杭州市2014年城区大气污染物浓度变化特征观测分析

为了研究杭州市城区大气污染物的浓度变化特征,本文选取了2014年杭州市环境监测中心站空气质量自动监测站的大气污染物浓度数据,并结合地面气象要素资料进行分析,结果表明,在观测期间,杭州市城区大气中的PM_2.5污染状况最严重,日平均浓度的超标率达30.7%;各污染物全年分布呈现明显的季节变化：O₃浓度呈现与该季节气温和太阳辐射强度在全年中的排列相一致的夏、秋、春和冬季依次递减的分布,NO₂则呈现冬高夏低,春秋介于两者之间的分布,SO₂浓度从高到低依次为冬季>春季>秋季>夏季,CO、PM_2.5和PM₁₀浓度都呈现出冬高夏季、春秋季变化平缓的季节变化特征;各污染物浓度日变化呈现不同变化规律：O₃和O_x浓度四季的日变化都呈单峰型分布,浓度峰值都出现在13:00～15:00,SO₂也呈现单峰型分布,在09:00～10:00左右达到峰值,于次日04:00左右达到谷值,NO₂、CO、PM_2.5和PM₁₀浓度的日变化特征类似,呈现双峰型变化,且峰值都与早晚高峰时间基本重合,冬季相对于其他季节首峰值时间推迟一小时左右;利用成对样本T检验进行比较,结果表明：NO₂浓度在17:00～次日09:00工作日均明显高于周末,而在09:00～14:00工作日略低于周末,14:00～17:00浓度基本相等,O₃浓度则在工作日的各时刻均高于周末;气象要素是大气污染物分布的重要影响因子,O₃与气温和风速呈极显著正相关关系,与湿度呈极显著负相关关系,NO₂与之相反,SO₂、CO、PM_2.5和PM₁₀与风速呈现一致的显著负相关关系外,与其他气象要素在不同季节差异性较大,SO₂和PM₁₀与相对湿度呈现极显著负相关关系,CO和PM_2.5与气温和湿度的相关性在不尽相同。     

Non-relativistic Limit of a Dirac Polaron in Relativistic Quantum Electrodynamics

A quantum system of a Dirac particle interacting with the quantum radiation field is considered in the case where no external potentials exist. Then the total momentum of the system is conserved and the total Hamiltonian is unitarily equivalent to the direct integral of a family of self-adjoint operators acting in the Hilbert space , where is the Hilbert space of the quantum radiation field. The fiber operator is called the Hamiltonian of the Dirac polaron with total momentum . The main result of this paper is concerned with the non-relativistic (scaling) limit of . It is proven that the non-relativistic limit of yields a self-adjoint extension of a Hamiltonian of a polaron with spin 1/2 in non-relativistic quantum electrodynamics.     

Magneto optics of single photons emitted from single InAs/GaAs self-assembled quantum dots in a planar microcavity

We fully characterize the fine spectral structure of neutral and negatively charged single microcavity quantum dot excitons, using polarization-sensitive magneto-photoluminescence spectroscopy. We show that the microcavity allows the simultaneous detection of both the bright and dark excitons using Faraday configuration. Thus, we were able to fully determine the fine structure and the g-factors of the neutral and negatively charged single exciton states within the same single quantum dot. Our measurements are in excellent agreement with novel, many carrier model calculations, which take into account Coulomb and exchange interactions among all the confined e–h pair states.     

The power of the likelihood ratio test for additional information in a multivariate linear model

Summary This paper deals with the likelihood ratio test for additional information in a multivariate linear model. It is shown that the power of the likelihood ratio test procedure has a monotonicity property. Asymptotic approximations for the power are also obtained.     

On bounded time-dependent perturbations of operator cosine functions

In this note it is shown that the Cauchy problem associated with the infinitesimal generatorA of a strongly continuous operator cosine function remains uniformly well-posed under bounded time-dependent perturbations ofA.     

Some bounds for partially balanced block designs

Bounds on eigenvalues of theC-matrix for a partially balanced block (PBB) design are given together with some bounds on the number of blocks. Furthermore, a certain equiblock-sized PBB design is characterized. These results contain, as special cases, the known results for variance-balanced block designs and so on.     

Factorizing multivariate time series operators

Motivated by problems occurring in the empirical identification and modelling of a n-dimensional ARMA time series X(t) we study the possibility of obtaining a factorization (I + a₁B + … + a_pB^p) X(t) = [Π_i=1^p (I ? α_iB)] X(t), where B is the backward shift operator. Using a result in [3] we conclude that as in the univariate case such a factorization always exists, but unlike the univariate case in general the factorization is not unique for given a₁, a₂,…, a_p. In fact the number of possibilities is limited upwards by $\text{(np)!}\text{(n!)}{}^{\mathrm{p}}$, there being cases, however, where this maximum is not reached. Implications for the existence and possible use of transformations which removes nonstationarity (or almost nonstationarity) of X(t) are mentioned.     

A note on realizing homomorphisms of category algebras

The complete Boolean homomorphisms from the category algebra $\text{C}$(X) of a complete matrix space X to the category algebra $\text{C}$(Y) of a Baire topological space Y are characterized as those σ-homomorphisms which are induced by continuous maps from dense G₈-subsets of Y into X. This result is used to deduce a series of related results in topology and measure theory (some of which are well-known). Finally a similar result for the complete Boolean homomorphisms from the category algebra $\text{C}$(X) of a compact Hausdorff space X tothe category algebra $\text{C}$(Y) of a Baire topological space Y is proved.