Overlap Configurations Research Articles

High-fidelity computational study of aerodynamic noise of side-by-side rotor in full configuration

This paper presents a numerical study of side-by-side rotor aircraft in full configuration during hover using high-fidelity computational fluid dynamics (CFD) and aeroacoustic simulations. CFD simulations are performed using HPCMP CREATE™-AV Helios, while acoustic calculations are conducted with PSU-WOPWOP. Overset structured grids are applied using the SA-DES turbulence model along with adaptive mesh refinement in the near- and off-body meshes. Four overlap cases at a specific collective pitch angle of 8° are considered. Results reveal a substantial influence of the fuselage on rotor performance, with improvement in the figure of merit being observed for each overlap configuration due to a partial ground effect. There is considerable increase in blade sectional thrust, pressure fluctuations, and noise levels seen in the 0% overlap configuration compared to the 25% overlap configuration. This increase is primarily due to the absence of rotor overlap, resulting in a lower induced velocity allowing for flow to travel upward, and reaching the rotor disk plane. The acoustic spectrum appears at all harmonics of the blade passing frequency for the 0% and 5% overlap configurations. In contrast, the acoustic spectrum is distinctly present only at even harmonics for the 15% and 25% overlap cases. A noise reduction benefit of 3-5 dBA is noticed in the full configuration cases having rotor overlap compared to the 0% overlap configuration. Acoustic destructive interference is observed in the directivity plot only for the 15% and 25% overlap configurations. Overall, this paper reveals that the fuselage has a significant impact on the performance, aerodynamics, and aeroacoustics of the side-by-side UAM vehicle in hover.

Crashworthy Behavior of Multilayered and Multitubular Glass/Epoxy Fiber Reinforced Composite Tube with Different Helical Overlap Configurations

Crashworthy Behavior of Multilayered and Multitubular Glass/Epoxy Fiber Reinforced Composite Tube with Different Helical Overlap Configurations

Optimizing Vision Transformers for Histopathology: Pretraining and Normalization in Breast Cancer Classification.

This paper introduces a self-attention Vision Transformer model specifically developed for classifying breast cancer in histology images. We examine various training strategies and configurations, including pretraining, dimension resizing, data augmentation and color normalization strategies, patch overlap, and patch size configurations, in order to evaluate their impact on the effectiveness of the histology image classification. Additionally, we provide evidence for the increase in effectiveness gathered through geometric and color data augmentation techniques. We primarily utilize the BACH dataset to train and validate our methods and models, but we also test them on two additional datasets, BRACS and AIDPATH, to verify their generalization capabilities. Our model, developed from a transformer pretrained on ImageNet, achieves an accuracy rate of 0.91 on the BACH dataset, 0.74 on the BRACS dataset, and 0.92 on the AIDPATH dataset. Using a model based on the prostate small and prostate medium HistoEncoder models, we achieve accuracy rates of 0.89 and 0.86, respectively. Our results suggest that pretraining on large-scale general datasets like ImageNet is advantageous. We also show the potential benefits of using domain-specific pretraining datasets, such as extensive histopathological image collections as in HistoEncoder, though not yet with clear advantages.

Physical insights of interface traps and self-heating effect on electrical response of DMG FinFETs in overlap and underlap configurations: analog/RF perspective

This paper presents a thorough analysis on analog/RF parameters including interface trap charges (ITCs) of two different densities of states (DOS) along with self-heating on the performance of DMG FinFETs in Overlap and Underlap configurations. Initially, the independent simulations for acceptor ITCs and Self-heating in conventional device reveals that performance degradation caused by Self-heating is more prominent (25.03%) than uniform acceptor ITCs (9.46%). In consecutive step, the cumulative impact of both acceptor ITCs and Self-heating on DC and RF/analog parameters are carried out. Investigation reveals that as the impact of self-heating is larger in overlap configuration, the degradation in drain current is higher in overlap configuration (45.2%, 54.5%) as compared to conventional (30.4%, 40.96%) and underlap (37.2%, 52.8%) configurations for both Uniform and Gaussian trap distributions, respectively.

