Search Results (90)

Accurate prediction of the Remaining Useful Life (RUL) of special gas cylinders is critical for industrial safety management. However, the nonlinear, strongly coupled degradation behaviors of these cylinders, combined with non-stationary and high-noise monitoring data, limit the performance of single deep learning models. Traditional hyperparameter tuning and signal processing methods often fail to meet the required prediction accuracy. To address these challenges, this study proposes a hybrid SSA–PSO–ResNet–LSTM–Attention framework for RUL prediction of special gas cylinders. The framework first applies Singular Spectrum Analysis (SSA) to decompose and reconstruct the 12-dimensional multi-source sensor signals, effectively suppressing noise while extracting core degradation trends. Subsequently, a ResNet–LSTM–Attention collaborative model is constructed, where ResNet ensures stable spatial feature propagation, LSTM captures long- and short-term temporal dependencies, and a multi-head attention mechanism emphasizes critical time steps associated with abrupt degradation. Furthermore, a Particle Swarm Optimization (PSO) algorithm is employed to globally optimize key hyperparameters, including the number of convolutional kernels, LSTM hidden units, and learning rate, mitigating the subjectivity of manual tuning. Experimental validation is conducted on 1000 real monitoring samples from 100 composite material gas cylinders, with a cylinder ID-based 7:1:2 train–validation–test split and stratified sampling covering four operating conditions. PSO optimizes hyperparameters using the validation set RMSE as the fitness function, and the test set is exclusively used for final performance evaluation. All results are reported as the mean ± standard deviation from grouped 5-fold cross-validation on the cylinder-wise partition. The proposed model achieves a test RMSE of 71.55, MAE of 50.63, and R² of 0.9584, representing a 34.2% and 30.2% reduction in RMSE and MAE, respectively, compared with the second-best CNN-LSTM model, and significantly outperforming SVR, MLP, and other benchmark models. Ablation studies confirm the positive synergistic effect of each component, with the removal of either the attention mechanism or the ResNet module causing substantial performance degradation. By employing physically calibrated RUL labels and a balanced multi-condition dataset, the proposed framework achieves high predictive accuracy and good potential for industrial application, providing an effective solution for RUL prediction of special gas cylinders and similar high-pressure vessels, with potential applications in intelligent maintenance of complex industrial equipment. Full article

The synergistic deformation and energy dissipation of backfill–surrounding rock composite structures under impact loading remain poorly understood, despite the frequent exposure of deep mine backfilled stopes to dynamic disturbances such as blasting and seismicity. In this study, Split Hopkinson Pressure Bar (SHPB) tests were conducted at a fixed impact pressure of 0.2 MPa on single-material specimens and bonded backfill–rock composite cylinders, with loading applied from both the backfill end and the surrounding rock end. Single backfill specimens exhibited dominant reflected energy (~90%) and low crushing energy consumption (<20%), whereas composite specimens displayed characteristic “double-peak” or “flat-peak” stress–strain signatures with peak strengths exceeding that of standalone backfill. When loading was directed from the high-strength surrounding rock into the backfill, the reflected energy ratio decreased to 60–80% and crushing energy consumption increased to 20–30%, demonstrating a loading-direction-dependent energy dissipation mechanism. These results provide a quantitative reference for optimizing blast sequence design in backfilled stopes. Full article

