Search Results (204)

Ubiquitous digital array radar (UDAR) extends the integration time of moving targets by deploying a wide transmitting beam and multiple narrow receiving beams to cover the entire observed airspace. By exchanging time for energy, it effectively improves the detection ability for weak targets. Nevertheless, target motion introduces severe across-range unit (ARU), across-Doppler unit (ADU), and across-beam unit (ABU) effects, dispersing target energy across the range–Doppler-beam space. This paper proposes a beam domain angle rotation compensation and keystone-matched filtering (BARC-KTMF) algorithm to address the “three-crossing” challenge. This algorithm first corrects ABU by rotating beam–domain coordinates to align scattered energy into the final beam unit, reshaping the signal distribution pattern. Then, the KTMF method is utilized to focus target energy in the time-frequency domain. Furthermore, a special spatial windowing technique is developed to improve computational efficiency through parallel block processing. Simulation results show that the proposed approach achieves an excellent signal-to-noise ratio (SNR) gain over the typical single-beam and multi-beam long-time coherent integration (LTCI) methods under low SNR conditions. Additionally, the presented algorithm also has the capability of coarse estimation for the target incident angle. This work extends the LTCI technique to the beam domain, offering a robust framework for high-speed weak target detection. Full article

Monopile foundation is an important foundation form for offshore wind turbines, and the stability of the seabed around it is affected by the combined effects of wave and pile vibration. Based on the Biot consolidation theory and elastoplastic constitutive model, a multi-physical field coupling model of wave–vibration–seabed–monopile is constructed, and the dynamic characteristics of seabed pore pressure around the monopile under the joint action of wave–vibration are systematically investigated, and the influences of waves, vibrations, and seabed parameters on the distribution of pore pressure amplitude are analysed in depth. The results show that the increase in wave incident energy will increase the seabed wave pressure, and the suction and pressure generated by pile vibration will change the soil force state; the coupling of waves and vibrations results in pile displacement difference, causing the seabed pore pressure dissipation depth dissimilarity, and the peak relative amplitude of pore pressure and the peak of vibration displacement are in a linear relationship; the wave parameters and seabed characteristics have a significant effect on the change in pore pressure amplitude distribution. Full article

The characteristics and types of the sky can greatly influence photovoltaic (PV) power generation, potentially leading to a reduction in both the lifespan and efficiency of the entire system. Driven by the challenge of addressing fluctuations in solar PV energy utilization, the aim was to assess the solar energy potential by analyzing the clear sky index $\left(K_t^{*}\right)$ across elevation profiles. To achieve this, a theoretical model for determining $K_t^{*}$ was employed, which encapsulated the solar energy analysis. Initially, solar energy data collected from approximately 16 stations in various provinces of Mozambique, as part of the solar energy measurement initiatives by INAM, FUNAE, AERONET, and Meteonorm, was processed. Subsequently, the clear sky radiation was calculated, and $K_t^{*}$ was established. The statistical findings indicate a reduction in energy contribution from the predictors, accounting for 28% of the total incident energy; however, there are progressive increases averaging around ~0.02, with $K_t^{*}$ values ranging from 0.4 to 0.9, demonstrating a strong correlation between 0.7 and 0.9 across several stations and predictor parameters. No significant climate change effects were noted. The radiation flux is directed from areas with higher $K_t^{*}$ to those with lower values, as illustrated in the heat map. The region experiences an increase in atmospheric parameter deposition, with concentrations around ~0.20, yet there remains a substantial energy flow potential of 92% for PV applications. This interaction can also be applied in other locations to assess the potential for available solar energy, as the analyzed solar energy spectrum aligns closely with the theoretical statistical calibration of energy distribution relevant to the global solar energy population process. Full article