Effect of overlapping and space between stages of a three-bladed double-stage Savonius hydrokinetic turbine for low flow speed perennial river application

ABSTRACT Savonius-like hydrokinetic turbine (SAHT) in low-speed flow streams of perennial rivers is not much explored. In this paper, a triple-bladed double-stage SAHT is designed, and its performance is investigated for low flow speeds within 0.45–0.65 m/s under the effect of blade overlapping (within 10–20% in each stage), turbine diameter (within 208–234 mm), and without and with space between the stages (5.0 mm) at different operating speed ratios. Different combinations of design and operating input parameters are studied to obtain a reliable assessment of SAHT performance. After analyzing the results, the best conditions of input parameters and output performance parameters are reported in their nondimensional forms for future use of the obtained results. The torque produced by the turbine increased with the applied brake load, leading to its maximum value at the highest brake load 0.83 times the maximum load. The highest coefficient of performance is obtained as 0.086 at a space 0.25 times the maximum space (i.e. 20 mm), overlapping 15%, brake load 0.83 times the maximum load, tip speed ratio 0.276. And for this, the corresponding power 0.85 times the maximum power (i.e. 0.201 W) at free-stream flow speed of 0.85 times the maximum flow speed (i.e. 0.65 m/s) is obtained. The present turbine with space and overlapping exhibits better performance than some available SAHT designs of single/double stage, two-blade/multi-blade with/without overlap configurations. The novelty of the work is that an improved SAHT has been developed for low-flow speed perennial river applications in the band of low tip speed ratios by combining design conditions like double-stage, space between stages, and overlapping.

Analysis on the impact of interface Trap distributions on SOI DMG FinFETs: Overlap/underlap configurations

This paper investigates the significance of interface trap charges (ITCs) distribution by introducing localized charges (donor/acceptor) at the interface of semiconductor/insulator on dual-material gate (DMG) FinFETs in gate Overlap and Underlap configurations in terms of DC and analog/RF parameters. Different charge density profiles like Uniform and Gaussian distribution of traps are considered at different energy levels for both donor and acceptor ITCs to evaluate the devices reliability. It is observed that the donor traps mainly affects the OFF-state current (IOFF) by insignificantly, while, acceptor traps mainly impacts ON state current significantly. The impact of Acceptor ITCs on various parameters such as transfer characteristics, electron density, conduction band energy, transconductance (gm), total gate capacitance (Cgg), device efficiency (gm/ID), and cut-off frequency (fT), for DMG FinFETs have been comprehensively analysed at trap concentration N0=1×1013 and compared with no traps among the three devices. An acceptor trap charges with Gaussian distribution has larger impact on devices performance. It degrades the ON state-current by 36.09 %, 25.72 %, and 41.9 % for conventional, Overlap, and Underlap configurations, respectively. It is evident from the results DMG underlap configuration is more vulnerable to ITCs, attributed to its larger interface charge region due to the increase in effective channel length while, the overlap configuration is more immune towards ITCs as, lesser electrons get trapped. Thus, the overlap configuration is the most reliable among underlap and conventional configurations.

Impact of self-heating on RF/analog and linearity parameters of DMG FinFETs in underlap and overlap configurations

