Search Results (280)

Static wake steering can increase wind-farm power production, but its application to floating offshore wind farms requires assessment of the coupled wake, platform, structural, and station-keeping response. This study evaluates whether power-maximizing static yaw setpoints identified using the steady, control-oriented FLORIS model retain their benefit when transferred without re-optimization to a coupled FAST.Farm floating wind-farm model. The reference farm comprises four IEA Wind 15 MW turbines mounted on VolturnUS-S semi-submersible platforms. Greedy and static wake-steering operations are compared at three below-rated wind speeds, three sea states, and five matched turbulent-inflow realizations, resulting in 90 farm-level FAST.Farm simulations. Wake behavior is characterized through wake-center deflection, meandering, and velocity-deficit profiles, while turbine and mooring fatigue responses are evaluated using paired damage-equivalent-load statistics. Static wake steering increases mean farm power under all nine investigated wind–wave conditions. The gains are approximately 5.1–$5.2\%$ at $7\mathrm{m}{\mathrm{s}}^{-1}$, $5.0$–$5.1\%$ at $8\mathrm{m}{\mathrm{s}}^{-1}$, and $4.0$–$4.2\%$ at $9\mathrm{m}{\mathrm{s}}^{-1}$, with all paired $95\%$ confidence intervals remaining above zero. The gain results from a power redistribution in which the intentionally yawed upstream turbine incurs a local loss that is exceeded by the combined recovery of the downstream turbines. The fatigue response is strongly component- and turbine-dependent. The paired farm-mean blade-root DEL decreases by $0.82$–$2.24\%$, whereas the tower-base DEL increases by $0.76$–$2.78\%$, and the FairTen1 response generally increases by $0.88$–$2.92\%$. The farm-mean yaw-bearing response is mixed, ranging from a $1.15\%$ reduction to a $4.32\%$ increase. Turbine-level analysis reveals larger localized penalties, reaching approximately $10.4\%$ for the yaw-bearing DEL and $12.8\%$ for FairTen1. Spectral analysis associates the yaw-bearing response with yaw-induced aerodynamic and structural excitation, while the tower-base response is strongly influenced by low-frequency wave–platform dynamics. A complementary FLORIS sensitivity analysis demonstrates that the optimized aerodynamic benefit depends strongly on wind direction, spacing, wind speed, and turbulence intensity. For a Tampen-derived 11-turbine layout, resource weighting over the modeled 4–$13\mathrm{m}{\mathrm{s}}^{-1}$ interval produces an annual energy-contribution increase of $3.653\mathrm{GWh}{\mathrm{year}}^{-1}$, or $0.921\%$. These results provide numerical evidence that static wake steering can retain a positive power benefit in a coupled floating wind-farm environment, but controller assessment must include turbine- and component-specific dynamic loads rather than farm power alone. Full article

A fail-safe topology optimization method for fiber-reinforced composite structures under dynamic loads is proposed to achieve the concurrent optimization of structural topology and fiber orientations, as well as enhance the structural redundancy subject to damage cracks of fiber-reinforced composite structures under external dynamic loads. To prevent fiber orientations from getting trapped in local optima, we employ a discrete–continuous parameterization method to convert the continuous orientation problem to a discrete subinterval selection problem and a continuous orientation optimization problem in a subinterval. To prevent structural catastrophic failure induced by damage cracks, we incorporate the fail-safe design concept by considering local damage via removing the stiffness of the composite in the predefined patch. Furthermore, to reduce the large computational burden involved in transient analysis under dynamic loads, we adopt the equivalent static loads method to transfer the dynamic loads into a set of static loads, thereby largely accelerating the optimization process while keeping the solution accuracy. The effectiveness of the method is verified by three numerical examples, showing that the equivalent static loads method-based fail-safe design of composite structures with concurrently optimized topology and fiber orientations can effectively resist the local damage induced by partial failure. Specifically, the method reduces the optimization time by around 40% while ensuring relative errors within 2% and convergence measures of fiber orientations larger than 95% in all examples, and can have up to six orders higher residual stiffness subjected to post-imposed damage patches compared to the traditional method, showing the efficiency of the proposed method. Full article

