Late Holocene palaeoenvironments of the Nutria Mansa 1 archaeological site,Argentina

This paper presents results of interdisciplinary palaeoenvironmental research carried out on a sediment sequence from the Nutria Mansa 1 archaeological site. This late Holocene site is located in the Pampean plains, Argentina. Siliceous microfossils were recorded (i.e. phytoliths, diatoms, chrysophytes, sponges) and micro-charcoal was analyzed. In addition, fauna identified at the site were correlated with regional palaeoclimatic evidence. Based on the microfossil associations, we concluded that the human occupations occurred beside a fluvial and brackish-freshwater lacustrine setting. Grass communities were located on its margins that developed under a warm temperate climate with evidence for dryness and marked seasonality in part of the record. Although some stratigraphic and faunal evidence indicates a possible temperature increase, these fluctuations were not sufficient to extirpate mammals of arid and cold environments.     

基于单程波方程的角度域保幅偏移(英文)

传统叠前深度偏移只能够提供地下的构造信息,但工业界在需要构造信息的同时还要与地下界面反射系数成比例的振幅信息。最近几年,基于单程波方程的保幅叠前深度偏移算法有了一定的发展,但是,基于炮域、单程波的保幅型叠前深度偏移必须应用反褶积型的成像条件,这种成像条件在构造复杂、速度变化剧烈的地区会出现不稳定现象。基于角度域的保幅深度偏移克服了这一不稳定性缺点的同时,还域的保幅深度偏移,模型和实际资料的试算分析验证该思路方法的正确性和有效性。     

Effect of Visitor Activities on Surface Soil Environmental Conditions and Aboveground Herbaceous Biomass in Ayder Natural Park

The effects of visitor activities on surface soil environmental conditions and aboveground herbaceous biomass in Ayder Natural Park, Turkey, were investigated. Soil properties and aboveground herbaceous biomass were identified and characterized as heavily trafficked site (HTS), moderately trafficked sites (MTS) and control (non‐trafficked site) in grassland in a forest gap. Some soil properties were measured on 60 pits at 0–5 and 5–10 cm soil depths. The intensity of visitor activities had a negative impact on both surface soil properties and the aboveground herbaceous plant biomass and root mass in the study area in Ayder. The soil bulk density and soil penetration resistance increased from 0.94 to 1.47 g cm^–3 and 0.55 to 1.65 MPa, respectively, saturated hydraulic conductivity decreased from 77.98 to 8.85 mm h^–1, and soil organic matter decreased from 6.71 to 1.77% in moderately and heavily trafficked sites, respectively, at 0–5 cm soil depth. The soil properties were degraded at both the surface layer and the subsurface layer and the greatest degradation was measured in the heavily trafficked site followed by the moderately trafficked site. There was a strong negative linear relationship between soil degradation and aboveground herbaceous plant biomass, which decreased by 50.05 and 78.19% in moderately and heavily trafficked sites, respectively.     

旅游产业集群形成条件与识别方法

根据"产业集聚"和"产业联系"两个识别旅游集群存在的标准,结合旅游业的特点,从旅游资源空间集聚条件、旅游要素集中度和集聚效果3个方面构造区位熵指数,再根据投入产出表,用主成份分析法,确定旅游产业联系,计算产业联系密度,最后结合区位熵指数和产业联系密度,得出旅游产业集群度,同时分析旅游产业集群的形成条件,有利于制定政策引导促进旅游产业发展.     

高精度瑞雷波有限差分数值模拟及波场分析

应用2×12阶高精度交错网格有限差分法,建立了震源位于自由表面时模拟瑞雷波的边界条件,通过对均匀半空间模型模拟得到的结果与解析解完全一致,证明了波场模拟的正确性.针对模拟得到的波场记录,从瑞雷波的传播速度、传播深度、能量衰减和频散特性等几个方面进行了分析,从波场模拟的角度完全证实了弹性波传播理论中的瑞雷波传播特征,加深了对瑞雷波传播过程的认识.在均匀介质模拟的基础上,对含有软弱夹层的三层介质模型进行了模拟,获得了更加接近实际情况的地震记录.为进一步开展对高模式下瑞雷波的反演研究和促进对瑞雷波勘探的应用提供了有益的帮助.     

Geologic characteristics,controlling factors and hydrocarbon accumulation mechanisms of China’s Large Gas Provinces of low porosity and permeability

