g因子的蒙特卡罗模拟计算

在电离辐射空气比释动能基准量值复现过程中, g因子作为关键组成部分之一,参与量值复现和不确定度计算,其量值的确定需要通过光子的质能传输系数和质能吸收系数计算得到。采用不同的软件,在不同参数设置条件下模拟计算并对结果进行比较。结果显示采用EGSnrc计算结果更为合理,而且对于低能光子来说,尽管g因子相对较小,但在不同的参数设置条件下所得到的数值差异较大。因此在涉及到低能光子的质能传输系数和质能吸收系数的计算和使用过程中,需对有关的相互作用的物理机制予以重视。     

Status and Development Prospects of Establishing Reference Tools for Reproducing the Units of Volumetric Activity of Radon and Thoron and Radon Flux Density from the Soil Surface

Measurement Techniques - An approach to creating reference tools for reproducing the units of volumetric activity of radon and thoron and radon flux density from the ground surface based on the...     

挖掘机工作空间求解的蒙特卡洛法改进

对常规蒙特卡洛法求解挖掘机工作空间的原理、算法流程分析与仿真,发现大量随机点的分布在空间内部,边界随机点分布少,使得求解结果误差较大且效率低下。对挖掘机工作空间边界形成的内在机理分析,发现其边界的界定本质是其中两组油缸取极限值,另一组油缸为变量,而非三组油缸变量耦合,从而使得随机点的分布集中在工作空间边界。采用改进后的蒙特卡洛法对挖掘机的工作空间进行仿真,对比常规法求解,结果证明改进蒙特卡洛法求解高效且误差极小。     

一种蒙特卡罗方法在测量不确定度评定中的新算法

通过对现有利用蒙特卡罗方法进行不确定度评定过程的分析,指出了目前评定过程中存在理论上的不衔接,并给出了一种全新的利用蒙特卡罗方法进行不确定度评定的算法,弥补了现有方法的缺憾。     

Dosimetry on sub-cellular level for intracellular incorporated auger-electron-emitting radionuclides: a comparison of Monte Carlo simulations and analytic calculations

A quantitative dosimetric comparison was performed between Monte Carlo (MC) simulations and analytic calculations at the (sub) cellular level (V79 cells) for four nucleus-incorporated radiochemicals ((125)I/(123)I/(77)Br-UdR and A (125)IP) and two radiochemicals that localised mainly in the cytoplasm of cells ((125)I-dihydrorhodamine and Na(2)(51)CrO(4)). A microscopic investigation around the decay site of the three DNA-incorporated radionuclides ((125)I/(123)I/(77)Br-UdR) was also carried out. On the whole, deviations between MC and analytic calculations for the absorbed dose and dose rate to the cell nucleus were within ～10%. The dose rate to the nucleus for the radiochemicals that mainly localised in the cytoplasm was greater than that for the nucleus-incorporated ones. Also evident was that the dose rate to the nucleus was approximately the same for the three DNA-incorporated radiochemicals. In contrast to the small differences found between MC and analytic calculations for the (average) absorbed dose to the nucleus, the dosimetric analysis at the microscopic level for the three DNA-incorporated radionuclides showed that the two computational approaches lead to a completely different energy deposition pattern around the decay site.     

Monte Carlo approach to PSA for dynamic process systems

The methodologies employed in the Probabilistic Safety Assessment of technological systems have nowadays reached a high level of maturity. However, there are still some important issues that need further investigations, in order to increase the confidence in the results obtained. Important areas such as human factors, expert judgement and physical modelling are considered to introduce large uncertainties in the probabilistic safety assessments and strong efforts are being devoted lately to the improvement of these aspects within the PSA methodology. Recently, a more ‘dynamic’ approach to PSA analysis has been proposed, with the intention of addressing those problems related to the mutual interactions of the hardware components and the physical evolution of the plant. In the present paper we outline this approach within the framework of the Monte Carlo simulation. The method is shown to provide a flexible environment in which many important issues of the plant's dynamics can be considered, such as the action of control/protection systems and its failures on demand, the effects of the process variables on the system stochastic characteristics and the delay with which a top event can occur. We refer, for our examples, to a simple case study taken from the literature. The limitations of the Monte Carlo method in treating rare-events is also discussed and we address the problem of biasing the probabilities of the control/ protection systems failing on demand.     

蒙特卡罗方法在贝叶斯统计质量控制中的应用

对小批量生产下的质量控制问题进行研究,在方差已知时的贝叶斯均值控制模型中,推导了蒙特卡罗方法确定模型中质量特性参数后验分布的过程,并且与基于共轭先验分布的理论方法进行比较,通过实例发现,基于蒙特卡罗确定质量特性参数统计值的方法与理论的共轭先验分布方法能达到相同的控制效果,并且蒙特卡罗方法不需要假设质量特性参数的先验分布,在实际的生产中具有较好的普适性。     

考虑非正定相关性的测量不确定度蒙特卡洛评定方法

当采用蒙特卡洛法评定测量不确定度考虑输入量相关性时,需基于Nataf逆变换产生服从任意边缘概率分布的相关多维随机变量。为了解决Nataf逆变换过程中输入量相关系数矩阵非正定时,无法产生线性变换矩阵的问题,提出了基于Barzilai-Borwein梯度法的迭代修正算法。进而探讨了输入量服从非正态分布且相关的蒙特卡洛法实施步骤。最后,采用提出的迭代修正算法并基于Nataf逆变换的蒙特卡洛方法,对高速轮轨试验台轮轨纵向蠕滑率不确定度进行了评定,验证了该算法的可行性及有效性。     

