Habitat, occurrence and conservation of Saharo-Arabian-Turanian element Forsskaolea tenacissima L. in the Iberian Peninsula   总被引：1，自引：0，他引：1  

Javier Cabello  Domingo Alcaraz  Francisco Gmez-Mercado  Juan F. Mota  Javier Navarro  Julio Peas  Esther Gimnez 《Journal of Arid Environments》2003,53(4):491-500

The aim of this study is to assess the Iberian populations of Forsskaolea tenacissima L. according to its biogeographical interest, habitat, geographical range and conservation status. Results point out that they are restricted to gravel wadis of Tabernas Desert (SE Spain), are scarcely included in protected areas and represent historically isolated populations with relict behaviour. We also describe a new association, Senecioni-Forsskaoleetum tenacissimae. Conservation status of species is cause for concern and two conservation actions must be carried out. Firstly, protected areas should house Forsskaolea populations and secondly, phytosociological characterization of a community allows inventorying its habitat and directing conservation efforts to community level.  相似文献   

吉林省土壤中有效锰、铜、钼和锌含量的时空变化   总被引：5，自引：0，他引：5  

杨娟  王冬艳 《世界地质》2003,22(4):392-395

选择吉林省的五个大豆种植区(敦化、桦甸、榆树、农安、白城)、四个水稻种植区(白城、九台、延吉、梅河口)及3个草场分布区(镇赉、洮南、大安)，对其土壤中有效锰、铜、钼和锌的含量在过去20年的变化作了比较和分析。经研究表明：吉林省土壤中有效锰和有效铜含量较20年前有所增高，有效钼含量总体呈降低趋势，中部部分地区和东部地区土壤有效锌含量降低，其余地区含量增高。空间分布东部高于中西部。  相似文献   

天然含钒金红石加热、淬火及电子辐射改性实验研究   总被引：4，自引：5，他引：4       下载免费PDF全文

刘娟鲁安怀  郭延军李宁  李巧荣郑佳 《岩石矿物学杂志》2003,22(4):339-344

天然含钒金红石样品经过1273K加热、淬火和高能电子辐照处理后性质发生不同程度的变化。XRD谱峰显示处理前后样品没有发生物相变化，显微IR图谱证明原样、加热、淬火样品的表面有少量吸附水存在，而辐射样品的显微IR图谱上没有检测到吸附水的吸收峰。用XPS分析比较了处理前后样品表面主要元素Ti、O和V的价态及含量，结果表明，原样经过处理后表面钒和氧的原子百分含量增加，其中淬火样品表面吸附水和钒的含量相对于原样增加最为明显，光催化活性相应较高；加热样品表面的吸附水和钒的含量比原样稍有增加，光催化活性与原样相当；电子辐射样品表面钒的原子百分含量相对原样增加不明显，而对水的吸附能力相对原样较低，光催化效率也略低。  相似文献   

An experimental study of nominally symmetric and asymmetric structures isolated with the FPS     

Juan C. de la Llera  Jos L. Almazn 《地震工程与结构动力学》2003,32(6):891-918

This experimental investigation deals with the earthquake behaviour of a nominally symmetric and a mass‐asymmetric three‐storey structural model isolated with the frictional pendulum system (FPS). Both accidental and natural torsion are evaluated in the structure by using recorded accelerations in all building floors and measured deformations at the isolation level. A 3D‐shaking table was used to subject the model to five different ground motions, including impulsive as well as far‐field subduction‐zone type earthquakes. Results show that the analytical predictions of the earthquake behaviour of the isolated structure, as obtained from a physical model of the FPS, are in close agreement with the true complex inelastic measured behaviour of the FPS. Besides, experimental results also validate previous observations about the importance of accounting for the variability of the normal loads in modelling the earthquake behaviour of FPS isolators. Measured torsional deformation amplifications at the base of the building vary, in the mean, from 2.5% to 6% for the symmetric and asymmetric structural configurations, respectively. In relation to the fixed base structure, the reduction factors for the base shear of the isolated structure are, in the mean, about 3.9 for both configurations. Finally, it is concluded that the FPS is capable of controlling the lateral–torsional motions of mass‐asymmetric structures quite effectively by aligning the centre of mass of the superstructure with the centre of pendular and frictional resistance of the isolation system. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Physical model for dynamic analysis of structures with FPS isolators     