Based on the analysis of the geological characteristics and controlling factors, we analyzed the formation mechanism of different types of gas reservoirs. The main characteristics of gas provinces with low porosity and permeability are mainly as follows: large area, low abundance, small gas pools and large gas provinces; widely distributed excellent hydrocarbon source rocks with closely contacted source-reservoir-cap association; development mainly in large continental depressions or in paralic shallow-river delta systems; many kinds of traps coexisting in large areas, dominantly para-layered lithologic, digenetic and capillary pressure traps; double fluid flow mechanisms of Darcy flow and non-Darcy flow; complicated gas and water relations; and having the resource distribution of highly productive “sweet spots”, banding concentration, and macroscopically large areas integrated. The main controlling factors of large sandstone gas provinces with low porosity and permeability are stable dynamic backgrounds and gentle structural frameworks which control the extensive distribution of alternate (interbedded) sandstones and mudstones; weak hydropower of large gentle lake basins controlling the formation of discontinuous, low porosity and permeability reservoirs in shallow-water deltas; regionally differential diagenesis and no homogeneous digenetic facies controlling the development of favorable reservoirs and digenetic traps; and weak and dispersive reservoir-forming dynamic forces leading to the widely distributed small traps with low abundance. Low porosity and permeability gas provinces with different trap types have different formation mechanisms which include fluid diversion pressure difference interactive mechanism of lithologic-trap gas accumulations, separated differential collection mechanism of digenetic-trap gas accumulations, and the Non-Darcy flow mechanism of capillary-pressure gas accumulations. Supported by PetroChina Science and Technology Project (Grant No. 07-01C-01-07) and Youth Innovation Fund Project (Grant Nos. 10100042KT96, 07-06D-01-04-01-03)     

呼吸道和心脑血管疾病与气象条件关系的研究进展

全球气候的变化,城市热岛效应的持续和加强以及热浪冲击频率的增多,给人类的健康带来了很大的影响。 随着经济和技术的发展,人们生活水平的提高,疾病与气象条件之间的关系越来越受到关注。通过分析总结主要气象因素气温、气压、风速对呼吸道和心脑血管疾病发病和死亡情况影响的研究成果。对气象条件与疾病之间关系研究中存在的问题,提出了一些意见和建议。     

Morphologic and sedimentologic patterns of active aeolian dune‐fields on the east coast of Maranhão,northeast Brazil

The eastern portion of the Maranhão coast is characterized by large active dune‐fields located in a tropical setting. This article combines the analysis of dune‐field morphologic patterns with the classical analysis of grain size and heavy minerals to study the sedimentary dynamics of the active aeolian system in this region. Based on the heavy mineral analysis, the main sedimentary suppliers feeding the system are the westward alongshore drift bringing sand from the coast east of the Parnaíba River mouth and the river itself. The absence of well‐defined variation patterns of the two morphometric parameters studied, dune spacing and crest length, reflects complex sedimentary dynamics and transport pathways, inside the aeolian system, despite the unidirectional wind. During the wet season, the interdune plains are flooded and the system is intensely reworked by intermittent drainages. During the dry season, the deposits formed by the drainages and interdune lakes become temporary internal sedimentary sources for the system. Due to this combined aeolian‐fluvial transport, the sediment source area has a planar geometry, with contributions from the beach and interdune plains, and not linear as expected in a typical case of source only in the beach. The areal limits of the dune‐fields is the main boundary condition controlling the dune‐field patterns, as dune spacing and crest length, by changing the sedimentary inflow–outflow balance and interactions between migration dunes. Copyright © 2015 John Wiley & Sons, Ltd.     

Historically unprecedented erosion from Tropical Storm Irene due to high antecedent precipitation

Lacustrine sediment archives indicate that flooding during Tropical Storm Irene (2011) in the north‐eastern United States caused the most severe erosion of any flood in the historic record, surpassing that of events with greater precipitation and peak discharges. Compared to deposition from historic floods, Irene's event layer was more massive and more enriched in unweathered upland sediments, indicating an anomalously high incidence of mass wasting and sediment entrainment. Precipitation records indicate that neither precipitation intensity nor total accumulation distinguished Irene from less erosive historic floods. However, cumulative precipitation prior to Irene exceeded the 95th percentile of all days in the record. When allowing for non‐stationarity in the twentieth century background precipitation, we find a four‐fold increase in the probability of Irene‐like conditions, where impacts of extreme rainfall are enhanced by high antecedent precipitation. We conclude that irrespective of increases in extreme precipitation, the risk of highly erosive flooding in the region is increasing due to the influence of wetter baseline conditions associated with a changing climate. Copyright © 2015 John Wiley & Sons, Ltd.     

Seismic ground response at Lotung: Hysteretic elasto-plastic-based 3D analyses

This paper presents a non-linear finite element study to back-interpret the free field seismic response recorded at the Lotung Large-Scale Seismic Test site. The study is carried out in the time domain by the Finite Element (FE) code PLAXIS 3D, considering the vertical wave propagation of both the horizontal components of motion. The non-linear soil behaviour is simulated through a constitutive model, the Hardening Soil model with Small-Strain Stiffness (HSsmall), capable of describing the cyclic response of the material at different strain levels. In the paper, the constitutive response of the HSsmall model is firstly investigated through numerical simulations of strain-controlled cyclic shear tests under single and multi-directional conditions at low strain levels. Then, it is adopted to back-analyse the recorded free field seismic response, comparing the FE numerical results to the in-situ down-hole and surface signals recorded during two earthquakes occurred on May 20th and July 17th 1986, characterized by different peak ground accelerations.