Varying Aspect Ratio Research Articles

Role of Size and Shape in Photoluminescence and Ultra-Low-Frequency Raman of Methylammonium Lead Iodide Perovskite Quantum Dots.

The photophysical properties of methylammonium lead iodide (MAPbI3) quantum dots (QDs) have not been systematically studied for size and shape dependence. Here, we synthesize MAPbI3 QDs using ligand-assisted reprecipitation, controlling the injection speed and reaction times to produce QDs with different sizes and shapes. Dropwise injection yields ∼5 nm spherical QDs, emitting photoluminescence (PL) at 2.06 eV. In contrast, swift injections yield larger (>10 nm) rectangular QDs with varying aspect ratios, supported by an infinite quantum well model. The PL lifetime of QDs increases with their size, and the size variation significantly influences the ultra-low-frequency Raman modes at 81, 107, and 127 cm-1, in contrast to what is observed in polymorphic MAPbI3 thin films. Our findings, supported by first-principles density functional theory, show that key PL and Raman properties are governed by the sizes and shapes of MAPbI3 QDs. This study contributes to the understanding of the optical behavior of these QDs, which is crucial for their potential applications and environmental implications.

Bipyramidal gold nanoparticles-assisted plasmonic photothermal therapy for ocular applications.

Gold nanoparticles (AuNPs) play a key role in the field of nanomedicine due to their fascinating plasmonic properties as well as their great biocompatibility. An intriguing application is the use of plasmonic photothermal therapy (PPTT) mediated by anisotropic AuNPs irradiated with a near-infrared (NIR) laser for treating ocular diseases in ophthalmology. For this purpose, bipyramidal-shaped AuNPs (BipyAu), which were surface-functionalized with three different organic ligands (citrate, polystyrene sulphonate (PSS), and cetyltrimethylammonium bromide (CTAB)), were synthesized. The long-term storage stability was assured, in terms of minimal variation in aspect ratio and localized surface plasmon resonance. Better performance was achieved with BipyAu@citrate and BipyAu@PSS NPs. PPTT experiments mediated with the synthesized BipyAu NPs demonstrated that BipyAu@citrate provided the highest value of temperature increase (40 °C at 2.0 W cm-2) after 15 min of 808 nm NIR laser irradiation. The potential future clinical application in ophthalmology was assessed by in vitro cytotoxicity analysis, confirming that BipyAu@citrate NPs were biocompatible for the three major corneal cell types. Furthermore, ex vivo analysis was performed by treating pig corneas with BipyAu@citrate NPs (0.18 μg Au) and subsequent NIR laser irradiation at 808 nm for 15 min, showing distortions in the collagen type I fibrils at the ultrastructural level and promoting the flattening of the corneal surface after treatment, without inducing cell cytotoxicity. This work suggests that a precise control of the fibril distortions can be provoked by PPTT mediated with BipyAu@citrate in the NIR region, paving the way for nanomedicine to correct common deficiencies in corneal diseases.

Parametric Study of Internal Curing of Concrete Using Brick Chips: A Review

Abstract: As urban landscapes evolve with taller skyscrapers, the design and safety of high-rise buildings under wind forces have become critical considerations. This study explores the impact of aspect ratios—height-to-width proportions—on the wind behavior of buildings. Tall, Shorter, wider structures are less vulnerable to wind-induced vibrations than slim buildings having high aspect ratios with low aspect ratios face challenges in stability and strength. The research examines how building shape and aspect ratios influence structural behavior under wind loads. Key parameters, including maximum displacements, story drift, shear forces, and bending moments, are analyzed to assess wind effects. The study also compares buildings of varying aspect ratios but equal floor areas to determine optimal designs. By identifying the most suitable aspect ratios for high-rise structures, this research aims to enhance safety, functionality, and aesthetic appeal while addressing the challenges posed by wind forces in urban environments.

