Search Results (219)

Finely dispersed Al–Ca–Ti composite alloys with a set of remarkable properties can be considered as new promising structural materials. For wider use of these alloys, data on their fatigue behavior are needed. In this work the comparative study of the low-cycle fatigue strength of hot-rolled Al–xCa–0.2Ti alloys with different eutectic fractions determined by different calcium contents was conducted. The fatigue tests were carried out according to a single-plane bending scheme using a dynamic mechanical analyzer. A symmetrical loading cycle (asymmetry coefficient R = −1) with a constant stress amplitude was used. The maximum number of cycles was 20,000. It was found that increasing the eutectic fraction from 40% to 80% led to a 75% increase in the fatigue limit—from 80 to 140 MPa—which directly correlated with the alloy’s yield strength. The fatigue crack propagation occurred with the formation of a scaly fracture surface, whereas final static rupture was associated with a ductile dimple fracture. The microstructural mechanisms of alloy fatigue failure were discussed. It was found that increasing the total length of the eutectic particles/aluminum matrix interphase boundaries changed the failure mechanism to a more brittle one. Full article

Accurate joint forecasting of electricity, cooling, heating, and gas loads is essential to the coordinated operation of integrated energy systems. However, multivariate energy load sequences exhibit strong cross-carrier coupling, non-stationarity, and heterogeneous fluctuation characteristics, which limits the performance of conventional independent forecasting and fixed-model approaches. To address these challenges, this study proposes a joint load forecasting framework that integrates tabular Q-learning-assisted multivariate variational mode decomposition, sample-entropy-based reconstruction, and dynamic model selection. First, tabular Q-learning is employed to select the MVMD penalty factor and the four load sequences are synchronously decomposed to preserve the coupling relationships among components with common center frequencies. Second, sample entropy is used to reconstruct the decomposed modes into high-frequency, low-frequency, and residual subsequences, thereby reducing forecasting complexity while retaining relevant temporal features. Third, a dynamic model selection mechanism evaluates SVR, BiLSTM, XGBoost, and LightGBM and assigns an appropriate predictor to each reconstructed subsequence according to its forecasting performance. The framework is evaluated using daily electricity, cooling, heating, and gas load data collected from the Tempe Campus of Arizona State University from 2016 to 2020. A rolling input window of 56 days is used to forecast the subsequent seven days. Compared with the benchmark methods, the proposed framework achieved the best overall composite performance and competitive forecasting accuracy across the four load types. These results provide a potentially useful forecasting basis for operational decision-making in integrated energy systems. Full article

A CFD-based constrained three-component aerodynamic-trim procedure is implemented to investigate the load balance and coupled flowfield response of a simplified shipborne helicopter hovering over a flight deck. During the unsteady CFD calculation, the collective and cyclic pitch controls are updated according to the period-averaged vertical force and the rolling and pitching moments of the helicopter center of gravity. A pre-trim initialization is introduced before the formal-trim process to avoid large pitch corrections from the initial fixed-pitch state. Under a 20 m/s headwind, the initial fixed-pitch case shows a vertical-force deficit and extra rolling and pitching moments. After dynamic trim, the pitch controls converge to ${\theta }_0=8.46°$, $A_1=-2.48°$, and $B_1=1.20°$. Over the final one-revolution interval of approximately t = 31.74–32.00 s, the period-averaged loads are $F_z=112.82 \mathrm{k}\mathrm{N}$, $M_x=-0.06 \mathrm{k}\mathrm{N}·\mathrm{m}$, and $M_y=-0.07 \mathrm{k}\mathrm{N}·\mathrm{m}$. Additional +30° and −30° oblique-wind calculations confirm convergence toward the prescribed three-component load targets under asymmetric inflow conditions. The instantaneous flowfield comparisons suggest local responses in the rotor-inflow and fuselage-pressure regions after trim. Frequency-domain analysis identifies a dominant blade-passing-frequency component together with additional low-frequency content characteristic of the coupled rotor–ship aerodynamic response. Full article