In this paper, the influence of self-heating effect (SHE) on the performance of Silicon on Insulator (SOI) dual material gate (DMG) FinFETs in underlap and overlap configurations for RF/analog applications is reported using three-dimensional TCAD simulators. The increase in electron velocity at channel surface is due to reduce effective electrical field at drain end, resulting in smaller DIBL and hot carrier effects. The device insights are reported by electron velocity, lattice temperature, thermal resistance, and output conductance versus frequency profiles. The findings on analog/RF figures of merit such as transconductance (gm), output conductance (gd), intrinsic gain (Ai), gate capacitance (Cgg), intrinsic delay (τ), cut-off frequency (fT), transconductance generation factor (TGF), gain frequency product (GFP), transconductance frequency product (TFP), and gain transconductance frequency product (GTFP) are reported with and without SHE. The results show that analog performance of Conventional and Underlap structures are improved but the influence of SHE is more deteriorating on Overlap structure. Furthermore, the linearity performance parameters VIP2, VIP3, IIP3, and 1 dB compression point are degraded with self-heating is due to increase in gm2 and gm3 values. It is seen that the gate overlap structure exhibits higher ON state performance which even after deterioration with Self-heating is still better than its counterparts as it has better gate controllability stemming from its lower effective channel length.

Optimal UAV Image Overlap for Photogrammetric 3D Reconstruction of Bridges

Unmanned Aerial Vehicles (UAVs) and photogrammetry have been widely used to reconstruct a photo-realistic 3D model of physical bridges for documentation of cultural bridges or remote bridge inspection. However, the optimal image overlap for photogrammetric bridge reconstruction that can trade off the model quality and overall mission time has not yet been studied. In this paper, a comparative experiment was conducted on a real girder bridge with three typical overlap configurations being implemented to capture corresponding UAV image sets, based on which bridge models were reconstructed using a commercial photogrammetry software package. Time consumption and the quality of reconstructed bridge models of these three experimental cases were compared and analysed. The results showed that the configuration of 66.7% forward overlap and 50% side overlap is the optimal overlap configuration for the reconstruction of a variety of bridge components, which can result in the minimum number of images while saving the overall mission time for image acquisition and processing. The overlap recommendation may also be applicable to the 3D reconstruction of other types of bridges and buildings with similar structural components.

The fire hazard potential of thermally thin cellulose nonwovens with different overlap configurations

The fire hazard potential of nonwovens with different overlap configurations and various thicknesses between 0.5 and 5 mm were investigated to clarify the possible worsening situation induced by the difference in overlapping configurations. The fire hazard of thermally thin nonwovens is characterized by flame spread, flame height, temperature distribution, and mass loss. The flame spread rate and FDI (fire development index) increase and then decrease as the thickness of the nonwovens increases. The fire hazard potential of samples with OL configuration (overlapping layer by layer configuration) is higher than that with AO configuration (accordion-style overlap configuration), which is reflected in the high FDI, average fire spread rate, and flame height, and low ignition time. The difference between the fire risk of the two overlapping configurations was confirmed by analyzing the heat transfer mechanism. Due to the different packaging methods, the AO and OL configurations of nonwovens show different degrees of shrinkage and curling effects during combustion. The large air gap between the layers and the weight of the sample edge are the reasons for the weak contraction of the sample with an AO configuration. The sample shrinkage with OL configuration strengthens the flame spread to a certain extent by increasing the convective heat transfer in the preheat zone.

Fundamental study of multi-track friction surfacing deposits for dissimilar aluminum alloys with application to additive manufacturing

Friction surfacing is an emerging solid-state coating technology based on frictional heat induced plastic deformation at the tip of a consumable metallic stud that allows to deposit layers with a fine-grained recrystallized microstructure at temperatures below the melting point. The generation of sound, defect-free metallurgical joints between multiple adjacent overlapping friction surfacing deposits, also referred to as multi-track friction surfacing, from dissimilar aluminum alloys is the focus of this experimental work. An extensive volumetric defect analysis is carried out for various overlap configurations, including post-processing strategies in order to assess the inter-track bonding integrity using microscopic characterization techniques and micro-computed tomography. The effect of layer arrangement and overlap distance on the volumetric defect formation in both inter-track and layer-to-substrate interface is quantified and discussed. Post-processing via hybrid friction diffusion bonding process demonstrates a significant reduction in defect volume ratio, proving higher material efficiency. The gained knowledge was used to successfully build a multi-track multi-layer friction surfacing stack, demonstrating the suitability of this process for large-scale additive manufacturing components. The subsequent mechanical analysis reveals excellent homogeneous isotropic tensile properties of the additive structure in the range of the base material tensile strength.

