Surface Redistribution Research Articles

Numerical investigation to the effect of wear on fretting fatigue life using CDM and fracture mechanics

Fretting fatigue is a common type of problem in the engineering fields. Due to its multiaxial characteristics, it leads to a shorter overall fatigue life compared to plain fatigue. Fretting fatigue is caused by the micro slip at the contact surface, which is always accompanied by interface wear. This paper presents a refined elastic numerical simulation method combining interfacial wear with continuum damage mechanics (CDM) and fracture mechanics to predict fatigue life. The crack initiation life is determined by damage evolution law and the initiation position is determined by the total dissipated energy. Crack propagation life and path can be predicted using stress intensity factor. The stress redistribution and geometric change of contact surface caused by wear are considered in the whole fatigue process. Results indicate that the fretting fatigue simulation method incorporating wear has higher accuracy compared with the experimental results in the literature. It is noteworthy that wear retards nucleation damage process and crack propagation. As stress amplitude decreases, fatigue life increases, and delay effect of wear becomes more obvious. Additionally, wear causes the crack initiation position to move out, but crack initiation region is still near the slipping zone and propagation path does not change.

Rab1b facilitates lipid droplet growth by ER-to-lipid droplet targeting of DGAT2.

Lipid droplets (LDs) comprise a triglyceride core surrounded by a lipid monolayer enriched with proteins, many of which function in LD homeostasis. How proteins are targeted to the growing LD is still unclear. Rab1b, a GTPase regulating secretory transport, was recently associated with targeting proteins to LDs in a Drosophila RNAi screen. LD formation was prevented in human hepatoma cells overexpressing dominant-negative Rab1b. We thus hypothesized that Rab1b recruits lipid-synthesizing enzymes, facilitating LD growth. Here, FRET between diacylglycerol acyltransferase 2 (DGAT2) and Rab1b and activity mutants of the latter demonstrated that Rab1b promotes DGAT2 ER to the LD surface redistribution. Last, alterations in LD metabolism and DGAT2 redistribution, consistent with Rab1b activity, were caused by mutations in the Rab1b-GTPase activating protein TBC1D20 in Warburg Micro syndrome (WARBM) model mice fibroblasts. These data contribute to our understanding of the mechanism of Rab1b in LD homeostasis and WARBM, a devastating autosomal-recessive disorder caused by mutations in TBC1D20.

Современные экологические проблемы эксплуатации коллекторно-дренажной сети и пути их решения

Purpose: to determine the environmental issues that arose during the operation of irrigation and drainage systems, and the basic principles of managing the quality of drainage water from irrigated lands. Discussion. Analytical data on the condition of reclaimed lands, changes in groundwater levels during the operation of irrigation systems, the use of water resources, the results of theoretical and experimental studies of the collector-drainage flow quality in the irrigation system diversion collectors in the south of Russia are considered. The main problems are identified: land resources degradation, rising groundwater levels, resalinization and salt accumulation during irrigation, especially with irrigation water with increased mineralization, changes in the hydrological and hydrochemical regime of water bodies – collector-drainage runoff intakes. Legal problems associated with the classification of irrigation and drainage systems as objects of category III are highlighted. Ways to solve environmental problems, methods for managing the quality of drainage runoff, including the creation of local treatment facilities based on routing the collector-drainage network to irrigated areas suspended from the drainage system, in the range of 10–200 ha with construction of storage drainage sumps as places for metering flow and regulating the chemical composition of drainage flow. Conclusions. Pollution problems are regional in nature and are determined not only by economic activities, but also by natural factors. The set of irrigation canals, collector-drainage networks and water intakes of drainage-discharge waters participates in the inter-basin redistribution of surface and underground runoff. In the process of managing the quality of drainage water from irrigated lands and the environmentally safe operation of hydro-reclamation systems, three parties must certainly participate: reclamation departments, agricultural producers and government agencies.