The stability and reliability of temperature sensors in industrial cooling systems are critical to process quality, energy efficiency, and operational safety. However, existing approaches lack systematic stability metrics and intelligent predictive capabilities. This study proposes an AI-driven framework integrating stability feature engineering with machine learning models for fault identification and early prediction of temperature sensors in power plant cooling systems. The framework introduces three physics-based stability indicators—rolling standard deviation (σ_roll), variation intensity index (VII), and short-term variation magnitude (ΔT_short)—to quantify sensor signal quality. These features, combined with operational parameters, are used to train support vector machine (SVM) and Long Short-Term Memory (LSTM) models for binary classification. The framework is validated using over 260,000 one-minute records per unit collected from three parallel steam-turbine generating units (Units 1, 2, and 3) of the same coastal thermal power plant. Each unit is served by an independent once-through seawater cooling loop instrumented with redundant Pt-100 temperature sensors at the inlet and outlet manifolds; the three units differ in their operating profile—Unit 1 operates under variable load with frequent cold-start events, Unit 2 under moderate variable load, and Unit 3 under stable high-load conditions—with data collected at 1 min intervals from January to June 2025. Under an explicitly anomaly-positive evaluation, with the full confusion matrix reported for every unit and model, classification performance is limited and strongly unit-dependent. In real-time identification, AUC-based ranking ability varies across units (SVM AUC = 0.65, 0.75, and 0.98 for Units 1–3; LSTM AUC = 0.66, 0.31, and 0.52), but under the extreme class imbalance (anomaly rate ≈ 0.07–0.13% in the test partitions), the calibrated operating-point precision and F1-scores remain low for all unit–model combinations (F1 ≤ 0.26, MCC ≤ 0.28). McNemar’s test indicates statistically significant paired differences for Units 1 and 2 but not for Unit 3. These results show that, on this dataset, neither model attains reliable anomaly classification, and that all reported metrics must be interpreted together with the disclosed confusion-matrix counts and severe class imbalance. The primary contribution of the framework is therefore methodological—physics-based stability indicators, redundant sensor cross-checking, and an operational false-alarm analysis—rather than high-accuracy prediction, and the study highlights the difficulty of learning-based prediction for rare, rule-defined thermal sensor anomalies. Full article

Adaptive locomotion across continuous terrain transitions remains difficult for hexapod robots because contact timing, body attitude, support height, and load distribution change simultaneously along a route. This paper presents a unified proprioception-driven deep reinforcement learning and central pattern generator (DRL-CPG) framework for terrain-transition locomotion without visual terrain classification, explicit terrain labels, or terrain-specific controller switching. A high-level proximal policy optimization policy maps a 46-dimensional proprioceptive observation to a three-dimensional CPG modulation action comprising oscillation amplitude, swing-phase frequency, and turn modulation. A coupled six-node Hopf oscillator network then expands these modulated parameters into phase-coordinated rhythmic commands, which are mapped to the 18 joint targets of a JetHexa hexapod and executed by a low-level proportional-derivative controller. The observation space contains body linear velocity, body angular velocity, relative joint positions, relative joint velocities, the previous three-dimensional policy action, and inertial measurement unit (IMU)yaw/heading relative to the initial track direction. A continuous route consisting of flat ground, uphill stairs, irregular terrain, downhill stairs, and a recovery segment is defined to evaluate transition-aware locomotion using route completion, velocity-tracking error, lateral deviation, and roll/pitch fluctuation. Compared with the fixed-parameter CPG and end-to-end DRL baselines, the proposed method increased the full-distance success rate at 4.7 m from 9% and 20%, respectively, to 88%, while maintaining smoother velocity, lateral deviation, and roll/pitch responses. The framework preserves the rhythmic prior of CPG control while reducing the exploration burden of reinforcement learning, providing a compact formulation for adaptive hexapod locomotion across terrain transitions. Full article

The high-speed, low-load twin-roll casting of Al-Si alloys with a Si content of approximately 1 at% is needed to prevent the occurrence of cracks. In twin-roll casting, however, the roll load reaches the lower limit required for the sufficient solidification of the aluminum alloy. In this study, a single-roll caster equipped with a scraper was used to cast strips without cracks. The semi-solid forming of the free-solidified surface of an Al-1%Si strip during casting using a single-roll caster was attempted with a scraper under a very small load at a high roll speed of 30 m/min. The effects of the scraper angle and the scraper load on the condition of the scraped surface were investigated. The roll-contact surface and scraped surface of the strips cast under the appropriate conditions were compared by bending and deep drawing tests. After cold-rolling and annealing, no differences were observed between the roll-contact surface and the scraped surface. A sound Al-1%Si strip without cracks can be cast using a single-roll caster equipped with a scraper at a speed of 30 m/min. Full article

