Breaking Process Research Articles

Ultrastable cobalt-based chainmail catalyst for degradation of emerging contaminants in water

Developing stable and efficient cobalt-based catalysts for degradation of emerging contaminants (ECs) in water is deemed as a practical strategy to avoid secondary pollution in advanced oxidation processes (AOPs). Herein, we developed a ultrastable cobalt-based chainmail catalysts (Co-NC900) using 2, 2’-bipyridine-assistant pyrolysis method. More than 96.6 % of imidacloprid (IMD) in water could be degraded within 5 min in the presence of Co-NC900 and peroxymonosulfate (PMS). Amazingly, Co-NC900 still give 95 % degradation efficacy for IMD after15 runs. And only 0.083 μg L−1 of Co could be detected in the reaction mixture after continuous using 7 d. Density Functional Theory (DFT) calculations demonstrated that Co-NC900 can efficiently activate PMS through unique ping-pong mechanism (C-N bond breaking and re-forming process), and further degrade ECs. This study presents a novel approach for the development of efficient and stable metal-based catalysts for the removal of ECs from water.

Fractal Analysis of Particle Size and Morphology in Single-Particle Breakage Based on 3D Images

The accurate modeling of single-particle breakage based on three-dimensional (3D) images is crucial for understanding the particle-level mechanics of granular materials. This study aims to propose a systematic framework incorporating single-particle breakage experiments and numerical simulations based on a novel 3D particle reconstruction technique for fractal analysis of particle size and morphology in single-particle breakage. First, the vision foundation model is used to generate accurate particles from 3D images. The numerical approach is validated by simulating the single-particle breakage test with multiple Fujian sand particles. Then, the breakage processes of reconstructed sand particles under axial compression are numerically modeled. The relationship between 3D fractal dimensions and particle size, particle crushing strength, and morphology is meticulously investigated. Furthermore, the implications of these relationships on the particle breakage processes are thoroughly discussed, shedding light on the underlying mechanisms that govern particle breakage. The framework offers an effective way to investigate the breakage behavior of single sand particles, which will enhance understanding of the mechanism of the whole particle breakage process.

Numerical estimation of wave breaking forces on seawalls

ABSTRACT This paper presents a computationally efficient numerical scheme to estimate wave forces from plunging breakers on vertical rigid seawalls. The approximated velocity equation, an asymptotical solution of the Green-Naghdi equation in the Camassa-Holm scaling, is utilized to obtain the evolution of the free surface and the depth-averaged horizontal velocity over time, leading to the formation of a plunging breaker. The uniform dynamic pressure along the depth is obtained by utilizing the unsteady Bernoulli equation. The wave forces on seawalls are then determined using Froude-Krylov theory, with adjustments for diffraction effects. The results, while being comparable to some existing formulations, notably differ with some others. This highlights the limitations imposed by the inherent assumptions in the existing empirical formulations and underlines the importance of the proposed methodology that is founded on an accurate modelling of the wave breaking process to estimate wave breaking forces on seawalls.

Full-scale test of disc cutter rotary cutting in TBM tunnelling: a case study of Mawan granite in Shenzhen, China

