Upper Surface Research Articles

Aspidistra leipingensis (Asparagaceae), a new species from Guangxi, China

Aspidistra leipingensis, a new species of Asparagaceae from Guangxi, southern China, is described and illustrated. The new species is morphologically similar to A. punctatoides, but can be distinguished by its shorter leaf blade and petiole, longer perianth tube, stamens inserted in the lower part of the perianth tube, stigma hemispherical shape, upper surface convex and glabrous. Colour plate and line drawing of the new species are provided.

Optimizing 3D Laser Foil Printing Parameters for AA 6061: Numerical and Experimental Analysis

Abstract This study utilizes a technology known as 3D laser foil printing (LFP) to create precise structures by layering metal foils using laser welding. Metal foils have the advantages of rapid cooling and efficient heat conduction, allowing for the formation of fine-grained structures. However, when dealing with materials like aluminum alloys in laser processes, defects can arise as a result of their high reflectivity. To address this challenge, laser circular oscillation welding (LCOW) is applied to the LFP process. LCOW's circular motions with higher scanning frequencies widen the keyholes and reduce some defects such as spattering, bubble formation, and microcracks. Simulation predictions with an error margin of approximately 10% in comparison to experimental results demonstrate the reliability of the model. Furthermore, the study integrates circular packing design with artificial neural networks to create comprehensive processing maps tailored to different criteria for extracting optimal welding parameters. As a result, for the optimized processing parameters screened using the above systematic process, no cracks were observed on the upper surface of the 3D LFP parts produced with a laser power of 800 W and a scanning speed of 550 mm/s, and only 0.12% porosity was observed from the cross section of the sample. Future research will focus on incorporating simulation results to model microstructures more precisely and continually refining LCOW parameters as new materials and technologies emerge, ensuring the ongoing enhancement of weld quality in the 3D LFP process.

Analysis of Fracturing Above Block Caving Back: A Spherical Shell Theory Approach and BEM Numerical Simulation

ABSTRACTExperiments and field monitoring have revealed that in block caving, fractures over the cave crown tend to form in narrow curved bands that are parallel or subparallel to the cave back surface. These fractures delineate curved shells of orebody between the bands and the cave back. The effectiveness of block caving hinges on the subsequent fracturing and fragmentation of these orebody shells. This study adopts a dual approach, combining thin spherical shell theory and full 3D numerical simulations along with principles of linear elastic fracture mechanics, to investigate the fracturing behaviour of these shells. Analytical analysis indicates that under axisymmetric loading, latitudinal tensile fractures predominantly initiate across the most part of the shell, occurring on both the upper and lower surfaces, except at a localised area. Additionally, longitudinal tensile fractures may initiate at the central area of the upper surface, while shear fractures tend to occur around the edge of the shell. Consequently, the shells become susceptible to fracturing, leading to the collapse or cave‐in of the orebody. Numerical simulations agree with these findings, illustrating that fracturing points within the shell region are longitudinally dispersed throughout the entire shell. Most of these fracturing points satisfy the criteria for tensile fracturing, particularly within the middle portion of the shell, aligning with the analytical results. Furthermore, simulations considering nonaxisymmetric loading patterns demonstrate that regions surrounding the caving cavity, aligned with the minimum principal in situ stress, exhibit heightened susceptibility to fracture initiation. This insight holds potential significance for optimising the design of the caving process.

