Depth Of Surface Layer Research Articles

Zooplankton seasonal vertical migration in an optimality-based plankton ecosystem model

Abstract Several species from various zooplankton taxa perform seasonal vertical migrations (SVM) of typically several hundred meters between the surface layer and overwintering depths, particularly in high-latitude regions. We use OPtimality-based PLAnkton (OPPLA) ecosystem model) to simulate SVM behavior in zooplankton in the Labrador Sea. Zooplankton in OPPLA is a generic functional group without life cycle, which facilitates analyzing SVM evolutionary stability and interactions between SVM and the plankton ecosystem. A sensitivity analysis of SVM-related parameters reveals that SVM can amplify the seasonal variations of phytoplankton and zooplankton and enhance the reduction of summer surface nutrient concentrations. SVM is often explained as a strategy to reduce exposure to visual predators during winter. We find that species doing SVM can persist and even dominate the summer-time zooplankton community, even in the presence of Stayers, which have the same traits as the migrators, but do not perform SVM. The advantage of SVM depends strongly on the timing of the seasonal migrations, particularly the day of ascent. The presence of higher (visual) predators tends to suppress the Stayers in our simulations, whereas the SVM strategy can persist in the presence of non-migrating species even without higher predators.

Study of the distribution of residual stresses across the surface layer depth following machining through probing hole drilling and digital image correlation

The article aims to study the distribution of residual stresses across the surface layer depth following the machining of test specimens (free orthogonal cutting and burnishing). The machining by cutting and burnishing of 45 steel specimens was carried out using a milling machine with numerical control under varying machining factors. For a comparative analysis, the processes were also modeled via the finite element method using identical experimental values of geometric parameters and machining modes. In order to obtain residual stress distributions across the surface layer depth, probe holes having depths of 0.5; 0.75; 1; 1.5; and 2 mm were drilled. By differentiating the displacement of specimen surface particles, measured using digital image correlation, radial strains around the probe holes were determined. Then, these values were used to determine the residual stress components for each probe hole, and the averaged values of each residual stress component were calculated using the calculation algorithm presented in this article. After burnishing the specimen with a force of 3400 N, the test value of the σx component within the depth range (from the surface) of 0.5–0.75 mm amounted to -250 MPa. Model and experimental distributions of residual stress tensor components across the surface layer depth were obtained following machining via two methods. The experimental values of residual stresses were found to have good convergence with each other and with model distributions at depths up to 1 mm from the machined surface at a drill diameter of 1.7 mm. The proposed approach provides a means to obtain the residual stress distribution across the surface layer depth by drilling probe holes of different depths and estimating radial strains on the specimen surface using the digital image correlation method.

A comparative study on the depth of cure, hardness and microleakage applied to primary teeth of different types of bulk-fill resins

Objective: To compare the depth of cure, surface hardness and microleakage applied to primary teeth of three types of bulk-fill resins, so as to provide reference for clinical application. Methods: Composite resin FiltekTM Z350 XT (group A) and giomer Beautifil Ⅱ (group B) were used as controls, high-viscosity bulk-fill resin FiltekTM Bulk Fill (group C), sonic-activated bulk-fill resin SonicFill 2 (group D) and flowable bulk-fill resin SDR® flow+(group E) were studied. The microstructure of each group was observed by scanning electron microscope (SEM). Specimens of each group were prepared (6 pieces per group), and the Vickers microhardness of the surface layer and different depths of each group were measured, and then the depths of cure were calculated. Twenty-five primary molars dentin were filled by resins of each group (5 teeth per group), sliced, then aged, slices of each group were developed by silver ion staining. SEM was used to observed the distribution of silver ions. Microleakage of each group were analyzed by Jonckheere-Terpstra rank sum test. Results: SEM showed that the filler particles in groups A and C were spherical and evenly distributed. The shape of the fillers in groups B, D and E were polygonal and unevenly distributed. The surface hardness of groups A, B, C, D and E were (84.97±6.30), (65.04±5.95), (57.80±1.18), (60.77±2.34), (33.32±1.83) MPa respectively. Group A had the highest hardness, while group E was the lowest, and the differences between the two groups and other groups was statistically significant (P<0.05). There were no statistically significant differences among groups B, C, and D (P>0.05). The curing depths of groups A, B, C, D and E were 2.6, 3.4, 5.8, 3.8 and 7.8 mm respectively. The largest microleakage was found in group E [2% (1/50) for grade 0, 22% (11/50) for grade 1, 30% (15/50) for grade 2, 24% (12/50) for grade 3, and 22% (11/50)for grade 4], which was statistically different from other groups (P<0.05). No statistically significant differences were found among other 3 groups (P>0.05). Conclusions: Both high-viscosity and sonic-activated bulk-fill resins have the greater depth of cure, the same hardness and microleakage as giomer, which might be an option for restoration in primary teeth.

