Performance Of Array Research Articles

Optimization of performance of the KM2A full array using the Crab Nebula* *Supported by the National Key R & D Program of China (2018YFA0404201, 2018YFA0404202, 2018YFA0404203, 2018YFA0404204), the National Natural Science Foundation of China (12022502, 12205314, 12105301, 12261160362, 12105294, U1931201), the Youth Innovation Promotion Association CAS (2022010) and in Thailand by the National Science and Technology Development Agency (NSTDA), and

The full array of the Large High Altitude Air Shower Observatory (LHAASO) has been in operation since July 2021. For its kilometer-square array (KM2A), we optimized the selection criteria for very high and ultra-high energy γ-rays using data collected from August 2021 to August 2022, resulting in an improvement in significance of the detection in the Crab Nebula of approximately 15%, compared with that of previous cuts. With the implementation of these new selection criteria, the angular resolution was also significantly improved by approximately 10% at tens of TeV. Other aspects of the full KM2A array performance, such as the pointing error, were also calibrated using the Crab Nebula. The resulting energy spectrum of the Crab Nebula in the energy range of 10-1000 TeV are well fitted by a log-parabola model, which is consistent with the previous results from LHAASO and other experiments.

Fiber Seismic Network on the Moon

Abstract Internal structures of the Moon are key to understanding the origin and evolution of the Earth–Moon system and other planets. The Apollo Passive Seismic Experiment detected thousands of lunar seismic events and vastly improved our understanding of the Moon’s interior. However, some critical questions like the state and composition of the core remain unsolved largely due to the sparsity of the Apollo seismic stations and the strong scattering of seismic waves in the top layer of the Moon. In this study, we propose the concept of a fiber seismic network on the Moon and discuss its potential in overcoming the challenges in imaging deep Moon structures. As an emerging technique, distributed acoustic sensing (DAS) can provide a cost-efficient solution for large-aperture and dense seismic network deployment in harsh environments. We compute lunar synthetic seismograms and evaluate the performance of DAS arrays of different configurations in retrieving the hidden core reflected seismic phase ScS from the strong scattered waves. We find that, compared to a sparse conventional seismic network, a fiber seismic network using tens of kilometers of cable can dramatically increase the chance of observing clear ScS by array stacking. Our results indicate that DAS could provide new opportunities for the future lunar seismic surveys, but more efforts and further evaluations are required to develop a space-proof DAS.

Insulator Metal Transition-Based Selector in Crossbar Memory Arrays

This article investigates resistive random access memory (ReRAM) crossbar memory arrays, which is a notable development in non-volatile memory technology. We highlight ReRAM’s competitive edge over NAND, NOR Flash, and phase-change memory (PCM), particularly in terms of endurance, speed, and energy efficiency. This paper focuses on the architecture of crossbar arrays, where memristive devices are positioned at intersecting metal wires. We emphasize the unique resistive switching mechanisms of memristors and the challenges of sneak path currents and delve into the roles and configurations of selectors, particularly focusing on the one-selector one-resistor (1S1R) architecture with an insulator–metal transition (IMT) based selector. We use SPICE simulations based on defined models to examine a 3 × 3 1S1R ReRAM array with vanadium dioxide selectors and titanium dioxide film memristors, assessing the impact of ambient temperature and critical IMT temperatures on array performance. We highlight the operational regions of low resistive state (LRS) and high resistive state (HRS), providing insights into the electrical behavior of these components under various conditions. Lastly, we demonstrate the impact of selector presence on sneak path currents. This research contributes to the overall understanding of ReRAM crossbar arrays integrated with IMT material-based selectors.

High-frequency surface-micromachined optical ultrasound transducer array for 3D micro photoacoustic computed tomography.

