Vertical Splitting Research Articles

Characterization of mechanical behavior and cementing mechanism of high-strength composites using biomimetic chemically induced calcium carbonate precipitation method

Biomimetic mineralized mortar (BMM) represents a novel green cementitious material, increasingly recognized for its environmental sustainability. In this study, four typical amino acids including acidic amino acids (aspartic acid, glutamic acid), neutral amino acid (threonine), and basic amino acid (arginine), are employed as crystal modifiers to develop the high-strength BMM (HBMM) based on the biomimetic chemically induced calcium carbonate precipitation (BCICP) method. The mechanical properties and failure morphology of HBMM were evaluated through unconfined compressive strength (UCS) test. The microstructure characteristics of HBMM were investigated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM) and contact angle test. The results show that amino acid-modified calcium carbonate precipitation can effectively cement loose sand particles and significantly improve the strength of the HBMM. The failure modes of HBMM observed include local failure, vertical splitting failure, shear failure, and splitting-shear mixed failure. Notably, aspartic acid and glutamic acid can induce the formation of vaterite-phase calcium carbonate crystals, while threonine and arginine facilitate the formation of aragonite-phase calcium carbonate crystals. The hydrogen bonding between modified calcium carbonate crystals and silanol groups on the silica surface ensures a tight adhesion of the precipitate to sand surfaces, filling gaps and cementing particles. This study elucidates that using amino acids as modifiers in the BCICP method can significantly enhance the strength of HBMM and influence its microstructure, offering valuable insights for its potential practical applications.

Influence of Rock Block Content on Mechanical Properties of Coarse-Grained Fillers Stabilized with Fiber and Geopolymer

This study employed fiber and geopolymer to enhance the engineering performance of coarse-grained fillers. By conducting a series of comparative mechanical tests, the ideal mass mixing ratio design of geopolymer and fiber was investigated first. Then, the influence of rock block content on the mechanical properties of coarse-grained fillers stabilized with fiber and geopolymer was explored. The deformation damage characteristics of fiber- and geopolymer-stabilized coarse-grained fillers with different rock block contents were also discussed in the final test. The results show that the ideal mass mixing ratio of geopolymer for coarse-grained filler stabilization was 15% of dry fine-grained soil in weight and the ideal dosage and length of fiber was 0.4% of dry fine-grained soil in weight and 1.2 × 10−2 m. The compressive strength of fiber- and geopolymer-stabilized coarse-grained fillers shows a tendency to increase first, then decrease, and then re-increase with the increase in rock block contents. The best compressive strength and resistance to deformation were achieved when the rock block content was 30%. The failure mode of fiber- and geopolymer-stabilized coarse-grained fillers translated from shearing slip to vertical splitting as the rock block content increased. This study can provide a reference and support for the engineering application of coarse-grained fillers stabilized with fiber and geopolymer.

Switchable VO₂ Metamaterial Based on Planar and Vertical Split Ring Resonators for High-Performance Sensing

Switchable VO₂ Metamaterial Based on Planar and Vertical Split Ring Resonators for High-Performance Sensing

Microstructures, mechanical properties, and strengthening mechanisms of the (NbMoTa)100−xCx refractory medium-entropy alloys

Refractory high/medium-entropy alloys (RH/MEAs) are known for their outstanding performance at elevated temperatures; however, they usually exhibit poor room-temperature plasticity, which can be attributed to the non-uniform deformation that occurs at room temperature. Once cracks nucleate, they will rapidly propagate into vertical splitting cracks. Here, we introduce multiple phases including FCC and HCP phases into the NbMoTa RMEA via appropriate addition of carbon. The results show that multiple-phase synergy effectively suppresses non-uniform deformation, thereby delaying the onset of vertical splitting cracks. An optimal combination of compressive strength-plasticity is achieved by the (NbMoTa)92.5C7.5 alloy. The significant improvement in room-temperature mechanical properties can be attributed to its hierarchical microstructure: in the mesoscale, the BCC matrix is divided by eutectic structures; while at the microscale, the BCC matrix is further refined by abundant lath-like FCC precipitates. The FCC precipitates contain high-density stacking faults, acting as a dislocation source under compressive loading. The HCP phase in the eutectic microstructures, in turn, acts as a strong barrier to dislocation movement and simultaneously increases the dislocation storage capacity. These findings open a new route to tailor the microstructure and mechanical properties of RH/MEAs.

