As the U.S. and Europe launched the very low frequency (VLF: 3-30 kHz) space-borne transmitting and propagation experiments during the past thirty years, space-borne antennas have been playing a more and more important role in contemporary VLF communication systems, which are very likely to become an indispensable approach for overwater/underwater communication and navigation in the future. In this paper, we propose a semianalytical method for evaluating the current distribution and input impedance of a VLF space-borne tubular antenna. By considering the effects of both the ordinary wave (O-wave) and the extraordinary wave (E-wave) in an anisotropic ionosphere, the analytical expression for the current distribution has a more complicated form and is derived via the method of moments (MoM) and the Gauss-Legendre quadrature (GLQ) algorithm. Computations show that the current distribution and input impedance under anisotropic conditions are very sensitive to parameter changes, but the overall trend for the input impedance will increase with the radius or electrical length of the antenna. Comparisons with linear models and numerical results obtained in FEKO verify the accuracy of this method. From simulations about the effect of the geomagnetic inclination angle to the input impedance, we advise that the parallel case can be preferred as an alternative for the best angle. Once all antenna parameters are determined, there is a possibility to find multiple optimal inclination angles. In addition, qualitative analyses of the impact of environmental changes to the antenna characteristics are also discussed. INDEX TERMS Anisotropic plasma, Current distribution, Tubular antenna.
Background. Elderly patients with chronic diseases (CDs) have a higher predilection for falls, with more severe consequences once they fall. Therefore, it is necessary to explore an effective way to prevent falls in elderly patients with CDs. Objective. To clarify the clinical effects of outpatient health education on fall prevention and self-health management in elderly patients with CDs. Methods. This retrospective study enrolled 102 elderly patients with CDs who received treatment in the School of Medicine, Sir Run Run Shaw Hospital of Zhejiang University, between January 2019 and December 2020. Patients intervened by routine nursing were assigned to the regular group (n = 48), and those additionally treated with outpatient health education were included in the research group (n = 54). Assessment of patients’ negative emotions (NEs) adopted the Self-Rating Anxiety/Depression Scale (SAS/SDS), determination of their sense of self-efficacy employed the Falls Efficacy Scale International (FES-I), and their self-care capacity evaluation used the Exercise of Self-Care Agency (ESCA). Patients’ falls, hospitalization time, fall prevention knowledge, fall prevention-related health behavior, and nursing satisfaction were recorded. Results. After the nursing intervention, lower SAS, SDS, and FES-I scores were determined in the research group versus the regular group; the total ESCA score assessed from various dimensions was higher in the research group; the research group also exhibited a markedly lower incidence of falls, and shorter hospitalization time than the regular group, with better mastery of fall prevention knowledge, fall prevention-related health behavior and nursing satisfaction. Conclusions. Outpatient health education intervention can prevent senile patients with CDs from falling, promote their rehabilitation, and enhance their mastery of fall prevention knowledge; moreover, it can improve patients’ healthy behaviors to prevent falls, mitigate their NEs, and improve their sense of self-efficacy and self-care ability, which has high clinical application value.
Objective The risk factors for residual dizziness (RD) after successful treatment of benign paroxysmal positional vertigo (BPPV) are poorly characterized. We determined the risk factors for RD in patients with benign unilateral posterior semicircular canal paroxysmal positional vertigo (pc-BPPV) after successful treatment. Methods We conducted a prospective study of patients diagnosed with unilateral pc-BPPV between March 2015 and January 2017. Bone mineral density (BMD) was measured by dual-energy X-ray bone mineral densitometry. Participants underwent bithermal caloric testing (C-test) using videonystagmography and a canalith repositioning procedure (CRP). The occurrence of RD was the primary outcome. The participants underwent follow-up 1 week, 1 month, and 1 year after successful CRP, consisting of outpatient visits, questionnaires, and telephone interviews. Results We assessed 115 participants with unilateral pc-BPPV (31 men and 84 women) who were 53.2 ± 8.8 years old. RD occurred in 60 (52.2%) participants. The participants who experienced RD were older, had vertigo for longer before treatment, and were more likely to show a positive C-test and significant BMD loss. Conclusions We found that a significant reduction in BMD (T-score < −1 standard deviation), a positive C-test, and older age are independently associated with RD in patients with pc-BPPV after successful CRP.
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