Ultimate Bending Capacity of Strain Hardening Steel Pipes

Based on Hencky’s total strain theory of plasticity, ultimate bending capacity of steel pipes can be determined analytically assuming an elastic-linear strain hardening material, the simplified analytical solution is proposed as well. Good agreement is observed when ultimate bending capacities obtained from analytical solutions are compared with experimental results from full-size tests of steel pipes. Parametric study conducted as part of this paper indicates that the strain hardening effect has significant influence on the ultimate bending capacity of steel pipes. It is shown that pipe considering strain hardening yields higher bending capacity than that of pipe assumed as elastic-perfectly plastic material. Thus, the ignorance of strain hardening effect, as commonly assumed in current codes, may underestimate the ultimate bending capacity of steel pipes. The solutions proposed in this paper are applicable in the design of offshore/onshore steel pipes, supports of offshore platforms and other tubular structural steel members.     

Statistical analyses of Global U-Pb Database 2017

The method of obtaining zircon samples affects estimation of the global U-Pb age distribution.Researchers typically collect zircons via convenience sampling and cluster sampling.When using these techniques,weight adjustments proportional to the areas of the sampled regions improve upon unweighted estimates.Here,grid-area and modern sediment methods are used to weight the samples from a new database of 418,967 U-Pb ages.Preliminary tests involve two age models.Model-1 uses the most precise U-Pb ages as the best ages.Model-2 uses the~(206)Pb/~(238)U age as the best age if it is less than a1000 Ma cutoff,otherwise it uses the~(207)Pb/~(206)Pb age as the best age.A correlation analysis between the Model-1 and Model-2 ages indicates nearly identical distributions for both models.However,after applying acceptance criteria to include only the most precise analyses with minimal discordance,a histogram of the rejected samples shows excessive rejection of the Model-2 analyses around the1000 Ma cutoff point.Because of the excessive rejection rate for Model-2,we select Model-1 as the preferred model.After eliminating all rejected samples,the remaining analyses use only Model-1 ages for five rock-type subsets of the database:igneous,meta-igneous,sedimentary,meta-sedimentary,and modern sediments.Next,time-series plots,cross-correlation analyses,and spectral analyses determine the degree of alignment among the time-series and their periodicity.For all rock types,the U-Pb age distributions are similar for ages older than 500 Ma,but align poorly for ages younger than 500 Ma.The similarities(500 Ma)and differences(500 Ma)highlight how reductionism from a detailed database enhances understanding of time-dependent sequences,such as erosion,detrital transport mechanisms,lithification,and metamorphism.Time-series analyses and spectral analyses of the age distributions predominantly indicate a synchronous period-tripling sequence of~91-Myr,~273-Myr,and~819-Myr among the various rock types.     

Gravimetric and magnetic fabric study of the Sintra Igneous complex: laccolith-plug emplacement in the Western Iberian passive margin

International Journal of Earth Sciences - The geometry and emplacement of the ~ 96 km2, Late Cretaceous Sintra Igneous complex (SIC, ca. 80 Ma) into the West Iberian passive...     

A Cambrian mixed carbonate–siliciclastic platform in SW Gondwana: evidence from the Western Sierras Pampeanas (Argentina) and implications for the early Paleozoic paleogeography of the proto-Andean margin

International Journal of Earth Sciences - The Western Sierras Pampeanas (WSP) of Argentina record a protracted geological history from the Mesoproterozoic assembly of the Rodinia supercontinent to...     

Increase in Dissolved Silica of Rivers Due to a Volcanic Eruption in an Estuarine Bay (Sorsogon Bay,Philippines)

Mount Bulusan, the Philippines’ fourth most active volcano, erupted in February 21, 2011, sending volcanic ash and pyroclastic materials to its surrounding rivers. The waters drained into the estuary of harmful algal blooms plagued Sorsogon Bay. We aim to determine the impact of the 2011 volcanic eruption and the preceding volcanic ash emissions to the dissolved silica concentration of rivers draining the flanks of Mt. Bulusan and its possible implications to the phytoplankton assemblage of the bay. Six river water sampling periods from August 2010 to October 2012 overlapped with Mt. Bulusan’s active phase of volcanism. Our data shows that mean river silica from pre-eruption levels of ~?500 μM increased by more than 200% during and post-eruption. Highest Si concentration of 2270 μM was measured from Cadacan River in August 2011. Here, we argue that the sustained general increase of dissolved silica is due to the silica-containing materials from Mt. Bulusan’s eruption and that their concentration in river waters is also a function of watershed lithology and precipitation. Increase in dissolved silica and other nutrients caused a shift to diatom domination and, possibly, termination of Pyrodinium bahamense var. compressum blooms. Silica load increase in embayments is a natural process that controls the dominance of algae. Our study also highlights the importance of Philippine rivers to the global ocean silica budget as a function of high precipitation, tectonics in general, and volcanism in particular.     