Politecnico di Milano is undergoing the design of a highly swept, low-aspect-ratio radio-controlled aircraft with reflex airfoils. This model is necessary to expand the automated flight-testing activities conducted inside the university, adding to the flying models a more unconventional one to verify the flight-testing technique implemented. Plain-type spoilerons were investigated as primary roll control devices and compared with conventional aerodynamic predictions and wind-tunnel data. The experimental tests assessed performance across spanwise and chordwise positions, angles of attack, and spoileron geometric variations. A normalized control effectiveness parameter, accounting for moment coefficient, spoileron surface area, and moment arm, was introduced to compare configurations. Results show consistent peak performance at intermediate incidence and highlight distinct degradation patterns near stall. Spanwise variations primarily affect roll authority, while yaw response remains weakly sensitive. Geometric analysis indicates span increases are more efficient than chord increases for equivalent performance, reducing actuator loads and aerodynamic penalties. Full article

To address the coordinated economic, low-carbon, and robust operation problem caused by source–load forecast uncertainty in hydrogen-based integrated energy systems, this paper proposes a multi-time-scale distributionally robust scheduling framework based on the Wasserstein distance. First, a hydrogen-based polygeneration model is established by coordinating an electrolyzer, a hydrogen storage tank, a methanation reactor, and a hydrogen fuel cell. A dual-heat-source organic Rankine cycle is further introduced to recover waste heat from the microturbine and hydrogen fuel cell, thereby strengthening the coupling among electricity, heat, gas, and hydrogen. Second, a source–load coordination mechanism is developed by integrating pre-contracted stepped demand response with output-based carbon allocation and stepped carbon trading. On this basis, a two-stage day-ahead Wasserstein distributionally robust optimization model is formulated to account for joint wind-power and multi-energy-load forecast errors, while 15 min intraday and 5 min real-time rolling optimization are used to correct scheduling deviations. Finally, mechanism-ablation, physical-feasibility, uncertainty-handling, and parameter-sensitivity studies are conducted. The results show that M-5 reduces the total operating cost and net carbon emissions by 13.66% and 23.87%, respectively, relative to M-1, while reducing the wind-curtailment rate from 16.43% to zero. Among the tested uncertainty-handling methods, W-DRO achieves the lowest held-out total cost with a 3% shortfall rate, and the lowest-cost range is obtained for Wasserstein radii of 0.02–0.05. These results demonstrate that the proposed framework provides a favorable case-specific trade-off among economic performance, carbon reduction, renewable-energy accommodation, and operational robustness. Full article

Smart grids with high renewable penetration are increasingly evaluated through long-horizon production simulation, but conventional decomposed simulation mainly reports energy balance and unit feasibility, while power-quality stress remains weakly quantified in the storage correction layer. This paper presents a power-quality-proxy-guided state-replay framework for renewable-rich smart grids. Instead of claiming feeder-level electromagnetic simulation, the method defines planning-level proxy indicators that can be exported by production-simulation software: a voltage-deviation proxy obtained from net-power sensitivity, a net-load ramp proxy, an inverter/charger harmonic-risk proxy, and a renewable-curtailment exposure proxy. These normalized indicators are combined into a composite score $S_{PQ}$, which is then used to distinguish two storage values: charge retention during renewable-surplus voltage-rise intervals and discharge support during voltage-dip, ramp-stress, or inverter-stress intervals. A base decomposed production-simulation schedule is first obtained. The proposed layer then constructs storage accounting cycles independent of monthly and rolling-window boundaries, attaches the proxy ledger to each interval, backtracks terminal residual storage energy to low-value charging actions, and reallocates physically feasible discharge to high-$S_{PQ}$ intervals. The corrected storage path is projected onto power and energy limits and replayed before storage and conventional-unit states are inherited by the next monthly solve; cycles outside the replay validity envelope are escalated to full redispatch rather than counted as successful corrections. An eight-interval case reports explicit $S_{PQ}$ values and shows that a trajectory ending 45 MWh above the 30 MWh reference can be corrected by trimming 35 MWh of low-proxy-value charging and adding 10 MWh of discharge in two high-score intervals. A 96-interval experiment further shows that the full method reduces explicitly discarded residual energy from 214 MWh to 31 MWh, provides 128 MWh of proxy-guided support, and lowers weighted PQ-proxy exposure by 46.3%. The framework links smart-grid data analysis, renewable integration, and power-quality improvement within a traceable production-simulation workflow. Full article

