Expansion Phenomenon Research Articles

Experimental study under thermal shock environment to investigate effect of welding width on properties of ultrasonically welded joints of multiple copper cables

Based on the ultrasonic welding technology, this study uses three different welding widths to weld copper cables with different specifications. The influence of welding width on the mechanical properties and microstructure of each group of welded joints was systematically studied for the first time. The thermal shock test was carried out for each group of welded joints under optimum welding width to simulate the influence of severe temperature change environment on joint performance. It is found that the cross-sectional area of joint is 20 mm2 and optimal welding width of joint composed of two and three cables is 7 mm. The optimal welding temperature of the joint composed of four cables is 5 mm. Under the optimal welding width, the average shear strength of two-cable joint reaches 309.4 N. The four-cable joint is only 232.2 N. Moreover, the welding strength weakens significantly as the number of cables and the peak temperature decreases. The high temperature of bonding interface is the key factor to form a good weld. The peak temperature during welding is negatively correlated with the porosity of joint and positively correlated with peeling strength of joint. In addition, the morphology of ultrasonically welded joints has changed obviously after thermal shock test. With the participation of oxygen, the surface of welded joint is gray and bright brass, while the interior of joint is purple due to lack of oxygen. Moreover, the phenomenon of atomic diffusion and thermal expansion generates joints which were initially in a mechanically interlocked form and welding interface of the metallurgical bond under the action of high temperature. So the maximum joint peel strength is slightly improved.

Sustainable stabilization/solidification of Cu-contaminated seasonal frozen soil by epoxy resin: environmental risk assessment and engineering applicability

There are significantly toxic Cu contaminants in seasonal frozen soil areas under industrial production and mineral exploitation. However, the hydration reactions of mainstream alkaline curing agents such as cement are disturbed by the solidification and thawing of moisture, and their solidification/stabilization is ineffective to heavy metals. Therefore, there is an urgent requirement to optimize the use of current curing agents to improve the solidification/stabilization (S/S) effect of Cu contaminants in seasonal frozen soil areas. In this study, the Epoxy resin (EP) with excellent waterproofing and frost resistance was incorporated into artificially prepared Cu-contaminated soil to maintain a steady engineering application strength and inhibit the outward diffusion of toxic Cu contaminants under freeze-thaw cycles. The freeze-thaw resistance of EP-cured Cu-contaminated soil and the feasibility of EP remediation technology have been investigated, including mechanical properties, environmental effects and microstructure. The decline in mechanical strength and the increment in Cu leaching during freeze-thaw cycles are effectively suppressed by the remediation of EP. Even after 8 freeze-thaw cycles, there is merely a mechanical strength decline of 5%, solely a secondary Cu leaching of 4.74mg/L, and astonishingly a leachable index of 11.70 in the specimens with 12% EP dosage. The expansion phenomenon of pores and clay fractures under freeze-thaw cycles were gradually alleviated after incorporation of EP. The above results demonstrate the Cu-contaminated seasonal frozen soil remedied by EP are high-strength, basically non-toxic, and environmentally friendly material which are suitable for in-situ stabilization/solidification in seasonal frozen soil areas.

Modeling the stability of air flows in inclined workings in case of fire

Purpose. Development of a mathematical model and study of the processes occurring during conveyor belt fires in inclined mines to determine the mechanism of air flow distribution under appropriate conditions. Methods. Practical measurements of the distribution of air flows in an inclined conveyor operated at the mining and processing plant of PJSC ArcelorMittal Kryvyi Rih were carried out. Based on the obtained data, a mathematical model was crea-ted, which was then used to perform Computational Fluid Dynamics (CFD) modeling of gas flows in the mine under normal conditions and in the event of a fire with a thermal capacity of 9 MW. Findings. The study reveals the peculiarities of gas flows during the combustion of a conveyor belt in inclined workings, as well as the influence of turbulence on the flow, changes in the density of gases during heating, and the impact of gravity on the distribution of gases in the cross-section and along the length of the workings. A fire centre with a heat output of 9 MW has a significant impact on the distribution of air flows. The phenomenon of thermal expansion results in a 59.2% increase in the volume of gases behind the fire. The thermal expansion of gases and their low density have a significant impact on the formation of gas flows in inclined workings. As the jet moves away from the centre of the fire, the velocity of the jet gradually increases, reaching a value of 12.4 m/s. This results in a notable alteration in the distribution of total pressure across adjacent workings, accompanied by an increase in flow turbulence. Consequently, the mass of air exiting the right branch is observed to have a five-fold increase in comparison to the pre-fire state. The overturning of the jet from the left branch of the workings gives rise to the exclusive distribution of combustion products along the right branch. Originality. The study helps to understand the mechanism of jet overturning and the peculiarities of the distribution of combustion products in case of fire in inclined conveyor workings. Practical implications. The results of the research allow us to predict the probability of fire, identify the most dangerous areas for fire, and plan the most rational actions for firefighting in specific unique conditions.

