Search Results (257)

Passive reception of spaceborne synthetic aperture radar (SAR) signals is of great significance for acquiring target characteristics and identifying SAR operating states. With the rapidly growing demand for high-quality SAR signal reception, signal-receiving arrays are prone to beam performance deterioration and difficulty in beamforming under wide-angle scanning conditions. Traditional uniform arrays fail to meet practical engineering requirements and cannot balance multiple conflicting performance indicators. To address the above technical bottlenecks, this paper proposes a design method of a non-uniform planar receiving array based on the MOEA/D-HPSO algorithm. Taking maximum sidelobe level (MSL), array gain (G), and beamwidth (BW) as core performance indicators, a multi-objective optimization model of SAR signal-receiving array for wide-angle scanning is established. This method integrates the multi-objective decomposition strategy and hybrid genetic particle swarm optimization mechanism, decomposes complex multi-objective problems into several scalar subproblems, obtains uniformly distributed Pareto fronts, and effectively improves the diversity of solution sets. Simulation experimental results show that the proposed algorithm is superior to traditional mainstream algorithms such as NSGA-II and MOEA/D-DE in terms of convergence accuracy, solution set distribution, and various performance indicators. Typical array design examples verify that the proposed method can adapt to various engineering application scenarios and provide technical support for spaceborne SAR signal reception and spectrum management. Full article

The two-year research involving laboratory and field studies supported by Geant4 computer simulation is aimed at determining the optimal parameters of 1 MeV accelerated electrons and 80 keV X-ray pre-planting irradiation of wheat seeds in order to find the optimal dose range which increases the crop yield while making wheat plants more resistant to fungal diseases caused by species of the genus Septoria. During the laboratory studies we measured the germination rate and biometric properties of plants, as well as the type, number, and average diameter of fungi found in the irradiated and non-irradiated seeds after irradiation with electrons and X-rays with the dose range 2–1000 Gy. Following the laboratory studies showing that the doses exceeding 30 $\mathrm{Gy}$ decreased the germination rate of wheat, field studies evaluated the impact of pre-planting irradiation with the doses in the range of 5–30 Gy on the wheat productivity and the rate of fungal diseases in wheat plants grown from irradiated and non-irradiated seeds. It has been found that the dose range 5–15 Gy is more preferable for pre-planting wheat irradiation, both for e-beam and X-rays, since it increases the crop yield while making wheat plants more resistant to fungal diseases caused by species of the genus Septoria. The X-ray dose of 15 $\mathrm{Gy}$ is found to be the most effective since it increased the yield up to 40% and also suppressed the Septoria glume blotch up to 40%. Since seed irradiation requires a particularly delicate approach given that the goal of irradiation is not only to reduce the rate of fungal diseases in the plants but also to increase the crop yield without detriment to the soil and the plant itself, consistency of dose uniformity across the seeds during pre-planting irradiation ensures the high reliability and repeatability of the irradiation effect. Our approach to irradiation planning with the use of Geant4 computer simulation allows us to precisely estimate the dose distribution in individual seeds and the distribution of radiation-chemical yield of radicals occurring as result of radiolysis in order to predict the effect of pre-planting irradiation and select the optimal irradiation parameters for maximizing the yield and crop quality. Full article

The effective length factor method cannot account for variations in axial forces between columns and the mutual assistance among columns, resulting in overestimation of the critical load of columns that receive assistance and underestimation of that of columns that provide assistance. Moreover, this method is not readily applicable to bent frames and frame structures with multi-story tie beams. The phenomenon of critical load redistribution among columns under non-uniform loading conditions is revealed in this paper, and its underlying mechanical mechanism is elucidated. Based on this, a two-stage loading procedure for critical load redistribution analysis is proposed, in which the instability process of irregular structures is divided into two stages: independent loading of individual columns and combined loading of the assembly. By superimposing the critical load of columns in regular structures with the remaining load capacity, a formula for evaluating the overall stability critical capacity of bent and frame structures is established. The proposed method effectively accounts for the restraint provided by tie beams between columns, eliminating the need for iterative solutions of transcendental equations or the construction of complex total potential energy equations, thereby significantly simplifying the computational process. Comparative analyses of numerical examples demonstrate that the proposed method achieves high accuracy and enables quantitative assessment of mutual assistance between columns. It provides a conceptually clear, computationally efficient, and reliable practical tool for the stability design of bent and frame structures under complex loading conditions. Full article

