Changes In Properties Research Articles

Numerical Analysis of the Effect of Crude Oil Pollution on Vertical Clay Trenches

ABSTRACT The presence of oil contamination causes changes in mechanical properties of clayey soil trenches with low liquid limits (CL) such as stress-strain behavior, rupture plain position, plastic zone, and strain energy for soil trenches compared with uncontaminated soils. These changes usually lead to a lower factor of safety against failure and expansion of the plastic zone. The effects of crude oil contamination on the soil shear strength were evaluated by direct shear and plate load tests for various clays and sandy soils. In this research, a numerical finite element modeling in ABAQUS software was used to estimate the effect of oil contamination in the range of 0 to 16% (0%–4%–8%–12%–16%) on the stability safety factor of vertical clayey trenches with heights of 3 m, 4 m, 5 m, and 6 m, and the results were compared with results of a limit state analysis. The findings of the limit equilibrium method show that adding 4% of oil contamination to a clayey trench will decrease 62% of its critical depth. Also, the numerical analysis results show that adding oil contamination in the range of 0 to 16% to the clayey soil will increase the maximum displacements of the trenches to five times their clean state.

Modelling lubricating oil wear using fuzzy logic

The content of this article presents research on used and fresh engine oils. The aim of the experiment is to preliminarily develop a method for assessing the condition of engine oil subjected to service. A four-ball tester was used to compare the lubricating properties of the engine oil as one component of the tribosystem under laboratory conditions. The method used to determine the mashing load consisted of subjecting the kinematic node to a linearly increasing load with a build-up rate of 409 N·s-1 under operating conditions of approximately 20°C and a spindle speed of 500 rpm. The presented article is a continuation of the consideration of the lubricating properties of engine oils subjected to operation. The tests carried out made it possible to observe that fresh oils are characterised by their ability to carry higher loads in relation to oils subjected to service. This is evidenced by the obtained values of scuffing loads, which have a higher value for fresh oils (The average percentage increase in scuffing load for fresh oils was 62.23%). Comparing the friction torque characteristics with each other, it can be seen that the values of maximum friction torque are also higher for the fresh oils group. The modelling process made it possible to characterise changes in the tribological properties of the lubricating oil being used. In the future, the described model will be extended to include further input parameters (viscosity, contaminant content, fractional composition, etc.), which will allow a multi-parametric assessment of lubricating oil wear.

The mechanistic basis of the membrane-permeabilizing activities of the virulence-associated protein A (VapA) from Rhodococcus equi.

Pathogenic Rhodococcus equi release the virulence-associated protein A (VapA) within macrophage phagosomes. VapA permeabilizes phagosome and lysosome membranes and reduces acidification of both compartments. Using biophysical techniques, we found that VapA interacts with model membranes in four steps: (i) binding, change of mechanical properties, (ii) formation of specific membrane domains, (iii) permeabilization within the domains, and (iv) pH-specific transformation of domains. Biosensor data revealed that VapA binds to membranes in one step at pH 6.5 and in two steps at pH 4.5 and decreases membrane fluidity. The integration of VapA into lipid monolayers was only significant at lateral pressures <20 mN m-1 indicating preferential incorporation into membrane regions with reduced integrity. Atomic force microscopy of lipid mono- and bilayers showed that VapA increased the surface heterogeneity of liquid disordered domains. Furthermore, VapA led to the formation of a new microstructured domain type and, at pH 4.5, to the formation of 5 nm high domains. VapA binding, its integration and lipid domain formation depended on lipid composition, pH, protein concentration and lateral membrane pressure. VapA-mediated permeabilization is clearly distinct from that caused by classical microbial pore formers and is a key contribution to the multiplication of Rhodococcus equi in phagosomes.

Photoelectric properties of monolayer 1T-CrS2 modified by doping non-metal atoms under strains

Based on the first principle, the change of photoelectric properties of non-metal-doped CrS2 under biaxial tension was studied. The formation energy indicates that the doping system is stable. Studies have shown that the partial doping system achieves a semiconductor metal phase transition. The strain opens the bandgap of the F-doped system, and the system changes from metal to n-type semiconductor. The Te-doped system realizes the transition from indirect bandgap to direct bandgap under the adjustment of 2% strain. The O and Se doping systems realize the reverse regulation of the bandgap under strain, and the conductivity gradually increases with the increase of strain. The absorption efficiency of Te doping under a certain strain is significantly enhanced, the static dielectric properties of the F doping system are increased by more than two times, the absorption spectrum response range is increased, and the absorption capacity of the system is enhanced. This lays a foundation for applying monolayer CrS2 in microelectronics and optoelectronics.

