Search Results (935)

Pyrolysis of refuse-derived fuel (RDF) is a promising waste-to-energy route, but its use in higher-value applications remains limited by tar carryover, benzene, toluene, ethylbenzene, and xylenes (BTEX), heteroatom-containing compounds, and pollutant accumulation in recirculated scrubber water. This study evaluated operating windows for RDF pyrolysis coupled with direct wet scrubbing and closed-loop water reuse, with the aim of identifying regimes suitable for different end-use tiers. A Taguchi L27 design of experiments (DOE), i.e., an orthogonal array comprising 27 experimental runs, was applied to evaluate the effects of pyrolysis temperature, residence time, scrubber liquid-to-gas ratio, and scrubber-water temperature, while sequential reuse of the same scrubber-water inventory was evaluated at 5, 10, and 15 cycles. Cleaned-gas pollutants were quantified by compound-resolved gas chromatography–mass spectrometry (GC–MS) after solid-phase adsorption (SPA) sampling, while phenolics and polycyclic aromatic hydrocarbons (PAHs) in scrubber water were determined by extraction followed by GC–MS. Feasibility within each end-use tier was defined as simultaneous satisfaction of tier-specific cleaned-gas thresholds (C_tar, C_BTEX, I_N, and I_S) and the corresponding water-loop hazard limit (I_tox), using literature-informed engineering screening criteria. The results showed that stronger scrubbing reduced gas-phase tar and BTEX burdens, whereas extended water reuse caused systematic accumulation of phenolics and PAHs and increased the composite water-loop hazard index. Boiler-grade operation remained feasible across a broad operating range, with 23 of the 27 tested conditions remaining robust, whereas internal combustion engine combined heat and power (ICE-CHP) feasibility was restricted to a narrow robust regime, and no robust microturbine-grade condition was identified. These findings show that operating windows for RDF pyrolysis must be defined jointly by gas cleanliness and water-loop management constraints. Full article

Vibration test fixtures are widely used to evaluate the dynamic characteristics of structures. However, their performance is often limited by their excessive weight and unintended resonances. Conventional optimization methods, such as genetic algorithms, have been applied to improve fixture design; however, they often require considerable computational effort and are inefficient for problems involving discrete design variables. To address these limitations, this study proposes a rib thickness optimization method based on an orthogonal array. The novelty of the proposed method lies in the introduction of an influence value that simultaneously reflects lightweighting effect and first natural frequency change. The proposed method generates orthogonal arrays for rib-thickness configurations, performs modal analyses, and applies analysis of means based on this influence value to identify ribs with low structural influence for thickness reduction. Its effectiveness was validated through comparison with a genetic algorithm under identical conditions. The results showed that the orthogonal array achieved rib reduction patterns similar to those of the genetic algorithm while requiring only 0.84% of the analyses and 1.14% of the computation time required by the genetic algorithm. These findings demonstrate that the orthogonal array provides an efficient and practical alternative for rib thickness optimization in vibration test fixtures. Full article

In order to reduce the environmental pollution caused by waste white mud from the papermaking process, this paper proposes a new method of preparing lightweight concrete using waste white mud and shale ceramsite, aiming to provide a new approach for the recycling of papermaking waste. The main objective of this study is to investigate the feasibility of utilizing paper-making white clay as a cement replacement in lightweight concrete and to systematically evaluate the influence of key parameters, such as white clay content, on its fundamental mechanical properties. Based on lightweight ceramsite concrete, paper-making white clay was used to replace cement in preparing white clay lightweight concrete. Through orthogonal tests, mix proportion design and optimization were carried out, and the effects of factors like water–binder ratio and white clay content on the compressive strength, splitting tensile strength, and early-age cracking resistance of the concrete were studied. The results show that with the increase in white clay content, the cube compressive strength of concrete first increases and then decreases. When the white clay content is 5%, the splitting tensile strength of the concrete is the highest at all ages, and when the white clay content is 15%, the internal structural compactness of the concrete is optimal. Full article

