定位技术在奥运“城市通”系统中的应用

作为2008年奥运会的举办城市,北京将会成为国内外游客主要聚集的地区,为了向用户提供"随时随地、方便快捷"的信息查询和位置查询服务,中国网通集团研究院开发了奥运"城市通"系统,通过该系统,用户可以使用一个具有定位功能的小灵通终端进行餐饮、娱乐、观光的出行导航和综合城市信息、企业信息的查询,因此,定位技术是实现"城市通"业务的核心,为开发其他增值业务提供了基础,本文将详细介绍定位技术在"城市通"业务中的应用。     

即时消息业务中SIMPLE和IMPS的Petri网互通模型

该文提出新的Petri网耦合规则对即时消息在SIMPLE和IMPS之间的映射建立了互通Petri网模型,通过对该模型进行严格的数学分析验证,该模型满足正确的Petri网模型所应具备的所有特性,证明了该互通映射的合理性以及可行性。     

Ka波段Si基微机械宽带垂直过渡

介绍了一种适用于三维毫米波集成电路的Si基微机械垂直过渡,该垂直过渡是两层0.1mm厚的共面波导传输线通过0.3mm厚中间层,在中间层采用了同轴结构,该同轴结构通过金属化通孔来实现。这一设计原理简单,结构简洁,便于优化设计,具有很宽的带宽和平坦的幅度响应。运用三维电磁场仿真软件对该垂直过渡结构进行了建模,并作了优化设计与仿真计算,运用微机械金属化通孔工艺和多层键合工艺研制了样品。在片测试结果表明该样品性能良好,在26.5～34.0GHz该过渡插入损耗小于3.5dB,带内起伏小于2dB。     

UWB对JTIDS二类端机的干扰研究

美军的联合战术分发系统（JTIDS）是目前为多国所使用的具有强抗干扰性能的相对导航系统。通过深入分析UWB技术与JTIDS的特点,提出了UWB干扰条件下JTIDS二类端机的性能衰减模型,并通过仿真分析了各具体因素的影响,为现存无线电设备同UWB发射源的电磁兼容性研究提供了参考。     

超远距离目标的交叉定位算法研究

从球面几何的角度入手,提出了一种高精度球面三角定位算法。该算法运算量小,定位速度快,尤其适合于超远距离地面目标的定位。分析表明,目标距离比较远时,球面三角定位要比平面交叉定位的定位误差小得多。目标距离一定时,要使圆概率误差半径最小,侦察站和目标须成等边三角形配置。     

基于图像处理的带钢打捆定位控制系统

本文针对带钢生产中“带钢尾端不好确认,打捆定位不准确”的瓶颈问题,首创性地运用计算机视觉检测技术,提出了一种新的带钢尾端自动定位控制系统。本系统由彩色摄像机、图像采集卡、PC机、PLC（可编程控制器）和执行机构组成。文中阐述了图像处理技术、PC机与PLC之间的通讯、PLC实现定位控制等关键问题。实践证明,系统使用后大大提了高定位的准确性和高效性,具有推广价值。     

H2 In Situ Inducing Strategy on Pt Surface Segregation Over Low Pt Doped PtNi5 Nanoalloy with Superhigh Alkaline HER Activity

Surface segregation constitutes an efficient approach to enhance the alkaline hydrogen evolution reaction (HER) activity of bimetallic Pt_xNi_y nanoalloys. Herein, a new strategy is proposed by utilizing the small gas molecule of H₂ as the structure directing agent (SDA) to in situ induce Pt surface segregations over a series of PtNi₅-n samples with extremely low Pt doping (Pt/Ni = 0.2). Impressively, the sample of PtNi₅-0.3 synthesized under 0.3 MPa H₂ delivers an extremely low overpotential of 26.8 mV (−10 mA cm⁻²) and Tafel slope of 19.2 mV dec⁻¹, which is superior to most of the previously reported Pt_xNi_y electrocatalysts. This is substantially related to the strong H₂ in situ inducing effect to generate Pt-rich@Ni-rich core-shell nanostructure of PtNi₅-0.3 with an ultrahigh Pt surface content of 46%. The specific mechanistic effects of H₂ during the PtNi₅-n synthesis process are well illustrated based on the combined experimental and theoretical studies. The density functional theory mechanism simulations further unravel that the evolved active site of PtNi₅-n can efficiently reduce the reaction Gibbs free energies; especially for the scenario of PtNi₅-0.3, the downward-shifted d band center of the Pt active site significantly reduces the Pt H bond strength, eventually resulting in the lowest absolute value of ΔG_H.     

