腐解9个月后杉木枯枝落叶化感物质对杉木的化感作用     

曹光球  刘学芝  林思祖  胡宗庆  王凌霄 《福建地理》2007,(2)

采用有机溶剂与蒸馏水混和浸提杉木枯枝落叶腐解9个月后化感物质,应用杉木种子发芽试验进行生物检测.结果表明:杉木枯枝落叶腐解9个月后,杉木枯枝落叶中的弱极性化感物质对绝对发芽率、绝对发芽势、胚根长、胚轴长及干物质量等指标表现为抑制作用,对鲜物质量则表现为轻微的促进作用;极性化感物质对杉木种子发芽各指标均等表现为抑制作用.腐解土中的弱极性化感物质对杉木种子发芽各指标均表现为抑制作用,极性化感物质对绝对发芽率、绝对发芽势、胚轴长及干物质量等表现为抑制作用,但对胚根长、鲜物质量表现为促进作用.  相似文献   

Time–frequency representation of earthquake accelerograms and inelastic structural response records using the adaptive chirplet decomposition and empirical mode decomposition     

P.D. Spanos  A. Giaralis  N.P. Politis 《Soil Dynamics and Earthquake Engineering》2007,27(7):675-689

In this paper, the adaptive chirplet decomposition combined with the Wigner-Ville transform and the empirical mode decomposition combined with the Hilbert transform are employed to process various non-stationary signals (strong ground motions and structural responses). The efficacy of these two adaptive techniques for capturing the temporal evolution of the frequency content of specific seismic signals is assessed. In this respect, two near-field and two far-field seismic accelerograms are analyzed. Further, a similar analysis is performed for records pertaining to the response of a 20-story steel frame benchmark building excited by one of the four accelerograms scaled by appropriate factors to simulate undamaged and severely damaged conditions for the structure. It is shown that the derived joint time–frequency representations of the response time histories capture quite effectively the influence of non-linearity on the variation of the effective natural frequencies of a structural system during the evolution of a seismic event; in this context, tracing the mean instantaneous frequency of records of critical structural responses is adopted.The study suggests, overall, that the aforementioned techniques are quite viable tools for detecting and monitoring damage to constructed facilities exposed to seismic excitations.  相似文献   

某隔震结构动力特性的理论分析与脉动测试   总被引：1，自引：1，他引：1  

贾洪  徐茂义  闫维明  李振宝 《震灾防御技术》2007,2(4):384-390

本文针对国内最大单体隔震建筑建立了SAP2000三维分析模型,并进行了动力特性的理论分析;现场对实际建筑进行了平移振动、扭转振动、垂直振动和平面内弯曲4个方面的脉动测试。利用工程振动反演理论分析了该结构的固有频率、振型、阻尼等动力特性,将实测结构动力特性与理论分析结果进行比较,详细分析实测结果与理论结果差别的原因,并据此对理论模型进行修正,为今后类似结构的设计积累了资料。  相似文献   

经验GREEN函数法研究丽江6.0级强余震的地震动及破裂特征   总被引：1，自引：1，他引：1  

王彬  罗奇峰 《地震研究》2001,24(1):40-47

利用经验Green函数方法，用1996年云南丽江地震后的ML4．7级地震合成了这次地震的最大余震Ms6．0的加速度记录，通过与实际记录在频域和时域的对比研究，分析研究了地震动特征和这次最大余震的可能破裂特征，并对经验Green函数方法进一步的改进方向进行了探讨。  相似文献   

The value of a physically based model versus an empirical approach in the prediction of ephemeral gully erosion for loess-derived soils   总被引：3，自引：0，他引：3  

Jeroen Nachtergaele  J. Poesen  A. Steegen  I. Takken  L. Beuselinck  L. Vandekerckhove  G. Govers 《Geomorphology》2001,40(3-4)

