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1.
采用集中塑性铰理论和SAP2000结构分析软件,对某体育练习馆(钢柱周边支承单层柱面网壳)整体结构进行了强震下弹塑性地震响应分析。分析中考虑了几何和材料双重非线性影响,获得了节点位移响应、杆件塑性铰的分布特征和结构的整体变形与失效形态,并评定了整体结构在强震下的极限承载力与失效类型。结果表明:该结构在强震下的失效界限地震加速度峰值为1260gal,最大竖向变形为短向跨度的1/163,满足"避难与救灾建筑结构"的抗震性能设防要求;结构的失效类型为动力失稳破坏,临界失效时出现塑性铰的杆件较少,结构塑性发展程度不充分;由整体稳定控制的单层柱面网壳在满足稳定承载力的要求下具有较大的抗震潜能。  相似文献   
2.
Climate change is identified as a major threat to wetlands. Altered hydrology and rising temperature can change the biogeochemistry and function of a wetland to the degree that some important services might be turned into disservices. This means that they will, for example, no longer provide a water purification service and adversely they may start to decompose and release nutrients to the surface water. Moreover, a higher rate of decomposition than primary production (photosynthesis) may lead to a shift of their function from being a sink of carbon to a source. This review paper assesses the potential response of natural wetlands (peatlands) and constructed wetlands to climate change in terms of gas emission and nutrients release. In addition, the impact of key climatic factors such as temperature and water availability on wetlands has been reviewed. The authors identified the methodological gaps and weaknesses in the literature and then introduced a new framework for conducting a comprehensive mesocosm experiment to address the existing gaps in literature to support future climate change research on wetland ecosystems. In the future, higher temperatures resulting in drought might shift the role of both constructed wetland and peatland from a sink to a source of carbon. However, higher temperatures accompanied by more precipitation can promote photosynthesis to a degree that might exceed the respiration and maintain the carbon sink role of the wetland. There might be a critical water level at which the wetland can preserve most of its services. In order to find that level, a study of the key factors of climate change and their interactions using an appropriate experimental method is necessary. Some contradictory results of past experiments can be associated with different methodologies, designs, time periods, climates, and natural variability. Hence a long-term simulation of climate change for wetlands according to the proposed framework is recommended. This framework provides relatively more accurate and realistic simulations, valid comparative results, comprehensive understanding and supports coordination between researchers. This can help to find a sustainable management strategy for wetlands to be resilient to climate change.  相似文献   
3.
华雨淋  吕彦 《地球物理学报》2019,62(8):2982-2990
利用云南腾冲火山地区15个固定台站记录到的7923次地震的P波到时资料,采用双差层析成像方法,反演得到腾冲火山及周边地区地壳及上地幔顶部三维P波速度结构和地震重定位结果.研究发现,腾冲火山区域地壳内存在明显的地震波低速区,P波速度低于整个区域地壳速度平均值超过15%,上地幔顶部存在规模较大的低速异常区.推测腾冲火山地区存在较大规模的地幔热物质上涌以及向地壳的侵入,热物质在地壳内以岩浆囊形式存储,并且壳内岩浆囊之间可能存在岩浆通道.通过联合反演获得的地震重定位结果显示,丛集地震位置更加集中,其展布特征与断裂构造具有显著的对应关系,表明研究区域断裂构造比较活跃.获得的高分辨率三维P波层析成像结果,为进一步认识火山地区岩浆存储特征以及地震分布与区域构造之间的关系提供了新的地震学依据.  相似文献   
4.
大气冰核观测是研究自然冷云降水和人工影响天气的一项基础性工作,滤膜—扩散云室法是观测冰核浓度的主要方法之一。为检测分析两种滤膜采集方法对冰核观测结果的影响,2011—2015年用自制的大气颗粒物采样器和FA-3型撞击式9级采样器开展了平行采样试验,采集的滤膜样本均在同一静力扩散云室中进行冰核活化显现分析。结果表明:自制采样器较9级采样器观测的冰核浓度高数倍甚至数十倍,但两者随季节和不同气象条件的变化表现出一致的起伏特征。自制采样器适用于对大气中总的冰核浓度分布及理化特征研究;9级采样器适用于对PM10中不同粒径段大气冰核浓度和尺度分布以及理化特征的研究。滤膜法对冰核数量的低估与采样体积成正比,改变采样器气泵的抽气流量和控制采样体积对改进“体积效应”影响均有明显效果。  相似文献   
5.
本文介绍了地震氡观测仪计量检定系统(氡室)的建设背景及结构组成。氡室具有氡体积活度(氡浓度)实时监测、动态补氡、氡期望值可调、稳定性好等特点。在氡室调试实验中进行了氡室的漏气率实验及4次补氡实验,计算出氡室的氡漏气率为0.0001393Bq/min,氡发生率为23.35Bq/min。根据《测氡仪检定规程》(JJG 825—2013)的技术要求进行计量效能验证,表明氡室的氡体积活度(氡浓度)为800Bq/m3、1500Bq/m3、3000Bq/m3、6000Bq/m3和15000Bq/m3时,连续8h稳定性均优于5%;为6000Bq/m3时,72h稳定性优于5%,符合国家计量技术规范对氡室计量标准的要求。  相似文献   
6.
