不同林龄人促更新林枯枝落叶层碳及养分贮量   总被引：1，自引：0，他引：1  

王小红  张金凤  林开淼  卢正立  曾宏达  郭剑芬 《亚热带资源与环境学报》2015,(1)

对福建南平顺昌县不同林龄米槠(Castanopsis carlesii)人促更新林枯枝落叶层和主要营养元素现存量进行测定,探究其随林龄的变化趋势。结果表明:不同林龄米槠人促更新林枯枝落叶层现存量为3.94~4.95 t·hm-2,其中49 a生人促林枯枝落叶层现存量最小,31 a生的最大。不同林龄枯枝落叶层C、N、P、K的浓度分别为44.09%~47.46%,11.9~13.8 g·kg-1,0.5~0.9 g·kg-1,1.4~5.1 g·kg-1。21 a生和49 a生人促更新林枯枝落叶层C浓度明显高于31 a生林分。49 a生人促更新林枯枝落叶层N和P浓度均高于21 a生和31 a生林分,但该林分枯枝落叶层K浓度却最低。21 a生米槠人促更新林枯枝落叶层C贮量分别是31 a生和49 a生林分的1.03倍和1.23倍,49 a生米槠人促更新林K贮量远低于21 a生和31 a生。不同林龄枯枝落叶层碳和养分贮量差异与林分特征、各林分枯枝落叶层现存量及养分浓度等有关。  相似文献   

Total and pyrogenic carbon stocks in black spruce forest floors from eastern Canada     

《Organic Geochemistry》2015

Pyrogenic carbon (PyC), a by-product of recurrent boreal wildfires, is an important component of the global soil C pool, although precise assessment of boreal PyC stock is scarce. The overall objective of this study was to estimate total C stock and PyC stock in forest floors of Eastern Canada boreal forests. We also investigated the environmental conditions controlling the stocks and characterized the composition of the forest floor layers. Forest floor samples were collected from mesic black spruce sites recently affected by fire (3–5 yr) and analyzed using elemental analysis and solid state ¹³C nuclear magnetic resonance (NMR) spectroscopy. PyC content was further estimated using a molecular mixing model. Total C stock in forest floors averaged 5.7 ± 2.9 kg C/m² and PyC stock 0.6 ± 0.3 kg C/m². Total stock varied with position in the landscape, with a greater accumulation of organic material on northern aspects and lower slope positions. In addition, total stock was significantly higher in spruce-dominated forest floors than stands where jack pine was present. The PyC stock was significantly related to the atomic H/C ratio (R² 0.84) of the different organic layers. ¹³C NMR spectroscopy revealed a large increase in aromatic carbon in the deepest forest floor layer (humified H horizon) at the organic-mineral soil interface. The majority of the PyC stock was located in this horizon and had been formed during past high severity fires rather than during the most recent fire event.  相似文献   

不动产登记数据的建筑分层分户三维建模关键技术     

熊成利  龚旭峥  沈正中  龙容  王硕 《测绘通报》2022,(4):149-153

随着实景三维建设的不断推进,城市管理向立体化、精细化和数字化发展,建筑分层分户三维模型能够承载更详细精准的属性信息,并能叠加倾斜三维模型进行场景渲染,可以更好地服务于城市不动产三维管理、数字赋能社会治理等工作。本文以“萧山区数字赋能社会治理”项目建设为背景,探索和实现了基于不动产登记数据的建筑分层分户三维建模关键技术,形成了从全空间多源异构数据归集至城市全域建筑分层分户三维模型建设的一整套生产技术流程,为城市不动产三维管理、数字赋能社会治理等提供了有效的技术支撑和数据基础。  相似文献   

近断层地震下楼层竖向加速度影响因素分析          下载免费PDF全文

戴靠山  钱雨凡  王健泽 《世界地震工程》2021,(2):192-202

现阶段基于性能的抗震设计思想不仅关注结构自身体系的安全,而且保护非结构构件在地震作用下使用功能完好。对于工业建筑结构,生产设备在地震作用下受损会影响震后功能恢复。加速度敏感型非结构构件一般采用楼层加速度指标来量化其地震损伤程度。以三个不同高度的钢抗弯框架规则结构体系为研究对象,采用与竖向目标谱匹配的近断层非脉冲和脉冲地震动作为竖向地震输入,考察不同质量不规则程度下,楼层竖向绝对加速度随建筑高度的变化趋势,并从反应谱角度分析不规则质量分布对楼层加速度响应的影响。结果表明:4层结构在非脉冲地震作用下楼层顶层处竖向绝对加速度是地面竖向峰值加速度的5倍之多,某一层质量的突变会引起该层及其他楼层竖向绝对加速度的明显变化。另外,对现有计算楼层竖向加速度响应的经验公式进行验证,发现美国ASCE 7-16规范的估计结果偏于保守。  相似文献   

