Search Results (4,082)

The use of artificial oxygenation to counteract the effects of hypoxia and improve living standards in high-altitude, low-oxygen settings is widespread. A recognized consequence of this intervention is that it elevates the risk of fire occurrence. In this study, we simulated a real fire environment with low-pressure oxygen enrichment in a plateau area. A new multi-measuring apparatus was constructed by integrating an electronic control cone heater and a low-pressure oxygen enrichment combustion platform to enable the simultaneous measurement of multiple parameters. The combined effects of varying oxygen concentrations and thermal irradiance on the combustion behavior of wood plastic composites (WPCs) under specific low-pressure conditions were investigated, and alterations in crucial combustion parameters were examined and evaluated. Increasing the oxygen concentration and heat flux significantly reduced the ignition and combustion times. For instance, at 50 kW/m², the ignition time decreased from 75 s to 16 s as the oxygen concentration increased from 21% to 35%. This effect was suppressed by higher heat fluxes. Compared with low oxygen concentrations and low thermal radiation environments, the ignition time of the material under high oxygen concentrations and high thermal radiation conditions was shortened by more than 78%, indicating that its flammability is enhanced under extreme conditions. Higher oxygen concentrations enhanced the heat feedback to the fuel surface, which accelerated pyrolysis and yielded a more compact flame with reduced dimensions and a color transition from blue-yellow to bright yellow. This intensified combustion was further manifested by an increased mass loss rate (MLR), elevated flame temperature, and a decline in residual mass percentage. The combustion of WPCs displayed distinct stage characteristics, exhibiting “double peak” features in both the MLR and flame temperature, which were attributed to the staged pyrolysis of its wood fiber and plastic components. Full article

Deep oil and gas reservoirs exist under high-temperature and high-pressure (HTHP) conditions. Conventional coring without thermal preservation during retrieval induces thermal imbalance, biasing petrophysical and phase measurements and distorting resource evaluation. Internationally, most temperature-preserved corers are designed for low-temperature conditions and rely on passive insulation, whereas existing HTHP simulators can reproduce pressure and temperature but lack the capability to evaluate active thermal retention throughout coring and retrieval. Here, we develop and validate a full-scale testing platform for active in situ temperature-preserved coring (active ITP-coring), consisting of a simulated HTHP core chamber, a through-chamber conductive module, a high-pressure simulation module, an ambient-temperature simulation module, and a data acquisition and control module. The system operates stably at 150 °C and 140 MPa, reproduces realistic ambient cooling histories (with maximum and average rates of 11.22 and 5.11 °C/min), and demonstrates that, under HTHP conditions, active preservation limits the internal temperature drop to 4.2 °C over 40.5 min (temperature retention of 98.93%), markedly outperforming the 13.1 °C decrease within 14.9 min without active preservation. These results verify the system’s reliability and, at the laboratory scale, demonstrate the feasibility of active ITP-coring, providing a reproducible methodology and quantitative evidence for engineering deployment in deep reservoirs. Full article

The Dual Fluid Reactor (DFR) is a Generation IV concept that relies on a phased development pathway using a low-temperature microdemonstrator ($\mu$DEMO) and a high-temperature minidemonstrator (mDEMO). A rigorous methodology is required to scale experimental data between these facilities to ensure the reliable design of the final reactor. This paper establishes such a methodology grounded in Similarity Theory. The Cathare-2 system code was used to perform a parametric study on a simplified model of the demonstrators, which use lead–bismuth eutectic and pure liquid lead, respectively. This study focused on identifying the specific operating conditions required to match key “defining” dimensionless numbers—the Reynolds number (Re) for dynamic similarity and the Peclet number (Pe_h) for thermal similarity. The analysis successfully identified and presented the distinct operating ranges of fluid velocity and mass flow required to achieve either state. Results show that matching the Reynolds number allows for the dimensionless pressure drop to be scaled with a deviation below 0.2%, while matching the Peclet number allows for the dimensionless temperature profile to be scaled with a deviation under 2.5%. The central finding is that dynamic and thermal similarity cannot be achieved simultaneously due to the different working fluids and temperatures of the demonstrators. This forces a strategic choice in experimental design, where an experiment must be tailored to investigate either fluid dynamics or heat transfer. This work provides the foundational “rulebook” for designing these crucial experiments, ensuring that data from the DFR demonstrator program is both reliable and scalable. Full article

