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1
Kozlov, Viktor V., Maria V. Litvinenko e Grigory V. Kozlov. "The Round Jet in a Cross-Flow (Review)". Siberian Journal of Physics 5, n. 1 (1 marzo 2010): 9–28. http://dx.doi.org/10.54362/1818-7919-2010-5-1-9-28.
Abstract (sommario):
Results of experimental and numerical studies on characteristics of the developing round jet with parabolic velocity profile in a crossflow are presented. The basic differences of characteristics (parameters, properties) of development of the round jet with parabolic velocity profile and «shock» velocity profile are showed. As it is outlined, the round jet with parabolic velocity profile in a crossflow is transformed to two stationary counter rotating vortices. In the current work it is shown, that the most unsteady high-frequency eigenmodes correspond wave packets onto the couple of counter rotating vortices. Decrease of frequency leads to development of the eigenmodes closer to wall in track of the jet. The growths of penetration of jet into a crossflow and air inflow by near-field of jet from crossflow are observed. In addition, it was shown, that boundary of the jet and crossflow can stretch and become thin under the influence of crossflow.
2
Pérez Ramírez, Lucía, Anthony Boucly, Florent Saudrais, Fabrice Bournel, Jean-Jacques Gallet, Emmanuel Maisonhaute, Aleksandar R. Milosavljević, Christophe Nicolas e François Rochet. "The Fermi level as an energy reference in liquid jet X-ray photoelectron spectroscopy studies of aqueous solutions". Physical Chemistry Chemical Physics 23, n. 30 (2021): 16224–33. http://dx.doi.org/10.1039/d1cp01511g.
3
ALVES, LEONARDO S. de B., ROBERT E. KELLY e ANN R. KARAGOZIAN. "Local stability analysis of an inviscid transverse jet". Journal of Fluid Mechanics 581 (22 maggio 2007): 401–18. http://dx.doi.org/10.1017/s0022112007005873.
Abstract (sommario):
A local linear stability analysis is performed for a round inviscid jet with constant density that is injected into a uniform crossflow of the same density. The baseflow is obtained from a modified version of the inviscid transverse jet near-field solution of Coelho & Hunt (J. Fluid Mech.vol. 200, 1989, p. 95) which is valid for small values of the crossflow-to-jet velocity ratio λ. A Fourier expansion in the azimuthal direction is used to couple the disturbances with the three-dimensional crossflow. The spatial growth rates of the modes corresponding to the axisymmetric and first helical modes of the free jet as λ → 0 increase as λ increases. The diagonal dominance of the dispersion relation matrix is used as a quantitative criterion to estimate the range of velocity ratios (0 < λ < λc) within which the transverse jet instability can be considered to have a structure similar to that of the free jet. Further, we show that for λ>0 positive and negative helical modes have different growth rates, suggesting an inherent weak asymmetry in the transverse jet.
4
Rui, Zilong, Kuibin Zhou, Ruixing Dong e Xia Shi. "Experimental Study on Double Jet Flames with Different Nozzle Diameters". Advances in Computer and Engineering Technology Research 1, n. 2 (18 aprile 2024): 460. http://dx.doi.org/10.61935/acetr.2.1.2024.p460.
Abstract (sommario):
Double jet flames are commonly observed in the energy industry. A facility consisting of a double jet flames apparatus, was designed to experimentally simulate the interaction of double jet fires with different spaces and nozzle diameters. It has been found that the exit momentum, nozzle diameters and nozzle spacing significantly affect the flame behavior. The experimental results show that the flame merging probability (Pm) of double jet fires with different nozzle diameters can be fitted with dimensionless parameters that couple the Froude number(Fr) and the distance between fire sources. Additionally, it has been observed that the difference in height between the two flames can be used as a parameter to determine the correlation between flame height and the distance to the nozzle center.
5
Haroon, R. F., e D. Roy. "A simulation study of the soft and hard radiations using jets at the LHC". Journal of Physics: Conference Series 2663, n. 1 (1 dicembre 2023): 012052. http://dx.doi.org/10.1088/1742-6596/2663/1/012052.
Abstract (sommario):
Abstract In this work, different aspects of the high-energy radiation are looked at considering the LHC scenario. An event-shape variable and several jet substructure observables are studied with the Mote Carlo event simulators at the 13 TeV center of mass energy scale to mimic the current LHC environment. The event-shape and the jet substructure observables are chosen such that they are not only sensitive to the different aspects of the high energy radiation measurement but also exhibit promising features to distinguish the possible existence of new physics that considers a dark matter candidate decaying into semi-visible jet. It is verified that the observables exhibit significant sensitivities to disentangle two jets to multi-jet radiations, presence of a final state and initial state radiations, presence of a large amount of missing transverse energy as a strong indication of the possible existence of a dark matter as well as couple of promising features of a semi-visible jet are explored.
6
RAMAN, GANESH, e RAY TAGHAVI. "Coupling of twin rectangular supersonic jets". Journal of Fluid Mechanics 354 (10 gennaio 1998): 123–46. http://dx.doi.org/10.1017/s0022112097007441.
Abstract (sommario):
Twin jet plumes on aircraft can couple, producing dynamic pressures significant enough to cause structural fatigue. For closely spaced jets with a moderate aspect ratio (e.g. 5), previous work has established that two coupling modes (antisymmetric and symmetric) are kinematically permissible. However, the dynamics of twin-jet coupling have remained unexplored. In this paper a more fundamental assessment of the steady and unsteady aspects of twin-jet coupling is attempted. While we document and discuss the nozzle spacings and Mach numbers over which phase-locked coupling occurs, our concentration is much more on answering the following questions: (a) What mechanism causes the jets to couple in one mode or the other? (b) Why do the jets switch from one mode to another? (c) Are the two modes mutually exclusive or do they overlap at the transition point? Our results reveal, among many things, the following. (i) For very closely spaced twin jets in the side-by-side configuration phased feedback based on source to nozzle exit distance of adjacent jets does not fully explain the coupling modes. However, the ‘null’ phase regions surrounding the jets where the phase of an acoustic wavefront (arriving from downstream) does not vary appears to correlate well with the existence of the symmetric mode. When the ‘null’ regions of adjacent jets do not overlap antisymmetric coupling occurs and when they do overlap the jets couple symmetrically. We provide a simple correlation using a parameter (α) that can be used as a simple test to determine the mode of coupling. (ii) The switch from the antisymmetric to the symmetric mode of coupling appears to occur because of an abrupt shift in the effective screech source from the third to the fourth shock, which in turn causes the ‘null’ phase region surrounding the jets to grow abruptly and overlap. (iii) The two modes are mutually exclusive. Our results provide considerable insight into the twin-jet coupling problem and offer hope for designing twin-jet configurations that minimize damage to aircraft components.
7
Cuahquentzi, Noel M., Luis H. H. Gómez, Pablo R. López, Guillermo Urriolagoitia-Calderón, Juan Alfonso Beltrán-Fernández, G. Urriolagoitia-Sosa, Enrique F. Cuamatzi, Arturo O. Ramírez e Beatriz R. Ángeles. "Evaluation of the Structural Integrity of the Jet Pumps of a Boiling Water Reactor under Hydrodynamic Loading". Defect and Diffusion Forum 348 (gennaio 2014): 261–70. http://dx.doi.org/10.4028/www.scientific.net/ddf.348.261.
Abstract (sommario):
The structural integrity of a jet pump assembly of a boiling water reactor (BWR) under hydrodynamic loading was evaluated. This arrangement, which has a riser joined with a couple of jet pumps by the transition piece, is part of the reactor recirculation system. It is submerged in water under pressure. The main function is to induce forced flow through the core of the reactor. A dynamic structural analysis was carried out with the finite element method. The first ten modes of vibration and their natural frequencies were calculated. The first five natural frequencies are in the range between 25 Hz and 40 Hz. In this analysis, it was considered that the jet pump assembly is supported at the riser brace. The restrainer bracket keeps together the riser with the two jet pumps and there is free movement at the slip joints.
