Characteristics Of Array Research Articles

Study on Sound Field Properties of Parametric Array Under the Influence of Underwater Waveguide Interface Scattering Based on Non-Paraxial Model—Theory and Experiment

This paper theoretically and experimentally studies the effect of underwater waveguide interface scattering on the nonlinear sound field characteristics of parametric array (PA) radiation. Based on the image source method, the components of the sound field in the waveguide are first analyzed. Then, a non-paraxial model is developed to account for the influence of interface scattering. This model enables accurate calculation of the wide-angle sound field. The impact of the sound source depth and the interface reflection coefficient on the distribution of the difference-frequency wave (DFW) sound field in the waveguide is studied. The interface alters the phase distribution of the DFW’s virtual source density function, thereby affecting the sound field accumulation process. Waveguide interfaces with different absorption coefficients influence the amplitude oscillation caused by interface reflection and change the sidelobe size of the DFW beam. The DFW sound field distribution is measured at three typical frequencies. Simulation and experimental results show that the attenuation of the DFW’s axial sound pressure level in the waveguide oscillates, and the DFW’s beamwidth gradually widens as the frequency decreases. The calculated results from the proposed model agree well with the measured data, with average errors along the sound axis and depth being less than 3 dB and 6 dB, respectively. This demonstrates the model’s superior applicability compared to the existing free-field model.

Evaluation of Photovoltaic Inverters According to Output Current Distortion in a Steady-State and Maximum Power Point Tracking

The limits of direct current (DC) injection and output current distortion of grid-connected photovoltaic (PV) inverters are specified in the IEEE 1547-2018 standard. The standard prescribes limits of output current harmonics, but the input voltage and power at which output current distortion is measured are not specified. This manuscript presents the results of DC injection and output current distortion measurements for three commercial single-phase PV inverters, with 3 kVA, 3.3 kVA, and 6 kVA rated power. During the measurements, the inverters are powered by a programmable DC source that emulates the power voltage characteristic of a PV array, providing different input conditions. In addition to steady-state measurements at constant input voltage and power, the change in the output current spectrum over time during the maximum power point tracking (MPPT) is also measured. The results show that the output current distortion depends on the input voltage and power. Moreover, the current distortion of some of the tested inverters exceeds the limits specified by the standard in some cases. The presented results suggest that further research on the dependence of the output current distortion from PV inverters on their input power and voltage is needed.

Picosecond Laser Direct Writing of Micro-Nano Structures on Flexible Thin Film for X-Band Transmittance Function.

Recently, ultrafast laser direct writing has become an effective method for preparing flexible films with micro-nano structures. However, effective control of laser parameters to obtain acceptable micro-nano structures and the effect of micro-nano structure sizes on function of the film remain challenges. Additionally, flexible films with high X-band transmittance are urgently required in aerospace and other fields. In this work, we evaluate the feasibility of applying picosecond laser direct writing for fabricating micro-nano structures on the surface of flexible thin film and the relationship between the size of square columnar micro-nano structures and the transmittance of the flexible thin film. The results show that an array of square columnar micro-nano structures was achieved by picosecond laser direct writing on the surface of flexible thin film (Au-SiO2-PI) with a thickness of 50 µm. Additionally, excellent micro-nano structures morphology of the square columnar arrays without burning through or destroying were obtained by laser direct writing with a pulse power and frequency of 2 W and 100 KHz, respectively. The results also show that the X-band transmittance was effected by the characteristic of the square columnar array on the surface of the flexible thin film. The X-band transmittance was significantly increased by decreasing the length of the square column on the surface of the flexible thin film. The X-band transmittance was slightly increased by decreasing the width of the groove of the square column on the surface of the flexible thin film.