Three-dimensional analysis of turbulent twin-swirling jets onto a heated rectangular prism in a channel

Purpose The purpose of this study is to investigate the impact of swirling jet flow on the cooling performance of a heated rectangular prism placed within a channel. The primary aim is to explore the influence of varying aspect ratios (AR) of the prism and different fluid Reynolds numbers (Re) on the cooling efficiency. Design/methodology/approach The numerical analysis is performed using a finite volume-based solver, which incorporates the large eddy simulations (LES) turbulence model. The setup consists of twin 45° swirling jets directed at isothermally heated bodies, with water used as the cooling medium. The rectangular prism is oriented perpendicularly to the channel flow direction, positioned one unit distance from the inlet. This study examines three distinct aspect ratios (AR = 0.5, 1 and 1.5) and a range of Reynolds numbers (6000 = Re = 20000). Findings The results indicate that cooling efficiency improves as the aspect ratio decreases and the Reynolds number increases. Higher Reynolds numbers enhance jet impingement and turbulent mixing, which are crucial for efficient heat transfer. Conversely, lower Reynolds numbers lead to diminished impingement and reduced cooling efficiency. Increasing the Reynolds number from 6000 to 20000 elevates the average Nusselt number by 35% (for AR = 0.5) and up to 45% (for AR = 1.5). It was observed that lower aspect ratios produce superior cooling effects due to intensified localized jet interactions. Originality/value This research significantly contributes to the fields of fluid dynamics and thermal engineering by elucidating the influence of swirling jet flows on the cooling of heated surfaces. The findings offer valuable insights for optimizing the design and performance of cooling systems across various industrial applications.

Effect of Aspect Ratio on Asymmetrical Wear of Brake Pads Under High-Speed and Heavy-Load Braking Conditions

This study investigates the influence and mechanisms of friction blocks with varying aspect ratios on the asymmetrical wear of brake pads under high-speed and heavy-load braking conditions. A large megawatt-level wind turbine brake device was used, and the Archard wear model was integrated into the analysis of brake interface wear characteristics through finite element method (FEM) and arbitrary Lagrangian-Eulerian (ALE) technology. A thermal-mechanical-wear coupling model was developed for brake systems with five different aspect ratio friction blocks, and its accuracy was validated through wear tests on an inertial brake test bench. A method for calculating tangential and radial wear is proposed to characterize the degree of asymmetrical wear at the friction interface. The study revealed a non-uniform wear distribution at the contact interface, with greater wear observed at the leading and outer edges of the friction block. A small aspect ratio (L/W < 1.5) predominantly results in radial wear, while a large aspect ratio (L/W > 1.5) leads to tangential wear. An aspect ratio of 2:1 balances radial and tangential wear, indicating improved wear resistance.

Investigation of flow behavior within staggered vegetation patches of various shapes in an open channel

The flow dynamics and river geomorphology are influenced by vegetation patches, which naturally exist in various patterns. Previous studies have not explored the effect of vegetation patches with different shapes placed in a staggered arrangement with varying aspect ratio (AR: longitudinal to lateral patch length). We used a numerical method to examine the flow around rigid, emerged vegetation patches in a rectangular flume. The impact of different vegetation patch shapes (circle, square, and rectangle) was investigated using the Computational Fluid Dynamics (CFD) software FLUENT. The findings indicate a decrease in mean streamwise velocity downstream of patches, while flow relaxation occurs in the alternate (free) regions. The flow was significantly affected by the shape of the vegetation patches, with the circular configuration offering the maximum flow resistance. Vortex shedding, including primitive Kármán vortex (PKV) and large-scale Kármán vortex (LKV) streets, behind patches are found to be strong and prominent first for circular and then for rectangular patch (with AR = 2) shapes. Flow through the rectangular patch configuration with AR = 2 appeared more uniform with a higher efficiency of velocity reduction than that of rectangular patch configuration with AR = 0.5. The findings of this research are helpful in assessing flow structure influenced by vegetation.