This Letter reports a new, to the best of our knowledge, high-frequency surface-micromachined optical ultrasound transducer (HF-SMOUT) array for micro photoacoustic computed tomography (µPACT). An 11 × 11 mm2 2D array of 220 × 220 elements (35 µm in diameter) is designed, fabricated, and characterized. The optical resonance wavelength (ORW) of ≥90% of the elements falls within a 6-nm range. The acoustic center frequency and bandwidth of the elements are ∼14 MHz and ∼18 MHz (129%), respectively. The noise equivalent pressure (NEP) is 161 Pa (or 18 m P a/H z) within a measurement bandwidth of 5-75 MHz. The standard deviation of the ORW drift is 0.45 nm and 0.93 nm within 25°C-55°C, respectively, and during a seven-day continuous water immersion. PACT experiments are conducted to evaluate the imaging performances of the HF-SMOUT array. The spatial resolution is estimated as 90 µm (axial) and 250-750 µm (lateral) within a 10 × 10 mm2 field of view (FoV) and the imaging depth of 16 mm. A 3D PA image of a knotted black hair target is also successfully acquired. These results demonstrate the feasibility of using the HF-SMOUT array for µPACT applications.

Outlier Detection-aided Supervised Learning for Modeling of Thinned Cylindrical Conformal Array

In this paper, a scheme of outlier detection-aided supervised learning (ODASL) is proposed for analyzing the radiation pattern of a thinned cylindrical conformal array (TCCA), considering the impact of mutual coupling. The ODASL model has the advantage in speed improvement and memory consumption reduction, which enables a quick generation of the synthesis results with good generalization. The utilization of the active element pattern (AEP) technique in the model also contributes to the prediction of the array performance involving mutual coupling. The effectiveness of the ODASL model is demonstrated through a numerical example of the 12-element TCCA.

TiO2 nanocone photoanodes by Ar ion-beam etching and physics-based electrochemical impedance spectroscopy

TiO2 nanocone (NC) arrays were produced by argon ion beam etching of nanotube (NT) arrays prepared by Ti anodizing. The anti-reflection performance of NC arrays was enhanced by anodizing a 1 μm-thick Ti film deposited on a p-type silicon substrate. The NC morphology was maintained upon heat treatment up to 400 °C, where the anatase phase was formed. Higher temperature treatments resulted in agglomeration and the formation of the rutile phase. The photoelectrochemical performances of the NC and NT arrays on Ti/Si substrates and the NTs on the Ti disk, both annealed at 400 °C, were compared. The photocurrent curves of the samples on Ti/Si were qualitatively different from NT on Ti. Impedance spectroscopy revealed that the response is dominantly from the p-Si substrates, which can be almost ideally described by the diffusion-recombination governed by the minority electronic carriers. NT on Ti can be characterized by the transmission line model for nanoporous electrodes where the transverse and interfacial capacitances are described by Havriliak-Negami capacitance functions with fixed exponents of either 1 and ½ at high- and low-frequency limits. The model then powerfully deconvolutes TiO2 response from the limited information at the low frequencies for NT and NC on Ti/Si, which can be related to the photoelectrochemical performance. Mott-Schottky analysis of well-defined capacitance parameters from the Havriliak-Negami function allows the physics-based description of the spatially and energetically distributed dopant defects in nanostructured materials.

RGMU: A High-flexibility and Low-cost Reconfigurable Galois Field Multiplication Unit Design Approach for CGRCA

Finite field multiplication is a non-linear transformation operator that appears in the majority of symmetric cryptographic algorithms. Numerous specified finite field multiplication units have been proposed as a fundamental module in the coarse-grained reconfigurable cipher logic array to support more cryptographic algorithms; however, it will introduce low flexibility and high overhead, resulting in reduced performance of the coarse-grained reconfigurable cipher logic array. In this article, a high-flexibility and low-cost reconfigurable Galois field multiplication unit (RGMU) is proposed to balance the tradeoffs between the function, delay, and area. All the finite field multiplication operations, including maximum distance separable matrix multiplication, parallel update of Fibonacci linear feedback shift register, parallel update of Galois linear feedback shift register, and composite field multiplication, are analyzed and two basic operation components are abstracted. Further, a reconfigurable finite field multiplication computational model is established to demonstrate the efficacy of reconfigurable units and guide the design of RGMU with high performance. Finally, the overall architecture of RGMU and two multiplication circuits are introduced. Experimental results show that the RGMU can not only reduce the hardware overhead and power consumption but also has the unique advantage of satisfying all the finite field multiplication operations in symmetric cryptography algorithms.