Experimental research on the temperature distribution characteristics of photovoltaic array

Experimental research on the temperature distribution characteristics of photovoltaic array

Bonobo optimizer: dynamically adaptive heuristic for enhanced MPPT in photovoltaic systems under partial shading – experimental validation with buck converter

Abstract The integration of shunt bypass diodes in photovoltaic (P-V) module to mitigate hot spots frequently leads to the emergence of multiple in the PV array characteristics. Researchers consistently strive to develop, integrate, and refine innovative techniques inspired by various natural processes to achieve a global optimum that enhances the overall efficiency of PV systems. However, these techniques face challenges in adapting parameters to strike a delicate balance between exploration and exploitation, which is essential for circumventing local optima, reducing computation times, and refining precision to optimize energy capture. In this context, this paper introduces a groundbreaking new adaptive Maximum Power Point Tracking (MPPT) controller inspired by the social behavior and reproductive tactics observed in bonobos (BO). This innovative approach is underpinned by two key strategies: fission and fusion, with dynamic parameter adjustment in real-time. this enables for efficient exploration and exploitation of the search space, following the positive and negative phases of the BO. This method was compared with three methods: PSO, DE, and ICS, and evaluated through six simulation scenarios, ranging from 1 to 6 peaks, as well as three experimental scenarios: one uniform and the other two involving partial shading, using an Arduino board and a buck converter. According to the comparative analysis, the new BO algorithm outperforms the three other approaches in all performance evaluation parameters. It shows an average improvement in convergence time of more than 39.18 % and an average precision exceeding 99 %, with minimal oscillation in steady-state operation. This translates into an average MPE efficiency of over 96.66 %. Additionally, the experimental results confirm the findings from the simulations.

Hierarchically Porous Polypyrrole Foams Contained Ordered Polypyrrole Nanowire Arrays for Multifunctional Electromagnetic Interference Shielding and Dynamic Infrared Stealth

As modern communication and detection technologies advance at a swift pace, multifunctional electromagnetic interference (EMI) shielding materials with active/positive infrared stealth, hydrophobicity, and electric-thermal conversion ability have received extensive attention. Meeting the aforesaid requirements simultaneously remains a huge challenge. In this research, the melamine foam (MF)/polypyrrole (PPy) nanowire arrays (MF@PPy) were fabricated via one-step electrochemical polymerization. The hierarchical MF@PPy foam was composed of three-dimensional PPy micro-skeleton and ordered PPy nanowire arrays. Due to the upwardly grown PPy nanowire arrays, the MF@PPy foam possessed good hydrophobicity ability with a water contact angle of 142.00° and outstanding stability under various harsh environments. Meanwhile, the MF@PPy foam showed excellent thermal insulation property on account of the low thermal conductivity and elongated ligament characteristic of PPy nanowire arrays. Furthermore, taking advantage of the high conductivity (128.2Sm-1), the MF@PPy foam exhibited rapid Joule heating under 3V, resulting in dynamic infrared stealth and thermal camouflage effects. More importantly, the MF@PPy foam exhibited remarkable EMI shielding effectiveness values of 55.77dB and 19,928.57dB cm2g-1. Strong EMI shielding was put down to the hierarchically porous PPy structure, which offered outstanding impedance matching, conduction loss, and multiple attenuations. This innovative approach provides significant insights to the development of advanced multifunctional EMI shielding foams by constructing PPy nanowire arrays, showing great applications in both military and civilian fields.

Potential applications of engineered bacteria in disease diagnosis and treatment

Probiotics are live microorganisms that confer health benefits to the host when administered in appropriate quantities. This beneficial effect has spurred extensive research in the medical and health fields. With rapid advancements in synthetic biology, the genetic and biological characteristics of a broad array of probiotics have been elucidated. Utilizing these insights, genetic editing technologies now enable the precise modification of probiotics, leading to the development of engineered bacteria. Emerging evidence underscores the significant potential of these engineered bacteria in disease management. This review explores the methodologies for creating engineered bacteria, their preliminary applications in healthcare, and the mechanisms underlying their functions. Engineered bacteria are being developed for roles such as in vivo drug delivery systems, biosensors, and mucosal vaccines, thereby contributing to the treatment, diagnosis, and prevention of conditions including inflammatory bowel disease (IBD), metabolic disorders, cancer, and neurodegenerative diseases. The review concludes by assessing the advantages and limitations of engineered bacteria in the context of disease management.