Foaming mechanisms in ball milling prepared borosilicate glass powder

Thanks to their exceptional thermal and electrical properties, borosilicate glasses are widely used in chip packaging and electronic pastes. Nonetheless, borosilicate glass powders suffer from the phenomenon of foaming and expansion during sintering process, which greatly affects the sintering densities of the powders and poses limitations to their applications. Herein, we explored the foaming mechanism of borosilicate glasses by ball milling. The foaming of borosilicate glass is due to the adsorption of CO2 from the atmosphere by the glass powder during ball milling. The CO2 forms carbonates on the surface of the glass powder and is released during the sintering process, leading to foaming. Additionally, as the specific surface area of the glass powder increases, its corrosion resistance decreases while its foaming strength increases. The foaming strength of the four glass powders, listed in ascending order, is: SrO-B2O3-SiO2, ZnO-B2O3-SiO2, BaO-B2O3-SiO2 and CaO-B2O3-SiO2. Meanwhile, it was found that the foaming strength could be weakened better by ball milling organic modification method. These findings contribute to a deeper understanding of the glass foaming phenomenon. Furthermore, they offer practical strategies to reduce the foaming and optimize the performance of borosilicate glass-based materials in applications of chip packaging and electronic pastes.

Influence of thermal expansion and wear on the temperatures and stresses in railway disc brakes

Thermo-mechanical coupled systems are typically complex, however, the demand for analyses of this kind of multi-physics system is increasing, for example, accurately predicting the temperature and thermal stress of the railway disc brakes. However, many models ignore the phenomenon of thermal expansion and wear on brake pads. Therefore, their influence on the result is unclear. This research aims to investigate the effect of these two phenomena on the temperatures and stresses. These influences represent different heat flux input methods. Based on the finite element method (FEM), a three-dimensional (3D) transient thermo-mechanical model is built up. Three cases with or without thermal expansion and wear are conducted. The model is validated against measurement data. Simulation results show that thermal expansion and wear on the brake pads cause a 10% difference in the average temperatures of the brake discs, while a 257% difference in the maximum temperatures. As for the equivalent stresses (Von Mises stress), the difference can reach 3500%. Overall, this research builds a thermo-mechanical model and quantifies the effects of thermal expansion and wear on the temperatures and stresses of railway brake discs. The model can be transferred to other thermo-mechanical coupled multi-physics systems.

A memory interaction quadratic interpolation whale optimization algorithm based on reverse information correction for high-dimensional feature selection

Feature selection is a key technique for data dimensionality reduction, and there are many challenges in facing the exponential expansion phenomenon of high-dimensional decision space. In order to improve the quality of feature selection, we propose a memory interaction quadratic interpolation whale optimization algorithm based on reverse information correction (RQWOA). First, in order to improve the convergence capability of the Whale Optimization Algorithm (WOA) in high-dimensional space, we propose a quadratic interpolation mechanism with memory information interaction, improve the quality of the datum points used for quadratic interpolation through the proposed memory interaction mechanism, and accelerate the convergence speed and accuracy of the algorithm with the help of the quadratic interpolation on the algorithm exploitation capability. In addition, to address the invalid probability flip in the feature selection subset when mapping to the discrete space, we propose a reverse information correction mechanism to judge and correct each dimension in the feature subset by using the reverse complementary information provided by individuals with poor fitness values in the population, so as to better remove invalid or redundant features and improve the quality of feature selection. Finally, in the 15 high-dimensional feature datasets compared with the comparison methods, the accuracy of RQWOA is improved by 7.49 % on average, and the number of features is compressed by 80.42 % on average, which indicates that the RQWOA algorithm has stronger feature identification and redundancy removal capabilities and can better solve the feature selection problem.

