Use of Mesoscopic Host Matrix to Induce Ferrimagnetism in Antiferromagnetic Spinel Oxide

Despite the advances in the methods for fabricating nanoscale materials, critical issues remain, such as the difficulties encountered in anchoring, and the deterioration in their stability after integration with other components. These issues need to be addressed to further increase the scope of their applicability. In this study, using epitaxial mesoscopic host matrices, materials are spatially confined at the nanoscale, and are supported, anchored, and stabilized. They also exhibit properties distinct from the bulk counterparts proving their high quality nanoscale nature. ZnFe₂O₄ and SrTiO₃ are used as the model confined material and host matrix, respectively. The ZnFe₂O₄ phases are spatially confined by the SrTiO₃ mesoscopic matrix and have strongly enhanced ferrimagnetic properties as compared to bulk and plain thin films of ZnFe₂O₄, with a Curie temperature of ≈500 K. The results of a series of control experiments and characterization measurements indicate that cationic inversion, which originates from the high interface‐to‐volume ratio of the ZnFe₂O₄ phase in the ZnFe₂O₄–SrTiO₃ nanocomposite film, is responsible for the magnetization enhancement. An exchange bias is observed, owing to the coexistence of ferrimagnetic and antiferromagnetic regions in the confined ZnFe₂O₄ phase. The magnetic properties are dependent on the ZnFe₂O₄ crystallite size, which can be controlled by the growth conditions.     

Free-Standing β-Ga<Subscript>2</Subscript>O<Subscript>3</Subscript> Thin Diaphragms

Free-standing, very thin, single-crystal β-gallium oxide (β-Ga₂O₃) diaphragms have been constructed and their dynamical mechanical properties characterized by noncontact, noninvasive optical measurements harnessing the multimode nanomechanical resonances of these suspended nanostructures. We synthesized single-crystal β-Ga₂O₃ using low-pressure chemical vapor deposition (LPCVD) on a 3C-SiC epilayer grown on Si substrate at temperature of 950°C for 1.5 h. The synthesized single-crystal nanoflakes had widths of ～ 2 μm to 30 μm and thicknesses of ～ 20 nm to 140 nm, from which we fabricated free-standing circular drumhead β-Ga₂O₃ diaphragms with thicknesses of ～ 23 nm to 73 nm and diameters of ～ 3.2 μm and ～ 5.2 μm using a dry stamp-transfer technique. Based on measurements of multiple flexural-mode mechanical resonances using ultrasensitive laser interferometric detection and performing thermal annealing at 250°C for 1.5 h, we quantified the effects of annealing and adsorption of atmospheric gas molecules on the resonant characteristics of the diaphragms. Furthermore, we studied the effects of structural nonidealities on these free-standing β-Ga₂O₃ nanoscale diaphragms. We present extensive characterization of the mechanical and optical properties of free-standing β-Ga₂O₃ diaphragms, paving the way for realization of resonant transducers using such nanomechanical structures for use in applications including gas sensing and ultraviolet radiation detection.     

系列程控真空计

本文概述了近几年迅速发展的由单片机控制的真空计的结构原理以及它的功能。     

水平路径上多帧湍流退化图像重建

为了重建水平路径上远距离成像系统获取的湍流退化图像,提出去除形变和振铃的分块多帧盲反卷积方法.首先按采集的顺序将图像序列分成若干图像组,通过B-spline基函数配准方法去除非等晕块之间的形变,第二步通过基于块的时域融合算法去除等晕块间的振铃,得到衍射受限的湍流退化图像,最后将所得的多帧图像进行频域重建,复原高质量图像.实验表明,所提出的算法适合于水平路径上获取的退化图像的重建,得到较高的主观视觉图像质量.     

Directly assembled quantum dots on one dimension ordered TiO2 nanostructure in aqueous solution for improving photocatalytic activity

One dimension (1D) ordered titanium dioxide (TiO2) nanostructured photocatalysts sensitized by quantum dots (QDs) are fabricated. Their morphologies, crystal structures and photocatalytic properties are characterized by scanning elec-tron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and ultraviolet-visible-near infrared (UV-vis-NIR) absorption spectroscopy, respectively. Compared with the original TiO2 nanostructure, the nanostructured TiO2 sensitized by QDs exhibits a good photocatalytic activity for the degradation of methyl orange (MO). The QDs with core-shell structure can reduce the photocatalytic ability due to the higher potential barrier of carrier transport in ZnS shell layer. The results indicate that the proposed photocatalyst shows promising potential for the application in organic dye degradation.     

光纤通信发展动向

本文对光纤通信在今后３－５年内的发展动向作简要论述。 着重在工程建设应用．特别是Ｏ－ＷＤＭ（Ｏｐｔｉｃａｌ Ｗａｖｅｌｅｎｇｔｈ Ｄｉｖｉｓｉｏｎ　 Ｍｕｌｔｉｐｌｅｘ简称ＷＤＭ）的技术突破后引起的新发展。     

UC3854的最小输出脉宽问题

在功率因数校正电路中,当负载很轻时,在时会出现ＵＣ３８５４的输出脉冲宽度不能相应减小,导致输出电压升,本文通过实验进行了细致的研究,认为是电流运放的输入失调电压所致,据此提出了补救措施,并由实验证明有效可行。     

开拓信息市场 建设“首都信息化工程”

北京是全国政治，经济，文化的中心，更是全国重要的信息中心、在国民经济信息化中起着举足轻重的作用。北京电信作为“首都信息化工程”的重要参与者和建设者，在研究市场，开拓信息，推动计算机互联网络和信息产业的发展主主动出击，做了一些有益的努力和尝试，在促进计算机互联网应用，发展北京信息产业方面，取得了明显的社会效益。     

光学和传感器的防护技术

近年来，光电技术发展异常迅速，在这些技术装备中，当用光学聚焦时，辐射能量对光学元件、探测器都会构成威胁。本文讨论辐射对光学和探测器的影响以及降低其影响的防护技术。     

A low-loss V-groove coplanar waveguide on an SOI substrate

eguide causes about 50% less loss than the conventional one at a high frequency of up to 40 GHz.