Spectrum Migration Approach Based on Pre-decision Aid and Interval Mamdani Fuzzy Inference in Cognitive Radio Networks

This study intends to improve the QoS of SUs and CRNs performance. A novel spectrum migration approach based on pre-decision aid and interval Mamdani fuzzy inference is presented. we first define spectrum migration factors as spectrum characteristic metrics for spectrum migration decision. In addition, we use predecision aid to reduce system complexity and improve spectrum migration efficiency. To shorten spectrum migration decision time and seek the optimal spectrum holes, interval Mamdani fuzzy inference is put forward. Finally, simulation results show the proposed approach can inhibit the upward trend of service retransmission probability and average migration times effectively, and improve the effective utilization of CRNs spectrum resource significantly

Study on the mechanism of tunable ferromagnetic composites with different rare earth ions

Size-controlled Fe3O4 nanoparticles doped with rare earth (RE) ions (La3+, Ce3+, and Dy3+) varying from 15 nm to 30 nm were successful synthesized by a hydrothermal method for potential applications in the fields of biomedicine, environmental protection and magnetic memory devices. They possessed good dispersibility, adjustable particle size and nearly spherical shape. The particle grain size was uniformly distributed and showed a low degree of agglomeration in comparison with undoped Fe3O4 nanoparticles. The FTIR results showed that the RE elements partially replaced Fe2+, occupied the octahedral position, and enhanced the vibration of the Fe–O bond. The XPS study further revealed that the valence states of La, Ce, and Dy are both positive trivalent. The XPS Fe 2p valence band spectra observed a shift in the peak position toward higher binding energy after RE doping, confirming the existence of RE ions in the octahedral position. This paper explains the mechanism of rare earth doping with Fe3O4, and clarifies the influence of the doping of different RE ions on its magnetic properties. The detailed analysis of RE-doped ferrite materials can open a new perspective in designing biomedical and spintronics materials with tailored properties by choosing suitable cation substitution

Estimation of canopy water content by means of hyperspectral indices based on drought stress gradient experiments of maize in the North Plain China

Here, we conducted drought stress gradient experiments of maize, and used ten water content related vegetation indices (VIs) to estimate widely variable canopy water content (CWC) and mean leaf equivalent water thickness at canopy level (${\overline{EWT}}$) based on in situ measurements of Lambertian equivalent reflectance and important biological and environmental factors during the 2013−2014 growing seasons in the North China Plain. Among ten VIs, the performances of green chlorophyll index (CIgreen), red edge chlorophyll index (CIred edge), and the red edge normalized ratio (NRred edge) were most sensitive to the variations of CWC and ${\overline{EWT}}$. Simulated drought in two differently managed irrigation years did not affect the sensitivities of VIs to the variations in CWC and ${\overline{EWT}}$. However, the relationships between CWC and VIs were more noticeable in 2014 than in 2013. In contrast,  ${\overline{EWT}}$ and VIs were more closely related in 2013 than in 2014. CWC and relative soil water content (RSWC) obviously exhibited a two-dimensional trapezoid space, which illustrated that CWC was determined not only by soil water status but also by crop growth and stage of development. This study demonstrated that nearly half of the variation in CWC explained by spectral information was derived from the variation in leaf area index (LAI)

Deriving a light use efficiency estimation algorithm using in situ hyperspectral and eddy covariance measurements for a maize canopy in Northeast China

We estimated the light use efficiency (LUE) via vegetation canopy chlorophyll content (CCCcanopy) based on in situ measurements of spectral reflectance, biophysical characteristics, ecosystem CO2 fluxes and micrometeorological factors over a maize canopy in Northeast China. The results showed that among the common chlorophyll-related vegetation indices (VIs), CCCcanopy had the most obviously exponential relationships with the red edge position (REP) (R-2 = .97, p < .001) and normalized difference vegetation index (NDVI) (R-2 = .91, p < .001). In a comparison of the indicating performances of NDVI, ratio vegetation index (RVI), wide dynamic range vegetation index (WDRVI), and 2-band enhanced vegetation index (EVI2) when estimating CCCcanopy using all of the possible combinations of two separate wavelengths in the range 400-1300 nm, EVI2 [1214, 1259] and EVI2 [726, 1248] were better indicators, with R-2 values of .92 and .90 (p < .001). Remotely monitoring LUE through estimating CCCcanopy derived from field spectrometry data provided accurate prediction of midday gross primary productivity (GPP) in a rainfed maize agro-ecosystem (R-2 = .95, p < .001). This study provides a new paradigm for monitoring vegetation GPP based on the combination of LUE models with plant physiological properties

Estimation of Canopy Water Content by Means of Hyperspectral Indices Based on Drought Stress Gradient Experiments of Maize in the North Plain China

Here, we conducted drought stress gradient experiments of maize, and used ten water content related vegetation indices (VIs) to estimate widely variable canopy water content (CWC) and mean leaf equivalent water thickness at canopy level (EWT) based on in situ measurements of Lambertian equivalent reflectance and important biological and environmental factors during the 2013-2014 growing seasons in the North China Plain. Among ten VIs, the performances of green chlorophyll index (CI greeir1, red edge chlorophyll, index (CI.d) and the red edge normalized ratio (NR red \--red edge) were most sensitive to the variations of CWC and EWT. Simulated drought in two differently managed irrigation years did not affect the sensitivities of VIs to the variations in CWC and EWT. However, the relationships between CWC and VIs were more noticeable in 2014 than in 2013. In contrast, EWT and VIs were more closely related in 2013 than in 2014. CWC and relative soil water content (RSWC) obviously exhibited a two-dimensional trapezoid space, which illustrated that CWC was determined not only by soil water status but also by crop growth and stage of development. This study demonstrated that nearly half of the variation in CWC explained by spectral information was derived from the variation in leaf area index (LA])

Estimation of Canopy Water Content by Means of Hyperspectral Indices Based on Drought Stress Gradient Experiments of Maize in the North Plain China

Here, we conducted drought stress gradient experiments of maize, and used ten water content related vegetation indices (VIs) to estimate widely variable canopy water content (CWC) and mean leaf equivalent water thickness at canopy level (EWT) based on in situ measurements of Lambertian equivalent reflectance and important biological and environmental factors during the 2013-2014 growing seasons in the North China Plain. Among ten VIs, the performances of green chlorophyll index (CI greeir1, red edge chlorophyll, index (CI.d) and the red edge normalized ratio (NR red \--red edge) were most sensitive to the variations of CWC and EWT. Simulated drought in two differently managed irrigation years did not affect the sensitivities of VIs to the variations in CWC and EWT. However, the relationships between CWC and VIs were more noticeable in 2014 than in 2013. In contrast, EWT and VIs were more closely related in 2013 than in 2014. CWC and relative soil water content (RSWC) obviously exhibited a two-dimensional trapezoid space, which illustrated that CWC was determined not only by soil water status but also by crop growth and stage of development. This study demonstrated that nearly half of the variation in CWC explained by spectral information was derived from the variation in leaf area index (LA])