Volume 40,Issue 4,2017 Table of Contents

1 Bumper structure optimization for pedestrian leg protection

XU Zhongming , LYU Weidong , XIA Xiaojun , LAI Shiyang , ZHANG Zhifei

2017, 40(4):1-8. DOI: 10.11835/j.issn.1000-582X.2017.04.001

[Abstract](1102) [HTML](366) [PDF 3.80 M](1310)

Abstract:
A finite element collision model was established to simulate the collision between pedestrian's lower leg and a car, and it was verified through experiment. In order to improve the performance of pedestrian protection, auxiliary bumper and energy-absorption foam were added in the car. With taking the thickness of energy-absorption foam, the vertical distance between bumper and auxiliary bumper and the thickness of auxiliary bumper as design variables, an optimized Latin hypercube experiment was conducted. The response surface model (RSM) for the injury index of leg was fit with experimental data by using the least square method, and the optimal design parameter of bumper was solved by multi objective genetic algorithm (MOGA). The results indicate that the injury of the pedestrian leg is reduced effectively by using the optimal structure, which meets the safety requirements.

2 The multi-axle fatigue analysis of welded joints based on notch stress method

LIU Xu , ZHANG Kailin , LIU Bin , YAO Yuan

2017, 40(4):9-17. DOI: 10.11835/j.issn.1000-582X.2017.04.002

[Abstract](1066) [HTML](973) [PDF 4.59 M](1324)

Abstract:
As the existing fatigue assessment curves of welded joints are only applicable to uniaxial load, we analyzed the multi-axial fatigue of welded joints on the basis of notch stress method. Firstly, through the combination of the nominal stress data in the multi-axial fatigue test of welded joints and the notch stress concentration factor calculated by finite element method, the notch stresses of 5 kinds of welded joints in different directions were obtained. Secondly, equivalent notch stresses were respectively calculated according to 3 kinds of multi-axial fatigue criteria, i.e. Von Mises, ⅡW (International Institute of Welding) and EESH (equivalent effective stress hypothesis), and they were unified into the same coordinate system. Finally, the fatigue life curves that were applicable to the assessment of the multi-axial notch fatigue were fitted out with the least square method. Compared with the uniaxial curve recommended by ⅡW, the multi-axial fatigue curves have lower inclination and higher fatigue class. The fatigue strength value within the mid-circle range from 10³ to 10⁶ circles is obviously reduced when multi-axial is loaded, while the influence on the high circle fatigue range from 10⁶ to 10⁷ circles is relatively limited.

3 Thermoelastic analysis of Al₂O₃ powder in pulse electric current sintering

ZHANG Long , ZHANG Xiaomin , CHU Zhongxiang , PENG Song

2017, 40(4):18-23. DOI: 10.11835/j.issn.1000-582X.2017.04.003

[Abstract](1190) [HTML](415) [PDF 2.27 M](1180)

Abstract:
The neck growth mechanism of pulse electric current sintering (PECS), especially for non-conductive powder, is a key problem to study. In this paper, the rapid sintering mechanism and local high temperature of the neck at the initial stage in pulse electric current sintering was investigated for non-conductive Al₂O₃ powders based on the L-S (Lord and Shulman) generalized thermoelastic theory. The Comsol Multiphysics was applied to numerically simulate temperature, stress distribution, and the chemical potential and the vacancy concentration of sintering neck. The results show that the heat propagated with a finite velocity, and superposition was produced at sintering neck, so local high temperature generates. The chemical potential on the edge and center of sintering neck shows that surface diffusion is main diffusion mechanism. Local vacancy concentration gradient is present on the sintering neck, promoting the sintering process and reducing the sintering time.

4 Research progress about the effect of neutron irradiation on the microstructure of zirconium alloys

WU Lu , QIU Shaoyu , WU Xiaoyong , ZHANG Wei , WEN Bang , WANG Fei , LI Guoyun , JIANG Linzhi , FENG Mingquan

2017, 40(4):24-34. DOI: 10.11835/j.issn.1000-582X.2017.04.004

[Abstract](1003) [HTML](528) [PDF 3.64 M](1293)

Abstract:
As the first safety shield of the nuclear reactor, the microstructure of zirconium alloys is one of the most popular research focuses in the world, especially for secondary phases, hydrides and oxidation film. In this paper, the research progress about the effect of neutron irradiation on secondary phases and hydrides in zirconium alloys was summarized. In addition, the shortages in present research were found and some suggestions were given, such as obtain the evolvement rules under actual employ conditions by using microstructure analysis methods to investigate the secondary phases, hydrides and oxidation film in zirconium alloy under different neutron fluence. Furthermore, theoretic supports for optimizing and improving on zirconium cladding materials in China would be given by this research.

