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Relaxation base seismic isolator

This paper deals with the use, for seismic applications, of a Maxwell element in parallel with a low damping isolator. The study of the properties of the frequency response function shows that this isolator is capable to reduce the base displacement of isolated structures with no considerable amplification of the non‐isolated modes. This is, also, confirmed by the floor response spectra under earthquake excitations. Hence, the previously mentioned isolator does not present the drawbacks met when base displacement is reduced by increasing damping. Moreover, it seems that its performance is comparable with that of more elaborated and expensive techniques combining passive and semi‐active devices. Copyright © 2016 John Wiley & Sons, Ltd.     

Regional gravity field modeling based on rectangular harmonic analysis

Regional gravity field modeling with high-precision and high-resolution is one of the most important scientific objectives in geodesy,and can provide fundamental information for geophysics,geodynamics,seismology,and mineral exploration.Rectangular harmonic analysis(RHA)is proposed for regional gravity field modeling in this paper.By solving the Laplace’s equation of gravitational potential in local Cartesian coordinate system,the rectangular harmonic expansions of disturbing potential,gravity anomaly,gravity disturbance,geoid undulation and deflection of the vertical are derived,and so are the formula for signal degree variance and error degree variance of the rectangular harmonic coefficients(RHC).We also present the mathematical model and detailed algorithm for the solution of RHC using RHA from gravity observations.In order to reduce the edge effects caused by periodic continuation in RHA,we propose the strategy of extending the size of computation domain.The RHA-based modeling method is validated by conducting numerical experiments based on simulated ground and airborne gravity data that are generated from geopotential model EGM2008 and contaminated by Gauss white noise with standard deviation of 2 mGal.The accuracy of the 2.5′×2.5′geoid undulations computed from ground and airborne gravity data is 1 and 1.4cm,respectively.The standard error of the gravity disturbances that downward continued from the flight height of 4 km to the geoid is only 3.1 mGal.Numerical results confirm that RHA is able to provide a reliable and accurate regional gravity field model,which may be a new option for the representation of the fine structure of regional gravity field.     

Deep soil water infiltration and its dynamic variation in the shifting sandy land of typical deserts in China

Soil moisture is the key resource constraint in arid ecosystems, and has been a focus of research on restoration. However, quantitative studies on the contribution of rainfall to deep soil rainfall infiltration are lacking. In this study, we used the YWB-01 Deep Soil Infiltration Water Recorder which had been invented by ourselves to measure the quantity of rain infiltration into deep soil, 150 cm below ground, in four locations in China: Mu Us Sandy Land and Ulan Buh, Tengger, and Badan Jilin deserts over a 2-year period. We found: (1) Deep soil rainfall infiltration decreased progressively from east to west and from semiarid to arid areas, with two locations completely lacking rainfall infiltration. Heavy rain was important to deep soil infiltration in shifting sandy land of arid and semiarid areas. (2) Seasonal variation of infiltration was correlated with rainfall, with a time lag that was less apparent in areas with more rainfall. (3) For single intense rainfall events, infiltration maximums occurred 40–55 h after the rainfall, during which the infiltration rates increased rapidly before reaching a peak, and then decreased slowly. Continuous infiltration could last about 150 h. Rainfall infiltration was determined by the combined action of intensity, quantity and duration. Rainfall with low intensity, long duration, and large quantity was most favorable for deep soil infiltration. Our results can be used in water resource assessments and protection during eco-restoration in the arid and semiarid areas in China.     

毛乌素沙地流动沙丘土壤水分对降雨的响应

为探讨半干旱区流动沙丘土壤水分对降雨的响应,采用AV-3665R型雨量传感器、ECH₂O-5土壤水分传感器同步监测毛乌素沙地东北缘流动沙丘2013年降雨及0～200 cm深度土壤体积含水量动态,分析土壤水分含量变化特征、降雨入渗特征及降雨对土壤水的补给作用。结果表明:5-11月累积降雨399.4 mm,显著(p<0.01)影响0～200 cm深度土壤水分含量; 且0～200 cm深度土壤体积含水量较低(6.49%±1.12%)时53.8 mm降雨、较高(10.22%±1.96%)时24.2 mm降雨湿润锋能够到达200 cm; 试验期间399.4 mm累积降雨对土壤水有一定补给作用,其中45.7±14.1 mm降雨蓄存在0～200 cm深度土壤中,占同期降雨的(11.4%±3.5%,且随着时间的延长,蓄存水大部分将渗漏到200 cm以下补给深层土壤水。     

