Variations In Physical Properties Research Articles

MICROCOMPOUNDING OF SMALL SAMPLES OF NATURAL RUBBER

ABSTRACT We describe a microcompounding method that can be used to characterize and compare cured small natural rubber samples. First, commercial Hevea and dried guayule (Parthenium argentatum) latex samples were microcompounded to validate the method. Latex was then extracted from the ground branches of six greenhouse shrubs of different ages and genotypes of wild type and transgenic guayule and coagulated into rubber samples. Size exclusion chromatography showed that the samples had different molecular weights and oligomer content. Little variation in physical properties was found between rubber extracted from shrubs of different age within a genotype, but a larger variation among genotypes was found. The new method allows testing of cured rubber samples from experimental variants and early screening out of genotypes to assess the impact of variations in cultivation practices or lab-scale processing conditions on rubber quality.

Development of a high-strength lightweight geopolymer concrete for structural and thermal insulation applications

Investigating the thermal insulation properties of lightweight geopolymer concrete is essential. This paper aims to develop a lightweight aggregate geopolymer concrete (LWAGC) with good density, compressive mechanical and thermal insulation properties. The dry density of LWAGC was adjusted by incorporating expanded perlite (EP). The variation in physical and mechanical properties of LWAGC with different EP content was discussed, including dry density, P-wave velocity, ultimate compression strength and elastic modulus. Based on infrared thermal imaging technology, a rapid measurement method was proposed to simulate the indoor temperature change of buildings at high ambient temperatures. The thermal insulation performance of the LWAGC with different EP contents was further evaluated. The findings show that as the EP content in LWAGC increases, there is a corresponding decrease in P-wave velocity, dry density, ultimate compressive stress, and elastic modulus. The lowest dry density of LWAGC reaches 1209kg/m3 while the ultimate compressive stress is still larger than 25.0MPa, which can used as LC25 building materials in load-bearing structures. The results also show that the addition of EP can improve the thermal insulation properties of LWAGC. The LWAGC with 50% EP content has the highest reduction rate of temperature and can maintain the indoor temperature lower than 35 °C under high ambient temperature, which have potential application prospects in the load-bearing structures and thermal insulation of tall buildings.

Utilizing the Gravity Method to Detect the Potential Effect of the Salt Dome in the Nahr Omar Oilfield, Southern Iraq

Geophysics is one of the branches of Earth sciences and deals with studying the Earth's interior by studying the variation of physical properties within rock layers. Applied geophysics depends on procedures that involve the measurements of potential fields, such as the gravitational method. One of the significant oil fields in southern Iraq is represented by the Nahr Omar structure. A power spectrum analysis (SPA) technique was used to collect gravity data within the chosen oil field area in order to confirm the salt dome in the subsurface layers. The analysis of SPA resulted from six surfaces representing the gravity variation values of the depths (m)14300, 3780, 3290, 2170, 810, and 93.5. Gravity surfaces have been converted to density surfaces to determine density and velocity models from these six depth slices. The inverted data were consistent with the Nafe and Drake standard curves of converting densities to average velocities. The current study illustrated the benefit/assist of the inversion technique of gravity data to average velocity, to a large extent, in detecting the salt dome effects on the subsurface strata for the Nahr Omar oilfield. In comparison, the decrease in the average velocity of the salt dome area is related to this effect. The acquired inversion results were supported by available seismic data within the Nahr Omar area and utilized the seismic attributes processing technique.