Subsurface chlorophyll maxima reduce the performance of non-photochemical quenching corrections in the Southern Ocean

Non-photochemical quenching (NPQ) within phytoplankton cells often causes the daytime suppression of chlorophyll fluorescence in the Southern Ocean. This is problematic and requires accurate correction when chlorophyll fluorescence is used as a proxy for chlorophyll-a concentration or phytoplankton abundance. In this study, we reveal that Southern Ocean subsurface chlorophyll maxima (SCMs) are the largest source of uncertainty when correcting for NPQ of chlorophyll fluorescence profiles. A detailed assessment of NPQ correction methods supports this claim by taking advantage of coincident chlorophyll fluorescence and chlorophyll concentration profiles. The best performing NPQ correction methods are conditional methods that consider the mixed layer depth (MLD), subsurface fluorescence maximum (SFM) and depth of 20% surface light. Compared to existing methods, the conditional methods proposed halve the bias in corrected chlorophyll fluorescence profiles and improve the success of replicating a SFM relative to chlorophyll concentration profiles. Of existing methods, the X12 and P18 methods, perform best overall, even when considering methods supplemented by beam attenuation or backscatter data. The widely-used S08 method, is more varied in its performance between profiles and its application introduced on average up to 2% more surface bias. Despite the significant improvement of the conditional method, it still underperformed in the presence of an SCM due to 1) changes in optical properties at the SCM and 2) large gradients of chlorophyll fluorescence across the pycnocline. Additionally, we highlight that conditional methods are best applied when uncertainty in chlorophyll fluorescence yields is within 50%. This highlights the need to better characterize the bio-optics of SCMs and chlorophyll fluorescence yields in the Southern Ocean, so that chlorophyll fluorescence data can be accurately converted to chlorophyll concentration in the absence of in situ water sampling.

CoCuMgAl-Mixed-Oxide-Based Catalysts with Fine-Tunable Composition for the Hydrogenation of Furan Compounds

Catalysts based on CoCuMgAl mixed oxides were synthesized and studied in the hydrogenations of furfural and 5-hydroxymethylfurfural under different conditions. The changes in the structural properties of the catalysts at different stages of their preparation were studied using a set of physical methods (XRD, SEM, and TEM). It was shown that the fine regulation of the chemical compositions of the mixed oxides (i.e., changes in the Co/Cu ratio) made it possible to vary the structure, morphology, and catalytic properties of the samples. The phase composition of catalysts with Co/Cu = 1 did not change during the catalytic reaction, although the initial catalysts had a less-homogeneous morphology. 5-hydroxymethylfurfural conversion was higher for the samples with Co/Cu = 1. Furfural conversion increased when raising the Co/Cu ratio. The selectivity toward furfuryl alcohol for the catalyst with Co/Cu = 2 under mild conditions of furfural hydrogenation was more than 99%. The results obtained are important for the development of the scientific foundations of the preparation of hydrogenation catalysts with a fine-tunable composition in order to obtain the desired hydrogenation products.

Interdependencies Between Wildfire‐Induced Alterations in Soil Properties, Near‐Surface Processes, and Geohazards

AbstractThe frequency, severity, and spatial extent of destructive wildfires have increased in several regions globally over the past decades. While direct impacts from wildfires are devastating, the hazardous legacy of wildfires affects nearby communities long after the flames have been extinguished. Post‐wildfire soil conditions control the persistence, severity, and timing of cascading geohazards in burned landscapes. The interplay and feedback between geohazards and wildfire‐induced changes to soil properties, land cover conditions, and near‐surface and surface processes are still poorly understood. Here, we synthesize wildfire‐induced processes that can affect the critical attributes of burned soils and their conditioning of subsequent geohazards. More specifically, we discuss the state of knowledge pertaining to changes in mineralogical, hydraulic, mechanical, and thermal properties of soil due to wildfire with a focus on advances in the past decade. We identify how these changes in soil properties alter evapotranspiration, interception, sediment transport, infiltration, and runoff. We then link these alterations to the evolution of different geohazards, including dry raveling, erosion, rockfalls, landslides, debris flows, and land subsidence. Finally, we identify research gaps and future directions to advance knowledge on how wildfires control the evolution of various earth surface processes and geohazards over time.