面向特大城市的风环境容量指标和区划初探——以北京为例

利用气象观测、高分辨率城市地理信息和卫星遥感数据,通过将气象类指标与城市类指标相结合,开展了北京地区风环境容量指标和区划的探索性研究。结果表明：水平风速和大气混合层厚度两个指标在空间上均呈北部和东部地区高、中心城区和西南地区低的特征;中心城核心区和卫星城的地表粗糙度长度较高,二环内老城区建筑多为平房,地表粗糙度长度小于二环外其他中心城区,形成较明显的空心环状结构;在中心城区外的植被地区,北部和西部山区粗糙度长度明显高于平原区;加权综合水平风速、大气混合层厚度和地表粗糙度长度3个指标,计算不同等级风环境容量指数阈值,在空间上西南地区的房山、门头沟、海淀、石景山、丰台以及中心城区的东城和西城等地风环境容量指数较低,其中二环至四环范围是风环境容量指数最低区域,这与北京经济、金融和商业中心空间分布一致;延庆、怀柔、密云的北部以及通州的绝大部分地区为风环境容量指数高值区,其他平原区多为中等风环境容量指数区。     

Tracing carbon transfer and assimilation by invertebrates and fish across a tropical mangrove ecosystem using stable isotopes

Mangroves are highly productive ecosystems that exhibit a diverse range of habitats, including tidal creeks and flats, forest gaps and interior forest with varying understory light intensity, tidal dynamics, geomorphological settings, and overall biological production. Within mangrove ecosystems, invertebrates and fish feed on heterogeneous food sources, the occurrence of which is unevenly distributed across the system. This provides a basis for testing models of carbon transfer across mangrove ecosystems. We hypothesized that the carbon transfer and assimilation by fish and invertebrates will vary across the different mangrove habitats and that such variations can be predicted by their stable isotope compositions. We analysed δ¹³C and δ¹⁵N signatures of consumers and their potential organic carbon sources across a tropical mangrove ecosystem in Vietnam. The δ¹³C values of crabs and snails significantly decreased from the tidal flat to interior forest, indicating that variations in carbon transfer and assimilation occurred at small scales <30 m. Reduced variation in δ¹³C of suspension‐feeding bivalves suggested that tidal water was a vector for large‐scale transport of carbon across the mangrove ecosystem. An analysis of co‐variance using habitat as a fixed factor and feeding habit and movement capacity of consumers as co‐variates indicated that habitat and feeding types were major features that affected the δ¹³C values of invertebrates and fish. The findings demonstrate that carbon transfer and assimilation across mangrove ecosystems occur as a diverse combination of small (<30 m) and large (>30 m) scale processes.     

气象计量实验室能力验证实施

针对气象计量检定机构在组织和参加实验室间比对活动中在编制比对方案、参考值来源、结果评价方法、粗大误差的剔除、比对报告编制等方面的内容进行分析,探讨气象计量实验室能力。通过开展气象计量实验室间的比对工作,确立气象计量检定机构在社会上的专业计量检定地位,确保各计量标准量值的准确、可靠、一致,也为考察各实验室计量检定人员技术水平和数据处理能力,发现问题、积累经验,更好地开展气象计量检定工作,可以识别与同行各机构之间存在的差异,发现自身存在的问题,为自身的持续改进和质量管理提供信息。     

风沙化土地典型区滑县土地利用时空变化研究

运用3S技术,分析了风沙化土地典型区滑县1979-2009年的土地利用数量变化特征,结果显示:该区的土地利用类型变化显著.耕地、水域和未利用地面积持续减少,林地和建设用地面积呈现不断增加的态势;风沙化土地利用对研究区各土地类型之间的平衡起了重要的作用.这集中反映了人口素质提高、环保意识增强、人口增长和经济建设需求对土地利用变化的积极影响,同时宜采取有效措施减缓或调控耕地持续减少的趋势.     

Chemical speciation of fine particle bound trace metals

This study reported quantifications of fine particle bound trace metals and their potential health risks for residents in Guangzhou, a rapidly developing and most populated city in South China. The fine particle samples were collected from October 29^th. to November 8^th. of 2006 at two different elevations in a mainly residential area and analyzed for the total concentration of aluminum, iron, zinc, lead, manganese, copper, arsenic, chromium, nickel, cadmium, molybdenum and cobalt. Results showed that the fine particle concentrations ranged from 95.8μg/m³to 194.7 μg/m³ at the ground and 83.3-190.0 μg/m³ on the roof, which were much higher than the 24 h fine particle standard (35 μg/m³) recommended by USEPA. The total concentrations of zinc, lead, arsenic, chromium and cadmium in fine particle were 504.8, 201.6, 24.3, 7.7 and 4.4 ng/m³, respectively, which were comparable to other major cities of China, but much higher than major cities outside of China. A sequential extraction procedure was used to fractionate these fine particle bound metals into four different fractions. Results indicated that most toxic metals were mainly distributed in bioavailable fractions. For instance, about 91 % of cadmium, 85 % of lead and 74 % of arsenic were in bioavailable forms. Risk calculations with a simple exposure assessment model showed that the cancer risks of the bioavailable fractions of arsenic, chromium and cadmium were 3 to 33 times greater than usual goal, indicating serious health risks to the residents in this urban area.