Cone Structure Research Articles

Synchrotron X-ray imaging of the onset of ultrasonic horn cavitation.

High-power ultrasonic horns operating at low frequency are known to generate a cone-shaped cavitation bubble cloud beneath them. The exact physical processes resulting in the conical structure are still unclear mainly due to challenges associated with their visualization. Herein, we address the onset of the cavitation cloud by exploiting high-speed X-ray phase contrast imaging. It reveals that the cone formation is not immediate but results from a three-step phenomenology: (i) inception and oscillation of single bubbles, (ii) individual cloud formation under splitting or lens effects, and (iii) cloud merging leading to the formation of a bubble layer and, eventually, to the cone structure due to the radial pressure gradient on the horn tip.

Improving combustion and lowering NO emissions of an industrial coal swirl burner by optimizing its nozzle structure

• Simulation and comparison are conducted for the burner before and after optimization. • Entrained effect of secondary air on primary air is enhanced with retrofitting ISACS. • Retrofitting ISACS has significant effects on the combustion characteristics. • Optimized burner performs better in NOx reduction, flame stability and burnout rate. To accommodate rapidly growing but highly variable renewable power in the grid and large variations in power demand, coal-fired power plants need to be flexibly operated through fast and wide load changes, still with high efficiency and reliability and low emissions. Towards reliable implementation in a power plant under flexible operation, this paper comprehensively investigates the improvement of an industrial low-NO x swirl burner via numerical simulation and various field tests. Burner aerodynamics, which play a vital role in its performance, are largely affected by the burner nozzle structure. For the low-NO x swirl burner under study, the inner secondary air cone structure is found to have the most significant impact on the burner aerodynamics and the combustion performance. For the coal fired in the power plant, the newly designed inner secondary air cone structure, which is a kind of an extended smooth diverging duct, greatly facilitates the entrainment of the primary air into the surrounding swirl secondary air stream and largely enhances lateral mixing. A large recirculation zone is formed between the primary air and the inner secondary air stream, stabilizing ignition and combustion under flexible operation conditions. This is particularly important for low-load operation. Comparatively, reducing the secondary air duct area for a higher axial momentum of the secondary air stream and adding a new particle separation ring for more dispersed particle distribution are found to have a minor impact on the burner aerodynamics. The optimized burner nozzle structure via numerical simulation has been finally adopted by the power plant for the burner retrofit, on which various field tests have been performed on the retrofitted burner. The tests show that the nozzle structure optimization remarkably improves the burner performance, which is also consistent with the numerical prediction. This study also provides useful guidance for optimizing the swirl burners of the similar type.

Effect of liquid surface tension coefficient on spray cone structure of ejection sprayer

The results of an experimental study of the effect of surfactants on the spatial distribution of droplet concentration in the spray cone of the ejective sprayer are presented. The spectral transparency method and a setup providing scanning the cross-section of the spray cone along its length are used for the study. It is shown that when surfactants are incorporated into distilled water, the radial distribution of the droplet concentration in the spray cone becomes more uniform, and the cone maximum length increases.

Bioinspired cone structures with helical micro-grooves for fast liquid transport and efficient fog collection

Inspired by cactus spines, cones with helical micro-grooves were created and shown to move droplets more efficiently than straight micro-grooved cones. The helix structure increases Laplace pressure, which leads to better fog collection.

A series of two-dimensional carbon allotropes with Dirac cone structure.

By combining a hexagon and square carbon ring, a series of two-dimensional (2D) carbon allotropes, named (HS)nm-graphene, can be obtained. Based on the first-principles calculations, the energetic, dynamical and mechanical stability were evaluated. Importantly, we predicted that some carbon allotropes possess the Dirac cone structure. A pair of Dirac points can be found for (HS)52-graphene and (HS)72-graphene in the first Brillouin zone. With varying the number of four- and six-membered rings, a distorted Dirac cone can be observed for (HS)41-graphene and (HS)71-graphene. To get insight into the features of the Dirac cone, the orbital decomposed band structure, the corresponding density of states, the projection map of the three-dimensional bands and Fermi velocity were investigated. Interestingly, the Fermi velocity of (HS)52-graphene is up to 8.8 × 105 m s-1 along the kx direction, which is higher than that of graphene, indicating higher potential application in electronic transport. Finally, we discuss the mechanical properties of (HS)nm-graphene. Our work provides a new way to design the stable 2D carbon allotropes with a Dirac cone.

