Four square loops antenna for circular polarisation and gain enhancement

2010 ◽  
Vol 46 (7) ◽  
pp. 475 ◽  
Author(s):  
Q. Yang ◽  
X. Zhang ◽  
X. Bai ◽  
N. Wang ◽  
Y. Wang ◽  
...  
Keyword(s):  
Circular Polarisation ◽  
Gain Enhancement ◽  
Four Square

Design and Analysis of Wideband Dielectric Resonator Antenna with Bandwidth and Gain Enhancement for C-Band Applications

2018 ◽  
Vol 11 (6) ◽  
pp. 352 ◽  
Author(s):  
Sharif Ahmed Qasem ◽  
Tan Kim Geok ◽  
Mohamad Yusoff Alias ◽  
Ferdous Hossain ◽  
Naif Alsowaidi
Keyword(s):  
Dielectric Resonator ◽  
Dielectric Resonator Antenna ◽  
Gain Enhancement

Gain Enhancement for Reflectarray

PIERS Online ◽  
2006 ◽  
Vol 2 (6) ◽  
pp. 601-604
Author(s):  
The-Nan Chang
Keyword(s):  
Gain Enhancement

scholarly journals Factors associated with dynamic balance in people with Persistent Postural Perceptual Dizziness (PPPD): a cross-sectional study using a virtual-reality Four Square Step Test

2021 ◽  
Vol 18 (1) ◽  
Author(s):  
Moshe M. H. Aharoni ◽  
Anat V. Lubetzky ◽  
Liraz Arie ◽  
Tal Krasovsky
Keyword(s):  
Virtual Reality ◽  
Trait Anxiety ◽  
Dynamic Balance ◽  
Step Test ◽  
Simulator Sickness ◽  
Balance Confidence ◽  
Task Duration ◽  
Head Kinematics ◽  
Perceived Disability ◽  
Four Square

Abstract Background Persistent postural-perceptual dizziness (PPPD) is a condition characterized by chronic subjective dizziness and exacerbated by visual stimuli or upright movement. Typical balance tests do not replicate the environments known to increase symptoms in people with PPPD—crowded places with moving objects. Using a virtual reality system, we quantified dynamic balance in people with PPPD and healthy controls in diverse visual conditions. Methods Twenty-two individuals with PPPD and 29 controls performed a square-shaped fast walking task (Four-Square Step Test Virtual Reality—FSST-VR) using a head-mounted-display (HTC Vive) under 3 visual conditions (empty train platform; people moving; people and trains moving). Head kinematics was used to measure task duration, movement smoothness and anterior–posterior (AP) and medio-lateral (ML) ranges of movement (ROM). Heart rate (HR) was monitored using a chest-band. Participants also completed a functional mobility test (Timed-Up-and-Go; TUG) and questionnaires measuring anxiety (State-Trait Anxiety Inventory; STAI), balance confidence (Activities-Specific Balance Confidence; ABC), perceived disability (Dizziness Handicap Inventory) and simulator sickness (Simulator Sickness Questionnaire). Main effects of visual load and group and associations between performance, functional and self-reported outcomes were examined. Results State anxiety and simulator sickness did not increase following testing. AP-ROM and HR increased with high visual load in both groups (p < 0.05). There were no significant between-group differences in head kinematics. In the high visual load conditions, high trait anxiety and longer TUG duration were moderately associated with reduced AP and ML-ROM in the PPPD group and low ABC and  high perceived disability were associated with reduced AP-ROM (|r| =  0.47 to 0.53; p < 0.05). In contrast, in controls high STAI-trait, low ABC and longer TUG duration were associated with increased AP-ROM (|r| = 0.38 to 0.46; p < 0.05) and longer TUG duration was associated with increased ML-ROM (r = 0.53, p < 0.01). Conclusions FSST-VR may shed light on movement strategies in PPPD beyond task duration. While no main effect of group was observed, the distinct associations with self-reported and functional outcomes, identified using spatial head kinematics, suggest that some people with PPPD reduce head degrees of freedom when performing a dynamic balance task. This supports a potential link between spatial perception and PPPD symptomatology.

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