Cubic polynomial patches through geodesics

We consider patches that contain any given 3D polynomial curve as a pregeodesic (i.e. geodesic up to reparametrization). A curve is a pregeodesic if and only if its rectifying plane coincides with the tangent plane to the surface, we use this fact to construct ruled cubic patches through pregeodesics and bicubic patches through pairs of pregeodesics. We also discuss the G¹ connection of (1,k) patches with abutting pregeodesics.     

JPEG2000中EBCOT算法的优化

JPEG2000是国际标准化组织(ISO)指定的新一代静止图像压缩标准,具有优良的压缩性能和很高的灵活性.在JPEG2000编码系统中优化截断的嵌入式分块编码(EBCOT)的第一层编码花费了大部分时间.为了提高编码的效率,在分析EBCOT算法的基础上提出了一种优化方案.实验结果表明,该方案提高了编码速度,增强了编码的实时性.     

空间光学遥感器CCD焦面组件的设计与分析

随着空间光学遥感器大视场高分辨力技术指标的不断提高,对CCD焦面组件的结构形式和材料选择提出了越来越高的要求.为了满足指标要求,设计了三片CCD机械交错拼接的焦面组件,阐述了该焦面组件的结构形式和材料的选取过程.应用有限元软件对其进行了均匀温升、模态和静力学分析.结果表明,所设计的焦面组件满足了空间光学遥感器的大视场高分辨力的技术要求,同时也能适应空间微重力、振动和温度变化等环境条件.设计和分析过程为三片以上CCD焦面组件的设计和分析提供了参考.     

可编程数据平面技术综述

在软件定义网络中,可编程数据平面提供的编程能力是网络功能虚拟化的基石。可编程数据平面技术的核心是可编程能力与数据包处理性能。首先从数据平面的可编程性出发,探讨现有数据平面的数据包处理抽象。然后,分别对数据平面实施的目标平台与对应平台上的主要流表算法进行介绍,详细论述现有数据平面技术。最后,探讨了高性能数据平面技术存在的关键挑战。     

小像元量子阱FPA抗光学串音的FDTD仿真

采用光栅耦合结构的焦平面阵列(Focal Plane Array,FPA)在工艺上难以制备,反射耦合结构较为容易。为探究反射耦合结构是否可以在小尺寸范围内替代光栅耦合结构,文章使用FDTD电磁场仿真软件MEEP构建了光栅耦合结构和反射结构GaAs/AlGaAs量子阱红外焦平面阵列三像元模。通过对器件内部光学串音进行仿真,验证了在逼近衍射极限时,采用全内反射结构的FPA在5~7μm和8.5~10μm之间的抗串音效果强于光栅耦合结构,而在6.5~8.5μm和10~12μm之间,光栅耦合结构的抗串音效果更好,在12~15μm范围内,两种结构的抗串音能力相当。针对15μm中心距全内反射结构量子阱FPA,探究了反射角度、刻蚀深度和量子阱周期对其串音的影响。     

One-Component Artificial Gustatory System Based on Hydrogen-Bond Organic Framework for Discrimination of Versatile Analytes

Hydrogen-bond organic frameworks (HOFs) with excellent structural and luminescent properties have emerged as a promising material for the construction of fluorescence sensors. However, designing a facile, universal and high throughput sensor with multiplex detection capacity still remains challenging. Herein, a one-component sensor array is constructed that mimics natural gustatory system for accurate and high-throughput discrimination and identification of versatile analytes. HOF as a single sensing element greatly simplifies the probe preparation in sensor array and detection procedure. Metal ions, proteins and bacteria as the model targets are rapid and accurately discriminated, presenting the universality of the system. Particularly, the system is successfully used for the classification of antibiotic mechanisms. The study expands the application scope of HOFs and provides a facile and universal system for sensing applications.     

Creating Atomic Ordering in Electrocatalysis

Catalysis always proceeds in a chaotic fashion. Therefore, identifying the working principles of heterogeneous catalysts is a challenging task. Creating atomic order in heterogeneous catalysts simplifies this task and also offers new opportunities for rationally designing active sites to manipulate catalytic performance. The recent rapid advances in heterogeneous electrocatalysis have led to exciting progress in the construction of atomically ordered materials. Here, the latest progress in electrocatalysts with the periodic atomic arrangement, including intermetallic compounds with long-range order and metal atom-array catalysts with short-range order is summarized. The synthesis principles and the intriguing physical and chemical properties of these electrocatalysts are discussed. Furthermore, the compelling prospects of atomically ordered catalysts in the frontier of catalyst research are outlined.     

基于FPGA的高性能可编程数据平面研究综述

可编程数据平面(PDP)一方面支持网络应用的卸载与加速, 给网络应用带来了革命性的发展机遇; 另一方面支持新协议、新服务的快速实现和部署, 促进了网络创新和演进, 是近年来网络领域的研究热点. FPGA因其通用的计算架构、丰富的片内资源和扩展接口提供了多种可编程数据平面的具体实现, 支持更广范围的应用场景. 同时, FPGA还为探索更通用的可编程数据平面抽象提供了可能. 因此, 基于FPGA的可编程数据平面受到了学术界与产业界的广泛关注. 首先分类别阐述基于FPGA的可编程数据平面(F-PDP)抽象. 接着, 介绍基于F-PDP快速构建网络应用的关键技术的研究进展. 之后, 介绍基于F-PDP的新型可编程网络设备. 此外, 从提升网络性能、构建网络测量框架以及部署网络安全应用这3个方面, 详细梳理近年来基于F-PDP的应用研究成果. 最后, 探讨F-PDP未来可能的研究趋势.     

A Cost‐Efficient Bifunctional Ultrathin Nanosheets Array for Electrochemical Overall Water Splitting

The design of cost‐efficient earth‐abundant catalysts with superior performance for the electrochemical water splitting is highly desirable. Herein, a general strategy for fabricating superior bifunctional water splitting electrodes is reported, where cost‐efficient earth‐abundant ultrathin Ni‐based nanosheets arrays are directly grown on nickel foam (NF). The newly created Ni‐based nanosheets@NF exhibit unique features of ultrathin building block, 3D hierarchical structure, and alloy effect with the optimized Ni₅Fe layered double hydroxide@NF (Ni₅Fe LDH@NF) exhibiting low overpotentials of 210 and 133 mV toward both oxygen evolution reaction and hydrogen evolution reaction at 10 mA cm^?2 in alkaline condition, respectively. More significantly, when applying as the bifunctional overall water splitting electrocatalyst, the Ni₅Fe LDH@NF shows an appealing potential of 1.59 V at 10 mA cm^?2 and also superior durability at the very high current density of 50 mA cm^?2.     

Crystallographic analysis on small fatigue crack propagation behaviour of a nickel-based single crystal superalloy

In situ observations by scanning electron microscopy show that small fatigue cracks in a nickel-based single crystal superalloy are inclined to the loading direction and propagate in dominant crystallographic manners. In order to evaluate the driving forces for inclined crack propagation, three-dimensional anisotropic linear elastic finite-element analysis is conducted. The plastic zone size on the dominant slip plane has been calculated and proposed to correlate the fatigue crack growth. It is shown that this parameter takes into account both material anisotropy and octahedral fracture modes, and it can effectively characterize small crack propagation behaviour.