Orbital-active Dirac materials from the symmetry principle

Dirac materials, starting with graphene, have drawn tremendous research interest in the past decade. Instead of focusing on the p_{z} orbital as in graphene, we move a step further and study orbital-active Dirac materials, where the orbital degrees of freedom transform as a two-dimensional irreducible representation of the lattice point group. Examples of orbital-active Dirac materials occur in a broad class of systems, including transition-metal-oxide heterostructures, transition-metal dichalcogenide monolayers, germanene, stanene, and optical lattices. Different systems are unified based on symmetry principles. The band structure of orbital-active Dirac materials features Dirac cones at K(K') and quadratic band touching points at Γ, regardless of the origin of the orbital degrees of freedom. In the strong anisotropy limit, i.e., when the π-bonding can be neglected, flat bands appear due to the destructive interference. These features make orbital-active Dirac materials an even wider playground for searching for exotic states of matter, such as the Dirac semi-metal, ferromagnetism, Wigner crystallization, quantum spin Hall state, and quantum anomalous Hall state.

A low-profile two-arm backfire tapered cone helical antenna for TT&C in microsatellites

AbstractA novel low-profile two-arm backfire tapered cone helical antenna for telemetry tracking and command (TT&C) is introduced theoretically and experimentally in this paper. Compared with the conventional helical antenna, this design has a substantial decrease in its height and an increase both in its half power beamwidth (HPBW) and 3-dB axial ratio beamwidth by replacing the uniform structure with two tapered cone structures. It provides a maximum gain of 5.1 dBi, an excellent circular polarization radiation over a wide angular range of more than 124°, a 3-dB axial ratio bandwidth of 18.8%, a wide HPBW of more than 125°, and nearly equal E- and H- plane far-field patterns with high degree of axial symmetry over S-band (2–2.3 GHz). These excellent radiation characteristics with an endurable and compact structure make it an attractive candidate for TT&C application in microsatellite system, where the installation envelope and space for antenna are extremely limited.

Classification of Ultrafine Particles Using a Novel 3D-Printed Hydrocyclone with an Arc Inlet: Experiment and CFD Modeling.

Ultrafine particle classification can be realized using hydrocyclones with novel structures to overcome the limitations of conventional hydrocyclones with tangential inlets or cone structures. Herein, the hydrocyclones with different inlet structures and cone angles were investigated for classifying ultrafine particles. Computational fluid dynamics (CFD) simulations were performed using the Eulerian-Eulerian method, and ultrafine MnO2 powder was used as a case study. The simulation results show a fine particle (≤5 μm) removal efficiency of 0.89 and coarse particle (>5 μm) recovery efficiency of 0.99 for a hydrocyclone design combining an arc inlet and a 30° cone angle under a solid concentration of 2.5 wt %. Dynamic analysis indicated that the novel arc inlet provided a preclassification effect to reduce the misplacement of fine/coarse particles, which cannot be provided by conventional tangential or involute inlets. Furthermore, the proposed design afforded comprehensive improvement in the flow field by regulating the residence time and radial acceleration. Subsequently, a novel hydrocyclone with an arc inlet and 30° cone angle was manufactured using the three-dimensional (3D) printing technology. Experiments were conducted for classifying ultrafine MnO2 particles using the novel 3D-printed hydrocyclone and conventional hydrocyclone. The results demonstrate that the classification performance of the 3D-printed hydrocyclone was superior to that of the conventional one, in particular, the removal efficiency of fine particles from 0.719 to 0.930 using a 10 wt % feed slurry.

