Sharp Bend Research Articles

Spatially controllable and mechanically switchable isomorphous organoferroeleastic crystal optical waveguides and networks

The precise, reversible, and diffusionless shape-switching ability of organic ferroelastic crystals, while maintaining their structural integrity, positions them as promising materials for next-generation hybrid photonic devices. Herein, we present versatile bi-directional ferroelasticity and optical waveguide properties of three isomorphous, halogen-based, Schiff base organic crystals. These crystals exhibit sharp bending at multiple interfaces driven by molecular movement around the CH = N bond and subsequent 180° rotational twinning, offering controlled light path manipulation. The ferroelastic nature of these crystals allowed the construction of robust hybrid photonic structures, including Z-shaped configurations, closed-loop networks, and staircase-like hybrid optical waveguides. This study highlights the potential of shape-switchable organoferroelastic crystals as waveguides for applications in programmable photonic devices.

Improvement of SAW Resonator Performance by Petal-like Topological Insulator.

This article introduces a novel petal-like SAW topology insulator, which can transmit sound waves with low loss and high flexibility in an ultra-wide frequency band by simultaneously adjusting multiple structural parameters of phononic crystals. Using finite element analysis, it was found that adjusting these parameters can generate a broadband gap of 55.8-65.7 MHz. This structure can also achieve defect immunity and sharp bending in waveguide transmission. When this topology insulator is applied to resonators, compared to traditional designs, the insertion loss is reduced by 22 dB, the on-load quality factor is increased by 227%, the off-load quality factor is increased by 1024.5%, and the quality sensitivity is improved by 3.7 times compared to bare devices.

Study on the effect of nonlinear inertia on the vibration isolation performance of quasi-zero-stiffness isolators

Typically, when subjected to excessive external force, quasi-zero-stiffness isolators with low damping will cause a sharp rightward bending of the transmissibility curve, resulting in a substantial decline in the performance of vibration isolation. The scheme with parallel tunable nonlinear inertia (PTNI) based on the triple-spring quasi-zero-stiffness (TS-QZS) isolator is designed to solve the above problems. To begin with, the kinetic equations are derived. Subsequently, the analysis of the primary response and stability involved the utilization of the Harmonic Balance Method (HBM), and the accuracy of the model was validated through numerical calculations. Finally, the impact of essential parameters is examined. The findings suggest that the QZS-PTNI isolator, without compromising the high frequency transmissibility, is capable of reducing peaks, suppressing the rightward trend of the transmissibility curve, narrowing the range of jump-up and jump-down frequency, and enhancing the vibration isolation performance.

Scour variations around pier groups at a sharp bend with triad vanes

This study applied triad submerged vanes upstream of piers and varied their submergence ratios in order to explore and reduce scouring around piers in a bend. The most important findings are presented as follows: Triad vanes decreased the scour hole volume by a minimum of 22 % in the triad transverse pier and by a maximum of 53 % in the single pier experiment. The highest maximum scour hole reduction was achieved in the longitudinal triad piers with triad vanes for about 35 % in comparison with the case of piers without any vanes. The pier test with three vanes of 50 % submergence ratio resulted in the lowest hole volume, scour area, maximum scour depth and maximum sedimentary ridge of all the tests.

Optimizing IoT Intrusion Detection Using Balanced Class Distribution, Feature Selection, and Ensemble Machine Learning Techniques.

Internet of Things (IoT) devices are leading to advancements in innovation, efficiency, and sustainability across various industries. However, as the number of connected IoT devices increases, the risk of intrusion becomes a major concern in IoT security. To prevent intrusions, it is crucial to implement intrusion detection systems (IDSs) that can detect and prevent such attacks. IDSs are a critical component of cybersecurity infrastructure. They are designed to detect and respond to malicious activities within a network or system. Traditional IDS methods rely on predefined signatures or rules to identify known threats, but these techniques may struggle to detect novel or sophisticated attacks. The implementation of IDSs with machine learning (ML) and deep learning (DL) techniques has been proposed to improve IDSs' ability to detect attacks. This will enhance overall cybersecurity posture and resilience. However, ML and DL techniques face several issues that may impact the models' performance and effectiveness, such as overfitting and the effects of unimportant features on finding meaningful patterns. To ensure better performance and reliability of machine learning models in IDSs when dealing with new and unseen threats, the models need to be optimized. This can be done by addressing overfitting and implementing feature selection. In this paper, we propose a scheme to optimize IoT intrusion detection by using class balancing and feature selection for preprocessing. We evaluated the experiment on the UNSW-NB15 dataset and the NSL-KD dataset by implementing two different ensemble models: one using a support vector machine (SVM) with bagging and another using long short-term memory (LSTM) with stacking. The results of the performance and the confusion matrix show that the LSTM stacking with analysis of variance (ANOVA) feature selection model is a superior model for classifying network attacks. It has remarkable accuracies of 96.92% and 99.77% and overfitting values of 0.33% and 0.04% on the two datasets, respectively. The model's ROC is also shaped with a sharp bend, with AUC values of 0.9665 and 0.9971 for the UNSW-NB15 dataset and the NSL-KD dataset, respectively.

