Circular Truncated Cone Research Articles

Self-assembly Ti3C2Tx MXene/ZnCo2O4@ZnO heterostructure with Schottky junction for regulating BIEF to enhance microwave absorption

Currently, heterogenous interface engineering on absorbers is shown to boost the electromagnetic wave absorption (EMA) performance effectively. However, challenges remain in investigating the mechanisms by studying heterojunctions between heterogeneous interfaces. Herein, a self-assembly Ti3C2Tx MXene/ZnCo2O4@ZnO (MZCZ) heterostructure with abundant Schottky heterogenous interfaces generating a controllable built-interface electric field (BIEF) effect is fabricated to achieve exceptional EMA ability. The formative BIEF between the unbalanced distribution charges promotes charge separation and migration, increasing polarization loss. Fortunately, the obtained MZCZ1 exhibits the reflection loss (RL) value of −69.78 dB under the ultralow thickness of 1.501 mm and the optimal minimum RL (RLmin) value of −74.41 dB, respectively. The excellent performance can be ascribed to the multiple polarization loss, conduction loss, natural resonance, and exchange resonance characteristics. Moreover, by the Computer Simulation Technology (CST) software, the designed circular cone and circular truncated cone periodicity structure with the MZCZ1 absorber both exhibit a super-wide effective absorption bandwidth (EAB) covering the whole C, X, and Ku band. This study can pioneer a novel approach to developing functional EMA materials and provide a valuable direction for further study of EMA mechanisms at heterogeneous interfaces.

Ultra-broadband terahertz metamaterial absorber based on a hollow vanadium dioxide circular-truncated cone resonator

Terahertz (THz) broadband metamaterial absorbers with high absorptivity have been of great interest due to their potential applications. However, their limited bandwidth severely hinders their further development and wide applications. To address this issue and achieve ultra-broadband and strong absorption properties at THz frequencies, we present an ultra-broadband THz perfect metamaterial absorber using a hollow vanadium dioxide (VO2) circular-truncated cone array and a VO2 film supported by an Au ground plane. Simulated results show that the absorptivity of the absorber reaches more than 90% in the frequency range of 0.31–10 THz at normal incidence with a relative absorption bandwidth of 188%. At the same time, the average absorptivity in the frequency range reaches 99.2%. The physical origin of broadband perfect absorption has been elucidated by impedance matching theory and wave interference theory, respectively. The electric field distribution is further discussed to explore the physical mechanism of this absorber. Additionally, it also has the characteristics of polarization insensitivity and wide incidence angle stability. The proposed absorber can have many promising applications in the THz region, such as thermal imaging, thermal detection, and cloaking.

Experimental and numerical investigations on jet impingement heat transfer with different nozzles and enhanced surfaces

Hot air anti-icing systems are essential in aviation engines, preventing ice formation on inlet components during high-altitude flights. A critical factor in enhancing these systems' effectiveness is the application of jet impingement technology. In order to further enhance the performance of jet impingement heat transfer in this application scenario, the research assesses the impact of nozzle type and surface protrusion type on the anti-icing system's performance by integrating experimental and numerical approaches. Findings reveal that circular nozzles outperform swirl and satellite nozzles in heat transfer efficiency in the application of aviation anti-icing system with high jet Reynolds number. The average Nusselt number, indicative of heat transfer rate, can be increased by up to 10.54 % with protrusions. For surface protrusions, sequentially-arranged cylinder protrusions are more effective at Reynolds numbers between 8000 and 48000. Cross-arranged circular truncated cone protrusions do better at higher Reynolds numbers, from 48000 to 80000 which is the range relevant to the hot air anti-icing system. Comparing concave and flat plates with the same type of protrusions, the former shows superior heat transfer performance. The study also establishes correlations for convective heat transfer coefficients and attenuation coefficients on the concave plate with sequentially-arranged cylinder protrusions. By applying the cross-arranged circular truncated cone protrusions, which proved to be the best in our experiments, to the engine nacelle's anti-icing section, the numerical results indicate a 6.21 % increase in anti-icing thermal efficiency and an 8.31 % decrease in air bleed capacity, all under the same heat transfer conditions. The use of protrusion structures in the anti-icing system of an engine nacelle boosts thermal efficiency, lowers air bleed capacity, and reduces the fuel penalty, thereby optimizing overall performance.