Clamp band separation mechanisms are widely used in spacecraft interfaces, and the clamp band preload is a key factor governing both connection reliability and separation performance. The conventional torque-control method is susceptible to friction-induced preload non-uniformity in clamp band separation mechanisms. To overcome this limitation, thermal preloading has been proposed as an alternative installation method. In this paper, a thermo-mechanical analytical model is established for clamp band separation mechanisms during thermal preloading based on curved-beam and thin-shell theories. Theoretical analysis shows that the preload distribution can be divided into three characteristic zones: a stick zone, a slip zone, and a separation zone. In the stick zone, the preload remains constant and is mainly governed by thermal stress and structural relative stiffness. In the slip zone, friction dominates the load transfer, leading to a non-uniform preload distribution. In the separation zone, local disengagement occurs near the clamp band joint end due to the eccentricity-induced bending moment. The proposed model is validated by finite element simulations, and parametric studies are conducted to reveal the effects of friction coefficient and structural geometric parameters on preload distribution. Based on the theoretical model, a zoned-heating method is proposed to improve preload uniformity, providing a useful reference for optimizing the thermal preloading method. Full article

Determining the safe thickness of a boundary crown pillar is critical during the transition from open-pit to underground mining, as it directly affects both mining safety and resource recovery. Crown pillar instability is commonly associated with asymmetric stress redistribution, nonuniform deformation, and progressive plastic failure. In this study, the Kumusayi Li-Nb-Ta mine in Xinjiang, China, was selected as an engineering case to optimize the boundary crown pillar thickness and evaluate its deformation characteristics. Four theoretical methods, namely the load transfer intersection method, span-to-thickness ratio method, simplified structural beam method, and Rubeneeite formula method, were first used to determine the feasible thickness range. The calculated thicknesses were 19.99, 14.00, 29.81, and 10.41 m, respectively, yielding an engineering design interval of 14.00–29.81 m. Based on this interval, four thickness schemes of 15, 20, 25, and 30 m were evaluated using FLAC3D simulations in terms of stress redistribution, displacement evolution, surface movement, plastic-zone development, and deformation symmetry. The results show that the 15 m pillar exhibits pronounced stress concentration, asymmetric deformation, and through-going plastic failure, indicating insufficient stability. Although the 20 m pillar improves the load-bearing capacity, a potential connected failure path remains. At 25 m, the high-stress zone becomes localized, the plastic zone no longer penetrates the pillar, and the maximum vertical displacement decreases by approximately 27.0% compared with the 15 m scheme. Increasing the thickness to 30 m provides limited additional improvement, with less than a 2% reduction in maximum vertical displacement compared with the 25 m scheme. Physical similarity model tests further confirm that a 20.8 cm model pillar, corresponding to a 25 m prototype pillar, effectively prevents through-going cracking and overall slope sliding. Therefore, a 25 m boundary crown pillar is recommended for the Kumusayi mine. Full article

Fault-crossing ground motions, characterized by velocity pulses, permanent fault dis-placement, and non-uniform support excitation associated with fault rupture, may significantly affect the seismic performance of siphon bridges crossing active faults. This study investigates a long-span siphon arch bridge subjected to pulse-type fault-crossing ground motions. A unified stochastic ground motion model is developed by integrating nonstationary high-frequency components based on the evolutionary power spectrum with low-frequency pulse components represented by an improved Gabor wavelet, capturing forward directivity effects, permanent displacement, and differential support input at the two sides of the fault. A three-dimensional nonlinear finite element model is established in OpenSees using fiber-based beam–column elements, with hydrodynamic effects incorporated through the added mass method. Parametric analyses consider pulse phase angle (0–90°), amplitude (Mw 6.0–7.5), and frequency (0–1 Hz). Results indicate that structural responses decrease with increasing phase angle, with 0° being most unfavorable, high-lighting the dominant influence of permanent displacement. Resonance amplification occurs when pulse frequencies approach the fundamental modes of the pier (0.345 Hz) and deck (0.51 Hz), while the arch is particularly sensitive near 0.439 Hz. Water added mass reduces natural frequencies by 8–14% and significantly amplifies internal forces. These findings provide guidance for seismic design of fault-crossing siphon bridges. Full article