Rapid pre-screening of inverter-interfaced energy storage system (ESS) connection locations remains challenging in planning studies for power systems with high renewable penetration and converter-interfaced ESSs. Active-power–voltage (P–V) curve analysis provides an efficient tool for this task, but the reliability of its screening results depends on how the converter-related voltage-support behavior of the ESS is represented in the static equivalent model. This paper develops a planning-stage ESS siting pre-screening workflow by incorporating existing dynamic-impedance equivalent results into the ESS static model and embedding the corrected model into target-bus P–V scans. An indicator P_0.85 is defined as the load level at which the target-bus voltage reaches a representative low-voltage boundary of 0.85 pu and is used to quantify the local load-growth margin. A P_0.85-based improvement matrix and comprehensive ranking indices are then constructed to compare voltage-margin improvements of different candidate ESS connection locations. Steady-state electromagnetic transient (EMT) operating points are used to evaluate voltage approximation errors and cross-check the improvement ranking trend. In the IEEE 39-bus test system, the scalar-form and complex-form dynamic-impedance-corrected static models reduce the mean absolute voltage error by approximately 57.7% and 59.1%, respectively, compared with the connection-branch impedance model. The first-tier candidate buses obtained from the static pre-screening are consistent with the EMT-interpolated ranking trend. A supplementary IEEE nine-bus case further illustrates the feasibility of applying the proposed procedure under a different network topology. The main contribution lies in integrating existing dynamic-impedance equivalents with a P_0.85-based ESS siting pre-screening framework for candidate-set reduction before detailed EMT studies and engineering assessment rather than final ESS siting optimization. Full article

The mechanical compatibility between dental restorative materials and the natural tooth structure is a relevant factor for long-term clinical performance. Although zirconia (yttria-stabilized tetragonal zirconia polycrystal, Y-TZP) and lithium disilicate are widely used for full-coverage crowns, their biomechanical interaction with the underlying dentin and pulp under functional loading remains insufficiently characterized. This study reports a comparative finite element analysis (FEA) of a mandibular first molar under vertical (200 N, axial) and oblique (200 N, 30°) loading, evaluating three configurations: an intact healthy tooth, a zirconia Y-TZP full-coverage crown, and a lithium disilicate full-coverage crown. The three-dimensional geometry was obtained from a cone-beam computed tomography (CBCT) study of a caries-free mandibular first molar, previously described and verified by the present group, and was analyzed in ANSYS Workbench (Static Structural). Von Mises equivalent stress, maximum principal stress and total deformation were obtained for enamel or restoration, dentin, and pulp in each configuration. Zirconia produced the highest stress concentrations in the coronal restoration (88.4 MPa vertical; 174.5 MPa oblique), exceeding the healthy enamel baseline by 57.6% and 89.7%, respectively. Both restorative materials reduced dentin stress relative to the healthy tooth, consistent with the stress-shielding effect driven by elastic-modulus mismatch. Under oblique loading, the maximum principal stress in healthy enamel reached 61.7 MPa, approaching or exceeding the upper bound of the reported tensile strength range (~10–40 MPa) and identifying oblique loading as the more demanding of the two conditions analyzed. Within the limitations of the present finite element model, lithium disilicate demonstrated a more favorable stress distribution, with dentin stress values closer to the intact-tooth baseline. The model does not include a luting cement layer, a periodontal ligament, the dentin–enamel junction, anisotropic tissue behavior or cyclic loading, and no experimental validation was performed; the results are therefore presented as a controlled numerical comparison between three configurations under the specific conditions simulated, and not as direct clinical selection criteria. Full article

Landslides in weathered gypsum deposits present significant geotechnical challenges because progressive weathering, groundwater fluctuations, and residual strength degradation strongly influence slope stability. This study investigates the failure mechanism and remediation of a large translational landslide in weathered gypsum deposits in Çankırı, Türkiye. An integrated engineering geological assessment was conducted using data from 16 boreholes, laboratory tests, and groundwater/inclinometer monitoring records, followed by residual shear strength back-analysis and slope stability evaluation. A three-dimensional geological model was developed, and cross-sections were analyzed using the Morgenstern–Price limit-equilibrium method. Back-analysis identified residual shear strength parameters of c′ = 7.5 kPa and ϕ′ = 10° for the weathered gypsum, while laboratory direct shear tests yielded c′ = 4.0 kPa and ϕ′ = 9.9°. The friction angles obtained from the two approaches are nearly identical, whereas the back-calculated cohesion is slightly higher than the laboratory-derived value. Back-analysis parameters were used to design remediation measures, including slope unloading, rock buttress construction, toe fill improvement, and surface/subsurface drainage. Stability analyses increased the factor of safety to 1.76 under static loading, while pseudo-static analyses satisfied the recommended seismic design criterion (FS ≥ 1.10). Equivalent-linear Newmark analyses predicted a permanent displacement of 15 cm, within acceptable limits. The methodology provides a practical framework for assessing and stabilizing landslides developed in weathered gypsum deposits in seismically active regions. Full article

