Search Results (268)

With the expansion of ammonia energy applications, long-distance liquid ammonia pipelines are expected to support large-scale cross-regional ammonia transport. In the liquid ammonia pipeline commissioning process, gaseous ammonia purging involves ammonia–nitrogen mixing and possible liquefaction, while liquid ammonia injection may induce flashing and severe local cooling, all of which can affect commissioning safety. To characterize these thermodynamic phenomena, a transient gas–liquid two-phase flow model was established and validated using OLGA 2022.1.0 software for simulating the long-distance liquid ammonia pipeline commissioning. The model adopts the cross-sectionally averaged one-dimensional approach. A volume-corrected Soave–Redlich–Kwong (SRK) equation of state for ammonia was adapted, validated, and used to generate OLGA-compatible thermodynamic property tables. The results show that, during gaseous ammonia purging, a higher flowrate shortens the displacement time by accelerating nitrogen removal, and this effect is more pronounced at higher ambient temperatures due to enhanced molecular diffusion. Along the pipeline, pressure gradually decreases from frictional resistance, with a steeper drop near the outlet caused by gas acceleration, and temperature gradually approaches ambient through heat exchange with the pipe wall and surrounding soil. A high gaseous ammonia flowrate can cause partial liquefaction, regasification, and temperature fluctuations. During liquid ammonia injection, local condensation and slight liquid accumulation occur before the liquid front arrives, and the low-temperature region moves with the liquid front. The liquid ammonia mass flowrate has the strongest influence on the injection process, as it reduces the completion time but increases the outlet temperature, outlet pressure, and the low-temperature risk downstream of the valve. Therefore, it should be controlled within an appropriate range to balance efficiency and low-temperature safety risks. This work provides a rapid and efficient prediction model for key thermo-hydraulic parameters during liquid ammonia pipeline commissioning, and the overall analyses offer insights for on-site process design and safety control. Full article

Chinese lacquerware is a multi-layered natural polymer composite whose characterization is complicated by burial degradation, organic–inorganic mixing, and the overlap of signals from lacquer, drying oils, proteins, polysaccharides, waxes, and pigments. This review evaluates analytical strategies for Chinese lacquerware by distinguishing three complementary levels of evidence: morphological and elemental observation, chemically specific molecular fingerprinting, and biomolecular source recognition. Microscopy, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and scanning electron microscopy–energy dispersive spectroscopy (SEM-EDS) are useful for identifying stratigraphy, pigments, fillers, and functional groups, but they are often insufficient for assigning degraded organic matrices and trace additives independently. Pyrolysis–gas chromatography/mass spectrometry provides more specific molecular evidence through diagnostic marker classes, including alkyl catechols, alkyl phenols, nitrogen-containing pyrolysis products, anhydrosugars, long-chain aliphatics, aldehydes, and ketones. Immunological assays based on lacquer glycoproteins further complement chemical analysis by supporting biological source differentiation, although their reliability depends on protein preservation, extraction efficiency, and antibody specificity. Representative case studies, including a seventeenth-century Swedish lacquered pipe, the Nanyue Kingdom lacquered ear cup, and a Tang Dynasty lacquered leather artifact, show that robust interpretation requires cross-validation among stratigraphic, elemental, spectroscopic, chromatographic, immunological, and archaeological evidence. The review concludes that integrated analytical workflows can improve material identification, clarify manufacturing sequences, assess degradation uncertainty, and provide more reliable evidence for conservation decision-making and the reconstruction of historical lacquer craftsmanship. Full article