Soil water infiltration characteristics of reforested areas in the paleo-periglacial eastern Liaoning mountainous regions, China

Plantation forests (PF) and natural secondary forests (NSF) are the primary reforestation approaches. The establishment of PF can affect forest hydrological processes by changing soil structure. To date, few studies have focused on these changes and the effects on hydrological processes for the paleo-periglacial landform. To reveal reforestation approaches effects on water infiltration, including soil water infiltration capacity, retention capacity, and waterflow path pattern, we conducted field dye-tracer investigations with rainfall and laboratory infiltration experiments for the paleo-periglacial landform of eastern Liaoning mountains, China. The results showed that (1) Soil physical properties (including total porosity (TP), capillary porosity (CP), non-capillary porosity (NCP), initial soil water content (IWC), field water capacity (FWC)) and root abundance (RA) decreased with soil depth in both PF and NSF, while the soil bulk density (BD) and distribution of gravel content showed opposite changes. (2) Establishment of PF reduced the infiltration capacity and water retention capacity in the 0–20 cm layer, but enhanced the water retention capacity in 20–30 cm layer. Low IWC was conducive to increase soil water content (SWC) after infiltration. (3) Infiltration capacity parameters (including saturated hydraulic conductivity (Ks), SWC, difference between SWC and IWC (SWC–IWC), dye coverage ratio (DC)) were significantly correlated with BD, TP, CP, NCP, FWC, and fine roots RA (P < 0.05). Better connectivity gravels were more conducive to water infiltration. (4) Preferential flow was the main infiltration type, but with different waterflow paths pattern, with the 'funnel', 'finger' shape for PF, NSF, respectively. Increasing infiltration could increase flow path connectivity. Our findings show that soil physical properties, roots, and gravel occurrence affected soil infiltration, and different reforestation approaches had varying impacts on soil infiltration, water redistribution, transportation, and storage of surface and groundwater, improving the understanding of ecohydrological processes and effects of water resources management in forest ecosystems of paleo-periglacial landform.

Cyclic Voltammetry as an Activation Method of TiO2 Nanotube Arrays for Improvement of Photoelectrochemical Water Splitting Performance

AbstractA facile and eco‐friendly method for activating anodic TiO2 nanotubes (TNTs) by cyclic voltammetry (CV) is proposed, and photoelectrochemical properties of CV‐activated TNTs are compared with those of non‐activated TNTs and of TNTs activated by hydrogen‐thermal reduction. EPR and luminescence studies show that the pristine samples demonstrate rather large content of paramagnetic and luminescing defects, while hydrogenation and CV‐activation lead to the different type of rearrangement of defects. TNTs activated by CV‐Na2SO4 demonstrate significantly improved photocurrent density (2.25 mA cm−2) in comparison with that of the hydrogen treated and pristine ones (0.93 mA cm−2 and 0.31 mA cm−2) under NUV‐irradiation at 0.2 V (RHE). Enhanced photoactivity of Na2SO4‐activated TNTs correlates with higher luminescence quantum yield, lowest paramagnetic defects content and larger decay time of the luminescence. Thus, a decrease in the content of defects is an important factor that reduces the non‐radiative recombination of charge carriers. The activation‐induced redistribution of surface and bulk defects in nanotubes explains the increased photoelectrochemical activity of TiO2‐based anodes. Cyclic voltammetry has been proved to be a reliable method to increase the efficiency of TNTs in PEC water splitting.

Gravity field changes reveal deep mass transfer before and after the 2013 Lushan earthquake

The 2013 MS7.0 Lushan earthquake, Sichuan, China, occurred on a blind thrust fault in the southern Longmenshan fault belt. The terrestrial hybrid repeated gravity observation enables us to investigate the redistribution of both surface and deep mass. Here, we find a transient increase in the gravity field about 2 years before the earthquake and a drop after the mainshock. A Bayesian inversion method with spatiotemporal smoothness is employed to extract the apparent density changes. The increase of apparent density on the south of the focal zone is assumed to be related to crustal mass transfer. We introduce a disc-shaped equivalent source model with a homogeneous density to address this hypothesis, and estimate the model parameters by Markov Chain Monte Carlo simulations. As a fluid diffusion footprint is indicated by the seismicity migration in this region, with a fitted diffusion rate of 10 m2 s−1, we conclude that such deep crustal mass transfer may be caused by fluid diffusion.

