Plane Of Array Research Articles

Acoustic imaging of geometrically shielded sound sources using tailored Green's functions.

In light of the growing market of urban air mobility, it is crucial to accurately detect the stationary or moving noise sources within the complex scattering environments caused by aircraft structures such as airframes and engines. This study combines conventional and wavelet-based beamforming techniques with an acoustic scattering prediction method to develop an acoustic imaging approach that considers scattering effects. Tailored Green's function is numerically evaluated and used to compute the steering vectors and the specific delayed time used in those beamforming methods. By examining common scenarios where a scatterer is positioned between the source plane and the array plane, it is observed that beamforming in a scattering environment differs from that in free space, leading to improved resolution alongside scattering-induced side lobes. The effectiveness of the developed method is validated through numerical simulations and experimental studies, confirming its improved ability to localize both stationary and rotating sound sources in a shielded environment. This advancement offers effective techniques for acoustic measurement and fault monitoring in the presence of structural scatterers.

Understanding Heat Dissipation Factors for Fixed‐Tilt and Single‐Axis Tracked Open‐Rack Photovoltaic Modules: Experimental Insights

ABSTRACTThis paper presents the results of long‐term experiments conducted on fixed‐tilt (FT) and single‐axis tracked (SAT) open‐rack photovoltaic (PV) modules in South Africa. Utilising Faiman's heat dissipation model and data filtering method, the study demonstrates favourable comparisons of FT experimental results with literature while yielding novel heat dissipation factors for SAT modules. Enhanced heat dissipation is observed in no/low wind conditions for SAT modules compared to FT modules. Analyses reveal the influence of plane‐of‐array (POA) irradiance, wind speed and direction on module temperature, with SAT modules exhibiting greater heat dissipation stability. An investigation into data filtering methods suggests minor sensitivity for both configurations, with a slightly more pronounced impact on SAT modules. Assessments comparing module temperature predictions using diverse heat dissipation factors for FT modules reveal negligible sensitivity. This suggests that exact heat dissipation factor values may not be crucial for accurate predictions of module temperature in FT open‐rack systems. Annual power output simulations using PVsyst software demonstrate a 2.9% and 3.3% enhancement for FT and SAT configurations, respectively, when employing experimentally determined heat dissipation factors. These findings highlight the importance of realistic, configuration‐specific heat dissipation factors in optimising PV system performance, particularly in the competitive context of modern PV power plant construction and techno‐economic calculations.

Moving sound source localization in 3D space based on time delay and energy ratio technique

Moving sound source localization has numerous applications in interdisciplinary realms such as in teleconferencing, in defense, in robotics, and fault localization in vehicles. Localization of moving source is more challenging than localizing stationary sources because the motion disturbs the sound field and manipulates the frequency and amplitude of the acoustic pressure at recording location, which hampers the accuracy of source localization. Existing moving source localization techniques have numerous restrictions such as source trajectory should be known beforehand as a straight line perpendicular to the array geometry, source should be in same plane or parallel to the microphone array plane, and source velocity should be known. Moreover, when the source elevation is high, these techniques give high error. This study proposes the time delay and energy ratio based real-time moving sound source localization technique that is free from above-mentioned restrictions and can track the source's 3D coordinates accurately. Six microphones are used to localize a moving source by processing the time delay and energy ratios between sensor pairs. The root mean square error found for low source speed and high source speed conditions are 0.73 m and 1.8 m respectively.