8
Guo, Wen Liang, e Zheng Guo. "Nozzle Spraying Model of Combustion Thermal Spray". Advanced Materials Research 655-657 (gennaio 2013): 211–17. http://dx.doi.org/10.4028/www.scientific.net/amr.655-657.211.
Abstract (sommario):
The flame used in combustion flame spraying is typical of a high-temperature free jet. The flow fields of free jets are multi-phase flows that couple the mass and heat transfer. The analytical and numerical solutions to turbulent flows are engineering approximations. This work uses Prandtle’s mixing-length theory to describe the flame spreading of free combustion spray jet and uses nozzle spray model to describe the distribution of the powder particles sprayed from powder nozzle to the substrate surface. The nozzle geometry and the parameters determine the distribution of the powder particles. The nozzle spray model has the same physical meaning with the jet spreading angle. Experimental measurements were carried by a high-speed CCD camera.
9
Guo, Wen Liang, e Zheng Guo. "Research on Jet Flame Extinguishing Process". Applied Mechanics and Materials 635-637 (settembre 2014): 80–83. http://dx.doi.org/10.4028/www.scientific.net/amm.635-637.80.
Abstract (sommario):
The flame used in combustion flame spraying is typical of a high-temperature free jet. The flow fields of free jets are multi-phase flows that couple the mass and heat transfer. This work develops an analytical method to describe free combustion spray jets. The aim of the research is to develop a fully understanding of the characteristics of free-flame jets. Experimental measurements were carried by a unique high-speed continuous CCD camera.
10
Zhang, Xinxin, Jianming Peng, Jingqing Chen, Kun Bo, Kun Yin e Dongyu Wu. "The effect of actuator parameters on the performance of a liquid-jet hammer associated with its jet behavior". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 231, n. 14 (26 dicembre 2016): 2610–20. http://dx.doi.org/10.1177/0954406216685350.
Abstract (sommario):
Bi-stable fluidic amplifier containing no moving parts was used for switching fluid flow passing through it into an actuator in a liquid-jet hammer. So far, there has been no design basis for developing a liquid-jet hammer with high performance. To provide a guidance, this paper elaborates on the computational fluid dynamics simulation method for investigating the effect of actuator parameters on the performance of a liquid-jet hammer associated with its jet behavior. Given that couple mechanism exists between the flow field in the bi-stable fluidic amplifier and the actuator, dynamic mesh technique and a user-defined function written in C programming language were used to update the mesh in the simulations. Two evaluation criteria—pressure recovery and flux utilization ratio—for a liquid-jet hammer were used in this study. Experimental tests were conducted to verify the simulation results, by which the accuracy and reliability of this computational fluid dynamics simulation method was proved. Besides, comprehensive analysis of the flow behavior in the fluidic amplifier of a liquid-jet hammer was performed by the use of computational fluid dynamics visualization method.
11
Hidalgo-Duque, Carlos, e Felipe J. Llanes-Estrada. "Soft interactions in jet quenching". International Journal of Modern Physics A 30, n. 13 (4 maggio 2015): 1550067. http://dx.doi.org/10.1142/s0217751x15500670.
Abstract (sommario):
We study the collisional aspects of jet quenching in a high-energy nuclear collision, especially in the final state pion gas. The jet has a large energy, and acquires momentum transverse to its axis more effectively by multiple soft collisions than by few hard scatterings (as known from analogous systems such as J/ψ production at Hera). Such regime of large E and small momentum transfer corresponds to Regge kinematics and is characteristically dominated by the pomeron. From this insight we estimate the jet quenching parameter in the hadron medium (largely a pion gas) at the end of the collision, which is naturally small and increases with temperature in line with the gas density and compare it to the jet quenching parameter obtained within the quark–gluon plasma (QGP) phase in widely known perturbative approximations. The physics in the quark–gluon plasma/liquid phase is less obvious, and here we revisit a couple of simple estimates that suggest indeed that the pomeron-mediated interactions are very relevant and should be included in analysis of the jet quenching parameter. Finally, since the occasional hard collisions produce features characteristic of a Lèvy flight in the [Formula: see text] plane perpendicular to the jet axis, we suggest one- and two-particle q⊥correlations as interesting experimental probes sensitive to the nature (softness versus hardness) of the interactions of a jet inside the QGP.
12
Hu, Shu, Zhaohui Teng, Shan Huang, Na Li e Qulan Zhou. "Transient Calculation Studies of Liquid–Solid Collision in Jet Descaling". Energies 16, n. 1 (27 dicembre 2022): 292. http://dx.doi.org/10.3390/en16010292.
Abstract (sommario):
Sichuan is gradually being transformed and is utilizing groundwater and thermal resources. However, this investigation found that the high mineralization rate of geothermal resources in the Sichuan Basin is common and efficient, and environmentally friendly descaling technology is the key to promoting the utilization of thermal resources in low-yield oil and gas wells. Due to the high efficiency, low cost, and lack of pollution of high-pressure jet descaling, it has attracted more and more attention recently, but the mechanism of jet descaling is still unclear. The key to jet descaling is the stress concentration in the scale caused by the impact of droplets from the jet. In this paper, the process of jet descaling is simplified as a 2D droplet–scale collision with a detailed theoretical analysis of the stress on the scale. A circular droplet was simulated to impact the surface of the scale. By using numerical methods for transient calculations, we couple the pressure of the droplets and the scale strain. We acquired transient equivalent stress fields inside scales and pressure distributions inside the water droplet. As a result of the impact, areas of high stress in the scale appeared. Due to the stress superposition, the highest stress is concentrated in two areas: the contact edge and the shaft. These results can identify the mechanism for high-pressure jet descaling and help improve the efficiency of high-pressure water-jet descaling.
13
Meenakshi, Moun, Dipanjan Mukherjee, Alexander Y. Wagner, Nicole P. H. Nesvadba, Raffaella Morganti, Reinier M. J. Janssen e Geoffrey V. Bicknell. "The extent of ionization in simulations of radio-loud AGNs impacting kpc gas discs". Monthly Notices of the Royal Astronomical Society 511, n. 2 (28 gennaio 2022): 1622–36. http://dx.doi.org/10.1093/mnras/stac167.
Abstract (sommario):
ABSTRACT We use the results of relativistic hydrodynamic simulations of jet-interstellar medium (ISM) interactions in a galaxy with a radio-loud AGN to quantify the extent of ionization in the central few kpcs of the gaseous galactic disc. We perform post-process radiative transfer of AGN radiation through the simulated gaseous jet-perturbed disc to estimate the extent of photo-ionization by the AGN with an incident luminosity of 1045 erg s−1. We also map the gas that is collisionally ionized due to shocks driven by the jet. The analysis was carried out for simulations with similar jet power (1045 erg s−1) but different jet orientations with respect to the gas disc. We find that the shocks from the jets can ionize a significant fraction (up to 33 ${{\ \rm per\ cent}}$) of dense gas ($n\gt 100\, \mathrm{cm^{-3}}$) in the disc, and that the jets clear out the central regions of gas for AGN radiation to penetrate to larger distances in the disc. Jets inclined towards the disc plane couple more strongly with the ISM and ionize a larger fraction of gas in the disc as compared to the vertical jet. However, similar to previous studies, we find that the AGN radiation is quickly absorbed by the outer layers of dense clouds in the disc, and is not able to substantially ionize the disc on a global scale. Thus, compared to jet–ISM interactions, we expect that photo-ionization by the AGN radiation only weakly affects the star-formation activity in the central regions of the galactic disc (≲ 1 kpc), although the jet-induced shocks can spread farther out.
14
Gao, Na, e Xiaobin Zhang. "Research on the Numerical Effect of VTD Model in Cross Jet". Journal of Physics: Conference Series 2381, n. 1 (1 dicembre 2022): 012016. http://dx.doi.org/10.1088/1742-6596/2381/1/012016.