Strain-rate effect on mechanical properties of rock-like specimens with narrow crack under uniaxial compression

Uniaxial compression tests were carried out on rock-like specimens containing prefabricated narrow crack under various strain rates. Experimental observations and numerical results show that narrow crack will close or partially close or expand under low compressive stress. Due to the unidirectional loading of loading device, the deformation degree of crack tip near the loading end was different with that of crack tip near the bearing end. With the increase of strain rate, the cracking modes can be divided into 3 categories, near vertical splitting failure affected by horizontal crack (α = 0°), anti-N-wing crack (15°≤α ≤ 60°) and wing crack (60°<α ≤ 90°). Both of the initiation angle θ1 of crack tip near the loading end and θ2 of crack tip near the bearing end decreased with the increase of α and strain rate. Specially, when α = 90°, both θ1 and θ2 rose with the increase of strain rate. Moreover, the value of θ2 was greater than that of θ1 under the same α value because of the different deformation characteristics at two tips. Besides, the mechanical properties of fissured rock including peak compressive stress, residual compressive stress, strain at peak stress, elastic modulus and post-peak softening modulus were significantly influenced by the strain rate and inclination angles.

Evaluation of Slow-Releasing Energy Material (SREMA) Injection for In-Situ Rock Breaking Under Uniaxial and Triaxial Loading: An Experimental Study

Permeability enhancement of impervious rock formations is crucial for the exploitation of ore deposits, which are uneconomic using conventional mining methods. These deposits have the potential to be mined with in-situ recovery (ISR) mining methods, provided the deposit’s permeability is enhanced artificially. Slow-releasing energy material (SREMA) has been identified as a promising preconditioning technique to enhance rock permeability for ISR. However, the fracturing potential of SREMA in the presence of in-situ stresses remains under-explored in laboratory experimental research studies and needs to be assessed in detail prior to field trials. A unique confining cell was developed in this study to represent realistic confining stresses underground, and the impacts of different stress conditions on the fracturing potential of SREMA were investigated. In addition, the effects of SREMA expansion in pre-existing joints were also assessed using laboratory fracturing experiments conducted by injecting SREMA into sandstone specimens with artificially created horizontal persistent joints, which is the first attempt to the best of the author’s knowledge. Under uniaxial stress conditions (10 MPa), multiple radial cracks emerged from the borehole at the centre of the specimen, while vertical splitting of the specimen was observed due to the outward expansion of SREMA inside the joint. In comparison, under triaxial confinement (5 MPa and 10 MPa), a decrease in the damage caused to the rock mass due to the expansive pressure generated by SREMA was observed, and this was overcome by introducing multiple injection holes and stress relief holes into the rock mass.

Structural performance of circular CFST columns with circumferential gap imperfections

The present study investigated the influence of circumferential uniform gap imperfections (≤ 1.0%) on the structural behavior of circular concrete-filled steel tube (CFST) columns under axial compression. The study involved testing 20 CFST columns with circumferential uniform gaps with varying gap ratios (0.2%–1.0%), diameter-to-thickness ratios (18–43), and concrete strength (68.5 MPa and 114 MPa). The presence of uniform gaps (0.2%–1.0%) reduced the confinement effect of steel tube on core concrete, and peak load capacity decreased by 9.0%–24.0%. The normalized concrete strength in high-strength concrete specimens with gap ratios ranged between 0.89 and 0.99, showing no interaction between steel tube and core concrete due to the less deformable nature of high-strength concrete. Core concrete exhibited a combination of vertical splitting and diagonal cracks distributed across the height of specimens with an increase in gap ratio, and local steel tube bulging was dispersed around the edge regions. A theoretical procedure was developed to assess the impact of uniform gaps on the stress state of steel tube and core concrete by determining their respective load contributions. The suggested approach reasonably estimated the gap ratio's nominal influence on the behavior of steel tubes and its considerable influence on the behavior of core concrete. Considering the experimental limitations, gap ratios were broadened through finite element modelling to investigate the gap ratio effect further. After examining the confinement mechanism of CFST columns and finite element results, an analytical formulation to predict the peak load capacity of CFST columns with circumferential uniform gaps was proposed and verified.

