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101.
In this paper, the applicability of an auto‐regressive model with exogenous inputs (ARX) in the frequency domain to structural health monitoring (SHM) is established. Damage sensitive features that explicitly consider non‐linear system input/output relationships are extracted from the ARX model. Furthermore, because of the non‐Gaussian nature of the extracted features, Extreme Value Statistics (EVS) is employed to develop a robust damage classifier. EVS provides superior performance to standard statistical methods because the data of interest are in the tails (extremes) of the damage sensitive feature distribution. The suitability of the ARX model, combined with EVS, to non‐linear damage detection is demonstrated using vibration data obtained from a laboratory experiment of a three‐story building model. It is found that the vibration‐based method, while able to discern when damage is present in the structure, is unable to localize the damage to a particular joint. An impedance‐based active sensing method using piezoelectric (PZT) material as both an actuator and a sensor is then investigated as an alternative solution to the problem of damage localization. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
102.
WENG Huanxin ZHANG Xingmao WU Nengyou WANG Ying CHEN Lihong ZHONG Hexian QIN Yachao 《中国科学D辑(英文版)》2006,49(3)
Since the discovery from the ice-core record of South Pole revealed that atmospheric concentration of CO2 of the last glacial was 80―100 ppm less than that of Holocene[1], many researchers[2―6] have obtained a series of important findings to seek the dominant fac- tors controlling its change from marine physical, chemical and biological processes, among which the view has gained increasing attention that phosphorus, as a macronutrient, is a crucial limitation to marine primary production, a… 相似文献
103.
Thorjorn Larssen 《中国地球化学学报》2006,25(B08):49-49
Acid rain is one of China's major environmental problems and emissions of sulphur and nitrogen are still increasing. The acid rain situation in China is somewhat different from what is seen in Europe and North America. Sulfur deposition is very high, but there is also very high deposition of calcium and other base cations. The sources of atmospheric Ca are not well understood, although it is important for understanding long term impacts of acid deposition. The fate of S, N and Ca^2+ in the catchment is crucial for the future development of the acidification situation of soils and waters in China. Very few studies presenting catchment input-output ion budgets in Chinese natural environments exist and there are several unknown factors regarding processes. Here, we present annual input-output budgets for three years (2001-2003) for major ions for four forested catchments in China receiving different loads of acid deposition. For the two sites receiving the highest SO4^2- inputs, the input-output budget for the upper 50 cm of soil is approximately balanced. For the most remote site the soil is a net sink for SO4^2-, suggesting that the pool of adsorbed SO4^2- in the soil is building up. This is in agreement with the fact that the site so far has received only moderate SO4^2- inputs. For the southemmost, the subtropical site there is a loss of SO4^2- in the soil, which at least partly may be related to high uptake from the dense and highly productive forest at the site. The Ca^2+ budgets for the upper 50 cm of soil show large variations both within and between sites. For most locations there is production of Ca^2+ in the soil that can be explained by weathering, and variation between years related to hydrology that can be explained by ion exchange. However, at some plots at the site receiving very high inputs of both SO4^2- and Ca^2+, there is an unknown sink of Ca^2+ in the soil at some plots. 相似文献
104.
105.
106.
Ye Huiwen 《吉林大学学报(地球科学版)》1990,(2)
本文对中国篮片岩中间石族矿物进行了综合研究,可将它们分为三个亚族:碱性问石亚族;钠钙闪石亚族;钙质闪石亚族。碱性闪石亚族再按Fe 、Mg、Al的比值,后二者按Si的含量划分为矿物种。编制了闪石成分分类图。碱性闪石的光学性质、红外吸收光谱和x射线衍射数据,与其它两个亚族有明显差异,但各亚族内特征基本相似。利用多色性和延性特征鉴别碱性问石各矿物种较为准确,并发现青铝闪石的多色性公式应为Ng-紫色、Nm-深蓝色、Np-浅黄色,与前人描述不一致。 相似文献
107.
150ka B.P.以来萨拉乌苏河流域的CaCO3旋回 总被引:6,自引:0,他引:6
以米浪沟湾地层剖面作为萨拉乌苏河流域的典型剖面,探讨了150kaB.P.以来的CaCO3含量分布与气候变化的关系。1)该剖面CaCO3含量及其低-高变化同古风成沙与上覆河湖相或古土壤构成的没积旋回呈现出明显的对应关系。与米浪沟湾剖面的沉积旋回一样,CaCO3在分布上相应地构成了27个含量高低变化旋回。2)CaCO3在风成沙中含量的分布比较稀散,0.8%-7.18%,平均值2.50%;在河湖相和古土壤中土壤中相对富集,2.20%-14.90%,平均值5.74%。从而揭示出其时两者的气候背景是不同的,前者是干旱寒冷气候作用下的风力的侵蚀、搬运与堆积的产物;而后者则与暖湿气候环境下萨拉乌苏河流域地处鄂尔多斯高原和黄土高原这间特殊的低洼地貌位置有关。气候暖湿,河湖沼泽发育、成土成壤作用增强,低洼的集水条件有利于CaCO3的聚集。3)导致米浪沟湾剖面CaCO3的多旋回相对稀钐与聚集的根本原因可能是150kaB.P.以来北半球冰期-间冰期气候波动影响下乌素沙漠冬夏季风的多次更迭所致。 相似文献
108.
CaCO3生物矿化的研究进展——有机质的控制作用 总被引:9,自引:0,他引:9
生物CaCO3是自然界分布最广泛的一类生物矿物,其组成除了无机相的CaCO3外,还含有少量的有机质,包括水可溶(SM)和水不可溶有机质(IM),SM富含阴离子基团,是控制CaCO3结晶的重要因素之一。通过有机—无机界面分子识别,有机质选择性地与CaCO3晶体特定方向的面网相互作用,从而对CaCO3的生长、形貌、多型及结晶学定向等产生明显的控制作用。有机—无机界面的分子识别机制包括静电、晶格几何匹配和立体化学互补等。仿生矿化的研究为进一步深入了解生物矿化的机理及制造高级复合材料提供了新的方法。 相似文献
109.
鄂西超细重碳酸钙产品开发应用研究 总被引:6,自引:0,他引:6
鄂西超细重碳酸钙产品开发应用研究沈上越潘铁虹张德李珍周明张汉凯(中国地质大学,武汉430074)关键词方解石矿工艺流程超细重碳酸钙鄂西1鄂西方解石矿质量概述鄂西方解石矿有数个矿区,每个矿区的矿体厚为几米至几十米,长几百米至上千米,储量巨大。经系统化学... 相似文献
110.
外生金包括砾岩金和松散砂金,是外能作用在地表开放条件下形成的。在地壳发展过程中,动力学成矿的时空演化是连续的,但主要集中在早、晚元古代及早、晚古生代和中生代,而大发展于新生代。依据演化规律和矿化环境,提出5个找矿有望的外生金成矿带。 相似文献