Abstract (sommario):
Abstract To deeply study the specific characteristics of the cross-scale phenomenon of fragmentation and atomization in the cross-jet process, this paper is based on the adaptive grid technology, using the RANS model, RNG k-ε model, LES model turbulence models, and VOF models, DPM model, VTD model multiphase flow models have carried out numerical calculations on the lateral jet process, and compared and analyzed the results to better solve the cross-scale problem and obtain more suitable research methods for the phenomenon of lateral jet breaking and atomization. It is found that: compared to the RANS model and RNG k-ε model, the LES model is more suitable for jet breaking; compared with the VOF model and DPM model, the VTD model is closer to the actual physical phenomenon in the cross jet breaking shape, and the initial surface of the liquid column is broken, the columnar broken and the band-shaped liquid filament is broken by a series of broken and atomized phenomena. And a large number of banded or filamentous liquid lumps can be captured in the continuous liquid film stage and the primary crushing stage of the jet, while discrete misty droplets can also be captured in the secondary crushing area. Based on this, this paper finds that the cross-scale VTD model is combined the phase gradient adaptive grid technology can couple the advantages of the VOF model and the DPM model to better solve the transition problem between the continuous phase and the discrete phase, thereby obtaining more accurate jet atomization characteristics.
15
Talbot, Rosie Y., Martin A. Bourne e Debora Sijacki. "Blandford–Znajek jets in galaxy formation simulations: method and implementation". Monthly Notices of the Royal Astronomical Society 504, n. 3 (26 marzo 2021): 3619–50. http://dx.doi.org/10.1093/mnras/stab804.
Abstract (sommario):
ABSTRACT Jets launched by active galactic nuclei (AGN) are believed to play a significant role in shaping the properties of galaxies and provide an energetically viable mechanism through which galaxies can become quenched. Here, we present a novel AGN feedback model, which we have incorporated into the arepo code, that evolves the black hole mass and spin as the accretion flow proceeds through a thin α-disc that we self-consistently couple to a Blandford–Znajek jet. We apply our model to the central region of a typical radio-loud Seyfert galaxy embedded in a hot circumgalactic medium (CGM). We find that jets launched into high-pressure environments thermalize efficiently due to the formation of recollimation shocks and the vigorous instabilities that these shocks excite increase the efficiency of the mixing of CGM and jet material. The beams of more overpressured jets, however, are not as readily disrupted by instabilities so the majority of the momentum flux at the jet base is retained out to the head, where the jet terminates in a reverse shock. All jets entrain a significant amount of cold circumnuclear disc material that, while energetically insignificant, dominates the lobe mass together with the hot, entrained CGM material. The jet power evolves significantly due to effective self-regulation by the black hole, fed by secularly driven, intermittent mass flows. The direction of jets launched directly into the circumnuclear disc changes considerably due to effective Bardeen–Petterson torquing. Interestingly, these jets obliterate the innermost regions of the disc and drive large-scale, multiphase, turbulent, bipolar outflows.
16
Gerber, Edwin P., e Geoffrey K. Vallis. "Eddy–Zonal Flow Interactions and the Persistence of the Zonal Index". Journal of the Atmospheric Sciences 64, n. 9 (1 settembre 2007): 3296–311. http://dx.doi.org/10.1175/jas4006.1.
Abstract (sommario):
Abstract An idealized atmospheric general circulation model is used to investigate the factors controlling the time scale of intraseasonal (10–100 day) variability of the extratropical atmosphere. Persistence on these time scales is found in patterns of variability that characterize meridional vacillations of the extratropical jet. Depending on the degree of asymmetry in the model forcing, patterns take on similar properties to the zonal index, annular modes, and North Atlantic Oscillation. It is found that the time scale of jet meandering is distinct from the obvious internal model time scales, suggesting that interaction between synoptic eddies and the large-scale flow establish a separate, intraseasonal time scale. A mechanism is presented by which eddy heat and momentum transport couple to retard motion of the jet, slowing its meridional variation and thereby extending the persistence of zonal index and annular mode anomalies. The feedback is strong and quite sensitive to model parameters when the model forcing is zonally uniform. However, the time scale of jet variation drops and nearly all sensitivity to parameters is lost when zonal asymmetries, in the form of topography and thermal perturbations that approximate land–sea contrast, are introduced. A diagnostic on the zonal structure of the zonal index provides intuition on the physical nature of the index and annular modes and hints at why zonal asymmetries limit the eddy–mean flow interactions.
17
Schulz, J., J. Bielecki, R. B. Doak, K. Dörner, R. Graceffa, R. L. Shoeman, M. Sikorski, P. Thute, D. Westphal e A. P. Mancuso. "A versatile liquid-jet setup for the European XFEL". Journal of Synchrotron Radiation 26, n. 2 (22 febbraio 2019): 339–45. http://dx.doi.org/10.1107/s1600577519000894.
Abstract (sommario):
The SPB/SFX instrument of the European XFEL provides unique possibilities for high-throughput serial femtosecond crystallography. This publication presents the liquid-jet sample delivery setup of this instrument. The setup is compatible with state-of-the-art gas dynamic virtual nozzle systems as well as high-viscosity extruders and provides space and flexibility for other liquid injection devices and future upgrades. The liquid jets are confined in a differentially pumped catcher assembly and can be replaced within a couple of minutes through a load-lock. A two-microscope imaging system allows visual control of the jets from two perspectives.
18
ARNE, WALTER, NICOLE MARHEINEKE, ANDREAS MEISTER e RAIMUND WEGENER. "NUMERICAL ANALYSIS OF COSSERAT ROD AND STRING MODELS FOR VISCOUS JETS IN ROTATIONAL SPINNING PROCESSES". Mathematical Models and Methods in Applied Sciences 20, n. 10 (ottobre 2010): 1941–65. http://dx.doi.org/10.1142/s0218202510004738.
Abstract (sommario):
This work deals with the curling behavior of slender viscous jets in rotational spinning processes. In terms of slender-body theory, an instationary incompressible viscous Cosserat rod model is formulated which differs from the approach of Ribe et al.,18 in the incompressibility approximation and reduces to the string model of Marheineke and Wegener13 for a vanishing slenderness parameter. Focusing exclusively on viscous and rotational effects on the jet in the exit plane near the spinning nozzle, the stationary two-dimensional scenario is described by a two-point boundary value problem of a system of first-order ordinary differential equations for jet's center-line, tangent, curvature, velocity, inner shear and traction force and couple. The numerical analysis shows that the rod model covers the string model in an inertia-dominated jet regime. Beyond that it overcomes the limitations of the string model studied by Götz et al.10 and enables even the handling of the viscous-inertial jet regime. Thus, the rod model shows its applicability for the simulation of industrially relevant parameter ranges and enlarges the domain of validity with respect to the string approach.
19
Oruba, Ludivine, Guillaume Lapeyre e Gwendal Rivière. "On the Northward Motion of Midlatitude Cyclones in a Barotropic Meandering Jet". Journal of the Atmospheric Sciences 69, n. 6 (1 giugno 2012): 1793–810. http://dx.doi.org/10.1175/jas-d-11-0267.1.
Abstract (sommario):
Abstract The combined effects of the deformation (horizontal stretching and shearing) and nonlinearities on the beta drift of midlatitude cyclones are studied using a barotropic quasigeostrophic model on the beta plane. It is found that, without any background flow, a cyclonic vortex moves more rapidly northward when it is initially strongly stretched along a mostly north–south direction. This meridional stretching is more efficient at forming an anticyclone to the east of the cyclone through Rossby wave radiation. The cyclone–anticyclone couple then forms a nonlinear vortex dipole that propagates mostly northward. The case of a cyclone embedded in uniformly sheared zonal flows is then studied. A cyclone evolving in an anticyclonic shear is stretched more strongly, develops a stronger anticyclone, and moves faster northward than a cyclone embedded in a cyclonic shear, which remains almost isotropic. Similar results are found in the general case of uniformly sheared nonzonal flows. The evolution of cyclones is also investigated in the case of a more realistic meandering jet whose relative vorticity gradient creates an effective beta and whose deformation field is spatially varying. A statistical study reveals a strong correlation among the cyclone’s stretching, the anticyclone strength, and the velocity toward the jet center. These different observations agree with the more idealized cases. Finally, these results provide a rationale for the existence of preferential zones for the jet-crossing phase: that is, the phase when a cyclone crosses a jet from its anticyclonic to its cyclonic side.
