Dense Product Research Articles

Abrupt and persistent shutdown of the thermohaline forcing during MIS5e in the Adriatic Sea: Insights from shallow-water sapropel sediments

During the Quaternary, the Eastern Mediterranean Sea (EMS) experienced cyclical events of stagnation driven by natural climate variability. The resulting deoxygenation left well-preserved evidence in the sedimentary record as organic carbon-rich deposits referred to as sapropels. Although drastic modifications in the degree of dense-water formation over the EMS shelves exerted first-order control on the deoxygenation, most of the focus has been traditionally placed on the deep EMS. To provide a shallow-water perspective, here we investigated the sapropel S5 in the Adriatic shelf (borehole PRAD1-2) deposited during MIS5e (129-116 ka). This archive is strategically located in a region where the Northern Adriatic Dense Water (NAdDW) interacts with the seabed before cascading across the continental slope. We used Zr/Rb and MgO/Al2O3 to assess bottom current energy and north-to-south sediment transport dynamics, both regulated by the changes in NAdDW production intensity. In addition, we used stable isotopes (δ13C and δ18O) of foraminifera, redox sensitive elements (U, Mo and Sb), foraminifera assemblages as well as alkenones to reconstruct the paleo-environmental conditions during the S5 formation.Our study provides an unprecedented reconstruction of the physical forcing controlling the deoxygenation during the S5 formation. Results reveal that the shutdown of the NAdDW occurred in a few centuries (0.67 ± 0.22 kyrs), when freshening of surface waters combined with warming of winter temperatures mutually hampered the dense water formation. A few centuries after the NAdDW shutdown, the Adriatic shelf experienced euxinic waters for about 2 kyrs followed by a progressive reoxygenation that lasted 4 kyrs. We explain this second phase as a general recovery driven by increased surface salinity over the EMS combined with winter cooling. This favoured surface water mixing without, however, producing dense water in the Northern Adriatic and thus collectively the interruption of the dense water production lasted for 6 kyrs since the onset of MIS5e. Overall, our finding highlights that the thermohaline forcing responded to climate change much quicker than inferred by earlier studies that suggested instead a millennial-scale prelude necessary to develop stagnation. In addition, our results provide solid evidence about the large-scale impact of the deoxygenation during S5 that is capable of invading the continental shelf. Comparison with the latest regional models illustrates how none of the future simulations covering different climate change scenarios reproduces an event over the EMS margins comparable with what described in this study.

Threshold sensitivity of the production network topology

Industries today are tightly interconnected, necessitating a systematic perspective in understanding the complexity of relations. Employing network science, the literature constructs dense production networks to address this challenge. However, handling this high density involves carefully choosing the level of pruning to retain as much information as possible. Yet, current research lacks comprehensive insight into the extent of distortion the data removal produces in the network structure. Our paper aims to examine how this widespread thresholding method changes the production network’s topology. We do this by studying the network topology and centrality metrics under various thresholds on inter-industry networks derived from the US input-output accounts. We find that altering even minor threshold values significantly reshapes the network’s structure. Core industries serving as hubs are also affected. Hence, research using the production network framework to explain the propagation of local shocks and disturbances should also take into account that even low-value monetary transactions contribute to the interrelatedness and complexity of production networks.

Actual Xisha marine atmospheric corrosion behavior of 30CrMnSiA steel in different parts of the aircraft

The corrosion behavior of 30CrMnSiA steel on the surface, inside, and belly of the aircraft was investigated by exposing it in Xisha outdoor, shelter and storehouse. The results show that the corrosion degrees of 30CrMnSiA steel are in the order of outdoor > shelter > storehouse in the same cycle. Based on the polarization curve, the corrosion current density of 30CrMnSiA steel is in the order of outdoor > shelter > storehouse after 1 month of exposure. The corrosion current density shows a decreased tendency with exposure time, which is related to the dense corrosion products on the surface. The corrosion products of 30CrMnSiA steel had the highest number and became gradually dense in outdoor conditions. The shelter had a few corrosion products in an unstable phase. It covered the full surface of the specimen at the late stage. The storehouse had the least corrosion products in an unstable phase. The products partially covered the full surface of the specimen at the late stage. The difference in the corrosion of 30CrMnSiA steel in environments is related to the humidity and Cl- in the exposure environment.