Study on the internal waves induced by a submerged body moving in a continuously stratified fluid

This paper studies the characteristics of internal waves induced by the motion of a submerged body through a combination of experimental and numerical methods. First, by deploying an array of conductivity probes in an experiment, the temporal evolution of the internal wave at the plane of the conductivity probe array is obtained and compared with numerical simulation results based on the Navier–Stokes equations, thereby validating the accuracy of the Computational Fluid Dynamics (CFD) model. Subsequently, utilizing CFD calculations, further exploration is conducted on the spatiotemporal distribution characteristics of the internal wave, encompassing its generation and evolution, velocity field distribution, wake angle, and wave profile features. Finally, the variation of the internal wave with the Froude number (Fr) is investigated, revealing that it varies apparently with Fr, including the wave component, wave mode, wake length, wake angle, wave amplitude, and so on. It is found that when Fr is large, the internal wave converges toward the centerline behind the body, until forming a line. The wave magnitude changes with Fr in four stages, i.e., increasing with Fr from zero in the first stage, reaching a peak and decreasing thereafter in the second stage, then changing little in the third stage, and finally increasing approximately linearly in the fourth stage.

Optimizing solar power efficiency in smart grids using hybrid machine learning models for accurate energy generation prediction

The fourth energy revolution is characterized by the incorporation of renewable energy supplies into intelligent networks. As the world is shifting towards cleaner energy sources, there is a need for efficient and reliable methods to predict the output of renewable energy plants. Hybrid machine learning modified models are emerging as a promising solution for energy generation prediction. Renewable energy generation plants, such as solar, biogas, hydropower plants, wind farms, etc. are becoming increasingly popular due to their environmental benefits. However, their output can be highly variable and dependent on weather conditions, making integrating them into the existing energy grid challenging. Smart grids with artificial intelligent systems have the potential to solve this challenge by using real-time data to optimize energy production and distribution. Although by incorporating sensors, analytics, and automation, these grids can manage energy demand and supply more efficiently, reducing carbon emissions, increase energy security, and improve access to electricity in remote areas. However, this research aims to enhance the efficiency of solar power generation systems in a smart grid context using machine learning hybrid models such as Hybrid Convolutional-Recurrence Net (HCRN), Hybrid Convolutional-LSTM Net (HCLN), and Hybrid Convolutional-GRU Net (HCGRN). For this purpose, this study considers various parameters of a solar plant such as power production (MWh), irradiance or plane of array (POA), and performance ratio (PR). The HCLN model demonstrates superior accuracy with the RMSE values of 0.012027 for MWh, 0.013734 for POA and 0.003055 for PR, along with the lowest MAE values of 0.069523 for MWh, 0.082813 for POA, and 0.042815 for PR. The obtained results suggest that the proposed machine learning models can effectively enhance the efficiency of solar power generation systems by accurately predicting the required measurements.

Characterizing Biphoton Spatial Wave Function Dynamics with Quantum Wavefront Sensing.

With an extremely high dimensionality, the spatial degree of freedom of entangled photons is a key tool for quantum foundation and applied quantum techniques. To fully utilize the feature, the essential task is to experimentally characterize the multiphoton spatial wave function including the entangled amplitude and phase information at different evolutionary stages. However, there is no effective method to measure it. Quantum state tomography is costly, and quantum holography requires additional references. Here, we introduce quantum Shack-Hartmann wavefront sensing to perform efficient and reference-free measurement of the biphoton spatial wave function. The joint probability distribution of photon pairs at the back focal plane of a microlens array is measured and used for amplitude extraction and phase reconstruction. In the experiment, we observe that the biphoton amplitude correlation becomes weak while phase correlation shows up during free-space propagation. Our work is a crucial step in quantum physical and adaptive optics and paves the way for characterizing quantum optical fields with high-order correlations or topological patterns.

Comprehensive comparisons of RANS, LES, and experiments over cross-ventilated building under sheltered conditions

