scholarly journals Radiation Resistance of a Helical Antenna in a Compressible Electron Plasma

1978 ◽  
Vol 31 (1) ◽  
pp. 71
Author(s):  
KR Soni
Keyword(s):  
Radiation Resistance ◽  
Pitch Angle ◽  
Electron Plasma ◽  
Travelling Wave ◽  
Helical Antenna ◽  
Radiation Fields ◽  
Integral Number ◽  
Circular Arcs ◽  
Small Pitch ◽  
Special Cases

Earlier work on the radiation fields of a travelling-wave helical antenna in a compressible electron plasma has been extended to evolve expressions for the electromagnetic mode component R. and the electroacoustic or plasma mode component Rp of its radiation resistance. These expressions, - which are general in nature but involve complicated integrals, cover the special cases of multiturn loops, circular arcs and linear antennas. Analytical expressions for R. are then derived for the particular example of a helical antenna of small pitch angle with a fractional or integral number of turns. It is found that R. increases with pitch angle for some values of plasma frequency.

Short helical antenna with extremely small pitch angle

2006 ◽  
Vol 49 (1) ◽  
pp. 17-19
Author(s):  
Ze-Hai Wu ◽  
Edward K. N. Yung
Keyword(s):  
Pitch Angle ◽  
Helical Antenna ◽  
Small Pitch

Axial-mode elliptical helical antenna with variable pitch angle

2008 ◽  
Vol 44 (19) ◽  
pp. 1103 ◽  
Author(s):  
F. Yang ◽  
P. Zhang ◽  
C.-J. Guo ◽  
J.-D. Xu
Keyword(s):  
Pitch Angle ◽  
Helical Antenna ◽  
Axial Mode ◽  
Variable Pitch

scholarly journals Improved Low-Profile Helical Antenna Design for INMARSAT Applications

2012 ◽  
Vol 2012 ◽  
pp. 1-5 ◽  
Author(s):  
Shiqiang Fu ◽  
Yuan Cao ◽  
Yue Zhou ◽  
Shaojun Fang
Keyword(s):  
Pitch Angle ◽  
Satellite Communication ◽  
Design Method ◽  
Impedance Matching ◽  
Axial Ratio ◽  
Antenna Element ◽  
Helical Antenna ◽  
Copper Strip ◽  
Antenna Structure ◽  
Low Profile

A new low-profile variable pitch angle cylindrical helical antenna employing a copper strip as impedance transformer is proposed in this paper. Under the circumstance of a limited antenna height, the circular polarization performance of the antenna has been enhanced by changing the pitch angle and the input impedance matching has been improved by adjusting the copper strip match stub. The design method of the proposed antenna is given. The optimal antenna structure for INMARSAT application has been fabricated and measured. The measured results show that in the whole maritime satellite communication work band the VSWR is less than 1.2, its antenna gain is higher than 9 dBi, and the axial ratio is lower than 2.5 dB. The experimental results have a good agreement with the simulations. The proposed antenna is compact and easy tuning. It provides a promising antenna element for maritime satellite communication applications.

Pattern generation and motion control of a vortex-like paramagnetic nanoparticle swarm

2018 ◽  
Vol 37 (8) ◽  
pp. 912-930 ◽  
Author(s):  
Jiangfan Yu ◽  
Lidong Yang ◽  
Li Zhang
Keyword(s):  
Magnetic Field ◽  
Targeted Delivery ◽  
Pitch Angle ◽  
Dynamic Equilibrium ◽  
Equilibrium Structure ◽  
Pattern Generation ◽  
Analytical Models ◽  
Generation Process ◽  
Rotating Magnetic Fields ◽  
Small Pitch

Controlling a swarm of microrobots with external fields is one of the major challenges for untethered microrobots. In this work, we present a new method to generate a vortex-like paramagnetic nanoparticle swarm (VPNS) from dispersed nanoparticles with a diameter of 500 nm, using rotating magnetic fields. The VPNS exhibits a dynamic-equilibrium structure, in which the nanoparticles perform synchronized motions. The mechanisms of the pattern-generation process are analyzed, simulated, and validated by experiments. By tuning the rotating frequency of the input magnetic field, the pattern of a VPNS changes accordingly. Analytical models for estimating the areal change of the pattern are proposed, and they have good agreement with the experimental data. Moreover, reversible merging and splitting of vortex-like swarms are demonstrated and investigated. Serving as a mobile robotic end-effector, a VPNS is capable of making locomotion by tuning the pitch angle of the actuating rotating field. With a small pitch angle, e.g. 2°, the whole swarm moves as an entity, and the shape of the pattern remains intact. In addition, the trapping forces of VPNSs are verified, showing the critical input parameters of the magnetic field that affect the morphology of the swarm. Finally, we demonstrate that VPNSs pass through curved and branched channels with high positioning precision, and the access rates for targeted delivery are over 90%, which are significantly higher than those in the cases of particle swarms moving with tumbling motions.