Study of Ionanofluids Behavior in PVT Solar Collectors: Determination of Thermal Fields and Characteristic Length by Means of HEATT® Platform

Solar electric and solar thermal energies are often considered as part of the solution to the current energy emergency. The pipes of flat plate solar devices are normally heated by their upper surfaces giving rise to an asymmetric temperature field in the bulk of the fluid, which influences the heat transfer process. In the present work, a study of the characteristic length of tubes, or most efficient distance at which heat transfer occurs, in flat photovoltaic-thermal (PVT) hybrid solar devices has been carried out using three heat transfer fluids: water, [Emim]Ac ionic liquid and ionanofluid of graphene nanoparticles suspended in the former ionic liquid. The mean objective of the study was to know whether the heat transfer occurs in optimal conditions. Experimental measurements have been made on a commercial PVT device, and numerical simulations have been performed using the HEATT® platform to determine the characteristic length of the process. The tests conducted showed a clear improvement in the temperature jump of the fluid inside the collector when INF is used compared to water and ionic liquid and even a higher overall energy efficiency. Electricity generation is not greatly affected by the fluid used, although it is slightly higher when water is used. Slower fluid velocities are recommended if high fluid outlet temperatures are the goal of the application, but this penalizes the overall thermal energy production. The characteristic process length is not typically achieved in parallel tube PVT collectors with ordinary flow rates, which would require a speed, and consequently, a flow rate, about 10 times lower, which penalizes the performance (up to four times), although it increases the fluid outlet temperature by 234%, which can be very interesting in certain applications. Ionanofluids may in the medium term become an alternative to water in flat plates or vacuum solar collectors for applications with temperatures close to or above 100 °C, when their costs will hopefully fall. The results and methodology developed in this work are applicable to solar thermal collectors other than PVT collectors.

Ocean weather systems on icy moons, with application to Enceladus.

We explore ocean circulation on a rotating icy moon driven by temperature gradients imposed at its upper surface due to the suppression of the freezing point of water with pressure, as might be induced by ice thickness variations on Enceladus. Using high-resolution simulations, we find that eddies dominate the circulation and arise from baroclinic instability, analogous to Earth's weather systems. Multiple alternating jets, resembling those of Jupiter's atmosphere, are sustained by these baroclinic eddies. We establish a theoretical model of the stratification and circulation and present scaling laws for the magnitude of the meridional heat transport. These are tested against numerical simulations. Through identification of key nondimensional numbers, our simplified model is applied to other icy moons. We conclude that baroclinic instability is central to the general circulation of icy moons.

Aerodynamic optimisation of flat-upper-surface wing

Purpose The paper aims to optimise several concepts of the flat-upper-surface wing that could install the largest possible number of photovoltaic cells and test them in flight. A wing ideal flat upper surface was necessary to provide the same lighting conditions for each tested cell. Design/methodology/approach The optimised wings were built based on a developed family of airfoils having 75% of their upper surface flat. Within the developed parametric model of the wings, the design parameters described the spanwise distribution of base airfoils. Maximisation of the endurance factor was assumed as the main objective. The aerodynamic properties of optimised wings were evaluated using a panel method coupled with boundary layer analysis. Findings The paper proves that it is possible to design wings with 75% of their upper surface perfectly flat, which are also characterised by good aerodynamic properties. Practical implications The research conducted will allow designing an experimental unmanned aerial vehicle dedicated to investigating the properties of electrical propulsion systems at various altitudes. Data obtained in these investigations will help in the development of future generations of electric-propulsion aircraft. Originality/value The innovative wings, developed within the research are unique due to their unusual geometric and aerodynamic properties. They have 75% of their upper surface perfectly flat. That makes them ideal for testing various photovoltaic cells in flight. The biggest challenge was to design the wings so that their specific geometric features did not impair their aerodynamic properties. The paper proves that this challenge has been fully overcome.

Analytical study on fire resistance performance of precast concrete hollow-core slabs for electric vehicle fire in parking structures

This study evaluated the effects of fires that occur in internal combustion engine vehicles (ICEVs) and battery electric vehicles (BEVs) on the structural safety of hollow-core slabs (HCS) installed in parking structures. A fire simulation of a prototype parking structure was performed using the time–heat release rate curves of ICEVs and BEVs derived from fire experiments, and fire behavior and temperature history were derived according to the fire curve. Additionally, nonlinear finite element analysis was conducted using a general-purpose finite element analysis program, and the fire resistance performance of HCS was evaluated according to the fire curve and slab load ratio. In the case of a fire in ICEVs, the performance criteria of ISO 834–1 were met even at a slab load ratio of 0.7. However, in the case of a fire in BEVs, the standard for insulation was not met as the temperature change of the upper surface of HCS exceeded 180 K, and the load-bearing capacity was also not satisfied as the limiting deflection reached a slab load ratio of 0.7.