Plasmonic Nanostructures for Broadband Solar Absorption Based on Synergistic Effect of Multiple Absorption Mechanisms.

The growing attention to solar energy has motivated the development of highly efficient solar absorbers. In this study, a high-performance meta-structure solar absorber (MSSA) based on a tungsten truncated cone structure combined with a film resonator structure has been proposed and demonstrated numerically. The designed structure exhibits over 97.1% total solar absorption efficiency and less than 8.5% total thermal emissivity under the condition of one solar concentration, hence reaching 91.6% photothermal conversion efficiency at 100 °C. In addition, the proposed MSSA achieves promisingly high spectrum absorptance of over 97.8% in the ultraviolet, visible and near-infrared regions (280-1700 nm). Based on the simulation analysis, the enhanced light absorption is attributed to the synergistic effect of the magnetic polaritons (MPs) on the nanostructured metal surface, the cavity plasmon resonance between the truncated cones that can form light-trapping structures, the magnetic field resonance of the metal-insulator-metal (MIM) optical resonator and the inherent loss of tungsten. The impedance of the absorber is well matched with free space. Furthermore, the optimized absorber shows great potential in solar thermophotovoltaic applications that require wide-angle polarization-independent ultra-broadband light response characteristics.

A novel vortex flocculation reactor for efficient water treatment: Kinetic modeling and experimental verification

We designed a novel vortex flocculation reactor with column-cone-column structure by adding vortex generators to form the micro-vortices to improve the flocculation efficiency. The vortex generators, actually wedge-shaped baffles, act as turbulence components to generate large flow resistance, thus reducing the size of the vortex to approach that of the floc. The inverted cone-cone-inverted cone structure in small-vortex flow flocculation zone prompts the fluid to form boundary layer dissociation phenomenon, thereby enhancing the relative motion of floc particles. The numerical simulation results of flow field structure indicated that the fluid presented a multiphase flow of “swirl flow-vortex flow-plug flow”; hence the fluid characteristic changed step by step. Moreover, the multistage velocity gradient of the fluid in different flow layers enhanced the probability of floc particles collision, thus strengthening the flocculation. Then the lab-scale vortex flocculation reactor was manufactured to conduct flocculation tests. The results revealed that the vortex flocculation reactor took the reaction time of only 10 s to achieve a superior chemical oxygen demand removal rate of 93.7%. The vortex flocculation reactor, based on the multiphase flow and multistage velocity gradient reinforcement flocculation strategy, can offer an effective way to improve the flocculation efficiency.

Assessment of the design influence of the vortex generator on the performance of the solar vortex engine

• Three different design configurations of the solar vortex engine are evaluated. • CFD simulation approach is used for the evaluation of the three SVE designs. • Vortex generator with transparent cover operates as a heat trap and enhances vortex. • Cone structure increases the air vorticity, temperature and buoyancy forces in the vortex. • A hole in the engine’s base produces high velocity with the least vortex stability. The vortex generator is an essential segment in the solar vortex engine (SVE). Its design could be modified to strengthen the generated air vortex and enhance the system's performance. This work aims to investigate the vortex generator design's influence on the SVE's performance. Three different vortex generator designs are studied employing three-dimensional CFD simulations. Experimental investigations have been utilised to support the CFD simulation. The considered designs are Case-1: basic design, Case-2: with a cone structure inside the arena and Case-3: with a hole at the bottom of the vortex generator. The cone structure increases the heat transfer area, increasing the vortex generator's air temperature and producing higher buoyancy forces for the flow field. Cases 1 and 2 produced the best vortex stability as the air vortex shape, pressure and vorticity distributions are uniform. The highest static pressure drop is achieved with the basic design. The basic design, Case-1, produces 1.0% and 5.0% higher static pressure drop than Case-2 and Case-3, respectively. The lower hole affected the air vortex stability negatively.