scholarly journals Implications of unusual pitch-angle distributions observed by ISEE-1 and 2

2006 ◽  
Vol 24 (11) ◽  
pp. 3099-3113 ◽  
Author(s):  
C. A. Zuluaga ◽  
E. S. Beiser ◽  
J. Chen ◽  
T. A. Fritz
Keyword(s):  
Charged Particle ◽  
High Latitude ◽  
Pitch Angle ◽  
Angular Resolution ◽  
Radial Distance ◽  
Local Magnetic Field ◽  
Particle Source ◽  
Small Pitch ◽  
Short Period ◽  
Geosynchronous Satellites

Abstract. Unusual energetic particle pitch angle distributions (PADs) were observed by the ISEE-1 and 2 satellites at 3 h MLT and a radial distance of about 10–15 RE during the time period of 07:00-14:00 UT on 3 March 1979. The ISEE-1 satellite obtained complete 3-D distributions of energetic proton and electron fluxes as a function of energy, while ISEE-2 was configured to provide higher time resolution but less angular resolution than ISEE-1. The ISEE-1 observed a butterfly PAD (a minimum in the 90° PA particle flux) for a period of about 2 h (10:00–12:00 UT) for the electrons, and 3 h (09:00–12:00 UT) for the protons over an energy range of 22.5–189 keV (E1–E4) for the electrons and 24–142 keV (P1–P4) for the protons. The small pitch angle (15°, 30°) charged particles (electrons and protons) are seen to behave collectively in all four energy ranges. The relative differences in electron fluxes between 15° PA and 90° PA are more significant for higher energy channels during the butterfly PAD period. Three different types of electron PADs (butterfly, isotropic, and peaked-at-90°) were observed at the same location and time as a function of energy for a short period of time before 10:00 UT. Electron butterfly distributions were also observed by the ISEE-2 for about 1.5 h over 28–62 keV (E2–E4), although less well resolved than ISEE-1. Unlike the ISEE-1, no butterfly distributions were resolved in the ISEE-2 proton PADs due to less angular resolution. The measured drift effects by ISEE-1 suggest that the detected protons were much closer to the particle source than the electrons along their trajectories, and thus ruled out a nightside source within 18:00 MLT to 03:00 MLT. Compared to 07:30 UT, the charged particle fluxes measured by ISEE-1 were enhanced by up to three orders of magnitude during the period 08:30–12:00 UT. From 09:10:00 UT to 11:50 UT, the geomagnetic conditions were quiet (AE<100 nT), the LANL geosynchronous satellites observed no substorms, and the local magnetic field measured by ISEE-1 was almost constant, while the small PA charged particle (both electron and proton) fluxes measured by ISEE-1 increased gradually, which implies a particle source other than the substorm source. Based on detailed particle trajectory tracings in a realistic geomagnetic field model, the 50–200 keV protons with small PA at 10:00 UT ISEE-1 location on 3 March 1979 were passing through the northern high-altitude and high-latitude morningside region where the cusp should be located under a dawnward IMF component condition, while those protons with large PA may connect to the high-latitude morningside magnetopause. It is possible that the cusp source is responsible for the all particles observed during the event.

Helices, Hasimoto Surfaces and Bäcklund Transformations

2000 ◽  
Vol 43 (4) ◽  
pp. 427-439 ◽  
Author(s):  
Thomas A. Ivey
Keyword(s):  
Travelling Wave ◽  
Travelling Wave Solutions ◽  
Similar Investigation ◽  
Screw Motion ◽  
Single Screw ◽  
Wave Solutions ◽  
First Case ◽  
Pseudospherical Surfaces ◽  
Special Cases ◽  
Constant Torsion

AbstractTravelling wave solutions to the vortex filament flow generated by elastica produce surfaces in ℝ3 that carry mutually orthogonal foliations by geodesics and by helices. These surfaces are classified in the special cases where the helices are all congruent or are all generated by a single screw motion. The first case yields a new characterization for the Bäcklund transformation for constant torsion curves in R3, previously derived fromthe well-known transformation for pseudospherical surfaces. A similar investigation for surfaces in H3 or S3 leads to a new transformation for constant torsion curves in those spaces that is also derived from pseudospherical surfaces.

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