Many older residential toilet designs may pose substantial biomechanical demands for older adults with reduced lower-extremity strength, as standard seat heights often require increased joint range of motion (ROM) and compensatory upper-limb support during sit-to-stand (STS) transfer. This exploratory, repeated-measures biomechanical study evaluated the effects of a biomimetic Stand-assist Toilet Seat (BSTS) designed to facilitate STS movement through a forward-and-upward curvilinear lifting trajectory. Thirty community-dwelling older adults were stratified into high-, moderate-, and low-functioning groups according to normative 30 s Chair Stand Test performance. Participants completed repeated STS trials under conventional and BSTS-assisted seating conditions in randomized order. A synchronized multimodal assessment integrating MediaPipe Pose-based motion tracking for sagittal-plane kinematic analysis was used to quantify lower-limb kinematics and upper-limb kinetics. Mixed-design ANOVA revealed significant main effects of seating condition on hip and knee ROM (all p < 0.001, η²p > 0.70), indicating reduced lower-limb joint motion requirements under the BSTS condition. Significant reductions were also observed in peak arm-support force (F (1,27) = 14.57, p = 0.001, η²p = 0.35) and arm-support impulse (F (1,27) = 20.21, p < 0.001, η²p = 0.42), demonstrating decreased upper-limb loading during STS transfer. No significant interaction effects between seating condition and functional group were identified. These findings suggest that the BSTS modified STS movement patterns and reduced upper-limb loading demands in community-dwelling older adults. The combined kinematic and kinetic assessment approach may provide a practical method for biomechanical evaluation of assistive seating technologies in rehabilitation and aging-related applications. Full article

Particle-laden pipe flows are ubiquitous in food, chemical and pharmaceutical processes, where solid particles significantly alter fluid deformation and mixing. Understanding these transport mechanisms is critical for process optimisation. A Lagrangian analysis framework based on a SPH-DEM simulation is proposed to compute finite-time Lyapunov exponent (FTLE) fields and extract Lagrangian coherent structures (LCSs) for non-Newtonian particle-laden pipe flows. The method directly exploits the inherently Lagrangian particle trajectories and computes the FTLE fields using the SPH interpolation scheme, avoiding the costly numerical integration required by conventional Eulerian approaches. Subsequently, LCSs are extracted via a ridge detection algorithm and the combined FTLE is introduced to quantify mixing intensity. The framework is validated against the Kármán vortex street benchmark, showing good agreement with experiment and numerical results. Then the validated framework is applied to non-Newtonian particle-laden pipe flows for a wide range (0 vol.%~30 vol.%) of particle loading. Results reveal a critical concentration range of 20 vol.%~30 vol.%, where the cross-sectionally average combined FTLE increases with concentration up to 20 vol.%, indicating enhanced mixing, but decreases beyond 30 vol.% as particle–particle interactions suppress near-wall fluid deformation. These findings provide a robust Lagrangian tool and new quantitative insights for optimising mixing and transport in industrial particulate flows, such as in food processing pipelines and chemical reactors. Full article

The mixing valve is a key component of an ultra-high-pressure premixed abrasive waterjet system, in which the abrasive–water mixing uniformity plays a decisive role in determining the erosion and cutting performance of the jet. The geometric parameters of the mixing chamber inside the valve are therefore critical factors affecting this uniformity. In this study, the liquid–solid two-phase flow within the mixing chamber was numerically investigated using the Eulerian k–ε turbulence model coupled with the Fluent–Rocky DEM approach. Single-factor simulations were first conducted to identify the effective ranges of key structural parameters influencing the mixing performance. Subsequently, a response surface model was established to describe the relationship between the mixing efficiency (ME) and four critical chamber parameters, namely the throat diameter (TD), throat length (TL), abrasive inlet pipe diameter (AD), and the distance between the throat exit and the abrasive inlet pipe center (TE). Based on this model, the optimal structural parameters of the mixing chamber were determined. The results indicate that when TD = 4 mm, TL = 12 mm, AD = 10 mm, and TE = 7 mm, the simulated ME reaches 34.40% ± 0.49%, which is in close agreement with the predicted value of 34.57%. Experimental validation conducted on a premixed abrasive waterjet test rig shows that the mean absolute relative error between the simulated and measured ME values is 7.54%, which is below the 10% threshold, confirming the reliability and accuracy of the numerical model. Full article