The Effect of Custom Insoles on Muscle Activity in Diabetic Individuals with Neuropathy

Foot ulcers are amongst the most serious complications of diabetes. Guidelines recommend that people with diabetes wear appropriate footwear or insoles to reduce repetitive stresses. Excessive plantar pressure has been recognized as the major risk factor for plantar ulcers in diabetic individuals; custom insoles are indicated as the gold standard treatment to unload the foot structure. The aim of this study was to investigate the effect of custom insoles on biomechanical and neuromuscular functions in diabetic neuropathic individuals. Ten diabetic subjects walked with and without custom insoles at their preferred speed; ten controls were assessed for comparison. Data were captured through seven video cameras, plantar pressure insoles, and surface electromyography. The electrical activity of Rectus Femoris, Tibialis Anterior, Medius Gluteus and Gastrocnemius Lateralis were acquired bilaterally. The plantar pressure and surface electromyographic variables were determined, while videos were used to detect the gait cycle. The following comparisons were made across the variables through the non-parametric SPM1D test (p &lt; 0.05): condition with vs. without insoles vs. controls. Custom insoles provided a reduction in plantar pressure through contact surface redistribution in association with a reduced electromyographic activity. Our results suggest optimizing the prevention approach by including personalized foot and ankle exercises.

ПРОБЛЕМЫ ИСПОЛЬЗОВАНИЯ ВОДНЫХ РЕСУРСОВ НИЖНЕГОРСКОГО РАЙОНА РЕСПУБЛИКИ КРЫМ

The uneven distribution of water resources in most of the Crimean Peninsula leads to the redistribution of surface and underground runoff between regions. The available volumes of water resources in the Nizhnegorsk District have been redistributed due to the construction of extended water supply routes and groundwater intakes. An assessment of the rationality of using artesian waters from wells in the Nizhnegorsk region of the Crimean peninsula is carried out.

Impacts of Landscape Evolution on Heterotrophic Carbon Loss in Intensively Managed Landscapes

Soil respiration that releases CO2 into the atmosphere roughly balances the net primary productivity and varies widely in space and time. However, predicting its spatial variability, particularly in intensively managed landscapes, is challenging due to a lack of understanding of the roles of soil organic carbon (SOC) redistribution resulting from accelerated soil erosion. Here we simulate the heterotrophic carbon loss (HCL)—defined as microbial decomposition of SOC—with soil transport, SOC surface redistribution, and biogeochemical transformation in an agricultural field. The results show that accelerated soil erosion extends the spatial variation of the HCL, and the mechanical-mixing due to tillage further accentuates the contrast. The peak values of HCL occur in areas where soil transport rates are relatively small. Moreover, HCL has a strong correlation with the SOC redistribution rate rather than the soil transport rate. This work characterizes the roles of soil and SOC transport in restructuring the spatial variability of HCL at high spatio-temporal resolution.

Extrusion of a nanosecond surface discharge plasma near a dielectric ledge

The presence of a dielectric ledge along the pulse discharge propagation led to a redistribution of the pulsed surface (plasma sheets) discharge glow. Discharge glow on the surface without the ledge, was uniform and lasted no more than 200 ns. Two plasma channels with increased glow intensity were observed near the rectangular ledge placed in the discharge area. The duration of these longitudinal plasma channels increased and lasted for about 0.9 μs (at a voltage of 25 kV and a density of 0.03 – 0.18 kg/m3 ). A nine-frame nanosecond camera recorded the evolution of the plasma glow. The dynamics of the flow induced by the pulse surface discharge was recorded using a high-speed shadow imaging during 40-50 μs after the ignition of the discharge.