Viscoelastic circular cell honeycomb helmet liners for reducing head rotation and brain strain in oblique impacts

Rotational head motion is one of the major contributors to brain tissue strain during head impacts, which damages axons and vessels and leads to traumatic brain injury. Helmet technologies have come to market promising enhanced protection against such rotational head motion. We recently introduced novel air-filled viscoelastic cell arrays and showed that their shear response under oblique impacts can be tailored through altering the cell wall curvature. We found that concave cells provide shear stiffness that is a few folds larger than that of convex cells. Here we test whether altering the cell curvature can reduce head rotational kinematics and brain strain and whether the viscoelastic cell arrays outperform the reference EPS foam-based liner. To test these hypotheses, we incorporate the viscoelastic cell arrays in a bicycle helmet liner. We use validated finite element models of the helmet and replace the liner with validated finite element models of the cellular cell arrays. We simulate oblique impacts at different locations to represent a wide range of real-world bicycle head impacts. In all cases, the head kinematics and brain deformation metrics indicate significant improvements with the novel cell arrays over the conventional EPS liner. We show that the shear-compliant cell arrays can reduce head rotational acceleration by as much as 64 % and brain strain by 69 %, but not in all impact locations. Cell arrays with similar axial stiffness yet lower shear stiffness often bottomed out, indicating that a considerable amount of energy is dissipated via cell shearing around the impact zone. Our results show that placement of cells with varying amounts of shear stiffness should be optimised, with the most shear-compliant cells near the crown and the least near the temples. This study shows the promising performance of viscoelastic cell arrays in protecting the head and brain under oblique impacts and provides avenues for optimising the distribution of their compressive-shear properties.

A Simple Method for Solving the Power Fluctuation Issue of a Base Station’s Surrounding Areas Based on Half Tyler Distribution

This paper proposes array antennas based on half Tyler (HT) distribution that can realize omnidirectional null-free (ONF) beams. Array 1 employs the usual edge feeding approach, working at 3.5 GHz with a bandwidth of 0.25 GHz, whereas array 2 operates at 26 GHz with a bandwidth of 3 GHz. We evaluated the far-field performance of linear arrays consisting of 6, 8, 12, and 16 elements. The simulation and measurement results show that the proposed HT approach can achieve a near-ONF pattern and cover a broad area of ±42° on an eight-element linear array. The ONF beam reduces community power fluctuations and increases power by 20 dBm in surrounding areas of the base station (BS). The fluctuation treatment effect can be influenced by adjusting the weighting of sidelobe depression (dp): compared to the uniformly excited one, for example, the maximum ONF gain of an eight-element linear operating at 3.5 GHz is only reduced by 0.5 dB when dp = −30 and by 1–2 dB when dp = −60.

Bio‐Inspired Porous Microneedles Dwelled Stem Cells for Diabetic Wound Treatment

AbstractDiabetic wound healing is a serious, complex, and chronic process; one current promising and focusing technology in this area is stem cell treatment. Here, novel porous microneedle (MN) arrays is fabricated, which can highly mimetic stem cell niches, through template filling, and particle etching method. The human adipose‐derived stem cells (ADSCs) are encapsulated in Matrigel then loaded into the porous MN arrays by post‐perfusion. Because of the extracellular matrix‐mimicking, the biocompatible Matrigel offers a bionic microenvironment of stem cell nest suitable for growth. Benefiting from the numerous pore structures of MNs, the loaded ADSCs have enough space to fully absorb nutrients, proliferate greatly and exhibit prompted function. In addition, the cell‐loaded MN arrays have enough mechanical strength to penetrate the skin, allowing the ADSCs to get into the deep wound areas. Based on these features, the performance of the resultant MN arrays in promoting tissue regeneration is demonstrated, collagen deposition and angiogenesis in diabetes wounds of rat models. Thus, it is believe that the bioinspired porous MNs can act as excellent stem cell scaffolds and will find many practical values in clinic wound healing.