Topology optimization of microreactors for hydrogen production by ammonia catalytic decomposition

Microreactor is a promising technique for producing hydrogen by ammonia catalytic decomposition. In this study, a topology optimization (TO) model is developed to optimize the distribution of porous catalysts in microreactors to improve the conversion from ammonia (NH3) to hydrogen (H₂), which considers the fully coupled processes of flow, heat transfer, mass transport and reaction with variable physical properties. Dual objectives of reducing the flow resistance and decreasing the average temperature of the microreactor are employed for the TO model to generate innovative structures. The effects of different weight coefficients, input heat, volume fractions of the catalyst, and microreactor sizes on TO structures are explored. As validated by three-dimensional (3D) simulations, the TO microreactor can obtain lower pressure drop, lower average temperature, and higher NH3 conversion compared to traditional microreactors. At a weight coefficient of 0.95 and a catalyst volume fraction of 0.6, the optimized microreactor shows a 5.78% increase in NH3 conversion, an 18.05% decrease in pressure drop, and a 4.26% decrease in average temperature compared to the traditional straight-channel microreactor. Finally, it is interesting to find that all TO structures generated are characterized by the gradually decreased size of the catalyst block along the flow direction which allows more NH3 to be decomposed at higher temperature regions with higher reaction rates, leading to higher conversion. The present study provides valuable insights for the design of next generation microreactors with enhanced performance.

Examining the brightness variability, accretion disk, and evolutionary stage of the binary OGLE-LMC-ECL-14413

Several intermediate-mass close binary systems exhibit photometric cycles longer than their orbital periods, potentially due to changes in their accretion disks. Past studies indicate that analyzing historical light curves can provide valuable insights into disk evolution and track variations in mass transfer rates within these systems. Our study aims to elucidate both short-term and long-term variations in the light curve of the eclipsing system with a particular focus on the unusual reversals in eclipse depth. We aim to clarify the role of the accretion disk in these fluctuations, especially in long-cycle changes spanning hundreds of days. Additionally, we seek to determine the evolutionary stage of the system and gain insights into the internal structure of its stellar components. We analyzed photometric time series from the Optical Gravitational Lensing Experiment (OGLE) project in the $I$ and $V$ bands, and from the MAssive Compact Halo Objects (MACHO) project in the $B_ M $ and $R_ M $ bands, covering a period of 30.85 years. Using light curve data from 27 epochs, we constructed models of the accretion disk. An optimized simplex algorithm was employed to solve the inverse problem, deriving the best-fit parameters for the stars, orbit, and disk. We also utilized the Modules for Experiments in Stellar Astrophysics ( MESA ) software to assess the evolutionary stage of the binary system, investigating the progenitors and potential future developments. We found an orbital period of 38.15917 pm 0.00054 days and a long-term cycle of approximately 780 days. Temperature, mass, radius, and surface gravity values were determined for both stars. The photometric orbital cycle and the long-term cycle are consistent with a disk containing variable physical properties, including two shock regions. The disk encircles the more massive star and the system brightness variations align with the long-term cycle at orbital phase 0.25. Our mass transfer rate calculations correspond to these brightness changes. MESA simulations indicate weak magnetic fields in the donor star's subsurface, which are insufficient to influence mass transfer rates significantly.

Oxidation effects on the optical and electrical properties of MoS2 under controlled baking temperatures

As silicon-based semiconductor technology scales down to the nanoscale, it encounters significant physical limitations, including reduced electron mobility, short-channel effects, and increased heat generation, which hinder device performance and reliability. Two-dimensional (2D) semiconductors, such as molybdenum disulfide (MoS2), offer great potential with superior electrical properties at the nanoscale, but the issue of excessive heat generation in highly integrated circuits persists. Therefore, it is essential to investigate the thermal durability of MoS2 under various heating conditions and its impact on physical properties and device performance. In this study, we systematically investigated the oxidation behavior and related physical property variations of CVD-grown MoS2 monolayers by baking them at different temperatures. It was clearly revealed that high-temperature baking induces p-doping and structural deformation, significantly altering optical and electrical properties. Despite the degradation in device performance, reduced interfacial Coulomb scattering was observed, suggesting potential for improved device stability. This study underscores the importance of understanding thermal stability to accelerate the development of 2D semiconductors for next-generation electronic devices.

Variation of Physical Properties of Eucalyptus globulus Grown in Ethiopia

Variation of Physical Properties of Eucalyptus globulus Grown in Ethiopia

Elevation-dependent dynamics of soil properties in a hilly watershed: a landform-based approach.