Effects of hillslope position on soil water infiltration and preferential flow in tropical forest in southwest China

The hillslope is an essential natural spatial gradient that influences hydrological processes by affecting water distribution, surface flow, soil erosion, and groundwater recharge. To date, few studies have addressed only the hydrological processes of tropical forest hillslopes. To reveal the effect of hillslope on soil hydrological functioning—including water distribution and exchange, infiltration capacity, and flow behaviour—we conducted 36 field infiltration and nine dye-tracer investigations of different hillslope locations in the natural rainforest of Xishuangbanna, southwest China. The soil physical properties—including soil noncapillary and total porosity, saturated water capacity, and field water capacity—decreased with decreasing elevation from hilltop to middle slope and the valley bottom. The water infiltration capacity—including the initial infiltration rate, saturated soil hydraulic conductivity, and average infiltration rate—decreased from the hilltop to the valley bottom. Preferential flow dominated soil water movement more in the upper locations than in the valley bottom. The infiltration capacity parameters and preferential flow were significantly correlated with soil water content, noncapillary and total porosity, root biomass, and termite holes. These results indicated that along with the soil physical properties, root systems, animal activity, cracks, and stones affected the soil infiltration capacity and preferential flow. Differences in the hydraulic processes of each hillslope position contributed to the redistribution, transportation, and storage of surface and belowground water, resulting in differing availabilities of soil water resources and utilisation by plants. The findings of this study can help understand eco-hydrological processes in the context of water resources management in tropical mountain ecosystems.

Oedometric compression of a granular material: computation of energies involved during breakage with a discrete element modelling

A numerical model able to simulate the grain breakage with the discrete element method, using the “Non-Smooth Contact Dynamics” is presented. The model reproduces 3D grains having complex shapes and is tested in single grain and in oedometric compressions. Numerical simulations are then carried out to evaluate the different energies active during breakage (surface creation and redistribution energies). The surface creation energy is estimated. Results are closed to the ones found in the literature.

An Evaluation Study of the Fully Coupled WRF/WRF-Hydro Modeling System for Simulation of Storm Events with Different Rainfall Evenness in Space and Time

With the aim of improving the understanding of water exchanges in medium-scale catchments of northern China, the spatiotemporal characteristics of rainfall and several key water cycle elements e.g., soil moisture, evapotranspiration and generated runoff, were investigated using a fully coupled atmospheric-hydrologic modeling system by integrating the Weather Research and Forecasting model (WRF) and its terrestrial hydrologic component WRF-Hydro (referred to as the fully coupled WRF/WRF-Hydro). The stand-alone WRF model (referred to as WRF-only) is also used as a comparison with the fully coupled system, which was expected to produce more realistic simulations, especially rainfall, by allowing the redistribution of surface and subsurface water across the land surface. Six storm events were sorted by different spatial and temporal distribution types, and categorical and continuous indices were used to distinguish the applicability in space and time between WRF-only and the fully coupled WRF/WRF-Hydro. The temporal indices showed that the coupled WRF-Hydro could improve the time homogeneous precipitation, but for the time inhomogeneous precipitation, it might produce a larger false alarm than WRF-only, especially for the flash storm that occurred in July, 2012. The spatial indices showed a lower mean bias error in the coupled system, and presented an enhanced simulation of both space homogeneous and inhomogeneous storm events than WRF-only. In comparison with WRF-only, the fully coupled WRF/WRF-Hydro had a closer to the observations particularly in and around the storm centers. The redistributions fluctuation of spatial precipitation in the fully coupled system was highly correlated with soil moisture, and a low initial soil moisture could lead to a large spatial fluctuated range. Generally, the fully coupled system produced slightly less runoff than WRF-only, but more frequent infiltration and larger soil moisture. While terrestrial hydrologic elements differed with relatively small amounts in the average of the two catchments between WRF-only and the fully coupled WRF/WRF-Hydro, the spatial distribution of elements in the water cycle before and after coupling with WRF-Hydro was not consistent. The soil moisture, runoff and precipitation in the fully coupled system had a similar spatial trend, but evapotranspiration did not always display the same.

INCREASING WATER AVAILABILITY IN THE NORTH-EASTERN CRIMEA

The formation of water-deficit conditions in most of the territory of the Crimean Peninsula causes the redistribution of surface and underground runoff between regions. Available volumes of water resources in various regions of the Crimea are distributed unevenly, which requires the construction of long water supply routes. To improve water supply, a water supply System has been developed for the Eastern Crimea with artesian water from wells in the South-Eastern part of the Crimean Peninsula.

