Reconstructing fluvial bar surfaces from compound cross‐strata and the interpretation of bar accretion direction in large river deposits

The interpretation of fluvial styles from the rock record is based for a significant part on the identification of different types of fluvial bars, characterized by the geometric relationship between structures indicative of palaeocurrent and surfaces interpreted as indicative of bar form and bar accretion direction. These surfaces of bar accretion are the boundaries of flood‐related bar increment elements, which are typically less abundant in outcrops than what would be desirable, particularly in large river deposits in which each flood mobilizes large volumes of sediment, causing flood‐increment boundary surfaces to be widely spaced. Cross‐strata set boundaries, on the other hand, are abundant and indirectly reflect the process of unit bar accretion, inclined due to the combined effect of the unit bar surface inclination and the individual bedform climbing angle, in turn controlled by changes in flow structure caused by local bar‐scale morphology. This work presents a new method to deduce the geometry of unit bar surfaces from measured pairs of cross‐strata and cross‐strata set boundaries. The method can be used in the absence of abundant flood‐increment bounding surfaces; the study of real cases shows that, for both downstream and laterally accreting bars, the reconstructed planes are very similar to measured bar increment surfaces.     

旋转扰动流体中壁面湍流不稳定及其拟序结构研究Ⅱ：数值模式

对第一部分的实验结果进行了讨论,指出局地最大、最小涡度的存在与所谓的正压不稳定和大气中经常观测到的滚动涡有关。速度廓线中的拐点和涡度极大值点对应不稳定发展的位置。另外,为了改进湍流的模拟,根据“准正则”近似,发展了一个三阶闭合模式。这个模型已被证明可以描述与湍流过程有关的流体动力学变量的趋势。     

Contribution of the tully groups to the soft X-ray background

We examine a model for the expected contributions to the soft X-ray background (SXRB) due to bremsstrahlung and re-combination radiation of gas, enriched with heavy elements, located in groups of galaxies taken from Tully'sCatalog of Nearby Groups of Galaxies. It is shown that the contribution to the SXRB of groups of galaxies can explain up to 20% of the observed flux depending on the chemical composition and ratio of emitting mass to assumed virial mass.     

Growth pattern and changes in abundance of the endangered bat star Asterina stellifera

The sea star Asterina stellifera has declined during the last decade and is currently abundant only in the southern limit of its former range. We surveyed this population over 5 years to model individual growth and explore the relationship of changes in local abundance with variation in environmental factors and the reproductive status of individuals. Our results show that A. stellifera is a species with slow growth and a relatively long lifespan. Contrary to expectations for temperate species, growth rates were fairly constant through the year and therefore models including seasonal oscillations were inappropriate. The abundance of this species increased significantly from early spring to early summer, likely due to augmented activity and small‐scale aggregation during the reproductive season that affected our estimates of abundance. No significant recruitment occurred during the 5 years studied. The lack of recruitment during long periods and the slow individual growth rates make A. stellifera particularly vulnerable to local extinction. This study was performed prior to the arrival in the study area of the invasive kelp Undaria pinnatifida and side‐gilled sea slug Pleurobranchaea maculata, species that threaten the community structure where A. stellifera lives. Therefore, the information reported here will be essential to assessing the impacts of these exotic species on this sea star population.     

An Innovative Post Grouting Technique for Soil Nails

This study presents an innovative technique of executing soil nails called sectorized post grouting (SPG). The most utilized technique of soil nail grouting is gravity grouting, with the literature reporting advances in pressurized grouting. Although obtaining higher pullout resistance of soil nails, pressurized grouting, mostly done in single-stage grouting, does not compensate for exudation and its use in higher nail lengths is difficult. Thus, a technique has been developed that compensates for exudation, with easier application in lengthier nails. The technique was qualitatively assessed to evaluate its surface roughness and later applied in seven real soil nailing works, where it could be quantitatively assessed. The results show that sectorized post-grouted nails obtained greater pullout resistances than gravity grouted and single-stage grouted nails. Although similar improvement was found in tube-à-manchette (TAM) grouted nails, this method presents lower economic efficiency than sectorized post grouting. The pullout resistance results obtained in this study can be utilized in future soil nailing works executed utilizing SPG.

     

Behaviour of Instrumented Hollow Auger Pile Groups in Sandy Soil

Geotechnical and Geological Engineering - Hollow auger piles are a new solution technique being used more often in recent years as a foundation for buildings of 15 floors or less in the coastal...     

What factors affect the decision making process when setting TACs?: The case of Chilean fisheries

Although failures and successes in fisheries management are related to decision making processes, these are rarely analyzed in detail and even less often following quantitative or semi-quantitative approaches. Herein, we study the decision making process for Chile's most important fisheries using a binary decision model. This model evaluates the probability that an annual total allowable catch (TAC) will or will not be modified by the National Fisheries Council (NFC) based on biological, economic, and social factors. We also analyze some aspects of individual voting, particularly whether the members vote against or abstain from voting on the proposed TAC and if they prioritize resource conservation objectives. Our results indicate that the risk of over exploitation for many important stocks in Chile is aggravated by failures at the decision making level: the scientifically recommended TACs for those fisheries that generate higher levels of employment and have greater economic value are normally increased. This analysis shows that the NFC has clearly prioritized short-term economic and social objectives over resource conservation goals. We discuss the need to adjust the composition and functioning of the NFC in order to ensure long-term sustainability of the fisheries.