High-resolution records of grain-size and depositional environment correlated to the Homo erectus Nariokotome Boy site, West Turkana, Kenya

<p>The Turkana Basin in northern Kenya contains a robust record of hominin fossils, including Nariokotome Boy (discovered from the NK3 site), the most complete H. erectus specimen found to date. Understanding the paleoenvironmental context in which hominins such as H. erectus evolved has been an objective of decades of research in eastern Africa. Here, we present a study using grain size analyses to infer the paleoenvironmental conditions responsible for the deposition of the sedimentary sequences directly associated with NK3. We resampled a ~14 m interval at from the West Turkana Kaitio (WTK13) core, collected as part of the Hominin Sites and Paleolakes Drilling Project. This interval ties directly to the outcrop where Nariokotome Boy was recovered. By sampling continuously at 0.5 cm intervals (~7 yrs/sample), we document the paleoenvironment in ultra high-resolution (i.e. a scale relevant to a hominin life) that directly correlates to the NK3 site. Over 350 sediment samples were pre-treated to remove carbonate, biogenic silica, and other organic material from detrital material. Grain size distributions were measured on a Malvern Mastersizer 3000 using wet suspension. Based on these analyses, the interval was dominated by silt, which was further investigated using end-member modeling. A four end-member solution explained on average 99% of the population variability. The bottom of the interval was more coarse-grained, with an abrupt fining transition at 38.83 meter below surface (mbsf), which corresponds with the transition out of a tuffaceous interval (Natoo tuff) and into a pedogenically modified interval. This correlation is significant as the top of this tuff is the surface upon which Nariokotome Boy was recovered. Previous facies and grain size analyses revealed and quantified Turkana’s dynamic lake level history. However, our grain size analysis provides unprecedented resolution for the paleoenvironment during which Nariokotome Boy lived. Our 0.5 cm sampling resolution enables us to quantify depositional changes on a scale comparable with previous descriptive facies analyses and to refine transitions between paleosols, fluvial deposits, and lacustrine deposition at the interface of these three paleoenvironments enabling us to reconstruct a dynamic lakeshore environment during the lifetime of the Nariokotome Boy.</p>

Modification of nanoporous structure and surface of carbon electrodes for use in power storage systems

Method for modification of nanoporous structure and surface of carbon materials to be used as supercapacitor electrodes has been developed and optimized as to the microwave treatment (MWT) regimes. Mechanisms of MWT due to the dielectric and Maxwell-Wagner polarization effects have been discussed. It has been found that due to the dielectric polarization and a fast increase in temperature inside pores, which were saturated with etching agents (water, oxalic or formic acid) beforehand, the selective pore etching “from inside” can occur that increases the pore size and, as a result, increases the electrostatic capacitance of supercapacitors by 20%. Processes of pore structure development have been optimized as to the treatment duration and the carbon material grain size. It has also been shown that the pore surface can be modified with Nitrogen heteroatoms due to the MWT of carbon and melamine powder mixtures. This modification enables to step up the supercapacitor rated voltage from commonly used 2.7V to 3.0V that additionally increases the supercapacitor energy density by 23%. Yet another advantage of MWT is a significant reduction in treatment duration (from hours to minutes) and in energy consumption; besides, the loss of carbon material does not exceed 10% due to the mostly “from inside” etching process.

A Constitutive Material Model Applied to Microforming Processes

The plastic treatment of products reduced to sizes corresponding to the microscale poses difficulties, due to the occurrence of the so-called size effect, which is responsible for the different behavior of the material during the realization of microforming. In this study, a constitutive equation was elaborated taking into account two types of size effects, with the use of a surface model as well as a composite material model. The influence of the size effect referring to both the material grain size and the geometric scaling of the sample size on the material’s flow stresses was considered. The surface model took into account the different grain shapes present in actual polycrystalline materials. After the application of the presented model for titanium Grade 2, a good agreement of the experimental results with the FEM simulation results was obtained. Thus, the proper FEM modeling of microforming processes should be conducted with the use of a material model, taking into account the occurring size effects.

