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31.
道路交通事故预测是保证道路佳通安全的重要技术,以往的道路交通事故预测方法往往具有预测精度不高和收敛速度慢的缺点,为此,设计了一种基于灰色Verhulst模型和隐形马尔科夫链的交通事故预测方法。首先,采用灰色Verhulst模型对观察事件在下一时刻的状态进行预测,采用最小二乘估计法去估计模型中的参数,将预测结果用于初始化HMM模型,并采用前向算法和后向算法对HMM模型进行训练,获得最终的初始分布矩阵、状态转移概率和观察概率分布矩阵,然后采用最终的HMM模型进行交通事故预测。仿真试验结果表明：文中方法能有效地实现交通事故预测,较其它方法相比,具有预测精度高和收敛速度快的优点,具有一定的优越性。 相似文献
32.
基于摩擦系数优化的车人碰撞事故再现研究 总被引：1，自引：0，他引：1
行人摩擦生物力学特性对车人碰撞事故再现结果有直接的影响,但由于人体结构的复杂性和交通事故的突发性特点,导致行人与汽车、道路的接触特性很难通过试验的方式获取,本文探讨了基于仿真试验的车人碰撞事故行人摩擦生物力学特性分析方法,并通过蒙特卡罗方法验证摩擦特性的可靠性.将该特性应用于车人碰撞类型的交通事故过程再现进行验证,仿真结果表明:所得到的摩擦特性精度高、可靠性高,能够满足车人碰撞交通事故再现对行人摩擦特性精度要求,为交通事故中所涉及的行人摩擦生物力学特性分析提供了新的途径. 相似文献
33.
基于最小二乘法的道路交通事故预测机理模型 总被引：1，自引：0，他引：1
基于相似理论提出一种新的道路交通事故预测方法,建立了新的交通事故预测非线性机理模型,作为道路交通事故预测的初步探讨.采用机动车保有量作为模型的输入变量,非线性最小二乘法求出模型参数.通过计算表明新预测模型预测精度较高,有应用价值,同时也为交通事故预测提出了新的预测理论. 相似文献
34.
After the accident at the Fukushima Daiichi nuclear power plant (NPP), outdoor school swimming pools at Fukushima were decontaminated to curb the redistribution of radioactivity into downstream farmlands. In the process, the radioactivity concentrations of the pool water and sediment substances (residue) were measured to estimate the deposition density of the fallout. At a pool situated 50 km away from the NPP, the average concentrations of radiocesium (134+137Cs) for the water and residue were quantified as 170 Bq L−1 and 3.6 × 105 Bq kg−1, respectively. Taking account of the radioactivity concentrations and of the water balance in and around the pool, the deposition density of radiocesium, as of August 2011, was precisely determined to be 0.32 ± 0.03 MBq m−2 (k = 1). The density corroborated the previous results obtained by other methods, i.e., airborne surveys, in-situ Ge surveys and soil samplings at neighboring locations. Other than radiocesium, the only gamma-emitting nuclide detected was 110mAg, with a concentration of 560 Bq kg−1 in the residue. The radioactivity concentrations of 89Sr, 90Sr, 238Pu and 239+240Pu in the water were all less than the minimum detectable activities – 2, 0.1, 0.002 and 0.002 Bq L−1, respectively. 相似文献
35.
In this paper, the influence of the interfacial drag on the pressure loss of combined liquid and vapour flow through particulate porous media is investigated. Motivation for this is the coolability of fragmented corium which may be expected during a severe accident in a nuclear power plant. Cooling water is evaporated due to the particles decay heat. To reach coolability, the outflowing steam has to be replaced by inflowing water. 相似文献
36.