Collars for Scour Reduction Around Different Shapes of Bridge Piers in a 180° Sharp Bend

Collars for Scour Reduction Around Different Shapes of Bridge Piers in a 180° Sharp Bend

Discharge evolution law of debris flow based on a sharp bend physical modeling test

Discharge evolution law of debris flow based on a sharp bend physical modeling test

An experimental comparison of 3D velocity components around single and twin piers installed in a sharp bend under the influence of upstream implemented vanes

To reduce the trend of scouring, understanding the flow pattern around the bridge piers is necessary. By using hydraulic structures such as submerged vanes, it is possible to alter the flow pattern of water, thus scouring process and sediment transport in riverbeds. Since the scouring mechanism for pier groups differs from single pier, experiments were conducted in a 180° sharp bend channel in the laboratory to investigate the flow pattern around pier group and single pier under the influence of 25% submerged vanes. Furthermore, a comparison was made between the flow patterns in single pier and pier group conditions. Three-dimensional velocities along the bend and different depths were measured using an Acoustic Doppler Velocimeter (ADV(. The results suggest that the maximum vorticity value at the apex position of the bend (location of piers) and the maximum secondary flow value, at the distance between the piers and the vanes, were found to be, 0.15 and 0.89, respectively. In the twin pier experiment, the maximum Reynolds shear stress value τyx\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ au }_{yx}$$\\end{document} decreased by about 36%, and the minimum value decreased by about 49% compared to the single pier experiment. The final results indicated that using submerged vanes obtained the maximum τyx\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ au }_{yx}$$\\end{document} and τzx\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ au }_{zx}$$\\end{document} near the vanes. Near the bed and mid-depth of the water flow, the geometric location of the maximum velocity also occurred around the vanes in both experiments. Therefore, the vanes are important in altering the water flow pattern, diverting the flow from around piers and consequently reducing the bridge pier scouring.

Topological protection of dual-polarization biphoton states in photonic crystals

Polarization control is a major issue in topological quantum optics that limits reliable generation and transmission of quantum states. This study presents what we believe to be a novel topological photonic crystal design that provides topological protection for biphoton pairs for both TE and TM polarization. By well-designed cell configurations within the lattice, two topological boundaries emerge that can accommodate TM and TE modes at the same time. By adjusting the dispersion curves, we can further design nonlinear four-wave mixing processes within the topological photonic crystals and provide theoretical explanations for the entanglement of the dual-polarization biphoton states. Numerical results confirm the robust transport of entangled photon pairs, even when subjected to sharp bending. Moreover, combining the dual-polarization topological photonic crystal with a polarization beam splitter enables the preparation of polarization-encoded maximally entangled states. Our work exhibits significant potential for applications in robust optical quantum information processing and quantum secure communication.

Retromer-mediated recruitment of the WASH complex involves discrete interactions between VPS35, VPS29, and FAM21.

Endosomal trafficking ensures the proper distribution of lipids and proteins to various cellular compartments, facilitating intracellular communication, nutrient transport, waste disposal, and the maintenance of cell structure. Retromer, a peripheral membrane protein complex, plays an important role in this process by recruiting the associated actin-polymerizing WASH complex to establish distinct sorting domains. The WASH complex is recruited through the interaction of the VPS35 subunit of retromer with the WASH complex subunit FAM21. Here, we report the identification of two separate fragments of FAM21 that interact with VPS35, along with a third fragment that binds to the VPS29 subunit of retromer. The crystal structure of VPS29 bound to a peptide derived from FAM21 shows a distinctive sharp bend that inserts into a conserved hydrophobic pocket with a binding mode similar to that adopted by other VPS29 effectors. Interestingly, despite the network of interactions between FAM21 and retromer occurring near the Parkinson's disease-linked mutation (D620N) in VPS35, this mutation does not significantly impair the direct association with FAM21 in vitro.