3D printed auxetic metamaterials with tunable mechanical properties and morphological fitting abilities

Research on creating special structures with a negative Poisson’s ratio, known as auxetic metamaterials, is widely conducted for potential applications in flexible electronics, aerospace, biomedicine, and other fields. Auxiticity is the phenomenon of transverse expansion that occurs when stretched longitudinally. However, conventional metamaterial tunable properties have certain limitations, mainly in the form of limited Poisson’s ratio tuning range and transverse deformation. In this work, a series of symmetric antichiral auxetic structures with significant auxetic effect and low Poisson’s ratio of −5 are designed and fabricated by 3D printing. Based on the manipulating of unit parameters and the use of shape memory polymers, the auxetic metamaterials exhibit tunable mechanical properties and programmable shape memory behaviors. Owing to these features, the auxetic metamaterials are demonstrated to achieve excellent shape-fitting and size-fitting capabilities, which are followed by expanding in a full range to contact any objects (due to auxiticity) and then contract to conform their shapes (due to shape memory). By integrating flexible electromyography(EMG) electrodes, the shape memory auxetic metamaterials can be used as self-adaptive wearable devices to fit with human limbs, which can ensure the good attachment, high signal to Noise Ratio (SNR), and breathability when collect EMG signals.

Energy bounds in f(R,T) gravity with anisotropic backgrounds

This research work discusses the energy bounds in [Formula: see text] gravity with an anisotropic background, where [Formula: see text] is the Ricci scalar and [Formula: see text] is the trace of the energy–momentum tensor. For our study, we consider the locally rotationally symmetric Bianchi Type-I space-time. Moreover, we calculate the field equations and find exact solutions by considering different [Formula: see text] gravity models. We investigate the graphical behavior of energy density and pressure components by considering these distinct gravity models. We further use Hubble, deceleration, jerk, and snap parameters to evaluate the viability of our models. We also perform the graphical analysis to observe the behavior of energy conditions especially null energy conditions, weak energy conditions, strong energy conditions, and dominant energy conditions. It can be noticed that all considered [Formula: see text] gravity models support the idea of the presence of exotic matter, which justifies the phenomenon of expansion of the universe.

Experimental Study of Auxetic Structures Made of Re-Entrant ("Bow-Tie") Cells.

This article presents a study of metamaterial structures that exhibit auxetic properties. This unusual phenomenon of simultaneous orthogonal expansion of the metamaterial in tension, and vice versa in compression, with vertical and horizontal contraction, is explored for structures made of re-entrant unit cells. The geometry of such structures is analysed in detail, and the relationships are determined by the value of the Poisson's ratio. It is shown that the Poisson's ratio depends not only on the geometry of the unit cell but also on the degree of strain. Depending on the dimensions of the structure's horizontal and inclined struts, the limit values are determined for the angle between them. By creating physical structures made of re-entrant cells, it is demonstrated that the mechanism of change in the structure's dimensions is not due to the hinging but to the bending of the struts. The experimental section contains the results of compression tests of a symmetrical structure and tensile tests of a flat mesh structure. In the case of the mesh structure, a modification of the re-entrant cells was used to create arched strut joints. This modification makes it possible to obtain greater elongation of the mesh structure and larger NPR values.

Droplet Bottom Expansion and Its Wettability Control Mechanism Based on Macroscopic Defects.

Biomimetic surfaces with special wettability have received much attention due to their promising prospects in droplet manipulation. Although some progress has been made, the manipulation of droplets by macroscopic defects of the millimeter structure and the wetting-state transition mechanism have rarely been reported. Herein, inspired by lotus leaves and desert beetles, biomimetic surfaces with macroscopic defects are prepared by laser processing and chemical modification. Various functions of droplet manipulation are achieved by controlling the millimeter-scale macroscopic defects, such as droplet capture, motion trajectory changing, and liquid well. And a droplet bottom expansion phenomenon is proposed: wetting-state transition in superhydrophobic regions around defects. The "edge failure effect" is proposed to explain the force analysis of droplet capture and the droplet bottom expansion to distinguish it from the adhesion phenomenon presented by the droplet sliding. 53.28° is defined as the expanded saturated angle of the as-prepared surface, which is used to distinguish whether the defect could cause the droplet bottom expansion. An enhanced edge failure effect experiment is designed to make the droplet bottom expansion more intuitive. This work provides a mechanistic explanation of the surfaces that utilize macroscopic defects for droplet manipulation. It can be applied to the monitoring of droplet storage limits, providing a perspective on the design and optimization of superhydrophobic surfaces with droplet manipulation.

