V-shaped Structures Research Articles

Anisotropic mechanical behavior and failure of foldcore structures of fibre-reinforced composites under impact loading

The foldcore sandwich structure presents a novel approach to impact resistance, making it a compelling subject for research into its mechanical and damage behaviors. This work investigates the damage fracture state and its anisotropic damage behaviour of foldcores subjected to impacts by both experimental and simulation methods. To explore the damage mechanisms of foldcore structures and assess how different foldcore types influence their fracture behaviour, we employed the hot-press method to fabricate V-shaped and S-shaped foldcore structures. Subsequently, impact tests were conducted on these structures to uncover their underlying mechanisms, and Hashin’s failure criterion was utilized in the in-face folding direction and out-face folding direction to simulate the damage process and investigate its anisotropy. This study revealed that foldcore structures exhibit anisotropic damage and fracture under impact loading. Damage is predominantly observed along the in-plane folding direction of the foldcore structure, with the damage primarily manifesting as tensile damage to the fibers. The damage incurred by foldcore structures mainly affects the bending region of the structure, where the V-shaped and S-shaped foldcore structures exhibit different damage geometries.

Kinematics and star formation of hub-filament systems in W49A

W49A is a prominent giant molecular cloud (GMC) that exhibits strong star formation activities, yet its structural and kinematic properties remain uncertain. Our study aims to investigate the large-scale structure and kinematics of W49A, and elucidate the role of filaments and hub-filament systems (HFSs) in its star formation activity. We utilized continuum data from Herschel and the James Clerk Maxwell Telescope (JCMT) as well as the molecular lines 12CO\,(3-2), 13CO\,(3-2), and C18O\,(3-2) to identify filaments and HFSs within W49A. Further analysis focused on the physical properties, kinematics, and mass transport within these structures. Additionally, recombination line emission from the I II region and ionized gas. Our findings reveal that W49A comprises one blue-shifted (B-S) HFS and one red-shifted (R-S) HFS, each with multiple filaments and dense hubs. Notably, significant velocity gradients were detected along these filaments, indicative of material transport toward the hubs. High mass accretion rates along the filaments facilitate the formation of massive stars in the HFSs. Furthermore, the presence of V-shaped structures around clumps in position-velocity diagrams suggests ongoing gravitational collapse and local star formation within the filaments. Our results indicate that W49A consists of one R-S HFS and one B-S HFS, and that the material transport from filaments to the hub promotes the formation of massive stars in the hub. These findings underscore the significance of HFSs in shaping the star formation history of W49A.

Abundant optical soliton solutions to the fractional perturbed Chen-Lee-Liu equation with conformable derivative

This research focuses on the space-time fractional nonlinear perturbed Chen-Lee-Liu model, which describes the propagation behavior of optical pulses in the fields of optical fiber and plasma. The equation is considered with respect to the conformable derivative, and a composite fractional wave transformation is employed to reformulate it into a nonlinear equation with a single variable. The improved tanh method has been applied to derive novel analytical wave solutions for the given equation. Consequently, various types of solitonic wave patterns emerge, including but not limited to periodic, bell-shaped, anti-bell-shaped, V-shaped, kink, and compacton solitonic structures. The acquired solutions could potentially aid in the analysis of signal transmission in optical fibers and the characterization of plasma properties. The physical interpretations of the solutions are investigated using three-dimensional surface plots and two-dimensional density plots. Additionally, combined two-dimensional plots are being used to discuss the effects of the order of the fractional derivative on the generated wave patterns. Moreover, this study demonstrates the efficacy and reliability of the chosen technique.

