Asymmetric Elements Research Articles

Self‐Decoupled Four/Six‐Element MIMO Antenna Designed With Manufactured Coconut Husk–Based Substrate and Its Measured Dielectric Properties

ABSTRACTThis paper presents a very low–profile self‐decoupled four/six‐element multiple‐input multiple‐output (MIMO) antenna. Dielectric properties as measured of a manufactured biomass substrate are used to design the antenna. On the antenna's top surface, two types of asymmetric antenna elements are used. Among the six elements—two pairs are symmetric, and the third pair is slightly different with respect to the first two pairs in dimension. The antenna covers the impedance bandwidth of 5.14 to 7.15 GHz. It confirms the WLAN (5.15–5.85 GHz) and C‐band uplink (5.925–6.425 GHz) application bands with greater than 20 dB of port isolation without exploring any additional decoupling network. A prototype of the assembly is fabricated and necessary parameters are measured. Very low correlations between the antenna elements are found. The evaluated diversity performances and radiation characteristics are good enough to recognize the proposed MIMO structure.

Dual-band high-Q near-perfect absorption by tilted Si-assisted metasurfaces.

All-dielectric metasurface perfect absorbers (MPAs) based on quasibound states in the continuum (QBICs) play a crucial role in optical and photonic devices as they can excite high-Q resonances. These structures require adding back reflectors or placing at least two asymmetric elements in each unit to break the absorption limit of 50%, which will increase the design complexity. In this work, we propose a high-Q monolayer MPA (MMPA) composed of a tilted Si nanocube array. By tuning the tilted angle of the nanocube, dual-QBIC modes at two different wavelengths are excited, which corresponds to magnetic quadrupole (MQ) and toroidal dipole (TD) modes, respectively. The high-reflection but low-Q magnetic dipole (MD) background mode excited by such a dual-band structure can decrease the radiative loss of transmission of MQ and TD modes, enabling the structure to break the absorption limit of 50%. The maximum absorption achieves 94% simultaneously at the wavelength of 933 and 961 nm, with the Q factors of 759 and 986, respectively. Our work provides a simple paradigm for designing dual-band high-Q MMPAs, which would greatly expand their range of applications, such as multiplexed optical nanodevices.

Mixing performance in an asymmetrical non-twin kneading element channel

Abstract The kneading elements play a crucial role in the distributive and dispersive mixing in the conventional co-rotating twin screw extruders. A novel kind of asymmetrical dual-speed co-rotating non-twin kneading elements (NTKE) with a zero staggered angle was designed to introduce symmetry break to improve mixing. Finite element method was applied to solve the time-dependent flow field where mesh superposition technique was used to impose the boundary conditions of moving parts and further to avoid the remeshing at every time steps. The flow and mixing of several fluids obeying the Carreau constitutive model with the different power law exponents were investigated numerically and compared with the conventional co-rotating twin kneading elements (TKE). Distributive mixing was evaluated through evolution of tracer droplets and decaying of variance index with time. Moreover, the dispersive mixing was examined in terms of the statistical distributions of mixing index. An integral function with regard to the mixing index was proposed to evaluate the proportion of tracer particles subjected to the elongation.

Planar Chlorination Engineering: A Strategy of Completely Breaking the Geometric Symmetry of Fe-N4 Site for Boosting Oxygen Electroreduction.

Introducing asymmetric elements and breaking the geometric symmetry of traditional metal-N4 site for boosting oxygen reduction reaction (ORR) are meaningful and challenging. Herein, the planar chlorination engineering of Fe-N4 site is first proposed for remarkably improving the ORR activity. The Fe-N4/CNCl catalyst with broken symmetry exhibits a half-wave potential (E1/2) of 0.917V versus RHE, 49 and 72mV higher than those of traditional Fe-N4/CN and commercial 20 wt% Pt/C catalysts. The Fe-N4/CNCl catalyst also has excellent stability for 25000 cycles and good methanol tolerance ability. For Zn-air battery test, the Fe-N4/CNCl catalyst has the maximum power density of 228mW cm-2 and outstanding stability during 150h charge-discharge test, as the promising substitute of Pt-based catalysts in energy storage and conversion devices. The density functional theory calculation demonstrates that the adjacent C─Cl bond effectively breaks the symmetry of Fe-N4 site, downward shifts the d-band center of Fe, facilitates the reduction and release of OH*, and remarkably lowers the energy barrier of rate-determining step. This work reveals the enormous potential of planar chlorination engineering for boosting the ORR activity of traditional metal-N4 site by thoroughly breaking their geometric symmetry.