From intrinsic magnetic-dielectric double loss to circular truncated cone array structural absorber: Dual strategies for ultra-broadband microwave absorption performances

Electromagnetic absorbers with wide effective absorption bandwidth are urgently sought for the cutting-edge electronic application. However, constrained by Kramers-Kronig relationship, expanding effective absorption bandwidth remains a huge challenge for traditional magnetic-dielectric double loss absorbers. In this work, dual strategies are proposed to prepare circular truncated cone array structural absorber for achieving ultra-broadband microwave absorption. Magnetic-dielectric loss components is fabricated with HNO3-oxided FeSiAl flakes/multi-wall carbon nanotubes composites for manipulating permittivity and permeability, which can realize effective absorption bandwidth of 4.0 GHz and optimal reflection loss of −45.49 dB with thickness of 1.3 mm. Sub-wavelength effect and structural design are applied for circular truncated cone array to reach broadband absorption via quarter-wave cancellation, multiple resonance at different thickness and coupling effect of structure and loss composites. The experimental results are in good agreement with the simulation and effective absorption bandwidth of 35 GHz in 5–40 GHz and minimum reflectivity of −38.25 dB at 10.26 GHz are realized, which demonstrates the effectiveness of microscale component and macroscopic structural design. This work proposes a rational route for designing high-efficiency microwave absorbers with both strong and ultra-broadband features.

High performance flexible PVDF film pressure sensor fabricated by femtosecond laser

Flexible pressure sensors have shown great potential for applications in detection and medical fields due to their unique piezoelectricity and high sensitivity. In this paper, micro-nano-perforated structures with different periods and diameters are fabricated on the polyester (PET) films by femtosecond laser direct writing (FsLDW), and then the perforated structures are embossed on polyvinylidene fluoride (PVDF) films to form sensors with circular truncated cone (CTC) structures. The effect of period and diameter on the sensitivity of the sensor is studied numerically and experimentally. The results show that the high sensitivity of 8.98 mV/KPa can be achieved in a PVDF film pressure sensor with a period of 50 μm and a diameter of 30 μm, which is about 10.9 times that of the structureless sensor. This work not only provide a fast fabricated method for the pressure sensor based on the femtosecond laser and hot embossing, but also has potential applications in the detection of the micro-signals.

Machine learning-enabled design of metasurface based near-perfect daytime radiative cooler

Global warming and the energy crisis are major challenges facing the world today. Traditional structural design methods for radiative coolers are no longer sufficient to meet the increasingly demanding realities of these challenges. Simplifying the design process and optimizing structural parameters have become pressing issues. In this paper, a new optimization method for metasurface based daytime radiative cooler is proposed, which utilizes the K-nearest neighbor (KNN) algorithm in machine learning (ML) to construct regression models and optimize designs for two structures of quadrangular prismatic metasurface (QPM) and circular truncated cone metasurface (CTCM). The results show that the atmospheric window emissivity (mainly in the 8–13 μm range) of QPM and CTCM reaches 96.98% and 97.81%, respectively, while the absorptivity/emissivity in solar spectrum is only 9.34% and 7.21%. The mean absolute percentage error (MAPE) of the KNN regression model is only 0.74% and 0.29%, which is significantly better than other classical ML algorithms. Meanwhile, the designed structures achieve net cooling power of 63.48 W/m2 and 90.13 W/m2 at ambient temperature for both QPM and CTCM. This systematic study provides a novel approach for the design of daytime radiative coolers.

Effects of Three-Dimensional Circular Truncated Cone Microstructures on the Performance of Flexible Pressure Sensors.