Enhanced corrosion resistance of Mg17Al12 compounds by Ce modification

Mg17Al12-xCe (x = 0, 0.1, 0.5, 1 wt%) intermetallic compounds have been prepared by vacuum induction melting, in order to enhance the corrosion resistance of Mg17Al12 compound by Ce modification. The results have showed that the Mg17Al12 compound compose of β-Mg17Al12 substrate and eutectic structure (α-Mg and β-Mg17Al12 phases) distributed continuously along grain boundaries under non-equilibrium solidification conditions. A high cathode to anode area ratio of the eutectic structure results in poor corrosion resistance of the Mg17Al12 compound. The eutectic structure distributed continuously along the grain boundaries can be interrupted and corrosion could not propagate along the grain boundaries in Mg17Al12 compound alloyed by 0.1 wt% Ce. Hence, the corrosion performance of Mg17Al12 compound has been improved by 0.1 wt% Ce. With the Ce content further increasing to 0.5 wt%, the corrosion resistance of the compounds could be effectively improved due to the formation of dense corrosion products film. Additionally, the complete suppression of eutectic structure effectively reduces electrochemical corrosion of compounds containing more than 0.5% Ce. On the contrary, due to the precipitation of more Al11Ce3 phase, the corrosion resistance of Mg17Al12–1Ce alloy is slightly deteriorated based on the galvanic corrosion mechanism.

Experimental Campaign of Massive CO2 Atmospheric Releases in an Urban Area

Over recent decades, several campaigns have been carried out to collect data regarding the release and atmospheric dispersion of dense chemical products in an open field. All these experimental data are valuable information to challenge the predictions of numerical tools (Gaussian, integral-type, and CFD) and, if needed, to improve the code itself and the way we are using it. On the other hand, little attention has been paid to atmospheric dispersion releases with massive flow rates in a complex urban environment. To fill this gap, Ineris carried out an experimental campaign intended to study the atmospheric dispersion of massive CO2 releases on the CENZUB site (an action training center in an urban area located in Sissonne, France). Three CO2 releases were performed with mass flow rates of about 7 kg/s in three different configurations: one axial street release and two impacting releases (against a small and high-rise building). Several technologies of CO2 sensors were used to ensure better measurement accuracy. The main experimental campaign features and preliminary data analysis are presented. The results demonstrated the influence of the built environment on dispersion patterns.

The Correlation between Green Fodder Yield and Fodder Quality Traits in Hybrids of Pearl Millet [Pennisetum glaucum (L.) R. Br.

Pearl millet is an ideal fodder crop having highly shiny, lush, palatable, nutrient- dense, excellent silage and biomass production potential and bestowed with various essential nutrients required for the livestock. The study material consists of 54 fodder pearl millet hybrids obtained through the hybridisation between 15 selected superior parents from ICRISAT gene-pool as well as gene pool of Department of Forage Crops, TNAU, Coimbatore. For the better understanding of the relationship between green fodder yield per plant, its contributing traits and various quality traits, genetic parameters such as genotypic and phenotypic correlation as well as path coefficients were analysed. Correlation studies revealed that out of all the seventeen biometric traits studied, all the traits are shown positive correlation with green fodder yield per plant whereas fifteen traits are found to have significant positive correlation with green fodder yield per plant. Ash content (rg =0.855), dry fodder yield per plant (rg =0.850), leaf-stem ratio (rg =0.710) have shown very strong significant positive correlation and plant height (rg =0.641), days to green fodder harvest (rg =0.630), stem girth (rg =0.616) and days to fifty per cent flowering (rg =0.606) have recorded with moderately strong significant positive correlation with green fodder yield per plant. Number of tillers per plant (0.859), internode length (0.574), ash content (0.421) and dry fodder yield per plant (0.372) revealed highly positive direct effects with green fodder yield per plant. Hence, selection for traits exhibiting positive association and direct effects for green fodder yield would help the breeder to enhance it further.