Wave propagation is impacted by the presence of ice floes. The influence of waves, on the other hand, causes ice floes to overlap and accumulate. In this paper, the interaction of ice floes and regular waves was simulated using the Finite Element Method. Firstly, natural ice floe fields were generated using the Python 3.10 programing language, with floe size distribution and randomness taken into consideration. Then, using the velocity inlet boundary wave generation method, regular simple harmonic waves were produced. The process where ice floes couple with waves was simulated with the Coupled Eulerian–Lagrangian (CEL) approach. Variations in wave height after passing through the ice floe field were investigated, and further research was conducted on the movement and fragmentation characteristics of ice floes. Simulations employing the Coupled Eulerian–Lagrangian (CEL) approach reveal that (1) ice floe motion exhibits periodic characteristics synchronized with incident wave periods; (2) wave height attenuation increases by 62–80% with rising ice concentration (70–90%); and (3) fragmentation predominantly occurs at wave trough phases due to flexural stress concentration. These findings quantitatively characterize wave–ice energy transfer mechanisms critical for polar navigation safety assessments. Full article

The earth’s surface has an uneven solar energy density that is sufficient to stimulate solar photovoltaic (PV) production. This causes variations in a solar plant’s output, which are impacted by geometrical elements and atmospheric conditions that prevent it from passing. Motivated by the focus on encouraging increased PV production efficiency, the goal was to use machine learning models (MLM) to map the distribution of solar energy in Mozambique in a regressive literal and geospatial–temporal manner on a short measurement scale. The clear-sky index $\left(K_t^{*}\right)$ theoretical approach was applied in conjunction with MLM that emphasized random forest (RF) and artificial neural networks (ANNs). Solar energy mapping was the result of the methodology, which involved statistically calculating $K_t^{*}$ for the analysis of solar energy in correlational and causal terms of the space-time distribution. Utilizing data from PVGIS, NOAA, NASA, and Meteonorm, a sample of solar energy was gathered at 11 measurement stations in Mozambique over a period of 1 to 10 min between 2012 and 2014 as part of the FUNAE and INAM measurement programs. The statistical findings show a high degree of solar energy incidence, with increments $\left(∆K_t^{*}\right)$ in the average order of −0.05 and $K_t^{*}$ mostly ranging between 0.4 and 0.9. In 2012 and 2014, $K_t^{*}$ was 0.8956 and 0.6986, respectively, because clear days had a higher incident flux and intermediate days have a higher frequency of ${∆K}_t^{*}$ on clear days and a higher occurrence density. There are more cloudy days now 0.5214 as opposed to 0.3569. Clear days are found to be influenced by atmospheric transmittance because of their high incident flux, whereas intermediate days exhibit significant variations in the region’s solar energy. Full article

The global pursuit of sustainable development increasingly depends on integrating renewable energy sources into power systems, with distributed generation (DG) playing a vital role. However, this integration presents technical challenges, particularly the risk of unintentional islanding. Anti-islanding protections are essential for detecting and isolating such events, as required by IEEE 1547, within two seconds. Yet, calibrating these protections to balance sensitivity and reliability remains a complex task, as evidenced by incidents like the UK power outage on 9 August 2019 and the Southwestern Utah event on 10 April 2023. This study introduces the Bayesian Entropy Methodology (BEM), an innovative approach that employs entropy as a model for uncertainty in protection decision-making. By leveraging Bayesian inference, BEM identifies optimal calibration settings for time delay and pick-up thresholds, minimizing uncertainty and effectively balancing sensitivity and reliability. The methodology incorporates a modified entropy surface to enhance optimization outcomes. Applied to the IEEE 34-node test system, BEM demonstrates the ability to determine optimal settings with a significantly reduced training dataset, leading to substantial computational savings. By enhancing the reliability of anti-islanding protections, BEM facilitates the secure integration of renewable DG, contributing to the sustainable development of modern power systems. Full article

This study investigates the aerodynamic behavior of roof structures under wind-induced forces, focusing on buildings equipped with photovoltaic panels. Experimental data were obtained through wind tunnel testing of three 1:100 scale models, each representing a distinct roof geometry: gabled, hipped, and multi-pitched. Measurements of dynamic pressure and pressure coefficients were conducted for various wind incidence angles, ranging from 0° to ±150°. The results highlight the impact of roof geometry and PV panel placement on the pressure distribution, with notable variations due to flow separation and vortex formation around the panels. Gabled roofs exhibited pronounced pressure gradients, while hipped roofs showed more uniform distributions. Multi-pitched roofs demonstrated the most complex aerodynamic behavior due to their variable slopes. These findings enhance the understanding of wind-structure interactions for buildings with roof photovoltaic panels, contributing to the development of more resilient and energy-efficient structures. The research supports sustainable construction practices by improving wind load predictions and informing design decisions that promote the safe integration of renewable energy systems into the built environment. Full article