One step reactive ion etching of black germanium conical nanostructures: Ultra-wide solar spectral absorption, finite element simulation, super hydrophilicity, photothermal conversion

We report a reactive ion etching process based on SF 6 –CHF 3 , which can prepare black germanium at low RF power and normal temperature. The absorption of black germanium in the spectral range of 300–1750 nm is greater than 99%. Spectral selectivity optimization allows nano tapered germanium to absorb nearly 98.1% of solar radiation. This nanostructure is uniform in a large area and also supports patterning design for the application in related fields such as photothermal imaging. Here, we discuss the effect of SF 6 and CHF 3 plasma concentrations on the progress of chemical reactions on the germanium surface and their essential role in forming tapered nanostructures. We observe its surface plasmon resonance by finite-difference time-domain way. Finally evaluate its feasibility in devices by photothermal conversion and water droplet evaporation experiments. The proposal of this work provides an available method for semiconductor micromachining, and also provides experimental and theoretical support for the efficient thermal utilization of solar energy. In conclusion, we analyzed the mechanism of one-step etching of highly absorbing tapered nanostructures by SF 6 –CHF 3 -based RIE process by SEM and XPS. The germanium surface tends to form particles at the initial stage of etching, and due to the very high concentration of negative ions in the SF 6 plasma, these particles gradually form GeS x clusters. The germanium fluoride is mainly present at the surface of the germanium sample, while the germanium sulfide extends to a greater depth, so these clusters are not effective in preventing etching. The CHF 3 plasma greatly reduces the negative ion concentration and reduces the tendency of particle formation in favor of smoother GeS x and C x H z F y layers, which are very favorable for the formation of nanostructures. Aggregation of the germanium sidewalls decreases with depth, so tapered nanostructures are gradually formed with etch time. In addition, over-etching leads to additional carbon deposition, which is mainly composed of fluorocarbon polymers (C x H y F z ) formed from the decomposition products of CHF 3 . The wide spatial distribution of the sizes of the tapered nanostructures makes the absorptivity of black germanium more than 99% in the 300–1750 nm spectral range. As an indirect bandgap semiconductor, the absorption of photons makes electrons excited from the valence band to the conduction band with a great probability of releasing energy to the lattice, converting it into phonons, and turning it into heat energy. The cone-shaped nanostructured germanium can be heated to 69.4 °C in 20 min, and the heating rate can reach 7.98 °C/min in 300 s. The conical nanostructure modification makes germanium exhibit superhydrophilicity, and the water droplets make wet contact with germanium and fill the grooves on the surface of the nanostructures, making it capable of completely evaporating 0.05 ml droplets within 101 s. It is very competitive in heating and evaporation of water droplets.a) Black germanium photos, and SEM images of nano cones; b) Comparison of absorptivity between black germanium and polished germanium; c) Infrared image of graphic germanium wafer; (the letter part is nano cone structure, and the rest is polished germanium) d) With the increase of etching time, the temperature change curve of the sample under simulated sunlight irradiation (1 solar intensity). • Disordered nanocrystalline germanium was prepared by metal induced one-step self masked RIE. • The absorbance in the 300-1750 nm regions was higher than 98%. • The structure has excellent optical properties due to light trapping effect and plasma resonance. • The excellent optical properties and super hydrophilic properties make the structure have excellent photothermal properties.

Dual-Scale Textured Broadband Si-Based Light Absorber

Various antireflective structures and methods are proposed to solve the optical loss of Si-based absorber devices. Dual-scale structures have received more concern from researchers in recent years. In this study, the finite difference time domain (FDTD) method is employed to investigate deeply the dependence of optical response on the geometric shape and size of structures. The micron cone shows lower reflectivity than other micron structures. Additionally, the lowest reflectivity region moves with the increasing height size of the cone structure. We proposed creatively a nanoripple-cone structure that maintains low reflectivity properties under varying incident angles whether in the visible region or the near-infrared region. Furthermore, the lower reflectivity is obtained with increasing micron cone and decreasing nanoripple. Finally, the dual-scale nanoripple-cone is fabricated directly and cost-effectively by a femtosecond laser instead of a two-step texture-on-texture way. The measured result shows that the high absorption above 98% extends to the mid-infrared region. This study provides directions for the fabrication of wideband Si-based absorber devices to reduce reflectivity, which exhibits a wide application potential and promotes the evolution of multi-laser processing.