Effect of Ni content on the corrosion behavior of Mo2NiB2–Ni cermet in H2SO4 solution

To promote the utilization of Mo2NiB2–Ni cermet under sulfuric acid drew corrosion conditions, it is essential to elucidate the resistance mechanism of these cermets to sulfuric acid corrosion. In this study, the corrosion behavior of Mo2NiB2–Ni cermets with different Ni content in 90 wt % H2SO4 solution at 110 °C was investigated, and the corrosion resistance mechanism was analyzed. The results reveal that the corrosion weight losses and corrosion rates of the cermets decreased with increasing Ni content. Mo2NiB2–Ni cermets with higher Ni contents exhibited improved corrosion resistance. This improvement can be attributed to the generation of a considerable amount of NiSO4 corrosion products from the Ni binder phase corroded by H2SO4, which led to the subsequent formation of a large-scale, flat, and dense corrosion products layer with a certain thickness. This effectively prevented further erosion of the inner matrix and improved the corrosion resistance of the cermet. Additionally, the electrochemical results indicate that the corrosion product layer hindered the passage of electric charges through the layer, which inhibited the corrosion reaction.

Np-Fe0 addition affects the microstructure and composition of the microwave-sintered lunar soil simulant CLRS-2

Microwave sintering is a key technology for future lunar habitats, which has been verified by various lunar soil simulant experiments. However, nanophase iron (np-Fe0), a unique component of the real lunar regolith, has been ignored in previous studies of the microwave sintering of lunar soil simulants. In this study, microwave-sintering experiments of lunar soil simulant CLRS-2 with and without np-Fe0 at different temperatures were conducted. A comparison of the microstructure and chemical composition of sintered products indicates that all products of samples with 1.0 wt% np-Fe0 exhibit better properties than those without np-Fe0 after heating at equivalent temperatures. Adding np-Fe0 to the lunar soil simulant CLRS-2 couples well with microwaves, which may increase the real heating temperature in a sample, resulting in the product being solidified at 700 °C and a relatively dense product forming at 900 °C, thus improving the sintering efficiency. This study suggests that microwave sintering is an effective potential technology for future lunar habitats and road hardening because of the wide distribution of np-Fe0 in the lunar regolith. The technical parameters given in this study can provide an important guide for future lunar construction by microwave sintering.

Fabrication, Microstructure and Corrosion Resistance of Zn/Al Composite Coating by Arc Spraying

In this work, the Zn/Al composite coating was prepared on the surface of Q345 steel using arc spraying. The simple and efficient cold-pressing technique was used for the composite coating. The cold pressure sealing (CPS) technique is proposed to reduce the porosity of the composite coating. The corrosion behavior of Zn/Al composite coatings without and with cold pressure sealing treatment in a corrosive environment was studied. The microstructures of composite coatings without and with CPS were studied by scanning electron microscope (SEM), and the corrosion properties of composite coating without and with CPS were comparatively investigated. The results showed that the porosity of the composite coating was significantly reduced to 2% by CPS. After 28 days of immersion, the dense corrosion products filled the defect area in the CPS sample. After CPS treatment, the corrosion potential is −0.829 V, and the corrosion current density is 5.636 × 10−6 A/cm2. After cold pressing, the bonding strength of the coating is 13.82 MPa, which is 43% higher than that before the sealing treatment. The Zn/Al composite coating treated by CPS exhibits excellent corrosion resistance in the simulated marine environment.

Effect of aging on corrosion and discharge performance of AZ63-1.5RE alloy as anode in magnesium-dissolved oxygen seawater batteries

This study aims to understand how aging treatment affects corrosion resistance and discharge performance of AZ63-1.5 rare earth mischmetals (AZ63-1.5RE) alloy in low-power dissolved oxygen seawater batteries. Solutionizing and aging treatment at 180 °C, 210 °C, and 240 °C for 16 h, 20 h, and 24 h is used to investigate the effects of heat treatment on corrosion and discharge performance. An XRD pattern of alloys after solutionizing and aging indicates a change in crystalline orientation and an increase in Mg phases proportion. A reduction in self-corrosion of alloys is achieved through solutionizing and aging. With solutionizing and aging of the alloys, their discharge potentials is shifted to more negative values by about 0.01–0.02 V. The anodic efficiency also is improved significantly from 53.89% for the as-cast alloy to 67.55% for the aged alloy at 210 °C for 20 h. Following 24 h of discharge, the aged alloy at 210 °C demonstrated the highest polarization resistance. The favorable corrosion performance can be attributed to grain refinement of the β-Mg17Al12 phase, the increased contribution of the Al-RE corrosion-resistant phase, the low contribution of the layered phase in the matrix, and the formation of dense discharge products on the surface.

