Optimization of fuselage arm cross-section on the aerodynamic performance of quadcopter Unmanned Aerial Vehicles: An experimental investigation

In this study, we investigate the optical response and plasmonic features of a multilayer 4π-spiral composed of metal-semiconductor arms, numerically, by employing a finite-difference time-domain method. We verified that the proposed structure is able to support strong plasmon and Fano resonances in the circular arms. We showed that the negative polarizability of the spiral provides an opportunity to consider the examined 4π-spiral structure as a meta-atom. Quantifying the effective refractive index of the structure for the presence of various semiconductor substances such as Si, GaP, and InP, we obtained the highest possible value for the associated figure of merit (FOM). Ultimately, for a finite spiral structure with a compositional and multilayer arrangement of Au and GaP arms, the FOM is determined as approximately ~62.3.

This article exposes how we improved (by more than a factor of four) the green Lunar Laser Ranging instrumental sensitivity of the French telemetric station of the “Observatoire de la Côte d’Azur” in 2012. The primary reason for this success is the doubling of the pulse energy of our green Nd:YAG laser, reaching now 200mJ at 10Hz. This first gain is due to the replacement (inside our oscillator cavity) of the dye cell with a CR4+:YAG crystal saturable absorber. Complementary spatial beam profile improvements are also described, regarding polarisation, flashlamp geometry and specific lens arrangements (to exclude ghosts from focusing on the 8m long amplification chain). Those combined laser enhancements pave the way to future science breakthrough linked to quasi-millimetric determination of the Earth–Moon dynamics (Murphy, 2013). Jointly, we propose an empirical thermal lensing model, varying with the cycle ratio of the flashlamps. Our model connects Koechner’s (1970) continuous pumping to our intermittent pumping case, with a “normalised heating coefficient” equalling 0.05 only if the electrical lamp input power is equal to 6kW and scaling as this [electrical input power into the lamps] to the power of [half the pumping cycle ratio].

This paper conducts theoretical and experimental investigations on a three-stage gas-coupled Stirling-type pulse tube cryocooler (SPTC). A two-dimensional computational fluid dynamics (CFD) model is established in which the interactions between compressor and cold finger (CF) are analyzed and the distributions of PV power simulated as well. The effects of operating frequency and charge pressure on the performances of both compressor and CF are modeled in detail. Based on the above theoretical studies, a three-stage gas-coupled SPTC is then worked out and tested. The experimental results show that it reaches a no-load temperature of 4.5 K. The electric input power and the motor efficiency of the compressor are 320 W and 81.5%, respectively. When using He-3, the no-load temperature reduces further to 4.0 K. Finally, the SPTC prototype shows great potential for 4-10 K space applications due to its compact configuration, high reliability, low vibration and high cooling efficiency.

We use both experimental diagnostics and computational modelling to characterize the electrical properties and vacuum ultraviolet emission of positive column discharges in both pure xenon and mixtures of xenon with other rare gases. Discharge conditions include xenon pressures of 10-100 mTorr at room temperature, discharge currents of 100-500 mA and positive column diameters of 1.1-5 cm. Our primary interest is the efficient generation of large quantities of ultraviolet radiation for use in fluorescent light sources. We therefore focus on the total output of atomic xenon resonance radiation at 147 nm, reported in units of watts of 147 nm radiation per unit length of positive column, and also the efficiency by which electrical input power is converted into 147 nm radiation. Over the range of discharge conditions considered, we observe outputs in excess of of discharge length and efficiencies in excess of 80%, but we also find that there is a strong tradeoff between efficiency and output, and that these two figures of merit cannot be simultaneously maximized. A change in the behaviour of the discharge is observed to occur near 25 mTorr in 2.2 cm diameter tubes and is attributed to the transition from a discharge sustained by multistep electron-impact ionization to one sustained by single-step electron-impact ionization.

Due to the inaccuracies of UAV models and the uncertainties introduced because of sensor measurement errors, noise, undesired environmental conditions as well as disturbances, stabilizing UAVs in real-time applications is a challenging task. Fuzzy logic controllers (FLCs) are capable of controlling a system without knowing much about the details of it's mathematical description. Particularly, type-2 FLCs are capable of effectively capturing and accommodating uncertainties. In this paper, therefore, we develop an interval type-2 (IT2) Takagi-Sugeno-Kang (TSK) fuzzy logic attitude controller for enhancing the performance of a quadcopter UAV. The effectiveness of the developed IT2 TSK FLC is verified by applying it to a software in the loop (SITL) simulation of a quadcopter UAV. The performance of the UAV when using the developed IT2 TSK FLC is compared with it's performance when using a classical PID controller.