An observing system experiment framework for the tropical Indian Ocean salinity: A case study using a constellation of three satellites

In this study impact of assimilating Sea Surface Salinity (SSS) from multi-satellites (SMOS, Aquarius and SMAP) on numerical ocean model simulations in the north Indian Ocean has been analysed under the observing system experiment (OSE) framework. Daily data sets of Aquarius, SMAP and SMOS, which were available for a common period of April–May 2015, are used to constrain the ocean model using ensemble optimal interpolation technique. Apart from the control simulation in which satellite data were not assimilated, a total of seven assimilation experiments using different combinations of satellite SSS were conducted. The impact of assimilation experiments is analysed by comparing the model-simulated variables with in situ observations. Assimilating satellite SSS results in a reduction in Root Mean Square Error (RMSE) in SSS (∼ 54%) and also in subsurface salinity (∼ 21%) over the control run. The impact of assimilating SMAP observations is maximum on model simulations with the errors reducing by ∼ 54%. Subsurface salinity improvement is better with three satellites with ∼31% improvement in RMSE in the halocline region, which was ∼11% more than single satellite assimilation. Assimilation of SSS also resulted in improved simulations of the model surface, subsurface temperature and mixed layer depth. Model results show the ability of SSS observations to complement other ocean observation networks. One important observation from this study is that while the impact of assimilating SSS observations from a single satellite was on par with the impact of assimilating SSS observations from two or three satellites in correcting simulated surface salinity, assimilation from more than one satellite had a larger impact in the salinity of deeper layers of the ocean.

Exploring the Benefits of Ablation Grid Adaptation in 2D/3D Laser Ablation Inductively Coupled Plasma Mass Spectrometry Mapping through Geometrical Modeling.

This study aims to investigate the potential benefits of adapting the ablating grid in two-dimensional (2D) and three-dimensional (3D) laser ablation inductively coupled plasma mass spectrometry in a single pulse mapping mode. The goals include enhancing the accuracy of surface sampling of element distributions, improving the control of depth-related sampling, smoothing the post-ablation surface for layer-by-layer sampling, and increasing the image quality. To emulate the capabilities of currently unavailable laser ablation stages, a computational approach using geometrical modeling was employed to compound square or round experimentally obtained 3D crater profiles on variable orthogonal or hexagonal ablation grids. These grids were optimized by minimizing surface roughness as a function of average ablation depth, followed by simulating the post-ablation surface and related image quality. An online application (https://laicpms-apps.ki.si/webapps/home/) is available for users to virtually experiment with contracting/expanding orthogonal and hexagonal ablation grids for generic 3D super-Gaussian laser crater profiles, allowing for exploration of the resulting post-ablation surface layer roughness and depth.

An investigation of seafloor and oceanographic characteristics in deep-water of north Labuan Bajo, Indonesia

On 12 December 1992, an earthquake, followed by a tsunami, occurred on Flores Islands, creating massive damage in the northern area and resulting in an early warning tsunami for the Labuan Bajo region. This area is a high-priority tourist designation in Indonesia with busy offshore activities and infrastructure development. Thus, earthquake and tsunami mitigation strategies are mandatory. Part of the mitigation effort is mapping the seafloor and characterizing oceanographic conditions in the deep-water north of this area. This paper describes the seafloor and oceanographic conditions using a multibeam echosounder (MBES) survey, conductivity-temperature-depth (CTD) measurement, and current observation. Results show that the rough and complex seafloor topography is revealed in the study area. Seafloor topography consists of a steep slope on the nearshore, flat topography in the sublittoral and shelf, a steeper slope in the bathyal zone, and relatively flat in the abyssal zone found from the south to north in the area. In addition, physical oceanographic properties are observed in two locations with a maximum depth measurement of 3,029 m. The result indicates that the water column is divided into three layers based on gradient changes: surface layer, thermocline layer, and colder depth layer. Moreover, two single-point current measurements at the exact locations are carried out at water depths of 3,029 m and 1,880 m. Result also describes that both stations have current directions of 128.14° and 124.49°, with current magnitudes of 0.1693 m/s and 0.3724 m/s, respectively. This investigation could serve as primary data and information in the study area. Furthermore, it could support the government and other stakeholders related to the development of Labuan Bajo, e.g., infrastructure (submarine cable, port, etc.) and resilience program (e.g., tsunami early warning system) that region