Understanding the distribution of cutting force provides a foundation for the design and optimization of cutterhead layout. The simulation of rotary cutting with a large cutting radius remains a challenge for laboratory tests. In this study, taking the driving condition of the Mawan Tunnel located in the Guangdong-Hong Kong-Macao Greater Bay Area as a case study, a full-scale rotary cutting platform with large cutting radius was used to investigate the rock-breaking effects. Rotary cutting with cutting depths of 1–8 mm and cutting radii of 200–1400 mm were carried out on the granite testing platform using a 19-in disc cutter. The normal force, rolling force, and side force during the cutting process were systematically monitored. Moreover, the time–frequency characteristics of the rock breaking process and the effects of cutting depth, cutting radius and stress state on the average and peak loads were investigated. The results show that the average normal force and rolling force increased with increasing cutting depth, while the side force was less affected by cutting depth through the Boltzman model analysis. The average normal force and rolling force were not significantly affected by the cutting radius, but the average side force decreased as a power function with increasing cutting radius, and showed a stable side force when the installation radius exceeded 1000 mm. The dominant frequency of the cutting force was 0–1.2 Hz, exhibiting notable low-frequency characteristics. Additionally, the ratio of peak to average (RPA) with respect to triaxial cutting force demonstrated an increase with the growth of cutting depth, while RPA in terms of side force exhibited a corresponding growth with the increasing cutting radius. In particular, the cutting force characteristics of the cutterhead obtained in this study can inform the layout of disc cutters and real-life TBM operations, thereby avoiding severe overloading of internal disc cutters.

Polar domain walls induced by sequential symmetry breaking in frustrated mechanical metamaterials

Frustration hinders ideal local interactions in systems ranging from artificial spin ices with ice rules to mechanical metamaterials featuring regular floppy modes. While geometric frustrations have been known to promote complex ordered patterns in tessellated lattice structures, there is growing interest in global frustrations due to the topologically nontrivial geometry of metamaterials. However, multiferroic orders in globally frustrated metamaterials have remained elusive. Here, we present polar domain walls constrained in flexible mechanical metamaterials with global frustration and sequential symmetry breaking. We showcase that under simple compressive loading, competing interactions in globally frustrated metamaterials give rise to mixed deformations with high-order buckling modes described by an emergent order parameter. Utilizing an elastic mechanism model, we unveil the process of sequential symmetry breaking and capture the formation of polar domain walls exhibiting a chiral distribution within a multi-well potential landscape. We further demonstrate how to eliminate frustration through torsional loading, leading to symmetry restoration. These results provide insights into the intricate interactions between order and frustration, inspiring the modulation of domain walls in macroscopic systems.

Interaction of H2S with perfect and O-covered Pd(100) surface: A first-principles study

Using density functional theory (DFT) calculations, we investigated the dissociative mechanism of H2S adsorption and its dissociation on both clean and oxygen covered Pd (100) surface. For adsorption mechanism, the site preference was considered for H2S and HS monomers on both surfaces. The results suggest that H2S is energetically adsorbed on high symmetry sites, particularly the hollow site, on clean surface and top site on O-covered Pd (100) surface. Chemisorption of HS is stronger than H2S at the favorable hollow site on clean surface and O-covered surface. The energy barriers for S–H bond-breaking during the first H2S dehydrogenation are 0.35, 0.07, 0.32, and 0.16 eV, while for second dehydrogenation are 0.32 and 0.30 eV, respectively. On the oxygen-covered surface, the H2S adsorption site transitions from bridge to the top site and their energy barrier for first-order decomposition is 0.05 eV, significantly lesser than that observed on a clean surface. To examine more, the electronic densities of states as well as d-band center model were used to characterize the interaction of adsorbed H2S with the surfaces. Overall, our findings show that H2S decomposition on these surfaces is exothermic and relatively easy, but the presence of surface oxygen hinders the breaking process of H–S bond due to kinetic and thermodynamic factors.

An analytic approach for nonlinear collisional fragmentation model arising in bubble column