Sharp bend and large FSR ring resonator based on the free-form curves on a thin-film lithium niobate platform.

Sharp bends are crucial for large-scale and high-density photonics integration on thin-film lithium niobate platform. In this study, we demonstrate low-loss (<0.05 dB) and sharp bends (Reff = 30 µm) using free-form curves with a 200-nm-thick slab and a rib height of 200 nm on x-cut lithium niobate. Employing the same design method, we successfully realize a compact fully-etched ring resonator with a remarkably large free spectral range of 10.36 nm experimentally. Notably, the equivalent radius of the ring resonator is a mere 15 µm, with a loaded Q factor reaching 2.2 × 104.

CFD analysis of novel two-pass, sinusoidal corrugated, trapezoidal channel for solar air heater

Solar is regarded as a clean and reliable source of energy. Solar air heaters (SAHs) are one of the most prevalent applications of solar energy. SAHs have normally low thermal efficiency. In order to increase thermal efficiency, a sinusoidal wave corrugation is employed on the base wall of the twin-pass channel of an absorbent plate with a sharp bend. A parametric study was conducted to study the effect of flow and geometric parameters i.e. wave height, pitch, and propagation angle of the wave with respect to flow inlet on performance parameters. Computational Fluid Dynamics (CFD) tool was implemented to examine the performance parameters i.e. heat transfer enhancement, pressure drop, and thermal performance factor. In comparison to the orthogonal ones, inclined corrugation is more efficient in terms of heat transfer. With the increase in roughness height, pitch, and corrugation angle, an increasing trend was observed in Thermal Performance Factor, followed by a diminishing trend. The corrugated channel having a roughness height ratio of 19, two waves in a single block with a 45° wave propagation angle seemed to be an optimal configuration with 35% enhancement in thermal performance factor as compared to the smooth channel, hence representing promising augmentation.

The numerical investigation of turbulence and scour interaction around the permeable groynes at the channel bend

Turbulence, particularly Reynolds Stress, plays a significant role in the flow field surrounding groynes, causing local scour. A limited number of studies have comprehensively analyzed the flow and turbulence structures encompassing a series of groynes in channel bends. This study numerically investigated the interplay between turbulence, sediment deposition, and scouring in a sharp channel bend with permeable groynes. The results show that the inner bank maintained high velocity, while permeable groynes decreased longitudinal velocity near the outer bank. Implementing permeable groynes structures reduced bottom velocity and increased flow separation. Turbulent kinetic energy distribution across the bend, particularly streamwise, influenced scour development more than vertical motion.

Late‐Holocene counterpoint deposition in the Lower Rhine River

ABSTRACTChannel deposits from meandering rivers have proven to be far more complex than the well‐known lithofacies model consisting of coarse‐grained channel, gravelly channel‐lag and fine‐grained overbank deposits. Sharp bends in rivers are subject to different hydraulic processes than bends with lower curvatures, enabling erosion of inner banks and deposition of fine‐grained sediments in the outer bend, resulting in downstream migration of river bends. This phenomenon is known as counterpoint deposition, forming counterpoint bars. This research investigates whether scroll bars associated with a sharp bend in the Lower Rhine River, The Netherlands, are such a counterpoint‐bar deposit. A counterpoint bar is expected based on: (i) the surface morphology of the scroll bar; (ii) the confinement of the river course by an ice‐pushed ridge resulting in a sharp bend; and (iii) the archaeological context of successive Roman settlements atop the ice‐pushed ridge, potentially moving downstream with the migrating river bend. This hypothesis is tested through detailed borehole descriptions combined with optically stimulated luminescence dating, the latter being a novel approach to identifying counterpoint deposits. The deposits consist of clays and sandy clays with fine sand laminations, and sporadic larger sand bodies. Further upstream these deposits grade into channel deposits dominated by coarser sands with gravels. These lithologies are explained using earlier proposed mechanisms for counterpoint formation; substrata match those described in previously studied counterpoint deposits and their point bar counterparts. Optically stimulated luminescence dates indicate that the Lower Rhine River bend migrated downstream, confirming counterpoint deposition. A migration rate of 1.93 m/year was established through weighted linear regression. This study demonstrates the potential of optically stimulated luminescence dating to investigate counterpoint bar presence. The identified counterpoint bars and associated bend migration provide insight into meandering river dynamics that is crucial for river management and in aiding river restoration and rewilding initiatives.