Performance evaluation of full-scale accelerated pavement using NDT and laboratory tests: A case study in Jiangsu, China

Maintenance of typical pavement structures is critical in Jiangsu, China. Therefore, a method combining accelerated testing, non-destructive testing, and laboratory tests was proposed in this study to achieve the performance evaluation and conservation measures analysis. After loading one million times on a full-scale road section of asphalt pavement with semi-rigid bases using a large mobile load simulator (MLS66), the material and structural properties were tested. Results showed that the rutting depth of asphalt surface layer reached 8.9 mm, indicating that the material had passed the compaction stage and entered the rheological stage (high-temperature rutting resistance declined). The compressive strength of the upper and lower base layers decreased by 24.2% and increased by 31.7%, respectively. Regarding pavement deflection, the asphalt layer showed a slight decrease in bearing capacity, but the base had virtually no change. Deflection decreased by 19.4% after adding an asphalt layer, indicating a significant increase in bearing capacity. Neither the asphalt surface nor the base layer showed abnormal signals in ground penetrating radar (GPR) images after loading, except where the sensor was buried. This study provides a timely and necessary study of the asphalt pavement maintenance in Jiangsu province and also could guide pavement maintenance in other regions of the world.

3D characterization of a nanostructured Al-Cu-Mg alloy

Three-dimensional (3D) characterization of variations in crystallography and chemistry of nanostructured metals will provide vital information to understand their mechanical and thermal behaviours. This study applied a surface sliding friction treatment (SSFT) at liquid nitrogen temperature to produce nanostructured surface layers in a peak-aged Al-Cu-Mg alloy. The nanostructured surface was characterized by means of 3D orientation mapping in the transmission electron microscope (3D-OMiTEM) and atom probe tomography (APT). 3D-OMiTEM results revealed a lamellar structure with an average lamellar boundary spacing of 26 nm at the topmost surface layer (depth < 20 μm), which is much finer than normally achievable in commercial purity Al deformed to high strain levels. Based on the 3D-OMiTEM data, a five-parameter grain boundary character analysis was carried out. It was found that low angle grain boundaries dominate the nanoscale structure and that the grain boundary plane distribution of high angle lamellar grain boundaries shows a preference around {101}. APT analysis showed segregation of Cu and Mg atoms at lamellar boundaries, which is believed to play a role in stabilizing the boundaries and enhancing the structural refinement during SSFT.

Global-Scale Environmental Niche and Habitat of Blue Shark (Prionace glauca) by Size and Sex: A Pivotal Step to Improving Stock Management

Blue shark (Prionace glauca) is amongst the most abundant shark species in international trade, however this highly migratory species has little effective management and the need for spatio-temporal strategies increases, possibly involving the most vulnerable stage or sex classes. We combined 265,595 blue shark observations (capture or satellite tag) with environmental data to present the first global-scale analysis of species’ habitat preferences for five size and sex classes (small juveniles, large juvenile males and females, adult males and females). We leveraged the understanding of blue shark biotic environmental associations to develop two indicators of foraging location: productivity fronts in mesotrophic areas and mesopelagic micronekton in oligotrophic environments. Temperature (at surface and mixed layer depth plus 100 m) and sea surface height anomaly were used to exclude unsuitable abiotic environments. To capture the horizontal and vertical extent of thermal habitat for the blue shark, we defined the temperature niche relative to both sea surface temperature (SST) and the temperature 100 m below the mixed layer depth (Tmld+100). We show that the lifetime foraging niche incorporates highly diverse biotic and abiotic conditions: the blue shark tends to shift from mesotrophic and temperate surface waters during juvenile stages to more oligotrophic and warm surface waters for adults. However, low productivity limits all classes of blue shark habitat in the tropical western North Atlantic, and both low productivity and warm temperatures limit habitat in most of the equatorial Indian Ocean (except for the adult males) and tropical eastern Pacific. Large females tend to have greater habitat overlap with small juveniles than large males, more defined by temperature than productivity preferences. In particular, large juvenile females tend to extend their range into higher latitudes than large males, likely due to greater tolerance to relatively cold waters. Large juvenile and adult females also seem to avoid areas with intermediate SST (~21.7-24.0°C), resulting in separation from large males mostly in the tropical and temperate latitudes in the cold and warm seasons, respectively. The habitat requirements of sensitive size- and sex-specific stages to blue shark population dynamics are essential in management to improve conservation of this near-threatened species.