Restoration and Transformation: The Response of Shocked and Oxidized Magnetite to Temperature

AbstractLarge impact craters on Earth are associated with prominent magnetic anomalies, residing in magnetite of the shocked target rocks and impactites. Shock experiments on magnetite suggest that up to 90% of magnetic susceptibility is lost at pressures &gt;5 GPa, but can be partially restored by post‐shock thermal annealing. The magnetic property changes are caused by shock induced grain size reduction and fragmentation, as well as domain wall‐pinning at crystal lattice defects. A recent study of granitoids from the peak‐ring of the Chicxulub crater found that annealing may occur naturally, but can also be overprinted by high‐temperature hematite‐to‐magnetite transformation in non‐oxidizing environments. In this study, we isolate the effect of defect annealing and hematite‐to‐magnetite transformation using the evolution of hysteresis, isothermal remanent magnetization components and first order reversal curve (FORC) diagrams at different high‐temperature steps. We used a laboratory‐shocked magnetite‐quartz ore, a non‐shocked naturally oxidized granite, and a naturally shocked and oxidized granite. Our findings suggest that annealing of shock‐induced lattice defects partially restores some pre‐shock magnetic behavior and causes an apparent average bulk‐sample domain state increase. Hematite‐to‐magnetite transformation creates new fine‐grained magnetite that strongly overprints the original signal, and decreases the average bulk‐sample domain state. Where annealing and hematite‐to‐magnetite transformation both occur, the new magnetite masks the annealing‐induced property restoration and apparent domain state modification in the shocked magnetite. As magnetite oxidation is a ubiquitous process in surface rocks, these findings are fundamental to understand hematite‐to‐magnetite transformation as a potential overprint mechanism, and could have broad implications for paleomagnetic interpretations.

Tensile Property Changes in Polyvinyl Alcohol Fiber-Reinforced Engineered Cementitious Composites at Sub-Elevated Temperatures

Tensile Property Changes in Polyvinyl Alcohol Fiber-Reinforced Engineered Cementitious Composites at Sub-Elevated Temperatures

Influence of environmental conditions on the degradation of rubber compounds

Rubber compounds are complex, chemically active and viscoelastic materials. In this material type, transient and transient changes in the individual rubber properties occur during the manufacturing processes. A large number of rubber compounds consist of a large number of elastomers and virtually all of them are made up of fillers such as (carbon black, silica, kaolin, calcium carbonate, etc.). A very important element of which rubber compounds are composed is sulphur. Its important function is to ensure the cross-linking process during vulcanisation. Lubricants, plasticizers and various organic substances used to modify the properties are also essential components of rubber compounds. The aim of this work is to assess the influence of natural environmental conditions (temperature, time, humidity, microorganisms, UV radiation) on the modification of the properties of rubber composites.

QUALITÀ ORGANOLETTICA DEI GAMBERI MARRONI (CRANGON CRANGON L.) CONSERVATI IN DIVERSE CONDIZIONI DI CONGELAMENTO PRIMA DELLA COTTURA

Freshly caught brown shrimp (Crangon crangon) are prone to rapid degradation after death. Freezing the unprocessed shrimp shortly after catch provides a possible solution to maintain product quality until further processing. In this study, Shrimp were frozen under three conditions (individually frozen, vacuum packed or glazed), either directly at −20°C or deep frozen at −50°C for three hours and subsequently stored at −20°C. A trained sensory panel assessed the organoleptic quality of brown shrimp that were cooked after 2 and 4 months of raw-frozen storage. Shrimp cooked under the same conditions immediately after the catch, then stored at −20 for maximum 1 month were used as reference. The quality of the frozen shrimp was also visually evaluated after one year. The individually frozen shrimp remained closest to the reference samples in terms of colour and odour when stored at −20°C, and closest to the reference for taste when initially frozen at −50°C. Vacuum-packed shrimp scored less well and glazed samples were omitted from the experiments beyond 2 months of storage due to visual deterioration. In conclusion frozen storage of raw shrimp is possible for short periods up to 4 months, albeit with perceivable changes in organoleptic properties of the final cooked product.