Red AIE Luminogens with Tunable Organelle Specific Anchoring for Live Cell Dynamic Super Resolution Imaging

Lysosomes and mitochondria play an important role in maintaining cell homeostasis. Visualizing the long-term activities of lysosomes and mitochondria on the nanometer scale in live cells is essential for further understanding their functions but remains challenging due to the limitations of existing fluorescent probes, such as aggregation-caused quenching (ACQ) effect, limited signal-to-noise ratio from fluorescence “always on” in the process of targeting organelle and poor photobleaching resistance. Herein, two efficient red-emitting aggregation-induced emission (AIE) luminogens are reported, which showed “off-on” fluorescence characteristic and specific lysosomes as well as mitochondria targeting capability. Owing to their AIE characteristics, a Stokes’ shift larger than 100 nm, good biocompatibility, and excellent photostability, the AIE luminogens have been successfully utilized for high fidelity imaging of lysosomes and mitochondria. By virtue of these two probes, stimulated emission depletion (STED) images of dynamic lysosomal fusion and mitochondrial fission with a high resolution of 65.6 nm are obtained. Furthermore, the interactions between lysosomes and mitochondria in the process of mitophagy are recorded. This study also provides practical guidance for designing specific organelle targeting probes to support live cell dynamic super-resolution imaging.     

High Mobility 3D Dirac Semimetal (Cd3As2) for Ultrafast Photoactive Terahertz Photonics

The Dirac semimetal cadmium arsenide (Cd₃As₂), a 3D electronic analog of graphene, has sparked renewed research interests for its novel topological phases and excellent optoelectronic properties. The gapless nature of its 3D electronic band facilitates strong optical nonlinearity and supports Dirac plasmons that are of particular interest to realize high-performance electronic and photonic devices at terahertz (1 THz = 4.1 meV) frequencies, where the performance of most dynamic materials are limited by the tradeoff between power-efficiency and switching speed. Here, all-optical, low-power, ultrafast broadband modulation of terahertz waves using an ultrathin film (100 nm, λ/3000) of Cd₃As₂ are experimentally demonstrated through active tailoring of the photoconductivity. The measurements reveal the photosensitive metallic behavior of Cd₃As₂ with high terahertz electron mobility of 7200 cm² (Vs)⁻¹. In addition, optical fluence dependent ultrafast charge carrier relaxation (15.5 ps), terahertz mobility, and long momentum scattering time (157 fs) comparable to superconductors that invoke kinetic inductance at terahertz frequencies are demonstrated. These remarkable properties of 3D Dirac topological semimetal envision a new class of power-efficient, high speed, compact, tunable electronic, and photonic devices.     

Pure Blue Electroluminescence by Differentiated Ion Motion in a Single Layer Perovskite Device

Blue electroluminescence is highly desired for emerging light-emitting devices for display applications and optoelectronics in general. However, saturated, efficient, and stable blue emission has been challenging to achieve, particularly in mixed-halide perovskites, where intrinsic ion motion and halide segregation compromises spectral purity. Here, CsPbBr_3−xCl_x perovskites, polyelectrolytes, and a salt additive are leveraged to demonstrate pure blue emission from single-layer light-emitting electrochemical cells (LECs). The electrolytes transport the ions from salt additives, enhancing charge injection and stabilizing the inherent perovskite emissive lattice for highly pure and sustained blue emission. Substituting Cl into CsPbBr₃ tunes the perovskite luminescence from green through blue. Sky blue and saturated blue devices produce International Commission on Illumination coordinates of (0.105, 0.129) and (0.136, 0.068), respectively, with the latter meeting the US National Television Committee standard for the blue primary. Likewise, maximum luminances of 2900 and 1000 cd m⁻², external quantum efficiencies (EQEs) of 4.3% and 3.9%, and luminance half-lives of 5.7 and 4.9 h are obtained for sky blue and saturated blue devices, respectively. Polymer and LiPF₆ inclusion increases photoluminescence efficiency, suppresses halide segregation, induces thin-film smoothness and uniformity, and reduces crystallite size. Overall, these devices show superior performance among blue perovskite light-emitting diodes (PeLEDs) and general LECs.