Wave Energy Converters (WECs) have excellent potential as a source of renewable energy that is yet to be commercially realised. Recent attention has focused on the installation of Oscillating Water Column (OWC) devices as a part of harbor walls to provide advantages of cost–sharing structures and proximity of power generation facilities to existing infrastructure. In this paper, an incompressible three–dimensional CFD model is constructed to simulate a fixed Multi–Chamber OWC (MC–OWC) device. The CFD model is validated; the simulation results are found to be in good agreement with experimental results obtained from a scale physical model tested in a wave tank. The validated CFD model is then used for a benchmark study of 96 numerical tests. These investigate the effects of the PTO damping caused by the power take–off (PTO) system on device performance. The performance is assessed for a range of regular wave heights and periods. The results demonstrate that a PTO system with an intermediate damping can be used for all chambers in the MC–OWC device for most wave period ranges, except for the long wave periods. These require a higher PTO damping. An increased incident wave height reduces the device capture width ratio, but there is a noticeable improvement for long wave periods.  相似文献   
7.
Riparian corridors have the potential to function as thermal refuges, moderating extremes of local temperature variation. However, although demonstrated at individual sites, and over short periods, the consistency of this effect at wider temporal and spatial scales is poorly understood. The aim of this study is to assess the temperature differences between riparian corridors and adjacent non-riparian habitats and to explore the influence of environmental characteristics on these differences. Air temperature was monitored hourly at 20 paired locations (riparian and non-riparian) for two consecutive years. Urban index and canopy cover were characterised by calculating the percentage of impervious surface area and tree canopy cover within a 100 m radius from the centre of each sampling site. Canopy cover reduced summer thermal stresses in both urban and rural areas whereas high urban index tended to increase the daily thermal indices. Rivers had a significant mitigating effect on the urban riparian thermal condition, particularly in extreme hot weather. Riparian corridors were generally 1 °C cooler than non-riparian locations in summer and could be up to 3 °C cooler at some sites in extreme hot weather. Furthermore, riparian corridors at some sites were warmer than non-riparian locations in winter. These findings suggest that the proximity of rivers can modify riparian thermal environments, potentially reducing the heat stress of riparian corridors across landscapes.  相似文献   
8.
空气(泡沫)潜孔锤钻进工艺在王家岭煤矿紧急避险孔钻进中,有效解决了钻孔垂直度要求高、地层漏失等施工难点,实现了高质量快速成孔。该工艺平均机械钻速高达7.99 m/h,终孔水平位移仅为0.48 m,二开孔段每米综合成本504.8元。邻孔SW1水文补勘孔以泥浆作为循环介质、采用牙轮回转正循环钻进工艺,平均机械钻速为0.86 m/h,二开孔段每米综合成本为820.5元。前者平均机械钻速约是后者的9倍,较后者节约成本38.5%。与邻孔泥浆正循环牙轮回转钻进工艺相比,该工艺不仅解决了紧急避险孔施工难点,还提高了孔身质量、节约了工期、降低了成本,达到降本增效的目的,值得类似工程借鉴。  相似文献   
9.
The concentration of ice nuclei (IN) and the relationship with aerosol particles were measured and analyzed using three 5-L mixing cloud chambers and a static diffusion cloud chamber at three altitudes in the Huangshan Mountains in Southeast China from May to September 2011.The results showed that the mean total number concentration of IN on the highest peak of the Huangshan Mountains at an activation temperature (Ta) of-20℃C was 16.6 L-1.When the supersaturation with respect to water (Sw) and with respect to ice (Si) were set to 5%,the average number concentrations of IN measured at an activation temperature of-20℃C by the static diffusion cloud chamber were 0.89 and 0.105 L-1,respectively.A comparison of the concentrations of IN at three different altitudes showed that the concentration of IN at the foot of the mountains was higher than at the peak.A further calculation of the correlation between IN and the concentrations of aerosol particles of different size ranges showed that the IN concentration was well correlated with the concentration of aerosol particles in the size range of 1.2-20 μtm.It was also found that the IN concentration varied with meteorological conditions,such as wind speed,with higher IN concentrations often observed on days with strong wind.An analysis of the backward trajectories of air masses showed that low IN concentrations were often related to air masses travelling along southwest pathways,while higher IN concentrations were usually related to those transported along northeast pathways.  相似文献   
10.
利用国际刻度参考装置AlphaGUARD测氡仪及水氡测量组件, 使用水中溶解氡(或豁免级氡气源), 开展代替目前氡气固体源校准方法实验。 对FD-125测氡仪标配的3个闪烁室(1#、 3#及5#)分别使用水中溶解氡和氡气固体源进行校准实验, 3个闪烁室的校准K值相对误差分别为5.06%, 1.92%及2.76%, 可以达到目前地震监测氡观测技术要求。 实验结果表明, 水中溶解氡代替氡气固体源校准, 可以解决目前氡气固体源校准中存在的运输困难、 维修技术要求高等问题, 是今后氡观测仪器校准技术的发展趋势。  相似文献   
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