The phenomenon of coagulation and breakage of particles plays a pivotal role in diverse fields. It aids in tracking the development of aerosols and granules in the pharmaceutical sector, coagulation or breakage of droplets in chemical engineering, understanding blood clotting mechanisms in biology, and facilitating cheese production through the action of enzymes within the dairy industry. A significant portion of research in this direction concentrates on coagulation or linear breakage processes. In the case of linear case, bubble particles break down due to inherent stresses or specific conditions of the breakage event. However, in many practical situations, particle division is primarily due to forces exerted during collisions between particles, necessitating an approach that accounts for nonlinear collisional breakage. Despite its critical role in a wide array of engineering and physical operations, the study of this nonlinear fragmentation phenomenon has not been extensively pursued. This article introduces an innovative semi-analytical method that leverages the beyond linear use of equation superposition function to address the nonlinear integro-partial differential model of collisional breakage population balance. This approach is versatile, allowing for the resolution of both linear/nonlinear equations while sidestepping the complexities associated with discretization of domain. To assess the precision of this method, we conduct a thorough convergence analysis. This process utilizes the principle of contractive mapping in the Banach space, a globally recognized strategy for verifying convergence. We explore a variety of kernel parameters associated with collisional kernels, alongside breakage and initial distribution functions, to derive novel iterative solutions. Comparing our findings with those obtained through the finite volume method regarding number density functions and their integral moments, we demonstrate the reliability and accuracy of our approach. The consistency and correctness of our method are further validated by depicting the errors between the exact and approximated solutions in graphical and tabular formats.

Dynamic Behavior of Impacting Droplet on the Edges of Different Wettability Surface.

The dynamic behavior of impacting droplet shearing by the surface edge with different wettabilities is complicated and has great significance for engineering application. The morphological evolution of droplet with various Weber numbers (We) and wettability impacting on the edge of square substrate is investigated by high-speed photography. Moreover, the effects of the contact angle (α) and Weber numbers (We) on the shear breaking process of droplets are obtained. There are three types morphological evolution of impacting droplet are observed experimentally, including unbroken, tensile breakup, and shear breakup. Contact angle and Weber number have been proved to be the significant factors affecting the type of droplet morphological evolution. Meanwhile, the critical Weber number of different types are obtained quantitatively. Moreover, as α increases, the critical Weber numbers for breakup increase. In the shear breakup process, the mass ratio between the droplets remaining on the substrate and the initial droplets is maintained at 50%. Particularly, a reliable prediction model for the spreading of droplet impacting the side wall is proposed and compared with the experimental data. Overall, this study provides new direction and guidance for exploring droplet breakup kinetics.

Three-dimensional wave breaking

Although a ubiquitous natural phenomenon, the onset and subsequent process of surface wave breaking are not fully understood. Breaking affects how steep waves become and drives air–sea exchanges1. Most seminal and state-of-the-art research on breaking is underpinned by the assumption of two-dimensionality, although ocean waves are three dimensional. We present experimental results that assess how three-dimensionality affects breaking, without putting limits on the direction of travel of the waves. We show that the breaking-onset steepness of the most directionally spread case is double that of its unidirectional counterpart. We identify three breaking regimes. As directional spreading increases, horizontally overturning ‘travelling-wave breaking’ (I), which forms the basis of two-dimensional breaking, is replaced by vertically jetting ‘standing-wave breaking’ (II). In between, ‘travelling-standing-wave breaking’ (III) is characterized by the formation of vertical jets along a fast-moving crest. The mechanisms in each regime determine how breaking limits steepness and affects subsequent air–sea exchanges. Unlike in two dimensions, three-dimensional wave-breaking onset does not limit how steep waves may become, and we produce directionally spread waves 80% steeper than at breaking onset and four times steeper than equivalent two-dimensional waves at their breaking onset. Our observations challenge the validity of state-of-the-art methods used to calculate energy dissipation and to design offshore structures in highly directionally spread seas.

A Goldstone boson equivalence for inflation

The effective field theory of single-field inflation characterizes the inflationary epoch in terms of a pattern of symmetry breaking. An operator acquires a time-dependent vacuum expectation value, defining a preferred spatial slicing. In the absence of dynamical gravity, the fluctuations around the time-dependent background are described by the Goldstone boson associated with this symmetry breaking process. With gravity, the Goldstone is eaten by the metric, becoming the scalar metric fluctuation. In this paper, we will show that in general single-field inflation, the statistics of scalar metric fluctuations are given by the statistics of this Goldstone boson decoupled from gravity up to corrections that are controlled as an expansion in slow-roll parameters. This even holds in the presence of additional parameters, like the speed of sound, that naively enhance the impact of the gravitational terms. In the process, we derive expressions for leading and sub-leading gravitational corrections to all-orders in the Goldstone boson.