Azimuthal rotation-controlled nanoinscribing for continuous patterning of period- and shape-tunable asymmetric nanogratings

We present an azimuthal-rotation-controlled dynamic nanoinscribing (ARC-DNI) process for continuous and scalable fabrication of asymmetric nanograting structures with tunable periods and shape profiles. A sliced edge of a nanograting mold, which typically has a rectangular grating profile, slides over a polymeric substrate to induce its burr-free plastic deformation into a linear nanopattern. During this continuous nanoinscribing process, the “azimuthal angle,” that is, the angle between the moving direction of the polymeric substrate and the mold’s grating line orientation, can be controlled to tailor the period, geometrical shape, and profile of the inscribed nanopatterns. By modulating the azimuthal angle, along with other important ARC-DNI parameters such as temperature, force, and inscribing speed, we demonstrate that the mold-opening profile and temperature- and time-dependent viscoelastic polymer reflow can be controlled to fabricate asymmetric, blazed, and slanted nanogratings that have diverse geometrical profiles such as trapezoidal, triangular, and parallelogrammatic. Finally, period- and profile-tunable ARC-DNI can be utilized for the practical fabrication of diverse optical devices, as is exemplified by asymmetric diffractive optical elements in this study.

Near-perfect absorption of a honeycomb metasurface through QBICs.

All-dielectric high-Q metasurface absorbers based on quasi-bound states in the continuum (QBICs) are essential for optical and photonic devices. However, achieving perfect absorption requires adding back reflectors at the bottom or placing at least four asymmetric elements in each unit of monolayer metasurfaces, which will increase the design complexity. This work proposes a honeycomb structure with units periodically arranged as a hexagonal lattice. Each unit cell is made of two nanopost elements. By only tuning the radius difference of two elements to break the in-plane symmetry, two orthogonal QBIC modes corresponding to toroidal dipole (TD) and electric dipole (ED) modes are excited, respectively. The maximum absorption reaches 92.3% at 955 nm with a Q factor of 1501, breaking the monolayer limit of 50% by the degenerate critical coupling. Our work may provide a promising route for designing high-Q all-dielectric metasurface absorbers applied in ultrafast optoelectronic devices.

Structural dynamics of RAF1-HSP90-CDC37 and HSP90 complexes reveal asymmetric client interactions and key structural elements

RAF kinases are integral to the RAS-MAPK signaling pathway, and proper RAF1 folding relies on its interaction with the chaperone HSP90 and the cochaperone CDC37. Understanding the intricate molecular interactions governing RAF1 folding is crucial for comprehending this process. Here, we present a cryo-EM structure of the closed-state RAF1-HSP90-CDC37 complex, where the C-lobe of the RAF1 kinase domain binds to one side of the HSP90 dimer, and an unfolded N-lobe segment of the RAF1 kinase domain threads through the center of the HSP90 dimer. CDC37 binds to the kinase C-lobe, mimicking the N-lobe with its HxNI motif. We also describe structures of HSP90 dimers without RAF1 and CDC37, displaying only N-terminal and middle domains, which we term the semi-open state. Employing 1 μs atomistic simulations, energetic decomposition, and comparative structural analysis, we elucidate the dynamics and interactions within these complexes. Our quantitative analysis reveals that CDC37 bridges the HSP90-RAF1 interaction, RAF1 binds HSP90 asymmetrically, and that HSP90 structural elements engage RAF1’s unfolded region. Additionally, N- and C-terminal interactions stabilize HSP90 dimers, and molecular interactions in HSP90 dimers rearrange between the closed and semi-open states. Our findings provide valuable insight into the contributions of HSP90 and CDC37 in mediating client folding.

Analogue tachyons in SNAIL transmission lines

Tachyons are hypothetical particles with imaginary mass that travel faster than light. However, methods to experimentally verify whether tachyons exist are lacking. Here, we propose a novel scheme to create analogue tachyons using a transmission line composed of superconducting nonlinear asymmetric inductive elements and to detect them by controlling the wavenumber in order to extend their lifetime. In particular, we numerically demonstrate the exotic property of tachyons where their velocity increases with decreasing energy. Our proposal offers a promising approach to understanding tachyon condensation, which is crucial for elucidating the origins of the Universe, in a realizable laboratory system.