Drag reduction design and experiments for the chisel-shaped shovel tip

To address the issue of high resistance encountered by traditional chisel-shaped shovel tips during tillage, this study drew inspiration from the micro V-shaped structures found in shark skin. Using laser cladding technology, a V-shaped wear-resistant coating was applied to the front surface of the shovel, with different drag-reducing V-shaped structures achieved by controlling the coating overlap ratio H (including 20%, 40%, and 60%). Additionally, the rear surface of the shovel tip was designed to mimic the V-shaped morphology of shark skin, proportionally amplified, and given a certain backward tilt angle θ to further reduce resistance. Through the discrete element simulation experiments while maintaining θ at 0°, it was found that the shovel tip achieved the best drag reduction effect when H was 40%. Based on this, the study varied the values of θ (including 0°, 1°, 3°, and 5°) while keeping H at 40%. Discrete element simulation experiments were conducted at depths of 250mm, 275mm, and 300mm to analyze the disturbance effect, fragmentation effect, and resistance of the shovel tip. Considering all factors, the shovel tip with θ of 5° was selected as the optimal choice. Finally, a soil trench experiment was conducted to verify the performance of the V-shaped shovel tip with H of 40% and θ of 5°, as well as the chisel-shaped shovel tip, in tillage operations. The experimental results showed good agreement with the simulation results, and the designed V-shaped shovel tip achieved a maximum drag reduction of 12.87%. This design provides valuable references for the structural optimization of subsoiler, contributing to the improvement of their performance and efficiency.

Ultrasonography and Postmortem Magnetic Resonance Imaging of Bilateral Ocular Disease in a Heifer

Bovine ocular diseases are typically characterized by the concurrent appearances of both macroscopic and intraocular abnormalities. This study examines the diagnostic efficacy of a combination of ultrasonography and magnetic resonance imaging (MRI) for the bilateral ocular disease observed in a 9-month-old Japanese Black heifer. This case presented with bilateral strabismus and a white-colored lens structure in the right eye. A combination of ultrasonography and MRI revealed formations of corn-like and V-shaped membranous structures within the vitreous cavities of the left and right eyeballs, respectively. In the right eye, a cataract was suspected on both ultrasonogram and MRI. This case involved bilateral retinal detachments and strabismus similar to the signs of an autosomal recessive hereditary ocular disease; however, the cataract in the right eye differed from that hereditary disease. Finally, in genetic analysis, a known mutation of the WFDC1 gene was not detected. Ultrasonography is superior to MRI in demonstrating intraocular pathological changes. On the other hand, MRI is helpful for evaluating invasiveness of the ocular lesions to the peripheral structures. Thus, the combined use of these imaging modalities is recommended for diagnosing various bovine ocular diseases.

Case Study of Analysis of Wind Load on U and V Shape High Rise Building: A Review

Conclusively, this case study provides an exhaustive and methodical investigation of wind load analysis on U and V-shaped high-rise structures, amalgamating conclusions from diverse scholars in the domain. The comprehensive examination and juxtaposition of current research techniques highlight the complex character of wind load assessment, utilizing a range of methods including wind tunnel testing, empirical observations, and Computational Fluid Dynamics (CFD) simulations. The research makes a substantial contribution to our comprehension of the complex relationships that exist between wind forces and the unique architectural arrangements of U and V shapes. By assimilating insights from numerous studies, the research successfully unveils commonalities, identifies divergences, and highlights emerging trends in the analysis of wind-induced effects on these high-rise structures. Professionals in high-rise building design, and architects and engineers. The goal of the research is to make a substantial contribution to the ongoing development of wind load analysis techniques.Understanding the building's response to wind rotation at different incident angles is a specific focus of this study. Validation against experimental data ensures the accuracy of CFD simulations, often involving model refinement based on real-world observations. Overall, this research contributes to a comprehensive understanding of building aerodynamics, offering insights into the intricate interplay between structures and wind forces. Keywords: High-rise building, ANSYS CFX, CFD, wind tunnel, pressure coefficient.