An experimental study on mechanical properties and fracturing characteristics of granite under high-temperature heating and liquid nitrogen cooling cyclic treatment

Liquid nitrogen (LN2) fracturing is a promising technology for efficient development of hot dry rock reservoir geothermal resources. To investigate the cracking mechanism of LN2 on high-temperature granite, heating and LN2 cooling cyclic treatment were applied to granite samples. Based on Brazilian splitting test, and different methods were employed to describe the crack propagation and failure mechanism, including acoustic emission monitoring, laser profile scanning, and scanning electron microscopy. The results demonstrate that heating and LN2 cooling cyclic treatment deteriorates the mechanical properties of granite. Specifically, after 20 cycles, the average P-wave velocity of the samples decreases by 34%, with the amplitude of the waveform decreasing from 130 dB to 50 dB. Moreover, the uniformity and integrity of the waveform worsen after cyclic treatment. The tensile strength, peak strain, and brittleness index of granite samples decrease with cycle numbers. From 3 to 20 cycles, the absorbed energy of the samples reduces by 53%, with thermal damage reducing the energy storage limit. The cyclic cooling treatment of LN2 increases the surface roughness and width of crack of the samples, resulting in obvious plastic failure at both ends of the samples. Furthermore, the height parameter Sa and area ratio Sdr of the fracture surface increase by 53.8% and 69.5%, respectively, as the number of cycles increase from 3 to 20. Additionally, the fractal dimension of the granite samples increases from 2.155 to 2.181, indicating an increase in the complexity of the cross-section. Following heating and LN2 cooling cyclic treatment, the failure mode of granite changes from vertical splitting to shear failure, with decreased brittleness and increased plasticity and ductility.

A Simplified Treatment Algorithm for the Management of Primary Double-headed Pterygium

Abstract Aim: To study different methods in the management of primary double-headed pterygium and to propose a simplified treatment algorithm for its surgical management. Methods: A retrospective study was performed on 335 eyes. All the surgeries were carried out under subconjunctival infiltrative anaesthesia. In Group I, patients underwent excision of pterygium with a horizontal conjunctival autograft (CAG). Patients in Group II underwent a vertical split CAG with limbal orientation, while in Group III, limbal orientation was not maintained. In Group IV, patients underwent conjunctival tissue graft from pterygium and conjunctival autografting. Results: Recurrence was observed in five of the 96 eyes in Group I (5.2%) and among 12 of the 99 eyes in Group II (4.04%). Recurrence was observed in three out of 87 eyes (3.45%) in Group III, and four out of 53 eyes (7.5%) in Group IV. All four groups had low and comparable recurrence rates. The follow-up period for all patients was extended for a minimum of 6 months, with mean follow-up durations of 16.79 months in Group I, 18.30 months in Group II, 17.28 months in Group III and 14 months in Group IV. Conclusion: Outcomes of horizontal and vertical split conjunctival autografting with/without limbal orientation and conjunctival tissue from pterygium with conjunctival autografting were studied. All these methods had low and comparable rates of recurrence and are therefore effective in the surgical treatment of double-headed pterygium.

Vertical Interaction Between NBC Rings and Its Implications for South Atlantic Water Export

AbstractNorthwestward‐propagating North Brazil Current (NBC) Rings are often destroyed upon reaching the Caribbean islands, carrying South Atlantic waters into the North Atlantic gyre and connecting the two branches of the Atlantic Meridional Overturning Circulation. Recent observations of NBC rings reported surface and subsurface cores separated by strong stratification. As independent structures, the subsurface eddies often appeared below—even if not aligned with—the surface rings. Motivated by these findings, this paper investigates the occurrence and consequences of vertical coupling between surface and subsurface NBC rings by applying a simplified theoretical model to a realistic numerical simulation. Eddy tracking in this complex simulation reveals around 1,600 instantaneous observations where eddies overlap. At each observation, we assess the eddies' vertical interaction with a 21/2‐layer quasi‐geostrophic framework. This interaction boils down to either coupling between the layers or a vertical splitting of the system, depending on eddy strength versus background shear. The effects of coupling include long‐lived eddies that can travel longer distances. These effects are particularly important for the lower layer, where differences between coupled and non‐coupled eddies are striking: about 40% of eddies with coupling travel 500 km, with ∼10% carrying South Atlantic Water up to the Caribbean sea. Without coupling, eddies propagate less than 150 km. During coupling, lower‐layer eddies could be driven by their surface counterparts to move offshore and bypass a topographic choke point, thus leaving the NBC retroflection region. Although still speculative, this idea explains the link between coupling and the increase in both lifetime and distance traveled for these eddies.