Numerical simulation of hydrate flow in gas-dominated undulating pipes considering nucleation and deposition behaviors

The distribution and deposition of hydrates in deep-water gas transportation pipelines are crucial for safety. Current simulations of hydrate flow based on the population balance model have predominantly focused on water-dominant systems and neglect the nucleation and deposition of hydrates. By establishing a model for a hydrate flow in a gas-dominant system that considers the uneven distribution of the liquid film on the wall, hydrate nucleation, gas–liquid mass transfer, particle adhesion and aggregation, and dynamic deposition, we achieved simulation of the entire process of hydrate formation, aggregation, breakage, and deposition. Simulations in undulating pipelines were carried out to investigate the effects of gas velocity, liquid injection, pressure, and pipeline structure on distribution patterns. The results showed increasing the gas velocity enhanced the dispersion of particles and increasing the pressure increased the rate of aggregation. The formation of blocky aggregates posed significant risk in the rear section of the lower-bend pipe.

Combination of two-fluid model and delayed equilibrium model for the critical flow in a slit

Accurately predicting the mass flux, pressure profile, and velocity profile of the critical flow in a slit is essential for analyzing the breaking process of the liquid phase and calculating the aerosol source term for leak-before-break (LBB) monitoring and Loss of Coolant Accident (LOCA) risk analysis. A new critical flow model combining Two-fluid Model (TFM) and Delayed Equilibrium Model (DEM) is built to get accurate profiles while avoiding the same phase velocity in DEM and the arbitrary critical flow criterion in TFM. The new model is verified using past experiments of the critical flow in a slit. It proves to be accurate in mass flux but not in critical pressure, with maximum relative errors of around 25% in mass flux and around 80% in critical pressure. The new model is optimized for higher accuracy in critical pressure. The empirical equation of saturated phase mass flow rate fraction gradient is optimized by conducting approximate pressure profile calculation and regression analysis. The maximum relative error decreases little while the ratio of critical pressure relative errors lying in the range of ±40% increases after optimization. In contrast, the difference in the average abstract relative error of pressure between original TFM-DEM and DEM is much larger, for the maximum relative error of mass flux and critical pressure are around 25% and 110%. The comparison between the original and optimized TFM-DEM proves that the new critical flow model is accurate in mass flux and can be optimized to raise pressure calculation accuracy. The comparison between the original TFM-DEM and DEM proves that the phase velocity difference is the major source of accuracy improvement in the pressure profile.

A novel design of energy absorption branch for HVDC circuit breakers

Metal oxide varistors (MOV) used for energy absorption branch in DC circuit breakers are complex enough to meet the requirements for small volume, light weight, and reliability in future high-voltage direct current (HVDC) grids. Therefore, a new energy absorption branch circuit that combines MOV and a liquid metal alloy energy absorber (LMEA) is proposed. Based on the constructed equivalent mathematical model of LMEA, the working principle and energy absorption process of MOV and LMEA in DC breaking process are analysed in PSCAD/EMTDC simulation software. Results demonstrate that LMEA, in contrast to MOV alone, absorbs 2.12 MJ of energy, constituting 35.6% of the total energy. Moreover, LMEA enhances energy dissipation density while reducing volume. Experimental analysis reveals MOV’s energy absorption mechanism via achieving residual voltage with ZnO varistor’s non-linear properties, swiftly transitioning from high to low resistance states to absorb energy. Conversely, LMEA relies on pulse current amplitude to initiate internal arcing, sharply increasing internal resistance for effective energy absorption. Experimental findings validate LMEA’s contribution of one-third of total energy absorption when pulse current amplitude reaches critical arcing threshold, consistent with simulation results. The results provide theoretical support for the engineering application of the new liquid metal alloy energy absorption in DC circuit breakers.