Impact of Malapposed and Overlapping Stents on Hemodynamics: A 2D Parametric Computational Fluid Dynamics Study

Despite significant progress, malapposed or overlapped stents are a complication that affects daily percutaneous coronary intervention (PCI) procedures. These malapposed stents affect blood flow and create a micro re-circulatory environment. These disturbances are often associated with a change in Wall Shear Stress (WSS), Time-averaged WSS (TAWSS), relative residence time (RRT) and oscillatory character of WSS and disrupt the delicate balance of vascular biology, providing a possible source of thrombosis and restenosis. In this study, 2D axisymmetric parametric computational fluid dynamics (CFD) simulations were performed to systematically analyze the hemodynamic effects of malapposition and stent overlap for two types of stents (drug-eluting stent and a bioresorbable stent). The results of the modeling are mainly analyzed using streamlines, TAWSS, oscillatory shear index (OSI) and RRT. The risks of restenosis and thrombus are evaluated according to commonly accepted thresholds for TAWSS and OSI. The small malapposition distances (MD) cause both low TAWSS and high OSI, which are potential adverse outcomes. The region of low OSI decrease with MD. Overlap configurations produce areas with low WSS and high OSI. The affected lengths are relatively insensitive to the overlap distance. The effects of strut size are even more sensitive and adverse for overlap configurations compared to a well-applied stent.

Influence of blade numbers, overlap ratio and modified blades on performance characteristics of the savonius hydro-kinetic turbine

Savonius turbine is a drag based simplest vertical axis turbine. More attention has been given to savonius hydrokinetic turbine compared to the savonius wind turbine for the last ten years due to the possibilities of rural electrification through savonius hydrokinetic turbine. Various research works on savonius wind turbine has been reported since invention but few works only reported on savonius hydrokinetic turbine. The present work is carried out to improve the power coefficient of savonius hydrokinetic turbine by varying blade numbers, overlap ratio and adding flips with the conventional savonius. Two blade savonius hydrokinetic turbine shown maximum power coefficient of 0.105 compared to 3, 4, 5 and 6 blade configuration. Savonius turbine with 0.2 overlap shown maximum power coefficient of 0.14 among the other overlap configurations of 0, 0.1, and 0.3. The maximum power coefficient of 0.154 was obtained in modified four bladed fixed flip type (M4FX2) savonius turbine in which the flips were arranged in front of the concave side of the conventional 0.2 overlap savonius turbine. Modified four bladed flip savonius turbine shown better power coefficient than the conventional savonius turbine.

Evaluation and characterization of crash-pulses for head-on collisions with varying overlap crash scenarios

Activation time for activating the occupant restraint systems (airbag and seatbelt) is very critical for an optimal safety action. A crash-pulse is the deceleration of the vehicle measured during in a crash. The shape, slope, maximum deceleration and duration of the crash-pulse provides significant information over the nature of occupant motions during in-crash phase and hence the crash severity. The above parameters of the crash-pulse not only depend on the mass and impact velocity but also on the crash configuration (position of impact, overlap, relative approach angle etc.).This study focuses on analysis and characterization of crash-pulses in head-on collision cases with varying overlap configurations. The paper describes causes for occupant injuries during a crash, crash-pulse and its important physical parameters, and different methodologies used to analyse the crash-pulse. Finite element simulation method is used to study the crash-pulses from different crash configurations. A new severity index that has direct influence on the occupant kinematics is defined. The results show that the steep decrease of crash-pulse for small overlap configurations (less than 25 percent of vehicle width) lags by 20 to 25 milliseconds as compared to configurations with large overlaps. The shape of the crash-pulse also changes for crash scenarios with different overlap configurations. The results, discussion and conclusion sections of this paper provide a summary of crash behaviour of varying overlap crash scenarios and insights that can be used for deployment of restraint systems.

