1,433 research outputs found
Low-complexity Noncoherent Iterative CPM Demodulator for FH Communication
In this paper, we investigate the noncoherent iterative demodulation of coded continuous phase modulation (CPM) in frequency hopped (FH) systems. In this field, one important problem is that the complexity of the optimal demodulator is prohibitive unless the number of symbols per hop duration is very small. To solve this problem, we propose a novel demodulator, which reduces the complexity by applying phase quantization and exploiting the phase rotational invariance property of CPM signals. As shown by computational complexity analysis and numerical results, the proposed demodulator approaches the performance of the optimal demodulator, and provides considerable performance improvement over the existing solutions with the same computational complexity
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Employing a Narrow-Band-Gap Mediator in Ternary Solar Cells for Enhanced Photovoltaic Performance.
Ternary organic solar cells (OSCs) provide a convenient and effective means to further improve the power conversion efficiency (PCE) of binary ones via composition control. However, the role of the third component remains to be explored in specific binary systems. Herein, we report ternary blend solar cells by adding the narrow-band-gap donor PCE10 as the mediator into the PBDB-T:IDTT-T binary blend system. The extended absorption, efficient fluorescence resonance energy transfer, enhanced charge dissociation, and induced tighter molecular packing of the ternary blend films enhance the photovoltaic properties of devices and deliver a champion PCE of 10.73% with an impressively high open-circuit voltage (VOC) of 1.03 V. Good miscibility and similar molecular packing behavior of the components guarantee the desired morphology in the ternary blend films, leading to solar cell devices with over 10% PCEs at a range of compositions. Our results suggest that ternary systems with properly aligned energy levels and overlapping absorption among the components hold great promises to further enhance the performance of corresponding binary ones
Research on dynamic load characteristics and active control strategy of electro-mechanical coupling powertrain of drum shearer cutting unit under impact load
In order to extend the service life of the long-chain gear transmission system of a drum shearer, an electro-mechanical coupling model of a drum shearer cutting unit is established. The model considers the dynamic characteristics of the motor, time-varying meshing stiffness, as well as the drum load characteristics. Additionally, the dynamic characteristics and control strategy for suppressing the dynamic load of the gear transmission system under impact load are investigated based on this model. Firstly, the influence of the gear transmission system of the drum shearer cutting unit under impact load is analyzed. Then, on that basis, the active control strategy based on motor torque compensation is proposed to suppress the dynamic load of the gear transmission system caused by mutational external load. Finally, the suppression effect on the dynamic load of the gear transmission system is analyzed. Research results indicate that this control strategy has good control effects to suppress the dynamic load caused by a mutational external load, which confirms the effectiveness of the proposed control strategy
Molecular simulations of sliding on SDS surfactant films
We use molecular dynamics simulations to study the frictional response of the
anionic surfactant sodium dodecyl sulfate (SDS) monolayers and hemicylindrical
aggregates physisorbed on gold. Our simulations of a sliding spherical asperity
reveals two friction regimes: At low loads, the films show Amontons' friction
with a friction force that rises linearly with normal load. At high loads, the
friction force is independent of load as long as no direct solid-solid contact
occurs. The transition between these two regimes happens when only a single
molecular layer is confined in the gap between the sliding bodies. The friction
force at high loads on a monolayer rises monotonically with film density and
drops slightly with the transition to hemicylindrical aggregates. This
monotonous increase of friction force is compatible with a traditional plowing
model of sliding friction. At low loads, the friction coefficient reaches a
minimum at intermediate surface concentrations. We attribute this behavior to a
competition between adhesive forces, repulsion of the compressed film, and the
onset of plowing.Comment: 14 pages, 10 figure
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