电气石的环境功能属性及其复合功能材料应用研究

电气石是非金属矿物领域中较为重要的一类硅酸盐类矿物,属非可再生类天然矿物。电气石晶体具有化学成分复杂、晶形及颜色多样等特征。电气石晶体内部的物质及结构特征,使其具有压电性、热释电性、自发极化效应和释放负离子等特性。近年来,关于利用电气石的环境功能属性制备各类复合功能材料的研究已成为备受关注的热点。基于电气石的来源、分类、晶体内部物质成分与结构组成等,概述了电气石的理化结构特征及各环境功能属性,进而论述电气石及其复合功能材料在各个实际领域中的应用,归纳并总结电气石在现今环境污染治理应用当中存在的相关问题,最后对电气石及其复合功能材料的发展前景进行了展望。     

Contextual heat island assessment for pavement preservation

Pavement preservation (PP) is a planned set of construction and material interventions that can extend the pavement’s service life and may also impact sustainability through Heat Island (HI) mitigation. The HI mitigation potential can vary from location-to-location and with time. For agencies to widely adopt the PP, it is necessary to quantify the benefits based on the context of the project. A method to calculate the Global Warming Potential (GWP) for the HI effect was developed and illustrated for four cities in the US: Chicago, Austin, San Diego and Philadelphia, for hypothetical pavements with three preservation options: chip seals, a concrete inlay, and an asphalt concrete inlay. The use phase GWP with respect to HI was estimated for all cases given a 2-, 5-, 7- or 10-year service life. Overall, the HI in the use phase was found to dominate the total GWP relative to the materials and construction phases. The HI GWP savings increase over time, with the 10-year savings being greatest for San Diego using the concrete inlay (22.5?kg CO₂-eq/m²) and smallest for Chicago with a chip seal (8.0?kg CO₂-eq/m²). The savings were found to increase in areas that have a more pronounced HI and could offset GWP in the other phases. The proposed method allows agencies to estimate HI GWP for a specific preservation strategy, location and service life.     

High‐Temperature Particulate Matter Filtration with Resilient Yttria‐Stabilized ZrO2 Nanofiber Sponge

Particulate matter (PM) is a major air pollutant in many regions, jeopardizing ecosystems and public health. Filtration at pollutant source is one of the most important ways to protect the environment, however, considering the high‐temperature exhaust gas emissions, effective removal of PM and related pollutants from their sources remains a major challenge. In this study, a resilient, heat‐resisting, and high‐efficiency PM filter based on yttria‐stabilized ZrO₂ (YSZ) nanofiber sponge produced with a scalable solution blow spinning process is reported. The porous 3D sponge composed of YSZ nanofibers is lightweight (density of 20 mg cm^?3) and resilient at both room temperature and high temperatures. At room‐temperature conditions, the YSZ nanofiber sponge exhibits 99.4% filtration efficiency for aerosol particles with size in the range of 20–600 nm, associated with a low pressure drop of only 57 Pa under an airflow velocity of 4.8 cm s^?1. At a high temperature of 750 °C, the ceramic sponge maintains a high filtration efficiency of 99.97% for PM_0.3–2.5 under a high airflow velocity of 10 cm s^?1. A practical vehicle exhaust filter to capture particles with filtration efficiency of >98.3% is also assembled. Hence, the YSZ nanofiber sponge has enormous potential to be applied in industry.     

理想条件下混合态量子系统的Lyapunov稳定化策略

在假定被控系统满足非退化、没有退化跃迁和完全连通的理想条件下,借助于带有附加自由度的Lyapunov函数研究了混合态量子系统的稳定化问题.基于LaSalle原理推导了闭环系统的最大不变集和任一初始态下的收敛状态集,给出了系统对最大不变集中任一平衡态渐近稳定化的自由度的构造原则.最后通过一个两能级系统的数值仿真,验证了所得理论结果的正确性.     