Phase misalignment between periodic pollutant emissions and receptor inhalation can fundamentally bias exposure estimations, yet it is rarely quantified in transient assessments. Here we propose Phase-Independent Pollutant Exposure (PIPE), a general exposure metric that removes this temporal randomness by integrating phase-resolved exposure over a phase-difference probability distribution. The phase-dependent exposure function is reconstructed efficiently using a Fourier series surrogate built from sparse samples, enabling deterministic calculation of the expected exposure without resource-demanding Monte Carlo sampling. We demonstrate the framework using a short-range indoor exposure case representative of periodic human emissions resolved by transient computational fluid dynamics (CFD). Results showed that across multiple breathing intensities, breathing/coughing waveforms, interpersonal distances (0.5–1.5 m), and exposure durations, phase-dependent variability was consistently pronounced and accurately captured by the proposed model. Phase differences increased cumulative inhaled exposure by up to 9.58 times, with the largest amplification occurring at close range (0.5 m) under intense breathing. Flow-field analysis indicates that specific phase relationships can suppress turbulent kinetic energy in the inter-person region, limiting dispersion and thereby elevating near-field concentrations and intake. Although phase effects attenuate with time due to accumulation and mixing, they remain non-negligible even over extended contact (up to 60 s). Notably, PIPE is generally lower than exposure under perfectly synchronized phases, but becomes 1.20–4.97 times higher in close-range, high-intensity scenarios. By explicitly accounting for phase uncertainty, PIPE provides a transferable and computationally efficient methodology to stabilize exposure assessment for periodic sources, improving the robustness of process-based risk metrics relevant to environmental and human exposure evaluation. Full article

In view of the severe performance requirements of high-strength drill pipe joint in deep drilling engineering, 130 ksi high-strength and toughness drill pipe joint is taken as the research object. Thermal deformation behavior and precision forming process of a new composition system joint are investigated. Wire-cut specimens (ϕ10 × 15 mm) are tested on a Gleeble-3500 machine under 900–1200 °C and 0.01–10 s⁻¹, with EBSD for microstructure observation. Results show that the small- and large-angle grain boundary cooperate to obtain the mixed structure of high dislocation density, fine substructure and fine grain, which makes the phase transformation products more fine and uniform. Combined with the finite element numerical simulation and experimental verification system, the effects of billet temperature, strain rate and die temperature on the microstructure and macro properties of the joint are analyzed, and the optimal combination of parameters is determined, including 880 °C billet temperature, 20 mm/s punch speed and 300 °C die temperature. The optimization scheme aims to achieve grain refinement and flow stress control, obtain fine and uniform tempered sorbite structure with grain size grade 10.0, and also achieve the optimal comprehensive strength and toughness, which can provide a theoretical basis and technical path for the industrial production of high-performance drill pipe joints. Full article

Marine benthic ecosystems along urbanised coastlines face heightened vulnerability due to the cumulative effects of chronic anthropogenic stressors. Climate change intensifies these pressures through more frequent and severe storms, while ongoing coastal development adds further stress through infrastructure projects. This study examined how soft-bottom communities in the coastal NW Mediterranean responded to two major disturbances: an exceptional storm in 2018 and the construction of a new wastewater pipeline in 2019. Sediment grain size, organic content, bacterial abundance and enzymatic activity, and metazoan communities were analysed during summer of 2018, 2019 and 2020 and in the following spring period. Hydrodynamic forcing caused a general increase in the grain size in 2019. Meiobenthos responded with a strong decline in abundance, especially crustaceans, while macrobenthos changed from a mixed deposit-feeder community to a suspension-feeder dominated one. In 2020, the improved trophic value of sediment organic matter in the pipe area favoured bacterial increase. While meiobenthos abundance slowly recovered, the differentiation increased due to macrobenthic juveniles, resulting from increased macrobenthic abundance and diversity (mainly pure deposit-feeders). A clear shift towards organic enrichment-tolerant taxa due to wastewater release was not observed, given the contemporary presence of very sensitive organisms, indicating that co-occurring stressors can lead to nonlinear responses of the communities.: Full article

The particle size distribution of backfill aggregate is a key factor affecting the performance of the -long-distance pipeline transport of backfill slurry. However, the understanding of its impact on slurry flow behavior, transportation resistance, and particle distribution mechanisms remains incomplete and calls for further investigation. This study first obtained the rheological parameters of slurry and their variation laws under the influence of particle size distribution through rheological experiments. Subsequently, CFD numerical simulations are used to investigate the flow characteristics of slurry under long-distance transportation conditions. The findings demonstrate that a reduction in the mixed aggregate particle size leads to a significant increase in both the yield stress and plastic viscosity of the backfill slurry. The conveying distance shows a positive correlation with the slurry transportation resistance. Furthermore, the slurry exhibits plug flow behavior in both the horizontal and vertical pipe sections, whereas this plug flow pattern is no longer observed in the bend section. The tailings particles exhibit a distinct stratified distribution within the pipeline. In the horizontal pipe section, the graded tailings predominantly settle at the bottom, whereas the fine tailings remain suspended near the top. In contrast, in the vertical pipe section, the graded tailings tend to accumulate in the central zone of the pipe, while the fine tailings are dispersed along the pipe wall. As the content of graded tailings increases from 30% to 50%, both the zones with increased and decreased particle volume fractions expand, while the steady flow zone correspondingly shrinks. Meanwhile, the volume fraction of graded tailings at the bottom of the pipe rises significantly from 0.12 to 0.61. This research provides important theoretical support for the optimized matching and rational application of tailings particle size distribution in the design of long-distance pipeline transportation systems for mine backfill. Full article