The integration of real-time monitoring capabilities into concrete materials offers significant potential for improving the safety and durability of building infrastructure. This study investigates the real-time electromechanical behavior of steel fiber-reinforced self-sensing concrete under compressive and splitting tensile loading. Eighteen cubes (150 × 150 × 150 mm) and eighteen cylinders (150 × 300 mm) containing 0.5%, 1.5%, and 3% steel fiber volume fractions were tested. Electrical resistance was continuously recorded at one-second intervals using an Arduino–ESP32-based system, enabling in situ tracking of damage evolution. The conductive steel fiber network functioned as an intrinsic sensing phase, where load-induced microstructural changes altered electrical pathways. Resistance variations consistently preceded visible cracking, with pronounced nonlinear increases observed at 65–80% of peak load, indicating micro-crack initiation. Distinct electromechanical stages were identified, including elastic stability, compaction-induced resistance reduction near yield, and rapid resistance growth during crack propagation. Higher fiber contents improved both mechanical performance and sensing sensitivity through enhanced crack-bridging and conductive network stability. Although curing age influenced baseline resistance, reliable real-time damage detection was achieved across all specimens. The findings demonstrate the feasibility of steel fiber-reinforced concrete as a cost-effective, distributed monitoring material for early damage detection in building structures. Full article

Foamed concrete is a lightweight, environmentally friendly civil engineering material with excellent absorption capacity. It has been widely applied in engineering fields such as building thermal insulation and pore filling of underground buried pipelines. But the mechanical properties of existing foamed concrete cannot meet the engineering requirements for support, pressure relief and filling of weak surrounding rock. The mechanical properties of foamed concrete were improved with CNTs to prepare CNT foamed concrete (CNTFC) pressure-relieving filling materials. The effects of five factors (the fly ash (FA) incorporation rate, aggregate–cement ratio, water–binder ratio, CNT incorporation rate and foam volume fraction) on the density and 2:1 cylinder strength (the ratio of uniaxial compressive strength to apparent density), splitting tensile (the ratio of splitting tensile strength to apparent density) and specific strength of the CNTFC were analyzed. By combining stress–strain and scanning electron microscopy analyses, the mechanism of improvement of the mechanical strength of CNTFC due to CNTs was clarified. The results show that the foam volume fraction, water–binder ratio and aggregate–cement ratio are the top three factors affecting its strength, followed by the CNT incorporation rate and FA incorporation rate. Among the five influencing factors, only the incorporation of CNTs increases the 2:1 cylinder strength, splitting tensile strength and specific strength. When the doping rate is 0.05%, this ratio specifically refers to the mass of CNTs accounting for 0.05% of the mass of the total cementitious materials of cement and fly ash. At this doping dosage, compared with the condition without CNTs (0% doping dosage), the uniaxial compressive strength increased from 6.23 MPa to 7.18 MPa (with an increase rate of 15.3%). The splitting tensile strength increased from 0.958 MPa to 1.02 MPa (with an increase rate of 6.5%). The density only slightly increased from 0.98 g/cm³ to 1.0 g/cm³ (with an increase rate of 2.0%), achieving the balance of “high strength-low density”. CNTs and cement hydrates are interwoven into a network structure, and the mechanical properties of the CNTFC are effectively improved by the excellent nanoscopic tensile properties. Excessive doping of CNTs takes 0.05% as the threshold. Exceeding this doping dosage (such as 0.10% and 0.15%) leads to a decrease in its strength and ductility due to CNT agglomeration and deterioration of pore structure. And 0.05% is the ratio of the mass of CNTs to the total cementitious materials of cement and fly ash. At this doping dosage, CNTs are uniformly dispersed and can balance the strength and density of CNTFC. The optimum proportion of CNTs is 0.05%. Full article