This study presents a parametric optimization model for the friction disc of a combined friction face milling cutter operating under intensive contact friction, high clamping forces, and cyclic thermomechanical loading. The computational framework integrates ANSYS Workbench, the Static Structural module, Design of Experiments (DOE), Kriging surrogate modeling, and Multi-Objective Genetic Algorithm (MOGA) optimization. The friction disc geometry is defined by two design variables: the radial depth of the relief groove, a (3–6 mm), and its axial width, b (3–8 mm). Structural performance is evaluated using the von Mises equivalent stress and axial displacement of the cutting zone. Heat-treated 65G spring steel, with a yield strength of 640 MPa, is selected as the material. Using a safety factor of four, the allowable stress is limited to 160 MPa, while the permissible axial displacement is 0.05 mm to satisfy axial runout requirements for face milling cutters. Finite element analysis and response surface modeling show that parameter a predominantly affects axial deformation, whereas the combined influence of a and b governs the acceptable stress region. Multi-Objective Genetic Algorithm (MOGA) optimization identifies design solutions satisfying both strength and stiffness constraints. The proposed approach enables the determination of the minimum admissible values of the geometric parameters a and b while satisfying the prescribed strength, stiffness, and axial displacement constraints. Full article

Rainbow tables are precomputed tables used to cache the output of cryptographic hash functions in a collection of chains consisting of alternating password and hash values constructed using a cryptographic hash function and a reduction function. Generating these tables is computationally intensive, and several researchers have proposed utilizing parallel computing to speed up the generation process. However, very little work was done on heterogeneous CPU clusters in the rainbow tables generation context. In this paper, we bridge this gap by proposing a parallel MPI-based rainbow tables generation method designed for heterogeneous CPU environments. We utilized the static load balancing algorithm using a simple weighting scheme to assign a different number of chains to different processes based on their speeds and capabilities. The experiments were executed on a cluster with ten nodes with heterogeneous CPU architectures: five nodes with the i7-12700 architecture featuring a hybrid architecture of P-cores and E-cores and an additional five with the i7-6700 architecture. In the experiments, rainbow tables were generated for four different cryptographic hash functions: SHA-256, SHA-512, MD5 and NTLMv2, with 90,000 rows each with 50,000 entries. During the experiments, we observed lower execution times as more processes join the work compared to a naïve implementation that shows jumps in execution times. Also, the speedup gained is much higher compared to the equivalent naïve implementation. In addition, our benchmark-based load balancing strategy significantly reduces the load imbalance to below 6%. Full article

The bent sub is a main deflection component in the near-bit assembly of small-diameter push-the-bit guided coring tools, and its parameters affect build-up capability and local structural response. Existing studies mainly focus on conventional rotary steerable drilling systems, whereas slim-hole constraints, including narrow annular clearance and cross-sectional weakening induced by internal coring channels, remain insufficiently considered. To address this problem, a static bending model of the near-bit section was established based on Euler–Bernoulli beam theory. Channel-induced cross-sectional weakening was represented using the actual concentric annular geometry of the primary load-bearing outer tube, and the bent-sub initial curvature, dual push-the-bit loads, axial weight on bit, and borehole-wall contact and friction effects were incorporated. The build-up rate (BUR), maximum equivalent stress, and maximum curvature served as response indicators. A control-variable approach was used to analyze the bent-sub length L_b, bend angle γ, and distance from the bit D_b. The results showed that D_b had the strongest effect on BUR, and all parameters exhibited a trade-off between steering performance and structural safety. Increasing L_b from 0.30 m to 0.80 m reduced BUR from 12.65°/30 m to 9.79°/30 m, whereas increasing γ from 0.5° to 2.5° increased BUR from 4.12°/30 m to 10.70°/30 m. Considering structural constraints and normalized BUR retention, the recommended engineering ranges are L_b = 0.65–0.80 m, γ = 1.3°–1.9°, and D_b = 0.50–0.70 m. Full article

