Monte Carlo method for evaluation of surface emission rate measurement uncertainty

The aim of this study is to evaluate the uncertainty of 2πα and 2πβ surface emission rates using the windowless multiwire proportional counter method.This study used the Monte Carlo method (MCM) to validate the conventional Guide to the Expression of Uncertainty in Measurement (GUM) method.A dead time measurement model for the two-source method was established based on the characteristics of a single-channel measurement system,and the voltage threshold correction factor measurement function was indirectly obtained by fitting the threshold correction curve.The uncertainty in the surface emission rate was calculated using the GUM method and the law of propagation of uncertainty.The MCM provided clear definitions for each input quantity and its uncertainty distribution,and the simulation training was realized with a complete and complex mathematical model.The results of the surface emission rate uncertainty evaluation for four radioactive plane sources using both methods showed the uncertainty’s consistency E_(n)<0.070 for the comparison of each source,and the uncertainty results of the GUM were all lower than those of the MCM.However,the MCM has a more objective evaluation process and can serve as a validation tool for GUM results.

Secondary electron emission and photoemission from a negative electron affinity semiconductor with large mean escape depth of excited electrons

The formulae for parameters of a negative electron affinity semiconductor(NEAS)with large mean escape depth of secondary electrons A(NEASLD)are deduced.The methods for obtaining parameters such asλ,B,E_(pom)and the maximumδandδat 100.0 keV≥E_(po)≥1.0 keV of a NEASLD with the deduced formulae are presented(B is the probability that an internal secondary electron escapes into the vacuum upon reaching the emission surface of the emitter,δis the secondary electron yield,E_(po)is the incident energy of primary electrons and E_(pom)is the E_(po)corresponding to the maximumδ).The parameters obtained here are analyzed,and it can be concluded that several parameters of NEASLDs obtained by the methods presented here agree with those obtained by other authors.The relation between the secondary electron emission and photoemission from a NEAS with large mean escape depth of excited electrons is investigated,and it is concluded that the presented method of obtaining A is more accurate than that of obtaining the corresponding parameter for a NEAS with largeλ_(ph)(λ_(ph)being the mean escape depth of photoelectrons),and that the presented method of calculating B at E_(po)>10.0 keV is more widely applicable for obtaining the corresponding parameters for a NEAS with largeλ_(ph).

Determination of absolute gamma-ray emission probabilities for ^(88)Kr

In preparation of homogeneous Kr and Rb sources,the Kr activity was determined by the decay relationship between ^(88)Kr and ^(88)Rb using an HPGe detector.The peak efficiencies of ^(88)Kr and ^(88)Rbγ-rays were calibrated.The results show that the absolute probabilities of 196.3,834.8,1529.8,2195.8 and 2392.1 keVγ-rays of ^(88)Kr were 25.1(5)%,12.9(2)%,10.7(2)%,13.3(2)%and 34.9(5)%,respectively.

A new perspective on the diffuse gamma-ray emission excess

The Large High-Altitude Air Shower Observatory(LHAASO)recently published measurements of diffuse Galactic gamma-ray emission(DGE)in the 10−1000 TeV energy range.The measured DGE flux is significantly higher than the expectation from hadronic interactions between cosmic rays(CRs)and the interstellar medium.This excess has been proposed to originate from unknown extended sources produced by electron radiation,such as pulsar wind nebulae or pulsar halos(PWNe/halos).In this paper,we propose a new perspective to explain the DGE excess observed by LHAASO.The masking regions used in the LHAASO DGE measurement may not fully encompass the extended signals of PWNe/halos.By employing a two-zone diffusion model for electrons around pulsars,we find that the DGE excess in most regions of the Galactic plane can be well explained by the signal leakage model under certain parameters.Our results indicate that this signal leakage from known sources and contributions from unresolved sources should be considered as complementary in explaining the DGE excess.

Emission Intensity in the Hydrogen Atom Calculated from a Non-Probabilistic Approach to the Electron Transitions

Quantum aspects of the Joule-Lenz law for the transmission of energy allowed us to calculate the time rate of energy transitions between the quantum states of the hydrogen atom in a fully non-probabilistic way. The calculation has been extended to all transitions between p and s states having main quantum numbers not exceeding 6. An evident similarity between the intensity pattern obtained from the Joule-Lenz law and the corresponding quantum-mechanical transition pro-babilities has been shown.