Air2water model with nine parameters for lake surface temperature assessment

The air2water model is a physically-based model in which major physical processes are parameterized. It allows to predict the surface lake temperature based solely on the time series of the air temperature. Due to its simplicity and very limited data requirements, it has found numerous applications around the globe. The air2water model defines the normalized depth of the well-mixed surface layer using a fixed parameter. This parameter is a threshold value that is set to 4 °C – the temperature of water with maximum density – for dimictic lakes, and to the minimum or to the maximum water temperature for warm or cold monomictic lakes, respectively. In this paper we propose to calibrate the threshold value as the ninth parameter of the model, instead of setting it fixed. We test the proposed approach on a set of 30-years long daily data from 22 lakes located in the lowland part of Poland and 25-years long daily data from the two Great Lakes – Huron and Eire. The proposed modification is very simple and improves the performance of the model, especially for winter-spring season, for the vast majority of lakes not only for the calibration, but also for the independent 8–10 years long validation data.

The Theoretical Approach to the Modelling of Gully Erosion in Cohesive Soil

The stochastic gully erosion model (STOGEM) is based on a combination of deterministic mechanics and a stochastic description of the erosion control factors. The main proposition in the model is that the depth of the active surface layer of eroded cohesive soil is equal to one particle diameter, and the deposition of eroded particles is negligible. The erosion rate at the gully bed is calculated directly from the equation of the balance between driving and resistance forces acting on soil particles in flowing water using the probability density functions of stochastic variables: flow velocity, soil aggregate size and cohesion. Probability density functions of cohesion in the model vary through time and space during the erosion event due to the changes in soil composition—armoring and loosening. This theory is still far from achieving practical application, but opens up a new way for better understanding the experimental results of gully erosion and shows the direction for future investigations.

Investigating Neutral and Stable Atmospheric Surface Layers Using Computational Fluid Dynamics

Computational fluid dynamics (CFD) is an effective technique for investigating atmospheric processes at a local scale. For example, in near-source atmospheric dispersion applications, the effects of meteorology, air-pollutant sources, and buildings can be included. A prerequisite is to establish realistic atmospheric conditions throughout the computational domain. This work investigates the modeling of the atmospheric surface layer under neutral and stable boundary-layer conditions, respectively. Steady-state numerical solutions of the Reynolds averaged Navier–Stokes equations were used, including the k-ε turbulence model. Atmospheric profiles derived from the Cooperative Atmosphere–Surface Exchange Study-99 (Kansas, USA) were used as reference data. The results indicate that the observed profiles of velocity and potential temperature can be reproduced with CFD, while turbulent kinetic energy showed less agreement with the observations. For the stable boundary layer, reasonable agreement of the numerical results with the observations was also obtained for surface layer depth, shear stress, and heat-flux profiles, respectively. The results are discussed in relation to the boundary conditions and sources, and the observation data.