Overlap length for confinement of carbon and glass FRP-jacketed concrete columns

This paper presents the experimental results of a study on the occurrence of debonding along the overlap length of fiber reinforced polymer (FRP) confined concrete prior to rupture of the FRP jacket. Plain concrete cylinders, twenty-six with 152 mm diameter and 305 mm height, and four with 100 mm diameter and 200 mm height, with cylinder compressive concrete strength 19 MPa, were wrapped with carbon- and glass-FRP jackets and tested under monotonic axial compression. Different overlap configurations and different FRP application methods were investigated. The parameters found to most significantly affect the bond resistance along the overlap zone are the type of the FRP material and the curing age of the resin when dry lay-up application is used.

Experiments and efficient simulations of distortions of laser beam–welded thin-sheet close beam steel structures

In this article, geometrical distortions of steel structures due to laser beam welding were analyzed. Two 700-mm-long U-beam structures were welded in overlap configurations: a double U-beam structure and a U-beam/flat structure. The structures were in different material combinations from mild steel to ultrahigh-strength steel welded with different process parameters. Different measures of distortions of the U-beam structures were evaluated after cooling. Significant factors of the welding process and the geometry of the structures were identified. Furthermore, welding distortions were modeled using two predictive finite element simulation models. The previously known shrinkage method and a newly developed time-efficient simulation method were evaluated. The new model describes the effects of expansion and shrinkage of the weld zone during welding and material plasticity at elevated temperatures. The new simulation method has reasonable computation times for industrial applications and improved agreement with experiments compared to the often used so-called shrinkage method.

An Empirical Study of Overlapping Rotor Interference for a Small Unmanned Aircraft Propulsion System

The majority of research into full-sized helicopter overlapping propulsion systems involves co-axial setups (fully overlapped). Partially overlapping rotor setups (tandem, multirotor) have received less attention, and empirical data produced over the years is limited. The increase in demand for compact small unmanned aircraft has exposed the need for empirical investigations of overlapping propulsion systems at a small scale (Reynolds Number < 250,000). Rotor-to-rotor interference at the static state in various overlapping propulsion system configurations was empirically measured using off the shelf T-Motor 16 inch × 5.4 inch rotors. A purpose-built test rig was manufactured allowing various overlapping rotor configurations to be tested. First, single rotor data was gathered, then performance measurements were taken at different thrust and tip speeds on a range of overlap configurations. The studies were conducted in a system torque balance mode. Overlapping rotor performance was compared to an isolated dual rotor propulsion system revealing interference factors which were compared to the momentum theory. Tests revealed that in the co-axial torque-balanced propulsion system the upper rotor outperforms the lower rotor at axial separation ratios between 0.05 and 0.85. Additionally, in the same region, thrust sharing between the two rotors changed by 21%; the upper rotor produced more thrust than the lower rotor at all times. Peak performance was recorded as a 22% efficiency loss when the axial separation ratio was greater than 0.25. The performance of a co-axial torque-balanced system reached a 27% efficiency loss when the axial separation ratio was equal to 0.05. The co-axial system swirl recovery effect was recorded to have a 4% efficiency gain in the axial separation ratio region between 0.05 and 0.85. The smallest efficiency loss (3%) was recorded when the rotor separation ratio was between 0.95 and 1 (axial separation ratio was kept at 0.05). Tests conducted at a rotor separation ratio of 0.85 showed that the efficiency loss decreased when the axial separation ratio was greater than 0.25. The lower rotor outperformed the upper rotor in the rotor separation ratio region from 0.95 to 1 (axial separation ratio was kept at 0.05) at an overall system thrust of 8 N, and matched the upper rotor performance at the tested overall thrust of 15 N.

Azimuthal Anisotropy in U+U and Au+Au Collisions at RHIC.

