Asymmetric Gap Research Articles

Accretion of ornamental equatorial ridges on Pan, Atlas and Daphnis

We explore scenarios for the accretion of ornamental ridges on Saturn’s moons Pan, Atlas, and Daphnis from material in Saturn’s rings. Accretion of complex shaped ridges from ring material should be possible when the torque from accreted material does not exceed the tidal torque from Saturn that ordinarily maintains tidal lock. This gives a limit on the maximum accretion rate and the minimum duration for equatorial ridge growth. We explore the longitude distribution of ridges accreted from ring material, initially in circular orbits, onto a moon that is on a circular, inclined or eccentric orbit. Sloped and lobed ridges can be accreted if the moon tidally realigns during accretion due to its change in shape or because the disk edge surface density profile allows ring material originating at different initial semi-major axes to impact the moon at different locations on its equatorial ridge. We find that accretion from an asymmetric gap might account for a depression on Atlas’s equatorial ridge. Accretion from an asymmetric gap at orbital eccentricity similar to the Hill eccentricity, might allow accretion of multiple lobes, as seen on Pan. Two possibly connected scenarios are promising for growth of ornamental equatorial ridges. The moon migrates through the ring, narrowing its gap and facilitating accretion. The moon’s orbital eccentricity could increase due to orbital resonance with another moon, pushing it into its gap edges and facilitating accretion.

Polarization and the Pandemic: American Political Discourse, March – May 2020

Polarization and the Pandemic: American Political Discourse, March – May 2020

Factors affecting corporate environmental disclosure in emerging markets: The role of corporate governance structures

AbstractThis study seeks to examine whether internal corporate governance (CG) mechanisms affect corporate environmental disclosure (CED) in emerging economies. Using a sample of 500 firm‐year observations, this study distinctively applies a linear panel quantile regression (PQR) model to examine the CG–CED nexus in Jordan. This technique is supplemented with conducting a two‐step dynamic generalised method of moment (GMM) model to overcome any potential occurrence of endogeneity problems. This study reports an increasing trend in CED practice among the sampled companies over the period of analysis, yet it is still at an early stage as compared with their developed counterparts. Furthermore, this study suggests that board size, board independence, CEO duality and foreign ownership have positive associations with CED. In contrast, managerial ownership, institutional ownership and ownership concentration are negatively associated with the disclosed amount of environmental information in the Jordanian context. Theoretically, board structures appeared to be more efficient than ownership structures in reducing agency conflicts by addressing the asymmetric gap of information and promoting the disclosure of environmental information. These findings add to the debate about whether ownership structures detrimental to CED in developing economies. Specifically, when it comes to spending money on CED, owners seemed to be more concerned about any reductions in their share of the pie and may, therefore, be less motivated to disclose their companies' environmental information. This paper provides managers, owners and policymakers with a set of context‐specific recommendations related to the crucial need for a more concerted effort to integrate governance and environmental regulations in order to ensure sustainability in emerging markets.

Thermal Expansion of MgTiO3 Made by Sol-Gel Technique at Temperature Range 25–890 °C

MgTiO3 is a material commonly used in the industry as capacitors and resistors. The high-temperature structure of MgTiO3 has been reported only for materials synthesized by the solid-state method. This study deals with MgTiO3 formed at low temperatures by the sol-gel synthesis technique. Co-precipitated xerogel precursors of nanocrystalline magnesium titanates, with Mg:Ti ratio near 1:1, were subjected to thermal treatment at 1200 °C for 5 h in air. A sample with fine powders of MgTiO3 (geikielite) as a major phase with Mg2TiO4 (qandilite) as a minor phase was obtained. The powder was scanned on a hot-stage X-ray powder diffractometer at temperatures between 25 and 890 °C. The lattice parameters and the atomic positions of the two phases were determined as a function of temperature. The thermal expansion coefficients of the geikielite were derived and compared with previously published data using the solid-state synthesis technique, providing insights on trends in materials properties at elevated temperature as a function of synthesis. It was found that the deviation of the present results in comparison to previously reported data do not originate from the method of synthesis but rather from the fact that there is an asymmetric solubility gap in geikielite. The lattice parameters of this study present the property of stoichiometric MgTiO3 and are compared to previously reported non-stoichiometric MgTiO3 with excess of Ti. The values of lattice parameters of the non-stoichiometric versus temperature of geikielite found the same for both solid-state reaction and sol-gel products.

