全数字超宽带系统的关键技术及其发展

介绍了超宽带无线通信系统的技术背景和标准的发展状况，重点阐述了几种基于窄脉冲的数字超宽带系统的体系结构，分析了全数字超宽带系统实现过程中的关键技术，包括脉冲成型、高速模数转换和信号检测与接收技术等，并且探讨了相应的解决方案。     

利用VB实现质量控制图系统

介绍了利用VB开发工具,在Windows平台上实现质量控制图的绘制和分析。以锻造活塞环工序为例,说明了质量控制图系统的应用,证明了该系统可提高作控制图的准确性与效率,具有很强的实用性。     

Dynamic behaviour of liquid water emerging from a GDL pore into a PEMFC gas flow channel

A numerical investigation of the dynamic behaviour of liquid water entering a polymer electrolyte membrane fuel cell (PEMFC) channel through a GDL pore is reported. Two-dimensional, transient simulations employing the volume of fluid (VOF) method are performed to explicitly track the liquid–gas interface, and to gain understanding into the dynamics of a water droplet subjected to air flow in the bulk of the gas channel. The modeled domain consists of a straight channel with air flowing from one side and water entering the domain from a pore at the bottom wall of the channel. The channel dimensions, flow conditions and surface properties are chosen to be representative of typical conditions in a PEMFC. A series of parametric studies, including the effects of channel size, pore size, and the coalescence of droplets are performed with a particular focus on the effect of geometrical structure. The simulation results and analysis of the time evolution of flow patterns show that the height of the channel as well as the width of the pore have significant impacts on the deformation and detachment of the water droplet. Simulations performed for droplets emerging from two pores with the same size into the channel show that coalescence of two water droplets can accelerate the deformation rate and motion of the droplets in the microchannel. Accounting for the initial connection of a droplet to a pore was found to yield critical air inlet velocities for droplet detachment that are significantly different from previous studies that considered an initially stagnant droplet sitting on the surface. The predicted critical air velocity is found to be sensitive to the geometry of the pore, with higher values obtained when the curvature associated with the GDL fibres is taken into account. The critical velocity is also found to decrease with increasing droplet size and decreasing GDL pore diameter.     

原油减压渣油馏分的油-水界面性质 Ⅹ.大庆减渣与伊朗轻质减渣馏分油-水薄液膜的性质

采用双分子类脂膜实验装置研究了大庆减压渣油与伊朗轻质减压渣油馏分的油-水薄液膜的膜电容(膜厚度)、排液-破裂方式、膜稳定时间(膜寿命)。结果表明,减渣馏分越重,分子吸附状态稳定,其油-水薄液膜越厚,膜稳定性越好。减渣馏分油-水薄液膜的排液-破裂有连续排液-破裂方式、“黑洞”排液-破裂方式和逐层破裂排液方式。当馏分越轻、馏分在油相中质量分数越低、表面活性剂加量越多时,以连续排液-破裂方式为主;而馏分越重、馏分在油相中的质量分数越高、表面活性剂加量越少时,以“黑洞”排液-破裂方式和逐层破裂排液方式为主。油相的组成,水相中的酸、碱、盐以及外加表面活性剂对减渣馏分的界面活性、吸附状态、电荷吸附量影响不同,相应的膜电容(膜厚度)和膜稳定时间也不同。     

The reliability of traditional authentication – A case of ginseng misfit

Ginseng is a famous herb in traditional Chinese medicine. Herbs like ginseng have traditionally been authenticated by morphological and histological means, but it is difficult to identify these herbs nowadays since they look morphologically similar. The quality of food and pharmaceutical products is important for ensuring efficacy and consumer safety. Although several studies have stated that these traditional methods of authenticating ginseng are now hardly reliable, there have been little or no studies which have documented the reliability of such approaches. We report in this study a case of misidentification of ginsengs based on traditional methods of authentication via morphology, and the ability of using infrared spectroscopy and principal component analysis as a rapid form of quality surveillance by discriminating this error.     

