Estimation of peak relative velocity and peak absolute acceleration of linear SDOF systems

In the seismic analysis and design of structures, the true velocity and absolute acceleration are usually approximated by their corresponding pseudo-values. This approach is simple and works well for structures with small damping (say, less than 15%). When the damping of a structure is enhanced for the purpose of response reduction, it may result in large analysis and design errors. Based on theory of random vibration and the established mechanism of seismic response spectra analysis, a method is developed (1) to predict the relative velocity spectra with any damping ratio level directly from the 5% standard pseudo-acceleration spectrum; and (2) to estimate the peak absolute acceleration. The accuracy of both is validated by using two selected ensembles of ground motion records.     

Habitat continuity effects on gradients of fish biomass across marine protected area boundaries

Marine protected areas (MPAs) could be useful as fisheries management tools for the exportation of pelagic eggs, larvae and adult fish. A decreasing gradient of fish biomass across MPAs boundary may indicate export. We determine whether gradients of decreasing biomass of fish assemblage occurred in Tabarca Marine Reserve over two habitats with different continuity across the boundaries, to test if the patchy nature of the marine environment might act as a barrier for the fish export. In general, significant decreasing gradients in total fish biomass and biomass of some species were observed on P. oceanica and rocky substrates, independently of their different continuity through the reserve boundaries. Changes in the multivariate structure of the fish assemblage were correlated with the distance from integral reserve. All of these results support the hypothesis that the exportation of adult fish from Tabarca Marine Reserve occurs, and this process may influence the surrounding fished areas.     

Challenges in the Detection and Attribution of Northern Hemisphere Surface Temperature Trends Since 1850

Since 2007, the Intergovernmental Panel on Climate Change(IPCC) has heavily relied on the comparison between global climate model hindcasts and global surface temperature(ST) estimates for concluding that post-1950s global warming is mostly human-caused. In Connolly et al., we cautioned that this approach to the detection and attribution of climate change was highly dependent on the choice of Total Solar Irradiance(TSI) and ST data sets.We compiled 16 TSI and five ST data sets and found by alter...     

Application of soft computing techniques for shallow foundation reliability in geotechnical engineering

This research focuses on the application of three soft computing techniques including Minimax Probability Machine Regression(MPMR),Particle Swarm Optimization based Artificial Neural Network(ANN-PSO)and Particle Swarm Optimization based Adaptive Network Fuzzy Inference System(ANFIS-PSO)to study the shallow foundation reliability based on settlement criteria.Soil is a heterogeneous medium and the involvement of its attributes for geotechnical behaviour in soil-foundation system makes the prediction of settlement of shallow a complex engineering problem.This study explores the feasibility of soft computing techniques against the deterministic approach.The settlement of shallow foundation depends on the parametersγ(unit weight),e0(void ratio)and CC(compression index).These soil parameters are taken as input variables while the settlement of shallow foundation as output.To assess the performance of models,different performance indices i.e.RMSE,VAF,R^2,Bias Factor,MAPE,LMI,U(95),RSR,NS,RPD,etc.were used.From the analysis of results,it was found that MPMR model outperformed PSO-ANFIS and PSO-ANN.Therefore,MPMR can be used as a reliable soft computing technique for non-linear problems for settlement of shallow foundations on soils.     

An index of biotic integrity based on the summer polyhaline zooplankton community of the Chesapeake Bay

A zooplankton index of biotic integrity was developed for the polyhaline waters of the Chesapeake Bay using data from a long-term environmental assessment program in which both zooplankton and water quality were regularly monitored. Summer (July to September) sampling events were classified as either coming from impaired or reference (least-impaired) conditions based on water quality conditions. Seventeen zooplankton community metrics were evaluated under these criteria and nine were chosen for a composite index. These were the Simpson diversity index, and abundance of barnacle larvae, rotifers, cladocerans, copepods, total mesozooplankton, and predators. The composite index of biotic integrity correctly classified about 94% of the impaired samples and about 82% of the reference samples. Average classification efficiency was 88%. This index appears to be an effective measure of eutrophication for the summer polyhaline waters of the Chesapeake Bay ecosystem.     

冲绳海槽浮岩包裹体的测温试验

对浮岩中斜长石斑晶中的包裹体及玻璃基质中的包裹体首先进行双面光薄片的镜下观察，然后进行了系统的均化法与爆裂法测温试验。观察与试验结果表明：(1)斜长石中的包裹体均为玻璃质+气泡的两相包裹体，未发现气—液包裹体。固化包裹体为玻璃质，非晶质的固化包裹体外即是大量的气泡，特别是基质当中气泡更为发育，说明熔浆中含有丰富的挥发性组分，同时也说明包裹体形成于较浅的地质条件下。(2)长石中包裹体的均化温度不受包裹体特征不同的影响，均化温度分布范围从910—1250℃，峰值明显，计算的均化温度为Tz=(1081.4±177.9)℃，但还存在有高于1250℃的均化温度峰。包裹体均化法测试结果说明浮岩中斜长石的形成过程至少有两个阶段：第一阶段的岩浆温度在1200—1300℃左右，在此温度下形成的是An值较高的基性斜长石，同时结晶的还有辉石等矿物，斜长石结晶第二个阶段时的熔浆温度在1100℃以下，这一阶段持续的时间长，跨越的温度范围大，应是岩浆在近地表和岩浆喷出过程中的岩浆快速冷却期，同时伴随有矿物大规模晶出。(3)包裹体中的气相部分均聚合成圆形或近圆形，说明温度下降速度较快。斑晶斜长石中部分包裹体与基质玻璃中包裹体的形成温度是连续变化的，这一事实应该与冲绳海槽特殊的地质条件有关     

Thermal fronts and cross-frontal heat flux in the southern Huanghai Sea and the East China Sea

Synoptic features in/around thermal fronts and cross-frontal heat fluxes in the southern Huanghai./Yellow Sea and East China Sea （HES） were examined using the data collected from four airborne expendable bathythermograph surveys with horizontal approxmately 35 km and vertical 1 m（from the surface to 400 m deep） spacings. Since the fronts are strongly affected by HES current system, the synoptic thermal features in/around them represent the interaction of currents with surrounding water masses. These features can not be obtained from climatological data. The identified thermal features are listed as follows ： （ 1 ） multiple boundaries of cold water, asymmetric thermocline intrusion, locally-split front by homogeneous water of approxmately 18 ℃, and mergence of the front by the Taiwan Warm Current in/around summertime southern Cheju - Changjiang/Yangtze front and Tsushima front; （2） springtime frontal eddy-like feature around Tsushima front; （3） year-round cyclonic meandering and summertime temperature-inversion at the bottom of the surface mixed layer in Cheju - Tsushima front; and （4） multistructure of Kuroshio front. In the Kuroshio front the mean variance of vertical temperature gradient is an order of degree smaller than that in other HES fronts. The southern Cheju- Changjiang front and Cheju -Tsushima front are connected with each other in the summer with comparable cross-frontal temperature gradient. However, cross-frontal heat flux and lateral eddy diffusivity are stronger in the southern Cheju - Changjiang front. The cross-frontal heat exchange is the largest in the mixing zone between the modified Huanghai Sea bottom cold water and the Tsushima Warm Current, which is attributable to enhanced thermocline intrusions.