A mathematical model for wind-generated particle–fluid flow fields with an application to the helicopter cloud problem

We develop a model for the interaction of a fluid flowing above an otherwise static particle bed, with generally the particles being entrained or detrained into the fluid from the upper surface of the particle bed, and thereby forming a fully two phase fluidized cloud above the particle bed. The flow in this large-scale fluidized region is treated as a two-phase flow, whilst the key processes of entrainment and detrainment from the particle bed are treated by examining the local dynamical force balances on the particles in a thin transition layer at the interface between the fully fluidized region and the static particle bed. This detailed consideration leads to the formation of an additional macroscopic boundary condition at this interface, which closes the two-phase flow problem in the bulk fluidized region above. We then introduce an elementary model of the well-known helicopter brownout problem, and use the theory developed in the first part of the paper to fully analyse this model, both analytically and numerically.

Comprehensive description of new and known stages of Americabaetis titthion Lugo-Ortiz & McCafferty (Ephemeroptera: Baetidae)

The male imago of Americabaetis titthion is described for the first time. It can be distinguished from other male imagos of the genus by the following combination of characteristics: turbinate portion of the eyes with upper surface ellipsoidal and separated by approximately the width of a lateral ocellus; costal area of fore wings tinged with reddish-brown; presence of pairs of soft, setose protuberances on the meso- and metasternum; subgenital plate slightly concave; forceps with segment I/II slightly tapering medioapically. Supplementary descriptions for the nymph and female imago are provided, as well as the first description of the eggs of a species of the genus.

Validation of heat transfer models and optimization of heat shielding performance of high-temperature multilayer insulations for hypersonic vehicles

Multilayer insulation (MLI) is widely used in hypersonic vehicles because of its low density and excellent thermal insulation performance. However, the insulation mechanism of MLI remains poorly understood, leading to conflicting views on how to enhance its thermal insulation capabilities. In this study, two different numerical models were built and validated with experiment data to investigate key factors influencing MLI performance. The analysis focused on the effects of reflective screen positioning, the surface emissivity of reflective screens and the radiation properties parameters of fibrous materials on the thermal insulation performance of the MLI. The results show that the thermal insulation performance is better when the reflective screens are placed close to the thermal boundary. Moreover, insulation materials with lower absorption coefficients enhance the effectiveness of the reflective screens, further improving the thermal insulation performance of MLI. In addition, the study reveals that the thermal insulation mechanisms differ between the upper and lower surfaces of the reflective screens. Lower emissivity on the upper surface combined with higher emissivity on the lower surface optimizes the thermal insulation performance of MLI. These findings offer valuable insights for advancing MLI designs and improving its application in future high-speed vehicles.

Hovering flapping wings with dynamic twist

The role of (active) dynamic wing twist on aerodynamic performance of three-dimensional hovering flapping flight is explored using numerical simulations. A variety of cases with different pitch angles and with (flexible wings) or without (rigid wings) dynamic twist are compared. The results show that changes in aerodynamic performance due to dynamic twist are comparable to those obtained without twist (rigid wing cases) by pitching the whole wing and that lift and lift-to-power ratio generally collapse onto a single curve when plotted as a function of the mid-stroke pitch angle at 2/3 wing radius. However, in some cases dynamic twist yields enhanced time-averaged efficiency. Using the force and power partitioning method, it is shown that this enhancement results from the absence of vortical structures near the wing root lower surface and to the presence of an extended leading edge vortex on the wing upper surface, when compared to the most efficient rigid wing case. These differences in flow topology lead to enhanced lift during the early phase of the strokes without changes in power consumption.

