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Class imbalance and noisy data widely exist in real-world problems, and the support vector machine (SVM) is hard to construct good classifiers on these data. Fuzzy SVMs (FSVMs), as variants of SVM, use a fuzzy membership function both to reflect the samples’ importance and to remove the impact of noises, and employ cost-sensitive technology to address the class imbalance. They can handle the noise and class imbalance problems in many cases; however, the fuzzy membership functions are often affected by the class imbalance data, leading to inaccurate measures for samples’ performance and affecting the performance of FSVMs. To solve this problem, we design a new fuzzy membership function and combine it with cost-sensitive learning to deal with the class imbalance problem with noisy data, named Slack-Factor-based FSVM (SFFSVM). In SFFSVM, the relative distances between samples and an estimated hyperplane, called slack factors, are used to define the fuzzy membership function. To eliminate the impact of class imbalance on the function and gain more accurate samples’ importance, we rectify the importance according to the positional relationship between the estimated hyperplane and the optimal hyperplane of the problem, and the slack factors of samples. Comprehensive experiments on artificial and real-world datasets demonstrate that SFFSVM outperforms other comparative methods on F1, MCC, and AUC-PR metrics.

All-solid-state batteries greatly rely on high-performance solid electrolytes. However, the bottlenecks in solid electrolytes are their low ionic conductivity and stability. Here we report a new series of amorphous xAgI·(1-x)Ag3PS4 (x = 0~0.8 with interval of 0.1) conductors, among which the sample with x = 0.8 exhibits the highest ionic conductivity (about 1.1 × 10-2 S cm-1) and ultrahigh chemical stability. We discovered the existence of mixed disordered Ag3PS4 and AgI clusters in the amorphous conductors using solid-state nuclear magnetic resonance spectroscopy. The high ionic conductivity was ascribed to the formation of the interconnecting AgI clusters, i.e., the percolative channels for superionic conduction. The composition dependence of the ionic conductivity for this series of amorphous conductors was clarified by a continuum percolation model. These findings provide fundamental guidance for designing and fabricating high-performance amorphous solid electrolytes for all-solid-state batteries.

In this paper, η-biharmonic hypersurfaces with constant scalar curvature in 5-dimensional pseudo-Riemannian space forms are studied. We prove that such hypersurfaces with diagonalizable shape operator have constant mean curvature, which gives an affirmative partial answer to the conjecture in [Arvanitoyeorgos, A.—Kaimakamis, F. G.: Hypersurfaces of type $\begin{array}{} \displaystyle M^3_2 \end{array}$ in $\begin{array}{} \displaystyle \mathbb{E}^4_2 \end{array}$ with proper mean curvature vector, J. Geom. Phys. 63 (2013), 99–106]. As a result, we give several partial classification results.

Understanding the role of network formers in affecting the electrochemical performances of the glass anodes for Li-ion batteries (LIBs) is of great importance for developing novel glass anode materials. In this work, we substitute the network former P2O5 for partial amount of TeO2 in V2O5-TeO2 glass composition and probe the effect of this substitution on both the microstructure and performances of the LIB anodes. The network structure of the glass before and after discharging/charging cycles is revealed at atomistic level by advanced Solid-State Nuclear Magnetic Resonance spectroscopy and X-ray photoelectron spectroscopy. The results show that, upon the insertion/extraction of Li+ ions, the structural network of the glass anode is irreversibly disassociated into many short polyhedral species that congregate to form different kinds of nanoclusters. The substitution of P2O5 for TeO2 promotes the formation of Li2Te and the reduction of V5+ to V4+, and thereby enhances the capacity of the glass anodes.

Fluorophosphate glass-ceramics containing Ba2LaF7:Er3+ nanocrystal upconversion-luminescent materials were prepared via a melt-quenching method, followed by heat treatment. The glass structure evol...