Long-wave infrared (LWIR) broadband absorption is of great significance in science and technology. The electromagnetic field energy is absorbed by the metamaterials material, leading to the enhanced light absorption, from which the Metal–Dielectric–Metal (MDM) structure is designed. FDTD simulation calculation indicate that the bandwidth within which the absorber absorption ratio greater than 90% is 11.04 μm, and the average absorption rate (9.10~20.14 μm) is 93.6%, which can be accounted for by the impedance matching theory. Upon the matching of the impedance of the metamaterial absorber with the impedance of the incident light, the light reflection is reduced to a minimum, and increase the absorption ratio. Meanwhile, the good incidence angle unsensitivity due to the metasurface structural symmetry and the characteristics of the electromagnetic field distribution at different incidence angles. Due to the form regularity of the nanoring–nanowire metasurface structure, the light acts similar in different polarization directions, and the surface plasmon resonance plays a key role. Using FDTD electromagnetic field analysis to visualize the electric field and magnetic field strength distribution within the absorber, the electromagnetic field at the interface in the nanoring–nanowire metasurface structure, promote the surface plasmon resonance and interaction with damaged materials, and improve the light absorption efficiency. Moreover, the different microstructures and the electrical and optical properties of different top materials affect the light absorption. Meanwhile, adjusting the absorption layer thickness and periodic geometry parameters will also change the absorption spectrum. The absorber has high practical value in thermal electronic devices, infrared imaging, and thermal detection. Full article

Background and Objectives: Distal radius fractures (DRFs) are among the most common fractures globally, with a lifetime incidence of around 9%. They typically present in two age peaks: high-impact trauma in patients under 40 and low-energy trauma in those over 40. Intra-articular DRFs are classified according to the Arbeitsgemeinschaft für Osteosynthesefragen (AO) classification, influencing the treatment approach. Surgical management, particularly open reduction and internal fixation (ORIF) using volar plate osteosynthesis, is considered the gold standard. This study aims to compare the treatment costs of fluoroscopy-assisted ORIF and arthroscopy-assisted ORIF for intra-articular DRF. The analysis includes surgical procedure costs, material expenses, and operating time to evaluate the cost-effectiveness of both methods, considering reimbursement within the German healthcare system. Materials and Methods: A retrospective, monocentric study was conducted at Ludwig-Maximilians-University (LMU) Hospital, a supraregional hand trauma center in southern Germany. Patients with DRFs requiring ORIF were treated either with fluoroscopy or arthroscopic assistance. Group 1 included patients treated by the Department of Hand Surgery (Plastic Surgery), subdivided into Group 1a (arthroscopy-assisted) and Group 1b (fluoroscopy-only). Group 2 comprised patients treated by Orthopaedics and Trauma Surgery (fluoroscopy-only). Costs associated with surgical procedures, including materials, operating time, and postoperative care, were analyzed. Results: A total of 43 DRFs were treated. Group 1 consisted of 17 cases, with an average age of 49.6 years (SD = 19.4) and a 64% majority of female patients. Of these, 10 cases were treated with arthroscopy-assisted ORIF (Group 1a) and 7 with fluoroscopy-only ORIF (Group 1b). In Group 1a, the average age was 53.9 years (SD = 16.3) with 60% female and 40% male patients, while in Group 1b, the average age was 43.6 years (SD = 23.1) with 71.4% female patients. Group 2 included 25 cases, with an average age of 54.2 years (SD = 21.0) and a distribution of 64% female and 36% male patients. There was no significant difference in age and gender distribution within the groups and subgroups (p > 0.05). The mean procedure time was longer for arthroscopically assisted ORIF (111.5 min) compared to fluoroscopy-only ORIF (80.1 min), and even longer compared to Group 2 (65.0 min). Material costs were slightly higher in Group 1. Total costs for Group 1 averaged EUR 4906.58, with subgroup costs of EUR 5448.24 for arthroscopy-assisted and EUR 4132.80 for fluoroscopy-only. In comparison, Group 2 costs averaged EUR 3344.08. Conclusions: Intra-articular DRFs with severely displaced fragments or concomitant injuries benefit from arthroscopically assisted fracture treatment. While material costs do not significantly differ between arthroscopically assisted and fluoroscopy-only treatments, the significantly longer procedure time for arthroscopy-assisted ORIF results in the largest cost component. Despite this, reimbursement through the DRG system remains fixed and does not account for the increased operative duration or complexity of arthroscopic procedures. Our findings demonstrate that DRF treatment, regardless of the method used, is either not or only marginally cost-covering under the current German reimbursement structure. In the context of the ongoing shift towards outpatient hand surgery, including the management of DRF, adequate reimbursement rates are necessary to ensure the economic viability of DRF management, particularly for complex intra-articular fractures requiring arthroscopic assistance. Full article