Three-dimensional microstructures play a key role in the fabrication of flexible electronic products. However, the development of flexible electronics is limited in further applications due to low positioning accuracy, the complex process, and low production efficiency. In this study, a novel method for fabricating three-dimensional circular truncated cone microstructures via low-frequency ultrasonic resonance printing is proposed. Simultaneously, to simplify the manufacturing process of flexible sensors, the microstructure and printed interdigital electrodes were fabricated into an integrated structure, and a flexible pressure sensor with microstructures was fabricated. Additionally, the effects of flexible pressure sensors with and without microstructures on performance were studied. The results show that the overall performance of the designed sensor with microstructures could be effectively improved by 69%. Moreover, the sensitivity of the flexible pressure sensor with microstructures was 0.042 kPa−1 in the working range of pressure from 2.5 to 10 kPa, and the sensitivity was as low as 0.013 kPa−1 within the pressure range of 10 to 30 kPa. Meanwhile, the sensor showed a fast response time, which was 112 ms. The stability remained good after the 100 cycles of testing. The performance was better than that of the flexible sensor fabricated by the traditional inverted mold method. This lays a foundation for the development of flexible electronic technology in the future.

Evolution of texture distribution in thickness direction of aluminum sheet in metal spinning

We evaluated the texture distribution in the thickness direction of the spun workpieces and clarified the mechanism of the change in the crystal orientation of the texture during metal spinning. Blank aluminum disks with a thickness of 1.44 mm were deformed into circular truncated cone cups by under-, true shear, and over-spinning and into cylindrical cups by 13 passes of conventional spinning. Crystal orientation analysis using electron backscatter diffraction revealed that the calculations of the orientation densities for small Miller indices could lead to a systematic evaluation of high intensity texture. The orientation density of Cu {121}<11¯1> decreased or that of B {110}<11¯2> increased on the roller side of the shear-spun part, of the workpieces formed by shear spinning, and on the roller side of the wall part and on the mandrel side of the open-edge part, of the workpieces formed by conventional spinning. The cosine similarity and Euclidean distance showed that the texture distributions obtained by shear spinning and that of the wall part obtained by conventional spinning were similar. Based on the stress state and preferred crystal orientation in deep drawing, the mechanism of the change in crystal orientation during spinning were described. The density of the texture with {110} (corresponding to B in this study) parallel to a disk plane increased when tensile stress was applied in the circumferential direction, contrarily, when compressive stress was applied in a similar fashion the density of the texture with {112} (corresponding to Cu) parallel to the disk plane increased.

A Structured Phase Change Material with Controllable Thermoconductive Highways Enables Unparalleled Electricity via Solar‐Thermal‐Electric Conversion

AbstractA solar thermoelectric generator (STEG) that harvests solar energy and converts it into electricity based on the fundamentals of the Seebeck effect is a promising alternative to photovoltaic technologies. The combination of a phase change material (PCM) with STEG further enables stable and durable energy output despite the variations of solar radiation flux. However, the widespread promotion of STEG is still impeded by its restricted output electricity (&lt;50 W m−2), attributed to the undesirable thermal management in PCMs. Herein, an ingenious phase change composite, with the typical conformation of circular truncated cone and embedded with the actinomorphic arrangement of polybenzobisoxazole fibers, is tailored by a mold processing strategy. The fibrous crystals in organic fibers offer temperature‐resistance thermal highways during the charging/discharging processes, while their actinomorphic configuration facilitates a controllable thermo‐conductive behavior. These structural features render concentrated thermal energy to be efficiently stored in the PCM and maximally discharged into the thermoelectric system. A record‐breaking power density as high as 198.70 W m−2 can be achieved in this powerful STEG via real‐environment solar‐thermal‐electric conversion, a value comparable to that of some commercial photovoltaic devices. This work opens up opportunities for durable and giant electricity supply from clean solar energy during real‐time STEG applications.