Analyzing Spatial–Temporal Characteristics and Influencing Mechanisms of Landscape Changes in the Context of Comprehensive Urban Expansion Using Remote Sensing

The phenomena of global climate change and comprehensive urban expansion have precipitated significant and unprecedented transformations in landscape patterns. To enhance the assessment of these spatio−temporal changes and their driving forces at a regional level, we developed a comprehensive landscape index (CLI) to quantify these patterns and conducted a detailed analysis of the spatio−temporal variations in Minnesota over the last two decades. Our analysis of the CLI was conducted by examining both its quantitative relationships and spatial distribution patterns. The findings indicate a consistent increase in Minnesota’s CLI over this period, marked by an escalation in landscape fragmentation and diversity, alongside a decline in landscape connectivity. Temporally, the CLI experienced a notable shift in 2010. Spatially, the clustering characteristics of landscape patterns have largely remained stable. Our analysis reveals that the CLI is most sensitive to total population (POP) and gross domestic product (GDP) factors, underscoring the significant impact of human activity on landscape patterns. Notably, the explanatory capacity of interactions between factors is substantially greater than that of individual factors, with the GDP and vegetation structure (VS) interaction demonstrating the greatest influence on the spatial distribution of landscape patterns. This highlights the critical role of the interplay between human socio−economic activity and vegetation coverage in shaping landscape configurations.

Identification of Clonal Hematopoiesis Driver Mutations through In Silico Saturation Mutagenesis.

Clonal hematopoiesis (CH) is a phenomenon of clonal expansion of hematopoietic stem cells driven by somatic mutations affecting certain genes. Recently, CH has been linked to the development of hematologic malignancies, cardiovascular diseases, and other conditions. Although the most frequently mutated CH driver genes have been identified, a systematic landscape of the mutations capable of initiating this phenomenon is still lacking. In this study, we trained machine learning models for 12 of the most recurrent CH genes to identify their driver mutations. These models outperform expert-curated rules based on prior knowledge of the function of these genes. Moreover, their application to identify CH driver mutations across almost half a million donors of the UK Biobank reproduces known associations between CH driver mutations and age, and the prevalence of several diseases and conditions. We thus propose that these models support the accurate identification of CH across healthy individuals. Significance: We developed and validated gene-specific machine learning models to identify CH driver mutations, showing their advantage with respect to expert-curated rules. These models can support the identification and clinical interpretation of CH mutations in newly sequenced individuals. See related commentary by Arends and Jaiswal, p. 1581.

Relevant interval perturbation method for uncertainty analysis of structural–acoustic coupling model

The parameters in structural–acoustic coupling models are often coupled with each other, and the independence of the uncertain parameters is a necessary condition for using the traditional interval perturbation method. This article proposes a relevant interval perturbation method for the uncertainty analysis of a structural–acoustic coupling model with uncertain-but-bounded parameters. Aiming at the linear inequality constraint relationship in the uncertain parameters, this method introduces a sensitivity ranking mechanism for the uncertainty parameters, which overcomes the limitation of uncertain parameter independence in the traditional interval model, and effectively restrains the interval expansion phenomenon of the system response in the uncertainty analysis. Through numerical examples, it is demonstrated that the relevant interval perturbation analysis method can effectively solve a constrained problem when there are uncertain parameters, and the obtained response interval radius is smaller than that of the traditional method under constraint conditions.