Analysis of different test techniques of DC circuit breaker

Abstract Amidst the escalating demand for energy and the proliferation of renewable energy sources, direct current (DC) systems have garnered increasing interest. As pivotal for the safety and reliability of DC systems, testing DC circuit breakers is a critical step to evaluate their performance and dependability. This study focuses on the breaking test method for medium and high-voltage DC circuit breakers. It compares and evaluates the current waveform, recovery voltage, and energy dissipation across various test circuit methodologies during the breaking process of DC circuit breakers and assesses the suitability of test methods across different voltage levels.

Simulation of auto-expansion high voltage SF6 circuit breaker breaking process considering valve motion

Simulation of auto-expansion high voltage SF6 circuit breaker breaking process considering valve motion

Numerical study on the influence of cemented components on the mechanical properties of Xiyu Conglomerate

Xiyu Conglomerate is a common type of weakly cemented gravel stone formation found in northwestern China. This material is mainly composed of mud, mud–calcium, and calcium cement, possessing mechanical properties that are superior to those of soils but significantly weaker than those of rocks. Assessing these properties is crucial in ensuring the successful implementation of hydraulic engineering projects involving this material. This work establishes a microscale contact bonding model with a mud–calcium transition by surveying Xiyu Conglomerate’s material composition in a typical engineering area. The particle flow code method is used to investigate the influence of cemented materials on the mechanical properties of the conglomerate. After appropriate model calibration, numerical results show that the difference between the vertical and lateral contact forces becomes increasingly significant as the proportion of mud cement decreases and the content of calcium cement increases. The bond breakage process within the cemented material can be divided into three stages: no bond breakage, rapid bond breakage, and differential bond breakage development. When the mud cement content exceeds 50 %, the characteristics tend toward a soil-like behavior, while it resembles a soft rock behavior if the calcium cement content exceeds 50 %. Mud cement connects particles internally, whereas calcium cement strengthens the structure, both contributing to the randomness, heterogeneity, and discontinuity of Xiyu Conglomerate. The results can serve as a reference for future construction and engineering practices in the region.

Role of the triangle singularity in the isospin breaking process J/ψ→ΛΛ¯π and the possible evidence of Σ*(12−) states

In this study, the impact of triangle singularity is investigated in the isospin breaking process J/ψ→ΛΛ¯π. The triangle singularity is found to play a significant role in the process, resulting in the creation of a resonancelike structure around 1.4 GeV in the Λπ(Λ¯π) invariant mass spectrum. To amplify the impact of this triangle singularity, the presence of two Σ*(12−) states around 1.4 GeV and 1.6 GeV is essential, yet these states have not been definitively identified in the current baryon spectrum. We recommend that experiments, particularly the Beijing Spectrometer and the future Super Tau-Charm Factory, investigate the process J/ψ→ΛΛ¯π to offer direct evidence for our predicted triangle singularity and additional evidence regarding the Σ(12−) states. Published by the American Physical Society 2024

Emergent chirality in active solid rotation of pancreas spheres

Collective cell dynamics play a crucial role in many developmental and physiological contexts. While two-dimensional (2D) cell migration has been widely studied, how three-dimensional (3D) geometry and topology interplay with collective cell behavior to determine dynamics and functions remains an open question. In this work, we elucidate the biophysical mechanism underlying rotation in spherical tissues, a phenomenon widely reported both and . Using murine pancreas-derived organoids as a model system, we find that epithelial spheres exhibit persistent rotation, rotational axis drift, and rotation arrest. Using a 3D vertex model, we demonstrate how the combined action of traction force and polarity alignment can account for these distinct rotational dynamics near a solid to flow transition. Furthermore, our analysis shows that the spherical tissue rotates as an active solid occasionally switching to a flowing state and exhibits spontaneous chiral symmetry breaking. Using a continuum model, we demonstrate how the topological defects in the polarity field underlie this symmetry breaking process, which is revealed by asymmetries in the cell elongation pattern. For cell elongation to reveal the chiral asymmetry, shear flow is required in addition to the solid body rotation. Altogether, our work reveals a robust chiral symmetry breaking mechanism with potential implications for left-right symmetry breaking processes in morphogenetic events. Published by the American Physical Society 2024

