer fluids. In addition, the dissipation process of vorticity was accelerated due to the promotion of the mixing effect by these devices. Moreover, in the current study, the area with high total pressure loss coefficients decreased gradually along with the intensity increase. Specifically, a maximum loss reduction of 5.9% was achieved when the pulse jet intensity was set to 0.31%, which means that the pulsed jet has great potential in controlling the flow separation in the S-duct.

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41

Makarov, G. N., D. E. Malinovsky, and D. D. Ogurok. "Single Pulse Carbon-13 Enrichment of CF3 Under IR MPD in A Short Gas Dynamic Flow." Laser Chemistry 17, no. 4 (January 1, 1998): 205–18. http://dx.doi.org/10.1155/1998/36263.

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An experimental approach is described for obtaining highly enriched residual gas under IR multiphoton dissociation (MPD) of molecules in one cycle of irradiation. The approach is based on utilization of a pulsed molecular flow of small length (Δxfl≤1cm). The use of a short flow length leads to high values of the dissociation yield of molecules (β≃1) in the whole volume of the flow. Owing to this, high enrichment of the residual gas is achieved in one cycle of irradiation. The isotopically-selective dissociation of CF3I+ in the pulsed gasdynamic flow of a small length was studied. About 400-fold enrichment of the 13C isotope in the residual gas was obtained following irradiation of a molecular flow of CF3I of natural isotope composition by a single laser pulse. The selectivity of dissociation was measured to be α≥10

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42

Polman, A., W. C. Sinke, M. J. Uttormark, and Michael O. Thompson. "Pulsed-laser induced transient phase transformations at the Si–H2O interface." Journal of Materials Research 4, no. 4 (August 1989): 843–56. http://dx.doi.org/10.1557/jmr.1989.0843.

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Phase transformations at the Si–H2O interface, induced by nanosecond pulsed laser irradiation, were studied in real time. Si samples were irradiated using a 4 ns pulse from a Q-switched frequency-doubled Nd:YAG laser while immersed in the transparent liquid. Using time-resolved conductivity and reflectivity techniques, in combination with modeling of optical parameters and heat flow, transient processes in the Si, the H2O, and at the interface have been unraveled. In the liquid, local rapid heating occurs as a result of heat flow across the interface, and formation of a low-density steam phase occurs on a nanosecond timescale. Expansion of this phase is followed by a collapse after 200 ns. These rapid phase transformations in the water initiate a shock wave with a pressure of 0.4± 0.3 kbar. Transient phase transformations and the heat flow into the water during the laser pulse influence the energy coupling into the sample, resulting in an effective laser pulse shortening. The pulse shortening and the additional heat flow into the water during solidification result in a 30% enhancement of the solidification velocity for 270 nm deep melts. Cross-section transmission electron microscopy data reveal that the Si surface is planar after irradiation and is inert to chemical reactions during irradiation. Recent experiments described in the literature concerning pulsed-laser induced synthesis at the solid-liquid interface are reviewed and discussed in the context of the fundamental phenomena presently observed.

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43

Oldham, James M., Chamara Abeysekera, Baptiste Joalland, Lindsay N. Zack, Kirill Prozument, Ian R. Sims, G. Barratt Park, Robert W. Field, and Arthur G. Suits. "A chirped-pulse Fourier-transform microwave/pulsed uniform flow spectrometer. I. The low-temperature flow system." Journal of Chemical Physics 141, no. 15 (October 21, 2014): 154202. http://dx.doi.org/10.1063/1.4897979.

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44

Ziborov, Vadim S., Tatyana O. Pleshakova, Ivan D. Shumov, Andrey F. Kozlov, Anastasia A. Valueva, Irina A. Ivanova, Maria O. Ershova, et al. "The Impact of Fast-Rise-Time Electromagnetic Field and Pressure on the Aggregation of Peroxidase upon Its Adsorption onto Mica." Applied Sciences 11, no. 24 (December 9, 2021): 11677. http://dx.doi.org/10.3390/app112411677.

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Our present study concerns the influence of the picosecond rise-time-pulsed electromagnetic field, and the impact of nanosecond pulsed pressure on the aggregation state of horseradish peroxidase (HRP) as a model enzyme. The influence of a 640 kV/m pulsed electromagnetic field with a pulse rise-time of ~200 ps on the activity and aggregation state of an enzyme is studied by the single-molecule atomic force microscopy (AFM) method. The influence of such a field is shown to lead to aggregation of the protein and to a decrease in its enzymatic activity. Moreover, the effect of a shock wave with a pressure front rise-time of 80 ns on the increase in the HRP aggregation is demonstrated. The results obtained herein can be of use in modeling the impact of electromagnetic and pressure pulses on enzymes and on whole living organisms. Our results are also important for taking into account the effect of pulsed fields on the body in the development of drugs, therapeutic procedures, and novel highly sensitive medical diagnosticums.