On the Origin of Görtler Vortices in Flow over a Multi-Element Airfoil

The flow characteristics of a 30P30N three-element high-lift airfoil at low Reynolds numbers O104 are examined through three-dimensional simulations using a high-order spectral element method. This study primarily investigates the flow structures of the slat cove and Görtler vortices formed on the upper surface of the main airfoil. Spanwise instability grows exponentially in the slat cove with a constant wavelength, corresponding to that of the subsequently formed Görtler vortices. Görtler number calculations show that curvature-induced centrifugal instability at the slat cusp leads to the subsequent formation of Görtler vortices. Proper orthogonal decomposition (POD) is used to analyze the development of flow structures in the slat cove in different time ranges. At early time, the flow in the slat cove is dominated by shear layers that evolve into spanwise perturbations. These perturbations further evolve into distinct bell-shaped structures close to the slat cusp and are advected to the upper surface of the main airfoil, leading to the formation of Görtler vortices.

Nonlinear incompressible shear wave models in hyperelasticity and viscoelasticity frameworks, with applications to Love waves

General equations describing shear displacements in incompressible hyperelastic materials, holding for an arbitrary form of strain energy density function, are presented and applied to the description of nonlinear Love-type waves propagating on an interface between materials with different mechanical properties. The model is valid for a broad class of hyper-viscoelastic materials. For the Murnaghan constitutive model, shear wave equations contain cubic and quintic differential polynomial terms, including viscoelasticity contributions in terms of dispersion terms that include mixed derivatives uxxt of the material displacement. Full (2+1)-dimensional numerical simulations of waves propagating in the bulk of a two-layered solid are undertaken and analysed with respect to the source position and mechanical properties of the layers. Interfacial nonlinear Love waves and free upper surface shear waves are tracked; it is demonstrated that in the fully nonlinear case, the variable wave speed of interface and surface waves generally satisfies the linear Love wave existence condition c1<v<c2, while tending to the larger material wave speed c1 or c2 for large times.

Densification behavior in compaction for Cu/TiB2 composite under electromagnetic impact

Cu/TiB2 composite combines electrical conductivity and wear resistance, leading to its wide application prospect in electrical contact. In this study, electromagnetic impact was applied to compact Cu/TiB2 powder. The interaction between powder and die under electromagnetic impact was analyzed by observing the surface quality, density, microstructure, and hardness. The results showed that when the energy was less than 21 kJ, the increase in energy could enhance density and tensile strength of the compact. However, when the energy exceeded 21 kJ, the state of compact hardly changed and burr near the edge would be worsened. Besides, the hardness of the upper surface increased gradually from the center to the edge, while the opposite was true for the lower surface, reflecting the spatial distribution of density. With the aid of simulation, it was found that the stress wave propagation influenced the densification behavior and led to the variation of density.

Surgical anatomy of the carotid sympathetic plexus in endoscopic endonasal approaches: strategies for preventing Horner syndrome.