Collisions between prolate uranium nuclei are used to study how particle production and azimuthal anisotropies depend on initial geometry in heavy-ion collisions. We report the two- and four-particle cumulants, v_{2}{2} and v_{2}{4}, for charged hadrons from U+U collisions at sqrt[s_{NN}]=193 GeV and Au+Au collisions at sqrt[s_{NN}]=200 GeV. Nearly fully overlapping collisions are selected based on the energy deposited by spectators in zero degree calorimeters (ZDCs). Within this sample, the observed dependence of v_{2}{2} on multiplicity demonstrates that ZDC information combined with multiplicity can preferentially select different overlap configurations in U+U collisions. We also show that v_{2} vs multiplicity can be better described by models, such as gluon saturation or quark participant models, that eliminate the dependence of the multiplicity on the number of binary nucleon-nucleon collisions.

Mechanical Behavior Analysis of Apus Bamboo (<i>Gygantochloa sp</i>) Thin Plate Composite due to Adhesive Joint and Water Absorption Using Experimental and Finite Element Method

The mechanics of adhesive-lap joints of apus bamboo thin plate composite were investigated experimentally and numerically. Tensile load were applied to determine mechanical strength of adhesive joint overlaps. Modal analysis were employed to determine natural frequency of bamboo apus single-lap joint for different overlap and plate thickness configurations. This research found the strength of bamboo adhesive joints decreased 11% due to the effect of 24 hours water immersion. Natural frequencies of single-lap adhesive joint configuration were equivalently decreased in decreament of overlap joint and thickness plate. Finite element models using ABAQUS Software were developed for static and dynamic analysis and compared with the experimental results. Compared to experimental results, numerical analysis gives the prediction with 4% difference for the mean shear stress at failure, and 7-12% difference for the natural frequencies.

Influence of overlap configuration on compressive behavior of CFRP-confined normal- and high-strength concrete

This paper presents the findings of an experimental investigation on the effect of overlap configuration on carbon fiber-reinforced polymer (CFRP)-confined normal- and high-strength concrete. A total of 33 specimens were prepared and tested under monotonic axial compression. All specimens were cylinders with 152 mm diameter and 305 mm height and confined by CFRP tubes. Two different concrete mixes were examined, with average compressive strengths of 52.0 and 84.7 MPa. The effect of overlap configuration was examined by manufacturing the specimens with different properties at the overlap region including overlap length, continuity and distribution. Axial and lateral behavior was recorded to observe the axial stress–strain relationship and hoop strain behavior for concentric compression. Ultimate axial and lateral conditions are tabulated and stress–strain curves have been provided. Detailed plots of hoop strain development and lateral confinement pressure at ultimate are presented. The results indicate that FRP overlap length has no significant influence on strain enhancement ratio (e cu /e co), but an increase in overlap length leads to a slight increase in strength enhancement ratio (f′ cc /f′ co), with these observations equally applicable to both continuously and discontinuously wrapped specimens. The results also indicate that continuity of the FRP sheet in the overlap region has some influence on the effectiveness of FRP confinement. Furthermore, it was observed that the distribution of FRP overlap regions for discontinuously wrapped specimens can influence the axial compressive behavior of these specimens in certain overlap configurations. Finally, it is found that the distribution of lateral confining pressure around specimen perimeter becomes less uniform for specimens with higher concrete strengths and those manufactured with overlap regions that are not evenly distributed.

Dissimilar Welding of H62 Brass-316L Stainless Steel Using Continuous-Wave Nd:YAG Laser

Continuous-wave Nd:YAG laser welding of H62 brass and 316L stainless steel was studied using welded joints made with different overlap configurations. Optical and scanning electron microscopies, energy-dispersive X-ray spectroscopy, and microhardness testing were used to analyze the microstructures and mechanical properties of the joints. The welded joints with the brass-on-steel overlap configuration exhibited better performance. Elemental diffusion and dissolution—in particular, the evaporation of zinc—were observed in the welded joints. Intermetallic compounds were absent in the joints because brass and stainless steel exhibit unlimited solid solubility. Finally, the microhardness of the joints was higher than that of the brass.