Variable cross-section cement–soil pipe piles are an innovative soft ground improvement technology. They are tubular, special-shaped cement–soil mixing piles characterized by a tapered profile along the pile shaft (larger diameter at the top and smaller at the bottom) and an internal soil core. They offer advantages including reduced material consumption, lower engineering cost, and shorter construction duration. However, the systematic theoretical understanding of their bearing performance remains insufficient. In this study, the bearing mechanism and influencing parameters of variable cross-section pipe piles were systematically investigated via full-scale field tests, numerical simulations, and laboratory model tests. An exponential decay constitutive model considering the strain-softening behavior of cement–soil was developed and implemented through secondary development in the ABAQUS platform for parametric analysis. Laboratory model tests were further conducted to advance the understanding of the bearing mechanism of variable cross-section pipe piles. The results show that the ultimate bearing capacity of the proposed variable cross-section cement–soil pipe pile is approximately 189% higher than that of the conventional ones. The expanded outer diameter and expanded height are the dominant factors affecting the bearing capacity, while the inner diameter and pile length have a comparatively minimal influence: increasing the expanded outer diameter from 0.6 m to 1.2 m and the expanded height from 0 m to 5 m increased the ultimate bearing capacity from 445 kN to 868 kN and 936 kN, respectively. The effective pile length is determined to be 6 m, and the recommended minimum wall thickness of the pipe pile is 1/4 of the inner diameter. Laboratory tests further demonstrated an abrupt change in axial force at the variable section. The findings provide reliable theoretical support for the engineering design and field application of cement–soil variable cross-section pipe piles. Full article

Traditional pipe roof support design methods generally assume horizontal ground conditions and treat the pipe roof as a monolithic beam, thereby neglecting the differential stress distribution among individual steel pipes under unsymmetrical loading. To address this gap, this paper presents two main contributions: a low-carbon cement-based grouting material suitable for pipe roof reinforcement, and a new mechanical model that simultaneously accounts for biased pressure conditions and the inter-pipe micro-arch effect. First, the working performance of limestone calcined clay cement (LC³) grout was systematically tested at a water–cement ratio of 1:1, and the optimal mix ratio was determined. Grout–soil reinforcement tests on weathered granite show that, for grout-to-soil volume ratios between 0.2 and 0.8, the compressive strength of the reinforced material exceeds 10 MPa and the elastic modulus exceeds 600 MPa. Second, a mechanical model for the pipe roof was established based on the Pasternak two-parameter foundation theory, incorporating both biased pressure conditions and the inter-pipe micro-arch effect. The model predictions were compared with existing field monitoring data in the literature, showing consistent trends and good agreement in peak deflection values. Parametric analysis reveals that under horizontal ground conditions, the pipe roof response is symmetric, with the vault as the most critical area. As the bias angle increases, the maximum response shifts toward the higher side of the terrain, and the stress difference between pipes on both sides increases significantly. Theoretical analysis of the low-carbon grouting material shows that pipe roof deflection is moderately reduced compared to traditional grouting materials, but at the cost of increasing bending moment and shear force within the steel pipes. The proposed low-carbon grouting material and the validated mechanical model provide theoretical support for the design optimization of pipe roof support in shallow unsymmetrical loading tunnels. Full article