Endoscopic endonasal approaches (EEAs) specifically for procedures involving manipulation of the internal carotid artery (ICA), such as the transcavernous and translacerum approaches, confer a potential risk of carotid sympathetic plexus injury, potentially leading to postganglionic Horner syndrome. The primary aim of this study was to delineate the surgical anatomy of the carotid sympathetic plexus from an endoscopic endonasal perspective, offering insights to facilitate intraoperative anatomical identification and injury prevention. A comprehensive dissection was conducted on 20 silicone-injected, lightly embalmed postmortem human heads. The segments, patterns, and surgical landmarks of the carotid sympathetic plexus were investigated in a stepwise manner. In addition, 3 illustrative cases highlighting the involvement of the carotid sympathetic plexus in EEAs are included to contextualize the anatomical findings. The carotid sympathetic plexus can be categorized into 3 segments: 1) the cavernous sinus (CS) segment, beginning at the upper surface of the petrolingual ligament and ascending anterosuperiorly along the inferior compartment of the CS (mean ± SD length 5 ± 0.5 mm); 2) the lacerum segment, starting at the exit of the petrous carotid canal and ascending laterally and vertically to the upper surface of the petrolingual ligament (mean ± SD length 10 ± 1 mm); and 3) the petrous segment, originating at the external opening of the carotid canal and terminating at the foramen lacerum (mean ± SD length 18 ± 1 mm). Two primary morphological patterns of the sympathetic plexus at the CS and lacerum segments were identified: a plexus-like pattern in 12 (30%) hemispheres, and a nerve-like pattern that was subcategorized as double (18 [45%] hemispheres) or single (10 [25%] hemispheres) trunks. Surgical strategies emphasize the importance of recognizing key landmarks when approaching the carotid sympathetic plexus, including the pterygosphenoidal triangle, lingual process, petrolingual ligament, lateral parasellar ligament, and abducens nerve. This article provides a comprehensive anatomical description of the carotid sympathetic plexus in EEAs, highlighting key anatomical segments and patterns for intraoperative identification. A better understanding of anatomical landmarks for the carotid sympathetic plexus could help reduce the incidence of postganglionic Horner syndrome, augmenting the safety and efficacy of endoscopic endonasal transcavernous surgery.

Construction of ultra-smooth and void-free buried interface via bilateral chemical bridging for efficient and hysteresis-suppressed perovskite solar cells

The surface properties are vital aspects in improving photovoltaic performance of perovskite solar cells (PSCs). Except for the upper surface of perovskite, the hidden buried interface which supports the beginning of perovskite film crystallization is of equal great importance for the construction of high-efficiency PSCs. Herein, we use urea phosphate (UPP) to build a bilateral chemical bridge in the buried interface under perovskite layer, to simultaneously improve the properties of SnO2 ETL and the upper perovskite. On one hand, the interaction between UPP and SnO2 passivates the defects of the SnO2 and facilitates the formation of ultra-smooth surface for superior interfacial contact. On the other hand, the chemical interaction between UPP and perovskite contributes to the optimization of crystal nucleation and growth, which improves the crystalline quality of perovskite, inhibits the formation of voids at the buried interface and reduces the defects of the grain boundary. Benefiting from the optimized buried interfacial contact, suppressed defects, accelerated charge extraction and modified energy level alignment, the UPP-processed device delivers an improved power conversion efficiency of 24.54 %, with effective suppression of hysteresis. Moreover, the stability of device is also improved owing to the reduction of trap defects. This work provides a feasible strategy to tune the buried interface between the charge transfer layer and perovskite layer for fabrication of efficient and stable PSCs.

Microstructure and mechanical properties of aluminum alloy laser welded joint assisted by alternating magnetic field

Magnetic field-assisted laser welding is an effective method to improve the quality of laser-welded joints. In this study, laser welding was conducted on a 2 mm thick sheet of 6061-T6 aluminum alloy, with the assistance of an alternating magnetic field oriented perpendicular to the surface of the sheet. The effects of the alternating magnetic field on the macrostructure, molten pool flow, porosity, grain morphology, and microhardness of the weld seam were analyzed. The results indicate that applying the alternating magnetic field results in more uniform and finer fish scale patterns on the upper surface of the weld. The porosity of the weld is significantly reduced. The Lorentz force generated by the alternating magnetic field suppresses liquid metal flow from the center to the edges of the molten pool, thereby hindering the heat flow and transfer within the pool. This concentration of heat in the lower part of the molten pool increases the size of equiaxed grains at the weld center and promotes the formation of more branches in the columnar grains near the fusion line. Some columnar grains in the columnar grain zone transform into equiaxed grains. Moreover, the microhardness distribution of the weld becomes more uniform, and the hardness in the heat-affected zone increases. Tensile tests revealed that all samples fractured within the weld seam, with the tensile strength of the welded joints increasing by 12.7%. The fracture mode transitions from a mixed ductile-brittle fracture to a purely ductile fracture.

