Investigation into the Role of Cold Atmospheric Plasma on the Precision Grinding of RB-SiC Ceramic at Room Temperature

RB-SiC ceramic is one of the most important and useful material as optical precision elements in many scientific research fields. In this paper, a novel cold atmospheric plasma (CAP), which is based on the precision grinding process in surface technology to modify at room temperature (RT) for grinding with a combination of plasma oxidation surface modification is proposed. To identify the performance of the proposed cold atmospheric plasma (CAP) method on the surface modification of RB-SiC ceramic, precision grinding test was conducted. To reveal the fundamental issue in the grinding of RB-SiC ceramic, numerical calculation and model analysis were conducted to investigate the effect of the composite process on grinding forces and the mechanism of subsurface material removal in the presence of plasma oxidation. As a result of the method included the kept constant during the precision grinding of the composite process self-adaption-grinding process to avoid the deviation caused by second grinding particle entry. As a summary, we provides a significant cold atmospheric plasma-precision grinding compound process toward the establishment of the basic theory by analyzing the mechanism of the simulated design and computation. The process and technical difficulties of RB-SiC ceramic and mechanism of subsurface material removal during precision grinding were be solved.

Development of a high frequency ultrasonic setup for measuring the parameters of thin films

In this report a novel method for measuring the elastic properties of thin 10 nm films is described. The method is based on the use of a nanosecond laser for generation acoustic waves in solids. Absorption of the incident laser pulse energy and the associated temperature gradients induces a rapidly changing strain field. This strain field, in turn, radiates energy as elastic (ultrasonic) waves. At low pulse power, this is an entirely thermo elastic process resulting in no damage to the sample. The acoustic echo arriving at the probed surface causes both the displacement of the surface (a few nanometres) and the strain in the subsurface material, which might be detected through the variation of the optical reflectivity of the material, i.e. through the acousto-optic effect.

Global Sensitivity Analysis of Groundwater Related Dike Stability under Extreme Loading Conditions

With up to 15% of the world’s population being protected by dikes from flooding, climate-change-induced river levels may dramatically increase the flood risk of these societies. Reliable assessments of dike stability will become increasingly important, but groundwater flow through dikes is often oversimplified due to limited understanding of the important process parameters. To improve the understanding of these parameters, we performed a global sensitivity analysis on a comprehensive hydro-stability model. The sensitivity analysis encompassed fifteen parameters related to geometry, drainage conditions and material properties. The following three sensitivity settings were selected to characterize model behavior: parameter prioritization, trend identification and interaction qualification. The first two showed that dike stability is mostly dependent on the dike slope, followed by the type of subsurface material. Interaction quantification indicated a very prominent interaction between the dike and subsurface material, as it influences both groundwater conditions and dike stability directly. Despite our relatively simple model setup, a database containing the results of the extensive Monte Carlo analysis succeeded in finding most of the unsafe sections identified by the official inspection results. This supports the applicability of our results and demonstrates that both geometry and subsurface parameters affect the groundwater conditions and dike stability.

Characterization of the craters’ surface at Ryugu using NIR spectroscopy

<div> <p>Asteroid Ryugu was observed up close for almost a year and a half by the instruments on-board the Japanese Aerospace eXploration Agency (JAXA) Hayabusa2 spacecraft. It has been shown that in the near-infrared wavelength ranges, the asteroid exhibits relatively homogeneous spectral characteristics: including a very low reflectance factor, a slight red slope towards longer wavelengths, and a narrow and weak absorption feature centered at 2.72 <span>μ</span>m. Numerous craters have been identified at the surface of Ryugu. These features provide good candidates for studying more recently exposed near-surface material to further assess potential spectral/compositional heterogeneities of Ryugu. We present here the results of a spectral survey of all previously identified and referenced craters (Hirata et al. 2020) based on reflectance data acquired by the NIRS3 spectrometer. Globally, we find that the spectral properties inside and outside of craters are very similar, indicating that subsurface material is either compositionally similar to material at the surface that has a longer exposure age or that material at Ryugu’s optical surface is spectrally altered over relatively short timescales by external factors such as space weathering. The 2.72 <span>μ</span>m band depth, present on the overall surface, exhibits a slight anti-correlation with the reflectance factor selected at 2 <span>μ</span>m, which could indicate different surface properties (<em>e.g.</em>, grain size and/or porosity) or different alteration processes (<em>e.g.</em>, space weathering, shock metamorphism and/or solar heating). We identified four different spectral classes based on their reflectance factor at 2 <span>μ</span>m and 2.72 <span>μ</span>m absorption strength. The most commonly spectral behavior associated with crater floors, is defined by a slightly lower reflectance at 2 <span>μ</span>m and deeper band depth. These spectral characteristics are similar to those of subsurface material excavated by the Hayabusa2 small carry-on impactor (SCI) experiment, suggesting these spectral characteristics may represent materials with a younger surface exposure age. Conversely, these materials may have experienced significant solar heating and desiccation to form finer grains that subsequently migrated towards and preferentially accumulated in areas of low geopotential, such as craters floors. Detailed analyses of the returned samples of Ryugu that are now being investigated at the curation facility in ISAS will allow for further testing of these formation and alteration hypotheses.<span> </span></p> </div>

What were the main sources of sediment and associated radiocesium transported during the heavy 2019 typhoons in rivers draining the main Fukushima radioactive plume, Japan ?