A novel microstructurally controlled graded micro-porous material was developed and experimentally validated for noise reduction through a normal incidence impedance test. Extensive parametric studies were conducted to understand the influence of test specimen size, particle size, porosity, pore size, and its distribution on acoustic absorption and transmission loss. Based on previous research, this study evaluates the application of graded microporous material as an acoustic liner technology for aircraft turbomachine engines. The liner was fabricated in eight 45° segments, assembled in an aluminum test rig, and tested on NASA Glenn Research Center’s Advanced Noise Control Fan (ANCF) low-speed test bed for tonal and broadband noise. The study demonstrates that microstructurally controlled graded microporous material is very effective in dissipating sound energy with reductions in tonal sound pressure level (SPL) of 2 to 13 dB at blade passing frequencies and reductions in broadband SPL of about 2 to 3 dB for the shaft order greater than 40. While the proposed two-layer graded liner model successfully validated the concept, additional design optimization is needed to enhance performance further. This work highlights the potential of graded microporous material as next-generation acoustic liners, offering lightweight, efficient, and scalable aircraft engine noise reduction solutions. Full article

The rapid integration of renewable energy and electric vehicles is challenging modern distribution networks with increased demand volatility and overload risks. To address these issues, we propose an integrated, multi-timescale battery dispatch framework that unifies long-term capacity planning, day-ahead/intra-day scheduling, and sub-minute real-time control. The framework combines HOMER Pro-based capacity sizing, a MISOCP model for economic scheduling, and an agent-based simulation for immediate overload mitigation. In a case study of a Danish distribution network projected to reach full EV penetration by 2034, our approach reduced moderate-to-severe overload incidents by 82.7%. Furthermore, a price-sensitive variant achieved a 27.4% reduction in operational costs, with only a 12.5% increase in minor overload events. These quantitative improvements, alongside qualitative enhancements in grid stability and battery longevity, provide actionable insights for distribution system operators. Full article

The surface scattering property is one of the important indicators of the optical properties of metal materials, which is of great significance for the development, processing, and application of optical devices. The bidirectional reflection distribution function (BRDF), as an optical mathematical model, describes the spatial distribution of reflected light energy on the surface of an object and can provide an important basis for the characterization of the optical properties of the surface of an object. In this paper, the white light scattering characteristics of the surfaces of four metallic materials, namely brass, aerospace aluminum, oxygen-free copper, and red copper, are investigated based on the BRDF microfacet metamodel, and the scattered field distributions are explored for different angles of incidence, scattering angles, and azimuthal angles. This study provides a reference for the evaluation of the optical properties of metal material surfaces and provides a theoretical basis and technical support for the design and application of optical devices. Full article