Study on Critical Hydraulic Gradient Theory of Flow Soil Failure in Cohesive Soil Foundation

The current formula of critical hydraulic gradient is not adapted to solve critical hydraulic gradient of cohesive soil. Assume that the seepage failure mode of the cohesive soil foundation was cylindrical or inverted circular truncated cone, based on the calculation formula of the critical hydraulic gradient of Terzaghi, the analytical formula of the critical hydraulic gradient considering the influence of the shear strength of the soil was derived. Then, the seepage failure process of the clay layer was simulated numerically, and the effects of the clay layer thickness, failure radius, and shear strength indexes on the critical hydraulic slope were analyzed. The comparison results show that the numerical test results are in good agreement with the calculated results of the new formula. In addition, the critical hydraulic gradient of sandy loam and loess under different working conditions was studied severally by a self-made permeation failure instrument. The results show that the critical hydraulic gradient decreases with the increase of soil thickness and failure radius, and the maximum error between the test and the corresponding formula results is no more than 16%.

Voltage response of three ionic polymer pressure sensors based on ion migration at different ambient humidities

Besides bending sensor, ionic polymer materials can work as pressure sensor based on ion migration and show more potential in engineering application. To explore a better ionic polymer material for pressure sensor, three typical ionic polymer materials, Nafion, poly(vinylidene fluoride)/ionic liquid (IL/PVDF) composite, thermoplastic polyurethane/ionic liquid (IL/TPU) composite, were selected to comparatively investigate the sensing properties under an applied pressure. Ionic polymer pressure sensors with circular truncated cone structure were developed by casting method. Their voltage responses were evaluated by a self-made test platform under a series of step force. The voltage sensitivity and the stability were obtained by performing the tests at different ambient humidity levels. The sensitivity of Nafion sensor was influenced by the ambient humidity heavily, which increased from 8.97 mV N−1 (28.17 mV MPa−1) to 31.11 mV N−1 (97.69 mV MPa−1) as the relative humidity (RH) increasing from 30% RH to 90% RH. In comparison, the voltage responses of IL/TPU sensor and IL/PVDF sensor were rarely influenced by the humidity because of the stability of IL, but strongly related to the content of IL. As the IL content increasing from 30 wt.% to 50 wt.%, the sensitivity of IL/TPU sensor increased from 5.65 mV N−1 (17.74 mV MPa−1) to 16.55 mV N−1 (51.97 mV MPa−1), that of IL/PVDF sensor increased from 14.12 mV N−1 (44.33 mV MPa−1) to 32.23 mV N−1 (101.20 mV MPa−1) monotonously. The underlying mechanisms were revealed based on water exchange in air and ion transport theory qualitatively. IL/PVDF sensor with 50 wt.% IL content shows the best sensing performance in air and is promising for practical application.

Three-junction tandem photovoltaic cell for a wide temperature range based on a multilayer circular truncated cone metamaterial emitter

To improve the conversion efficiency of thermophotovoltaic devices, we designed a thermophotovoltaic system based on an InAs/InGaAsSb/GaSb three-junction tandem cell. The tandem cell can recover photons in the wavelength range of 200–3650 nm and therefore enhance the output power of the system. To further improve system performance, we designed a multilayer circular truncated cone metamaterial emitter matching the tandem cell. Existing TPV systems based on multi-junction tandem PV cells can achieve conversion efficiencies of 33.3%–41%, while the thermophotovoltaic system coupled with the multilayer circular truncated cone metamaterial can recover more photons of 1.44 mol/(m2·s) and achieve a higher conversion efficiency of 52.8% at 1773 K. The thermophotovoltaic system designed here demonstrates an extremely high energy conversion efficiency and has good application prospects.

Broadband and high gain dielectric‐rod end‐fire antenna fed by a tapered ridge waveguide for K/Ka bands applications

In this study, a broadband and high gain dielectric-rod end-fire antenna are proposed for applications on both the K and Ka bands. By employing the double-ridged waveguide (DRW) feeding structure which is composed of a coaxial line to tapered DRW transition, a parabolic tapered DRW, and a parabolic-tapered flared parallel waveguide section, the impedance bandwidth of this proposed antenna is broadened to 84.5%. The dielectric-rod with the double circular truncated cone structure acted as the main radiator of the proposed antenna is adopted to achieve higher gains and lower side-lobe levels as compared to the traditional circular cone dielectric-rod, while the four-wedges structure inserted in the waveguide is developed as the matching section of the dielectric-rod to further improve the impedance matching. The measured results show that this antenna can be operated in 17.9–44.1 GHz, and the measured gain changes from 9.9 to 15.5 dBi. Moreover, the radiation patterns are demonstrated with observed end-fire characteristic in the overall operating band.

