TiO2 Nanotube Array/Monolayer Graphene Film Schottky Junction Ultraviolet Light Photodetectors

Schottky junctions made from a titanium dioxide nanotube (TiO₂NT) array in contact with a monolayer graphene (MLG) film are fabricated and utilized for UV light detection. The TiO₂NT array is synthesized by the anodization and the MLG through a simple chemical vapor deposition process. Photoconductive analysis shows that the fabricated Schottky junction photodetector (PD) is sensitive to UV light illumination with good stability and reproducibility. The corresponding responsivity (R), photoconductive gain (G), and detectivity (D*) are calculated to be 15 A W^?1, 51, and 1.5 × 10¹² cm Hz^1/2 W^?1, respectively. It is observed that the fabricated PD exhibits spectral sensitivity and a simple power‐law dependence on light intensity. Moreover, the height of the Schottky junction diode is derived to be 0.59 V by using a low temperature I–V measurement. Finally, the working mechanism of the TiO₂NT array/MLG film Schottky junction PD is elucidated.     

Tribological Behavior of Multiply-Alkylated Cyclopentanes (MACs)-Cu Nanoparticles Composite Thin Film

Multiply-alkylated cyclopentanes (MACs) composite thin films containing Cu nanoparticles are fabricated on the octadecyltrichlorosilane (OTS)-modified substrate by a spin-coating technique. The thickness, wetting behavior, and nanoscale morphologies of the films are characterized by means of ellipsometry, contact angle measurement, and atomic force microscope (AFM). The friction and wear behaviors of the thin films sliding against Si₃N₄ ball are examined on a UMT-2MT tribometer in a ball-on-disk contact mode. The worn surfaces of the OTS-MAC-Cu composite film and the counterpart Si₃N₄ balls are investigated with a scanning electron microscope. Water contact angle on OTS-MAC-Cu composite film is higher than that of OTS-MAC film. OTS-MAC-Cu composite film exhibits higher load-carrying capacity and better friction reduction and antiwear behavior as compared with OTS-MAC film. This may be attributed to the load-carrying and self-repairing property of the Cu nanoparticles in the composite film and the formation of a transfer layer composed of OTS, MAC, and Cu on the rubbing surface of the counterpart ball.     

Image denoising using trivariate prior model in nonsubsampled dual-tree complex contourlet transform domain and non-local means filter in spatial domain

Image denoising is always the basic problem of image processing, and the main challenge is how to effectively remove the noise and preserve the detailed information. This paper presents a new image denoising algorithm based on the combination of trivariate prior model in nonsubsampled dual-tree complex contourlet transformlet transform (NSDTCT) domain and non-local means filter (NLMF) in spatial domain. Firstly, NSDTCT is constructed by combining the dual-tree complex wavelet transform (DTCWT) and nonsubsampled directional filter banks (NSDFB). The noisy image is decomposed by using NSDTCT. Secondly, based on the correlation between the interscale and intrascale dependencies of NSDTCT coefficients, the distribution of the high frequency coefficients is modeled with the trivariate non-Gaussian distribution model. A nonlinear trivariate shrinkage function is derived in the framework of Bayesian theory, and then the denoised coefficients are obtained and inverse NSDTCT is performed to get the initial denoised image. Finally, NLMF is used to smooth the initial denoised image. Simulation experiment shows that our algorithm can obtain better performances than those outstanding denoising algorithms in terms of peak signal-to-noise ratio (PSNR), mean structural similarity (MSSIM) as well as visual quality.     

A NOTE ON REGULARITY AND EXISTENCE OF SOLUTIONS FOR A CLASS OF NON－UNIFORMLY DEGENERATE ELLIPTIC EQUATIONS

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带有随机波动率的交换期权定价

通过利用计价单位的变换及等价鞅测度,得到了在随机波动率下的交换期权定价公式.     

An improved evaluation of the neutron background in the PandaX-Ⅱ experiment

In dark matter direct detection experiments,neutron is a serious source of background,which can mimic the dark matter-nucleus scattering signals.In this paper,we present an improved evaluation of the neutron background in the PandaX-II dark matter experiment by a novel approach.Instead of fully relying on the Monte Carlo simulation,the overall neutron background is determined from the neutron-induced high energy signals in the data.In addition,the probability of producing a dark-matter-like background per neutron is evaluated with a complete Monte Carlo generator,where the correlated emission of neutron(s)andγ(s)in the(α,n)reactions and spontaneous fissions is taken into consideration.With this method,the neutron backgrounds in the Run 9(26-ton-day)and Run 10(28-ton-day)data sets of PandaX-II are estimated to be(0.66±0.24)and(0.47±0.25)events,respectively.     

绝缘环打火研究

绝缘问题是高电压、高场强器件和设备中不可回避的问题,是决定器件、设备运行参数和稳定性的重要因素。针对一台直线感应加速器调试中出现的加速腔绝缘环在带束负载情况下的真空沿面闪络现象,进行了分析和研究。分析表明,在排除设计、材料、加工、洁净和真空度等常规异常因素后,导致绝缘环真空沿面闪络的可能因素是电子在绝缘环表面的吸附和累积,绝缘环上累积的电子来源和加速器中加速、传输的电子束的丢失有关。从加速腔工作状态出发,分析绝缘环表面积累电荷和丢失电子束的相关途径,进而提出相应的技术措施,以提高加速腔运行稳定性。     

Polarization in D-shaped fiber modulated by magneto-optical dichroism of magnetic fluid

The polarization of a D-shaped fiber is modulated after immersing it in magnetic fluid(MF)and applying a magnetic field.Theoretical analysis predicts that magneto-optical dichroism of MF plays a key role in light polarization modulation.During light polarization modulation,the evanescent wave polarized parallel to the magnetic field has greater loss than its orthogonal component.Light polarization of a D-shaped fiber with a wide polished surface can be modulated easily.High concentration MF and a large magnetic field all have great ability to modulate light polarization.     

Evaluation of Charged Defect Energy in Two-Dimensional Semiconductors for Nanoelectronics: The WLZ Extrapolation Method

Defects play a central role in controlling the electronic properties of two-dimensional (2D) materials and realizing the industrialization of 2D electronics. However, the evaluation of charged defects in 2D materials within first-principles calculation is very challenging and has triggered a recent development of the WLZ (Wang, Li, Zhang) extrapolation method. This method lays the foundation of the theoretical evaluation of energies of charged defects in 2D materials within the first-principles framework. Herein, the vital role of defects for advancing 2D electronics is discussed, followed by an introduction of the fundamentals of the WLZ extrapolation method. The ionization energies (IEs) obtained by this method for defects in various 2D semiconductors are then reviewed and summarized. Finally, the unique defect physics in 2D dimensions including the dielectric environment effects, defect ionization process, and carrier transport mechanism captured with the WLZ extrapolation method are presented. As an efficient and reasonable evaluation of charged defects in 2D materials for nanoelectronics and other emerging applications, this work can be of benefit to the community.