Understanding the variation of soil physical properties in relation to land use and elevation is essential for modeling soil-landscape relationships and sustainable land management. Hence, this study investigates the spatio-temporal variability of soil physical properties in a lower Himalayan watershed, where agriculture, forest, and grasslands are dominant. Samples from 104 sites in a 422 km2 watershed were collected using a gridded sampling scheme (2km × 2km resolution) over 57weeks. Spatial patterns were analyzed using the Kriging technique, and Spearman rank correlation was employed to identify landform-dependent correlations between soil properties and elevation. The interdependence of the properties was detected using principal component analysis (PCA), while the random forest (RF) approach explored the factors influencing electrical conductivity (EC), organic content (OC), soil temperature (ST), and soil moisture (SM). The results revealed that forest landforms have higher coarser fractions (40%) compared to other landforms, while grasslands have higher soil fines (66%). A positive correlation was observed for elevation with sand content (0.15*), organic content (0.42*), and specific gravity (0.03), while a negative correlation was observed for silt (0.10), clay (0.21*), bulk density (0.52*), electrical conductivity (0.41*), soil moisture (0.28*), and temperature (0.31*). Elevation, soil texture, and specific gravity were identified as critical controls for EC, OC, ST, and SM, emphasizing the importance of soil properties, especially elevation and texture, in shaping spatial distributions. These findings contribute to creating a high-resolution regional inventory for effective land use management, adaptation to climate change, and improved livelihood, specifically for mountain people.

Amorphous to Polycrystalline Phase Transition of In Situ Annealed Ge Films: Structural, Morphological, Optical, and Electrical Characteristics

AbstractRadio Frequency (RF) sputtered germanium (Ge) thin films were deposited on glass substrate at in situ annealing temperatures of 400, 450, 500, 550, and 600 °C. X‐ray diffraction (XRD) and Raman spectroscopy revealed that the Ge films were initially amorphous but transformed to polycrystalline after annealing at 450 °C. Further annealing up to 600 °C resulted in improved crystallinity. Strain studies of the films using XRD and Raman showed compressive (out‐of‐plane) and tensile (in‐plane) strains, respectively, throughout all the annealing temperatures. The surface morphology of the films was recorded using atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM), which showed grain growth with annealing temperatures. The optical energy gap evaluated from absorption spectra for crystalline films decreased with annealing temperature, indicating improvement in crystallinity of films. The resistivity of the films deduced using current‐voltage measurements was found to decrease with annealing temperature, which can be attributed to enhancement in grain size. This study establishes a correlation between strain, grain size, optical energy gap, and electrical resistivity with temperature for Ge films deposited on glass substrates. Thus, the present study provides insights into variation in physical and electrical properties of films with in situ annealing temperature for their applicability in optoelectronic devices.

Effects of alpine meadow degradation on the soil physical and chemical properties in Maqu, China

While alpine meadow degradation presents a significant ecological challenge, research on the complex patterns of soil property changes induced by degradation has been somewhat limited. In this study, we investigated the Maqu alpine meadow, meticulously categorizing it into different grassland types exhibiting varying degrees of degradation based on factors such as vegetation coverage and community, soil characteristics, and landscape features. These classifications included typical grassland, degraded grassland, desertified grassland, and sandy land. In August 2018, we established three quadrats at each sample point and collected soil samples at five depths (surface (0–2 cm), 2–5 cm, 5–10 cm, 10–20 cm, and 20–40 cm) to analyze soil particle size distribution (PSD) and nutrients content. The results revealed a discernible trend: alpine meadow degradation led to selective loss of nutrient-rich soil fine particles, resulting in significant alterations in soil PSD and nutrients, particularly pronounced in grasslands with low degrees of degradation. Moreover, within a specific range of degradation degree, the clay content in the shallow soil of alpine meadow increased with the degradation degree, but it declined when the degradation degree exceeded a certain threshold. Degradation also disrupted the intricate relationship between soil nutrients, with notable variations in their coupling. This difference was also reflected in the influence of soil physical and chemical properties on soil nutrients, with the explanatory power of each environmental indicator on soil nutrients decreasing significantly with increasing degradation. This study systematically analyzed the variation in soil physical and chemical properties throughout the degradation process, revealing the mechanism of soil nutrient imbalance and decline caused by the degradation process. It provides crucial theoretical foundations and reference points for the preservation and rejuvenation of alpine meadows, enriching the methodology for assessing the impact of grassland degradation.