The use of RANS (Reynolds-Averaged Navier-Stokes) simulations to study airflow over cross-ventilated buildings has been widely performed under both isolated and sheltered conditions. For a sheltered environment, great efforts still need to be made as few studies have been conducted on cross-ventilated buildings, located far downstream of the urban morphology. Therefore, in this study, a series of simulations with different turbulence models were conducted to determine the performance in predicting the external and internal airflows of a cross-ventilated building under sheltered conditions and to evaluate the ventilation performance. Two urban building dispositions were considered, namely square (SQ) and staggered (ST) layouts. The evaluation of the velocity profiles was performed in the vertical and horizontal planes of the target building to systematically determine the accuracy of each model. The qualitative results showed that several RANS models are able to generate the main features of the external (in-canyon) and internal flows. In addition, the quantitative evaluations of the internal flow showed that the vertical velocity in the vertical plane and the lateral velocity in the horizontal plane are poorly predicted in the SQ array. Furthermore, the prediction of the streamwise velocity in the horizontal plane of the ST array is not satisfactory. The RANS ventilation rates are comparable to the large-eddy simulation (LES) results for certain models in the SQ array, but the deviations are large for all models in the case of the ST array, with the highest predicted ventilation rate being 40% lower compared to LES.

Magnetic interactions in vortex-state nanodisk arrays characterized by gradient magnetic vortex echo

Magnetic vortices have potential applications in the field of spintronics and medicine and studying their magnetic interactions is crucial for future applications. This work introduces a new method based on obtaining the gradient magnetic vortex echo (GMVE) using micromagnetic simulations following a magnetic resonance imaging protocol. The results show that it is possible to characterize the magnetic interaction of arrays of nanodisks, having equal diameter and vortex configuration, as a function of disk separation. This characterization was performed by creating an inhomogeneity in the system through the application of a magnetic field gradient perpendicular to the plane of the nanodisk array. The inhomogeneity allows refocusing the magnetization in a time-controlled way by inverting the sign of the gradient and obtaining the characteristic transverse relaxation time T2∗ from the GMVE that contains the information on the magnetic interaction.

Higher-order fractal transverse modes observed in microlasers

Two classes of higher-order, fractal spatial eigenmodes have been predicted computationally and observed experimentally in microlasers. The equatorial plane of a close-packed array of microspheres, lying on one mirror within a Fabry-Pérot resonator and immersed in the laser gain medium, acts as a refractive slit array in a plane transverse to the optical axis. Edge diffraction from the slit array generates the high spatial frequencies (>104 cm−1) required for the formation of high-order laser fractal modes, and fractal transverse modes are generated, amplified, and evolve within the active medium. With a quasi-rectangular (4-microsphere) aperture, the fundamental mode and several higher-order eigenmodes (m = 2,4,5) are observed in experiments, whereas only the m = 1,2 modes are observed experimentally for the higher-loss resonators defined by triangular (3-microsphere) apertures. The fundamental and 2nd-order modes (m = 1,2) for the 4-sphere aperture are calculated to have qualitatively similar intensity profiles and nearly degenerate resonant frequencies that differ by less than <0.1% of the free-spectral range (375 GHz) but exhibit even and odd parity, respectively. For all of the observed fractal modes, the fractal dimension (D) rises rapidly beyond the intracavity aperture array as a result of the high spatial frequencies introduced into the mode profile. Elsewhere, D varies gradually along the resonator axis and 2.2 < D < 2.5. Generating fractal laser modes in an equivalent optical waveguide is expected to allow the realization of new optical devices and imaging protocols based on the spatial frequencies and variable D values available.

Improvement of misalignment tolerance in free-space optical interconnects

In this paper, the use of micro lenses with non-uniform transmittance apertures as an alternative to those with uniform transmittance apertures in optical communication systems is proposed. In particular, we consider the use of micro lenses with tapered Gaussian transmittance profiles to improve the misalignment tolerance in optical interconnects. We study the effects of utilizing Gaussian transmittance profiles on the propagation of light beams and the signal to crosstalk ratio of misaligned optical systems. Moreover, we consider the use of uniform transmittance profiles in optical systems for the sake of comparison. To this end, the crosstalk optical noise is modeled at the plane of the detectors array considering the two scenarios of uniform and Gaussian apertures. This was possible after finding the optical field for both scenarios at the of the detectors array. Numerical results clearly demonstrate the significant improvement in decreasing the crosstalk and increasing the signal to crosstalk ratio in the considered optical systems upon utilizing the Gaussian profiles.