Mixed steel/polyethylene gas distribution pipelines are increasingly used in congested urban environments where conventional layouts are restricted by existing underground utilities, safety constraints, and site-specific construction conditions. In such systems, buried steel transition sections may become particularly vulnerable to electrical perturbation and corrosion, especially when installed near electrified transport infrastructure. This paper presents a field case study on a recently installed mixed steel/polyethylene gas distribution pipeline located on Lunca Street, Petroșani, Romania, approximately parallel to an electrified railway. Electrical and electrochemical investigations were carried out eight months after installation and included 24 h monitoring of pipe-to-soil potential versus Cu/CuSO₄, 24 h monitoring of alternating current pipe-to-soil voltage, mixed alternating current and direct current signal visualization, and coating insulation resistance measurements. The results showed that alternating current pipe-to-soil voltage was present at all monitored points, with weighted mean values ranging from 0.41 to 1.23 Vrms, while pipe-to-soil potential values ranged from −0.120 to −0.238 V versus Cu/CuSO₄. Although the measured average coating insulation resistance remained relatively high, the combined electrical and electrochemical data indicate that alternating current interference associated with the nearby electrified railway is the most plausible dominant contributing source of the recorded electrical perturbation. Within the analyzed site perimeter, no other nearby electrical infrastructures with comparable interference potential were identified. The highest alternating-current exposure and the least favorable electrochemical values were recorded on the longer metallic segment, showing that metallic length and local configuration strongly influenced the severity of the effect. A mitigation strategy based on polarized electrical decoupling and dedicated grounding is proposed as a practical means of improving electrical safety and reducing corrosion risk in the exposed and buried steel sections. 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

The chemical agent injection modes and displacement characteristics of chemical compound flooding, consisting of a plugging agent, an oil displacement agent, and a viscosity reducer, were investigated by laboratory experiments for target heavy oil reservoirs after multiple cycles of huff-and-puff. The performances of the oil displacement agent, viscosity reducer and plugging agent were evaluated, and the formulation and concentration were optimized. The oil displacement effects and displacement characteristics of different injection modes were studied by sand-filled two-pipe models. The experiment results showed that alternating injections of the oil displacement agent and viscosity reducer yielded better results than their mixed injection, and small segments alternating injections achieved the highest recovery. The larger the dosage of the oil displacement agent, the larger the maximum liquid production ratio between the high- and low-permeability layers, but with the smaller the liquid production reverse duration. The larger the dosage of the viscosity reducer, the greater the water cut decrease but the smaller the maximum liquid production ratio. For chemical compound flooding in the Zhong’er block in the Gudao oilfield, the recommended injection mode was 0.1 PV plugging agent + 2000 mg/L of oil displacement agent + 0.5% viscosity reducer, with small segments of the oil displacement agent being followed by a viscosity reducer at an injection slug ratio of 6:4. However, the injection mode depends on the prices of oil and the chemical agent. When prices fluctuate, the chemical agent concentration should be adjusted accordingly. Full article

When a H₂S-containing gas kick occurs during drilling, the formation fluid containing hydrogen sulfide is mixed into the drilling fluid. Drilling fluid containing hydrogen sulfide is prone to causing hydrogen embrittlement when it comes into contact with the drill string during the upward return process. However, research on the risk and timing of hydrogen embrittlement in drill pipes remains limited. This study constructed a risk area and hydrogen embrittlement time analysis model. The risk area and time of hydrogen embrittlement in the drill pipe of the Jinyue 402 well in Tarim Oilfield were analyzed using the constructed model. The results indicate that the concentration of hydrogen sulfide in the Jinyue 402 well is in the area where the corrosion rate of steel increases rapidly, and the partial pressure of hydrogen sulfide is higher than the critical partial pressure at which corrosion cracking occurs. Taking into account the pH of the drilling fluid, fluid flow rate, hydrogen sulfide partial pressure, drill pipe tensile stress, hydrogen sulfide concentration, and gas partial pressure, the high-risk area for hydrogen sulfide corrosion damage in the Jinyue 402 well is 0–1680 m. The predicted highest risk point location and hydrogen embrittlement time are at a well length of 280 m and 21 h. Further predictions were made for the hydrogen embrittlement length and time of the Tazhong 83 and Zhonggu 503 wells in the Tarim Oilfield. The maximum prediction errors for the hydrogen embrittlement position and time of the drill pipe in the three wells were 4.8% and 5.2%, respectively. This indicates that the model can be applied to wells with different geological conditions and hydrogen sulfide concentrations. Full article