20
Yu, An, Qinghong Tang e Daqing Zhou. "Cavitation Evolution around a NACA0015 Hydrofoil with Different Cavitation Models Based on Level Set Method". Applied Sciences 9, n. 4 (21 febbraio 2019): 758. http://dx.doi.org/10.3390/app9040758.
Abstract (sommario):
Cavitation is a complex multiphase flow phenomenon that is usually involved in marine propulsion systems, and can be simulated with a couple of methods. In this study, three widespread cavitation models were compared using experimental data and a new modified simulation method. The accuracy of the three cavitation models was evaluated regarding their steady and unsteady characteristics, such as the flow field, re-entrant jet, vortex-shedding, and so on. Based on the experimental data and numerical results, the applicability of different cavitation models in different conditions was obtained. The Kunz model can accurately capture both the adverse pressure gradient and the action of the re-entrant jet in sheet cavitation, while the full cavitation model (FCM) has an accurate prediction for the flow field structure and the shedding characteristic of cloud cavitation. Through comparing the results, the optimal selection of cavitation models for further study at different conditions was obtained.
21
Sutherland, B. R. "Rayleigh Wave–Internal Wave Coupling and Internal Wave Generation above a Model Jet Stream". Journal of the Atmospheric Sciences 63, n. 3 (1 marzo 2006): 1042–55. http://dx.doi.org/10.1175/jas3658.1.
Abstract (sommario):
Abstract Linear theory for modes in a nonuniformly stratified, semi-infinite shear flow demonstrates that Rayleigh waves (stable waves propagating in fluid with spatially varying shear) couple with evanescent internal waves. If the bulk Richardson number (the squared ratio of the buoyancy frequency and shear) lies between 1/4 and 1, the waves have infinite e-folding depth for waves with critical relative horizontal wavenumbers. Fully nonlinear numerical simulations examine the effect of Rayleigh wave–internal wave coupling when the shear layer is localized and is thus Kelvin–Helmholtz unstable. Diagnostics examining profiles of the wave-induced mean flow show that if the bulk Richardson number is of order unity, significant momentum is extracted from a shear layer as a consequence of transport by waves. The work is extended to the study of unstable jet flows and applications of this work for internal wave generation by dynamic instability of the upper flank of the jet stream are discussed.
22
Iurea, Corina. "The Imbalance Between Professional Life and the Couple Relationship". JUS ET CIVITAS A Journal of Social and Legal Studies 74, n. 1 (30 dicembre 2023): 29–34. http://dx.doi.org/10.51865/jetc.2023.1.05.
Abstract (sommario):
This theme is relevant in modern society, where many people face challenges in maintaining a healthy balance between career and personal life. The study is important for understanding the impact that imbalance has on the individual and his or her relationships and on the life of the couple, as well as for outlining recommendations needed to achieve an optimal balance between these two areas of life.
23
Park, Ji-Yeon, e Yong-Jin Yoon. "Lifeworld conflicts and relation rebirth of couple dancing sport participants". Journal of Exercise Rehabilitation 9, n. 2 (25 aprile 2013): 304–8. http://dx.doi.org/10.12965/jer.130015.
24
Hamdi, Jana, Kamel Abed-Meraïm, Hassan Assoum, Anas Sakout, Marwan Al-Kheir, Tarek Mrach, Laurent Rambault, Sebastien Cauet e Eric Etien. "Tomographic and Time-Resolved PIV measurement of an Impinging Jet on a Slotted Plate". MATEC Web of Conferences 261 (2019): 03004. http://dx.doi.org/10.1051/matecconf/201926103004.
Abstract (sommario):
In order to reveal the complete topology of unsteady coherent flow structures the instantaneous measurement of the 3D velocity field is being of the great interest in fluid mechanic. Several different methods were proposed to achieve a 3D version of the technique (scanning light sheet, holography, 3D PTV). We aimed in our study to develop a 3D technique than enables to obtain the 3D kinematic field of an impinging jet by using 2D measurements. In this study and in order to validate the proposed technique [1], the tomographic particle image velocimetry technique has been applied to time resolved PIV recordings. The first step before the validation was to study the vortex shedding phenomena between the jet exit and the slotted plate. The experiments were performed at a Re = 4458 with an initial velocity U0=7m/s using three cameras Phantom V711 and a Nd: YLF LDY 300 Litron laser. In the present study, we analyzed the coherent structures organization by a 3D-velocity visualization. Both mean and fluctuating part of velocity were analyzed for several positions in z. The results has shown that a couple of vortex rolls are created downstream the flow at y/H=2.
25
Morganti, Raffaella, Tom Oosterloo, Robert Schulz, Clive Tadhunter e J. B. Raymond Oonk. "Young radio jets breaking free: molecular and HI outflows in their centers". Proceedings of the International Astronomical Union 14, S342 (maggio 2018): 85–89. http://dx.doi.org/10.1017/s1743921318003836.
Abstract (sommario):
AbstractOur view of the central regions of AGN has been enriched by the discovery of fast and massive outflows of H I and molecular gas. Here we present a brief summary of results obtained for young (and restarted) radio AGN. We find that H I outflows tend to be particularly common in this group of objects. This supports the idea that the jet, expanding in a clumpy medium, plays a major role in driving these outflows. The clumpiness of the medium is confirmed by VLBI and ALMA observations. The H I observations reveal that, at least part of the gas, is distributed in clouds with sizes up to a few tens of pc and mass ~104Mȯ. A change of the conditions in the outflow, with an increasing fraction of diffuse components, as the radio jets grow, is suggested by the high resolution H I observations. The molecular gas completes the picture, showing that the radio plasma jet can couple well with the ISM, strongly affecting the kinematics, but also the physical conditions of the molecular gas. This is confirmed by numerical simulations reproducing, to first order, the kinematics of the gas.
26
Singh, Tej Pratap, Amitesh Kumar e Ashok Kumar Satapathy. "Enhancement of heat transfer using turbulent wall jet". Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering 234, n. 1 (3 dicembre 2019): 123–36. http://dx.doi.org/10.1177/0954408919891391.
Abstract (sommario):
Enhancement of heat transfer is very important in many engineering applications. The present study explores one of such possibilities by increasing the surface area of a plane wall. The effect of wavy wall on thermal and flow characteristics of a turbulent wall jet is studied in detail. The amplitude of the wavy surface is varied between 0.1 and 0.7 with an interval of 0.1. The Reynolds number is set to 15,000. The Reynolds averaged Navier Stokes equations are solved using the finite volume approach. The semi-implicit pressure linked equation algorithm is used to couple the pressure and velocity. A new scale, other than the traditional outer scaling, is defined for carrying out the self-similar behavior of the flow. Unlike the plane wall case, the self-similar characteristic is obtained at the respective crests and the troughs. However, it is also noticed that the two characteristics differ significantly with each other. Even, these characteristics are found to differ with each other for different amplitudes. The minimum pressure near the nozzle decreases as the amplitude increases and it is noted to be equal to −0.541 for the highest amplitude, i.e. A = 0.7. It is observed that the strength of convection near the exit of the jet is very high, and it decreases in the downstream direction. This increase in convection augments heat transfer by almost 10% as compared to the plane wall case. Based on the results, a quartic curve is fit for the average Nusselt number with a 99.75% goodness of fit. It is expected that the present study opens a new line in designing a proper cooling system.
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Reddy, Y. Rameswara. "Response Optimization of Machining Parameters using MCDA-Vikor Method for Acrylic Glass with AHAJM". International Journal for Research in Applied Science and Engineering Technology 11, n. 7 (31 luglio 2023): 217–25. http://dx.doi.org/10.22214/ijraset.2023.54596.