Impact Analysis of Orthogonal Circular-Polarized Interference on GNSS Spatial Anti-Jamming Array

With the continuous advancement of electromagnetic countermeasures, new types of interference signals (e.g., multi-polarization suppression interference) pose a significant threat to conventional Global Navigation Satellite System (GNSS) services, even when the receiver employs a right-handed circularly polarized (RHCP) anti-jamming array. This paper proposes a receiving signal model for orthogonal circularly polarized (OCP) interference signals based on conventional arrays, following an analysis of the non-ideal characteristics of actual arrays. Furthermore, the mechanism by which OCP interference signals affect anti-jamming performance is examined. Power inversion (PI) and linear constrained minimum variance (LCMV) techniques, applied to both uniform linear arrays and central circular arrays, are utilized to verify the impact of these interference signals. Simulation and physical testing demonstrate that OCP interference significantly affects the interference subspace of the conventional RHCP array, potentially leading to a reduction in the anti-jamming performance of the receiver. To effectively suppress multi-polarization interference, anti-jamming GNSS receivers must either ensure the consistency of cross-polarization among the elements of the array or adopt polarization-sensitive arrays.

Study of the destructive response of charge array to reinforced concrete plate under contact explosion conditions

Abstract According to the needs of urban counter-terrorism operations, the military needs to enhance its ability to quickly maneuver in cities. The use of explosives to quickly open holes in walls is an effective means of achieving this capability. This article studies the relationship between the damage characteristics of charge array on reinforced concrete plates under contact explosion conditions and the parameters of array explosives through dimensional analysis. Numerical simulation of target plate penetration damage caused by explosive detonation using finite element analysis software, and model correction combined with experiments. Simulate using the modified model to fit the empirical formula of the damage characteristics of the target plate caused by various parameters of the charge array. The results indicate that within the range of working conditions studied in this article, the penetration diameter reaches its maximum when the spacing d between the charge blocks is 20-22cm. The spacing d corresponding to the maximum varies less under different charge block sizes and array arrangements. The ratio of the diameter of the through hole to the side length of the charge block gradually decreases with the increase of the length to height ratio of the charge block. This phenomenon indicates that the effective charge ratio is higher when the length to height ratio of the charge block is low. When the spacing between the charge blocks is too large, the combined effect of the charge array on the target plate weakens. The damage situation is close to that of a single small-sized charge damaging the target plate. The damage to the target plate at the interval between the charge blocks is relatively small. The maximum penetration diameter caused by charge array is 38% - 46% larger than that of group charge, which can effectively improve the destructive ability of explosives of the same mass and enhance combat effectiveness.

High-density, high-frequency and large-scale electrohydrodynamic drop-on-demand jetting via a protruding polymer-based printhead design

Electrohydrodynamic (EHD) printing has critical merits in micro/nanoscale additive manufacturing because of its ultrahigh resolution and wide ink compatibility, making it an advantageous choice for electronics manufacturing, high-resolution prototyping, and biological component fabrication. However, EHD printing is currently limited by its rather low throughput due to the lack of high-frequency and high-density multi-nozzle printheads. This paper presents a novel EHD printhead with a protruding polymer-based nozzle design. An insulated, hydrophobic, and protruding polymer nozzle array with an appropriate geometric structure can effectively address key problems in multi-nozzle jetting, such as electrical crosstalk, electrical discharge, liquid flooding, and nonuniform jetting. By investigating the influence of the electrical and geometric characteristics of the nozzle arrays on the electrical crosstalk behavior and fabricating the optimized nozzle array via MEMS technology, we achieve an EHD printhead with a large scale (256), high density (127 dpi), and high jetting frequency (23 kHz), and addressable jetting can be realized by adding independently controllable extractors underneath the nozzle array. Many functional materials, such as quantum dots, perovskite, and nanosilver inks, can be ejected into high-resolution patterns through the optimized nozzle array, demonstrating the great prospects of our designed printhead in electronics manufacturing. This MEMS-compatible printhead design lays the foundation for high-throughput fabrication of micro/nanostructures and promotes practical applications of EHD printing in functional electronics and biomedical/energy devices.