Quantifying robustness against sharp bending in an integrated topological interface of valley photonic crystals

Abstract Sharp-bending waveguide is a key element for ultra-compact and densely integrated photonic devices, which is promising to enlarge the capability of modern information processing in a single chip. Topological photonics manifest the nature of robust propagation against sharp bending and such robustness has been experimentally demonstrated in topological integrated interfaces. It is important to quantify the bending loss of topological interface but has remained exclusive. In this work, we report on the characterization of sharp-bending robustness in the integrated topological interface of valley photonic crystals (VPCs) by experimentally quantifying the ultralow bending loss. The VPCs are designed on a standard silicon-on-insulator platform with the inversion-symmetry broken in honeycomb lattice, and four types of topological interfaces can be constructed by two topologically-distinct VPCs. As one of the representative cases, zigzag-AA interface is applied to demonstrate the robust propagation along sharp bending. In experiment, we fabricate a series of VPC interfaces with different turn number and the same transmission distance, which perform the ultralow bending loss less than 0.02 dB per 120-deg turning. Furthermore, we experimentally characterize the propagation loss in the integrated interfaces. Our approach not only shows the ability of VPC topological interfaces to suppress backscattering stemming from sharp bending, but also paves the way for topological nanophotonic dense integration.

Large transmittance contrast via 90-degree sharp bends in square lattice glide-symmetric photonic crystal waveguides.

We demonstrate an intriguing transmittance contrast in a glide-symmetric square-lattice photonic crystal waveguide with a 90-degree sharp bend. The glide-symmetry gives rise to a degeneracy point in the band structure and separates a high-frequency and a low-frequency band. Previously, a similar large transmittance contrast between these two bands has been observed in glide-symmetric triangular- or honeycomb-lattice photonic crystals without inversion symmetry, and this phenomenon has been attributed to the valley-photonic effect. In this study, we demonstrate the first example of this phenomenon in square-lattice photonic crystals, which do not possess the valley effect. Our result sheds new light onto unexplored properties of glide-symmetric waveguides. We show that this phenomenon is related to the spatial distribution of circular polarization singularities in glide-symmetric waveguides. This work expands the possible designs of low-loss photonic circuits and provides a new understanding of light transmission via sharp bends in photonic crystal waveguides.

Optimization of colored pavement considering driving behavior and psychological characteristics under dynamic low-visibility conditions related to fog—a driving simulator study

Objective Colored pavement is commonly used to reduce the road traffic risk and promote road traffic safety, but its performance in foggy environments has not been fully assessed. The goal of this research is to explore the effectiveness and optimization of colored pavement in a dynamic low-visibility environment. Methods A driving simulation experiment is conducted. Three road risk sections in which collisions are common, including a long straight section, a sharp bend section, and a long downslope section, are considered, and three forms of colored pavement are used in five different visibility environments. The effectiveness of the colored pavement is explored by collecting and analyzing driving behavior and physiological characteristic data for 30 drivers in the established driving environment, and information is obtained through a subjective colored evaluation questionnaire. Eight evaluation indexes are selected from the perspectives of driving behavior and physiological characteristics, and the gray premium evaluation method is applied to evaluate the effectiveness of different forms of colored pavement considering the influence of visibility. Finally, the optimal colored pavement under various visibility and road alignment conditions is proposed. Results The results show that reasonably selecting colored pavement can effectively improve drivers’ behaviors and physiological characteristics under foggy conditions. For different road alignments and visibility conditions, different forms of colored pavement should be used to ensure road traffic safety. Conclusions The findings provide a theoretical reference for the optimization of colored pavement in foggy conditions.