A reinforcement learning model is proposed for the problem of UAV cluster autonomy in air combat environment. A theoretical motion model was established for the quadcopter unmanned aerial vehicle to describe its motion states, and a framework for adversarial algorithms based on reinforcement learning was proposed. A series of simulation experiments are carried out to verify the influence of quadcopter UAV parameters change on the cluster game performance of both quadcopter UAV by constantly adjusting the parameter setting of quadcopter UAV.

In this work, a novel approach to realize a plasmonic sensor is presented. The proposed optical sensor device is designed, manufactured, and experimentally tested. Two photo-curable resins are used to 3D print a surface plasmon resonance (SPR) sensor. Both numerical and experimental analyses are presented in the paper. The numerical and experimental results confirm that the 3D printed SPR sensor presents performances, in term of figure of merit (FOM), very similar to other SPR sensors made using plastic optical fibers (POFs). For the 3D printed sensor, the measured FOM is 13.6 versus 13.4 for the SPR-POF configuration. The cost analysis shows that the 3D printed SPR sensor can be manufactured at low cost (∼15 €) that is competitive with traditional sensors. The approach presented here allows to realize an innovative SPR sensor showing low-cost, 3D-printing manufacturing free design and the feasibility to be integrated with other optical devices on the same plastic planar support, thus opening undisclosed future for the optical sensor systems.

Three-dimensional (3D) printing is one of the most widely used additive manufacturing techniques which is able to produce physical objects from geometrical illustrations using the applicable material. Polyethylene Terephthalate Glycol (PETG) is an additively manufacturable polymer material which is gaining attention for its excellent mechanical and chemical properties. However, it has mechanical limitations that restrict its broader use in 3D printing. Thus, reinforcing with natural fibers like rice husk (RH), an agricultural byproduct, show potentials in improving polymer composites. Nonetheless, their potential when blended with PETG for 3D printing applications are insufficiently explored, emphasizing the need for a systematic investigation. Henceforth, the present work seeks to formulate a 3D printing filament using PETG with RH powder that aims to enhance the mechanical properties of 3D-printed filament. This work also finds the mechanical interactions between varying ratios of PETG and RH to determine optimal composition for enhanced properties focusing on surface roughness, hardness and tensile strength. The PETG/RH filaments were produced from crushed raw RH and pellet form PETG. The varying ratios of RH at 0%, 2%, 6%, and 10% were blended with PETG into an extruder. The roughness of the surface was evaluated by direct imaging. The smoother filament was observed when loading up to 6 wt.% RH. In hardness and tensile strength test, the hardness and strength increased with loading up to 6 wt.% RH. This paper presents the results of optimal ratios of PETG/RH at 6 wt.%, as it improves surface roughness, hardness and tensile strength of PETG. This study adopted the same stance and claimed that the fiber’s tensile strength and hardness increased along with its weight until an optimal level. However, further increase in the sample leads to a stronger fiber-fiber bond which it weakens the interfacial bond of fiber-matrix. Weak interfacial bond of fiber-matrix resulting in inefficient load transfer, hence decrease the sample’s mechanical properties.

This study provides a detailed analysis of power consumption ([Formula: see text] and surface roughness ([Formula: see text] in three-dimensional (3D) printing of polylactic acid (PLA), which has not been addressed before. Additionally, this research addresses the influence of machine tool vibration on surface morphology and the influence of layer thickness on surface wettability of printed parts. Three key process variables, including nozzle temperature (NT), printing speed (PS), and layer thickness, are taken into consideration during the 27 trials as per a full factorial design of experiments. The combined approach of analysis of variance (ANOVA) and response surface method (RSM), in association with desirability function analysis (DFA), has been utilized for assessment, predictive modeling, and multi-response optimization of performance characteristics ([Formula: see text], [Formula: see text] in 3D printing. Finally, the optimal process parametric condition has been applied for carbon footprint analysis, with the goal of reducing power consumption and greenhouse gas emissions. According to results, layer thickness (73.62%) and PS (2.25%) significantly affect surface roughness, while NT (55.77%), PS (25.46%), and layer thickness (15.8%) impact power consumption in PLA 3D printing. Higher speeds and temperatures increase the power consumption, and thinner layers extend the printing duration with an increase in power consumption. Moreover, increasing layer thickness reduces the water contact angle, improves surface wettability by creating a rougher texture with more pronounced layer lines, provides more areas for liquid adhesion, and reduces surface hydrophobicity. Increased printing speeds cause mechanical vibrations in the print head and build platform, leading to material deviations, layer distortion, and surface roughness. The developed RSM models accurately predict PLA 3D printing performance, supported by low p-value (<0.05), high [Formula: see text] value, and significant Anderson–Darling (AD)-test results. Optimal conditions — 100 mm/min printing speed, 210∘C nozzle temperature, and 0.1[Formula: see text]mm layer thickness — yielded 0.1604[Formula: see text]W of power consumption and 4.549[Formula: see text] [Formula: see text]m of surface roughness. These parameters reduced energy consumption and carbon footprint, advancing greener additive manufacturing.