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45

Gribacheva, V., and S. Shcherbakov. "THE COOLING SYSTEM OF THE PERIODIC PULSED REACTOR." PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. SERIES: NUCLEAR AND REACTOR CONSTANTS 2021, no. 2 (June 26, 2021): 256–67. http://dx.doi.org/10.55176/2414-1038-2021-2-256-267.

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The paper proposes the configuration and composition equipment of the cooling system of the designed periodic pulsed reactor (PPR) of high power. The special features of the PPR are a small flow section, a large heating of the coolant in the power pulse and the impossibility of useful use of thermal energy in the periodic mode of operation. Liquid lithium is proposed as a coolant and heat is discharged through air heat exchangers (AHE). The goal was to achieve compactness and low power consumption, the ability to work with frequent stops and optimize the operation of equipment in pulse modes. For this purpose, high-temperature AHE with a small heat exchange surface and forced air cooling are used, the circulation circuit is divided into two parts - the reactor circuit and the AHE circuit with two circulation pumps and a common drain tank. The separation of the circuit allows to independently perform the operations of starting, stopping and heating the circuits in a periodic mode. The drain tank limits the composition of the equipment exposed to temperature pulses. Numerical studies of the temperature regime of the coolant in the equipment of the PDR cooling system are carried out. The calculations were performed using the TURBOFLOW code in two-dimensional terms for all the main elements of the equipment. Quasi-stationary (nominal and partial power levels) and pulse modes of operation are considered. Calculated characteristics for forced and natural air circulation are obtained. The limits of the air circulation modes under the conditions of non-freezing of the coolant are determined. The obtained values of the maximum temperatures of the coolant: in the pulsed mode is 750 °C, in the quasi-stationary mode - 490 °C with an average power of 15 MW, air flow of 150 m3/s and the size of the AHE in the plan of 5×5 m, 100 panels of 1.08×0.025×5 m.

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46

Graham, L. J. W., and K. Bremhorst. "Application of the k–ε Turbulence Model to the Simulation of a Fully Pulsed Free Air Jet." Journal of Fluids Engineering 115, no. 1 (March 1, 1993): 70–74. http://dx.doi.org/10.1115/1.2910116.

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The work describes application of the k–ε turbulence model to a fully pulsed air jet. The standard model failed to predict the change in slope of the velocity decay where the jet changes from pulsed to steady jet behavior. A change in one of the constants of the k–ε model based on the behavior of the periodic velocity component relative to the intrinsic component yielded satisfactory results. Features of the pulsed jet which were successfully simulated included the flow reversal near the edge of the jet, increased entrainment when compared to steady jets and large radial outflow near the leading edge of the pulse and large radial inflow near the outer edge of the jet for the remainder of the pulse.

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47

Chen, Yuxi, Jie Xu, Bin Guo, and Debin Shan. "Effect of Pulsed Current-Assisted Tension on the Mechanical Behavior and Local Strain of Nickel-Based Superalloy Sheet." Materials 16, no. 4 (February 14, 2023): 1589. http://dx.doi.org/10.3390/ma16041589.

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Electrically assisted (EA) forming is a plastic forming technique under the coupling action of multiple energy fields, such as force field, temperature field, and electric field. It is suitable for the forming of difficult-to-deform materials such as nickel-based superalloys. In this paper, uniaxial tensile tests on nickel-based superalloy sheets were carried out using the pulsed current assisted with different parameters. The experimental results show that the flow stress of the material decreased with the increase in the current density under a high-frequency pulsed current, and the Joule heating effect explains the flow stress drop. In the pulsed current application process, the different types of Portevin–Le Chatelier phenomena appeared with the increase in the current density. The decrease in elongation assisted by the pulsed current was explained by analyzing the inhomogeneity of the maximum Joule heating temperature distribution. In addition, the digital image correlation (DIC) analysis was used to analyze the local strain behavior of the pulsed current-assisted tensile process. Under the application of a high-frequency pulse current, the specimen exerted an inhomogeneous temperature increase and local hot pressing stress, which resulted in the inhomogeneous distribution of the local strain.

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Nakagawa, Atsuhiro, Takayuki Hirano, Hidefumi Jokura, Hiroshi Uenohara, Tomohiro Ohki, Tokitada Hashimoto, Viren Menezes, et al. "Pulsed holmium:yttrium-aluminum-garnet laser—induced liquid jet as a novel dissection device in neuroendoscopic surgery." Journal of Neurosurgery 101, no. 1 (July 2004): 145–50. http://dx.doi.org/10.3171/jns.2004.101.1.0145.

