Indoor Noise Reduction Index with an open window (Part II)

An index to evaluate indoor noise level reduction with an open window Noise Reduction Index (NRI) was proposed [Buratti C. Indoor Noise Reduction Index with open window. Appl Acoust 2002;63(4):431-51]. The reduction was due to the installation of a false ceiling in the room, thus reducing the contribution of the reverberant field. Experimental data related to two different kinds of false ceiling were compared to the results obtained by an original calculation model. Good agreement was found between experiments with two different materials and predictions. The present paper examines six different kinds of false ceiling and arrives at a new validation of the model. Calculations of NRI show good agreement with experimental data: a maximum difference of −1.2 dB(A) was found with a mean difference of 0.5 dB(A) for a wide range of absorption coefficient values. Hence the model represents a reliable instrument for indoor NRI prediction, if the acoustic absorption characteristics of materials are known.     

统计自相似集的重分形分解

设K是由Graf定义的统计自相似集.本文构造了一支撑在K上的随机测 度p,并研究了结合P的K的重分形分解,得到了分形谱函数f(α)的表达式.     

聚偏氯乙烯热解动力学研究

聚偏氯乙烯的热不稳定性被用作制备含碳材料的前驱体。本工作利用红外光谱在线检测功能，原位测定了聚偏氯乙烯热分解动力学过程的红外谱图，分析并计算了聚偏氯乙烯分子链中C-H和C-C1键断裂的反应活化能，得到了聚偏氯乙烯分解过程的动力学特性。     

Determination of the optimum electrical bandwidth for spectral slicing

The implementation of wavelength division multiplexing (WDM) in communication access networks is dependent upon the availability of low cost optical sources. One possible alternative to lasers is to employ slices of a broadband optical source obtained via optical filters, which may be tuneable. This paper considers the behaviour of such a spectrally sliced optical transmission system as a function of the bandwidth of a realistic receiver electrical filter for the first time. The treatment includes distortion from optical fibre dispersion over several kilometres of fibre. The optimum ratio between the electrical bandwidth and the optical bit rate is found to be ~0.6 for a fifth-order Bessel filter     

Analytically Class A operators and Weyl's theorem

Using the new spectrum set defined in this note, we give the necessary and sufficient condition for T which the Weyl's theorem holds. We also consider how the Weyl's theorem survives for analytically Class A operators.     

N，N-二甲基苯胺和苯醌间光诱导电荷转移

研究了N ,N 二甲基苯胺和苯醌间光诱导电荷转移的溶剂效应 .首先在B3LYP/ 6 31G 水平上对给体和受体进行构型优化 ,然后采用优化的给受体构型在Cs 对称性下计算得到两种相对稳定的复合物构象P和T .在CIS/ 6 31+G 水平上计算复合物气相激发态 ,结果发现 ,构象P的第三单重激发态发生分子间的完全电荷分离 ,构象T的第三激发单重态发生分子间的部分电荷分离 .在上述同样水平上计算复合物溶剂条件下的激发态性质 ,与气相结果相比表明 ,溶剂中两种构象的第三单重激发态均发生完全电荷分离 ,吸收光谱均发生较大红移 .     

Weyl spectra and Weyl's theorem

Two variants of the Weyl spectrum are discussed. We find, for example, that if one of them coincides with the Browder spectrum then Weyl's theorem holds, and conversely for isoloid operators.     

解析动态光谱的奇异值分解最小二乘法的改进

本文改进了处理动态光谱的奇异值分解最小二乘法（SVDLS），通过对模拟的蛋白质二级结构的动态圆二色谱和小牛胸腺DNA在电化学过程中动态紫外光谱的分析，表明该方法不仅给出动态过程中所包含的组分数，而且可同时获得各组分的光谱和各组分分数的分布曲线，是多种动态光谱数据处理的有效的无模型方法。     

双水相体系中镍的光谱性能及测定

本文研究了聚乙二醇 硫酸铵 锌试剂双水相体系中镍的光谱性能及测定。结果表明 ,该体系显色的最佳酸度为pH 8 5 ,络合物光谱最大吸收波长位于 6 75nm ,摩尔吸光系数ε=1 2 6× 10 4 L·mol- 1 ·cm- 1 ,Ni(Ⅱ )线性范围为 0 2～ 2 4 μg·mL 1 。Ni(Ⅱ )和锌试剂络合比为 1∶3。与一般水溶液光度法比较 ,络合物光谱最大吸收波长红移 10nm ,络合比增加 (由 1∶1到 1∶3) ,显色反应的灵敏度和稳定性提高。该方法用于铝合金中镍的测定 ,获得满意结果。     

尖-板电晕放电光谱分析

电晕放电是高电压设备中的一种典型的具有危害性的物理过程。对其物理机制进行分析,以及对其进行早期检测以便预防其发展,有助于提高电力绝缘系统的使用寿命和安全可靠程度。本文建立了一套高灵敏度的光谱分析系统,对空气中几种不同放电条件下的电晕放电进行了光谱分析。结果表明,电晕放电光谱由连续谱、谱带和谱线三部分组成。此外,光谱在红外区、可见光区和紫外区的辐射具有不同的特征,辐射强度随具体放电条件的变化规律也各不相同。与文献中的结果进行比较,发现各种条件下的电晕放电的可见光区辐射强度一般都比较弱,而紫外区与红外区辐射的强弱则与具体的放电条件有关。