Experimental investigation on the thermal performance of a novel thermosyphon heat pipe with truncated cone for heat recovery systems

A Thermosyphon Heat Pipe (THP) is an effective heat transfer device primarily deployed in the field of energy conversion and heat recovery systems. Among the various working fluids, deionized (DI) water exerts higher latent heat of vaporization making it suitable for efficient performance testing of THPs. The novel design of a THP in a non-uniform geometry-based truncated cone structure is suggested to recover waste heat from various sources. A detailed parametric study is carried out on the non-uniform structure THPs to analyze the thermal performance. This study examines the thermal performance of the Convergent Truncated Cone (CTC) THP and the effect of modifying the influencing factors of its diameter, length, heat flux, inclinations, and mass flow rate. Based on the experimental results, it is seen that the CTC helps to reduce the overall thermal resistance by 48.94 %, 35.15 %, and 34.69 % for 90°, 60°, and 30° inclinations, respectively. Similarly, the temperature difference between the evaporator and the adiabatic sections shows an average thermal resistance reduction of 36.38 %, 30.3 %, and 55.82 % under the same operating conditions. Additionally, the results of the current investigation indicate that there are two positive outcomes for the supplied heat input range of 30–300 W. It is observed that the THP is 2.54 % more efficient than a conventional THP at an angle of 90° for a heat input range of 30–150 W. The maximum augmentation of thermal efficiency is noted to be 4.12 % and is attained at 30° inclination for the input range of 180–300 W.

Mapping cone of k-entanglement breaking maps

In \cite{CMW19}, the authors introduced $k$-entanglement breaking linear maps to understand the entanglement breaking property of completely positive maps on taking composition. In this article, we do a systematic study of $k$-entanglement breaking maps. We prove many equivalent conditions for a $k$-positive linear map to be $k$-entanglement breaking, thereby study the mapping cone structure of $k$-entanglement breaking maps. We discuss examples of $k$-entanglement breaking maps and some of their significance. As an application of our study, we characterize completely positive maps that reduce Schmidt number on taking composition with another completely positive map.

Structure optimization of Spindt-type emitter fabricated by triode high power pulsed magnetron sputtering

Spindt-type emitters were fabricated with cavities made of Al/Mo/SiO2 using the triode high power pulsed magnetron sputtering method. We explored the process parameters (gas pressure and voltage of the additional cap electrode) to optimize the sharpness of the emitter shape. We found that the intermediate pressure and voltage were suited to obtain sharp emitters. Further, we elucidated the crucial effect of the cavity dimensions, such as the cavity depth and hole diameter in the cavity ceiling, on the emitter shape. At a cavity depth of 480 nm, the aspect ratio (AR) of the emitter increased monotonously with an increase in the hole diameter. With a large hole diameter (900 nm) and even shallower cavity (380 nm depth), we attempted to reoptimize the process parameters. Consequently, a very sharp emitter cone structure with an AR exceeding 1.3 was obtained. The cap voltage that produced the optimum AR was found to decrease for the larger-hole and shallower-depth cavities. Finally, the applicability of the process for preparing a working emitter is discussed.

Ultrathin polyamide membrane tailored by mono-(6-ethanediamine-6-deoxy)-β-cyclodextrin for CO2 separation

The fabrication of membranes with high CO2 separation performances is an urgent need for clean energy supply and environmental remediation. In this work, the mono-(6-ethanediamine-6-deoxy)-β-cyclodextrin (MEDβCD) fillers are intentionally constructed to tailor the polyamide membranes (MEDβCD/PA) by interfacial polymerization (IP) for CO2 separation. The unique hollow cone structure of MEDβCD alleviates the vigorous IP process, generating a thinner separation layer with larger chain d-spacing. Additionally, the introduction of CO2-philic groups from MEDβCD can facilitate CO2 molecule transport. The fabricated MEDβCD/PA membrane exhibits remarkable increases in CO2 permeance, CO2/H2, CO2/N2, and CO2/CH4 selectivities, which are 39, 17, 11, and 25 times higher than those of the pure PA membrane, respectively. This work provides a straightforward route to fabricate composite membranes tailored by macrocyclic molecules with cone structures and other cavitands for gas separation.