Temperature dependence of infrared photoresponse from lead sulfide film grown by chemical bath deposition

Due to the lower Auger recombination coefficient of lead salts, the study of room temperature infrared detectors based on lead salt is reemerges as a hot research topic. In this paper, we prepared polycrystalline lead sulfide (PbS) films using chemical bath deposition and fabricated a photovoltage infrared detector with Si. Different from normal PbS photodetectors, which usually show positive photoconductivity, our device demonstrated both positive and negative photoconductivity under 1550 nm laser illumination. The switching of positive and negative photoconductivity was found to be depended on temperature and applied bias. We proposed that the change of photoconductivity is due to the electron traps from S vacancies. Furthermore, we also tested the photoresponse under infrared blackbody radiation, which confirms that the device exhibits high sensitivity. The temperature dependence of PbS infrared photodetector demonstrated in this paper could be useful for applications involving focal array planes based on lead-related materials.

A Low RCS Waveguide Slot Antenna array with Metamaterial Absorber

We propose a novel design to reduce the radar cross section (RCS) of ridged waveguide slot antenna array with metamaterial absorber (MMA). The MMA consists of metallic pattern and solid metal on sides of a dielectric slab, of which the absorbing characteristics and mechanism are analyzed. The PEC ground plane of a ridged waveguide slot antenna array is covered by MMA. Both the simulated and measured results show that compared with the waveguide slot antenna array with a PEC ground plane, the RCS of proposed antenna array are reduced dramatically without degradation of antenna performance. Combining with the bandpass frequency selective surfaces technology, the guideline illustrated by the proposed examples will serve as a good candidate for the future design of low RCS antenna.

Open‐source photovoltaic model pipeline validation against well‐characterized system data

AbstractAll freely available plane‐of‐array (POA) transposition models and photovoltaic (PV) temperature and performance models in pvlib‐python and pvpltools‐python were examined against multiyear field data from Albuquerque, New Mexico. The data include different PV systems composed of crystalline silicon modules that vary in cell type, module construction, and materials. These systems have been characterized via IEC 61853‐1 and 61853‐2 testing, and the input data for each model were sourced from these system‐specific test results, rather than considering any generic input data (e.g., manufacturer's specification [spec] sheets or generic Panneau Solaire [PAN] files). Six POA transposition models, 7 temperature models, and 12 performance models are included in this comparative analysis. These freely available models were proven effective across many different types of technologies. The POA transposition models exhibited average normalized mean bias errors (NMBEs) within ±3%. Most PV temperature models underestimated temperature exhibiting mean and median residuals ranging from −6.5°C to 2.7°C; all temperature models saw a reduction in root mean square error when using transient assumptions over steady state. The performance models demonstrated similar behavior with a first and third interquartile NMBEs within ±4.2% and an overall average NMBE within ±2.3%. Although differences among models were observed at different times of the day/year, this study shows that the availability of system‐specific input data is more important than model selection. For example, using spec sheet or generic PAN file data with a complex PV performance model does not guarantee a better accuracy than a simpler PV performance model that uses system‐specific data.

Source identification of a vibrating plate using phase conjugation and interior boundary element method

Noise pollution is the most serious environmental pollution, which seriously affects people’s normal life and physical and mental health, as well as normal production work. Therefore, noise control is necessary, but before noise control, the first thing to do is to identify the location of the noise source, and the noise control work is meaningless when the noise cannot be identified. Flat plate structures are a fundamental part of complex ship structures, and their vibration, noise, and their interrelationships when excited by the outside world are receiving increasing attention. The core of the research in this paper is the identification of the sound source of the vibrating plate. A method combining phase conjugation with interior boundary element method is developed for the identification of the pressure and normal velocity distribution of a vibrating plate. An interior problem is formed by enclosing the phase conjugation array plane and the plate surface. The pressures at the array elements are phase-conjugated as the specified pressure boundary condition. The impedance relationship between the surface pressure and the surface normal velocity of the plate is utilized as a specified impedance boundary condition. The interior boundary element method is applied to solve the interior problem. The identification of the surface pressure and normal velocity distribution is studied numerically. The numerical results show that with the array located in the near field the proposed method achieves subwavelength focusing to identify the surface pressure and normal velocity distribution and clearly shows the response shapes.

