Downlink Performance Analysis of MIMO Relaying Networks

In recent years, there has been an upsurge of interest in relay-augmented infrastructure-based networks. On the other hand, multiple-input-multiple-output (MIMO) wireless system becomes a hot topic for it can achieve significant increases in overall system performance. This paper gives a detailed analysis of downlink performance of MIMO relaying networks, in which different channel models and classic MIMO cellular system model with fixed relay are considered. Our results in single cell scenario show that when meeting effective relay system efficiency of 100%, the required relay SNR gain of 2-antenna system can be reduced to less than half of that with only one transceiver antenna. We also observe that MIMO is more tolerant to interference compared with the one-transceiver antenna system. After that, multi-hop architecture is researched and statistics figures out the tolerable number of hops which is supported in wireless communication with a view to real application. In addition, multi-cell scenario is also studied. Statistics results show that there is more 8 dB average spectral efficiency gain in a two-hop fixed relay 4 × 4 MIMO system than that in a SISO system. These results present significant indications in deployment and optimization of relay-based MIMO networks.     

Lithium Phosphonate Functionalized Polymer Coating for High-Energy Li[Ni0.8Co0.1Mn0.1]O2 with Superior Performance at Ambient and Elevated Temperatures

High-energy Ni-rich lithium transition metal oxides such as Li[Ni_0.8Co_0.1Mn_0.1]O₂ (NCM₈₁₁) are appealing positive electrode materials for next-generation lithium batteries. However, the high sensitivity toward moist air during storage and the high reactivity with common organic electrolytes, especially at elevated temperatures, are hindering their commercial use. Herein, an effective strategy is reported to overcome these issues by coating the NCM₈₁₁ particles with a lithium phosphonate functionalized poly(aryl ether sulfone). The application of this coating allows for a substantial reduction of lithium-based surface impurities (e.g., LiOH, Li₂CO₃) and, generally, the suppression of detrimental side reactions upon both storage and cycling. As a result, the coated NCM₈₁₁-based cathodes reveal superior Coulombic efficiency and cycling stability at ambient and, particularly, at elevated temperatures up to 60 ° C (a temperature at which the non-coated NCM₈₁₁ electrodes rapidly fail) owing to the formation of a stable cathode electrolyte interphase with enhanced Li⁺ transport kinetics and the well-retained layered crystal structure. These results render the herein presented coating strategy generally applicable for high-performance lithium battery cathodes.     

On the effects of a spacecraft subcarrier unbalanced modulator

This paper presents mathematical models with associated analysis of the deleterious effects which a spacecraft's subcarrier unbalanced modulator has on the performance of a phase-modulated residual carrier communications link. The undesired spectral components produced by the phase and amplitude imbalances in the subcarrier modulator can cause (1) potential interference to the carrier tracking and (2) degradation in the telemetry bit signal-to-noise ratio (SNR). A suitable model for the unbalanced modulator is developed and the threshold levels of undesired components that fall into the carrier tracking loop are determined. The distribution of the carrier phase error caused by the additive White Gaussian noise (AWGN) and undesired component at the residual RF carrier is derived for the limiting cases. Further, this paper analyses the telemetry bit signal-to-noise ratio degradations due to undesirable spectral components as well as the carrier tracking phase error induced by phase and amplitude imbalances. Numerical results which indicate the sensitivity of the carrier tracking loop and the telemetry symbol-error rate (SER) to various parameters of the models are also provided as a tool in the design of the subcarrier balanced modulator.     

Wavelength and power stabilisation of uncooled 975 nm thick quantum well lasers over 110/spl deg/C temperature range

The use of a thick quantum well enables coherence-collapse operation of a Bragg grating stabilised laser diode over 110/spl deg/C temperature range, yielding 975 nm wavelength emission with >40 dB sidemode suppression ratio, <1% power variation, and fibre-output power as high as 293 mW at 15/spl deg/C and 168 mW at 125/spl deg/C.     