To enhance the overall performance of direct coal liquefaction residue (DCLR)-modified asphalt, particularly its low-temperature cracking resistance, SBS and aromatic oil were employed for composite modification. Nine composite-modified asphalt formulations were prepared based on an orthogonal experimental design. High-and low-temperature rheological properties and microstructure of all modified asphalts were systematically evaluated using a dynamic shear rheometer (DSR), a bending beam rheometer (BBR), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The results indicate that composite modification significantly enhanced the high-temperature performance of the asphalt. Modified asphalt labeled as Sample No. 9 (9% DCLR, 4% SBS, and 6% aromatic oil) demonstrated the minimal non-recoverable creep compliance ($J_{nr}$) value of 0.58 kPa⁻¹ at 64 °C, indicating a 78.6% decrease relative to the matrix asphalt. In terms of low-temperature performance, Sample No. 3 satisfied the Superpave cracking resistance criterion, exhibiting a creep rate ($m$-value) of 0.312 at −12 °C. It was revealed by FTIR analysis that the interaction between the composite modifier and the base asphalt was mainly physical blending, and no new functional groups were generated either before or after aging. The improvement in performance was attributed to the physical compatibility and structural reorganization among the components. Microstructural analysis revealed that the uniform dispersion of modifiers in matrix asphalt and the subsequent formation of a dense micelle structure after aging contributed to the enhanced macroscopic performance. This study provides theoretical and technical support for the high-value application of DCLR in asphalt pavements. Full article

With the need for increasing energy demand due to population growth in cities, and advancements in the efficiency of semi-transparent photovoltaic (ST-PV) technology, the integration of ST-PV modules into building windows has become feasible. This manuscript presents a novel analytical methodology for estimating incident solar energy on vertical PV modules integrated into building facades in an urban environment, emphasizing shade caused by nearby buildings. Monthly and annual direct-beam, diffusion, and global energies are calculated for different wall heights, building separation, and orientation. In addition, the distribution of the incident energy along the height of the wall is evaluated, indicating a non-uniform distribution. The incident diffusion energy is compared between isotropic and anisotropic models. The anisotropic model predicts higher diffusion energy by 3.5% to 14.5%, depending on the building separation. The incident energy on building facades is calculated for locations at low-mid ($32°6’ N$) and at high-mid ($52.2° N$) latitudes. The results show, for example, that both the front side of a front-building wall and the front side of a rear-building wall receive the same amount of annual global energy—$913 kWh/m^2$—for a separation of 25 m between the buildings. Decreasing the distance from 25 m to 10 m decreases the annual incident global energy on a rear-building wall by 15%. Full article

Background and purpose: Organ-preservation strategies are increasingly being incorporated into rectal cancer management, but the role of HDR endorectal/endoluminal brachytherapy boost remains less well defined than that of broader non-operative treatment pathways. Existing literature is frequently mixed with contact X-ray brachytherapy series, neoadjuvant protocols with planned surgery, or heterogeneous watch-and-wait cohorts, limiting the interpretation of this specific strategy. Materials and methods: We performed a PROSPERO-registered systematic review and meta-analysis of studies evaluating definitive-intent external beam radiotherapy (EBRT), with or without chemotherapy, followed by HDR endorectal/endoluminal brachytherapy boost in histologically confirmed rectal adenocarcinoma managed without planned surgery. Pooled analyses were performed for clinical complete response (cCR) and late grade ≥3 gastrointestinal (GI) toxicity. Regrowth/local failure outcomes were synthesized descriptively because of heterogeneity in endpoint definitions, denominator selection, and follow-up structure. Results: Six studies were included in the quantitative evidence base, with one additional small feasibility report summarized narratively. The pooled cCR proportion was 69.2% (95% confidence interval [CI], 43.7–86.6). The pooled proportion of late grade ≥3 GI toxicity was 18.1% (95% CI, 10.9–28.6). Reported regrowth/local failure outcomes were not suitable for formal pooling because of inconsistent definitions, differing denominator structures, and non-uniform follow-up frameworks across studies. Conclusion: Current evidence suggests that EBRT plus HDR endorectal/endoluminal brachytherapy boost may represent a selective organ-preservation strategy for carefully chosen patients with rectal adenocarcinoma, particularly where surgery is not feasible or not desired. Its broader clinical use remains limited not only by the small size of the evidence base, but also by fragmented endpoint definitions, inconsistent denominator reporting, and insufficiently standardized durable local-control outcomes. These findings support cautious interpretation of the current evidence and highlight priorities for future prospective studies in rectal cancer management. Full article