Fly Ash and Natural Pozzolana Impacts on Sustainable Concrete Permeability and Mechanical Properties

This paper studied the effect of fly ash (FA) and natural pozzolana (NP) as partial cement substitutes on sustainable concrete permeability and mechanical and microstructural properties. Batches with 10, 20, 30, 40, and 50% FA and NP replacements for cement were prepared and tested for compressive strength after 7, 28, and 56 curing days and for flexural strength after 28 curing days. Permeability testing was conducted on all samples. A qualitative microstructural analysis was performed using scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX). The mechanical properties results showed slight strength improvements when replacing the cement with low percentages of the pozzolanic materials. The compressive strengths of the batches with 10% FA and NP replacements of cement showed compressive strength increases of 11.63 and 8.75%, respectively, compared to that of plain concrete. On the other hand, the flexural strength for the batches with FA replacement of cement achieved at least a 15.6% increase compared to that of the control. Moreover, FA and NP replacement of cement had a positive impact on batch permeability, with decreased permeability values reaching 78.3 and 56.5%, respectively, compared to that of the control. Furthermore, the microstructural analysis indicated that adding FA and NP would enhance cement hydration by the formation of dense hydration products such as calcium–silicate–hydrate (C-S-H) crystals, which increased hardened concrete strength. Finally, the cost analysis showed that the batch with a 10% FA replacement of cement is the ideal one in this study.

The role of shallow and deep circulations in the Tropical Pacific Ocean heat budget

The Tropical Pacific Ocean plays an important role in setting the global ocean heat content and redistribution. We examined the role of the shallow and deep circulations in the tropical Pacific in unperturbed and transient climate change conditions in a global ocean model. We found that, in the Control state, the shallow circulation is by far the largest contributor to the overall balance of the column, where the balance is set as the residual between advective cooling and warming by vertical diffusive mixing. Subject to surface flux perturbations, changes in the tropical Pacific ocean heat budget can be explained by shallow wind-driven overturning circulation changes. For wind stress anomalies, the shallow ocean heat budget imbalance is directly related to overturning circulation changes, whereas under heat flux perturbations, warming of the shallow ocean is related to strengthened mid-latitude subduction and weakened dense water production at higher latitudes.

Influence of CrFeCoNiCu high-entropy alloy and ultrasonic stirring on the thermal, electrochemical and mechanical properties of Zn-30Sn high-temperature solder alloy

In this study, the thermal, electrochemical and mechanical properties of Zn-30Sn solder alloy with different contents of CrFeCoNiCu high-entropy alloy (HEA) (0, 0.5 and 1 wt%) were investigated. At the same time, ultrasonic stirring was introduced into the melting process. The results suggested that the addition of HEA could refine the microstructure and the Zn matrix phases accelerated to dissolve to form more precipitation phases with the increase of HEA content from 0 to 1.0 wt%. The application of ultrasound could make the distribution of the phases disperse and facilitate the formation of dense and uniform corrosion products during the corrosion process. The electrochemical corrosion test and tensile test results showed that the ultrasonically treated Zn-30Sn solder alloy containing 1.0 wt% HEA had the lowest corrosion current density (Icorr = 1.11 μA·cm−2), the highest ultimate tensile strength (101.13 MPa) and yield strength (25.55 MPa), indicating that the corrosion resistance and mechanical properties were most outstanding. Moreover, the melting temperature of the composite solder alloys was slightly decreased from 379.5 °C to 377.5 °C.

