Purpose: Surface electromyography (sEMG) is a non-invasive technique to characterize muscle electrical activity. The analysis of sEMG signals under muscle fatigue play a crucial part in the branch of neurorehabilitation, sports medicine, biomechanics, and monitoring neuromuscular pathologies. In this work, a method to transform sEMG signals to complex networks under muscle fatigue conditions using Markov transition field (MTF) is proposed. The importance of normalization to a constant Maximum voluntary contraction (MVC) is also considered. Methods: For this, dynamic signals are recorded using two different experimental protocols one under constant load and another referenced to 50% MVC from Biceps brachii of 50 and 45 healthy subjects respectively. MTF is generated and network graph is constructed from preprocesses signals. Features such as average self-transition probability, average clustering coefficient and modularity are extracted. Results: All the extracted features showed statistical significance for the recorded signals. It is found that during the transition from non-fatigue to fatigue, average clustering coefficient decreases while average self-transition probability and modularity increases. Conclusion: The results indicate higher degree of signal complexity during non-fatigue condition. Thus, the MTF approach may be used to indicate the complexity of sEMG signals. Although both datasets showed same trend in results, sEMG signals under 50% MVC exhibited higher separability for the features. The inter individual variations of the MTF features is found to be more for the signals recorded using constant load. The proposed study can be adopted to study the complex nature of muscles under various neuromuscular conditions.

This paper presents thermal and electrical analyses of solar linear parabolic trough concentrating photovoltaic (CPV) collector system under different design and operating conditions. The receiver tube receives concentrated non-uniform solar flux over its outer surface, leading to high local temperature and large circumferential temperature difference. A Compound Parabolic Collector (CPC) has been incorporated as a secondary reflector to homogenize the flux. The co-generation system consists of a Parabolic Trough Collector (PTC) with 5.1 m2 aperture area (AAP) and a highly reflective mirror with dual axis tracking. The study envisages maximizing electrical output using CPV with non-uniform thermal energy over receiver tube. Various configurations are analyzed which include 2-cell and 3-cell strings without CPC and 3-cell and 4-cell strings with CPC. The detailed thermal and electrical analysis carried out for all the cases using Al2O3/Water nanofluid with 0%, 1% and 6% vol. and various synthetic fluids with constant velocity of 0.1 m/s. The flux values for the thermal analysis have been imported from the non-sequential ray tracing optical simulation software ASAP. Maximum thermal and electrical output is computed to be 2592.42 W with 78.2% thermal efficiency by 2-cell without CPC configuration using Syltherm-800 and 692.2 W with 20.88% electrical efficiency by 3-cell without CPC with Al2O3/Water (φ = 1%) respectively. Reduction in electrical output by ∼7.2–9.8% and enhancement in thermal output by ∼0.91–1.16% has been observed on replacing nanofluids with synthetic fluids. Long lasting synthetic fluids leads to higher cell temperatures hence higher cell degradation but nanofluids give optimized electrical and thermal output with lower cell temperatures. Numerical results are compared with reference data which shows the reasonable agreement.