Mapping Microplastic Movement: A Phase Diagram to Predict Nonbuoyant Microplastic Modes of Transport at the Particle Scale.

Microplastics pose numerous threats to aquatic environments, yet understanding their transport mechanisms remains limited. Drawing from natural sediment research provides valuable insights to address this knowledge gap. One key dimensionless number used to describe sediment transport is the transport stage, referring to the ratio between the flow shear velocity and the particle settling velocity. However, variations in physical properties, such as shape and density, raise concerns about the applicability of existing sediment transport theories to microplastics. To address this challenge, we employed a physical modeling approach, examining 24 different nonbuoyant microplastic particles in a turbulent open channel flow. Utilizing 3D particle tracking, a total of 720 trajectories were recorded and analyzed. Microplastic particles exhibited transport modes akin to natural sediments, including rolling/sliding, saltation, and suspension. The transport stage strongly correlated with these modes, as well as with the mean forward velocity and mean position in the water column. Notably, particle shape emerged as a critical factor influencing transport dynamics. Due to their lower settling velocity, fibers tended to stay closer to the water surface with lower forward velocities compared to spheres. Based on the laboratory results, a new phase diagram for microplastics is introduced analogous to an existing diagram for sediments.

Thermal calculation and experimental study of a double-disk magnetic coupler

Aiming to tackle the difficulties and inaccuracies in calculating the temperature field of double-disk magnetic coupler, a novel thermal calculation method is proposed, integrating the equivalent thermal network method and CFD method. This approach deviates from traditional methods that substitute empirical formulas with rotational speed. An equivalent thermal network model is established to ascertain the temperature rise at each network node. Additionally, a fluid-solid coupling model is constructed, and the impact of uneven air temperature distribution on air density, specific heat capacity, dynamic viscosity, and thermal conductivity is analyzed using the least squares method. The results reveal that after incorporating variable temperature air physical properties, the high-temperature area of the copper conductor decreases, the calculated temperature rise aligns closer to actual values, and air friction loss on the copper surface is reduced by 6.5 %. Experimental verification, conducted on a 55 kW double-disk magnetic coupler, demonstrates maximum errors of 8.86 % and 6.53 % when comparing experimental values to those calculated by the equivalent thermal network method and CFD method, respectively, thereby validating the proposed method. This research provides a theoretical reference for thermal calculations in double-disk magnetic coupler.

Effects of overconsolidation on seismic rock physics — A comparative study between unconsolidated sands and weakly cemented sandstone

In seismic rock physics, models typically assume rocks are normally consolidated, often neglecting the effects of overconsolidation. Recent studies reveal that overconsolidated sands, resulting from stress release, show different physical property variations than normally consolidated sands. However, similar research is lacking for weakly cemented sandstones, a common reservoir analog. This study aims to systematically compare the effects of overconsolidation and stress direction on unconsolidated sandstones and weakly cemented sandstones. It also assesses the impact of overconsolidation on seismic interpretation, monitoring, and rock physics modeling applied to the two types of rocks. Experimental measurements of porosity, P-wave, and S-wave velocities were collected under different stress paths between loading and unloading. For weakly cemented sandstone, well-log data from the Norwegian Sea and Barents Sea were compared with experimental data. Analyses focused on the velocity-porosity relationship, VP/VS ratio vs. AI, and VP/VS ratio vs. effective stress.