Abstract (sommario):
Abstract: Abrasive Hot Air Jet Machining (AHJM) is becoming one of the most prominent machining techniques forPolymethyl Methacrylate (PMMA) and other brittle materials. In this attempt has been made to combine abrasive and hot air to form an abrasive hot air jet. Abrasive hot air jet machining can be connected to different tasks, for example, boring, surface scratching, scoring and small scale completing on the glass and its composites. The impact of air temperature onthe material expulsion rate connected to the procedure of glass carving and scoring is talked about in this article. The unpleasantness of the machined surface is additionally investigated. It is discovered that the material removal rate (MRR) increments as the temperature of transporter media (air) is expanded. In the present work to be attempt to investigate machining characteristics of PMMA material on hot air abrasive jet machining. In hot air abrasive jet machining(HAJM) abrasive particles stay on abrasive particle stay molten by compacted air in a closed chamber and are intensive over the objective surface over a nozzle the stream of particles coming out of the nozzle through very high velocity’s (175-300m/s) impacts the objective surface and eliminates the material by destruction. The investigation has to be carried on to study the effect of process parameters as material removal rate(MRR) as surface roughness(SR) with different input parameters like Air Pressure, , Size Of Abrasives , Stand-Off Distance ,Temperature Of Carrier Gas. In this experimental process Tungstencarbide coated nozzles were to be used flow of silicon carbide(sic) particles will be used.The Poly(methyl methacrylate) (PMMA), furthermore saw as acrylic glass, acrylic material, or plexiglass as suitably as by using the change names Plexiglas, Crylux, Lucite, Acrylate. PMMA it is an unquestionable thermoplastic .the creation formula of PMMA is (C5O2H8)n it has incredible properties to, for instance, lightweight, 92% Transparent observable light effect inside 3mm of thick material, extraordinary solidarity to consider another polystyrene. it's for the most part important in these zones, for instance, Because of its direct properties, lightweight and preferable quality took a gander at over glass, It was broadly usedto make aircraft windshields, shades and weapon turrets. After this couple of different business applications were made for PMMA, for instance, glass material, façade arrangement, publicizing, vehicle headlamps, etc.,
28
Watanabe, M., Z. Horita, David J. Smith, M. R. McCartney, T. Sano e M. Nemoto. "Study of Ni/Ni3Al diffusion-couple interface by AEM and HREM". Proceedings, annual meeting, Electron Microscopy Society of America 50, n. 1 (agosto 1992): 54–55. http://dx.doi.org/10.1017/s0424820100120679.
Abstract (sommario):
The interface between the Ni-rich solid solution phase (γ phase) and the intermetallic phase (γ'phase) with the Ll2-ordered Ni3Al structure plays an important role in the strengthening of Ni-based two-phase alloys such as superalloys. In this study, we have examined microstructure and diffusional phenomena across the ϒ/ϒ' interface by analytical electron microscopy (AEM) and high resolution electron microscopy (HREM).Fully annealed high-purity Ni (99.9%) was coupled with Ni-25mol%Al and subjected to diffusion anneal at temperatures of 1073 and 1173K. Thin specimens were prepared from these diffusion couples by careful cutting, grinding, electro-polishing and ion-milling, details of which are described elsewhere. We used three different types of electron microscopes: (a) JEM-2000FX (at 200kV) for measurements of the overall concentration gradient with a probe size of ∼20nm, microstructure observations and selected area diffraction analyses, (b) EM400T-FEG (at 100kV) for high spatial resolution micro-chemical analysis with a probe size of ∼3nm, and (c) JEM-4000EX (at 400kV) for observations of lattice images at the interface. Characteristic x-ray lines of Ni Kα, Al Kα, and Ni La were measured by energy dispersive x-ray spectrometers with a Be-type window which were attached on both JEM-2000FX and EM400T-FEG. Ni Kα and Al Kα lines were used for the determination of compositions, and Ni Kα and Ni Lα lines were for the determination of local thicknesses. X-ray absorption corrections were made by the differential x-ray absorption (DXA) method when determining concentration gradients and by the extrapolation method when determining k-factors.
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Cai, Wen Bin, Guo Wei Qin e Yan He. "Design of Sand Washing and Plug Removal Device with High Pressure Foam Fluid Jet". Applied Mechanics and Materials 155-156 (febbraio 2012): 722–25. http://dx.doi.org/10.4028/www.scientific.net/amm.155-156.722.
Abstract (sommario):
In the oil and gas production process, serious sand production causes reservoir and pipe blocked, which makes productivity declined, even stopped. It's the efficient means of sand washing and plug removal by using high-pressure foam fluid jet. The structure and performance of sand washing device determines the efficiency of sand washing and plug removal. The device's nozzle consists of anti-blocking valves, three kinds of nozzles with self-drive, rotation characteristics during the operation. The nozzles include sand washing nozzle, couple nozzle and power nozzle. This device can be used in horizontal wells with complex well bore situation to carry out sand and plug removal. The device has a good effect on sand washing and plug removal in the oil field.
30
Iceland, John. "The "family/couple/household" unit of measurement in poverty estimation". Journal of Economic and Social Measurement 26, n. 3-4 (1 ottobre 2000): 253–65. http://dx.doi.org/10.3233/jem-2000-0189.
31
Sekiya, Hiroshi, Taiji Nakajima, Hidenori Hamabe, Akira Mori, Hitoshi Takeshita e Yukio Nishimura. "Proton Tunneling In 5-Chlorotropolone-M1 (M = Kr, Xe, CH4) Van Der Waals Complexes". Laser Chemistry 15, n. 2-4 (1 gennaio 1995): 229–47. http://dx.doi.org/10.1155/1995/28981.
Abstract (sommario):
The S1-S0 fluorescence excitation spectra of 5-chlorotropolone-M1 (M = Kr, Xe, CH4) van der Waals (vdW) complexes in the region near the electronic origin have been measured in a supersonic free jet to investigate the effect of the vdW interactions on proton tunneling. Tunneling splittings have been observed in the vdW vibrations as well as in the 000 transitions of the Kr and Xe complexes. The 000 tunneling splitting of the 5-chlorotropolone-(CH4)1 complex is significantly smaller than those of the Kr and Xe complexes. It has been suggested that the vdW vibrations couple with intramolecular motions, leading to a higher potential energy barrier to tunneling in the CH4 complex. The results of the 5- chlorotropolone complexes have been compared to those of the tropolone complexes.
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Kim, Kyoung Jin. "Development of Waxless Wafer Mounting System for Silicon Wafer Polishing Process". Applied Mechanics and Materials 339 (luglio 2013): 762–65. http://dx.doi.org/10.4028/www.scientific.net/amm.339.762.
Abstract (sommario):
In the silicon wafer polishing process, the mounting of wafer on the polishing head could be greatly influential in final quality of finished wafers. This paper focuses on the waxless wafer mounting technique which could replace the traditional wax wafer mounting. Mounting of wafers on the carrier block using a wetted porous template provides a simple way of securing wafer on polishing head for precision wafer polishing. Demounting of wafers from the porous pad is carried out by using the water jet impingement which takes only a couple of seconds for wafer demounting. A series of wafer polishing tests of 8 inch silicon wafers using the present wafer mounting system found that the developed waxless wafer mounting could be quite suitable for producing the wafers of the excellent surface qualities by meeting industry standard such as SBIR, LLS, and production yield.
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Kodaira, Felipe Vicente de Paula, Ana Carla de Paula Leite Almeida, Thayna Fernandes Tavares, Antje Quade, Luis Rogério de Oliveira Hein e Konstantin Georgiev Kostov. "Study of a Conical Plasma Jet with a Cloth-Covered Nozzle for Polymer Treatment". Polymers 15, n. 16 (9 agosto 2023): 3344. http://dx.doi.org/10.3390/polym15163344.
