退火质子交换法制作LiNbO_3光波导

文章介绍了退火质子交换机理和制作LiNbO3光波导的工艺过程。     

0.22THz折叠波导行波管放大器理论分析与数值模拟

为了解折叠波导行波管放大器的性能影响因素,在理论分析的基础上,对0.22 THz折叠波导行波管放大器进行系统的数值模拟与分析,重点讨论电子束压、束流、输入信号功率、结构周期数、材料电导率、引导磁场大小、电子能散度以及发射度对器件输出功率水平的影响.发现束压存在最佳工作范围,增加束流可以有效提高器件增益;输入信号不宜过强...     

From Geometry to Activity: A Quantitative Analysis of WO3/Si Micropillar Arrays for Photoelectrochemical Water Splitting

The photoelectrochemical (PEC) activity of microstructured electrodes remains low despite the highly enlarged surface area and enhanced light harvesting. To obtain a deeper understanding of the effect of 3D geometry on the PEC performance, well‐defined WO₃/n‐Si and WO₃/pn‐Si micropillar arrays are fabricated and subjected to a quantitative analysis of the relationship between the geometry of the micropillars (length, pitch) and their PEC activity. For WO₃/n‐Si micropillars, it is found that the photocurrent increases for WO₃/n‐Si pillars, but not in proportion to the increase in surface area that results from increased pillar length or reduced pillar pitch. Optical simulations show that a reduced pillar pitch results in areas of low light intensity due to a shadowing effect. For WO₃/pn‐Si micropillar photoelectrodes, the p–n junction enhances the photocurrent density up to a factor of 4 at low applied bias potential (0.8 V vs RHE) compared to the WO₃/n‐Si. However, the enhancement in photocurrent density increases first and then decreases with reduced pillar pitch, which scales with the photovoltage generated by the p–n junction. This is related to an increased dead layer of the p–n junction Si surface, which results in a decreased photovoltage even though the total surface area increases.     

Interfacial Strain Gradients Control Nanoscale Domain Morphology in Epitaxial BiFeO3 Multiferroic Films

Domain switching pathways fundamentally control performance in ferroelectric thin film devices. In epitaxial bismuth ferrite (BiFeO₃) films, the domain morphology is known to influence the multiferroic orders. While both striped and mosaic domains have been observed, the origins of the latter have remained unclear. Here, it is shown that domain morphology is defined by the strain profile across the film–substrate interface. In samples with mosaic domains, X‐ray diffraction analysis reveals strong strain gradients, while geometric phase analysis using scanning transmission electron microscopy finds that within 5 nm of the film–substrate interface, the out‐of‐plane strain shows an anomalous dip while the in‐plane strain is constant. Conversely, if uniform strain is maintained across the interface with zero strain gradient, striped domains are formed. Critically, an ex situ thermal treatment, which eliminates the interfacial strain gradient, converts the domains from mosaic to striped. The antiferromagnetic state of the BiFeO₃ is also influenced by the domain structure, whereby the mosaic domains disrupt the long‐range spin cycloid. This work demonstrates that atomic scale tuning of interfacial strain gradients is a powerful route to manipulate the global multiferroic orders in epitaxial films.     

关于3GPP R5核心网规划的综合思考

文章介绍了3GPP核心网的架构,并提出R5版本核心网电路域、分组域的规划方案,同时介绍了IMS的系统架构及技术特点,并就IMS的优势、存在的问题、引入策略等问题进行了探讨。     

AVS3视频编码关键技术及应用

超高清(UHD)视频能为用户带来质量更高、沉浸感更强的视觉体验,但高带宽成本限制了其推广和应用。为解决超高清视频传输和存储的难题,中国数字音视频编解码技术标准(AVS)工作组制定了新一代视频编码标准——AVS3,并在超高清产业化应用方面取得重要进展。介绍了AVS3视频编码关键技术,以及其与AVS2、多功能视频编码(VVC)、开放媒体联盟视频(AV1)等标准的性能对比情况。     

MgO缓冲层对Si衬底上制备Fe3Si薄膜性能的影响

采用磁控溅射方法和热加工工艺在n型Si衬底上溅射不同厚度的MgO层并制备Fe-Si薄膜层,退火后形成Fe3Si/MgO/Si多层膜结构.利用MgO缓冲层对退火时Si衬底扩散原子进行屏蔽,并分析MgO层对Fe3Si薄膜结构和电学性质的影响.通过X射线衍射仪(XRD)、扫描电子显微镜(SEM)和四探针测试仪对Fe3Si薄膜的晶体结构、表面形貌、断面形貌和电阻率进行表征与分析.研究结果表明:当MgO层厚度为20 nm时生成Fe0.9Si0.1薄膜,当厚度为50,100,150和200 nm时都生成了Fe3Si薄膜,生成的Fe3Si和Fe0.9Si0.1薄膜以(110)和(211)取向为主.随MgO缓冲层厚度增加,Si衬底扩散原子对Fe3Si薄膜的影响减小,Fe3 Si薄膜的晶格常数逐渐减小,晶粒大小趋向均匀,平均电阻率呈现先增大后减小趋势.研究结果为后续基于Fe3 Si薄膜的器件设计与制备提供了参考.     

全球3G业务发展与展望

2009年在2G业务发展趋缓的情况下,3G业务发展开始提速。其特点是应用范围不断扩大,中心由话音转向数据,且由通信类向媒体、娱乐和商务类等转移。此外,3G增强型技术对应用提供了更多支持,促进了移动互联网的发展。手机应用软件商店成推动业务应用的平台;业界着手规划基于LTE的新应用未来引人关注。     

3G时代有线宽带和无线宽带的协同共进

2009年是中国的3G元年,中国电信、中国移动、中国联通三大运营商在无线宽带市场展开角逐,无线宽带上网体验有了质的飞跃.本文从客户需求、竞争形势、国外经验等多个角度,讨论了在目前市场环境下,固网优势运营商和移动优势运营商的有线宽带和无线宽带如何协同发展.     

带光隔离器的双包层EYDFA特性研究

基于速率方程和光传输方程,对带光隔离器的级联双包层铒镱共掺光纤放大器(EYDFA)进行了研究.结果发现小信号条件下与单级结构相比,在三种泵浦方式中,前向泵浦级联结构的增益增加最多达到4.4dB,后向泵浦的增益最大,前向和双向泵浦的噪声系数接近理论极限3dB,前向泵浦的最佳光纤长度增大近1倍.