Effect of printing strategies on the properties of product in selective Sorel cement activation

PurposeParticles bed binding by selective cement activation (SCA) method is a computer-aided manufacturing (CAM) technique used to produce cementitious elements. A computer-aided design file is sliced to generate G-codes before printing. This paper aims to study the effect of key input parameters for slicer software on the final properties of printed products.Design/methodology/approachThe one factor at a time (OFAT) methodology is used to investigate the impact of selected parameters on the final properties of printed specimens, and the causes for the variations in outcomes of each variable are discussed.FindingsFiner aggregates can generate a more compact layer, resulting in a denser product with higher strength. Fluid pressure is directly determined by voxel rate (rV); however, high pressures enable better fluid penetration control for fortified products; for extreme rVs, residual voids in the interfaces between successive layers and single-line primitives impair mechanical strength. It was understood that printhead movement along the orientation of the parts in the powder bed improved the mechanical properties.Originality/valueThe design of experiment (DOE) method assesses the influence of process parameters on various input printing variables at the same time. As the resources are limited, a fractional factorial plan is carried out on a subset of a full factorial design; hence, providing physical interpretation behind changes in each factor is difficult. OFAT aids in analyzing the effect of a change in one factor on output while all other parameters are kept constant. The results assist engineers in properly considering the influence of variable variations for future DOE designs.

Changing the second phase distribution shape and improving the corrosion resistance of Mg-6.7Y-2.5Zn alloy by addition of trace Ta

Of the alloying additions to magnesium to date, Ta has not been widely studied. Herein, the effect of Ta on the microstructure and corrosion of Mg-6.7Y-2.5Zn was investigated using optical microscopy, scanning electron microscopy, electrochemical measurements and mass loss. The results showed that the addition of Ta can effectively improve the corrosion resistance of Mg-6.7Y-2.5Zn alloy and change the local corrosion to uniform corrosion. The addition of Ta can rapidly form a dense corrosion product film on Mg-6.7Y-2.5Zn alloy, thus effectively preventing the later corrosion.

Miniaturized Vis–NIR handheld spectrometer for non-invasive pigment quantification in agritech applications

Advanced precision agriculture requires the objective measurement of the structural and functional properties of plants. Biochemical profiles in leaves can differ depending on plant growing conditions. By quantitatively detecting these changes, farm production processes can be optimized to achieve high-yield, high-quality, and nutrient dense agricultural products. To enable the rapid and non-destructive detection on site, this study demonstrates the development of a new custom-designed portable handheld Vis–NIR spectrometer that collects leaf reflectance spectra, wirelessly transfers the spectral data through Bluetooth, and provides both raw spectral data and processed information. The spectrometer has two preprogramed methods: anthocyanin and chlorophyll quantification. Anthocyanin content of red and green lettuce estimated with the new spectrometer showed an excellent correlation coefficient of 0.84 with those determined by a destructive gold standard biochemical method. The differences in chlorophyll content were measured using leaf senescence as a case study. Chlorophyll Index calculated with the handheld spectrometer gradually decreased with leaf age as chlorophyll degrades during the process of senescence. The estimated chlorophyll values were highly correlated with those obtained from a commercial fluorescence-based chlorophyll meter with a correlation coefficient of 0.77. The developed portable handheld Vis–NIR spectrometer could be a simple, cost-effective, and easy to operate tool that can be used to non-invasively monitor plant pigment and nutrient content efficiently.

Room-Temperature Single-Step Production of Ultrafine-Grained Bulk Metallic Sheets From Al Powder

Abstract Obtaining fully dense products with high strength in one step at room temperature by powder metallurgy (PM) is generally not possible. However, doing so would reduce manufacturing and energy costs substantially. In this work, we have attempted to achieve this on commercially pure aluminum by utilizing the friction-assisted lateral extrusion process (FALEP), which has the capability of producing sheets from bulk or powder metal in a single step, by applying large shear strain. The texture, microstructure, and mechanical properties of the fully compacted powder sample were examined and compared to the bulk sheet’s properties obtained also by FALEP. The powder-FALEP sample showed a smaller grain size and significantly higher strength. Simulations carried out by the Taylor-type lattice curvature-based polycrystal model shed light on the texture characteristics of the obtained materials and were in good agreement with the experiments.