A Refined Model to Predict Boundary of Instability of Axial Compressors

A quantitative model to predict the boundary of instability of axial compressors based on their maximum loading capability is proposed in this paper, which is an improved version of the classic method of stalling pressure rise. The original model correlates the maximum pressure rise of a compressor to a characteristic geometric parameter, which is an analogue of the normalized length of diffusion in two-dimensional diffusers. However, the influence of the aspect ratio of the passage is overlooked in this analogy, which leads to significant discrepancies in its predictions for compressors, especially those with varying blade aspect ratios. Our model contains two improvements to address this issue. The first involves refining in the definition of the normalized length of diffusion, whereas the second introduces a supplementary correction factor for the aspect ratio of the blades. Nearly 20 low-speed compressor configurations, with variations in solidity, aspect ratio, tip clearance, and axial spacing, were tested to develop the proposed model. It can reduce error in the predicted stalling static pressure rise from 10% to 5%. Experimental data robustly verify the accuracy of our model, making it a more reliable predictive tool of instability boundary in the preliminary design of axial compressors.

Engineering magnetic chirality in FeGe nanocylinders: Exploring topological states for spintronic applications

Iron germanide (FeGe) emerges as a promising magnetic alloy for spintronics and high-density data storage, owing to its distinctive magnetic properties and compatibility with existing fabrication techniques. This compatibility enables the synthesis of customized FeGe nanocylinders characterized by chirality, where their magnetization asymmetrically twists. Within specific size parameters, these nanocylinders can accommodate skyrmions—swirling magnetic structures with significant implications for information storage and processing technologies. This study investigates the response of FeGe nanocylinders to external magnetic fields, focusing on how their magnetic properties vary with dimensions (diameter and length). Specifically, we analyze the impact of length on the pseudo-static properties of short FeGe nanocylinders and examine the average topological charge and remanence states across different aspect ratios. Our investigation underscores the relationship between chirality and diverse magnetization states in four types of nanocylinders with varying aspect ratios. This comprehensive analysis elucidates the connection between nanocylinder magnetic states and the average topological charge—a critical factor in advancing ultra-low-energy data storage and logic devices.

Effects of Elliptical and Circular Nozzles on Diesel Spray Characteristics Under High Ambient Density

In this paper, the macroscopic and microscopic characteristics of diesel spray with elliptical and circular nozzles were investigated under an ambient density of 65.6 kg/m3 by combining an optical test and numerical simulation method of VOF-Spray One-Way Coupling and Large Eddy Simulation. Two elliptical nozzles with varying aspect ratios (1.25 and 1.5) and a circular nozzle were employed for comparison, with the same cross-sectional area. The results demonstrated that the spray tip penetration (STP) of elliptical nozzles was significantly diminished in comparison to that of the circular nozzle and that STP for the elliptical nozzle with a larger aspect ratio was observed to be smaller, primarily due to the elevated aerodynamic drag and accelerated kinetic energy dissipation. The spray cone angle (SCA) of elliptical nozzles was greater than that of the circular nozzle. The average SCA of the elliptical nozzle with a larger aspect ratio was the greatest in both planes. The spray asymmetry with elliptical nozzles resulted in the instability of the spray boundary, leading to the earlier fragmentation and atomization of the spray and faster radial diffusion. For the same STP, the elliptical nozzle with a larger aspect ratio exhibited the greatest spray area in both planes. Elliptical nozzles are subject to a greater degree of inhomogeneous shear than circular nozzles, which results in an accelerated rate of droplet breakage and a concomitant decrease in Sauter Mean Diameter.

Exploring Aerodynamics: The Impact of Aspect Ratio on Paper Airplane Flight Dynamics

Aspect Ratio significantly influences the aerodynamic performance of aircraft, dictating crucial factors such as lift and glide efficiency. This paper investigates the impact of varying Aspect Ratios on the Gliding Angle of paper airplanes, serving as analogs for larger aircraft. Different models of paper airplanes, each with unique Aspect Ratios, are constructed and tested under controlled conditions to measure their aerodynamic responses. The experiment employs video tracking and statistical analysis to precisely gauge the glide angles and correlate these with Aspect Ratios. Results indicate that an increase in Aspect Ratio generally leads to a decrease in the Gliding Angle, suggesting enhanced aerodynamic performance. However, this relationship exhibits complexity beyond a straightforward linear association, hinting at the nuanced interactions between wing geometry and airflow dynamics. Further, the study explores the Lift to Drag ratio, revealing its dependency on the glide dynamics shaped by Aspect Ratio variations. These findings contribute to a deeper understanding of flight mechanics, potentially guiding the design of more efficient gliders and other aircraft by optimizing Aspect Ratios to suit specific flight requirements.

