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81.
Extracted and unextracted black cherry (Prunus serotina), red oak (Quercus rubra), and red pine (Pinus resinosa) wood specimens were exposed to artificial weathering, and their discoloration process was investigated to obtain basic understanding on the role of wood extractives in the weathering of hardwoods and softwoods. Color measurements were made with a spectrometer according to ISO 2470 standards, using the CIELAB system. Results obtained showed that the rate of whiteness was not significantly affected by extractives removed with organic solvents, but were significantly affected when organic solvent extraction was followed by water extraction. The total discoloration rate had the same pattern, and chromaticity coordinates were less affected by wood extractives. These results confirm the hypothesis that some extractives contained in wood act as antioxidants and are able to provide some protection to wood surfaces against weathering degradation. However, more work is needed to understand the chemistry and mechanism of action of these extractives so as to develop any practical use for this property. © 2006 Wiley Periodicals, Inc. Col Res Appl, 31, 425–434, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20248 相似文献
82.
This study deals with evaluating the energy and exergy utilization efficiencies in the Turkish agricultural sector over a 12‐year period from 1990 to 2001. In the energy and exergy analyses, two main energy sources, namely fuels and electricity, are taken into consideration, while the sectoral energy and exergy efficiencies are compared for this period. These main energy sources include diesel for tractors and other vehicles, and electricity for pumps. Overall energy utilization efficiencies are obtained to vary between 29.1 and 41.1%, while overall exergy utilization efficiencies are found to range from 27.9 to 37.4% in the analysed years, respectively. It may be concluded that the present technique proposed here may be used as a useful tool in analysing and evaluating the energy and exergy utilization efficiencies, identifying energy efficiency and/or energy conservation opportunities and dictating the energy strategies of countries. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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全文围绕树立和落实科学发展观这一主题 ,研究和探索如何在新时期、新阶段进一步做好国土资源管理工作的新思路、新途径和新方法。提出要进一步加强国土资源宏观管理 ,更好地为甘肃省经济社会的协调、可持续发展提供保障服务。 相似文献
85.
刘永增 《石油化工管理干部学院学报》2003,(2):58-59
阐述了人力资源管理在企业发展中的重要作用;对如何引入竞争机制、知人善任、建立科学的激励机制和约束机制、改革管理体制等方面进行了论述。 相似文献
86.
焦作市石灰岩储量极为丰富,要把资源优势转变为经济优势,就要搞好综合开发利用,生产出科技含量高,具有市场竞争能力的新产品。本文旨在探讨石灰岩资源综合利用的新途径,为焦作矿业经济可持续发展作出新贡献,并为焦作市矿产资源规划提供科学依据。 相似文献
87.
H. Djidjelli A. Boukerrou A. Rabouhi R. Founas M. Kaci O. Zefouni N. Djillali L. Belmouhoub 《应用聚合物科学杂志》2008,107(3):1459-1465
The changes in mechanical properties, the thermal stability, and the water absorption capacity of poly (vinyl chloride)/olive residue flour composites were studied as a function of various residue olive flour ratios, i.e., 0, 5, 15, and 25% by weight taking into account the effect of benzylation chemical treatment of the filler. The study showed that composite samples prepared with the untreated filler exhibited higher tensile modulus and hardness compared with the neat resin, whereas elongation and tensile strength were observed to decline. On the other hand, the PVC hardness was found to increase with addition of the untreated olive residue flour (ORF), however the composite samples prepared with the benzylated flour exhibited lower hardness than those prepared with untreated olive residue. Moreover, the amount of absorbed water depends on the amount of filler in the composite. The comparison of the results obtained from the samples of F5, F20, and F30 formulations between the untreated and treated ORF indicated a reduction in absorbed water for the composite samples containing treated ORF with benzyl chloride. As a result, the mechanical properties of the treated composites were improved. Furthermore, the thermal characterization of the different samples carried out by color change test and thermogravimetric analysis revealed an increase in the onset temperatures of decomposition for the treated composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
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