基于改进兴趣度度量与Apriori算法的交通事故多发点成因分析

人、车、路、环境和交通管理构成了道路交通系统,造成道路交通事故的原因是综合、复杂的。正确快速地分析事故成因,有助于提升交通管理水平,减少交通事故的发生。近年来,关联规则模型及其扩展在事故多发点成因分析中备受关注。针对关联规则分析中传统的兴趣度度量方法和Apriori算法的局限,考虑小概率因子对交通事故的影响,提出了改进的交通事故多发点成因分析方法,明确评价因素和结果之间的关联程度,提高挖掘效率。基于浙江省某市交通事故数据,结合人、车、环境与时空因素对方法进行了验证,并对方法的分析效率和结果的有效性进行了讨论。     

Observation of fallout deposition in an outdoor swimming pool 50 km away from the Fukushima Daiichi nuclear power plant

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.     

中国知网高校实验室事故文献研究热点与趋势*

以“高校实验室事故”为主题,对中国知网载文进行关键词频次分析,展示我国高校实验室事故的研究脉络,从整体上把握其研究热点和发展趋势,为后续高校实验室安全管理的研究与实践提供参考。     

基于真实临界事故的CAACS程序验证

核临界安全是核工业发展过程中最重要的安全问题之一,其中对临界事故的评价和分析是临界事故后屏蔽设计、应急计划等的基础,因此具有重要的研究意义和工程价值。CAACS是自主开发的溶液系统临界事故分析程序,可计算临界事故的裂变次数、裂变功率、温度随时间变化等。在临界基准实验验证的基础上,利用CAACS对2个真实的临界事故进行分析和计算,并与事故估计值进行对比,结果表明,CAACS的计算结果与事故估计值符合较好,可为后处理厂的工程设计提供临界事故分析的技术手段,为后续的临界瞬态研究打下基础。     

BEPU分析方法在CNP600弹棒事故中的应用

最佳估算加不确定性（BEPU）事故分析方法同传统的保守性事故分析方法相比,可获取现实的分析结果和安全裕量,在保证核电厂安全性的前提下,提高核电厂的经济效益和运行灵活性。针对CNP600的设计特点,利用最佳估算程序RELAP5-3D建立热态满功率（HFP）和热态零功率（HZP）条件下的弹棒事故（REA）分析模型。通过弹棒事故现象识别分级表（PIRT）识别事故瞬态下重要的过程和现象,筛选出对关键安全参数有重要影响的输入参数。利用DAKOTA程序对重要不确定性输入参数进行拉丁超立方抽样（LHS）,通过非参数统计方法计算关键安全参数的单侧容忍上限。计算结果显示：两种弹棒条件下,REA瞬态过程中的最大芯块平均焓值、芯块峰值温度、包壳峰值温度、系统峰值压力均满足弹棒事故验收准则;利用非参数统计方法计算的核功率峰值单侧容忍上限结果合理,最大芯块平均焓值单侧容忍上限计算值同传统弹棒事故保守计算值相比具有可观的安全裕量。     

用力学分析一起特大交通事故

交通事故中某些条件作合理设定，应用牛顿力学，推算肇事车辆的速度．     

基于最小二乘法的道路交通事故预测机理模型

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.     

Analyzing the causation of a railway accident based on a complex network

In this paper, a new model is constructed for the causation analysis of railway accident based on the complex network theory. In the model, the nodes are defined as various manifest or latent accident causal factors. By employing the complex network theory, especially its statistical indicators, the railway accident as well as its key causations can be analyzed from the overall perspective. As a case, the ＂7.23＂ China-Yongwen railway accident is illustrated based on this model. The results show that the inspection of signals and the checking of line conditions before trains run played an important role in this railway accident. In conclusion, the constructed model gives a theoretical clue for railway accident prediction and, hence, greatly reduces the occurrence of railway accidents.     

ITER 失真空事故下铍灰尘分布的数值研究

采用计算流体动力学方法,通过对ITER 装置的设计结构进行合理简化,建立了ITER 装置的三维计算模型,研究了失真空事故下铍灰尘在ITER 装置内的迁移进程,得到了铍灰尘在ITER 装置内的分布情况。通过分析铍灰尘在不同截面高度、不同时刻的分布特性,得到以下结论：随着高度增加,截面位置上的铍灰尘体积分数呈下降趋势;随着时间推移,截面位置上的铍灰尘体积分数呈上升趋势。     

Evolving genetic code

In 1985, we reported that a bacterium, Mycoplasma capricolum, used a deviant genetic code, namely UGA, a "universal" stop codon, was read as tryptophan. This finding, together with the deviant nuclear genetic codes in not a few organisms and a number of mitochondria, shows that the genetic code is not universal, and is in a state of evolution. To account for the changes in codon meanings, we proposed the codon capture theory stating that all the code changes are non-disruptive without accompanied changes of amino acid sequences of proteins. Supporting evidence for the theory is presented in this review. A possible evolutionary process from the ancient to the present-day genetic code is also discussed.