Evaluation of LNAPL Behavior in Water Table Inter-Fluctuate Zone under Groundwater Drawdown Condition

We investigate the movement of LNAPL (light non-aqueous phase liquid) into and out of monitoring wells in an immediate-scale experimental cell. Aquifer material grain size and LNAPL viscosity are two factors that are varied in three experiments involving lowering and rising water levels. There are six monitoring wells at varying distances from a LNAPL injection point and a water pumping well. We established steady water flow through the aquifer materials prior to LNAPL injection. Water pumping lowered the water levels in the aquifer materials. Terminating water pumping raised the water levels in the aquifer materials. Our focus was to record the LNAPL thickness in the monitoring wells under transient conditions. Throughout the experiments, we measured the elevations of the air-LNAPL and LNAPL-water interfaces in the monitoring wells to obtain the LNAPL thicknesses in the wells. We analyze the results and give plausible explanations. The data presented can be employed to test multiphase flow numerical models.

Image-Based Bed Material Mapping of a Large River

The composition or bed material plays a crucial role in the physical hydromorphological processes of fluvial systems. However, conventional bed material sampling methods provide only pointwise information, which can be inadequate when investigating large rivers of inhomogeneous bed material characteristics. In this study, novel, image-based approaches are implemented to gain areal information of the bed surface composition using two different techniques: monocular and stereo computer vision. Using underwater videos, captured in shorter reaches of the Hungarian Danube River, a comparison of the bed material grain size distributions from conventional physical samplings and the ones reconstructed from the images is carried out. Moreover, an attempt is made to quantify bed surface roughness, using the so-called Structure from Motion image analysis method. Practical aspects of the applicability of image-based bed material mapping are discussed and future improvements towards an automatized mapping methodology are outlined.

granular effects in debris flows

<p>Granular effects in debris flows are usually assessed by dimensionless numbers, such as numbers of Savage, Bagnold, and Iverson, which measure the relative significance of granular interaction, and the values indicate that the granular effects are generally ignorable. But observations suggest robust phenomena pertain to grain composition in many ways. This implies that the dimension analysis does not apply to the recognition of granular behaviors in debris flows, partly because we have not really a direct description of changes in grain compositions of debris flows. We have proposed and confirmed that for debris flows the material grain size distribution (GSD) satisfies a unified function, P(D) = C*power(D, – μ)*exp(–D/D<sub>c</sub>), where P(D) is the exceedance percentage of grains beyond size D (mm), and C, μ, and D<sub>c</sub> are parameters, with a semi-log relationship between C and μ. Then the grain composition is characterized by the GSD parameters μ, and D<sub>c</sub>, respectively representing the fine and coarse content of the materials. In this study we present a variety of appearances to illustrate how grain compositions impact on the initiation, formation, motion, and deposition of debris flow. Results indicate that debris flow occurs through a selection mechanism in which soil or sediment blocks of different grain compositions initiate in different ways and form separate surges in different flow regimes. The flow properties (X), such as the speed, the discharge, the density, are all dependent on the GSD parameters in power laws: X ~ power(μ, –m) and X ~ power (D<sub>c</sub>, n); and the power laws impose constraints on the fluctuation of the dynamical quantities. In particular, the GSD evolves from the randomly aggregated grains to the fluid with some self-organized constitute.</p><p> </p>

Contact of Working Surfaces for Spherical Washers and Recommendations for Determining the Gap in the Joint

In article analyzes the technical requirements for spherical washers used in threaded connections of pumps, which made it possible to highlight contradictions in paragraphs of the current standards for pump fasteners. They regarding recommendations for manufacturing technology and control of the working surfaces of washers. Publication analysis in the spherical surfaces lapping showed the absence of research in the spherical surfaces contact after lapping and the dependence of contact parameters by the technological parameters for this operation. The presence of a gap in conjunction with spherical washers after the lapping process was proved geometrically. Its location was determined, and a mathematical dependence was obtained to determine the maximum gap value in conjunction. It was found that the gap depends on the design parameters of the washers’ conjunction and the abrasive material grain size used for lapping. Recommendations for selecting the abrasive material grain size for the lapping operation for the most common values of the roughness parameters for the working surfaces of spherical washers have been formed. In the article was proposed to introduce into the technical requirements for the spherical washers drawings changes concerning the gap size allowable in the conjunction, and as well as tolerances value changes of the radii of the working surfaces of the washers, thus increasing their manufacturability without conflicting with the requirements of the current standards.