An efficient conflict analysis method based on splitting and merging of formal contexts

Conflict situations are widespread nearly in all corners of social life, and the efficiency of conflict analysis still has much room especially for large-scale data sets. To this end, this study presents an information fusion method of fast conflict analysis based on formal concept analysis. Firstly, a novel type of three-way concepts is defined to neatly deal with three-valued formal contexts. Then, fast computation of conflict analysis is explored by using an information fusion technique. Specifically, conflict analysis based on horizontal splitting and merging of formal contexts and the one based on vertical splitting and merging of formal contexts are respectively investigated. Finally, systematic experiments are carried out on both synthetic data sets and real cases to evaluate the performance of the proposed method. According to the experimental results, conflict analysis based on vertical splitting and merging of formal contexts can effectively improve the performance, which may not be realized by using the horizontal splitting and merging strategy in some cases. This study may shed light on formal concept analysis based multi-source big data analysis.

Experimentally Validated Finite Element Analysis of Thoracic Spine Compression Fractures in a Porcine Model.

Vertebral compression fractures (VCFs) occur in 1 to 1.5 million patients in the US each year and are associated with pain, disability, altered pulmonary function, secondary vertebral fracture, and increased mortality risk. A better understanding of VCFs and their management requires preclinical models that are both biomechanically analogous and accessible. We conducted a study using twelve spinal vertebrae (T12-T14) from porcine specimens. We created mathematical simulations of vertebral compression fractures (VCFs) using CT scans for reconstructing native anatomy and validated the results by conducting physical axial compression experiments. The simulations accurately predicted the behavior of the physical compressions. The coefficient of determination for stiffness was 0.71, the strength correlation was 0.88, and the failure of the vertebral bodies included vertical splitting on the lateral sides or horizontal separation in the anterior wall. This finite element method has important implications for the preventative, prognostic, and therapeutic management of VCFs. This study also supports the use of porcine specimens in orthopedic biomechanical research.

On the dynamics of air disk contraction

Contraction of an air disk in liquid was investigated by direct numerical simulations of the Navier–Stokes equations in an axisymmetric framework. Five mechanisms of the first breakup were revealed: End-pinching, center-opening, cross-splitting, vertical splitting and no-breakup, and a parameter space as a function of the Ohnesorge number Oh and the aspect ratio Γ was established. Similar to air film contraction of other geometries, the contraction velocity of the air disk increases from rest to a maximum velocity, then decreases. Theories involving volume conservation, hydrodynamic drag, or added mass were proposed to predict the contraction velocity at different stages. Interaction between complicated morphological changes and vortex dynamics was studied. Generation and shedding of vortices around the bubble were responsible for the complex contraction dynamics.

Characterization of mechanical behavior of different types of masonry with a detailed investigation of full-field strain using digital image correlation

This article presents an experimental study on the mechanical characterization of three different types of masonry: burnt clay bricks, fly ash bricks, and autoclaved aerated concrete (AAC) blocks, with a detailed focus on strain distribution and failure mechanism. The specimens were subjected to direct and diagonal compression loading, and the stress–strain curves and failure modes were studied. Digital image correlation (DIC) was used to obtain full-field strain data, allowing for detailed analysis of failure mechanisms, tracking of crack propagation, and examination of other intricate details. The DIC analysis showed that in burnt clay brick and fly ash brick masonry, failure under compression was initiated by the tensile splitting of the brick, while in AAC block masonry, it was initiated by the tensile splitting of the mortar. Additionally, the study identified that the failure modes under diagonal compression were different for each type of masonry, with bed joint sliding being the dominant failure mode in fly ash brick and AAC block masonry. In contrast, the failure mode in burnt clay brick masonry was due to vertical splitting along the loaded diagonal. In the diagonal compression test, the shear strain along both diagonals was negligible, and principal strain directions were observed to be aligned along the two diagonals.