Effects of wind on cooling and performance of photovoltaic arrays: A case study CFD modeling

As photovoltaic (PV) power plants become more popular, it is important to understand how wind affects the temperature distribution and consequently performance of modules placed in different rows of a PV array. This study conducts a comprehensive three dimensional CFD simulation for two 5 by 10 PV arrays (with and without inter-row module spacing) to assess the effects of wind on PV array power output. By solving the continuity, momentum, and energy equations simultaneously, the temperature distribution in the PV modules and the surrounding air along with the resulting velocity profiles are obtained and investigated for two wind directions (northerly and southerly) and two wind speeds of 2 and 5 m/s. The electrical output of PV modules for the respective cases are then compared. The results show that the PV array with zero inter-row module spacing performs better under northerly wind and experiences a 5.3% increase in power output with increasing wind speed. However, the PV array with 3 cm spacing performs better under southerly wind and experiences a 4.6% increase in power output with increasing wind speed. It is found that the PV array with inter-row spacing generally performs better than the one with zero inter-row module spacing.

Thermal performance of flat plate heat pipe array with surface wettability modification: An experimental and simulation study

Surface wettability has a significant effect on the heat transfer characteristics of the flat plate heat pipe array (FPHPA). In this study, an aluminum based FPHPA measuring 250 × 100 × 3 mm3, comprising of 9 independent channels, was developed to investigate the impact on wettability segmented modification through experiment and simulation. After chemical etching, the micro-nano structure of the surface can produce a hydrophilic effect, while hydrophobic effect can be achieved after spraying polydimethylsiloxane mixture, and the two modification methods passed the heat resistance and durability tests. The FPHPA, equipped with a hydrophilic evaporator, a hydrophobic adiabatic, and a condenser, exhibited enhanced heat transfer characteristics, lower wall temperature, a higher heat transfer limit, and reduced sensitivity to inclination angle. Simulation results revealed that the hydrophilic surface promoted bubbles to break away from the wall surface and improved the critical heat flux of the evaporator, while the hydrophobic surface had a faster droplet return rate and a thinner liquid film thickness, which improved the convective heat transfer coefficient of the condenser. Compared to conventional flat heat pipes, hybrid wetting modified FPHPA shows a higher overall effective thermal conductivity at thermal powers above 90 W. The findings from this study contribute to a better understanding of the heat transfer mechanism following surface modification and offer a practical method for modifying FPHPA.

Hydrodynamic performance of a periodic array of flap-type devices installed on the stepped bottom topography in the front of the coastal wall

Harnessing wave energy stands as a promising method to mitigate carbon dioxide emissions and address the global energy shortage. The strategic placement of wave energy converters (WECs) in offshore areas is contingent upon the distinctive features of the coastline and the topographical layout. This study is dedicated to scrutinizing the hydrodynamic characteristics and the wave energy absorption of a periodic array of flap-type WECs situated on a stepped bottom topography, strategically positioned in front of a straight coast. The coastline is modeled as a fully reflecting vertical wall. To analyze the oblique wave interaction with this system, we have developed a semi-analytical solution grounded in the linear potential flow theory. We evaluated key performance metrics, including hydrodynamic efficiency, reflection coefficient, wave excitation torque, added inertia torque, and radiation damping. Case studies were conducted to assess the impacts of varying parameters, such as the distance between the flap and the wall, the wave depth above the step, the incident angle, and the step length on the hydrodynamic performance of the current system. The results underscore the substantial influence of the distance between the flap and the coastal wall on wave power efficiency. The trigger condition's frequency downshift, indicative of the standing wave field between the flap and the coastal wall, is observed with a reduction in the wave depth above the step, in contrast to scenarios without the step. In addition, wave resonance above the stepped bottom topography amplifies wave power extraction, albeit with the caveat of a diminished hydrodynamic efficiency due to the presence of Rayleigh–Bloch waves.

The investigation of V-shaped arrays with non-uniform diameter cylinders for high performance hydrokinetic energy conversion