解读数字电影《间谍·佐尔格》的制作工艺

本文通过对日本数字电影《间谍·佐尔格》的解读，帮助读者深入了解电影数字制作工艺和表现手段。该片利用数字技术再现了第二次世界大战时期的历史场景、历史人物和历史事件；利用网络传输技术完成了影片异地制作的素材传输和在线编辑，探索了高清拍摄、数字同期录音的新方法。     

基于机器视觉的波纹补偿器轴向尺寸检测方法

波纹补偿器是现代管路中进行补偿的关键部件，波纹补偿器通过自身弹性元件的有效伸缩变形来吸收管路中由热胀冷缩、压强过大等原因而产生尺寸变化的一种补偿装置，为实时检测工业管道中波纹补偿器轴向尺寸变化过大导致的故障状况。本文设计了一种基于机器视觉技术改进的边缘检测算子对波纹补偿器轴向尺寸进行检测，采用混合滤波代替高斯滤波过滤噪声，通过形态学处理对图像细化，最后使用OTSU算法实现待测物体和背景的分离。实验证明，机器视觉技术可以检测出波纹补偿器的轴向尺寸，该方法可以解决工业管道中波纹补偿器轴向尺寸难以实时检测的问题，同时检测设备安装方便、使用安全、精度也能达到预期指标。     

3–1-type PZT-based porous ceramic and composites with highly oriented pore structure for acoustic applications

Journal of Materials Science: Materials in Electronics - Pure tert-butyl alcohol as vehicle was used to fabricate 3–1-type porous lead zirconate titanate ceramics (3–1-type porous PZT...     

Cup-stacked carbon nanotubes hybridized Si3N4/Si3N4 composite ceramics for high-effciency microwave absorption with excellent thermal stability

Hybridization between carbon nanotubes (CNTs) and Si₃N₄ is a promising strategy for developing high-temperature microwave absorption (MA) materials for military application. Toward long-life services, it's important to achieve strong MA at a filler loading as low as possible on account of antioxidant protection against CNTs wastage. Herein, cup-stacked CNTs (CSCNTs) have been prepared in porous Si₃N₄ ceramics by chemical vapor deposition (CVD) and then CVD Si₃N₄ has been coated on them, forming CSCNT-Si₃N₄/Si₃N₄ composite ceramics. Results show that CSCNTs possess abundant exposed atomic edges on the outer surface and in the inner channel. Such unique defects not only benefit the impedance match but also cause considerable conductive loss, which helps CSCNT-Si₃N₄/Si₃N₄ with a filler content of only 0.79 wt% to achieve an effective absorption bandwidth (EAB) of 3.74 GHz in the X band at a thickness of 3.5 mm coupled with a minimum reflection loss of ?43.3 dB and an EAB covering the entire Ku band at a thickness of 2.25 mm. The ultralow filler loading generates a high efficiency of CVD Si₃N₄ in protecting CSCNTs against high-temperature oxidation, leading to a steady MA performance for CSCNT-Si₃N₄/Si₃N₄ during 23–1200 °C thermal shock tests in air.     

Interface-Induced Electrocatalytic Enhancement of CO2-to-Formate Conversion on Heterostructured Bismuth-Based Catalysts

Electrochemical CO₂ reduction reaction (CO₂RR) is a promising approach to convert CO₂ to carbon-neutral fuels using external electric powers. Here, the Bi₂S₃-Bi₂O₃ nanosheets possessing substantial interface being exposed between the connection of Bi₂S₃ and Bi₂O₃ are prepared and subsequently demonstrate to improve CO₂RR performance. The electrocatalyst shows formate Faradaic efficiency (FE) of over 90% in a wide potential window. A high partial current density of about 200 mA cm^?2 at ?1.1 V and an ultralow onset potential with formate FE of 90% are achieved in a flow cell. The excellent electrocatalytic activity is attributed to the fast-interfacial charge transfer induced by the electronic interaction at the interface, the increased number of active sites, and the improved CO₂ adsorption ability. These collectively contribute to the faster reaction kinetics and improved selectivity and consequently, guarantee the superb CO₂RR performance. This study provides an appealing strategy for the rational design of electrocatalysts to enhance catalytic performance by improving the charge transfer ability through constructing a functional heterostructure, which enables interface engineering toward more efficient CO₂RR.