Potential Salinity and Temperature Futures for the Chesapeake Bay Using a Statistical Downscaling Spatial Disaggregation Framework

Estuaries are productive and ecologically important ecosystems, incorporating environmental drivers from watersheds, rivers, and the coastal ocean. Climate change has potential to modify the physical properties of estuaries, with impacts on resident organisms. However, projections from general circulation models (GCMs) are generally too coarse to resolve important estuarine processes. Here, we statistically downscaled near-surface air temperature and precipitation projections to the scale of the Chesapeake Bay watershed and estuary. These variables were linked to Susquehanna River streamflow using a water balance model and finally to spatially resolved Chesapeake Bay surface temperature and salinity using statistical model trees. The low computational cost of this approach allowed rapid assessment of projected changes from four GCMs spanning a range of potential futures under a high CO₂ emission scenario, for four different downscaling methods. Choice of GCM contributed strongly to the spread in projections, but choice of downscaling method was also influential in the warmest models. Models projected a ~2–5.5 °C increase in surface water temperatures in the Chesapeake Bay by the end of the century. Projections of salinity were more uncertain and spatially complex. Models showing increases in winter-spring streamflow generated freshening in the Upper Bay and tributaries, while models with decreased streamflow produced salinity increases. Changes to the Chesapeake Bay environment have implications for fish and invertebrate habitats, as well as migration, spawning phenology, recruitment, and occurrence of pathogens. Our results underline a potentially expanded role of statistical downscaling to complement dynamical approaches in assessing climate change impacts in dynamically challenging estuaries.     

Bioaccumulation of heavy metals in <Emphasis Type="Italic">Limnobium laevigatum</Emphasis> and <Emphasis Type="Italic">Ludwigia peploides</Emphasis>: their phytoremediation potential in water contaminated with heavy metals

Contamination with heavy metals in surface and groundwater is a threat to human health and ecosystems. Due to this, the need arises to remediate water polluted through ecological and profitable technologies, such as phytoremediation. The objective of the work was to evaluate the concentration of lead (Pb) and zinc (Zn) in the floating macrophytes Limnobium laevigatum and Ludwigia peploides, after being exposed to contaminated water experimentally. In this way to be able to determine if these plants have mechanisms that allow them to accumulate the metals in the roots and to perform the translocation of these to different vegetative organs, L. laevigatum and L. peploides were placed in solutions contaminated with Pb ([Pb]?=?5 mg/l) and Zn ([Zn]?=?20 mg/l). The concentrations of metals in water, root and leaf samples were evaluated as a function of time (0, 1, 2 and 4 days). The determination of the metals was performed by the atomic absorption spectrophotometry technique. After 4 days of exposure to Pb and Zn, the plants showed high metal removal efficiencies of water, more to 70% in all cases. Pb was accumulated fundamentally by roots, while Zn was accumulated more in the leaves. In addition, the bioconcentration and translocation factors for each metal were calculated.     

陕西凤太矿集区多金属成矿作用的构造控制

陕西凤县-太白(简称凤太)矿集区铅、锌、金、银、铜多金属资源丰富,已发现二十余个大中小型矿床。在大地构造位置上,凤太矿集区位于南秦岭造山带北缘,紧邻商丹缝合带。以往的工作缺乏对矿集区整体的构造研究,本次工作通过比较系统的构造测量和解析,提出在南秦岭晚三叠世碰撞造山过程中,凤太矿集区南北两条边界断裂带的左行走滑运动导致在区内衍生了NNE向主压应力场,从而形成了NWW向复式褶皱、脆韧性剪切带、断裂和节理(纵向破裂)、B型线理,以及NNE向断裂和节理(横向破裂)、劈理、张裂隙等一系列构造组合,所有构造形迹都是在统一构造应力场下随着构造层次不断抬升,脆韧性和脆性递进变形叠加的产物,共同构成了一个大型压扭性走滑双重构造变形系统。在构造几何学上,凤太矿集区整体上表现为一个隔档式复式褶皱,由一组NWW向紧闭复背斜和一组相对宽缓复向斜组成。区内的多金属成矿作用、岩浆活动、动力变质变形作用的同位素年龄数据集中于230~190Ma。综合地质演化和成矿作用的研究成果,提出在南秦岭碰撞造山过程中引发的动力变质变形作用和岩浆活动提供了成矿元素和成矿流体,在温压梯度以及浮力效应的驱动下向上运移至走滑双重构造变形系统中的有利扩容空间中发生充填型和交代型矿化,即凤太矿集区多金属矿床是区域大规模变形变质-岩浆活动-流体作用的产物,是在构造作用这一主导因素控制下形成的一个多金属后生热液成矿系统。