Gouy and spatial-curvature-induced phase shifts of light in two-dimensional curved space

Gouy phase is the axial phase anomaly of converging light waves discovered over one century ago, and is so far widely studied in various systems. In this work, we have theoretically calculated Gouy phase of light beams in both paraxial and nonparaxial regime on two-dimensional curved surface by generalizing angular spectrum method. We find that curvature of surface will also introduce an extra phase shift, which is named as spatial curvature-induced (SCI) phase. The behaviors of both phase shifts are illustrated on two typical surfaces of revolution, circular truncated cone and spherical surface. Gouy phase evolves slower on surface with greater spatial curvature on circular truncated cone, which is however opposite on spherical surface, while SCI phase evolves faster with curvature on both surfaces. On circular truncated cone, both phase shifts approach to a limit value along propagation, which does not happen on spherical surface due to the existence of singularity on the pole. An interpretation is presented to explain this peculiar phenomenon. Finally we also provide the analytical expression of paraxial Gaussian beam on general SORs. By comparing the result with the exact method we find the analytical expression is valid under the approximation that beam waist and scale of surface are beyond order of wavelength. We expect this work will enhance the comprehension about the behavior of electromagnetic wave in curved space, and further contribute to the study of general relativity phenomena in laboratory.

Absorption Enhancement of Ultrathin Crystalline Silicon Solar Cells with Dielectric Si3N4 Nanostructures**Project supported by National Science Foundation of China (NSFC) (U1765105, 61604087); The Hebei Provincial Young Top-notch Talent Support Program (BJRC2013); Alexander von Humboldt-Stiftung (AUS-1141939-HFST-E)

A design of ultrathin crystalline silicon solar cell with Si3N4 circular truncated cone holes (CTCs) arrays on the top is proposed. In this article, we perform an optical simulation of the structure. The finite-difference time-domain method is used to calculate the optical absorption of different periods, radius of top and bottom circles and depth of Si3N4 CTCs. The short-circuit current density generated by the optimized cells (30.17 mA/cm2) is 32.44% more than the value gained by control group (with flat Si3N4). Then adding a layer of back silver to allow us to better analyze optical absorption. Later, we simulate the optimization of the same configuration of different silicon thicknesses and find that our structure does enhance the light absorption. This work uses a combined path towards achieving higher photocurrent ultrathin crystalline silicon solar cells by constructing the texture of anti-reflection coating.

Modeling of Oxidation Process of Coal Tar Pitch in Rotating Kilns

In this paper, a three‐dimensional numerical model has been developed to study the process of oxidative weight increment of coal tar pitch in a rotating kiln. Based on the two‐fluid method, the gas phase is modeled by realizable k‐ε turbulent model and the solid phase is modeled by kinetic theory of granular flow. The dense gas‐solid flow, heat transfer, and oxidation reaction for the bed and freeboard regions are simultaneously solved. The model is applied to a rotating kiln with a cylinder of 0.75 m length and 0.4 m diameter in the front and circular truncated cone on exit side. The detailed verification of model is firstly performed by comparisons with the available experimental data. The particle velocity profiles, product gas compositions, and various forms of solid motion in rotary kilns are contrastively analyzed. Afterwards, simulations are carried out to obtain the primary hydrodynamic and reactive characteristics in the rotary kiln. At the steady state, the particle velocity peak is located at the active layer surface, while the velocity has the opposite direction in the passive layer. The bed region generally has a higher temperature than the freeboard due to the large thermal capacity. The concentrations of product gas compositions, such as CO2, CO, and CH4, and solid product of oxidation, increase sharply near the surface and then keep on the steady values inside the bed. The effects of rotational speed of the rotary kiln and flow rate of air are also studied. The increasing rotational speed significantly accelerates the particle movement of the active layer and raises the final oxidative yield of coal pitch spheres. By contrast, increasing the flow rate of air has little effect on the particle motion and oxidation yield of coal pitch.