Fabrication of blazed gratings by tilted reactive ion beam etching with the side mask for augmented reality applications

A novel manufacturing method using the side mask and tilted reactive ion beam etching (RIBE) is proposed for the fabrication of blazed gratings. Electron beam lithography was carried out to pattern a groove with a nanoscale line width, and then appropriate mask materials were filled into the SiO2 trench by atomic layer deposition. After being etched by RIBE at specific tilted angles, the required blazed gratings were achieved. In contrast to the typical fabrication process with a patterned mask on top of the surface to be etched, V-shaped nano structures filled into the trenches were used as the side mask. During etching, the surface material located in the shadow of the side mask along incident ion beams was not etched. The depth and blazed angle of blazed gratings are determined by the height of the side mask and the mounting angle of the sample, respectively. In addition, the fabricated blazed gratings can be used as imprinting moulds to duplicate blazed gratings for augmented reality applications. Due to more options for side mask materials, this method is able to provide high repeatability and accurate controllability for fabricating blazed gratings.

Theoretical study on photoinduced charge transfer in one-photon and two-photon absorption of branching oligofluorenes

Oligofluorenes have been identified as very promising two-photon absorption (TPA) materials and present great application potential for the fabrication of nonlinear optical devices, but the TPA mechanism and corresponding electron excitation properties have not been studied. Here, the photoinduced charge transfer characteristics of V-shaped and Y-shaped branching oligofluorenes that consist of two and three fluorene units in each branch during one-photon absorption (OPA) and TPA processes are analyzed theoretically using the density functional theory and visualization sum-over-states model. The calculated results show that the OPA intensity and TPA cross-section are significantly enhanced by increasing the branch length or changing the structure from V-shaped to Y-shaped. The long-distance charge transfer only occurs on the second transition of TPA at high excited states. Compared to Y-shaped molecules, V-shaped structures exhibit a stronger cooperative effect among the different branches.

Study on damage failure for a new double-triangular truss core sandwich structure

In order to solve the inherent problems of low bonding strength between face and core, a new double triangular truss core sandwich structure with reinforced frame is proposed, and the face and core are melt connected by thermoplastic composite carbon fiber reinforced polyether ether ketone (CF/PEEK). The response of the new double-triangular truss core sandwich structure under three-point bending load is investigated by both theoretical and finite element methods. Firstly, the theoretical prediction equation of bending stiffness and strength of double-triangular truss core sandwich structure is established, and the failure mechanism diagram is constructed. A valid three-point bending finite element model is established by Abaqus to predict the damage pattern of the structure and obtain the results of damage initiation location, damage process, final failure modes and load-displacement curve. The effect of geometric parameters on the bending performance of the sandwich structure was investigated. The results show that the calculated theoretical deflection curves and the ones obtained by numerical simulation are in good agreement. The average error between the two is 7.94%, verifying the reasonableness of the theoretical prediction model. The effect of geometric parameters on the bending performance of the sandwich structure was investigated. The new sandwich structure has stronger bending resistance and better ultimate load capacity than traditional honeycomb and V-shaped structures. Failure modes such as panel crumpling and crushing, fracture of reinforcement frames, buckling and fracture of core rods occur in sandwich structures under bending loads.

Equivalent Magnetic Network Modeling of Variable-Reluctance Fractional-Slot V-Shaped Vernier Permanent Magnet Machine Based on Numerical Conformal Mapping

The V-shaped permanent magnet synchronous machine (PMSM) has been successfully commercialized in hybrid-and all-electric vehicles fabricated by several famous companies. The advantages of PMSMs are a wide constant torque-speed range, high torque development capability and high power factor, and low torque ripple. In addition, the Vernier-PM (VPM) machines supersede conventional PMSM’s torque density and cogging torque. This paper presents a variable-reluctance fractional-slot V-shaped VPM (VR-FS-VVPM) machine with special rotor core surface. Hence, varying the air gap length over the direct and quadrature axes decreases the torque ripple considerably. Moreover, design of the PM-housing differs from previously introduced V-shaped VPM structures. As a result, the leakage flux in the yoke-side end-portion of the PM pieces reduces, enhancing the flux-linkage and power factor. To facilitate the design process further, an innovative equivalent magnetic network (EMN) model is established to improve performance prediction analytically. Moreover, conformal mapping is applied to create the permeance network for complex geometry air gap region. Here, a pentagonal-shape mesh-cell is used in the air gap region for capturing flux behaviour more accurately. The introduced method predicts the performance of the proposed VR-FS-VVPM machine. Finally, a typical 500 W, 12-slot/16-pole motor is designed and prototyped to validate the EMN-modelling against finite element analysis and experimental results.