Little research is reported on the properties of Portland cement concrete (PCC) mixtures comprising plastic waste materials. Therefore, this novel study was initiated to evaluate the effects of plastic waste materials on different properties of PCC. Plastic boxes and containers made of polypropylene were cut, grinded, pulverized, and incorporated into PCC mixtures. Sand was partially replaced by plastic waste materials with 0%, 5%, 10%, 15%, and 20% volume ratios. Experiments were conducted using PCC cylinders and prisms to evaluate several unique properties of PCC containing plastic waste. Innovative interactions and contributions of several PCC properties including workability, air content, density, water absorption, mechanical properties, rapid chloride ion penetration, and freeze–thaw deterioration are investigated. The new experimental data indicated that the workability and density of PCC decreased with increasing plastic waste replacement levels. The maximum decreases in workability and density were 23% and 6.2% for the PCC with 20% plastic replacement, respectively. On the other hand, our research has shown that air content and water absorption of PCC increases with increasing plastic waste amount. The maximum increase in air content and water absorption were 78% and 29% for the PCC with 20% plastic waste. This study also shows that the mechanical properties of PCC (e.g., compressive and splitting strengths) after 7 and 28 days of moist curing decreased with increasing plastic waste content. Another new finding is that the rapid chloride permeability of PCC increased and the freeze–thaw durability of PCC decreased with an increase in plastic waste amount. One of the most critical discoveries of this experimental study is that plastic waste increases the durability of PCC, i.e., durability factor of PCC with 20% plastic waste was 9.3% compared to 28.5% for the control PCC without plastic waste materials. Full article

One of the challenges in inertia sensor applications is the need for a class of devices that operate at one of the ring resonant frequencies to achieve large amplitudes of vibration. However, large amplitudes tend to produce undesirable nonlinear effects due to geometrical nonlinearities. Hence, a rigorous experimental dynamic analysis of rotating thin circular ring-type structures is considered important to gain a deeper understanding of the device’s nonlinear behavior as well as the potential performance improvements. This study aims to experimentally investigate the nonlinear dynamic behavior of rotating thin circular rings and the effects of angular rate as well as mass mismatch variations on the system natural frequency. A prototype made of a macroscale thin cylindrical structure is employed to study the nonlinear dynamic behavior of rotating thin circular rings. Using a precision rate table equipped with a slip ring as well as non-contact sensors/actuators, experiments that closely represent the actual physical operating conditions of angular rate sensors are developed. Natural frequency variations due to the input angular rate changes are measured in time and frequency domains. Useful experimental observations on the frequency split and mass mismatch effects have been performed. Typical nonlinear behavior, such as jump phenomena of a rotating thin circular cylinder, is noted. The nonlinear dynamic behavior of a ring-type resonator system, which is subjected to external excitations, is experimentally investigated. Results from the present experimental study on the mechanics of the ring structure are expected to provide further insight into the design and operation of ring-type resonators for angular rate sensing applications. Full article

Fly ash, as the main solid waste of coal-fired power plants, is an environmental problem that needs to be solved due to its massive accumulation. The mechanical properties and optimization mechanism of lightweight aggregate concrete prepared by using new single-cylinder rotary kiln fly ash ceramic granules as aggregate were systematically investigated. Through orthogonal experimental design, combined with macro-mechanical testing and microscopic characterization techniques, the effects of cement admixture and ceramic granule admixture on the properties of concrete, such as compressive strength, split tensile strength, and modulus of elasticity, were analyzed, and the optimization scheme of key parameters was proposed. The results show that the new single rotary kiln fly ash ceramic particles significantly improve the mechanical properties of concrete by optimizing the porosity (water absorption ≤ 5%), and its 28-day compressive strength reaches 46~50.9 MPa, which is 53.3~69.7% higher than that of the ordinary ceramic concrete, and the apparent density is ≤1900 kg/m³, showing lightweight and high-strength characteristics. X-ray diffraction (XRD) analysis shows that the new ceramic grains form a more uniform, dense structure through the synergistic effect of internal mullite crystals and dense glass phase; computed tomography (CT) scanning shows that the total volume rate of cracks of the new ceramic concrete was reduced by up to 63.8% compared with that of ordinary ceramic concrete. This study provides technical support for the utilization of fly ash resources, and the prepared vitrified concrete meets the demand of green building while reducing structural deadweight (20~30%), which has significant environmental and economic benefits. Full article