The development of rare-earth-free permanent magnets represents a strategic direction in advanced magnetic materials research. Among the most promising candidates, the metastable α″-Fe₁₆N₂ phase stands out due to its exceptionally high saturation magnetization. In this work, α″-Fe₁₆N₂ powders produced by gas atomization followed by nitriding were consolidated via Spark Plasma Sintering (SPS). The effects of sintering temperature (498–598 K) and pressure (40–80 MPa) on phase evolution, densification, microstructure, and magnetic properties have been systematically investigated. Optimal processing conditions were identified at 548 K and 60 MPa, providing a balance between densification (~80% of the theoretical density), phase stability, and magnetic performance. X-ray diffraction revealed that the α″-Fe₁₆N₂ phase remains stable up to ~523 K, while its decomposition into α-Fe and γ′-Fe₄N becomes significant at higher temperatures. The consolidated samples exhibited a saturation magnetization of ~230 Am²/kg, a maximum coercivity of ~86.5 kA/m, and a Mr/Ms ratio of 0.42. δM curve analysis indicated a transition from magnetostatic interactions (at low pressures) to exchange-dominated coupling (at intermediate and high pressures). These findings demonstrate the potential of SPS processing to preserve the α″-Fe₁₆N₂ phase and produce rare-earth-free magnetic compacts with competitive magnetic performance, providing a basis for further process optimization. Full article

Background: The aim of the study was to analyze the clinical characteristics and circumstances of relapses in the patients with relapsing-remitting multiple sclerosis (MS). Objectives: The eighty patients with clinically definite MS and relapsing-remitting course were enrolled in the retrospective study. Methods: The calendar of documented recurrences was analyzed, looking for any patterns across years, warm and cold periods, and seasons and months. Results: In the years 2015–2020 the majority of relapses occurred in March, June–July, and October; with regard to seasons, the relapse rate peaked during spring and summer. In 2021–2023 there was significant increase in relapses in May and in February. In these years, most cases occurred in spring, and the least in autumn. The most significant coincidences were found for sensory symptoms in January, optic neuritis in March, motor deficit with pyramidal signs in May and June, cerebellar symptoms in March and July, and spinal cord involvement signs in August. Conclusions: Observation of seasonal occurrence of relapses revealed periods with high temperature, low humidity, and variable atmospheric pressure as potential contributors. Better recognition of these issues within future investigations could be considered in the complex approach to the management of MS outcomes. Full article

The present paper proposes a novel approach for the estimation of the in-cylinder pressure and heat release in diesel engines from basic testbed measurements (i.e., brake mean effective pressure (BMEP), gross indicated mean effective pressure (IMEP360), peak firing pressure (PFP), crank angle at which 50% of fuel mass has burnt (MFB50) and exhaust gas temperature (T_exh). The method exploits a previously developed low-throughput combustion model, based on the accumulated fuel mass approach, which has been tuned by a genetic algorithm (GA) optimizer. The latter adjusts the main combustion model parameters to minimize an objective function, which depends on the prediction errors of BMEP, IMEP360, PFP, MFB50 and T_exh. Several scenarios were evaluated in which different subsets of the four previous quantities were assumed to be known from experimental activities. The proposed method is particularly useful when in-cylinder pressure traces are unavailable and only basic testbed data exist. The results show that the in-cylinder pressure and heat release profiles are estimated with a high level of accuracy, since the root mean squared error is of the order of 1–2.5 bar and 2–2.7 × 10⁻² kJ, respectively, depending on the considered scenario, while requiring a modest computational effort which is of the order of 3–6 min per test. Moreover, the low-throughput nature of the method makes it straightforward for other researchers to implement and reproduce results on different engines. The approach is also fuel-independent and can be applied to engines running on alternative/zero-carbon fuels, which are currently being extensively studied as potential ways to reduce the environmental impact of internal combustion engines. Full article

