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51.
52.
导热油为热介质的转子式刨花干燥机的热量计算 总被引:1,自引:1,他引:1
阐述了利用导热油为热介质的转子式刨花干燥机优良的干燥性能,并对转子式刨花干燥机单位耗热量进行了计算,并根据耗热量计算出了转子的散热面积。为了便于导热油的传热和防止结焦现象,根据雷诺准则确定了导热油在管束内的流速。 相似文献
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54.
铅笔板高温热压改性技术研究 总被引:1,自引:0,他引:1
为克服高温烤板处理的缺点 ,进行了椴木铅笔板热压干燥基本规律及温度、时间与含水率的关系研究和热压干燥的铅笔板与烤板的吸湿性、脆性对比试验。研究结果表明 :高温热压可使木材进行热分解 ,热压干燥后的铅笔板的吸湿性和脆性能达到烤板的要求 ,并在质量稳定性方面优于烤板 ,更重要的是它解决了烤板对环境的污染问题 相似文献
55.
Lucian Wielopolski Ruth D. Yanai Carrie R. Levine Sudeep Mitra Matthew A. Vadeboncoeur 《Forest Ecology and Management》2010
Forest soils are pivotal to understanding global carbon (C) cycling and evaluating policies for mitigating global change. However, they are very difficult to monitor because of the heterogeneity of soil characteristics, the difficulty of representative sampling, and the slow time scale of response to environmental change. Here we demonstrate that use of gamma-ray spectroscopy facilitates in situ non-destructive analysis of C and other elements in forest soils. In this approach the element-specific gamma-rays are induced by fast and thermal neutrons interacting with the nuclei of the elements present in the soil. Background gamma-rays emanating from naturally occurring radionuclides in the forest are recorded as well. We applied this approach in a mature northern hardwood forest on glacial till soils at the Bartlett Experimental Forest in New Hampshire, USA. The inelastic neutron scattering (INS) system yielded strong signals in gamma-ray counts/h, from C and other elements present in the soil matrix that included silicon, oxygen, hydrogen, iron, aluminum, manganese and potassium. The INS sensitivity for carbon was 20.656 counts h−1 kg−1 C m−2 based on current net C gamma-ray counts and the data for the O horizon and mineral soil to a depth of 30 cm obtained from a nearby quantitative soil pit (7.35 kg C m−2). We estimate the minimum detectable change to be ∼0.34 kg C m−2, which is ∼5% of the current soil C content, and the minimum detectable limit to be ∼0.23 kg C m−2. Eight % reproducibility from 11 measurements was limited, in part, by the large variability in the system counting geometry due to the uneven forest microtopography. The INS approach has the potential to revolutionize belowground monitoring of C and other elements, because the possibility of detecting a 5% change in forest soils has not been possible with destructive sampling methods. 相似文献
56.
IntroductionCharcoal, produced by the paFtial pyrolysis of woodin an inert atmosphere, is a complex material of whichthe physical and chemical characteristics may varywidely. The properties may vary with the type of woodused, the part of the tree from which the wood is cut,as well as the pyrolysis regime tO which the wood issubjeCt6d. The aim of the present work is tO develop arange of t6sts for the charaCt6rization of compositionand reactivity of charcoals for use in gunpoWder.Compositiona… 相似文献
57.
《Wood material science & engineering》2013,8(2):111-118
Abstract Wood is being used heavily in single-family residential dwellings. Therefore, it is important to categorize their response when exposed to elevated temperatures for a sustained period of time. An important aspect of structural fire design is to assess postfire residual strength of existing structures. This study addresses this issue by developing models to predict strength degradation of wood after exposure to elevated temperature. The objectives were to (a) study the effect of exposure time on bending strength [Modulus of Rupture (MOR)] of wood at elevated temperatures, (b) interpret any relationships between different temperature and time of exposure using kinetics and a statistical approach, and (c) compare the two approaches. Two hundred thirty-two samples in total were tested in flexure as a function of exposure time and several temperatures. MOR of wood decreased as a function of temperature and exposure time. Rate of degradation was higher at higher temperatures. These results were fit to a simple kinetics model, based on the assumption of degradation kinetics following an Arrhenius activation energy model with apparent activation energy of 37.4 kJ/mol. A regression-based statistical model was also developed. The kinetics-based model fit the data better with one less parameter and predictions consistently matched the observed values, making the model preferred over the regression approach. 相似文献
58.
D. Skipnes S. O. Johnsen T. Skåra M. Sivertsvik O. Lekang 《Journal Of Aquatic Food Product Technology》2013,22(3):331-340
Convenience products of fish that are heat processed in-pack are often subjected to a compromise between quality and durability within the framework of required safety. The purpose of this study was to provide knowledge for optimizing pasteurization of cod muscle by quantifying changes in water holding capacity (WHC), cook loss, color, and texture within a wide range of processing times and temperatures. A heat load equivalent to 2 min at 70°C may be applied to the cod while maintaining the WHC above 66%, the cook loss below 5.6%, and keeping hardness and whiteness low, provided that the processing temperature is kept in the range 68 ± 4°C. 相似文献
59.
杉木采伐对集水区土壤热状况的影响 总被引:2,自引:0,他引:2
土壤作为森林生态系统的子体系 ,是林木扎根并赖以生存的基础 ,也是土壤微生物一切生命活动的场所。因此 ,有关土壤养分、水分及其土壤物理结构特征等方面的研究报告颇多 (王政权等 ,2 0 0 0 ;张合平等 ,1 997)。但是有关森林土壤的热状况 ,以及林木采伐后对土壤热状况影响的研究报导很少 (康文星等 ,1 989;刘煊景等 ,1 993)。本文在获得采伐前连续 3年和采伐后连续 3年的观测数据的基础上 ,就杉木人工林生态系统土壤的热状况各因子之间 ,土壤各组成成分对热状况的单一或组合效应 ,以及皆伐这种人为强烈干扰对土壤热状况的影响进行了剖析。… 相似文献
60.
Low temperature is one of the major limiting environmental factors which constitutes the growth, development,productivity and distribution of plants. Over the past several years, the proteins and genes associated with freezing resistance of plants have been widely studied. The recent progress of domestic and foreign research on plant antifreeze proteins and the identification and characterization of plant antifreeze protein genes, especially on expression regulatory mechanism of plant antifreeze proteins are reviewed in this paper. Finally, some unsolved problems and the trend of research in physiological functions and gene expression regulatory mechanism of plant antifreeze proteins are discussed. 相似文献