Medical image fusion plays an important role in clinical applications, such as imageguided surgery, image-guided radiotherapy, non-invasive diagnosis and treatment planning. Shearlet is a novel multi-scale geometric analysis (MGA) tool proposed recently. In order to overcome the drawback of the shearlet-based fusion methods that the pseudo-Gibbs phenomenon is easily caused around the singularities of the fused image, a new multi-modal medical image fusion method is proposed in shift-invariant shearlet transform domain. First, the original images are decomposed into lowpass sub-bands and highpass sub-bands; then, the lowpass sub-bands and high sub-bands are combined according to the fusion rules, respectively. All the operations are performed in shift-invariant shearlet domain. The final fused image is obtained by directly applying inverse shift-invariant shearlet transform to the fused lowpass sub-bands and highpass sub-bands. Experimental results demonstrate that the proposed method can not only suppress the pseudo-Gibbs phenomenon efficiently, but perform better than the popular wavelet transform-based method, contourlet transform-based method and nonsubsampled contourlet transform-based method.

In this letter, the degradation and recovery characteristics of E-mode AlGaN/GaN high-electron mobility transistors (HEMTs) were investigated under repetitive short-circuit (SC) stress. Output, transfer, transconductance and gate-leakage characteristics were analyzed in detail before and after repetitive SC stress. After stress, the electrical characteristics of the devices gradually degraded as the SC pules increased. Low-frequency noise measurements are performed over the frequency range of 1 Hz–10 KHz by increasing SC pulses. Furthermore, the recovery tendency of DC characteristics and trap density is observed between repetitive SC measurements, and this physically confirms that the mechanism of the performance degradation could be attributed to the trapping and releasing processes of electrons in the p-GaN layer and AlGaN barrier layer of AlGaN/GaN HEMTs, which change the electric field distribution under the gate.

Using the argon ion-beam sputtering technique, 0.5, 1 or 2 µm of Ba 1−x La x Nb y Ti 1−y O 3 (x = 0.25%, y = 0.25%) film was deposited on a SiO 2 /Si substrate to make metal-insulator-semiconductor capacitors. The dependence of the humidity sensitivity of the device on the film thickness was studied. The sensor with the 0.5 µm film was nine times more sensitive than that with the 2 µm film. The results are explained by the porosity and pore-volume distribution of the films, which were extracted from the device capacitance at different relative humidities based on a physical model. The thinner the thin film, the higher was the porosity, and thus the higher was the sensitivity of the device to humidity. Compared with the porosity, the pore-volume distribution hardly affected the humidity sensitivity because the fractions of pores with radii smaller than 50 Å were almost the same (∼70%) for the three film thicknesses.

No abstract

The optical characteristics of barium-strontium titanate-niobate (Ba 1−x Sr x Nb y Ti 1−y O 3 ) thin-film resistor are investigated and the effects of annealing gas and annealing temperature on photoelectrical properties are studied. Experimental results show that Ba 1−x Sr x Nb y Ti 1−y O 3 thin films are highly sensitive not only to visible light, but also to ultraviolet light. As compared to N 2 -annealed devices, O 2 -annealed devices have higher photosensitivity and lower dark current. Moreover, the photosensitivity of the O 2 -annealed devices is reduced for higher annealing temperature. Based on scanning electron microscope (SEM) study and grain-boundary theory, it can be concluded that 400 • C in O 2 is the optimal annealing condition, which can give a photosensitivity as high as 8400% to visible light and 5500% to ultraviolet light.