5 Network static equivalent model for power system reliability evaluation

YANG Jingang , LI Shunxin , ZHAO Weiwei , LYU Yin , ZHAO Yuan , LU Zhiran

2017, 40(4):35-43. DOI: 10.11835/j.issn.1000-582X.2017.04.005

[Abstract](1123) [HTML](765) [PDF 2.26 M](1290)

Abstract:
To alleviate the computational complexity of power system reliability evaluation, the probabilistic model of external system static equivalence was proposed in this paper. With using the traditional static Ward technique, the equivalent parameters of extern system in the state of random failures of generator and transmission line in the extern system were calculated, and then the joint probability density distribution for equivalent injection powers and series branch impedances of the extern system was achieved by utilizing probability density estimation technique. As the randomness of extern system equivalent parameters are considered, the proposed model can improve both calculation accuracy and efficiency. The proposed model is verified through the RBTS and IEEE-RTS79 test system.

6 An AHP-based quantified method of information security risk assessment elements

CHAI Jiwen , WANG Sheng , LIANG Huihui , HU Bing , XIANG Hong

2017, 40(4):44-53. DOI: 10.11835/j.issn.1000-582X.2017.04.006

[Abstract](1228) [HTML](1086) [PDF 1.45 M](2250)

Abstract:
Information security risk assessment is an important foundation work for security protection of information systems, but the assessment results of the existing risk assessment criteria and related research models and calculation methods cannot effectively reflect different security needs and risks of the confidentiality, the integrity and the availability of information system assets. In this paper, we used analytic hierarchy process (AHP) to establish a risk assessment analytic hierarchy process model first, then improved vulnerability factor quantitative methods based on the common vulnerability scoring system evaluation index system, and finally used the model's deviator judgment matrix to compute“security incident loss”,“security event possibility”and“value-at-risk”. Experiment results show the proposed method can more intuitively reflect different risks of the confidentiality, the integrity and the availability of assets than conventional methods, and it can provide more accurate and reasonable recommendations for the development of risk control measures.

7 Photovoltaic power forecasting based on unscented Kalman filtering neural network

LI Chunlai , ZHANG Haining , YANG Libin , YANG Jun , WANG Ping

2017, 40(4):54-61. DOI: 10.11835/j.issn.1000-582X.2017.04.007

[Abstract](1031) [HTML](353) [PDF 6.10 M](1396)

Abstract:
As the existing photovoltaic power prediction methods have low robustness under different weather conditions, we proposed a new method for the prediction of photovoltaic power system based on the unscented Kalman filtering (UKF) neural network. The method uses the unscented Kalman filter to update the weight of the neural network model in real time, and establishes two independent dual-input-single-output models with taking DC voltage and current as input and active power and reactive power as output. The experimental results indicate that the proposed UKF neural network model can accurately forecast the photovoltaic power, the best fit of active and reactive power are 97.3% and 94.2% respectively, and the method is robust to weather conditions.

8 Enhancement of chemiluminescence of Luminol-EDTA system by CuFe₂O₄ nanoparticals and its application

CHEN Hua , YANG Min , CHEN Zuqin

2017, 40(4):62-69. DOI: 10.11835/j.issn.1000-582X.2017.04.008

[Abstract](878) [HTML](338) [PDF 2.02 M](1138)

Abstract:
A new chemiluminescence system of Luminol-EDTA-CuFe₂O₄ NPs was firstly developed based on the fact that CuFe₂O₄ nanoparticals (NPs) could significantly enhance the chemiluminescence (CL) intensity of the Luminol-EDTA system. The UV-Vis spectra and the chemiluminescence spectra suggested that no new luminophor formed after the introducing of CuFe₂O₄ NPs in the Luminol-EDTA system. The possible mechanism of CuFe₂O₄ NPs participated in Luminol-EDTA system was proposed by combining with the property of CuFe₂O₄ NPs. Additionally, it was found that rutin could inhibit the chemiluminescence of the proposed Luminol-EDTA-CuFe₂O₄ NPs system. Combined with flow injection, the system was applied to the determination of rutin in rutin tablets. Under the optimal conditions, the relationship between the relative CL intensity and the logarithm of concentration of rutin was linear when the concentration of ratin ranged from 2×10^-8 mol/L to 2×10^-5 mol/L with the detection limit of 1.21×10^-9 mol/L. The recommended method has been successfully applied to the determination of rutin tablets and the recovery was between 97%-102% and RSD (c=1×10^-7mol/L, n=11) was 2.54%.

9 Measurement of hydrolysis degree of mixed silane system for surface treatment of mental

XIAN Xiaochao , LI Lixin , ZHAO Shuo , TAN Shiyu , ZHOU Zhiming

2017, 40(4):70-77. DOI: 10.11835/j.issn.1000-582X.2017.04.009

[Abstract](1077) [HTML](401) [PDF 2.21 M](2131)

Abstract:
The data of hydrolysis degree is an important operation parameter for the cycling utilization of silanes and dilution of concentrated solution in the building of silane bath. In this paper, bis-[trimethoxysilylpropyl] amine (BAS) and vinyltriacetoxysilane (VTAS) were used as raw materials, isopropyl alcohol was adopted as internal standard, and gas chromatography was used to determine the hydrolysis degree BAS and VTAS by measuring the concentration of their hydrolysates, CH₃OH and CH₃COOH, respectively. The effectiveness of the gas chromatography was confirmed further by infrared spectrum, polarization curves and CuSO₄ drop test. The results indicate that gas chromatography can character effectively and rapidly the hydrolysis degree of silanes in BAS/VTAS system, and the results can offer quantitative basis for the evaluation of the property of silane.