A data set on soil losses and controlling factors for 58 ephemeral gullies has been collected in the Belgian loess belt from March 1997 to March 1999. Of the observed ephemeral gullies, 32 developed at the end of winter or in early spring (winter gullies) and 26 ephemeral gullies developed during summer (summer gullies). The assessed data have been used to test the physically based Ephemeral Gully Erosion Model (EGEM) and to compare its performance with the value of simple topographical and morphological indices in the prediction of ephemeral gully erosion.Analysis shows that EGEM is not capable of predicting ephemeral gully cross-sections well. Although conditions for input parameter assessment were ideal, some parameters such as channel erodibility, critical flow shear stress and local rainfall depth showed great uncertainty. Rather than revealing EGEM's inability of predicting ephemeral gully erosion, this analysis stresses the problematic nature of physically based models, since they often require input parameters that are not available or can hardly be obtained.With respect to the value of simple topographical and morphological indices in predicting ephemeral gully erosion, this study shows that for winter gullies and summer gullies, respectively, over 80% and about 75% of the variation in ephemeral gully volume can be explained when ephemeral gully length is known. Moreover, when previously collected data for ephemeral gullies in two Mediterranean study areas and the data for summer gullies formed in the Belgian loess belt are pooled, it appears that one single length (L)–volume (V) relation exists (V=0.048 L^1.29; R²=0.91). These findings imply that predicting ephemeral gully length is a valuable alternative for the prediction of ephemeral gully volume. A simple procedure to predict ephemeral gully length based on topographical thresholds is presented here. Secondly, the empirical length–volume relation can also be used to convert ephemeral gully length data extracted from aerial photos into ephemeral gully volumes.  相似文献   

青藏高原OLR的气候特征及其对北半球大气环流的影响   总被引：3，自引：5，他引：3  

李栋梁  章基嘉 《高原气象》1996,15(3):259-268

利用１９７４－１９９０年青藏高原地区地－气系统月平均射出长波辐射资料，采用ＥＯＦ方法分析了前３个特征向量场，得到了青藏高原地区地－气系统射出长波辐射的几种异常形式，阐述了它们的天气气候特征，并对不同气候区的持续 及其与北半球大气环流的关系作了研究。  相似文献   

气象场经验正交函数不同展开方案收敛性问题的探讨   总被引：15，自引：0，他引：15  

丁裕国  施能 《大气科学》1992,16(4):436-443

本文从理论上证明EOFs(经验正交函数)用于气象场时,三种不同计算方案特征值的相互关系.指出利用原始场积和矩阵展开的特征值λ_j等于用协方差阵展开的特征值λ_j~*加上平均场方差引起的特征值λ_j.进而论证了收敛速度差舁的原因.最后又以实例表明,不同展开方案的典型场意义及其与时间权重系数的对应关系.  相似文献   

三维绿色生物量的遥感模式研究与绿化环境效益估算   总被引：4，自引：0，他引：4  

周坚华  孙天纵 《遥感学报》1995,(3)

本文从理论和技术上叙述了绿量的遥感模式研究和绿化环境效益估算，并取得了以下几个方面的进展：（１）提出了绿量的概念，进一步完善了城市绿化的量化指标体系；（２）成功地修正了“逻辑斯蒂曲线”方程，并以平面量模拟立体量的方法测算了上海市全市的绿量，不仅节省了人力物力，而且提高了精度；（３）提出了模式林的概念及测定了以绿量估算绿化环境效益中所必须的标准换算量；（４）首次用绿量在全市范围估算了绿化群落的吸碳产氧、吸收二氧化硫、滞尘及夏季降温等环境效益。为分析现有绿化群落布局与结构的合理性，及为绿化规划乃至整个城市的总体规划提供了很有价值的技术参数。  相似文献   

中国东部地区断裂的缜奏性活动     

谢广林 《华南地震》1993,(3)

对中国东部地区断裂的节奏性活动进行了探讨,认为这种节奏性活动主要根据构造地貌进行鉴别,并可分为六种型式:稳定—蠕滑错动;稳定—急速错动;蠕滑—急速错动;交替型蠕滑错动;交替型急速错动和复式错动。地震活动周期与断裂的节奏性活动相关联。断裂活动产生强震的型式有单发式、对偶式和连发式,这三种形式分别出现在不同的断裂中,并取决于不同区域、不同断裂的活动特征。  相似文献   

InSAR相位分解及其在生成DEM和研究地震形变场中的应用   总被引：1，自引：1，他引：1       下载免费PDF全文

罗小军  黄丁发  刘国祥 《地震工程学报》2006,28(3):204-209,190

InSAR是极具发展潜力的微波遥感新技术,可应用于数字高程模型的产生、制图和大范围微小地表形变的测量。考虑参考面、地形和地表形变等因素,本文从几何角度分析和讨论了In-SAR的相位分解,并给出了各相位分量的函数表达式,阐述了地表高程和形变信息提取的基本原理。最后以JERS和ENVISAT卫星数据为例,展示了合成孔径雷达干涉测量在生成数字高程模型和提取地震形变场中的应用及其数据处理过程。  相似文献