Polycrystalline Diamond Compacts (PDC) face thermal damage and insufficient wear resistance in complex strata due to the high thermal expansion coefficient of Co binder and its catalysis on diamond graphitization. Existing studies lack a systematic comparison of HfB₂, ZrB₂, and Al-Ni (1.5wt.%Al + 1.5wt.%Ni) on PDC performance under a unified process, and their synergistic mechanism with the PDC matrix remains unclear. Herein, 3wt.% of these additives were incorporated into diamond micropowder to prepare PDC via unified high-temperature and high-pressure (HTHP) sintering. XRD/SEM-EDS characterized the phase/microstructure, while thermal expansion and Vertical Turret Lathe (VTL) tests evaluated their properties. Results: (1) ZrB₂-modified PDC performed the best, with a thermal failure temperature of 800 °C (8.5% higher than the blank group), VTL wear cycles of 110 Pass (22.2% higher), and ZrC (confirmed by XRD) enhancing interface bonding; (2) HfB₂-modified PDC reduced the wear area by 18% (vs. the blank group) via low-expansion HfC (6.5 × 10⁻⁶/°C) and maintained a continuous structure; (3) Al-Ni-modified PDC had a wear ratio of 1.945 × 10⁴ (4.5% higher) but only 60 Pass and structural defects. This study confirms ZrB₂ as the optimal additive for PDC’s comprehensive properties, supporting high-performance PDC development for complex downhole environments. Full article

As a critical ecological barrier in the arid and semi-arid regions of northwestern China, the spatio-temporal evolution of vegetation carbon sequestration in the Hexi Corridor is of great significance to the ecological security of this region. Based on multi-source remote sensing and meteorological data, this study integrated second-order partial correlation analysis, ridge regression, and other methods to reveal the spatio-temporal evolution patterns of Gross Primary Productivity (GPP) in the Hexi Corridor from 2003 to 2022, as well as the response characteristics of GPP to air temperature, precipitation, and Vapor Pressure Deficit (VPD). From 2003 to 2022, GPP in the Hexi Corridor showed an overall increasing trend, the spatial distribution of GPP showed a pattern of being higher in the east and lower in the west. In the central oasis region, intensive irrigation agriculture supported consistently high GPP values with sustained growth. Elevated air temperatures extended the growing season, further promoting GPP growth. Due to irrigation and sufficient soil moisture, the contributions of precipitation and VPD were relatively low. In contrast, desert and high-altitude permafrost areas, constrained by water and heat limitations, exhibited consistently low GPP values, which further declined due to climate fluctuations. In desert regions, high air temperatures intensified evaporation, suppressing GPP, while precipitation and VPD played more significant roles. This study provides a detailed analysis of the spatio-temporal change patterns of GPP in the Hexi Corridor and its response to climatic factors. In the future, the Hexi Corridor needs to adopt dual approaches of natural restoration and precise regulation, coordinate ecological security, food security, and economic development, and provide a scientific paradigm for carbon neutrality and ecological barrier construction in arid areas of Northwest China. Full article

The exploration and development of deep marine resources are faced with the problems of poor drill ability and serious wellbore instability in high temperature and high-pressure formations. The bottom hole dynamic drilling tool with low vibration characteristics is the best choice for deep well drilling. The output torque of the turbodrill is relatively small, which limits its application potential. In this study, intelligent optimization algorithms are used to improve the blade shape design to improve its output torque. Firstly, based on the moment of momentum theorem, the key blade profile parameters and range affecting the output characteristics of the turbodrill are analyzed and summarized. Subsequently, the five-order polynomial method and UG software (version 10.0) are used to complete the three-dimensional configuration of the bent-twisted blade. Then, based on the GA-LSSVM-MOPSO-TOPSIS intelligent optimization algorithm, the two-dimensional and three-dimensional modeling design parameters under the optimal hydraulic performance are optimized, and the accuracy of the intelligent optimization algorithm and parameters is verified by CFD simulation analysis. The results show that the hydraulic efficiency of only 4.9% is sacrificed, and the output torque is increased by 36.61%, which significantly improves the hydraulic performance of the turbodrill and provides guidance for the design of low-speed and high-torque turbodrills. Full article