Using the method of relief plasters to highlight potentially erosion-hazardous areas on agricultural land

With the strong development of soil erosion, land fertility decreases, crops are damaged, ravines turn agricultural land into uncomfortable land and make field cultivation difficult, siltation of rivers and reservoirs occurs. In this regard, issues of land protection from erosion are relevant. The article discusses the issues of identifying potentially erosion-hazardous lands using the method of relief plasters, previously used in landscape science. This method allows to facilitate the identification of destructive processes at an early stage of development and to prevent them in advance. The location of the zones identified by this method (morphoisographs), and their dynamics, characterizes the changes associated with ecological-landscape measures, for example, planting of forest belts, afforestation of ravines and, accordingly, redistribution of surface and underground waters. A morphoisograph, as the line most sensitive to negative phenomena (changes in the chemical, biological, and mechanical composition of soils, soil erosion, etc.) can become the main criterion for identifying potentially unstable zones. The authors highlighted agricultural land that is potentially unstable to erosion. The introduction of a morphoisograph into ecological landscape design expands the possibilities of detailed accounting for the development of erosion processes in the future.

Can intercrops improve soil water infiltrability and preferential flow in rubber-based agroforestry system?

Land-use change due to the widespread practice of rubber-based agroforestry influences ecosystem services. However, little is known about their soil hydrological functioning associated with infiltration and water flow behaviour which affects surface runoff, soil erosion, and groundwater recharge. In order to clarify whether the intercrop can promote soil water infiltrability and water movement in rubber-based agroforestry system, 66 field infiltration and 2 dye tracer experiments were performed in this study on undisturbed soil in a rubber-tea agroforestry system in Xishuangbanna, SW China. The results showed that the field saturated soil hydraulic conductivity (Ks) exhibited a high spatial heterogeneity. The Ks, initial infiltration rate (IIR), and actual steady-state infiltration rate (Is) were significantly higher in the tea tree planting zone (TT) than in the rubber tree planting zone (RT). The Ks decreased with distance from the trunks of tea trees, and the Ks between rubber trees in a row was lower than that between rubber rows. Along with improved soil physical properties, increased root and faunal activities, and more inhomogeneous cracks and stones, there was higher soil water infiltrability and more preferential flow in the TT than in the RT. Therefore, tea shrubs in rubber agroforestry systems may function as water harvesters, contributing to deeper drainage and recharge. In contrast, the rubber trees function as water consumers, causing soil desiccation and water scarcity. Differences in the soil hydraulic properties among different zones in a rubber-tea agroforestry system can lead to the spatial redistribution of surface and belowground water, increasing water availability for various plants with different root systems. Better infiltration and increased preferential flow beneath tea trees potentially reduce runoff generation and erosion risk, promote groundwater recharge, and increase water storage that may counteract the interception and transpiration losses from intercrops and rubber trees, thereby contributing to the management of water resources.

Leaded Bronze Alloy as a Catalyst for the Electroreduction of CO2

AbstractThe performance of a leaded bronze alloy with CuSn7Pb15 (wt %) chemical composition is studied as a cathode material for CO2 electroreduction (CO2RR) in aqueous 0.5 M KHCO3 electrolyte. It was found that the catalytic characteristics of the proposed CO2RR electrocatalyst are dominated by elemental lead. Surface characterization by means of digital 3D optical microscopy, white light interferometry, scanning electron microscopy (SEM), energy dispersive X‐ray spectroscopy (EDX) and scanning auger microscopy (SAM) revealed that segregated Pb clusters embedded in a Cu‐rich Cu/Sn matrix are, to a large extent, dispersed on the cathode surface upon sample preparation through mechanical polishing. Identical location SEM‐EDX studies before and after CO2 electrolysis revealed that further Pb surface redistribution takes place under operando CO2RR conditions, provided sufficiently high potentials are applied. The as‐prepared electrocatalyst proved to be a suitable and powerful alternative for the selective and efficient production of formate (maximum achieved faradaic efficiency and partial current density for formate are 58.6 % and −11.08 mA cm−2 at −1.07 V and −1.17 V vs. RHE, respectively). Moreover, in comparison to neat lead, this material can be handled with less precaution.