Ku/Ka-Band Dual-Frequency Shared-Aperture Antenna Array With High Isolation Using Frequency Selective Surface

In this letter, a high-gain, high-efficiency, and high-isolation Ku/Ka-band dual-frequency shared-aperture antenna array using frequency selective surface (FSS) is investigated. The antenna consists of an 8×8 Ka-band and a 4×4 Ku-band printed double-sided dipole arrays in the upper and lower substrate layers, respectively. To realize high efficiency, the feeding networks are realized with double-sided parallel striplines. A low-pass FSS structure, sandwiched by the Ku-band array and the Ka-band array, works as the ground plane of the Ka-band array and is transparent to the Ku-band array, and it can also isolate the two antenna arrays for high isolations. In addition, a third-order impedance transform filter is integrated into the feed network of the Ka-band array. Ultimately, the antenna array has -10 dB impedance bandwidths of 14.47–17.52 GHz (19.07%) and 30.19–38.29 GHz (23.66%) with the peak antenna gain of 18.9 dBi at 16 GHz and 24.85 dBi at 35 GHz, respectively. High aperture efficiencies of 79% and 65% are realized. Meanwhile, the isolations between the two ports are better than 20 dB in low band and 30 dB in high band. For verification, a prototype is fabricated, and the measured results agree with the simulated ones.

Genetic algorithm optimization for parametrization, digital twinning, and now-casting of unknown small- and medium-scale PV systems based only on on-site measured data

Accurately predicting and balancing energy generation and consumption are crucial for grid operators and asset managers in a market where renewable energy is increasing. To speed up the process, these predictions should ideally be performed based only on on-site measured data and data available within the monitoring platforms, data which are scarce for small- and medium-scale PV systems. In this study, we propose an algorithm that can now-cast the power output of a photovoltaic (PV) system with high accuracy. Additionally, it offers physical information related to the configuration of such a PV system. We adapted a genetic algorithm-based optimization approach to parametrize a digital twin of unknown PV systems, using only on-site measured PV power and irradiance in the plane of array. We compared several training datasets under various sky conditions. A mean deviation of −1.14 W/kWp and a mean absolute percentage deviation of 1.81% were obtained when we analyzed the accuracy of the PV power now-casting for the year 2020 of the 16 unknown PV systems used for this analysis. This level of accuracy is significant for ensuring the efficient now-casting and operation of PV assets.

Acceleration Factors for Combined‐Accelerated Stress Testing of Photovoltaic Modules

Combined‐accelerated stress testing (C‐AST) is developed to establish the durability of photovoltaic (PV) products, including for degradation modes that are not a priori known or examined in standardized tests. C‐AST aims to comprehensively represent the sample, stress factors, and their combinations using levels at the statistical tails of the natural environment. Acceleration factors for relevant climate sequences within the C‐AST cycle with respect to the Florida USA climate are estimated for selected degradation mechanisms. It is found that for degradation of the outer backsheet polymer layer, the acceleration factor of the tropical climate sequence (the longest of the climate sequences) isf(T,G) = 17.3 with ultraviolet photodegradation; for polyethylene terephthalate hydrolysis (backsheets),f(T,RH) = 426; for electrochemical corrosion (PV cell),f(I) = 14.1; and for PbSn solder fatiguef(ΔT,r(T)) = 17.3. Here,Tis the module temperature,Gis the broadband spectrum irradiance on the plane of array of the module,RHis the relative humidity on the module surface,Iis the leakage current through the module packaging, andr(T), the number of temperature reversals. The methods discussed herein are generally applicable for evaluating acceleration factors in other accelerated test methods.