<p>The Fukushima nuclear accident released large quantities of radionuclides into the environment in March 2011 and generated a 3000-km² plume of soils heavily contaminated with Cs-137. Soil erosion in the region mainly takes place during typhoons generally occurring between July and October (Laceby et al., 2016). During these events, rivers draining the main plume may transport large quantities of sediment and radiocesium. Typhoon Hagibis that occurred in October 2019 was the most intense rainfall event affecting the Fukushima region (rainfall range: 77–558 mm) since the nuclear accident in 2011. It led to extensive landsliding and river overflow.</p><p>The impact of this event on sediment sources and Cs-137 contamination was quantified through the implementation of sediment fingerprinting using geochemistry and spectrocolorimetry as potential input properties. The signature of potential source material (including cropland prepared for recultivation after decontamination, forests and subsurface material originating from landslides and channel bank collapse; n=57) was compared with that of sediment deposits collected in the Mano and Niida River catchments late in October 2019. Results show that cropland supplied the main source of sediment (average: 54%) along with forests (41%). In contrast, the contribution of subsurface material (5%) was much lower, likely because landslides and channel bank erosion mainly took place after the flood peak (Evrard et al., 2020). However, this material that deposited at the foot of hillslopes after the typhoon may be mobilized and delivered to the river network by subsequent rainfall events.</p><p>Overall, this flood did not modify the decreasing trend observed in terms of Cs-137 contamination in sediment transiting these rivers between 2011 and 2019. Concentrations in Cs-137 observed in sediment collected in 2019 were on average 84–93% lower than those measured after the accident in 2011. These results demonstrate the effectiveness of decontamination conducted on agricultural and residential soils in the region (Evrard et al., 2019), although the role of forests – that have not been remediated – as a perennial source of sediment and radiocesium in the region remains to be investigated over the longer term.</p><p>References</p><p>Evrard, O., Durand, R., Nakao, A., Patrick Laceby, J., Lefèvre, I., Wakiyama, Y., Hayashi, S., Asanuma-Brice, C. and Cerdan, O., 2020. Impact of the 2019 typhoons on sediment source contributions and radiocesium concentrations in rivers draining the Fukushima radioactive plume, Japan. Comptes Rendus Géoscience, 352(3): 199-211.</p><p>Evrard, O., Laceby, J.P. and Nakao, A., 2019. Effectiveness of landscape decontamination following the Fukushima nuclear accident: a review. SOIL, 5(2): 333-350.</p><p>Laceby, J.P., Chartin, C., Evrard, O., Onda, Y., Garcia-Sanchez, L. and Cerdan, O., 2016. Rainfall erosivity in catchments contaminated with fallout from the Fukushima Daiichi nuclear power plant accident. Hydrology and Earth System Sciences, 20(6): 2467-2482.</p><p> </p>

Potential of Bio-Inspiration in 3- and 4-D Printing

This chapter explores the potential of bio-inspiration in 3- and 4-D printing. The authors argue that the true potential of texturing hasn't been realized yet not because of the lack of enabling texturing technologies but because of the severe lack of detailed information about the functional details of texturing in a tribological situation, that is, how surface features, their geometry, interact with the functional gradients present within the subsurface layers to control the friction profile of a structure. The material emphasizes the potential of bio-inspired surfaces in providing a pathway for realizing true synchronization of function through a layer-by-layer customization of surface and subsurface material. In particular the chapter discusses methodologies to extract design parameters that lead to manifesting 4-D printed tribological constructs where surface and sub-surfaces respond optimally to external stimulants represented by the operation conditions of load, speed, and ambient temperature. Successful design of functional deterministic surfaces is not a product of mere biomimicry. Rather, it culminates probing the geometry, texture, form, and construction of the bio-analogue and linking these ingredients to the desired functional profile of the surface in the human engineering domain, that is, generation of bio-inspired functional surface designs stems from implementing design rules rather than replication of natural constructions. Deduction of design rules requires decoding the metrological features and the analysis of surface performance, of bio-analogues using standardized engineering methods. Success in designing a bio-inspired surface, therefore, requires a trans-disciplinary approach that combines engineering, physics, and biology. These don't combine naturally since they entail different methodologies of problem solving and investigations. It is hoped that this book would bridge the gap between the disciplines in the context of biomimetic surface design and construction. Further, it is hoped that the material would equip the reader with the basic skills needed to navigate between the biological and the engineering domains.

Quantitative Assessment of Hab Watershed Using Geoinformatics

Morphometric assessment of the watersheds is considered highly critical to appraise its hydrological characteristics, such as, general geology, structure, geomorphology and climate conditions. In this study, morphometric analysis of Hab Watershed has been carried out through Geospatial Technology (RS & GIS) in a systematic manner to examine its Geo-hydrological characteristics. The drainage network of Hab is typically dendritic and semi-dendritic indicating its heterogeneous lithology. Recent study reveals increase in stream order, substantially decreases the stream total length. drainage density of the Hab Watershed indicates the characteristics of its typical soil. Drainage texture value for Hab watershed is 0.18. Low drainage density value reveals that the region has a permeable and porous subsurface material with low relief. The shape of the basin has been observed as quite elongated. The findings of this study reveal that GIS based morphometric analysis is highly effective tool for geo-hydrological study of watersheds.