Developing a circular economy from plastic waste and identifying microplastics in domestic water supplies in Ho Chi Minh City and the Southeastern provinces

Abstract While humans are struggling to deal with plastic waste, the plastic decomposition products, namely microplastics, have silently infiltrated almost all environmental states. This study examines the feasibility of a circular economy approach for addressing plastic waste and reducing microplastics in source water in Southeastern provinces. Of the 400 households surveyed, there were 200 households in Ho Chi Minh, 50 households in Dong-naiand 150 households in Binh Duong, only 10% of household plastic waste is recycled, 33% of them are sold as scrap and 57% of them are completely processed. Out of the remaining 57% of waste, it can be the starting material to produce later stage products and create income opportunities of hundreds of billions of VND per month for Ho Chi Minh and Binh Duong province. The process of breaking down plastic waste into microplastics in the Sai Gon River and Dong Nai River has resulted in the emergence of microplastic polymers such as Polypropylene (27.1%), Polyethylene (51.2%), Polyvinyl Chloride (13.4%), and 8.3% of other plastics. These microplastics pose a significant threat to human health. The SWOT analysis identifies opportunities and challenges for implementing a circular economy approach to minimize plastic waste and microplastics in the study area.

Damage and fracture characteristics of thermal-treated granite subjected to ultra-high pressure jet

The water jet rock breaking technology has broad application prospects in geoenergy development engineering. However, the influence of reservoir temperature on the rock breaking effect is still unclear during the jet rock breaking process. To explore the mechanism of temperature on rock breaking by high-pressure water jets, experiments on the erosion of high-temperature granite by ultra-high pressure pure water jets (UHP-PWJ) and ultra-high pressure abrasive water jet (UHP-AWJ) were conducted at five rock temperatures: 25 °C, 100 °C, 200 °C, 300 °C, and 400 °C. Through three-dimensional reconstruction and microscopic observation techniques, the macroscopic and microscopic characteristics of rock fragmentation were analyzed, ultimately revealing the dynamic damage and rock breaking mechanisms of ultra-high pressure water jet. The results indicated that rock temperature influences result in different fragmentation characteristics under the action of two types of jets, with UHP-PWJ demonstrating significantly superior rock-breaking effects on high-temperature granite compared to UHP-AWJ. As granite temperature increases from 25 °C to 400 °C, the damage depth range for the UHP-PWJ is 30–75 times the nozzle diameter, while for the UHP-AWJ, it is only 30–40 times the nozzle diameter. For UHP-PWJ, the rock breaking mechanism is mainly driven by thermal stress, supplemented by high-speed jet impact. The significant increase in rock temperature significantly enhances its rock breaking effect, with erosion pits appearing in a spindle shape and more complex crack distribution around the pores. Compared with 25 °C granite, the damage caused by 400 °C granite jet impact increased by 6.8 times and the surface area of cracks increased by 6.5 times. For UHP-AWJ, high temperature hard rock fragmentation still relies mainly on jet impact and abrasive grinding. The thermal stress caused by rock temperature has a relatively small impact on its rock breaking effect, and the D value of the internal damage degree of granite at different temperatures is less than 0.005. The erosion pits are conical in shape, and no macroscopic cracks caused by jet impact and thermal cracking can be clearly observed around the pit. The research results can provide a theoretical basis for optimizing the parameters of high-pressure jet development technology for deep geoenergy.