Staphylococcus aureus responds to oxygen-restricted growth conditions by triggering changes in membrane biophysical properties through shifts in lipid composition

Staphylococcus aureus responds to oxygen-restricted growth conditions by triggering changes in membrane biophysical properties through shifts in lipid composition

Development of cutting force components in high-speed cutting on turning centre

The article deals with the investigation of high-speed cutting. The influence of cutting speed on the development of individual cutting force components in turning was determined. Cutting tests were carried out on turning centre during the machining of C45 medium carbon steel material. The cutting tool material was cubic boron nitride. Cutting speed was selected with respect to the high-speed cutting (HSC) based on previous studies. In the experiment, cutting force components were recorded. From the results, a decreasing trend in the cutting force values was observed from the cutting speed higher than 1100 m.min-1. It can be caused by changing of metallurgical and mechanical properties in the cutting zone because the overall cutting resistance during HSC was reduced. Chips changed colour to orange during the machining due to temperature changes. No great benefit was observed when high-speed cutting for turning medium carbon steel material. The inefficiency, in this case, is caused by the high price and low tool life of the CBN cutting inserts as well as the cutting force that decreases slowly after the initial increase with a rapidly increasing cutting speed.

Change in the molecular properties of CH1641 prions after transmission to wild-type mice: Evidence for a single strain.

CH1641 was discovered in 1970 as a scrapie isolate that was unlike all other classical strains of scrapie isolated so far. We performed bio-assays of CH1641 in mice in order to further characterise this specific isolate. We inoculated the original CH1641 isolate into ovine and bovine prion protein (PrP) transgenic mice as well as wild-type mice. In addition, we performed cross- and back passages between the various mouse lines to examine if one identical prion strain was isolated in all mouse lines or whether multiple prion strains exist in CH1641. We report the first successful transmission of CH1641 to wild-type RIII mice and via RIII mice to wild-type VM mice. Unexpectedly, analysis of the protease-resistant prion protein (PrPres ) in wild-type mice showed a classical scrapie banding pattern differing from the banding pattern of the original CH1641 isolate. Cross- and back passages of CH1641 between the various mouse lines confirmed that the same prion strain had been isolated in all mouse lines. The CH1641 isolate consists of a single prion strain but its molecular banding pattern of PrPres differs between wild-type mice and PrP transgenic mice. Consequently, molecular banding patterns of PrPres should be used with caution in strain typing since they do not solely depend on the properties of the prion strain but also on the host prion protein.

Cooling Techniques for Enhanced Efficiency of Photovoltaic Panels—Comparative Analysis with Environmental and Economic Insights

Photovoltaic panels play a pivotal role in the renewable energy sector, serving as a crucial component for generating environmentally friendly electricity from sunlight. However, a persistent challenge lies in the adverse effects of rising temperatures resulting from prolonged exposure to solar radiation. Consequently, this elevated temperature hinders the efficiency of photovoltaic panels and reduces power production, primarily due to changes in semiconductor properties within the solar cells. Given the depletion of limited fossil fuel resources and the urgent need to reduce carbon gas emissions, scientists and researchers are actively exploring innovative strategies to enhance photovoltaic panel efficiency through advanced cooling methods. This paper conducts a comprehensive review of various cooling technologies employed to enhance the performance of PV panels, encompassing water-based, air-based, and phase-change materials, alongside novel cooling approaches. This study collects and assesses data from recent studies on cooling the PV panel, considering both environmental and economic factors, illustrating the importance of cooling methods on photovoltaic panel efficiency. Among the investigated cooling methods, the thermoelectric cooling method emerges as a promising solution, demonstrating noteworthy improvements in energy efficiency and a positive environmental footprint while maintaining economic viability. As future work, studies should be made at the level of different periods of time throughout the years and for longer periods. This research contributes to the ongoing effort to identify effective cooling strategies, ultimately advancing electricity generation from photovoltaic panels and promoting the adoption of sustainable energy systems.

Heavy-duty gas turbine 3D blade modelling and flow field analysis

Hydrogen-fuelled heavy-duty gas turbine is an important trend of gas turbine due to its low emission characteristics. Due to the change of components and thermodynamic properties of the fuel, the physical properties of the working fluid of the turbine will change and affect the performance of the gas turbine. In this study, through 3D scanning and inverse modelling, the parametric models of the turbine blades were obtained. CFD analysis was conducted to analyse the change of thermodynamic performance and flow field under different fuel, which is natural gas, 50% natural gas and 50% hydrogen and hydrogen. The result of the CFD indicated that the efficiency of natural gas fuelled working flux is 92.86%, and decreased by 0.19% and 0.83% with hydrogen doped in. It is analysed that though the increased magnitude of relative velocity with hydrogen doped in, the increased flow attack angle of the rotor, from -4.74°, to -3,61°, to -1.88° with hydrogen doped in, caused the split of rotor leading edge cooling air and decreased the efficiency of the turbine stage. Modification of blade metal angle could boost the efficiency of the turbine stage under hydrogen-doped fuel.