Three-dimensional (3D) printing is one of the most widely used additive manufacturing techniques which is able to produce physical objects from geometrical illustrations using the applicable material. Polyethylene Terephthalate Glycol (PETG) is an additively manufacturable polymer material which is gaining attention for its excellent mechanical and chemical properties. However, it has mechanical limitations that restrict its broader use in 3D printing. Thus, reinforcing with natural fibers like rice husk (RH), an agricultural byproduct, show potentials in improving polymer composites. Nonetheless, their potential when blended with PETG for 3D printing applications are insufficiently explored, emphasizing the need for a systematic investigation. Henceforth, the present work seeks to formulate a 3D printing filament using PETG with RH powder that aims to enhance the mechanical properties of 3D-printed filament. This work also finds the mechanical interactions between varying ratios of PETG and RH to determine optimal composition for enhanced properties focusing on surface roughness, hardness and tensile strength. The PETG/RH filaments were produced from crushed raw RH and pellet form PETG. The varying ratios of RH at 0%, 2%, 6%, and 10% were blended with PETG into an extruder. The roughness of the surface was evaluated by direct imaging. The smoother filament was observed when loading up to 6 wt.% RH. In hardness and tensile strength test, the hardness and strength increased with loading up to 6 wt.% RH. This paper presents the results of optimal ratios of PETG/RH at 6 wt.%, as it improves surface roughness, hardness and tensile strength of PETG. This study adopted the same stance and claimed that the fiber’s tensile strength and hardness increased along with its weight until an optimal level. However, further increase in the sample leads to a stronger fiber-fiber bond which it weakens the interfacial bond of fiber-matrix. Weak interfacial bond of fiber-matrix resulting in inefficient load transfer, hence decrease the sample’s mechanical properties.

Anisotropic mechanical performance of 3D printed fiber reinforced sustainable construction material

Inclined 3D concrete printing: Build-up prediction and early-age performance optimization

ABSTRACT: Some researchers have explored the feasibility of replicating the crack behavior of natural rocks with defects using three-dimensional (3D) printing technology. However, few have investigated changes in strain fields during compression experiments, even though this is crucial for understanding the crack behavior of 3D-printed rock-like specimens. This study examines the crack evolution and strain field distribution in the 3D-printed rock-like specimen to address this gap during the compression tests. In this study, a set of in-situ uniaxial compression tests was performed on 3D-printed rock-like specimens with an initial flaw with various inclined angles (α = 30°, 45°, 60°) using the high-resolution Micro-CT scanner with a loading apparatus. Based on the CT images of 3D-printed rock-like specimens obtained at different scanning steps, the 3D reconstruction and digital volume correlation (DVC) processes were applied to illustrate the damage evolution and quantify the 3D interior deformation of 3D-printed rock-like specimens. The results indicated that within the 3D-printed specimens, tensile cracks were first initiated near the internal flaw, followed by shear cracks or tensile-shear mixed cracks at the flaw tips. The characteristics of internal strain distribution before cracking indicated strain localization, and the cracking process of specimens was strongly correlated with radial strain distribution. 1. BACKGROUND Currently, methods for studying rocks' crack behavior, damage characteristics, and failure mechanisms in compression experiments include experimental approaches (such as rock coring and rock analog materials) and numerical simulation methods (such as finite element methods, discrete element methods, and finite difference methods). Due to their superior control and reproducibility, rock analog materials offer a better understanding of the crack behavior of rocks in compression tests. Traditional rock analog materials, including gypsum, sand, and cement-based materials, are prepared by casting methods. However, this method is low-precision, time-consuming, ineffective, and cannot produce samples with complex internal structures. 3D printing technology, one of the representative technologies of the Fourth Industrial Revolution, has been widely used in various fields, including rock mechanics and geotechnical engineering (Jiang et al., 2016; Song et al., 2018; Zhu et al., 2018). Researchers (Shao et al., 2023; Song et al., 2020; Zhou et al., 2020) have found through uniaxial and triaxial compression experiments that powder-based 3D-printed specimens exhibit lower strength, with their mechanical properties only matching those of low-strength sandstones, while resin-based 3D-printed specimens can match the high strength of natural rocks. Asadizadeh et al. (2019) studied the full-field strain evolution and crack propagation behavior of 3D-printed gypsum specimens with different initial defects in Brazilian split tests using Digital Image Correlation (DIC) technology based on powder-based 3D printers. They concluded that tensile cracking dominates fracturing under loading, while shear cracking is challenging. Song et al. (2023a) explored the mechanical response and deformation-cracking behavior of 3D-printed sand specimens with prefabricated flaws, shedding light on how fracture characteristics impact strength and failure modes. The results indicate that the fracture mode of 3D-printed sand specimens strongly depends on the inclination angle of the initial defect.

