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At present, wearable electronic sensors are widely investigated and applied for human life usage especially for the flexible piezoelectric sensor based on piezoelectric fibers. However, most of these fiber-based piezoelectric sensors are thin films, which might had poor air permeability, or do not adapt to complex body movements. In this study, a piezoelectric sensing fabric was proposed based on core-spun Cu/P(VDF-TrFE) nanofibrous yarns. These yarns were fabricated by P(VDF-TrFE) as a piezoelectric material and Cu wire as an inner electrode layer through a one-step conjugate electrospinning process. The Cu/ P(VDF-TrFE) fabrics showed good flexibility, breathability, mechanical stability, and sensing capability after continuous running for 60 min or after washing. A 4 cm × 4 cm fabric could generate a current of 38 nA and voltage of 2.7 V under 15 N pressure. Once the fabric was fixed onto the clothes, human motion could be monitored by collecting its generated current, and the signal could be wirelessly transmitted onto a smartphone. Therefore, this study may provide a simple and promising approach to design a smart textile for human motion monitoring.

Asingle software framework is introduced to evaluate numerical accuracy of theA-grid (NICAM) versus C-grid (MPAS) shallow-water model solvers on icosahedral grids. The C-grid staggering scheme excels in numerical noise control and total energy conservation, which results in exceptional long-time integration stability. Its weakness lies in the lack of model error reduction with increasing resolution in specific test cases (especially the root-mean-square error). The A-grid method conserves well potential enstrophy and shows a linear reduction of error with increasing resolution. The grid point noise manifests itself clearly on A-grid, much less on C-grid. We show that the Coriolis force term on C-grid has a larger error than on A-grid. To treat the Coriolis term and kinetic energy gradient on an equal footing on C-grid, we propose combining these two terms for a linear combination operation. This modification alone reduces numerical errors, but still fails to converge the maximum error with resolution. The method of Peixoto (2016) can solve the maximum-error non-convergence problem on C-grid, but degrades the numerical stability. For the steady-state thin layer test (0.01 m in depth), the A-grid method is less susceptible than C-grid methods, which are presumably disrupted by the Hollingsworth instability. The effect of horizontal diffusion on model accuracy and energy conservation is shown in detail. Programming experience shows that software implementation and optimization can strongly influence model performance, although memory requirement and computational load of the two schemes are comparable.

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We investigate the temperature dependence of current-voltage and spectral response characteristics of a 4H-SiC metal-semiconductor-metal (MSM) ultraviolet photodetector in the temperature range from room temperature to 800 K with two-dimensional (2D) numerical simulator ISE-DESSIS. It is found that the dark current and photocurrent increase with the increasing temperature. For the range of 500-800 K, the dark current increases by nearly a factor 3.5 every 150 K larger than that of photocurrent, leading to a negative effect on photodetector current ratio (PDCR). Nevertheless, the PDCR is still greater than 200 even at 800 K, which exhibits the excellent thermal stability. In addition, the responsivity has an unsymmetrical trend. As temperature rises, it is clear that a remarkable red-shift of 12 nm occurs and overall responsivity is enhanced for longer wavelength. While the short-wavelength response remains relatively independent of temperature. The mechanism of indirect and direct band absorption transition is responsible for temperature-dependent spectrum distribution. These findings provide a significant insight on the design of the MSM detector operated at elevated temperature. silicon carbide, ultraviolet photodetector, temperature dependence Citation:Chen B, Yang Y T, Xie X R, et al. Analysis of temperature-dependent characteristics of a 4H-SiC metal-semiconductor-metal ultraviolet photodetector. Chin Sci Bull, 2012Bull, , 57: 44274433, doi: 10.1007 In despite of having an indirect bandgap, silicon carbide (SiC) has emerged as an appropriate material for the fabrication of ultraviolet (UV)/visible optoelectronic devices over the last few years due to the available substrates [1], the lower defect density and a more mature process technology [2]. Typically, 4H-SiC based UV photodetectors achieve photosensitivity spectrum of 220-380 nm and peak responsivity at around 290 nm. Photodetectors based on Schottky contacts have an enhanced sensitivity to shorter wavelength radiation as well as a reduced response time as no minority carriers are involved [3]. Especially, the metalsemiconductor-metal (MSM) photodetectors possess potential merits of large device bandwidth, small intrinsic capacitance, and sub-nanosecond response time. Whilst the planar process of MSM detectors may be accomplished with as little as one photolithography step and allows their monolithic integration with other optical and electronic circuits [4]. Recent achievements include nano-structured MSM photodetector with high peak voltage [5], MSM solar-blind photodetector with fast rise and decay times of 10 ns and 150 ns [6], high responsivity MSM photodetector with 26000 A/W at 8 V bias via a carrier-trapping process [7]. More recently, MSM UV detectors exhibit UV-photo generated current to dark current ratio up to 1.34×10 8 with colloidal nanoparticles [8], realize a photocurrent gain around 40 at 2 V bias using CaF 2 as the insulator [9], and achieve a very low dark current density of 3.84 nA/cm 2 at 5 V bias based on sol-gel-derived TiO 2 f...