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针对传统大数据特征加密方法中大数据精度较差、加密耗时较长的问题,提出基于信息熵抑制的大数据特征隐匿性加密方法。分析信息熵抑制相关理论,采用信息熵映射函数对大数据分类,将信息熵抑制过程转化为计算2个文件相似性的过程,并根据余弦相似度公式以及Hamming距离值计算数据相似度,完成数据消冗。在完成数据消冗的基础上,分析分组密码方法和ECC加密方法,结合两种方法得到大数据特征隐匿性加密处理计算公式,实现基于信息熵抑制的大数据特征隐匿性加密。实验研究结果表明,所提方法能够有效去除冗余数据,提升大数据精度,加快数据加密的处理速度,高效完成大数据加密过程。 相似文献
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开关磁阻电机结构性转矩脉动抑制方法 总被引:5,自引:0,他引:5
开关磁阻电机具有结构简单、成本低和调速范围广等优势,但其双凸极结构和控制器的开关特性,导致存在转矩脉动现象,使得抑制转矩脉动成为焦点问题。首先从开关磁阻电机的结构和运行机理出发,针对线性解析方法难以分析转矩特征的问题,建立电机有限元模型求解出转矩特征并进行样机验证试验。分析样机结构参数对转矩脉动的影响,针对结构参数耦合问题,选择NSGA-Ⅱ算法在参数优化平台上对样机结构参数进行多目标寻优,在保证优化后样机的转矩脉动系数和平均转矩均优于初始电机的条件下,最终获得样机最优化结果。结果表明,不同结构参数对电机转矩的影响有较大的差异,对结构参数的优化能有效地抑制转矩脉动,该参数优化方法可以为开关磁阻电机结构性转矩脉动抑制提供参考。 相似文献
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Xiao Zhang Zhao Yang Xin Huang Xingyu Wang Yuelei Pan Xiaomeng Zhou 《International Journal of Hydrogen Energy》2021,46(41):21704-21714
Hydrogen enriched with compressed natural gas is an efficient and environment-friendly gaseous fuel. However, the safety issues of mixture and the method to control or weaken their combustion are highly concerned. To explore the inhibition effect of halogenated fire suppressants on the mixture, the effect of HFC-227ea on the laminar premixed methane/air flames, with different fractions of H2, have been studied. Burning velocities have been measured with constant-volume combustion chamber and kinetically modelled a recently assembled kinetic mechanism. The fractions of H2 influence the enhancement and inhibition effect of HFC-227ea, and it is less effective with the lean mixture. In stoichiometric condition, HFC-227ea showed good inhibition effect on the mixture flames. The HFC-227ea increased the burning velocities of CH4-0% H2-air and CH4-10% H2-air flames at leanest condition, whereas the increased burning velocity arising from HFC-227ea not occurred as the addition of H2 above 20%. Experimental results coincided well with numerical results, however the agreement was poor for the leanest flames at low agent loading. Lastly, kinetic mechanism analysis was used to interpret the combustion enhancement and inhibition effect of hydrogen-doped methane flame by HFC-227ea. 相似文献
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Ball screws are crucial for improving the reliability and interchangeability of transmission mechanical systems; however, existing contact measurement methods that utilise stylus contact are not efficient, which precludes their use for rapid in-situ geometry evaluation. This paper presents a vision-based two-stage method for rapid measurement of key parameters (raceway arc radii and centre distance) of ball screws. The edge contour information is extracted from the acquired image using the dual-tree complex wavelet transform and non-maximal suppression. In the matching stage, a shape-matching algorithm is used for detecting approximate geometrical centres of raceway arcs. The refinement stage, on the other hand, is implemented for acquiring precise dimensional results. Furthermore, the method of averaging multiple measurements is performed to suppress random noise. A comparative experiment is presented to validate the robustness of the proposed method. Based on experimental results, the calculated mean absolute errors in the measurement of the two raceway arc radii and the centre distance are found to be 0.0082 mm, 0.0079 mm and 0.0055 mm, respectively. This study therefore paves the way for key parameter measurement without removing ball screws. 相似文献
7.
