氢化物—石墨炉原位富集原子吸收光谱法测定痕量锑

本文对标示问题进行了研究，自行设计了氢化物发生器，采用以石墨炉两端输入氢化物方式，载气流向用活塞控制，大幅度减少原子化阶段石墨炉内氢气分压，提高了锑的灵敏度，对氢化锑的石墨炉表面分解沉积和原子化机理进行了讨论，方法有于矿泉水和自来水痕量锑的测定，结果令人满意，锑的特征浓度为３０ｐｇ／０．００４４Ａ。     

An airborne diode laser spectrometer for the simultaneous measurement of H2O and HNO3 content of stratospheric cirrus clouds

We describe a tunable diode laser spectrometer for the in situ simultaneous detection of the nitric acid and the water vapour by means of high resolution absorption spectroscopy on rovibronic lines, using a single laser emitting in the mid-infrared (5.8 μm) and a multipass cell. The instrument was designed to be installed on a high altitude aircraft, as a part of a composite payload for atmospheric aerosol studies. The instrument design criteria are discussed and the expected performances are compared with results of laboratory and field operation. Due to the high chemical activity of HNO₃, that makes difficult to use a reference cell, a fast sweep detection of direct absorption was used for the measurement. An absorption sensitivity of about 2×10⁻⁴ was achieved with an integration time of 2.5 s, corresponding to a concentration of about 4 ppb of HNO₃ in the cell and 0.1 ppb in the external aerosol. The data acquisition and processing techniques, based on the full molecular lineshape fitting are also shown and discussed, including some examples of the data acquired during the scientific flights.     

Aspects of discrete mathematics and probability in the theory of machine learning

This paper discusses the applications of certain combinatorial and probabilistic techniques to the analysis of machine learning. Probabilistic models of learning initially addressed binary classification (or pattern classification). Subsequently, analysis was extended to regression problems, and to classification problems in which the classification is achieved by using real-valued functions (where the concept of a large margin has proven useful). Another development, important in obtaining more applicable models, has been the derivation of data-dependent bounds. Here, we discuss some of the key probabilistic and combinatorial techniques and results, focusing on those of most relevance to researchers in discrete applied mathematics.     

高精密度无损伤检测黄金首饰技术

本文提出了一种高精密度无损伤检测黄金首饰技术。通过测定黄金首饰在测量液中的浮力后计算密度再查表而得。其特征是测量液为表面张力和粘度均较小的有机溶剂或其溶液，而且在测定浮力的同时同步测定该测量液的密度或温度。本技术简便可靠，标准偏差Ｓ＝±０．００３５，Ｔ检法ｔ９０＝０．１５。精密度±０．０１％，速率１２样／小时，既快又准，易于普及推广。     

A variational problem with lack of compactness for H(S;S) maps of prescribed degree

We consider, for maps in H^1/2(S¹;S¹), a family of (semi)norms equivalent to the standard one. We ask whether, for such a norm, there is some map in H^1/2(S¹;S¹) of prescribed topological degree equal to 1 and minimal norm. In general, the answer is no, due to concentration phenomena. The existence of a minimal map is sensitive to small perturbations of the norm. We derive a sufficient condition for the existence of minimal maps. In particular, we prove that, for every given norm, there are arbitrarily small perturbations of it for which the minimum is attained. In case there is no minimizer, we determine the asymptotic behavior of minimizing sequences. We prove that, for such minimizing sequences, the energy concentrates near a point of S¹. We describe this concentration in terms of bubbling-off of circles.     

ICP-AES测定土壤中钡、铬和锰含量的不确定度评定

电感耦合等离子体-原子发射光谱法(ICP-AES)测定土壤中钡、铬和锰含量的不确定度主要来源于样品称量、样品消解液定容体积和测定样品消解液中各元素的浓度,对这些分量进行了量化计算。土壤中钡、铬和锰的质量分数可分别表示为218.5±17.1,342.5±40.4,1468.9±47.1mg/kg。影响各元素含量测量不确定度的主要因素是测量样品消解液中各元素的浓度引起的不确定度。     

Concentration for Poisson U-statistics: Subgraph counts in random geometric graphs

Concentration bounds for the probabilities $\mathbb{P}(N\ge M+r)$ and $\mathbb{P}(N\le M?r)$ are proved, where $M$ is a median or the expectation of a subgraph count $N$ associated with a random geometric graph built over a Poisson process. The lower tail bounds have a Gaussian decay and the upper tail inequalities satisfy an optimality condition. A remarkable feature is that the underlying Poisson process can have a.s. infinitely many points.The estimates for subgraph counts follow from tail inequalities for more general local Poisson U-statistics. These bounds are proved using recent general concentration results for Poisson U-statistics and techniques involving the convex distance for Poisson processes.     

Quantum dice

In a letter to Born, Einstein wrote  [42]: “Quantum mechanics is certainly imposing. But an inner voice tells me that it is not yet the real thing. The theory says a lot, but does not really bring us any closer to the secret of the ‘old one.’ I, at any rate, am convinced that He does not throw dice.” In this paper we take seriously Einstein’s famous metaphor, and show that we can gain considerable insight into quantum mechanics by doing something as simple as rolling dice. More precisely, we show how to perform measurements on a single die, to create typical quantum interference effects, and how to connect (entangle) two identical dice, to maximally violate Bell’s inequality.