Jos L. Almazn  Juan C. De la Llera 《地震工程与结构动力学》2003,32(8):1157-1184

This article presents a physical model for frictional pendulum isolators (FPS) that is ready to be implemented in most commercial software. The model is capable of accounting for effects such as large deformations, sticking, and uplift and impact by sensing the normal loads in the isolators through a gap element. Sticking has been incorporated into the model by extending the Park–Wen hysteretic model to the case of large deformations. The proposed model has been tested against a theoretically ‘exact’ formulation leading to essentially identical results. To facilitate its use, the physical FPS model has been cast into a typical non‐linear structural element format, i.e. with deformation as input and restoring force as output. Examples of a building and a bridge have been chosen to show the potential of the element and to provide further insight into the earthquake response of structures with FPS isolators; in particular, in aspects such as the orientation in placement of the isolator, sticking, P? Δ, and other large deformation effects. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

从激光扫描数据中进行建筑物特征提取研究   总被引：42，自引：4，他引：42  

李必军  方志祥  任娟 《武汉大学学报(信息科学版)》2003,28(1):65-70

提出了一套基于建筑物几何特征的信息挖掘方案，并具体介绍了研究中采用的一些原理、方法与实用算法，从而可以直接从激光扫描数据中提取建筑物的平面外轮廓信息。利用本方案对车载激光扫描系统获取的城市建筑物试验数据进行了具体的处理，并给出了三维建模和可视化表达结果。  相似文献   

3G技术与现代物流管理技术的集成模式研究   总被引：3，自引：1，他引：3  

霍亮  李欣 《测绘科学》2003,28(3):59-61

3G技术能够对现代物流作业与管理进行有效地监督和控制,3G技术与现代物流管理技术的集成是物流业发展的客观需要。探讨了3G技术与现代物流管理技术的集成模式,对于以GIS技术为平台支撑、以定位技术和无线通信技术为辅助手段的分布式空间物流信息系统的建设具有一定的意义。  相似文献   

Is Prediction of Future Landslides Possible with a GIS?   总被引：5，自引：0，他引：5  

Fabbri  Andrea G.  Chung  Chang-Jo F.  Cendrero  Antonio  Remondo  Juan 《Natural Hazards》2003,30(3):487-503

This contribution explores a strategy for landslide hazard zonation inwhich layers of spatial data are used to represent typical settings inwhich given dynamic types of landslides are likely to occur. Theconcepts of assessment and prediction are defined to focus on therepresentation of future hazardous events and in particular on themyths that often provide obstacles in the application of quantitativemethods. The prediction rate curves for different applications describethe support provided by the different data layers in experiments inwhich the typical setting of hazardous events is approximated bystatistically integrating the spatial information.  相似文献   

An Unusual Texture: Skeletal Sphalerite in Pyrite from Dajing Tin-polymetallic Deposit, China     

Yu Wang Wang    Jing Bin Wang  Li Juan Wang 《Resource Geology》2003,53(1):67-72

Abstract. Skeletal sphalerite with stellar, cruciform and snowflake-like (or cauliflower-like) shapes included in pyrite is widely found in the Dajing tin-polymetallic deposit. It occurs only in chalcopyrite-pyrite mineralization stage. The compositions of all sphalerites in the chalcopyrite-pyrite stage are characterized by high Cu content (3.9 - 7.0 wt% with a mean of 5.4 wt%), while the skeletal crystal sphalerite has higher zinc and cadmium contents, and lower copper and iron contents, compared with other sphalerites of the same stage. The skeletal crystal sphalerite in pyrite is possibly generated by exsolution.  相似文献   

Tree growth response to the 1913 eruption of Volcán de Fuego de Colima, Mexico     

Franco Biondi  Ignacio Galindo Estrada  Juan Carlos Gavilanes Ruiz  Alejandro Elizalde Torres 《Quaternary Research》2003,59(3):293-299

The impact of volcanic eruptions on forest ecosystems can be investigated using dendrochronological records. While long-range effects are usually mediated by decreased air temperatures, resulting in frost rings or reduced maximum latewood density, local effects include abrupt suppression of radial growth, occasionally followed by greater than normal growth rates. Annual rings in Mexican mountain pine (Pinus hartwegii Lindl.) on Nevado de Colima, at the western end of the Mexican Neovolcanic Belt, indicate extremely low growth in 1913 and 1914, following the January 1913 Plinian eruption of Volcán de Fuego, 7.7 km to the south. That event, which is listed among the largest explosive eruptions since A.D. 1500, produced ashflow deposits up to 40 m thick and blanketed our study area on Nevado de Colima with a tephra fallout 15–30 cm deep. Radial growth reduction in 1913–14 was ≥30% in 73% of the sampled trees. We geostatistically investigated the ecological impact of the eruption by mapping the decrease in xylem increment and found no evidence of a spatial structure in growth reduction. Little information has been available to date on forest species as biological archives of past environments in the North American tropics, yet this historical case study suggests that treeline tropical sites hold valuable records of prehistoric phenomena, including volcanic eruptions.  相似文献