Water wave radiation by an array of bottom-mounted surface-piercing concentric cylinders

This paper develops a wave radiation analysis model in horizontal oscillation mode for concentric cylindrical arrays with arbitrary numbers and arrangements within the framework of linear potential flow theory. The concentric cylinders have solid inner cylinders and porous outer cylinders, and they are both bottom-mounted and surface-piercing. The porous boundary conditions of the outer cylinders are treated using Darcy's law, and the flow field is divided into one outer region and N (number of cylinders) inner regions with the outer cylinders as the boundary. Employing eigenfunction expansion and region-matching methods, expressions for the radiation velocity potential of each region are obtained, and then expressions of the added mass and damping coefficient of each cylinder are obtained. Following a rigorous verification of the results against published literature, this paper proceeds to analyze the impact of various parameters, including oscillation modes, outer cylinder permeability, radius ratio, spacing, and the number of cylinders, on the wave radiation characteristics of tandem-arranged cylindrical arrays. The research reveals that when the oscillation direction of the structure is parallel with its arrangement direction, the hydrodynamic coefficient curves exhibit significant spikes, attributed to the influence of the Dirichlet trapped mode. Outside the peak regions, the hydrodynamic coefficient curves display regular fluctuations, which are attributed to the alternating occurrence of constructive and destructive interference effects within the wave field.

The double almost-Riordan group

In this paper, we define double almost-Riordan arrays and find that the set of all double almost-Riordan arrays forms a group, called the double almost-Riordan group. We also obtain the sequence characteristics of double almost-Riordan arrays and give the production matrices of two types for double almost-Riordan arrays. In addition, we discuss the algebraic properties of the double almost-Riordan group, and finally give the compression of double almost-Riordan arrays and their sequence characteristics.

Atlas of Microscopic Images of Raw Biomass Used in Fuel Production

As nations strive toward achieving sustainability and reducing reliance on fossil fuels, biomass has emerged as an indispensable component of worldwide energy portfolios. Biomass, derived from organic materials such as plants, agricultural residues, forestry byproducts, and organic waste, is a renewable energy source and abundant resource with significant potential across various sectors. Responsible biomass energy production can aid in waste management, reduce greenhouse gas emissions, and mitigate environmental pollution by utilizing organic materials that would otherwise be discarded. With the anticipated growth in biomass use for energy, it is essential to establish analytical techniques for assessing the quality of the fuel feedstock materials. This will enable to better comprehend the implications of using biomass fuels on public health and our ecosystem. One such technique is reflected light microscopy, which has the potential to significantly enhance the conventional (physical and chemical) quality assessment of biomass-derived fuels. This technique enables rapid observations of material constituents and identification of impurities, and it can be applied not only to fuels but also to biomass-based pellets used in animal feed and bedding. Given the scarcity of publicly accessible microscopic images of biomass materials, the “Atlas of Microscopic Images of Raw Biomass” fills this gap by offering a comprehensive collection of 553 images. These photomicrographs capture the optical characteristics of a diverse array of biomass feedstock, demonstrating unique morphological and structural features. This visual documentation can serve as a valuable resource for researchers, industry professionals, educators, and enthusiasts interested in investigating the complexities of biomass forms.

Research on the NI-MLA Method for Enhancing the Spot Position Detection Accuracy of Quadrant Detectors Under Atmospheric Turbulence

