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This paper considers an uplink cell-free massive multi-input multi-output (mMIMO) system with multi-antenna access points (APs) and users, assuming low-resolution analog-to-digital converter (ADC) architecture is employed at the APs. Leveraging on the additive quantization noise model (AQNM), we derive a tight approximate expression for uplink spectral efficiency (SE). This trackable finding provides us with a tool for easily quantifying the impacts of the number of antenna arrays and the number of quantization bit of low-resolution ADCs. We find 5-bit is required in a cell-free mMIMO with low-resolution ADCs to achieve the same SE as a cell-free mMIMO with full-precision ADCs. Besides, when the number of antennas of the user is small, deploying more antennas at the users can boost the sum SE. Then, to further highlight the potential of low-resolution ADCs architecture, we also investigate the tradeoff between the SE and energy efficiency (EE) with design issues surrounding the quantization bit of low-resolution ADCs and the number of antenna arrays. The resulting observations reveal that by choosing a proper quantization bit, the cell-free mMIMO with low-resolution ADCs has the capability to enjoy a better SE-EE tradeoff compared to the perfect ADCs counterpart.INDEX TERMS Cell-free mMIMO, low-resolution ADC, AQNM, spectral efficiency, energy efficiency.

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This work provides a technique allowing bidirectional optical transportation and controllable positioning of nanoparticles using two counter-propagating laser beams at a wavelength of 980 nm in an optical nanofiber. With the assistance of an evanescent wave at the fiber surface, particles suspended in water were trapped onto the fiber by a gradient force and then transported along the fiber by a scattering force. By changing the difference between the input laser powers coupled into two ends of the fiber with ΔP = -10 to 10 mW, the magnitude and direction of the scattering force that acted on the particles were changed, and thus the transportation direction and velocity of the particles were controlled. According to these properties, the bidirectional optical transportation of the particles along the fiber can be realized by coupling different laser powers into the two ends of the fiber (ΔP≠ 0 mW). At the same time, the transported particles can be controllably positioned on the fiber by coupling the same laser powers into the two ends of the fiber (ΔP = 0 mW). The relationship between the transportation velocity of the particles and the input optical power difference was investigated. Experiments were conducted with a 910 nm diameter fiber and 713 nm diameter polystyrene (PS) particle suspensions to demonstrate the effectiveness of this method. The experimental results were interpreted by numerical simulation and theoretical analysis.

To predict the best management practices for Kentucky bluegrass (Poa pratensis L.) lawns in Colorado, the DAYCENT ecosystem model was parameterized and applied on a turfgrass ecosystem. In this study, field‐measured data on clipping yields, leaf N content, evapotranspiration (ET), deep percolation, nitrate leaching, and soil temperature from a 3‐yr lysimeter study were used for parameterization and validation. The simulation result for clipping yield was improved compared to the monthly time step CENTURY ecosystem model, with correlation coefficient (r) increased from −0.32 to 0.74. The prediction of ET and deep percolation was acceptable for the 3 yr. The long‐term irrigation and fertilization effects on Kentucky bluegrass biomass and soil C and N were also examined. We predicted a 50% reduction in the annual net production as irrigation decreases from 100% potential evapotranspiration (PET) to 60% PET in this semiarid region. The simulation result suggests that the annual fertilization rates should be gradually reduced for both moderately and highly managed lawns with increasing age of the turfgrass stand.

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