Functionally Antagonistic Hybrid Electrode with Hollow Tubular Graphene Mesh and Nitrogen‐Doped Crumpled Graphene for High‐Performance Ionic Soft Actuators

Ionic soft actuators, which exhibit large mechanical deformations under low electrical stimuli, are attracting attention in recent years with the advent of soft and wearable electronics. However, a key challenge for making high‐performance ionic soft actuators with large bending deformation and fast actuation speed is to develop a stretchable and flexible electrode having high electrical conductivity and electrochemical capacitance. Here, a functionally antagonistic hybrid electrode with hollow tubular graphene meshes and nitrogen‐doped crumpled graphene is newly reported for superior ionic soft actuators. Three‐dimensional network of hollow tubular graphene mesh provides high electrical conductivity and mechanically resilient functionality on whole electrode domain. On the contrary, nitrogen‐doped wrinkled graphene supplies ultrahigh capacitance and stretchability, which are indispensably required for improving electrochemical activity in ionic soft actuators. Present results show that the functionally antagonistic hybrid electrode greatly enhances the actuation performances of ionic soft actuators, resulting in much larger bending deformation up to 620%, ten times faster rise time and much lower phase delay in a broad range of input frequencies. This outstanding enhancement mostly attributes to exceptional properties and synergistic effects between hollow tubular graphene mesh and nitrogen‐doped crumpled graphene, which have functionally antagonistic roles in charge transfer and charge injection, respectively.     

A displacement measurement technique using millimeter-wave interferometry

A displacement measurement sensor, capable of sub-millimeter resolution, using millimeter-wave interferometry has been developed. The sensor operates at 37.6 GHz and is realized using both microwave integrated circuits and monolithic microwave integrated circuits. It has been used to accurately measure the displacement of metal plate location and water level. A resolution of only 0.05 mm is achieved. A maximum error of 0.3 mm is also attained without correction for the nonlinearity of the phase-detection processor and agrees well with the theoretical calculation.     

Very large temperature-induced absorptive loss in high Te-containing chalcogenide fibers

The change in the absorption loss relative to room temperature of the infrared (IR)-transmitting Ge/sub 15/As/sub 35/Se/sub (50-x)/Te/sub x/ glass fibers in the temperature range of -110/spl deg/C/spl les/T/spl les/110/spl deg/C was investigated. The attenuation increased significantly at T/spl ges/40/spl deg/C. This is mainly attributed to thermally activated free carriers associated with the semimetallic character of the Te atom. For /spl lambda//spl les/4.2 /spl mu/m, the loss due to electronic and free-carrier absorption was strongly affected by temperature. In the wavelength region of 5-11 /spl mu/m, the loss was mainly due to free-carrier absorption. Beyond /spl lambda//spl ges/11 /spl mu/m, multiphonon absorption dominated the loss spectrum at T/spl les/60/spl deg/C while free-carrier absorption contributed mainly to the total loss at T/spl ges/80/spl deg/C.     

LCD motion blur reduction: a signal processing approach.

Liquid crystal displays (LCDs) have shown great promise in the consumer market for their use as both computer and television displays. Despite their many advantages, the inherent sample-and-hold nature of LCD image formation results in a phenomenon known as motion blur. In this work, we develop a method for motion blur reduction using the Richardson-Lucy deconvolution algorithm in concert with motion vector information from the scene. We further refine our approach by introducing a perceptual significance metric that allows us to weight the amount of processing performed on different regions in the image. In addition, we analyze the role of motion vector errors in the quality of our resulting image. Perceptual tests indicate that our algorithm reduces the amount of perceivable motion blur in LCDs.     

High-mobility low band-to-band-tunneling strained-Germanium double-gate heterostructure FETs: Simulations

Large band-to-band tunneling (BTBT) leakage currents can ultimately limit the scalability of high-mobility (small-bandgap) materials. This paper presents a novel heterostructure double-gate FET (DGFET) that can significantly reduce BTBT leakage currents while retaining its high mobility, making it suitable for scaling into the sub-20-nm regime. In particular, through one-dimensional Poisson-Schrodinger, full-band Monte Carlo, and detailed BTBT simulations, the tradeoffs between carrier transport, electrostatics, and BTBT leakage in high-mobility sub-20-nm Si-strained SiGe-Si (high germanium concentration) heterostructure PMOS DGFETs are thoroughly analyzed. The results show a dramatic (>100/spl times/) reduction in BTBT and an excellent electrostatic control of the channel while maintaining very high drive currents and switching frequencies in these nanoscale transistors.