To investigate the Axial–Shear–Flexure Interaction (ASFI) of precast segmental assembled bridge piers, this study proposes a connection system using tapered-sleeve locking steel bar joints and fiber-reinforced concrete (FRC). Four 1:2.5-scaled pier specimens—including single- and double-column configurations, with both cast-in-place and precast segmental designs—were tested under quasi-static cyclic loading. The experimental results show that the precast components exhibited comparable or superior seismic performance, with peak loads in single/double columns being 4% and 5% higher than those in cast-in-place components, respectively; the equivalent viscous damping ratio was 2–4% higher, and residual displacement was reduced by approximately 20%. In addition, an ASFI-based calculation program is developed in Python 3.9 to predict the load–displacement response under combined axial, shear, and flexural actions. The program predicts the peak load of all specimens with errors within 10% but systematically underestimates the peak displacement. Deformation decomposition reveals that shear deformation accounts for 2–7% of the total deformation in single-column piers but increases to 10–17% in double-column piers, confirming the necessity of ASFI modeling for shear-critical configurations. This connection system meets the performance requirement of being “equivalent to cast-in-place,” but the program is only applicable to bearing capacity estimation, and its universality requires further parameter verification. Full article

The retreating roadway is a critical passage for the safe and efficient retreat of equipment from a fully mechanized longwall face. Its roof stability directly affects the transportation safety of large equipment such as hydraulic supports and the shearer. However, the structural evolution of the overlying strata of the retreating roadway and the roof stability under monorail crane loading have not been systematically investigated. Therefore, taking the retreating roadway of the 1093 fully mechanized longwall face in a coal mine in Anhui Province as the engineering background, this study combined physical similarity simulation, digital image correlation (DIC), and theoretical analysis to investigate the evolution of overlying strata fracture, caving, displacement, and stress fields during face extraction and retreating roadway formation. An analytical model was established to calculate bed separation between the immediate roof and the main roof under an equivalent static concentrated monorail crane load. The results indicate that the vertical displacement field of the overlying strata exhibits an overall trapezoidal distribution and continuously extends toward the higher overlying strata as the longwall face advances. In the physical model, no further propagation of fractures or bed separation toward the retreating roadway was observed after either roof-cutting operation. The withdrawal of hydraulic supports caused no significant changes in the stress or displacement of the overlying strata of the retreating roadway, indicating that the integrity of the overlying strata structure was well maintained. The model predicted a maximum bed separation of 6.39 mm between the immediate roof and the main roof at the gob-side end. The model can assist in identifying critical roof locations susceptible to bed separation and in prioritizing roof monitoring and support optimization during monorail-assisted equipment withdrawal. Full article

Two design solutions such as modular and mono-block Ti6Al4V porous implants for femoral defect repair were implemented and compared. Static stress analysis on each model was performed via finite element analysis to investigate potential critical elements that might cause system failure under physiological loads. Prior to calculations, a mesh convergence study was realized by varying the minimum element sizes. The entire bone–prosthetic system was modeled, and design optimization was performed. For mono-block implants, a less stressed configuration was found by changing the plate design. Comparison of the maximum Von Mises stress ${\sigma }_{max}$ and equivalent strain ${\epsilon }_{eq}$ between the models allowed for an understanding of the distribution of the loads and identify areas with critical stress concentration. The modular implant appeared to be highly solicited with stress shielding on epiphyses due to enhanced rigidity at the metal/bone interface. Finally, a study of the deformation on cancellous and cortical bone suggested that a more elastic junction with balanced strain delivery to the bone might improve tissue regeneration when using a mono-block implant. Full article

Mixed mode I–III fracture commonly occurs in rock masses under complex three-dimensional stress states, yet the combined effects of loading conditions and fracture mode remain unclear. In this study, a heterogeneous sandstone disc model is developed in ABAQUS by coupling the Drucker–Prager elastoplastic model, an equivalent-strain damage model, and cohesive elements. The model is validated against static Brazilian splitting tests and dynamic SHPB tests. ENDB specimens are then employed to investigate mode I, mode III, and mixed mode I–III fracture under static and dynamic loading with offset angles ranging from 0° to 62.5°. As the offset angle increases, crack propagation evolves from straight tensile extension to deflected, twisted, and fragmented patterns dominated by anti-plane shear. Dynamic loading intensifies crack segmentation, localized damage, and transient instability while increasing the peak load, fracture toughness, and fracture energy. In contrast, the effective fracture toughness and fracture energy decrease monotonically with increasing offset angle under both loading conditions. A linear trend consistent with R² > 0.99 is observed between the mode I–III mixing coefficient and the effective fracture toughness based on single-realization simulations, the effective fracture toughness under dynamic loading is approximately 2.22 times that under static loading based on direct comparison of calculated values. These findings improve the understanding of loading-dependent mixed mode I–III fracture in sandstone and provide guidance for rock mass stability assessment. Full article