Laser fiber-based collimation straightness measurement can eliminate the intrinsic drift of the laser source while offering a simple configuration and simultaneous measurement of straightness in two orthogonal directions. As a high-precision optoelectronic sensing method, it has been widely used for the measurement of straightness, parallelism, perpendicularity, and multi-degree-of-freedom geometric errors. However, two common issues remain in practical applications. One is the nonlinear response of the four-quadrant detector, the core position-sensitive sensor, which is caused by detector nonuniformity and the quasi-Gaussian distribution of the spot. The other is the degradation of measurement performance by atmospheric inhomogeneity and air turbulence along the optical path, particularly in long-distance measurements. To address these issues, a two-dimensional planar calibration method is first proposed to replace conventional one-dimensional linear calibration. A polynomial surface-fitting model is introduced to correct the nonlinear response and inter-axis coupling errors of the four-quadrant photoelectric sensor. Simulation and experimental results show that the proposed method significantly reduces the standard deviation of calibration residuals and improves measurement accuracy. In addition, based on our previously developed common-path beam-drift digital compensation method, comparative experiments were carried out on double-pass common-path and single-pass optical configurations employing corner-cube retroreflectors, and theoretical simulations were performed to analyze the influence of air-turbulence disturbances on measurement stability. Both theoretical and experimental results show that the double-pass common-path configuration exhibits more pronounced temporal drift. Therefore, a real-time digital compensation method for beam drift in long-distance single-pass common-path measurements is proposed. Experimental results demonstrate that the proposed method effectively suppresses drift induced by environmental air turbulence and thereby improving the accuracy and stability of long-travel geometric-error and related straightness measurement for machine-tool linear axes. Full article

This article investigates the response of an unprotected three-storey steel moment-resisting frame subjected to a suite of horizontally traveling fire scenarios. A series of multi-step finite-element simulations was conducted to analyze the impact of traveling fires on both the global and local responses of a low-rise building frame. The research considers a range of fire types, both uniform and spatially varying, as well as different locations, and sizes to capture a diverse array of fire scenarios. Non-uniform compartment fires are modeled using the improved traveling fire method (iTFM), while uniform fires are simulated using the Eurocode parametric (EC) fire model. Four traveling fire scenarios with floor area coverage ranging from 5% to 48% are examined. The resulting deformation patterns, along with bending moment and axial force distributions in critical beam and column sections within the fire compartments, are thoroughly evaluated. The findings reveal that, within the case study frame and the range of parametric analyses, a uniform compartment fire does not necessarily yield the worst-case scenario commonly assumed in design codes. Instead, global and local structural responses are primarily influenced by traveling fire scenarios. Full article

Cone-beam computed tomography (CBCT) offers advantages of low radiation dose and rapid acquisition but suffers from scatter-induced shading artifacts that limit diagnostic value compared to multi-detector CT (MDCT). While CycleGAN enables unpaired image translation, its uniform loss application struggles with localized artifact removal. We propose a two-stage learning framework with YOLO-based region correction loss. Stage 1 trains a standard CycleGAN to establish stable CBCT-MDCT domain mapping. Stage 2 fine-tunes the model by applying gradient magnitude minimization loss selectively to artifact regions detected by a pretrained YOLO detector, enabling focused correction while preserving anatomical structures. Using 11,000 2D CBCT slices from 17 patients (14 training, 3 testing) and 23,500 2D MDCT slices from 50 patients, our method achieves a 14.0% reduction in artifact score compared to baseline CycleGAN while maintaining high structural similarity (SSIM > 0.96). Independent evaluation using integral nonuniformity (INU) and shading index (SI) confirms consistent improvement across physics-based metrics. The self-regulating mechanism, where YOLO detection confidence naturally decreases as artifacts diminish, provides automatic adjustment without manual intervention. This work demonstrates that combining staged learning with object detection offers an effective solution for localized artifact removal in medical image translation, potentially improving diagnostic accuracy while preserving the low-dose benefits of CBCT. Full article