This study addresses computational challenges in the immersed boundary method (IBM) with the pressure implicit with split operator (PISO) algorithm for simulating incompressible flows. We introduce a novel time-step splitting method to implement communication overlapping optimization, aiming to reduce costs dominated by the pressure Poisson solver. Using a fast Fourier transform (FFT)-based approach, the Poisson equation is solved efficiently with $O(NlogN)$ complexity. Our method interleaves IBM force calculations with Poisson phases, employing asynchronous communication to overlap computation with global data exchanges. This reduces communication overhead, enhancing scalability. Validation through benchmark simulations, including flow around a cylinder and particle-laden flows, shows improved efficiency and accuracy comparable with traditional methods. Implemented in a custom C++ solver using the FFTW library, tests indicate substantial acceleration, with results showing a 40% speed-up and less than 3% deviation in drag and lift coefficients. This research provides an efficient and promising simulation tool for complex flow. Full article

Control of buoyancy-assisted convective flow and the associated thermal behavior of nanofluids in finite-sized conduits has become a great challenge for the design of many types of thermal equipment, particularly for heat exchangers. This investigation discusses the numerical simulation of the buoyancy-driven convection (BDC) of a nanofluid (NF) in a differently heated cylindrical annular domain with an interior cylinder attached with a thin baffle. The annular region is filled with non-Darcy porous material saturated-nanofluid and both NF and the porous structure are in local thermal equilibrium (LTE). Higher thermal conditions are imposed along the interior cylinder as well as the baffle, while the exterior cylinder is maintained with lower or cold thermal conditions. The Darcy–Brinkman–Forchheimer model, which accounts for inertial, viscous, and non-linear drag forces was adopted to model the momentum equations. An implicit finite difference methodology by considering time-splitting methods for transient equations and relaxation-based techniques is chosen for the steady-state model equations. The impacts of various pertinent parameters, such as the Rayleigh and Darcy numbers, baffle dimensions, like length and position, on flow, thermal distributions, as well as thermal dissipation rates are systematically estimated through accurate numerical predictions. It was found that the baffle dimensions are very crucial parameters to effectively control the flow and associated thermal dissipation rates in the domain. In addition, machine learning techniques were adopted for the chosen analysis and an appropriate model developed to predict the outcome accurately among the different models considered. Full article

Considering the urgent need for sustainable construction materials, this study investigates the mechanical and microstructural responses of novel hybrid geopolymer concrete blends incorporating Fly Ash (FA), Ground Granulated Blast Furnace Slag (GGBS), Cement (C) and Precipitated Silica (PS) as partial replacements for traditional cementitious materials. The motive lies in reducing CO₂ emissions associated with Ordinary Portland Cement (OPC). The main aim of the study was to optimise the proportions of industrial wastes for enhanced performance and sustainability. The geopolymer mixes were activated using a 10 M sodium hydroxide (NaOH)—Sodium Silicate (Na₂SiO₃) solution and cast into cubes (100 mm), cylinders (100 mm × 200 mm) and prism specimens for compressive, split tensile and flexural strength testing, respectively. Six combinations of mixes were studied: FA/C (50:50), GGBS/C (50:50), FA/C/PS (50:40:10), FA/GGBS/PS (50:40:10), GGBS/C (50:50) and GGBS/FA/PS (50:40:10). The results indicated that the blend with 50% FA, 40% GGBS and 10% PS exhibited higher strength. Mixes with GGBS and PS presented a l0 lower slump due to rapid setting and higher water demand, while GGBS-FA-cement mixes indicated better workability. GGBS/C exhibited a 24.6% rise in compressive strength for 7 days, whereas FA/C presented a 31.3% rise at 90 days. GGBS/FA mix indicated a 35.5% strength drop from 28 days to 90 days. SEM and EDS analyses showed that FA-rich mixes had porous microstructures, while GGBS-based mixes formed denser matrices with increased calcium content. Full article

