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Energy-efficient data aggregation is important for underwater acoustic sensor networks due to its energy constrained character. In this paper, we propose a kind of energy-efficient data aggregation scheme to reduce communication cost and to prolong network lifetime based on distributed compressed sensing theory. First, we introduce a distributed compressed sensing model for a cluster-based underwater acoustic sensor network in which spatial and temporal correlations are both considered. Second, two schemes, namely, BUTM-DCS (block upper triangular matrix DCS) and BDM-DCS (block diagonal matrix DCS), are proposed based on the design of observation matrix with strictly restricted isometric property. Both schemes take multihop underwater acoustic communication cost into account. Finally, a distributed compressed sensing reconstruction algorithm, DCS-SOMP (Simultaneous Orthogonal Matching Pursuit for DCS), is adopted to recover raw sensor readings at the fusion center. We performed simulation experiments on both the synthesized and real sensor readings. The results demonstrate that the new data aggregation schemes can reduce energy cost by more than 95 percent compared with conventional data aggregation schemes when the cluster number is 20. [ABSTRACT FROM AUTHOR]

Compared with traditional microbial fuel cells, the microfluidic microbial fuel cells have higher performance and energy efficiency due to their co-laminar flow characteristic and micro-scale structure. However, there are very few numerical studies on microfluidic microbial fuel cells, which makes it difficult to study the operating mechanism. In this study, a three-dimensional numerical model is developed to characterize and predict the comprehensive performance of a biofilm-based Y-typed microfluidic microbial fuel cell. Multiple physical fields, containing the bioelectrochemical reaction kinetics, mass transport, hydrodynamics and thermal equilibrium, are coupled in this model to investigate the effects of various parameters on cell performance. The model reliability is validated through the previous experiment. Simulation results reveal the non-linear performance trend of microfluidic microbial fuel cells with the augment of temperature. In addition, high fuel concentration can cause the substrate inhibition phenomenon and affect bacterial activity. Model applicability for different parametric analyses is emphasized by exploring the effect of ionic strength on cell performance. Finally, considering the catholyte diffusion, optimization strategies for energy efficiency are presented. The proposed numerical model can be helpful for the experimental guidance and optimal design of microfluidic microbial fuel cells. [Display omitted] • The first three-dimensional model for microfluidic microbial fuel cell is proposed. • Hydrodynamics and thermal equilibrium are coupled together. • Effects of temperature on anode reaction and catholyte property are considered. • Fuel utilization and exergy efficiency are introduced to evaluate performances. [ABSTRACT FROM AUTHOR]

[Display omitted] • The effects of crucial parameters on cell performance are studied. • Through reactant concentration distributions to reveal mass transfer mechanism. • Multi-objective particle swarm algorithm is employed to optimize the cell performance. • The overall cell performance is improved by at least 20.87% after the optimization. Microfluidic microbial fuel cell has lower costs and greater potential than typical microbial fuel cell due to the elimination of proton exchange membrane. However, the development has mostly relied on experiments, and there has been little research on numerical simulations. Based on experimental validation, a reliable and universal model for microfluidic microbial fuel cell without quantifying the biomass concentration is proposed. Subsequently, the primary work is to study the output performance and energy efficiency of the microfluidic microbial fuel cell under different operating conditions and to comprehensively optimize the cell performance by employing the multi-objective particle swarm algorithm. Compared the optimal case with the base case, the increase ratios of maximum current density, power density, fuel utilization and exergy efficiency are 40.96%, 20.87%, 61.58% and 32.19%, respectively. On the basis of improving energy efficiency, the maximum power density and current density can reach 1.193 W/m2 and 3.51 A/m2. [ABSTRACT FROM AUTHOR]

Under the dual pressure of energy consumption and environmental pollution, mankind hopes to develop clean and renewable alternative energy, and the rapid development of fuel cells meets people's demand for energy-efficient power systems. The emergence of portable micro energy systems represented by microfluidic fuel cells, such as paper-based microfluidic fuel cells, has greatly enriched the means of medical detection to better cope with the threat of disease transmission. In this work, the numerical simulation method is innovatively introduced to study the paper-based microfluidic fuel cells. Both transient and steady-state modes are employed to demonstrate the whole operation process of the paper-based microfluidic fuel cell. In addition, the different structural parameters, including electrode spacing, the distance between electrode and inlet, channel thickness, and electrode length, are also investigated their influence mechanisms on cell performance. Results show that the increase of most structural parameters decreases cell output power in different degrees. Even on the premise that increasing channel thickness has a positive impact on the output power, the fuel utilization still shows a downward trend. These conclusions provide theoretical support and reference for future optimization work and accelerate the development of microfluidic fuel cells. • Numerical simulation is employed to study paper-based microfluidic fuel cell. • The effects of structure parameters on cell performance are discussed. • Through fuel concentration distribution to reveal cell performance mechanism. • Fuel utilization is used to evaluate energy efficiency. [ABSTRACT FROM AUTHOR]

Fuel cells are an efficient, environmentally friendly and renewable energy device, which is synonymous with the green age. Microfluidic fuel cells are an excellent solution to the energy needs of portable electronic devices. In the present study, both vapor- and liquid-feed modes are established, which are combined with physical fields. Moreover, the accuracy of the models is verified. According to the results, the vapor-feed microfluidic fuel cell achieves higher tolerance to low flow rates while realizing a much higher energy efficiency than the liquid-feed microfluidic fuel cell. In addition, the performance of these microfluidic fuel cells is significantly improved by increasing the electrolyte and fuel concentrations. In terms of fuel utilization, the vapor-feed mode performs much better than that of liquid-feed mode no matter what parameters are changed, which shows the superiority of vapor-feed microfluidic fuel cell. Sensitivity analysis shows that either the electrolyte or fuel concentration significantly affects the power output of these microfluidic fuel cells. Although their growth can improve the power output of the fuel cells, they have adverse effects on energy efficiency. Conclusions indicate that the vapor-feed microfluidic fuel cell is more suitable for portable electronic products, and it is worthy of further development. [Display omitted] • Microfluidic fuel cell models with different fuel supply modes are established. • Vapor-feed mode are highlighted through comprehensive comparison. • Energy efficiency is evaluated by fuel utilization and exergy efficiency. • Sensitivity analysis is used to study the vapor-feed microfluidic fuel cell. [ABSTRACT FROM AUTHOR]