Simulation of the L-valve in the circulating fluidized bed with a coarse-grained discrete particle method

Stable and controllable solid flow is essential in circulating fluidized bed (CFB) systems. The L-valve is a typical non-mechanical valve that can provide flexible solid feeding. The investigation of the solid circulation rate and the hydrodynamic characteristics of the L-valve is crucial to its design and operation. The gas-solid flow in the L-valve of a full-loop CFB is studied with the coarse-grained discrete particle method (EMMS-DPM). Good agreements on the solid circulation rate and the pressure drop through the L-valve are achieved between the simulated and experimental data. The solid circulation rate increases linearly with the aeration velocity until the stable particle circulation of the CFB is destroyed. The flow patterns in the horizontal section of L-valve are gas-solid slug flow above the stationary solid layer and the moving solid layer, respectively. The effects of L-valve geometric parameters on the solid flow characteristics are also investigated. The results indicate that reducing the diameter and length of the horizontal section of L-valve can improve the solid transport efficiency, especially at low aeration velocity. Besides, the solid conveying capacity and flow stability are improved when the sharp bend of L-valve is modified to be a gradual bend.

Assessment of sediment transport in Luxiapuqu watershed using RUSLE-TLSD and InSAR techniques: Yarlung Tsangpo River, China.

The Yarlung Tsangpo River Basin is characterized by its intricate topography and a significant presence of erosive materials. These often coincide with heavy localized precipitation, resulting in pronounced hydraulic erosion and geological hazards in mountainous regions. To tackle this challenge, we integrated the RUSLE-TLSD (Revised Universal Soil Loss Equation-Transportation-limited sediment delivery) model with InSAR (Interferometric Synthetic Aperture Radar) data, aiming to explore the sediment transport process and pinpoint hazard-prone sites within mountainous small watershed. The RUSLE-TLSD model aids in evaluating multi-year sediment transport dynamics in mountainous zones. And, the InSAR data precisely delineates changes in sediment scouring and siltation at sites vulnerable to hazards. Our research estimates that the potential average soil erosion within the watershed stands at 52.33 t/(hm2 a), with a net soil erosion of 0.69 t/(hm2 a), the sediment transport pathways manifest within the watershed's gullies and channels. Around 4.32% of the watershed area undergoes sedimentation, predominantly at the base of slopes and within channels. Notably, areas (d) and (e) emerge as the most susceptible to disasters within the watershed. Further analysis of the InSAR data highlighted four regions in the typical area (e) from 2017 that are either sedimentation- or erosion-prone, referred to as "hotspots." Among them, R1 exhibits a strong interplay between water and sediment, rendering it highly sensitive to environmental factors. In contrast, R4, characterized by a sharp bend in siltation, remains relatively impervious to external elements. The NDVI (normalized difference vegetation index) stands out as the pivotal determinant influencing sediment transport within the watershed, exerting a pronounced impact on the outlet section, especially in spring. By employing this approach, we gained a deeper understanding of sediment transport mechanisms and potential hazards in small watershed in uninformative mountainous areas. This study furnishes a robust scientific framework beneficial for erosion mitigation and disaster surveillance in mountainous watersheds.

Hydrodynamic and Morphological Adaptation of Two Consecutive Sharp Bends of the Middle Yangtze River to Upstream Damming

AbstractIt remains an open question how the hydrodynamics and morphology in sharp meander bends adapt to the changes in flow and sediment conditions induced by upstream damming. This study reports a comprehensive investigation into the morphological changes, patterns of mean and secondary flows and sediment transport around two consecutive sharp bends in the Middle Yangtze River (MYR), and explains these changes from the viewpoint of flow‐sediment transport‐morphology interaction based on field measurements. With the Three Gorges Project operation, the MYR suffered a remarkable channel degradation due to a sudden decrease of incoming sediment discharge. The point bars were removed, and outer‐bank benches (OBB) formed upstream of the bend apices, which resulted in quite different flow and sediment transport patterns in the bends. The highest velocity zones and center‐region cells of secondary flow were more toward the inner bank due to the lack of point bars, and the outward migration of momentum was delayed. Flow recirculation zones were observed over the OBBs, covering 12%–58% of the channel width. The transport rates of suspended load accounted for 98% of the total sediment load, and the outward shift of the highest transport rate zone was confined by the OBBs, which reduced the effective width of sediment transport. These changes in flow and sediment transport re‐inforced the morphological changes around the sharp bends: the velocity redistribution and evolution of scour factor lagged more behind planform curvature, which further promoted the erosion of point bars and the development of OBB.