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The gas-sensing performance of PbSnS2 monolayer to sulfur hexafluoride (SF6) decompositions (SO2, H2S, HF, SOF2, and SO2F2) has been systematically studied by density functional theory and nonequilibrium Green’s function calculations. The most stable adsorption configurations, adsorption energies, charge transfer, electron localization function (ELF), density of states (DOS), and ${I}$ – ${V}$ curves of gas molecules on PbSnS2 are calculated and discussed. SO2 exhibits the largest adsorption energy of −0.74 eV with the charge transfer of −0.39 e and HF possesses the biggest charge transfer of −0.66 e with the adsorption energy of −0.46 eV. The results of ELF and DOS show that the interaction between SO2 and PbSnS2 may be stronger than those of other gases. Moreover, ${I}$ – ${V}$ curves show that the responses of PbSnS2 to SO2 is up to 65.5% at the bias of 2.2 V. Therefore, PbSnS2 monolayer may be a qualified material for detecting SF6 decompositions.

It is found that many two-dimensional materials are easy to obtain out-of-plane piezoelectric properties because of their Janus structure. Here, based on the monolayer GeSe and SnSe, we study the electronic structure and piezoelectricity of the Janus M2SeX (M=Ge, Sn; X=S, Te) monolayers. Due to the lack of inversion symmetry and mirror symmetry, as well as flexible mechanical properties, the 2D Janus M2SeX monolayers have large in-plane piezoelectric coefficients d11 (up to 345.08pm/V) and out-of-plane piezoelectric coefficients d31 (up to 3.83pm/V). All energy band structures of two-dimensional (2D) Janus M2SeX monolayers show indirect bandgap and Zeeman-type spin splitting after considering spin orbit coupling (SOC). The lack of mirror symmetry leads to out-of-plane spin polarization. In addition, the calculation based on the deformation potential theory shows that the 2D Janus M2SeX monolayers have high carrier mobility. The large piezoelectric properties and high carrier mobility show the application potential of 2D Janus M2SeX monolayers in flexible electronic devices and piezoelectric devices.

Sintered Cu is considered as the most promising strategy in die-attachment, since its capacities of low-temperature bonding and high-temperature working. Many studies have reported the excellent properties of sintered Cu, but there is still some room for improvement. Here, strong Cu–Cu joints and insulated-gate bipolar transistor (IGBT) devices are achieved by sintering Cu paste and three composite pastes, and the mechanical, electrical, and microstructure properties of joints are investigated. The shear strength of pure Cu bonded joint is 23.4 MPa, which is improved to 26.64 MPa by introducing 0.6 wt% N-doped multi-walled carbon nanotubes (N-doped MWCNTs) into Cu paste. Excellent electrical properties are achieved as the resistivities of sintered Cu/N-doped MWCNTs layer and Cu/carboxylated WMCNTs are 2.252 and 2.551 μ Ω·cm, respectively, which are lower than the sintered pure Cu layer (3.473 μ Ω·cm). In addition, the functionalized MWCNTs are found exerted positive effects on the joint reliability. The enhancements on the joint qualities are attributed to that the functionalized MWCNTs improve the affinity of the Cu and CNTs and increase the density of bonding layer. This article provides an effective way to improve the sintered Cu joints sintering qualities, which is suitable for the attachment of next-generation devices and substrates.

We propose a high-resolution static-strain sensor based on a π-phase-shifted Bragg grating (π-FBG) combined with a wavelet threshold denoising algorithm. The Pound–Drever–Hall (PDH) technique based on a narrow-linewidth fiber laser is used to interrogate the sensor. A reference FBG-based Fabry–Perot interferometer (FBG-FP) is used to compensate the temperature and laser source frequency fluctuation. As the reflect spectrums of π-FBG have a higher SNR than FBG-FP, the SNR of PDH signals from FBG-FP and π-FBG is increased from 18.1 to 35.6 dB. Wavelet threshold denoising algorithm is used to further improve the SNR of the PDH signals (about 8 dB). As a result, a static-strain resolution of 1.0 ne is obtained in the laboratory test.

Static-strain can be detected by measuring a cross-correlation of two FBG-based Fabry-Perot interferometers (FBG-FPs). This letter addresses applying the wavelet transform to cross-correlation processing in noise-contaminated FBG-FP reflection spectrums for crust deformation measurement. Since the wavelet transform has a unique feature of varying time-frequency resolution, cross-correlation processing in the wavelet domain is more robust with correlated noise and window size and is less sensitive to nonstationary data. We discuss the experimental results in respect of the factors that could influence the sensor resolution. In addition, a staticstrain resolution of 1.3 n\(\varepsilon \) , higher than conventional cross-correlation method is obtained in the laboratory test by using this technique.

The fast Fourier transform (FFT) cannot be directly used in the harmonic analysis of an electric power system because of its higher errors, especially the phase error. This paper discusses the leakage phenomenon of FFT and presents a new amending algorithm, poly-item cosine window interpolation, which is based on the interpolating algorithm proposed by V. Jain and T Grandke. This new algorithm improves the accuracy of the FFT, so it can be applied to the precision analysis for electrical harmonics. The simulation result shows that applying different windows has different effects on the accuracy, and the Blackman-Harris window has the highest accuracy.