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11.
采用单包分析技术的网络入侵检测系统常具有较高的误报率,影响其实用性。本文针对误用网络型入侵检测系统建立一个警报过滤机制,该机制找出攻击成功时所需具备的环境条件。当入侵检测系统发现可疑入侵时,依据环境条件加以实时确认查核,从而减少误报。 相似文献
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Experimental study and simulation of a hydraulic engine mount with fully coupled fluid-structure interaction finite element analysis model 总被引:1,自引:0,他引:1
Non-linear properties of a generic hydraulic engine mount (HEM) are identified and characterized by experiment and simulation approaches. The experimental methods for obtaining static and dynamic performances of the HEM are presented. The characteristics of two configurations of the take-apart HEMs (one is with an inertia track and a free decoupler and the other one is only with an inertia track) and their rubber springs are studied. The relations between static stiffness of an HEM and its rubber springs in three orthogonal directions are investigated. The influences of preload, excitation amplitudes and frequencies on the dynamic stiffness of an HEM are verified. The effects of the free decoupler on dynamic characteristics of the HEM are studied by comparisons of the test results of the two HEMs. The dynamic fluid pressure and the temperature in the upper chamber of an HEM are measured under different excitation conditions. A fully coupled fluid-structure interaction (FSI) and finite element analysis (FEA) model for simulation of HEMs is developed in this paper, which can be used to simulate the static and dynamic performances of the HEMs with only stress versus strain relations of the rubber materials, the fluid physical parameters and the HEMs sizes. The simulated results of one HEM with the proposed model are given, and the results match well with the measured data, or in coincidence with the working mechanisms of HEMs. 相似文献
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Enbo Shangguan Jing Li Dan Guo Zhaorong Chang Xiao-Zi Yuan Haijiang Wang 《International Journal of Hydrogen Energy》2014
To improve the high-temperature performance of the nickel hydroxide electrodes in nickel–metal hydride batteries, sodium tungstate (Na2WO4) used as an electrolyte additive has been added into two types of binary electrolytes (KOH–LiOH and NaOH–LiOH) in this study. The effects of electrolyte composition on the electrochemical performance of nickel electrodes have been systematically investigated via a combination of cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning electron microscope (SEM), energy-dispersive X-ray analysis (EDX), X-ray diffraction (XRD) and charge/discharge tests. It is found that by adding (1.0 wt.%) Na2WO4, the performance of nickel electrodes is significantly improved in both NaOH and KOH electrolytes at 70 °C. The improved performance can be attributed to the deposition of WO3·2H2O solid film on the surface of nickel electrode, which is beneficial to the increase in oxygen evolution overpotential, the slow-down of oxygen evolution rate and the decrease in charge-transfer resistance. 相似文献
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Jinhang Fan Yanpeng Dou Rui Jiang Kaifa Du Bowen Deng Dihua Wang 《International Journal of Hydrogen Energy》2021,46(28):14932-14943
Energy-efficient production of hydrogen through urea electrolysis is still challenging due to the lack of satisfactory catalysts for urea oxidation reaction (UOR) and hydrogen evolution reaction (HER) in urea containing solution. In this study, Ni–WxC/C (x = 1,2) composite with high activity for urea electrocatalysis was prepared by direct electro-reduction of affordable feedstock of NiO–CaWO4–C in molten CaCl2–NaCl at 873–973 K. The addition of graphite in precursor decreases the particle size of Ni. Introducing WxC into Ni particles can reduce the overpotential for UOR. As a result, the obtained Ni-WxC/graphite composite exhibits high current density for urea oxidation, which is about 11-folds and 52-folds higher than that of Ni/graphite and Ni (@1.53 V vs. RHE), respectively. After changing the carbon source from graphite to CNTs, the anodic current density was further increased by 43%, reaching 50.31 mA cm?2. Moreover, the cathodic catalyst WxC/CNTs obtained by the same preparation process exhibits high performance towards HER, with a low onset potential of 131.5 mV and a Tafel slope of 69.5 mV dec?1. Assembling an electrolyzer using Ni-WxC/CNTs as anode and WxC/CNTs as cathode can yield a current density of 10 mA cm?2 at merely 1.65 V in 1 M KOH/0.33 M urea aqueous solution, with excellent long-term electrochemical durability. The environmental-friendly production process uses affordable feedstocks for the synthesis of efficient catalysts toward urea electrolysis, promising an energy-saving hydrogen production as well as waste treatment. 相似文献
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光催化制氢是利用太阳能获取氢能的重要途径,是当前研究热点。长期以来,人们致力于各种新型可见光光催化制氢材料的研究并取得较大进展。反应体系的设计和选择是实现高效光催化制氢和能否走向工业化的核心问题之一,因此,近年来研究者开始对光催化制氢反应体系加大研究。光催化制氢主要有非均相光催化制氢(HPC)和光电催化制氢(PEC),不同的体系具有各自的优缺点和应用范围。重点介绍光催化制氢半反应、光催化完全分解水和光电催化分解水3种主要反应体系,分析各种反应体系的特点,阐述各个体系涉及的光催化材料的发展进程,并展望太阳能光催化制氢研究前景,其中,新型高效的PEC-PV(光伏)耦合光化学转化系统有望为光解水制氢实现工业化提供一种重要的发展途径。 相似文献
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有效调控污染物的运移是实现污染土工程再利用的前提。考虑石油污染盐渍土的特殊性及工程利用的力学需求,优选石灰和粉煤灰为改性材料,结合静态动态试验,研究石灰和粉煤灰对滨海盐渍土中石油污染物的吸附解吸行为的影响。结果表明:单独的石灰和粉煤灰,对石油污染物的吸附率分别为26%和14%,两者联合作用时,吸附率提高到39%,在盐渍土中加入石灰和粉煤灰可有效提高对石油污染物的吸附量,加快吸附稳定速率;盐渍土、石灰+盐渍土、粉煤灰+盐渍土、石灰+粉煤灰+盐渍土对石油的吸附动力学均符合Lagergren二级动力学非线性方程,联合作用可使吸附平衡时间由400min缩短至60min;石灰、粉煤灰有利于吸附赋存于土颗粒孔隙中未被盐渍土颗粒吸附的呈自由态的石油;盐渍土、石灰+盐渍土、粉煤灰+盐渍土、石灰+粉煤灰+盐渍土对石油污染物的吸附等温线均为非线性Freundlich模式;石油被解吸的能力依次为盐渍土粉煤灰+盐渍土石灰+盐渍土石灰+粉煤灰+盐渍土,石灰+粉煤灰对石油污染物的吸附以化学吸附为主,具有不可逆性,有助于缓解环境温度的影响,增强稳定性。 相似文献
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介绍了遂昌县农村水电开发取得的成效及该县推行水电开发资源、经济和生态补偿制度的主要内容,分析了实践中存在的问题,提出了对策和措施。 相似文献
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