Evaluating YOLO Models for Efficient Crack Detection in Concrete Structures Using Transfer Learning

The You Only Look Once (YOLO) network is considered highly suitable for real-time object detection tasks due to its characteristics, such as high speed, single-shot detection, global context awareness, scalability, and adaptability to real-world conditions. This work introduces a comprehensive analysis of various YOLO models for detecting cracks in concrete structures, aiming to assist in the selection of an optimal model for future detection and segmentation tasks. The YOLO models are initially trained on a dataset containing both images with and without cracks, producing a generalized model capable of extracting abstract features beneficial for crack detection. Subsequently, transfer learning is employed using a dataset that reflects real-world conditions, such as occlusions, varying crack sizes, and rotations, to further refine the model. Crack detection in concrete remains challenging due to the wide variation in crack sizes, aspect ratios, and complex backgrounds. To achieve optimal performance, we test different versions of YOLO, a state-of-the-art single-shot detector, and aim to balance inference speed and mean average precision (mAP). Our results indicate that YOLOv10 demonstrates superior performance, achieving a mean average precision (mAP) of 74.52% with an inference time of 19.5 milliseconds per image, making it the most effective among the models tested.

Heat Transfer and Flow Field Characteristics of Variable Aspect Ratio, Serpentine Passages

Heat Transfer and Flow Field Characteristics of Variable Aspect Ratio, Serpentine Passages

Effects of vertical greening on the thermal environment and energy consumption in different street canyons

Vertical greening is vital for energy conservation and urban sustainability. However, previous studies have seldom considered the energy-saving effects of vertical greening within street canyons—an important representative urban model. This study employs ENVI-met and EnergyPlus to evaluate the energy savings of vertical greening in twelve typical street canyon scenarios with varying aspect ratios (H/W = 1, 2, 4) and orientations (North–South, East–West, Northeast–Southwest, Northwest–Southeast). We quantified the relative contributions of building surface temperature reduction (Δ Tse) and air temperature reduction (ΔTa) to overall energy efficiency. Remarkably, our findings reveal that Δ Tse accounts for over 97 % of the total energy-saving contribution—a novel insight contrasting with previous studies that emphasized combined impacts. Additionally, the results indicate that stronger solar radiation in street canyons leads to greater reductions in building surface temperatures. To achieve maximum daily energy savings, the optimal combinations of street orientation and aspect ratio are: North–South orientation when H/W = 1, Southwest–Northeast when H/W = 2, and Northwest–Southeast when H/W = 4. This study is among the first to quantify the combined effects of different street canyon configurations and vertical greening on urban energy savings, providing effective methodologies and new insights for implementing sustainable urban vertical greening.

Numerical Investigation of Turbulent Convection Flow in a Rectangular Closed Cavity

Natural turbulent convection in closed cavities has many practical applications in the field of engineeringsuch as the design of electronic computer chips, atomic installation and industrial cooling among others. Inparticular, it enables in achieving a desired micro-climate and efficient ventilation in a building. Recent studiesshow that turbulent flow is affected by variations in Rayleigh numbers, aspect ratio, and heater positionamong others. Temperature is kept constant in all these studies hence inadequate literature on the effectsof temperature on a turbulent flow. In this study, aspect ratio and Rayleigh numbers are kept constant at2 and 1012 respectively and natural turbulent convection flow in a closed rectangular cavity is investigatednumerically as the operating temperature is varied from 285.5K to 293K. The rectangular cavity’s lower wallwas heated and cooling done at the top face wall while the rest of the vertical walls were kept in adiabaticcondition. Material properties such as density of the fluid kept on changing at any given temperature. Thethermal profile data generated influenced the nature of the turbulent flow. The non-linear averaged continuity,momentum, and energy equation terms were modeled by the SST k − ω model to generate streamlines,isotherms, and velocity magnitude for a different operating temperature and presented graphically. The finitedifference method and FLUENT were used to solve two SST k − ω model equations, vortices, and energy withboundary conditions. It was discovered that, as the operating temperature increased turbulence decreaseddue to a decrease in the velocity of the elements and vortices became more parallel and smaller.