The Role of Ultra-High-Frequency Ultrasound in Pyoderma Gangrenosum: New Insights in Pathophysiology and Diagnosis.

Pyoderma gangrenosum (PG) is a neutrophilic dermatological disease, whose pathogenesis is still poorly clarified. Because of the lack of validated criteria for diagnosis and response, PG treatment is still challenging and should be differentiated in the inflammatory and non-inflammatory phases. Our study aimed to provide a new semi-quantitative approach for PG diagnosis and monitoring, identifying ultra-high-frequency ultrasound (UHFUS) early biomarkers associated with the transition between the two phases. We enrolled 13 patients affected by painful PG lesions evaluated during the inflammatory phase (T0) and during the non-inflammatory phase (T1): pain was measured by the Visual Analogue Scale (VAS); clinical features were recorded through digital photography; epidermis and dermis ultrasound (US) characteristics were evaluated by UHFUS examination with a 70 MHz probe (Vevo MD® FUJIFILM VisualSonics). In T1 UHFUS examination, the presence of hyperechoic oval structures was lower compared to T0 (p value < 0.05). An hyperechogenic structure within the oval structure, suggestive of a hair tract, was evident in T0 and absent in T1 (p value < 0.05). In T0, blood vessels appear as U-shaped and V-shaped anechoic structures with a predominance of U-shaped vessels (p value < 0.05) compared to the more regular distribution found in T1. Finding early biomarkers of the transition from the inflammatory to the non-inflammatory phase could provide new insight in terms of therapeutic decision making and response monitoring. The differences found by this study suggest a potential use of UHFUS for the development of an objective standardized staging method. Further investigations will be necessary to confirm our preliminary results, thus providing a turning point in PG early detection, differential diagnosis and treatment monitoring.

Defect-Mediated Growth of Crystallographic Shear Plane.

As representative extended planar defects, crystallographic shear (CS) planes, namely Wadsley defects, play an important role in modifying the physical and chemical properties of metal oxides. Although these special structures have been intensively investigated for high-rate anode materials and catalysts, it is still experimentally unclear how the CS planes form and propagate at the atomic scale. Here, the CS plane evolution in monoclinic WO3 is directly imaged via in situ scanning transmission electron microscope. It is found that the CS planes nucleate preferentially at the edge step defects and proceed by the cooperative migration of WO6 octahedrons along particular crystallographic orientations, passing through a series of intermediate states. The local reconstruction of atomic columns tends to form (102) CS planes featured with four edge-sharing octahedrons in preference to the (103) planes, which matches well with the theoretical calculations. Associated with the structure evolution, the sample undergoes a semiconductor-to-metal transition. In addition, the controlled growth of CS planes and V-shaped CS structures can be achieved by artificial defects for the first time. These findings enable an atomic-scale understanding of CS structure evolution dynamics.