The distorted spots induced by atmospheric turbulence significantly degrade the spot position detection accuracy of the quadrant detector (QD). In this paper, we utilize angular measurement and homogenization characteristics of non-imaging microlens array (NI-MLA) systems, effectively reducing the distortion degree of the spots received on the QD target surface, thereby significantly enhancing the spot detection accuracy of the QD. First, based on the principles of geometric optics and Fourier optics, it is proved that the NI-MLA system possesses the angular measurement characteristic (AMC) within the paraxial region while deriving and verifying the focal length of the system. Then, the QD computation curve characteristics of the system under non-turbulence are explored. This study further elucidates the mathematical principle of the NI-MLA system for mitigating the spot position detection random error of QD (SPDRE-QD) and discusses in depth the relationship between the NI-MLA system’s capability to mitigate the SPDRE-QD and the system’s parameters under various turbulence intensities. Finally, it is experimentally verified that the root-mean-square error (RMSE) of the QD computation values using the NI-MLA system are reduced by a significant improvement of at least 2.44 times and up to 17.36 times compared with that of the conventional optical system of QD (COS-QD) under turbulence conditions ranging from weak to strong.

Experimental study on the operating characteristics of multiple collector direct expansion solar-assisted heat pump

Solar thermal application is one of the most important ways to replace fossil energy. The discontinuous heating character and low heating efficiency are two key factors that limit the large-scale promotion of solar thermal application. Large-scale direct expansion solar heat pump systems (DX-SAHP) can provide high efficiency and low-cost continuous heating. However, the characteristics of multiple collector arrays and the system's performance still need more research and exploration. In this paper, a DX-SAHP system with multiple solar collectors was constructed and the work process of the system under different operation conditions was expressed. An experimental platform with two DX-SAHP system was built and studied, and each system contained a 10HP compressor, 16 set solar collectors and one fin evaporator in parallel. The results show that the coefficient of performance (COP) of the system running with solar collectors was nearly 30 % higher than that with the fin evaporator under constant frequency mode, and nearly 45 % under variable frequency mode, indicating that such a system has better performance under variable frequency operation mode. The refrigerant in the collector/evaporators were distributed uniformly in equal-path connection mode, which was beneficial in promoting the system's performance. The heating performance of the system under sunny and cloudy weather conditions was analyzed and discussed, respectively. The test results indicated that the COP of the system on sunny or cloudy days was higher than 4.0, and the maximum hourly COP can reach 11.3 and the maximum hourly heating capacity was 27 kW.

Learned liquid crystal microlens array for joint optimized deep optical architecture in identifying metameric materials.

Multispectral imaging holds great promise for the detection of metameric materials. However, traditional multispectral imaging systems are characterized by their large volume, complex structure, and high computational requirements, limiting their practical application. We propose a jointly optimized deep optical architecture that combines the liquid crystal (LC) microlens array (MLA) characteristics and a multi-level perceptual spectral reconstruction network (MLP-SRN). The core of the architecture is to integrate the physical properties of the LC-MLA into the MLP-SRN using point spread function (PSF) optical convolution kernels, decoupling the light-field characteristic information collected by the LC-MLA at different voltages. Experimental results demonstrate that the incorporation of the physical properties of the LC-MLA not only reduces the system size and computational complexity but demonstrates excellent performance in identifying a metameric material.

Effect of yaw on wake and load characteristics of two tandem offshore wind turbines under neutral atmospheric boundary layer conditions

In this work, we numerically investigated the effects of yaw angle on the wake and power characteristics of two National Renewable Energy Laboratory (NREL) 5 MW wind turbines based on actuator line method (ALM) and large eddy simulation (LES) under a neutral atmospheric boundary layer (ABL) with specified offshore surface roughness. The turbines are placed in tandem, with a spacing of seven rotor diameters, and the yaw angles range from 0° to 30°. The results indicate that under coordinated yaw conditions, the wakes of the two turbines significantly shift with increasing yaw angles, encroaching on the trailing edge of the turbines. The expansion of the wakes also gradually weakens, leading to a reduction in width. The superposition of the wake generated by the downstream turbine diminishes, leading to both turbines exhibiting approximately comparable physical characteristics within their respective wakes. As the wake of the upstream turbine propagates downstream, a secondary low-speed region emerges between the primary low-speed zone of the wake of downstream turbine and the surrounding atmosphere. With the increase in yaw angle, this secondary low-speed region significantly enhances the rate of wake recovery while also inducing a more pronounced deflection of the wake, thereby demonstrating a stronger entrainment effect. Regarding load characteristics, the time history of power characteristics and the power spectral density (PSD) spectra indicate a good turbine response to the inflow. The power characteristics of the upstream turbine exhibit a scaling law is closely related to the yaw angle. The quantitative relationship is established between yaw angle and the power distribution of the turbines, alongside a proposed correlation between the yaw angle and the cos 2(γ) scaled power curve. The power of upstream turbine decreases and the power of downstream turbine gradually increases with the increase in yaw angle. It is further found that the downstream turbine demonstrates optimal performance at a yaw angle of 20°due to the influence of the yawed upstream turbine. These analyses provide insights into the characteristics of wind turbine arrays under yaw conditions from the perspective of unsteady wake features, interactions, and aerodynamic performance, which can aid in wind farm unit planning and control strategies.