Application of machine learning standardized integral area algorithm in measuring the scoliosis

This study was to develop a computer vision evaluation method to automatically measure the degree of scoliosis based on the machine learning algorithm. For the X-ray images of 204 patients with idiopathic scoliosis who underwent full-spine radiography, histogram equalization of original image was performed before a flipping method was used to magnify asymmetric elements, search for the global maximum pixel value in each line, and scan local maximal pixel value, with the intersection set of two point sets being regarded as candidate anchor points. All fine anchors were fitted with cubic spline algorithm to obtain the approximate curve of the spine, and the degree of scoliosis was measured by the standardized integral area. All measured data were analyzed. In manual measurement, the Cobb angle was 11.70–25.00 (20.15 ± 3.60), 25.20–44.70 (33.89 ± 5.41), and 45.10–49.40 (46.98 ± 1.25) in the mild, moderate and severe scoliosis group, respectively, whereas the value for the standardized integral area algorithm was 0.072–0.298 (0.185 ± 0.040), 0.100–0.399 (0.245 ± 0.050), and 0.246–0.901 (0.349 ± 0.181) in the mild, moderate and severe scoliosis group, respectively. Correlation analysis between the manual measurement of the Cobb angle and the evaluation of the standardized integral area algorithm demonstrated the Spearman correlation coefficient r = 0.643 (P < 0.001). There was a positive correlation between the manual measurement of the Cobb angle and the measurement of the standardized integral area value. Two methods had good consistency in evaluating the degree of scoliosis. ROC curve analysis of the standardized integral area algorithm to measure the degree of scoliosis showed he cutoff value of the standardized integral area algorithm was 0.20 for the moderate scoliosis with an AUC of 0.865, sensitivity 0.907, specificity 0.635, accuracy 0.779, positive prediction value 0.737 and negative prediction value 0.859, and the cutoff value of the standardized integral area algorithm was 0.40 for the severe scoliosis with an AUC of 0.873, sensitivity 0.188, specificity 1.00, accuracy 0.936, positive prediction value 1 and a negative prediction value 0.935. Using the standardized integral area as an independent variable and the Cobb angle as a dependent variable, a linear regression equation was established as Cobb angle = 13.36 + 70.54 × Standardized area, the model has statistical significance. In conclusion, the integrated area algorithm method of machine learning can quickly and efficiently assess the degree of scoliosis and is suitable for screening the degree of scoliosis in a large dataset as a useful supplement to the fine measurement of scoliosis Cobb angle.

The Neogondolella constricta (Mosher and Clark, 1965) group in the Middle Triassic of North America: speciation and distribution

AbstractNeogondolella constricta (Mosher and Clark, 1965) from the Prida Formation at Fossil Hill in central Nevada was the first conodont described from Middle Triassic strata in North America. The species has since been widely reported from elsewhere despite uncertainties about its taxonomic scope and that of similar related taxa. Poor definition of these taxa has spawned a diverse nomenclature and inhibited use of the group in biozonation. Starting with a growth series of topotype N. constricta, we reassess allied contemporaneous taxa from North America. In Nevada, 11 conodont taxa are identified: N. constricta, N. aldae Kozur, Krainer, and Mostler, 1994b, N. cornuta Budurov and Stefanov, 1972, N. ex gr. mesotriassica (Kozur and Mostler, 1982), N. postcornuta (Kovács, 1994), N. posterolonga Kozur, Krainer, and Mostler, 1994b, N. quasiconstricta n. sp., N. quasicornuta n. sp., and three subspecies of N. excentrica Budurov and Stefanov, 1972. Successive associations of taxa display symmetry transition in posterior platform configuration. Subdivision of the upper Anisian–lower Ladinian is provided by dominant N. constricta plus relatively uncommon N. quasiconstricta n. sp. and N. excentrica primitiva n. subsp. in the Rotelliformis ammonoid zone. This is followed in the Meeki through the Subasperum zones by dominant N. cornuta, associated N. posterolonga, plus relatively uncommon N. quasicornuta n. sp., and a variety of asymmetric elements: the Meeki Zone includes N. aff. N. cornuta; the Occidentalis Zone adds N. e. excentrica; and finally, N. e. sigmoidalis n. subsp. appears in the Subasperum Zone. In British Columbia, the three subspecies of N. excentrica are recognized in, respectively, the Deleeni, Chischa, and Matutinum (and younger) ammonoid zones.UUID: http://zoobank.org/7d58c8c8-cd68-498f-bb84-5d43de47f779

Compact Dual-Polarized Filtering Dipole Antenna by Using Asymmetric Parasitic Elements

Compact Dual-Polarized Filtering Dipole Antenna by Using Asymmetric Parasitic Elements

Ultrathin Pyroelectric Photodetector with Integrated Polarization-Sensing Metasurface.

