Flame Atomic Absorption Spectroscopy in the Undergraduate Laboratory: Assessment of a NSF‐CCLI Supported Project. What Did the Students Learn and What Did We Learn?

In traditional chemistry curricula, students may encounter a particular instrument only once in their undergraduate career. We have developed an approach that exposes students multiple times to selected instruments, with early encounters focusing on fundamental aspects of the techniques and later encounters building in complexity and sophistication. We recently finished the assessment phase of a curricular project centered on the incorporation of flame atomic absorption spectroscopy throughout the undergraduate chemistry curriculum. Our assessment indicates that this approach is successful and our initial goals were largely achieved.     

基于组合权重和模糊随机方法的台风灾害风险评估

利用2000~2016年登陆华南地区的24个台风样本的灾情与致灾源数据,建立台风灾害风险评估模型。首先,运用层次分析法和熵权法构建一种新的组合权重;然后,利用组合权重构建灾情指数序列和致灾源指数序列,计算每个台风灾害风险值,并将风险值从小到大划分为五个区间;最后,采用模糊随机方法建立华南地区台风灾害模糊风险评估模型,计算得到五个风险等级区间的模糊可能性,以此来表示各等级台风灾害发生的可能性大小。结果表明,基于组合权重构造的灾情指数序列与致灾源指数序列相关性较强;华南地区发生第二风险等级台风灾害的可能性最大,发生第五风险等级台风灾害的可能性最小,与实际情况较为吻合。     

新疆巴州出口番茄酱中重金属的风险评估

采用微波消解,火焰与石墨炉原子吸收光谱法、氢化物发生-原子荧光光谱法对新疆巴州辖区出口番茄酱中的铜、铅、镉、铁、锌、砷、汞元素进行了分析,结果表明以上元素无超标,均能满足欧盟、日本、美国等出口国的标准。故其重金属残留的风险较低,属于中低风险项目。     

基于虚拟样本的火工品可靠性评估

为了提高小样本下火工品可靠性评估的精度,研究了升降法实验及其数据分析方法。结合火工品升降法实验数据的特点,给出了一种数据填充方法,把二元成败型数据转化为虚拟完全样本数据。模拟结果表明,与基于二元成败型数据的估计相比,基于虚拟完全样本数据的位置参数估计基本一致,而刻度参数估计具有更优的统计性质。利用该虚拟样本数据,结合信仰推断方法,给出了火工品可靠性评估方法。最后将该方法应用于某产品的可靠性评估,并与大样本评估方法进行了比较,表明该方法可以在较小样本下实现对高可靠性火工品的可靠性评估。     

GPU-accelerated real-time IR smoke screen simulation and assessment of its obscuration

With the growing demand for the Battlefield Environment Simulation (BES), IR smoke screen, which is computationally expensive and absolutely indispensable, should be modeled true to life and correct in its thermal radiation characteristics. This paper analyzes the features of an IR smoke screen, and represents an IR smoke screen model based on light extinction, particle dispersion and temperature attenuation, which is calculated by GPU and rendered to screen in real time. Thus a method considering both the real-life in profile and the real-time in efficiency is presented. Additionally, the comparison between the simulated results and the measured data is made to verify the correctness of the smoke screen’s obscuration, which illustrates the effect of its interference feature in an infrared scene.     

Discussion on sources of uncertainty for two TLD albedo dosimetry systems in a comparison of individual monitors in a reference 241Am–Be field

Under standard conditions, several studies assess uncertainty values for individual dosimetry for photons, but seldom for neutrons. The Thermoluminescent Dosimetry Laboratory (LDT) of the Instituto de Radioproteção e Dosimetria (IRD), Brazil, has been running a neutron individual monitoring service using two different albedo monitors. This paper presents a study of the contribution of relevant sources of uncertainty for neutron dose evaluation, for both systems (called System 1 and System 2), using a reference ²⁴¹Am–Be field, at normal incidence. The combined and expanded uncertainties were calculated using GUM methodology and follows RP160 from the European Commission. This methodology was applied to calculate the uncertainties associated with the LDT assessment of neutron doses in the First Brazilian National Comparison on Measurements for Neutron Individual Monitors. The LDT participated in this comparison with its two systems, both presenting satisfactory performance. For System 1, at low neutron doses, the reproducibility of the apparent neutron dose is the more relevant source of uncertainty. However, for higher doses, the neutron calibration factor, NCF, becomes more important. For System 2, NCF is the main source of uncertainty for low and high doses. For occupational doses, the uncertainty will be much higher due to the need of additional correction factors, which depend on stray neutron field.     

C3I系统知识库的类特征模式

在Ｃ３Ｉ系统知识库中引入了条件事件推理规则以及类与特征的概念,并给出了进行动态管理知识库的有效方法。     

Types of reasoning required in university exams in mathematics

Empirical research shows that students often use reasoning founded on copying algorithms or recalling facts (imitative reasoning) when solving mathematical tasks. Research also indicate that a focus on this type of reasoning might weaken the students’ understanding of the underlying mathematical concepts. It is therefore important to study the types of reasoning students have to perform in order to solve exam tasks and pass exams. The purpose of this study is to examine what types of reasoning students taking introductory calculus courses are required to perform. Tasks from 16 exams produced at four different Swedish universities were analyzed and sorted into task classes. The analysis resulted in several examples of tasks demanding different types of mathematical reasoning. The results also show that about 70% of the tasks were solvable by imitative reasoning and that 15 of the exams could be passed using only imitative reasoning.