二次型时频分析技术的开发与应用

基于二次型的时频分析是高分辨率时频分析技术的有效方法之一，该项技术能够有效反映时变信号的频谱特性，具有分辨率高、能量集中和跟踪瞬时频率的特点。从时变信号的特点出发，阐述了二次型时频分析技术的基本方法原理，采用正演模型分析验证了该方法的有效性，并在实际地震资料中应用于识别物源方向、划分沉积相带、预测储层结构以及相对厚度等诸多方面，均取得了较好的效果。     

Effect of storage temperature on phenolics stability in hawthorn (Crataegus pinnatifida var. major) fruits and a hawthorn drink

The stability of five major phenolics, namely (−)-epicatechin (EC), procyanidin B₂ (PC-B₂), chlorogenic acid (ChA), hyperoside (HP) and isoquercitrin (IQ), in hawthorn fruits and a canned hawthorn drink were evaluated during 6 months of storage in the dark at three different temperatures (4, 23 and 40 °C). HPLC with a diode-array detector was used to determine the contents of the individual compounds. The results showed that the studied phenolics in the hawthorn fruits and the drink were both stable at 4 °C and relatively unstable at 23 and 40 °C with varied extents of degradation. At room temperature (23 °C), marked degradations of EC and PC-B₂ were observed in both the fruits and the drink with around 50% and 30% decrease after a 6-month storage, respectively. A more significant decrease of the phenolics was observed at 40 °C, especially for EC and PC-B₂, which were almost completely degraded after a 6-month storage. HP, IQ and ChA were relatively stable at 23 °C, but unstable at 40 °C. Therefore, low-temperature storage is recommended for maintaining the quality and efficacy of hawthorn fruits and its preparations.     

国外复合材料用高级增强纤维的发展现状

本文综述了国外碳纤维、陶瓷、聚芳酰胺、超高分子量聚乙烯、液晶聚合物纤维的发展现状,包括它们的生产能力、消费情况、性能特点,主要生产国和生产公司、产品牌号以及应用领域等,并指出了其生产进展和发展动向。     

隧道工程施工中应注意的问题

通过对海南省东线高速公路大茅山隧道施工的全程监理,阐明了在施工中应重点注意的几个问题,在此基础上,总结出隧道工程质量监督中必须做到的几点,以确保隧道工程施工安全及工程质量.     

Grafting of maleic anhydride onto polyethylene through a green chemistry approach

The grafting of a polymer can lead to the improvement and modification of the polymer and thus expand its applications. Grafting methods include solution grafting in organic solvents, melt grafting at high temperatures, and light grafting with radioactive sources. These methods have their advantages and disadvantages. The disadvantages include waste treatment, consumption of energy, and so on. In this study, a hydrothermal process which is called the green approach, was developed to prepare graft copolymers. The effect of various factors on the grafting degree was investigated in detail. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Studies of substrate specificities of lipases from different sources

Although lipases are widely applied in a wide variety of reactions, available information on the factors that are responsible for the substrate specificities of lipases from different sources is scarce. In this paper, nine lipase‐producing microorganism strains were isolated from oil‐containing samples. The properties of these enzymes, including pH optima, temperature optima, thermal stability, and pH stability, vary significantly with the different sources from which these lipases were isolated. The substrate specificities of the nine lipases, including fatty acid and positional specificities, were also studied. The fatty acid specificities of the nine lipases were observably different toward 15 substrates with different carbon chain lengths, different saturation degrees and different side chains. The lipases from S₃ Penicillium citrinum (PCL), MJ₁ Aspergillus niger (ANL), MJ₂ Aspergillus oryzae (AOL), YM Bacillus coughing (BCL), S₉ Geotrichum candidum (GCL), and S₁₁ Candida lypolytica (CLL) showed the strongest specificities to short‐chain esters, and the other lipases showed strong selectivity for medium‐ or long‐chain and branched esters. The positional specificities were examined by analyzing the hydrolytic products of triolein catalyzed by the nine lipases, using TLC. The lipases can be mainly classified into two groups by their specificities for the ester bond at position 2 of triglycerides; one group can selectively hydrolyze the ester bond at position 2 of the triglycerides, the other group cannot. All these nine lipases were divided into four groups by hierarchical clustering analysis on the basis of the results of fatty acid and positional specificities.     

尼龙6/改性双马来酰亚胺共混物的制备

将尼龙6与改性双马来酰亚胺熔融共混形成合金以提高其热稳定性能.用转矩流变仪考察了尼龙6/改性双马来酰亚胺共混体系熔融反应过程中的流变行为,用TG-DSC测试了共混物的热性能.结果表明:熔融共混时,2组分间的化学反应进行很快,改性双马来酰亚胺用量增加,共混物的熔融粘度增大,温度或转速升高,平衡转矩降低;改性双马来酰亚胺可明显改善尼龙6的高温热稳定性能,当尼龙6与改性双马来酰亚胺的质量比为20/1时,共混物在236-340℃温度范围内有很好的热稳定性.     

Matlab软件在分形几何上的应用

以Koch曲线和塞尔平斯基三角形为例,介绍了Ma tlab软件在分形几何方面,对不规则图形进行直观描绘的方法。     

杀菌剂异螺环-4-烯-2,3-5''''-氯-吲哚的合成

研究了以薯蓣皂素(diosgenin)为原料,根据活性叠加原理,在分子中引入一个新的活性基团吲哚环,合成了全新化合物异螺环-4-烯-2,3-5'-氯-吲哚.杀菌药效试验结果表明:所设计的全新目标化合物具有原料所没有的杀菌活性.