Spring-in behavior of woven carbon fiber/polycarbonate thermoplastic composites

The spring-in behavior of woven carbon fiber/polycarbonate thermoplastic composite is investigated by both the experiment and simulation ways. These thermoplastic composite plates are thermoformed into V-shaped structures, and the final bending angle is measured after demolding. In the finite element simulation to describe the thermoforming and spring-in behavior of the composite, the discrete approach is adopted to simulate the behavior of woven carbon fabric and combined with a resin model. The results from both the experiment and the simulation indicate the spring-in behavior of this thermoplastic composite. For [(±45)]6 blanks, the spring-in angle is around 2.60° for a 60-degree V-shape and around 1.72° for a 90-degree V-shape. For [(0/90)]6 blanks, the spring-in angle is around 2.38° and 1.19° for 60-degree and 90-degree V-shapes, respectively. The [(±45)]6 blank always has a slightly higher spring-in angle than the [(0/90)]6 blank, even though the difference is small. The finite element results show 6% to 12% differences with the experimental values if the spring-in angle is used, and the error is less than 0.6% when the bending angle is compared. By using the present finite element analysis, the results indicate that the stacking sequence could have an evident effect on the spring-in angle, and symmetric laminates have less spring-in effect as compared to their unsymmetric counterparts.

Diffraction-Limited Focusing of Acoustic Waves by a Mesoscopic Flat Janus Lens

Anisotropic focusing by a mesoscopic (Mie size parameter of about 18) acoustic cubic lens based on V-shaped plate structures has been simulated numerically and confirmed experimentally. It has been shown for the first time that this lens with an edge dimension of about three wavelengths ensures the focusing of an acoustic wave in air into a diffraction-limited region. In the inverse geometry of the structure, the lens completely reflects the incident acoustic wave.

Numerical investigation and optimization of the geometric profiles of dimple bottom structure in frictional interaction pairs

Dimple texture forming in the interaction pairs is a wear reduction technique like lubrication. Dimple-texturing is an efficient and sustainable way of altering the surface topography to improve the tribological characteristics of interacting surfaces. In this work, sliding interaction pairs with circular dimples, three different dimple bottom structures, namely flat, V-shaped and U-shaped, are selected for numerical investigation using the Reynolds equation to enhance the hydrodynamic characteristics. The numerical design and investigation on the dimple area density (ρ), aspect ratio (λ), and flow velocity (V) is done using unblocked central-composite design (UCD) under response surface methodology (RSM) along with multi-objective gray relation analysis method for individual dimple bottom structures to minimize the coefficient of friction and increase the load bearing capacity in the interaction pairs. The flat bottom structure exhibits excellent load-bearing capacity and minimum coefficient of friction when compared to V-shaped and U-shaped bottom structures. Compared to flat bottom structure, the V-shaped and U-shaped bottom structures has 40.37% and 7.81% lesser load-bearing capacity, respectively, and 54.08% and 7.81% higher coefficient of friction, respectively. In a flat bottom structure, the flow velocity is identified as an effective variable factor to improve the outcome characteristics, followed by dimple area density and aspect ratio. The optimal dimple area density and aspect ratio values are observed in the range of 30–40% and 0.025 – 0.030, respectively. In addition, the optimal value of flow velocity is observed to be 2.5 m/s.

Aerodynamic performance of dragonfly wing model that starts impulsively: how vortex motion works

The cross-section of dragonfly wings has corrugated structures. In particular, the leading-edge side of the wing consists of V-shaped structures. According to previous studies, a corrugated wing may exhibit high aerodynamic performance at low Reynolds numbers (Re = O(103)), and vortex dynamics associated with wing structure are expected to play an important role. We study the relationship between the wing structure and vortex dynamics by direct numerical simulations. It is known that, when a two-dimensional flat wing impulsively starts from a rest state, a coherent vortex called lambda vortex, which has the opposite sign to a leading-edge vortex (LEV), is generated and remains for a time interval. Our previous study suggests that, in the case of the corrugated wing, the lambda vortex collapses and is stuck inside V-shaped structures near the leading edge. The collapse of the lambda vortex was proposed as a key factor of high performance for the particular shape of the corrugated wing. In this paper, we investigate the relationship between vortex dynamics and high performance in a wider parameter range than in our previous studies. We analyse two corrugated models with different Reynolds numbers. It is revealed that the collapse of the lambda vortex is also the key to high performance for these cases.

