We investigate quadratic solitons consisting of fundamental waves and oscillatory second harmonics, which can be stable when subject to boundary confinement. A family of quadratic solitons whose fundamental waves can be monopole, dipole, or even multipole are found numerically. The existence of solitons, depending on the sample size and degree of nonlocality, are given for strongly, generally, and weakly nonlocal cases, respectively.

A compact ultra-wideband circularly polarized crossed-dipole antenna with post fence and parasitic elements is proposed in this paper. The proposed antenna consists of two dipoles with unequal semi-ellipses, four symmetrical rectangular patches, and a post fence structure. Two vacant-quarter rings are utilized to provide the 90° phase difference for feeding the cross-arranged dipoles. Wide axial ratio bandwidth (ARBW) is achieved by employing a metal pillar-back cavity through the introduction of five cavity modes, while also compacting the overall antenna structure. Four sequential rotating patches are positioned along the substrate edges to improve the axial ratio at higher frequencies. The proposed antenna exhibits an impedance bandwidth (IBW) from 0.87 to 3.17 GHz and an axial ratio bandwidth (ARBW) from 0.98 to 2.99 GHz. This indicates that the overlapped IBW and ARBW reaches 101.3%. Moreover, the overall dimensions of the proposed antenna are 0.52×0.83×0.17•L3 corresponding to the lowest operating frequency, showing that it has great potential in wireless communications.

The application of hyperspectral image (HSI) clustering has become widely used in the field of remote sensing. Traditional fuzzy K-means clustering methods often struggle with HSI data due to the significant levels of noise, consequently resulting in segmentation inaccuracies. To address this limitation, this letter introduces an innovative outlier indicator-based projection fuzzy K-means clustering (OIPFK) algorithm for clustering of HSI data, enhancing the efficacy and robustness of previous fuzzy K-means methodologies through a two-pronged strategy. Initially, an outlier indicator vector is constructed to identify noise and outliers by computing the distances between each data point in a reduced dimensional space. Subsequently, the OIPFK algorithm incorporates the fuzzy membership relationships between samples and clustering centers within this lower-dimensional framework, along with the integration of the outlier indicator vectors, to significantly mitigates the influence of noise and extraneous features. Moreover, an efficient iterative optimization algorithm is employed to address the optimization challenges inherent to OIPKM. Experimental results from three real-world hyperspectral image datasets demonstrate the effectiveness and superiority of our proposed method.

An ultra-wideband H-plane horn antenna excited by modified double-sleeve monopole is proposed in this paper. Two sets of circularly arranged metallic posts around the feeding probe are employed to form a double-sleeve structure for the bandwidth enhancement purpose. Three pairs of posts are utilized in the waveguide to achieve the higher-order modes suppression and impedance matching improvement. A tapered horn aperture is mainly employed to smoothen the transition between the waveguide and free space for improving the impedance matching. Additionally, corrugated surface is designed at the horn aperture to improve the E-field distribution at high frequencies and achieve better front-to-back ratio. The proposed antenna demonstrates nearly end-fire radiation within the entire frequency band from 2.08 to 9.3 GHz with |S11| < -10 dB, indicating that an ultra-wideband of 126.8% is obtained. The proposed structure features a compact size of 0.52×0.83×0.17•L3 corresponding to the lowest operating frequency, which is promising for platform-mounted applications.

The hole mobility enhancement mechanism of wurtzite (0001)-oriented gallium nitride (GaN)/AlN heterojunction quantum well (QW) under stress engineering is investigated to overcome the low hole mobility, which is considered to be the fundamental obstacle toward the realization of GaN-based complementary electronics. The hole mobility model is obtained by the six-band stress-dependent $\textit{k}$ $\times$ $\textit{p}$ Hamiltonian and the Kubo–Greenwood formula, taking the scattering rates of acoustic phonon, polar optical phonon, and surface roughness into account. Using these methods, the microscopic relationship between stress and hole mobility can be predicted according to the variation of 2-D valence subband dispersion. We demonstrate that the biaxial tensile stress is not a desirable way in the hole mobility enhancement because a large compressive strain induced by the pseudomorphic GaN/AlN heterointerface has to be overcome. We also find that due to the efficient achievements in both effective mass reduction and hole scattering suppression, the uniaxial compressive stress along the current channel and the uniaxial tensile stress perpendicular to the current channel can increase the hole mobility significantly. Under the combined effect of these two 8 GPa non-exclusive mechanisms, a sevenfold mobility enhancement can be obtained, up to the theoretical value of 190 cm $^{\text{2}}$ /Vs at room temperature.