In response to the shortcomings still observed in polyethylene (PE)/ethylene-vinyl acetate (EVA)/styrene-butadiene-styrene (SBS) composite modified bitumen regarding storage stratification and low-temperature performance, this paper further introduces furfural extract, elemental sulphur, stabilisers and Z-6036 into this ternary system, and employs orthogonal design to screen the additive ratios. Tests were conducted on conventional physical properties, rotational viscosity, dynamic shear rheology and bending beam rheology, focusing on the material’s temperature sensitivity, rheological behaviour, low-temperature creep resistance and phase characteristics. The modification effects were analysed using fluorescence microscopy, scanning electron microscopy and infrared spectroscopy. Compared with the control group composed of 4% PE, 4% EVA and 2% SBS, the samples obtained from the orthogonal design showed an increase in elongation at 5 °C ranging from 52.5% to 213.9%; the difference in softening points decreased from 35.2 °C to a minimum of 0.1 °C, indicating improved storage stability. The temperature sensitivity of all sample groups was reduced, with the optimal group achieving a VTS of −0.4413, representing a 46.7% improvement over the control group. At −12 °C, the m-values of all nine orthogonal samples were higher than those of the control group, with seven groups reaching m ≥ 0.3, indicating improved low-temperature stress relaxation capability. A comprehensive analysis of the experimental results indicates that the selected chemical additives are beneficial for optimising the dispersion state and compatibility of the SBS/PE/EVA ternary modified bitumen, whilst also balancing rheological properties and low-temperature crack resistance to a certain extent. Microscopic and spectroscopic analyses further suggest that internal interactions within the system have been enhanced and the phase distribution has become more uniform; however, the current evidence is insufficient to conclusively determine that a specific form of chemical cross-linking reaction has occurred. Full article

Vegetation eco-concrete (VEC) is a novel material for slope stabilization, effectively integrating ecological restoration with engineering protection. Its primary supporting skeleton consists of aggregates with specific particle sizes, bonded by cementitious materials, and is characterized by numerous interconnected pores, along with certain mechanical properties. However, VEC still faces challenges in practical application, such as inaccuracies in the optimal mix design and poor vegetative compatibility between the structural material and plants. To determine the optimal mix for porous VEC, this study utilizes Portland cement to design the VEC mix proportions based on orthogonal tests. The study further conducts VEC paving and plant experiments based on the optimal mix obtained. The results indicate the following: (1) The optimal mix consists of a water–cement ratio of 0.27, a cement particle diameter of 10 mm, a cement particle content of 70–75 wt%, a mortar binder content of 0.1 wt%, and a polypropylene fiber content of 0.16 wt%. (2) VEC with nutrient-enriched particles exhibited excellent vegetative compatibility, providing root penetration channels and creating a conducive environment. (3) Plant species with strong adaptability and well-developed root systems that integrate with VEC can enhance both the engineering protection and ecological benefits of VEC. Full article

Urban underground construction in water-rich sandy strata produces large quantities of high-fluidity pipe-jacking spoil whose high water content, residual conditioning agents and heavy metal contaminants make conventional dewatering and landfilling increasingly unsustainable under carbon peaking and neutrality targets. This study explores a low-carbon route that converts such spoil into CO₂ foamed concrete through a coupled alkali activation–CO₂ foaming process. Ground granulated blast furnace slag and fly ash are used as geopolymer precursors, while a CO₂-based aqueous foam is introduced as both a pore-forming phase and carbon source. Single-factor tests and an L16(4⁴) orthogonal design are conducted to quantify the effects of CO₂ concentration, foam volume fraction, geopolymer dosage and alkali activator content on fluidity, setting time and compressive strength. Scanning electron microscopy (SEM) is employed to examine pore structure, gel morphology, carbonate precipitation and the interfacial transition zone around spoil particles. The results identify an optimum mix window (CO₂ 60–80%, foam 70–80%, geopolymer ≈ 20% and alkali activator ≈ 10% of solids) that delivers a fluidity above 210 mm, 28-day strength exceeding 3.0 MPa and a uniform closed-pore network. A multi-scale mechanism is proposed in which physical foaming, chemical carbonation and spoil particle immobilization act synergistically to form a dense gas–solid–soil composite suitable for in situ backfilling. Full article