Effect of Notch Structure and Notch Bottom Diameter on the Tensile Load of a Certain GH4169 Notch Bolt for a Device for Longitudinal Separation of Fairing

The effect of the notch structure and bottom diameter of a GH4169 notch bolt for an explosive separation device used for longitudinal separation of the fairing, and GH4169 strength range on the tensile load was studied by combing simulations with tests. The results show that the V-shaped, arc-shaped and square notch structures can improve the tensile load of the bolt but to a lesser degree in sequence, and the arc-shaped notch structure performs best in terms of tensile load, fracture appearance and shear resistance. In order to meet the design requirements of 14–15.5 KN tensile load for the notch bolt with an arc-shaped structure, four raw material tensile intervals corresponding to the notch bottom diameters were established by using domestic GH4169 grade C cold-drawn bars.

Modulation of Surface Plasmonic Bending Beam via Nanoslit Interactions

The discussion of resonance mechanisms for artificial structural units has always been a key to producing highly efficient, active and tunable meta-devices in the fields of controlling surface plasmon polaritons (SPPs) to generate surface plasmonic bending beams (SPBs). In this study, an array of 20 antisymmetric double V-shaped structures was designed to generate an SPB. The arms of the double V-shaped structures were panned to control the electric field intensity distributions of the SPB. The influence of the polarization states (such as polarization angles, linearly polarized (LP), left-circularly polarized (LCP) and right-circularly polarized (RCP) light) of the incident light on electric field intensity of SPB is discussed. These results can be well explained by the theory of dipole radiation. The numerical simulation results are in good agreement with the theoretical analysis. It is hoped that these results will help guide subsequent work in optimizing SPB generators.

Structural characteristics of 3C–SiC thin films grown on Si-face and C-face 4H–SiC substrates by high temperature chemical vapor deposition

Hetero-epitaxy of 3C–SiC on Si-face and C-face 4H–SiC is experimentally investigated and corresponding growth model is identified. This study of polytypes of SiC will be useful for band-gap engineering, optical, electrical, and electronic applications of SiC. 3C–SiC was epitaxially deposited on 4H–SiC using a high temperature chemical vapor deposition. The primary factor affecting the epi-quality on Si-face SiC is double positioning boundary (DPB) defect. An adatom migration model elucidates the formation of the V-shaped DPB defect structures. On C-terminated 4H–SiC, super-V-shaped-structure (SVSS) defects and polycrystalline complexes in 3C–SiC are formed. These characteristics of 3C–SiC are measured and analyzed using transmission electron microscopy, X-ray diffraction, atomic force microscopy, and scanning electron microscopy techniques. A model considering adatoms' migration in step-flow direction and anti-step-flow direction explains the SVSS defects. Effects of both step-flow and anti-step-flow growth mode on the atom adsorption near the step edge are discussed.

On applicability of von Karman’s momentum theory in predicting the water entry load of V-shaped structures with varying initial velocity

The water landing of an amphibious aircraft is a complicated problem that can lead to uncomfortable riding situation and structural damage due to large vertical accelerations and the consequent dynamic responses. The problem herein is investigated by solving unsteady incompressible Reynolds-averaged Navier–Stokes equations with a standard k−ω turbulence closure model. The theoretical solutions established by the von Karman’s momentum theory are also employed. In order to validate the relationships between the initial vertical velocity and the peak value of vertical acceleration, free fall test cases of 2D symmetric wedge oblique entry and 3D cabin section vertical entry are presented first. The other parameters at which the maximum acceleration occurs, such as time, penetration depth, velocity, are also evaluated. Hence, the quantitative relations are investigated to water landing event for amphibious aircraft. Detailed results in terms of free surface shape and pressure distribution are provided to show the slamming effects. The results show that a linear dependence of the maximal acceleration from the square of initial vertical velocity can be derived for two-dimensional wedge, three-dimensional cabin section and seaplane with V-shaped hull. Moreover, the ratio between the corresponding velocity and the initial vertical velocity tends to a constant threshold value, 5/6, derived from the theoretical solution, when increasing the initial vertical velocity in all three cases.