The density profile of a fluid bounded by a soft wall

Numerical calculations of spiral shocks in the gas discs of galaxies (1,2,3) usually assume that the disc is flat, i.e. the gas motion is purely horizontal. However there is abundant evidence that the discs of galaxies are warped and corrugated (4,5,6) and it is therefore of interest to consider the effect of the consequent vertical motion on the structure of spiral shocks. If one uses the tightly wound spiral approximation to calculate the gas flow in a vertical cut around a circular orbit (i.e the ⊝ -z plane, see Nelson & Matsuda (7) for details), then for a gas disc with Gaussian density profile in the z-direction and initially zero vertical velocity a doubly periodic spiral potential modulation produces the steady shock structure shown in Fig. 1. The shock structure is independent of z, and only a very small vertical motion appears with anti-symmetry about the mid-plane.

Download Full-text

Critical exponents of finite temperature chiral phase transition in soft-wall AdS/QCD models

Journal of High Energy Physics ◽

10.1007/jhep01(2019)165 ◽

2019 ◽

Vol 2019 (1) ◽

Cited By ~ 8

Author(s):

Jianwei Chen ◽

Song He ◽

Mei Huang ◽

Danning Li

Keyword(s):

Phase Transition ◽

Critical Exponents ◽

Finite Temperature ◽

Chiral Phase ◽

Chiral Phase Transition ◽

Soft Wall

Download Full-text

A reconfigurable soft wall-climbing robot actuated by electromagnet

International Journal of Advanced Robotic Systems ◽

10.1177/1729881421992285 ◽

2021 ◽

Vol 18 (2) ◽

pp. 172988142199228

Author(s):

Wendong Zhang ◽

Wen Zhang ◽

Zhenguo Sun

Keyword(s):

Working Conditions ◽

Horizontal Plane ◽

Vertical Wall ◽

Flaw Detection ◽

Surface Cleaning ◽

Electromagnetic Actuator ◽

Climbing Robot ◽

Soft Wall ◽

Power Frequency

This article demonstrates a reconfigurable soft wall-climbing robot actuated by electromagnet. The robot follows the earthworm movement gait and is capable of translation, deflection, and rotation movement while working on a sloping ferromagnetic wall. Also the electromagnetic actuator provides a significant improvement in expeditiousness compared with existing actuation modes. The speed of the robot can be adjusted by modulating the power frequency. When the period of motion cycle is 30 ms, the speed is about 26.5 mm s−1, and the robot can rotate with a velocity of 14.1° s−1 on the horizontal plane. It can also climb a vertical wall at the speed of 12.6 mm s−1. The robot is composed of two kinds of modules which can be connected by the magnets embedded. It can also be reconfigured in different working conditions, such as crossing an inaccessible gap, and thus has the potential to be used in flaw detection, surface cleaning, and exploration of ferromagnetic structures.

Download Full-text

Radial density profile and stability of capillary discharge plasma waveguides of lengths up to 40 cm

High Power Laser Science and Engineering ◽

10.1017/hpl.2021.6 ◽

2021 ◽

Vol 9 ◽

Author(s):

M. Turner ◽

A. J. Gonsalves ◽

S. S. Bulanov ◽

C. Benedetti ◽

N. A. Bobrova ◽

...

Keyword(s):

Laser Pulse ◽

Electron Density ◽

Density Profile ◽

Pulse Propagation ◽

Spot Size ◽

Capillary Discharge ◽

Electron Density Profile ◽

Plasma Waveguide ◽

Wakefield Acceleration ◽

Plasma Wakefield

Abstract We measured the parameter reproducibility and radial electron density profile of capillary discharge waveguides with diameters of 650 $\mathrm{\mu} \mathrm{m}$ to 2 mm and lengths of 9 to 40 cm. To the best of the authors’ knowledge, 40 cm is the longest discharge capillary plasma waveguide to date. This length is important for $\ge$ 10 GeV electron energy gain in a single laser-driven plasma wakefield acceleration stage. Evaluation of waveguide parameter variations showed that their focusing strength was stable and reproducible to $<0.2$ % and their average on-axis plasma electron density to $<1$ %. These variations explain only a small fraction of laser-driven plasma wakefield acceleration electron bunch variations observed in experiments to date. Measurements of laser pulse centroid oscillations revealed that the radial channel profile rises faster than parabolic and is in excellent agreement with magnetohydrodynamic simulation results. We show that the effects of non-parabolic contributions on Gaussian pulse propagation were negligible when the pulse was approximately matched to the channel. However, they affected pulse propagation for a non-matched configuration in which the waveguide was used as a plasma telescope to change the focused laser pulse spot size.

Download Full-text