Timber frame diaphragms play a central role in the lateral stability of modern timber buildings, yet current design codes insufficiently capture their nonlinear behaviour and governing failure mechanisms. This study evaluates two finite element modelling strategies to improve the prediction of diaphragm response. The first strategy, implemented in MATLAB^®, explicitly models the nonlinear behaviour of sheathing-to-framing (STF) connections using an oriented orthogonal multilinear damage law. Validation against experimental tests on partially anchored and fully anchored diaphragms as well as in-plane bending specimens demonstrated accurate predictions of stiffness and force–displacement behaviour in both the linear-elastic and elastoplastic ranges. Deviations in peak load predictions for the detailed model reached up to approximately 25%, while stiffness predictions remained within approximately 10% of the experimental values. The second approach, implemented in commercial structural engineering software, represents STF connections by uncoupled elastoplastic spring elements. Although post-peak softening cannot be captured, peak capacities were predicted within approximately 3–5% for several configurations, with reliable stiffness estimates in most cases. A quantitative comparison using the normalised root mean square error between experimental and numerical force-displacement curves yielded values between approximately 5% and 14%, indicating good agreement between the numerical predictions and the experimental behaviour. Overall, the detailed model enables high-fidelity nonlinear analysis and insight into failure mechanisms, whereas the simplified spring approach offers a practical and computationally efficient modelling strategy suitable for routine engineering design. Full article

In response to the pressing issues of unclear adhesion mechanisms during the soil-removal process in peanut harvesting, poor soil fragmentation quality, and difficulties in separating the pods from the soil. Based on TRIZ theory, this study has innovatively designed a separation device that relies on external forces, such as kneading and squeezing. A mechanical model of soil fragmentation and separation was developed. The key factors affecting the device’s operational performance were identified. Through theoretical analysis and discrete element simulation, this study elucidates the working principle by which the device crushes and separates soil particles using kneading and squeezing forces. Through analysis of one-factor and orthogonal experiments, the optimal operating parameter combination for the device was determined to be: a drum installation clearance of 104.7 mm, a rotational speed difference of 75.2 rpm, and a pattern roughness of Grade III (reticulated). The system’s performance metrics are a soil removal rate of 96.59% and a pod damage rate of 2.48%. Field tests have confirmed that the deviation from simulation results is minimal. The device’s performance meets the requirements of actual production. Full article

This study investigated the enhancement mechanisms and optimal mix proportion of basalt fiber (BF) in concrete for ship lock galleries. It focused on improving crack resistance, freeze–thaw resistance, impermeability, and abrasion–erosion resistance under complex hydraulic environments. Single-factor tests first determined the reasonable parameter ranges, which were subsequently used in a three-factor, four-level orthogonal experiment to analyze the effects of the water-to-binder ratio, fiber content, and fiber length on concrete’s mechanical properties. Range analysis of the orthogonal experiment indicated that the water-to-binder ratio was the most dominant factor (R = 57.4), followed by fiber content. Based on this, further durability tests were conducted, including ring restraint cracking, impermeability, freeze–thaw resistance, and abrasion–erosion resistance. Multi-objective optimization was performed using full factorial experiments and a comprehensive performance evaluation system. The final optimal mix proportion was determined as: a water-to-binder ratio of 0.35, a fiber content of 0.2%, and a fiber length of 12 mm. With this mix, the concrete’s ring cracking time was extended by 69.9%, the relative dynamic elastic modulus retention reached 73.0% after 100 freeze–thaw cycles, the relative permeability coefficient was 1.04 × 10⁻⁶ cm/h, and the abrasion–erosion resistance strength increased to 7.05 h·m²/kg, which achieved an optimal synergy among the mechanical properties, key durability indicators, and their workability. Mechanism analysis revealed that BF formed a three-dimensional, randomly distributed fiber network that comprehensively enhanced concrete performance through multi-scale mechanisms, including bridging, pore refinement, and energy dissipation. This research has provided systematic experimental evidence and mix proportion support for the durability design and engineering application of BF concrete in ship lock galleries. Full article

