ABSTRACT
To improve the performance of underwater wireless optical communication (UWOC) systems, we propose a relay-assisted UWOC system model based on adaptive optics (AO). The closed expressions of the scintillation index, composite channel probability density function, and outage probability of the Gaussian beam before and after AO compensation are derived using the extended Rytov theory and Meijer G-function. The performance variation of an UWOC system with different parameters is analyzed by simulation. The results show that AO correction can compensate for the distorted wavefront and significantly reduce the intensity fluctuation at the receiving end. The proposed system can efficiently alleviate channel fading, improving the outage probability performance of the UWOC system.
ABSTRACT
In this study, we examined the performance of an underwater wireless optical communication (UWOC) system employing a single-input to multiple-output (SIMO) scheme and proposed an equalization equal gain combining (EEGC) algorithm for it under Gaussian beam conditions. Furthermore, based on a Yue spectrum with the instability of oceanic water stratification and a finite outer scale, we derived the closed analytical formulas for the scintillation index and spatial coherence radius in weak oceanic turbulence for a Gaussian beam, from which we could obtain the threshold of the detector spacing and the strength of oceanic turbulence. We then derived the closed-form formula for the upper bound average bit error rate of the EEGC SIMO system with ON-OFF keying modulation by using the hyperbolic tangent distribution function. Our simulations demonstrate two issues if oceanic water stratification is treated as a steady state: the performance of the diversity receiver system will be significantly underestimated in salinity-dominated weak oceanic turbulence channels and will be significantly overestimated in temperature-dominated weak oceanic turbulence channels. Additionally, the SIMO system performance improvement using the proposed EEGC algorithm was more evident with increasing detector spacing, and the EEGC algorithm reduced the impact of the layout of the avalanche photodiode arrays on the UWOC system performance, in contrast to the equal gain combining algorithm.
ABSTRACT
OBJECTIVE: To evaluate the clinical efficacy of traditional Chinese medicine in the treatment of arrhythmia. METHODS: The researchers searched CNKI, VIP, WF, PubMed, Web of Science, and Cochrane Library with the set-up themes as randomized controlled trials (RCTs) on the clinical efficacy of traditional Chinese medicine in the treatment of arrhythmia. This research evaluated all the retrieve literature and conducted selection based on the evaluation. Stata software was applied for meta-analysis. RESULTS: 23 articles were retrieved with a total patient number of 2846. The results observed from the meta-analysis indicated the following: (1) compared with the result showed in placebo group, the traditional Chinese medicine group presented to have good efficacy, especially in the treatment of premature ventricular contractions. (2) In comparison with the western medicine group, the curative effect of Chinese medicine could approximately equal the therapeutic effect as western medicine. (3) Compared with the application of sole western medicine group, the combination of both traditional Chinese medicine and western medicine could have a better curative effect. CONCLUSION: In the treatment of arrhythmia disease, the application of traditional Chinese medicine can be considered as an effective method. In addition to that, the therapeutic effect obtained from the combination of both Chinese traditional medicine and western medicine is clinically better than that of the sole use of western medicine.
ABSTRACT
A novel method to control the parameters of a chiral fiber grating structure is proposed. Mode couplings are controlled in real time during the twisting fabrication process. This chiral grating structure can satisfy the phase-matching condition for generating high-quality orbital angular momentum (OAM) beams, with an order mode of conversion efficiency over 99.9%. Both theoretical analysis and experimental results of this OAM mode conversion have been investigated, with good agreement. The results demonstrate a dual-OAM beam converter with a charge of ±1 for the right- and left-handed CLPGs, respectively. The high-quality OAM beam generated in this twisted single-mode fiber process may find excellent applications in optical communications.
