Spatial error propagation when computing linear combinations of spectral bands: The case of vegetation indices

The collection of accurate and timely information on land use, crops, forest and vegetation are increasingly based on remote sensing spectral measurements produced by satellites. The most recent spacecrafts like the Earth Observing 1 (EO-1) produce a rich source of information being endowed with hyperspectral sensors that can provide up to 200 or more channels. In many instances such a multivariate signal has to be reduced to just one single value per pixel representing a particular characteristic of land. Linear combinations of bands are the general form of many indices. Since each individual image used to construct indices contains errors, when combined they produce a propagation of errors, a process that can distort a final output map. In this paper we measure the extent of error propagation when building linear vegetation indices. We consider three types of indices: the difference vegetation index (DVI), selected Kauth-Thomas indices (SBI, GVI and WET), and principal components, using benchmarking examples taken from the remote sensing literature. The main implication emerging from these examples is that the SBI and the first principal component are the indices more prone to error propagation. The formalization presented here allows a user to derive measures of error propagation in cases where technical characteristics of a sensor and physical characteristics of a landscape are known. These results can help a user to choose between alternative vegetation indices, and to associate a measure of reliability with such indices.     

原子吸收法测定人发中的铜锌铁钙

以家用微波炉，全聚四氟乙烯微波消化罐和ＨＮＯ３／Ｈ２Ｏ２消解体系溶样，选择最佳溶样条件，对发样和标准物质进行测定，并和传统湿法（ＨＮＯ３／ＨＣＬＯ４）消解体系溶样做了对比，通过测定和比较，表明微波溶样具有较好的精密度和准确度，证明这一方法是可行的。     

Locational Errors in Maps from Environmental Surveys and Their Implications for Information Extraction

1.Information on all maps, including those which depict characters of the natural environment, is subject to locational error. 2.Locational errors on field-sketched maps are attributable to inaccuracies both in the base map itself and in the method of locating and recording features onto the base map. 3.Two main sources of error associated with field sketch mapping were quantified using the River Corridor Survey maps as an example. First, channel widths are routinely exaggerated on these maps to allow recording of in-channel features. Distortions of river bank length of the order of 25% were shown to arise from a four-fold exaggeration of the width of a sinuous channel. Second, discrepancies in feature location of the order of 20% were found along a 500 m river stretch, although errors could be reduced to approximately 2% if undistorted, large-scale base maps were used. 4.An abundance scale appropriate to the inherent locational inaccuracy was devised to extract semi-quantitative information from River Corridor Surveys recorded on distorted base maps. Application of this scale to 29 River Corridor Survey maps of a 14·5 km river corridor produced a useful representation of environmental gradients within the corridor. 5.With the increasing potential to integrate and analyse environmental information within large computer databases including Geographic Information Systems, it is essential that the level of accuracy is recognised and quantified so that the errors can be allowed for in the development of methods of extracting information from the maps.     

双样图在质量控制考核中的应用

双样图可应用于实验室分析质量考核中，除了判断测定数据的质量外，也可以利用双样图来分析不同实验室或同一实验室不同分析人员测定数据误差大小及主要来源。应用双样图具有速度快、方便、效果好的特点，避免了实验室工作质量控制考核中，仅凭双样的保证值判断数据合格与否的单一性和不完全性。     

人的失误本质及检测的研究

对人的失误本质、定义及特点作了系统的分析研究。针对人的失误产生条件、原因及类型，提出了检测失误与控制失误的技术     

An incident investigation on an unexpected loss of containment and damage to PHI-TEC II during acrylonitrile runaway tests

This article investigates a laboratory incident that occurred during the analysis of a thermal runaway reaction of acrylonitrile monomer. This failure, which was attributed to an human error, resulted in financial losses and corresponding unexpected results. The incident not only damaged the interior of the vessel and other instrument parts, but also exposed the researchers to considerable danger, necessitating their escape from the laboratory. The failure characteristics are discussed, and countermeasures are developed to prevent such a type of incident from reoccurring.     

第二代人的可靠性分析方法的进展

在探讨第一代人的可靠性分析 (HRA)方法的局限性之后 ,笔者进而探讨第二代HRA方法的模型 ,建立在多种学科 (认知心理学、行为科学、可靠性工程等 )相互结合的基础上 ,又着重研究产生人的行为 /绩效的情景环境以及它们是如何影响人的行为 /动作的 ,并与工业系统的运行经验和现场或模拟机获得的信息紧密结合。重点介绍了以“失误分析技术”(ATHEANA)和“认知可靠性和失误分析方法”(CREAM)为代表的第二代HRA方法。它们是当前HRA领域中的具有应用和发展前景的新框架思想。     

Misuse of booster cushions among children and adults in Shanghai—an observational and attitude study during buckling up

Objective: Traffic crashes are one of the leading causes of fatalities among Chinese children. Booster cushion usage in China is low, and there are no studies showing how a population with limited experience handles booster cushions during buckling up. The purpose of this study was to evaluate the handling of and explore the attitudes toward booster cushions among children, parents, and grandparents in Shanghai.

Methods: An observational study including a convenience sample of 254 children aged 4–12 years was conducted in 2 passenger cars at a shopping center in Shanghai. Parents, grandparents, or the children themselves buckled up the child on 2 types of booster cushions, a 2-stage integrated booster cushion (IBC) and an aftermarket booster cushion (BC). The test participants were observed during buckling up, first without and then with instructions. The test leaders conducted structured interviews.

Results: Ninety-eight percent of the uninstructed participants failed to buckle up without identified misuse on the aftermarket booster cushion and 31% of those uninstructed on the integrated booster cushion. The majority of misuse was severe, including placing the belt behind the arm and the lap belt routing above the guiding loops. Instruction reduced misuse to 58% (BC) and 12% (IBC), respectively, and, in particular, severe misuse. Some misuse was related to limited knowledge of how to buckle up on the booster cushion, and some misuse was intentional in order to reduce discomfort.

The participants, both children and adults, reported that they preferred the IBC due to good comfort and convenience. Safety was reported as the main reason for adults using booster cushions in general, whereas children reported comfort as the most important motivation.

Conclusions: Education is needed to ensure frequent and correct use of booster cushions in China and to raise safety awareness among children and adults. Furthermore, it is important that the booster cushions offer intuitively correct usage to a population with limited experience of booster cushions.

This is the first study published on the handling of and attitude toward booster cushions after child restraints laws were introduced in Shanghai 2014.     

HpGe γ谱仪本底变化对环境样品放射性测量结果的影响

在环境样品测量过程中,本底涨落对天然核素测量结果的影响应根据其在谱仪中计数率的高低具体分析.用γ谱仪测量介质中天然放射性核素的活度浓度时,必然要进行本底谱的扣除,由此会带来一定的误差.对一台N型HpGe γ谱仪在8年间的23个本底谱进行了研究,并分析了本底涨落对测量结果的影响.研究发现,被测介质中天然放射性核素的活度浓度越低,本底涨落越大,由扣除本底引入的误差就越大.