THE EFFECT OF MARKETING MIX ON PURCHASE DECISIONS AT MIXUE

There is a phenomenon of massive expansion by Mixue in Indonesia. The Mixue company has proven to be aggressive in expanding new outlets in Indonesia. According to one expert in marketing strategy, the mixue-ization phenomenon occurred because Mixue succeeded in applying the concepts of marketing strategy appropriately. In this case, Mixue succeeded in using the four marketing mix variables namely price, product, place, and promotion well. However, along with its development to dominate the market share quite rapidly, Mixue now looks only crowded for a moment and many outlets are threatened with closure.This study was conducted with the aim of analyzing the effect of marketing mix 7P on purchase decisions at Mixue Mojokerto Outlet. The data analysis used in this study used SEM-PLS analysis with the WarpPLS approach. The use of the PLS method as an analysis technique has the advantage that the sample used does not have to be large and can be used in developing a theory. The sample used amounted to 50 respondents who were consumers with more than 17 years of age with minimum one time purchasing at Mixue Mojokerto Outlet. The sampling employed nonprobability with a purposive sampling technique. The results of this study indicate that product, price, place, promotion, people, process and physical evidence has a positive and significant effect on purchase decision at Mixue Mojokerto Outlet

Can large lattice volume always facilitate ion diffusion in solids?

Large lattice volume is usually expected to expand the bottleneck size and enlarge free volume for fast Li ion transport in solids. But the universality of lattice expansion decreasing activation energy barrier for Li ion migration is still debatable. Herein, our molecular dynamics simulations and density functional theory calculations detect the unconventional phenomenon of lattice expansion increasing activation energy barrier for Li ion migration in β-Li3PS4, Li4SnS4 and Li4GeS4 sulfides with the hcp-type anion sublattice, and discover the underlying mechanism. On one hand, lattice expansion enlarges the relative energies between the octahedral and tetrahedral Li sites, and correspondingly increase activation energy barrier for tetrahedral Li ions migration along the Tet-Oct-Tet migration paths in β-Li3PS4, Li4SnS4 and Li4GeS4. On the other hand, the lattice dynamics calculations show Li energy landscapes of β-Li3PS4, Li4SnS4 and Li4GeS4 are anharmonic and enlarging lattice volume make the local minimum of Li potential energy surface flatter, simultaneously reduce the relative energy of Li occupation site, eventually resulting in the higher activation energy barrier for Li ion migration. Thus, understanding the effect of lattice volume on ion migration in solids should not only consider the factor of bottleneck size and free volume, but also combine the aspects of Li ion occupation type, Li ion migration path and anion sublattice type. These new understandings of the lattice expansion increasing activation energy barrier for ion migration would further promote the further optimization and rational design of superionic conductors by element doping or strain engineering.

Formation of bubbles and microexplosions in burning boron agglomerates

Combining laser ignition tests with quenched particle cross-sectional analyses, this study explores the formation of bubbles and microexplosions in burning boron agglomerates, and discusses the plausible mechanisms behind the microexplosion (expansion–rupture) phenomenon. High-resolution images reveal that these phenomena are caused by bubble nucleation and growth within the molten droplet. Based on the timescale, it is categorized into weak expansion and strong expansion phenomena. The expansion rate of droplets during the weak expansion process mostly ranges between 0.006 m/s and 0.4 m/s, while during the strong expansion process, it predominantly falls between 0.4 m/s and 1 m/s. An increase in ambient pressure results in the delayed occurrence and reduced frequency of the expansion–rupture phenomenon. When the ambient pressure exceeds 3 atm, the expansion phenomenon no longer occurs. In addition, a decrease in the initial diameter of the agglomerates lowers the overall occurrences of expansion–rupture. Analysis of the quenched particle cross-sections reveals that the size and density distributions of the pores within the boron agglomerates reduce gradually during the combustion process. In addition, the surface oxide layers of certain pores are removed during combustion. Estimates of the vaporization rates of (BO)n and B2O3 support the speculation that the expansion of molten boron droplets is attributed to the evaporation of boron oxide layer. In this process, the molten boron acts as a heating surface to evaporate the boron oxide trapped inside the droplet, thus producing B2O3, B2O2, and BO, and leading to droplet growth and tearing of the liquid film. Analysis of bubble growth indicates that the merging of adjacent bubbles to reach the critical nucleation size is probable the starting point of the expansion process. These results can be helpful in promoting the combustion efficiency of boron within the combustion chamber.