Effect of gamma and neutron irradiations on the physical, magnetic and electrical properties of Ni–Cu–Cd nano-ferrites

The physical, magnetic and electrical properties variations for the sol-gel auto combustion synthesized Ni0.3Cu0.2Cd0.5Fe2O4 by gamma (γ) and neutron irradiations dose applications are studied in this research. The irradiation have been done through 2.0 × 1011 and 1.9 × 1012 cm−2s−1 per min fast neutron flux and γ rays from the research reactor of TRIGA MARK-II and 64 KCi cylindrical 60Co source respectively within room temperature. The rate of 1 Mrad and 3 Mrad dose is 1.067 Mrad/h. XRD results show greater intensities for the irradiation doses. Due to the redistribution of ions, changes in the lattice constant have been found by the irradiation through the results of XRD and Rietveld Refinement process. The saturated magnetization obtained from the VSM is found to decrease first by the irradiation and then increase drastically. This analysis is performed by the popular pulse field technique of hysteresis loop for nano ferrites and further analyzed by LAS. The frequency dependent characteristics such as dielectric constant, electric modulus, impedance analysis and ac conductivity are inspected for all samples with both types of irradiation process. The electrical modulus Cole-Cole plots insure the dominant property as electric stiffness for investigated ferrties. Extreme decrease has been found in the dielectric natures which also show good agreement in the higher ac conductivity nature at the higher frequencies. Electrical parametric dependent overlapping two semicircles which are not complete have been found in the plots of Cole-Cole for impedance data. The energy of activation for the process of diffusion decreases by the irradiation.

Numerical simulation of heat transfer properties of skin tissue acted on repetitive laser irradiation

Pulsed laser has been widely used in the clinical treatment of various diseases and injuries due to its unique advantages in the process of interaction with skin tissue. In order to ensure the therapeutic effect and patient safety, it is necessary to accurately monitor the time-space response of the whole-field temperature of the target tissue irradiated by pulsed laser. A research strategy to explore the thermal response and incidental thermal damage of skin tissue induced by repeated pulses laser has been proposed in present work. A theoretical model involved variable physical properties was first proposed, in which the dual-phase lag (DPL) equation and Henrique burn equation were employed to evaluate the tissue temperature and thermal damage induced by repeated pulse laser irradiation. With the help of finite difference method, the governing equation with variable physical properties was then numerical solved to obtain the time-space distribution of tissue temperature, and the evolution process of the thermal damage was further calculated. The effects of laser input parameters and variable physical parameters on the laser penetration depth, temperature distribution and burn degree of the irradiated tissue were analyzed.

Li2O concentration influenced local structure and properties of molten LiCl salt by machine learning driven molecular dynamics simulation

Pyroprocessing is one of the promising technologies for the reprocessing of spent nuclear fuel. In the electrolytic reduction process of pyroprocessing, LiCl serves as the electrolyte with a minor addition of Li2O as the initial oxygen ion input. Investigating the impact of Li2O concentration on the molten salt system is essential for enhancing the efficiency of electrolytic reduction. In the present study, the LiCl-Li2O system is simulated using deep potential molecular dynamics simulation. The properties including self-diffusion coefficient, shear viscosity, ionic conductivity, heat capacity, radial distribution functions, coordination numbers, short-range order, medium-range order, Voronoi structure, and angle distribution functions are explored at different Li2O concentrations. This study reveals that the variations of physical properties at different Li2O concentrations in LiCl molten salt can be attributed to the changes in local structure. For example, unnormal high proportions of two Voronoi structures are found in the molten salt when the Li2O concentration increases, which may explain the changes of properties. These findings offer valuable insights for refining the parameters of electrolytic reduction and elucidating the correlation between microscopic and macroscopic phenomena.