JWST Imaging of Edge-on Protoplanetary Disks. III. Drastic Morphological Transformation Across the Mid-infrared in Oph163131

We present JWST broadband images of the highly inclined protoplanetary disk SSTc2d J163131.2-242627 (Oph163131) from 2.0 to 21 μm. The images show a remarkable evolution in disk structure with wavelength, quite different from previous JWST observations of other edge-on disks. At 2.0 and 4.4 μm, Oph163131 shows two scattering surfaces separated by a dark lane, typical of highly inclined disks. Starting at 7.7 μm, however, (1) the two linear nebulosities flanking the dark lane disappear; (2) the brighter nebula tracing the disk upper surface transitions into a compact central source distinctly larger than the JWST point-spread function and whose intrinsic size increases with wavelength; and (3) patches of extended emission appear at low latitudes, and at surprisingly large radii nearly twice that of the scattered light seen with Hubble Space Telescope and NIRCam, and of the gas. We interpret the compact central source as thermal emission from the star and the inner disk that is not seen directly, but which instead is able to progressively propagate to greater distances at longer wavelengths. The lack of sharp-edged structures in the extended patchy emission argues against the presence of shocks and suggests photoexcitation or stochastic heating of material smoothly flowing away from the star along the disk surface. Finally, the dark lane thickness decreases significantly between 0.6 and 4.4 μm, which indicates that the surface layers of Oph163131 lack grains larger than 1 μm.

A compact dual‐band omnidirectional antenna with folded microstrip lines and slotlines for 5G applications

AbstractA compact dual‐band omnidirectional antenna with folded microstrip lines and slotlines is proposed. The antenna is composed of a substrate and a superstrate. The superstrate is employed to broaden the antenna bandwidth. The radiating patch is situated on the upper surface of the substrate and consists of folded microstrip lines. The performance of the high‐frequency band can be optimized based on the analysis of the current distribution intensity. The bottom of the substrate is composed of a ground plane with slotlines. The introduction and improvement of the low‐frequency band are achieved by modifying the ground plane structure with characteristic modal analysis. The antenna demonstrates omnidirectional radiation characteristics across both frequency bands. The dimensions of the antenna are π × 0.178 λ0 × 0.178 λ0 × 0.049 λ0 (π × 22 × 22 × 6 mm). The antenna achieves a maximum gain of 3.37 dBi at 2.5 GHz and 2.74 dBi at 5.8 GHz. The measured impedance bandwidths for the two frequency bands are 17.3% and 21.7%, respectively.

Experiments for the Assessment of the Probabilistic Multistage Algorithm for Damage Detection in Flat and Curved CFRP Panels

The Probabilistic Multistage (PM) algorithm was developed by authors for identifying and localizing damages in isotropic plates. More specifically, PM algorithm consists of a fully automated probabilistic damage imaging methodology based on ultrasonic guided wave propagation and a 5-sensor array working in a pitch-catch approach. The algorithm processes the gathered data in three steps to identify key features associated with damage. The aim of this work is to assess the effectiveness of the PM algorithm on more complex structures. Specifically, the study investigates three cases of study, made of Carbon Fiber Reinforced Plastic (CFRP) composite, characterized by different geometries and layups. The algorithm is initially tested on panels with artificial damage in the form of a Teflon disk located in a specific location between the middle laminae of the panels, which is used to replicate the effect of delamination. In order to expand the experimental dataset without incurring additional costs or waste, new damage conditions are simulated by adding masses on the upper surface of the panels. Each plate is investigated considering three different damage sizes and 16 different damage locations. The proposed algorithm successfully detects damages both within and outside the sensor network. The PM algorithm produces a clear damage positioning map and a positioning (probabilistic field) range for the identified damage. This information can be used to assist operators in conducting inspections more efficiently by focusing on the highlighted areas, which may potentially lead to reduced maintenance and repair expenses.