Abstract (sommario):
Although atmospheric pressure plasma jets (APPJs) have been widely employed for materials modification, they have some drawbacks, such as the small treatment area (couple of cm2). To overcome this limitation, a funnel-like APPJ with a wide exit has been proposed. In this work, a gas-permeable cotton cloth covered the nozzle of the device to improve the gas flow dynamics and increase its range of operation. The funnel jet was flushed with Ar, and the plasma was ignited in a wide range of gas flow rates and the gap distances between the exit nozzle and the sample holder. The device characterization included electric measurements and optical emission spectroscopy (OES). To evaluate the size of the treatment and the degree of surface modification, large samples of high-density polyethylene (PE) were exposed to plasma for 5 min. Afterward, the samples were analyzed via water contact angle WCA measurements, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). It was found that surface modification occurs simultaneously on the top and bottom faces of the samples. However, the treatment incorporated different functional groups on each side.
34
Stump, David A. "Twenty Years Trying to Protect the Brain: What Do We Know?" Journal of ExtraCorporeal Technology 39, n. 4 (dicembre 2007): 302–4. http://dx.doi.org/10.1051/ject/200739302.
Abstract (sommario):
Thirty-five years ago at the Nixon Watergate hearings, a young attorney named Fred Thompson, current US presidential candidate, asked “What did the President know and when did he know it?” A couple of word changes and this question would be appropriate to ask any number of surgical specialties regarding negative neurologic outcomes. Even today, some specialties are in denial about impaired brain function after surgical intervention. Fortunately, the cardiac surgery community has been in the forefront in efforts to protect the brain.
35
Tafoya, D., G. Orosz, W. H. T. Vlemmings, R. Sahai e A. F. Pérez-Sánchez. "Spatio-kinematical model of the collimated molecular outflow in the water-fountain nebula IRAS 16342–3814". Astronomy & Astrophysics 629 (22 agosto 2019): A8. http://dx.doi.org/10.1051/0004-6361/201834632.
Abstract (sommario):
Context. Water-fountain nebulae are asymptotic giant branch (AGB) and post-AGB objects that exhibit high-velocity outflows traced by water-maser emission. Their study is important for understanding the interaction between collimated jets and the circumstellar material that leads to the formation of bipolar and/or multi-polar morphologies in evolved stars. Aims. The aim of this paper is to describe the three-dimensional morphology and kinematics of the molecular gas of the water-fountain nebula IRAS 16342−3814. Methods. Data was retrieved from the ALMA archive for analysis using a simple spatio-kinematical model. The software SHAPE was employed to construct a three-dimensional, spatio-kinematical model of the molecular gas in IRAS 16342−3814, and to then reproduce the intensity distribution and position-velocity diagram of the CO emission from the ALMA observations to derive the morphology and velocity field of the gas. Data from CO(J = 1 → 0) supported the physical interpretation of the model. Results. A spatio-kinematical model that includes a high-velocity collimated outflow embedded within material expanding at relatively lower velocity reproduces the images and position-velocity diagrams from the observations. The derived morphology is in good agreement with previous results from IR and water-maser emission observations. The high-velocity collimated outflow exhibits deceleration across its length, while the velocity of the surrounding component increases with distance. The morphology of the emitting region, the velocity field, and the mass of the gas as function of velocity are in excellent agreement with the properties predicted for a molecular outflow driven by a jet. The timescale of the molecular outflow is estimated to be ~70–100 yr. The scalar momentum carried by the outflow is much larger than it can be provided by the radiation of the central star. An oscillating pattern was found associated with the high-velocity collimated outflow. The oscillation period of the pattern is T ≈ 60–90 yr and its opening angle is θop ≈ 2°. Conclusions. The CO (J = 3 → 2) emission in IRAS 16342−3814 is interpreted in terms of a jet-driven molecular outflow expanding along an elongated region. The position-velocity diagram and the mass spectrum reveal a feature due to entrained material that is associated with the driving jet. This feature is not seen in other more evolved objects that exhibit more developed bipolar morphologies. It is likely that the jet in those objects has already disappeared since it is expected to last only for a couple hundred years. This strengthens the idea that water fountain nebulae are undergoing a very short transition during which they develop the collimated outflows that shape the circumstellar envelopes. The oscillating pattern seen in the CO high-velocity outflow is interpreted as due to precession with a relatively small opening angle. The precession period is compatible with the period of the corkscrew pattern seen at IR wavelengths. We propose that the high-velocity molecular outflow traces the underlying primary jet that produces such a pattern.
36
Orr, Andrew, Thomas J. Bracegirdle, J. Scott Hosking, Thomas Jung, Joanna D. Haigh, Tony Phillips e Wuhu Feng. "Possible Dynamical Mechanisms for Southern Hemisphere Climate Change due to the Ozone Hole". Journal of the Atmospheric Sciences 69, n. 10 (10 maggio 2012): 2917–32. http://dx.doi.org/10.1175/jas-d-11-0210.1.
Abstract (sommario):
Abstract The authors report a hypothesis for the dynamical mechanisms responsible for the strengthening of the Southern Hemisphere circumpolar winds from the lower stratosphere to the surface due to the ozone hole. A general circulation model forced by stratospheric ozone depletion representative of the ozone hole period successfully reproduced these observed changes. Investigation of the dynamical characteristics of the model therefore provides some insight into the actual mechanisms. From this the authors suggest the following: 1) An initial (radiative) strengthening of the lower-stratospheric winds as a result of ozone depletion conditions the polar vortex so that fewer planetary waves propagate up from the troposphere, resulting in weaker planetary wave driving. 2) This causes further strengthening of the vortex, which results in an additional reduction in upward-propagating planetary waves and initiates a positive feedback mechanism in which the weaker wave driving and the associated strengthened winds are drawn downward to the tropopause. 3) In the troposphere the midlatitude jet shifts poleward in association with increases in the synoptic wave fluxes of heat and momentum, which are the result of a positive feedback mechanism consisting of two components: 4) increases in low-level baroclinicity, and the subsequent generation of baroclinic activity (associated with a poleward heat flux), are collocated with the jet latitudinal position, and 5) strengthening anticyclonic shear increases the refraction of wave activity equatorward (associated with a poleward momentum flux). Finally, 6) confinement of planetary waves in the high-latitude troposphere is an important step to couple the stratospheric changes to the tropospheric response.
37
Omidi, Mahmoud, Ali Ghafarian-Bahraman e Afshin Mohammadi-Bardbori. "GSH/GSSG redox couple plays central role in aryl hydrocarbon receptor-dependent modulation of cytochrome P450 1A1". Journal of Biochemical and Molecular Toxicology 32, n. 7 (luglio 2018): e22164. http://dx.doi.org/10.1002/jbt.22164.
38
Abhishek J., Parekh. "Research on Aerofoil Shape to Increase the Effectiveness of Aeroplanes". International Journal for Research in Applied Science and Engineering Technology 9, n. 9 (30 settembre 2021): 2165–69. http://dx.doi.org/10.22214/ijraset.2021.38267.
Abstract (sommario):
Abstract: In the modern era where emphasis on air travels is increasing day by day. There is no near alternative of jet fuel. In such situation where fossil fuel use becomes bounded than, we should try to increase efficiency from available resources so as to push world towards sustainable development. Efficiency of aeroplanes greatly depends on couple of major factors like load carried, type of fuel used, power of engine installed, etc. But if we take similar aircrafts with similar loads than one criterion plays pivotal role in efficiency of aircrafts and that is shape of aerofoil wings. Angle of attack also depends on this. Optimum shape of aerofoil has always been topic of research for engineers. In present paper, an aerofoil shape with bottom surface backlash is analysed in ABAQUS software. Different modes of failure help in better designing as well as maximum bearable load by aerofoil shape. Keyword: 1. Aeronautical engineering, 2. Fluid Mechanics, 3. Analysis on ABAQUS, 4. Computational fluid dynamics.
39
Bourne, Martin A. "Simulation of AGN feedback and its impact on galaxies". Proceedings of the International Astronomical Union 12, S324 (settembre 2016): 231–34. http://dx.doi.org/10.1017/s1743921317001508.