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Object. A pressure-driven continuous jet of water has been reported to be a feasible tool for neuroendoscopic dissection owing to its superiority at selective tissue dissection in the absence of thermal effects. With respect to a safe, accurate dissection, however, continuous water flow may not be suitable for intraventricular use. The authors performed experiments aimed at solving problems associated with continuous flow by using a pulsed holmium:yttrium-aluminum-garnet (Ho:YAG) laser-induced liquid jet (LILJ). They present this candidate neuroendoscopic LILJ dissection system, having examined its mechanical characteristics and evaluated its controllability both in a tissue phantom and in a rabbit cadaveric ventricle wall. Methods. The LILJ generator was incorporated into the tip of a No. 4 French catheter so that the LILJ could be delivered via a neuroendoscope. Briefly, the LILJ was generated by irradiating an internally supplied column of physiological saline with a pulsed Ho:YAG laser (pulse duration time 350 µsec; laser energy 250–700 mJ/pulse) within a No. 4 French catheter (internal diameter 1 mm) and ejecting it from a metal nozzle (internal diameter 100 µm). The Ho:YAG laser energy pulses were conveyed by an optical fiber (core diameter 400 µm) at 3 Hz, whereas physiological saline (4°C) was supplied at a rate of 40 ml/hour. The mechanical characteristics of the pulsed LILJ were investigated using high-speed photography and pressure measurements; thermal effects and controllability were analyzed using an artificial tissue model (10% gelatin of 1 mm thickness). Finally, the ventricle wall of a rabbit cadaver was dissected using the LILJ. Jet pressure increased in accordance with laser energy from 0.1 to 2 bar; this translated into a penetration depth of 0.08 to 0.9 mm per shot in the ventricle wall of the rabbit cadaver. The gelatin phantom could be cut into the desired shape without significant thermal effects and in the intended manner, with a good surgical view. Conclusions. The present results show that the pulsed LILJ has the potential to become a safe and reliable dissecting method for endoscopic procedures.

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McWilliams, K. A., T. K. Yeoman, and G. Provan. "A statistical survey of dayside pulsed ionospheric flows as seen by the CUTLASS Finland HF radar." Annales Geophysicae 18, no. 4 (April 30, 2000): 445–53. http://dx.doi.org/10.1007/s00585-000-0445-8.

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Abstract. Nearly two years of 2-min resolution data and 7- to 21-s resolution data from the CUTLASS Finland HF radar have undergone Fourier analysis in order to study statistically the occurrence rates and repetition frequencies of pulsed ionospheric flows in the noon-sector high-latitude ionosphere. Pulsed ionospheric flow bursts are believed to be the ionospheric footprint of newly reconnected geomagnetic field lines, which occur during episodes of magnetic flux transfer to the terrestrial magnetosphere - flux transfer events or FTEs. The distribution of pulsed ionospheric flows were found to be well grouped in the radar field of view, and to be in the vicinity of the radar signature of the cusp footprint. Two thirds of the pulsed ionospheric flow intervals included in the statistical study occurred when the interplanetary magnetic field had a southward component, supporting the hypothesis that pulsed ionospheric flows are a reconnection-related phenomenon. The occurrence rate of the pulsed ionospheric flow fluctuation period was independent of the radar scan mode. The statistical results obtained from the radar data are compared to occurrence rates and repetition frequencies of FTEs derived from spacecraft data near the magnetopause reconnection region, and to ground-based optical measurements of poleward moving auroral forms. The distributions obtained by the various instruments in different regions of the magnetosphere were remarkably similar. The radar, therefore, appears to give an unbiased sample of magnetopause activity in its routine observations of the cusp footprint.Key words: Magnetospheric physics (magnetosphere-ionosphere interactions; plasma convection; solar wind-magnetosphere interactions)

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Liu, Guojun, Xuhao Yang, Yan Li, Zhigang Yang, Wen Hong, and JianFang Liu. "Continuous Flow Controlled Synthesis of Gold Nanoparticles Using Pulsed Mixing Microfluidic System." Advances in Materials Science and Engineering 2015 (2015): 1–11. http://dx.doi.org/10.1155/2015/160819.

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To prepare the gold nanoparticles (AuNPs) with uniform sizes, fine morphology, and good monodispersity, a pulsed mixing microfluidic system based on PZT actuation was presented. The system includes PZT micropump and Y type micromixer. By adjusting voltage (entrance flow rate), pulsed frequency, phase, and other parameters, a variety of mixing modes can be achieved, so as to realize the controllable synthesis of nanoparticles in a certain range. By numerical simulation and analysis, the channel section size, entrance angle, and pulse frequency were optimized. Based on the optimized structure and working parameters, the test prototype has been manufactured in lab, and the related synthesis tests of AuNPs were carried out. The test results indicate that AuNPs with uniform morphology and good monodispersity can be synthesized using the system with the section size (0.4 mm × 0.4 mm), the entrance channel angle (60°) under condition of the pulsed frequency (300 Hz), and the entrance flow rate (4 mL/min). The average diameter and its standard deviation of AuNPs synthesized were 21.6 nm, 4.83 nm, respectively. The research work above can be applied to the fields such as the controlled synthesis of noble metal nanoparticles, biomedicine, and microchemical system.

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Journal articles on the topic 'Pulsed flow'

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