基于DSP的小型化高精度频标比对系统研制     

唐升  刘娅  李孝辉 《时间频率学报》2012,35(4):205-211

针对传统双混频时差法测频的局限性,提出了一种差拍数字化精密频率测量方法,基于正弦差拍技术、同步采样技术和数字信号处理技术设计实现了一种新型频标比对系统,可实现对5MHz、10MHz等频标信号的比对测量。实验结果证明,测量10MHz频标信号时系统本底噪声约为1×10^-12／s。系统拥有测量精度高,体积小以及成本低的特点,在时频测量领域具有良好的推广和应用价值。  相似文献   

新型预制楼盖的装配整体式框架剪力墙结构振动台试验研究   总被引：2，自引：0，他引：2  

郑先超  李青宁  潘树宾  姜维山 《地震工程与工程振动》2013,33(3)

基于发展装配式建筑是实现建筑节能的重要举措,从楼盖要满足平面内刚性的要求,结合实际工程进行了不加后浇面层的新型预制楼盖的中间钢板剪力墙边榀钢框架三层结构模型的振动台试验,并对采用新型预制板和新型连接的装配整体楼盖的面内变形、传递水平地震作用力的性能进行了分析.研究结果表明:采用新型预制板和新型连接的不加后浇面层楼盖的刚性可以保证结构的空间整体性和水平力的有效传递,在高烈度地区可以考虑用不加后浇面层的装配整体式楼盖代替现浇楼盖.  相似文献   

突水系数的产生及修正过程   总被引：2，自引：0，他引：2  

管恩太 《中国煤炭地质》2012,(2):30-32

从煤层底板突水预测预报问题出发,就突水系数评价水害方面,从1964年煤炭部焦作水文地质会战开始,到2009年的《煤矿防治水规定》,分析了各个阶段突水系数公式及其修正过程。结合实例,对弃用修正突水系数的意义进行了全面阐述。研究认为：在所有的预测预报方法中,煤层底板突水系数在煤层底板突水评价中最为简单实用;突水系数的意义在于简明扼要,符合实际,应大胆使用;突水系数演化到今天并不影响我国煤矿水害的研究和进展,反而对我国煤矿水害评价起到了正确的指导作用。  相似文献   

Alluvial fans of the Eastern Italian Alps: morphometry and depositional processes     

L. Marchi  P.R. Tecca 《Geodinamica Acta》2013,26(1):20-27

Abstract

Alluvial fans are abundant in many valleys of the Alps, consisting of important sites for human settlements. Relationships between alluvial fan morphometry and drainage basin characteristics have been investigated in six valleys of the Eastern Italian Alps, displaying different geological and morphological conditions. Both debris flow fans and fluvial fans are present in the studied region, the latest occurring only in quite large basins. Expansion of alluvial fans is greatly determined by the topographic characteristics of receiving valleys. Fan gradient is mainly affected by basin ruggedness conditioning depositional processes, by debris size, and, in some cases, by post-depositional reworking of fan surfaces.  相似文献   

Horizontal floor response spectra of base‐isolated buildings due to vertical excitation     

Ioannis Politopoulos  Nadim Moussallam 《地震工程与结构动力学》2012,41(3):587-592

A mechanism of horizontal floor response spectra amplification in the vicinity of higher modes' frequencies is investigated. It is demonstrated, by means of a simple two‐degrees‐of‐freedom model, that in the case of unsymmetrical superstructure, such amplification may occur because of the coupling between vertical excitation and horizontal response of the non‐isolated modes. This phenomenon is further illustrated by the results of analyses of a model of a nuclear plant. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Development of deformable connection for earthquake‐resistant buildings to reduce floor accelerations and force responses          下载免费PDF全文

Georgios Tsampras  Richard Sause  Dichuan Zhang  Robert B. Fleischman  Jose I. Restrepo  David Mar  Joseph Maffei 《地震工程与结构动力学》2016,45(9):1473-1494

This paper presents the development of a deformable connection that is used to connect each floor system of the flexible gravity load resisting system (GLRS) with the stiff lateral force resisting system (LFRS) of an earthquake‐resistant building. It is shown that the deformable connection acts as a seismic response modification device, which limits the lateral forces transferred from each floor to the LFRS and allows relative motion between the GLRS and LFRS. In addition, the floor accelerations and the LFRS story shears related to the higher‐mode responses are reduced. The dispersion of peak responses is also significantly reduced. Numerical simulations of the earthquake response of a 12‐story reinforced concrete shear wall example building with deformable connections are used to define an approximate feasible design space for the deformable connection. The responses of the example building model with deformable connections and the example building model with rigid‐elastic connections are compared. Two configurations of the deformable connection are studied. In one configuration, a buckling restrained brace is used as the limited‐strength load‐carrying hysteretic component of the deformable connection, and in the other configuration, a friction device is used. Low damping laminated rubber bearings are used in both configurations to ensure the out‐of‐plane stability of the LFRS and to provide post‐elastic stiffness to the deformable connection. Important experimental results from full‐scale tests of the deformable connections are presented and used to calibrate numerical models of the connections. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献