Semiclassical and Quantum-Mechanical Formalism Applied in Calculating the Emission Intensity of the Atomic Hydrogen

The energy spectrum of the hydrogen atom has been applied in calculating the time rate of energy transitions between the quantum states of the atom. The formal basis of the approach has been provided by the quantum properties of energy and time deduced from the Joule-Lenz law. The rates of the energy transitions obtained in this way were compared with the quantum-mechanical probabilities of transitions calculated earlier by Bethe and Condon and Shortley for the same pairs of the quantum states.

Secondary electron emission model for photo-emission from metals in the vacuum ultraviolet

This study investigates two secondary electron emission(SEE)models for photoelectric energy distribution curves f(E_(ph),hγ),B,E_(mean),absolute quantum efficiency(AQE),and the mean escape depth of photo-emitted electronsλof metals.The proposed models are developed from the density of states and the theories of photo-emission in the vacuum ultraviolet and SEE,where B is the mean probability that an internal photo-emitted electron escapes into vacuum upon reaching the emission surface of the metal,and E_(mean)is the mean energy of photo-emitted electrons measured from vacuum.The formulas for f(E_(ph),hγ),B,λ,E_(mean),and AQE that were obtained were shown to be correct for the cases of Au at hγ=8.1–11.6 eV,Ni at hγ=9.2–11.6 eV,and Cu at hγ=7.7–11.6 eV.The photoelectric cross sections(PCS)calculated here are analyzed,and it was confirmed that the calculated PCS of the electrons in the conduction band of Au at hγ=8.1–11.6eV,Ni at hγ=9.2–11.6 eV,and Cu at hγ=7.7–11.6 eV are correct.

X and γ-rays emission probabilities of ^(131)I and ^(133)Xe

Radioactive nuclides as 131I and 133Xe are increasingly used for both clinical diagnosis and therapeutic treatment of the patient. For example, 131I is used for the treatment of thyroid gland cancer. Otherwise, 133Xe is used in ventilation studies to assess and evaluate pulmonary function and to provide images of the lungs in both cardiac and pulmonary diseases, such as asthma, pulmonary emphysema, bronchiectasis, carcinoma of the lung, and pulmonary embolism [1,2]. Furthermore, cerebral blood flow is measured using 133Xe inhalation. In this study, the X and γ-rays emission probabilities in the decay of 131I and 133Xe were precisely measured with a calibrated Si(Li) detector. Results of this study were compared using available results in the literature. Good agreement was observed between our results and available results in the literature.

基于绿电和自愿减排量交易的园区低碳电力运营优化

为保证园区电力运营经济性,提高清洁电能的使用比例,文章提出了一种基于绿电和自愿减排量交易的园区低碳电力运营优化模型。该模型综合考虑了绿电和火电的购电成本、光伏发电成本及自愿减排量收益,以总运营成本最小为目标函数,结合随机概率约束,分中长期、日前和实时三阶段对绿电、火电电量以及光伏发电量进行优化。以南京市某企业园区的数据为基础,在自愿减排量价格合理的前提下,该优化模型可小幅降低园区总运营成本,并且显著提高了清洁电能的使用比例和园区应对扰动的能力。另外,就自愿减排量价格以及置信度取值对优化结果的影响进行了分析。

含T型与L型裂纹杉木构件损伤声发射参数特性研究

为研究不同裂纹木构件的声发射参数变化规律,以含T型和L型裂纹杉木构件为研究对象,利用声发射系统(AE)检测木构件在轴压荷载下的声学信号,并使用声发射参数分析法、概率密度和最大似然法分析声学数据特征。结果表明:声发射参数对轴向荷载作用下木构件的裂纹萌生、扩展规律具有良好的预判性。概率密度分析和最大似然法得出的木构件在轴压荷载下声发射能量信号符合幂律分布特征,其中T型和L型裂纹幂律指数分别为1.37和1.52。试验结论可为其他木构件的损伤评估提供方法依据。