An abundance of metallic metasurfaces have been realized with miniscule, intricate features capable of tailored scattering, reflection, and absorption; however, high losses through heat limit their use in optoelectronics. Here, codesign of a detector and a polarization-sensing metasurface overcomes this challenge by utilizing the heat generation for integrated pyroelectric detection of the incoming light polarization. Using a nanogap metasurface with asymmetric metallic elements, polarization-sensitive photodetection exhibits high extinction ratios up to 19 for orthogonally polarized light and allows extraction of Stokes parameters with <12% deviation from theoretical values. This polarization-sensitive photodetector is ultrathin, consisting of active layers of only 290 nm, and exhibits fast response times of ∼2 ns. The structure is fully integrated, requiring no external cameras, detectors, or power sources, and points toward the creation of layered, multifunctional devices that utilize exotic metasurface properties for novel and compact sensing and imaging.

Analog black-white hole solitons in traveling wave parametric amplifiers with superconducting nonlinear asymmetric inductive elements

Analog black-white hole solitons in traveling wave parametric amplifiers with superconducting nonlinear asymmetric inductive elements

Design of High-Gain Single-Layer Endfire Antenna Using Phase-Reversed Asymmetric Spoof Surface Plasmon Polaritons

We present a novel endfire antenna based on asymmetric spoof surface plasmon polaritons (SSPPs) and phase-reversal technique. SSPPs structure allows it to be fabricated on a single-layer printed circuit board. Asymmetric SSPPs elements were employed to fulfill the condition of endfire radiation, and meanwhile, phase-reversal technique provides a high gain for the antenna. To verify the proposed design principle, a prototype was fabricated and measured. It exhibits a peak gain of 16.2 dBi within the operational frequency band of 17–19 GHz, featuring the highest endfire gain among all single-layer designs.

Effective medium theory with hybrid impacts of phase symmetry and asymmetry for analyzing phase transition behavior

Recent research found a hysteresis phenomenon of electric conductance against metallic phase ratio during the thermally driven metal-insulator transition in the vanadium trioxide system. Profoundly exploring the hysteresis mechanism might help analyze the phase transition behavior. However, there is no complete analytical theory to give a quantitative description. In this work, we developed an effective medium theory to predict the relationships between the effective electric conductance and the metallic phase ratio during warming and cooling processes. It reveals that the above hysteresis is due to the hybrid impacts of phase symmetry and asymmetry in spatial distribution (termed space factor). Then, we applied this theory to deduce the nucleation and growth behavior of the minority phase in the majority phase during phase transition. The predicted relationship between metallic phase ratio and temperature is consistent with the experimental results obtained by scanning microwave impedance microscopy. It shows that the above dynamic behaviors during the warming and cooling processes are asymmetrical (termed dynamic factor). Combining the space and dynamic factors, we summarized the thermal hysteresis mechanism of the metal-insulator transition. Finally, we analyzed the influence of these two factors on the electric conductance difference during the warming and cooling processes. The result indicates that adjusting asymmetrical elements in space and dynamic factors is key to controlling thermal hysteresis magnitude. Since the electric conductance in our theory can be replaced by other physical properties, such as thermal conductivity, dielectric constant, and magnetic permeability, this work might help analyze many different phase transition behaviors.

Broadband SNAIL parametric amplifier with microstrip impedance transformer

Josephson parametric amplifiers are an important part of a modern superconducting quantum computing platform and squeezed quantum states generation devices. Traveling wave and impedance-matched parametric amplifiers provide broad bandwidth for high-fidelity single-shot readout of multiple qubit superconducting circuits. Here, we present a quantum-limited 3-wave-mixing parametric amplifier based on superconducting nonlinear asymmetric inductive elements (SNAILs), whose useful bandwidth is enhanced with an on-chip two-section impedance-matching circuit based on microstrip transmission lines. The amplifier dynamic range is increased using an array of 67 SNAILs with 268 Josephson junctions, forming a nonlinear quarter-wave resonator. Operating in a current-pumped mode, we experimentally demonstrate an average gain of 17 dB across 300 MHz bandwidth, along with an average saturation power of –100 dBm, which can go as high as −97 dBm with quantum-limited noise performance. Moreover, the amplifier can be fabricated using a simple technology with just one e-beam lithography step.