Band bending and zero-conductance resonances controlled by edge electric fields in zigzag silicene nanoribbons

We study the band structure and transport property of a zigzag silicene nanoribbon when electric fields are applied to the edges. It is found that band bending could be induced and controlled by the antisymmetric edge fields, which can be understood based on the wave functions of the edge states. The highest valence band and the lowest conduction band coexist in the band-bending region. With the narrowing of edge potentials, the bending increases gradually. When the edge fields become symmetric, an asymmetric band gap at the Dirac points can be obtained due to the intrinsic spin-orbit interaction, suggesting a valley-polarized quantum spin Hall state. The gap could reach a maximum value rapidly and then decrease slowly as the electric fields increase. Due to the combining effect of the band bending, band-selective rule, and resonant states, many zero-conductance resonances and resonance peaks appear in different regions, which could be described by the Fano resonance effect. Furthermore, the band bending and zero-conductance resonances are robust against the Hubbard interaction. The Hubbard interaction could work as a spin-dependent edge field, together with the edge electric fields, leading to a spin-dependent band gap and various quantum phases such as metal and half-metal.

Relevance of asymmetric extension gap on initial post-operative and weight-bearing x-rays after total knee replacement

Introduction Asymmetric gap between the femoral and tibial component after primary total knee replacement (TKR) is a known cause of post-operative pain. This study investigates whether significant asymmetric extension gaps seen on initial post-operative non-weight-bearing (NWB) radiographs persist on follow-up weight-bearing (WB) radiographs. Method 203 consecutive patients who underwent primary TKR, and had adequate radiographic follow-up during a four-year period, were included. The distance between the tibial tray and femoral condyle on the medial and lateral sides was measured on initial NWB and follow-up WB radiographs, to identify significant asymmetric extension gaps. Previous studies showed medial extension gaps of ≥1.5mm may be associated with increased pain post-operatively. Therefore, we defined a significant gap as ≥1.5mm. The results were examined to determine whether initial post-operative gaps remain appreciable on follow-up x-rays. Results Of the 203 radiographs reviewed, 29 (14.3%) patients had an extension gap mismatch of ≥1.5mm on initial post-operative imaging. 13 (44.8%) patients had a medial opening gap whilst 16 (55.2%) had a lateral opening. Only 4 (13.8%) of these patients showed no significant change in the asymmetrical extension gap (remained ≥1.5mm) on WB x-rays. In the remaining patients, the gap was no longer appreciable. Conclusion The study showed that if patients present with post-TKR pain, which could be related to a medial opening extension gap, clinicians should use initial NWB x-rays to investigate as the gap mismatch may not be detectable on follow-up WB radiographs.

Relevance of Asymmetric Extension Gap on Initial Post-Operative and Weight-Bearing X-Rays After Total Knee Replacement

Introduction Asymmetric gap between the femoral and tibial component after primary total knee replacement (TKR) is a known cause of post-operative pain. This study investigates whether significant asymmetric extension gaps seen on initial post-operative non-weight-bearing (NWB) radiographs persist on follow-up weight-bearing (WB) radiographs. Method 203 consecutive patients who underwent primary TKR, and had adequate radiographic follow-up during a four-year period, were included. The distance between the tibial tray and femoral condyle on the medial and lateral sides was measured on initial NWB and follow-up WB radiographs, to identify significant asymmetric extension gaps. Previous studies showed medial extension gaps of ≥1.5mm may be associated with increased pain post-operatively. Therefore, we defined a significant gap as ≥1.5mm. The results were examined to determine whether initial post-operative gaps remain appreciable on follow-up x-rays. Results Of the 203 radiographs reviewed, 29 (14.3%) patients had an extension gap mismatch of ≥1.5mm on initial post-operative imaging. 13 (44.8%) patients had a medial opening gap whilst 16 (55.2%) had a lateral opening. Only 4 (13.8%) of these patients showed no significant change in the asymmetrical extension gap (remained ≥1.5mm) on WB x-rays. In the remaining patients, the gap was no longer appreciable. Conclusion The study showed that if patients present with post-TKR pain, which could be related to a medial opening extension gap, clinicians should use initial NWB x-rays to investigate as the gap mismatch may not be detectable on follow-up WB radiographs.