The research conducted in this paper is a practical example of the Design of Experiments methodology. In accordance with the assumptions of the experimental design, the authors drew attention to the problem: how should the spark plasma sintering process be planned to obtain the maximum amount of information needed to optimise the consolidation of the WC-6Co composite at the lowest possible cost? The DOE methodology—a powerful technique for investigating new processes and gaining knowledge about existing ones in order to optimise them for high performance—was employed in the study. The aim of the research was to optimise the consolidation of the spark-plasma sintering process of the WC-6Co composite using the DoE (Design of Experiments) methodology. Four sintering factors were selected for the study: sintering temperature (factor A, 1300–1400 °C); heating rate (factor B, 100–300 °C/min); sintering time (factor C, 150–600 s); and pressure (factor D, 40–50 MPa). Each consolidation factor was designed to cover three levels. The L9 orthogonal array was used. It was found that sintering temperature and heating rate had the greatest impact on apparent density. To validate the statistical model, sintering tests were performed at a temperature of 1380 °C, a heating rate of 100 °C/min, a sintering time of 150 s and a pressing pressure of 45 MPa. Validation analysis of the statistical model demonstrated consistency with the experimental results. The WC-6Co composite achieved an apparent density of 14.85 g/cm³, corresponding to 97.42% of the theoretical density, with a hardness of 1809 HV30 and total porosity of 2.583%. X-ray diffraction studies revealed the presence of tungsten carbide and cobalt in the structure. Full article

To investigate the load characteristics and rock-breaking efficiency of the hobs on the conical cutterhead, a theoretical model of the hob’s rock-breaking load was established based on the plastic-brittle characteristics of rock, with a verification error of less than 5%. A numerical model of dual-hob rotary rock breaking was developed using ABAQUS 2022 software to comparatively study the influence of penetration depth (P), cutter spacing (S), and rotational speed (V) on the hob’s load behavior and rock-breaking efficiency. The specific energy of rock breaking under various test conditions was obtained through orthogonal experiments. The results indicate that, as the penetration depth increases, the average rock-breaking load of the hob gradually increases, while the specific energy first decreases and then increases. With larger cutter spacing, the average load shows a modest increase, and the specific energy exhibits a gradually rising trend with a diminishing growth rate. As the rotational speed increases, the average load increases slightly, while the specific energy rises with an accelerating growth rate. Range analysis revealed that the order of influence of factors on rock-breaking efficiency is P > S > V. The highest rock-breaking efficiency was achieved at P = 2 mm, S = 60 mm, and V = 7 r/min. At a significance level of 0.05, the penetration depth was found to have a significant effect on specific energy. This study provides a valuable reference for the design of hob layouts and parameter settings of conical cutterheads, contributing to improved rock-breaking efficiency. Full article

To address the current absence of targeted gradation design for porous asphalt pavements both domestically and internationally, this study employs the Coarse Aggregate Void Filling (CAVF) method to design the gradation of porous asphalt mixtures. Marshall stability tests, rutting tests, and scattering tests were conducted to investigate the relationship between coarse aggregate proportions and the structural stability of the mixture skeleton. An orthogonal experimental design was further utilized to examine the influence of three levels of fine aggregate gradation on the acoustic absorption characteristics of the mixture, and to analyze the effects of aggregate gradation on the primary pore diameter, connected pore diameter, and connected pore length. The results indicate that the coarse aggregate gradation predominantly governs the skeleton strength and overall pavement performance of the mixture, whereas the fine aggregate gradation exhibits significant effects on the interconnected void ratio, pore structure, and sound absorption performance. The optimal roughness range of coarse aggregates in porous asphalt mixtures is determined to be 0.46–0.52. The proportion of 0.6–1.18 mm aggregates has a pronounced influence on the primary pore diameter, connected pore diameter, and connected pore length. By integrating the design considerations for both coarse and fine aggregate gradations, a recommended gradation range for porous asphalt mixtures is proposed that achieves a balance between pavement performance and sound absorption/noise-reduction effectiveness. Full article