CaO:Tb&lt;sup&gt;3+ &lt;/sup&gt; green-emitting phosphor for white light-emitted diode-phosphor applications: the improvement of light output intensity

The use of CaO:Tb3+ with light green emission on for improvement of both luminescent output and chromatic fidelity of the white light emitted from a light-emitting diode (LED). The CaO:Tb3+ is combined with the yellow-emitting phosphor of YAG:Ce3+ to provide sufficient colored spectral proportion for the white light generation, enhancing the color performance. The phosphor combination is utilized for the three most applied LED structures: conformal, in-cup, and remote phosphor structures. The changes in optical properties of these three LEDs are monitored with adjustments in the proportion of CaO:Tb3+. The higher proportion of the green phosphor results in higher scattering efficiency in all structures, offering better color coordination and stronger luminous flux. The color quality scale is somehow reduced when CaO:Tb3+ concentration is more than a certain level. Therefore, depending on the phosphor configuration of the white light-emitting diode (WLED), the concentration of CaO:Tb3+ should be modified to achieve a good color rendition with improved color consistency and luminous properties.

Experimental Research on Mechanism Impairment and Reinforcement of Empty Bucket Wall

In this study, the raw material for the empty bucket wall consists of Dalun bricks unique to South Zhejiang. The investigation focuses on the changes in compressive properties of the empty bucket wall with masonry mortar strength grades of M 2.5, M 5.0, M 7.5, and M 10.0 after a designated period of maintenance in both dry and wet environments. Following this, the empty bucket wall undergoes reinforcement, and the compressive properties are studied. The ensuing comparisons yield pertinent conclusions. Unreinforced walls maintained with varying mortar strengths in a wet environment exhibit reduced cracking loads by 5.8 to 30% and damage loads by 5.6 to 10.8% compared to their counterparts in a dry environment. Reinforced walls, maintained with different mortar strengths in wet environments, show reduced cracking loads by 6.2% to 36% and damage loads by 2.5% to 5.7% compared to those in dry environments. The stress–strain curves of unreinforced and reinforced barrel walls of various strength classes are obtained by fitting the test stress–strain data to the stress–strain data derived from corresponding model equations. These stress–strain curves for unreinforced and reinforced walls align well with the model curves, affirming the precision of the tests.

Effect of Irradiation Temperature and Atmosphere on Aging of Epoxy Resins for Superconducting Magnets.

The superconducting magnets of future particle accelerators will be exposed to high irradiation doses at cryogenic temperatures. To investigate the effect of irradiation temperature and atmosphere on the aging behavior, we have characterized the changes in thermomechanical properties of six epoxy resins for potential use in superconducting magnets after irradiation up to 20 MGy in ambient air, inert gas, and liquid helium. Based on the results obtained by Dynamic Mechanical Analysis (DMA), we discuss the effect of irradiation temperature and the presence of oxygen. The irradiation temperature can have a strong influence on the rates at which cross-linking and chain scission occur.

Bandgap engineering—Influence of the evolution of (Zn/Mg)Al2O4:Cr3+ spinel phosphors on the photoluminescence properties

AbstractAs a luminescent center ion in materials for deep red and near‐infrared light, Cr3+ has been extensively studied in octahedral host materials. In this study, using zinc aluminate (ZnAl2O4) and magnesium aluminate (MgAl2O4) spinels with abundant octahedra as substrates, a series of Zn1−xMgxAl2O4:0.5%Cr3+ (x = 0, 0.2, 0.4, 0.6, 0.8, and 1) fluorescent powders were first prepared via a high‐temperature solid‐state method. The influence of different Mg/Zn ratios on (Zn/Mg)Al2O4:0.5%Cr3+ optical properties was thoroughly explored. Experimental results show that an increase in the Mg/Zn ratio reduces the crystal field strength (Dq) and leads to distortion of the [AlO6] octahedra, resulting in broadening of the photoluminescence emission spectrum. Furthermore, the addition of Mg gradually reduces the formation of inverse spinel. An appropriate Mg/Zn ratio can improve luminescent intensity and quantum efficiency. In summary, this paper, through bandgap engineering by adjusting the Mg/Zn ratio, provides a detailed account of the changes in optical properties and the underlying mechanisms during the transition from ZnAl2O4:0.5%Cr3+ to MgAl2O4:0.5%Cr3+ spinels. It offers valuable insights for further research on the practical applications of Cr3+ in areas such as lighting displays and bioimaging.