The purpose of this study is to develop a multiphysical model of agglomeration of low-grade phosphorites with the addition of phosphate-siliceous shales and oil sludge. To achieve these tasks, a numerical approach was used in the COMSOL Multiphysics environment, based on solving the related problems of heat transfer and hydrodynamics during heat treatment of the material. A laboratory vertical tubular furnace made of heat-resistant quartz glass with electric heating was used to study the effect of the temperature field and the velocity of gases on the degree of sintering and the dynamics of phosphorous agglomerate formation under various technological conditions. It has been established that the optimal temperature for the agglomeration process is a layer temperature of 950–1000 °C at a gas flow rate of 1.5–2 m/s, which ensures the formation of durable granules and minimizes sintering heterogeneity. The maximum sintering layer height of the test charge reaches 210–230 mm at pressures of 0.015–0.027 MPa. A comparison of the numerical simulation results with experimental data showed a good agreement, which confirms the practical significance of the proposed model for the design and optimization of industrial processes of agglomeration of phosphorous raw materials. Modern physical and chemical analyses have established the phase, microstructural, and element-by-element characteristics of the studied phosphate-siliceous shale and the product of agglomeration firing. The results of modeling the hydrodynamics of the charge agglomeration process can be recommended to increase the efficiency of processing phosphate-containing waste and reduce energy consumption. Full article

Polymer solutions play a crucial role in the polymer flooding process by influencing the flow characteristics of formation fluids and enhancing recovery efficiency. Their properties are influenced by the transient coupling of temperature, pressure, and viscosity, yet the underlying patterns remain unclear. This study establishes a non-steady-state coupling model of polymer temperature–pressure–viscosity in wellbores, solved numerically using a staggered-grid fully implicit scheme in Matlab. At a depth of 1000 m, the polymer viscosity is measured in the field as 102.12 mPa·s, while the simulated value is 107.46 mPa·s (4.97% error), indicating good agreement with the wellbore viscosity distribution. Wellbore temperature is the dominant factor, whereas injection pressure has minor effects. Injection flow rate governs heat exchange with the formation; low flow causes larger temperature and viscosity fluctuations, while high flow leads to insufficient heat transfer. With prolonged injection, wellbore temperature approaches dynamic equilibrium, viscosity decreases, and sand-carrying capacity weakens. These findings provide theoretical guidance for optimizing polymer flooding. Full article

Understanding the thermal behaviour of radioisotope generators under Martian conditions is essential for the safe and efficient operation of planetary exploration rovers. This study investigates the heat transfer and flow mechanisms around a simplified full-scale model of the Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) by means of Computational Fluid Dynamics (CFD) simulations performed with ANSYS Fluent 2023 R1. The model consists of a central cylindrical core and eight radial fins, operating under pure CO₂ at a pressure of approximately 600 Pa, representative of the Martian atmosphere. Four cases were simulated, varying both the reactor surface temperature (373–453 K) and the ambient temperature (248 to 173 K) to reproduce typical diurnal and seasonal scenarios on Mars. The results show the formation of a buoyancy-driven plume rising above the generator, with peak velocities between 1 and 3.5 m/s depending on the thermal load. Temperature fields reveal that the fins generate multiple localized hot spots that merge into a single vertical plume at higher elevations. The calculated dimensionless numbers (Grashof ≈ 10⁵, Rayleigh ≈ 10⁵, Reynolds ≈ 10², Prandtl ≈ 0.7, Nusselt ≈ 4) satisfy the expected range for natural convection in low-density CO₂ atmospheres, confirming the laminar regime. These results contribute to a better understanding of heat dissipation processes in Martian environments and may guide future design improvements of thermoelectric generators and passive thermal management systems for space missions. Full article