To address the trade-off between stiffness and auxeticity in conventional star-shaped honeycombs (SH), this study introduces a novel star-ellipse honeycomb (SEH) design, incorporating elliptical stiffeners that enhance both load-bearing capacity and energy absorption. The mechanical performance of SEH was comprehensively evaluated using FE simulations, theoretical modeling, and quasi-static tests on 3D-printed multi-cell specimens. An equivalent Cauchy model using the Variational Asymptotic Method (VAM) was established and validated against experiment and finite element results, demonstrating high predictive accuracy in elastic behavior analysis while significantly reducing computational costs. Based on the collapse mechanism of a representative unit cell, a theoretical model was proposed to estimate the plateau stress. Comparative analyses show that the elliptical stiffener mitigates the classic stiffness–auxeticity trade-off by enabling cooperative deformation, which results in a simultaneous increase in elastic modulus and a stronger negative Poisson’s ratio compared to conventional star-shaped honeycombs. Additionally, the SEH exhibited a unique progressive folding mode under compression, delivering enhanced stiffness and energy dissipation, albeit with reduced ductility. The elliptical aspect ratio of 1.3, length ratio of 2.1, thickness ratio of 1.0, and star angle of 45–50° offer the best compromise between stiffness, energy dissipation, and auxetic performance, providing clear guidelines for tailoring SEH structures toward specific lightweight protective applications. Full article

As an innovative structural system aligned with construction industrialization, prefabricated Steel-Reinforced Concrete (SRC) structures are characterized by high load-bearing capacity, efficient material utilization, and rapid construction. In this study, the mechanical behavior, failure mechanisms, and ductility characteristics of a prefabricated SRC multi-floored grain warehouse frame were investigated through quasi-static cyclic loading tests. To complement the experimental program, high-fidelity numerical models were developed using Abaqus, incorporating concrete plastic damage and steel material nonlinearity. The simulation results were rigorously validated against the experimental data. The findings indicate that the specimens exhibited typical shear failure modes with full hysteretic loops, demonstrating substantial energy dissipation capacity (equivalent viscous damping coefficient of 0.261). Notably, the results of the parametric study indicate that the integration of wall panels can significantly increase the load-bearing capacity and lateral stiffness of the frame system. The ductility of the samples was excellent, with displacement ductility coefficients ranging from 3.1 to 3.7. The ultimate inter-story drift angles at failure (1/49–1/38) substantially exceeded the code-specified limit (1/50), indicating robust collapse-prevention capacity. The numerical results strongly agreed with the experimental observations in terms of the hysteretic behavior, failure patterns, and skeleton curves, confirming the reliability of the modeling strategy for subsequent seismic performance analyses and parametric evaluations. Full article

In order to meet its need of functional improvement, the existing masonry structure generally adopts the method of replacing partial walls with concrete frame columns to expand the openings and reduce the number of the longitudinal walls. However, the partial removal of longitudinal masonry walls and the introduction of large openings may result in a nonuniform distribution of lateral stiffness in plan and consequently induce torsional response under horizontal seismic loading. In order to investigate the seismic performance of the existing masonry structure after replacement, a 1:4 scale four-story brick masonry–concrete structure model was designed and made. Based on the principle of stiffness equivalence, the partial walls on the side of the large openings of the model ground-level floor were replaced by frame columns and frame beams, and then the pseudo-static test was conducted on the model. Through the test, the failure patterns of each floor in the structure and the seismic performance indexes such as hysteresis curve, skeleton curve, displacement ductility, stiffness degradation, and energy dissipation capacity, were obtained. The results showed that the yield load of the ground-level floor with the equivalent frame columns is approximately 138% of that of the second and third floors, while its yield displacement is approximately 59% of that of them. That is, after the structure enters the yield stage, its ground-level floor has good bearing capacity and resistance to deformation. The ground-level floor of the structure consumes the least energy as compared to the second and third floors, while the second floor consumes the most energy and has stiffness mutation, and the damage to the walls in such layer is also the most serious. Hence, seismic strengthening of the second story should be considered to prevent the formation of a weak or soft story and the consequent risk of structural collapse. Although there is a significant difference in the material properties between reinforced concrete frames and masonry structures, it is feasible to use the replacement method based on the stiffness equivalence to solve the problem of structure torsion caused by the irregular plane arrangement. Full article