Low-Profile Beamforming-Network-Avoiding Multi-Beam Antenna Based on Parasitic Patch and Shorting-Pin

In this paper, a new method to design multi-beam antenna based on parasitic patch and shorting-pin is proposed and demonstrated through two cases of singleand multi-source. For the single-source multi-beam antenna, by arranging the parasitic patch shorted with pins around a square patch, the beam is divided into four parts and a multi-beam radiation is realized. Also, arc slots in the parasitic patch are added to improve the bandwidth and shorting-pins located along the edges of square patch are introduced to adjust the operating frequency, gain and pitch angle. The multi-source multi-beam antenna has a similar construction with the single-source case except it has four ports. In addition, an asymmetric gap is added in the square patch to improve the isolation between the four ports. Finally, both the simulated and measured results verify the proposed methodology. The realized single-source antenna operates in the range of 5.22 - 5.42 GHz. Four beams point at (φ, 8) = (0°, 41°), (90°, 35°), (180°, 41°) and (270°, 38°). For the multi-source case, the corresponding bandwidth is 5.25 - 5.48 GHz. The radiation beams are steered to (φ, 8) = (0°, 30°), (270°, 37°), (90°, 30°) and (180°, 37°).

Deflected oscillatory wake pattern behind two side-by-side circular cylinders

Wake flow behind structures is of fundamental significance and practical interest in ocean engineering. Several asymmetric flow patterns, such as the deflected stationary, flip-flop and deflected oscillatory wakes, behind two cylinders in a side-by-side arrangement have been reported most recently. In the present work, direct numerical simulations together with the state-of-art dynamic mode decomposition are used to reveal the underlying physics of deflected oscillatory wake pattern with low Reynolds number and intermediate gap ratio. Asymmetric flow structures are observed numerically in certain arrangements. Specially, the structure for gap flow is similar to that observed in flip-flop pattern induced by the secondary instability, but asymmetric here. It is found that the drag coefficient and lift coefficient under such circumstances are dominated by the asymmetric gap flow structure rather than the vortex street in the downstream. The present work provides a new scenario to the wake flow patterns behind two side-by-side cylinders with intermediate gap ratios, and it is potentially helpful in understanding the vibrating behaviors of adjacent cylinders.

Composition dependent gradient energy coefficient: How the asymmetric miscibility gap affects spinodal decomposition in Ag-Cu?

We report results for spinodal decomposition in Ag-Cu binary system. The asymmetric miscibility gap of any binary system necessarily means that the gradient energy coefficient κ is composition dependent. We demonstrate that while this composition dependence of κ does not modify the solubility curve and even the equilibrium interface profile hardly changes, the cutoff wavelength for spinodal decomposition does. Many calculations usually use composition independent gradient energy coefficient and the analytical expression for calculating the cutoff wavelength is valid also only for composition independent κ. We show that the κ-composition function can be calculated from the interaction energy V(c): κ=−1/12r02∂[(1−2c)V(c)]/∂c, where r0 is the interatomic distance. In this work we apply the Cahn-Hilliard theory and a 3D atomistic kinetic model, the Stochastic Kinetic Mean Field (SKMF), what we further developed purposefully. The improvement is not restricted to the Ag-Cu system, though, as the composition dependent interaction energy can be deduced e.g. from Redlich-Kister polynomials.

Dissipative generation for steady-state entanglement of two transmons in circuit QED

We present a dissipative scheme to generate an entangled steady-state between two superconducting transmon qutrits separately embedded in two coupled transmission line resonators in a circuit quantum electrodynamics (QED) setup. In our scheme, the resonant qutrit-resonator interaction and photon hopping between resonators jointly induce asymmetric energy gaps in the dressed state subspaces. The coherent driving fields induce the specific dressed state transition and the dissipative processes lead to the gradual accumulation in the population of target state, combination of both drives the system into a steady-state entanglement. Numerical simulation shows that the maximally entangled state can be produced with high fidelity and strong robustness against the cavity decay and qutrit decay, and no requirements for accurate time control. The scheme is achievable with the current experimental technologies.

Investigation of Systematic Efficiency in a High-Speed Single-Phase Brushless DC Motor Using Multi-Physics Analysis for a Vacuum Cleaner

This paper discusses systematic efficiency considering the efficiency of both a motor and airflow in an inverter-driven single-phase brushless direct-current (BLDC) motor with two different lamination designs for a cordless vacuum cleaner. In other words, multi-physical lamination design has to be conducted, and hence, the shape and placement of a whole electromagnetic structure are investigated in terms of a tradeoff between the electrical and mechanical efficiencies. In this paper, a single-phase BLDC motor for cordless vacuum cleaners is designed to satisfy starting and continuous torques by means of asymmetric air gap, and fluid analysis is performed to determine which shape of a single-phase BLDC motor has better system efficiency. The prototype of a single-phase BLDC motor has been tested, and the speed of the operation is ranged from 84468 r/min up to the rated speed of 100020 r/min. The motor efficiency of 94.7% has been measured to verify a good match with the estimated efficiency of 94.5%.