Proton Exchange Membrane Fuel Cells (PEMFCs) represent a class of fuel cells that transform the chemical energy of fuels, ideally hydrogen and oxygen, into electrical power. Utilized in diverse applications, PEMFCs power vehicles and supply backup energy to buildings. The core of a PEMFC is the membrane electrode assembly (MEA), composed of a polymer electrolyte membrane, an anode, and a cathode. Oxygen, protons, and electrons merge at the cathode, forming water. One challenge PEMFCs face is water-induced cathode flooding at low temperatures, a consequence of the electrochemical reaction's water accumulation. This reduces the oxygen supply, potentially leading to decreased cell performance or even failure. This issue can have substantial undesired consequences, as PEMFCs depend on oxygen availability at the cathode to generate electricity.Gas Diffusion Layers (GDLs) serve as critical PEMFC components, providing porous structures that facilitate reactant access to the catalyst layer and enabling electron flow through the external circuit. GDLs also offer structural support and promote reactant distribution across the membrane surface. Water accumulation in the cathode may cause pore clogging within the GDL, restricting reactant flow, and reducing cell performance. Additionally, water build-up increases pressure drop across the GDL, hindering reactant access to the catalyst layer and diminishing fuel cell efficiency.Three-dimensional (3D) printing has emerged as a potential technique for fabricating GDLs in PEMFCs. 3D printing enables the creation of GDLs with ordered pore size structures, offering a more uniform surface than traditional GDLs with randomly oriented fibres. This uniformity enhances reactant distribution across the membrane surface and mitigates water accumulation risks. In addition, to prevent cathode flooding, 3D printed GDLs are immersed in PTFE solution to increase hydrophobicity.This talk delves into the creation and evaluation of 3D printed carbonized GDLs for PEMFC implementation. A desktop 3D printer constructed a polymer framework, which was subsequently carbonized in a high-temperature tube furnace. Isothermal thermogravimetric analysis (TGA) tests were performed to identify weight change across a temperature range of 30-900 °C under an N2 atmosphere, optimizing the carbonization step to reduce structural distortion and increase electrical conductivity.The 3D printed GDLs displayed pore size diameters spanning 80 to 120 μm and fibre radii of 20-30 μm. The 3D printing technique produced GDLs characterized by a consistent, planar structure without blocked pores that are normally caused by excess resin residue. Electrical conductivity assessments were conducted on the carbonized specimens, and tensile and compression tests measured their mechanical properties.GDLs possessing minimal pore sizes and thicknesses were integrated into membrane electrode assemblies (MEAs) and examined in low-temperature PEMFCs. Diverse spraying methodologies were investigated, involving either the catalyst being sprayed onto the 3D printed GDL or the membrane receiving a catalyst coating. Commercial MEAs, comprising Nafion membranes and platinum electrodes, acted as benchmarks for MEAs featuring 3D printed GDLs. Furthermore, the current challenges facing 3D printed GDLs, including material selection, production consistency, compatibility with other PEMFC components, costs, and scaling up are highlighted in the talk.These findings underscore the promise of 3D printed carbonized GDLs in boosting PEMFC performance, showing their potential as a cost-effective and proficient substitute for conventional carbon paper based GDLs. Figure 1

Experimental investigation on the aerodynamic performance and aeroacoustic characteristics of model rotors with different tip anhedral angles in hover are conducted in the paper. Three sets of model rotors with blade-tip anhedral angle 0°(reference rotor), 20° and 45° respectively are designed to analyze the influence of the anhedral angle on the hovering performance and aeroacoustics of rotor. In the environment of anechoic chamber, the hover experiments under the different collective pitch and blade numbers, are carried out to measure the figure of merit (FM), time history of sound pressure and sound pressure level (SPL) of the three rotor models. Based on test results, the comparison and analysis of hovering performance and aeroacoustic characteristics among the three rotor models have been done. Meanwhile, for the sake of analysis, the rotor wake and blade pressure distribution are simulated by means of computational fluid method (CFD). At last, some conclusions about the effects of blade-tip anhedral angle on the aerodynamic performance and aeroacoustic characteristics in hover are obtained. An anhedral blade tip can enhance the FM of the rotor, and decrease the rotor loads noise to some extent.