Metamaterials with Reprogrammable Reciprocity

Metamaterials composed of asymmetric elements have been shown to break reciprocity; permitting the propagation of waves in one direction. The configuration of these metamaterials typically limits the propagation of the wave to a single direction, speed, or occurrence with little or no tunability. Here we present---theoretically, numerically, and experimentally---a simple design approach for reprogrammable metamaterials, which allows for all of these parameters to be tuned, enabled, disabled, or reset. We present a map of different geometries that allow for reciprocal and nonreciprocal wave propagation and attenuation. We show how a single design can be programmed on demand to support wave propagation and attenuation in both directions (reciprocal) or wave propagation in only one direction (nonreciprocal). In addition, we demonstrate real-time control of the wave velocity, both in amplitude and direction, as it propagates through the metamaterial. We show speeding up, slowing down, or complete reversal of the propagating wave direction. Furthermore, we show that the waves maintain a constant velocity regardless of the impulse magnitude, and even along a curved path. Our metamaterial could open exciting possibilities for designing nonlinear materials with exotic topological properties.

Hybrid phase error analysis for dual-polarized reflectarray antenna using asymmetric split patch element

ABSTRACT A hybrid phase error analysis for dual-polarized reflectarray antenna using asymmetric split patch element is proposed in this article. The asymmetric split patch consists of a four-leaf patch and two split rings of different size where small one makes the patch asymmeric along y-axis and large one is used for impedance matching. And a complete 360° phase shift is obtained by using variable-size approach and flipping split patch 180° along y-axis. Then, we use hybrid phase error analysis approach to analyze and optimize the influence of phase sensitivity, quasi-periodic influence and phase constant on the reflectarray antenna. The simulated results show that maximum of element phase sensitivity is reduced by 275°/mm and element quasi-periodic phase error is dropped by 38°. Furthermore, dual-polarized reflectarray composed of 676 asymmetric split patch elements is designed, fabricated and measured. The measured gain of the proposed antenna is 29.9 dBi @10.0 GHz with aperture efficiency of 46%. The −1 dB gain bandwidth is 12% @10.0 GHz. The measured results show that the proposed antenna can improve phase accuracy effectively by using hybrid phase error analysis approach with asymmetric split patch.

Neural Network Training With Asymmetric Crosspoint Elements.

Analog crossbar arrays comprising programmable non-volatile resistors are under intense investigation for acceleration of deep neural network training. However, the ubiquitous asymmetric conductance modulation of practical resistive devices critically degrades the classification performance of networks trained with conventional algorithms. Here we first describe the fundamental reasons behind this incompatibility. Then, we explain the theoretical underpinnings of a novel fully-parallel training algorithm that is compatible with asymmetric crosspoint elements. By establishing a powerful analogy with classical mechanics, we explain how device asymmetry can be exploited as a useful feature for analog deep learning processors. Instead of conventionally tuning weights in the direction of the error function gradient, network parameters can be programmed to successfully minimize the total energy (Hamiltonian) of the system that incorporates the effects of device asymmetry. Our technique enables immediate realization of analog deep learning accelerators based on readily available device technologies.

A Review on Hot Stamping of Advanced High-Strength Steels: Technological-Metallurgical Aspects and Numerical Simulation

The production of ultra-high strength automotive components requires a multi-directional approach. Hot stamping combines both forming and heat treatment processes to obtain a usually martensitic structure of complicated shaped automotive parts. The preparation for production using hot stamping must involve the latest methods of numerical analysis of both temperature changes and forming, which are applied for an increasing range of materials used. In this paper, the current state of knowledge about the basics of hot stamping, used technological lines, and the current state of material used with applied heat treatments and possible coatings have been reviewed. Moreover, the numerical modeling process has been described. The most important aspects of process automation, including the use of digital twins for simulation and optimization of operational kinetics of the robots accomplishing the production process, analysis and minimization of time of production cycles, and searching for weak operational points of the control systems and for real time visualization of operation of complete line, are considered. The digital twins and corresponding numerical models enable the symmetrical design of real production lines. The details of heat treatment profiles with so called tailored zone heat treatment are provided. Hot stamping is a dynamically developing technology as evidenced by the increasing range of materials used, also from the 3rd generation of advanced high strength (AHSS) steels. It starts to combine forming of symmetric or asymmetric elements with more complex heat treatment processes as required for dual phase (DP) stainless steels or the newest generation of high-strength and ductile medium-manganese steels.