Implementing information encoding in laser acoustic signals by altering the medium’s color is one of the current hot research topics. Modulating the color of the medium can modulate the directionality of laser acoustic signals; however, there has been little research on the impact of water color on laser acoustic signals. This paper investigates the relationship between the directionality of laser acoustic signals and water color, innovatively proposing a conical sound source model. It points out that the ratio of the model’s radius (r) to the model’s vertical line (d) is a decisive factor affecting directionality. Through simulations and experiments, it has been verified that laser acoustic signals exhibit no significant directionality (r/d = 10) and that the energy distribution of sound signals in the vertical direction significantly decreases (r/d = 0.4). Sound signal directivity and absorption rate were studied in the environment of red, blue, and yellow water, and the time–frequency characteristics were also studied. The acoustic signals produced by laser breakdown of different colors have obvious time–frequency characteristic differences, among which the signal intensity generated by laser incident on yellow water is 180.13 dB and the signal intensity generated by laser incident on black water is 168.31 dB. The peak frequency of sound signal generated by laser breakdown of yellow water is the highest, which is 21,240 Hz, and the peak frequency of sound signal generated by laser breakdown of water is the lowest, which is 8828 Hz. There is an obvious positive correlation between the peak frequency of sound signals and the laser absorption rate, and calculation of the optimal water color corresponding to the highest detection threshold at different distances provides guidance for the application of laser acoustic communication. Full article

High-purity germanium (HPGe) detectors occupy a prominent position in fields such as radiation detection and aerospace because of their excellent energy resolution and wide detection range. To achieve a broader detection range, conventional HPGe detectors often need to be expanded to cubic-centimeter-scale volumes. However, this increase in volume leads to a large detector area, which in turn increases the detector capacitance, affecting the detector’s noise level and performance. To address this issue, this study proposes a novel high-purity germanium drift detector (HPGeDD). The design features a small-area central collecting cathode surrounded by concentric anode rings, with a resistive chain interposed between the anode rings to achieve self-dividing voltage. This design ensures that the detector’s capacitance is only related to the area of the central collecting cathode, independent of the overall active area, thus achieving a balance between a small capacitance and large active area. Electrical performance simulations of the novel detector were conducted using the semiconductor simulation software Sentaurus TCAD (P-2019.03). The results show a smooth electric potential distribution within the detector, forming a lateral electric field, as well as a lateral hole drift channel precisely directed toward the collecting cathode. Furthermore, simulations of heavy ion incidence were performed to investigate the detector’s carrier collection characteristics. The simulation results demonstrate that the HPGeDD exhibits advantages such as fast signal response and short collection time. The design proposal presented in this study offers a new solution to the problem of excessive capacitance in conventional HPGe detectors, expands their application scope, and provides theoretical guidance for subsequent improvements, optimizations, and practical manufacturing. Full article

Epitaxial growth can be used to guide the controllable growth of one metal on the surface of another substrate by matching the interface lattice, thus improving the dendrite tendency of metal growth. The atomic arrangement of the Cu (111) crystal plane of the FCC structure is similar to that of the Zn (0002) crystal plane of the HCP structure, which is theoretically expected to promote the heterogeneous epitaxial nucleation growth of metal zinc under low strain. In this paper, the molecular dynamics method is used to simulate the atomic process of zinc film growth on the Cu (111) surface. It is found that the behavior of zinc-adsorbed atoms on the substrate surface conforms to the epitaxial growth mode. The close-packed structure grown along the (0002) direction of the layered clusters is tiled on the Cu (111) surface, forming a highly ordered low-lattice-mismatch interface. When a large area of layered zinc clusters cover the substrate, the growth mode will change from heteroepitaxial growth to homoepitaxial growth of Zn atoms on the zinc film, forming a lamellar distribution composed of FCC and HCP structure grains. Polycrystalline zinc film with a planar structure with a (0002) surface preferred a crystal plane. The increase in incident energy is helpful in improving the quality of zinc films, while the deposition rate, corresponding to the deposition temperature and electrolyte ion concentration, has no significant effect on the surface morphology and crystal structure of single metal films. In summary, the atomic arrangement of the Cu (111) surface has a strong guiding effect on the atomic ordered arrangement in the zinc film crystal, which is suitable for the epitaxial deposition of the substrate to induce the ordered growth of the Zn (0002) crystal plane. Full article