GWECS: An indicator to describe the energy absorption characteristics of wave energy converter arrays in real sea states

Grouping wave energy converters (WECs) into an array has become a trend to improve power production and achieve economies of scale. Therefore, the performance of a WEC array in real sea states is of vital importance. To intuitively reflect an array's frequency-based energy absorption characteristics instead of only the total extractable power in given irregular wave conditions, a new indicator of group wave energy capture spectrum (GWECS) is proposed by extending the concept of wave energy capture spectrum (WECS) to an array. A practical method to measure the indicator by estimating the absorbed wave surface from the array's power signal is also given. Simulations in two-dimensional conditions with a 2-cuboid WEC array and in three-dimensional conditions with a 2-cylinder WEC array are conducted to study the concept. The results examine the consistency in capture efficiency between the newly proposed indicator and conventional ones, and present the effect of various parameters, including linear power take-off (PTO) damping, buoy permutation, separation distance, and incident wave angle on the GWECS.

Speech Masking of Authorship in Conflict-Prone Texts: Linguistic, Legal and Psychological Aspects

The article introduces a comprehensive interdisciplinary approach to authorship speech masking identification and classification as a research domain of the linguistics of lies. The material for the study was a corpus of conflict-prone texts, which, among other things, contained deliberately falsified information about the author. The paper discloses the issues of conflict-prone texts authorship investigation. It presents the description of the main types of speech masking and linguistic ways of their expression. The legal aspects of the concept are revealed, in particular, the description of crimes is given, the compositions of which may include a speech masking of authorship. Some features of the subjective side of the offense (intent, motive) are studied, thus it enables qualifying the speech behavior of a person as a disguise. The psychological aspect of speech masking in the author’s text is highlighted, trends in psychological influence orientation in the context of various types of its implementation are noted. The comprehensive study resulted in the establishment and description of the types of authorship masking. Based on the study of the text array, the linguistic and psychological characteristics of each of the diagnosed types of disguise were identified in terms of legislative norms and relevant law enforcement practice.

Study of ash deposition characteristics of photovoltaic arrays taking into account the effect of photovoltaic module spacing and its effect on output characteristics: Indoor experiment

The problem of ash deposition on the surface of photovoltaic (PV) arrays during actual operation seriously affects their power generation efficiency. Because traditional research does not consider the PV module spacing, it cannot reflect the actual PV array ash deposition problem. This study explored the influence of PV module spacing, combined with different tilt angles and inlet wind speeds, on the characteristics of ash deposition and power output of the PV array through indoor experiments. The study designed a set of experimental equipment for simulating the formation process of ash deposition on the surface of PV arrays and set up an experimental platform to measure the influence of ash deposition on the maximum output power (Pmax), open-circuit voltage (Uoc), and short-circuit current (Isc) of the PV modules. The findings indicate that as the tilt angle increases, the PV array experiences reduced ash deposition and increased output power. Conversely, higher inlet wind speeds lead to greater ash deposition and decreased output power. Moreover, widening the spacing between PV modules results in increased ash deposition and reduced output power. Notably, within the PV array, the front PV module accumulates more ash than the rear module, with larger particle sizes. These research findings have significant implications for optimizing PV array design and enhancing power generation efficiency.