The Geologic History of Plants and Climate in India

India's diverse vegetation and landscapes provide an opportunity to understand the responses of vegetation to climate change. By examining pollen and fossil records along with carbon isotopes of organic matter and leaf wax, this review uncovers the rich vegetational history of India. Notably, during the late Miocene (8 to 6 Ma), the transition from C3 to C4 plants in lowland regions was a pivotal ecological shift, with fluctuations in their abundance during the late Quaternary (100 ka to the present). In India, the global phenomenon of C4 expansion was driven by the combined feedback of climate variations, changes in substrate conditions, and habitat disturbances. The Himalayan region has experienced profound transformations, including tree-line migrations, shifts in flowering and fruiting times, species loss, and shifts in plant communities due to changing monsoons and westerlies. Coastal areas, characterized by mangroves, have been dynamically influenced by changing sea extents driven by climate changes. In arid desert regions, the interplay between summer and westerlies rainfall has shaped vegetation composition. This review explores vegetation and climate history since 14 Ma and emphasizes the need for more isotope data from contemporary plants, precise sediment dating, and a better understanding of fire's role in shaping vegetation. ▪This review highlights diverse vegetation and landscapes of India as a valuable source for understanding the vegetation-climate link during the last 14 Myr.▪A significant ecological shift occurred during 8 to 6 Ma in India, marked by the transition from C3 to C4 plants in the lowland regions.▪The abundance of C3 and C4 plants varied in India during the late Quaternary (100 ka to present).▪This review emphasizes the importance of more isotope data, precise sediment dating, and a better understanding of fire's role in shaping vegetation.

Type-B Carbonated Hydroxyapatite Based on Crab Shells: A Review on Synthesis and Characterization

The synthesis and characterization of B-type CHAp based on mangrove crab shells (Scylla serrata) as a source of calcium using the precipitation method has been successfully carried out. Based on the FTIR results, the substitution of carbonate ion for phosphate, which indicates the formation of B-type CHAp, is characterized by the appearance of absorption at wave numbers (CO32-) 1426 and 875 cm-1, PO43- at wave numbers 965, 619 & 569 cm-1. The XRD results show that diffraction peaks (211), (300), and (202) appear at an angle of 2θ ranging from 31°-34°, and there is a phenomenon of a-axis contraction and c-axis expansion in the HAp lattice structure. The SEM-EDX results show that the Ca/P ratio is 1.72, and the carbonate content is 5.01 wt%. All of these parameters are characteristics of CHAp, so it can be concluded that type-B CHAp has been formed.

Thermodynamically extended symplectic numerical simulation of viscoelastic, thermal expansion and heat conduction phenomena in solids

AbstractSymplectic numerical schemes for reversible dynamical systems predict the solution reliably over large times as well, and are a good starting point for extension to schemes for simulating irreversible situations like viscoelastic wave propagation and heat conduction coupled via thermal expansion occuring in rocks, plastics, biological samples etc. Dissipation error (artificial nonpreservation of energies and amplitudes) of the numerical solution should be as small as possible since it should not be confused with the real dissipation occurring in the irreversible system. In addition, the other well-known numerical artefact, dispersion error (artificial oscillations emerging at sharp changes), should also be minimal to avoid confusion with the true wavy behavior. The continuum thermodynamical aspects (respect for balances with fluxes, systematic constitutive relationships between intensive quantities and fluxes, the second law of thermodynamics with positive definite entropy production, and the spacetime-based kinematic viewpoint) prove valuable for obtaining such extended schemes and for monitoring the solutions. Generalizing earlier works in this direction, here, we establish and investigate such a numerical scheme for one-dimensional viscoelastic wave propagation in the presence of heat conduction coupled via thermal expansion, demonstrating long-term reliability and the applicability of thermodynamics-based quantities in supervising the quality of the solution.

The Linguistic Breadth of Badr al-Din al-Ayni : Adding to Meaning as a Model

ABSTRACT The Arabic language has a linguistic phenomenon of expansion that has contributed to its continuity and survival, following its preservation by God. Al-Ayni (d.: 855 AH) extensively studied the phenomenon of conceptualization in his works. He provided clarification on its issues, explanation of its phenomena, and analysis of its elements.