Soil Physical and Chemical Properties under Shea Tree (Vitellaria paradoxa) at Different Stages of Growth

Shea tree (Vitellaria paradoxa), is one of the dominant agro-forestry species in Otuke district of Northern Uganda. Due to its economic importance and, in line with the numerous threats the tree is faced with, there is an urgent need for measures to conserve this species, for example, through incorporating annual food crops in the Shea tree parkland. This, however, requires a better understanding of tree-soil-food crop interactions. A number of studies of this aspect either considered only the mature Shea tree gardens or did not provide a clear distinction between the physiological states of the Shea tree. This was the motivation for this study where we compare variation in soil properties under mature and young Shea tree gardens with sites not having trees in Okwang sub-county, Otuke district. Five soil samples (up to 15 cm deep for top soil and 15-30 cm for sub-soil) were obtained per treatment using a soil auger. Our results show that in the top soil, only percent sand varied among the treatments, while, in the sub-soil, only percentage nitrogen and average phosphorus varied among the treatments. We also found that percentage top soil organic matter and percentage of sub-soil sand had negative strong correlations with maize and soybean yields, while percentage sub-soil clay had a strong positive correlation with maize and soybean yield. We conclude that variations in soil physical and chemical properties under Mature and Young Shea gardens only occur for those properties that have a direct link to tree residues

A low-Mach volume-of-fluid model for the evaporation of suspended droplets in buoyancy-driven flows

This study introduces a comprehensive numerical model capable of simulating the evaporation of suspended droplets under different gravity conditions. Unlike previous studies, this work provides a detailed description of the multicomponent evaporation process by integrating: (i) interface-resolved evaporation; (ii) suspension by the action of the surface tension force, and (iii) variable physical properties. The model effectively captures complex phenomena such as thermal expansion, natural convective fluxes, and liquid internal recirculation, which cannot be directly resolved using more widespread spherically-symmetric models. Validation against experimental data confirms the model’s accuracy in predicting the droplet evaporation dynamics, and its utility in resolving discrepancies between prior numerical simulations results and experimental data. The model was implemented in the Basilisk framework; both the code and the simulations setups are freely available on the Basilisk sandbox.

Aggression to Biomembranes by Hydrophobic Tail Chains under the Stimulus of Reductant.

Stimulus-responsive materials hold significant promise for antitumor applications due to their variable structures and physical properties. In this paper, a series of peptides with a responsive viologen derivative, Pep-CnV (n = 1, 2, 3) were designed and synthesized. The process and mechanism of the interaction were studied and discussed. An ultraviolet-visible (UV) spectrophotometer and fluorescence spectrophotometer were used to study their redox responsiveness. Additionally, their secondary structures were measured by Circular Dichroism (CD) in the presence or absence of the reductant, Na2SO3. DPPC and DPPG liposomes were prepared to mimic normal and tumor cell membranes. The interaction between Pep-CnV and biomembranes was investigated by the measurements of surface tension and cargo leakage. Results proved Pep-CnV was more likely to interact with the DPPG liposome and destroy its biomembrane under the stimulus of the reductant. And the destruction increased with the length of the hydrophobic tail chain. Pep-CnV showed its potential as an intelligent antitumor agent.

Numerical simulation of the thermo-mechanical coupling behavior of skin tissue exposed to repetitive pulse laser irradiation

A thorough understanding of the thermo-mechanical coupling behavior during the interaction between pulsed laser and skin tissue is a prerequisite for successful application of pulsed laser technology in the treatment of various skin diseases and injuries. Taking into account the complex physiological structure of skin tissue, a theoretical model is established to characterize the thermo-mechanical response of multi-layer skin tissue with variable physical properties, in which the non-linear governing equations of bio-thermo-mechanics with dual-phase lag mechanism and Henrique burn equation are involved. The finite difference method was employed to obtain the time-space distribution of skin temperature, displacement and stress under repeated pulse laser action, and the incidental thermal damage was further evaluated on this basis. The numerical results stated that: i) repeated pulse laser can significant reduce the peak temperature of skin tissue and further reduce or even eliminate thermal damage under the premise of required energy threshold, ii) the thermo-mechanical coupling response and potential thermal damage will be inhibited when the temperature dependence of physical parameter is considered, in which the thermal stress is more sensitive to the temperature dependence than others, iii) the thermal damage is more sensitive to the input parameters than that of thermo-mechanical response, and the burn time can be effectively delayed or even avoided for appropriate input options.