In this work, an accelerated non-uniform corrosion method controlled by time and current was employed to fabricate power-on accelerated corrosion specimens of hybrid steel fiber-reinforced concrete (HSFRC) gradient beams. Experimental research was conducted to investigate their impact resistance, revealing the dynamic response patterns of these gradient beams with varying steel fiber contents. By analyzing the evolutionary characteristics of impact load, displacement, energy dissipation, equivalent impact bearing capacity, and dynamic amplification factor, the influence of steel fibers with different sizes and contents on the bearing capacity degradation and mechanical properties of HSFRC gradient beams under the same corrosion conditions was clarified. The synergistic enhancement mechanism of multi-scale steel fibers in the beams was elucidated, highlighting the complementary effects of long fibers and short fibers at different stages of material damage. Results show that the incorporation of steel fibers can effectively improve the impact resistance of reinforced concrete gradient beams, with a maximum improvement of approximately 2.5 times. Compared with gradient beams reinforced with single long fibers, the peak impact force of HSFRC gradient beams increases by about 16%, and different steel fiber ratio plays a significant role in regulating impact resistance. Within the corrosion range of 3% to 5%, the equivalent impact bearing capacity of gradient beams is negatively correlated with the reinforcement corrosion rate. Full article

Standard compatibility-based truss models, including the Disturbed Stress Field Model (DSFM), often underestimate the shear strength and deformation capacity of reinforced-concrete (RC) beam-column joints. This study investigates the origin of this bias through a systematic inverse identification framework and derives joint-core constitutive relationships tailored to the highly confined, nonuniform stress states of joints. Inverse analyses show that improving confinement effectiveness alone leads to unrealistic parameter saturation and cannot reproduce the measured energy absorption, indicating that conventional compression-softening formulations remain excessively punitive for joint cores. When confinement activation and softening are identified simultaneously, a clear mechanism shift emerges: unlike panel-based theories that link softening to tensile-cracking measures (principal strain ratio), joint softening is overwhelmingly governed by the principal compressive strain, consistent with crushing-dominated damage accumulation. Based on these trends, unified power-law expressions are proposed for both passive confinement activation and damage-induced softening as functions of principal compressive strain only, adhering to a parsimonious formulation without auxiliary variables such as concrete strength or reinforcement ratio ($R^2\approx 0.89$). The model is validated on an independent database of 113 specimens, including high-strength concrete and exterior joints, eliminating the systematic conservatism of the standard DSFM and improving the mean experimental-to-predicted strength ratio from 0.85 to 1.01 while reducing the coefficient of variation from 34.5% to 13%. The proposed formulation supports more reliable joint shear backbone predictions for seismic assessment of RC frame buildings. Full article

This study presents a newly conducted comprehensive investigation into the lateral torsional buckling (LTB) behavior of un-bonded pre-stressed (PS) thin-walled steel I-beams subjected to non-uniform bending moments, combining a numerical study with a machine learning (ML) approach and experimental validation. Despite extensive prior work, no exact analytical solution exists particularly for non-uniform bending or can be extremely complicated, as the resulting differential equations contain variable coefficients particularly under non-uniform bending due to the complexity of the PS system. To overcome this limitation, a numerical study using finite element (FE) analysis is first conducted with emphasis on the key geometric and pre-stressing parameters, including unbraced beam length, tendon eccentricity, deviators configurations, and pre-stressing force, to evaluate the LTB behavior. The FE modeling was then validated against experimental testing to ensure the accuracy and reliability of the FE solutions. Subsequently, a comprehensive dataset is generated using FE simulations to train the ML models aimed at predicting the LTB resistance of the PS system. This study presents three ML approaches, including support vector regression (SVR), random forest (RF) and least-square boosting (LSBoost), and their optimal hyperparameters are determined using Bayesian optimization (BO) to enhance the prediction performance. The results indicate that the LTB capacity predicted by the Bayesian-optimized ML models achieve high predictive accuracy and are in close agreement with numerical FE simulations, thereby highlighting their potential in capturing the complex, underlying non-linear interactions influencing the buckling behavior of the PS structural system. Accordingly, the proposed framework offers a robust and effective predictive tool for evaluating LTB resistance, particularly under non-uniform bending where exact analytical solutions are not available, and for supporting the design and assessment of PS steel structures. Full article