In this letter, the design of reflective frequency selective surface (RFSS) using low-permittivity dielectrics is proposed based on effective medium theory. The effective medium approach is based on quasi-static extension of the Maxwell-Garnett model. Unlike conventional RFSSs, such RFSS is composed of low-permittivity dielectrics rather than high-permittivity or metallic materials. By drilling periodic hole arrays in multi-layer continuum dielectric plates, strong electric and magnetic resonances are introduced to produce drastic changes in effective parameters, leading to impedance mismatch and band-stop response. The band-stop response can be tailored by adjusting the size and spacing of the unit cell. As an example, an RFSS with rectangular hole element is demonstrated at K-band. The mechanism is analyzed by presenting the effective electromagnetic parameters and dynamic field distributions. A prototype was fabricated and measured. Excellent agreements between measured and simulated results were obtained. The method can also be used to design RFSS in THz and optical frequencies.

In this paper, we demonstrate a dual-band bandpass all-dielectric frequency selective surface (FSS), the building elements of which are high-permittivity ceramic particles rather than metallic patterns. With proper structural design and parameter adjustment, the resonant frequency can be tuned at will. Dual-band bandpass response can be realized due to the coupling between electric and magnetic resonances. As an example, a dual-band bandpass FSS is designed in Ku band, which is composed of two-dimensional periodic arrays of complementary quatrefoil structures (CQS) cut from dielectric plates. Moreover, cylindrical dielectric resonators are introduced and placed in the center of each CQS to broaden the bandwidth and to sharpen the cut-off frequency. Theoretical analysis shows that the bandpass response arises from impedance matching caused by electric and magnetic resonances. In addition, effective electromagnetic parameters and dynamic field distributions are presented to explain the mechanism of impedance matching. The proposed FSS has the merits of polarization independence, stable transmission, and sharp roll-off frequency. The method can also be used to design all-dielectric FSSs with continuum structures at other frequencies.

Most of the existing research papers study the emotion recognition of Minnan songs from the perspectives of music analysis theory and music appreciation. However, these investigations do not explore any possibility of carrying out an automatic emotion recognition of Minnan songs. In this paper, we propose a model that consists of four main modules to classify the emotion of Minnan songs by using the bimodal data—song lyrics and audio. In the proposed model, an attention-based Long Short-Term Memory (LSTM) neural network is applied to extract lyrical features, and a Convolutional Neural Network (CNN) is used to extract the audio features from the spectrum. Then, two kinds of extracted features are concatenated by multimodal compact bilinear pooling, and finally, the concatenated features are input to the classifying module to determine the song emotion. We designed three experiment groups to investigate the classifying performance of combinations of the four main parts, the comparisons of proposed model with the current approaches and the influence of a few key parameters on the performance of emotion recognition. The results show that the proposed model exhibits better performance over all other experimental groups. The accuracy, precision and recall of the proposed model exceed 0.80 in a combination of appropriate parameters.

In this paper, we simulate and experimentally validate a polarization-independent transmission absorption metamaterial absorber based on electromagnetic resonance. The metamaterial absorber can absorb the high-frequency electromagnetic wave, and the low-frequency wave can transmit through the absorber. The tested results indicate that the metamaterial absorber can achieve a narrow bandwidth high absorption with a peak absorption of 83.6% at 6.77 GHz, and a full width at half maximum (FWHM) of 4.3%. To further broaden the absorption bandwidth of the resonant metamaterial absorber, we place two absorbers with different working frequencies together for its low-frequency transmitted characteristic. The measured data show that the composite metamaterial absorber can increase the FWHM to 10.9%, and can enhance the absorption slightly. The metamaterial absorber has some advantages, such as simple design, strong practicability, and important application foreground.