Harnessing hydrokinetic energy through vortex-induced vibration (VIV) is of great significance. The energy capture efficiency of VIV cylindrical arrays still has great potentials for making further progress. This paper investigates the energy conversion performance of cylinder cluster arrays with non-uniform diameter positioned at the upstream, midstream, and downstream locations, utilizing the downstream VIV enhancement effect. The cylinder arrays consist of five cylinders with non-uniform diameters of 2, 3, and 4 cm, resulting in a total of eight different V-shaped configuration scenarios. Through numerical simulation, it is found that the optimal flow velocity for maximizing the cylinder vibration amplitude is 0.8 m/s. In the condition of 0.8 m/s flow velocity, this study investigates the impact of cylinder diameter and the array arrangement on lift force, amplitude response, vortex shedding frequency, converted power, and efficiency. If the diameter of a cylinder is smaller than that of its upstream cylinder, cylinder experiences an enhanced amplitude, and the magnitude of this enhancement increases with the difference in diameters between the two cylinders. The blocking effect in the cylinder array occurs at a distance of two times the diameter. It has been observed that the small diameter cylinder demonstrates exceptional performance, achieving the highest converted power of 6.58 W (88% higher than the single cylinder) and the highest conversion efficiency of 68 % (75% higher than the single cylinder) in the convergent V-shaped array. The divergent V-shaped array achieves a maximum total converted power of 17.12 W (14% higher than the average conversion efficiency of single 2 cm, 3 cm, 4 cm cylinders), while the convergent V-shaped array achieves a maximum total conversion efficiency of 44% (24% higher than the average conversion efficiency of single 2 cm, 3 cm, 4 cm cylinders). This study presents an innovative perspective on the VIV enhancement effect in energy conversion, specifically focusing on multi-cylinder arrays with non-uniform diameters.

High performance field emission cathode based on the diamond nanowires prepared by nanocrystalline diamond films annealed in air

This paper reports the field emission (FE) characteristics of a diamond nanowires (DNWs) array. The nanocrystalline diamond (NCD) film was deposited on silicon by microwave plasma chemical vapor deposition (MPCVD) and then annealed in air forming DNWs and hydrogenated at last. A high-field flat-plate emission test structure with a 1.03 μm gap between anode and cathode was prepared and the electrical properties proved it feasible. The FE performance of DNWs array was measured in a vacuum test system and that of NCDs film as a comparison. Finally, their FE parameters were analyzed and extracted based on the Fowler–Nordheim (F-N) theory. The results show that transforming NCDs film into DNWs array can improve the FE characteristics greatly. The turn-on field is as low as 1.36 V μm−1 dropping by one order of magnitude, while the field enhancement factor and FE current density are up to 156.68 and 484.75 mA cm−2 respectively rising both by two orders of magnitude. This excellent FE performance stems from the characteristics of large aspect ratio, very small tip radius and high density of DNWs.

Potential of tensegrity racking structures for enhanced bifacial PV array performance

Bifacial PV has emerged as the de-facto choice for utility-scale ground-mounted PV arrays due to their ability to collect solar irradiance from both the front and rear surfaces. However, conventional racking structures were not designed to minimize shadowing of the rear surface since they were developed with only monofacial panels in mind. In this study, we explore the utilization of tensegrity racking structures as an alternative to conventional PV rackings. Tensegrity structures are comprised of rods and cables that achieve structural integrity while minimizing mass, form factor, and possibly cost. In order to explore the potential of tensegrity structures, Radiance optical ray-tracing simulation was used to compare the bifacial performance between the two types of racking solutions. The simulation model was built using the on-site array configurations and the racking geometry obtained from a commercial array that features both monofacial and bifacial panels. High-level results show that the racking and mounting structure contribute to about 18% shading. With other parameters kept unchanged, the tensegrity structure is found to enable up to 60% increase in rear surface irradiance by mainly reducing the rear surface shading caused by the on-site racking structures. The work, through its novel approach of detailed modeling of racking geometry, demonstrates the potential of tensegrity racking structures for bifacial PV arrays.

Experimental investigation on the heat transfer performance of a microchannel thermosiphon array for 5G telecommunication base stations

In response to the increasing demand for enhanced heat dissipation in 5G telecommunication base stations, an innovative heatsink solution that employs air cooling was designed in this paper, namely, the microchannel thermosiphon array. The temperature characteristics, startup behavior, and temperature uniformity were experimentally investigated under various filling ratios, heating power levels and wind speeds. The results indicate that the optimal filling ratio for the microchannel thermosiphon array is 20 %. With a liquid filling ratio of 20 % and a heating power of 80 W, the total thermal resistance of the thermosiphon is 0.28 ℃/W. An increase in input power can expedite the initiation process, aiding its transition into a stable phase of heat transfer and fluid flow, characterized by evaporative rise and condensate return. Under natural convection, the microchannel thermosiphon array has a power limit of 40 W. With a wind speed of 6 m/s, the power limit increases to 140 W, resulting in a total thermal resistance of less than 0.4℃/W and a temperature lower than 74.3 °C. The research results provide guidance for optimizing the design of 5G heat dissipation devices.