ABSTRACTThree soil depth profiles of 210Pb, 137Cs and 40K at different areas of Algeria were studied. The soil sampling areas are near the location where the French nuclear tests took place at 1960–1966. The two depth soil profiles were collected at Ghardaia region and the third one at Reggane region. The vertical distributions of radionuclides at the two soil depth profiles from Ghardaia region are different, probably due to the different soil composition. The soil depth profile from sandy soil show uniformity in the distribution of radionuclides without a clear maximum (peak). The soil depth profile that characterised by silty sand show a clear peak at 20–50?cm depth for all studied radioactive nuclides, while the observed activities are two times higher than the corresponding values in sandy soil samples. More specifically in Ghardaia region the 210Pb, 137Cs, 40K activity concentrations ranged between 27 and 50?Bq?kg?1, 0.2 and 3?Bq?kg?1 and 75 and 90?Bq?kg?1 respectively in sandy soil type and between 37 and 75?Bq?kg?1, 4 and 6?Bq?kg?1 and 140 and 180?Bq?kg?1 respectively in silty sand soil type. Finally, the third depth soil profile collected from Reggane site presents a completely different distribution of the studied radionuclides. The activity concentrations of 210Pb, 137Cs, 40K ranged between 37 and 51?Bq?kg?1, 0.16 and 0.39?Bq?kg?1 and 120 and 309?Bq?kg?1 respectively. Three peaks in the 137Cs distribution revealed, were most probably, Chernobyl related 137Cs accounts for the surface peak, while the deeper peaks are connected to the weapons fallout. 相似文献
37.
Pamela Ercegovac Gordan Stoji&#x; Milo&#x; Kopi&#x;
eljko Stevi&#x; Feta Sinani Ilija Tanackov 《Entropy (Basel, Switzerland)》2021,23(9)
There is not a single country in the world that is so rich that it can remove all level crossings or provide their denivelation in order to absolutely avoid the possibility of accidents at the intersections of railways and road traffic. In the Republic of Serbia alone, the largest number of accidents occur at passive crossings, which make up three-quarters of the total number of crossings. Therefore, it is necessary to constantly find solutions to the problem of priorities when choosing level crossings where it is necessary to raise the level of security, primarily by analyzing the risk and reliability at all level crossings. This paper presents a model that enables this. The calculation of the maximal risk of a level crossing is achieved under the conditions of generating the maximum entropy in the virtual operating mode. The basis of the model is a heterogeneous queuing system. Maximum entropy is based on the mandatory application of an exponential distribution. The system is Markovian and is solved by a standard analytical concept. The basic input parameters for the calculation of the maximal risk are the geometric characteristics of the level crossing and the intensities and structure of the flows of road and railway vehicles. The real risk is based on statistical records of accidents and flow intensities. The exact reliability of the level crossing is calculated from the ratio of real and maximal risk, which enables their further comparison in order to raise the level of safety, and that is the basic idea of this paper. 相似文献
38.
致因因素间复杂的非线性交互作用是造成复杂系统安全事故成因复杂性的主要原因.在提取出复杂系统安全事故的致因因素后,给出了集成DEMATEL/ISM方法分析事故致因因素的算法步骤.基于航空复杂系统实例,采用集成DEMA-TEL/ISM方法求得了致因因素间的综合影响关系、关键致因因素及致因因素多级递阶结构模型,通过复杂网络理论分析节点度,度数大的节点与关键致因因素吻合.所提方法可以用于提取事故关键致因因素和分析因素间的层次关系. 相似文献
39.
A method for sampling and measurement of krypton 85 in the atmosphere was developed based on the technique described by Stockburger et al. [1, 2]. The air is pumped through charcoal cooled with liquid nitrogen. Krypton is obtained from the air sample by fractionated desorption followed by gaschromatographic separation with simultaneous determination of the krypton volume. The 85Kr activity is measured in a proportional counter. The calibration was carried out with an accuracy of ±5.2% (significance level 95%). The 85Kr activity concentration of a sample collected from 30 April to 3 May 1986 (Chernobyl accident) in Neuherberg near Munich was more than twice of the mean value of 1 Bq/m3 air. Subsequently a continuous 14-day sampling along the north-south direction at three locations in Bavaria was carried out. From 1986 to 1991 a mean linear increase of the atmospheric 85Kr activity concentration of 0.037 ± 0.010 Bq/m3 per year (significance level 95%) was determined. 相似文献
40.