Structures and Molecular Composition of Schmidt-Lanterman Incisures.

Schmidt-Lanterman incisure (SLI) is a circular-truncated cone shape in the myelin internode that is a specific feature of myelinated nerve fibers formed in Schwann cells in the peripheral nervous system (PNS). The SLI circular-truncated cones elongate like spring at the narrow sites of beaded appearance nerve fibers under the stretched condition. In this chapter, we demonstrate various molecular complexes in SLI, and especially focus on membrane skeleton, protein 4.1G-membrane protein palmitoylated 6 (MPP6)-cell adhesion molecule 4 (CADM4). 4.1G was essential for the molecular targeting of MPP6 and CADM4 in SLI. Motor activity and myelin ultrastructures were abnormal in 4.1G-deficient mice, indicating the 4.1G function as a signal for proper formation of myelin in PNS. Thus, SLI probably has potential roles in the regulation of adhesion and signal transduction as well as in structural stability in Schwann cell myelin formation.

Effects of different thermal storage tank structures on temperature stratification and thermal efficiency during charging

In solar water heating systems, the structures of thermal storage devices have played essential roles in the improvement of thermal charging efficiency and system performance. This article was focused on the optimization of thermal storage tanks, as well as the influences of thermal storage tank structures on the temperature stratification and heat storage capacity. The thermal characteristics of three shapes of thermal storage tanks were investigated and analyzed through CFD (Computational Fluid Dynamics) simulation, which were: (a) Cylindrical tank, (b) Circular truncated cone tank and (c) Spherical tank. It was observed that among the three thermal storage tanks, the spherical tank had significant symmetrical temperature stratification, while the truncated circular cone tank had the best temperature stratification and thermal charging efficiency. For the circular truncated cone tank, it was found that when the radius ratio (n) of the water tank was 0.554, it could approach the excellent characteristics of temperature stratification and thermal storage performance. This study could provide a theoretical basis for the structure optimization of the solar energy storage devices, as well as proving to be beneficial to the enhancement of thermal charging efficiency.

Characteristics of nanosecond pulse dielectric surface flashover in high pressure SF6

Surface electrical insulation performance is an important issue in pulse power devices. In order to investigate the surface flashover characteristics in an environment of high pressure SF6, a flashover experiment platform was established with nanosecond pulse voltage supply. The flashover characteristics of polymethylmethacrylate (PMMA) specimens with circular truncated cone shapes were subsequently determined under incremental SF 6 pressures from 0.2 to 1.0 MPa. As the angle of cone increased, the flashover voltage (FV) rose under low pressure condition, but fell at first and then rose at high pressure. The surface length and the field nonuniform factor were the main influences of FV with angle. In addition, the FV rose linearly at first and then reached its maximum when gas pressure increased, and it was easier to reach the maximum when the field nonuniform factor was higher. A high speed camera was also applied to get the photos at different period of flashover, and the luminous processes of flashover along different specimens were discussed in particle perspective.

Low‐cost metamaterial absorber using three‐dimensional circular truncated cone

AbstractIn this article, we propose a low‐cost three‐dimensional (3D) printed metamaterial absorber. The proposed metamaterial consists of a periodic structure of circular truncated cones. The dielectric materials supporting the circular truncated cone are made from a poly(lactic acid) filament using the 3D printer. The conductor of the circular truncated cone is developed by spraying silver‐coated copper. The performance of the proposed absorber is numerically and experimentally investigated. The simulated and measured absorptivity are 91% and 95% at 10.8 and 10.81 GHz, respectively. As a result of the 3D printing and silver spray coating processes, the proposed absorber can be easily fabricated at a low cost.