Wall-mounted circular cylinder flows

The flow over wall-mounted circular cylinders is influenced by variations in aspect ratio, Reynolds number, and boundary layer thickness, all of which affect the vortical structures in the wake. In this study, we conducted direct numerical simulations and data-driven techniques, including proper orthogonal decomposition (POD) and dynamic mode decomposition, to examine vortical flows behind wall-mounted circular cylinders with aspect ratios of 4, 8, and 12 at Reynolds numbers ranging from 60 to 800, based on cylinder diameter. The incoming boundary layer thickness varied from 0.05 to 0.25. Our findings reveal that a thicker boundary layer promotes the development of low-frequency symmetric vortical structures along the wall surface, suppressing antisymmetric wake shedding. Consequently, the induced upwashing motion of the flow behind the cylinder pushes the wake shedding region closer to the free-end side, facilitating quadrupole mean streamwise vortices. The wake shedding frequency is significantly altered as the symmetric low-frequency mode intensifies along the boundary. POD analysis demonstrates the coexistence of symmetric and antisymmetric vortical structures in the wake region. The presence of either antisymmetric or symmetric wake shedding is determined by the dominant frequency in the instantaneous flow. These findings substantiate previous conjectures about the simultaneous presence of symmetric and antisymmetric wake shedding modes and enhance our understanding of vortical flows around wall-mounted circular cylinders.

Morphology-Based Feature Extraction Network for Arbitrary-Oriented SAR Vehicle Detection

In recent years, synthetic aperture radar (SAR) vehicle detection has become a research hotspot. However, algorithms using horizontal bounding boxes can lead to redundant detection areas due to the varying aspect ratio and arbitrary orientation of vehicle targets. This paper proposes a morphology-based feature extraction network (MFE-Net), which fully uses the prior shape knowledge of the vehicle targets. Specifically, we adopt rotatable bounding boxes to predict the targets, and a novel rectangular rotation-invariant coordinate convolution (RRICC) is proposed to extract the feature, which can determine more accurately the convolutional sampling location of the vehicles. The adaptive thresholding denoising module (ATDM) is designed to suppress background clutter. Furthermore, inspired by the convolutional neural networks (CNNs) and self-attention, we propose the hybrid representation enhancement module (HREM) to highlight the vehicle target features. The experiment results show that the proposed model obtains an average precision (AP) of 93.1% on the SAR vehicle detection data set (SVDD).

DAG-YOLO: A Context-Feature Adaptive fusion Rotating Detection Network in Remote Sensing Images

Object detection in remote sensing image (RSI) research has seen significant advancements, particularly with the advent of deep learning. However, challenges such as orientation, scale, aspect ratio variations, dense object distribution, and category imbalances remain. To address these challenges, we present DAG-YOLO, a one-stage context-feature adaptive weighted fusion network that incorporates through three innovative parts. First, we integrate 1D Gaussian Angle-coding with YOLOv5 to convert the angle regression task into a classification task, establishing a more robust rotating object detection baseline, GLR-YOLO. Second, we introduce the Dual Branch Context Adaptive Modeling module, which enhances feature extraction capabilities by capturing global context information. Third, we design an adaptive detect head with the Adaptive Global Feature Aggregation and Reweighting (AGFAR) module. AGFAR addresses feature inconsistency among different output layers of the Feature Pyramid Network, retaining useful semantic information and elevating detection accuracy. Extensive experiments on public datasets DOTA-v1.0, DOTA-v1.5, and UCAS-AOD showcase mAP scores of 77.75%, 73.79%, and 90.27%, respectively. Our proposed method has the best performance among the current mainstream SOTA methods, which proves its effectiveness in RSI object detection.