The unbalanced excitation of a rotor has a significant impact on the dynamic stiffness of the bearing. Traditional unbalanced excitation force models for the calculation of bearing stiffness are usually simplified as single-directional excitation models, which cannot fully reflect the impact of unbalanced excitation of the rotor on the dynamic stiffness of the bearing. A bidirectional excitation model based on orthogonal decomposition is used in this paper and is introduced into the finite element model of the bearing based on ABAQUS. The proposed bearing mechanics model is verified through numerical software and a bearing rotor system test rig. The effects of single/bidirectional excitation models on the dynamic stiffness of bearings were compared. The variation in bearing dynamic stiffness characteristics under rotor excitation and axial load were discussed. The results show that the presented model has good consistency with experimental results (the proposed model yields a maximum stress deviation of only 2.42% compared to MESYS numerical results and a maximum dynamic stiffness difference of 9.12% against experimental data). The traditional unidirectional excitation force model can only consider the influence of excitation frequency on the dynamic stiffness of bearings. However, the unbalanced excitation force model considering bidirectional excitation can further take into account the influence of excitation amplitude on the dynamic stiffness of bearings. Under the combined effect of excitation frequency and excitation amplitude, the radial dynamic stiffness of bearings shows a quadratic nonlinear hardening trend with rotational speed. As the rotational speed increases, the contribution of axial load to the radial stiffness significantly enhances: in the low-speed zone, its influence is only approximately 8%, while in the high-speed zone, it increases to 34%. Although the modeling method formed in this paper does not take into account the thermal–fluid dynamic coupling effect of the lubricating oil film, the obtained laws can provide a basis for the dynamic design of rotor systems of actual liquid rocket engines and have certain engineering application value. Full article

In this study, we explore the stability of shield tunnel faces excavated entirely within confined aquifers through a combined physical investigation. A series of orthogonally designed model tests were performed to examine how the hydraulic head difference (Δh) and aquitard thickness (M) jointly influence face stability and seepage behavior. Our results reveal a distinct concave-downward pore-pressure profile and a steep hydraulic gradient immediately ahead of the excavation face. Excavation-induced stress redistribution was largely restricted to the aquifer, whereas the overlying aquitard exhibited negligible disturbance due to its low permeability and higher strength. The evolution of stress disturbance followed a three-stage process encompassing initial disturbance, progressive development, and large-scale destabilization. Deformation contours exhibited a conical failure zone with normalized width and height ranging from 0.7D to 1.0D and 1.7D to 1.86D. Surface settlements remained within ±1 mm, confirming that deformation was effectively confined below the aquitard. Numerical simulations reproduced the overall hydro-mechanical response, validating the experimental observations but slightly overpredicting support pressures due to the absence of arching effects. The findings highlight Δh/M as the dominant control parameter, with aquitard thickness exerting a moderating influence. Full article

Circular pipe-jacking construction in gravel strata faces significant technical challenges, including high frictional resistance, elevated permeability, and susceptibility to collapse. Optimizing the formulation of thixotropic slurry is crucial for improving the construction quality and efficiency of such projects. This study, based on the Ruyang Water Supply Project of the North Main Canal in the Qianping Irrigation Area, Henan Province, China, systematically investigated slurry formulation using bentonite, soda ash, sodium carboxymethyl cellulose (CMC), polyacrylamide (PAM), and shell powder as raw materials. An orthogonal experimental design was employed to optimize the mix proportions, and the friction-reduction performance was validated through drag-friction model tests. The results indicate that the optimal slurry formulation is: bentonite 8%, soda ash 0.3%, CMC 0.2%, PAM 0.15%, shell powder 4%, and water 87.35%. This formulation exhibits excellent fluidity and thixotropy, facilitating the formation of a stable slurry film. Consequently, the friction coefficient between concrete specimens and gravel soil was reduced by 35.6%. The inclusion of shell powder significantly enhanced the slurry’s cohesiveness and improved the anti-seepage capacity of the surrounding stratum due to its filling effect. The optimized thixotropic slurry effectively mitigates frictional resistance during pipe jacking in gravel strata and enhances the formation’s resistance to collapse. The findings of this study provide a viable technical reference for pipe-jacking projects under similar geological conditions. Full article