基于声子晶体的声发射波源检测概率研究

声发射(acoustic emission,AE)检测就是利用采集和分析声发射现象所产生的信号从而实现对材料进行无损评价的技术,该技术具有实时监测并定位破坏源的能力但是由于检测过程中声发射源信号未知,因此评价检测可靠性的检测概率(probability of detection,POD)研究仍然是空白。进一步来说,在利用声发射监测损伤过程时,声发射波源直接决定其检测结果的可靠性,因此波源的检测概率可以成为量化声发射检测有效性的一个重要指标。为了确定声发射波源的检测概率,利用声子晶体(phononic crystals,PCs)的特性,通过部署声子晶体形成物理带隙,滤除噪声信号,从而获得铝合金试件在紧凑拉伸试验下由于疲劳裂缝活动而引起的声发射信号,最终确定声发射源的检测概率及其影响因素。结果表明,检测概率会随着疲劳裂缝扩展而提高,但裂缝长度达到一定值后开始下降,最终趋于一个平稳值,另外通过设置阈值和选择适当的滤波器,能有效提高检测概率,保证声发射评价结构损伤的有效性。该研究对声发射源识别和检测可靠性评价具有重要意义。

数据透视方法下的充电桩低频辐射特性分析

GB/T 18487.2—2017新增对充电桩设备低频电磁辐射发射的具体要求,但大量测试数据仅以“频率-幅度”二维数据表格的形式记录和呈现。为直观获得大样本直流充电桩低频辐射干扰的分布特点和趋势,采用数据透视的分析方法对大样本数据进行分析。将直流充电桩关键字作为信息标签,针对信息标签对测试数据进行筛选排序、分类汇总和交互式查询。通过平面投影、直方图、区间化幅度概率分布等数据可视化方法,呈现大样本数据的统计特性。采用数据透视方法进行直流充电桩低频辐射特性分析,以直观获得样本数据的统计规律。该规律能够为统计产品特性、提高产品性能提供直观的参考依据。数据透视分析方法同样适用于其他测试数据的统计特性分析。

Exciton-Dependent Pre-formation Probability of Composite Particles

In Iwamoto-Harada model the whole phase space is full of fermions. When the momentum distributions of the exciton states are taken into account, the pre-formation probability of light composite particles could be improved, and the exciton state-dependent pre-formation probability has been proposed. The calculated results indicate that the consideration of the momentum distribution enhances the pre-formation probability of [1, m] configuration, and suppresses that of [ι 〉 1, m] configurations seriously.

气候变化影响下钢筋混凝土碳化损伤不确定性分析

CO_(2)的累积排放会对钢筋混凝土造成严重不可逆的腐蚀损伤。此外,温度的升高也会加速腐蚀速率。因此,探究气候变化对未来混凝土的耐久性的影响具有重要意义。依据优化的碳化深度预测模型,结合世界气候变化研究组织机构(IPCC)预测的大气CO_(2)浓度最新数据,描述了不同排放策略下的CO_(2)浓度和全球表面平均气温变化的规律,并分析两者对混凝土结构碳化损伤的影响。由此提出一种在不同CO_(2)排放策略作用下,同时考虑空间变异性、偶然和认知不确定性的混凝土碳化腐蚀概率评估方法,以此来计算不同服役时间下的混凝土碳化深度和碳化腐蚀开始概率。研究表明:根据最新气候报告数据,随着水灰比的增加,碳化深度在不断增加且增幅也不断变大;当考虑空间变异性时,会使RCP2.6和RCP8.5排放策略的碳化深度都增加12%以上。而无论是否考虑空间变异性,RCP8.5对应的碳化深度都是RCP2.6的1.77倍以上。在RCP8.5排放策略下,同时考虑空间变异性、偶然和认知不确定性的混凝土碳化腐蚀开始时间比仅考虑偶然不确定性提早了16 a。研究结果证明了研究混凝土碳化损伤考虑未来的气候变化和不确定性分析的必要性。