Numerical Investigation into the Effect of Geometric Gap Idealisation on Wheel-Rail Rolling Contact in Presence of Yaw Angle

For a fast calculation of vehicle-track dynamics and wheel-rail contact mechanics, wheel-rail contact geometric gap is usually idealised in elliptic or nonelliptic form. These two idealisations deviate from the actual one if the lateral combined curvature within the contact patch is not constant or the yaw angle of wheelset exists. The influence of these idealisations on contact solution has not yet been deeply understood, and thus the accuracy of simplified contact modelling applied to vehicle-track dynamics and wheel-rail contact mechanics remains uncertain. This paper presents a numerical methodology to treat 3D wheel-rail rolling contact, in which the asymmetric geometric gap due to yaw angle is fully taken into account. The attention of this work is placed on investigating the effect of geometric gap idealisation on wheel-rail contact force, rolling contact solution, and wear distribution. It can help with the effective wheel-rail contact modelling on the computation of both vehicle-track dynamics and wheel-rail contact mechanics.

Design of a Single-Phase BLDC Motor for a Cordless Vacuum Cleaner Considering the Efficiency of Airflow

This paper discusses an inverter-driven single-phase brushless direct-current (BLDC) motor assembled by a housing for a cordless vacuum cleaner. Air gap in the single-phase BLDC motor is asymmetrically designed to satisfy starting and continuous torque by considering voltage fluctuation in a battery. By varying both advance and conduction angles in response to the change of battery voltage, the proposed single-phase BLDC motor with asymmetric air gap is able to maintain sufficient output power. The system efficiency of a vacuum cleaner driven by the proposed motor assembly is estimated by means of fluid dynamics in air watt, and it is also verified experimentally. From the results of the condition of 100,020 r/min, it was confirmed that the motor efficiency was in good agreement with the estimated efficiency, and air flow efficiency of 45.7% and system efficiency of 41.8% were achieved.

Flux Characteristics Analysis of a Double-Sided Switched Reluctance Linear Machine Under the Asymmetric Air Gap

This paper analyzes the flux characteristics and normal force of the double-sided switched reluctance linear machine (SRLM) under the asymmetric air gap. The magnetic equivalent circuit (MEC) of the machine and the details of the flux paths configuration at six distinct mover positions under the asymmetric air gap are included. Then, six special mover position magnetization curves are calculated by solving the MEC with the method of Gauss–Seidel. The magnetic flux-linkage model and thrust model based on six distinct mover positions are established by analytical polynomial. Three-dimensional (3-D) finite-element method (FEM) simulation and the experimental study with the prototype hardware are carried out to validate the accuracy of the MEC model calculated for the flux linkage and normal force. The six distinct mover positions flux linkage and normal force calculated by the MEC are consistent with the 3-D FEM calculated data and experimental data. It indicates that the proposed method to calculate the flux linkage and the normal force is feasible and effective. The dynamic analysis is also conducted. The simulated phase current waveforms are also consistent with the experimental results. It indicates that the presented method can be used to simulate the phase current under the asymmetry air gap effectively. The normal force under different asymmetry rates is analyzed, which provides the theoretical basis for reducing the unbalanced force of the double-sided SRLM.

Nonreciprocal spin waves in a chiral antiferromagnet without the Dzyaloshinskii-Moriya interaction

Non-reciprocal spin wave can facilitate the realization of spin wave logic devices. It has been demonstrated that the non-reciprocity can emerge when an external magnetic field is applied to chiral magnets, of which spin structures depend crucially on an asymmetric exchange interaction, that is, the Dzyaloshinskii-Moriya interaction (DMI). Here we demonstrate that the non-reciprocity can arise even without the DMI. We demonstrate this idea for the chiral antiferromagnet Ba$_2$NbFe$_3$Si$_2$O$_{14}$, of which DMI is very small and chiral spin structure arises mainly from the competition between symmetric exchange interactions. We show that when an external magnetic field is applied, asymmetric energy gap shift occurs and the spin wave becomes non-reciprocal from the competition between symmetric exchange interactions and the external magnetic field.

