Detecting and characterizing the community structure of complex network is fundamental. We compare the classical optimization indexes of modularity and modularity density, which are quality indexes for a partition of a network into communities. Based on this, we propose a quantitative function for community partition, named communitarity or C value. We demonstrate that the quantitative is superior to modularity Q and modularity density D. Both theoretical and numerical results show that optimizing the new index not only can resolve small modules, but also can correctly identify the number of communities.

Abstract:The spatiotemporal distribution of soil moisture over the Tibetan Plateau is important for understanding the regional water cycle and climate change. In this paper, the surface soil moisture in the northeastern Tibetan Plateau is estimated from time-series VV-polarized Sentinel-1A observations by coupling the water cloud model (WCM) and the advanced integral equation model (AIEM). The vegetation indicator in the WCM is represented by the leaf area index (LAI), which is smoothed and interpolated from Terra Moderate Resolution Imaging Spectroradiometer (MODIS) LAI eight-day products. The AIEM requires accurate roughness parameters, which are parameterized by the effective roughness parameters. The first halves of the Sentinel-1A observations from October 2014 to May 2016 are adopted for the model calibration. The calibration results show that the backscattering coefficient (σ • ) simulated from the coupled model are consistent with those of the Sentinel-1A with integrated Pearson's correlation coefficients R of 0.80 and 0.92 for the ascending and descending data, respectively. The variability of soil moisture is correctly modeled by the coupled model. Based on the calibrated model, the soil moisture is retrieved using a look-up table method. The results show that the trends of the in situ soil moisture are effectively captured by the retrieved soil moisture with an integrated R of 0.60 and 0.82 for the ascending and descending data, respectively. The integrated bias, mean absolute error, and root mean square error are 0.006, 0.048, and 0.073 m 3 /m 3 for the ascending data, and are 0.012, 0.026, and 0.055 m 3 /m 3 for the descending data, respectively. Discussions of the effective roughness parameters and uncertainties in the LAI demonstrate the importance of accurate parameterizations of the surface roughness parameters and vegetation for the soil moisture retrieval. These results demonstrate the capability and reliability of Sentinel-1A data for estimating the soil moisture over the Tibetan Plateau. It is expected that our results can contribute to developing operational methods for soil moisture retrieval using the Sentinel-1A and Sentinel-1B satellites.

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Highly transparent ceramics of La‐doped 0.75Pb(Mg1/3Nb2/3)O3–0.25PbTiO3 were fabricated by a two‐stage sintering method from conventional raw materials. The ceramics exhibited a transparency as high as 65% for the infrared wavelength. Large quadratic electro‐optic coefficient of 66 × 10−16 (m/v)2 was obtained, which was the highest value reported so far in Pb(Mg1/3Nb2/3)O3–PbTiO3 ceramics. The ferroelectric phase inducing the threshold electric field Eth and the domain structure of the transparent ceramics were studied.

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Spinel LiMn 2 O 4 is an appealing candidate cathode material for Li-ion rechargeable batteries, but it suffers from severe capacity fading, especially at higher temperature (55 °C) during discharging/charging. In recent years, many attempts have been made to synthesize modified LiMn 2 O 4 . This paper reviews the recent research on the preparation and doping modes of doped LiMn 2 O 4 for modifying the LiMn 2 O 4. We firstly compared preparation methods for doped spinel LiMn 2 O 4 , such as solid state reactions and solution synthetic methods. Then we mainly discuss doping modes reported in recent years, such as bulk doping, surface doping and combined doping. A comparison of different doping modes is also provided. The research shows that the multiple-ion doping and combined doping modes of LiMn 2 O 4 used in Li-ion battery are excellent for improving different aspects of the electrochemical performance which holds great promise in the future. From this paper, we also can see that spinel LiMnO 4 as an attractive candidate cathode material for Li-ion batteries.

Large piezoelectric effect is achieved in Li-doped Ba 0.85 Ca 0.15 Ti 0.90 Zr 0.10 O 3 (BCTZ) ceramics by use of tuning the phase boundaries. Rhombohedral-orthorhombic (R-O) and orthorhombic-tetragonal (O-T) multiphase coexistence is constructed in the ceramics by changing Li contents. The high piezoelectric constant d 33 (493 pC/N) and large electrostrain (dS max /dE max = 931 pm/V) have been observed in the Lidoped (Ba, Ca)(Ti, Zr)O 3 ceramics at low sintering temperature (1350°C/2 h). The significant enhancement in materials properties is ascribed to the multiphase region around room temperature induced by Li-doped effect.