Recent Convection Decline in the Greenland Sea: Insights From the Mercator Ocean System Over 2008–2020

AbstractWe investigated wintertime convection evolution in recent years over the Greenland Sea. This area is a major location regarding dense water production and supply of the lower limb of the Atlantic Meridional Overturning Circulation, a key component of the global climate. Previous studies mentioned an increase in Greenland Sea wintertime convection intensity during the 2000s in comparison with the previous decade till 2015/2016. Here, we further document the ongoing oceanic changes within the Greenland Sea through the Mercator Ocean Physical System, an operational ocean model with data‐assimilation. The model has shown a large variability, a later start and a decline of convection in the Greenland Sea in recent years. In particular, the depth of the annual maximum mixed layer diminished by 52% between 2008–2014 and 2015–2020, from 1,168 to 559 m, over the convective area. This decline of the convection depth is corroborated with Argo float observations. Within the Greenland Sea, hydrographic changes especially the increasing temperature are associated with isopycnal deepening and stratification strengthening. The stratification is building up at a larger rate in the Boreas Basin compared to the Greenland Basin. The changes of the Greenland Sea hydrography in the model are in part related to Atlantic Water spreading over the Boreas Basin and the eastern part of the Greenland Basin. The model also indicates a decrease in the intensity of the gyre in accordance with the isopycnal deepening while local surface winds and fluxes do not exhibit significant trends nor significant interannual variations.

Assessing plant diversity change in logged and unlogged dense semi-deciduous production forest of eastern Cameroon

This study was carried out in the dense semi-deciduous production forest of East Cameroon. The objective of this work of this study was to provide comparative floristic knowledge that can serve as a basis for the planning and sustainable management of ligneous plant resources in Communal Forests before and after logging. Sampling was done in unlogged and logged forest. Data collection was carried out using the linear transects subdivided into 10 plots of 25 m × 20 m (500 m2) with an equidistance of 225 m for the inventory of all trees with dbh ≥10 cm installed measured at 1.3 m above ground level. Nested quadrats 5 m × 5 m, oriented south-west and north-east were set up in each plot for the counting and identification of all individuals with a diameter less than 10 cm. The analysis of inventory data showed that the floristic composition was higher in the unlogged forest. The individuals were more evenly distributed in the logged (Pielou's equitability index = 0.83) than in the unlogged forest. The study of the functional spectra showed that the flora of the two forest types was dominated by Guinean-Congolese species (67.57% in the unlogged forest and 63.07% in the logged forest) and Phanerophytes, particularly Mesophanerophytes. The dominance of sarcochorous species reveals that the main mode of dissemination in this forest is zoochory, particularly endozoochory. The presence of pleochroic species in the logged forest reveals the importance of dissemination by water in the environment. The plants surveyed were divided into five plant assemblages (three for logged forest and two for unlogged forest) based on ecological parameters. The findings of this study suggest that forest management which combines assisted natural regeneration with the natural process of secondary succession facilitates the reconstitution of the vegetation cover and, by extension, the conservation of biodiversity in post-logging forest concessions.

FTIR Study of Enriched Bituminous Ukhaa-Khudag Coal

In the present work we pay an attention to the molecular structural changes between raw coal and its enriched, dense productions. Bituminous Ukhaa-Khudag coal in the form of an enriched, dense coal product is currently used as an energy source by Mongolian consumers for everyday need. There are three types of samples from one source: it is a raw coal (sample 1) and two of industrial prod- ucts as an enriched, dopant (organic based) added coal (sample 2) and simply enriched coal (sample 3). The raw coal general characterization is given through the elemental analysis, thermogravimetry analysis, moreover functional groups were identified by Fourier Transform infrared spectroscopy. The differences in the FTIR spectra of the samples were done.Some details are as follows: hydroxyl group vibrations are existing, rather weak in agreement of TG result; vibrations of aliphatic group were rarely in the long wave near region, carbonate minerals in the region of 1300-900 cm−1 are visible but overlapped, and an isolated out-of-plane deformational vibration (around 800 cm−1) or two-adjacent (800-750 cm−1) or three-adjacent (around 700 cm−1) of sp2-hybrid bonded aromatic CHx-groups were still presenting.After the processing hydroxyl group bands were affected in enriched coals, sample 2 and 3. In the spectrum of the sample 2 the long wave bands were intensively blurred.Industry processing retains an amount of water in the productions. Water excess influenced absorbance bands were able to be removed via the drying processing, however, the affection to the spectral struc- ture in sample 2 was unrecoverable.