Interannual and intra-annual cycles of satellite-derived chlorophyll-a concentrations in the Caspian Sea

Variability of phytoplankton in the Caspian Sea (CS) is related to the complex orography, the variety of physical and chemical processes, and climatic indices. Here, interannual and intra-annual variability of satellite-derived chlorophyll-a concentrations (Chl-a) were studied using wavelet analysis during 2002–2019 in different regions of the CS. Self-Organizing Maps (SOM) analysis performed to classify the CS into the areas of similar variability of satellite-derived Chl-a. Wavelet spectral analysis showed that the Chl-a variability regulated by four primary periodic cycles: 0.5-year, 1-year, 2 to 2.5-year, and 3 to 5-year. The 0.5 and 1-year wavelet cycles mostly depicted the intensity of seasonality patterns. The 2–2.5-year and 3–5-year cycles of Chl-a showed non-stationary coherence with corresponding low-frequency cycles of NAO and ENSO. The 3–5-year wavelet amplitudes of Chl-a strongly correlated with NAO and ENSO in the southern CS. Weak correlations of 2–2.5-year cycle wavelet amplitudes of Chl-a with NAO and ENSO suggested that variations do not always directly translate to a biological response. A negative anomaly in the Chl-a autumn peaks observed during 2011–2016 in the middle and southern CS, when NAO phases were persistently positive. The interannual variations of summer peaks in the northern CS, and autumn peaks in the middle and southern CS were broadly related to the precipitation. SST and wind stress. Moreover, it was shown that the Volga discharge has a significant influence on Chl-a variability in the northern CS.     

TGA analysis of γ‐irradiated linear low‐density polyethylene

Linear low‐density polyethylene (LLDPE), based on butene‐1 or hexene‐1, was irradiated with γ‐rays under vacuum or in the presence of air. The study focused on the influence of the dose rate and the γ‐dose on the thermal properties of LLDPE. Differential scanning calorimetry, thermogravimetric analysis (TGA), and TGA/FTIR techniques were used to address the thermal behavior as a result of γ‐irradiation. During this irradiation, competition between crosslinking and scission reactions, subsequent to oxidation reactions, occurred in the polymeric material, which strongly depends on the experimental conditions. A decrease of the crystallinity for γ‐irradiated samples was observed in particular for samples irradiated under vacuum. This observation may be explained by increased hindrance of segment mobility due to crosslinking reactions that prevent crystal growth. TGA investigations revealed an enhancement of the thermal stability for samples irradiated under vacuum but not for those irradiated in air. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2790–2795, 2006     

几种光谱方法(FTIR、FT-Raman,NMR)在橡胶分析中的应用

综述了傅里叶变换红外光谱 ,傅里叶变换拉曼光谱以及核磁共振波谱在橡胶结构的定性、定量分析中的应用     

基于灰度形态重构的颗粒图像分割方法

提出了一种基于距离变换、形态重构和分水岭算法的图像分割算法。将一幅图像通过距离变换得到距离灰度图,与形态重构算法结合,得到颗粒图像的标识点图,用标识点图对距离灰度图进行分割,再用分水岭变换对分割后的距离灰度图进行变换。试验表明,该算法能有效合理地解决粘连或者重叠颗粒等物体的分割。     

Computing a compact spline representation of the medial axis transform of a 2D shape

We present a full pipeline for computing the medial axis transform of an arbitrary 2D shape. The instability of the medial axis transform is overcome by a pruning algorithm guided by a user-defined Hausdorff distance threshold. The stable medial axis transform is then approximated by spline curves in 3D to produce a smooth and compact representation. These spline curves are computed by minimizing the approximation error between the input shape and the shape represented by the medial axis transform. Our results on various 2D shapes suggest that our method is practical and effective, and yields faithful and compact representations of medial axis transforms of 2D shapes.     

依托软件和信息技术服务业,助推大连经济转型升级

软件和信息技术服务业作为信息化的核心和灵魂,对经济社会发展具有重要的支撑和引领作用。然而,在当前国际金融危机、人力资本上升、国内外城市激烈竞争等众多不利因素的影响下,软件和信息技术服务业发展面临艰巨的挑战。因此,本文以大连为研究对象,结合当前的形势,分析发展软件和信息服务业的重要作用,并为如何发展好软件和信息技术服务业提出对策建议。     

粗集理论及其在旋转机械故障诊断中的应用 (二)旋转机械故障诊断知识库的形成

旋转机械故障诊断知识库形成的主要环节是信号的采集和信号的分析、整理 ;在所有的机械故障信号中 ,振动诊断技术是故障诊断的常用手段 ,对振动信号实现连续、在线诊断的最重要的数学工具是快速傅里叶变换(FFT)和小波理论。通过对实验的观察 ,建立转子故障特征向量和故障类型之间对应关系的数据库 ,为基于粗集理论故障诊断的决策表的形成提供了原始的知识库     

Lipid adsorption on commercial silica hydrogels from hexane and changes in triglyceride complexes with time

The structures of and lipid complexes with two commercial silica hydrogels (Trisyl and Sorbsil 40), which contain about 60% moisture, were examined by diffuse reflectance Fourier transform infrared spectroscopy. The spectra suggested that Trisyl contained less moisture than Sorbsil 40. However, the silanol groups of Sorbsil 40 were more active in adsorbing oleic acid, triglyceride, and phosphatidylcholine (PC) from hexane than those of Trisyl. Both adsorbents strongly bound PC through the PC carbonyl and phosphate groups. Lipid adsorption from hexane solution by Trisyl depended solely on trapped moisture, while Sorbsil 40 used moisture and silanol groups on the silica surface. Spectra of triglyceride-silica hydrogel complexes, obtained 24 and 72 h after obtaining the initial spectra, showed that Sorbsil 40 adsorption was by Van der Waals forces, but the triglyceride reoriented over time with an increase in hydrogen bonding. In contrast, Trisyl initially adosorbed triglyceride by hydrogen bonding which was stable for at least 72 h.     

基于不可分小波分解的图像配准方法

张量积小波强调的是图像中水平和垂直方向的高频信息,而不可分小波具有各向同性,可以提取图像中各个方向的边缘,能获得比较完整的图像轮廓,将这种特点应用于图像配准时,能准确定位图像仿射不变点的位置。为此,提出一种通过求取不可分小波分解后的高频子图像配准参数来配准原图像的方法,把图像的配准问题转化为其不可分小波分解后的高频子图像配准问题。从不可分小波分解的快速算法理论出发,证明该配准方法的正确性。构造一组四通道不可分小波滤波器组,在此基础上给出配准的方法和步骤。实验结果表明,该方法具有较好的配准效果,其求取图像配准参数的运算量比直接求取原图像配准参数运算量的1/4还少,与基于张量积小波分解的图像配准方法相比,具有较高的配准精度。