The oil layers in the Dongying Formation offshore oilfield are severely contaminated. The near-wellbore reservoir pore throats are blocked, which seriously affects the development effect. It has become urgent to implement acidizing stimulation measures. However, the target reservoir is deeply buried, has high reservoir pressure, and is highly sensitive. These factors result in high pressure during acidizing operations, a long single-trip time for raising and lowering the tubing string, and high costs. Moreover, acid that is not promptly returned to the surface after acidizing can cause secondary pollution to the reservoir. This work proposes an integrated tubing string to perform reverse displacement and reverse squeeze. With this, acid can be injected into the formation through the annulus between the casing and tubing. The residual acid and its post-acidizing derivative residues are rapidly lifted to the surface by the reciprocating suction action of the return pump. Based on this, the structure and specifications of the acidizing-flowback tubing string are designed through the flow rate analysis method. The tubing string is mainly affected by mechanical effects, including buoyancy, piston effect, flow viscosity effect, helical bending effect, temperature difference effect, and expansion effect. The maximum deformations are 1.4 m, 1.9 m, 0.18 m, 2.7 m, 1.8 m, and 2.5 m, respectively. The total deformation is less than 3 m. Simulation results from three groups of oil wells at different depths indicate that the axial force of the tubing string ranges from 400 to 600 kN. The stress ranges from 260 to 350 MPa, deformation is 1.1–2.4 mm, and the safety factor exceeds 3.0. This can effectively ensure the safety of on-site operations. Based on the actual field conditions, the acidizing-flowback tubing string is evaluated. This verifies the effectiveness of the acidizing-flowback tubing string. This research provides an economical and efficient operation process for acidizing operations in the Dongying Formation offshore oilfield. It achieves the goal of removing reservoir contamination and provides guidance for the unblocking and stimulation of low-permeability and sensitive reservoirs in the middle and deep layers of offshore oilfields. Full article

Maintaining an effective facial seal is critical for the performance of tight-fitting industrial respirators used in high-risk sectors such as mining, manufacturing, and construction. Traditional fit verification methods—Qualitative Fit Testing (QLFT) and Quantitative Fit Testing (QNFT)—are limited to periodic assessments and cannot detect fit degradation during active use. This study presents a real-time fit detection system based on embedded breath sensors and machine learning algorithms. A compact sensor module inside the respirator continuously measures pressure, temperature, and humidity, transmitting data via Bluetooth Low Energy (BLE) to a smartphone for on-device inference. This system functions as a multimodal biosensor: intra-mask pressure tracks flow-driven mechanical dynamics, while temperature and humidity capture the thermal–hygrometric signature of exhaled breath. Their cycle-synchronous patterns provide an indirect yet reliable readout of respirator–face sealing in real time. Data were collected from 20 healthy volunteers under fit and misfit conditions using OSHA-standardized procedures, generating over 10,000 labeled breathing cycles. Statistical features extracted from segmented signals were used to train Random Forest, Support Vector Machine (SVM), and XGBoost classifiers. Model development and validation were conducted using variable-size sliding windows depending on the person’s breathing cycles, k-fold cross-validation, and leave-one-subject-out (LOSO) evaluation. The best-performing models achieved F1 scores approaching or exceeding 95%. This approach enables continuous, non-invasive fit monitoring and real-time alerts during work shifts. Unlike conventional techniques, the system relies on internal physiological signals rather than external particle measurements, providing a scalable, cost-effective, and field-deployable solution to enhance occupational safety and regulatory compliance. Full article

As terrestrial oil and gas resources continue to decline, deep-sea oil and gas development has become a strategic priority. A wide range of production equipment must be deployed on the seabed, among which subsea wet-mateable connectors are indispensable. To address the challenges of high pressure, low temperature, and corrosion in deep-sea environments, this study proposes a cooperative sealing strategy between the annular protrusion on the entry casing and a sliding sleeve. The leakage per single mate/demate cycle is quantified under varying insertion speeds and pressure differentials. By examining the effects of protrusion geometry, insertion speed, friction coefficient, and radial compression on sealing performance, the optimal parameters are identified: a friction coefficient of 0.15 and a trapezoidal-rib seal with 0.015 mm radial compression for dynamic sealing, yielding a contact pressure of 27.5 MPa and a mating/demating force of 197.26 N—satisfying the manipulation requirements of a remotely operated vehicle. Hydrostatic pressure tests demonstrate that the dynamic sealing design of the underwater connector achieves a balance between high reliability and low insertion resistance, and the prototype meets the operational requirements for deep-sea service. Full article