Developing low-cost, Co-free high-entropy alloys (HEAs) that retain both high strength and useful ductility at cryogenic temperatures remains challenging because hard strengthening phases usually intensify strain localization and accelerate plastic instability. In this work, a Fe-enriched Al₁₁Cr₁₄Fe₅₀Ni₂₅ HEA was designed and processed by heavy cold rolling followed by short-time annealing at 900 °C for 10 min to construct a hierarchical heterogeneous microstructure. The alloy consists of an FCC-dominated matrix and an ordered B2 phase distributed in recrystallized and unrecrystallized domains over multiple length scales. Tensile testing shows that the alloy achieves a yield strength of 953 MPa, an ultimate tensile strength of 1160 MPa, and an elongation of 21.1% at 298 K, while these values increase to 1268 MPa, 1686 MPa, and 28.6%, respectively, at 77 K. Load–unload–reload analysis at 77 K reveals that the hetero-deformation-induced stress reaches about 804 MPa at a true strain of 25%, contributing more than 52% of the total flow stress. The superior cryogenic strength–ductility synergy is attributed to strain partitioning between soft FCC and hard B2 phases and between recrystallized and unrecrystallized regions, which promotes geometrically necessary dislocation accumulation, back-stress strengthening, and sustained work hardening. This study demonstrates that hierarchical heterostructure design provides an effective route for developing cost-conscious Co-free HEAs for cryogenic structural applications. Full article

In electricity–hydrogen coupling systems (EHCSs), the uncertainty of renewable energy generation (REG) tends to impact electrolyzers (ELs) in the following ways: (1) input powers of ELs are prone to fluctuations; (2) ELs are forced to operate under variable load states. Consequently, both impacts will reduce the service life of ELs. In this paper, considering the start–stop characteristics and combined operation modes of multiple ELs, a two-stage multi-time-scale energy allocation strategy (MSEAS) is proposed to mitigate the impacts of REG uncertainty and optimize the energy allocation for EHCSs. First, five refined operating states of ELs, such as shutdown, cold standby, low-load, variable-load and overload, are formulated as mixed-integer constraints and embedded into the system-level energy optimization model. Second, to mitigate power fluctuations caused by REG, a day-ahead optimization is employed to plan the power allocations of ELs, lithium batteries, fuel cells, and the grid with a 1 h time step; and then an intra-day rolling optimization is employed to adjust the operating states and power outputs of the above units with a 4 h window and 15 min step. Third, by enabling multiple ELs to flexibly operate in a combined mode, power-sharing mode and switching mode, the proposed MSEAS can refine the operation powers of ELs and reduce their start-up frequency. Comparative case studies are conducted in the off-grid and grid-connected operation tests, and the relevant results verify that the proposed MSEAS can effectively prevent the frequent start–stop of ELs, which contributes to extending the service life of ELs and reducing the system operating cost. Full article

Fixed-wing unmanned aircraft are widely used for aerial mapping because they can acquire high-resolution data at relatively low cost, but maintaining both energy efficiency and image quality in the presence of wind and flight-performance limits remains challenging. In practice, operators introduce buffer regions and extended waypoints outside the area of interest to cope with deviations during turning, which increases flight distance and energy use; yet, this approach can still degrade image overlap near the boundary. This paper presents a path-planning framework that designs turning maneuvers compatible with bank-angle, stall-margin, and roll-rate constraints while aligning mapping lanes directly with the area of interest. The framework combines analytically structured turn patterns, an energy-based metric that accounts for increased aerodynamic load in banked flight, and a two-stage path-angle selection procedure that uses a fast, simplified model to guide a more detailed optimization. Simulation studies on both idealized and real survey geometries indicate that, within the considered maneuver families and assumptions, the proposed method can reduce the integrated aerodynamic energy metric and improve coverage compliance relative to a conventional path-following approach that relies on overshoot points. Full article