随机特性下考虑碳排放的公交优先控制优化模型

在交通强国建设的大背景下,大力发展城市公共交通,推动城市可持续发展已然成为城市交通发展的必然要求。公交信号优先控制作为一种主动优先策略,可有效减少公交车辆在信号交叉口处产生的碳排放和延误,提升公交服务质量。为研究公交优先控制策略对交通碳排放的影响,基于交叉口车速随机特性,引入公交车速概率密度函数,分析了延误、停车次数、速度等主要参数对交通碳排放的影响。采用车速引导与绿时延长的组合控制策略,以交叉口上游路段以及交叉口范围内不同燃料类型的公交车和小汽车的碳排放减少量最优为上层目标,以人总延误减少量最优为下层目标,以引导速度以及非公交优先相位被压缩的绿灯时间为决策变量,建立单交叉口公交优先控制双层优化模型,并采用Gauss-Seidel迭代算法对模型进行求解。最后,将所建立的模型应用算例进行分析,结果表明,在引导提速与绿时延长策略下,交叉口整体的碳排放和人总延误减少量可分别达到25.63%和36.27%。模型有效降低了交叉口上游路段以及交叉口范围内的碳排放和人总延误,在推动可持续发展的同时,实现了交叉口整体通行效益最优。

Evaluation of the 1077 keV γ-ray emission probability from ^(68)Ga decay

6SGa decays to the excited states of aSzn through the electron capture decay mode. New recommended values for the emission probability of 1077 keV γ-ray given by the ENSDF and DDEP databases all use data from absolute measurements. In 2011, JIANG Li-Yang deduced a new value for 1077 keV γ-ray emission probability by measuring the 69Ga（n,2n） 6SGa reaction cross section. The new value is about 20% lower than values obtained from previous absolute measurements and evaluations. In this paper, the discrepancies among the measurements and evaluations are analyzed carefully and the new values are re-recommended. Our recommended value for the emission probability of 1077 keV γ-ray is （2.72±0.16）%.

NITROGEN DETERMINATION IN THE SURFACE OF NITRIDED STEEL USING PROTON INDUCED GAMMA-RAY EMISSION ANALYSIS

Ⅰ. INTRODUCTIONIt has been established for some time that introduction of nitrogen in the surface and near surface regions of metal alloys can make important modifications in surface properties of the alloys such as hardness, wear and friction, corrosion resistance and fatigue time. Proton induced gamma-ray emission (PIGE) analysis provides a useful method for direct determination of nitrogen concentration in the surface of nitrided samples and also for its quality test and the investigation of new nitriding technology.The aims of the present work are to study the optimum conditions of

离散隐半马尔科夫跳跃系统的稳定性

研究了一类离散隐半马尔科夫跳跃线性系统的稳定性问题,通过改进引理,构造合适的Lyapunov函数、利用半马尔科夫核方法和发射概率等技巧。解决闭环系统的稳定性。

2050年中国碳排放量的情景预测--碳排放与社会发展Ⅳ

在简要评价碳排放预测方法和模型的基础上,对我国2050年的碳排放量进行了预测。结果表明,我国2050年碳排放量最佳可能范围为2.4～3.3PgC/a;人均碳排放量为1.7～2.3tC。最佳可能上限预测的碳排放量峰值年为2035年,碳排放量峰值为4.4PgC/a,人均碳排放量峰值为3.0tC。2006—2050年我国累计碳排放总量的最佳可能范围为102～156PgC,人均累计碳排放量为71～109tC。人均累计排放最佳预测上限低于美国同期累计人均排放,与发达国家同期累计人均排放相差不大,但在1850—2005年,我国累计人均排放分别是发达国家和美国的约1/10和1/20。这些表明就人均累计排放而言,我国与发达国家间仍然有较大的差距。

基于巴西劈裂试验的页岩声发射与能量分布特征研究

为探究不同角度层理下页岩力学特性和声发射特征,通过对不同角度层理龙马溪组页岩的巴西劈裂试验、声发射测试以及3DEC数值模拟研究,对页岩破坏模式进行了对比分析。研究结果表明:由于页岩具有明显的层理构造,其抗拉强度具有明显的各向异性。页岩巴西劈裂应力-时间曲线可划分为3个阶段,对低角度层理,受载的累计声发射曲线表现为"平缓—陡增"增长模式;对高层理角度,累计声发射曲线表现为"台阶式"增长模式。研究物理实验与3DEC数值模拟结果均表明页岩破裂模式与层理角度密切相关,页岩声发射能量概率密度P(E)均较好的满足幂定律,层理效应并不改变声发射能量的尺度不变性。层理角度为90°时,能量概率密度曲线的临界参数最大,在低能量区间的声发射信号所占比例更大,利用临界参数可以对巴西劈裂试验过程中页岩损伤程度进行表征。研究成果可对页岩气压裂工程的设计提供借鉴。