Foveal Cone Structure in Patients With Blue Cone Monochromacy.

Blue cone monochromacy (BCM) is a rare inherited cone disorder in which both long- (L-) and middle- (M-) wavelength sensitive cone classes are either impaired or nonfunctional. Assessing genotype-phenotype relationships in BCM can improve our understanding of retinal development in the absence of functional L- and M-cones. Here we examined foveal cone structure in patients with genetically-confirmed BCM, using adaptive optics scanning light ophthalmoscopy (AOSLO). Twenty-three male patients (aged 6-75 years) with genetically-confirmed BCM were recruited for high-resolution imaging. Eight patients had a deletion of the locus control region (LCR), and 15 had a missense mutation-Cys203Arg-affecting the first two genes in the opsin gene array. Foveal cone structure was assessed using confocal and non-confocal split-detection AOSLO across a 300 × 300 µm area, centered on the location of peak cell density. Only one of eight patients with LCR deletions and 10 of 15 patients with Cys203Arg mutations had analyzable images. Mean total cone density for Cys203Arg patients was 16,664 ± 11,513 cones/mm2 (n = 10), which is, on average, around 40% of normal. Waveguiding cone density was 2073 ± 963 cones/mm2 (n = 9), which was consistent with published histological estimates of S-cone density in the normal eye. The one patient with an LCR deletion had a total cone density of 10,246 cones/mm2 and waveguiding density of 1535 cones/mm2. Our results show that BCM patients with LCR deletions and Cys203Arg mutations have a population of non-waveguiding photoreceptors, although the spectral identity and level of function remain unknown.

ITO/Si/ITO semi-cone-shell chiral complexes on silicon nanocones with broadband circular dichroism in the mid-infrared wavelength.

This paper proposed ITO/Si/ITO semi-cone-shell chiral complexes on silicon nanocones with broadband CD in the mid-infrared band. The experimental results show that when the deposition angle θ = 45°, the first ITO deposition of ta = 100 nm, the second Si deposition of tb = 200 nm with the azimuth angle unchanged, and the third ITO deposition of tc = 200 nm after rotating the azimuth angle of 60°, the prepared chiral structure has a broadband CD response in the mid-infrared band of 2.5-4 µm. The broadband CD effect is produced by the internal resonance of the three-dimensional open cavity. The cone structure can be regarded as a plurality of planar open resonant rings with different diameters, and these rings resonate at different wavelengths. The experimental results also show that the proposed chiral ITO structure exhibits a better broadband CD response than that of the structure composed of traditional metal Ag. Such a chiral structure provides a new method for the design of CD devices in the mid-infrared band.

Degeneration of 3-dimensional hyperbolic cone structures with decreasing cone angles

For 3-dimensional hyperbolic cone structures with cone angles θ \theta , local rigidity is known for 0 ≤ θ ≤ 2 π 0 \leq \theta \leq 2\pi , but global rigidity is known only for 0 ≤ θ ≤ π 0 \leq \theta \leq \pi . The proof of the global rigidity by Kojima is based on the fact that hyperbolic cone structures with cone angles at most π \pi do not degenerate in deformations decreasing cone angles to zero. In this paper, we give an example of a degeneration of hyperbolic cone structures with decreasing cone angles less than 2 π 2\pi . These cone structures are constructed on a certain alternating link in the thickened torus by gluing four copies of a certain polyhedron. For this construction, we explicitly describe the isometry types on such a hyperbolic polyhedron.