An experimental analysis of electrostatically vibrated array of polysilicon cantilevers

Micromechanical cantilevers are one of the most fundamental and widely studied structures in micro-electromechanical systems. Dynamic response of such cantilevers has long been an interesting subject to researchers and different analytical and experimental approaches have been reported to determine it. Theoretical estimation of different damping mechanisms have been reported over years which are relevant particularly in studying the dynamics of the micro-mechanical structures. Most properties and functionalities of the MEMS devices are invariably dependant on the dynamic response of the devices, which in turn depends on the quality factor of the devices or in other words the overall damping present in the system. This paper presents a thorough experimental analysis of vibration characteristics of micro-mechanical cantilevers of different dimensions. Arrays of polysilicon micro-cantilevers of different dimensions have been designed and fabricated using surface micromachining process. The beams are resonated by electrostatic actuation and their vibration characteristics have been observed using Laser Doppler Vibrometer. Also a thorough analysis of modal behaviour of the beams is presented using analytical approach and finite element method based simulation. Different damping mechanisms have been critically reviewed and a semi-analytical estimation of the overall damping is presented. The results are compared with experimental values.     

基于入侵检测技术和诱骗技术的网络安全

该文介绍了基于诱骗技术的网络入侵检测系统(IDS),它是传统入侵检测系统的延伸。首先讨论了基于网络的入侵检测系统,然后分析了入侵诱骗技术和Honeypot技术,最后讨论了基于诱骗技术的入侵检测系统的设计和实现,特别是重定向模块和诱骗网络的设计和实现。     

Laser‐irradiated zinc oxide thin‐film transistors fabricated by solution processing

Abstract— This study investigates the effects of subjecting zinc oxide (ZnO) thin films to laser irradiation. The optical, structural, and electrical properties of the as‐deposited and laser‐irradiated films at different laser energies were studied. The transmittances without/with laser irradiation showed a net increase from 85 to 92% (@550 nm) for 250‐nm ZnO films, indicating an improvement in sample crystal linity. In addition, laser treatment decreased the ZnO band gap. Composition structure analysis shows that the crystallinity increased when the laser energy increased. Thin‐film transistors (TFTs) with a ZnO active layer were fabricated. The mobility of as‐deposited ZnO TFT devices (0.19 cm²/V‐sec) increased more than 2.5 times for ZnO of unirradiated laser treatment (0.49 cm²/V‐sec).     

矿井安全监控电源系统的研究

介绍了电气防爆原理;从理论研究和产品发展两个方面阐述了本质安全防爆型式在国内外的发展状况;重点讨论了目前国内矿井安全监控电源系统存在的问题,即系统输入适应性问题、系统智能化问题、备用电源优化设计问题、系统抗干扰能力问题以及大容量本质安全型电源问题;介绍了一种新型的矿井安全监控电源系统,该电源系统抗干扰能力强,且具有系统运行参数智能监控、预警和故障诊断功能。     

Energy-efficient adaptive sensor scheduling for target tracking in wireless sensor networks

Sensor scheduling is essential to collaborative target tracking in wireless sensor networks (WSNs). In the existing works for target tracking in WSNs, such as the information-driven sensor query (IDSQ), the tasking sensors are scheduled to maximize the information gain while minimizing the resource cost based on the uniform sampling intervals, ignoring the changing of the target dynamics and the specific desirable tracking goals. This paper proposes a novel energyefficient adaptive sensor scheduling approach that jointly selects tasking sensors and determines their associated sampling intervals according to the predicted tracking accuracy and tracking energy cost. At each time step, the sensors are scheduled in alternative tracking mode, namely, the fast tracking mode with smallest sampling interval or the tracking maintenance mode with larger sampling interval, according to a specified tracking error threshold. The approach employs an extended Kalman filter (EKF)-based estimation technique to predict the tracking accuracy and adopts an energy consumption model to predict the energy cost. Simulation results demonstrate that, compared to a non-adaptive sensor scheduling approach, the proposed approach can save energy cost significantly without degrading the tracking accuracy.     

基于Curvelet变换的鲁棒信息隐藏算法

基于图像分块的Curvelet变换,根据Detail尺度层系数变化在脊形区域内能量守恒的特点,块量化嵌入秘密信息,提出一种鲁棒性较好的盲提取信息隐藏算法.实验结果表明,该算法选择Detaill和Detail2尺度层可以提高嵌入容量,适应于抗JPEG压缩的隐蔽通信;仅选择Detaill尺度层嵌入可以获得更强的鲁棒性,满足...