Concrete printing in three dimensions is believed to be an innovative construction method. Numerous researchers conducted laboratory experiments over the past decade to examine the behavior of concrete mixtures and the material properties that are pertinent to the 3D concrete printing industry. Furthermore, the global warming effect is being further exacerbated by the increased use of cement, which increases carbon dioxide (CO₂) emissions and pollution. Various standards endorse the utilization of Portland-composite cement in construction to mitigate CO₂ emissions, particularly cement CEM II/A-P. This research provides an experimental and numerical study to examine the evolution of cementitious composite utilizing cement CEM II/A-P for three-dimensional concrete printing, combining three different types of synthetic fiber. The thorough experimental analysis includes three combinations integrating diverse fiber types (polypropylene, high-modulus polyacrylonitrile, and alkali-resistant glass fibers) alongside a reference mixture devoid of fiber. The three distinct fiber types in the mixtures (polypropylene, high modulus polyacrylonitrile, and alkali-resistant glass fibers) were evaluated to assess their impact on (i) the flowability of the cementitious mortar and the slump flow test of fresh concrete, (ii) the concrete compressive strength, (iii) the uniaxial tensile strength, (iv) the splitting tensile strength, and (v) the flexural tensile strength. Previous researchers designed a cylinder stability test to determine the shape stability of the 3D concrete layers and their capacity to support the stresses from subsequent layers. Furthermore, the numerical analysis corroborated the experimental findings with the finite element software ANSYS 2023 R2. The flexural performance of the examined beams was validated using the Menetrey–Willam constitutive model, which has recently been incorporated into ANSYS. The experimental data indicated that the incorporation of synthetic fiber into the CEM II/A-P mixtures enhanced the concrete’s compressive strength, the splitting tensile strength, and the flexural tensile strength, particularly in combination including alkali-resistant glass fibers. The numerical results demonstrated the efficacy of the Menetrey–Willam constitutive model, featuring a linear softening yield function in accurately simulating the flexural behavior of the analyzed beams with various fiber types. Full article

Innovative and creative solutions are needed to reduce the substantial carbon footprint of the concrete industry using low-carbon materials. Biochar has been recognised as an environmentally efficient material for concrete production. Also, it is required to build interpretable predictive models to advance modelling-based mix design optimisation. This study uses biochar as a cement substitute in concrete and assesses the mechanical strength using lab tests followed by predictive modelling approaches. Two types of biochar derived from olive pits and wood were used in 2.5 and 5 wt.% of cement. Cubes, cylinders, and beams were cast to test biochar concrete’s compressive, tensile, and flexural strength. The test data were used to develop and validate prediction models for the compressive strength (CS) using linear regression and gene expression programming (GEP) techniques. Moreover, SHapley Additive exPlanation (SHAP) analysis was performed to evaluate the influence of parameters on the CS. The results showed that olive pit biochar was more effective in enhancing the concrete strength than wood biochar due to the reduced particle size. The optimal replacement levels for olive pit biochar were 2.5 wt.% for the CS and 5 wt.% for the split tensile and flexural strength. The GEP model effectively captured the non-linear behaviour of biochar concrete and was more accurate than the linear regression model for the CS. The approach adopted in this study can be used to optimise mix design formulations for biochar concrete. These findings highlight the potential of biochar as a sustainable and effective cement substitute, contributing to the development of greener concrete with improved mechanical performance. Integrating biochar into concrete production can significantly lower the industry’s carbon footprint, promoting environmentally responsible construction practices while maintaining structural integrity. Full article