Mechanical properties and energy absorption performance of foamed geopolymer under quasi-static and dynamic compression

To assess the potential for substituting foam concrete with low-carbon foamed geopolymer (FG) in the field of structural protection, a series of quasi-static and dynamic compression tests were conducted. These tests aimed to examine the mechanical performance and energy absorption of FG while considering the factors of FG density, granulated blast furnace slag (GBFS) replacement rate, and water–solid ratio. Additionally, supplementary investigations involving XRD analysis, indentation tests, X-CT scanning, and 3D reconstruction techniques were conducted to explore the influence of GBFS replacement rate on the energy absorption of FG in terms of base material properties and internal pore structure. The results of the quasi-static compressive tests showed that increasing the FG density and reducing the water–solid ratio had a positive effect on energy absorption, however, it also resulted in a notable increase in peak strength. Increasing the GBFS replacement rate not only enhanced the load-bearing capacity but also increased the extent of spalling damage, thus FG with a moderate GBFS replacement rate of 20% demonstrated superior performance in terms of energy absorption and load transfer. Under dynamic compression, all specimens predominantly experienced vertical splitting failure. However, with increasing loading velocity, crushing failure emerged at the two ends of the specimens, particularly in the case of low-density specimens. As the loading velocity increased, the specimen exhibited a significant increase in peak strength, demonstrating a notable strain rate effect, however, the energy absorption of the specimen remained relatively stable without significant alterations. In addition, a simplified DIF was proposed to predict the peak strength of FG with varying densities and two distinct GBFS replacement rates under different strain rates. It provided some valuable insights into the potential application of FG in the field of structural protection.

Observation of Two Splitting Processes in a Partial Filament Eruption on the Sun: The Role of Breakout Reconnection

Partial filament eruptions have often been observed; however, the physical mechanisms that lead to filament splitting are not yet fully understood. In this study, we present a unique event of a partial filament eruption that undergoes two distinct splitting processes. The first process involves vertical splitting and is accompanied by brightenings inside the filament, which may result from internal magnetic reconnection within the filament. Following the first splitting process, the filament is separated into an upper part and a lower part. Subsequently, the upper part undergoes a second splitting, which is accompanied by a coronal blowout jet. An extrapolation of the coronal magnetic field reveals a hyperbolic flux tube structure above the filament, indicating the occurrence of breakout reconnection that reduces the constraining field above. Consequently, the filament is lifted up, but at a nonuniform speed. The high-speed part reaches the breakout current sheet to generate the blowout jet, while the low-speed part falls back to the solar surface, resulting in the second splitting. In addition, continuous brightenings are observed along the flare ribbons, suggesting the occurrence of a slipping reconnection process. This study presents, for the first time, the unambiguous observation of a two-stage filament-splitting process, advancing our understanding of the complex dynamics of solar eruptions.

Success rates of lateral canthotomy and cantholysis for treatment of orbital compartment syndrome

PurposeVision loss after facial trauma can occur from orbital compartment syndrome (OCS). Orbital compartment syndrome is commonly treated surgically with a lateral canthotomy and cantholysis (C&C). Our study investigates success rates of lateral C&C for the treatment of OCS amongst emergency medicine (EM) and ophthalmology providers. MethodsA retrospective cohort study was performed. Cases were identified and the electronic medical record of patients was interrogated for clinical and procedural information. Success of a lateral C&C was defined as a decrease in intraocular pressure (IOP) to <30 mmHg after the first attempt at the procedure. Inclusion criteria included documentation of a procedural attempt, a pre-procedure IOP >30 mmHg and a post-procedure IOP measurement; or alternatively if no pre-procedure IOP was documented but the IOP was >30 on arrival to the level 1 trauma center. Exclusion criteria included periprocedural use of ocular hypotensive medications and comorbid hyphema. ResultsThe final analysis included 74 eyes from 64 patients. Emergency medicine providers performed the initial lateral C&C in 68% of cases compared to 32% by ophthalmologists, and success rates were comparable – 68% vs 79.2%, respectively (p = 0.413). Poorer visual outcomes were associated with the initial failure of a lateral C&C and head trauma without an orbital fracture. All patients treated with a vertical lid split procedure met the criteria for ‘success’ as defined by this study. ConclusionsThe success rate of a lateral C&C is comparable amongst EM and ophthalmology providers. Improved training of physicians on the lateral C&C or other simpler procedures, such as the vertical lid split, could improve outcomes in OCS.