We studied the effect of silicon doping on the structure and crystallization behavior of 50V2O5-50TeO2 (mol%) (VT) glass by performing solid-state nuclear magnetic resonance (NMR), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and differential scanning calorimetry (DSC). We observed two interesting phenomena. First, when the mixture of glass and Si is heated in argon to 560 K (1.1Tg), Si starts to react with VT glass and is oxidized to amorphous silica, being confirmed by NMR and FTIR. Second, Si suppresses the formation of the Te2V2O9 phase in VT glass during heating process up to 650 K (about 1.3Tg), whereas it leads to the formation of the new crystalline phase TeVO4 during heating to 725 K (1.4Tg). We discuss the origin of these two phenomena by considering the changes both in glass structure and in the redox reaction.

We prepared four Er3+-Yb3+ co-doped oxyfluoride precursor glass (PG) samples with the same chemical composition at different melt-homogenization temperatures (Thomo), respectively, at the same melt-quenching rate. We investigated the effect of Thomo and heat-treatment (HT) on the crystallization, structure, and optical properties of the four samples. The results show that the structural heterogeneity in the PG sample increases with lowering Thomo, and this promotes phase-separation, and hence, formation of Ba2LaF7 crystals. Consequently, the light transmittance of PG samples is decreased, but the up-conversion (UC) luminescence is enhanced. Moreover, the crystallinity of the four PG samples was increased by HT, and this altered the light transmittance, and greatly enhanced the UC luminescence. The mechanism of these discovered phenomena was discussed in terms of structure and crystal evolution. This work provides an effective way to optimize the optical and photonic performances of the rare earth doped oxyfluoride glass-ceramics.

It is known that the optical transparency of an oxide glass decreases with an increase in the size and fraction of crystals in the glass during heat-treatment. Here, the authors report an opposite scenario, where a translucent Er3+−Yb3+ doped oxyfluoride precursor glass-ceramic (P-GC) becomes transparent with increasing crystal size and crystallinity. Specifically, in the heat-treated P-GC samples, the authors observe that the growth of the existing Ba2LaF7 crystals and particularly the formation of small spherical Ba2LaF7 crystals greatly enhanced the light transmittance. To reveal the origin of this anomalous phenomenon, the authors perform detailed morphology and structure analyses on both P-GC and the heat-treated P-GC samples and molecular dynamics simulations of the precursor glass. The results show that the composition of the residual glass phase is altered (e.g., depletion of La3+) in the way that the differences in refractive index between the glass matrix and the crystals are greatly reduced. As a consequence, the light scattering of the heat-treated P-GC is suppressed, and hence, the derived P-GC becomes transparent. In addition, a proper heat-treatment can also enhance the luminescence of the studied P-GC system.

Highly Yb-doped silica glass with low refractive index for fabrication of Yb-doped large-mode-area photonic crystal fiber (LMA PCF) is in favor of decreasing fiber length and thus increasing the threshold of nonlinear effects in pulse laser amplification. Accordingly, fluorine incorporation in highly Yb-doped silica glass is vitally important to compensate the sharp increase in refractive index caused by ytterbium and aluminum ions. In this work, the fluorine doping concentration in Yb/Al/P/F co-doped silica glass was significantly improved by a modified sol-gel method combined with high temperature sintering. The effects of fluorine doping on glass structure have been investigated in details by Raman spectra, nuclear magnetic resonance (NMR) and advanced pulse electron paramagnetic resonance (EPR) measurements. The incorporation of fluorine yields Si-F bonds and Yb-F bonds formation and leads to the mild change in spectroscopic properties. An optimized silica core glass rod with high Yb (0.77 wt.%) and fluorine (0.8 wt.%) doping concentration, low refractive index and acceptable optical quality was prepared. Based on the highly fluorine and ytterbium doped silica core glass, a polarization maintaining (PM) photonic crystal fiber with 40 µm core was prepared and the pump absorption coefficient at 976 nm was ∼6.5 dB/m. An average amplified power of 103 W was achieved from a 2-m-long PCF with the bend diameter of 23 cm. The slope efficiency (with respect to pump power) was 52% with laser beam quality factor M2 of 1.46.