Increasing the Resolution and Spectral Range of Measured Direct Irradiance Spectra for PV Applications

The spectral distribution of the solar irradiance incident on photovoltaic (PV) modules is a key variable controlling their power production. It is required to properly simulate the production and performance of PV plants based on technologies with different spectral characteristics. Spectroradiometers can only sense the solar spectrum within a wavelength range that is usually too short compared to the actual spectral response of some PV technologies. In this work, a new methodology based on the Simple Model of the Atmospheric Radiative Transfer of Sunshine (SMARTS) spectral code is proposed to extend the spectral range of measured direct irradiance spectra and to increase the spectral resolution of such experimental measurements. Satisfactory results were obtained for both clear and hazy sky conditions at a radiometric station in southern Spain. This approach constitutes the starting point of a general methodology to obtain the instantaneous spectral irradiance incident on the plane of array of PV modules and its temporal variations, while evaluating the magnitude and variability of the abundance of atmospheric constituents with the most impact on surface irradiance, most particularly aerosols and water vapor.

Study of beam divergence and thrust vector eccentricity characteristics of the Hall thruster based on dual Faraday probe array planes and its applications

The accurate knowledge of the thrust vector eccentricity and beam divergence characteristics of Hall thrusters are of significant engineering value for the beneficial integration and successful application of Hall thrusters on spacecraft. For the characteristics of the plume bipolar diffusion due to the annular discharge channel of the Hall thruster, a Gaussian-fitted method for thrust vector deviation angle and beam divergence of Hall thrusters based on dual Faraday probe array planes was proposed in respect of the Hall thruster beam characteristics. The results show that the ratios of the deviation between the maximum and minimum values of the beam divergence angle and the thrust vector eccentricity angle using a Gaussian fit to the optimized Faraday probe dual plane to the mean value are 1.4% and 11.5%, respectively. The optimized thrust vector eccentricity angle obtained has been substantially improved, by approximately 20%. The beam divergence angle calculated using a Gaussian fitting to the optimized Faraday probe dual plane is approximately identical to the non-optimized one. The beam divergence and thrust vector eccentricity angles for different anode mass flow rates were obtained by averaging the beam divergence and thrust vector eccentricity angles calculated by the dual-plane, Gaussian-fitted ion current density method for different cross-sections. The study not only allows for an immediate and effective tool for determining the design of thrust vector adjustment mechanisms of spacecraft with different power Hall thrusters but also for characterizing the 3D spatial distribution of the Hall thruster plume.

On-Orbit Relative Radiometric Calibration of the Bayer Pattern Push-Broom Sensor for Zhuhai-1 Video Satellites

The two video satellites of the second and third batch of Zhuhai-1 microsatellites (referred to as OVS-2A/3A) are operational with their hyperspectral satellites, which improves the data acquisi-tion capability of the Zhuhai-1 remote sensing satellite constellation. Contrary to the linear array push-broom hyperspectral satellites and plane array CCD video satellites, the OVS satellite is equipped with a planar array Bayer pattern sensor, which can obtain single-band grayscale images by push-broom imaging. Additionally, the Bayer color reconstruction algorithm can interpolate sensor data to provide RGB color band information. Therefore, for the Bayer pattern push-broom sensor, the relative calibration method of linear push-broom or array cameras cannot be directly applied. The radiometric calibration of the Bayer pattern push-broom imaging mode has become a matter of concern; therefore, this study developed a radiometric calibration method for the Bayer pattern push-broom sensor of the OVS satellite and verified its effectiveness and accuracy. OVS images were used to perform on-orbit relative radiometric calibration, and the calibration accu-racy, including streaking metrics and root-mean-square error, was better than 1%, meeting the specification requirements for the OVS satellite. Visually, after calibration correction, the streaking and striping noise of the Bayer images was removed, and the radiometric quality of the image was considerably improved, providing a good data basis for subsequent research in remote sensing applications.