The influence of intergranular and interphase boundaries and δ-ferrite volume fraction on hydrogen embrittlement of high-nitrogen steel

We study the effect of grain size of austenitic and ferritic phases and volume fraction of δ-ferrite, which were obtained in different solution-treatment regimes (at 1050, 1100, 1150 and 1200 °C), on hydrogen embrittlement of high-nitrogen steel (HNS). The amount of dissolved hydrogen is similar for the specimens with different densities of interphase (γ-austenite/δ-ferrite) and intergranular (γ-austenite/γ-austenite, δ-ferrite/δ-ferrite) boundaries. Despite, the susceptibility of the specimens to hydrogen embrittlement, depth of the hydrogen-assisted surface layers, hydrogen transport during tensile tests and mechanisms of the hydrogen-induced brittle fracture all depend on grain size and ferrite content. The highest hydrogen embrittlement index IH = 32%, the widest hydrogen-affected layer and a pronounced solid-solution hardening by hydrogen atoms is typical of the specimens with the lowest fraction of the boundaries. Even though fast hydrogen transport via coarse ferritic grains provides longer diffusion paths during H-changing, the width of the H-affected surface layer in the dual-phase structure of the HNS specimens is mainly determined by the hydrogen diffusivity in austenite. In tension, hydrogen transport with dislocations increases with the decrease in density of boundaries due to the longer dislocation free path, but stress-assisted diffusion transport does not depend on grain size and ferrite fraction. The contribution from intergranular fracture increases with an increase in the density of intergranular and interphase boundaries.

Microstructural Features and Surface Hardening of Ultrafine-Grained Ti-6Al-4V Alloy through Plasma Electrolytic Polishing and Nitrogen Ion Implantation

This work studies a near-surface layer microstructure in Ti-6Al-4V alloy samples subjected to plasma electrolytic polishing (PEP) and subsequent high-energy ion implantation with nitrogen (II). Samples with a conventional coarse-grained (CG) structure with an average α-phase size of 8 μm and an ultrafine-grained (UFG) structure (α-phase size up to 0.35 μm) produced by equal channel angular pressing were used in the studies. Features of phase composition and substructure in the thin surface layers are shown after sequential processing by PEP and II of both substrates with CG and UFG structures. Irrespective of a substrate structure, the so-called “long-range effect” was observed, which manifested itself in enhanced microhardness to a depth of surface layer up to 40 μm, exceeding the penetration distance of an implanted ion he. The effect of a UFG structure on depth and degree of surface hardening after PEP and ion-implantation is discussed.

Advanced Complex Analysis of the Thermal Softening of Nitrided Layers in Tools during Hot Die Forging.

This article is devoted to the issues of thermal softening of materials in the surface layer of forging tools. The research covers numerical modeling of the forging process, laboratory tests of tempering of nitrided layers, and the analysis of tempering of the surface layer of tools in the actual forging process. Numerical modeling was supported by measuring the temperature inside the tools with a thermocouple inserted into the tool to measure the temperature as close to the surface as possible. The modeling results confirmed the possibility of tempering the die material. The results of laboratory tests made it possible to determine the influence of temperature on tempering at different surface layer depths. Numerical analysis and measurement of surface layer microhardness of tools revealed the destructive effect of temperature during forging on the tempering of the nitrided layer and on the material layers located deeper below the nitrided layer. The results have shown that in the hot forging processes carried out in accordance with the adopted technology, the surface layer of working tools is overheated locally to a temperature above 600 °C and tempering occurs. Moreover, overheating effects are visible, because the surface layer is tempered to a depth of 0.3 mm. Finally, such tempering processes lead to a decrease in the die hardness, which causes accelerated wear because of the abrasion and plastic deformation. The nitriding does not protect against the tempering phenomenon, but only delays the material softening process, because tempering occurs in the nitrided layer and in the layers deeper under the nitrided layer. Below the nitrided layer, tempering occurs relatively quickly and a soft layer is formed with a hardness below 400 HV.

МОДЕЛИ МАТЕРИАЛОВ ПРИ ИССЛЕДОВАНИИ ВОЛНОВОГО ДЕФОРМАЦИОННОГО УПРОЧНЕНИЯ МЕТОДОМ КОНЕЧНЫХ ЭЛЕМЕНТОВ

The problem of necessity in the development of loading environment models (materials processed) which has great importance at the finite element simulation of basic processes (technologies) is considered. &#x0D; As a rule, material model programs embedded into CAE cannot be used completely in the computations because of their limited set of physical-mechanical properties, most often insufficient for the adequate simulation of the process under investigation. By the example of the technology of wave deformation strengthening taking into account its peculiarities in the paper for the first time there are developed material models: steel45, BrAZh9-4; VT1-0; B-95 and the estimation of their adequacy is carried out. The creation of each model of material is a unique process and implies not only the pattern completion with data from reference books, but also with data obtained as a result of the fulfillment of corresponding experimental investigations of properties peculiar to material under working. As a result there are developed adequate models of materials having an admissible error (not exceeding 7.4%) for micro-hardness and depth of surface layer strengthening that allows recommending their use at the investigation of wave deformation strengthening through a finite element method.