Overcoming the trade-off between Voc and Jsc: Asymmetric chloro-substituted two-dimensional benzo[1,2-b:4,5-b′]dithiophene-based polymer solar cells

To achieve the high PCE and simultaneously overcome the trade-off between open circuit voltage (VOC) and short-circuit current density (JSC), the reasonable design of the donor material is still a great challenge in non-fullerene polymer solar cells (PSCs). Herein, a pair of asymmetric 2D BDT-based wide band gap polymers, named PBPTBz-1Cl and PBPTBz-2Cl, respectively, were designed and synthesized through simultaneously introducing a chloro-substituted thiophene and another alkoxylphenyl groups as side chains onto the same BDT unit. As expected, the polymers PBPTBz-1Cl and PBPTBz-2Cl exhibit the deeper HOMO levels of −5.32 and −5.41 eV, respectively, compared with the HOMO value of −5.27 eV for chlorine-free substituted polymer PBPTBz-0Cl. Therefore, the PBPTBz-2Cl:IT-M based PSCs exhibited a higher Voc of 0.99 V, with an enhanced Jsc of 14.92 mA cm−2 and PCE of 7.18%. The Voc, Jsc and PCE were simultaneously enhanced from PBPTBz-0Cl:IT-M to PBPTBz-1Cl:IT-M, then to PBPTBz-2Cl:IT-M based PSCs successively. These results demonstrate that the challenge of the trade-off between Voc and Jsc could be overcome through the asymmetric strategy of the chloro-substituted thiophene and alkylphenyl groups as different side chains onto the same BDT unit. Hence, considering the low cost of starting materials and convenient introduction of chlorine atoms, the asymmetric chlorination of the side chain of BDT unit would be the great potential for achieving the high-performance PSCs.

Asymmetric hydrodynamic roll gap model and its experimental validation

In tandem hot strip rolling mills, different friction between the rolls and the strip material on the upper and lower strip surface can occur due to asymmetric surface temperatures or different conditions of oil lubrication. To capture these effects, this paper presents a hydrodynamic roll gap model with asymmetric friction. Based on similarities between the rolled material and viscous fluids, fluid mechanics theory is used to derive this model. Due to the nature of this model, the influence of the rolling speed is inherently taken into account, which allows an accurate prediction of the rolling force and the forward slip. As an analytic solution for the hydrodynamic roll gap model is available, it is well suited for online applications in rolling plants. For validation of the proposed model, an experiment with asymmetric work roll roughness was performed. A specimen of steel strip with copper pins inserted was repeatedly rolled to visualize the material flow inside the roll gap for multiple passes. The resulting deformed copper pins were cut out of the strip and show good agreement with the deformation profiles calculated by the developed model.

Magnetic-free nonreciprocal photonic platform based on time-modulated graphene capacitors

We propose a paradigm for the realization of nonreciprocal photonic devices based on time-modulated graphene capacitors coupled to photonic waveguides, without relying on magneto-optic effects. The resulting hybrid graphene-dielectric platform is low loss, silicon compatible, robust against graphene imperfections, scalable from terahertz to near-infrared frequencies, and it exhibits large nonreciprocal responses using realistic biasing schemes. We introduce an analytical framework based on solving the eigenstates of the modulated structure and on spatial coupled mode theory, unveiling the physical mechanisms that enable nonreciprocity and enabling a quick analysis and design of optimal isolator geometries based on synthetic linear and angular momentum bias. Our results, validated through harmonic-balance full-wave simulations, confirm the feasibility of the introduced low-loss ($l3$ dB) platform to realize large photonic isolation through various mechanisms, such as narrow-band asymmetric band gaps and interband photonic transitions that allow multiple isolation frequencies and large bandwidths. We envision that this technology may pave the wave to magnetic-free, fully integrated, and CMOS--compatible nonreciprocal components with wide applications in photonic networks and thermal management.

Non-linear asymmetric gap models of residential satisfaction: Formulation and empirical evidence

This paper proposes non-linear asymmetric gap–satisfaction models to assess the influence of the gap between aspirations and perceived residential attributes on residential satisfaction. Two variants of the residential gap are specified based on the difference and ratio between aspiration and reality. Besides the influence of residential gap, the interactions with social-demographics are incorporated in three specifications of gap–satisfaction relationship. Using empirical data collected from eight renovated historical blocks in two Chinese cities, the relative performances of the proposed gap models are compared with truncated linear symmetric gap models and traditional linear (absolute) difference models for housing, living environmental and neighbourhood attributes. The estimation results indicate that overall the non-linear asymmetric gap models outperform the linear gap models. The model fit for housing and living environmental attributes are very good. Satisfaction for housing attributes is predicted best with non-linear asymmetric gap ratio models, while the environmental attributes are best represented by non-linear asymmetric difference models. In case of the neighbourhood dimension, non-linear asymmetric gap ratio models show the best performance, while these models yield a good fit only for two attributes. The interaction effect of social-demographics is found to vary between residential attributes.