Abstract (sommario):
AbstractFeedback released during the growth of supermassive black holes is expected to play a key role in shaping black hole-host galaxy co-evolution. Powerful, accretion disc driven winds have been invoked to explain both observed scaling relations (e.g., M − σ) and large-scale outflows with mass outflow rates of ~ 100 − 1000 M⊙ yr−1 and momentum rates of up to ~ 30 LAGN/c. Critically, how these winds couple to the host galaxy depends on if they are momentum or energy conserving. I outline observational signatures that could distinguish between these regimes and discuss their roles in establishing galaxy properties. Furthermore, I discuss high-resolution simulations exploring feedback in a multi-phase medium, highlighting how structural properties of galaxies can impact feedback efficiency. Finally, feedback, in the form of collimated jets, is expected to regulate cooling in galaxy clusters. I discuss new simulations of jet feedback using the moving-mesh code AREPO and outline the scope of our new study.
40
Bhatta, Gopal. "Study of Periodic Signals from Blazars". Proceedings 17, n. 1 (10 dicembre 2019): 15. http://dx.doi.org/10.3390/proceedings2019017015.
Abstract (sommario):
The search for periodic signals from blazars has become an actively pursued field of research in recent years. This is because periodic signals bring us information about the processes occurring near the innermost regions of blazars, which are mostly inaccessible to our direct view. Such signals provide insights into some of the extreme conditions that take place in the vicinity of supermassive black holes that lead to the launch of the relativistic jets. In addition, studies of characteristic timescales in blazar light curves shed light on some of the challenging issues in blazar physics that include disk-jet connection, strong gravity near fast-rotating supermassive black holes and release of gravitational waves from binary supermassive black hole systems. However, a number of issues associated with the search for quasi-periodic oscillations (QPOs) in blazars e.g., red-noise dominance, modest significance of the detection, periodic modulation lasting for only a couple of cycles and their transient nature, make it difficult to estimate the true significance of the detection. Consequently, it also becomes difficult to make meaningful inferences about the nature of the on-going processes. In this proceedings, results of study focused on searching for QPOs in a number of blazar multi-frequency light curves are summarized. The time series analyses of long term observations of the blazars revealed the presence of year-timescale QPOs in the sources including OJ 287 (optical), Mrk 501 (gamma-ray), J1043+2408 (radio) and PKS 0219-164 (radio). A likely explanations, we discuss a number of scenarios including binary supermassive black hole systems, lense-thirring precession, and jet precession.
41
Nguyen, Anh-Tu. "A numerical research on the interaction between underwater explosion bubble and deformable structure using CEL technique". EUREKA: Physics and Engineering, n. 1 (19 gennaio 2023): 134–51. http://dx.doi.org/10.21303/2461-4262.2023.002637.
Abstract (sommario):
The dynamic process of an underwater explosion (UNDEX) bubble in the vicinity of deformable structures is a complex phenomenon that has been studied by many researchers. The dynamic process of a UNDEX bubble is a complex transient problem that results in a highly distorted bubble and large deformation of the structure. The previous work has introduced various solutions for studying the interaction between the UNDEX bubble and deformable structure. The interaction between the bubble and nearby structures has been widely solved by the combination of the boundary element method (BEM) and the finite element method (FEM). However, this couple requires tight time-step controlling, long-time analysis, and large computer resources. Furthermore, this combination is not widely used as the FEM code in commercially available software for solving UNDEX bubble problems. This paper presents a coupled Eulerian-Lagrangian (CEL) approach in commercial software to deal with the fluid-structure interaction (FSI). The numerical model of a UNDEX bubble is first developed and verified by comparing results with experimental, BEM, and empirical data. Then both bubble behavior and structural deformation are examined in various case studies. The numerical results show that the stiffness of the structure has strongly influenced the bubble behavior and the water jet development. The pressure pulse becomes significantly large as the bubble collapse. Besides, this numerical approach also can reproduce crucial phenomena of a UNDEX bubble, such as the whipping effect and water jet attacks. Although the numerical model is developed using simplified boundary conditions, the proposed approach shows the feasibility of simulating the important features of a UNDEX bubble process as well as the response of nearby structures.
42
Wang, Ji, e Wenwu Zhang. "High Repetition Frequency Solid-State Green Laser with Large Stable Area for Water Jet Guided". Micromachines 14, n. 12 (12 dicembre 2023): 2231. http://dx.doi.org/10.3390/mi14122231.
Abstract (sommario):
This paper presents the design and experimental results of a long cavity length Nd:YAG laser with a large stable zone for water jet-guided laser (WJGL) applications. The design is based on the light transmission matrix and resonator stability conditions, aiming to achieve a large stable zone and a short cut-off thermal focal length (CTFL). A folded concave resonator is researched to enhance the cavity length, and the influence of the tunable cavity arm length on the oscillating beam in the resonator and in the YAG crystal is theoretically studied. Moreover, the effects of the output mirror curvature and the cavity arm length on the range of the stable area and the cut-off thermal focal length are also investigated. Experimental results show that a stable green laser output is obtained after second harmonic generation (SHG) with a pulse width ranging from 43 to 143 ns within the laser operating frequency range of 5–20 kHz. At an operation frequency of 10 kHz, the output power is 21.33 W, and the instability of the output power within 400 min is 0.88%. The laser source achieves a maximum power of 25.7 W at 20 kHz, and the maximum single pulse energy reaches 2.7 mJ at 6 kHz. Finally, this is used as the laser source to couple with a water jet with a diameter of 100 microns, achieving a lossless water conductivity transmission over 60 mm length. These results demonstrate the suitability of the designed laser source for WJGL technology research. In precision machining applications, this technology exhibits processing advantages of low thermal damage (~2 μm) and large depth (>10 mm), for 7075 aluminum alloy.
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Bhattacharya, Sudipto. "Corporate Finance and the Legacy of Miller and Modigliani". Journal of Economic Perspectives 2, n. 4 (1 novembre 1988): 135–47. http://dx.doi.org/10.1257/jep.2.4.135.
Abstract (sommario):
[This is a comment on “The Modigliani-Miller Propositions after Thirty Years” by Merton H. Miller in this same issue.] The influence of the Modigliani-Miller (1958) propositions on capital structure and the Miller-Modigliani (1961) theses on dividend policy permeates almost all aspects of financial economics to this day. In this commentary, I shall focus on the influence of Miller's and Modigliani's contributions on a couple of key areas in corporation finance, and review research progress by later contributors. Broadly speaking, these two themes can be summarized as: (A) integrated tax- and information-related considerations in capital structure and dividend policy choices; and (B) the impact of inflation and nominally denominated debt contracts on the valuation of corporate equity.
44
Liang, Zhaoming, Robert G. Fovell e Ying Liu. "Observational Analysis of the Characteristics of the Synoptic Situation and Evolution of the Organized Warm-Sector Rainfall in the Coastal Region of South China in the Pre-Summer Rainy Season". Atmosphere 10, n. 11 (18 novembre 2019): 722. http://dx.doi.org/10.3390/atmos10110722.
Abstract (sommario):
The characteristics of the synoptic situation and the evolution of the organized warm-sector rainfalls (OWSRs) in the coastal region of South China in the pre-summer rainy season were investigated, using a period (2011–2016) of high-resolution observational data and European Centre for Medium-Range Weather Forecasts Re-Analysis Interim (ERA-Interim) data. The results show that a strong southwesterly low-level jet (LLJ) ahead of a trough over southwestern China with a marked boundary-layer jet (BLJ) over the northern South China Sea (synoptic situation SWLLJ) or a prominent, low-level anticyclone over the Yangtze River Basin (synoptic situation ACR) is present when the OWSRs occur in the coastal region of South China. The OWSRs are prone to initiate on the windward side of the coastal mountains, owing to the convergence enhanced by the colliding of the BLJ with the mountains and the coupling of double LLJs near the coast (for SWLLJ), or due to the convergence between northerly and southeasterly winds near the coastal mountains (for ACR). The OWSRs present a long extension when the LLJ axis is nearby. The translation of the LLJ itself also promotes the long extension of the OWSRs. In contrast, the OWSRs show a short extension when the LLJ axis is farther away or ACR occurs. Meanwhile, the OWSRs are directed northeastward in Guangxi Province and more eastward in Guangdong Province, probably owing to the orientation difference of the LLJ in these two provinces. The rainfall systems in the ACR situation tend to move eastward, whereas those in the SWLLJ situation are prone to move eastward when equivalently strong or much-stronger upper-level winds overlay the LLJ, but move northeastward when much weaker upper-level winds couple with the LLJ.