Concrete production has increasingly used seawater to overcome the challenge of freshwater scarcity. Although the use of seawater in concrete still has a controversial reputation, it is a promising application, particularly when combined with mineral admixtures such as natural zeolitic tuffs (ZT). This paper aims to investigate the effect of using locally quarried ZT on the strength of unreinforced concrete mixed and/or cured using seawater. The mix proportions of the concrete were selected to obtain the optimum combination for the M20 grade of concrete with a water-to-cement ratio of 0.69. Moreover, 150mm-cubes and cylinders of 100 mm diameter by 200mm height were cast from the concrete mixtures, which contain 0%, 5%, 7.5%, 10%, and 25% of ZT as a partial replacement of silica sand. Splitting tensile tests and compressive strength tests were conducted on these specimens at 7, 28, and 90 days. The results show the harmful effect of seawater on the strength of plain concrete (without ZT) at 7, 28, and 90 days of curing, especially when seawater is used in both mixing and curing of the concrete. However, adding ZT in seawater-based concrete improved its strength apparently, especially at early curing ages. For example, using 10% of ZT as a partial replacement of silica sand increased the compressive strength of seawater based-concrete by 105.4%, 28.3%, and 34.6% after 7, 28, and 90 days of curing, compared with concrete without ZT and produced using seawater. These results contribute to the enhancement of the sustainability of both freshwater and concrete material through the use of ZT in producing concrete, particularly in areas where freshwater is scarce or expensive. Full article

Fiber-reinforced cement matrix composites (CMCs) have gained significant attention due to their ability to enhance material properties for use in demanding environments. This study investigated the workability and mechanical properties of polyvinyl alcohol (PVA) fiber-reinforced CMCs, focusing on compressive strength, split tensile strength, and flexural strength. It also assessed water absorption capacity through immersive water absorption tests using cubes and capillary water absorption tests using cylinders, alongside bulk density measurements for both shapes. The results indicated that the dosage of PVA fibers significantly influences the workability of CMCs, while the water-to-binder ratio has a minimal effect. Increasing the dosage of PVA fibers in CMCs from 0.5 vol.% to 1 vol.% led to a decrease in several properties: compressive strength decreased by 13.38%, split tensile strength by 21.05%, flexural strength by 9.23%, bulk density of cube samples by 4.14%, and bulk density of cylindrical sample by 6.36%. Conversely, both immersive water absorption and capillary water absorption increased, rising by 10.87% and 77.71%, respectively. Compressive strength was found to increase with the bulk density of the cubes and to decrease with rising immersive water absorption. Similarly, split tensile strength increased with the bulk density of the cylinders and decreased as capillary water absorption increased. Strong correlations were observed among three key pairwise combinations: the bulk density of cubes and immersive water absorption (R² = 94%), compressive strength and bulk density of cubes (R² = 96%), and compressive strength and immersive water absorption (R² = 92%). Furthermore, the analysis and comparison of carbon fiber-reinforced and PVA fiber-reinforced CMCs will provide important references for the field, especially in cases where material availability or cost varies. Full article

In the current global scenario, it is essential to find more effective and practical solutions to mitigate the problem of particulate emissions from vehicles. In this research, particulate emission characteristics with changing GDI pressure or applying a split GDI strategy with different second injection timings were initially explored in a Dual-Fuel Spark Ignition (DFSI) engine, which employs Ethanol Port Injection (EPI) plus Gasoline Direct Injection (GDI). The experimental results show that by increasing GDI pressure ($P_{GDI}$) from 5.5 MPa to 18 MPa, ignition delay (${\theta }_F$) shows a small decrease of 0.68 degrees. The parameters, such as maximum in-cylinder temperature ($T_{MI}$) and exhaust gas temperature ($T_{EG}$), each increase by 53.75 K and 13.84 K. An apparent reduction of 59.5% and 36.26% was achieved for the concentrations of particulate number ($N_P$) and particulate mass ($M_P$), respectively. Particulate emissions are effectively reduced by a split GDI strategy with an appropriate range of second injection timing ($t_{GDI2}$). Under $t_{GDI2}$ = −260 °CA, $N_P$ and $M_P$ concentrations exhibit a relatively lower level. However, by delaying $t_{GDI2}$ from −260 °CA to −140 °CA, there is an increase of more than 60% in $N_P$ concentration. The research findings help offer new and valuable insights into optimising particulate number and mass emissions from DFSI engines. Moreover, the findings could contribute novel and valuable insights into the optimisation of particulate emission characteristics in DFSI engines. Full article