In this study, the effects of log loading on the lateral overturning of an unmanned, remote-controlled forestry crawler tractor were analyzed through simulation-based analysis. A 3D model was constructed and validated in terms of actual dimensions, static sidelong falling angle, and turning area radius. The errors in both actual dimensions and turning area radius were below 5%, and the static sidelong falling angle was consistent with test results, thereby confirming the model’s reproducibility. Simulations combined three loading levels (0, 50, and 100%), 11 ground slope angles (0 to 50° at 5° intervals), four obstacle heights (0 to 300 mm at 100 mm intervals), and two driving speeds (3.6 and 5.8 km/h). The maximum roll angular velocity within the obstacle contact zone, taken as a safety indicator, was derived for each loading condition. The results showed that lateral overturning occurred before reaching the obstacle, at lower ground slope angles under log loading than without loading. This shows that loading conditions affect lateral discharge safety. Roll angular velocity increased rapidly at high ground slope angles regardless of loading condition, confirming that ground slope angle is key for lateral overturning. Four-way ANOVA results showed that ground slope angle and obstacle height had the greatest impact on roll angular velocity. Although the main effect of loading was relatively small compared to environmental factors, its interaction with ground slope angle was significant, redefining the tractor’s stability limits. Thus, while loading is not a primary factor causing lateral overturning, it influences the sensitivity of roll angular velocity to ground slope angle. These results can be interpreted within a quasi-static framework under low-speed operating conditions, and by using roll angular velocity as an indicator of transient response during obstacle interaction, they provide foundational data for establishing load-dependent safety standards and determining optimal loading limits to prevent lateral overturning in forestry operations. Full article

Sulfur-containing medium-carbon microalloyed steel blooms are widely used for high-load automotive components, and reducing surface defects is important for improving product yield and lowering downstream processing costs. To address surface defects such as star cracks and microcracks in the continuous casting of these steel blooms, this study redesigned the mold flux on the basis of the steel’s solidification characteristics and crack susceptibility and carried out a twin-strand industrial comparative casting trial. Thermodynamic and thermophysical analyses indicated that the relatively high contents of S, Mn, and Ti/N in the steel promoted the precipitation of MnS and TiN–MnS complex inclusions along grain boundaries, severely weakening grain boundary cohesion. Meanwhile, the high specific heat capacity and low thermal conductivity further intensified thermal stress concentration in the solidifying shell, rendering the steel highly susceptible to cracking. Evaluation of the originally used mold flux (Flux A) revealed that its high melting temperature (1189 °C), long melting time (106 s), high break temperature (1170 °C), and poor crystallization behavior resulted in an excessively thin liquid slag layer (<5 mm) within the mold, making it difficult to provide adequate lubrication and stable heat transfer; these were key external factors inducing surface defects. Accordingly, the optimized mold flux (Flux B) was designed and prepared by increasing the basicity from 0.95 to 1.1, raising the Al₂O₃ content from 9.48% to 11.16%, increasing the F content from 4.93% to 5.58%, and reducing the carbon content from 13.85% to 6.97%. The rheological and crystallization properties of the flux were optimized in a coordinated manner, allowing uniform heat transfer through the crystalline slag layer while maintaining adequate lubrication. Industrial comparative trials demonstrated that Flux B stabilized the liquid slag layer at 8–10 mm, increased slag consumption to 0.56 kg/t, and significantly reduced surface defects such as star cracks and microcracks on blooms. The ultrasonic testing acceptance rate for rolled products increased to 98.6%, thereby meeting stringent quality requirements for the continuous casting of sulfur-containing, medium-carbon, microalloyed steel blooms. Full article

Waste heat recovery from automotive exhaust gases represents an important strategy for improving vehicle energy efficiency. This study experimentally investigates the performance of a thermoelectric generator (TEG) system based on TEC1-12706 modules running under different cold-side cooling conditions and incorporating a Hot Rolled Steel (HRS) protective layer on the hot side. The HRS plate was used to ensure uniform heat distribution and protect the thermoelectric module against thermal shocks generated by a 250 °C heat source. Four cooling regimes were experimentally analyzed: natural convection and forced airflows equivalent to 40, 60, and 90 km/h. The results proved that increasing airflow intensity significantly improved the temperature difference across the module, from approximately 16 ± 2 °C under natural convection to nearly 40 ± 2 °C at the highest airflow velocity. Correspondingly, the steady-state voltage generated increased from approximately 0.25 ± 0.01 V to over 0.60 ± 0.01 V under an 82 Ω resistive load. The measured hot-side temperature remained below 75 °C in all experimental conditions, confirming the thermal protection capability of the HRS layer. The experimental data also revealed a near-linear relationship between voltage and temperature difference, consistent with the Seebeck effect. The proposed configuration shows the feasibility of combining thermal protection and forced convection cooling to improve the stability and electrical performance of thermoelectric waste heat recovery systems intended for low-power automotive auxiliary applications. Full article