Electromigration of Cell Surface Macromolecules during Galvanotaxis

Weak, DC electric fields (EFs) direct cellular polarity, migration and outgrowth. They are used to induce polarity during tissue engineering and direct migration to promote epidermal wound repair. Fields as weak as 10 mV/mm, are sufficient to direct migration, although the mechanisms used by cells to sense such weak fields are still debated as weaknesses exist in the competing models. We hypothesize that cellular polarization is achieved by the redistribution of a cell surface, electric field receptor (EFR) in the presence of an applied EF. We are investigating the electromigration model that depends on electrically generated forces in the plane of the plasma membrane and parallel to the electric field vector, specifically, electrophoretic and electro-osmotic forces. Electrophoretic force drives net negatively charged macromolecules to the anode while electro-osmotic flow of water, in the boundary layer, drives macromolecules with large extracellular domains to the cathode. We have derived a model based on these opposing forces, to predict the relative concentration of surface proteins over space and time, allowing us to test the redistribution of known plasma membrane surface macromolecules in applied EFs and under controlled conditions. The model closely describes accumulation of a net negatively charged, GPI-anchored, fluorescent protein to the cathode under different field strengths, showing that redistribution reaches steady-state within minutes, significantly faster than cathodally migrating cells turn toward the cathode. The model is useful for determining the most likely candidates for the EFR on many different cell types.

Synthesis of bimetallic AuPt/CeO2 catalysts and their comparative study in CO oxidation under different reaction conditions

In the present work, ceria-supported Au–Pt catalyst with metal ratio 3:2 was prepared using a “single-source precursor” concept. The double complex salt [AuEn2]2[Pt(NO2)4]3·6H2O was used as such precursor. CeO2 of unique morphology with developed surface area (120 m2/g) obtained by urea precipitation technique was used as a support. According to XRD data, size of the alloyed Au–Pt particles was estimated to be less than 3 nm. It was shown that bimetallic Au–Pt system intensifies release of oxygen from the CeO2 lattice. The 0.5%Au2Pt3/CeO2 catalyst was comparatively studied in low temperature CO oxidation (simplified model reaction mixture) and under prompt thermal aging conditions (complex reaction mixture) with regard to monometallic reference samples 0.2%Au/CeO2 and 0.3%Pt/CeO2. The catalytic performance of the samples was found to be significantly dependent on the reaction and pre-treatment conditions. In the case of the bimetallic catalyst, reversible redistribution and enrichment of the nanoparticle surface with Pt or Au were shown to be the key factor defining the activity.

Origin of spatial variation in US East Coast sea-level trends during 1900-2017.

Identifying the causes of historical trends in relative sea level-the height of the sea surface relative to Earth's crust-is a prerequisite for predicting future changes. Rates of change along the eastern coast of the USA (the US East Coast) during the past century were spatially variable, and relative sea level rose faster along the Mid-Atlantic Bight than along the South Atlantic Bight and the Gulf of Maine. Past studies suggest that Earth's ongoing response to the last deglaciation1-5, surface redistribution of ice and water5-9 and changes in ocean circulation9-13 contributed considerably to this large-scale spatial pattern. Here we analyse instrumental data14,15 and proxy reconstructions4,12 using probabilistic methods16-18 to show that vertical motions of Earth's crust exerted the dominant control on regional spatial differences in relative sea-level trends along the US East Coast during 1900-2017, explaining most of the large-scale spatial variance. Rates of coastal subsidence caused by ongoing relaxation of the peripheral forebulge associated with the last deglaciation are strongest near North Carolina, Maryland and Virginia. Such structure indicates that Earth's elastic lithosphere is thicker than has been assumed in other models19-22. We also find a substantial coastal gradient in relative sea-level trends over this period that is unrelated to deglaciation and suggests contributions from twentieth-century redistribution of ice and water. Our results indicate that the majority of large-scale spatial variation in long-term rates of relative sea-level rise on the US East Coast is due to geological processes that will persist at similar rates for centuries.