A simple ion chromatography-mass spectrometry method for amino acid analysis in beer.

The amino acid footprint of different beer samples was analyzed using ion chromatography coupled with electrospray ionization mass spectrometry. A tailor-made polymer-based cation-exchange resin was operated with a mass spectrometry-compatible eluent under isocratic conditions on a standard high-performance liquid chromatography system coupled to a single quadrupole mass spectrometer using formic acid as a volatile eluent ion source. The partially separated peaks of the isomeric pair isoleucine/leucine were processed according to their area response ratio using vertical peak splitting or Gaussian fit. Additionally, the chromatographic resolution of the isomers was optimized with an adjusted, solely aqueous mobile phase from 0.85 to 2.92. Ion suppression in the electrospray ion source was investigated for the derivatization-free method and found to be insignificant (recovery value 100±15%) for 15 out of the 20 analytes. Quantitative results for various beer and mixed-beer beverages were found to be in high agreement with existing methods. Simultaneous photometric detection demonstrated the method's ability to successfully remove most of the interfering matrix compounds.

Certification-Constrained Vertical Tail Sizing and Power Split Optimization for Distributed Electric Propulsion Aircraft

Distributed electric propulsion (DEP) concepts leverage the synergistic benefits of aeropropulsive coupling and improve the overall flight efficiency by placing propulsors at optimal locations, such as the wingtip. However, placing propulsors far away from the aircraft centerline may bring aircraft difficulties in complying with critical-engine-inoperative flight certification rules. To investigate the impact of certification requirements on the DEP aircraft design, this paper takes NASA’s PEGASUS concept as a use case and presents a study of certification-constrained vertical tail sizing and propulsive power split optimization. For comparison, a vertical tail retrofit study is also conducted on the ATR 42-500 aircraft using the same design space, to gain insights into the different impacts of certification constraints on the design process between conventional and unconventional aircraft. In each study, a design space exploration is performed, including a feasibility test and a multi-objective optimization. The feasibility test shows that the certification constraints yield a much smaller feasible design space for the DEP concept when compared to the conventional aircraft. Despite a much smaller feasible design space, the constrained Pareto optima of the PEGASUS still exhibit lower cruise drag coefficient, fuel burn, and operational energy cost when compared to those of the ATR 42.

Experimental and Numerical Investigation on the Triaxial Compressive Behavior of Steamed Recycled Aggregate Concrete

The use of recycled aggregates to produce precast concrete products is conductive to the green development of construction industrialization. This paper aimed to study the effects of curing regimes and confining pressures on the triaxial compression behavior of recycled aggregate concrete (RAC). Triaxial compression tests were carried out on RAC under different curing regimes (standard curing, 60 °C—12 h and 80 °C—9 h), and the designed confining pressures were 0 MPa, 2.5 MPa, 5 MPa, and 10 MPa. The results show that the increase of confining pressure limits the expansion of cracks, causing the failure mode to change from vertical splitting to oblique shearing, and the triaxial compressive strength is doubled at most. Compared with standard curing, steam curing significantly weakened the triaxial compressive strength of RAC, which was related to the reduction of RAC cohesion, and the cohesion of RAC steam cured at 80 °C was reduced by 30%. The triaxial compression failure of RAC closely follows the Mohr–Coulomb criterion. Based on the discrete element method and test results, an RAC triaxial compression numerical model considering the shape of the actual coarse aggregate was established, and the propagation of cracks was discussed at the mesoscopic level.