Experimental study of flame morphology in slope buildings under the influence of aspect ratio and ambient wind

Slope structures are commonly used in buildings, but such slope structures can exacerbate the rate of fire spread, complicate building fire safety and suppression, and lead to injuries, deaths, and property damage. Particularly, the thermal hazards posed by ambient wind on sloped fires remain unquantified. In this study, a propane burner was used to simulate the flame morphology behavior of a sloped building fire. 480 tests were conducted with varying aspect ratios (1∼8) of the fire source, different ambient winds (0 m/s∼3.5 m/s), and slope inclination angles (0°∼40°). Results demonstrate that the flame length initially increases and then decreases with an increment in ambient wind velocity. Moreover, with an increased aspect ratio of the fire source (length-to-width ratio), the turning point at which the flame length peaks shift to occur at a lower wind velocity threshold. The tilt angle and height of the flame change (respectively increases and decreases) significantly at lower ambient wind speeds and they tend to asymptotically approach respective constant values. As the ambient wind is further promoted. Existing physical models of flame morphology do not consider the combined effects of fire source aspect ratio, slope inclination angle, and ambient wind. A new slope entrainment restriction factor (EF) was proposed based on an analysis of the upward and leeward entrainment volumes. Using this factor, new models for flame morphology (including flame length, flame tilt angle, and flame height) were established. The accuracy and generalizability of the new flame models have been validated using reference data.

Advances in predicting surface shape changes of mirror blanks through elliptical nozzle gas jet forming

To facilitate the formation of bifocal aspheric optical surfaces, we present an approach for predicting the surface profile of bifocal aspheric surfaces formed by the gas-liquid interface when an elliptical nozzle gas jet is employed. Through an analysis of the gas flow field morphology emanating from the elliptical nozzle, we inferred the impact of gas jet parameters on the gas-liquid interface surface shape within the core region of the gas jet. By analyzing the variation in the gas flow field morphology emitted from an elliptical nozzle, we deduced the influence patterns of gas jet parameters on the gas-liquid interface surface shape within the gas jet's core region. Theoretical analysis is substantiated by numerical simulations, confirming regular changes in the vertex curvature and conic constant of mirror blanks concerning variations in jet initial velocity and nozzle aspect ratio. A comparison between experimental data and numerical simulation results reveals an average prediction deviation of 0.0083 mm−1 for the vertex curvature and a prediction deviation of 10.7 % for the conic constant, challenging to rectify within numerical simulations. Hence, an empirical model, incorporating jet parameters, is developed based on experimental data to predict the vertex curvature and conic constant of mirror blanks. This model demonstrates an average prediction error of 2.901 × 10−3 mm−1 for the vertex curvature and 7.64 % for the conic constant, surpassing the predictive accuracy of the numerical simulation model.

Influence of shear strength parameters on loose fine sand treated with coir fiber and microbially induced calcite precipitation

In recent years, there has been an increasing use of Microbially Induced Calcite Precipitation (MICP) technology in ground improvement. Adding fiber to bio-cemented sand leads to significant improvements in its properties. This paper examines how coir fiber and microbially induced calcite precipitation (MICP) might be used to improve the engineering qualities of fine sand. The sand was mixed with Coir fiber at varying Fiber Contents (FC) of 0.1%, 0.2%, 0.3%, 0.4%, and 0.5% by weight of sand. Additionally, varied Aspect Ratios (AR) of 45, 90, 136, 182, and 227 were considered. The mixture also included urease-producing bacteria (Sporosarcina Pasteurii), as well as solutions of urea and calcium chloride with 3M molarity. The untreated and treated sand samples were submitted to a Direct Shear Test (DST). The study found that the shear strength parameters, such as the angle of internal friction, increased by 1.1 times compared to standard fine sand. Additionally, the angle of internal friction (ϕ) of fiber-reinforced sand with MICP showed 1.4 times increase, while the cohesion values demonstrated a sixfold increase compared to MICP fine sand. It was determined that the optimal aspect ratio was 182, and the optimal fiber content was 0.3%. Moreover, the Scanning Electron Microscope (SEM) was utilized to examine the calcite formations present in the treated sand samples, and calcite precipitation was observed between the pores of the soils.