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981.
A Tetraphenylethylene Core‐Based 3D Structure Small Molecular Acceptor Enabling Efficient Non‐Fullerene Organic Solar Cells 下载免费PDF全文
982.
983.
Multimodal medical image fusion based on discrete Tchebichef moments and pulse coupled neural network 下载免费PDF全文
Lu Tang Jiansheng Qian Leida Li Junfeng Hu Xiang Wu 《International journal of imaging systems and technology》2017,27(1):57-65
Multimodal medical image fusion plays a vital role in clinical diagnoses and treatment planning. In many image fusion methods‐based pulse coupled neural network (PCNN), normalized coefficients are used to motivate the PCNN, and this makes the fused image blur, detail loss, and decreases contrast. Moreover, they are limited in dealing with medical images with different modalities. In this article, we present a new multimodal medical image fusion method based on discrete Tchebichef moments and pulse coupled neural network to overcome the aforementioned problems. First, medical images are divided into equal‐size blocks and the Tchebichef moments are calculated to characterize image shape, and energy of blocks is computed as the sum of squared non‐DC moment values. Then to retain edges and textures, the energy of Tchebichef moments for blocks is introduced to motivate the PCNN with adaptive linking strength. Finally, large firing times are selected as coefficients of the fused image. Experimental results show that the proposed scheme outperforms state‐of‐the‐art methods and it is more effective in processing medical images with different modalities. © 2017 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 27, 57–65, 2017 相似文献
984.
985.
986.
Ferroelectric Localized Field–Enhanced ZnO Nanosheet Ultraviolet Photodetector with High Sensitivity and Low Dark Current 下载免费PDF全文
Peng Wang Yang Wang Lei Ye Mingzai Wu Runzhang Xie Xudong Wang Xiaoshuang Chen Zhiyong Fan Jianlu Wang Weida Hu 《Small (Weinheim an der Bergstrasse, Germany)》2018,14(22)
Zinc oxide (ZnO) nanosheets have demonstrated outstanding electrical and optical properties, which are well suited for ultraviolet (UV) photodetectors. However, they have a high density of intrinsically unfilled traps, and it is difficult to achieve p‐type doping, leading to the poor performance for low light level switching ratio and a high dark current that limit practical applications in UV photodetection. Here, UV photodetectors based on ZnO nanosheets are demonstrated, whose performance is significantly improved by using a ferroelectric localized field. Specifically, the photodetectors have achieved a responsivity of up to 3.8 × 105 A W?1, a detectivity of 4.4 × 1015 Jones, and a photocurrent gain up to 1.24 × 106. These device figures of merit are far beyond those of traditional ZnO ultraviolet photodetectors. In addition, the devices' initial dark current can be easily restored after continuous photocurrent measurement by using a positive gate voltage pulse. This study establishes a new approach to produce high‐sensitivity and low‐dark‐current ultraviolet photodetectors and presents a crucial step for further practical applications. 相似文献
987.
988.
采用原位自生法制备了Ti-17Al-1.5B复合材料,并用XRD、SEM对复合材料的相组成和微观组织进行了研究。结果表明:该合金由Ti3Al和TiB两相组成。初生TiB多呈较粗长的空心管状,共晶TiB呈短纤维状。根据晶体生长的固-液界面稳定性理论分析认为:TiB的B27晶体结构和晶体生长过程中的棱边效应导致初生TiB容易生长成空心管状。这是因为,在初生TiB晶体的[010]方向的固-液界面生长至一临界尺寸以后,晶面中心处因扩散受阻(热扩散和溶质扩散)而存在非常大的扩散过冷使晶面中心的台阶停止生长,这时TiB优先在棱边处长大;另外,TiB [010]方向生长速度非常快。二者的共同作用使初生TiB易于长成与 方向一致的空心管状。而共晶TiB则由于径向尺寸很小(呈纤维状),不易于长成空心管状。 相似文献
989.
CuO nanowires with high crystalline quality are synthesized via a simple thermal oxidation method. Charge conduction on individual nanowires under a transverse electric field exhibits an intrinsic p-type semiconducting behavior. Variations in signal transducer in different chemical gas environments are measured on individual CuO nanowire field effect transistors. They demonstrate good performance to both NO(2) and ethanol gasses. In particular, the nanowire chemical sensor reveals a reverse response to ethanol vapor under temperature variation. Experimental results and first-principles calculations indicate that ethanol is oxidized in air at high temperature, resulting in the production of CO(2) and H(2)O. The strong H(2)O adsorption leads to the reversal behavior, due to the electron transfer from H(2)O molecules to the CuO surface. 相似文献
990.
Investigation of small fatigue crack initiation and growth behaviour of nickel base superalloy GH4169 下载免费PDF全文
L. Zhu Z. R. Wu X. T. Hu Y. D. Song 《Fatigue & Fracture of Engineering Materials & Structures》2016,39(9):1150-1160
Surface replication method was utilized to monitor the small fatigue crack initiation and growth process of single‐edge‐notch tension specimens fabricated by nickel base superalloy GH4169. Three different stress levels were selected. Results showed that small fatigue cracks of nickel base superalloy GH4169 initiated from grain boundaries or surface inclusions. The small fatigue crack initiation and growth stages took up about 80–90% of the total fatigue life. Multiple major cracks were observed in the notch root, and specimen with more major cracks seemed to have smaller fatigue life under the same test conditions. At the early growth stage, small crack behaviour might be strongly influenced by microstructures; thus, the crack growth rates had high fluctuations. However, the stress level effect on the small fatigue crack growth rates was not distinguishable for the three different stress levels. And no clear differences were found among the crack initiation lives by using replication technique. 相似文献