45
Munk, Martin D., Till Nikolka e Panu Poutvaara. "International family migration and the dual-earner model". Journal of Economic Geography 22, n. 2 (27 gennaio 2022): 263–87. http://dx.doi.org/10.1093/jeg/lbab050.
Abstract (sommario):
Abstract We analyze couples’ joint decisions about emigration and labor force participation using survey data on Danish emigrants, combined with full population administrative data. Couples are most likely to emigrate if the male partner or both partners hold a college degree and least likely to emigrate if neither of the partners is college educated. Probability that a dual-earner couple emigrates increases with the primary earner’s income. In most couples, both partners work before emigration, while after migrating outside the Nordic countries almost half of the women stay at home. Survey responses reveal that men mainly migrate for work reasons and women for family reasons. Our findings suggest that the dual-earner model may not be strongly ingrained among emigrating couples. Instead, female labor force participation abroad varies widely between different destinations.
46
Teeter, Ryan A., Michael G. Alles e Miklos A. Vasarhelyi. "The Remote Audit". Journal of Emerging Technologies in Accounting 7, n. 1 (1 gennaio 2010): 73–88. http://dx.doi.org/10.2308/jeta.2010.7.1.73.
Abstract (sommario):
ABSTRACT: Audit practitioners have been progressively adopting communications and analytic technology to extend the scope, change the timing, and reduce the costs of audit processes. These efforts have been mainly ad hoc, lacking an integrative theoretical positioning. This paper redefines the concept of the “remote audit” as the process by which internal auditors couple information and communication technology (ICT) with analytical procedures to gather electronic evidence, interact with the auditee, and report on the accuracy of financial data and internal controls, independent of the physical location of the auditor. Building on research on virtual teams and an analysis of internal audit activities, we present a research framework identifying areas where ICT and automated audit analytics enable auditors to work remotely, reduce travel costs and latency, and increase efficiency and coverage.
47
Harada, Yohsuke, Yasuyo Harada, Chris Elly, Ge Ying, Ji-Hye Paik, Ronald A. DePinho e Yun-Cai Liu. "Transcription factors Foxo3a and Foxo1 couple the E3 ligase Cbl-b to the induction of Foxp3 expression in induced regulatory T cells". Journal of Experimental Medicine 207, n. 7 (3 maggio 2010): 1381–91. http://dx.doi.org/10.1084/jem.20100004.
Abstract (sommario):
The transcription factor Foxp3 is essential for optimal regulatory T (T reg) cell development and function. Here, we show that CD4+ T cells from Cbl-b RING finger mutant knockin or Cbl-b–deficient mice show impaired TGF-β–induced Foxp3 expression. These T cells display augmented Foxo3a phosphorylation, but normal TGF-β signaling. Expression of Foxo3a rescues Foxp3 expression in Cbl-b–deficient T cells, and Foxo3a deficiency results in defective TGF-β–driven Foxp3 induction. A Foxo3a-binding motif is present in a proximal region of the Foxp3 promoter, and is required for Foxo3a association. Foxo1 exerts similar effects as Foxo3a on Foxp3 expression. This study reveals that Foxo factors promote transcription of the Foxp3 gene in induced T reg cells, and thus provides new mechanistic insight into Foxo-mediated T cell regulation.
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Kucera, Vojtech, Zuzana Zofkova, Christopher DiGiovanni, Liu He e Dalibor Vojtěch. "Investigation of Liquid Metal Embrittlement during Resistance Spot Welding of Martensitic Steel with Zn Jet Vapor-Deposited Coating". Metals 11, n. 11 (11 novembre 2021): 1813. http://dx.doi.org/10.3390/met11111813.
Abstract (sommario):
Advanced high-strength steels protected by zinc coatings have contributed to a reduction in CO2 emissions in the automotive industry. However, the liquid metal embrittlement (LME) of the Fe/Zn couple induced by simultaneously acting stresses and high temperatures during resistance spot welding could be the cause of unexpected failure. We investigated the possible risk of LME in spot-welded martensitic steel with Zn jet vapor-deposited coating and its influence on weld strength. The weld nugget cross-sections were analyzed (optical microscopy, SEM-EDS), and their tensile shear strengths were compared with their uncoated counterparts. LME cracks were observed in all samples meeting the process window (6, 6.5, 7 kA) located at the edge of the sheet/electrode indentation area. The frequency and length of cracks increased with current, and the occurrence of Zn within cracks indicated the LME mechanism. The shear tests showed the Zn-coated sample underwent a decrease in tensile shear strength that was most evident at a welding current of 7 kA (13.2%). However, LME was excluded as a cause of lower strength. The decrease was attributed to the smaller nugget diameter and the thin slit of Zn coating remaining in the weld notch.
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Jo, Eun-Kyeong, Hongyan Wang e Christopher E. Rudd. "An essential role for SKAP-55 in LFA-1 clustering on T cells that cannot be substituted by SKAP-55R". Journal of Experimental Medicine 201, n. 11 (6 giugno 2005): 1733–39. http://dx.doi.org/10.1084/jem.20042577.
Abstract (sommario):
Lymphocyte function-associated antigen (LFA)-1 clustering, which is needed for high avidity binding to intercellular adhesion molecule (ICAM)-1 and -2, regulates T cell motility and T cell–antigen-presenting cell (APC) conjugation. In this study, down-regulation of SKAP-55 by small interfering RNAs (siRNAs) identified an essential role for this adaptor molecule in the T cell receptor (TCR)–mediated ”inside-out signaling” that is needed for LFA-1 clustering and T cell–APC conjugation. In contrast, down-regulation of SKAP-55 had no effect on TCR–CD3 clustering. Furthermore, the expression of the related protein SKAP-55R failed to compensate for the loss of SKAP-55 in LFA-1 clustering, indicating that SKAP-55 has a unique function that cannot be replaced by this closely related protein. Our findings therefore indicate that SKAP-55, unlike SKAP-55R, is specifically tailored as an essential component of the inside-out signaling events that couple the TCR to LFA-1 clustering and T cell–APC conjugation.
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Robinson, Matthew J., Fabiola Osorio, Marcela Rosas, Rui P. Freitas, Edina Schweighoffer, Olaf Groß, J. Sjef Verbeek et al. "Dectin-2 is a Syk-coupled pattern recognition receptor crucial for Th17 responses to fungal infection". Journal of Experimental Medicine 206, n. 9 (24 agosto 2009): 2037–51. http://dx.doi.org/10.1084/jem.20082818.
Abstract (sommario):
Innate immune cells detect pathogens via pattern recognition receptors (PRRs), which signal for initiation of immune responses to infection. Studies with Dectin-1, a PRR for fungi, have defined a novel innate signaling pathway involving Syk kinase and the adaptor CARD9, which is critical for inducing Th17 responses to fungal infection. We show that another C-type lectin, Dectin-2, also signals via Syk and CARD9, and contributes to dendritic cell (DC) activation by fungal particles. Unlike Dectin-1, Dectin-2 couples to Syk indirectly, through association with the FcRγ chain. In a model of Candida albicans infection, blockade of Dectin-2 did not affect innate immune resistance but abrogated Candida-specific T cell production of IL-17 and, in combination with the absence of Dectin-1, decreased Th1 responses to the organism. Thus, Dectin-2 constitutes a major fungal PRR that can couple to the Syk–CARD9 innate signaling pathway to activate DCs and regulate adaptive immune responses to fungal infection.