Performance Evaluation of an Existing Renewable Energy System at Gilutongan Island, Cebu, Philippines

Solar photovoltaics are considered the practical solution to energy access and climate change issues, especially in tropical countries that receive relatively more sunlight throughout the year. However, questions arise on the reliability of these systems in providing sufficient supply to meet the users’ electricity needs. This paper looks at the reliability of a solar project installed on two rooftops on an off-grid island in Cebu, Philippines, that provides increased electricity access to 11 households. PVSyst and HOMER Pro software analyzed solar PV systems performance and techno-economics. The simulations yielded the annual mean values of reference yield, array yield, final yield, array capture loss, system loss, performance ratio, and capacity factor are 5.66 kWh/m2/day, 3.51 kWh/kWp/day, 3.23 kWh/kWp/day, 2.15, 0.278, 57.10%, and 18.96%, respectively. The peak PV resource of 3.30 kWp/day can supply the 1.66 kWp/day of the consumer’s electrical demand. It was concluded that the current installation could supply the electrical load demand of the residents; however, consideration for the potential increase in demand must be in place. While renewable energy sources are relevant in achieving 100% electrification in rural communities, their ability to address the energy demands of the users must be carefully considered in planning and design.

HSAS: Efficient task scheduling for large scale heterogeneous systolic array accelerator cluster

To efficiently process a large amount of deep neural network models can be challenging, due to significant differences among models and even layers. Nowadays, systolic array has become a common architecture for processing neural networks. With this architecture, different array sizes can lead to huge difference in hardware utilization for the same network. Therefore, to achieve the optimal processing efficiency for a large amount of models, a heterogeneous systolic array accelerator cluster could be more advantageous than a homogeneous architecture. In this work, we propose such heterogeneous architecture, and design its scheduling algorithm HSAS. HSAS can evaluate how models fit with systolic arrays, by our systolic array performance and energy models. Meanwhile, HSAS also takes load balance and preemption into consideration. We further introduce a task decomposition algorithm and subtask priority management table, to enable more fine-grained subtask level scheduling. Our evaluation shows task level HSAS can improve average normalized turnaround time, system throughput and fairness by up to more than 80% compared with classic and state-of-the-art methods, while subtask level HSAS can achieve 18%–63% improvement compared to other methods.

Performance and degradation assessment of two different solar PV cell technologies in the remote region of eastern India

The sole reliance on conventional energy sources proves inadequate to meet the surging energy demand. To address this challenge, a self-sustainable hybrid system based on solar PV emerges as a promising solution. In light of this issue, it becomes important to analyze the performance of a solar PV array. The study aims to assess the performance and degradation of two distinct solar PV technologies, polycrystalline silicon PV (Poly-Si PV) and monocrystalline silicon PV (Mono-Si PV), under the tropical climatic conditions of eastern India. Various performance indices of solar PV arrays, such as reference yield, array yield, final yield, array capture loss, capacity factor (CF) and performance ratio (PR) for the two PV technologies, have been meticulously calculated to analyze the performance of solar PV arrays. The Linear regression (LR) method is employed to assess the degradation rate of both technologies. The results show better performance for Mono-Si PV in terms of yield outcomes and losses compared to its Poly-Si PV counterpart. The yield outcome of Mono-Si PV is approximately 12 % higher, whereas losses are around 32 % lower than Poly-Si PV. The annual average PR for Mono-Si PV and Poly-Si PV is obtained as 77.5 % and 72.42 %, respectively. Correspondingly, the average yearly CF is 16.78 % for Mono-Si PV and 15.44 % for Poly-Si PV. Results also show that Poly-Si PV degrades faster as compared to Mono-Si PV, with an annual average degradation rate of 0.67 % for Mono-Si PV and 0.73 % for Poly-Si PV. Finally, economic analysis of the two systems reveals that Mono-Si PV provides energy at a 9 % lower cost than Poly-Si PV, with a levelized cost of energy (LCOE) of 0.248 $/kWh for Mono-Si PV and 0.273 $/kWh for Poly-Si PV.