Sangeetha Thangavel Po-Tuan Chen Wei-Mon Yan Cheng-Jung Yang K. David Huang 《国际能源研究杂志》2020,44(14):11883-11893
Zinc (Zn) particles in alkaline electrolyte of a Zn-air battery (ZAB) are unstable and prone to corrosion. Zinc oxide (ZnO) generated on the surface of Zn particles affects the electrochemical reactions and reduces the battery efficiency. Thus, inhibiting the self-corrosion rate of Zn particles has become acritical issue for the development of these batteries. In this study, a research endeavor has been attempted by employing three types and concentrations of organic inhibitors in ZABs to constrain Zn anode corrosion. Significant analyses like polarization curve, constant current discharge, AC impedance, and dendrite growth are executed for in-depth understanding of the influences of these inhibitors. The experimental results reveal that the inhibiting efficiency of 10 wt% Sodium dodecyl benzene sulfonate surpassed polyethylene glycol 600 (PEG 600) and polysorbate 20 (Tween 20), with a maximum current density of 476.20 mA/cm2 and voltage output of 1.4 V along with discharge capacitance of 10.31 Ah for 2 hours and 8 minutes. Zn anode surface analysis exposes significant dendrite growth and elemental Zn required for passivation suppression. Nevertheless, the results are also justified by Nyquist and Bode plots. Thus, the selected inhibitor will proficiently guarantee the enhanced performance and stability of the ZABs obtained and provide enormous opportunities for its applications. 相似文献
8.
《International Journal of Hydrogen Energy》2020,45(7):4490-4500
Al2O3 and MgAl2O4 supported 10% (w/w) Ni catalysts having a dispersion of 1.5 and 2.0% are active for DRM at 600 and 750 °C. High temperature reduction of both the calcined catalysts resulted in metallic Ni being formed, suggesting strong support metal interactions. The CH4 and CO2 conversion during DRM are relatively constant with time-on-stream, and are higher for Ni/MgAl2O4 than Ni/Al2O3. Carbon-whiskers are also detected on both catalysts. O2 co-feed of 2.6% (v/v) and increasing reaction temperature to 750 °C helped in decreasing the amount of carbon deposited, except for Ni/MgAl2O4 at 600 °C. Furthermore, higher conversions and H2/CO ratios are achieved. It appears that on spent Ni/MgAl2O4 a different type of carbon species was formed, and this carbon species was difficult to remove by oxygen at 600 °C. Thus, co-feeding O2, using an appropriate temperature, and choosing a suitable support can reduce the carbon present on the nickel catalysts during DRM. 相似文献
9.
In the present study, the effect of fine water mist on extinguishment of a methane–air counterflow diffusion flame was investigated to understand the underlying physics of fire extinguishment of highly stretched diffusion flame by water mist. Twin-fluid atomizers were used to generate polydisperse water mist of which Sauter mean diameters were 10, 20, 40, and 60 μm. When water mist is not added, the critical stretch rate at extinguishment is 439 s−1 as compared to the theoretical value of 460 s−1. For the case with water mist addition, when the stretch rate is small enough, almost all the water mist evaporates within the flame zone. On the other hand, for high stretch rate case, large mist droplets pass through the flame zone and can reach the stagnation plane. However, no oscillatory motion was found around the stagnation plane. Critical stretch rate at extinguishment decreases monotonously with the mass fraction of water mist independently of the mist diameter within the range of D32 from 10 μm to 60 μm. On the other hand, with increase in the surface area parameter, the critical stretch rate at extinguishment decreases rapidly and becomes less sensitive at large surface area parameter, of which tendency is qualitatively in good agreement with theoretical predictions. For a constant surface area parameter, the critical stretch rate decreases with mist diameter because the mass fraction of water mist should increase in proportion to the mist diameter to keep the surface area parameter constant. When the water mist evaporates completely in the flame zone as in the present study, the mass fraction of the water mist is the dominant factor for fire extinguishment, rather than the surface area parameter. Therefore, an appropriate combination of stretch rate and water mist mass fraction should be provided to suppress effectively a given fire with a small amount of water mist. 相似文献
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A method for estimating the sway angle using an observer has already been proposed. The state observer estimates the sway angle accurately and must use the detected sway angle value. However, the estimated sway angle has an error owing to rope length error, friction force, and wind. Moreover, the container mass cannot be determined, and therefore the observer parameter is not suitable. We already proposed robust antisway control for overcoming rope length error without adding a new sensor. Further, we designed a friction disturbance observer to cancel out the influence of the friction force. In this paper, we first propose a container mass estimation method when a crane system performs rolling up control. The observer parameter can be selected using the estimated mass value. Second, in crane parallel shift control, we propose a robust antisway control even when there is a wind disturbance. We design a wind disturbance observer and propose a wind disturbance estimator to separate the friction observer output from the wind disturbance observer output. We confirm through experiments that the proposed method can reduce vibration. 相似文献