Study on flexible structure with waterproof, breathable and thermal insulation in concrete construction

with the development scale of urbanization construction in China, the technical standard of concrete construction is getting higher and higher. It is the key breakthrough direction of technology to strengthen waterproof and air permeability in concrete construction. Nonwoven formwork lining technology is a way to improve the impermeability of concrete structure surface to achieve the overall durability of concrete structure. Some hydrated residual water and large bubbles of concrete at a certain depth of surface layer are discharged, thus reducing the water-cement ratio of concrete, realizing the compactness of structural surface, increasing the strength and hardness of concrete surface, and achieving the purpose of improving the performance of surface concrete. This paper mainly analyzes the flexible structure of waterproof, breathable and heat preservation, and puts forward personal views and viewpoints.

Technological capabilities for control of effective cold working depth of surface layer by wave strain hardening

The parameters of wave deformation are described. The results of studies of the effect of the diameter of the instrument used for wave deformation of flat surfaces on the quality parameters of the hardened surface layer are presented. A significant increase in depth and degree of hardening after processing has been established, and the parameters of the tool and the technology of its application to obtain the most effective results have been determined.

Short-term effects of olive oil mill wastewater application on soil water repellency

Land spreading of olive mill wastewater (OMW) allows a cheap and environmentally sound effluent disposal. However, this practice requires suitable application protocols, in order to avoid negative effects on soil hydrological properties, such as the increase of soil water repellency (SWR). The effects of OMW land spreading on SWR, mainly evaluated in the long term, have been rarely measured few days or weeks after land spreading. To this purpose, this study has evaluated the short-term effects of OMW land spreading on SWR of olive groves (with silt, loam or silty clay loam soil texture) using the Water Drop Penetration Test (WDPT) at laboratory scale. SWR significantly (p < 0.001) varied with the soil texture and depth (surface layer or 10-cm depth) as well as the treatment (land spreading of OMW or fresh water, FW) and time elapsed from land application. More specifically, SWR was significantly higher (p < 0.001) in the topsoil than the sub-surface layer. Compared to the soils irrigated with FW, a two-fold WDPT (thus a slightly higher SWR) was found after OMW application in both soil layers, regardless of the texture. However, this weak SWR disappears just after 2weeks from land spreading, and the hydrophobicity of the soils treated with OMW and FW becomes very similar. Moreover, the topsoil and sub-surface layer showed the same SWR after 4weeks. The high coefficients of determination (r2 >0.86) in the linear regressions between WDPT and OM content of soils proved the clear influence of the organic compounds on SWR, which decreases with OM, as expected. Overall, OMW land spreading has not significantly changed SWR, at least under the limited hydraulic and organic loads adopted in this study, and less noticeably on loam or silty clay loam soil compared to sandy loam texture. However, this practice is more viable in spring or autumn, since in these seasons the risk of groundwater contamination is particularly reduced.

Surface Integrity of AISI 52100 Bearing Steel after Robot-Based Machine Hammer Peening

AISI 52100 steel is often used as material for highly loaded rolling bearings in machine tools. An improved surface integrity, which can be achieved by means of mechanical surface layer finishing, can avoid premature failure. One of these finishing processes is machine hammer peening (MHP) which is a high-frequency incremental forming process and mostly used on machining centers. However, the influence of robot-guided MHP processing on the surface integrity of AISI 52100 steel is still unknown. Therefore, the objective of this work is to investigate experimentally the robot-based influences during MHP processing and the resulting surface integrity of unhardened AISI 52100 steel. The results show that the axial and lateral deviations of the robot due to process vibrations are in the lower µm range, thus enabling stable and reproducible MHP processing. By selecting suitable MHP process parameters and thus defined contact energies, even ground surfaces can be further smoothed and a hardness increase of 75% in the energy range considered can be achieved. In addition, compressive residual stress maxima of 950 MPa below the surface and a grain size reduction to a surface layer depth of 150 µm can be realized.