10 The corrosion behavior of Q235 steel spraying epoxy composite coating in substation environment

LI Yong , FU Jin , CHEN Wei , YANG Wenjing , LI Xueming , YIN Yanjun , WANG Tao

2017, 40(4):78-84. DOI: 10.11835/j.issn.1000-582X.2017.04.010

[Abstract](955) [HTML](358) [PDF 2.94 M](1174)

Abstract:
The epoxy composite coating composited by zinc rich epoxy primer, waterborne polyurethane intermediate coating and silver epoxy enamel was sprayed on the surface of Q235 steel. The anticorrosion of as-prepared samples in substation environment with atmospheric exposure for 18 months, and in 5% NaCl aqueous solution for 250 days were evaluated and compared, respectively. Electrochemical impedance spectroscopy(EIS) was employed to analyze the corrosive behavior of epoxy composite coating in 5% NaCl aqueous solution, the weather and the salt resistance were also evaluated. Additionally, the structure changes of the epoxy composite coating induced by salt immersion and atmospheric exposure were characterized by Fourier transform infrared(FT-IR). The results are demonstrated that the epoxy composite coating is corroded to be invalid after immersed into 5% NaCl aqueous solution for 250 days, and the impedance decreases from 3.967×10⁹ Ω·cm² to 9.780×10² Ω·cm². The mechanism of corrosion is the corrosive medium gradually penetrates into the composite coating to form micro electric circuit through micro pores, resulting in the increase of porosity and corrosive rate for the composite coating. However, the impedance of epoxy composite coating in substation environment for 18 months is still 2.708×10⁶ Ω·cm², indicating good corrosion resistance.

11 Experimental study of the impact of ash on spontaneous combustion characteristics of coal

LI Lin , CHEN Junchao , JIANG Deyi , CHEN Jie , FAN Jinyang , CHU Tingxiang

2017, 40(4):85-92. DOI: 10.11835/j.issn.1000-582X.2017.04.011

[Abstract](1076) [HTML](390) [PDF 1.83 M](1378)

Abstract:
In order to study the influence of ash on the ability of coal spontaneous combustion, we used coal samples with different ash content to carry out temperature rising oxidation experiments in adiabatic oxidation device, and characterized the effects of the different ash content on the coal spontaneous oxidation process with 3 indicators (R₇₀, T_CPT, B). The results indicate that (1) the larger the ash content is, the slower the coal spontaneous oxidation process is. In low-temperature oxidation stage, the smaller the heating rate is, the higher the acceleration point of temperature-rising is and the more difficult the coal is to burn spontaneously. When the ash content is greater than 40%, the coal spontaneous combustion tendency is rapidly weakened. The acceleration point of temperature-rising is the accumulated results of temperature of zero-activation which reflects microscopic information, and it is intuitive and delayed. The larger the ash content is, the more obvious the lag is and the greater the difference in temperature is .(2) The relationship between ash content and the 3 indicators (R₇₀,T_CPT,B) is quadratic function. R₇₀ and T_CPT indicators show the larger the ash is, the weaker the coal spontaneous combustion tendency is, and that is in accordance with experience. Affected by the weight of water, B indicator shows when coal ash is less than 40%, the larger the ash content is, the stronger the coal spontaneous combustion tendency is, which is contrary to experience. Therefore, B indicator has certain limitations in the determination of the impact of ash on the coal spontaneous combustion tendency.

12 Pedestrian-bridge dynamic interaction in the vertical based on biodynamic model

ZHANG Qiong , NAN Nana , ZHU Qiankun , DU Yongfeng

2017, 40(4):93-100. DOI: 10.11835/j.issn.1000-582X.2017.04.012

[Abstract](748) [HTML](628) [PDF 5.13 M](1392)

Abstract:
The vertical dynamic interaction of pedestrian-bridge is studied by using biodynamic model. The biodynamic model adopts the stiffness-mass-damping (SMD) model expressed by pedestrian's step frequency and weight, under the assumption that the foot bridge is of Euler-Bernoulli model, and the control equation of pedestrian-bridge dynamic interaction in the vertical is established. The state-space method is used to solve the instantaneous model of non-proportionally damped system, and the time-varying frequency and damping ratio are obtained. The time-varying control equation is determined by using variable step four-level-five-order Runge-Kutta-Felhberg algorithm, and the dynamic responses of pedestrian bridge were compared with considering pedestrian-bridge vertical dynamic interaction and under the action of the pedestrian load. The calculated results show that with considering the pedestrian-bridge dynamic interaction in the vertical, the frequency of the foot bridge is lowered slightly, and the damping is increased significantly. When pedestrians walk at the frequency of foot bridge, the dynamic response with considering the Pedestrian-bridge dynamic interaction in the vertical should be obviously lower than that without considering pedestrian-bridge interaction.

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