蒙特卡罗方法在微波功率测量不确定度分析中的应用

蒙特卡罗方法是一种统计模拟的方法,近年来国际上将其应用于计量学中的不确定度评定.对蒙特卡罗方法进行了系统的描述,就蒙特卡罗方法在计量中的不确定度分析中的应用进行了详细的论述.采用蒙特卡罗方法对微波功率座的测量问题进行了数学建模及蒙特卡罗仿真,对蒙特卡罗方法进行不确定度分析和评定的原理、步骤进行了阐述.给出了微波功率座校准因子的实测值、仿真值及不确定度评定结果.     

The Use of Monte Carlo Simulation Methods to Calculate the Radiation of Jets of Combustion Products in View of Rotational Spectral Structure

Monte Carlo simulation algorithms are given which are intended for the calculation of the spectral emissivity of jets of combustion products of solid-propellant rocket motors (SRM). A distinguishing feature of these algorithms is the inclusion of the rotational structure of the spectrum of combustion products. Analysis is made of the prospects for the use of line-by-line (LBL) methods of calculations of the spectral emissivity and hybrid methods which combine simulation methods with statistical models of rotational-line spectrum.     

利用蒙特卡罗对偶变量的方差减小技术进行B类标准不确定度评定

提出了在使用蒙特卡罗进行B类标准不确定度评定时,利用对偶变量的方差减小技术提高B类不确定度评定的速度和精度的一种算法.     

Benchmarking of Monte Carlo based shutdown dose rate calculations for applications to JET

The calculation of dose rates after shutdown is an important issue for operating nuclear reactors. A validated computational tool is needed for reliable dose rate calculations. In fusion reactors neutrons induce high levels of radioactivity and presumably high doses. The complex geometries of the devices require the use of sophisticated geometry modelling and computational tools for transport calculations. Simple rule of thumb laws do not always apply well. Two computational procedures have been developed recently and applied to fusion machines. Comparisons between the two methods showed some inherent discrepancies when applied to calculation for the ITER while good agreement was found for a 14 MeV point source neutron benchmark experiment. Further benchmarks were considered necessary to investigate in more detail the reasons for the different results in different cases. In this frame the application to the Joint European Torus JET machine has been considered as a useful benchmark exercise. In a first calculational benchmark with a representative D-T irradiation history of JET the two methods differed by no more than 25%. In another, more realistic benchmark exercise, which is the subject of this paper, the real irradiation history of D-T and D-D campaigns conducted at JET in 1997-98 were used to calculate the shut-down doses at different locations, irradiation and decay times. Experimental dose data recorded at JET for the same conditions offer the possibility to check the prediction capability of the calculations and thus show the applicability (and the constraints) of the procedures and data to the rather complex shutdown dose rate analysis of real fusion devices. Calculation results obtained by the two methods are reported below, comparison with experimental results give discrepancies ranging between 2 and 10. The reasons of that can be ascribed to the high uncertainty on the experimental data and the unsatisfactory JET model used in the calculation. A new dedicated JET benchmark experiment will be performed trying to solve these issues.     

Using computer techniques for vibration damage estimation under stochastic loading using the Monte Carlo Method for aerospace applications

The main focus of this article is a review of legacy methods for vibration damage estimation under stochastic loading and extending research made by Dirlik and Bendat using two combined methods: FEM and Monte Carlo simulation, for which we used Python programming for aerospace applications. For some aircraft, regulated by the RTCA international aviation standard DO-160G (Environmental Conditions and Test Procedures for Airborne Equipment), stochastic loading is defined as one of the requirements. This article will focus on the stochastic loading impact on the fatigue life assessment made on a dummy sample, and frequency and time domain damage estimation shall be considered in parallel to compare both results. Additionally, dummy PSD responses shall be defined in the frequency domain for signal statistical parameters research. The article introduces Rainflow Cycle Counting methods in the frequency domain for procedures used commercially in aerospace applications. The first method introduced and developed further is the Dirlik method of Rainflow Cycle Counting in the frequency domain, which is the most popular method in commercial use. The second technique introduced and developed further was established by Bendat — the Narrow Band Method. The new empirical equation presented in this paper is the modification of the Narrow Band Method fitted for general use (narrow band, wide band, and white noise signals). A new approach for the integration of spectral moments is introduced in this paper, allowing for an accurate evaluation of the signal statistic parameters in the frequency domain for use in the modified Dirlik and Narrow Band methods. Research results also revealed new phenomena not researched by Dirlik, such as high vibration damage variation from stochastic loading, which depends on the frequency resolution (the block size used in Inverse Fourier Transformation). This discovery will be the subject of further study. Research results presented in this paper will also be utilised to combine stochastic and deterministic loading scenarios for military helicopters, as well as fighter aircraft, and will be the subject of further research.     

蒙特卡罗模拟计算中能X射线自由空气电离室电子损失修正因子

采用蒙特卡罗模拟方法计算了中能X射线自由空气电离室在入射不同能量光子时的电子损失修正因子.根据此结果,获得中能X射线基准电离室在5个辐射束规范下的电子损失修正因子,为中能X射线空气比释动能的绝对测量和国际比对提供了重要数据.